bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multimedia Risk‐Based Soil Cleanup at a Gasoline‐Contaminated Site Using Vapor Extraction
Authors: Mills William B. , Johnson Kay M. , Liu Sally , Loh John Y. , Lew Christine S. 
Published: February 2007

AbstractAt a utility service center, gasoline from an underground storage tank had leaked into subsurface vadose zone soils for several years. To remediate the site, a soil vapor extraction (SVE) system was installed and operated. At the completion of the SVE operation, gasoline‐containing residues in several confirmation soil borings exceeded agency‐mandated cleanup levels. Rather than continue with SVE, a risk‐based approach was developed to evaluate what levels of gasoline‐containing residues could be left in the soil and still protect human health. The risk‐based approach consisted of simulating the fate of chemical residues through the vadose zone and then into both the ground water and atmosphere. Receptor point concentrations were predicted, and health risks were assessed. The risk assessment concluded that ingestion of contaminated ground water and inhalation of air while showering were the largest potential contributors to risk, and that risks associated with inhalation of vapor‐containing ambient air are small. However, all predicted risks are below the acceptable risk levels of 10−6 individual cancer risk probability and 1.0 hazard index. Therefore, the lead agency accepted the recommendation that the site requires no further remediation. The service center continues normal operations today.
Temporal Changes in VOC Discharge to Surface Water from a Fractured Rock Aquifer During Well Installation and Operation, Greenville, South Carolina
Authors: Vroblesky D. A. , Robertson J. F. 
Published: February 2007

AbstractAnalysis of the vapor in passive vapor samplers retrieved from a streambed in fractured rock terrain implied that volatile organic carbon (VOC) discharge from ground water to surface water substantially increased following installation of a contaminant recovery well using air rotary drilling. The air rotary technique forced air into the aquifer near the stream. The injection produced an upward hydraulic gradient that appears to have transported water and contaminants from deeper parts of the aquifer through fractures into shallow parts of the aquifer. Once in the shallow flow regime, the contamination was transported to the stream, where it discharged during the next several weeks following well installation. After the recovery well was activated and began continuously pumping contaminated ground water to a treatment facility, the VOC concentrations in the stream bottom passive vapor samplers decreased to below detectable concentrations, suggesting that the withdrawal had captured the contaminated ground water that previously had discharged to the stream.
Evaluation of Subsurface Oxygen Sensors for Remediation Monitoring
Authors: Li Dong X. , Lundegard Paul D. 
Published: February 2007

AbstractContinuous remediation monitoring using sensors is potentially a more effective and inexpensive alternative to current methods of sample collection and analysis. Gaseous components of a system are the most mobile and easiest to monitor. Continuous monitoring of soil gases such as oxygen, carbon dioxide, and contaminant vapors can provide important quantitative information regarding the progress of bioremediation efforts and the area of influence of air sparging or soil venting. Laboratory and field tests of a commercially available oxygen sensor show that the subsurface oxygen sensor provides rapid and accurate data on vapor phase oxygen concentrations. The sensor is well suited for monitoring gas flow and oxygen consumption in the vadose zone during air sparging and bioventing. The sensor performs well in permeable, unsaturated soil environments and recovers completely after being submerged during temporary saturated conditions. Calibrations of the in situ oxygen sensors were found to be stable after one year of continuous subsurface operation. However, application of the sensor in saturated soil conditions is limited. The three major advantages of this sensor for in situ monitoring arc as follows: (1) it allows data acquisition at any specified time interval; (2) it provides potentially more accurate data by minimizing disturbance of subsurface conditions; and (3) it minimizes the cost of field and laboratory procedures involved in sample retrieval and analysis.
Ground Water Contamination from Creosote Sites
Authors: Kiilerich Ole , Arvin Erik 
Published: February 2007

AbstractField data from 44 waste sites contaminated with creosote have been compiled in a database. The data from each site included geological and hydrogeological parameters and the concentrations of creosote compounds in the ground water at various distances from the pollution sources. The creosote compounds that were measured included mononuclear aromatic hydrocarbons and polynuclear aromatic hydrocarbons (PAH) and phenols. Already 50 m down‐gradient of the creosote waste sites, 90 percent of the concentrations were from three to 50 times lower than at the source, and most of the median concentrations were below detection limit (0.1 to 0.5 μg/L). The maximum concentrations of benzene, toluene, and xylenes (BTX) and phenols were much lower under aerobic than under anaerobic conditions. Among the phenols, the xylenols (dimethylphenols) appear in higher concentrations under aerobic conditions than phenol and the cresols do. The highest concentrations found were of the same order of magnitude as the calculated solubilities found in the literature, except the chrysene and benz(a)pyrene concentrations, which were one to two orders of magnitude higher than the solubilities.
Arrays of Unpumped Wells for Plume Migration Control by Semi‐Passive In Situ Remediation
Authors: Wilson Ryan D. , Mackay Douglas M. , Cherry John A. 
Published: February 2007

AbstractArrays of unpumped wells can be used as discontinuous permeable walls in which each well serves both as a means to focus ground water flow into the well for treatment and as a container either for permeable reactive media which directly destroy dissolved ground water contaminants or for devices or materials which release amendments that support in situ degradation of contaminants within the aquifer downgradient of the wells. This paper addresses the use of wells for amendment delivery, recognizing the potential utility of amendments such as electron acceptors (e.g., oxygen nitrate), electron donors (primary substrates), and microbial nutrients for stimulating bioremediation, and the potential utility of oxidizers, reducers, etc., for controlled abiotic degradation. Depending on its rate and constraints, the remedial reaction may occur within the well and/or downgradient. For complete remediation of ground water passing through the well array, the total flux of amendment released must meet or exceed the total flux demand imposed by the plume. When there are constraints on the released concentration of amendment (relative to the demand), close spacing of the wells may be required. If the flux balance allows wider spacing, it is likely that limited downgradient spreading of the released amendment will then be the primary constraint on interwell spacing. Divergent flow from the wells, roughly two times the well diameter, provides the bulk of downgradient spreading and constrains maximum well spacing in the absence of significant lateral dispersion. Stronger lateral dispersion enhances the spreading of amendment, thereby increasing the lateral impact of each well, which allows for wider well spacing.
Use of Aerobic and Anaerobic Microcosms to Assess BTEX Biodegradation in Aquifers
Authors: Salanitro J.P. , Wisniewski H.L. , Byers D.L. , Neaville C.C. , Schroder R.A. 
Published: February 2007

AbstractThe natural attenuation of soluble aromatic hydrocarbons (BTEX) in aquifer plumes is controlled by several factors, including the concentration of BTEX and dissolved oxygen (DO) or other electron acceptors (EA), hydrogeological factors (dispersion, dilution, aquifer reaeration rate), and the presence of BTEX‐degrading microbes. We have investigated three laboratory soil and/or well water systems (aerobic, anaerobic, and chronic low DO) which may represent field plume conditions. Microcosm prepared with sufficient DO always degraded hydrocarbons ( 10,000 ppb) at high rates ( 0.10/d) with no lag phase. Experimental simulations of chronic low DO were performed in a pressure transducer‐controlled respirometer in which O2 was maintained at constant low levels (e.g., 0.2 to 2 mg/L). BTX also biodegraded rapidly (0.3 to 0.7/d) at all DO levels. These results suggest that plumes which appear to have low DO but continuous O2 infiltration significantly bioattenuate hydrocarbons. The anaerobic biodegradation potential of BTEX was determined in microcosms prepared with subsoil or well water samples amended with NO3‐, Fe‐3, SO4‐2, or no added EA. Well water from the “aerobic” or “anaerobic” portions of one site plume showed losses in BTEX, but there was no correlation between the presence of reduced EA and degradation. Anaerobic slurries prepared from subsoil of another site showed a significant decrease (0.02 to 0.25/d) in BTEX with lag times of 0 to 40 days. Reduced gases (CH4, H2S, H2) were not produced, but high concentrations of soil‐bound Fe+2 formed, suggesting that Fe+3 may have been a predominant anaerobic EA. These data indicate that the presumed consumption/reduction of anaerobic EA may not always be coupled to BTEX losses in ground water plumes.
Horizontal and Vertical Well Comparison for In Situ Air Sparging
Authors: Plummer Charles R. , Nelson James D. , Zumwalt Gary S. 
Published: February 2007

AbstractA laboratory study was conducted to determine the effectiveness ol vertical and horizontal well configurations for ground water remediation using in situ air sparging. A lexan lank was designed and constructed to allow both the visualization of air flow and quantitative measurement of the distribution of air flow. Two media, sand and glass beads. were tested with both Vertical and horizontal air sources. In each case, most of the air traveled through preferential channels as continuous flow rather than as discrete bubbles as reported in other studies. Liven though glass beads were selected to have the same grain‐size distribution as the sand, air flow was quite different through the two media. Results show that glass beads are not a suitable material for modeling air flow through natural sediments. In this study, the horizontal well proved to be more effective than the vertical well by impacting more of the media with a uniform distribution of air throughout the media. The vertical well resulted in a nonuniform distribution of air flow with most of the air concentrated directly above the well.
Byproduct Formation During the Reduction of TCE by Zero‐Valence Iron and Palladized Iron
Authors: Liang Liyuan , Korte Nic , Goodlaxson J.D. , Clausen Jay , Fernando Quintus , Muftikian Rosy 
Published: February 2007

AbstractTrichloroethene (TCE) was reduced with zero‐valence iron and palladized iron in zero‐head‐space extractors. Progress of the reaction in these batch studies was monitored with purge‐and‐trap gas chromatography and a flame ionization detector. When a 5 ppm initial concentration of TCF. reacts with zero‐valence iron, approximately 140 ppb of vinyl chloride persists for as long as 73 days. The concentration of vinyl chloride (approximately If) ppb) remaining with palladized iron is approximately an order of magnitude less than when zero‐valence iron is the reductant. These data suggest that volatile byproducts may be under‐represented in oilier published data regarding reduction with zero‐valence metals. These results also demonstrate that the reduction of TCE with palladized iron (0.05 percent palladium) is more than an order of magnitude faster than with zero‐valence iron. Wilh a 5:1 solution‐to‐solid ratio the TCE half‐life with zero‐valence iron is 7.41 hours. but is only 0.59 hours with the palladized iron.
Fate of MTBE Relative to Benzene in a Gasoline‐Contaminated Aquifer (1993–98)
Authors: Landmeyer James E. , Chapelle Francis H. , Bradley Paul M. , Pankow James F. , Church Clinton D. , Tratnyek Paul G. 
Published: February 2007

AbstractMethyl tert‐butyl ether (MTBE) and benzene have been measured since 1993 in a shallow, sandy aquifer contaminated by a mid‐1980s release of gasoline containing fuel oxygenates. In wells downgradient of the release area, MTBK was detected before benzene, reflecting a chromatographic‐like separation of these compounds in the direction of ground water flow. Higher concentrations of MTBE and benzene were measured in the deeper sampling ports of multilevel sampling wells located near the release area, and also up to 10 feet (3 m) below the water table surface in nested wells located farther from the release area. This distribution of higher concentrations at depth is caused by recharge events that deflect originally horizontal ground water flowlines. In the laboratory, microcosms containing aquifer material incubated with uniformly labeled 14C‐MTBE under aerobic and anaerobic. Fe(III)‐reducing conditions indicated a low but measurable biodegradation potential (<3%14C‐MTBW as 14CO2) after a seven‐month incubation period, Tert‐butyl alcohol (TBA), a proposed microbial‐MTBE transformation intermediate, was detected in MTBE‐contaminated wells, but TBA was also measured in unsaturated release area sediments. This suggests that TBA may have been present in the original fuel spilled and does not necessarily reflect microbial degradation of MTBE. Combined, these data suggest that milligram per liter to microgram per liter decreases in MTBE concentrations relative to benzene are caused by the natural attenuation processes of dilution and dispersion with less‐contaminated ground water in the direction of flow rather than biodegradation at this point source gasoline release site.
A Method for Installing Piezometers in Large Cobble Bed Rivers
Authors: Geist David R. , Joy Mark C. , Lee David R. , Gonser Tom 
Published: February 2007

AbstractAn impact drive point method is described for emplacing piezometers in a cobble river bottom where this has previously been difficult without the use of drilling rigs. To force the drive point piezometers through coble, the vibrational impact of an air‐powered hammer was carried directly to the drive point by the use of an internal drive rod. After insertion to depth, the drive rod was removed from the lower portion of the piezometer and a standpipe was added to extend the piezometer above the river level. Piezometers installed in this way have permitted water quality analysis and dynamic measurement of vertical potentials in cobble sediments ranging in size from 2.5 to >30 cm and the method has been successfully used in the Columbia River, USA, and Töss River, Switzerland. This innovative method provides information on the hydrodynamics of pore water in highly permeable, cobble deposits that are common in high‐energy river and lake bottoms. Piezometers installed using the internal drive rod method facilitate the assessment of the temporal and spatial dynamics of recharge and discharge at the ground water/surface water interface and analyses of the ecological connectivity between the hyporheic zone and surface water of rivers and streams. This information will lead to improved management decisions related to our nation's ground water and surface water supplies.
Enhancement of In Situ Bioremediation of BTEX‐Contaminated Ground Water by Oxygen Diffusion from Silicone Tubing
Authors: Gibson Thomas L. , Abdul Abdul S. , Chalmer Paul D. 
Published: February 2007

AbstractA field study of oxygen‐enhanced biodegradation was carried out in a sandy iron‐rich ground water system contaminated with gasoline hydrocarbons. Prior to the oxygen study, intrinsic microbial biodegradation in the contaminant plume had depleted dissolved oxygen and created anaerobic conditions. An oxygen diffusion system made of silicone polymer tubing was installed in an injection well within an oxygen delivery zone containing coarse highly permeable sand. During the study, this system delivered high dissolved oxygen (DO) levels (39 mg/L) to the ground water within a part of the plume. The ground water was sampled at a series of monitors in the test zone downgradient of the delivery well to determine the effect of oxygen on dissolved BTEX, ground water geochemistry, and microbially mediated biodegradation processes. The DO levels and Eh increased markedly at distances up to 2.3 m (7.5 feet) downgradient. Potential biofouling and iron precipitation effects did not clog the well screens or porous medium. The increased dissolved oxygen enhanced the population of aerobes while the activity of anaerobic sulfate‐reducing bacteria and methanogens decreased. Based on concentration changes, the estimated total rate of BTEX biodegradation rose from 872 mg/day before enhancement to 2530 mg/day after 60 days of oxygen delivery. Increased oxygen flux to the test area could account for aerobic biodegradation of 1835 mg/day of the BTEX. The estimated rates of anaerobic biodegradation processes decreased based on the flux of sulfate, iron (II), and methane. Two contaminants in the plume, benzene and ethylbenzene, are not biodegraded as readily as toluene or xylenes under anaerobic conditions. Following oxygen enhancement, however, the benzene and ethylbenzene concentrations decreased about 98%, as did toluene and total xylenes.
Modeling Multispecies Reactive Transport in Ground Water
Authors: Clement T.P. , Sun Y. , Hooker B.S. , Petersen J.N. 
Published: February 2007

AbstractIn this paper, the details of RT3D, a general purpose, multispecies, reactive transport code, are presented. The code uses MODFLOW to simulate flow and several MT3D sub‐programs to simulate advection and dispersion. A set of reaction modules were developed and incorporated into RT3D to simulate various types of multispecies reactive transport. This new computer model can be used for analyzing different types of subsurface contaminant reactions, microbial metabolisms, and microbial transport kinetics. Details of the model and numerical solution procedure are presented. The numerical formulation of the code is general enough to allow description of any type of reaction with any number of mobile/immobile species. Several example problems are presented to test the performance of the code, and to illustrate its features. The presented numerical model is shown to be a useful tool for analyzing different types of subsurface bioremediation systems. Prediction based on this model can be used for screening remediation alternatives including natural attenuation and/or for forecasting contaminant exposure levels and environmental risks at sensitive, downgradient receptors.
A Study of Long‐Term MTBE Attenuation in the Borden Aquifer, Ontario, Canada
Authors: Schirmer Mario , Barker James F. 
Published: February 2007

AbstractIn 1988 and 1989, a natural gradient tracer test was performed in the shallow, aerobic and aquifer at Canadian Forces Base (CFB) Borden. A mixture of ground water containing dissolved oxygenated gasoline was injected below the water table along with chloride (Cl‐) as a conservative tracer. The migration of BTEX, MTBE, and Cl was monitored in detail for 16 moths. The mass of BTEX compounds in the plume diminished significantly with time due to intrinsic aerobic biodegradation, while MTBE showed only a small decrease in mass over the 16‐month period. In 1995/96, a comprehensive ground water sampling program was undertaken to define the mass of MTBE still present in the aquifer. Since the plume had migrated into an unmonitored section of the Borden Aquifer, numerical modeling and geostatistical methods were applied to define an optimal sampling grid and to improve the level of confidence in the results. A drive point profiling system was used to obtain ground water samples. Numerical modeling with no consideration of degradation pedicted maximum concentrations in excess of 3000 μg/L; field sampling found maximum concentrations of less than 200 μg/L. A mass balance for the remaining MTBE mass in the aquifer eight years after injection showed that only 3% of the original mass remained. Sorption, volatilization, a biotic degradation, and plant uptake are not considered significant attenuation processes for the field conditions. Therefore, we suggest that biodegradation may have played a major role in the attenuation of MTBE within the Borden Aquifer.
LNAPL Volume Calculation: Parameter Estimation by Nonlinear Regression of Saturation Profiles
Authors: Lundegard Paul D. , Mudford Brett S. 
Published: February 2007

AbstractAn estimation of the volume of light nonaqueous phase liquids (LNAPL) is often required during site assessment, remedial design, or litigation. LNAPL volume can be estimated by a strictly empirical approach whereby core samples, distributed throughout the vertical and lateral extent of LNAPL, are analyzed for LNAPL content, and these data are then integrated to compute a volume. Alternatively, if the LNAPL has obtained vertical equilibrium, the thickness of LNAPL in monitoring wells can be used to calculate of LNAPL in monitoring wells can be used to calculate LNAPL volume at the well locations if appropriate soil and LNAPL properties can be estimated.A method is described for estimating key soil and LNAPL properties by nonlinear regression of vertical profiles of LNAPL saturation. The methods is relatively fast, cost effective, and amenable to quantitative analysis of uncertainty. Optionally, the method allows statistical determination of best‐fit values for the Van Genuchten capillary parameters (n, αoil‐water and αoil‐air), residual water saturation and ANAPL density. The sensitivity of the method was investigated by fitting field LNAPL saturation profiles and then determining the variation in misfit (mean square residual) as a function of parameter value for each parameter. Using field data from a sandy aquifer, the fitting statistics were found to be highly sensitive to LNAPL density, αoil‐water and αoil‐air moderately sensitive to the Van Genuchten n value, and weakly sensitive to residual water saturation. The regression analysis also provides information that can be used to estimate uncertainty in the estimated parameters, which can then be used to estimate uncertainty in calculated values of specific volume.
Diisopropanolamine Biodegradation Potential at Sour Gas Plants
Authors: Gieg Lisa M. , Greene E. Anne , Coy Debora L. , Fedorak Phillip M. 
Published: February 2007

AbstractThe potential for aerobic and anaerobic biodegradation of a sour gas treatment chemical, diisopropanolamine (DIPA), was studied using contaminated aquifer materials from three sour gas treatment sites in western Canada. DIPA was found to be readily consumed under aerobic conditions at 8°C and 28°C in shake flask cultures incubated with aquifer material from each of the sites, and this removal was characterized by first‐order kinetics. In addition, DIPA biodegradation was found to occur under nitrate‐, Min(IV)., and Fe(III)‐reducing conditions at 28°C, and in some cases at 8°C, in laboratory microcosms, DIPA loss corresponded to consumption of nitrate, and production of Mn(II) and Fe(II) in viable microcosms compared to corresponding sterile controls. A threshold DIPA concentration near 40 mg/L was observed in the anaerobic microcosms. This report provides the first evidence that DIPA is biodegraded under anaerobic conditions, and our data suggest that biodegradation may contribute to DIPA attenuation under aerobic and anaerobic conditions in aquifers contaminated with this sour gas treatment chemical.