bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Ground‐Water Tracer Test with Deuterated Compounds for Monitoring In Situ Biodegradation and Retardation of Aromatic Hydrocarbons
Authors: Thierrin Joseph , Davis Gregory B. , Barber Chris 
Published: August 2005

AbstractFully deuterated benzene, toluene, p‐xylene, and naphthalene were used with bromide (inert reference) as ground‐water and pollutant tracers inside a BTEX contaminated plume of anoxic ground water in the Swan coastal plain, Western Australia. Besides the determination of local aquifer parameters and retardation coefficients for several organic pollutants within the contaminated site, this natural gradient ground‐water tracer test shows that deuterated organic compounds can be successfully used for in situ determination of natural biodegradation rates of organic pollutants. It suggests that toluene, p‐xylene, and naphthalene, but not benzene, degrade under sulfate‐reducing conditions.
An Adaptive Finite‐Element Model for Calculating Subsurface Transport of Contaminant
Authors: Pepper D. W. , Stephenson D. E. 
Published: August 2005

AbstractA finite‐element method which incorporates mesh adaptation is used to calculate ground‐water flow and pollutant transport. The formulation is based on the equations for conservation of mass, Darcy's law for an anisotropic medium, and the time‐dependent species transport equation. Modifications have been implemented to the finite‐element formulation to enhance computational speed and reduce storage; Petrov‐Galerkin weighting of the advection terms provides numerical stability. An explicit time marching scheme is used to solve the transient equations. By utilizing unstructured adaptive meshing, species concentration and location of steep fronts are accurately resolved, even though one begins with a coarse mesh. The algorithm currently runs on PC and workstation class computers.
Practical Probabilistic Ground‐Water Modeling
Authors: Woodbury Allan , Render Frank , Ulrych Tad 
Published: August 2005

AbstractThe major obstruction to the effective use of probabilistic models is the determination of the statistical properties of unknown model parameters. In this paper we use the principle of minimum relative entropy (MRE) to determine the prior pdf, p(m) of a set of model parameters, (m) based on limited information. The pdf is of the form of a multivariate truncated exponential distribution. In this paper we use p(m) in Monte Carlo simulations to provide expected values in field variables such as drawdowns, pumping rates, and confidence limits. The examples presented illustrate some dangers associated with the practice in probabilistic modeling of assigning Gaussian pdf's as priors. First, such an assumption for the input parameters actually injects more information into the problem than may actually exist, whether consciously or unconsciously. This fact is born out by comparison with minimum relative entropy theory. Second, the output parameters as suggested from the Monte Carlo analysis cannot be assumed to be Gaussian distributed even when the prior pdf is in Gaussian form. In a practical setting, the significance of this result and the approximation of Gaussian form would depend on the cost, risk, and consequences of the decision being made.
Use of Electric Logs to Estimate Water Quality of Pre‐Tertiary Aquifers
Authors: Lindner‐Lunsford J. B. , Bruce Breton W. 
Published: August 2005

AbstractElectric logs provide a means of estimating ground‐water quality in areas where water analyses are not available. Most of the methods for interpreting these logs have been developed for the petroleum industry and are most reliable in saline aquifers (concentration of dissolved solids as sodium chloride greater than about 50,000 mg/l). The resistivity‐porosity and spontaneous‐potential methods were evaluated to determine if they could be applied to identify zones of fresh water (concentration of dissolved solids as sodium chloride less than 1,000 mg/l) in three potential aquifers in central Wyoming. The potential aquifers have different lithologies–sandstone, clayey sandstone, and carbonate. The two methods generally were reliable predictors of water quality in the sandstone and carbonate potential aquifers. In the clayey sandstone potential aquifer, predictions of the dissolved‐solids concentration using the two methods differed by more than an order of magnitude in several cases. When the resistivity values are corrected for the presence of clay and shale as identified on a natural gamma log, the agreement between the results of the two methods improved by an average of 58 percent.
Virus and Bacteria Transport in a Sandy Aquifer, Cape Cod, MA
Authors: Bales Roger C. , Li Shimin , Maguire Kimberly M. , Yahya Moyasar T. , Gerba Charles P. , Harvey Ronald W. 
Published: August 2005

AbstractTransport of the bacteriophage PRD‐1, bacteria, and latex microspheres was studied in a sandy aquifer under natural‐gradient conditions. The field injection was carried out at the U.S. Geological Survey's Toxic Substances Hydrology research site on Cape Cod. The three colloids and a salt tracer (Br−) moved along the same path. There was significant attenuation of the phage, with PRD‐1 peak concentrations less than 0.001 percent of Br− peaks 6 m from the source; but the low detection limit (one per ml) enabled tracking movement of the PRD‐1 plume for 12 m downgradient over the 25‐day experiment. Attenuation of phage was apparently due to retention on soil particles (adsorption). Attenuation of bacteria and microspheres was less, with peak concentrations 6 m from the source on the order of 10 and 0.4 percent of Br−, respectively. Injection of a high‐pH pulse of water 20 days into the experiment resulted in significant remobilization of retained phage, demonstrating that attached phage remained viable, and that PRD‐1 attachment to and detachment from the sandy soil particles was highly pH dependent. Phage behavior in this experiment, i.e. attenuation at pH 5.7 and rapid resuspension at pH 6–8, was consistent with that observed previously in laboratory column studies. Results illustrate that biocolloids travel in a fairly narrow plume in sandy (relatively homogeneous) media, with virus concentrations dropping below detection limit several meters away from the source; bacteria concentrations above detection limits can persist over longer distances.
Estimation of Unsteady, Three‐Dimensional Drawdown in Single, Vertically Heterogeneous Aquifers
Authors: Székely Ferenc 
Published: August 2005

AbstractA quasi, a mixed, and a weighted three‐dimensional model are applied to approximate the three‐dimensional, unsteady drawdown in vertical pumping and observation wells, fully or partially penetrating a single, vertically heterogeneous, anisotropic aquifer. Cases of confined, semiconfined, and unconfined flow conditions are considered. Numerical examples are used to quantify the numerical error of the methods, introduced by the vertical heterogeneity of the aquifer. Results of pumping test data analysis in a three‐layer, anisotropic aquifer with multiple screens in the pumping well are presented.
Applicability of Slug Interference Tests for Hydraulic Characterization of Unconfined Aquifers: (1) Analytical Assessment
Authors: Spane F. A. 
Published: August 2005

AbstractSlug interference responses within unconfined aquifers are characterized by an initial wave or “hump,” which is followed by a flat transitional plateau region and then by a declining, recessional limb segment. The shape and amplitude of the initial wave are primarily controlled by the elastic characteristics (i.e., S) and degree of anisotropy within the aquifer, while transmissivity is the principal parameter affecting the transmission (i.e., arrival time) of the slug interference response. Wellbore storage and delayed‐yield effects tend to attenuate the test response. The transitional and late‐time recessional segments are significantly influenced by the aquifer's specific yield. In addition, test well/aquifer relationships, e.g., observation well distance, aquifer thickness, and well depth/aquifer penetration, also strongly affect slug interference characteristics. The sensitivity of the propagated response to test well/aquifer relationships indicates that slug interference tests can be designed to maximize the expected response for aquifer property characterization.
Trace Element Geochemistry in Water from Selected Springs in Death Valley National Park, California
Authors: Kreamer David K. , Hodge Vernon F. , Rabinowitz Irving , Johannesson Kevin H. , Stetzenbach Klaus J. 
Published: August 2005

AbstractConcentrations of 40 trace elements and other constituents in ground water from springs in Death Valley National Park were measured to investigate whether trace element composition of the ground water can be related to the aquifer materials. Samples from these springs were analyzed by inductively coupled plasma‐mass spectrometry (ICP‐MS) for the trace elements and by ion chromatography (IC) for the major anions. A Principal Component Analysis was performed on the data set. Surprise and Scotty's Springs formed one group; Texas, Nevares, and Travertine Springs formed another group; and Mesquite Springs did not group with any of the others. Scotty's and Surprise Spring issued from volcanic rocks; Texas, Nevares, and Travertine discharge from carbonate rocks; and Mesquite Spring is located in alluvial basin‐fill deposits. The first three components in each Principal Component Analysis accounted for approximately 95% of the variance in the data set. The Principal Component Analysis suggests that ground water inherits its trace element composition from the rocks or aquifer material with which it has interacted and may be used for the purpose of identifying ground‐water movement and source.
Surfactant Solutions Developed for NAPL Recovery in Contaminated Aquifers
Authors: Martel Richard , Gélinas Pierre J. 
Published: August 2005

AbstractPhase diagrams can be used to select surfactant solutions for diesel dissolution and extraction in contaminated aquifers. They indicate the active matter concentrations which can be injected into an aquifer. Due to surfactant precipitation or fine particles dispersion in sediments, surfactant solutions concentration greater than 5% and less than their solubility limit can be used for injections. Surfactant solution effects on interfacial tension (IFT) are consistent with predictions from phase diagrams. For similar active matter concentrations, IFT are lower for surfactant solutions that dissolve more diesel. IFT values between equilibrated diesel and surfactant solutions and observation of the oil‐in‐water microemulsions in column effluents confirm that solubilization of oil can occur in a Winsor type I system without oil mobilization. More than 50 sand column experiments were done for this study and a good agreement is observed between diesel dissolved in sand column experiments (with downward injection) and diesel dissolution predicted from phase diagrams. However, sand columns experiments showed significant decrease in efficiency with a drop in temperature from 25° C to 8° C (phase diagrams predict no change) and they are essential to check efficiencies of washing solution selected by phase diagrams. Optimal injection concentration of solutions decreases as the alcohols ratio (n‐AmOH:n‐BuOH) increases and as the temperature decreases. In columns, optimal concentration of surfactant solutions has a maximum efficiency of 0.4 (dissolved diesel/active matter). This limited performance is explained by: (1) the use of water to push a slug of washing solution creates dilution and thus demixing of the oil‐in‐water microemulsion in the column; (2) the limited interfacial area between diesel and washing solution in the porous media; (3) surface effects on the solid phase. Diesel extraction in sand columns is strongly influenced by the flow direction (up/down), the volume of the solution, and to a lesser extent by water salinity. Small modifications of flow velocity (three times faster) do not have a significant effect on diesel dissolution. Efficiency of diesel dissolution by surfactant solutions decreases as washing progresses because interfacial area (diesel/surfactant solution) decreases. The selection of a surfactant for diesel recovery is not based on efficiency alone but must also consider the costs of the ingredients.
Geophysics and Shallow Faults in Unconsolidated Sediments
Authors: Wyatt Douglass E. , Waddell Michael G. , Sexton G. Boyd 
Published: August 2005

AbstractThis paper presents a case study using various geophysical techniques in unconsolidated sediments where shallow faulting is probable and most likely affects ground‐water flow. Wenner and dipole‐dipole resistivity, ground penetrating radar (GPR), and high resolution reflection seismic data are compared with cone penetrometer (CPT) information, existing monitoring well data and models of anticipated fault styles. The results of this study suggest that (1) the CPT study, combined with monitoring well data may suggest that discontinuities in corrrelatable zones indicate that faulting is present; (2) the addition of Wenner and dipole‐dipole data may further suggest that offset zones exist in the shallow subsurface but make it difficult to map specific faults; (3) the high resolution seismic data will image faults to within a few meters of the surface but cannot identify faulting on the scale of our models; (4) offset 100 MHz and 200 MHz common mid‐point (CMP) GPR will image features that may be fault planes and strands similar to the models; and (5) the combination of all the tools in this study, particularly the GPR and seismic, may allow for the mapping of small‐scale, shallow faults in unconsolidated sediments that affect ground‐water flow.
Effect of Artificial Ground‐Water Recharge on Aquifer Parameters Using Cavity Well
Authors: Taneja D. S. , Khepar S. D. 
Published: August 2005

AbstractCavity wells are shallow wells without strainers and are installed in confined aquifers. These wells are commonly installed in alluvial tracts in the Indian subcontinent, and can be used as discharge as well as recharge wells. However, during recharge, the value of aquifer parameters may change. This study was undertaken to address these changes. A cavity well was developed in a simulated circular sand tank model of a confined aquifer. The cavity thus developed was observed to be a part of a hemisphere. An analytical solution of the hydraulics of this cavity well was developed. The well was initially discharged and then recharged at various rates, and experimental data on drawdown and rise of head were collected. Aquifer parameters were calculated by substituting these data in the analytical solution. It was observed that during recharge through the well, the hydraulic conductivity and specific storage coefficient of the aquifer decreased by 15% and 13%, respectively in relation to those of discharge. Also, the aquifer parameters were found to be least affected with the change in rate of recharge or discharge.
A Test of the In Situ Permeable Flow Sensor at Savannah River, SC
Authors: Ballard Sanford , Barker Glenn T. , Nichols Ralph L. 
Published: August 2005

AbstractA test of the In Situ Permeable Flow Sensor was conducted in which ground‐water flow velocity measurements made by the flow sensors were directly compared to velocity estimates obtained using standard hydrologic techniques. Two flow sensors were deployed in a confined aquifer in close proximity to a well which was screened over the entire vertical extent of the aquifer. When the well was pumped at four different pumping rates, the horizontal component of the flow velocity measured by the flow sensors was directed toward the pumping well, within the uncertainty in the measurements, and the magnitude of the horizontal component of the velocity increased linearly with pumping rate, as predicted by theoretical considerations. The measured magnitudes differed from predicted values, calculated with the assumption that the hydraulic properties of the aquifer were homogeneous and isotropic, by less than a factor of two. Vertical components of ground‐water flow observed with the flow sensors are qualitatively consistent with the vertical distribution of hydraulic conductivity estimated from grain‐size analysis but are significantly larger in magnitude than predicted. This is likely due to the creation of a vertical conduit of increased hydraulic conductivity during emplacement of the probes. The results suggest that while the flow sensors measured the local ground‐water flow velocity vector during the test quite accurately, care must be exercised to disturb the formation as little as possible during emplacement. The technology has many potential uses, particularly in the area of environmental site characterization and remediation process monitoring.
Optimal Ground‐Water Remediation Design Using Multiple Control Technologies
Authors: Marryott Robert A. 
Published: August 2005

AbstractCombined optimization‐simulation models for designing ground‐water remediation systems generally focus on design strategies that use only one remedial technology, typically pumping. In practice, many field remediation programs use pumping along with one or more additional ground‐water control technologies, such as drains, trenches, slurry walls, and low permeability caps. Simulated annealing provides a flexible optimization framework that can incorporate a number of different remedial technologies into the design process. Using simulated annealing, additional remedial technologies can be added to or subtracted from the optimization at any time. This flexibility can provide for remedial design evaluations that are more consistent with current field implementations. The use of simulated annealing is demonstrated by a series of hypothetical remediation design problems that incorporate four different remedial technologies. The computed optimal design solution depends on the relative costs of the remedial tools as specified by the cost function and on the effects that each tool has on the system behavior. A sensitivity analysis can reveal which costs are critical to the outcome of the optimization.
Analytical Modeling of Effects of Application Frequency on Pesticide Concentrations in Wells
Authors: Beltman W.H.J. , Boesten J.J.T.I. , van der Zee S.E.A.T.M. , Quist J. J. 
Published: August 2005

AbstractPesticide transport from the soil surface to the ground‐water table was modeled by means of an analytical solution of the convection‐dispersion equation, assuming steady water flow, a linear sorption isotherm and first‐order transformation kinetics. Pesticide transport in the saturated zone to a well was described by means of an analytical solution of the conservation equation for a cylindrical flow system, assuming steady flow, no dispersion, linear sorption, and first‐order transformation. We derived an analytical solution for this coupled unsaturated‐saturated system. We limited our analysis to systems that are difficult to protect with a protection zone. The strongest fluctuations in the pesticide concentration in the well were calculated for the lowest frequency of application, shortest characteristic travel time in the saturated zone and shortest half‐life in the saturated zone. A simplified model, ignoring the variation of travel times in the unsaturated zone, resulted in concentration fluctuations in the well. The peak concentrations differed less than two times from those calculated with the analytical coupled unsaturated‐saturated model, except for cases with the combination of a short characteristic travel time and a short half‐life in the saturated zone.
Improving the Quality of Parameter Estimates Obtained from Slug Tests
Authors: Butler James J. , McElwee Carl D. , Liu Wenzhi 
Published: August 2005

AbstractThe slug test is one of the most commonly used field methods for obtaining in situ estimates of hydraulic conductivity. Despite its prevalence, this method has received criticism from many quarters in the ground‐water community. This criticism emphasizes the poor quality of the estimated parameters, a condition that is primarily a product of the somewhat casual approach that is often employed in slug tests. Recently, the Kansas Geological Survey (KGS) has pursued research directed at improving methods for the performance and analysis of slug tests. Based on extensive theoretical and field research, a series of guidelines have been proposed that should enable the quality of parameter estimates to be improved. The most significant of these guidelines are: (1) three or more slug tests should be performed at each well during a given test period; (2) two or more different initial displacements (H0) should be used at each well during a test period; (3) the method used to initiate a test should enable the slug to be introduced in a near‐instantaneous manner and should allow a good estimate of Ho to be obtained; (4) data‐acquisition equipment that enables a large quantity of high quality data to be collected should be employed; (5) if an estimate of the storage parameter is needed, an observation well other than the test well should be employed; (6) the method chosen for analysis of the slug‐test data should be appropriate for site conditions; (7) use of pre‐and post‐analysis plots should be an integral component of the analysis procedure, and (8) appropriate well construction parameters should be employed. Data from slug tests performed at a number of KGS field sites demonstrate the importance of these guidelines.
In Situ Hydraulic Conductivity of Clay and Silty‐Clay Fluvial‐Deltaic Sediments, Texas Gulf Coast
Authors: Capuano R. M. , Jan R. Z. 
Published: August 2005

AbstractTwo aquifer pumping tests (13 and 24 hours) and a tracer injection test were performed on shallow (7.5 m) clay and silty‐clay sediments of the fluvial‐deltaic Beaumont Formation from the U.S. Gulf Coast. The in situ horizontal hydraulic conductivity determined from these tests is found to be approximately 10−3 cm/sec. This value is one to three orders of magnitude larger than that of typical silts and clays, and two to four orders of magnitude larger than the vertical hydraulic conductivity measured on core in laboratory permeameter experiments. A uniformity of the drawdown curves from different observation wells strongly suggests that hydraulic conductivity is relatively homogeneous and isotropic in the horizontal plane at the scale of the test. This relatively large in situ horizontal hydraulic conductivity for these clay‐rich sediments is attributed to macroporosity rather than matrix porosity.
Flow to a Well in a Water‐Table Aquifer: An Improved Laplace Transform Solution
Authors: Moench Allen F. 
Published: August 2005

AbstractAn alternative Laplace transform solution for the problem, originally solved by Neuman, of constant discharge from a partially penetrating well in a water‐table aquifer was obtained. The solution differs from existing solutions in that it is simpler in form and can be numerically inverted without the need for time‐consuming numerical integration. The derivation involves the use of the Laplace transform and a finite Fourier cosine series and avoids the Hankel transform used in prior derivations. The solution allows for water in the overlying unsaturated zone to be released either instantaneously in response to a declining water table as assumed by Neuman, or gradually as approximated by Boulton's convolution integral. Numerical evaluation yields results identical with results obtained by previously published methods with the advantage, under most well‐aquifer configurations, of much reduced computation time.