bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Small‐Scale Ground Water Leaching Study for a Primisulfuron Herbicide
Authors: Chang H. Ted , Ying Weiming 
Published: February 2007

AbstractPrimisulfuron 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

AbstractWashing 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

AbstractThe 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

AbstractA 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

AbstractWaste 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.
Multiport Sock Samplers: A Low‐Cost Technology for Effective Multilevel Ground Water Sampling
Authors: Jones Ian , Lerner David N. , Baines Owen P. 
Published: February 2007

AbstractThe importance of obtaining depth‐specific ground water samples is now well recognized among practitioners and scientists alike. Many methods and technologies are available for level discrete or depth‐specific ground water sampling in consolidated aquifers. All methods have their associated advantages and drawbacks, however. One common disadvantage is that they are expensive. A large number of point discrete ground water samples were required for a UK research project aimed at quantifying natural attenuation processes in ground water contaminated by a former coal carbonization plant. Based on experience from a previous project to develop novel level accurate sampling methodologies for use in existing boreholes, the Ground Water Protection and Restoration Research Unit (GWPRRU) produced and tested a low‐cost design multiport sock sampler for ground water monitoring. The sock sampler design allowed the recovery of multiple depth‐specific ground water samples from depths of 150 feel (45 m) from individual boreholes in the sandstone aquifer at the field site. Because of their use of inexpensive materials, simple design, installation and use that does not require gravel packs, packers, or grouting, sock samplers were found to be the most cost effective, convenient, and reliable method of obtaining multiple depth‐specific ground water samples at the project field site.
Removal of Perchloroethylene from a Layered Soil System by Steam Flushing
Authors: She Hugh Y. , Sleep Brent E. 
Published: February 2007

AbstractSteam flushing experiments were concluded in a two‐dimensional chamber containing two layers of F75 silica sand separated by a layer of finer F10 silica sand. Perchloroelhylene (PCE), which had spilled into the chamber under water‐saturated conditions, formed a pool on the F110 sand layer. Steam was injected above the F110 sand layer. Temperatures, moisture content, and PCE concentrations in the chamber were monitored. Samples, taken from the various locations in the sand chamber, indicated that complete removal of PCE from the steam zone was achieved, with an 84% overall recovery. Some downward displacement of PCE‐contaminated water through the F110 sand layer was observed and a small amount of gravity override occurred. Channeling of steam was minimal. The experiment indicates that steam flushing may be used successfully for removal of PCE from relatively homogeneous soils. Issues of gravity override and downward mobilization of contaminants must be considered in applying steam flushing at the field scale.
Elements in Cottonwood Trees as an Indicator of Ground Water Contaminated by Landfill Leachate
Authors: Erdman James A. , Christenson Scott 
Published: February 2007

AbstractGround water at the Norman Landfill Research Site is contaminated by a leachate plume emanating from a closed, unlined landfill formerly operated by the city of Norman, Oklahoma, Ground water contaminated by the leachate plume is known to be elevated in the concentration of many, organic and inorganic constituents. Specific conductance, alkalinity, chloride, dissolved organic carbon, boron, sodium, strontium, and deuterium in ground water are considered to be indicators of the leachate plume at this site.Leaf samples of broad‐leafed cottonwood, Populus deltoides, were collected from 57 sites around the closed landfill. Cottonwood, a phreatophyte or “well plant,” functions as a & surrogate well and serves as a ground water quality sampler. The leaf samples were combusted to ash and analyzed by instrumental neutron activation for 35 elements and by prompt‐gamma instrumental neutron activation, for boron. A monitoring well was located within a few meters of a sampled cottonwood tree at 15 of the 57 sites, and ground water samples were collected from these monitoring wells simultaneously with a leaf sample. The chemical analyses of the ground water and leaf samples from these 15 sites indicated that boron, bromine, sodium, and strontium concentrations in leaves were significantly correlated with leachate indicator constituents in ground water. A point‐plot map of selected percentiles indicated high concentrations of boron, bromine, and sodium in leaf ash from sites downgradient of the most recent landfill and from older landfills nearby.Data from leaf analysis greatly extended the known areal extent of the leachate plume previously determined from a network of monitoring wells and geophysical surveys. This phytosgeochemical study provided a cost‐effective method for assessing the extent of a leachate plume from an old landfill. Such a method may be useful as a preliminary sampling tool to guide the design of hydrogeochemical and geophysical studies.
Creation of a Subsurface Permeable Treatment Zone for Aqueous Chromate Contamination Using In Situ Redox Manipulation
Authors: Fruchter J.S. , Cole C.R. , Williams M.D. , Vermeul V.R. , Amonette J.E. , Szecsody J.E. , Istok J.D. , Humphrey M.D. 
Published: February 2007

AbstractAn in situ redox manipulation (ISRM) method for creating a permeable treatment zone in the subsurface has been developed at the laboratory bench and intermediate scales and deployed at the field scale for reduction/immobilization of chrornate contamination. At other sites, the same redox technology is currently being tested for dechlorination of TCE. The reduced zone is created by injected reagents that reduce iron naturally present in the aquifer sediments from Fe(III) to surface‐bound and structural Fe(II) species. Standard ground water wells are used, allowing treatment of contaminants too deep below the ground surface for conventional treneh‐and‐fill technologies.A proof‐of‐principle field experiment was conducted in September 1995 at a chromate (hexavalent chromium) contaminated ground water site on the Hartford Site in Washington. The test created a 15 m (˜50 feet) diameter cylindrical treatment zone. The three phases of the test consisted of (1) injection of 77, 000 L (20, 500 gallons) of buffered sodium dithionite solution in 17.1 hours, (2) reaction for 18.5 hours, and (3) withdrawal of 375, 000 L (99, 600 gallons) in 83 hours. The withdrawal phase recovered 87% to 90% of the reaction products. Analysis of post‐experimental sediment cores indicated that 60% to 100% of the available reactive iron in the treated zone was reduced. The longevity of the reduced zone is estimated between seven and 12 years based on the post‐experiment core samples. Three and half years after the field test, the treatment zone remains anoxic, and hexavalent chromium levels have been reduced from 0.060 mg/L to below detection limits (0.008 mg/L). Additionally, no significant permeability changes have been detected during any phase of the experiment.
Spatial and Temporal Variability in Seepage Between a Contaminated Aquifer and Tributaries to the Ohio River
Authors: Fryar Alan E. , Wallin Eric J. , Brown David L. 
Published: February 2007

AbstractAlthough ground water discharge‐can limit plume migration and transfer contaminants to streams, interactions among ground water, rivers, and tributaries in contaminated watersheds have received relatively little attention. We used multiple methods to delineate seepage along Little Bayou and Bayou Creeks, tributaries to the Ohio River in McCracken County, Kentucky, from July 1996 through July 1998. The Paducah Gaseous Diffusion Plant (PGDP) lies between the creeks. Trichloroethene (TCE) and technetium‐99 plumes within the underlying Regional Gravel Aquifer (RGA) extend several kilometers from PGDP toward the river. Both creeks tend to gain flow where they are incised into the RGA or contiguous strata in the Ohio flood plain. Bayou Creek also gains flow upstream of PGDP; other reaches of both creeks tend to lose flow. Local storms, river floods, and seasonal dry periods caused temporary changes in seepage rates and reversals in hydraulic gradients. Gaining conditions were indicated by seeps, springs, and boils, by upward hydraulic gradients from bank wells and bed piezometers to the stream, and by mixing models using chloride and oxygen‐18. Mixing models and downward hydraulic gradients from the stream to wells indicated losing conditions. Annual ranges of stream, bed, and bank temperatures tended to be narrower, bed and bank temperatures in summer and early autumn tended to be cooler, and maximum values of specific discharge measured by seepage meters were greater along gaining than along losing reaches. Estimates of specific discharge from stream gauging and one‐dimensional flow‐modeling did not conclusively identify losing and gaining reaches, but absolute values of those estimates fell within the range of seepage‐meter measurements. Contaminants discharging to Little Bayou Creek were diluted downstream by uncontaminated ground water. Volatilization, biodegradation, or sorption probably removed TCE from stream water. These results indicate that discharge to tributaries can limit seepage of contaminants to rivers.
Site‐Specific Design for Dual Phase Recovery and Stabilization of Pooled DNAPL
Authors: Gerhard Jason I. , Kueper Bernard H. , Hecox Gary R. , Schwarz Eric J. 
Published: February 2007

AbstractVolume reduction and lowering of capillary pressure within a large DNAPL pool are utilized as objectives in the design of a large‐scale dual phase recovery system at a chemical manufacturing facility in the United States. By reducing DNAPL pool height through mass removal, capillary pressure is lowered, resulting in a reduced potential for future vertical and horizontal mobilization of the chlorinated solvent DNAPL pool. The DNAPL pool extends over an approximately 200 m by 275 m area in low permeability fill deposits overlying a clay aquitard. A three‐dimensional multiphase flow model was employed to arrive at a final design incorporating nine horizontal drains (total length 664 m) and a pulsed pumping system. The numerical model was calibrated to the results of a 42‐day field pilot‐test involving the removal of approximately 25,000 L of DNAPL from a single, 55 m long horizontal drain. Numerical simulation revealed that gravity drainage, as opposed to hydraulic gradients in the water phase, is the dominant recovery mechanism at this site. This stems from the relatively high density and the viscosity of the DNAPL, and the relatively low permeability of the formation deposits. The use of pulsed pumping is shown to reduce the volume of contaminated ground water recovered from the 9‐drain system, without significant reduction of the total volume of DNAPL recovered.
Limitations of ROI Testing for Venting Design: Description of an Alternative Approach Based on Attainment of a Critical Pore‐Gas Velocity in Contaminated Media
Authors: DiGiulio Dominic C. , Varadhan Ravi 
Published: February 2007

AbstractWe utilize data from a Superfund site where radius of influence (ROI) testing was conducted in support of a venting design to describe limitations of ROI evaluation in more detail than has been done previously, and to propose an alternative method of design based on specification and attainment of a critical pore‐gas velocity in contaminated subsurface media. Since accurate gas permeability estimation is critical to pore‐gas velocity computation, we assess the usefulness of ROI testing data on estimation of radial permeability, vertical permeability, and leakance. We apply information from published studies on rate‐limited vapor transport to provide the basis for selection of a critical design pore‐gas velocity for soils at this site. Using single‐well gas flow simulations, we evaluate whether this critical pore‐gas velocity was achieved at measured ROIs. We then conduct a series of multi‐well gas flow simulations to assess how variation in anisotropy and leakance affect three‐dimensional vacuum and pore‐gas velocity profiles and determination of an ROI. Finally, when attempting to achieve a critical design pore‐gas velocity we evaluate whether it is more efficient to install additional wells or pump existing wells at a higher flow rate.
A Graphical Approach for Determining Dilution‐Attenuation Factors: Basic Theory and Approach for Submerged Sources
Authors: Abrano ic David , Johnson Paul C. , Charbeneau Randall. J. , Hemstreet Timothy J. 
Published: February 2007

AbstractThe dilution attenuation factor (DAF) is a quantity used to relate the concentration of leachate leaving a source zone (e.g., landfill, impoundment, or contaminated soils) to its impact on down‐gradient ground water quality. The DAF is of importance because it plays a key role in U.S. Environmental Protection Agency (EPA)'s methodologies for developing soil cleanup goals and for managing hazardous wastes. In this work, a simplistic graphically‐based approach for determining site‐specific and generic DAFs was developed. In this case the DAF is based on time‐and vertically‐averaged concentrations along the plume centerline, and the mathematical framework employs well‐known analytical and semianalytical solutions for dissolved contaminant transport. Finite sources with a range of decay characteristics are allowed for. One unique feature of this work is that the graphical approach allows for varying levels of sitespecificity, and thus can be used when one has a little, or a lot, of site‐specific information. The graphs visually indicate the sensitivity to various parameters, which is valuable information not easily gleaned from most numerical software simulators. This approach is, however, not applicable to very complex hydrogeologic settings (e.g., fractured geology), or to ground water flows that cannot be reasonably approximated as one‐dimensional.
Implications of Subsurface Heterogeneity at a Potential Monitored Natural Attenuation Site
Authors: Hurt Kelly L. , Beck Frank P. , Wilson John T. 
Published: February 2007

AbstractDirect‐push sampling was conducted at a site previously characterized with conventional monitoring wells. Hydrogeological and chemical heterogeneities not represented in the original site conceptual model were detected by direct‐push sampling. These heterogeneities were important in terms of their impact on the assessment of monitored natural attenuation at the site. This research suggests that additional sampling efforts could be attempted at some sites to test the accuracy of site conceptual models. The leading edge of a contaminant plume must be examined closely, because conceptual errors in this area could easily allow impacts to receptors to remain undetected.
Successful Use of an Innovative Horizontal/Vertical Well Couplet in Fractured Bedrock to Intercept a Mobile Gasoline Plume
Authors: Carlisle Dana , Cook David A. , Miller James A. 
Published: February 2007

AbstractThe horizontal directional drilling (HDD) technology was successfully used in a fracture‐controlled sandstone matrix to intercept a gasoline plume and create a 150‐foot‐long hydrodynamic barrier preventing seepage of gasoline and contaminated ground water into a salmon‐bearing stream within a public park. A 36‐foot‐deep vertical recovery well (VW) intercepts the central low point of the 420‐foot‐long HDD borehole to pump recovered fluids. Contaminant seepage into the creek ceased within hours of starting up the HDD/VW interceptor system in August 1999. Approximately 325 gallons of gasoline and 2 million gallons of contaminated ground water have been recovered to date.