ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Electronic Resource

Trichlorofluoroethene: A reactive tracer for evaluating reductive dechlorination in large-diameter permeable columns (2005)

Field, Jennifer A. ; Reed, Ralph L. ; Istok, Jonathan D. ; [et al.]

Oxford, UK; Malden, USA : Blackwell Science Inc

Ground water monitoring & remediation 25 (2005), S. 0

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ISSN: 1745-6592

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences

Notes: Trichlorofluoroethene (TCFE) was used as a reactive tracer to determine the in situ rate of reductive dechlorination in treatment zones impacted by three large-diameter permeable columns (LDPCs) that were installed at a trichloroethene (TCE)–contaminated site. The LDPCs were part of a pilot study to evaluate the effectiveness of hydrogen, lactate, and zero-valent iron for remediating TCE-contaminated ground water. The rate of TCFE reductive dechlorination was determined for each LDPC by means of push-pull tests conducted in each treatment layer. In addition, the distribution of TCFE's lesser chlorinated transformation products was determined. The rates of TCFE reductive dechlorination ranged from 0.05/d to 0.20/d and corresponded to half-lives ranging from 3.5 to 13.9 d. cis-Dichlorofluoroethene was the dominant transformation product detected in all the tests, which is consistent with the findings from pilot tests conducted in the LDPCs prior to the TCFE push-pull tests. cis-Chlorofluoroethene (CFE) and 1,1-CFE also were detected and indicate the potential for vinyl chloride to form under all treatment regimes. Significant production of fluoroethene (FE), the analog of ethene, was observed for only one of the hydrogen treatments. Unambiguous and sensitive detection of the lesser chlorinated products, such as CFE and FE, is possible because TCFE and its transformation products are not found in the background ground water at contaminated sites. Good agreement between the rates and transformation product profiles for TCFE and TCE in both field and laboratory experiments indicates the suitability of TCFE as a surrogate for predicting the rates of TCE reductive dechlorination.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1745-6592.2005.0016.x

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2

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Approximate solution for solute transport during spherical-flow push-pull tests (2005)

Schroth, Martin H. ; Istok, Jonathan D.

Oxford, UK; Malden, USA : Blackwell Science Inc

Ground water 43 (2005), S. 0

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ISSN: 1745-6584

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences

Notes: An approximate analytical solution to the advection-dispersion equation was derived to describe solute transport during spherical-flow conditions in single-well push-pull tests. The spherical-flow case may be applicable to aquifer tests conducted in packed intervals or partially penetrating wells. Using results of two-dimensional numerical simulations, we briefly illustrate the applicability of the derived spherical-flow solution and provide a comparison with its cylindrical-flow counterpart. Good agreement between simulated extraction-phase breakthrough curves and the spherical-flow solution was found when the length of the injection/extraction region was small compared to both aquifer thickness and maximum solute frontal position at the end of the injection phase. On the other hand, discrepancies between simulated breakthrough curves and the spherical-flow solution increased with increasing anisotropy in hydraulic conductivities. Several inherent limitations embedded in its derivation such as assumptions of isotropy and homogeneity warrant the cautious use of the spherical-flow solution.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1745-6584.2005.0002.x

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3

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Push-Pull Tests for Assessing In Situ Aerobic Cometabolism (2004)

Kim, Young ; Istok, Jonathan D. ; Semprini, Lewis

Oxford, UK : Blackwell Publishing Ltd

Ground water 42 (2004), S. 0

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ISSN: 1745-6584

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences

Notes: Three types of single-well push-pull tests were developed for use in assessing the feasibility of in situ aerobic cometabolism of chlorinated aliphatic hydrocarbons (CAHs). These included transport tests, biostimulation tests, and activity tests. Transport tests are conducted to evaluate the mobility of solutes used in subsequent tests. These included bromide or chloride (conservative tracers), propane (growth substrate), ethylene, propylene (CAH surrogates), dissolved oxygen (electron acceptor), and nitrate (a minor nutrient). Tests were conducted at an experimental wellfield of Oregon State University. At this site, extraction phase breakthrough curves for all solutes were similar, indicating apparent conservative transport of the dissolved gases and nitrate prior to biostimulation. Biostimulation tests were conducted to stimulate propane-utilizing activity of indigenous microorganisms and consisted of sequential injections of site ground water containing dissolved propane and oxygen. Biostimulation was detected by the increase in rates of propane and oxygen utilization after each injection. Activity tests were conducted to quantify rates of substrate utilization and to confirm that CAH-transforming activity had likely been stimulated. In particular, the transformation of injected CAH surrogates ethylene and propylene to the cometabolic byproducts ethylene oxide and propylene oxide provided evidence that activity of the monooxygenase enzyme system, responsible for aerobic cometabolic transformations of CAHs, had likely also been stimulated. Estimated zero-order transformation rates decreased in the order propane 〉 ethylene 〉 propylene. The series of push-pull tests developed and field tested in this study should prove useful for conducting rapid, low-cost feasibility assessments for in situ aerobic cometabolism of CAHs.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1745-6584.2004.tb02681.x

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4

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Multivariate Geostatistïcal Analysis of Ground-Water Contamination: A Case History (1993)

Istok, Jonathan D. ; Smyth, Jeffrey D. ; Flint, Alan L.

Oxford, UK : Blackwell Publishing Ltd

Ground water 31 (1993), S. 0

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ISSN: 1745-6584

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences

Notes: A case history is presented for the application of multivariate geostatistical methods to the problem of estimating pesticide concentrations in ground water from measured concentrations of nitrate and pesticide, when pesticide is under-sampled. The shallow, poorly confined, sand and gravel aquifer underlying the lower Malheur River basin near Ontario, Oregon is contaminated by nitrate and metabolites of the herbicide Dacthal (dimethyl tetrachloroterephthalate) or DCPA. The results of extensive ground-water sampling indicate that a significant positive correlation exists between measured nitrate and DCPA concentrations in the aquifer. This suggests that future sampling should include a large number of the less-expensive nitrate analyses, and these data should be used to support the interpretation of fewer, more expensive DCPA analyses. Sample variograms were computed for nitrate and DCPA concentrations and were fit with isotropic, spherical variogram models with correlation ranges of 4 km. Incorporating measured nitrate concentrations in the DCPA estimates obtained by cokriging reduced estimation variances from 14 to 34%. A simple economic analysis demonstrated that for this aquifer, acquiring additional nitrate samples is a cost-effective way to reduce estimation variances for DCPA.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1745-6584.1993.tb00829.x

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5

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Probabilistic Assessment of Ground-Water Contamination: 1. Geostatistical Framework (1996)

Rautman, Christopher A. ; Istok, Jonathan D.

Oxford, UK : Blackwell Publishing Ltd

Ground water 34 (1996), S. 0

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ISSN: 1745-6584

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences

Notes: Characterizing the extent and severity of ground-water contamination at waste sites is expensive and time-consuming. A probabilistic approach, based on the acceptance of uncertainty and a finite probability of making classification errors (contaminated relative to a regulatory threshold vs. uncontaminated), is presented as an alternative to traditional site characterization methodology. The approach utilizes geostatistical techniques to identify and model the spatial continuity of contamination at a site (variography) and to develop alternate plausible simulations of contamination fields (conditional simulation). Probabilistic summaries of many simulations provide tools for (a) estimating the range of plausible contaminant concentrations at unsampled locations, (b) identifying the locations of boundaries between contaminated and uncontaminated portions of the site and the degree of certainty in those locations, and (c) estimating the range of plausible values for total contaminant mass. The first paper in the series presents the geostatistical framework and illustrates the approach using synthetic data for a hypothetical site. The second paper presents an application of the proposed methodology to the probabilistic assessment of ground-water contamination at a site involving ground-water contamination by nitrate and herbicide in a shallow, unconfined alluvial aquifer in an agricultural area in eastern Oregon.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1745-6584.1996.tb02084.x

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6

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Probabilistic Assessment of Ground-Water Contamination: 2. Results of Case Study (1996)

Istok, Jonathan D. ; Rautman, Christopher A.

Oxford, UK : Blackwell Publishing Ltd

Ground water 34 (1996), S. 0

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ISSN: 1745-6584

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences

Notes: The first paper in this series (Rautman and Istok, 1996) presented a geostatistical framework for obtaining a probabilistic assessment of ground-water contamination. This paper presents the results of a case study that applies this framework to define the spatial extent and severity of nitrate and Dacthal (dimethyl tetrachloroterephthalate or DCPA, a herbicide) contamination in the unsaturated and saturated zones for a 150 km2 site near Ontario, Oregon. Sediment samples collected from 35 boreholes were used to compute vertical accumulations of nitrate and DCPA in the unsaturated zone. Measured nitrate and DCPA concentrations in ground-water samples collected from 42 wells were used to compute vertical accumulations of nitrate and DCPA in the saturated zone. Sample variograms were fit with nugget and spherical models to describe the pattern of spatial continuity of nitrate and DCPA concentrations and accumulations. Conditional, sequential Gaussian simulation was used to generate 100 simulations for each variable on a 0.5 × 0.5 km grid. Probabilistic summaries of these simulations were used to develop (a) maps showing the probability of contamination exceeding specified theshold values, (b) probability distributions for contaminant accumulation and concentration at unsampled locations, (c) probabilistic descriptions for the location of contaminant-plume boundaries, and (d) probability distributions for the total contaminated area and total contaminant mass. The results demonstrate that interpretations of site characterization data to determine the extent and magnitude of contamination at a site will vary depending upon the level of uncertainty that will be tolerated by the decision maker. This case study also illustrates the potential applicability and utility of the probabilistic approach for the interpretation of site characterization data and the design of future data collection activities.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1745-6584.1996.tb02171.x

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7

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Effect of Trapped Gas on Dissolved Oxygen Transport — Implications for In Situ Bioremediation (1996)

Fry, Virginia A. ; Istok, Jonathan D. ; O'Reilly, Kirk T.

Oxford, UK : Blackwell Publishing Ltd

Ground water 34 (1996), S. 0

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ISSN: 1745-6584

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences

Notes: In situ bioremediation of contaminated aquifers is often limited by the concentration of dissolved oxygen in the ground water. Various methods have been used to increase dissolved oxygen concentrations in ground water, but the effect of a trapped gas phase on the distribution and transport of dissolved oxygen needs to be understood. The two-dimensional transport of dissolved oxygen is investigated in experiments conducted in a large-scale physical aquifer model (2 m × 4 m × 0.2 m) where a gas phase is trapped in the pore spaces of an otherwise-saturated porous medium. The transport of dissolved oxygen is shown to be retarded up to 11.2 times the transport of the bulk water due to the mass transfer of oxygen between the aqueous phase and the trapped gas phase. The theoretical model for dissolved gas transport in the presence of a trapped gas phase is evaluated in a two-dimensional ground-water flow field using the U.S.G.S. numerical model MOC. The results show that dissolved oxygen transport can be modeled with the advection-dispersion equation with linear equilibrium mass transfer but only when the longitudinal dispersion is increased compared to the value determined using a bromide tracer of the water flow. Increased longitudinal dispersion of the dissolved oxygen plume may be due to a temporally or spatially varying retardation factor or rate-limited mass transfer. The presence of even a small amount of a trapped gas phase in an aquifer will significantly affect the distribution and transport of dissolved oxygen (trapped gas filling only 5% of the pore space will cause a retardation factor for oxygen of 2.6 at T = 15°C) and thus should be considered when designing ways to increase the dissolved oxygen concentration in ground water for in situ bioremediation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1745-6584.1996.tb01880.x

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8

Electronic Resource

Laboratory Investigation of Buoyancy-Induced Flow (Plume Sinking) During Two-Well Tracer Tests (1995)

Istok, Jonathan D. ; Humphrey, Mark D.

Oxford, UK : Blackwell Publishing Ltd

Ground water 33 (1995), S. 0

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ISSN: 1745-6584

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences

Notes: The occurrence of buoyancy-induced vertical flow (sinking) of a bromide (Br−) tracer plume at small injection concentrations is investigated in transport experiments conducted in a large-scale physical aquifer model containing a homogeneous and isotropic sand pack. Two-well tracer tests are conducted using Br− at concentrations ranging from 50 to 1000 mg/1, corresponding to relative densities between 7.5 × 10−5 and 1.5 × 10−3. Analysis of three-dimensional solute concentration data indicates that the center of mass of the Br− plume was displaced downward as the denser tracer solution sank through the sand pack. Plume sinking occurred at all solute concentrations investigated; the magnitude of the vertical displacement increased with increasing Br− concentration of the injected tracer solution. The dynamic collapse of the Br−plume caused by buoyancy forces resulted in increased apparent transverse and longitudinal dispersivities. The results suggest that the possibility of buoyancy-induced flow must be considered when interpreting tracer tests conducted with anion concentrations as low as 50 mg/1. The occurrence of buoyancy-induced flows at such low relative densities also suggest that the phenomenon may be more widespread than is generally recognized.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1745-6584.1995.tb00315.x

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9

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Retardation of Dissolved Oxygen Due to a Trapped Gas Phase in Porous Media (1995)

Fry, Virginia A. ; Istok, Jonathan D. ; Semprini, Lewis ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Ground water 33 (1995), S. 0

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ISSN: 1745-6584

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences

Notes: Information on the transport of dissolved gases in ground water is needed to design ways to increase dissolved gas concentrations in ground water for use in in situ bioremediation (e.g., O2 and CH4) and to determine if dissolved gases are conservative tracers of ground-water flow (e.g., He). A theoretical model was developed to describe the effect of small quantities of trapped gas bubbles on the transport of dissolved gases in otherwise saturated porous media. Dissolved gas transport in porous media can be retarded by gas partitioning between the mobile aqueous phase and a stationary trapped gas phase. The model assumes equilibrium partitioning where the retardation factor is defined as R = 1 + H′(Vg/Vw) where H' is the dimensionless Henry's Law constant for the dissolved gas, and Vg and Vw are the volumes of the trapped gas and water phases, respectively. At 15°C and with Vg/ Vw= 0.05, the predicted retardation factors for He, O2, and CH4 are 5.8, 2.4, and 2.3, respectively. The validity of the model was tested for dissolved oxygen in small-scale column experiments over a range of trapped gas volumes. Retardation factors of dissolved oxygen increased from 1 to 6.6 as Vg/Vw increased from 0 to 0.123 and are in general agreement with model predictions except for the larger values of Vg/Vw. The theoretical and experimental results suggest that gas partitioning between the aqueous phase and a trapped gas phase can greatly influence rates of dissolved gas transport in ground water.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1745-6584.1995.tb00295.x

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