bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Modified Mise‐A'‐La‐Masse Method for Contaminant Plume Delineation
Authors: Osiensky James L. , Donaldson Paul R. 
Published: August 2005

AbstractGround‐water monitoring to delineate contaminant plumes in complex hydrogeologic settings often is uncertain. This uncertainty is manifested by the fact that ground‐water contaminants often migrate along preferred pathways formed by lateral and vertical heterogeneity within definable stratigraphic units. A somewhat obscure surface, electrical geophysical method first suggested in 1920 holds great promise as a tool to help delineate conductive contaminant plumes in suitable hydrogeologic environments. This tool known as the mise‐a'‐la‐masse method has been used with success by other investigators to map conductive orebodies.A modified mise‐a'‐la‐masse method was used with great success in this investigation during a controlled field experiment. The method was used to track the evolution of a conductive tracer plume migrating through fluvial sands and gravels under a forced hydraulic gradient. Voltage differences between 171 stationary, surface electrodes and a reference electrode were monitored over time to map an evolving tracer plume. For this particular experiment, the method proved to be sensitive to changes in the specific electrical conductance of the ground water of less than 10% above the baseline values. Data derived by the modified mise‐a'‐la‐masse method show close agreement to specific electrical conductance measurements of ground‐water samples collected from wells during the tracer experiment. However, uncertainty in the significance of the variable specific electrical conductance data, especially at early times during the experiment, is reduced greatly by comparison with the plume maps generated by the modified mise‐a'‐la‐masse method.
In Situ Remediation of Contaminated Ground Water: The Funnel‐and‐Gate System
Authors: Starr Robert C. , Cherry John A. 
Published: August 2005

AbstractThe funnel‐and‐gate system for in situ treatment of contaminant plumes consists of low hydraulic conductivity cutoff walls with gaps that contain in situ reactors, such as reactive porous media, that remove contaminants by abiotic or biological processes. Funnel‐and‐gate systems can be installed at the front of plumes to prevent further plume growth, or immediately downgradient of contaminant source zones to prevent contaminants from moving into plumes. Cutoff walls (the funnel) modify flow patterns so that ground water flows primarily through high conductivity gaps (the gates). This approach is largely passive in that after installation, in situ reactors are intended to function with little or no maintenance for long periods. This approach contrasts with the energy and maintenance‐intensive character of pump‐and‐treat systems. This paper describes the funnel‐and‐gate concept, and uses two‐dimensional computer simulations to illustrate the effects of cutoff wall and gate configuration on capture zone size and shape and on the residence time for reaction of contaminants in gates.
Geochemical Reduction of Hexavalent Chromium in the Trinity Sand Aquifer
Authors: Henderson Thomas 
Published: August 2005

AbstractGround water of the Trinity Sand aquifer at the Odessa I site has become contaminated with hexavalent chromium due to release of plating wastes during the 1970s. Measured hexavalent chromium partition coefficients for Trinity Sand aquifer sediments compare favorably with values derived from the literature, and with retardation factors calculated from observed plume migration rates between 1986 and 1991. Dissolved and adsorbed masses of hexavalent chromium were calculated from contoured plume maps using ground‐water data collected between 1986 and 1991 to estimate the total mass of hexavalent chromium in the aquifer. Comparison of the calculations from each year indicated that only 30 percent of the hexavalent chromium present in the aquifer in 1986 remained in 1991.Decreasing hexavalent chromium mass in the Trinity Sand aquifer at the Odessa I site indicates that natural geochemical reactions are occurring to reduce mobile hexavalent chromium to the insoluble trivalent form. Thermodynamic calculations based on platinum electrode redox and pH measurements indicate that solid trivalent chromium hydroxide species are the stable phase in these ground waters. Reduction of hexavalent chromium to the trivalent state results in precipitation from solution of a solid chromium (III) hydroxide, probably in association with iron oxyhydroxides present in the aquifer. Two possible reducing agents in the Trinity Sand aquifer are naturally occurring organic carbon and ferrous iron.Laboratory measurements of the rate of hexavalent chromium reduction indicate that the reaction proceeds slowly at near‐neutral pH values representative of the Odessa I site. Assuming first‐order reaction kinetics, these laboratory reduction rates are consistent with the rate of hexavalent chromium loss at the Odessa I site between 1986 and 1991, and indicate a hexavalent chromium half‐life of approximately 2.5 years. An analytical contaminant transport model was calibrated to simulate historical chromium concentrations for the aquifer, and then used to predict that hexavalent chromium will naturally decrease below the drinking water standard within approximately 10 years.
Modifications to the Computer Program TENSOR2D
Authors: Maslia Morris L. 
Published: August 2005

AbstractThe U.S. Geological Survey computer program TENSOR2D may be used to compute the directional components of the anisotropic transmissivity tensor of two‐dimensional ground‐water flow. In this note, modifications to the original computer code, developed in 1987, are described. Because of the modifications, TENSOR2D now conforms to the Fortran 77 Standard and can be run on most personal computers without user modification. Additionally, a new routine generates the polar coordinates of the computed theoretical transmissivity (or diffusivity) ellipse.
Evaluation of Fluorobenzoate Tracers in Surface Soils
Authors: Jaynes Dan B. 
Published: August 2005

AbstractThe availability of several conservative, noninteracting tracers is desirable for the study of water movement in porous media. Recent studies have identified a family of fluorinated benzoic acid derivatives as having transport properties similar to Br. The transport properties of 2,6‐difluorobenzoate (2,6‐DFBA), 2,5‐difluorobenzoate (2,5‐DFBA), 3,4‐difluorobenzoate (3,4‐DFBA), 3,5‐difluorobenzoate (3,5‐DFBA), o‐(trifluoromethyl)benzoate (o‐TFMBA), m‐(trifluoromethyl)benzoate (m‐TFMBA), and pentafluorobenzoate (PFBA) were compared to Br in two neutral pH, high organic soils from Iowa. Batch equilibrium studies and column transport studies showed that 2,6‐DFBA, PFBA, and o‐TFMBA have transport properties very similar to Br, although their behavior may deviate slightly as the organic carbon and clay fractions of the soil increase. 2,5‐DFBA is retarded less and dispersed slightly more than the above tracers in these soils, but may be a useful tracer since it is still conservative. The other fluorobenzoates showed greater degrees of interaction with the soil matrix and were not conservative precluding their use as acceptable tracers. Plant growth studies using corn (Zea mays L.) and soybean (Glycine max [L] Merr.) showed significantly (P = 0.05) decreased growth for treatments using 3,4‐DFBA and 3,5‐DFBA, precluding their use in agronomic settings. Given the variation shown here and in earlier studies, the transport behavior of any of the fluorobenzoates should be evaluated prior to use in new environments.
Solubilization and Microemulsification of Chlorinated Solvents Using Direct Food Additive (Edible) Surfactants
Authors: Shiau Bor‐Jier , Sabatini David A. , Harwell Jeffrey H. 
Published: August 2005

AbstractSurfactant enhanced subsurface remediation is being evaluated as an innovative technology to expedite contaminant extraction from the subsurface. Regulatory approval of this technology will likely be enhanced by use of surfactants with FDA direct food additive status (“edible” surfactants). This research establishes edible surfactant systems capable of solubilizing (via micellar partitioning) and microemulsifying (via middle phase microemulsions) chlorinated solvents (PCE, TCE, and trans 1,2‐DCE). Micellar partition coefficients with edible surfactants are observed to be comparable to values previously reported for other surfactants, with solubilization increasing aqueous concentrations by one to two orders of magnitude for the chlorinated organics. Middle phase microemulsion formation is dependent on surfactant structure and cosurfactant concentration. Solubility enhancement in the middle phase systems (microemulsification) is at least one to two orders of magnitude higher than solubilization for the same surfactant concentration, but is much more sensitive to the surfactant system and the contaminant. In addition, successful microemulsion formation is seen to be a function of ground‐water temperature and hardness, indicating the need to consider these and additional factors for successful design and implementation of surfactant enhanced subsurface remediation. This research thus establishes a variety of edible surfactant systems that can significantly expedite subsurface remediation of chlorinated solvents, and illustrates the importance of proper selection and design of surfactant systems.
Regional Scale Ground‐Water Vulnerability Estimates: Impact of Reducing Data Uncertainties for Assessments in Hawaii
Authors: Loague Keith 
Published: August 2005

AbstractNonpoint source ground‐water contamination, resulting from regional scale applications of agrichemicals, is a major environmental issue. Several federal and state government funded modeling efforts were undertaken in the 1980s to assess ground‐water vulnerability from past and current chemical use and to potentially aid in the regulation of new chemicals. This paper is concerned with the impact of data uncertainties in regional scale pesticide leaching assessments for the chemical diuron in the Pearl Harbor Basin on the Hawaiian island of Oahu. In the first part of the paper uncertainties in soil, recharge, and chemical data are artificially reduced to study the impact of reduced data uncertainties on ground‐water vulnerability assessments made with simple mobility indices; the greatest improvements were realized for improvements in the chemical data. In the second part of the paper the impact of improvements to the Hawaii soil data, in the form of new soil organic carbon information, is characterized relative to changes in ground‐water vulnerability assessments made with a simple index. The additional soil organic carbon data does not yield improvements to the original vulnerability assessment that would be considered justifiable. The best use of regional scale chemical leaching assessments based upon modeling approaches as simple as index methods is for guiding data collection strategies.
Biogeochemical Evolution of Domestic Waste Water in Septic Systems: 1. Conceptual Model
Authors: Wilhelm Sheryl R. , Schiff Sherry L. , Cherry John A. 
Published: August 2005

AbstractThis paper presents a conceptual model, developed by synthesizing the results of many researchers, which describes the geochemical evolution of domestic waste water in conventional on‐site septic systems as the result of the interactions of a few major constituents. As described by the model, the evolution of waste water is driven by the microbially catalyzed redox reactions involving organic C and N in waste water and occurs in as many as three different redox zones. Anaerobic digestion of organic matter and production of CO2, CH4, and NH4+ predominate in the first zone, which consists mainly of the septic tank. In the second zone, gaseous diffusion through the unsaturated sediments of the drain field supplies O2 for aerobic oxidation of organic C and NH4+ and a consequent decrease in waste‐water alkalinity. The NO3− formed by NH4+ oxidation in this zone is the primary adverse impact of septic systems at most sites and is generally an unavoidable consequence of the proper functioning of conventional septic systems. If adequate O2 is not available in the drain field, aerobic digestion is incomplete, and the accumulation of organic matter may cause septic‐system failure. In the third redox zone, NO3 is reduced to N2 by the anaerobic process of denitrification. However, this setting is rarely found below septic systems due to a lack of labile organic C in the natural setting. Consideration of the changing redox and pH conditions in each zone aids our understanding of the fate of other constituents in septic systems.
Enhanced Degradation of Halogenated Aliphatics by Zero‐Valent Iron
Authors: Gillham Robert W. , O'Hannesin Stephanie F. 
Published: August 2005

AbstractLaboratory tests were conducted to examine zero‐valent iron as an enhancing agent in the dehalogenation of 14 chlorinated methanes, ethanes, and ethenes. All compounds were tested by batch procedures in which 10 g of 100‐mesh electrolytic iron was added to 40 ml hypovials. Aqueous solutions of the respective compounds were added to the hypovials, and the decline in concentration was monitored over time. Substantial rates of degradation were observed for all compounds tested with the exception of dichloromethane. The degradation process appeared to be pseudo first‐order with respect to the organic compound, with the rate constant appearing to be directly proportional to the surface area to volume ratio and increasing with increasing degree of chlorination. Column tests showed the process to proceed under flow conditions with degradation rates indpendent of velocity and consistent with those measured in the batch tests. When normalized to 1 m2/ml, the t50 values ranged from 0.013 to 20 hr, and were about 5 to 15 orders of magnitude lower than values reported for natural rates of abiotic degradation. The results indicate abiotic reductive dechlorination, with iron serving as the source of electrons; the mechanism is, however, uncertain. Based on the rapid rates of degradation, both in situ and aboveground applications for remediation of contaminated ground water are proposed.
Some Calculations on Multicomponent Transport with Cation Exchange in Aquifers
Authors: Appelo C.A.J. 
Published: August 2005

AbstractMulticomponent transport with cation exchange induces a separation of cations during displacement of waters in aquifers. The spatial separation is due to different retardations of the various cations which originate from differences in selectivity of the exchange complex. The composition patterns are complex, and calculated mostly with numerical models. However, a basic notion of features such as salinity fronts, chromatographic sequence, and front type is useful for general understanding of the processes. These aspects have not obtained the level of generality in hydrochemical studies that they deserve, and are introduced and applied in the paper. Demonstrated are: (1) the calculation of a multicomponent exchange complex from solution composition with the law of mass action; (2) the front type (broadening, indifferent, sharpening) that develops in relation to the slope of the sorption isotherm; (3) the calculation of a chromatographic pattern for the case of sharp fronts; (4) the effects of salinity changes on solution composition. All these features are illustrated with examples and then applied to calculate and compare water compositions in an observation well from two field studies, one of a salt‐water injection which displays the salinity effects very clearly in accordance with theory, and one of a fresh‐water injection for which the complete sequence of three ions Na+, Mg2+, and Ca2+ can be calculated simply with a quadratic equation.
Ground Water for WindowsTM— A New Ground‐Water Information System Software
Authors: Karanjac Jasminko 
Published: August 2005

AbstractAs suggested in the computer note printed in this journal in March‐April 1993 and titled “United Nations Ground‐Water Software,” to which this note is a sequel, the Windows version is completed and ready for distribution. The software, known as Ground Water for Windows (GWW), is the United Nations contribution to the ground‐water data information processing and management. GWW is flexible, user‐controlled, sophisticated, and versatile. It is an object oriented, relational data base and tailored for use as a ground‐water information system (GWIS). The software integrates classical ground‐water information (lithology, hydrographs, chemistry, pumping tests, etc.) with geographic displays. The software is programmed as a Windows application, and it uses all Windows resources: memory management, fonts, colors, screen, printer, and plotter drivers, etc. It is input and output device independent, and has no memory limitations except for the ones that are intrinsic to any Windows application. The data base can be filtered; that is, a large set of information can be reduced to subset having user‐selected attributes on any part of the data. The user designs the structure of the data base and creates entry and reporting forms. The software is primarily intended for the creation of large relational data bases on a site, region, province, county, or country wide basis.In addition to ground‐water data processing, GWW has its own powerful mapping utility. Various location and thematic content maps become an integral part of the ground‐water base. The exchange of information with other software packages is enabled via import and export of AutoCad's DXF and ASCII files.Following the philosophy that a picture is worth a thousand words, GWW emphasizes graphics on screen and printed in: maps, logs, cross sections, hydrographs, various chemical diagrams, etc. The current version of this software is in the public domain and is available through the United Nations for the developing world or through educational courses for the developed world.
A Computer Model for DNAPL Potential Migration Study
Authors: Yan Song‐kai , Landry Glen R. , Tate Tim 
Published: August 2005

AbstractA computer model, named DNAPMIG (DNAPL Potential Migration), was developed to calculate the dense nonaqueous phase liquid (DNAPL) critical length required to initiate movement and direction of potential migration at locations within an area of interest. The model takes into consideration the potentiometric gradient, bottom structure elevation, DNAPL density, interfacial tension, contact angle, soil grain size, partitioning coefficient, effective solubility, and water saturation. The model is interfaced with SURFER graphics software to use vectors to indicate the DNAPL critical length and the potential migration direction. The potential for DNAPL existence and migration at a specific site can be estimated by relating chemical concentration in the ground water to its solubility limit and the DNAPL critical length. The possibility of vertical migration can also be determined.This model can be used to determine and compare the effectiveness of existing or alternative recovery well systems to capture a DNAPL plume or arrest its movement; to help determine optimum locations and pumping rates of recovery wells; and to help determine the optimum location of environmental borings to locate DNAPL. This paper presents two hypothetical examples and two site applications in south Louisiana.
The Relationship Between Monitoring Well and Aquifer Solute Concentrations
Authors: Chiang Chen , Raven Gary , Dawson Clint 
Published: August 2005

AbstractDisparities between organic solute concentration in the aquifer and that in monitoring wells have been observed; an order of magnitude disparity had been recorded in some cases. Therefore, it is important to be able to relate concentrations between the two media for design of remediation systems. More significantly, to assess the impact of leachate from a landfill on a downgradient drinking water well, it is important to correlate aquifer concentration with that in a drinking water well such that the true risk is properly estimated. A three‐dimensional finite‐difference flow and transport model has been applied to demonstrate that the disparity between aquifer and well concentrations results primarily from advective flow phenomena and can be quantified. The modeling shows that the concentration in the well is a function of the initial vertical concentration profile in the aquifer, the volumetric flow rate from below the partially penetrated well, the penetration fraction, and the amount of water purged before sampling. Under steady‐state conditions, the dilution of concentrations in monitoring wells may be expressed as a simple analytic function of the above parameters. The result from this analytic function agrees well with numerical solutions and field sampling data.
Simultaneous Determination of Argon and Nitrogen
Authors: Martin Glen E. , Snow Daniel D. , Kim Euisik , Spalding Roy F. 
Published: August 2005

AbstractDenitrification can be confirmed by the presence of excess N2 as indicated by measurement of argon and nitrogen. Previously reported Ar/N2 ratios in ground water have been measured by static gas mass spectrometry, quadrupole mass spectrometry, and gas chromatography. The detector geometry and flared flight tube of the VG Optima isotope ratio mass spectrometer (IRMS) were determined to be fortuitously engineered for the simultaneous and highly precise measurement of Ar (mass 40) and N2+ (mass 28). Certified gas mixtures containing known Ar/N2 ratios were analyzed to assess instrument accuracy. A preparation system for the extraction and purification of Ar and N2 from water samples was developed and tested. δ(Ar/N2) values for prepared air‐saturated water (ASW) samples (24°C) averaged + 1149 ± 8‰ and did not significantly differ from the predicted value relative to atmospheric Ar/N2 of + 1144‰) (p < 0.001). The δ(Ar/N2) from in situ microcosms averaged +1280 ± 22‰ versus atmospheric Ar/N2 and approximated the expected level for ASW of + 1218 at 12°C. Much lower δ5(Ar/N2) values were measured in 18 ground‐water samples collected from a site where denitrification had previously been documented. Samples collected from a site where conditions indicate little or no denitrification have δ(Ar/N2) values close to those for ASW.
Sensitivity of Drawdown to Parameters and Its Influence on Parameter Estimation for Pumping Tests in Large‐Diameter Wells
Authors: Jiao Jiu J. , Rushton Ken R. 
Published: August 2005

AbstractThe sensitivity features of drawdown to aquifer parameters and their influence on parameter estimation and pumping‐test design are investigated in terms of pumping tests conducted in a large‐diameter well. It is concluded that the well storage reduces the sensitivities of drawdown to transmissivity and storativity, and increases the correlation between them. This leads to uncertainties in estimating the aquifer parameters, especially storativity. The most informative drawdowns in terms of parameter estimation change with time and space. This is instructive for pumping‐test design in a large‐diameter well. Both hypothetical and real examples are used to demonstrate key ideas.