Pathogen transport in groundwater systems: contrasts with traditional solute transport
Hunt, Randall J.; Johnson, William P.
2017-06-01
Water quality affects many aspects of water availability, from precluding use to societal perceptions of fit-for-purpose. Pathogen source and transport processes are drivers of water quality because they have been responsible for numerous outbreaks resulting in large economic losses due to illness and, in some cases, loss of life. Outbreaks result from very small exposure (e.g., less than 20 viruses) from very strong sources (e.g., trillions of viruses shed by a single infected individual). Thus, unlike solute contaminants, an acute exposure to a very small amount of contaminated water can cause immediate adverse health effects. Similarly, pathogens are larger than solutes. Thus, interactions with surfaces and settling become important even as processes important for solutes such as diffusion become less important. These differences are articulated in "Colloid Filtration Theory", a separate branch of pore-scale transport. Consequently, understanding pathogen processes requires changes in how groundwater systems are typically characterized, where the focus is on the leading edges of plumes and preferential flow paths, even if such features move only a very small fraction of the aquifer flow. Moreover, the relatively short survival times of pathogens in the subsurface require greater attention to very fast (<10 year) flow paths. By better understanding the differences between pathogen and solute transport mechanisms discussed here, a more encompassing view of water quality and source water protection is attained. With this more holistic view and theoretical understanding, better evaluations can be made regarding drinking water vulnerability and the relation between groundwater and human health.
Pathogen transport in groundwater systems: contrasts with traditional solute transport
Hunt, Randall J.; Johnson, William P.
2016-12-01
Water quality affects many aspects of water availability, from precluding use to societal perceptions of fit-for-purpose. Pathogen source and transport processes are drivers of water quality because they have been responsible for numerous outbreaks resulting in large economic losses due to illness and, in some cases, loss of life. Outbreaks result from very small exposure (e.g., less than 20 viruses) from very strong sources (e.g., trillions of viruses shed by a single infected individual). Thus, unlike solute contaminants, an acute exposure to a very small amount of contaminated water can cause immediate adverse health effects. Similarly, pathogens are larger than solutes. Thus, interactions with surfaces and settling become important even as processes important for solutes such as diffusion become less important. These differences are articulated in "Colloid Filtration Theory", a separate branch of pore-scale transport. Consequently, understanding pathogen processes requires changes in how groundwater systems are typically characterized, where the focus is on the leading edges of plumes and preferential flow paths, even if such features move only a very small fraction of the aquifer flow. Moreover, the relatively short survival times of pathogens in the subsurface require greater attention to very fast (<10 year) flow paths. By better understanding the differences between pathogen and solute transport mechanisms discussed here, a more encompassing view of water quality and source water protection is attained. With this more holistic view and theoretical understanding, better evaluations can be made regarding drinking water vulnerability and the relation between groundwater and human health.
[Solute transport modeling application in groundwater organic contaminant source identification].
Wang, Shu-Fang; Wang, Li-Ya; Wang, Xiao-Hong; Lin, Pei; Liu, Jiu-Rong; Xin, Bao-Dong; He, Guo-Ping
2012-03-01
Investigation and numerical simulation, based on RT3D (reactive transport in 3-dimensions)were used to identify the source of tetrachloroethylene (PCE) and trichloroethylene (TCE) in the groundwater of a city in the north of China and reverse the input intensity. Multiple regressions were applied to analyze the influenced factors of input intensity of PCE and TCE using Stepwise function in Matlab. The results indicate that the factories and industries are the source of the PCE and TCE in groundwater. Natural attenuation was identified and the natural attenuation rates are 93.15%, 61.70% and 61.00% for PCE, and 70.05%, 73.66% and 63.66% for TCE in 173 days. The 4 source points identified by the simulation have released 0.910 6 kg PCE and 95.693 8 kg TCE during the simulation period. The regression analysis results indicate that local precipitation and the thickness of vadose zone are the main factors influencing organic solution transporting from surface to groundwater. The PCE and TCE concentration are found to be 0 and 5 mg x kg(-1) from surface to 35 cm in vadose zone. All above results suggest that PCE and TCE in groundwater are from the source in the surface. Natural attenuation occurred when PCE and TCE transporting from the surface to groundwater, and the rest was transported to groundwater through vadose zone. Local precipitation was one of the critical factors influencing the transportation of PCE and TCE to aquifer through sand, pebble and gravel of the Quaternary.
Groundwater and solute transport modeling at Hyporheic zone of upper part Citarum River
Iskandar, Irwan; Farazi, Hendy; Fadhilah, Rahmat; Purnandi, Cipto; Notosiswoyo, Sudarto
2017-06-01
Groundwater and surface water interaction is an interesting topic to be studied related to the water resources and environmental studies. The study of interaction between groundwater and river water at the Upper Part Citarum River aims to know the contribution of groundwater to the river or reversely and also solute transport of dissolved ions between them. Analysis of drill logs, vertical electrical sounding at the selected sections, measurement of dissolved ions, and groundwater modeling were applied to determine the flow and solute transport phenomena at the hyporheic zone. It showed the hyporheic zone dominated by silt and clay with hydraulic conductivity range from 10-4∼10-8 m/s. The groundwater flowing into the river with very low gradient and it shows that the Citarum River is a gaining stream. The groundwater modeling shows direct seepage of groundwater into the Citarum River is only 186 l/s, very small compared to the total discharge of the river. Total dissolved ions of the groundwater ranged from 200 to 480 ppm while the river water range from 200 to 2,000 ppm. Based on solute transport modeling it indicates dissolved ions dispersion of the Citarum River into groundwater may occur in some areas such as Bojongsoang-Dayeuh Kolot and Nanjung. This situation would increase the dissolved ions in groundwater in the region due to the contribution of the Citarum River. The results of the research can be a reference for further studies related to the mechanism of transport of the pollutants in the groundwater around the Citarum River.
Numerical study of wave effects on groundwater flow and solute transport in a laboratory beach
Geng, Xiaolong; Boufadel, Michel C.; Xia, Yuqiang; Li, Hailong; Zhao, Lin; Jackson, Nancy L.; Miller, Richard S.
2014-09-01
A numerical study was undertaken to investigate the effects of waves on groundwater flow and associated inland-released solute transport based on tracer experiments in a laboratory beach. The MARUN model was used to simulate the density-dependent groundwater flow and subsurface solute transport in the saturated and unsaturated regions of the beach subjected to waves. The Computational Fluid Dynamics (CFD) software, Fluent, was used to simulate waves, which were the seaward boundary condition for MARUN. A no-wave case was also simulated for comparison. Simulation results matched the observed water table and concentration at numerous locations. The results revealed that waves generated seawater-groundwater circulations in the swash and surf zones of the beach, which induced a large seawater-groundwater exchange across the beach face. In comparison to the no-wave case, waves significantly increased the residence time and spreading of inland-applied solutes in the beach. Waves also altered solute pathways and shifted the solute discharge zone further seaward. Residence Time Maps (RTM) revealed that the wave-induced residence time of the inland-applied solutes was largest near the solute exit zone to the sea. Sensitivity analyses suggested that the change in the permeability in the beach altered solute transport properties in a nonlinear way. Due to the slow movement of solutes in the unsaturated zone, the mass of the solute in the unsaturated zone, which reached up to 10% of the total mass in some cases, constituted a continuous slow release of solutes to the saturated zone of the beach. This means of control was not addressed in prior studies.
Directory of Open Access Journals (Sweden)
S.M. Ghoraba
2013-06-01
Full Text Available Groundwater contamination is a major problem related strongly to both; protection of environment and the need of water. In the present study groundwater quality was investigated in the central part of the Nile Delta (El-Gharbiya Governorate. El-Gharbiya Governorate is an agricultural land and its densely populated area inhabited, includes small communities which totally not served by public sewers. Hydrochemical analyses were used to assess the quality of water in samples taken from the canals, drains and groundwater. A laboratory study and mathematical modeling works were presented. Two numerical computer models by the applying of finite difference method were adopted. Both models deal with the flow as a three-dimensional and unsteady. Results obtained include determining the levels of water and the values of solute concentration and distribution of it in the region at different times. The groundwater model MODFLOW was used to deal with the hydrodynamics of the flow through porous media. A solute transport model which can be communicated with MODFLOW through data files MT3DMS, was used to solve the problem of contaminants transport and the change of their concentrations with time. A proposed groundwater remediation scheme by using group of extraction wells was suggested at Birma region where the concentration values of ammonium contaminant are the up most according to hydrochemical analyses results. Proposed scenario for cleaning is to use a set of wells to pump contaminated groundwater extraction for treatment and reused to irrigation.
Park, D. K.; Bae, G. O.; Joun, W.; Park, B. H.; Park, J.; Park, I.; Lee, K. K.
2015-12-01
The GWHP system uses a stable temperature of groundwater for cooling and heating in buildings and thus has been known as one of the most energy-saving and cost-efficient renewable energy techniques. A GWHP facility was installed at an island located at the confluence of North Han and South Han rivers, Korea. Because of well-developed alluvium, the aquifer is suitable for application of this system, extracting and injecting a large amount of groundwater. However, the numerical experiments under various operational conditions showed that it could be vulnerable to thermal interference due to the highly permeable gravel layer, as a preferential path of thermal plume migration, and limited space for well installation. Thus, regional groundwater flow must be an important factor of consideration for the efficient operation under these conditions but was found to be not simple in this site. While the groundwater level in this site totally depends on the river stage control of Paldang dam, the direction and velocity of the regional groundwater flow, observed using the colloidal borescope, have been changed hour by hour with the combined flows of both the rivers. During the pumping and injection tests, the water discharges in Cheongpyeong dam affected their respective results. Moreover, the measured NO3-N concentrations might imply the effect of agricultural activities around the facility on the groundwater quality along the regional flow. It is obvious that the extraction and injection of groundwater during the facility operation will affect the fate of the agricultural contaminants. Particularly, the gravel layer must also be a main path for contaminant migration. The simulations for contaminant transport during the facility operation showed that the operation strategy for only thermal efficiency could be unsafe and unstable in respect of groundwater quality. All these results concluded that the integrated approach on groundwater flow and heat/solute transport is necessary
Submarine groundwater discharge and solute transport under a transgressive barrier island
Evans, Tyler B.; Wilson, Alicia M.
2017-04-01
Many recent investigations of groundwater dynamics in beaches employed groundwater models that assumed isotropic, numerically-convenient hydrogeological conditions. Real beaches exhibit local variability with respect to stratigraphy, sediment grain size and associated topographic profile, so that groundwater flow may diverge significantly from idealized models. We used a combination of hydrogeologic field methods and a variable-density, saturated-unsaturated, transient groundwater flow model to investigate SGD and solute transport under Cabretta Beach, a small transgressive barrier island seaward of Sapelo Island, Georgia. We found that the inclusion of real beach heterogeneity drove important deviations from predictions based on theoretical beaches. Cabretta Beach sustained a stronger upper saline plume than predicted due to the presence of a buried silty mud layer beneath the surface. Infiltration of seawater was greater for neap tides than for spring tides due to variations in beach slope. The strength of the upper saline plume was greatest during spring tides, contrary to recent model predictions. The position and width of the upper saline plume was highly dynamic through the lunar cycle. Our results suggest that field measurements of salinity gradients may be useful for estimating rates of tidally and density driven recirculation through the beach. Finally, our results indicate that several important biogeochemical cycles recently studied at Cabretta Beach were heavily influenced by groundwater flow and associated solute transport.
Effects of alongshore morphology on groundwater flow and solute transport in a nearshore aquifer
Zhang, Ying; Li, Ling; Erler, Dirk V.; Santos, Isaac; Lockington, David
2016-02-01
Variations of beach morphology in both the cross-shore and alongshore directions, associated with tidal creeks, are common at natural coasts, as observed at a field site on the east coast of Rarotonga, Cook Islands. Field investigations and three-dimensional (3-D) numerical simulations were conducted to study the nearshore groundwater flow and solute transport in such a system. The results show that the beach morphology, combined with tides, induced a significant alongshore flow and modified local pore water circulation and salt transport in the intertidal zone substantially. The bathymetry and hydraulic head of the creek enabled further and more rapid landward intrusion of seawater along the creek than in the aquifer, which created alongshore hydraulic gradient and solute concentration gradient to drive pore water flow and salt transport in the alongshore direction within the aquifer. The effects of the creek led to the formation of a saltwater plume in groundwater at an intermediate depth between fresher water zones on a cross-shore transect. The 3-D pore water flow in the nearshore zone was also complicated by the landward hydraulic head condition, resulting in freshwater drainage across the inland section of the creek while seawater infiltrating the seaward section. These results provided new insights into the complexity, intensity, and time scales of mixing among fresh groundwater, recirculating seawater and creek water in three dimensions. The 3-D characteristics of nearshore pore water flow and solute transport have important implications for studies of submarine groundwater discharge and associated chemical input to the coastal sea, and for evaluation of the beach habitat conditions.
Sanskrityayn, Abhishek; Suk, Heejun; Kumar, Naveen
2017-04-01
In this study, analytical solutions of one-dimensional pollutant transport originating from instantaneous and continuous point sources were developed in groundwater and riverine flow using both Green's Function Method (GFM) and pertinent coordinate transformation method. Dispersion coefficient and flow velocity are considered spatially and temporally dependent. The spatial dependence of the velocity is linear, non-homogeneous and that of dispersion coefficient is square of that of velocity, while the temporal dependence is considered linear, exponentially and asymptotically decelerating and accelerating. Our proposed analytical solutions are derived for three different situations depending on variations of dispersion coefficient and velocity, respectively which can represent real physical processes occurring in groundwater and riverine systems. First case refers to steady solute transport situation in steady flow in which dispersion coefficient and velocity are only spatially dependent. The second case represents transient solute transport in steady flow in which dispersion coefficient is spatially and temporally dependent while the velocity is spatially dependent. Finally, the third case indicates transient solute transport in unsteady flow in which both dispersion coefficient and velocity are spatially and temporally dependent. The present paper demonstrates the concentration distribution behavior from a point source in realistically occurring flow domains of hydrological systems including groundwater and riverine water in which the dispersivity of pollutant's mass is affected by heterogeneity of the medium as well as by other factors like velocity fluctuations, while velocity is influenced by water table slope and recharge rate. Such capabilities give the proposed method's superiority about application of various hydrological problems to be solved over other previously existing analytical solutions. Especially, to author's knowledge, any other solution doesn
Parkhurst, David L.; Kipp, Kenneth L.; Charlton, Scott R.
2010-01-01
The computer program PHAST (PHREEQC And HST3D) simulates multicomponent, reactive solute transport in three-dimensional saturated groundwater flow systems. PHAST is a versatile groundwater flow and solute-transport simulator with capabilities to model a wide range of equilibrium and kinetic geochemical reactions. The flow and transport calculations are based on a modified version of HST3D that is restricted to constant fluid density and constant temperature. The geochemical reactions are simulated with the geochemical model PHREEQC, which is embedded in PHAST. Major enhancements in PHAST Version 2 allow spatial data to be defined in a combination of map and grid coordinate systems, independent of a specific model grid (without node-by-node input). At run time, aquifer properties are interpolated from the spatial data to the model grid; regridding requires only redefinition of the grid without modification of the spatial data. PHAST is applicable to the study of natural and contaminated groundwater systems at a variety of scales ranging from laboratory experiments to local and regional field scales. PHAST can be used in studies of migration of nutrients, inorganic and organic contaminants, and radionuclides; in projects such as aquifer storage and recovery or engineered remediation; and in investigations of the natural rock/water interactions in aquifers. PHAST is not appropriate for unsaturated-zone flow, multiphase flow, or density-dependent flow. A variety of boundary conditions are available in PHAST to simulate flow and transport, including specified-head, flux (specified-flux), and leaky (head-dependent) conditions, as well as the special cases of rivers, drains, and wells. Chemical reactions in PHAST include (1) homogeneous equilibria using an ion-association or Pitzer specific interaction thermodynamic model; (2) heterogeneous equilibria between the aqueous solution and minerals, ion exchange sites, surface complexation sites, solid solutions, and gases; and
Parkhurst, David L.; Kipp, Kenneth L.; Engesgaard, Peter; Charlton, Scott R.
2004-01-01
The computer program PHAST simulates multi-component, reactive solute transport in three-dimensional saturated ground-water flow systems. PHAST is a versatile ground-water flow and solute-transport simulator with capabilities to model a wide range of equilibrium and kinetic geochemical reactions. The flow and transport calculations are based on a modified version of HST3D that is restricted to constant fluid density and constant temperature. The geochemical reactions are simulated with the geochemical model PHREEQC, which is embedded in PHAST. PHAST is applicable to the study of natural and contaminated ground-water systems at a variety of scales ranging from laboratory experiments to local and regional field scales. PHAST can be used in studies of migration of nutrients, inorganic and organic contaminants, and radionuclides; in projects such as aquifer storage and recovery or engineered remediation; and in investigations of the natural rock-water interactions in aquifers. PHAST is not appropriate for unsaturated-zone flow, multiphase flow, density-dependent flow, or waters with high ionic strengths. A variety of boundary conditions are available in PHAST to simulate flow and transport, including specified-head, flux, and leaky conditions, as well as the special cases of rivers and wells. Chemical reactions in PHAST include (1) homogeneous equilibria using an ion-association thermodynamic model; (2) heterogeneous equilibria between the aqueous solution and minerals, gases, surface complexation sites, ion exchange sites, and solid solutions; and (3) kinetic reactions with rates that are a function of solution composition. The aqueous model (elements, chemical reactions, and equilibrium constants), minerals, gases, exchangers, surfaces, and rate expressions may be defined or modified by the user. A number of options are available to save results of simulations to output files. The data may be saved in three formats: a format suitable for viewing with a text editor; a
Bobo, A. M.; Boufadel, M. C.; Abdollahi Nasab, A.
2009-12-01
We investigated beach hydraulics in a gravel beach on Eleanor Island, Prince William Sound, Alaska that was previously polluted with the Exxon Valdez oil spill in 1989. The beach contains trace amounts of oil such that they don’t affect beach hydraulics. Measurements of water pressure and salinity were analyzed and simulated using the model SUTRA (Saturated-Unsaturated Groundwater Flow and Solute Transport). The results indicated that the beach consists of two layers with contrasting hydraulic properties: an upper layer with a hydraulic conductivity of 10-2 m/s, and a lower layer with a hydraulic conductivity of 10-5 m/s. The presence of the layer of low hydraulic conductivity constrained the fall of the water table resulting in a water table fluctuation that is almost independent of distance from the shoreline. This is unlike previous studies, which occurred in sandy beaches, and where the fluctuation decreased going landward. The water table remained above the layers’ interface, which suggests that the oil did not penetrate the lower layer. This could explain the presence of only tracer amount of oil in the beach. A sudden seaward increase of the slope of the two layers’ interface resulted in water leaving the lower layer near the mid-intertidal zone, and draining to the sea through the upper layer. This created the effect of a hydraulic rupture separating the hydraulics in the seaward portion of the beach from the rest of beach, especially at low tide.
Langevin, Christian D.
2009-01-01
SEAWAT is a MODFLOW-based computer program designed to simulate variable-density groundwater flow coupled with multi-species solute and heat transport. The program has been used for a wide variety of groundwater studies including saltwater intrusion in coastal aquifers, aquifer storage and recovery in brackish limestone aquifers, and brine migration within continental aquifers. SEAWAT is relatively easy to apply because it uses the familiar MODFLOW structure. Thus, most commonly used pre- and post-processors can be used to create datasets and visualize results. SEAWAT is a public domain computer program distributed free of charge by the U.S. Geological Survey.
Krabbenhoft, David P.; Anderson, Mary P.; Bowser, Carl J.
1990-01-01
A three-dimensional groundwater flow and solute transport model was calibrated to a plume of water described by measurements of δ18O and used to calculate groundwater inflow and outflow rates at a lake in northern Wisconsin. The flow model was calibrated to observed hydraulic gradients and estimated recharge rates. Calibration of the solute transport submodel to the configuration of a stable isotope (18O) plume in the contiguous aquifer on the downgradient side of the lake provides additional data to constrain the model. A good match between observed and simulated temporal variations in plume configuration indicates that the model closely simulated the dynamics of the real system. The model provides information on natural variations of rates of groundwater inflow, lake water outflow, and recharge to the water table. Inflow and outflow estimates compare favorably with estimates derived by the isotope mass balance method (Krabbenhoft et al., this issue). Model simulations agree with field observations that show groundwater inflow rates are more sensitive to seasonal variations in recharge than outflow.
Stanko, Z.; Boyce, S. E.; Yeh, W. W. G.
2015-12-01
Model reduction techniques using proper orthogonal decomposition (POD) have been very effective in applications to confined groundwater flow models. These techniques consist of performing a projection of the solution of the full model onto a reduced basis. POD combined with the snapshot approach has been successfully applied to highly discretized linear models. In many cases, the reduced model is orders of magnitude smaller than the full model and runs 1,000 times faster. For nonlinear models, such as the unconfined groundwater flow, direct application of POD requires additional calls to the full model to generate additional snapshots. This is time consuming and increases the dimension of the reduced model. The discrete empirical interpolation method (DEIM) is a technique that avoids the additional full model calls and captures the dynamics of the nonlinear term while reducing the dimensions. Here, POD and DEIM are combined to reduce both the nonlinear unconfined groundwater flow and solute transport equations. To prove the concept, simple one-dimensional models are created for MODFLOW and MT3DMS separately. The dual approach is then tested on a density-dependent flow and transport simulation using the LMT package developed for MODFLOW. For each iteration of the nonlinear flow solver and the transport solver, the respective reduced models are solved instead. Numerical experiments show that significant reduction is obtainable before errors become too large. This method is well suited for a coastal aquifer seawater intrusion scenario, where nonlinearities only exist in small subregions of the model domain. A fine discretization can be utilized and POD will effectively eliminate unnecessary parameterization by projecting the full model system matrix onto a subspace with fewer column dimensions. DEIM can then reduce the row dimension of the original system by using only those state variable nodes with the most influence. This combined approach allows for full
A NEW NUMERICAL METHOD FOR GROUNDWATER FIOW AND SOLUTE TRANSPORT USING VELOCITY FIELD
Institute of Scientific and Technical Information of China (English)
ZHANG Qian-fei; LAN Shou-qi; WANG Yan-ming; XU Yong-fu
2008-01-01
A new numerical method for groundwater flow analysis was introduced to estimate simultaneously velocity vectors and water pressure head. The method could be employed to handle the vertical flow under variably saturated conditions and for horizontal flow as well. The method allows for better estimation of velocities at the element nodes which can be used as direct input to transport models. The advection-dispersion process was treated by the Eulerian-Lagrangian approach with particle tracking technique using the velocities at FEM nodes. The method was verified with the classical one dimensional model and applied to simulate contaminant transport process through a slurry wall as a barrier to prevent leachate pollution from a sanitary landfill.
Bailey, Ryan T.; Morway, Eric D.; Niswonger, Richard G.; Gates, Timothy K.
2013-01-01
A numerical model was developed that is capable of simulating multispecies reactive solute transport in variably saturated porous media. This model consists of a modified version of the reactive transport model RT3D (Reactive Transport in 3 Dimensions) that is linked to the Unsaturated-Zone Flow (UZF1) package and MODFLOW. Referred to as UZF-RT3D, the model is tested against published analytical benchmarks as well as other published contaminant transport models, including HYDRUS-1D, VS2DT, and SUTRA, and the coupled flow and transport modeling system of CATHY and TRAN3D. Comparisons in one-dimensional, two-dimensional, and three-dimensional variably saturated systems are explored. While several test cases are included to verify the correct implementation of variably saturated transport in UZF-RT3D, other cases are included to demonstrate the usefulness of the code in terms of model run-time and handling the reaction kinetics of multiple interacting species in variably saturated subsurface systems. As UZF1 relies on a kinematic-wave approximation for unsaturated flow that neglects the diffusive terms in Richards equation, UZF-RT3D can be used for large-scale aquifer systems for which the UZF1 formulation is reasonable, that is, capillary-pressure gradients can be neglected and soil parameters can be treated as homogeneous. Decreased model run-time and the ability to include site-specific chemical species and chemical reactions make UZF-RT3D an attractive model for efficient simulation of multispecies reactive transport in variably saturated large-scale subsurface systems.
Simulation of ground-water flow and solute transport in the Glen Canyon aquifer, East-Central Utah
Freethey, Geoffrey W.; Stolp, Bernard J.
2010-01-01
The extraction of methane from coal beds in the Ferron coal trend in central Utah started in the mid-1980s. Beginning in 1994, water from the extraction process was pressure injected into the Glen Canyon aquifer. The lateral extent of the aquifer that could be affected by injection is about 7,600 square miles. To address regional-scale effects of injection over a decadal time frame, a conceptual model of ground-water movement and transport of dissolved solids was formulated. A numerical model that incorporates aquifer concepts was then constructed and used to simulate injection. The Glen Canyon aquifer within the study area is conceptualized in two parts-an active area of ground-water flow and solute transport that exists between recharge areas in the San Rafael Swell and Desert, Waterpocket Fold, and Henry Mountains and discharge locations along the Muddy, Dirty Devil, San Rafael, and Green Rivers. An area of little or negligible ground-water flow exists north of Price, Utah, and beneath the Wasatch Plateau. Pressurized injection of coal-bed methane production water occurs in this area where dissolved-solids concentrations can be more than 100,000 milligrams per liter. Injection has the potential to increase hydrologic interaction with the active flow area, where dissolved-solids concentrations are generally less than 3,000 milligrams per liter. Pressurized injection of coal-bed methane production water in 1994 initiated a net addition of flow and mass of solutes into the Glen Canyon aquifer. To better understand the regional scale hydrologic interaction between the two areas of the Glen Canyon aquifer, pressurized injection was numerically simulated. Data constraints precluded development of a fully calibrated simulation; instead, an uncalibrated model was constructed that is a plausible representation of the conceptual flow and solute-transport processes. The amount of injected water over the 36-year simulation period is about 25,000 acre-feet. As a result
Foose, Gary J
2010-01-01
New adaptations of analytical equations for predicting the impact of solute transport through composite landfill liners on groundwater quality for steady-state conditions are presented. Analytical equations are developed for evaluating average concentration and mass flow rate in an underlying aquifer resulting from diffusion of volatile organic compounds (VOCs) through intact composite liners and transport of inorganic constituents through defects in composite liners. The equations are applied to evaluate the effectiveness and equivalency of composite liners having either a 0.6 m-thick compacted soil liner or a 6.5 mm-thick geosynthetic clay liner (GCL) overlying an intermediate attenuation layer and an aquifer having horizontal flow. Example analyses for designing composite liners meeting particular performance criteria are also provided. The analytical equations are relatively simple to apply and can be used for preliminary design and analysis, to evaluate experimental results, and to possibly verify more complex numerical models for evaluating the impact of landfills on groundwater quality if consistency of the assumptions of the analytical equations and the more complex numerical models can be specified.
Gusyev, M. A.; D. Abrams; Toews, M. W.; U. Morgenstern; M. K. Stewart
2014-01-01
The purpose of this study is to simulate tritium concentrations and groundwater transit times in river water with particle-tracking (MODPATH) and compare them to solute transport (MT3DMS) simulations. Tritium measurements in river water are valuable for the calibration of particle-tracking and solute transport models as well as for understanding of watershed storage dynamics. In a previous study, we simulated tritium concentrations in river water of the western Lake Taupo...
Lee, Jonghyun; Rolle, Massimo; Kitanidis, Peter K
2017-09-15
Most recent research on hydrodynamic dispersion in porous media has focused on whole-domain dispersion while other research is largely on laboratory-scale dispersion. This work focuses on the contribution of a single block in a numerical model to dispersion. Variability of fluid velocity and concentration within a block is not resolved and the combined spreading effect is approximated using resolved quantities and macroscopic parameters. This applies whether the formation is modeled as homogeneous or discretized into homogeneous blocks but the emphasis here being on the latter. The process of dispersion is typically described through the Fickian model, i.e., the dispersive flux is proportional to the gradient of the resolved concentration, commonly with the Scheidegger parameterization, which is a particular way to compute the dispersion coefficients utilizing dispersivity coefficients. Although such parameterization is by far the most commonly used in solute transport applications, its validity has been questioned. Here, our goal is to investigate the effects of heterogeneity and mass transfer limitations on block-scale longitudinal dispersion and to evaluate under which conditions the Scheidegger parameterization is valid. We compute the relaxation time or memory of the system; changes in time with periods larger than the relaxation time are gradually leading to a condition of local equilibrium under which dispersion is Fickian. The method we use requires the solution of a steady-state advection-dispersion equation, and thus is computationally efficient, and applicable to any heterogeneous hydraulic conductivity K field without requiring statistical or structural assumptions. The method was validated by comparing with other approaches such as the moment analysis and the first order perturbation method. We investigate the impact of heterogeneity, both in degree and structure, on the longitudinal dispersion coefficient and then discuss the role of local dispersion
Task force on modelling of groundwater flow and transport of solutes. Task 5 Summary report
Energy Technology Data Exchange (ETDEWEB)
Rhen, Ingvar [SWECO VIAK AB, Goeteborg (Sweden); Smellie, John [Conterra AB, Uppsala (Sweden)
2003-02-01
The Aespoe Hard Rock Laboratory is located in the Simpevarp area, southeast Sweden, some 35 km north of Oskarshamn. Construction of the underground laboratory commenced in 1990 and was completed in 1995, consisting of a 3.6 km. long tunnel excavated in crystalline rock to a depth of approximately 460 m. Prior to, during and subsequent to completion, research concerning the deep geological disposal of nuclear waste in fractured crystalline rock has been carried out. Central to this research has been the characterisation of the groundwater flow system and the chemistry of the groundwaters at Aespoe prior to excavation (Pre-investigation Phase) and subsequently to monitor changes in these parameters during the evolution of laboratory construction (Construction Phase). The principle aim of the Aespoe Task 5 modelling exercise has been to compare and ultimately integrate hydrogeochemistry and hydrogeology using the input data from the pre-investigation and construction phases. The main objectives were: to assess the consistency of groundwater-flow models and hydrogeochemical mixing-reaction models through integration and comparison of hydraulic and hydrogeochemical data obtained before and during tunnel construction, and to develop a procedure for integration of hydrological and hydrogeochemical information which could be used for disposal site assessments. Task 5 commenced in 1998 and was finalised in 2002. Participating modelling teams in the project represented ANDRA (France; three modelling teams - ANTEA, ITASCA, CEA), BMWi/BGR (Germany), ENRESA (Spain), JNC (Japan), CRIEPI (Japan), Posiva (Finland) and SKB (Sweden; two modelling teams - CFE and Intera (now GeoPoint)). Experience from Task 5 has highlighted several important aspects for site investigations facilitating the possibilities for mathematically integrated modelling and consistency checks that should be taken into account for future repository performance assessments. Equally important is that Task 5 has
Transient transport of reactive and non-reactive solutes in groundwater
Fares, Y. R.; Giacobbe, D.
2004-06-01
A numerical model capable of predicting the transient changes in concentration levels of a solute along a homogeneous aquifer system is presented. The advection-dispersion equation (ADE) is utilised in predicting the concentration levels for cases of continuous and instantaneous release modes. The Crank-Nicholson equation is employed in the presented finite difference model. The numerical calculations are carried out using the implicit Gauss-Seidel method with over- and under-relaxation coefficients depending on the state of convergence. The correction terms resulting from the removal of zero- and first-order truncation errors in the ADE with a reaction term have significantly improved the performance of the numerical scheme. Comparisons between the numerically predicted concentrations with analytical and measured values were carried out for cases of non-reactive (tracer) and reactive (organic) solutes with continuous injection in homogeneous isotropic soils. The overshooting problems experienced in the numerical calculations are minimised by refining the finite grid size. The analysis of results has shown that the model can produce reliable simulations for cases of non-reactive solutes. While for the case of solutes undergoing adsorption, accurate concentrations can be predicted by adjusting the influent pore water velocity through the use of a retardation factor, which is suitable for aquifers with low organic carbon content and undergoing hydrophobic partitioning.
Simmons, Craig; Narayan, Kumar; Woods, Juliette; Herczeg, Andrew
2002-03-01
Saline groundwater and drainage effluent from irrigation are commonly stored in some 200 natural and artificial saline-water disposal basins throughout the Murray-Darling Basin of Australia. Their impact on underlying aquifers and the River Murray, one of Australia's major water supplies, is of serious concern. In one such scheme, saline groundwater is pumped into Lake Mourquong, a natural groundwater discharge complex. The disposal basin is hydrodynamically restricted by low-permeability lacustrine clays, but there are vulnerable areas in the southeast where the clay is apparently missing. The extent of vertical and lateral leakage of basin brines and the processes controlling their migration are examined using (1) analyses of chloride and stable isotopes of water (2H/1H and 18O/16O) to infer mixing between regional groundwater and lake water, and (2) the variable-density groundwater flow and solute-transport code SUTRA. Hydrochemical results indicate that evaporated disposal water has moved at least 100 m in an easterly direction and that there is negligible movement of brines in a southerly direction towards the River Murray. The model is used to consider various management scenarios. Salt-load movement to the River Murray was highest in a "worst-case" scenario with irrigation employed between the basin and the River Murray. Present-day operating conditions lead to little, if any, direct movement of brine from the basin into the river. Résumé. Les eaux souterraines salées et les effluents de drainage de l'irrigation sont stockés dans environ 200 bassins naturels ou artificiels destinés à retenir les eaux salines dans tout le bassin de Murray-Darling, en Australie. Leur impact sur les aquifères sous-jacents et sur la rivière Murray, l'une des principales ressources en eau d'Australie, constitue un problème grave. Dans une telle situation, les eaux souterraines salines sont pompées dans le lac Mourquong, complexe dans lequel les nappes se d
Solutions Remediate Contaminated Groundwater
2010-01-01
During the Apollo Program, NASA workers used chlorinated solvents to clean rocket engine components at launch sites. These solvents, known as dense non-aqueous phase liquids, had contaminated launch facilities to the point of near-irreparability. Dr. Jacqueline Quinn and Dr. Kathleen Brooks Loftin of Kennedy Space Center partnered with researchers from the University of Central Florida's chemistry and engineering programs to develop technology capable of remediating the area without great cost or further environmental damage. They called the new invention Emulsified Zero-Valent Iron (EZVI). The groundwater remediation compound is cleaning up polluted areas all around the world and is, to date, NASA's most licensed technology.
Michael, Holly A.; Khan, Mahfuzur R.
2016-12-01
Aquifer heterogeneity presents a primary challenge in predicting the movement of solutes in groundwater systems. The problem is particularly difficult on very large scales, across which permeability, chemical properties, and pumping rates may vary by many orders of magnitude and data are often sparse. An example is the fluvio-deltaic aquifer system of Bangladesh, where naturally-occurring arsenic (As) exists over tens of thousands of square kilometers in shallow groundwater. Millions of people in As-affected regions rely on deep (≥150 m) groundwater as a safe source of drinking water. The sustainability of this resource has been evaluated with models using effective properties appropriate for a basin-scale contamination problem, but the extent to which preferential flow affects the timescale of downward migration of As-contaminated shallow groundwater is unknown. Here we embed detailed, heterogeneous representations of hydraulic conductivity (K), pumping rates, and sorptive properties (Kd) within a basin-scale numerical groundwater flow and solute transport model to evaluate their effects on vulnerability and deviations from simulations with homogeneous representations in two areas with different flow systems. Advective particle tracking shows that heterogeneity in K does not affect average travel times from shallow zones to 150 m depth, but the travel times of the fastest 10% of particles decreases by a factor of ∼2. Pumping distributions do not strongly affect travel times if irrigation remains shallow, but increases in the deep pumping rate substantially reduce travel times. Simulation of advective-dispersive transport with sorption shows that deep groundwater is protected from contamination over a sustainable timeframe (>1000 y) if the spatial distribution of Kd is uniform. However, if only low-K sediments sorb As, 30% of the aquifer is not protected. Results indicate that sustainable management strategies in the Bengal Basin should consider impacts of both
Rogiers, Bart
2015-04-01
Since a few years, an increasing number of contributed R packages is becoming available, in the field of hydrology. Hydrological time series analysis packages, lumped conceptual rainfall-runoff models, distributed hydrological models, weather generators, and different calibration and uncertainty estimation methods are all available. Also a few packages are available for solving partial differential equations. Subsurface hydrological modelling is however still seldomly performed in R, or with codes interfaced with R, despite the fact that excellent geostatistical packages, model calibration/inversion options and state-of-the-art visualization libraries are available. Moreover, other popular scientific programming languages like matlab and python have packages for pre- and post-processing files of MODFLOW (Harbaugh 2005) and MT3DMS (Zheng 2010) models. To fill this gap, we present here the development versions of the RMODFLOW and RMT3DMS packages, which allow pre- and post-processing MODFLOW and MT3DMS input and output files from within R. File reading and writing functions are currently available for different packages, and plotting functions are foreseen making use of the ggplot2 package (plotting system based on the grammar of graphics; Wickham 2009). The S3 generic-function object oriented programming style is used for this. An example is provided, making modifications to an existing model, and visualization of the model output. References Harbaugh, A. (2005). MODFLOW-2005: The US Geological Survey Modular Ground-water Model--the Ground-water Flow Process, U.S. Geological Survey Techniques and Methods 6-A16 (p. 253). Wickham, H. (2009). ggplot2: elegant graphics for data analysis. Springer New York, 2009. Zheng, C. (2010). MT3DMS v5.3, a modular three-dimensional multispecies transport model for simulation of advection, dispersion and chemical reactions of contaminants in groundwater systems. Supplemental User's Guide. (p. 56).
Voss, Clifford I.; Provost, A.M.
2002-01-01
SUTRA (Saturated-Unsaturated Transport) is a computer program that simulates fluid movement and the transport of either energy or dissolved substances in a subsurface environment. This upgraded version of SUTRA adds the capability for three-dimensional simulation to the former code (Voss, 1984), which allowed only two-dimensional simulation. The code employs a two- or three-dimensional finite-element and finite-difference method to approximate the governing equations that describe the two interdependent processes that are simulated: 1) fluid density-dependent saturated or unsaturated ground-water flow; and 2) either (a) transport of a solute in the ground water, in which the solute may be subject to: equilibrium adsorption on the porous matrix, and both first-order and zero-order production or decay; or (b) transport of thermal energy in the ground water and solid matrix of the aquifer. SUTRA may also be used to simulate simpler subsets of the above processes. A flow-direction-dependent dispersion process for anisotropic media is also provided by the code and is introduced in this report. As the primary calculated result, SUTRA provides fluid pressures and either solute concentrations or temperatures, as they vary with time, everywhere in the simulated subsurface system. SUTRA flow simulation may be employed for two-dimensional (2D) areal, cross sectional and three-dimensional (3D) modeling of saturated ground-water flow systems, and for cross sectional and 3D modeling of unsaturated zone flow. Solute-transport simulation using SUTRA may be employed to model natural or man-induced chemical-species transport including processes of solute sorption, production, and decay. For example, it may be applied to analyze ground-water contaminant transport problems and aquifer restoration designs. In addition, solute-transport simulation with SUTRA may be used for modeling of variable-density leachate movement, and for cross sectional modeling of saltwater intrusion in
Energy Technology Data Exchange (ETDEWEB)
Molinero, J.; Samper, J.
2003-07-01
Several countries around the world are considering the final disposal of high-level radioactive waste in deep repositories located in fractured granite formations. Evaluating the long term safety of such repositories requires sound conceptual and numerical models which must consider simultaneously groundwater flow, solute transport and chemical and radiological processes. These models are being developed from data and knowledge gained from in situ experiments carried out at deep underground laboratories such as that of Aspo, Sweden, constructed in fractured granite. The Redox Zone Experiment is one of such experiments performed at Aspo in order to evaluate the effects of the construction of the access tunnel on the hydrogeological and hydrochemical conditions of a fracture zone intersected by the tunnel. Previous authors interpreted hydrochemical and isotopic data of this experiment using a mass-balance approach based on a qualitative description of groundwater flow conditions. Such an interpretation, however, is subject to uncertainties related to an over-simplified conceptualization of groundwater flow. Here we present numerical models of groundwater flow and solute transport for this fracture zone. The first model is based on previously published conceptual model. It presents noticeable un consistencies and fails to match simultaneously observed draw downs and chloride breakthrough curves. To overcome its limitations, a revised flow and transport model is presented which relies directly on available hydrodynamic and transport parameters, is based on the identification of appropriate flow and transport boundary conditions and uses, when needed, solute data extrapolated from nearby fracture zones. A significant quantitative improvement is achieved with the revised model because its results match simultaneously drawdown and chloride data. Other improvements are qualitative and include: ensuring consistency of hydrodynamic and hydrochemical data and avoiding
Gusyev, M. A.; Abrams, D.; Toews, M. W.; Morgenstern, U.; Stewart, M. K.
2014-08-01
The purpose of this study is to simulate tritium concentrations and groundwater transit times in river water with particle-tracking (MODPATH) and compare them to solute transport (MT3DMS) simulations. Tritium measurements in river water are valuable for the calibration of particle-tracking and solute transport models as well as for understanding of watershed storage dynamics. In a previous study, we simulated tritium concentrations in river water of the western Lake Taupo catchment (WLTC) using a MODFLOW-MT3DMS model (Gusyev et al., 2013). The model was calibrated to measured tritium in river water at baseflows of the Waihaha, Whanganui, Whareroa, Kuratau, and Omori river catchments of the WLTC. Following from that work we now utilized the same MODFLOW model for the WLTC to calculate the pathways of groundwater particles (and their corresponding tritium concentrations) using steady-state particle tracking MODPATH model. In order to simulate baseflow tritium concentrations with MODPATH, transit time distributions (TTDs) are necessary to understand the lag time between the entry and discharge points of a tracer and are generated for the river networks of the five WLTC outflows. TTDs are used in the convolution integral with an input tritium concentration time series obtained from the precipitation measurements. The resulting MODPATH tritium concentrations yield a very good match to measured tritium concentrations and are similar to the MT3DMS-simulated tritium concentrations, with the greatest variation occurring around the bomb peak. MODPATH and MT3DMS also yield similar mean transit times (MTTs) of groundwater contribution to river baseflows, but the actual shape of the TTDs is strikingly different. While both distributions provide valuable information, the methodologies used to derive the TTDs are fundamentally different and hence must be interpreted differently. With the current MT3DMS model settings, only the methodology used with MODPATH provides the true TTD
Huan, Huan; Wang, Jinsheng; Lai, Desheng; Teng, Yanguo; Zhai, Yuanzheng
2015-05-01
Well vulnerability assessment is essential for groundwater source protection. A quantitative approach to assess well vulnerability in a well capture zone is presented, based on forward solute transport modeling. This method was applied to three groundwater source areas (Jiuzhan, Hadawan and Songyuanhada) in Jilin City, northeast China. The ratio of the maximum contaminant concentration at the well to the released concentration at the contamination source ( c max/ c 0) was determined as the well vulnerability indicator. The results indicated that well vulnerability was higher close to the pumping well. The well vulnerability in each groundwater source area was low. Compared with the other two source areas, the cone of depression at Jiuzhan resulted in higher spatial variability of c max/ c 0 and lower minimum c max/ c 0 by three orders of magnitude. Furthermore, a sensitivity analysis indicated that the denitrification rate in the aquifer was the most sensitive with respect to well vulnerability. A process to derive a NO3-N concentration at the pumping well is presented, based on determining the maximum nitrate loading limit to satisfy China's drinking-water quality standards. Finally, the advantages, disadvantages and prospects for improving the precision of this well vulnerability assessment approach are discussed.
Energy Technology Data Exchange (ETDEWEB)
Samper, Javier; Molinero, Jorg; Changbing, Yang; Zhang, Guoxiang
2003-12-01
The Redox Zone Experiment was carried out at the Aespoe HRL in order to study the redox behavior and the hydrochemistry of an isolated vertical fracture zone disturbed by the excavation of an access tunnel. Overall results and interpretation of the Redox Zone Project were reported by /Banwart et al, 1995/. Later, /Banwart et al, 1999/ presented a summary of the hydrochemistry of the Redox Zone Experiment. Coupled groundwater flow and reactive transport models of this experiment were carried out by /Molinero, 2000/ who proposed a revised conceptual model for the hydrogeology of the Redox Zone Experiment which could explain simultaneously measured drawdown and salinity data. The numerical model was found useful to understand the natural system. Several conclusions were drawn about the redox conditions of recharge waters, cation exchange capacity of the fracture zone and the role of mineral phases such as pyrite, calcite, hematite and goethite. This model could reproduce the measured trends of dissolved species, except for bicarbonate and sulfate which are affected by microbially-mediated processes. In order to explore the role of microbial processes, a coupled numerical model has been constructed which accounts for water flow, reactive transport and microbial processes. The results of this model is presented in this report. This model accounts for groundwater flow and reactive transport in a manner similar to that of /Molinero, 2000/ and extends the preliminary microbial model of /Zhang, 2001/ by accounting for microbially-driven organic matter fermentation and organic matter oxidation. This updated microbial model considers simultaneously the fermentation of particulate organic matter by yeast and the oxidation of dissolved organic matter, a product of fermentation. Dissolved organic matter is produced by yeast and serves also as a substrate for iron-reducing bacteria. Model results reproduce the observed increase in bicarbonate and sulfate concentration, thus
Energy Technology Data Exchange (ETDEWEB)
Samper, Javier; Molinero, Jorge; Changbing Yang; Guoxiang Zhang [Univ. Da Coruna (Spain)
2003-12-01
The Redox Zone Experiment was carried out at the Aespoe HRL in order to study the redox behaviour and the hydrochemistry of an isolated vertical fracture zone disturbed by the excavation of an access tunnel. Overall results and interpretation of the Redox Zone Project were reported by Banwart et al. Later, Banwart presented a summary of the hydrochemistry of the Redox Zone Experiment. Coupled groundwater flow and reactive transport models of this experiment were carried out by Molinero who proposed a revised conceptual model for the hydrogeology of the Redox Zone Experiment which could explain simultaneously measured drawdown and salinity data. The numerical model was found useful to understand the natural system. Several conclusions were drawn about the redox conditions of recharge waters, cation exchange capacity of the fracture zone and the role of mineral phases such as pyrite, calcite, hematite and goethite. This model could reproduce the measured trends of dissolved species, except for bicarbonate and sulphate which are affected by microbially-mediated processes. In order to explore the role of microbial processes, a coupled numerical model has been constructed which accounts for water flow, reactive transport and microbial processes. The results of this model is presented in this report. This model accounts for groundwater flow and reactive transport in a manner similar to that of Molinero and extends the preliminary microbial model of Zhang by accounting for microbially-driven organic matter fermentation and organic matter oxidation. This updated microbial model considers simultaneously the fermentation of particulate organic matter by yeast and the oxidation of dissolved organic matter, a product of fermentation. Dissolved organic matter is produced by yeast and serves also as a substrate for iron-reducing bacteria. Model results reproduce the observed increase in bicarbonate and sulfaphe concentration, thus adding additional evidence for the possibility
Porosity, Dispersivity, and Contaminant Transport in Groundwater
Institute of Scientific and Technical Information of China (English)
MOIWO Juana P.
2001-01-01
Porosity (n) and Dispersivity (D) were modeled in relation to Solute Transport Time (t) in a saturated, homogeneous, isotropic, unconfined aquifer using the MOC model. It was noted that n and D have an important influence on solute transport time t in groundwater, with a consistently strong and direct relationship between n, D, and t. In the case of porosity, the relationship was found to be directly related to t when other aquifer properties remained unchanged. This was also mathematically argued using a form of the flow equation put forward by Henry Darcy (1856). Dispersivity on the other hand had somehow the same relationship with solute transport time t as porosity, but with much less effect. That is, higher dispersions lead to longer solute transport time within the aquifer system. This was because as the individual solute particles set off from the average seepage velocity, they traversed through longer distances due to tortuosity, mechanical mixing, diffusion, and microscopic heterogeneity latent in the porous media. Also when n and D were co- treated over t, n was noted to be dominant over D with regard t. This follows that the effect of porosity on solute transport time far out shadowed that of dispersivity. Stated in other words, the dispersivity of a substance in any porous medium is to a large extent a function of the porosity of that medium.
Energy Technology Data Exchange (ETDEWEB)
Kellner, Erik [Dept. of Forest Ecology, Univ. of Helsinki (Finland)
2007-02-15
In this report it is examined to what extent the variation in hydraulic conductivity within a peatland and adjoining sediments would affect the flow patterns within it under some certain hydraulic-head gradients and other certain border conditions. The first part of the report contains a short review of organic and mineral-soil sediment types and characteristics and what we know about present peatlands and underlying sediments in the SKB investigation areas today. In the next part, a 2-dimensional model is used to simulate flows and transports in different settings of a peatland, with the objective of studying the effects of some particular factors: 1. The magnitude of the hydraulic conductivity of the peat and of underlying layers. 2. Presence and positions of cracks in underlying clay layers. 3. Anisotropy and heterogeneity in peat hydraulic conductivity. 4. The size of the water recharge at the peatland surface. 5. The seasonal variation of the water recharge. The modelling results show that the importance of flow direction decreases with decreasing hydraulic conductivity in the peatland. This occurs as the convective flux is slowed down and the transport is taken over by the diffusive flux. Because the lowest hydraulic conductivity layer to large extent determines the size of the flow, presence of a low-conductivity layer, such as a layer of clay, is an important factor. Presence of cracks in such tight layers can increase the transport of solutes into the peat. The highest inflow rates are reached when such cracks occur in discharge areas with strong upward flow. On the other hand, a conservative solute can spread efficiently if there is a crack in low-flow locations. The effect of anisotropy is found to be small, partly because the horizontal gradients become smaller as distances are larger. The effect of layers with high or low permeability varies depending on the location and the prevailing gradients. One tight layer has a strong effect on the flow pattern
SPECIFIC SOLUTIONS GROUNDWATER FLOW EQUATION
Syahruddin, Muhammad Hamzah
2014-01-01
Geophysic publication Groundwater flow under surface, its usually slow moving, so that in laminer flow condition can find analisys using the Darcy???s law. The combination between Darcy law and continuity equation can find differential Laplace equation as general equation groundwater flow in sub surface. Based on Differential Laplace Equation is the equation that can be used to describe hydraulic head and velocity flow distribution in porous media as groundwater. In the modeling Laplace e...
Energy Technology Data Exchange (ETDEWEB)
Hodgkinson, David (Quintessa, Henley-on-Thames (GB))
2007-09-15
This report forms part of an independent review of the specifications, execution and results of Task 6 of the Aespoe Task Force on Modelling of Groundwater Flow and Transport of Solutes, which is seeking to provide a bridge between site characterization and performance assessment approaches to modelling solute transport in fractured rock. The objectives of Task 6 are: To assess simplifications used in Performance Assessment (PA) models. To determine how, and to what extent, experimental tracer and flow experiments can constrain the range of parameters used in PA models. To support the design of Site Characterisation (SC) programmes to ensure that the results have optimal value for performance assessment calculations. To improve the understanding of site-specific flow and transport behaviour at different scales using site characterisation models. The present report is concerned with Tasks 6D, 6E, 6F and 6F2. It follows on from two previous reviews of Tasks 6A, 6B and 6B2, and Task 6C. In Task 6D the transport of tracers through a fracture network is modelled using the conditions of the C2 TRUE-Block Scale tracer test, based on the synthetic structural model developed in Task 6C. Task 6E extends the Task 6D transport calculations to a reference set of PA time scales and boundary conditions. Task 6F consists of a series of 'benchmark' studies on single features from the Task 6C hydrostructural model in order to improve the understanding of differences between the participating models. Task 6F2 utilises models set up for Tasks 6E and 6F to perform additional sensitivity studies with the aim of increasing the understanding of how models behave, the reason for differences in modelling results, and the sensitivity of models to various assumptions and parameter values. Eight modelling teams representing five organisations participated in this exercise using Discrete Fracture Network (DFN), continuum and channel network concepts implemented in a range of different
One-dimensional spatially dependent solute transport in semi ...
African Journals Online (AJOL)
Development of an analytical solutions for groundwater pollution problems are major ... parameters for description of solute transport in porous media. ..... in Department of Mathematics & Astronomy, Lucknow University, Lucknow, India.
Hong, Qingquan; Cai, Pinghe; Shi, Xiangming; Li, Qing; Wang, Guizhi
2017-02-01
Pore water exchange (PEX) and submarine groundwater discharge (SGD) represent two mechanisms for solute transport from the seabed into the coastal ocean. However, their relative importance remains to be assessed. In this study, we pursued the recently developed 224Ra/228Th disequilibrium approach to quantify PEX fluxes of 224Ra into the Jiulong River estuary, China. By constructing a full mass balance of water column 224Ra, we were allowed to put various source terms, i.e., SGD, diffusive and advective pore water flow (PEX), and river input in a single context. This led to the first quantitative assessment of the relative importance of PEX vs. SGD in the delivery of solutes into an estuary. We carried out two surveys in the Jiulong River estuary: one in January 2014 (winter survey), the other in August 2014 (summer survey). By virtue of a 1-D mass balance model of 224Ra in the sediment column, we demonstrated that PEX fluxes of 224Ra were highly variable, both temporally and spatially, and can change by 1-2 orders of magnitude in our study area. Moreover, we identified a strong correlation between 224Ra-based irrigation rate and 234Th-based sediment mixing rate. Our results highlighted irrigation as the predominant PEX process for solute transfer across the sediment-water interface. Total PEX flux of 224Ra (in 1010 dpm d-1) into the Jiulong River estuary was estimated to be 22.3 ± 3.0 and 33.7 ± 5.5 during the winter and summer surveys, respectively. In comparison, total SGD flux of 224Ra (in 1010 dpm d-1) was 11.3 ± 8.6 and 49.5 ± 16.3 in the respective seasons. By multiplying the PEX fluxes of 224Ra by the ratio of the concentration gradients of component/224Ra at the sediment-water interface, we quantified the total PEX fluxes of dissolved inorganic carbon (DIC) and nutrients (NH4+, NO3-, and H4SiO4) into the Jiulong River estuary. In the meantime, net export of DIC and nutrients via SGD were estimated by multiplying the SGD fluxes of 224Ra by the DIC
Energy Technology Data Exchange (ETDEWEB)
Molinero Huguet, J.
2001-07-01
This work deals with numerical modeling of groundwater flow, solute transport and chemical reactions through fractured media. These models have been developed within the framework of research activities founded by ENRESA , the Spanish Company for Nuclear Waste Management. This project is the result of a collaborative agreement between ENRESA and his equivalent Swedish Company (SKB) through the research project Task Force 5 of the Aspo Underground Laboratory. One of the objectives of this project is to assess quantitatively th hydrogeological and hydrochemical impact produced by the construction of a Deep Geological Repository in fractured granites. This is important because the new conditions altered construction impact will constitute the initial conditions for the repository closure stage. A second goo l of this work deals with testing the ability of current numerical tools to cope simultaneously with the complex hydrogeological and hydrochemical settlings, which are expected to take place in actual nuclear waste underground repositories constructed in crystalline fractured bed racks. This study has been undertaken through the performance of numerical models, which have subsequently been applied to simulate the hydrogeological and hydrochemical behavior of a granite massif, at a kilo metrical scale, during construction of the Aspo Hard Rock Underground Laboratory (Sweden). The Aspo Hard Rock Laboratory is a prototype, full-scale underground facility launched and operated by SKB. The main aim of the laboratory is to provide an opportunity for research, development and demonstration in a realistic rock environment down to the depth planned for the future deep repository. The framework of this underground facility provides a unique opportunity to attempt the objectives of the present dissertation. (Author)
ANALYTICAL SOLUTION OF GROUNDWATER FLUCTUATIONS IN ESTUARINE AQUIFER
Institute of Scientific and Technical Information of China (English)
CHEN Jing; ZHOU Zhi-fang; JIA Suo-bao
2005-01-01
As a basic factor in the environment of estuary, tidal effects in the coastal aquifer have recently attracted much attention because tidal dynamic also greatly influences the solute transport in the coastal aquifer. Previous studies on tidal dynamic of coastal aquifers have focused on the inland propagation of oceanic tides in the cross-shore direction, a configuration that is essentially one-dimensional. Two-dimensional analytical solutions for groundwater level fluctuation in recent papers are localized in presenting the effect of both oceanic tides and estuarine tides in quadrantal aquifer. A two-dimensional model of groundwater fluctuations in estuarine zone in proposed in this paper. Using complex transform, the two-dimensional flow equation subject to periodic boundary condition is changed into time-independent elliptic problem. Based on Green function method, an analytical solution for groundwater fluctuations in fan-shaped aquifer is derived. The response to of groundwater tidal loading in an estuary and ocean is discussed. The result show that its more extensive application than recent studies.
Transport and Degradation of Phenol in Groundwater at Four Ashes
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
Drift deposits and Triassic Sandstone of the Bromsgrove and Wildmoor Formations, 700m thick, form the main aquifers at Four Ashes. The coal tar and products from early plant and tank storage facilities constructed over unprotected ground directly and indirectly caused significant groundwater pollution. The organic pollutants include phenol, cresol, and xylenol. The maximum phenol concentration in the groundwater reached 12000mg/L, with an average of 1300mg/L, which accounts for 40%-60% of the total organic contaminants. Three computer codes, Visual Modflow, MT3D, and BioRedox, which solute transport model to groundwater flow were used to simulate and predict the distribution, transport, and degradation of phenol in the polluted groundwater. Over about 46 years, the phenol moved from the pollutant source to the plume front and it will take 220 years to reach the main pumping wells. The BioRebox model was used to simulate the aerobic, sulfidogenic, nitrate-reducing, ferrogenic, manganogenic, and methanogenic zones. The residual mass in the groundwater will decrease from 1600 t to 400 t by the year 2080, with 80% of total phenol eventually lost with maximum concentration declining from 15000mg/L to 2000mg/L.
Reliability Analyses of Groundwater Pollutant Transport
Energy Technology Data Exchange (ETDEWEB)
Dimakis, Panagiotis
1997-12-31
This thesis develops a probabilistic finite element model for the analysis of groundwater pollution problems. Two computer codes were developed, (1) one using finite element technique to solve the two-dimensional steady state equations of groundwater flow and pollution transport, and (2) a first order reliability method code that can do a probabilistic analysis of any given analytical or numerical equation. The two codes were connected into one model, PAGAP (Probability Analysis of Groundwater And Pollution). PAGAP can be used to obtain (1) the probability that the concentration at a given point at a given time will exceed a specified value, (2) the probability that the maximum concentration at a given point will exceed a specified value and (3) the probability that the residence time at a given point will exceed a specified period. PAGAP could be used as a tool for assessment purposes and risk analyses, for instance the assessment of the efficiency of a proposed remediation technique or to study the effects of parameter distribution for a given problem (sensitivity study). The model has been applied to study the greatest self sustained, precipitation controlled aquifer in North Europe, which underlies Oslo`s new major airport. 92 refs., 187 figs., 26 tabs.
Modeling Reactive Transport in Coupled Groundwater-Conduit Systems
Spiessl, S. M.; Sauter, M.; Zheng, C.; Viswanathan, H. S.
2002-05-01
Modeling reactive transport in coupled groundwater-conduit systems requires consideration of two transport time scales in the flow and transport models. Consider for example a subsurface mine consisting of a network of highly conductive shafts, drifts or ventilation raises (i.e., conduits) within the considerably less permeable ore material (i.e., matrix). In the conduits, potential contaminants can travel much more rapidly than in the background aquifer (matrix). Since conduits cannot necessarily be regarded as a continuum, double continuum models are only of limited use for simulation of contaminant transport in such coupled groundwater-conduit systems. This study utilizes a "hybrid" flow and transport model in which contaminants can in essence be transported at a slower time scale in the matrix and at a faster time scale in the conduits. The hybrid flow model uses an approach developed by Clemens et al. (1996), which is based on the modelling of flow in a discrete pipe network, coupled to a continuum representing the low-permeability inter-conduit matrix blocks. Laminar or turbulent flow can be simulated in the different pipes depending on the flow conditions in the model domain. The three-dimensional finite-difference groundwater flow model MODFLOW (Harbaugh and McDonald, 1996) is used to simulate flow in the continuum. Contaminant transport within the matrix is simulated with a continuum approach using the three-dimensional multi-species solute transport model MT3DMS (Zheng and Wang, 1999), while that in the conduit system is simulated with a one-dimensional advective transport model. As a first step for reactive transport modeling in such systems, only equilibrium reactions among multiple species are considered by coupling the hybrid transport model to a geochemical speciation package. An idealized mine network developed by Viswanathan and Sauter (2001) is used as a test problem in this study. The numerical experiment is based on reference date collected from
Coupling of Groundwater Transport and Plant Uptake Models
DEFF Research Database (Denmark)
Rein, Arno; Bauer-Gottwein, Peter; Trapp, Stefan
2010-01-01
Plants significantly influence contaminant transport and fate. Important processes are uptake of soil and groundwater contaminants, as well as biodegradation in plants and their root zones. Models for the prediction of chemical uptake into plants are required for the setup of mass balances...... to groundwater transport simulation tools. Exemplary simulations of plant uptake were carried out, in order to estimate concentrations in the soilplant- air system and the influence of plants on contaminant mass fluxes from soil to groundwater....
Peritoneal transport with icodextrin solution.
Heimbürger, Olof
2006-01-01
Icodextrin is the only large molecular weight osmotic agent available in peritoneal dialysis solutions. Icodextrin (compared to glucose) has a prolonged positive ultrafiltration because of the slow absortion of icodextrin due to its large molecular weight. As icodextrin induces transcapillary ultrafiltration by a mechanism resembling 'colloid' osmosis (with the ultrafiltration occurring mainly through the small pores) almost no sieving of solutes is observed with icodextrin-based solution resulting in increased convective transport and clearance of small solutes. In general, the transport characteristics of the peritoneal membrane are similar with glucose- and icodextrin-based solution, but results from the EAPOS study suggests that use of icodextrin-based solution may be associated with less changes in peritoneal transport with time.
Energy Technology Data Exchange (ETDEWEB)
Elert, M.; Svensson, Haakan [Kemakta Konsult AB, Stockholm (Sweden)
2001-05-01
The Aespoe Task Force on Modelling of Groundwater Flow and Transport of Solutes is a forum for the international organisations supporting the Aespoe HRL Project. The purpose of the Task Force is to interact in the area of conceptual and numerical modelling of groundwater flow and solute transport in fractured rock. Task 4 of the Aespoe Modelling Task Force consists of modelling exercises in support of the TRUE-1 tracer tests. In this report, the modelling work performed within Tasks 4E and 4F is evaluated, which comprised predictive modelling of the tracer tests (STT-1, STT-1b and STT-2) performed within the TRUE-1 project using sorbing and non-sorbing tracers. The tests were made between packed off boreholes penetrating a water-conducting geological feature with a simple structure (Feature A). Nine modelling teams representing eight organisations have performed predictive modelling of the tracer tests using different modelling approaches and models. The modelling groups were initially given data from the site characterisation, data from preliminary tracer tests performed with non-sorbing tracers and data on the experimental set-up of the sorbing tracer tests. Based on this information, model predictions were made of drawdown, tracer mass recovery and tracer breakthrough. For the predictions of the STT-1b and STT-2 tests results from previous tracer tests with sorbing tracer were also available. The predictions of the sorbing tracer breakthrough in the initial tracer test (STT-1) generally underestimated the breakthrough time, suggesting the need to include additional processes and evaluate the application of the laboratory data. As a result of model calibration and modification the predictions were considerably improved for the latter tracer tests (STT-1b and STT-2). Task 4E and 4F have proved to be very valuable in increasing the understanding of non-sorbing tracer transport in fractured rock. There is a general consensus on the major processes responsible for
Improving fresh groundwater supply - problems and solutions
Oude Essink, Gualbert
2001-01-01
Many coastal regions in the world experience an intensive salt water intrusion in aquifers due to natural and anthropogenic causes. The salinisation of these groundwater systems can lead to a severe deterioration of the quality of existing fresh groundwater resources. In this paper, the
Energy Technology Data Exchange (ETDEWEB)
Elert, M. [Kemakta Konsult AB, Stockholm (Sweden)
1999-05-01
The `Aespoe task force on modelling of groundwater flow and transport of solutes` is a forum for the international organisations supporting the Aespoe HRL Project. The purpose of the Task Force is to interact in the area of conceptual and numerical modelling of groundwater flow and solute transport in fractured rock. Task 4 of the Aespoe Modelling Task Force consists of modelling exercises in support of the TRUE-1 tracer tests. In this report, the modelling work performed within Tasks 4C and 4D is evaluated, which comprised predictive modelling of the radially converging tracer tests and dipole tracer tests performed within the TRUE-1 tests using non-sorbing tracers. The tests were performed between packed off boreholes penetrating a water-conducting geological feature with a simple structure (Feature A). These tests are to a great extent preparatory steps for the subsequent tests with sorbing radioactive tracers. In Tasks 4E and 4F of the Aespoe Modelling Task Force predictive modelling of the sorbing tracer tests is performed. Eight modelling teams representing seven organisations have performed predictive modelling using different modelling approaches and models. The modelling groups were initially given data from the site characterisation and data on the experimental set-up of the tracer tests. Based on this information model predictions were performed of drawdown, tracer mass recovery and tracer breakthrough. The performed predictions shows that the concept of Feature A as a singular well-connected feature with limited connectivity to its surroundings is quite adequate for predictions of drawdown in boreholes and conservative tracer breakthrough. Reasonable estimates were obtained using relatively simple models. However, more elaborate models with calibration or conditioning of transmissivities and transport apertures are required for more accurate predictions. The general flow and transport processes are well understood, but the methodology to derive the
Groundwater transport modeling with nonlinear sorption and intraparticle diffusion
Singh, Anshuman; Allen-King, Richelle M.; Rabideau, Alan J.
2014-08-01
Despite recent advances in the mechanistic understanding of sorption in groundwater systems, most contaminant transport models provide limited support for nonideal sorption processes such as nonlinear isotherms and/or diffusion-limited sorption. However, recent developments in the conceptualization of "dual mode" sorption for hydrophobic organic contaminants have provided more realistic and mechanistically sound alternatives to the commonly used Langmuir and Freundlich models. To support the inclusion of both nonlinear and diffusion-limited sorption processes in groundwater transport models, this paper presents two numerical algorithms based on the split operator approach. For the nonlinear equilibrium scenario, the commonly used two-step split operator algorithm has been modified to provide a more robust treatment of complex multi-parameter isotherms such as the Polanyi-partitioning model. For diffusion-limited sorption, a flexible three step split-operator procedure is presented to simulate intraparticle diffusion in multiple spherical particles with different sizes and nonlinear isotherms. Numerical experiments confirmed the accuracy of both algorithms for several candidate isotherms. However, the primary advantages of the algorithms are: (1) flexibility to accommodate any isotherm equation including "dual mode" and similar expressions, and (2) ease of adapting existing grid-based transport models of any dimensionality to include nonlinear sorption and/or intraparticle diffusion. Comparisons are developed for one-dimensional transport scenarios with different isotherms and particle configurations. Illustrative results highlight (1) the potential influence of isotherm model selection on solute transport predictions, and (2) the combined effects of intraparticle diffusion and nonlinear sorption on the plume transport and flushing for both single-particle and multi-particle scenarios.
Institute of Scientific and Technical Information of China (English)
王树芳; 王丽亚; 王晓红; 林沛; 刘久荣; 辛宝东; 贺国平
2012-01-01
Investigation and numerical simulation,based on RT3D（reactive transport in 3-dimensions）were used to identify the source of tetrachloroethylene（PCE） and trichloroethylene（TCE） in the groundwater of a city in the north of China and reverse the input intensity.Multiple regressions were applied to analyze the influenced factors of input intensity of PCE and TCE using Stepwise function in Matlab.The results indicate that the factories and industries are the source of the PCE and TCE in groundwater.Natural attenuation was identified and the natural attenuation rates are 93.15%、 61.70% and 61.00% for PCE,and 70.05%、 73.66% and 63.66% for TCE in 173 days.The 4 source points identified by the simulation have released 0.910 6 kg PCE and 95.693 8 kg TCE during the simulation period.The regression analysis results indicate that local precipitation and the thickness of vadose zone are the main factors influencing organic solution transporting from surface to groundwater.The PCE and TCE concentration are found to be 0 and 5 mg·kg-1from surface to 35 cm in vadose zone.All above results suggest that PCE and TCE in groundwater are from the source in the surface.Natural attenuation occurred when PCE and TCE transporting from the surface to groundwater,and the rest was transported to groundwater through vadose zone.Local precipitation was one of the critical factors influencing the transportation of PCE and TCE to aquifer through sand,pebble and gravel of the Quaternary.%采用现场调查与数值模拟的方法,借助RT3D（reactive transport in 3-dimensions）,对我国北方某城市局部地区地下水中的四氯乙烯（PCE）和三氯乙烯（TCE）污染来源进行了识别,对污染输入强度进行了反演,并利用Matlab中的Stepwise函数,对影响污染物输入强度的因素进行了多元回归分析.研究结果显示,研究区地下水中的PCE和TCE主要来源于区内使用有机溶剂的工厂和企业.地下水
Boufadel, Michel C.
2000-09-01
Two laboratory experiments were conducted to investigate the effects of tides and buoyancy on beach hydraulics in the presence of a seaward groundwater flow due to an elevated "regional" water table. In the first experiment, case 1, the difference in concentration between the salt water at sea and the water of the regional aquifer was small, 2.4 g L-1, such that it did not engender density gradients; the salt acts as a tracer in this case. In the second experiment, case 2, the difference was ˜32.0 g L-1, which creates a significant density gradient. This case corresponds to the presence of fresh groundwater in the subsurface of the coasts of the continental United States. The experiments were numerically simulated by the marine unsaturated (MARUN) model, a numerical model for density-and-viscosity-dependent flows in two-dimensional variably saturated media. The long-term experimental and numerical results showed that the seawater plume entered the beach from the sea and occupied most of the intertidal zone. The maximum depth of the seawater plume was near the midsection of the intertidal zone, and it decreased near the low and high tide lines. When viewed in the context of case 2, these results indicate an inverted salinity distribution in beaches subjected to tides with salt water from sea overtopping the freshwater lens. For both cases, water from the regional aquifer moved seaward beneath the seawater in the intertidal zone and pinched out near the low tide mark. We also noted that beach hydraulics are highly two dimensional with water entering the beach at a near-vertical angle and leaving it at a near-horizontal angle, which casts doubts on analyses of beach hydraulics based on the Dupuit assumption. Findings from this work have direct implications within the practice of bioremediation of oil spills on beaches. We found that applying dissolved nutrients on the beach surface at low tide is superior to applying them in a trench landward of the beach. This is
Energy Technology Data Exchange (ETDEWEB)
Zachara, John M. [Pacific Northwest National Laboratory, Richland Washington USA; Chen, Xingyuan [Pacific Northwest National Laboratory, Richland Washington USA; Murray, Chris [Pacific Northwest National Laboratory, Richland Washington USA; Hammond, Glenn [Sandia National Laboratories, Albuquerque New Mexico USA
2016-03-01
A tightly spaced well-field within a groundwater uranium (U) plume in the groundwater-surface water transition zone was monitored for a three year period for groundwater elevation and dissolved solutes. The plume discharges to the Columbia River, which displays a dramatic spring stage surge resulting from mountain snowmelt. Groundwater exhibits a low hydrologic gradient and chemical differences with river water. River water intrudes the site in spring. Specific aims were to assess the impacts of river intrusion on dissolved uranium (Uaq), specific conductance (SpC), and other solutes, and to discriminate between transport, geochemical, and source term heterogeneity effects. Time series trends for Uaq and SpC were complex and displayed large temporal well-to well variability as a result of water table elevation fluctuations, river water intrusion, and changes in groundwater flow directions. The wells were clustered into subsets exhibiting common temporal behaviors resulting from the intrusion dynamics of river water and the location of source terms. Concentration hot spots were observed in groundwater that varied in location with increasing water table elevation. Heuristic reactive transport modeling with PFLOTRAN demonstrated that mobilized U was transported between wells and source terms in complex trajectories, and was diluted as river water entered and exited the groundwater system. While uranium time-series concentration trends varied significantly from year to year as a result of climate-caused differences in the spring hydrograph, common and partly predictable response patterns were observed that were driven by water table elevation, and the extent and duration of the river water intrusion event.
Groundwater and contaminant transport modelling at the Sydney Tar Ponds
Energy Technology Data Exchange (ETDEWEB)
King, M. [Groundwater Insight Inc., Halifax, NS (Canada); Check, G. [Jacques Whitford Environment Ltd., Halifax, NS (Canada); Carey, G. [Environmental Inst. for Continuing Education, Waterloo, ON (Canada); Abbey, D. [Waterloo Hydrogeologic, Waterloo, ON (Canada); Baechler, F. [ADI Ltd., Sydney, NS (Canada)
2003-07-01
The Muggah Creek Watershed, a tidal estuary located in Sydney, Nova Scotia, is known locally as the Tar Ponds. Over the past century, the Tar Ponds have accumulated contaminants in the contributing watershed from the iron, steel and coke manufacturing. There are sediments contaminated with polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). A groundwater modelling program was developed to estimate current contaminant fluxes to the estuary and site streams, through groundwater. Attempts were made to incorporate a complex stratigraphic profile, where groundwater flow and contaminant transport is strongly controlled by shallow fractured bedrock, into the conceptual model developed for the site. This conceptual model for groundwater flow and contaminant transport at the Sydney Tar Ponds site was presented. The complex flow patterns between bedrock and overburden, and between the bedrock units and surface water bodies were illustrated with model simulations. It was found that groundwater flow was dominated by discharge to the streams and the estuary. 6 refs., 2 tabs., 11 figs.
Scaling of flow and transport behavior in heterogeneous groundwater systems
Scheibe, Timothy; Yabusaki, Steven
1998-11-01
Three-dimensional numerical simulations using a detailed synthetic hydraulic conductivity field developed from geological considerations provide insight into the scaling of subsurface flow and transport processes. Flow and advective transport in the highly resolved heterogeneous field were modeled using massively parallel computers, providing a realistic baseline for evaluation of the impacts of parameter scaling. Upscaling of hydraulic conductivity was performed at a variety of scales using a flexible power law averaging technique. A series of tests were performed to determine the effects of varying the scaling exponent on a number of metrics of flow and transport behavior. Flow and transport simulation on high-performance computers and three-dimensional scientific visualization combine to form a powerful tool for gaining insight into the behavior of complex heterogeneous systems. Many quantitative groundwater models utilize upscaled hydraulic conductivity parameters, either implicitly or explicitly. These parameters are designed to reproduce the bulk flow characteristics at the grid or field scale while not requiring detailed quantification of local-scale conductivity variations. An example from applied groundwater modeling is the common practice of calibrating grid-scale model hydraulic conductivity or transmissivity parameters so as to approximate observed hydraulic head and boundary flux values. Such parameterizations, perhaps with a bulk dispersivity imposed, are then sometimes used to predict transport of reactive or non-reactive solutes. However, this work demonstrates that those parameters that lead to the best upscaling for hydraulic conductivity and head do not necessarily correspond to the best upscaling for prediction of a variety of transport behaviors. This result reflects the fact that transport is strongly impacted by the existence and connectedness of extreme-valued hydraulic conductivities, in contrast to bulk flow which depends more strongly on
Uffink GJM; Romkens PFAM; LBG
2001-01-01
Nitrate measurements from the Netherlands Groundwater Monitoring Network and model simulations were compared for deep aquifers in the eastern part of the Netherlands. The area studied measured 40 x 30 km2. The model describes advective-dispersive solute transport in groundwater and utilizes a first-
Energy Technology Data Exchange (ETDEWEB)
Travis, C.C.
1978-10-01
This report reviews selected literature related to the mathematical description of the transport of reactive solutes through soil. The primary areas of the literature reviewed are (1) mathematical models in current use for description of the adsorption-desorption interaction between the soil solution and the soil matrix and (2) analytic solutions of the differential equations describing the convective-dispersive transport of reactive solutes through soil.
Filtered density function approach for reactive transport in groundwater
Suciu, Nicolae; Schüler, Lennart; Attinger, Sabine; Knabner, Peter
2016-04-01
Spatial filtering may be used in coarse-grained simulations (CGS) of reactive transport in groundwater, similar to the large eddy simulations (LES) in turbulence. The filtered density function (FDF), stochastically equivalent to a probability density function (PDF), provides a statistical description of the sub-grid, unresolved, variability of the concentration field. Besides closing the chemical source terms in the transport equation for the mean concentration, like in LES-FDF methods, the CGS-FDF approach aims at quantifying the uncertainty over the whole hierarchy of heterogeneity scales exhibited by natural porous media. Practically, that means estimating concentration PDFs on coarse grids, at affordable computational costs. To cope with the high dimensionality of the problem in case of multi-component reactive transport and to reduce the numerical diffusion, FDF equations are solved by particle methods. But, while trajectories of computational particles are modeled as stochastic processes indexed by time, the concentration's heterogeneity is modeled as a random field, with multi-dimensional, spatio-temporal sets of indices. To overcome this conceptual inconsistency, we consider FDFs/PDFs of random species concentrations weighted by conserved scalars and we show that their evolution equations can be formulated as Fokker-Planck equations describing stochastically equivalent processes in concentration-position spaces. Numerical solutions can then be approximated by the density in the concentration-position space of an ensemble of computational particles governed by the associated Itô equations. Instead of sequential particle methods we use a global random walk (GRW) algorithm, which is stable, free of numerical diffusion, and practically insensitive to the increase of the number of particles. We illustrate the general FDF approach and the GRW numerical solution for a reduced complexity problem consisting of the transport of a single scalar in groundwater
PCR detection of groundwater bacteria associated with colloidal transport
Energy Technology Data Exchange (ETDEWEB)
Cruz-Perez, P.; Stetzenbach, L.D.; Alvarez, A.J.
1996-02-29
Colloidal transport may increase the amount of contaminant material than that which could be transported by water flow alone. The role of colloids in groundwater contaminant transport is complicated and may involve many different processes, including sorption of elements onto colloidal particles, coagulation/dissolution, adsorption onto solid surfaces, filtration, and migration. Bacteria are known to concentrate minerals and influence the transport of compounds in aqueous environments and may also serve as organic colloids, thereby influencing subsurface transport of radionuclides and other contaminants. The initial phase of the project consisted of assembling a list of bacteria capable of sequestering or facilitating mineral transport. The development and optimization of the PCR amplification assay for the detection of the organisms of interest, and the examination of regional groundwaters for those organisms, are presented for subsequent research.
Analytic solutions for unconfined groundwater flow over a stepped base
Fitts, Charles R.; Strack, Otto D. L.
1996-03-01
Two new exact solutions are presented for uniform unconfined groundwater flow over a stepped base; one for a step down in the direction of flow, the other for a step up in the direction of flow. These are two-dimensional solutions of Laplace's equation in the vertical plane, and are derived using the hodograph method and conformal mappings on Riemann surfaces. The exact solutions are compared with approximate one-dimensional solutions which neglect the resistance to vertical flow. For small horizontal hydraulic gradients typical of regional groundwater flow, little error is introduced by neglecting the vertical resistance to flow. This conclusion may be extended to two-dimensional analytical models in the horizontal plane, which neglect the vertical resistance to flow and treat the aquifer base as a series of flat steps.
Transport and biodegradation of benzene in the saturated groundwater layer
Directory of Open Access Journals (Sweden)
Khongnakorn, W.
2004-11-01
Full Text Available The objective of this study was to investigate the biotic and abiotic processes that affected benzene transportation in the saturated groundwater layer. The study was performed in the laboratory using synthetic groundwater and soil sample from Maptaput Industrial Estate, Rayong. This study was divided into 3 parts; batch test, column test and computer modeling. The biotic, biodegradation, and the abiotic processes were studied in the batch system. The column experiment was performed to investigate the transport behavior of benzene. The computer program, CXTFIT, with parameters acquired from batch and column experiments was used to simulate the benzene transport behavior. It was found that benzene adsorption followed the linear adsorption isotherm with its coefficient (Kd of 0.544 cm3/g and the retardation factor of 5.43. The biodegradation rate could be estimated using the firstorder biodegradation rate equation with the degradation rate of 0.0009- 0.0092 per day. The dispersion coefficient estimated from column experiments was 0.0102 cm2/s. The results from computer simulation did not fit the experimental data well. It can be concluded that the transport of benzene was a non-equilibrium transport. It was also found that biodegradation of benzene had significant effect on benzene transportation in saturated groundwater. The simulated transport with biodegradation process fitted the data fairly.
Energy Technology Data Exchange (ETDEWEB)
Simmons, Rashad N. [Department of Chemistry and Center for Integrative Toxicology, Michigan State University, East Lansing, MI 48824-1322 (United States); McGuffin, Victoria L. [Department of Chemistry and Center for Integrative Toxicology, Michigan State University, East Lansing, MI 48824-1322 (United States)], E-mail: jgshabus@aol.com
2007-11-05
The effects of hydrocarbon and perfluorinated surfactants, above their critical micelle concentration (CMC), on the transport of neutral environmental pollutants are compared. Reversed-phase micellar liquid chromatography is used to model the groundwater system. The octadecylsilica stationary phase serves to simulate soil particles containing organic matter, whereas the aqueous surfactant mobile phases serve to simulate groundwater containing a surfactant at varying concentrations. Sodium dodecyl sulfate and lithium perfluorooctane sulfonate are used as representatives of the hydrocarbon and perfluorinated surfactants, respectively. Benzene, mono- and perhalogenated benzenes, and polycyclic aromatic hydrocarbons are used as models for environmental pollutants. Transport effects were elucidated from the retention factor, k, and the equilibrium constant per micelle, K{sub eq}, of the model pollutants in the individual surfactants. Based on k values, the transport of the model pollutants increased in both surfactant solutions in comparison to pure water. As the concentration of the surfactants increased, the transport of the pollutants increased as well. Notably, the K{sub eq} values of the pollutants in the perfluorinated surfactant were at least an order of magnitude less than those in the hydrocarbon surfactant. Overall, these results suggest that the presence of a perfluorinated surfactant, above its CMC, increases the transport of pollutants in a groundwater system. However, the perfluorinated surfactant exhibits a lesser transport effect than the hydrocarbon surfactant.
The secret to successful solute-transport modeling
Konikow, L.F.
2011-01-01
Modeling subsurface solute transport is difﬁcult—more so than modeling heads and ﬂows. The classical governing equation does not always adequately represent what we see at the ﬁeld scale. In such cases, commonly used numerical models are solving the wrong equation. Also, the transport equation is hyperbolic where advection is dominant, and parabolic where hydrodynamic dispersion is dominant. No single numerical method works well for all conditions, and for any given complex ﬁeld problem, where seepage velocity is highly variable, no one method will be optimal everywhere. Although we normally expect a numerically accurate solution to the governing groundwater-ﬂow equation, errors in concentrations from numerical dispersion and/or oscillations may be large in some cases. The accuracy and efﬁciency of the numerical solution to the solute-transport equation are more sensitive to the numerical method chosen than for typical groundwater-ﬂow problems. However, numerical errors can be kept within acceptable limits if sufﬁcient computational effort is expended. But impractically long
Column Holdup Formula of Soil Solute Transport
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The shortcomings of the present two formulae for describing column holdup are analyzed and deductions are made to find a new formula. The column holdup, Hw, described by the new formula is dimensional,and related to soil solute transport kinesis and column physical properties. Compared with the other two column holdups, Hw is feasible to describe dimensional column holdup during solute transport process. The relationships between Hw and retardation factor, R, in different solute transport boundary conditions are established.
Assessment of parametric uncertainty for groundwater reactive transport modeling,
Shi, Xiaoqing; Ye, Ming; Curtis, Gary P.; Miller, Geoffery L.; Meyer, Philip D.; Kohler, Matthias; Yabusaki, Steve; Wu, Jichun
2014-01-01
The validity of using Gaussian assumptions for model residuals in uncertainty quantification of a groundwater reactive transport model was evaluated in this study. Least squares regression methods explicitly assume Gaussian residuals, and the assumption leads to Gaussian likelihood functions, model parameters, and model predictions. While the Bayesian methods do not explicitly require the Gaussian assumption, Gaussian residuals are widely used. This paper shows that the residuals of the reactive transport model are non-Gaussian, heteroscedastic, and correlated in time; characterizing them requires using a generalized likelihood function such as the formal generalized likelihood function developed by Schoups and Vrugt (2010). For the surface complexation model considered in this study for simulating uranium reactive transport in groundwater, parametric uncertainty is quantified using the least squares regression methods and Bayesian methods with both Gaussian and formal generalized likelihood functions. While the least squares methods and Bayesian methods with Gaussian likelihood function produce similar Gaussian parameter distributions, the parameter distributions of Bayesian uncertainty quantification using the formal generalized likelihood function are non-Gaussian. In addition, predictive performance of formal generalized likelihood function is superior to that of least squares regression and Bayesian methods with Gaussian likelihood function. The Bayesian uncertainty quantification is conducted using the differential evolution adaptive metropolis (DREAM(zs)) algorithm; as a Markov chain Monte Carlo (MCMC) method, it is a robust tool for quantifying uncertainty in groundwater reactive transport models. For the surface complexation model, the regression-based local sensitivity analysis and Morris- and DREAM(ZS)-based global sensitivity analysis yield almost identical ranking of parameter importance. The uncertainty analysis may help select appropriate likelihood
Transient solutions to groundwater mounding in bounded and unbounded aquifers.
Korkmaz, Serdar
2013-01-01
In this study, the well-known Hantush solution procedure for groundwater mounding under infinitely long infiltration strips is extended to finite and semi-infinite aquifer cases. Initially, the solution for infinite aquifers is presented and compared to those available in literature and to the numerical results of MODFLOW. For the finite aquifer case, the method of images, which is commonly used in well hydraulics, is used to be able to represent the constant-head boundaries at both sides. It is shown that a finite number of images is enough to obtain the results and sustain the steady state. The effect of parameters on the growth of the mound and on the time required to reach the steady state is investigated. The semi-infinite aquifer case is emphasized because the growth of the mound is not symmetric. As the constant-head boundary limits the growth, the unbounded side grows continuously. For this reason, the groundwater divide shifts toward the unbounded side. An iterative solution procedure is proposed. To perform the necessary computations a code was written in Visual Basic of which the algorithm is presented. The proposed methodology has a wide range of applicability and this is demonstrated using two practical examples. The first one is mounding under a stormwater dispersion trench in an infinite aquifer and the other is infiltration from a flood control channel into a semi-infinite aquifer. Results fit very well with those of MODFLOW.
Advances in Dynamic Transport of Organic Contaminants in Karst Groundwater Systems
Padilla, I. Y.; Vesper, D.; Alshawabkeh, A.; Hellweger, F.
2011-12-01
Karst groundwater systems develop in soluble rocks such as limestone, and are characterized by high permeability and well-developed conduit porosity. These systems provide important freshwater resources for human consumption and ecological integrity of streams, wetlands, and coastal zones. The same characteristics that make karst aquifers highly productive make them highly vulnerable to contamination. As a result, karst aquifers serve as an important route for contaminants exposure to humans and wildlife. Transport of organic contaminants in karst ground-water occurs in complex pathways influenced by the flow mechanism predominating in the aquifer: conduit-flow dominated systems tend to convey solutes rapidly through the system to a discharge point without much attenuation; diffuse-flow systems, on the other hand, can cause significant solute retardation and slow movement. These two mechanisms represent end members of a wide spectrum of conditions found in karst areas, and often a combination of conduit- and diffuse-flow mechanisms is encountered, where both flow mechanisms can control the fate and transport of contaminants. This is the case in the carbonate aquifers of northern Puerto Rico. This work addresses advances made on the characterization of fate and transport processes in karst ground-water systems characterized by variable conduit and/or diffusion dominated flow under high- and low-flow conditions. It involves laboratory-scale physical modeling and field-scale sampling and historical analysis of contaminant distribution. Statistical analysis of solute transport in Geo-Hydrobed physical models shows the heterogeneous character of transport dynamics in karstic units, and its variability under different flow regimes. Field-work analysis of chlorinated volatile organic compounds and phthalates indicates a large capacity of the karst systems to store and transmit contaminants. This work is part of the program "Puerto Rico Testsite for Exploring Contamination
Types of solutions improving passenger transport interconnectivity
Directory of Open Access Journals (Sweden)
Monika BĄK
2012-01-01
Full Text Available The objective of the paper is to present different types of solutions which could improve interconnectivity of passenger transport especially within interconnections between long and short transport distance. The topic has particular relevance at the European level because the European transport networks’ role as integrated international networks is compromised by poor interconnectivity and because the next generation of European transport policies will have to be sensitive to the differences between short, medium and long-term transport markets and the market advantages of each transport mode. In this context, a realistic assessment of intermodal opportunities is a key ingredient to future policy development.Effective interconnection requires the provision of integrated networks and services which are attractive to potential users and this is likely to require co-operation between a range of authorities and providers in the public and private sectors and may necessitate a wider vision than might otherwise prevail.The paper is based on the results of the project realised by the team of the University of Gdansk in the EU funded 7 Framework Programme - INTERCONNECT (Interconnection between short- and long-distance transport networks with partners in the UK, Germany, Denmark, Poland, Spain and Italy. Different types of solutions will be summarized in the paper including e.g. local link infrastructure solutions, improved local public transport services, improvements at the interchange, solutions involving improved procedures for check-in or luggage transfer & documentation, pricing and ticketing solutions, solutions involving marketing, information and sales.
Urban Transportation: Issue and Solution
Directory of Open Access Journals (Sweden)
Haryati Shafii
2011-10-01
Full Text Available Generally, quality of life of urban population is heavily dependent on social facilities provided within the environment. One of the most important facilities is transportations. Study on transportation mode in an urban area is especially very important because for almost every individual living in a large and densely populated area, mobility is one of the most crucial issues in everyday life. Enhance mobility, faster journey to work and less pollution from petrol-propelled vehicles can increase the quality of life, which in turn lead to a sustainable urban living. The study present transportation mode usage issues faced by community related to quality of life in an urban area. This study identifies several issues of transportation mode in urban areas and its impact on the quality of life. The study areas are Putrajaya, Kuala Lumpur and Bandar Kajang, Selangor. The methodology used in this research is secondary and primary data. The questionnaires for the survey were distributed from May 2008 to Jun 2008. These researches were conducted on 144 respondents for to evaluate their perception of transportation mode correlated to the quality of life. The collected data were then analyzed using “Statistical Packages for the Social Science” (SPSS. The respondents comprise of 61 males and 84 females from the age group of 18 to 57 years. This study identifies the percentage of public transportation mode usage in urban area, such as buses (16.7%, train (ERL, monorail and commuter-6.4%; which is very low compared to owning personal car (45.8% and motorcycle (25.4%.The result shows owning personal car is the highest (45.8% in three study areas and monorail and taxi are the lowest (1.4%. The Chi Square Test shows that among the mode transportation with traffic jam is quite difference in Kuala Lumpur, Putrajaya and Kajang. Analysis of the Chi Square Test shows the result is 0.000 (two sides to respondent answering “yes” and analysis of Spearman
Simulation Of Groundwater Flow And Reactive Transport In A Tidally Influenced Estuarine Aquifer
Mao, X.; Barry, D. A.; Enot, P.; Li, L.
2003-12-01
Existing groundwater monitoring data from an estuarine sandy aquifer situated below an old industrial landfill (Scotland) showed that (1) leaching from sulphurous waste located in the landfill has generated an acidic plume; (2) associated with the low pH, metal contaminants within the acidic plume are slowly migrating towards the estuary; and (3) the groundwater fluctuations are influenced by the tidal oscillations of the estuary. In order to test the possible influence of rainfall/precipitation, tidal fluctuation and salt water intrusion on the groundwater flow and reactive chemical transport, a model for multi-component reactive transport with density dependent flow was developed and applied to the site. The groundwater flow and chemical transport in this coastal aquifer were simulated. Both the field observations and numerical simulations showed that the tidal influence on the groundwater table fluctuations was great even far inland. This influence could not be explained by standard analytical solutions. It is expected that the local morphology and hydro-geological conditions cause this behaviour. The simulation performed with a conservative tracer showed that it took much less time to reach the estuary than the acidic plume originating from the landfill, with the rate of movement influenced by recharge and tidal oscillations. Due to buffering reactions occurring in the geochemical system during the migration of the contaminants (ion exchange, mineral precipitation/dissolution and oxidation/reduction), the movement of the acidic plume and associated metals is strongly retarded. Sharp differences are apparent in chemical concentrations, pH and pe, between the plume location and unaffected areas.
Kolditz, Olaf; Ratke, Rainer; Diersch, Hans-Jörg G.; Zielke, Werner
This work examines variable density flow and corresponding solute transport in groundwater systems. Fluid dynamics of salty solutions with significant density variations are of increasing interest in many problems of subsurface hydrology. The mathematical model comprises a set of non-linear, coupled, partial differential equations to be solved for pressure/hydraulic head and mass fraction/concentration of the solute component. The governing equations and underlying assumptions are developed and discussed. The equation of solute mass conservation is formulated in terms of mass fraction and mass concentration. Different levels of the approximation of density variations in the mass balance equations are used for convection problems (e.g. the Boussinesq approximation and its extension, fully density approximation). The impact of these simplifications is studied by use of numerical modelling. Numerical models for nonlinear problems, such as density-driven convection, must be carefully verified in a particular series of tests. Standard benchmarks for proving variable density flow models are the Henry, Elder, and salt dome (HYDROCOIN level 1 case 5) problems. We studied these benchmarks using two finite element simulators - ROCKFLOW, which was developed at the Institute of Fluid Mechanics and Computer Applications in Civil Engineering and FEFLOW, which was developed at the Institute for Water Resources Planning and Systems Research Ltd. Although both simulators are based on the Galerkin finite element method, they differ in many approximation details such as temporal discretization (Crank-Nicolson vs predictor-corrector schemes), spatial discretization (triangular and quadrilateral elements), finite element basis functions (linear, bilinear, biquadratic), iteration schemes (Newton, Picard) and solvers (direct, iterative). The numerical analysis illustrates discretization effects and defects arising from the different levels of the density of approximation. We contribute
Weerd, van de H.; Leijnse, A.; Riemsdijk, van W.H.
1998-01-01
Transport of reactive colloids in groundwater may enhance the transport of contaminants in groundwater. Often, the interpretation of results of transport experiments is not a simple task as both reactions of colloids with the solid matrix and reactions of contaminants with the solid matrix and
Measurement and modeling of phosphorous transport in shallow groundwater environments.
Hendricks, G S; Shukla, S; Obreza, T A; Harris, W G
2014-08-01
Leaching of phosphorus (P) from agricultural soils, especially those that are sandy, is adversely impacting P-limited ecosystems like Florida's Everglades. A more developed understanding of P and water management strategies and their effects on P leaching is needed to achieve reductions in subsurface P losses, especially from intensively managed dual cropping systems under plastic mulch in shallow water regions. We compared the effects of conservation P and water management strategies with traditional practices on P transport to groundwater. A 3-year experiment was conducted on hydrologically isolated plots with plastic-mulched successive cropping systems to compare high (HEI) and soil test based recommended (REI) external input (water and fertilizer P) systems with traditional sub-irrigation (seepage), and REI with a potential water conservation subsurface drip irrigation system (REI-SD) with regard to groundwater P concentrations above and below the low conductivity spodic horizon (Bh). The REI treatments had higher available storage for rainfall and P than HEI. Use of both REI systems (REI=2098μg/L and REI-SD=2048μg/L) reduced groundwater P concentrations above the Bh horizon by 33% compared to HEI (3090μg/L), and results were significant at the 0.05 level. Although the subsurface drip system saved water, it did not offer any groundwater quality (P) benefit. Mixing and dilution of influent P below the low conductivity Bh horizon between treatments and with the regional groundwater system resulted in no significant differences in groundwater P concentration below the Bh horizon. Groundwater P concentrations from this study were higher than reported elsewhere due to low soil P storage capacity (SPSC), high hydraulic conductivity of sandy soils, and a high water table beneath crop beds. The HEI system leached more P due to ferilizer P in excess of SPSC and used higher irrigation volumes compared with REI systems. Despite a 40% difference in the average amount of
Performance Analysis of Solution Transportation Absorption Chiller
Kiani, Behdad; Hamamoto, Yoshinori; Akisawa, Atsushi; Kashiwagi, Takao
Thermally activated advanced absorption cycles are considered promising candidates to replace CFCs, HCFCs and HFCs for residential and commercial applications. In such absorption systems, it is desirable to utilize the waste heat from industries for heating and cooling applications in commercial and residential sectors. For this purpose, it is necessary to transport energy over some distance because the waste heat source and demand are generally located apart from each other. Transportation of steam, hot water or chilled water requires high construction costs for insulation. There is an efficient method of energy transportation using absorption system called “ Solution Transportation Absorption System (STA)”. The solution is transported at an ambient temperature so that tube-insulations not required. This paper shows the simulation of the abovementioned system and the optimal result, using mathematical optimization. The optimum system with industry‧s waste heat utilization is obtained. At the end, the effect on the pollution emission and energy conservation is obtained.
The solute carrier 6 family of transporters
DEFF Research Database (Denmark)
Bröer, Stefan; Gether, Ulrik
2012-01-01
The solute carrier 6 (SLC6) family of the human genome comprises transporters for neurotransmitters, amino acids, osmolytes and energy metabolites. Members of this family play critical roles in neurotransmission, cellular and whole body homeostasis. Malfunction or altered expression...... of these transporters is associated with a variety of diseases. Pharmacological inhibition of the neurotransmitter transporters in this family is an important strategy in the management of neurological and psychiatric disorders. This review provides an overview of the biochemical and pharmacological properties...... of the SLC6 family transporters....
Stollenwerk, K.G.
1998-01-01
A natural-gradient tracer test was conducted in an unconfined sand and gravel aquifer on Cape Cod, Massachusetts. Molybdate was included in the injectate to study the effects of variable groundwater chemistry on its aqueous distribution and to evaluate the reliability of laboratory experiments for identifying and quantifying reactions that control the transport of reactive solutes in groundwater. Transport of molybdate in this aquifer was controlled by adsorption. The amount adsorbed varied with aqueous chemistry that changed with depth as freshwater recharge mixed with a plume of sewage-contaminated groundwater. Molybdate adsorption was strongest near the water table where pH (5.7) and the concentration of the competing solutes phosphate (2.3 micromolar) and sulfate (86 micromolar) were low. Adsorption of molybdate decreased with depth as pH increased to 6.5, phosphate increased to 40 micromolar, and sulfate increased to 340 micromolar. A one-site diffuse-layer surface-complexation model and a two-site diffuse-layer surface-complexation model were used to simulate adsorption. Reactions and equilibrium constants for both models were determined in laboratory experiments and used in the reactive-transport model PHAST to simulate the two-dimensional transport of molybdate during the tracer test. No geochemical parameters were adjusted in the simulation to improve the fit between model and field data. Both models simulated the travel distance of the molybdate cloud to within 10% during the 2-year tracer test; however, the two-site diffuse-layer model more accurately simulated the molybdate concentration distribution within the cloud.
Oehlmann, Sandra; Geyer, Tobias; Licha, Tobias; Sauter, Martin
2014-05-01
Distributive numerical simulations are an effective, process-based method for predicting groundwater resources and quality. They are based on conceptual hydrogeological models that characterize the properties of the catchment area and aquifer. Karst systems play an important role in water supply worldwide. Conceptual models are however difficult to build because of the highly developed heterogeneity of the systems. The geometry and properties of highly conductive karst conduits are generally unknown and difficult to characterize with field experiments. Due to these uncertainties numerical models of karst areas usually cannot simulate the hydraulic head distribution in the area, spring discharge and tracer breakthrough curves simultaneously on catchment scale. Especially in complex hydrogeological systems, this approach would reduce model ambiguity, which is prerequisite to predict groundwater resources and pollution risks. In this work, a distributive numerical groundwater flow and transport model was built for a highly heterogeneous karst aquifer in south-western Germany. For this aim, a solute transport interface for one-dimensional pipes was implemented in the software Comsol Multiphysics® and coupled to the standard three-dimensional solute transport interface for domains. The model was calibrated and hydraulic parameters could be obtained. The simulation was matched to the steady-state hydraulic head distribution in the model area, the spring discharge of several springs and the transport velocities of two tracer tests. Furthermore, other measured parameters such as hydraulic conductivity of the fissured matrix and the maximal karst conduit volume were available for model calibration. Parameter studies were performed for several karst conduit geometries to analyze their influence in a large-scale heterogeneous karst system. Results show that it is not only possible to derive a consistent flow and transport model for a 150 km2 karst area to be employed as a
Price, A. C.; Mendoza, C. A.
2004-05-01
Large volumes of sand tailings are produced during the extraction of bitumen from the oil sands of Northeastern Alberta. The long-term groundwater response and subsequent movement of water and solutes within the large permeable sand tailings storage areas is uncertain. At the Southwest Sand Storage (SWSS) Facility, located at Syncrude's Mildred Lake operations near Ft. McMurray, there is concern that salts from the tailings water may discharge to newly placed reclamation material that covers the sand tailings. This saline discharge water could destroy the reclamation soil structure and negatively impact vegetation. The steady-state groundwater flow and transient movement of salts at the local (bench and slope) and intermediate (pile) scales in the SWSS are investigated. Water levels, seepage and groundwater quality (including TDS) have been measured for over a year along two transects of piezometers installed in the SWSS. The field data have been used to complete traditional hydrogeological interpretations of the site, and to develop a conceptual model of flow and transport. The local and intermediate flow systems and salt transport in the dam are being evaluated with numerical models. The models will allow possible future hydrogeological behaviour of the structure to be tested. Preliminary results show differences in flow systems and salinity distribution that depend on the deposition of the SWSS. This research will facilitate better long-term environmental management of this and similar sites.
Janssen, G.; Del Val Alonso, L.; Groenendijk, P.; Griffioen, J.
2012-12-01
We developed an on-line coupling between the 1D/quasi-2D nutrient transport model ANIMO and the 3D groundwater transport model code MT3DMS. ANIMO is a detailed, process-oriented model code for the simulation of nitrate leaching to groundwater, N- and P-loads on surface waters and emissions of greenhouse gasses. It is the leading nutrient fate and transport code in the Netherlands where it is used primarily for the evaluation of fertilization related legislation. In addition, the code is applied frequently in international research projects. MT3DMS is probably the most commonly used groundwater solute transport package worldwide. The on-line model coupling ANIMO-MT3DMS combines the state-of-the-art descriptions of the biogeochemical cycles in ANIMO with the advantages of using a 3D approach for the transport through the saturated domain. These advantages include accounting for regional lateral transport, considering groundwater-surface water interactions more explicitly, and the possibility of using MODFLOW to obtain the flow fields. An additional merit of the on-line coupling concept is that it preserves feedbacks between the saturated and unsaturated zone. We tested ANIMO-MT3DMS by simulating nutrient transport for the period 1970-2007 in a Dutch agricultural polder catchment covering an area of 118 km2. The transient groundwater flow field had a temporal resolution of one day and was calculated with MODFLOW-MetaSWAP. The horizontal resolution of the model grid was 100x100m and consisted of 25 layers of varying thickness. To keep computation times manageable, we prepared MT3DMS for parallel computing, which in itself is a relevant development for a large community of groundwater transport modelers. For the parameterization of the soil, we applied a standard classification approach, representing the area by 60 units with unique combinations of soil type, land use and geohydrological setting. For the geochemical parameterization of the deeper subsurface, however, we
Validation Analysis of the Shoal Groundwater Flow and Transport Model
Energy Technology Data Exchange (ETDEWEB)
A. Hassan; J. Chapman
2008-11-01
Environmental restoration at the Shoal underground nuclear test is following a process prescribed by a Federal Facility Agreement and Consent Order (FFACO) between the U.S. Department of Energy, the U.S. Department of Defense, and the State of Nevada. Characterization of the site included two stages of well drilling and testing in 1996 and 1999, and development and revision of numerical models of groundwater flow and radionuclide transport. Agreement on a contaminant boundary for the site and a corrective action plan was reached in 2006. Later that same year, three wells were installed for the purposes of model validation and site monitoring. The FFACO prescribes a five-year proof-of-concept period for demonstrating that the site groundwater model is capable of producing meaningful results with an acceptable level of uncertainty. The corrective action plan specifies a rigorous seven step validation process. The accepted groundwater model is evaluated using that process in light of the newly acquired data. The conceptual model of ground water flow for the Project Shoal Area considers groundwater flow through the fractured granite aquifer comprising the Sand Springs Range. Water enters the system by the infiltration of precipitation directly on the surface of the mountain range. Groundwater leaves the granite aquifer by flowing into alluvial deposits in the adjacent basins of Fourmile Flat and Fairview Valley. A groundwater divide is interpreted as coinciding with the western portion of the Sand Springs Range, west of the underground nuclear test, preventing flow from the test into Fourmile Flat. A very low conductivity shear zone east of the nuclear test roughly parallels the divide. The presence of these lateral boundaries, coupled with a regional discharge area to the northeast, is interpreted in the model as causing groundwater from the site to flow in a northeastward direction into Fairview Valley. Steady-state flow conditions are assumed given the absence of
A dual-porosity model for simulating solute transport in oil shale
Glover, K.C.
1987-01-01
A model is described for simulating three-dimensional groundwater flow and solute transport in oil shale and associated geohydrologic units. The model treats oil shale as a dual-porosity medium by simulating flow and transport within fractures using the finite-element method. Diffusion of solute between fractures and the essentially static water of the shale matrix is simulated by including an analytical solution that acts as a source-sink term to the differential equation of solute transport. While knowledge of fracture orientation and spacing is needed to effectively use the model, it is not necessary to map the locations of individual fractures. The computer program listed in the report incorporates many of the features of previous dual-porosity models while retaining a practical approach to solving field problems. As a result the theory of solute transport is not extended in any appreciable way. The emphasis is on bringing together various aspects of solute transport theory in a manner that is particularly suited to the unusual groundwater flow and solute transport characteristics of oil shale systems. (Author 's abstract)
Multilevel transport solution of LWR reactor cores
Energy Technology Data Exchange (ETDEWEB)
Jose Ignacio Marquez Damian; Cassiano R.E. de Oliveira; HyeonKae Park
2008-09-01
This work presents a multilevel approach for the solution of the transport equation in typical LWR assemblies and core configurations. It is based on the second-order, even-parity formulation of the transport equation, which is solved within the framework provided by the finite element-spherical harmonics code EVENT. The performance of the new solver has been compared with that of the standard conjugate gradient solver for diffusion and transport problems on structured and unstruc-tured grids. Numerical results demonstrate the potential of the multilevel scheme for realistic reactor calculations.
Energy Technology Data Exchange (ETDEWEB)
TP Clement
1999-06-24
RT3DV1 (Reactive Transport in 3-Dimensions) is computer code that solves the coupled partial differential equations that describe reactive-flow and transport of multiple mobile and/or immobile species in three-dimensional saturated groundwater systems. RT3D is a generalized multi-species version of the US Environmental Protection Agency (EPA) transport code, MT3D (Zheng, 1990). The current version of RT3D uses the advection and dispersion solvers from the DOD-1.5 (1997) version of MT3D. As with MT3D, RT3D also requires the groundwater flow code MODFLOW for computing spatial and temporal variations in groundwater head distribution. The RT3D code was originally developed to support the contaminant transport modeling efforts at natural attenuation demonstration sites. As a research tool, RT3D has also been used to model several laboratory and pilot-scale active bioremediation experiments. The performance of RT3D has been validated by comparing the code results against various numerical and analytical solutions. The code is currently being used to model field-scale natural attenuation at multiple sites. The RT3D code is unique in that it includes an implicit reaction solver that makes the code sufficiently flexible for simulating various types of chemical and microbial reaction kinetics. RT3D V1.0 supports seven pre-programmed reaction modules that can be used to simulate different types of reactive contaminants including benzene-toluene-xylene mixtures (BTEX), and chlorinated solvents such as tetrachloroethene (PCE) and trichloroethene (TCE). In addition, RT3D has a user-defined reaction option that can be used to simulate any other types of user-specified reactive transport systems. This report describes the mathematical details of the RT3D computer code and its input/output data structure. It is assumed that the user is familiar with the basics of groundwater flow and contaminant transport mechanics. In addition, RT3D users are expected to have some experience in
Evaluation of oscillatory integrals for analytical groundwater flow and mass transport models
Ledder, Glenn; Zlotnik, Vitaly A.
2017-06-01
Modeling of transient dynamics of an interface between fluids of identical density and viscosity, but different otherwise, is of great interest in aquifer hydraulic, and advective contaminant transport, and has broad application. Closed-form solutions are often available for problems with simple, practically important geometry, but the integrals that appear in such solutions often have integrands with two or more oscillatory factors. Such integrals pose difficulties for numerical evaluation because the positive and negative contributions of the integrand largely cancel and the integrands decay very slowly in the integration domain. Some problems with integrands with a single oscillatory factor were tackled in the past with an integration/summation/extrapolation (ISE) method: breaking the integrand at consecutive zeros to obtain an alternating series and then using the Shanks algorithm to accelerate convergence of the series. However, this technique is ineffective for problems with multiple oscillatory factors. We present a comprehensive strategy for evaluation of such integrals that includes a better ISE method, an interval truncation method, and long-time asymptotics; this strategy is applicable to a large class of integrals with either single or multiple oscillatory factors that arise in modeling of groundwater flow and transport. The effectiveness of this methodology is illustrated by examples of integrals used in well hydraulics, groundwater recharge design, and particle tracking.
Pursuing Solutions to Sustain Groundwater in California's Changing Climate
Gilbert, James
2014-08-01
A century of groundwater development in California with comparatively little regulation has yielded enduring legal, political, and hydrologic challenges compounded by drought, population growth and shifts, and climate change. With the debate over state and local roles in managing the resource garnering considerable attention, focus is shifting to how best to address groundwater issues for future sustainability. Groundwater does not exist in isolation, and sustainable management requires understanding interconnections with climate, land surface, and human actions. This integrated approach to California's groundwater raises significant cross-disciplinary questions that will need to be answered by the next generation of scientists, managers, and policy makers.
Singha, Kamini; Li, Li; Day-Lewis, Frederick D.; Regberg, Aaron B.
2012-01-01
The concept of a nonreactive or conservative tracer, commonly invoked in investigations of solute transport, requires additional study in the context of electrical geophysical monitoring. Tracers that are commonly considered conservative may undergo reactive processes, such as ion exchange, thus changing the aqueous composition of the system. As a result, the measured electrical conductivity may reflect not only solute transport but also reactive processes. We have evaluated the impacts of ion exchange reactions, rate-limited mass transfer, and surface conduction on quantifying tracer mass, mean arrival time, and temporal variance in laboratory-scale column experiments. Numerical examples showed that (1) ion exchange can lead to resistivity-estimated tracer mass, velocity, and dispersivity that may be inaccurate; (2) mass transfer leads to an overestimate in the mobile tracer mass and an underestimate in velocity when using electrical methods; and (3) surface conductance does not notably affect estimated moments when high-concentration tracers are used, although this phenomenon may be important at low concentrations or in sediments with high and/or spatially variable cation-exchange capacity. In all cases, colocated groundwater concentration measurements are of high importance for interpreting geophysical data with respect to the controlling transport processes of interest.
Energy Technology Data Exchange (ETDEWEB)
NONE
1998-04-01
The over-reaching goal of the Groundwater Grand Challenge component of the Partnership in Computational Science (PICS) was to develop and establish the massively parallel approach for the description of groundwater flow and transport and to address the problem of uncertainties in the data and its interpretation. This necessitated the development of innovative algorithms and the implementation of massively parallel computational tools to provide a suite of simulators for groundwater flow and transport in heterogeneous media. This report summarizes the activities and deliverables of the Groundwater Grand Challenge project funded through the High Performance Computing grand challenge program of the Department of Energy from 1995 through 1997.
Directory of Open Access Journals (Sweden)
Swati Verma
2015-09-01
New hydrological insights for the region: Most groundwater solutes of RCD and YA terrains were derived from both silicate weathering and carbonate dissolution, while silicate weathering process dominates the solute contribution in OA groundwater. Groundwater samples from all terrains are postoxic with mean pe values between Fe(III and As(V–As(III reductive transition. While, reductive dissolution of (Fe–MnOOH is the dominant mechanism of As mobilization in RCD and YA aquifers, As in OA and PD aquifers could be mobilized by combined effect of pH dependent sorption and competitive ion exchange. The present study focuses on the major ion chemistry as well as the chemistry of the redox sensitive solutes of the groundwater in different geomorphic settings and their links to arsenic mobilization in groundwater.
Braids, Olin C.; Gillies, Nola P.
1978-01-01
Presents a literature review of groundwater quality covering publications of 1977. This review includes: (1) sources of groundwater contamination; and (2) management of groundwater. A list of 59 references is also presented. (HM)
Applying dispersive changes to Lagrangian particles in groundwater transport models
Konikow, Leonard F.
2010-01-01
Method-of-characteristics groundwater transport models require that changes in concentrations computed within an Eulerian framework to account for dispersion be transferred to moving particles used to simulate advective transport. A new algorithm was developed to accomplish this transfer between nodal values and advecting particles more precisely and realistically compared to currently used methods. The new method scales the changes and adjustments of particle concentrations relative to limiting bounds of concentration values determined from the population of adjacent nodal values. The method precludes unrealistic undershoot or overshoot for concentrations of individual particles. In the new method, if dispersion causes cell concentrations to decrease during a time step, those particles in the cell having the highest concentration will decrease the most, and those with the lowest concentration will decrease the least. The converse is true if dispersion is causing concentrations to increase. Furthermore, if the initial concentration on a particle is outside the range of the adjacent nodal values, it will automatically be adjusted in the direction of the acceptable range of values. The new method is inherently mass conservative.
Heywood, Charles E.
2013-01-01
flow and transport through these wells requires time discretization that adequately represents periods of pumping and non-pumping. The effects of intra-borehole flow are not fully represented in the simulation because it employs seasonal stress periods, which are longer than periods of pumping and non-pumping. Further simulations utilizing daily pumpage data and model stress periods may help quantify the relative effects of intra-borehole versus advective aquifer flow on the transport of contaminants near the public-supply wells. The fraction of young water withdrawn from the studied supply well varies with simulated pumping rates due to changes in the relative contributions to flow from different aquifer intervals. The advective transport of dissolved solutes from a known contaminant source to the public-supply wells was simulated by using particle-tracking. Because of the transient groundwater flow field, scenarios with alternative contaminant release times result in different simulated-particle fates, most of which are withdrawn from the aquifer at wells that are between the source and the studied supply well. The relatively small effective porosity required to simulate advective transport from the simulated contaminant source to the studied supply well is representative of a preferential pathway and not the predominant aquifer effective porosity that was estimated by the calibration of the model to observed chemical-tracer concentrations.
Water flow and solute transport in floating fen root mats
Stofberg, Sija F.; EATM van der Zee, Sjoerd
2015-04-01
be very similar and likely functionally related. Our experimental field data were used for modelling water flow and solute transport in floating fens, using HYDRUS 2D. Fluctuations of surface water and root mat, as well as geometry and unsaturated zone parameters can have a major influence on groundwater fluctuations and the exchange between rain and surface water and the water in the root mats. In combination with the duration of salt pulses in surface water, and sensitivity of fen plants to salinity (Stofberg et al. 2014, submitted), risks for rare plants can be anticipated.
Exact solution of the neutron transport equation in spherical geometry
Energy Technology Data Exchange (ETDEWEB)
Anli, Fikret; Akkurt, Abdullah; Yildirim, Hueseyin; Ates, Kemal [Kahramanmaras Suetcue Imam Univ. (Turkey). Faculty of Sciences and Letters
2017-03-15
Solution of the neutron transport equation in one dimensional slab geometry construct a basis for the solution of neutron transport equation in a curvilinear geometry. Therefore, in this work, we attempt to derive an exact analytical benchmark solution for both neutron transport equations in slab and spherical medium by using P{sub N} approximation which is widely used in neutron transport theory.
Model-data integration for predictive assessment of groundwater reactive transport systems
Carniato, L.
2014-01-01
Predicting the evolution of groundwater contamination is a major concern for society, in particular when investments are made to remediate the contamination. Groundwater reactive transport models are valuable tools to integrate the available measurements in a consistent framework, improving our unde
Metropol, a computer code for the simulation of transport of contaminants with groundwater
Sauter FJ; Hassanizadeh SM; Leijnse A; Glasbergen P; Slot AFM
1990-01-01
In this report a description is given of the computer code METROPOL. This code simulates the three dimensional flow of groundwater with varying density and the simultaneous transport of contaminants in low concentration and is based on the finite element method. The basic equations for groundwater
Weerd, van de H.
2000-01-01
Transport of contaminants constitutes a potential threat for public health and ecosystems. One of the potential pathways for contaminant transport in groundwater systems is transport adsorbed to carriers (colloidal particles, large molecules). Figure 1 shows a detail of a
Weerd, van de H.
2000-01-01
Transport of contaminants constitutes a potential threat for public health and ecosystems. One of the potential pathways for contaminant transport in groundwater systems is transport adsorbed to carriers (colloidal particles, large molecules). Figure 1 shows a detail of a grou
González De Posada, Francisco
2012-01-01
From the perspective of Hydrogeology, the concept and an introductory general typology of groundwater are established. From the perspective of Geotechnical Engineering works, the physical and mathematical equations of the hydraulics of permeable materials, which are implemented, by electric analogical simulation, to two unique cases of global importance, are considered: the bailing during the construction of the dry dock of the "new shipyard of the Bahia de Cádiz" and the waterproofing of the "Hatillo dam" in the Dominican Republic. From a physical fundamental perspective, the theories which are the subset of "analogical physical theories of Fourier type transport" are related, among which the one constituted by the laws of Adolf Fick in physiology occupies a historic role of some relevance. And finally, as a philosophical abstraction of so much useful mathematical process, the one which is called "the Galilean principle of the mathematical design of the Nature" is dealt with.
Pérez Guerrero, J. S.; Skaggs, T. H.
2010-08-01
SummaryMathematical models describing contaminant transport in heterogeneous porous media are often formulated as an advection-dispersion transport equation with distance-dependent transport coefficients. In this work, a general analytical solution is presented for the linear, one-dimensional advection-dispersion equation with distance-dependent coefficients. An integrating factor is employed to obtain a transport equation that has a self-adjoint differential operator, and a solution is found using the generalized integral transform technique (GITT). It is demonstrated that an analytical expression for the integrating factor exists for several transport equation formulations of practical importance in groundwater transport modeling. Unlike nearly all solutions available in the literature, the current solution is developed for a finite spatial domain. As an illustration, solutions for the particular case of a linearly increasing dispersivity are developed in detail and results are compared with solutions from the literature. Among other applications, the current analytical solution will be particularly useful for testing or benchmarking numerical transport codes because of the incorporation of a finite spatial domain.
Li, Weiyao; Huang, Guanhua; Xiong, Yunwu
2016-04-01
The complexity of the spatial structure of porous media, randomness of groundwater recharge and discharge (rainfall, runoff, etc.) has led to groundwater movement complexity, physical and chemical interaction between groundwater and porous media cause solute transport in the medium more complicated. An appropriate method to describe the complexity of features is essential when study on solute transport and conversion in porous media. Information entropy could measure uncertainty and disorder, therefore we attempted to investigate complexity, explore the contact between the information entropy and complexity of solute transport in heterogeneous porous media using information entropy theory. Based on Markov theory, two-dimensional stochastic field of hydraulic conductivity (K) was generated by transition probability. Flow and solute transport model were established under four conditions (instantaneous point source, continuous point source, instantaneous line source and continuous line source). The spatial and temporal complexity of solute transport process was characterized and evaluated using spatial moment and information entropy. Results indicated that the entropy increased as the increase of complexity of solute transport process. For the point source, the one-dimensional entropy of solute concentration increased at first and then decreased along X and Y directions. As time increased, entropy peak value basically unchanged, peak position migrated along the flow direction (X direction) and approximately coincided with the centroid position. With the increase of time, spatial variability and complexity of solute concentration increase, which result in the increases of the second-order spatial moment and the two-dimensional entropy. Information entropy of line source was higher than point source. Solute entropy obtained from continuous input was higher than instantaneous input. Due to the increase of average length of lithoface, media continuity increased, flow and
Modelling regional transport of pesticide residues in groundwater
Leistra, M.; Beltman, W.H.J.; Boesten, J.J.T.I.; Matser, A.M.; Zee, van der S.E.A.T.M.
1996-01-01
The movement of pesticides through soil and groundwater to pumping wells for drinking-water supply was modelled. Most of the retardation and transformation occurs when a pesticide moves through the unsaturated zone. Computed leaching to groundwater increased when soil heterogeneity was taken into
Energy Technology Data Exchange (ETDEWEB)
Roth, T.L.; Bowman, R.S. [New Mexico Tech, Socorro, NM (United States). Dept. of Geoscience
1995-12-31
With the rapid growth of the Albuquerque region, groundwater contamination from nonpoint sources has become an increasing concern. Agriculture, one major land usage of the basin area, can abe responsible for the leaching of nutrients and chemicals to shallow groundwater via irrigation return flows. Even so, there is almost no available information regarding agricultural impacts on groundwater quality in New Mexico. The major objective of this project has been to develop a data base pertaining to this issue. The main goals of this project are: to adapt the tile drainage system to allow for the collection of irrigation return flows on an actual, operating farm; to utilize the tile drain sampling system to quantify nutrient and pesticide levels in the irrigation return flow; to determine the local hydrology in an around the field site; and to use the collected field data to test the two-dimensional water flow and chemical transport model (CHAIN 2-D).
Factors Controlling the Groundwater Transport of U, Th, Ra, and Rn
Indian Academy of Sciences (India)
A Tricca; D Porcelli; G J Wasserburg
2000-03-01
A model for the groundwater transport of naturally occurring U, Th, Ra, and Rn nuclides in the 238U and 232Th decay series is discussed. The model developed here takes into account transport by advection and the physico-chemical processes of weathering, decay, -recoil, and sorption at the water-rock interface. It describes the evolution along a flowline of the activities of the 238U and 232Th decay series nuclides in groundwater. Simple sets of relationships governing the activities of the various species in solution are derived, and these can be used both to calculate effective retardation factors and to interpret groundwater data. For the activities of each nuclide, a general solution to the transport equation has been obtained, which shows that the activities reach a constant value after a distance $\\bar{x}_i$, characteristic of each nuclide. Where $\\bar{x}_i$ is much longer than the aquifer length, (for 238U, 234U, and 232Th), the activities grow linearly with distance. Where $\\bar{x}_i$ is short compared to the aquifer length, (for 234Th, 230Th, 228Th, 228Ra, and 224Ra), the activities rapidly reach a constant or quasi-constant activity value. For 226Ra and 222Rn, the limiting activity is reached after 1 km. High 234U values (proportional to the ratio 234Th/W238U) can be obtained through high recoil fraction and/or low weathering rates. The activity ratios 230Th/232Th, 228Ra/226Ra and 224Ra/226Ra have been considered in the cases where either weathering or recoil is the predominant process of input from the mineral grain. Typical values for weathering rates and recoil fractions for a sandy aquifer indicate that recoil is the dominant process for Th isotopic ratios in the water. Measured data for Ra isotope activity ratios indicate that recoil is the process generally controlling the Ra isotopic composition in water. Higher isotopic ratios can be explained by different desorption kinetics of Ra. However, the model does not provide an explanation for 228Ra
Solute transport in cracking clay soils
Bronswijk, J.J.B.; Ritsema, C.J.; Oostindie, K.; Hamminga, P.
1996-01-01
A bromide tracer applied to a cracked clay soil was adsorbed in the soil matrix close to the soil surface. Upon subsequent precipitation, a small part of the bromide dissolved and flowed rapidly through cracks to the subsoil and the groundwater. As a result, the groundwater and the drain discharge
García-Gil, Alejandro; Epting, Jannis; Ayora, Carlos; Garrido, Eduardo; Vázquez-Suñé, Enric; Huggenberger, Peter; Gimenez, Ana Cristina
2016-11-01
Shallow geothermal resource exploitation through the use of groundwater heat pump systems not only has hydraulic and thermal effects on the environment but also induces physicochemical changes that can compromise the operability of installations. This study focuses on chemical clogging and dissolution subsidence processes observed during the geothermal re-injection of pumped groundwater into an urban aquifer. To explain these phenomena, two transient reactive transport models of a groundwater heat pump installation in an alluvial aquifer were used to reproduce groundwater-solid matrix interactions occurring in a surrounding aquifer environment during system operation. The models couple groundwater flow, heat and solute transport together with chemical reactions. In these models, the permeability distribution in space changes with precipitation-dissolution reactions over time. The simulations allowed us to estimate the calcite precipitation rates and porosity variations over space and time as a function of existent hydraulic gradients in an aquifer as well as the intensity of CO2 exchanges with the atmosphere. The results obtained from the numerical model show how CO2 exolution processes that occur during groundwater reinjection into an aquifer and calcite precipitation are related to hydraulic efficiency losses in exploitation systems. Finally, the performance of reinjection wells was evaluated over time according to different scenarios until the systems were fully obstructed. Our simulations also show a reduction in hydraulic conductivity that forces re-injected water to flow downwards, thereby enhancing the dissolution of evaporitic bedrock and producing subsidence that can ultimately result in a dramatic collapse of the injection well infrastructure.
Rolle, Massimo; Chiogna, Gabriele; Hochstetler, David L; Kitanidis, Peter K
2013-10-01
Mixing processes significantly affect and limit contaminant transport and transformation rates in the subsurface. The correct quantification of mixing in groundwater systems must account for diffusion, local-scale dispersion and the flow variability in heterogeneous flow fields (e.g., flow-focusing in high-conductivity and de-focusing in low-conductivity zones). Recent results of multitracer laboratory experiments revealed the significant effect of compound-specific diffusive properties on the physical displacement of dissolved species across a representative range of groundwater flow velocities. The goal of this study is to investigate the role of diffusion and compound-specific mixing for solute transport across a range of scales including: (i) pore-scale (~10⁻² m), (ii) laboratory bench-scale (~10⁰ m) and (iii) field-scale (~10² m). We investigate both conservative and mixing-controlled reactive transport using pore-scale modeling, flow-through laboratory experiments and simulations, and field-scale numerical modeling of complex heterogeneous hydraulic conductivity fields with statistical properties similar to the ones reported for the extensively investigated Borden aquifer (Ontario, Canada) and Columbus aquifer (Mississippi, USA, also known as MADE site). We consider different steady-state and transient transport scenarios. For the conservative cases we use as a metric of mixing the exponential of the Shannon entropy to quantify solute dilution either in a given volume (dilution index) or in a given solute flux (flux-related dilution index). The decrease in the mass and the mass-flux of the contaminant plumes is evaluated to quantify reactive mixing. The results show that diffusive processes, occurring at the small-scale of a pore channel, strongly affect conservative and reactive solute transport at larger macroscopic scales. The outcomes of our study illustrate the need to consider and properly account for compound-specific diffusion and mixing
Berglund, Sten; Bosson, Emma; Selroos, Jan-Olof; Sassner, Mona
2013-05-01
This paper describes solute transport modeling carried out as a part of an assessment of the long-term radiological safety of a planned deep rock repository for spent nuclear fuel in Forsmark, Sweden. Specifically, it presents transport modeling performed to locate and describe discharge areas for groundwater potentially carrying radionuclides from the repository to the surface where man and the environment could be affected by the contamination. The modeling results show that topography to large extent determines the discharge locations. Present and future lake and wetland objects are central for the radionuclide transport and dose calculations in the safety assessment. Results of detailed transport modeling focusing on the regolith and the upper part of the rock indicate that the identification of discharge areas and objects considered in the safety assessment is robust in the sense that it does not change when a more detailed model representation is used.
Energy Technology Data Exchange (ETDEWEB)
Berglund, Sten [HydroResearch AB, Taeby (Sweden)], E-mail: sten.berglund@hydroresearch.se; Bosson, Emma; Selroos, Jan-Olof [Swedish Nuclear Fuel and Waste Management Co (SKB), Stockholm (Sweden); Sassner, Mona [DHI Sverige AB, Stockholm (Sweden)
2013-05-15
This paper describes solute transport modeling carried out as a part of an assessment of the long-term radiological safety of a planned deep rock repository for spent nuclear fuel in Forsmark, Sweden. Specifically, it presents transport modeling performed to locate and describe discharge areas for groundwater potentially carrying radionuclides from the repository to the surface where man and the environment could be affected by the contamination. The modeling results show that topography to large extent determines the discharge locations. Present and future lake and wetland objects are central for the radionuclide transport and dose calculations in the safety assessment. Results of detailed transport modeling focusing on the regolith and the upper part of the rock indicate that the identification of discharge areas and objects considered in the safety assessment is robust in the sense that it does not change when a more detailed model representation is used.
Ciriello, V.; Di Federico, V.; Riva, M.; Cadini, F.; De Sanctis, J.; Zio, E.; Guadagnini, A.
2012-04-01
We perform a Global Sensitivity Analysis (GSA) of a transport model used to compute the peak radionuclide concentration at a given control location in a randomly heterogeneous aquifer, following a release from a near surface repository of radioactive waste and subsequent contaminant migration within the host porous medium. We illustrate how uncertainty stemming from incomplete characterization of (a) the correlation scale of the variogram of hydraulic conductivity, (b) the partition coefficient associated with sorption of the migrating radionuclide, and (c) the effective dispersivity at the scale of interest propagates to the first two (ensemble) moments of the peak solute concentration detected at a target location within a two-dimensional randomly heterogeneous hydraulic conductivity field. We treat the uncertain system parameters as independent random variables and perform a variance-based GSA within a numerical Monte Carlo framework. Groundwater flow and transport are solved by randomly sampling the space of the uncertain parameters for an ensemble of generated hydraulic conductivity realizations. The Sobol indices are adopted as sensitivity measures. These are calculated by employing a Polynomial Chaos Expansion (PCE) technique. The PCE-based representation of the response surface of the adopted transport model is then adopted as a surrogate model of the transport process to reduce the computational burden associated with a standard Monte Carlo solution of the original governing equations. This methodology allows identifying the relative influence of the selected uncertain parameters on the target (ensemble) moments of peak concentrations. Our results suggest that the ensemble mean of peak concentration is strongly influenced by the partition coefficient and the longitudinal dispersivity for the scenario analyzed. On the other hand, the hydraulic conductivity correlation scale plays an important role in the variance of the calculated peak concentration values
Towards a filtered density function approach for reactive transport in groundwater
Suciu, N.; Schüler, L.; Attinger, S.; Knabner, P.
2016-04-01
Evolution equations for probability density functions (PDFs) and filtered density functions (FDFs) of random species concentrations weighted by conserved scalars are formulated as Fokker-Planck equations describing stochastically equivalent processes in concentration-position spaces. This approach provides consistent numerical PDF/FDF solutions, given by the density in the concentration-position space of an ensemble of computational particles governed by the associated Itô equations. The solutions are obtained by a global random walk (GRW) algorithm, which is stable, free of numerical diffusion, and practically insensitive to the increase of the number of particles. The general FDF approach and the GRW numerical solution are illustrated for a reduced complexity problem consisting of the transport of a single scalar in groundwater. Randomness is induced by the stochastic parameterization of the hydraulic conductivity, characterized by short range correlations and small variance. The objective is to infer the statistics of the random concentration sampled at the plume center of mass, integrated over the transverse dimension of a two-dimensional spatial domain. The PDF/FDF problem can therefore be formulated in a two-dimensional domain as well, a spatial dimension and one in the concentration space. The upscaled drift and diffusion coefficients describing the PDF transport in the physical space are estimated on single-trajectories of diffusion in velocity fields with short-range correlations, owing to their self-averaging property. The mixing coefficients describing the PDF transport in concentration spaces are parameterized by the trend and the noise inferred from the statistical analysis of an ensemble of simulated concentration time series, as well as by classical mixing models. A Gaussian spatial filter applied to a Kraichnan velocity field generator is used to construct coarse-grained simulations (CGS) for FDF problems. The purposes of the CGS simulations are
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Jarsjoe, Jerker; Destouni, Georgia; Persson, Klas; Prieto, Carmen (Dept. of Physical Geography, Quaternary Geology, Stockholm Univ., Stockholm (Sweden))
2007-12-15
We formulate a general theoretical conceptualisation of solute transport from inland sources to downstream recipients, considering main recipient load contributions from all different nutrient and pollutant sources that may exist within any catchment. Since the conceptualisation is model independent, its main hydrological factors and mass delivery factors can be quantified on the basis of inputs to and outputs from any considered analytical or numerical model. Some of the conceptually considered source contribution and transport pathway combinations are however commonly neglected in catchment-scale solute transport and attenuation modelling, in particular those related to subsurface sources, diffuse sources at the land surface and direct groundwater transport into the recipient. The conceptual framework provides a possible tool for clarification of underlying and often implicit model assumptions, which can be useful for e.g. inter-model comparisons. In order to further clarify and explain research questions that may be of particular importance for transport pathways from deep groundwater surrounding a repository, we concretise and interpret some selected transport scenarios for model conditions in the Forsmark area. Possible uncertainties in coastal discharge predictions, related to uncertain spatial variation of evapotranspiration within the catchment, were shown to be small for the relatively large, focused surface water discharges from land to sea, because local differences were averaged out along the length of the main water flow paths. In contrast, local flux values within the diffuse groundwater flow field from land to sea are more uncertain, although estimates of mean values and total sums of submarine groundwater discharge (SGD) along some considerable coastline length may be robust. The present results show that 80% to 90% of the total coastal discharge of Forsmark occurred through focused flows in visible streams, whereas the remaining 10% to 20% was
Energy Technology Data Exchange (ETDEWEB)
Jarsjoe, Jerker; Destouni, Georgia; Persson, Klas; Prieto, Carmen (Dept. of Physical Geography, Quaternary Geology, Stockholm Univ., Stockholm (Sweden))
2007-12-15
We formulate a general theoretical conceptualisation of solute transport from inland sources to downstream recipients, considering main recipient load contributions from all different nutrient and pollutant sources that may exist within any catchment. Since the conceptualisation is model independent, its main hydrological factors and mass delivery factors can be quantified on the basis of inputs to and outputs from any considered analytical or numerical model. Some of the conceptually considered source contribution and transport pathway combinations are however commonly neglected in catchment-scale solute transport and attenuation modelling, in particular those related to subsurface sources, diffuse sources at the land surface and direct groundwater transport into the recipient. The conceptual framework provides a possible tool for clarification of underlying and often implicit model assumptions, which can be useful for e.g. inter-model comparisons. In order to further clarify and explain research questions that may be of particular importance for transport pathways from deep groundwater surrounding a repository, we concretise and interpret some selected transport scenarios for model conditions in the Forsmark area. Possible uncertainties in coastal discharge predictions, related to uncertain spatial variation of evapotranspiration within the catchment, were shown to be small for the relatively large, focused surface water discharges from land to sea, because local differences were averaged out along the length of the main water flow paths. In contrast, local flux values within the diffuse groundwater flow field from land to sea are more uncertain, although estimates of mean values and total sums of submarine groundwater discharge (SGD) along some considerable coastline length may be robust. The present results show that 80% to 90% of the total coastal discharge of Forsmark occurred through focused flows in visible streams, whereas the remaining 10% to 20% was
Packman, A. I.
2012-12-01
Thirty years after Bencala and Walters' landmark paper on transient storage seems like a good time to reflect on our understanding of hyporheic exchange and solute transport in rivers. Bencala and Walters' work, and the related fieldwork of many others at the U.S. Geological Survey, changed the paradigm for flow in river corridors. Previously, the prevailing view had been that in-stream transport was regulated primarily by advection and dispersion. This thinking was rooted in well-established theory derived from the work of G.I. Taylor on dispersion processes, and supported by extensive fieldwork in the 1960's and 1970's. River and groundwater flow were strictly separated at the channel boundary. After Bencala and Walters (and a lot of follow-up work!) we now understand that water continuously exchanges across stream channel boundaries. This has profound implications for not only solute transport in rivers, but also a wide variety of biogeochemical, ecological, and even geomorphological processes. In this talk, I will review the historical development of theory for solute transport in rivers, try to convey why Bencala and Walters was so important to both hydrology and biogeochemistry, and discuss how recent developments in measurement methods and stochastic transport theory can be used to further advance our understanding of surface-groundwater connectivity.
Can We Remove Secular Terms for Analytical Solution of Groundwater Response under Tidal Influence?
Munusamy, Selva Balaji
2016-01-01
This paper presents a secular term removal methodology based on the homotopy perturbation method for analytical solutions of nonlinear problems with periodic boundary condition. The analytical solution for groundwater response to tidal fluctuation in a coastal unconfined aquifer system with the vertical beach is provided as an example. The non-linear one-dimensional Boussinesq's equation is considered as the governing equation for the groundwater flow. An analytical solution is provided for non-dimensional Boussinesq's equation with cosine harmonic boundary condition representing tidal boundary condition. The analytical solution is obtained by using homotopy perturbation method with a virtual embedding parameter. The present approach does not require pre-specified perturbation parameter and also facilitates secular terms elimination in the perturbation solution. The solutions starting from zeroth-order up to third-order are obtained. The non-dimensional expression, $A/D_{\\infty}$ emerges as an implicit parame...
Ganguli, P.M.; Conaway, C.H.; Swarzenski, P.W.; Izbicki, J.A.; Flegal, A.R.
2012-01-01
We measured total mercury (Hg T) and monomethylmercury (MMHg) concentrations in coastal groundwater and seawater over a range of tidal conditions near Malibu Lagoon, California, and used 222Rn-derived estimates of submarine groundwater discharge (SGD) to assess the flux of mercury species to nearshore seawater. We infer a groundwater-seawater mixing scenario based on salinity and temperature trends and suggest that increased groundwater discharge to the ocean during low tide transported mercury offshore. Unfiltered Hg T (U-Hg T) concentrations in groundwater (2.2-5.9 pM) and seawater (3.3-5.2 pM) decreased during a falling tide, with groundwater U-Hg T concentrations typically lower than seawater concentrations. Despite the low Hg T in groundwater, bioaccumulative MMHg was produced in onshore sediment as evidenced by elevated MMHg concentrations in groundwater (0.2-1 pM) relative to seawater (???0.1 pM) throughout most of the tidal cycle. During low tide, groundwater appeared to transport MMHg to the coast, resulting in a 5-fold increase in seawater MMHg (from 0.1 to 0.5 pM). Similarly, filtered Hg T (F-Hg T) concentrations in seawater increased approximately 7-fold during low tide (from 0.5 to 3.6 pM). These elevated seawater F-Hg T concentrations exceeded those in filtered and unfiltered groundwater during low tide, but were similar to seawater U-Hg T concentrations, suggesting that enhanced SGD altered mercury partitioning and/or solubilization dynamics in coastal waters. Finally, we estimate that the SGD Hg T and MMHg fluxes to seawater were 0.41 and 0.15 nmol m -2 d -1, respectively - comparable in magnitude to atmospheric and benthic fluxes in similar environments. ?? 2012 American Chemical Society.
Mao, X.; Prommer, H.; Barry, D.A.; Langevin, C.D.; Panteleit, B.; Li, L.
2006-01-01
PHWAT is a new model that couples a geochemical reaction model (PHREEQC-2) with a density-dependent groundwater flow and solute transport model (SEAWAT) using the split-operator approach. PHWAT was developed to simulate multi-component reactive transport in variable density groundwater flow. Fluid density in PHWAT depends not on only the concentration of a single species as in SEAWAT, but also the concentrations of other dissolved chemicals that can be subject to reactive processes. Simulation results of PHWAT and PHREEQC-2 were compared in their predictions of effluent concentration from a column experiment. Both models produced identical results, showing that PHWAT has correctly coupled the sub-packages. PHWAT was then applied to the simulation of a tank experiment in which seawater intrusion was accompanied by cation exchange. The density dependence of the intrusion and the snow-plough effect in the breakthrough curves were reflected in the model simulations, which were in good agreement with the measured breakthrough data. Comparison simulations that, in turn, excluded density effects and reactions allowed us to quantify the marked effect of ignoring these processes. Next, we explored numerical issues involved in the practical application of PHWAT using the example of a dense plume flowing into a tank containing fresh water. It was shown that PHWAT could model physically unstable flow and that numerical instabilities were suppressed. Physical instability developed in the model in accordance with the increase of the modified Rayleigh number for density-dependent flow, in agreement with previous research. ?? 2004 Elsevier Ltd. All rights reserved.
Evaluation of Monensin Transport to Shallow Groundwater after Irrigation with Dairy Lagoon Water.
Hafner, Sarah C; Harter, Thomas; Parikh, Sanjai J
2016-03-01
Animal waste products from concentrated animal feeding operations are a significant source of antibiotics to the environment. Monensin, an ionophore antibiotic commonly used to increase feed efficiency in livestock, is known to have varied toxicological effects on nontarget species. The current study builds on prior studies evaluating the impact of dairy management on groundwater quality by examining the transport of monensin in an agricultural field with coarse-textured soils during irrigation with lagoon wastewater. The dairy is located in California's San Joaquin Valley, where groundwater can be encountered Groundwater samples were collected from a network of monitoring wells installed throughout the dairy and adjacent to irrigated fields before and after an irrigation event, which allowed for measurement of monensin potentially reaching the shallow groundwater as a direct result of irrigation with lagoon water. Monensin was extracted from water samples via hydrophilic-lipophilic balance solid-phase extraction and quantified with liquid chromatography-mass spectrometry. Irrigation water was found to contain up to 1.6 μg L monensin, but monensin was only detected in monitoring wells surrounding the waste storage lagoon. Water chemistry changes in the wells bordering the irrigated field suggest that up to 7% of irrigation water reached groundwater within days of irrigation. The study suggests that contamination of groundwater with monensin can occur primarily by compromised waste storage systems and that rapid transport of monensin to groundwater is not likely to occur from a single irrigation event.
Xu, Cundong; Zhang, Hongyang; Han, Liwei; Zhai, Luxin
2014-11-01
The rules of microscopic water-salt transportation can be revealed and the impact on the macroscopic water and soil resources can be further predicted by selecting a typical study area and carrying out continuous monitoring. In this paper, Jingtaichuan Electrical Lifting Irrigation District in Gansu Province (hereinafter called as JingDian irrigation district (JID)) located at the inland desert region of northwest China was selected as study area. Based on the groundwater-salt transportation data of representative groundwater monitoring wells in different hydrogeological units, the groundwater-salt evolution and transportation tendency in both closed and unclosed hydrogeological units were analyzed and the quantity relative ratio relationship of regional water-salt input-excretion was calculated. The results showed that the salt brought in by artificial irrigation accounts for the highest proportion of about 63.99% and the salt carried off by the discharge of irrigation water accounts for 66.42%, namely, the water-salt evolution and transportation were mainly controlled by artificial irrigation. As the general features of regional water-salt transportation, groundwater salinity and soil salt content variation were mainly decided by the transportation of soil soluble salt which showed an obvious symbiosis gathering regularity, but the differentiation with insoluble salt components was significant in the transportation process. Besides, groundwater salinity of the unclosed hydrogeological unit presented a periodically fluctuating trend, while the groundwater salinity and soil salt content in water and salt accumulation zone of the closed hydrogeological unit showed an increasing tendency, which formed the main occurrence area of soil secondary salinization.
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Geier, Joel (Clearwater Hardrock Consulting, Corvallis, OR (US))
2008-03-15
. The variants completed thus far do not include alternative conceptual models for the DFN submodel, or variants with respect to its key properties, such as the assumed correlation of size to transmissivity. The flow distribution to deposition holes is not strongly sensitive to the hydrologic properties of the large-scale deformation zones or the time-dependent boundary conditions in a temperate setting. The main controls appear to be the DFN submodel, the excavation damaged zone (EDZ) around tunnels, and spalled zones in the deposition-hole walls (if present). Advective-dispersive particle-tracking results are presented for a suite of Forsmark model variants. A continuous EDZ intersecting all deposition holes and extending along all repository tunnels is included in all of these variants presented here. This is a significant feature for flow and transport, due to the apparent sparseness of the fracture population in the repository volume at Forsmark. For the Forsmark model variants considered here, the safety-critical lower portion of the distribution of transport resistance Fr is not strongly sensitive to most of the variants that have been modelled. Spalling around deposition holes produces a slight reduction in the lowest values of Fr below about 2x103 yr/m, but apparently yields an increase in Fr for the remainder of the distribution. This result is likely sensitive to the assumptions regarding hydraulic properties of the spalled zones, which have been arbitrarily specified for lack of relevant data. Further investigation of the sensitivity of the Fr distribution to assumptions regarding these parameters is warranted. The lower end of the Fr distribution also shows some sensitivity to stochastic realizations of the DFN submodel. This indicates that further exploration of uncertainties in the DFN submodel, including major conceptual uncertainties (clustering or hierarchical structure) is needed
On Limiting Behavior of Contaminant Transport Models in Coupled Surface and Groundwater Flows
Directory of Open Access Journals (Sweden)
Vincent J. Ervin
2015-11-01
Full Text Available There has been a surge of work on models for coupling surface-water with groundwater flows which is at its core the Stokes-Darcy problem. The resulting (Stokes-Darcy fluid velocity is important because the flow transports contaminants. The analysis of models including the transport of contaminants has, however, focused on a quasi-static Stokes-Darcy model. Herein we consider the fully evolutionary system including contaminant transport and analyze its quasi-static limits.
Combinatorial model of solute transport in porous media
Institute of Scientific and Technical Information of China (English)
张妙仙; 张丽萍
2004-01-01
Modeling of solute transport is a key issue in the area of soil physics and hydrogeology. The most common approach (the convection-dispersion equation) considers an average convection flow rate and Fickian-like dispersion. Here,we propose a solute transport model in porous media of continuously expanding scale, according to the combinatorics principle. The model supposed actual porous media as a combinative body of many basic segments. First, we studied the solute transport process in each basic segment body, and then deduced the distribution of pore velocity in each basic segment body by difference approximation, finally assembled the solute transport process of each basic segment body into one of the combinative body. The simulation result coincided with the solute transport process observed in test. The model provides useful insight into the solute transport process of the non-Fickian dispersion in continuously expanding scale.
Webb, M. D.; Genereux, D. P.; Solomon, D. K.
2008-12-01
Major ion, 18O, and water budget data from previous hydrologic studies at a Costa Rica lowland rainforest site, La Selva Biological station at the foot of Volcan Barva, indicate the presence and mixing of two distinct groundwaters: - bedrock groundwater: relatively high-solute groundwater that represents interbasin groundwater flow into the lowland rainforest watersheds, and - local groundwater: more dilute groundwater recharged locally in the lowlands. In this study we found that C, He, and Cl concentrations and isotope data (ä13C, 14C, 3He/4He, 36Cl/Cl), in groundwater and surface water at La Selva and upslope in Braulio Carillo National Park, are strongly consistent with the mixing hypothesis and provide insight into the age and origin of the two groundwaters. Highly significant linear trends on plots of isotopic abundance vs. the inverse of concentration support the mixing of two groundwaters. High ä13C (-4.89), low 14C (7.98 pmC), high R/RA for He (6.88), and low 36Cl/Cl (17 x 10-15) of bedrock groundwater indicate that elevated C, He, and Cl concentrations in this groundwater are derived from magmatic outgassing and/or weathering of volcanic rock, most likely beneath nearby Volcan Barva. The estimated ä13C of magmatic CO2 was -2.6 , almost identical to the previously- measured ä13C of CO2 in high-temperature gases from two volcanoes in the region (-2.9 at Momotombo in Nicaragua and -2.7 at Arenal in Costa Rica). Concentrations and isotopic ratios of C, He, and Cl in local water are consistent with atmospheric/precipitation sources for He and Cl and a biogenic soil-gas CO2 source for DIC. 14C dating, using NETPATH (a geochemical mass-balance model), indicate an apparent age of bedrock groundwater in the range 2700-4300 years. Local groundwater has 14C concentrations >100 pmC, indicating the presence of anthropogenic "bomb carbon" and thus ages less than ~55 years for these samples collected in 2006. Overall the data are fully consistent with the conceptual
Solute transport processes in flow-event-driven stream-aquifer interaction
Xie, Yueqing; Cook, Peter G.; Simmons, Craig T.
2016-07-01
The interaction between streams and groundwater controls key features of the stream hydrograph and chemograph. Since surface runoff is usually less saline than groundwater, flow events are usually accompanied by declines in stream salinity. In this paper, we use numerical modelling to show that, at any particular monitoring location: (i) the increase in stream stage associated with a flow event will precede the decrease in solute concentration (arrival time lag for solutes); and (ii) the decrease in stream stage following the flow peak will usually precede the subsequent return (increase) in solute concentration (return time lag). Both arrival time lag and return time lag increase with increasing wave duration. However, arrival time lag decreases with increasing wave amplitude, whereas return time lag increases. Furthermore, while arrival time lag is most sensitive to parameters that control river velocity (channel roughness and stream slope), return time lag is most sensitive to groundwater parameters (aquifer hydraulic conductivity, recharge rate, and dispersitivity). Additionally, the absolute magnitude of the decrease in river concentration is sensitive to both river and groundwater parameters. Our simulations also show that in-stream mixing is dominated by wave propagation and bank storage processes, and in-stream dispersion has a relatively minor effect on solute concentrations. This has important implications for spreading of contaminants released to streams. Our work also demonstrates that a high contribution of pre-event water (or groundwater) within the flow hydrograph can be caused by the combination of in-stream and bank storage exchange processes, and does not require transport of pre-event water through the catchment.
Institute of Scientific and Technical Information of China (English)
姚磊华
1997-01-01
A generalized upwind scheme with fractional steps for 3-D mathematical models of convection dominating groundwater quality is suggested. The mass transport equation is split into a convection equation and a dispersive equation. The generalized upwind scheme is used to solve the convection equation and the finite element method is used to compute the dispersive equation. These procedures which not only overcome the phenomenon of the negative concentration and numerical dispersion appear frequently with normal FEM or FDM to solve models of convection dominating groundwater transport but also avoid the step for computing each node velocity give a more suitable method to calculate the concentrations of the well points.
Application of Harmony Search algorithm to the solution of groundwater management models
Tamer Ayvaz, M.
2009-06-01
This study proposes a groundwater resources management model in which the solution is performed through a combined simulation-optimization model. A modular three-dimensional finite difference groundwater flow model, MODFLOW is used as the simulation model. This model is then combined with a Harmony Search (HS) optimization algorithm which is based on the musical process of searching for a perfect state of harmony. The performance of the proposed HS based management model is tested on three separate groundwater management problems: (i) maximization of total pumping from an aquifer (steady-state); (ii) minimization of the total pumping cost to satisfy the given demand (steady-state); and (iii) minimization of the pumping cost to satisfy the given demand for multiple management periods (transient). The sensitivity of HS algorithm is evaluated by performing a sensitivity analysis which aims to determine the impact of related solution parameters on convergence behavior. The results show that HS yields nearly same or better solutions than the previous solution methods and may be used to solve management problems in groundwater modeling.
Analytical Solutions of a Space-Time Fractional Derivative of Groundwater Flow Equation
Directory of Open Access Journals (Sweden)
Abdon Atangana
2014-01-01
Full Text Available The classical Darcy law is generalized by regarding the water flow as a function of a noninteger order derivative of the piezometric head. This generalized law and the law of conservation of mass are then used to derive a new equation for groundwater flow. Two methods including Frobenius and Adomian decomposition method are used to obtain an asymptotic analytical solution to the generalized groundwater flow equation. The solution obtained via Frobenius method is valid in the vicinity of the borehole. This solution is in perfect agreement with the data observed from the pumping test performed by the institute for groundwater study on one of their boreholes settled on the test site of the University of the Free State. The test consisted of the pumping of the borehole at the constant discharge rate Q and monitoring the piezometric head for 350 minutes. Numerical solutions obtained via Adomian method are compared with the Barker generalized radial flow model for which a fractal dimension for the flow is assumed. Proposition for uncertainties in groundwater studies was given.
Groundwater quality across scales: impact on nutrient transport to large water bodies
Dürr, Hans; Moosdorf, Nils; Mallast, Ulf
2017-04-01
High concentrations of dissolved nutrients such as nitrogen (N) and phosphorus (P) in groundwater are an increasing concern in many areas of the world. Especially regions with high agriculture impact see widespread declining groundwater quality, with considerable uncertainty mainly regarding the impact of phosphorus (P). Implications reach from direct impacts on different water users to discharge of nutrient-rich groundwater to rivers, lakes and coastal areas, where it can contribute to eutrophication, hypoxia or harmful algal blooms. While local-scale studies are abundant and management options exist, quantitative approaches at regional to continental scales are scarce and frequently have to deal with data inconsistencies or are temporally sparse. Here, we present the research framework to combine large databases of local groundwater quality to data sets of climatical, hydrological, geological or landuse parameters. Pooling of such information, together with robust methods such as water balances and groundwater models, can provide constraints such as upper boundaries and likely ranges of nutrient composition in various settings, or for the nutrient transport to large water bodies. Remote Sensing can provide spatial information on the location of groundwater seepage. Results will eventually help to identify focus areas and lead to improved understanding of the role of groundwater in the context of global biogeochemical cycles.
One-dimensional spatially dependent solute transport in semi ...
African Journals Online (AJOL)
One-dimensional spatially dependent solute transport in semi-infinite porous media: an analytical solution. ... Journal Home > Vol 9, No 4 (2017) > ... In this mathematical model the dispersion coefficient is considered spatially dependent while ...
Jansen, Gijs M.C.; Del Val Alonso, Laura; Griffioen, Jasper; Groenendijk, P.
2012-01-01
We developed an on-line coupling between the 1D/quasi-2D nutrient transport model ANIMO and the 3D groundwater transport model code MT3DMS. ANIMO is a detailed, process-oriented simulation model code for the simulation of nitrate leaching to groundwater, N- and P-loads on surface waters and emission
A quasilinear model for solute transport under unsaturated flow
Energy Technology Data Exchange (ETDEWEB)
Houseworth, J.E.; Leem, J.
2009-05-15
We developed an analytical solution for solute transport under steady-state, two-dimensional, unsaturated flow and transport conditions for the investigation of high-level radioactive waste disposal. The two-dimensional, unsaturated flow problem is treated using the quasilinear flow method for a system with homogeneous material properties. Dispersion is modeled as isotropic and is proportional to the effective hydraulic conductivity. This leads to a quasilinear form for the transport problem in terms of a scalar potential that is analogous to the Kirchhoff potential for quasilinear flow. The solutions for both flow and transport scalar potentials take the form of Fourier series. The particular solution given here is for two sources of flow, with one source containing a dissolved solute. The solution method may easily be extended, however, for any combination of flow and solute sources under steady-state conditions. The analytical results for multidimensional solute transport problems, which previously could only be solved numerically, also offer an additional way to benchmark numerical solutions. An analytical solution for two-dimensional, steady-state solute transport under unsaturated flow conditions is presented. A specific case with two sources is solved but may be generalized to any combination of sources. The analytical results complement numerical solutions, which were previously required to solve this class of problems.
Directory of Open Access Journals (Sweden)
N.Natarajan
2010-10-01
Full Text Available Modeling of solute transport through fractured rock is an important component of in many disciplines especially groundwater contamination and nuclear waste disposal. Several studies have been conducted on single rock fracture using parallel plate model and recently solute and thermal transport has been numerically modeled in the sinusoidal fracture matrix coupled system. The effect of linear sorption has been studied on the same. Results suggest the high matrix porosity and matrix diffusion coefficient enhance the sorption process and reduce the matrix diffusion of solutes. The velocity of the fluid reduces with increment in fracture aperture.
Modeling substrate-bacteria-grazer interactions coupled to substrate transport in groundwater
Bajracharya, Bijendra M.; Lu, Chuanhe; Cirpka, Olaf A.
2014-05-01
Models of microbial dynamics coupled to solute transport in aquifers typically require the introduction of a bacterial capacity term to prevent excessive microbial growth close to substrate-injection boundaries. The factors controlling this carrying capacity, however, are not fully understood. In this study, we propose that grazers or bacteriophages may control the density of bacterial biomass in continuously fed porous media. We conceptualize the flow-through porous medium as a series of retentostats, in which the dissolved substrate is advected with water flow whereas the biomasses of bacteria and grazers are considered essentially immobile. We first model a single retentostat with Monod kinetics of bacterial growth and a second-order grazing law, which shows that the system oscillates but approaches a stable steady state with nonzero concentrations of substrate, bacteria, and grazers. The steady state concentration of the bacteria biomass is independent of the substrate concentration in the inflow. When coupling several retentostats in a series to mimic a groundwater column, the steady state bacteria concentrations thus remain at a constant level over a significant travel distance. The one-dimensional reactive transport model also accounts for substrate dispersion and a random walk of grazers influenced by the bacteria concentration. These dispersive-diffusive terms affect the oscillations until steady state is reached, but hardly the steady state value itself. We conclude that grazing, or infection by bacteriophages, is a possible explanation of the maximum biomass concentration frequently needed in bioreactive transport models. Its value depends on parameters related to the grazers or bacteriophages and is independent of bacterial growth parameters or substrate concentration, provided that there is enough substrate to sustain bacteria and grazers.
CFEST Coupled Flow, Energy & Solute Transport Version CFEST005 Theory Guide
Energy Technology Data Exchange (ETDEWEB)
Freedman, Vicky L.; Chen, Yousu; Gupta, Sumant K.
2005-11-01
This document presents the mathematical theory implemented in the CFEST (Coupled Flow, Energy, and Solute Transport) simulator. The simulator is a three-dimensional finite element model that can be used for evaluating flow and solute mass transport. Although the theory for thermal transport is presented in this guide, it has not yet been fully implemented in the simulator. The flow module is capable of simulating both confined and unconfined aquifer systems, as well as constant and variable density fluid flows. For unconfined aquifers, the model uses a moving boundary for the water table, deforming the numerical mesh so that the uppermost nodes are always at the water table. For solute transport, changes in concentration of a single dissolved chemical constituent are computed for advective and hydrodynamic transport, linear sorption represented by a retardation factor, and radioactive decay. Once fully implemented, transport of thermal energy in the groundwater and solid matrix of the aquifer can also be used to model aquifer thermal regimes. Mesh construction employs “collapsible”, hexahedral finite elements in a three-dimensional coordinate system. CFEST uses the Galerkin finite element method to convert the partial differential equations to algebraic form. To solve the coupled equations for momentum, solute and heat transport, either Picard or Newton-Raphson iterative schemes are used to treat nonlinearities. An upstream weighted residual finite-element method is used to solve the advective-dispersive transport and energy transfer equations, which circumvents problems of numerical oscillation problems. Matrix solutions of the flow and transport problems are performed using efficient iterative solvers available in ITPACK and PETSc, solvers that are available in the public domain. These solvers are based on the preconditioned conjugate gradient and ORTHOMIN methods for symmetric and a nonsymmetric matrices, respectively.
Yin, Jun; Haggerty, Roy; Stoliker, Deborah L.; Kent, Douglas B.; Istok, Jonathan D.; Greskowiak, Janek; Zachara, John M.
2011-01-01
In the 300 Area of a U(VI)-contaminated aquifer at Hanford, Washington, USA, inorganic carbon and major cations, which have large impacts on U(VI) transport, change on an hourly and seasonal basis near the Columbia River. Batch and column experiments were conducted to investigate the factors controlling U(VI) adsorption/desorption by changing chemical conditions over time. Low alkalinity and low Ca concentrations (Columbia River water) enhanced adsorption and reduced aqueous concentrations. Conversely, high alkalinity and high Ca concentrations (Hanford groundwater) reduced adsorption and increased aqueous concentrations of U(VI). An equilibrium surface complexation model calibrated using laboratory batch experiments accounted for the decrease in U(VI) adsorption observed with increasing (bi)carbonate concentrations and other aqueous chemical conditions. In the column experiment, alternating pulses of river and groundwater caused swings in aqueous U(VI) concentration. A multispecies multirate surface complexation reactive transport model simulated most of the major U(VI) changes in two column experiments. The modeling results also indicated that U(VI) transport in the studied sediment could be simulated by using a single kinetic rate without loss of accuracy in the simulations. Moreover, the capability of the model to predict U(VI) transport in Hanford groundwater under transient chemical conditions depends significantly on the knowledge of real-time change of local groundwater chemistry.
Chatton, Eliot; Labasque, Thierry; Guillou, Aurélie; Béthencourt, Lorine; de La Bernardie, Jérôme; Boisson, Alexandre; Koch, Florian; Aquilina, Luc
2017-04-01
Identification of biogeochemical reactions in aquifers and determining kinetics is important for the prediction of contaminant transport in aquifers and groundwater management. Therefore, experiments accounting for both conservative and reactive transport are essential to understand the biogeochemical reactivity at field scale. This study presents the results of a groundwater tracer test using the combined injection of dissolved conservative and reactive tracers (He, Xe, Ar, Br-, O2 and NO3-) in order to evaluate the transport properties of a fractured media in Brittany, France. Dissolved gas concentrations were continuously monitored in situ with a CF-MIMS (Chatton et al, 2016) allowing a high frequency (1 gas every 2 seconds) multi-tracer analysis (N2, O2, CO2, CH4, N2O, H2, He, Ne, Ar, Kr, Xe) over a large resolution (6 orders of magnitude). Along with dissolved gases, groundwater biogeochemistry was monitored through the sampling of major anions and cations, trace elements and microbiological diversity. The results show breakthrough curves allowing the combined quantification of conservative and reactive transport properties. This ongoing work is an original approach investigating the link between heterogeneity of porous media and biogeochemical reactions at field scale. Eliot Chatton, Thierry Labasque, Jérôme de La Bernardie, Nicolas Guihéneuf, Olivier Bour and Luc Aquilina; Field Continuous Measurement of Dissolved Gases with a CF-MIMS: Applications to the Physics and Biogeochemistry of Groundwater Flow; Environmental Science & Technology, in press, 2016.
Energy Technology Data Exchange (ETDEWEB)
Todd Arbogast; Steve Bryant; Clint N. Dawson; Mary F. Wheeler
1998-08-31
This report describes briefly the work of the Center for Subsurface Modeling (CSM) of the University of Texas at Austin (and Rice University prior to September 1995) on the Partnership in Computational Sciences Consortium (PICS) project entitled Grand Challenge Problems in Environmental Modeling and Remediation: Groundwater Contaminant Transport.
An adaptive approach to implementing innovative urban transport solutions
Marchau, V.; Walker, W.; Van Duin, R.
2009-01-01
Urban transport is facing an increasing number of problems. Innovative technological solutions have been proposed for many of these problems. The implementation of these solutions, however, is surrounded by many uncertainties—for example, future relevant developments for urban transport demand and s
Transport phenomena during nanofiltration of concentrated solutions
Bargeman, Gerrald
2016-01-01
In most scientific studies on nanofiltration either the development of new membrane materials or the characterization of membranes is reported. In the latter case most studies use single solute salt or sugar solutions and/or investigate nanofiltration of solutions with mixtures of ions at low concen
Kulasiri, Don
2002-01-01
Most of the natural and biological phenomena such as solute transport in porous media exhibit variability which can not be modeled by using deterministic approaches. There is evidence in natural phenomena to suggest that some of the observations can not be explained by using the models which give deterministic solutions. Stochastic processes have a rich repository of objects which can be used to express the randomness inherent in the system and the evolution of the system over time. The attractiveness of the stochastic differential equations (SDE) and stochastic partial differential equations (SPDE) come from the fact that we can integrate the variability of the system along with the scientific knowledge pertaining to the system. One of the aims of this book is to explaim some useufl concepts in stochastic dynamics so that the scientists and engineers with a background in undergraduate differential calculus could appreciate the applicability and appropriateness of these developments in mathematics. The ideas ...
Nitrate Biogeochemistry and Reactive Transport in California Groundwater: LDRD Final Report
Energy Technology Data Exchange (ETDEWEB)
Esser, B K; Beller, H; Carle, S; Cey, B; Hudson, G B; Leif, R; LeTain, T; Moody-Bartel, C; Moore, K; McNab, W; Moran, J; Tompson, A
2006-02-24
Nitrate is the number one drinking water contaminant in the United States. It is pervasive in surface and groundwater systems,and its principal anthropogenic sources have increased dramatically in the last 50 years. In California alone, one third of the public drinking-water wells has been lost since 1988 and nitrate contamination is the most common reason for abandonment. Effective nitrate management in groundwater is complicated by uncertainties related to multiple point and non-point sources, hydrogeologic complexity, geochemical reactivity, and quantification of denitrification processes. In this paper, we review an integrated experimental and simulation-based framework being developed to study the fate of nitrate in a 25 km-long groundwater subbasin south of San Jose, California, a historically agricultural area now undergoing rapid urbanization with increasing demands for groundwater. The modeling approach is driven by a need to integrate new and archival data that support the hypothesis that nitrate fate and transport at the basin scale is intricately related to hydrostratigraphic complexity, variability of flow paths and groundwater residence times, microbial activity, and multiple geochemical reaction mechanisms. This study synthesizes these disparate and multi-scale data into a three-dimensional and highly resolved reactive transport modeling framework.
Warner, James W.
1979-01-01
Diisopropylmethylphosphonate (DIMP) is an organic compound produced as a by-product of the manufacture and detoxification of GB nerve gas. Ground-water contamination by DIMP from the disposal of wastes into unlined surface ponds at the Rocky Mountain Arsenal occurred from 1952 to 1956. A digital-transport model was used to determine the effects on ground-water movement and on DIMP concentrations in the ground water of a bentonite barrier in the aquifer near the northern boundary of the arsenal. The transport model is based on an iterative-alternating-direction-implicit mathematical solution of the ground-water-flow equation coupled with a method-of-characteristics solution of the solute-transport equation. The model assumes conservative (nonreactive) transient transport of DIMP and steady-state ground-water flow. In the model simulations, a bentonite barrier was assumed that was impermeable and penetrated the entire saturated thickness of the aquifer. Ground water intercepted by the barrier was assumed to be pumped by wells located south (upgradient) of the barrier, to be treated to remove DIMP, and to be recharged by pits or wells to the aquifer north (downgradient) of the barrier. The amount of DIMP transported across the northern boundary of the arsenal was substantially reduced by a ground-water-barrier system of this type. For a 1,500-foot-long bentonite barrier located along the northern boundary of the arsenal near D Street, about 50 percent of the DIMP that would otherwise cross the boundary would be intercepted by the barrier. This barrier configuration and location were proposed by the U.S. Army. Of the ground water with DIMP concentrations greater than 500 micrograms per liter, the safe DIMP-concentration level determined by the U.S. Army, about 72 percent would be intercepted by the barrier system. The amount of DIMP underflow intercepted may be increased to 65 percent by doubling the pumpage, or to 73 percent by doubling the length of the barrier
CFEST Coupled Flow, Energy & Solute Transport Version CFEST005 User’s Guide
Energy Technology Data Exchange (ETDEWEB)
Freedman, Vicky L.; Chen, Yousu; Gilca, Alex; Cole, Charles R.; Gupta, Sumant K.
2006-07-20
The CFEST (Coupled Flow, Energy, and Solute Transport) simulator described in this User’s Guide is a three-dimensional finite-element model used to evaluate groundwater flow and solute mass transport. Confined and unconfined aquifer systems, as well as constant and variable density fluid flows can be represented with CFEST. For unconfined aquifers, the model uses a moving boundary for the water table, deforming the numerical mesh so that the uppermost nodes are always at the water table. For solute transport, changes in concentra¬tion of a single dissolved chemical constituent are computed for advective and hydrodynamic transport, linear sorption represented by a retardation factor, and radioactive decay. Although several thermal parameters described in this User’s Guide are required inputs, thermal transport has not yet been fully implemented in the simulator. Once fully implemented, transport of thermal energy in the groundwater and solid matrix of the aquifer can also be used to model aquifer thermal regimes. The CFEST simulator is written in the FORTRAN 77 language, following American National Standards Institute (ANSI) standards. Execution of the CFEST simulator is controlled through three required text input files. These input file use a structured format of associated groups of input data. Example input data lines are presented for each file type, as well as a description of the structured FORTRAN data format. Detailed descriptions of all input requirements, output options, and program structure and execution are provided in this User’s Guide. Required inputs for auxillary CFEST utilities that aide in post-processing data are also described. Global variables are defined for those with access to the source code. Although CFEST is a proprietary code (CFEST, Inc., Irvine, CA), the Pacific Northwest National Laboratory retains permission to maintain its own source, and to distribute executables to Hanford subcontractors.
Modelling multicomponent solute transport in structured soils
Beinum, van G.W.
2007-01-01
The mobility of contaminants in soil is an important factor in determining their ability to spread into the wider environment. For non-volatile substances, transport within the soil is generally dominated by transport of dissolved fractions in the soil water phase, via either diffusion or convection
Hazen, T. C.; Faybishenko, B.; Beller, H. R.; Brodie, E. L.; Sonnenthal, E. L.; Steefel, C.; Larsen, J.; Conrad, M. E.; Bill, M.; Christensen, J. N.; Brown, S. T.; Joyner, D.; Borglin, S. E.; Geller, J. T.; Chakraborty, R.; Nico, P. S.; Long, P. E.; Newcomer, D. R.; Arntzen, E.
2011-12-01
The primary contaminant of concern in groundwater at the DOE Hanford 100 Area (Washington State) is hexavalent chromium [Cr(VI)] in Hanford coarse-grained sediments. Three lactate injections were conducted in March, August, and October 2010 at the Hanford 100-H field site to assess the efficacy of in situ Cr(VI) bioreductive immobilization. Each time, 55 gal of lactate solution was injected into the Hanford aquifer. To characterize the biogeochemical regimes before and after electron donor injection, we implemented a comprehensive plan of groundwater sampling for microbial, geochemical, and isotopic analyses. These tests were performed to provide evidence of transformation of toxic and soluble Cr(VI) into less toxic and poorly soluble Cr(III) by bioimmobilization, and to quantify critical and interrelated microbial metabolic and geochemical mechanisms affecting chromium in situ reductive immobilization and the long-term sustainability of chromium bioremediation. The results of lactate injections were compared with data from two groundwater biostimulation tests that were conducted in 2004 and 2008 by injecting Hydrogen Release Compound (HRC°), a slow-release glycerol polylactate, into the Hanford aquifer. In all HRC and lactate injection tests, 13C-labeled lactate was added to the injected solutions to track post-injection carbon pathways. Monitoring showed that despite a very low initial total microbial density (from 107 cells/mL (including sulfate- and nitrate-reducing bacteria), resulting in a significant decrease in soluble Cr(VI) concentrations to below the MCL. In all tests, lactate was consumed nearly completely within the first week, much faster than HRC. Modeling of biogeochemical and isotope fractionation processes with the reaction-transport code TOUGHREACT captured the biodegradation of lactate, fermentative production of acetate and propionate, the evolution of 13C in bicarbonate, and the rate of sulfate reduction. In contrast to the slow-release HRC
Core 2D. A code for non-isothermal water flow and reactive solute transport. Users manual version 2
Energy Technology Data Exchange (ETDEWEB)
Samper, J.; Juncosa, R.; Delgado, J.; Montenegro, L. [Universidad de A Coruna (Spain)
2000-07-01
Understanding natural groundwater quality patterns, quantifying groundwater pollution and assessing the effects of waste disposal, require modeling tools accounting for water flow, and transport of heat and dissolved species as well as their complex interactions with solid and gases phases. This report contains the users manual of CORE ''2D Version V.2.0, a COde for modeling water flow (saturated and unsaturated), heat transport and multicomponent Reactive solute transport under both local chemical equilibrium and kinetic conditions. it is an updated and improved version of CORE-LE-2D V0 (Samper et al., 1988) which in turns is an extended version of TRANQUI, a previous reactive transport code (ENRESA, 1995). All these codes were developed within the context of Research Projects funded by ENRESA and the European Commission. (Author)
Solute Transport in a Heterogeneous Aquifer: A Nonlinear Deterministic Dynamical Analysis
Sivakumar, B.; Harter, T.; Zhang, H.
2003-04-01
Stochastic approaches are widely used for modeling and prediction of uncertainty in groundwater flow and transport processes. An important reason for this is our belief that the dynamics of the seemingly complex and highly irregular subsurface processes are essentially random in nature. However, the discovery of nonlinear deterministic dynamical theory has revealed that random-looking behavior could also be the result of simple deterministic mechanisms influenced by only a few nonlinear interdependent variables. The purpose of the present study is to introduce this theory to subsurface solute transport process, in an attempt to investigate the possibility of understanding the transport dynamics in a much simpler, deterministic, manner. To this effect, salt transport process in a heterogeneous aquifer medium is studied. Specifically, time series of arrival time of salt particles are analyzed. These time series are obtained by integrating a geostatistical (transition probability/Markov chain) model with a groundwater flow model (MODFLOW) and a salt transport (Random Walk Particle) model. The (dynamical) behavior of the transport process (nonlinear deterministic or stochastic) is identified using standard statistical techniques (e.g. autocorrelation function, power spectrum) as well as specific nonlinear deterministic dynamical techniques (e.g. phase-space diagram, correlation dimension method). The sensitivity of the salt transport dynamical behavior to the hydrostratigraphic parameters (i.e. number, volume proportions, mean lengths, and juxtapositional tendencies of facies) used in the transition probability/Markov chain model is also studied. The results indicate that the salt transport process may exhibit very simple (i.e. deterministic) to very complex (i.e. stochastic) dynamical behavior, depending upon the above parameters (i.e. characteristics of the aquifer medium). Efforts towards verification and strengthening of the present results and prediction of salt
Solute transport scales in an unsaturated stony soil
Coppola, Antonio; Comegna, Alessandro; Dragonetti, Giovanna; Dyck, Miles; Basile, Angelo; Lamaddalena, Nicola; Kassab, Mohamed; Comegna, Vincenzo
2011-06-01
Solute transport parameters are known to be scale-dependent due mainly to the increasing scale of heterogeneities with transport distance and with the lateral extent of the transport field examined. Based on a transect solute transport experiment, in this paper we studied this scale dependence by distinguishing three different scales with different homogeneity degrees of the porous medium: the observation scale, transport scale and transect scale. The main objective was to extend the approach proposed by van Wesenbeeck and Kachanoski to evaluating the role of textural heterogeneities on the transition from the observation scale to the transport scale. The approach is based on the scale dependence of transport moments estimated from solute concentrations distributions. In our study, these moments were calculated starting from time normalized resident concentrations measured by time domain reflectometry (TDR) probes at three depths in 37 soil sites 1 m apart along a transect during a steady state transport experiment. The Generalized Transfer Function (GTF) was used to describe the evolution of apparent solute spreading along the soil profile at each observation site by analyzing the propagation of the moments of the concentration distributions. Spectral analysis was used to quantify the relationship between the solid phase heterogeneities (namely, texture and stones) and the scale dependence of the solute transport parameters. Coupling the two approaches allowed us to identify two different transport scales (around 4-5 m and 20 m, respectively) mainly induced by the spatial pattern of soil textural properties. The analysis showed that the larger transport scale is mainly determined by the skeleton pattern of variability. Our analysis showed that the organization in hierarchical levels of soil variability may have major effects on the differences between solute transport behavior at transport scale and transect scale, as the transect scale parameters will include
Zhang, Kejiang; Achari, Gopal; Li, Hua
2009-11-01
Traditionally, uncertainty in parameters are represented as probabilistic distributions and incorporated into groundwater flow and contaminant transport models. With the advent of newer uncertainty theories, it is now understood that stochastic methods cannot properly represent non random uncertainties. In the groundwater flow and contaminant transport equations, uncertainty in some parameters may be random, whereas those of others may be non random. The objective of this paper is to develop a fuzzy-stochastic partial differential equation (FSPDE) model to simulate conditions where both random and non random uncertainties are involved in groundwater flow and solute transport. Three potential solution techniques namely, (a) transforming a probability distribution to a possibility distribution (Method I) then a FSPDE becomes a fuzzy partial differential equation (FPDE), (b) transforming a possibility distribution to a probability distribution (Method II) and then a FSPDE becomes a stochastic partial differential equation (SPDE), and (c) the combination of Monte Carlo methods and FPDE solution techniques (Method III) are proposed and compared. The effects of these three methods on the predictive results are investigated by using two case studies. The results show that the predictions obtained from Method II is a specific case of that got from Method I. When an exact probabilistic result is needed, Method II is suggested. As the loss or gain of information during a probability-possibility (or vice versa) transformation cannot be quantified, their influences on the predictive results is not known. Thus, Method III should probably be preferred for risk assessments.
Zhang, Kejiang; Achari, Gopal; Li, Hua
2009-11-03
Traditionally, uncertainty in parameters are represented as probabilistic distributions and incorporated into groundwater flow and contaminant transport models. With the advent of newer uncertainty theories, it is now understood that stochastic methods cannot properly represent non random uncertainties. In the groundwater flow and contaminant transport equations, uncertainty in some parameters may be random, whereas those of others may be non random. The objective of this paper is to develop a fuzzy-stochastic partial differential equation (FSPDE) model to simulate conditions where both random and non random uncertainties are involved in groundwater flow and solute transport. Three potential solution techniques namely, (a) transforming a probability distribution to a possibility distribution (Method I) then a FSPDE becomes a fuzzy partial differential equation (FPDE), (b) transforming a possibility distribution to a probability distribution (Method II) and then a FSPDE becomes a stochastic partial differential equation (SPDE), and (c) the combination of Monte Carlo methods and FPDE solution techniques (Method III) are proposed and compared. The effects of these three methods on the predictive results are investigated by using two case studies. The results show that the predictions obtained from Method II is a specific case of that got from Method I. When an exact probabilistic result is needed, Method II is suggested. As the loss or gain of information during a probability-possibility (or vice versa) transformation cannot be quantified, their influences on the predictive results is not known. Thus, Method III should probably be preferred for risk assessments.
Examining the influence of heterogeneous porosity fields on conservative solute transport
Hu, B.X.; Meerschaert, M.M.; Barrash, W.; Hyndman, D.W.; He, C.; Li, X.; Guo, Laodong
2009-01-01
It is widely recognized that groundwater flow and solute transport in natural media are largely controlled by heterogeneities. In the last three decades, many studies have examined the effects of heterogeneous hydraulic conductivity fields on flow and transport processes, but there has been much less attention to the influence of heterogeneous porosity fields. In this study, we use porosity and particle size measurements from boreholes at the Boise Hydrogeophysical Research Site (BHRS) to evaluate the importance of characterizing the spatial structure of porosity and grain size data for solute transport modeling. Then we develop synthetic hydraulic conductivity fields based on relatively simple measurements of porosity from borehole logs and grain size distributions from core samples to examine and compare the characteristics of tracer transport through these fields with and without inclusion of porosity heterogeneity. In particular, we develop horizontal 2D realizations based on data from one of the less heterogeneous units at the BHRS to examine effects where spatial variations in hydraulic parameters are not large. The results indicate that the distributions of porosity and the derived hydraulic conductivity in the study unit resemble fractal normal and lognormal fields respectively. We numerically simulate solute transport in stochastic fields and find that spatial variations in porosity have significant effects on the spread of an injected tracer plume including a significant delay in simulated tracer concentration histories.
SEAWAT Version 4: A Computer Program for Simulation of Multi-Species Solute and Heat Transport
Langevin, Christian D.; Thorne, Daniel T.; Dausman, Alyssa M.; Sukop, Michael C.; Guo, Weixing
2008-01-01
The SEAWAT program is a coupled version of MODFLOW and MT3DMS designed to simulate three-dimensional, variable-density, saturated ground-water flow. Flexible equations were added to the program to allow fluid density to be calculated as a function of one or more MT3DMS species. Fluid density may also be calculated as a function of fluid pressure. The effect of fluid viscosity variations on ground-water flow was included as an option. Fluid viscosity can be calculated as a function of one or more MT3DMS species, and the program includes additional functions for representing the dependence on temperature. Although MT3DMS and SEAWAT are not explicitly designed to simulate heat transport, temperature can be simulated as one of the species by entering appropriate transport coefficients. For example, the process of heat conduction is mathematically analogous to Fickian diffusion. Heat conduction can be represented in SEAWAT by assigning a thermal diffusivity for the temperature species (instead of a molecular diffusion coefficient for a solute species). Heat exchange with the solid matrix can be treated in a similar manner by using the mathematically equivalent process of solute sorption. By combining flexible equations for fluid density and viscosity with multi-species transport, SEAWAT Version 4 represents variable-density ground-water flow coupled with multi-species solute and heat transport. SEAWAT Version 4 is based on MODFLOW-2000 and MT3DMS and retains all of the functionality of SEAWAT-2000. SEAWAT Version 4 also supports new simulation options for coupling flow and transport, and for representing constant-head boundaries. In previous versions of SEAWAT, the flow equation was solved for every transport timestep, regardless of whether or not there was a large change in fluid density. A new option was implemented in SEAWAT Version 4 that allows users to control how often the flow field is updated. New options were also implemented for representing constant
Directory of Open Access Journals (Sweden)
M. M. Potsane
2014-01-01
Full Text Available The transport of chemicals through soils to the groundwater or precipitation at the soils surfaces leads to degradation of these resources. Serious consequences may be suffered in the long run. In this paper, we consider macroscopic deterministic models describing contaminant transport in saturated soils under uniform radial water flow backgrounds. The arising convection-dispersion equation given in terms of the stream functions is analyzed using classical Lie point symmetries. A number of exotic Lie point symmetries are admitted. Group invariant solutions are classified according to the elements of the one-dimensional optimal systems. We analyzed the group invariant solutions which satisfy the physical boundary conditions.
Development of a Groundwater Transport Simulation Tool for Remedial Process Optimization
Energy Technology Data Exchange (ETDEWEB)
Ivarson, Kristine A.; Hanson, James P.; Tonkin, M.; Miller, Charles W.; Baker, S.
2015-01-14
The groundwater remedy for hexavalent chromium at the Hanford Site includes operation of five large pump-and-treat systems along the Columbia River. The systems at the 100-HR-3 and 100-KR-4 groundwater operable units treat a total of about 9,840 liters per minute (2,600 gallons per minute) of groundwater to remove hexavalent chromium, and cover an area of nearly 26 square kilometers (10 square miles). The pump-and-treat systems result in large scale manipulation of groundwater flow direction, velocities, and most importantly, the contaminant plumes. Tracking of the plumes and predicting needed system modifications is part of the remedial process optimization, and is a continual process with the goal of reducing costs and shortening the timeframe to achieve the cleanup goals. While most of the initial system evaluations are conducted by assessing performance (e.g., reduction in contaminant concentration in groundwater and changes in inferred plume size), changes to the well field are often recommended. To determine the placement for new wells, well realignments, and modifications to pumping rates, it is important to be able to predict resultant plume changes. In smaller systems, it may be effective to make small scale changes periodically and adjust modifications based on groundwater monitoring results. Due to the expansive nature of the remediation systems at Hanford, however, additional tools were needed to predict the plume reactions to system changes. A computer simulation tool was developed to support pumping rate recommendations for optimization of large pump-and-treat groundwater remedy systems. This tool, called the Pumping Optimization Model, or POM, is based on a 1-layer derivation of a multi-layer contaminant transport model using MODFLOW and MT3D.
Frampton, Andrew; Destouni, Georgia
2016-04-01
In cold regions, flow in the unsaturated zone is highly dynamic with seasonal variability and changes in temperature, moisture, and heat and water fluxes, all of which affect ground freeze-thaw processes and influence transport of inert and reactive waterborne substances. In arctic permafrost environments, near-surface groundwater flow is further restricted to a relatively shallow and seasonally variable active layer, confined by perennially frozen ground below. The active layer is typically partially saturated with ice, liquid water and air, and is strongly dependent on seasonal temperature fluctuations, thermal forcing and infiltration patterns. Here there is a need for improved understanding of the mechanisms controlling subsurface solute transport in the partially saturated active layer zone. Studying solute transport in cold regions is relevant to improve the understanding of how natural and anthropogenic pollution may change as activities in arctic and sub-arctic regions increase. It is also particularly relevant for understanding how dissolved carbon is transported in coupled surface and subsurface hydrological systems under climate change, in order to better understand the permafrost-hydrological-carbon climate feedback. In this contribution subsurface solute transport under surface warming and degrading permafrost conditions is studied using a physically based model of coupled cryotic and hydrogeological flow processes combined with a particle tracking method. Changes in subsurface water flows and solute transport travel times are analysed for different modelled geological configurations during a 100-year warming period. Results show that for all simulated cases, the minimum and mean travel times increase non-linearly with warming irrespective of geological configuration and heterogeneity structure. The travel time changes are shown to depend on combined warming effects of increase in pathway length due to deepening of the active layer, reduced transport
Directory of Open Access Journals (Sweden)
Shutang Zhu
2008-01-01
Full Text Available The coupling of groundwater movement and reactive transport during groundwater recharge with wastewater leads to a complicated mathematical model, involving terms to describe convection-dispersion, adsorption/desorption and/or biodegradation, and so forth. It has been found very difficult to solve such a coupled model either analytically or numerically. The present study adopts operator-splitting techniques to decompose the coupled model into two submodels with different intrinsic characteristics. By applying an upwind finite difference scheme to the finite volume integral of the convection flux term, an implicit solution procedure is derived to solve the convection-dominant equation. The dispersion term is discretized in a standard central-difference scheme while the dispersion-dominant equation is solved using either the preconditioned Jacobi conjugate gradient (PJCG method or Thomas method based on local-one-dimensional scheme. The solution method proposed in this study is applied to the demonstration project of groundwater recharge with secondary effluent at Gaobeidian sewage treatment plant (STP successfully.
Turkeltaub, Tuvia; Kurtzman, Daniel; Dahan, Ofer
2016-08-01
Nitrate is considered the most common non-point pollutant in groundwater. It is often attributed to agricultural management, when excess application of nitrogen fertilizer leaches below the root zone and is eventually transported as nitrate through the unsaturated zone to the water table. A lag time of years to decades between processes occurring in the root zone and their final imprint on groundwater quality prevents proper decision-making on land use and groundwater-resource management. This study implemented the vadose-zone monitoring system (VMS) under a commercial crop field. Data obtained by the VMS for 6 years allowed, for the first time known to us, a unique detailed tracking of water percolation and nitrate migration from the surface through the entire vadose zone to the water table at 18.5 m depth. A nitrate concentration time series, which varied with time and depth, revealed - in real time - a major pulse of nitrate mass propagating down through the vadose zone from the root zone toward the water table. Analysis of stable nitrate isotopes indicated that manure is the prevalent source of nitrate in the deep vadose zone and that nitrogen transformation processes have little effect on nitrate isotopic signature. The total nitrogen mass calculations emphasized the nitrate mass migration towards the water table. Furthermore, the simulated pore-water velocity through analytical solution of the convection-dispersion equation shows that nitrate migration time from land surface to groundwater is relatively rapid, approximately 5.9 years. Ultimately, agricultural land uses, which are constrained to high nitrogen application rates and coarse soil texture, are prone to inducing substantial nitrate leaching.
Zhu, Chen; Hu, Fang Q.; Burden, David S.
2001-11-01
Natural attenuation of an acidic plume in the aquifer underneath a uranium mill tailings pond in Wyoming, USA was simulated using the multi-component reactive transport code PHREEQC. A one-dimensional model was constructed for the site and the model included advective-dispersive transport, aqueous speciation of 11 components, and precipitation-dissolution of six minerals. Transport simulation was performed for a reclamation scenario in which the source of acidic seepage will be terminated after 5 years and the plume will then be flushed by uncontaminated upgradient groundwater. Simulations show that successive pH buffer reactions with calcite, Al(OH) 3(a), and Fe(OH) 3(a) create distinct geochemical zones and most reactions occur at the boundaries of geochemical zones. The complex interplay of physical transport processes and chemical reactions produce multiple concentration waves. For SO 42- transport, the concentration waves are related to advection-dispersion, and gypsum precipitation and dissolution. Wave speeds from numerical simulations compare well to an analytical solution for wave propagation.
Solute transport in a well under slow-purge and no-purge conditions
Plummer, M. A.; Britt, S. L.; Martin-Hayden, J. M.
2010-12-01
Non-purge sampling techniques, such as diffusion bags and in-situ sealed samplers, offer reliable and cost-effective groundwater monitoring methods that are a step closer to the goal of real-time monitoring without pumping or sample collection. Non-purge methods are, however, not yet completely accepted because questions remain about how solute concentrations in an unpurged well relate to concentrations in the adjacent formation. To answer questions about how undisturbed well water samples compare to formation concentrations, and to provide the information necessary to interpret results from non-purge monitoring systems, we have conducted a variety of physical experiments and numerical simulations of flow and transport in and through monitoring wells under low-flow and ambient flow conditions. Previous studies of flow and transport in wells used a Darcy’s law - based continuity equation for flow, which is often justified under the strong, forced-convection flow caused by pumping or large vertical hydraulic potential gradients. In our study, we focus on systems with weakly forced convection, where density-driven free convection may be of similar strength. We therefore solved Darcy’s law for porous media domains and the Navier Stokes equations for flow in the well, and coupled solution of the flow equations to that of solute transport. To illustrate expected in-well transport behavior under low-flow conditions, we present results of three particular studies: (1) time-dependent effluent concentrations from a well purged at low-flow pumping rates, (2) solute-driven density effects in a well under ambient horizontal flow and (3) temperature-driven mixing in a shallow well subject to seasonal temperature variations. Results of the first study illustrate that assumptions about the nature of in-well flow have a significant impact on effluent concentration curves even during pumping, with Poiseuille-type flow producing more rapid removal of concentration differences
TOUGH2. Unsaturated Groundwater and Heat Transport Model
Energy Technology Data Exchange (ETDEWEB)
Pruess, K. [Lawrence Berkeley National Lab., CA (United States)
1991-05-01
TOUGH2 is a new and improved version of TOUGH. TOUGH2 offers added capabilities and user features, including the flexibility to handle different fluid mixtures (water, water with tracer; water, CO2; water, air; water, air, with vapor pressure lowering and water, hydrogen), facilities for processing of geometric data (computational grids), and an internal version control system to ensure referenceability of code applications. TOUGH2 is a multi-dimensional numerical model for simulating the coupled transport of water, vapor, air, and heat in porous and fractured media. The program provides options for specifying injection or withdrawal of heat and fluids. Although primarily designed for studies of high-level nuclear waste isolation in partially saturated geological media, it should also be useful for a wider range of problems in heat and moisture transfer, and in the drying of porous materials. For example, geothermal reservoir simulation problems can be handled simply by setting the air mass function equal to zero on input. The TOUGH2 simulator was developed for problems involving strongly heat-driven flow. To describe these phenomena a multi-phase approach to fluid and heat flow is used, which fully accounts for the movement of gaseous and liquid phases, their transport of latent and sensible heat, and phase transitions between liquid and vapor. TOUGH2 takes account of fluid flow in both liquid and gaseous phases occurring under pressure, viscous, and gravity forces according to Darcy`s law. Interference between the phases is represented by means of relative permeability functions. The code handles binary, but not Knudsen, diffusion in the gas phase and capillary and phase adsorption effects for the liquid phase. Heat transport occurs by means of conduction with thermal conductivity dependent on water saturation, convection, and binary diffusion, which includes both sensible and latent heat.
A generalized solution for groundwater head fluctuation in a tidal leaky aquifer system
Indian Academy of Sciences (India)
Mo-Hsiung Chuang; Hund-Der Yeh
2011-12-01
A new analytical solution is developed for describing groundwater level fluctuations in a coupled leaky confined aquifer system which consists of an unconfined aquifer, confined aquifer, and an aquitard in between. The aquifer system has a tidal boundary at the seashore, a no flow boundary at remote inland side, and a confined aquifer extending under the sea and terminated with an outlet-capping. This new solution has shown to be a generalisation of most existing analytical solutions for a tidal aquifer system which includes single confined and leaky confined aquifers. In addition, the solution is used to explore the influences of the dimensionless leakance of the outlet-capping, the dimensionless hydraulic diffusivities, and the leakages of the inland and offshore aquitards on the head responses in the leaky confined aquifer.
Energy Technology Data Exchange (ETDEWEB)
Drici, Warda
2003-08-01
This report documents the analysis of the available transport parameter data conducted in support of the development of a Corrective Action Unit (CAU) groundwater flow model for Central and Western Pahute Mesa: CAUs 101 and 102.
RAFT: A simulator for ReActive Flow and Transport of groundwater contaminants
Energy Technology Data Exchange (ETDEWEB)
Chilakapati, A
1995-07-01
This report documents the use of the simulator RAFT for the ReActive flow and Transport of groundwater contaminants. RAFT can be used as a predictive tool in the design and analysis of laboratory and field experiments or it can be used for the estimation of model/process parameters from experiments. RAFT simulates the reactive transport of groundwater contaminants in one, two-, or three-dimensions and it can model user specified source/link configurations and arbitrary injection strategies. A suite of solvers for transport, reactions and regression are employed so that a combination of numerical methods best suited for a problem can be chosen. User specified coupled equilibrium and kinetic reaction systems can be incorporated into RAFT. RAFT is integrated with a symbolic computational language MAPLE, to automate code generation for arbitrary reaction systems. RAFT is expected to be used as a simulator for engineering design for field experiments in groundwater remediation including bioremediation, reactive barriers and redox manipulation. As an integrated tool with both the predictive ability and the ability to analyze experimental data, RAFT can help in the development of remediation technologies, from laboratory to field.
THE GENERATION OF METABOLIC ENERGY BY SOLUTE TRANSPORT
Konings, W.N; Lolkema, J.S.; Poolman, B.
1995-01-01
Secondary metabolic-energy-generating systems generate a proton motive force (pmf) or a sodium ion motive force (smf) by a process that involves the action of secondary transporters. The (electro)chemical gradient of the solute(s) is converted into the electrochemical gradient of protons or sodium i
Sustainable freight transport in South Africa:Domestic intermodal solutions
Directory of Open Access Journals (Sweden)
Jan H. Havenga
2011-11-01
Full Text Available Due to the rapid deregulation of freight transport in South Africa two decades ago, and low historical investment in rail (with resultant poor service delivery, an integrated alternative to road and rail competition was never developed. High national freight logistics costs, significant road infrastructure challenges and environmental impact concerns of a road-dominated freight transport market have, however, fuelled renewed interest in intermodal transport solutions. In this article, a high-level business case for domestic intermodal solutions in South Africa is presented. The results demonstrate that building three intermodal terminals to connect the three major industrial hubs (i.e. Gauteng, Durban and Cape Town through an intermodal solution could reduce transport costs (including externalities for the identified 11.5 million tons of intermodalfriendly freight flows on the Cape and Natal corridors by 42% (including externalities.
Effect of cell physicochemical characteristics and motility on bacterial transport in groundwater
Becker, M.W.; Collins, S.A.; Metge, D.W.; Harvey, R.W.; Shapiro, A.M.
2004-01-01
The influence of physicochemical characteristics and motility on bacterial transport in groundwater were examined in flow-through columns. Four strains of bacteria isolated from a crystalline rock groundwater system were investigated, with carboxylate-modified and amidine-modified latex microspheres and bromide as reference tracers. The bacterial isolates included a gram-positive rod (ML1), a gram-negative motile rod (ML2), a nonmotile mutant of ML2 (ML2m), and a gram-positive coccoid (ML3). Experiments were repeated at two flow velocities, in a glass column packed with glass beads, and in another packed with iron-oxyhydroxide coated glass beads. Bacteria breakthrough curves were interpreted using a transport equation that incorporates a sorption model from microscopic observation of bacterial deposition in flow-cell experiments. The model predicts that bacterial desorption rate will decrease exponentially with the amount of time the cell is attached to the solid surface. Desorption kinetics appeared to influence transport at the lower flow rate, but were not discernable at the higher flow rate. Iron-oxyhydroxide coatings had a lower-than-expected effect on bacterial breakthrough and no effect on the microsphere recovery in the column experiments. Cell wall type and shape also had minor effects on breakthrough. Motility tended to increase the adsorption rate, and decrease the desorption rate. The transport model predicts that at field scale, desorption rate kinetics may be important to the prediction of bacteria transport rates. ?? 2003 Elsevier B.V. All rights reserved.
Yimer Ebrahim, Girma; Jonoski, Andreja; van Griensven, Ann; Dujardin, Juliette; Baetelaan, Okke; Bronders, Jan
2010-05-01
Chlorinated-solvent form one of the largest groups of environmental chemicals. Their use and misuse in industry have lead to a large entry of these chemicals into the environment, resulting in widespread dissemination and oftentimes environmental contamination. Chlorinated solvent contamination of groundwater resources has been widely reported. For instance, there has been much interest in the assessment of these contaminant levels and their evolutions with time in the groundwater body below the Vilvoorde-Machelen industrial area (Belgium). The long industrial history of the area has lead to complex patterns of pollution from multiple sources and the site has been polluted to the extent that individual plumes are not definable any more. Understanding of groundwater/surface water interaction is a critical component for determining the fate of contaminant both in streams and ground water due to the fact that groundwater and surface water are in continuous dynamic interaction in the hydrologic cycle. The interaction has practical consequences in the quantity and quality of water in either system in the sense that depletion and/or contamination of one of the system will eventually affect the other one. The transition zone between a stream and its adjacent aquifer referred to as the hyporheic zone plays a critical role in governing contaminant exchange and transformation during water exchange between the two water bodies. The hyporheic zone of Zenne River ( the main receptor ) is further complicated due to the fact that the river banks are artificially trained with sheet piles along its reach extending some 12 m below the surface. This study demonstrates the use of MODFLOW, a widely used modular three-dimensional block-centred finite difference, saturated flow model for simulating the flow and direction of movement of groundwater through aquifer and stream-aquifer interaction and the use of transport model RT3D, a three-dimensional multi-species reactive transport model
Transport of Nitrogen and Phosphorus from Onsite Wastewater Treatment Systems to Shallow Groundwater
Toor, G.
2014-12-01
The knowledge about the nutrients transport from the vadose zone of onsite wastewater treatment systems (commonly called septic systems) is crucial to protect groundwater quality as 25% of US population uses septic systems to discharge household wastewater. For example, our preliminary data showed that about 47% of applied water was recovered at 60-cm below drainfield of septic systems. This implies that contaminants present in wastewater, if not attenuated in the vadose zone, can be transported to shallow groundwater. This presentation will focus on the biophysical and hydrologic controls on the transport of nitrogen (N) and phosphorus (P) from the vadose of two conventional (drip dispersal, gravel trench) and an advanced (with aerobic and anaerobic medias) system. These systems were constructed using two rows of drip pipe (37 emitters/mound) placed 0.3 m apart in the center of 6 m x 0.6 m drainfield. Each system received 120 L of wastewater per day. During 20-month period (May 2012 to December 2013), soil-water samples were collected from the vadose zone using suction cup lysimeters installed at 0.30, 0.60, and 1.05 m depth and groundwater samples were collected from piezometers installed at 3-3.30 m depth below the drainfield. A complimentary 1-year study using smaller drainfields (0.5 m long, 0.9 m wide, 0.9 m high) was conducted to obtain better insights in the vadose zone. A variety of instruments (multi-probe sensors, suction cup lysimeters, piezometers, tensiometers) were installed in the vadose zones. Results showed that nitrification controlled N evolution in drainfield and subsequent transport of N plumes (>10 mg/L) into groundwater. Most of the wastewater applied soluble inorganic P (>10 mg/L) was quickly attenuated in the drainfield due to fixation (sorption, precipitation) in the vadose zone (advanced system was extremely effective as it removed >95% N from wastewater, but was less effective at removing P. This presentation will conclude with
Bailey, Ryan T.
2016-12-01
Selenium (Se) is an essential micro-nutrient for humans, but can be toxic at high levels of intake. Se deficiency and Se toxicity are linked with serious diseases, with some regions worldwide experiencing Se deficiency due to Se-poor rocks and soils and other areas dealing with Se toxicity due to the presence of Se-enriched geologic materials. In addition, Se is consumed primarily through plants that take up Se from soil and through animal products that consume these plants. Hence, the soil and groundwater system play important roles in determining the effect of Se on human health. This paper reviews current understanding of Se fate and transport in soil and groundwater systems and its relation to human health, with a focus on alluvial systems, soil systems, and the interface between alluvial systems and Cretaceous shale that release Se via oxidation processes. The review focuses first on the relation between Se and human health, followed by a summary of Se distribution in soil-aquifer systems, with an emphasis on the quantitative relationship between Se content in soil and Se concentration in underlying groundwater. The physical, chemical, and microbial processes that govern Se fate and transport in subsurface systems then are presented, followed by numerical modeling techniques used to simulate these processes in study regions and available remediation strategies for either Se-deficient or Se-toxic regions. This paper can serve as a guide to any field, laboratory or modeling study aimed at assessing Se fate and transport in groundwater systems and its relation to human health.
Bailey, Ryan T.
2017-06-01
Selenium (Se) is an essential micro-nutrient for humans, but can be toxic at high levels of intake. Se deficiency and Se toxicity are linked with serious diseases, with some regions worldwide experiencing Se deficiency due to Se-poor rocks and soils and other areas dealing with Se toxicity due to the presence of Se-enriched geologic materials. In addition, Se is consumed primarily through plants that take up Se from soil and through animal products that consume these plants. Hence, the soil and groundwater system play important roles in determining the effect of Se on human health. This paper reviews current understanding of Se fate and transport in soil and groundwater systems and its relation to human health, with a focus on alluvial systems, soil systems, and the interface between alluvial systems and Cretaceous shale that release Se via oxidation processes. The review focuses first on the relation between Se and human health, followed by a summary of Se distribution in soil-aquifer systems, with an emphasis on the quantitative relationship between Se content in soil and Se concentration in underlying groundwater. The physical, chemical, and microbial processes that govern Se fate and transport in subsurface systems then are presented, followed by numerical modeling techniques used to simulate these processes in study regions and available remediation strategies for either Se-deficient or Se-toxic regions. This paper can serve as a guide to any field, laboratory or modeling study aimed at assessing Se fate and transport in groundwater systems and its relation to human health.
A stochastic method of solution of the Parker transport equation
Wawrzynczak, A; Gil, A
2015-01-01
We present the stochastic model of the galactic cosmic ray (GCR) particles transport in the heliosphere. Based on the solution of the Parker transport equation we developed models of the short-time variation of the GCR intensity, i.e. the Forbush decrease (Fd) and the 27-day variation of the GCR intensity. Parker transport equation being the Fokker-Planck type equation delineates non-stationary transport of charged particles in the turbulent medium. The presented approach of the numerical solution is grounded on solving of the set of equivalent stochastic differential equations (SDEs). We demonstrate the method of deriving from Parker transport equation the corresponding SDEs in the heliocentric spherical coordinate system for the backward approach. Features indicative the preeminence of the backward approach over the forward is stressed. We compare the outcomes of the stochastic model of the Fd and 27-day variation of the GCR intensity with our former models established by the finite difference method. Both ...
Institute of Scientific and Technical Information of China (English)
Xiao-Yang CHEN; Jia-Ping YAN; Shi-Wen ZHANG
2013-01-01
Chloride ion transport in reclaimed soil solutions filled with fly ash (FA) was investigated by measuring the hydraulic parameters (i.e.water retention curves and hydraulic conductivity) of three substrates,namely GSL,GFA,and CFA.Similar simulations were carried out under certain weather conditions.The different boundary conditions of chloride transport were also discussed from FA texture,cover soil thickness,groundwater table level,and initial chloride concentration.Furthcrmore,the sensitivities of chloride ions to these effect factors were analyzed.The results show that the different top soil thickness and initial chloride concentration have no effect on salinity of topsoil solution in the monitoring points,but they can clearly change the chloride concentration of FA layers.The sensibilities from top soil thickness and initial chloride content are exceedingly weak to the salinity balance based on two dimensions of the time and concentration.While the different FA texture and groundwater table not only affect the salinity equilibrium process of the whole reclaimed soil profile,but also change its balance state.Generally,coarse FA particles and high groundwater table can defer the salinity balance process of the reclaimed soil solution,and they also increase the chloride concentration of FA layer solutions,and even topsoil ones.
Genesis and transport of hexavalent chromium in the system ophiolitic rocks - groundwater
Shchegolikhina, Anastasia; Guadagnini, Laura; Guadagnini, Alberto
2015-04-01
Our study aims at contributing to the quantification and characterization of chromium transport processes from host rocks and soil matrices to groundwater. We focus on dissolved hexavalent chromium detected in groundwaters of geological regions with ophiolitic rocks (ophiolites and serpentinites) inclusions due to its critical ecological impact. (Oze et al., 2004). Despite the large number of analyses on the occurrence of high concentrations of hazardous hexavalent chromium ions in natural waters, only few studies were performed with the objective of identifying and investigating the geochemical reactions which could occur in the natural system rock - groundwater - dissolved chromium (Fantoni et al., 2002, Stephen and James, 2004, Lelli et al., 2013). In this context, there is a need for integration of results obtained from diverse studies in various regions and settings to improve our knowledge repository. Our theoretical analyses are grounded and driven by practical scenarios detected in subsurface reservoirs exploited for civil and industrial use located in the Emilia-Romagna region (Italy). Available experimental datasets are complemented with data from other international regional-scale settings (Altay mountains region, Russia). Modeling of chromium transformation and migration particularly includes characterization of the multispecies geochemical system. A key aspect of our study is the analysis of the complex competitive sorption processes governing heavy metal evolution in groundwater. The results of the research allow assessing the critical qualitative features of the mechanisms of hexavalent chromium ion mobilization from host rocks and soils and the ensuing transformation and migration to groundwater under the influence of diverse environmental factors. The study is then complemented by the quantification of the main sources of uncertainty associated with prediction of heavy metal contamination levels in the groundwater system explored. Fantoni, D
Tenbus, Frederick J.; Fleck, William B.
2001-01-01
Military activity at Graces Quarters, a former open-air chemical-agent facility at Aberdeen Proving Ground, Maryland, has resulted in ground-water contamination by chlorinated hydrocarbons. As part of a ground-water remediation feasibility study, a three-dimensional model was constructed to simulate transport of four chlorinated hydrocarbons (1,1,2,2-tetrachloroethane, trichloroethene, carbon tetrachloride, and chloroform) that are components of a contaminant plume in the surficial and middle aquifers underlying the east-central part of Graces Quarters. The model was calibrated to steady-state hydraulic head at 58 observation wells and to the concentration of 1,1,2,2-tetrachloroethane in 58 observation wells and 101direct-push probe samples from the mid-1990s. Simulations using the same basic model with minor adjustments were then run for each of the other plume constituents. The error statistics between the simulated and measured concentrations of each of the constituents compared favorably to the error statisticst,1,2,2-tetrachloroethane calibration. Model simulations were used in conjunction with contaminant concentration data to examine the sources and degradation of the plume constituents. It was determined from this that mixed contaminant sources with no ambient degradation was the best approach for simulating multi-species solute transport at the site. Forward simulations were run to show potential solute transport 30 years and 100 years into the future with and without source removal. Although forward simulations are subject to uncertainty, they can be useful for illustrating various aspects of the conceptual model and its implementation. The forward simulation with no source removal indicates that contaminants would spread throughout various parts of the surficial and middle aquifers, with the100-year simulation showing potential discharge areas in either the marshes at the end of the Graces Quarters peninsula or just offshore in the estuaries. The
Curtis, Gary P.; Lu, Dan; Ye, Ming
2015-01-01
While Bayesian model averaging (BMA) has been widely used in groundwater modeling, it is infrequently applied to groundwater reactive transport modeling because of multiple sources of uncertainty in the coupled hydrogeochemical processes and because of the long execution time of each model run. To resolve these problems, this study analyzed different levels of uncertainty in a hierarchical way, and used the maximum likelihood version of BMA, i.e., MLBMA, to improve the computational efficiency. This study demonstrates the applicability of MLBMA to groundwater reactive transport modeling in a synthetic case in which twenty-seven reactive transport models were designed to predict the reactive transport of hexavalent uranium (U(VI)) based on observations at a former uranium mill site near Naturita, CO. These reactive transport models contain three uncertain model components, i.e., parameterization of hydraulic conductivity, configuration of model boundary, and surface complexation reactions that simulate U(VI) adsorption. These uncertain model components were aggregated into the alternative models by integrating a hierarchical structure into MLBMA. The modeling results of the individual models and MLBMA were analyzed to investigate their predictive performance. The predictive logscore results show that MLBMA generally outperforms the best model, suggesting that using MLBMA is a sound strategy to achieve more robust model predictions relative to a single model. MLBMA works best when the alternative models are structurally distinct and have diverse model predictions. When correlation in model structure exists, two strategies were used to improve predictive performance by retaining structurally distinct models or assigning smaller prior model probabilities to correlated models. Since the synthetic models were designed using data from the Naturita site, the results of this study are expected to provide guidance for real-world modeling. Limitations of applying MLBMA to the
Bradley, P. M.; Barber, L. B.; Duris, J. W.; Foreman, W. T.; Furlong, E. T.; Hubbard, L. E.; Hutchinson, K. J.; Keefe, S. H.; Kolpin, D. W.
2014-12-01
Wastewater pharmaceutical contamination of shallow groundwater is a substantial concern in effluent-dominated streams, due to aqueous mobility and designed bioactivity of pharmaceuticals and due to effluent-driven hydraulic gradients. Improved understanding of the environmental fate and transport of wastewater-derived pharmaceuticals is essential for effective protection of vital aquatic ecosystem services, environmental health, and drinking-water supplies. Substantial longitudinal (downstream) transport of pharmaceutical contaminants has been documented in effluent-impacted streams. The comparative lack of information on vertical and lateral transport (infiltration) of wastewater contaminants from surface-water to hyporheic and shallow groundwater compartments is a critical scientific data gap, given the potential for contamination of groundwater supplies in effluent-impacted systems. Growing dependencies on bank filtration and artificial recharge applications for release of wastewater to the environment and for pretreatment of poor-quality surface-water for drinking water emphasize the critical need to better understand the exchange of wastewater contaminants, like pharmaceuticals, between surface-water and groundwater compartments. The potential transport of effluent-derived pharmaceutical contaminants from surface-water to hyporheic-water and shallow groundwater compartments was examined in a wastewater-treatment-facility (WWTF) impacted stream in Ankeny, Iowa under effluent-dominated (71-99% of downstream flow) conditions. Strong hydraulic gradients and hydrologic connectivity were evident between surface-water and shallow-groundwater compartments in the vicinity of the WWTF outfall. Carbamazepine, sulfamethoxazole, and immunologically-related compounds were detected in groundwater 10-20 meters from the stream bank. Direct aqueous-injection HPLC-MS/MS revealed high percentage detections of pharmaceuticals (110 total analytes) in surface-water and groundwater
End-Member Formulation of Solid Solutions and Reactive Transport
Energy Technology Data Exchange (ETDEWEB)
Lichtner, Peter C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2015-09-01
A model for incorporating solid solutions into reactive transport equations is presented based on an end-member representation. Reactive transport equations are solved directly for the composition and bulk concentration of the solid solution. Reactions of a solid solution with an aqueous solution are formulated in terms of an overall stoichiometric reaction corresponding to a time-varying composition and exchange reactions, equivalent to reaction end-members. Reaction rates are treated kinetically using a transition state rate law for the overall reaction and a pseudo-kinetic rate law for exchange reactions. The composition of the solid solution at the onset of precipitation is assumed to correspond to the least soluble composition, equivalent to the composition at equilibrium. The stoichiometric saturation determines if the solid solution is super-saturated with respect to the aqueous solution. The method is implemented for a simple prototype batch reactor using Mathematica for a binary solid solution. Finally, the sensitivity of the results on the kinetic rate constant for a binary solid solution is investigated for reaction of an initially stoichiometric solid phase with an undersaturated aqueous solution.
Energy Technology Data Exchange (ETDEWEB)
George J. Moridis
2001-10-01
In this paper, semianalytical solutions are developed for the problem of transport of radioactive or reactive solute tracers through a layered system of heterogeneous fractured media with misaligned fractures. The tracer transport equations in the non-flowing matrix account for (a) diffusion, (b) surface diffusion, (c) mass transfer between the mobile and immobile water fractions, (d) linear kinetic or equilibrium physical, chemical, or combined solute sorption or colloid filtration, and (e) radioactive decay or first-order chemical reactions. The tracer-transport equations in the fractures account for the same processes, in addition to advection and hydrodynamic dispersion. Any number of radioactive decay daughter products (or products of a linear, first-order reaction chain) can be tracked. The solutions, which are analytical in the Laplace space, are numerically inverted to provide the solution in time and can accommodate any number of fractured and/or porous layers. The solutions are verified using analytical solutions for limiting cases of solute and colloid transport through fractured and porous media. The effect of important parameters on the transport of {sup 3}H, {sup 237}Np and {sup 239}Pu (and its daughters) is investigated in several test problems involving layered geological systems of varying complexity.
Energy Technology Data Exchange (ETDEWEB)
Moridis, George J.
2001-10-10
In this paper, semianalytical solutions are developed for the problem of transport of radioactive or reactive solute tracers through a layered system of heterogeneous fractured media with misaligned fractures. The tracer transport equations in the non-flowing matrix account for (a) diffusion, (b) surface diffusion, (c) mass transfer between the mobile and immobile water fractions, (d) linear kinetic or equilibrium physical, chemical, or combined solute sorption or colloid filtration, and (e) radioactive decay or first-order chemical reactions. The tracer-transport equations in the fractures account for the same processes, in addition to advection and hydrodynamic dispersion. Any number of radioactive decay daughter products (or products of a linear, first-order reaction chain) can be tracked. The solutions, which are analytical in the Laplace space, are numerically inverted to provide the solution in time and can accommodate any number of fractured and/or porous layers. The solutions are verified using analytical solutions for limiting cases of solute and colloid transport through fractured and porous media. The effect of important parameters on the transport of {sup 3}H, {sup 237}Np and {sup 239}Pu (and its daughters) is investigated in several test problems involving layered geological systems of varying complexity.
Kirshen, P. H.; Knott, J. F.; Ray, P.; Elshaer, M.; Daniel, J.; Jacobs, J. M.
2016-12-01
Transportation climate change vulnerability and adaptation studies have primarily focused on surface-water flooding from sea-level rise (SLR); little attention has been given to the effects of climate change and SLR on groundwater and subsequent impacts on the unbound foundation layers of coastal-road infrastructure. The magnitude of service-life reduction depends on the height of the groundwater in the unbound pavement materials, the pavement structure itself, and the loading. Using a steady-state groundwater model, and a multi-layer elastic pavement evaluation model, the strain changes in the layers can be determined as a function of parameter values and the strain changes translated into failure as measured by number of loading cycles to failure. For a section of a major coastal road in New Hampshire, future changes in sea-level, precipitation, temperature, land use, and groundwater pumping are characterized by deep uncertainty. Parameters that describe the groundwater system such as hydraulic conductivity can be probabilistically described while road characteristics are assumed to be deterministic. To understand the vulnerability of this road section, a bottom-up planning approach was employed over time where the combinations of parameter values that cause failure were determined and their plausibility of their occurring was analyzed. To design a robust adaptation strategy that will function reasonably well in the present and the future given the large number of uncertain parameter values, performance of adaptation options were investigated. Adaptation strategies that were considered include raising the road, load restrictions, increasing pavement layer thicknesses, replacing moisture-sensitive materials with materials that are not moisture sensitive, improving drainage systems, and treatment of the underlying materials.
Gamazo, P. A.; Colina, R.; Victoria, M.; Alvareda, E.; Burutaran, L.; Ramos, J.; Lopez, F.; Soler, J.
2014-12-01
In many areas of Uruguay groundwater is the only source of water for human consumption and for industrial-agricultural economic activities. Traditionally considered as a safe source, due to the "natural filter" that occurs in porous media, groundwater is commonly used without any treatment. The Uruguayan law requires bacteriological analysis for most water uses, but virological analyses are not mentioned in the legislation. In the Salto district, where groundwater is used for human consumption and for agricultural activities, bacterial contamination has been detected in several wells but no viruses analysis have been performed. The Republic University (UDELAR), with the support of the National Agency for Research and Innovation (ANII), is studying the incidence of virus in groundwater on an intensive agriculture area of the Salto district. In this area water is pumped from the "Salto Aquifer", a free sedimentary aquifer. Below this sedimentary deposit is the "Arapey" basaltic formation, which is also exploited for water productions on its fractured zones. A screening campaign has been performed searching for bacterial and viral contamination. Total and fecal coliforms have been found on several wells and Rotavirus and Adenovirus have been detected. A subgroup of the screening wells has been selected for an annual survey. On this subgroup, besides bacteria and viruses analysis, a standard physical and chemical characterization was performed. Results show a significant seasonal variation on microbiological contamination. In addition to field studies, rotavirus circulation experiments on columns are being performed. The objective of this experiments is to determinate the parameters that control virus transport in porous media. The results of the study are expected to provide an insight into the impacts of groundwater on Salto's viral gastroenterocolitis outbreaks.
Long-term transport behavior of psychoactive compounds in sewage-affected groundwater
Nham, Hang Thuy Thi; Greskowiak, Janek; Hamann, Enrico; Meffe, Raffaella; Hass, Ulrike; Massmann, Gudrun
2016-11-01
The present study provides a model-based characterization of the long-term transport behavior of five psychoactive compounds (meprobamate, pyrithyldione, primidone, phenobarbital and phenylethylmalonamide) introduced into groundwater via sewage irrigation in Berlin, Germany. Compounds are still present in the groundwater despite the sewage farm closure in the year 1980. Due to the limited information on (i) compound concentrations in the source water and (ii) substance properties, a total of 180 cross-sectional model realizations for each compound were carried out, covering a large range of possible parameter combinations. Results were compared with the present-day contamination patterns in the aquifer and the most likely scenarios were identified based on a number of model performance criteria. The simulation results show that (i) compounds are highly persistent under the present field conditions, and (ii) sorption is insignificant. Thus, back-diffusion from low permeability zones appears as the main reason for the compound retardation.
Directory of Open Access Journals (Sweden)
Solomon Ndubuisi Eluozo
2012-11-01
Full Text Available Development of mathematical model to predict the transport of dissolved arsenic in groundwater influenced by seepage velocity has been carried out. This model was developed to monitor the rate of concentration at different period and depths. High and low concentrations were observed at different periods and depth as presented in the figures. These conditions can be attributed to soil stratification deposition in the study location and the influence of man-made activities. Based on these facts, it is recommended that risk assessment should be thoroughly done for soil and water and the predicted model should be applied in design and construction of groundwater system in the study area.
Large-scale modeling of reactive solute transport in fracture zones of granitic bedrocks
Molinero, Jorge; Samper, Javier
2006-01-01
Final disposal of high-level radioactive waste in deep repositories located in fractured granite formations is being considered by several countries. The assessment of the safety of such repositories requires using numerical models of groundwater flow, solute transport and chemical processes. These models are being developed from data and knowledge gained from in situ experiments such as the Redox Zone Experiment carried out at the underground laboratory of Äspö in Sweden. This experiment aimed at evaluating the effects of the construction of the access tunnel on the hydrogeological and hydrochemical conditions of a fracture zone intersected by the tunnel. Most chemical species showed dilution trends except for bicarbonate and sulphate which unexpectedly increased with time. Molinero and Samper [Molinero, J. and Samper, J. Groundwater flow and solute transport in fracture zones: an improved model for a large-scale field experiment at Äspö (Sweden). J. Hydraul. Res., 42, Extra Issue, 157-172] presented a two-dimensional water flow and solute transport finite element model which reproduced measured drawdowns and dilution curves of conservative species. Here we extend their model by using a reactive transport which accounts for aqueous complexation, acid-base, redox processes, dissolution-precipitation of calcite, quartz, hematite and pyrite, and cation exchange between Na + and Ca 2+. The model provides field-scale estimates of cation exchange capacity of the fracture zone and redox potential of groundwater recharge. It serves also to identify the mineral phases controlling the solubility of iron. In addition, the model is useful to test the relevance of several geochemical processes. Model results rule out calcite dissolution as the process causing the increase in bicarbonate concentration and reject the following possible sources of sulphate: (1) pyrite dissolution, (2) leaching of alkaline sulphate-rich waters from a nearby rock landfill and (3) dissolution of
2D-Cell Experiment on Methyl Tert-Butyl Ether Transport in Saturated Zone of Groundwater
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
As an additive of gasoline, methyl tert-butyl ether (MTBE) has a higher solubility in water, which is about 20 times as high as that of benzene. This characteristic results in MTBE dissolving out of the gasoline into the soil and groundwater. Due to relative unique physicochemical behavior of MTBE it would be an ideal candidate for use in environmental forensic investigations. In order to study the transport and distribution of MTBE in saturated zone of ground water, a two-dimensional experimental cell was setup to simulate the real environment of the groundwater flow.The effects of soil and groundwater flow velocity on the MTBE transport were investigated. The results show that the mobile distance of MTBE in vertical direction was smaller than that in horizontal direction paralleling with the groundwater flow. Because the main dynamics of groundwater flow direction was convection and dispersion, the movement of MTBE is also diffusion in the vertical direction. In addition, the transport of MTBE was more quick in high permeability porous media, and the increase of groundwater flow velocity can accelerate the MTBE plume development, but the irregularity and randomness of the plume are enhanced synchronously. These research results can give some helps for the investigation of MTBE movement in the groundwater, also can make some references for other petroleum contamination behavior.
Ghasemizadeh, Reza; Yu, Xue; Butscher, Christoph; Hellweger, Ferdi; Padilla, Ingrid; Alshawabkeh, Akram
2015-01-01
Karst aquifers have a high degree of heterogeneity and anisotropy in their geologic and hydrogeologic properties which makes predicting their behavior difficult. This paper evaluates the application of the Equivalent Porous Media (EPM) approach to simulate groundwater hydraulics and contaminant transport in karst aquifers using an example from the North Coast limestone aquifer system in Puerto Rico. The goal is to evaluate if the EPM approach, which approximates the karst features with a conceptualized, equivalent continuous medium, is feasible for an actual project, based on available data and the study scale and purpose. Existing National Oceanic Atmospheric Administration (NOAA) data and previous hydrogeological U. S. Geological Survey (USGS) studies were used to define the model input parameters. Hydraulic conductivity and specific yield were estimated using measured groundwater heads over the study area and further calibrated against continuous water level data of three USGS observation wells. The water-table fluctuation results indicate that the model can practically reflect the steady-state groundwater hydraulics (normalized RMSE of 12.4%) and long-term variability (normalized RMSE of 3.0%) at regional and intermediate scales and can be applied to predict future water table behavior under different hydrogeological conditions. The application of the EPM approach to simulate transport is limited because it does not directly consider possible irregular conduit flow pathways. However, the results from the present study suggest that the EPM approach is capable to reproduce the spreading of a TCE plume at intermediate scales with sufficient accuracy (normalized RMSE of 8.45%) for groundwater resources management and the planning of contamination mitigation strategies.
The role of groundwater chemistry in the transport of bacteria to water-supply wells
Harvey, R.W.; Metge, D.W.
1999-01-01
Static mini-columns and in situ injection and recovery tests were used to assess the effects of modest changes in groundwater chemistry upon the pH-dependence of bacterial attachment, a primary determinant of bacterial mobility in drinking water aquifers. In uncontaminated groundwater (surfactants can also substantively alter the attraction of groundwater bacteria for grain surfaces and, therefore can alter the transport of bacteria to water-supply wells. This phenomenon was pH-sensitive and dependent upon the nature of the surfactant. At pH 7.6, 200 mg l-1 of the non-ionic surfactant, Imbentin, caused a doubling of fractional bacterial attachment in aquifer-sediment columns, but had little effect under slightly acidic conditions (e.g. at pH 5.8). In contrast, 1 mg l-1 of linear alkylbenzene sulphonate (LAS) surfactant, a common sewage-derived contaminant, decreased the fractional bacterial attachment by more than 30% at pH 5.8, but had little effect at pH 7.3.Static mini-columns and in situ injection and recovery tests were used to assess the effects of modest changes in groundwater chemistry upon the pH-dependence of bacterial attachment, a primary determinant of bacterial mobility in drinking water aquifers. In uncontaminated groundwater (surfactants can also substantively alter the attraction of groundwater bacteria for grain surfaces and, therefore can alter the transport of bacteria to water-supply wells. This phenomenon was pH-sensitive and dependent upon the nature of the surfactant. At pH 7.6, 200 mg l-1 of the non-ionic surfactant, Imbentin, caused a doubling of fractional bacterial attachment in aquifer-sediment columns, but had little effect under slightly acidic conditions (e.g. at pH 5.8). In contrast, 1 mg l-1 of linear alkylbenzene sulphonate (LAS) surfactant, a common sewage-derived contaminant, decreased the fractional bacterial attachment by more than 30% at pH 5.8, but had little effect at pH 7.3.
Molecular level water and solute transport in reverse osmosis membranes
Lueptow, Richard M.; Shen, Meng; Keten, Sinan
2015-11-01
The water permeability and rejection characteristics of six solutes, methanol, ethanol, 2-propanol, urea, Na+, and Cl-, were studied for a polymeric reverse osmosis (RO) membrane using non-equilibrium molecular dynamics simulations. Results indicate that water flux increases with an increasing fraction of percolated free volume in the membrane polymer structure. Solute molecules display Brownian motion and hop from pore to pore as they pass through the membrane. The solute rejection depends on both the size of the solute molecule and the chemical interaction of the solute with water and the membrane. When the open spaces in the polymeric structure are such that solutes have to shed at least one water molecule from their solvation shell to pass through the membrane molecular structure, the water-solute pair interaction energy governs solute rejection. Organic solutes more easily shed water molecules than ions to more readily pass through the membrane. Hydrogen-bonding sites for molecules like urea also lead to a higher rejection. These findings underline the importance of the solute's solvation shell and solute-water-membrane chemistry in solute transport and rejection in RO membranes. Funded by the Institute for Sustainability and Energy at Northwestern with computing resources from XSEDE (NSF grant ACI-1053575).
DEFF Research Database (Denmark)
Larsen, Erik Hviid; Sørensen, Jakob Balslev; Sørensen, Jens Nørkær
2000-01-01
A mathematical model of an absorbing leaky epithelium is developed for analysis of solute coupled water transport. The non-charged driving solute diffuses into cells and is pumped from cells into the lateral intercellular space (lis). All membranes contain water channels with the solute passing...... concentration of fluid emerging from lis is then significantly larger than the concentration in lis. Thus, in absence of external driving forces the model generates isotonic transport provided a component of the solute flux emerging downstream lis is taken up by cells through the serosal membrane and pumped...... back into lis, i.e., the solute would have to be recirculated. With input variables from toad intestine (Nedergaard, S., E.H. Larsen, and H.H. Ussing, J. Membr. Biol. 168:241-251), computations predict that 60-80% of the pumped flux stems from serosal bath in agreement with the experimental estimate...
Nonrelativistic grey Sn-transport radiative-shock solutions
Ferguson, J. M.; Morel, J. E.; Lowrie, R. B.
2017-06-01
We present semi-analytic radiative-shock solutions in which grey Sn-transport is used to model the radiation, and we include both constant cross sections and cross sections that depend on temperature and density. These new solutions solve for a variable Eddington factor (VEF) across the shock domain, which allows for interesting physics not seen before in radiative-shock solutions. Comparisons are made with the grey nonequilibrium-diffusion radiative-shock solutions of Lowrie and Edwards [1], which assumed that the Eddington factor is constant across the shock domain. It is our experience that the local Mach number is monotonic when producing nonequilibrium-diffusion solutions, but that this monotonicity may disappear while integrating the precursor region to produce Sn-transport solutions. For temperature- and density-dependent cross sections we show evidence of a spike in the VEF in the far upstream portion of the radiative-shock precursor. We show evidence of an adaptation zone in the precursor region, adjacent to the embedded hydrodynamic shock, as conjectured by Drake [2,3], and also confirm his expectation that the precursor temperatures adjacent to the Zel'dovich spike take values that are greater than the downstream post-shock equilibrium temperature. We also show evidence that the radiation energy density can be nonmonotonic under the Zel'dovich spike, which is indicative of anti-diffusive radiation flow as predicted by McClarren and Drake [4]. We compare the angle dependence of the radiation flow for the Sn-transport and nonequilibrium-diffusion radiation solutions, and show that there are considerable differences in the radiation flow between these models across the shock structure. Finally, we analyze the radiation flow to understand the cause of the adaptation zone, as well as the structure of the Sn-transport radiation-intensity solutions across the shock structure.
Robertson, Andrew J.; Ranalli, Anthony J.; Austin, Stephen A.; Lawlis, Bryan R.
2016-04-21
The Shiprock Disposal Site is the location of the former Navajo Mill (Mill), a uranium ore-processing facility, located on a terrace overlooking the San Juan River in the town of Shiprock, New Mexico. Following the closure of the Mill, all tailings and associated materials were encapsulated in a disposal cell built on top of the former Mill and tailings piles. The milling operations, conducted at the site from 1954 to 1968, created radioactive tailings and process-related wastes that are now found in the groundwater. Elevated concentrations of constituents of concern—ammonium, manganese, nitrate, selenium, strontium, sulfate, and uranium—have also been measured in groundwater seeps in the nearby Many Devils Wash arroyo, leading to the inference that these constituents originated from the Mill. These constituents have also been reported in groundwater that is associated with Mancos Shale, the bedrock that underlies the site. The objective of this report is to increase understanding of the source of water and solutes to the groundwater beneath Many Devils Wash and to establish the background concentrations for groundwater that is in contact with the Mancos Shale at the site. This report presents evidence on three working hypotheses: (1) the water and solutes in Many Devils Wash originated from the operations at the former Mill, (2) groundwater in deep aquifers is upwelling under artesian pressure to recharge the shallow groundwater beneath Many Devils Wash, and (3) the groundwater beneath Many Devils Wash originates as precipitation that infiltrates into the shallow aquifer system and discharges to Many Devils Wash in a series of springs on the east side of the wash. The solute concentrations in the shallow groundwater of Many Devils Wash would result from the interaction of the water and the Mancos Shale if the source of water was upwelling from deep aquifers or precipitation.In order to compare the groundwater from various wells to groundwater that has been
Harvey, R.W.; Kinner, N.E.; Bunn, A.; MacDonald, D.; Metge, D.
1995-01-01
Transport behaviors of unidentified flagellated protozoa (flagellates) and flagellate-sized carboxylated microspheres in sandy, organically contaminated aquifer sediments were investigated in a small-scale (1 to 4-m travel distance) natural-gradient tracer test on Cape Cod and in flow-through columns packed with sieved (0.5-to 1.0-mm grain size) aquifer sediments. The minute (average in situ cell size, 2 to 3 ??m) flagellates, which are relatively abundant in the Cape Cod aquifer, were isolated from core samples, grown in a grass extract medium, labeled with hydroethidine (a vital eukaryotic stain), and coinjected into aquifer sediments along with bromide, a conservative tracer. The 2-??m flagellates appeared to be near the optimal size for transport, judging from flowthrough column experiments involving a polydispersed (0.7 to 6.2 ??m in diameter) suspension of carboxylated microspheres. However, immobilization within the aquifer sediments accounted for a log unit reduction over the first meter of travel compared with a log unit reduction over the first 10 m of travel for indigenous, free-living groundwater bacteria in earlier tests. High rates of flagellate immobilization in the presence of aquifer sediments also was observed in the laboratory. However, immobilization rates for the laboratory-grown flagellates (initially 4 to 5 ??m) injected into the aquifer were not constant and decreased noticeably with increasing time and distance of travel. The decrease in propensity for grain surfaces was accompanied by a decrease in cell size, as the flagellates presumably readapted to aquifer conditions. Retardation and apparent dispersion were generally at least twofold greater than those observed earlier for indigenous groundwater bacteria but were much closer to those observed for highly surface active carboxylated latex microspheres. Field and laboratory results suggest that 2- ??m carboxylated microspheres may be useful as analogs in investigating several abiotic
Uncertainty Analysis Framework - Hanford Site-Wide Groundwater Flow and Transport Model
Energy Technology Data Exchange (ETDEWEB)
Cole, Charles R.; Bergeron, Marcel P.; Murray, Christopher J.; Thorne, Paul D.; Wurstner, Signe K.; Rogers, Phillip M.
2001-11-09
Pacific Northwest National Laboratory (PNNL) embarked on a new initiative to strengthen the technical defensibility of the predictions being made with a site-wide groundwater flow and transport model at the U.S. Department of Energy Hanford Site in southeastern Washington State. In FY 2000, the focus of the initiative was on the characterization of major uncertainties in the current conceptual model that would affect model predictions. The long-term goals of the initiative are the development and implementation of an uncertainty estimation methodology in future assessments and analyses using the site-wide model. This report focuses on the development and implementation of an uncertainty analysis framework.
Cremer, Clemens; Neuweiler, Insa
2016-04-01
Flow and solute transport in the shallow subsurface is strongly governed by atmospheric boundary conditions. Erratically varying infiltration and evaporation cycles lead to alternating upward and downward flow, as well as spatially and temporally varying water contents and associated hydraulic conductivity of the prevailing materials. Thus presenting a highly complicated, dynamic system. Knowledge of subsurface solute transport processes is vital to assess e.g. the entry of, potentially hazardous, solutes to the groundwater and nutrient uptake by plant roots and can be gained in many ways. Besides field measurements and numerical simulations, physical laboratory experiments represent a way to establish process understanding and furthermore validate numerical schemes. With the aim to gain a better understanding and to quantify solute transport in the unsaturated shallow subsurface under natural precipitation conditions in heterogeneous media, we conduct physical laboratory experiments in a 22 cm x 8 cm x 1 cm flow cell that is filled with two types of sand and apply cyclic infiltration-evaporation phases at the soil surface. Pressure at the bottom of the domain is kept constant. Following recent studies (Lehmann and Or, 2009; Bechtold et al., 2011a), heterogeneity is introduced by a sharp vertical interface between coarse and fine sand. Fluorescent tracers are used to i) qualitatively visualize transport paths within the domain and ii) quantify solute leaching at the bottom of the domain. Temporal and spatial variations in water content during the experiment are derived from x-ray radiographic images. Monitored water contents between infiltration and evaporation considerably changed in the coarse sand while the fine sand remained saturated throughout the experiments. Lateral solute transport through the interface in both directions at different depths of the investigated soil columns were observed. This depended on the flow rate applied at the soil surface and
Delsman, Joost R.; Winters, Pieter; Vandenbohede, Alexander; Oude Essink, Gualbert H. P.; Lebbe, Luc
2016-03-01
The use of additional types of observational data has often been suggested to alleviate the ill-posedness inherent to parameter estimation of groundwater models and constrain model uncertainty. Disinformation in observational data caused by errors in either the observations or the chosen model structure may, however, confound the value of adding observational data in model conditioning. This paper uses the global generalized likelihood uncertainty estimation methodology to investigate the value of different observational data types (heads, fluxes, salinity, and temperature) in conditioning a groundwater flow and transport model of an extensively monitored field site in the Netherlands. We compared model conditioning using the real observations to a synthetic model experiment, to demonstrate the possible influence of disinformation in observational data in model conditioning. Results showed that the value of different conditioning targets was less evident when conditioning to real measurements than in a measurement error-only synthetic model experiment. While in the synthetic experiment, all conditioning targets clearly improved model outcomes, minor improvements or even worsening of model outcomes was observed for the real measurements. This result was caused by errors in both the model structure and the observations, resulting in disinformation in the observational data. The observed impact of disinformation in the observational data reiterates the necessity of thorough data validation and the need for accounting for both model structural and observational errors in model conditioning. It further suggests caution when translating results of synthetic modeling examples to real-world applications. Still, applying diverse conditioning data types was found to be essential to constrain uncertainty, especially in the transport of solutes in the model.
Directory of Open Access Journals (Sweden)
Hengzhen Li
2013-12-01
Full Text Available Micro-nano bubbles (MNBs are tiny bubbles with diameters on the order of micrometers and nanometers, showing great potential in environmental remediation. However, the application is only in the beginning stages and remains to be intensively studied. In order to explore the possible use of MNBs in groundwater contaminant removal, this study focuses on the transport of MNBs in porous media and dissolution processes. The bubble diameter distribution was obtained under different conditions by a laser particle analyzer. The permeability of MNB water through sand was compared with that of air-free water. Moreover, the mass transfer features of dissolved oxygen in water with MNBs were studied. The results show that the bubble diameter distribution is influenced by the surfactant concentration in the water. The existence of MNBs in pore water has no impact on the hydraulic conductivity of sand. Furthermore, the dissolved oxygen (DO in water is greatly increased by the MNBs, which will predictably improve the aerobic bioremediation of groundwater. The results are meaningful and instructive in the further study of MNB research and applications in groundwater bioremediation.
The prediction of solute transport in surcharged manholes using CFD.
Lau, S D; Stovin, V R; Guymer, I
2007-01-01
Solute transport processes occur within a wide range of water engineering structures, and urban drainage engineers increasingly rely on modelling tools to represent the transport of dissolved materials. The models take as input representative travel time and dispersion characteristics for key system components, and these generally have to be identified via field or laboratory measurements. Computational Fluid Dynamics (CFD) has the potential to reveal the underlying hydraulic processes that control solute transport, and to provide a generic means of identifying relevant parameter values. This paper reports on a study that has been undertaken to evaluate the feasibility of utilising a CFD-based approach to modelling solute transport. Discrete phase modelling has been adopted, as this is computationally efficient and robust when compared with the time-dependent solution of the advection-dispersion equation. Simulation results are compared with published laboratory data characterising the dispersion effects of surcharged manholes, focusing specifically on an 800 mm diameter laboratory manhole for a flowrate of 0.002 m(3)/s and a range of surcharge depths. Preliminary indications are that the CFD results adequately replicate the measured downstream temporal concentration profiles, and that a threshold surcharge depth, corresponding to a change in hydraulic regime within the manhole, can also be identified.
Solute transport through porous media using asymptotic dispersivity
Indian Academy of Sciences (India)
P K Sharma; Teodrose Atnafu Abgaze
2015-08-01
In this paper, multiprocess non-equilibrium transport equation has been used, which accounts for both physical and chemical non-equilibrium for reactive transport through porous media. An asymptotic distance dependent dispersivity is used to embrace the concept of scale-dependent dispersion for solute transport in heterogeneous porous media. Semi-analytical solution has been derived of the governing equations with an asymptotic distance dependent dispersivity by using Laplace transform technique and the power series method. For application of analytical model, we simulated observed experimental breakthrough curves from 1500 cm long soil column experiments conducted in the laboratory. The simulation results of break-through curves were found to deviate from the observed breakthrough curves for both mobile–immobile and multiprocess non-equilibrium transport with constant dispersion models. However, multiprocess non-equilibrium with an asymptotic dispersion model gives better fit of experimental breakthrough curves through long soil column and hence it is more useful for describing anomalous solute transport through hetero-geneous porous media. The present model is simpler than the stochastic numerical method.
Phenrat, Tanapon; Schoenfelder, Daniel; Kirschling, Teresa L; Tilton, Robert D; Lowry, Gregory V
2015-08-02
For in situ groundwater remediation, polyelectrolyte-modified nanoscale zerovalent iron particles (NZVIs) have to be delivered into the subsurface, where they degrade pollutants such as trichloroethylene (TCE). The effect of groundwater organic and ionic solutes on TCE dechlorination using polyelectrolyte-modified NZVIs is unexplored, but is required for an effective remediation design. This study evaluates the TCE dechlorination rate and reaction by-products using poly(aspartate) (PAP)-modified and bare NZVIs in groundwater samples from actual TCE-contaminated sites in Florida, South Carolina, and Michigan. The effects of groundwater solutes on short- and intermediate-term dechlorination rates were evaluated. An adsorbed PAP layer on the NZVIs appeared to limit the adverse effect of groundwater solutes on the TCE dechlorination rate in the first TCE dechlorination cycle (short-term effect). Presumably, the pre-adsorption of PAP "trains" and the Donnan potential in the adsorbed PAP layer prevented groundwater solutes from further blocking NZVI reactive sites, which appeared to substantially decrease the TCE dechlorination rate of bare NZVIs. In the second and third TCE dechlorination cycles (intermediate-term effect), TCE dechlorination rates using PAP-modified NZVIs increased substantially (~100 and 200%, respectively, from the rate of the first spike). The desorption of PAP from the surface of NZVIs over time due to salt-induced desorption is hypothesized to restore NZVI reactivity with TCE. This study suggests that NZVI surface modification with small, charged macromolecules, such as PAP, helps to restore NZVI reactivity due to gradual PAP desorption in groundwater.
Win-Win transportation solutions price reforms with multiple benefits
Energy Technology Data Exchange (ETDEWEB)
Litman, T. [Victoria Transport Policy Institute, BC (Canada)
2001-07-01
Reform strategies in the transportation market, such as the Win-Win Transportation Solutions, can provide several economic, social and environmental benefits. The strategies are cost effective, technically feasible reforms based on market principles which help create a more equitable and efficient transportation system that supports sustainable economic development. The benefits they provide include reduced traffic congestion, road and parking facility savings, consumer savings, equity, safety and environmental protection. They also increase economic productivity. If fully implemented, they could reduce motor vehicle impacts by 15 to 30 per cent and could help achieve the Kyoto emission reduction targets. Examples of Win-Win strategies at the federal level include: (1) removal of subsidies to oil production and internalized costs, and (2) tax exempt employer provided transfer benefits. Examples of Win-Win strategies at the state/provincial level include: (1) distance-based vehicle insurance and registration fees, (2) least-coast transportation planning and funding, (3) revenue-neutral tax shifting, (4) road pricing, (5) reform motor carrier regulations for competition and efficiency, (6) local and regional transportation demand management programs, (7) more efficient land use, (8) more flexible zoning requirements, (9) parking cash out, (10) transportation management associations, (11) location-efficient housing and mortgages, (12) school and campus trip management, (13) car sharing, (14) non-motorized transport improvements, and (15) traffic calming. It was noted that any market reform that leads to more efficient use of existing transportation systems can provide better economic development benefits. 9 refs., 1 tab., 1 fig.
Herod, Matt N.; Suchy, Martin; Cornett, R. Jack; Kieser, W. E.; Clark, Ian D.; Graham, Gwyn
2015-12-01
The Fukushima-Daiichi nuclear accident (FDNA) released iodine-129 (15.7 million year half-life) and other fission product radionuclides into the environment in the spring and summer of 2011. 129I is recognized as a useful tracer for the short-lived radiohazard 131I, which has a mobile geochemical behavior with potential to contaminate water resources. To trace 129I released by the FDNA reaching Canada, pre-accident and post-accident rain samples collected in Vancouver, on Saturna Island and from the National Atmospheric Deposition Program in Washington State were measured. Groundwater from the Abbotsford-Sumas Aquifer was sampled to determine the fate of 129I that infiltrates below the root zone. Modeling of vadose zone transport was performed to constrain the travel time and retardation of 129I. The mean pre-accident 129I concentration in rain was 31 × 106 atoms/L (n = 4). Immediately following the FDNA, 129I values increased to 211 × 106 atoms/L and quickly returned to near-background levels. However, pulses of elevated 129I continued for several months. The increases in 129I concentrations from both Vancouver and Saturna Island were synchronized, and occurred directly after the initial release from the FDNA. The 129I in shallow (3H/3He age March 2013 with an average of 3.2 × 106 atoms/L (n = 32) that was coincident with modeled travel times for Fukushima 129I. The groundwater response and the modeling results suggest that 129I was partially attenuated in soil, which is consistent with its geochemical behavior; however, we conclude that the measured variability may be due to Fukushima 129I entering groundwater.
Energy Technology Data Exchange (ETDEWEB)
Pohll, G.; Chapman, J.; Hassan, A.; Papelis, C.; Andricevic, R.; Shirley, C.
1998-07-01
Since 1962, all United States nuclear tests have been conducted underground. A consequence of this testing has been the deposition of large amounts of radioactive materials in the subsurface, sometimes in direct contact with groundwater. The majority of this testing occurred on the Nevada Test Site, but a limited number of experiments were conducted in other locations. One of these is the subject of this report, the Project Shoal Area (PSA), located about 50 km southeast of Fallon, Nevada. The Shoal test consisted of a 12-kiloton-yield nuclear detonation which occurred on October 26, 1963. Project Shoal was part of studies to enhance seismic detection of underground nuclear tests, in particular, in active earthquake areas. Characterization of groundwater contamination at the Project Shoal Area is being conducted by the US Department of Energy (DOE) under the Federal Facility Agreement and Consent Order (FFACO) with the State of Nevada Department of Environmental Protection and the US Department of Defense (DOD). This order prescribes a Corrective Action Strategy (Appendix VI), which, as applied to underground nuclear tests, involves preparing a Corrective Action Investigation Plan (CAIP), Corrective Action Decision Document (CADD), Corrective Action Plan, and Closure Report. The scope of the CAIP is flow and transport modeling to establish contaminant boundaries that are protective of human health and the environment. This interim report describes the current status of the flow and transport modeling for the PSA.
Reactive chemical transport in ground-water hydrology: Challenges to mathematical modeling
Energy Technology Data Exchange (ETDEWEB)
Narasimhan, T.N.; Apps, J.A.
1990-07-01
For a long time, earth scientists have qualitatively recognized that mineral assemblages in soils and rocks conform to established principles of chemistry. In the early 1960's geochemists began systematizing this knowledge by developing quantitative thermodynamic models based on equilibrium considerations. These models have since been coupled with advective-dispersive-diffusive transport models, already developed by ground-water hydrologists. Spurred by a need for handling difficult environmental issues related to ground-water contamination, these models are being improved, refined and applied to realistic problems of interest. There is little doubt that these models will play an important role in solving important problems of engineering as well as science over the coming years. Even as these models are being used practically, there is scope for their improvement and many challenges lie ahead. In addition to improving the conceptual basis of the governing equations, much remains to be done to incorporate kinetic processes and biological mediation into extant chemical equilibrium models. Much also remains to be learned about the limits to which model predictability can be reasonably taken. The purpose of this paper is to broadly assess the current status of knowledge in modeling reactive chemical transport and to identify the challenges that lie ahead.
Bencala, K. E.; Kimball, B. A.; Gooseff, M. N.
2007-12-01
In-stream tracer experiments are a well-established method for determining flow data to be incorporated in solute transport modeling. For a gaining stream, this method is implemented to provide spatial flow data at scales of minutes and tens of meters without physical disturbance to the flow of water, the streambed, or biota. Of importance for solute transport modeling, solute inflow loading along the stream can be estimated with this spatial data. The tracer information can also be interpreted to characterize hyporheic exchange time-scales for a stream with hyporheic exchange flowpaths (HEFs) that are short relative to the distance over which the stream gains water. The interpretation of tracer data becomes uncertain for a stream that is not gaining water continuously over intended study reach. We demonstrate, with straight-forward mass-balances, uncertainties for solute loading which arise in the analysis of streams locally losing water while predominantly gaining water (and solutes) over a larger scale. With field data from Mineral Creek (Silverton, Colorado) we illustrate the further uncertainty distinguishing HEFs from (locally) losing segments of the stream. Comparison of bromide tracer with ambient sulfate concentrations suggests that subsurface inflows and outflows, concurrent with likely HEFs, occur in a hydrogeochemical setting of multiple, dispersed and mixed, sources of water along a 64 m sub-reach of the predominately gaining, but locally losing, stream. To compute stream-reach mass-balances (the simplest of water quality models) there is a need to quantitatively define the character and source of contaminants entering streams from ground-water pathways, as well as the potential for changes in water chemistry and contaminant concentrations along flow paths crossing the sediment-water interface. Identification of inflow solute mass requires quantifying water gain, loss, and hyporheic exchange in addition to concentration.
Conservative and reactive solute transport in constructed wetlands
Keefe, S.H.; Barber, L.B.; Runkel, R.L.; Ryan, J.N.; McKnight, Diane M.; Wass, R.D.
2004-01-01
The transport of bromide, a conservative tracer, and rhodamine WT (RWT), a photodegrading tracer, was evaluated in three wastewater-dependent wetlands near Phoenix, Arizona, using a solute transport model with transient storage. Coupled sodium bromide and RWT tracer tests were performed to establish conservative transport and reactive parameters in constructed wetlands with water losses ranging from (1) relatively impermeable (15%), (2) moderately leaky (45%), and (3) significantly leaky (76%). RWT first-order photolysis rates and sorption coefficients were determined from independent field and laboratory experiments. Individual wetland hydraulic profiles influenced the extent of transient storage interaction in stagnant water areas and consequently RWT removal. Solute mixing and transient storage interaction occurred in the impermeable wetland, resulting in 21% RWT mass loss from main channel and storage zone photolysis (10%) and sorption (11%) reactions. Advection and dispersion governed solute transport in the leaky wetland, limiting RWT photolysis removal (1.2%) and favoring main channel sorption (3.6%). The moderately leaky wetland contained islands parallel to flow, producing channel flow and minimizing RWT losses (1.6%).
Combined physical and chemical nonequilibrium transport model for solution conduits.
Field, Malcolm S; Leij, Feike J
2014-02-01
Solute transport in karst aquifers is primarily constrained to relatively complex and inaccessible solution conduits where transport is often rapid, turbulent, and at times constrictive. Breakthrough curves generated from tracer tests in solution conduits are typically positively-skewed with long tails evident. Physical nonequilibrium models to fit breakthrough curves for tracer tests in solution conduits are now routinely employed. Chemical nonequilibrium processes are likely important interactions, however. In addition to partitioning between different flow domains, there may also be equilibrium and nonequilibrium partitioning between the aqueous and solid phases. A combined physical and chemical nonequilibrium (PCNE) model was developed for an instantaneous release similar to that developed by Leij and Bradford (2009) for a pulse release. The PCNE model allows for partitioning open space in solution conduits into mobile and immobile flow regions with first-order mass transfer between the two regions to represent physical nonequilibrium in the conduit. Partitioning between the aqueous and solid phases proceeds either as an equilibrium process or as a first-order process and represents chemical nonequilibrium for both the mobile and immobile regions. Application of the model to three example breakthrough curves demonstrates the applicability of the combined physical and chemical nonequilibrium model to tracer tests conducted in karst aquifers, with exceptionally good model fits to the data. The three models, each from a different state in the United States, exhibit very different velocities, dispersions, and other transport properties with most of the transport occurring via the fraction of mobile water. Fitting the model suggests the potentially important interaction of physical and chemical nonequilibrium processes.
Water, solute and heat transport in the soil: the Australian connection
Knight, John
2016-04-01
The interest of Peter Raats in water, solute and heat transport in the soil has led to scientific and/or personal interactions with several Australian scientists such as John Philip, David Smiles, Greg Davis and John Knight. Along with John Philip and Robin Wooding, Peter was an early user of the Gardner (1958) linearised model of soil water flow, which brought him into competition with John Philip. I will discuss some of Peter's solutions relevant to infiltration from line and point sources, cavities and basins. A visit to Canberra, Australia in the early 1980s led to joint work on soil water flow, and on combined water and solute movement with David Smiles and others. In 1983 Peter was on the PhD committee for Greg Davis at the University of Wollongong, and some of the methods in his thesis 'Mathematical modelling of rate-limiting mechanisms of pyritic oxidation in overburden dumps' were later used by Peter's student Sjoerd van der Zee. David Smiles and Peter wrote a survey article 'Hydrology of swelling clay soils' in 2005. In the last decade Peter has been investigating the history of groundwater and vadose zone hydrology, and recently he and I have been bringing to light the largely forgotten work of Lewis Fry Richardson on finite difference solution of the heat equation, drainage theory, soil physics, and the soil-plant-atmosphere continuum.
McKenzie, J.M.; Voss, C.I.; Siegel, D.I.
2007-01-01
In northern peatlands, subsurface ice formation is an important process that can control heat transport, groundwater flow, and biological activity. Temperature was measured over one and a half years in a vertical profile in the Red Lake Bog, Minnesota. To successfully simulate the transport of heat within the peat profile, the U.S. Geological Survey's SUTRA computer code was modified. The modified code simulates fully saturated, coupled porewater-energy transport, with freezing and melting porewater, and includes proportional heat capacity and thermal conductivity of water and ice, decreasing matrix permeability due to ice formation, and latent heat. The model is verified by correctly simulating the Lunardini analytical solution for ice formation in a porous medium with a mixed ice-water zone. The modified SUTRA model correctly simulates the temperature and ice distributions in the peat bog. Two possible benchmark problems for groundwater and energy transport with ice formation and melting are proposed that may be used by other researchers for code comparison. ?? 2006 Elsevier Ltd. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Clark, I. [Univ. of Ottawa, Ottawa, ON (Canada); Al, T. [Univ. of New Brunswick, Fredericton, NB (Canada); Jensen, M.; Kennell, L. [Nuclear Waste Management Organization, Toronto, ON (Canada); Raven, K. [Geofirma Engineering Limited, Ottawa, ON (Canada)
2011-07-01
Investigations of the controls on solute transport in porewater and groundwater below the Bruce nuclear site involved laboratory-scale diffusion measurements, as well as measurements of natural tracer (δ{sup 18}O, δ{sup 2}H, {sup 87}Sr/{sup 86}Sr, Cl and Br) distributions and isotopic compositions of CH{sub 4}, CO{sub 2} and helium ({sup 3}He/{sup 4}He) in the porewaters and groundwaters. The analyses were performed on samples collected from drilled boreholes, DGR-1 through DGR-6, during site characterization activities and the results are summarized below. With the exception of just a few samples from the Upper Silurian, the effective diffusion coefficient (D {sub e}) values measured from DGR cores are all less than 10{sup -11} m{sup 2}/s, which is approximately one order of magnitude lower than measured De values from international programs in sedimentary rock. The majority of the data are in the range 10{sup -13} < D{sub e} < 10{sup -11} m{sup 2}/s, with Lower Silurian and Upper Ordovician shale samples representing the higher end of this range because of their relatively high porosity (7 to 9%). The low porosity of the Middle Ordovician limestone (< 2%) results in low D{sub e} values, clustering in the range 10{sup -13} < D{sub e} < 10{sup -12} m{sup 2}/s. The δ{sup 18}O, Cl, and Br profiles in the Middle Ordovician carbonates define trends of decreasing δ{sup 18}O values and tracer concentrations with depth, and are interpreted to result from an extremely long period of diffusion-dominated transport (~300 Ma). Near the base of the Middle Ordovician carbonates the δ{sup 2}H data display a slight enrichment, which could represent upward diffusion of deuterium-enriched water originating in the underlying Precambrian shield. A Precambrian shield influence on the Ordovician porewater chemistry is inferred from the measured {sup 87}Sr/{sup 86}Sr ratios in the Middle Ordovician carbonates, which are elevated above values expected for porewater in equilibrium
Transport processes in space physics and astrophysics problems and solutions
Dosch, Alexander
2016-01-01
This is the problems and solution manual for the graduate text with the same title and published as Lecture Notes in Physics Vol 877 which provides the necessary mathematical and physics background to understand the transport of gases, charged particle gases, energetic charged particles, turbulence, and radiation in an astrophysical and space physics context. The very detailed and self-contained problems and solutions will be an essential part of the training of any graduate student wishing to enter and pursuing research in this field. .
2014-03-27
Web: http://www.epa.gov/superfund/sites/rods/fulltext/e1098040. pdf InsideEPA.com. "EPA Seeks To Ease Groundwater Cleanup Policy Following NAS...PERMEABILITY LAYERS IN A GROUNDWATER SOURCE ZONE ON DISSOLVED CONTAMINANT FATE AND TRANSPORT THESIS James M. Bell, Captain, USAF AFIT-ENV-14-M-08...MODELING THE IMPACT OF LOW PERMEABILITY LAYERS IN A GROUNDWATER SOURCE ZONE ON DISSOLVED CONTAMINANT FATE AND TRANSPORT THESIS Presented
Experimental Study of Preferential Solute Transportation During Dump Leaching
Institute of Scientific and Technical Information of China (English)
YIN Sheng-hua; WU Ai-xiang
2006-01-01
The production of dump leaching of the Dexing Copper Mine was affected by a preferential solution flow. Formative mechanism of the preferential solution flow was investigated by analyzing the relationship between both dump permeability and surface tension and ore diameter. The preferential solution flow occurred in the fine ore area when the application rate was low. The preferential solution flow entered into the coarse ore area because the negative pore water pressure disappeared with an increase of the application rate. The preferential solute transportation experiment was conducted by selecting NaCl as mineral. Results of the experiment showed that the concentration of the outflow solution reduced over time. The concentration of the coarse ore area outflow solution was greater than that of the fine ore area. The process of NaCl leaching can be divided into two stages. NaCl was carried out directly by diffusion-convection during the first stage, so the leaching rate increased sharply. But in the second stage, only a small amount of NaCl dissolved in the immobile water. The leaching rate increased slowly because NaCl, dissolved in the immobile water, can only be leached by diffusion.
Energy Technology Data Exchange (ETDEWEB)
S. J. Goldstein, S. Luo, T. L. Ku, and M. T. Murrell
2006-04-01
Uranium-series data for groundwater samples from the vicinity of the Nopal I uranium ore deposit are used to place constraints on radionuclide transport and hydrologic processes at this site, and also, by analogy, at Yucca Mountain. Decreasing uranium concentrations for wells drilled in 2003 suggest that groundwater flow rates are low (< 10 m/yr). Field tests, well productivity, and uranium isotopic constraints also suggest that groundwater flow and mixing is limited at this site. The uranium isotopic systematics for water collected in the mine adit are consistent with longer rock-water interaction times and higher uranium dissolution rates at the front of the adit where the deposit is located. Short-lived nuclide data for groundwater wells are used to calculate retardation factors that are on the order of 1,000 for radium and 10,000 to 10,000,000 for lead and polonium. Radium has enhanced mobility in adit water and fractures near the deposit.
Daughney, C.; Toews, M. W.; Morgenstern, U.; Cornaton, F. J.; Jackson, B. M.
2013-12-01
Lake Rotorua is a focus of culture and tourism in New Zealand. The lake's water quality has declined since the 1970s, partly due to nutrient inputs that reach the lake via the groundwater system. Improved land use management within the catchment requires prediction of the spatial variations of groundwater transit time from land surface to the lake, and from this the prediction of current and future nutrient inflows to the lake. This study combines the two main methods currently available for determination of water age: numerical groundwater models and hydrological tracers. A steady-state 3D finite element model was constructed to simulate groundwater flow and transport of tritium and age at the catchment scale (555 km2). The model materials were defined using a 3D geologic model and included ignimbrites, rhyolites, alluvial and lake bottom sediments. The steady-state saturated groundwater flow model was calibrated using observed groundwater levels in boreholes (111 locations) and stream flow measurements from groundwater-fed streams and springs (61 locations). Hydraulic conductivities and Cauchy boundary conditions associated with the streams, springs and lake were parameterized. The transport parameters for the model were calibrated using 191 tritium samples from 105 locations (springs, streams and boreholes), with most locations having two sample dates. The transport model used steady-state flow, but simulated the transient transport and decay of tritium from rainfall recharge between 1945 and 2012. An additional 1D unsaturated sub-model was added to account for tritium decay from the ground surface to the water table. The sub-model is linked on top of the 3D model, and uses the water table depths and material properties from the 3D model. The adjustable calibration parameters for the transport model were porosity and van Genuchten parameters related to the unsaturated sub-models. Calibration of the flow model was achieved using a combination of automated least
Clark, Brian R.; Landon, Matthew K.; Kauffman, Leon J.; Hornberger, George Z.
2008-01-01
Contamination of public-supply wells has resulted in public-health threats and negative economic effects for communities that must treat contaminated water or find alternative water supplies. To investigate factors controlling vulnerability of public-supply wells to anthropogenic and natural contaminants using consistent and systematic data collected in a variety of principal aquifer settings in the United States, a study of Transport of Anthropogenic and Natural Contaminants to public-supply wells was begun in 2001 as part of the U.S. Geological Survey National Water-Quality Assessment Program. The area simulated by the ground-water flow model described in this report was selected for a study of processes influencing contaminant distribution and transport along the direction of ground-water flow towards a public-supply well in southeastern York, Nebraska. Ground-water flow is simulated for a 60-year period from September 1, 1944, to August 31, 2004. Steady-state conditions are simulated prior to September 1, 1944, and represent conditions prior to use of ground water for irrigation. Irrigation, municipal, and industrial wells were simulated using the Multi-Node Well package of the modular three-dimensional ground-water flow model code, MODFLOW-2000, which allows simulation of flow and solutes through wells that are simulated in multiple nodes or layers. Ground-water flow, age, and transport of selected tracers were simulated using the Ground-Water Transport process of MODFLOW-2000. Simulated ground-water age was compared to interpreted ground-water age in six monitoring wells in the unconfined aquifer. The tracer chlorofluorocarbon-11 was simulated directly using Ground-Water Transport for comparison with concentrations measured in six monitoring wells and one public supply well screened in the upper confined aquifer. Three alternative model simulations indicate that simulation results are highly sensitive to the distribution of multilayer well bores where leakage
Energy Technology Data Exchange (ETDEWEB)
Dai, Heng [Pacific Northwest National Laboratory, Richland Washington USA; Chen, Xingyuan [Pacific Northwest National Laboratory, Richland Washington USA; Ye, Ming [Department of Scientific Computing, Florida State University, Tallahassee Florida USA; Song, Xuehang [Pacific Northwest National Laboratory, Richland Washington USA; Zachara, John M. [Pacific Northwest National Laboratory, Richland Washington USA
2017-05-01
Sensitivity analysis is an important tool for quantifying uncertainty in the outputs of mathematical models, especially for complex systems with a high dimension of spatially correlated parameters. Variance-based global sensitivity analysis has gained popularity because it can quantify the relative contribution of uncertainty from different sources. However, its computational cost increases dramatically with the complexity of the considered model and the dimension of model parameters. In this study we developed a hierarchical sensitivity analysis method that (1) constructs an uncertainty hierarchy by analyzing the input uncertainty sources, and (2) accounts for the spatial correlation among parameters at each level of the hierarchy using geostatistical tools. The contribution of uncertainty source at each hierarchy level is measured by sensitivity indices calculated using the variance decomposition method. Using this methodology, we identified the most important uncertainty source for a dynamic groundwater flow and solute transport in model at the Department of Energy (DOE) Hanford site. The results indicate that boundary conditions and permeability field contribute the most uncertainty to the simulated head field and tracer plume, respectively. The relative contribution from each source varied spatially and temporally as driven by the dynamic interaction between groundwater and river water at the site. By using a geostatistical approach to reduce the number of realizations needed for the sensitivity analysis, the computational cost of implementing the developed method was reduced to a practically manageable level. The developed sensitivity analysis method is generally applicable to a wide range of hydrologic and environmental problems that deal with high-dimensional spatially-distributed parameters.
Characterizing the Occurrence and Transport of Brackish Groundwater in Southwest Bangladesh
worland, S.; Hornberger, G. M.
2013-12-01
Bangladesh is host to the largest and the most active delta system in the world. The morphology of the southern part of the country is characterized by low lying deltaic plains partitioned by the distributary networks of the Ganges, Brahmaputra and Meghna river systems. Much of the tidal mangrove forest ecosystem of the lower delta has been converted into poldered islands that sustain shrimp farming and rice production. The polder inhabitants depend on shallow groundwater as a primary source for drinking water and sanitation. Understanding the origin and hydrologic controls on the distribution of the brackish water and freshwater on the polder is a necessary step to ensuring a sustainable and potable freshwater source for drinking and irrigation. Preliminary sampling from shallow tube wells on Polder 32 in southwest Bangladesh suggests sporadic lateral apportioning of fresh water in the primarily brackish aquifer. This research characterizes the occurrence, transport and fate of the brackish groundwater through a combination of 3H and 14C dating, geochemical signatures, subsurface mapping using inversions from electromagnetic induction, and a 1D finite difference model and a 2D finite element model. The geochemical analysis and radiometric dating suggest that the salt water originates from paleo-brackish estuarine water deposited ~5000 years ago along with the sediments that compose the shallow aquifer. Inversions of electromagnetic survey data show potential freshwater recharge areas where the clay cap pinches out. The finite difference model demonstrates that recharge from the distributary channels is unlikely due to the low transmissivity of the clay channel beds. The finite element model gives reasonable estimates of the flushing rates of the connate brackish water beneath the polder. Inversion of electromagnetic data from a two hundred meter transect taken on Polder 32 Head gradient and groundwater flow vectors for fixed head boundary conditions across Polder
Comparison of approaches for predicting solute transport: sandbox experiments.
Illman, Walter A; Berg, Steven J; Yeh, Tian-Chyi Jim
2012-01-01
The main purpose of this paper was to compare three approaches for predicting solute transport. The approaches include: (1) an effective parameter/macrodispersion approach (Gelhar and Axness 1983); (2) a heterogeneous approach using ordinary kriging based on core samples; and (3) a heterogeneous approach based on hydraulic tomography. We conducted our comparison in a heterogeneous sandbox aquifer. The aquifer was first characterized by taking 48 core samples to obtain local-scale hydraulic conductivity (K). The spatial statistics of these K values were then used to calculate the effective parameters. These K values and their statistics were also used for kriging to obtain a heterogeneous K field. In parallel, we performed a hydraulic tomography survey using hydraulic tests conducted in a dipole fashion with the drawdown data analyzed using the sequential successive linear estimator code (Yeh and Liu 2000) to obtain a K distribution (or K tomogram). The effective parameters and the heterogeneous K fields from kriging and hydraulic tomography were used in forward simulations of a dipole conservative tracer test. The simulated and observed breakthrough curves and their temporal moments were compared. Results show an improvement in predictions of drawdown behavior and tracer transport when the K tomogram from hydraulic tomography was used. This suggests that the high-resolution prediction of solute transport is possible without collecting a large number of small-scale samples to estimate flow and transport properties that are costly to obtain at the field scale.
Guide to the Revised Ground-Water Flow and Heat Transport Simulator: HYDROTHERM - Version 3
Kipp, Kenneth L.; Hsieh, Paul A.; Charlton, Scott R.
2008-01-01
The HYDROTHERM computer program simulates multi-phase ground-water flow and associated thermal energy transport in three dimensions. It can handle high fluid pressures, up to 1 ? 109 pascals (104 atmospheres), and high temperatures, up to 1,200 degrees Celsius. This report documents the release of Version 3, which includes various additions, modifications, and corrections that have been made to the original simulator. Primary changes to the simulator include: (1) the ability to simulate unconfined ground-water flow, (2) a precipitation-recharge boundary condition, (3) a seepage-surface boundary condition at the land surface, (4) the removal of the limitation that a specified-pressure boundary also have a specified temperature, (5) a new iterative solver for the linear equations based on a generalized minimum-residual method, (6) the ability to use time- or depth-dependent functions for permeability, (7) the conversion of the program code to Fortran 90 to employ dynamic allocation of arrays, and (8) the incorporation of a graphical user interface (GUI) for input and output. The graphical user interface has been developed for defining a simulation, running the HYDROTHERM simulator interactively, and displaying the results. The combination of the graphical user interface and the HYDROTHERM simulator forms the HYDROTHERM INTERACTIVE (HTI) program. HTI can be used for two-dimensional simulations only. New features in Version 3 of the HYDROTHERM simulator have been verified using four test problems. Three problems come from the published literature and one problem was simulated by another partially saturated flow and thermal transport simulator. The test problems include: transient partially saturated vertical infiltration, transient one-dimensional horizontal infiltration, two-dimensional steady-state drainage with a seepage surface, and two-dimensional drainage with coupled heat transport. An example application to a hypothetical stratovolcano system with unconfined
Robertson, Andrew J.; Ranalli, Anthony J.; Austin, Stephen A.; Lawlis, Bryan R.
2016-04-21
The Shiprock Disposal Site is the location of the former Navajo Mill (Mill), a uranium ore-processing facility, located on a terrace overlooking the San Juan River in the town of Shiprock, New Mexico. Following the closure of the Mill, all tailings and associated materials were encapsulated in a disposal cell built on top of the former Mill and tailings piles. The milling operations, conducted at the site from 1954 to 1968, created radioactive tailings and process-related wastes that are now found in the groundwater. Elevated concentrations of constituents of concern—ammonium, manganese, nitrate, selenium, strontium, sulfate, and uranium—have also been measured in groundwater seeps in the nearby Many Devils Wash arroyo, leading to the inference that these constituents originated from the Mill. These constituents have also been reported in groundwater that is associated with Mancos Shale, the bedrock that underlies the site. The objective of this report is to increase understanding of the source of water and solutes to the groundwater beneath Many Devils Wash and to establish the background concentrations for groundwater that is in contact with the Mancos Shale at the site. This report presents evidence on three working hypotheses: (1) the water and solutes in Many Devils Wash originated from the operations at the former Mill, (2) groundwater in deep aquifers is upwelling under artesian pressure to recharge the shallow groundwater beneath Many Devils Wash, and (3) the groundwater beneath Many Devils Wash originates as precipitation that infiltrates into the shallow aquifer system and discharges to Many Devils Wash in a series of springs on the east side of the wash. The solute concentrations in the shallow groundwater of Many Devils Wash would result from the interaction of the water and the Mancos Shale if the source of water was upwelling from deep aquifers or precipitation.In order to compare the groundwater from various wells to groundwater that has been
Directory of Open Access Journals (Sweden)
Stanko Ružičić
2012-12-01
Full Text Available Conceptual model of flow and solute transport in unsaturated zone at Kosnica site, which is the basis for modeling pollution migration through the unsaturated zone to groundwater, is set up. The main characteristics of the unsaturated zone of the Kosnica site are described. Detailed description of investigated profile of unsaturated zone, with all necessary analytical results performed and used in building of conceptual models, is presented. Experiments that are in progress and processes which are modeled are stated. Monitoring of parameters necessary for calibration of models is presented. The ultimate goal of research is risk assessment of groundwater contamination at Kosnica site that has its source in or on unsaturated zone.
Liu, Yueqiang; Phenrat, Tanapon; Lowry, Gregory V
2007-11-15
Nanoscale zero-valent iron (NZVI) is used to remediate contaminated groundwater plumes and contaminant source zones. The target contaminant concentration and groundwater solutes (NO3-, Cl-, HCO3-, SO4(2-), and HPO4(2-)) should affect the NZVI longevity and reactivity with target contaminants, but these effects are not well understood. This study evaluates the effect of trichloroethylene (TCE) concentration and common dissolved groundwater solutes on the rates of NZVI-promoted TCE dechlorination and H2 evolution in batch reactors. Both model systems and real groundwater are evaluated. The TCE reaction rate constant was unaffected by TCE concentration for [TCE] TCE concentration up to water saturation (8.4 mM). For [TCE] > or = 0.46 mM, acetylene formation increased, and the total amount of H2 evolved at the end of the particle reactive lifetime decreased with increasing [TCE], indicating a higher Fe0 utilization efficiency for TCE dechlorination. Common groundwater anions (5mN) had a minor effect on H2 evolution but inhibited TCE reduction up to 7-fold in increasing order of Cl- TCE reduction but increased acetylene production and decreased H2 evolution. NO3- present at > 3 mM slowed TCE dechlorination due to surface passivation. NO3- present at 5 mM stopped TCE dechlorination and H2 evolution after 3 days. Dissolved solutes accounted for the observed decrease of NZVI reactivity for TCE dechlorination in natural groundwater when the total organic content was small (< 1 mg/L).
A cellular automaton model adapted to sandboxes to simulate the transport of solutes
Lora, Boris; Donado, Leonardo; Castro, Eduardo; Bayuelo, Alfredo
2016-04-01
The increasingly use of groundwater sources for human consumption and the growth of the levels of these hydric sources contamination make imperative to reach a deeper understanding how the contaminants are transported by the water, in particular through a heterogeneous porous medium. Accordingly, the present research aims to design a model, which simulates the transport of solutes through a heterogeneous porous medium, using cellular automata. Cellular automata (CA) are a class of spatially (pixels) and temporally discrete mathematical systems characterized by local interaction (neighborhoods). The pixel size and the CA neighborhood were determined in order to reproduce accurately the solute behavior (Ilachinski, 2001). For the design and corresponding validation of the CA model were developed different conservative tracer tests using a sandbox packed heterogeneously with a coarse sand (size # 20 grain diameter 0,85 to 0,6 mm) and clay. We use Uranine and a saline solution with NaCl as a tracer which were measured taking snapshots each 20 seconds. A calibration curve (pixel intensity Vs Concentration) was used to obtain concentration maps. The sandbox was constructed of acrylic (caliber 0,8 cms) with 70 x 45 x 4 cms of dimensions. The "sandbox" had a grid of 35 transversal holes with a diameter of 4 mm each and an uniform separation from one to another of 10 cms. To validate the CA-model it was used a metric consisting in rating the number of correctly predicted pixels over the total per image throughout the entire test run. The CA-model shows that calibrations of pixels and neighborhoods allow reaching results over the 60 % of correctly predictions usually. This makes possible to think that the application of the CA- model could be useful in further researches regarding the transport of contaminants in hydrogeology.
Particle Swarm Optimization for inverse modeling of solute transport in fractured gneiss aquifer
Abdelaziz, Ramadan; Zambrano-Bigiarini, Mauricio
2014-08-01
Particle Swarm Optimization (PSO) has received considerable attention as a global optimization technique from scientists of different disciplines around the world. In this article, we illustrate how to use PSO for inverse modeling of a coupled flow and transport groundwater model (MODFLOW2005-MT3DMS) in a fractured gneiss aquifer. In particular, the hydroPSO R package is used as optimization engine, because it has been specifically designed to calibrate environmental, hydrological and hydrogeological models. In addition, hydroPSO implements the latest Standard Particle Swarm Optimization algorithm (SPSO-2011), with an adaptive random topology and rotational invariance constituting the main advancements over previous PSO versions. A tracer test conducted in the experimental field at TU Bergakademie Freiberg (Germany) is used as case study. A double-porosity approach is used to simulate the solute transport in the fractured Gneiss aquifer. Tracer concentrations obtained with hydroPSO were in good agreement with its corresponding observations, as measured by a high value of the coefficient of determination and a low sum of squared residuals. Several graphical outputs automatically generated by hydroPSO provided useful insights to assess the quality of the calibration results. It was found that hydroPSO required a small number of model runs to reach the region of the global optimum, and it proved to be both an effective and efficient optimization technique to calibrate the movement of solute transport over time in a fractured aquifer. In addition, the parallel feature of hydroPSO allowed to reduce the total computation time used in the inverse modeling process up to an eighth of the total time required without using that feature. This work provides a first attempt to demonstrate the capability and versatility of hydroPSO to work as an optimizer of a coupled flow and transport model for contaminant migration.
Directory of Open Access Journals (Sweden)
Sangwoo Park
2016-04-01
Full Text Available Groundwater flow is one of the most important factors for the design of a ground heat exchanger (GHEX since the thermal environment of the ground around the buried GHEX is significantly affected by heat convection due to the groundwater flow. Several preceding studies have been conducted to develop analytical solutions to the heat transfer model of GHEX with consideration of groundwater flow. One of these solutions is the combined heat transfer model of conduction and convection. However, the developed combined analytical models are inapplicable to all of the configurations of ordinary GHEXs because these solutions assume that the inner part of the borehole is thermally inert or consists of the same material as that of the surrounding ground. In this paper, the applicability of the combined solid cylindrical heat source model, which is the most suitable to energy piles until now, was evaluated by performing a series of numerical analyses. In the numerical analysis, the inner part of the borehole was modeled as two different materials (i.e., permeable ground formation and impermeable fill such as concrete to evaluate applicability of the analytical solution along with different diameter-length (D/L ratios of borehole. In a small value of the D/L ratio, the analytical solution to the combined heat transfer model is in good agreement with the result of numerical analysis. On the other hand, when increasing the D/L ratio, the analytical solution significantly overestimates the effect of groundwater flow on the heat transfer of GHEXs because the analytical solution disregards the existence of the impermeable region in the borehole. Consequently, such tendency is more critical in the GHEX with a large D/L ratio such as large-diameter energy piles.
Energy Technology Data Exchange (ETDEWEB)
Cliffe, K.A.; Morris, S.T.; Porter, J.D. [AEA Technology, Harwell (United Kingdom)
1998-05-01
NAMMU is a computer program for modelling groundwater flow and transport through porous media. This document provides an overview of the use of the program for geosphere modelling in performance assessment calculations and gives a detailed description of the program itself. The aim of the document is to give an indication of the grounds for having confidence in NAMMU as a performance assessment tool. In order to achieve this the following topics are discussed. The basic premises of the assessment approach and the purpose of and nature of the calculations that can be undertaken using NAMMU are outlined. The concepts of the validation of models and the considerations that can lead to increased confidence in models are described. The physical processes that can be modelled using NAMMU and the mathematical models and numerical techniques that are used to represent them are discussed in some detail. Finally, the grounds that would lead one to have confidence that NAMMU is fit for purpose are summarised.
Association between arterial stiffness and peritoneal small solute transport rate.
Zhe, Xing-wei; Tian, Xin-kui; Chen, Wei; Guo, Li-juan; Gu, Yue; Chen, Hui-min; Tang, Li-jun; Wang, Tao
2008-05-01
While cardiovascular disease accounts for 40-50% of the mortality in dialysis patients, and while a high peritoneal transport in continuous ambulatory peritoneal dialysis (CAPD) is an independent predictor of outcome, it is unclear if there are any links. Aortic stiffness has become established as a cardiovascular risk factor. We thus studied pulse wave velocity (PWV) in CAPD patients to explore the possible link between peritoneal small solute transport and aortic stiffness. CAPD patients (n = 76, 27 M/49 F) in our center were included in the present study. Aortic stiffness was assessed by brachial pulse pressure (PP) and carotid-femoral PWV. Patients' peritoneal small solute transport rate was assessed by D/P(cr) at 4 h. Extracellular water over total body water (E/T ratio) was assessed by means of bioimpedance analysis. C-reactive protein was also measured. Carotid-femoral PWV was positively associated with patients' age (r = 0.555; P < 0.01), time on peritoneal dialysis (r = 0.332; P < 0.01), diabetic status (r = 0.319; P < 0.01), D/P(cr) (r = 0.241; P < 0.05), PP (r = 0.475; P < 0.01), and E/T (r = 0.606; P < 0.01). In a multivariate regression analysis, carotid-femoral PWV was independently determined by E/T (P < 0.01), PP (P < 0.01), age (P < 0.01), and D/P(cr) (P < 0.05). D/P(cr), in addition to E/T, age, and PP, was an independent predictor of elevated carotid-femoral PWV in CAPD patients, suggesting that there might be a link between high aortic stiffness and increased peritoneal small solute transport rate.
Nyenje, P.
2014-01-01
This study investigates the generation, transport and fate of sanitation-related nutrients in groundwater and surface water in an urban slum area in sub-Saharan Africa. In excess, nutrients can cause eutrophication of downstream water bodies. The study argues that nitrogen-containing rains and
Nyenje, P.
2014-01-01
This study investigates the generation, transport and fate of sanitation-related nutrients in groundwater and surface water in an urban slum area in sub-Saharan Africa. In excess, nutrients can cause eutrophication of downstream water bodies. The study argues that nitrogen-containing rains and domes
The effect of EDTA on the groundwater transport of thorium through sand.
May, Colin C; Young, Lindsay; Worsfold, Paul J; Heath, Sarah; Bryan, Nick D; Keith-Roach, Miranda J
2012-10-01
The effect of the anthropogenic complexing agent EDTA on thorium transport in groundwater has been studied using sand-packed columns and flow rates in the range of 20-100 m y⁻¹. The concentrations injected into the columns were in the range of 0.4-4 mM for Th and 4-40 mM for EDTA, and with EDTA:Th ratios in the range 1:1 to 10:1. The results show that EDTA can significantly increase Th transport, but two very different behaviours are observed at Th concentrations of 0.4 and 4 mM. At the lower concentration, Th breakthrough is retarded with respect to a conservative tracer, with a peak width that is consistent with a single K(d) value, followed by a longer tail, and the behaviour is very sensitive to the flow rate. However at 4 mM Th, the breakthrough peak appears near to that of the tracer, and the width of the peak is consistent with a distribution of K(d) values and/or a larger dispersivity than the tracer. Speciation and transport modelling have been used to interpret the data, and a model was developed that could explain the 0.4 mM behaviour. This suggests that ternary surface complexes are important in these systems, with at least two different species involved, although the complexity of Th speciation in these systems leads to significant uncertainty in the values of the equilibrium and kinetic parameters. For the 4 mM systems, the rapid transport observed could not be explained by a simple chemical model; instead it is likely that EDTA plays an important role in stabilising and transporting thorium colloids and clusters.
Institute of Scientific and Technical Information of China (English)
KONG Jun; SONG Zhi-yao; XIN Pei; SHEN Cheng-ji
2011-01-01
Deriving analytical solutions for tide-induced groundwater fluctuations in unconfined aquifers confronts two problems:(1) As the Boussinesq equation itself contains nonlinear terms,the “secular term” would be generated in derivation,thus making perturbation solution unable to be deduced to higher order; (2) for aquifers with sloping beaches,the perturbation parameter in existing analytical solution integrating the beach slope and hydrogeological property would be sometimes larger than 1.So the application of perturbation solutions is relatively limited.Furthermore,as the beach slope decreases,the error of analytical solution would gradually increase.Given that water table over-height would increase the aquifer thickness and speed up wave propagation,this paper integrates over-height into the perturbation parameter and adjusts boundary conditions to settle the problem of “secular term” and to derive a new high-order analytical solution for nonlinear Boussinesq equation in terms of sloping beaches.Results show that the new analytical solution is more reasonable,and the analytical accuracy is obviously improved in comparison with the existing analytical solution for a gentle slope.The new analytical solution provides a theoretical basis for analyzing the propagation characteristics (e.g.,wave length and over-height variation) of tide-induced groundwater wave in unconfined aquifers,particularly those with sloping beaches.
Kim, Yongcheol; Lee, Bongju; Ha, Kucheol; Yoon, Yunyeol; Moon, Sangho; Cho, Suyoung; Kim, Seongyun
2013-04-01
Protected water curtain cultivation system is an energy saving technique for winter season by splashing groundwater on the inner roof of the green house. But the issue is that the method results in groundwater level deterioration because it disposes the used groundwater to nearby stream. Reuse of the groundwater for water curtain cultivation is important Groundwater level, steam level, and groundwater usage rate are investigated at the five green house concentrated areas such as Cheongwon, Namyangju, Choongju, Namwon, Jinju. Groundwater usage rate is estimated using a ultrasonic flowmeter for a specific well and using the combination of pressure sensor and propeller type velocity counting equipment at a water disposal channel from November to April which is water curtain cultivating season. Groundwater usage rate ranges from 46.9m3/d to 108.0m3/d for a 10a greenhouse. Groundwater level change is strongly influenced by seasonal variation of rainfall and concentrated pumping activities in winter but the level is lower than stream level all year long resulting in all year around losing stream at Cheongwon, Namyangju, Jinju. At Nanwon, the stream is converted from losing one in winter to gaining one in summer. Groundwater level deterioration at concentrated water curtain cultivation area is found to be severe for some area where circulating water curtain cultivation system is need to be applied for groundwater restoration and sustainable cultivation in winter. Circulating water curtain cultivation system can restore the groundwater level by recharging the used groundwater through injection well and then pumping out from pumping well.
Computer model of two-dimensional solute transport and dispersion in ground water
Konikow, Leonard F.; Bredehoeft, J.D.
1978-01-01
This report presents a model that simulates solute transport in flowing ground water. The model is both general and flexible in that it can be applied to a wide range of problem types. It is applicable to one- or two-dimensional problems involving steady-state or transient flow. The model computes changes in concentration over time caused by the processes of convective transport, hydrodynamic dispersion, and mixing (or dilution) from fluid sources. The model assumes that the solute is non-reactive and that gradients of fluid density, viscosity, and temperature do not affect the velocity distribution. However, the aquifer may be heterogeneous and (or) anisotropic. The model couples the ground-water flow equation with the solute-transport equation. The digital computer program uses an alternating-direction implicit procedure to solve a finite-difference approximation to the ground-water flow equation, and it uses the method of characteristics to solve the solute-transport equation. The latter uses a particle- tracking procedure to represent convective transport and a two-step explicit procedure to solve a finite-difference equation that describes the effects of hydrodynamic dispersion, fluid sources and sinks, and divergence of velocity. This explicit procedure has several stability criteria, but the consequent time-step limitations are automatically determined by the program. The report includes a listing of the computer program, which is written in FORTRAN IV and contains about 2,000 lines. The model is based on a rectangular, block-centered, finite difference grid. It allows the specification of any number of injection or withdrawal wells and of spatially varying diffuse recharge or discharge, saturated thickness, transmissivity, boundary conditions, and initial heads and concentrations. The program also permits the designation of up to five nodes as observation points, for which a summary table of head and concentration versus time is printed at the end of the
JOVIAN STRATOSPHERE AS A CHEMICAL TRANSPORT SYSTEM: BENCHMARK ANALYTICAL SOLUTIONS
Energy Technology Data Exchange (ETDEWEB)
Zhang Xi; Shia Runlie; Yung, Yuk L., E-mail: xiz@gps.caltech.edu [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States)
2013-04-20
We systematically investigated the solvable analytical benchmark cases in both one- and two-dimensional (1D and 2D) chemical-advective-diffusive systems. We use the stratosphere of Jupiter as an example but the results can be applied to other planetary atmospheres and exoplanetary atmospheres. In the 1D system, we show that CH{sub 4} and C{sub 2}H{sub 6} are mainly in diffusive equilibrium, and the C{sub 2}H{sub 2} profile can be approximated by modified Bessel functions. In the 2D system in the meridional plane, analytical solutions for two typical circulation patterns are derived. Simple tracer transport modeling demonstrates that the distribution of a short-lived species (such as C{sub 2}H{sub 2}) is dominated by the local chemical sources and sinks, while that of a long-lived species (such as C{sub 2}H{sub 6}) is significantly influenced by the circulation pattern. We find that an equator-to-pole circulation could qualitatively explain the Cassini observations, but a pure diffusive transport process could not. For slowly rotating planets like the close-in extrasolar planets, the interaction between the advection by the zonal wind and chemistry might cause a phase lag between the final tracer distribution and the original source distribution. The numerical simulation results from the 2D Caltech/JPL chemistry-transport model agree well with the analytical solutions for various cases.
Coutelot, F; Sappin-Didier, V; Keller, C; Atteia, O
2014-12-01
The unsaturated zone plays a major role in elemental fluxes in terrestrial ecosystems. A representative chemical analysis of soil pore water is required for the interpretation of soil chemical phenomena and particularly to assess Trace Elements (TEs) mobility. This requires an optimal sampling system to avoid modification of the extracted soil water chemistry and allow for an accurate estimation of solute fluxes. In this paper, the chemical composition of soil solutions sampled by Rhizon® samplers connected to a standard syringe was compared to two other types of suction probes (Rhizon® + vacuum tube and Rhizon® + diverted flow system). We investigated the effects of different vacuum application procedures on concentrations of spiked elements (Cr, As, Zn) mixed as powder into the first 20 cm of 100-cm columns and non-spiked elements (Ca, Na, Mg) concentrations in two types of columns (SiO2 sand and a mixture of kaolinite + SiO2 sand substrates). Rhizon® was installed at different depths. The metals concentrations showed that (i) in sand, peak concentrations cannot be correctly sampled, thus the flux cannot be estimated, and the errors can easily reach a factor 2; (ii) in sand + clay columns, peak concentrations were larger, indicating that they could be sampled but, due to sorption on clay, it was not possible to compare fluxes at different depths. The different samplers tested were not able to reflect the elemental flux to groundwater and, although the Rhizon® + syringe device was more accurate, the best solution remains to be the use of a lysimeter, whose bottom is kept continuously at a suction close to the one existing in the soil.
Representing solute transport through the multi-barrier disposal system by simplified concepts
Energy Technology Data Exchange (ETDEWEB)
Poteri, A.; Nordman, H.; Pulkkanen, V-M. [VTT Technical Research Centre of Finland, Espoo (Finland); Kekaelaeinen, P. [Jyvaeskylae Univ. (Finland). Dept. pf Physics; Hautojaervi, A.
2012-02-15
, because the reservoir capacities of and mass transfer coefficients between adjacent barriers may differ significantly. Characterisation of these properties of the repository system by the simplified approach is straightforward. The relative efficiency of the different barriers in attenuating transport of radionuclides can be determined by comparing the solute's half-times in the barriers. Solute's half-times in different barriers can also be compared with the radioactive half-lives of the nuclides. Already the first barrier along the release path in which the solute's half-time is longer than the nuclide's radioactive half-life will be an efficient transport barrier for that nuclide, although the barrier with longest solute half-time will be the most efficient barrier. The release rates of radionuclides from a leaking waste canister may also be dominated by their source term instead of the barrier system of the repository. Spent nuclear fuel is a ceramic material that dissolves slowly into groundwater. Waste dissolution can also be treated as a barrier in which the dissolution time (or half of it) corresponds to a solute's half-times in a barrier, and can be readily compared with the other barriers. The validity of the simplified description was tested against numerical transport simulations for three representative nuclides: C-14, I-129 and Pu-239. The results of these simulations showed reasonable agreement with those of the simplified approach. (orig.)
Energy Technology Data Exchange (ETDEWEB)
None
1997-10-01
The groundwater flow system of the Nevada Test Site and surrounding region was evaluated to estimate the highest potential current and near-term risk to the public and the environment from groundwater contamination downgradient of the underground nuclear testing areas. The highest, or greatest, potential risk is estimated by assuming that several unusually rapid transport pathways as well as public and environmental exposures all occur simultaneously. These conservative assumptions may cause risks to be significantly overestimated. However, such a deliberate, conservative approach ensures that public health and environmental risks are not underestimated and allows prioritization of future work to minimize potential risks. Historical underground nuclear testing activities, particularly detonations near or below the water table, have contaminated groundwater near testing locations with radioactive and nonradioactive constituents. Tritium was selected as the contaminant of primary concern for this phase of the project because it is abundant, highly mobile, and represents the most significant contributor to the potential radiation dose to humans for the short term. It was also assumed that the predicted risk to human health and the environment from tritium exposure would reasonably represent the risk from other, less mobile radionuclides within the same time frame. Other contaminants will be investigated at a later date. Existing and newly collected hydrogeologic data were compiled for a large area of southern Nevada and California, encompassing the Nevada Test Site regional groundwater flow system. These data were used to develop numerical groundwater flow and tritium transport models for use in the prediction of tritium concentrations at hypothetical human and ecological receptor locations for a 200-year time frame. A numerical, steady-state regional groundwater flow model was developed to serve as the basis for the prediction of the movement of tritium from the
Transport Process of Isopropanol Aqueous Solution by Pervaporation
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
To study the transport process of isopropanol aqueous solution by pervaporation, the transport model of isopropanol and that of water at 323 K in polyvinyl alcohol(PVA) membrane were obtained in this paper. Theoretical predictions agreed well with the experimental results. The interactional parameter between water and PVA membrane is less than that between isopropanol and PVA membrane, which shows that water is preferentially dissolved in PVA membrane. The plasticizing coefficient and diffusion coefficient at infinite dilution of water are larger than those of isopropanol,which shows that the dissolution and permeation in PVA membrane of water are greater than those of isopropanol. Both the interactional parameter between water and isopropanol in the membrane and that in feed rise with the increase of isopropanol content in feed, which shows that the larger isopropanol content is, the higher selectivity of the membrane is and the more remarkable separation effect of pervaporation is.
Fang, Yilin; Scheibe, Timothy D.; Mahadevan, Radhakrishnan; Garg, Srinath; Long, Philip E.; Lovley, Derek R.
2011-03-01
The activity of microorganisms often plays an important role in dynamic natural attenuation or engineered bioremediation of subsurface contaminants, such as chlorinated solvents, metals, and radionuclides. To evaluate and/or design bioremediated systems, quantitative reactive transport models are needed. State-of-the-art reactive transport models often ignore the microbial effects or simulate the microbial effects with static growth yield and constant reaction rate parameters over simulated conditions, while in reality microorganisms can dynamically modify their functionality (such as utilization of alternative respiratory pathways) in response to spatial and temporal variations in environmental conditions. Constraint-based genome-scale microbial in silico models, using genomic data and multiple-pathway reaction networks, have been shown to be able to simulate transient metabolism of some well studied microorganisms and identify growth rate, substrate uptake rates, and byproduct rates under different growth conditions. These rates can be identified and used to replace specific microbially-mediated reaction rates in a reactive transport model using local geochemical conditions as constraints. We previously demonstrated the potential utility of integrating a constraint-based microbial metabolism model with a reactive transport simulator as applied to bioremediation of uranium in groundwater. However, that work relied on an indirect coupling approach that was effective for initial demonstration but may not be extensible to more complex problems that are of significant interest (e.g., communities of microbial species and multiple constraining variables). Here, we extend that work by presenting and demonstrating a method of directly integrating a reactive transport model (FORTRAN code) with constraint-based in silico models solved with IBM ILOG CPLEX linear optimizer base system (C library). The models were integrated with BABEL, a language interoperability tool. The
A Solution Proposal To Indefinite Quadratic Interval Transportation Problem
Directory of Open Access Journals (Sweden)
Hasan Dalman
2013-12-01
Full Text Available The data of real world applications generally cannot be expressed strictly. An efficient way of handling this situation is expressing the data as intervals. Thus, this paper focus on the Indefinite Quadratic Interval Transportation Problem (IQITP in which all the parameters i.e. cost and risk coefficients of the objective function, supply and demand quantities are expressed as intervals. A Taylor series approach is presented for the solution of IQITP by means of the expression of intervals with its left and right limits. Also a numerical example is executed to illustrate the procedure.
The numerical solution of the vorticity transport equation
Dennis, S C R
1973-01-01
A method of approximating the two-dimensional vorticity transport equation in which the matrix associated with the difference equations is diagonally dominant and the truncation error is the same as that of the fully central-difference approximation, is discussed. An example from boundary layer theory is given by calculating the viscous stagnation point flow at the nose of a cylinder. Some new solutions of the Navier-Stokes equations are obtained for symmetrical flow past a flat plate of finite length. (16 refs).
Spiteri, C.
2007-01-01
The quality of groundwater, in particular in coastal areas, is increasingly deteriorating due to the input of nutrients (NO3-, NH4+ and PO4) from septic systems and agricultural leaching. The discharge of groundwater to coastal waters, termed submarine groundwater discharge (SGD), is now recognized
Coarse grained modeling of transport properties in monoclonal antibody solution
Swan, James; Wang, Gang
Monoclonal antibodies and their derivatives represent the fastest growing segment of the bio pharmaceutical industry. For many applications such as novel cancer therapies, high concentration, sub-cutaneous injections of these protein solutions are desired. However, depending on the peptide sequence within the antibody, such high concentration formulations can be too viscous to inject via human derived force alone. Understanding how heterogenous charge distribution and hydrophobicity within the antibodies leads to high viscosities is crucial to their future application. In this talk, we explore a coarse grained computational model of therapeutically relevant monoclonal antibodies that accounts for electrostatic, dispersion and hydrodynamic interactions between suspended antibodies to predict assembly and transport properties in concentrated antibody solutions. We explain the high viscosities observed in many experimental studies of the same biologics.
A Finite-Difference Solution of Solute Transport through a Membrane Bioreactor
Directory of Open Access Journals (Sweden)
B. Godongwana
2015-01-01
Full Text Available The current paper presents a theoretical analysis of the transport of solutes through a fixed-film membrane bioreactor (MBR, immobilised with an active biocatalyst. The dimensionless convection-diffusion equation with variable coefficients was solved analytically and numerically for concentration profiles of the solutes through the MBR. The analytical solution makes use of regular perturbation and accounts for radial convective flow as well as axial diffusion of the substrate species. The Michaelis-Menten (or Monod rate equation was assumed for the sink term, and the perturbation was extended up to second-order. In the analytical solution only the first-order limit of the Michaelis-Menten equation was considered; hence the linearized equation was solved. In the numerical solution, however, this restriction was lifted. The solution of the nonlinear, elliptic, partial differential equation was based on an implicit finite-difference method (FDM. An upwind scheme was employed for numerical stability. The resulting algebraic equations were solved simultaneously using the multivariate Newton-Raphson iteration method. The solution allows for the evaluation of the effect on the concentration profiles of (i the radial and axial convective velocity, (ii the convective mass transfer rates, (iii the reaction rates, (iv the fraction retentate, and (v the aspect ratio.
Cui, Yi-an; Liu, Lanbo; Zhu, Xiaoxiong
2017-08-01
Monitoring the extent and evolution of contaminant plumes in local and regional groundwater systems from existing landfills is critical in contamination control and remediation. The self-potential survey is an efficient and economical nondestructive geophysical technique that can be used to investigate underground contaminant plumes. Based on the unscented transform, we have built a Kalman filtering cycle to conduct time-lapse data assimilation for monitoring the transport of solute based on the solute transport experiment using a bench-scale physical model. The data assimilation was formed by modeling the evolution based on the random walk model and observation correcting based on the self-potential forward. Thus, monitoring self-potential data can be inverted by the data assimilation technique. As a result, we can reconstruct the dynamic process of the contaminant plume instead of using traditional frame-to-frame static inversion, which may cause inversion artifacts. The data assimilation inversion algorithm was evaluated through noise-added synthetic time-lapse self-potential data. The result of the numerical experiment shows validity, accuracy and tolerance to the noise of the dynamic inversion. To validate the proposed algorithm, we conducted a scaled-down sandbox self-potential observation experiment to generate time-lapse data that closely mimics the real-world contaminant monitoring setup. The results of physical experiments support the idea that the data assimilation method is a potentially useful approach for characterizing the transport of contamination plumes using the unscented Kalman filter (UKF) data assimilation technique applied to field time-lapse self-potential data.
Suk, Heejun
2012-01-01
In articles published in 2009 and 2010, Suk and Yeh reported the development of an accurate and efficient particle tracking algorithm for simulating a path line under complicated unsteady flow conditions, using a range of elements within finite elements in multidimensions. Here two examples, an aquifer storage and recovery (ASR) example and a landfill leachate migration example, are examined to enhance the practical implementation of the proposed particle tracking method, known as Suk's method, to a real field of groundwater flow and transport. Results obtained by Suk's method are compared with those obtained by Pollock's method. Suk's method produces superior tracking accuracy, which suggests that Suk's method can describe more accurately various advection-dominated transport problems in a real field than existing popular particle tracking methods, such as Pollock's method. To illustrate the wide and practical applicability of Suk's method to random-walk particle tracking (RWPT), the original RWPT has been modified to incorporate Suk's method. Performance of the modified RWPT using Suk's method is compared with the original RWPT scheme by examining the concentration distributions obtained by the modified RWPT and the original RWPT under complicated transient flow systems.
Blaen, Phillip; Kurz, Marie; Knapp, Julia; Mendoza-Lera, Clara; Lee-Cullin, Joe; Klaar, Megan; Drummond, Jen; Jaeger, Anna; Zarnetske, Jay; Lewandowski, Joerg; Marti, Eugenia; Ward, Adam; Fleckenstein, Jan; Datry, Thibault; Larned, Scott; Krause, Stefan
2016-04-01
Nutrient concentrations in surface waters and groundwaters are increasing in many agricultural catchments worldwide as a result of anthropogenic activities. Increasing geomorphological heterogeneity in river channels may help to attenuate nutrient pollution by facilitating water exchange fluxes with the hyporheic zone; a site of intense microbial activity where biogeochemical transformation rates (e.g. denitrification) can be high. However, the controls on spatial variability in biogeochemical cycling, particularly at scales relevant for river managers, are not well understood. Here, we aimed to assess: 1) how differences in geomorphological heterogeneity control river solute transport and rates of biogeochemical cycling at sub-reach scales (102 m); and 2) the relative magnitude of these differences versus those relating to reach scale substrate variability (103 m). We used the reactive 'smart' tracer resazurin (Raz), a weakly fluorescent dye that transforms to highly fluorescent resorufin (Rru) under mildly reducing conditions, as a proxy to assess rates of biogeochemical cycling in a lowland river in southern England. Solute tracer tests were conducted in two reaches with contrasting substrates: one sand-dominated and the other gravel-dominated. Each reach was divided into sub-reaches that varied in geomorphic complexity (e.g. by the presence of pool-riffle sequences or the abundance of large woody debris). Slug injections of Raz and the conservative tracer fluorescein were conducted in each reach during baseflow conditions (Q ≈ 80 L/s) and breakthrough curves monitored using in-situ fluorometers. Preliminary results indicate overall Raz:Rru transformation rates in the gravel-dominated reach were more than 50% higher than those in the sand-dominated reach. However, high sub-reach variability in Raz:Rru transformation rates and conservative solute transport parameters suggests small-scale targeted management interventions to alter geomorphic heterogeneity may be
Fate of Uranium During Transport Across the Groundwater-Surface Water Interface
Energy Technology Data Exchange (ETDEWEB)
Jaffe, Peter R. [Princeton Univ., NJ (United States); Kaplan, Daniel I. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
2017-06-30
Discharge of contaminated groundwater to surface waters is of concern at many DOE facilities. For example, at F-Area and TNX-Area on the Savannah River Site, contaminated groundwater, including uranium, is already discharging into natural wetlands. It is at this interface where contaminants come into contact with the biosphere. These this research addressed a critical knowledge gap focusing on the geochemistry of uranium (or for that matter, any redox-active contaminant) in wetland systems. Understanding the interactions between hydrological, microbial, and chemical processes will make it possible to provide a more accurate conceptual and quantitative understanding of radionuclide fate and transport under these unique conditions. Understanding these processes will permit better long-term management and the necessary technical justification for invoking Monitored Natural Attenuation of contaminated wetland areas. Specifically, this research did provide new insights on how plant-induced alterations to the sediment biogeochemical processes affect the key uranium reducing microorganisms, the uranium reduction, its spatial distribution, the speciation of the immobilized uranium, and its long-term stability. This was achieved by conducting laboratory mesocosm wetland experiments as well as field measurements at the SRNL. Results have shown that uranium can be immobilized in wetland systems. To a degree some of the soluble U(VI) was reduced to insoluble U(IV), but the majority of the immobilized U was incorporated into iron oxyhydroxides that precipitated onto the root surfaces of wetland plants. This U was immobilized mostly as U(VI). Because it was immobilized in its oxidized form, results showed that dry spells, resulting in the lowering of the water table and the exposure of the U to oxic conditions, did not result in U remobilization.
Mendes, B. S.; Draper, D.
2008-12-01
The issue of model uncertainty and model choice is central in any groundwater modeling effort [Neuman and Wierenga, 2003]; among the several approaches to the problem we favour using Bayesian statistics because it is a method that integrates in a natural way uncertainties (arising from any source) and experimental data. In this work, we experiment with several Bayesian approaches to model choice, focusing primarily on demonstrating the usefulness of the Reversible Jump Markov Chain Monte Carlo (RJMCMC) simulation method [Green, 1995]; this is an extension of the now- common MCMC methods. Standard MCMC techniques approximate posterior distributions for quantities of interest, often by creating a random walk in parameter space; RJMCMC allows the random walk to take place between parameter spaces with different dimensionalities. This fact allows us to explore state spaces that are associated with different deterministic models for experimental data. Our work is exploratory in nature; we restrict our study to comparing two simple transport models applied to a data set gathered to estimate the breakthrough curve for a tracer compound in groundwater. One model has a mean surface based on a simple advection dispersion differential equation; the second model's mean surface is also governed by a differential equation but in two dimensions. We focus on artificial data sets (in which truth is known) to see if model identification is done correctly, but we also address the issues of over and under-paramerization, and we compare RJMCMC's performance with other traditional methods for model selection and propagation of model uncertainty, including Bayesian model averaging, BIC and DIC.References Neuman and Wierenga (2003). A Comprehensive Strategy of Hydrogeologic Modeling and Uncertainty Analysis for Nuclear Facilities and Sites. NUREG/CR-6805, Division of Systems Analysis and Regulatory Effectiveness Office of Nuclear Regulatory Research, U. S. Nuclear Regulatory Commission
TURBULENCE TRANSPORT OF SURFACTANT SOLUTION FLOW DURING DRAG REDUCTION DEGENERATION
Institute of Scientific and Technical Information of China (English)
GU Wei-guo; WANG De-zhong
2012-01-01
Turbulence transport of surfactant solution flow during drag reduction degeneration is investigated experimentally in a two-dimensional channel.Particle Image Velocimetry (P1V) system is used to take two-dimensional velocity frames in the streamwise and wall-normal plane.The additive of surfactant is cetyltrimethyl ammonium chloride (CTAC) with the mass concentration of 25 ppm.Drag reduction degeneration happens in the CTAC solution flow,exhibiting the maximal drag reduction at Re =25000and losing drag reduction completely at Re =40 000.The velocity frames are statistically analyzed in four quadrants which are divided by the u -axis and v-axis.It is found that the phenomenon of“Zero Reynolds shear stress” is caused by the decrease of wallnormal fluctuations and its symmetrical distribution in quadrants.The increase of Reynolds number leads to the enhancement of turbulence burst phenomenon.During thc drag reduction degeneration,the CTAC solution flow contains both high turbulence intensity and drag reduction states.
Siade, A. J.; Prommer, H.; Welter, D.
2014-12-01
Groundwater management and remediation requires the implementation of numerical models in order to evaluate the potential anthropogenic impacts on aquifer systems. In many situations, the numerical model must, not only be able to simulate groundwater flow and transport, but also geochemical and biological processes. Each process being simulated carries with it a set of parameters that must be identified, along with differing potential sources of model-structure error. Various data types are often collected in the field and then used to calibrate the numerical model; however, these data types can represent very different processes and can subsequently be sensitive to the model parameters in extremely complex ways. Therefore, developing an appropriate weighting strategy to address the contributions of each data type to the overall least-squares objective function is not straightforward. This is further compounded by the presence of potential sources of model-structure errors that manifest themselves differently for each observation data type. Finally, reactive transport models are highly nonlinear, which can lead to convergence failure for algorithms operating on the assumption of local linearity. In this study, we propose a variation of the popular, particle swarm optimization algorithm to address trade-offs associated with the calibration of one data type over another. This method removes the need to specify weights between observation groups and instead, produces a multi-dimensional Pareto front that illustrates the trade-offs between data types. We use the PEST++ run manager, along with the standard PEST input/output structure, to implement parallel programming across multiple desktop computers using TCP/IP communications. This allows for very large swarms of particles without the need of a supercomputing facility. The method was applied to a case study in which modeling was used to gain insight into the mobilization of arsenic at a deepwell injection site
Barnhart, K.; Urteaga, I.; Han, Q.; Porta, L.; Jayasumana, A.; Illangasekare, T.
2007-12-01
Groundwater transport modeling is intended to aid in remediation processes by providing prediction of plume location and by helping to bridge data gaps in the typically undersampled subsurface environment. Increased availability of computer resources has made computer-based transport models almost ubiquitous in calculating health risks, determining cleanup strategies, guiding environmental regulatory policy, and in determining culpable parties in lawsuits. Despite their broad use, very few studies exist which verify model correctness or even usefulness, and those that have shown significant discrepancies between predicted and actual results. Better predictions can only be gained from additional and higher quality data, but this is an expensive proposition using current sampling techniques. A promising technology is the use of wireless sensor networks (WSNs) which are comprised of wireless nodes (motes) coupled to in-situ sensors that are capable of measuring hydrological parameters. As the motes are typically battery powered, power consumption is a major concern in routing algorithms. By supplying predictions about the direction and arrival time of the contaminant, the application-driven routing protocol would then become more efficient. A symbiotic relationship then exists between the WSN, which is supplying the data to calibrate the transport model, and the model, which may be supplying predictive information to the WSN for optimum monitoring performance. Many challenges exist before the above can be realized: WSN protocols must mature, as must sensor technology, and inverse models and tools must be developed for integration into the system. As current model calibration, even automatic calibration, still often requires manual tweaking of calibration parameters, implementing this in a real-time closed-loop process may require significant work. Based on insights from a previous proof-of-concept intermediate-scale tank experiment, we are developing the models, tools
A model for managing sources of groundwater pollution.
Gorelick, S.M.
1982-01-01
The waste disposal capacity of a groundwater system can be maximized while maintaining water quality at specified locations by using a groundwater pollutant source management model that is based upon linear programing and numerical simulation. The decision variables of the management model are solute waste disposal rates at various facilities distributed over space. A concentration response matrix is used in the management model to describe transient solute transport and is developed using the US Geological Survey solute transport simulation model. The management model was applied to a complex hypothetical groundwater system. -from Author
Guan, C; Xie, H J; Wang, Y Z; Chen, Y M; Jiang, Y S; Tang, X W
2014-01-01
An analytical model for solute advection and dispersion in a two-layered liner consisting of a geosynthetic clay liner (GCL) and a soil liner (SL) considering the effect of biodegradation was proposed. The analytical solution was derived by Laplace transformation and was validated over a range of parameters using the finite-layer method based software Pollute v7.0. Results show that if the half-life of the solute in GCL is larger than 1 year, the degradation in GCL can be neglected for solute transport in GCL/SL. When the half-life of GCL is less than 1 year, neglecting the effect of degradation in GCL on solute migration will result in a large difference of relative base concentration of GCL/SL (e.g., 32% for the case with half-life of 0.01 year). The 100-year solute base concentration can be reduced by a factor of 2.2 when the hydraulic conductivity of the SL was reduced by an order of magnitude. The 100-year base concentration was reduced by a factor of 155 when the half life of the contaminant in the SL was reduced by an order of magnitude. The effect of degradation is more important in approving the groundwater protection level than the hydraulic conductivity. The analytical solution can be used for experimental data fitting, verification of complicated numerical models and preliminary design of landfill liner systems.
SOLUTE TRANSPORT IN NATURAL FRACTURES BASED ON DIGITAL IMAGE TECHNOLOGY
Institute of Scientific and Technical Information of China (English)
TAN Ye-fei; ZHOU Zhi-fang; HUANG Yong
2009-01-01
A method of fracture boundary extraction was developed using the Gaussian template and Canny boundary detection on the basis of the collected digital images of natural fractures. The roughness and apertures of the fractures were briefly discussed from the point of view of digital image analysis. The extracted fractured image was translated into a lattice image which can be directly used in numerical simulation. The lattice Boltzmann and modified moment propagation mixed method was then applied to the simulation of solute transport in a natural single fracture, and this mixed method could take the advantages of the lattice Boltzmann method in dealing with complex physical boundaries. The obtained concentrations was fitted with the CXTFIT2.1 code and compared with the results obtained with the commercial software Feflow. The comparison indicates that the simulation using the mixed method is sound.
Soil properties and preferential solute transport at the field scale
DEFF Research Database (Denmark)
Koestel, J K; Minh, Luong Nhat; Nørgaard, Trine
An important fraction of water flow and solute transport through soil takes place through preferential flow paths. Although this had been already observed in the nineteenth century, it had been forgotten by the scientific community until it was rediscovered during the 1970s. The awareness...... of the relevance of preferential flow was broadly re-established in the community by the early 1990s. However, since then, the notion remains widespread among soil scientists that the occurrence and strength of preferential flow cannot be predicted from measurable proxy variables such as soil properties or land...... management practices (e.g. Beven, K., 1991, modeling preferential flow - an uncertain future, Preferential Flow, 1-11). In our study, we present evidence that disproves this notion. We evaluated breakthrough curve experiments under a constant irrigation rate of 1 cm/h conducted on 65 soil columns (20 cm...
Engineering charge transport by heterostructuring solution-processed semiconductors
Voznyy, Oleksandr; Sutherland, Brandon R.; Ip, Alexander H.; Zhitomirsky, David; Sargent, Edward H.
2017-06-01
Solution-processed semiconductor devices are increasingly exploiting heterostructuring — an approach in which two or more materials with different energy landscapes are integrated into a composite system. Heterostructured materials offer an additional degree of freedom to control charge transport and recombination for more efficient optoelectronic devices. By exploiting energetic asymmetry, rationally engineered heterostructured materials can overcome weaknesses, augment strengths and introduce emergent physical phenomena that are otherwise inaccessible to single-material systems. These systems see benefit and application in two distinct branches of charge-carrier manipulation. First, they influence the balance between excitons and free charges to enhance electron extraction in solar cells and photodetectors. Second, they promote radiative recombination by spatially confining electrons and holes, which increases the quantum efficiency of light-emitting diodes. In this Review, we discuss advances in the design and composition of heterostructured materials, consider their implementation in semiconductor devices and examine unexplored paths for future advancement in the field.
Michael, H. A.; Voss, C. I.
2009-12-01
Widespread arsenic poisoning is occurring in large areas of Bangladesh and West Bengal, India due to high arsenic levels in shallow groundwater, which is the primary source of irrigation and drinking water in the region. The high-arsenic groundwater exists in aquifers of the Bengal Basin, a huge sedimentary system approximately 500km x 500km wide and greater than 15km deep in places. Deeper groundwater (>150m) is nearly universally low in arsenic and a potential source of safe drinking water, but evaluation of its sustainability requires understanding of the entire, interconnected regional aquifer system. Numerical modeling of flow and arsenic transport in the basin introduces problems of scale: challenges in representing the system in enough detail to produce meaningful simulations and answer relevant questions while maintaining enough simplicity to understand controls on processes and operating within computational constraints. A regional groundwater flow and transport model of the Bengal Basin was constructed to assess the large-scale functioning of the deep groundwater flow system, the vulnerability of deep groundwater to pumping-induced migration from above, and the effect of chemical properties of sediments (sorption) on sustainability. The primary challenges include the very large spatial scale of the system, dynamic monsoonal hydrology (small temporal scale fluctuations), complex sedimentary architecture (small spatial scale heterogeneity), and a lack of reliable hydrologic and geologic data. The approach was simple. Detailed inputs were reduced to only those that affect the functioning of the deep flow system. Available data were used to estimate upscaled parameter values. Nested small-scale simulations were performed to determine the effects of the simplifications, which include treatment of the top boundary condition and transience, effects of small-scale heterogeneity, and effects of individual pumping wells. Simulation of arsenic transport at the large
Friedly, J.C.; Davis, J.A.; Kent, D.B.
1995-01-01
A plausible and consistent model is developed to obtain a quantitative description of the gradual disappearance of hexavalent chromium (Cr(VI)) from groundwater in a small-scale field tracer test and in batch kinetic experiments using aquifer sediments under similar chemical conditions. The data exhibit three distinct timescales. Fast reduction occurs in well-stirred batch reactors in times much less than 1 hour and is followed by slow reduction over a timescale of the order of 2 days. In the field, reduction occurs on a timescale of the order of 8 days. The model is based on the following hypotheses. The chemical reduction reaction occurs very fast, and the longer timescales are caused by diffusion resistance. Diffusion into the secondary porosity of grains causes the apparent slow reduction rate in batch experiments. In the model of the field experiments, the reducing agent, heavy Fe(II)-bearing minerals, is heterogeneously distributed in thin strata located between larger nonreducing sand lenses that comprise the bulk of the aquifer solids. It is found that reducing strata of the order of centimeters thick are sufficient to contribute enough diffusion resistance to cause the observed longest timescale in the field. A one-dimensional advection/dispersion model is formulated that describes the major experimental trends. Diffusion rates are estimated in terms of an elementary physical picture of flow through a stratified medium containing identically sized spherical grains. Both reduction and sorption reactions are included. Batch simulation results are sensitive to the fraction of reductant located at or near the surface of grains, which controls the amount of rapid reduction, and the secondary porosity, which controls the rate of slow reduction observed in batch experiments. Results of Cr(VI) transport simulations are sensitive to the thickness and relative size of the reducing stratum. Transport simulation results suggest that nearly all of the reductant must be
Irvine, Dylan J.; Cartwright, Ian; Post, Vincent E. A.; Simmons, Craig T.; Banks, Eddie W.
2016-02-01
Steady state 1-D analytical solutions to estimate groundwater fluxes from temperature profiles are an attractive option because they are simple to apply, with no complex boundary or initial conditions. Steady state solutions have been applied to estimate both aquifer scale fluxes as well as to estimate groundwater discharge to streams. This study explores the sources of uncertainty in flux estimates from regional scale aquifers caused by sensor precision, aquifer heterogeneity, multidimensional flow and variations in surface temperature due to climate change. Synthetic temperature profiles were generated using 2-D groundwater flow and heat transport models with homogeneous and heterogeneous hydraulic and thermal properties. Temperature profiles were analyzed assuming temperature can be determined with a precision between 0.1°C and 0.001°C. Analysis of synthetic temperature profiles show that the Bredehoeft and Papadopulos (1965) method can provide good estimates of the mean vertical Darcy flux over the length of the temperature profile. Reliable flux estimates were obtained when the ratio of vertical to horizontal flux was as low as 0.1, and in heterogeneous media, providing that temperature at the upper boundary was constant in time. However, temporal increases in surface temperature led to over-estimation of fluxes. Overestimates increased with time since the onset of, and with the rate of surface warming. Overall, the Bredehoeft and Papadopulos (1965) method may be more robust for the conditions with constant temperature distributions than previously thought, but that transient methods that account for surface warming should be used to determine fluxes in shallow aquifers.
Reactive transport modeling has been conducted to describe the performance of the permeable reactive barrier at the Coast Guard Support Center near Elizabeth City, NC. The reactive barrier was installed to treat groundwater contaminated by hexavalent chromium and chlorinated org...
Adar, Elanur; Bilgili, Mehmet Sinan
2015-01-01
The aim of this study was to investigate the efficiency of four different mineral liners (clay, bentonite, kaoline, and zeolite) which could be utilized to prevent the transport of phenolic compounds to groundwater through alternative liner systems. Four laboratory-scale HDPE reactors with 80 cm height and 40 cm inner diameter were operated for a period of 180 days. Results indicated that the transport of mono- or dichlorophenols is significantly prevented by the liner systems used, while the transport of highly chlorinated phenolic compounds cannot be prevented by the landfill liner system effectively. Highly chlorinated phenolic compounds in groundwater can be found in higher concentrations than the leachate, as a result of the degradation and transformation of these compounds. Thus, the analysis of highly chlorinated phenolic compounds such as 2,4,6-TCP, 2,3,6-TCP, 3,4,5-TCP, and PCP is of great significance for the studies to be conducted on the contamination of groundwater around landfills.
Directory of Open Access Journals (Sweden)
Elanur Adar
2015-01-01
Full Text Available The aim of this study was to investigate the efficiency of four different mineral liners (clay, bentonite, kaoline, and zeolite which could be utilized to prevent the transport of phenolic compounds to groundwater through alternative liner systems. Four laboratory-scale HDPE reactors with 80 cm height and 40 cm inner diameter were operated for a period of 180 days. Results indicated that the transport of mono- or dichlorophenols is significantly prevented by the liner systems used, while the transport of highly chlorinated phenolic compounds cannot be prevented by the landfill liner system effectively. Highly chlorinated phenolic compounds in groundwater can be found in higher concentrations than the leachate, as a result of the degradation and transformation of these compounds. Thus, the analysis of highly chlorinated phenolic compounds such as 2,4,6-TCP, 2,3,6-TCP, 3,4,5-TCP, and PCP is of great significance for the studies to be conducted on the contamination of groundwater around landfills.
Improved parallel solution techniques for the integral transport matrix method
Energy Technology Data Exchange (ETDEWEB)
Zerr, R. Joseph, E-mail: rjz116@psu.edu [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA (United States); Azmy, Yousry Y., E-mail: yyazmy@ncsu.edu [Department of Nuclear Engineering, North Carolina State University, Burlington Engineering Laboratories, Raleigh, NC (United States)
2011-07-01
Alternative solution strategies to the parallel block Jacobi (PBJ) method for the solution of the global problem with the integral transport matrix method operators have been designed and tested. The most straightforward improvement to the Jacobi iterative method is the Gauss-Seidel alternative. The parallel red-black Gauss-Seidel (PGS) algorithm can improve on the number of iterations and reduce work per iteration by applying an alternating red-black color-set to the subdomains and assigning multiple sub-domains per processor. A parallel GMRES(m) method was implemented as an alternative to stationary iterations. Computational results show that the PGS method can improve on the PBJ method execution time by up to 10´ when eight sub-domains per processor are used. However, compared to traditional source iterations with diffusion synthetic acceleration, it is still approximately an order of magnitude slower. The best-performing cases are optically thick because sub-domains decouple, yielding faster convergence. Further tests revealed that 64 sub-domains per processor was the best performing level of sub-domain division. An acceleration technique that improves the convergence rate would greatly improve the ITMM. The GMRES(m) method with a diagonal block pre conditioner consumes approximately the same time as the PBJ solver but could be improved by an as yet undeveloped, more efficient pre conditioner. (author)
Improved parallel solution techniques for the integral transport matrix method
Energy Technology Data Exchange (ETDEWEB)
Zerr, Robert J [Los Alamos National Laboratory; Azmy, Yousry Y [NORTH CAROLINA STATE UNIV.
2010-11-23
Alternative solution strategies to the parallel block Jacobi (PBJ) method for the solution of the global problem with the integral transport matrix method operators have been designed and tested. The most straightforward improvement to the Jacobi iterative method is the Gauss-Seidel alternative. The parallel red-black Gauss-Seidel (PGS) algorithm can improve on the number of iterations and reduce work per iteration by applying an alternating red-black color-set to the subdomains and assigning multiple sub-domains per processor. A parallel GMRES(m) method was implemented as an alternative to stationary iterations. Computational results show that the PGS method can improve on the PBJ method execution by up to {approx}50% when eight sub-domains per processor are used. However, compared to traditional source iterations with diffusion synthetic acceleration, it is still approximately an order of magnitude slower. The best-performing case are opticaUy thick because sub-domains decouple, yielding faster convergence. Further tests revealed that 64 sub-domains per processor was the best performing level of sub-domain division. An acceleration technique that improves the convergence rate would greatly improve the ITMM. The GMRES(m) method with a diagonal block preconditioner consumes approximately the same time as the PBJ solver but could be improved by an as yet undeveloped, more efficient preconditioner.
Larson, T.; Nicot, J. P.; Mickler, P. J.; Darvari, R.
2015-12-01
Dissolved methane in shallow groundwater drives public concern about the safety of hydraulic fracturing. We report dissolved alkane and nitrogen gas concentrations and their stable isotope values (δ13C and δ15N, respectively) from 208 water wells in Parker county, Texas. These data are used to differentiate 'stray' natural gas and low temperature microbial methane, and (2) estimate the ratio of stray gas to groundwater. The ratio of (gas-phase) stray natural gas to groundwater is estimated by correlating dissolved methane and nitrogen concentrations and dissolved nitrogen δ15N values. Our hypothesis is groundwater exposed to high volumes of stray natural gas have high dissolved methane concentrations and low dissolved nitrogen concentrations and δ15N values. Alternatively, groundwater exposed to low volumes of stray gas-phase natural gas have elevated dissolved methane, but the concentration of dissolved nitrogen and its d15N value is atmospheric. A cluster of samples in Parker county have high concentrations of dissolved methane (>10mg/L) with d13Cmethane and alkane ratios (C1/C2+C3) typical of natural gas from the Barnett Shale and the Strawn Formation. Coupling dissolved nitrogen concentrations and δ15N values with these results, we suggest that few of the wells in this cluster preserve large gas to water ratios. Many samples with high dissolved methane concentrations have atmospheric dissolved nitrogen concentrations and δ15N values, providing evidence against high flux natural gas transport into shallow groundwater. These results demonstrate that dissolved nitrogen chemistry, in addition to dissolved alkane and noble gas measurements, may be useful to discern sources of dissolved methane and estimate ratios of stray natural gas-water ratios.
Brink, C.v.d.; Zaadnoordijk, W.J.; Burgers, S.; Griffioen, J.
2008-01-01
Groundwater quality management relies more and more on models in recent years. These models are used to predict the risk of groundwater contamination for various land uses. This paper presents an assessment of uncertainties and sensitivities to input parameters for a regional model. The model had
Assessing uncertainties in solute transport models: Upper Narew case study
Osuch, M.; Romanowicz, R.; Napiórkowski, J. J.
2009-04-01
This paper evaluates uncertainties in two solute transport models based on tracer experiment data from the Upper River Narew. Data Based Mechanistic and transient storage models were applied to Rhodamine WT tracer observations. We focus on the analysis of uncertainty and the sensitivity of model predictions to varying physical parameters, such as dispersion and channel geometry. An advection-dispersion model with dead zones (Transient Storage model) adequately describes the transport of pollutants in a single channel river with multiple storage. The applied transient storage model is deterministic; it assumes that observations are free of errors and the model structure perfectly describes the process of transport of conservative pollutants. In order to take into account the model and observation errors, an uncertainty analysis is required. In this study we used a combination of the Generalized Likelihood Uncertainty Estimation technique (GLUE) and the variance based Global Sensitivity Analysis (GSA). The combination is straightforward as the same samples (Sobol samples) were generated for GLUE analysis and for sensitivity assessment. Additionally, the results of the sensitivity analysis were used to specify the best parameter ranges and their prior distributions for the evaluation of predictive model uncertainty using the GLUE methodology. Apart from predictions of pollutant transport trajectories, two ecological indicators were also studied (time over the threshold concentration and maximum concentration). In particular, a sensitivity analysis of the length of "over the threshold" period shows an interesting multi-modal dependence on model parameters. This behavior is a result of the direct influence of parameters on different parts of the dynamic response of the system. As an alternative to the transient storage model, a Data Based Mechanistic approach was tested. Here, the model is identified and the parameters are estimated from available time series data using
Energy Technology Data Exchange (ETDEWEB)
Steirer, K. Xerxes; Berry, Joseph J.; Chesin, Jordan P.; Lloyd, Matthew T.; Widjonarko, Nicodemus Edwin; Miedaner, Alexander; Curtis, Calvin J.; Ginley, David S.; Olson, Dana C.
2017-01-10
A method for the application of solution processed metal oxide hole transport layers in organic photovoltaic devices and related organic electronics devices is disclosed. The metal oxide may be derived from a metal-organic precursor enabling solution processing of an amorphous, p-type metal oxide. An organic photovoltaic device having solution processed, metal oxide, thin-film hole transport layer.
Directory of Open Access Journals (Sweden)
Stefano L. Russo
2010-01-01
Full Text Available Problem statement: The increasing diffusion of low-enthalpy geothermal open-loop Groundwater Heat Pumps (GWHP providing buildings air conditioning requires a careful assessment of the overall effects on groundwater system, especially in the urban areas. The impact on the groundwater temperature in the surrounding area of the re-injection well is directly linked to the aquifer properties. Physical processes affecting heat transport within an aquifer include advection (or convection and hydrodynamic thermodispersion (diffusion and mechanical dispersion. If the groundwater flows, the advective components tend to dominate the heat transfer process within the aquifer and the diffusion can be considered negligible. This study illustrates the experimental results derived from the groundwater monitoring in the surrounding area of an injection well connected to an open-loop GWHP plant which has been installed in the "Politecnico di Torino" (NW Italy for cooling some of the university buildings. Groundwater pumping and injection interfere only with the upper unconfined aquifer. Approach: After the description of the hydrogeological setting the authors examined the data deriving from multiparameter probes installed inside the pumping well (P2, the injection well (P4 and a downgradient piezometer (S2. Data refers to the summer 2009. To control the aquifer thermal stratification some multi-temporal temperature logs have been performed in the S2. Results: After the injection of warm water in P4 the plume arrived after 30 days in the S2. That delay is compatible with the calculated plume migration velocity (1.27 m d-1 and their respective distance (35 m. The natural temperature in the aquifer due to the switching-off of the GWHP plant has been reached after two month. The Electrical Conductivity (EC values tend to vary out of phase with the temperature. The temperature logs in the S2 highlighted a thermal stratification in the aquifer due to a low vertical
Integrating Water Flow, Solute Transport and Crop Production Models At The Farm-scale
Assinck, F. B. T.; de Vos, J. A.
Minimising nitrate pollution of ground and surface water and optimising agricultural yields are problems which have to be addressed at the farm-scale. However, simulation models usually operate at the field-scale. We coupled the subsurface hydrology model SWAP with other existing deterministic (sub)models for solute transport, organic mat- ter dynamics, crop growth, and dairy farm management at the farm-scale, resulting in the model WATERPAS. The (sub)models are coupled in a Framework environment obeying the principles of object oriented modelling. Based on daily weather data, groundwater regimes, soil and farm characteristics WATERPAS is able to simulate the water and nutrient balances, grass production, economical benefits, nitrate leaching and greenhouse gas emissions at a farm. Problems of coupling, such as data-transfer, quality checks, over-parameterisation, complexity and sensitivity of the systems are discussed. Application of deducted simpler models and expert judgement can be use- ful for practical use. However, we believe that integrated models are a powerful tool to understand the complex relationships between the different processes. It also gives opportunities to perform scenario analysis for future boundary conditions, i.e. due to changing farm management, (sea) water levels and climate change.
Modeling vertical and horizontal solute transport for the Weldon Spring Site Remedial Action Project
Energy Technology Data Exchange (ETDEWEB)
Tomasko, D.
1992-11-01
This technical memorandum presents a one-dimensional model to simulate the transport of a contaminant that originates as a liquid release, moves vertically downward through a vadose zone, mixes with initially clean groundwater in an unconfined aquifer, and ends at a downgradient extraction well. Vertical and horizontal segments of the contaminant pathway are coupled by assuming that the breakthrough curve of the contaminant at the water table acts as a contaminant source for the unconfined aquifer. For simplicity, this source is assumed to be a time-shifted unit square wave having an amplitude equal to the peak breakthrough concentration at the water table and a duration equal to the full width of the breakthrough curve at the half-maximum concentration value. The effects of dilution at the water-table interface are evaluated with a simple mass-balance equation. Comparing the model results for the chemical plant area of the Weldon Spring site near St. Louis, Missouri, and the Envirocare facility located near Salt Lake City, Utah, with those obtained from a solution formulated with the real and imaginary parts of a Fourier series in Laplace space indicates that the model provides a conservative estimate of the contaminant breakthrough curve at the receptor.
TRANSOL, a dynamic simulation model for transport and transformation of solutes in soils
Kroes, J.G.; Rijtema, P.E.
1996-01-01
The dynamic simulation model TRANSOL has been developed to fulfil the need for a tool to analyse leaching of solutes from the soil surface to groundwater and surface waters. A description is given of the modelled processes: conversion, formation, cropuptake, precipitation, equilibrium and non-equili
Transport of Gas and Solutes in Permeable Estuarine Sediments
2013-09-30
profiles in sediment affected by groundwater seepage. Free methane gas builds up below 10 cm depth. The average gas production rate recorded at St...of the nearshore zone (< 2 m water depth), which according to the National Geophysical data center (ETOPO data set, http://www.ngdc.noaa.gov
Product Lifecycle Management and the Quest for Sustainable Space Transportation Solutions
Caruso, Pamela W.
2009-01-01
This viewgraph presentation reviews NASA Marshall's effort to sustain space transportation solutions through product lines that include: 1) Propulsion and Transportation Systems; 2) Life Support Systems; and 3) and Earth and Space Science Spacecraft Systems, and Operations.
Hydrogeologic Setting of A/M Area: Framework for Groundwater Transport. Book 1
Energy Technology Data Exchange (ETDEWEB)
Van Pelt, R.; Lewis, S.E.; Aadland, R.K.
1994-03-11
This document includes a brief summary of the regional geology within a 200--mile radius of the A/M Area, a summary of stratigraphy and hydrostratigraphic nomenclature as it applies to the A/M Area, and a summary of stratigraphy and hydrostratigraphy specific to the A/M Area. Five different stratigraphic cross sections show site-specific geology of the Tertiary section of the Upper Atlantic Coastal Plain geologic province within the A/M Area. The Cretaceous section lacks detail because the deepest wells penetrate only the uppermost part of the Upper Cretaceous sediments. Most of the wells are confined to the Tertiary section. The A/M Area is located in the northwestern corner of the Savannah River Site (SRS). The area serves as a main administrative hub for the site. Between 1958 and 1985, approximately 2,000,000 pounds of volatile organic solvents (metal degreasers, primarily trichloroethylene and tetrachloroethylene) were routed to the M Area Settling Basin. Between 1954 and 1958, effluent also was discharged to Tim`s Branch via the A014 Outfall. In the main M Area Solvent Handling/Storage Area, a significant amount of leakage occurred from drums stored during this time period. Extensive quantities of solvents were transported, via the Process Sewer Line, to the M Area Settling Basin, and leaks occurred along this line as well. A smaller source area has been identified and is centered around the Savannah River Laboratory (SRL) (now called the Savannah River Technology Center [SRTC]) Complex. All of these source areas are represented by solvent contamination in the groundwater system. (Abstract Truncated)
New constructive solutions for building of transport construction facilities
Directory of Open Access Journals (Sweden)
Babayev Vladimir
2017-01-01
Full Text Available New structural systems for civil and transport engineering were examined. The basis for the formation of the proposed reinforced concrete structures is the ideology of reducing its dead weight, with a given bearing capacity, the realization of which is accomplished by burial during concreting large-sized liners of a given shape and manufactured from lightweight, inexpensive composite materials. The process of erecting these systems is presented in two forms: for flat structures - using self-tightening concrete, and for curvilinear ones - by using shotcrete technologies. The second direction is presented by steel-reinforced concrete structures. These structural systems were created on the basis of innovative component and methods of rationalization of parameters. The basis of the above methods is a compiler which includes the finite element method, adaptive evolution method and special iterative procedures. Experimental verification of structural solutions and formation procedures for suggested systems was performed. Comparison between theoretical and experimental data is given. Suggested systems were implemented in a number of building companies.
An optimized transport-of-intensity solution for phase imaging
Banerjee, Partha; Basunia, Mahmudunnabi; Poon, Ting-Chung; Zhang, Hongbo
2016-05-01
The transport-of-intensity equation (TIE) is often used to determine the phase and amplitude profile of a complex object by monitoring the intensities at different distances of propagation or around the image plane. TIE results from the imaginary part of the paraxial wave equation and is equivalent to the conservation of energy. The real part of the paraxial wave equation gives the eikonal equation in the presence of diffraction. Since propagation of the optical field between different planes is governed by the (paraxial) wave equation, both real and imaginary parts need to be satisfied at every propagation plane. In this work, the solution of the TIE is optimized by using the real part of the paraxial wave equation as a constraint. This technique is applied to the more exact determination of imaging the induced phase of a liquid heated by a focused laser beam, which has been previously computed using TIE only. Retrieval of imaged phase using the TIE is performed by using the constraint that naturally arises from the real part of the paraxial wave equation.
Energy Technology Data Exchange (ETDEWEB)
Zhang, Guannan [ORNL; Webster, Clayton G [ORNL; Gunzburger, Max D [ORNL
2012-09-01
Although Bayesian analysis has become vital to the quantification of prediction uncertainty in groundwater modeling, its application has been hindered due to the computational cost associated with numerous model executions needed for exploring the posterior probability density function (PPDF) of model parameters. This is particularly the case when the PPDF is estimated using Markov Chain Monte Carlo (MCMC) sampling. In this study, we develop a new approach that improves computational efficiency of Bayesian inference by constructing a surrogate system based on an adaptive sparse-grid high-order stochastic collocation (aSG-hSC) method. Unlike previous works using first-order hierarchical basis, we utilize a compactly supported higher-order hierar- chical basis to construct the surrogate system, resulting in a significant reduction in the number of computational simulations required. In addition, we use hierarchical surplus as an error indi- cator to determine adaptive sparse grids. This allows local refinement in the uncertain domain and/or anisotropic detection with respect to the random model parameters, which further improves computational efficiency. Finally, we incorporate a global optimization technique and propose an iterative algorithm for building the surrogate system for the PPDF with multiple significant modes. Once the surrogate system is determined, the PPDF can be evaluated by sampling the surrogate system directly with very little computational cost. The developed method is evaluated first using a simple analytical density function with multiple modes and then using two synthetic groundwater reactive transport models. The groundwater models represent different levels of complexity; the first example involves coupled linear reactions and the second example simulates nonlinear ura- nium surface complexation. The results show that the aSG-hSC is an effective and efficient tool for Bayesian inference in groundwater modeling in comparison with conventional
Semianalytical Solutions of Radioactive or Reactive Tracer Transport in Layered Fractured Media
Energy Technology Data Exchange (ETDEWEB)
G.J. Moridis; G. S. Bodvarsson
2001-10-01
In this paper, semianalytical solutions are developed for the problem of transport of radioactive or reactive tracers (solutes or colloids) through a layered system of heterogeneous fractured media with misaligned fractures. The tracer transport equations in the matrix account for (a) diffusion, (b) surface diffusion (for solutes only), (c) mass transfer between the mobile and immobile water fractions, (d) linear kinetic or equilibrium physical, chemical, or combined solute sorption or colloid filtration, and (e) radioactive decay or first order chemical reactions. Any number of radioactive decay daughter products (or products of a linear, first-order reaction chain) can be tracked. The tracer-transport equations in the fractures account for the same processes, in addition to advection and hydrodynamic dispersion. Additionally, the colloid transport equations account for straining and velocity adjustments related to the colloidal size. The solutions, which are analytical in the Laplace space, are numerically inverted to provide the solution in time and can accommodate any number of fractured and/or porous layers. The solutions are verified using analytical solutions for limiting cases of solute and colloid transport through fractured and porous media. The effect of important parameters on the transport of {sup 3}H, {sup 237}Np and {sup 239}Pu (and its daughters) is investigated in several test problems involving layered geological systems of varying complexity. {sup 239}Pu colloid transport problems in multilayered systems indicate significant colloid accumulations at straining interfaces but much faster transport of the colloid than the corresponding strongly sorbing solute species.
Semianalytical solutions of radioactive or reactive tracer transport in layered fractured media
Energy Technology Data Exchange (ETDEWEB)
Moridis, G.J.; Bodvarsson, G.S.
2001-10-10
In this paper, semianalytical solutions are developed for the problem of transport of radioactive or reactive tracers (solutes or colloids) through a layered system of heterogeneous fractured media with misaligned fractures. The tracer transport equations in the matrix account for (a) diffusion, (b) surface diffusion (for solutes only), (c) mass transfer between the mobile and immobile water fractions, (d) linear kinetic or equilibrium physical, chemical, or combined solute sorption or colloid filtration, and (e) radioactive decay or first order chemical reactions. Any number of radioactive decay daughter products (or products of a linear, first-order reaction chain) can be tracked. The tracer-transport equations in the fractures account for the same processes, in addition to advection and hydrodynamic dispersion. Additionally, the colloid transport equations account for straining and velocity adjustments related to the colloidal size. The solutions, which are analytical in the Laplace space, are numerically inverted to provide the solution in time and can accommodate any number of fractured and/or porous layers. The solutions are verified using analytical solutions for limiting cases of solute and colloid transport through fractured and porous media. The effect of important parameters on the transport of {sup 3}H, {sup 237}Np and {sup 239}Pu (and its daughters) is investigated in several test problems involving layered geological systems of varying complexity. {sup 239}Pu colloid transport problems in multilayered systems indicate significant colloid accumulations at straining interfaces but much faster transport of the colloid than the corresponding strongly sorbing solute species.
Energy Technology Data Exchange (ETDEWEB)
None
1997-10-01
The groundwater flow system of the Nevada Test Site and surrounding region was evaluated to estimate the highest potential current and near-term risk to the public and the environment from groundwater contamination downgradient of the underground nuclear testing areas. The highest, or greatest, potential risk is estimated by assuming that several unusually rapid transport pathways as well as public and environmental exposures all occur simultaneously. These conservative assumptions may cause risks to be significantly overestimated. However, such a deliberate, conservative approach ensures that public health and environmental risks are not underestimated and allows prioritization of future work to minimize potential risks. Historical underground nuclear testing activities, particularly detonations near or below the water table, have contaminated groundwater near testing locations with radioactive and nonradioactive constituents. Tritium was selected as the contaminant of primary concern for this phase of the project because it is abundant, highly mobile, and represents the most significant contributor to the potential radiation dose to humans for the short term. It was also assumed that the predicted risk to human health and the environment from tritium exposure would reasonably represent the risk from other, less mobile radionuclides within the same time frame. Other contaminants will be investigated at a later date. Existing and newly collected hydrogeologic data were compiled for a large area of southern Nevada and California, encompassing the Nevada Test Site regional groundwater flow system. These data were used to develop numerical groundwater flow and tritium transport models for use in the prediction of tritium concentrations at hypothetical human and ecological receptor locations for a 200-year time frame. A numerical, steady-state regional groundwater flow model was developed to serve as the basis for the prediction of the movement of tritium from the
DEFF Research Database (Denmark)
Malaguerra, Flavio; Binning, Philip John; Albrechtsen, Hans-Jørgen
2009-01-01
Chlorinated hydrocarbons originating from point sources are amongst the most prevalent contaminants of ground water and surface water resources. Riparian zones may play an important role in the attenuation of contaminant concentrations when contaminant plumes flow from groundwater to surface water...... because of the occurrence of redox gradients, strongly reductive conditions and high biological activity. In order to meet the expectations of the EU Water Framework Directive, an evaluation of the impact of such plumes on surface water is needed. The aim of this work is to develop a groundwater transport...... number of geochemical processes, allows the simulation of soil geochemical transformations when microbial by-products are released to surface water, and the consideration of non-linear feedbacks on bacterial growth and pollutant transformations. Sensitivity analysis is performed through Monte Carlo...
Engeler, I.; Hendricks Franssen, H. J.; Müller, R.; Stauffer, F.
2011-02-01
SummaryThis paper focuses on the role of heat transport in river-aquifer interactions for the study area Hardhof located in the Limmat valley within the city of Zurich (Switzerland). On site there are drinking water production facilities of Zurich water supply, which pump groundwater and infiltrate bank filtration water from river Limmat. The artificial recharge by basins and by wells creates a hydraulic barrier against the potentially contaminated groundwater flow from the city. A three-dimensional finite element model of the coupled variably saturated groundwater flow and heat transport was developed. The hydraulic conductivity of the aquifer and the leakage coefficient of the riverbed were calibrated for isothermal conditions by inverse modelling, using the pilot point method. River-aquifer interaction was modelled using a leakage concept. Coupling was considered by temperature-dependent values for hydraulic conductivity and for leakage coefficients. The quality of the coupled model was tested with the help of head and temperature measurements. Good correspondence between simulated and measured temperatures was found for the three pumping wells and seven piezometers. However, deviations were observed for one pumping well and two piezometers, which are situated in an area, where zones with important hydrogeological heterogeneity are expected. A comparison of simulation results with isothermal leakage coefficients with those of temperature-dependent leakage coefficients shows that the temperature dependence is able to reduce the head residuals close to the river by up to 30%. The largest improvements are found in the zone, where the river stage is considerably higher than the groundwater level, which is in correspondence with the expectations. Additional analyses also showed that the linear leakage concept cannot reproduce the seepage flux in a downstream section during flood events. It was found that infiltration is enhanced during flood events, which is
Energy Technology Data Exchange (ETDEWEB)
Carnahan, C.L.; Remer, J.S.
1981-04-01
Analytical solutions have been developed for the problem of solute transport in a steady, three dimensional field of groundwater flow with non-equilibrium mass transfer of a radioactive species between fluid and solid phases and with anisotropic hydrodynamic dispersion. Interphase mass transport is described by a linear rate expression. Solutions are presented also for the case of equilibrium distribution of solute between fluid and solid phases. Three types of release from a point source were considered: instantaneous release of a finite mass of solute, continuous release at an exponentially decaying rate, and release for a finite period of time. Graphical displays of computational results for point-source solutions show the expected variation of sorptive retardation effects progressing from the case of no sorption, through several cases of non-equilibrium sorption, to the case of equilibrium sorption. The point-source solutions can be integrated over finite regions of a space to provide analytical solutions for regions of solute release having finite spatial extents and various geometrical shapes, thus considerably extending the utility of the point-source solutions.
Cremer, Clemens; Neuweiler, Insa
2017-04-01
Knowledge of subsurface solute transport processes is vital to investigate e.g. groundwater contamination, nutrient uptake by plant roots and to implement remediation strategies. Beside field measurements and numerical simulations, physical laboratory experiments represent a way to establish process understanding and furthermore validate numerical schemes. Atmospheric forcings, such as erratically varying infiltration and evaporation cycles, subject the shallow subsurface to local and temporal variations in water content and associated hydraulic conductivity of the prevailing porous media. Those variations in material properties can cause flow paths to differ between upward and downward flow periods. Thereby, the unsaturated subsurface presents a highly complicated, dynamic system. Following an extensive systematical numerical investigation of flow and transport through bimodal, unsaturated porous media under dynamic boundary conditions (Cremer et al., 2016), we conduct physical laboratory experiments in a 22 cm x 8 cm x 1 cm flow cell where we introduce structural heterogeneity in the form sharp material interfaces between different porous media. In all experiments, a constant pressure head is implemented at the lower boundary, while cyclic infiltration-evaporation phases are applied at the soil surface. As a reference case a stationary infiltration with a rate corresponding to the cycle-averaged infiltration rate is applied. By initial application of dye tracers, solute transport within the domain is visualized such that transport paths and redistribution processes can be observed in a qualitative manner. Solute leaching is quantified at the bottom outlet, where breakthrough curves are obtained via spectroscopy. Liquid and vapor flow in and out of the domain is obtained from multiple balances. Thereby, the interplay of material structural heterogeneity and alternating flow (transport) directions and flow (transport) paths is investigated. Results show lateral
Institute of Scientific and Technical Information of China (English)
黎勇; 陈丽
2002-01-01
In this paper, we study the asymptotic behavior of global smooth solution to the initial boundary problem for the 1-D energy transport model in semiconductor science. We prove that the smooth solution of the problem converges to a stationary solution exponentially fast as t - ∞ when the initial data is a small perturbation of the stationary solution.
Self-similar Solutions for a Transport Equation with Non-local Flux
Institute of Scientific and Technical Information of China (English)
Angel CASTRO; Diego C(O)RDOBA
2009-01-01
The authors construct self-similar solutions for an N-dimensional transport equation,where the velocity is given by the Riezs transform.These solutions imply nonuniqueness of weak solution.In addition,self-similar solution for a one-dimensional conservative equation involving the Hilbert transform is obtained.
Briseño, Jessica; Herrera, Graciela S.
2010-05-01
Herrera (1998) proposed a method for the optimal design of groundwater quality monitoring networks that involves space and time in a combined form. The method was applied later by Herrera et al (2001) and by Herrera and Pinder (2005). To get the estimates of the contaminant concentration being analyzed, this method uses a space-time ensemble Kalman filter, based on a stochastic flow and transport model. When the method is applied, it is important that the characteristics of the stochastic model be congruent with field data, but, in general, it is laborious to manually achieve a good match between them. For this reason, the main objective of this work is to extend the space-time ensemble Kalman filter proposed by Herrera, to estimate the hydraulic conductivity, together with hydraulic head and contaminant concentration, and its application in a synthetic example. The method has three steps: 1) Given the mean and the semivariogram of the natural logarithm of hydraulic conductivity (ln K), random realizations of this parameter are obtained through two alternatives: Gaussian simulation (SGSim) and Latin Hypercube Sampling method (LHC). 2) The stochastic model is used to produce hydraulic head (h) and contaminant (C) realizations, for each one of the conductivity realizations. With these realization the mean of ln K, h and C are obtained, for h and C, the mean is calculated in space and time, and also the cross covariance matrix h-ln K-C in space and time. The covariance matrix is obtained averaging products of the ln K, h and C realizations on the estimation points and times, and the positions and times with data of the analyzed variables. The estimation points are the positions at which estimates of ln K, h or C are gathered. In an analogous way, the estimation times are those at which estimates of any of the three variables are gathered. 3) Finally the ln K, h and C estimate are obtained using the space-time ensemble Kalman filter. The realization mean for each one
Reactive transport modeling of coupled inorganic and organic processes in groundwater
Energy Technology Data Exchange (ETDEWEB)
Brun, Adam
1997-12-31
The main goals of this project are to develop and apply a reactive transport code for simulation of coupled organic and inorganic processes in the pollution plume in the ground water down-gradient from the Vejen landfill, Denmark. The detailed field investigations in this aquifer have previously revealed a complex pattern of strongly interdependent organic and inorganic processes. These processes occur simultaneously in a flow and transport system where the mixing of reactive species is influenced by the rather complex geology in the vicinity of the landfill. The removal of organic matter is influenced by the presence of various electron acceptors that also are involved in various inorganic geochemical reactions. It was concluded from the investigations that degradation of organic matter, complexation, mineral precipitation and dissolution, ion-exchange and inorganic redox reactions, as a minimum, should be included in the formulation of the model. The coupling of the organic and inorganic processes is developed based on a literature study. All inorganic processes are as an approximation described as equilibriumm processes. The organic processes are described by a maximum degradation rate that is decreased according to the availability of the participants in the processes, the actual pH, and the presence of inhibiting species. The reactive transport code consists of three separate codes, a flow and transport code, a geochemical code, and a biodegradation code. An iterative solution scheme couples the three codes. The coupled code was successfully verified for simple problems for which analytical solutions exist. For more complex problems the code was tested on synthetic cases and expected plume behavior was successfully simulated. Application of the code to the Vejen landfill aquifer was successful to the degree that the redox zonation down-gradient from the landfill was simulated correctly and that several of the simulated plumes showed a reasonable agreement with
Solute dilution at the Borden and Cape Cod groundwater tracer tests
Thierrin, Joseph; Kitanidis, Peter K.
1994-01-01
This study presents an analysis of the rate of dilution of a conservative nonreactive tracer in two well-known field experiments: The Borden (Ontario, Canada) experiment and the Cape Cod (Massachusetts) experiment. In evaluating the dilution of injected sodium bromide, in addition to computing the second spatial moments, we have used the dilution index and the reactor ratio. The dilution index is a measure of the formation volume occupied by the solute plume, and the reactor ratio is a shape factor, which measures how stretched and deformed the plume is. Unlike the second moments, which may go up or down during an experiment, the dilution index should increase monotonically. The results for both plumes were quite similar. After an initial period the dilution index increased linearly with time, which is macroscopically equivalent to transport in two-dimensional uniform flow. The reactor ratio was relatively constant during the period of the experiments. Their values, about 0.72 for the Borden test and 0.63 for the Cape Cod test, indicate that the Cape Cod plume was more stretched and deformed than the Borden plume. The maximum concentration, which is an alternative to the dilution index for quantifying dilution, was found to be more erratic and more susceptible to sampling error.
Directory of Open Access Journals (Sweden)
Jacek Waniewski
2016-01-01
Full Text Available During peritoneal dialysis (PD, the peritoneal membrane undergoes ageing processes that affect its function. Here we analyzed associations of patient age and dialysis vintage with parameters of peritoneal transport of fluid and solutes, directly measured and estimated based on the pore model, for individual patients. Thirty-three patients (15 females; age 60 (21–87 years; median time on PD 19 (3–100 months underwent sequential peritoneal equilibration test. Dialysis vintage and patient age did not correlate. Estimation of parameters of the two-pore model of peritoneal transport was performed. The estimated fluid transport parameters, including hydraulic permeability (LpS, fraction of ultrasmall pores (αu, osmotic conductance for glucose (OCG, and peritoneal absorption, were generally independent of solute transport parameters (diffusive mass transport parameters. Fluid transport parameters correlated whereas transport parameters for small solutes and proteins did not correlate with dialysis vintage and patient age. Although LpS and OCG were lower for older patients and those with long dialysis vintage, αu was higher. Thus, fluid transport parameters—rather than solute transport parameters—are linked to dialysis vintage and patient age and should therefore be included when monitoring processes linked to ageing of the peritoneal membrane.
Waniewski, Jacek; Antosiewicz, Stefan; Baczynski, Daniel; Poleszczuk, Jan; Pietribiasi, Mauro; Lindholm, Bengt; Wankowicz, Zofia
2016-01-01
During peritoneal dialysis (PD), the peritoneal membrane undergoes ageing processes that affect its function. Here we analyzed associations of patient age and dialysis vintage with parameters of peritoneal transport of fluid and solutes, directly measured and estimated based on the pore model, for individual patients. Thirty-three patients (15 females; age 60 (21-87) years; median time on PD 19 (3-100) months) underwent sequential peritoneal equilibration test. Dialysis vintage and patient age did not correlate. Estimation of parameters of the two-pore model of peritoneal transport was performed. The estimated fluid transport parameters, including hydraulic permeability (LpS), fraction of ultrasmall pores (α u), osmotic conductance for glucose (OCG), and peritoneal absorption, were generally independent of solute transport parameters (diffusive mass transport parameters). Fluid transport parameters correlated whereas transport parameters for small solutes and proteins did not correlate with dialysis vintage and patient age. Although LpS and OCG were lower for older patients and those with long dialysis vintage, αu was higher. Thus, fluid transport parameters--rather than solute transport parameters--are linked to dialysis vintage and patient age and should therefore be included when monitoring processes linked to ageing of the peritoneal membrane.
Zhao, Yuqing; Zhang, You-Kuan; Liang, Xiuyu
2016-08-01
A semi-analytical solution was presented for groundwater flow due to pumping in a leaky sloping fault-zone aquifer surrounded by permeable matrices. The flow in the aquifer was descried by a three-dimensional flow equation, and the flow in the upper and lower matrix blocks are described by a one-dimensional flow equation. A first-order free-water surface equation at the outcrop of the fault-zone aquifer was used to describe the water table condition. The Laplace domain solution was derived using Laplace transform and finite Fourier transform techniques and the semi-analytical solutions in the real time domain were evaluated using the numerical inverse Laplace transform method. The solution was in excellent agreement with Theis solution combined with superposition principle as well as the solution of Huang et al. (2014). It was found that the drawdown increases as the sloping angle of the aquifer increases in early time and the impact of the angle is insignificant after pumping for a long time. The free-water surface boundary as additional source recharges the fault aquifer and significantly affect the drawdown at later time. The surrounding permeable matrices have a strong influence on drawdown but this influence can be neglected when the ratio of the specific storage and the ratio of the hydraulic conductivity of the matrices to those of the fault aquifer are less than 0.001.
Directory of Open Access Journals (Sweden)
M. A. Gusyev
2013-03-01
Full Text Available Here we present a general approach of calibrating transient transport models to tritium concentrations in river waters developed for the MT3DMS/MODFLOW model of the western Lake Taupo catchment, New Zealand. Tritium has a known pulse-shaped input to groundwater systems due to the bomb tritium in the early 1960s and, with its radioactive half-life of 12.32 yr, allows for the determination of the groundwater age. In the transport model, the tritium input (measured in rainfall passes through the groundwater system, and the simulated tritium concentrations are matched to the measured tritium concentrations in the river and stream outlets for the Waihaha, Whanganui, Whareroa, Kuratau and Omori catchments from 2000–2007. For the Kuratau River, tritium was also measured between 1960 and 1970, which allowed us to fine-tune the transport model for the simulated bomb-peak tritium concentrations. In order to incorporate small surface water features in detail, an 80 m uniform grid cell size was selected in the steady-state MODFLOW model for the model area of 1072 km2. The groundwater flow model was first calibrated to groundwater levels and stream baseflow observations. Then, the transient tritium transport MT3DMS model was matched to the measured tritium concentrations in streams and rivers, which are the natural discharge of the groundwater system. The tritium concentrations in the rivers and streams correspond to the residence time of the water in the groundwater system (groundwater age and mixing of water with different age. The transport model output showed a good agreement with the measured tritium values. Finally, the tritium-calibrated MT3DMS model is applied to simulate groundwater ages, which are used to obtain groundwater age distributions with mean residence times (MRTs in streams and rivers for the five catchments. The effect of regional and local hydrogeology on the simulated groundwater ages is investigated by demonstrating groundwater ages
Energy Technology Data Exchange (ETDEWEB)
Simmons, C.S.; Cole, C.R.
1985-05-01
This document was written to provide guidance to managers and site operators on how ground-water transport codes should be selected for assessing burial site performance. There is a need for a formal approach to selecting appropriate codes from the multitude of potentially useful ground-water transport codes that are currently available. Code selection is a problem that requires more than merely considering mathematical equation-solving methods. These guidelines are very general and flexible and are also meant for developing systems simulation models to be used to assess the environmental safety of low-level waste burial facilities. Code selection is only a single aspect of the overall objective of developing a systems simulation model for a burial site. The guidance given here is mainly directed toward applications-oriented users, but managers and site operators need to be familiar with this information to direct the development of scientifically credible and defensible transport assessment models. Some specific advice for managers and site operators on how to direct a modeling exercise is based on the following five steps: identify specific questions and study objectives; establish costs and schedules for achieving answers; enlist the aid of professional model applications group; decide on approach with applications group and guide code selection; and facilitate the availability of site-specific data. These five steps for managers/site operators are discussed in detail following an explanation of the nine systems model development steps, which are presented first to clarify what code selection entails.
Energy Technology Data Exchange (ETDEWEB)
Robinson, K.L.
1997-09-01
Between 1976 and 1986, groundwater samples from more than 60 locations in the vicinity of the Waste Isolation Pilot Plant site were collected and analyzed for a variety of major, minor, and trace solutes. Most of the samples were from the Rustler Formation (the Culebra Dolomite, the Magenta Dolomite, or the zone at the contact between the Rustler and underlying Salado Formations) or the Dewey Lake Red Beds. The analytical data from the laboratories are presented here with accompanying discussions of sample collection methods, supporting field measurements, and laboratory analytical methods. A comparison of four data sets and a preliminary evaluation of the data for the major solutes (Cl{sup {minus}}, SO{sub 4}{sup {minus}2}, Na, K, Ca, and Mg) shows that the data for samples analyzed by UNC/Bendix for SNL seem to be the most reliable, but that at some locations, samples representative of the native, unperturbed groundwater have not been collected. At other locations, the water chemistry has apparently changed between sampling episodes.
Cook, S. J.; Li, X.; Watanabe, N.; Atwill, R.; Puente, C. E.; Harter, T.
2010-12-01
Land applications to crops of diluted animal manure associated with concentrated animal feeding operations (CAFOs) and field discharges from municipal wastewater treatment plants are potential pathways for the contamination of shallow domestic and agricultural wells by pathogenic microorganisms. Sampling of soil and groundwater for the indicator and pathogenic microorganisms; Enterococcus spp., Escherichia coli, Campylobacter spp. and Salmonella was undertaken at two CAFOs in the San Joaquin Valley, California between 2006 and 2009. Observed concentrations are highly variable in both magnitude and frequency of detection and indicated no clear relationship to field applications or seasonal effects. To investigate if the observed variability in microorganism concentrations in groundwater could be attributed to aquifer heterogeneity, we developed multiple conceptual frameworks employing nonpoint source loading functions and groundwater transport models to simulate a shallow agricultural monitoring well catchment. We developed both, homogenous and heterogeneous aquifer representations, the latter using stochastic transition probability Markov chain representation. Also, we developd homogeneous and spatio-temporally heterogeneous loading models. Model sensitivity to conceptual frameworks, transport parameters, and spatio-temporal variations in diffuse pathogen loading at the water table was determined by comparing simulated frequency of pathogen detection with measured monitoring well breakthrough curves. Model results indicate that field scale aquifer heterogeneity cannot fully account for the variation in concentrations observed in shallow monitoring wells and that microorganism loading at the water table must also be highly heterogeneous. A two dimensional Neyman-Scott cluster process was found to provide the best representation of heterogeneity in recharge concentration and is conceptually consistent with the presence of low attenuation transport pathways in the
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Based on the first linearized Boussinesq equation, the analytical solution of the transient groundwater model, which is used for describing phreatic flow in a semiinfinite aquifer bounded by a linear stream and subjected to time-dependent vertical seepage, is derived out by Laplace transform and the convolution integral.According to the mathematical characteristics of the solution, different methods for estimating aquifer parameters are constructed to satisfy different hydrological conditions.Then, the equation for estimating water exchange between stream and aquifer is proposed, and a recursion equation or estimating the intensity of phreatic evaporation is also proposed.A phreatic aquifer stream system located in Huaibei Plain, Anhui Province, China, is taken as an example to demonstrate the estimation process of the methods stated herein.
Electrical characterization of non-Fickian transport in groundwater and hyporheic systems
Singha, Kamini; Pidlisecky, Adam; Day-Lewis, Frederick D.; Gooseff, Michael N.
2008-04-01
Recent work indicates that processes controlling solute mass transfer between mobile and less mobile domains in porous media may be quantified by combining electrical geophysical methods and electrically conductive tracers. Whereas direct geochemical measurements of solute preferentially sample the mobile domain, electrical geophysical methods are sensitive to changes in bulk electrical conductivity (bulk EC) and therefore sample EC in both the mobile and immobile domains. Consequently, the conductivity difference between direct geochemical samples and remotely sensed electrical geophysical measurements may provide an indication of mass transfer rates and mobile and immobile porosities in situ. Here we present (1) an overview of a theoretical framework for determining parameters controlling mass transfer with electrical resistivity in situ; (2) a review of a case study estimating mass transfer processes in a pilot-scale aquifer storage recovery test; and (3) an example application of this method for estimating mass transfer in watershed settings between streams and the hyporheic corridor. We demonstrate that numerical simulations of electrical resistivity studies of the stream/hyporheic boundary can help constrain volumes and rates of mobile-immobile mass transfer. We conclude with directions for future research applying electrical geophysics to understand field-scale transport in aquifer and fluvial systems subject to rate-limited mass transfer.
Electrical characterization of non-Fickian transport in groundwater and hyporheic systems
Singha, K.; Pidlisecky, A.; Day-Lewis, F. D.; Gooseff, M.N.
2010-01-01
Recent work indicates that processes controlling solute mass transfer between mobile and less mobile domains in porous media may be quantified by combining electrical geophysical methods and electrically conductive tracers. Whereas direct geochemical measurements of solute preferentially sample the mobile domain, electrical geophysical methods are sensitive to changes in bulk electrical conductivity (bulk EC) and therefore sample EC in both the mobile and immobile domains. Consequently, the conductivity difference between direct geochemical samples and remotely sensed electrical geophysical measurements may provide an indication of mass transfer rates and mobile and immobile porosities in situ. Here we present (1) an overview of a theoretical framework for determining parameters controlling mass transfer with electrical resistivity in situ; (2) a review of a case study estimating mass transfer processes in a pilot-scale aquifer storage recovery test; and (3) an example application of this method for estimating mass transfer in watershed settings between streams and the hyporheic corridor. We demonstrate that numerical simulations of electrical resistivity studies of the stream/hyporheic boundary can help constrain volumes and rates of mobile-immobile mass transfer. We conclude with directions for future research applying electrical geophysics to understand field-scale transport in aquifer and fluvial systems subject to rate-limited mass transfer.
Energy Technology Data Exchange (ETDEWEB)
Gustafsson, Lars-Goeran; Sassner, Mona (DHI Sverige AB, Stockholm (Sweden)); Bosson, Emma (Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden))
2008-12-15
The Swedish Nuclear Fuel and Waste Management Company (SKB) is performing site investigations at two different locations in Sweden, referred to as the Forsmark and Laxemar areas, with the objective of siting a final repository for high-level radioactive waste. Data from the site investigations are used in a variety of modelling activities. This report presents model development and results of numerical transport modelling based on the numerical flow modelling of surface water and near-surface groundwater at the Forsmark site. The numerical modelling was performed using the modelling tool MIKE SHE and is based on the site data and conceptual model of the Forsmark areas. This report presents solute transport applications based on both particle tracking simulations and advection-dispersion calculations. The MIKE SHE model is the basis for the transport modelling presented in this report. Simulation cases relevant for the transport from a deep geological repository have been studied, but also the pattern of near surface recharge and discharge areas. When the main part of the modelling work presented in this report was carried out, the flow modelling of the Forsmark site was not finalised. Thus, the focus of this work is to describe the sensitivity to different transport parameters, and not to point out specific areas as discharge areas from a future repository (this is to be done later, within the framework of the safety assessment). In the last chapter, however, results based on simulations with the re-calibrated MIKE SHE flow model are presented. The results from the MIKE SHE water movement calculations were used by cycling the calculated transient flow field for a selected one-year period as many times as needed to achieve the desired simulation period. The solute source was located either in the bedrock or on top of the model. In total, 15 different transport simulation cases were studied. Five of the simulations were particle tracking simulations, whereas the rest
Dam, van J.C.
2000-01-01
Water flow and solute transport in top soils are important elements in many environmental studies. The agro- and ecohydrological model SWAP (Soil-Water-Plant-Atmosphere) has been developed to simulate simultaneously water flow, solute transport, heat flow and crop growth at field scale level. The ma
Goldstein, Steven J; Abdel-Fattah, Amr I; Murrell, Michael T; Dobson, Patrick F; Norman, Deborah E; Amato, Ronald S; Nunn, Andrew J
2010-03-01
Uranium-series data for groundwater samples from the Nopal I uranium ore deposit were obtained to place constraints on radionuclide transport and hydrologic processes for a nuclear waste repository located in fractured, unsaturated volcanic tuff. Decreasing uranium concentrations for wells drilled in 2003 are consistent with a simple physical mixing model that indicates that groundwater velocities are low ( approximately 10 m/y). Uranium isotopic constraints, well productivities, and radon systematics also suggest limited groundwater mixing and slow flow in the saturated zone. Uranium isotopic systematics for seepage water collected in the mine adit show a spatial dependence which is consistent with longer water-rock interaction times and higher uranium dissolution inputs at the front adit where the deposit is located. Uranium-series disequilibria measurements for mostly unsaturated zone samples indicate that (230)Th/(238)U activity ratios range from 0.005 to 0.48 and (226)Ra/(238)U activity ratios range from 0.006 to 113. (239)Pu/(238)U mass ratios for the saturated zone are 1000 times lower than the U mobility. Saturated zone mobility decreases in the order (238)U approximately (226)Ra > (230)Th approximately (239)Pu. Radium and thorium appear to have higher mobility in the unsaturated zone based on U-series data from fractures and seepage water near the deposit.
Energy Technology Data Exchange (ETDEWEB)
Goldstein, S.J.; Abdel-Fattah, A.I.; Murrell, M.T.; Dobson, P.F.; Norman, D.E.; Amato, R.S.; Nunn, A. J.
2009-10-01
Uranium-series data for groundwater samples from the Nopal I uranium ore deposit were obtained to place constraints on radionuclide transport and hydrologic processes for a nuclear waste repository located in fractured, unsaturated volcanic tuff. Decreasing uranium concentrations for wells drilled in 2003 are consistent with a simple physical mixing model that indicates that groundwater velocities are low ({approx}10 m/y). Uranium isotopic constraints, well productivities, and radon systematics also suggest limited groundwater mixing and slow flow in the saturated zone. Uranium isotopic systematics for seepage water collected in the mine adit show a spatial dependence which is consistent with longer water-rock interaction times and higher uranium dissolution inputs at the front adit where the deposit is located. Uranium-series disequilibria measurements for mostly unsaturated zone samples indicate that {sup 230}Th/{sup 238}U activity ratios range from 0.005-0.48 and {sup 226}Ra/{sup 238}U activity ratios range from 0.006-113. {sup 239}Pu/{sup 238}U mass ratios for the saturated zone are <2 x 10{sup -14}, and Pu mobility in the saturated zone is >1000 times lower than the U mobility. Saturated zone mobility decreases in the order {sup 238}U{approx}{sup 226}Ra > {sup 230}Th{approx}{sup 239}Pu. Radium and thorium appear to have higher mobility in the unsaturated zone based on U-series data from fractures and seepage water near the deposit.
Energy Technology Data Exchange (ETDEWEB)
Kwicklis, Edward Michael [Los Alamos National Laboratory; Becker, Naomi M [Los Alamos National Laboratory; Ruskauff, Gregory [NAVARRO-INTERA, LLC.; De Novio, Nicole [GOLDER AND ASSOC.; Wilborn, Bill [US DOE NNSA NSO
2010-11-10
A set of groundwater flow and transport models were created for the Central Testing Area of Frenchman Flat at the former Nevada Test Site to investigate the long-term consequences of a radionuclide migration experiment that was done between 1975 and 1990. In this experiment, radionuclide migration was induced from a small nuclear test conducted below the water table by pumping a well 91 m away. After radionuclides arrived at the pumping well, the contaminated effluent was discharged to an unlined ditch leading to a playa where it was expected to evaporate. However, recent data from a well near the ditch and results from detailed models of the experiment by LLNL personnel have convincingly demonstrated that radionuclides from the ditch eventually reached the water table some 220 m below land surface. The models presented in this paper combine aspects of these detailed models with concepts of basin-scale flow to estimate the likely extent of contamination resulting from this experiment over the next 1,000 years. The models demonstrate that because regulatory limits for radionuclide concentrations are exceeded only by tritium and the half-life of tritium is relatively short (12.3 years), the maximum extent of contaminated groundwater has or will soon be reached, after which time the contaminated plume will begin to shrink because of radioactive decay. The models also show that past and future groundwater pumping from water supply wells within Frenchman Flat basin will have negligible effects on the extent of the plume.
Institute of Scientific and Technical Information of China (English)
LI Xun; YANG Zeping; ZHENG Zhihong; WU Hongmei
2008-01-01
In order to know the mechanism of groundwater transport and the variation of ion concentrations in the near-field of the high-level radioactive waste repository, the whole process was simulated by EOS3 module of TOUGHREACT. Generally, the pH and cation concentrations vary obviously in the near-field saturated zone due to interaction between groundwater and bentonite. Moreover, the simulated results showed that calcite precipitation could not cause obvious variations in the porosity of media in the near-filed if the chemical components and their concentrations of groundwater and bentonite pore water are similar to those used in this study.
Energy Technology Data Exchange (ETDEWEB)
Moran, J E; McNab, W; Esser, B; Hudson, G; Carle, S; Beller, H; Kane, S; Tompson, A B; Letain, T; Moore, K; Eaton, G; Leif, R; Moody-Bartel, C; Singleton, M
2005-06-29
A critical component of the State Water Resource Control Board's Groundwater Ambient Monitoring and Assessment (GAMA) Program is to assess the major threats to groundwater resources that supply drinking water to Californians (Belitz et al., 2004). Nitrate is the most pervasive and intractable contaminant in California groundwater and is the focus of special studies under the GAMA program. This report presents results of a study of nitrate contamination in the aquifer beneath the cities of Morgan Hill and Gilroy, CA, in the Llagas Subbasin of Santa Clara County, where high nitrate levels affect several hundred private domestic wells. The main objectives of the study are: (1) to identify the main source(s) of nitrate that issue a flux to the shallow regional aquifer (2) to determine whether denitrification plays a role in the fate of nitrate in the subbasin and (3) to assess the impact that a nitrate management plan implemented by the local water agency has had on the flux of nitrate to the regional aquifer. Analyses of 56 well water samples for major anions and cations, nitrogen and oxygen isotopes of nitrate, dissolved excess nitrogen, tritium and groundwater age, and trace organic compounds, show that synthetic fertilizer is the most likely source of nitrate in highly contaminated wells, and that denitrification is not a significant process in the fate of nitrate in the subbasin except in the area of recycled water application. In addition to identifying contaminant sources, these methods offer a deeper understanding of how the severity and extent of contamination are affected by hydrogeology and groundwater management practices. In the Llagas subbasin, the nitrate problem is amplified in the shallow aquifer because it is highly vulnerable with high vertical recharge rates and rapid lateral transport, but the deeper aquifers are relatively more protected by laterally extensive aquitards. Artificial recharge delivers low-nitrate water and provides a means of
Muna, Joseph T.; Prescott, Kevin
2011-08-01
Traditionally, freight transport and telematics solutions that exploit the GPS capabilities of in- vehicle devices to provide innovative Location Based Services (LBS) including track and trace transport systems have been the preserve of a select cluster of transport operators and organisations with the financial resources to develop the requisite custom software and hardware on which they are deployed. The average cost of outfitting a typical transport vehicle or truck with the latest Intelligent Transport System (ITS) increases the cost of the vehicle by anything from a couple to several thousand Euros, depending on the complexity and completeness of the solution. Though this does not generally deter large fleet transport owners since they typically get Return on Investment (ROI) based on economies of scale, it presents a barrier for the smaller independent entities that constitute the majority of freight transport operators [1].The North Sea Freight Intelligent Transport Solution (NS FRITS), a project co-funded by the European Commission Interreg IVB North Sea Region Programme, aims to make acquisition of such transport solutions easier for those organisations that cannot afford the expensive, bespoke systems used by their larger competitors.The project addresses transport security threats by developing a system capable of informing major actors along the freight logistics supply chain, of changing circumstances within the region's major transport corridors and between transport modes. The project also addresses issues of freight volumes, inter-modality, congestion and eco-mobility [2].
High Order Numerical Solution of Integral Transport Equation in Slab Geometry
Institute of Scientific and Technical Information of China (English)
沈智军; 袁光伟; 沈隆钧
2002-01-01
@@ There are some common numerical methods for solving neutron transport equation, which including the well-known discrete ordinates method, PN approximation and integral transport methods[1]. There exists certain singularities in the solution of transport equation near the boundary and interface[2]. It gives rise to the difficulty in the construction of high order accurate numerical methods. The numerical solution obtained by now can not attain the second order convergent accuracy[3,4].
Li, Tianxin; Li, Li; Song, Hongqing; Meng, Linglong; Zhang, Shuli; Huang, Gang
2016-01-01
This study focused on using analytical and numerical models to develop and manage groundwater resources, and predict the effects of management measurements in the groundwater system. Movement of contaminants can be studied based on groundwater flow characteristics. This study can be used for prediction of ion concentration and evaluation of groundwater pollution as the theoretical basis. The Yimin open-pit mine is located in the northern part of the Inner Mongolia Autonomous Region of China. High concentrations of iron and manganese are observed in Yimin open-pit mine because of exploitation and pumping that have increased the concentration of the ions in groundwater. In this study, iron was considered as an index of contamination, and the solute model was calibrated using concentration observations from 14 wells in 2014. The groundwater flow model and analytical solutions were used in this study to forecast pollution concentration and variation trend after calibration. With continuous pumping, contaminants will migrate, and become enriched, towards the wellhead in the flow direction. The concentration of the contaminants and the range of pollution increase with the flow rate increased. The suitable flow rate of single well should be <380 m/day at Yimin open-pit for the standard value of pollution concentration.
Effects of climate and sewer condition on virus transport to groundwater
Pathogen contamination from leaky sanitary sewers poses a threat to groundwater quality in urban areas, yet the spatial and temporal dimensions of this contamination are not well understood. In this study, 16 monitoring wells and six municipal wells were repeatedly sampled for human enteric viruses....
Effect of hydrochemical conditions in transport properties of viruses in groundwater
Sadeghi, G.R.
2012-01-01
Knowledge of virus removal in subsurface environments is pivotal for assessing the risk of viral contamination of drinking water wells and to adequately protect groundwater resources. Laboratory and field experiments are necessary to obtain values for kinetic parameters needed to describe virus
Solutions of Multi Objective Fuzzy Transportation Problems with Non-Linear Membership Functions
Directory of Open Access Journals (Sweden)
Dr. M. S. Annie Christi
2016-11-01
Full Text Available Multi-objective transportation problem with fuzzy interval numbers are considered. The solution of linear MOTP is obtained by using non-linear membership functions. The optimal compromise solution obtained is compared with the solution got by using a linear membership function. Some numerical examples are presented to illustrate this.
Shojae Ghias, Masoumeh; Therrien, René; Molson, John; Lemieux, Jean-Michel
2016-12-01
Numerical simulations of groundwater flow and heat transport are used to provide insight into the interaction between shallow groundwater flow and thermal dynamics related to permafrost thaw and thaw settlement at the Iqaluit Airport taxiway, Nunavut, Canada. A conceptual model is first developed for the site and a corresponding two-dimensional numerical model is calibrated to the observed ground temperatures. Future climate-warming impacts on the thermal regime and flow system are then simulated based on climate scenarios proposed by the Intergovernmental Panel on Climate Change (IPCC). Under climate warming, surface snow cover is identified as the leading factor affecting permafrost degradation, including its role in increasing the sensitivity of permafrost degradation to changes in various hydrogeological factors. In this case, advective heat transport plays a relatively minor, but non-negligible, role compared to conductive heat transport, due to the significant extent of low-permeability soil close to surface. Conductive heat transport, which is strongly affected by the surface snow layer, controls the release of unfrozen water and the depth of the active layer as well as the magnitude of thaw settlement and frost heave. Under the warmest climate-warming scenario with an average annual temperature increase of 3.23 °C for the period of 2011-2100, the simulations suggest that the maximum depth of the active layer will increase from 2 m in 2012 to 8.8 m in 2100 and, over the same time period, thaw settlement along the airport taxiway will increase from 0.11 m to at least 0.17 m.
Shojae Ghias, Masoumeh; Therrien, René; Molson, John; Lemieux, Jean-Michel
2017-05-01
Numerical simulations of groundwater flow and heat transport are used to provide insight into the interaction between shallow groundwater flow and thermal dynamics related to permafrost thaw and thaw settlement at the Iqaluit Airport taxiway, Nunavut, Canada. A conceptual model is first developed for the site and a corresponding two-dimensional numerical model is calibrated to the observed ground temperatures. Future climate-warming impacts on the thermal regime and flow system are then simulated based on climate scenarios proposed by the Intergovernmental Panel on Climate Change (IPCC). Under climate warming, surface snow cover is identified as the leading factor affecting permafrost degradation, including its role in increasing the sensitivity of permafrost degradation to changes in various hydrogeological factors. In this case, advective heat transport plays a relatively minor, but non-negligible, role compared to conductive heat transport, due to the significant extent of low-permeability soil close to surface. Conductive heat transport, which is strongly affected by the surface snow layer, controls the release of unfrozen water and the depth of the active layer as well as the magnitude of thaw settlement and frost heave. Under the warmest climate-warming scenario with an average annual temperature increase of 3.23 °C for the period of 2011-2100, the simulations suggest that the maximum depth of the active layer will increase from 2 m in 2012 to 8.8 m in 2100 and, over the same time period, thaw settlement along the airport taxiway will increase from 0.11 m to at least 0.17 m.
Directory of Open Access Journals (Sweden)
M. Golzar
2014-01-01
Full Text Available Recently, iron nanoparticles have attracted more attention for groundwater remediation due to its potential to reduce subsurface contaminants such as PCBs, chlorinated solvents, and heavy metals. The magnetic properties of iron nanoparticles cause to attach to each other and form bigger colloid particles of iron nanoparticles with more rapid sedimentation rate in aqueous environment. Using the surfactants such as poly acrylic acid (PAA prevents iron nanoparticles from forming large flocs that may cause sedimentation and so increases transport distance of the nanoparticles. In this study, the transport of iron oxide nanoparticles (Fe3O4 stabilized with PAA in a one-dimensional porous media (column was investigated. The slurries with concentrations of 20,100 and 500 (mg/L were injected into the bottom of the column under hydraulic gradients of 0.125, 0.375, and 0.625. The results obtained from experiments were compared with the results obtained from numerical solution of advection-dispersion equation based on the classical colloid filtration theory (CFT. The experimental and simulated breakthrough curves showed that CFT is able to predict the transport and fate of iron oxide nanoparticles stabilized with PAA (up to concentration 500 ppm in a porous media.
Energy Technology Data Exchange (ETDEWEB)
Nathan Bryant
2008-05-01
This document presents a summary and framework of available transport data and other information directly relevant to the development of the Rainier Mesa/Shoshone Mountain (RMSM) Corrective Action Unit (CAU) 99 groundwater transport model. Where appropriate, data and information documented elsewhere are briefly summarized with reference to the complete documentation.
Simulating water, solute, and heat transport in the subsurface with the VS2DI software package
Healy, R.W.
2008-01-01
The software package VS2DI was developed by the U.S. Geological Survey for simulating water, solute, and heat transport in variably saturated porous media. The package consists of a graphical preprocessor to facilitate construction of a simulation, a postprocessor for visualizing simulation results, and two numerical models that solve for flow and solute transport (VS2DT) and flow and heat transport (VS2DH). The finite-difference method is used to solve the Richards equation for flow and the advection-dispersion equation for solute or heat transport. This study presents a brief description of the VS2DI package, an overview of the various types of problems that have been addressed with the package, and an analysis of the advantages and limitations of the package. A review of other models and modeling approaches for studying water, solute, and heat transport also is provided. ?? Soil Science Society of America. All rights reserved.
Green transportation logistics: the quest for win-win solutions
DEFF Research Database (Denmark)
This book examines the state of the art in green transportation logistics from the perspective of balancing environmental performance in the transportation supply chain while also satisfying traditional economic performance criteria. Part of the book is drawn from the recently completed European...... Union project Super Green, a three-year project intended to promote the development of European freight corridors in an environmentally friendly manner. Additional chapters cover both the methodological base and the application context of green transportation logistics. Individual chapters look......-down, pop-up”, where in a change in one aspect of a problem can cause another troubling aspect to arise. For example, speed reduction in maritime transportation can reduce emissions and fuel costs, but could require additional ships and could raise in-transit inventory costs. Or, regulations to reduce...
UrbanTransport Solution An Experience From Prague
African Journals Online (AJOL)
unique firstlady
upsurge in the use of private cars which was not possible during ... associated with road transport like its impact on environment, accidents, congestion, but these are ... struggling with huge increase in car ownership and use. Roadway ...
Effects of Aging and Colloids on Iron Nanoparticle Transport in Groundwater
Johnson, R. L.; Tratnyek, P. G.; Nurmi, J. T.
2007-12-01
Most studies of manufactured nanoparticle transport in aquifer materials have used "fresh" particles in homogenous solutions. However, the role of particle aging and the presence of other colloidal materials may have a significant impact on mobility. We have examined both of these processes using reactive nano-iron particles (RNIP), dynamic light scattering, column studies, and deep-bed filtration theory. In the absence of colloidal materials, RNIP are rapidly removed from porous media by coagulation and attachment to aquifer materials (due in part to their magnetic properties). However, upon aging (in the presence of oxidants ranging in strength from water to carbon tetrachloride), the outer shell of the RNIP will be converted to oxides that are less magnetic and have very different surface charges that result in different sticking coefficients. The presence of colloids (both organic and inorganic) may modify the surfaces of aquifer materials and/or bind with the nanoparticles, and as a consequence, aggregation and sticking coefficients of the nanoparticles can also be significantly altered.
Energy Technology Data Exchange (ETDEWEB)
Ahmed Hassan
2003-01-01
Many sites of groundwater contamination rely heavily on complex numerical models of flow and transport to develop closure plans. This has created a need for tools and approaches that can be used to build confidence in model predictions and make it apparent to regulators, policy makers, and the public that these models are sufficient for decision making. This confidence building is a long-term iterative process and it is this process that should be termed ''model validation.'' Model validation is a process not an end result. That is, the process of model validation cannot always assure acceptable prediction or quality of the model. Rather, it provides safeguard against faulty models or inadequately developed and tested models. Therefore, development of a systematic approach for evaluating and validating subsurface predictive models and guiding field activities for data collection and long-term monitoring is strongly needed. This report presents a review of model validation studies that pertain to groundwater flow and transport modeling. Definitions, literature debates, previously proposed validation strategies, and conferences and symposia that focused on subsurface model validation are reviewed and discussed. The review is general in nature, but the focus of the discussion is on site-specific, predictive groundwater models that are used for making decisions regarding remediation activities and site closure. An attempt is made to compile most of the published studies on groundwater model validation and assemble what has been proposed or used for validating subsurface models. The aim is to provide a reasonable starting point to aid the development of the validation plan for the groundwater flow and transport model of the Faultless nuclear test conducted at the Central Nevada Test Area (CNTA). The review of previous studies on model validation shows that there does not exist a set of specific procedures and tests that can be easily adapted and
Phosphate transporters: a tale of two solute carrier families.
Virkki, Leila V; Biber, Jürg; Murer, Heini; Forster, Ian C
2007-09-01
Phosphate is an essential component of life and must be actively transported into cells against its electrochemical gradient. In vertebrates, two unrelated families of Na+ -dependent P(i) transporters carry out this task. Remarkably, the two families transport different P(i) species: whereas type II Na+/P(i) cotransporters (SCL34) prefer divalent HPO(4)(2-), type III Na(+)/P(i) cotransporters (SLC20) transport monovalent H2PO(4)(-). The SCL34 family comprises both electrogenic and electroneutral members that are expressed in various epithelia and other polarized cells. Through regulated activity in apical membranes of the gut and kidney, they maintain body P(i) homeostasis, and in salivary and mammary glands, liver, and testes they play a role in modulating the P(i) content of luminal fluids. The two SLC20 family members PiT-1 and PiT-2 are electrogenic and ubiquitously expressed and may serve a housekeeping role for cell P(i) homeostasis; however, also more specific roles are emerging for these transporters in, for example, bone mineralization. In this review, we focus on recent advances in the characterization of the transport kinetics, structure-function relationships, and physiological implications of having two distinct Na+/P(i) cotransporter families.
Hunt, Allen G; Ghanbarian, Behzad
2013-01-01
We apply our theory of conservative solute transport, based on concepts from percolation theory, directly and without modification to reactive solute transport. This theory has previously been shown to predict the observed range of dispersivity values for conservative solute transport over ten orders of magnitude of length scale. We now show that the temporal dependence derived for the solute velocity accurately predicts the time-dependence for the weathering of silicate minerals over nine orders of magnitude of time scale, while its predicted length dependence agrees with data obtained for reaction rates over five orders of magnitude of length scale. In both cases, it is possible to unify lab and field results. Thus, net reaction rates appear to be limited by solute transport velocities. We suggest the possible relevance of our results to landscape evolution of the earth's terrestrial surface.
Shen, Meng; Lueptow, Richard M
2016-01-01
The Angstrom-scale transport characteristics of water and six different solutes, methanol, ethanol, 2-propanol, urea, Na+, and Cl-, were studied for a polyamide reverse osmosis (RO) membrane, FT-30, using non-equilibrium molecular dynamics (NEMD) simulations. Results indicate that water transport increases with an increasing fraction of connected percolated free volume, or water-accessible open space, in the membrane polymer structure. This free volume is enhanced by the dynamic structure of the membrane at the molecular level as it swells when hydrated and vibrates due to molecular collisions allowing a continuous path connecting the opposite membrane surfaces. The tortuous paths available for transport of solutes result in Brownian motion of solute molecules and hopping from pore to pore as they pass through the polymer network structure of the membrane. The transport of alcohol solutes decreases for solutes with larger Van der Waals volume, which corresponds to less available percolated free volume, or sol...
Silliman, S. E.; Zheng, L.; Conwell, P.
Laboratory experiments on heterogeneous porous media (otherwise known as intermediate scale experiments, or ISEs) have been increasingly relied upon by hydrogeologists for the study of saturated and unsaturated groundwater systems. Among the many ongoing applications of ISEs is the study of fluid flow and the transport of conservative solutes in correlated permeability fields. Recent advances in ISE design have provided the capability of creating correlated permeability fields in the laboratory. This capability is important in the application of ISEs for the assessment of recent stochastic theories. In addition, pressure-transducer technology and visualization methods have provided the potential for ISEs to be used in characterizing the spatial distributions of both hydraulic head and local water velocity within correlated permeability fields. Finally, various methods are available for characterizing temporal variations in the spatial distribution (and, thereby, the spatial moments) of solute concentrations within ISEs. It is concluded, therefore, that recent developments in experimental techniques have provided an opportunity to use ISEs as important tools in the continuing study of fluid flow and the transport of conservative solutes in heterogeneous, saturated porous media. Résumé Les hydrogéologues se sont progressivement appuyés sur des expériences de laboratoire sur des milieux poreux hétérogènes (connus aussi par l'expression "Expériences àéchelle intermédiaire", ISE) pour étudier les zones saturées et non saturées des aquifères. Parmi les nombreuses applications en cours des ISE, il faut noter l'étude de l'écoulement de fluide et le transport de solutés conservatifs dans des champs aux perméabilités corrélées. Les récents progrès du protocole des ISE ont donné la possibilité de créer des champs de perméabilités corrélées au laboratoire. Cette possibilité est importante dans l'application des ISE pour l'évaluation des th
Umari, A.M.; Gorelick, S.M.
1986-01-01
It is possible to obtain analytic solutions to the groundwater flow and solute transport equations if space variables are discretized but time is left continuous. From these solutions, hydraulic head and concentration fields for any future time can be obtained without ' marching ' through intermediate time steps. This analytical approach involves matrix exponentiation and is referred to as the Matrix Exponential Time Advancement (META) method. Two algorithms are presented for the META method, one for symmetric and the other for non-symmetric exponent matrices. A numerical accuracy indicator, referred to as the matrix condition number, was defined and used to determine the maximum number of significant figures that may be lost in the META method computations. The relative computational and storage requirements of the META method with respect to the time marching method increase with the number of nodes in the discretized problem. The potential greater accuracy of the META method and the associated greater reliability through use of the matrix condition number have to be weighed against this increased relative computational and storage requirements of this approach as the number of nodes becomes large. For a particular number of nodes, the META method may be computationally more efficient than the time-marching method, depending on the size of time steps used in the latter. A numerical example illustrates application of the META method to a sample ground-water-flow problem. (Author 's abstract)
Solute or Heat Transport in a Flat Duct
Directory of Open Access Journals (Sweden)
Elijah Johnson
2008-01-01
Full Text Available Steady state solute and heat transfer for laminar flow in a flat duct has been widely studied[1-4]. The same problem in a circular tube is called the Graetz Problem[5,6]. The transfer rate of solute and heat from fluids is of importance in a number of processes, such as diffusion of drugs in the blood stream and the uptake of environmental contaminants by animals in aquatic media[7]. In this study the rate of solute or heat transfer from fluids was determined by solving the associated differential equation. Solution by the series approach in the complex plane was used with a series that had a gaussian factor. The eigenfunctions and eigenvalues involved were examined for two different sets of boundary conditions.
Groundwater contributions to metal transport in a small river affected by mining and smelting waste
Energy Technology Data Exchange (ETDEWEB)
Coynel, A.; Schafer, J.; Dabrin, A.; Girardot, N.; Blanc, G. [University of Bordeaux, Talence (France)
2007-08-15
The Riou Mort watershed, strongly affected by former coal mining and ZEE ore treatment, has been the major source of the historical polymetallic pollution of the Lot-Garonne-Gironde fluvial-estuarine system. Two decades after the end of ore treatment, the former industrial area still contributes important amounts of metals/metalloids from various, partly unidentified, sources to the downstream river system. This study presents the high spatial variability of metal/metalloid (Cd, Zn, As, Sb, U, V) concentrations in water and suspended particulate matter (SPM) from eight observation sites during a short, intense flood event. Despite important dilution effects, the observed concentration levels at the different sites suggested additional Cd and Zn inputs, probably from polluted groundwater. This formerly unknown metal source was then localized and characterized by sampling water and SPM along two longitudinal profiles during different hydrological situations. Groundwater inputs of 'truly dissolved' (<0.02pm) Cd and Zn occurred along -200m, contributing 43% and 28% to the total annual (2004) Cd and Zn fluxes in the Riou Mort River. The estimated groundwater concentrations of Cd and Zn (2500-6700 and 83,000-170,000 mu g1{sup -1}, respectively) in the source zone were consistent with values measured in samples from the near aquifer (5400-13,000 and 200,000-400,000 mu g1{sup -1}). The present work induced concrete remediation actions (pumping and treatment of the polluted groundwater), that are expected to strongly reduce dissolved Cd and Zn emissions into the Riou Mort River.
Continuous monitoring of water flow and solute transport using vadose zone monitoring technology
Dahan, O.
2009-04-01
Groundwater contamination is usually attributed to pollution events that initiate on land surface. These may be related to various sources such as industrial, urban or agricultural, and may appear as point or non point sources, through a single accidental event or a continuous pollution process. In all cases, groundwater pollution is a consequence of pollutant transport processes that take place in the vadose zone above the water table. Attempts to control pollution events and prevent groundwater contamination usually involve groundwater monitoring programs. This, however, can not provide any protection against contamination since pollution identification in groundwater is clear evidence that the groundwater is already polluted and contaminants have already traversed the entire vadose zone. Accordingly, an efficient monitoring program that aims at providing information that may prevent groundwater pollution has to include vadose-zone monitoring systems. Such system should provide real-time information on the hydrological and chemical properties of the percolating water and serve as an early warning system capable of detecting pollution events in their early stages before arrival of contaminants to groundwater. Recently, a vadose-zone monitoring system (VMS) was developed to allow continuous monitoring of the hydrological and chemical properties of percolating water in the deep vadose zone. The VMS includes flexible time-domain reflectometry (FTDR) probes for continuous tracking of water content profiles, and vadose-zone sampling ports (VSPs) for frequent sampling of the deep vadose pore water at multiple depths. The monitoring probes and sampling ports are installed through uncased slanted boreholes using a flexible sleeve that allows attachment of the monitoring devices to the borehole walls while achieving good contact between the sensors and the undisturbed sediment column. The system has been successfully implemented in several studies on water flow and
Groundwater contributions to metal transport in a small river affected by mining and smelting waste.
Coynel, Alexandra; Schäfer, Jörg; Dabrin, Aymeric; Girardot, Naïg; Blanc, Gérard
2007-08-01
The Riou Mort watershed, strongly affected by former coal mining and Zn ore treatment, has been the major source of the historical polymetallic pollution of the Lot-Garonne-Gironde fluvial-estuarine system. Two decades after the end of ore treatment, the former industrial area still contributes important amounts of metals/metalloids from various, partly unidentified, sources to the downstream river system. This study presents the high spatial variability of metal/metalloid (Cd, Zn, As, Sb, U, V) concentrations in water and suspended particulate matter (SPM) from eight observation sites during a short, intense flood event. Despite important dilution effects, the observed concentration levels at the different sites suggested additional Cd and Zn inputs, probably from polluted groundwater. This formerly unknown metal source was then localized and characterized by sampling water and SPM along two longitudinal profiles during different hydrological situations. Groundwater inputs of "truly dissolved" (treatment of the polluted groundwater), that are expected to strongly reduce dissolved Cd and Zn emissions into the Riou Mort River.
Light-driven solute transport in Halobacterium halobium
Lanyi, J. K.
1979-01-01
The cell membrane of Halobacterium halobium exhibits differential regions which contain crystalline arrays of a single kind of protein, termed bacteriorhodopsin. This bacterial retinal-protein complex resembles the visual pigment and, after the absorption of protons, translocates H(+) across the cell membrane, leading to an electrochemical gradient for protons between the inside and the outside of the cell. Thus, light is an alternate source of energy in these bacteria, in addition to terminal oxidation. The paper deals with work on light-driven transport in H. halobium with cell envelope vesicles. The discussion covers light-driven movements of H(+), Na(+), and K(+); light-driven amino acid transport; and apparent allosteric control of amino acid transport. The scheme of energy coupling in H. halobium vesicles appears simple, its quantitative details are quite complex and reveal regulatory phenomena. More knowledge is required of the way the coupling components are regulated by the ion gradients present.
Optimal dynamic management of groundwater pollutant sources.
Gorelick, S.M.; Remson, I.
1982-01-01
The linear programing-superposition method is presented for managing multiple sources of groundwater pollution over time. The method uses any linear solute transport simulation model to generate a unit source-concentration response matrix that is incorporated into a management model. -from Authors
Numerical Solution of the Equation of Electron Transport in Matter
Golovin, A I
2002-01-01
One introduces a numerical approach to solve equation of fast electron transport in a matter in plane and spherical geometry with regard to fluctuations of energy losses and generation of secondary electrons. Calculation results are shown to be in line with the experimental data. One compared the introduced approach with the method of moments
Brine transport in porous media self-similar solutions
C.J. van Duijn (Hans); L.A. Peletier (Bert); R.J. Schotting
1996-01-01
textabstractIn this paper we analyze a model for brine transport in porous media, which includes a mass balance for the fluid, a mass balance for salt, Darcy's law and an equation of state, which relates the fluid density to the salt mass fraction. This model incorporates the effect of local volume
Lohse, K. A.; Gallo, E.; Carlson, M.; Riha, K. M.; Brooks, P. D.; McIntosh, J. C.; Sorooshian, A.; Michalski, G. M.; Meixner, T.
2011-12-01
Semi-arid regions are experiencing disproportionate increases in human population and land transformation worldwide, taxing limited water resources and altering nitrogen (N) biogeochemistry. How the redistribution of water and N by urbanization affects semi-arid ecosystems and downstream water quality (e.g. drinking water) is unclear. Understanding these interactions and their feedbacks will be critical for developing science-based management strategies to sustain these limited resources. This is especially true in the US where some of the fastest growing urban areas are in semi-arid ecosystems, where N and water cycles are accelerated, and intimately coupled, and where runoff from urban ecosystems is actively managed to augment a limited water supply to the growing human population. Here we synthesize several ongoing studies from the Tucson Basin in Arizona and examine how increasing urban land cover is altering rainfall-runoff relationships, groundwater recharge, water quality, and long range transport of atmospheric N. Studies across 5 catchments varying in impervious land cover showed that only the least impervious catchment responded to antecedent moisture conditions while hydrologic responses were not statistically related to antecedent rainfall conditions at more impervious sites. Regression models indicated that rainfall depth, imperviousness, and their combined effect control discharge and runoff ratios (p < 0.01, r2 = 0.91 and 0.75, respectively). In contrast, runoff quality was not predictably related to imperviousness or catchment size. Rather, rainfall depth and duration, time since antecedent rainfall, and stream channel characteristics and infrastructure controlled runoff chemistry. Groundwater studies showed nonpoint source contamination of CFCs and associated nitrate in areas of rapid recharge along ephemeral channels. Aerosol measurements indicate that both long-range transport of N and N emissions from Tucson are being transported and deposited
Analytical solutions for reactive transport under an infiltration-redistribution cycle.
Severino, Gerardo; Indelman, Peter
2004-05-01
Transport of reactive solute in unsaturated soils under an infiltration-redistribution cycle is investigated. The study is based on the model of vertical flow and transport in the unsaturated zone proposed by Indelman et al. [J. Contam. Hydrol. 32 (1998) 77], and generalizes it by accounting for linear nonequilibrium kinetics. An exact analytical solution is derived for an irreversible desorption reaction. The transport of solute obeying linear kinetics is modeled by assuming equilibrium during the redistribution stage. The model which accounts for nonequilibrium during the infiltration and assumes equilibrium at the redistribution stage is termed partial equilibrium infiltration-redistribution model (PEIRM). It allows to derive approximate closed form solutions for transport in one-dimensional homogeneous soils. These solutions are further applied to computing the field-scale concentration by adopting the Dagan and Bresler [Soil Sci. Soc. Am. J. 43 (1979) 461] column model. The effect of soil heterogeneity on the solute spread is investigated by modeling the hydraulic saturated conductivity as a random function of horizontal coordinates. The quality of the PEIRM is illustrated by calculating the critical values of the Damköhler number which provide the achievable accuracy in estimating the solute mass in the mobile phase. The distinguishing feature of transport during the infiltration-redistribution cycle as compared to that of infiltration only is the finite depth of solute penetration. For irreversible desorption, the maximum solute penetration W/theta(r) is determined by the amount of applied water W and the residual water content theta(r). For sorption-desorption kinetics, the maximum depth of penetration z(r)(e, infinity ) also depends on the ratio between the rate of application and the column-saturated conductivity. It is shown that z(r)(e, infinity ) is bounded between the depths W/(theta(r)+K(d)) and W/theta(r) corresponding to the maximum solute
Modeling of Groundwater Flow and Radionuclide Transport at the Climax Mine sub-CAU, Nevada Test Site
Energy Technology Data Exchange (ETDEWEB)
K. Pohlmann; M. Ye; D. Reeves; M. Zavarin; D. Decker; J. Chapman
2007-09-28
The Yucca Flat-Climax Mine Corrective Action Unit (CAU) on the Nevada Test Site comprises 747 underground nuclear detonations, all but three of which were conducted in alluvial, volcanic, and carbonate rocks in Yucca Flat. The remaining three tests were conducted in the very different hydrogeologic setting of the Climax Mine granite stock located in Area 15 at the northern end of Yucca Flat. As part of the Corrective Action Investigation (CAI) for the Yucca Flat-Climax Mine CAU, models of groundwater flow and radionuclide transport will be developed for Yucca Flat. However, two aspects of these CAU-scale models require focused modeling at the northern end of Yucca Flat beyond the capability of these large models. First, boundary conditions and boundary flows along the northern reaches of the Yucca Flat-Climax Mine CAU require evaluation to a higher level of detail than the CAU-scale Yucca Flat model can efficiently provide. Second, radionuclide fluxes from the Climax tests require analysis of flow and transport in fractured granite, a unique hydrologic environment as compared to Yucca Flat proper. This report describes the Climax Mine sub-CAU modeling studies conducted to address these issues, with the results providing a direct feed into the CAI for the Yucca Flat-Climax Mine CAU. Three underground nuclear detonations were conducted for weapons effects testing in the Climax stock between 1962 and 1966: Hard Hat, Pile Driver, and Tiny Tot. Though there is uncertainty regarding the position of the water table in the stock, it is likely that all three tests were conducted in the unsaturated zone. In the early 1980s, the Spent Fuel Test-Climax (SFT-C) was constructed to evaluate the feasibility of retrievable, deep geologic storage of commercial nuclear reactor wastes. Detailed mapping of fractures and faults carried out for the SFT-C studies greatly expanded earlier data sets collected in association with the nuclear tests and provided invaluable information for
Energy Technology Data Exchange (ETDEWEB)
Zhang, Fan [ORNL; Yeh, Gour-Tsyh [University of Central Florida, Orlando; Parker, Jack C [ORNL; Brooks, Scott C [ORNL; Pace, Molly [ORNL; Kim, Young Jin [ORNL; Jardine, Philip M [ORNL; Watson, David B [ORNL
2007-01-01
This paper presents a reaction-based water quality transport model in subsurface flow systems. Transport of chemical species with a variety of chemical and physical processes is mathematically described by M partial differential equations (PDEs). Decomposition via Gauss-Jordan column reduction of the reaction network transforms M species reactive transport equations into two sets of equations: a set of thermodynamic equilibrium equations representing NE equilibrium reactions and a set of reactive transport equations of M-NE kinetic-variables involving no equilibrium reactions (a kinetic-variable is a linear combination of species). The elimination of equilibrium reactions from reactive transport equations allows robust and efficient numerical integration. The model solves the PDEs of kinetic-variables rather than individual chemical species, which reduces the number of reactive transport equations and simplifies the reaction terms in the equations. A variety of numerical methods are investigated for solving the coupled transport and reaction equations. Simulation comparisons with exact solutions were performed to verify numerical accuracy and assess the effectiveness of various numerical strategies to deal with different application circumstances. Two validation examples involving simulations of uranium transport in soil columns are presented to evaluate the ability of the model to simulate reactive transport with complex reaction networks involving both kinetic and equilibrium reactions.
Zhang, Fan; Yeh, Gour-Tsyh; Parker, Jack C.; Brooks, Scott C.; Pace, Molly N.; Kim, Young-Jin; Jardine, Philip M.; Watson, David B.
2007-06-01
This paper presents a reaction-based water quality transport model in subsurface flow systems. Transport of chemical species with a variety of chemical and physical processes is mathematically described by M partial differential equations (PDEs). Decomposition via Gauss-Jordan column reduction of the reaction network transforms M species reactive transport equations into two sets of equations: a set of thermodynamic equilibrium equations representing NE equilibrium reactions and a set of reactive transport equations of M- NE kinetic-variables involving no equilibrium reactions (a kinetic-variable is a linear combination of species). The elimination of equilibrium reactions from reactive transport equations allows robust and efficient numerical integration. The model solves the PDEs of kinetic-variables rather than individual chemical species, which reduces the number of reactive transport equations and simplifies the reaction terms in the equations. A variety of numerical methods are investigated for solving the coupled transport and reaction equations. Simulation comparisons with exact solutions were performed to verify numerical accuracy and assess the effectiveness of various numerical strategies to deal with different application circumstances. Two validation examples involving simulations of uranium transport in soil columns are presented to evaluate the ability of the model to simulate reactive transport with complex reaction networks involving both kinetic and equilibrium reactions.
Modeling solute transport in distribution networks with variable demand and time step sizes.
Energy Technology Data Exchange (ETDEWEB)
Peyton, Chad E.; Bilisoly, Roger Lee; Buchberger, Steven G. (University of Cincinnati, Cincinnati, OH); McKenna, Sean Andrew; Yarrington, Lane
2004-06-01
The effect of variable demands at short time scales on the transport of a solute through a water distribution network has not previously been studied. We simulate flow and transport in a small water distribution network using EPANET to explore the effect of variable demand on solute transport across a range of hydraulic time step scales from 1 minute to 2 hours. We show that variable demands at short time scales can have the following effects: smoothing of a pulse of tracer injected into a distribution network and increasing the variability of both the transport pathway and transport timing through the network. Variable demands are simulated for these different time step sizes using a previously developed Poisson rectangular pulse (PRP) demand generator that considers demand at a node to be a combination of exponentially distributed arrival times with log-normally distributed intensities and durations. Solute is introduced at a tank and at three different network nodes and concentrations are modeled through the system using the Lagrangian transport scheme within EPANET. The transport equations within EPANET assume perfect mixing of the solute within a parcel of water and therefore physical dispersion cannot occur. However, variation in demands along the solute transport path contribute to both removal and distortion of the injected pulse. The model performance measures examined are the distribution of the Reynolds number, the variation in the center of mass of the solute across time, and the transport path and timing of the solute through the network. Variation in all three performance measures is greatest at the shortest time step sizes. As the scale of the time step increases, the variability in these performance measures decreases. The largest time steps produce results that are inconsistent with the results produced by the smaller time steps.
Carter, Janet M.; Moran, Michael J.; Zogorski, John S.; Price, Curtis V.
2012-01-01
Multiple lines of evidence for indicating factors associated with the sources, transport, and fate of chloroform and three other trihalomethanes (THMs) in untreated groundwater were revealed by evaluating low-level analytical results and logistic regression results for THMs. Samples of untreated groundwater from wells used for drinking water were collected from 1996-2007 from 2492 wells across the United States and analyzed for chloroform, bromodichloromethane, dibromochloromethane, and bromoform by a low-level analytical method implemented in April 1996. Using an assessment level of 0.02 μg/L, chloroform was detected in 36.5% of public-well samples and 17.6% of domestic-well samples, with most concentrations less than 1 μg/L. Brominated THMs occurred less frequently than chloroform but more frequently in public-well samples than domestic-well samples. For both public and domestic wells, THMs occurred most frequently in urban areas. Logistic regression analyses showed that the occurrence of THMs was related to nonpoint sources such as urban land use and to point sources like septic systems. The frequent occurrence and concentration distribution pattern of THMs, as well as their frequent co-occurrence with other organic compounds and nitrate, all known to have anthropogenic sources, and the positive associations between THM occurrence and dissolved oxygen and recharge indicate the recycling of water that contains THMs and other anthropogenic contaminants.
Adrian, Yorck; Schneidewind, Uwe; Fernandez-Steeger, Tomas; Azzam, Rafig
2016-04-01
Engineered silver nanoparticles (AgNP) are used in various consumer products such as cloth or personal care products due to their antimicrobial properties (Benn et al., 2010). Their transport behavior in the environment is still under investigation. Previous studies have been focusing on the transport of AgNP in simple test systems with glass beads or soil materials (Braun et al., 2015), but studies investigating aquifer material are rare. However, the protection of fresh water resources in the subsurface is an important part in the protection of human health and the assurance of future economic activities. Therefore, expert knowledge regarding the transport and fate of engineered nanoparticles as potential contaminants in aquifers is essential. Within the scope of the research project NanoMobil funded by German Federal Ministry of Education and Research, the transport and retention behavior of AgNP in aquifer material was investigated under saturated conditions in laboratory columns for different flow velocities, ionic strengths (IS) and background solutions. The used aquifer material consisted mainly of quartz and albite. The quartz grains were partially coated with iron hydroxides and oxides. Furthermore, 1% hematite was present in the silicate dominated aquifer material. The experiments were conducted using NaNO3 and Ca(NO3)2 background solutions to examine the effects of monovalent and divalent cations on the transport of AgNP. Flow velocities in the columns were chosen to represent typical flow velocities of groundwater in the subsurface. For the experiments two mean grain sizes of 0.3 and 0.7 mm were used to investigate the effect of the grain size on the transport behavior. Particle concentration was measured using ICP-MS and particle size was determined using flow field-flow fractionation (FlFFF). HYDRUS-1D (Šimůnek et al., 2013) was used to elucidate the transport and retention processes of the AgNP in the aquifer material. The obtained results show
Cho, Kyu-Hyang; Do, Jun-Young; Park, Jong-Won; Yoon, Kyung-Woo; Kim, Yong-Lim
2013-01-01
Several studies have reported benefits for human peritoneal mesothelial cell function of a neutral-pH dialysate low in glucose degradation products (GDPs). However, the effects of low-GDP solution on ultrafiltration (UF), transport of solutes, and control of body water remain elusive. We therefore investigated the effect of low-GDP solution on UF, solute transport, and control of body water. Among 79 new continuous ambulatory peritoneal dialysis (CAPD) patients, 60 completed a 12-month protocol (28 in a lactate-based high-GDP solution group, 32 in a lactate-based low-GDP solution group). Clinical indices--including 24-hour UF volume (UFV), 24-hour urine volume (UV), residual renal function, and dialysis adequacy--were measured at months 1, 6, and 12. At months 1, 6, and 12, UFV, glucose absorption, 4-hour dialysate-to-plasma (D/P) creatinine, and 1-hour D/P Na(+) were assessed during a modified 4.25% peritoneal equilibration test (PET). Body composition by bioelectric impedance analysis was measured at months 1 and 12 in 26 CAPD patients. Daily UFV was lower in the low-GDP group. Despite similar solute transport and aquaporin function, the low-GDP group also showed lower UFV and higher glucose absorption during the PET. Factors associated with UFV during the PET were lactate-based high-GDP solution and 1-hour D/P Na(+). No differences in volume status and obesity at month 12 were observed, and improvements in hypervolemia were equal in both groups. Compared with the high-GDP group, the low-GDP group had a lower UFV during a PET and a lower daily UFV during the first year after peritoneal dialysis initiation. Although the low-GDP group had a lower daily UFV, no difficulties in controlling edema were encountered.
Progress in solutions of the non-linear Boussinesq groundwater equation (Invited)
Dias, N. L.; Chor, T. L.; de Zarate, A. R.
2013-12-01
An existing truncated series solution, previously obtained from inversion techniques from the solution for the Blasius boundary-layer equation, is obtained directly for the Boussinesq equation in terms of a recurrence relation. The series is found to have a finite radius of convergence, which also explains why previous approximations to the solution of the Boussinesq equation had to resort to a combination of series/Padé expressions for small values of the independent variable and asymptotic approximations for large ones. The radius of convergence is obtained numerically to a high accuracy by means of path integration techniques that are able to identify the complex-plane singularities which determine that radius. New variable transformations are proposed for numerical integration of the equation that avoid singularities at the origin, and further asymptotic approximations, which remain necessary due to the finite radius of convergence, are also obtained. The approach can be extended to non-homogeneous boundary conditions at the origin, which is important in realistic scenarios where an aquifer discharges into a channel of finite-depth. Further recurrence relations are found for series solutions of the non-homogeneous case, as well as their radii of convergence and corresponding asymptotic approximations. Results obtained by joining ten terms of the series solution and the asymptotic approximation obtained by Heaslet and Alksne (1961).
Directory of Open Access Journals (Sweden)
Roman Cherniha
2016-06-01
Full Text Available The nonlinear mathematical model for solute and fluid transport induced by the osmotic pressure of glucose and albumin with the dependence of several parameters on the hydrostatic pressure is described. In particular, the fractional space available for macromolecules (albumin was used as a typical example and fractional fluid void volume were assumed to be different functions of hydrostatic pressure. In order to find non-uniform steady-state solutions analytically, some mathematical restrictions on the model parameters were applied. Exact formulae (involving hypergeometric functions for the density of fluid flux from blood to tissue and the fluid flux across tissues were constructed. In order to justify the applicability of the analytical results obtained, a wide range of numerical simulations were performed. It was found that the analytical formulae can describe with good approximation the fluid and solute transport (especially the rate of ultrafiltration for a wide range of values of the model parameters.
A computational approach to calculate the heat of transport of aqueous solutions
Di Lecce, Silvia; Albrecht, Tim; Bresme, Fernando
2017-01-01
Thermal gradients induce concentration gradients in alkali halide solutions, and the salt migrates towards hot or cold regions depending on the average temperature of the solution. This effect has been interpreted using the heat of transport, which provides a route to rationalize thermophoretic phenomena. Early theories provide estimates of the heat of transport at infinite dilution. These values are used to interpret thermodiffusion (Soret) and thermoelectric (Seebeck) effects. However, accessing heats of transport of individual ions at finite concentration remains an outstanding question both theoretically and experimentally. Here we discuss a computational approach to calculate heats of transport of aqueous solutions at finite concentrations, and apply our method to study lithium chloride solutions at concentrations >0.5 M. The heats of transport are significantly different for Li+ and Cl− ions, unlike what is expected at infinite dilution. We find theoretical evidence for the existence of minima in the Soret coefficient of LiCl, where the magnitude of the heat of transport is maximized. The Seebeck coefficient obtained from the ionic heats of transport varies significantly with temperature and concentration. We identify thermodynamic conditions leading to a maximization of the thermoelectric response of aqueous solutions.
The transport of solutes and colloids in porous media is influenced by a variety of physical and chemical nonequilibrium processes. A combined physical–chemical nonequilibrium (PCNE) model was therefore used to describe general mass transport. The model partitions the pore space into “mobile” and “i...
Energy Technology Data Exchange (ETDEWEB)
Ahmed Hassan
2004-09-01
The groundwater flow and radionuclide transport model characterizing the Shoal underground nuclear test has been accepted by the State of Nevada Division of Environmental Protection. According to the Federal Facility Agreement and Consent Order (FFACO) between DOE and the State of Nevada, the next steps in the closure process for the site are then model validation (or postaudit), the proof-of-concept, and the long-term monitoring stage. This report addresses the development of the validation strategy for the Shoal model, needed for preparing the subsurface Corrective Action Decision Document-Corrective Action Plan and the development of the proof-of-concept tools needed during the five-year monitoring/validation period. The approach builds on a previous model, but is adapted and modified to the site-specific conditions and challenges of the Shoal site.
A note on the solution of fuzzy transportation problem using fuzzy linear system
Directory of Open Access Journals (Sweden)
P. Senthilkumar
2013-08-01
Full Text Available In this paper, we discuss the solution of a fuzzy transportation problem, with fuzzy quantities. The problem is solved in two stages. In the first stage, the fuzzy transportation problem is reduced to crisp system by using the lower and upper bounds of fuzzy quantities. In the second stage, the crisp transportation problems are solved by usual simplex method. The procedure is illustrated with numerical examples.
Groundwater in geologic processes, 2nd edition
Ingebritsen, Steven E.; Sanford, Ward E.; Neuzil, Christopher E.
2006-01-01
Interest in the role of Groundwater in Geologic Processes has increased steadily over the past few decades. Hydrogeologists and geologists are now actively exploring the role of groundwater and other subsurface fluids in such fundamental geologic processes as crustal heat transfer, ore deposition, hydrocarbon migration, earthquakes, tectonic deformation, diagenesis, and metamorphism.Groundwater in Geologic Processes is the first comprehensive treatment of this body of inquiry. Chapters 1 to 4 develop the basic theories of groundwater motion, hydromechanics, solute transport, and heat transport. Chapter 5 applies these theories to regional groundwater flow systems in a generic sense, and Chapters 6 to 13 focus on particular geologic processes and environments. Relative to the first edition of Groundwater in Geologic Processes , this second edition includes a much more comprehensive treatment of hydromechanics (the coupling of groundwater flow and deformation). It also includes new chapters on "compaction and diagenesis," "metamorphism," and "subsea hydrogeology." Finally, it takes advantage of the substantial body of published research that has appeared since the first edition in 1998. The systematic presentation of theory and application, and the problem sets that conclude each chapter, make this book ideal for undergraduate- and graduate-level geology courses (assuming that the students have some background in calculus and introductory chemistry). It also serves as an invaluable reference for researchers and other professionals in the field
Huang, Ching-Sheng; Yeh, Hund-Der; Chang, Chia-Hao
2012-05-01
This paper develops a general mathematical model for describing head fluctuations in an aquifer of long but narrow islands subject to a dual tide effect. The upper boundary condition of the aquifer is represented by an equation combining the simplified free surface equation with a leakage term. Such an equation is considered as a general expression representing the upper boundary condition of a confined, unconfined, or leaky confined aquifer. The closed-form solution of the model represented by two series terms is developed by the direct Fourier method and finite Fourier sine transform. One of the series can reduce to a closed-form expression by means of contour integral and residue theorem. If the width of the island is very large, this solution gives the predicted head almost the same as that of the solution for an aquifer subject to a single tide effect. It is found that the presence of an upper aquitard produces significant vertical flow in the lower leaky confined aquifer even if the aquitard permeability is low. Neglecting such vertical flow may result in an overestimate of hydraulic head in the leaky confined aquifer. The attenuation factor and phase lag predicted from the present solution subject to the dual tide effect agree well with those estimated from 57 day head fluctuation data observed at Garden Island, Australia.
Quantum transport in 1d systems via a master equation approach: numerics and an exact solution
Znidaric, Marko
2010-01-01
We discuss recent findings about properties of quantum nonequilibrium steady states. In particular we focus on transport properties. It is shown that the time dependent density matrix renormalization method can be used successfully to find a stationary solution of Lindblad master equation. Furthermore, for a specific model an exact solution is presented.
New approach to the solution of the Boltzmann radiation transport equation
Boffi, Vinicio C.; Dunn, William L.
1987-03-01
Transport monodimensional stationary solutions for the angular space-energy neutron flux, of interest in radiation penetration problems, are studied by Green's function method. Explicit analytical results for the spatial moments of the sought solution are obtained for the case of an isotropically scattering slab of infinite thickness and of a continuous slowing down model in energy.
The Fourier transform solution for the Green's function of monoenergetic neutron transport theory
Ganapol, Barry D.
2014-01-01
Nearly 45 years ago, Ken Case published his seminal paper on the singular eigenfunction solution for the Green's function of the monoenergetic neutron transport equation with isotropic scattering. Previously, the solution had been obtained by Fourier transform. While it is apparent the two had to be equivalent, a convincing equivalence proof for general anisotropic scattering remained a challenge until now.
Yang, Jianwen
2012-04-01
A general analytical solution is derived by using the Laplace transformation to describe transient reactive silica transport in a conceptualized 2-D system involving a set of parallel fractures embedded in an impermeable host rock matrix, taking into account of hydrodynamic dispersion and advection of silica transport along the fractures, molecular diffusion from each fracture to the intervening rock matrix, and dissolution of quartz. A special analytical solution is also developed by ignoring the longitudinal hydrodynamic dispersion term but remaining other conditions the same. The general and special solutions are in the form of a double infinite integral and a single infinite integral, respectively, and can be evaluated using Gauss-Legendre quadrature technique. A simple criterion is developed to determine under what conditions the general analytical solution can be approximated by the special analytical solution. It is proved analytically that the general solution always lags behind the special solution, unless a dimensionless parameter is less than a critical value. Several illustrative calculations are undertaken to demonstrate the effect of fracture spacing, fracture aperture and fluid flow rate on silica transport. The analytical solutions developed here can serve as a benchmark to validate numerical models that simulate reactive mass transport in fractured porous media.
Cellular automaton model of precipitation/dissolution coupled with solute transport
Karapiperis, T
1995-01-01
ABSTRACT Precipitation/dissolution reactions coupled with solute transport are modelled as a cellular automaton in which solute molecules perform a random walk on a regular lattice and react according to a local probabilistic rule. Stationary solid particles dissolve with a certain probability and, provided solid is already present or the solution is saturated, solute particles have a probability to precipitate. In our simulation of the dissolution of a solid block inside uniformly flowing water we obtain solid precipitation downstream from the original solid edge, in contrast to the standard reaction-transport equations. The observed effect is the result of fluctuations in solute density and diminishes when we average over a larger ensemble. The additional precipitation of solid is accompanied by a substantial reduction in the relatively small solute concentration. The model is appropriate for the study of the rôle of intrinsic fluctuations in the presence of reaction thresholds and can be employed to inves...
SIMULATION OF SOLUTE TRANSPORT IN A PARALLEL SINGLE FRACTURE WITH LBM/MMP MIXED METHOD
Institute of Scientific and Technical Information of China (English)
TAN Ye-fei; ZHOU Zhi-fang
2008-01-01
This article deals with the solute transport in a single fracture with the combination of the Lattice Boltzmann Method (LBM) and Modified Moment Propagation (MMP) method, and this mixed method is proved to have several advantages over the LBM and Moment Propagation (MP) mixed method which leads to negative concentrations under some conditions in computation. The disadvantage of LBM/MP has been overcome to a certain extent. Also, this work presents an LBM solution of modeling single fractures with uniformly or randomly distributed grains, which can provide a new path of applying the LBM in solute transport simulation in fractures.
Solute transport modeling using morphological parameters of step-pool reaches
JiméNez, Mario A.; Wohl, Ellen
2013-03-01
Step-pool systems have been widely studied during the past few years, resulting in enhanced knowledge of mechanisms for sediment transport, energy dissipation and patterns of self-organization. We use rhodamine tracer data collected in nine step-pool reaches during high, intermediate and low flows to explore scaling of solute transport processes. Using the scaling patterns found, we propose an extension of the Aggregated Dead Zone (ADZ) approach for solute transport modeling based on the morphological features of step-pool units and their corresponding inherent variability within a stream reach. In addition to discharge, the reach-average bankfull width, mean step height, and the ratio of pool length to step-to-step length can be used as explanatory variables for the dispersion process within the studied reaches. These variables appeared to be sufficient for estimating ADZ model parameters and simulating solute transport in predictive mode for applications in reaches lacking tracer data.
Gatel, L.; Lauvernet, C.; Carluer, N.; Paniconi, C.
2016-12-01
In the context of the European Water Framework Directive (WFD, 2000/60/EC), which aims to achieve a good ecological and chemical status for all natural aquatic environments, tools to help understand and quantify pesticide transfers in agricultural watersheds are necessary. Models which are physically based and spatially distributed can be particularly useful for representing in detail processes and interactions between the soil surface and subsurface and thus to evaluate the management of landscape elements remediation. The present study aims to test and validate a recently added reactive transport to the coupled surface water/groundwater model CATHY, in order to represent pesticide transfers. Contaminant reactions implemented in CATHY for this study are linear adsorption and degradation (first order kinetics). The advection part of the model is solved according to the finite volume method and reactions are computed on volumes using a sequential non-iterative approach. The CATHY model has been tested on laboratory data and with a Morris sensitivity analysis and is applied now in real field conditions, on a vegetative buffer strip monitored by Irstea in a vineyard catchment (Beaujolais, France). The site is instrumented with lysimeters, flow and solute concentration measurement devices. This test represents a complex step into the model validation, initial and boundary conditions are not fully controlled, and field parameters measurement are not fully known.
Stream riparian zones are often thought of as areas that provide natural remediation for groundwater contaminants, especially agricultural nitrogen (N). While denitrification and vegetative uptake tend to be efficient N removal processes in slow moving shallow groundwater, these mechanisms decrease ...
Background/Question/MethodsGroundwater nitrate contamination affects thousands of households in Oregon's southern Willamette Valley and many more across the Pacific Northwest. The southern Willamette Valley Groundwater Management Area (SWV GWMA) was established in 2004 due to nit...
On the multiplicity of solutions of the nonlinear reactive transport model
Directory of Open Access Journals (Sweden)
Elyas Shivanian
2014-06-01
Full Text Available The generalization of the nonlinear reaction–diffusion model in porous catalysts the so called one dimensional steady state reactive transport model is revisited. This model, which originates also in fluid and solute transport in soft tissues and microvessels, has been recently given analytical solution in terms of Taylor’s series for different families of reaction terms. This article considers the mentioned model without advective transport in the case of including Michaelis–Menten reaction term and shows that it is exactly solvable and furthermore, gives analytical exact solution in the implicit form for further physical interpretation. It is also revealed that the problem may admit unique or dual or even more triple solutions in some domains for the parameters of the model.
Urinary solute transport by ileal segments. I. Effects of nicotinic acid.
Martínez-Piñeiro, L; Mateos, F; Montero, A; Madero, R; Martínez-Piñeiro, J A
1993-12-01
This study was conducted to quantify urinary solute transport by the ileum, using an in vivo human model, and to determine the effect of nicotinic acid on this process. Patients were studied under both basal conditions and niacin therapy. The rates of solute transport were established by analysis of excretion indexes for each solute. Potassium and ammonium were absorbed by the ileum, while phosphorus, sodium and bicarbonate were secreted. The percentage excretion index of sodium and bicarbonate increased by approximately 100 and 600% respectively, causing a significant rise in urinary pH. Although not statistically significant, there was a tendency for chloride to be absorbed and for water to pass into the bowel lumen. Nicotinic acid 3 g/day had no significant effect on urinary solute transport.
Evaluation of Front Morphological Development of Reactive Solute Transport Using Behavior Diagrams
Directory of Open Access Journals (Sweden)
Jui-Sheng Chen
2009-01-01
-uniformity strength ratio and reaction rate constant are identified as two important factors that govern the interaction of dissolution and solute transport in groundwater systems.
Energy Technology Data Exchange (ETDEWEB)
Whelan, G.; McDonald, J.P. [Pacific Northwest National Lab., Richland, WA (United States); Sato, C. [Idaho State Univ., Pocatello, ID (United States)
1996-06-01
This report describes the mathematical formulations used for contaminant fate and transport in the groundwater pathway of the Multimedia Environmental Pollutant Assessment System (MEPAS). It is one in a series of reports that collectively describe the components of MEPAS. The groundwater component of the MEPAS methodology models solute transport through the groundwater environment (i.e., partially saturated and saturated zones). Specifically, this component provides estimates of groundwater contaminant fluxes at various transporting medium interfaces (e.g., water table or aquifer/river interface) and contaminant concentrations at withdrawal wells. Contaminant fluxes at transporting medium interfaces represent boundary conditions for the next medium in which contaminant migration and fate is to be simulated (e.g., groundwater contamination entering a surface-water environment). Contaminant concentrations at withdrawal wells provide contaminant levels for the exposure assessment component of MEPAS. A schematic diagram illustrating the groundwater environment is presented. The migration and fate of contaminants through the groundwater environment are described by the three-dimensional, advective-dispersive equation for solute transport. The results are based on semianalytical solutions (i.e., solutions that require numerical integration) that are well established in the scientific literature. To increase computational efficiency, limits of integration are also identified.
Review of strategies for handling geological uncertainty in groundwater flow and transport modeling
DEFF Research Database (Denmark)
Refsgaard, Jens Christian; Christensen, Steen; Sonnenborg, Torben O.;
2012-01-01
The geologically related uncertainty in groundwater modeling originates from two main sources: geological structures and hydraulic parameter values within these structures. Within a geological structural element the parameter values will always exhibit local scale heterogeneity, which can...... be accounted for, but is often neglected, in assessments of prediction uncertainties. Strategies for assessing prediction uncertainty due to geologically related uncertainty may be divided into three main categories, accounting for uncertainty due to: (a) the geological structure; (b) effective model...... parameters; and (c) model parameters including local scale heterogeneity. The most common methodologies for uncertainty assessments within each of these categories, such as multiple modeling, Monte Carlo analysis, regression analysis and moment equation approach, are briefly described with emphasis...
Kim, M; Kim, S B
2007-02-01
Colloid-facilitated contaminant transport was simulated in this study for the three-phase groundwater system where one or more sorption processes can be described with nonlinear sorption isotherm (Freundlich isotherm). A concise form of contaminant transport equation was derived from the mass balance equation of the contaminant. The developed model was numerically solved by the finite difference method along with the Picard iteration. The simulation results were used to quantitatively analyze the previously reported column data showing nonlinear sorption behavior. The analysis led to the following observations: (i) increases of the distribution coefficient of contaminant between the aqueous and solid phases (K(S)c) and the one between the dissolved natural organic matters and solid phase ( K(S)OM) generate less facilitation (i.e., late arrival of contaminant breakthrough curves (BTCs), and the distribution coefficient of contaminant between the aqueous and the solid phases (K(OM)c) gives the opposite result; (ii) the increase of the Freundlich constant for the sorption isotherm between the aqueous and the solid phases (N(S)c) yields the late arrival of BTC, and the other two Freundlich constants produce the opposite results; (iii) the Freundlich constants generally yield a sharper front as the BTC arrives at later pore volumes, while the distribution coefficients generally yield a more spread of the BTC as it arrives at later volumes. This modeling study shows that transport modeling provides a more efficient analyzing tool than the retardation factor alone concerning the colloid-facilitated contaminant transport with nonlinear sorption processes.
Use of Emulsions with Surfactant Solutions for Viscous Fluids Transportation
Directory of Open Access Journals (Sweden)
Erich Martínez Martín
2015-01-01
Full Text Available The needs for improving the fluidity of fluids is present in the industry, because of the expenses that it takes and its relation with the achievement of the consumers’ demand according to volumes required for its different uses. In this way, the Oil Industry shows several methods to achieve this purpose, taking into account the characteristics of this substance. A method that can be used is the oil emulsions. Emulsions provide good results if they gather certain requirements for its use. In thispaper are shown the results of a research about the use of surfactant solutions in emulsions W/O. Oil transmission is used in this work because of its similar properties to oil.
DEFF Research Database (Denmark)
Andersen, Theis Raaschou; Poulsen, Søren Erbs; Thomsen, Peter
2015-01-01
. Remediation is time consuming and expensive and it is often difficult to identify the original source of the contamination that would otherwise give indications to its extent and composition. Moreover, as cities grew, many contaminations are now located in urban areas where data compilation and remediation...... efforts are often challenged by logistics. The general lack of knowledge about theses contaminations introduces significant uncertainties in the projections on the fate of the contaminant. We carry out a geological characterization of two contaminated sites situated in urban areas. The existing data from...... of the two sites were constructed. The 3D geological models serve as a basis for simulating groundwater flow and contaminant transport at the field sites. The study demonstrates how detailed information about the geological setting in conjunction with contaminant transport modelling, can minimize...
Dynamic estimation of transport demand: solutions - requirements - problems
Energy Technology Data Exchange (ETDEWEB)
Beckmann, K.J.; Rindsfueser, G. [Technische Hochschule Aachen (Germany). Lehrstuhl und Inst. fuer Stadtbauwesen
1999-07-01
The following contribution presents requirements, difficulties and first attempts at modelling a temporal short interval estimation of transport demand. For the simulation of motorway traffic (for an area within the state of North-Rhine-Westfalia, NRW) methods of temporal disaggregation of existing tripmatrices have been worked out within the framework of the Northrhine-Westfalian research cooperation for traffic simulation and environmental impacts 'NRW-FVU' (Nordrhein-Westfaelischer Forschungsverbund Verkehrssimulation und Umweltwirkungen). To simulate urban traffic (example: Wuppertal) methods of estimating temporal short interval trip-matrices were conceived and tested. The matrices were supplied for microsimulation with Cellular Automat (CA) and for the dynamic route choice and traffic assignment (DRUM, Dynamische Routensuche und Umlegung). The comparison of both methods, based on the estimated link loads (ADT and hourly loads), supplies deviations ranging within the mean variation of counted values. It therefore can be inferred that these methods, which are different with regard to computing intensity and data requirements, should be used depending on the tasks and the intended precision of the results. The specific pros and cons are important operational criteria. It also becomes obvious that in future methodical advancements should be examined on the basis of activity(-chain)-based approaches. (orig.)
ORGANIZATIONAL STRESS SOURCES AND SOLUTION PROPOSALS IN PUBLIC TRANSPORT
Directory of Open Access Journals (Sweden)
Mehmet Zennur GÜRBÜZ
2017-09-01
Full Text Available Organizational stress is a concept which can have negative effects for both the workers and the organizations. The purpose of this study is to determine and classify the organizational stress sources that public transportation are exposed to, and to provide suggestions for managing these stress factors. A comprehensive literature survey is made in organizational stress factors and the following classes are identified: work structure, organizational structure, organizational policy, within-company relations and physical conditions. A questionnaire is developed forAnkara EGO General Directorate; applied to 2.137 drivers in Ankara in 2016 with a meaningful return of 1.554 data sets, representing 72% of the population and results are statistically analysed. Descriptive statistics, factor analysis and related validity and regional variance analyses are performed by SPSS (22.0 software. The study revealed that: drivers are exposed to mid-level stess; and most critical stress causes are “injustice and/or insufficiency of salaries”, “aggresive, violent behavior and verbal abuse of passengers towards drivers”, “fear of losing jobs or renewal of the contract”. A significant level of variation in stres levels are identified with respect to different regions of Ankara where drivers are assigned. Suggestions are made in relation to different stres causes to lower the stress levels exposed.
Stochastic models of solute transport in highly heterogeneous geologic media
Energy Technology Data Exchange (ETDEWEB)
Semenov, V.N.; Korotkin, I.A.; Pruess, K.; Goloviznin, V.M.; Sorokovikova, O.S.
2009-09-15
A stochastic model of anomalous diffusion was developed in which transport occurs by random motion of Brownian particles, described by distribution functions of random displacements with heavy (power-law) tails. One variant of an effective algorithm for random function generation with a power-law asymptotic and arbitrary factor of asymmetry is proposed that is based on the Gnedenko-Levy limit theorem and makes it possible to reproduce all known Levy {alpha}-stable fractal processes. A two-dimensional stochastic random walk algorithm has been developed that approximates anomalous diffusion with streamline-dependent and space-dependent parameters. The motivation for introducing such a type of dispersion model is the observed fact that tracers in natural aquifers spread at different super-Fickian rates in different directions. For this and other important cases, stochastic random walk models are the only known way to solve the so-called multiscaling fractional order diffusion equation with space-dependent parameters. Some comparisons of model results and field experiments are presented.
Development of technical solutions for realisation of intelligent transport systems
Directory of Open Access Journals (Sweden)
Anatoliy KULIK
2013-01-01
Full Text Available This article focuses on the development of architecture and technicalsolutions for implementation intelligent transport systems (ITS. The presented system will perform the following functions: monitoring the movement of an object collecting and displaying information about the state of the road, warning of the approaching object to obstacles, routing, as well as control of movement and speed of the output parameters of the recommendations of the movement, the development of intelligent decisions about the choice of optimal routes, intellectual analysis of data (IAD of the style and movement of the driver (the influence of alcohol, IAD on the technical parameters of the vehicle. Thus, it is advisable for ITS to be divided into several subsystems, which are related but are responsible for one or more functional tasks. Consequently, the need for monitoring the movement subsystem, the database on the state of the object database onthe location of an object, display subsystem, the subsystem of control of the road, the engine safety (prevention of obstacles, the subsystem control parameters of movement, routing subsystem.
Flow dynamics and solute transport in unsaturated rock fractures
Energy Technology Data Exchange (ETDEWEB)
Su, Grace Woan-chee [Univ. of California, Berkeley, CA (United States)
1999-10-01
Rock fractures play an important role in flow and contaminant transport in fractured aquifers, production of oil from petroleum reservoirs, and steam generation from geothermal reservoirs. In this dissertation, phenomenological aspects of flow in unsaturated fractures were studied in visualization experiments conducted on a transparent replica of a natural, rough-walled rock fracture for inlet conditions of constant pressure and flow rate over a range of angles of inclination. The experiments demonstrated that infiltrating liquid proceeds through unsaturated rock fractures along non-uniform, localized preferential flow paths. Even in the presence of constant boundary conditions, intermittent flow was a persistent flow feature observed, where portions of the flow channel underwent cycles of snapping and reforming. Two modes of intermittent flow were observed, the pulsating blob mode and the rivulet snapping mode. A conceptual model for the rivulet snapping mode was proposed and examined using idealized, variable-aperture fractures. The frequency of intermittent flow events was measured in several experiments and related to the capillary and Bond numbers to characterize this flow behavior.
Botter, Gianluca; Benettin, Paolo; Rinaldo, Andrea
2015-04-01
Advection-dispersion equations have been extensively used to model flow and transport processes through heterogeneous media like hillslopes and groundwater systems. Therein, the spreading of solute plumes and the shape of the breakthrough curve is known to be controlled by the macrodispersion coefficient, which embeds the underlying heterogeneity of velocities and flowpaths. On a nearly parallel track, the use of travel time distributions (TTDs) has become increasingly widespread in catchment hydrology, to establish a formal linkage between input and output chemographs through suitable transfer functions. Recent theoretical advances and real-world applications have shown that the structure of travel time distributions in time variable flow systems like watersheds is strongly related to the time variability of the water storage and input/output fluxes. The dynamical structure of TTDs has been proved to be effectively parametrized through suitable StorAge Selection (SAS) functions, that express in a spatially integrated fashion how the set of ages available within a control volume are selected and removed by the output fluxes. In this contribution, we analyze the relationship between Advection-Dispersion Models and StorAge Selection Functions, with examples for one-dimensional transport in a finite domain with constant convection and dispersion coefficient. Our results show that when the dispersion is high (say, Pe plane is similar to the distribution of ages available within the storage, thereby leading to uniform SAS functions (random sampling). Implications for the interpretation and the prediction of the chemical response of rivers are discussed through the application of the SAS functions to model solute circulation in highly monitored watersheds belonging to diverse regions of the world. We suggest that the use of Storage Selection functions in different fields of hydrology may bring important advances to our understanding of pollutant persistence in river
Wang, Yahui; Yan, Liming; Ma, Yu
2017-06-01
Applications of the transient Boltzmann transport equation (BTE) have undergone much investigation, such as radiative heat transfer and neutron transport. This paper provides a lattice Boltzmann model to efficiently resolve the multidimensional transient BTE. For a higher angular resolution, enough transport directions are considered while the transient BTE in each direction is treated as a conservation law equation and solved independently. Both macroscopic equations recovered from a Chapman-Enskog expansion and simulated results of typical benchmark problems show not only the second-order accuracy but also the flexibility and applicability of the proposed lattice Boltzmann model. This approach may contribute a powerful technique for the parallel simulation of large-scale engineering and some alternative perspectives for solving the nonlinear transport problem further.
Reactive Solute Transport in Streams: 1. Development of an Equilibrium-Based Model
Runkel, Robert L.; Bencala, Kenneth E.; Broshears, Robert E.; Chapra, Steven C.
1996-02-01
An equilibrium-based solute transport model is developed for the simulation of trace metal fate and transport in streams. The model is formed by coupling a solute transport model with a chemical equilibrium submodel based on MINTEQ. The solute transport model considers the physical processes of advection, dispersion, lateral inflow, and transient storage, while the equilibrium submodel considers the speciation and complexation of aqueous species, precipitation/dissolution and sorption. Within the model, reactions in the water column may result in the formation of solid phases (precipitates and sorbed species) that are subject to downstream transport and settling processes. Solid phases on the streambed may also interact with the water column through dissolution and sorption/desorption reactions. Consideration of both mobile (water-borne) and immobile (streambed) solid phases requires a unique set of governing differential equations and solution techniques that are developed herein. The partial differential equations describing physical transport and the algebraic equations describing chemical equilibria are coupled using the sequential iteration approach.
Reactive solute transport in streams. 1. Development of an equilibrium- based model
Runkel, R.L.; Bencala, K.E.; Broshears, R.E.; Chapra, S.C.
1996-01-01
An equilibrium-based solute transport model is developed for the simulation of trace metal fate and transport in streams. The model is formed by coupling a solute transport model with a chemical equilibrium submodel based on MINTEQ. The solute transport model considers the physical processes of advection, dispersion, lateral inflow, and transient storage, while the equilibrium submodel considers the speciation and complexation of aqueous species, precipitation/dissolution and sorption. Within the model, reactions in the water column may result in the formation of solid phases (precipitates and sorbed species) that are subject to downstream transport and settling processes. Solid phases on the streambed may also interact with the water column through dissolution and sorption/desorption reactions. Consideration of both mobile (water-borne) and immobile (streambed) solid phases requires a unique set of governing differential equations and solution techniques that are developed herein. The partial differential equations describing physical transport and the algebraic equations describing chemical equilibria are coupled using the sequential iteration approach.
LABORATORY EXPERIMENTS ON SOLUTE TRANSPORT IN A PARTIAL TRANSFIXION SINGLE FRACTURE
Institute of Scientific and Technical Information of China (English)
CAI Jin-long; ZHOU Zhi-fang; HUANG Yong
2011-01-01
In the study of solute transport in rough single fracture,the contact area is an important factor.The single fracture is defined as two categories in this article:the full transfixion single freeture and the partial transfixion single fracture.The purpose of this article is to research how the contact area affects the solute transport in partial transfixion single fracture.The contact area is generalized as square blocks with three sizes,and contact rate is variable,a series of experiments for solute transport were conducted in a simulation model which can simulate the two types of fractures in the laboratory.Based on the analysis of the breakthrough curves and the experiment phenomena,it is concluded that the difference of breakthrough curves of various contact rates is evident and increases with the increase of contact rate,the relative error curves reflect the difference of block sizes,and the maximum errors increase from smaller than 0.2 to about 0.8 with the increase of contact rate.These phenomena are also explained qualitatively in this article.It is concluded that the contact area strongly affects solute transport,and the research of channels formed by contact area is useful to further understand the rule of solute transport in partial transfixion single fracture.
Institute of Scientific and Technical Information of China (English)
薛强; 梁冰; 刘晓丽; 李宏艳
2003-01-01
The process of contaminant transport is a problem of multicomponent and multiphase flow in unsaturated zone. Under the presupposition that gas existence affects water transport , a coupled mathematical model of contaminant transport in unsaturated zone has been established based on fluid-solid interaction mechanics theory. The asymptotical solutions to the nonlinear coupling mathematical model were accomplished by the perturbation and integral transformation method. The distribution law of pore pressure,pore water velocity and contaminant concentration in unsaturated zone has been presented under the conditions of with coupling and without coupling gas phase. An example problem was used to provide a quantitative verification and validation of the model. The asymptotical solution was compared with Faust model solution. The comparison results show reasonable agreement between asymptotical solution and Faust solution, and the gas effect and media deformation has a large impact on the contaminant transport. The theoretical basis is provided for forecasting contaminant transport and the determination of the relationship among pressure-saturation-permeability in laboratory.
Sund, N. L.; Bolster, D.; Benson, D. A.
2015-12-01
In order to predict transport of solutes, upscaling techniques are often applied. After the amount of time it takes the solute to sample all of the velocities in the system, the upscaling process is well understood and fairly simple to implement. But in highly heterogeneous velocity fields, this amount of time may be prohibitively long. When there is a need to predict transport at earlier times, the upscaling process is more difficult because the solute tends to stay on or near its initial streamline, inducing a correlation between its average velocity over fixed distances (or times), which must be accounted for. A Spatial Markov model was developed in 2008 that does just that[1]. It accounts for the velocity correlation by treating the transport process as a Markov Chain. This model has been successfully applied to predict solute transport in a large variety of complicated flow fields and is becoming increasing popular. It almost seems as though it works for every situation, but so far no rigorous study has gone into determining its limitations. So we have decided to take a step back and ask: when is this model valid? We understand the asymptotic behavior in the limit as t→ ∞, but what about in the limit as 1/t→ ∞ (or t→ 0)? Are the assumptions of the Spatial Markov model valid over all length (and time) scales? It turns out that the answer is no. At very early times, the transport process is diffusion dominated, leading to non-monotonic correlation between solute particles' average velocity over consecutive space and time steps. The assumptions of the Spatial Markov model only hold after this early diffusive regime ends and the correlation function peaks. We find the location of the peak in the correlation function for transport in simple stratified flows and show the effect of using the Spatial Markov model over length scales on either side of the peak.REFERENCES[1] T.L. Borgne, M. Dentz, J. Carrera: Spatial Markov processes for modeling Lagrangian
Temporal moment analysis of solute transport in a coupled fracture-skin-matrix system
Indian Academy of Sciences (India)
V Renu; G Suresh Kumar
2014-04-01
In the present study, method of temporal moments has been used to analyse the transport characteristics of reactive solute along fracture in a coupled fracture-skin-matrix system. In order to obtain the concentration distribution within the fracture, a system of coupled partial differential equations for fracture, fractureskin and rock-matrix has been solved numerically in a pseudo two-dimensional domain using implicit finite difference method. Subsequently, lower order temporal moments of solute have been computed from the concentration distribution to analyse the transport characteristics of solutes in the fracture. This study has been done by considering an inlet boundary condition of constant continuous source in a single fracture. The effect of various fracture-skin parameters like porosity, thickness and diffusion coefficient on the transport of solutes have been studied by doing sensitivity analyses. The effect of nonlinear sorption and radioactive decay of solutes have also been analysed by carrying out simulations for different sorption intensities and decay constants. Numerical results suggested that the presence of fracture-skin significantly influences the transport characteristics of reactive solutes along the fracture.
Bahr, J.M.
1990-01-01
This paper extends a four-step derivation procedure, previously presented for cases of transport affected by surface reactions, to transport problems involving homogeneous reactions. Derivations for these classes of reactions are used to illustrate the manner in which mathematical differences between reaction classes are reflected in the mathematical derivation procedures required to identify kinetically influenced terms. Simulation results for a case of transport affected by a single solution phase complexation reaction and for a case of transport affected by a precipitation-dissolution reaction are used to demonstrate the nature of departures from equilibrium-controlled transport as well as the use of kinetically influenced terms in determining criteria for the applicability of the local equilibrium assumption. A final derivation for a multireaction problem demonstrates the application of the generalized procedure to a case of transport affected by reactions of several classes. -from Author
Padilla, I. Y.; Cotto, I.; Torres, P. M.
2014-12-01
tap water (30%). Results indicated that most CVOCs on tap water come from groundwater sources. Spatial-temporal analysis of CVOC data shows that transport through karst system is highly heterogeneous variable, and reflect high capacity of the system to store and slowly release contaminants through rate-limited mass transport process.
A comparison of four inverse approaches to groundwater flow and transport parameter identification
DEFF Research Database (Denmark)
Keidser, Allan; Rosbjerg, Dan
1991-01-01
of the log transmissivities are obtained by repeating the optimization of stage one. The formulated objective functions are minimized using Levenberg-Marquardt's algorithm. The models are applied to synthetic two-dimensional transport problems in steady state flow regimes. The "true" log transmissivity...
Stability and transport of graphene oxide nanoparticles in groundwater and surface water
A transport study investigating the effects of natural organic matter (NOM) in the presence of monovalent (KCl) and divalent (CaCl2) salts was performed in a packed bed column. The electrophoretic mobility (EPM) and effective diameter of the graphene oxide nanoparticles (GONPs) were measured as a fu...
Niazi, Nabeel Khan; Bibi, Irshad; Shahid, Muhammad; Ok, Yong Sik; Burton, Edward D; Wang, Hailong; Shaheen, Sabry M; Rinklebe, Jörg; Lüttge, Andreas
2017-09-28
In this study, we examined the removal of arsenite (As(III)) and arsenate (As(V)) by perilla leaf-derived biochars produced at 300 and 700 °C (referred as BC300 and BC700) in aqueous environments. Results revealed that the Langmuir isotherm model provided the best fit for As(III) and As(V) sorption, with the sorption affinity following the order: BC700-As(III) > BC700-As(V) > BC300-As(III) > BC300-As(V) (QL = 3.85-11.01 mg g(-1)). In general, As removal decreased (76-60%) with increasing pH from 7 to 10 except for the BC700-As(III) system, where notably higher As removal (88-90%) occurred at pH from 7 to 9. Surface functional moieties contributed to As sequestration by the biochars examined here. However, significantly higher surface area and aromaticity of BC700 favored a greater As removal compared to BC300, suggesting that surface complexation/precipitation dominated As removal by BC700. Arsenic K-edge X-ray absorption near edge structure (XANES) spectroscopy demonstrated that up to 64% of the added As(V) was reduced to As(III) in BC700- and BC300-As(V) sorption experiments, and in As(III) sorption experiments, partial oxidation of As(III) to As(V) occurred (37-39%). However, XANES spectroscopy was limited to precisely quantify As binding with sulfur species as As2S3-like phase. Both biochars efficiently removed As from natural As-contaminated groundwater (As: 23-190 μg L(-1); n = 12) despite in the presence of co-occurring anions (e.g., CO3(2-), PO4(3-), SO4(2-)) with the highest levels of As removal observed for BC700 (97-100%). Overall, this study highlights that perilla leaf biochars, notably BC700, possessed the greatest ability to remove As from solution and groundwater (drinking water). Significantly, the integrated spectroscopic techniques advanced our understanding to examine complex redox transformation of As(III)/As(V) with biochar, which are crucial to determine fate of As on biochar in aquatic environments. Copyright © 2017
Analytical solutions of a fractional diffusion-advection equation for solar cosmic-ray transport
Energy Technology Data Exchange (ETDEWEB)
Litvinenko, Yuri E.; Effenberger, Frederic, E-mail: yuril@waikato.ac.nz [Department of Mathematics, University of Waikato, P.B. 3105 Hamilton (New Zealand)
2014-12-01
Motivated by recent applications of superdiffusive transport models to shock-accelerated particle distributions in the heliosphere, we analytically solve a one-dimensional fractional diffusion-advection equation for the particle density. We derive an exact Fourier transform solution, simplify it in a weak diffusion approximation, and compare the new solution with previously available analytical results and with a semi-numerical solution based on a Fourier series expansion. We apply the results to the problem of describing the transport of energetic particles, accelerated at a traveling heliospheric shock. Our analysis shows that significant errors may result from assuming an infinite initial distance between the shock and the observer. We argue that the shock travel time should be a parameter of a realistic superdiffusive transport model.
Explicit solutions of the radiative transport equation in the P{sub 3} approximation
Energy Technology Data Exchange (ETDEWEB)
Liemert, André, E-mail: andre.liemert@ilm.uni-ulm.de; Kienle, Alwin [Institut für Lasertechnologien in der Medizin und Meßtechnik an der Universität Ulm, Helmholtzstr.12, Ulm D-89081 (Germany)
2014-11-01
Purpose: Explicit solutions of the monoenergetic radiative transport equation in the P{sub 3} approximation have been derived which can be evaluated with nearly the same computational effort as needed for solving the standard diffusion equation (DE). In detail, the authors considered the important case of a semi-infinite medium which is illuminated by a collimated beam of light. Methods: A combination of the classic spherical harmonics method and the recently developed method of rotated reference frames is used for solving the P{sub 3} equations in closed form. Results: The derived solutions are illustrated and compared to exact solutions of the radiative transport equation obtained via the Monte Carlo (MC) method as well as with other approximated analytical solutions. It is shown that for the considered cases which are relevant for biomedical optics applications, the P{sub 3} approximation is close to the exact solution of the radiative transport equation. Conclusions: The authors derived exact analytical solutions of the P{sub 3} equations under consideration of boundary conditions for defining a semi-infinite medium. The good agreement to Monte Carlo simulations in the investigated domains, for example, in the steady-state and time domains, as well as the short evaluation time needed suggests that the derived equations can replace the often applied solutions of the diffusion equation for the homogeneous semi-infinite medium.
Identification of key target markets for intermodal freight transport solutions in South Africa
Directory of Open Access Journals (Sweden)
Joubert van Eeden
2010-11-01
Full Text Available The Accelerated and Shared Growth Initiative for South Africa (AsgiSA identified South Africa's freight logistics challenges as among the key binding constraints on the country's growth aspirations. The research presented here points to the structural imbalance between road and rail freight transport as one of the key contributors to this state of affairs. Most long-distance corridor transport has been captured by road. However, long-distance transport is a market segment that is very suitable for intermodal transportation : rail is utilised for the high-density, long-distance component and road for the feeder and distribution services at the corridor end points. A market segmentation approach is developed to identify the corridors and industries that are natural candidates for such solutions, thereby paving the way for role-players and stakeholders to initiate a dialogue on the development of appropriate solutions.
TRACKING AND TRACING SOLUTION FOR DANGEROUS GOODS CARRIED BY INTERMODAL TRANSPORT
Directory of Open Access Journals (Sweden)
Marek Kvet
2014-03-01
Full Text Available This paper deals with the problem of designing a complex tracking and tracing solution for dangerous goods transportation with the support of modern information technologies. This research activity presents a part of the “ChemLogTT” [2] project solved at the University of Žilina. The main goal of our contribution is to present basic conception of a complex developed software tool for monitoring and analyzing mentioned dangerous goods transportation.
MODELING OF THE GROUNDWATER TRANSPORT AROUND A DEEP BOREHOLE NUCLEAR WASTE REPOSITORY
Energy Technology Data Exchange (ETDEWEB)
N. Lubchenko; M. Rodríguez-Buño; E.A. Bates; R. Podgorney; E. Baglietto; J. Buongiorno; M.J. Driscoll
2015-04-01
The concept of disposal of high-level nuclear waste in deep boreholes drilled into crystalline bedrock is gaining renewed interest and consideration as a viable mined repository alternative. A large amount of work on conceptual borehole design and preliminary performance assessment has been performed by researchers at MIT, Sandia National Laboratories, SKB (Sweden), and others. Much of this work relied on analytical derivations or, in a few cases, on weakly coupled models of heat, water, and radionuclide transport in the rock. Detailed numerical models are necessary to account for the large heterogeneity of properties (e.g., permeability and salinity vs. depth, diffusion coefficients, etc.) that would be observed at potential borehole disposal sites. A derivation of the FALCON code (Fracturing And Liquid CONvection) was used for the thermal-hydrologic modeling. This code solves the transport equations in porous media in a fully coupled way. The application leverages the flexibility and strengths of the MOOSE framework, developed by Idaho National Laboratory. The current version simulates heat, fluid, and chemical species transport in a fully coupled way allowing the rigorous evaluation of candidate repository site performance. This paper mostly focuses on the modeling of a deep borehole repository under realistic conditions, including modeling of a finite array of boreholes surrounded by undisturbed rock. The decay heat generated by the canisters diffuses into the host rock. Water heating can potentially lead to convection on the scale of thousands of years after the emplacement of the fuel. This convection is tightly coupled to the transport of the dissolved salt, which can suppress convection and reduce the release of the radioactive materials to the aquifer. The purpose of this work has been to evaluate the importance of the borehole array spacing and find the conditions under which convective transport can be ruled out as a radionuclide transport mechanism
Kinetic theory the Chapman-Enskog solution of the transport equation for moderately dense gases
Brush, S G
1972-01-01
Kinetic Theory, Volume 3: The Chapman-Enskog Solution of the Transport Equation for Moderately Dense Gases describes the Chapman-Enskog solution of the transport equation for moderately dense gases. Topics covered range from the propagation of sound in monatomic gases to the kinetic theory of simple and composite monatomic gases and generalizations of the theory to higher densities. The application of kinetic theory to the determination of intermolecular forces is also discussed. This volume is divided into two sections and begins with an introduction to the work of Hilbert, Chapman, and Ensko
Analytical solutions for transport processes fluid mechanics, heat and mass transfer
Brenn, Günter
2017-01-01
This book provides analytical solutions to a number of classical problems in transport processes, i.e. in fluid mechanics, heat and mass transfer. Expanding computing power and more efficient numerical methods have increased the importance of computational tools. However, the interpretation of these results is often difficult and the computational results need to be tested against the analytical results, making analytical solutions a valuable commodity. Furthermore, analytical solutions for transport processes provide a much deeper understanding of the physical phenomena involved in a given process than do corresponding numerical solutions. Though this book primarily addresses the needs of researchers and practitioners, it may also be beneficial for graduate students just entering the field. .
Strategic network design of Java Island fuel supply with production-transportation solution
Dianawati, Fauzia; Farizal, -; Surjandari, Isti; Marzuli, Rully
2011-10-01
This study aims to find more efficient supply network, from refineries / imports to fuel terminal, which still uses the Tanker, Tank Trucks or Rail Tank Wagon with an alternative pipeline that are considered more efficient than other transport modes, as well as gaining pipeline transportation network optimization analysis tailored to the capabilities/ capacity of refinery production and capacity of the pipe mode. With the complexity of the number of 3 point sources of supply, 19 destination of terminal, 4 kinds of products and 4 types of transport modes, transport-production model modified by adding multi-modal transport and investment costs of new pipeline. Then coded in Lingo program which adopts Branch & Bound technique and input the processed data in order to obtain an optimal distribution pattern produced the lowest distribution costs. This B&B solution was also compared with SCO solution which is a metaheuristic method. The results of this study lead to the development of new modes of pipeline connections in amount of 4 alternatives, generated from the optimal solution, but still potentially earned savings of about IDR 1 Trillion per year from cost-efficiency of product procurement and transportation costs.
Energy Technology Data Exchange (ETDEWEB)
Morel, J.E.
1981-01-01
A collocation method is developed for the solution of the one-dimensional neutron transport equation in slab geometry with both symmetric and polarly asymmetric scattering. For the symmetric scattering case, it is found that the collocation method offers a combination of some of the best characteristics of the finite-element and discrete-ordinates methods. For the asymmetric scattering case, it is found that the computational cost of cross-section data processing under the collocation approach can be significantly less than that associated with the discrete-ordinates approach. A general diffusion equation treating both symmetric and asymmetric scattering is developed and used in a synthetic acceleration algorithm to accelerate the iterative convergence of collocation solutions. It is shown that a certain type of asymmetric scattering can radically alter the asymptotic behavior of the transport solution and is mathematically equivalent within the diffusion approximation to particle transport under the influence of an electric field. The method is easily extended to other geometries and higher dimensions. Applications exist in the areas of neutron transport with highly anisotropic scattering (such as that associated with hydrogenous media), charged-particle transport, and particle transport in controlled-fusion plasmas. 23 figures, 6 tables.
Used Fuel Logistics: Decades of Experience with transportation and Interim storage solutions
Energy Technology Data Exchange (ETDEWEB)
Orban, G.; Shelton, C.
2015-07-01
Used fuel inventories are growing worldwide. While some countries have opted for a closed cycle with recycling, numerous countries must expand their interim storage solutions as implementation of permanent repositories is taking more time than foreseen. In both cases transportation capabilities will have to be developed. AREVA TN has an unparalleled expertise with transportation of used fuel. For more than 50 years AREVA TN has safely shipped more than 7,000 used fuel transport casks. The transportation model that was initially developed in the 1970s has been adapted and enhanced over the years to meet more restrictive regulatory requirements and evolving customer needs, and to address public concerns. The numerous “lessons learned” have offered data and guidance that have allowed for also efficient and consistent improvement over the decades. AREVA TN has also an extensive experience with interim dry storage solutions in many countries on-site but also is working with partners to developed consolidated interim storage facility. Both expertise with storage and transportation contribute to safe, secure and smooth continuity of the operations. This paper will describe decades of experience with a very successful transportation program as well as interim storage solutions. (Author)
Joekar-Niasar, V.
2013-01-25
Upscaling electroosmosis in porous media is a challenge due to the complexity and scale-dependent nonlinearities of this coupled phenomenon. "Pore-network modeling" for upscaling electroosmosis from pore scale to Darcy scale can be considered as a promising approach. However, this method requires analytical solutions for flow and transport at pore scale. This study concentrates on the development of analytical solutions of flow and transport in a single rectangular channel under combined effects of electrohydrodynamic forces. These relations will be used in future works for pore-network modeling. The analytical solutions are valid for all regimes of overlapping electrical double layers and have the potential to be extended to nonlinear Boltzmann distribution. The innovative aspects of this study are (a) contribution of overlapping of electrical double layers to the Stokes flow as well as Nernst-Planck transport has been carefully included in the analytical solutions. (b) All important transport mechanisms including advection, diffusion, and electromigration have been included in the analytical solutions. (c) Fully algebraic relations developed in this study can be easily employed to upscale electroosmosis to Darcy scale using pore-network modeling. © 2013 Springer Science+Business Media Dordrecht.
Three-dimensional Solute Transport Modeling in Coupled Soil and Plant Root Systems
2014-01-01
Many environmental and agricultural challenges rely on the proper understanding of water flow and solute transport in soils, for example the carbon cycle, crop growth, irrigation scheduling or fate of pollutants in subsoil. Current modeling approaches typically simulate plant uptake via empirical approaches, which neglect the three-dimensional (3D) root architecture. Yet, nowadays 3D soil-root water and solute models on plant-scale exist, which can be used for assessing the impact of root arc...
Zheng, Chunmiao; Hill, Mary Catherine; Hsieh, Paul A.
2001-01-01
MODFLOW-2000, the newest version of MODFLOW, is a computer program that numerically solves the three-dimensional ground-water flow equation for a porous medium using a finite-difference method. MT3DMS, the successor to MT3D, is a computer program for modeling multi-species solute transport in three-dimensional ground-water systems using multiple solution techniques, including the finite-difference method, the method of characteristics (MOC), and the total-variation-diminishing (TVD) method. This report documents a new version of the Link-MT3DMS Package, which enables MODFLOW-2000 to produce the information needed by MT3DMS, and also discusses new visualization software for MT3DMS. Unlike the Link-MT3D Packages that coordinated previous versions of MODFLOW and MT3D, the new Link-MT3DMS Package requires an input file that, among other things, provides enhanced support for additional MODFLOW sink/source packages and allows list-directed (free) format for the flow model produced flow-transport link file. The report contains four parts: (a) documentation of the Link-MT3DMS Package Version 6 for MODFLOW-2000; (b) discussion of several issues related to simulation setup and input data preparation for running MT3DMS with MODFLOW-2000; (c) description of two test example problems, with comparison to results obtained using another MODFLOW-based transport program; and (d) overview of post-simulation visualization and animation using the U.S. Geological Survey?s Model Viewer.
Transport solutions of the Lamé equations and shock elastic waves
Alexeyeva, L. A.; Kaishybaeva, G. K.
2016-07-01
The Lamé system describing the dynamics of an isotropic elastic medium affected by a steady transport load moving at subsonic, transonic, or supersonic speed is considered. Its fundamental and generalized solutions in a moving frame of reference tied to the transport load are analyzed. Shock waves arising in the medium at supersonic speeds are studied. Conditions on the jump in the stress, displacement rate, and energy across the shock front are obtained using distribution theory. Numerical results concerning the dynamics of an elastic medium influenced by concentrated transport loads moving at sub-, tran- and supersonic speeds are presented.
Impact of Soil Water Flux on Vadose Zone Solute Transport Parameters
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The transport processes of solutes in two soil columns filled with undisturbed soil material collected from an unsaturated sandy aquifer formation in Belgium subjected to a variable upper boundary condition were identified from breakthrough curves measured by means of time domain refiectometry (TDR). Solute breakthrough was measured with 3 TDR probes inserted into each soil column at three different depths at a 10 minutes time interval. In addition, soil water content and pressure head were measured at 3 different depths. Analytical solute transport models were used to estimate the solute dispersion coefficient and average pore-water velocity from the observed breakthrough curves. The results showed that the analytical solutions were suitable in fitting the observed solute transport. The dispersion coefficient was found to be a function of the soil depth and average pore-water velocity, imposed by the soil water flux. The mobile moisture content on the other hand was not correlated with the average pore-water velocity and the dispersion coefficient.
A comprehensive one-dimensional numerical model for solute transport in rivers
Barati Moghaddam, Maryam; Mazaheri, Mehdi; MohammadVali Samani, Jamal
2017-01-01
One of the mechanisms that greatly affect the pollutant transport in rivers, especially in mountain streams, is the effect of transient storage zones. The main effect of these zones is to retain pollutants temporarily and then release them gradually. Transient storage zones indirectly influence all phenomena related to mass transport in rivers. This paper presents the TOASTS (third-order accuracy simulation of transient storage) model to simulate 1-D pollutant transport in rivers with irregular cross-sections under unsteady flow and transient storage zones. The proposed model was verified versus some analytical solutions and a 2-D hydrodynamic model. In addition, in order to demonstrate the model applicability, two hypothetical examples were designed and four sets of well-established frequently cited tracer study data were used. These cases cover different processes governing transport, cross-section types and flow regimes. The results of the TOASTS model, in comparison with two common contaminant transport models, shows better accuracy and numerical stability.
Quantifying the relative contributions of different solute carriers to aggregate substrate transport
Taslimifar, Mehdi; Oparija, Lalita; Verrey, Francois; Kurtcuoglu, Vartan; Olgac, Ufuk; Makrides, Victoria
2017-01-01
Determining the contributions of different transporter species to overall cellular transport is fundamental for understanding the physiological regulation of solutes. We calculated the relative activities of Solute Carrier (SLC) transporters using the Michaelis-Menten equation and global fitting to estimate the normalized maximum transport rate for each transporter (Vmax). Data input were the normalized measured uptake of the essential neutral amino acid (AA) L-leucine (Leu) from concentration-dependence assays performed using Xenopus laevis oocytes. Our methodology was verified by calculating Leu and L-phenylalanine (Phe) data in the presence of competitive substrates and/or inhibitors. Among 9 potentially expressed endogenous X. laevis oocyte Leu transporter species, activities of only the uniporters SLC43A2/LAT4 (and/or SLC43A1/LAT3) and the sodium symporter SLC6A19/B0AT1 were required to account for total uptake. Furthermore, Leu and Phe uptake by heterologously expressed human SLC6A14/ATB0,+ and SLC43A2/LAT4 was accurately calculated. This versatile systems biology approach is useful for analyses where the kinetics of each active protein species can be represented by the Hill equation. Furthermore, its applicable even in the absence of protein expression data. It could potentially be applied, for example, to quantify drug transporter activities in target cells to improve specificity. PMID:28091567
Energy Technology Data Exchange (ETDEWEB)
Simmons, C.S.; Cole, C.R.
1985-08-01
This document was written for the National Low-Level Waste Management Program to provide guidance for managers and site operators who need to select ground-water transport codes for assessing shallow-land burial site performance. The guidance given in this report also serves the needs of applications-oriented users who work under the direction of a manager or site operator. The guidelines are published in two volumes designed to support the needs of users having different technical backgrounds. An executive summary, published separately, gives managers and site operators an overview of the main guideline report. Volume 1, titled ''Guideline Approach,'' consists of Chapters 1 through 5 and a glossary. Chapters 2 through 5 provide the more detailed discussions about the code selection approach. This volume, Volume 2, consists of four appendices reporting on the technical evaluation test cases designed to help verify the accuracy of ground-water transport codes. 20 refs.
Osmosis and solute-solvent drag: fluid transport and fluid exchange in animals and plants.
Hammel, H T; Schlegel, Whitney M
2005-01-01
, (3) the return of interstitial fluid to the vasa recta, (4) return of aqueous humor to the episcleral veins, and (5) flow of phloem from source to sink in higher plants and many more examples of fluid transport and fluid exchange in animal and plant physiology. When a membrane is permeable to water only and when it separates differing aqueous solutions, the flow of water is from the solution with the lower osmotic pressure to the solution with the higher osmotic pressure.
Larson, T.; Sathaye, K.
2014-12-01
A dramatic expansion of hydraulic fracturing and horizontal drilling for natural gas in unconventional reserves is underway. This expansion is fueling considerable public concern, however, that extracted natural gas, reservoir brines and associated fracking fluids may infiltrate to and contaminate shallower (development of a 'bank' of methane depleted in 13C relative to 12C at the front of a plume of fugitive natural gas. These results, therefore, suggest that transport of natural gas through water saturated geological media may complicate attribution methods needed to distinguish thermogenic and microbial methane.
Zurek, A. J.; Witczak, S.; Dulinski, M.; Wachniew, P.; Rozanski, K.; Kania, J.; Postawa, A.; Karczewski, J.; Moscicki, W. J.
2015-02-01
Groundwater-dependent ecosystems (GDEs) have important functions in all climatic zones as they contribute to biological and landscape diversity and provide important economic and social services. Steadily growing anthropogenic pressure on groundwater resources creates a conflict situation between nature and man which are competing for clean and safe sources of water. Such conflicts are particularly noticeable in GDEs located in densely populated regions. A dedicated study was launched in 2010 with the main aim to better understand the functioning of a groundwater-dependent terrestrial ecosystem (GDTE) located in southern Poland. The GDTE consists of a valuable forest stand (Niepolomice Forest) and associated wetland (Wielkie Błoto fen). It relies mostly on groundwater from the shallow Quaternary aquifer and possibly from the deeper Neogene (Bogucice Sands) aquifer. In July 2009 a cluster of new pumping wells abstracting water from the Neogene aquifer was set up 1 km to the northern border of the fen. A conceptual model of the Wielkie Błoto fen area for the natural, pre-exploitation state and for the envisaged future status resulting from intense abstraction of groundwater through the new well field was developed. The main aim of the reported study was to probe the validity of the conceptual model and to quantify the expected anthropogenic impact on the studied GDTE. A wide range of research tools was used. The results obtained through combined geologic, geophysical, geochemical, hydrometric and isotope investigations provide strong evidence for the existence of upward seepage of groundwater from the deeper Neogene aquifer to the shallow Quaternary aquifer supporting the studied GDTE. Simulations of the groundwater flow field in the study area with the aid of a 3-D flow and transport model developed for Bogucice Sands (Neogene) aquifer and calibrated using environmental tracer data and observations of hydraulic head in three different locations on the study area
Energy Technology Data Exchange (ETDEWEB)
Kay H. Birdsell; Kathleen M. Bower; Andrew V. Wolfsberg; Wendy E. Soll; Terry A. Cherry; Tade W. Orr
1999-07-01
Numerical simulations are used to predict the migration of radionuclides from the disposal units at Material Disposal Area G through the vadose zone and into the main aquifer in support of a radiological performance assessment and composite analysis for the site. The calculations are performed with the finite element code, FEHM. The transport of nuclides through the vadose zone is computed using a three-dimensional model that describes the complex mesa top geology of the site. The model incorporates the positions and inventories of thirty-four disposal pits and four shaft fields located at Area G as well as those of proposed future pits and shafts. Only three nuclides, C-14, Tc-99, and I-129, proved to be of concern for the groundwater pathway over a 10,000-year period. The spatial and temporal flux of these three nuclides from the vadose zone is applied as a source term for the three-dimensional saturated zone model of the main aquifer that underlies the site. The movement of these nuclides in the aquifer to a downstream location is calculated, and aquifer concentrations are converted to doses. Doses related to aquifer concentrations are six or more orders of magnitude lower than allowable Department of Energy performance objectives for low-level radioactive waste sites. Numerical studies were used to better understand vadose-zone flow through the dry mesa-top environment at Area G. These studies helped define the final model used to model flow and transport through the vadose zone. The study of transient percolation indicates that a steady flow vadose-zone model is adequate for computing contaminant flux to the aquifer. The fracture flow studies and the investigation of the effect of basalt and pumice properties helped us define appropriate hydrologic properties for the modeling. Finally, the evaporation study helped to justify low infiltration rates.
An analytical approach to the solution of the transport equation for photons
Energy Technology Data Exchange (ETDEWEB)
Reichert, Janice Teresinha, E-mail: janice.reichert@gmail.com [Universidade Tecnologica Federal do Parana (UTFPR), Pato Branco, PR (Brazil); Barichello, Liliane Basso, E-mail: lbaric@mat.ufrgs.br [Universidade Federal do Rio Grande do Sul (UFRS), Porto Alegre, RS (Brazil)
2011-07-01
An analytical solution is developed to the one-dimensional transport equation for photons, for the case which includes spectral dependence. The Klein-Nishina kernel for Compton scattering is considered and an analytical discrete ordinates method, the ADO method, is used to solve the resulting angular dependent problem. Numerical simulations are performed to evaluate the buildup factor. (author)
Pore-network modeling of solute transport and biofilm growth in porous media
Qin, Chao Zhong; Hassanizadeh, S. Majid
2015-01-01
In this work, a pore-network (PN) model for solute transport and biofilm growth in porous media was developed. Compared to previous studies of biofilm growth, it has two new features. First, the constructed pore network gives a better representation of a porous medium. Second, instead of using a con
Modelling Water Flow and Solute Transport for Horticultural and Environmental Management
Feddes, R.A.; Dam, van J.C.
2002-01-01
During the past 10 years, the simulation model SWAP (Soil, Water, Atmosphere, Plant) was developed by the Sub-Department Water Resources of Wageningen University jointly with the Department Water and Environment of Alterra Green World Research. SWAP simulates vertical transport of water, solutes and
Semianalytical Solutions for Transport in Aquifer and Fractured Clay Matrix System
A three-dimensional mathematical model that describes transport of contaminant in a horizontal aquifer with simultaneous diffusion into a fractured clay formation is proposed. A group of analytical solutions is derived based on specific initial and boundary conditions as well as ...
Kokkonen, H T; Chin, H C; Töyräs, J; Jurvelin, J S; Quinn, T M
2017-04-01
Solute transport through the extracellular matrix (ECM) is crucial to chondrocyte metabolism. Cartilage injury affects solute transport in cartilage due to alterations in ECM structure and solute-matrix interactions. Therefore, cartilage injury may be detected by using contrast agent-based clinical imaging. In the present study, effects of mechanical injury on transport of negatively charged contrast agents in cartilage were characterized. Using cartilage plugs injured by mechanical compression protocol, effective partition coefficients and diffusion fluxes of iodine- and gadolinium-based contrast agents were measured using high resolution microCT imaging. For all contrast agents studied, effective diffusion fluxes increased significantly, particularly at early times during the diffusion process (38 and 33% increase after 4 min, P integrity in cartilage superficial zone. This study suggests that alterations in contrast agent diffusion flux, a non-equilibrium transport parameter, provides a more sensitive indicator for assessment of cartilage matrix integrity than partition coefficient and the equilibrium distribution of solute. These findings may help in developing clinical methods of contrast agent-based imaging to detect cartilage injury.
Pore-network modeling of solute transport and biofilm growth in porous media
Qin, Chao Zhong; Hassanizadeh, S. Majid
2015-01-01
In this work, a pore-network (PN) model for solute transport and biofilm growth in porous media was developed. Compared to previous studies of biofilm growth, it has two new features. First, the constructed pore network gives a better representation of a porous medium. Second, instead of using a
Raina, Shweta A; Zhang, Geoff G Z; Alonzo, David E; Wu, Jianwei; Zhu, Donghua; Catron, Nathaniel D; Gao, Yi; Taylor, Lynne S
2014-09-01
Amorphous solid dispersions (ASDs) give rise to supersaturated solutions (solution concentration greater than equilibrium crystalline solubility). We have recently found that supersaturating dosage forms can exhibit the phenomenon of liquid-liquid phase separation (LLPS). Thus, the high supersaturation generated by dissolving ASDs can lead to a two-phase system wherein one phase is an initially nanodimensioned and drug-rich phase and the other is a drug-lean continuous aqueous phase. Herein, the membrane transport of supersaturated solutions, at concentrations above and below the LLPS concentration has been evaluated using a side-by-side diffusion cell. Measurements of solution concentration with time in the receiver cell yield the flux, which reflects the solute thermodynamic activity in the donor cell. As the nominal concentration of solute in the donor cell increases, a linear increase in flux was observed up to the concentration where LLPS occurred. Thereafter, the flux remained essentially constant. Both nifedipine and felodipine solutions exhibit such behavior as long as crystallization is absent. This suggests that there is an upper limit in passive membrane transport that is dictated by the LLPS concentration. These results have several important implications for drug delivery, especially for poorly soluble compounds requiring enabling formulation technologies.
Jackman, A.P.; Walters, R.A.; Kennedy, V.C.
1984-01-01
Models describing low-flow transport of conservative (nonreactive) and reactive solutes, which adsorb on the streambed, are developed and tested. Temporary storage within the bed plays an important role in solute movement. Three different models of bed-storage processes are developed for conservative solutes. One model assumes the bed is a well-mixed, nondiffusing, nonreacting zone. Solute flux into the bed is then proportional to the difference between stream and bed-solute concentrations. A second model assumes that solute is transported within the bed by a vertical diffusion process. The bed-solute concentration, which matches the stream concentration at the interface, varies with depth in the bed according to Fick 's law. A third model assumes convection in the downstream direction occurs in certain parts of the bed, while the mechanism of the first model functions elsewhere. Storage of absorbing species is assumed to occur by equilibrium adsorption within streambed particles. Uptake rate is described by an intraparticle diffusion process. Model equations were solved using finite element numerical methods. Models were calibrated using data from a 24-hour injection of conservative chloride and adsorptive Sr ions at Uvas Creek near Morgan Hill, California. All models predict well except for some overestimation by the adsorption model during dieaway. (USGS)
Solution-processable graphene oxide as an efficient hole transport layer in polymer solar cells.
Li, Shao-Sian; Tu, Kun-Hua; Lin, Chih-Cheng; Chen, Chun-Wei; Chhowalla, Manish
2010-06-22
The utilization of graphene oxide (GO) thin films as the hole transport and electron blocking layer in organic photovoltaics (OPVs) is demonstrated. The incorporation of GO deposited from neutral solutions between the photoactive poly(3-hexylthiophene) (P3HT):phenyl-C61-butyric acid methyl ester (PCBM) layer and the transparent and conducting indium tin oxide (ITO) leads to a decrease in recombination of electrons and holes and leakage currents. This results in a dramatic increase in the OPV efficiencies to values that are comparable to devices fabricated with PEDOT:PSS as the hole transport layer. Our results indicate that GO could be a simple solution-processable alternative to PEDOT:PSS as the effective hole transport and electron blocking layer in OPV and light-emitting diode devices.
New Travelling Wave Solutions of Burgers Equation with Finite Transport Memory
Sakthivel, Rathinasamy; Chun, Changbum; Lee, Jonu
2010-09-01
The nonlinear evolution equations with finite memory have a wide range of applications in science and engineering. The Burgers equation with finite memory transport (time-delayed) describes convection-diffusion processes. In this paper, we establish the new solitary wave solutions for the time-delayed Burgers equation. The extended tanh method and the exp-function method have been employed to reveal these new solutions. Further, we have calculated the numerical solutions of the time-delayed Burgers equation with initial conditions by using the homotopy perturbation method (HPM). Our results show that the extended tanh and exp-function methods are very effective in finding exact solutions of the considered problem and HPM is very powerful in finding numerical solutions with good accuracy for nonlinear partial differential equations without any need of transformation or perturbation
[Groundwater organic pollution source identification technology system research and application].
Wang, Xiao-Hong; Wei, Jia-Hua; Cheng, Zhi-Neng; Liu, Pei-Bin; Ji, Yi-Qun; Zhang, Gan
2013-02-01
Groundwater organic pollutions are found in large amount of locations, and the pollutions are widely spread once onset; which is hard to identify and control. The key process to control and govern groundwater pollution is how to control the sources of pollution and reduce the danger to groundwater. This paper introduced typical contaminated sites as an example; then carried out the source identification studies and established groundwater organic pollution source identification system, finally applied the system to the identification of typical contaminated sites. First, grasp the basis of the contaminated sites of geological and hydrogeological conditions; determine the contaminated sites characteristics of pollutants as carbon tetrachloride, from the large numbers of groundwater analysis and test data; then find the solute transport model of contaminated sites and compound-specific isotope techniques. At last, through groundwater solute transport model and compound-specific isotope technology, determine the distribution of the typical site of organic sources of pollution and pollution status; invest identified potential sources of pollution and sample the soil to analysis. It turns out that the results of two identified historical pollution sources and pollutant concentration distribution are reliable. The results provided the basis for treatment of groundwater pollution.
Wingle, William L.; Poeter, Eileen P.; McKenna, Sean A.
1999-05-01
UNCERT is a 2D and 3D geostatistics, uncertainty analysis and visualization software package applied to ground water flow and contaminant transport modeling. It is a collection of modules that provides tools for linear regression, univariate statistics, semivariogram analysis, inverse-distance gridding, trend-surface analysis, simple and ordinary kriging and discrete conditional indicator simulation. Graphical user interfaces for MODFLOW and MT3D, ground water flow and contaminant transport models, are provided for streamlined data input and result analysis. Visualization tools are included for displaying data input and output. These include, but are not limited to, 2D and 3D scatter plots, histograms, box and whisker plots, 2D contour maps, surface renderings of 2D gridded data and 3D views of gridded data. By design, UNCERT's graphical user interface and visualization tools facilitate model design and analysis. There are few built in restrictions on data set sizes and each module (with two exceptions) can be run in either graphical or batch mode. UNCERT is in the public domain and is available from the World Wide Web with complete on-line and printable (PDF) documentation. UNCERT is written in ANSI-C with a small amount of FORTRAN77, for UNIX workstations running X-Windows and Motif (or Lesstif). This article discusses the features of each module and demonstrates how they can be used individually and in combination. The tools are applicable to a wide range of fields and are currently used by researchers in the ground water, mining, mathematics, chemistry and geophysics, to name a few disciplines.
Joshi, Nitin; Ojha, C. S. P.; Sharma, P. K.
2012-10-01
In this study a conceptual model that accounts for the effects of nonequilibrium contaminant transport in a fractured porous media is developed. Present model accounts for both physical and sorption nonequilibrium. Analytical solution was developed using the Laplace transform technique, which was then numerically inverted to obtain solute concentration in the fracture matrix system. The semianalytical solution developed here can incorporate both semi-infinite and finite fracture matrix extent. In addition, the model can account for flexible boundary conditions and nonzero initial condition in the fracture matrix system. The present semianalytical solution was validated against the existing analytical solutions for the fracture matrix system. In order to differentiate between various sorption/transport mechanism different cases of sorption and mass transfer were analyzed by comparing the breakthrough curves and temporal moments. It was found that significant differences in the signature of sorption and mass transfer exists. Applicability of the developed model was evaluated by simulating the published experimental data of Calcium and Strontium transport in a single fracture. The present model simulated the experimental data reasonably well in comparison to the model based on equilibrium sorption assumption in fracture matrix system, and multi rate mass transfer model.
Salas, J; Ayora, C
2004-03-01
The stability of uranium-bearing minerals in natural environments is of interest to evaluate the feasibility of radioactive waste repositories. The uraninite bodies, UO2(s), in the Oklo district (Gabon) are the result of a natural fission process, which took place 1970 Ma ago. These deposits can be regarded as natural analogues for spent fuel. One of the uraninite bodies, the Okélobondo deposit, is located at a depth of 300 m. Groundwater samples from boreholes located at shallow depths (100-200 m) show neutral to basic pH, anoxic conditions (Eh = 0.10 to -0.05 V) and are saturated with respect to uraninite. In contrast, deeper samples collected in the vicinity of the ore body are oxidising (Eh = 0.32-0.47 V), slightly basic (pH = 7.0-8.5) and undersaturated with respect to uraninite. These oxidising conditions at depth, if present under repository conditions, may affect the stability of uranium oxide. In order to improve our understanding of the observed site geochemistry, the available information on the lithology and groundwater flow was integrated in a reactive transport model. The chemical composition and the pH-Eh values of the water sampled above and in the western side of the Okélobondo deposit can be explained by the interaction of meteoric recharge with pelites, dolomites and sandstones. The dissolution of Fe(II)-silicates and the oxidation of the Fe(II)-aqueous species maintained the pH-Eh distribution along the Fe(2+)-Fe(OH)3(am) equilibrium, with the result that uraninite does not dissolve. This may explain the lower uranium content in the water samples from pelites and dolomites above the Okélobondo deposit. The high Mn/Fe ratio and the high pH-Eh values of the water sampled at depth, close to the Okélobondo deposit, suggest a control by the Mn(2+)-MnOOH(s) equilibrium. This control is attributed to the dissolution of a large rhodochrosite, MnCO3(s), and manganite, MnOOH(s) deposit in the recharge area on the eastern side.
Salas, J.; Ayora, C.
2004-03-01
The stability of uranium-bearing minerals in natural environments is of interest to evaluate the feasibility of radioactive waste repositories. The uraninite bodies, UO 2(s), in the Oklo district (Gabon) are the result of a natural fission process, which took place 1970 Ma ago. These deposits can be regarded as natural analogues for spent fuel. One of the uraninite bodies, the Okélobondo deposit, is located at a depth of 300 m. Groundwater samples from boreholes located at shallow depths (100-200 m) show neutral to basic pH, anoxic conditions (Eh=0.10 to -0.05 V) and are saturated with respect to uraninite. In contrast, deeper samples collected in the vicinity of the ore body are oxidising (Eh=0.32-0.47 V), slightly basic (pH=7.0-8.5) and undersaturated with respect to uraninite. These oxidising conditions at depth, if present under repository conditions, may affect the stability of uranium oxide. In order to improve our understanding of the observed site geochemistry, the available information on the lithology and groundwater flow was integrated in a reactive transport model. The chemical composition and the pH-Eh values of the water sampled above and in the western side of the Okélobondo deposit can be explained by the interaction of meteoric recharge with pelites, dolomites and sandstones. The dissolution of Fe(II)-silicates and the oxidation of the Fe(II)-aqueous species maintained the pH-Eh distribution along the Fe 2+-Fe(OH) 3(am) equilibrium, with the result that uraninite does not dissolve. This may explain the lower uranium content in the water samples from pelites and dolomites above the Okélobondo deposit. The high Mn/Fe ratio and the high pH-Eh values of the water sampled at depth, close to the Okélobondo deposit, suggest a control by the Mn 2+-MnOOH(s) equilibrium. This control is attributed to the dissolution of a large rhodochrosite, MnCO 3(s), and manganite, MnOOH(s) deposit in the recharge area on the eastern side.
Cosmogenic 22Na as a steady-state tracer of solute transport and water age in first-order catchments
Kaste, James M.; Lauer, Nancy E.; Spaetzel, Alana B.; Goydan, Claire
2016-12-01
Naturally-occurring cosmogenic 22Na (T1/2 = 2.6 yr) is a potentially powerful tracer of solute and water movement in catchments. However, due to its low abundance in precipitation (∼10-20 molL-1), there are only a handful of datasets documenting cosmogenic 22Na atmospheric fluxes and concentrations in surface waters. Here we present the first record of cosmogenic 22Na fallout to North America and test its use as a radiometric tracer of water age in three small catchments in the Eastern United States. We show that 22Na deposition to southeastern Virginia, USA during 2012-2014 was 187 ± 10 mBqm-2yr-1 and that flux is largely additive with precipitation amounts. Our measurements of fallout combined with previous 22Na deposition data from other regions indicate that approximately 77% of the variability in the annual global 22Na atmospheric flux is controlled by precipitation. Export of 22Na in drainage waters from three first-order forested catchments ranged from 12.5 to 174 mBq m-2 yr-1 and can be explained by a flux-based radioactive decay model, indicating that the watersheds are in steady-state with respect to cosmogenic 22Na on annual timescales. We conclude that in temperate climates with no systematic changes in rainfall amounts at the annual timescale, 22Na may be useful for quantifying the recharge age of relatively young (<20 yr) surface waters and groundwaters and for tracing solute transport at the watershed scale.
Macropore system characteristics controls on non-reactive solute transport at different flow rates
Larsbo, Mats; Koestel, John
2014-05-01
Preferential flow and transport in macroporous soils are important pathways for the leaching of agrochemicals through soils. Preferential solute transport in soil is to a large extent determined by the macropore system characteristics and the water flow conditions. The importance of different characteristics of the macropore system is likely to vary with the flow conditions. The objective of this study was to determine which properties of the macropore system that control the shape of non-reactive tracer solute breakthrough curves at different steady-state flow rates. We sampled five undisturbed columns (20 cm high, 20 cm diameter) from the soil surface of four soils with clay contents between 21 and 50 %. Solute transport experiments were carried out under unsaturated conditions at 2, 4, 6, 8 and 12 mm h-1 flow rates. For each flow rate a pulse of potassium bromide solution was applied at the soil surface and the electrical conductivity was measured with high temporal resolution in the column effluent. We used the 5 % arrival time and the holdback factor to estimate the degree of preferential transport from the resulting breakthrough curves. Unsaturated hydraulic conductivities were measured at the soil surface of the columns using a tension disc infiltrometer. The macropore system was imaged by industrial X-ray computed tomography at a resolution of 125 μm in all directions. Measures of the macropore system characteristics including measures of pore continuity were calculated from these images using the ImageJ software. Results show that the degree of preferential transport is generally increasing with flow rate when larger pores become active in the transport. The degree of preferential flow was correlated to measures of macropore topology. This study show that conclusions drawn from experiments carried out at one flow rate should generally not be extrapolated to other flow rates.
Pang, Liping; Goltz, Mark; Close, Murray
2003-01-01
In this note, we applied the temporal moment solutions of [Das and Kluitenberg, 1996. Soil Sci. Am. J. 60, 1724] for one-dimensional advective-dispersive solute transport with linear equilibrium sorption and first-order degradation for time pulse sources to analyse soil column experimental data. Unlike most other moment solutions, these solutions consider the interplay of degradation and sorption. This permits estimation of a first-order degradation rate constant using the zeroth moment of column breakthrough data, as well as estimation of the retardation factor or sorption distribution coefficient of a degrading solute using the first moment. The method of temporal moment (MOM) formulae was applied to analyse breakthrough data from a laboratory column study of atrazine, hexazinone and rhodamine WT transport in volcanic pumice sand, as well as experimental data from the literature. Transport and degradation parameters obtained using the MOM were compared to parameters obtained by fitting breakthrough data from an advective-dispersive transport model with equilibrium sorption and first-order degradation, using the nonlinear least-square curve-fitting program CXTFIT. The results derived from using the literature data were also compared with estimates reported in the literature using different equilibrium models. The good agreement suggests that the MOM could provide an additional useful means of parameter estimation for transport involving equilibrium sorption and first-order degradation. We found that the MOM fitted breakthrough curves with tailing better than curve fitting. However, the MOM analysis requires complete breakthrough curves and relatively frequent data collection to ensure the accuracy of the moments obtained from the breakthrough data.
Intercomparison of 3D pore-scale flow and solute transport simulation methods
Yang, Xiaofan; Mehmani, Yashar; Perkins, William A.; Pasquali, Andrea; Schönherr, Martin; Kim, Kyungjoo; Perego, Mauro; Parks, Michael L.; Trask, Nathaniel; Balhoff, Matthew T.; Richmond, Marshall C.; Geier, Martin; Krafczyk, Manfred; Luo, Li-Shi; Tartakovsky, Alexandre M.; Scheibe, Timothy D.
2016-09-01
Multiple numerical approaches have been developed to simulate porous media fluid flow and solute transport at the pore scale. These include 1) methods that explicitly model the three-dimensional geometry of pore spaces and 2) methods that conceptualize the pore space as a topologically consistent set of stylized pore bodies and pore throats. In previous work we validated a model of the first type, using computational fluid dynamics (CFD) codes employing a standard finite volume method (FVM), against magnetic resonance velocimetry (MRV) measurements of pore-scale velocities. Here we expand that validation to include additional models of the first type based on the lattice Boltzmann method (LBM) and smoothed particle hydrodynamics (SPH), as well as a model of the second type, a pore-network model (PNM). The PNM approach used in the current study was recently improved and demonstrated to accurately simulate solute transport in a two-dimensional experiment. While the PNM approach is computationally much less demanding than direct numerical simulation methods, the effect of conceptualizing complex three-dimensional pore geometries on solute transport in the manner of PNMs has not been fully determined. We apply all four approaches (FVM-based CFD, LBM, SPH and PNM) to simulate pore-scale velocity distributions and (for capable codes) nonreactive solute transport, and intercompare the model results. Comparisons are drawn both in terms of macroscopic variables (e.g., permeability, solute breakthrough curves) and microscopic variables (e.g., local velocities and concentrations). Generally good agreement was achieved among the various approaches, but some differences were observed depending on the model context. The intercomparison work was challenging because of variable capabilities of the codes, and inspired some code enhancements to allow consistent comparison of flow and transport simulations across the full suite of methods. This study provides support for confidence
Ranathunge, Kosala; Kim, Yangmin X; Wassmann, Friedrich; Kreszies, Tino; Zeisler, Viktoria; Schreiber, Lukas
2017-03-01
Roots have complex anatomical structures, and certain localized cell layers develop suberized apoplastic barriers. The size and tightness of these barriers depend on the growth conditions and on the age of the root. Such complex anatomical structures result in a composite water and solute transport in roots. Development of apoplastic barriers along barley seminal roots was detected using various staining methods, and the suberin amounts in the apical and basal zones were analysed using gas chromatography-mass spectometry (GC-MS). The hydraulic conductivity of roots ( Lp r ) and of cortical cells ( Lp c ) was measured using root and cell pressure probes. When grown in hydroponics, barley roots did not form an exodermis, even at their basal zones. However, they developed an endodermis. Endodermal Casparian bands first appeared as 'dots' as early as at 20 mm from the apex, whereas a patchy suberin lamellae appeared at 60 mm. The endodermal suberin accounted for the total suberin of the roots. The absolute amount in the basal zone was significantly higher than in the apical zone, which was inversely proportional to the Lp r . Comparison of Lp r and Lp c suggested that cell to cell pathways dominate for water transport in roots. However, the calculation of Lp r from Lp c showed that at least 26 % of water transport occurs through the apoplast. Roots had different solute permeabilities ( P sr ) and reflection coefficients ( σ sr ) for the solutes used. The σ sr was below unity for the solutes, which have virtually zero permeability for semi-permeable membranes. Suberized endodermis significantly reduces Lp r of seminal roots. The water and solute transport across barley roots is composite in nature and they do not behave like ideal osmometers. The composite transport model should be extended by adding components arranged in series (cortex, endodermis) in addition to the currently included components arranged in parallel (apoplastic, cell to cell pathways).
Klager, Brian J.; Kelly, Brian P.; Ziegler, Andrew C.
2014-01-01
The Equus Beds aquifer in south-central Kansas is a primary water-supply source for the city of Wichita. Water-level declines because of groundwater pumping for municipal and irrigation needs as well as sporadic drought conditions have caused concern about the adequacy of the Equus Beds aquifer as a future water supply for Wichita. In March 2006, the city of Wichita began construction of the Equus Beds Aquifer Storage and Recovery project, a plan to artificially recharge the aquifer with excess water from the Little Arkansas River. Artificial recharge will raise groundwater levels, increase storage volume in the aquifer, and deter or slow down a plume of chloride brine approaching the Wichita well field from the Burrton, Kansas area caused by oil production activities in the 1930s. Another source of high chloride water to the aquifer is the Arkansas River. This study was prepared in cooperation with the city of Wichita as part of the Equus Beds Aquifer Storage and Recovery project. Chloride transport in the Equus Beds aquifer was simulated between the Arkansas and Little Arkansas Rivers near the Wichita well field. Chloride transport was simulated for the Equus Beds aquifer using SEAWAT, a computer program that combines the groundwater-flow model MODFLOW-2000 and the solute-transport model MT3DMS. The chloride-transport model was used to simulate the period from 1990 through 2008 and the effects of five well pumping scenarios and one artificial recharge scenario. The chloride distribution in the aquifer for the beginning of 1990 was interpolated from groundwater samples from around that time, and the chloride concentrations in rivers for the study period were interpolated from surface water samples. Five well-pumping scenarios and one artificial-recharge scenario were assessed for their effects on simulated chloride transport and water levels in and around the Wichita well field. The scenarios were: (1) existing 1990 through 2008 pumping conditions, to serve as a
Control and optimization of solute transport in a thin porous tube
Griffiths, I. M.
2013-03-01
Predicting the distribution of solutes or particles in flows within porous-walled tubes is essential to inform the design of devices that rely on cross-flow filtration, such as those used in water purification, irrigation devices, field-flow fractionation, and hollow-fibre bioreactors for tissue-engineering applications. Motivated by these applications, a radially averaged model for fluid and solute transport in a tube with thin porous walls is derived by developing the classical ideas of Taylor dispersion. The model includes solute diffusion and advection via both radial and axial flow components, and the advection, diffusion, and uptake coefficients in the averaged equation are explicitly derived. The effect of wall permeability, slip, and pressure differentials upon the dispersive solute behaviour are investigated. The model is used to explore the control of solute transport across the membrane walls via the membrane permeability, and a parametric expression for the permeability required to generate a given solute distribution is derived. The theory is applied to the specific example of a hollow-fibre membrane bioreactor, where a uniform delivery of nutrient across the membrane walls to the extra-capillary space is required to promote spatially uniform cell growth. © 2013 American Institute of Physics.
Directory of Open Access Journals (Sweden)
A. J. Zurek
2014-08-01
Full Text Available A dedicated study was launched in 2010 with the main aim to better understand the functioning of groundwater dependent terrestrial ecosystem (GDTE located in southern Poland. The GDTE consists of a valuable forest stand (Niepolomice Forest and associated wetland (Wielkie Bloto fen. A wide range of tools (environmental tracers, geochemistry, geophysics, 3-D flow and transport modeling was used. The research was conducted along three major directions: (i quantification of the dynamics of groundwater flow in various parts of the aquifer associated with GDTE, (ii quantification of the degree of interaction between the GDTE and the aquifer, and (iii 3-D modeling of groundwater flow in the vicinity of the studied GDTE and quantification of possible impact of enhanced exploitation of the aquifer on the status of GDTE. Environmental tracer data (tritium, stable isotopes of water strongly suggest that upward leakage of the aquifer contributes significantly to the present water balance of the studied wetland and associated forest. Physico-chemical parameters of water (pH, conductivity, Na / Cl ratio confirm this notion. Model runs indicate that prolonged groundwater abstraction through the newly-established network of water supply wells, conducted at maximum permitted capacity (ca. 10 000 m3 d−1, may trigger drastic changes in the ecosystem functioning, eventually leading to its degradation.
Zurek, A. J.; Witczak, S.; Dulinski, M.; Wachniew, P.; Rozanski, K.; Kania, J.; Postawa, A.; Karczewski, J.; Moscicki, W. J.
2014-08-01
A dedicated study was launched in 2010 with the main aim to better understand the functioning of groundwater dependent terrestrial ecosystem (GDTE) located in southern Poland. The GDTE consists of a valuable forest stand (Niepolomice Forest) and associated wetland (Wielkie Bloto fen). A wide range of tools (environmental tracers, geochemistry, geophysics, 3-D flow and transport modeling) was used. The research was conducted along three major directions: (i) quantification of the dynamics of groundwater flow in various parts of the aquifer associated with GDTE, (ii) quantification of the degree of interaction between the GDTE and the aquifer, and (iii) 3-D modeling of groundwater flow in the vicinity of the studied GDTE and quantification of possible impact of enhanced exploitation of the aquifer on the status of GDTE. Environmental tracer data (tritium, stable isotopes of water) strongly suggest that upward leakage of the aquifer contributes significantly to the present water balance of the studied wetland and associated forest. Physico-chemical parameters of water (pH, conductivity, Na / Cl ratio) confirm this notion. Model runs indicate that prolonged groundwater abstraction through the newly-established network of water supply wells, conducted at maximum permitted capacity (ca. 10 000 m3 d-1), may trigger drastic changes in the ecosystem functioning, eventually leading to its degradation.
The adjoint neutron transport equation and the statistical approach for its solution
Saracco, Paolo; Ravetto, Piero
2016-01-01
The adjoint equation was introduced in the early days of neutron transport and its solution, the neutron importance, has ben used for several applications in neutronics. The work presents at first a critical review of the adjoint neutron transport equation. Afterwards, the adjont model is constructed for a reference physical situation, for which an analytical approach is viable, i.e. an infinite homogeneous scattering medium. This problem leads to an equation that is the adjoint of the slowing-down equation that is well-known in nuclear reactor physics. A general closed-form analytical solution to such adjoint equation is obtained by a procedure that can be used also to derive the classical Placzek functions. This solution constitutes a benchmark for any statistical or numerical approach to the adjoint equation. A sampling technique to evaluate the adjoint flux for the transport equation is then proposed and physically interpreted as a transport model for pseudo-particles. This can be done by introducing appr...
Stochastic approach to the numerical solution of the non-stationary Parker's transport equation
Wawrzynczak, A.; Modzelewska, R.; Gil, A.
2015-01-01
We present the newly developed stochastic model of the galactic cosmic ray (GCR) particles transport in the heliosphere. Mathematically Parker transport equation (PTE) describing non-stationary transport of charged particles in the turbulent medium is the Fokker-Planck type. It is the second order parabolic time-dependent 4-dimensional (3 spatial coordinates and particles energy/rigidity) partial differential equation. It is worth to mention that, if we assume the stationary case it remains as the 3-D parabolic type problem with respect to the particles rigidity R. If we fix the energy/rigidity it still remains as the 3-D parabolic type problem with respect to time. The proposed method of numerical solution is based on the solution of the system of stochastic differential equations (SDEs) being equivalent to the Parker's transport equation. We present the method of deriving from PTE the equivalent SDEs in the heliocentric spherical coordinate system for the backward approach. The advantages and disadvantages of the forward and the backward solution of the PTE are discussed. The obtained stochastic model of the Forbush decrease of the GCR intensity is in an agreement with the experimental data.
Thermal effect of climate change on groundwater-fed ecosystems
Burns, Erick; Zhu, Yonghui; Zhan, Hongbin; Manga, Michael; Williams, Colin F.; Ingebritsen, Steven E.; Dunham, Jason
2017-01-01
Groundwater temperature changes will lag surface temperature changes from a changing climate. Steady state solutions of the heat-transport equations are used to identify key processes that control the long-term thermal response of springs and other groundwater discharge to climate change, in particular changes in (1) groundwater recharge rate and temperature and (2) land-surface temperature transmitted through the vadose zone. Transient solutions are developed to estimate the time required for new thermal signals to arrive at ecosystems. The solution is applied to the volcanic Medicine Lake highlands, California, USA, and associated springs complexes that host groundwater-dependent ecosystems. In this system, upper basin groundwater temperatures are strongly affected only by recharge conditions. However, as the vadose zone thins away from the highlands, changes in the average annual land-surface temperature also influence groundwater temperatures. Transient response to temperature change depends on both the conductive time scale and the rate at which recharge delivers heat. Most of the thermal response of groundwater at high elevations will occur within 20 years of a shift in recharge temperatures, but the large lower elevation springs will respond more slowly, with about half of the conductive response occurring within the first 20 years and about half of the advective response to higher recharge temperatures occurring in approximately 60 years.
Directory of Open Access Journals (Sweden)
Özgür Başkan
2014-09-01
Full Text Available Differential Evolution algorithm has effectively been used to solve engineering optimization problems recently. The Differential Evolution algorithm, which uses similar principles with Genetic Algorithms, is more robust on obtaining optimal solution than many other heuristic algorithms with its simpler structure. In this study, Differential Evolution algorithm is applied to the transportation network design problems and its effectiveness on the solution is investigated. In this context, Differential Evolution based models are developed using bi-level programming approach for the solution of the transportation network design problem and determination of the on-street parking places in urban road networks. In these models, optimal investment and parking strategies are investigated on the upper level. On the lower level, deterministic traffic assignment problem, which represents drivers' responses, is solved using Frank-Wolfe algorithm and VISUM traffic modeling software. In order to determine the effectiveness of the proposed models, numerical applications are carried out on Sioux-Falls test network. Results showed that the Differential Evolution algorithm may effectively been used for the solution of transportation network design problems.
Kim, Tae-Uk; Drewes, Jörg E; Scott Summers, R; Amy, Gary L
2007-09-01
Rejection of trace organic compounds, including disinfection by-products (DBPs) and pharmaceutical active compounds (PhACs), by high-pressure membranes has become a focus of public interest internationally in both drinking water treatment and wastewater reclamation/reuse. The ability to simulate, or even predict, the rejection of these compounds by high-pressure membranes, encompassing nanofiltration (NF) and reverse osmosis (RO), will improve process economics and expand membrane applications. The objective of this research is to develop a membrane transport model to account for diffusive and convective contributions to solute transport and rejection. After completion of cross-flow tests and diffusion cell tests with target compounds, modeling efforts were performed in accordance with a non-equilibrium thermodynamic transport equation. Comparing the percentages of convection and diffusion contributions to transport, convection is dominant for most compounds, but diffusion is important for more hydrophobic non-polar compounds. Convection is also more dominant for looser membranes (i.e., NF). In addition, higher initial compound concentrations and greater J(0)/k ratios contribute to solute fluxes more dominated by convection. Given the treatment objective of compound rejection, compound transport and rejection trends are inversely related.
Energy Technology Data Exchange (ETDEWEB)
NONE
2001-08-01
The First Stage of the Tracer Retention Understanding Experiments (TRUE-1) was initiated in 1994 and the experimental activities were officially concluded in December 1998 with the termination of the final test with radioactive sorbing tracers. The programme also included a laboratory programme focused on both generic (Aespoe HRL) and site-specific (Feature A) geological material. Modelling, both scopings, predictions and evaluation of the final tests with sorbing tracers has been performed parallel to the experimental work. The work and conclusions of the SKB TRUE project team have been published in a SKB technical report. The TRUE-1 experiments have also been subject to blind prediction and evaluation by an international group of modelling teams within the auspices of the Aespoe Task Force on Groundwater on Modelling of Groundwater Flow and Solute Transport. A list of relevant reports and publications related to the First TRUE Stage are presented in Appendix A. The present seminar provides a venue to present and discuss the results of the TRUE-1 experiments in terms of identified transport and retention processes and concepts/approaches used to model. However, given the fact that may international programs, including that of SKB, are either underway or preparing for site characterisation programs, the seminar provides a possibility to discuss research priorities and the specific data needs for development of a geological repository. In his opening address, the director of the Aespoe Hard Rock Laboratory emphasised the need to carefully integrate available experience from other research sites, e.g. Grimsel (Switzerland), Stripa (Sweden) and El Berrocal (Spain). The two important questions to be asked are; What do we know? What is the way forward? For the subsequent discussions four different discussion themes were identified; 1. Identification of transport processes. 2. Model concepts. 3. Site-specific data needs for a geological repository. 4. Research priorities
One-dimensional unsteady solute transport along unsteady flow through inhomogeneous medium
Indian Academy of Sciences (India)
Sanjay K Yadav; Atul Kumar; Dilip K Jaiswal; Naveen Kumar
2011-04-01
The one-dimensional linear advection–diffusion equation is solved analytically by using the Laplace integral transform. The solute transport as well as the flow field is considered to be unsteady, both of independent patterns. The solute dispersion occurs through an inhomogeneous semi-infinite medium. Hence, velocity is considered to be an increasing function of the space variable, linearly interpolated in a finite domain in which solute dispersion behaviour is studied. Dispersion is considered to be proportional to the square of the spatial linear function. Thus, the coefficients of the advection–diffusion equation are functions of both the independent variables, but the expression for each coefficient is considered in degenerate form. These coefficients are reduced into constant coefficients with the help of a new space variable, introduced in our earlier works, and new time variables. The source of the solute is considered to be a stationary uniform point source of pulse type.
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SÁVIO LEANDRO BERTOLI
2016-07-01
Full Text Available In the engineering courses the field of Transport Phenomena is of significant importance and it is in several disciplines relating to Fluid Mechanics, Heat and Mass Transfer. In these disciplines, problems involving these phenomena are mathematically formulated and analytical solutions are obtained whenever possible. The aim of this paper is to emphasize the possibility of extending aspects of the teaching-learning in this area by a method based on time scales and limit solutions. Thus, aspects relative to the phenomenology naturally arise during the definition of the scales and / or by determining the limit solutions. Aspects concerning the phenomenology of the limit problems are easily incorporated into the proposed development, which contributes significantly to the understanding of physics inherent in the mathematical modeling of each limiting case studied. Finally the study aims to disseminate the use of the limit solutions and of the time scales in the general fields of engineering.
Shiel, A. E.; Johnson, T. M.; Lundstrom, C. C.; Laubach, P. G.; Long, P. E.; Williams, K. H.
2016-08-01
We conducted a detailed investigation of U isotopes in conjunction with a broad geochemical investigation during field-scale biostimulation and desorption experiments. This investigation was carried out in the uranium-contaminated alluvial aquifer of the Rifle field research site. In this well-characterized setting, a more comprehensive understanding of U isotope geochemistry is possible. Our results indicate that U isotope fractionation is consistently observed across multiple experiments at the Rifle site. Microbially-mediated reduction is suggested to account for most or all of the observed fractionation as abiotic reduction has been demonstrated to impart much smaller, often near-zero, isotopic fractionation or isotopic fractionation in the opposite direction. Data from some time intervals are consistent with a simple model for transport and U(VI) reduction, where the fractionation factor (ε = +0.65‰ to +0.85‰) is consistent with experimental studies. However, during other time intervals the observed patterns in our data indicate the importance of other processes in governing U concentrations and 238U/235U ratios. For instance, we demonstrate that departures from Rayleigh behavior in groundwater systems arise from the presence of adsorbed species. We also show that isotope data are sensitive to the onset of oxidation after biostimulation ends, even in the case where reduction continues to remove contaminant uranium downstream. Our study and the described conceptual model support the use of 238U/235U ratios as a tool for evaluating the efficacy of biostimulation and potentially other remedial strategies employed at Rifle and other uranium-contaminated sites.
Frohnert, Anne; Apelt, Susann; Klitzke, Sondra; Chorus, Ingrid; Szewzyk, Regine; Selinka, Hans-Christoph
2014-11-01
To protect groundwater as a drinking water resource from microbiological contamination, protection zones are installed. While travelling through these zones, concentrations of potential pathogens should decline to levels that pose no risks to human health. Removal of viruses during subsurface passage is influenced by physicochemical conditions, such as oxygen concentration, which also affects virus survival. The aim of our study was to evaluate the effect of redox conditions on the removal of viruses during sand filtration. Experiments in glass columns filled with medium-grained sand were conducted to investigate virus removal in the presence and absence of dissolved oxygen. Bacteriophages MS2 and PhiX174, as surrogates for human enteric viruses were spiked in pulsed or in continuous mode and pumped through the columns at a filter velocity of about 1m/d. Virus breakthrough curves were analyzed by calculating total viral elimination and fitted using one-dimensional transport models (CXTFIT and HYDRUS-1D). While short-term experiments with pulsed virus application showed only small differences with regard to virus removal under oxic and anoxic conditions, a long-term experiment with continuous dosing revealed a clearly lower elimination of viruses under anoxic conditions. These findings suggest that less inactivation and less adsorption of viruses in anoxic environments affect their removal. Therefore, in risk assessment studies aimed to secure drinking water resources from viral contamination and optimization of protection zones, the oxic and anoxic conditions in the subsurface should also be considered. Copyright © 2014 Elsevier GmbH. All rights reserved.
Geochemical Investigations of Groundwater Stability
Energy Technology Data Exchange (ETDEWEB)
Bath, Adrian [Intellisci Ltd., Loughborough (United Kingdom)
2006-05-15
local palaeohydrogeological conditions. It is likely that inland areas have had longer durations of post-glacial fresh water infiltration than coastal areas, possibly causing greater degrees of dilution and dispersion of preexisting groundwaters and thus overprinting their hydrochemical and isotopic 'fingerprints'. Lower post-glacial hydraulic gradients relative to inland sites may account for the occurrence of more relict cold-climate water at coastal sites. Some general observations are based on rather thin evidence and therefore speculative. Firstly, it seems that glacial melt water penetrated many hundreds of metres and in some places to at least 1,000 m depth. However the low remaining proportions of melt water and of much older saline Shield water suggest that melt water flux did not fully displace pre-existing groundwaters at these depths. Secondly, where there has been post-glacial infiltration of palaeo-Baltic sea water, the density stratification or compartmentalisation effect coupled with low hydraulic gradient has reduced rates of subsequent fresh water circulation after shoreline recession. There are many uncertainties in interpreting these geochemical indicators in terms of the penetration depths of glacial melt waters and the degree to which they replace preexisting groundwaters, of other aspects of groundwater stability, and of comparisons between inland and coastal groundwater systems. Uncertainties derive partly from the reliability of groundwater samples as being representative of in situ conditions, and partly from the non-uniqueness of interpretative models. Future investigations using these approaches need to improve sampling, to make conjunctive use of geochemical and isotopic indicators which have varying timescales and sensitivities, and to integrate these indicators with palaeohydrogeological modelling to support the development of reliable groundwater flow and solute transport models for Performance Assessment.
Intragranular diffusion: An important mechanism influencing solute transport in clastic aquifers?
Wood, W.W.; Kraemer, T.F.; Hearn, P.P.
1990-01-01
Quantification of intragranular porosity in sand-size material from an aquifer on Cape Cod, Massachusetts, by scanning electron microscopy, mercury injection, and epifluorescence techniques shows that there are more reaction sites and that porosity is greater that indicated by standard short-term laboratory tests and measurement techniques. Results from laboratory and field tracer tests show solute nonequilibrium for a reacting ion consistent with a model of diffusion into, and exchange within, grain interiors. These data indicate that a diffusion expression needs to be included in transport codes, particularly for simulation of the transport of radioactive and toxic wastes.
Osmosis in groundwater: chemical and electrical extensions to Darcy's Law
Bader, S.
2005-01-01
In problems of groundwater flow and solute transport in clayey soils subject to salt concentration gradients, chemical and electro-osmosis can be too important to disregard, as is commonly done in geohydrology. In this thesis, we consider the quantification of these couple effects to be able to
Osmosis in groundwater: chemical and electrical extensions to Darcy's Law
Bader, S.
2005-01-01
In problems of groundwater flow and solute transport in clayey soils subject to salt concentration gradients, chemical and electro-osmosis can be too important to disregard, as is commonly done in geohydrology. In this thesis, we consider the quantification of these couple effects to be able to simu
Field scale variability of solute transport parameters and related soil properties
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B. Lennartz
1997-01-01
Full Text Available The spatial variability of transport parameters has to be taken into account for a reliable assessment of solute behaviour in natural field soils. Two field sites were studied by collecting 24 and 36 small undisturbed soil columns at an uniform grid of 15 m spacing. Displacement experiments were conducted in these columns with bromide traced water under unsaturated steady state transport conditions. Measured breakthrough curves (BTCs were evaluated with the simple convective-dispersive equation (CDE. The solute mobility index (MI calculated as the ratio of measured to fitted pore water velocity and the dispersion coefficient (D were used to classify bromide breakthrough behaviour. Experimental BTCs were classified into two groups: type I curves expressed classical solute behaviour while type II curves were characterised by the occurrence of a bromide concentration maximum before 0.35 pore volumes of effluent (MI<0.35 resulting from preferential flow conditions. Six columns from site A and 8 from site B were identified as preferential. Frequency distributions of the transport parameters (MI and D of both sites were either extremely skewed or bimodal. Log-transformation did not lead to a normal distribution in any case. Contour maps of bromide mass flux at certain time steps indicated the clustering of preferential flow regions at both sites. Differences in the extent of preferential flow between sites seemed to be governed by soil structure. Linear cross correlations among transport parameters and independently measured soil properties revealed relations between solute mobility and volumetric soil water content at time of sampling, texture and organic carbon content. The volumetric field soil water content, a simple measure characterising the soil hydraulic behaviour at the sampling location, was found to be a highly sensitive parameter with respect to solute mobility and preferential flow situations. Almost no relation was found between solute
An analytical solution to contaminant transport through composite liners with geomembrane defects
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
To investigate the performance of landfill composite liner system,a one-dimensional model was developed for solute transport through composite liners containing geomembrane defects.An analytical solution to the model was obtained by the method of Laplace transformation.The results obtained by the presented solution agree well with those obtained by the numerical method.Results show that leachate head and construction quality of geomembrane(GM) have significant influences on the performance of the composite liners for heavy metal ions.The breakthrough time of lead decreases from 50 a to 19 a when the leachate head increases from 0.3 m to 10 m.It is also indicated that the contaminant mass flux of volatile organic compounds(VOCs) induced by leakage can not be neglected in case of poor construction quality of the landfill barrier system.It is shown that diffusion coefficient and partition coefficient of GM have great influences on solute transport through composite liners for VOCs.The breakthrough time of heavy metal ions will be greatly overestimated if the effects of diffusion and adsorption of clay and geosynthetic clay liner(GCL) are neglected.The composite liner consisting of a geomembrane and a GCL provides a poor barrier for VOCs.The presented analytical solution is relatively simple to apply and can be used for preliminary design of composite liners,evaluating experimental results,and verifying more complex numerical models.
Electroosmotic fluid motion and late-time solute transport at non-negligible zeta potentials
Energy Technology Data Exchange (ETDEWEB)
S. K. Griffiths; R. H. Nilson
1999-12-01
Analytical and numerical methods are employed to determine the electric potential, fluid velocity and late-time solute distribution for electroosmotic flow in a tube and channel when the zeta potential is not small. The electric potential and fluid velocity are in general obtained by numerical means. In addition, new analytical solutions are presented for the velocity in a tube and channel in the extremes of large and small Debye layer thickness. The electroosmotic fluid velocity is used to analyze late-time transport of a neutral non-reacting solute. Zeroth and first-order solutions describing axial variation of the solute concentration are determined analytically. The resulting expressions contain eigenvalues representing the dispersion and skewness of the axial concentration profiles. These eigenvalues and the functions describing transverse variation of the concentration field are determined numerically using a shooting technique. Results are presented for both tube and channel geometries over a wide range of the normalized Debye layer thickness and zeta potential. Simple analytical approximations to the eigenvalues are also provided for the limiting cases of large and small values of the Debye layer thickness. The methodology developed here for electroosmotic flow is also applied to the Taylor problem of late-time transport and dispersion in pressure-driven flows.
Influence of Billet Size on Flow, Solidification and Solute Transport