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  • Articles  (7)
  • NAPL  (7)
  • 2000-2004  (7)
  • Technology  (7)
  • Electrical Engineering, Measurement and Control Technology
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  • Articles  (7)
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  • 1
    Electronic Resource
    Electronic Resource
    Effects of NAPL Contaminants on the Permeability of a Soil‐Bentonite Slurry Wall Material (2000)
    Springer
    Transport in porous media 38 (2000), S. 43-56 
    Details
    ISSN: 1573-1634
    Keywords: NAPL ; hydraulic conductivity ; permeability ; slurry walls ; soil ; bentonite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Soil‐bentonite slurry walls are designed to inhibit the subsurface movement of contaminants from hazardous waste sites. Although it is generally accepted that high concentrations of organic compounds will adversely affect soil‐bentonite slurry walls and clay liners, previous research investigating the effects of NAPLs on the conductivity of clay wall materials has been inconclusive. In this study the effects of various organics (benzene, aniline, trichloroethylene, ethylene dichloride, methylene chloride) on the effective conductivity of a typical soil‐bentonite slurry wall material were studied under two effective stress conditions, 200 and 52 kPa. The hydraulic conductivity for the soil‐bentonite material permeated with water averaged 1.52×10-8 cm s-1. Compared to water, there was little change in conductivity when the sample was permeated with a solution containing a NAPL compound at its solubility limit, except for aniline. However, there was a one to two order of magnitude decrease in conductivity when the sample was permeated with a pure NAPL for all NAPLs tested. When the soil‐bentonite material was permeated with a water/NAPL/water/NAPL sequence, the conductivity decreased one to two orders of magnitude when a NAPL was introduced following water; however, when water was reintroduced after the NAPL, the conductivity increased to the initial hydraulic conductivity. The conductivity again decreased one to two orders of magnitude when the NAPL was reintroduced. This trend occurred for all NAPLs tested, and the fluid properties of the NAPL compounds alone did not account for the decrease in conductivity compared to water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006655015509
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  • 2
    Electronic Resource
    Electronic Resource
    Regression and Dimensional Analysis for Modeling Two‐Phase Flow (2000)
    Springer
    Transport in porous media 38 (2000), S. 205-221 
    Details
    ISSN: 1573-1634
    Keywords: regression analysis ; dimensionless analysis ; NAPL ; artificial neural network ; capillary processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Numerical models describing multiphase flow phenomena are typically used to predict the displacement of water during the infiltration of non‐aqueous phase liquids (NAPLs) into a groundwater system. In this paper, the applicability of regression and dimensional analysis to develop simple tools to by‐pass these time consuming numerical simulations is assessed. In particular, the infiltration of NAPL through a vertical, homogeneous soil column initially saturated with water is quantified. Two output variables defining the extent of infiltration were considered – the elevation of the NAPL front and the volume of NAPL which had entered the system. Dimensional analysis was initially performed to identify dimensionless terms associated with the underlying relations between these two output variables and the input variables (independent variables and system parameters). Artificial neural network techniques were then employed to develop regression equations for approximating the input–output relationships over a given domain. Application of these equations illustrated the interrelationships among capillary, buoyancy, and viscous forces driving the NAPL infiltration process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006607132347
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of Organic Base Chemistry on Interfacial Tension, Wettability, and Capillary Pressure in Multiphase Subsurface Waste Systems (2000)
    Springer
    Transport in porous media 38 (2000), S. 79-92 
    Details
    ISSN: 1573-1634
    Keywords: surfactant ; dodecylamine ; capillary pressure ; interfacial tension ; wettability ; NAPL ; organic base
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The presence of surfactants may have profound effects on the transport of organic contaminants in multiphase systems. It is a common practice, however, to model the subsurface migration of liquids independently of the aqueous phase composition. As such, transport in these systems may not be adequately characterized. This study investigates the impact of pH on interfacial tension, wettability, and the drainage capillary pressure–saturation relationship in air–water–quartz and o‐xylene–water–quartz systems containing dodecylamine, an organic base. In these systems, three mechanisms, speciation, partitioning, and sorption, are important in determining the interfacial tension and contact angle, and consequently, important in determining the capillary pressure. By adjusting the pH above and below, the pKa of the base, the relative importance of these mechanisms was altered. Below dodecylamine's pKa of 10.6, the base was primarily in a cationic form resulting in minimal partitioning into the nonaqueous liquid and greater sorption at the quartz surface. Above the pKa, the base was primarily in a neutral form which did not sorb to the quartz, and, furthermore, partitioned into the organic liquid phase where its surface activity was minimized. The combination of these processes caused the capillary pressure to change in a manner consistent with pore‐scale theory of capillarity. The utility in this approach lies in the possibility of predicting transport properties in multiphase systems while incorporating the direct effects of solution chemistry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006659116417
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  • 4
    Electronic Resource
    Electronic Resource
    Multicomponent NAPL Solidification Thermodynamics (2000)
    Springer
    Transport in porous media 38 (2000), S. 57-77 
    Details
    ISSN: 1573-1634
    Keywords: NAPL ; solidification ; polycyclic aromatic hydrocarbon ; PAH ; coal tar ; multicomponent phase equilibrium ; thermodynamics ; ideal solution theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Nonaqueous phase liquid (NAPL) contaminants that are chemical mixtures often contain compounds that are solids in their pure states. In the environment, weathering processes cause shifts in multicomponent NAPL composition, thereby enriching the NAPL in the less soluble compounds which may result in their eventual solidification. In this paper, we review the thermodynamic theory governing solid–liquid phase equilibria for the multicomponent NAPLs, and we present experimental observations of such phase equilibria for binary, ternary, and quaternary mixtures of polycyclic aromatic hydrocarbons (PAHs). If the NAPL phase behaves as an ideal solution and if the solid precipitate is pure, then a compound's mole fraction solubility limit in the NAPL phase equals its solid–liquid reference fugacity ratio. This value is a constant at the temperature of the system. If the NAPL phase is a non‐ideal solvent or if the solid is a solid solution, prediction of NAPL solidification in the environment is considerably more difficult. Experimental results indicate that for compounds such as naphthalene and acenaphthene, the solid–liquid reference fugacity ratio serves as a good indicator of the solubility limits in the NAPL phase. For phenanthrene, the solids that form when this compound exceeds its solubility limit are solid solutions that consistently include large portions of 2‐methylnaphthalene. These results suggest that the independent behavior implied by ideal solubility theory may not be an accurate descriptor of NAPL solidification phenomena for all PAH‐containing NAPLs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006615301396
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  • 5
    Electronic Resource
    Electronic Resource
    Behavior of Nonaqueous Phase Liquids in Fractured Porous Media under Two‐Phase Flow Conditions (2000)
    Springer
    Transport in porous media 38 (2000), S. 189-203 
    Details
    ISSN: 1573-1634
    Keywords: NAPL ; capillary pressure ; relative permeability ; network model ; multiphase flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract After dense nonaqueous phase liquids (DNAPLs) travel downward through the subsurface, they typically come to rest on fractured bedrock or tight clay layers, which become additional pathways for DNAPL migration. DNAPLs trapped in fractures are continuous sources of groundwater contamination. To decide whether they can be left in place to dissolve or volatilize, or must be removed with active treatment, the movement of DNAPLs in fractured media must be understood at a fundamental level. This work presents numerical simulations of the movements of DNAPLs in naturally fractured media under two‐phase flow conditions. The flow is modeled using a multiphase network flow model, used to develop predictive capabilities for DNAPL flow in fractures. Capillary pressure–saturation–relative permeability curves are developed for two‐phase flow in fractures. Comparisons are made between the behavior in crystalline, almost impermeable rocks (e.g. granite) and more permeable rocks like sandstone, to understand the effects of the rock matrix on the displacement of the DNAPLs in the fracture. For capillary‐dominated flow, displacements occur as a sequence of jumps, as the invading phase overcomes the capillary pressure at downgradient apertures. Preferential channels for the displacement of nonaqueous phase are formed due to high fracture aperture in some regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006619402305
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  • 6
    Electronic Resource
    Electronic Resource
    Nonaqueous Phase Liquid Dissolution in Porous Media: Current State of Knowledge and Research Needs (2000)
    Springer
    Transport in porous media 38 (2000), S. 3-28 
    Details
    ISSN: 1573-1634
    Keywords: NAPL ; dissolution ; mass transfer ; morphology ; multicomponent ; up‐scaling ; inverse modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Our understanding of nonaqueous phase liquid (NAPL) dissolution in the subsurface environment has been increasing rapidly over the past decade. This knowledge has provided the basis for recent developments in the area of NAPL recovery, including cosolvent and surfactant flushing. Despite these advances toward feasible remediation technologies, there remain a number of unresolved issues to motivate environmental researchers in this area. For example, the lack of an effective NAPL‐location methodology precludes effective deployment of NAPL recovery technologies. The objectives of this paper are to critically review the state of knowledge in the area of stationary NAPL dissolution in porous media and to identify specific research needs. The review first compares NAPL dissolution‐based mass transfer correlations reported for environmental systems with more fundamental results from the literature involving model systems. This comparison suggests that our current understanding of NAPL dissolution in small‐scale (on the order of cm) systems is reasonably consistent with fundamental mass transfer theory. The discussion then expands to encompass several issues currently under investigation in NAPL dissolution research, including: characterizing NAPL morphology (i.e. effective size and surface area); multicomponent mixtures; scale-related issues (dispersion, flow by-passing); locating NAPL in the subsurface and enhanced NAPL recovery. Research needs and potential approaches are discussed throughout the paper. This review supports the following conclusions: (1) Our knowledge related to local dissolution and remediation issues is maturing, but should be brought to closure with respect to the link between NAPL emplacement theory (as it impacts NAPL morphology) and NAPL dissolution; (2) The role of nonideal NAPL mixtures, and intra-NAPL mass transfer processes must be clarified; (3) Valid models for quantifying and designing NAPL recovery schemes with chemical additives need to be refined with respect to chemical equilibria, mass transfer and chemical delivery issues; (4) Computational and large-scale experimental studies should begin to address parameter up-scaling issues in support of model application at the field scale; and (5) Inverse modeling efforts aimed at exploiting the previous developments should be expanded to support field-scale characterization of NAPL location and strength as a dissolving source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006667318234
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  • 7
    Electronic Resource
    Electronic Resource
    A Physically Based Model of Dissolution of Nonaqueous Phase Liquids in the Saturated Zone (2000)
    Springer
    Transport in porous media 39 (2000), S. 227-255 
    Details
    ISSN: 1573-1634
    Keywords: corner diffusion ; pore diffusion ; mixing and multiple contact ; bundle of parallel pores in series ; blob ; ganglia ; dissolution rate coefficient ; dissolution ; NAPL
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The design of remediation strategies for nonaqueous phase liquid (NAPL) contaminants involves predicting the rate of NAPL dissolution. A physically based model of an idealized pore geometry was developed to predict nonaqueous phase liquid dissolution rate coefficients. A bundle of parallel pores in series model is used to represent NAPL dissolution as a function of three processes: pore diffusion, corner diffusion, and mixing and multiple contact. The dissolution rate coefficient is expressed in terms of the modified Sherwood number (Sh′) and is a function of Peclet (Pe) number. The model captures the complex behavior of Sh′ versus Pe data for both water-wet (Powers, 1992) and NAPL-wet (Parker et al., 1991) media. For water-wet media, the observed behavior can be broken down into four distinct regions. Each region represents a different physical process controlling NAPL dissolution: the low-Pe region is controlled by pore diffusion; the low- to moderate-Pe region is a transition zone; the moderate-Pe region is controlled by mixing and multiple contact; and the high-Pe region is controlled by corner diffusion. For the high-Pe conditions typical of most column experiments, the model involves only one fitting parameter. For NAPL-wet media, NAPL dissolution is governed exclusively by corner diffusion, and the model again involves only one fitting parameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006693126316
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