bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Fiberglass and Other Polymeric Well Casings Part II. Sorption and Leaching of Trace‐Level Organics
Authors: Ranney Thomas A. , Parker Louise V. 
Published: February 2007

AbstractThis paper contains the results of a laboratory study that was designed to compare sorption of low (mg/L) concentrations of 11 organic solutes by six polymeric materials (acrylonitrile butadiene styrene [ABS], fluorinated ethylene propylene [FEP], fiberglass‐reinforced epoxy [FRE] and fiberglass‐reinforced plastic [FRP], polyvinyl chloride [PVC], and poly‐tetrafluoroethylene [PTFE]).During this six‐week study, ABS sorbed analytes much more rapidly and to a greater extent than did the other materials, and PVC and FRE sorbed analytes more slowly and to a lesser extent than the other materials tested.As the study progressed, an increasing number of spurious peaks were found in the high performance liquid chromatography (HPLC) chromatograms of some of our samples, indicating that leaching of some consituents had occurred. By the end of the study, there were 11 additional peaks in the ABS samples, five in the FRP samples, and one in the FRE samples. Analysis by purge and trap gas chromatography/mass spectrometry (GC/MS) of those samples and of well water samples that were exposed to the casings for 500 hours revealed the identity of some of the leached constituents; acrylonitrile and styrene (components of ABS), chloroform and ethylbenzene (an intermediate in the production of styrene) from the ABS pipe, and toluene, 1,1,1‐trichloroethane, and ethylbenzene from the FRP casing.
Modeling of Plume Capture by Continuous, Low‐Permeability Barriers
Authors: Garon Kevin P. , Schultz Dale S. , Landis Richard C. 
Published: February 2007

AbstractModeling was performed to simulate ground water flow through reactive barriers of lower hydraulic conductivity than the surrounding aquifer to determine the plume capture widths. As a plume approaches such a barrier, it spreads laterally. Therefore, to intercept an entire plume, the barrier must be wider than the upgradient width of the undisturbed plume. The results indicate that, for practical values of barrier thickness and plume width, hydraulic conductivities ten‐fold less than that of the aquifer can be accommodated by making the width of the barrier approximately 20% greater than the upgradient width of the plume. Barrier hydraulic conductivities one‐hundred‐fold less than that of the aquifer may require barrier widths up to twice the width of the upgradient plume for plumes 100 feet wide (33 m) and as little as 1.1 times for plumes 1000 feet wide (325 m). The results presented here lend support to the view that novel emplacement methods that create zones of slightly lower hydraulic conductivity than the native aquifer may be viable alternatives to the excavation‐and‐backfill approaches which have thus far been used for installing permeable reactive barriers.
Characterization of a TCE DNAPL Zone in Alluvium by Partitioning Tracers
Authors: Young C. M. , Jackson R. E. , Jin M. , Londergan J. T. , Mariner P. E. , Pope G. A. , Anderson F. J. , Houk T. 
Published: February 2007

AbstractPartitioning interwell tracer tests (PITT) were used ID determine the spatial distribution and volume of residual trichloroethene (TCE) present in alluvium beneath the Portsmouth Gaseous Diffusion Plain in southern Ohio. Its first use at this site was in support of the design of a surfactant flood to remove the residual DNAPL (dense nonaqueous phase liquids) from the alluvial aquifer. The second application assessed the performance of the surfactant flood. The average DNAPL saturation in the first PITT was 0.1 to 0.2% in a swept pore volume of 4500 gallons (17.000 L). A second PITT was undertaken following the surfactant flood and yielded an average residual saturation of 0.06% in a swept pore volume of 3400 gallons (13.000 L), the reduction in pore volume being due to the confinement of the tracers to the lower sand and gravel unit of the alluvium. The design, operation, and analysis of the two PM Is provided strong evidence of a buried channel that controls the spatial distribution of the residual TCI: DNAPL in the basal sand and gravel aquifer and must be considered in the eventual full remediation of this aquifer.
Using Hydrochemical Fades to Delineate Ground Water Flowpaths in Fractured Shale
Authors: Schreiber M. E. , Moline G. R. , Bahr J. M. 
Published: February 2007

AbstractLarge differences in chemistry between sampling points separated In short vertical intervals are often observed in contaminant plumes in both granular and fractured aquifers. However, most regional models assume that such differences will be reduced by dispersive mixing during transport. At a field site located in a discharge area on the Oak Ridge Reservation, Tennessee, ground water flows along discrete flowpaths, as evidenced by the presence of four distinct water types—Ca‐HCO3, Ca‐Na‐HCO3, and Na‐Ca‐HCO3, and Na‐Ca‐HCO3‐S04—in samples collected from shallow (< 3D in) multilevel wells. The preservation of distinct chemical signatures suggests that ground water must he contained in discrete flow zones during much of its transport time. The chemical composition of the water types can be explained primarily by strata‐bound flow over varying flowpath lengths and secondarily by mixing of waters during cross‐formational flow in a discharge zone. The hydrochemical facies identified by correlation of water types between the boreholes indicate the general orientation of ground water How paths. These inferred flowpaths are oblique to the orientation of the measured hydraulic gradient and are more closely aligned with bedding and the calculated flow direction. Results of this study indicate that discrete multilevel sampling for analysis of major ions, in addition to information gathered from tracer tests, borehole flow tests. and visual core observations, can provide valuable information on flow directions and preferential flowpaths for contaminant transport.
Demonstrating Localized Intrinsic Biodegradation of Chlorinated Aliphatic Hydrocarbons Using Time Series Sampling
Authors: Schilling Keith E. 
Published: February 2007

AbstractLocalized intrinsic biodegradation of chlorinated aliphatic hydrocarbons (CAHs) was investigated by pumping from a monitoring well screened in a low conductivity carbonate mudstone. Two time series tests were conducted to assess the relative potential for intrinsic biodegradation in occur in the mudstone compared to the surrounding highly productive carbonate aquifer. Water samples were collected during pumping and analyzed for CAHs (tests 1 and 2). and water quality parameters (pH, specific conductance, dissolved oxygen, redox), election donors and acceptors, and biodegradation indicators (chloride, alkalinity) (test 2). During both lime series tests, concentrations of TCE breakdown products— DCE, vinyl chloride and ethane—decreased significantly after pumping 500 gallons of water from the well. During lest 2. concentrations of electron donors and acceptors and biodegradation indicators decreased, whereas dissolved oxygen and redox remained at low levels. Multiple lines of evidence demonstrated that that intrinsic bioremediation of CAHs is occurring in the mudstone, including: (1) presence of anaerobic conditions in the mudstone conducive for reductive dechlorination: (2) progression of electron acceptors and presence of methanogenic conditions; (3) available supply of electron donors in the mudstone: (4) occurrence of TCE breakdown products; and (5) increased chloride and alkalinity concentrations in the zone of active biodegradation.Time series testing indicated that during the early stages of pumping, effluent consisted mainly of ground water derived from the mudstone unit. With continued pumping, an increasing percentage of effluent water was derived from the less contaminated, permeable carbonate units which bounded the mudstone layer. Differences in permeabilities between the carbonate aquifer and mudstone layer probably accounted for the varying degree of intrinsic biodegradation observed between the two systems. Future remedial efforts should consider avoiding ground water extraction from the mudstone and disturbing the intrinsic biodegradation processes that are reducing contaminant mass in the aquifer.
Fluoride in Nebraska's Ground Water
Authors: Gosselin David C. , Headrick Jacqueline , Harvey F. Edwin , Tremblay Rod , McFarland Kimberly 
Published: February 2007

AbstractFluoride concentrations in ground water are generally low but play an important role in dental health. This study evaluates the vertical and spatial distribution of fluoride in Nebraska's ground water and examines the geological and geochemical processes that control its concentration. Data from 1794 domestic wells sampled by the Nebraska Department of Health and Human Services. Regulation, and Licensure (NDOH) had a range of fluoride concentrations from <0.1 to 2.6 mg/L. and a median concentration of 0.3 mg/L. The median fluoride concentrations for Nebraska's 13 ground water regions varied from 0.2 to 0.7 mg/L. In each of these regions, individual wells may have either insufficient or overabundant F concentrations; we recommend that individual private water systems be tested for fluoride. Based on these data, system‐specific recommendations can be made regarding the necessity for fluoridation.Geochemical data indicated that the majority of fluoride occurs as F. Dissolution of F‐bearing minerals controls fluoride occurrence. Apatite plus minor amounts of fluorite along with significant ground water residence times are the primary factors controlling F in the water from the Dakota Formation in Knox County, as well as in other parts of northeastern Nebraska. In western and southwestern Nebraska, dissolution of volcanic glass is the most probable source of F Long residence times plus fluorite also may contribute to the F concentrations in the Chadron Formation.
Construction and Testing of a Durable Platinum Wire Eh Electrode for In Situ Redox Measurements in the Subsurface
Authors: Swerhone G. D. W. , Lawrence J. R. , Richards J. G. , Hendry M. J. 
Published: February 2007

AbstractWe have developed a rugged, durable platinum wire Eh electrode for application in subsurface environments. The electrode design is described in detail and its performance under aerobic and anaerobic steady‐state and transient conditions is assessed. The electrode consists of a 0.5‐mm‐diameter platinum wire (99.99% purity) cast in a glass fiber‐reinforced epoxy jacket. The construction allowed installation through direct insertion into sandy media to depths up to several meters. Data collection was through connection to a datalogger with high impedance input; data points were collected every 10 seconds and averaged and stored once an hour. The electrodes functioned in situ for periods of more than three years and gave reliable readings during oxic, anoxic, and transitional conditions. Performance testing and examination of electrodes recovered after three years in situ indicated that they were not impacted by corrosion, dissolution, or poisoning.
Investigation and Remediation of a 1,2–Dichloroethane Spill Part I: Short and Long‐Term Remediation Strategies
Authors: Sehayek Lily , Vandell Terry D. , Sleep Brent E. , Lee Michael D. , Chien Calvin 
Published: February 2007

AbstractRelease of an estimated 150,000 gallons (568,000 L).of 1.2–dichloroethane (EDC) from a buried pipeline into a ditch and surrounding soil resulted in shallow subsurface contamination of a Gulf Coast site. Short‐term remediation included removal of EDC DNAPI. (dense nonaqueous phase liquid) by dredging and vacuuming the ditch, and by dredging the river where the ditch discharged. EDC saturation in shallow impacted sediments located beneath the ditch was at or below residual saturation and these sediments were therefore left in place. The ditch was lined, backfilled, and capped. Long‐term remediation includes EDC DNAPL recovery and hydraulic containment from the shallow zone with long‐term monitoring of the shallow, intermediate, and deep (200 foot) aquifers. Ground water, DNAPL., and dissolved phase models were used to guide field investigations and the selection of an effective remedial action strategy. The DNAPL. modeling was conducted for a two‐dimensional vertical cross section of the site, and included the three aquifers separated by two aquitards with microfractures. These aquitards were modeled using a dual porosity approach. Matrix and fracture properties of the aquitards used for DNAPL modeling were determined from small‐scale laboratory properties. These properties were consistent with effective hydraulic conductivity determined from ground water flow modeling. A sensitivity analysis demonstrated that the vertical migration of EDC was attenuated by dissolution of EDC into the matrix of the upper aquitard. When the organic/water entry pressure of the aquitard matrix, or the solubility of EDC were decreased to unrealislically low values. EDC DNAPL. accumulated in the aquifer below the upper aquitard.EDC DNALM, did not reach the regional (deepest) aquifer in any of the cases modeled. The limited extent of vertical EDC migration predicted is supported by ground water monitoring conducted over the four years since the spill.
Design of Dry Barriers for Containment of Contaminants in Unsaturated Soils
Authors: Morris Carl E. , Thomson Bruce M. , Stormont John C. 
Published: February 2007

AbstractA dry barrier consists of a laterally continuous soil layer that is dried by air flow. Dry atmospheric air is passed through a soil layer (preferably of a coarse texture). accumulates water vapor, then emerges from the formation as moist air. Removal of soil moisture limits or prevent downward water movement. Drying a soil layer with air is possible when atmospheric air contains less water vapor than soil pore gas. The design of an effective dry barrier is highly site dependent and requires knowledge of the site geology, of the extent of the contaminant plume, and climatic conditions. Climatic conditions at the site are important in two ways: (1) the efficiency of atmospheric air in drying: soil depends on its absolute humidity: and (2) the amount of infiltration from precipitation influences how much water has to be removed from the soil to maintain a dry barrier. The size of the barrier, combined with the climatic conditions, determines the air flow required to maintain the system. while the hydraulic characteristics of the soils determine the location and design of air injection and extraction wells. The electric power rate structure must be known to calculate operating costs. The principal factors which determine the feasibility of a dry barrier include: (1) the climate at the site and, most importantly, low‐absolute atmospheric humidity during much of the year; (2) a substantial unsaturated zone; and (3) the ability to circulate air through the unsaturated zone. The amount of initial soil moisture in the layer through which air is circulated may be an important factor in the feasibility of a dry barrier. A design study is presented that illustrates the trade‐offs between high capital costs of constructing a large number of air circulation wells vs. the high operating costs required to pump large volume of air over long distances through fewer wells. This study found that, under conditions similar to those in many arid regions, a dry barrier may be a technically and economically viable method of providing temporary waste containment.
Robowell: An Automated Process for Monitoring Ground Water Quality Using Established Sampling Protocols
Authors: Granato Gregory E. , Smith Kirk P. 
Published: February 2007

AbstractRobowell is an automated process for monitoring selected ground water quality properties and constituents by pumping a well or multilevel sampler. Robowell was developed and tested to provide a cost‐effective monitoring system that meets protocols expected for manual sampling. The process uses commercially available electronics, instrumentation, and hardware, so it can be configured to monitor ground water quality using the equipment, purge protocol, and monitoring well design most appropriate for the monitoring site and the contaminants of interest. A Robowell prototype was installed on a sewage‐treatment plant infiltration bed that overlies a well‐studied u neon fined sand and gravel aquifer at the Massachusetts Military Reservation, Cape Cod, Massachusetts, during a time when two distinct plumes of constituents were released. The prototype was operated from May 10 to November 13, 1996, and quality‐assurance/quality‐control measurements demonstrated that the data obtained by the automated method was equivalent to data obtained by manual sampling methods using the same sampling protocols. Water level, specific conductance, pH, water temperature, dissolved oxygen, and dissolved ammonium were monitored by the prototype as the wells were purged according to U.S. Geological Survey (LJSGS) ground water sampling protocols. Remote access to the data record, via phone modem communications, indicated the arrival of each plume over a few days and the subsequent geochemical reactions over the following weeks. Real‐time availability of the monitoring record provided the information needed to initiate manual sampling efforts in response to changes in measured ground water quality, which proved the method and characterized the screened portion of the plume in detail through time. The methods and the case study described are presented to document the process for future use.
Chlorinated Decreasing Solvents: Physical‐Chemical Properties Affecting Aquifer Contamination and Remediation
Authors: Jackson Richard E. , Dwarakanath Varadarajan 
Published: February 2007

AbstractChlorinated degreasing solvents are multicomponent liquids containing not only the chlorinated hydrocarbons with which their name is associated (e.g., trichloroethylene or |TCE]. perchloroethylene or [PCE], 1,1,1‐trichlorocihane [TCA]) but also a number of organic additives included as corrosion inhibitors and antioxidants. The additives, such as 1,4‐dioxane, are likely to be of significant public‐health importance as ground water contaminants due to their toxicity, solubility, and mobility. Following their use in vapor degreasing systems by industry, chlorinated degreasing solvents will also contain about 25% solubilized oil and grease.A number of physical‐chemical properties become especially important in the light of the multicomponent nature of these solvents. First, the higher aqueous solubility and lower sorption of the additives makes it is reasonable to expect that faster moving plumes of these solvent additives will precede plumes of the chlorinated hydrocarbons. Second, due to high losses of chlorinated hydrocarbons by volatilization from vapor degreasers during years in the middle of the century, it is probable that background concentrations of these hydrocarbons are present in ground water flow systems due to their downwind washout. Finally, the solubilized oil and grease may cause profound changes to the wettability of aquifer materials contacted by the solvents during their subsurface migration. It is argued, therefore, that the wettability of aquifer materials contaminated by chlorinated degreasing solvents needs to be experimentally determined before remediation of DNAPL at each site, rather than being simply assumed as water wet.
Instrumentation Design and Installation for Monitoring Air Injection Ground Water Remediation Technologies
Authors: Hall B.L. , Baldwin C.K. , Lachmar T.E. , Dupont R.R. 
Published: February 2007

AbstractAn in situ instrumentation bundle was designed for inclusion in monitoring wells that were installed at the Wasatch Trailer Sales site in Layton, Utah, to evaluate in situ air sparging (IAS) and in‐well aeration (IWA). Sensors for the bundle were selected based on laboratory evaluation of accuracy and precision, as well as consideration of size and cost. SenSym pressure transducers, Campbell Scientific Inc. (CSI) T‐type thermocouples, and dissolved oxygen (DO) probes manufactured by Technalithics Inc. (Waco, Texas), were selected for each of the 27 saturated zone bundles. Each saturated zone bundle also included a stirring blade to mix water near the DO probe. A Figaro oxygen sensor was included in the vadose zone bundle. The monitoring wells were installed by direct push technique to minimize soil disruption and to ensure intimate contact between the 18 inch (46 cm) long screens and the soil. A data acquisition system, comprised of a CSI 21X data logger and four CSI AM416 multiplexers, was used to control the stirring blades and record signals from more than 70 in situ sensors. The instrumentation performed well during evaluation of IAS and IWA at the site. However, the SenSym pressure transducers were not adequately temperature compensated and will need to be replaced.
Evaluation of Hydrogeo‐chemical Conditions for Development of Nuclear Criticality in Low‐Level Waste Disposal Facilities
Authors: Toran Laura , Cohen‐Bradley Virginia 
Published: February 2007

AbstractThe under ground disposal of fissile isotope‐bearing wastes poses some unique issues. Specifically, radionuclides such as 235U disposed in low‐level waste facilities, if present in the correct concentration and geometry, can create a nuclear criticality event that releases radioactivity to ground water. This paper reports the results of a study of the potential for 235U to be transported by ground water within low‐level waste facilities and to concentrate to form a critical mass. Coupled hydrologic and geochemical modeling was used to investigate two possible mechanisms for concentrating mobile uranium: sorption on high capacity sites and precipitation in a reducing zone. The hydrogeochemical modeling showed that (1) it is difficult to mobilize uranium from sorption sites then re‐deposit it; (2) if uranium is already in solution it can accumulate in zones of high sorption, and (3) reducing zones can accumulate sufficient uranium in the presence of oxygenated ground water. Site‐specific disposal practices, such as the commingling of large quantities of depleted (nonfissile) uranium and the difficulty of bringing sufficient mass together in the correct geometry, limit the potential for criticality safety concerns. In order to determine appropriate disposal practices, hydrogeochemical modeling can be used to study the future mobility and accumulation of the waste.
Denitrification and Phosphate Removal in Experiments Using Al Stearate
Authors: Stoessell R.K. , Easley D.H. , Yamazaki G.P. 
Published: February 2007

AbstractHydrophobic Al monostearate was tested as a low‐solubility denitrification substrate for anaerobic bacteria and a source of aluminum for phosphate precipitation. Flow‐through laboratory columns at 25 ± 2°C were used with O2‐saturated solutions containing 1x, 2x, 8x, and 16x concentrations of 2.26 mg/L NO3‐N and 3.26 mg/L PO4‐P. Denitrification was exponential, approximating first‐order reaction kinetics with the rate constant being a function of the initial nitrate concentration. The half life in minutes can be approximated by 5.29 (mg/L NO3‐ N°)1/2 where NO3‐N° was the initial input nitrate concentration. The reaction times were significantly shorter than those required using Ca distearate as a carbon source and much shorter than those using cellulose (white pine shavings) as a carbon source. Al stearate has potential for use in a flow‐through container for denitrification of oxidized effluent from home sewage systems.Aqueous phosphate removal with Al stearate depended upon dissolution of the Al stearate followed by precipitation of Al phosphate. Only 5% to 10% of the phosphate was removed from the solution. The amounts removed were similar to those obtained using bauxite grains as an aluminum source, following saturation of sorption sites with phosphate on bauxite. Aqueous phosphate removal with Ca stearate was insignificant, as the released calcium was apparently precipitated as calcite rather than as hydroxyapatite.