bluuebunny/crossref_metadata_2025_split huggingface dataset:
Source of Ground Water in the Deserts of Northern Chile: Evidence of Deep Circulation of Ground Water from the Andes
Authors: Magaritz M. , Aravena R. , Peña H. , Suzuki O. , Grilli A. 
Published: August 2005

AbstractGround water in the Pampa del Tamarugal basin part of the desert of Northern Chile is the main water resource for cities and agricultural activities in the region. As the area received virtually no precipitation, the source of the ground water is rains in the high Andes. Aquifer recharge has been linked to a drainage system associated with this part of the Andes. Ground‐water flow is from northeast to southwest, and a flow component from east to west is also observed in some parts of the basin. In general, the water becomes very saline towards the western part of the basin, giving rise to salt lakes (salares) in ground‐water discharge areas. However, isotopic, chemical, and geological evidence plus ground‐water temperatures distribution, suggest the existence of a different recharge mechanism linked to a regional ground‐water flow system. It is suggested that low‐salinity water emerges from ground water recharged in the high Andes through a basement fault system underneath the basin. This model has implications for the future exploration for new fresh‐water resources.
Particle–Tracking Analysis of Flow Paths and Traveltimes from Hypothetical Spill Sites Within the Capture Area of a Wellfield
Authors: Bair E. Scott , Sheets Rodney A. , Eberts Sandra M. 
Published: August 2005

AbstractVelocity fields computed from simulated flows from a steady–state, three–dimensional numerical model of a glacialdrift/carbonate–bedrock aquifer system were used in conjunction with a particle–tracking program to delineate traveltimerelated capture areas of a municipal wellfield and to compute flow paths and advective traveltimes from hypothetical spill sites located along interstate highways and heavily traveled State routes. Results indicate the municipal wells operated by the City of Columbus, Ohio, capture flow from certain highway segments but other discharge points, including quarrydewatering systems, the Scioto River, and Big Walnut Creek, capture flow from other highway segments. Advective traveltimes from three hypothetical spill sites to the municipal wells range from 900 to 5,100 days under normal pumping rates and from 450 to 3,100 days under estimated maximum pumping rates. The 2,000–day capture area of the wellfield is approximately 30 percent larger (16 square miles) and contains approximately 4.5 more miles of highway under estimated maximum pumping rates compared to normal pumping rates.
A Device for In Situ Determination of Geochemical Transport Parameters 1. Retardation
Authors: Gillham R. W. , Robin M.J.L. , Ptacek C. J. 
Published: August 2005

AbstractThe retardation factor for dissolved chemicals in ground water is an important parameter in predicting the rate of migration of contaminants and in the design of remediation schemes for contaminated aquifers. Conventional methods for evaluating retardation factors include laboratory batch and column tests, and in the case of nonpolar organic contaminants, correlations with the organic carbon content of the aquifer material. In these procedures it is difficult to insure the geochemical integrity of the sediment material and the solutions used in the tests, leading to uncertainties concerning the applicability of the results. Alternatively, large‐scale tracer tests can be conducted; however, because of the time and cost requirements, these procedures have generally been limited to research applications.This paper describes an in situ column procedure for measuring retardation factors. The column is installed in advance of the cutting head of hollow‐stem augers, minimizing geochemical disturbance of the sediment, and the sediment within the column is exposed only to natural ground water from the immediate vicinity of the test device. By maintaining geochemical integrity, the method has considerable advantages over laboratory procedures, while being substantially less costly than conventional field tracer tests. Two tests are described in which retardation factors for strontium and for five halogenated organic compounds, obtained using the in situ device, were found to be in good agreement with results obtained by conventional methods.
Expert Testimony for the Plaintiffs in the Case that Brought Ohio Ground‐Water Law into the 20th Century
Authors: Bair E. Scott , Norris Stanley E. 
Published: August 2005

Abstract. The 1984 Ohio Supreme Court ruling on Cline v. American Aggregates changed Ohio's ground‐water law from an 1861 ruling based on the English Rule of absolute ownership to a doctrine of reasonable use which recognizes that landowners have the privilege to use the water beneath their land but can be held liable to others if their use of ground water causes others unreasonable harm. The Ohio Supreme Court did not define unreasonable harm in the Cline case. As a result, unreasonable harm is being established through case law, the first such case being the relitigation of Cline v. American Aggregates.Depositions and expert testimony presented during the Cline cases, which represent a group of 56 landowners in a single lawsuit, showed the diverse ways in which the quantity and quality of ground water used for domestic‐water supplies were affected by operation of a dewatering system at an aggregate mine. The testimony highlighted the complex interaction between regional hydrodynamics, variations in local hydrogeologic settings, well‐construction methods, spatial variations in infiltration and recharge, and vertical leakage with the effects of the regional decline in water levels produced by the dewatering system.
“Where's the Benzene?”— Examining California Ground‐Water Quality Surveys
Authors: Hadley Paul W. , Armstrong Richard 
Published: August 2005

AbstractThousands of leaking underground gasoline tanks have been found throughout California from which a tremendous amount of gasoline has leaked into ground water over the last half century. The most water‐soluble constituent of gasoline is benzene, and it typically contaminates ground water below leaking underground tanks. In a state‐mandated program 7,167 wells serving water‐supply systems throughout California were tested for a broad panel of organic contaminants. Of the wells tested, 812 (11.3%) had detectable concentrations of at least one of the contaminants tested for. Detectable concentrations of benzene were reported for only 10 wells. Similar findings were reported in surveys focused on San Gabriel and San Fernando Basins. While many processes influence the environmental fates of organic contaminants in ground water, the most likely explanation for the nonoccurrence of benzene is that it is destroyed near its source by biodegradation.
Ground‐Water Discharge to Lakes: Focusing in Embayments
Authors: Cherkauer Douglas S. , McKereghan Peter F. 
Published: August 2005

AbstractSeepage of ground water to Green Bay and Lake Michigan from a fractured dolomite aquifer beneath the Door Peninsula of Wisconsin is examined to determine the influences of embayments on the relative amounts of ground‐water discharge. A digital simulation has been used to calculate the quantity and distribution of that discharge. The simulated results are based on the net recharge which occurs on the land portion of the study area. They compare favorably with discharges calculated by flow net using observed hydraulic gradients and conductivities, and are in relative agreement with direct measurements made by seepage meters. The simulation has not been verified (due to lack of independent observations), but the similarity of the discharges from the three methods is argued to indicate the model's validity.In the study area, 66,000 m3/day of ground water is discharged directly to Green Bay (26,000 m3/day) and Lake Michigan (40,000 m3/day). Almost 60% of this total occurs in 20 embayments along the shore, even though they occupy only about 33% of the shoreline length as measured parallel to the long axis of the peninsula.Discharge is focused into embayments by distortion of equipotential lines caused by a bay's penetration into the ground‐water system. In the study area, it is shown that flow amplifications of up to 500% vary directly with two measures of the shoreline shape at bays, horizontal penetration (defined as the ratio of a bay's axial length to the distance to the ground‐water divide), and vertical penetration (the ratio of the maximum bay depth to aquifer thickness). Both factors have equal influence on the amplification of discharge. A graphical means of predicting the effect of coastal configuration on other bays is presented, but its applicability outside the study area is unknown.
Impact of the Proposed Qattara Reservoir on the Moghra Aquifer of Northwestern Egypt
Authors: Rizk Zein S. , Davis Arden D. 
Published: August 2005

AbstractThis paper examines hydrogeologie effects of proposed diversion of water from the Mediterranean Sea to the Qattara Depression for generation of electricity in northwestern Egypt. The Lower Miocene Moghra aquifer directly underlies the Qattara Depression, extending to the east and dipping beneath younger formations to the north. The Qattara Depression is a sink for ground‐water flow from the Nile Delta aquifer in the east, the Mediterranean Sea in the north, and the Nubian artesian aquifer in the south. In this study, a two‐dimensional finite‐difference model was used in conjunction with available meteorologie, geologic, and hydrologie data to characterize the present ground‐water conditions in this aquifer and to make predictions about the water‐table rise which could occur as a result of the proposed Qattara Reservoir. Model predictions indicate that creation of the reservoir could cause a 30‐meter rise of the Moghra aquifer's water table in the central part of the Qattara Depression. This water‐table rise decreases to the north and east. Transient simulations indicate that steady‐state conditions in the modeled area of the Moghra aquifer are not likely to be reached during the expected 100‐year lifetime of the reservoir.
Model for Predicting Virus Movement Through Soils
Authors: Tim Udoyara S. , Mostaghimi Saied 
Published: August 2005

AbstractA numerical model, VIROTRANS, is developed for simulating the vertical movement of water and virus through soils treated with waste‐water effluents and sewage sludges. The expression describing transient flow of water is coupled with the convective‐dispersive equation for subsurface solute transport. The resulting methodology is a coupled set of partial differential equations that describe the transient flow of water and suspended virus particle movement through variably saturated media. Solutions to the partial differential equations are accomplished by a Galerkin finite element method. Several example problems are used to provide a quantitative verification and validation of the model. The model simulations are compared to an analytical solution and to experimental measurements of soil moisture content and poliovirus 1 transport. The comparisons show reasonable agreement between model simulations and measured data. Sensitivity of the model's prediction to variations in pertinent input parameters are also analyzed.
Comparison Between Model Simulations and Field Results for In‐Situ Biorestoration of Chlorinated Aliphatics: Part 1. Biostimulation of Methanotrophic Bacteria
Authors: Semprini Lewis , McCarty Perry L. 
Published: August 2005

AbstractA nonsteady‐state model is presented for the in‐situ biostimulation of a microbial population in saturated porous media. The model includes basic processes of microbial growth, utilization of electron donor and acceptor, advective transport, dispersion, and sorption in porous media. Model simulations are compared with results from a series of controlled field experiments at the Moffett Naval Air Station, where the growth of an indigenous population of methane‐utilizing bacteria (methanotrophs) was stimulated by the controlled addition of dissolved methane and oxygen (DO) into a semiconfined aquifer. Simulations provide good matches to the observed transient uptake of methane and DO, demonstrating that the observed response resulted from the growth of methanotrophs in the test zone. Simulations duplicate results from alternate pulsed addition of methane (electron donor) and oxygen (electron acceptor), used as a means for distributing microbial growth throughout the test zone. The model permits estimation of changes in microbial population distribution at various stages of the two‐year experiment. Temporal changes in model‐fitted kinetic parameters indicate that the microbial population evolved to one that more effectively utilized the methane at lower concentrations. These analyses demonstrate that a relatively simple model, which includes basic microbial and transport processes, can be of use in the design and evaluation of in‐situ biotreatment processes. The model user, however, must provide judgment in the selection of appropriate input parameters, as well as being aware of model limitations.
Delineation of a Discontinuous Aquitard with Vertical Electrical Soundings, San Bernardino Valley, Southern California
Authors: Owen William P. , Park Stephen K. , Lee Tien‐Chang 
Published: August 2005

AbstractVertical electrical soundings were used to map the presence or absence of an aquitard separating a shallow, contaminated aquifer from a deeper, uncontaminated one in San Bernardino Valley, California. Correlation of vertical electrical soundings with lithologie logs from adjacent wells allowed us to also map local variations in the elevation of the water table Comparison of known waste sites, the distribution of the aquitard, and elevation of the water table yielded probable directions of contaminant transport. We conclude that there is a significant hazard to municipal water wells due to possible transport of contaminants between the shallow and deeper aquifers.
Short‐Term Plume Containment: Multiobjective Comparison
Authors: Peralta Richard C. , Ward Robert L. 
Published: August 2005

AbstractMultiobjective strategies and models for optimizing the short‐term containment of a 2‐D ground‐water contaminant plume are compared. These are designed for cases in which an appropriate means of treating the contaminated water is unavailable or unauthorized, and the management goal is to prevent plume movement, without pumping contaminated water and without importing or exporting water. Because optimal unsteady strategies are usually more efficient than optimal steady strategies at achieving goals at a prespecified time, the models optimize the needed time‐varying rates of extracting and injecting water. The objective function can use coefficients to consider, one at a time, the objectives of minimizing final hydraulic gradients between observation wells and the plume source, minimizing the cost of pumping, or minimizing the volume of pumping. Alternatively, the model can simultaneously consider the gradient objective and one of the other two objectives in developing a compromise strategy. If the plume must be contained only for the period of optimal unsteady pumping, either the minimizing cost or the minimizing pumping volume objective is most appropriate. For short periods, a minimum pumping strategy, which is the easiest to use, is almost the same as a least‐cost strategy. If the plume must be contained for a longer period, the hydraulic objective becomes increasingly important because it causes a more horizontal potentiometric surface, and less additional pumping is needed to maintain that surface after the end of unsteady pumping.
Effect of Nitrate Addition on Biorestoration of Fuel‐Contaminated Aquifer: Field Demonstration
Authors: Hutchins S. R. , Downs W. C. , Wilson J. T. , Smith G. B. , Kovacs D. A. , Fine D. D. , Douglass R. H. , Hendrix D. J. 
Published: August 2005

AbstractA spill of JP‐4 jet fuel at the U.S. Coast Guard Air Station in Traverse City, Michigan, contaminated a water‐table aquifer. An infiltration gallery (30 ft × 30 ft) was installed above a section of the aquifer containing 700 gal JP‐4. Purge wells recirculated three million gallons of ground water per week through the infiltration gallery at a rate designed to raise the water table above the contaminated interval. Ground water containing ambient concentrations of oxygen and nitrate was first recirculated for 40 days. Concentrations of benzene in monitoring wells beneath the infiltration gallery were reduced from 760 to <1μ/1. Concentrations of toluene, ethylbenzene,m,p‐xylene, ando‐xylene were reduced from 4500 to 17, 840 to 44, 2600 to 490, and 1400 to 260 μ/1, respectively. Average core concentrations of benzene, toluene, ethylbenzene,m,p‐xylene, ando‐xylene were reduced from 0.84 to 0.032, 33 to 0.13, 18 to 0.36, 58 to 7.4, and 26 to 3.2 mg/kg, respectively. Ground water amended with nitrate (10 mg/1 nitrate‐nitrogen) and nutrients was then recirculated for 76 days. Final core concentrations of benzene, toluene, ethylbenzene,m,p‐xylene, ando‐xylene were 0.017,0.036,0.019,0.059, and 0.27 mg/kg, respectively. Final aqueous concentrations were <1 μ/1 for benzene and toluene, 6 μ/1 for ethylbenzene, and 20 to 40 μ/1 for the xylene isomers, in good agreement with predicted values based on residual fuel content and partitioning theory. Although alkylbenzene concentrations have been substantially reduced, the test plot is still contaminated with the weatheredfuel. Based on stoichiometry, approximately 10 times more nitrate was consumed than could be accounted for by BTX degradation alone, indicating that other compounds were also degraded under denitrifying conditions.
Theoretical Evaluation of Modified Wenner Array for Shallow Resistivity Exploration
Authors: Goyal Vikas C. , Niwas Sri , Gupta Pravin K. 
Published: August 2005

AbstractA mathematical study has been carried out for critical evaluation of the earlier reported Modified Wenner method for shallow resistivity exploration. It provides a theoretical basis for quantitative interpretation of the measured resistivity data and quantification of the depth of investigation at various potential electrode separations. Synthetic resistivity data for a few three‐layer models have been generated and compared with the Wenner, Schlumberger, and two‐electrode curves. It is established that the MWA and TEA lead to identical theoretical response.
Embedded Knowledge in Software: 1. Description of a System for Contaminant Transport Modeling
Authors: McClymont G. L. , Schwartz F. W. 
Published: August 2005

AbstractComputer software with embedded knowledge has the potential to improve the utility and usability of computer models. We explore these opportunities with the software package Expert ROKEY that includes EXPAR, a knowledge‐based system to assist in the preparation of input data for a simple mass transport model. EXPAR is partitioned into two levels. At the top level is a set of computer forms that contain groups of related parameters and corresponding entry fields. Users can either volunteer parameter values or request help from an assistance program. Elaboration programs provide supporting information for each parameter and brief tutorials for the mass transport processes included in the model. The sets of assistance and elaboration programs represent the bottom level of EXPAR. This model preprocessor contains useful features like tutorial and data‐base information, systematic procedures for deriving parameter values, capabilities for checking the completeness and consistency of data, and a virtually transparent user interface with the computer, which are applicable to codes of all types.
Modeling the Density‐Driven Movement of Liquid Wastes in Deep Sloping Aquifers
Authors: Dorgarten Hans‐Wilhelm , Tsang Chin‐Fu 
Published: August 2005

AbstractOne method for the disposal of hazardous liquid wastes is by injection into deep aquifers. Although these aquifers may be separated from underground sources of drinking water by thick formations of low permeability, their mobility due to different migration mechanisms has to be studied carefully, since the injected wastes remain toxic over periods of thousands of years. One possible mechanism for waste movement is density‐driven flow and transport, due to density differences between the waste and the surrounding water in the injection zone. In the present paper the importance of this phenomenon is studied mathematically by means of analytical and numerical calculations for typical deep injection conditions. The analytical estimates reveal that density‐driven movement of liquid wastes in sloping aquifers can be much stronger than plume migration due to natural hydraulic gradients. This finding is emphasized by the results of a two‐dimensional vertical finite element model, which is applied for detailed numerical simulations. Results show that during the initial stage, waste can be expected to spread into all directions due to density‐induced stratification effects. Later on, it mainly moves laterally along the slope of either aquifer top or aquifer bottom, depending on the waste density. If regional ground‐water flow is directed the same way, transport is accelerated. If regional ground‐water flow is in the opposite direction, on the other hand, transport to both sides must be expected to occur. Thus, the aquifer slope and regional hydraulic gradient may be equally significant factors in estimating potential migration of disposed liquid wastes.
Subsurface Partitioning of Volatile Organic Compounds: Effects of Temperature and Pore‐Water Content
Authors: Kerfoot H. B. 
Published: August 2005

AbstractEquations describing the three‐phase equilibrium of contaminants between the pore‐gas, pore‐water, and solid‐sorbed phases in the unsaturated zone are presented. These relationships are then used to derive general expressions for the temperature‐dependence of the equilibrium in a three‐phase system, and those relationships are applied to derive expressions for the temperature‐dependence of the concentrations in the three phases when the total contaminant mass present and the gas‐filled and water‐filled porosities are constant. The temperature‐dependence of the three‐phase equilibrium is dictated by the enthalpies of phase transition and the appropriate equilibrium constants. As the temperature increases, contaminants move from the more‐dense to the less‐dense phases, so that the pore‐gas‐phase concentration increases to an upper limit; the pore‐water‐phase concentration increases, reaches a maximum, and then decreases; and the solid‐sorbed concentration decreases. Equations describing the effects of changes in the water‐filled porosity, such as those that would be caused by infiltration of either clean or contaminated pore water, on the gas‐phase and pore‐water‐phase concentrations of contaminants are presented. For compounds with a Henry's Law constant (H, dimensionless) greater than one, an increase in water‐filled porosity results in an increase in the pore‐gas concentration, while for compounds with H less than one, such a change results in a decrease in the pore‐gas concentration. The applicability of the thermodynamic relationships developed is limited by the assumption of ideal‐gas behavior, isothermal phase transition, and isobaric conditions. The stoichiometric relationships developed are limited by the assumption of complete mixing. They are used to develop equations that allow calculation of the equilibrium fraction of the total contaminant mass present in each phase on the basis of pore‐gas monitoring data, site properties, and equilibrium constants. Based on observed natural seasonal changes in subsurface temperatures and moisture contents, the effects predicted in the derived equations could result in significant changes in gas‐phase concentrations without changes in the total contaminant mass present.