bluuebunny/crossref_metadata_2025_split huggingface dataset:
Single Well Tracer Tests in Aquifer Characterization
Authors: Hall Stephen H. 
Published: February 2007

AbstractWhen the purpose of aquifer testing is to yield data for modeling aqueous mass transport, pumping tests and gradient measurement can only partially satisfy characterization requirements. Effective porosity, ground water flow velocity, and the vertical distribution of hydraulic conductivity within the aquifer are left as unknowns. Single well tracer methods, when added to the testing program, can be used to estimate these parameters. A drift, and pumpback test yields porosity and velocity, and point‐dilution testing yields depth‐discrete hydraulic information, A single emplacement of tracer into a test well is sufficient to conduct both tests. The tracer tests are facilitated by a simple method for injecting and evenly distributing the tracer solution into a wellbore, and by new ion‐selective electrode instrumentation, specifically designed for submersible service, for monitoring the concentration of tracers such as bromide.
Laboratory Study of Air Sparging: Air Flow Visualization
Authors: Ji Wei , Dahmani Amine , Ahlfeld David P. , Lin Jia Ding , Hill Edward 
Published: February 2007

AbstractLaboratory flow visualization experiments, using glass beads as the porous medium, were conducted to study air sparging, an innovative technology for subsurface contaminant remediation. The purpose of these experiments was to observe how air flows through saturated porous media and to obtain a basic understanding of air plume formation and medium heterogeneity effects. The experiments indicate that air flow occurring in discrete, stable channels is the most probable flow behavior in medium to fine grained water saturated porous media and that medium heterogeneity plays an important role in the development of air channels. Several simulated scales of heterogeneities, from pore to field, have been studied. The results suggest that air channel formation is sensitive to the various scales of heterogeneities. Site‐specific hydrogeologic settings have to be carefully reviewed before air sparging is applied to remediate sites contaminated by volatile organic compounds.
An Overview of In Situ Air Sparging
Authors: Johnson R.L. , Johnson P.C. , McWhorter D.B. , Hinchee R.E. , Goodman I. 
Published: February 2007

AbstractIn situ air sparging (IAS) is becoming a widely used technology for remediating sites contaminated by volatile organic materials such as petroleum hydrocarbons. Published data indicate that the injection of air into subsurface water saturated areas coupled with soil vapor extraction (SVE) can increase removal rates in comparison to SVE alone for cases where hydrocarbons are distributed within the water saturated zone. However, the technology is still in its infancy and has not been subject to adequate research, nor have adequate monitoring methods been employed or even developed. Consequently, most IAS applications are designed, operated, and monitored based upon the experience of the individual practitioner.The use of in situ air sparging poses risks not generally associated with most practiced remedial technologies: air injection can enhance the undesirable off‐site migration of vapors and ground water contamination plumes. Migration of previously immobile liquid hydrocarbons can also be induced. Thus, there is an added incentive to fully understand this technology prior to application.This overview of the current state of the practice of air sparging is a review of available published literature, consultation with practitioners, a range of unpublished data reports, as well as theoretical considerations. Potential strengths and weaknesses of the technology are discussed and recommendations for future investigations are given.
Method for Determining the Age of Diesel Oil Spills in the Soil
Authors: Christensen Lars Bo , Larsen Thomas Hauerberg 
Published: February 2007

AbstractThis study evaluates the changes in the composition of diesel oil as a function of the time during which the oil has been present in the vadose zone. The study also develops a reliable method for determining the age of diesel oil in the subsurface soil environment at service stations, oil terminals, and similar locations where the diesel is protected from direct exposure to factors increasing the rate of microbial activity.Analyses demonstrate that n‐alkanes are the dominant components of fresh diesel oil and isoprenoids the dominant components of degraded diesel oil. The analyses also show that the composition of fresh diesel oil produced in 1992 and that produced in 1974 is basically the same.The difference in composition between fresh and degraded oil is the basis for defining a degradation ratio or rate of alteration in the composition of the diesel oil expressed in terms of a ratio between n‐alkanes and isoprenoids. At 12 test locations where the date of property damage was known, the C17/pristane ratio had by far the highest correlation factor (.89) with the residence time of the diesel based on the average degradation ratio for each location. Based on this high correlation factor, the C17/pristane ratio can be used to estimate the age of a diesel oil spill. The standard error of such an estimate is approximately two years.
Effects of Sample Isolation and Handling on the Recovery of Purgeable Organic Compounds
Authors: Gibs Jacob , Imbrigiotta Thomas E. , Ficken James H. , Pankow James F. , Rosen Michael E. 
Published: February 2007

AbstractThis report compares the recovery of purgeable organic compounds (POCs) obtained by using a downhole isobaric sampler developed by the U.S. Geological Survey, a helical‐rotor submersible pump, and a point source bailer to collect and isolate samples of ground water from three wells in Now York and New Jersey: the samples contained a total of 13 PCX's delectable at concentrations ranging from 0.5 μg/L to about 400 μg/L. This report also compares the effects of sample handling, specifically the differences in PCX concentration recovery when an isobaric sample container is filled at land surface vs. when it is filled downhole. and when samples art taken using a bailer with and without a bottom‐emptying device. These case studies are used to quantify the possible effects of different sample‐isolation find sample‐handling techniques on POC recovery.The relative effectiveness of the three devices varied by site and by compound. Overall, the POC recoveries achieved by using the helical‐rotor submersible pump and the downlink isobaric sampler were not significantly different at the 95 percent confidence, level. POC recovery obtained by using the point source bailer was 11 percent lower overall. The downhole isobaric sampler results exhibited smaller coefficients of variation than did the helical‐rotor submersible pump or the point‐source bailer results. However, the differences between the coefficients of variation of the downhole isobaric sampler and those of the helical‐rotor submersible pump were not significant at the 95 percent confidence level. The nonsignificant smaller coefficient of variation of the downhole isobaric sampler apparently resulted from two fewer sample handling steps that exposed the sample water to ambient air. An independent experiment performed with a different downhole sampler at one of the wells used in this investigation produced a similar statistical result. Also, the POC recovery obtained by pouring sample water out the lop of a point source bailer into 40‐mL vials was S percent lower than that obtained by filling vials from a bailer with a bottom‐emptying device.
Ground Water Monitoring Statistics Update: Part I: Progress Since 1988
Authors: Davis Charles B. , McNichols Roger J. 
Published: February 2007

AbstractCurrent federal ground water monitoring statistical regulation dates from the revised RCRA Subtitle C Final Rule of 1988. That rule was a considerable advance over previous RCRA statistical rules. However, two major problem areas remained: facility‐wide false positive rate (FWFPR) control and spatial variability. Progress has been made in the 1991 Subtitle D Final Rule and in guidance: the 1992 Addendum to Interim Final Guidance in particular includes a substantial conceptual advance toward resolving the FWFPR problem. Other areas of improvement include normality testing and distribution assumptions, dropping the four independent samples per monitoring period requirement, allowing a preliminary evaluation short of a 40 CFR Part 258 Appendix II assessment upon finding a statistically significant increase, and suggesting superior alternatives to analyses of variance (ANOVAs) and tests of proportions.The problem of dealing with natural spatial variability remains. Although certain techniques listed in the regulations can control for inherent spatial variability and the performance standards require doing so “when necessary,” little attention has been paid to the ubiquity of such spatial variation. Moreover, regulatory traditions favoring upgradient‐downgradient comparisons often make control of natural spatial variation difficult and ineffective. With new. lined facilities easily implemented statistical solutions are available; however, dealing with the several existing solid waste facilities which will now be regulated under Subtitle D will present major challenges.In short, the 1988 revision of the Subtitle C rules made it more possible to provide statistically sound monitoring programs, and there has been steady progress since then. Challenges remain, however. These vary from slate to slate, particularly with regard to controlling false positives and false negatives in the presence of natural spatial variability.
Field Comparison of Micropurging vs. Traditional Ground Water Sampling
Authors: Kearl Peter M. , Korte Nic E. , Stites Mike , Baker Joe 
Published: February 2007

AbstractMicropurge sampling of ground water wells has been suggested as a possible replacement to traditional purge and sample methods. To compare methods, duplicate ground water samples were collected at two field sites using iraditional and micropurge methods. Samples were analyzed for selected organic and inorganic constituents, and the results were compared statistically. Analysis of the data using the nonparametric sign test indicates that within a 95 percent confidence interval, there was no significant difference between the two methods for the site contaminants and the majority of analytes. These analytical results were supported by visual observations with the colloidal borescope, which demonstrated impacts on the flow system in the well when using traditional sampling methods. Under selected circumstances, the results suggest replacing traditional sampling with micropurging based on reliability, cost, and waste minimization.
Increased Thermal‐Pulse Flowmeter Resolution by Adding a Packer and Computer
Authors: Lyles Brad F. 
Published: February 2007

AbstractMeasurement accuracy was increased by nearly one order of magnitude by outfitting the thermal‐pulse flowmeter (TFM) with an inflatable packer. To accurately measure slow water velocities in boreholes greater than 15 cm diameter, it is necessary to divert borehole fluids through the TFM by inflating a packer. During calibration it was noted that the TFM's accuracy decreased as the borehole diameter increased. With Lhe packer inflated the TFM has a useful flow measurement range of 0.08 to 15 L/min (with flow velocities of 0.24 ± 0.012 cm/inin to 45.7 ± 0.61 cm/min, respectively, in 20‐cm‐diameter pipe), compared to 0.8 to 57 L/min for a packcrless TFM. A computer interlace was added to the TFM to provide a real‐time graphical display of the differential voltage output from the TFM, a running mean and standard deviation of the pulse‐response time, and a mean flow rate and velocity based on calibration curve fits.
Analytical Solutions for Determination of Non‐Steady‐ State and Steady‐State Capture Zones
Authors: Yang Y. Jeffrey , Spencer Richard D. , Gates Todd M. 
Published: February 2007

AbstractThis paper presents analytical solutions for determining non‐steady‐state capture zones produced by a single recovery well and steady‐state capture zones produced by multiple recovery wells. Analysis of non‐steady‐slate capture zones is based on the lime‐dependent location of caplure zone stagnation points and the geometric similarity between steady‐slate and non‐steady‐state capture zones. The analytical solution of steady‐state capture zones is obtained from spatial variations of discharge potential across the capture zone boundary. Both capture zone analyses are based on the assumptions of uniform flow field with a constant hydraulic conductivity, the Dupuit assumption of insignificant vertical flow, a negligible delayed yield, and a fully penetrating well with a constant pumping rate. For a ground water pump‐and‐trcat remediation program, the pumping rate and well location design variables can be adjusted to ensure containment of the ground water contaminant plume.
Overexploitation and Deterioration of Aquifers in Venezuela
Authors: Jegat H. , Alvarado J. , Loaiciga H.A. 
Published: February 2007

AbstractApproximately 50 percent of the potable, industrial, and agricultural water supply in Venezuela comes from ground water, mined through some 40,000 wells scattered around the country. The majority of the productive aquifers consist of quaternary deposits in mountain valleys and coastal lowlands, all of which are situated in areas with limited or low precipitation. Intensive exploitation of several of these aquifers for the last 30 years has resulted in overdraft conditions and ground water contamination, causing serious socio‐economic consequences in various regions of Venezuela. This paper reviews the quality and quantity aspects of overdrafted aquifers in Venezuela, which can he classified into three major categories: (1) aquifers in the coastal lowlands in the stales of Falcon and Zulia of northern Venezuela: (2) the intermontane Carora and Quibor Valley Aquifers: and (3) aquifers in the Lake Valencia Watershed. If current trends of aquifer overexploitation continue, further water deficits and irreversible environmental damage are predicted.
Vadose Zone Monitoring: Experiences and Trends in the United States
Authors: Cullen Stephen J. 
Published: February 2007

AbstractThe vadose zone is the portion of the geologic profile above a perennial aquifer. Inclusion of mandatory vadose zone monitoring techniques as an approach to aquifer protect ion was first proposed under the Resource Conservation and Recovery Act in the United States in 1978 and has since received increasing acceptance at federal and stale levels. The goals of a vadose zone characterization and monitoring effort are to establish background conditions, identify contaminant transport pathways, identify the extent and degree of existing contamination, establish the basis for monitoring network design, measure the parameters needed in a risk assessment, and provide detection of contaminant migration toward ground water resources. The benefits of vadose zone monitoring include early warning of contaminant migration, potential reduction of ground water monitoring efforts, reduction of contaminant spreading and volume, and reduced time and cost of remediation once a contaminant release occurs. Vadose zone characterization and monitoring techniques should be considered as critical hydrologic tools in the prevention of ground water resource degradation.
Radium in Coastal Sarasota County Ground Water
Authors: Walters Michael O. 
Published: February 2007

AbstractSarasota County is one of 10 generalized areas of the continental United States known to haw high concentrations of naturally occurring radium in fresh ground water (Chandler 1989). Various authors have conducted investigations to examine the distribution of radium in ground water, rivers, and estuaries. They concluded that ground water was the source of radium, but rivers were also enriched with radium as a result of the interaction with ground water. The Glulf of Mexico also has areas with radium enrichment resulting from geothermal springs with concentrations as high as 51 picocuries per liter. During 1986 and 1987. the Health and Rehabilitative Services of the state of Florida collected ground water data for radium analysis of private drinking water wells. These data were used to develop a contour map of radium‐226 concentrations for coastal Sarasota County.
Design of a Multi‐Level Monitoring Well for Continuous Sample Collection
Authors: Ayers Jerry F. , Gosselin David C. 
Published: February 2007

AbstractAs part of a study of the flow dynamics and sampling environment around a high‐capacity irrigation well, it was necessary to design and install a multi‐level monitoring well network close to the production well. A requirement of the monitoring well network was the capability of continuous pumping over periods typical of those used during water sample collection. This was accomplished through the use of a control valve and air manifold system connected 10 a common gasoline engine‐operated air compressor. The system provided adequate air pressure to operate 24 half‐size bladder pumps to depths between 21 feet (6.4 m) and 56 feet (17.1 m) below the surface. Preliminary data collected from the monitoring well network indicate that the system will meet the requirements of the high‐capacity well study.
DNAPL Flow Behavior in a Contaminated Aquifer: Evaluation of Field Data
Authors: Oolman T. , Godard S. T. , Pope G.A. , Jin M. , Kirchner K. 
Published: February 2007

AbstractA pool of dense nonaqueous phase liquid (DNAPI.) containing TCE and other chlorinated solvents has been removed from the subsurface at Hill Air Force Base, Uthah. as part of an interim remedial action. The removal of the DNAPI. pool means that future off‐site migration of dissolved contaminants in the ground water is minimized, and costs for final remedial actions are reduced. A pump‐and‐treat system recovered more than 23.000) gallons of DNAPI. and one million gallons of contaminated ground water from the aquifer. The efficiency of this remedial action was evaluated on the basis of extensive field and laboratory data. The behavior of DNAPI. flow in the aquifer sands was characterized by collecting core samples from two borings in the DNAPL pool and measuring relative permeabilities and DMAPI. saturation. Core Hooding results show that approximately one‐third of the DNAPI. originally in the pool is not recovered by water displacement, but remains as a residual saturation held in place by capillary pressure. However, subsequent Hooding with two pore volumes of surfactant solution reduced the residual DNAPI. saturation in the sand by one order of magnitude. Analytical and numerical models for the DNAPI flow behavior at the site were developed. This is the first time that such models have been developed and applied to an actual DNAPI. pumping lest conducted in the field. Because measured permeabilities and residual saturations were used lo calibrate the models. the model predictions could be used lo provide valuable insights into the controlling mechanisms for DNAPL recovery. The data collection and modeling procedures outlined in this paper can be used lo enhance the efficiency and minimize the cost 10 clean up this and other DNAPI.‐contaminated sites.
Estimation of Leakage Rates Through Flexible Membrane Liners
Authors: Murray Gordon B. , McBean Edward A. , Sykes Jonathan F. 
Published: February 2007

AbstractLeakage rate calculations for both low‐ permeability soil liners and composite liners using flexible membrane liners (FMLs) overlying low‐permeability soil are developed. Latin‐Hypercube simulations with uncertainly assigned to the soil liner hydraulic conductivity value and the spatial frequency of FML holes are used to examine the variability in the liner leakage rates. The low‐permeability soil hydraulic conductivity is the parameter with the greatest effect on landfill liner leakages rates. Composite liners have a significant impact on reducing leakage rates through the landfill liner.
Comparability of Large‐Scale Studies of Agricultural Chemical Contamination of Rural Private Wells
Authors: Ray Chittaranjan , Schock Susan C. 
Published: February 2007

AbstractDetection of agricultural chemicals in ground water has prompted numerous studies. Federal, state, and regional studies were conducted in the last 10 years in order to assess the occurrence of agricultural chemicals in ground water. The results of the studies present the number or percentage of samples with agricultural chemicals above the drinking water standard or health advisory levels as well as samples with detections of one or more compounds. Data comparison from one state or region to another are frequently referred to by regulatory and agency personnel involved in water quality and agriculture issues. Unless the history of pesticide use, method of chemical analyses, detection limits, statistical design of the sampling plan, well type, well depth, geology of the formation material, and typical land use around the wellhead are known, such comparisons can be misleading. Reporting the limitations or presenting a disclaimer should be a key element for a study so that “apples and oranges” are not compared.
The Use of Invertebrates in Ground Water Monitoring: A Rising Research Field
Authors: Malard Florian , Plenet Sandrine , Gibert Janine 
Published: February 2007

AbstractThe use of invertebrates as biomonitors of ground water quality is a relatively new approach that has come of age with the development of ground water ecology. The benefits of such an approach are illustrated by four examples of field biomonitoring from several sites in various hydrogeological settings. Contamination of the interstitial zone by heavy metals in some sectors of the Rhóne River (France) was shown by the scarcity of insect species; sewage pollution in the saturated zone of a karstic aquifer was indicated by the low relative abundances of stygobites as compared with those of stygophiles and stygoxenes; and enrichment with organic matter of an underflow was clearly demonstrated by the extremely high density of ground water invertebrates such as oligochaetes, ostracods, and isopods. Examination of the spatial changes in the composition and abundance of invertebrate assemblages was also useful in determining the direction and intensity of water fluxes between a river and its underflow, as well as in delineating the reduced or oxidized zones in a manganese‐polluted aquifer. Finally, the selected case studies emphasized the variety of methodological approaches that could be developed in ground water contamination biomonitoring, as well as the complementary and sometimes new information provided by this innovative method in comparison with that obtained by conventional pollution monitoring techniques.