bluuebunny/crossref_metadata_2025_split huggingface dataset:
Planning of Soil‐Pore Water Sampling Campaigns Using Pesticide Transport Modeling
Authors: Banton O. , Lafranee P. , Martel R. , Villeneuve J.P. 
Published: February 2007

AbstractSoil‐pore water sampling by suction lysimeters monitors the fate of soil contaminants as a function of depth and time. However, sampling campaigns must be planned to most effectively monitor the migration of contaminants with a minimum expenditure of resources. The vertical migration of pesticides was studied at two sites treated with systemic s‐triazine herbicides and equipped with suction lysimeters. The measured concentrations were compared with those calculated by a simulation model. This modeling was based on the processes that control the transport and fate of pesticide within the soil. The usefulness of such a tool was demonstrated by the good approximation obtained for pesticide concentrations and arrival times. Moreover, the significant spatial variability of concentrations observed justifies the use of a stochastic approach in modeling that takes into account the spatial variability of soil parameters. Also, the rapid transformation of herbicides observed in unsaturated soil zones demonstrates the importance of taking into account the sum of the toxic residues when evaluating the fate of s‐triazines in soil.
Mapping a Brine Plume Using Surface Geophysical Methods in Conjunction with Ground Water Quality Data
Authors: Chapman Melinda J. , Bair E. Scott 
Published: February 2007

AbstractOil field brine was applied to a gravel roadbed at an instrumented study site in Newark, Ohio, to simulate the use of brine as a deicer on roads in certain areas of Ohio. Brine was applied on a weekly basis eight times during the winter of 1988 as part of the deicing simulation. Eleven wells were installed at the site prior to brine application to permit collection of ground water quality samples. Surface geophysical methods — electrical resistivity and electromagnetic conductivity — were used to map the resulting brine plume. The accuracy of the methods was evaluated by comparing geophysical and ground water quality data. The presence of brine in ground water resulted in a decrease in resistivity and an increase in conductivity. Specific conductance measured in the field was used as a general indicator of the presence of the brine plume in ground water. Chloride concentration was an indicator of brine in the ground water. Results of the surface geophysical surveys correlated best with chloride and dissolved solids concentrations, and with specific conductance in ground water. The surface geophysical methods were found to be useful for qualitative interpretations of ground water quality changes resulting from the application of brine on roads.
Conceptual Model of Ground Water Flow in Fractured Siltstone Based on Analysis of Rock Cores, Borehole Geophysics, and Thin Sections
Authors: Merin Ira S. 
Published: February 2007

AbstractThe flow of ground water in flat‐lying sedimentary rocks of the Appalachian Plateau is significantly influenced by the vertical and horizontal distribution of vertical joints and horizontal bedding plane fractures. Although considerable published data document the geographic distribution of joints in outcrops in this region, few data have been published on the vertical distribution of joints and on the vertical and horizontal distribution of bedding plane fractures.The vertical and horizontal distribution of bedding plane fractures at a site located in central New York was investigated by examination of borehole geophysical logs, continuous rock cores from boreholes drilled to a maximum depth of 175 feet, and rock outcrops. This investigation reveals that three zones of bedding plane fractures can be delineated based on the vertical distribution of horizontal fractures, and that the spacing between these horizontal fractures increases with depth. The occurrence of vertical joints is not noticeably influenced by depth. Because bedrock at this site consists of several hundred feet of relatively homogeneous, thin‐bedded, fractured siltstone (the Genesee Formation) having essentially no visible microscopic intergranular porosity, ground water flows exclusively through fractures. Caliper, density, temperature, and neutron logs indicate that submillimeter‐wide fractures serve as conduits that transmit ground water. Slug test data reveal that shallower wells exhibit hydraulic conductivities 10 to 100 times greater than those of deeper wells, confirming that increased (wider) fracture spacing at depth results in a lower permeability.Because the spacing of horizontal fractures increases with depth, ground water flow in shallow bedrock is expected to be very different than that in deeper bedrock. Because both vertical joints and horizontal bedding plane fractures are conduits in shallow bedrock, flow might approximate equivalent porous media conditions. However, flow in deeper bedrock might approach fracture flow because bedding plane fractures are sparse and the principal conduits are only vertical joints. These differences can have important implications for modeling ground water flow.
A New Method for Collecting Core Samples Without a Drilling Rig
Authors: Starr Robert C. , Ingleton Robert A. 
Published: February 2007

AbstractA new piston sampler allows the collection of high‐quality core samples from sand, silt or clay, up to depths of 18 meters. The sampler is operated by a one‐ or two‐person crew without a drilling rig. The sampler and ancillary equipment fit easily into a half‐ton truck, making this a highly portable sampling system. Other advantages include minimal mechanical disturbance and precisely known sample depth. Casing is not required to maintain an open corehole below the water table and drilling fluid is not used in the corehole, so the solids and pore water of the sample should not be contaminated by foreign fluids. High‐quality samples for physical, geochemical, and microbiological characterization of the subsurface are easily obtained with this new device.
Application of VLEACH to Vadose Zone Transport of VOCs at an Arizona Superfund Site
Authors: Rosenbloom J. , Mock P. , Lawson P. , Brown J. , Turin H.J. 
Published: February 2007

AbstractCleanup standards for volatile organic compounds in thick vadose zones can be based on indirect risk (transport to ground water) when contamination is below depths of significant direct risk. At one Arizona Superfund site, a one‐dimensional vadose zone transport model (VLE‐ACH) was used to estimate the continued transport of VOCs from the vadose zone to ground water. VLEACH is a relatively simple and readily available model that proved useful for estimating indirect risk from VOCs in the vadose zone at this site. The estimates of total soil concentrations used as initial conditions for VLF.ACH incorporated a variety of data from the site. Soil gas concentrations were found to be more useful than soil matrix data for estimating total soil concentrations at this arid‐zone site. A simple mixing cell model was used with the VLEACH‐derived mass loading estimates from the vadose zone over time to estimate the resulting changes in ground water concentrations. For this site, the results of the linked VLEACH/mixing cell simulations indicate it is likely that the federal MCI. for TCE will be exceeded in underlying ground water if remedial action on I he vadose zone is not pursued.
Effects of River Stage and Waste Water Discharges on the Unconfined Aquifer, Hanford, Washington
Authors: Gilmore T. J. , Borghese J. V. , Newcomer D. R. 
Published: February 2007

AbstractThis study examined the effects of river stage and waste water discharge on the unconfined aquifer near the N nuclear reactor on the U.S. Department of Energy‐operated Hanford site in Washington State. River levels were statistically correlated with water‐level data from 12 wells.During the course of this study, water table elevations declined in the study area primarily as a result of a significant decrease in discharge to waste water disposal facilities, A minor contributing factor was the regional decline of the water table caused by decreasing waste water discharges upgradient of the study area.High‐frequency river‐level fluctuations (e.g., short‐term daily fluctuations) had good correlation with water‐level variations in a well approximately 750 feet inland. Low‐frequency river‐level fluctuations (e.g., long‐term seasonal fluctuations) had good correlation with water‐level variations in a well approximately 1000 feet from the river shore. Time lags and attenuation generally increased with distance from the river as expected, with the exception of two northern wells. These two wells were relatively more responsive to river‐level fluctuations at a greater distance inland from the river. This suggests that hydraulic properties (e.g., hydraulic conductivity) are a control on the aquifer reponses.During peak river stage in June, the river level rose above water table elevations in several wells implying a temporary reversal in ground water flow direction near the river.
Effects of Improper Characterization of Aquifer Thickness on Estimates of Hydraulic Conductivity from Pumping Tests
Authors: Hudak Paul F. 
Published: February 2007

AbstractPumping test data for surficial aquifers are commonly analyzed under the assumption that the base of the aquifer corresponds to the bottom of the test wells (i.e., the aquifer is truncated). This practice can lead to inaccurate hydraulic conductivity estimates, resulting from the use of low saturated thickness values with transmissivity estimates, and not accounting for the effects of partially penetrating wells. Theoretical time‐drawdown data were generated at an observation well in a hypothetical unconfined aquifer for various values of saturated thickness and were analyzed by standard curve‐matching techniques. The base of the aquifer was assumed to be the bottom of the pumping and observation wells. The overestimation of horizontal hydraulic conductivity was found to be directly proportional to the error in assumed saturated thickness, and to the (actual) ratio of vertical to horizontal hydraulic conductivity (Kv/Kh). Inaccurately high estimates of hydraulic conductivity obtained by aquifer truncation can lead to overestimates of ground water velocity and contaminant plume spreading, narrow capture zone configuration estimates, and overestimates of available ground water resources.
Landfill Performance Assessment at a Semiarid Site: Modeling and Validation
Authors: Stephens Daniel B. , Coons Larry M. 
Published: February 2007

AbstractThe HELP model (Version 2.05) was applied to simulate the long‐term percolation from a proposed landfill in southern New Mexico. The model predicted percolation would be about 0.0012 in/yr (10‐10 cm/s). This result compared very favorably with independent estimates of recharge at the site which used the chloride mass balance method and hydrogeologic properties. The recharge estimates at this site are also quite similar to values obtained at other sites in New Mexico and west Texas. The long‐term percolation through a closed landfill at this site is very small and would be nearly 1000‐fold smaller than the saturated hydraulic conductivity of a typical clay liner.
Fate of Chlorinated Aliphatic Hydrocarbons in the Vadose Zone and Ground Water
Authors: Barbee Gary C. 
Published: February 2007

AbstractThe large‐scale production and use of chlorinated aliphatic hydrocarbons (CHC) in the United Suites has resulted in numerous documented cases of soil and ground water contamination. Potential chronic exposure from contaminated soil and ground water, as well as from products used in the home, is sufficient reason to develop a thorough understanding of the environmental fate of these known and possible human carcinogens.Most CHCs are very mobile in the subsurface environment, either as volatilized constituents in the vadose zone due to their high vapor pressure and low water solubility: as dissolved constituents in ground water since they are not strongly adsorbed by aquifer materials: and as dense nonaqueous phase liquids (DNAPLs) in ground water, primarily because they have low water solubility and densities greater than water. As free‐phase chemicals (i.e., DNAPLs). CHCs may pool on low‐permeability subsurface stratum and cause shrinkage and cracking of clay minerals, thereby significantly increasing the stratum's hydraulic conductivity and allowing rapid CHC breakthrough and migration. Although laboratory and field studies have demonstrated this effect, additional investigations are needed to determine the impact CHC DNAPLs have on low‐permeability in situ sediments.CHCs are persistent environmental contaminants because they resist chemical and biological degradation. I'hc average half‐life for CHC abiotic transformations ranges from two months to greater than 1010 years. Chlorinated ethenes are the most resistant CHCs to abiotic degradation. Biodegradation half‐lives for CHCs may vary considerably but range from about two weeks to eight months or more. Anaerobic reductive dehalogenation is recognized as a primary CHC biodegradation process in ground water, although aerobic CHC hiodegradation may be a significant process in the shallow subsurface.Technological applications of remedial processes fur stimulating in situ CHC biodegradation in soils and ground water need to be developed, particularly with regard to CHCs entrained as residual saturation.
Rapid Assessment of Trichloroethylene in Ground Water
Authors: Hewitt Alan D. , Shoop Sally A. 
Published: February 2007

AbstractOn‐site analysis of trichloroethylene (TCE) in aqueous samples by head‐ space sample preparation and gas chromatography (HS/GC) provides for quick and precise concentration estimates. This analytical approach is well suited for the on‐site determination of volatile organic compounds (VOCs) in a variety of sample matrices, including ground water and saturated and unsatured soils. For these reasons, HS/GC can be used to establish analyte concentrations on a near real time basis to help select appropriate casing material during monitoring well installation. This application and the collection of multiple well samples during sampling events facilitates the hydrogeological site interpretation and the formulation of remediation strategies.
An Assessment of the Nguyen and Finder Method for Slug Test Analysis
Authors: Butler James J. , Hyder Zafar 
Published: February 2007

AbstractThe Nguyen and Pinder method is one of four techniques commonly used for analysis of response data from slug tests. Limited field research has raised questions about the reliability of the parameter estimates obtained with this method. A theoretical evaluation of this technique reveals that errors were made in the derivation of the analytical solution upon which the technique is based. Simulation and field examples show that the errors result in parameter estimates that can differ from actual values by orders of magnitude. These findings indicate that the Nguyen and Pinder method should no longer be a tool in the repertoire of the field hydrogeologist. If data from a slug test performed in a partially penetrating well in a confined aquifer need to be analyzed, recent work has shown that the Hvorslev method is the best alternative among the commonly used techniques.
Generation of Hydrogen Gas as a Result of Drilling Within the Saturated Zone
Authors: Bjornstad Bruce N. , McKinley James P. , Stevens Todd O. , Rawson Shirley A. , Fredrickson James K. , Long Philip E. 
Published: February 2007

AbstractHydrogen gas was discovered within the steel casing above standing water in a percussion‐drilled borehole on the Hanlord Site in south‐central Washington state. In situ measurements of the borehole fluids indicated anoxic, low‐Eh (<‐400 mV) conditions. Ground water sampled from adjacent wells in the same formation indicated that the ground water was oxygenated. H2 was generated during percussion drilling, due to the decomposition of borehole waters as a result of aqueous reactions with drilled sediment and steel from the drilling tools or casing. The generation of H2 within percussion‐drilled boreholes that extend below the water table may be more common than previously realized. The ambient concentration of H2 produced during drilling was limited by microbial activity within the casing‐resident fluids. H2 was generated abiotically in the laboratory, whereby sterilized borehole slurry samples produced 100 times more H2 than unsterilizcd samples. It appears that H2 is metabolized by microorganisms and concentrations might be significantly greater if not for microbial metabolism.
Vertical Contaminant Profiling of Volatile Organic* in a Deep Fractured Basalt Aquifer
Authors: Kaminsky J.F. , Wylie A.H. 
Published: February 2007

AbstractVolatile organic compounds delected in ground water from wells at Test Area North (TAN) at the Idaho National Engineering Laboratory (INEL) prompted RCRA facility investigations in 1989 and 1990 and a CERCLA‐driven RI/FS in 1992. In order to address ground water treatment feasibility, one of the main objectives, of the 1992 remedial investigation was to determine the vertical extent of ground water contamination, where the principle contaminant, of concern is trichloroethylene (TCE). It was hypothesized that a sedimentary interbed at depth in the fractured basalt aquifer could be inhibiting vertical migration of contaminants to lower aquifers. Due to the high cost of drilling and installation of ground water monitoring wells at this facility (greater than $100,000 per well), a real time method was proposed for obtaining and analyzing ground water samples during drilling to allow accurate placement of well screens in zones of predicted VOC contamination. This method utilized an inflatable pump packer pressure transducer system interfaced with a datalogger and PC at land surface. This arrangement allowed for real lime monitoring of hydraulic head above and below the packer to detect leakage around the packer during pumping and enabled collection of head data during pumping for estimating hydrologic properties. Analytical results were obtained in about an hour from an on‐site mobile laboratory equipped with a gas chromalograplvmass spectrometer (GC/MS). With the hydrologic and analytical results in hand, a decision was made to either complete the well or continue drilling to the next test zone. In almost every case, analytical results of ground water samples taken from the newly installed wells closely replicated the water quality of ground water samples obtained through the pump packer system.
Accuracy, Precision, and Stability of a Vibrating‐Wire Transducer Measurement System to Measure Hydraulic Head
Authors: Zarriello Phillip J. 
Published: February 2007

AbstractA vibrating‐wire transducer measurement system was investigated to determine its accuracy, precision, and stability for use in a study of ground water movement in low‐permeability material. Twenty transducers with a pressure range of 10 psi were tested for stability over 100 days. half under low pressure (0.256 psi) and half under approximately full‐scale pressure (10 psi). Measurement precision and stability were far better than measurement accuracy. Random noise in the data indicates that the transducers were precise to within 0.02 psi. The transducer measurements were generally stable to within 0.05 psi. but most showed a blight decrease in pressure over time. Measurements by transducers under low pressure were within 0.038 psi of actual pressure, and those made by transducers under high pressure were within −0.20 psi. as indicated by the difference between the mean measurement of each transducer and the mean measurement of all transducers. These measurements were within the reported accuracy for transducers under low pressure, but differed by more than the reported accuracy for transducers under high pressure: this indicates that transducer accuracy is largely determined by the pressure coefficient used to convert transducer readings to pressure units. Pressure coefficient calibration of selected transducers by a water filled standpipe and a digital manometer indicate that hysteresis could be the most significant factor affecting the transducer accuracy Standpipe calibrations indicate a pressure coefficient difference of about 13 percent between increasing and decreasing pressure, but deadweight calibrations indicate a difference of only 1.5 percent. The observed measurement and equipment error could affect interpretation of water level measurements; thus, independent water level measurements and rigorous review of the data arc needed to evaluate the accuracy of transducer measurements.
A Systematic Approach to Designing a Multiphase Unsaturated Zone Monitoring Network
Authors: Cullen Stephen J. , Kramer John H. , Luellen Jon R. 
Published: February 2007

AbstractA systematic approach is presented for the design of a multiphase vadose zone monitoring system recognizing that, as in ground water monitoring system design, complete subsurface coverage is not practical. The approach includes identification and prioritization of vulnerable areas: select ion of cost‐effective indirect monitoring methods that will provide early warning of contaminant migration: selection of direct monitoring methods for diagnostic confirmation; identification of background monitoring locations; and identification of an appropriate temporal monitoring plan. An example of a monitoring system designed for a solid waste landfill is presented and utilized to illustrate the approach and provide details of system implementation. The example design described incorporates the use of neutron moisture probes deployed in both vertical and horizontal access tubes beneath the lcachate recovery collection system of the landfill. Early warning of gaseous phase contaminant migration is monitored utilizing whole‐air active soil gas sampling points deployed in gravel‐ filled trenches beneath the subgrade. Diagnostic confirmation of contaminant migration is provided utilizing pore‐ liquid samplers. Conservative tracers can be used to distinguish between chemical species released by a landfill from those attributable to other (e.g. off‐site) sources or present naturally in the subsurface. A discussion of background monitoring point location is also presented.
Experimental and Numerical Study of the Transport of Acid Solutions and Copper in Tailings Impoundments
Authors: Munoz Jose Francisco , Rengifo Pablo 
Published: February 2007

AbstractA two‐dimensional mathematical model for acid leaching of copper from mine tailings using injection and pumping wells is presented. The model considers the transport mechanisms of convection and dispersion with reactions that govern the fates of copper and acid. Reactions considered are acid neutralization, copper solubilization, and copper adsorption. The results of acid leaching experiments in laboratory columns (one‐ dimensional) and in the field at a tailings impoundment are presented. The proposed model was validated for a one‐dimensional experiment, and the model parameter fitting was found to be adequate in terms of the field experiment.