bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of a Desert Aquitard— Hydrologic and Hydrochemical Considerations
Authors: Nativ Ronit , Nissim Ilan 
Published: August 2005

AbstractThe northern Negev desert has become a prime area for siting potentially contaminating facilities, including chemical industries and the Israeli national site for isolation and treatment of hazardous waste. The area is underlain by chalk formations having low matrix permeability. However, abundant fractures create preferential pathways for contaminant migration from the land surface to ground water in the chalk aquitard and, possibly, to adjacent aquifers. Geologic investigations preceding the construction of these industries assumed that the combination of the arid climate and low matrix permeability of the aquitard was sufficient to prevent any contaminant movement into its ground water. Solute transport through fractures and dissolution channels was never considered. However, contamination has been recently observed in the aquitard. Observations regarding the seasonal fluctuation of ground‐water levels, oxygen‐18 and deuterium composition, and the measurable tritium (0.3 to 15.9 TU) provide the basis for the following conclusions: (1) Ground‐water recharge by winter precipitation and runoff water occurs rapidly despite the regions's aridity and the low permeability of the overlying chalk matrix, (2) recharge occurs along fractures in all regions and is not restricted to hydrologically upgradient areas, and (3) recently recharged water is being mixed with the base flow of older water. Older ground water may flow along smaller, less developed fracture systems or through the porous matrix, whereas recent water probably moves along wider fractures or karst channels formed underneath ephemeral streams.
Relationships Between Saline Ground Water Soil, and Leaf Tissue Composition of the Phreatophyte Mezquite
Authors: García‐Carreño F. L. , Troyo‐Diéguez E. , Ochoa J. L. 
Published: August 2005

AbstractThe chemical and biochemical composition of leaf tissue from 24 mezquites (Prosopis articulata) was correlated with the ion content of soils and ground waters from six separate sites supporting plant growth. The peroxidase responses varied at different salinities; however, this enzyme activity decreased as the electrical conductivity of the ground water increased. Chlorophyll content of the leaves increased with the electrical conductivity (EC) of the well water, but the response was not statistically significant. The ion concentration (Ca++, Mg++, Na+, HCO3−, and Cl−), pH, and SAR (sodium adsorption ratio) in leaf tissue showed no correlation with their corresponding values for soil and ground water, confirming earlier reports on the ion‐exclusion mechanism of the mezquite root system. Likewise, low molecular weight metabolites such as glycerol, amino acids, and hexoses showed no correspondence with the salt content in ground waters. Of all the studied ions, chemical parameters, and biochemical compounds, EC in the ground water, leaves, and soil in the open field midway between mezquites, as well as peroxidase activity of foliar extracts showed the highest correlation with the salinity of ground water. The results of this research suggest that measuring EC and biochemical mezquite parameters may provide an alternative to drilling to evaluate ground‐water quality.
Unsaturated and Saturated Flow in Response to Pumping of an Unconfined Aquifer: Field Evidence of Delayed Drainage
Authors: Nwankwor G. I. , Gillham R. W. , van der Kamp G. , Akindunni F. F. 
Published: August 2005

AbstractThis paper revisits a long‐standing problem in aquifer analysis. In particular, it provides a physically consistent explanation of the characteristic time‐drawdown response of unconfined sand or gravel aquifers to pumping. It also provides a physical explanation for the low values of specific yield commonly obtained by type‐curve matching procedures. Tensiometers and piezometers distributed throughout the saturated thickness were used to monitor, in great detail, the hydraulic response of an unconfined sand aquifer to pumping. A gamma moisture gauge and core samples were also used to obtain measurements of water content in the region of the declining water table. The results showed the early period of time‐drawdown graphs to correspond with the period of increasing gradients. Excess storage of water was observed above the water table and was shown to be a necessary consequence of the vertical hydraulic gradients and the water‐content/pressurehead relationship for the aquifer material. The excess storage decreased during the period of decreasing vertical gradients. The period of delayed drawdown was shown to be the result of the decline in excess storage. Contrary to most of the recent literature, the results show that drainage processes above the water table have a very significant effect on the response of unconfined aquifers to pumping. The results indicate further that the normal methods of analyzing time‐drawdown curves for unconfined aquifers give excessively high values of storativity and values of specific yield that are unrealistically low.
Storage Coefficients and Vertical Hydraulic Conductivities in Aquitards Using Extensometer and Hydrograph Data
Authors: Cleveland Theodore G. , Bravo Rolando , Rogers Jerry R. 
Published: August 2005

AbstractA method is presented to estimate elastic and inelastic specific storage and vertical hydraulic conductivities in aquitards in multilayered flow systems. Borehole extensometer records and ground‐water hydrographs from piezometers are used to construct plots of effective stress and deformation. Elastic and inelastic specific storage are estimated from the plots of effective stress and deformation during loading and unloading cycles. The elapsed loading time is estimated from the same plots and is used to calculate vertical hydraulic conductivity using Terzaghi's consolidation theory. The method is applied to three sites in Houston, Texas.
Relation Between Anisotropic Transmissivity and Azimuthal Resistivity Surveys in Shallow, Fractured, Carbonate Flow Systems
Authors: Ritzi Robert William , Andolsek Robert Henry 
Published: August 2005

AbstractIn an investigation of a near‐surface, fractured, carbonate ground‐water flow system, the axes of the apparent resistivity ellipse determined from an azimuthal resistivity survey were shown to coincide with both the ellipse of depression during an aquifer test, and the eigenvectors of the transmissivity tensor determined from the aquifer test analysis. Thus, for such relatively shallow, fractured flow regimes, azimuthal resistivity surveys may be a useful methodology for determining the principal directions of transmissivity prior to conducting anisotropic pumping tests, and thus aid in designing the emplacement of observation wells.
Comparison of Purge and Trap GC/MS and Purgeable Organic Chloride Analysis for Monitoring Volatile Chlorinated Hydrocarbons
Authors: Barber Larry B. , Michael Thurman E. , Takahashi Yoshi , Noriega Mary C. 
Published: August 2005

AbstractA combined field and laboratory study was conducted to compare purge and trap gas chromatography/mass spectrometry (PT‐GC/MS) and purgeable organic chloride (POC1) analysis for measuring volatile chlorinated hydro‐carbons (VCH) in ground water. Distilled‐water spike and recovery experiments using 10 VCH indicate that at concentrations greater than 1 /ig/1 recovery is more than 80 percent for both methods with relative standard deviations of about 10 percent. Ground‐water samples were collected from a site on Cape Cod, Massachusetts, where a shallow unconfined aquifer has been contaminated by VCH, and were analyzed by both methods. Results for PT‐GC/MS and POC1 analysis of the ground‐water samples were not significantly different (alpha = 0.05, paired t‐test analysis) and indicated little bias between the two methods. Similar conclusions about concentrations and distributions of VCH in the ground‐water contamination plume were drawn from the two data sets. However, only PT‐GC/MS analysis identified the individual compounds present and determined their concentrations, which was necessary for toxicological and biogeochemical evaluation of the contaminated ground water. POC1 analysis was a complimentary method for use with PT‐GC/MS analysis for identifying samples with VCH concentrations below the detection limit or with high VCH concentrations that require dilution. Use of POC1 as a complimentary monitoring method for PT‐GC/MS can result in more efficient use of analytical resources.
Patterns and Rates of Ground‐Water Flow on Long Island, New York
Authors: Buxton Herbert T. , Modica Edward 
Published: August 2005

AbstractIncreased ground‐water contamination from human activities on Long Island has prompted studies to define the pattern and rate of ground‐water movement. A two‐dimensional, fine‐mesh, finite‐element model consisting of 11,969 nodes and 22,880 elements was constructed to represent ground‐water flow along a north‐south section through central Long Island. The model represents average hydrologic conditions within a corridor approximately 15 miles wide. The model solves discrete approximations of both the potential and stream functions. The resulting flownet depicts flow paths and defines the vertical distribution of flow within the section. Ground‐water flow rates decrease with depth. Sixty‐two percent of the water flows no deeper than the upper glacial (water‐table) aquifer, 38 percent enters the underlying Magothy aquifer, and only 3.1 percent enters the Lloyd aquifer. The limiting streamlines for flow to the Magothy and Lloyd aquifers indicate that aquifer recharge areas are narrow east‐west bands through the center of the island. The recharge area of the Magothy aquifer is only 5.4 miles wide; that of the Lloyd aquifer is less than 0.5 miles.The distribution of ground‐water traveltime and a flownet are calculated from model results; both are useful in the investigation of contaminant transport or the chemical evolution of ground water within the flow system. A major discontinuity in traveltime occurs across the streamline which separates the flow subsystems of the two confined aquifers. Water that reaches the Lloyd aquifer attains traveltimes as high as 10,000 years, whereas water that has not penetrated deeper than the Magothy aquifer attains traveltimes of only 2,000 years. The finite‐element approach used in this study is particularly suited to ground‐water systems that have complex hydrostratigraphy and cross‐sectional symmetry.
Hydrogeologic Factors Affecting New Sinkhole Development in the Orlando Area, Florida
Authors: Wilson William L. , Beck Barry F. 
Published: August 2005

AbstractSinkhole development affects approximately 15 percent of the land area of the world. Development of new sinkholes is extremely site‐specific, but general associations between new sinkhole development and hydrogeologic factors can be established for areas with adequate historical records of sinkhole development. In the Orlando area, east‐central Florida, at least 140 sinkholes have developed between 1961 and 1986. The Orlando area is situated on a thickly mantled karst area, and sinkholes form by cover collapse or, less commonly, cover subsidence. On the average, 11 new sinkholes collapse each year. The mean diameter is 30.8 feet and the mean depth is 15.5 feet. Eighty‐five percent of the new sinkholes occur in high recharge areas (10 to 15 inches/year) on slightly elevated, sandy ridges. Few or no sinkholes occur in discharge areas where net downward erosion of surficial sediment is very unlikely. Forty‐two percent of all new sinkholes occur during April and May when ground‐water levels are usually at seasonal low stands. When the potentiometric surface declines 5 feet below its mode, then more sinkholes than expected per unit time begin to occur. When the potentiometric surface declines 10 feet below its mode, then more than 10 times as many sinkholes as expected per unit time begin to occur. Management of ground‐water withdrawal to avoid drawdowns in excess of 5 feet in sinkhole‐prone areas will minimize new sinkhole development induced by man.
Chromatographic Evidence for Nonlinear Partitioning of Aromatic Compounds Between Petroleum and Water
Authors: Wise William R. , Robinson George C. , Bedient Philip B. 
Published: August 2005

AbstractChromatographic analysis of published laboratory data suggests that the observed tailing behavior of aromatics (benzene, toluene, ethylbenzene, and xylene) being leached from a residual‐petroleum phase into a flushing‐water phase is explicable using nonlinear (specifically favorable) partitioning relations in the absence of kinetic limitations. This result raises questions regarding the legitimacy of deducing kinetic limitations of interphase transfer based upon the assumption of linear partitioning.
In Situ Surfactant Washing of Polychlorinated Biphenyls and Oils from a Contaminated Site
Authors: Abdul A. S. , Gibson T. L. , Ang Carolina C. , Smith Julie C. , Sobczynski R. E. 
Published: August 2005

AbstractOver the past four years, we have been developing an in situ surfactant‐washing method to decontaminate soil systems. This study addresses another major step in that development: a field test of the surfactant‐washing method at a site contaminated with polychlorinated biphenyls (PCBs) and oils. A test plot, 10‐ft diameter by 5‐ft deep, was selected in an area of high levels of contaminataion. The study involved applying a surfactant solution on the plot to wash the site material and carry the leachate down to the depressed water table, where it was collected by pumping a recovery well installed through the center of the plot. The leachate pumped to the surface was biotreated to degrade the oils and surfactant, and the PCBs were removed from the leachate by an activated carbon system. Soil cores from the test plot indicated concentrations of up to 6,223 mg/kg PCBs and 67,000 mg/kg oils. The test plot initially contained about 15 kg of PCBs and 157 kg of oils. The hydraulic response of the test plot to washing was monitored by measuring the water levels in wells around the test plot and the fluid pressure and saturation through the plot. These real‐time data were used to adjust the surfactant‐application rate to minimize lateral spread of the surfactant and leachate and the pumping rate to capture all the leachate by the recovery well. The response of contaminant concentrations in the test plot to washing and the performance of the leachate‐treatment system were also monitored during the test by collecting and analyzing samples from the recovery well and from the treatment system. An on‐site laboratory was used for these analyses. During the 70 days of the washing test, 5,375 gallons of a 0.75% aqueous surfactant solution was applied on the test plot at an average rate of 77 gal/day. During the same period, 10,981 gallons of leachate were recovered at an average rate of 157 gal/day. A total of 1.6 kg of PCBs and 16.9 kg of oils (about 10% of the initial mass) was washed from the test plot during the test. Maximum concentrations of 65 mg/1 PCBs and 709 mg/1 oils were measured in leachate samples. The leachate was adequately treated before it was discharged. These test results indicate that in situ surfactant washing is a promising candidate for the remediation of contaminated soil systems.
Analysis of Unsteady Flow to a Large‐Diameter Well Experiencing Well Loss
Authors: Chachadi A. G. , Mishra G. C. 
Published: August 2005

AbstractUnsteady flow to a large‐diameter well in a confined aquifer experiencing well loss has been analyzed by the discrete kernel approach. The well storage reduces the well loss component and the well storage is effective in the beginning of pumping. The inefficiency of a well is overcome by increasing the well radius. The variation of specific drawdown in a large‐diameter well experiencing well loss with pumping rate is nonlinear. The nondimensional time drawdown graph at a large‐diameter well, in which the well loss component follows the Jacob's equation, is not unique but dependent on pumping rate.
Confining Unit Effects on Water Quality in the New Jersey Coastal Plain
Authors: Pucci Amleto A. , Ehlke Ted A. , Owens James P. 
Published: August 2005

AbstractSediment and pore‐water samples from Tertiary and Cretaceous strata in the New Jersey Coastal Plain were collected from cores from Freehold Township, Monmouth County; Howell Township, Monmouth County; and from Clayton Township, Gloucester County. These strata form a multilayered aquifer system in which upper units are marine origin and lower units are predominantly nonmarine.Concentrations of major constituents in pore‐water samples from confining units and aquifers were highly variable: calcium (1.7–660 mg/I), magnesium (0.3–140 mg/l), sulfate (1.52200 mg/l), and dissolved inorganic carbon (9–290 mg/l); with large differences between marine confining units and aquifers. Where the aquifers are unconfined and oxic, well waters in the Potomac‐Raritan‐Magothy aquifer system in the northern Coastal Plain have higher concentrations of nitrate, chloride, and dissolved oxygen. In areas where the aquifer system is confined and anoxic, there are higher concentrations of sulfate and bicarbonate. Differences in bicarbonate concentrations between two wells (12 and 67 mg/l) along a regional flow path can be caused by mixing of water in a nonmarine aquifer with leached sulfate‐enriched, marine confining‐unit water, and subsequent reduction of sulfate.Bacterially mediated organic carbon oxidation, iron reduction, and sulfate reduction, and ion‐exchange reactions may explain constituent variations. Bacteriological assays of core sections from the Howell and Clayton Township coreholes showed viable sulfate‐reducing bacteria as deep as 558 feet below land surface. Sediments from a depth of 210 feet showed populations of sulfate‐reducing bacteria of 103–l06 organisms per gram of soil.
Combined Mathematical Model of Flow in an Aquifer‐Vertical Well System
Authors: Tarshish Michael 
Published: August 2005

AbstractA mathematical model and calculation method were developed for steady‐state flow in a confined aquifer‐vertical well system without the usual assumption that the specific discharge in the radial direction to the screen is constant along its axis.A vertical well is represented as a linear sink located along the well axis with nonuniform inflow (specific discharges) for description of a flow in an aquifer. Flow in the screen channels is described by taking into account energy losses and the momentum flux change along the well screen's axial (vertical) orifice. Substantial errors are avoided by the use of the proposed model in calculations of drawdown‐well discharge function and maximum specific discharge to the screen which influences sand pumping, incrustation, and corrosion processes.
The Occurrence and Effect of Sulfate Reduction and Sulfide Oxidation on Coastal Limestone Dissolution in Yucatan Cenotes
Authors: Stoessell Ronald K. , Moore Yolanda H. , Coke James G. 
Published: August 2005

AbstractDissolution of carbonate minerals in the coastal halocline is taking place in the karst terrain along the northeastern coast of the Yucatan Peninsula. The dissolution is being accelerated in cenotes (sinkholes) where sulfate reduction and oxidation of the produced sulfide is occurring.Hydrogen‐sulfide concentrations ranged from 0.06 to 4 mmolal within the halocline in two sinkholes. Relative to concentrations expected by conservative mixing, fluids with high hydrogen‐sulfide concentrations were correlated with low sulfate concentrations, high alkalinities, low pH values, and heavy sulfur isotope values for sulfate. Hydrogen‐sulfide concentrations were less than those predicted from sulfate reduction, calculated from deficiencies in measured sulfate concentrations, indicating mobility and loss of aqueous sulfide.Fluids with low hydrogen‐sulfide concentrations were correlated with very high calcium concentrations, high strontium and sulfate concentrations, slightly elevated alkalinities, low pH values, and sea‐water sulfur isotope values for sulfate. Gypsum dissolution is supported by the sulfur isotopes as the major process producing high sulfate concentrations. However, oxidation of aqueous sulfide to sulfuric acid, resulting in carbonate‐mineral dissolution is needed to explain the calcium concentrations, low pH values, and only slightly elevated alkalinities.The halocline may trap hydrogen sulfide that has been stripped from the underlying anoxic salt water. The halocline can act as a stable, physical boundary, holding some of the hydrogen sulfide until it is oxidized back to sulfuric acid through interaction with the overlying, oxygenated fresh water or through the activity of sulfide‐oxidizing bacteria.
Database Management System for a Ground‐Water Regime
Authors: Jin Menggui , Wu Beiyi , Zhang Binhai 
Published: August 2005

AbstractThis paper presents the structure and function of a database system for a ground‐water regime in the case study of Geermu, Qinghai Province, northwestern China. This database system was constructed by combining the Chinese dBASE3 with other computer languages, such as BASIC, FORTRAN, etc. It systematically organizes the hydrogeological data and information, and automatically stores, queries, and manipulates ground‐water observation and related data, including an analysis and forecast of the ground‐water regime and the generation of various report forms and related graphics or maps.
Retardation of Tritium and Cesium in Brine‐Saturated Mudstone, Halite, and Carbonate Porous Media
Authors: Voudrias Evangelos A. , Means Jeffrey L. , Kittel Jeffrey 
Published: August 2005

AbstractBatch and column sorption/desorption experiments were conducted to quantify the retardation of tritium and cesium in brine‐saturated mudstone, halite, and carbonate rocks from Palo Duro Basin, Texas, one of the three sites originally nominated by the U.S. Department of Energy for construction of a civilian nuclear waste repository. Retardation factors (R) were determined using six different methods, including batch sorption equilibrium, fitting of two transport models, breakthrough area integration, and pore volume displacement at C/C0= 0.5, for both the sorption and desorption parts of the breakthrough curves. The breakthrough area integration method resulted in R values consistently lower than the other methods, which were in reasonable agreement. The data indicated very small retardation for cesium in all the media, except mudstone, which exhibited moderate retardation (R < 3.5). It was shown that the small extent of cesium retardation was most possibly caused by the strong competition for sorption sites of the components of the saturated brine, which were several orders of magnitude higher in concentration than cesium. Tritium breakthrough curves for all media tested were accurately simulated by the local equilibrium advection‐dispersion model (model I). With the exception of mudstone, cesium breakthrough curves were also adequately simulated by model I. The cesium breakthrough curve for mudstone exhibited considerable tailing on the desorption side of the curve, which was best described by the two‐site kinetic sorption model II. This was attributed to chemical nonequilibrium (two types of sorption sites). Predicted breakthrough curves for cesium using model I were in good to reasonable agreement with measured breakthrough curves.