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  • 1
    Language: English
    In: 2012
    Description: Acknowledgment is made to the Donors of the American ChemicalSociety Petroleum Research Fund for support (or partial support)of this research (grant number 48505-AC9) and by US NSF(EAR 337711 and EAR 0610108). Microtomography was performedat GeoSoilEnviroCARS (Sector 13), Advanced Photon Source (APS),Argonne National Laboratory. GeoSoilEnviroCARS is supported by the National Science Foundation-Earth Sciences (EAR-0217473),Dept. of Energy-Geosciences (DE-FG01-94ER14466) and the Stateof Illinois. Additionally, we would like to acknowledge the followingpeople for their help with either collecting the data: Mark Rivers(GSECARS APS/University of Chicago), or with interpreting theresults: James McClure (University of North Carolina), Casey Miller(University of North Carolina), William Gray (University of NorthCarolina), and Adrian Sheppard (Australian National University).
    Description: Synchrotron-based tomographic datasets of oil–water drainage and imbibition cycles have been analyzed to quantify phase saturations and interfacial curvature as well as connected and disconnected fluid configurations. This allows for close observation of the drainage and imbibition processes, assessment of equilibrium states, and studying the effects of fluid phase disconnection and reconnection on the resulting capillary pressures and interfacial curvatures. Based on this analysis estimates of capillary pressure calculated from interfacial curvature can be compared to capillary pressure measured externally with a transducer. Results show good agreement between curvature-based and transducer-based measurements when connected phase interfaces are considered. Curvature measurements show a strong dependence on whether an interface is formed by connected or disconnected fluid and the time allowed for equilibration. The favorable agreement between curvature-based and transducer-based capillary pressure measurements shows promise for the use of image-based estimates of capillary pressure for interfaces that cannot be probed with external transducers as well as opportunities for a detailed assessment of interfacial curvature during drainage and imbibition.
    Description: This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/advances-in-water-resources/. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. ; 10.1016/j.advwatres.2012.05.009
    Keywords: Drainage ; Computed Microtomography ; Capillary Pressure ; Young–Laplace ; Interfacial Curvature ; Imbibition
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 2
    Language: English
    In: Advances in water resources, 2009, Vol.32, pp.1632-1640
    Description: Includes references ; p. 1632-1640.
    Keywords: Hysteresis ; Computed Tomography ; Porous Media ; Drainage ; Water Flow ; Mathematical Models ; Unsaturated Conditions ; Simulation Models ; Unsaturated Flow ; Lattice-Boltzmann Simulation ; Capillary Pressure ; Capillary Pressure-Saturation-Interfacial Relationship ; Computed Microtomography
    ISSN: 0309-1708
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 3
    In: Water Resources Research, December 2007, Vol.43(12), pp.n/a-n/a
    Description: A Shan‐Chen–type multiphase lattice Boltzmann (LB) model was applied to observed computed microtomography data from water‐air and water‐Soltrol displacement experiments in a glass bead porous medium. Analysis of the Bond, Reynolds, and Capillary numbers for these systems showed that capillary forces were dominant removing the need to model viscous, gravitational, and density effects. A numerical parameterization of the LB model yielded lattice surface tension and contact angle, and appropriate pressure boundary conditions. Two scaling relations provided a link between lattice pressure and physical pressure and lattice time and physical time. Results showed that there was a good match between measured and simulated pressure‐saturation data for the water‐air system, but that there were large differences between the simulations and observations for the water‐Soltrol system. The discrepancies for the water‐Soltrol system were probably due to inconsistencies between experimental conditions and simulated conditions such as nonzero contact angle in the experiments. Analysis of saturation profiles indicated increasing saturation near the wetting boundary and decreasing saturations near the nonwetting boundary. We attribute these saturation transitions to pore‐neck and percolation effects. While computationally intensive, results of this study were very encouraging for the application of LB simulations to microscale interfacial phenomena. Future studies will carry out a further validation in terms of interfacial areas, contact lines, and fluid distributions.
    Keywords: Lattice Boltzmann ; Pressure Saturation ; Comparison
    ISSN: 0043-1397
    E-ISSN: 1944-7973
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  • 4
    Language: English
    Description: Few studies have examined both long-term and fine-scale spatial variations inwater quality of small streams in the Pacific Northwest. As such, a case study wasconducted to determine if current physical and chemical properties of water in threestreams located in the Oregon Coast Range differed from historically measuredconditions, taking differences in past management regimes into account. In addition,this research provides an assessment of spatial and temporal variability in nitratenitrogen(N) concentrations and summer stream temperatures within each catchment.The three research catchments were part of the Alsea Watershed Study (1959-1973), where effects of forest management practices were examined using a pairedwatershedstudy design. One catchment, Needle Branch, was clear-cut with noprotection provided to the stream. Harvesting in Needle Branch was followed by anintense broadcast burn to remove logging slash. Another catchment, Deer Creek, waspatch-cut in three small units resulting in a 25% harvest of the total catchment area,but buffers were retained along fish-bearing streams. The third catchment, FlynnCreek, was used as a control.In this revisit to the Alsea Watersheds, measurements were conductedcontinuously (discharge, turbidity), intermittently (suspended sediments), and atregular intervals (nitrate-N) for one year between October 2005 and September 2006.Summertime stream temperature was also measured every half-hour from mid-June tomid-September.Comparisons of recent data with historic data show no detectable changes overtime for streamflow characteristics (annual runoff volume, peak flow discharges, andnumber of low-flow days), annual sediment yield, or summer maximum streamtemperatures. Current nitrate-N export was similar to historically measured values forFlynn Creek and Deer Creek; however, export at Needle Branch was increased overpast levels. This observation may be caused by dense colonization of the riparian areawith red alder (Alnus rubra), a N-fixing species, following the 1966 harvest. Patternsof nitrate-N concentration varied throughout each catchment and are likely influencedby the current distribution of red alder stands. Synoptically measured streamtemperatures were variable along each stream’s longitudinal profile. The ability tomeet Oregon’s water quality standard for temperature was dependent on measurementlocation and method of analysis. Evaluating individual sampling points as discreterecords resulted in each stream exceeding the standard for at least one measurementlocation, whereas evaluating the criteria based on the mean of all data collected withinthe mainstem stream excluded Flynn Creek and Needle Branch from violation. Theseresults highlight the physical and chemical variability of stream water draining OregonCoast Range headwater catchments and provide insight as to where future workshould be focused to gain a more thorough understanding of these dynamic systems. ; Graduation date: 2008
    Keywords: Water Quality -- Oregon -- Needle Branch ; Water Temperature -- Oregon -- Flynn Creek ; Water Temperature -- Oregon -- Deer Creek (Lincoln County) ; Forest Management -- Oregon -- Flynn Creek Watershed ; Forest Management -- Oregon -- Deer Creek (Lincoln County) Watershed ; Water Quality -- Oregon -- Flynn Creek ; Alsea Watershed Study ; Paired-Watershed Study ; Water Quality -- Oregon -- Deer Creek (Lincoln County) ; Water Temperature -- Oregon -- Needle Branch ; Forest Management -- Oregon -- Needle Branch Watershed
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 5
    Language: English
    Description: Metal and hydrogen ion acidity and extreme nitrate concentrations typical ofDepartment of Energy (DOE) legacy waste sites pose formidable challenges tosuccessful implementation of in situ bio-immobilization. Intermediate-scale (~ 2.5 m),flow through models of an in situ bio-barrier were constructed to investigate U and Tcremoval from groundwater at a contaminated site in Oak Ridge, TN. In one study,ethanol additions to pH-neutral contaminated site groundwater, flowing through amixture of site sediment and crushed limestone, effectively stimulated iron- and sulfatereducingconditions and sustained U and Tc removal for 20 months. In a related study,ethanol additions to nitric acid contaminated site groundwater, flowing through amixture of site sediment and crushed limestone, effectively promoted denitrification forover 20 months. A combined signature lipid and nucleic acid-based approach was usedto spatially characterize microbial communities at relatively small spatial scales (〈67cm) in sediment along the groundwater flow paths in both experimental systems. Theresults showed that ethanol additions stimulated growth of a distinct microbialcommunity in both the pH-neutral and nitric acid-contaminated systems, and that shiftsin community composition were spatially correlated with geochemistry along thegroundwater flow paths. Collectively, these results suggest that an in situ bio-barriercould be potentially effective for U and Tc removal from nitric-acid contaminatedgroundwater at the FRC. Hydraulic conductivity decreased by an order of magnitude inboth experimental systems due primarily to solids deposition. Preferential flow pathformation, due to biomass accumulation or solids deposition, could ultimately reduceresidence time within the treatment zone and decrease U and Tc removal efficiency. ; Graduation date: 2007
    Keywords: Technetium -- Environmental Aspects -- Tennesee -- Oak Ridge ; Uranium -- Environmental Aspects -- Tennesee -- Oak Ridge ; Technetium ; Uranium ; Groundwater -- Purification -- Tennesee -- Oak Ridge ; In Situ Remediation -- Tennesee -- Oak Ridge ; Groundwater Remediation ; Groundwater -- Pollution -- Tennesee -- Oak Ridge
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 6
    Language: English
    Description: Elevated groundwater nitrate (NO3-) concentrations in the Southern WillametteValley (SWV) caused the Oregon Department of Environmental Quality (ODEQ) todeclare a Groundwater Management Area (GWMA) in Spring, 2004. To betterunderstand direction of groundwater flow, groundwater age, and nitrate transportpathways of the SWV we developed a steady-state numerical groundwater flow modelusing MODFLOW with MODPATH. Model development was supplemented by fieldinvestigations of local outcrops, pump and slug tests, and laboratory analyses todetermine groundwater age and groundwater chemistry.Field work included the construction/collection of cross-sections and stratigraphiccolumns; 12 slug tests and 3 pump tests to determine hydraulic conductivity andstorativity; 10 groundwater ages using CFC-11, CFC-12, and CFC-113; 3 wellsinstrumented to collect long-term continuous water level measurements; 42 wells selectedfor quarterly manual water level measurements; and 14 groundwater samples todetermine pH, dissolved oxygen, specific electrical conductance, chloride, sulfate, andnitrate concentrations.Slug tests determined horizontal hydraulic conductivities (Kx) from4.19 x 10-8 m/s to 4.62 x 10-4 m/s. Pump tests determined Kx-values from 3.59 x 10-4 m/sto 7.22 x 10-3 m/s, vertical hydraulic conductivities (Kv) from 3.48 x 10-6 m/s to3.84 x 10-6 m/s, and storage coefficients from 0.05 to 0.15. Groundwater age rangedfrom 13 years to 〉50 years, with the greatest ages resulting from wells that penetrated thesemi-confining Willamette Silt. Groundwater ages were compared to model particletravel times using MODPATH and used as calibration targets. Groundwater ages alongwith nitrate, chloride, sulfate, and dissolved oxygen concentrations were used toreconstruct past contaminant loading and observe data trends. Spatial distributions ofhydraulic conductivity were estimated using wells with specific capacity data and anempirical relationship (T = 158.48sc, where T = transmissivity (ft2/d) andsc = (gal/min/ft); R2 = 0.61) between wells in the study area that contained both specificcapacity and aquifer test data.The calibrated groundwater flow model is intended to help make managementdecisions, establish monitoring programs, and to be used as an outreach education tool.Model simulations were run in key areas to demonstrate model capabilities and createvisual aids for outreach education. This study suggests it may take 10’s of years to seemeasurable declines of groundwater nitrate in some locations. It is our hope thateducating stakeholders about local groundwater flow along with stressing the use of BestManagement Practices (BMPs) will result in better decision making and lead to areduction of groundwater nitrate concentration in the SWV. ; Graduation date: 2006
    Keywords: Groundwater ; Groundwater Flow -- Oregon -- Willamette River Valley ; Model ; Groundwater -- Quality ; Hydrogeology -- Oregon -- Willamette River Valley ; Modflow ; Nitrate ; Cfcs
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 7
    Language: English
    Description: Groundwater nitrate contamination is a well-documented issue in the SouthernWillamette Valley (SWV) of Oregon, as a Groundwater Management Area (GWMA) hasrecently been declared. As a GWMA, groundwater nitrate monitoring must occur untilregional concentrations are below 7 mg/L NO3-N. However, the presence of temporalvariability can make it difficult to determine if contamination exceeds a threshold and ifcontamination is increasing or decreasing over time. To examine the potential impact oftemporal variability on groundwater nitrate monitoring in the SWV, a well network wascreated and sampled monthly for 15 months. Results indicate that substantial intra-welltemporal variability is present, and that spatial variability of groundwater nitrate isgreater than temporal variability. Generally, temporal variability was associated withrecharge events, which flushed higher concentration soil-water into the aquifer. Thoughindividual wells showed seasonality, network-wide seasonal trends were not statisticallysignificant (which is believed to be caused by a dampening effect due to localheterogeneities). From a monitoring perspective, this implies that less frequentgroundwater nitrate sampling (such as quarterly) can capture network-wide seasonalresponse to the same degree as monthly sampling.To determine how long-term land management practices are likely to impactregional nitrate leaching and future monitoring trends, a nitrogen loading model wascreated for the SWV. Present-day data were used to calibrate and validate the Soil andWater Assessment Tool (SWAT) model, with 3 alternative future scenarios then beingevaluated. The effects of agrarian Groundwater Best Management Practices (GW-BMPs)were examined with respect to nitrate leaching in present and future scenarios. Modeledvalues indicate that agrarian GW-BMP implementation is a more effective agent forreduced nitrate leaching than land use change alone. Together, land use change and theadoption of GW-BMPs were found to decrease nitrate leaching values by 32 to 46% oftheir present-day rates. These predicted results do not include the impact ofdenitrification or changes in septic leaching, and therefore should be regarded withcaution as they do not completely represent future conditions. Considering this, aconservative conclusion which can be drawn is that GW-BMP implementation is a saferalternative than reliance on projected land use/crop change alone for lesseninggroundwater nitrate concentrations in the GWMA. This is the first study to successfullyapply SWAT as a tool to examine the spatial and temporal variability of nitrate leaching. ; Graduation date: 2007
    Keywords: Nitrate ; Variability ; Groundwater -- Pollution -- Oregon -- Willamette River Valley ; Seasonal ; Swat ; Groundwater ; Nitrates -- Environmental Aspects -- Oregon -- Willamette River Valley ; Groundwater -- Nitrogen Content -- Oregon -- Willamette River Valley
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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