bluuebunny/crossref_metadata_2025 huggingface dataset:
A Practical Application of Multiphase Transport Theory to Ground Water Contamination Problems
Authors: Hinchee Robert E. , Reisinger H. James
Published: February 2007

Hydrocarbon transport in the subsurface environment occurs in several phases, chiefly the non‐aqueous phase liquid (NAPL), dissolved and vapor phases. Mechanisms that influence transport include the physicochemical properties of the specific compounds present (density, vapor pressure, viscosity, hydrophobicity) and the physical and chemical properties of the subsurface environment, including geology, aquifer minerology and ground water hydrology. Hydrocarbon liquids are typically complex mixtures composed of numerous compounds, each with its own individual physicochemical and, therefore, transport properties. Examination of chemical data can provide insights into the transport mechanisms operating at a site: Ground water transport results in relative enrichment by more soluble, less hydrophobic hydrocarbon compounds as a function of distance from a spill; vapor phase transport typically results in relative enrichment in more volatile hydrocarbon compounds.

Two sites at which subsurface fuel spills resulted in ground water contamination will illustrate the use of transport mechanism theory. At Site 1 a subsurface spill resulted in a NAPL plume approximately 150m (500 feet) and a dissolved hydrocarbon plume resulting from ground water transport of dissolved hydrocarbon approximately 350m (1150 feet) hydraulically downgradient of the source. At Site 2 there was a sudden subsurface fuel spill; ground water pumping with hydrocarbon recovery was begun within a week of spillage. Vapor phase transport resulted in contaminated ground water hydraulically upgradient of the source. In addition, there was cross‐contamination at Site 2, probably as the result of contaminated water level gauging equipment, but the chemical characteristics of this contamination were sufficiently obvious to permit its identification. An understanding of transport mechanisms is instrumental in contamination assessment source identification, contaminant fate prediction and design of an appropriate remedial program.
Measurement of Carbon Dioxide in Soil Gases for Indication of Subsurface Hydrocarbon Contamination
Authors: Kerfoot H.B. , Mayer C.L. , Durgin P.B. , D'Lugosz J.J.
Published: February 2007

A preliminary field evaluation of a new application of soil‐gas measurement for delineation of subsurface organic contamination is described. The method measures carbon dioxide concentrations in soil gases and is based on the hypothesis that carbon dioxide concentrations from subsurface oxidation of organic compounds will be porportional to the extent of organic contamination. A correlation coefficient (r) of 0.81 (n=6) was observed between ground water dissolved organic carbon ground water concentrations and carbon dioxide concentrations in the overlying soil gases at one site. Soil‐gas carbon dioxide concentrations measured ranged from 0.09 percent to 0.45 percent.
Oxygen Transfer Through Flexible Tubing and Its Effects on Ground Water Sampling Results
Authors: Holm Thomas R. , George Gregory K. , Barcelona Michael J.
Published: February 2007

A model for the diffusion of gases through polymeric tubing was derived which predicts that the amount of gas transferred is proportional to the tubing length and inversely proportional to the pumping rate. The model was experimentally tested and confirmed for oxygen transfer through fluorinated ethylene‐propylene copolymer (FEP) tubing using tubing lengths and flow rates typical of ground water sampling. Diffusion can introduce measurable concentrations of oxygen into initially anoxic water. Diffusive loss of carbon dioxide from water that is oversaturated with respect to atmospheric CO2 does not measurably affect pH under similar usage conditions.
Changes in Volatile Organic Chemical Concentrations After Purging Slowly Recovering Wells
Authors: Herzog Beverly L. , Chou Sheng‐Fu J. , Valkenburg John R. , Griffin Robert A.
Published: February 2007

Most guidelines for sampling ground water require the evacuation of multiple bore volumes from the well before a sample is collected. Such recommendations are impractical for wells that are finished in fine‐grained deposits with such slow recharge that they cannot recover rapidly enough for the requisite number of well volumes to be removed. In such situations, the sample is usually collected either 24 hours after evacuation or sometime during well recovery. Neither of these strategies has been supported by field evidence.

The purpose of this study was to determine the changes in volatile organic chemical concentration during well recovery. Three hundred samples were analyzed for up to 19 different volatile organic compounds from 11 wells that were finished in fine‐grained glacial tills. Each well was sampled before purging and at several time intervals up to 48 hours after purging. The experiment was conducted three to five times on each well. Samples were collected with dedicated point‐source PTFE bailers equipped with bottom‐emptying devices that were designed for collecting samples for volatile organic chemical analysis. All wells were evacuated with a bailer because they were finished in slowly recharging materials having hydraulic conductivities of between 1 × 10−6 and 7 × 10−5 cm/sec.

Results of the chemical analyses were examined statistically using a general linear model and the Tukey honestly significant difference test to ascertain whether the changes in water quality with time after purging were statistically significant. At the 95 percent confidence level, there was no significant difference in chemical compositions at any time interval after purging, although samples collected at four hours had slightly higher concentrations than did earlier or later samples. However, concentrations of volatile organics were significantly lower before purging than after purging. These results clearly show that wells finished in fine‐grained sediments should be purged before samples are collected for volatile organic chemical analysis.
Modeling Ground Water Quality Sampling Decisions
Authors: Hsueh Ya‐Wen , Rajagopal R.
Published: February 2007

Questions such as what, where, when, and how often to sample play a central role in the development of monitoring strategies. Limited resources will not permit sampling for many contaminants at the same frequency at all well sites. Therefore, a resource allocation strategy is necessary to arrive at answers for the preceding types of questions. Such a strategy for a ground water quality monitoring program is formulated as an integer programming model (an optimization model). The model will be of use in the process of deciding what constituents to sample and where to sample them so as to maximize a given objective, subject to a set of budget, sampling, and regulatory constraints. The maximization objective in the model is defined as a weighted function of population exposure to a scaled measure of observed chemical concentrations. The sampling constraints are based on the observed variability of contaminants in the aquifer, needed precision in estimates, a chosen level of significance, the available budget for implementing the program, and selected regulatory constraints. The model is tested with field data obtained for 10 selected constituents from more than 650 wells in the Cambrian‐Ordovician aquifer in Iowa. Results from two alternative formulations of the model are compared, analyzed, and discussed. Further avenues for research are briefly outlined.
A National Evaluation of the Leaching Potential of Aldicarb Part 1. An Integrated Assessment Methodology
Authors: Lorber Matthew N. , Cohen Stuart Z. , Noren Stephen E. , De Buchananne George D.
Published: February 2007

A methodology was developed to determine the potential for aldicarb to leach to ground water and appear at or near concentrations of concern in different areas of the continental United States. Aldicarb use in 11 “ground water regions,”as defined by Heath (1984), was evaluated. These regions were selected based on significant use of aldicarb on citrus, cotton, potatoes, peanuts, and soybeans. The unit of study, therefore, became known as “crop/Heath‐Region combinations”(CHRCs). A total of 32 CHRCs were evaluated. Three measures of leaching potential were used to evaluate each CHRC. One was based on hydrogeologic vulnerability, one was based on agronomic and site‐specific characteristics, and one was based on ground water monitoring data. Each measure was rated as “high,””medium,””low” or “insufficient data” in terms of potential for aldicarb to leach for crop‐growing areas in the region. Using a weight‐of‐evidence approach, each CHRC was given a final rating of “high,”“medium,” and “low” potential to leach based on the three measures within the CHRC. Potatoes in Heath Regions 7 (Glaciated Central) and 9 (Northeast and Superior Uplands) were rated high, whereas potatoes in Regions 1 (Western Mountain Ranges), 3 (Columbia Lava Plateau), and 11 (Southeast Coastal Plain) were rated low. Cotton in Regions 1,2 (Alluvial Basins), 5 (High Plains), 10B (Gulf Coastal Plain), and 11 were rated low. Citrus and peanuts in Region 11 were rated high. All other CHRCs, including all soybean CHRCs, were rated medium.
EPA's Approach to Evaluating and Cleaning Up Ground Water Contamination at Superfund Sites
Authors: Haley Jennifer L. , Lang David J. , Herrinton Lisa
Published: February 2007

EPA's approach for developing, evaluating, and selecting ground water response actions at Superfund sites with contaminated ground water involves a series of key decisions to support necessary actions. These actions include the following:

Planning how the site will be managed

Determining data needs

Determining remedial action objectives

Developing alternatives

Selecting and implementing the remedy.

The key decisions should reflect a policy and decision‐making approach developed within the framework of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA 1980) as amended by the Superfund Amendments and Reauthorization Act (SARA 1986) and program policies to implement these acts. This paper outlines a flexible, iterative process, described in detail in the Guidance on Remedial Actions for Contaminated Ground Water at Superfund Sites (U.S. EPA 1988), by which ground water remedies can be identified, evaluated, selected, and implemented at Superfund sites beginning with initial site investigation tasks and ending with evaluation of implemented actions. Proper consideration of the factors presented in this paper should result in an efficient, effective procedure for making remedial action decisions for contaminated ground water that ensures protection of human health and the environment.
The Ground Water Recharge and Pollution Potential of Dry Wells in Pima County, Arizona
Authors: Wilson L.G. , Osborn M.D. , Olson K.L. , Maida S.M. , Katz L.T.
Published: February 2007

This paper summarizes a study to estimate the potential for dry‐well drainage of urban runoff to recharge and pollute ground water in Tucson, Arizona. We selected three candidate dry wells for study. At each site we collected samples of runoff, dry‐well sediment, vadose‐zone sediment, perched ground water, and ground water. Water content data from vadose‐zone samples suggest that dry‐well drainage has created a transmission zone for water movement at each site. Volatile organic compounds, while undetected in runoff samples, were present in dry‐well sediment, perched ground water at one site, and ground water at two sites. The concentrations of volatile organics (toluene and ethylbenzene) in the water samples were less than the corresponding EPA human health criteria. Pesticides were detected only in runoff and dry‐well sediment. Lead and chromium occurred in runoff samples at concentrations above drinking water standards. Nickel, chromium, and zinc concentrations were elevated in vadose‐zone samples at the commercial site. Of the metals, only manganese, detected at the residential site, exceeded Secondary Drinking Water Standards in ground water. It is concluded that the three dry wells examined during this study are currently not a major source of ground water pollution.
Soil‐Gas Surveying for Subsurface Gasoline Contamination Using Total Organic Vapor Detection Instruments Part I. Theory and Laboratory Experimentation
Authors: Robbins Gary A. , Deyo Brendan G. , Temple Mark R. , Stuart James D. , Lacy Michael J.
Published: February 2007

Factors influencing the response of total organic vapor detection instruments used in soil‐gas surveying for subsurface gasoline leakage were investigated through performing theoretical assessments and laboratory experiments. Theoretical assessments indicate that total organic vapor measurements will depend on response conditions and the relative concentration of constituents in soil gas, in addition to absolute constituent levels. Laboratory tests conducted using flame ionization, photoionization and explosimeter devices indicated that conditions influencing their responses included instrument flow rate and soil‐air permeability when performing direct‐probe sampling; the linear range of the instrument; the multicomponent nature of gasoline vapors; and levels of oxygen, nitrogen, carbon dioxide and relative humidity in soil air. If an instrument's response to these conditions is not taken into account, survey results may be misleading. To circumvent adverse instrument responses, a serial dilution technique is presented.
Hydrogeology of the Brunswick (Passaic) Formation and Implications for Ground Water Monitoring Practice
Authors: Michalski Andrew
Published: February 2007

Fractured shales of the Brunswick Formation provide a major aquifer in the most industrialized region of New Jersey. Numerous cases of ground water contamination have been documented in this formation. However, effectiveness of monitoring and remediation efforts is often hampered by the use of inappropriate concepts regarding ground water flow controls in this complex aquifer system. One such concept presumes that near‐vertical fractures parallel to the strike of beds provide principal passages for the flow and produce an anisotropic response to pumping stress. Field evidence presented in this paper confirms that the Brunswick Formation hosts a gently dipping, multiunit, leaky aquifer system that consists of thin water‐bearing units and thick intervening aquitards. The water‐bearing units are associated with major bedding partings and/or intensely fractured seams. Layered heterogeneity of such a dipping multiunit aquifer system produces an anisotropic flow pattern with preferential flow along the strike of beds. Within the weathered zone, the permeability of the water‐bearing units can be greatly reduced. The commonly used hydrogeologic model of the Brunswick as a one‐aquifer system, sometimes with vaguely defined “shallow” and “deep” zones, often leads to the development of inadvertent cross‐flows within monitoring wells. If undetected, cross‐flows may promote contaminant spread into deeper units and impair the quality of hydrogeologic data. Hydrogeologic characterization of the Brunswick shales at any given site should be aimed primarily at identification of the major water‐bearing and aquitard units. Recommended techniques for this characterization include fluid logging and other in‐well tests.
Agricultural Chemicals and Ground Water Quality ‐ Issues and Challenges
Authors: Bouwer Herman
Published: February 2007

Anthropogenic agricultural chemicals of concern in ground water include nitrate and pesticides. Increased legislation and regulation of contaminant levels in ground water can be expected. Ground water contamination should be prevented from getting worse, but more research is necessary so as to base regulations on sound criteria. Health effects and acceptable risks must be better formulated. More research on chemical movement in the vadose zone is necessary for accurate predictive modeling of pesticide transport to ground water. Best management practices need to be developed so that farmers will be able to farm profitably while complying with regulations for maximum contaminant levels in underlying ground water. People from all concerned disciplines, citizens’groups, and policy‐makers need to work together to develop realistic regulatory policies and management practices that will effectively protect public health while ensuring a viable and sustainable agriculture.
Small‐Scale Retrospective Ground Water Monitoring Study for Simazine in Different Hydrogeological Settings
Authors: Roux Paul H. , Hall Robert L. , Ross Richard H.
Published: February 2007

A ground water monitoring study was conducted for the triazine herbicide simazine at 11 sites in the United States. The study used carefully selected, small‐scale sites (average size: about 33 acres) with documented product use and sensitive hydrogeological settings. The sites selected were Tulare County, California (two sites); Fresno County, California; Sussex County, Delaware; Hardee and Palm Beach counties, Florida; Winnebago County, Illinois; Jackson County, Indiana; Van Buren and Berrien counties, Michigan; and Jefferson County, West Virginia. These sites satisfied the following criteria: a history of simazine use, including the year prior to the start of the study; permeable soil and vadose zone; shallow depth to water; no restrictive soil layers above the water table; and gentle slopes not exceeding 2 percent. A variety of crop types, climates, and irrigation practices were included. Monitoring well clusters (shallow and deep) were installed at each site except in California and West Virginia, where only shallow wells were installed. Simazine was monitored at these sites at quarterly intervals for a two‐year period during 1986–1988.

The results of the study showed that out of 153 samples analyzed, 45 samples showed simazine detections. A substantial majority of the detections (32 out of 45) occurred in Tulare, Fresno, and Jefferson counties. The detections in these areas were attributed to mechanisms other than leaching, such as drainage wells, karst areas, surface water recharge, or point source problems. An additional 11 detections in Van Buren County were apparently due to an unknown upgradient source. Only one detection (in Palm Beach County, Florida) near the screening level of 0.1 ppb was attributed to possible leaching. The results of this investigation support the hypothesis that simazine does not leach significantly under field use conditions.
A Gas Chromatographic/Chemical Indicator Approach to Assessing Ground Water Contamination by Petroleum Products
Authors: Thomas Debra H. , Delfino Joseph J.
Published: February 2007

The water‐soluble fractions of unleaded gasoline, kerosene and diesel fuel were evaluated by U.S. EPA Methods 602, 610, and 625.

Several chemical indicator compounds useful in assessing petroleum contamination of ground water, including benzene, substituted benzenes, n‐alkanes, and polynuclear aromatic hydrocarbons, were identified. These were applied to the interpretation of data collected from monitoring wells at gasoline service stations that were undergoing ground water remediation. The chemical indicators are used to identify the likely type(s) of petroleum contamination. Certain hydrocarbons may be unique to specific fuel types.

Gas chromatograms of field sample extracts were compared with chromatograms of laboratory water‐soluble fractions (WSFs) and neat fuels (unleaded gasoline, kerosene, and diesel). In some situations, field samples represented water‐soluble fractions of the contaminating fuel. In others, a fuel‐water agglomeration was indicated, with the chromatograms showing peaks that represented components of both the WSFs and the neat fuels.

The use of both gas chromatography pattern identification and chemical indicators appears to be a viable approach to assessing ground water contamination caused by petroleum products.
Ground Water Modeling for Risk Assessment Purposes: Use of a Gaussian‐Distributed Transport Model and a Batch Flush Model
Authors: Cushman David J. , Ball Stephen D.
Published: February 2007

Several state regulatory agencies require that risk assessments be performed at contaminated sites to quantify the contaminant levels that may reach the nearest receptors and to evaluate the health risks associated with exposure to such contaminant levels. Petroleum retail facilities with leaking underground storage tanks are prime examples of sites where risk assessments may be required. Ground water modeling is often necessary when evaluating future completed exposure pathways associated with dissolved contaminants. If the aquifer conditions are relatively homogeneous, analytical contaminant transport models may be used in place of complex numerical models. A two‐dimensional, Gaussian‐distributed boundary condition transport model and a batch flush model may be combined to simulate contaminant transport with linear equilibrium adsorption/desorption and biodegradation effects, This enables a relatively rapid and cost‐effective prediction of contaminant levels at sensitive downgradient receptors. The predicted contaminant levels may then be evaluated through an exposure assessment, toxicity assessment, and risk characterization in accordance with U.S. EPA risk assessment protocols.

A case study was presented for a gasoline station with a leaking underground storage tank system. The two‐dimensional, Gaussian‐distributed transport model and batch flush model were used to predict dissolved phase contaminant concentration profiles at a downgradient drinking water well. The predicted contaminant concentrations were subsequently converted to chronic daily intakes which were evaluated in terms of toxicity. Reasonable maximum exposures were developed for both carcinogens and non‐carcinogens. The results of the risk assessment indicated that there were no unacceptable risks posed by the residual ground water contamination at the site. This led to the recommendation that the project be closed out in the absence of a demonstrated need for active ground water remediation. The State Water Control Board concurred with the recommendation.
Comparison Between Pump and Treat, Biorestoration, and Biorestoration/ Pump and Treat Combined: Lessons from Computer Modeling
Authors: Marquis Samuel A. , Dineen Dennis
Published: February 2007

This study compares pump and treat, bioremediation. and bioremediation/pump and treat for cleanup of a chemical plume using BIOPLUME II, a numerical solute transport code which simulates the transport of dissolved hydrocarbons under oxygen‐limited biodegradation. Nineteen remediation scenarios were evaluated under one set of hydrogeologic and chemical conditions using different injection and extraction well configurations and injected dissolved oxygen (D.O.) concentrations of 8 or 50 parts per million (ppm). The cleanup objective was to reduce the concentration of naphthalene in the plums by the greatest percentage without increasing the volume of contaminated ground water in the aquifer. Each scenario was ranked in terms of plume control and contaminant concentration reduction for a one‐year remediation period.

Based on the performance criteria, scenarios that included pump and treat were superior in containing the migration of the plume and in restricting the plume from separating into smaller, localized plumes or “hot spots.” Bioremediation and bioremediation/pump‐and‐treat scenarios in which 50 ppm D.O. was injected throughout the plume (areal injection) or in the most concentrated portion of the plume (interior injection) achieved the greatest plume control and concentration reductions. Bioremediation cases with 8 ppm D.O. did not successfully control the plume or achieve major reductions in concentrations. The important conclusions drawn from the results were the following: (1) minimize the distance that the plume needs to be pulled toward extraction wells or that the D.O. needs to be circulated through to reach the contaminant zone; (2) inject water containing as high a level of D.O. as possible while meeting microbial and oxygen demand requirements: and (3) design the wellfield to produce convergent flow toward a central location and to minimize divergent flow and upgradient and intraplume stagnation areas.

The study results suggest that bioremediation and bioremediation/ pump and treat should perform better than pump and treat for sand and gravel aquifers contaminated with biodegradable hydrocarbons. In particular, four remediation scenarios should be seriously considered in the design phase of biorestoration projects: areal injection/downgradient extraction, interior injection, interior extraction/exterior (i.e., outside of the plume) injection, and areal injection. Although the actual number of wells, injection and extraction rates, and D.O. concentrations will vary for each site, it is expected that areal injection: downgradient extraction and interior injection should perform well under high natural flow velocities, whereas interior extraction/exterior injection and areal injection should be more amenable to sites with lower natural flow velocities.
The Effects of Ground Water Sampling Devices on Water Quality: A Literature Review
Authors: Parker Louise V.
Published: February 2007

This paper reviews both field and laboratory studies that tested or compared the ability of various types of sampling devices to deliver representative ground water samples. Several types of grab samplers, positive displacement devices, and suction‐lift devices were evaluated, Gas‐lift and inertial‐lift pumps were also evaluated. This study found that most of these devices can. under certain circumstances, alter the chemistry of ground water samples, das‐lift pumps, older types of submersible centrifugal pumps, and suction‐lift devices are not recommended when sampling for sensitive constituents such as volatile organics and inorganics, or inorganics that are subject to oxidation/precipitation reactions. In general, of the devices reviewed in this paper, bladder pumps gave the best recovery of sensitive constituents. However, better performance could be achieved for several devices if improved operational guidelines were developed by additional testing, especially at lower flow rates. Clearly, further research is warranted. Future studies should focus on pumping rate, flow control mechanisms, and dedication or decontamination of sampling devices.
Pump‐and‐Treat Accomplishments: A Review of the Effectiveness of Ground Water Remediation in Santa Clara Valley, California
Authors: Bartow Gregory , Davenport Clifton
Published: February 2007

Pump and treat has been successful in significantly reducing the volatile organic contaminant concentrations in ground water in Santa Clara Valley. California. The California Regional Water Quality Control Board. San Francisco Bay Region, currently oversees 61 sites in Santa Clara Valley with operating pump‐and‐treat systems, of which 42 sites have been extracting ground water since at least 1987. This review‐ evaluates the effects of ground water extraction on contaminant concentrations at 37 of those 42 sites. The evaluation focuses on trichloroethane, trichloroethene, and dichloroethane, as these were the most prevalent contaminants encountered at the sites. The majority of sites obtained greater than 90 percent reduction in maximum concentrations for one or more of the three contaminants. While only one of the 37 sites obtained maximum contaminant levels (MCL) for all contaminants, six of the sites included in the analyses reached MCLs for one or more of the sampled contaminants, and an additional seven of the sites are near MCLs for al least one contaminant. Our findings indicate that, while pump and treat successfully reduced maximum concentrations al most of the sites reviewed, successful attempts to reduce maximum contaminant concentrations to below MCLs are limited.
Radionuclide Sorption on Well Construction Materials
Authors: Thompson Joseph L.
Published: February 2007

Laboratory experiments were conducted to measure the extent to which trace concentrations of radioactive materials would sorb on well construction materials and to assess the rapidity with which sorption would occur. The radionuclides employed in these studies were tritium, Cs‐137, and Co‐57, Solutions with trace concentrations of these radionuclides were contracted with casings of PVC, fiberglass‐epoxy, stainless steel, carbon steel, and steel rods coated wtih expoy. The PVC showed no interaction with the tritium or Cs‐137 during contact times of two hours to these weeks; however, it did sorb Co‐57. The fiberglass‐epoxy also interacted only with the cobalt. The stainless steel sorbed cesium and cobalt. The carbon steel (or the ferric hydroxide forming on its surface) also sorbed both cesium and cobalt. The epoxy‐coated steel rods did not interact measurably with day of the radio‐nuclides so long as the coating was intact. The sorption reactions generally were apparent after a few days of contact: in the case of carbon steel, they were detectable in a few hours.
A Method to Assess Analytical Uncertainties Over Large Concentration Ranges With Reference to Volatile Organics in Water
Authors: Devlin J. F.
Published: February 2007

The uncertainty associated with a volatile organic concentration measurement is a function of variability and bias introduced at the various levels of sample handling: collection, storage, and analysis. During the past decade, sampling materials and the development and/or improvement of sampling protocols have been the subject of considerable research activity. As a result, in cases of samples properly handled, the analytical variability can be the dominant source of uncertainty in a given concentration value. Here analytical variability refers to any error that might arise during analysis, including the detector response error and any sample handling errors common to both standards and samples. This can be a particular concern for field analyses by gas chromatography (GC), Well‐established statistical methods are available to estimate analytical uncertainty from linear calibration curves, but these methods are poorly suited for the analysis of volatile organics because organic samples frequently require instrument calibration (usually GC) over several orders of magnitude in concentration. If a single linear calibration curve is used to determine sample concentrations and uncertainties, then unrealistically large uncertainties may be assigned to low concentration samples. However, the methods can be adopted for extended concentration range calibration curves by breaking the overall calibration line down into smaller sub‐calibration lines that span smaller ranges. These can then be examined and used selectively to determine concentrations with more appropriate uncertainties attached. The method of multiple callbration line analysis described here is suitable for programming with any high level computer language. It can be used to calculate meaningful analytical uncertainty values for any substance analyzed over a wide range in concentrations (i.e., an order of magnitude or more).
Petroleum Hydrocarbon Bioventing Kinetics Determined in Soil Core, Microcosm, and Tubing Cluster Studies
Authors: Moyer Ellen E. , Ostendorf David W. , Richards Robin J. , Goodwin Steve
Published: February 2007

Aerobic biodegradation of vapor‐phase petroleum hydrocarbons was evaluated in an intact soil core from the site of an aviation gasoline release. An unsaturated zone soil core was subjected to a flow of nitrogen gas, oxygen, water vapor, and vapor‐phase hydrocarbons in a configuration analogous to a biofilter or an in situ bioventing or sparging situation. The vertical profiles of vapor‐phase hydrocarbon concentration in the soil core were determined by gas chromatography of vapor samples. Biodegradation reduced low influent hydrocarbon concentrations by 45 to 92 percent over a 0.6‐m interval of an intact soil core. The estimated total hydrocarbon concentration was reduced by 75 percent from 26 to 7 parts per million. Steady‐state concentrations were input to a simple analytical model balancing advection and first‐order biodegradation of hydrocarbons. First‐order rate constants for the major hydrocarbon compounds were used to calibrate the model to the concentration profiles. Rate constants for the seven individual hydrocarbon compounds varied by a factor of 4. Compounds with lower molecular weights, fewer methyl groups, and no quaternary carbons tended to have higher rate constants. The first‐order rate constants were consistent with kinetic parameters determined from both microcosm and tubing cluster studies at the field site.
Evaluating Natural Attentuation with Spreadsheet Analytical Fate and Transport Models
Authors: Ollila Paul W.
Published: February 2007

Superposition techniques can extend the capabilities of relatively simple analytical fate and transport models. Complex source geometries, simple aquifer boundaries, and electron acceptor limited biodegradation can be simulated by using superposition techniques in computer spreadsheets. Spreadsheet models are an easily used tool for interpreting sampling results and for estimating attenuation and degradation rates in relatively homogeneous aquifers. Analytical spreadsheet models are based on the Domenico analytical model and can provide results that are in close agreement with the numerical model UIOPLUMH II.
Neutron Moisture Probe Measurements of Fluid Displacement During In Situ Air Sparging
Authors: McKay Daniel J. , Acomb Lawrence J.
Published: February 2007

Strawberry Point, located on Hinchinbrook Island, Alaska, is the site of a Federal Aviation Administration air navigation facility that is contaminated with gasoline‐ and diesel‐range hydrocarbons in soil and ground water. An air sparging system was installed to promote bioremediation in the zone of seasonal ground water fluctuation where the contaminant is concentrated. The sparge wells were placed in a homogeneous formation, consisting of fine‐grain beach and eolian sands. The system was then evaluated to determine the ground water region of influence and optimum frequency of operation. Neutron probe borehole measurements of percentage; of fluid displacement during sparging at two wells revealed dynamic air distributions defined by an initial and relatively rapid expansion phase followed by a consolidation phase. Air distribution was stable within 12 hours after startup, reaching a peak air saturation of greater than 50 percent. The radius of peak expansion varied with time and depth, with measurable fluid displacement occurring beyond 12 feel from the sparge well near the water table. The percentage of air saturation stabilized within one hour following cutoff of the air flow, leaving pockets of entrapped air near the water table. When air injection was resumed, air saturation levels were found to be repeatable. The observations at this site indicated that the effective region of influence is relatively small and that frequent pulsing is needed to optimize oxygen distribution.
Patterns of Chemical Changes During Environmental Alteration of Hydrocarbon Fuels
Authors: Kaplan Isaac R. , Galperin Yakov , Alimi Hossein , Lee Ru‐Po , Lu Shan‐Tan
Published: February 2007

This paper discusses major environmental alteration processes and describes a set of chemical tests that have been developed to monitor compositional changes in hydrocarbon fuels released into the environment. The methods examine various homologous series of hydrocarbons including straight chain (paraffins or n‐alkanes), branched chain (isoparaffins or isoprenoids), alicyclic (naphthenes or alkylated cyclohexanes), polycyclic (steranes and terpanes), and aromatic structures (benzene, toluene, ethylbenzene. xylenes, alkylated benzenes, polycyclic aromatic hydrocarbons, and aromatic steranes). Each one of these groups of hydrocarbons has a different tolerance to environmental alteration by evaporation, dissolution (water washing), and biodegradation. When used as an analytical system on environmental samples, the data obtained provide information on fuel type recognition patterns and on degradation levels of the various fuels, allowing for an estimate of residence time.
Hot Methanol Extraction for the Analysis of Volatile Organic Chemicals in Subsurface Core Samples from Dover Air Force Base, Delaware
Authors: Ball W.P. , Xia G. , Durfee D.P. , Wilson R.D. , Brown M.J. , Mackay D.M.
Published: February 2007

The evaluation of contaminant concentrations in ground water and soil is an essential aspect of most hazardous waste remedial investigations. This paper describes methods applied toward obtaining, preserving, and analyzing subsurface samples for the determination of VOC concentrations in the saturated region of an unconfined coastal plain aquifer at Dover Air Force Base (DAFB). Delaware. The described protocol involved headspace‐free subsampling of cores, field preservation of subsamples in methanol, and overnight extraction of the VOCs at elevated temperature (70°C). Methanol‐extracted compounds were subsequently transferred to hexane and analyzed by gas chromatography. The method was found to achieve quantitative extraction from the aquifer sands in a single step, although extraction from fine‐grained and more strongly sorbing aquitard samples required multiple methanol extractions to achieve comparable recovery. An extensive set of DAFB results is presented as an indication of how these methods can be applied toward characterizing field‐scale contamination with a high degree of resolution and accuracy. These data have enabled a quantitative estimate of the contaminant distribution at this site and offer valuable insight into processes of contaminant migration into the underlying aquitard. In these regards, the methods used are believed to have provided much more accurate results than could have been obtained using more commonly applied techniques.
Impact of Turbidity on TCE and Degradation Products in Ground Water
Authors: Paul Cynthia J. , Puls Robert W.
Published: February 2007

Elevated particulate concentrations in ground water samples can bias contaminant concentration data. This has been particularly problematic for metal analyses where artificially increased turbidity levels can affect metals concentrations and confound interpretation of the data. However, few studies have been conducted to determine the impact of particulates on trichloroethylene (TCE), cis‐dichloroethylene (c‐DCE), and vinyl chloride concentrations.

Laboratory batch studies and field investigations were conducted to evaluate the effects of suspended solids on VOC concentrations in ground water samples analyzed by purge‐and‐trap gas chromatography. Three different solids were used to assess the effects of suspended particulates. The solids were aquifer material from a field site in North Carolina and two reference clay minerals (kaolinite and Namontimorillonite). During the laboratory portion of this study, the solids were used to determine effects on TCE concentrations under controlled laboratory conditions.

The same solids were used in a field study to compare the laboratory results with field results. Solids were added to the sample vials prior it) sample collection to intentionally increase turbidity levels in the water samples. Results of the study indicate essentially no decrease in TCE, c‐DCH, or vinyl chloride concentrations due to increased turbidity levels.
Successful Evaluation of EPA's New Screening Model
Authors: Cohen Stuart
Published: February 2007

“A successful test of such a conservative screening tool would predict concentrations of pesticides that are in the upper 95 to 99% confidence interval of appropriate monitoring results.”
A Small‐Scale Ground Water Leaching Study for a Primisulfuron Herbicide
Authors: Chang H. Ted , Ying Weiming
Published: February 2007

Primisulfuron is a sulfonyl urea herbicide designed lo control broad‐leaf weeds in fields of small grain crops. The pesticide is potent, requiring only a low dosage. It is designed to replace many existing pesticides that are suspected to contaminate the nation's ground water resources. Under the auspices of the Federal Insecticide Fungicide and Rodenticide Act (FIFRA), the pesticides must be demonstrated to be environmentally safe in a field study for registration with the U.S. Environmental Protection Agency (EPA). This paper presents the design and results of a ground water leaching study for the successful registration of primisulfuron.

A systematic approach was employed to identity a suitable site for the ground water study. Agricultural, ground water, and soil databases were carefully reviewed lo quickly determine, from a national level down to an individual farmer, a suitable candidate site. The site selected had a shallow ground water table and a highly permeable soil matrix. The site ground water was highly vulnerable to pesticide contamination exceeding EPA site requirements. A total of eight monitoring wells, 12 lysimeters, four tensiometers, and four rain gauges were installed in four sampling clusters to collect ground water and soil‐pore water samples. Bromide was used as a tracer to follow the movement of infiltrating water.

The results showed that the downward migration of primisulfuron was retarded by the site soils. The average breakthrough lime for the pesticide at 3‐foot lysimeters was equal to 109±19 days, which was 36 days longer than that of bromide (73±12 days). The retardation was apparently caused by the adsorption of primisulfuron to the site soils, which could be attributed to the hydrophobicity of the compound and the organic matter of the site soils. The field half‐life for primisulfuron was determined to be 5.1 days, which was much shorter than the 14 days required by EPA. It was concluded that primisulfuron did not leach to the ground water table at the site under normal use conditions.
Mobilization and Co‐Transport of Pyrene in the Presence of Pseudomonas aeruginosa UG2 Biosurfactants in Sandy Soil Columns
Authors: Lafrance Pierre , Lapointe Mireille
Published: February 2007

Washing technologies are currently applied for the remediation of contaminated soils. The efficiency of biosurfactants produced by Pseudomonas aeruginosa strains to mobilize some hydrocarbons sorbed on soils has already been demonstrated. However, few studies have been made to define optimal procedures for the injection of these rhamnolipids in soil. This study examines (1) the efficiency of the biosurfactants produced by P. aeruginosa UG2 to mobilize pyrene from a contaminated sandy loam as compared to that of sodium dodecyl sulfate (SDS); (2) the injection procedures (surfactant concentration, pore water velocity, continuous or interrupted flow) that might affect the efficiency of pyrene mobilization using UG2 biosurfactants; and (3) the co‐transport of UG2 biosurfactants and pyrene. The UG2 biosurfactants were more efficient for pyrene mobilization than SDS and had much less impact on soil. The mobilization of pyrene was approximately proportional to the mass of UG2 biosurfactants injected for both the 0.25% and the 0.50% (w/v) concentrations used. Pyrene mobilization was not greatly dependent on either the pore water velocity—about 5.9 and 10.2 inch/h (15 and 26 cm/h)—or the duration of flow interruption (5 or 15 h), suggesting that mobilization was not rate limited under these conditions. The rhamnolipids appeared to be weakly retained in the soil. Based on the experimental results, it would be advantageous to use a high UG2 biosurfactant concentration, a high pore water velocity, and possibly a flow interruption of more than 15 h in order to reduce the injected volume and the duration of the treatment required. The 0.25% UG2 biosurfactant concentration greatly enhanced pyrene transport and could facilitate contaminant recovery.
Transport and Biological Fate of Toluene in Low‐Permeability Soils
Authors: Venkatraman Sankar N. , Kosson David S. , Schuring John R.
Published: February 2007

The effect of simultaneous sorption, diffusion, and biodegradation on the fate and transport of toluene in low‐permeability soil formations was examined. A transport model accounting for vapor and liquid sorption, vapor diffusions, and first‐order biodegradation was developed to describe the movement of volatile solute in unsaturated soils. Modeling studies were followed with laboratory batch and column studies on fine‐grained soil samples obtained from a gasoline‐contaminated site. Batch experiments yielded the sorption and diffusion coefficients for generating theoretical solute transport profiles. Column studies were conducted to examine toluene sorption, diffusion, and biodegradation under aerobic and denitrifying conditions. Results from the column studies indicated that vapor sorption onto the soil was minimal due to the high moisture content of the soil. Comparison of model predictions with experimental results indicated that the SASK model, which is based on the resistivity theory, provided a more accurate prediction of the vapor phase tortuosity than the frequently used Millington‐Quirk equation. Laboratory results of toluene concentration profiles matched well with the model predictions and yielded degradation rates comparable to those obtained in the field. Column studies, examining toluene biodegradation under aerobic and denitrifying conditions in low‐permeability soils, indicated that the presence of excess nitrate in aerobic environments yielded higher solute degradation rates than those observed under exclusively aerobic systems.
Ground Water Replenishment with Reclaimed Water in the City of Los Angeles
Authors: Karimi Ali A. , Redman Jeremy A. , Ruiz Roberto F.
Published: February 2007

A two‐year pilot study involving the recharge of a ground water basin with reclaimed water was completed in the city of Los Angeles. The city's Department of Water and Power is planning to initiate several ground water recharge projects using reclaimed water in the near future. One such project is the Headworks Recharge Project, the focus of this paper, Approximately 1 cfs of the Los Angeles (LA) River water comprised of 70% tertiary treated reclaimed water was recharged on a two‐day wet and five‐day dry cycle. The recharge water was then extracted from the basin approximately 1000 feet downgradient. Results showed greater than 4‐log removal of coliform bacteria, up to 87% reduction in TOC, and compliance of the product water with federal and state drinking water standards. Model simulation showed after 15 years of recharging 3000 acre‐feet per year of the LA River water and extracting about 10,000 acre‐feet from the basin, the product water would contain from 5% to 15% reclaimed water. This is well below the maximum allowable limit of 20% stipulated by the California regulation.
Design, Installation, and Uses of Combination Ground Water and Gas Sampling Wells
Authors: Hubbell Joel M. , Wood Thomas R. , Higgs Brian , Wylie Allan H. , McElroy Deborah L.
Published: February 2007

Waste disposal sites with volatile organic compounds (VOCs) frequently contain contaminants that are present in both the ground water and vadose zone. Vertical sampling is useful where transport of VOCs in the vadose zone may effect ground water and where steep vertical gradients in chemical concentrations are anticipated. Designs for combination ground water and gas sampling wells place the tubing inside the casing with the sample port penetrating the casing for sampling. This physically interferes with pump or sampler placement. This paper describes a well design that combines a ground water well with gas sampling ports by attaching the gas sampling tubing and ports to the exterior of the casing. Placement of the tubing on the exterior of the casing allows exact definition of gas port depth, reduces physical interference between the various monitoring equipment, and allows simultaneous remediation and monitoring in a single well. The usefulness and versatility of this design was demonstrated at the Idaho National Engineering and Environmental Laboratory (INEEL) with the installation of seven wells with 53 gas ports, in a geologic formation consisting of deep basalt with sedimentary interbeds at depths from 7.2 to 178 m below land surface. The INEEL combination well design is easy to construct, install, and operate.