bluuebunny/crossref_metadata_2025_split huggingface dataset:
Methodology for the Study of Unexploited Aquifers with Thermal Waters: Application to the Aquifer of the Alhama de Aragon Hot Springs
Authors: Sanz Eugenio , Yelamos Javier G. 
Published: August 2005

AbstractA methodology for the study of thermal waters in unexploited aquifers is proposed. This methodology has been applied to the Alhama Aquifer, which is the origin of the most important thermal springs of the Iberian Peninsula. A conceptual model was made of the aquifer by integrating data such as (1) the geometry at depth (on the basis of deep geophysics) and at the surface (from conventional geological maps); (2) hydrographic analysis of the aquifer discharge; (3) a study of the recharge by classic hydrometeo‐rological methods; and (4) conventional and isotopic hydrochemistry. In addition to the hydraulic regional parameters it provides, the model explains the origin of the Alhama springs in terms of simple circulation at a depth of some 900 m and a normal geothermal gradient (3°C/100 m), with no requirement of contact with a source of heat at the bottom of the aquifer.
Type Curves to Determine the Relative Importance of Advection and Dispersion for Solute and Vapor Transport
Authors: Garges John A. , Baehr Arthur L. 
Published: August 2005

AbstractThe relative importance of advection and dispersion for both solute and vapor transport can be determined from type curves for concentration, flux, or cumulative flux. The dimensionless form of the type curves provides a means to directly evaluate the importance of mass transport by advection relative to that of mass transport by diffusion and dispersion. Type curves based on an analytical solution to the advection‐dispersion equation are plotted in terms of dimensionless time and Peclet number. Flux and cumulative flux type curves provide additional rationale for transport regime determination in addition to the traditional concentration type curves. The extension of type curves to include vapor transport with phase partitioning in the unsaturated zone is a new development. Type curves for negative Peclet numbers also are presented. A negative Peclet number characterizes a problem in which the direction of flow is toward the contamination source, and thereby diffusion and advection can act in opposite directions. Examples are the diffusion of solutes away from the downgradient edge of a pump‐and‐treat capture zone, the upward diffusion of vapors through the unsaturated zone with recharge, and the diffusion of solutes through a low hydraulic conductivity cutoff wall with an inward advective gradient.
Use of Multiple Isotope Tracers to Evaluate Denitrification in Ground Water: Study of Nitrate from a Large‐Flux Septic System Plume
Authors: Aravena Ramon , Robertson William D. 
Published: August 2005

AbstractThis study explores the use of multiple isotopic tracers to evaluate the processes involved in nitrate attenuation in ground water. δ15N and δ18O are used to provide information about the role of denitrification on nitrate attenuation, and δ34S, δ18O, and δ13C are used to evaluate the role of reduced sulfur and carbon as electron donors for nitrate reduction. The focus of this study is a zone of significant NO3−1 attenuation occurring in a sand aquifer impacted by septic system contamination. The NO3−1 pattern, the ground water flow system, and changes in other chemical parameters suggest that the NO3−1 depletion is caused by denitrification. This is supported by the nitrate δ15N and δ18O data which both show significant isotopic enrichment as NO3−1 depletion proceeds along the flow path. The increase of sulfate and dissolved inorganic carbon observed in the zone of nitrate attenuation suggests that reduced sulfur in addition to carbon is also involved in denitrification. This is supported by a trend toward depleted sulfate δ34S and δ18O values in the zone of sulfate increase, which reflects the input of sulfate formed by the oxidation of biogenic pyrite present in the aquifer sediments. The trend toward depleted δ13 values in the zone of increasing dissolved inorganic carbon reflects the input of organic carbon into this carbon pool. Chemical mass balance indicates that carbon is the dominant electron donor; however, this study demonstrates the effectiveness of using multiple isotopic tracers for providing insight into the processes affecting nitrate attenuation in ground water.
Imaging the Water Table by Filtering Self‐Potential Profiles
Authors: Birch F.S. 
Published: August 2005

AbstractIn suitable cases, digital filtering of self‐potential anomalies produces images of the water table. Two hypothetical cases and four field examples from New Hampshire yield images in reasonable agreement with known water tables. Filtering for a sheet of dipolar sources (that is, the water table) would be a useful addition to routine interpretation of self‐potential data.
Solute Transport Processes in a Highly Permeable Fault Zone of Lindau Fractured Rock Test Site (Germany)
Authors: Himmelsbach Thomas , Hbtzl Heinz , Maloszewski Piotr 
Published: August 2005

AbstractThe results of field tracer experiments performed in the Lindau fractured rock test site (southern Black Forest, Germany) and subsequent modeling are presented. A vertical, hydrothermally mineralized fault zone, with a permeability much greater than the surrounding granite mass, lies beneath a planned dam site. A dense network of boreholes and tunnels were used to investigate scaling effects of solute transport processes in fractured rock. A series of tracer experiments using deuterium and dye tracers (uranine, eosine, and pyranine) were performed over varying distances and under different testing procedures, resulting in different flow field conditions. Large‐scale tracer experiments (21 to 346 m) were performed under natural flow field conditions, while small‐scale tracer experiments (11 to 16 m) were performed under artificially induced radial‐convergent and injection‐withdrawal flow fields. The tracer concentration curves observed in all experiments were strongly influenced by the matrix diffusion. The curves were evaluated with the one‐dimensional single fissure dispersion model (SFDM) (advective‐dispersive transport in the fractures coupled with diffusive transport in the adjacent rock matrix) adjusted for the different flow field conditions. The fitting model parameters found determined the fracture aperture, and matrix and fissure porosities. The determined fracture aperture varied between the sections having different hydraulic conductivities (100 to 270 um and 430 to 580 um, respectively). The determined values of matrix porosity (3 to 7%) seemed to be independent of the scale of the experiment. The modeled matrix porosities agreed well with values determined in independent laboratory investigations of drill cores using mercury porosimetry. In situ fissure porosity, determined only in small‐scale experiments, was independent of the applied geometry of the artificially induced flow fields. The dispersivities were found to be independent of the scale of experiment but dependent on the flow conditions. The values found in forced gradient tests lie between 0.2 and 0.3 m, while values in experiments performed under natural flow conditions were one order of magnitude higher.
Hydrogeochemical Interaction Between a Wetland and an Unconfined Glacial Drift Aquifer Southwestern Michigan
Authors: Kehew Alan E. , Passero Richard N. , Krishnamurthya R.V. , Lovett Cole K. , Bettsc Marilyn A. , Dayharsh Brent A. 
Published: August 2005

AbstractIn the glacial topography of southwestern Michigan, the water table does not always conform exactly to the land surface and flow‐through wetlands, those with both ground water recharge and discharge, are common. The W‐l wetland in Cass County, Michigan, a flow‐through system, shows a distinct contrast between upgradient and downgradient ground water quality. Ground water discharging into the wetland is oxic, has up to 40 mg/L NO3‐N derived from fertilizer and hog manure application to corn fields, and has major ion concentrations typical of the shallow unconfined aquifer in the area. In contrast, shallow ground water that originates as recharge from the wetland forms a plume extending downgradient that can be identified by isotopic enrichment in 18O and deuterium resulting from evaporation in the wetland prior to recharge and by distinct chemical characteristics similar to the wetland surface water (low conductivity and alkalinity, low concentrations of sulfate, nitrate and dissolved oxygen and high concentrations of ammonia, and DOC). As the wetland surface water infiltrates into the unconfined aquifer, conductivity and alkalinity increase due to carbonate mineral dissolution and iron concentrations increase as ferric iron in the aquifer solids serves as an electron acceptor in microbially mediated reactions. The other chemical characteristics, including the lack of nitrate, persist in the flow system for significant distances downgradient from the wetland.The chemical and isotopic composition of shallow ground water around wetlands can be used to spatially delineate areas of ground‐water discharge to the wetland and ground water recharge from the wetland, thereby providing a supplemental method to the use of sometimes inconclusive hydraulic head data in the determination of wetland recharge‐discharge function. In this study, the chemical and isotopic data confirm that the water table does not replicate surface topography around closed depressions in the landscape.
Incorporation of Total Stress Changes into the Ground Water Model SUTRA
Authors: Reeves Howard W. , Thibodeau Peter M. , Underwood Robert G. , Gardner Leonard R. 
Published: August 2005

AbstractTo model ground water flow in a shallow aquifer underlying a salt marsh, the impact of total stress changes due to tidal loading of the marsh surface on the piezometric head within the aquifer must be considered. If the deformation of the porous medium is negligible, a ground water flow model may be modified to account for the changing total stress. The incorporation of these modifications into the U.S. Geological Survey (USGS) numerical model SUTRA is discussed, and example problems for which analytic solutions are available are presented to demonstrate the behavior and validity of the modified model. In addition, the form of the specific pressure storativity term used in the SUTRA model is discussed and modifications of this form are suggested.
Using Ternary Diagrams to Characterize Transport and Attenuation of BTX
Authors: Lipson D. , Siegel D.I. 
Published: August 2005

AbstractDuring the past decade or longer, large amounts of data on the concentrations of dissolved aromatic hydrocarbons have been obtained from routine monitoring of leaky underground storage tanks (USTs). Commonly, aromatic hydrocarbon concentration data is interpreted only within the context of regulatory maximum allowable concentration levels. We show in this paper how ternary diagrams can clearly characterize the physical and chemical controls governing the fate and transport of aromatic hydrocarbons in ground water from routine monitoring data.The results of type mathematical modeling experiments for BTX solute transport show that changes in BTX concentrations, when plotted as proportions on ternary diagrams, form clear “trajectories” documenting major attenuation or transport processes. For example, BTX concentrations affected by biodegradation form a trajectory from the source BTX location on the ternary diagram to the benzene apex. In contrast, BTX concentrations affected by volatilization form a trajectory trending from the source to the xylene apex. Ternary diagrams are easy and effective tools to determine from routine monitoring data (1) whether proposed natural attentuation processes are in fact present, and (2) the efficiency of different remediation efforts used to clean up UST sites.
The Effect of Measurement Error on Estimating the Hydraulic Gradient in Three Dimensions
Authors: Silliman S.E. , Mantz G. 
Published: August 2005

AbstractBased on a series of analyses of published data sets, it was observed that there is a consistent problem in the estimation of the vertical component of the hydraulic gradient. In most cases investigated, data collected for a single field site led to individual estimates of the orientation of the gradient that fell close to both +90 degrees and ‐90 degrees relative to the horizontal plane (i.e., the gradient was estimated to be oriented both vertically upward and vertically downward at the same site). Being consistent across most field sites analyzed, but inconsistent with our basic knowledge of hydrology (the impact of heterogeneity is distinct from the behavior presented here), alternative explanations for these observations were sought. Analysis using a simple numerical study showed that this behavior could be attributed to the presence of measurement error in the field data. The consistency of the field observations with the numerical study shows that errors in measuring the elevation of water in a well or piezometer may result in estimates of the vertical component of the gradient that are unreliable, effectively being measures of the difference in measurement error among wells. It is noted that this measurement error is in addition to local variations in the vertical component of the gradient that are related to heterogeneity or transients in the flow field. A formula is presented for the standard deviation of the error of the estimated vertical gradient as a function of both the measurement error and the relative location of the data points used in completing the estimate.
Field and Laboratory Evaluation of a Diffusive Emitter for Semipassive Release of PCE to an Aquifer
Authors: Arildskov N.P. , Devlin J.F. 
Published: August 2005

AbstractIn controlled field experiments or model aquifers, it is sometimes desirable to introduce solutes below the water table without perturbing the flow system. Diffusive emitters offer a means of achieving that goal. In this study, two laboratory experiments were conducted to evaluate nylon tubing as a diffusive emitter for tetrachloroethene (PCE). The initial approach was to pump a saturated aqueous PCE solution through a piece of nylon tubing immersed in a flow‐through contactor vessel. Millipore water was pumped through the contactor vessel at a constant rate. Due to PCE diffusion through the nylon, a steady‐state concentration in the contactor vessel eventually developed. The process was well described by a computer model that accounted for retarded diffusion through the nylon. In a second experiment, pieces of nylon tubing were exposed to a relatively low concentration of PCE in water for 10 days in gently rotated hypovials. With the aid of a second diffusion model, the bulk diffusion coefficient (lumped with the retardation factor) was obtained from the concentration history of the solution. With the different experimental conditions taken into account, there was reasonably good agreement between the bulk diffusion coefficients in the two experiments (a factor of 3.5 difference). The results were used in the field design of a semipassive release system. Evaluation of this system showed a lower than expected steady‐state concentration of PCE inside the releasing wells. The difference is likely due to lower temperature, variable PCE concentrations in the nylon tubing, and nonideal mixing in the wells. The work has shown that laboratory derived diffusion coefficients for polymeric materials are likely to be larger than, but within an order of magnitude of, the effective diffusion coefficients exhibited by emitters in the field. Nevertheless, with temperature corrections taken into account and proper well development, these values could be used to design emitters that would suit most practical applications.
Problems Associated with Estimating Ground Water Discharge and Recharge from Stream‐Discharge Records
Authors: Halford Keith J. , Mayer Gregory C. 
Published: August 2005

AbstractGround water discharge and recharge frequently have been estimated with hydrograph‐separation techniques, but the critical assumptions of the techniques have not been investigated. The critical assumptions are that the hydraulic characteristics of the contributing aquifer (recession index) can be estimated from stream‐discharge records; that periods of exclusively ground water discharge can be reliably identified; and that stream‐discharge peaks approximate the magnitude and timing of recharge events. The first assumption was tested by estimating the recession index from stream‐discharge hydrographs, ground water hydrographs, and hydraulic diffusivity estimates from aquifer tests in basins throughout the eastern United States and Montana. The recession index frequently could not be estimated reliably from stream‐discharge records alone because many of the estimates of the recession index were greater than 1000 days. The ratio of stream discharge during base flow periods was two to 36 times greater than the maximum expected range of ground water discharge at 12 of the 13 field sites. The identification of the ground water component of stream‐discharge records was ambiguous because drainage from bank‐storage, wetlands, surface water bodies, soils, and snowpacks frequently exceeded ground water discharge and also decreased exponentially during recession periods. The timing and magnitude of recharge events could not be ascertained from stream‐discharge records at any of the sites investigated because recharge events were not directly correlated with stream peaks. When used alone, the recession‐curve‐displacement method and other hydrograph‐separation techniques are poor tools for estimating ground water discharge or recharge because the major assumptions of the methods are commonly and grossly violated. Multiple, alternative methods of estimating ground water discharge and recharge should be used because of the uncertainty associated with any one technique.
Microbial H2 Cycling Does Not Affect δ2H Values of Ground Water.
Authors: Landmeyer James E. , Chapelle Francis H. , Bradley Paul M. 
Published: August 2005

AbstractStable hydrogen‐isotope values of ground water (δ2H) and dissolved hydrogen concentrations (H2(aq)) were quantified in a petroleum‐hydrocarbon contaminated aquifer to determine whether the production/consumption of H2 by subsurface microorganisms affects ground water δ2H values. The range of δ2H observed in monitoring wells sampled (−27.8 %c to −15.5 %c) was best explained, however, by seasonal differences in recharge temperature as indicated using ground water δ18O values, rather than iso‐topic exchange reactions involving the microbial cycling of H2 during anaerobic petroleum‐hydrocarbon biodegradation. The absence of a measurable hydrogen‐isotope exchange between microbialy cycled H2 and ground water reflects the fact that the amount of H2 available from the anaerobic decomposition of petroleum hydrocarbons is small relative to the amount of hydrogen present in water, even though milligram per liter concentrations of readily biodegradable contaminants are present at the study site. Additionally, isotopic fractionation calculations indicate that in order for H2 cycling processes to affect δ2H values of ground water, relatively high concentrations of H2 (>0.080 M) would have to be maintained, considerably higher than the 0.2 to 26 nM present at this site and characteristic of anaerobic conditions in general. These observations suggest that the conventional approach of using δ2H and δ18O values to determine recharge history is appropriate even for those ground water systems characterized by anaerobic conditions and extensive microbial H2 cycling.
Stream and Fluvial Plain Ground Water Interactions: Rescaling Hydrogeologic Thought
Authors: Woessner William W. 
Published: August 2005

AbstractManagement of near‐channel ground water and surface water to maintain stream health and flood plain ecological function requires hydrogeologists to refocus their conceptual models of water exchange between the aquifer and stream. The high hydraulic conductivity fluvial plain directs ground water flow down‐plain where it exchanges with the stream channel creating gaining, losing, flow‐through, and parallel‐flow reaches. The resulting complex flow system requires consideration when profiles representing ground water flowpaths are constructed. In addition to interaction at the scale of the fluvial plain, exchange of ground water and surface water within and immediately adjacent to the stream channel creates hyporheic zones. The physical and bio‐geochemical extent of these zones depends on the head distribution and ground water flow directions, stream hydraulics, and channel bed conditions, and magnitudes and distributions of hydrogeologic parameters. Simulated conceptualizations of flow dynamics caused by slight increases in hydraulic potentials at the surface water‐stream bed interface indicate stream‐ground water mixing could occur to a depth of 1.7 m below the channel. Rescaling of traditional hydrogeologic approaches to include the fluvial plain and channel scale will result in opportunities to expand hydrogeologic research and participate in interdisciplinary research teams attempting to decipher and manage fluvial systems.
CRAFIT: A Computer Program for Calibrating Breakthrough Curves of CRAFLUSH, a One‐Dimensional Fracture Flow and Transport Model
Authors: Toran Laura 
Published: August 2005

AbstractThis Computer note presents a program called CRAFIT, which automates trial and error curve fitting of breakthrough curves for CRAFLUSH, a one‐dimensional fracture flow and transport code. CRAFIT is useful for modeling column experiments where the source function is well‐known but fracture geometry and matrix are to be characterized. CRAFIT is demonstrated for curve fitting with three unknowns and five unknowns, and found a single best‐fit solution for each case.
Hydraulic Characterization and Design of a Full‐Scale Biocurtain
Authors: Hyndman David W. , Dybas M.J. , Forney L. , Heine R. , Mayottee T. , Phanikumar M.S. , Tatara G. , Tiedje J. , Voice T. , Wallace R. , Wiggert D. , Zhao X. , Criddle C.S. 
Published: August 2005

AbstractThis paper deseribes the design and hydraulic characterization of a cost‐effective biocurtain that is currently being used to remove carbon tetrachloride from an aquifer in Schoolcraft, Michigan. Novel aspects of the design are the use of closely spaced wells to recirculate solutes through a biocurtain, well screens spanning the vertical extent of contamination, and a semipassive mode of Operation, with only six hours of low‐level pumping per week. This design was developed by coupling flow and transport sim‐ulations with a cost optimization algorithm, based on initial hydraulic conductivity data and system design constraints from a previous pilot‐scale experiment adjacent to the current site, The hydraulic conductivity of the site was characterized using permeameter analysis on more than 200 samples from continuous well cores that were collected during well Installation. The subset of availablc conductivity data was used to predict tracer transport through the biocurtain during System Operation. Observed tracer conecntration arrival histories during initial system Operation confirmed model predictions. Modeling also established that closely spaced wells operated for brief periods each week could effectively deliver the agents needed for remediation across the biocurtain. This was confirmed during long‐term Operation of the System, which has resulted in highly efficient contamination degra‐dation. The delivery well design methodology is expected to be broadly applicable at other sites where flow can be recirculated between a series of delivery wells.