bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design Screening Tools for Passive Funnel and Gate Systems
Authors: Sedivy Robert A. , Shafer John M. , Bilbrey Lacrecia C. 
Published: February 2007

AbstractThe funnel and gate remediation concept (Star and Cherry 1993) represents a promising, yet relatively under‐developed, technology for the passive control and in situ remediation of contaminated ground water. Effective design and implementation of such a system may, however, prove difficult under conditions of large or unpredictable variations in contaminant migration or ground water flow.Numerical modeling of two‐dimensional ground water flow has been used to predict the hydraulic performance of passive, straight, or winged funnel and gate configurations over a range of hydrogeologic and ambient ground water flow conditions. The results of these analyses were used to construct generic correlation diagrams relating upstream capture zone or gale through put to the barrier, gale, and aquifer characteristics. These diagrams serve as useful screening tools to (1) quantitatively estimate the capture zone of pre‐determined funnel and gale configurations, or (2) develop preliminary funnel and gale designs that will yield a desired capture zone, independent of aquifer characteristics.
Compatibility of Bentonite and DNAPLs
Authors: McCaulou Douglas R. , Huling Scott G. 
Published: February 2007

AbstractThe compatibility of dense nonaqueous phase liquids (DNAPLs). triehloroelhylene (TCE), methylene chloride (MC), and creosote with commercially available sodium bentonite pellets was evaluated using stainless steel, double ring, falling head permeameters. The hydraulic conductivity (K) of the bentonite clay was measured under three experimental conditions: (1) water soluble constituents of the DNAPLs were used to hydrate and permeate the bentonite: (2) bentonite pellets were submersed in DNAPL prior to hydration and permeation with water: and (3) DNAPLs were pooled on water‐hydrated bentonite. Further, the effect of hydraulic head (2.5. 145, and 710 cm) on water‐hydrated bentonite permeated with TCE and the effects of TCE exposure time to mixtures of bentonite grout and sand were measured. Solubility concentrations of DNAPL constituents did not effect the hydraulic conductivity of the bentonite pellets relative to baseline (water only) measurements; a competent hydraulic barrier was formed (K < 5 × 10−9 cm/s). Bentonite pellets submersed in DNAPLs retained their rigid shape, did not swell, and did not perform as a hydraulic barrier. However, when the DNAPL was removed and replaced with water, the DNAPL‐wetted pellets imbibed water to swell and form an adequate hydraulic barrier (K < 6 × 10−9 cm/s). Competent hydraulic barriers constructed with bentonite pellets and hydrated with water were subsequently permeated with TCE, MC, or creosote DNAPLs developing desiccation cracks up to 5 mm wide. The intrinsic permeability of water‐hydrated bentonite was 46 to 2640 limes greater to DNAPLs relative to water, indicating that the desiccation cracks predominantly facilitated preferential DNAPL transport. The propagation rate of cracks was positively correlated to the hydraulic gradient, bin the formation of cracks is chemically dependent on the contact lime of DNAPL. Silica sand is expansively inert, yet 95, 90, 83, 75, and 50% (wt sand/wt bentonite) mixtures with bentonite grout were insufficient to prevent desiccation cracks and hydraulic failure. The incompatibility between DNAPLs and bentonite observed in this study is important due id the numerous exploratory borings in DNAPL/ones, the increasing dependency on hydraulic containment as a remedial alternative, and the fact that such remedial systems are often designed to be functional for many years.
Naturally Occurring Arsenic in Sandstone Aquifer Water Supply Wells of Northeastern Wisconsin
Authors: Burkel Rebecca S. , Stoll Richard C. 
Published: February 2007

AbstractThe U.S. Environmental Protection Agency (EPA) maximum contaminant level (MCL) of 50 μg/L for arsenic was exceeded in 86 of 2125 water supply wells sampled over a broad geographic range in pails of Drown. Outagamie and Winnebago Counties, Wisconsin. The hydrologic and geochemical properties of the area were examined and the source of arsenic was determined to be natural, Ground water collected from two geologic formations, the St. Peter Sandstone and the overlying Platteville/Galena Dolomite, was found to be the principal source of the elevated arsenic concentrations. These two Formations supply a large portion of eastern Wisconsin private wells with their drinking water.Three wells were found within Outagamie County to have an unusually low pH. Results suggest that the cause of the low pH in these wells is of natural origin induced by the oxidation of iron sulfide minerals. In this reaction iron sulfide minerals are oxidized. forming sulfuric acid causing a low pH and a high concentration of various metals to leach from native rock formations into the water supply.Based on the data gathered from this study, an arsenic advisory area was designated for both Outagamie and Winnebago Counties. Guidelines were developed for well drillers and owners constructing new wells within the advisory area to reduce the likelihood of arsenic presence in the water supply. Fifteen wells containing arsenic exceeding the MCL were successfully reconstructed or new wells were constructed based on the guidelines developed. These constructions substantially reduced arsenic levels in the well water supplies.
Statistical Comparison of Leachate from Hazardous, Codisposal, and Municipal Solid Waste Landfills
Authors: Gibbons Robert D. , Dolan David G. , May Helen , O'Leary Kevin , O'Hara Richard 
Published: February 2007

AbstractThere has been considerable debate regarding the chemical characterization of landfill leachate in general and the comparison of various types of landfill leachate (e.g., hazardous, codisposal, and municipal) in particular. For example, the preamble to the U.S. EPA Subtitle D regulation (40 CFR Parts 257 and 258) suggests that there are no significant differences between the number and concentration of toxic constituents in hazardous versus municipal solid waste landfill leachate. The purpose of this paper is to statistically test this hypothesis in a large leachate database comprising 1490 leachate samples from 283 sample points (i.e., monitoring location such as a leachate sump) in 93 landfill waste cells (i.e., a section of a facility that took a specific waste slream or collection of similar waste streams) from 48 sites with municipal, codisposal, or hazardous waste site histories. Results of the analysis reveal clear differention between landfill leachate types, both in terms of constituents detected and their concentrations. The result of the analysis is a classification function that can estimate the probability that new leachate or ground water sample was produced by the disposal of municipal, codisposal, or hazardous waste. This type of computation is illustrated, and applications of the model to Superfund cost‐allocation problems are discussed.
Nitrogen Removal from Landfill Leachate Using an Infiltration Bed Coupled with a Denitrification Barrier
Authors: Robertson W.D. , Anderson M.R. 
Published: February 2007

AbstractTreatment of nitrogen in landfill leachate has received considerable attention recently because of the relatively low levels at which some nitrogen species (i.e., NH3) can be toxic to aquatic life forms. This study reports on the results of a three‐year, pilot‐scale field trial demonstrating the use of infiltration bed and nitrate barrier technology to achieve nitrogen removal in landfill leachate. The infiltration bed comprises an unsaturated sand layer overlying a saturated layer of waste cellulose solids (sawdust), which acts as a carbon source for heterotrophic denitrification. When loaded at a rate of 1 to 3 cm/day, the infiltration bed was successful at lowering leachate inorganic nitrogen (NH4++ NO3‐) levels averaging 24.8 mg/L N by 89%, including 96% in the third year of operation. The surface water discharge criteria for un‐ionized ammonia (NH3) were met on all occasions in the treated leachate during the second and third years of operation. Nitrogen attenuation is presumed to occur by a two‐step process in which leachate NH4+ is first oxidized to NO3‐ in the unsaturated sand layer and then is converted to nitrogen gas (N2) by denitrification occurring in the underlying sawdust layer. Mass balance calculations suggest that the sawdust layer has sufficient carbon to allow denitrification to proceed for long periods (1.0 to 30 years) without replenishment. Because this technology is simple to construct and is relatively maintenance free, it should be attractive for use at smaller landfills where the installation of conventional treatment plants may not be feasible.
Decontaminating Materials Used in Ground Water Sampling Devices: Organic Contaminants
Authors: Parker Louise V. , Ranney Thomas A. 
Published: February 2007

AbstractIn these studies, the efficiency of various decontamination protocols was tested on small pieces of materials commonly used in ground water sampling devices. Three materials, which ranged in ability to sorb organic solutes, were tested: stainless steel (SS), rigid polyvinyl chloride (PVC), and polytetrafluoroethylene (PTFE). The test pieces were exposed to two aqueous test solutions: One contained three volatile organic compounds (VOCs) and one nitroaromatic compound, and the other contained four pesticides. Also, three types of polymeric tubing were exposed to pesticide solutions. Generally, the contact times were 10 minutes and 24 hours for sorption and desorption.The contaminants were removed from the nonpermeable SS and the less‐sorptive rigid PVC test pieces simply by washing with a hot detergent solution and rinsing with hot water. Additional treatment was required for the PTFE test pieces exposed to the VOCs and for the low‐density polyethylene (LDPE) tubing exposed to the pesticide test solution. Solvent rinsing did not improve removal of the three VOCs from the PTFE and only marginally improved removal of the residual pesticides from the LDPE. However, a hot water and detergent wash and rinse followed by oven drying at approximately 105°C was effective for removing the VOCs from the PTFE and substantially reduced pesticide contamination from the LDPE.
Ground Water Sampling Bias Observed in Shallow, Conventional Wells
Authors: Hutchins Stephen R. , Acree Steven D. 
Published: February 2007

AbstractA previous field demonstration project on nitrate‐based bioremediation of a fuel‐contaminated aquifer used short‐screened clustered well points in addition to shallow (10 foot), conventional monitoring wells to monitor the progress of remediation during surface application of recharge. These well systems were placed in the center and at one edge of each of two treatment cells. One cell received recharge amended with nitrate (nitrate cell), and the other received unamended recharge (control cell). Data from the clustered well points were averaged to provide a mean estimate for comparison with the associated conventional monitoring well.Conservative tracer profiles were similar for each of the four systems, with better fits obtained for well systems located at the edge of the treatment cells. However, aromatic hydrocarbon and electron acceptor profiles varied greatly for the two center well systems, with the conventional monitoring well data suggesting that remediation was proceeding at a much more rapid rate than indicated by the cluster well points. Later tests with an electromagnetic borehole flowmeter demonstrated a significant vertical flow through the well‐bore of the conventional monitoring well under simulated operating conditions. This created an artifact during sampling, thought to arise from preferential flow of recharge water from the water table to deeper portions of the contaminated zone resulting in several effects, including an actual decreased residence time of water sampled by the conventional well. These data provide additional evidence that conventional monitoring wells may be inadequate for monitoring remediation in the presence of significant vertical hydraulic gradients, even for fairly shallow homogeneous aquifers.
Cyclodextrin‐Enhanced Solubilization of Organic Contaminants with Implications for Aquifer Remediation
Authors: McCray John E. , Boving Thomas B. , Brusseau Mark L. 
Published: February 2007

AbstractReagents that enhance the aqueous solubility of non‐aqueous phase organic liquid (NAPL) contaminants are under investigation for use in enhanced subsurface remediation technologies. Cyclodextrin, a glucose‐based molecule, is such a reagent. In this paper, laboratory experiments and numerical model simulations are used to evaluate and understand the potential remediation performance of cyclodextrin. Physical properties of cyclodextrin solutions such as density, viscosity, and NAPL‐aqueous inter‐facial tension are measured. Our analysis indicates that no serious obstacles exist related to fluid properties that would prevent the use of cyclodextrin solutions for subsurface NAPL remediation. Cyclodextrin‐enhanced solubilization for a large suite of typical ground water contaminants is measured in the laboratory, and the results are related to the physicochemical properties of the organic compounds. The most‐hydrophobic contaminants experience a larger relative solubility enhancement than the less‐hydrophobic contaminants but have lower aqueous‐phase apparent solubilities. Numerical model simulations of enhanced‐solubilization flushing of NAPL‐contaminated soil demonstrate that the more‐hydrophilic compounds exhibit the greatest mass‐removal rates due to their greater apparent solubilities, and thus are initially more effectively removed from soil by enhanced‐solubilization‐flushing reagents. However, the relatively more hydrophobic contaminants exhibit a greater improvement in contaminant mass‐removal (compared with water flushing) than that exhibited for the relatively hydrophilic contaminants.
Remedial Options for Creosote‐ Contaminated Sites
Authors: Wu Wei‐Jr , Delshad Mojdeh , Oolman Timothy , Pope Gary A. 
Published: February 2007

AbstractFree‐phase DNAPL recovery operations are becoming increasingly prevalent at creosote‐contaminated aquifer sites. This paper illustrates the potential of both classical and innovative recovery methods. The UTCHEM multiphase flow and transport numerical simulator was used to predict the migration of creosote DNAPL during a hypothetical spill event, during a long‐term redistribution after the spill, and for a variety of subsequent free‐phase DNAPL recovery operations. The physical parameters used for the DNAPL and the aquifer in the model are estimates for a specific creosote DNAPL site. Other simulations were also conducted using physical parameters that are typical of a trichloroethene (TCE) DNAPL. Dramatic differences in DNAPL migration were observed between these simulations.
Using the Stabilization Plateau to Estimate Optimum Well Purge Volume
Authors: Hurt Burhara F. , Tomlinson Rodger B. , Chaseling Janet 
Published: February 2007

AbstractThis study concerns the problem of pump position in landfill monitoring wells and the correct time to stop purging and start sampling. Literature purge volume determination methods fail to use sufficient analyte values for comprehensive study of the stabilization plateau. From field studies it is recommended that prior to commencement of a sampling program a purge study be undertaken to determine pump position and optimum purge volume by conducting (1) a preliminary vertical electrical conductivity (EC) profile: (2) vertical profiling of formation water EC values by low‐flow pumping at 0.5 m vertical intervals‐while also noting EC vertical profile values to assure minimal effect on the water column water quality; and (3) a low‐flow, purge EC stabilization test with the pump positioned at highest formation water EC values. Sufficient EC values are needed to fulfill Conover's (1980) nonparametric tolerance interval sample size criteria, and to graphically delineate the stabilization plateau. This information will allow you to choose an optimum purge volume that allows a margin for error.
A Method for Predicting Chloride Concentrations in Leachate at Natural Attenuation Landfills in the Precambrian Shield Regions of Ontario, Canada
Authors: Gehrels Jim , Puumala Mark 
Published: February 2007

AbstractNatural attenuation landfill sites continue to be the preferred method of domestic waste disposal in the Precambrian Shield regions of Ontario due to economic factors. The main challenge in siting these landfills is ensuring that there will be no adverse impact on off‐site water resources. Impact risk assessments are generally based on estimated volumes and strengths of chloride in the leachate. While volumes can be estimated using simple water balances, peak chloride concentration predictions are based on judgment and are quite variable. Since design chloride strengths dictate the size of the required attenuation zone, overestimating concentrations will typically make it impossible to find a suitable site, while underestimating concentrations increases the potential for adverse off‐site impacts occurring.Hydrogeological data from active and closed landfills in the Precambrian Shield region were collected to help develop a reliable method of predicting peak chloride concentrations in leachate. This study focused on 21 sites located on relatively permeable sandy soils since landfills underlain by low permeability clayey soils retain leachate similar to lined facilities.Linear regression analyses were conducted to determine if source chloride concentrations at the “sand” sites are significantly influenced by waste thickness, fill area, waste volume, waste deposition rate, hydraulic conductivity, upgradient flow length, depth to the water table, and moisture surplus.A strong relationship (R = 0.957) was found to exist between source chloride concentrations and waste volume. This empirical volume versus chloride regression equation can be used as the basis for establishing design chloride concentrations at new natural attenuation landfills developed over sandy soils in the Precambrian Shield regions of Ontario. An alternative risk assessment approach is required for sites developed over clay soils.
Internet Listservices as a Valuable Resource for Environmental Professionals in Soil and Ground Water Remediation
Authors: Guerin Turlough F. , Schaffner I. Richard 
Published: February 2007

AbstractIn 1957, four computers across the United States were linked to form the first version of what we now know as the Internet. The Internet has grown beyond what anyone working in the U.S. Department of Defense Advanced Research Projects Agency (DARPA) more than 40 years ago could have imagined. Yet despite the phenomenal growth of Internet users, and access to information in all fields of endeavor, finding genuinely useful and helpful resources is still a challenge. This article distils information on the most useful Internet listservers for environmental professionals working the site remediation.
A Novel View of Wellbore Flow and Partial Mixing: Digital Image Analyses
Authors: Martin‐Hayden James M. , Wolfe Natalie 
Published: February 2007

AbstractAlthough theories of thoroughly mixed and unmixed wellbore flow have been developed, recent studies suggest that ground water data variability and bias can result from various types of partial mixing. In this study, digital images of dye distributions within a vertical cross‐sectional model of a screened monitoring well allowed mixing processes to be recorded and characterized. Given the conditions represented by this study, two scales of well water mixing are evident: small‐scale mixing adjacent to the well screen and larger‐scale mixing with the water from the casing above the screen section. Evidence suggested that the small‐scale mixing initially caused concentrations at the pump to change more rapidly than the aforementioned theories predicted and to stabilize at biased concentrations. Larger‐scale mixing of casing water and screen section water resulted from either turbulent/viscous entrainment or, more likely, a slightly elevated casing water density. If this mixing occurs due to wellhead cooling where the casing water is significantly chemically altered, bias would result. These results suggest that concentration variability and bias before and during pumping are, in part, controlled by the characteristics and prevalence of small and large scale partial mixing throughout the wellbore in the presence of wellbore‐concentration heterogeneities. The bias and variability could be on the order of those concentration heterogeneities where concentration heterogeneities and partial mixing are present. Bias and variability of the type observed under these experimental conditions call for investigations into conditions that lead to partial mixing in the field and into the possible magnitude of the influences of these processes.
Can Contaminant Transport Models Predict Breakthrough?
Authors: Peng Wei‐Shyuan “Stone” , Hampton Duane R. , Konikow Leonard F. , Kambham Kiran , Benegar Jeffrey J. 
Published: February 2007

AbstractA solute breakthrough curve measured during a two‐well tracer test was successfully predicted in 1986 using specialized contaminant transport models. Water was injected into a confined, unconsolidated sand aquifer and pumped out 125 feet (38.3 m) away at the same steady rate. The injected water was spiked with bromide for over three days; the outflow concentration was monitored for a month. Based on previous tests, the horizontal hydraulic conductivity of the thick aquifer varied by a factor of seven among 12 layers. Assuming stratified flow with small dispersivities, two research groups accurately predicted breakthrough with three‐dimensional (12‐layer) models using curvilinear elements following the arc‐shaped flowlines in this test.Can contaminant transport models commonly used in industry, that use rectangular blocks, also reproduce this breakthrough curve? The two‐well test was simulated with four MODFLOW‐based models, MT3D (FD and HMOC options), MODFLOWT, MOC3D, and MODFLOW‐SURFACT.Using the same 12 layers and small dispersivity used in the successful 1986 simulations, these models fit almost as accurately as the models using curvilinear blocks. Subtle variations in the curves illustrate differences among the codes. Sensitivities of the results to number and size of grid blocks, number of layers, boundary conditions, and values of dispersivity and porosity are briefly presented. The fit between calculated and measured breakthrough curves degenerated as the number of layers and/or grid blocks decreased, reflecting a loss of model predictive power as the level of characterization lessened. Therefore, the breakthrough curve for most field sites can be predicted only qualitatively due to limited characterization of the hydrogeology and contaminant source strength.