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Numerical simulation of DNAPL-infiltration processes in saturated heterogeneous porous media
HYDROGEOLOGY:PHYSICO-CHEMICAL CHANGES organic carbon fraction of the aquifer sand. A low dispersivity of the aquifer material indicated that dispersion was negligible with respect to the advective flow. Variable advective flow at distinct levels in the aquifer profile is shown to produce tailing of the depth-averaged breakthrough curves. The C-D bond of the deuterated TCE was stable, indicating the usefulness of deuterated TCE as a tracer within the contaminated zone. (from Authors)
957101 Numerical simulation of DNAPL-infiltration processes in saturated heterogeneous porous media J. Croise, R. Helmig & H. Sheta, in: Groundwater quality: remediation and protection. Proc. conference, Prague, 1995, ed K. Kovar & J. Krasny, (IAHS; publication, 225), 1995, pp 247-256. The infiltration of DNAPL into saturated heterogeneous porous media is studied by means of numerical simulations using the finite element method. Differences in parameterization of the constitutive relationships (capillary pressurerelative permeability-saturation relationships) are shown to have a significant impact on DNAPL-migration in homogeneous media. (from Authors)
957102 Enhanced seif-remediation of aquifers from oily pollutants J. M. Stopa & T. Solecki, in: Groundwater quality: remediation and protection. Proc. conference, Prague, 1995, ed K. Kovar & J. Krasny, (IAHS; Publication, 225), 1995, pp 439-448. Hydrocarbon pollution can exist in soil for many years. Moreover, it may migrate with groundwaters for long distances, being dangerous in drinking water, rivers, etc. For these reasons, hydrocarbons should be removed from groundwater. Many methods have been developed for this purpose. Such methods include: pumping using skimmers, air stripping, micro-biological and chemical methods. However, the first step is always to pump the pollution from groundwater. The pumping should be performed by specially designed systems utilizing the natural mechanisms of hydrocarbon migration in groundwaters. This method is termed 'enhanced self-remediation' (ESR). The advantages of this kind of system is that it can be made by the polluter to reduce the costs of operation, and it is neutral for the natural environment. This paper describes the main methods at design used by the authors. (from Authors)
957103 Quantification of hydrocarbon mineralization in a diesel fuel contaminated aquifer treated by in situ biorestoration D. Hunkeler, P. Hohener, A. Haner, T. Bregnard & J. Zeyer, in: Groundwater quality: remediation and protection. Proc. conference, Prague, 1995, ed K. Kovar & J. Krasny, (IAHS; Publication, 225), 1995, pp 421-430. A method is presented to quantify the mineralization of contaminants in a polluted aquifer by alkalinity, inorganic carbon and stable carbon isotope balances. This method is applied to a diesel fuel contaminated aquifer biorestored by infiltration of oxidants and nutrients using a groundwater recirculation system. The observed inorganic carbon production within the biologically active zone is larger than the corresponding calculated inorganic carbon production based on the consumption of electron a cceptors+(O2, NO~, SO~4-), production of reduced species (Mn 2+, Fe2 , H2S, CH4) and dissolution of carbonates. Stable carbon isotope measurements suggest that the additional inorganic carbon mainly originates from a source with a isotopic composition corresponding to hydrocarbons in mineral oil. (Authors)
317A
957104 The fate of dissolved creosote compounds in an intact fractured clay column K. Broholm, E. Arvin, A. Hansen, K. Hinsby & P. Jorgensen, in: Groundwater quality: remediation and protection. Proc. conference, Prague, 1995, ed K. Kovar & J. Kxasny, (IAHS; Publication, 225), 1995, pp 115-123. The fate of 16 different organics typical for creosote was studied under aerobic conditions in a large intact fractured clay column experiment. A simple transport model was applied to some of the data. It was possible to model the early part of the breakthrough curves for retarded organics (naphthalene, quinoline, and 2,4-dimethylphenol) but not the later part since the compounds were degraded. Retardation factors of 8, 9, and 8 for naphthalene, quinoline, and 2,4dimethylphenol, respectively were estimated. This column experiment revealed that transport of organics through fractured clay is an important process. It may in many cases cause groundwater contamination of aquifers, so far believed to be protected by overlying clay layers. (from Authors)
957105 A composite modeling approach for subsurface transport of degrading contaminants from land-disposal sites J. B. gool, P. S. Huyakorn, E. A. Sudicky & Z. A. Saleem, Journal of Contaminant Hydrology, 17(1), 1994, pp 69-90. A composite modeling approach is presented for simulating the three-dimensional (3-D) subsurface transport of dissolved contaminants with transformation products. The approach is based on vertical infiltration and contaminant transport in the unsaturated zone and 3-D groundwater flow and contaminant migration in the saturated zone. Model formulations and solution schemes are verified by comparison against a fully 3-D, variably saturated flow and transport code for a hypothetical problem which represents a typical landfill. The model is applied also to simulate a controlled release field experiment and the model predictions compare well with groundwater monitoring data for the site. (from Authors)
957106 Assessing risk of ground-water pollution from landdisposed wastes K. Unlu, Journal of Environmental Engineering - ,4SCE, 120(6), 1994, pp 1578-1597. A stochastic modeling approach for the migration of contaminants in soil and ground water is doveloped to assess the expected magnitude of contamination at receptors located downgradient from a waste pit. The model evaluates uncertainties in contaminant concentrations due to uncertainties in waste composition and hydrogeological properties of waste sites, and determines the exceedance probabilities of a specified concentration level at receptor points using Monte Carlo first-order and point-estimate methods. A comparison of the three error-analysis methods is performed to evaluate the efficiency and accuracy of the FO and PE methods relative to the MC method. (from Author) 957107 A fast coupled geochemical and transport program and appfications to waste leaching and contaminant transport C. Baverman, L. Moreno & I. Neretnieks, in: Groundwater quality: remediation and protection. Proc. conference, Prague, 1995, ed K. Kovar & J. Krasny, (IAHS; Publication, 225), 1995, pp 231-238. To assess what will happen to waste heaps and mine tailings in the future, knowledge about the processes controlling long term leaching is essential. As experiments cannot proceed for centuries computer simulations, based on results from experiments and field observations, can predict the long term reactions. A computer program, CHEMFRONTS, has been
957101 Numerical simulation of DNAPL-infiltration processes in saturated heterogeneous porous media J. Croise, R. Helmig & H. Sheta, in: Groundwater quality: remediation and protection. Proc. conference, Prague, 1995, ed K. Kovar & J. Krasny, (IAHS; publication, 225), 1995, pp 247-256. The infiltration of DNAPL into saturated heterogeneous porous media is studied by means of numerical simulations using the finite element method. Differences in parameterization of the constitutive relationships (capillary pressurerelative permeability-saturation relationships) are shown to have a significant impact on DNAPL-migration in homogeneous media. (from Authors)
957102 Enhanced seif-remediation of aquifers from oily pollutants J. M. Stopa & T. Solecki, in: Groundwater quality: remediation and protection. Proc. conference, Prague, 1995, ed K. Kovar & J. Krasny, (IAHS; Publication, 225), 1995, pp 439-448. Hydrocarbon pollution can exist in soil for many years. Moreover, it may migrate with groundwaters for long distances, being dangerous in drinking water, rivers, etc. For these reasons, hydrocarbons should be removed from groundwater. Many methods have been developed for this purpose. Such methods include: pumping using skimmers, air stripping, micro-biological and chemical methods. However, the first step is always to pump the pollution from groundwater. The pumping should be performed by specially designed systems utilizing the natural mechanisms of hydrocarbon migration in groundwaters. This method is termed 'enhanced self-remediation' (ESR). The advantages of this kind of system is that it can be made by the polluter to reduce the costs of operation, and it is neutral for the natural environment. This paper describes the main methods at design used by the authors. (from Authors)
957103 Quantification of hydrocarbon mineralization in a diesel fuel contaminated aquifer treated by in situ biorestoration D. Hunkeler, P. Hohener, A. Haner, T. Bregnard & J. Zeyer, in: Groundwater quality: remediation and protection. Proc. conference, Prague, 1995, ed K. Kovar & J. Krasny, (IAHS; Publication, 225), 1995, pp 421-430. A method is presented to quantify the mineralization of contaminants in a polluted aquifer by alkalinity, inorganic carbon and stable carbon isotope balances. This method is applied to a diesel fuel contaminated aquifer biorestored by infiltration of oxidants and nutrients using a groundwater recirculation system. The observed inorganic carbon production within the biologically active zone is larger than the corresponding calculated inorganic carbon production based on the consumption of electron a cceptors+(O2, NO~, SO~4-), production of reduced species (Mn 2+, Fe2 , H2S, CH4) and dissolution of carbonates. Stable carbon isotope measurements suggest that the additional inorganic carbon mainly originates from a source with a isotopic composition corresponding to hydrocarbons in mineral oil. (Authors)
317A
957104 The fate of dissolved creosote compounds in an intact fractured clay column K. Broholm, E. Arvin, A. Hansen, K. Hinsby & P. Jorgensen, in: Groundwater quality: remediation and protection. Proc. conference, Prague, 1995, ed K. Kovar & J. Kxasny, (IAHS; Publication, 225), 1995, pp 115-123. The fate of 16 different organics typical for creosote was studied under aerobic conditions in a large intact fractured clay column experiment. A simple transport model was applied to some of the data. It was possible to model the early part of the breakthrough curves for retarded organics (naphthalene, quinoline, and 2,4-dimethylphenol) but not the later part since the compounds were degraded. Retardation factors of 8, 9, and 8 for naphthalene, quinoline, and 2,4dimethylphenol, respectively were estimated. This column experiment revealed that transport of organics through fractured clay is an important process. It may in many cases cause groundwater contamination of aquifers, so far believed to be protected by overlying clay layers. (from Authors)
957105 A composite modeling approach for subsurface transport of degrading contaminants from land-disposal sites J. B. gool, P. S. Huyakorn, E. A. Sudicky & Z. A. Saleem, Journal of Contaminant Hydrology, 17(1), 1994, pp 69-90. A composite modeling approach is presented for simulating the three-dimensional (3-D) subsurface transport of dissolved contaminants with transformation products. The approach is based on vertical infiltration and contaminant transport in the unsaturated zone and 3-D groundwater flow and contaminant migration in the saturated zone. Model formulations and solution schemes are verified by comparison against a fully 3-D, variably saturated flow and transport code for a hypothetical problem which represents a typical landfill. The model is applied also to simulate a controlled release field experiment and the model predictions compare well with groundwater monitoring data for the site. (from Authors)
957106 Assessing risk of ground-water pollution from landdisposed wastes K. Unlu, Journal of Environmental Engineering - ,4SCE, 120(6), 1994, pp 1578-1597. A stochastic modeling approach for the migration of contaminants in soil and ground water is doveloped to assess the expected magnitude of contamination at receptors located downgradient from a waste pit. The model evaluates uncertainties in contaminant concentrations due to uncertainties in waste composition and hydrogeological properties of waste sites, and determines the exceedance probabilities of a specified concentration level at receptor points using Monte Carlo first-order and point-estimate methods. A comparison of the three error-analysis methods is performed to evaluate the efficiency and accuracy of the FO and PE methods relative to the MC method. (from Author) 957107 A fast coupled geochemical and transport program and appfications to waste leaching and contaminant transport C. Baverman, L. Moreno & I. Neretnieks, in: Groundwater quality: remediation and protection. Proc. conference, Prague, 1995, ed K. Kovar & J. Krasny, (IAHS; Publication, 225), 1995, pp 231-238. To assess what will happen to waste heaps and mine tailings in the future, knowledge about the processes controlling long term leaching is essential. As experiments cannot proceed for centuries computer simulations, based on results from experiments and field observations, can predict the long term reactions. A computer program, CHEMFRONTS, has been