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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. 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.

  1. 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

  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. 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.

  7. 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).

  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

    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.

  20. 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

  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

    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.

  8. 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

  9. 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.

  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. 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

  17. 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

  18. 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

  19. 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.

  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. 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

  5. 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

  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.