bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of Geophysical Logs to Estimate Water Quality of Basal Pennsylvanian Sandstones, Southwestern Illinois
Authors: Poole V. L. , Cartwright K. , Leap D. 
Published: August 2005

ABSTRACTFresh water is found at depths up to 1000 feet in basal Pennsylvanian sandstone aquifers along the southern margin of the Illinois Basin. These aquifers, though not highly productive, represent a significant potential source of ground water in a region of very limited ground‐water supplies. A pilot study was undertaken in southwestern Illinois using geophysical logs and limited hydrologic data to evaluate the potential of these aquifers. Water quality, porosity, and permeability were estimated from the geophysical logs; these data were then used in conjunction with data from aquifer performance tests to delineate zones of potable water. The data indicate that fresh‐water lenses extend basinward in sandstone paleochannels.
Accurate Estimation of Conductivity of Water from Geoelectrical Measurements— A New Way to Correct for Clay
Authors: Park Stephen K. , Dickey Stephen K. 
Published: August 2005

ABSTRACTWe propose a new way to correct estimates of solution conductivity for the effects of clay in a rock. The bulk electrical conductivity of a rock is dependent on its porosity, the conductivity of the pore fluid, and its clay content. Archie's law relates the bulk electrical conductivity to the first two factors only. The third factor, clay, enhances a rock's conductivity through surface conduction, and simple application of Archie's law will lead to overestimates of the solution conductivity. The enhancement due to clay can be estimated from measurements of induced polarization, however, and the bulk conductivity of the rock can be corrected. This correction will then lead to a more accurate estimate of the solution conductivity. Both resistivity and induced polarization can be measured by geophysical techniques. Interpretations of geophysical data are inherently nonunique, however, unless wells are correlated with the data. The method proposed here requires calibration with subsurface samples from at least one location. We have tested the method we propose to correct for clay in an area already sampled by monitoring wells. The corrections lead to substantial improvements in the correlation between solution conductivities from wells and from geophysical measurements. We are not proposing replacement of wells with geophysical soundings. Rather, the geophysical measurements, which are obtained at a fraction of the cost of a well, can be used to site wells and minimize the amount of drilling needed.
Geochemical Variations in a Core of Hydrogeologic Units Near Freehold, New Jersey
Authors: Pucci Amleto A. , Owens James P. 
Published: August 2005

ABSTRACTSolutes were determined for 26 pore‐water samples extracted from Tertiary and Cretaceous core material from a 1,320‐foot‐deep test borehole at Freehold, New Jersey. The cored materials are sediments that form a multilayered aquifer system of seven aquifers and eight confining units in the New Jersey Coastal Plain. The sediments are of marine origin in the upper 650 feet of the core and primarily nonmarine below 650 feet. Total concentrations of silica and major anions (SO4‐2 and Cl‐) and cations (Ca+2, Mg+2, total Fe, Mn+2, Na+, and K+) in the pore‐water samples varied with depth. Three core intervals are defined by water‐ chemistry variations, the environment of deposition (marine or nonmarine), and the degree of alteration (weathered or unweathered) of the units. Calcium, magnesium, sulfate, and total‐ion concentrations were greater in the midcore (unweathered marine) interval than in the upper (weathered marine) and lower (fluviodeltaicsilicate) intervals of the core. Generally, pore‐water chemical types in confining units were distinct from those found in aquifers–particularly in the midcore interval. In this interval, observed variations in pore‐water chemistry in part reflect carbonate dissolution and cation exchange reactions common in Coastal Plain sediments. However, high concentrations of sulfate in unweathered marine sediments indicate novel processes may be important factors influencing pore‐water chemistry in confining units.
Ionic Composition of Vadose Zone Water in an Arid Regiona
Authors: Rice R. C. , Bowman R. S. , Bouwer H. 
Published: August 2005

ABSTRACTThe ionic composition of water in the vadose zone of the Salt River Valley in south central Arizona was studied for three different water regimes: desert, irrigated, and flooded by urban runoff. The desert area exhibited high salinity in the top 10 m, probably due to concentration of salts over several years. Below 15 m, the salinity decreased with depth and approached the salinity of the native ground water. For the irrigated area, the chemical composition of the soil water was similar to that of the applied water but concentrations were higher. The irrigation efficiency calculated from the salinities of the irrigation and soil water was 78%.The average NO3‐concentration from five of six sites was 100 mg/l, but was as high as 24,000 mg/l at another. Soil water from the urban runoff site had an electrical conductivity that was about three times less than that from the irrigated site, showing the effect of leaching with rain water. The observed salt distributions in the vadose zone were reasonably correlated to land use at the sites sampled.
The Occurrence of Perennial Seaward Seepages of Potable Water in Parts of Niger Delta, Nigeria
Authors: Amadi P. Abi‐Bezam 
Published: August 2005

ABSTRACTThe water‐supply scheme in many rural and periurban communities in the Niger Delta of Nigeria occurs as underground seaward seepages that are under cover of sea water about twice daily all the year round. Their shoreline environment notwithstanding, they remain soft and fresh throughout the year, and they are slightly acidic with pH ranges from 5·0 to 6·0. Partial chemical analysis shows that the pattern of changes in the geochemistry of the seaward seepages between seasons differs markedly from that of the ground water of the Niger Delta. The observed pattern suggests that these potable seepages do not originate from the ground‐water regime of the Delta but from another portion of the hydrologic cycle that probably involves some seaward‐bound underground streams which, due to changes in lithology or to the gradual land‐to‐sea break of slope or both, have been forced to surface at the coastal tip as seepages.
Automated Calibration of a Contaminant Transport Model for a Shallow Sand Aquifer
Authors: Holmes K. John , Chu Wen‐sen , Erickson Denis R. 
Published: August 2005

ABSTRACTThis paper presents an application of an automated calibration technique for the United States Geological Survey Method of Characteristics (USGS‐MOC) code. The model was applied to a shallow sand aquifer where contamination due to leakage from a solvent recycling plant was detected. Using available water‐table observations, transmissivity parameters for the USGS‐MOC model were calibrated by an automated parameter identification (PI) technique. Dispersivity was determined from trial‐and‐error simulations. For comparison purposes, the transmissivity parameters were also independently calibrated by trial‐and‐error simulations. The study results show that, although the PI‐calibrated model can produce water‐table contours that are in good agreement with observations and the contaminant plumes produced by the USGS‐MOC using parameters determined from the PI technique and the trial‐and‐error approach are not vastly different, the parameters determined by this technique are not considered to be physically plausible in all cases. The best strategy in model calibration would be to use both methods conjunctively.
An Approach to the Field Study of Hydraulic Gradients in Variable‐Salinity Ground Water
Authors: Hickey John J. 
Published: August 2005

ABSTRACTUnderstanding what can and cannot be determined about hydraulic gradients in field studies of variable‐salinity ground water is becoming increasingly important because of the use of subsurface injection as a waste‐disposal method in saline aquifers throughout the country. A field study approach is proposed for reliably estimating hydraulic gradients in subregions within a region of variable‐salinity ground water. It is based upon Hubbert's concept about the kind of density distributions that are required for ground water to have a potential. The approach consists of dividing a region of variable‐salinity ground water into subregions with constant density, subregions with only vertical variations in density, and subregions with vertical and lateral variations in density before determining magnitude and direction of hydraulic gradients. Subregions with constant density and subregions with only vertical variations in density according to Hubbert can have a potential; because of this, hydraulic gradients in such subregions may be reliably estimated. Subregions with vertical and lateral variations in density according to Hubbert may not have a potential; because of this, hydraulic gradients in such subregions cannot be reliably estimated. The approach was applied to an unconfined coastal aquifer and also to a confined and layered coastal aquifer that is used for subsurface injection. As the two applications show, the analysis of water levels and pressures from subregions with constant or approximately constant density and the analysis of pressures from subregions with only vertical variations in density provide simple and direct means for deducing the characteristics of hydraulic gradients within a region of variable‐salinity ground water.
Application and Comparison of Shallow Seismic Methods in the Study of an Alluvial Aquifer
Authors: Ayers Jerry F. 
Published: August 2005

ABSTRACTSeismic refraction, common‐offset, and common‐depth‐point methods were applied to an area on the flood‐plain of the Platte River in east‐central Nebraska to map the configuration of the bedrock surface, determine the thickness of the alluvial overburden, and define the hydrostratigraphy of the aquifer. Refraction results indicate a complex channelized bedrock surface that ranges in depth from 15 m to 40 m. At most stations, seismic velocities determined for the bedrock could be used to distinguish between rocks of the Dakota Group and Pennsylvanian‐age limestones and shales. Bedrock is overlain by alluvium with velocities typical of saturated sediments. A near‐surface clay unit was identified at a few refraction stations. Seismic velocities measured for the saturated sediments were used, in conjunction with an empirical relationship between velocity and bulk density, to obtain an estimate of 0.25 to 0.43 for the bulk porosity of the aquifer.A comparison of survey results shows that depths to bedrock obtained from the three methods are in good agreement where coincident measurements were made. The comparison also shows that the relief along the bedrock surface is defined in greater detail using reflection techniques, particularly the common‐depth‐point method. The shallow limit of investigation for the common‐offset method, at least for the field conditions present in the lower Platte Valley, is about 15 m, or one‐half of the limit previously considered by other workers.
Well Location in Capture Zone Design Using Simulation and Optimization Techniques
Authors: Ahlfeld David P. , Sawyer Charles S. 
Published: August 2005

AbstractA new computational methodology for capture zone design for contaminated ground‐water remediation is described. This method has been implemented in a computer model which utilizes both simulation and optimization techniques. The procedure determines the well locations and pump rates which will produce a desired ground‐water flow field at minimum cost. In this paper, the design procedure is described along with an example of its use on a hypothetical aquifer system. Numerical experiments are presented which determine the effect on remediation cost of alternate well locations. It is found that different well locations can have a major impact on the overall cost of remediation.
A Geoelectrical Investigation for Ground Water in Crystalline Terrains of Central Bahia, Brazil
Authors: Medeiros Walter E. , de Lima Olivar A. L. 
Published: August 2005

AbstractThe best locations for water wells in crystalline terrains of semiarid lands are narrow, densely fractured and altered belts, normally associated with fault zones and folding axes. A simple electrical procedure, based on vertical soundings and multiple resistivity profiling, has been successfully applied for the structural mapping of these two‐dimensional aquifers in northeast Brazil. The apparent resistivity sections constructed from partial electrical sounding measurements taken at a closely spaced interval along a traverse were interpreted using a finite‐difference algorithm. This scheme allowed detailed description of the lateral and vertical extent of fractured aquifers and some of their hydrogeophysical characteristics. The results of a selected case study from Bahia state compare satisfactorily with available geophysical logs and production data of existing wells.
Laboratory Studies of the Flow of Some Organic Solvents and Their Aqueous Solutions Through Bentonite and Kaolin Clays
Authors: Abdul A. S. , Gibson T. L. , Rai D. N. 
Published: August 2005

AbstractA laboratory study was undertaken to evaluate the flow of the following organic solvents and their aqueous solutions through bentonite and kaolin clays: benzene, toluene, p‐xylene, nitrobenzene, trichloroethylene, tetrachloroethylene, ethyl acetate, 2‐butanone, and phenol. In each experiment, one pore volume of a 0.005 N CaSO4 solution (water) flowed through the clays, followed by several pore volumes of an aqueous solution of one of the organic solvents, and then by about three pore volumes of the neat organic solvent. The hydraulic conductivity for the aqueous organic solutions was not significantly different from those for water, and ranged from 4.6 × 10‐7 to 14.4 × 10‐7 and from 0.6 × 10‐7 to 0.8 × 10‐7 cm/sec through the kaolin and bentonite clays, respectively. The flow of the neat solvents through either the bentonite or kaolin clay increased by up to two orders of magnitude. The aqueous solutions did not change the physical appearance of the clays. In general, the more hydrophobic solvents caused the clays to shrink, producing distinct large vertical cracks. The hydrophilic solvents typically caused the clays to aggregate and fracture, forming a network of cracks. The kaolin clay appeared to aggregate more readily than the bentonite clay. The higher swelling of the clays in water than in the neat organic solvents likely caused the physical changes in the clays and the rapid flow of the neat solvents through them.
Use of Resistivity Soundings to Determine Landfill Structure
Authors: Carpenter P. J. , Kaufmann R. S. , Price B. 
Published: August 2005

AbstractSixteen Wenner and Schlumberger array electrical soundings were made over portions of the Mallard North landfill in DuPage County, Illinois, to map the gross layered structure of a closed landfill. Sounding curves were fit to standard type curves and values inverted in a least‐squares procedure to yield multilayer geoelectrical models. Wood, newspaper, cloth, glass, plastic, and metal refuse interspersed with soil exhibited resistivities of 9–19 ohm‐m (unsaturated) and 2–7 ohm‐m (leachatesaturated). Mature unfractured clay‐till cover material exhibited a resistivity of about 30 ohm‐m, and its thickness was estimated to within 27% of its true thickness. Larger errors were encountered over fractured and freshly emplaced cover. Soundings were also inverted to yield accurate leachate levels and refuse thicknesses (errors for both averaged about 30%). While Schlumberger and Wenner soundings produced models with comparable accuracy, Schlumberger soundings were less sensitive to cover heterogeneities and easier to deploy. Moore's cumulative resistivity interpretation method was found to be unreliable in interpreting this type of resistivity data. Fractures present in the cover material, lateral changes in leachate level, and variations in cover thickness and resistivity contributed to errors in interpretation. Despite these limitations, models generated from electrical resistivity soundings are reasonably accurate in their depictions of internal conditions in this type of landfill. Such soundings could be used to map internal structure in other layered landfills that lack construction and operational records.
Measurement and Interpretation of Low Levels of Dissolved Oxygen in Ground Water
Authors: White Art F. , Peterson Maria L. , Solbau Ray D. 
Published: August 2005

AbstractA Rhodazine‐D colorimetric technique was adapted to measure low‐level dissolved oxygen concentrations in ground water. Prepared samples containing between 0 and 8.0 μmoles · 1‐1 dissolved oxygen in equilibrium with known gas mixtures produced linear spectrophotometric absorbance with a lower detection limit of 0.2 μmoles · 1‐1. Excellent reproducibility was found for solutions ranging in composition from deionized water to sea water with chemical interferences detected only for easily reduced metal species such as ferric ion, cupric ion, and hexavalent chromium. Such effects were correctable based on parallel reaction stoichiometries relative to oxygen. The technique, coupled with a downhole wire line tool, permitted low‐level monitoring of dissolved oxygen in wells at the selenium‐contaminated Kesterson Reservoir in California. Results indicated a close association between low but measurable dissolved oxygen concentrations and mobility of oxidized forms of selenium in the shallow aquifer which were in general electrochemical disequilibrium.
Field Evidence for the Effect of Acetate on Leachate Alkalinity
Authors: Devlin J. F. 
Published: August 2005

AbstractAlkalinity measurements are routinely conducted as part of standard water–quality determinations. Often, very little interpretation of the values is attempted, and the entire alkalinity is attributed to carbonate or bicarbonate. When landfill leachates are involved, this assumption could be misleading in terms of plume mapping, determining the incrustation potential of the water, or assessing the likelihood of methane generation because substances other than carbonate, for example acetate, can contribute significantly to the sample's alkalinity.A set of landfill leachate samples was collected and analyzed for alkalinity and volatile fatty acids. Acetate was the only organic acid identified. A very strong correlation was observed between acetate and alkalinity. Actual titration curves (volume of acid vs. pH) were compared with curves calculated assuming that acetate and bicarbonate were the two major species contributing the total alkalinity. Excellent agreement was observed between the experimental and theoretical data. Distinct differences in the shapes of the curves for carbonate–dominated and acetate‐dominated alkalinities make it possible to distinguish these two classes of water solely on the basis of alkalinity measurements. Water containing acetate titrates with an equivalence point which is less distinct than water containing only carbonate.
Determination of Specific Storage by Measurement of Aquifer Compression Near a Pumping Well
Authors: Robson S. G. , Banta E. R. 
Published: August 2005

AbstractAquifer tests of confined aquifers in deep formations can yield inaccurate specific–storage and storage‐coefficient estimates if the distance between the pumped and observation wells is imprecisely known. The distance between the wells can be uncertain because small deviations in the vertical alignment of deep wells can markedly change the distance between the perforated intervals of the wells. Uncertain distance between wells may seriously degrade the accuracy of specific‐storage or storage–coefficient values calculated from aquifer–test data obtained from closely spaced wells.A method is proposed whereby compression of the aquifer matrix can be measured during an aquifer test and used to calculate specific‐storage and storage–coefficient values without knowledge of the distance between the pumped and observation wells. In a field trial of the method, specific–storage and storage‐coefficient values calculated from aquifercompression data were 8.16 × 10 ‐7 and 3.04 × 10 ‐4, which is nearly identical to values (8.04 × 10 ‐7 and 2.99 × 10 ‐4) obtained from longer–term monitoring of aquifer barometric efficiency. Additional comparison with results of a Theis analysis of drawdown data indicates that the aquifer compression data may provide a more accurate determination of specific–storage and storage–coefficient values than would be possible even if the vertical alignment of the pumped and observation wells had been surveyed.
The Shallow Weathered Fracture Layer in the Near–Stream Zone
Authors: Gburek W. J. , Urban J. B. 
Published: August 2005

AbstractThe bedrock profile of an east–central Pennsylvania watershed contains a shallow weathered fracture layer. To begin quantifying the effects of this fracture layer on ground–water movement, two valley cross sections were chosen for detailed investigation. One section represents the typical upland watershed situation where the regional ground water is in contact with the stream for only part of the year, while at the other section the regional ground water is in perennial contact with the stream. Rock cores extracted from the sections reveal a pattern of extensive fracturing to approximately 50 ft directly under the stream thinning to a relatively uniform 30–ft deep fracture layer away from the channel. Limited seismic investigations support these observations. Piezometers within each cross section show that hydraulic conductivity differs between the shallow fracture layer and the relatively unfractured zone below and that there is great variability in conductivity within the fracture layer itself. Lateral flow generally occurs within the fracture layer to within approximately 50 ft of the stream; here a converging flow pattern indicates ground–water discharge to the stream. Under wet conditions, the stream in each section serves as a point of ground‐water discharge, while under dry conditions, the more upland section shows no ground–water discharge to the land surface. Rather, subsurface flow is likely occurring beneath and parallel to the channel controlled by a discharge point at some downstream location. Finally, water–quality samples from the piezometers indicate a direct effect of overlying land use on water quality within the shallow fracture layer.