bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulating Errors in Statistical Tests of Leachate‐lmpacted Ground‐Water Quality
Authors: Milke M. W. , Huitric R. L. 
Published: August 2005

AbstractData on 13 median leachate qualities at 56 landfills show a multivariate character, A simulation technique is used to include this multivariate character of leachate quality in assessing false negative error rates for statistical tests of ground‐water quality. Although the technique makes gross simplifying assumptions regarding the conservative mixing of leachate and ground water, the technique is more appropriate than traditional statistical methods for simulating false negative error rates that neglect correlations among water quality parameters. The technique is applied to the simple case of a control chart, intrawell statistical test of ground‐water contamination. Simulation results show that both the false positive and false negative errors of statistical tests can be reduced when tests include more parameters and a higher confidence level; thus, the technique can provide a “win‐win” situation for regulators and the regulated.
Air Sparging in Gate Wells in Cutoff Walls and Trenches for Control of Plumes of Volatile Organic Compounds (VOCs)
Authors: Pankow James F. , Johnson Richard L. , Cherry John A. 
Published: August 2005

AbstractVolatile organic compounds (VOCs) can be stripped from ground water by sparging air into water in wells or in trenches. This well/trench sparging (“WTS”) can remove VOCs from plumes of contaminated ground water as that water passes across the sparge zone. With sparging in wells, cutoff walls will be needed to force the contaminated water through the “gate” wells. With in situ sparging (“ISS”), air is sparged directly into a contaminated aquifer. ISS may be useful in treating local zones of high contamination, but WTS is better suited for treating large plumes of contaminated ground water. Interest in sparging methods is growing because: (1) they do not remove water from the subsurface, and so difficult disposal issues are avoided and an increasingly valuable water resource is not depleted; and (2) the Darcy velocity v in many systems is low, and so only a relatively small volume of water must be treated per unit time.The theoretical fractional efficiency of WTS is given by E = S/(l + S). The parameter S is named here as the “dimensionless sparge number,” with S = HRg/(RTyzv) where H (atm‐m3/mol) = Henry's Law constant for the compound of interest; Rg (m3/s, at 1 atm pressure) = gas sparging rate; R = gas constant (= 8.2 X 10˜5 m3‐atm/mol‐deg); T = temperature (K); yz (m2) = cross‐sectional area producing the water which is passing into the sparging zone; and v = Darcy velocity (m/s). E increases as S increases. E increases as H increases because the volatility of a compound goes up as its H increases. Plots for E in WTS are given vs. S as well as vs. some of the variables making up S.Well/trench sparging (WTS) has the potential to become a useful treatment method for removing VOCs from contaminated ground‐water plumes. It is suited for use with most of the solvents and petroleum products which have caused extensive ground‐water contamination. The theory of the method is simple, and the theoretical removal efficiencies are predictable as well as adjustable.
Analytical Model for Estimation of Steady‐State Capture Zones of Pumping Wells in Confined and Unconfined Aquifers
Authors: Grubb Stuart 
Published: August 2005

AbstractThe analysis of capture zones of pumping wells is useful for designing pumping systems and wellhead protection programs. Using discharge potentials, equations are derived that can be applied to confined, unconfined, or combined confined and unconfined aquifers. The transient equations are transcendental and cannot be solved explicitly. However, infinite‐time (steady‐state) equations are presented which can be solved. They define an area in which, theoretically, all the water in the aquifer will eventually reach the pumping well, although the equations do not consider the effects of hydrodynamic dispersion. Equations for calculating the stagnation point, upgradient divide, and dividing streamline within the aquifer and an example problem are presented.
Testing Fournier's Method for Finding Water Table from Self‐Potential
Authors: Birch F. S. 
Published: August 2005

AbstractFournier's approximate method for relating self‐potential anomalies to water‐table elevation is satisfactory for five of the six sites where it has been tested in New Hampshire. At these sites water‐table elevations were determined independently from observation of surface‐water bodies and by seismic refraction at the times of the self‐potential surveys.At three sites on drumlins formed of glacial till, the apparent coupling coefficients range from 0.95 to 4 mV/m whereas two surveys on sand and gravel deltas yield apparent coupling coefficients of −16 and −17 mV/m. At a third delta the apparent coupling coefficient suggests that the water table is in an underlying till rather than in the deltaic deposits.Modeling of self‐potential anomalies using Fournier's method may permit isolation of anomalies caused by sources other than ground‐water flow as well as location of significant geological inhomogeneities. Because of nonuniqueness it is not possible to determine water‐table elevations from self‐potential surveys alone.
Multivariate Geostatistïcal Analysis of Ground‐Water Contamination: A Case History
Authors: Istok Jonathan D. , Smyth Jeffrey D. , Flint Alan L. 
Published: August 2005

AbstractA case history is presented for the application of multivariate geostatistical methods to the problem of estimating pesticide concentrations in ground water from measured concentrations of nitrate and pesticide, when pesticide is under‐sampled. The shallow, poorly confined, sand and gravel aquifer underlying the lower Malheur River basin near Ontario, Oregon is contaminated by nitrate and metabolites of the herbicide Dacthal (dimethyl tetrachloroterephthalate) or DCPA. The results of extensive ground‐water sampling indicate that a significant positive correlation exists between measured nitrate and DCPA concentrations in the aquifer. This suggests that future sampling should include a large number of the less‐expensive nitrate analyses, and these data should be used to support the interpretation of fewer, more expensive DCPA analyses. Sample variograms were computed for nitrate and DCPA concentrations and were fit with isotropic, spherical variogram models with correlation ranges of 4 km. Incorporating measured nitrate concentrations in the DCPA estimates obtained by cokriging reduced estimation variances from 14 to 34%. A simple economic analysis demonstrated that for this aquifer, acquiring additional nitrate samples is a cost‐effective way to reduce estimation variances for DCPA.
Double Porosity Well Testing in the Fractured Carbonate Rocks of the Ozarks
Authors: McConnell Cary L. 
Published: August 2005

AbstractThe objective of this research was to determine a well test model which could be used for determining the hydraulic parameters of T and S in the complex fractured carbonates of the Ozarks of southern Missouri. Municipal water well testing in the Ozarks is performed on deep wells completed in confined fractured carbonate aquifers where all of the flow to the wellbore is through the fractures but most of the storage is in the matrix blocks. Observation wells are not used because of cost. The methodology uses double porosity well test analysis including the inner boundary conditions of skin and wellbore storage. Using this method, S and T are obtained as well as the storativity ratio, ω, and the block to fracture flow parameter λ. Because wellbore storage, skin, and storativity are interrelated, a computer simulation to find the final S was necessary. Derivative curve analysis provided a constraint in determining the correctness of the simulation results. Failure to use this well test method proved to result in storativities which are much too large. An example is presented.
Reservoir Characterization Applying High‐Resolution Seismic Profiling, Rabis Creek, Denmark
Authors: Olsen Henrik , Ploug Garsten , Nielsen Uffe , Sorensen Kurt 
Published: August 2005

AbstractOnshore reflection seismics have been used to characterize the geometry and lithology of ground‐water reservoirs. The study was carried out as a seismic sequence and facies analysis along Rabis Creek in western Denmark. A1350 m long seismic section was produced on a presumed homogeneous outwash sand plain. High resolution data to a depth of 160 m (200 msec two‐way time) were obtained along most of this section, and reflections from more than 400 m in depth were obtained locally. The seismic data have been correlated with electrical resistivity logs. The reservoir is, in contrast to the expectations, highly heterogeneous, composed of three distinguishable seismic sequences of unconsolidated sediments. Layers down to 1.5 m thick were recognized in the seismic data. The study shows that onshore reflection seismics provide a unique possibility of 2‐D reservoir scale characterization of geological structures. Combined with seismic facies and sequence analysis, seismic profiling forms a strong hydrogeological tool that may supplement traditional boring and logging methods.
Assessing Public Exposure to Pesticide‐Contaminated Ground Water
Authors: Kastenberg William E. , Yeh H. C. 
Published: August 2005

AbstractLong‐term exposure assessments regarding four commonly used pesticides are presented in this paper. Alachlor, aldicarb, lindane, and parathion have been detected in ground‐water monitoring wells. A multimedia transport model is employed to predict the long‐term fate of these chemicals in the environment. Concentrations in each environmental compartment are calculated and used to determine the dominant exposure pathways and hence dose rate.Aldicarb is shown to move from the upper soil compartment, through the lower soil compartment, and accumulate at a rate which is several orders of magnitude greater than the other pesticides. Lindane moves faster to the biota compartment than the other pesticides. The dominant exposure pathway for aldicarb and alachlor is drinking water ingestion for both adults and children. For lindane and parathion, the dominant exposure pathway is biota ingestion for children and fish ingestion for adults. The methods presented in this paper can be used as screening tools for designing remediation, mitigation, or interdiction measures and can serve as a basis for evaluating risk management strategies.
Development of Transparent Porous Media with Permeabilities and Porosities Comparable to Soils, Aquifers, and Petroleum Reservoirs
Authors: Mannheimer R. J. , Oswald C. J. 
Published: August 2005

AbstractModel porous media made from glass beads and matched refractive index liquids have made it possible to visualize displacement processes in heterogeneous porous media and to obtain in situ concentration profiles to validate flow codes. However, glass beads produce porous media that are translucent rather than transparent. Thus, these models cannot be used to observe 3‐D effects. Furthermore, the current necessity of using relatively large glass beads results in permeabilities that are several orders of magnitude larger than natural porous media. This paper describes a new approach for making transparent porous media by consolidating suspensions of amorphous silica in matched refractive index liquids. The resulting porous media can be made to have porosities and permeabilities comparable to a very wide range of soils and reservoir materials by the appropriate choice of particle size and/or consolidation pressure. Because these porous media are truly transparent and not merely translucent, relatively simple optical techniques can be used to map variations in porosity and to measure 3‐D flow processes.
Phase Diagrams to Optimize Surfactant Solutions for Oil and DNAPL Recovery in Aquifers
Authors: Martel Richard , Gelinas Pierre J. , Desnoyers Jacques E. , Masson Anne 
Published: August 2005

AbstractPhase diagrams can be used to optimize the composition of surfactant solutions (cosurfactant/surfactant) designed for the recovery of DNAPLs at residual saturation in aquifer formations. The study also shows that the combination of cosurfactant (alcohol) and surfactant is more effective than the use of alcohols or surfactants separately. The suggested approach is based on miscible oil displacement using surfactant solutions at high concentrations. Most of the recent projects using surfactants for aquifer cleanup use low‐concentration solutions that promote immiscible oil displacement. The goal of the present study is to demonstrate the potential of optimized surfactant solutions to restore oil and DNAPL‐contaminated sites such as the one in Ville Mercier, Quebec (site contaminated with a mixture of petroleum and chlorinated solvents). The results show that alcohol/surfactant systems can be used to solubilize chlorinated solvents (TCE, PCE) and light oils (gasoline, diesel). For the dissolution of heavy and viscous oils (motor oil, ATF, creosote, Ville Mercier oil), an organic solvent must be added to the alcohol/surfactant system.
DERIV: A Computer Program for Calculating Pressure Derivatives for Use in Hydraulic Test Analysis
Authors: Spane F. A. , Wurstner S. K. 
Published: August 2005

AbstractHydrologie test analysis based on the derivative of pressure (i.e., rate of pressure change) with respect to the natural logarithm of time has been shown to significantly improve the diagnostic and quantitative analysis of slug and constant‐rate pumping tests. The improvement in test analysis is attributed to the sensitivity of the derivative to small variations in the pressure change that occurs during testing, which would otherwise be less obvious with standard pressure change versus time analysis. The sensitivity of the pressure derivative to pressure change facilitates its use in identifying the effects of wellbore storage, boundaries, and establishment of radial flow conditions on the test.DERIV is a program for converting slug and pumping test data and associated type curves to derivative format. The program has features that permit the smoothing of noisy test data, accounts for pressure derivative end‐effects, and can be used to convert slug test data to equivalent pumping test responses. Test examples that demonstrate the use of pressure derivatives also are provided.
Estimation of Ground‐Water Mounding Beneath Septic Drain Fields
Authors: Finnemore E. John 
Published: August 2005

AbstractLocalized ground‐water mounding beneath larger on‐site sewage disposal fields (septic drain fields) can reduce and even eliminate the waste‐water treatment that occurs in the unsaturated soil zone. Such mounding was previously predicted for longer times by a procedure of uncertain accuracy and having a number of limitations. In this paper, a new procedure is developed on a stronger theoretical basis. The governing equation may be solved by four different methods. The new procedure considerably extends the time range of applicability, and no longer restricts the proportions of the rectangular disposal field. Errors in the previous methods approached 20% in some cases. Comparisons of different methods to reduce mound heights where they are critical indicate that the most effective method is to subdivide the disposal field into separated subareas.
Numerical Simulation of Ground‐Water Interaction with Lakes Allowing for Fluctuating Lake Levels
Authors: Cheng Xiangxue , Anderson Mary P. 
Published: August 2005

AbstractMost numerical models of ground‐water flow incorporate lakes as constant head nodes. We developed a computer package for the widely used MODFLOW code to simulate three‐dimensional steady‐state and transient ground‐water flow with fluctuating lake levels. This package considers precipitation to and evaporation from the lake surface, stream flow, and ground‐water inflow and outflow for multiple lakes. We demonstrate the use of the package through the results of steady‐state and transient simulations for a hypothetical ground‐water flow problem involving a lake and two streams.
A Program of Frequency Analysis Using Gumbel's Method
Authors: El‐Naqa Ali , Zeid Nasser Abu 
Published: August 2005

AbstractA program (GUMBEL) has been written in QBASIC language to carry out the mathematical procedure for preparing frequency curves using Gumbel's extreme value distribution. The program can be used to analyze hydrologie and meteorologie events so as to establish a relationship between the magnitude of extreme events and their frequency through the use of probabilistic distributions.Six different plotting positions formulae are included in the program so as to select the most reliable formula of these graphical fitting methods in analyzing the observed hydrologie data. A sample input data file of annual rainfall data from Jordan has been tested, in order to show the applicability and usefulness of the program.
A Stochastic Method for Characterizing Ground‐Water Contamination
Authors: McLaughlin Dennis , Reid Lynn B. , Li Shu‐Guang , Hyman Jennifer 
Published: August 2005

AbstractIt is becoming widely recognized that field‐scale ground‐water contaminant plumes are irregular and difficult to predict. Factors which complicate the characterization of such plumes include geological variability, data limitations, and uncertainties about the source of contamination. This paper describes a new approach to site characterization which accounts for variability and uncertainty in a systematic way. The site characterization procedure extracts more information from limited data by combining field measurements with predictions from a stochastic ground‐water model. The model provides prior estimates of the mean and standard deviation of solute concentration throughout a contaminated site. These estimates are updated whenever new measurements of hydraulic conductivity, head, and/or concentration become available. The updated concentration standard deviation estimates may be used to guide the placement of sampling wells and to evaluate the accuracy of the site characterization. If updating and data collection are carried out sequentially, over a series of discrete sampling rounds, the sampling network can evolve in response to new information. A case study described in the paper illustrates how the characterization procedure can be applied to a typical field site.
Model Development and Simulation of Bioremediation in Soil Beds with Aggregates
Authors: Dhawan S. , Erickson L. E. , Fan L. T. 
Published: August 2005

AbstractOne method of remediating contaminated soil and ground water is through management of the subsurface environment so that indigenous microorganisms can biodegrade organic contaminants. Modeling and simulation offer promising means of assessing the migration and attenuation of such contaminants being treated in situ in the subsurface. In this paper, a macropore flow model has been developed to account for bioremediation in the interstitial spaces among soil aggregates. This model has been combined with another bioremediation model which accounts for diffusion and Biodegradation in the micropores and soil particles in the aggregates. The combined model comprises a system of six coupled equations, of which three are nonlinear ordinary differential equations and three are nonlinear partial differential equations. Dimensional analysis of these equations has yielded useful dimensionless parameters for evaluating the relative significance of each mechanism in remediation. Numerical experiments have been conducted to evaluate the effects of initial contaminant concentration, aggregate size, and soil‐water partition factor. The total time of remediation has been found to depend on the rate at which contaminants are consumed within the large aggregates which, in turn, depends on the Biodegradation kinetics and the rates of diffusion of substrate and oxygen in the aggregates. For soil with aggregates whose radius is 1 cm or larger, the results of simulation indicate that the remediation time for the aggregates is significantly longer compared to the corresponding result for homogeneous soil. For contaminants with large partition coefficients, the estimated time for remediation achieved through microbial oxidation in situ is much shorter than that achieved through purely diffusional transport of the contaminants out of the soil bed.
United Nations Ground Water Software
Authors: Karanjac Jasminko 
Published: August 2005

AbstractA newly developed ground‐water software package, known as the United Nations Ground Water Software, is a dedicated hydrogeological software, which helps the user create ground‐water data bases on lithology, ground‐water chemistry, water levels, and pumping tests. The emphasis is on graphics screen display and printing or plotting of graphics. The software is in colors, with impermeable formations displayed or printed in red and permeable formations in blue. The software is user friendly and transparent to the user. It combines the functions of ground‐water data base management and digital mapping. The software is in public domain, although the ownership of the United Nations is acknowledged. It is intended primarily for developing countries which do not have easy access to advanced CAD or GIS systems.
Risk‐Based Evaluation of Ground‐Water Contamination by Agricultural Pesticides
Authors: Varshney Peeyush , Tim U. Sunday , Anderson Carl E. 
Published: August 2005

AbstractThe recently completed National Pesticide Survey conducted by the United States Environmental Protection Agency (EPA) has identified the presence of various pesticides in ground water. The detection of pesticides in the nation's ground water has raised concerns for public health which has led resource managers in federal and state agencies to recognize that risk assessment is vital for water quality protection. This paper presents a methodology for risk‐based evaluation of ground‐water contamination by agricultural pesticides. The methodology utilizes the Risk of Unsaturated/Saturated Transport and Transformation of Chemical Concentrations (RUSTIC) model to provide simulations that yield the probable risks associated with a given pesticide. Risk is expressed in terms of the probability of predicted pesticide mass exceeding its recommended health standards. Three widely used agricultural herbicides, simazine, atrazine, and alachlor, were evaluated using long‐term (1960–1986) meteorological data for Ames, Iowa. Results indicate that for a well 8 m deep located 200 m horizontally from a pesticide application area in an alluvial sand and gravel setting, the probability of exceeding the maximum contaminant level (MCL) for simazine is about 35%, whereas it is nearly zero for both atrazine and alachlor. Prudent use of simazine in very susceptible areas is recommended.
A Simple Analytical Approach for Predicting Nitrate Concentrations in Pumped Ground Water
Authors: Lerner D. N. , Papatolios K. T. 
Published: August 2005

AbstractA simple analytical expression is presented which predicts how solute concentrations evolve with time in a pumped well. The basic expression is for uniform recharge and uniform concentration of a conservative solute (e.g. nitrate) in the recharge. It shows that pumped concentrations are independent of pumping rates. The expression can be developed to allow for more complex patterns of recharge and solute loading, and an example is given with three zones of recharge and concentrations, induced river recharge, and a cross‐boundary inflow. Predictions are made for Edgmond Bridge, a new pumping station which lies in a drift‐filled valley in the Triassic sandstone aquifer of Shropshire, UK. The model predicts that concentrations of nitrate will stay below the drinking water limit for 78 years, although this would be substantially reduced if the aquifer were significantly layered or if nitrate loads from agriculture increased. Predictions were reevaluated after two years and found to be consistent with observed patterns once actual, rather than expected, conditions were incorporated in the model.