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Sample records for gradient tracer test

  1. Forced Gradient Tracer Tests In A Highly Permeable Fault Zone

    NASA Astrophysics Data System (ADS)

    Himmelsbach, T.; Hötzl, H.; Maloszewski, P.

    1994-03-01

    In the area of a planned dam site in the southern Black Forest, an observation tunnel with boreholes drilled into an adjacent vertically orientated ore body offered nearly ideal conditions to investigate transport phenomena in a highly permeable fault and fracture zone. The experimental array, consisting of horizontal and inclined boreholes lying within distances of ten to twelve meters apart, gave the opportunity to perform forced gradient tracer tests over varying distances under fixed hydraulic boundary conditions. The breakthrough curves of the tracer experiments were analyzed using an adequate transport model. The fitting procedure yielded hydraulic parameters such as fissure and matrix porosities and first estimations of the average fracture aperture.

  2. Evaluation of longitudinal dispersivity estimates from forced-gradient tracer tests in heterogeneous aquifers

    USGS Publications Warehouse

    Tiedeman, C.R.; Hsieh, P.A.

    2002-01-01

    Converging radial-flow and two-well tracer tests are simulated in two-dimensional aquifers to investigate the effects of heterogeneity and forced-gradient test configuration on longitudinal dispersivity (??L) estimates, and to compare ??L estimates from forced-gradient tests with ??L values that characterize solute spreading under natural-gradient flow. Results indicate that in mildly heterogeneous aquifers, for tests with relatively large tracer transport distances, ??L estimates from the two test types are generally similar, and are also similar to ??L values determined from natural-gradient tracer simulations. In highly heterogeneous aquifers, ??L estimates from two-well tests are generally larger than those from radial-flow tests, and the ??L estimates from both test types are typically smaller than the ??L values determined from natural-gradient simulations.

  3. Evaluation of longitudinal dispersivity estimates from forced-gradient tracer tests in heterogeneous aquifers

    USGS Publications Warehouse

    Tiedeman, C.R.; Hsieh, P.A.

    2002-01-01

    Converging radial-flow and two-well tracer tests are simulated in two-dimensional aquifers to investigate the effects of heterogeneity and forced-gradient test configuration on longitudinal dispersivity (??L) estimates, and to compare ??L estimates from forced-gradient tests with ??L values that characterize solute spreading under natural-gradient flow. Results indicate that in both mildly and highly heterogeneous aquifers, ??L estimates from two-well tests are generally larger than those from radial-flow tests. In mildly heterogeneous aquifers, ??L estimates from two-well tests with relatively large tracer transport distances are similar to ??L values from natural-gradient simulations. In highly heterogeneous aquifers, ??L estimates from two-well tests at all tracer transport distances are typically smaller than ??L values from natural-gradient simulations.

  4. Double forced gradient tracer test: Performance and interpretation of a field test using a new solute transport model

    NASA Astrophysics Data System (ADS)

    Vandenbohede, A.; Lebbe, L.

    2006-02-01

    A double forced gradient tracer test was performed in heterogeneous quaternary deposits of the Scheldt river in Belgium. The objectives of the test were to derive reliable hydraulic and solute transport parameters, to study the heterogeneity of the groundwater reservoir and to illustrate the practical utility of forced gradient tracer tests. Salt water was used as a conservative tracer. The tracer was injected with two injection wells and both plumes were pumped towards one intermediately placed pumping well. Before the forced gradient tracer test a short lasting pumping test was performed. Drawdown and concentration measurements were made in different observation wells during the pumping and forced gradient tracer test. The movement of the salt water was followed by measuring the electrical conductivity of the sediments around observation wells using a focussed electromagnetic induction method. The drawdown and concentration observations were then interpreted together. By combining these two sets of data, hydraulic and solute transport parameters were derived simultaneously and more accurately than in the case only one type of data is used. For this, a new 3D solute transport model TRACER3D, specifically designed to simulate accurately flow and solute transport towards a well, was developed. The behaviour of the two tracer plumes was totally different due to varying hydraulic and dispersive properties in the aquifer. Horizontal and vertical conductivity, specific elastic storage, effective porosity and longitudinal dispersivity were derived and brought into relation with the site's heterogeneity, visualised by natural gamma logs in the different wells.

  5. In situ measurement of methane oxidation in groundwater by using natural-gradient tracer tests.

    PubMed Central

    Smith, R L; Howes, B L; Garabedian, S P

    1991-01-01

    Methane oxidation was measured in an unconfined sand and gravel aquifer (Cape Cod, Mass.) by using in situ natural-gradient tracer tests at both a pristine, oxygenated site and an anoxic, sewage-contaminated site. The tracer sites were equipped with multilevel sampling devices to create target grids of sampling points; the injectate was prepared with groundwater from the tracer site to maintain the same geochemical conditions. Methane oxidation was calculated from breakthrough curves of methane relative to halide and inert gas (hexafluroethane) tracers and was confirmed by the appearance of 13C-enriched carbon dioxide in experiments in which 13C-enriched methane was used as the tracer. A Vmax for methane oxidation could be calculated when the methane concentration was sufficiently high to result in zero-order kinetics throughout the entire transport interval. Methane breakthrough curves could be simulated by modifying a one-dimensional adevection-dispersion transport model to include a Michaelis-Menten-based consumption term for methane oxidation. The Km values for methane oxidation that gave the best match for the breakthrough curve peaks were 6.0 and 9.0 microM for the uncontaminated and contaminated sites, respectively. Natural-gradient tracer tests are a promising approach for assessing microbial processes and for testing in situ bioremediation potential in groundwater systems. PMID:1892389

  6. In situ measurement of methane oxidation in groundwater by using natural-gradient tracer tests

    USGS Publications Warehouse

    Smith, R.L.; Howes, B.L.; Garabedian, S.P.

    1991-01-01

    Methane oxidation was measured in an unconfined sand and gravel aquifer (Cape Cod, Mass.) by using in situ natural-gradient tracer tests at both a pristine, oxygenated site and an anoxic, sewage-contaminated site. The tracer sites were equipped with multilevel sampling devices to create target grids of sampling points; the injectate was prepared with groundwater from the tracer site to maintain the same geochemical conditions. Methane oxidation was calculated from breakthrough curves of methane relative to halide and inert gas (hexafluoroethane) tracers and was confirmed by the appearance of 13C-enriched carbon dioxide in experiments in which 13C-enriched methane was used as the tracer. A V(max) for methane oxidation could be calculated when the methane concentration was sufficiently high to result in zero-order kinetics throughout the entire transport interval. Methane breakthrough curves could be simulated by modifying a one-dimensional advection-dispersion transport model to include a Michaelis-Menten-based consumption term for methane oxidation. The K(m) values for methane oxidation that gave the best match for the breakthrough curve peaks were 6.0 and 9.0 ??M for the uncontaminated and contaminated sites, respectively. Natural-gradient tracer tests are a promising approach for assessing microbial processes and for testing in situ bioremediation potential in groundwater systems.

  7. Evaluation of longitudinal dispersivity estimates from simulated forced- and natural-gradient tracer tests in heterogeneous aquifers

    USGS Publications Warehouse

    Tiedeman, C.R.; Hsieh, P.A.

    2004-01-01

    We simulate three types of forced-gradient tracer tests (converging radial flow, unequal strength two well, and equal strength two well) and natural-gradient tracer tests in multiple realizations of heterogeneous two-dimensional aquifers with a hydraulic conductivity distribution characterized by a spherical variogram. We determine longitudinal dispersivities (??L) by analysis of forced-gradient test breakthrough curves at the pumped well and by spatial moment analysis of tracer concentrations during the natural-gradient tests. Results show that among the forced-gradient tests, a converging radial-flow test tends to yield the smallest ??L, an equal strength two-well test tends to yield the largest ??L, and an unequal strength two-well test tends to yield an intermediate value. This finding is qualitatively explained by considering the aquifer area sampled by a particular test. A converging radial-flow test samples a small area, and thus the tracer undergoes a low degree of spreading and mixing. An equal strength two-well test samples a much larger area, so the tracer is spread and mixed to a greater degree. Results also suggest that if the distance between the tracer source well and the pumped well is short relative to the lengths over which velocity is correlated, then the ??L estimate can be highly dependent on local heterogeneities in the vicinity of the wells. Finally, results indicate that ??L estimated from forced-gradient tracer tests can significantly underestimate the ??L needed to characterize solute dispersion under natural-gradient flow. Only a two-well tracer test with a large well separation in an aquifer with a low degree of heterogeneity can yield a value of ??L that characterizes natural-gradient tracer spreading. This suggests that a two-well test with a large well separation is the preferred forced-gradient test for characterizing solute dispersion under natural-gradient flow.

  8. A note on the recent natural gradient tracer test at the Borden site

    USGS Publications Warehouse

    Naff, R.L.; Yeh, T.-C.J.; Kemblowski, M.W.

    1988-01-01

    The variance in particle position, a measure of dispersion, is reviewed in the context of certain models of flow in random porous media. Asymptotic results for a highly stratified medium and an isotropic medium are particularly highlighted. Results of the natural gradient tracer test at the Borden site are reviewed in light of these models. This review suggests that the moments obtained for the conservative tracers could as well be explained by a model that more explicitly represents the three-dimensional nature of the flow field. -Authors

  9. Comparison of denitrification activity measurements in groundwater using cores and natural-gradient tracer tests

    USGS Publications Warehouse

    Smith, R.L.; Garabedian, S.P.; Brooks, M.H.

    1996-01-01

    The transport of many solutes in groundwater is dependent upon the relative rates of physical flow and microbial metabolism. Quantifying rates of microbial processes under subsurface conditions is difficult and is most commonly approximated using laboratory studies with aquifer materials. In this study, we measured in situ rates of denitrification in a nitrate- contaminated aquifer using small-scale, natural-gradient tracer tests and compared the results with rates obtained from laboratory incubations with aquifer core material. Activity was measured using the acetylene block technique. For the tracer tests, co-injection of acetylene and bromide into the aquifer produced a 30 ??M increase in nitrous oxide after 10 m of transport (23-30 days). An advection-dispersion transport model was modified to include an acetylene-dependent nitrous oxide production term and used to simulate the tracer breakthrough curves. The model required a 4-day lag period and a relatively low sensitivity to acetylene to match the narrow nitrous oxide breakthrough curves. Estimates of in situ denitrification rates were 0.60 and 1.51 nmol of N2O produced cm-3 aquifer day-1 for two successive tests. Aquifer core material collected from the tracer test site and incubated as mixed slurries in flasks and as intact cores yielded rates that were 1.2-26 times higher than the tracer test rate estimates. Results with the coring-dependent techniques were variable and subject to the small- scale heterogeneity within the aquifer, while the tracer tests integrated the heterogeneity along a flow path, giving a rate estimate that is more applicable to transport at the scale of the aquifer.

  10. Evaluation of Heat as a Tracer in a Forced-Gradient Test at the MADE Site

    NASA Astrophysics Data System (ADS)

    Huang, A.; Tick, G. R.; Keasberry, A.; Zheng, C.

    2011-12-01

    Tracer tests conducted at the Macrodispersion Experiment (MADE) site in Columbus Air Force Base in Mississippi have contributed significantly to the understanding of contaminant transport processes in highly-heterogeneous media. Previous experiments have revealed a network of interconnected preferential flow paths within the underlying aquifer. Only solute tracers including bromide and tritium have been used in previous experiments. In this new study, a forced-gradient experiment based on heated water injection was conducted to evaluate the feasibility of heat as a substitute for a solute tracer to study aquifer heterogeneity at the MADE site. We injected a pulse of heated water, recorded the breakthrough curves, and used numerical modeling to characterize the heat transport behavior and its relationship to subsurface heterogeneity. The results were compared with those from a previous experiment based on the bromide tracer. This research suggests heat can be a cheaper and environmentally-friendly alternative to traditional solute tracers, and improves our understanding of contaminant transport processes in highly-heterogeneous systems.

  11. FORCED-GRADIENT TRACER TESTS AND INFERRED HYDRAULIC CONDUCTIVITY DISTRIBUTIONS AT THE MOBILE SITE (JOURNAL VERSION)

    EPA Science Inventory

    Four single-well tracer tests and a two-well tracer test performed in a 21-m thick confined granular aquifer at a field site near Mobile, Alabama are described. The data from these tests together with previously published data from a single-well test and a two-well test allow one...

  12. LARGE-SCALE NATURAL GRADIENT TRACER TEST IN SAND AND GRAVEL, CAPE COD, MASSACHUSETTS - 1. EXPERIMENTAL DESIGN AND OBSERVED TRACER MOVEMENT

    EPA Science Inventory

    A large-scale natural gradient tracer experiment was conducted on Cape Cod, Massachusetts, to examine the transport and dispersion of solutes in a sand and gravel aquifer. The nonreactive tracer, bromide, and the reactive tracers, lithium and molybdate, were injected as a pulse i...

  13. Assessing denitrification in groundwater using natural gradient tracer tests with 15N: In situ measurement of a sequential multistep reaction

    USGS Publications Warehouse

    Smith, R.L.; Böhlke, J.K.; Garabedian, S.P.; Revesz, K.M.; Yoshinari, T.

    2004-01-01

    Denitrification was measured within a nitrate-contaminated aquifer on Cape Cod, Massachusetts, using natural gradient tracer tests with 15N nitrate. The aquifer contained zones of relatively high concentrations of nitrite (up to 77 ??M) and nitrous oxide (up to 143 ??M) and has been the site of previous studies examining ground water denitrification using the acetylene block technique. Small-scale (15-24 m travel distance) tracer tests were conducted by injecting 15N nitrate and bromide as tracers into a depth interval that contained nitrate, nitrite, nitrous oxide, and excess nitrogen gas. The timing of the bromide breakthrough curves at down-gradient wells matched peaks in 15N abundance above background for nitrate, nitrite, nitrous oxide, and nitrogen gas after more than 40 days of travel. Results were simulated with a one-dimensional transport model using linked reaction kinetics for the individual steps of the denitrification reaction pathway. It was necessary to include within the model spatial variations in background concentrations of all nitrogen oxide species. The model indicated that nitrite production (0.036-0.047 ??mol N (L aquifer)-1 d -1) was faster than the subsequent denitrification steps (0.013-0.016 ??mol N (L aquifer)-1 d-1 for nitrous oxide and 0.013-0.020 ??mol N (L aquifer)-1 d-1 for nitrogen gas) and that the total rate of reaction was slower than indicated by both acetylene block tracer tests and laboratory incubations. The rate of nitrate removal by denitrification was much slower than the rate of transport, indicating that nitrate would migrate several kilometers down-gradient before being completely consumed.

  14. Fate and transport of linear alkylbenzenesulfonate in a sewage- contaminated aquifer: A comparison of natural-gradient pulsed tracer tests

    USGS Publications Warehouse

    Krueger, C.J.; Barber, L.B.; Metge, D.W.; Field, J.A.

    1998-01-01

    Two natural-gradient tracer tests were conducted to determine the transport and biodegradation behavior of linear alkylbenzenesulfonate (LAS) surfactant under in situ conditions in a sewage-contaminated aquifer. The tests were conducted in two biogeochemically distinct zones of the aquifer: (1) an aerobic uncontaminated zone (oxic zone) and (2) a moderately aerobic, sewage-contaminated zone (transition zone). Chromatographic separation of the surfactant mixture was observed in both zones and attributed to the retardation of the longer alkyl chain homologues during transport. No significant loss of IAS mass was observed for the oxic zone while 20% of the LAS mass injected into the transition zone was removed due to biodegradation. Biodegradation preferentially removed the longer alkyl chain homologues and the external isomers (i.e., 2- and 3-phenyl). The removal of LAS mass coincided with a decrease in dissolved oxygen concentrations, the appearance of LAS metabolites, and an increase in the number of free-living bacteria with a concomitant change in bacteria morphology. The formation of LAS metabolites accounted for 86% of the LAS mass removed in the transition zone. Over the duration of the test, sorption and biodegradation enriched the LAS mixture in the more water-soluble and biologically resistant components.Two natural-gradient tracer tests were conducted to determine the transport and biodegradation behavior of linear alkylbenzenesulfonate (LAS) surfactant under in situ conditions in a sewage-contaminated aquifer. The tests were conducted in two biogeochemically distinct zones of the aquifer: (1) an aerobic uncontaminated zone (oxic zone) and (2) a moderately aerobic, sewage-contaminated zone (transition zone). Chromatographic separation of the surfactant mixture was observed in both zones and attributed to the retardation of the longer alkyl chain homologues during transport. No significant loss of LAS mass was observed for the oxic zone while 20% of the LAS

  15. Numerical evaluation of apparent transport parameters from forced-gradient tracer tests in statistically anisotropic heterogeneous formations

    NASA Astrophysics Data System (ADS)

    Pedretti, D.; Fernandez-Garcia, D.; Bolster, D.; Sanchez-Vila, X.; Benson, D.

    2012-04-01

    For risk assessment and adequate decision making regarding remediation strategies in contaminated aquifers, solute fate in the subsurface must be modeled correctly. In practical situations, hydrodynamic transport parameters are obtained by fitting procedures, that aim to mathematically reproduce solute breakthrough (BTC) observed in the field during tracer tests. In recent years, several methods have been proposed (curve-types, moments, nonlocal formulations) but none of them combine the two main characteristic effects of convergent flow tracer tests (which are the most used tests in the practice): the intrinsic non-stationarity of the convergent flow to a well and the ubiquitous multiscale hydraulic heterogeneity of geological formations. These two effects separately have been accounted for by a lot of methods that appear to work well. Here, we investigate both effects at the same time via numerical analysis. We focus on the influence that measurable statistical properties of the aquifers (such as the variance and the statistical geometry of correlation scales) have on the shape of BTCs measured at the pumping well during convergent flow tracer tests. We built synthetic multigaussian 3D fields of heterogeneous hydraulic conductivity fields with variable statistics. A well is located in the center of the domain to reproduce a forced gradient towards it. Constant-head values are imposed on the boundaries of the domains, which have 251x251x100 cells. Injections of solutes take place by releasing particles at different distances from the well and using a random walk particle tracking scheme with constant local coefficient of dispersivity. The results show that BTCs partially display the typical anomalous behavior that has been commonly referred to as the effect of heterogeneity and connectivity (early and late arrival times of solute differ from the one predicted by local formulations). Among the most salient features, the behaviors of BTCs after the peak (the slope

  16. Design and analysis of a natural-gradient ground-water tracer test in a freshwater tidal wetland, West Branch Canal Creek, Aberdeen Proving Ground, Maryland

    USGS Publications Warehouse

    Olsen, Lisa D.; Tenbus, Frederick J.

    2005-01-01

    A natural-gradient ground-water tracer test was designed and conducted in a tidal freshwater wetland at West Branch Canal Creek, Aberdeen Proving Ground, Maryland. The objectives of the test were to characterize solute transport at the site, obtain data to more accurately determine the ground-water velocity in the upper wetland sediments, and to compare a conservative, ionic tracer (bromide) to a volatile tracer (sulfur hexafluoride) to ascertain whether volatilization could be an important process in attenuating volatile organic compounds in the ground water. The tracer test was conducted within the upper peat unit of a layer of wetland sediments that also includes a lower clayey unit; the combined layer overlies an aquifer. The area selected for the test was thought to have an above-average rate of ground-water discharge based on ground-water head distributions and near-surface detections of volatile organic compounds measured in previous studies. Because ground-water velocities in the wetland sediments were expected to be slow compared to the underlying aquifer, the test was designed to be conducted on a small scale. Ninety-seven ?-inch-diameter inverted-screen stainless-steel piezometers were installed in a cylindrical array within approximately 25 cubic feet (2.3 cubic meters) of wetland sediments, in an area with a vertically upward hydraulic gradient. Fluorescein dye was used to qualitatively evaluate the hydrologic integrity of the tracer array before the start of the tracer test, including verifying the absence of hydraulic short-circuiting due to nonnatural vertical conduits potentially created during piezometer installation. Bromide and sulfur hexafluoride tracers (0.139 liter of solution containing 100,000 milligrams per liter of bromide ion and 23.3 milligrams per liter of sulfur hexafluoride) were co-injected and monitored to generate a dataset that could be used to evaluate solute transport in three dimensions. Piezometers were sampled 2 to 15 times

  17. Identification of small-scale low and high permeability layers using single well forced-gradient tracer tests: fluorescent dye imaging and modelling at the laboratory-scale.

    PubMed

    Barns, Gareth L; Thornton, Steven F; Wilson, Ryan D

    2015-01-01

    Heterogeneity in aquifer permeability, which creates paths of varying mass flux and spatially complex contaminant plumes, can complicate the interpretation of contaminant fate and transport in groundwater. Identifying the location of high mass flux paths is critical for the reliable estimation of solute transport parameters and design of groundwater remediation schemes. Dipole flow tracer tests (DFTTs) and push-pull tests (PPTs) are single well forced-gradient tests which have been used at field-scale to estimate aquifer hydraulic and transport properties. In this study, the potential for PPTs and DFTTs to resolve the location of layered high- and low-permeability layers in granular porous media was investigated with a pseudo 2-D bench-scale aquifer model. Finite element fate and transport modelling was also undertaken to identify appropriate set-ups for in situ tests to determine the type, magnitude, location and extent of such layered permeability contrasts at the field-scale. The characteristics of flow patterns created during experiments were evaluated using fluorescent dye imaging and compared with the breakthrough behaviour of an inorganic conservative tracer. The experimental results show that tracer breakthrough during PPTs is not sensitive to minor permeability contrasts for conditions where there is no hydraulic gradient. In contrast, DFTTs are sensitive to the type and location of permeability contrasts in the host media and could potentially be used to establish the presence and location of high or low mass flux paths. Numerical modelling shows that the tracer peak breakthrough time and concentration in a DFTT is sensitive to the magnitude of the permeability contrast (defined as the permeability of the layer over the permeability of the bulk media) between values of 0.01-20. DFTTs are shown to be more sensitive to deducing variations in the contrast, location and size of aquifer layered permeability contrasts when a shorter central packer is used

  18. Identification of small-scale low and high permeability layers using single well forced-gradient tracer tests: Fluorescent dye imaging and modelling at the laboratory-scale

    NASA Astrophysics Data System (ADS)

    Barns, Gareth L.; Thornton, Steven F.; Wilson, Ryan D.

    2015-01-01

    Heterogeneity in aquifer permeability, which creates paths of varying mass flux and spatially complex contaminant plumes, can complicate the interpretation of contaminant fate and transport in groundwater. Identifying the location of high mass flux paths is critical for the reliable estimation of solute transport parameters and design of groundwater remediation schemes. Dipole flow tracer tests (DFTTs) and push-pull tests (PPTs) are single well forced-gradient tests which have been used at field-scale to estimate aquifer hydraulic and transport properties. In this study, the potential for PPTs and DFTTs to resolve the location of layered high- and low-permeability layers in granular porous media was investigated with a pseudo 2-D bench-scale aquifer model. Finite element fate and transport modelling was also undertaken to identify appropriate set-ups for in situ tests to determine the type, magnitude, location and extent of such layered permeability contrasts at the field-scale. The characteristics of flow patterns created during experiments were evaluated using fluorescent dye imaging and compared with the breakthrough behaviour of an inorganic conservative tracer. The experimental results show that tracer breakthrough during PPTs is not sensitive to minor permeability contrasts for conditions where there is no hydraulic gradient. In contrast, DFTTs are sensitive to the type and location of permeability contrasts in the host media and could potentially be used to establish the presence and location of high or low mass flux paths. Numerical modelling shows that the tracer peak breakthrough time and concentration in a DFTT is sensitive to the magnitude of the permeability contrast (defined as the permeability of the layer over the permeability of the bulk media) between values of 0.01-20. DFTTs are shown to be more sensitive to deducing variations in the contrast, location and size of aquifer layered permeability contrasts when a shorter central packer is used

  19. Tracer testing for reservoir description

    SciTech Connect

    Brigham, W.E.; Abbaszadeh-Dehghani, M.

    1987-05-01

    When a reservoir is studied in detail for an EOR project, well-to-well tracers should be used as a tool to help understand the reservoir in a quantitative way. Tracers complement the more traditional reservoir evaluation tools. This paper discusses the concepts underlying tracer testing, the analysis methods used to produce quantitative results, and the meaning of these results in terms of conceptual picture of the reservoir. Some of the limitations of these analysis methods are discussed, along with ongoing research on tracer flow.

  20. Assessing the effect of natural attenuation on oxygen consumption processes in a sewage-contaminated aquifer by use of a natural-gradient tracer test

    NASA Astrophysics Data System (ADS)

    Mathisen, P. P.; Kent, D. B.; Smith, R. L.; Barber, L. B.; Harvey, R. W.; Metge, D. W.; Hess, K. M.; Leblanc, D. R.; Koch, J. C.

    2003-12-01

    Processes associated with aquifer restoration subsequent to cessation of treated-sewage loading in a sand and gravel aquifer are being investigated at the USGS Toxic Substances Hydrology Site on Cape Cod, MA. Restoration has been slow because of significant oxygen depletion resulting from biogeochemical processes associated with residual sorbed pools of organic carbon, ammonium, and reduced metals in the aquifer. The in situ interaction of the physical, chemical, and biological processes governing oxygen consumption was examined by using a natural-gradient tracer test in fall 2001, 6 years after sewage disposal had been discontinued. Ground water with a high dissolved oxygen (DO) concentration was withdrawn from an uncontaminated zone of the aquifer and re-injected with a conservative tracer, bromide, into an anoxic zone directly below a former sewage-effluent disposal bed where Fe and sulfide concentrations were below detection and the DO was less than 5 uM. An injection with negligible ammonium, a nitrate concentration of 22 uM, and DO of approximately 260 uM was maintained at approximately 15 L/hr for a period of 75 days. An array of multi-level samplers (MLS), placed at distances ranging from 1 to 7 m down-gradient from the injection well, was sampled prior to and throughout the 75-day injection, and during a 25-day period after the injection. Water samples from the MLS were analyzed for DO and a variety of aqueous constituents. The DO decreased from approximately 260 uM to 210 uM over 7 m of transport, indicating the presence of rate-limited oxygen consumption. An increase in nitrate from 22 to approximately 36 uM indicated the presence of rate-limited ammonium oxidation. However, this ammonium oxidation was not sufficient to account for all of the DO consumption. Further characterization of these processes was accomplished by use of PHREEQC, a one-dimensional, geochemical reactive transport model. The 1D model is based on an ion association model for aqueous

  1. 3-D numerical evaluation of density effects on tracer tests.

    PubMed

    Beinhorn, M; Dietrich, P; Kolditz, O

    2005-12-01

    In this paper we present numerical simulations carried out to assess the importance of density-dependent flow on tracer plume development. The scenario considered in the study is characterized by a short-term tracer injection phase into a fully penetrating well and a natural hydraulic gradient. The scenario is thought to be typical for tracer tests conducted in the field. Using a reference case as a starting point, different model parameters were changed in order to determine their importance to density effects. The study is based on a three-dimensional model domain. Results were interpreted using concentration contours and a first moment analysis. Tracer injections of 0.036 kg per meter of saturated aquifer thickness do not cause significant density effects assuming hydraulic gradients of at least 0.1%. Higher tracer input masses, as used for geoelectrical investigations, may lead to buoyancy-induced flow in the early phase of a tracer test which in turn impacts further plume development. This also holds true for shallow aquifers. Results of simulations with different tracer injection rates and durations imply that the tracer input scenario has a negligible effect on density flow. Employing model cases with different realizations of a log conductivity random field, it could be shown that small variations of hydraulic conductivity in the vicinity of the tracer injection well have a major control on the local tracer distribution but do not mask effects of buoyancy-induced flow. PMID:16183165

  2. Tracers and Tracer Testing: Design, Implementation, Tracer Selection, and Interpretation Methods

    SciTech Connect

    G. Michael Shook; Shannon L.; Allan Wylie

    2004-01-01

    Conducting a successful tracer test requires adhering to a set of steps. The steps include identifying appropriate and achievable test goals, identifying tracers with the appropriate properties, and implementing the test as designed. When these steps are taken correctly, a host of tracer test analysis methods are available to the practitioner. This report discusses the individual steps required for a successful tracer test and presents methods for analysis. The report is an overview of tracer technology; the Suggested Reading section offers references to the specifics of test design and interpretation.

  3. TRACER-TEST PLANNING USING THE EFFICIENT HYDROLOGIC TRACER-TEST DESIGN (EHTD) PROGRAM 2003

    EPA Science Inventory

    Hydrological tracer testing is the most reliable diagnostic technique available for establishing flow trajectories and hydrologic connections and for determining basic hydraulic and geometric parameters necessary for establishing operative solute-transport processes. Tracer-test ...

  4. TRACER-TEST PLANNING USING THE EFFICIENT HYDROLOGIC TRACER-TEST DESIGN (EHTD) PROGRAM 2005

    EPA Science Inventory

    Hydrological tracer testing is the most reliable diagnostic technique available for establishing flow trajectories and hydrologic connections and for determining basic hydraulic and geometric parameters necessary for establishing operative solute-transport processes. Tracer-test ...

  5. Identification of transport processes in Southern Indian fractured crystalline rock using forced-gradient tracer experiments

    NASA Astrophysics Data System (ADS)

    Guihéneuf, Nicolas; Bour, Olivier; Boisson, Alexandre; Le Borgne, Tanguy; Becker, Matthew R.; Nigon, Benoit; Wajiduddin, Mohammed; Ahmed, Shakeel; Maréchal, Jean-Christophe

    2015-04-01

    Understanding dominant transport processes is essential to improve prediction of contaminants transfer in fractured crystalline rocks. In such fractured media, solute transport is characterized by fast advection within open and connected fractures and sometimes by matrix diffusion that may be enhanced by chemical weathering. To investigate this phenomenon, we carried out radially convergent and push-pull tracer experiments in the fractured granite of the Experimental Hydrogeological Park of Choutuppal (Southern India). Tracer tests were performed in the same permeable fracture from few meters to several ten meters and from few hours to two weeks to check the consistency of the results at different spatial and temporal scales. These different types of forced gradient tracer experiments allow separation of the effects of advection and diffusion on transport. Breakthrough curves from radially convergent tracer tests display systematically a -2 power law slope on the late time behavior. This tailing can be adequately represented by a transport model that only takes into account heterogeneous advection caused by fluid flow channeling. The negligible impact of matrix diffusion was confirmed by the push-pull tracer tests, at least for the duration of experiments. A push-pull experiment carried out with a cocktail of two conservative tracers having different diffusion coefficients displayed similar breakthrough curves. Increasing the resting phase during the experiments did not lead to a significant decline of peak concentration. All these results suggest a negligible impact of matrix diffusion. However, increasing the scales of investigation during push-pull tracer tests led to a decrease of the power law slope on the late time behavior. This behavior that cannot be modeled with a transport model based on independent flow paths and indicate non-reversible heterogeneous advection. This process could be explained by the convergence of streamlines after a certain distance

  6. Tracer Testing for Estimating Heat Transfer Area in Fractured Reservoirs

    SciTech Connect

    Pruess, Karsten; van Heel, Ton; Shan, Chao

    2004-05-12

    A key parameter governing the performance and life-time of a Hot Fractured Rock (HFR) reservoir is the effective heat transfer area between the fracture network and the matrix rock. We report on numerical modeling studies into the feasibility of using tracer tests for estimating heat transfer area. More specifically, we discuss simulation results of a new HFR characterization method which uses surface-sorbing tracers for which the adsorbed tracer mass is proportional to the fracture surface area per unit volume. Sorption in the rock matrix is treated with the conventional formulation in which tracer adsorption is volume-based. A slug of solute tracer migrating along a fracture is subject to diffusion across the fracture walls into the adjacent rock matrix. Such diffusion removes some of the tracer from the fluid in the fractures, reducing and retarding the peak in the breakthrough curve (BTC) of the tracer. After the slug has passed the concentration gradient reverses, causing back-diffusion from the rock matrix into the fracture, and giving rise to a long tail in the BTC of the solute. These effects become stronger for larger fracture-matrix interface area, potentially providing a means for estimating this area. Previous field tests and modeling studies have demonstrated characteristic tailing in BTCs for volatile tracers in vapor-dominated reservoirs. Simulated BTCs for solute tracers in single-phase liquid systems show much weaker tails, as would be expected because diffusivities are much smaller in the aqueous than in the gas phase, by a factor of order 1000. A much stronger signal of fracture-matrix interaction can be obtained when sorbing tracers are used. We have performed simulation studies of surface-sorbing tracers by implementing a model in which the adsorbed tracer mass is assumed proportional to the fracture-matrix surface area per unit volume. The results show that sorbing tracers generate stronger tails in BTCs, corresponding to an effective

  7. Analysis of tracer responses in the BULLION Forced-Gradient Experiment at Pahute Mesa, Nevada

    SciTech Connect

    Paul W. Reimus; Marc J. Haga

    1999-10-01

    This report presents an analysis of the tracer data from the BULLION forced-gradient experiment (FGE) conducted on Pahute Mesa at the Nevada Test Site from June 2, 1997 through August 28, 1997, for the Underground Test Area (UGTA) Program. It also serves to document the polystyrene microsphere data from the FGE. The FGE involved the injection of solute and colloid tracers into wells ER-20-6 No. 1 and ER-20-6 No. 2 while ER-20-6 No. 3 was pumped at approximately 116 gallons per minute (gpm). The experimental configuration and test design are described briefly in this report; more details are provided elsewhere (IT, 1996, 1997, 1998). The tracer responses in the various wells yielded valuable information about transport processes such as longitudinal dispersion, matrix diffusion and colloid transport in the hydrogeologic system in the vicinity of the BULLION nuclear test cavity. Parameter values describing these processes are derived from the semi-analytical model interpretations presented in this report. A companion report (IT, 1998) presents more detailed numerical modeling interpretations of the solute tracer responses.

  8. LARGE-SCALE NATURAL GRADIENT TRACER TEST IN SAND AND GRAVEL, CAPE CODE, MASSACHUSETTS 3. HYDRAULIC CONDUCTI- VITY AND CALCULATED MACRODISPERSIVITIES

    EPA Science Inventory

    Hydraulic conductivity (K) variability in a sand and gravel aquifer on Cape Cod, Massachusetts, was measured and subsequently used in stochastic transport theories to estimate macrodispersivities. Nearly 1500 K measurements were obtained by borehole flowmeter tests ...

  9. Long residence times - bad tracer tests?

    NASA Astrophysics Data System (ADS)

    Ghergut, Julia; Behrens, Horst; Sauter, Martin

    2015-04-01

    Tracer tests conducted at geothermal well doublets or triplets in the Upper Rhine Rift Valley [1] all face, with very few exceptions so far, one common issue: lack of conclusive tracer test results, or tracer signals still undetectable for longer than one or two years after tracer injection. While the reasons for this surely differ from site to site (Riehen, Landau, Insheim, Bruchsal, ...), its effects on how the usefulness of tracer tests is perceived by the non-tracer community are pretty much the same. The 'poor-signal' frustration keeps nourishing two major 'alternative' endeavours : (I) design and execute tracer tests in single-well injection-withdrawal (push-pull), 'instead of' inter-well flow-path tracing configurations; (II) use 'novel' tracer substances instead of the 'old' ones which have 'obviously failed'. Frustration experienced with most inter-well tracer tests in the Upper Rhine Rift Valley has also made them be regarded as 'maybe useful for EGS' ('enhanced', or 'engineered' geothermal systems, whose fluid RTD typically include a major share of values below one year), but 'no longer worthwhile a follow-up sampling' in natural, large-scale hydrothermal reservoirs. We illustrate some of these arguments with the ongoing Bruchsal case [2]. The inter-well tracer test conducted at Bruchsal was (and still is!) aimed at assessing inter-well connectivity, fluid residence times, and characterizing the reservoir structure [3]. Fluid samples taken at the geothermal production well after reaching a fluid turnover of about 700,000 m3 showed tracer concentrations in the range of 10-8 Minj per m3, in the liquid phase of each sample (Minj being the total quantity of tracer injected as a short pulse at the geothermal re-injection well). Tracer signals might actually be higher, owing to tracer amounts co-precipitated and/or adsorbed onto the solid phase whose accumulation in the samples was unavoidable (due to pressure relief and degassing during the very sampling

  10. Transport of microspheres and indigenous bacteria through a sandy aquifer: Results of natural- and forced-gradient tracer experiments

    USGS Publications Warehouse

    Harvey, R.W.; George, L.H.; Smith, R.L.; LeBlanc, D.R.

    1989-01-01

    Transport of indigenous bacteria through sandy aquifer sediments was investigated in forced- and natural-gradient tracer teste. A diverse population of bacteria was collected and concentrated from groundwater at the site, stained with a DNA-specific fluorochrome, and injected back into the aquifer. Included with the injectate were a conservative tracer (Br- or Cl-) and bacteria-sized (0.2-1.3-??m) microspheres having carboxylated, carbonyl, or neutral surfaces. Transport of stained bacteria and all types and size classes of microspheres was evident. In the natural-gradient test, both surface characteristics and size of microspheres affected attenuation. Surface characteristics had the greatest effect upon retardation. Peak break-through of DAPI-stained bacteria (forced-gradient experiment) occurred well in advance of bromide at the more distal sampler. Transport behavior of bacteria was substantially different from that of carboxylated microspheres of comparable size. ?? 1988 American Chemical Society.

  11. MULTISPECIES REACTIVE TRACER TEST IN A SAND AND GRAVEL AQUIFER, CAPE COD, MASSACHUSETTS: PART 2: TRANSPORT OF CHROMIUM (VI) AND LEAD-, COPPER-, AND ZINC-EDTA TRACERS

    EPA Science Inventory

    This report discusses the transport of a group of reactive tracers over the course of a large-scale, natural gradient tracer test conducted at the USGS Cape Cod Toxic Substances Hydrology Research site, near Falmouth, Massachusetts. The overall objectives of the experiment were ...

  12. Tracer mass recovery in fractured aquifers estimated from multiple well tests.

    PubMed

    Sanford, William E; Cook, Peter G; Robinson, Neville I; Weatherill, Douglas

    2006-01-01

    Forced-gradient tracer tests in fractured aquifers often report low mass recoveries. In fractured aquifers, fractures intersected by one borehole may not be intersected by another. As a result (1) injected tracer can follow pathways away from the withdrawal well causing low mass recovery and (2) recovered water can follow pathways not connected to the injection well causing significant tracer dilution. These two effects occur along with other forms of apparent mass loss. If the strength of the connection between wells and the amount of dilution can be predicted ahead of time, tracer tests can be designed to optimize mass recovery and dilution. A technique is developed to use hydraulic tests in fractured aquifers to calculate the conductance (strength of connection) between well pairs and to predict mass recovery and amount of dilution during forced gradient tracer tests. Flow is considered to take place through conduits, which connect the wells to each other and to distant sources or sinks. Mass recovery is related to the proportion of flow leaving the injection well and arriving at the withdrawal well, and dilution is related to the proportion of the flow from the withdrawal well that is derived from the injection well. The technique can be used to choose well pairs for tracer tests, what injection and withdrawal rates to use, and which direction to establish the hydraulic gradient to maximize mass recovery and/or minimize dilution. The method is applied to several tracer tests in fractured aquifers in the Clare Valley, South Australia. PMID:16857034

  13. Analysing the capabilities and limitations of tracer tests in stream-aquifer systems

    USGS Publications Warehouse

    Wagner, B.J.; Harvey, J.W.

    2001-01-01

    The goal of this study was to identify the limitations that apply when we couple conservative-tracer injection with reactive solute sampling to identify the transport and reaction processes active in a stream. Our methodology applies Monte Carlo uncertainty analysis to assess the ability of the tracer approach to identify the governing transport and reaction processes for a wide range of stream-solute transport and reaction scenarios likely to be encountered in high-gradient streams. Our analyses identified dimensionless factors that define the capabilities and limitations of the tracer approach. These factors provide a framework for comparing and contrasting alternative tracer test designs.

  14. EFFICIENT HYDROLOGICAL TRACER-TEST DESIGN (EHTD) MODEL

    EPA Science Inventory

    Hydrological tracer testing is the most reliable diagnostic technique available for establishing flow trajectories and hydrologic connections and for determining basic hydraulic and geometric parameters necessary for establishing operative solute-transport processes. Tracer-test...

  15. Interpreting tracer breakthrough tailing from different forced-gradient tracer experiment configurations in fractured bedrock

    USGS Publications Warehouse

    Becker, M.W.; Shapiro, A.M.

    2003-01-01

    Conceptual and mathematical models are presented that explain tracer breakthrough tailing in the absence of significant matrix diffusion. Model predictions are compared to field results from radially convergent, weak-dipole, and push-pull tracer experiments conducted in a saturated crystalline bedrock. The models are based upon the assumption that flow is highly channelized, that the mass of tracer in a channel is proportional to the cube of the mean channel aperture, and the mean transport time in the channel is related to the square of the mean channel aperture. These models predict the consistent -2 straight line power law slope observed in breakthrough from radially convergent and weak-dipole tracer experiments and the variable straight line power law slope observed in push-pull tracer experiments with varying injection volumes. The power law breakthrough slope is predicted in the absence of matrix diffusion. A comparison of tracer experiments in which the flow field was reversed to those in which it was not indicates that the apparent dispersion in the breakthrough curve is partially reversible. We hypothesize that the observed breakthrough tailing is due to a combination of local hydrodynamic dispersion, which always increases in the direction of fluid velocity, and heterogeneous advection, which is partially reversed when the flow field is reversed. In spite of our attempt to account for heterogeneous advection using a multipath approach, a much smaller estimate of hydrodynamic dispersivity was obtained from push-pull experiments than from radially convergent or weak dipole experiments. These results suggest that although we can explain breakthrough tailing as an advective phenomenon, we cannot ignore the relationship between hydrodynamic dispersion and flow field geometry at this site. The design of the tracer experiment can severely impact the estimation of hydrodynamic dispersion and matrix diffusion in highly heterogeneous geologic media.

  16. Simulation and interpretation of inter-well tracer tests

    NASA Astrophysics Data System (ADS)

    Huseby, Olaf; Sagen, Jan; Viig, Sissel; Dugstad, Øyvind

    2013-05-01

    In inter-well tracer tests (IWTT), chemical compounds or radioactive isotopes are used to label injection water and gas to establish well connections and fluid patterns in petroleum reservoirs. Tracer simulation is an invaluable tool to ease the interpretation of IWTT results and is also required for assisted history matching application of tracer data. In this paper we present a new simulation technique to analyse and interpret tracer results. Laboratory results are used to establish and test formulations of the tracer conservation equations, and the technique is used to provide simulated tracer responses that are compared with observed tracer data from an extensive tracer program. The implemented tracer simulation methodology use a fast post-processing of previously simulated reservoir simulation runs. This provides a fast, flexible and powerful method for analysing gas tracer behaviour in reservoirs. We show that simulation time for tracers can be reduced by factor 100 compared to solving the tracer flow equations simultaneously with the reservoir fluid flow equations. The post-processing technique, combined with a flexible built-in local tracer-grid refinement is exploited to reduce numerical smearing, particularly severe for narrow tracer pulses.

  17. EVALUATION OF LEAKAGE FROM FUME HOODS USING TRACER GAS, TRACER NANOPARTICLES AND NANOPOWDER HANDLING TEST METHODOLOGIES

    PubMed Central

    Dunn, Kevin H.; Tsai, Candace Su-Jung; Woskie, Susan R.; Bennett, James S.; Garcia, Alberto; Ellenbecker, Michael J.

    2015-01-01

    The most commonly reported control used to minimize workplace exposures to nanomaterials is the chemical fume hood. Studies have shown, however, that significant releases of nanoparticles can occur when materials are handled inside fume hoods. This study evaluated the performance of a new commercially available nano fume hood using three different test protocols. Tracer gas, tracer nanoparticle, and nanopowder handling protocols were used to evaluate the hood. A static test procedure using tracer gas (sulfur hexafluoride) and nanoparticles as well as an active test using an operator handling nanoalumina were conducted. A commercially available particle generator was used to produce sodium chloride tracer nanoparticles. Containment effectiveness was evaluated by sampling both in the breathing zone (BZ) of a mannequin and operator as well as across the hood opening. These containment tests were conducted across a range of hood face velocities (60, 80, and 100 feet/minute) and with the room ventilation system turned off and on. For the tracer gas and tracer nanoparticle tests, leakage was much more prominent on the left side of the hood (closest to the room supply air diffuser) although some leakage was noted on the right side and in the BZ sample locations. During the tracer gas and tracer nanoparticle tests, leakage was primarily noted when the room air conditioner was on for both the low and medium hood exhaust air flows. When the room air conditioner was turned off, the static tracer gas tests showed good containment across most test conditions. The tracer gas and nanoparticle test results were well correlated showing hood leakage under the same conditions and at the same sample locations. The impact of a room air conditioner was demonstrated with containment being adversely impacted during the use of room air ventilation. The tracer nanoparticle approach is a simple method requiring minimal setup and instrumentation. However, the method requires the reduction in

  18. 76 FR 71610 - Market Test of First-Class Tracer

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-18

    ... Market Test of First-Class Tracer AGENCY: Postal Regulatory Commission. ACTION: Notice. SUMMARY: The Commission is noticing a recently-field Postal Service proposal to conduct a market test of a market dominant product, First- Class Tracer. This document describes the proposed test, addresses procedural aspects...

  19. Lidar Tracking of Multiple Fluorescent Tracers: Method and Field Test

    NASA Technical Reports Server (NTRS)

    Eberhard, Wynn L.; Willis, Ron J.

    1992-01-01

    Past research and applications have demonstrated the advantages and usefulness of lidar detection of a single fluorescent tracer to track air motions. Earlier researchers performed an analytical study that showed good potential for lidar discrimination and tracking of two or three different fluorescent tracers at the same time. The present paper summarizes the multiple fluorescent tracer method, discusses its expected advantages and problems, and describes our field test of this new technique.

  20. Direct Quantification of Microbial Community Respiration along a Contamination Gradient using a novel Hydrologic Smart Tracer

    NASA Astrophysics Data System (ADS)

    Stanaway, D. J.; Haggerty, R.; Feris, K. P.

    2010-12-01

    Heavy metal contamination in lotic ecosystems is a major health and environmental concern worldwide. The Resazurin Resorufin (Raz Rru) Smart Tracer system (Haggerty et al., 2008) provides a novel approach to test current models of microbial ecosystem response to chronic stressors such as heavy metals. These models predict that functional redundancy of metabolic capabilities of community members (e.g. respiration rate and enzyme activity) will compensate for decreases in species diversity until a stress threshold is reached. At this point, species diversity and function are expected to decline rapidly. Contrary to this model, microbial communities of the Clark Fork River (CF), Montana, demonstrate high levels of species diversity along the contamination gradient, whereas community function is inversely proportional to the level of contamination. The Raz Rru tool, a metabolically reactive hydrologic tracer, allows for direct quantification of in-situ microbial respiration rates. Therefore, this tool provides an opportunity to build upon studies of ecosystem response to contamination previously limited to extrapolation of point scale measurements to reach scale processes. The Raz Rru tool is used here to quantify the magnitude of metal induced limits on heterotrophic microbial respiration in communities that have evolved to different levels of chronic metal exposure. In this way we propose to be able to test a novel hypothesis concerning the nature of evolution of community processes to chronic stress and persistent environmental pollutants. Specifically, we hypothesize that metal contamination produces a measureable metabolic cost to both tolerant and intolerant communities. To test this hypothesis, rates of respiration associated with hyporheic sediments, supporting intact microbial communities, were quantified in the presence and absence of an acute Cd exposure in column experiments. Hyporheic sediment was collected from differently contaminated locations within

  1. Integrating Tracer Test Data into Geostatistical Aquifer Characterization at the Hanford 300 Area

    NASA Astrophysics Data System (ADS)

    Chen, X.; Murakami, H.; Hahn, M. S.; Rockhold, M. L.; Vermeul, V.; Rubin, Y.

    2009-12-01

    Tracer testing under natural or forced gradient flow is an efficient method for characterizing subsurface properties, by monitoring and modeling the tracer plume migration in a heterogeneous aquifer. At the Hanford 300 area, non-reactive tracer experiments, in addition to constant-rate injection tests and electromagnetic borehole flow meter profiling, were conducted to characterize the heterogeneous hydraulic conductivity field at the site. The tracer was injected at a near-constant rate for 10 hours, and the tracer concentrations were monitored for 12 days in a network of observation wells. This work presents a Bayesian inverse modeling technique to infer the heterogeneity structure of the hydraulic conductivity in the saturated zone of the Hanford formation, using the breakthrough curves at various observation wells. Analytical or semi-analytical solutions for mass transport in divergent radial flow fields are adopted whenever possible to avoid expensive numerical forward simulations. Compared to the case conditioned on the constant-rate injection tests and electromagnetic borehole flow meter profiling, this study finds that the inclusion of tracer test data can improve the estimation of heterogeneity structure and reduce the prediction uncertainty of the solute transport at given locations. With the availability of observation wells at varying distances, we also investigate the worth of data in each observation well, which can be used to evaluate the effectiveness of current experimental setup and guide further data collection practices at the site.

  2. Heat tracer test in an alluvial aquifer: Field experiment and inverse modelling

    NASA Astrophysics Data System (ADS)

    Klepikova, Maria; Wildemeersch, Samuel; Hermans, Thomas; Jamin, Pierre; Orban, Philippe; Nguyen, Frédéric; Brouyère, Serge; Dassargues, Alain

    2016-09-01

    Using heat as an active tracer for aquifer characterization is a topic of increasing interest. In this study, we investigate the potential of using heat tracer tests for characterization of a shallow alluvial aquifer. A thermal tracer test was conducted in the alluvial aquifer of the Meuse River, Belgium. The tracing experiment consisted in simultaneously injecting heated water and a dye tracer in an injection well and monitoring the evolution of groundwater temperature and tracer concentration in the pumping well and in measurement intervals. To get insights in the 3D characteristics of the heat transport mechanisms, temperature data from a large number of observation wells closely spaced along three transects were used. Temperature breakthrough curves in observation wells are contrasted with what would be expected in an ideal layered aquifer. They reveal strongly unequal lateral and vertical components of the transport mechanisms. The observed complex behavior of the heat plume is explained by the groundwater flow gradient on the site and heterogeneities in the hydraulic conductivity field. Moreover, due to high injection temperatures during the field experiment a temperature-induced fluid density effect on heat transport occurred. By using a flow and heat transport numerical model with variable density coupled with a pilot point approach for inversion of the hydraulic conductivity field, the main preferential flow paths were delineated. The successful application of a field heat tracer test at this site suggests that heat tracer tests is a promising approach to image hydraulic conductivity field. This methodology could be applied in aquifer thermal energy storage (ATES) projects for assessing future efficiency that is strongly linked to the hydraulic conductivity variability in the considered aquifer.

  3. Heat tracer test in an alluvial aquifer: field experiment and inverse modelling

    NASA Astrophysics Data System (ADS)

    Klepikova, Maria; Wildemeersch, Samuel; Jamin, Pierre; Orban, Philippe; Hermans, Thomas; Nguyen, Frederic; Brouyère, Serge; Dassargues, Alain

    2016-04-01

    Using heat as an active tracer for aquifer characterization is a topic of increasing interest. In this study, we investigate the potential of using heat tracer tests for characterization of a shallow alluvial aquifer. A thermal tracer test was conducted in the alluvial aquifer of the Meuse River, Belgium. The tracing experiment consisted in simultaneously injecting heated water and a dye tracer in a piezometer and monitoring the evolution of groundwater temperature and tracer concentration in the recovery well and in monitoring wells. To get insights in the 3D characteristics of the heat transport mechanisms, temperature data from a large number of observation wells distributed throughout the field site (space-filling arrangement) were used. Temperature breakthrough curves in observation wells are contrasted with what would be expected in an ideal layered aquifer. They reveal strongly unequal lateral and vertical components of the transport mechanisms. The observed complex behavior of the heat plume was explained by the groundwater flow gradient on the site and heterogeneity of hydraulic conductivity field. Moreover, due to high injection temperatures during the field experiment a temperature-induced fluid density effect on heat transport occurred. By using a flow and heat transport numerical model with variable density coupled with the pilot point inverse approach, main preferential flow paths were delineated.

  4. Simple Spreadsheet Models For Interpretation Of Fractured Media Tracer Tests

    EPA Science Inventory

    An analysis of a gas-phase partitioning tracer test conducted through fractured media is discussed within this paper. The analysis employed matching eight simple mathematical models to the experimental data to determine transport parameters. All of the models tested; two porous...

  5. Field tracer-transport tests in unsaturated fractured tuff.

    PubMed

    Hu, Q; Salve, R; Stringfellow, W T; Wang, J S

    2001-09-01

    This paper presents the results of a field investigation in the unsaturated, fractured welded tuff within the Exploratory Studies Facility (ESF) at Yucca Mountain, NV. This investigation included a series of tests during which tracer-laced water was released into a high-permeability zone within a horizontal injection borehole. The tracer concentration was monitored in the seepage collected in an excavated slot about 1.6 m below the borehole. Results showed significant variability in the hydrologic response of fractures and the matrix. Analyses of the breakthrough curves suggest that flow and transport pathways are dynamic, rather than fixed, and related to liquid-release rates. Under high release rates, fractures acted as the predominant flow pathways, with limited fracture-matrix interaction. Under low release rates, fracture flow was comparatively less dominant, with a noticeable contribution from matrix flow. Observations of tracer concentrations rebounding in seepage water, following an interruption of flow, provided evidence of mass exchange between the fast-flowing fractures and slow- or non-flowing regions. The tests also showed the applicability of fluorinated benzoate tracers in situations where multiple tracers of similar physical properties are warranted. PMID:11530924

  6. Testing fundamentals: The chemical state of geochemical tracers in biominerals.

    NASA Astrophysics Data System (ADS)

    Branson, O.; Redfern, S. A. T.; Read, E.; Elderfield, H.

    2015-12-01

    The use of many carbonate-derived geochemical proxies is underpinned by the assumption that tracer elements are incorporated 'ideally' as impurities the mineral lattice, following relatively straightforward kinetic and thermodynamic drives. This allows comparison to inorganic precipitation experiments, and provides a systematic starting point from which to translate geochemical tracers to environmental records. Biomineral carbonates are a prominent source of geochemical proxy material, and are far from an ideal inorganic system. They are structurally and compositionally heterogeneous mineral-organic composites, produced in tightly controlled biological environments, possibly via non-classical crystal growth mechanisms. Biominerals offer numerous opportunities for tracers to be incorporated in a 'non-ideal' state. For instance, tracers could be hosted within the organic component of the structure, in interstitial micro-domains of a separate mineral phase, or in localized high-impurity clusters. If a proxy element is hosted in a non-ideal state, our understanding of its incorporation and preservation is flawed, and the theoretical basis behind the proxies derived from it must be reevaluated. Thus far, the assumption of ideal tracer incorporation has remained largely untested, owing to the spatial resolution and sensitivity limits of available techniques. Developments in high-resolution, high-sensitivity X-ray spectroscopy at Scanning Transmission X-Ray Microscopes (STXMs) have allowed us to measure trace element coordination in foraminiferal calcite, at length-scales relevant to biomineralisation processes and tracer incorporation. This instrument has allowed us to test the fundamental assumptions behind several geochemical proxy elements. We present a summary of four STXM studies, assessing the chemical state and distribution of Mg (Branson et al, 2014), B (Branson et al, 2015), S and Na (unpub.), and highlight the implications of these data for the use of these

  7. TRAC, a collaborative computer tool for tracer-test interpretation

    NASA Astrophysics Data System (ADS)

    Gutierrez, A.; Klinka, T.; Thiéry, D.; Buscarlet, E.; Binet, S.; Jozja, N.; Défarge, C.; Leclerc, B.; Fécamp, C.; Ahumada, Y.; Elsass, J.

    2013-05-01

    Artificial tracer tests are widely used by consulting engineers for demonstrating water circulation, proving the existence of leakage, or estimating groundwater velocity. However, the interpretation of such tests is often very basic, with the result that decision makers and professionals commonly face unreliable results through hasty and empirical interpretation. There is thus an increasing need for a reliable interpretation tool, compatible with the latest operating systems and available in several languages. BRGM, the French Geological Survey, has developed a project together with hydrogeologists from various other organizations to build software assembling several analytical solutions in order to comply with various field contexts. This computer program, called TRAC, is very light and simple, allowing the user to add his own analytical solution if the formula is not yet included. It aims at collaborative improvement by sharing the tool and the solutions. TRAC can be used for interpreting data recovered from a tracer test as well as for simulating the transport of a tracer in the saturated zone (for the time being). Calibration of a site operation is based on considering the hydrodynamic and hydrodispersive features of groundwater flow as well as the amount, nature and injection mode of the artificial tracer. The software is available in French, English and Spanish, and the latest version can be downloaded from the web site http://trac.brgm.fr">http://trac.brgm.fr.

  8. Absolute hydraulic conductivity estimates from aquifer pumping and tracer tests in a stratified aquifer

    SciTech Connect

    Thorbjarnarson, K.W.; Huntley, D.; McCarty, J.J.

    1998-01-01

    Independent estimates of absolute hydraulic conductivity were obtained by a standard aquifer pumping test and a forced-gradient tracer test in a highly heterogeneous aquifer. An aquifer hydraulic test was conducted to evaluate the average hydraulic conductivity (K), and to establish steady-state flow for the tracer test. An average K of 48 m/day was interpreted from the draw-down data in a fully screened well. Type-curve matching and simulation with MODFLOW of the hydraulic response in partially screened wells indicates K of 10 to 15 m/day for the upper section and 71 to 73 m/day for the deeper section. Iodide and fluorescent dye tracers were injected at low rates in wells located approximately 8 m upgradient of the production well. Tracer breakthrough was monitored in the production well and at ten depth intervals within the fully screened monitoring well. Interpretation of tracer response in the production well reveals tracer transport is limited to a 3.9 m thick section of the 20 m thick aquifer, with a hydraulic conductivity of 248 m/day. However, the depth distribution of these permeable strata cannot be determined from the production well tracer response. When sampled at 1.5 m depth intervals in the monitoring well, breakthrough was observed in only three intervals along the entire 18.2 m screened well. K estimates from tracer travel time within discrete high-permeability strata range from 31 to 317 m/day. Inclusion of permeameter K estimates for the lower permeability aquifer sands result in a range in relative K of 0.01 to 1.0. This field site has the highest absolute K estimate for a discrete stratum and the widest range in relative hydraulic conductivity among research field sites with K estimates for discrete strata. Within such a highly stratified aquifer, the use of an average K from an aquifer pumping test to predict solute transport results in great underestimation of transport distances for a given time period.

  9. Design and Inversion of Tomographic Heat-Tracer Tests (Invited)

    NASA Astrophysics Data System (ADS)

    Cirpka, O. A.; Schwede, R. L.; Leven, C.

    2013-12-01

    The main purpose of groundwater inverse modeling lies in estimating the hydraulic-conductivity field of an aquifer. Traditionally, hydraulic-head measurements, possibly obtained in tomographic setups, are used as data. Because the groundwater-flow equation is diffusive, many pumping and observation wells would be necessary to obtain a high resolution of hydraulic conductivity, which is typically not possible. We suggest performing heat-tracer tests using the same pumping wells and thermometers in observation planes to amend the hydraulic-head data set by the arrival times of the heat signals. We recommend installing an outer pair of pumping wells, generating artificial ambient flow, and an inner well pair in which the tests are performed. We jointly invert heads and thermal arrival times in 3-D by the quasi-linear geostatistical approach using an efficiently parallelized code running on a mid-range cluster. In the present study, we evaluate the value of heat-tracer versus head data in a synthetic test case, where the estimated fields can be compared to the synthetic truth. Because the sensitivity patterns of the thermal arrival times differ from those of head measurements, a significantly higher resolution of the estimate is obtained by adding the tracer data. Also, in contrast to head measurements, reverting the flow field and repeating the heat-tracer test improves the estimate. Based on the synthetic test case, we recommend performing the tests in four principal directions, requiring in total eight pumping wells and four intersecting observation planes for heads and temperature in each direction.

  10. Geothermal reservoir characterization by tracer and well testing

    SciTech Connect

    Akin, S.; Okandan, E.

    1997-12-31

    This work presents the analysis of experimental data obtained on a lab scale fractured geothermal model where matrix block sizes, fracture apertures and distributions are known. The ultimate goal is to obtain the fracture aperture which is a key parameter in determining the flow and transport characteristics of fractured media. For the tracer tests, 4,000 ppm potassium iodide solution slug was injected from the corner of the model prepared using seventy stacked marble blocks and production concentration of the tracer was monitored from the other end of the diagonal. Drawdown pressure transient tests were conducted using the same model. Results indicated that flow was mainly through a major fracture path and tracer also entered to this path from auxiliary side fractures. The apparent size of the main fracture path was calculated as average 30 microns and secondary fractures had the average size of 10 microns which was found to be in good agreement with the mechanical aperture of 13.58 microns. The apparent fracture apertures, calculated using the permeability obtained from the well test analysis, changed from 70 microns to 116 microns overestimating the mechanical fracture aperture.

  11. Active thermal tracer testing in a shallow aquifer of the Thur valley, Switzerland

    NASA Astrophysics Data System (ADS)

    Schweingruber, Mischa; Somogyvári, Márk; Bayer, Peter

    2015-04-01

    Tracer tests are one of the standard methods for investigating groundwater processes. Among the range of different test variants, using heat as a tracer has gained substantial interest during the last decade. Temperature measurements have become essential ingredients for example for characterization of river-aquifer interactions and in the field of geothermics. Much less attention than on natural temperature signals has been devoted to induced synthetic temperature signals, even though it is well known that temperature is an easy to measure, invisible but sensitive system property. Design, application and inversion of such active thermal tracer tests represent one focus of our work. We build up on the experience from related field experiments, where heated water was injected and the propagation of the generated thermal anomaly was monitored. In this presentation, we show the results from first field-testing in an alluvial aquifer at the Widen site in the Thur valley in Switzerland. The thermal evolution of groundwater was monitored in summer 2014 during and after several days of heated water injection. By this test, we want to derive insights into the prevailing hydraulic heterogeneity of the shallow aquifer at the site. The results are used for calibration of a two dimensional hydrogeological numerical model. With the calibrated hydraulic conductivity field, the experiment is simulated and the transient evolution of the heat plume is visualized. Hydraulic heterogeneity is identified as one main factor for lateral spreading of the heat plume. The most important result of the experiment is that the significance of the ambient flow field is very high and even with high pumping rates to establish forced gradient conditions its effect cannot be overridden. During the test, precious technical experience was gained, which will be beneficial for subsequent heat tracer applications. For example, the challenge of maintaining a constant injection rate and temperature could

  12. Chemical tracer test at the Dixie Valley geothermal field, Nevada. Geothermal Reservoir Technology research program

    SciTech Connect

    Adams, M.C.; Moore, J.N.; Benoit, W.R.; Doughty, C.; Bodvarsson, G.S.

    1993-10-01

    In the injection test described, chemical tracers established the fluid flow between one injection well and one production well. Measured tracer concentrations, calculated flow rates, sampling schedules, and the daily events of the tracer test are documented. This experiment was designed to test the application of organic tracers, to further refine the predictive capability of the reservoir model, and to improve the effectiveness of Oxbow`s injection strategy.

  13. Results of ground-water tracer tests using tritiated water at Oak Ridge National Laboratory, Tennessee

    USGS Publications Warehouse

    Webster, D.A.

    1996-01-01

    Ground-water tracer test were conducted at two sites in the radioactive-waste disposal area of Oak Ridge National Laboratory from 1977 to 1982. The purpose of the tests was to determine if the regolith beds had weathered sufficiently to permit the substantial flow of water across them. About 50 curies of tritium dissolved in water were used as the tracer in one site, and about 100 curies at the other. Results demonstrated that ground water is able to flow through joints in the weathered bedding and that the direction of the water-table gradient is the primary factor governint flow direction. Nevertheless, the substantial lateral spread of the plume as it developed showed that bedding-plane openings can still exert a significant secondary influence on flow direction in weathered rock. About 3,500 water samples from the injection and observation wells were analyzed for tritium during the test period. Concentrations detected spanned 11 orders of magnitude. Measurable concentrations were still present in the two injection wells and most observation wells 5 years after the tracer was introduced. Matrix diffusion may have played a significant role in these tests. The process would account for the sustained concentrations of tritium at many of the observation wells, the long-term residual concentrations at the injection and observation wells, and the apparent slow movement of the centers of mass across the two well fields. The process also would have implications regarding aquifer remediation. Other tracer tests have been conducted in the regolith of the Conasauga Group. Results differ from the results described in this report.

  14. Transport and attenuation of carboxylate-modified latex microspheres in fractured rock laboratory and field tracer tests

    USGS Publications Warehouse

    Becker, M.W.; Reimus, P.W.; Vilks, P.

    1999-01-01

    Understanding colloid transport in ground water is essential to assessing the migration of colloid-size contaminants, the facilitation of dissolved contaminant transport by colloids, in situ bioremediation, and the health risks of pathogen contamination in drinking water wells. Much has been learned through laboratory and field-scale colloid tracer tests, but progress has been hampered by a lack of consistent tracer testing methodology at different scales and fluid velocities. This paper presents laboratory and field tracer tests in fractured rock that use the same type of colloid tracer over an almost three orders-of-magnitude range in scale and fluid velocity. Fluorescently-dyed carboxylate-modified latex (CML) microspheres (0.19 to 0.98 ??m diameter) were used as tracers in (1) a naturally fractured tuff sample, (2) a large block of naturally fractured granite, (3) a fractured granite field site, and (4) another fractured granite/schist field site. In all cases, the mean transport time of the microspheres was shorter than the solutes, regardless of detection limit. In all but the smallest scale test, only a fraction of the injected microsphere mass was recovered, with the smaller microspheres being recovered to a greater extent than the larger microspheres. Using existing theory, we hypothesize that the observed microsphere early arrival was due to volume exclusion and attenuation was due to aggregation and/or settling during transport. In most tests, microspheres were detected using flow cytometry, which proved to be an excellent method of analysis. CML microspheres appear to be useful tracers for fractured rock in forced gradient and short-term natural gradient tests, but longer residence times may result in small microsphere recoveries.Understanding colloid transport in ground water is essential to assessing the migration of colloid-size contaminants, the facilitation of dissolved contaminant transport by colloids, in situ bioremediation, and the health risks

  15. Estimation of Fluorescent Dye Amount in Tracer Dye Test

    NASA Astrophysics Data System (ADS)

    Pekkan, Emrah; Balkan, Erman; Balkan, Emir

    2015-04-01

    Karstic groundwater is more influenced by human than the groundwater that disperse in pores. On the other hand karstic groundwater resources, in addition to providing agricultural needs, livestock breeding, drinking and domestic water in most of the months of the year, they also supply drinking water to the wild life at high altitudes. Therefore sustainability and hydrogeological investigation of karstic resources is critical. Tracing techniques are widely used in hydrologic and hydrogeologic studies to determine water storage, flow rate, direction and protection area of groundwater resources. Karanfil Mountain (2800 m), located in Adana, Turkey, is one of the karstic recharge areas of the natural springs spread around its periphery. During explorations of the caves of Karanfil mountain, a 600 m deep cave was found by the Turkish and Polish cavers. At the bottom of the cave there is an underground river with a flow rate of approximately 0.5 m3/s during August 2014. The main spring is located 8 km far from the cave's entrance and its mean flow rate changes between 3.4 m3/s and 0.21 m3/s in March and September respectively according to a flowrate observation station of Directorate of Water Works of Turkey. As such frequent storms, snowmelt and normal seasonal variations in rainfall have a significant and rapid effect on the volume of this main spring resource. The objective of our research is to determine and estimate dye amount before its application on the field inspired from the previously literature on the subject. This estimation is intended to provide a preliminary application of a tracer test of a karstic system. In this study dye injection, inlet point will be an underground river located inside the cave and the observation station will be the spring that is approximately 8 km far from the cave entrance. On the other hand there is 600 meter elevation difference between cave entrance and outlet spring. In this test Rodamin-WT will be used as tracer and the

  16. Filtering a statistically exactly solvable test model for turbulent tracers from partial observations

    SciTech Connect

    Gershgorin, B.; Majda, A.J.

    2011-02-20

    A statistically exactly solvable model for passive tracers is introduced as a test model for the authors' Nonlinear Extended Kalman Filter (NEKF) as well as other filtering algorithms. The model involves a Gaussian velocity field and a passive tracer governed by the advection-diffusion equation with an imposed mean gradient. The model has direct relevance to engineering problems such as the spread of pollutants in the air or contaminants in the water as well as climate change problems concerning the transport of greenhouse gases such as carbon dioxide with strongly intermittent probability distributions consistent with the actual observations of the atmosphere. One of the attractive properties of the model is the existence of the exact statistical solution. In particular, this unique feature of the model provides an opportunity to design and test fast and efficient algorithms for real-time data assimilation based on rigorous mathematical theory for a turbulence model problem with many active spatiotemporal scales. Here, we extensively study the performance of the NEKF which uses the exact first and second order nonlinear statistics without any approximations due to linearization. The role of partial and sparse observations, the frequency of observations and the observation noise strength in recovering the true signal, its spectrum, and fat tail probability distribution are the central issues discussed here. The results of our study provide useful guidelines for filtering realistic turbulent systems with passive tracers through partial observations.

  17. Encapsulated cell bioremediation: Evaluation on the basis of particle tracer tests

    SciTech Connect

    Petrich, C.R.; Stormo, K.E.; Ralston, D.R.; Crawford, R.L.

    1998-09-01

    Microencapsulation of degradative organisms enhances microorganism survivability. The use of encapsulated cell microbeads for in situ biodegradation depends not only on microorganism survival but also on microbead transport characteristics. Two forced-gradient, recirculating-loop tracer experiments were conducted to evaluate the feasibility of encapsulated cell transport and bioremediation on the basis of polystyrene microsphere transport results. The tracer tests were conducted in a shallow, confined, unconsolidated, heterogeneous, sedimentary aquifer using bromide ion and 2 {micro}m, 5 {micro}m, and 15{micro}m microsphere tracers. Significant differences were observed in the transport of bromide solute and polystyrene microspheres. Microspheres reached peak concentrations in monitoring wells before bromide, which was thought to reflect the influence of aquifer heterogeneity. Greater decreases in microsphere C/C{sub 0} ratios were observed with distance from the injection wells than in bromide C/C{sub 0} ratios, which was attributed to particle filtration and/or settling. Several methods might be considered for introducing encapsulated cell microbeads into a subsurface environment, including direct injection into a contaminated aquifer zone, injection through a recirculating ground water flow system, or emplacement in a subsurface microbial curtain in advance of a plume. However, the in situ use of encapsulated cells in an aquifer is probably limited to aquifers containing sufficiently large pore spaces, allowing passage of at least some encapsulated cells. The use of encapsulated cells may also be limited by differences in solute and microbead transport patterns and flowpath clogging by larger encapsulated cell microbeads.

  18. HYDROGEL TRACER BEADS: THE DEVELOPMENT, MODIFICATION, AND TESTING OF AN INNOVATIVE TRACER FOR BETTER UNDERSTANDING LNAPL TRANSPORT IN KARST AQUIFERS

    SciTech Connect

    Amanda Laskoskie, Harry M. Edenborn, and Dorothy J. Vesper

    2012-01-01

    The goal of this specific research task is to develop proxy tracers that mimic contaminant movement to better understand and predict contaminant fate and transport in karst aquifers. Hydrogel tracer beads are transported as a separate phase than water and can used as a proxy tracer to mimic the transport of non-aqueous phase liquids (NAPL). They can be constructed with different densities, sizes & chemical attributes. This poster describes the creation and optimization of the beads and the field testing of buoyant beads, including sampling, tracer analysis, and quantitative analysis. The buoyant beads are transported ahead of the dissolved solutes, suggesting that light NAPL (LNAPL) transport in karst may occur faster than predicted from traditional tracing techniques. The hydrogel beads were successful in illustrating this enhanced transport.

  19. Tritium tracer test to estimate aquifer recharge under irrigated conditions

    NASA Astrophysics Data System (ADS)

    Jimenez-Martinez, J.; Tamoh, K.; Candela, L.

    2009-12-01

    Environmental tracers, as tritium, have been generally used to estimate aquifer recharge under natural conditions. A tritium tracer test to estimate recharge under semi-arid and irrigated conditions is presented. The test was carried out in an experimental plot under drip irrigation, located in SE Spain, with annual row crops (rotation lettuce and melon), following common agricultural practices in open air. Tritiated water was applied as an irrigation pulse, soil cores were taken at different depths and a liquid scintillation analyzer was used to measure the concentration of tritium in soil samples. Transport of tritium was simulated with SOLVEG code, a one-dimensional numerical model for simulating transport of heat, water and tritiated water in liquid and gas phase, which has been modified and adapted for this experience, including ground cover, root growth and root water uptake. One crop has been used to calibrate the modeling approach and other three crops to validate it. Results of flow and transport modelling show a good agreement between observed and estimated tritium concentration profile. For the period October 2007-September 2008, total drainage obtained value was 441 mm.

  20. THE QTRACER2 PROGRAM FOR TRACER-BREAKTHROUGH CURVE ANALYSIS FOR TRACER TESTS IN KARSTIC AQUIFERS AND OTHER HYDROLOGIC SYSTEMS

    EPA Science Inventory

    Tracer testing is generally regarded as the most reliable and efficient method of gathering surface and subsurface hydraulic information. This is especially true for karstic and fractured-rock aquifers. Qualitative tracing tests have been conventionally employed in most karst s...

  1. Inversion of Hydrological Tracer Test Data Using TomogrpahicConstraints

    SciTech Connect

    Linde, Niklas; Finsterle, Stefan; Hubbard, Susan

    2004-11-11

    A reasonable description of the hydraulic conductivity structure is a prerequisite for modeling contaminant transport. However, formulations of hydrogeological inverse problems utilizing hydrogeological data only often fail to reliably resolve features at a resolution required for accurately predicting transport. Incorporation of geophysical data into the inverse problem offers the potential to increase this resolution. In this study, we invert hydrological tracer test data using the shape and relative magnitude variations derived from geophysical tomographic data to regionalize a hydrogeological inverse problem in order to estimate the hydraulic conductivity structure. Our approach does not require that the petrophysical relationship be known a-priori, but that it is linear and stationary within each geophysical anomaly. However, tomograms are imperfect models of geophysical properties and geophysical properties are not necessarily strongly linked to hydraulic conductivity. Therefore, we focus on synthetic examples where the correlation between radar velocity and hydraulic conductivity, as well as the geophysical data acquisition errors, are varied in order to assess what aspects of the hydraulic conductivity structure we can expect to resolve under different conditions. The results indicate that regularization of the tracer inversion procedure using geophysical data improves estimates of hydraulic conductivity. We find that even under conditions of corrupted geophysical data, we can accurately estimate the effective hydraulic conductivity and areas of high and low hydraulic conductivity. However, given imperfect geophysical data, our results suggest that we cannot expect accurate estimates of the variability of the hydraulic conductivity structure.

  2. Borehole flowmeter logging for the accurate design and analysis of tracer tests.

    PubMed

    Basiricò, Stefano; Crosta, Giovanni B; Frattini, Paolo; Villa, Alberto; Godio, Alberto

    2015-04-01

    Tracer tests often give ambiguous interpretations that may be due to the erroneous location of sampling points and/or the lack of flow rate measurements through the sampler. To obtain more reliable tracer test results, we propose a methodology that optimizes the design and analysis of tracer tests in a cross borehole mode by using vertical borehole flow rate measurements. Experiments using this approach, herein defined as the Bh-flow tracer test, have been performed by implementing three sequential steps: (1) single-hole flowmeter test, (2) cross-hole flowmeter test, and (3) tracer test. At the experimental site, core logging, pumping tests, and static water-level measurements were previously carried out to determine stratigraphy, fracture characteristics, and bulk hydraulic conductivity. Single-hole flowmeter testing makes it possible to detect the presence of vertical flows as well as inflow and outflow zones, whereas cross-hole flowmeter testing detects the presence of connections along sets of flow conduits or discontinuities intercepted by boreholes. Finally, the specific pathways and rates of groundwater flow through selected flowpaths are determined by tracer testing. We conclude that the combined use of single and cross-borehole flowmeter tests is fundamental to the formulation of the tracer test strategy and interpretation of the tracer test results. PMID:25417730

  3. Inverse Modeling of Tracer Tests in Streams Undergoing Hyporheic Exchange

    NASA Astrophysics Data System (ADS)

    Liao, Zijie; Arie Cirpka, Olaf

    2010-05-01

    requires successive linearization (Gauss-Newton scheme), stabilized by a line-search, and forward simulation in the Laplace domain with numerical back-transformation. Once the hyporheic travel-time distribution p(?) has been identified, the transport model can be extended to include nonlinear reactions of river-borne compound within the hyporheic zone thus facilitating the simulation of biogeochemical cycling in streams undergoing hyporheic exchange. This method has been tested by virtual conservative and reactive tracer experiments undergoing hyporheic exchange. Joint inversion of conservative and reactive tracer BTCs is essential for distinguishing the effects of in-stream dispersion from hyporheic exchange. Applications to field data are on the way.

  4. High-resolution Electrical Resistivity Tomography monitoring of a tracer test in a confined aquifer

    NASA Astrophysics Data System (ADS)

    Wilkinson, P. B.; Meldrum, P. I.; Kuras, O.; Chambers, J. E.; Holyoake, S. J.; Ogilvy, R. D.

    2010-04-01

    A permanent geoelectrical subsurface imaging system has been installed at a contaminated land site to monitor changes in groundwater quality after the completion of a remediation programme. Since the resistivities of earth materials are sensitive to the presence of contaminants and their break-down products, 4-dimensional resistivity imaging can act as a surrogate monitoring technology for tracking and visualising changes in contaminant concentrations at much higher spatial and temporal resolution than manual intrusive investigations. The test site, a municipal car park built on a former gasworks, had been polluted by a range of polycyclic aromatic hydrocarbons and dissolved phase contaminants. It was designated statutory contaminated land under Part IIA of the UK Environmental Protection Act due to the risk of polluting an underlying minor aquifer. Resistivity monitoring zones were established on the boundaries of the site by installing vertical electrode arrays in purpose-drilled boreholes. After a year of monitoring data had been collected, a tracer test was performed to investigate groundwater flow velocity and to demonstrate rapid volumetric monitoring of natural attenuation processes. A saline tracer was injected into the confined aquifer, and its motion and evolution were visualised directly in high-resolution tomographic images in near real-time. Breakthrough curves were calculated from independent resistivity measurements, and the estimated seepage velocities from the monitoring images and the breakthrough curves were found to be in good agreement with each other and with estimates based on the piezometric gradient and assumed material parameters.

  5. Development of Models to Simulate Tracer Tests for Characterization of Enhanced Geothermal Systems

    SciTech Connect

    Williams, Mark D.; Reimus, Paul; Vermeul, Vincent R.; Rose, Peter; Dean, Cynthia A.; Watson, Tom B.; Newell, D.; Leecaster, Kevin; Brauser, Eric

    2013-05-01

    A recent report found that power and heat produced from enhanced (or engineered) geothermal systems (EGSs) could have a major impact on the U.S energy production capability while having a minimal impact on the environment. EGS resources differ from high-grade hydrothermal resources in that they lack sufficient temperature distribution, permeability/porosity, fluid saturation, or recharge of reservoir fluids. Therefore, quantitative characterization of temperature distributions and the surface area available for heat transfer in EGS is necessary for the design and commercial development of the geothermal energy of a potential EGS site. The goal of this project is to provide integrated tracer and tracer interpretation tools to facilitate this characterization. This project was initially focused on tracer development with the application of perfluorinated tracer (PFT) compounds, non-reactive tracers used in numerous applications from atmospheric transport to underground leak detection, to geothermal systems, and evaluation of encapsulated PFTs that would release tracers at targeted reservoir temperatures. After the 2011 midyear review and subsequent discussions with the U.S. Department of Energy Geothermal Technology Program (GTP), emphasis was shifted to interpretive tool development, testing, and validation. Subsurface modeling capabilities are an important component of this project for both the design of suitable tracers and the interpretation of data from in situ tracer tests, be they single- or multi-well tests. The purpose of this report is to describe the results of the tracer and model development for simulating and conducting tracer tests for characterizing EGS parameters.

  6. Determination of Water Saturation in Relatively Dry Porous Media Using Gas-phase Tracer Tests

    SciTech Connect

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

    2011-04-15

    Soil desiccation (drying), involving water evaporation induced by dry air injection and extraction, is a potentially robust remediation process to slow migration of inorganic or radionuclide contaminants through the vadose zone. The application of gas-phase partitioning tracer tests has been proposed as a means to estimate initial water volumes and to monitor the progress of the desiccation process at pilot-test and field sites. In this paper, tracer tests have been conducted in porous medium columns with various water saturations using sulfur hexafluoride as the conservative tracer and tricholorofluoromethane and difluoromethane as the water-partitioning tracers. For porous media with minimal silt and/or organic matter fractions, tracer tests provided reasonable saturation estimates for saturations close to zero. However, for sediments with significant silt and/or organic matter fractions, tracer tests only provided satisfactory results when the water saturation was at least 0.1 - 0.2. For dryer conditions, the apparent tracer retardation increases due to air – soil sorption, which is not included in traditional retardation coefficients derived from advection-dispersion equations accounting only for air – water partitioning and water – soil sorption. Based on these results, gas-phase partitioning tracer tests may be used to determine initial water volumes in sediments, provided the initial water saturations are sufficiently large. However, tracer tests are not suitable for quantifying moisture content in desiccated sediments.

  7. COMPARISON OF THREE TRACER TESTS AT THE RAFT RIVER GEOTHERMAL SITE

    SciTech Connect

    Earl D Mattson; Mitchell Plummer; Carl Palmer; Larry Hull; Samantha Miller; Randy Nye

    2011-02-01

    Three conservative tracer tests have been conducted through the Bridge Fault fracture zone at the Raft River Geothermal (RRG) site. All three tests were conducted between injection well RRG-5 and production wells RRG-1 (790 m distance) and RRG-4 (740 m distance). The injection well is used during the summer months to provide pressure support to the production wells. The first test was conducted in 2008 using 136 kg of fluorescein tracer. Two additional tracers were injected in 2010. The first 2010 tracer injected was 100 kg fluorescein disodium hydrate salt on June, 21. The second tracer (100 kg 2,6-naphthalene disulfonic acid sodium salt) was injected one month later on July 21. Sampling of the two productions wells is still being performed to obtain the tail end of the second 2010 tracer test. Tracer concentrations were measured using HPLC with a fluorescence detector. Results for the 2008 test, suggest 80% tracer recover at the two production wells. Of the tracer recovered, 85% of tracer mass was recovered in well RRG-4 indicating a greater flow pathway connection between injection well and RRG-4 than RRG-1. Fluorescein tracer results appear to be similar between the 2008 and 2010 tests for well RRG-4 with peak concentrations arriving approximately 20 days after injection despite the differences between the injection rates for the two tests (~950 gpm to 475 gpm) between the 2008 and 2010. The two 2010 tracer tests will be compared to determine if the results support the hypothesis that rock contraction along the flow pathway due to the 55 oC cooler water injection alters the flow through the ~140 oC reservoir.

  8. Characterization of scale-dependent dispersivity in fractured formations through a divergent flow tracer test.

    PubMed

    Sharifi Haddad, Amin; Hassanzadeh, Hassan; Abedi, Jalal; Chen, Zhangxin; Ware, Antony

    2015-04-01

    Scale-dependency of dispersivity has been reported from field tracer tests. We present a simple methodology for characterization of dispersivity as a linear function of scale around an injection well using divergent flow tracer test data conducted in fractured formations. Results show that the slope of this linear dispersivity function can be estimated using tracer concentration measurements in a monitoring well. The characterized dispersivity function has applications in modeling of field-scale transport processes in fractured formations. PMID:24660811

  9. USE OF PERFLUOROCARBON TRACER (PFT) TECHNOLOGY FOR SUBSURFACE BARRIER INTEGRITY VERIFICATION AT THE WALDO TEST SITE.

    SciTech Connect

    SULLIVAN,T.

    1999-06-01

    Testing of perfluorocarbon gas tracers (PFT) on a subsurface barrier with known flaws was conducted at the Waldo Test Site operated by Science and Engineering Associates, Inc (SEA). The tests involved the use of five unique PFTs with a different tracer injected along the interior of each wall of the barrier. A fifth tracer was injected exterior to the barrier to examine the validity of diffusion controlled transport of the PFTs. The PFTs were injected for three days at a nominal flow rate of 15 cm{sup 3}/min and concentrations in the range of a few hundred ppm. Approximately 65 liters of air laced with tracer was injected for each tracer. The tracers were able to accurately detect the presence of the engineered flaws. Two flaws were detected on the north and east walls, and one flaw was detected on the south and west walls. In addition, one non-engineered flaw at the seam between the north and east walls was also detected. The use of multiple tracers provided independent confirmation of the flaws and permitted a distinction between tracers arriving at a monitoring port after being released from a nearby flaw and non-engineered flaws. The PFTs detected the smallest flaw, 0.5 inches in diameter. Visual inspection of the data showed excellent agreement with the known flaw locations and the relative size of the flaws was accurately estimated. Simultaneous with the PFT tests, SEA conducted tests with another gas tracer sulfur hexafluoride (SF{sub 6}).

  10. DESIGN AND PERFORMANCE OF SINGLE-WELL TRACER TESTS AT THE MOBILE SITE

    EPA Science Inventory

    Tracer tests are the most reliable field methods for obtaining information describing advection and dispersion in aquifers. The paper describes the design and performance of single-well tracer tests utilizing multilevel observation wells at a field site near Mobile, Alabama. In a...

  11. A dual-surfactant approach for the interfacial partitioning tracer test measurement of air-water interfacial area

    NASA Astrophysics Data System (ADS)

    El Ouni, A.; Brusseau, M. L.

    2013-12-01

    Interfacial partitioning tracer tests (IPTT) are one method available for measuring air-water interfacial area (A_ia). The method has been shown to provide uncertain measurements that are influenced by surfactant-enhanced drainage. The purpose of this work is to test a revised method that minimizes formation of interfacial-tension gradients in order to prevent surfactant-induced drainage. The method employs a dual-surfactant injection under steady unsaturated-flow conditions. Sodium dodecylbezene sulfonate (SDBS) and pentafluorobenzoic acid (PFBA) were used as the partitioning and nonreactive tracers, respectively. Sodium dodecyl sulfate (SDS) was used as the surfactant in the background solution. Three types of porous media were used for the study: a sandy soil, a well-sorted sand, and glass beads. Water saturation was monitored gravimetrically during the experiments. The results obtained with the revised method are compared to those obtained with the standard IPTT method.

  12. Can one identify karst conduit networks geometry and properties from hydraulic and tracer test data?

    NASA Astrophysics Data System (ADS)

    Borghi, Andrea; Renard, Philippe; Cornaton, Fabien

    2016-04-01

    Karst aquifers are characterized by extreme heterogeneity due to the presence of karst conduits embedded in a fractured matrix having a much lower hydraulic conductivity. The resulting contrast in the physical properties of the system implies that the system reacts very rapidly to some changes in the boundary conditions and that numerical models are extremely sensitive to small modifications in properties or positions of the conduits. Furthermore, one major issue in all those models is that the location and size of the conduits is generally unknown. For all those reasons, estimating karst network geometry and their properties by solving an inverse problem is a particularly difficult problem. In this paper, two numerical experiments are described. In the first one, 18,000 flow and transport simulations have been computed and used in a systematic manner to assess statistically if one can retrieve the parameters of a model (geometry and radius of the conduits, hydraulic conductivity of the conduits) from head and tracer data. When two tracer test data sets are available, the solution of the inverse problems indicate with high certainty that there are indeed two conduits and not more. The radius of the conduits are usually well identified but not the properties of the matrix. If more conduits are present in the system, but only two tracer test data sets are available, the inverse problem is still able to identify the true solution as the most probable but it also indicates that the data are insufficient to conclude with high certainty. In the second experiment, a more complex model (including non linear flow equations in conduits) is considered. In this example, gradient-based optimization techniques are proved to be efficient for estimating the radius of the conduits and the hydraulic conductivity of the matrix in a promising and efficient manner. These results suggest that, despite the numerical difficulties, inverse methods should be used to constrain numerical

  13. USE OF PERFLUOROCARBON TRACER (PFT) TECHNOLOGY FOR SUBSURFACE BARRIER INTEGRITY VERIFICATION AT THE WALDO TEST SITE

    SciTech Connect

    SULLIVAN,T.; HEISER,J.; SENUM,G.; MILLIAN,L.

    2000-02-27

    Researchers from Brookhaven National Laboratory (BNL) tested perfluorocarbon (PFT) gas tracers on a subsurface barrier with known flaws at the Waldo test facility [operated by Science and Engineering Associates, Inc (SEA)]. The tests involved the use of five unique PFT tracers with a different tracer injected along the interior of each wall of the barrier. A fifth tracer was injected exterior to the barrier to examine the validity of diffusion controlled transport of the PFTs. The PFTs were injected for three days at a nominal flow rate of 15 cm{sup 3}/min and a concentrations in the range of a few hundred ppm. Approximately 65 liters of air laced with tracer was injected for each tracer. The tracers were able to accurately detect the presence of the engineered flaws. Two flaws were detected on the north and east walls and lane flaw was detected on the south and west walls. In addition, one non-engineered flaw at the seam between the north and east walls was also detected. The use of multiple tracers provided independent confirmation of the flaws and permitted a distinction between tracers arriving at a monitoring port after being released from a nearby flaw and non-engineered flaws. The PFTs detected the smallest flaw, 0.5 inches in diameter. Visual inspection of the data showed excellent agreement with the known flaw locations and the relative size of the flaws was accurately estimated.

  14. ANALYSIS OF A GAS-PHASE PARTITIONING TRACER TEST CONDUCTED THROUGH FRACTURED MEDIA

    EPA Science Inventory

    The gas-phase partitioning tracer method was used to estimate non-aqueous phase liquid (NAPL), water, and air saturations in the vadose zone at a chlorinated-solvent contaminated field site in Tucson, AZ. The tracer test was conducted in a fractured clay system that is the confin...

  15. First Tracer Test After Circulation in Desert Peak 27-15

    DOE Data Explorer

    Rose, Peter

    2013-11-16

    Following the successful stimulation of Desert Peak target EGS well 27-15, a circulation test was initiated by injecting a conservative tracer (1,5-nds) in combination with a reactive tracer (7-amino-1,3-naphthalene disulfonate). The closest production well 74-21 was monitored over the subsequent several months.

  16. Numerical Modeling for Integrated Design of a DNAPL Partitioning Tracer Test

    NASA Astrophysics Data System (ADS)

    McCray, J. E.; Divine, C. E.; Dugan, P. J.; Wolf, L.; Boving, T.; Louth, M.; Brusseau, M. L.; Hayes, D.

    2002-12-01

    Partitioning tracer tests (PTTs) are commonly used to estimate the location and volume of nonaqueous-phase liquids (NAPLs) at contaminated groundwater sites. PTTs are completed before and after remediation efforts as one means to assess remediation effectiveness. PTT design is complex. Numerical models are invaluable tools for designing a PTT, particularly for designing flow rates and selecting tracers to ensure proper tracer breakthrough times, spatial design of injection-extraction wells and rates to maximize tracer capture, well-specific sampling density and frequency, and appropriate tracer-chemical masses. Generally, the design requires consideration of the following factors: type of contaminant; distribution of contaminant at the site, including location of hot spots; site hydraulic characteristics; measurement of the partitioning coefficients for the various tracers; the time allotted to conduct the PTT; evaluation of the magnitude and arrival time of the tracer breakthrough curves; duration of the tracer input pulse; maximum tracer concentrations; analytical detection limits for the tracers; estimation of the capture zone of the well field to tracer ensure mass balance and to limit residual tracer concentrations left in the subsurface; effect of chemical remediation agents on the PTT results, and disposal of the extracted tracer solution. These design principles are applied to a chemical-enhanced remediation effort for a chlorinated-solvent dense NAPL (DNAPL) site at Little Creek Naval Amphibious Base in Virginia Beach, Virginia. For this project, the hydrology and pre-PTT contaminant distribution were characterized using traditional methods (slug tests, groundwater and soil concentrations from monitoring wells, and geoprobe analysis), as well as membrane interface probe analysis. Additional wells were installed after these studies. Partitioning tracers were selected based on the primary DNAPL contaminants at the site, expected NAPL saturations

  17. NATURAL GRADIENT EXPERIMENT ON SOLUTE TRANSPORT IN A SAND AQUIFER. 2. SPATIAL MOMENTS AND THE ADVECTION AND DISPERSION OF NONREACTIVE TRACERS

    EPA Science Inventory

    The three-dimensional movement of a tracer plume containing bromide and chloride is investigated using the data base from a large-scale natural gradient field experiment on groundwater solute transport. The analysis focuses on the zeroth-, first-, and second-order spatial moments...

  18. An Analytical Solution for Slug-Tracer Tests in FracturedReservoirs

    SciTech Connect

    Shan, Chao; Pruess, Karsten

    2005-03-02

    The transport of chemicals or heat in fractured reservoirs is strongly affected by the fracture-matrix interfacial area. In a vapor-dominated geothermal reservoir, this area can be estimated by inert gas tracer tests, where gas diffusion between the fracture and matrix causes the tracer breakthrough curve (BTC) to have a long tail determined by the interfacial area. For water-saturated conditions, recent studies suggest that sorbing solute tracers can also generate strong tails in BTCs that may allow a determination of the fracture-matrix interfacial area. To theoretically explore such a useful phenomenon, this paper develops an analytical solution for BTCs in slug-tracer tests in a water-saturated fractured reservoir. The solution shows that increased sorption should have the same effect on BTCs as an increase of the diffusion coefficient. The solution is useful for understanding transport mechanisms, verifying numerical codes, and for identifying appropriate chemicals as tracers for the characterization of fractured reservoirs.

  19. A test of geographic assignment using isotope tracers in feathers of known origin.

    PubMed

    Wunder, Michael B; Kester, Cynthia L; Knopf, Fritz L; Rye, Robert O

    2005-08-01

    We used feathers of known origin collected from across the breeding range of a migratory shorebird to test the use of isotope tracers for assigning breeding origins. We analyzed deltaD, delta13C, and delta15N in feathers from 75 mountain plover (Charadrius montanus) chicks sampled in 2001 and from 119 chicks sampled in 2002. We estimated parameters for continuous-response inverse regression models and for discrete-response Bayesian probability models from data for each year independently. We evaluated model predictions with both the training data and by using the alternate year as an independent test dataset. Our results provide weak support for modeling latitude and isotope values as monotonic functions of one another, especially when data are pooled over known sources of variation such as sample year or location. We were unable to make even qualitative statements, such as north versus south, about the likely origin of birds using both deltaD and delta13C in inverse regression models; results were no better than random assignment. Probability models provided better results and a more natural framework for the problem. Correct assignment rates were highest when considering all three isotopes in the probability framework, but the use of even a single isotope was better than random assignment. The method appears relatively robust to temporal effects and is most sensitive to the isotope discrimination gradients over which samples are taken. We offer that the problem of using isotope tracers to infer geographic origin is best framed as one of assignment, rather than prediction. PMID:15891836

  20. 100-NR-2 Apatite Treatability Test: Fall 2010 Tracer Infiltration Test (White Paper)

    SciTech Connect

    Vermeul, Vincent R.; Fritz, Brad G.; Fruchter, Jonathan S.; Greenwood, William J.; Johnson, Timothy C.; Horner, Jacob A.; Strickland, Christopher E.; Szecsody, James E.; Williams, Mark D.

    2011-04-14

    The primary objectives of the tracer infiltration test were to 1) determine whether field-scale hydraulic properties for the compacted roadbed materials and underlying Hanford fm. sediments comprising the zone of water table fluctuation beneath the site are consistent with estimates based laboratory-scale measurements on core samples and 2) characterize wetting front advancement and distribution of soil moisture achieved for the selected application rate. These primary objectives were met. The test successfully demonstrated that 1) the remaining 2 to 3 ft of compacted roadbed material below the infiltration gallery does not limit infiltration rates to levels that would be expected to eliminate near surface application as a viable amendment delivery approach and 2) the combined aqueous and geophysical monitoring approaches employed at this site, with some operational adjustments based on lessons learned, provides an effective means of assessing wetting front advancement and the distribution of soil moisture achieved for a given solution application. Reasonably good agreement between predicted and observed tracer and moisture front advancement rates was observed. During the first tracer infiltration test, which used a solution application rate of 0.7 cm/hr, tracer arrivals were observed at the water table (10 to 12 ft below the bottom of the infiltration gallery) after approximately 5 days, for an advancement rate of approximately 2 ft/day. This advancement rate is generally consistent with pre-test modeling results that predicted tracer arrival at the water table after approximately 5 days (see Figure 8, bottom left panel). This agreement indicates that hydraulic property values specified in the model for the compacted roadbed materials and underlying Hanford formation sediments, which were based on laboratory-scale measurements, are reasonable estimates of actual field-scale conditions. Additional work is needed to develop a working relationship between resistivity

  1. Ambiguity in measuring matrix diffusion with single-well injection/recovery tracer tests

    USGS Publications Warehouse

    Lessoff, S.C.; Konikow, L.F.

    1997-01-01

    Single-well injection/recovery tracer tests are considered for use in characterizing and quantifying matrix diffusion in dual-porosity aquifers. Numerical modeling indicates that neither regional drift in homogeneous aquifers, nor heterogeneity in aquifers having no regional drift, nor hydrodynamic dispersion significantly affects these tests. However, when drift is coupled simultaneously with heterogeneity, they can have significant confounding effects on tracer return. This synergistic effect of drift and heterogeneity may help explain irreversible flow and inconsistent results sometimes encountered in previous single-well injection/recovery tracer tests. Numerical results indicate that in a hypothetical single-well injection/recovery tracer test designed to demonstrate and measure dual-porosity characteristics in a fractured dolomite, the simultaneous effects of drift and heterogeneity sometimes yields responses similar to those anticipated in a homogeneous dual-porosity formation. In these cases, tracer recovery could provide a false indication of the occurrence of matrix diffusion. Shortening the shut-in period between injection and recovery periods may make the test less sensitive to drift. Using multiple tracers having different diffusion characteristics, multiple tests having different pumping schedules, and testing the formation at more than one location would decrease the ambiguity in the interpretation of test data.

  2. PARTITIONING TRACERS FOR MEASURING RESIDUAL NAPL: FIELD-SCALE TEST RESULTS

    EPA Science Inventory

    The difficult task of locating and quantifying nonaqueous phase liquids (NAPLs) present in the vadose and saturated zones has prompted the development of innovative, nondestructive characterization techniques. The use of the interwell partitioning tracer's (IWPT) test, in which ...

  3. PARTITIONING INTERWELL TRACER TEST FOR NAPL SOURCE CHARACTERIZATION: A GENERAL OVERVIEW

    EPA Science Inventory

    Innovative and nondestructive characterization techniques have been developed to locate and quantify nonaqueous phase liquids (NAPLs) in the vadose and saturated zones in the subsurface environment. One such technique is the partitioning interwell tracer test (PITT). The PITT i...

  4. Conservative tracers for the C-well hydraulic testing

    SciTech Connect

    Dombrowski, T.; Coates, G.; Stetzenbach, K.J.

    1992-11-01

    This paper reports that work is being done to identify and characterize conservative organic tracers for use as groundwater tracers at the C-well complex. An evaluation of the chemical and biological stability of several compounds including fluorinated aliphatic and aromatic acids, fluorinated salicylic acids, and fluorinated cinnamic acids was carried out using tuff samples from the Yucca Mountain area and J13 or de-ionized water. Samples were monitored over a 60-day period for any decrease in concentration; the resulting data was evaluated for possible sorption or biological degradation of the candidate compound. The fluorinated benzoic acids show the greatest stability over the 60-day period. All analyses were carried out using an HPLC system, with either a fluorescence detector, a variable wavelength UV-VIS detector, or a quadrupole mass spectrometer.

  5. Perfluoro(Methylcyclohexane) Tracer Tagging Test and Demonstration

    SciTech Connect

    Sigman, M.E.

    2000-09-26

    On February 14 and 15, 2000, a demonstration of current perfluorocarbon tagging technology and the future potential of these methods was held at Oak Ridge National Laboratory (ORNL). The demonstration consisted of a brief technical discussion followed by a laboratory demonstration. The laboratory demonstrations included the detection of letters, parcels, briefcases and lockers containing perfluorocarbon-tagged papers. Discrimination between tagged and non-tagged items and between three perfluorocarbon tags was demonstrated along with the detection of perfluorocarbon in a background of non-fluorinated volatile organic solvent. All demonstrations involved real-time detection using a direct sampling ion trap mass spectrometer. The technical results obtained at ORNL during and in preparation for the demonstration are presented in Appendix 1 to assist Tracer Detection Technology Corp. in further evaluating their position on development and marketing of perfluorocarbon tracer technology.

  6. Photoacoustic infrared spectroscopy for conducting gas tracer tests and measuring water saturations in landfills.

    PubMed

    Jung, Yoojin; Han, Byunghyun; Mostafid, M Erfan; Chiu, Pei; Yazdani, Ramin; Imhoff, Paul T

    2012-02-01

    Gas tracer tests can be used to determine gas flow patterns within landfills, quantify volatile contaminant residence time, and measure water within refuse. While gas chromatography (GC) has been traditionally used to analyze gas tracers in refuse, photoacoustic spectroscopy (PAS) might allow real-time measurements with reduced personnel costs and greater mobility and ease of use. Laboratory and field experiments were conducted to evaluate the efficacy of PAS for conducting gas tracer tests in landfills. Two tracer gases, difluoromethane (DFM) and sulfur hexafluoride (SF(6)), were measured with a commercial PAS instrument. Relative measurement errors were invariant with tracer concentration but influenced by background gas: errors were 1-3% in landfill gas but 4-5% in air. Two partitioning gas tracer tests were conducted in an aerobic landfill, and limits of detection (LODs) were 3-4 times larger for DFM with PAS versus GC due to temporal changes in background signals. While higher LODs can be compensated by injecting larger tracer mass, changes in background signals increased the uncertainty in measured water saturations by up to 25% over comparable GC methods. PAS has distinct advantages over GC with respect to personnel costs and ease of use, although for field applications GC analyses of select samples are recommended to quantify instrument interferences. PMID:21996285

  7. Photoacoustic infrared spectroscopy for conducting gas tracer tests and measuring water saturations in landfills

    SciTech Connect

    Jung, Yoojin; Han, Byunghyun; Mostafid, M. Erfan; Chiu, Pei; Yazdani, Ramin; Imhoff, Paul T.

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Photoacoustic infrared spectroscopy tested for measuring tracer gas in landfills. Black-Right-Pointing-Pointer Measurement errors for tracer gases were 1-3% in landfill gas. Black-Right-Pointing-Pointer Background signals from landfill gas result in elevated limits of detection. Black-Right-Pointing-Pointer Technique is much less expensive and easier to use than GC. - Abstract: Gas tracer tests can be used to determine gas flow patterns within landfills, quantify volatile contaminant residence time, and measure water within refuse. While gas chromatography (GC) has been traditionally used to analyze gas tracers in refuse, photoacoustic spectroscopy (PAS) might allow real-time measurements with reduced personnel costs and greater mobility and ease of use. Laboratory and field experiments were conducted to evaluate the efficacy of PAS for conducting gas tracer tests in landfills. Two tracer gases, difluoromethane (DFM) and sulfur hexafluoride (SF{sub 6}), were measured with a commercial PAS instrument. Relative measurement errors were invariant with tracer concentration but influenced by background gas: errors were 1-3% in landfill gas but 4-5% in air. Two partitioning gas tracer tests were conducted in an aerobic landfill, and limits of detection (LODs) were 3-4 times larger for DFM with PAS versus GC due to temporal changes in background signals. While higher LODs can be compensated by injecting larger tracer mass, changes in background signals increased the uncertainty in measured water saturations by up to 25% over comparable GC methods. PAS has distinct advantages over GC with respect to personnel costs and ease of use, although for field applications GC analyses of select samples are recommended to quantify instrument interferences.

  8. Distinctive stable isotope ratios in important zooplankton species in relation to estuarine salinity gradients: Potential tracer of fish migration

    NASA Astrophysics Data System (ADS)

    Suzuki, Keita W.; Kasai, Akihide; Isoda, Takane; Nakayama, Kouji; Tanaka, Masaru

    2008-07-01

    To assess the potential of stable isotope ratios as an indicator of fish migration within estuaries, stable isotope ratios in important zooplankton species were analyzed in relation to estuarine salinity gradients. Gut contents from migratory juveniles of the euryhaline marine fish Lateolabrax japonicus were examined along the Chikugo River estuary of the Ariake Sea, which has the most developed estuarine turbidity maximum (ETM) in Japan. Early juveniles in March and April preyed primarily on two copepod species; Sinocalanus sinensis at lower salinities and Acartia omorii at higher salinities. Late juveniles (standard length > 40 mm) at lower salinities preyed exclusively on the mysid Acanthomysis longirostris until July and complementarily on the decapod Acetes japonicus in August. These prey species were collected along the estuary during the spring-summer seasons of 2003 and 2004, and their carbon and nitrogen stable isotope ratios ( δ13C and δ15N) were evaluated. The δ13C values of prey species were distinct from each other and were primarily depleted within and in close proximity to the ETM (salinity < 10); S. sinensis (-26.6‰) < Acanthomysis longirostris (-23.3‰) < Acartia omorii (-21.1‰) < Acetes japonicus (-18.5‰). The overall gradient of δ13C with salinity occurred for all prey species and showed minor temporal fluctuations, while it was not directly influenced by the δ13C values in particulate organic matter along the estuary. In contrast to δ13C, the δ15N values of prey species did not exhibit any clear relationship with salinity. The present study demonstrated that δ13C has the potential for application as a tracer of fish migration into lower salinity areas including the ETM.

  9. Integration of stable isotopes and tracer test to establish the shallow groundwater system in the Tatun Volcano Group (TVG), Taiwan

    NASA Astrophysics Data System (ADS)

    Kuo, Ching-Huei; Liu, Chia-Mei; Lee, Pin-Yi

    2016-04-01

    Over 200 water samples including rain water, surface water and groundwater from August 2012 to June 2015 in the Tatun volcano group were collected and analyzed. The results show that the isotope composition of surface water are enriched in winter (δ18O=-6.03 ‰, δD= -27.27‰) and depleted in summer (δ18O= -6.12‰, δD=-29.25‰), indicate that the water mass comes from different sources in summer and winter in the region, respectively. The seasonal variations of groundwaters (δ18O=-5.9 ‰, δD= -28.4‰) are significant different from that of surface water. This indicates that it takes a significant period of time to have the rain water mixed with groundwater. The main recharge season of groundwater in the northern Cising Mountain is winter while summer is the main recharge season of groundwater in the south of the mountain. Inter-well natural-gradient tracer tests were conducted in the south and north of Cising Mountain to identify shallow groundwater flow path, respectively. Different tracer breakthrough curves observed from north and south indicate different transport mechanisms may be involved. It took 286 hours for tracer to transport through 860m arriving at Well-17 in the south while 9 hours for tracer to flow through 690m to arrive at Well-30 in the north. Based on borehole properties, we suggest that the groundwater transport is mainly controlled by the formation fractures in the south of Cising Mountain with slower velocity while the groundwater in the north region is dominated by the flow along the boundaries of lava layers with faster velocity. Integrated the stable isotope compositions with tracer tests, we concluded that the major groundwater recharge to the south Cising Mountain region comes from the Caigongkeng Mountain. On the other hand, the groundwater recharge for the north Cising Mountain region primary comes from the Eastern Cising Mountain with minor contribution from the Caigongkeng Mountain. Keywords: stable isotope, groundwater

  10. IMAGE Project: Results of Laboratory Tests on Tracers for Supercritical Conditions.

    NASA Astrophysics Data System (ADS)

    Brandvoll, Øyvind; Opsahl Viig, Sissel; Nardini, Isabella; Muller, Jiri

    2016-04-01

    The use of tracers is a well-established technique for monitoring dynamic behaviour of water and gas through a reservoir. In geothermal reservoirs special challenges are encountered due to high temperatures and pressures. In this work, tracer candidates for monitoring water at supercritical conditions (temperature > 374°C, pressure ca 218 bar), are tested in laboratory experiments. Testing of tracers at supercritical water conditions requires experimental set-ups which tolerate harsh conditions with respect to high temperature and pressure. In addition stringent HES (health, environment and safety) factors have to be taken into consideration when designing and performing the experiments. The setup constructed in this project consists of a pressure vessel, high pressure pump, instrumentation for pressure and temperature control and instrumentation required for accurate sampling of tracers. In order to achieve accurate results, a special focus has been paid to the development of the tracer sampling technique. Perfluorinated cyclic hydrocarbons (PFCs) have been selected as tracer candidates. This group of compounds is today commonly used as gas tracers in oil reservoirs. According to the literature they are stable at temperatures up to 400°C. To start with, five PFCs have been tested for thermal stability in static experiments at 375°C and 108 bar in the experimental setup described above. The tracer candidates will be further tested for several months at the relevant conditions. Preliminary results indicate that some of the PFC compounds show stability after three months. However, in order to arrive at conclusive results, the experiments have to be repeated over a longer period and paying special attention to more accurate sampling procedures.

  11. Laboratory characterization of non-aqueous phase liquid/tracer interaction in support of a vadose zone partitioning interwell tracer test

    NASA Astrophysics Data System (ADS)

    Deeds, Neil E.; McKinney, Daene C.; Pope, Gary A.

    2000-01-01

    Contaminant characterization is important for successful remediation of non-aqueous phase liquids (NAPLs) in the unsaturated zone. A partitioning interwell tracer test (PITT) can provide a good estimate of average subsurface NAPL saturations. Screening experiments were completed in the laboratory to evaluate several gas tracers for a PITT study to be completed in the vadose zone at Kirtland Air Force Base in Albuquerque, NM. Four perfluorocarbon tracers were found to be suitable for this PITT. Further laboratory column studies were completed using contaminated field soil to measure the partition coefficients between the tracers and the NAPL. The results from the column studies showed that the air/NAPL tracer partition coefficients ranged from 8.8±0.6 to 71±3. This range of partition coefficients is suitable for detection of NAPL saturations in the field of 0.002 to 0.14.

  12. Measuring Air-Water Interfacial Area via the Interfacial Partitioning Tracer Test Method

    NASA Astrophysics Data System (ADS)

    El Ouni, A.; Zhong, H.; Mainhagu, J.; Araujo, J. B.; Brusseau, M. L.

    2012-12-01

    Interfacial partitioning tracer tests (IPTT) are one method available for measuring air-water interfacial area (Aa-w). Two variations of the aqueous IPTT method are compared. One involves the standard approach comprising tracer injection under steady unsaturated-flow conditions with a uniform water-saturation distribution within the column. The other involves tracer injection under steady saturated-flowconditions in the presence of trapped residual air. Sodium dodecylbezenesulfonate (SDBS) and pentafluorobenzoic acid (PFBA) were used as the partitioning andnonreactive tracers, respectively. A sandy soil with a median grain diameter of 0.234 mm was used as the porous medium. Initial water saturation, Sw,was approximately 80%. Water saturation was monitored gravimetrically during the experiments. The results of the experiments will be assessed and compared to those of prior studies.

  13. Estimation of Fracture Porosity in an Unsaturated Fractured Welded Tuff Using Gas Tracer Testing

    SciTech Connect

    B.M. Freifeild

    2001-10-18

    Kinematic fracture porosity is an important hydrologic transport parameter for predicting the potential of rapid contaminant migration through fractured rock. The transport velocity of a solute moving within a fracture network is inversely related to the fracture porosity. Since fracture porosity is often one or two orders of magnitude smaller than matrix porosity, and fracture permeability is often orders of magnitude greater than matrix permeability, solutes may travel significantly faster in the fracture network than in the surrounding matrix. This dissertation introduces a new methodology for conducting gas tracer tests using a field portable mass spectrometer along with analytical tools for estimating fracture porosity using the measured tracer concentration breakthrough curves. Field experiments were conducted at Yucca Mountain, Nevada, consisting of air-permeability transient testing and gas-tracer-transport tests. The experiments were conducted from boreholes drilled within an underground tunnel as part of an investigation of rock mass hydrological behavior. Air-permeability pressure transients, recorded during constant mass flux injections, have been analyzed using a numerical inversion procedure to identify fracture permeability and porosity. Dipole gas tracer tests have also been conducted from the same boreholes used for air-permeability testing. Mass breakthrough data has been analyzed using a random walk particle-tracking model, with a dispersivity that is a function of the advective velocity. The estimated fracture porosity using the tracer test and air-injection test data ranges from .001 to .015. These values are an order of magnitude greater than the values estimated by others using hydraulically estimated fracture apertures. The estimates of porosity made using air-permeability test data are shown to be highly sensitive to formation heterogeneity. Uncertainty analyses performed on the gas tracer test results show high confidence in the parameter

  14. Laboratory testing and modeling to evaluate perfluorocarbon compounds as tracers in geothermal systems

    SciTech Connect

    Reimus, Paul W

    2011-01-21

    The thermal stability and adsorption characteristics of three perfluorinated hydrocarbon compounds were evaluated under geothermal conditions to determine the potential to use these compounds as conservative or thermally-degrading tracers in Engineered (or Enhanced) Geothermal Systems (EGS). The three compounds tested were perfluorodimethyl-cyclobutane (PDCB), perfluoromethylcyclohexane (PMCH), and perfluorotrimethylcyclohexane (PTCH), which are collectively referred to as perfluorinated tracers, or PFTs. Two sets of duplicate tests were conducted in batch mode in gold-bag reactors, with one pair of reactors charged with a synthetic geothermal brine containing the PFTs and a second pair was charged with the brine-PFT mixture plus a mineral assemblage chosen to be representative of activated fractures in an EGS reservoir. A fifth reactor was charged with deionized water containing the three PFTs. The experiments were conducted at {approx}100 bar, with temperatures ranging from 230 C to 300 C. Semi-analytical and numerical modeling was also conducted to show how the PFTs could be used in conjunction with other tracers to interrogate surface area to volume ratios and temperature profiles in EGS reservoirs. Both single-well and cross-hole tracer tests are simulated to illustrate how different suites of tracers could be used to accomplish these objectives. The single-well tests are especially attractive for EGS applications because they allow the effectiveness of a stimulation to be evaluated without drilling a second well.

  15. Interpretations of Tracer Tests Performed in the Culebra Dolomite at the Waste Isolation Pilot Plant Site

    SciTech Connect

    MEIGS,LUCY C.; BEAUHEIM,RICHARD L.; JONES,TOYA L.

    2000-08-01

    This report provides (1) an overview of all tracer testing conducted in the Culebra Dolomite Member of the Rustler Formation at the Waste Isolation Pilot Plant (WPP) site, (2) a detailed description of the important information about the 1995-96 tracer tests and the current interpretations of the data, and (3) a summary of the knowledge gained to date through tracer testing in the Culebra. Tracer tests have been used to identify transport processes occurring within the Culebra and quantify relevant parameters for use in performance assessment of the WIPP. The data, especially those from the tests performed in 1995-96, provide valuable insight into transport processes within the Culebra. Interpretations of the tracer tests in combination with geologic information, hydraulic-test information, and laboratory studies have resulted in a greatly improved conceptual model of transport processes within the Culebra. At locations where the transmissivity of the Culebra is low (< 4 x 10{sup -6} m{sup 2}/s), we conceptualize the Culebra as a single-porosity medium in which advection occurs largely through the primary porosity of the dolomite matrix. At locations where the transmissivity of the Culebra is high (> 4 x 10{sup -6} m{sup 2}/s), we conceptualize the Culebra as a heterogeneous, layered, fractured medium in which advection occurs largely through fractures and solutes diffuse between fractures and matrix at multiple rates. The variations in diffusion rate can be attributed to both variations in fracture spacing (or the spacing of advective pathways) and matrix heterogeneity. Flow and transport appear to be concentrated in the lower Culebra. At all locations, diffusion is the dominant transport process in the portions of the matrix that tracer does not access by flow.

  16. Bounding flow and transport analysis of proposed 105A mock-up tank tracer test

    SciTech Connect

    Piepho, M.G.

    1994-08-01

    The purpose of this bounding analysis was to determine bounding estimates of salt concentrations in the aquifer below the salt-tracer plume test at the 105A mockup-tank site near the inactive Semi-Works Plant in the 200 East Area. The objective was to calculate the bounding salt concentrations and compare them to the appropriate maximum contamination level (MCL) allowed by state law, which for sodium chloride is 415 mg/l as a secondary standard. The tracer test is part of the Electrical-Resistance Tomography (ERT) demonstration, which will provide an effective method of detecting tank leaks if it is shown to be successful. The basic idea of ERT method is that the electrical resistance in the soils will change enough to be detected when water with salts infiltrate the soils, even if a high-conductance metal tank is just above the leak. The 105A mockup tank did not have an impermeable bottom and was open at the top until the time of the test. It was assumed, at the time of the tracer test or shortly afterwards, that an impermeable bottom (concrete) would be placed at the bottom of the tank, but still remain open at the top. Hence, in this analysis, no artificial recharge is produced due to water running off a tank top, since no top is assumed. The conceptual model is discussed in Section 2.0 with the mathematical and numerical models briefly discussed in Section 3.0. The main results are given in Section 4.0 with the conclusions drawn in Section 5.0. These calculations were made before the tracer test. A similar set of calculations will be performed after the tracer test assuming more details concerning leak location and soil properties are available. The tracer test could be used to validate or confirm the modeling methodology/capability of plumes in the vadose zone at the Hanford site.

  17. Semi-analytic approach to analyze single well tracer tests TR-44

    SciTech Connect

    Antunez, E.U.

    1984-08-01

    Residual oil saturation is one of the most important parameters to be considered when analyzing a prospective field for enhanced oil recovery. Traditionally, residual oil saturation has been estimated from cores or well logs. These methods have a small radius of investigation, evaluating saturations in a region close to the wellbore. This region is often affected by injection or production operations. Single well tracer tests have proven to be a better alternative to estimate residual oil saturation since they cover a substantially larger volume of the reservoir, and thus measure a more representative residual oil saturation of the target formation. The method consists of the injection of a reactive tracer that is soluble in oil and water. This tracer slowly hydrolyzes forming a secondary tracer as a product of an irreversible chemical reaction. After injection, the well is shut in to allow the formation of a detectable amount of secondary tracer, which is soluble only in water. When the well is open to production, each tracer arrives to the well at different times. From the separation between the concentration peaks, residual oil saturation is estimated. However, the determination of the residual oil saturation through the analysis of single well tracer test production data, in the past, has required: 1) the use of finite difference simulators, 2) five fitting parameters and 3) considerable man-computer interaction time. In addition finite difference simulators give results that are affected by numerical dispersion. This, and the fitting parameters, add uncertainty to the uniqueness of the solution. In this work, a new approach is presented. The test is analyzed. 28 references, 70 figures, 7 tables.

  18. Analytical solutions for efficient interpretation of single-well push-pull tracer tests

    EPA Science Inventory

    Single-well push-pull tracer tests have been used to characterize the extent, fate, and transport of subsurface contamination. Analytical solutions provide one alternative for interpreting test results. In this work, an exact analytical solution to two-dimensional equations descr...

  19. PERFORMANCE, ANALYSIS AND SIMULATION OF A TWO-WELL TRACER TEST AT THE MOBILE SITE

    EPA Science Inventory

    Single-well tracer tests in conjunction with multi-level observation wells were performed by Auburn University during the summer of 1984. The purpose of the tests was to determine the vertical variation of horizontal hydraulic conductivity in a confined aquifer. The results, whic...

  20. Partitioning gas tracer tests for measurement of water in municipal solid waste.

    PubMed

    Imhoff, Paul T; Jakubowitch, Andrew; Briening, Michele L; Chiu, Pei C

    2003-11-01

    A key component in the operation of almost all bioreactor landfills is the addition of water to maintain optimal moisture conditions. To determine how much water is needed and where to add it, in situ methods are required to measure water within solid waste. Existing technologies often result in measurements of unknown accuracy, because of the variability of solid waste materials and time-dependent changes in packing density, both of which influence most measurement methods. To overcome these problems, a new technology recently developed by hydrologists for measuring water in the vadose zone--the partitioning gas tracer test--was tested. In this technology, the transport behavior of two gas tracers within solid waste is used to measure the fraction of the void space filled with water. One tracer is conservative and does not react with solids or liquids, while a second tracer partitions into the water and is separated from the conservative tracer during transport. This technology was tested in four different solid waste packings and was capable of determining the volumetric water content to within 48% of actual values, with most measurement errors less than 15%. This technology and the factors that affect its applicability to landfills are discussed in this paper. PMID:14649759

  1. Transfer function approach for artificial tracer test interpretation in karstic systems

    NASA Astrophysics Data System (ADS)

    Labat, D.; Mangin, A.

    2015-10-01

    A karstic formation consists in a three-dimensional hydrological system which involves horizontal and vertical, diphasic or saturated water transfers characterised by a large range of velocity. These subsurface flow processes correspond to various water pathways through fractured, fissured, and underground streams or conduits leading to a nonlinear global behaviour of the system. An efficient way of investigating of a karstic system behaviour consists in the injection of artificial tracer tests at loss points and in careful analysis of the recovery tracer fluxes at one or several outlets of the systems. These injections are also an efficient way of providing hypotheses on characteristic time of contaminant transfer in these type of aquifers. Here, we propose a Laplace-transform transfer function of the Residence Time Distribution function that allows to discriminate between a quick-flow advection-dominated component and a slow-flow advection-dispersion/dominated component in the artificial tracer transfer in the system. We apply this transfer function on five high resolution sampling rate artificial tracer tests operated on the Baget system in the Pyrenees (France) in order to illustrate the advantages and limitations of this approach. We provide then an interpretation of the relationship between tracer test recovery shape and karstic system organisation between inlet and outlet site.

  2. Multiple-tracer tests for contaminant transport process identification in saturated municipal solid waste

    SciTech Connect

    Woodman, N.D. Rees-White, T.C.; Stringfellow, A.M.; Beaven, R.P.; Hudson, A.P.

    2015-04-15

    Highlights: • Multiple tracers were applied to saturated MSW to test dual-porosity properties. • Lithium demonstrated to be non-conservative as a tracer. • 260 mm diameter column too small to test transport properties of MSW. • The classical advection-dispersion mode was rejected due to high dispersivity. • Characteristic diffusion times did not vary with the tracer. - Abstract: Two column tests were performed in conditions emulating vertical flow beneath the leachate table in a biologically active landfill to determine dominant transport mechanisms occurring in landfills. An improved understanding of contaminant transport process in wastes is required for developing better predictions about potential length of the long term aftercare of landfills, currently measured in timescales of centuries. Three tracers (lithium, bromide and deuterium) were used. Lithium did not behave conservatively. Given that lithium has been used extensively for tracing in landfill wastes, the tracer itself and the findings of previous tests which assume that it has behaved conservatively may need revisiting. The smaller column test could not be fitted with continuum models, probably because the volume of waste was below a representative elemental volume. Modelling compared advection-dispersion (AD), dual porosity (DP) and hybrid AD–DP models. Of these models, the DP model was found to be the most suitable. Although there is good evidence to suggest that diffusion is an important transport mechanism, the breakthrough curves of the different tracers did not differ from each other as would be predicted based on the free-water diffusion coefficients. This suggested that solute diffusion in wastes requires further study.

  3. Tracer dilution measurements for two-phase geothermal production: Comparative testing and operating experience

    SciTech Connect

    Hirtz, P.; Lovekin, J.

    1995-12-31

    The tracer dilution technique for the measurement of steam and water mass flowrates and total enthalpy of two-phase geothermal fluids has been in routine use in the U.S.A. for almost three years. The tracer technique was first tested and adopted on a field-wide basis at the Coso geothermal field in California. Validation of the method was performed at the Roosevelt Hot Springs geothermal project in Utah and the Salton Sea and Heber geothermal projects in California by direct comparison to orifice-plate flowmeter measurements of the separated phases. Production well mass flowrates and total enthalpy are now regularly measured by this technique in the Coso, Salton Sea and Heber geothermal fields. Implementation of the tracer method is currently underway for the Tiwi and Bulalo geothermal fields in the Philippines. This paper presents the conceptual design of the measurement process, the results of field validations, and operating experience during field-wide testing in Coso.

  4. Leak testing of bubble-tight dampers using tracer gas techniques

    SciTech Connect

    Lagus, P.L.; DuBois, L.J.; Fleming, K.M.

    1995-02-01

    Recently tracer gas techniques have been applied to the problem of measuring the leakage across an installed bubble-tight damper. A significant advantage of using a tracer gas technique is that quantitative leakage data are obtained under actual operating differential pressure conditions. Another advantage is that leakage data can be obtained using relatively simple test setups that utilize inexpensive materials without the need to tear ducts apart, fabricate expensive blank-off plates, and install test connections. Also, a tracer gas technique can be used to provide an accurate field evaluation of the performance of installed bubble-tight dampers on a periodic basis. Actual leakage flowrates were obtained at Zion Generating Station on four installed bubble-tight dampers using a tracer gas technique. Measured leakage rates ranged from 0.01 CFM to 21 CFM. After adjustment and subsequent retesting, the 21 CFM damper leakage was reduced to a leakage of 3.8 CFM. In light of the current regulatory climate and the interest in Control Room Habitability issues, imprecise estimates of critical air boundary leakage rates--such as through bubble-tight dampers--are not acceptable. These imprecise estimates can skew radioactive dose assessments as well as chemical contaminant exposure calculations. Using a tracer gas technique, the actual leakage rate can be determined. This knowledge eliminates a significant source of uncertainty in both radioactive dose and/or chemical exposure assessments.

  5. Single well surfactant test to evaluate surfactant floods using multi tracer method

    DOEpatents

    Sheely, Clyde Q.

    1979-01-01

    Data useful for evaluating the effectiveness of or designing an enhanced recovery process said process involving mobilizing and moving hydrocarbons through a hydrocarbon bearing subterranean formation from an injection well to a production well by injecting a mobilizing fluid into the injection well, comprising (a) determining hydrocarbon saturation in a volume in the formation near a well bore penetrating formation, (b) injecting sufficient mobilizing fluid to mobilize and move hydrocarbons from a volume in the formation near the well bore, and (c) determining the hydrocarbon saturation in a volume including at least a part of the volume of (b) by an improved single well surfactant method comprising injecting 2 or more slugs of water containing the primary tracer separated by water slugs containing no primary tracer. Alternatively, the plurality of ester tracers can be injected in a single slug said tracers penetrating varying distances into the formation wherein the esters have different partition coefficients and essentially equal reaction times. The single well tracer method employed is disclosed in U.S. Pat. No. 3,623,842. This method designated the single well surfactant test (SWST) is useful for evaluating the effect of surfactant floods, polymer floods, carbon dioxide floods, micellar floods, caustic floods and the like in subterranean formations in much less time and at much reduced cost compared to conventional multiwell pilot tests.

  6. Measurement of LNAPL flux using single-well intermittent mixing tracer dilution tests.

    PubMed

    Smith, Tim; Sale, Tom; Lyverse, Mark

    2012-01-01

    The stability of subsurface Light Nonaqueous Phase Liquids (LNAPLs) is a key factor driving expectations for remedial measures at LNAPL sites. The conventional approach to resolving LNAPL stability has been to apply Darcy's Equation. This paper explores an alternative approach wherein single-well tracer dilution tests with intermittent mixing are used to resolve LNAPL stability. As a first step, an implicit solution for single-well intermittent mixing tracer dilution tests is derived. This includes key assumptions and limits on the allowable time between intermittent mixing events. Second, single-well tracer dilution tests with intermittent mixing are conducted under conditions of known LNAPL flux. This includes a laboratory sand tank study and two field tests at active LNAPL recovery wells. Results from the sand tank studies indicate that LNAPL fluxes in wells can be transformed into formation fluxes using corrections for (1) LNAPL thicknesses in the well and formation and (2) convergence of flow to the well. Using the apparent convergence factor from the sand tank experiment, the average error between the known and measured LNAPL fluxes is 4%. Results from the field studies show nearly identical known and measured LNAPL fluxes at one well. At the second well the measured fluxes appear to exceed the known value by a factor of two. Agreement between the known and measured LNAPL fluxes, within a factor of two, indicates that single-well tracer dilution tests with intermittent mixing can be a viable means of resolving LNAPL stability. PMID:22489832

  7. SIMPLIFIED ANALYSIS OF TWO-WELL TRACER TESTS IN STRATIFIED AQUIFERS

    EPA Science Inventory

    The paper illustrates several interesting effects of aquifer stratification on the results of two-well tracer tests by means of a simplified computer model. In the model, it is assumed that the aquifer is horizontal, confined, of constant thickness and porosity, and perfectly str...

  8. A Tracer Test to Characterize Treatment of TCE in a Permeable Reactive Barrier

    EPA Science Inventory

    A tracer test was conducted to characterize the flow of ground water surrounding a permeable reactive barrier constructed with plant mulch (a biowall) at the OU-1 site on Altus Air Force Base, Oklahoma. This biowall is intended to intercept and treat ground water contaminated by ...

  9. On the upscaling of mass transfer rate expressions for interpretation of source zone partitioning tracer tests

    NASA Astrophysics Data System (ADS)

    Boroumand, Ali; Abriola, Linda M.

    2015-02-01

    Analysis of partitioning tracer tests conducted in dense nonaqueous phase liquid (DNAPL) source zones relies on conceptual models that describe mass exchange between the DNAPL and aqueous phases. Such analysis, however, is complicated by the complex distribution of entrapped DNAPL mass and formation heterogeneity. Due to parameter uncertainty in heterogeneous regions and the desire to reduce model complexity, the effect of mass transfer limitations is often neglected, and an equilibrium-based model is typically used to interpret test results. This work explores the consequences of that simplifying assumption on test data interpretation and develops an alternative upscaled modeling approach to quantify effective mass transfer rates. To this end, a series of partitioning tracer tests is numerically simulated in heterogeneous two-dimensional PCE-DNAPL source zones, representative of a range of hydraulic conductivity and DNAPL mass distribution characteristics. The effective mass transfer coefficient corresponding to each test is determined by fitting an upscaled model to the simulated data, and regression analysis is performed to explore the correlation between various source zone metrics and the effective mass transfer coefficient. Results suggest that vertical DNAPL spreading, Reynolds number, pool fraction, and the effective organic phase saturation are the most significant parameters controlling tracer partitioning rates. Finally, a correlation for prediction of the effective (upscaled) mass transfer coefficient is proposed and verified using existing experimental data. The developed upscaled model incorporates the influence of physical heterogeneity on the rate of tracer partitioning and, thus, can be used for the estimation of source zone mass distribution characteristics from tracer test results.

  10. Characterization of thermal tracer tests and heat exchanges in fractured media

    NASA Astrophysics Data System (ADS)

    de La Bernardie, Jérôme; Bour, Olivier; Guihéneuf, Nicolas; Chatton, Eliot; Labasque, Thierry; Longuevergne, Laurent; Le Lay, Hugo; Koch, Florian; Gerard, Marie-Françoise; Lavenant, Nicolas; Le Borgne, Tanguy

    2016-04-01

    Geothermal energy is a renewable energy source particularly attractive due to associated low greenhouse gas emission rates. Crystalline rocks are in general considered of poor interest for geothermal applications at shallow depths (< 100m), because of the low permeability of the medium. In some cases, fractures may enhance permeability, but thermal energy storage at these shallow depths is still remaining very challenging because of the low storativity of the medium. Within this framework, the purpose of this study is to test the possibility of efficient thermal energy storage in shallow fractured rocks with a single well semi open loop heat exchanger (standing column well). For doing so, several heat tracer tests have been achieved along a borehole between two connected fractures. The heat tracer tests have been achieved at the experimental site of Ploemeur (H+ observatory network). The tracer tests consist in monitoring the temperature in the upper fracture while injecting hot water in the deeper one thanks to a field boiler. For such an experimental setup, the main difficulty to interpret the data comes from the requirement for separating the temperature advective signal of the tracer test (temperature recovery) from the heat increase due to injection of hot water through the borehole which induces heat losses all along the injection tube in the water column. For doing so, in addition to a double straddle packer used for isolating the injection chamber, the particularity of the experimental set up is the use of fiber optic distributed temperature sensing (FO-DTS); an innovative technology which allows spatial and temporal monitoring of the temperature all along the well. Thanks to this tool, we were able to estimate heat increases coming from diffusion along the injection tube which is found much lower than localized temperature increases resulting from tracer test recovery. With local temperatures probes, separating both effects would not have been feasible. We

  11. Application of the tracer-aerosol gradient interpretive technique to sulfur attribution for the big bend regional aerosol and visibility observational study.

    PubMed

    Green, Mark; Kuhns, Hampden; Pitchford, Marc; Dietz, Russell; Ashbaugh, Lowell; Watson, Tom

    2003-05-01

    A simple data analysis method called the Tracer-Aerosol Gradient Interpretive Technique (TAGIT) is used to attribute particulate S and SO2 at Big Bend National Park in Texas and nearby areas to local and regional sources. Particulate S at Big Bend is of concern because of its effects on atmospheric visibility. The analysis used particulate S, SO2, and perfluorocarbon tracer data from six 6-hr sampling sites in and near Big Bend National Park. The data were collected in support of the Big Bend Regional Aerosol and Visibility Observational (BRAVO) Study; the field portion was conducted from July through October 1999. Perfluorocarbon tracer was released continuously from a tower at Eagle Pass, TX, approximately 25 km northeast of two large coal-fired power plants (Carbon I and II) in Coahuila, Mexico, and approximately 270 km east-southeast of Big Bend National Park. The perfluorocarbon tracer did not properly represent the location of the emissions from the Carbon power plants for individual 6-hr sampling periods and attributed only 3% of the particulate S and 27% of the SO2 at the 6-hr sites in and near Big Bend to sources represented by the tracer. An alternative approach using SO2 to tag "local" sources such as the Carbon plants attributed 10% of the particulate S and 75% of the SO2 at the 6-hr sites to local sources. Based on these two approaches, most of the regional (65-86%) and a small fraction (19-31%) of the local SO2 was converted to particulate S. The analysis implies that substantial reductions in particulate S at Big Bend National Park cannot be achieved by only reducing emissions from the Carbon power plants; reduction of emissions from many sources over a regional area would be necessary. PMID:12774992

  12. Ultra-Gradient Test Cavity for Testing SRF Wafer Samples

    SciTech Connect

    N.J. Pogue, P.M. McIntyre, A.I. Sattarov, C. Reece

    2010-11-01

    A 1.3 GHz test cavity has been designed to test wafer samples of superconducting materials. This mushroom shaped cavity, operating in TE01 mode, creates a unique distribution of surface fields. The surface magnetic field on the sample wafer is 3.75 times greater than elsewhere on the Niobium cavity surface. This field design is made possible through dielectrically loading the cavity by locating a hemisphere of ultra-pure sapphire just above the sample wafer. The sapphire pulls the fields away from the walls so the maximum field the Nb surface sees is 25% of the surface field on the sample. In this manner, it should be possible to drive the sample wafer well beyond the BCS limit for Niobium while still maintaining a respectable Q. The sapphire's purity must be tested for its loss tangent and dielectric constant to finalize the design of the mushroom test cavity. A sapphire loaded CEBAF cavity has been constructed and tested. The results on the dielectric constant and loss tangent will be presented

  13. Modeling a tracer test at the Grimsel Test Site (GTS) using a lattice Boltzmann method and transmissivity field

    NASA Astrophysics Data System (ADS)

    Kim, J. W.; Lanyon, G. W.; Baik, M. H.; Blechschmidt, I.

    2015-12-01

    A series of tracer tests have been conducted in the Migration (MI) Shear Zone at the Grimsel Test Site (GTS) for the Colloid Formation and Migration Project (CFM). As a part of the series, a dipole test (Tracer Test Run 13-05) using radionuclides, colloids and conservative tracers was performed to determine the breakthrough between CRR99.002-i2 and BOMI87.010-i2. To date, the breakthrough data of only the conservative dye tracer (Amino-G acid) are available. In the preceding project, the Colloid and Radionuclide Retardation Project (CRR), a transmissivity field for the MI shear zone was obtained by the geostatistical inverse modeling approach. In this study, the breakthrough of the tracer was computed by a gray lattice Boltzmann method (LBM). The transmissivity field with finite elements grid was transformed to the effective fracture aperture or flow porosity according to the cubic law, and the grid was uniformalized by the interpolation. The uniform mesh of the effective aperture was utilized as the model domain of the gray LBM. In the gray LBM, the heterogeneity of the aperture was dealt with a partial-bounceback scheme. The profiles of hydraulic heads monitored at the boreholes nearby were used as the reference values in the calculation of the pressure distribution in the model domain. The modeling results could reveal a dominant pathway of tracers in the dipole test. The developed model can be utilized in the calculation of the reactive transports of radionuclides and colloids by coupling with a geochemical model, such as Phreeqc, the Geochemist's Workbench, etc.

  14. SIMULATIONS OF TWO-WELL TRACER TESTS IN STRATIFIED AQUIFERS AT THE CHALK RIVER AND THE MOBILE SITES

    EPA Science Inventory

    A simulation of two-well injection-withdrawal tracer tests in stratified granular aquifers is presented for two widely separated sites substantially different in terms of vertical distributions of hydraulic conductivity, well spacings, flow rates, test durations and tracer travel...

  15. Interpretation of Colloid-Homologue Tracer Test 10-03, Including Comparisons to Test 10-01

    SciTech Connect

    Reimus, Paul W.

    2012-06-26

    This presentation covers the interpretations of colloid-homologue tracer test 10-03 conducted at the Grimsel Test Site, Switzerland, in 2010. It also provides a comparison of the interpreted test results with those of tracer test 10-01, which was conducted in the same fracture flow system and using the same tracers than test 10-03, but at a higher extraction flow rate. A method of correcting for apparent uranine degradation in test 10-03 is presented. Conclusions are: (1) Uranine degradation occurred in test 10-03, but not in 10-01; (2) Uranine correction based on apparent degradation rate in injection loop in test 11-02 seems reasonable when applied to data from test 10-03; (3) Colloid breakthrough curves quite similar in the two tests with similar recoveries relative to uranine (after correction); and (4) Much slower apparent desorption of homologues in test 10-03 than in 10-01 (any effect of residual homologues from test 10-01 in test 10-03?).

  16. Using predictive uncertainty analysis to optimise tracer test design and data acquisition

    NASA Astrophysics Data System (ADS)

    Wallis, Ilka; Moore, Catherine; Post, Vincent; Wolf, Leif; Martens, Evelien; Prommer, Henning

    2014-07-01

    Tracer injection tests are regularly-used tools to identify and characterise flow and transport mechanisms in aquifers. Examples of practical applications are manifold and include, among others, managed aquifer recharge schemes, aquifer thermal energy storage systems and, increasingly important, the disposal of produced water from oil and shale gas wells. The hydrogeological and geochemical data collected during the injection tests are often employed to assess the potential impacts of injection on receptors such as drinking water wells and regularly serve as a basis for the development of conceptual and numerical models that underpin the prediction of potential impacts. As all field tracer injection tests impose substantial logistical and financial efforts, it is crucial to develop a solid a-priori understanding of the value of the various monitoring data to select monitoring strategies which provide the greatest return on investment. In this study, we demonstrate the ability of linear predictive uncertainty analysis (i.e. “data worth analysis”) to quantify the usefulness of different tracer types (bromide, temperature, methane and chloride as examples) and head measurements in the context of a field-scale aquifer injection trial of coal seam gas (CSG) co-produced water. Data worth was evaluated in terms of tracer type, in terms of tracer test design (e.g., injection rate, duration of test and the applied measurement frequency) and monitoring disposition to increase the reliability of injection impact assessments. This was followed by an uncertainty targeted Pareto analysis, which allowed the interdependencies of cost and predictive reliability for alternative monitoring campaigns to be compared directly. For the evaluated injection test, the data worth analysis assessed bromide as superior to head data and all other tracers during early sampling times. However, with time, chloride became a more suitable tracer to constrain simulations of physical transport

  17. Capability of EnKF to assimilate tracer test data at the lower detection limit

    NASA Astrophysics Data System (ADS)

    Bruckmann, Johanna; Vogt, Christian; Clauser, Christoph

    2014-05-01

    We model water flow and estimate permeability distribution to improve regional groundwater management for a tectonically limited hard-rock aquifer. Management of groundwater resources for drinking water supply requires understanding and quantifying of the regional groundwater flow and groundwater budget which depends largely on the petrophysical transport properties (e. g., porosity and permeability) of the underground. We study a structurally complex and thus highly heterogeneous area on a regional scale: the Hastenrather Graben 15 km northeast of Aachen, Germany. Here, groundwater is produced from a carbonate aquifer for drinking water supply. However, direct data on the geometry and petrophysical properties of the underground are sparse and most data are only one-dimensional. For overcoming this limitation and coping with the heterogeneity of the underground we use the Ensemble Kalman Filter (EnKF) for stochastic parameter estimation and statistical ensemble analysis. Assimilating time-dependent tracer test data will help estimating permeability. The fact that the aquifer is used for drinking water supply prevents using of any artificial tracer such as radioactive or fluorescent tracer. Instead, drinking water with a lower salinity compared to the groundwater (e.g., dam water) will be used. The detection limit will be relatively low due to the low salinity contrast between reservoir water and tracer. It might even be in the range of measuring error. For studying the sensitivity of EnKF at the limit of detection we set up a synthetic scenario based on the conditions in our study area. Performing EnKF assimilation runs based on perturbed observations characterized by different measurement error levels yields information on the acceptable signal-to-noise-ratio required by EnKF for successful estimates of the given synthetic permeability distribution. This, in turn, provides information on the limits of the real-world's tracer test at low salinity contrast.

  18. Flow channeling and analysis of tracer tests in heterogeneous porous media

    SciTech Connect

    Moreno, Luis; Tsang, Chin-Fu

    2001-11-03

    Flow and solute transport through porous medium with strongly varying hydraulic conductivity are studied by numerical simulations. The heterogeneity of the porous medium is defined by {sigma} and {lambda}{prime}, which are, respectively, the standard deviation of natural log of permeability values and its correlation range {lambda} divided by transport distance L. The development of flow channeling as a function of these two parameters is demonstrated. The results show that for large heterogeneities, the flow is highly channelized and solute is transported through a few fast paths, and the corresponding breakthrough curves show a high peak at very early times, much shorter than the mean residence time. This effect was studied for a converging radial flow, to simulate tracer tests in a fracture zone or contact-thickness aquifer. It is shown that {sigma}{sup 2}{lambda}{prime} is an appropriate parameter to characterize the tracer dispersion and breakthrough curves. These results are used to study tracer breakthrough data from field experiments performed with nonsorbing tracers. A new procedure is proposed to analyze the results. From the moments of the residence-time distribution represented by the breakthrough curves, the heterogeneity of the porous medium, as characterized by {sigma}{sup 2}{lambda}{prime} and the mean residence time t{sub o}, may be determined.

  19. MULTISPECIES REACTIVE TRACER TEST IN A SAND AND GRAVEL AQUIFER, CAPE COD, MASSACHUSETTS: PART 1: EXPERIMENTAL DESIGN AND TRANSPORT OF BROMIDE AND NICKEL-EDTA TRACERS

    EPA Science Inventory

    In this report, we summarize a portion of the results of a large-scale tracer test conducted at the U. S. Geological Survey research site on Cape Cod, Massachusetts. The site is located on a large sand and gravel glacial outwash plain in an unconfined aquifer. In April 1993, ab...

  20. Testing Method for Heat Resistance Under Temperature Gradient

    NASA Astrophysics Data System (ADS)

    Takagi, K.; Kawasaki, A.; Itoh, Y.; Harada, Y.; Ono, F.

    2007-12-01

    Testing Method for Heat Resistance under Temperature Gradient” is a Japanese Industrial Standard (JIS) newly established by the Minister of Economy, Trade and Industry, after deliberations by the Japanese Industrial Standards Committee, in accordance with the Industrial Standardization Law. This standard specified the testing method for heat resistance under temperature gradient of materials and coated members of equipment exposed to high temperature, such as aircraft engines, gas turbines, and so on. This paper introduces the principle and overview of the established standard. In addition, taking the heat cycle test using the burner rig for instance, we specifically illustrate the acquirable data and their analysis in the standard. Monitoring of the effective thermal conductivity and acoustic emission particularly enables to the non-destructive evaluation of failure cycle.

  1. Fractional flow in fractured chalk; a flow and tracer test revisited

    NASA Astrophysics Data System (ADS)

    Odling, N. E.; West, L. J.; Hartmann, S.; Kilpatrick, A.

    2013-04-01

    A multi-borehole pumping and tracer test in fractured chalk is revisited and reinterpreted in the light of fractional flow. Pumping test data analyzed using a fractional flow model gives sub-spherical flow dimensions of 2.2-2.4 which are interpreted as due to the partially penetrating nature of the pumped borehole. The fractional flow model offers greater versatility than classical methods for interpreting pumping tests in fractured aquifers but its use has been hampered because the hydraulic parameters derived are hard to interpret. A method is developed to convert apparent transmissivity and storativity (L4-n/T and S2-n) to conventional transmissivity and storativity (L2/T and dimensionless) for the case where flow dimension, 2 < n < 3. These parameters may then be used in further applications, facilitating application of the fractional flow model. In the case illustrated, improved fits to drawdown data are obtained and the resultant transmissivities and storativities are found to be lower by 30% and an order of magnitude respectively, than estimates from classical methods. The revised hydraulic parameters are used in a reinterpretation of a tracer test using an analytical dual porosity model of solute transport incorporating matrix diffusion and modified for fractional flow. Model results show smaller fracture apertures, spacings and dispersivities than those when 2D flow is assumed. The pumping and tracer test results and modeling presented illustrate the importance of recognizing the potential fractional nature of flow generated by partially penetrating boreholes in fractured aquifers in estimating aquifer properties and interpreting tracer breakthrough curves.

  2. ANALYSIS OF A GAS-PHASE PARTITIONING TRACER TEST CONDUCTED IN AN UNSATURATED FRACTURED-CLAY FORMATION

    EPA Science Inventory

    The gas-phase partitioning tracer method was used to estimate non-aqueous phase liquid (NAPL), water, and air saturations in the vadose zone at a chlorinated-solvent contaminated field site in Tucson, AZ. The tracer test was conducted in a fractured-clay system that is the confin...

  3. Evaluation of the radionuclide tracer test conducted at the project Gnome Underground Nuclear Test Site, New Mexico

    SciTech Connect

    Pohll, G.; Pohlmann, K.

    1996-08-01

    A radionuclide tracer test was conducted in 1963 by the U.S. Geological Survey at the Project Gnome underground nuclear test site, approximately 40 km southeast of Carlsbad, New Mexico. The tracer study was carried out under the auspices of the U.S. Atomic Energy Commission (AEC) to study the transport behavior of radionuclides in fractured rock aquifers. The Culebra Dolomite was chosen for the test because it was considered to be a reasonable analogue of the fractured carbonate aquifer at the Nevada Test Site (NTS), the principal location of U.S. underground nuclear tests. Project Gnome was one of a small number of underground nuclear tests conducted by the AEC at sites distant from the NTS. The Gnome device was detonated on December 10, 1961 in an evaporate unit at a depth of 360 m below ground surface. Recently, the U.S. Department of Energy (DOE) implemented an environmental restoration program to characterize, remediate, and close these offsite nuclear test areas. An early step in this process is performance of a preliminary risk analysis of the hazard posed by each site. The Desert Research Institute has performed preliminary hydrologic risk evaluations for the groundwater transport pathway at Gnome. That evaluation included the radioactive tracer test as a possible source because the test introduced radionuclides directly into the Culebra Dolomite, which is the only aquifer at the site. This report presents a preliminary evaluation of the radionuclide tracer test as a source for radionuclide migration in the Culebra Dolomite. The results of this study will assist in planning site characterization activities and refining estimates of the radionuclide source for comprehensive models of groundwater transport st the Gnome site.

  4. Preliminary Interpretation of a Radionuclide and Colloid Tracer Test in a Granodiorite Shear Zone at the Grimsel Test Site, Switzerland

    SciTech Connect

    Reimus, Paul W.

    2012-08-30

    In February and March 2012, a tracer test involving the injection of a radionuclide-colloid cocktail was conducted in the MI shear zone at the Grimsel Test Site, Switzerland, as part of the Colloids Formation and Migration (CFM) project. The colloids were derived from FEBEX bentonite, which is mined in Spain and is being considered as a potential waste package backfill in a Spanish nuclear waste repository. The tracer test, designated test 12-02 (second test in 2012), involved the injection of the tracer cocktail into borehole CFM 06.002i2 and extraction from the Pinkel surface packer at the main access tunnel wall approximately 6.1 m from the injection interval. The test configuration is depicted in Figure 1. This configuration has been used in several conservative tracer tests and two colloid-homologue tracer tests since 2007, and it is will be employed in an upcoming test involving the emplacement of a radionuclide-doped bentonite plug into CFM 06.002i2 to evaluate the swelling and erosion of the bentonite and the transport of bentonite colloids and radionuclides from the source to the extraction point at the tunnel wall. Interpretive analyses of several of the previous tracer tests, from 09-01 through 12-02 were provided in two previous Used Fuel Disposition Program milestone reports (Arnold et al., 2011; Kersting et al., 2012). However, only the data for the conservative tracer Amino-G Acid was previously analyzed from test 12-02 because the other tracer data from this test were not available at the time. This report documents the first attempt to quantitatively analyze the radionuclide and colloid breakthrough curves from CFM test 12-02. This report was originally intended to also include an experimental assessment of colloid-facilitated transport of uranium by bentonite colloids in the Grimsel system, but this assessment was not conducted because it was reported by German collaborators at the Karlsruhe Institute of Technology (KIT) that neither uranium nor

  5. Evaluation of Partitioning Gas Tracer Tests for Measuring Water in Landfills

    NASA Astrophysics Data System (ADS)

    Imhoff, P. T.; Han, B.; Jafarpour, Y.; Gallagher, V. N.; Chiu, P. C.; Fluman, D. A.; Vasuki, N. C.; Yazdani, R.; Augenstein, D.; Cohen, K. K.

    2003-12-01

    Methane is an important greenhouse gas, and landfills are the largest anthropogenic source in many developed countries. Bioreactor landfills have been proposed as one means of abating greenhouse gas emissions from landfills. Here, the decomposition of organic wastes is enhanced by the controlled addition of water or leachate to maintain optimal conditions for waste decomposition. Greenhouse gas abatement is accomplished by sequestration of photosynthetically derived carbon in wastes, CO2 offsets from energy use of waste derived gas, and mitigation of methane emission from the wastes. An important issue in the operation of bioreactor landfills is knowing how much water to add and where to add it. Accurate methods for measuring the amount of water in landfills would be valuable aids for implementing leachate recirculation systems. Current methods for measuring water are inadequate, though, since they provide point measurements and are frequently affected by heterogeneity of the solid waste composition and solid waste compaction. The value of point measurements is significantly reduced in systems where water flows preferentially, such as in landfills. Here, spatially integrated measurements might be of greater value. We are evaluating a promising technology, the partitioning gas tracer test, to measure the water saturation within landfills, the amount of free water in solid waste divided by the volume of the voids. The partitioning gas tracer test was recently developed by researchers working in the vadose zone. We report the results from laboratory and field tests designed to evaluate the partitioning gas tracer test within an anaerobic landfill operated by the Delaware Solid Waste Authority. Vertical wells were installed within the landfill to inject and extract tracer gases. Gas flow and tracer gas movement in the solid waste were controlled by the landfill's existing gas collection system, which included vertical wells installed throughout the landfill through

  6. Are single-well "push-pull" tests suitable tracer methods for aquifer characterization?

    NASA Astrophysics Data System (ADS)

    Hebig, Klaus; Zeilfelder, Sarah; Ito, Narimitsu; Machida, Isao; Scheytt, Traugott; Marui, Atsunao

    2013-04-01

    Recently, investigations were conducted for geological and hydrogeological characterisation of the sedimentary coastal basin of Horonobe (Hokkaido, Japan). Coastal areas are typical geological settings in Japan, which are less tectonically active than the mountain ranges. In Asia, and especially in Japan, these areas are often densely populated. Therefore, it is important to investigate the behaviour of solutes in such unconsolidated aquifers. In such settings sometimes only single boreholes or groundwater monitoring wells are available for aquifer testing for various reasons, e.g. depths of more than 100 m below ground level and slow groundwater velocities due to density driven flow. A standard tracer test with several involved groundwater monitoring wells is generally very difficult or even not possible at these depths. One of the most important questions in our project was how we can obtain information about chemical and hydraulic properties in such aquifers. Is it possible to characterize solute transport behaviour parameters with only one available groundwater monitoring well or borehole? A so-called "push-pull" test may be one suitable method for aquifer testing with only one available access point. In a push-pull test a known amount of several solutes including a conservative tracer is injected into the aquifer ("push") and afterwards extracted ("pull"). The measured breakthrough curve during the pumping back phase can then be analysed. This method has already been used previously with various aims, also in the recent project (e.g. Hebig et al. 2011, Zeilfelder et al. 2012). However, different test setups produced different tracer breakthrough curves. As no systematic evaluation of this aquifer tracer test method was done so far, nothing is known about its repeatability. Does the injection and extraction rate influence the shape of the breakthrough curve? Which role plays the often applied "chaser", which is used to push the test solution out from the

  7. CO2CRC's Otway Residual Saturation and Dissolution Test: Using Reactive Ester Tracers to Determine Residual CO2 Saturation

    NASA Astrophysics Data System (ADS)

    Myers, M.; Stalker, L.; LaForce, T.; Pejcic, B.; Dyt, C.; Ho, K.; Ennis-King, J.

    2013-12-01

    Residual trapping, that is CO2 held in the rock pore space due to capillarity, is an important storage mechanism in geo-sequestration of over the short to medium term (up to 1000 years). As such residual CO2 saturation is a critical reservoir parameter for assessing the storage capacity and security of carbon capture and storage (CCS). As a component of the CO2CRC's Residual Gas Saturation and Dissolution Test at the CO2CRC Otway Project site in Victoria (Australia), we have recently tested a suite of reactive esters (triacetin, tripropionin and propylene glycol diacetate) in a single well chemical tracer test to determine residual CO2 saturation. The goal of this project was to assess and validate a suite of possible tests that could be implemented to determine residual CO2 saturation. For this test, the chemical tracers were injected with a saturated CO2/water mixture into the formation (that is already at residual CO2 saturation) where they were allowed to 'soak' for approximately 10 days allowing for the partial hydrolysis of the esters to their corresponding carboxylic acids and alcohols. Water containing the tracers was then produced from the well resulting in over 600 tracer samples over a period of 12 hours. A selection of these samples were analysed for tracer content and to establish tracer breakthrough curves. To understand the behaviour of these chemical tracers in the downhole environment containing residually trapped supercritical CO2 and formation water, it is necessary to determine the supercritical CO2/water partition coefficients. We have previously determined these in the laboratory (Myers et al., 2012) and they are used here to model the tracer behaviour and provide an estimate of the residual CO2 saturation. Two different computational simulators were used to analyse the tracer breakthrough profiles. The first is based on simple chromatographic retardation and has been used extensively in single well chemical tracer tests to determine residual

  8. Application of tracer tests using SF6 and chloride for hydrogeological characterization of a CCS site, Eumseong, Korea

    NASA Astrophysics Data System (ADS)

    Kim, H. H.; Lee, S. S.; Kim, T. W.; Lee, K.; Kim, M.; Lee, K. K.

    2015-12-01

    Push-pull tracer test was conducted to acquire precise site information and characteristics on a Carbon Capture and Storage (CCS)-site at Eumseong, Korea. Push-pull test is very simple to design, and perform. The test is also convenient to set a duration of experiment period based on the background ground-water velocity. In this study, SF6 and Chloride were used as tracers known as non-reactive tracers. The performed push-pull tests were consisted of 3 phases: 1) solution injection phase; 2) rest phase; and 3) pumping phase. We used a portable multi-level packer to isolate the injection interval. Samples were obtained during pumping phase at every 2 minutes. LTC level-logger was installed to record real-time water level, temperature, and electric conductivity before and during the experiment. A breakthrough curve was obtained by analyzing LTC level-logger data and tracer concentration of water samples. The values of ground water velocity and effective porosity from two tracers came out similar values. SF6 and chloride did not show intervening effect and display similar transport behavior. It seems that both tracers can be applied independently or together to perform tracer tests for estimation of transport behaviors of dissolved volatile components. Acknowledgement: Financial support was provided by the "R&D Project on Environmental Management of Geologic CO2 Storage" from the KEITI (Project Number: 2014001810003) and Korea Ministry of Environment as "The GAIA project(2014000540010)"

  9. Synchrotron X-Ray Microtomography and Interfacial Partitioning Tracer Test Measurements of Napl-Water Interfacial Areas

    NASA Astrophysics Data System (ADS)

    Brusseau, M. L.; Janousek, H.; Murao, A.; Schnaar, G.

    2007-12-01

    Interfacial areas between an immiscible organic liquid (NAPL) and water were measured for two natural porous media using two methods, aqueous-phase interfacial partitioning tracer tests and synchrotron X-ray microtomography. The interfacial areas measured with the tracer tests were similar to previously reported values obtained with the method. The values were, however, significantly larger than those obtained from microtomography. Analysis of microtomography data collected before and after introduction of the interfacial tracer solution indicated that the surfactant tracer had minimal impact on fluid-phase configuration and interfacial areas under conditions associated with typical laboratory application. The disparity between the tracer-test and microtomography values is attributed primarily to the inability of the microtomography method to resolve interfacial area associated with microscopic surface heterogeneity. This hypothesis is consistent with results recently reported for a comparison of microtomographic analysis and interfacial tracer tests conducted for an air-water system. The tracer-test method provides a measure of effective, total (capillary and film) interfacial area, whereas microtomography can be used to determine separately both capillary-associated and film-associated interfacial areas. Both methods appear to provide useful information for given applications. A key to their effective use is recognizing the specific nature of the information provided by each, as well as associated limitations.

  10. Using seismic reflection to locate a tracer testing complex south of Yucca Mountain, Nye County, Nevada

    NASA Astrophysics Data System (ADS)

    Kryder, Levi

    Tracer testing in the fractured volcanic aquifer near Yucca Mountain, and in the alluvial aquifer south of Yucca Mountain, Nevada has been conducted in the past to determine the flow and transport properties of groundwater in those geologic units. However, no tracer testing has been conducted across the alluvium/volcanic interface. This thesis documents the investigative process and subsequent analysis and interpretations used to identify a location suitable for installation of a tracer testing complex, near existing Nye County wells south of Yucca Mountain. The work involved evaluation of existing geologic data, collection of wellbore seismic data, and a detailed surface seismic reflection survey. Borehole seismic data yielded useful information on alluvial P-wave velocities. Seismic reflection data were collected over a line of 4.5-km length, with a 10-m receiver and shot spacing. Reflection data were extensively processed to image the alluvium/volcanic interface. A location for installation of an alluvial/volcanic tracer testing complex was identified based on one of the reflectors imaged in the reflection survey; this site is located between existing Nye County monitoring wells, near an outcrop of Paintbrush Tuff. Noise in the reflection data (due to some combination of seismic source signal attenuation, poor receiver-to-ground coupling, and anthropogenic sources) were sources of error that affected the final processed data set. In addition, in some areas low impedance contrast between geologic units caused an absence of reflections in the data, complicating the processing and interpretation. Forward seismic modeling was conducted using Seismic Un*x; however, geometry considerations prevented direct comparison of the modeled and processed data sets. Recommendations for additional work to address uncertainties identified during the course of this thesis work include: drilling additional boreholes to collect borehole seismic and geologic data; reprocessing a

  11. Measurement of the Tracer Gradient and Sampling System Bias of the Hot Fuel Examination Facility Stack Air Monitoring System

    SciTech Connect

    Glissmeyer, John A.; Flaherty, Julia E.

    2011-07-20

    This report describes tracer gas uniformity and bias measurements made in the exhaust air discharge of the Hot Fuel Examination Facility at Idaho National Laboratory. The measurements were a follow-up on earlier measurements which indicated a lack of mixing of the two ventilation streams being discharged via a common stack. The lack of mixing is detrimental to the accuracy of air emission measurements. The lack of mixing was confirmed in these new measurements. The air sampling probe was found to be out of alignment and that was corrected. The suspected sampling bias in the air sample stream was disproved.

  12. A simple urban dispersion model tested with tracer data from Oklahoma City and Manhattan

    NASA Astrophysics Data System (ADS)

    Hanna, Steven; Baja, Emmanuel

    A simple urban dispersion model is tested that is based on the Gaussian plume model and modifications to the Briggs urban dispersion curves. An initial dispersion coefficient ( σo) of 40 m is assumed to apply in built-up downtown areas, and the stability is assumed to be slightly unstable during the day and slightly stable during the night. Observations from tracer experiments during the Joint Urban 2003 (JU2003) field study in Oklahoma City and the Madison Square Garden 2005 (MSG05) field study in Manhattan are used for model testing. The tracer SF 6 was released during JU2003 near ground level in the downtown area and concentrations were observed at over 100 locations within 4 km from the source. Six perfluorocarbon tracer (PFT) gases were released near ground level during MSG05 and sampled by about 20 samplers at the surface and on building roofs. The evaluations compare concentrations normalized by source release rate, C/ Q, for each sampler location and each tracer release, where data were used only if both the observed and predicted concentrations exceeded threshold levels. At JU2003, for all samplers and release times, the fractional mean bias (FB) is about 0.2 during the day (20% mean underprediction) and 0.0 during the night. About 45 -50% of the predictions are within a factor of two (FAC2) of the observations day and night at JU2003. The maximum observed C/ Q is about two times the maximum predicted C/ Q both day and night. At MSG05, for all PFTs, surface samplers, and release times, FB is 0.14 and FAC2 is about 45%. The overall 60 min-averaged maximum C/ Q is underpredicted by about 40% for the surface samplers and is overpredicted by about 25% for the building-roof samplers.

  13. Concurrent conservative and reactive tracer tests in a stream undergoing hyporheic exchange

    NASA Astrophysics Data System (ADS)

    Lemke, Dennis; Liao, Zijie; WöHling, Thomas; Osenbrück, Karsten; Cirpka, Olaf A.

    2013-05-01

    Knowledge about the strength and travel times of hyporheic exchange is vital to predict reactive transport and biogeochemical cycling in streams. In this study, we outline how to perform and analyze stream tracer tests using pulse injections of fluorescein as conservative and resazurin as reactive tracer, which is selectively transformed to resorufin when exposed to metabolically active zones, presumably located in the hyporheic zone. We present steps of preliminary data analysis and apply a conceptually simple mathematical model of the tracer tests to separate effects of in-stream transport from hyporheic exchange processes. To overcome the dependence of common parameter estimation schemes on the initial guess, we derive posterior parameter probability density functions using an adaptive Markov chain Monte Carlo scheme. By this, we can identify maximum-likelihood parameter values of in-stream transport, strength of hyporheic exchange, distribution of hyporheic travel times as well as sorption and reactivity coefficients of the hyporheic zone. We demonstrate the approach by a tracer experiment at River Goldersbach in southern Germany (60 L/s discharge). In-stream breakthrough curves were recorded with online fluorometers and jointly fitted to simulations of a one-dimensional reactive transport model assuming an exponential hyporheic travel-time distribution. The findings show that the additional analysis of resazurin not only improved the physical basis of the modeling, but was crucial to differentiate between surface transport and hyporheic transient storage of stream solutes. Parameter uncertainties were usually small and could not explain parameter variability between adjacent monitoring stations. The latter as well as a systematic underestimation of the tailing are due to structural errors of the model, particularly the exponential hyporheic travel-time distribution. Mean hyporheic travel times were in the range of 12 min, suggesting that small streambed

  14. Push pull partitioning tracer tests using radon-222 to quantify non-aqueous phase liquid contamination

    NASA Astrophysics Data System (ADS)

    Davis, B. M.; Istok, J. D.; Semprini, L.

    2002-09-01

    Naturally occurring radon in groundwater can be used as an in situ partitioning tracer for locating and quantifying non-aqueous phase liquid (NAPL) contamination in the subsurface. When combined with the single-well, push-pull test, this methodology has the potential to provide a low-cost alternative to inter-well partitioning tracer tests. During a push-pull test, a known volume of test solution (radon-free water containing a conservative tracer) is first injected ("pushed") into a well; flow is then reversed and the test solution/groundwater mixture is extracted ("pulled") from the same well. In the presence of NAPL radon transport is retarded relative to the conservative tracer. Assuming linear equilibrium partitioning, retardation factors for radon can be used to estimate NAPL saturations. The utility of this methodology was evaluated in laboratory and field settings. Laboratory push-pull tests were conducted in both non-contaminated and trichloroethene NAPL (TCE)-contaminated sediment. The methodology was then applied in wells located in non-contaminated and light non-aqueous phase liquid (LNAPL)-contaminated portions of an aquifer at a former petroleum refinery. The method of temporal moments and an approximate analytical solution to the governing transport equations were used to interpret breakthrough curves and estimate radon retardation factors; estimated retardation factors were then used to calculate TCE saturations. Numerical simulations were used to further investigate the behavior of the breakthrough curves. The laboratory and field push-pull tests demonstrated that radon retardation does occur in the presence of TCE and LNAPL and that radon retardation can be used to calculate TCE saturations. Laboratory injection-phase test results in TCE-contaminated sediment yielded radon retardation factors ranging from 1.1 to 1.5, resulting in calculated TCE saturations ranging from 0.2 to 0.9%. Laboratory extraction-phase test results in the same sediment

  15. Non-Fickian dispersion in porous media: 1. Multiscale measurements using single-well injection withdrawal tracer tests

    NASA Astrophysics Data System (ADS)

    Gouze, P.; Le Borgne, T.; Leprovost, R.; Lods, G.; Poidras, T.; Pezard, P.

    2008-06-01

    We present a set of single-well injection withdrawal tracer tests in a paleoreef porous reservoir displaying important small-scale heterogeneity. An improved dual-packer probe was designed to perform dirac-like tracer injection and accurate downhole automatic measurements of the tracer concentration during the recovery phase. By flushing the tracer, at constant flow rate, for increasing time duration, we can probe distinctly different reservoir volumes and test the multiscale predictability of the (non-Fickian) dispersion models. First we describe the characteristics, from microscale to meter scale, of the reservoir rock. Second, the specificity of the tracer test setup and the results obtained using two different tracers and measurement methods (salinity-conductivity and fluorescent dye-optical measurement, respectively) are presented. All the tracer tests display strongly tailed breakthrough curves (BTC) consistent with diffusion in immobile regions. Conductivity results, measured over 3 orders of magnitude only, could have been easily interpreted by the conventional mobile-immobile (MIM) diffusive mass transfer model of asymptotic log-log slope of -2. However, the fluorescent dye sensor, which allows exploring much lower concentration values, shows that a change in the log-log slope occurs at larger time with an asymptotic value of -1.5, corresponding to the double-porosity model. These results suggest that the conventional, one-slope MIM transfer rate model is too simplistic to account for the real multiscale heterogeneity of the diffusion-dominant fraction of the reservoir.

  16. Application of a NAPL partitioning interwell tracer test (PITT) to support DNAPL remediation at the Sandia National Laboratories/New Mexico chemical waste landfill

    SciTech Connect

    Studer, J.E.; Mariner, P.; Jin, M.

    1996-05-01

    Chlorinated solvents as dense non-aqueous phase liquid (DNAPL) are present at a large number of hazardous waste sites across the U.S. and world. DNAPL is difficult to detect in the subsurface, much less characterize to any degree of accuracy. Without proper site characterization, remedial decisions are often difficult to make and technically effective, cost-efficient remediations are even more difficult to obtain. A new non-aqueous phase liquid (NAPL) characterization technology that is superior to conventional technologies has been developed and applied at full-scale. This technology, referred to as the Partitioning Interwell Tracer Test (PITT), has been adopted from oil-field practices and tailored to environmental application in the vadose and saturated zones. A PITT has been applied for the first time at full-scale to characterize DNAPL in the vadose zone. The PITT was applied in December 1995 beneath two side-by-side organic disposal pits at Sandia National Laboratories/New Mexico (SNL/NM) RCRA Interim Status Chemical Waste Landfill (CWL), located in Albuquerque, New Mexico. DNAPL, consisting of a mixture of chlorinated solvents, aromatic hydrocarbons, and PCE oils, is known to exist in at least one of the two buried pits. The vadose zone PITT was conducted by injecting a slug of non-partitioning and NAPL-partitioning tracers into and through a zone of interest under a controlled forced gradient. The forced gradient was created by a balanced extraction of soil gas at a location 55 feet from the injector. The extracted gas stream was sampled over time to define tracer break-through curves. Soil gas sampling ports from multilevel monitoring installations were sampled to define break-through curves at specific locations and depths. Analytical instrumentation such as gas chromatographs and a photoacoustical analyzers operated autonomously, were used for tracer detection.

  17. Well ER-6-1 Tracer Test Analysis: Yucca Flat, Nevada Test Site, Nye County, Nevada, Rev. No.: 0

    SciTech Connect

    Greg Ruskauff

    2006-09-01

    The ER-6-1 multiple-well aquifer test-tracer test (MWAT-TT) investigated groundwater flow and transport processes relevant to the transport of radionuclides from sources on the Nevada Test Site (NTS) through the lower carbonate aquifer (LCA) hydrostratigraphic unit (HSU). The LCA, which is present beneath much of the NTS, is the principal aquifer for much of southern Nevada. This aquifer consists mostly of limestone and dolomite, and is pervasively fractured. Groundwater flow in this aquifer is primarily in the fractures, and the hydraulic properties are primarily related to fracture frequency and fracture characteristics (e.g., mineral coatings, aperture, connectivity). The objective of the multiple-well aquifer test (MWAT) was to determine flow and hydraulic characteristics for the LCA in Yucca Flat. The data were used to derive representative flow model and parameter values for the LCA. The items of specific interest are: Hydraulic conductivity; Storage parameters; Dual-porosity behavior; and Fracture flow characteristics. The objective of the tracer transport experiment was to evaluate the transport properties and processes of the LCA and to derive representative transport parameter values for the LCA. The properties of specific interest are: Effective porosity; Matrix diffusion; Longitudinal dispersivity; Adsorption characteristics; and Colloid transport characteristics. These properties substantially control the rate of transport of contaminants in the groundwater system and concentration distributions. To best support modeling at the scale of the corrective action unit (CAU), these properties must be investigated at the field scale. The processes represented by these parameters are affected by in-situ factors that are either difficult to investigate at the laboratory scale or operate at a much larger scale than can be reproduced in the laboratory. Measurements at the field scale provide a better understanding of the effective average parameter values. The

  18. Evaluating Microbial Purification during Soil Treatment of Wastewater with Multicomponent Tracer and Surrogate Tests

    USGS Publications Warehouse

    Van Cuyk, S.; Siegrist, R.L.; Lowe, K.; Harvey, R.W.

    2004-01-01

    Soil treatment of wastewater has the potential to achieve high purification efficiency, yet the understanding and predictability of purification with respect to removal of viruses and other pathogens is limited. Research has been completed to quantify the removal of virus and bacteria through the use of microbial surrogates and conservative tracers during controlled experiments with three-dimensional pilot-scale soil treatment systems in the laboratory and during the testing of full-scale systems under field conditions. The surrogates and tracers employed included two viruses (MS-2 and PRID-1 bacteriophages), one bacterium (ice-nucleating active Pseudomonas), and one conservative tracer (bromide ion). Efforts have also been made to determine the relationship between viruses and fecal coliform bacteria in soil samples below the wastewater infiltrative surface, and the correlation between Escherichia coil concentrations measured in percolating soil solution as compared with those estimated from analyses of soil solids. The results suggest episodic breakthrough of virus and bacteria during soil treatment of wastewater and a 2 to 3 log (99-99.9%) removal of virus and near complete removal of fecal coliform bacteria during unsaturated flow through 60 to 90 cm of sandy medium. Results also suggest that the fate of fecal coliform bacteria may be indicative of that of viruses in soil media near the infiltrative surface receiving wastewater effluent. Concentrations of fecal coliform in percolating soil solution may be conservatively estimated from analysis of extracted soil solids.

  19. Differential gauging and tracer tests resolve seepage fluxes in a strongly-losing stream

    NASA Astrophysics Data System (ADS)

    Ruehl, C.; Fisher, A. T.; Hatch, C.; Huertos, M. Los; Stemler, G.; Shennan, C.

    2006-10-01

    SummaryThe Pajaro River, central coastal California, consistently loses 0.2-0.4 m 3/s of discharge along an 11.42-km experimental reach late in the water year, when discharge is ⩽4.5 m 3/s. Channel loss occurs throughout this reach, but is greatest in magnitude near the bottom of the reach. Water isotopic data and other observations suggest that channel loss results mainly from streambed seepage, as opposed to evapotranspiration. If it occurs throughout the year, the channel loss along this short stream reach could contribute 6-13 × 10 6 m 3 of annual aquifer recharge, or ˜20-40% of current sustainable basin yield. We performed a series of tracer injections along this reach to determine if hydrologic exchange occurs within this strongly-losing stream. We found that during periods of high channel loss, there were also comparable storage exchange fluxes and lateral inflow of tracer-free water. Within upper and lower parts of the experimental reach, storage exchange fluxes are about 10 times greater than lateral inflow. The former are associated with the movement of water between the main channel and surface or subsurface storage zones. In this system, it is likely that the latter are primarily associated with spatially- or temporally-long subsurface flow paths within the shallow streambed, as opposed to inflow of ground water from deeper in the basin. Along both upper and lower parts of the experimental reach, lateral inflow tends to increase as channel discharge decreases. In contrast, storage exchange fluxes increase with decreasing discharge along the upper parts of the reach, but decrease with decreasing discharge along the lower parts. Gauging and tracer test results suggest that subsurface storage exchange and loss may occur simultaneously, and that the lateral inflow of tracer-free water can be caused by long-scale subsurface flow as well as ground water making its first appearance in the channel.

  20. Nano-iron Tracer Test for Characterizing Preferential Flow Path in Fractured Rock

    NASA Astrophysics Data System (ADS)

    Chia, Y.; Chuang, P. Y.

    2015-12-01

    Deterministic description of the discrete features interpreted from site characterization is desirable for developing a discrete fracture network conceptual model. It is often difficult, however, to delineate preferential flow path through a network of discrete fractures in the field. A preliminary cross-borehole nano-iron tracer test was conducted to characterize the preferential flow path in fractured shale bedrock at a hydrogeological research station. Prior to the test, heat-pulse flowmeter measurements were performed to detect permeable fracture zones at both the injection well and the observation well. While a few fracture zones are found permeable, most are not really permeable. Chemical reduction method was used to synthesize nano zero-valent iron particles with a diameter of 50~150 nm. The conductivity of nano-iron solution is about 3100 μs/cm. The recorded fluid conductivity shows the arrival of nano-iron solution in the observation well 11.5 minutes after it was released from the injection well. The magnetism of zero-valent iron enables it to be absorbed on magnet array designed to locate the depth of incoming tracer. We found nearly all of absorbed iron on the magnet array in the observation well were distributed near the most permeable fracture zone. The test results revealed a preferential flow path through a permeable fracture zone between the injection well and the observation well. The estimated hydraulic conductivity of the connected fracture is 2.2 × 10-3 m/s. This preliminary study indicated that nano-iron tracer test has the potential to characterize preferential flow path in fractured rock.

  1. Rate-limited U(VI) desorption during a small-scale tracer test in a heterogeneous uranium-contaminated aquifer

    NASA Astrophysics Data System (ADS)

    Fox, Patricia M.; Davis, James A.; Hay, Michael B.; Conrad, Mark E.; Campbell, Kate M.; Williams, Kenneth H.; Long, Philip E.

    2012-05-01

    A tracer test was performed at the Rifle Integrated Field Research Challenge site to assess the effect of addition of bicarbonate on U(VI) desorption from contaminated sediments in the aquifer and to compare equilibrium and rate-limited reactive transport model descriptions of mass transfer limitations on desorption. The tracer test consisted of injection of a 37 mM NaHCO3solution containing conservative tracers followed by down-gradient sampling of groundwater at various elevations and distances from the point of injection. Breakthrough curves show that dissolved U(VI) concentrations increased 1.2-2.6-fold above background levels, resulting from increases in bicarbonate alkalinity (from injectate solution) and Ca concentrations (from cation exchange). In general, more U(VI) was mobilized in shallower zones of the aquifer, where finer-grained sediments and higher solid phase U content were found compared to deeper zones. An equilibrium-based reactive transport model incorporating a laboratory-based surface complexation model derived from the same location predicted the general trends in dissolved U(VI) during the tracer test but greatly overpredicted the concentrations of U(VI), indicating that the system was not at equilibrium. Inclusion of a multirate mass transfer model successfully simulated the nonequilibrium desorption behavior of U(VI). Local sediment properties such as sediment texture (weight percent <2 mm), surface area, cation exchange capacity, and adsorbed U(VI) were heterogeneous at the meter scale, and it was important to incorporate these values into model parameters in order to produce accurate simulations.

  2. Radioactive tracer test to develop a recycling system for operating reactor scrap metal

    SciTech Connect

    Umemura, A.; Kimura, K.; Takahashi, K.; Sakurai, D.; Yamamoto, M.; Abe, S.

    1995-12-31

    A demonstration test using radio-isotope (RI) tracers during the manufacturing of inner drum shielding material from the recycling of operating reactor scrap metal was completed and the following results were obtained. The behavior of five radionuclides (Mn-54, Co-60, Zn-65, Sr-85 and Cs-137) was established. The time-dependent behaviors of the radionuclides in molten steel and in slag were investigated. The radioactivity distributions in metal products were homogeneous. Dose equivalent rates in the working area were below background levels and radioactive dust concentrations in the air were below detection limits.

  3. Insight from simulations of single-well injection-withdrawal tracer tests on simple and complex fractures

    SciTech Connect

    Tsang, C.-F.; Doughty, C.

    2009-08-06

    The single-well injection withdrawal (SWIW) test, a tracer test utilizing only one well, is proposed as a useful contribution to site characterization of fractured rock, as well as providing parameters relevant to tracer diffusion and sorption. The usual conceptual model of flow and solute transport through fractured rock with low matrix permeability involves solute advection and dispersion through a fracture network coupled with diffusion and sorption into the surrounding rock matrix. Unlike two-well tracer tests, results of SWIW tests are ideally independent of advective heterogeneity, channeling and flow dimension, and, instead, focus on diffusive and sorptive characteristics of tracer (solute) transport. Thus, they can be used specifically to study such characteristics and evaluate the diffusive parameters associated with tracer transport through fractured media. We conduct simulations of SWIW tests on simple and complex fracture models, the latter being defined as having two subfractures with altered rock blocks in between and gouge material in their apertures. Using parameters from the Aspo site in Sweden, we calculate and study SWIW tracer breakthrough curves (BTCs) from a test involving four days of injection and then withdrawal. By examining the peak concentration C{sub pk} of the SWIW BTCs for a variety of parameters, we confirm that C{sub pk} is largely insensitive to the fracture advective flow properties, in particular to permeability heterogeneity over the fracture plane or to subdividing the flow into two subfractures in the third dimension orthogonal to the fracture plane. The peak arrival time t{sub pk} is not a function of fracture or rock properties, but is controlled by the time schedule of the SWIW test. The study shows that the SWIW test is useful for the study of tracer diffusion-sorption processes, including the effect of the so-called flow-wetted surface (FWS) of the fracture. Calculations with schematic models with different FWS values are

  4. Dual-porosity analysis of conservative tracer testing in saturated volcanic rocks at Yucca Mountain in Nye County, Nevada

    USGS Publications Warehouse

    Fahy, M.F.

    1997-01-01

    A radially convergent conservative tracer injection test was conducted between boreholes UE-25 #2 and UE-25 c #3 of the C-hole complex at Yucca Mountain to determine effective porosity and longitudinal dispersivity. Approximately 47% of the tracer mass was recovered and a dual-porosity analytical model replicates the breakthrough curve. Fractured-rock analyses focus on the fracture-porosity and geometry as the controlling factors in transport.

  5. A spreadsheet program for two-well tracer test data analysis.

    PubMed

    Tang, Guoping; Watson, David B; Parker, Jack C; Brooks, Scott C

    2012-01-01

    Two-well tracer tests are often conducted to investigate subsurface solute transport in the field. Analyzing breakthrough curves in extraction and monitoring wells using numerical methods is nontrivial due to highly nonuniform flow conditions. We extended approximate analytical solutions for the advection-dispersion equation for an injection-extraction well doublet in a homogeneous confined aquifer under steady-state flow conditions for equal injection and extraction rates with no transverse dispersion and negligible ambient flow, and implemented the solutions in Microsoft Excel using Visual Basic for Application (VBA). Functions were implemented to calculate concentrations in extraction and monitoring wells at any location due to a step or pulse injection. Type curves for a step injection were compared with those calculated by numerically integrating the solution for a pulse injection. The results from the two approaches are similar when the dispersivity is small. As the dispersivity increases, the latter was found to be more accurate but requires more computing time. The code was verified by comparing the results with published-type curves and applied to analyze data from the literature. The method can be used as a first approximation for two-well tracer test design and data analysis, and to check accuracy of numerical solutions. The code and example files are publicly available. PMID:21797850

  6. A Microsoft Excel Program for Two-Well Tracer Test Data Analysis

    SciTech Connect

    Tang, Guoping; Watson, David B; Parker, Jack C.; Brooks, Scott C

    2012-01-01

    Two-well tracer tests are often conducted to investigate subsurface solute transport in the field. Analyzing breakthrough curves in the extraction and monitoring wells using numerical methods is nontrivial due to highly nonuniform flow conditions. We extended, and implemented analytical solutions for the convection-dispersion equation for an injection-extraction well-duplet in a homogeneous confined aquifer under steady state conditions. Functions were provided to calculate the concentrations in the extraction and monitoring wells at any location due to a step or pulse injection. Type curves for a step injection were compared with those calculated by numerically integrating the solution for a pulse injection. The results from the two approaches are similar when the dispersivity is small. As the dispersivity increases, the latter was found to be more accurate but requires more computing time. The code was verified by comparing the results with published type curves and applied to analyze data from the literature. It can be used as a first approximation for two-well tracer test data analysis, and to check accuracy of numerical solutions. The code and example files are publically-available.

  7. A Spreadsheet Program for Two-Well Tracer Test Data Analysis

    SciTech Connect

    Tang, Guoping; Watson, David; Parker, Jack C.; Brooks, Scott C

    2011-01-01

    Two-well tracer tests are often conducted to investigate subsurface solute transport in the field. Analyzing breakthrough curves in extraction and monitoring wells using numerical methods is nontrivial due to highly nonuniform flow conditions. We extended approximate analytical solutions for the advection-dispersion equation for an injection-extraction well doublet in a homogeneous confined aquifer under steady-state flow conditions for equal injection and extraction rates with no transverse dispersion and negligible ambient flow, and implemented the solutions in Microsoft Excel using Visual Basic for Application (VBA). Functions were implemented to calculate concentrations in extraction and monitoring wells at any location due to a step or pulse injection. Type curves for a step injection were compared with those calculated by numerically integrating the solution for a pulse injection. The results from the two approaches are similar when the dispersivity is small. As the dispersivity increases, the latter was found to be more accurate but requires more computing time. The code was verified by comparing the results with published-type curves and applied to analyze data from the literature. The method can be used as a first approximation for two-well tracer test design and data analysis, and to check accuracy of numerical solutions. The code and example files are publicly available.

  8. Investigation of tracer and steam tests on the Western Research Institute 150-ton retort

    SciTech Connect

    Turner, T.F.; Moore, D.F.; Merriam, N.W.; Covell, J.R.

    1984-04-01

    Gas tracer and steam front velocities in addition to flow model calculations are used to characterize rubble bed structure in an oil shale retort. The gas tracer method is shown to have superior resolution to the steam front method in detecting rubble bed variations. The tracer method is potentially less expensive. Recommendations for further research are made.

  9. Thermal Gradient Behavior of TBCs Subjected to a Laser Gradient Test Rig: Simulating an Air-to-Air Combat Flight

    NASA Astrophysics Data System (ADS)

    Lima, Rogerio S.; Marple, Basil R.; Marcoux, P.

    2016-01-01

    A computer-controlled laser test rig (using a CO2 laser) offers an interesting alternative to traditional flame-based thermal gradient rigs in evaluating thermal barrier coatings (TBCs). The temperature gradient between the top and back surfaces of a TBC system can be controlled based on the laser power and a forced air back-face cooling system, enabling the temperature history of complete aircraft missions to be simulated. An air plasma spray-deposited TBC was tested and, based on experimental data available in the literature, the temperature gradients across the TBC system (ZrO2-Y2O3 YSZ top coat/CoNiCrAlY bond coat/Inconel 625 substrate) and their respective frequencies during air-to-air combat missions of fighter jets were replicated. The missions included (i) idle/taxi on the runway, (ii) take-off and climbing, (iii) cruise trajectory to rendezvous zone, (iv) air-to-air combat maneuvering, (v) cruise trajectory back to runway, and (vi) idle/taxi after landing. The results show that the TBC thermal gradient experimental data in turbine engines can be replicated in the laser gradient rig, leading to an important tool to better engineer TBCs.

  10. Vadose Zone Tracer Testing in the UK Sherwood Sandstone: Hydrogeophysical Data Report

    SciTech Connect

    Binley, A

    2003-10-08

    In 1998 a joint project between the universities of Lancaster and Leeds, funded by the UK Natural Environment Research Council and the UK Environment Agency, was initiated to examine, using geophysical methods, unsaturated flow and transport processes at two purposely developed field sites in the UK Sherwood Sandstone. More recently work by Lancaster university funded by a UK Natural Environment Research Council PhD studentship (awarded to Peter Winship) has continued the investigation at the two sites. This work, so far, has demonstrated: how cross-borehole (borehole to borehole) radar tomography can be used to monitor changes in moisture content in the unsaturated zone due to natural and forced (tracer) inputs (Binley et al., 2001); the evaluation of seasonal variation of moisture content profiles using high-resolution borehole resistivity and radar profiling (Binley et al., 2002a); initial attempts to utilize the geophysical data to develop numerical predictive models of unsaturated flow (Binley et al., 2002b; Binley et al, 2003; Binley and Beven, 2003). In addition, petrophysical models relating geophysical data to hydrological properties have been developed (West et al., 2003). Here we provide a data report on two tracer experiments conducted at one of the field sites. Within the report we describe the site layout and present summary results from the two tracer tests. In the appendix a file map is provided to allow identification of relevant files in the dataset accompanying this report. The two techniques used here are three-dimensional time-lapse electrical resistivity tomography (ERT) and lime-lapse cross-borehole radar tomography and profiling. They provide geophysical measurements that can be related to the moisture content of the subsurface, and subsequently to the conductivity of that moisture content. They also yield data on a scale that is appropriate for numerical simulations of water movement in the subsurface. The two methods have been applied at a

  11. Evaluation of Floors and Item Gradients for Reading and Math Tests for Young Children

    ERIC Educational Resources Information Center

    Bradley-Johnson, Sharon; Durmusoglu, Gokce

    2005-01-01

    Ignoring the adequacy of floors and item gradients for tests used with young children can have serious consequences. Thus, because of the importance of early intervention for reading and math problems, we used the criteria suggested by Bracken for adequate floors and item gradients, and reviewed 15 reading tests and 12 math tests for ages 4-0…

  12. Gas-partitioning tracer test to quantify trapped gas during recharge

    USGS Publications Warehouse

    Heilweil, V.M.; Solomon, D.K.; Perkins, K.S.; Ellett, K.M.

    2004-01-01

    Dissolved helium and bromide tracers were used to evaluate trapped gas during an infiltration pond experiment. Dissolved helium preferentially partitioned into trapped gas bubbles, or other pore air, because of its low solubility in water. This produced observed helium retardation factors of as much as 12 relative to bromide. Numerical simulations of helium breakthrough with both equilibrium and kinetically limited advection/dispersion/retardation did not match observed helium concentrations. However, better fits were obtained by including a decay term representing the diffusive loss of helium through interconnected, gas-filled pores. Calculations indicate that 7% to more than 26% of the porosity beneath the pond was filled with gas. Measurements of laboratory hydraulic properties indicate that a 10% decrease in saturation would reduce the hydraulic conductivity by at least one order of magnitude in the well-sorted sandstone, but less in the overlying soils. This is consistent with in situ measurements during the experiment, which show steeper hydraulic gradients in sandstone than in soil. Intrinsic permeability of the soil doubled during the first six months of the experiment, likely caused by a combination of dissolution and thermal contraction of trapped gas. Managers of artificial recharge basins may consider minimizing the amount of trapped gas by using wet, rather than dry, tilling to optimize infiltration rates, particularly in well-sorted porous media in which reintroduced trapped gas may cause substantial reductions in permeability. Trapped gas may also inhibit the amount of focused infiltration that occurs naturally during ephemeral flood events along washes and playas.

  13. Using sequential self-calibration method to identify conductivity distribution: Conditioning on tracer test data

    USGS Publications Warehouse

    Hu, B.X.; He, C.

    2008-01-01

    An iterative inverse method, the sequential self-calibration method, is developed for mapping spatial distribution of a hydraulic conductivity field by conditioning on nonreactive tracer breakthrough curves. A streamline-based, semi-analytical simulator is adopted to simulate solute transport in a heterogeneous aquifer. The simulation is used as the forward modeling step. In this study, the hydraulic conductivity is assumed to be a deterministic or random variable. Within the framework of the streamline-based simulator, the efficient semi-analytical method is used to calculate sensitivity coefficients of the solute concentration with respect to the hydraulic conductivity variation. The calculated sensitivities account for spatial correlations between the solute concentration and parameters. The performance of the inverse method is assessed by two synthetic tracer tests conducted in an aquifer with a distinct spatial pattern of heterogeneity. The study results indicate that the developed iterative inverse method is able to identify and reproduce the large-scale heterogeneity pattern of the aquifer given appropriate observation wells in these synthetic cases. ?? International Association for Mathematical Geology 2008.

  14. Study of the effects of the chaser in push-pull tracer tests by using temporal moment analysis

    NASA Astrophysics Data System (ADS)

    Hebig, Klaus; Zeilfelder, Sarah; Ito, Narimitsu; Machida, Isao; Marui, Atsunao; Scheytt, Traugott

    2015-04-01

    "Push-pull" tracer tests are a suitable tracer test method for hydrochemical charac-terization of an aquifer in a single-well setting (e.g. in deep geothermal systems). A known amount of selected solutes as conservative and reactive tracers is injected into the aquifer ("push") and afterwards extracted ("pull"). In many cases, a so-called "chaser", which is just original groundwater without any added solutes, is injected directly after the injection of the test solution. Its objective is to push the test solution out of the bore-hole into the aquifer and therefore to mini-mize the influence of the gravel pack on the shape of the breakthrough curve. The influence of the chaser on the tracer breakthrough curve is unknown so far. Also, the determination of the appropriate volume for the chaser is a difficult task if at all applied. A first experiment was conducted with the objective to compare three push-pull tests with similar injection volumes, two tests with and one without a chaser. Results show that the application of a chaser lowers the main peak concentration. However, it does not alter the tailing of the breakthrough curve nor does it have a negative in-fluence on tracer mass recovery. In a second experiment, a new method was developed to determine the optimal chaser volume by testing seven different chaser injection volumes combined with temporal moment analysis and comparison of the mean residence times of the in-jected tracer fluid. As a result, the application of a chaser is recommended, when reactions of injected solutes within the open well or the gravel pack should be avoided. If a chaser is used, the new method mentioned above can easily be used to determine the required chaser injection volume. The experiments were conducted at the Hamasato test site in Horonobe (Hokkaido, Japan).

  15. Constraining performance assessment models with tracer test results: a comparison between two conceptual models

    NASA Astrophysics Data System (ADS)

    McKenna, Sean A.; Selroos, Jan-Olof

    Tracer tests are conducted to ascertain solute transport parameters of a single rock feature over a 5-m transport pathway. Two different conceptualizations of double-porosity solute transport provide estimates of the tracer breakthrough curves. One of the conceptualizations (single-rate) employs a single effective diffusion coefficient in a matrix with infinite penetration depth. However, the tracer retention between different flow paths can vary as the ratio of flow-wetted surface to flow rate differs between the path lines. The other conceptualization (multirate) employs a continuous distribution of multiple diffusion rate coefficients in a matrix with variable, yet finite, capacity. Application of these two models with the parameters estimated on the tracer test breakthrough curves produces transport results that differ by orders of magnitude in peak concentration and time to peak concentration at the performance assessment (PA) time and length scales (100,000 years and 1,000 m). These differences are examined by calculating the time limits for the diffusive capacity to act as an infinite medium. These limits are compared across both conceptual models and also against characteristic times for diffusion at both the tracer test and PA scales. Additionally, the differences between the models are examined by re-estimating parameters for the multirate model from the traditional double-porosity model results at the PA scale. Results indicate that for each model the amount of the diffusive capacity that acts as an infinite medium over the specified time scale explains the differences between the model results and that tracer tests alone cannot provide reliable estimates of transport parameters for the PA scale. Results of Monte Carlo runs of the transport models with varying travel times and path lengths show consistent results between models and suggest that the variation in flow-wetted surface to flow rate along path lines is insignificant relative to variability in

  16. Diffusive partitioning tracer test for the quantification of nonaqueous phase liquid (NAPL) in the vadose zone: Performance evaluation for heterogeneous NAPL distribution

    NASA Astrophysics Data System (ADS)

    Werner, David; Karapanagioti, Hrissi K.; Höhener, Patrick

    2009-08-01

    A partitioning tracer test based on gas-phase diffusion in the vadose zone yields estimates of the residual nonaqueous phase liquid (NAPL) saturation. The present paper investigates this technique further by studying diffusive tracer breakthrough curves in the vadose zone for a heterogeneous NAPL distribution. Tracer experiments were performed in a lysimeter with a horizontal layer of artificial kerosene embedded in unsaturated sand. Tracer disappearance curves at the injection point and tracer breakthrough curves at some distance from the injection point were measured inside and outside of the NAPL layer. A numerical code was used to generate independent model predictions based on the physicochemical sand, NAPL, and tracer properties. The measured and modeled tracer breakthrough curves were in good agreement confirming the validity of important modeling assumptions such as negligible sorption of chlorofluorocarbon (CFC) tracers to the uncontaminated sand and their fast reversible partitioning between the soil air and the NAPL phase. Subsequently, the model was used to investigate different configurations of NAPL contamination. The experimental and model results show that the tracer disappearance curves of a single-well diffusive partitioning tracer test (DPTT) are dominated by the near-field presence of NAPL around the tip of the soil gas probe. In contrast, breakthrough curves of inter-well tracer tests reflect the NAPL saturation in between the probes, although there is no unique interpretation of the tracer signals if the NAPL distribution is heterogeneous. Numerical modeling is useful for the planning of a DPTT application. Simulations suggest that several cubic meters of soil can be investigated with a single inter-well partitioning tracer test of 24-hour duration by placing the injection point in the center of the investigated soil volume and probes at up to 1 m distance for the monitoring of gaseous tracers.

  17. Gas-partitioning tracer test to quantify trapped gas during recharge.

    PubMed

    Heilweil, Victor M; Solomon, D Kip; Perkins, Kim S; Ellett, Kevin M

    2004-01-01

    Dissolved helium and bromide tracers were used to evaluate trapped gas during an infiltration pond experiment. Dissolved helium preferentially partitioned into trapped gas bubbles, or other pore air, because of its low solubility in water. This produced observed helium retardation factors of as much as 12 relative to bromide. Numerical simulations of helium breakthrough with both equilibrium and kinetically limited advection/dispersion/retardation did not match observed helium concentrations. However, better fits were obtained by including a decay term representing the diffusive loss of helium through interconnected, gas-filled pores. Calculations indicate that 7% to more than 26% of the porosity beneath the pond was filled with gas. Measurements of laboratory hydraulic properties indicate that a 10% decrease in saturation would reduce the hydraulic conductivity by at least one order of magnitude in the well-sorted sandstone, but less in the overlying soils. This is consistent with in situ measurements during the experiment, which show steeper hydraulic gradients in sandstone than in soil. Intrinsic permeability of the soil doubled during the first six months of the experiment, likely caused by a combination of dissolution and thermal contraction of trapped gas. Managers of artificial recharge basins may consider minimizing the amount of trapped gas by using wet, rather than dry, tilling to optimize infiltration rates, particularly in well-sorted porous media in which reintroduced trapped gas may cause substantial reductions in permeability. Trapped gas may also inhibit the amount of focused infiltration that occurs naturally during ephemeral flood events along washes and playas. PMID:15318781

  18. Delineation of Groundwater Flow Pathway in Fractured Bedrock Using Nano-Iron Tracer Test in the Sealed Well

    NASA Astrophysics Data System (ADS)

    Chuang, Po-Yu; Chia, Yeeping; Chiu, Yung-Chia; Liou, Ya-Hsuan; Teng, Mao-Hua; Liu, Ching-Yi; Lee, Tsai-Ping

    2016-04-01

    Deterministic delineation of the preferential flow paths and their hydraulic properties are desirable for developing hydrogeological conceptual models in bedrock aquifers. In this study, we proposed using nanoscale zero-valent iron (nZVI) as a tracer to characterize the fractured connectivity and hydraulic properties. Since nZVI particles are magnetic, we designed a magnet array to attract the arriving nZVI particles in the observation well for identifying the location of incoming tracer. This novel approach was examined at two experiment wells with well hydraulic connectivity in a hydrogeological research station in the fractured aquifer. Heat-pulse flowmeter test was used to detect the vertical distribution of permeable zones in the borehole, providing the design basis of tracer test. Then, the less permeable zones in the injection well were sealed by casing to prevent the injected nZVI particles from being stagnated at the bottom hole. Afterwards, hydraulic test was implemented to examine the hydraulic connectivity between two wells. When nZVI slurry was released in the injection well, they could migrate through connected permeable fractures to the observation well. A breakthrough curve was obtained by the fluid conductivity sensor in the observation well, indicating the arrival of nZVI slurry. The iron nanoparticles that were attracted to the magnets in the observation well provide the quantitative information to locate the position of tracer inlet, which corroborates well with the depth of a permeable zone delineated by the flowmeter. Finally, the numerical method was utilized to simulate the process of tracer migration. This article demonstrates that nano-iron tracer test can be a promising approach for characterizing connectivity patterns and transmissivities of the flow paths in the fractured rock.

  19. INL Tracer Interpretation

    Energy Science and Technology Software Center (ESTSC)

    2007-03-27

    This spreadsheet application is for tracer test analysis. The analyses are based on the first temporal moment of a tracer. The governing equations are briefly discussed, and the individual steps required of the user are outlined. A series of Excel macros written in Visual Basic calculate mean residence time, swept pore volume, and flow-storage geometry from a tracer history.

  20. Methodology, results, and significance of an unsaturated-zone tracer test at an artificial-recharge facility, Tucson, Arizona

    USGS Publications Warehouse

    Graham, D.D.

    1989-01-01

    A tracer test conducted in 1987 at an artificial-recharge facility in Tucson, Arizona, indicates that solute movement through the poorly sorted stratified alluvial sediments in the unsaturated zone beneath a recharge basin takes place along preferential-flow paths. Movement of a tracer-laced pulse of reclaimed wastewater was monitored using pressure-vacuum lysimeters installed at depths that range from 11 to 45 ft below the bottom of the recharge basin. Tracer-breakthrough curves do not indicate a consistent relation between maximum tracer concentration and depth or between time of tracer breakthrough and depth. Apparent dispersion, as indicated by the slope of the rising leg of the tracer-breakthrough curve, shows no apparent relation with depth. In some cases, the tracer arrived earlier at deep sampling locations than at shallow ones. Velocity of solute flow ranged from 1.9 to 9.0 ft/day. Less interaction between recharge water and solid-phase materials in the unsaturated zone occurs under preferential-flow conditions than if flow occurred as a uniform wetting front. Flow of water through the unsaturated zone is concentrated into fingers or channels under preferential-flow conditions, and the renovating capability of soil is reduced because of the reduced surface area and reduced contact time in the biologically active part of the unsaturated profile. Chemical substances that normally would be decomposed by microbial activity or sorbed by sediment particles can move through the unsaturated zone and cause groundwater contamination under preferential-flow conditions. (USGS)

  1. Phenols and hydroxy-PAHs (arylphenols) as tracers for coal smoke particulate matter: source tests and ambient aerosol assessments

    SciTech Connect

    Bernd R.T. Simoneit; Xinhui Bi; Daniel R. Oros; Patricia M. Medeiros; Guoying Sheng; Jiamo Fu

    2007-11-01

    Source tests were conducted to analyze and characterize diagnostic key tracers for emissions from burning of coals with various ranks. Coal samples included lignite from Germany, semibituminous coal from Arizona, USA, bituminous coal from Wales, UK and sample from briquettes of semibituminous coal, bituminous coal and anthracite from China. Ambient aerosol particulate matter was also collected in three areas of China and a background area in Corvallis, OR (U.S.) to confirm the presence of tracers specific for coal smoke. The results showed a series of aliphatic and aromatic hydrocarbons and phenolic compounds, including PAHs and hydroxy-PAHs as the major tracers, as well as a significant unresolved complex mixture (UCM) of compounds. The tracers that were found characteristic of coal combustion processes included hydroxy-PAHs and PAHs. Atmospheric ambient samples from Beijing and Taiyuan, cities where coal is burned in northern China, revealed that the hydroxy-PAH tracers were present during the wintertime, but not in cities where coal is not commonly used (e.g., Guangzhou, South China). Thus, the mass of hydroxy-PAHs can be apportioned to coal smoke and the source strength modeled by summing the proportional contents of EC (elemental carbon), PAHs, UCM and alkanes with the hydroxy-PAHs. 36 refs., 2 figs., 3 tabs.

  2. Dye Tracer Tests to Determine Time-of-Travel in Iowa Streams, 1990-2006

    USGS Publications Warehouse

    Christiansen, Daniel E.

    2009-01-01

    Dye-tracing tests have been used by the U.S. Geological Survey, Iowa Water Science Center to determine the time-of-travel in selected Iowa streams from 1990-2006. Time-of-travel data are tabulated for 309 miles of stream reaches in four Iowa drainage basins: the Des Moines, Raccoon, Cedar, and Turkey Rivers. Time-of-travel was estimated in the Des Moines River, Fourmile Creek, North Raccoon River, Raccoon River, Cedar River, and Roberts Creek. Estimation of time-of-travel is important for environmental studies and in determining fate of agricultural constituents and chemical movement through a waterway. The stream reaches range in length from slightly more than 5 miles on Fourmile Creek, to more than 137 miles on the North Raccoon River. The travel times during the dye-tracer tests ranged from 7.5 hours on Fourmile Creek to as long as 200 hours on Roberts Creek; velocities ranged from less than 4.50 feet per minute on Roberts Creek to more than 113 feet per minute on the Cedar River.

  3. Validation studies of tracer tests in a fracture zone at the Finnsjön research area

    NASA Astrophysics Data System (ADS)

    Kimura, Hideo; Munakata, Masahiro

    Tracer experiments were performed in a fracture zone, extending several hundred metres, in crystalline rock in Sweden. This paper describes modellings of tracer experiments (radially converging and dipole test) and their numerical results. We have applied a variable aperture channeling model to both tracer tests and evaluated steady-state channel flows in the fracture zone. Solute transport in the channel flows was simulated by a particle-tracking technique considering matrix diffusion. Calculated breakthrough curves and pressures were compared with experimental ones. The calculated breakthrough curve obtained by an equivalen porous medium model was also compared with data from the dipole experiment. Our models seem to explain the experimental results well, but some important assumptions are necessary for calibration of the breakthrough curves. Further experimental data related to the assumptions and geostatistics would be needed for the full validation of the flow and transport model. Study shows that the mean apertures of fractures calibrated with the tracer tests increase with increasing flow rates.

  4. Use of Time-lapse Mise-á-la-Masse Measurements to Monitor a Saline Tracer Test: Advantages and Limitations.

    NASA Astrophysics Data System (ADS)

    Perri, M. T.; De Vita, P.; Cassiani, G.; Masciale, R.; Portoghese, I.; Chirico, G. B.

    2015-12-01

    This work presents the results of a saline tracer test conducted on an alluvial aquifer placed in the Alento River Valley (Campania region, Southern Italy) and monitored by time-lapse Mise-á-la-Masse measurements. The principal aim of this study is the characterization of the groundwater flow field, both in velocity and direction. The results of the geophysical survey are described and compared to several simulated datasets conducted on a 3D model simulating flow, transport and electrical current. In this manner it is possible to assess the information content of the Mise-á-la-Masse dataset with respect to the groundwater field characteristics. The study shows how a combination of three-dimensional time-lapse modelling of flow, tracer transport and electrical current can substantially contribute towards a quantitative interpretation of Mise-á-la-Masse measurements during saline tracer tests. This approach can thus revive the use of Mise-á-la-Masse as a practical, low cost field technique for tracer test monitoring, particularly for shallow aquifers, providing critical information concerning the natural groundwater flow direction and velocity.

  5. Measured Air-Water and Napl-Water Interfacial Areas for Sandy Porous Media: Comparing X-Ray Microtomography and Partitioning Tracer Test Methods

    NASA Astrophysics Data System (ADS)

    Brusseau, M.; Schnaar, G.; Murao, A.; Sheng, P.

    2006-12-01

    Water-NAPL and water-air interfacial areas were measured for sandy, natural porous media using two methods, partitioning tracer tests and synchrotron X-ray microtomography. The tracer-test method provides a measure of effective total (capillary and film) interfacial area, whereas microtomography can be used to determine both capillary-associated and total areas. The areas measured with the tracer-test method were similar to previously reported values. The areas measured with the microtomography method were similar to values obtained from a previously reported computational-based analysis. The areas obtained with the tracer- test method were significantly larger than those obtained from microtomography. The disparity between the tracer-test and microtomography values is attributed to the inability of the microtomography method to resolve interfacial area associated with microscopic surface heterogeneity.

  6. Atmospheric tracer monitoring and surface plume development at the ZERT pilot test in Bozeman, Montana, USA

    SciTech Connect

    Wells, Arthur; Strazisar, Brian; Rodney Diehl, J.; Veloski, Garret

    2010-03-01

    A controlled release of CO2 was conducted at a field site in Bozeman, Montana, USA in July of 2008 in a multi-laboratory study of near surface transport and detection technologies. The development of a subsurface CO2 plume near the middle packer section of the horizontal release was studied using soil-gas and surface flux measurements of CO2. A perfluorocarbon tracer was added to the CO2 released from this section of the horizontal well, and the development of atmospheric plumes of the tracer was studied under various meteorological conditions using horizontal and vertical grids of monitors containing sorbent material to collect the tracer. This study demonstrated the feasibility of using remote sensing for the ultra low level detection of atmospheric plumes of tracers as means to monitor the near surface leakage of sequestered CO2.

  7. Biodegradation of the surfactant linear alkylbenzenesulfonate in sewage- contaminated groundwater: A comparison of column experiments and field tracer tests

    USGS Publications Warehouse

    Krueger, C.J.; Radakovich, K.M.; Sawyer, T.E.; Barber, L.B.; Smith, R.L.; Field, J.A.

    1998-01-01

    Transport and biodegradation of linear alkylbenzenesulfonate (LAS) in sewage-contaminated groundwater were investigated for a range of dissolved oxygen concentrations. Both laboratory column and an 80-day continuous injection tracer test field experiments were conducted. The rates of LAS biodegradation increased with increasing dissolved oxygen concentrations and indicated the preferential biodegradation of the longer alkyl chain LAS homologues (i.e., C12 and C13) and external isomers (i.e., 2-and 3- phenyl). However, for similar dissolved oxygen concentrations, mass removal rates for LAS generally were 2-3 times greater in laboratory column experiments than in the field tracer test. Under low oxygen conditions (<1 mg/L) only a fraction of the LAS mixture biodegraded in both laboratory and field experiments. Biodegradation rate constants for the continuous injection field test (0.002-0.08 day-1) were comparable to those estimated for a 3-h injection (pulsed) tracer test conducted under similar biogeochemical conditions, indicating that increasing the exposure time of aquifer sediments to LAS did not increase biodegradation rates.Transport and biodegradation of linear alkylbenzenesulfonate (LAS) in sewage-contaminated groundwater were investigated for a range of dissolved oxygen concentrations. Both laboratory column and an 80-day continuous injection tracer test field experiments were conducted. The rates of LAS biodegradation increased with increasing dissolved oxygen concentrations and indicated the preferential biodegradation of the longer alkyl chain LAS homologues (i.e., C12 and C13) and external isomers (i.e., 2- and 3-phenyl). However, for similar dissolved oxygen concentrations, mass removal rates for LAS generally were 2-3 times greater in laboratory column experiments than in the field tracer test. Under low oxygen conditions (<1 mg/L) only a fraction of the LAS mixture biodegraded in both laboratory and field experiments. Biodegradation rate constants

  8. Transport properties of iodide in a sandy aquifer: Hydrogeological modelling and field tracer tests

    NASA Astrophysics Data System (ADS)

    Razafindratsima, Stephen; Péron, Olivier; Piscitelli, Anne; Gégout, Claire; Schneider, Vincent; Barbecot, Florent; Giffaut, Eric; Robinet, Jean-Charles; Le Cointe, Pierre; Montavon, Gilles

    2015-01-01

    The release of radioactive iodine into geological media from nuclear waste disposal is an issue that has to be considered since iodine is a biophilic element. 129I is, with 99Tc, one of the two long-lived radionuclides that have the highest mobility in radioactive waste disposal. Within this context, iodide retardation is still a matter of debate. A low value of the retardation factor is generally accepted in soils without organic matter, but the possibility for sorption cannot be completely ruled out. Since isotopic exchange with naturally occurring iodine is one of the main potential sorption mechanisms, site-specific retention parameters are needed. In the present paper, we study iodide transport in a sandy aquifer. A hydrogeological model was built to fit deuterium, bromide and iodide breakthrough data from in situ tracer test experiments. Within the precision range of the fitting, iodide is excluded from 2.5% of the effective porosity by anionic exclusion and presents a field retention factor (Kd) lower than 0.025 L/kg.

  9. Characterization of preferential flow paths between boreholes in fractured rock using a nanoscale zero-valent iron tracer test

    NASA Astrophysics Data System (ADS)

    Chuang, Po-Yu; Chia, Yeeping; Liou, Ya-Hsuan; Teng, Mao-Hua; Liu, Ching-Yi; Lee, Tsai-Ping

    2016-05-01

    Recent advances in borehole geophysical techniques have improved characterization of cross-hole fracture flow. The direct detection of preferential flow paths in fractured rock, however, remains to be resolved. In this study, a novel approach using nanoscale zero-valent iron (nZVI or `nano-iron') as a tracer was developed for detecting fracture flow paths directly. Generally, only a few rock fractures are permeable while most are much less permeable. A heat-pulse flowmeter can be used to detect changes in flow velocity for delineating permeable fracture zones in the borehole and providing the design basis for the tracer test. When nano-iron particles are released in an injection well, they can migrate through the connecting permeable fracture and be attracted to a magnet array when arriving in an observation well. Such an attraction of incoming iron nanoparticles by the magnet can provide quantitative information for locating the position of the tracer inlet. A series of field experiments were conducted in two wells in fractured rock at a hydrogeological research station in Taiwan, to test the cross-hole migration of the nano-iron tracer through permeable connected fractures. The fluid conductivity recorded in the observation well confirmed the arrival of the injected nano-iron slurry. All of the iron nanoparticles attracted to the magnet array in the observation well were found at the depth of a permeable fracture zone delineated by the flowmeter. This study has demonstrated that integrating the nano-iron tracer test with flowmeter measurement has the potential to characterize preferential flow paths in fractured rock.

  10. TESTING FOR AZIMUTHAL ABUNDANCE GRADIENTS IN M101

    SciTech Connect

    Li, Yanxia; Bresolin, Fabio; Kennicutt, Robert C. Jr.

    2013-03-20

    New optical spectra of 28 H II regions in the M101 disk have been obtained, yielding 10 new detections of the [O III] {lambda}4363 auroral line. The oxygen abundance gradient measured from these data, combined with previous observations, displays a local scatter of 0.15 {+-} 0.03 dex along an arc in the west side of the galaxy, compared with a smaller scatter of 0.08 {+-} 0.01 dex in the rest of the disk. One of the H II regions in our sample (H27) has a significantly lower oxygen abundance than surrounding nebulae at a similar galactocentric distance, while an additional, relatively nearby one (H128) was already known to have a high oxygen abundance for its position in the galaxy. These results represent marginal evidence for the existence of moderate deviations from chemical abundance homogeneity in the interstellar medium of M101. Using a variety of strong-line abundance indicators, we find no evidence for significant large-scale azimuthal variations of the oxygen abundance across the whole disk of the galaxy.

  11. Assessment of local hydraulic properties from electrical resistivity tomography monitoring of a three-dimensional synthetic tracer test experiment

    NASA Astrophysics Data System (ADS)

    Camporese, M.; Cassiani, G.; Deiana, R.; Salandin, P.

    2011-12-01

    In recent years geophysical methods have become increasingly popular for hydrological applications. Time-lapse electrical resistivity tomography (ERT) represents a potentially powerful tool for subsurface solute transport characterization since a full picture of the spatiotemporal evolution of the process can be obtained. However, the quantitative interpretation of tracer tests is difficult because of the uncertainty related to the geoelectrical inversion, the constitutive models linking geophysical and hydrological quantities, and the a priori unknown heterogeneous properties of natural formations. Here an approach based on the Lagrangian formulation of transport and the ensemble Kalman filter (EnKF) data assimilation technique is applied to assess the spatial distribution of hydraulic conductivity K by incorporating time-lapse cross-hole ERT data. Electrical data consist of three-dimensional cross-hole ERT images generated for a synthetic tracer test in a heterogeneous aquifer. Under the assumption that the solute spreads as a passive tracer, for high Peclet numbers the spatial moments of the evolving plume are dominated by the spatial distribution of the hydraulic conductivity. The assimilation of the electrical conductivity 4D images allows updating of the hydrological state as well as the spatial distribution of K. Thus, delineation of the tracer plume and estimation of the local aquifer heterogeneity can be achieved at the same time by means of this interpretation of time-lapse electrical images from tracer tests. We assess the impact on the performance of the hydrological inversion of (i) the uncertainty inherently affecting ERT inversions in terms of tracer concentration and (ii) the choice of the prior statistics of K. Our findings show that realistic ERT images can be integrated into a hydrological model even within an uncoupled inverse modeling framework. The reconstruction of the hydraulic conductivity spatial distribution is satisfactory in the portion

  12. An analytical model for solute transport in an infiltration tracer test in soil with a shallow groundwater table

    NASA Astrophysics Data System (ADS)

    Liang, Ching-Ping; Hsu, Shao-Yiu; Chen, Jui-Sheng

    2016-09-01

    It is recommended that an in-situ infiltration tracer test is considered for simultaneously determining the longitudinal and transverse dispersion coefficients in soil. Analytical solutions have been derived for two-dimensional advective-dispersive transport in a radial geometry in the literature which can be used for interpreting the result of such a tracer test. However, these solutions were developed for a transport domain with an unbounded-radial extent and an infinite thickness of vadose zone which might not be realistically manifested in the actual solute transport during a field infiltration tracer test. Especially, the assumption of infinite thickness of vadose zone should be invalid for infiltration tracer tests conducted in soil with a shallow groundwater table. This paper describes an analytical model for interpreting the results of an infiltration tracer test based on improving the transport domain with a bounded-radial extent and a finite thickness of vadose zone. The analytical model is obtained with the successive application of appropriate integral transforms and their corresponding inverse transforms. A comparison of the newly derived analytical solution against the previous analytical solutions in which two distinct sets of radial extent and thickness of vadose zone are considered is conducted to determine the influence of the radial and exit boundary conditions on the solute transport. The results shows that both the radial and exit boundary conditions substantially affect the trailing segment of the breakthrough curves for a soil medium with large dispersion coefficients. Previous solutions derived for a transport domain with an unbounded-radial and an infinite thickness of vadose zone boundary conditions give lower concentration predictions compared with the proposed solution at late times. Moreover, the differences between two solutions are amplified when the observation positions are near the groundwater table. In addition, we compare our

  13. On the late-time behavior of tracer test breakthrough curves

    SciTech Connect

    HAGGERTY,ROY; MCKENNA,SEAN A.; MEIGS,LUCY C.

    2000-06-12

    The authors investigated the late-time (asymptotic) behavior of tracer test breakthrough curves (BTCs) with rate-limited mass transfer (e.g., in dual or multi-porosity systems) and found that the late-time concentration, c, is given by the simple expression: c = t{sub ad} (c{sub 0}g {minus} m{sub 0}{partial_derivative}g/{partial_derivative}t), for t >> t{sub ad} and t{sub a} >> t{sub ad} where t{sub ad} is the advection time, c{sub 0} is the initial concentration in the medium, m{sub 0} is the 0th moment of the injection pulse; and t{sub a} is the mean residence time in the immobile domain (i.e., the characteristic mass transfer time). The function g is proportional to the residence time distribution in the immobile domain, the authors tabulate g for many geometries, including several distributed (multirate) models of mass transfer. Using this expression they examine the behavior of late-time concentration for a number of mass transfer models. One key results is that if rate-limited mass transfer causes the BTC to behave as a power-law at late-time (i.e., c {approximately} t{sup {minus}k}), then the underlying density function of rate coefficients must also be a power-law with the form a{sup k{minus}}, as a {r_arrow}0. This is true for both density functions of first-order and diffusion rate coefficients. BTCs with k < 3 persisting to the end of the experiment indicate a mean residence time longer than the experiment and possibly infinite, and also suggest an effective rate coefficient that is either undefined or changes as a function of observation time. They apply their analysis to breakthrough curves from Single-Well Injection-Withdrawal tests at the Waste Isolation Pilot Plant, New Mexico.

  14. The anomaly in a breakthrough curve of a single well "push-pull" tracer test: A density driven effect?

    NASA Astrophysics Data System (ADS)

    Zeilfelder, Sarah; Hebig, Klaus; Ito, Narimitsu; Machida, Isao; Scheytt, Traugott; Marui, Atsunao

    2013-04-01

    What method is appropriate to investigate an aquifer when there is only one well available? A single well "push-pull" tracer test (PP Test) may be a suitable method in order to characterize an aquifer and to obtain information about the hydraulic and chemical properties when only one well is available for the investigations. In a PP test, a test solution that contains a known amount of solutes and a conservative tracer is injected into the aquifer ("push") and extracted afterwards ("pull"). Optionally, the test solution is flushed out of the well and the casing with untreated test solution with a so called "chaser" before being extracted. Also between the injection and the extraction phase a drifting time may be included. The breakthrough of the tracer during the extraction phase is measured and used for analyses and interpretation. In the last three years, several PP Test campaigns were conducted at two different test sites in Japan (Hebig et al. 2011, Zeilfelder et al. 2012). The aim was to investigate the applicability of the PP Test method in different geological settings and in different types of aquifers. The latest field campaign thus focussed on the question how variations of the setup are influencing the breakthrough curve of the PP Test in order to develop and enhance this method. Also the standardization of the PP Test was an aim of this study. During the campaign, a total of seven PP Tests were performed, while only single aspects of the setup were varied from test to test. The tests differed in injection and extraction rate, in the salinity of the injected test solution and in the use of a chaser solution. The general shapes of the breakthrough curves were similar and conclusions about the repeatability of the PP Test could be drawn. However, a sharp anomaly was observed in the breakthrough curve of one specific setup type. By repeating this PP test under the same boundary conditions, we were able to recreate the anomaly and could exclude any technical

  15. Constraining performance assessment models with tracer test results: a comparison between two conceptual models

    NASA Astrophysics Data System (ADS)

    McKenna, Sean A.; Selroos, Jan-Olof

    Tracer tests are conducted to ascertain solute transport parameters of a single rock feature over a 5-m transport pathway. Two different conceptualizations of double-porosity solute transport provide estimates of the tracer breakthrough curves. One of the conceptualizations (single-rate) employs a single effective diffusion coefficient in a matrix with infinite penetration depth. However, the tracer retention between different flow paths can vary as the ratio of flow-wetted surface to flow rate differs between the path lines. The other conceptualization (multirate) employs a continuous distribution of multiple diffusion rate coefficients in a matrix with variable, yet finite, capacity. Application of these two models with the parameters estimated on the tracer test breakthrough curves produces transport results that differ by orders of magnitude in peak concentration and time to peak concentration at the performance assessment (PA) time and length scales (100,000 years and 1,000 m). These differences are examined by calculating the time limits for the diffusive capacity to act as an infinite medium. These limits are compared across both conceptual models and also against characteristic times for diffusion at both the tracer test and PA scales. Additionally, the differences between the models are examined by re-estimating parameters for the multirate model from the traditional double-porosity model results at the PA scale. Results indicate that for each model the amount of the diffusive capacity that acts as an infinite medium over the specified time scale explains the differences between the model results and that tracer tests alone cannot provide reliable estimates of transport parameters for the PA scale. Results of Monte Carlo runs of the transport models with varying travel times and path lengths show consistent results between models and suggest that the variation in flow-wetted surface to flow rate along path lines is insignificant relative to variability in

  16. Assessment of transport parameters in a karst system under various flow periods through extensive analysis of artificial tracer tests

    NASA Astrophysics Data System (ADS)

    Doummar, J.; Margane, A.; Sauter, M.; Geyer, T.

    2012-04-01

    It is primordial to understand the sensibility of a catchment or a spring against contamination to secure a sustainable water resource management in karst aquifers. Artificial tracer tests have proven to be excellent tools for the simulation of contaminant transport within an aquifer before its arrival at a karst spring as they provide information about transit times, dispersivities and therefore insights into the vulnerability of a water body against contamination (Geyer et al. 2007). For this purpose, extensive analysis of artificial tracer tests was undertaken in the following work, in order to acquire conservative transport parameters along fast and slow pathways in a mature karst system under various flow conditions. In the framework of the project "Protection of Jeita Spring" (BGR), about 30 tracer tests were conducted on the catchment area of the Jeita spring in Lebanon (Q= 1 to 20 m3/s) under various flow conditions and with different injection points (dolines, sinkholes, subsurface, and underground channel). Tracer breakthrough curves (TBC) observed at karst springs and in the conduit system were analyzed using the two-region non-equilibrium approach (2NREM) (Toride & van Genuchten 1999). The approach accounts for the skewness in the TBCs long tailings, which cannot be described with one dimensional advective-dispersive transport models (Geyer et al. 2007). Relationships between the modeling parameters estimated from the TBC were established under various flow periods. Rating curves for velocity and discharge show that the flow velocity increases with spring discharge. The calibrated portion of the immobile region in the conduit system is relatively low. Estimated longitudinal dispersivities in the conduit system range between 7 and 10 m in high flow periods and decreases linearly with increasing flow. In low flow periods, this relationship doesn't hold true as longitudinal dispersivities range randomly between 4 and 7 m. The longitudinal dispersivity

  17. Database dictionary for the results of groundwater tracer tests using tritiated water, conducted at the Oak Ridge National Laboratory

    SciTech Connect

    Thompson, B.K.; Huff, D.D.

    1997-05-01

    In 1977, the United States Geological Survey (USGS) conducted two tracer tests at the Oak Ridge National Laboratory (ORNL) using tritiated water to study the relative importance of bedding-plane openings on shallow groundwater flow. Through a cooperative agreement between the USGS and the US Department of Energy (DOE), the data were made available to researchers at the Oak Ridge National Laboratory (ORNL), who organized the data into a data management format. The results of these groundwater tracer tests have been compiled into a collection of four SAS data sets. This report documents these SAS data sets, including their structure, methodology, and content. The SAS data sets include information on precipitation, tritium, water levels, and well construction for wells at or near ORNL radioactive waste burial grounds 4, 5, and 6.

  18. The NPE gas tracer test and the development of on-site inspection techniques

    SciTech Connect

    Carrigan, Charles; Heinle, Ray; Zucca, J. J.

    1995-04-13

    Tracer gases emplaced in or near the detonation cavity of the 1-kiloton NonProliferation Event required 1.5 and 13.5 months for sulfur hexaflouride and helium-3, respectively, to reach the surface of Rainier Mesa from an emplacement depth of 400 meters. The sites that first produced tracer gases are those located in known faults and fractures. Numerical modeling suggests that transport to the surface is accomplished within this time frame through atmospheric pumping along high permeability pathways such as fractures. The difference in travel time between the two tracers is due to differences in gas diffusivity and can also be explained by our numerical modeling. 2 refs, 3 figs

  19. Testing mixing models of old and young groundwater in a tropical lowland rain forest with environmental tracers

    NASA Astrophysics Data System (ADS)

    Solomon, D. Kip; Genereux, David P.; Plummer, L. Niel; Busenberg, Eurybiades

    2010-04-01

    We tested three models of mixing between old interbasin groundwater flow (IGF) and young, locally derived groundwater in a lowland rain forest in Costa Rica using a large suite of environmental tracers. We focus on the young fraction of water using the transient tracers CFC-11, CFC-12, CFC-113, SF6, 3H, and bomb 14C. We measured 3He, but 3H/3He dating is generally problematic due to the presence of mantle 3He. Because of their unique concentration histories in the atmosphere, combinations of transient tracers are sensitive not only to subsurface travel times but also to mixing between waters having different travel times. Samples fall into three distinct categories: (1) young waters that plot along a piston flow line, (2) old samples that have near-zero concentrations of the transient tracers, and (3) mixtures of 1 and 2. We have modeled the concentrations of the transient tracers using (1) a binary mixing model (BMM) of old and young water with the young fraction transported via piston flow, (2) an exponential mixing model (EMM) with a distribution of groundwater travel times characterized by a mean value, and (3) an exponential mixing model for the young fraction followed by binary mixing with an old fraction (EMM/BMM). In spite of the mathematical differences in the mixing models, they all lead to a similar conceptual model of young (0 to 10 year) groundwater that is locally derived mixing with old (>1000 years) groundwater that is recharged beyond the surface water boundary of the system.

  20. Testing mixing models of old and young groundwater in a tropical lowland rain forest with environmental tracers

    USGS Publications Warehouse

    Solomon, D. Kip; Genereux, David P.; Plummer, L. Niel; Busenberg, Eurybiades

    2010-01-01

    We tested three models of mixing between old interbasin groundwater flow (IGF) and young, locally derived groundwater in a lowland rain forest in Costa Rica using a large suite of environmental tracers. We focus on the young fraction of water using the transient tracers CFC-11, CFC-12, CFC-113, SF6, 3H, and bomb 14C. We measured 3He, but 3H/3He dating is generally problematic due to the presence of mantle 3He. Because of their unique concentration histories in the atmosphere, combinations of transient tracers are sensitive not only to subsurface travel times but also to mixing between waters having different travel times. Samples fall into three distinct categories: (1) young waters that plot along a piston flow line, (2) old samples that have near-zero concentrations of the transient tracers, and (3) mixtures of 1 and 2. We have modeled the concentrations of the transient tracers using (1) a binary mixing model (BMM) of old and young water with the young fraction transported via piston flow, (2) an exponential mixing model (EMM) with a distribution of groundwater travel times characterized by a mean value, and (3) an exponential mixing model for the young fraction followed by binary mixing with an old fraction (EMM/BMM). In spite of the mathematical differences in the mixing models, they all lead to a similar conceptual model of young (0 to 10 year) groundwater that is locally derived mixing with old (>1000 years) groundwater that is recharged beyond the surface water boundary of the system.

  1. Interpretation of tracer tests performed in fractured rock of the Lange Bramke basin, Germany

    NASA Astrophysics Data System (ADS)

    Maloszewski, Piotr; Herrmann, Andreas; Zuber, Andrzej

    Two multitracer tests performed in one of the major cross-fault zones of the Lange Bramke basin (Harz Mountains, Germany) confirm the dominant role of the fault zone in groundwater flow and solute transport. Tracers having different coefficients of molecular diffusion (deuterium, bromide, uranine, and eosine) yielded breakthrough curves that can only be explained by a model that couples the advective-dispersive transport in the fractures with the molecular diffusion exchange in the matrix. For the scale of the tests (maximum distance of 225m), an approximation was used in which the influence of adjacent fractures is neglected. That model yielded nearly the same rock and transport parameters for each tracer, which means that the single-fracture approximation is acceptable and that matrix diffusion plays an important role. The hydraulic conductivity of the fault zone obtained from the tracer tests is about 1.5×10-2m/s, whereas the regional hydraulic conductivity of the fractured rock mass is about 3×10-7m/s, as estimated from the tritium age and the matrix porosity of about 2%. These values show that the hydraulic conductivity along the fault is several orders of magnitude larger than that of the remaining fractured part of the aquifer, which confirms the dominant role of the fault zones as collectors of water and conductors of fast flow. Résumé Deux multitraçages ont été réalisés dans l'une des zones principales de failles du bassin de Lange Bramke (massif du Harz, Allemagne); les résultats confirment le rôle prédominant de la zone de failles pour l'écoulement souterrain et le transport de soluté. Les traceurs, possédant des coefficients de diffusion différents (deutérium, bromure, uranine et éosine), ont fourni des courbes de restitution qui ne peuvent être expliquées que par un modèle qui associe un transport advectif-dispersif dans les fractures à un échange par diffusion moléculaire dans la matrice. A l'échelle des expériences (distance

  2. Interpretation of tracer tests performed in fractured rock of the Lange Bramke basin, Germany

    NASA Astrophysics Data System (ADS)

    Maloszewski, Piotr; Herrmann, Andreas; Zuber, Andrzej

    Two multitracer tests performed in one of the major cross-fault zones of the Lange Bramke basin (Harz Mountains, Germany) confirm the dominant role of the fault zone in groundwater flow and solute transport. Tracers having different coefficients of molecular diffusion (deuterium, bromide, uranine, and eosine) yielded breakthrough curves that can only be explained by a model that couples the advective-dispersive transport in the fractures with the molecular diffusion exchange in the matrix. For the scale of the tests (maximum distance of 225m), an approximation was used in which the influence of adjacent fractures is neglected. That model yielded nearly the same rock and transport parameters for each tracer, which means that the single-fracture approximation is acceptable and that matrix diffusion plays an important role. The hydraulic conductivity of the fault zone obtained from the tracer tests is about 1.5×10-2m/s, whereas the regional hydraulic conductivity of the fractured rock mass is about 3×10-7m/s, as estimated from the tritium age and the matrix porosity of about 2%. These values show that the hydraulic conductivity along the fault is several orders of magnitude larger than that of the remaining fractured part of the aquifer, which confirms the dominant role of the fault zones as collectors of water and conductors of fast flow. Résumé Deux multitraçages ont été réalisés dans l'une des zones principales de failles du bassin de Lange Bramke (massif du Harz, Allemagne); les résultats confirment le rôle prédominant de la zone de failles pour l'écoulement souterrain et le transport de soluté. Les traceurs, possédant des coefficients de diffusion différents (deutérium, bromure, uranine et éosine), ont fourni des courbes de restitution qui ne peuvent être expliquées que par un modèle qui associe un transport advectif-dispersif dans les fractures à un échange par diffusion moléculaire dans la matrice. A l'échelle des expériences (distance

  3. High-Gradient Tests of the Single-Cell SC Cavity with a Feedback Waveguide

    SciTech Connect

    Yakovlev, V.; Solyak, N.; Wu, G.; Ge, M.; Gonin, I.; Khabiboulline, T.; Ozelis, J.; Rowe, A.; Avrakhov, P.; Kanareykin, A.; Rathke, J.

    2010-11-04

    Use of a superconducting (SC) traveling-wave accelerating (STWA) structure with a small phase advance per cell, rather than a standing-wave structure, may provide a significant increase in the accelerating gradient in the ILC linac [1]. For the same surface electric and magnetic fields, the STWA achieves an accelerating gradient 1.2 larger than TESLA-like standing-wave cavities. In addition, the STWA allows longer acceleration cavities, reducing the number of gaps between them. However, the STWA structure requires a SC feedback waveguide to return the few hundreds of MW of circulating RF power from the structure output to the structure input. A test single-cell cavity with feedback was designed and manufactured to demonstrate the possibility of proper processing to achieve a high accelerating gradient. The first results of high-gradient tests of a prototype 1.3 GHz single-cell cavity with feedback waveguide will be presented.

  4. Using noble gas tracers to estimate residual CO2 saturation in the field: results from the CO2CRC Otway residual saturation and dissolution test

    NASA Astrophysics Data System (ADS)

    LaForce, T.; Ennis-King, J.; Paterson, L.

    2013-12-01

    Residual CO2 saturation is a critically important parameter in CO2 storage as it can have a large impact on the available secure storage volume and post-injection CO2 migration. A suite of single-well tests to measure residual trapping was conducted at the Otway test site in Victoria, Australia during 2011. One or more of these tests could be conducted at a prospective CO2 storage site before large-scale injection. The test involved injection of 150 tonnes of pure carbon dioxide followed by 454 tonnes of CO2-saturated formation water to drive the carbon dioxide to residual saturation. This work presents a brief overview of the full test sequence, followed by the analysis and interpretation of the tests using noble gas tracers. Prior to CO2 injection krypton (Kr) and xenon (Xe) tracers were injected and back-produced to characterise the aquifer under single-phase conditions. After CO2 had been driven to residual the two tracers were injected and produced again. The noble gases act as non-partitioning aqueous-phase tracers in the undisturbed aquifer and as partitioning tracers in the presence of residual CO2. To estimate residual saturation from the tracer test data a one-dimensional radial model of the near-well region is used. In the model there are only two independent parameters: the apparent dispersivity of each tracer and the residual CO2 saturation. Independent analysis of the Kr and Xe tracer production curves gives the same estimate of residual saturation to within the accuracy of the method. Furthermore the residual from the noble gas tracer tests is consistent with other measurements in the sequence of tests.

  5. Characterization of Anomalous Contaminant Transport via Push-Pull Tracer Tests

    NASA Astrophysics Data System (ADS)

    Hansen, S. K.; Vesselinov, V. V.; Berkowitz, B.

    2015-12-01

    Push-pull (single-well-injection-withdrawal) tracer tests are widely used as an economical means of characterizing field-scale solute transport properties such as sorption and dispersion. Typically, these are analyzed by means of analytic solutions that assume transport obeys the radial advection-dispersion equation. We revisit this approach as: (1) Recognition of the ubiquity of anomalous transport and its impact on contaminant remediation necessitates the use of new methods to characterize it, and (2) Improved computational power and numerical methods have rendered reliance on analytical solutions obsolete. Here, we present a technique for characterizing diffusion-driven anomalous transport (i.e., anomalous transport driven by a "trapping" process whose trapping and release statistics are independent of the groundwater flow velocity). Examples include diffusion into low permeability zones, kinetic sorption, and matrix diffusion. Using field observations, we simultaneously calibrate an exponential probability distribution for time spent on a single sojourn in the mobile domain and a truncated power law probability distribution for time spent on a single sojourn in the immobile domain via a stochastic global optimization technique. The calibrated distributions, being independent of the flow regime, are applicable to the same domain under any flow conditions, including linear flow. In the context of the continuous time random walk (CTRW), one may simply define a transition to represent a single trap-and-release cycle, and directly compute the spatiotemporal transition distribution that defines the CTRW from the two calibrated distributions and the local seepage velocity (so that existing CTRW transport theory applies). A test of our methodology against a push-pull test from the MADE site demonstrated fitting performance comparable to that of a 3-D MODFLOW/MT3DMS model with a variety of hydraulic conductivity zones and explicit treatment of mobile-immobile mass

  6. Thermal single-well injection-withdrawal tracer tests for determining fracture-matrix heat transfer area

    SciTech Connect

    Pruess, K.; Doughty, C.

    2010-01-15

    Single-well injection-withdrawal (SWIW) tracer tests involve injection of traced fluid and subsequent tracer recovery from the same well, usually with some quiescent time between the injection and withdrawal periods. SWIW are insensitive to variations in advective processes that arise from formation heterogeneities, because upon withdrawal, fluid parcels tend to retrace the paths taken during injection. However, SWIW are sensitive to diffusive processes, such as diffusive exchange of conservative or reactive solutes between fractures and rock matrix. This paper focuses on SWIW tests in which temperature itself is used as a tracer. Numerical simulations demonstrate the sensitivity of temperature returns to fracture-matrix interaction. We consider thermal SWIW response to the two primary reservoir improvements targeted with stimulation, (1) making additional fractures accessible to injected fluids, and (2) increasing the aperture and permeability of pre-existing fractures. It is found that temperature returns in SWIW tests are insensitive to (2), while providing a strong signal of more rapid temperature recovery during the withdrawal phase for (1).

  7. Results of the 1988 geothermal gradient test drilling project for the State of Washington

    SciTech Connect

    Barnett, D.B.; Korosec, M.A.

    1989-05-01

    During late summer and early fall of 1988, the Washington Department of Natural Resources, Division of Geology and Earth Resources (DGER) completed drilling eight shallow geothermal gradient test wells in the southern Washington Cascade Range. This report describes the preliminary results of the 1988 drilling and gradient measuring, and summarizes our current perspectives on distribution and magnitude of the geothermal resource potential in the southern Washington Cascades. 18 refs., 11 figs., 11 tabs.

  8. Analysis of Tracer Tests with Multirate Diffusion Models: Recent Results and Future Directions within the WIPP Project

    SciTech Connect

    ALTMAN, SUSAN J.; HAGGERTY, ROY; MCKENNA, SEAN A.; MEIGS, LUCY C.

    1999-10-01

    A series of single-well injection-withdrawal (SWIW) and two-well convergent-flow (TWCF) tracer tests were conducted in the Culebra dolomite at the WIPP site in late 1995 and early 1996. Modeling analyses over the past year have focused on reproducing the observed mass-recovery curves and understanding the basic physical processes controlling tracer transport in SWIW and TWCF tests. To date, specific modeling efforts have focused on five SWIW tests and one TWCF pathway at each of two different locations (H-11 and H-19 hydropads). An inverse parameter-estimation procedure was implemented to model the SWIW and TWCF tests with both traditional and multirate double-porosity formulations. The traditional model assumes a single diffusion rate while the multirate model uses a first-order approximation to model a continuous distribution of diffusion coefficients. Conceptually, the multirate model represents variable matrix block sizes within the Culebra as observed in geologic investigations and also variability in diffusion rates within the matrix blocks as observed with X-ray imaging in the laboratory. Single-rate double-porosity models cannot provide an adequate match to the SWIW data. Multirate double-porosity models provide excellent fits to all five SWIW mass-recovery curves. Models of the TWCF tests show that, at one location, the tracer test can be modeled with both single-rate and multirate double-porosity models. At the other location, only the multi-rate double-porosity model is capable of explaining the test results.

  9. Experimental high gradient testing of a 17.1 GHz photonic band-gap accelerator structure

    NASA Astrophysics Data System (ADS)

    Munroe, Brian J.; Zhang, JieXi; Xu, Haoran; Shapiro, Michael A.; Temkin, Richard J.

    2016-03-01

    We report the design, fabrication, and high gradient testing of a 17.1 GHz photonic band-gap (PBG) accelerator structure. Photonic band-gap (PBG) structures are promising candidates for electron accelerators capable of high-gradient operation because they have the inherent damping of high order modes required to avoid beam breakup instabilities. The 17.1 GHz PBG structure tested was a single cell structure composed of a triangular array of round copper rods of radius 1.45 mm spaced by 8.05 mm. The test assembly consisted of the test PBG cell located between conventional (pillbox) input and output cells, with input power of up to 4 MW from a klystron supplied via a TM01 mode launcher. Breakdown at high gradient was observed by diagnostics including reflected power, downstream and upstream current monitors and visible light emission. The testing procedure was first benchmarked with a conventional disc-loaded waveguide structure, which reached a gradient of 87 MV /m at a breakdown probability of 1.19 ×10-1 per pulse per meter. The PBG structure was tested with 100 ns pulses at gradient levels of less than 90 MV /m in order to limit the surface temperature rise to 120 K. The PBG structure reached up to 89 MV /m at a breakdown probability of 1.09 ×10-1 per pulse per meter. These test results show that a PBG structure can simultaneously operate at high gradients and low breakdown probability, while also providing wakefield damping.

  10. Stronger Tests of Mechanisms Underlying Geographic Gradients of Biodiversity: Insights from the Dimensionality of Biodiversity

    PubMed Central

    Stevens, Richard D.; Tello, J. Sebastián; Gavilanez, María Mercedes

    2013-01-01

    Inference involving diversity gradients typically is gathered by mechanistic tests involving single dimensions of biodiversity such as species richness. Nonetheless, because traits such as geographic range size, trophic status or phenotypic characteristics are tied to a particular species, mechanistic effects driving broad diversity patterns should manifest across numerous dimensions of biodiversity. We develop an approach of stronger inference based on numerous dimensions of biodiversity and apply it to evaluate one such putative mechanism: the mid-domain effect (MDE). Species composition of 10,000-km2 grid cells was determined by overlaying geographic range maps of 133 noctilionoid bat taxa. We determined empirical diversity gradients in the Neotropics by calculating species richness and three indices each of phylogenetic, functional and phenetic diversity for each grid cell. We also created 1,000 simulated gradients of each examined metric of biodiversity based on a MDE model to estimate patterns expected if species distributions were randomly placed within the Neotropics. For each simulation run, we regressed the observed gradient onto the MDE-expected gradient. If a MDE drives empirical gradients, then coefficients of determination from such an analysis should be high, the intercept no different from zero and the slope no different than unity. Species richness gradients predicted by the MDE fit empirical patterns. The MDE produced strong spatially structured gradients of taxonomic, phylogenetic, functional and phenetic diversity. Nonetheless, expected values generated from the MDE for most dimensions of biodiversity exhibited poor fit to most empirical patterns. The MDE cannot account for most empirical patterns of biodiversity. Fuller understanding of latitudinal gradients will come from simultaneous examination of relative effects of random, environmental and historical mechanisms to better understand distribution and abundance of the current biota. PMID

  11. Three-dimensional geostatistical inversion of synthetic tomographic pumping and heat-tracer tests in a nested-cell setup

    NASA Astrophysics Data System (ADS)

    Schwede, Ronnie L.; Li, Wei; Leven, Carsten; Cirpka, Olaf A.

    2014-01-01

    A main purpose of groundwater inverse modeling lies in estimating the hydraulic conductivity field of an aquifer. Traditionally, hydraulic head measurements, possibly obtained in tomographic setups, are used as data. Because the groundwater flow equation is diffusive, many pumping and observation wells would be necessary to obtain a high resolution of hydraulic conductivity, which is typically not possible. We suggest performing heat tracer tests using the same already installed pumping wells and thermometers in observation planes to amend the hydraulic head data set by the arrival times of the heat signals. For each tomographic combinations of wells, we recommend installing an outer pair of pumping wells, generating artificial ambient flow, and an inner well pair in which the tests are performed. We jointly invert heads and thermal arrival times in 3-D by the quasi-linear geostatistical approach using an efficiently parallelized code running on a mid-range cluster. In the present study, we evaluate the value of heat tracer versus head data in a synthetic test case, where the estimated fields can be compared to the synthetic truth. Because the sensitivity patterns of the thermal arrival times differ from those of head measurements, the resolved variance in the estimated field is 6 to 10 times higher in the joint inversion in comparison to inverting head data only. Also, in contrast to head measurements, reversing the flow field and repeating the heat-tracer test improves the estimate in terms of reducing the estimation variance of the estimate. Based on the synthetic test case, we recommend performing the tests in four principal directions, requiring in total eight pumping wells and four intersecting observation planes for heads and temperature in each direction.

  12. A video imaging technique for assessing dermal exposure. II. Fluorescent tracer testing.

    PubMed

    Fenske, R A; Wong, S M; Leffingwell, J T; Spear, R C

    1986-12-01

    Laboratory and field evaluations were conducted to determine the suitability of employing a fluorescent tracer in conjunction with video imaging analysis to measure dermal exposure during pesticide applications. The Fluorescent Whitening Agent 4-methyl-7-diethylaminocoumarin and the organophosphate malathion were highly correlated (r = .985) when sprayed under controlled conditions. Deposition levels during field studies were correlated similarly (r = .942); however, variability in deposition ratios requires that field sampling be conducted to determine the ratio for a particular application. Penetration of the two compounds through cotton/polyester workshirt material demonstrated a high correlation (r = .979), whereas penetration of cotton/polyester coverall material was more variable (r = .834). The slopes of the regression lines for the two materials were not significantly different. The ratio of pesticide and tracer recovered from targets was consistently higher than the initial tank ratio due to differences in solubility and mixing. PMID:3799477

  13. Convergent radial dispersion: a Laplace transform solution for aquifer tracer testing

    USGS Publications Warehouse

    Moench, A.F.

    1989-01-01

    A Laplace transform solution was obtained for the injection of a tracer in a well situated in a homogeneous aquifer where steady, horizontal, radially convergent flow has been established due to pumping at a second well. The standard advection-dispersion equation for mass transfer was used as the controlling equation. For boundary conditions, mass balances that account for mixing of the tracer with the fluid residing in the injection and pumping wells were used. The derived solution, which can be adapted for either resident or flux-averaged concentration, is of practical use only for the pumped well. This problem is of interest because it is easily applied to field determination of aquifer dispersivity and effective porosity. Breakthrough curves were obtained by numerical inversion of the Laplace transform solution. -from Author

  14. Estimation of αL, velocity, Kd and confidence limits from tracer injection test data

    USGS Publications Warehouse

    Broermann, James; Bassett, R.L.; Weeks, Edwin P.; Borgstrom, Mark

    1997-01-01

    Bromide and boron were used as tracers during an injection experiment conducted at an artificial recharge facility near Stanton, Texas. The Ogallala aquifer at the Stanton site represents a heterogeneous alluvial environment and provides the opportunity to report scale dependent dispersivities at observation distances of 2 to 15 m in this setting. Values of longitudinal dispersivities are compared with other published values. Water samples were collected at selected depths both from piezometers and from fully screened observation wells at radii of 2, 5, 10 and 15 m. An exact analytical solution is used to simulate the concentration breakthrough curves and estimate longitudinal dispersivities and velocity parameters. Greater confidence can be placed on these data because the estimated parameters are error bounded using the bootstrap method. The non-conservative behavior of boron transport in clay rich sections of the aquifer were quantified with distribution coefficients by using bromide as a conservative reference tracer.

  15. Use of single-well tracer dilution tests to evaluate LNAPL flux at seven field sites.

    PubMed

    Mahler, Nicholas; Sale, Tom; Smith, Tim; Lyverse, Mark

    2012-01-01

    Petroleum liquids, referred to as light non-aqueous phase liquids (LNAPLs), are commonly found beneath petroleum facilities. Concerns with LNAPLs include migration into clean soils, migration beyond property boundaries, and discharges to surface water. Single-well tracer dilution techniques were used to measure LNAPL fluxes through 50 wells at 7 field sites. A hydrophobic tracer was mixed into LNAPL in a well. Intensities of fluorescence associated with the tracer were measured over time using a spectrometer and a fiber optic cable. LNAPL fluxes were estimated using observed changes in the tracer concentrations over time. Measured LNAPL fluxes range from 0.006 to 2.6 m/year with a mean and median of 0.15 and 0.064 m/year, respectively. Measured LNAPL fluxes are two to four orders of magnitude smaller than a common groundwater flux of 30 m/year. Relationships between LNAPL fluxes and possible governing parameters were evaluated. Observed LNAPL fluxes are largely independent of LNAPL thickness in wells. Natural losses of LNAPL through dissolution, evaporation, and subsequent biodegradation, were estimated using a simple mass balance, measured LNAPL fluxes in wells, and an assumed stable LNAPL extent. The mean and median of the calculated loss rates were found to be 24.0 and 5.0 m3/ha/year, respectively. Mean and median losses are similar to values reported by others. Coupling observed LNAPL fluxes to observed rates of natural LNAPL depletion suggests that natural losses of LNAPL may be an important parameter controlling the overall extent of LNAPL bodies. PMID:23289131

  16. Characterization of Min-K TE-1400 Thermal Insulation (Two-Year Gradient Stress Relaxation Testing Update)

    SciTech Connect

    Hemrick, James Gordon; Lara-Curzio, Edgar; King, James

    2009-09-01

    Min-K 1400TE insulation material was characterized at Oak Ridge National Laboratory for use in structural applications under gradient temperature conditions. A previous report (ORNL/TM-2008/089) discusses the testing and results from the original three year duration of the project. This testing included compression testing to determine the effect of sample size and test specimen geometry on the compressive strength of Min-K, subsequent compression testing on cylindrical specimens to determine loading rates for stress relaxation testing, isothermal stress relaxation testing, and gradient stress relaxation testing. This report presents the results from the continuation of the gradient temperature stress relaxation testing and the resulting updated modeling.

  17. A field test of tracer transport and organic contaminant elution in a stratified aquifer at the Rocky Mountain Arsenal (Denver, Colorado, U.S.A.)

    NASA Astrophysics Data System (ADS)

    Thorbjarnarson, Kathryn W.; Mackay, Douglas M.

    1997-01-01

    A tracer-elution experiment was conducted in a 9-m-thick alluvial sand aquifer at the Rocky Mountain Arsenal, Denver, Colorado, within an extensive 1,1,1-trichloroethene and trichloroethene plume. The forced-gradient flow field was controlled by an injection well and an extraction well separated by 8.4 m and aligned in the direction of the natural-gradient flow. Upon extraction, the contaminant-laden water was treated by air stripping and reinjected into the injection well. Iodide tracer was added to the injection flow during the initial 27.5 h of the experiment. Tracer transport and organic contaminant elution were monitored by four 0.15-m-screened drive points and a fully penetrating monitoring well. Relative permeabilities, dispersivities and retardation factors were estimated from tracer breakthrough and contaminant elution curves by the moment method and by curve-fitting with an advection-dispersion model. Tracer transport through the four strata sampled by the drive points indicated a permeability variation of three orders of magnitude. Contaminant elution was not observed in the lowest-permeability stratum monitored during the experiment. In all monitored strata, contaminant elution was controlled primarily by permeability effects on water flow and exhibited minimal retardation or desorption effects. The fully penetrating monitoring well exhibited a tracer response primarily from the more permeable strata with the addition of tracer from the less permeable strata producing an increased breakthrough spreading. This increased spreading or dispersion was reflected in a higher longitudinal dispersivity estimate (1.2 m assuming a homogeneous aquifer) than dispersivity estimates from the drive-point sampler tracer curves (ranging from 5 to 21 cm). Contaminant elution curves from the fully penetrating monitoring well exhibited an initial response primarily from the more permeable strata (rapid elution of contaminants) and provided no insight into the elution

  18. PILOT-SCALE FIELD TESTS OF HIGH-GRADIENT MAGNETIC FILTRATION

    EPA Science Inventory

    The report gives results of using a 5100 cu m/hr mobile pilot plant to evaluate the effectiveness and economics of applying high-gradient magnetic filtration (HGMF) to particulate emission control. A 4-1/2 month test program was conducted at a Pennsylvania sintering plant to char...

  19. Application of separable parameter space techniques to multi-tracer PET compartment modeling

    PubMed Central

    Zhang, Jeff L; Morey, A Michael; Kadrmas, Dan J

    2016-01-01

    Multi-tracer positron emission tomography (PET) can image two or more tracers in a single scan, characterizing multiple aspects of biological functions to provide new insights into many diseases. The technique uses dynamic imaging, resulting in time-activity curves that contain contributions from each tracer present. The process of separating and recovering separate images and/or imaging measures for each tracer requires the application of kinetic constraints, which are most commonly applied by fitting parallel compartment models for all tracers. Such multi-tracer compartment modeling presents challenging nonlinear fits in multiple dimensions. This work extends separable parameter space kinetic modeling techniques, previously developed for fitting single-tracer compartment models, to fitting multi-tracer compartment models. The multi-tracer compartment model solution equations were reformulated to maximally separate the linear and nonlinear aspects of the fitting problem, and separable least-squares techniques were applied to effectively reduce the dimensionality of the nonlinear fit. The benefits of the approach are then explored through a number of illustrative examples, including characterization of separable parameter space multi-tracer objective functions and demonstration of exhaustive search fits which guarantee the true global minimum to within arbitrary search precision. Iterative gradient-descent algorithms using Levenberg–Marquardt were also tested, demonstrating improved fitting speed and robustness as compared to corresponding fits using conventional model formulations. The proposed technique overcomes many of the challenges in fitting simultaneous multi-tracer PET compartment models. PMID:26788888

  20. Application of separable parameter space techniques to multi-tracer PET compartment modeling

    NASA Astrophysics Data System (ADS)

    Zhang, Jeff L.; Morey, A. Michael; Kadrmas, Dan J.

    2016-02-01

    Multi-tracer positron emission tomography (PET) can image two or more tracers in a single scan, characterizing multiple aspects of biological functions to provide new insights into many diseases. The technique uses dynamic imaging, resulting in time-activity curves that contain contributions from each tracer present. The process of separating and recovering separate images and/or imaging measures for each tracer requires the application of kinetic constraints, which are most commonly applied by fitting parallel compartment models for all tracers. Such multi-tracer compartment modeling presents challenging nonlinear fits in multiple dimensions. This work extends separable parameter space kinetic modeling techniques, previously developed for fitting single-tracer compartment models, to fitting multi-tracer compartment models. The multi-tracer compartment model solution equations were reformulated to maximally separate the linear and nonlinear aspects of the fitting problem, and separable least-squares techniques were applied to effectively reduce the dimensionality of the nonlinear fit. The benefits of the approach are then explored through a number of illustrative examples, including characterization of separable parameter space multi-tracer objective functions and demonstration of exhaustive search fits which guarantee the true global minimum to within arbitrary search precision. Iterative gradient-descent algorithms using Levenberg-Marquardt were also tested, demonstrating improved fitting speed and robustness as compared to corresponding fits using conventional model formulations. The proposed technique overcomes many of the challenges in fitting simultaneous multi-tracer PET compartment models.

  1. Simulations of Two-Well Tracer Tests in Stratified Aquifers at the Chalk River and the Mobile Sites

    NASA Astrophysics Data System (ADS)

    Huyakorn, Peter S.; Andersen, Peter F.; Molz, Fred J.; Güven, Oktay; Melville, Joel G.

    1986-07-01

    A simulation study of two-well injection-withdrawal tracer tests in stratified granular aquifers at two widely separated sites is presented. The first site is located near the Chalk River Nuclear Laboratories in Canada, and the second site is located in Mobile, Alabama. Field data and test conditions at these sites are substantially different in terms of vertical distributions of hydraulic conductivity, well spacings, flow rates, test durations, and tracer travel distances. Furthermore, the test at the Chalk River site was conducted in a recirculating mode, whereas the test at the Mobile site was conducted in a nonrecirculating mode. Simulations of these tests were performed in three dimensions using the curvilinear finite element model developed in the previous paper of this series. The simulations incorporated measured vertical variations in relative hydraulic conductivity and local dispersivity values that are small fractions (between 1/1000 and 1/100) of the spacing between the injection and the withdrawal wells. The local dispersivities are used to account for local hydrodynamic dispersion and are chosen independently so that they are not affected by the scales of the tests. Simulation results obtained from the model are presented. Interpretation of these results is made in conjunction with measured breakthrough curves at the withdrawal well and multilevel observation wells. For the Chalk River site, predicted and measured breakthrough curves at the withdrawal well are in good agreement over the earlier part of the test duration. Deviation of the field data from the model prediction occurs over the second part, where the predicted breakthrough curves show a declining trend but the field data plot does not. For the Mobile site, predicted and measured breakthrough curves at the withdrawal well show similar trends throughout the entire test duration and are in good agreement overall. Model predictions of the effect of hydraulic conductivity stratification on

  2. Tracer tests, hydrochemical and microbiological investigations as a basis for groundwater protection in a remote tropical mountainous karst area, Vietnam

    NASA Astrophysics Data System (ADS)

    Nguyet, Vu Thi Minh; Goldscheider, Nico

    2006-11-01

    The Tam Duong karst area in NW Vietnam is among the poorest and remotest regions in the country. The local population largely depends on water from two main karst springs. Due to agricultural activity and untreated domestic wastewaters, the spring water is often microbiologically contaminated. In order to provide a scientific basis for groundwater protection in the area, different field methods have been applied including hydrogeological framework investigations, tracer tests, and hydrochemical and microbiological sampling and analyses. All methods had to be adapted to the conditions of a poor and remote area. These adaptations included, amongst other measures, the use of a portable microbiological water_testing kit and the involvement of the local population in the sampling campaign. The tracer tests showed simple and direct connections between two important swallow holes and the two main springs, and made it possible to determine the linear groundwater flow velocities, which are extremely high (up to 875 m/h). The hydrochemical and microbiological data confirmed the strong impact of the streams sinking into the swallow holes on the spring water quality. Future groundwater source protection strategies should consequently focus on the reduction of polluting activities near the sinking streams and within their catchment areas.

  3. Comparison of agar dilution and antibiotic gradient strip test with broth microdilution for susceptibility testing of swine Brachyspira species.

    PubMed

    Mirajkar, Nandita S; Gebhart, Connie J

    2016-03-01

    Production-limiting diseases in swine caused by Brachyspira are characterized by mucohemorrhagic diarrhea (B. hyodysenteriae and "B. hampsonii") or mild colitis (B. pilosicoli), while B. murdochii is often isolated from healthy pigs. Emergence of novel pathogenic Brachyspira species and strains with reduced susceptibility to commonly used antimicrobials has reinforced the need for standardized susceptibility testing. Two methods are currently used for Brachyspira susceptibility testing: agar dilution (AD) and broth microdilution (BMD). However, these tests have primarily been used for B. hyodysenteriae and rarely for B. pilosicoli. Information on the use of commercial susceptibility testing products such as antibiotic gradient strips is lacking. Our main objective was to validate and compare the susceptibility results, measured as the minimum inhibitory concentration (MIC), of 6 antimicrobials for 4 Brachyspira species (B. hyodysenteriae, "B. hampsonii", B. pilosicoli, and B. murdochii) by BMD and AD (tiamulin, valnemulin, lincomycin, tylosin, and carbadox) or antibiotic gradient strip (doxycycline) methods. In general, the results of a high percentage of all 4 Brachyspira species differed by ±1 log2 dilution or less by BMD and AD for tiamulin, valnemulin, lincomycin, and tylosin, and by BMD and antibiotic gradient strip for doxycycline. The carbadox MICs obtained by BMD were 1-5 doubling dilutions different than those obtained by AD. BMD for Brachyspira was quicker to perform with less ambiguous interpretation of results when compared with AD and antibiotic gradient strip methods, and the results confirm the utility of BMD in routine diagnostics. PMID:26965233

  4. Functional linear models to test for differences in prairie wetland hydraulic gradients

    USGS Publications Warehouse

    Greenwood, Mark C.; Sojda, Richard S.; Preston, Todd M.

    2010-01-01

    Functional data analysis provides a framework for analyzing multiple time series measured frequently in time, treating each series as a continuous function of time. Functional linear models are used to test for effects on hydraulic gradient functional responses collected from three types of land use in Northeastern Montana at fourteen locations. Penalized regression-splines are used to estimate the underlying continuous functions based on the discretely recorded (over time) gradient measurements. Permutation methods are used to assess the statistical significance of effects. A method for accommodating missing observations in each time series is described. Hydraulic gradients may be an initial and fundamental ecosystem process that responds to climate change. We suggest other potential uses of these methods for detecting evidence of climate change.

  5. Testing the stress gradient hypothesis in herbivore communities facilitation peaks at intermediate nutrient levels.

    PubMed

    Bakker, Elisabeth S; Dobrescu, Ioana; Straile, Dietmar; Holmgren, Milena

    2013-08-01

    The role of positive interactions in structuring plant and animal communities is increasingly recognized, but the generality of current theoretical models has remained practically unexplored in animal communities. The stress gradient hypothesis predicts a linear increase in the intensity of facilitation as environmental conditions become increasingly stressful, whereas other theoretical models predict a maximum at intermediate environmental stress. We tested how competition and facilitation between herbivores change over a manipulated gradient of nutrient availability. We studied the effect of grazing by pond snails (Lymnaea stagnalis L.) as bulk grazers on aquatic caterpillars (Acentria ephemerella Denis and Schiffermüller) as small specialist grazers along an experimental gradient of environmental nutrient concentration. Higher nutrient levels increased overall total plant biomass but induced a shift toward dominance of filamentous algae at the expense of macrophytes. Facilitation of caterpillars by snail presence peaked at intermediate nutrient levels. Both caterpillar biomass and caterpillar grazing on macrophytes were highest at intermediate nutrient levels. Snails facilitated caterpillars possibly by removing filamentous algae and increasing access to the macrophyte resource, whereas they did not affect macrophyte biomass or C: nutrient ratios, a measure of food quality. We conclude that competition and facilitation in herbivore communities change along nutrient availability gradients that affect plant biomass and community composition. Understanding how interspecific interactions may change in strength and direction along environmental gradients is important to predict how the diversity and structure of communities may respond to the introduction or removal of herbivore species in ecosystems. PMID:24015521

  6. Analysis of three sets of SWIW tracer-test data using a two-population complex fracture model for matrix diffusion and sorption

    SciTech Connect

    Doughty, C.; Tsang, C.F.

    2009-08-01

    A complex fracture model employing two populations for diffusion and sorption is proposed to analyze three representative single-well injection-withdrawal (SWIW) tracer tests from Forsmark and Laxemar, the two sites under investigation by the Swedish Nuclear Fuel and Waste Management Company (SKB). One population represents the semi-infinite rock matrix and the other represents finite blocks that can become saturated, thereafter accepting no further diffusion or sorption. The diffusion and sorption parameters of the models are inferred by matching tracer breakthrough curves (BTCs). Three tracers are simultaneously injected, uranine (Ur), which is conservative, and rubidium (Rb) and cesium (Cs), which are non-conservative. For non-sorbing tracer uranine, the finite blocks become saturated with test duration of the order of 10 hours, and both the finite and the semi-infinite populations play a distinct role in controlling BTCs. For sorbing tracers Rb and Cs, finite blocks do not saturate, but act essentially as semi-infinite, and thus BTC behavior is comparable to that obtained for a model containing only a semi-infinite rock matrix. The ability to obtain good matches to BTCs for both sorbing and non-sorbing tracers for these three different SWIW data sets demonstrates that the two-population complex fracture model may be a useful conceptual model to analyze all SWIW tracer tests in fractured rock, and perhaps also usual multiwell tracer tests. One of the two populations should be semi-infinite rock matrix and the other finite blocks that can saturate. The latter can represent either rock blocks or gouge within the fracture, a fracture skin zone, or stagnation zones.

  7. A servo controlled gradient loading triaxial model test system for deep-buried cavern.

    PubMed

    Chen, Xu-guang; Zhang, Qiang-yong; Li, Shu-cai

    2015-10-01

    A servo controlled gradient loading model test system is developed to simulate the gradient geostress in deep-buried cavern. This system consists of the gradient loading apparatus, the digital servo control device, and the measurement system. Among them, the gradient loading apparatus is the main component which is used for exerting load onto the model. This loading apparatus is placed inside the counterforce wall/beam and is divided to several different loading zones, with each loading zone independently controlled. This design enables the gradient loading. Hence, the "real" geostress field surrounding the deep-buried cavern can be simulated. The loading or unloading process can be controlled by the human-computer interaction machines, i.e., the digital servo control system. It realizes the automation and visualization of model loading/unloading. In addition, this digital servo could control and regulate hydraulic loading instantaneously, which stabilizes the geostress onto the model over a long term. During the loading procedure, the collision between two adjacent loading platens is also eliminated by developing a guide frame. This collision phenomenon is induced by the volume shrinkage of the model when compressed in true 3D state. In addition, several accurate measurements, including the optical and grating-based method, are adopted to monitor the small deformation of the model. Hence, the distortion of the model could be accurately measured. In order to validate the performance of this innovative model test system, a 3D geomechanical test was conducted on a simulated deep-buried underground reservoir. The result shows that the radial convergence increases rapidly with the release of the stress in the reservoir. Moreover, the deformation increases with the increase of the gas production rate. This observation is consistence with field observation in petroleum engineering. The system is therefore capable of testing deep-buried engineering structures. PMID

  8. A servo controlled gradient loading triaxial model test system for deep-buried cavern

    NASA Astrophysics Data System (ADS)

    Chen, Xu-guang; Zhang, Qiang-yong; Li, Shu-cai

    2015-10-01

    A servo controlled gradient loading model test system is developed to simulate the gradient geostress in deep-buried cavern. This system consists of the gradient loading apparatus, the digital servo control device, and the measurement system. Among them, the gradient loading apparatus is the main component which is used for exerting load onto the model. This loading apparatus is placed inside the counterforce wall/beam and is divided to several different loading zones, with each loading zone independently controlled. This design enables the gradient loading. Hence, the "real" geostress field surrounding the deep-buried cavern can be simulated. The loading or unloading process can be controlled by the human-computer interaction machines, i.e., the digital servo control system. It realizes the automation and visualization of model loading/unloading. In addition, this digital servo could control and regulate hydraulic loading instantaneously, which stabilizes the geostress onto the model over a long term. During the loading procedure, the collision between two adjacent loading platens is also eliminated by developing a guide frame. This collision phenomenon is induced by the volume shrinkage of the model when compressed in true 3D state. In addition, several accurate measurements, including the optical and grating-based method, are adopted to monitor the small deformation of the model. Hence, the distortion of the model could be accurately measured. In order to validate the performance of this innovative model test system, a 3D geomechanical test was conducted on a simulated deep-buried underground reservoir. The result shows that the radial convergence increases rapidly with the release of the stress in the reservoir. Moreover, the deformation increases with the increase of the gas production rate. This observation is consistence with field observation in petroleum engineering. The system is therefore capable of testing deep-buried engineering structures.

  9. A servo controlled gradient loading triaxial model test system for deep-buried cavern

    SciTech Connect

    Chen, Xu-guang; Zhang, Qiang-yong; Li, Shu-cai

    2015-10-15

    A servo controlled gradient loading model test system is developed to simulate the gradient geostress in deep-buried cavern. This system consists of the gradient loading apparatus, the digital servo control device, and the measurement system. Among them, the gradient loading apparatus is the main component which is used for exerting load onto the model. This loading apparatus is placed inside the counterforce wall/beam and is divided to several different loading zones, with each loading zone independently controlled. This design enables the gradient loading. Hence, the “real” geostress field surrounding the deep-buried cavern can be simulated. The loading or unloading process can be controlled by the human-computer interaction machines, i.e., the digital servo control system. It realizes the automation and visualization of model loading/unloading. In addition, this digital servo could control and regulate hydraulic loading instantaneously, which stabilizes the geostress onto the model over a long term. During the loading procedure, the collision between two adjacent loading platens is also eliminated by developing a guide frame. This collision phenomenon is induced by the volume shrinkage of the model when compressed in true 3D state. In addition, several accurate measurements, including the optical and grating-based method, are adopted to monitor the small deformation of the model. Hence, the distortion of the model could be accurately measured. In order to validate the performance of this innovative model test system, a 3D geomechanical test was conducted on a simulated deep-buried underground reservoir. The result shows that the radial convergence increases rapidly with the release of the stress in the reservoir. Moreover, the deformation increases with the increase of the gas production rate. This observation is consistence with field observation in petroleum engineering. The system is therefore capable of testing deep-buried engineering structures.

  10. Experimental study of the effect of test-well arrangement for partitioning interwell tracer test on the estimation of NAPL saturation

    NASA Astrophysics Data System (ADS)

    Kim, B.; Kim, Y.; Yeo, I.; Yongcheol Kim, In Wook Yeo

    2011-12-01

    Partitioning interwell tracer test (PITT) is a method to quantify and qualify a contaminated site with NAPLs through a degree of retardation of partitioning tracers compared to a conservative one. Although PITT is known to be a more effective method to measure the saturation of spatially-distributed NAPL contaminant than the point investigation method, the saturation estimation from PITT is reported to be underestimated due to various factors including heterogeneity of the media, adsorption, source zone NAPL architecture, and long tailing in breakthrough curves of partitioning tracers. Analytical description of PITT assumes that the injection-pumping well pair is on the line of ambient groundwater flow direction, but the test-well pair could easily be off the line in the field site, which could be another erroneous factor in analyzing PITT data. The purpose of this work is to study the influence of the angle of the test-well pair to ambient groundwater flow direction based on the result from PITT. The experiments were conducted in a small-scale 3D sandbox with dimensions of 0.5 m × 0.4 m × 0.15 m (LWH) of stainless steel. The surface is covered and sealed with a plexiglass plate to make the physical model a confined aquifer. Eight full-screened wells of Teflon material were installed along the perimeter of a 50 mm circle with 45 degree intervals in the middle of the physical model. Both ends of the sand box are connected to constant head reservoirs. The physical model was wet-packed with sieved and washed sand. Trichloroethylene (TCE) and bromide were used as the contaminant and the conservative tracer, respectively. Hexanol, 2,4-dimethyl-3-pentanol and 6-methyl-2-heptanol were used as partitioning tracers. Before the injection of TCE, a PITT was conducted to measure adsorption coefficient of partitioning tracers to the sand material. TCE of 4.5 mL, dyed with Sudan IV, was injected into the inner part of the circle of the wells. PITTs using the test-well pair

  11. Contaminant transfer and hydrodispersive parameters in basaltic lava flows: artificial tracer test and implications for long-term management

    NASA Astrophysics Data System (ADS)

    Bertrand, G.; Celle-Jeanton, H.; Huneau, F.; Baillieux, A.; Mauri, G.; Lavastre, V.; Undereiner, G.; Girolami, L.; Moquet, J. S.

    2015-10-01

    The aim of this paper is to evaluate the vulnerability after point source contamination and characterize water circulations in volcanic flows located in the Argnat basin volcanic system (Chaîne des Puys, French Massif Central) using a tracer test performed by injecting a iodide solution. The analysis of breakthrough curves allowed the hydrodispersive characteristics of the massive lava flows to be determined. Large Peclet numbers indicated a dominant advective transport. The multimodal feature of breakthrough curves combined with high values of mean velocity and low longitudinal dispersion coefficients indicated thatwater flows in an environment analogous to a fissure system, and only slightly interacts with a low porosity matrix (ne < 1%). Combining this information with lava flow stratigraphy provided by several drillings allowed a conceptual scheme of potential contaminant behaviour to be designed. Although lava flows are vulnerable to point source pollution due to the rapid transfer of water within fractures, the saturated scoriaceous layers located between massive rocks should suffice to strongly buffer the transit of pollution through dilution and longer transit times. This was consistent with the low recovery rate of the presented tracer test.

  12. Insights about fracture shape and aperture from push-pull thermal tracer tests achieved at different scales

    NASA Astrophysics Data System (ADS)

    Klepikova, Maria V.; Le Borgne, Tanguy; Bour, Olivier; Hochreutener, Rebecca; Lavenant, Nicolas

    2015-04-01

    The prediction of transport patterns in fractured media is a challenging task. Different transport mechanisms are generally contributing: dispersion at fracture scale related to aperture variability, dispersion at network scale due to transport in different flowpaths and matrix diffusion. It is however difficult to know which mechanism is dominant. In this study we test the interest of heat tracer tests for providing new constraints on transport in fractured media by interpreting three push-pull tests of different duration. A series of heat and solute push-pull tracer test with Dirac-type injection was conducted in fractured aquifer of Ploemeur, France. The comparison of solute and heat breakthrough curves shows that due to thermal loss to the rock matrix temperature recovery peak arrives earlier than concentration peak. Moreover, the peak is significantly smaller for temperature recovery while it exhibits a longest tailing. Finally, we found that the recovered peak temperature decreases with scale and has a power law slope of -1 on a log-log plot. By means of flow and heat numerical model, we investigate the relevance of different conceptual models: single 'plate', 'tube' and 'ellipse' homogeneous fracture models at different scales. For all tested fracture geometries temperature breakthrough curves were found to be sensitive to fracture aperture. An 'elliptical tube' fracture model was found to provide the best fit to the data and based on this model, we were able to estimate the aperture of the fracture in the present case. Moreover, the comparison of experimental breakthrough curves and modelling results also suggests that the effective fracture aperture may increase with scale. This work emphasizes that multiple-scale push-pull thermal tests can provide valuable insights on fracture geometry and fracture aperture.

  13. Cosmological constraints from the redshift dependence of the Alcock-Paczynski test: galaxy density gradient field

    SciTech Connect

    Li, Xiao-Dong; Park, Changbom; Forero-Romero, J. E.; Kim, Juhan E-mail: cbp@kias.re.kr E-mail: kjhan@kias.re.kr

    2014-12-01

    We propose a method based on the redshift dependence of the Alcock-Paczynski (AP) test to measure the expansion history of the universe. It uses the isotropy of the galaxy density gradient field to constrain cosmological parameters. If the density parameter Ω {sub m} or the dark energy equation of state w are incorrectly chosen, the gradient field appears to be anisotropic with the degree of anisotropy varying with redshift. We use this effect to constrain the cosmological parameters governing the expansion history of the universe. Although redshift-space distortions (RSD) induced by galaxy peculiar velocities also produce anisotropies in the gradient field, these effects are close to uniform in magnitude over a large range of redshift. This makes the redshift variation of the gradient field anisotropy relatively insensitive to the RSD. By testing the method on mock surveys drawn from the Horizon Run 3 cosmological N-body simulations, we demonstrate that the cosmological parameters can be estimated without bias. Our method is complementary to the baryon acoustic oscillation or topology methods as it depends on D{sub AH} , the product of the angular diameter distance and the Hubble parameter.

  14. Peak and tail scaling of breakthrough curves in hydrologic tracer tests

    NASA Astrophysics Data System (ADS)

    Aquino, T.; Aubeneau, A.; Bolster, D.

    2015-04-01

    Power law tails, commonly observed in solute breakthrough curves, are notoriously difficult to measure with confidence as they typically occur at low concentrations. This leads us to ask if other signatures of anomalous transport can be sought. We develop a general stochastic transport framework and derive an asymptotic relation between the tail scaling of a breakthrough curve for a conservative tracer at a fixed downstream position and the scaling of the peak concentration of breakthrough curves as a function of downstream position, demonstrating that they provide equivalent information. We then quantify the relevant spatiotemporal scales for the emergence of this asymptotic regime, where the relationship holds, and validate our results in the context of a very simple model that represents transport in an idealized river.

  15. Single-well and inter-well dual-tracer tests for CCS pilot site characterization at Heletz (Israel): scope and limitations

    NASA Astrophysics Data System (ADS)

    Ghergut, Julia; Bensabat, Jac; Niemi, Auli; Licha, Tobias; Lange, Torsten; Tatomir, Alexandru; Sauter, Martin

    2013-04-01

    A semi-analytical approximation to tracer signals is proposed for evaluating the chances of unambiguous tracer test interpretation for the CCS pilot site at Heletz (www.co2mustang.eu/Heletz.aspx), given the multiple constraints imposed upon tracer test execution at any deep geological formation regarding maximum pressure buildup admissible, fluid turnover rates, injection-fluid availability and conditioning capabilities, fluid disposal capacity, maximum test duration, tracer quantities/species available, tracer metering costs, etc. At the Ketzin site in Germany (www.co2sink.org), such constraints acted prohibitively towards conducting any tracer tests prior to CO2 injection (cf. EGU2009-11625, EGU2011-2823-1). In contrast, at the Heletz site within the MUSTANG project, a particular sequence of single-well (SW) and inter-well (IW) tracer tests to be conducted prior to CO2 injection (Bensabat et al. 2011, Niemi et al. 2011) is being regarded as a critical, indispensable contribution towards the goal of georeservoir characterization. An advantage of the proposed approach, expressing tracer signals U in terms of fluid volume recovery fraction f (rather than time), is its independence upon IW distance and upon fluid injection/production rates (which may be difficult to prescribe in advance). It roughly predicts conservative- and sorptive-tracer signals, fluid mixing and temperature evolution in SW and IW tests, for stratified georeservoirs whose high- and low-permeability layers have thicknesses of same magnitude order. Thus, besides the CCS context, it can be extended to a range of geothermal applications, including some aquifer-dominated systems in the Upper Rhine Rift Valley, S-German Malm/Molasse Basin, N-German Sedimentary Basin, but excluding fracture-dominated (petrothermal) systems. IW tracer signals are sensitive to storage capacity (measured by transport-effective porosities n), but suffer from ambiguity between longitudinal heterogeneity (Peclet number Pe

  16. Hydrodispersive characterization of a sandy porous medium by tracer tests carried out in laboratory on undisturbed soil samples

    NASA Astrophysics Data System (ADS)

    Ferrante, Aldo Pedro; Fallico, Carmine; Rios, Ana C.; Fernanda Rivera, Maria; Santillan, Patricio; Salazar, Mario

    2013-04-01

    The contamination of large areas and correspondent aquifers often imposes to implement some recovery operations which are generally complex and very expensive. Anyway, these interventions necessarily require the preventive characterization of the aquifers to be reclaimed and in particular the knowledge of the relevant hydrodispersive parameters. The determination of these parameters requires the implementation tracer tests for the specific site (Sauty JP, 1978). To reduce cost and time that such test requires tracer tests on undisturbed soil samples, representative of the whole aquifer, can be performed. These laboratory tests are much less expensive and require less time, but the results are certainly less reliable than those obtained by field tests for several reasons, including the particular scale of investigation. In any case the hydrodispersive parameters values, obtained by tests carried out in laboratory, can provide useful information on the considered aquifer, allowing to carry out initial verifications on the transmission and propagation of the pollutants in the aquifer considered. For this purpose, tracer tests with inlet of short time were carried out in the Soil Physics Laboratory of the Department of Soil Protection (University of Calabria), on a series of sandy soil samples with six different lengths, repeating each test with three different water flow velocities (5 m/d; 10 m/s and 15 m/d) (J. Feyen et al., 1998). The lengths of the samples taken into account are respectively 15 cm, 24 cm, 30 cm, 45 cm, 60 cm and 75 cm, while the solution used for each test was made of 100 ml of water and NaCl with a concentration of this substance corresponding to 10 g/L. For the porous medium taken into consideration a particle size analysis was carried out, resulting primarily made of sand, with total porosity equal to 0.33. Each soil sample was placed in a flow cell in which was inlet the tracer from the bottom upwards, measuring by a conductivimeter the

  17. Solving large test-day models by iteration on data and preconditioned conjugate gradient.

    PubMed

    Lidauer, M; Strandén, I; Mäntysaari, E A; Pösö, J; Kettunen, A

    1999-12-01

    A preconditioned conjugate gradient method was implemented into an iteration on a program for data estimation of breeding values, and its convergence characteristics were studied. An algorithm was used as a reference in which one fixed effect was solved by Gauss-Seidel method, and other effects were solved by a second-order Jacobi method. Implementation of the preconditioned conjugate gradient required storing four vectors (size equal to number of unknowns in the mixed model equations) in random access memory and reading the data at each round of iteration. The preconditioner comprised diagonal blocks of the coefficient matrix. Comparison of algorithms was based on solutions of mixed model equations obtained by a single-trait animal model and a single-trait, random regression test-day model. Data sets for both models used milk yield records of primiparous Finnish dairy cows. Animal model data comprised 665,629 lactation milk yields and random regression test-day model data of 6,732,765 test-day milk yields. Both models included pedigree information of 1,099,622 animals. The animal model ¿random regression test-day model¿ required 122 ¿305¿ rounds of iteration to converge with the reference algorithm, but only 88 ¿149¿ were required with the preconditioned conjugate gradient. To solve the random regression test-day model with the preconditioned conjugate gradient required 237 megabytes of random access memory and took 14% of the computation time needed by the reference algorithm. PMID:10629827

  18. An ensemble Kalman filter approach to identify the hydraulic conductivity spatial distribution from electrical resistivity tomography time-lapse monitoring of three-dimensional tracer test experiments

    NASA Astrophysics Data System (ADS)

    Camporese, M.; Cassiani, G.; Deiana, R.; Perri, M. T.; Salandin, P.

    2012-04-01

    An approach based on the Lagrangian formulation of transport and the ensemble Kalman filter (EnKF) is applied to assess the spatial distribution of hydraulic conductivity K by assimilating time-lapse cross-hole electrical resistivity tomography (ERT) images generated for a synthetic tracer test in a heterogeneous aquifer. Assuming that the solute spreads as a passive tracer, for high Peclet numbers the spatial moments of the evolving plume are dominated by the spatial distribution of the hydraulic conductivity. The assimilation of the electrical conductivity 4D images allows updating both the hydrological state in terms of solute concentration and the spatial distribution of K. Thus, delineation of the tracer plume and estimation of the aquifer heterogeneity at the local scale can be achieved at the same time by means of this interpretation of time-lapse electrical images from tracer tests. We assess the impact on the performance of the hydrological inversion of the uncertainty inherently affecting ERT inversions in terms of tracer concentration and the choice of the prior statistics of K. The results show that realistic ERT images can be integrated into a hydrological model even within an uncoupled inverse modeling framework, the reconstruction of the hydraulic conductivity spatial distribution being satisfactory in the portion of the domain directly covered by the passage of the tracer. Aside from the issues commonly affecting inverse models, the proposed approach is subject to the problem of the filter inbreeding and the retrieval performance is sensitive to the choice of K prior geostatistical parameters.

  19. Modified Whole Effluent Toxicity Test to Assess and Decouple Wastewater Effects from Environmental Gradients

    PubMed Central

    Sauco, Sebastián; Gómez, Julio; Barboza, Francisco R.; Lercari, Diego; Defeo, Omar

    2013-01-01

    Environmental gradients and wastewater discharges produce aggregated effects on marine populations, obscuring the detection of human impact. Classical assessment methods do not include environmental effects in toxicity tests designs, which could lead to incorrect conclusions. We proposed a modified Whole Effluent Toxicity test (mWET) that includes environmental gradients in addition to effluent dilutions, together with the application of Generalized Linear Mixed Models (GLMM) to assess and decouple those effects. We tested this approach, analyzing the lethal effects of wastewater on a marine sandy beach bivalve affected by an artificial canal freshwater discharge used for rice crops irrigation. To this end, we compared bivalve mortality between canal water dilutions (CWd) and salinity controls (SC: without canal water). CWd were prepared by diluting the water effluent (sampled during the pesticide application period) with artificial marine water. The salinity gradient was included in the design by achieving the same final salinities in both CWd and SC, allowing us to account for the effects of salinity by including this variable as a random factor in the GLMM. Our approach detected significantly higher mortalities in CWd, indicating potential toxic effects of the effluent discharge. mWET represents an improvement over the internationally standardized WET tests, since it considers environmental variability and uses appropriate statistical analyses. PMID:23755304

  20. First high gradient test results of a dressed 325 MHz superconducting single spoke resonator at Fermilab

    SciTech Connect

    Webber, R.C.; Khabiboulline, T.; Madrak, R.; Nicol, T.; Ristori, L.; Soyars, W.; Wagner, R.; /Fermilab

    2010-09-01

    A new superconducting RF cavity test facility has been commissioned at Fermilab in conjunction with first tests of a 325 MHz, {beta} = 0.22 superconducting single-spoke cavity dressed with a helium jacket and prototype tuner. The facility is described and results of full gradient, CW cavity tests with a high Q{sub ext} drive coupler are reported. Sensitivities to Q disease and externally applied magnetic fields were investigated. Results are compared to bare cavity results obtained prior to hydrogen degassing and welding into the helium jacket.

  1. Application of tracer injection tests to characterize rock matrix block size distribution and dispersivity in fractured aquifers

    NASA Astrophysics Data System (ADS)

    Sharifi Haddad, Amin; Hassanzadeh, Hassan; Abedi, Jalal; Chen, Zhangxin

    2014-03-01

    The complexity of mass transfer processes between the mobile and immobile zones in geohydrologic settings and the limitations that currently exist in the characterization of contaminated sites demand the development of improved models. In this work, we present a model that describes the mass transfer in structured porous media. This model considers divergent radial advective-dispersive transport in fractures and diffusive mass transfer inside rock matrix blocks. The heterogeneous nature of fractured formations is included with the integration of various distributions of rock matrix block sizes into the transport model. Breakthrough curves generated based on the developed model are analyzed to investigate the effects of the rate of injection, dispersivity and the immobile to mobile porosity ratio on mass transfer between mobile and immobile zones. It is shown that the developed model, in conjunction with tracer data collected from a monitoring well, can be used to estimate the dispersivity and fracture intensity. Results reveal that the dispersivity is independent of the rock matrix block size distribution for dispersion-dominant transport in fractures. These findings are used to develop a methodology to characterize rock matrix block size distribution in fractured aquifers and to estimate dispersivity based on a tracer test, which will improve our decisions concerning the remediation of contaminated sites.

  2. Technological Issues and High Gradient Test Results on X-Band Molybdenum Accelerating Structures

    SciTech Connect

    Spataro, B.; Alesini, D.; Chimenti, V.; Dolgashev, V.; Haase, A.; Tantawi, S.G.; Higashi, Y.; Marrelli, C.; Mostacci, A.; Parodi, R.; Yeremian, A.D.; /SLAC

    2012-04-24

    Two 11.424 GHz single cell standing wave accelerating structures have been fabricated for high gradient RF breakdown studies. Both are brazed structures: one made from copper and the other from sintered molybdenum bulk. The tests results are presented and compared to those of similar devices constructed at SLAC (Stanford Linear Accelerator Center) and KEK (Ko Enerugi Kasokuki Kenkyu Kiko). The technological issues to build both sections are discussed.

  3. Geology, hydrology, and results of tracer testing in the Galena-Platteville aquifer at a waste-disposal site near Byron, Illinois

    USGS Publications Warehouse

    Kay, Robert T.; Yeskis, Douglas J.; Prinos, Scott T.; Morrow, William S.; Vendl, Mark

    1999-01-01

    A study was conducted by the U.S. Geological Survey and the U.S. Environmental Protection Agency of the geohydrology of the dolomite bedrock at a waste-disposal site near Byron, Illinois. The study was designed to identify and characterize the flow pathways through the bedrock aquifer beneath the site. The geologic units of concern at the site are the Glenwood Formation of the Ancell Group, and the Platteville and Galena Groups. These deposits compose the Galena-Platteville aquifer and the underlying Harmony Hill Shale semiconfining unit. The Galena-Platteville aquifer is an unconfined aquifer. Geophysical logging, water levels, and aquifer-test data indicate the presence of interconnected, hydraulically active fractures in the middle of the Galena-Platteville aquifer (the upper flow pathway), and a second set of hydraulically active fractures (the lower flow pathway). The lower flow pathway may be present through much of the site. Few hydraulically active fractures are present in the upper part of the aquifer near the center of the site, but appear to be more numerous in the upper part of the aquifer in the western and northeastern parts of the site. Water-level data obtained during the tracer test indicate that pumping effects were present near the pumped wells. Pumping effects may have been present at several wells located along directions of identified fracture orientation from the pumped well. The upper part of the aquifer did not appear to be hydraulically well connected to the flow pathways supplying water to the pumped well. Large background changes in water levels obscured the effects of pumping and prevented calculation of aquifer properties. The velocity of the bromide tracer through the lower flow pathway under the hydraulic gradient resulting from the pumping was about 152 feet per day. Solution of the Darcy velocity equation results in a calculated effective porosity for this interval of 3.5 percent, indicating hydraulic interconnection between the

  4. Single-well and inter-well dual-tracer test design for quantifying phase volumes and interface areas in subsurface flow and transport systems

    NASA Astrophysics Data System (ADS)

    Ghergut, I.; Behrens, H.; Licha, T.; Maier, F.; Nottebohm, M.; Schaffer, M.; Sauter, M.

    2012-04-01

    Technology-relevant georeservoirs in the realm of energy production (such as: spent-radionuclide repositories, gas-storage, geothermal, as well as CCS candidate reservoirs) contain mobile and immobile fluid regions, and often also different fluid and solid phases. The lifetime of a particular reservoir (from a hydraulic, thermal, geomechanical and/or hydrogeochemical point of view) depends on the volumes and/or interface areas of some of these regions and/or phases. Mostly, their lifetime-effective values cannot be measured by geophysical and hydraulic methods. Since they essentially relate to fluid-based transport processes, attempting to measure them by tracer tests is a sensible endeavour. However, in designing and dimensioning such tracer tests, one should keep in mind that not every tracer test is sensitive w. r. to every fluid transport parameter. A certain complementarity exists, w. r. to parameter sensitivity, between single-well and inter-well methods, between equilibrium and kinetic exchange processes, between volume and area parameters. Mobile-fluid volumes can be measured from inter-well conservative-tracer tests, whereas single-well push-pull tests are generally insensitive w. r. to mobile-fluid volumes. Immobile-fluid volumes, in single-phase systems, are rather difficult to measure, by either kind of test. Different-phase volumes can be determined from inter-well tests using partitioning tracers at equilibrium exchange between phases; whereas single-well tracer push-pull tests are rather insensitive w. r. to tracer exchange processes at equilibrium. Im-/mobile fluid, or inter-phase interface areas can be determined from single-well tracer push-pull tests relying on kinetic exchange processes between compartments or phases. Single-well tests are often believed to be more sensitive w. r. to such processes than w. r. to advective-dispersive processes, and than inter-well tests. Inter-well tests are not physically insensitive w. r. to kinetic exchange

  5. Temporal Changes in Education Gradients of ‘Preventable’ Mortality: A Test of Fundamental Cause Theory

    PubMed Central

    Masters, Ryan K.; Link, Bruce G.; Phelan, Jo C.

    2015-01-01

    Fundamental cause theory explains persisting associations between socioeconomic status and mortality in terms of personal resources such as knowledge, money, power, prestige, and social connections, as well as disparate social contexts related to these resources. We review evidence concerning fundamental cause theory and test three central claims using the National Health Interview Survey Linked Mortality Files 1986-2004. We then examine cohort-based variation in the associations between a fundamental social cause of disease, educational attainment, and mortality rates from heart disease, other “preventable” causes of death, and less preventable causes of death. We further explore race/ethnic and gender variation in these associations. Overall, findings are consistent with nearly all features of fundamental cause theory. Results show, first, larger education gradients in mortality risk for causes of death that are under greater human control than for less preventable causes of death, and, second, that these gradients grew more rapidly across successive cohorts than gradients for less preventable causes. Results also show that relative sizes and cohort-based changes in the education gradients vary substantially by race/ethnicity and gender. PMID:25556675

  6. USE OF TRACER DATA FROM THE MADISON SQUARE GARDEN 2005 FIELD EXPERIMENT TO TEST A SIMPLE URBAN DISPERSION MODEL

    SciTech Connect

    Hanna, Steven R.; Baja, Emmanuel; Flaherty, Julia E.; Allwine, K Jerry

    2008-01-30

    A simple urban dispersion model is tested that is based on the Gaussian plume model and the Briggs’ urban dispersion curves. A key aspect of the model is that an initial dispersion coefficient (sigma) of 40 m is assumed to apply in the x, y, and z directions in built-up downtown areas. This initial sigma accounts for mixing in the local street canyon and/or building wakes. At short distances (i.e., when the release is in the same street canyon as the receptor and there are no obstructions in between), the initial lateral sigma is assumed to be less, 10 m. Observations from tracer experiments during the Madison Square Garden 2005 (MSG05) field study are used for model testing. MSG05 took place in a 1 km by 1 km area in Manhattan surrounding Madison Square Garden. Six different perfluorocarbon tracer (PFT) gases were released concurrently from five different locations around MSG, and concentrations in the air were observed by 20 samplers near the surface and seven samplers on building tops. There were two separate continuous 60 minute tracer release periods on each day, beginning at 9 am and at 11:30 am. Releases took place on two separate days (March 10 and 14). The samplers provided 30 minute averaged PFT concentrations from 9 am through 2 pm. This analysis focuses on the maximum 60-minute averaged PFT gas concentration at each sampler location for each PFT for each release period. Stability was assumed to be nearly neutral, because of the moderate winds and the mechanical mixing generated by the buildings. Input wind direction was the average observed building-top wind direction (285° on March 10 and 315° on March 14). Input wind speed was the average street-level observed wind speed (1.5 m/s for both days). To be considered in the evaluation, both the observed and predicted concentration had to exceed the threshold. Concentrations normalized by source release rate, C/Q, were tested. For all PFTs, samplers, and release times, the median observed and predicted

  7. Innovative techniques for the description of reservoir heterogeneity using tracers

    SciTech Connect

    Pope, G.; Sepehrnoori, K.

    1991-09-01

    The objective of this research is to develop an advanced, innovative technique for the description of reservoir heterogeneity. This proposed method consists of using tracers in single-well backflow tests. The general idea is to make use of fluid drift in the reservoir either due to naturally occurring pressure gradients in the reservoir, or by deliberately imposed pressure gradients using adjacent injection and production wells in the same reservoir. The analytical tool that will be used to design and interpret these tests is a compositional reservoir simulator with special features added and tested specifically for this purpose. 2 refs., 5 figs.

  8. Peak and Tail Scaling of Breakthrough Curves in Hydrologic Tracer Tests

    NASA Astrophysics Data System (ADS)

    Aquino, T.; Aubeneau, A. F.; Bolster, D.

    2014-12-01

    Power law tails, a marked signature of anomalous transport, have been observed in solute breakthrough curves time and time again in a variety of hydrologic settings, including in streams. However, due to the low concentrations at which they occur they are notoriously difficult to measure with confidence. This leads us to ask if there are other associated signatures of anomalous transport that can be sought. We develop a general stochastic transport framework and derive an asymptotic relation between the tail scaling of a breakthrough curve for a conservative tracer at a fixed downstream position and the scaling of the peak concentration of breakthrough curves as a function of downstream position, demonstrating that they provide equivalent information. We then quantify the relevant spatiotemporal scales for the emergence of this asymptotic regime, where the relationship holds, in the context of a very simple model that represents transport in an idealized river. We validate our results using random walk simulations. The potential experimental benefits and limitations of these findings are discussed.

  9. Characterizing Aquifer Heterogeneity Using Bacterial and Bacteriophage Tracers.

    PubMed

    Flynn, Raymond M; Mallèn, German; Engel, Marion; Ahmed, Ashraf; Rossi, Pierre

    2015-09-01

    Gravel aquifers act as important potable water sources in central western Europe, yet they are subject to numerous contamination pressures. Compositional and textural heterogeneity makes protection zone delineation around groundwater supplies in these units challenging; artificial tracer testing aids characterization. This paper reappraises previous tracer test results in light of new geological and microbiological data. Comparative passive gradient testing, using a fluorescent solute (Uranine), virus (H40/1 bacteriophage), and comparably sized bacterial tracers and , was used to investigate a calcareous gravel aquifer's ability to remove microbiological contaminants at a test site near Munich, Germany. Test results revealed relative recoveries could exceed those of H40/1 at monitoring wells, 10 m and 20 m from an injection well, by almost four times; recoveries varied by a factor of up to three between wells. Application of filtration theory suggested greater attenuation of H40/1 relative to similarly charged occurred due to differences in microorganism size, while estimated collision efficiencies appeared comparable. By contrast, more positively charged experienced greater attenuation at one monitoring point, while lower attenuation rates at the second location indicated the influence of geochemical heterogeneity. Test findings proved consistent with observations from nearby fresh outcrops that suggested thin open framework gravel beds dominated mass transport in the aquifer, while discrete intervals containing stained clasts reflect localized geochemical heterogeneity. Study results highlight the utility of reconciling outcrop observations with artificial tracer test responses, using microbiological tracers with well-defined properties, to characterize aquifer heterogeneity. PMID:26436262

  10. High gradient test of the HINS SSR1 single spoke resonator

    SciTech Connect

    Gonin, I.; Khabibouline, T.; Lanfranco, G.; Mukherjee, A.; Ozelis, JH.; Ristori, L.; Sergatskov, A.; Wagner, R.; Webber, R.; /Fermilab

    2008-09-01

    Eighteen {beta} = 0.21 superconducting single spoke resonators comprise the first state in the cold section of the 8-GeV H{sup -} Linac for Fermilab's proposed Project X. After Buffered Chemical Polishing and High Pressure Rinse, one resonator has undergone high gradient RF testing at 2.0-4.5 K in the Vertical Test Stand at Fermilab. They present measurements of the surface resistance as a function of temperature and the quality factor as a function of accelerating field. The resonator reached an accelerating field of 18.0 MV/m.

  11. Production of stream habitat gradients by montane watersheds: Hypothesis tests based on spatially explicit path analyses

    USGS Publications Warehouse

    Isaak, D.J.; Hubert, W.A.

    2001-01-01

    We studied how the features of mountain watersheds interact to cause gradients in three stream attributes: baseflow stream widths, total alkalinity, and stream slope. A priori hypotheses were developed before being tested in a series of path analyses using data from 90 stream reaches on 24 second- to fourth-order streams across a fifth-order Rocky Mountain watershed. Because most of the conventional least squares regressions initially calculated for the path analyses had spatially correlated residuals (13 of 15 regressions), spatially explicit regressions were often used to derive more accurate parameter estimates and significance tests. Our final working hypotheses accounted for most of the variation in baseflow stream width (73%), total alkalinity (74%), and stream slope (78%) and provide systemic views of watershed function by depicting interactions that occur between geomorphology, land surface features, and stream attributes. Stream gradients originated mainly from the unidirectional changes in geomorphic features that occur over the lengths of streams. Land surface features were of secondary importance and, because they change less predictably relative to the stream, appear to modify the rate at which stream gradients change.

  12. Interfacial Partitioning Tracer Test Measurement of NAPL-Water Interfacial Areas in Porous Media under Two-Phase Flow Condition

    NASA Astrophysics Data System (ADS)

    Zhong, H.; El Ouni, A.; Lin, D.; Wang, B.; Brusseau, M. L.

    2013-12-01

    The NAPL-water interface is of critical importance for the transport, fate, and remediation of organic contaminants in the subsurface due to its influence on contaminant mass transfer, transport, and biotransformation. In this work, the interfacial areas between tetrachloroethene (PCE) liquid (non-wetting phase) and water (wetting phase) in porous media were measured under two-phase flow conditions using the interfacial partitioning tracer test (IPTT) method. Three wetting scenarios of primary drainage, secondary imbibition, and secondary drainage were investigated. Two porous media were used, a well-sorted 45/50 mesh quartz sand and a sandy soil. The theoretical maximum interfacial areas determined from the measured data are compared to the specific solid surface area determined in two ways, based on geometrical calculations for smooth spheres and as measured with the N2/BET method. The results obtained for the NAPL-water system are compared to measurements conducted for comparable air-water systems.

  13. Hydrological parameter estimations from a conservative tracer test with variable-density effects at the Boise Hydrogeophysical Research Site

    NASA Astrophysics Data System (ADS)

    Dafflon, B.; Barrash, W.; Cardiff, M.; Johnson, T. C.

    2011-12-01

    Reliable predictions of groundwater flow and solute transport require an estimation of the detailed distribution of the parameters (e.g., hydraulic conductivity, effective porosity) controlling these processes. However, such parameters are difficult to estimate because of the inaccessibility and complexity of the subsurface. In this regard, developments in parameter estimation techniques and investigations of field experiments are still challenging and necessary to improve our understanding and the prediction of hydrological processes. Here we analyze a conservative tracer test conducted at the Boise Hydrogeophysical Research Site in 2001 in a heterogeneous unconfined fluvial aquifer. Some relevant characteristics of this test include: variable-density (sinking) effects because of the injection concentration of the bromide tracer, the relatively small size of the experiment, and the availability of various sources of geophysical and hydrological information. The information contained in this experiment is evaluated through several parameter estimation approaches, including a grid-search-based strategy, stochastic simulation of hydrological property distributions, and deterministic inversion using regularization and pilot-point techniques. Doing this allows us to investigate hydraulic conductivity and effective porosity distributions and to compare the effects of assumptions from several methods and parameterizations. Our results provide new insights into the understanding of variable-density transport processes and the hydrological relevance of incorporating various sources of information in parameter estimation approaches. Among others, the variable-density effect and the effective porosity distribution, as well as their coupling with the hydraulic conductivity structure, are seen to be significant in the transport process. The results also show that assumed prior information can strongly influence the estimated distributions of hydrological properties.

  14. Evidence of distinct contaminant transport patterns in rivers using tracer tests and a multiple domain retention model

    NASA Astrophysics Data System (ADS)

    Bottacin-Busolin, Andrea; Marion, Andrea; Musner, Tommaso; Tregnaghi, Matteo; Zaramella, Mattia

    2011-06-01

    Solute transport in rivers is controlled by surface hydrodynamics and by mass exchanges with distinct retention zones. Surface and hyporheic retention processes can be accounted for separately in solute transport models with multiple storage compartments. In the simplest two component model, short term storage can be associated to in-channel transient retention, e.g. produced by riparian vegetation or surface dead zones, and the long-term storage can be associated to hyporheic exchange. The STIR (Solute Transport In Rivers) multiple domain transport model is applied here to tracer test data from three very different Mediterranean streams with distinctive characteristics in terms of flow discharge, vegetation and substrate material. The model is used with an exponential residence time distribution (RTD) to represent surface storage processes and two distinct modeling closures are tested to simulate hyporheic retention: a second exponential RTD and a power-law distribution approximating a known solution for bedform-induced hyporheic exchange. Each stream shows distinct retention patterns characterized by different timescales of the storage time distribution. Both modeling closures lead to very good approximations of the observed breakthrough curves in the two rivers with permeable bed exposed to the flow, where hyporheic flows are expected to occur. In the one case where the occurrence of hyporheic flows is inhibited by bottom vegetation, only the two exponential RTD model is acceptable and the time scales of the two components are of the same magnitude. The significant finding of this work is the recognition of a strong signature of the river properties on tracer data and the evidence of the ability of multiple-component models to describe individual stream responses. This evidence may open a new perspective in river contamination studies, where rivers could possibly be classified based on their ability to trap and release pollutants.

  15. In situ tracer tests to determine retention properties of a block scale fracture network in granitic rock at the Äspö Hard Rock Laboratory, Sweden

    NASA Astrophysics Data System (ADS)

    Andersson, Peter; Byegård, Johan; Tullborg, Eva-Lena; Doe, Thomas; Hermanson, Jan; Winberg, Anders

    2004-06-01

    Experiments were conducted at the Äspö Hard Rock Laboratory in order to improve the understanding of radionuclide retention properties of fractured crystalline bedrock in the 10-100 m scale (TRUE Block Scale Project, jointly funded by ANDRA, ENRESA, Nirex, JNC, Posiva and SKB). A series of tracer experiments were performed using sorbing tracers in three different flow paths. The different flow paths had Euclidian lengths of 14, 17 and 33 m, respectively, and one to three water conducting structures. Four tests were performed using different cocktails made up of radioactive sorbing tracers ( 22,24Na +, 42K +, 47Ca 2+, 85Sr 2+, 83,86Rb +, 131,133Ba 2+ and 134,137Cs +). For each tracer injection, the breakthrough of sorbing tracers was compared to the breakthrough of a conservative tracer, 82Br -, 131I -, HTO and 186ReO 4-, respectively. In the two longer flow paths, no breakthrough of 83Rb + and 137Cs + was observed after 8 months of pumping. Selected tracer tests were subject to basic modelling in which a one-dimensional (1D) advection-dispersion model, including surface sorption, and an unlimited matrix diffusion were used for the interpretation of the results. The results of the modelling indicated that there is a slightly higher mass transfer into a highly porous material in the block-scale experiment compared with in situ experiments performed over shorter distances and significantly higher than what would have been expected from laboratory data obtained from studies of the interactions in nonaltered intact rock.

  16. LARGE-SCALE NATURAL GRADIENT TRACER TEST IN SAND AND GRAVEL, CAPE COD, MASSACHUSETTS 3. HYDRAULIC CONDUCTIVITY AND CALCULATED MACRODISPERSIVITIES

    EPA Science Inventory

    Development of methodologies to evaluate certain classes of polycyclic aromatic compounds (PAC) detected in complex mixtures to which humans are xposed ould greatly improve the diagnostic potential of 32P-postlabeling analysis. dentification of DNA adduct patterns or specific exp...

  17. Cyclic Failure Mechanisms of Thermal and Environmental Barrier Coating Systems Under Thermal Gradient Test Conditions

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Lee, Kang N.; Miller, Robert A.

    2002-01-01

    Plasma-sprayed ZrO2-8wt%Y2O3 and mullite+BSAS/Si multilayer thermal and environmental barrier coating (TBC-EBC) systems on SiC/SiC ceramic matrix composite (CMC) substrates were thermally cyclic tested under high thermal gradients using a laser high-heat-flux rig in conjunction with furnace exposure in water-vapor environments. Coating sintering and interface damage were assessed by monitoring the real-time thermal conductivity changes during the laser heat-flux tests and by examining the microstructural changes after exposure. Sintering kinetics of the coating systems were also independently characterized using a dilatometer. It was found that the coating failure involved both the time-temperature dependent sintering and the cycle frequency dependent cyclic fatigue processes. The water vapor environments not only facilitated the initial coating conductivity increases due to enhanced sintering and interface reaction, but also promoted later conductivity reductions due to the accelerated coating cracking and delamination. The failure mechanisms of the coating systems are also discussed based on the cyclic test results and are correlated to the sintering and thermal stress behavior under the thermal gradient test conditions.

  18. Interpretation of Perfluorocarbon Tracer Data Collected During the Frio Carbon Dioxide Sequestration Test

    NASA Astrophysics Data System (ADS)

    McCallum, S. D.; Phelps, T. J.; Riestenberg, D. E.; Freifeld, B. M.; Trautz, R. C.

    2005-12-01

    In October of 2004 over 1600 tons of CO2 was injected into a brine-bearing sandstone unit within the Frio Formation. An injection well was used to introduce the CO2 into the Frio at a depth of 1540 meters below the surface. A monitoring well located 31 meters updip from the injection well was used to sample formation fluids and detect the breakthrough of the CO2 plume. Perfluorocarbon tracers (PFTs) were injected in three paired intervals at the beginning and middle of the CO2 injection. The four PFTs selected for injection were perfluoromethylcyclopentane (PMCP), perfluoromethylcyclohexane (PMCH), perfluorodimethylcyclohexane (PDCH), and perfluorotrimethylcyclohexane (PTCH). The PFTs were used as a means to monitor CO2 plume breakthroughs and aid in the interpretation of CO2 flow path development. Fluid samples were collected at the monitoring well during and after the CO2 and PFT injections. These samples were later analyzed in the laboratory to measure the concentration of PFTs. Laboratory analysis was performed using a gas chromatograph (GC) equipped with an electron capture detector (ECD). Standardization of the data set was achieved by dividing C by Cno (C/Cno), where C is the molar mass of PFT and CO2 recovered and Cno is the initial molar mass of PFT and CO2 injected. The C/Cno data showed the amount of PFT dilution that occurred between injection and collection. Analysis of the C/Cno data revealed three breakthrough peaks corresponding with the three PFT injections at 54, 157, and 173 hours after the start of CO2 injection, with an average travel time of 51 hours for each injection. With each subsequent PFT peak a greater amount of PFT dilution was observed along with a broadening of the breakthrough peak. The first PFT breakthrough spans 10 hours, the second spans 20 hours and the third spans 24 hours. The increase in peak broadness observed in each subsequent breakthrough may have been caused by increased CO2 saturation. Since PFTs are more soluble in CO

  19. Ellenberg's water table experiment put to the test: species optima along a hydrological gradient.

    PubMed

    Bartelheimer, Maik; Poschlod, Peter

    2016-08-01

    An important aspect of niche theory is the position of species' optima along ecological gradients. It is widely believed that a species' ecological optimum takes its shape only under competitive pressure. The ecological optimum, therefore, is thought to differ from the physiological optimum in the absence of interspecific competition. Ellenberg's Hohenheim water table experiment has been very influential in this context. However, the water table gradient in Ellenberg's experiment was produced by varying the soil thickness above the water table, which confounded the potentially disparate impacts of water table depth (WTD) and soil depth on species growth. Accordingly, here we have re-evaluated Ellenberg's work. Specifically, we tested the hypothesis that physiological and ecological optima are identical and unaffected by interspecific interaction. We used the same six grasses as in Ellenberg's experiments, but in our mesocosms, WTD was varied but soil depth kept constant. The design included both an additive component (with/without plant interaction) and a substitutive component (monocultures vs. species mixtures). The results show that the physiological optima along the hydrological gradient varied greatly between species, even in the absence of interspecific interaction. Within species, however, physiological and ecological optima appeared identical in most cases, irrespective of the competition treatment. We conclude that the 'physiological capacity' of species largely determines where they are able to persist and that any impact of interspecific interaction is only marginal. These findings are at variance with Ellenberg's rule, where competition is considered to shift the distribution of a species away from its physiological optimum. PMID:27094542

  20. Electrochemical Potential Gradient as a Quantitative in Vitro Test Platform for Cellular Oxidative Stress.

    PubMed

    Bryant, Carson; Atha, Donald; Reipa, Vytas

    2016-01-01

    Oxidative stress in a biological system is often defined as a redox imbalance within cells or groups of cells within an organism. Reductive-oxidative (redox) imbalances in cellular systems have been implicated in several diseases, such as cancer. To better understand the redox environment within cellular systems, it is important to be able to characterize the relationship between the intensity of the oxidative environment, characterized by redox potential, and the biomolecular consequences of oxidative damage. In this study, we show that an in situ electrochemical potential gradient can serve as a tool to simulate exogenous oxidative stress in surface-attached mammalian cells. A culture plate design, which permits direct imaging and analysis of the cell viability, following exposure to a range of solution redox potentials, was developed. The in vitro oxidative stress test vessel consists of a cell growth flask fitted with two platinum electrodes that support a direct current along the flask bottom. The applied potential span and gradient slope can be controlled by adjusting the constant current magnitude across the vessel with spatially localized media potentials measured with a sliding reference electrode. For example, the viability of Chinese Hamster Ovary cells under a gradient of redox potentials indicated that cell death was initiated at approximately 0.4 V vs. standard hydrogen electrode (SHE) media potential and this potential could be modified with antioxidants. This experimental platform may facilitate studies of oxidative stress characteristics on different types of cells by enabling imaging live cell cultures that have been exposed to a gradient of exogenous redox potentials. PMID:27409641

  1. Inferences about Shear Zone Flow Pathways between CFM 06.002i2 and Pinkel from Tracer Tests 10-01 to 12-02

    SciTech Connect

    Reimus, Paul W.

    2012-06-26

    This presentation provides an analysis of several tracer tests conducted at the Grimsel Test Site, Switzerland, between 2010 and early 2012, with the objective of testing a conceptual model of flow through the shear zone in which the tracer tests were conducted. The analysis includes predictions of tracer residence times in each of two flow pathways in the shear zone as a function of injection and extraction flow rates in the tracer tests. Conclusions are: (1) Separation of shear zone flow between CFM 06.002i2 and Pinkel into two predominant flow pathways seems reasonable; (2) Conceptual model is that travel time in pathway 1 is dependent on injection flow rate, and travel time in pathway 2 is dependent on extraction flow rate; (3) Predict residence time (in hours) in Pathway 1 equal to {approx}9.9/(Injection Flow Rate, ml/min), provided injection interval flow is greater than about 0.15 ml/min (which is not reliably achieved under natural flow/dilution conditions after installation of CFM 11.00X holes); and (4) Predict residence time of {approx}8 hrs in Pathway 2 with extraction flow rate of 25 ml/min.

  2. On the use of flow-storage repartitions derived from artificial tracer tests for geothermal reservoir characterization in the Malm-Molasse basin: a theoretical study

    NASA Astrophysics Data System (ADS)

    Dewi, Dina Silvia; Osaigbovo Enomayo, Augustine; Mohsin, Rizwan; Karmakar, Shyamal; Ghergut, Julia; Sauter, Martin

    2016-04-01

    Flow-storage repartition (FSR) analysis (Shook 2003) is a versatile tool for characterizing subsurface flow and transport systems. FSR can be derived from measured signals of inter-well tracer tests, if certain requirements are met - basically, the same as required for equivalence between fluid residence time distribution (RTD) and a measured inter-well tracer signal (pre-processed and de-convolved if necessary). Nominally, a FSR is derived from a RTD as a trajectory in normalized {1st, 0th}-order statistical moment space; more intuitively, as a parametric plot of 0th-order against 1st-order statistical moments of RTD truncated at time t, with t as a parameter running from the first tracer input to the latest available tracer sampling; 0th-order moments being normalized by the total tracer recovery, and 1st-order moments by the mean RT. Fracture-dominated systems plot in the upper left (high F , low S) region of FSR diagrams; a homogeneous single-continuum with no dispersion (infinite Peclet number) displays a straight line from {F ,S}={0,0} to {F ,S}={1,1}. This analysis tool appears particularly attractive for characterizing markedly-heterogeneous, porous-fissured-fractured (partly karstified) formations like those targeted by geothermal exploration in the Malm-Molasse basin in Southern Germany, and especially for quantifying flow and transport contributions from contrasting facies types ('reef' versus 'bedded'). However, tracer tests conducted in such systems with inter-well distances of some hundreds of metres (as required by economic considerations on geothermal reservoir sizing) face the problem of very long residence times - and thus the need to deal with incomplete (truncated) signals. For the geothermal well triplet at the Sauerlach site near Munich, tracer peak arrival times exceeding 2 years have been predicted, and signal tails decreasing by less than 50% over >10 years, which puts great uncertainty on the (extrapolation-based) normalizing factors

  3. Southeast Geyers Cooperative Tracer Evaluation and Testing Program for the Purpose of Estimating The Efficiency of Injection

    SciTech Connect

    J.L. Smith

    2001-02-12

    The Southeast Geysers Cooperative Tracer Evaluation Program has been a joint project located in the SE part of the Geysers geothermal field, in Lake and Sonoma Counties, California. A new generation of environmentally benign vapor-phase tracers has been used to estimate the varying degrees to which injectate is being recovered following the significant increase of injected volumes within the Southeast Geysers.

  4. Predicting the denitrification capacity of sandy aquifers from in situ measurements using push-pull 15N tracer tests

    NASA Astrophysics Data System (ADS)

    Eschenbach, W.; Well, R.; Walther, W.

    2015-04-01

    Knowledge about the spatial variability of in situ denitrification rates (Dr(in situ)) and their relation to the denitrification capacity in nitrate-contaminated aquifers is crucial to predict the development of groundwater quality. Therefore, 28 push-pull 15N tracer tests for the measurement of in situ denitrification rates were conducted in two sandy Pleistocene aquifers in northern Germany. The 15N analysis of denitrification-derived 15N-labelled N2 and N2O dissolved in water samples collected during the push-pull 15N tracer tests was performed using isotope ratio mass spectrometry (IRMS) in the lab and additionally for some tracer tests online in the field with a quadrupole membrane inlet mass spectrometer (MIMS) in order to test the feasibility of on-site real-time 15N analysis. Aquifer material from the same locations and depths as the push-pull injection points was incubated, and the initial and cumulative denitrification after 1 year of incubation (Dcum(365)) as well as the stock of reduced compounds (SRC) was compared with in situ measurements of denitrification. This was done to derive transfer functions suitable to predict Dcum(365) and SRC from Dr(in situ). Dr(in situ) ranged from 0 to 51.5 μg N kg-1 d-1. Denitrification rates derived from on-site isotope analysis using MIMS satisfactorily coincided with laboratory analysis by conventional IRMS, thus proving the feasibility of in situ analysis. Dr(in situ) was significantly higher in the sulfidic zone of both aquifers compared to the zone of non-sulfidic aquifer material. Overall, regressions between the Dcum(365) and SRC of the tested aquifer material with Dr(in situ) exhibited only a modest linear correlation for the full data set. However, the predictability of Dcum(365) and SRC from Dr(in situ) data clearly increased for aquifer samples from the zone of NO3--bearing groundwater. In the NO3--free aquifer zone, a lag phase of denitrification after NO3- injections was observed, which confounded the

  5. Predicting the denitrification capacity of sandy aquifers from in situ measurements using push-pull 15N tracer tests

    NASA Astrophysics Data System (ADS)

    Eschenbach, W.; Well, R.; Walther, W.

    2014-12-01

    Knowledge about the spatial variability of in situ denitrification rates (Dr(in situ)) and their relation to the denitrification capacity in nitrate-contaminated aquifers is crucial to predict the development of groundwater quality. Therefore, 28 push-pull 15N tracer tests for the measurement of in situ denitrification rates were conducted in two sandy Pleistocene aquifers in Northern Germany. The 15N analysis of denitrification derived 15N labelled N2 and N2O dissolved in water samples collected during the push-pull 15N tracer tests was performed by isotope ratio mass spectrometry (IRMS) in the lab and additionally for some tracer tests online in the field with a quadrupole membrane inlet mass spectrometer (MIMS), in order to test the feasibility of on-site real-time 15N analysis. Aquifer material from the same locations and depths as the push-pull injection points was incubated and the initial and cumulative denitrification after one year of incubation (Dcum(365)) as well as the stock of reduced compounds (SRC) was compared with in situ measurements of denitrification. This was done to derive transfer functions suitable to predict Dcum(365) and SRC from Dr(in situ). Dr(in situ) ranged from 0 to 51.5 μg N kg-1 d-1. Denitrification rates derived from on-site isotope analysis using membrane-inlet mass spectrometry satisfactorily coincided with laboratory analysis by conventional isotope ratio mass spectrometry, thus proving the feasibility of in situ analysis. Dr(in situ) was significantly higher in the sulphidic zone of both aquifers compared to the zone of non-sulphidic aquifer material. Overall, regressions between the Dcum(365) and SRC of the tested aquifer material with Dr(in situ) exhibited only a modest linear correlation for the full data set. But the predictability of Dcum(365) and SRC from Dr(in situ) data clearly increased for aquifer samples from the zone of NO3--bearing groundwater. In the NO3--free aquifer zone a lag phase of denitrification after NO3

  6. Reactivity of Hontomín carbonate rocks to acidic solution injection: reactive "push-pull" tracer tests results

    NASA Astrophysics Data System (ADS)

    De Gaspari, Francesca; Cabeza, Yoar; Luquot, Linda; Rötting, Tobias; Saaltink, Maarten W.; Carrera, Jesus

    2014-05-01

    Several field tests will be carried out in order to characterize the reservoir for CO2 injection in Hontomín (Burgos, Spain) as part of the Compostilla project of "Fundación Ciudad de la Energía" (CIUDEN). Once injected, the dissolution of the CO2 in the resident brine will increase the acidity of the water and lead to the dissolution of the rocks, constituted mainly by carbonates. This mechanism will cause changes in the aquifer properties such as porosity and permeability. To reproduce the effect of the CO2 injection, a reactive solution with 2% of acetic acid is going to be injected in the reservoir and extracted from the same well (reactive "push-pull" tracer tests) to identify and quantify the geochemical reactions occurring into the aquifer. The reactivity of the rock will allow us also to evaluate the changes of its properties. Previously, theoretical calculations of Damkhöler numbers were done to determine the acid concentrations and injection flow rates needed to generate ramified-wormholes patterns, during theses "push-pull" experiments. The aim of this work is to present the results and a preliminary interpretation of the field tests.

  7. The use of perfluorocarbon tracer (PFT) technology to determine fine leaks in hermeticity testing of semiconductor devices

    SciTech Connect

    Dietz, R.N.

    1991-05-01

    The BNL-developed perfluorocarbon tracer (PFT) technology includes a rapid-response real-time (5-second) analyzer (COPS) which can detect PFT concentrations as low as 1 {times} 10{sup {minus}11} mL/mL and a concentrating analyzer (DTA) which can measure down to 1 {times} 10{sup {minus}12} mL of PFT--separately quantifying up to 4 PFTs in a 6-min cycle time or less. Based on this technology, experimental leak- rate design concepts are proposed for determining the effectiveness (hermeticity) of the seal of semiconductor devices with internal cavities from 0.01 to 1 mL. The concept is based on pressurizing with PFT-containing air for 60 seconds, purging with PFT-free air for 60 seconds, pressure pulsing with air or He to extract the PFT leaked into the internal volume, and finally detecting the PFT vapor concentration with one of the two instruments. The COPS analyzer can quantify gross leaks from 1 {times} 10{sup {minus}7} to 1 {times} 10{sup {minus}3} mL/s in just 3 minutes for the complete test. The more-sensitive concentrating analyzer (DTA) can quantify fine leaks from 0.2 {times} 10{sup {minus}8} to 1 {times} 10{sup {minus}3} mL/s in just 12 minutes for the complete test; the latter procedure includes two determinations per test. 5 refs., 2 tabs.

  8. Migration of fission products at the Nevada Test Site: Detection with an isotopic tracer

    SciTech Connect

    Thompton, J.L.; Gilmore, J.S. )

    1989-01-01

    Researchers at Los Alamos National Laboratory are studying the migration of fission products away from explosion cavities formed by underground nuclear tests at the Nevada Test Site. In some cases, the isotopic composition of the fission products or activation products associated with a particular test are distinctive and we may identify them many years after the event. In this paper we describe a case in which we used rhodium isotopes to identify the source of radioactive material that had moved some 350 m from the explosion site. 4 refs., 2 figs., 2 tabs.

  9. Tracer Tests in a Fractured Dolomite: 2. Controls on Mass-Recovery Rates for a Single-Porosity, Heterogeneous Conceptualization

    SciTech Connect

    Altman, S.J.; Meigs, L.C.; Jones, T.L.

    1999-03-04

    A single-well injection-withdrawal (SWIW) test is evaluated as a tool to differentiate between single- and double-porosity conceptualizations of a system. Results from single-porosity simulations incorporating plume drift are also compared to observed data from a recent series of SWIW tests conducted in a fractured dolomite unit, for which a double-porosity conceptualization has been proposed. We evaluate the difficulty of differentiating the response for a double-porosity conceptualization from that for a heterogeneous, single-porosity conceptualization incorporating plume drift. Results of sensitivity studies on multiple, stochastically generated, heterogeneous transmissivity fields indicate that to simulate extremely slow mass-recovery rates for a SWIW test with a single-porosity conceptualization, the following conditions must be present: plume drift, extreme heterogeneities (high {sigma}InT), and an unusual configuration of the high and low transmissivity regions relative to the well location. A compilation of existing data suggests that the high degree of heterogeneity necessary is rare at the SWIW test scale.The observed data from the SWIW tracer tests cannot be matched to numerical simulation results when a single-porosity conceptualization is assumed. A signature of significant drift is less than 100% mass recovery with a zero derivative with respect to time of the late-time normalized cumulative mass curve indicating mass transported outside the capture zone of the withdrawal well. To minimize the risk of misinterpretation, an important design feature for SWIW tests is the collection of late-time data so that percent total mass recovery can be calculated.

  10. A new tracer-density criterion for heterogeneous porous media

    USGS Publications Warehouse

    Barth, G.R.; Illangasekare, T.H.; Hill, M.C.; Rajaram, H.

    2001-01-01

    Tracerexperiments provide information about aquifer material properties vital for accurate site characterization. Unfortunately, density-induced sinking can distort tracer movement, leading to an inaccurate assessment of material properties. Yet existing criteria for selecting appropriate tracer concentrations are based on analysis of homogeneous media instead of media with heterogeneities typical of field sites. This work introduces a hydraulic-gradient correction for heterogeneous media and applies it to a criterion previously used to indicate density-induced instabilities in homogeneous media. The modified criterion was tested using a series of two-dimensional heterogeneous intermediate-scale tracer experiments and data from several detailed field tracer tests. The intermediate-scale experimental facility (10.0 ?? 1.2 ?? 0.06 m) included both homogeneous and heterogeneous (??2/In ?? = 1.22) zones. The field tracer tests were less heterogeneous (0.24 < ??2/ln ?? < 0.37), but measurements were sufficient to detect density-induced sinking. Evaluation of the modified criterion using the experiments and field tests demonstrates that the new criterion appears to account for the change in density-induced sinking due to heterogeneity. The criterion demonstrates the importance of accounting for heterogeneity to predict density-induced sinking and differences in the onset of density induced sinking in two-and three-dimensional systems.

  11. Towards Truly Quiet MRI: animal MRI magnetic field gradients as a test platform for acoustic noise reduction

    NASA Astrophysics Data System (ADS)

    Edelstein, William; El-Sharkawy, Abdel-Monem

    2013-03-01

    Clinical MRI acoustic noise, often substantially exceeding 100 dB, causes patient anxiety and discomfort and interferes with functional MRI (fMRI) and interventional MRI. MRI acoustic noise reduction is a long-standing and difficult technical challenge. The noise is basically caused by large Lorentz forces on gradient windings--surrounding the patient bore--situated in strong magnetic fields (1.5 T, 3 T or higher). Pulsed currents of 300 A or more are switched through the gradient windings in sub-milliseconds. Experimenting with hardware noise reduction on clinical scanners is difficult and expensive because of the large scale and weight of clinical scanner components (gradient windings ~ 1000 kg) that require special handling equipment in large engineering test facilities. Our approach is to produce a Truly Quiet (<70 dB) small-scale animal imager. Results serve as a test platform for acoustic noise reduction measures that can be implemented in clinical scanners. We have so far decreased noise in an animal scale imager from 108 dB to 71 dB, a 37 dB reduction. Our noise reduction measures include: a gradient container that can be evacuated; inflatable antivibration mounts to prevent transmission of vibrations from gradient winding to gradient container; vibration damping of wires going from gradient to the outside world via the gradient container; and a copper passive shield to prevent the generation of eddy currents in the metal cryostat inner bore, which in turn can vibrate and produce noise.

  12. Implications of a Multi-well Tracer Test in the Transport of Pathogens at a Riverbank Filtration Experiment Site.

    NASA Astrophysics Data System (ADS)

    Langford, R. P.; Pillai, S.; Schulze-Makuch, D.; Widmer, K.; Abdel-Fattah, A.; Lerhner, T.

    2003-12-01

    This study tracks the transport of bromide and microspheres mimicking pathogens in an arid environment. The study site uses the Rio Grande that experiences significant annual fluctuations in both water quantity and quality. The pumping well is 17 m from the stream bank and the water table was 2 m below the stream surface. The aquifer is medium and fine-grained sand comprising two flow units. Observation wells are screened over 1 or 1.5 m intervals. The average hydraulic conductivity was about 2 x 10-3 m/s based on a test analysis, however, the responses indicated that sediment heterogeneities affected the hydraulic behavior. A 427 hour tracer test using bromide and fluorescent microspheres provides initial results that are relevant to the transport of pathogens through the subsurface under riverbank filtration conditions. Bromide was injected into an observation well at the channel margin. Differently colored fluorescent microspheres (0.25nm, 1?m, 6?m and 10?m) were injected into the stream bottom and into two observation wells. Conclusions from the tracer test are: 1) Both bromide and microspheres continued to be observed throughout the 18 days of the experiment. 2) The bromide recovery in the pumping well and in the deeper observation wells showed early and late peaks with a long tails indicating that the geological medium at the field site behaves like a double-porosity medium allowing the tracer to move relatively quickly through the higher conductivity units while being significantly retarded in the low hydraulic conductivity units. 3) Some wells showed consistently higher concentrations of bromide. 4) The 1? micospheres were abundant in the observation wells and allowed tracing of flowpaths. These showed multiple peaks similar to the bromide results. This indicates highly preferential transport paths in the sediment. 5) Microspheres from the three injection sites had distinctly different transport paths and rates. 6) Both bromide and microspheres appeared in

  13. Shape-free inference of hyporheic traveltime distributions from synthetic conservative and “smart” tracer tests in streams

    NASA Astrophysics Data System (ADS)

    Liao, Zijie; Cirpka, Olaf A.

    2011-07-01

    The hyporheic zone has been identified as important for river ecology, natural biogeochemical turnover, filtration of particles, degradation of dissolved pollutants—and thus for the self-cleaning capacity of streams, and for groundwater quality. Good estimation of the traveltime distribution in the hyporheic zone is required to achieve a better understanding of transport in the river system. The transient-storage model has been accepted as an appropriate tool for reach-scale transport in rivers undergoing hyporheic exchange, but the choice of the best parametric function for the hyporheic traveltime distribution has remained unclear. We present an approach to obtaining hyporheic traveltime distributions from synchronous conservative and "smart" tracer experiments that does not rely on a particular functional form of the hyporheic traveltime distribution, but treats the latter as a continuous function. Nonnegativity of the hyporheic traveltime distribution is enforced by the application of Lagrange multipliers. A smoothness parameter, needed for regularization, and uncertainty bounds are obtained by the expectation-maximization method relying on conditional realizations. The shape-free inference provides the opportunity for capturing unconventional shapes, e.g., multiple peaks, in the estimation. We test the approach by applying it to a virtual test case with a bimodal hyporheic traveltime distribution, which is recaptured in the inversion of noisy data.

  14. Microstructural evolutions and stability of gradient nano-grained copper under tensile tests and subsequent storage

    NASA Astrophysics Data System (ADS)

    Chen, W.; You, Z. S.; Tao, N. R.; Lu, L.

    2015-08-01

    A gradient nano-grained (GNG) surface layer is produced on a bulk coarse-grained Cu by means of a surface mechanical grinding treatment. Homogeneous grain coarsening induced by mechanical deformation is observed in the GNG Cu layer under tensile tests at both 300 K and 123 K. The concurrent grain coarsening during tensile deformation is proven to be also thermally activated, because the extent of grain coarsening of the GNG Cu layer is less significant at 123 K than at 300 K, although a higher flow stress is achieved at 123 K. During the subsequent storage at 258 K after tensile tests, no obvious change can be found for the grain size in the GNG Cu layer deformed at 300 K. In contrast, widespread abnormal grain coarsening is frequently observed in the GNG Cu layer deformed at 123 K and stored for 100 days, which may be caused by the higher stored energy in the non-equilibrium grain boundary structures.

  15. Tracer Technique

    NASA Astrophysics Data System (ADS)

    Haba, H.; Motomura, S.; Kamino, S.; Enomoto, S.

    In radioactive tracer technique, radioactive nuclides are used to follow the behavior of elements or chemical species in chemical and other processes. This is realized by means of radioactivity measurement. In 1913, Hevesy and Paneth succeeded in determining the extremely low solubility of lead salts by using naturally occurring 210Pb as a radioactive tracer. As various radioactive nuclides became artificially available, this technique has been widely employed in studies of chemical equilibrium and reactions as well as in chemical analysis. It is also an essential technique in biochemical, biological, medical, geological, and environmental studies. Medical diagnosis and industrial process control are the fields of its most important practical application. In this chapter, fundamental ideas concerning radioactive tracers will be described followed by their application with typical examples. Detailed description on their application to life sciences and medicine is given in Vol. 4.

  16. Deuterium stable isotope ratios as tracers of water resource use: an experimental test with rock doves.

    PubMed

    McKechnie, Andrew E; Wolf, Blair O; Martínez del Rio, Carlos

    2004-07-01

    Naturally-occurring deuterium stable isotope ratios can potentially be used to trace water resource use by animals, but estimating the contribution of isotopically distinct water sources requires the accurate prediction of isotopic discrimination factors between water inputs and an animal's body water pool. We examined the feasibility of using estimates of water fluxes between a bird and its environment with a mass-balance model for the deuterium stable isotope ratio of avian body water (deltaDbody) to predict isotopic discrimination factors. Apparent fractionation and thus discrimination factors were predicted to vary with the proportion of an animal's total water losses than could be attributed to evaporative processes. To test our ability to predict isotopic discrimination, we manipulated water intake and evaporative water loss in rock doves (Columba livia) by providing them with fresh water or 0.15 M NaCl solution in thermoneutral or hot environments. After we switched the birds from drinking water with deltaD=-95 per thousand VSMOW (Vienna Standard Mean Ocean Water) to enriched drinking water with deltaD=+52 per thousand VSMOW, steady-state deltaDbody was approached asymptotically. The equilibrium deltaDbody was enriched by 10-50 per thousand relative to water inputs. After isotopic equilibrium was reached, the degree of enrichment was positively related (r2=0.34) to the fraction of total water loss that occurred by evaporation (revap/rH2O)supporting the major prediction of the model. The variation we observed in discrimination factors suggests that the apparent fractionation of deuterium will be difficult to predict accurately under natural conditions. Our results show that accurate estimates of the contribution of different water sources to a bird's body water pool require large deuterium isotopic differences between the sources. PMID:15185137

  17. Miniaturized Antimicrobial Susceptibility Test by Combining Concentration Gradient Generation and Rapid Cell Culturing

    PubMed Central

    Kim, Samuel C.; Cestellos-Blanco, Stefano; Inoue, Keisuke; Zare, Richard N.

    2015-01-01

    Effective treatment of bacterial infection relies on timely diagnosis and proper prescription of antibiotic drugs. The antimicrobial susceptibility test (AST) is one of the most crucial experimental procedures, providing the baseline information for choosing effective antibiotic agents and their dosages. Conventional methods, however, require long incubation times or significant instrumentation costs to obtain test results. We propose a lab-on-a-chip approach to perform AST in a simple, economic, and rapid manner. Our assay platform miniaturizes the standard broth microdilution method on a microfluidic device (20 × 20 mm) that generates an antibiotic concentration gradient and delivers antibiotic-containing culture media to eight 30-nL chambers for cell culture. When tested with 20 μL samples of a model bacterial strain (E. coli ATCC 25922) treated with ampicillin or streptomycin, our method allows for the determination of minimum inhibitory concentrations consistent with the microdilution test in three hours, which is almost a factor of ten more rapid than the standard method. PMID:27025635

  18. Coupled and uncoupled hydrogeophysical inversions using ensemble Kalman filter assimilation of ERT-monitored tracer test data

    NASA Astrophysics Data System (ADS)

    Camporese, Matteo; Cassiani, Giorgio; Deiana, Rita; Salandin, Paolo; Binley, Andrew

    2015-05-01

    Recent advances in geophysical methods have been increasingly exploited as inverse modeling tools in groundwater hydrology. In particular, several attempts to constrain the hydrogeophysical inverse problem to reduce inversion errors have been made using time-lapse geophysical measurements through both coupled and uncoupled (also known as sequential) inversion approaches. Despite the appeal and popularity of coupled inversion approaches, their superiority over uncoupled methods has not been proved conclusively; the goal of this work is to provide an objective comparison between the two approaches within a specific inversion modeling framework based on the ensemble Kalman filter (EnKF). Using EnKF and a model of Lagrangian transport, we compare the performance of a fully coupled and uncoupled inversion method for the reconstruction of heterogeneous saturated hydraulic conductivity fields through the assimilation of ERT-monitored tracer test data. The two inversion approaches are tested in a number of different scenarios, including isotropic and anisotropic synthetic aquifers, where we change the geostatistical parameters used to generate the prior ensemble of hydraulic conductivity fields. Our results show that the coupled approach outperforms the uncoupled when the prior statistics are close to the ones used to generate the true field. Otherwise, the coupled approach is heavily affected by "filter inbreeding" (an undesired effect of variance underestimation typical of EnKF), while the uncoupled approach is more robust, being able to correct biased prior information, thanks to its capability of capturing the solute travel times even in presence of inversion artifacts such as the violation of mass balance. Furthermore, the coupled approach is more computationally intensive than the uncoupled, due to the much larger number of forward runs required by the electrical model. Overall, we conclude that the relative merit of the coupled versus the uncoupled approach cannot

  19. Test of simultaneous synthetic DNA tracer injections for the estimation of the englacial and subglacial drainage system structure of Storglaciären, northern Sweden

    NASA Astrophysics Data System (ADS)

    Dahlke, H. E.; Leung, S.; Lyon, S. W.; Sharma, A. N.; Walter, M. T.; Williamson, A.

    2013-12-01

    Storglaciären glacier, located in the sub-arctic Tarfala catchment, in northern Sweden is one of the world's longest continuously monitored glaciers which provides a unique research platform for the long-term assessment of glacier and ice sheet processes. For example, small mountain glacier hydrological knowledge of the subglacial water distribution at the ice-bed interface has been applied to ice sheets to predict basal sliding processes. Basal sliding promoted by hydraulic jacking is an important glacial-velocity control that is dependent on the subglacial flow pathways' morphology. Thus, understanding subglacial water distribution and drainage system structure and morphology is crucial for modeling ice masses' flow. In order to estimate subglacial drainage system structure and morphology dye tracing experiments are widely employed. Tracer experiments provide quantitative parameters for any input location including tracer transit velocity, dispersivity, recovery and storage. However, spatial data coverage is limited by the finite number of tracers available for simultaneous tracing. In the presented study we test the use of synthetic DNA tracers for the assessment of the englacial and subglacial drainage system structure of Storglaciären. The synthetic DNA tracer is composed of polylactic acid (PLA) microspheres into which short strands of synthetic DNA and paramagnetic iron oxide nanoparticles are incorporated (Sharma et al., 2012, Environmental Science & Technology). Because the DNA sequences can be randomly combined the synthetic DNA tracer provides an enormous number of unique tracers (approximately 1.61 x 1060). Thus, these synthetic tracers have the advantage that multiple (>10) experiments can be conducted simultaneously, allowing a greater information gain within a shorter measurement period. Quantities of a certain DNA strand can be detected using biotechnology tools such as polymerase chain reaction (PCR) and quantitative PCR (qPCR). During the 2013

  20. Damage Characterization of EBC-SiCSiC Ceramic Matrix Composites Under Imposed Thermal Gradient Testing

    NASA Technical Reports Server (NTRS)

    Appleby, Matthew P.; Morscher, Gregory N.; Zhu, Dongming

    2014-01-01

    Due to their high temperature capabilities, Ceramic Matrix Composite (CMC) components are being developed for use in hot-section aerospace engine applications. Harsh engine environments have led to the development of Environmental Barrier Coatings (EBCs) for silicon-based CMCs to further increase thermal and environmental capabilities. This study aims at understanding the damage mechanisms associated with these materials under simulated operating conditions. A high heat-flux laser testing rig capable of imposing large through-thickness thermal gradients by means of controlled laser beam heating and back-side air cooling is used. Tests are performed on uncoated composites, as well as CMC substrates that have been coated with state-of-the-art ceramic EBC systems. Results show that the use of the EBCs may help increase temperature capability and creep resistance by reducing the effects of stressed oxidation and environmental degradation. Also, the ability of electrical resistance (ER) and acoustic emission (AE) measurements to monitor material condition and damage state during high temperature testing is shown; suggesting their usefulness as a valuable health monitoring technique. Micromechanics models are used to describe the localized stress state of the composite system, which is utilized along with ER modeling concepts to develop an electromechanical model capable of characterizing material behavior.

  1. Gradient limiting defects in 9-cell cavities EP processed and RF tested at Jefferson Lab

    SciTech Connect

    Geng, Rongli; Ciovati, Giovanni; Crawford, Anthony C.

    2009-11-01

    Several 9-cell cavities processed by electropolishing (EP) and RF tested at Jefferson Lab are found to be quench-limited. Pass-band mode excitation measurements provide the first clue of candidate cells responsible for the limit. A second RF test with thermometers attached to the equator region of candidate cells (typically only 2 candidates) reveals a hot spot caused by excessive heating of the operational defect and hence determines its location. High resolution optical tools inspect the RF surface corresponding to the hot spot to image and document the defect. All defects in cavities quench limited < 21 MV/m are sub-mm sized irregularities near but outside of the equator EBW. In contrast, no observable irregularities are found in some other cavities that are quench-limited ~ 30 MV/m. These two types of quench limited cavities have different response to a second EP processing. In this paper, we will give a summary of the test results and attempt to catalog the observed defects. An equation for quench gradient is given.

  2. Tests of regional elemental tracers of pollution aerosols. 1. Distinctness of regional signatures, stability during transport, and empirical validation

    SciTech Connect

    Lowenthal, D.H.; Wunschel, K.R.; Rahn, K.A. )

    1988-04-01

    The two major requirements for a successful regional tracer system are distinctness of signatures and stability of signatures during transport. Dissimilarity of the five regional signatures from eastern North America is shown by collinearity diagnostics and by apportionment of synthetic samples generated randomly. Stability of regional signatures during transport is shown first by use of tracer elements in coarse and fine aerosol to predict the maximum possible change of ratios from particle-size effects alone and then by examination of actual changes in signatures during transport from the Midwest to Underhill, VT. Two recent empirical validations of the tracer system are presented: qualitative agreement of pulses of mid-western aerosol in Vermont with pulses of perfluorocarbon tracer gas released in Ohio during CAPTEX '83 and reproduction of our three major northeastern and mid-western signatures by other investigators. The tracer system currently uses the seven elements As, Se, Sb, Zn, In, noncrustal Mn, and noncrustal V as measured by instrumental neutron activation.

  3. Evaluation of the heat-storage capability of shallow aquifers using active heat tracer tests and Fiber-Optics Distributed-Temperature-Sensing

    NASA Astrophysics Data System (ADS)

    Suibert Oskar Seibertz, Klodwig; Chirila, Marian Andrei; Bumberger, Jan; Dietrich, Peter; Vienken, Thomas

    2015-04-01

    In the course of the energy transition, geothermal energy storage and heat generation and cooling have proven to be environmental friendly alternatives to conventional energy. However, to ensure sustain usage, the heat transport behavior of aquifers and its distribution has to be studied. A tool to achieve this is the active heat tracer test, eg. Leaf et al. (2012). If active heat tracer tests are combined with in aquifer heat testing via electric heating-cables, eg. Liu et al. (2013), it is possible to observe heat transport and temperature signal decay without disturbing the original pressure field within the aquifer. In this field study a two channel High-Resolution-Fiber-Optic-Distributed-Temperature-Sensing and Pt100 were used to measure temperature signals within in two wells of 1.4 m distance, where the temperature difference was generated using a self regulating heating cable in the upstream well. High resolution Distributed-Temperature-Sensing measurements were achieved by coiling the fiber around screened plastic tubes. The upstream well was also used to observe heating (Δ Tmax approx. 24K) and temperature signal decay, while the downstream well was used to observe heat transport between both wells. The data was analyzed and compared to thermal conductivity of soil samples and Direct-Push (DP) Electrical-Conductivity-Logging and DP Hydraulic-Profiling results. The results show good agreement between DP data and temperature measurements proving the active heat tracer test is a suitable tool for providing reliable information on aquifer heat-storage capability. References Leaf, A.T., Hart, D.J., Bahr, J.M.: Active Thermal Tracer Tests for Improved Hydrostratigraphic Characterization. Ground Water, vol. 50, 2012 Liu, G., Knobbe, S., Butler, J.J.Jr.: Resolving centimeter-scale flows in aquifers and their hydrostratigraphic controls. Geophysical Research Letters, vol. 40, 2013

  4. Multispecies reactive tracer test in an aquifer with spatially variable chemical conditions, Cape Cod, Massachusetts: Dispersive transport of bromide and nickel

    USGS Publications Warehouse

    Hess, K.M.; Davis, J.A.; Kent, D.B.; Coston, J.A.

    2002-01-01

    Dispersive transport of groundwater solutes was investigated as part of a multispecies reactive tracer test conducted under spatially variable chemical conditions in an unconfined, sewage-contaminated sand and gravel aquifer on Cape Cod, Massachusetts. Transport of the nonreactive tracer bromide (Br) reflected physical and hydrologic processes. Transport of the reactive tracer nickel (Ni) complexed with an organic ligand (NiEDTA) varied in response to pH and other chemical conditions within the aquifer. A loss of about 14% of the Ni mass was calculated from the distribution of tracers through time. This loss is consistent with reversible adsorption of NiEDTA onto the iron and aluminum oxyhydroxide coatings on the aquifer sediments. The Ni consistently lagged behind Br with a calculated retardation coefficient of 1.2. Longitudinal dispersivities reached constant values of 2.2 and 1.1 m for Br and Ni, respectively, by at least 69 m of travel. The smaller dispersivity for Ni possibly was due to nonlinear or spatially variant adsorption of NiEDTA. In the upper, uncontaminated zone of the aquifer, longitudinal dispersion of Ni was greater than that of Br early in the test as a result of reversible adsorption of NiEDTA. In general, transverse dispersivities were much smaller (horizontal: 1.4-1.5 ?? 10-2 m; vertical: 0.5-3.8 ?? 10-3 m) than the longitudinal dispersivities. The Br results are similar to those from a test conducted eight years earlier, suggesting that transport parameters are spatially stationary within the aquifer at the scale of 300 m covered by the spatially overlapping tests. A significant difference between the two tests was the travel distance (69 and 26 m) needed to reach a constant longitudinal dispersivity.

  5. Renal epithelia in long term gradient culture for biomaterial testing and tissue engineering.

    PubMed

    Minuth, Will W; Schumacher, Karl; Strehl, Raimund

    2005-01-01

    In the organism epithelia perform perfect barrier functions. Strong rheological and mechanical influences constitute the normal environment of this tissue throughout life. Most epithelia are exposed to different fluids at the luminal and basal sides. To obtain realistic information about tissue development in modern biomaterial testing and tissue engineering it is necessary to mimick the natural environment of epithelia. Cultured cells are brought in contact with an artificial extracellular matrix to determine whether proper development into a functional epithelium occurs. As under natural conditions the cultures have to withstand mechanical and fluid stress over a prolonged period of time in close contact to a selected biomaterial. However, development of tissue-specific features such as polarization, tightness and transport under in vitro conditions will only occur, if the biomaterial and the culture conditions support tissue development. Leakage, edge damage and pressure differences during culture have to be avoided so that the natural functions of the growing epithelium can develop. Our aim is to generate functional epithelia derived from renal explants containing stem cells, which are microsurgically isolated and placed into specific O-ring carriers for optimal handling. The cells develop in combination with a collagenous matrix from an embryonic into a functional collecting duct (rCD) epithelium. To achieve optimal culture conditions the tissue is placed in a gradient culture container. A typical environment can be simulated by superfusing different culture media at the luminal and basal sides. Within days epithelia growing inside the gradient container build up a physiological barrier, which is maintained during the whole culture period. The described method allows to investigate the influence of new biomaterials over prolonged periods of time. PMID:15623930

  6. Cycling Performance of a Columnar-Structured Complex Perovskite in a Temperature Gradient Test

    NASA Astrophysics Data System (ADS)

    Schlegel, N.; Sebold, D.; Sohn, Y. J.; Mauer, G.; Vaßen, R.

    2015-10-01

    To increase the efficiency of turbines for the power generation and the aircraft industry, advanced thermal barrier coatings (TBCs) are required. They need to be long-term stable at temperatures higher than 1200 °C. Nowadays, yttria partially stabilized zirconia (YSZ) is applied as standard TBC material. But its long-term application at temperatures higher than 1200 °C leads to detrimental phase changes and sintering effects. Therefore, new materials have to be investigated, for example, complex perovskites. They provide high melting points, high thermal expansion coefficients and thermal conductivities of approx. 2.0 W/(m K). In this work, the complex perovskite La(Al1/4Mg1/2Ta1/4)O3 (LAMT) was investigated. It was deposited by the suspension plasma spraying (SPS) process, resulting in a columnar microstructure of the coating. The coatings were tested in thermal cycling gradient tests and they show excellent results, even though some phase decomposition was found.

  7. Impact of non-idealities in gas-tracer tests on the estimation of reaeration, respiration, and photosynthesis rates in streams.

    PubMed

    Knapp, Julia L A; Osenbrück, Karsten; Cirpka, Olaf A

    2015-10-15

    Estimating respiration and photosynthesis rates in streams usually requires good knowledge of reaeration at the given locations. For this purpose, gas-tracer tests can be conducted, and reaeration rate coefficients are determined from the decrease in gas concentration along the river stretch. The typical procedure for analysis of such tests is based on simplifying assumptions, as it neglects dispersion altogether and does not consider possible fluctuations and trends in the input signal. We mathematically derive the influence of these non-idealities on estimated reaeration rates and how they are propagated onto the evaluation of aerobic respiration and photosynthesis rates from oxygen monitoring. We apply the approach to field data obtained from a gas-tracer test using propane in a second-order stream in Southwest Germany. We calculate the reaeration rate coefficients accounting for dispersion as well as trends and uncertainty in the input signals and compare them to the standard approach. We show that neglecting dispersion significantly underestimates reaeration, and results between sections cannot be compared if trends in the input signal of the gas tracer are disregarded. Using time series of dissolved oxygen and the various estimates of reaeration, we infer respiration and photosynthesis rates for the same stream section, demonstrating that the bias and uncertainty of reaeration using the different approaches significantly affects the calculation of metabolic rates. PMID:26150069

  8. A novel test ground for the equipment qualification of magnetic gradient sensors used for unexploded bomb detection

    NASA Astrophysics Data System (ADS)

    Hiergeist, Robert; Ketzler, Rainer; Harcken, Hans; Lüdke, Joachim; Albrecht, Martin; Brand, Thomas; Fischer, Andreas

    2015-01-01

    Scanning of the ground level by magnetic gradient sensors (fluxgate sensors) is the primary detection technique for unexploded bombs (UXBs). In order to allow a classification of the test equipment (magnetic sensors and associated evaluation software) as well as training and examination of the skills of sensor operating teams we built up a test facility. In the first step to generate the stray magnetic fields of UXBs, we positioned solenoids of the same dimension as the simulated bombs under a test ground using the principle of the equivalent current shell. From numerical investigations it has been found, that for depths exceeding 1.2 m, the gradient field profiles of these solenoids and the gradient field profiles of small multi-layer split coils agree very well (far field regime). This was verified later experimentally: By positioning these movable small multi-layer split coils in tubes running diagonally underneath the test ground and controlling the current flowing through these coils, we were able to find a good agreement between calculated and experimental data of the gradiometer signal scans on the measurement plane for (i) tests of the signal resolution and (ii) tests of the relative spatial resolution of the gradient sensors.

  9. Testing thermal gradient driving force for grain boundary migration using molecular dynamics simulations

    SciTech Connect

    Bai, Xian-Ming; Zhang, Yongfeng; Tonks, Michael R.

    2015-02-01

    Strong thermal gradients in low-thermal-conductivity ceramics may drive extended defects, such as grain boundaries and voids, to migrate in preferential directions. In this work, molecular dynamics simulations are conducted to study thermal gradient driven grain boundary migration and to verify a previously proposed thermal gradient driving force equation, using uranium dioxide as a model system. It is found that a thermal gradient drives grain boundaries to migrate up the gradient and the migration velocity increases under a constant gradient owing to the increase in mobility with temperature. Different grain boundaries migrate at very different rates due to their different intrinsic mobilities. The extracted mobilities from the thermal gradient driven simulations are compared with those calculated from two other well-established methods and good agreement between the three different methods is found, demonstrating that the theoretical equation of the thermal gradient driving force is valid, although a correction of one input parameter should be made. The discrepancy in the grain boundary mobilities between modeling and experiments is also discussed.

  10. Single-well tracer test sensitivity w. r. to hydrofrac and matrix parameters (case study for the Horstberg site in the N-German Sedimentary Basin)

    NASA Astrophysics Data System (ADS)

    Ghergut, I.; Behrens, H.; Holzbecher, E.; Jung, R.; Sauter, M.; Tischner, T.

    2012-04-01

    At the geothermal pilot site Horstberg in the N-German Sedimentary Basin, a complex field experiment program was conducted (2003-2007) by the Federal Institute for Geosciences and Natural Resources (BGR) together with the Leibniz Institute for Applied Geosciences (GGA), aimed at evaluating the performance of innovative technologies for heat extraction, for direct use, from a single geothermal well[1],[2]. The envisaged single-well operation schemes comprised inter-layer circulation through a large-area hydrofrac (whose successful creation could thus be demonstrated), and single-screen 'huff-puff' in suitable (stimulated) layers, seated in sandstone-claystone formations in 3-4 km depth, with temperatures exceeding 160 ° C. Relying on Horstberg tracer-test data, we analyze heat and solute tracer transport in three characteristic hydraulic settings: (A) single-screen, multi-layer push-pull, with spiking and sampling at lower well-screen in low-permeability sandstone layer ('Detfurth'), from which hydrofrac propagation (through several adjacent layers) was initiated; (B) single-screen, single-layer push-pull, with spiking and sampling at upper well-screen within a more permeable sandstone layer ('Solling'); (C) inter-layer vertical push through above-mentioned hydrofrac, with spiking at well-screen of A, and sampling at well-screen of B. Owing to drill-hole deviation, the hydraulically-induced frac will, in its vertical propagation, reach the upper sandstone layer in a certain horizontal distance X from the upper well-screen, whose value turns out to be the major controlling parameter for the system's thermal lifetime under operation scheme C (values of X below ~8 m leading to premature thermal breakthrough, with the minimum-target rate of fluid turnover; however, the injection pressure required for maintaining the target outflow rate will also increase with X, which renders scheme C uneconomical, or technically-infeasible, when X exceeds ~15 m). Tracer signals in C

  11. Analysis of tracer and thermal transients during reinjection

    SciTech Connect

    Kocabas, I.

    1989-10-01

    This work studied tracer and thermal transients during reinjection in geothermal reserviors and developed a new technique which combines the results from interwell tracer tests and thermal injection-backflow tests to estimate the thermal breakthrough times. Tracer tests are essential to determine the degree of connectivity between the injection wells and the producing wells. To analyze the tracer return profiles quantitatively, we employed three mathematical models namely, the convection-dispersion (CD) model, matrix diffusion (MD) model, and the Avodnin (AD) model, which were developed to study tracer and heat transport in a single vertical fracture. We considered three types of tracer tests namely, interwell tracer tests without recirculation, interwell tracer tests with recirculation, and injection-backflow tracer tests. To estimate the model parameters, we used a nonlinear regression program to match tracer return profiles to the solutions.

  12. Using a Gas-Phase Tracer Test to Characterize the Impact of Landfill Gas Generation on Advective-Dispersive Transport of VOCs in the Vadose Zone

    PubMed Central

    Monger, Gregg R.; Duncan, Candice Morrison; Brusseau, Mark L.

    2015-01-01

    A gas-phase tracer test (GTT) was conducted at a landfill in Tucson, AZ, to help elucidate the impact of landfill gas generation on the transport and fate of chlorinated aliphatic volatile organic contaminants (VOCs). Sulfur hexafluoride (SF6) was used as the non-reactive gas tracer. Gas samples were collected from a multiport monitoring well located 15.2 m from the injection well, and analyzed for SF6, CH4, CO2, and VOCs. The travel times determined for SF6 from the tracer test are approximately two to ten times smaller than estimated travel times that incorporate transport by only gas-phase diffusion. In addition, significant concentrations of CH4 and CO2 were measured, indicating production of landfill gas. Based on these results, it is hypothesized that the enhanced rates of transport observed for SF6 are caused by advective transport associated with landfill gas generation. The rates of transport varied vertically, which is attributed to multiple factors including spatial variability of water content, refuse mass, refuse permeability, and gas generation. PMID:26380532

  13. Perturbations and gradients as fundamental tests for modeling the soil carbon cycle

    NASA Astrophysics Data System (ADS)

    Bond-Lamberty, B. P.; Bailey, V. L.; Becker, K.; Fansler, S.; Hinkle, C.; Liu, C.

    2013-12-01

    An important step in matching process-level knowledge to larger-scale measurements and model results is to challenge those models with site-specific perturbations and/or changing environmental conditions. Here we subject modified versions of an ecosystem process model to two stringent tests: replicating a long-term climate change dryland experiment (Rattlesnake Mountain) and partitioning the carbon fluxes of a soil drainage gradient in the northern Everglades (Disney Wilderness Preserve). For both sites, on-site measurements were supplemented by laboratory incubations of soil columns. We used a parameter-space search algorithm to optimize, within observational limits, the model's influential inputs, so that the spun-up carbon stocks and fluxes matched observed values. Modeled carbon fluxes (net primary production and net ecosystem exchange) agreed with measured values, within observational error limits, but the model's partitioning of soil fluxes (autotrophic versus heterotrophic), did not match laboratory measurements from either site. Accounting for site heterogeneity at DWP, modeled carbon exchange was reasonably consistent with values from eddy covariance. We discuss the implications of this work for ecosystem- to global scale modeling of ecosystems in a changing climate.

  14. Urbanization Across Gradients: Testing Hypotheses on Effects of Land Change at Multiple Scales

    NASA Astrophysics Data System (ADS)

    Grimm, N. B.; Foster, D.; Groffman, P.; Grove, M.; Hopkinson, C.; Nadelhoffer, K.; Pataki, D.; Peters, D.

    2008-12-01

    Urbanization alters both biotic and abiotic ecosystem properties within, surrounding and even at great distances from urban areas. Ecosystem responses to these land changes are complex and interacting as a consequence of connectivity of resources, energy, and information among social, physical and biological systems. Research on urban ecology has generally focused on studies within single urban ecosystems, but the time is ripe for synthesis and comparison. For understanding of urban ecosystems and associated environmental problems to advance, research must consider urban areas in the context of physicochemical, social, geographical, and other contexts. We present testable hypotheses on the effects of urbanization at multiple scales (local, regional, continental, and global). Comparative studies across gradients, as well as spatially continuous coverage of land change, contribute to an approach to test these hypotheses. We argue that such research will permit robust forecasts of how land change and human settlement patterns alter ecosystem services and resource utilization across the North American continent, and that these forecasts can be applied globally.

  15. Testing Taxon Tenacity of Tortoises: evidence for a geographical selection gradient at a secondary contact zone.

    PubMed

    Edwards, Taylor; Berry, Kristin H; Inman, Richard D; Esque, Todd C; Nussear, Kenneth E; Jones, Cristina A; Culver, Melanie

    2015-05-01

    We examined a secondary contact zone between two species of desert tortoise, Gopherus agassizii and G. morafkai. The taxa were isolated from a common ancestor during the formation of the Colorado River (4-8 mya) and are a classic example of allopatric speciation. However, an anomalous population of G. agassizii comes into secondary contact with G. morafkai east of the Colorado River in the Black Mountains of Arizona and provides an opportunity to examine reinforcement of species' boundaries under natural conditions. We sampled 234 tortoises representing G. agassizii in California (n - 103), G. morafkai in Arizona (n - 78), and 53 individuals of undetermined assignment in the contact zone including and surrounding the Black Mountains. We genotyped individuals for 25 STR loci and determined maternal lineage using mtDNA sequence data. We performed multilocus genetic clustering analyses and used multiple statistical methods to detect levels of hybridization. We tested hypotheses about habitat use between G. agassizii and G. morafkai in the region where they co-occur using habitat suitability models. Gopherus agassizii and G. morafkai maintain independent taxonomic identities likely due to ecological niche partitioning, and the maintenance of the hybrid zone is best described by a geographical selection gradient model. PMID:26045959

  16. Testing taxon tenacity of tortoises: evidence for a geographical selection gradient at a secondary contact zone

    USGS Publications Warehouse

    Edwards, Taylor; Berry, Kristin H.; Inman, Richard D.; Esque, Todd C.; Nussear, Kenneth E.; Jones, Cristina A.; Culver, Melanie

    2015-01-01

    We examined a secondary contact zone between two species of desert tortoise, Gopherus agassizii and G. morafkai. The taxa were isolated from a common ancestor during the formation of the Colorado River (4-8 mya) and are a classic example of allopatric speciation. However, an anomalous population of G. agassizii comes into secondary contact with G. morafkai east of the Colorado River in the Black Mountains of Arizona and provides an opportunity to examine reinforcement of species' boundaries under natural conditions. We sampled 234 tortoises representing G. agassizii in California (n = 103), G. morafkai in Arizona (n = 78), and 53 individuals of undetermined assignment in the contact zone including and surrounding the Black Mountains. We genotyped individuals for 25 STR loci and determined maternal lineage using mtDNA sequence data. We performed multilocus genetic clustering analyses and used multiple statistical methods to detect levels of hybridization. We tested hypotheses about habitat use between G. agassizii and G. morafkai in the region where they co-occur using habitat suitability models. Gopherus agassizii and G. morafkai maintain independent taxonomic identities likely due to ecological niche partitioning, and the maintenance of the hybrid zone is best described by a geographical selection gradient model.

  17. Testing Taxon Tenacity of Tortoises: evidence for a geographical selection gradient at a secondary contact zone

    PubMed Central

    Edwards, Taylor; Berry, Kristin H; Inman, Richard D; Esque, Todd C; Nussear, Kenneth E; Jones, Cristina A; Culver, Melanie

    2015-01-01

    We examined a secondary contact zone between two species of desert tortoise, Gopherus agassizii and G. morafkai. The taxa were isolated from a common ancestor during the formation of the Colorado River (4–8 mya) and are a classic example of allopatric speciation. However, an anomalous population of G. agassizii comes into secondary contact with G. morafkai east of the Colorado River in the Black Mountains of Arizona and provides an opportunity to examine reinforcement of species' boundaries under natural conditions. We sampled 234 tortoises representing G. agassizii in California (n - 103), G. morafkai in Arizona (n - 78), and 53 individuals of undetermined assignment in the contact zone including and surrounding the Black Mountains. We genotyped individuals for 25 STR loci and determined maternal lineage using mtDNA sequence data. We performed multilocus genetic clustering analyses and used multiple statistical methods to detect levels of hybridization. We tested hypotheses about habitat use between G. agassizii and G. morafkai in the region where they co-occur using habitat suitability models. Gopherus agassizii and G. morafkai maintain independent taxonomic identities likely due to ecological niche partitioning, and the maintenance of the hybrid zone is best described by a geographical selection gradient model. PMID:26045959

  18. Simulation of variable-density flow and transport of reactive and nonreactive solutes during a tracer test at Cape Cod, Massachusetts

    USGS Publications Warehouse

    Zhang, H.; Schwartz, F.W.; Wood, W.W.; Garabedian, S.P.; LeBlanc, D.R.

    1998-01-01

    A multispecies numerical code was developed to simulate flow and mass transport with kinetic adsorption in variable-density flow systems. The two-dimensional code simulated the transport of bromide (Br-), a nonreactive tracer, and lithium (Li+), a reactive tracer, in a large-scale tracer test performed in a sand-and-gravel aquifer at Cape Cod, Massachusetts. A two-fraction kinetic adsorption model was implemented to simulate the interaction of Li+ with the aquifer solids. Initial estimates for some of the transport parameters were obtained from a nonlinear least squares curve-fitting procedure, where the breakthrough curves from column experiments were matched with one-dimensional theoretical models. The numerical code successfully simulated the basic characteristics of the two plumes in the tracer test. At early times the centers of mass of Br- and Li+ sank because the two plumes were closely coupled to the density-driven velocity field. At later times the rate of downward movement in the Br- plume due to gravity slowed significantly because of dilution by dispersion. The downward movement of the Li+ plume was negligible because the two plumes moved in locally different velocity regimes, where Li+ transport was retarded relative to Br-. The maximum extent of downward transport of the Li+ plume was less than that of the Br- plume. This study also found that at early times the downward movement of a plume created by a three-dimensional source could he much more extensive than the case with a two-dimensional source having the same cross-sectional area. The observed shape of the Br- plume at Cape Cod was simulated by adding two layers with different hydraulic conductivities at shallow depth across the region. The large dispersion and asymmetrical shape of the Li+ plume were simulated by including kinetic adsorption-desorption reactions.

  19. Analysis of Conservative Tracer Tests in the Bullfrog, Tram, and Prow Pass Tuffs, 1996 to 1998, Yucca Mountain, Nye County, Nevada

    USGS Publications Warehouse

    Umari, Amjad; Fahy, Michael F.; Earle, John D.; Tucci, Patrick

    2008-01-01

    To evaluate the potential for transport of radionuclides in ground water from the proposed high-level nuclear-waste repository at Yucca Mountain, Nevada, conservative (nonsorbing) tracer tests were conducted among three boreholes, known as the C-hole Complex, and values for transport (or flow) porosity, storage (or matrix) porosity, longitudinal dispersivity, and the extent of matrix diffusion were obtained. The C-holes are completed in a sequence of Miocene tuffaceous rock, consisting of nonwelded to densely welded ash-flow tuff with intervals of ash-fall tuff and volcaniclastic rocks, covered by Quaternary alluvium. The lower part of the tuffaceous-rock sequence includes the Prow Pass, Bullfrog, and Tram Tuffs of the Crater Flat Group. The rocks are pervaded by tectonic and cooling fractures. Paleozoic limestone and dolomite underlie the tuffaceous rocks. Four radially convergent and one partially recirculating conservative (nonsorbing) tracer tests were conducted at the C-hole Complex from 1996 to 1998 to establish values for flow porosity, storage porosity, longitudinal dispersivity, and extent of matrix diffusion in the Bullfrog and Tram Tuffs and the Prow Pass Tuff. Tracer tests included (1) injection of iodide into the combined Bullfrog-Tram interval; (2) injection of 2,6 difluorobenzoic acid into the Lower Bullfrog interval; (3) injection of 3-carbamoyl-2-pyridone into the Lower Bullfrog interval; and (4) injection of iodide and 2,4,5 trifluorobenzoic acid, followed by 2,3,4,5 tetrafluorobenzoic acid, into the Prow Pass Tuff. All tracer tests were analyzed by the Moench single- and dual-porosity analytical solutions to the advection-dispersion equation or by superposition of these solutions. Nonlinear regression techniques were used to corroborate tracer solution results, to obtain optimal parameter values from the solutions, and to quantify parameter uncertainty resulting from analyzing two of the three radially convergent conservative tracer tests

  20. Noctuid moth diversity along a temperate elevational gradient: testing the role of environmental factors, MDE, and Rapoport's rule

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many factors, including climate, area, and habitat diversity likely influence spatial variation in species diversity along elevational gradients. In this study, we test the relative influence of energy availability, habitat diversity, mid-domain effects, and area on the diversity of noctuid moths i...

  1. Accounting for Dispersion and time-dependent Input Signals during Gas Tracer Tests and their Effect on the Estimation of Reaeration, Respiration and Photosynthesis in Streams

    NASA Astrophysics Data System (ADS)

    Knapp, Julia; Osenbrück, Karsten; Olaf, Cirpka

    2015-04-01

    The variation of dissolved oxygen (DO) in streams, are caused by a number of processes, of which respiration and primary production are considered to be the most important ones (Odum, 1956; Staehr et al., 2012). Measuring respiration and photosynthesis rates in streams based on recorded time series of DO requires good knowledge on the reaeration fluxes at the given locations. For this, gas tracer tests can be conducted, and reaeration coefficients determined from the observed decrease in gas concentration along the stretch (Genereux and Hemond, 1990): ( ) --1- -cup- k2 = t2 - t1 ln Rcdown (1) with the gas concentrations measured at an upstream location, cup[ML-3], and a downstream location, cdown. t1[T] andt2 [T] denote the measurement times at the two locations and R [-] represents the recovery rate which can also be obtained from conservative tracer data. The typical procedure for analysis, however, contains a number of assumptions, as it neglects dispersion and does not take into account possible fluctuations of the input signal. We derive the influence of these aspects mathematically and illustrate them on the basis of field data obtained from a propane gas tracer test. For this, we compare the reaeration coefficients obtained from approaches with dispersion and/or a time-dependent input signals to the standard approach. Travel times and travel time distributions between the different measurement stations are obtained from a simultaneously performed conservative tracer test with fluorescein. In order to show the carry-over effect to metabolic rates, we furthermore estimate respiration and photosynthesis rates from the calculated reaeration coefficients and measured oxygen data. This way, we are able to show that neglecting dispersion significantly underestimates reaeration, and the impact of the time-dependent input concentration cannot be disregarded either. When estimated reaeration rates are used to calculate respiration and photosynthesis from measured

  2. Ecological impacts of invasive alien species along temperature gradients: testing the role of environmental matching.

    PubMed

    Iacarella, Josephine C; Dick, Jaimie T A; Alexander, Mhairi E; Ricciardi, Anthony

    2015-04-01

    Invasive alien species (IAS) can cause substantive ecological impacts, and the role of temperature in mediating these impacts may become increasingly significant in a changing climate. Habitat conditions and physiological optima offer predictive information for IAS impacts in novel environments. Here, using meta-analysis and laboratory experiments, we tested the hypothesis that the impacts of IAS in the field are inversely correlated with the difference in their ambient and optimal temperatures. A meta-analysis of 29 studies of consumptive impacts of IAS in inland waters revealed that the impacts of fishes and crustaceans are higher at temperatures that more closely match their thermal growth optima. In particular, the maximum impact potential was constrained by increased differences between ambient and optimal temperatures, as indicated by the steeper slope of a quantile regression on the upper 25th percentile of impact data compared to that of a weighted linear regression on all data with measured variances. We complemented this study with an experimental analysis of the functional response (the relationship between predation rate and prey supply) of two invasive predators (freshwater mysid shrimp, Hemimysis anomala and Mysis diluviana) across. relevant temperature gradients; both of these species have previously been found to exert strong community-level impacts that are corroborated by their functional responses to different prey items. The functional response experiments showed that maximum feeding rates of H. anomala and M. diluviana have distinct peaks near their respective thermal optima. Although variation in impacts may be caused by numerous abiotic or biotic habitat characteristics, both our analyses point to temperature as a key mediator of IAS impact levels in inland waters and suggest that IAS management should prioritize habitats in the invaded range that more closely match the thermal optima of targeted invaders. PMID:26214916

  3. Stratospheric Tracer Spectra.

    NASA Astrophysics Data System (ADS)

    Haynes, P. H.; Vanneste, J.

    2004-01-01

    The combined effects of advection and diffusion on the equilibrium spatial structure of a tracer whose spatial variation is maintained by a large-scale forcing are considered. Motivated by the lower stratosphere, the flow is taken to be large-scale, time-dependent, and purely horizontal but varying in the vertical, with the vertical shear much larger than horizontal velocity gradients. As a result, the ratio α between horizontal and vertical tracer scales is large. (For the lower stratospheric surf zone α has been shown to be about 250.) The diffusion parameterizes the mixing effects of small-scale processes.The three space dimensions and the large range between the forcing scale and the diffusive scale mean that direct numerical simulation would be prohibitively expensive for this problem. Instead, an ensemble approach is used that takes advantage of the separation between the large scale of the flow and the small scale of the tracer distribution. This approach, which has previously been used in theoretical investigations of two-dimensional flows, provides an efficient technique to derive statistical properties of the tracer distributions such as horizontal-wavenumber spectrum.First, the authors consider random-strain models in which the velocity gradient experienced by a fluid parcel is modeled by a random process. The results show the expected k-1 Batchelor spectrum at large scales, with a deviation from this form at a scale that is larger by a factor α than the diffusive scale found in the absence of vertical shear. This effect may be crudely captured by replacing the diffusivity κ by an “=uivalent diffusivity” α2κ, but the diffusive dissipation is then substantially overestimated, and the spectrum at large k is too steep. This may be attributed to the failure of the equivalent diffusivity to capture the variability of the vertical shear.The technique is then applied to lower-stratospheric velocity fields. For realistic values of the diffusivity κ

  4. Gradient Index Microlens Implanted in Prefrontal Cortex of Mouse Does Not Affect Behavioral Test Performance over Time

    PubMed Central

    Lee, Seon A.; Holly, Kevin S.; Voziyanov, Vladislav; Villalba, Stephanie L.; Tong, Rudi; Grigsby, Holly E.; Glasscock, Edward; Szele, Francis G.; Vlachos, Ioannis; Murray, Teresa A.

    2016-01-01

    Implanted gradient index lenses have extended the reach of standard multiphoton microscopy from the upper layers of the mouse cortex to the lower cortical layers and even subcortical regions. These lenses have the clarity to visualize dynamic activities, such as calcium transients, with subcellular and millisecond resolution and the stability to facilitate repeated imaging over weeks and months. In addition, behavioral tests can be used to correlate performance with observed changes in network function and structure that occur over time. Yet, this raises the questions, does an implanted microlens have an effect on behavioral tests, and if so, what is the extent of the effect? To answer these questions, we compared the performance of three groups of mice in three common behavioral tests. A gradient index lens was implanted in the prefrontal cortex of experimental mice. We compared their performance with mice that had either a cranial window or a sham surgery. Three presurgical and five postsurgical sets of behavioral tests were performed over seven weeks. Behavioral tests included rotarod, foot fault, and Morris water maze. No significant differences were found between the three groups, suggesting that microlens implantation did not affect performance. The results for the current study clear the way for combining behavioral studies with gradient index lens imaging in the prefrontal cortex, and potentially other regions of the mouse brain, to study structural, functional, and behavioral relationships in the brain. PMID:26799938

  5. Potential soluble, reactive, adsorptive and particulate tracers for source-receptor experiments in MATEX

    SciTech Connect

    Senum, G.I.; Dietz, R.N.

    1985-07-01

    A survey of potential non-conservative tracers for use in source-receptor studies in acid deposition is presented. Classes of tracers considered were water soluble tracers, chemically reactive tracers, adsorptive tracers and particulate tracers. A criterion used for the selection of compounds for nonconservative tracers is that they be as reasonably compatible in the analytical detection system used for the conservative perfluorocarbon tracers. For each class of non-conservative tracers several example compounds are given and discussed, along with the research needed to develop these tracers. A reasonable development time for these tracers is as follows; adsorptive tracers, 2 years; particulate tracers, 2 1/2 years; soluble tracers, 3 years and reactive tracers, 3 1/2 years. By development, it is meant that 1 or 2 tracers have been developed and at least demonstrated in a small field test. 6 refs., 2 tabs.

  6. Summary and interpretation of dye-tracer tests to investigate the hydraulic connection of fractures at a ridge-and-valley-wall site near Fishtrap Lake, Pike County, Kentucky

    USGS Publications Warehouse

    Taylor, C.J.

    1994-01-01

    decreasing-head conditions resulted in dye being trapped in hydraulically dead zones in water- depleted fractures. Residual dye was remobilized from storage and transported (over periods ranging from several months to about 2 years) by increased recharge to the hydrologic system. Subsequent fluctuations in hydraulic gradients, resulting from increases or decreases in recharge to the hydrologic system, acted to speed or slow the transport of dye along the fracture-controlled flow paths. The dye-tracer tests also demonstrated that mining-related disturbances significantly altered the natural fracture-controlled flow paths of the hydrologic system over time. An abandoned underground mine and subsidence-related surface cracks extend to within 250 ft of the principal dye- injection core hole. Results from two of the dye-tracer tests at the site indicate that the annular seal in the core hole was breached by subsurface propagation of the mining-induced fractures. This propagation of fractures resulted in hydraulic short-circuiting between the dye-injection zone in the core hole and two lower piezometer zones, and a partial disruption of the hydraulic connection between the injection core hole and downgradient piezometers on the ridge crest and valley wall. In addition, injected dye was detected in piezometers monitoring a flooded part of the abandoned underground mine. Dye was apparently transported into the mine through a hydraulic connection between the injection core hole and subsidence-related fractures.

  7. Comparison of interfacial partitioning tracer test and high-resolution microtomography measurements of fluid-fluid interfacial areas for an ideal porous medium

    NASA Astrophysics Data System (ADS)

    Narter, Matt; Brusseau, Mark L.

    2010-08-01

    Fluid-fluid interfacial area for porous media systems can be measured with the aqueous phase interfacial partitioning tracer test (IPTT) method or with high-resolution microtomography. The results of prior studies have shown that interfacial areas measured with the IPTT method are larger than values measured with microtomography. The observed disparity has been hypothesized to result from the impact of porous medium surface roughness on film-associated interfacial area, wherein the influence of surface roughness is characterized to some extent by the IPTT method but not by microtomography due to resolution constraints. This hypothesis was tested by using the two methods to measure interfacial area between an organic immiscible liquid and water for an ideal glass beads medium that has no measurable surface roughness. The tracer tests yielded a mean interfacial area of 2.8 (±5 cm-1), while microtomography produced an interfacial area of 2.7 (±2 cm-1). Maximum specific interfacial areas, equivalent to areas normalized by nonwetting fluid volume, were calculated and compared to measures of the specific solid surface area. The normalized interfacial areas were similar to the specific solid surface area calculated using the smooth sphere assumption and to the specific solid surface area measured using the N2/Brunauer, Emmett, and Teller (BET) method. The results presented herein indicate that both the IPTT and microtomography methods provide robust characterization of fluid-fluid interfacial area and that they are comparable in the absence of the impact of surface roughness.

  8. COMPARISON OF INTERFACIAL PARTITIONING TRACER TEST AND HIGH-RESOLUTION MICROTOMOGRAPHY MEASUREMENTS OF FLUID-FLUID INTERFACIAL AREAS FOR AN IDEAL POROUS MEDIUM.

    PubMed

    Narter, Matt; Brusseau, Mark L

    2010-08-01

    Fluid-fluid interfacial area for porous-media systems can be measured with the aqueous-phase interfacial partitioning tracer test (IPTT) method or with high-resolution microtomography. The results of prior studies have shown that interfacial areas measured with the IPTT method are larger than values measured with microtomography. The observed disparity has been hypothesized to result from the impact of porous-medium surface roughness on film-associated interfacial area, wherein the influence of surface roughness is characterized to some extent by the IPTT method but not by microtomography due to resolution constraints. This hypothesis was tested by using the two methods to measure interfacial area between an organic immiscible liquid and water for an ideal glass-beads medium that has no measurable surface roughness. The tracer tests yielded a mean interfacial area of 2.8 (± 5 cm(-1)), while microtomography produced an interfacial area of 2.7 (± 2 cm(-1)). Maximum specific interfacial areas, equivalent to areas normalized by non-wetting fluid volume, were calculated and compared to measures of the specific solid surface area. The normalized interfacial areas were similar to the specific solid surface area calculated using the smooth-sphere assumption, and to the specific solid surface area measured using the N2/BET method. The results presented herein indicate that both the IPTT and microtomography methods provide robust characterization of fluid-fluid interfacial area, and that they are comparable absent the impact of surface roughness. PMID:24604925

  9. Comparison of results of two dye-tracer tests at the Chestnut Ridge Security Pits, Y-12 Plant, Oak Ridge, Tennessee

    SciTech Connect

    Goldstrand, P.M.; Haas, J.

    1994-01-01

    Personnel from Martin Marietta Energy Systems, Inc. (Energy Systems) manage a closed hazardous waste disposal unit the Chestnut Ridge Security Pits (CRSP), located on the crest of Chestnut Ridge near the Y-12 Plant, Oak Ridge, Tennessee. To investigate the discharge of groundwater from CRSP to springs and streams located along the flanks and base of Chestnut Ridge, an initial dye-tracer study was conducted during 1990. A hydraulic connection was inferred to exist between the injection well (GW-178) on Chestnut Ridge and several sites to the east-northeast, east, and southeast of CRSP. A second dye-tracer study was conducted in 1992 to verify the results of the initial test and identify additional discharge points that are active during wet-weather conditions. No definitive evidence for the presence of dye was identified at any of the 35 locations monitored during the second dye study. Although interpretations of the initial dye test suggest a hydraulic connection with several sites and CRSP, reevaluation of the spectrofluorescence data from this test suggests that dye may not have been detected during the initial test. A combination of relatively high analytical detection limits during the initial test, and high natural background interference spectral peaks observed during the second test, suggest that high natural background emission spectra near the wavelength of the dye used during the initial test may have caused the apparently high reported concentrations. The results of these two tests do not preclude that a hydraulic connection exists; dye may be present in concentrations below the analytical detection limits or has yet to emerge from the groundwater system. The dye injection well is not completed within any significant karst features. Dye migration therefore, may be within a diffuse, slow-flow portion of the aquifer, at least in the immediate vicinity of the source well.

  10. Generalization Gradients in Human Predictive Learning: Effects of Discrimination Training and within-Subjects Testing

    ERIC Educational Resources Information Center

    Vervliet, Bram; Iberico, Carlos; Vervoort, Ellen; Baeyens, Frank

    2011-01-01

    Generalization gradients have been investigated widely in animal conditioning experiments, but much less so in human predictive learning tasks. Here, we apply the experimental design of a recent study on conditioned fear generalization in humans (Lissek et al., 2008) to a predictive learning task, and examine the effects of a number of relevant…

  11. Dissolved gas dynamics in wetland soils: Root-mediated gas transfer kinetics determined via push-pull tracer tests

    NASA Astrophysics Data System (ADS)

    Reid, Matthew C.; Pal, David S.; Jaffé, Peter R.

    2015-09-01

    Gas transfer processes are fundamental to the biogeochemical and water quality functions of wetlands, yet there is limited knowledge of the rates and pathways of soil-atmosphere exchange for gases other than oxygen and methane (CH4). In this study, we use a novel push-pull technique with sulfur hexafluoride (SF6) and helium (He) as dissolved gas tracers to quantify the kinetics of root-mediated gas transfer, which is a critical efflux pathway for gases from wetland soils. This tracer approach disentangles the effects of physical transport from simultaneous reaction in saturated, vegetated wetland soils. We measured significant seasonal variation in first-order gas exchange rate constants, with smaller spatial variations between different soil depths and vegetation zones in a New Jersey tidal marsh. Gas transfer rates for most biogeochemical trace gases are expected to be bracketed by the rate constants for SF6 and He, which ranged from ˜10-2 to 2 × 10-1 h-1 at our site. A modified Damköhler number analysis is used to evaluate the balance between biochemical reaction and root-driven gas exchange in governing the fate of environmental trace gases in rooted, anaerobic soils. This approach confirmed the importance of plant gas transport for CH4, and showed that root-driven transport may affect nitrous oxide (N2O) balances in settings where N2O reduction rates are slow.

  12. Tracer test with As(V) under variable redox conditions controlling arsenic transport in the presence of elevated ferrous iron concentrations.

    PubMed

    Höhn, R; Isenbeck-Schröter, M; Kent, D B; Davis, J A; Jakobsen, R; Jann, S; Niedan, V; Scholz, C; Stadler, S; Tretner, A

    2006-11-20

    To study transport and reactions of arsenic under field conditions, a small-scale tracer test was performed in an anoxic, iron-reducing zone of a sandy aquifer at the USGS research site on Cape Cod, Massachusetts, USA. For four weeks, a stream of groundwater with added As(V) (6.7 muM) and bromide (1.6 mM), was injected in order to observe the reduction of As(V) to As(III). Breakthrough of bromide (Br(-)), As(V), and As(III) as well as additional parameters characterizing the geochemical conditions was observed at various locations downstream of the injection well over a period of 104 days. After a short lag period, nitrate and dissolved oxygen from the injectate oxidized ferrous iron and As(V) became bound to the freshly formed hydrous iron oxides. Approximately one week after terminating the injection, anoxic conditions had been reestablished and increases in As(III) concentrations were observed within 1 m of the injection. During the observation period, As(III) and As(V) were transported to a distance of 4.5 m downgradient indicating significant retardation by sorption processes for both species. Sediment assays as well as elevated concentrations of hydrogen reflected the presence of As(V) reducing microorganisms. Thus, microbial As(V) reduction was thought to be one major process driving the release of As(III) during the tracer test in the Cape Cod aquifer. PMID:16945450

  13. Design of a tracer test experience and dynamic calibration of the hydraulic model for a full-scale wastewater treatment plant by use of AQUASIM.

    PubMed

    Fall, C; Loaiza-Navia, J L

    2007-08-01

    The setup of the hydraulic model structure of wastewater treatment plants (WWTPs) is an important step in the calibration of activated sludge models. The hydrodynamics of a full-scale municipal WWTP (Monterrey, Mexico) has been studied by means of the use of tracer tests and of a commercial simulator. A presimulation approach allowed the authors to quantify the appropriate rhodamine mass, set up a sampling plan, and evaluate the anticipated visual effect of the tracer test in the receiving river. The hydraulic behavior of the aeration tank for the first treatment line, a 7-cell plug-flow reactor, was shown to be best represented by 5 virtual mixed-tanks-in-series. The second treatment line, which included a vertical loop reactor (VLR), was best modeled as 3 tanks-in-series. The VLR, alone, was shown to be similar to a continuously stirred tank reactor, and not a circuit of tanks, as generally used to represent oxidation ditch reactors. PMID:17824536

  14. Evaluation of tracer tests completed in 1999 and 2000 on the upper Santa Clara River, Los Angeles and Ventura Counties, California

    USGS Publications Warehouse

    Cox, Marisa H.; Mendez, Gregory O.; Kratzer, Charles R.; Reichard, Eric G.

    2003-01-01

    The interaction of surface water and hyporheic water along the Santa Clara River in Los Angeles and Ventura Counties, California, was evaluated by conducting tracer tests and analyzing water-quality data under different flow conditions in October 1999 and May 2000. Tracer and water-quality samples were collected at multiple river and hyporheic sites as well as at the Los Angeles County Sanitation Districts Saugus and Valencia Water Reclamation Plants. These water reclamation plants provide the main source of base flow in the river. Rhodamine WT dye was injected into the river to determine river traveltimes and to indicate when Lagrangian water-quality sampling could be performed at each site. Sodium bromide was injected into the river at a constant rate at the water reclamation plants to evaluate the surface-water and shallow ground-water interactions in the hyporheic zone. In the upper reach of the study area, which extends 2.9 river miles downstream from the Saugus Water Reclamation Plant, traveltime was 3.2 hours during May 2000. In the lower reach, which extends 14.1 river miles downstream from the Valencia Water Reclamation Plant, traveltime was 9.6 hours during October 1999 and 7.1 hours during May 2000. The sodium bromide tracer was detected at both hyporheic locations sampled during October 1999, and at two of the three hyporheic locations sampled during May 2000. On the basis of Rhodamine dye tests, flow curves were constructed from the discharge measurements in the Valencia reach. Flow-curve results indicate net gains in flow throughout most, but not all, of the upper parts of the reach and net losses in flow at the lower part of the reach. Lagrangian water-quality sampling provides information on the changes in chemistry as the water flows downstream from the water reclamation plants. Along both reaches there is an increase in sulfate (40-60 mg/L in the Saugus reach and 160 mg/L in the Valencia reach) and a decrease in chloride (about 45 mg/L in the

  15. The use of air as a natural tracer infractured hydrothermal systems, Los Azufres, Mexico, case study

    SciTech Connect

    Mario Cesar Sudrez Arriaga; Hector Gutierrez Puente, Josefina Moreno Ochoa

    1991-01-01

    Injection of atmospheric air mixed with cold water has been occurring since 1982 at the Los Azufres geothermal field. Several chemical and thermodynamical evidences show that air injection into this fractured hydrothermal system could be considered as a long term natural tracer test. Nitrogen and Argon separated from the air mixture migrate, under the action of the induced injection-extraction gradient, from reinjection sectors to production zones following preferential paths closely related to high permeability conduits. A coarse numerical estimation of the average permeability tensor existing at Tejamaniles, the southern sector, explains the unsuccessful recovery of the artificial tracer tests performed in past years: the anisotropic nature of the fractured volcanic rock would demand considerably quantities of tracer in order to be detected at the producing wells, especially when fluid extraction was low. At the same time concentrations of calcium, cesium, chloride, potassium, rubidium and sodium, are increasing in the liquid produced by the oldest wells of this field's sector.

  16. [Modified Gedelisa test (electrophoresis in gradient of polyacrylamide gel combined with Elisa test). Applications to Toxoplasma gondii exo-antigens (author's transl)].

    PubMed

    Desgeorges, P T; Ambroise-Thomas, P; Falanga, P; Renversez, J C

    1980-01-01

    The authors describe a modified Gedelisa test made up an electrophorese in gradient polyacrylamide gel plus an Elisa test. The gel gradient, after electrophoretic migration is cut longitudinaly. One half is stained with Coomassie blue and the second half is cut in slices of 1 mm thick. Each slice is placed in a well of a microtitration polystirene plate, filled up with carbonate buffer pH 9,6 and then scrached. Proteins diffuse out of the gel and coated on the polystirene. The antigenicity of the coated proteins is revealed by Elisa test. This technique was applied to the study of Toxoplasma gondii exo-antigens obtained from medium of in vitro culture on Vero cells. This antigen contains four fractions, three of them are stained with Coomassie blue, their molecular weights are 160 000, 830 000 and more than one million daltons. PMID:7212392

  17. First Beam and High-Gradient Cryomodule Commissioning Results of the Advanced Superconducting Test Accelerator at Fermilab

    SciTech Connect

    Crawford, Darren; et al.

    2015-06-01

    The advanced superconducting test accelerator at Fermilab has accelerated electrons to 20 MeV and, separately, the International Linear Collider (ILC) style 8-cavity cryomodule has achieved the ILC performance milestone of 31.5 MV/m per cavity. When fully completed, the accelerator will consist of a photoinjector, one ILC-type cryomodule, multiple accelerator R&D beamlines, and a downstream beamline to inject 300 MeV electrons into the Integrable Optics Test Accelerator (IOTA). We report on the results of first beam, the achievement of our cryomodule to ILC gradient specifications, and near-term future plans for the facility.

  18. Tracer tomography (in) rocks!

    NASA Astrophysics Data System (ADS)

    Somogyvári, Márk; Jalali, Mohammadreza; Jimenez Parras, Santos; Bayer, Peter

    2016-04-01

    Physical behavior of fractured aquifers is rigorously controlled by the presence of interconnected conductive fractures, as they represent the main pathways for flow and transport. Ideally, they are simulated as a discrete fracture network (DFN) in a model to capture the role of fracture system geometry, i.e. fracture length, height, and width (aperture/transmissivity). Such network may be constrained by prior geological information or direct data resources such as field mapping, borehole logging and geophysics. With the many geometric features, however, calibration of a DFN to measured data is challenging. This is especially the case when spatial properties of a fracture network need to be calibrated to flow and transport data. One way to increase the insight in a fractured rock is by combining the information from multiple field tests. In this study, a tomographic configuration that combines multiple tracer tests is suggested. These tests are conducted from a borehole with different injection levels that act as sources. In a downgradient borehole, the tracer is recorded at different levels or receivers, in order to maximize insight in the spatial heterogeneity of the rock. As tracer here we chose heat, and temperature breakthrough curves are recorded. The recorded tracer data is inverted using a novel stochastic trans-dimensional Markov Chain Monte Carlo procedure. An initial DFN solution is generated and sequentially modified given available geological information, such as expected fracture density, orientation, length distribution, spacing and persistency. During this sequential modification, the DFN evolves in a trans-dimensional inversion space through adding and/or deleting fracture segments. This stochastic inversion algorithm requires a large number of thousands of model runs to converge, and thus using a fast and robust forward model is essential to keep the calculation efficient. To reach this goal, an upwind coupled finite difference method is employed

  19. Planned High-gradient Flat-beam-driven Dielectric Wakefield Experiments at the Fermilab’s Advanced Superconducting Test Accelerator

    SciTech Connect

    Lemery, Francois; Mihalcea, Daniel; Piot, Philippe; Zhu, Jun

    2014-07-01

    In beam driven dielectric wakefield acceleration (DWA), high-gradient short-wavelength accelerating fields are generally achieved by employing dielectric-lined waveguides (DLWs)  with small aperture which constraints the beam sizes. In this paper we investigate the possibility of using a low-energy (50-MeV) flat beams to induce high-gradient wakes in a slab-symmetric DLW. We demonstrate via numerical simulations the possibility to produce axial electric field with peak amplitude close to 0.5 GV/m. Our studies are carried out using the Fermilab's Advanced Superconducting Test Accelerator (ASTA) photoinjector beamline. We finally discuss a possible experiment that could be performed in the ASTA photoinjector and eventually at higher energies.  

  20. Analysis of Single-Hole and Cross-Hole Tracer Tests Conducted at the Nye County Earl Warning Drilling Program Well Complex, Nye County, Nevada

    SciTech Connect

    A. Umari; J.D. Earle; M.F. Fahy

    2006-03-17

    As part of the effort to understand the flow and transport characteristics downgradient from the proposed high-level radioactive waste geologic repository at Yucca Mountain, Nevada, single- and cross-hole tracer tests were conducted from December 2004 through October 2005 in boreholes at the Nye County 22 well complex. The results were analyzed for transport properties using both numerical and analytical solutions of the governing advection dispersion equation. Preliminary results indicate effective flow porosity values ranging from 1.0 x 10{sup -2} for an individual flow path to 2.0 x 10{sup -1} for composite flow paths, longitudinal dispersivity ranging from 0.3 to 3 m, and a transverse horizontal dispersivity of 0.03 m. Individual flow paths identified from the cross-hole testing indicate some solute diffusion into the stagnant portion of the alluvial aquifer.

  1. Analysis of single-hole and cross-hole tracer tests conducted at the Nye County early warning drilling program well complex, Nye County, Nevada

    USGS Publications Warehouse

    Umari, A.; Earle, J.D.; Fahy, M.F.

    2006-01-01

    As part of the effort to understand the flow and transport characteristics downgradient from the proposed high-level radioactive waste geologic repository at Yucca Mountain, Nevada, single- and cross-hole tracer tests were conducted from December 2004 through October 2005 in boreholes at the Nye County 22 well complex. The results were analyzed for transport properties using both numerical and analytical solutions of the governing advection dispersion equation. Preliminary results indicate effective flow porosity values ranging from 1.0 ?? 10-2 for an individual flow path to 2.0 ?? 10 -1 for composite flow paths, longitudinal dispersivity ranging from 0.3 to 3 m, and a transverse horizontal dispersivity of 0.03 m. Individual flow paths identified from the cross-hole testing indicate some solute diffusion into the stagnant portion of the alluvial aquifer.

  2. Tracer-monitored flow titrations.

    PubMed

    Sasaki, Milton K; Rocha, Diogo L; Rocha, Fábio R P; Zagatto, Elias A G

    2016-01-01

    The feasibility of implementing tracer-monitored titrations in a flow system is demonstrated. A dye tracer is used to estimate the instant sample and titrant volumetric fractions without the need for volume, mass or peak width measurements. The approach was applied to spectrophotometric flow titrations involving variations of sample and titrant flow-rates (i.e. triangle programmed technique) or concentration gradients established along the sample zone (i.e. flow injection system). Both strategies required simultaneous monitoring of two absorbing species, namely the titration indicator and the dye tracer. Mixing conditions were improved by placing a chamber with mechanical stirring in the analytical path aiming at to minimize diffusional effects. Unlike most of flow-based titrations, the innovation is considered as a true titration, as it does not require a calibration curve thus complying with IUPAC definition. As an application, acidity evaluation in vinegars involving titration with sodium hydroxide was selected. Phenolphthalein and brilliant blue FCF were used as indicator and dye tracer, respectively. Effects of sample volume, titrand/titrant concentrations and flow rates were investigated aiming at improved accuracy and precision. Results were reliable and in agreement with those obtained by a reference titration procedure. PMID:26703261

  3. Evaluating the techniques for a tiered testing approach to dredged sediment assessment--a study over a metal concentration gradient

    SciTech Connect

    Porebski, L.M.; Doe, K.G.; Zajdlik, B.A.; Lee, D.; Pocklington, P.; Osborne, J.M.

    1999-11-01

    A sediment quality triad approach was used to evaluate Environment Canada's battery of marine bioassays and the proposed pass/fail criteria along a metals gradient in Belledune Harbour, New Brunswick, Canada. Most assays performed consistently, but certain tests provided less response than expected at the more contaminated stations (amphipod survival and light reduction in photoluminescent bacteria tests passed according to proposed pass/fail criteria). Echinoid fertilization tests were quite sensitive. Bioaccumulation of lead and benthic community structure were related to bulk sediment values. Test interpretation criteria appear reasonable, but as the response rate was low in certain tests, further assessment is recommended. With respect to species suitability, only the clam Macoma balthica used in the bioaccumulation test was thought to be less than optimal for routine use on a large scale because of practical handling and cost considerations. Canadian draft Interim Sediment Quality Guidelines, which the Disposal at Sea Program may use for screening purposes in a tiered testing approach, were used in this study as the chemical benchmarks to select test stations on the basis of the relative probability of effects. Guidelines at the threshold effects level (TEL) performed well in the study as levels below which unacceptable biological effects were unlikely to occur. The ratio of simultaneously extractable metals to acid volatile sulfides was also used in addition to the guideline levels to help explain responses (or lack thereof) along the gradient. Each of the chemical approaches was useful in the prediction/explanation of some but not all of the responses seen in the toxicity and/or benthic community results.

  4. Mississippian coral latitudinal diversity gradients (western interior United States): Testing the limits of high resolution diversity data

    USGS Publications Warehouse

    Webb, G.E.; Sando, W.J.; Raymond, A.

    1997-01-01

    Analysis of high resolution diversity data for Mississippian corals in the western interior United States yielded mild latitudinal diversity gradients despite the small geographic area covered by samples and a large influence on diversity patterns by geographic sampling intensity (sample bias). Three competing plate tectonic reconstructions were tested using the diversity patterns. Although none could be forcefully rejected, one reconstruction proved less consistent with diversity patterns than the other two and additional coral diversity data from farther north in Canada would better discriminate the two equivalent reconstructions. Despite the relatively high sampling intensity represented by the analyzed database, diversity patterns were greatly affected by sample abundance and distribution. Hence, some effort at recognizing and accounting for sample bias should be undertaken in any study of latitudinal diversity gradients. Small-scale geographic lumping of sample localities had only small effects on geographic diversity patterns. However, large-scale (e.g., regional) geographic lumping of diversity data may not yield latitudinally sensitive diversity patterns. Temporal changes in coral diversity in this region reflect changes in eustacy, local tectonism, and terrigenous sediment flux, far more than they do shifting latitude. Highest regional diversity occurred during the interval when the studied region occupied the highest latitude. Therefore, diversity data from different regions may not be comparable, in terms of latitudinal inference. Small-scale stratigraphic lumping of the data caused a nearly complete loss of the latitudinal diversity patterns apparent prior to lumping. Hence, the narrowest possible stratigraphic resolution should be maintained in analyzing latitudinal diversity gradients.

  5. Development of a method for in situ measurement of denitrification in aquifers using 15N tracer tests and membrane inlet mass spectrometry

    NASA Astrophysics Data System (ADS)

    Eschenbach, W.; Well, R.; Flessa, H.; Walther, W.; Duijnisveld, W. H. M.

    2009-04-01

    In NO3- contaminated aquifers containing reduced compounds like organic carbon or sulfides, denitrification is an intense process. Its characterization is of interest because NO3- consump-tion improves water quality and N2O production can cause emission of this greenhouse gas to the atmosphere. Spatial distribution of NO3- and N2 produced by denitrification in groundwa-ter (excess N2) reflects the NO3- input as well as cumulative denitrification during aquifer pas-sage. Reaction progress (RP) at a given location, i.e. the relative consumption by denitrifica-tion of the NO3- that had been leached to the aquifers, characterizes the stage of the denitrifi-cation process. RP can be derived from the ratio between accumulated gaseous denitrification products and initial NO3- concentrations. The amount and spatial distribution of reduced com-pounds within denitrifying aquifers is not well known. Recent findings from parallel investi-gations on in situ denitrification and reactive compounds suggests that single-well 15N tracer tests might be suitable to characterize the stock of reduced compounds in aquifers (Konrad 2007). The overall objective of our studies is measure the spatial dynamics of denitrification within two sandy aquifers in northern Germany. This includes measurement of the actually occurring denitrification process. Moreover we want to determine the long-term denitrification potential which is governed by the stock of reactive material. Here we present a new approach for in situ-measurement of denitrification at monitoring wells using a combination of 15N-tracer push-pull experiments with in situ analysis of 15N-labled N2 and N2O using membrane inlet mass spectrometry (MIMS). We will present first results from a laboratory test with aquifer mesocosms using the MIMS method. In this test we supplemented aquifer material of two depths (2 and 7 m below surface) of a drinking water catchment in Northwest Germany with K15NO3 solution. After tracer application we

  6. Tracer Interpretation Using Temporal Moments on a Spreadsheet

    SciTech Connect

    G. Michael Shook; J. Hope Forsmann

    2005-06-01

    This report presents a method for interpreting geothermal tracer tests. The method is based on the first temporal moment (mean residence time) of the tracer in the subsurface. The individual steps required to interpret a tracer test are reviewed and discussed. And an example tracer test directs the user through the interpretation method. An Excel spreadsheet application of the interpretation method is a companion document to this report.

  7. Statistical analysis and mathematical modeling of a tracer test on the Santa Clara River, Ventura County, California

    USGS Publications Warehouse

    Paybins, Katherine S.; Nishikawa, Tracy; Izbicki, John A.; Reichard, Eric G.

    1998-01-01

    To better understand flow processes, solute-transport processes, and ground-water/surface-water interactions on the Santa Clara River in Ventura County, California, a 24-hour fluorescent-dye tracer study was performed under steady-state flow conditions on a 28-mile reach of the river. The study reach includes perennial (uppermost and lowermost) subreaches and ephemeral subreaches of the lower Piru Creek and the middle Santa Clara River. Dye was injected at a site on Piru Creek, and fluorescence of river water was measured continuously at four sites and intermittently at two sites. Discharge measurements were also made at the six sites. The time of travel of the dye, peak dye concentration, and time-variance of time-concentration curves were obtained at each site. The long tails of the time-concentration curves are indicative of sources/sinks within the river, such as riffles and pools, or transient bank storage. A statistical analysis of the data indicates that, in general, the transport characteristics follow Fickian theory. These data and previously collected discharge data were used to calibrate a one-dimensional flow model (DAFLOW) and a solute-transport model (BLTM). DAFLOW solves a simplified form of the diffusion-wave equation and uses empirical relations between flow rate and cross-sectional area, and flow rate and channel width. BLTM uses the velocity data from DAFLOW and solves the advection-dispersion transport equation, including first-order decay. The simulations of dye transport indicated that (1) ground-water recharge explains the loss of dye mass in the middle, ephemeral, subreaches, and (2) ground-water recharge does not explain the loss of dye mass in the uppermost and lowermost, perennial, subreaches. This loss of mass was simulated using a linear decay term. The loss of mass in the perennial subreaches may be caused by a combination of photodecay or adsorption/desorption.

  8. Final report of the second dye-tracer test at the Chesnut Ridge Security Pits, Y-12 Plant, Oak Ridge, Tennessee

    SciTech Connect

    1992-11-01

    Martin Marietta Energy Systems, Inc. (Energy Systems) manages a closed hazardous waste disposal unit, Chestnut Ridge Security Pits (CRSP), in the form of two trenches and several auger-holes, located on top of the eastern portion of Chestnut Ridge at the Department of Energy (DOE) Oak Ridge Y-12 Plant in Tennessee. The groundwater monitoring system for the unit presently consists of a network of upgradient and downgradient monitor wells. To investigate the discharge of groundwater to springs and streams, Energy Systems, through Geraghty and Miller, Inc., conducted an initial dye-tracer study during the driest part of 1990. The dye was detected at some of the monitoring sites, but verification was necessary due to the proximity of some sites to extraneous dye sources. Based on the results of the initial study, Energy Systems recommended to the Tennessee Department of Environment and Conservation (TDEC) in the 1990 Groundwater Quality Assessment Report (GWQAR) (HSW 1991) for the CRSP that a second dye-tracer study be conducted during the wet weather season. The procedures and materials were reviewed, and a field inspection of the monitoring sites was performed in the fall of 1991. The actual test commenced during the first week of February 1992 with a 4-week baseline monitoring period to determine the inherent variability of the emission spectra within the wavelength range characteristic of Rhodamine WT (RWT) and Fluorescent Brightener 28 (FB28) or similar naturally occuring compounds within in the aquifer. This is commonly referred as background in discussion of minimum detectable levels of dyes. On March 13, RWT and FB28 were injected; weekly monitoring began with the collection of the first set of detectors on March 19. The test was originally scheduled to conclude after 12 weeks but was extended to 18 weeks when no definitive results were obtained.

  9. Comparison of Interfacial Partitioning Tracer Test and X-ray Microtomography Measurements of Immiscible Fluid-Fluid Interfacial Areas within the Identical System

    NASA Astrophysics Data System (ADS)

    Carroll, K. C.; McDonald, K.; Brusseau, M. L. L.

    2015-12-01

    The interfacial area between immiscible fluids in porous media has been demonstrated to be a critical entity for improved understanding, characterization, and simulation of multiphase flow and mass transport in the subsurface. Two general methods are available for measuring interfacial areas for 3-D porous-media systems, high-resolution microtomographic imaging and interfacial partitioning tracer tests (IPTT). Each method has their associated advantages and disadvantages. A few prior research efforts have conducted comparative analyses of the two methods, which have generally indicated disparities in measured values for natural geomedia. For these studies, however, interfacial areas were measured for separate samples with each method due to method restrictions. Thus, to date, there has been no comparative analysis conducted wherein the two measurement methods were applied to the exact same sample. To address this issue, trichloroethene-water interfacial areas were measured for a system comprising a well-sorted, natural sand (median grain diameter of 0.323 mm) using both X-ray microtomography and IPTTs. The microtomographic imaging was conducted on the same packed columns used to conduct the IPTTs. Columns were imaged before and after the IPTTs to evaluate potential impacts of the tracer tests on fluid configuration. The interfacial areas measured using IPTT were 4-6 times larger than the microtomography results, which is consistent with previous work. This disparity was attributed to the inability of the microtomography method to characterize interfacial area associated with microscopic surface roughness. The results indicate that both methods provide useful measures of interfacial area as long as their limitations are recognized.

  10. Combining Push Pull Tracer Tests and Microbial DNA and mRNA Analysis to Assess In-Situ Groundwater Nitrate Transformations

    NASA Astrophysics Data System (ADS)

    Henson, W.; Graham, W. D.; Huang, L.; Ogram, A.

    2015-12-01

    Nitrogen transformation mechanisms in the Upper Floridan Aquifer (UFA) are still poorly understood because of karst aquifer complexity and spatiotemporal variability in nitrate and carbon loading. Transformation rates have not been directly measured in the aquifer. This study quantifies nitrate-nitrogen transformation potential in the UFA using single well push-pull tracer injection (PPT) experiments combined with microbial characterization of extracted water via qPCR and RT-qPCR of selected nitrate reduction genes. Tracer tests with chloride and nitrate ± carbon were executed in two wells representing anoxic and oxic geochemical end members in a spring groundwater contributing area. A significant increase in number of microbes with carbon addition suggests stimulated growth. Increases in the activities of denitrification genes (nirK and nirS) as measured by RT-qPCR were not observed. However, only microbes suspended in the tracer were obtained, ignoring effects of aquifer material biofilms. Increases in nrfA mRNA and ammonia concentrations were observed, supporting Dissimilatory Reduction of Nitrate to Ammonia (DNRA) as a reduction mechanism. In the oxic aquifer, zero order nitrate loss rates ranged from 32 to 89 nmol /L*hr with no added carbon and 90 to 240 nmol /L*hr with carbon. In the anoxic aquifer, rates ranged from 18 to 95 nmol /L*hr with no added carbon and 34 to 207 nmol /L*hr with carbon. These loss rates are low; 13 orders of magnitude less than the loads applied in the contributing area each year, however they do indicate that losses can occur in oxic and anoxic aquifers with and without carbon. These rates may include, ammonia adsorption, uptake, or denitrification in aquifer material biofilms. Rates with and without carbon addition for both aquifers were similar, suggesting aquifer redox state and carbon availability alone are insufficient to predict response to nutrient additions without characterization of microbial response. Surprisingly, these

  11. Assessing the Feasibility of In-Situ Aerobic Cometabolism of Chlorinated Solvents by a Single-Well Push-Pull and Natural Gradient Drift Tests in McClellan AFB, CA

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Istok, J. D.; Semprini, L.

    2001-12-01

    A single-well push-pull test has been developed to evaluate in-situ aerobic cometabolic treatment of chlorinated aliphatic hydrocarbons (CAHs), such as trichloroethylene (TCE) and cis-1,2-dichloroethylene (c-DCE). A series of single-well natural gradient drift and push-pull tests were conducted in two monitoring wells at the McClellan Air Force Base, CA, where aquifer is contaminated mainly with c-DCE and TCE. Transport characteristics of dissolved solutes [bromide (tracer), propane (growth substrate), ethylene, propylene (nontoxic surrogates to probe for CAH transformation activity), DO and nitrate (nutrient)] were evaluated in push-pull transport tests by injecting 200-L of groundwater containing the solutes into the aquifer (Push), providing a rest period of 18 hours (Reaction), and then extracting 400-L of the test solution/groundwater mixtures (Pull). Mass balances showed over 95% of the injected bromide was recovered, and the recoveries of the other solutes were comparable with bromide. The dispersion of all the solutes was similar indicating sorption or other partitioning processes were minimal. These results indicate that bromide could be used as a conservative tracer for biological activity tests and that little loss of the dissolved gaseous substrates occurred prior to biostimulation of the aquifer. A series of biostimulation tests were performed by injecting 500 L-groundwater containing propane (6 mg/L), DO (25 mg/L), nitrate (9 mg/L as N) and bromide (100 mg/L) into the aquifer. Temporal groundwater samples were obtained from the injection well under natural gradient drift conditions. With repeating biostimulation tests the rates of both propane and DO utilization were increased significantly. The results demonstrated that the progress of biostimulation could be assessed by injecting and monitoring under natural gradient drift conditions. Successive push-pull activity tests were performed after biostimulation was achieved using the same procedures as

  12. Chemical bond as a test of density-gradient expansions for kinetic and exchange energies

    NASA Astrophysics Data System (ADS)

    Perdew, John P.; Levy, Mel; Painter, G. S.; Wei, Siqing; Lagowski, Jolanta B.

    1988-01-01

    Errors in kinetic and exchange contributions to the molecular bonding energy are assessed for approximate density functionals by reference to near-exact Hartree-Fock values. From the molecular calculations of Allan et al.and of Lee and Ghosh, it is demonstrated that the density-gradient expansion does not accurately describe the noninteracting kinetic contribution to the bonding energy, even when this expansion is carried to fourth order and applied in its spin-density-functional form to accurate Hartree-Fock densities. In a related study, it is demonstrated that the overbinding of molecules such as N2 and F2, which occurs in the local-spin-density (LSD) approximation for the exchange-correlation energy, is not attributable to errors in the self-consistent LSD densities. Contrary to expectations based upon the Gunnarsson-Jones nodality argument, it is found that the LSD approximation for the exchange energy can seriously overbind a molecule even when bonding does not create additional nodes in the occupied valence orbitals. LSD and exact values for the exchange contribution to the bonding energy are displayed and discussed for several molecules.

  13. Chemical bond as a test of density-gradient expansions for kinetic and exchange energies

    SciTech Connect

    Perdew, J.P.; Levy, M.; Painter, G.S.; Wei, S.; Lagowski, J.B.

    1988-01-15

    Errors in kinetic and exchange contributions to the molecular bonding energy are assessed for approximate density functionals by reference to near-exact Hartree-Fock values. From the molecular calculations of Allan et al. and of Lee and Ghosh, it is demonstrated that the density-gradient expansion does not accurately describe the noninteracting kinetic contribution to the bonding energy, even when this expansion is carried to fourth order and applied in its spin-density-functional form to accurate Hartree-Fock densities. In a related study, it is demonstrated that the overbinding of molecules such as N/sub 2/ and F/sub 2/, which occurs in the local-spin-density (LSD) approximation for the exchange-correlation energy, is not attributable to errors in the self-consistent LSD densities. Contrary to expectations based upon the Gunnarsson-Jones nodality argument, it is found that the LSD approximation for the exchange energy can seriously overbind a molecule even when bonding does not create additional nodes in the occupied valence orbitals. LSD and exact values for the exchange contribution to the bonding energy are displayed and discussed for several molecules.

  14. Identification and characterization of freshwater algae from a pollution gradient using rbcL sequencing and toxicity testing.

    PubMed

    Novis, Phil M; Halle, Cornelia; Wilson, Belinda; Tremblay, Louis A

    2009-10-01

    One approach in toxicity testing using microalgae is to assess the modulation of light energy absorbed as a result of exposure to contaminants. In this study, four strains of microalgae were isolated to obtain a variety of taxa for testing from sites receiving various levels of environmental stressors around Christchurch, New Zealand. The strains were characterized by partially sequencing rbcL, a routinely used gene in plant phylogenetics with a large existing database of strains. Based on morphological observation and gene sequences, the strains were identified as Chlorella sp., Neochloris sp., and Choricystis minor. The isolates were exposed to the herbicide glyphosate and the metal zinc, and their responses were measured using the ToxY-PAM system. Chlorella sp. was the most sensitive. Two strains of Choricystis minor were isolated from different ponds in an effluent gradient at a sewage treatment plant. Analysis of variance indicated that the isolate from the least contaminated pond was more sensitive to zinc (although regression analysis did not show this result). This suggests that the selective pressure exerted on algal strains by a contamination gradient over short a distance is detectable by both genetic and physiological methods, with implications for sourcing appropriate indicator organisms from the environment. PMID:19308636

  15. Analysis of a Multi-Well Tracer Test at a Bank Filtration Site in an Arid Environment of El Paso, Texas

    NASA Astrophysics Data System (ADS)

    Abdel-Fattah, A. N.; Langford, R.; Schulze-Makuch, D.; Sheng, Z.

    2005-12-01

    River bank filtered water is an important component of the drinking water production in many areas of the world. In riverbank filtration, the removal of pathogens is an important task for the production of good quality drinking water. The hydrogeological factors and spatial changes in the water's microbiology during the transport from the river to the aquifer have important implications on the quality of the produced water. The goal of this study was to investigate riverbank infiltration effectiveness in arid environments such as that of El Paso, Texas. The hydrostratigraphic units and hydrogeologic conditions were characterized with lithologic samples obtained from all boreholes collected during the construction of twelve observation wells and one production well in the site, which were constructed near the artificial stream to provide geologic and hydrologic information. The shallow aquifer is composed of three unites: high hydraulic conductivity layers on the top and bottom, and low conductivity layer in the middle. In this study advective transport of microspheres was compared with a conservative tracer such as bromide. Bromide was injected into an observation well at the channel margin. Simultaneously, 1, 6 and 10 micron-diameter fluorescent microspheres equivalent to Giardia, Cryptosporidium, and bacteria sizes were injected into the stream bottom and two observation wells to assess the suitability of microspheres as abiotic analogs in future investigations involving the physical aspects of bacteria and protozoa transport behavior. The 17.8 day-tracer test provided valuable results that are relevant to the transport of pathogens through the subsurface under riverbank filtration conditions. The 1 micron-size microspheres were abundant in the pumping and observation wells and showed multiple peaks similar to the bromide results. Microspheres from the three injection sites had distinctly different transport paths and rates. The 6 and 10 micron-size microspheres

  16. Final report of the second dye-tracer test at the Chestnut Ridge Security Pits, Y-12 Plant, Oak Ridge, Tennessee

    SciTech Connect

    Not Available

    1992-11-01

    Martin Marietta Energy Systems, Inc. (Energy Systems) manages a closed hazardous waste disposal unit, Chestnut Ridge Security Pits (CRSP), in the form of two trenches and several auger-holes, located on top of the eastern portion of Chestnut Ridge at the Department of Energy (DOE) Oak Ridge Y-12 Plant in Tennessee. The groundwater monitoring system for the unit presently consists of a network of upgradient and downgradient monitor wells. To investigate the discharge of groundwater to springs and streams. An initial dye-tracer study was conducted during the driest part of 1990. The dye was detected at some of the monitoring sites, but verification was necessary due to the proximity of some sites to extraneous dye sources. A second dye-tracer was conducted during the wet weather season. The actual test commenced during the first week of February 1992 with a 4-week baseline monitoring period to determine the inherent variability of the emission spectra within the wavelength range characteristic of Rhodamine WT (RWT) and Fluorescent Brightener 28 (FB28) or similar naturally occuring compounds within in the aquifer. This is commonly referred as background in discussion of minimum detectable levels of dyes. Because two monitoring stations produced dye/optical brightener emission spectra during the baseline period, no results could be characterized on a quantitative or qualitative basis as positively indicating the detection of RWT or FB28 at these monitoring locations. The remaining monitoring produced no results which could be positively characterized as a detection of RWT or FB28. At no time was a characteristic dye spectrum that could be resolved from the background levels or interfering peaks recorded for any sample, nor could any of the results be qualitatively characterized as dye detection.

  17. Fires in Seasonally Dry Tropical Forest: Testing the Varying Constraints Hypothesis across a Regional Rainfall Gradient

    PubMed Central

    Mondal, Nandita; Sukumar, Raman

    2016-01-01

    The “varying constraints hypothesis” of fire in natural ecosystems postulates that the extent of fire in an ecosystem would differ according to the relative contribution of fuel load and fuel moisture available, factors that vary globally along a spatial gradient of climatic conditions. We examined if the globally widespread seasonally dry tropical forests (SDTFs) can be placed as a single entity in this framework by analyzing environmental influences on fire extent in a structurally diverse SDTF landscape in the Western Ghats of southern India, representative of similar forests in monsoonal south and southeast Asia. We used logistic regression to model fire extent with factors that represent fuel load and fuel moisture at two levels—the overall landscape and within four defined moisture regimes (between 700 and1700 mm yr-1)—using a dataset of area burnt and seasonal rainfall from 1990 to 2010. The landscape scale model showed that the extent of fire in a given year within this SDTF is dependent on the combined interaction of seasonal rainfall and extent burnt the previous year. Within individual moisture regimes the relative contribution of these factors to the annual extent burnt varied—early dry season rainfall (i.e., fuel moisture) was the predominant factor in the wettest regime, while wet season rainfall (i.e., fuel load) had a large influence on fire extent in the driest regime. Thus, the diverse structural vegetation types associated with SDTFs across a wide range of rainfall regimes would have to be examined at finer regional or local scales to understand the specific environmental drivers of fire. Our results could be extended to investigating fire-climate relationships in STDFs of monsoonal Asia. PMID:27441689

  18. SOFI/Substrate integrity testing for cryogenic propellant tanks at extreme thermal gradient conditions

    NASA Astrophysics Data System (ADS)

    Haynes, M.; Fabian, P.

    2015-12-01

    Liquid propellant tank insulation for space flight requires low weight as well as high insulation factors. Use of Spray-On Foam Insulation (SOFI) is an accepted, cost effective technique for insulating a single wall cryogenic propellant tank and has been used extensively throughout the aerospace industry. Determining the bond integrity of the SOFI to the metallic substrate as well as its ability to withstand the in-service strains, both mechanical and thermal, is critical to the longevity of the insulation. This determination has previously been performed using highly volatile, explosive cryogens, which increases the test costs enormously, as well as greatly increasing the risk to both equipment and personnel. CTD has developed a new test system, based on a previous NASA test that simulates the mechanical and thermal strains associated with filling a large fuel tank with a cryogen. The test enables a relatively small SOFI/substrate sample to be monitored for any deformations, delaminations, or disjunctures during the cooling and mechanical straining process of the substrate, and enables the concurrent application of thermal and physical strains to two specimens at the same time. The thermal strains are applied by cooling the substrate to the desired cryogen temperature (from 4 K to 250 K) while maintaining the outside surface of the SOFI foam at ambient conditions. Multiple temperature monitoring points are exercised to ensure even cooling across the substrate, while at the same time, surface temperatures of the SOFI can be monitored to determine the heat flow. The system also allows for direct measurement of the strains in the substrate during the test. The test system as well as test data from testing at 20 K, for liquid Hydrogen simulation, will be discussed.

  19. Results from air-injection and tracer testing in the upper Tiva Canyon, Bow Ridge Fault, and upper Paintbrush contact alcoves of the Exploratory Studies Facility, August 1994 through July 1996, Yucca Mountain, Nevada

    USGS Publications Warehouse

    LeCain, Gary D.

    1998-01-01

    Air-injection and tracer testing were conducted in the upper Tiva Canyon, Bow Ridge Fault, and upper Paintbrush contact alcoves in the Exploratory Studies Facility at Yucca Mountain, Nevada, from August 1994 to July 1991. The study was conducted by the U.S. Geological Survey, in cooperation with the U.S. Department of Energy.

  20. Analytic energy gradient of excited electronic state within TDDFT/MMpol framework: Benchmark tests and parallel implementation

    SciTech Connect

    Zeng, Qiao; Liang, WanZhen

    2015-10-07

    The time-dependent density functional theory (TDDFT) has become the most popular method to calculate the electronic excitation energies, describe the excited-state properties, and perform the excited-state geometric optimization of medium and large-size molecules due to the implementation of analytic excited-state energy gradient and Hessian in many electronic structure software packages. To describe the molecules in condensed phase, one usually adopts the computationally efficient hybrid Quantum Mechanics/Molecular Mechanics (QM/MM) models. Here, we extend our previous work on the energy gradient of TDDFT/MM excited state to account for the mutual polarization effects between QM and MM regions, which is believed to hold a crucial position in the potential energy surface of molecular systems when the photoexcitation-induced charge rearrangement in the QM region is drastic. The implementation of a simple polarizable TDDFT/MM (TDDFT/MMpol) model in Q-Chem/CHARMM interface with both the linear response and the state-specific features has been realized. Several benchmark tests and preliminary applications are exhibited to confirm our implementation and assess the effects of different treatment of environmental polarization on the excited-state properties, and the efficiency of parallel implementation is demonstrated as well.

  1. A test for community saturation along the Himalayan bird diversity gradient, based on within-species geographical variation.

    PubMed

    Ghosh-Harihar, Mousumi; Price, Trevor D

    2014-05-01

    The idea that ecological communities are unsaturated is central to many explanations for regional gradients in species diversity. We describe a test for differing degrees of saturation across a regional diversity gradient, based on within-species geographical variation in ecological attributes. If communities in species-poor regions are less saturated than communities in species-rich regions, species that straddle both regions should have broader niches in species-poor regions, exploiting resources that are consumed by other species in species-rich regions. We studied 10 species of Old World leaf warblers that range across the Himalayas. Elevational range and feeding method showed niche contractions in the species-poor north-west Himalayas with respect to the species-rich south-east Himalayas, whereas prey size did not vary geographically. Niche contractions are contrary to the expectation of character release in depauperate environments, as has been shown, for example in mainland-island comparisons. We show that arthropod abundances are likely a limiting resource, and that niche contractions are consistent with measurements of a narrowing of resource availability. Results suggest that north-western warbler communities are at least as saturated as the south-east and that lower resource diversity drives reduced species numbers. PMID:24219104

  2. Analytic energy gradient of excited electronic state within TDDFT/MMpol framework: Benchmark tests and parallel implementation.

    PubMed

    Zeng, Qiao; Liang, WanZhen

    2015-10-01

    The time-dependent density functional theory (TDDFT) has become the most popular method to calculate the electronic excitation energies, describe the excited-state properties, and perform the excited-state geometric optimization of medium and large-size molecules due to the implementation of analytic excited-state energy gradient and Hessian in many electronic structure software packages. To describe the molecules in condensed phase, one usually adopts the computationally efficient hybrid Quantum Mechanics/Molecular Mechanics (QM/MM) models. Here, we extend our previous work on the energy gradient of TDDFT/MM excited state to account for the mutual polarization effects between QM and MM regions, which is believed to hold a crucial position in the potential energy surface of molecular systems when the photoexcitation-induced charge rearrangement in the QM region is drastic. The implementation of a simple polarizable TDDFT/MM (TDDFT/MMpol) model in Q-Chem/CHARMM interface with both the linear response and the state-specific features has been realized. Several benchmark tests and preliminary applications are exhibited to confirm our implementation and assess the effects of different treatment of environmental polarization on the excited-state properties, and the efficiency of parallel implementation is demonstrated as well. PMID:26450289

  3. Calorimeter measures high nuclear heating rates and their gradients across a reactor test hole

    NASA Technical Reports Server (NTRS)

    Burwell, D.; Coombe, J. R.; Mc Bride, J.

    1970-01-01

    Pedestal-type calorimeter measures gamma-ray heating rates from 0.5 to 7.0 watts per gram of aluminum. Nuclear heating rate is a function of cylinder temperature change, measured by four chromel-alumel thermocouples attached to the calorimeter, and known thermoconductivity of the tested material.

  4. Tracers for Characterizing Enhanced Geothermal Systems

    SciTech Connect

    Karen Wright; George Redden; Carl D. Palmer; Harry Rollins; Mark Stone; Mason Harrup; Laurence C. Hull

    2010-02-01

    Information about the times of thermal breakthrough and subsequent rates of thermal drawdown in enhanced geothermal systems (EGS) is necessary for reservoir management, designing fracture stimulation and well drilling programs, and forecasting economic return. Thermal breakthrough in heterogeneous porous media can be estimated using conservative tracers and assumptions about heat transfer rates; however, tracers that undergo temperature-dependent changes can provide more detailed information about the thermal profile along the flow path through the reservoir. To be effectively applied, the thermal reaction rates of such temperature sensitive traces must be well characterized for the range of conditions that exist in geothermal systems. Reactive tracers proposed in the literature include benzoic and carboxylic acids (Adams) and organic esters and amides (Robinson et al.); however, the practical temperature range over which these tracers can be applied (100-275°C) is somewhat limited. Further, for organic esters and amides, little is known about their sorption to the reservoir matrix and how such reactions impact data interpretation. Another approach involves tracers where the reference condition is internal to the tracer itself. Two examples are: 1) racemization of polymeric amino acids, and 2) mineral thermoluminescence. In these cases internal ratios of states are measured rather than extents of degradation and mass loss. Racemization of poly-L-lactic acid (for example) is temperature sensitive and therefore can be used as a temperature-recording tracer depending on the rates of racemization and stability of the amino acids. Heat-induced quenching of thermoluminescence of pre-irradiated LiF can also be used. To protect the tracers from alterations (extraneous reactions, dissolution) in geothermal environments we are encapsulating the tracers in core-shell colloidal structures that will subsequently be tested for their ability to be transported and to protect the

  5. Analysis of multicomopnent groundwater flow in karst aquifer by CFC, tritium, tracer test and modelling, case study at Skaistkalnes vicinity, Latvia

    NASA Astrophysics Data System (ADS)

    Bikshe, Janis; Babre, Alise; Delina, Aija; Popovs, Konrads

    2014-05-01

    Groundwater in karst environments tends to have difficulties to distinguish multiple flows if several sources of water are present. Skaistkalne vicinity faces with such situation where old groundwater, fresh groundwater and inflow from river Iecava occurs. Attempts were made to distinguish groundwater residence time of multiple components of water applying CFC and tritium dating techniques supplied by tracer test and numerical model of study area. Study area covers territory between two rivers Iecava and Memele with water level difference of 7 meters and horizontal distance of 2.2 kilometres between both. Study area consists of karst affected Devonian gypsum and carbonaceous rocks covered by Quaternary low to high permeable deposits. Confined groundwater at depth of 10-25 meters where analysed by CFC's and tritium. At this depth groundwater exhibits anoxic reducing environment that has caused degradation of CFC's at similar degree in all samples. Taking it into account, mean residence time based on CFC piston flow model is 22 - 42 years and 28 - 34 years based on binary mixing model. Tritium results show signs of incensement of groundwater residence time towards discharge area. CFC combined with tritium proved increased vertical velocity in middle part between the rivers likely caused by hydrogeological window in Quaternary deposits created by karst processes. Numerical model (Delina et al. 2012) was applied and calculations yielded groundwater flow velocity rate at 0.3 - 1 m/day in area between the rivers. Investigation of CFC data resulted in possible groundwater flow rate of at a minimum of 0.2 m/day although it's not applicable to all sampled wells due to specific hydrogeological conditions. Tracer test was made between the rivers in order to distinguish main water flow paths and flow velocity. Results showed that very high permeable conduits connect rivers and karst lakes with velocity rates of 800 - 1300 m/day. Complex investigation leads to conclude that

  6. Is pre-conditioning required for the measurement of in situ denitrification rates with push-pull 15N-tracer tests?

    NASA Astrophysics Data System (ADS)

    Eschenbach, Wolfram; Well, Reinhard

    2013-04-01

    Diffuse NO3 emissions derived from agricultural N surpluses are the main cause of NO3 pollution of aquifers and open water bodies. Denitrification is the key process for the attenuation of this anthropogenic NO3 in groundwater. Knowledge about the spatial variability denitrification rates in nitrate-contaminated aquifers is crucial to predict the development of groundwater quality. However, the spatial distribution and intensity of denitrification in aquifers is difficult to predict. But precisely this knowledge is important for an effective implementation of measures for the reduction of agricultural N-surpluses to gain a good chemical status of groundwater bodies. Push-pull tests have proven to be a relatively low-cost instrument to obtain quantitative information about aquifer properties and microbial activities in aquifers. These tests have been already successfully used for the measurement of in situ denitrification rates (Dr(in situ); Well and Myrold, 2002;Konrad, 2007). We conducted 28 push-pull tracer tests in the Großen Kneten (GKA) and the Furberger Feld aquifer (FFA), two Pleistocene sandy aquifers in Lower Saxony (Germany) to measure Dr(in situ) and to derive an estimate on the stock of reactive compounds. In the deeper NO3-free zone of the aquifer, Dr(in situ) was relatively low despite the high abundance of reductants. Our aim was to check whether pre-conditioning by repeated NO3-injections would stimulate indigenous denitrifiers and thus lead to increased reduction rates of NO3 corresponding to the stock of reductants. Pre-conditioning by the injection of the electron acceptor NO3 prior to subsequent push-pull tracer tests with 15N labelled NO3 was performed at 4 depths in the NO3-free groundwater zone in the Fuhrberger Feld aquifer. We compared unconditioned and pre-conditioned in situ denitrification rates with laboratory denitrification rates measured during one year laboratory incubations with corresponding aquifer material (Dr(365)). Our

  7. Tracer-level radioactive pilot-scale test of in situ vitrification for the stabilization of contaminated soil sites at ORNL

    SciTech Connect

    Spalding, B.P.; Jacobs, G.K.; Naney, M.T.; Dunbar, N.W.; Tixier, J.S.; Powell, T.D.

    1992-11-01

    A field demonstration of in situ vitrification (ISV) was completed in May 1991, and produced approximately 12 Mg of melted earthen materials containing 12.7 mCi of radioactivity within 500 g of sludge in amodel of an old seepage trench waste disposal unit. Past waste disposal operations at Oak Ridge National Laboratory have left several contaminated seepage sites. In planning for remediation of such sites, ISV technology has been identified as a leading candidate because of the high risks associated with any retrieval option and because of the usual high quality of vitreous waste form. Major isotopes placed in the test trench were {sup 137}Cs and {sup 90}Sr, with lesser amounts of {sup 6O}Co, {sup 241}Am, and {sup 239,240}Pu. A total of 29 MWh of electrical power was delivered to the ground over a 5-day period producing a melt depth of 8.5 ft. During melting, 2.4% of the {sup 137}Cs volatilized from the melt into an off-gas containment hood and was captured quantitatively on a high efficiency particulate air filter. No volatilization of {sup 90}Sr, {sup 241}Am, or {sup 239,240}Pu was detected and > 99.993% retention of these isotopes in the melt was estimated. The use of added rare earth tracers (Ce, La, and Nd), as surrogates for transuranic isotopes, led to estimated melt retentions of >99.9995% during the test. The molten material, composed of the native soil and dolomitic limestone used for filling the test trench, reached a processing temperature of 1500{degrees}C. Standardized leaching procedures using Product Consistency Testing indicated that the ISV product has excellent characteristics relative to other vitreous nuclear waste forms.

  8. Tracer-level radioactive pilot-scale test of in situ vitrification for the stabilization of contaminated soil sites at ORNL

    SciTech Connect

    Spalding, B.P.; Jacobs, G.K.; Naney, M.T. ); Dunbar, N.W. ); Tixier, J.S.; Powell, T.D. )

    1992-11-01

    A field demonstration of in situ vitrification (ISV) was completed in May 1991, and produced approximately 12 Mg of melted earthen materials containing 12.7 mCi of radioactivity within 500 g of sludge in amodel of an old seepage trench waste disposal unit. Past waste disposal operations at Oak Ridge National Laboratory have left several contaminated seepage sites. In planning for remediation of such sites, ISV technology has been identified as a leading candidate because of the high risks associated with any retrieval option and because of the usual high quality of vitreous waste form. Major isotopes placed in the test trench were [sup 137]Cs and [sup 90]Sr, with lesser amounts of [sup 6O]Co, [sup 241]Am, and [sup 239,240]Pu. A total of 29 MWh of electrical power was delivered to the ground over a 5-day period producing a melt depth of 8.5 ft. During melting, 2.4% of the [sup 137]Cs volatilized from the melt into an off-gas containment hood and was captured quantitatively on a high efficiency particulate air filter. No volatilization of [sup 90]Sr, [sup 241]Am, or [sup 239,240]Pu was detected and > 99.993% retention of these isotopes in the melt was estimated. The use of added rare earth tracers (Ce, La, and Nd), as surrogates for transuranic isotopes, led to estimated melt retentions of >99.9995% during the test. The molten material, composed of the native soil and dolomitic limestone used for filling the test trench, reached a processing temperature of 1500[degrees]C. Standardized leaching procedures using Product Consistency Testing indicated that the ISV product has excellent characteristics relative to other vitreous nuclear waste forms.

  9. Dual-tracer receptor concentration imaging using tracers with different tissue delivery kinetics

    NASA Astrophysics Data System (ADS)

    Tichauer, Kenneth M.; Diop, Mamadou; Elliott, Jonathan T.; Samkoe, Kimberley S.; Hasan, Tayyaba; St. Lawrence, Keith; Pogue, Brian W.

    2014-03-01

    Simultaneous dynamic fluorescent imaging of a suitable untargeted tracer in conjunction with any molecular targeted fluorescent agent has been shown to be a powerful approach for quantifying cancer-specific cell surface receptors in vivo in the presence of non-specific uptake and tracer delivery variability. The identification of a "suitable" untargeted tracer (i.e., one having equivalent plasma and tissue delivery pharmacokinetics to the targeted tracer) for every targeted tracer, however, may not always be feasible or could require extensive testing. This work presents a "deconvolution" approach capable of correcting for plasma and tissue-delivery pharmacokinetic differences between tracers by quantifying dynamic differences in targeted and untargeted tracer uptake in a receptor-free tissue (one devoid of targeted molecular species) and correcting uptake in all other tissues accordingly. This deconvolution correction approach is evaluated in theoretical models and explored in an in vivo mouse xenograft model of human glioma. In the animal experiments, epidermal growth factor receptor (EGFR: a receptor known to be overexpressed in the investigated glioma cell line) was targeted using a fluorescent tracer with very different plasma pharmacokinetics than a second untargeted fluorescent tracer. Without correcting for these differences, the dual-tracer approach yielded substantially higher estimations of EGFR concentration in all tissues than expected; however, deconvolution correction was able to produce estimates that matched ex vivo validation.

  10. TESTING 24 {mu}m AND INFRARED LUMINOSITY AS STAR FORMATION TRACERS FOR GALACTIC STAR-FORMING REGIONS

    SciTech Connect

    Vutisalchavakul, Nalin; Evans, Neal J. II

    2013-03-10

    We have tested some relations for star formation rates used in extragalactic studies for regions within the Galaxy. In nearby molecular clouds, where the initial mass function is not fully sampled, the dust emission at 24 {mu}m greatly underestimates star formation rates (by a factor of 100 on average) when compared to star formation rates determined from counting young stellar objects. The total infrared emission does no better. In contrast, the total far-infrared method agrees within a factor of two on average with star formation rates based on radio continuum emission for massive, dense clumps that are forming enough massive stars to have L{sub TIR} exceed 10{sup 4.5} L{sub Sun }. The total infrared and 24 {mu}m also agree well with each other for both nearby, low-mass star-forming regions and the massive, dense clump regions.

  11. Biological tracer method

    DOEpatents

    Strong-Gunderson, Janet M.; Palumbo, Anthony V.

    1998-01-01

    The present invention is a biological tracer method for characterizing the movement of a material through a medium, comprising the steps of: introducing a biological tracer comprising a microorganism having ice nucleating activity into a medium; collecting at least one sample of the medium from a point removed from the introduction point; and analyzing the sample for the presence of the biological tracer. The present invention is also a method for using a biological tracer as a label for material identification by introducing a biological tracer having ice nucleating activity into a material, collecting a sample of a portion of the labelled material and analyzing the sample for the presence of the biological tracer.

  12. Biological tracer method

    DOEpatents

    Strong-Gunderson, J.M.; Palumbo, A.V.

    1998-09-15

    The present invention is a biological tracer method for characterizing the movement of a material through a medium, comprising the steps of: introducing a biological tracer comprising a microorganism having ice nucleating activity into a medium; collecting at least one sample of the medium from a point removed from the introduction point; and analyzing the sample for the presence of the biological tracer. The present invention is also a method for using a biological tracer as a label for material identification by introducing a biological tracer having ice nucleating activity into a material, collecting a sample of a portion of the labelled material and analyzing the sample for the presence of the biological tracer. 2 figs.

  13. Microfluidic system with integrated electroosmotic pumps, concentration gradient generator and fish cell line (RTgill-W1)--towards water toxicity testing.

    PubMed

    Glawdel, Tomasz; Elbuken, Caglar; Lee, Lucy E J; Ren, Carolyn L

    2009-11-21

    This study presents a microfluidic system that incorporates electroosmotic pumps, a concentration gradient generator and a fish cell line (rainbow trout gill) to perform toxicity testing on fish cells seeded in the system. The system consists of three mechanical components: (1) a toxicity testing chip containing a microfluidic gradient generator which creates a linear concentration distribution of toxicant in a cell test chamber, (2) an electroosmotic (EO) pump chip that controls the flow rate and operation of the toxicity chip, and (3) indirect reservoirs that connect the two chips allowing for the toxicant solution to be pumped separately from the electroosmotic pump solution. The flow rate and stability of the EO pumps was measured and tested by monitoring the gradient generator using fluorescence microscopy. Furthermore, a lethality test was performed with this system setup using a rainbow trout gill cell line (RTgill-W1) as the test cells and sodium dodecyl sulfate as a model toxicant. A gradient of sodium dodecyl sulfate, from 0 to 50 microg mL(-1), was applied for 1 hr to the attached cells, and the results were quantified using a Live/Dead cell assay. This work is a preliminary study on the application of EO pumps in a living cell assay, with the potential to use the pumps in portable water quality testing devices with RTgill-W1 cells as the biosensors. PMID:19865731

  14. Tracer Lamination in the Stratosphere: A Global Climatology

    NASA Technical Reports Server (NTRS)

    Appenzeller, Christof; Holton, James R.

    1997-01-01

    Vertical soundings of stratospheric ozone often exhibit laminated tracer structures characterized by strong vertical tracer gradients. The change in time of these gradients is used to define a tracer lamination rate. It is shown that this quantity can be calculated by the cross product of the horizontal temperature and horizontal tracer gradients. A climatology based on UARS satellite-borne ozone data and on ozone-like pseudotracer data is presented. Three stratospheric regions with high lamination rates were found: the part of the stratospheric overworld which is influenced by the polar vortex, the part of the lowermost stratosphere which is influenced by the tropopause and a third region in the subtropical lower stratosphere mainly characterized with strong vertical shear. High lamination rates in the stratospheric overworld were absent during summer, whereas in the lowermost stratosphere high lamination rates were found year-round. This is consistent with the occurrence and seasonal variation of the horizontal tracer gradient and vertical shear necessary for tilting the tracer surfaces. During winter, high lamination rates associated with the stratospheric polar vortex are present down to approximately 100 hPa. Several features of the derived climatology are roughly consistent with earlier balloon-borne studies. The patterns in the southern and northern hemisphere are comparable, but details differ as anticipated from a less disturbed and more symmetric southern polar vortex.

  15. Nonlinear Advection Algorithms Applied to Inter-related Tracers: Errors and Implications for Modeling Aerosol-Cloud Interactions

    SciTech Connect

    Ovtchinnikov, Mikhail; Easter, Richard C.

    2009-02-01

    Monotonicity constraints and gradient preserving flux corrections employed by many advection algorithms used in atmospheric models make these algorithms non-linear. Consequently, any relations among model variables transported separately are not necessarily preserved in such models. These errors cannot be revealed by traditional algorithm testing based on advection of a single tracer. New type of tests are developed and conducted to evaluate the preservation of a sum of several number mixing ratios advected independently of each other, as is the case, for example, in models using bin or sectional representation of aerosol or cloud particle size distribution. The tests show that when three tracers are advected in 1D uniform constant velocity flow, local errors in the sum can be on the order of 10%. When cloud-like interactions are allowed among the tracers, errors in total sum of three mixing ratios can reach up to 30%. Several approaches to eliminate the error are suggested, all based on advecting the sum as a separate variable and then normalizing mixing ratios for individual tracers to match the total sum. A simple scalar normalization preserves the total number mixing ratio and positive definiteness of the variables but the monotonicity constraint for individual tracers is no longer maintained. More involved flux normalization procedures are developed for the flux based advection algorithms to maintain the monotonicity for individual scalars and their sum.

  16. Does nitrogen saturation theory apply to unpolluted temperate forests? A test along a forest soil nitrogen gradient in Oregon

    NASA Astrophysics Data System (ADS)

    Perakis, S. S.; Sinkhorn, E. R.

    2011-12-01

    Natural gradients of soil nitrogen (N) can be used to evaluate the consequences of long-term ecosystem N enrichment, and to test the applicability of N saturation theory as a general framework for understanding ecosystem N dynamics. Temperate forest soils of the Oregon Coast Range experience low rates of atmospheric N deposition, yet display among the highest soil N accumulations ever reported worldwide. We measured plant and soil (0-1m) N stocks and natural abundance delta15N, plant production, N uptake and return in litterfall, soil gross and net N mineralization rates, and hydrologic N losses of nine Douglas-fir forests growing across an exceptionally wide soil N gradient in the Oregon Coast Range. Ecosystem N content ranged from 8,788 to 22,667 kg N/ha across sites, with highest N accumulations near the coast, and 96-98% of total ecosystem N residing in mineral soil. Ecosystem delta15N displayed a curvilinear relationship with ecosystem N content that reflected competing influences of N input from biological fixation at low-N sites and fractionating N losses at high-N sites. Simulation modeling of ecosystem N and delta15N mass balance suggest that cycles of wildfire can promote unusually high natural N accumulation by fostering early successional biological nitrogen fixation. Surface mineral soil (0 - 10 cm) N concentrations were tightly correlated to total soil N stocks to 1 m depth, and in contrast to predictions of N saturation theory, were linearly related to 10-fold variation in net N mineralization from 8 - 82 kg N/ha-yr. Net N mineralization was unrelated to soil C:N, soil texture, precipitation and temperature differences among sites. Net nitrification accounted for < 20% of net N mineralization at low N sites, increasing to 85 - 100% of net N mineralization at intermediate and high N sites, and was associated with soil pH decline from 5.8 to 4.1 across sites. The ratio of net:gross N mineralization and nitrification increased along the gradient

  17. Sediment connectivity in a small catchment with badlands: Testing connectivity indices using fallout radionuclide tracers at the Vallcebre Research Catchments.

    NASA Astrophysics Data System (ADS)

    Gallart, Francesc; Latron, Jérôme; Vuolo, Diego; Martínez-Carreras, Núria; Pérez-Gallego, Nuria; Estrany, Joan; Ferrer, Laura

    2015-04-01

    deposited on stream beds, the fine sediments would have an increasing downstream time to receive radionuclide fallout. Results to date showed that Pbx-210 activities of fine bed and suspended sediments were usually below detectable levels or with large uncertainty bounds, confirming that they come mainly from fresh rocks but making difficult the hypotheses testing. A relevant decrease in Pbx-210 activity was observed in suspended sediments during summer 2013, confirming the temporal accumulation of FRN on badland regoliths and the subsequent depletion of FRN-rich horizons, along with a significant connectivity of sediment. Shorter-lived Be-7 activity was detectable only on badland regoliths and suspended sediments, with activities increasing downstream; this cannot be attributed to the accumulation of FRN in old sediments, because of the short life of Be-7. Instead, fine bed sediments might be brought into suspension by raindrop impacts, and most of the FRN content of these raindrops would be flushed with the suspended sediment, in partial conflict with the hypothesis supporting the second index.

  18. Testing fine sediment connectivity hypotheses using fallout radionuclide tracers in a small catchment with badlands. Vallcebre Research Catchments (NE Spain)

    NASA Astrophysics Data System (ADS)

    Gallart, Francesc; Latron, Jérôme; Vuolo, Diego; Martínez-Carreras, Núria; Pérez-Gallego, Nuria; Ferrer, Laura; Estrany, Joan

    2016-04-01

    . Indeed, long residence time of stream bed sediments allowing FRN accumulation is suggested by (i) fine in-stream sediment activities higher than those measured at their sources and (ii) increasing activities downstream. Results showed a more intricate behaviour than expected. Pbx-210 activities of fine bed and suspended sediments were usually below detectable levels or had large uncertainty bounds, confirming that they come mainly from fresh rocks but making difficult the hypotheses testing. Fine sediments on the stream beds had low activities in contradiction with hypothesis 2. Activities of in-stream suspended sediments partly followed hypothesis 1 but they decreased with the increasing capacity of runoff events to mobilise low-activity sediments from the stream bed. Shorter-lived Be-7 activity was detectable only on badland regoliths and suspended sediments, with activities increasing downstream; this cannot be attributed to the accumulation of FRN in old sediments, because of the short life of Be-7. Instead, fine bed sediments might be brought into suspension by raindrop impacts, and most of the FRN content of these raindrops would be flushed with the suspended sediment, impeding its accumulation on bed sediments and disabling hypothesis 2. Overall, several lines of evidence suggest that FRNs were quickly sequestered by the more dynamic sediment particles, preventing its accumulation on coarser sediment particles and surfaces exposed to overland or stream flow.

  19. Tracer-based prediction of thermal reservoir lifetime: scope, limitations, and the role of thermosensitive tracers

    NASA Astrophysics Data System (ADS)

    Ghergut, I.; Behrens, H.; Karmakar, S.; Licha, T.; Nottebohm, M.; Sauter, M.

    2012-04-01

    Thermal-lifetime prediction is a traditional endeavour of inter-well tracer tests conducted in geothermal reservoirs. Early tracer test signals (detectable within the first few years of operation) are expected to correlate with late-time production temperature evolutions ('thermal breakthrough', supposed to not occur before some decades of operation) of a geothermal reservoir. Whenever a geothermal reservoir can be described as a single-fracture system, its thermal lifetime will, ideally, be determined by two parameters (say, fracture aperture and porosity), whose inversion from conservative-tracer test signals is straightforward and non-ambiguous (provided that the tracer tests, and their interpretation, are performed in accordance to the rules of the art). However, as soon as only 'few more' fractures are considered, this clear-cut correlation is broken. A given geothermal reservoir can simultaneously feature a single-fracture behaviour, in terms of heat transport, and a multiple-fracture behaviour, in terms of solute tracer transport (or vice-versa), whose effective values of fracture apertures, spacings, and porosities are essentially uncorrelated between heat and solute tracers. Solute transport parameters derived from conservative-tracer tests will no longer characterize the heat transport processes (and thus temperature evolutions) taking place in the same reservoir. Parameters determining its thermal lifetime will remain 'invisible' to conservative tracers in inter-well tests. We demonstrate this issue at the example of a five-fracture system, representing a deep-geothermal reservoir, with well-doublet placement inducing fluid flow 'obliquely' to the fractures. Thermal breakthrough in this system is found to strongly depend on fracture apertures, whereas conservative-solute tracer signals from inter-well tests in the same system do not show a clear-cut correlation with fracture apertures. Only by using thermosensitive substances as tracers, a reliable

  20. Scaling up from traits to communities to ecosystems across broad climate gradients: Testing Metabolic Scaling Theories predictions for forests

    NASA Astrophysics Data System (ADS)

    Enquist, B. J.; Michaletz, S. T.; Buzzard, V.

    2015-12-01

    Key insights in global ecology will come from mechanistically linking pattern and process across scales. Macrosystems ecology specifically attempts to link ecological processes across spatiotemporal scales. The goal s to link the processing of energy and nutrients from cells all the way ecosystems and to understand how shifting climate influences ecosystem processes. Using new data collected from NSF funded Macrosystems project we report on new findings from forests sites across a broad temperature gradient. Our study sites span tropical, temperate, and high elevation forests we assess several key predictions and assumptions of Metabolic Scaling Theory (MST) as well as several other competing hypotheses for the role of climate, light, and plant traits on influencing forest demography and forest ecosystems. Specifically, we assess the importance of plant size, light limitation, size structure, and various climatic factors on forest growth, demography, and ecosystem functioning. We provide some of the first systematic tests of several key predictions from MST. We show that MST predictions are largely upheld and that new insights from assessing theories predictions yields new observations and findings that help modify and extend MST's predictions and applicability. We discuss how theory is critically needed to further our understanding of how to scale pattern and process in ecology - from traits to ecosystems - in order to develop a more predictive global change biology.

  1. Methodology for Quantitative Rapid Multi-Tracer PET Tumor Characterizations

    PubMed Central

    Kadrmas, Dan J.; Hoffman, John M.

    2013-01-01

    Positron emission tomography (PET) can image a wide variety of functional and physiological parameters in vivo using different radiotracers. As more is learned about the molecular basis for disease and treatment, the potential value of molecular imaging for characterizing and monitoring disease status has increased. Characterizing multiple aspects of tumor physiology by imaging multiple PET tracers in a single patient provides additional complementary information, and there is a significant body of literature supporting the potential value of multi-tracer PET imaging in oncology. However, imaging multiple PET tracers in a single patient presents a number of challenges. A number of techniques are under development for rapidly imaging multiple PET tracers in a single scan, where signal-recovery processing algorithms are employed to recover various imaging endpoints for each tracer. Dynamic imaging is generally used with tracer injections staggered in time, and kinetic constraints are utilized to estimate each tracers' contribution to the multi-tracer imaging signal. This article summarizes past and ongoing work in multi-tracer PET tumor imaging, and then organizes and describes the main algorithmic approaches for achieving multi-tracer PET signal-recovery. While significant advances have been made, the complexity of the approach necessitates protocol design, optimization, and testing for each particular tracer combination and application. Rapid multi-tracer PET techniques have great potential for both research and clinical cancer imaging applications, and continued research in this area is warranted. PMID:24312149

  2. Vertical diffusivities of active and passive tracers

    NASA Astrophysics Data System (ADS)

    Canuto, V. M.; Cheng, Y.; Howard, A. M.

    The climate models that include a carbon-cycle need the vertical diffusivity of a passive tracer. Since an expression for the latter is not available, it has been common practice to identify it with that of salt. The identification is questionable since T, S are active, not passive tracers. We present the first derivation of the diffusivity of a passive tracer in terms of Ri (Richardson number) and R ρ (density ratio, ratio of salinity over temperature z-gradients). The following results have emerged: The passive tracer diffusivity is an algebraic function of Ri, R ρ. In doubly stable regimes (DS, ∂ T/∂z > 0, ∂S/∂ z < 0), the passive scalar diffusivity is nearly the same as that of salt/heat for any values of R ρ < 0 and Ri > 0. In DC regimes (diffusive convection, ∂ T/∂ z < 0, ∂ S/∂ z < 0, R ρ > 1), the passive scalar diffusivity is larger than that of salt. At Ri = O(1), it can be more than twice as large. In SF regimes (salt fingers, ∂ T/∂ z > 0, ∂ S/∂ z > 0, R ρ < 1), the passive scalar diffusivity is smaller than that of salt. At Ri = O(1), it can be less than half of it. The passive tracer diffusivity predicted at the location of NATRE (North Atlantic Tracer Release Experiment) is discussed. Perhaps the most relevant conclusion is that the common identification of the tracer diffusivity with that of salt is valid only in DS regimes. In the Southern Ocean, where there is the largest CO 2 absorption, the dominant regime is diffusive convection discussed in (c) above.

  3. Vertical Diffusivities of Active and Passive Tracers

    NASA Technical Reports Server (NTRS)

    Canuto, V. M.; Cheng, Y.; Howard, A. M.

    2010-01-01

    The climate models that include a carbon-cycle need the vertical diffusivity of a passive tracer. Since an expression for the latter is not available, it has been common practice to identify it with that of salt. The identification is questionable since T, S are active, not passive tracers. We present the first derivation of the diffusivity of a passive tracer in terms of Ri (Richardson number) and Rq (density ratio, ratio of salinity over temperature z-gradients). The following results have emerged: (a) The passive tracer diffusivity is an algebraic function of Ri, Rq. (b) In doubly stable regimes (DS, partial derivative of T with respect to z > 0, partial derivative of S with respect to z < 0), the passive scalar diffusivity is nearly the same as that of salt/heat for any values of Rq < 0 and Ri > 0. (c) In DC regimes (diffusive convection, partial derivative of T with respect to z < 0, partial derivative of S with respect to z < 0, Rq > 1), the passive scalar diffusivity is larger than that of salt. At Ri = O(1), it can be more than twice as large. (d) In SF regimes (salt fingers, partial derivative of T with respect to z > 0, partial derivative of S with respect to z > 0, Rq < 1), the passive scalar diffusivity is smaller than that of salt. At Ri = O(1), it can be less than half of it. (e) The passive tracer diffusivity predicted at the location of NATRE (North Atlantic Tracer Release Experiment) is discussed. (f) Perhaps the most relevant conclusion is that the common identification of the tracer diffusivity with that of salt is valid only in DS regimes. In the Southern Ocean, where there is the largest CO2 absorption, the dominant regime is diffusive convection discussed in (c) above.

  4. Analysis of colloid and tracer breakthrough curves

    NASA Astrophysics Data System (ADS)

    Grindrod, Peter; Edwards, Mark S.; Higgo, Jenny J. W.; Williams, Geoffrey M.

    1996-02-01

    We consider the dispersion and elution of colloids and dissolved nonsorbing tracers within saturated heterogeneous porous media. Since flow path geometry in natural systems is often ill-characterized macroscopic (mean) flow rates and dispersion tensors are utilized in order to account for the sub-model scale microscopic fluctuations in media structure (and the consequent hydrodynamic profile). Even for tracer migration and dispersal this issue is far from settled. Here we consider how colloid and tracer migration phenomena can be treated consistently. Theoretical calculations for model flow geometries yield two quantitative predictions for the transport of free (not yet captured) colloids with reference to a non-sorbing dissolved tracer within the same medium: the average migration velocity of the free colloids is higher than that of the tracer; and that the ratio of the equivalent hydrodynamic dispersion rates of colloids and tracer is dependent only upon properties of the colloids and the porous medium, it is independent of pathlengths and fluid flux, once length scales are large enough. The first of these is well known, since even in simple flow paths free colloids must stay more centre stream. The second, if validated suggests how solute and colloid dispersion may be dealt with consistently in macroscopic migration models. This is crucial since dispersion is usually ill-characterized and unaddressed by the experimental literature. In this paper we present evidence based upon an existing Drigg field injection test for the validity of these predictions. We show that starting from experimental data the fitted dispersion rates of both colloids and non-sorbing tracers increase with the measured elution rates (obeying slightly different rules for tracers and colloids); and that the ratio of colloid and nonsorbing tracer elution rates, and the ratio of colloid and nonsorbing tracer dispersion rates may be dependent upon properties of the colloids and the medium (not

  5. Experimental design for estimating parameters of rate-limited mass transfer: Analysis of stream tracer studies

    USGS Publications Warehouse

    Wagner, B.J.; Harvey, J.W.

    1997-01-01

    Tracer experiments are valuable tools for analyzing the transport characteristics of streams and their interactions with shallow groundwater. The focus of this work is the design of tracer studies in high-gradient stream systems subject to advection, dispersion, groundwater inflow, and exchange between the active channel and zones in surface or subsurface water where flow is stagnant or slow moving. We present a methodology for (1) evaluating and comparing alternative stream tracer experiment designs and (2) identifying those combinations of stream transport properties that pose limitations to parameter estimation and therefore a challenge to tracer test design. The methodology uses the concept of global parameter uncertainty analysis, which couples solute transport simulation with parameter uncertainty analysis in a Monte Carlo framework. Two general conclusions resulted from this work. First, the solute injection and sampling strategy has an important effect on the reliability of transport parameter estimates. We found that constant injection with sampling through concentration rise, plateau, and fall provided considerably more reliable parameter estimates than a pulse injection across the spectrum of transport scenarios likely encountered in high-gradient streams. Second, for a given tracer test design, the uncertainties in mass transfer and storage-zone parameter estimates are strongly dependent on the experimental Damkohler number, DaI, which is a dimensionless combination of the rates of exchange between the stream and storage zones, the stream-water velocity, and the stream reach length of the experiment. Parameter uncertainties are lowest at DaI values on the order of 1.0. When DaI values are much less than 1.0 (owing to high velocity, long exchange timescale, and/or short reach length), parameter uncertainties are high because only a small amount of tracer interacts with storage zones in the reach. For the opposite conditions (DaI >> 1.0), solute exchange

  6. Tracer attenuation in groundwater

    NASA Astrophysics Data System (ADS)

    Cvetkovic, Vladimir

    2011-12-01

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

  7. Effect of different transport observations on inverse modeling results: case study of a long-term groundwater tracer test monitored at high resolution

    PubMed Central

    Rasa, Ehsan; Foglia, Laura; Mackay, Douglas M.; Scow, Kate M.

    2014-01-01

    Conservative tracer experiments can provide information useful for characterizing various subsurface transport properties. This study examines the effectiveness of three different types of transport observations for sensitivity analysis and parameter estimation of a three-dimensional site-specific groundwater flow and transport model: conservative tracer breakthrough curves (BTCs), first temporal moments of BTCs (m1), and tracer cumulative mass discharge (Md) through control planes combined with hydraulic head observations (h). High-resolution data obtained from a 410-day controlled field experiment at Vandenberg Air Force Base, California (USA), have been used. In this experiment, bromide was injected to create two adjacent plumes monitored at six different transects (perpendicular to groundwater flow) with a total of 162 monitoring wells. A total of 133 different observations of transient hydraulic head, 1,158 of BTC concentration, 23 of first moment, and 36 of mass discharge were used for sensitivity analysis and parameter estimation of nine flow and transport parameters. The importance of each group of transport observations in estimating these parameters was evaluated using sensitivity analysis, and five out of nine parameters were calibrated against these data. Results showed the advantages of using temporal moment of conservative tracer BTCs and mass discharge as observations for inverse modeling. PMID:24672283

  8. ANALYSIS OF ESTUARINE TRACER-GAS TRANSPORT AND DESORPTION.

    USGS Publications Warehouse

    Bales, Jerad D.; Holley, Edward R.

    1987-01-01

    The riverine tracer-gas technique provides a direct, reach-averaged measure of gas exchange, is fairly simple to implement, and is widely accepted for determining reaeration-rate coefficients in rivers. The method, however, is not directly applicable to flows having vertical density gradients. Consequently, studies were undertaken to develop and evaluate methods for obtaining surface-exchange coefficients from estuarine tracer-gas data. Reasonable estimates of the desorption coefficient (within 50 percent of the correct value) were obtained when an analytical solution of the transport equation was compared with data from a numerically simulated continuous release of tracer gas.

  9. Testing Cort-Fitness and Cort-Adaptation hypotheses in a habitat suitability gradient for roe deer

    NASA Astrophysics Data System (ADS)

    Escribano-Avila, Gema; Pettorelli, Nathalie; Virgós, Emilio; Lara-Romero, Carlos; Lozano, Jorge; Barja, Isabel; Cuadra, Felipe S.; Puerta, Marisa

    2013-11-01

    According to the Cort-Fitness Hypothesis, higher stress levels (glucocorticoids) in vertebrates are correlated to lower fitness. However, recent studies have failed to validate this hypothesis. A proposed wider framework suggests that reproduction can be perceived as an overload adds up to other environmental challenges that individuals must adjust to. In this case, elevated glucocorticoids could help individuals to allocate resources to reproduction without comprising other functions, leading to the expectation of a positive cort-fitness relationship. This has been proposed as the Cort-Adaptation Hypothesis. Stress levels result from a complex interaction between the environment and the neuroendocrine system of animals. Accounting for physiological functions involved in how animals cope with their environment would help to clarify the relationship between glucocorticoids and animal performance. We used roe deer (Capreolus capreolus) inhabiting diverse habitats in the Iberian Peninsula to: i) test the Cort-Fitness and Cort-Adaptation hypotheses by indexing fitness using a comprehensive physiological approach which takes into account fundamental physiological functions and their trade-offs; and ii) evaluate the link between primary productivity and individuals' condition in a seasonal environment. We evaluated spatial and temporal variation in stress levels, reproductive hormone levels, nutritional status and immune function from fecal samples collected in 2010. Lower stress levels were related to better condition in non-reproductive seasons but not to higher primary productivity. In contrast, stress levels were always positively related to reproductive condition, which was better in most productive habitats. Summer and winter were the less productive seasons and the more challenging for the species in the habitat gradient studied. In winter, reproductive condition traded off against immune function being biased toward immune function in less productive habitats. In

  10. Perfluorocarbon tracer technology

    SciTech Connect

    Dietz, R.N.

    1986-01-01

    Perfluorocarbon tracer technology developments at Brookhaven is described, including the latest identified as well as available PFTs and air sampling and analysis tools, to demonstrate their utility in a number of different atmospheric tracer experiments as well as in other applications, and to provide food-for-thought on new ways in which the PFTs can be applied in other research objectives. All of the important tools are described, but emphasis is given to the latest developments in the technology.

  11. Is fully coupled hydrogeophysical inversion really better than uncoupled? A comparison study using ensemble Kalman filter assimilation of ERT-monitored tracer test data. (Invited)

    NASA Astrophysics Data System (ADS)

    Camporese, M.; Cassiani, G.; Deiana, R.; Salandin, P.; Binley, A. M.

    2013-12-01

    Recent advances in geophysical methods have been increasingly exploited as inverse modeling tools in groundwater hydrology. In particular, several attempts to constrain the hydrogeophysical inverse problem to reduce inversion error have been made using time-lapse geophysical measurements through both coupled and uncoupled inversion approaches. On one hand, the main advantage of coupled approaches is that the numerical models for the geophysical and hydrological processes are linked together such that the geophysical data are inverted directly for the hydrological properties of interest, avoiding artifacts related to the classical geophysical inversions. On the other hand, uncoupled approaches, relying upon a geophysical inversion that is carried out before estimating the hydrological variable of interest, could reveal something about the process that is not accounted for in a model, i.e., they are not constrained by the conceptualization of the hydrological model. In spite of the appeal and popularity of fully coupled inversion approaches, their superiority over more traditional uncoupled methods still needs to be objectively proven; the aim of this work is to shed some light on this debate. An approach based on the Lagrangian formulation of transport and the ensemble Kalman filter (EnKF) is here applied to assess the spatial distribution of hydraulic conductivity (K) by assimilating time-lapse cross-hole electrical resistivity tomography (ERT) data generated for a synthetic tracer test in a heterogeneous aquifer. In the coupled version of the proposed inverse modeling approach, the K distribution is retrieved by assimilating raw ERT resistance data without the need for a preliminary geoelectrical inversion. In the uncoupled version, K is estimated by assimilating electrical conductivity data derived from a previously performed classical geophysical inversion of the same resistance dataset. We compare the performance of the two approaches in a number of simulation

  12. Geophysical monitoring of solute transport in dual-domain environments through laboratory experiments, field-scale solute tracer tests, and numerical simulation

    NASA Astrophysics Data System (ADS)

    Swanson, Ryan David

    The advection-dispersion equation (ADE) fails to describe non-Fickian solute transport breakthrough curves (BTCs) in saturated porous media in both laboratory and field experiments, necessitating the use of other models. The dual-domain mass transfer (DDMT) model partitions the total porosity into mobile and less-mobile domains with an exchange of mass between the two domains, and this model can reproduce better fits to BTCs in many systems than ADE-based models. However, direct experimental estimation of DDMT model parameters remains elusive and model parameters are often calculated a posteriori by an optimization procedure. Here, we investigate the use of geophysical tools (direct-current resistivity, nuclear magnetic resonance, and complex conductivity) to estimate these model parameters directly. We use two different samples of the zeolite clinoptilolite, a material shown to demonstrate solute mass transfer due to a significant internal porosity, and provide the first evidence that direct-current electrical methods can track solute movement into and out of a less-mobile pore space in controlled laboratory experiments. We quantify the effects of assuming single-rate DDMT for multirate mass transfer systems. We analyze pore structures using material characterization methods (mercury porosimetry, scanning electron microscopy, and X-ray computer tomography), and compare these observations to geophysical measurements. Nuclear magnetic resonance in conjunction with direct-current resistivity measurements can constrain mobile and less-mobile porosities, but complex conductivity may have little value in relation to mass transfer despite the hypothesis that mass transfer and complex conductivity lengths scales are related. Finally, we conduct a geoelectrical monitored tracer test at the Macrodispersion Experiment (MADE) site in Columbus, MS. We relate hydraulic and electrical conductivity measurements to generate a 3D hydraulic conductivity field, and compare to

  13. Technical and theoretical considerations about gradient perfusion culture for epithelia used in tissue engineering, biomaterial testing and pharmaceutical research.

    PubMed

    Minuth, Will W; Strehl, Raimund

    2007-06-01

    Epithelia act as biological barriers, which are exposed to different environments at the luminal and basal sides. To simulate this situation and to improve functional features an in vitro gradient perfusion culture technique was developed in our laboratory. This innovative technique appears to be simple at first sight, but the performance needs practical and theoretical knowledge. To harvest intact epithelia after a long-term gradient culture period of many days, leakage, edge damage and pressure differences in the system have to be avoided so that the epithelial barrier function is maintained continuously. Unexpectedly, one of the major obstacles are micro-injuries in the epithelia caused by gas bubbles, which arise during transportation of the medium or due to respiration of the cultured tissue. Gas bubbles randomly accumulate either at the luminal or basal fluid flow of the gradient perfusion culture container. This phenomenon results in fluid pressure differences between the luminal and basal perfusion compartments of the gradient container, which in turn leads to damage of the barrier function. Consequently, the content of gas bubbles in the transported culture medium has to be minimized. Thus, our technical concept is the reduction of gas bubbles while keeping the content of oxygen constant. To follow this strategy we developed a new type of screw cap for media bottles specifically designed to allow fluid contact only with tube and not with cap material. Furthermore, a gas expander module separates gas bubbles from the liquid phase during transportation of the medium. Finally, a new type of gradient culture container allows a permanent elimination of transported gas bubbles. Application of this innovative equipment optimizes the parallel transportation of fluid in the luminal and basal compartments of a gradient culture container. PMID:18458434

  14. PROOF OF CONCEPT TEST OF A UNIQUE GASEOUS PERFLUROCARBON TRACER SYSTEM FOR VERIFICATION AND LONG TERM MONITORING OF CAPS AND COVER SYSTEMS CONDUCTED AT THE SAVANNAH RIVER SITE BENTONITE MAT TEST FACILITY.

    SciTech Connect

    HEISER,J.; SULLIVAN,T.; SERRATO,M.

    2002-02-24

    Engineered covers have been placed on top of buried/subsurface wastes to minimize water infiltration and therefore, release of hazardous contaminants. In order for the cover to protect the environment it must remain free of holes and breaches throughout its service life. Covers are subject to subsidence, erosion, animal intrusion, plant root infiltration, etc., all of which will affect the overall performance of the cover. The U.S. Department of Energy Environmental Management (DOE-EM) Program 2006 Accelerated Cleanup Plan is pushing for rapid closure of many of the DOE facilities. This will require a great number of new cover systems. Some of these new covers are expected to maintain their performance for periods of up to 1000 years. Long-term stewardship will require monitoring/verification of cover performance over the course of the designed lifetime. In addition, many existing covers are approaching the end of their design life and will need validation of current performance (if continued use is desired) or replacement (if degraded). The need for a reliable method of verification and long-term monitoring is readily apparent. Currently, failure is detected through monitoring wells downstream of the waste site. This is too late as the contaminants have already left the disposal area. The proposed approach is the use of gaseous Perfluorocarbon tracers (PFT) to verify and monitor cover performance. It is believed that PFTs will provide a technology that can verify a cover meets all performance objectives upon installation, be capable of predicting changes in cover performance and failure (defined as contaminants leaving the site) before it happens, and be cost-effective in supporting stewardship needs. The PFTs are injected beneath the cover and air samples taken above (either air samples or soil gas samples) at the top of the cover. The location, concentrations, and time of arrival of the tracer(s) provide a direct measure of cover performance. PFT technology can

  15. Geologic flow characterization using tracer techniques

    SciTech Connect

    Klett, R. D.; Tyner, C. E.; Hertel, Jr., E. S.

    1981-04-01

    A new tracer flow-test system has been developed for in situ characterization of geologic formations. This report describes two sets of test equipment: one portable and one for testing in deep formations. Equations are derived for in situ detector calibration, raw data reduction, and flow logging. Data analysis techniques are presented for computing porosity and permeability in unconfined isotropic media, and porosity, permeability and fracture characteristics in media with confined or unconfined two-dimensional flow. The effects of tracer pulse spreading due to divergence, dispersion, and porous formations are also included.

  16. TREATMENT OF COMBINED SEWER OVERFLOWS BY HIGH GRADIENT MAGNETIC SEPARATION. ON-SITE TESTING WITH MOBILE PILOT PLANT TRAILER

    EPA Science Inventory

    Seeded water treatment using a SALA high gradient magnetic separator pilot plant system was conducted on combined sewer overflows and raw sewage at SALA Magnetics in Cambridge, MA and at on-site locations in the Boston area. Special emphasis was placed on specific design and oper...

  17. A CO2 concentration gradient facility for testing CO2 enrichment and soil effects on grassland ecosystem function

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Continuing increases in atmospheric CO2 concentrations mandate techniques for examining impacts on terrestrial ecosystems. Most experiments examine only two or a few levels of CO2 concentration and a single soil type, but if CO2 can be varied as a gradient from subambient to superambient concentra...

  18. Tracer Partitioning in Two-Phase Flow

    NASA Astrophysics Data System (ADS)

    Sathaye, K.; Hesse, M. A.

    2012-12-01

    The concentration distributions of geochemical tracers in a subsurface reservoir can be used as an indication of the reservoir flow paths and constituent fluid origin. In this case, we are motivated by the origin of marked geochemical gradients in the Bravo Dome natural CO2 reservoir in northeastern New Mexico. This reservoir contains 99% CO2 with various trace noble gas components and overlies the formation brine in a sloping aquifer. It is thought that magmatic CO2 entered the reservoir, and displaced the brine. This displacement created gradients in the concentrations of the noble gases. Two models to explain noble gas partitioning in two-phase flow are presented here. The first model assumes that the noble gases act as tracers and uses a first order non-linear partial differential equation to compute the volume fraction of each phase along the displament path. A one-way coupled partial differential equation determines the tracer concentration, which has no effect on the overall flow or phase saturations. The second model treats each noble gas as a regular component resulting in a three-component, two-phase system. As the noble gas injection concentration goes to zero, we see the three-component system behave like the one-way coupled system of the first model. Both the analytical and numerical solutions are presented for these models. For the process of a gas displacing a liquid, we see that a noble gas tracer with greater preference for the gas phase, such as Helium, will move more quickly along the flowpath than a heavier tracer that will more easily enter the liquid phase, such as Argon. When we include partial miscibility of both the major and trace components, these differences in speed are shown in a bank of the tracer at the saturation front. In the three component model, the noble gas bank has finite width and concentration. In the limit where the noble gas is treated as a tracer, the width of the bank is zero and the concentration increases linearly

  19. Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air Injection Testing and Tracer Testing in the Northern Ghost Dance Fault, YUCCA Mountain, Nevada, November 1996 to August 1998

    SciTech Connect

    Lecain, G.D.; Anna, L.O.; Fahy, M.F.

    1998-08-01

    Geothermal logging, air and core-water chemistry sampling, air-injection testing, and tracer testing were done in the northern Ghost Dance Fault at Yucca Mountain, Nevada, from November 1996 to August 1998. The study was done by the U.S. Geological Survey, in cooperation with the U.S. Department of Energy. The fault-testing drill room and test boreholes were located in the crystal-poor, middle nonlithophysal zone of the Topopah Spring Tuff, a tuff deposit of Miocene age. The drill room is located off the Yucca Mountain underground Exploratory Studies Facility at about 230 meters below ground surface. Borehole geothermal logging identified a temperature decrease of 0.1 degree Celsius near the Ghost Dance Fault. The temperature decrease could indicate movement of cooler air or water, or both, down the fault, or it may be due to drilling-induced evaporative or adiabatic cooling. In-situ pneumatic pressure monitoring indicated that barometric pressure changes were transmitted from the ground surface to depth through the Ghost Dance Fault. Values of carbon dioxide and delta carbon-13 from gas samples indicated that air from the underground drill room had penetrated the tuff, supporting the concept of a well-developed fracture system. Uncorrected carbon-14-age estimates from gas samples ranged from 2,400 to 4,500 years. Tritium levels in borehole core water indicated that the fault may have been a conduit for the transport of water from the ground surface to depth during the last 100 years.

  20. B-10 enriched boric acid, bromide, and heat as tracers of recycled groundwater flow near managed aquifer recharge operations

    NASA Astrophysics Data System (ADS)

    Clark, J. F.; Becker, T.; Johnson, T. A.

    2013-12-01

    Recycling wastewater for potable and nonpotable use by artificially recharging aquifers is a decades-old but increasingly popular practice. Natural attenuation processes in the subsurface, known as soil aquifer treatment (SAT), purify recycled water during recharge and subsequent groundwater flow. Travel time criteria are often used to regulate managed aquifer recharge (MAR) operations. California state draft regulations currently gives preference to groundwater tracers to quantify underground residence time, with a target retention time of >6 months from infiltration to drinking water extraction for surface spreading projects using tertiary treated wastewater (less time may be possible if full advanced treated water is utilized). In the past sulfur hexafluoride, a very strong greenhouse gas, has been the principle deliberate tracer for this work. However, its emission has recently become regulated in California and new tracers are needed. Here, two prospective tracers are evaluated: boron-10 (B-10), the least abundant boron isotope, and heat (with recharging water naturally warmed at the sewage treatment plants and in surface-spreading basins). An additional deliberate tracer, bromide (Br), which is a well-studied conservative tracer, was released as a control. Tracer injection occurred at the San Gabriel Spreading Grounds research test basin in Los Angeles County, CA, USA. The basin was constructed and characterized by the US Geological Survey in the mid-1990s. Recycled wastewater was piped directly to this basin at a known rate (about 1.5 m3/day). Down gradient from the test basin are nine high quality monitoring wells in a line that extends from the center of the basin to 150 m down gradient. All of the wells were equipped with temperature loggers that recorded groundwater temperatures every hour with an accuracy of one thousandth of a degree. The pre-experiment expected arrival times ranged from less than one day to six months. Arrival of Br was always

  1. A Stochastic Non-Gaussian Velocity Model for Tracer Dispersion in Heterogeneous Porous Media

    NASA Astrophysics Data System (ADS)

    Meyer, D. W.; Tchelepi, H. A.

    2009-12-01

    Dispersion, Lévy Motion, and the MADE Tracer Tests." Transport in Porous Media 42(1): 211-240. [4] Berkowitz, B., A. Cortis, et al. (2006). "Modeling non-Fickian transport in geological formations as a continuous time random walk." Reviews of Geophysics 44(2). [5] Freyberg, D. L. (1986). "A Natural Gradient Experiment on Solute Transport in a Sand Aquifer. 2. Spatial Moments and the Advection and Dispersion of Nonreactive Tracers." Water Resources Research 22(13): 2031-2046. [6] Silliman, S. E. and E. S. Simpson (1987). "Laboratory Evidence of the Scale Effect in Dispersion of Solutes in Porous-Media." Water Resources Research 23(8): 1667-1673.

  2. Biomarker Pigment Divinyl Chlorophyll a as a Tracer of Water Masses?

    NASA Technical Reports Server (NTRS)

    Mejdandzic, Maja; Mihanovic, Hrvoje; Silovic, Tina; Henderiks, Jorijntje; Supraha, Luka; Polovic, Dorotea; Bosak, Suncica; Bosnjak, Ivana; Cetinic, Ivona; Olujic, Goran; Ljubesic, Zrinka

    2015-01-01

    The ecological preferences of different Phytoplankton types drive their temporal and spatial distributions, reflecting their dependence on certain temperature ranges, light levels, nutrient availability and other environmental gradients. Hence, some phytoplankton taxa can be used as water mass tracers (biotracers).

  3. Selection of Actinide Chemical Analogues for WIPP Tests: Potential Nonradioactive Sorbing and Nonsorbing Tracers for Study of Ion Transport in the Environment

    SciTech Connect

    Dale Spall; Robert Villarreal

    1998-08-01

    Chemical characteristics of the actinides (Th, U, Np, Pu, Am) have been studied relative to nonradioactive chemical elements that have similar characteristics in an attempt to identify a group of actinide chemical analogues that are nonradioactive. In general, the chemistries of the actinides, especially U, Np, Pu, and Am, are very complex and attempts to identify a single chemical analogue for each oxidation state were not successful. However, the rationale for selecting a group of chemical analogues that would mimic the actinides as a group is provided. The categorization of possible chemical analogues (tracers) with similar chemical properties was based on the following criteria. Categorization was studied according.

  4. Tracers of Past Ocean Circulation

    NASA Astrophysics Data System (ADS)

    Lynch-Stieglitz, J.

    2003-12-01

    , tracers capable of giving information on deep-water flow rate, rather than nutrient content alone, were needed. Differences between surface water (measured on planktonic foraminifera) and deep-water (measured on coexisting benthic foraminifera) radiocarbon concentrations provided the first rate constraint (Broecker et al., 1988; Shackleton et al., 1988). Reduced amounts of protactinium relative to the more particle-reactive thorium in the glacial Atlantic suggested that deep water was exported from the Atlantic during glacial times ( Yu et al., 1996). More recently, density gradients in upper waters have been used to infer changes in the upper ocean return flow that compensates the deep-water export ( Lynch-Stieglitz et al., 1999b).Many of these tracers of paleo-ocean flow have been applied to all of the ocean basins, and have been extended in time throughout the Neogene. Despite this progress, a consistent picture of the circulation of the ocean during even the last ice age has yet to emerge. While circulation tracers suggest a rearrangement of water masses in the Atlantic, there is still considerable disagreement about the water masses and circulation in the rest of the World Ocean. Some of this arises from still insufficient data coverage, but some is the result of conflicting information from the various deep circulation tracers. In this chapter, we examine in more detail the methods used to reconstruct past ocean circulation, which will illuminate the source of some of this conflicting information.

  5. Testing the Stress-Gradient Hypothesis at the Roof of the World: Effects of the Cushion Plant Thylacospermum caespitosum on Species Assemblages

    PubMed Central

    Dvorský, Miroslav; Doležal, Jiří; Kopecký, Martin; Chlumská, Zuzana; Janatková, Kateřina; Altman, Jan; de Bello, Francesco; Řeháková, Klára

    2013-01-01

    Many cushion plants ameliorate the harsh environment they inhabit in alpine ecosystems and act as nurse plants, with significantly more species growing within their canopy than outside. These facilitative interactions seem to increase with the abiotic stress, thus supporting the stress-gradient hypothesis. We tested this prediction by exploring the association pattern of vascular plants with the dominant cushion plant Thylacospermum caespitosum (Caryophyllaceae) in the arid Trans-Himalaya, where vascular plants occur at one of the highest worldwide elevational limits. We compared plant composition between 1112 pair-plots placed both inside cushions and in surrounding open areas, in communities from cold steppes to subnival zones along two elevational gradients (East Karakoram: 4850–5250 m and Little Tibet: 5350–5850 m). We used PERMANOVA to assess differences in species composition, Friedman-based permutation tests to determine individual species habitat preferences, species-area curves to assess whether interactions are size-dependent and competitive intensity and importance indices to evaluate plant-plant interactions. No indications for net facilitation were found along the elevation gradients. The open areas were not only richer in species, but not a single species preferred to grow exclusively inside cushions, while 39–60% of 56 species detected had a significant preference for the habitat outside cushions. Across the entire elevation range of T. caespitosum, the number and abundance of species were greater outside cushions, suggesting that competitive rather than facilitative interactions prevail. This was supported by lower soil nutrient contents inside cushions, indicating a resource preemption, and little thermal amelioration at the extreme end of the elevational gradient. We attribute the negative associations to competition for limited resources, a strong environmental filter in arid high-mountain environment selecting the stress-tolerant species

  6. Testing the stress-gradient hypothesis at the roof of the world: effects of the cushion plant Thylacospermum caespitosum on species assemblages.

    PubMed

    Dvorský, Miroslav; Doležal, Jiří; Kopecký, Martin; Chlumská, Zuzana; Janatková, Kateřina; Altman, Jan; de Bello, Francesco; Řeháková, Klára

    2013-01-01

    Many cushion plants ameliorate the harsh environment they inhabit in alpine ecosystems and act as nurse plants, with significantly more species growing within their canopy than outside. These facilitative interactions seem to increase with the abiotic stress, thus supporting the stress-gradient hypothesis. We tested this prediction by exploring the association pattern of vascular plants with the dominant cushion plant Thylacospermum caespitosum (Caryophyllaceae) in the arid Trans-Himalaya, where vascular plants occur at one of the highest worldwide elevational limits. We compared plant composition between 1112 pair-plots placed both inside cushions and in surrounding open areas, in communities from cold steppes to subnival zones along two elevational gradients (East Karakoram: 4850-5250 m and Little Tibet: 5350-5850 m). We used PERMANOVA to assess differences in species composition, Friedman-based permutation tests to determine individual species habitat preferences, species-area curves to assess whether interactions are size-dependent and competitive intensity and importance indices to evaluate plant-plant interactions. No indications for net facilitation were found along the elevation gradients. The open areas were not only richer in species, but not a single species preferred to grow exclusively inside cushions, while 39-60% of 56 species detected had a significant preference for the habitat outside cushions. Across the entire elevation range of T. caespitosum, the number and abundance of species were greater outside cushions, suggesting that competitive rather than facilitative interactions prevail. This was supported by lower soil nutrient contents inside cushions, indicating a resource preemption, and little thermal amelioration at the extreme end of the elevational gradient. We attribute the negative associations to competition for limited resources, a strong environmental filter in arid high-mountain environment selecting the stress-tolerant species that do

  7. Gradient Driven Fluctuations

    NASA Technical Reports Server (NTRS)

    Cannell, David

    2005-01-01

    We have worked with our collaborators at the University of Milan (Professor Marzio Giglio and his group-supported by ASI) to define the science required to measure gradient driven fluctuations in the microgravity environment. Such a study would provide an accurate test of the extent to which the theory of fluctuating hydrodynamics can be used to predict the properties of fluids maintained in a stressed, non-equilibrium state. As mentioned above, the results should also provide direct visual insight into the behavior of a variety of fluid systems containing gradients or interfaces, when placed in the microgravity environment. With support from the current grant, we have identified three key systems for detailed investigation. These three systems are: 1) A single-component fluid to be studied in the presence of a temperature gradient; 2) A mixture of two organic liquids to be studied both in the presence of a temperature gradient, which induces a steady-state concentration gradient, and with the temperature gradient removed, but while the concentration gradient is dying by means of diffusion; 3) Various pairs of liquids undergoing free diffusion, including a proteidbuffer solution and pairs of mixtures having different concentrations, to allow us to vary the differences in fluid properties in a controlled manner.

  8. Fractal tracer distributions in turbulent field theories

    NASA Astrophysics Data System (ADS)

    Hansen, Jonas Lundbek; Bohr, Tomas

    1998-07-01

    We study the motion of passive tracers in a two-dimensional turbulent velocity field generated by the Kuramoto-Sivashinsky equation. By varying the direction of the velocity-vector with respect to the field-gradient we can continuously vary the two Lyapunov exponents for the particle motion and thereby find a regime in which the particle distribution is a strange attractor. We compare the Lyapunov dimension to the information dimension of actual particle distributions and show that there is good agreement with the Kaplan-Yorke conjecture. Similar phenomena have been observed experimentally.

  9. Geoelectrical and colour tracer monitoring with direct push observation wells

    NASA Astrophysics Data System (ADS)

    Dietrich, P.; Dietze, M.; Hoffmann, R.

    2003-04-01

    Borehole - borehole tracer tests are a hydrogeological method to characterize groundwater flow parameters. Breakthrough curves of colour tracers, injected in one borehole and measured in one or more observation wells downstream of the first, give exact but locally very limited information about groundwater flow direction and velocity. At heterogeneous subsurface conditions a large number of investigation wells and frequent sample drawing is necessary to assure recovery of the tracer, which makes the experiments very expensive. Yet, these experiments often fail or do not give sufficient information about the flow regime in the aquifer. Monitoring of salt tracers with geoelectrical methods gives an integral information about flow parameters which in most cases is a more useful information. Especially in deeper aquifers though, it is a problem to place a high number of electrodes close enough to the moving tracer to gain precise results. To assess the mentioned problems we carried out a combined geoelectrical salt and conventional colour tracer test. Our equipment for both tests was placed in direct push boreholes, which are a lot cheaper than groundwater wells, quickly installed and much less invasive. The boreholes were installed at 10 meters distance on a 120 m long profile, to form a control plane 25 meters downstream of the tracer injection. The injection took place in three different groundwater wells at a time, to provide for a good overview of the flow regime along the control plane. We show, how integral information from the geoelectrical tracer tests can be used to design a refined borehole placement for a successful colour tracer test. Our results, quite different from groundwater modelling results, strongly support the necessity to carry out precise field tracer tests for the investigation of groundwater flow parameters.

  10. Radiopharmaceutical Tracers for Neural Progenitor Cells

    SciTech Connect

    Mangner, Thomas J.

    2006-09-29

    The Technical Report summarizes the results of the synthesis and microPET animal scanning of several compounds labeled with positron-emitting isotopes in normal, neonatal and kainic acid treated (seizure induced) rats as potential PET tracers to image the process of neurogenesis using positron emission tomography (PET). The tracers tested were 3'-deoxy-3'-[F-18]fluorothymidine ([F-18]FLT) and 5'-benzoyl-FTL, 1-(2'-deoxy-2'-[F-18]fluoro-B-D-arabinofuranosyl)-5-bromouracil (FBAU) and 3',5'-dibenzoyl-FBAU, N-[F-18]fluoroacetyl-D-glucosamine (FLAG) and tetraacetyl-FLAG, and L-[1-C-11]leucine.

  11. Subsurface barrier integrity verification using perfluorocarbon tracers

    SciTech Connect

    Sullivan, T.M.; Heiser, J.; Milian, L.; Senum, G.

    1996-12-01

    Subsurface barriers are an extremely promising remediation option to many waste management problems. Gas phase tracers include perfluorocarbon tracers (PFT`s) and chlorofluorocarbon tracers (CFC`s). Both have been applied for leak detection in subsurface systems. The focus of this report is to describe the barrier verification tests conducted using PFT`s and analysis of the data from the tests. PFT verification tests have been performed on a simulated waste pit at the Hanford Geotechnical facility and on an actual waste pit at Brookhaven National Laboratory (BNL). The objective of these tests were to demonstrate the proof-of-concept that PFT technology can be used to determine if small breaches form in the barrier and for estimating the effectiveness of the barrier in preventing migration of the gas tracer to the monitoring wells. The subsurface barrier systems created at Hanford and BNL are described. The experimental results and the analysis of the data follow. Based on the findings of this study, conclusions are offered and suggestions for future work are presented.

  12. Tracer for circulation determinations

    SciTech Connect

    Moore, H.; Santos, S.; Wysong, R. D.

    1985-03-19

    An improved tracer particle is described comprising an ion exchange core having a polymer coating thereon, the coated ion exchange core having a reaction site capable of reacting with a compound containing an oxirane group, said coated ion exchange core having been treated with a compound containing an oxirane group to react with said coated ion exchange core causing an increase in mass of the tracer particle. Preferably, the ion exchange core is labelled with a radionuclide. These particles have improved characteristics including improved stability against leaching and improved handling properties. Such particles are useful in circulatory determinations involving the injection of the particles as a suspension in a physiologically acceptable carrier or medium into the circulatory system of animals.

  13. A continuous fast-response dual-tracer analyzer for halogenated atmospheric tracer studies

    SciTech Connect

    Rydock, J.P.; Lamb, B.K.

    1994-10-01

    An apparatus for the simultaneous measurement of two tracers, sulfur hexafluoride (SF6) and a perfluorocarbon compound, is introduced. The new instrument is a modification of a commercially available fast-response, continuous analyzer for single halogenated atmospheric tracer studies. A two-channel flow system was implemented consisting of an alumina cartridge in one channel and a glass beads cartridge of equal flow resistance in the second channel. The alumina passes only sulfur hexafluoride, while the glass beads pass both SF6 and the perfluoroarbon tracer. The SF6 is quantified directly from the electron capture detector (ECD) signal in the alumina channel, and the perfluorocarbon concentration is obtained from the difference of the ECD responses in the two channels. The dual-tracer analyzer is field portable for mobile operations or fixed-location monitoring, has a response time of 1.2 s, and has limits of detection of about 15 pptv for SF6 and 10 pptv for perfluoro-methylcyclohexane, which was the principal perfluorocarbon tracer used in this study. The present instrument configuration, which requires periodic purging of the adsorbent trap, can obtain continuous measurements for a 10-15-min segment in every half hour of operation. Dual-tracer data from a field demonstration test are presented.

  14. Analysis of Particle Transport Using a Particulate Tracer Modeling

    NASA Astrophysics Data System (ADS)

    Wang, P.; Linker, L. C.; Lung, W.; Batiuk, R. A.

    2002-05-01

    Understanding the transport of dissolved and particulate materials in the Chesapeake Bay estuary is critical to allocating nutrient and sediment load reduction goals to the seven watershed states. A computer simulation of a particulate conservative tracer was conducted to help determine the transport mechanism. Tracers were loaded daily at the fall-line of Potomac River (a middle Bay's tributary). The settling rate is set at 0.1 m/day, with the assumption of neither scour nor re-suspension of tracer from the bed to allow continuous accumulation of tracers on bed. The low settling rate was used to allow tracer to transport widely in the estuary to provide information on the transport of fine particulates such as dead algae. After the tracers reach the mouth of Potomac River, most of them are further transported into the lower main-stem Bay. Flood tide is the main force for tracers transported north to the upper main-stem Bay and to the upstream of non-source rivers. In the main stem of the Bay, there exist concentration gradients from the Potomac River mouth to the opposite shore (the Maryland and Virginia eastern shore), to the lower Bay, and to the upper Bay. Concentration gradients also exist from the fall-line to the mouth in the source river, and from the mouth to the upstream in non-source rivers. These gradients are usually disturbed across trenches, due to a so-called "trench effect". A trench either deposits more or less tracers than its shallower sides, depending on the trench to be hydrologically landward from the source (i.e., the Potomac fall line) or the sub-source (e.g., the Rappahannock River mouth for the trench in the upstream of Rappahannock River), or hydrologically seaward from the source or the sub-source. Depending on the layer (saline water-rich or fresh water-rich) in which tracers reside and the direction (landward or seaward) along which tracers transport, the transport/deposit of tracer may be favored along trench over its shallower sides

  15. Soil microbial nutrient constraints along a tropical forest elevation gradient: a belowground test of a biogeochemical paradigm

    NASA Astrophysics Data System (ADS)

    Nottingham, A. T.; Turner, B. L.; Whitaker, J.; Ostle, N.; McNamara, N. P.; Bardgett, R. D.; Salinas, N.; Meir, P.

    2015-04-01

    Aboveground primary productivity is widely considered to be limited by phosphorus (P) availability in lowland tropical forests and by nitrogen (N) availability in montane tropical forests. However, the extent to which this paradigm applies to belowground processes remains unresolved. We measured indices of soil microbial nutrient status in lowland, sub-montane and montane tropical forests along a natural gradient spanning 3400 m in elevation in the Peruvian Andes. With increasing elevation there were marked increases in soil concentrations of total N, total P, and readily-extractable P, but a decrease in N mineralization determined by in situ resin bags. Microbial carbon (C) and N increased with increasing elevation, but microbial C:N:P ratios were relatively constant, suggesting homeostasis. The activity of hydrolytic enzymes, which are rich in N, decreased with increasing elevation, while the ratios of enzymes involved in the acquisition of N and P increased with increasing elevation, further indicating a shift in the relative demand for N and P by microbial biomass. We conclude that soil microorganisms shift investment in nutrient acquisition from P to N between lowland and montane tropical forests, suggesting that different nutrients regulate soil microbial metabolism and the soil carbon balance in these ecosystems.

  16. Soil microbial nutrient constraints along a tropical forest elevation gradient: a belowground test of a biogeochemical paradigm

    NASA Astrophysics Data System (ADS)

    Nottingham, A. T.; Turner, B. L.; Whitaker, J.; Ostle, N. J.; McNamara, N. P.; Bardgett, R. D.; Salinas, N.; Meir, P.

    2015-10-01

    Aboveground primary productivity is widely considered to be limited by phosphorus (P) availability in lowland tropical forests and by nitrogen (N) availability in montane tropical forests. However, the extent to which this paradigm applies to belowground processes remains unresolved. We measured indices of soil microbial nutrient status in lowland, sub-montane and montane tropical forests along a natural gradient spanning 3400 m in elevation in the Peruvian Andes. With increasing elevation there were marked increases in soil concentrations of total N, total P, and readily exchangeable P, but a decrease in N mineralization determined by in situ resin bags. Microbial carbon (C) and N increased with increasing elevation, but microbial C : N : P ratios were relatively constant, suggesting homeostasis. The activity of hydrolytic enzymes, which are rich in N, decreased with increasing elevation, while the ratio of enzymes involved in the acquisition of N and P increased with increasing elevation, further indicating an increase in the relative demand for N compared to P with increasing elevation. We conclude that soil microorganisms shift investment in nutrient acquisition from P to N between lowland and montane tropical forests, suggesting that different nutrients regulate soil microbial metabolism and the soil carbon balance in these ecosystems.

  17. Manufacture and Testing of a High Field Gradient Magnetic Fractionation System for Quantitative Detection of Plasmodium falciparum Gametocytes

    NASA Astrophysics Data System (ADS)

    Karl, Stephan; Woodward, Robert C.; Davis, Timothy M. E.; St. Pierre, Tim G.

    2010-12-01

    Plasmodium falciparum is the most dangerous of the human malaria parasite species and accounts for millions of clinical episodes of malaria each year in tropical countries. The pathogenicity of Plasmodium falciparum is a result of its ability to infect erythrocytes where it multiplies asexually over 48 h or develops into sexual forms known as gametocytes. If sufficient male and female gametocytes are taken up by a mosquito vector, it becomes infectious. Therefore, the presence and density of gametocytes in human blood is an important indicator of human-to-mosquito transmission of malaria. Recently, we have shown that high field gradient magnetic fractionation improves gametocyte detection in human blood samples. Here we present two important new developments. Firstly we introduce a quantitative approach to replace the previous qualitative method and, secondly, we describe a novel method that enables cost-effective production of the magnetic fractionation equipment required to carry out gametocyte quantification. We show that our custom-made magnetic fractionation equipment can deliver results with similar sensitivity and convenience but for a small fraction of the cost.

  18. An automated method for producing synoptic regional maps of river gradient variation: Procedure, accuracy tests, and comparison with other knickpoint mapping methods

    NASA Astrophysics Data System (ADS)

    Gonga-Saholiariliva, Nahossio; Gunnell, Yanni; Harbor, David; Mering, Catherine

    2011-11-01

    The study of abrupt changes in longitudinal river profiles, or knickpoints, is currently approached through an empirical power law: the slope-area relationship. Results based on digital elevation model (DEM) analyses and stream extractions are generally intended to determine crustal uplift rates and identify transient landscape conditions. In this article, we present an alternative geomorphometric method for locating knickpoints and knickzones based on local slope gradient and curvature attributes. Intended as a rapid, regional scale, automated knickpoint detection technique, the accuracy of this slope-curvature method is tested on two digital elevation grids, NASA's SRTM (ground resolution of 90 m, resampled here to 75 m) and the ASTER DEM (15 m) in the Sierra Nacimiento (New Mexico, USA), a basement-cored mountain range recently exhumed by waves of headward drainage integration in response to remote tectonic deformation in the adjacent Rio Grande rift. Out of every 10 gradient anomalies detected by the SRTM-derived numeric routine, up to 8 are certifiable knickpoints recognized among a population of georeferenced occurrences surveyed in the field. An independent comparison with the slope-area method provided a further accuracy test, which was particularly useful at sites that could not be validated in the field for practical reasons. Given the low tectonic activity of the study area, the majority of knickpoints was also found to coincide with lithologic boundaries, making it difficult without further geomorphological data to single out dynamic knickpoints directly caused by the upstream propagation of channel instabilities relating to base level change.

  19. Travel-time-based thermal tracer tomography

    NASA Astrophysics Data System (ADS)

    Somogyvári, Márk; Bayer, Peter; Brauchler, Ralf

    2016-05-01

    Active thermal tracer testing is a technique to get information about the flow and transport properties of an aquifer. In this paper we propose an innovative methodology using active thermal tracers in a tomographic setup to reconstruct cross-well hydraulic conductivity profiles. This is facilitated by assuming that the propagation of the injected thermal tracer is mainly controlled by advection. To reduce the effects of density and viscosity changes and thermal diffusion, early-time diagnostics are used and specific travel times of the tracer breakthrough curves are extracted. These travel times are inverted with an eikonal solver using the staggered grid method to reduce constraints from the pre-defined grid geometry and to improve the resolution. Finally, non-reliable pixels are removed from the derived hydraulic conductivity tomograms. The method is applied to successfully reconstruct cross-well profiles as well as a 3-D block of a high-resolution fluvio-aeolian aquifer analog data set. Sensitivity analysis reveals a negligible role of the injection temperature, but more attention has to be drawn to other technical parameters such as the injection rate. This is investigated in more detail through model-based testing using diverse hydraulic and thermal conditions in order to delineate the feasible range of applications for the new tomographic approach.

  20. Irradiance gradients

    SciTech Connect

    Ward, G.J. Ecole Polytechnique Federale, Lausanne ); Heckbert, P.S. . School of Computer Science Technische Hogeschool Delft . Dept. of Technical Mathematics and Informatics)

    1992-04-01

    A new method for improving the accuracy of a diffuse interreflection calculation is introduced in a ray tracing context. The information from a hemispherical sampling of the luminous environment is interpreted in a new way to predict the change in irradiance as a function of position and surface orientation. The additional computation involved is modest and the benefit is substantial. An improved interpolation of irradiance resulting from the gradient calculation produces smoother, more accurate renderings. This result is achieved through better utilization of ray samples rather than additional samples or alternate sampling strategies. Thus, the technique is applicable to a variety of global illumination algorithms that use hemicubes or Monte Carlo sampling techniques.

  1. High gradient superconducting quadrupoles

    SciTech Connect

    Lundy, R.A.; Brown, B.C.; Carson, J.A.; Fisk, H.E.; Hanft, R.H.; Mantsch, P.M.; McInturff, A.D.; Remsbottom, R.H.

    1987-07-01

    Prototype superconducting quadrupoles with a 5 cm aperture and gradient of 16 kG/cm have been built and tested as candidate magnets for the final focus at SLC. The magnets are made from NbTi Tevatron style cable with 10 inner and 14 outer turns per quadrant. Quench performance and multipole data are presented. Design and data for a low current, high gradient quadrupole, similar in cross section but wound with a cable consisting of five insulated conductors are also discussed.

  2. Gradient tabu search.

    PubMed

    Stepanenko, Svetlana; Engels, Bernd

    2007-01-30

    This paper presents a modification of the tabu search called gradient tabu search (GTS). It uses analytical gradients for a fast minimization to the next local minimum and analytical diagonal elements of the Hessian to escape local minima. For an efficient blocking of already visited areas tabu regions and tabu directions are introduced into the tabu list (TL). Trials with various well-known test functions indicate that the GTS is a very promising approach to determine local and global minima of differentiable functions. Possible application areas could be optimization routines for force field parameters or conformational searches for large molecules. PMID:17186482

  3. Testing Associations of Plant Functional Diversity with Carbon and Nitrogen Storage along a Restoration Gradient of Sandy Grassland

    PubMed Central

    Zuo, Xiaoan; Zhou, Xin; Lv, Peng; Zhao, Xueyong; Zhang, Jing; Wang, Shaokun; Yue, Xiyuan

    2016-01-01

    The trait-based approach shows that ecosystem function is strongly affected by plant functional diversity as reflected by the traits of the most abundant species (community-weighted mean, CWM) and functional dispersion (FDis). Effects of CWM and FDis individually support the biomass ratio hypothesis and the niche complementarity hypothesis. However, there is little empirical evidence on the relative roles of CWM traits and FDis in explaining the carbon (C) and nitrogen (N) storage in grassland ecosystems. We measured plant functional traits in the 34 most abundant species across 24 sites along a restoration gradient of sandy grassland (mobile dune, semi-fixed dune, fixed dune, and grassland) in Horqin Sand Land, northern China. Thereafter, we calculated the CWM traits, the functional divergence of each single trait (FDvar) and the trait dispersion of multiple traits (FDis). We also measured the C and N storage in plant, litter, root, and soil. Using a stepwise multiple regression analysis, we further assessed which of the functional diversity components best explained C and N storage in the sandy grassland restoration. We found consistent links between C or N storage and leaf traits related to plant resource use strategy. However, the CWM of plant height was retained as an important predictor of C and N storage in plant, litter, soil, and total ecosystem in the final multiple models. CWMs of specific leaf area and plant height best predicted soil C and N storage and total ecosystem N storage. FDis was one of good predictors of litter C and N storage as well as total ecosystem C storage. These results suggest that ecosystem C and N pools in the sandy grassland restoration are primarily associated with the traits of the most abundant species in communities, thereby supporting the biomass ratio hypothesis. The positive associations of FDis with C storage in litter and total ecosystem provide evidence to support the niche complementarity hypothesis. Both functional

  4. Short-term fluid, heat, and solute transport in deep 'georeservoirs' likely to become 'EGS': some challenges to ICDP hydrogeologists who might like using artificial tracers

    NASA Astrophysics Data System (ADS)

    Ghergut, Julia; Behrens, Horst; Huenges, Ernst; Rose, Peter; Sauter, Martin

    2014-05-01

    During Fall 2013, the Integrated Continental Scientific Drilling Programme (ICDP) set out to define a new Science Plan that shall replace its past-decade version (Harms et al., eds., 2005) for the decade to come. Geoscientists worldwide were welcomed to suggest new imaging and exploration methods, new sites to drill, new challenges to be addressed with a view at new 'societal needs' (Harms and Wiersberg 2013). Save for two outstanding exceptions at the Mutnovsky volcano in Russia and the KTB site in Germany, the use of artificial tracers, especially within forced-gradient tests, has not been on the agenda of most ICDP projects so far (other than for purposes of monitoring microbial contamination in conjunction with drilling activities); deep-reservoir exploration and characterization efforts were restrained to non-fluid-invasive techniques on the one hand, and to sites featuring some unique earth-historical traits, on the other hand. Surely, this was not for lack of interest in quantifying fluid transport in the deep subsurface in general, but mainly due to operational, technical, and financial constraints (lack of resources / lack of opportunity for significant fluid turnover within the target, deep-seated georeservoirs, and fear of persistent, large-scale georeservoir contamination by non-pristine fluids). - This is likely to change during the forthcoming decade(s), owing to worldwide increased interest in some 'georesource' or 'georeservoir' play types (Moeck 2013) that have not been in the ICDP focus so far, including non-volcanogenic geothermal, and allowing for man-made design and intervention into how those 'georesources' or 'georeservoirs' shall work for us. Among the latter, petrothermal systems (Jung 2013, Huenges and Jung 2004) acquire growing recognition as a promising (and maybe unique) option for baseload energy supply in vast areas of the Northern hemisphere, at very low emissions and (in the long run) moderate costs. With petrothermal coming into

  5. Comparison of different undulator schemes with superimposed alternating gradients for the VUV-FEL at the TESLA Test Facility

    SciTech Connect

    Pflueger, J.; Nikitina, Y.M.

    1995-12-31

    For the VUV-FEL at the TESLA Test Facility an undulator with a total length of 30 m is needed. In this study three different approaches to realize an undulator with a sinusoidal plus a superimposed quadrupolar field were studied with the 3D code MAFIA.

  6. TESTING THE FLORISTIC QUALITY ASSESSMENT INDEX AS AN INDICATOR OF WETLAND CONDITION ALONG GRADIENTS OF HUMAN INFLUENCE

    EPA Science Inventory

    Biological indicators of ecosystem integrity are increasingly being sought for use in ecosystem assessment and goal-setting for restoration projects. We tested the effectiveness of a plant community-based bioassessment tool, the floristic quality assessment index (FQAI) in 20 dep...

  7. Tempest: Mesoscale test case suite results and the effect of order-of-accuracy on pressure gradient force errors

    NASA Astrophysics Data System (ADS)

    Guerra, J. E.; Ullrich, P. A.

    2014-12-01

    Tempest is a new non-hydrostatic atmospheric modeling framework that allows for investigation and intercomparison of high-order numerical methods. It is composed of a dynamical core based on a finite-element formulation of arbitrary order operating on cubed-sphere and Cartesian meshes with topography. The underlying technology is briefly discussed, including a novel Hybrid Finite Element Method (HFEM) vertical coordinate coupled with high-order Implicit/Explicit (IMEX) time integration to control vertically propagating sound waves. Here, we show results from a suite of Mesoscale testing cases from the literature that demonstrate the accuracy, performance, and properties of Tempest on regular Cartesian meshes. The test cases include wave propagation behavior, Kelvin-Helmholtz instabilities, and flow interaction with topography. Comparisons are made to existing results highlighting improvements made in resolving atmospheric dynamics in the vertical direction where many existing methods are deficient.

  8. Changes in permeability and fluid chemistry of the Topopah Spring Member of the Paintbrush tuff (Nevada Test Site) when held in a temperature gradient: summary of results

    SciTech Connect

    Moore, D.E.; Morrow, C.A.; Byerlee, J.D.

    1984-06-01

    The permeability and groundwater chemistry results for the Topopah Spring Member are reported and compared with the results from the previous work on Bullfrog. Permeability measurements made on samples of the Topopah Spring Member of the Paintbrush Tuff at room-temperature and in a temperature gradient show that the initially high (3-65 {mu}da) permeabilities are little affected by heating to at least 150{sup 0}C. These permeability relationships are favvorable for the disposal of nuclear waste in this stuff in an unsaturated zone at the Nevada Test Site. The fluids discharged from the samples of tuff during the experiments are dilute, nearly neutral solutions that differ only slightly from the starting groundwater composition. 8 references, 10 figures, 5 tables.

  9. Innovative techniques for the description of reservoir heterogeneity using tracers. Final report, October 1992--December 1993

    SciTech Connect

    Pope, G.A.; Sepehrnoori, K.; Delshad, M.; Ferreira, L.; Gupta, A.; Maroongroge, V.

    1994-11-01

    This is the final report of a three year research project on the use of tracers for reservoir characterization. The objective of this research was to develop advanced, innovative techniques for the description of reservoir characteristics using both single-well backflow and interwell tracer tests. (1) The authors implemented and validated tracer modeling features in a compositional simulator (UTCOMP). (2) They developed and applied a new single well tracer test for estimating reservoir heterogeneity. (3) They developed and applied a new single well tracer test for estimating reservoir wettability in-situ. (4) They developed a new, simple and efficient method to analyze two well tracer tests based upon type curve matching and illustrated its use with actual field tracer data. (5) They developed a new method for deriving an integrated reservoir description based upon combinatorial optimization schemes. (6) They developed a new, interwell tracer test for reservoir heterogeneity called vertical tracer profiling (VTP) and demonstrated its advantages over conventional interwell tracer testing. (7) They developed a simple and easy analytical method to estimate swept pore volume from interwell tracer data and showed both the theoretical basis for this method and its practical utility. (8) They made numerous enhancements to our compositional reservoir simulator such as including the full permeability tensor, adding faster solvers, improving its speed and robustness and making it easier to use (better I/0) for tracer simulation problems. (9) They applied the enhanced version of UTCOMP to the analysis of interwell tracer data using perfluorocarbons at Elks Hill Naval Petroleum Reserve. All of these accomplishments taken together have significantly improved the state of reservoir tracer technology and have demonstrated that it is a far more powerful and useful tool for quantitative reservoir characterization than previously realized or practiced by the industry.

  10. Performance of a high-work, low-aspect-ratio turbine stator tested with a realistic inlet radial temperature gradient

    NASA Technical Reports Server (NTRS)

    Stabe, Roy G.; Schwab, John R.

    1991-01-01

    A 0.767-scale model of a turbine stator designed for the core of a high-bypass-ratio aircraft engine was tested with uniform inlet conditions and with an inlet radial temperature profile simulating engine conditions. The principal measurements were radial and circumferential surveys of stator-exit total temperature, total pressure, and flow angle. The stator-exit flow field was also computed by using a three-dimensional Navier-Stokes solver. Other than temperature, there were no apparent differences in performance due to the inlet conditions. The computed results compared quite well with the experimental results.

  11. Field-scale sulfur hexafluoride tracer experiment to understand long distance gas transport in the deep unsaturated zone

    USGS Publications Warehouse

    Walvoord, Michelle Ann; Andraski, Brian; Green, Christopher T.; Stonestrom, David A.; Striegl, Rob

    2014-01-01

    A natural gradient SF6 tracer experiment provided an unprecedented evaluation of long distance gas transport in the deep unsaturated zone (UZ) under controlled (known) conditions. The field-scale gas tracer test in the 110-m-thick UZ was conducted at the U.S. Geological Survey’s Amargosa Desert Research Site (ADRS) in southwestern Nevada. A history of anomalous (theoretically unexpected) contaminant gas transport observed at the ADRS, next to the first commercial low-level radioactive waste disposal facility in the United States, provided motivation for the SF6 tracer study. Tracer was injected into a deep UZ borehole at depths of 15 and 48 m, and plume migration was observed in a monitoring borehole 9 m away at various depths (0.5–109 m) over the course of 1 yr. Tracer results yielded useful information about gas transport as applicable to the spatial scales of interest for off-site contaminant transport in arid unsaturated zones. Modeling gas diffusion with standard empirical expressions reasonably explained SF6 plume migration, but tended to underpredict peak concentrations for the field-scale experiment given previously determined porosity information. Despite some discrepancies between observations and model results, rapid SF6 gas transport commensurate with previous contaminant migration was not observed. The results provide ancillary support for the concept that apparent anomalies in historic transport behavior at the ADRS are the result of factors other than nonreactive gas transport properties or processes currently in effect in the undisturbed UZ.

  12. Empirical tests of harvest-induced body-size evolution along a geographic gradient in Australian macropods.

    PubMed

    Prowse, Thomas A A; Correll, Rachel A; Johnson, Christopher N; Prideaux, Gavin J; Brook, Barry W

    2015-01-01

    Life-history theory predicts the progressive dwarfing of animal populations that are subjected to chronic mortality stress, but the evolutionary impact of harvesting terrestrial herbivores has seldom been tested. In Australia, marsupials of the genus Macropus (kangaroos and wallabies) are subjected to size-selective commercial harvesting. Mathematical modelling suggests that harvest quotas (c. 10-20% of population estimates annually) could be driving body-size evolution in these species. We tested this hypothesis for three harvested macropod species with continental-scale distributions. To do so, we measured more than 2000 macropod skulls sourced from wildlife collections spanning the last 130 years. We analysed these data using spatial Bayesian models that controlled for the age and sex of specimens as well as environmental drivers and island effects. We found no evidence for the hypothesized decline in body size for any species; rather, models that fit trend terms supported minor body size increases over time. This apparently counterintuitive result is consistent with reduced mortality due to a depauperate predator guild and increased primary productivity of grassland vegetation following European settlement in Australia. Spatial patterns in macropod body size supported the heat dissipation limit and productivity hypotheses proposed to explain geographic body-size variation (i.e. skull size increased with decreasing summer maximum temperature and increasing rainfall, respectively). There is no empirical evidence that size-selective harvesting has driven the evolution of smaller body size in Australian macropods. Bayesian models are appropriate for investigating the long-term impact of human harvesting because they can impute missing data, fit nonlinear growth models and account for non-random spatial sampling inherent in wildlife collections. PMID:25039424

  13. A Wavelet Based Suboptimal Kalman Filter for Assimilation of Stratospheric Chemical Tracer Observations

    NASA Technical Reports Server (NTRS)

    Auger, Ludovic; Tangborn, Andrew; Atlas, Robert (Technical Monitor)

    2002-01-01

    A suboptimal Kalman filter system which evolves error covariances in terms of a truncated set of wavelet coefficients has been developed for the assimilation of chemical tracer observations of CH4. The truncation is carried out in such a way that the resolution of the error covariance, is reduced only in the zonal direction, where gradients are smaller. Assimilation experiments which last 24 days, and used different degrees of truncation were carried out. These reduced the covariance, by 90, 97 and 99 % and the computational cost of covariance propagation by 80, 93 and 96 % respectively. The difference in both error covariance and the tracer field between the truncated and full systems over this period were found to be not growing in the first case, and a growing relatively slowly in the later two cases. The largest errors in the tracer fields were found to occur in regions of largest zonal gradients in the tracer field.

  14. Tracer-dilution method indicates flowrate through compressor

    SciTech Connect

    Lagus, P.L.; Flanagan, B.S. ); Peterson, M.E. ); Clowney, S.L. )

    1991-02-25

    A technique for measuring compressor flowrate through an operating natural-gas centrifugal compressor has been tested and found to have a precisions approaching {plus minus}1.5%. The technique employs constant-flow tracer dilution. Testing demonstrated that use of a critical-flow nozzle to inject a constant, known flow of tracer into a flowing natural-gas stream is feasible. Effects of potential pulsation on a tracer flow measurement appear to be eliminated by this technique. With experimental and operational streamlining, the constant-flow tracer dilution technique is capable of being used to measure the flowrate through operating centrifugal compressors with sufficient precisions and accuracy to allow compressor operating characteristics to be determined. This technique is especially useful in situations in which an orifice-flow measurement cannot be performed because of physical space limits or economic considerations.

  15. Field measurements of tracer gas transport by barometric pumping

    SciTech Connect

    Lagus, P.L.; McKinnis, W.B.; Hearst, J.R.; Burkhard, N.R.; Smith, C.F.

    1994-07-28

    Vertical gas motions induced by barometric pressure variations can carry radioactive gases out of the rubblized region produced by an underground nuclear explosion, through overburden rock, into the atmosphere. To better quantify transit time and amount of transport, field experiments were conducted at two sites on Pahute Mesa, Kapelli and Tierra, where radioactive gases had been earlier detected in surface cracks. At each site, two tracer gases were injected into the rubblized chimney 300-400 m beneath the surface and their arrival was monitored by concentration measurements in gas samples extracted from shallow collection holes. The first ``active`` tracer was driven by a large quantity of injected air; the second ``passive`` tracer was introduced with minimal gas drive to observe the natural transport by barometric pumping. Kapelli was injected in the fall of 1990, followed by Tierra in the fall of 1991. Data was collected at both sites through the summer of 1993. At both sites, no surface arrival of tracer was observed during the active phase of the experiment despite the injection of several million cubic feet of air, suggesting that cavity pressurization is likely to induce horizontal transport along high permeability layers rather than vertical transport to the surface. In contrast, the vertical pressure gradients associated with barometric pumping brought both tracers to the surface in comparable concentrations within three months at Kapelli, whereas 15 months elapsed before surface arrival at Tierra. At Kapelli, a quasisteady pumping regime was established, with tracer concentrations in effluent gases 1000 times smaller than concentrations thought to exist in the chimney. Tracer concentrations observed at Tierra were typically an order of magnitude smaller. Comparisons with theoretical calculations suggest that the gases are traveling through {approximately}1 millimeter vertical fractures spaced 2 to 4 meters apart. 6 refs., 18 figs., 3 tabs.

  16. Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site characterization study. Progress report, July 1, 1995--September 30, 1995

    SciTech Connect

    Stetzenbach, K.; Farnham, I.

    1995-12-01

    Laboratory work on tracers to be used for C-Well tracer tests is complete. Solubilities for fluorinated benzoic acids in J13 water were determined and the stability of these compounds to both degradation and sorption on ground tuff measured in batch and column tests.

  17. Tracer dating and ocean ventilation

    SciTech Connect

    Thiele, G.; Sarmiento, J.L. )

    1990-06-15

    The interpretation of transient tracer observations depends on difficult to obtain information on the evolution in time of the tracer boundary conditions and interior distributions. Recent studies have attempted to circumvent this problem by making use of a derived quantity, age, based on the simultaneous distribution of two complementary tracers, such as tritium and its daughter, helium 3. The age is defined with reference to the surface such that the boundary condition takes on a constant value of zero. The authors use a two-dimensional model to explore the circumstances under which such a combination of conservation equations for two complementary tracers can lead to a cancellation of the time derivative terms. An interesting aspect of this approach is that mixing can serve as a source or sink of tracer based age. The authors define an idealized ventilation age tracer that is conservative with respect to mixing, and they explore how its behavior compares with that of the tracer-based ages over a range of advective and diffusive parameters.

  18. Comparison of different tracers for PIV measurements in EHD airflow

    NASA Astrophysics Data System (ADS)

    Hamdi, M.; Havet, M.; Rouaud, O.; Tarlet, D.

    2014-04-01

    In this study, a proposed method for selecting a tracer for particle imaging velocimetry (PIV) measurement in electrohydrodynamics flows was developed. To begin with, several published studies were identified that exploit different tracers, such as oil smoke, cigarette smoke and titanium dioxide (TiO2). An assortment of tracers was then selected based on comparisons with conventional dimensionless numbers; Stokes number ( St), Archimedes number ( Ar) and electrical mobility ratio ( M). Subsequently, an experimental study for testing tracers was developed, which enabled the velocity profile of an ionic wind generated by a needle/ring configuration to be measured. Air velocity measurements carried out with a Pitot tube, considered as the reference measurements, were compared to PIV measurements for each tracer. In addition, the current-voltage curves and the evolution of the current during seeding were measured. All the experimental results show that TiO2, SiO2 microballoons and incense smoke are the ideal tracers in the series of tracers investigated.

  19. Tracer airflow measurement system (TRAMS)

    DOEpatents

    Wang, Duo

    2007-04-24

    A method and apparatus for measuring fluid flow in a duct is disclosed. The invention uses a novel high velocity tracer injector system, an optional insertable folding mixing fan for homogenizing the tracer within the duct bulk fluid flow, and a perforated hose sampling system. A preferred embodiment uses CO.sub.2 as a tracer gas for measuring air flow in commercial and/or residential ducts. In extant commercial buildings, ducts not readily accessible by hanging ceilings may be drilled with readily plugged small diameter holes to allow for injection, optional mixing where desired using a novel insertable foldable mixing fan, and sampling hose.

  20. Quantifying capture efficiency of gas collection wells with gas tracers.

    PubMed

    Yazdani, Ramin; Imhoff, Paul; Han, Byunghyun; Mei, Changen; Augenstein, Don

    2015-09-01

    A new in situ method for directly measuring the gas collection efficiency in the region around a gas extraction well was developed. Thirteen tests were conducted by injecting a small volume of gas tracer sequentially at different locations in the landfill cell, and the gas tracer mass collected from each test was used to assess the collection efficiency at each injection point. For 11 tests the gas collection was excellent, always exceeding 70% with seven tests showing a collection efficiency exceeding 90%. For one test the gas collection efficiency was 8±6%. Here, the poor efficiency was associated with a water-laden refuse or remnant daily cover soil located between the point of tracer injection and the extraction well. The utility of in situ gas tracer tests for quantifying landfill gas capture at particular locations within a landfill cell was demonstrated. While there are certainly limitations to this technology, this method may be a valuable tool to help answer questions related to landfill gas collection efficiency and gas flow within landfills. Quantitative data from tracer tests may help assess the utility and cost-effectiveness of alternative cover systems, well designs and landfill gas collection management practices. PMID:26148643

  1. Estimating sewer leakage from continuous tracer experiments.

    PubMed

    Rieckermann, Jörg; Bares, Vojtech; Kracht, Oliver; Braun, Daniel; Gujer, Willi

    2007-05-01

    Direct measurements of sewer leakage with continuous dosing of tracers are often considered too imprecise for practical applications. However, no mathematical framework for data analysis is reported in literature. In this paper, we present an improved experimental design and data analysis procedure together with a comprehensive framework for uncertainty assessment. Test runs in a 700 m-long watertight sewer showed no significant bias and a very high precision of the methodology. The standard error in the results was assessed to 2.6% of the labeled flow with a simplified model. It could be reduced to 1.2% when a dynamic data analysis procedure was applied. The major error contribution was caused by transient transport phenomena, which suggests that careful choosing of the experimental time is more important than the choice of a very specific tracer substance. Although the method is not intended to replace traditional CCTV inspections, it can provide complementary information for rational rehabilitation planning. PMID:17363025

  2. Is the tracer velocity of a fluid continuum equal to its mass velocity?

    PubMed

    Brenner, Howard

    2004-12-01

    Owing to its size independence in the so-called near-continuum vanishingly small Knudsen number regime (Kn<1) , thermophoretic particle motion occurring in an otherwise quiescent gas under the influence of a temperature gradient is here interpreted as representing the motion of a tracer, namely, an effectively point-size test particle monitoring the local velocity of the undisturbed, particle-free, compressible gas continuum through space. "Compressibility" refers here not to the usual effect of pressure on the gas's mass density rho but rather to the effect thereon of temperature. Our unorthodox continuum interpretation of thermophoresis differs from the usual one, which regards the existence of thermophoretic forces in gases as a strictly noncontinuum phenomenon, involving thermal stress-induced Maxwell slip ("thermal creep") of the gas's mass velocity vm at the surface of the particle, with vm denoting the velocity appearing in the continuity equation expressing the law of conservation of mass. Explicitly, instead of regarding the thermally animated particle as moving through the gas, we regard the particle (in its hypothesized role as a tracer of the undisturbed, particle-free, fluid motion) as moving with the gas, through space; that is, the particle is viewed as simply being entrained in the flowing gas, which, as a result of an externally applied temperature gradient, was already in motion prior to the tracer's introduction into the fluid--albeit not mass motion (which is, in fact, identically zero) but rather volume motion. This tracer-particle interpretation of experimental thermophoretic particle velocity measurements raises fundamental issues in regard to the universally accepted Newtonian rheological law constitutively specifying the viscous or deviatoric stress T as being proportional to the (symmetrized, traceless) fluid velocity gradient inverted Deltav , with v identified as being the fluid's mass velocity vm . Rather, it is argued in the case of

  3. In-Situ Characterization of Dense Non-Aqueous Phase Liquids Using Partitioning Tracers

    SciTech Connect

    Gary A. Pope; Daene C. McKinney; Akhil Datta Gupta; Richard E. Jackson; Minquan Jin

    2000-03-20

    Majors advances have been made during the past three years in our research on interwell partitioning tracers tests (PITTs). These advances include (1) progress on the inverse problem of how to estimate the three-dimensional distribution of NAPL in aquifers from the tracer data, (2) the first ever partitioning tracer experiments in dual porosity media, (3) the first modeling of partitioning tracers in dual porosity media (4) experiments with complex NAPLs such as coal tar, (5) the development of an accurate and simple method to predict partition coefficients using the equivalent alkane carbon number approach, (6) partitioning tracer experiments in large model aquifers with permeability layers, (7) the first ever analysis of partitioning tracer data to estimate the change in composition of a NAPL before and after remediation (8) the first ever analysis of partitioning tracer data after a field demonstration of surfactant foam to remediate NAPL and (9) experiments at elevated temperatures .

  4. Atmospheric and soil-gas monitoring for surface leakage at the San Juan Basin CO{sub 2} pilot test site at Pump Canyon New Mexico, using perfluorocarbon tracers, CO{sub 2} soil-gas flux and soil-gas hydrocarbons

    SciTech Connect

    Wells, Arthur W; Diehl, J Rodney; Strazisar, Brian R; Wilson, Thomas; H Stanko, Dennis C

    2012-05-01

    Near-surface monitoring and subsurface characterization activities were undertaken in collaboration with the Southwest Regional Carbon Sequestration Partnership on their San Juan Basin coal-bed methane pilot test site near Navajo City, New Mexico. Nearly 18,407 short tons (1.670 × 107 kg) of CO{sub 2} were injected into 3 seams of the Fruitland coal between July 2008 and April 2009. Between September 18 and October 30, 2008, two additions of approximately 20 L each of perfluorocarbon (PFC) tracers were mixed with the CO{sub 2} at the injection wellhead. PFC tracers in soil-gas and in the atmosphere were monitored over a period of 2 years using a rectangular array of permanent installations. Additional monitors were placed near existing well bores and at other locations of potential leakage identified during the pre-injection site survey. Monitoring was conducted using sorbent containing tubes to collect any released PFC tracer from soil-gas or the atmosphere. Near-surface monitoring activities also included CO{sub 2} surface flux and carbon isotopes, soil-gas hydrocarbon levels, and electrical conductivity in the soil. The value of the PFC tracers was demonstrated when a significant leakage event was detected near an offset production well. Subsurface characterization activities, including 3D seismic interpretation and attribute analysis, were conducted to evaluate reservoir integrity and the potential that leakage of injected CO{sub 2} might occur. Leakage from the injection reservoir was not detected. PFC tracers made breakthroughs at 2 of 3 offset wells which were not otherwise directly observable in produced gases containing 20–30% CO{sub 2}. These results have aided reservoir geophysical and simulation investigations to track the underground movement of CO{sub 2}. 3D seismic analysis provided a possible interpretation for the order of appearance of tracers at production wells.

  5. Redesigning TRACER trial after TRITON.

    PubMed

    Serebruany, Victor L

    2015-10-15

    Designing of smart clinical trials is critical for regulatory approval and future drug utilization. Importantly, trial design should be reconsidered if the interim analyses suggest unexpected harm, or conflicting results were yielded from the other trials within the same therapeutic area. With regard to antiplatelet agents, the perfect example is redesigning of the ongoing PRoFESS trial by eliminating aspirin from clopidogrel arm after the earlier MATCH trial results became available. The goal was to aseess the unchanged TRACER trial design in light of the evidence yielded from the earlier completed TRITON trial. TRACER was designed as a triple versus dual antiplatelet trial in NSTEMI patients with no previous long-term outcome data supporting such aggressive strategy. TRITON data represented dual versus dual antiplatelet therapy, and became available before TRACER enrollment starts revealing prasugrel front-loaded early vascular benefit predominantly in STEMI patients with the growing over time bleeding and cancer risks. Moreover, large prasugrel NSTEMI TRITON cohort exhibited trend towards excess mortality in experimental arm warning against aggressive TRACER design. The long-term TRITON results in general, and especially in the NSTEMI patients challenge unchanged TRACER trial design. Applying dual, rather than triple antiplatelet therapy protocol modification should be considered in TRACER to minimize bleeding, cancer, and non-cardiovascular death risks. PMID:26126053

  6. Tracer Verification of Trajectory Models.

    NASA Astrophysics Data System (ADS)

    Haagenson, Philip L.; Kuo, Ying-Hwa; Syumanich, Marina; Seaman, Nelson L.

    1987-03-01

    Perfluorocarbon tracer data collected during the Cross Appalachian Tracer Experiment (CAPTEX '83) are used to determine the accuracy of three trajectory models: an isentropic, an isobaric, and a dimensional sigma model. The root-mean-square separation between model trajectories and trajectories derived from the surface tracer concentration is used to evaluate the models and assess the validity of isobaric, isentropic, isosigma, and mean transport vector assumptions. The root-mean-square data suggest that wind flow corresponding approximately to the low to middle boundary layer is the most appropriate for simulating the transport of boundary layer pollutants, and that the isentropic and isosigma transport assumptions are more realistic than the isobaric assumption, The results also indicate that synoptic type and the diurnal variation of mixing and wind shell within the boundary layer can affect the magnitude of root-mean-square separation between tracer trajectory and transport model trajectories. The uncertainty of the trajectory error suggested by the root-mean- square separation is approximately 50 km. Comparison of the tracer study with a theoretical study suggests that surface tracer data are useful for quantifying the magnitude of error in trajectory model calculations of boundary layer transport.

  7. Innovative techniques for the description of reservoir heterogeneity using tracers. Second technical annual progress report, October 1991--September 1992

    SciTech Connect

    Pope, G.A.; Sepehrnoori, K.

    1992-12-31

    This second annual report on innovative uses of tracers for reservoir characterization contains four sections each describing a novel use of oilfield tracers. The first section describes and illustrates the use of a new single-well tracer test to estimate wettability. This test consists of the injection of brine containing tracers followed by oil containing tracers, a shut-in period to allow some of the tracers to react, and then production of the tracers. The inclusion of the oil injection slug with tracers is unique to this test, and this is what makes the test work. We adapted our chemical simulator, UTCHEM, to enable us to study this tracer method and made an extensive simulation study to evaluate the effects of wettability based upon characteristic curves for relative permeability and capillary pressure for differing wetting states typical of oil reservoirs. The second section of this report describes a new method for analyzing interwell tracer data based upon a type-curve approach. Theoretical frequency response functions were used to build type curves of ``transfer function`` and ``phase spectrum`` that have dimensionless heterogeneity index as a parameter to characterize a stochastic permeability field. We illustrate this method by analyzing field tracer data. The third section of this report describes a new theory for interpreting interwell tracer data in terms of channeling and dispersive behavior for reservoirs. Once again, a stochastic approach to reservoir description is taken. The fourth section of this report describes our simulation of perfluorocarbon gas tracers. This new tracer technology developed at Brookhaven National Laboratory is being tested at the Elk Hills Naval Petroleum Reserve No. 1 in California. We report preliminary simulations made of these tracers in one of the oil reservoirs under evaluation with these tracers in this field. Our compostional simulator (UTCOMP) was used for this simulation study.

  8. Solute transport in heterogeneous karst systems: Dimensioning and estimation of the transport parameters via multi-sampling tracer-tests modelling using the OTIS (One-dimensional Transport with Inflow and Storage) program

    NASA Astrophysics Data System (ADS)

    Dewaide, Lorraine; Bonniver, Isabelle; Rochez, Gaëtan; Hallet, Vincent

    2016-03-01

    This paper presents the modelling results of several tracer-tests performed in the cave system of Han-sur-Lesse (South Belgium). In Han-sur-Lesse, solute flows along accessible underground river stretches and through flooded areas that are rather unknown in terms of geometry. This paper focus on the impact of those flooded areas on solute transport and their dimensioning. The program used (One-dimensional Transport with Inflow and Storage: OTIS) is based on the two-region non equilibrium model that supposes the existence of an immobile water zone along the main flow zone in which solute can be caught. The simulations aim to replicate experimental breakthrough curves (BTCs) by adapting the main transport and geometric parameters that govern solute transport in karst conduits. Furthermore, OTIS allows a discretization of the investigated system, which is particularly interesting in systems presenting heterogeneous geometries. Simulation results show that transient storage is a major process in flooded areas and that the crossing of these has a major effect on the BTCs shape. This influence is however rather complex and very dependent of the flooded areas geometry and transport parameters. Sensibility tests performed in this paper aim to validate the model and show the impact of the parametrization on the BTCs shape. Those tests demonstrate that transient storage is not necessarily transformed in retardation. Indeed, significant tailing effect is only observed in specific conditions (depending on the system geometry and/or the flow) that allow residence time in the storage area to be longer than restitution time. This study ends with a comparison of solute transport in river stretches and in flooded areas.

  9. On gradient field theories: gradient magnetostatics and gradient elasticity

    NASA Astrophysics Data System (ADS)

    Lazar, Markus

    2014-09-01

    In this work, the fundamentals of gradient field theories are presented and reviewed. In particular, the theories of gradient magnetostatics and gradient elasticity are investigated and compared. For gradient magnetostatics, non-singular expressions for the magnetic vector gauge potential, the Biot-Savart law, the Lorentz force and the mutual interaction energy of two electric current loops are derived and discussed. For gradient elasticity, non-singular forms of all dislocation key formulas (Burgers equation, Mura equation, Peach-Koehler stress equation, Peach-Koehler force equation, and mutual interaction energy of two dislocation loops) are presented. In addition, similarities between an electric current loop and a dislocation loop are pointed out. The obtained fields for both gradient theories are non-singular due to a straightforward and self-consistent regularization.

  10. The ATLAS DDM Tracer monitoring framework

    NASA Astrophysics Data System (ADS)

    Zang, Dongsong; Garonne, Vincent; Barisits, Martin; Lassnig, Mario; Stewart, Graeme Andrew; Molfetas, Angelos; Beermann, Thomas

    2012-12-01

    The DDM Tracer monitoring framework is aimed to trace and monitor the ATLAS file operations on the Worldwide LHC Computing Grid. The volume of traces has increased significantly since the framework was put in production in 2009. Now there are about 5 million trace messages every day and peaks can be near 250Hz, with peak rates continuing to climb, which gives the current structure a big challenge. Analysis of large datasets based on on-demand queries to the relational database management system (RDBMS), i.e. Oracle, can be problematic, and have a significant effect on the database's performance. Consequently, We have investigated some new high availability technologies like messaging infrastructure, specifically ActiveMQ, and key-value stores. The advantages of key value store technology are that they are distributed and have high scalability; also their write performances are usually much better than RDBMS, all of which are very useful for the Tracer monitoring framework. Indexes and distributed counters have been also tested to improve query performance and provided almost real time results. In this paper, the design principles, architecture and main characteristics of Tracer monitoring framework will be described and examples of its usage will be presented.

  11. Characteristics and Evolution of Passive Tracers in the Oceanic Mixed Layer

    NASA Astrophysics Data System (ADS)

    Smith, Katherine; Hamlington, Peter; Fox-Kemper, Baylor

    2015-11-01

    Ocean tracers such as CO2 and plankton reside primarily in the mixed layer where air-sea gas exchange occurs and light is plentiful for photosynthesis. There can be substantial heterogeneity in the distributions of these tracers due to turbulent mixing, particularly in the submesoscale range where partly geostrophic eddies and small-scale 3D turbulence are both active. In this talk, LES spanning scales from 20km down to 5m are used to examine the role of turbulent mixing on nonreactive passive ocean tracers. The simulations include the effects of both wave-driven Langmuir turbulence and submesoscale eddies, and tracers with different initial and boundary conditions are examined. Tracer properties are characterized using spatial fields, statistics, multiscale fluxes, and spectra, and results show that passive tracer mixing depends on air-sea flux rate, release depth, and flow regime. The results indicate that while submesoscale eddies transport buoyancy upward to extract potential energy, the same is not true of passive tracers, whose entrainment is instead suppressed. Early in the evolution of some tracers, counter-gradient transport occurs co-located with regions of negative potential vorticity, suggesting that symmetric instabilities may act to oppose turbulent mixing.

  12. Wind tunnel evaluation of several tracer and collection techniques for the measurement of spray drift.

    PubMed

    Brusselman, E; Van Driessen, K; Steurbaut, W; Gabriels, D; Cornelis, W; Nuyttens, D; Sonck, B; Baetens, K; Nicolai, B; Verboven, P; Ramon, H

    2004-01-01

    In the history of pesticide drift measuring techniques, different tracers and a lot of different collection techniques have been used. At the start of a new Flemish project 'Protecting the Flemish environment against drift - The importance of drift-reducing techniques', wind tunnel tests have been executed to select the most efficient tracer and collection technique. As tracer types a fluorescent tracer Renaissance W15, 2 different chelates, a NaCl-solution and a fungicide Tolylfluanide were used. 2 different collection techniques were tested: drains incorporated in the wind tunnel floor filled with filter paper and filled with cloths. The recovery of the different tracers combined with the 2 collection materials was calculated. The advantages and disadvantages of the tracers and collection materials are enumerated in this article. PMID:15756877

  13. Study of North Atlantic ventilation using transient tracers. Doctoral Thesis

    SciTech Connect

    Doney, S.C.

    1991-08-01

    Tritium, (3)He, and chlorofluorocarbon distributions in the North Atlantic provide constraints on the ventilation time-scales for the thermocline and abyssal water. A new model function based on a factor analysis of the WMO/IAEA precipitation data set is developed for predicting the spatial and temporal patterns of bomb-tritium in precipitation. Model atmospheric and advective tritium inputs to the North Atlantic are compared with the observed bomb-tritium inventories calculated from the 1972 GEOSECS and 1981-1983 TTO data sets. The observed growth of bomb-tritium levels in the deep North Atlantic are used, along with the tracer gradients ((3)H and (3)He) in the Deep Western Boundary Current, to estimate abyssal ventilation rates and boundary current recirculation. The surface boundary conditions for different transient tracers are found to profoundly effect thermocline ventilation rates estimates. Tracers that equilibrate rapidly with the atmosphere, such as (3)He and the CFCs, have faster apparent ventilation rates and are more appropriate for estimating oxygen utilization rates than tracers that are reset slowly in the surface ocean (e.g. (3)H and (14)C). The chlorofluorocarbon data for a new section in the eastern North Atlantic are presented and used to illustrate the ventilation time-scales for the major water masses in the region. (Copyright (c) Scott C. Doney, 1991.)

  14. Tracer Transport in the Tropical Lower Stratosphere

    NASA Astrophysics Data System (ADS)

    Trepte, Charles Raymond

    1993-01-01

    Distributions of aerosol extinction ratio ( beta_{r}) and ozone, derived from the Stratospheric Aerosol and Gas Experiment (SAGE I/II) satellite experiments (1979-1981 and 1984-1992), are used in conjunction with conventional meteorological analyses to deduce patterns of stratospheric tracer transport. Following volcanic eruptions at low latitudes, the aerosol observations suggest that two transport regimes exist in the tropical lower stratosphere. Aerosols disperse rapidly poleward and downward within a layer several kilometers above the tropopause. More pronounced transport is biased toward the winter hemisphere. At higher altitudes, however, volcanic aerosols tend to remain over the equator in a reservoir bounded by strong meridional gradients near 20 ^circN and S. Over the equator, enhanced lofting of aerosols occurs during QBO easterly shear, while subsidence relative to the mean meridional flow takes place during QBO westerly shear. While particle growth and evaporation effects are important, many interesting features of the aerosol distribution can only be explained by air motions. It is also shown that QBO induced ozone anomalies over the equator are also consistent with QBO aerosol variations. In the upper transport regime, the subtropical gradients of beta_{r} coincide with the location of a meridional gradient in potential vorticity. Since isentropic transport is inhibited across potential vorticity gradients, the tropics are temporarily isolated from eddy mixing taking place in the winter extratropics. Zonal mean distributions of ozone; however, do not have similar meridional gradients in the subtropics. This difference probably reflects a different source/sink distribution for ozone in comparison to that for aerosol and potential vorticity. Detrainment of aerosol from the equatorial reservoir depends upon the phase of the QBO and the strength of winter eddy disturbances in the subtropics. Anticyclonic circulation systems form occasionally in the

  15. Flow-through column experiments to determine the geochemical behavior of common hydrological tracers

    NASA Astrophysics Data System (ADS)

    Moola, P. S. N.; Sigfússon, B.; Stefansson, A.

    2015-12-01

    Tracer testing is one of the most effective methods used to study groundwater flow, reservoir characteristics and subsurface properties in geohydrology. Hydrological tracer tests were conducted with the basic assumption that the tracer is chemically inert and non-reactive. However, not all tracers behave non-reactive at different pH conditions, the particular tracer may interact with mineral surfaces in the reservoir. In order to study the geochemical behavior of some common hydrological tracers flow-through column experiments were conducted at 25°C. Six common hydrological tracers were investigated, amino G acid, fluorescein, napthionic acid, pyranine, rhodamine B and rhodamine G in porous rocks consisting of basaltic glass, quartz or rhyolite at pH 3, 6.5 and 9. Homogenous porous material of fixed grain size 45-125μm were dry packed in the column to conduct flow through column experiments. Tracers were pumped at fixed flow rates for 20 minutes and switched back to experimental blank solution and the tracer concentration monitored at the outlet. The measured break-through tracer curves were compared to theoretical 1-D reactive transport simulations calculated using the PHREEQC program (Parkhurst and Appelo, 1999). The data obtained from the breakthrough curves suggest that the tracers may be reactive, non-reactive and partially reactive depending on the rock type and solution pH. The tracers that were observed to be reactive showed the influence of adsorption and desorption. The results suggest that some tracers commonly used in ground water hydrology are not suitable under all conditions as they may react with the rocks of the groundwater system.

  16. Final Progress Report for Project Entitled: Quantum Dot Tracers for Use in Engineered Geothermal Systems

    SciTech Connect

    Rose, Peter; Bartl, Michael; Reimus, Paul; Williams, Mark; Mella, Mike

    2015-09-12

    The objective of this project was to develop and demonstrate a new class of tracers that offer great promise for use in characterizing fracture networks in EGS reservoirs. From laboratory synthesis and testing through numerical modeling and field demonstrations, we have demonstrated the amazing versatility and applicability of quantum dot tracers. This report summarizes the results of four years of research into the design, synthesis, and characterization of semiconductor nanocrystals (quantum dots) for use as geothermal tracers.

  17. Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site Characterization Study; Progress report, June 1--December 31, 1990

    SciTech Connect

    Stetzenbach, K.J.

    1990-12-31

    Ground water tracers are solutes dissolved in or carried by ground water to delineate flow pathways. Tracers provide information on direction and speed of water movement and that of contaminants that might be conveyed by the water. Tracers can also be used to measure effective porosity, hydraulic conductivity, dispersivity and solute distribution coefficients. For most applications tracers should be conservative, that is, move at the same rate as the water and not sorb to aquifer materials. Tracers must have a number of properties to be functional. Regardless of the desired properties, the chemical and physical behavior of a tracer in ground water and the porous medium under study must be understood. Good estimates of tracer behavior can be obtained from laboratory studies. Studies in this proposal will address tracer properties with analytical method development, static sorption and degradation studies and column transport studies, Mutagenicity tests will be performed on promising candidates. The tracers that will be used for these experiments are fluorinated organic acids and other organic compounds that have the chemical and biological stability necessary to be effective in the Yucca Mountain environment. Special emphasis will be placed on compounds that fluoresce or have very large ultraviolet absorption coefficients for very high analytical sensitivity.

  18. Contribution of time-related environmental tracing combined with tracer tests for characterization of a groundwater conceptual model: a case study at the Séchilienne landslide, western Alps (France)

    NASA Astrophysics Data System (ADS)

    Vallet, A.; Bertrand, C.; Mudry, J.; Bogaard, T.; Fabbri, O.; Baudement, C.; Régent, B.

    2015-12-01

    Groundwater-level rise plays an important role in the activation or reactivation of deep-seated landslides and so hydromechanical studies require a good knowledge of groundwater flows. Anisotropic and heterogeneous media combined with landslide deformation make classical hydrogeological investigations difficult. Hydrogeological investigations have recently focused on indirect hydrochemistry methods. This study aims at determining the groundwater conceptual model of the Séchilienne landslide and its hosting massif in the western Alps (France). The hydrogeological investigation is streamlined by combining three approaches: a one-time multi-tracer test survey during high-flow periods, a seasonal monitoring of the water stable-isotope content and electrical conductivity, and a hydrochemical survey during low-flow periods. The complexity of the hydrogeological setting of the Séchilienne massif leads to development of an original method to estimate the elevations of the spring recharge areas, based on topographical analyses and water stable-isotope contents of springs and precipitation. This study shows that the massif supporting the Séchilienne landslide is characterized by a dual-permeability behaviour typical of fractured-rock aquifers where conductive fractures play a major role in the drainage. There is a permeability contrast between the unstable zone and the intact rock mass supporting the landslide. This contrast leads to the definition of a shallow perched aquifer in the unstable zone and a deep aquifer in the intact massif hosting the landslide. The perched aquifer in the landslide is temporary, mainly discontinuous, and its extent and connectivity fluctuate according to the seasonal recharge.

  19. Tracer transport in fractured crystalline rock: Evidence of nondiffusive breakthrough tailing

    USGS Publications Warehouse

    Becker, M.W.; Shapiro, A.M.

    2000-01-01

    Extended tailing of tracer breakthrough is often observed in pulse injection tracer tests conducted in fractured geologic media. This behavior has been attributed to diffusive exchange of tracer between mobile fluids traveling through channels in fractures and relatively stagnant fluid between fluid channels, along fracture walls, or within the bulk matrix. We present a field example where tracer breakthrough tailing apparently results from nondiffusive transport. Tracer tests were conducted in a fractured crystalline rock using both a convergent and weak dipole injection and pumping scheme. Deuterated water, bromide, and pentafluorobenzoic acid were selected as tracers for their wide range in molecular diffusivity. The late time behavior of the normalized breakthrough curves were consistent for all tracers, even when the pumping rate was changed. The lack of separation between tracers of varying diffusivity indicates that strong breakthrough tailing in fractured geologic media may be caused by advective transport processes. This finding has implications for the interpretation of tracer tests designed to measure matrix diffusion in situ and the prediction of contaminant transport in fractured rock.

  20. Inexpensive perfluorocarbon tracer technique for wide-scale infiltration measurements in homes

    SciTech Connect

    Dietz, R.N.; Cote, E.A.; Senum, G.I.; Wieser, R.F.

    1981-08-01

    A perfluorocarbon tracer technique to determine infiltration rates in homes is described. A tracer kit, coined the Brookhaven National Laboratory Air Infiltration Measurement System, which can be deployed by the average homeowner, is briefly described. The tracer source is a fluoroelastomer plug impregnated with a known mass of perfluorocarbon tracers (PFT) and crimped within a metal shell. The PFT diffuses from the end of the plug. Two samplers briefly described are: the capillary adsorption tube sampler (CATS) and the programmable Brookhaven Atmospheric Tracer Sampler (BATS). Deployment of one of the diffusion sources in a home and use of a BATS unit to measure the increase in the tracer concentration perfluorodimethylcyclohexane (PDCH) are discussed. Results of the tests are presented. (MCW)

  1. Human calcium metabolism including bone resorption measured with {sup 41}Ca tracer

    SciTech Connect

    Freeman, S.P.H.T.; King, J.C.; Vieira, N.E.; Woodhouse, L.R.; Yergey, A.L.

    1996-08-01

    Accelerator mass spectrometry is so sensitive to small quantities of {sup 41}Ca that it might be used as a tracer in the study of human calcium kinetics to generate unique kinds of data. In contrast with the use of other Ca isotopic tracers, {sup 41}Ca tracer can be so administered that the tracer movements between the various body pools achieve a quasi steady state. Resorbing bone may thus be directly measured. We have tested such a protocol against a conventional stable isotope experiment with good agreement.

  2. Short-term fluid, heat, and solute transport in deep 'georeservoirs' likely to become 'EGS': some challenges to ICDP hydrogeologists who might like using artificial tracers

    NASA Astrophysics Data System (ADS)

    Ghergut, Julia; Behrens, Horst; Huenges, Ernst; Rose, Peter; Sauter, Martin

    2014-05-01

    During Fall 2013, the Integrated Continental Scientific Drilling Programme (ICDP) set out to define a new Science Plan that shall replace its past-decade version (Harms et al., eds., 2005) for the decade to come. Geoscientists worldwide were welcomed to suggest new imaging and exploration methods, new sites to drill, new challenges to be addressed with a view at new 'societal needs' (Harms and Wiersberg 2013). Save for two outstanding exceptions at the Mutnovsky volcano in Russia and the KTB site in Germany, the use of artificial tracers, especially within forced-gradient tests, has not been on the agenda of most ICDP projects so far (other than for purposes of monitoring microbial contamination in conjunction with drilling activities); deep-reservoir exploration and characterization efforts were restrained to non-fluid-invasive techniques on the one hand, and to sites featuring some unique earth-historical traits, on the other hand. Surely, this was not for lack of interest in quantifying fluid transport in the deep subsurface in general, but mainly due to operational, technical, and financial constraints (lack of resources / lack of opportunity for significant fluid turnover within the target, deep-seated georeservoirs, and fear of persistent, large-scale georeservoir contamination by non-pristine fluids). - This is likely to change during the forthcoming decade(s), owing to worldwide increased interest in some 'georesource' or 'georeservoir' play types (Moeck 2013) that have not been in the ICDP focus so far, including non-volcanogenic geothermal, and allowing for man-made design and intervention into how those 'georesources' or 'georeservoirs' shall work for us. Among the latter, petrothermal systems (Jung 2013, Huenges and Jung 2004) acquire growing recognition as a promising (and maybe unique) option for baseload energy supply in vast areas of the Northern hemisphere, at very low emissions and (in the long run) moderate costs. With petrothermal coming into

  3. Isotopic Tracers for Delineating Non-Point Source Pollutants in Surface Water

    SciTech Connect

    Davisson, M L

    2001-03-01

    This study tested whether isotope measurements of surface water and dissolved constituents in surface water could be used as tracers of non-point source pollution. Oxygen-18 was used as a water tracer, while carbon-14, carbon-13, and deuterium were tested as tracers of DOC. Carbon-14 and carbon-13 were also used as tracers of dissolved inorganic carbon, and chlorine-36 and uranium isotopes were tested as tracers of other dissolved salts. In addition, large databases of water quality measurements were assembled for the Missouri River at St. Louis and the Sacramento-San Joaquin Delta in California to enhance interpretive results of the isotope measurements. Much of the water quality data has been under-interpreted and provides a valuable resource to investigative research, for which this report exploits and integrates with the isotope measurements.

  4. Simulation of tracer concentration data in the Brush Creek Drainage flow using an integrated puff model

    SciTech Connect

    Rao, K. S.; Eckman, R. M.; Hosker, R. P., Jr.

    1989-07-01

    During the 1984 ASCOT field study in Brush Creek Valley, two perfluorocarbon tracers were released into the nocturnal drainage flow at two different heights. The resulting surface concentrations were sampled at 90 sites, and vertial concentration profiles at 11 sites. These detailed tracer measurements provide a valuable dataset for developing and testing models of pollutant transport and dispersion in valleys.

  5. Comparison of tracer methods to quantify hydrodynamic exchange within the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Engelhardt, I.; Piepenbrink, M.; Trauth, N.; Stadler, S.; Kludt, C.; Schulz, M.; Schüth, C.; Ternes, T. A.

    2011-03-01

    SummaryHydrodynamic exchange between surface-water and groundwater was studied at a river located within the Rhine Valley in Germany. Piezometric pressure heads and environmental tracers such as temperature, stable isotopes, chloride, X-ray contrast media, and artificial sweetener were investigated within the hyporheic zone and river water plume. Vertical profiles of environmental tracers were collected using multi-level wells within the neutral up-gradient zone, beneath the river bed, and within the horizontal proximal and distal down-gradient zone. Infiltration velocities were calculated from pressure heads, temperature fluctuations and gradients. The amount of river water within groundwater was estimated from vertical profiles of chloride, stable isotopes, and persistent pharmaceuticals. Profiles of stable isotopes and chloride reveal the existence of down-welling within the shallow hyporheic zone that is generated by river bed irregularities. Due to down-welling an above-average migration of river water into the hyporheic zone establishes even under upward hydraulic pressure gradients. The investigated environmental tracers could not distinctively display short-time-infiltration velocities representative for flood waves, while average infiltration velocities calculated over several months are uniform displayed. Based on vertical temperature profiles the down-gradient migration of the river water plume could be observed even after long periods of effluent conditions and over a distance of 200 m from the river bank. X-ray contrast media and artificial sweeteners were observed in high concentrations within the proximal zone, but were not detected at a distance of 200 m from the river bank. Using temperature as environmental tracer within the hyporheic zone may result in overestimating the migration of pollutants within the river water plume as the process of natural attenuation will be neglected. Furthermore, temperature was not able to display the effect of down

  6. PIV tracer behavior on propagating shock fronts

    NASA Astrophysics Data System (ADS)

    Glazyrin, Fyodor N.; Mursenkova, Irina V.; Znamenskaya, Irina A.

    2016-01-01

    The present work was aimed at the quantitative particle image velocimetry (PIV) measurement of a velocity field near the front of a propagating shock wave and the study of the dynamics of liquid tracers crossing the shock front. For this goal, a shock tube with a rectangular cross-section (48  ×  24 mm) was used. The flat shock wave with Mach numbers M  =  1.4-2.0 propagating inside the tube channel was studied as well as an expanding shock wave propagating outside the channel with M  =  1.2-1.8 at its main axis. The PIV imaging of the shock fronts was carried out with an aerosol of dioctyl sebacate (DEHS) as tracer particles. The pressures of the gas in front of the shock waves studied ranged from 0.013 Mpa to 0.1 MPa in the series of experiments. The processed PIV data, compared to the 1D normal shock theory, yielded consistent values of wake velocity immediately behind the plain shock wave. Special attention was paid to the blurring of the velocity jump on the shock front due to the inertial particle lag and peculiarities of the PIV technique. A numerical algorithm was developed for analysis and correction of the PIV data on the shock fronts, based on equations of particle-flow interaction. By application of this algorithm, the effective particle diameter of the DEHS aerosol tracers was estimated as 1.03  ±  0.12 μm. A number of different formulations for particle drag were tested with this algorithm, with varying success. The results show consistency with previously reported experimental data obtained for cases of stationary shock waves.

  7. Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site characterization study. Progress report, January 1, 1995--March 31, 1995

    SciTech Connect

    Stetzenbach, K.; Farnham, I.

    1995-05-01

    Fluorinated organic acids were utilized in a test study as hydrologic tracers for the Yucca Mountain Project. Fluorinated acids included cinnamic acid; benzoic acid, and toluic acid. Results are discussed pertaining to retention time, elution time, and stability.

  8. Using molecular-scale tracers to investigate transport of agricultural pollutants in soil and water

    NASA Astrophysics Data System (ADS)

    Lloyd, C.; Michaelides, K.; Chadwick, D.; Dungait, J.; Evershed, R. P.

    2012-12-01

    We explore the use of molecular-scale tracers to investigate the transport of potential pollutants due to the application of slurry to soil. The molecular-scale approach allows us to separate the pollutants which are moved to water bodies through sediment-bound and dissolved transport pathways. Slurry is applied to agricultural land to as a soil-improver across a wide-range of topographic and climatic regimes, hence a set of experiments were designed to assess the effect of changing slope gradient and rainfall intensity on the transport of pollutants. The experiments were carried out using University of Bristol's TRACE (Test Rig for Advancing Connectivity Experiments) facility. The facility includes a dual axis soil slope (6 x 2.5 x 0.3 m3) and 6-nozzle rainfall simulator, which enables the manipulation of the slope to simulate different slope gradient and rainfall scenarios. Cattle slurry was applied to the top 1 metre strip of the experimental soil slope followed by four rainfall simulations, where the gradient (5° & 10°) and the rainfall intensity (60 & 120 mm hr-1) were co-varied. Leachate was sampled from different flow pathways (surface, subsurface and percolated) via multiple outlets on the slope throughout the experiments and soil cores were taken from the slope after each experiment. Novel tracers were used to trace the pollutants in both dissolved and sediment-bound forms. Fluorescence spectroscopy was used to trace dissolved slurry-derived material via water flow pathways, as the slurry was found to have a distinct signature compared with the soil. The fluorescence signatures of the leachates were compared with those of many organic compounds in order to characterise the origin of the signal. This allowed the assessment of the longevity of the signal in the environment to establish if it could be used as a robust long-term tracer of slurry material in water or if would be subject to transform processes through time. 5-βstanols, organic compounds

  9. Effects of a descending lithospheric slab on yield estimates of Aleutian nuclear tests. Incorporation of velocity gradients in the synthesis of complete seismograms by the locked-mode method

    SciTech Connect

    Cormier, V.F.

    1990-08-10

    The locked mode method of synthesizing complete regional seismograms (Harvey, 1981) was modified to include the Langer uniform asymptotic approximation to vertical wave-functions within layers having linear vertical velocity gradients. Good agreement is obtained in gradient models between synthetics computed using the Langer-locked mode method, the colocation method, and the conventional locked mode method in models parameterized by thin homogeneous layers. Errors in calculated displacement introduced by the use of the Langer approximation remain less than several percent for wavelengths lambda < or = 0.2V/nabla operator V. Whenever it is necessary to represent gradients accurately, the Langer-locked mode method is computationally more efficient than the locked mode method using thin homogeneous layers. By reducing the number of parameters needed to describe an Earth model, the Langer-locked method will also simplify the inverse problem of determining structure using observed and synthetic regional seismograms. Test calculations of regional seismograms confirm that the Pn and Sn phases are strongly affected by the magnitude of the velocity gradients beneath the Moho, but that Lg is only weakly affected by the details of crustal layering.

  10. Preliminary assessment of halogenated alkanes as vapor-phase tracers

    SciTech Connect

    Adams, Michael C.; Moore, Joseph N.; Hirtz, Paul

    1991-01-01

    New tracers are needed to evaluate the efficiency of injection strategies in vapor-dominated environments. One group of compounds that seems to meet the requirements for vapor-phase tracing are the halogenated alkanes (HCFCs). HCFCs are generally nontoxic, and extrapolation of tabulated thermodynamic data indicate that they will be thermally stable and nonreactive in a geothermal environment. The solubilities and stabilities of these compounds, which form several homologous series, vary according to the substituent ratios of fluorine, chlorine, and hydrogen. Laboratory and field tests that will further define the suitability of HCFCs as vapor-phase tracers are under way.

  11. Chemical tracers of particulate emissions from commercial shipping.

    PubMed

    Viana, Mar; Amato, Fulvio; Alastuey, Andrés; Querol, Xavier; Moreno, Teresa; Dos Santos, Saúl García; Herce, María Dolores; Fernández-Patier, Rosalía

    2009-10-01

    Despite the increase of commercial shipping around the world, data are yet relatively scarce on the contribution of these emissions to ambient air particulates. One of the reasons is the complexity in the detection and estimation of shipping contributions to ambient particulates in harbor and urban environments, given the similarity with tracers of other combustion sources. This study aimed to identify specific tracers of shipping emissions in a Mediterranean city with an important harbor (Melilla, Spain). Results showed that for 24 h PM10 and PM2.5 samples, valid tracers of commercial shipping emissions were ratios of V/Ni = 4-5 and V/EC < 2, whereas V/EC > 8 excluded the influence of shipping emissions. Other ratios (V/ S, La/Ce, Zn/Ni, Pb/Zn, OC/EC) and tracers (Pb, Zn) were also tested but did not correlate with this source. Due to the changing composition of diesel fuels, tracers in the Mediterranean Sea may not be representative in other regions of the world and vice versa. The contribution of shipping emissions to ambient particulate matter (PM) urban background levels was quantified by positive matrix factorization (PMF), resulting in 2% and 4% of mean annual PM10 levels (0.8 microg/m3 primary particles and 1.7 microg/m3 secondary particles, with 20% uncertainty) and 14% of mean annual PM2.5 levels (2.6 microg/m3). PMID:19848163

  12. TRACER DISPERSION STUDIES FOR HYDRAULIC CHARACTERIZATION OF PIPES

    EPA Science Inventory

    A series of experiments were conducted at the U. S. Environmental Protection Agency (EPA) Test & Evaluation (T&E) Facility in Cincinnati, Ohio, to quantify longitudinal dispersion of a sodium fluoride tracer in polyvinyl chloride (PVC) pipe and ductile iron pipe under laminar, tr...

  13. Matching tracer selection to georeservoir typology - A note on geothermal reservoir classification

    NASA Astrophysics Data System (ADS)

    Ghergut, Julia; Behrens, Horst; Licha, Tobias; Sauter, Martin

    2013-04-01

    Thermal-lifetime prediction is a traditional endeavor of inter-well tracer tests conducted in geothermal reservoirs. Early tracer test signals (detectable within the first few years of operation) are expected to correlate with late-time production temperature drop (so-called 'thermal breakthrough', supposed to not occur before some decades of operation) of a geothermal reservoir. Whenever a geothermal reservoir can be described as a single-fracture system, its thermal lifetime will, ideally, be determined by two parameters, whose inversion from conservative-tracer test signals is straightforward and non-ambiguous (provided that the tracer tests, and their interpretation, are performed in accordance to the rules of the art). However, as soon as just few more fractures are considered, this clear-cut correlation is broken. A given geothermal reservoir can simultaneously exhibit a single-fracture behavior, in terms of heat transport, and a multiple-fracture behavior, in terms of solute tracer transport (or vice-versa), whose effective values of fracture apertures, spacings, and porosities are essentially uncorrelated between heat and solute tracers. Solute transport parameters derived from conservative-tracer tests will no longer characterize the heat transport processes (and thus temperature evolutions) taking place in the same reservoir. Parameters determining its thermal lifetime will remain invisible to conservative tracers in inter-well tests. Non-conservative tracers, in particular sorptive and thermo-sensitive compounds, can be used to overcome this gap between heat and tracer transport. However, significant differences exist, w. r. to tracer functionality, between different geothermal systems: (I) hot natural aquifers (with predominantly 'porous media' character), (II) aquifer-based EGS, (III) petrothermally-based EGS, (IV) naturally-fractured systems. Conservative tracers are indispensable to characterizing any of (I) - (IV), but their residence time

  14. Stream solute tracer timescales changing with discharge and reach length confound process interpretation

    NASA Astrophysics Data System (ADS)

    Schmadel, Noah M.; Ward, Adam S.; Kurz, Marie J.; Fleckenstein, Jan H.; Zarnetske, Jay P.; Hannah, David M.; Blume, Theresa; Vieweg, Michael; Blaen, Phillip J.; Schmidt, Christian; Knapp, Julia L. A.; Klaar, Megan J.; Romeijn, Paul; Datry, Thibault; Keller, Toralf; Folegot, Silvia; Arricibita, Amaia I. Marruedo; Krause, Stefan

    2016-04-01

    Improved understanding of stream solute transport requires meaningful comparison of processes across a wide range of discharge conditions and spatial scales. At reach scales where solute tracer tests are commonly used to assess transport behavior, such comparison is still confounded due to the challenge of separating dispersive and transient storage processes from the influence of the advective timescale that varies with discharge and reach length. To better resolve interpretation of these processes from field-based tracer observations, we conducted recurrent conservative solute tracer tests along a 1 km study reach during a storm discharge period and further discretized the study reach into six segments of similar length but different channel morphologies. The resulting suite of data, spanning an order of magnitude in advective timescales, enabled us to (1) characterize relationships between tracer response and discharge in individual segments and (2) determine how combining the segments into longer reaches influences interpretation of dispersion and transient storage from tracer tests. We found that the advective timescale was the primary control on the shape of the observed tracer response. Most segments responded similarly to discharge, implying that the influence of morphologic heterogeneity was muted relative to advection. Comparison of tracer data across combined segments demonstrated that increased advective timescales could be misinterpreted as a change in dispersion or transient storage. Taken together, our results stress the importance of characterizing the influence of changing advective timescales on solute tracer responses before such reach-scale observations can be used to infer solute transport at larger network scales.

  15. Multiple-tracer gas analyzer

    SciTech Connect

    Uhl, J.E.

    1982-01-01

    A multi-gas tracer system has been designed, built, and used on an explosively fractured oil shale rubble bed. This paper deals exclusively with the hardware, software, and overall operation of the tracer system. This system is a field portable, self-contained unit, which utilizes a mass spectrometer for gas analysis. The unit has a 20 channel sample port capability and is controlled by a desk top computer. The system is configured to provide a dynamic sensitivity range of up to six orders of magnitude. A roots blower is manifolded to the unit to provide continuous flow in all sample lines. The continuous flow process allows representative samples as well as decreasing the time between each measurement. Typical multiplex cycle time to evaluate four unique gases is approximately 12 seconds.

  16. Oxidation in a temperature gradient

    SciTech Connect

    Holcomb, Gordon R.; Covino, Bernard S., Jr.; Russell, James H.

    2001-01-01

    The effects of a temperature gradient and heat flux on point defect diffusion in protective oxide scales were examined. Irreversible thermodynamics were used to expand Fick's first law of diffusion to include a heat flux term--a Soret effect. Oxidation kinetics were developed for the oxidation of cobalt and for nickel doped with chromium. Research in progress is described to verify the effects of a heat flux by oxidizing pure cobalt in a temperature gradient above 800 C, and comparing the kinetics to isothermal oxidation. The tests are being carried out in the new high temperature gaseous corrosion and corrosion/erosion facility at the Albany Research Center.

  17. Predicted fate of tritium residuum from groundwater tracer experiments in the Amargosa Desert, southern Nevada

    SciTech Connect

    Brikowski, T.

    1993-07-01

    Analytic solutions are used in this study to evaluate potential groundwater transport of tritium used in goundwater tracer tests southwest of the Nevada Test Site. Possible transport from this site is of interest because initial radionuclide concentrations were high and the site is close to goundwater discharge points (12 km). Anecdotal evidence indicates that 90 percent of these tracers were removed by pumping at the completion of the tests; this study examines the probable transport of the tracers with and without the removal. Classical dispersive transport analytic solutions are used, treating the tracer test as a point slug injection. Input parameters for the solutions were measured at the site, and consideration of parameter uncertainty is incorporated in the results. With removal of the tracer, the maximum expected region with above-Safe Drinking Water Act (40 CFR 121) concentrations of tritium extends 5 km from the injection point, and does not reach any sites of public access. Detectable tritium from the tests is likely to have reached the Ash Meadows fault zone, but flow along the fault probably diluted the tracer to below detection limits before arrival at springs along the fault. Arrival at the springs would have occurred 20 to 25 years after the tests. Without removal of the tracer, the solutions indicate that tritium concentrations just above Safe Drinking Water Act standards would have reached the Ash Meadows fault zone. In this case, detectable tritium might have been found in Devil`s Hole or Longstreet Spring, the nearest points of possible public exposure.

  18. Off-gassing induced tracer release from molten basalt pools

    SciTech Connect

    Cronenberg, A.W.; Callow, R.A.

    1994-01-01

    Two in situ vitrification (ISV) field tests were conducted at the Idaho National Engineering Laboratory (INEL) during the summer of 1990 to assess ISV suitability for long-term stabilization of buried waste that contains transuranic and other radionuclide contaminants. The ISV process uses electrical resistance heating to melt buried waste and soil in place, which upon cooldown and resolidification fixes the waste into a vitrified (glass-like) form. In these two ISV field tests, small quantities of rare-earth oxides (tracers DY{sub 2}O{sub 3}, Yb{sub 2}O{sub 3}, and Tb{sub 4}O{sub 7}) were placed in the test pits to simulate the presence of plutonium oxides and assess plutonium retention/release behavior. The analysis presented in this report indicates that dissolution of tracer oxides into basaltic melts can be expected with subsequent tracer molecular or microparticle carry-off by escaping gas bubbles, which is similar to adsorptive bubble separation and ion flotation processes employed in the chemical industry to separate dilute heavy species from liquids under gas sparging conditions. Gaseous bubble escape from the melt surface and associated aerosolization is believed to be responsible for small quantities of tracer ejection from the melt surface to the cover hood and off-gas collection system. Methods of controlling off-gassing during ISV would be expected to improve the overall retention of such heavy oxide contaminants during melting/vitrification of buried waste.

  19. Biomimetic Gradient Polymers with Enhanced Damping Capacities.

    PubMed

    Wang, Dong; Zhang, Huan; Guo, Jing; Cheng, Beichen; Cao, Yuan; Lu, Shengjun; Zhao, Ning; Xu, Jian

    2016-04-01

    Designing gradient structures, mimicking biological materials, such as pummelo peels and tendon, is a promising strategy for developing advanced materials with superior energy damping capacities. Here a facile and effective approach for fabricating polymers with composition gradients at millimeter length scale is presented. The gradient thiol-ene polymers (TEPs) are created by the use of density difference of ternary thiol-ene-ene precursors and the subsequent photo-crosslinking via thiol-ene reaction. The compositional gradients are analyzed via differential scanning calorimeter (DSC), compressive modulus testing, atomic force microscopy (AFM) indentation, and swelling measurements. In contrast to homogeneous TEPs networks, the resultant gradient polymer shows a broader effective damping temperature range combining with good mechanical properties. The present result provides an effective route toward high damping materials by the fabrication of gradient structures. PMID:26776353

  20. Open Clusters as Tracers of the Galactic Disk

    NASA Astrophysics Data System (ADS)

    Cantat-Gaudin, Tristan

    2015-01-01

    for star formation mechanisms. * the study of the OCs can shed light on the disk properties, in particular on the presence of a chemical gradient. Studying the distribution of chemical elements across the Galactic disk has been a central question in astronomy for the past decade. The exact shape of this metallicity gradient, revealed by various tracers such as Cepheids, Planetary Nebulae or HII regions is not quite clear. OCs suggest a flattening of the gradient in the outer disk. Here I will investigate the issue using the GES data set. Methods: The data analysis of the GES is a complex task carried out by different groups. When dealing with a huge quantity of astronomical data, it is essential to have tools that economically process large amounts of information and produce repeatable results. As part of the GES I developed an automated tool to measure the EWs in spectra of FGK stars in a fully automatic way. This tool, called DAOSPEC Option Optimizer pipeline (DOOp), uses DAOSPEC and optimizes its key parameters in order to make the measurements as robust as possible. This tool was widely tested on synthetic and observational spectra. Stellar parameters and elemental abundances are derived with the code FAMA developed with the aim of dealing with large batches of stars. FAMA uses the widely used software MOOG and optimizes stellar parameters in order to satisfy the excitation and ionization balance, following the classical equivalent width procedure. The construction of a metallicity scale, based on high-quality spectra of benchmark stars is fundamental to interpret the spectroscopic results in the context of the Galaxy formation and evolution. We take advantage of the variety of analysis methods represented within the GES collaboration, including DOOp + FAMA in order to produce a homogeneous metallicity scale. Those reference stars can be used to assess the precision and accuracy of a given method. Results: Using archival photometric data, I presents an in

  1. Petroleum characterization by perfluorocarbon tracers

    SciTech Connect

    Senum, G.I.; Fajer, R.W. ); Harris, B.R. Jr. ); DeRose, W.E. ); Ottaviani, W.L. )

    1992-02-01

    Perfluorocarbon tracers (PFTs), a class of six compounds, were used to help characterize the Shallow Oil Zone (SOZ) reservoir at the Naval Petroleum Reserve in California (NPRC) at Elk Hills. The SOZ reservoir is undergoing a pilot gas injection program to assess the technical feasibility and economic viability of injecting gas into the SOZ for improved oil recovery. PFTs were utilized in the pilot gas injection to qualitatively assess the extent of the pilot gas injection so as to determine the degree of gas containment within the SOZ reservoir.

  2. Tracer transport in a distributed water and energy balance model: concept and first results for Berchtesgadener Land

    NASA Astrophysics Data System (ADS)

    Marshall, Florian; Kunstmann, Harald

    2015-04-01

    We present first results of the new model extension GEOtop-iso, where we extend the hydrological model GEOtop with a tracer module for the calculation of transport and fractionation of stable water isotopes, in order to develop a better understanding of the overlapping hydrological processes, like precipitation, evapotranspiration and snow melt. GEOtop is a physically based, spacial distributed hydrological model, which combines water and energy balance. The water balance is computed for channels, surface and subsurface, whereas the subsurface is treated with a 3-dimensional, integral form of the Richards equation for saturated and unsaturated condisions with an implicit time discretion sceme. Moreover, the energy balance is also taking into account processes with strong influence on the water budget, such as evapotranspiration, soil freezing and snow melt. This makes the model suitable especially for complex mountain regions. Stable water isotopes carry information about origin and evolution of the water, which makes them to an ideal tracer used in hydrology and meteorology. In this study they are used to distinguish direct discharge response to precipitation and indirect discharge reponse to other processes like snow and glacier melt in spring. A first evaluation of the isotope modul with artificial test cases has shown a reasonable conservation of the mass of the tracers. Furthermore, we apply GEOtop-iso to the catchment of the river Hinterseeau within the National Park Berchtesgadener Land located in South-East of Germany, since this domain is well monitored with meteorological and hydrological observation stations, including measurements of stable water isotopes, as well it has strong elevation gradients. The catchment is convenient for further model evaluation.

  3. Effects of submesoscale turbulence on ocean tracers

    NASA Astrophysics Data System (ADS)

    Smith, Katherine M.; Hamlington, Peter E.; Fox-Kemper, Baylor

    2016-01-01

    Ocean tracers such as carbon dioxide, nutrients, plankton, and oil advect, diffuse, and react primarily in the oceanic mixed layer where air-sea gas exchange occurs and light is plentiful for photosynthesis. There can be substantial heterogeneity in the spatial distributions of these tracers due to turbulent stirring, particularly in the submesoscale range where partly geostrophic fronts and eddies and small-scale three-dimensional turbulence are simultaneously active. In this study, a large eddy simulation spanning horizontal scales from 20 km down to 5 m is used to examine the effects of multiscale turbulent mixing on nonreactive passive ocean tracers from interior and sea-surface sources. The simulation includes the effects of both wave-driven Langmuir turbulence and submesoscale eddies, and tracers with different initial and boundary conditions are examined in order to understand the respective impacts of small-scale and submesoscale motions on tracer transport. Tracer properties are characterized using spatial fields and statistics, multiscale fluxes, and spectra, and the results detail how tracer mixing depends on air-sea tracer flux rate, tracer release depth, and flow regime. Although vertical fluxes of buoyancy by submesoscale eddies compete with mixing by Langmuir turbulence, vertical fluxes of tracers are often dominated by Langmuir turbulence, particularly for tracers that are released near the mixed-layer base or that dissolve rapidly through the surface, even in regions with pronounced submesoscale activity. Early in the evolution of some tracers, negative eddy diffusivities occur co-located with regions of negative potential vorticity, suggesting that symmetric instabilities or other submesoscale phenomenon may act to oppose turbulent mixing.

  4. Streamer-induced transport in electron temperature gradient turbulence

    SciTech Connect

    Hauff, T.; Jenko, F.

    2009-10-15

    The question if and how streamers (i.e., radially elongated vortices) can lead to an enhancement of the electron heat transport in electron temperature gradient turbulence is addressed. To this aim, the electrons are treated as passive tracers, and their decorrelation mechanisms with respect to the advecting electrostatic potential are studied. A substantial transport enhancement is found in a wide region of parameter space.

  5. The fluorescent tracer experiment on Holiday Beach near Mugu Canyon, Southern California

    USGS Publications Warehouse

    Kinsman, Nicole; Xu, J. P.

    2012-01-01

    After revisiting sand tracer techniques originally developed in the 1960s, a range of fluorescent coating formulations were tested in the laboratory. Explicit steps are presented for the preparation of the formulation evaluated to have superior attributes, a thermoplastic pigment/dye in a colloidal mixture with a vinyl chloride/vinyl acetate copolymer. In September 2010, 0.59 cubic meters of fluorescent tracer material was injected into the littoral zone about 4 kilometers upcoast of Mugu submarine canyon in California. The movement of tracer was monitored in three dimensions over the course of 4 days using manual and automated techniques. Detailed observations of the tracer's behavior in the coastal zone indicate that this tracer successfully mimicked the native beach sand and similar methods could be used to validate models of tracer movement in this type of environment. Recommendations including how to time successful tracer studies and how to scale the field of view of automated camera systems are presented along with the advantages and disadvantages of the described tracer methodology.

  6. Characterization of regional transport and dispersion using Project MOHAVE tracer data.

    PubMed

    Pitchford, M; Green, M; Kuhns, H; Farber, R J

    2000-05-01

    Perfluorocarbon tracers were released continuously from several surface locations and one power plant stack location during the winter (30 days) and summer (50 days) intensive studies as part of Project MOHAVE. Tracers were released in winter from the Mohave Power Plant (MPP) and Dangling Rope, UT, located on the shore of Lake Powell near Page, AZ; and in summer from MPP, the Tehachapi Pass between the Mojave Desert and the Central Valley in California, and El Centro, CA, on the California-Mexico border. At the Tehachapi tracer release site six-hour pulses of a separately identifiable perfluorocarbon tracer were released every four days in order to assess the time for the tracer to clear the monitoring network. Daily 24-hr integrated samples were collected at about 30 sites in four states. Limited tracer concentration data with higher time resolution is also available. Graphical displays and analyses identify several regional transport paths, including a convergence zone in the Mojave Desert, the importance of terrain channeling, especially in winter, and a relationship between 24-hr maximum influence function and distance that may prove useful as a scoping tool and to test regional scale air quality models. In winter, Dangling Rope tracer was routinely transported through the entire length of the Grand Canyon, while in summer, MPP tracer was routinely transported over most of Lake Mead. PMID:10842938

  7. Temperature As Tracer of the Groundwater Circulation within a Complex Volcano-Detritic System

    NASA Astrophysics Data System (ADS)

    Selles, A.; Violette, S.; Goblet, P.; Hendrayana, H.

    2014-12-01

    The understanding of groundwater circulations into a volcano-detritic edifice is difficult because of the heterogeneous geological formations and the alternating construction and dismantling phases. In Indonesia, most of the groundwater resources are located into these complex volcanic systems. Furthermore, over the world this kind of context is poorly documented. In this study, we used a multi-disciplinary method based on field observations at watershed scale (geology, geomorphology, pumping tests, physico-chemical monthly monitoring over two hydrological years, etc.) and water stable isotope analysis to built a conceptual model of the hydrogeological behaviour of the Merapi volcano located in Central Java. Temperature appears to be a relevant tracer of local and regional groundwater circulations. A numerical model (METIS code) was used to verify the hydrogeological conceptual model. The steady state flow simulations were constrained first by isotope ratios (δ18O) dispersion transport and then by heat dispersion transfer in 2D vertical cross section. The heat spatial distribution and especially the "spring temperature anomaly" have been reproduced. The numerical code allowed us to describe the relation between the geothermal gradient and the relatively cold groundwater circulations provide by the high elevation recharge. Therefore, the results of this study highlight that water temperature offers several advantages as a tracer of groundwater circulations because it is easy, quick, and inexpensive to measure accurately in the field even in volcanic systems under tropical conditions. We show also that a simple but relatively accurate numerical modelling can be achieved when it is constrained by multi-disciplinary study results.

  8. Ammonium transport and reaction in contaminated groundwater: Application of isotope tracers and isotope fractionation studies

    USGS Publications Warehouse

    Böhlke, J.K.; Smith, R.L.; Miller, D.N.

    2006-01-01

    Ammonium (NH4+) is a major constituent of many contaminated groundwaters, but its movement through aquifers is complex and poorly documented. In this study, processes affecting NH4+ movement in a treated wastewater plume were studied by a combination of techniques including large-scale monitoring of NH4+ distribution; isotopic analyses of coexisting aqueous NH4+, NO3-, N2, and sorbed NH 4+; and in situ natural gradient 15NH 4+ tracer tests with numerical simulations of 15NH4+, 15NO3-, and 15N2 breakthrough data. Combined results indicate that the main mass of NH4+ was moving downgradient at a rate about 0.25 times the groundwater velocity. Retardation factors and groundwater ages indicate that much of the NH4+ in the plume was recharged early in the history of the wastewater disposal. NO3- and excess N2 gas, which were related to each other by denitrification near the plume source, were moving downgradient more rapidly and were largely unrelated to coexisting NH 4+. The ??15N data indicate areas of the plume affected by nitrification (substantial isotope fractionation) and sorption (no isotope fractionation). There was no conclusive evidence for NH 4+-consuming reactions (nitrification or anammox) in the anoxic core of the plume. Nitrification occurred along the upper boundary of the plume but was limited by a low rate of transverse dispersive mixing of wastewater NH4+ and O2 from overlying uncontaminated groundwater. Without induced vertical mixing or displacement of plume water with oxic groundwater from upgradient sources, the main mass of NH4+ could reach a discharge area without substantial reaction long after the more mobile wastewater constituents are gone. Multiple approaches including in situ isotopic tracers and fractionation studies provided critical information about processes affecting NH4+ movement and N speciation.

  9. Balloon tracer for atmospheric pollutants

    SciTech Connect

    Lichfield, E.W.; Ivey, M.D.; Zak, B.D.; Church, H.W.

    1985-01-01

    An operational prototype of the Balloon Tracer was developed and described. This prototype was designed to be capable of meeting all of the desired specifications for the Balloon Tracer. Its buoyancy adjustment subsystem is shown. Three Gilian instrument pumps operating in parallel provide a flow of about 12 litres per minute, depending upon backpressure. The miniature Klippard mechanical valves are actuated by a servo mechanism which only requires power when the state of the valves is being changed. The balloon itself for the operational prototype is just under 3 meters in diameter. A block diagram of the operational prototype payload measures ambient pressure, temperature, and humidity obtained from AIR which outputs its data in ASCII format. The vertical anemometer, which has a measured starting speed of under 2 cm/s, makes use of a Gill styrofoam propeller and a Spaulding Instruments rotation sendor. The command decoder is built around a chip developed originally for remote control television tuners. The command receiver operating on 13.8035 MHz was developed and built by Hock Engineering. The Argos transmitter is a Telonics platform transmitter terminal. The heart of the control system is an Intel 8052AH BASIC microcomputer with both random access and read only memory.

  10. Natural iodine-129 as an environmental tracer

    NASA Astrophysics Data System (ADS)

    Fabryka-Martin, J.; Bentley, H.; Elmore, D.; Airey, P. L.

    1985-02-01

    Iodine-129 ( t 1/2, 16 My) is a naturally-occurring tracer which can be used to study hydrologic and geologic processes on time scales up to 100 My. The pre-bomb atmospheric ratio 129I /I should have been constant in time and space and is the starting value in ground-water recharge. Subsequent ratio changes in ground water should be determined by isotope contributions from three sources: recharge water, iodine leached from the formation, and in situ uranium fission. The mathematical expression of these time-dependent processes forms the basis for dating and tracing applications. The expected behavior of natural 129I in ground water is compared to results from field studies. Ground-water samples from the Great Artesian Basin, Australia, provide an estimate of the atmospheric equilibrium ratio, 6 × 10 -13. Down-gradient changes in water up to 1 My old suggest that subsurface production can be significant. The usefulness of 129I as an indicator of brine source and age is verified in brines collected in and around Louisiana salt domes. The method leads to ages of 7 and 9 My for two brine pockets trapped within Jurassic salt, and 32 to >40 My for oil-field brines in Miocene sands adjacent to the domes. The results demonstrate the capability of tandem accelerator mass spectrometry to measure as few as 10 7 atoms of 129I in 10 mg I with 10% precision. Although such atom sensitivity can be achieved otherwise, the accelerator technique is necessary to measure naturally low pre-1945 cosmogenic isotope ratios.

  11. Cardiac PET perfusion tracers: current status and future directions.

    PubMed

    Maddahi, Jamshid; Packard, René R S

    2014-09-01

    PET myocardial perfusion imaging (MPI) is increasingly being used for noninvasive detection and evaluation of coronary artery disease. However, the widespread use of PET MPI has been limited by the shortcomings of the current PET perfusion tracers. The availability of these tracers is limited by the need for an onsite ((15)O water and (13)N ammonia) or nearby ((13)N ammonia) cyclotron or commitment to costly generators ((82)Rb). Owing to the short half-lives, such as 76 seconds for (82)Rb, 2.06 minutes for (15)O water, and 9.96 minutes for (13)N ammonia, their use in conjunction with treadmill exercise stress testing is either not possible ((82)Rb and (15)O water) or not practical ((13)N ammonia). Furthermore, the long positron range of (82)Rb makes image resolution suboptimal and its low myocardial extraction limits its defect resolution. In recent years, development of an (18)F-labeled PET perfusion tracer has gathered considerable interest. The longer half-life of (18)F (109 minutes) would make the tracer available as a unit dose from regional cyclotrons and allow use in conjunction with treadmill exercise testing. Furthermore, the short positron range of (18)F would result in better image resolution. Flurpiridaz F 18 is by far the most thoroughly studied in animal models and is the only (18)F-based PET MPI radiotracer currently undergoing clinical evaluation. Preclinical and clinical experience with Flurpiridaz F 18 demonstrated a high myocardial extraction fraction, high image and defect resolution, high myocardial uptake, slow myocardial clearance, and high myocardial-to-background contrast that was stable over time-important properties of an ideal PET MPI radiotracer. Preclinical data from other (18)F-labeled myocardial perfusion tracers are encouraging. PMID:25234078

  12. Cardiac PET Perfusion Tracers: Current Status and Future Directions

    PubMed Central

    Maddahi, Jamshid; Packard, René R. S.

    2015-01-01

    Positron emission tomography (PET) myocardial perfusion imaging (MPI) is increasingly used for non-invasive detection and evaluation of coronary artery disease (CAD). However, the widespread use of PET MPI has been limited by shortcomings of the current PET perfusion tracers. Availability of these tracers is limited by need for an on-site (15O water and 13N ammonia) or nearby (13N ammonia) cyclotron or commitment to costly generators (82Rb). Due to short half-lives ranging from 76sec for 82Rb, to 2.1min for 15O water and 10min for 13N ammonia, their use in conjunction with treadmill exercise stress testing is either not possible (82Rb and 15O water) or is not practical (13N ammonia). Furthermore, the long positron range of 82Rb makes image resolution suboptimal and its low extraction limits its defect resolution. In recent years, development of an 18F labeled PET perfusion tracer has gathered considerable interest. The longer half-life of 18F (108 minutes) would make the tracer available as a unit dose from regional cyclotrons and allow use in conjunction with treadmill exercise testing. Furthermore, the short positron range of 18F would result in better image resolution. 18F flurpiridaz is by far the most thoroughly studied in animal models, and is the only F18-based PET MPI radiotracer currently undergoing clinical evaluation. Pre-clinical and clinical experience with 18F flurpiridaz demonstrated a high myocardial extraction fraction, high image and defect resolution, high myocardial uptake, slow myocardial clearance, and high myocardial-to-background contrast which was stable over time – important properties of an ideal PET MPI radiotracer. Pre-clinical data from other 18F labeled myocardial perfusion tracers are encouraging. PMID:25234078

  13. Unit vent airflow measurements using a tracer gas technique

    SciTech Connect

    Adams, D.G.; Lagus, P.L.; Fleming, K.M.

    1997-08-01

    An alternative method for assessing flowrates that does not depend on point measurements of air flow velocity is the constant tracer injection technique. In this method one injects a tracer gas at a constant rate into a duct and measures the resulting concentration downstream of the injection point. A simple equation derived from the conservation of mass allows calculation of the flowrate at the point of injection. Flowrate data obtained using both a pitot tube and a flow measuring station were compared with tracer gas flowrate measurements in the unit vent duct at the Callaway Nuclear Station during late 1995 and early 1996. These data are presented and discussed with an eye toward obtaining precise flowrate data for release rate calculations. The advantages and disadvantages of the technique are also described. In those test situations for which many flowrate combinations are required, or in large area ducts, a tracer flowrate determination requires fewer man-hours than does a conventional traverse-based technique and does not require knowledge of the duct area. 6 refs., 10 figs., 6 tabs.

  14. Preparation of intravenous cholesterol tracer using current good manufacturing practices.

    PubMed

    Lin, Xiaobo; Ma, Lina; Racette, Susan B; Swaney, William P; Ostlund, Richard E

    2015-12-01

    Studies of human reverse cholesterol transport require intravenous infusion of cholesterol tracers. Because insoluble lipids may pose risk and because it is desirable to have consistent doses of defined composition available over many months, we investigated the manufacture of cholesterol tracer under current good manufacturing practice (CGMP) conditions appropriate for phase 1 investigation. Cholesterol tracer was prepared by sterile admixture of unlabeled cholesterol or cholesterol-d7 in ethanol with 20% Intralipid(®). The resulting material was filtered through a 1.2 micron particulate filter, stored at 4°C, and tested at time 0, 1.5, 3, 6, and 9 months for sterility, pyrogenicity, autoxidation, and particle size and aggregation. The limiting factor for stability was a rise in thiobarbituric acid-reacting substances of 9.6-fold over 9 months (P < 0.01). The emulsion was stable with the Z-average intensity-weighted mean droplet diameter remaining at 60 nm over 23 months. The zeta potential (a measure of negative surface charge protecting from aggregation) was unchanged at -36.2. Rapid cholesterol pool size was 25.3 ± 1.3 g. Intravenous cholesterol tracer was stable at 4°C for 9 months postproduction. CGMP manufacturing methods can be achieved in the academic setting and need to be considered for critical components of future metabolic studies. PMID:26416797

  15. Noninvasive Imaging of Tracer Experiments in a Soil Column

    NASA Astrophysics Data System (ADS)

    Jelinkova, V.; Pohlmeier, A.; van Dusschoten, D.; Vereecken, H.; Cislerova, M.

    2008-12-01

    A set of tracer-infiltration experiments on soil columns by means of magnetic resonance imaging (MRI) was performed. Computed tomography (CT) was applied in order to map the spatial distribution of porous media, namely the local densities and porosities, and their variation within the soil sample under test. The CT visualisation was done in order to trace disturbances in the structure as a possible source of preferential flow. By means of MRI the flow paths during the infiltration experiment were visualized using a tracer pulse containing Ni(NO3)2 in a concentration of 0.05 mol/litre. The pulse was added under hydraulic steady state conditions. The tracer motion was monitored through its effect on the signal relaxation of 1H using a 7 Tesla vertical magnet system equipped with a 40 mm RF probe. The boundary condition at the top of the soil columns was maintained using a dripping system connected to a HPLC pump with flow rate set to 0.5 ml/min. Free outflow was used as the bottom boundary condition. The vertical component of the local velocity value was calculated after the experiment. Small disturbances in the tracer front observed during the break-through could be related to the preferential flow phenomena in combination with the air bubble entrapment. This research has been supported by research project SP/2e7/229/07 and DBU - Deutsche Bundesstiftung Umwelt.

  16. Quantification of hyporheic exchange using conservative and reactive tracers

    NASA Astrophysics Data System (ADS)

    Lemke, D.; Liao, Z.; Cirpka, O. A.; Osenbrück, K.

    2012-04-01

    The transition zone between groundwater and surface water is commonly referred to as the hyporheic zone. In the so-called hyporheic exchange river water penetrates into the subsurface, remains there for a certain time, and then returns into the active water channel at a location further downstream. Hence, solutes enter the sediment where they can potentially be retained or degraded so that the hyporheic exchange is of particular importance for the prediction of reactive solute transport in rivers. In the past, tracer experiments where a conservative tracer is added into the river and measured further downstream were used to characterize hyporheic exchange. The problem is that the hyporheic exchange has similar effects on the measured tracer breakthrough curves than mixing processes in the river itself (e.g. dispersion). In order to separate these processes, we carried out tracer tests where the compound resazurin was used as a reactive tracer in addition to a conservative tracer (uranine). Resazurin degrades selectively and irreversibly in the hyporheic zone and thus provides additional information specifically on the hyporheic exchange. We performed a total of five tracer tests at two different tributaries of the river Neckar (Goldersbach