bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Situ Estimation of Transport Parameters: A Field Demonstration
Authors: Wise William R. , Charbeneau Randall J. 
Published: August 2005

AbstractLinear sorption coefficients and first‐order biotransformation rates for para‐dichlorobenzene (pDCB) and naphthalene are fit to data from a three‐well forced‐gradient (injection‐production) field test performed at the site of an abandoned creosoting facility in Conroe, Texas. The breakthrough curve of an injected inert tracer, chloride, is used to describe the hydraulics of the field test. Along each streamline, the movement of a reactive solute is described by a one‐dimensional transport equation. The hydraulic and streamline transport models are coupled through a combination integral, the evaluation of which yields the effluent concentration (at the production well) of that reactive solute as a function of time. Transport parameters for the field site, sorption coefficients and biotransformation rates for pDCB and naphthalene, are obtained through inverse analysis of effluent data obtained at one of the production wells. The method is formulated such that no formal treatment of dispersion is required.
Two Methods for the Laboratory Identification of Transversal Dispersivity
Authors: Pisani Stefano , Tosi Nicola 
Published: August 2005

AbstractThe experimental identification of transversal dispersivity in the laboratory is not a very developed subject; the authors herein propose two methods for identifying transversal dispersivity in laboratory experiments, based on the analytical solution of a continuous, point‐like, injection of a nonreactive solute in a flow tank packed with a homogeneous porous medium. The solute transport is supposedly two‐dimensional, whereas the hydraulic flow is monodimensional with a uniform velocity.Each identification method is based on the measurement of concentration in pairs of points. In the first method the points are taken along lines normal to the direction of the fluid flow, with one of the two points set on the central axis of the flow tank. In the second method the two measurement points are placed on lines passing through the solute injection point.The stability of the two methods, with respect to concentration measurement errors, is analyzed to assess the reliability of the transversal dispersivity estimate. Furthermore, the two methods are found to be sensitive to variations of the concentrations.
Use of a Geographic Information System in Site‐Specific Ground‐Water Modelinga
Authors: El‐Kadi A. I. , Oloufa A. A. , Eltahan A. A. , Malik H. U. 
Published: August 2005

AbstractGround‐water modeling is hindered, in general, by the lack of adequate information about the ground‐water system and hence the need for an interactive and efficient system for data preparation and results analysis. Such a lack of information usually necessitates the use of a tedious iterative methodology within a sensitivity analysis scheme. This study facilitates modeling efforts by using the data‐handling and graphical capabilities of a geographic information system in site‐specific, numerical modeling of ground‐water resources. Data for the island of Oahu, Hawaii, are given to illustrate the approach. The modeling procedure is integrated within the GIS as an item in the main menu. A USGS model, known as MOC, is linked into the system and applied to a case study to illustrate the procedure. The linkage is generic in nature and can be extended to other models as well. The availability of a programming language in the GIS package facilitates pre‐ and post‐processing efforts within custom‐made dialogue boxes and pull‐down menus. On‐line help screens for modeling as well as data handling can also be designed.
Nonaqueous Phase Hydrocarbon in a Fine‐Grained Sandstone: 1. Comparison Between Measured and Predicted Saturations and Mobility
Authors: Huntley David , Hawk Robert N. , Corley Helen P. 
Published: August 2005

AbstractThe distribution and mobility of light, nonaqueous phase hydrocarbons in the subsurface is poorly understood, particularly in relation to observations of hydrocarbons in monitoring wells. Recent work by Lenhard and Parker (1990) and Farr et al. (1990) resulted in an equilibrium model in which the degree of hydrocarbon saturation was shown to be a function of the apparent thickness of hydrocarbon in a monitoring well, the height above the oil/water interface, and the capillary pressure/saturation characteristics of the soil. The current investigation compared measured hydrocarbon saturations, hydrocarbon volumes, and hydrocarbon mobility to those predicted by the capillary characteristic model of Farr et al. (1990) and Lenhard and Parker (1990). Five monitoring wells were completed in boreholes drilled in a hydrocarbon‐contaminated area of downtown San Diego, where apparent hydrocarbon thickness varied from zero to over 1.5 meters. Up to 2.5 meters of continuous core was obtained from each of the boreholes and split into 3 cm intervals. Alternating 3 cm samples were analyzed for total petroleum hydrocarbon, and the remaining samples were used for grain‐size analysis and measurement of capillary characteristic curves. Slug‐withdrawal tests were conducted on the hydrocarbon intervals, and constant‐rate discharge tests were conducted on the water‐saturated intervals of the monitoring wells.The results show typical hydrocarbon saturations of 5% to 20%, with one borehole showing a limited zone of up to 50% saturation. Hydrocarbon mobility (relative permeability) is greatly reduced due to the low saturations, as predicted by capillary theory. These observations are consistent with both the capillary model of hydrocarbon distribution and with the very low recoveries achieved using hydrocarbon skimming systems.
Modeling Chemical Transformation Products Using Asymptotic Solutions
Authors: Mills William B. , Liu Sally 
Published: August 2005

AbstractA method is developed to predict time‐variable concentrations of a degrading chemical and its first‐ and second‐generation transformation products for randomly located receptors in ground water. An asymptotically approximate solution for chemical concentrations is derived. To evaluate uncertainties in predicted concentrations, a Monte Carlo approach is implemented. Substantial computational savings are realized when asymptotically approximate solutions are used rather than the exact solutions; yet, the accuracy of the solutions is comparable.
Temporal Changes in Manganèse Concentrations in Water from the Fredericton Aquifer, New Brunswick
Authors: Thomas N. E. , Kan K. T. , Bray D. I. , MacQuarrie K.T.B. 
Published: August 2005

AbstractA geochemical field study was conducted on the municipal aquifer in Fredericton, New Brunswick, Canada to determine the cause of increased manganese levels, from 0.02 mg/1 to about 1.0 mg/1 over a 34‐year period, in three of five production wells. The source of water for each of the five production wells has been determined to be infiltrated river water or precipitation, or a mixture of these sources. Wells that are predominately withdrawing infiltrated river water have corresponding high manganese concentrations, and redox potential data indicate that manganese tends to be in the aqueous form Mn2+. Geochemical modeling further suggests that the ground water is undersaturated with several common manganese minerals, while remaining supersaturated with iron oxide‐hydroxide minerals. The primary cause of the temporal increase in manganese concentrations is attributed to increased dissolved organic carbon introduced to the aquifer as a result of the escalating contribution of river water to the aquifer with time. Oxidation of organic matter proceeds in a ground‐water environment, as dissolved oxygen is depleted, by utilizing manganese oxides as electron acceptors.
Hydrology and Chemistry of Thermal Waters Near Wells, Nevada
Authors: Jewell Paul W. , Rahn Thomas A. , Bowman John R. 
Published: August 2005

AbstractAnomalously warm water in shallow wells and surface springs is found in and around the town of Wells, Nevada. The geology of the Wells area is dominated by Paleozoic and Miocene sedimentary rocks which are cut by high angle normal faults. Thermal springs are associated with the normal faults, whereas thermal water from wells is the result of upward vertical fluid infiltration through the porous, Miocene lacustrine sedimentary rocks and Quaternary alluvium. Temperature logs from a nearby oil exploration well show locally high geothermal gradients (> 50° C/km). Analysis of static water heads indicates that vertical flow is greater than or equal to horizontal flow in low‐lying areas near the town of Wells. Solution of the advection‐diffusion equation using temperature data from the upper portion of the oil well suggests upward flow velocities of approximately 2–10 m/yr. Cold waters have a mixed cation‐bicarbonate chemistry whereas thermal waters are dominantly (Na + K)‐bicarbonate. Chemical geothermometers indicate fluid circulation to depths between 1–2 km. Deuterium and oxygen‐18 analyses have considerable variability, with modest deviations from the global meteoric water line. The occurrence of deuterium as light as – 145% suggests significant recharge to the hydrothermal system from very high elevations or water which has had a long subsurface residence time and is recording the signal of a cooler climate.
In Situ Surfactant Washing of Polychlorinated Biphenyls and Oils from a Contaminated Field Site: Phase II Pilot Study
Authors: Abdul Abdul S. , Ang Carolina C. 
Published: August 2005

AbstractAn in situ surfactant washing process was previously developed and successfully pilot‐tested at a field site contaminated with polychlorinated biphenyls (PCBs) and oils (Abdul et al., 1992). A second phase of the pilot study, conducted the following year at the same site, confirmed the technical viability of this process. The results of the phase II study surpassed the predictions of the long‐term performance of this technology based on the phase I results. Soil cores taken from the plot before the phase I and phase II studies and after the phase II study showed mass reduction and redistribution of the contaminants.A continuous column washing study using the same contaminated soil showed consistency with field results. The amounts of PCBs removed in the laboratory and field studies, respectively, are 7% and 10% after 5.7 pore volume (PV) washings (phase I) and 19% and 24% after 8 PV washings (phase II). More than 85% of the PCBs were removed from the laboratory soil column after 105 PV washings. This study supports the phase I study which indicates that the in situ surfactant washing process is a viable remediation technology for hydrophobic contaminants.
A Geochemical and Isotopic Approach to Delineate Landfill Leachates in an RCRA Study
Authors: Fritz Steven J. , Bryan Jeffrey D. , Harvey F. Edwin , Leap Darrell I. 
Published: August 2005

AbstractUnder many circumstances during an RCRA investigation, the EPA will not allow intrusive sampling of an SWMU (Solid Waste Management Unit, or “waste dump”). This presented difficulties in characterizing the waste within a closed landfill identified as an SWMU located on land owned by Purdue University, 3 kilometers northwest of the West Lafayette (Indiana) campus because there were few records of what was discarded into this public dump during its operation from 1958–87. Chemical and isotopic data of shallow ground water and surface runoff provided a realistic means to infer movement of contaminants away from the landfill.Leachate is characterized by high concentrations of Na+ and Cl− (∼ 4mN), sulfate (∼ 8 mN), total hardness (Ca+2+ Mg+2∼ 19 mN), and alkalinity (∼ 12mN). Disposal of road salt is responsible for the NaCl concentrations, while dissolution of concrete explains the high Ca+2, Mg+2, and alkalinity values for waters having a pC02 only slightly above the regional level for ground waters (10−1.82atm).Deep and shallow uncontaminated ground waters in the vicinity of the SWMU have an average δ34S value of 0.5 per mil (CDT). Since the δ34S of leachate lies between + 10 and + 17 per mil (CDT), the high sulfate concentrations are most likely due to dissolution of interred plasterboard consisting primarily of gypsum.Tritium activities for the leachate in two shallow wells emplaced 15 meters from the toe of the SWMU ranged from 55 to 85 TU. Correcting for half‐lives and correlating these activities to historical records of tritium in rainfall as measured at Chicago, these 3H activities suggest that the travel time between the SWMU interior and these wells is between 15 and 20 years.
Modeling the Effects of Salt‐Water Intrusion Dynamics for a Coastal Karstified Block Connected to a Detrital Aquifer
Authors: Calvache M. Luisa , Pulido‐Bosch Antonio 
Published: August 2005

AbstractThe contamination by salt‐water intrusion affecting the coastal aquifer at Castell de Ferro (Granada, Spain) is especially influenced by the coexistence of two coastline lithological formations with highly differing transmissivity (highly karstified limestones and detrital sediments). Despite not having a very high intrusion volume (0.1–0.2 hm3/year), the aquifer does have a high saline content. In order to explain this phenomenon, we first of all modeled the ground‐water flow (MODFLOW) in the aquifer. Two models were then used for the fresh‐water/salt‐water contact: one assuming a sharp interface (BADON2) and the other taking into account density‐dependent mass transport (MOCDENSE). Our conclusion is that the high saline content of the aquifer is due to the existence of a preferential route for ground‐water flow through the karstified materials in contact with the detrital materials and the sea. The detrital materials located beside the karstified massif therefore constitute the route for only 10%‐20% of the system's total outlet to the sea, which is not enough water to wash the salts resulting from salt‐water intrusion. We also find that in this type of aquifer two‐dimensional transport models do not provide the most realistic results, since the effect in a direction transverse to the ground‐water flow of very transmissive material cannot be simulated in this type of profile. In this case, and despite its limitations, better results are obtained using the sharp interface model.
Diffusive Disappearance of Immiscible‐Phase Organic Liquids in Fractured Geologic Media
Authors: Parker Beth L. , Gillham Robert W. , Cherry John A. 
Published: August 2005

AbstractIn a new conceptual model for immiscible‐phase organic liquids in fractured porous media that specifically includes the effect of molecular diffusion on the persistence of organic liquid in fractures, dissolved contaminant mass from the liquid in fractures is lost by diffusion from the fractures into the porous matrix between the fractures. Theoretical calculations for one‐dimensional diffusive fluxes from single, parallel‐plate fractures using parameter values typical of fractured porous geologic media establishes the concept of immiscible‐phase disappearance time, which is the time required for a given volume of immiscible liquid in a specified aperture to disappear following its arrival in the fracture. Nonlithified surficial clayey deposits with matrix porosities ranging from 25 to 70% are extensive across many regions of North America and Europe, and at shallow depth, typically have fractures with apertures in the range of 1 to 100 microns. The common chlorinated solvents such as dichloromethane (DCM), trichloroethene (TCE), and tetrachloroethene (PCE) are expected to completely disappear in these deposits within a few days to weeks. For fractured sedimentary rocks with much lower matrix porosities (5–15%), disappearance times for these solvents are generally less than several years for fracture apertures ranging from 10 to 200 microns typical for shales, siltstones, sandstones, and carbonate rocks. This is sufficient time for the immiscible phase of chlorinated solvent contamination to have disappeared at many industrial sites. This conceptual model has important implications with respect to ground‐water monitoring, diagnosis of the nature and degree of contamination, and expectations for ground‐water remediation at many contaminated sites. Proposed methods for enhancing immiscible‐phase mass removal using hydraulic manipulation, surfactants, or alcohols will be futile where the immiscible phase has disappeared into the clay or rock matrix, and reverse diffusion and desorption will control clean‐up time frames. Therefore, prospects for permanent restoration of many DNAPL and LNAPL sites in fractured porous media are more limited than previously thought.
A Refraction Statics Method for Mapping Bedrock
Authors: Taucher Paul , Fuller Brian N. 
Published: August 2005

AbstractThe bedrock surface beneath unconsolidated eolian sand and garbage at the active Casper, Wyoming landfill was successfully imaged using a refraction statics method. The method employed the summation of common‐detector refraction seismic traces in a manner analogous to common midpoint (CMP) reflection seismic methods. The method produces a seismic time section that is interpreted in much the same way as reflection seismic time sections. The method was very robust in imaging the bedrock surface, even when the refractions were poorly defined on both unprocessed and filtered shot records. Processing of a refraction statics data set is less expensive than CMP high‐resultion reflection processing and does not rely on the detailed graphical constructs of the more commonly used refraction seismic analysis methods. This alternative to more commonly used refraction and reflection seismic methods should be applicable in noisy and otherwise difficult data acquisition areas where the resolution of first breaks and/or reflections is difficult. The summation of data traces enhances the signal to noise ratio allowing direct observation of the bedrock image on the time section. A depth section can be calculated from the final time section. In poor data quality settings, the enhancement of the refraction signal by summation of multiple, common‐detector data traces is the significant advantage of the refraction statics method over other refraction seismic interpretation methods which are dependent on accurately picking refracted arrivals on individual data traces.An ICP‐MS, equipped with an ultrasonic nebulizer and active‐film multiplier detector, is used to attempt to determine 54 trace elements directly in ground water. Lithium, arsenic, rubidium, strontium, barium, and antimony are found in the microgram‐per‐liter (part‐per‐billion = ppb) range. Most of the other elements are present at nanogram‐per‐liter (part‐per‐trillion = ppt) concentrations. Ion exchange preconcentration is utilized in order to improve the sensitivity for measuring the rare earth elements that exist at concentrations as low as 0.05 ppt for lutetium, thulium, and terbium. The formation of molecular species in the plasma produces false positive results for some of the elements. The presence of silicon or carbon dioxide interferes with the measurement of scandium, strontium interferes with rhodium and palladium, and barium interferes with europium. Correction procedures for these interferences are discussed. All together, the concentrations of the 54 elements in water from four Nevada springs span almost seven orders of magnitude.
Numerical Modeling of Ground‐Water Resource Management Options in Kuwait
Authors: Mukhopadhyay Amitabha , Al‐Sulaimi Jawad , Barrat Jean Marie 
Published: August 2005

AbstractKuwait is an arid country with no surface water and very limited resources of useable ground water. These ground‐water reserves have been heavily exploited since the 1960s, which has led to substantial decline in the potentiometric surface of the aquifers. A regional numerical model, calibrated under both steady and unsteady‐state conditions, has been used to investigate the hydrodynamic impacts of different ground‐water management options on the potentiometry of the aquifers. The results indicate that there is a real danger of either dewatering the aquifers, or deteriorating water quality by upconing and sea‐water intrusion, if the present trend of increasing withdrawal rates continues unchecked. In fact, the study suggests that even if the withdrawals are completely stopped in the near future, the aquifers will not be restored to their pre‐1960 conditions by the year 2010. Artificial recharge of the aquifers will have, however, beneficial effects on the potentiometric surfaces and should be considered.
Monte Carlo Simulation and Effective Medium Approximation in Subsurface Flow Modeling
Authors: Shrestha S. P. , Loganathan G. V. 
Published: August 2005

AbstractA refined Monte Carlo (MC) simulation procedure and an Effective Medium Approximation (EMA) are presented for solving the stochastic subsurface flow problem. The refined MC simulation procedure uses analytical means to estimate the sample size by controlling the error incurred in using the sample average in place of its population mean at a chosen confidence level for the pressure head. Also, an unbiased estimator of the pressure head that takes advantage of its correlation with the saturated conductivity to reduce its variance is proposed. This reduced variance results in a smaller width of uncertainty about the predicted pressure head thereby improving the precision. The EMA permits one to solve the stochastic subsurface flow problem in a single run to generate the expected pressure head field with the aid of a field‐scale effective hydraulic conductivity that has a form similar to the Gardner equation. Both the MC and the EMA approaches perform well when applied to example problems taken from the literature.
An Evaluation of the Reproducibility of Forced‐Gradient Solute Transport Tests
Authors: Bianchi‐Mosquera Gino C. , Mackay Douglas M. 
Published: August 2005

AbstractTwo forced‐gradient ground‐water transport tests were conducted in the Summers of 1989 and 1990 at Borden, Ontario. The tests were nearly identical in several respects and allow an assessment of the reproducibility of such efforts. In both experiments, carbon tetrachloride, tetrachloroethene, and a conservative tracer were injected as a pulse into the aquifer and monitored as they migrated towards an extraction well. Data were analyzed using moment techniques and fitted with a 1‐D transport model accounting for physical nonequilibrium conditions for the sorbing solutes. Visual inspection and simulations of the results indicate that the tests are reproducible. However, results from the moment analyses are less conclusive, perhaps due to data truncation. The differences in the modeling results or the parameter estimates derived from them are likely to have resulted from differences in the experimental conditions or duration. Simulations conducted using either year's fitted parameters are essentially indistinguishable from a practical point of view.