Low-rank Kalman filtering for efficient state estimation of subsurface advective contaminant transport models

KAUST Repository

El Gharamti, Mohamad; Hoteit, Ibrahim; Sun, Shuyu

2012-01-01

Accurate knowledge of the movement of contaminants in porous media is essential to track their trajectory and later extract them from the aquifer. A two-dimensional flow model is implemented and then applied on a linear contaminant transport model

Low-Rank Kalman Filtering in Subsurface Contaminant Transport Models

KAUST Repository

El Gharamti, Mohamad

2010-01-01

Understanding the geology and the hydrology of the subsurface is important to model the fluid flow and the behavior of the contaminant. It is essential to have an accurate knowledge of the movement of the contaminants in the porous media in order to track them and later extract them from the aquifer. A two-dimensional flow model is studied and then applied on a linear contaminant transport model in the same porous medium. Because of possible different sources of uncertainties, the deterministic model by itself cannot give exact estimations for the future contaminant state. Incorporating observations in the model can guide it to the true state. This is usually done using the Kalman filter (KF) when the system is linear and the extended Kalman filter (EKF) when the system is nonlinear. To overcome the high computational cost required by the KF, we use the singular evolutive Kalman filter (SEKF) and the singular evolutive extended Kalman filter (SEEKF) approximations of the KF operating with low-rank covariance matrices. The SEKF can be implemented on large dimensional contaminant problems while the usage of the KF is not possible. Experimental results show that with perfect and imperfect models, the low rank filters can provide as much accurate estimates as the full KF but at much less computational cost. Localization can help the filter analysis as long as there are enough neighborhood data to the point being analyzed. Estimating the permeabilities of the aquifer is successfully tackled using both the EKF and the SEEKF.

Low-Rank Kalman Filtering in Subsurface Contaminant Transport Models

KAUST Repository

El Gharamti, Mohamad

2010-12-01

Understanding the geology and the hydrology of the subsurface is important to model the fluid flow and the behavior of the contaminant. It is essential to have an accurate knowledge of the movement of the contaminants in the porous media in order to track them and later extract them from the aquifer. A two-dimensional flow model is studied and then applied on a linear contaminant transport model in the same porous medium. Because of possible different sources of uncertainties, the deterministic model by itself cannot give exact estimations for the future contaminant state. Incorporating observations in the model can guide it to the true state. This is usually done using the Kalman filter (KF) when the system is linear and the extended Kalman filter (EKF) when the system is nonlinear. To overcome the high computational cost required by the KF, we use the singular evolutive Kalman filter (SEKF) and the singular evolutive extended Kalman filter (SEEKF) approximations of the KF operating with low-rank covariance matrices. The SEKF can be implemented on large dimensional contaminant problems while the usage of the KF is not possible. Experimental results show that with perfect and imperfect models, the low rank filters can provide as much accurate estimates as the full KF but at much less computational cost. Localization can help the filter analysis as long as there are enough neighborhood data to the point being analyzed. Estimating the permeabilities of the aquifer is successfully tackled using both the EKF and the SEEKF.

Using Contaminant Transport Modeling to Determine Historical Discharges at the Surface

Science.gov (United States)

Fogwell, T. W.

2013-12-01

When it is determined that a contaminated site needs to be remediated, the issue of who is going to pay for that remediation is an immediate concern. This means that there needs to be a determination of who the responsible parties are for the existing contamination. Seldom is it the case that records have been made and kept of the surface contaminant discharges. In many cases it is possible to determine the relative amount of contaminant discharge at the surface of the various responsible parties by employing a careful analysis of the history of contaminant transport through the surface, through the vadose zone, and within the saturated zone. The process begins with the development of a dynamic conceptual site model that takes into account the important features of the transport of the contaminants through the vadose zone and in the groundwater. The parameters for this model can be derived from flow data available for the site. The resulting contaminant transport model is a composite of the vadose zone transport model, together with the saturated zone (groundwater) flow model. Any calibration of the model should be carefully employed in order to avoid using information about the conclusions of the relative discharge amounts of the responsible parties in determining the calibrated parameters. Determination of the leading edge of the plume is an important first step. It is associated with the first discharges from the surface of the site. If there were several discharging parties at the same time, then it is important to establish a chemical or isotopic signature of the chemicals that were discharged. The time duration of the first discharger needs to be determined as accurately as possible in order to establish the appropriate characterization of the leading portion of the resulting plume in the groundwater. The information about the first discharger and the resulting part of the plume associated with this discharger serves as a basis for the determination of the

Grand challenge problems in environmental modeling and remediation: groundwater contaminant transport

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.

Contaminant transport at a waste residue deposit: 1. Inverse flow and non-reactive transport modelling

DEFF Research Database (Denmark)

Sonnenborg, Torben Obel; Engesgaard, Peter Knudegaard; Rosbjerg, Dan

1996-01-01

An application of an inverse flow and transport model to a contaminated aquifer is presented. The objective of the study is to identify physical and nonreactive flow and transport parameters through an optimization approach. The approach can be classified as a statistical procedure, where a flow...... to steady state versus transient flow conditions and to the amount of hydraulic and solute data used is investigated. The flow parameters, transmissivity and leakage factor, are estimated simultaneously with the transport parameters: source strength, porosity, and longitudinal dispersivity. This paper...

A deterministic-probabilistic model for contaminant transport. User manual

Energy Technology Data Exchange (ETDEWEB)

Schwartz, F W; Crowe, A

1980-08-01

This manual describes a deterministic-probabilistic contaminant transport (DPCT) computer model designed to simulate mass transfer by ground-water movement in a vertical section of the earth's crust. The model can account for convection, dispersion, radioactive decay, and cation exchange for a single component. A velocity is calculated from the convective transport of the ground water for each reference particle in the modeled region; dispersion is accounted for in the particle motion by adding a readorn component to the deterministic motion. The model is sufficiently general to enable the user to specify virtually any type of water table or geologic configuration, and a variety of boundary conditions. A major emphasis in the model development has been placed on making the model simple to use, and information provided in the User Manual will permit changes to the computer code to be made relatively easily for those that might be required for specific applications. (author)

Comparison of different modeling approaches to simulate contaminant transport in a fractured limestone aquifer

DEFF Research Database (Denmark)

Mosthaf, Klaus; Rosenberg, L.; Balbarini, Nicola

. Given available field data and model purpose, this paper therefore aims to develop, examine and compare modeling approaches for transport of contaminants in fractured limestone aquifers. The model comparison was conducted for a contaminated site in Denmark, where a plume of a dissolved contaminant (PCE...... was combined with an analysis of heterogeneities and fractures from a nearby excavation (analog site). Methods for translating the geological information and fracture mapping into each of the model concepts were examined. Each model was compared with available field data, considering both model fit...... of field data is the determination of relevant hydraulic properties and interpretation of aqueous and solid phase contaminant concentration sampling data. Traditional water sampling has a bias towards fracture sampling, however concentrations in the limestone matrix are needed for assessing contaminant...

Modelling water and contaminant transport in the Rum Jungle Mine overburden heaps

International Nuclear Information System (INIS)

Pantelis, G.

1987-04-01

An outline is given of a computer model for water and contaminant transport in and around overburden heaps, with those at the Rum Jungle mine site as a specific example. The model assumes the heaps to lie on a sloping shallow aquifer with identical hydraulic properties. The simulation is carried out for a 40 year period. After the first 20 years a cover which is effectively impermeable to infiltrating rainwater and air is introduced on the heap. The restriction of oxygen supply to the heap terminates contaminant production which results from oxidation of pyrite. Leaching of contaminants from the heap in the following 20-year period is examined

Modelling contaminant transport using site specific data from Vaalputs

International Nuclear Information System (INIS)

Botha, J.F.

1986-01-01

The transport of a contaminant through the upper layers of the earth's surface is a complex phenomenon. To develop a model for this, requires a good understanding of the physical nature of the phenomenon. This paper discusses two difficulties frequently encountered in developing such a model - the nature of the subsurface and the mathematical representation of the unsaturated hydraulic parameters. It is proposed that information obtained from pump- and packer tests be used to circumvent the first difficulty, and that the unsaturated flow parameters be approximated by C -∞ continuous function

One-dimensional contaminant transport model for the design of soil-bentonite slurry walls

International Nuclear Information System (INIS)

Khandelwal, A.; Rabideau, A.; Su, J.

1997-01-01

A user oriented computer model (TRANS1D) was developed for application to the analysis and design of vertical soil-bentonite barriers. TRANS1D is a collection of analytical and numerical solutions to the one dimensional advective-dispersive-reactive (ADR) equation. The primary objective in developing TRANS1D was to enable the designer of a barrier system to evaluate the potential system performance with respect to contaminant transport, without performing difficult and time consuming field or laboratory experiments. Several issues related to model application are discussed, including identification of governing transport processes, specification of boundary conditions, and parameter estimation. Model predictions are compared with the results of laboratory column experiments conducted with soil bentonite barrier material under diffusion-dominated conditions. Good agreement between model calibrations and experimental results was noted, with calibrated diffusion coefficients for organic contaminants consistent with literature values

Modeling contaminant plumes in fractured limestone aquifers

DEFF Research Database (Denmark)

Mosthaf, Klaus; Brauns, Bentje; Fjordbøge, Annika Sidelmann

Determining the fate and transport of contaminant plumes from contaminated sites in limestone aquifers is important because they are a major drinking water resource. This is challenging because they are often heavily fractured and contain chert layers and nodules, resulting in a complex transport...... model. The paper concludes with recommendations on how to identify and employ suitable models to advance the conceptual understanding and as decision support tools for risk assessment and the planning of remedial actions....... behavior. Improved conceptual models are needed for this type of site. Here conceptual models are developed by combining numerical models with field data. Several types of fracture flow and transport models are available for the modeling of contaminant transport in fractured media. These include...... the established approaches of the equivalent porous medium, discrete fracture and dual continuum models. However, these modeling concepts are not well tested for contaminant plume migration in limestone geologies. Our goal was to develop and evaluate approaches for modeling the transport of dissolved contaminant...

Effects of lag and maximum growth in contaminant transport and biodegradation modeling

International Nuclear Information System (INIS)

Wood, B.D.; Dawson, C.N.

1992-06-01

The effects of time lag and maximum microbial growth on biodegradation in contaminant transport are discussed. A mathematical model is formulated that accounts for these effects, and a numerical case study is presented that demonstrates how lag influences biodegradation

Transportation cask contamination weeping

International Nuclear Information System (INIS)

Bennett, P.C.; Doughty, D.H.; Chambers, W.B.

1993-01-01

This paper describes the problem of cask contamination weeping, and efforts to understand the phenomenon and to eliminate its occurrence during spent nuclear fuel transport. The paper summarizes analyses of field experience and scoping experiments, and concentrates on current modelling and experimental validation efforts. (J.P.N.)

Importance of hydrological parameters in contaminant transport modeling in a terrestrial environment

International Nuclear Information System (INIS)

Tsuduki, Katsunori; Matsunaga, Takeshi

2007-01-01

A grid type multi-layered distributed parameter model for calculating discharge in a watershed was described. Model verification with our field observation resulted in different sets of hydrological parameter values, all of which reproduced the observed discharge. The effect of those varied hydrological parameters on contaminant transport calculation was examined and discussed by simulation of event water transfer. (author)

Flow and contaminant transport in an airliner cabin induced by a moving body: Model experiments and CFD predictions

Science.gov (United States)

Poussou, Stephane B.; Mazumdar, Sagnik; Plesniak, Michael W.; Sojka, Paul E.; Chen, Qingyan

2010-08-01

The effects of a moving human body on flow and contaminant transport inside an aircraft cabin were investigated. Experiments were performed in a one-tenth scale, water-based model. The flow field and contaminant transport were measured using the Particle Image Velocimetry (PIV) and Planar Laser-Induced Fluorescence (PLIF) techniques, respectively. Measurements were obtained with (ventilation case) and without (baseline case) the cabin environmental control system (ECS). The PIV measurements show strong intermittency in the instantaneous near-wake flow. A symmetric downwash flow was observed along the vertical centerline of the moving body in the baseline case. The evolution of this flow pattern is profoundly perturbed by the flow from the ECS. Furthermore, a contaminant originating from the moving body is observed to convect to higher vertical locations in the presence of ventilation. These experimental data were used to validate a Computational Fluid Dynamic (CFD) model. The CFD model can effectively capture the characteristic flow features and contaminant transport observed in the small-scale model.

Sediment and contaminant transport in a marine environment

International Nuclear Information System (INIS)

Onishi, Y.; Thompson, F.L.

1986-01-01

The finite-element model FETRA is an unsteady, verically averaged two-dimensional model to simulate the transport of sediment and contaminants (radionuclides, heavy metals, pesticides, etc.) in coastal and estuarine water. The model, together with the hydrodynamic model CAFE-I, was applied to the Irish Sea to predict the migration and accumulation of sediment (both cohesive and noncohesive) and of a radionuclide (dissolved and sediment-sorbed) in a tide- and wind-driven system. The study demonstrated that FETRA is a useful tool for assessing sediment and toxic contaminant transport in a marine environment

Influence of particle sorting in transport of sediment-associated contaminants

International Nuclear Information System (INIS)

Lane, L.J.; Hakonson, T.E.

1982-01-01

Hydrologic and sediment transport models are developed to route the flow of water and sediment (by particle size classes) in alluvial stream channels. A simplified infiltration model is used to compute runoff from upland areas and flow is routed in ephemeral stream channels to account for infiltration or transmission losses in the channel alluvium. Hydraulic calculations, based on the normal flow assumption and an approximating hydrograph, are used to compute sediment transport by particle size classes. Contaminants associated with sediment particles are routed in the stream channels to predict contaminatant transport by particle size classes. An empirical adjustment factor, the enrichment ratio, is shown to be a function of the particle size distribution of stream bed sediments, contaminant concentrations by particle size, differential sediment transport rates, and the magnitude of the runoff event causing transport of sediment and contaminants. This analysis and an example application in a liquid effluent-receiving area illustrate the significance of particle sorting in transport of sediment associated contaminants

Modeling hydrology and reactive transport in roads: The effect of cracks, the edge, and contaminant properties

International Nuclear Information System (INIS)

Apul, Defne S.; Gardner, Kevin H.; Eighmy, T. Taylor

2007-01-01

The goal of this research was to provide a tool for regulators to evaluate the groundwater contamination from the use of virgin and secondary materials in road construction. A finite element model, HYDRUS2D, was used to evaluate generic scenarios for secondary material use in base layers. Use of generic model results for particular applications was demonstrated through a steel slag example. The hydrology and reactive transport of contaminants were modeled in a two-dimensional cross section of a road. Model simulations showed that in an intact pavement, lateral velocities from the edge towards the centerline may transport contaminants in the base layer. The dominant transport mechanisms are advection closer to the edge and diffusion closer to the centerline. A shoulder joint in the pavement allows 0.03 to 0.45 m 3 /day of infiltration per meter of joint length as a function of the base and subgrade hydrology and the rain intensity. Scenario simulations showed that salts in the base layer of pavements are depleted by 99% in the first 20 years, whereas the metals may not reach the groundwater in 20 years at any significant concentrations if the pavement is built on adsorbing soils

Modeling for Airborne Contamination

International Nuclear Information System (INIS)

F.R. Faillace; Y. Yuan

2000-01-01

The objective of Modeling for Airborne Contamination (referred to from now on as ''this report'') is to provide a documented methodology, along with supporting information, for estimating the release, transport, and assessment of dose to workers from airborne radioactive contaminants within the Monitored Geologic Repository (MGR) subsurface during the pre-closure period. Specifically, this report provides engineers and scientists with methodologies for estimating how concentrations of contaminants might be distributed in the air and on the drift surfaces if released from waste packages inside the repository. This report also provides dose conversion factors for inhalation, air submersion, and ground exposure pathways used to derive doses to potentially exposed subsurface workers. The scope of this report is limited to radiological contaminants (particulate, volatile and gaseous) resulting from waste package leaks (if any) and surface contamination and their transport processes. Neutron activation of air, dust in the air and the rock walls of the drift during the preclosure time is not considered within the scope of this report. Any neutrons causing such activation are not themselves considered to be ''contaminants'' released from the waste package. This report: (1) Documents mathematical models and model parameters for evaluating airborne contaminant transport within the MGR subsurface; and (2) Provides tables of dose conversion factors for inhalation, air submersion, and ground exposure pathways for important radionuclides. The dose conversion factors for air submersion and ground exposure pathways are further limited to drift diameters of 7.62 m and 5.5 m, corresponding to the main and emplacement drifts, respectively. If the final repository design significantly deviates from these drift dimensions, the results in this report may require revision. The dose conversion factors are further derived by using concrete of sufficient thickness to simulate the drift

Anthropogenic contamination of a phreatic drinking water winning: 3-dimensional reactive transport modelling

NARCIS (Netherlands)

Griffioen, J.|info:eu-repo/dai/nl/091129265; van der Grift, B.|info:eu-repo/dai/nl/373433484; Maas, D.; van den Brink, C.|info:eu-repo/dai/nl/187443416; Zaadnoordijk, J. W.

2003-01-01

Groundwater is contaminated at the regional scale by agricultural activities and atmospheric deposition. A 3-D transport model was set-up for a phreatic drinking water winning, where the groundwater composition was monitored accurately. The winning is situated at an area with unconsolidated

Approach to uncertainty assessment for fluid flow and contaminant transport modeling in heterogeneous groundwater systems

International Nuclear Information System (INIS)

Nelson, R.W.; Jacobson, E.A.; Conbere, W.

1985-06-01

There is a growing awareness of the need to quantify uncertainty in groundwater flow and transport model results. Regulatory organizations are beginning to request the statistical distributions of predicted contaminant arrival to the biosphere, so that realistic confidence intervals can be obtained for the modeling results. To meet these needs, methods are being developed to quantify uncertainty in the subsurface flow and transport analysis sequence. A method for evaluating this uncertainty, described in this paper, considers uncertainty in material properties and was applied to an example field problem. Our analysis begins by using field measurements of transmissivity and hydraulic head in a regional, parameter estimation method to obtain a calibrated fluid flow model and a covariance matrix of the parameter estimation errors. The calibrated model and the covariance matrix are next used in a conditional simulation mode to generate a large number of 'head realizations.' The specific pore water velocity distribution for each realization is calculated from the effective porosity, the aquifer parameter realization, and the associated head values. Each velocity distribution is used to obtain a transport solution for a contaminant originating from the same source for all realizations. The results are the statistical distributions for the outflow arrival times. The confidence intervals for contamination reaching the biosphere are obtained from the outflow statistical distributions. 20 refs., 12 figs

A reactive transport model for mercury fate in contaminated soil--sensitivity analysis.

Science.gov (United States)

Leterme, Bertrand; Jacques, Diederik

2015-11-01

We present a sensitivity analysis of a reactive transport model of mercury (Hg) fate in contaminated soil systems. The one-dimensional model, presented in Leterme et al. (2014), couples water flow in variably saturated conditions with Hg physico-chemical reactions. The sensitivity of Hg leaching and volatilisation to parameter uncertainty is examined using the elementary effect method. A test case is built using a hypothetical 1-m depth sandy soil and a 50-year time series of daily precipitation and evapotranspiration. Hg anthropogenic contamination is simulated in the topsoil by separately considering three different sources: cinnabar, non-aqueous phase liquid and aqueous mercuric chloride. The model sensitivity to a set of 13 input parameters is assessed, using three different model outputs (volatilized Hg, leached Hg, Hg still present in the contaminated soil horizon). Results show that dissolved organic matter (DOM) concentration in soil solution and the binding constant to DOM thiol groups are critical parameters, as well as parameters related to Hg sorption to humic and fulvic acids in solid organic matter. Initial Hg concentration is also identified as a sensitive parameter. The sensitivity analysis also brings out non-monotonic model behaviour for certain parameters.

Generalizing Source Geometry of Site Contamination by Simulating and Analyzing Analytical Solution of Three-Dimensional Solute Transport Model

Directory of Open Access Journals (Sweden)

Xingwei Wang

2014-01-01

Full Text Available Due to the uneven distribution of pollutions and blur edge of pollutant area, there will exist uncertainty of source term shape in advective-diffusion equation model of contaminant transport. How to generalize those irregular source terms and deal with those uncertainties is very critical but rarely studied in previous research. In this study, the fate and transport of contaminant from rectangular and elliptic source geometry were simulated based on a three-dimensional analytical solute transport model, and the source geometry generalization guideline was developed by comparing the migration of contaminant. The result indicated that the variation of source area size had no effect on pollution plume migration when the plume migrated as far as five times of source side length. The migration of pollution plume became slower with the increase of aquifer thickness. The contaminant concentration was decreasing with scale factor rising, and the differences among various scale factors became smaller with the distance to field increasing.

Contaminant Attenuation and Transport Characterization of 200-UP-1 Operable Unit Sediment Samples

Energy Technology Data Exchange (ETDEWEB)

Lee, Brady D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Szecsody, James E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Qafoku, Nikolla [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); McElroy, Erin M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Baum, Steven R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Snyder, Michelle MV [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lawter, Amanda R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Resch, Charles T. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Gartman, Brandy N. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zhong, Lirong [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Saunders, Danielle L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Williams, Benjamin D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Horner, Jacob A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Leavy, Ian I. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Christiansen, Beren B. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Clayton, Ray E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Johnson, Kayla C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2017-09-27

Contaminants disposed of at the land surface migrate through the vadose zone, forming plumes in groundwater. Processes that occur in the groundwater can attenuate contaminant concentrations during transport through the aquifer. For this reason, quantifying contaminant attenuation and contaminant transport processes in the aquifer, in support of the conceptual site model (CSM) and fate and transport modeling, are important for assessing the need for, and type of, remediation in the groundwater, including monitored natural attenuation (MNA). The framework to characterize attenuation and transport processes provided in U.S. Environmental Protection Agency (EPA) guidance documents was used to guide the laboratory effort reported herein.

Code-To-Code Benchmarking Of The Porflow And GoldSim Contaminant Transport Models Using A Simple 1-D Domain - 11191

International Nuclear Information System (INIS)

Hiergesell, R.; Taylor, G.

2010-01-01

An investigation was conducted to compare and evaluate contaminant transport results of two model codes, GoldSim and Porflow, using a simple 1-D string of elements in each code. Model domains were constructed to be identical with respect to cell numbers and dimensions, matrix material, flow boundary and saturation conditions. One of the codes, GoldSim, does not simulate advective movement of water; therefore the water flux term was specified as a boundary condition. In the other code, Porflow, a steady-state flow field was computed and contaminant transport was simulated within that flow-field. The comparisons were made solely in terms of the ability of each code to perform contaminant transport. The purpose of the investigation was to establish a basis for, and to validate follow-on work that was conducted in which a 1-D GoldSim model developed by abstracting information from Porflow 2-D and 3-D unsaturated and saturated zone models and then benchmarked to produce equivalent contaminant transport results. A handful of contaminants were selected for the code-to-code comparison simulations, including a non-sorbing tracer and several long- and short-lived radionuclides exhibiting both non-sorbing to strongly-sorbing characteristics with respect to the matrix material, including several requiring the simulation of in-growth of daughter radionuclides. The same diffusion and partitioning coefficients associated with each contaminant and the half-lives associated with each radionuclide were incorporated into each model. A string of 10-elements, having identical spatial dimensions and properties, were constructed within each code. GoldSim's basic contaminant transport elements, Mixing cells, were utilized in this construction. Sand was established as the matrix material and was assigned identical properties (e.g. bulk density, porosity, saturated hydraulic conductivity) in both codes. Boundary conditions applied included an influx of water at the rate of 40 cm/yr at one

Monitoring of transport contamination

International Nuclear Information System (INIS)

Turkin, N.F.

1980-01-01

Organization of monitoring of transport contamination is considered. A particularly thorough monitoring is recommended to be carried out in loading-unloading operations. The monitoring is performed when leaving loading-unloading site and zone under control and prior to preventive examination, technical service or repair. The method of monitoring of auto transport contamination with high-energy β-emitters by means of a special stand permitting the automation of the monitoring process is described [ru

A combined PHREEQC-2/parallel fracture model for the simulation of laminar/non-laminar flow and contaminant transport with reactions

Science.gov (United States)

Masciopinto, Costantino; Volpe, Angela; Palmiotta, Domenico; Cherubini, Claudia

2010-09-01

A combination of a parallel fracture model with the PHREEQC-2 geochemical model was developed to simulate sequential flow and chemical transport with reactions in fractured media where both laminar and turbulent flows occur. The integration of non-laminar flow resistances in one model produced relevant effects on water flow velocities, thus improving model prediction capabilities on contaminant transport. The proposed conceptual model consists of 3D rock-blocks, separated by horizontal bedding plane fractures with variable apertures. Particle tracking solved the transport equations for conservative compounds and provided input for PHREEQC-2. For each cluster of contaminant pathways, PHREEQC-2 determined the concentration for mass-transfer, sorption/desorption, ion exchange, mineral dissolution/precipitation and biodegradation, under kinetically controlled reactive processes of equilibrated chemical species. Field tests have been performed for the code verification. As an example, the combined model has been applied to a contaminated fractured aquifer of southern Italy in order to simulate the phenol transport. The code correctly fitted the field available data and also predicted a possible rapid depletion of phenols as a result of an increased biodegradation rate induced by a simulated artificial injection of nitrates, upgradient to the sources.

An adaptive hybrid EnKF-OI scheme for efficient state-parameter estimation of reactive contaminant transport models

KAUST Repository

El Gharamti, Mohamad; Valstar, Johan R.; Hoteit, Ibrahim

2014-01-01

Reactive contaminant transport models are used by hydrologists to simulate and study the migration and fate of industrial waste in subsurface aquifers. Accurate transport modeling of such waste requires clear understanding of the system's parameters, such as sorption and biodegradation. In this study, we present an efficient sequential data assimilation scheme that computes accurate estimates of aquifer contamination and spatially variable sorption coefficients. This assimilation scheme is based on a hybrid formulation of the ensemble Kalman filter (EnKF) and optimal interpolation (OI) in which solute concentration measurements are assimilated via a recursive dual estimation of sorption coefficients and contaminant state variables. This hybrid EnKF-OI scheme is used to mitigate background covariance limitations due to ensemble under-sampling and neglected model errors. Numerical experiments are conducted with a two-dimensional synthetic aquifer in which cobalt-60, a radioactive contaminant, is leached in a saturated heterogeneous clayey sandstone zone. Assimilation experiments are investigated under different settings and sources of model and observational errors. Simulation results demonstrate that the proposed hybrid EnKF-OI scheme successfully recovers both the contaminant and the sorption rate and reduces their uncertainties. Sensitivity analyses also suggest that the adaptive hybrid scheme remains effective with small ensembles, allowing to reduce the ensemble size by up to 80% with respect to the standard EnKF scheme. © 2014 Elsevier Ltd.

An adaptive hybrid EnKF-OI scheme for efficient state-parameter estimation of reactive contaminant transport models

KAUST Repository

El Gharamti, Mohamad

2014-09-01

Reactive contaminant transport models are used by hydrologists to simulate and study the migration and fate of industrial waste in subsurface aquifers. Accurate transport modeling of such waste requires clear understanding of the system\\'s parameters, such as sorption and biodegradation. In this study, we present an efficient sequential data assimilation scheme that computes accurate estimates of aquifer contamination and spatially variable sorption coefficients. This assimilation scheme is based on a hybrid formulation of the ensemble Kalman filter (EnKF) and optimal interpolation (OI) in which solute concentration measurements are assimilated via a recursive dual estimation of sorption coefficients and contaminant state variables. This hybrid EnKF-OI scheme is used to mitigate background covariance limitations due to ensemble under-sampling and neglected model errors. Numerical experiments are conducted with a two-dimensional synthetic aquifer in which cobalt-60, a radioactive contaminant, is leached in a saturated heterogeneous clayey sandstone zone. Assimilation experiments are investigated under different settings and sources of model and observational errors. Simulation results demonstrate that the proposed hybrid EnKF-OI scheme successfully recovers both the contaminant and the sorption rate and reduces their uncertainties. Sensitivity analyses also suggest that the adaptive hybrid scheme remains effective with small ensembles, allowing to reduce the ensemble size by up to 80% with respect to the standard EnKF scheme. © 2014 Elsevier Ltd.

Contaminant transport modeling studies of Russian sites

International Nuclear Information System (INIS)

Tsang, Chin-Fu

1993-01-01

Lawrence Berkeley Laboratory (LBL) established mechanisms that promoted cooperation between U.S. and Russian scientists in scientific research as well as environmental technology transfer. Using Russian experience and U.S technology, LBL developed approaches for field investigations, site evaluation, waste disposal, and remediation at Russian contaminated sites. LBL assessed a comprehensive database as well as an actual, large-scale contaminated site to evaluate existing knowledge of and test mathematical models used for the assessment of U.S. contaminated sites

Simulation of contaminated sediment transport in White Oak Creek basin

International Nuclear Information System (INIS)

Bao, Y.; Clapp, R.B.; Brenkert, A.L.; Moore, T.D.; Fontaine, T.A.

1995-01-01

This paper presents a systematic approach to management of the contaminated sediments in the White Oak Creek watershed at Oak Ridge National Laboratory near Oak Ridge, Tennessee. The primary contaminant of concern is radioactive cesium-137 ( 137 Cs), which binds to soil and sediment particles. The key components in the approach include an intensive sampling and monitoring system for flood events; modeling of hydrological processes, sediment transport, and contaminant flux movement; and a decision framework with a detailed human health risk analysis. Emphasis is placed on modeling of watershed rainfall-runoff and contaminated sediment transport during flooding periods using the Hydrologic Simulation Program- Fortran (HSPF) model. Because a large number of parameters are required in HSPF modeling, the major effort in the modeling process is the calibration of model parameters to make simulation results and measured values agree as closely as possible. An optimization model incorporating the concepts of an expert system was developed to improve calibration results and efficiency. Over a five-year simulation period, the simulated flows match the observed values well. Simulated total amount of sediment loads at various locations during storms match with the observed values within a factor of 1.5. Simulated annual releases of 137 Cs off-site locations match the data within a factor of 2 for the five-year period. The comprehensive modeling approach can provide a valuable tool for decision makers to quantitatively analyze sediment erosion, deposition, and transport; exposure risk related to radionuclides in contaminated sediment; and various management strategies

Contaminant transport model validation: The Oak Ridge Reservation

International Nuclear Information System (INIS)

Lee, R.R.; Ketelle, R.H.

1988-09-01

In the complex geologic setting on the Oak Ridge Reservation, hydraulic conductivity is anisotropic and flow is strongly influenced by an extensive and largely discontinuous fracture network. Difficulties in describing and modeling the aquifer system prompted a study to obtain aquifer property data to be used in a groundwater flow model validation experiment. Characterization studies included the performance of an extensive suite of aquifer test within a 600-square-meter area to obtain aquifer property values to describe the flow field in detail. Following aquifer test, a groundwater tracer test was performed under ambient conditions to verify the aquifer analysis. Tracer migration data in the near-field were used in model calibration to predict tracer arrival time and concentration in the far-field. Despite the extensive aquifer testing, initial modeling inaccurately predicted tracer migration direction. Initial tracer migration rates were consistent with those predicted by the model; however, changing environmental conditions resulted in an unanticipated decay in tracer movement. Evaluation of the predictive accuracy of groundwater flow and contaminant transport models on the Oak Ridge Reservation depends on defining the resolution required, followed by field testing and model grid definition at compatible scales. The use of tracer tests, both as a characterization method and to verify model results, provides the highest level of resolution of groundwater flow characteristics. 3 refs., 4 figs

Chaotic-Dynamical Conceptual Model to Describe Fluid Flow and Contaminant Transport in a Fractured Vadose Zone

International Nuclear Information System (INIS)

Faybishenko, Boris; Doughty, Christine; Geller, Jil T.

1999-01-01

DOE faces the remediation of numerous contaminated sites, such as those at Hanford, INEEL, LLNL, and LBNL, where organic and/or radioactive wastes were intentionally or accidentally released to the vadose zone from surface spills, underground tanks, cribs, shallow ponds, and deep wells. Migration of these contaminants through the vadose zone has led to the contamination of (or threatens to contaminate) underlying groundwater. A key issue in choosing a corrective action plan to clean up contaminated sites is the determination of the location, total mass, mobility and travel time to receptors for contaminants moving in the vadose zone. These problems are difficult to solve in a technically defensible and accurate manner because contaminants travel downward intermittently, through narrow pathways, driven by variations in environmental conditions. These preferential flow pathways can be difficult to find and predict. The primary objective of this project is to determine if and when dynamical chaos theory can be used to investigate infiltration of fluid and contaminant transport in heterogeneous soils and fractured rocks. The objective of this project is being achieved through the following activities: Development of multi scale conceptual models and mathematical and numerical algorithms for flow and transport, which incorporate both (a) the spatial variability of heterogeneous porous and fractured media and (b) the temporal dynamics of flow and transport; Development of appropriate experimental field and laboratory techniques needed to detect diagnostic parameters for chaotic behavior of flow; Evaluation of chaotic behavior of flow in laboratory and field experiments using methods from non-linear dynamics; Evaluation of the impact these dynamics may have on contaminant transport through heterogeneous fractured rocks and soils and remediation efforts. This approach is based on the consideration of multi scale spatial heterogeneity and flow phenomena that are affected by

Application of SPARROW modeling to understanding contaminant fate and transport from uplands to streams

Science.gov (United States)

Ator, Scott; Garcia, Ana Maria.

2016-01-01

Understanding spatial variability in contaminant fate and transport is critical to efficient regional water-quality restoration. An approach to capitalize on previously calibrated spatially referenced regression (SPARROW) models to improve the understanding of contaminant fate and transport was developed and applied to the case of nitrogen in the 166,000 km2 Chesapeake Bay watershed. A continuous function of four hydrogeologic, soil, and other landscape properties significant (α = 0.10) to nitrogen transport from uplands to streams was evaluated and compared among each of the more than 80,000 individual catchments (mean area, 2.1 km2) in the watershed. Budgets (including inputs, losses or net change in storage in uplands and stream corridors, and delivery to tidal waters) were also estimated for nitrogen applied to these catchments from selected upland sources. Most (81%) of such inputs are removed, retained, or otherwise processed in uplands rather than transported to surface waters. Combining SPARROW results with previous budget estimates suggests 55% of this processing is attributable to denitrification, 23% to crop or timber harvest, and 6% to volatilization. Remaining upland inputs represent a net annual increase in landscape storage in soils or biomass exceeding 10 kg per hectare in some areas. Such insights are important for planning watershed restoration and for improving future watershed models.

A nonequilibrium model for reactive contaminant transport through fractured porous media: Model development and semianalytical solution

Science.gov (United States)

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.

A novel modeling tool with multi-stressor functionality for organic contaminant transport and fate in the Baltic Sea

Energy Technology Data Exchange (ETDEWEB)

Undeman, E., E-mail: emma.undeman@itm.su.se [Baltic Nest Institute, Baltic Sea Centre, Stockholm University, 10691 Stockholm (Sweden); Department of Applied Environmental Science, Stockholm University, 11418 Stockholm (Sweden); Gustafsson, E., E-mail: erik.gustafsson@su.se [Baltic Nest Institute, Baltic Sea Centre, Stockholm University, 10691 Stockholm (Sweden); Gustafsson, B.G., E-mail: bo.gustafsson@su.se [Baltic Nest Institute, Baltic Sea Centre, Stockholm University, 10691 Stockholm (Sweden)

2014-11-01

The coupled physical–biogeochemical model BALTSEM, previously used to assess nutrient/carbon cycles and eutrophication in the Baltic Sea, has been expanded to include algorithms for calculations of organic contaminant environmental transport and fate. This novel model version (BALTSEM-POP) is evaluated for polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and hexachlorobenzene (HCB) in Baltic Sea surface water and sediment. Modeled dissolved concentrations are usually within a factor of 2–4 of observed concentrations, however with larger deviations for furans. Calculated concentrations in particulate organic matter are less accurate (within factors of 1–700), likely due to errors in estimated pelagic biomass, particulate matter–water partitioning, and large natural variability in field data. Concentrations in sediments are usually predicted within a factor of 6. The good performance of the model illustrates its usefulness for exploration of contaminant fate in response to variations in nutrient input and climatic conditions in the Baltic Sea marine environment. - Highlights: • A new model for organic chemical transport and fate in the Baltic Sea is presented. • Physical and biogeochemical processes are linked to organic contaminant transport. • The model is evaluated for PCBs, HCB and PCDD/Fs. • The model can predict dissolved concentrations within a factor of ca 2–4. • Predictions for concentrations in particulate matter and sediment are less accurate.

Flow and contaminant transport in fractured rocks

International Nuclear Information System (INIS)

Bear, J.; Tsang, C.F.; Marsily, G. de

1993-01-01

This book is a compilation of nine articles dealing with various aspect of flow in fractured media. Articles range from radionuclide waste to multiphase flow in petroleum reservoirs to practical field test methods. Each chapter contains copious figures to aid the reader, but is also a detailed in-depth analysis of some major flow problem. The subjects covered are as follows: an introduction to flow and transport models; solute transport in fractured rock with application to radioactive waste repositories; solute transport models through fractured networks; theoretical view of stochastic models of fracture systems; numerical models of tracers; multiphase flow models in fractured systems and petroleum reservoirs; unsaturated flow modeling; comparative analysis of various flow modeling techniques in fractured media; and, a summary of field methods for measuring transfers of mass, heat, contaminant, momentum, and electrical charge in fractured media

Development and applications of two finite element groundwater flow and contaminant transport models: FEWA and FEMA

International Nuclear Information System (INIS)

Yeh, G.T.; Wong, K.V.; Craig, P.M.; Davis, E.C.

1985-01-01

This paper presents the construction, verification, and application of two groundwater flow and contaminant transport models: A Finite Element Model of Water Flow through Aquifers (FEWA) and A Finite Element Model of Material Transport through Aquifers (FEMA). The construction is based on the finite element approximation of partial differential equations of groundwater flow (FEWA) and of solute movement (FEMA). The particular features of FEWA and FEMA are their versatility and flexibility for dealing with nearly all vertically integrated two-dimensional problems. The models were verified against both analytical solutions and widely used US Geological Survey finite difference approximations. They were then applied for calibration and validation, using data obtained in experiments at the Engineering Test Facility at Oak Ridge National Laboratory. Results indicated that the models are valid for this specific site. To demonstrate the versatility anf flexibility of the models, they were applied to two hypothetical, but realistic, complex problems and three field sites across the United States. In these applications the models yielded good agreement with the field data for all three sites. Finally, the predictive capabilities of the models were demonstrated using data obtained at the Hialeah Preston site in Florida. This case illustrates the capability of FEWA and FEMA as predictive tools and their usefulness in the management of groundwater flow and contaminant transport. 25 refs

Low-rank Kalman filtering for efficient state estimation of subsurface advective contaminant transport models

KAUST Repository

El Gharamti, Mohamad

2012-04-01

Accurate knowledge of the movement of contaminants in porous media is essential to track their trajectory and later extract them from the aquifer. A two-dimensional flow model is implemented and then applied on a linear contaminant transport model in the same porous medium. Because of different sources of uncertainties, this coupled model might not be able to accurately track the contaminant state. Incorporating observations through the process of data assimilation can guide the model toward the true trajectory of the system. The Kalman filter (KF), or its nonlinear invariants, can be used to tackle this problem. To overcome the prohibitive computational cost of the KF, the singular evolutive Kalman filter (SEKF) and the singular fixed Kalman filter (SFKF) are used, which are variants of the KF operating with low-rank covariance matrices. Experimental results suggest that under perfect and imperfect model setups, the low-rank filters can provide estimates as accurate as the full KF but at much lower computational effort. Low-rank filters are demonstrated to significantly reduce the computational effort of the KF to almost 3%. © 2012 American Society of Civil Engineers.

Contaminant fate and transport in the Venice Lagoon: results from a multi-segment multimedia model.

Science.gov (United States)

Sommerfreund, J K; Gandhi, N; Diamond, M L; Mugnai, C; Frignani, M; Capodaglio, G; Gerino, M; Bellucci, L G; Giuliani, S

2010-03-01

Contaminant loadings to the Venice Lagoon peaked from 1950s-1980s and although they have since declined, contaminant concentrations remain elevated in sediment and seafood. In order to identify the relative importance of contaminant sources, inter-media exchange and removal pathways, a modified 10-segment fugacity/aquivalence-based model was developed for octachlorodibenzodioxin/furan (OCDD/F), PCB-180, Pb and Cu in the Venice Lagoon. Results showed that in-place pollution nearby the industrial area, current industrial discharges, and tributary loadings were the main sources of contaminants to the lagoon, with negligible contributions from the atmosphere. The fate of these contaminants was governed by sediment-water exchange with simultaneous advective transport by water circulation. Contaminants circulated amongst the northern and central basins with a small fraction reaching the far southern basin and the Chioggia inlet. As a consequence, we estimated limited contaminant transfer to the Adriatic Sea, trapping the majority of contaminants in the sediment in this "average" circulation scenario which does not account for periodic flooding events. (c) 2009 Elsevier Inc. All rights reserved.

An Iterative Ensemble Kalman Filter with One-Step-Ahead Smoothing for State-Parameters Estimation of Contaminant Transport Models

KAUST Repository

Gharamti, M. E.; Ait-El-Fquih, Boujemaa; Hoteit, Ibrahim

2015-01-01

Numerical experiments are conducted with a two-dimensional synthetic subsurface transport model simulating the migration of a contaminant plume in a heterogenous aquifer domain. Contaminant concentration data are assimilated to estimate both the contaminant state and the hydraulic conductivity field. Assimilation runs are performed under imperfect modeling conditions and various observational scenarios. Simulation results suggest that the proposed scheme efficiently recovers both the contaminant state and the aquifer conductivity, providing more accurate estimates than the standard Joint and Dual EnKFs in all tested scenarios. Iterating on the update step of the new scheme further enhances the proposed filter’s behavior. In term of computational cost, the new Joint-EnKF is almost equivalent to that of the Dual-EnKF, but requires twice more model integrations than the standard Joint-EnKF.

Semianalytical solutions for contaminant transport under variable velocity field in a coastal aquifer

Science.gov (United States)

Koohbor, Behshad; Fahs, Marwan; Ataie-Ashtiani, Behzad; Simmons, Craig T.; Younes, Anis

2018-05-01

Existing closed-form solutions of contaminant transport problems are limited by the mathematically convenient assumption of uniform flow. These solutions cannot be used to investigate contaminant transport in coastal aquifers where seawater intrusion induces a variable velocity field. An adaptation of the Fourier-Galerkin method is introduced to obtain semi-analytical solutions for contaminant transport in a confined coastal aquifer in which the saltwater wedge is in equilibrium with a freshwater discharge flow. Two scenarios dealing with contaminant leakage from the aquifer top surface and contaminant migration from a source at the landward boundary are considered. Robust implementation of the Fourier-Galerkin method is developed to efficiently solve the coupled flow, salt and contaminant transport equations. Various illustrative examples are generated and the semi-analytical solutions are compared against an in-house numerical code. The Fourier series are used to evaluate relevant metrics characterizing contaminant transport such as the discharge flux to the sea, amount of contaminant persisting in the groundwater and solute flux from the source. These metrics represent quantitative data for numerical code validation and are relevant to understand the effect of seawater intrusion on contaminant transport. It is observed that, for the surface contamination scenario, seawater intrusion limits the spread of the contaminant but intensifies the contaminant discharge to the sea. For the landward contamination scenario, moderate seawater intrusion affects only the spatial distribution of the contaminant plume while extreme seawater intrusion can increase the contaminant discharge to the sea. The developed semi-analytical solution presents an efficient tool for the verification of numerical models. It provides a clear interpretation of the contaminant transport processes in coastal aquifers subject to seawater intrusion. For practical usage in further studies, the full

Recent developments on surface contamination limits for packages and conveyances in transport regulations

International Nuclear Information System (INIS)

Thierfeldt, S.; Woerlen, S.; Lorenz, B.; Schwarz, W.

2009-01-01

The IAEA Regulations for the Safe Transport of Radioactive Material [1] contain requirements for contamination limits on packages and conveyances used for the transport of radioactive material. Current contamination limits for packages and conveyances under routine transport conditions have been derived from a model proposed by Fairbairn nearly 50 years ago [3]. This model has proven effective if used with pragmatism, but is based on very conservative as well as extremely simple assumptions which is in no way appropriate any more and which is not compatible with ICRP recommendations regarding radiation protection standards. Therefore, a new model has been developed over the last 8 years which reflects all steps of the transport process. The derivation of this model has been fostered by the IAEA by initiating a Co-ordinated Research Project (see section 2). The results of the calculations using this model could be directly applied as new nuclide specific transport limits for the non-fixed contamination. A corresponding regulatory text has been drafted by an IAEA technical meeting TM-36514, which was held in Tokyo November 10-14, 2008 (see section 4). (orig.)

Recent developments on surface contamination limits for packages and conveyances in transport regulations

Energy Technology Data Exchange (ETDEWEB)

Thierfeldt, S.; Woerlen, S. [Brenk Systemplanung GmbH, Aachen (Germany); Lorenz, B. [GNS Gesellschaft fuer Nuklear-Service mbH, Essen (Germany); Schwarz, W. [VGB PowerTech e.V., Essen (Germany)

2009-07-01

The IAEA Regulations for the Safe Transport of Radioactive Material [1] contain requirements for contamination limits on packages and conveyances used for the transport of radioactive material. Current contamination limits for packages and conveyances under routine transport conditions have been derived from a model proposed by Fairbairn nearly 50 years ago [3]. This model has proven effective if used with pragmatism, but is based on very conservative as well as extremely simple assumptions which is in no way appropriate any more and which is not compatible with ICRP recommendations regarding radiation protection standards. Therefore, a new model has been developed over the last 8 years which reflects all steps of the transport process. The derivation of this model has been fostered by the IAEA by initiating a Co-ordinated Research Project (see section 2). The results of the calculations using this model could be directly applied as new nuclide specific transport limits for the non-fixed contamination. A corresponding regulatory text has been drafted by an IAEA technical meeting TM-36514, which was held in Tokyo November 10-14, 2008 (see section 4). (orig.)

Analytical analysis of soil-moisture and trace-contaminant transport

International Nuclear Information System (INIS)

Larson, N.M.; Reeves, M.

1976-03-01

A transport model is presented which predicts the coupled movement of both water and trace contaminants through a layered and unsaturated soil-moisture zone. In order to achieve computation speeds suitable for watershed implementations, moisture properties are approximated as exponential functions of pressure head, and lateral flows are treated as sinks in a basically vertical one-dimensional analysis. In addition, only advection by the Darcy-flow velocities and linear adsorption by the soil matrix are considered in depicting movement of the trace contaminant. Formal solution of the resulting transport equations is obtained through use of both eigenfunction-expansion and coordinate-transformation methods. Numerical solution is effected by means of a program written in FORTRAN IV and implemented on an IBM 360/91 computer. Two example calculations illustrate both strengths and weaknesses of our model

Contaminant flow and transport simulation in cracked porous media using locally conservative schemes

KAUST Repository

Song, Pu

2012-10-25

The purpose of this paper is to analyze some features of contaminant flow passing through cracked porous medium, such as the influence of fracture network on the advection and diffusion of contaminant species, the impact of adsorption on the overall transport of contaminant wastes. In order to precisely describe the whole process, we firstly build the mathematical model to simulate this problem numerically. Taking into consideration of the characteristics of contaminant flow, we employ two partial differential equations to formulate the whole problem. One is flow equation; the other is reactive transport equation. The first equation is used to describe the total flow of contaminant wastes, which is based on Darcy law. The second one will characterize the adsorption, diffusion and convection behavior of contaminant species, which describes most features of contaminant flow we are interested in. After the construction of numerical model, we apply locally conservative and compatible algorithms to solve this mathematical model. Specifically, we apply Mixed Finite Element (MFE) method to the flow equation and Discontinuous Galerkin (DG) method for the transport equation. MFE has a good convergence rate and numerical accuracy for Darcy velocity. DG is more flexible and can be used to deal with irregular meshes, as well as little numerical diffusion. With these two numerical means, we investigate the sensitivity analysis of different features of contaminant flow in our model, such as diffusion, permeability and fracture density. In particular, we study K d values which represent the distribution of contaminant wastes between the solid and liquid phases. We also make omparisons of two different schemes and discuss the advantages of both methods. © 2012 Global Science Press.

A chromate-contaminated site in southern Switzerland – Part 2: Reactive transport modeling to optimize remediation options

International Nuclear Information System (INIS)

Wanner, Christoph; Eggenberger, Urs; Mäder, Urs

2012-01-01

A 2D horizontal reactive transport model of a chromate-contaminated site near Rivera, Switzerland, was developed using the computer code CrunchFlow to evaluate site remediation strategies. Transport processes were defined according to the results of an existing hydrological model, and the definition of geochemical (reactive) processes is based on the results of a detailed mineralogical and geochemical site characterization leading to a comprehensive conceptual site model. Kinetics of naturally occurring Cr(VI) reduction by Fe(II) and natural solid organic matter is quantified by fitting measured Cr isotope ratios to a modeled 1D section along the best constrained flow line. The simulation of Cr isotope fractionation was also incorporated into the 2D model. Simulation of the measured present day Cr(VI) plume and δ 53 Cr value distribution was used for the 2D model calibration and corresponds to a situation where only monitored natural attenuation (MNA) is occurring. Other 2D model runs simulate alternate excavation scenarios. The simulations show that with an excavation of the top 2–4 m the groundwater Cr(VI) plume can be minimized, and that a deeper excavation depth only diminishes the plume if all the contaminants can be removed. A combination of an excavation of the top 2–4 m and monitoring of the ongoing natural Cr(VI) reduction is suggested as the most ecological and economical remediation strategy, even though a remaining time period with ongoing subsoil Cr(VI) contamination in the order of 1 ka is predicted.

Predicting soil, water, and air concentrations of environmental contaminants locally and regionally: Multimedia transport and transformation models

International Nuclear Information System (INIS)

McKone, T.E.; Daniels, J.I.

1991-10-01

Environmental scientists recognize that the environment functions as a complex, interconnected system. A realistic risk-management strategy for many contaminants requires a comprehensive and integrated assessment of local and regional transport and transformation processes. In response to this need, we have developed multimedia models that simulate the movement and transformation of chemicals as they spread through air, water, biota, soils, sediments, surface water, and ground water. Each component of the environment is treated as a homogeneous subsystem that can exchange water, nutrients, and chemical contaminants with other adjacent compartments. In this paper, we illustrate the use of multimedia models and measurements as tools for screening the potential risks of contaminants released to air and deposited onto soil and plants. The contaminant list includes the volatile organic compounds (VOCs) tetrachloroethylene (PCE) and trichloroethylene (TCE), the semi-volatile organic compound benzo(a)pyrene, and the radionuclides tritium and uranium-238. We examine how chemical properties effect both the ultimate route and quantity of human and ecosystem contact and identify sensitivities and uncertainties in the model results

Predicting soil, water and air concentrations of environmental contaminants locally and regionally; multimedia transport and transformation models

International Nuclear Information System (INIS)

McKone, T.E.; Daniels, J.I.

1991-01-01

Environmental scientists recognize that the environment functions as a complex, interconnected system. A realistic risk-management strategy for many contaminants requires a comprehensive and integrated assessment of local and regional transport and transformation processes. In response to this need, we have developed multimedia models that simulate the movement and transformation of chemicals as they spread through air, water, biota, soils, sediments, surface water and ground water. Each component of the environment is treated as a homogeneous subsystem that can exchange water, nutrients, and chemical contaminants with other adjacent compartments. In this paper, we illustrate the use of multimedia models and measurements as tools for screening the potential risks of contaminants released to air and deposited onto soil and plants. The contaminant list includes the volatile organic compounds (VOCs) tetrachloroethylene (PCE) and trichloroethylene (TCE), the semi-volatile organic compound benzo(a)pyrene, and the radionuclides tritium and uranium-238. We examine how chemical properties effect both the ultimate route and quantity of human and ecosystem contact and identify sensitivities and uncertainties in the model results. We consider the advantages of multimedia models relative to environmental monitoring data. (au)

Transport modeling of sorbing tracers in artificial fractures

International Nuclear Information System (INIS)

Keum, Dong Kwon; Baik, Min Hoon; Park, Chung Kyun; Cho, Young Hwan; Hahn, Phil Soo.

1998-02-01

This study was performed as part of a fifty-man year attachment program between AECL (Atomic Energy Canada Limited) and KAERI. Three kinds of computer code, HDD, POMKAP and VAMKAP, were developed to predict transport of contaminants in fractured rock. MDDM was to calculate the mass transport of contaminants in a single fracture using a simple hydrodynamic dispersion diffusion model. POMKAP was to predict the mass transport of contaminants by a two-dimensional variable aperture model. In parallel with modeling, the validation of models was also performed through the analysis of the migration experimental data obtained in acrylic plastic and granite artificial fracture system at the Whiteshell laboratories, AECL, Canada. (author). 34 refs., 11 tabs., 76 figs

Transport modeling of sorbing tracers in artificial fractures

Energy Technology Data Exchange (ETDEWEB)

Keum, Dong Kwon; Baik, Min Hoon; Park, Chung Kyun; Cho, Young Hwan; Hahn, Phil Soo

1998-02-01

This study was performed as part of a fifty-man year attachment program between AECL (Atomic Energy Canada Limited) and KAERI. Three kinds of computer code, HDD, POMKAP and VAMKAP, were developed to predict transport of contaminants in fractured rock. MDDM was to calculate the mass transport of contaminants in a single fracture using a simple hydrodynamic dispersion diffusion model. POMKAP was to predict the mass transport of contaminants by a two-dimensional variable aperture model. In parallel with modeling, the validation of models was also performed through the analysis of the migration experimental data obtained in acrylic plastic and granite artificial fracture system at the Whiteshell laboratories, AECL, Canada. (author). 34 refs., 11 tabs., 76 figs.

Savannah River Laboratory DOSTOMAN code: a compartmental pathways computer model of contaminant transport

International Nuclear Information System (INIS)

King, C.M.; Wilhite, E.L.; Root, R.W. Jr.

1985-01-01

The Savannah River Laboratory DOSTOMAN code has been used since 1978 for environmental pathway analysis of potential migration of radionuclides and hazardous chemicals. The DOSTOMAN work is reviewed including a summary of historical use of compartmental models, the mathematical basis for the DOSTOMAN code, examples of exact analytical solutions for simple matrices, methods for numerical solution of complex matrices, and mathematical validation/calibration of the SRL code. The review includes the methodology for application to nuclear and hazardous chemical waste disposal, examples of use of the model in contaminant transport and pathway analysis, a user's guide for computer implementation, peer review of the code, and use of DOSTOMAN at other Department of Energy sites. 22 refs., 3 figs

Modeling uranium transport in acidic contaminated groundwater with base addition

Energy Technology Data Exchange (ETDEWEB)

Zhang, Fan [Institute of Tibetan Plateau Research, Chinese Academy of Sciences; Luo, Wensui [ORNL; Parker, Jack C. [University of Tennessee, Knoxville (UTK); Brooks, Scott C [ORNL; Watson, David B [ORNL; Jardine, Philip [University of Tennessee, Knoxville (UTK); Gu, Baohua [ORNL

2011-01-01

This study investigates reactive transport modeling in a column of uranium(VI)-contaminated sediments with base additions in the circulating influent. The groundwater and sediment exhibit oxic conditions with low pH, high concentrations of NO{sub 3}{sup -}, SO{sub 4}{sup 2-}, U and various metal cations. Preliminary batch experiments indicate that additions of strong base induce rapid immobilization of U for this material. In the column experiment that is the focus of the present study, effluent groundwater was titrated with NaOH solution in an inflow reservoir before reinjection to gradually increase the solution pH in the column. An equilibrium hydrolysis, precipitation and ion exchange reaction model developed through simulation of the preliminary batch titration experiments predicted faster reduction of aqueous Al than observed in the column experiment. The model was therefore modified to consider reaction kinetics for the precipitation and dissolution processes which are the major mechanism for Al immobilization. The combined kinetic and equilibrium reaction model adequately described variations in pH, aqueous concentrations of metal cations (Al, Ca, Mg, Sr, Mn, Ni, Co), sulfate and U(VI). The experimental and modeling results indicate that U(VI) can be effectively sequestered with controlled base addition due to sorption by slowly precipitated Al with pH-dependent surface charge. The model may prove useful to predict field-scale U(VI) sequestration and remediation effectiveness.

Modeling uranium transport in acidic contaminated groundwater with base addition

International Nuclear Information System (INIS)

Zhang Fan; Luo Wensui; Parker, Jack C.; Brooks, Scott C.; Watson, David B.; Jardine, Philip M.; Gu Baohua

2011-01-01

This study investigates reactive transport modeling in a column of uranium(VI)-contaminated sediments with base additions in the circulating influent. The groundwater and sediment exhibit oxic conditions with low pH, high concentrations of NO 3 - , SO 4 2- , U and various metal cations. Preliminary batch experiments indicate that additions of strong base induce rapid immobilization of U for this material. In the column experiment that is the focus of the present study, effluent groundwater was titrated with NaOH solution in an inflow reservoir before reinjection to gradually increase the solution pH in the column. An equilibrium hydrolysis, precipitation and ion exchange reaction model developed through simulation of the preliminary batch titration experiments predicted faster reduction of aqueous Al than observed in the column experiment. The model was therefore modified to consider reaction kinetics for the precipitation and dissolution processes which are the major mechanism for Al immobilization. The combined kinetic and equilibrium reaction model adequately described variations in pH, aqueous concentrations of metal cations (Al, Ca, Mg, Sr, Mn, Ni, Co), sulfate and U(VI). The experimental and modeling results indicate that U(VI) can be effectively sequestered with controlled base addition due to sorption by slowly precipitated Al with pH-dependent surface charge. The model may prove useful to predict field-scale U(VI) sequestration and remediation effectiveness.

Modeling uranium transport in acidic contaminated groundwater with base addition

Energy Technology Data Exchange (ETDEWEB)

Zhang Fan, E-mail: zhangfan@itpcas.ac.cn [Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, P.O. Box 2871, Beijing, 100085 (China); Luo Wensui [Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021 (China); Parker, Jack C. [Institute for a Secure and Sustainable Environment, Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Brooks, Scott C.; Watson, David B. [Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Jardine, Philip M. [Biosystems Engineering and Soil Science Department, University of Tennessee, Knoxville, TN 37996 (United States); Gu Baohua [Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

2011-06-15

This study investigates reactive transport modeling in a column of uranium(VI)-contaminated sediments with base additions in the circulating influent. The groundwater and sediment exhibit oxic conditions with low pH, high concentrations of NO{sub 3}{sup -}, SO{sub 4}{sup 2-}, U and various metal cations. Preliminary batch experiments indicate that additions of strong base induce rapid immobilization of U for this material. In the column experiment that is the focus of the present study, effluent groundwater was titrated with NaOH solution in an inflow reservoir before reinjection to gradually increase the solution pH in the column. An equilibrium hydrolysis, precipitation and ion exchange reaction model developed through simulation of the preliminary batch titration experiments predicted faster reduction of aqueous Al than observed in the column experiment. The model was therefore modified to consider reaction kinetics for the precipitation and dissolution processes which are the major mechanism for Al immobilization. The combined kinetic and equilibrium reaction model adequately described variations in pH, aqueous concentrations of metal cations (Al, Ca, Mg, Sr, Mn, Ni, Co), sulfate and U(VI). The experimental and modeling results indicate that U(VI) can be effectively sequestered with controlled base addition due to sorption by slowly precipitated Al with pH-dependent surface charge. The model may prove useful to predict field-scale U(VI) sequestration and remediation effectiveness.

Chaotic-dynamical conceptual model to describe fluid flow and contaminant transport in a fractured vadose zone. 1998 annual progress report

International Nuclear Information System (INIS)

Doughty, C.; Dragila, M.I.; Faybishenko, B.; Podgorney, R.K.; Stoops, T.M.; Wheatcraft, S.W.; Wood, T.R.

1998-01-01

'DOE faces the remediation of numerous contaminated sites, such as those at Hanford, INEEL, LLNL, and LBNL, where organic and/or radioactive wastes were intentionally or accidentally released to the vadose zone from surface spills, underground tanks, cribs, shallow ponds, and deep wells. Migration of these contaminants through the vadose zone has lead to the contamination of or threatens to contaminate underlying groundwater. A key issue in choosing a corrective action plan to clean up contaminated sites is to determine the location, total mass, mobility and travel time to receptors for contaminants moving in the vadose zone. These problems are difficult to solve in a technically defensible and accurate manner because contaminants travel downward intermittently through narrow pathways driven by variations in environmental conditions. These preferential pathways can be difficult to find and predict. The primary objective of this project is to determine if and when dynamical chaos theory can be used to investigate infiltration of fluid and contaminant transport in heterogeneous soils and fractured rocks. The objective of this project is being achieved through the following Activities (1) Evaluation of chaotic behavior of flow in laboratory and field experiments using methods from non-linear dynamics; (2) Evaluation of the impact these dynamics may have on contaminant transport through heterogeneous fractured rocks and soils, and how it can be used to guide remediation efforts; (3) Development of a conceptual model and mathematical and numerical algorithms for flow and transport, which incorporate both: (a) the spatial variability of heterogeneous porous and fractured media, and (b) the description of the temporal dynamics of flow and transport, which may be chaotic; and (4) Development of appropriate experimental field and laboratory techniques needed to detect diagnostic parameters for chaotic behavior of flow. This approach is based on the assumption that spatial

In-stream contaminant interaction and transport

International Nuclear Information System (INIS)

Whelan, G.

1983-07-01

In order to assess contaminant exposure levels in biotic and abiotic pathways from waste-disposal sites, a comprehensive Multimedia Contaminant Environmental Exposure Assessment (MCEA) methodology using several mathematical models is being developed. Prior to a full development of the proposed methodology, a scaled-down version involving terrestrial plants, overland, and in-stream compartments was applied to an actual shallow land waste-disposal site. The purpose was to evaluate and demonstrate the attributes of the methodology. The in-stream component of the abbreviated methodology as it relates to Mortandad Canyon in Los Alamos, New Mexico is discussed herein. A two-year period was simulated consisting of six major runoff events which possessed a variety of distributions and magnitudes. The in-stream component of the methodology was composed of two models integrated to simulate the migration of radionuclides: DKWAV and TODAM. DKWAV is an unsteady, one-dimensional, second-order, explicit, finite difference, channel flow code which simulates the hydrodynamics in dendritric river systems and includes point and/or continuous lateral inflow and channel seepage. TODAM is an unsteady, one-dimensional, finite element, sediment-contaminant transport code which simulates the migration and fate of sediment and radionuclides in their dissolved and particulate phases by solving the general advection/diffusion equation with sink and source terms

Phase I Contaminant Transport Parameters for the Groundwater Flow and Contaminant Transport Model of Corrective Action Unit 97: Yucca Flat/Climax Mine, Nevada Test Site, Nye County, Nevada, Revision 0

International Nuclear Information System (INIS)

John McCord

2007-01-01

This report documents transport data and data analyses for Yucca Flat/Climax Mine CAU 97. The purpose of the data compilation and related analyses is to provide the primary reference to support parameterization of the Yucca Flat/Climax Mine CAU transport model. Specific task objectives were as follows: (1) Identify and compile currently available transport parameter data and supporting information that may be relevant to the Yucca Flat/Climax Mine CAU. (2) Assess the level of quality of the data and associated documentation. (3) Analyze the data to derive expected values and estimates of the associated uncertainty and variability. The scope of this document includes the compilation and assessment of data and information relevant to transport parameters for the Yucca Flat/Climax Mine CAU subsurface within the context of unclassified source-term contamination. Data types of interest include mineralogy, aqueous chemistry, matrix and effective porosity, dispersivity, matrix diffusion, matrix and fracture sorption, and colloid-facilitated transport parameters

Phase I Contaminant Transport Parameters for the Groundwater Flow and Contaminant Transport Model of Corrective Action Unit 97: Yucca Flat/Climax Mine, Nevada Test Site, Nye County, Nevada, Revision 0

Energy Technology Data Exchange (ETDEWEB)

John McCord

2007-09-01

This report documents transport data and data analyses for Yucca Flat/Climax Mine CAU 97. The purpose of the data compilation and related analyses is to provide the primary reference to support parameterization of the Yucca Flat/Climax Mine CAU transport model. Specific task objectives were as follows: • Identify and compile currently available transport parameter data and supporting information that may be relevant to the Yucca Flat/Climax Mine CAU. • Assess the level of quality of the data and associated documentation. • Analyze the data to derive expected values and estimates of the associated uncertainty and variability. The scope of this document includes the compilation and assessment of data and information relevant to transport parameters for the Yucca Flat/Climax Mine CAU subsurface within the context of unclassified source-term contamination. Data types of interest include mineralogy, aqueous chemistry, matrix and effective porosity, dispersivity, matrix diffusion, matrix and fracture sorption, and colloid-facilitated transport parameters.

Estimation of transport parameters of phenolic compounds and inorganic contaminants through composite landfill liners using one-dimensional mass transport model

International Nuclear Information System (INIS)

Varank, Gamze; Demir, Ahmet; Yetilmezsoy, Kaan; Bilgili, M. Sinan; Top, Selin; Sekman, Elif

2011-01-01

Highlights: → We conduct 1D advection-dispersion modeling to estimate transport parameters. → We examine fourteen phenolic compounds and three inorganic contaminants. → 2-MP, 2,4-DCP, 2,6-DCP, 2,4,5-TCP, 2,3,4,6-TeCP have the highest coefficients. → Dispersion coefficients of Cu are determined to be higher than Zn and Fe. → Transport of phenolics can be prevented by zeolite and bentonite in landfill liners. - Abstract: One-dimensional (1D) advection-dispersion transport modeling was conducted as a conceptual approach for the estimation of the transport parameters of fourteen different phenolic compounds (phenol, 2-CP, 2-MP, 3-MP, 4-MP, 2-NP, 4-NP, 2,4-DNP, 2,4-DCP, 2,6-DCP, 2,4,5-TCP, 2,4,6-TCP, 2,3,4,6-TeCP, PCP) and three different inorganic contaminants (Cu, Zn, Fe) migrating downward through the several liner systems. Four identical pilot-scale landfill reactors (0.25 m 3 ) with different composite liners (R1: 0.10 + 0.10 m of compacted clay liner (CCL), L e = 0.20 m, k e = 1 x 10 -8 m/s, R2: 0.002-m-thick damaged high-density polyethylene (HDPE) geomembrane overlying 0.10 + 0.10 m of CCL, L e = 0.20 m, k e = 1 x 10 -8 m/s, R3: 0.002-m-thick damaged HDPE geomembrane overlying a 0.02-m-thick bentonite layer encapsulated between 0.10 + 0.10 m CCL, L e = 0.22 m, k e = 1 x 10 -8 m/s, R4: 0.002-m-thick damaged HDPE geomembrane overlying a 0.02-m-thick zeolite layer encapsulated between 0.10 + 0.10 m CCL, L e = 0.22 m, k e = 4.24 x 10 -7 m/s) were simultaneously run for a period of about 540 days to investigate the nature of diffusive and advective transport of the selected organic and inorganic contaminants. The results of 1D transport model showed that the highest molecular diffusion coefficients, ranging from 4.77 x 10 -10 to 10.67 x 10 -10 m 2 /s, were estimated for phenol (R4), 2-MP (R1), 2,4-DNP (R2), 2,4-DCP (R1), 2,6-DCP (R2), 2,4,5-TCP (R2) and 2,3,4,6-TeCP (R1). For all reactors, dispersion coefficients of Cu, ranging from 3.47 x 10 -6 m 2 /s to 5

An Iterative Ensemble Kalman Filter with One-Step-Ahead Smoothing for State-Parameters Estimation of Contaminant Transport Models

KAUST Repository

Gharamti, M. E.

2015-05-11

The ensemble Kalman filter (EnKF) is a popular method for state-parameters estimation of subsurface flow and transport models based on field measurements. The common filtering procedure is to directly update the state and parameters as one single vector, which is known as the Joint-EnKF. In this study, we follow the one-step-ahead smoothing formulation of the filtering problem, to derive a new joint-based EnKF which involves a smoothing step of the state between two successive analysis steps. The new state-parameters estimation scheme is derived in a consistent Bayesian filtering framework and results in separate update steps for the state and the parameters. This new algorithm bears strong resemblance with the Dual-EnKF, but unlike the latter which first propagates the state with the model then updates it with the new observation, the proposed scheme starts by an update step, followed by a model integration step. We exploit this new formulation of the joint filtering problem and propose an efficient model-integration-free iterative procedure on the update step of the parameters only for further improved performances. Numerical experiments are conducted with a two-dimensional synthetic subsurface transport model simulating the migration of a contaminant plume in a heterogenous aquifer domain. Contaminant concentration data are assimilated to estimate both the contaminant state and the hydraulic conductivity field. Assimilation runs are performed under imperfect modeling conditions and various observational scenarios. Simulation results suggest that the proposed scheme efficiently recovers both the contaminant state and the aquifer conductivity, providing more accurate estimates than the standard Joint and Dual EnKFs in all tested scenarios. Iterating on the update step of the new scheme further enhances the proposed filter’s behavior. In term of computational cost, the new Joint-EnKF is almost equivalent to that of the Dual-EnKF, but requires twice more model

Mathematical simulation of sediment and contaminant transport in surface waters. Annual report, October 1977--September 1978

International Nuclear Information System (INIS)

Onishi, Y.; Arnold, E.M.; Serne, R.J.; Cowan, C.E.; Thompson, F.L.; Mayer, D.W.

1979-01-01

Various pathways exist for exposure of humans and biota to radioactive materials released from nuclear facilities. Hydrologic transport (liquid pathway) is one element in the evaluation of the total radiation dose to man. Mathematical models supported by well-planned field data collection programs can be useful tools in assessing the hydrologic transport and ultimate fate of radionuclides. Radionuclides with high distribution coefficients or radionuclides in surface waters with high suspended sediment concentrations are, to a great extent, adsorbed by river and marine sediments. Thus, otherwise dilute contaminants are concentrated. Contaminated sediments may be deposited on the river and ocean beds creating a significant pathway to man. Contaminated bed sediment in turn may become a long-term source of pollution through desorption and resuspension. In order to assess migration and accumulation of radionuclides in surface waters, mathematical models must correctly simulate essential mechanisms of radionuclide transport. The objectives of this study were: (1) to conduct a critical review of (a) radionuclide transport models as well as sediment transport and representative water quality models in rivers, estuaries, oceans, lakes, and reservoirs, and (b) adsorption and desorption mechanisms of radionuclides with sediments in surface waters; (2) to synthesize a mathematical model capable of predicting short- and long-term transport and accumulation of radionuclides in marine environments

Applicability of the Linear Sorption Isotherm Model to Represent Contaminant Transport Processes in Site Wide Performance Assessments

International Nuclear Information System (INIS)

FOGWELL, T.W.; LAST, G.V.

2003-01-01

The estimation of flux of contaminants through the vadose zone to the groundwater under varying geologic, hydrologic, and chemical conditions is key to making technically credible and sound decisions regarding soil site characterization and remediation, single-shell tank retrieval, and waste site closures (DOE 2000). One of the principal needs identified in the science and technology roadmap (DOE 2000) is the need to improve the conceptual and numerical models that describe the location of contaminants today, and to provide the basis for forecasting future movement of contaminants on both site-specific and site-wide scales. The State of Knowledge (DOE 1999) and Preliminary Concepts documents describe the importance of geochemical processes on the transport of contaminants through the Vadose Zone. These processes have been identified in the international list of Features, Events, and Processes (FEPs) (NEA 2000) and included in the list of FEPS currently being developed for Hanford Site assessments (Soler et al. 2001). The current vision for Hanford site-wide cumulative risk assessments as performed using the System Assessment Capability (SAC) is to represent contaminant adsorption using the linear isotherm (empirical distribution coefficient, K d ) sorption model. Integration Project Expert Panel (PEP) comments indicate that work is required to adequately justify the applicability of the linear sorption model, and to identify and defend the range of K d values that are adopted for assessments. The work plans developed for the Science and Technology (S and T) efforts, SAC, and the Core Projects must answer directly the question of ''Is there a scientific basis for the application of the linear sorption isotherm model to the complex wastes of the Hanford Site?'' This paper is intended to address these issues. The reason that well documented justification is required for using the linear sorption (K d ) model is that this approach is strictly empirical and is often

Contaminant transport in aquifers: improving the determination of model parameters

International Nuclear Information System (INIS)

Sabino, C.V.S.; Moreira, R.M.; Lula, Z.L.; Chausson, Y.; Magalhaes, W.F.; Vianna, M.N.

1998-01-01

Parameters conditioning the migration behavior of cesium and mercury are measured with their tracers 137 Cs and 203 Hg in the laboratory, using both batch and column experiments. Batch tests were used to define the sorption isotherm characteristics. Also investigated were the influences of some test parameters, in particular those due to the volume of water to mass of soil ratio (V/m). A provisional relationship between V/m and the distribution coefficient, K d , has been advanced, and a procedure to estimate K d 's valid for environmental values of the ratio V/m has been suggested. Column tests provided the parameters for a transport model. A major problem to be dealt with in such tests is the collimation of the radioactivity probe. Besides mechanically optimizing the collimator, a deconvolution procedure has been suggested and tested, with statistical criteria, to filter off both noise and spurious tracer signals. Correction procedures for the integrating effect introduced by sampling at the exit of columns have also been developed. These techniques may be helpful in increasing the accuracy required in the measurement of parameters conditioning contaminant migration in soils, thus allowing more reliable predictions based on mathematical model applications. (author)

Development of one-dimensional computational fluid dynamics code 'GFLOW' for groundwater flow and contaminant transport analysis

International Nuclear Information System (INIS)

Rahatgaonkar, P. S.; Datta, D.; Malhotra, P. K.; Ghadge, S. G.

2012-01-01

Prediction of groundwater movement and contaminant transport in soil is an important problem in many branches of science and engineering. This includes groundwater hydrology, environmental engineering, soil science, agricultural engineering and also nuclear engineering. Specifically, in nuclear engineering it is applicable in the design of spent fuel storage pools and waste management sites in the nuclear power plants. Ground water modeling involves the simulation of flow and contaminant transport by groundwater flow. In the context of contaminated soil and groundwater system, numerical simulations are typically used to demonstrate compliance with regulatory standard. A one-dimensional Computational Fluid Dynamics code GFLOW had been developed based on the Finite Difference Method for simulating groundwater flow and contaminant transport through saturated and unsaturated soil. The code is validated with the analytical model and the benchmarking cases available in the literature. (authors)

Modelling of contamination of surface atmosphere for deflation of Cesium-137 on contaminated territories

International Nuclear Information System (INIS)

Bogdanov, A.P.; Zhmura, G.M.

1994-01-01

Presence of Cesium 137 in near land air is caused at the contaminated territories by 'local' dusting and transport of the dust from the zone of strong contamination. For large distance is it caused by resuspension of radioactive dust from the surface in the given region. In accordance with the models of dusting round square sources based on Gauss statistical model of dissemination of admixtures in the atmosphere, the contaminated areas of european part of the former of USSR with the density of contamination over 1 Ci/km 2 with Cesium 137 were represented by 30 round square sources covering the main spots of contamination. The results of calculation of contamination of the atmosphere for several cities of Belarus, Russia and Ukraine, where there are the permanent points of observation for the content of radionuclides in the air, have shown that the proposed model of dusting sources describes the contamination of near land air with Cesium 137 reasonably well. 7 refs., 3 tabs

Characterization of Contaminant Transport using Naturally-Occurring U-Series Disequilibria - Final Report

International Nuclear Information System (INIS)

Murrell, Michael T.; Ku, Teh-Lung

2001-01-01

The interactions of mixed wastes containing radionuclides with solid rock surface and the mobility of the radionuclides in aquifer systems depend not only on the chemistry of the nuclides and the physico-chemical effects of radioactive decay, but also on the site-specific hydrogeology. Thus, to characterize contaminant transport, it is best to cross-check figures derived from any small-scale laboratory experiments over limited times with that obtained from field-oriented, natural analog studies. We propose such a study using the naturally-occurring U and Th decay-series disequilibria. The work of ours and other researchers have shown that the parent/daughter disequilibrium patterns existing in groundwater systems can be modeled in terms of local nuclide mass balance to arrive at such information as the rock-water contact time (fluid flow) and rates of contaminant transport, taking into account the retardation effect due to nuclide/rock interaction contaminants at INEL by grouping them into three categories, represented by isotopes of (1) Th and Pa, (2) U and (3) Ra. Mass spectrometric measurements of these elements will be emphasized in order to minimize sample size requirements and to maximize precision. Results will form the data base for a model code for computing: (1) Fluid residence time (transport rates) in the basalt aquifers at various locations, (2) The in-situ adsorption and desorption rate constants, as well as the retardation factors, of various radionuclide wastes, and (3) Rock dissolution rate and its relation to preferential flow and contamination transport in the fractured rock

Contaminant transport in Massachusetts Bay

Science.gov (United States)

Butman, Bradford

Construction of a new treatment plant and outfall to clean up Boston Harbor is currently one of the world's largest public works projects, costing about $4 billion. There is concern about the long-term impact of contaminants on Massachusetts Bay and adjacent Gulf of Maine because these areas are used extensively for transportation, recreation, fishing, and tourism, as well as waste disposal. Public concern also focuses on Stellwagen Bank, located on the eastern side of Massachusetts Bay, which is an important habitat for endangered whales. Contaminants reach Massachusetts Bay not only from Boston Harbor, but from other coastal communities on the Gulf of Maine, as well as from the atmosphere. Knowledge of the pathways, mechanisms, and rates at which pollutants are transported throughout these coastal environments is needed to address a wide range of management questions.

Analytical methods for predicting contaminant transport

International Nuclear Information System (INIS)

Pigford, T.H.

1989-09-01

This paper summarizes some of the previous and recent work at the University of California on analytical solutions for predicting contaminate transport in porous and fractured geologic media. Emphasis is given here to the theories for predicting near-field transport, needed to derive the time-dependent source term for predicting far-field transport and overall repository performance. New theories summarized include solubility-limited release rate with flow backfill in rock, near-field transport of radioactive decay chains, interactive transport of colloid and solute, transport of carbon-14 as carbon dioxide in unsaturated rock, and flow of gases out of and a waste container through cracks and penetrations. 28 refs., 4 figs

Modelling contaminant transport in saturated aquifers

International Nuclear Information System (INIS)

Lakshminarayana, V.; Nayak, T.R.

1990-01-01

With the increase in population and industrialization the problem of pollution of groundwater has become critical. The present study deals with modelling of pollutant transport through saturated aquifers. Using this model it is possible to predict the concentration distribution, spatial as well as temporal, in the aquifer. The paper also deals with one of the methods of controlling the pollutant movement, namely by pumping wells. A simulation model is developed to determine the number, location and rate of pumping of a number of wells near the source of pollution so that the concentration is within acceptable limits at the point of interest. (Author) (18 refs., 14 figs., tab.)

Modeling the migration of radioactive contaminants in groundwater of in situ leaching uranium mine

International Nuclear Information System (INIS)

Li Chunguang; Tai Kaixuan

2011-01-01

The radioactive contamination of groundwater from in situ leaching (ISL) of uranium mining is a widespread environmental problem. This paper analyzed the monitor results of groundwater contaminations for a in situ leaching uranium mine. A dynamic model of contaminants transport in groundwater in ISL well field was established. The processes and mechanisms of contaminant transport in groundwater were simulated numerically for a ISL well field. A small quantity of U and SO 4 2- migrate to outside of well field during ISL production stage. But the migration velocity and distance of contaminations is small, and the concentration is low. Contaminants migrate as anomalistic tooth-shape. The migration trend of U and SO 4 2- is consistent. Numerical modeling can provide an effective approach to analyse the transport mechanism, and forecast and control the migration of contaminants in groundwater in ISL well field. (authors)

3-dimensional self-calibrating coastal oil spill trajectory tracking and contaminant transport using HF radar

International Nuclear Information System (INIS)

Ojo, T.O.; Bonner, J.S.

2002-01-01

A study was conducted to demonstrate the dynamic behaviour of the turbulent mixing process in coastal environments for both advection and dispersion transport. The spatial variability of the coefficients that characterize the process was also examined. Every transport model should be calibrated to include specific information regarding geomorphology and climatic conditions. HF-radar equipment eliminates the need for model-recalibration and validation for transport models of coefficients which have spatial-temporal variations. The HF-radar has a grid resolution of 1000 m, providing real-time velocity coefficients by measuring surface currents. Dispersion coefficients can be derived from velocity time-series using the principle of Autocorrelation Functions (ACF) for time series. This concept was applied to two Gulf of Mexico bays in Texas, Corpus Christi and Matagorda. It was determined that the within-bay spatial variability of dispersion coefficients were many orders of magnitude higher than between-bay variability. The proposed model effectively reduced model complexity. The results of a 3-D dimensional contaminant transport model was presented. It was successfully used in the simulation of a contaminant spill scenario in the two bays using spatially distributed time-dependent transport coefficients. 5 refs., 8 figs

Evaluation of soil flushing of complex contaminated soil: An experimental and modeling simulation study

Energy Technology Data Exchange (ETDEWEB)

Yun, Sung Mi; Kang, Christina S. [Department of Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 143-701 (Korea, Republic of); Kim, Jonghwa [Department of Industrial Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 143-701 (Korea, Republic of); Kim, Han S., E-mail: hankim@konkuk.ac.kr [Department of Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 143-701 (Korea, Republic of)

2015-04-28

Highlights: • Remediation of complex contaminated soil achieved by sequential soil flushing. • Removal of Zn, Pb, and heavy petroleum oils using 0.05 M citric acid and 2% SDS. • Unified desorption distribution coefficients modeled and experimentally determined. • Nonequilibrium models for the transport behavior of complex contaminants in soils. - Abstract: The removal of heavy metals (Zn and Pb) and heavy petroleum oils (HPOs) from a soil with complex contamination was examined by soil flushing. Desorption and transport behaviors of the complex contaminants were assessed by batch and continuous flow reactor experiments and through modeling simulations. Flushing a one-dimensional flow column packed with complex contaminated soil sequentially with citric acid then a surfactant resulted in the removal of 85.6% of Zn, 62% of Pb, and 31.6% of HPO. The desorption distribution coefficients, K{sub Ubatch} and K{sub Lbatch}, converged to constant values as C{sub e} increased. An equilibrium model (ADR) and nonequilibrium models (TSNE and TRNE) were used to predict the desorption and transport of complex contaminants. The nonequilibrium models demonstrated better fits with the experimental values obtained from the column test than the equilibrium model. The ranges of K{sub Ubatch} and K{sub Lbatch} were very close to those of K{sub Ufit} and K{sub Lfit} determined from model simulations. The parameters (R, β, ω, α, and f) determined from model simulations were useful for characterizing the transport of contaminants within the soil matrix. The results of this study provide useful information for the operational parameters of the flushing process for soils with complex contamination.

FLAME: A finite element computer code for contaminant transport n variably-saturated media

International Nuclear Information System (INIS)

Baca, R.G.; Magnuson, S.O.

1992-06-01

A numerical model was developed for use in performance assessment studies at the INEL. The numerical model referred to as the FLAME computer code, is designed to simulate subsurface contaminant transport in a variably-saturated media. The code can be applied to model two-dimensional contaminant transport in an and site vadose zone or in an unconfined aquifer. In addition, the code has the capability to describe transport processes in a porous media with discrete fractures. This report presents the following: description of the conceptual framework and mathematical theory, derivations of the finite element techniques and algorithms, computational examples that illustrate the capability of the code, and input instructions for the general use of the code. The development of the FLAME computer code is aimed at providing environmental scientists at the INEL with a predictive tool for the subsurface water pathway. This numerical model is expected to be widely used in performance assessments for: (1) the Remedial Investigation/Feasibility Study process and (2) compliance studies required by the US Department of energy Order 5820.2A

FLAME: A finite element computer code for contaminant transport n variably-saturated media

Energy Technology Data Exchange (ETDEWEB)

Baca, R.G.; Magnuson, S.O.

1992-06-01

A numerical model was developed for use in performance assessment studies at the INEL. The numerical model referred to as the FLAME computer code, is designed to simulate subsurface contaminant transport in a variably-saturated media. The code can be applied to model two-dimensional contaminant transport in an and site vadose zone or in an unconfined aquifer. In addition, the code has the capability to describe transport processes in a porous media with discrete fractures. This report presents the following: description of the conceptual framework and mathematical theory, derivations of the finite element techniques and algorithms, computational examples that illustrate the capability of the code, and input instructions for the general use of the code. The development of the FLAME computer code is aimed at providing environmental scientists at the INEL with a predictive tool for the subsurface water pathway. This numerical model is expected to be widely used in performance assessments for: (1) the Remedial Investigation/Feasibility Study process and (2) compliance studies required by the US Department of energy Order 5820.2A.

UNCERT: geostatistics, uncertainty analysis and visualization software applied to groundwater flow and contaminant transport modeling

International Nuclear Information System (INIS)

Wingle, W.L.; Poeter, E.P.; McKenna, S.A.

1999-01-01

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. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

Implications and concerns of deep-seated disposal of hydrocarbon exploration produced water using three-dimensional contaminant transport model in Bhit Area, Dadu District of Southern Pakistan.

Science.gov (United States)

Ahmad, Zulfiqar; Akhter, Gulraiz; Ashraf, Arshad; Fryar, Alan

2010-11-01

A three-dimensional contaminant transport model has been developed to simulate and monitor the migration of disposal of hydrocarbon exploration produced water in Injection well at 2,100 m depth in the Upper Cretaceous Pab sandstone, Bhit area in Dadu district of Southern Pakistan. The regional stratigraphic and structural geological framework of the area, landform characteristics, meteorological parameters, and hydrogeological milieu have been used in the model to generate the initial simulation of steady-state flow condition in the underlying aquifer's layers. The geometry of the shallow and deep-seated characteristics of the geological formations was obtained from the drilling data, electrical resistivity sounding surveys, and geophysical well-logging information. The modeling process comprised of steady-state simulation and transient simulation of the prolific groundwater system of contamination transport after 1, 10, 30 years of injection. The contaminant transport was evaluated from the bottom of the injection well, and its short- and long-term effects were determined on aquifer system lying in varying hydrogeological and geological conditions.

Estimating fate and transport of multiple contaminants in the vadose zone using a multi-layered soil column and three-phase equilibrium partitioning model

International Nuclear Information System (INIS)

Rucker, Gregory G.

2007-01-01

Soils at waste sites must be evaluated for the potential of residual soil contamination to leach and migrate to the groundwater beneath the disposal area. If migration to the aquifer occurs, contaminants can travel vast distances and pollute drinking water wells, thus exposing human receptors to harmful levels of toxins and carcinogens. To prevent groundwater contamination, a contaminant fate and transport analysis is necessary to assess the migration potential of residual soil contaminants. This type of migration analysis is usually performed using a vadose zone model to account for complex geotechnical and chemical variables including: decay processes, infiltration rate, soil properties, vadose zone thickness, and chemical behavior. The distinct advantage of using a complex model is that less restrictive, but still protective, soil threshold levels may be determined avoiding the unnecessary and costly remediation of marginally contaminated soils. However, the disadvantage of such modeling is the additional cost for data collection and labor required to apply these models. In order to allay these higher costs and to achieve a less restrictive but still protective clean-up level, a multiple contaminant and multi layered soil column equilibrium partitioning model was developed which is faster, simpler and less expensive to use. (authors)

Simulations of groundwater flow, transport, and age in Albuquerque, New Mexico, for a study of transport of anthropogenic and natural contaminants (TANC) to public-supply wells

Science.gov (United States)

Heywood, Charles E.

2013-01-01

Vulnerability to contamination from manmade and natural sources can be characterized by the groundwater-age distribution measured in a supply well and the associated implications for the source depths of the withdrawn water. Coupled groundwater flow and transport models were developed to simulate the transport of the geochemical age-tracers carbon-14, tritium, and three chlorofluorocarbon species to public-supply wells in Albuquerque, New Mexico. A separate, regional-scale simulation of transport of carbon-14 that used the flow-field computed by a previously documented regional groundwater flow model was calibrated and used to specify the initial concentrations of carbon-14 in the local-scale transport model. Observations of the concentrations of each of the five chemical species, in addition to water-level observations and measurements of intra-borehole flow within a public-supply well, were used to calibrate parameters of the local-scale groundwater flow and transport models. The calibrated groundwater flow model simulates the mixing of “young” groundwater, which entered the groundwater flow system after 1950 as recharge at the water table, with older resident groundwater that is more likely associated with natural contaminants. Complexity of the aquifer system in the zone of transport between the water table and public-supply well screens was simulated with a geostatistically generated stratigraphic realization based upon observed lithologic transitions at borehole control locations. Because effective porosity was simulated as spatially uniform, the simulated age tracers are more efficiently transported through the portions of the simulated aquifer with relatively higher simulated hydraulic conductivity. Non-pumping groundwater wells with long screens that connect aquifer intervals having different hydraulic heads can provide alternate pathways for contaminant transport that are faster than the advective transport through the aquifer material. Simulation of

Modelling of contaminant release from a uranium mine tailings site

International Nuclear Information System (INIS)

Kahnt, Rene; Metschies, Thomas

2007-01-01

Available in abstract form only. Full text of publication follows: Uranium mining and milling continuing from the early 1960's until 1990 close to the town of Seelingstaedt in Eastern Germany resulted in 4 tailings impoundments with a total tailings volume of about 105 Mio. m 3 . Leakage from these tailings impoundments enters the underlying aquifers and is discharged into surface water streams. High concentration of salts, uranium and several heavy metals are released from the tailings. At present the tailings impoundments are reshaped and covered. For the identification of suitable remediation options predictions of the contaminant release for different remediation scenarios have to be made. A compartment model representing the tailings impoundments and the surrounding aquifers for the calculation of contaminant release and transport was set up using the software GOLDSIM. This compartment model describes the time dependent hydraulic conditions within the tailings and the surrounding aquifers taking into account hydraulic and geotechnical processes influencing the hydraulic properties of the tailings material. A simple geochemical approach taking into account sorption processes as well as retardation by applying a k d -approach was implemented to describe the contaminant release and transport within the hydraulic system. For uranium as the relevant contaminant the simple approach takes into account additional geochemical conditions influencing the mobility. Alternatively the model approach allows to include the results of detailed geochemical modelling of the individual tailings zones which is than used as source term for the modelling of the contaminant transport in the aquifer and to the receiving streams. (authors)

Contaminant transport at a waste residue deposit

DEFF Research Database (Denmark)

Engesgaard, Peter Knudegaard; Traberg, Rikke

1996-01-01

Contaminant transport in an aquifer at an incinerator waste residue deposit in Denmark is simulated. A two-dimensional, geochemical transport code is developed for this purpose and tested by comparison to results from another code, The code is applied to a column experiment and to the field site...

Modified finite element transport model, FETRA, for sediment and radionuclide migration in open coastal waters

International Nuclear Information System (INIS)

Onishi, Y.; Arnold, E.M.; Mayer, D.W.

1979-08-01

The finite element model, FETRA, simulates transport of sediment and radionuclides (and other contaminants, such as heavy metals, pesticides, and other toxic substances) in surface water bodies. The model is an unsteady, two-dimensional (longitudinal and lateral) model which consists of the following three submodels coupled to include sediment-contaminant interactions: (1) sediment transport submodel, (2) dissolved contaminant transport submodel, and (3) particulate contaminant (contaminant adsorbed by sediment) transport submodel. Under the current phase of the study, FETRA was modified to include sediment-wave interaction in order to extend the applicability of the model to coastal zones and large lakes (e.g., the Great Lakes) where wave actions can be one of the dominant mechanisms to transport sediment and toxic contaminant. FETRA was further modified to handle both linear and quadratic approximations to velocity and depth distributions in order to be compatible with various finite element hydrodynamic models (e.g., RMA II and CAFE) which supply hydrodynamic input data to FETRA. The next step is to apply FETRA to coastal zones to simulate transport of sediment and radionuclides with their interactions in order to test and verify the model under marine and large lacustrine environments

BETR global - A geographically-explicit global-scale multimedia contaminant fate model

International Nuclear Information System (INIS)

MacLeod, Matthew; Waldow, Harald von; Tay, Pascal; Armitage, James M.; Woehrnschimmel, Henry; Riley, William J.; McKone, Thomas E.; Hungerbuhler, Konrad

2011-01-01

We present two new software implementations of the BETR Global multimedia contaminant fate model. The model uses steady-state or non-steady-state mass-balance calculations to describe the fate and transport of persistent organic pollutants using a desktop computer. The global environment is described using a database of long-term average monthly conditions on a 15 o x 15 o grid. We demonstrate BETR Global by modeling the global sources, transport, and removal of decamethylcyclopentasiloxane (D5). - Two new software implementations of the Berkeley-Trent Global Contaminant Fate Model are available. The new model software is illustrated using a case study of the global fate of decamethylcyclopentasiloxane (D5).

Transport Limits for Non-Fixed Contamination: A Hazard to Optimization in Radioprotection

International Nuclear Information System (INIS)

Theis, S.; Lorenz, B.; Schwarz, W.

2004-01-01

Current contamination limits for packages and conveyances under routine transport conditions have been derived from the Fairbairn model more than 40 years ago. This model has proved to be effective if used with pragmatism, but conservative. In some countries the limits are handled as action levels. Actions are taken if contamination levels are exceeded, but instant reporting to authorities is only necessary if the excess is higher than a certain factor of e.g. 10. In countries like Germany the limits are regarded as strictly binding. As could be seen after contamination incidents with transport casks for spent fuel assembly, the reporting by the media and perception by the public was not in accordance with the real radiation risk, which could in any case be neglected. However, exceeding the limits by only one percent lead in some cases immediately to legal actions. To avoid such actions, any practice with relevance for possible contamination or decontamination must consider an additional safety margin which is usually a factor of 10. This results -by the definition of TS-R1 recommendations- in a complete removal of non fixed contamination. For two examples the tremendous amount of decontamination work as well as measurements, which are necessary to reach this aim, is quantified. The first example focuses on the clearance measurements of 20' standard ISO-containers, (which are used exclusively for the transport of radioactive materials,) as conveyances for shipment of radioactive packages. In the second example (a loaded cask awaiting shipment) such actions lead to a real operational exposure which -according to good health physics practice- should otherwise be subject to minimization. These information is compared with the results of an IAEA working group, which was set up in 2000 with the aim of remodeling the exposure conditions for all persons involved in the transport of radioactive material, even members of the public. This international group combined members

Transport Limits for Non-Fixed Contamination: A Hazard to Optimization in Radioprotection

Energy Technology Data Exchange (ETDEWEB)

Theis, S.; Lorenz, B.; Schwarz, W.

2004-07-01

Current contamination limits for packages and conveyances under routine transport conditions have been derived from the Fairbairn model more than 40 years ago. This model has proved to be effective if used with pragmatism, but conservative. In some countries the limits are handled as action levels. Actions are taken if contamination levels are exceeded, but instant reporting to authorities is only necessary if the excess is higher than a certain factor of e.g. 10. In countries like Germany the limits are regarded as strictly binding. As could be seen after contamination incidents with transport casks for spent fuel assembly, the reporting by the media and perception by the public was not in accordance with the real radiation risk, which could in any case be neglected. However, exceeding the limits by only one percent lead in some cases immediately to legal actions. To avoid such actions, any practice with relevance for possible contamination or decontamination must consider an additional safety margin which is usually a factor of 10. This results -by the definition of TS-R1 recommendations- in a complete removal of non fixed contamination. For two examples the tremendous amount of decontamination work as well as measurements, which are necessary to reach this aim, is quantified. The first example focuses on the clearance measurements of 20' standard ISO-containers, (which are used exclusively for the transport of radioactive materials,) as conveyances for shipment of radioactive packages. In the second example (a loaded cask awaiting shipment) such actions lead to a real operational exposure which -according to good health physics practice- should otherwise be subject to minimization. These information is compared with the results of an IAEA working group, which was set up in 2000 with the aim of remodeling the exposure conditions for all persons involved in the transport of radioactive material, even members of the public. This international group combined

Real time simulation of the release and transport of radioactive contaminants

International Nuclear Information System (INIS)

Popa, F.; Weber, M.

1991-01-01

Calculating the responses of the radiation monitoring system (RMS) remains one of the most difficult aspects of nuclear power plant simulation to bring into the post-TMI, first principles simulator era. This task requires the simulation of the transport of radioactive contaminants, the transport of the radiation itself, and the instrument channel including the detector. The complex physics and lack of knowledge of input parameters have made these models lag the general simulator trend away from logical/heuristic modeling of physical systems. This paper describes a series of advances to the modeling methodology to change this situation. The objective in the design of this real time simulation model was to always calculate qualitatively reasonable radiation detector readings

Computer modelling of contaminant migration in natural disperse media

International Nuclear Information System (INIS)

Kundas, S.P.; Gishkelyuk, I.A.; Khil'ko, O.S.

2012-01-01

The theoretical foundations for modeling of the contaminants migration in natural disperses media taking into account interconnected heat and moisture transport are developed. The calculation of mass transfer parameters based on adsorption isotherms of water and thermodynamic equations in the developed mathematical models. The artificial neural networks use to predict migration of contaminants in natural disperse media is proposed. The developed software package is presented and results of practical application of models and software are discussed. (authors)

Methane Bubbles Transport Particles From Contaminated Sediment to a Lake Surface

Science.gov (United States)

Delwiche, K.; Hemond, H.

2017-12-01

Methane bubbling from aquatic sediments has long been known to transport carbon to the atmosphere, but new evidence presented here suggests that methane bubbles also transport particulate matter to a lake surface. This transport pathway is of particular importance in lakes with contaminated sediments, as bubble transport could increase human exposure to toxic metals. The Upper Mystic Lake in Arlington, MA has a documented history of methane bubbling and sediment contamination by arsenic and other heavy metals, and we have conducted laboratory and field studies demonstrating that methane bubbles are capable of transporting sediment particles over depths as great as 15 m in Upper Mystic Lake. Methane bubble traps were used in-situ to capture particles adhered to bubble interfaces, and to relate particle mass transport to bubble flux. Laboratory studies were conducted in a custom-made 15 m tall water column to quantify the relationship between water column height and the mass of particulate transport. We then couple this particle transport data with historical estimates of ebullition from Upper Mystic Lake to quantify the significance of bubble-mediated particle transport to heavy metal cycling within the lake. Results suggest that methane bubbles can represent a significant pathway for contaminated sediment to reach surface waters even in relatively deep water bodies. Given the frequent co-occurrence of contaminated sediments and high bubble flux rates, and the potential for human exposure to heavy metals, it will be critical to study the significance of this transport pathway for a range of sediment and contaminant types.

Modeling to Support Groundwater Contaminant Boundaries for the Shoal Underground Nuclear Test

Energy Technology Data Exchange (ETDEWEB)

K. Pohlmann; G. Pohll; J. Chapman; A. Hassan; R. Carroll; C. Shirley

2004-03-01

Groundwater flow and radionuclide transport at the Shoal underground nuclear test are characterized using three-dimensional numerical models, based on site-specific hydrologic data. The objective of this modeling is to provide the flow and transport models needed to develop a contaminant boundary defining the extent of radionuclide-contaminated groundwater at the site throughout 1,000 years at a prescribed level of confidence. This boundary will then be used to manage the Project Shoal Area for the protection of the public and the environment.

Study on Contaminant Transportation of a Typical Chemical Industry Park Based on GMS Software

Science.gov (United States)

Huang, LinXian; Liu, GuoZhen; Xing, LiTing; Liu, BenHua; Xu, ZhengHe; Yang, LiZhi; Zhu, HebgHua

2018-03-01

The groundwater solute transport model can effectively simulated the transport path, the transport scope, and the concentration of contaminant which can provide quantitative data for groundwater pollution repair and groundwater resource management. In this study, we selected biological modern technology research base of Shandong province as research objective and simulated the pollution characteristic of typicalcontaminant cis-1, 3-dichloropropene under different operating conditions by using GMS software.

Time-lapse electrical resistivity anomalies due to contaminant transport around landfills

Directory of Open Access Journals (Sweden)

J. Yang

2007-06-01

Full Text Available The extent of landfill leachate can be delineated by geo-electrical imaging as a response to the varying electrical resistivity in the contaminated area. This research was based on a combination of hydrogeological numerical simulation followed by geophysical forward and inversion modeling performed to evaluate the migration of a contaminant plume from a landfill. As a first step, groundwater flow and contaminant transport was simulated using the finite elements numerical modeling software FEFLOW. The extent of the contaminant plume was acquired through a hydrogeological model depicting the distributions of leachate concentration in the system. Next, based on the empirical relationship between the concentration and electrical conductivity of the leachate in the porous media, the corresponding geo-electrical structure was derived from the hydrogeological model. Finally, forward and inversion computations of geo-electrical anomalies were performed using the finite difference numerical modeling software DCIP2D/DCIP3D. The image obtained by geophysical inversion of the electric data was expected to be consistent with the initial hydrogeological model, as described by the distribution of leachate concentration. Numerical case studies were conducted for various geological conditions, hydraulic parameters and electrode arrays, from which conclusions were drawn regarding the suitability of the methodology to assess simple to more complex geo-electrical models. Thus, optimal mapping and monitoring configurations were determined.

A risk-informed basis for establishing non-fixed surface contamination limits for spent fuel transportation casks

International Nuclear Information System (INIS)

Rawl, R.R.; Eckerman, K.F.; Bogard, J.S.; Cook, J.R.

2004-01-01

The current limits for non-fixed contamination on packages used to transport radioactive materials were introduced in the 1961 edition of the International Atomic Energy Agency (IAEA) transport regulations and were based on radiation protection guidance and practices in use at that time. The limits were based on exposure scenarios leading to intakes of radionuclides by inhalation and external irradiation of the hands. These considerations are collectively referred to as the Fairbairn model. Although formulated over 40 years ago, the model remains unchanged and is still the basis of current regulatory-derived limits on package non-fixed surface contamination. There can also be doses that while not resulting directly from the contamination, are strongly influenced by and attributable to transport regulatory requirements for contamination control. For example, actions necessary to comply with the current derived limits for light-water-reactor (LWR) spent nuclear fuel (SNF) casks can result in significant external doses to workers. This is due to the relatively high radiation levels around the loaded casks, where workers must function during the measurement of contamination levels and while decontaminating the cask. In order to optimize the total dose received due to compliance with cask contamination levels, it is necessary to take into account all the doses that vary as a result of the regulatory limit. Limits for non-fixed surface contamination on spent fuel casks should be established by using a model that considers and optimizes the appropriate exposure scenarios both in the workplace and in the public environment. A risk-informed approach is needed to ensure optimal use of personnel and material resources for SNF-based packaging operations. This paper is a summary of a study sponsored by the US Nuclear Regulatory Commission and performed by Oak Ridge National Laboratory that examined the dose implications for removable surface contamination limits on spent fuel

FACT (Version 2.0) - Subsurface Flow and Contaminant Transport Documentation and User's Guide

Energy Technology Data Exchange (ETDEWEB)

Aleman, S.E.

2000-05-05

This report documents a finite element code designed to model subsurface flow and contaminant transport, named FACT. FACT is a transient three-dimensional, finite element code designed to simulate isothermal groundwater flow, moisture movement, and solute transport in variably saturated and fully saturated subsurface porous media.

Intermediate-field transport of contaminants

International Nuclear Information System (INIS)

Ahn, J.; Kim, C.L.; Chambre, P.L.; Pigford, T.H.; Lee, W.W.L.

1989-06-01

This report is about ''intermediate-field'' transport or the migration of contaminants from arrays of discrete waste packages or sources. In constructing nuclear waste repositories in rock, it may be necessary to place a waste package across a rock fracture, or a rock fracture may develop some time after waste packages have been emplaced. To predict the spatial and temporal distribution of contaminant species from a line of waste packages facing a rock fracture may be important, because such fractures may now be considered a preferential pathway for released radionuclides to re-enter the biosphere. In land disposal of hazardous wastes, individual barrels may contain especially toxic material whose dispersion special attention. We have published analytic solutions for the multidimensional advective transport of contaminants from arrays of waste packages and multiple areal sources into a planar fracture. The results show a near region in which the concentrations vary greatly in the direction transverse to ground-water flow, an intermediate region in which the array can be treated as an infinite plane source of dissolving species, and a far-field region in which the array can be treated as a plane source of finite extent. The array equations have been developed for both porous and fractured media. In this paper we summarize and compare the work with multiple areal sources facing a planar fracture and an array of point sources in porous media. 5 refs., 5 figs

Wind-induced contaminant transport in near-surface soils with application to radon entry into buildings

International Nuclear Information System (INIS)

Riley, W.J.

1996-05-01

Indoor air exposures to gaseous contaminants originating in soil can cause large human health risks. To predict and control these exposures, the mechanisms that affect vapor transport in near-surface soils need to be understood. In particular, radon exposure is a concern since average indoor radon concentrations lead to much higher risks than are generally accepted for exposure to other environmental contaminants. This dissertation examines an important component of the indoor radon problem: the impacts of wind on soil-gas and radon transport and entry into buildings. The research includes experimental and modeling studies of wind's interactions with a building's superstructure and the resulting soil-gas and radon flows in the surrounding soil. In addition to exploring the effects of steady winds, a novel modeling technique is developed to examine the impacts of fluctuating winds on soil-gas and radon transport

Wind-induced contaminant transport in near-surface soils with application to radon entry into buildings

Energy Technology Data Exchange (ETDEWEB)

Riley, William Jowett [Univ. of California, Berkeley, CA (United States)

1996-05-01

Indoor air exposures to gaseous contaminants originating in soil can cause large human health risks. To predict and control these exposures, the mechanisms that affect vapor transport in near-surface soils need to be understood. In particular, radon exposure is a concern since average indoor radon concentrations lead to much higher risks than are generally accepted for exposure to other environmental contaminants. This dissertation examines an important component of the indoor radon problem: the impacts of wind on soil-gas and radon transport and entry into buildings. The research includes experimental and modeling studies of wind`s interactions with a building`s superstructure and the resulting soil-gas and radon flows in the surrounding soil. In addition to exploring the effects of steady winds, a novel modeling technique is developed to examine the impacts of fluctuating winds on soil-gas and radon transport.

Release of Aged Contaminants from weathered sediments: Effects of sorbate speciation on scaling of reactive transport

Energy Technology Data Exchange (ETDEWEB)

Chorover, Jon [Univ. of Arizona, Tucson, AZ (United States); Perdrial, Nico [Univ. of Arizona, Tucson, AZ (United States); Mueller, Karl [Pennsylvania State Univ., University Park, PA (United States); Strepka, Caleb [Pennsylvania State Univ., University Park, PA (United States); O' Day, Peggy [Univ. of California, Merced, CA (United States); Rivera, Nelson [Univ. of California, Merced, CA (United States); Um, Wooyong [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Chang, Hyun-Shik [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Steefel, Carl [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Thompson, Aaron [Univ. of Georgia, Athens, GA (United States)

2012-08-14

Hanford sediments impacted by hyperalkaline high level radioactive waste have undergone incongruent silicate mineral weathering concurrent with contaminant uptake (Chorover et al., 2008). In this project, we studied the impact of background pore water (BPW) on strontium, cesium and iodine desorption and transport in Hanford sediments that were experimentally weathered by contact with simulated hyperalkaline tank waste leachate (STWL) solutions. Using those lab-weathered Hanford sediments (HS) and model precipitates formed during nucleation from homogeneous STWL solutions (HN), we (i) provided thorough characterization of reaction products over a matrix of field-relevant gradients in contaminant concentration, P_CO2, and reaction time; (ii) improved molecular-scale understanding of how sorbate speciation controls contaminant desorption from weathered sediments upon removal of caustic sources; and (iii) developed a mechanistic, predictive model of meso- to field-scale contaminant reactive transport under these conditions. Below, we provide some detailed descriptions of our results from this three year study, recently completed following a one-year no cost extension.

Release of aged contaminants from weathered sediments: Effects of sorbate speciation on scaling of reactive transport

Energy Technology Data Exchange (ETDEWEB)

Chorover, Jon; Perdrial, Nico; Mueller, Karl; Strepka, Caleb; O’Day, Peggy; Rivera, Nelson; Um, Wooyong; Chang, Hyun-Shik; Steefel, Carl; Thompson, Aaron

2012-11-05

Hanford sediments impacted by hyperalkaline high level radioactive waste have undergone incongruent silicate mineral weathering concurrent with contaminant uptake. In this project, we studied the impact of background pore water (BPW) on strontium, cesium and iodine desorption and transport in Hanford sediments that were experimentally weathered by contact with simulated hyperalkaline tank waste leachate (STWL) solutions. Using those lab-weathered Hanford sediments (HS) and model precipitates formed during nucleation from homogeneous STWL solutions (HN), we (i) provided thorough characterization of reaction products over a matrix of field-relevant gradients in contaminant concentration, partial pressure of carbon dioxide, and reaction time; (ii) improved molecular-scale understanding of how sorbate speciation controls contaminant desorption from weathered sediments upon removal of caustic sources; and (iii) developed a mechanistic, predictive model of meso- to field-scale contaminant reactive transport under these conditions. In this final report, we provide detailed descriptions of our results from this three-year study, completed in 2012 following a one-year no cost extension.

Modelling assessment of regional groundwater contamination due to historic smelter emissions of heavy metals

NARCIS (Netherlands)

Grift, B. van der; Griffioen, J.

2008-01-01

Historic emissions from ore smelters typically cause regional soil contamination. We developed a modelling approach to assess the impact of such contamination on groundwater and surface water load, coupling unsaturated zone leaching modelling with 3D groundwater transport modelling. Both historic

A Coupled model for ERT monitoring of contaminated sites

Science.gov (United States)

Wang, Yuling; Zhang, Bo; Gong, Shulan; Xu, Ya

2018-02-01

The performance of electrical resistivity tomography (ERT) system is usually investigated using a fixed resistivity distribution model in numerical simulation study. In this paper, a method to construct a time-varying resistivity model by coupling water transport, solute transport and constant current field is proposed for ERT monitoring of contaminated sites. Using the proposed method, a monitoring model is constructed for a contaminated site with a pollution region on the surface and ERT monitoring results at different time is calculated by the finite element method. The results show that ERT monitoring profiles can effectively reflect the increase of the pollution area caused by the diffusion of pollutants, but the extent of the pollution is not exactly the same as the actual situation. The model can be extended to any other case and can be used to scheme design and results analysis for ERT monitoring.

Microbial behaviour and cross contamination between cargoes in containerized transportation of food

DEFF Research Database (Denmark)

Abban, Stephen

Transportation is central to the global food and feed supply chain. Thus issues of safety, especially cross contamination with pathogens during food transit should be important in food handling operations. A large proportion of the worlds’ food cargo is moved using intermodal cargo containers...... chain, its role in food safety cannot be ignored. Unfortunately not much effort has been put, scientifically, into understanding the role of the various features of the transportation links in food cross contamination (compared to studies for homes, processing factories and farm yards). The PhD project...... has attempted to shed light on containerized food transport and some of its important attributes as regards hygiene and cross contamination. The overall aim of the study was to ‘identify possible microbial hazards and ways of cross contamination during containerized transportation of foods...

Contaminant Attenuation and Transport Characterization of 200-DV-1 Operable Unit Sediment Samples

Energy Technology Data Exchange (ETDEWEB)

Truex, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Szecsody, James E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Qafoku, Nikolla [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Strickland, Christopher E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Moran, James J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lee, Brady D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Snyder, Michelle M.V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lawter, Amanda R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Resch, Charles T. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Gartman, Brandy N. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zhong, Lirong [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Nims, Megan K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Saunders, Danielle L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Williams, Benjamin D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Horner, Jacob A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Leavy, Ian I. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Baum, Steven R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Christiansen, Beren B. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Clayton, Ray E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); McElroy, Erin M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Appriou, Delphine [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Tyrrell, Kimberly J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Striluk, Miranda L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2017-05-15

A laboratory study was conducted to quantify contaminant attenuation processes and associated contaminant transport parameters that are needed to evaluate transport of contaminants through the vadose zone to the groundwater. The laboratory study information, in conjunction with transport analyses, can be used as input to evaluate the feasibility of Monitored Natural Attenuation and other remedies for the 200-DV-1 Operable Unit at the Hanford Site.

Fate and transport modelling of uranium in Port Hope Harbour

International Nuclear Information System (INIS)

Pinilla, C.E.; Garisto, N.; Peters, R.

2010-01-01

Fate and transport modelling of contaminants in Port Hope Harbour and near-shore Lake Ontario was undertaken in support of an ecological and human health risk assessment. Uranium concentrations in the Harbour and near-shore Lake Ontario due to groundwater and storm water loadings were estimated with a state-of-the-art 3D hydrodynamic and contaminant transport model (ECOMSED). The hydrodynamic model was simplified to obtain a first estimate of the flow pattern in the Harbour. The model was verified with field data using a tracer (fluoride). The modelling results generally showed good agreement with the tracer field data. (author)

Dual states estimation of a subsurface flow-transport coupled model using ensemble Kalman filtering

KAUST Repository

El Gharamti, Mohamad; Hoteit, Ibrahim; Valstar, Johan R.

2013-01-01

Modeling the spread of subsurface contaminants requires coupling a groundwater flow model with a contaminant transport model. Such coupling may provide accurate estimates of future subsurface hydrologic states if essential flow and contaminant data

Numerical modeling of the groundwater contaminant transport for the Lake Karachai Area: The methodological approach and the basic two- dimensional regional model

International Nuclear Information System (INIS)

Petrov, A.V.; Samsonova, L.M.; Vasil'kova, N.A.; Zinin, A.I.; Zinina, G.A.

1994-06-01

Methodological aspects of the numerical modeling of the groundwater contaminant transport for the Lake Karachay area are discussed. Main features of conditions of the task are the high grade of non-uniformity of the aquifer in the fractured rock massif and the high density of the waste solutions, and also the high volume of the input data: both on the part of parameters of the aquifer (number of pump tests) and on the part of observations of functions of processes (long-time observations by the monitoring well grid). The modeling process for constructing the two dimensional regional model is described, and this model is presented as the basic model for subsequent full three-dimensional modeling in sub-areas of interest. Original powerful mathematical apparatus and computer codes for finite-difference numerical modeling are used

Color image analysis of contaminants and bacteria transport in porous media

Science.gov (United States)

Rashidi, Mehdi; Dehmeshki, Jamshid; Daemi, Mohammad F.; Cole, Larry; Dickenson, Eric

1997-10-01

Transport of contaminants and bacteria in aqueous heterogeneous saturated porous systems have been studied experimentally using a novel fluorescent microscopic imaging technique. The approach involves color visualization and quantification of bacterium and contaminant distributions within a transparent porous column. By introducing stained bacteria and an organic dye as a contaminant into the column and illuminating the porous regions with a planar sheet of laser beam, contaminant and bacterial transport processes through the porous medium can be observed and measured microscopically. A computer controlled color CCD camera is used to record the fluorescent images as a function of time. These images are recorded by a frame accurate high resolution VCR and are then analyzed using a color image analysis code written in our laboratories. The color images are digitized this way and simultaneous concentration and velocity distributions of both contaminant and bacterium are evaluated as a function of time and pore characteristics. The approach provides a unique dynamic probe to observe these transport processes microscopically. These results are extremely valuable in in-situ bioremediation problems since microscopic particle-contaminant- bacterium interactions are the key to understanding and optimization of these processes.

Field validation of the contaminant transport model, FEMA

International Nuclear Information System (INIS)

Wong, K.-F.V.

1986-01-01

The work describes the validation with field data of a finite element model of material transport through aquifers (FEMA). Field data from the Idaho Chemical Processing Plant, Idaho, USA and from the 58th Street landfill in Miami, Florida, USA are used. In both cases the model was first calibrated and then integrated over a span of eight years to check on the predictive capability of the model. Both predictive runs gave results that matched well with available data. (author)

Modeling to Support Groundwater Contaminant Boundaries for the Shoal Underground Nuclear Test

Energy Technology Data Exchange (ETDEWEB)

K. Pohlmann; G. Pohll; J. Chapman; A. Hassan; R. Carroll; C. Shirley

2004-03-01

The purpose of this work is to characterize groundwater flow and contaminant transport at the Shoal underground nuclear test through numerical modeling using site-specific hydrologic data. The ultimate objective is the development of a contaminant boundary, a model-predicted perimeter defining the extent of radionuclide-contaminated groundwater from the underground test throughout 1,000 years at a prescribed level of confidence. This boundary will be developed using the numerical models described here, after they are approved for that purpose by DOE and NDEP.

Modeling to Support Groundwater Contaminant Boundaries for the Shoal Underground Nuclear Test

International Nuclear Information System (INIS)

K. Pohlmann; G. Pohll; J. Chapman; A. Hassan; R. Carroll; C. Shirley

2004-01-01

The purpose of this work is to characterize groundwater flow and contaminant transport at the Shoal underground nuclear test through numerical modeling using site-specific hydrologic data. The ultimate objective is the development of a contaminant boundary, a model-predicted perimeter defining the extent of radionuclide-contaminated groundwater from the underground test throughout 1,000 years at a prescribed level of confidence. This boundary will be developed using the numerical models described here, after they are approved for that purpose by DOE and NDEP

Final Project Report: Release of aged contaminants from weathered sediments: Effects of sorbate speciation on scaling of reactive transport

Energy Technology Data Exchange (ETDEWEB)

Jon Chorover, University of Arizona; Peggy O' €™Day, University of California, Merced; Karl Mueller, Penn State University; Wooyong Um, Pacific Northwest National Laboratory; Carl Steefel, Lawrence Berkeley National Laboratory

2012-10-01

Hanford sediments impacted by hyperalkaline high level radioactive waste have undergone incongruent silicate mineral weathering concurrent with contaminant uptake. In this project, we studied the impact of background pore water (BPW) on strontium, cesium and iodine desorption and transport in Hanford sediments that were experimentally weathered by contact with simulated hyperalkaline tank waste leachate (STWL) solutions. Using those lab-weathered Hanford sediments (HS) and model precipitates formed during nucleation from homogeneous STWL solutions (HN), we (i) provided detailed characterization of reaction products over a matrix of field-relevant gradients in contaminant concentration, PCO2, and reaction time; (ii) improved molecular-scale understanding of how sorbate speciation controls contaminant desorption from weathered sediments upon removal of caustic sources; and (iii) developed a mechanistic, predictive model of meso- to field-scale contaminant reactive transport under these conditions.

A transportable system for radioactivity contaminated water treatment

International Nuclear Information System (INIS)

2013-01-01

Contaminated water treatment system called SARRY for retrieval and recovery of water in operation at the site of Fukushima Daiichi Nuclear Power Plant since August 2011 has been modified by compacting the system size to develop a mobile system SARRY-Aqua that can process Cs-contaminated water (one ton/hour) to the level of 10 Bq/kg. Installing the system in a small container with dimensions conforming to the international standards facilitates transportation by truck and enables the contaminated water treatment occurring in a variety of locations. (S. Ohno)

ALGE3D: A Three-Dimensional Transport Model

Science.gov (United States)

Maze, G. M.

2017-12-01

Of the top 10 most populated US cities from a 2015 US Census Bureau estimate, 7 of the cities are situated near the ocean, a bay, or on one of the Great Lakes. A contamination of the water ways in the United States could be devastating to the economy (through tourism and industries such as fishing), public health (from direct contact, or contaminated drinking water), and in some cases even infrastructure (water treatment plants). Current national response models employed by emergency response agencies have well developed models to simulate the effects of hazardous contaminants in riverine systems that are primarily driven by one-dimensional flows; however in more complex systems, such as tidal estuaries, bays, or lakes, a more complex model is needed. While many models exist, none are capable of quick deployment in emergency situations that could contain a variety of release situations including a mixture of both particulate and dissolved chemicals in a complex flow area. ALGE3D, developed at the Department of Energy's (DOE) Savannah River National Laboratory (SRNL), is a three-dimensional hydrodynamic code which solves the momentum, mass, and energy conservation equations to predict the movement and dissipation of thermal or dissolved chemical plumes discharged into cooling lakes, rivers, and estuaries. ALGE3D is capable of modeling very complex flows, including areas with tidal flows which include wetting and drying of land. Recent upgrades have increased the capabilities including the transport of particulate tracers, allowing for more complete modeling of the transport of pollutants. In addition the model is capable of coupling with a one-dimension riverine transport model or a two-dimension atmospheric deposition model in the event that a contamination event occurs upstream or upwind of the water body.

Chemical Contaminants in the Wadden Sea: sources, transport, fate and effects

NARCIS (Netherlands)

Laane, R.W.P.M.; Vethaak, A.D.; Gandrass, J.; Vorkamp, K.; Köhler, A.; Larsen, M.M.; Strand, J.

2013-01-01

The Wadden Sea receives contaminants from various sources and via various transport routes. The contaminants described in this overview are various metals (Cd, Cu, Hg, Pb and Zn) and various organic contaminants (polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and lindane

Characterization of contaminant transport by gravity, capillarity and barometric pumping in heterogeneous vadose regimes. 1998 annual progress report

International Nuclear Information System (INIS)

Carrigan, C.R.; Hudson, G.B.

1998-01-01

'The intent of this research program is to obtain an improved understanding of vadose zone transport processes and to develop field and modeling techniques required to characterize contaminant transport in the unsaturated zone at DOE sites. For surface spills and near-surface leaks of chemicals, the vadose zone may well become a long-term source of contamination for the underlying water table. Transport of contaminants can occur in both the liquid and gas phases of the unsaturated zone. This transport occurs naturally as a result of diffusion, buoyancy forces (gravity), capillarity and barometric pressure variations. In some cases transport can be enhanced by anisotropies present in hydrologic regimes. This is particularly true for gas-phase transport which may be subject to vertical pumping resulting from atmospheric pressure changes. For liquid-phase flows, heterogeneity may enhance the downward transport of contaminants to the water table depending on soil properties and the scale of the surface spill or near-surface leak. Characterization techniques based upon the dynamics of transport processes are likely to yield a better understanding of the potential for contaminant transport at a specific site than methods depending solely on hydrologic properties derived from a borehole. Such dynamic-characterization techniques can be useful for evaluating sites where contamination presently exists as well as for providing an objective basis to evaluate the efficacy of proposed as well as implemented clean-up technologies. The real-time monitoring of processes that may occur during clean-up of tank waste and the mobility of contaminants beneath the Hanford storage tanks during sluicing operations is one example of how techniques developed in this effort can be applied to current remediation problems. In the future, such dynamic-characterization methods might also be used as part of the site-characterization process for determining suitable locations of new DOE facilities

Mesoscale modelling of radioactive contamination formation in Ukraine caused by the Chernobyl accident

International Nuclear Information System (INIS)

Talerko, Nikolai

2005-01-01

This work is devoted to the reconstruction of time-dependent radioactive contamination fields in the territory of Ukraine in the initial period of the Chernobyl accident using the model of atmospheric transport LEDI (Lagrangian-Eulerian DIffusion model). The modelling results were compared with available 137 Cs air and ground contamination measurement data. The 137 Cs atmospheric transport over the territory of Ukraine was simulated during the first 12 days after the accident (from 26 April to 7 May 1986) using real aerological information and rain measurement network data. The detailed scenario of the release from the accidental unit of the Chernobyl nuclear plant has been built (including time-dependent radioactivity release intensity and time-varied height of the release). The calculations have enabled to explain the main features of spatial and temporal variations of radioactive contamination fields over the territory of Ukraine on the regional scale, including the formation of the major large-scale spots of radioactive contamination caused by dry and wet deposition

Modeled Watershed Runoff Associated with Variations in Precipitation Data with Implications for Contaminant Fluxes

Science.gov (United States)

Watershed-scale fate and transport models are important tools for estimating the sources, transformation, and transport of contaminants to surface water systems. Precipitation is one of the primary inputs to watershed biogeochemical models, influencing changes in the water budge...

Experimental Model of Contaminant Transport by a Moving Wake Inside an Aircraft Cabin

Science.gov (United States)

Poussou, Stephane; Sojka, Paul; Plesniak, Michael

2008-11-01

The air cabin environment in jetliners is designed to provide comfortable and healthy conditions for passengers. The air ventilation system produces a recirculating pattern designed to minimize secondary flow between seat rows. However, disturbances are frequently introduced by individuals walking along the aisle and may significantly modify air distribution and quality. Spreading of infectious aerosols or biochemical agents presents potential health hazards. A fundamental study has been undertaken to understand the unsteady transport phenomena, to validate numerical simulations and to improve air monitoring systems. A finite moving body is modeled experimentally in a 10:1 scale simplified aircraft cabin equipped with ventilation, at a Reynolds number (based on body height) of the order of 10,000. Measurements of the ventilation and wake velocity fields are obtained using PIV and PLIF. Results indicate that the evolution of the typical downwash behind the body is profoundly perturbed by the ventilation flow. Furthermore, the interaction between wake and ventilation flow significantly alters scalar contaminant migration.

Conjunction of radial basis function interpolator and artificial intelligence models for time-space modeling of contaminant transport in porous media

Science.gov (United States)

Nourani, Vahid; Mousavi, Shahram; Dabrowska, Dominika; Sadikoglu, Fahreddin

2017-05-01

As an innovation, both black box and physical-based models were incorporated into simulating groundwater flow and contaminant transport. Time series of groundwater level (GL) and chloride concentration (CC) observed at different piezometers of study plain were firstly de-noised by the wavelet-based de-noising approach. The effect of de-noised data on the performance of artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) was evaluated. Wavelet transform coherence was employed for spatial clustering of piezometers. Then for each cluster, ANN and ANFIS models were trained to predict GL and CC values. Finally, considering the predicted water heads of piezometers as interior conditions, the radial basis function as a meshless method which solves partial differential equations of GFCT, was used to estimate GL and CC values at any point within the plain where there is not any piezometer. Results indicated that efficiency of ANFIS based spatiotemporal model was more than ANN based model up to 13%.

A model to determine the radiological implications of non-fixed radioactive contamination on the surfaces of packages and conveyances

International Nuclear Information System (INIS)

Hughes, J.S.; Warner Jones, S.M.; Lizot, M.T.; Perrin, M.L.; Thierfeld, S.; Schroedl, E.; Schwarz, G.; Rawl, R.; Munakata, M.; Hirose, M.

2004-01-01

The surfaces of packages and conveyances used to transport radioactive materials can sometimes become contaminated with radioactive material. This usually occurs as a result of the transfer of radioactive material from areas in which these packages and conveyances are handled. This contamination may subsequently be transferred to transport equipment, workers and to areas accessible to the public. This can represent a significant radiation safety issue that requires careful management. The current regulatory limits for non-fixed contamination on packages and conveyances have been in use for over 40 years, and are based on a simple exposure model. However, the bases on which these limits were derived have been subject to changes, as a result of successive revisions of international recommendations. In recognition of this need for a review and analysis of the current contamination limits an IAEA Co-ordinated Research Project (CRP) on the ''Radiological Aspects of Package and Conveyance Non-Fixed Contamination'' was initiated to review the scientific basis for the current regulatory limits for surface contamination. The CRP was also to develop guidance material for evaluating the radiological significance of surface contamination to workers and the public in light of state-of-the-art research, technical developments and current transport practices. The specific objectives of the work undertaken within this multi-national CRP were, in accordance with the terms of reference: To ensure that appropriate models exist for all package types including consideration of the aspects pertinent for assessing and revising a surface contamination model for transport. To collect - where possible - contamination, operational and dosimetric data to ensure modelling consistency. To use models for assessing the limitations and optimisation of radiation doses incurred in transport operations, and to consider preventive methods for package and conveyance contamination

INEEL Subregional Conceptual Model Report; Volume 1 - Summary of Existing Knowledge of Natural and Anthropogenic Influences Governing Subsurface Contaminant Transport in the INEEL Subregion of the Eastern Snake River Plain

Energy Technology Data Exchange (ETDEWEB)

Wichlacz, Paul Louis; Orr, Brennan

2002-08-01

The National Research Council has defined a conceptual model as ''an evolving hypothesis identifying the important features, processes, and events controlling fluid flow and contaminant transport of consequence at a specific field site in the context of a recognized problem''. Presently, several subregional conceptual models are under development at the Idaho National Engineering and Environmental Laboratory (INEEL). Additionally, facility-specific conceptual models have been described as part of INEEL environmental restoration activities. Compilation of these models is required to develop a comprehensive conceptual model that can be used to strategically plan for future groundwater research activities at the INEEL. Conceptual models of groundwater flow and contaminant transport at the INEEL include the description of the geologic framework, matrix hydraulic properties, and inflows and outflows. They also include definitions of the contaminant source term and contaminant transport mechanisms. The geologic framework of the INEEL subregion is described by the geometry of the system, stratigraphic units within the system, and structural features that affect groundwater flow and contaminant transport. These elements define geohydrologic units that make up the Snake River Plain Aquifer (SRPA). The United States Geological Survey (USGS) conceptual model encompasses approximately 1,920 mi2 of the eastern Snake River Plain. The Waste Area Group (WAG)-10 model includes the USGS area and additional areas to the northeast and southeast. Both conceptual models are bounded to the northwest by the Pioneer Mountains, Lost River Range, and Lemhi Mountains. They are bounded to the southeast by groundwater flow paths determined from aquifer water-level contours. The upgradient extent of the USGS model is a water-level contour that includes the northeastern boundary of the INEEL. The WAG-10 model includes more of the Mud Lake area to utilize previous estimates of

Numerical modeling of contaminant transport in fractured porous media using mixed finite-element and finitevolume methods

KAUST Repository

Dong, Chen

2011-01-01

A mathematical model for contaminant species passing through fractured porous media is presented. In the numerical model, we combine two locally conservative methods; i.e., the mixed finite-element (MFE) method and the finite-volume method. Adaptive triangle mesh is used for effective treatment of the fractures. A hybrid MFE method is employed to provide an accurate approximation of velocity fields for both the fractures and matrix, which are crucial to the convection part of the transport equation. The finite-volume method and the standard MFE method are used to approximate the convection and dispersion terms, respectively. The temporary evolution for the pressure distributions, streamline fields, and concentration profiles are obtained for six different arrangements of fractures. The results clearly show the distorted concentration effects caused by the ordered and disordered (random) patterns of the fractures and illustrate the robustness and efficiency of the proposed numerical model. © 2011 by Begell House Inc.

Can Bayesian Belief Networks help tackling conceptual model uncertainties in contaminated site risk assessment?

DEFF Research Database (Denmark)

Troldborg, Mads; Thomsen, Nanna Isbak; McKnight, Ursula S.

different conceptual models may describe the same contaminated site equally well. In many cases, conceptual model uncertainty has been shown to be one of the dominant sources for uncertainty and is therefore essential to account for when quantifying uncertainties in risk assessments. We present here......A key component in risk assessment of contaminated sites is the formulation of a conceptual site model. The conceptual model is a simplified representation of reality and forms the basis for the mathematical modelling of contaminant fate and transport at the site. A conceptual model should...... a Bayesian Belief Network (BBN) approach for evaluating the uncertainty in risk assessment of groundwater contamination from contaminated sites. The approach accounts for conceptual model uncertainty by considering multiple conceptual models, each of which represents an alternative interpretation of the site...

Modeling Contamination Migration on the Chandra X-ray Observatory - II

Science.gov (United States)

O'Dell, Stephen L.; Swartz, Douglas A.; Tice, Neil W.; Plucinsky, Paul P.; Grant, Catherine E.; Marshall, Herman L.; Vikhlinin, Alexey A.; Tennant, Allyn F.

2013-01-01

During its first 14 years of operation, the cold (about -60C) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), aboard the Chandra X-ray Observatory, has accumulated a growing layer of molecular contamination that attenuates low-energy x rays. Over the past few years, the accumulation rate, spatial distribution, and composition have changed. This evolution has motivated further analysis of contamination migration within and near the ACIS cavity. To this end, the current study employs a higher-fidelity geometric model of the ACIS cavity, detailed thermal modeling based upon temperature data, and a refined model of the molecular transport.

A Stochastic Multi-Media Model of Microbial Transport in Watersheds

Science.gov (United States)

Yeghiazarian, L.; Safwat, A.; Whiteaker, T.; Teklitz, A.; Nietch, C.; Maidment, D. R.; Best, E. P.

2012-12-01

Fecal contamination is the leading cause of surface-water impairment in the US, and fecal pathogens are capable of triggering massive outbreaks of gastrointestinal disease. The difficulty in prediction of water contamination has its roots in the stochastic variability of fecal pathogens in the environment, and in the complexity of microbial dynamics and interactions on the soil surface and in water. To address these challenges, we have developed a stochastic model whereby the transport of microorganisms in watersheds is considered in two broad categories: microorganisms that are attached to mineral or organic substrates in suspended sediment; and unattached microorganisms suspended in overland flow. The interactions of microorganisms with soil particles on the soil surface and in the overland flow lead to transitions of microorganisms between solid and aqueous media. The strength of attachment of microorganisms to soil particles is determined by the chemical characteristics of soils which are highly correlated with the particle size. The particle size class distribution in the suspended sediment is predicted by the Water Erosion Prediction Project (WEPP). The model is integrated with ArcGIS, resulting in a general transport-modeling framework applicable to a variety of biological and chemical surface water contaminants. Simulations are carried out for a case study of contaminant transport in the East Fork Little Miami River Watershed in Ohio. Model results include the spatial probability distribution of microbes in the watershed and can be used for assessment of (1) mechanisms dominating microbial transport, and (2) time and location of highest likelihood of microbial occurrence, thus yielding information on best water sampling strategies.

Local and distant residence times of contaminants in multi-compartment models. Part II: Application to assessing environmental mobility and long-range atmospheric transport

International Nuclear Information System (INIS)

Reid, Liisa; Mackay, Don

2008-01-01

In Part I, the concepts of inherent, local and distant residence times (DRTs) were reviewed as metrics of the extent to which chemical discharges or emissions in one region or box are transported to distant regions. In this second part, the concepts are applied to geographically relevant systems to illustrate their applicability to the assessment of chemicals for long-range transport potential (LRTP). It is shown that the relative ranking of chemicals as characterized by the DRT method is similar to that of the characteristic travel distance concept. A DRT source-receptor matrix is developed that can express the chemical-specific potential of source regions to contaminate a specific receptor region of concern such as the Arctic. The matrix can be modified to identify for a specific source region the likely destinations of emissions as well as to assess the relative vulnerability of regions in the global environment to contaminants of concern. - The DRT concept is applied to multi-box and geographically explicit models to assess the long-range transport potential of 10 chemicals

GWSCREEN: A semi-analytical model for assessment of the groundwater pathway from surface or buried contamination: Theory and user's manual

International Nuclear Information System (INIS)

Rood, A.S.

1992-03-01

GWSCREEN was developed for assessment of the groundwater pathway from leaching of radioactive and non radioactive substances from surface or buried sources. The code was designed for implementation in the Track 1 and Track 2 assessment of Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) sites identified as low probability hazard at the Idaho National Engineering Laboratory (DOE, 1991). The code calculates the limiting soil concentration such that regulatory contaminant levels in groundwater are not exceeded. The code uses a mass conservation approach to model three processes: Contaminant release from a source volume, contaminant transport in the unsaturated zone, and contaminant transport in the saturated zone. The source model considers the sorptive properties and solubility of the contaminant. Transport in the unsaturated zone is described by a plug flow model. Transport in the saturated zone is calculated with a semi-analytical solution to the advection dispersion equation for transient mass flux input

Evaluation of Triple Containment Method for Air Transport of Contaminated Human

National Research Council Canada - National Science Library

Neville, J

2003-01-01

A triple containment system intended for transport of biologically contaminated human remains was tested for its ability to maintain integrity during exposure to altitude changes representative of air transport...

Modeling Contamination Migration on the Chandra X-ray Observatory II

Science.gov (United States)

O'Dell, Steve; Swartz, Doug; Tice, Neil; Plucinsky, Paul; Grant, Catherine; Marshall, Herman; Vikhlinin, Alexey

2013-01-01

During its first 14 years of operation, the cold (about -60degC) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), aboard the Chandra X-ray Observatory, has accumulated a growing layer of molecular contamination that attenuates low-energy x rays. Over the past few years, the accumulation rate, spatial distribution, and composition may have changed, perhaps partially related to changes in the operating temperature of the ACIS housing. This evolution of the accumulation of the molecular contamination has motivated further analysis of contamination migration on the Chandra X-ray Observatory, particularly within and near the ACIS cavity. To this end, the current study employs a higher-fidelity geometric model of the ACIS cavity, detailed thermal modeling based upon monitored temperature data, and an accordingly refined model of the molecular transport.

Phase I Hydrologic Data for the Groundwater Flow and Contaminant Transport Model of Corrective Action Unit 97: Yucca Flat/Climax Mine, Nevada Test Site, Nye County, Nevada, Rev. No.: 0

Energy Technology Data Exchange (ETDEWEB)

John McCord

2006-06-01

The U.S. Department of Energy (DOE), National Nuclear Security Administration Nevada Site Office (NNSA/NSO) initiated the Underground Test Area (UGTA) Project to assess and evaluate the effects of the underground nuclear weapons tests on groundwater beneath the Nevada Test Site (NTS) and vicinity. The framework for this evaluation is provided in Appendix VI, Revision No. 1 (December 7, 2000) of the Federal Facility Agreement and Consent Order (FFACO, 1996). Section 3.0 of Appendix VI ''Corrective Action Strategy'' of the FFACO describes the process that will be used to complete corrective actions specifically for the UGTA Project. The objective of the UGTA corrective action strategy is to define contaminant boundaries for each UGTA corrective action unit (CAU) where groundwater may have become contaminated from the underground nuclear weapons tests. The contaminant boundaries are determined based on modeling of groundwater flow and contaminant transport. A summary of the FFACO corrective action process and the UGTA corrective action strategy is provided in Section 1.5. The FFACO (1996) corrective action process for the Yucca Flat/Climax Mine CAU 97 was initiated with the Corrective Action Investigation Plan (CAIP) (DOE/NV, 2000a). The CAIP included a review of existing data on the CAU and proposed a set of data collection activities to collect additional characterization data. These recommendations were based on a value of information analysis (VOIA) (IT, 1999), which evaluated the value of different possible data collection activities, with respect to reduction in uncertainty of the contaminant boundary, through simplified transport modeling. The Yucca Flat/Climax Mine CAIP identifies a three-step model development process to evaluate the impact of underground nuclear testing on groundwater to determine a contaminant boundary (DOE/NV, 2000a). The three steps are as follows: (1) Data compilation and analysis that provides the necessary modeling

Monitoring Potential Transport of Radioactive Contaminants in Shallow Ephemeral Channels: FY2015 and FY2016

Energy Technology Data Exchange (ETDEWEB)

Mizell, Steve A [Desert Research Inst. (DRI), Las Vegas, NV (United States); Miller, Julianne J [Desert Research Inst. (DRI), Las Vegas, NV (United States); McCurdy, Greg [Desert Research Inst. (DRI), Las Vegas, NV (United States); Campbell, Scott A [Desert Research Inst. (DRI), Las Vegas, NV (United States)

2017-10-01

The Desert Research Institute (DRI) is conducting a field assessment of the potential for contaminated soil to be transported from the Smoky Contamination Area (CA) as a result of storm runoff. This activity supports Nevada Nuclear Security Administration (NNSA) efforts to complete regulatory closure of the Soils Corrective Action Unit (CAU) contamination areas. The work is intended to confirm the likely mechanism of transport and determine the meteorological conditions that might cause movement of contaminated soils, as well as determine the particle size fraction that is most closely associated with transported radionuclide-contaminated soils. These data will facilitate the appropriate closure design and post-closure monitoring program.

BETR Global - A geographically explicit global-scale multimedia contaminant fate model

Energy Technology Data Exchange (ETDEWEB)

Macleod, M.; Waldow, H. von; Tay, P.; Armitage, J. M.; Wohrnschimmel, H.; Riley, W.; McKone, T. E.; Hungerbuhler, K.

2011-04-01

We present two new software implementations of the BETR Global multimedia contaminant fate model. The model uses steady-state or non-steady-state mass-balance calculations to describe the fate and transport of persistent organic pollutants using a desktop computer. The global environment is described using a database of long-term average monthly conditions on a 15{sup o} x 15{sup o} grid. We demonstrate BETR Global by modeling the global sources, transport, and removal of decamethylcyclopentasiloxane (D5).

The use of tracer techniques in the study of soil water flows and contaminant transport

International Nuclear Information System (INIS)

Reeves, A.D.; Beven, K.J.

1990-04-01

This report reviews the use of different types of tracers in the characterisation of soil water flows and the implications of tracer studies for modelling contaminant transport. The tracers considered are a number of different anions, stable isotopes, radioactive tracers, organic dyes, fluorocarbons, gases, solid particles and water temperature. The theoretical basis for modelling the results of tracer experiments in terms of the traditional convective-dispersion equation (CDE) is outlined. A number of alternative modelling strategies are reviewed: the mobile/immobile water extension of the CDE; the Jury Transfer Function Model (TFM); the Aggregated Mixing Zone (AMZ) model and Random Particle Tracking models. The first will form the basis of the Systeme Hydrologique Europeen (SHE) contaminant transport component. The Jury and AMZ models are both linear models and are consequently limited to applications in which the flows may be considered to be quasi-steady or repeatable. Random particle tracking models have the advantage of both flexibility and applicability to transient and spatially variable flow domains. A random particle model is being implemented on a transputer workstation at Lancaster and will be used to explore the effect of sub-grid scale complexities on effective grid-scale parameter values for distributed models such as SHE. (author)

Assessment of applications of transport models on regional scale solute transport

Science.gov (United States)

Guo, Z.; Fogg, G. E.; Henri, C.; Pauloo, R.

2017-12-01

Regional scale transport models are needed to support the long-term evaluation of groundwater quality and to develop management strategies aiming to prevent serious groundwater degradation. The purpose of this study is to evaluate the capacity of previously-developed upscaling approaches to accurately describe main solute transport processes including the capture of late-time tails under changing boundary conditions. Advective-dispersive contaminant transport in a 3D heterogeneous domain was simulated and used as a reference solution. Equivalent transport under homogeneous flow conditions were then evaluated applying the Multi-Rate Mass Transfer (MRMT) model. The random walk particle tracking method was used for both heterogeneous and homogeneous-MRMT scenarios under steady state and transient conditions. The results indicate that the MRMT model can capture the tails satisfactorily for plume transported with ambient steady-state flow field. However, when boundary conditions change, the mass transfer model calibrated for transport under steady-state conditions cannot accurately reproduce the tailing effect observed for the heterogeneous scenario. The deteriorating impact of transient boundary conditions on the upscaled model is more significant for regions where flow fields are dramatically affected, highlighting the poor applicability of the MRMT approach for complex field settings. Accurately simulating mass in both mobile and immobile zones is critical to represent the transport process under transient flow conditions and will be the future focus of our study.

A 3D FINITE ELEMENT ANALYSIS OF INCOMPRESSIBLE FLUID FLOW AND CONTAMINANT TRANSPORT THROUGH A POROUS LANDFILL

Directory of Open Access Journals (Sweden)

ADEGUN, I. K.

2014-08-01

Full Text Available The paper investigated the flow of incompressible fluid and contaminant transport through a Porous Landfill using a numerical technique. A threedimensional finite element analysis technique was adopted for the solution. The problem was based on the Darcy’s Law and the Advection-Dispersion equation. The solutions of the Darcy’s and Advection-Dispersion equations were generated using Finite Element Analysis Software known as COMSOL Multiphysics. This simulation tool tracked the contaminant transport in the Landfill for 360 days at 10 days interval. It first modeled steady-state fluid flow by employing the Darcy’s Law Application Mode and then followed up with a transient solute-transport simulation by employing the Solute-Transport Application Mode from the Earth Science Module of COMSOL. The solution results obtained from this model were found to be in close agreement with reallife data obtained at the 130- million ton Bukit Tagar Mega Sanitary Landfill site, Selangor near Kuala Lumpur, Malaysia. This showed that the model can effectively predict the trends in the distributions of pollutants from a Municipal Solid Waste Landfill into nearby land and water sources. The model is thus applicable to the issues of environmental protection and safety of groundwater.

Modeling field scale unsaturated flow and transport processes

International Nuclear Information System (INIS)

Gelhar, L.W.; Celia, M.A.; McLaughlin, D.

1994-08-01

The scales of concern in subsurface transport of contaminants from low-level radioactive waste disposal facilities are in the range of 1 to 1,000 m. Natural geologic materials generally show very substantial spatial variability in hydraulic properties over this range of scales. Such heterogeneity can significantly influence the migration of contaminants. It is also envisioned that complex earth structures will be constructed to isolate the waste and minimize infiltration of water into the facility. The flow of water and gases through such facilities must also be a concern. A stochastic theory describing unsaturated flow and contamination transport in naturally heterogeneous soils has been enhanced by adopting a more realistic characterization of soil variability. The enhanced theory is used to predict field-scale effective properties and variances of tension and moisture content. Applications illustrate the important effects of small-scale heterogeneity on large-scale anisotropy and hysteresis and demonstrate the feasibility of simulating two-dimensional flow systems at time and space scales of interest in radioactive waste disposal investigations. Numerical algorithms for predicting field scale unsaturated flow and contaminant transport have been improved by requiring them to respect fundamental physical principles such as mass conservation. These algorithms are able to provide realistic simulations of systems with very dry initial conditions and high degrees of heterogeneity. Numerical simulation of the movement of water and air in unsaturated soils has demonstrated the importance of air pathways for contaminant transport. The stochastic flow and transport theory has been used to develop a systematic approach to performance assessment and site characterization. Hypothesis-testing techniques have been used to determine whether model predictions are consistent with observed data

Ground water contamination analysis by using a fully coupled numerical model

International Nuclear Information System (INIS)

Yahya Sukirman; Norhan Abd Rahman; Raihan Ismail

1999-01-01

Groundwater contamination in the subsurface is not a new or emerging issue, which can be highly toxic at very low concentrations. It can cause a great damage to our environment and public health. In recent years, accidental oil spill, leaking from underground storage and pipeline are getting more and more attention from various parties. There are very important to improve the understanding of the mobilization, transport mechanism and fate of hydrocarbon in the subsurface in checking the risk of public exposure to the contaminants and in evaluating various remediation scenarios. In this paper, groundwater contamination by nonaqueous phase liquids (NAPLs), such as organic solvents and petroleum hydrocarbons, will be simulated for a multiphase flow, heat flow and pollutant transport phenomenon in a semisaturated porous medium. The governing partial differential equations, in terms of soil displacements, fluid pressures, energy balance and concentrations are coupled and behave non-linearly but can be solved by a numerical method. Finally, the developed finite element model has been applied to analyze the transport behavior of hydrocarbon pollutant in subsurface, which can be used to propose a suitable remedial scheme for the groundwater contamination problems. (Author)

Evaluation of modeling approaches to simulate contaminant transport in a fractured limestone aquifer

DEFF Research Database (Denmark)

Mosthaf, Klaus; Fjordbøge, Annika Sidelmann; Broholm, Mette Martina

in fractured limestone aquifers. The model comparison is conducted for a contaminated site in Denmark, where a plume of dissolved PCE has migrated through a fractured limestone aquifer. Field data includes information on spill history, distribution of the contaminant (multilevel sampling), geology...... and hydrogeology. To describe the geology and fracture system, data from borehole logs and cores was combined with an analysis of heterogeneities and fractures from a nearby excavation and pump test data. We present how field data is integrated into the different model concepts. A challenge in the use of field...... and remediation strategies. Each model is compared with field data, considering both model fit and model suitability. Results show a considerable difference between the approaches, and that it is important to select the right one for the actual modeling purpose. The comparison with data showed how much...

Modelling post-depositional transport of PAHs in aquatic bed sediments using CoReTranS

Energy Technology Data Exchange (ETDEWEB)

Go, Jason [Imperial College London, London (United Kingdom). Dept. of Earth Science and Engineering; Stegemann, Julia A. [Imperial College London, London (United Kingdom). Dept. of Civil, Environmental and Geomatic Engineering

2012-12-15

Purpose: Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous and persistent contaminants in aquatic bed sediments. A better understanding of their in-bed fate and transport is therefore key in minimising the risk to the environment over time through various remediation and monitoring strategies. Since ecological effects and risks are related to contaminant concentrations, this study developed CoReTranS, a predictive model that simulates one-dimensional organic contaminant reaction and transport in bed sediments. Materials and methods: CoReTranS was benchmarked against analytical solutions of simplified reactive transport models and validated using a published study of marsh sediments contaminated with petroleum-derived hydrocarbons from Wild Harbour, West Falmouth, MA, USA. Results and discussion: The CoReTranS model effectively predicted the vertical distribution of PAHs in the Wild Harbour sediments as confirmed by the modelling results from the published study. The CoReTranS model was also used to interpret results from a published study of PAH-contaminated fjord sediments from Kitimat Arm in British Columbia, Canada. Specific insights into the post-depositional fate and transport of selected PAHs in the Kitimat fjord sediments were obtained by comparing the measured concentration-depth profiles with the numerical results from the CoReTranS model. Key parameters such as effective diffusivity of contaminants and burial velocities of sediment particles were shown to possibly account for the predicted concentrations-depth profiles in the Kitimat fjord sediments. Conclusions: As demonstrated, CoReTranS can simulate reactive transport models in order to predict PAH concentration profiles in porewater under site-specific conditions. The information derived from the use of the CoReTranS model highlighted practical application of such information by engineers to site-specific risk assessment and remediation. (orig.)

Overview of research and development in subsurface fate and transport modeling

International Nuclear Information System (INIS)

Sullivan, T.M.; Chehata, M.

1995-05-01

The US Department of Energy is responsible for the remediation of over 450 different subsurface-contaminated sites. Contaminant plumes at these sites range in volume from several to millions of cubic yards. The concentration of contaminants also ranges over several orders of magnitude. Contaminants include hazardous wastes such as heavy metals and organic chemicals, radioactive waste including tritium, uranium, and thorium, and mixed waste, which is a combination of hazardous and radioactive wastes. The physical form of the contaminants includes solutes, nonaqueous phase liquids (NAPLs), and vapor phase contaminants such as volatilized organic chemicals and radon. The subject of contaminant fate and transport modeling is multi-disciplinary, involving hydrology, geology, microbiology, chemistry, applied mathematics, computer science, and other areas of expertise. It is an issue of great significance in the United States and around the world. As such, many organizations have substantial programs in this area. In gathering data to prepare this report, a survey was performed of research and development work that is funded by US government agencies to improve the understanding and mechanistic modeling of processes that control contaminant movement through subsurface systems. Government agencies which fund programs that contain fate and transport modeling components include the Environmental Protection Agency, Nuclear Regulatory Commission, Department of Agriculture, Department of Energy, National Science Foundation, Department of Defense, United States Geological Survey, and National Institutes of Health

Characterization and Remediation of Contaminated Sites:Modeling, Measurement and Assessment

Science.gov (United States)

Basu, N. B.; Rao, P. C.; Poyer, I. C.; Christ, J. A.; Zhang, C. Y.; Jawitz, J. W.; Werth, C. J.; Annable, M. D.; Hatfield, K.

2008-05-01

small computation time and their inclusion of spatially integrated parameters that can be measured in the field using tracer tests. Analytical models that couple source depletion to plume transport were used for optimization of source and plume treatment. These models are being used for the development of decision and management tools (for DNAPL sites) that consider uncertainty assessments as an integral part of the decision-making process for contaminated site remediation.

Subsurface Flow and Contaminant Transport Documentation and User's Guide

Energy Technology Data Exchange (ETDEWEB)

Aleman, S.E.

1999-07-28

This report documents a finite element code designed to model subsurface flow and contaminant transport, named FACT. FACT is a transient three-dimensional, finite element code designed to simulate isothermal groundwater flow, moisture movement, and solute transport in variably saturated and fully saturated subsurface porous media. The code is designed specifically to handle complex multi-layer and/or heterogeneous aquifer systems in an efficient manner and accommodates a wide range of boundary conditions. Additionally, 1-D and 2-D (in Cartesian coordinates) problems are handled in FACT by simply limiting the number of elements in a particular direction(s) to one. The governing equations in FACT are formulated only in Cartesian coordinates.

GWSCREEN: A semi-analytical model for assessment of the groundwater pathway from surface or buried contamination: Theory and user`s manual

Energy Technology Data Exchange (ETDEWEB)

Rood, A.S.

1992-03-01

GWSCREEN was developed for assessment of the groundwater pathway from leaching of radioactive and non radioactive substances from surface or buried sources. The code was designed for implementation in the Track 1 and Track 2 assessment of Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) sites identified as low probability hazard at the Idaho National Engineering Laboratory (DOE, 1991). The code calculates the limiting soil concentration such that regulatory contaminant levels in groundwater are not exceeded. The code uses a mass conservation approach to model three processes: Contaminant release from a source volume, contaminant transport in the unsaturated zone, and contaminant transport in the saturated zone. The source model considers the sorptive properties and solubility of the contaminant. Transport in the unsaturated zone is described by a plug flow model. Transport in the saturated zone is calculated with a semi-analytical solution to the advection dispersion equation for transient mass flux input.

Transport of Aquatic Contaminant and Assessment of Radioecological Exposure with Spatial and Temporal Effects

Science.gov (United States)

Feng, Ying

1995-01-01

A comprehensive study of the radioecological exposure assessment for a contaminated aquatic ecosystem has been performed in this dissertation. The primary objectives of this research were to advance the understanding of radiation exposure in nature and to increase current capabilities for estimating aquatic radiation exposure with the consideration of spatial and temporal effect in nature. This was accomplished through the development of a two-dimensional aquatic exposure assessment framework and by applying the framework to the contaminated Chernobyl cooling lake (pond). This framework integrated spatial and temporal heterogeneity effects of contaminant concentration, abundance and distribution of ecosystem populations, spatial- and temporal-dependent (or density-dependent) radionuclide ingestion, and alternative food web structures. The exposure model was built on the population level to allow for the integration of density dependent population regulation into the exposure assessment. Plankton population dynamics have been integrated into the hydrodynamic-transport model to determine plankton biomass density changes and distributions. The distribution of contaminant in water was also calculated using a hydrodynamic-transport model. The significance of adding spatial and temporal effects, spatial and temporal related ecological functions, and hydrodynamics in the exposure assessment was illustrated through a series of case studies. The results suggested that the spatial and temporal heterogeneity effects of radioactive environments were substantial. Among the ecological functions considered, the food web structure was the most important contributor to the variations of fish exposure. The results obtained using a multiple prey food web structure differed by a factor of 20 from the equilibrium concentration, and by a factor of 2.5 from the concentration obtained using a single-prey food web. Impacts of changes in abundance and distribution of biomass on contaminant

Unsaturated zone leaching models for assessing risk to groundwater of contaminated sites

DEFF Research Database (Denmark)

Troldborg, Mads; Binning, Philip John; Nielsen, Signe

2009-01-01

and aqueous phase contaminant transport equation. The equation has the same general form as the standard advection-diffusion equation for which many analytical solutions have been derived. Four new analytical solutions are developed using this approach: a three-dimensional solution accounting for infiltration......, lateral gas diffusion, sorption and degradation; a simple one-dimensional screening model, and two one-dimensional radial gas diffusion models for use in simulating volatile organic contaminant diffusion in unsaturated soils with an impermeable cover. The models show that both degradation and diffusion...

Abstracts of the symposium on unsaturated flow and transport modeling

International Nuclear Information System (INIS)

1982-03-01

Abstract titles are: Recent developments in modeling variably saturated flow and transport; Unsaturated flow modeling as applied to field problems; Coupled heat and moisture transport in unsaturated soils; Influence of climatic parameters on movement of radionuclides in a multilayered saturated-unsaturated media; Modeling water and solute transport in soil containing roots; Simulation of consolidation in partially saturated soil materials; modeling of water and solute transport in unsaturated heterogeneous fields; Fluid dynamics and mass transfer in variably-saturated porous media; Solute transport through soils; One-dimensional analytical transport modeling; Convective transport of ideal tracers in unsaturated soils; Chemical transport in macropore-mesopore media under partially saturated conditions; Influence of the tension-saturated zone on contaminant migration in shallow water regimes; Influence of the spatial distribution of velocities in porous media on the form of solute transport; Stochastic vs deterministic models for solute movement in the field; and Stochastic analysis of flow and solute transport

The effect of precipitation on contaminant dissolution and transport: Analytic solutions

International Nuclear Information System (INIS)

Light, W.B.; Chambre, P.L.; Pigford, T.H.; Lee, W.W.L.

1988-09-01

We analysed the effect of precipitation on the dissolution and transport rates of a nondecaying contaminant. Precipitation near the waste surface can have a profound effect on dissolution and transport rates. The mass-transfer rate at the waste surface is controlled by the solid-liquid reaction rate to an extent determined by the modified reaction-rate modulus, α. At later times extending to steady state, the mass-transfer rate depends on the location of the precipitation front r/sub p/ and on the solubility ratio C/sub o//C/sub p/. A precipitation front very near the waste surface can change the dissolution mechanism from solubility-diffusion-controlled to chemical-reaction-rate controlled. Precipitation limits the concentration of the contaminant at r > r/sub p/ to C/sub p/, steepening the concentration gradient for dissolution on the waste package side of the front and flattening the gradient for transport in the region outside the front. This increases the rate of contaminant transport from the waste to the front while decreasing the rate of transport away from the front, when compared to the situation without precipitation. The difference in the transport rates at the front is the rate of precipitation. For large changes in solubility, most of the contaminant is immobilized by precipitation, as was observed in a parallel study. The effect of a precipitation front located nearby in surrounding rock is to increase the release rate at the waste surface/rock interface. The increase in release rate at the waste surface is greater the closer the precipitation and the larger the ratio C/sub o//C/sub p/, also observed by others. The release rates of other waste constituents that dissolve congruently with the solubility-controlling matrix can be increased by a local high-solubility region between the waste surface and the precipitation front. 10 refs., 5 figs

Discriminative Random Field Models for Subsurface Contamination Uncertainty Quantification

Science.gov (United States)

Arshadi, M.; Abriola, L. M.; Miller, E. L.; De Paolis Kaluza, C.

2017-12-01

Application of flow and transport simulators for prediction of the release, entrapment, and persistence of dense non-aqueous phase liquids (DNAPLs) and associated contaminant plumes is a computationally intensive process that requires specification of a large number of material properties and hydrologic/chemical parameters. Given its computational burden, this direct simulation approach is particularly ill-suited for quantifying both the expected performance and uncertainty associated with candidate remediation strategies under real field conditions. Prediction uncertainties primarily arise from limited information about contaminant mass distributions, as well as the spatial distribution of subsurface hydrologic properties. Application of direct simulation to quantify uncertainty would, thus, typically require simulating multiphase flow and transport for a large number of permeability and release scenarios to collect statistics associated with remedial effectiveness, a computationally prohibitive process. The primary objective of this work is to develop and demonstrate a methodology that employs measured field data to produce equi-probable stochastic representations of a subsurface source zone that capture the spatial distribution and uncertainty associated with key features that control remediation performance (i.e., permeability and contamination mass). Here we employ probabilistic models known as discriminative random fields (DRFs) to synthesize stochastic realizations of initial mass distributions consistent with known, and typically limited, site characterization data. Using a limited number of full scale simulations as training data, a statistical model is developed for predicting the distribution of contaminant mass (e.g., DNAPL saturation and aqueous concentration) across a heterogeneous domain. Monte-Carlo sampling methods are then employed, in conjunction with the trained statistical model, to generate realizations conditioned on measured borehole data

Contaminant transport and accumulation in Massachusetts Bay and Boston Harbor; a summary of U.S. Geological Survey studies

Science.gov (United States)

Butman, Bradford; Bothner, Michael H.; Hathaway, J.C.; Jenter, H.L.; Knebel, H.J.; Manheim, F.T.; Signell, R.P.

1992-01-01

The U.S. Geological Survey (USGS) is conducting studies in Boston Harbor, Massachusetts Bay, and Cape Cod Bay designed to define the geologic framework of the region and to understand the transport and accumulation of contaminated sediments. The region is being studied because of environmental problems caused by the introduction of wastes for a long time, because a new ocean outfall (to begin operation in 1995) will change the location for disposal of treated Boston sewage from Boston Harbor into Massachusetts Bay, and because of the need to understand the transport of sediments and associated contaminants in order to address a wide range of management questions. The USGS effort complements and is closely coordinated with the research and monitoring studies supported by the Massachusetts Environmental Trust, the Massachusetts Bays Program, and by the Massachusetts Water Resources Authority. The USGS study includes (1) geologic mapping, (2) circulation studies, (3) long-term current and sediment transport observations, (4) measurements of contaminant inventories and rates of sediment mixing and accumulation, (5) circulation modeling, (6) development of a contaminated sediments data base, and (7) information exchange. A long-term objective of the program is to develop a predictive capability for sediment transport and accumulation.

OSPW contamination transport through peat soils : laboratory and greenhouse study

Energy Technology Data Exchange (ETDEWEB)

Rezanezhad, F.; Price, J.S. [Waterloo Univ., ON (Canada). Dept. of Geography; Rochefort, L.; Pouliot, R. [Laval Univ., Quebec City, PQ (Canada). Dept. of Phytology; Andersen, R. [Laval Univ., Quebec City, PQ (Canada). Dept. of Phytology; Macaulay Land Use Research Inst., Aberdeen (United Kingdom); Daly, C. [Suncor Energy, Fort McMurray, AB (Canada)

2010-07-01

Large portions of northern Canada are covered by peatlands, and the majority of post-mined landscapes have increased salinity, heavy metals and naphthenic acids (NA). This PowerPoint presentation discussed laboratory and greenhouse studies conducted to determine oil sands process water (OSPW) contamination transport through peat soils. Peat is a highly complex porous media. The presence of sodium and NA has a toxic effect on aquatic life. Greenhouse studies were conducted to determine the changes caused by OSPW in the microbial community of a peat matrix over 2 growing seasons. The study showed that peat has an exceptional ability to absorb the contaminants in OSPW water. NA and sodium transport through peat was significantly delayed by sorption, and by diffusion into immobile water contained in the peat matrix. The vegetation in the study was healthy and tolerant to the contaminants in the OSPW. tabs., figs.

Monitoring Potential Transport of Radioactive Contaminants in Shallow Ephemeral Channels: FY2013 and FY2014 (revised)

Energy Technology Data Exchange (ETDEWEB)

Mizell, Steve A. [Desert Research Inst. (DRI), Las Vegas, NV (United States); Miller, Julianne J. [Desert Research Inst. (DRI), Las Vegas, NV (United States); McCurdy, Greg D. [Desert Research Inst. (DRI), Reno, NV (United States); Campbell, Scott A. [Desert Research Inst. (DRI), Las Vegas, NV (United States)

2017-06-01

The Desert Research Institute (DRI) is conducting a field assessment of the potential for contaminated soil to be transported from the Smoky Contamination Area (CA) as a result of storm runoff, which supports National Nuclear Security Administration (NNSA) efforts to complete regulatory closure of the Soils Corrective Action Unit (CAU) contamination areas. The work is intended to confirm the likely mechanism of transport and determine the meteorological conditions that might cause movement of contaminated soils, as well as determine the particle size fraction that is most closely associated with transported radionuclide-contaminated soils. These data will facilitate the appropriate closure design and post-closure monitoring program.

GWSCREEN: A semi-analytical model for assessment of the groundwater pathway from surface or buried contamination: Theory and user's manual

Energy Technology Data Exchange (ETDEWEB)

Rood, A.S.

1992-03-01

GWSCREEN was developed for assessment of the groundwater pathway from leaching of radioactive and non radioactive substances from surface or buried sources. The code was designed for implementation in the Track 1 and Track 2 assessment of Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) sites identified as low probability hazard at the Idaho National Engineering Laboratory (DOE, 1991). The code calculates the limiting soil concentration such that regulatory contaminant levels in groundwater are not exceeded. The code uses a mass conservation approach to model three processes: Contaminant release from a source volume, contaminant transport in the unsaturated zone, and contaminant transport in the saturated zone. The source model considers the sorptive properties and solubility of the contaminant. Transport in the unsaturated zone is described by a plug flow model. Transport in the saturated zone is calculated with a semi-analytical solution to the advection dispersion equation for transient mass flux input.

Simulation of contaminant transport in fractured porous media on triangular meshes

KAUST Repository

Dong, Chen

2010-12-01

A mathematical model for contaminant species passing through fractured porous media is presented. In the numerical model, we combine two locally conservative methods, i.e. mixed finite element (MFE) and the finite volume (FV) methods. Adaptive triangle mesh is used for effective treatment of the fractures. A hybrid MFE method is employed to provide an accurate approximation of velocities field for both the fractures and matrix which are crucial to the convection part of the transport equation. The FV method and the standard MFE method are used to approximate the convection and dispersion terms respectively. Numerical examples in a medium containing fracture network illustrate the robustness and efficiency of the proposed numerical model. © 2010 IEEE.

Simulation of contaminant transport in fractured porous media on triangular meshes

KAUST Repository

Dong, Chen; Sun, Shuyu

2010-01-01

A mathematical model for contaminant species passing through fractured porous media is presented. In the numerical model, we combine two locally conservative methods, i.e. mixed finite element (MFE) and the finite volume (FV) methods. Adaptive triangle mesh is used for effective treatment of the fractures. A hybrid MFE method is employed to provide an accurate approximation of velocities field for both the fractures and matrix which are crucial to the convection part of the transport equation. The FV method and the standard MFE method are used to approximate the convection and dispersion terms respectively. Numerical examples in a medium containing fracture network illustrate the robustness and efficiency of the proposed numerical model. © 2010 IEEE.

Radioactive contamination level of vehicles resulted from transporting fine rare-earth minerals by rail

International Nuclear Information System (INIS)

Han Kaichun; Yu Boyong; Gao Shengwei

1997-01-01

This paper presents monitoring results of radioactive contamination level of steel open wagon surface resulted from transporting fine rare-earth minerals. Under promising transport conditions (the packaging consists of two layers of plastic bags and two layers of plastic net sacks, each package contains 50 kg of minerals, each vehicle carries 60 t), the surface radioactivity (total α and total β) of 16 vehicles on two lines from Baotou to Wujiachuan (924 km) and from Baotou to Sankeshu (2236 km) was measured before loading, after unloading and washing, using α and β surface contamination detector. The results showed that the radioactive contamination level of the vehicle surface after unloading appeared significantly different. The contamination level of vehicle bases was higher than that of both sides, long distance vehicles was higher than that of short distance vehicles. The radioactive contamination level of vehicles surface after washing was below the standard limits, these vehicles can be used for ordinary goods transport

Reduction of spatial distribution of risk factors for transportation of contaminants released by coal mining activities.

Science.gov (United States)

Karan, Shivesh Kishore; Samadder, Sukha Ranjan

2016-09-15

It is reported that water-energy nexus composes two of the biggest development and human health challenges. In the present study we presented a Risk Potential Index (RPI) model which encapsulates Source, Vector (Transport), and Target risks for forecasting surface water contamination. The main aim of the model is to identify critical surface water risk zones for an open cast mining environment, taking Jharia Coalfield, India as the study area. The model also helps in feasible sampling design. Based on spatial analysis various risk zones were successfully delineated. Monthly RPI distribution revealed that the risk of surface water contamination was highest during the monsoon months. Surface water samples were analysed to validate the model. A GIS based alternative management option was proposed to reduce surface water contamination risk and observed 96% and 86% decrease in the spatial distribution of very high risk areas for the months June and July respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dual states estimation of a subsurface flow-transport coupled model using ensemble Kalman filtering

KAUST Repository

El Gharamti, Mohamad

2013-10-01

Modeling the spread of subsurface contaminants requires coupling a groundwater flow model with a contaminant transport model. Such coupling may provide accurate estimates of future subsurface hydrologic states if essential flow and contaminant data are assimilated in the model. Assuming perfect flow, an ensemble Kalman filter (EnKF) can be used for direct data assimilation into the transport model. This is, however, a crude assumption as flow models can be subject to many sources of uncertainty. If the flow is not accurately simulated, contaminant predictions will likely be inaccurate even after successive Kalman updates of the contaminant model with the data. The problem is better handled when both flow and contaminant states are concurrently estimated using the traditional joint state augmentation approach. In this paper, we introduce a dual estimation strategy for data assimilation into a one-way coupled system by treating the flow and the contaminant models separately while intertwining a pair of distinct EnKFs, one for each model. The presented strategy only deals with the estimation of state variables but it can also be used for state and parameter estimation problems. This EnKF-based dual state-state estimation procedure presents a number of novel features: (i) it allows for simultaneous estimation of both flow and contaminant states in parallel; (ii) it provides a time consistent sequential updating scheme between the two models (first flow, then transport); (iii) it simplifies the implementation of the filtering system; and (iv) it yields more stable and accurate solutions than does the standard joint approach. We conducted synthetic numerical experiments based on various time stepping and observation strategies to evaluate the dual EnKF approach and compare its performance with the joint state augmentation approach. Experimental results show that on average, the dual strategy could reduce the estimation error of the coupled states by 15% compared with the

Monte Carlo simulation of nonlinear reactive contaminant transport in unsaturated porous media

International Nuclear Information System (INIS)

Giacobbo, F.; Patelli, E.

2007-01-01

In the current proposed solutions of radioactive waste repositories, the protective function against the radionuclide water-driven transport back to the biosphere is to be provided by an integrated system of engineered and natural geologic barriers. The occurrence of several nonlinear interactions during the radionuclide migration process may render burdensome the classical analytical-numerical approaches. Moreover, the heterogeneity of the barriers' media forces approximations to the classical analytical-numerical models, thus reducing their fidelity to reality. In an attempt to overcome these difficulties, in the present paper we adopt a Monte Carlo simulation approach, previously developed on the basis of the Kolmogorov-Dmitriev theory of branching stochastic processes. The approach is here extended for describing transport through unsaturated porous media under transient flow conditions and in presence of nonlinear interchange phenomena between the liquid and solid phases. This generalization entails the determination of the functional dependence of the parameters of the proposed transport model from the water content and from the contaminant concentration, which change in space and time during the water infiltration process. The corresponding Monte Carlo simulation approach is verified with respect to a case of nonreactive transport under transient unsaturated flow and to a case of nonlinear reactive transport under stationary saturated flow. Numerical applications regarding linear and nonlinear reactive transport under transient unsaturated flow are reported

Mathematical Modeling of Non-Fickian Diffusional Mass Exchange of Radioactive Contaminants in Geological Disposal Formations

Directory of Open Access Journals (Sweden)

Anna Suzuki

2018-01-01

Full Text Available Deep geological repositories for nuclear wastes consist of both engineered and natural geologic barriers to isolate the radioactive material from the human environment. Inappropriate repositories of nuclear waste would cause severe contamination to nearby aquifers. In this complex environment, mass transport of radioactive contaminants displays anomalous behaviors and often produces power-law tails in breakthrough curves due to spatial heterogeneities in fractured rocks, velocity dispersion, adsorption, and decay of contaminants, which requires more sophisticated models beyond the typical advection-dispersion equation. In this paper, accounting for the mass exchange between a fracture and a porous matrix of complex geometry, the universal equation of mass transport within a fracture is derived. This equation represents the generalization of the previously used models and accounts for anomalous mass exchange between a fracture and porous blocks through the introduction of the integral term of convolution type and fractional derivatives. This equation can be applied for the variety of processes taking place in the complex fractured porous medium, including the transport of radioactive elements. The Laplace transform method was used to obtain the solution of the fractional diffusion equation with a time-dependent source of radioactive contaminant.

Modelling the transport of solid contaminants originated from a point source

Science.gov (United States)

Salgueiro, Dora V.; Conde, Daniel A. S.; Franca, Mário J.; Schleiss, Anton J.; Ferreira, Rui M. L.

2017-04-01

The solid phases of natural flows can comprise an important repository for contaminants in aquatic ecosystems and can propagate as turbidity currents generating a stratified environment. Contaminants can be desorbed under specific environmental conditions becoming re-suspended, with a potential impact on the aquatic biota. Forecasting the distribution of the contaminated turbidity current is thus crucial for a complete assessment of environmental exposure. In this work we validate the ability of the model STAV-2D, developed at CERIS (IST), to simulate stratified flows such as those resulting from turbidity currents in complex geometrical environments. The validation involves not only flow phenomena inherent to flows generated by density imbalance but also convective effects brought about by the complex geometry of the water basin where the current propagates. This latter aspect is of paramount importance since, in real applications, currents may propagate in semi-confined geometries in plan view, generating important convective accelerations. Velocity fields and mass distributions obtained from experiments carried out at CERIS - (IST) are used as validation data for the model. The experimental set-up comprises a point source in a rectangular basin with a wall placed perpendicularly to the outer walls. Thus generates a complex 2D flow with an advancing wave front and shocks due to the flow reflection from the walls. STAV-2D is based on the depth- and time-averaged mass and momentum equations for mixtures of water and sediment, understood as continua. It is closed in terms of flow resistance and capacity bedload discharge by a set of classic closure models and a specific high concentration formulation. The two-layer model is derived from layer-averaged Navier-Stokes equations, resulting in a system of layer-specific non-linear shallow-water equations, solved through explicit first or second-order schemes. According to the experimental data for mass distribution, the

Modeling of radiocesium transport kinetics in system water-aquatic plants

International Nuclear Information System (INIS)

Svadlenkova, M.

1988-01-01

Compartment models were used to describe the kinetics of the transport of radionuclides in the system water-biomass of aquatic plants. Briefly described are linear models and models with time variable parameters. The model was tested using data from a locality in the environs of the Bohunice nuclear power plant. Cladophora glomerata algae were the monitored plants, 137 Cs the monitored radionuclide. The models may be used when aquatic plants serve as bioindicators of the radioactive contamination of surface waters, for monitoring the transport of radionuclides in food chains. (M.D.). 10 refs

Contaminant transport, revegetation, and trace element studies at inactive uranium mill tailings piles

International Nuclear Information System (INIS)

Dreesen, D.R.; Marple, M.L.; Kelley, N.E.

1978-01-01

The stabilization of inactive uranium mill tailings piles is presently under study. These studies have included investigations of stabilizing tailings by attempting to establish native vegetation without applying irrigation. Examination of processes which transport tailings or associated contaminants into the environment has been undertaken to better understand the containment provided by various stabilization methods. The uptake of toxic trace elements and radionuclides by vegetation has been examined as a mechanism of contaminant transport. The source terms of 222 Rn from inactive piles have been determined as well as the attenuation of radon flux provided by shallow soil covers. The possibility of shallow ground water contamination around an inactive pile has been examined to determine the significance of ground water transport as a mode of contaminant migration. The rationale in support of trace element studies related to uranium milling activities is presented including the enrichment, migration, and toxicities of trace elements often associated with uranium deposits. Some concepts for the stabilization of inactive piles are presented to extrapolate from research findings to practical applications. 25 references, 8 tables

Modeling Np and Pu transport with a surface complexation model and spatially variant sorption capacities: Implications for reactive transport modeling and performance assessments of nuclear waste disposal sites

Science.gov (United States)

Glynn, P.D.

2003-01-01

One-dimensional (1D) geochemical transport modeling is used to demonstrate the effects of speciation and sorption reactions on the ground-water transport of Np and Pu, two redox-sensitive elements. Earlier 1D simulations (Reardon, 1981) considered the kinetically limited dissolution of calcite and its effect on ion-exchange reactions (involving 90Sr, Ca, Na, Mg and K), and documented the spatial variation of a 90Sr partition coefficient under both transient and steady-state chemical conditions. In contrast, the simulations presented here assume local equilibrium for all reactions, and consider sorption on constant potential, rather than constant charge, surfaces. Reardon's (1981) seminal findings on the spatial and temporal variability of partitioning (of 90Sr) are reexamined and found partially caused by his assumption of a kinetically limited reaction. In the present work, sorption is assumed the predominant retardation process controlling Pu and Np transport, and is simulated using a diffuse-double-layer-surface-complexation (DDLSC) model. Transport simulations consider the infiltration of Np- and Pu-contaminated waters into an initially uncontaminated environment, followed by the cleanup of the resultant contamination with uncontaminated water. Simulations are conducted using different spatial distributions of sorption capacities (with the same total potential sorption capacity, but with different variances and spatial correlation structures). Results obtained differ markedly from those that would be obtained in transport simulations using constant Kd, Langmuir or Freundlich sorption models. When possible, simulation results (breakthrough curves) are fitted to a constant K d advection-dispersion transport model and compared. Functional differences often are great enough that they prevent a meaningful fit of the simulation results with a constant K d (or even a Langmuir or Freundlich) model, even in the case of Np, a weakly sorbed radionuclide under the

Understanding Contaminant Transport Pathways at Rocky Flats - A Basis for the Remediation Strategy

International Nuclear Information System (INIS)

Paton, Ian

2008-01-01

The Rocky Flats Environmental Technology Site (RFETS) is a Department of Energy facility located approximately 16 miles northwest of Denver, Colorado. Processing and fabrication of nuclear weapons components occurred at Rocky Flats from 1952 through 1989. Operations at the Site included the use of several radionuclides, including plutonium-239/240 (Pu), americium-241 (Am), and various uranium (U) isotopes, as well as several types of chlorinated solvents. The historic operations resulted in legacy contamination, including contaminated facilities, process waste lines, buried wastes and surface soil contamination. Decontamination and removal of buildings at the site was completed in late 2005, culminating more than ten years of active environmental remediation work. The Corrective Action Decision/Record of Decision was subsequently approved in 2006, signifying regulatory approval and closure of the site. The use of RFETS as a National Wildlife Refuge is scheduled to be in full operation by 2012. To develop a plan for remediating different types of radionuclide contaminants present in the RFETS environment required understanding the different environmental transport pathways for the various actinides. Developing this understanding was the primary objective of the Actinide Migration Evaluation (AME) project. Findings from the AME studies were used in the development of RFETS remediation strategies. The AME project focused on issues of actinide behavior and mobility in surface water, groundwater, air, soil and biota at RFETS. For the purposes of the AME studies, actinide elements addressed included Pu, Am, and U. The AME program, funded by DOE, brought together personnel with a broad range of relevant expertise in technical investigations. The AME advisory panel identified research investigations and approaches that could be used to solve issues related to actinide migration at the Site. An initial step of the AME was to develop a conceptual model to provide a

DNA-labeled micro- and nanoparticles: a new approach to study contaminant transport in the subsurface

Science.gov (United States)

McNew, C.; Wang, C.; Kocis, T. N.; Murphy, N. P.; Dahlke, H. E.

2017-12-01

Though our understanding of contaminant behavior in the subsurface has improved, our ability to measure and predict complex contaminant transport pathways at hillslope to watershed scales is still lacking. By utilizing bio-molecular nanotechnology developed for nano-medicines and drug delivery, we are able to produce DNA-labeled micro- and nanoparticles for use in a myriad of environmental systems. Control of the fabrication procedure allows us to produce particles of custom size, charge, and surface functionality to mimic the transport properties of the particulate contaminant or colloid of interest. The use of custom sequenced DNA allows for the fabrication of an enormous number of unique particle labels (approximately 1.61 x 1060 unique sequences) and the ability to discern between varied spatial and temporal applications, or the transport effect of varied particle size, charge, or surface properties. To date, this technology has been utilized to study contaminant transport from lab to field scales, including surface and open channel flow applications, transport in porous media, soil retention, and even subglacial flow pathways. Here, we present the technology for production and detection of the DNA-labeled particles along with the results from a current hillslope study at the Sierra Foothills Research and Extension Center (SFREC). This field study utilizes spatial and temporal variations in DNA-labeled particle applications to identify subsurface pollutant transport pathways through the four distinct soil horizons present at the SFREC site. Results from this and previous studies highlight the tremendous potential of the DNA-labeled particle technology for studying contaminant transport through the subsurface.

Long-term environmental and health implications of morphological change and sediment transport with respect to contaminants

Science.gov (United States)

Sneddon, Christopher; Copplestone, David; Tyler, Andrew; Hunter, Peter; Smith, Nick

2014-05-01

The EPSRC-funded Adaptation and Resilience of Coastal Energy Supply (ARCoES) project encompasses four research strands, involving 14 institutions and six PhD studentships. ARCoES aims to determine the threats posed to future energy generation and the distribution network by flooding and erosion, changing patterns of coastal sedimentation, water temperature and the distribution of plants and animals in the coastal zone. Whilst this research has direct benefits for the operation of coastal power stations, ARCoES aims to have a wider stakeholder engagement through assessing how the resilience of coastal communities may be altered by five hundred years of coastal evolution. Coastal evolution will have substantial implications for the energy sector of the North West of England as former waste storage sites are eroded and remobilised within the intertidal environment. The current intertidal environmental stores of radioactivity will also experience reworking as ocean chemistry changes and saltmarsh chronologies are reworked in response to rising sea levels. There is a duel requirement to understand mass sediment movement along the North West coast of England as understanding the sediment transport dynamics is key to modelling long term coastal change and understanding how the environmental store of radioactivity will be reworked. The University of Stirling is researching the long-term environmental and health implications of remobilisation and transport of contaminated sediments around the UK coastline. Using a synergy of hyperspectral and topographic information the mobilisation of sediment bound contaminants within the coastal environment will be investigated. Potential hazards posed by contaminants are determined by a set of environmental impact test criteria which evaluate the bio-accessibility and ionising dose of contaminants. These test criteria will be used to comment on the likely environmental impact of modelled sediment transport and anticipated changes in

Vadose Zone Contaminant Fate and Transport Analysis for the 216-B-26 Trench

Energy Technology Data Exchange (ETDEWEB)

Ward, Andy L.; Gee, Glendon W.; Zhang, Z. F.; Keller, Jason M.

2004-10-14

The BC Cribs and Trenches, part of the 200 TW 1 OU waste sites, received about 30 Mgal of scavenged tank waste, with possibly the largest inventory of 99Tc ever disposed to the soil at Hanford and site remediation is being accelerated. The purpose of this work was to develop a conceptual model for contaminant fate and transport at the 216-B-26 Trench site to support identification and development and evaluation of remediation alternatives. Large concentrations of 99Tc high above the water table implicated stratigraphy in the control of the downward migration. The current conceptual model accounts for small-scale stratigraphy; site-specific changes soil properties; tilted layers; and lateral spreading. It assumes the layers are spatially continuous causing water and solutes to move laterally across the boundary if conditions permit. Water influx at the surface is assumed to be steady. Model parameters were generated with pedotransfer functions; these were coupled high resolution neutron moisture logs that provided information on the underlying heterogeneity on a scale of 3 inches. Two approaches were used to evaluate the impact of remedial options on transport. In the first, a 1-D convolution solution to the convective-dispersive equation was used, assuming steady flow. This model was used to predict future movement of the existing plume using the mean and depth dependent moisture content. In the second approach, the STOMP model was used to first predict the current plume distribution followed by its future migration. Redistribution of the 99Tc plume was simulated for the no-action alternative and on-site capping. Hypothetical caps limiting recharge to 1.0, 0.5, and 0.1 mm yr-1 were considered and assumed not to degrade in the long term. Results show that arrival time of the MCLs, the peak arrival time, and the arrival time of the center of mass increased with decreasing recharge rate. The 1-D convolution model is easy to apply and can easily accommodate initial

GWSCREEN: A semi-analytical model for assessment of the groundwater pathway from surface or buried contamination: Version 2.0 theory and user's manual

International Nuclear Information System (INIS)

Rood, A.S.

1993-06-01

GWSCREEN was developed for assessment of the groundwater pathway from leaching of radioactive and non radioactive substances from surface or buried sources. The code was designed for implementation in the Track I and Track II assessment of CERCLA (Comprehensive Environmental Response, Compensation and Liability Act) sites identified as low probability hazard at the Idaho National Engineering Laboratory (DOE, 1992). The code calculates the limiting soil concentration such that, after leaching and transport to the aquifer, regulatory contaminant levels in groundwater are not exceeded. The code uses a mass conservation approach to model three processes: contaminant release from a source volume, contaminant transport in the unsaturated zone, and contaminant transport in the saturated zone. The source model considers the sorptive properties and solubility of the contaminant. Transport in the unsaturated zone is described by a plug flow model. Transport in the saturated zone is calculated with a semi-analytical solution to the advection dispersion equation in groundwater. In Version 2.0, GWSCREEN has incorporated an additional source model to calculate the impacts to groundwater resulting from the release to percolation ponds. In addition, transport of radioactive progeny has also been incorporated. GWSCREEN has shown comparable results when compared against other codes using similar algorithms and techniques. This code was designed for assessment and screening of the groundwater pathway when field data is limited. It was not intended to be a predictive tool

ITE CHARACTERIZATION TO SUPPORT CONCEPTUAL MODEL DEVELOPMENT FOR SUBSURFACE RADIONUCLIDE TRANSPORT

Science.gov (United States)

Remediation of radionuclide contaminants in ground water often begins with the development of conceptual and analytical models that guide our understanding of the processes controlling radionuclide transport. The reliability of these models is often predicated on the collection o...

Auxiliary analyses in support of performance assessment of a hypothetical low-level waste facility: Two-phase flow and contaminant transport in unsaturated soils with application to low-level radioactive waste disposal. Volume 2

International Nuclear Information System (INIS)

Binning, P.; Celia, M.A.; Johnson, J.C.

1995-05-01

A numerical model of multiphase air-water flow and contaminant transport in the unsaturated zone is presented. The multiphase flow equations are solved using the two-pressure, mixed form of the equations with a modified Picard linearization of the equations and a finite element spatial approximation. A volatile contaminant is assumed to be transported in either phase, or in both phases simultaneously. The contaminant partitions between phases with an equilibrium distribution given by Henry's Law or via kinetic mass transfer. The transport equations are solved using a Galerkin finite element method with reduced integration to lump the resultant matrices. The numerical model is applied to published experimental studies to examine the behavior of the air phase and associated contaminant movement under water infiltration. The model is also used to evaluate a hypothetical design for a low-level radioactive waste disposal facility. The model has been developed in both one and two dimensions; documentation and computer codes are available for the one-dimensional flow and transport model

Simulation of windblown dust transport from a mine tailings impoundment using a computational fluid dynamics model

Science.gov (United States)

Stovern, Michael; Felix, Omar; Csavina, Janae; Rine, Kyle P.; Russell, MacKenzie R.; Jones, Robert M.; King, Matt; Betterton, Eric A.; Sáez, A. Eduardo

2014-01-01

Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of dust and aerosol from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are heavily contaminated with lead and arsenic. Using a computational fluid dynamics model, we model dust transport from the mine tailings to the surrounding region. The model includes gaseous plume dispersion to simulate the transport of the fine aerosols, while individual particle transport is used to track the trajectories of larger particles and to monitor their deposition locations. In order to improve the accuracy of the dust transport simulations, both regional topographical features and local weather patterns have been incorporated into the model simulations. Results show that local topography and wind velocity profiles are the major factors that control deposition. PMID:25621085

Simulation of windblown dust transport from a mine tailings impoundment using a computational fluid dynamics model.

Science.gov (United States)

Stovern, Michael; Felix, Omar; Csavina, Janae; Rine, Kyle P; Russell, MacKenzie R; Jones, Robert M; King, Matt; Betterton, Eric A; Sáez, A Eduardo

2014-09-01

Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of dust and aerosol from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are heavily contaminated with lead and arsenic. Using a computational fluid dynamics model, we model dust transport from the mine tailings to the surrounding region. The model includes gaseous plume dispersion to simulate the transport of the fine aerosols, while individual particle transport is used to track the trajectories of larger particles and to monitor their deposition locations. In order to improve the accuracy of the dust transport simulations, both regional topographical features and local weather patterns have been incorporated into the model simulations. Results show that local topography and wind velocity profiles are the major factors that control deposition.

Modeling radiocesium transport from a river catchment based on a physically-based distributed hydrological and sediment erosion model.

Science.gov (United States)

Kinouchi, Tsuyoshi; Yoshimura, Kazuya; Omata, Teppei

2015-01-01

The accident at the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) in March 2011 resulted in the deposition of large quantities of radionuclides, such as (134)Cs and (137)Cs, over parts of eastern Japan. Since then high levels of radioactive contamination have been detected in large areas, including forests, agricultural land, and residential areas. Due to the strong adsorption capability of radiocesium to soil particles, radiocesium migrates with eroded sediments, follows the surface flow paths, and is delivered to more populated downstream regions and eventually to the Pacific Ocean. It is therefore important to understand the transport of contaminated sediments in the hydrological system and to predict changes in the spatial distribution of radiocesium concentrations by taking the land-surface processes related to sediment migration into consideration. In this study, we developed a distributed model to simulate the transport of water and contaminated sediment in a watershed hydrological system, and applied this model to a partially forested mountain catchment located in an area highly contaminated by the radioactive fallout. Observed discharge, sediment concentration, and cesium concentration measured from June 2011 until December 2012 were used for calibration of model parameters. The simulated discharge and sediment concentration both agreed well with observed values, while the cesium concentration was underestimated in the initial period following the accident. This result suggests that the leaching of radiocesium from the forest canopy, which was not considered in the model, played a significant role in its transport from the catchment. Based on the simulation results, we quantified the long-term fate of radiocesium over the study area and estimated that the effective half-life of (137)Cs deposited in the study area will be approximately 22 y due to the export of contaminated sediment by land-surface processes, and the amount of (137)Cs remaining in the

Analysis of contamination in liquids hydrocarbons transport for pipes

Directory of Open Access Journals (Sweden)

Eddy Ricardo Zárate Neira

2003-01-01

Full Text Available Pipeline contamination is usually understood to mean both the mixing effect produced when two different products transported by the same pipeline come into contact qith each other and often product of such mixing as well. This product os often referred to as "contamination" or as "interface" Cleary such intermixing is generally less serious in crude carrying, pipelines where each batch can become somewhat polluted by the batches inmediately preceding and immediately following without significant damage. However, the situation is different in a finished products pipeline, which may carry products as different as aircraft gasoline and light fuel oils. This article presents a brief description of the main factors influencing contamination with the objective of optimize conditions operating and to drive the more important respects about them.

Modeling multi-component transport and enhanced anaerobic dechlorination processes in a single fracture-clay matrix system

DEFF Research Database (Denmark)

Chambon, Julie Claire Claudia; Broholm, Mette Martina; Binning, Philip John

2010-01-01

Clayey tills contaminated with chlorinated solvents are a threat to groundwater and are difficult to remediate. A numerical model is developed for assessing leaching processes and for simulating the remediation via enhanced anaerobic dechlorination. The model simulates the transport...... to the physical processes, mainly diffusion in the matrix, than to the biogeochemical processes, when dechlorination is assumed to take place in a limited reaction zone only. The inclusion of sequential dechlorination in clay fracture transport models is crucial, as the contaminant flux to the aquifer...

GWSCREEN: A semi-analytical model for assessment of the groundwater pathway from surface or buried contamination: Version 2.0 theory and user`s manual

Energy Technology Data Exchange (ETDEWEB)

Rood, A.S.

1993-06-01

GWSCREEN was developed for assessment of the groundwater pathway from leaching of radioactive and non radioactive substances from surface or buried sources. The code was designed for implementation in the Track I and Track II assessment of CERCLA (Comprehensive Environmental Response, Compensation and Liability Act) sites identified as low probability hazard at the Idaho National Engineering Laboratory (DOE, 1992). The code calculates the limiting soil concentration such that, after leaching and transport to the aquifer, regulatory contaminant levels in groundwater are not exceeded. The code uses a mass conservation approach to model three processes: contaminant release from a source volume, contaminant transport in the unsaturated zone, and contaminant transport in the saturated zone. The source model considers the sorptive properties and solubility of the contaminant. Transport in the unsaturated zone is described by a plug flow model. Transport in the saturated zone is calculated with a semi-analytical solution to the advection dispersion equation in groundwater. In Version 2.0, GWSCREEN has incorporated an additional source model to calculate the impacts to groundwater resulting from the release to percolation ponds. In addition, transport of radioactive progeny has also been incorporated. GWSCREEN has shown comparable results when compared against other codes using similar algorithms and techniques. This code was designed for assessment and screening of the groundwater pathway when field data is limited. It was not intended to be a predictive tool.

Contaminant geochemistry. Interactions and transport in the subsurface environment

Energy Technology Data Exchange (ETDEWEB)

Berkowitz, Brian; Dror, Ishai; Yaron, Bruno [Weizmann Institute of Science, Rehovot (Israel). Dept. of Environmental Sciences and Energy Research

2008-07-01

This book combines earth science, subsurface hydrology and environmental geochemistry, providing a comprehensive background for specialists interested in the protection and sustainable management of the subsurface environment. The reader is introduced to the chemistry of contaminants, which usually disturb the natural equilibrium in the subsurface as a result of human activity. The major focus of the book is on contaminant reactions in soil solutions, groundwater and porous media solid phases, accounting for their persistence and transformation in the subsurface, as they are transported from the land surface into groundwater. Discussions on selected case studies are provided. (orig.)

BLT-EC (Breach, Leach and Transport-Equilibrium Chemistry) data input guide. A computer model for simulating release and coupled geochemical transport of contaminants from a subsurface disposal facility

International Nuclear Information System (INIS)

MacKinnon, R.J.; Sullivan, T.M.; Kinsey, R.R.

1997-05-01

The BLT-EC computer code has been developed, implemented, and tested. BLT-EC is a two-dimensional finite element computer code capable of simulating the time-dependent release and reactive transport of aqueous phase species in a subsurface soil system. BLT-EC contains models to simulate the processes (container degradation, waste-form performance, transport, chemical reactions, and radioactive production and decay) most relevant to estimating the release and transport of contaminants from a subsurface disposal system. Water flow is provided through tabular input or auxiliary files. Container degradation considers localized failure due to pitting corrosion and general failure due to uniform surface degradation processes. Waste-form performance considers release to be limited by one of four mechanisms: rinse with partitioning, diffusion, uniform surface degradation, and solubility. Transport considers the processes of advection, dispersion, diffusion, chemical reaction, radioactive production and decay, and sources (waste form releases). Chemical reactions accounted for include complexation, sorption, dissolution-precipitation, oxidation-reduction, and ion exchange. Radioactive production and decay in the waste form is simulated. To improve the usefulness of BLT-EC, a pre-processor, ECIN, which assists in the creation of chemistry input files, and a post-processor, BLTPLOT, which provides a visual display of the data have been developed. BLT-EC also includes an extensive database of thermodynamic data that is also accessible to ECIN. This document reviews the models implemented in BLT-EC and serves as a guide to creating input files and applying BLT-EC

A study on contaminant transport in indoor air

International Nuclear Information System (INIS)

Pujala, Usha; Sen, Soubhadra; Subramanian, V.; Srinivas, C.V.; Baskaran, R.; Venkatraman, B.

2016-01-01

In case of an accidental release of radioactive contaminant inside a well-ventilated room, the same will be transported to the different parts of the room due to the circulation of indoor air. To ensure safety of the operating personnel, it is important to identify the ideal locations for keeping the warning alarm systems. To address the problem, a detailed study is required where numerical simulation has to be supported by experimental verification. A computational methodology has already been verified for this purpose (IGC report-no.323). In this work, a study on the transport of an inert aerosol inside a well-ventilated isolated room has been carried out

A Generalized Model for Transport of Contaminants in Soil by Electric Fields

DEFF Research Database (Denmark)

Paz-Garcia, Juan Manuel; Baek, Kitae; Alshawabkeh, Iyad D.

2012-01-01

with geochemical reactions such as aqueous equilibrium, sorption, precipitation and dissolution. The enhanced model is used to simulate electrokinetic cleanup of lead and copper contaminants at an Army Firing Range. Acid enhancement is achieved by the use of adipic acid to neutralize the basic front produced...... for the cathode electrochemical reaction. The model is able to simulate enhanced application of the process by modifying the boundary conditions. The model showed that kinetics of geochemical reactions, such as metals dissolution/leaching and redox reactions might be significant for realistic prediction...... of enhanced electrokinetic extraction of metals in real world applications....

A chaotic-dynamical conceptual model to describe fluid flow and contaminant transport in a fractured vadose zone. 1997 progress report and presentations at the annual meeting, Ernest Orlando Lawrence Berkeley National Laboratory, December 3-4, 1997

International Nuclear Information System (INIS)

Faybishenko, B.; Doughty, C.; Geller, J.

1998-07-01

Understanding subsurface flow and transport processes is critical for effective assessment, decision-making, and remediation activities for contaminated sites. However, for fluid flow and contaminant transport through fractured vadose zones, traditional hydrogeological approaches are often found to be inadequate. In this project, the authors examine flow and transport through a fractured vadose zone as a deterministic chaotic dynamical process, and develop a model of it in these terms. Initially, the authors examine separately the geometric model of fractured rock and the flow dynamics model needed to describe chaotic behavior. Ultimately they will put the geometry and flow dynamics together to develop a chaotic-dynamical model of flow and transport in a fractured vadose zone. They investigate water flow and contaminant transport on several scales, ranging from small-scale laboratory experiments in fracture replicas and fractured cores, to field experiments conducted in a single exposed fracture at a basalt outcrop, and finally to a ponded infiltration test using a pond of 7 by 8 m. In the field experiments, they measure the time-variation of water flux, moisture content, and hydraulic head at various locations, as well as the total inflow rate to the subsurface. Such variations reflect the changes in the geometry and physics of water flow that display chaotic behavior, which they try to reconstruct using the data obtained. In the analysis of experimental data, a chaotic model can be used to predict the long-term bounds on fluid flow and transport behavior, known as the attractor of the system, and to examine the limits of short-term predictability within these bounds. This approach is especially well suited to the need for short-term predictions to support remediation decisions and long-term bounding studies. View-graphs from ten presentations made at the annual meeting held December 3--4, 1997 are included in an appendix to this report

Simulations of Ground-Water Flow, Transport, Age, and Particle Tracking near York, Nebraska, for a Study of Transport of Anthropogenic and Natural Contaminants (TANC) to Public-Supply Wells

Science.gov (United States)

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

Mathematical modeling of solute transport in the subsurface

International Nuclear Information System (INIS)

Naymik, T.G.

1987-01-01

A review of key works on solute transport models indicates that solute transport processes with the exception of advection are still poorly understood. Solute transport models generally do a good job when they are used to test scientific concepts and hypotheses, investigate natural processes, systematically store and manage data, and simulate mass balance of solutes under certain natural conditions. Solute transport models generally are not good for predicting future conditions with a high degree of certainty, or for determining concentrations precisely. The mathematical treatment of solute transport far surpasses their understanding of the process. Investigations of the extent of groundwater contamination and methods to remedy existing problems show the along-term nature of the hazard. Industrial organic compounds may be immiscible in water, highly volatile, or complexed with inorganic as well as other organic compounds; many remain stable in nature almost indefinitely. In the worst case, future disposal of hazardous waste may be restricted to deep burial, as is proposed for radioactive wastes. For investigations pertinent to transport of radionuclides from a geologic repository, the process cannot be fully understood without adequate thermodynamic and kinetic data bases

Monitoring Potential Transport of Radioactive Contaminants in Shallow Ephemeral Channels

International Nuclear Information System (INIS)

Miller Julianne J.; Mizell Steve A.; Nikolich George; Campbell Scott A.

2012-01-01

The U.S. Department of Energy (DOE) National Nuclear Security Administration (NNSA), Nevada Site Office (NSO), Environmental Restoration Soils Activity has authorized the Desert Research Institute (DRI) to conduct field assessments of potential sediment transport of contaminated soil from Corrective Action Unit (CAU) 550, Area 8 Smoky Contamination Area (CA), during precipitation runoff events. CAU 550 includes Corrective Action Sites (CASs) 08-23-03, 08-23-04, 08-23-06, and 08-23-07; these CASs are associated with tests designated Ceres, Smoky, Oberon, and Titania, respectively.

Organic contaminant transport and fate in the subsurface: evolution of knowledge and understanding

Science.gov (United States)

Essaid, Hedeff I.; Bekins, Barbara A.; Cozzarelli, Isabelle M.

2015-01-01

Toxic organic contaminants may enter the subsurface as slightly soluble and volatile nonaqueous phase liquids (NAPLs) or as dissolved solutes resulting in contaminant plumes emanating from the source zone. A large body of research published in Water Resources Research has been devoted to characterizing and understanding processes controlling the transport and fate of these organic contaminants and the effectiveness of natural attenuation, bioremediation, and other remedial technologies. These contributions include studies of NAPL flow, entrapment, and interphase mass transfer that have advanced from the analysis of simple systems with uniform properties and equilibrium contaminant phase partitioning to complex systems with pore-scale and macroscale heterogeneity and rate-limited interphase mass transfer. Understanding of the fate of dissolved organic plumes has advanced from when biodegradation was thought to require oxygen to recognition of the importance of anaerobic biodegradation, multiple redox zones, microbial enzyme kinetics, and mixing of organic contaminants and electron acceptors at plume fringes. Challenges remain in understanding the impacts of physical, chemical, biological, and hydrogeological heterogeneity, pore-scale interactions, and mixing on the fate of organic contaminants. Further effort is needed to successfully incorporate these processes into field-scale predictions of transport and fate. Regulations have greatly reduced the frequency of new point-source contamination problems; however, remediation at many legacy plumes remains challenging. A number of fields of current relevance are benefiting from research advances from point-source contaminant research. These include geologic carbon sequestration, nonpoint-source contamination, aquifer storage and recovery, the fate of contaminants from oil and gas development, and enhanced bioremediation.

Characterization of calculation of in-situ retardation factors of contaminant transport using naturally-radionuclides and rock/water interaction occurring U-Series disequilibria timescales. 1997 annual progress report

International Nuclear Information System (INIS)

Goldstein, S.; Ku, T.L.; Luo, S.; Murrel, M.; Roback, R.

1997-01-01

'The research is directed toward a quantitative assessment of contaminant transport rates in fracture-rock systems using uranium-series radionuclides. Naturally occurring uranium-and thorium-series radioactive disequilibria will provide information on the rates of adsorption-desorption and transport of radioactive contaminants as well as on fluid transport and rock dissolution in a natural setting. This study will also provide an improved characterization of preferential flow and contaminant transport at the Idaho Environmental and Engineering Lab. (INEEL) site. To a lesser extent, the study will include rocks in the unsaturated zone. The authors will produce a realistic model of radionuclide migration under unsaturated and saturated field conditions at the INEEL site, taking into account the retardation processes involved in the rock/water interaction. The major tasks are to (1) determine the natural distribution of U, Th, Pa and Ra isotopes in rock minerals. sorbed phases on the rocks, and in fluids from both saturated and unsaturated zones at the site, and (2) study rock/water interaction processes using U/Th series disequilibrium and a statistical analysis-based model for the Geologic heterogeneity plays an important role in transporting contaminants in fractured rocks. Preferential flow paths in the fractured rocks act as a major pathway for transport of radioactive contaminants in groundwaters. The weathering/dissolution of rock by groundwater also influences contaminant mobility. Thus, it is important to understand the hydrogeologic features of the site and their impact on the migration of radioactive contaminants. In this regard, quantification of the rock weathering/dissolution rate and fluid residence time from the observed decay-series disequilibria will be valuable. By mapping the spatial distribution of the residence time of groundwater in fractured rocks, the subsurface preferential flow paths (with high rock permeability and short fluid residence

Modeling and preliminary assessment of crude oil contaminated soil in Ogoni (Nigeria)

Energy Technology Data Exchange (ETDEWEB)

Thiergaertner, Hannes [Free Univ. Berlin (Germany). Faculty of Geosciences; Holtzmann, Kay

2014-07-01

In 2010, a severe contamination of soil and groundwater caused by the production and transportation of crude oil were detected in the Ogoni area, Federal Republic of Nigeria. A linear correlation between aliphatics and aromatics and the missing link between the degree of contamination and the depth of the soil samples indicate incomplete earlier remediation activities. 665 analyzed samples were mathematically reduced to 28 contamination patterns that can be distinguished by type and degree of pollution, environmentally assessed and visualized by a quasi 3-D model. Case studies taken from the Local Government Areas Eleme, Gokana, Khana, and Tai show the methodology and results.

Deterministic sensitivity analysis for the numerical simulation of contaminants transport

International Nuclear Information System (INIS)

Marchand, E.

2007-12-01

The questions of safety and uncertainty are central to feasibility studies for an underground nuclear waste storage site, in particular the evaluation of uncertainties about safety indicators which are due to uncertainties concerning properties of the subsoil or of the contaminants. The global approach through probabilistic Monte Carlo methods gives good results, but it requires a large number of simulations. The deterministic method investigated here is complementary. Based on the Singular Value Decomposition of the derivative of the model, it gives only local information, but it is much less demanding in computing time. The flow model follows Darcy's law and the transport of radionuclides around the storage site follows a linear convection-diffusion equation. Manual and automatic differentiation are compared for these models using direct and adjoint modes. A comparative study of both probabilistic and deterministic approaches for the sensitivity analysis of fluxes of contaminants through outlet channels with respect to variations of input parameters is carried out with realistic data provided by ANDRA. Generic tools for sensitivity analysis and code coupling are developed in the Caml language. The user of these generic platforms has only to provide the specific part of the application in any language of his choice. We also present a study about two-phase air/water partially saturated flows in hydrogeology concerning the limitations of the Richards approximation and of the global pressure formulation used in petroleum engineering. (author)

Characterization of contaminant transport by gravity, capilliarity and barometric pumping in heterogeneous vadose regimes. 1997 annual progress report

International Nuclear Information System (INIS)

Carrigan, C.R.

1997-01-01

'Vadose regimes can be the sites of complex interactions between the atmosphere and groundwater. When a volatile contaminant exists as free product or in dissolved form in the vadose environment, upward transport can occur with the contaminant ultimately being vented as a vapor into the atmosphere. This transport happens naturally and can be enhanced by anisotropy resulting from heterogenities in the vadose regime. Several stages in the transport process are involved in going from a volatile, liquid state contaminant to a contaminant vapor vented at the surface. In a three-year effort, called the Vadose Zone Transport Study, the authors are investigating, with the aid of existing data, new field studies involving dissolved tracer gases and 3-D diagnostic computer simulations that provide a framework to interpret the observations, the detailed nature of each of these stages of transport in several different kinds of vadose regimes. They are emphasizing the impact of features specific to a site, that is, the local geology and hydrology, on each stage of the transport process. In particular they want to better understand how the time scales for (1) partitioning contaminants from the liquid to the vapor states and then (2) transporting the vapor out of the vadose regime are dependent on the specific character of a site. Such time-scale information will be important for evaluating the potential of contaminant sources as well as remediation strategies including natural remediation approaches.'

Heterogeneity and contaminant transport modeling for the Savannah River integrated demonstration site

International Nuclear Information System (INIS)

Chesnut, D.A.

1992-11-01

The effectiveness of remediating aquifers and vadose zone sediments is frequently controlled by spatial heterogeneities. A continuing and long-recognized problem in selecting, planning, implementing, and operating remediation projects is the development of methods for quantitatively describing heterogeneity and predicting its effects on process performance. The similarity to and differences from modeling oil recovery processes in the petroleum industry are illustrated by the extension to contaminant extraction processes of an analytic model originally developed for waterflooding petroleum reservoirs. The resulting equations incorporate the effects of heterogeneity through a single parameter, σ. Fitting this model to the Savannah River in situ Air Stripping test data suggests that the injection of air into a horizontal well below the water table may have improved performance by changing the flow pattern in the vadose zone. This change increased the capture volume, and consequently the contaminant mass inventory, of the horizontal injection well completed in the vadose zone. The apparent increases (compared to extraction only from the horizontal well) are from 10,200 to 21,000 pounds for TCE and from 3,600 pounds to 59,800 pounds for PCE. The predominance of PCE in this calculated increase suggests that redistribution of flow paths in the vadose zone, rather than in-situ stripping, may provide most of the improvement. Although this preliminary conclusion remains to be reinforced by more sophisticated modeling currently in progress, there appears to be a definite improvement, which is attributable to air injection, over conventional remediation methods

Multiple-tracer tests for contaminant transport process identification in saturated municipal solid waste

International Nuclear Information System (INIS)

Woodman, N.D.; Rees-White, T.C.; Stringfellow, A.M.; Beaven, R.P.; Hudson, A.P.

2015-01-01

Highlights: • Multiple tracers were applied to saturated MSW to test dual-porosity properties. • Lithium demonstrated to be non-conservative as a tracer. • 260 mm diameter column too small to test transport properties of MSW. • The classical advection-dispersion mode was rejected due to high dispersivity. • Characteristic diffusion times did not vary with the tracer. - Abstract: Two column tests were performed in conditions emulating vertical flow beneath the leachate table in a biologically active landfill to determine dominant transport mechanisms occurring in landfills. An improved understanding of contaminant transport process in wastes is required for developing better predictions about potential length of the long term aftercare of landfills, currently measured in timescales of centuries. Three tracers (lithium, bromide and deuterium) were used. Lithium did not behave conservatively. Given that lithium has been used extensively for tracing in landfill wastes, the tracer itself and the findings of previous tests which assume that it has behaved conservatively may need revisiting. The smaller column test could not be fitted with continuum models, probably because the volume of waste was below a representative elemental volume. Modelling compared advection-dispersion (AD), dual porosity (DP) and hybrid AD–DP models. Of these models, the DP model was found to be the most suitable. Although there is good evidence to suggest that diffusion is an important transport mechanism, the breakthrough curves of the different tracers did not differ from each other as would be predicted based on the free-water diffusion coefficients. This suggested that solute diffusion in wastes requires further study

Multiple-tracer tests for contaminant transport process identification in saturated municipal solid waste

Energy Technology Data Exchange (ETDEWEB)

Woodman, N.D., E-mail: n.d.woodman@soton.ac.uk; Rees-White, T.C.; Stringfellow, A.M.; Beaven, R.P.; Hudson, A.P.

2015-04-15

Highlights: • Multiple tracers were applied to saturated MSW to test dual-porosity properties. • Lithium demonstrated to be non-conservative as a tracer. • 260 mm diameter column too small to test transport properties of MSW. • The classical advection-dispersion mode was rejected due to high dispersivity. • Characteristic diffusion times did not vary with the tracer. - Abstract: Two column tests were performed in conditions emulating vertical flow beneath the leachate table in a biologically active landfill to determine dominant transport mechanisms occurring in landfills. An improved understanding of contaminant transport process in wastes is required for developing better predictions about potential length of the long term aftercare of landfills, currently measured in timescales of centuries. Three tracers (lithium, bromide and deuterium) were used. Lithium did not behave conservatively. Given that lithium has been used extensively for tracing in landfill wastes, the tracer itself and the findings of previous tests which assume that it has behaved conservatively may need revisiting. The smaller column test could not be fitted with continuum models, probably because the volume of waste was below a representative elemental volume. Modelling compared advection-dispersion (AD), dual porosity (DP) and hybrid AD–DP models. Of these models, the DP model was found to be the most suitable. Although there is good evidence to suggest that diffusion is an important transport mechanism, the breakthrough curves of the different tracers did not differ from each other as would be predicted based on the free-water diffusion coefficients. This suggested that solute diffusion in wastes requires further study.

Experimental and modelling studies of radionuclide migration from contaminated groundwaters

International Nuclear Information System (INIS)

Tompkins, J. A.; Butler, A. P.; Wheater, H. S.; Shaw, G.; Wadey, P.; Bell, J. N. B.

1994-01-01

Lysimeter-based studies of radionuclide uptake by winter wheat are being undertaken to investigate soil-to-plant transfer processes. A five year multi-disciplinary research project has concentrated on the upward migration of contaminants from near surface water-tables and their subsequent uptake by a winter wheat crop. A weighted transfer factor approach and a physically based modelling methodology, for the simulation and prediction of radionuclide uptake, have been developed which offer alternatives to the traditional transfer factor approach. Integrated hydrological and solute transport models are used to simulate contaminant movement and subsequent root uptake. This approach enables prediction of radionuclide transport for a wide range of soil, plant and radionuclide types. This paper presents simulated results of 22 Na plant uptake and soil activity profiles, which are verified with respect to lysimeter data. The results demonstrate that a simple modelling approach can describe the variability in radioactivity in both the harvested crop and the soil profile, without recourse to a large number of empirical parameters. The proposed modelling technique should be readily applicable to a range of scales and conditions, since it embodies an understanding of the underlying physical processes of the system. This work constitutes part of an ongoing research programme being undertaken by UK Nirex Ltd., to assess the long term safety of a deep level repository for low and intermediate level nuclear waste. (author)

How historical copper contamination affects soil structure and mobilization and transport of colloids

DEFF Research Database (Denmark)

Paradelo, Marcos; Møldrup, Per; Holmstrup, Martin

between 0.01 to 0.43 pore volumes, with longer times for the most contaminated point, likely related with its higher soil density and lower air permeability. The copper pollution affected colloid and tracer transport in the soil columns. The release of colloids especially in the most contaminated points...

Three-dimensional analysis of future groundwater flow conditions and contaminant plume transport in the Hanford Site unconfined aquifer system: FY 1996 and 1997 status report

Energy Technology Data Exchange (ETDEWEB)

Cole, C.R.; Wurstner, S.K.; Williams, M.D.; Thorne, P.D.; Bergeron, M.P.

1997-12-01

A three-dimensional numerical model of groundwater flow and transport, based on the Coupled Fluid Energy, and Solute Transport (CFEST) code, was developed for the Hanford Site to support the Hanford Groundwater Project (HGWP), managed by Pacific Northwest National Laboratory. The model was developed to increase the understanding and better forecast the migration of several contaminant plumes being monitored by the HGWP, and to support the Hanford Site Composite Analysis for low-level waste disposal in the 200-Area Plateau. Recent modeling efforts have focused on continued refinement of an initial version of the three-dimensional model developed in 1995 and its application to simulate future transport of selected contaminant plumes in the aquifer system. This version of the model was updated using a more current version of the CFEST code called CFEST96. Prior to conducting simulations of contaminant transport with the three-dimensional model, a previous steady-state, two-dimensional model of the unconfined aquifer system was recalibrated to 1979 water-table conditions with a statistical inverse method implemented in the CFEST-INV computer code. The results of the recalibration were used to refine the three-dimensional conceptual model and to calibrate it with a conceptualization that preserves the two-dimensional hydraulic properties and knowledge of the aquifer`s three-dimensional properties for the same 1979 water-table conditions. The transient behavior of the three-dimensional flow model was also calibrated by adjusting model storage properties (specific yield) until transient water-table predictions approximated observed water-table elevations between 1979 and 1996.

Three-dimensional analysis of future groundwater flow conditions and contaminant plume transport in the Hanford Site unconfined aquifer system: FY 1996 and 1997 status report

International Nuclear Information System (INIS)

Cole, C.R.; Wurstner, S.K.; Williams, M.D.; Thorne, P.D.; Bergeron, M.P.

1997-12-01

A three-dimensional numerical model of groundwater flow and transport, based on the Coupled Fluid Energy, and Solute Transport (CFEST) code, was developed for the Hanford Site to support the Hanford Groundwater Project (HGWP), managed by Pacific Northwest National Laboratory. The model was developed to increase the understanding and better forecast the migration of several contaminant plumes being monitored by the HGWP, and to support the Hanford Site Composite Analysis for low-level waste disposal in the 200-Area Plateau. Recent modeling efforts have focused on continued refinement of an initial version of the three-dimensional model developed in 1995 and its application to simulate future transport of selected contaminant plumes in the aquifer system. This version of the model was updated using a more current version of the CFEST code called CFEST96. Prior to conducting simulations of contaminant transport with the three-dimensional model, a previous steady-state, two-dimensional model of the unconfined aquifer system was recalibrated to 1979 water-table conditions with a statistical inverse method implemented in the CFEST-INV computer code. The results of the recalibration were used to refine the three-dimensional conceptual model and to calibrate it with a conceptualization that preserves the two-dimensional hydraulic properties and knowledge of the aquifer's three-dimensional properties for the same 1979 water-table conditions. The transient behavior of the three-dimensional flow model was also calibrated by adjusting model storage properties (specific yield) until transient water-table predictions approximated observed water-table elevations between 1979 and 1996

Groundwater Flow and Transport Model in Cecina Plain (Tuscany, Italy) using GIS processing

OpenAIRE

Riccardo Armellini; Elena Baldini; Dario Del Seppia; Fabrizio Franceschini; Natacha Gori; Stefano Menichetti; Stefano Tessitore

2015-01-01

This work provides a groundwater flow and transport model of trichlorethylene and tetrachlorethylene contamination in the Cecina’s coastal aquifer. The contamination analysis, with source located in the Poggio Gagliardo area (Montescudaio, Pisa), was necessary to optimize the groundwater monitoring and remediation design. The work was carried out in two phases: • design of a conceptual model of the aquifer using GIS analysis of many stratigraphic, chemical and hydrogeological data, collected ...

A Bayesian belief network approach for assessing uncertainty in conceptual site models at contaminated sites

Science.gov (United States)

Thomsen, Nanna I.; Binning, Philip J.; McKnight, Ursula S.; Tuxen, Nina; Bjerg, Poul L.; Troldborg, Mads

2016-05-01

A key component in risk assessment of contaminated sites is in the formulation of a conceptual site model (CSM). A CSM is a simplified representation of reality and forms the basis for the mathematical modeling of contaminant fate and transport at the site. The CSM should therefore identify the most important site-specific features and processes that may affect the contaminant transport behavior at the site. However, the development of a CSM will always be associated with uncertainties due to limited data and lack of understanding of the site conditions. CSM uncertainty is often found to be a major source of model error and it should therefore be accounted for when evaluating uncertainties in risk assessments. We present a Bayesian belief network (BBN) approach for constructing CSMs and assessing their uncertainty at contaminated sites. BBNs are graphical probabilistic models that are effective for integrating quantitative and qualitative information, and thus can strengthen decisions when empirical data are lacking. The proposed BBN approach facilitates a systematic construction of multiple CSMs, and then determines the belief in each CSM using a variety of data types and/or expert opinion at different knowledge levels. The developed BBNs combine data from desktop studies and initial site investigations with expert opinion to assess which of the CSMs are more likely to reflect the actual site conditions. The method is demonstrated on a Danish field site, contaminated with chlorinated ethenes. Four different CSMs are developed by combining two contaminant source zone interpretations (presence or absence of a separate phase contamination) and two geological interpretations (fractured or unfractured clay till). The beliefs in each of the CSMs are assessed sequentially based on data from three investigation stages (a screening investigation, a more detailed investigation, and an expert consultation) to demonstrate that the belief can be updated as more information

Modeling of 1-D nitrate transport in single layer soils | Dike | Journal ...

African Journals Online (AJOL)

The transport of nitrate in laboratory single soil columns of sand, laterite and clay were investigated after 21 days. The 1-D contaminant transport model by Notodarmojo et al (1991) for single layer soils were calibrated and verified using field data collected from a refuse dump site at avu, owerri, Imo state. The experimental ...

Mechanisms of hydrologic transport of soil contaminants in Mortandad Canyon

International Nuclear Information System (INIS)

Hakonson, T.E.; White, G.C.

1981-01-01

The initial focus of this research will be on the selective sorting and transport of soil particles as they relate to altering the distribution of contaminants in soils and sediments. Several field experiments employing radionuclide-labeled soil particle size fractions are planned to accomplish research objectives

Neural Networks Simulation of the Transport of Contaminants in Groundwater

Directory of Open Access Journals (Sweden)

Enrico Zio

2009-12-01

Full Text Available The performance assessment of an engineered solution for the disposal of radioactive wastes is based on mathematical models of the disposal system response to predefined accidental scenarios, within a probabilistic approach to account for the involved uncertainties. As the most significant potential pathway for the return of radionuclides to the biosphere is groundwater flow, intensive computational efforts are devoted to simulating the behaviour of the groundwater system surrounding the waste deposit, for different values of its hydrogeological parameters and for different evolution scenarios. In this paper, multilayered neural networks are trained to simulate the transport of contaminants in monodimensional and bidimensional aquifers. The results obtained in two case studies indicate that the approximation errors are within the uncertainties which characterize the input data.

Model Intercomparison Study to Investigate a Dense Contaminant Plume in a Complex Hydrogeologic System

International Nuclear Information System (INIS)

Williams, Mark D.; Cole, Charles R.; Foley, Michael G.; Zinina, Galina A.; Zinin, Alexander I.; Vasil'Kova, Nelly A.; Samsonova, Lilia M.

2001-01-01

A joint Russian and U.S. model intercomparison study was undertaken for developing more realistic contaminant transport models of the Mayak Site, Southern Urals. The test problems were developed by the Russian Team based on their experience modeling contaminant migration near Lake Karachai. The intercomparison problems were designed to address lake and contaminant plume interactions, as well as river interactions and plume density effects. Different numerical codes were used. Overall there is good agreement between the results of both models. Features shown by both models include (1) the sinking of the plume below the lake, (2) the raising of the water table in the fresh water adjacent to the lake in response to the increased pressure from the dense plume, and (3) the formation of a second sinking plume in an area where evapotranspiration exceeded infiltration, thus increasing the solute concentrations above the source (i.e., lake) values

Developing an integrated 3D-hydrodynamic and emerging contaminant model for assessing water quality in a Yangtze Estuary Reservoir.

Science.gov (United States)

Xu, Cong; Zhang, Jingjie; Bi, Xiaowei; Xu, Zheng; He, Yiliang; Gin, Karina Yew-Hoong

2017-12-01

An integrated 3D-hydrodynamic and emerging contaminant model was developed for better understanding of the fate and transport of emerging contaminants in Qingcaosha Reservoir. The reservoir, which supplies drinking water for nearly half of Shanghai's population, is located in Yangtze Delta. The integrated model was built by Delft3D suite, a fully integrated multidimensional modeling software. Atrazine and Bisphenol A (BPA) were selected as two representative emerging contaminants for the study in this reservoir. The hydrodynamic model was calibrated and validated against observations from 2011 to 2015 while the integrated model was calibrated against observations from 2014 to 2015 and then applied to explore the potential risk of high atrazine concentrations in the reservoir driven by agriculture activities. Our results show that the model is capable of describing the spatial and temporal patterns of water temperature, salinity and the dynamic distributions of two representative emerging contaminants (i.e. atrazine and BPA) in the reservoir. The physical and biodegradation processes in this study were found to play a crucial role in determining the fate and transport of atrazine and BPA in the reservoir. The model also provides an insight into the potential risk of emerging contaminants and possible mitigation thresholds. The integrated approach can be a very useful tool to support policy-makers in the future management of Qingcaosha Reservoir. Copyright © 2017 Elsevier Ltd. All rights reserved.

Testing of a benchscale Reverse Osmosis/Coupled Transport system for treating contaminated groundwater

International Nuclear Information System (INIS)

Hodgson, K.M.; Lunsford, T.R.; Panjabi, G.

1994-01-01

The Reverse Osmosis/Coupled Transport process is a innovative means of removing radionuclides from contaminated groundwater at the Hanford Site. Specifically, groundwater in the 200 West Area of the Hanford Site has been contaminated with uranium, technetium, and nitrate. Investigations are proceeding to determine the most cost effective method to remove these contaminants. The process described in this paper combines three different membrane technologies (reverse osmosis, coupled transport, and nanofiltration to purify the groundwater while extracting and concentrating uranium, technetium, and nitrate into separate solutions. This separation allows for the future use of the radionuclides, if needed, and reduces the amount of waste that will need to be disposed of. This process has the potential to concentrate the contaminants into solutions with volumes in a ratio of 1/10,000 of the feed volume. This compares to traditional volume reductions of 10 to 100 for ion exchange and stand-alone reverse osmosis. The successful demonstration of this technology could result in significant savings in the overall cost of decontaminating the groundwater

Contaminant transport in soils and its significance in the design of waste management facilities

International Nuclear Information System (INIS)

Barbour, S.L.; Krahn, J.

1984-01-01

Transport of contaminants in soils is governed by advection, dispersion, geochemical mass transfer and decay in the case of radioactive materials. Advection is the process whereby the contaminant is being carried along by moving water. Dispersion arises from mechanical mixing due to velocity distributions between soil particles and molecular diffusion. Geochemical mass transfer retards the migration because of adsorption and/or precipitation. Decay results in a decrease of contaminant concentrations for radioactive materials. Studies on the effectiveness of a cutoff wall in granular soils beneath a tailings dyke show that the most important parameter is the groundwater flow velocity. It not only controls the advective transport but also directly affects the dispersive component and the attenuation that may be obtained through adsorption and decay

Packaging, Transportation, and Disposal Logistics for Large Radioactively Contaminated Reactor Decommissioning Components

International Nuclear Information System (INIS)

Lewis, Mark S.

2008-01-01

The packaging, transportation and disposal of large, retired reactor components from operating or decommissioning nuclear plants pose unique challenges from a technical as well as regulatory compliance standpoint. In addition to the routine considerations associated with any radioactive waste disposition activity, such as characterization, ALARA, and manifesting, the technical challenges for large radioactively contaminated components, such as access, segmentation, removal, packaging, rigging, lifting, mode of transportation, conveyance compatibility, and load securing require significant planning and execution. In addition, the current regulatory framework, domestically in Titles 49 and 10 and internationally in TS-R-1, does not lend itself to the transport of these large radioactively contaminated components, such as reactor vessels, steam generators, reactor pressure vessel heads, and pressurizers, without application for a special permit or arrangement. This paper addresses the methods of overcoming the technical and regulatory challenges. The challenges and disposition decisions do differ during decommissioning versus component replacement during an outage at an operating plant. During decommissioning, there is less concern about critical path for restart and more concern about volume reduction and waste minimization. Segmentation on-site is an available option during decommissioning, since labor and equipment will be readily available and decontamination activities are routine. The reactor building removal path is also of less concern and there are more rigging/lifting options available. Radionuclide assessment is necessary for transportation and disposal characterization. Characterization will dictate the packaging methodology, transportation mode, need for intermediate processing, and the disposal location or availability. Characterization will also assist in determining if the large component can be transported in full compliance with the transportation

Contaminant transport in the sub-surface soil of an uncontrolled landfill site in China: site investigation and two-dimensional numerical analysis.

Science.gov (United States)

Xie, Haijian; Chen, Yunmin; Thomas, Hywel R; Sedighi, Majid; Masum, Shakil A; Ran, Qihua

2016-02-01

A field investigation of contaminant transport beneath and around an uncontrolled landfill site in Huainan in China is presented in this paper. The research aimed at studying the migration of some chemicals present in the landfill leachate into the surrounding clayey soils after 17 years of landfill operation. The concentrations of chloride and sodium ions in the pore water of soil samples collected at depths up to 15 m were obtained through an extensive site investigation. The contents of organic matter in the soil samples were also determined. A two-dimensional numerical study of the reactive transport of sodium and chloride ion in the soil strata beneath and outside the landfill is also presented. The numerical modelling approach adopted is based on finite element/finite difference techniques. The domain size of approximately 300 × 30 m has been analysed and major chemical transport parameters/mechanisms are established via a series of calibration exercises. Numerical simulations were then performed to predict the long-term behaviour of the landfill in relation to the chemicals studied. The lateral migration distance of the chloride ions was more than 40 m which indicates that the advection and mechanical dispersion are the dominant mechanism controlling the contaminant transport at this site. The results obtained from the analysis of chloride and sodium migration also indicated a non-uniform advective flow regime of ions with depth, which were localised in the first few metres of the soil beneath the disposal site. The results of long-term simulations of contaminant transport indicated that the concentrations of ions can be 10 to 30 times larger than that related to the allowable limit of concentration values. The results of this study may be of application and interest in the assessment of potential groundwater and soil contamination at this site with a late Pleistocene clayey soil. The obtained transport properties of the soils and the contaminant transport

Reactive dispersive contaminant transport in coastal aquifers: Numerical simulation of a reactive Henry problem

KAUST Repository

Nick, H.M.

2013-02-01

The reactive mixing between seawater and terrestrial water in coastal aquifers influences the water quality of submarine groundwater discharge. While these waters come into contact at the seawater groundwater interface by density driven flow, their chemical components dilute and react through dispersion. A larger interface and wider mixing zone may provide favorable conditions for the natural attenuation of contaminant plumes. It has been claimed that the extent of this mixing is controlled by both, porous media properties and flow conditions. In this study, the interplay between dispersion and reactive processes in coastal aquifers is investigated by means of numerical experiments. Particularly, the impact of dispersion coefficients, the velocity field induced by density driven flow and chemical component reactivities on reactive transport in such aquifers is studied. To do this, a hybrid finite-element finite-volume method and a reactive simulator are coupled, and model accuracy and applicability are assessed. A simple redox reaction is considered to describe the degradation of a contaminant which requires mixing of the contaminated groundwater and the seawater containing the terminal electron acceptor. The resulting degradation is observed for different scenarios considering different magnitudes of dispersion and chemical reactivity. Three reactive transport regimes are found: reaction controlled, reaction-dispersion controlled and dispersion controlled. Computational results suggest that the chemical components\\' reactivity as well as dispersion coefficients play a significant role on controlling reactive mixing zones and extent of contaminant removal in coastal aquifers. Further, our results confirm that the dilution index is a better alternative to the second central spatial moment of a plume to describe the mixing of reactive solutes in coastal aquifers. © 2012 Elsevier B.V.

Simulation of reactive geochemical transport in groundwater using a semi-analytical screening model

Science.gov (United States)

McNab, Walt W.

1997-10-01

A reactive geochemical transport model, based on a semi-analytical solution to the advective-dispersive transport equation in two dimensions, is developed as a screening tool for evaluating the impact of reactive contaminants on aquifer hydrogeochemistry. Because the model utilizes an analytical solution to the transport equation, it is less computationally intensive than models based on numerical transport schemes, is faster, and it is not subject to numerical dispersion effects. Although the assumptions used to construct the model preclude consideration of reactions between the aqueous and solid phases, thermodynamic mineral saturation indices are calculated to provide qualitative insight into such reactions. Test problems involving acid mine drainage and hydrocarbon biodegradation signatures illustrate the utility of the model in simulating essential hydrogeochemical phenomena.

Theoretical and Numerical Modeling of Transport of Land Use-Specific Fecal Source Identifiers

Science.gov (United States)

Bombardelli, F. A.; Sirikanchana, K. J.; Bae, S.; Wuertz, S.

2008-12-01

Microbial contamination in coastal and estuarine waters is of particular concern to public health officials. In this work, we advocate that well-formulated and developed mathematical and numerical transport models can be combined with modern molecular techniques in order to predict continuous concentrations of microbial indicators under diverse scenarios of interest, and that they can help in source identification of fecal pollution. As a proof of concept, we present initially the theory, numerical implementation and validation of one- and two-dimensional numerical models aimed at computing the distribution of fecal source identifiers in water bodies (based on Bacteroidales marker DNA sequences) coming from different land uses such as wildlife, livestock, humans, dogs or cats. These models have been developed to allow for source identification of fecal contamination in large bodies of water. We test the model predictions using diverse velocity fields and boundary conditions. Then, we present some preliminary results of an application of a three-dimensional water quality model to address the source of fecal contamination in the San Pablo Bay (SPB), United States, which constitutes an important sub-embayment of the San Francisco Bay. The transport equations for Bacteroidales include the processes of advection, diffusion, and decay of Bacteroidales. We discuss the validation of the developed models through comparisons of numerical results with field campaigns developed in the SPB. We determine the extent and importance of the contamination in the bay for two decay rates obtained from field observations, corresponding to total host-specific Bacteroidales DNA and host-specific viable Bacteroidales cells, respectively. Finally, we infer transport conditions in the SPB based on the numerical results, characterizing the fate of outflows coming from the Napa, Petaluma and Sonoma rivers.

Assessment of the Forward Contamination Risk of Mars by Clean Room Isolates from Space-Craft Assembly Facilities through Aeolian Transport - a Model Study

Science.gov (United States)

van Heereveld, Luc; Merrison, Jonathan; Nørnberg, Per; Finster, Kai

2017-06-01

The increasing number of missions to Mars also increases the risk of forward contamination. Consequently there is a need for effective protocols to ensure efficient protection of the Martian environment against terrestrial microbiota. Despite the fact of constructing sophisticated clean rooms for spacecraft assembly a 100 % avoidance of contamination appears to be impossible. Recent surveys of these facilities have identified a significant number of microbes belonging to a variety of taxonomic groups that survive the harsh conditions of clean rooms. These microbes may have a strong contamination potential, which needs to be investigate to apply efficient decontamination treatments. In this study we propose a series of tests to evaluate the potential of clean room contaminants to survive the different steps involved in forward contamination. We used Staphylococcus xylosus as model organism to illustrate the different types of stress that potential contaminants will be subjected to on their way from the spacecraft onto the surface of Mars. Staphylococcus xylosus is associated with human skin and commonly found in clean rooms and could therefore contaminate the spacecraft as a result of human activity during the assembling process. The path the cell will take from the surface of the spacecraft onto the surface of Mars was split into steps representing different stresses that include desiccation, freezing, aeolian transport in a Martian-like atmosphere at Martian atmospheric pressure, and UV radiation climate. We assessed the surviving fraction of the cellular population after each step by determining the integrated metabolic activity of the survivor population by measuring their oxygen consumption rate. The largest fraction of the starting culture (around 70 %) was killed during desiccation, while freezing, Martian vacuum and short-term UV radiation only had a minor additional effect on the survivability of Staphylococcus xylosus. The study also included a simulation

Packaging and transportation of radioactively contaminated lead

International Nuclear Information System (INIS)

Gleason, Eugene; Holden, Gerard

2007-01-01

Under the management of the Nuclear Decommissioning Authority (NDA) the government of the United Kingdom has launched an ambitious program to remediate the nation's nuclear waste legacy. Over a twenty-five year period NDA plans to decommission several first generation nuclear power plants and other radioactive facilities. The use innovative, safe 'fit for purpose' technologies will be a major part of this complex program. This paper will present a case study of a recently completed project undertaken in support of the nuclear decommissioning activities at the Sellafield site in the United Kingdom. The focus is on an innovative application of new packaging technology developed for the safe transportation of radioactively contaminated lead objects. Several companies collaborated on the project and contributed to its safe and successful conclusion. These companies include British Nuclear Group, Gravatom Engineering, W. F. Bowker Transport, Atlantic Container Lines, MHF Logistical Solutions and Energy Solutions. New containers and a new innovative inter-modal packaging system to transport the radioactive lead were developed and demonstrated during the project. The project also demonstrated the potential contribution of international nuclear recycling activities as a safe, economic and feasible technical option for nuclear decommissioning in the United Kingdom. (authors)

Sediment and radionuclide transport in rivers: radionuclide transport modeling for Cattaraugus and Buttermilk Creeks, New York

International Nuclear Information System (INIS)

Onishi, Y.; Yabusaki, S.B.; Kincaid, C.T.; Skaggs, R.L.; Walters, W.H.

1982-12-01

SERATRA, a transient, two-dimensional (laterally-averaged) computer model of sediment-contaminant transport in rivers, satisfactorily resolved the distribution of sediment and radionuclide concentrations in the Cattaraugus Creek stream system in New York. By modeling the physical processes of advection, diffusion, erosion, deposition, and bed armoring, SERATRA routed three sediment size fractions, including cohesive soils, to simulate three dynamic flow events. In conjunction with the sediment transport, SERATRA computed radionuclide levels in dissolved, suspended sediment, and bed sediment forms for four radionuclides ( 137 Cs, 90 Sr, 239 240 Pu, and 3 H). By accounting for time-dependent sediment-radionuclide interaction in the water column and bed, SERATA is a physically explicit model of radionuclide fate and migration. Sediment and radionuclide concentrations calculated by SERATA in the Cattaraugus Creek stream system are in reasonable agreement with measured values. SERATRA is in the field performance phase of an extensive testing program designed to establish the utility of the model as a site assessment tool. The model handles not only radionuclides but other contaminants such as pesticides, heavy metals and other toxic chemicals. Now that the model has been applied to four field sites, including the latest study of the Cattaraugus Creek stream system, it is recommended that a final model be validated through comparison of predicted results with field data from a carefully controlled tracer test at a field site. It is also recommended that a detailed laboratory flume be tested to study cohesive sediment transport, deposition, and erosion characteristics. The lack of current understanding of these characteristics is one of the weakest areas hindering the accurate assessment of the migration of radionuclides sorbed by fine sediments of silt and clay

Summary of Vadose -- Zone Conceptual Models for Flow and Contaminant Transport and 1999 - 2003 Progress on Resolving Deficiencies in Understanding the Vadose Zone at the INEEL

Energy Technology Data Exchange (ETDEWEB)

Robert C. Starr; Dana L. Dettmers; Brennon R. Orr; Thomas R. Wood

2003-12-01

The thick vadose zone that underlies the Idaho National Engineering and Environmental Laboratory has been recognized both as an avenue through which contaminants disposed at or near the ground surface can migrate to groundwater in the underlying Eastern Snake River Plain aquifer, and as a barrier to the movement of contaminants into the aquifer. Flow and contaminant transport in the vadose zone at the INEEL is complicated by the highly heterogeneous nature of the geologic framework and by the variations in the behavior of different contaminants in the subsurface. The state of knowledge concerning flow and contaminant transport in the vadose zone at and near the INEEL IN 1999 was summarized in Deficiencies in Vadose Zone Understanding at the Idaho National Engineering and Environmental Laboratory (Wood et al., 2000). These authors identified deficiencies in knowledge of flow and contaminant transport processes in the vadose zone, and provided recommendations for additional work that should be conducted to address these deficiencies. In the period since (Wood et al., 2000) was prepared, research has been published that, to some degree, address these deficiencies. This document provides a bibliography of reports, journal articles, and conference proceedings published 1999 through mid-2003 that are relevant to the vadose zone at or near the INEEL and provides a brief description of each work. Publications that address specific deficiencies or recommendations are identified, and pertinent information from selected publications is presented.

Modeling the Influence of Variable Tributary Inflow on Circulation and Contaminant Transport in a Water Supply Reservoir

Science.gov (United States)

Nguyen, L. H.; Wildman, R.

2012-12-01

This study characterizes quantitatively the flow and mixing regimes of a water supply reservoir, while also conducting numerical tracer experiments on different operation scenarios. We investigate the effects of weather events on water quality via storm water inflows. Our study site the Kensico Reservoir, New York, the penultimate reservoir of New York City's water supply, is never filtered and thus dependent on stringent watershed protection. This reservoir must meet federal drinking water standards under changing conditions such as increased suburban, commercial, and highway developments that are much higher than the rest of the watershed. Impacts from these sources on water quality are magnified by minor tributary flows subject to contaminants from development projects as other tributaries providing >99% of water to this reservoir are exceedingly clean due to management practices upstream. These threats, coupled with possible changes in the frequency/intensity of weather events due to climate change, increase the potential for contaminants to enter the reservoir and drinking water intakes. This situation provides us with the unique ability to study the effects of weather events on water quality via insignificant storm water inflows, without influence from the major tributaries due to their pristine water quality characteristics. The concentration of contaminants at the drinking water intake depends partially on transport from their point of entry in the reservoir. Thus, it is crucial to understand water circulation in this reservoir and to estimate residence times and water ages at different locations and under different hydrologic scenarios. We described water age, residence time, thermal structure, and flow dynamics of tributary plumes in Kensico Reservoir during a 22-year simulation period using a two-dimensional hydrodynamic and water quality model (CE-QUAL-W2). Our estimates of water age can reach a maximum of ~300 days in deep-reservoir-cells, with

Configuration Management Plan for Long Length Contaminated Equipment Receiver and Transport Trailers

International Nuclear Information System (INIS)

DALE, R.N.

2000-01-01

Long Length Contaminated Equipment Removal System Receiver Trailer and Transport Trailer require a configuration management plan for design, requirements and operations baseline documents. This report serves as the plan for the Trailers

Sensitivity Analysis of Unsaturated Flow and Contaminant Transport with Correlated Parameters

Science.gov (United States)

Relative contributions from uncertainties in input parameters to the predictive uncertainties in unsaturated flow and contaminant transport are investigated in this study. The objectives are to: (1) examine the effects of input parameter correlations on the sensitivity of unsaturated flow and conta...

Phase II Contaminant Transport Parameters for the Groundwater Flow and Contaminant Transport Model of Corrective Action Unit 98: Frenchman Flat, Nye County, Nevada, Rev. No.: 0

Energy Technology Data Exchange (ETDEWEB)

DeNovio, Nicole M.; Bryant, Nathan; King, Chrissi B.; Bhark, Eric; Drellack, Sigmund L.; Pickens, John F.; Farnham, Irene; Brooks, Keely M.; Reimus, Paul; Aly, Alaa

2005-04-01

This report documents pertinent transport data and data analyses as part of the Phase II Corrective Action Investigation (CAI) for Frenchman Flat (FF) Corrective Action Unit (CAU) 98. The purpose of this data compilation and related analyses is to provide the primary reference to support parameterization of the Phase II FF CAU transport model.

Numerical modeling of contaminant transport in fractured porous media using mixed finite-element and finitevolume methods

KAUST Repository

Dong, Chen; Sun, Shuyu; Taylor, Glenn A.

2011-01-01

A mathematical model for contaminant species passing through fractured porous media is presented. In the numerical model, we combine two locally conservative methods; i.e., the mixed finite-element (MFE) method and the finite-volume method. Adaptive

Discrete Fracture Network Modeling and Simulation of Subsurface Transport for the Topopah Springs and Lava Flow Aquifers at Pahute Mesa, FY 15 Progress Report

Energy Technology Data Exchange (ETDEWEB)

Makedonska, Nataliia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kwicklis, Edward Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Birdsell, Kay Hanson [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Harrod, Jeremy Ashcraft [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Karra, Satish [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-10-18

This progress report for fiscal year 2015 (FY15) describes the development of discrete fracture network (DFN) models for Pahute Mesa. DFN models will be used to upscale parameters for simulations of subsurface flow and transport in fractured media in Pahute Mesa. The research focuses on modeling of groundwater flow and contaminant transport using DFNs generated according to fracture characteristics observed in the Topopah Spring Aquifer (TSA) and the Lava Flow Aquifer (LFA). This work will improve the representation of radionuclide transport processes in large-scale, regulatory-focused models with a view to reduce pessimistic bounding approximations and provide more realistic contaminant boundary calculations that can be used to describe the future extent of contaminated groundwater. Our goal is to refine a modeling approach that can translate parameters to larger-scale models that account for local-scale flow and transport processes, which tend to attenuate migration.

Groundwater Flow and Transport Model in Cecina Plain (Tuscany, Italy using GIS processing

Directory of Open Access Journals (Sweden)

Riccardo Armellini

2015-03-01

Full Text Available This work provides a groundwater flow and transport model of trichlorethylene and tetrachlorethylene contamination in the Cecina’s coastal aquifer. The contamination analysis, with source located in the Poggio Gagliardo area (Montescudaio, Pisa, was necessary to optimize the groundwater monitoring and remediation design. The work was carried out in two phases: • design of a conceptual model of the aquifer using GIS analysis of many stratigraphic, chemical and hydrogeological data, collected from 2004 to 2012 in six aqueduct wells; • implementation of a groundwater flow and transport numerical model using the MODFLOW 88/96 and MT3D code and the graphical user interface GroundWaterVistas 5. The conceptual model hypothesizes a multilayer aquifer in the coastal plain extended to the sandy-clay hills, recharged by rainfall and by the Cecina River. The aquifer shows important hydrodynamic features affecting both the contamination spreading, due to the presence of a perched and heavily polluted layer separate from the underlying productive aquifer, and the hydrological balance, due to a thick separation layer that limits exchanges between the river and the second groundwater aquifer. The numerical model, built using increasingly complex versions of the initial conceptual model, has been calibrated using monitoring surveys conducted by the Environmental Protection Agency of Regione Toscana (ARPAT, in order to obtain possible forecast scenarios based on the minimum and maximum flow periods, and it is currently used as a tool for decision support regarding the reclamation and/or protection of the aquifer. Future developments will regard the implementation of the multilayer transport model, based on a new survey, and the final coupling with the regional hydrological model named MOBIDIC.

A preliminary investigation of the applicability of surface complexation modeling to the understanding of transportation cask weeping

International Nuclear Information System (INIS)

Granstaff, V.E.; Chambers, W.B.; Doughty, D.H.

1994-01-01

A new application for surface complexation modeling is described. These models, which describe chemical equilibria among aqueous and adsorbed species, have typically been used for predicting groundwater transport of contaminants by modeling the natural adsorbents as various metal oxides. Our experiments suggest that this type of modeling can also explain stainless steel surface contamination and decontamination mechanisms. Stainless steel transportation casks, when submerged in a spent fuel storage pool at nuclear power stations, can become contaminated with radionuclides such as 137 Cs, 134 Cs, and 60 Co. Subsequent release or desorption of these contaminants under varying environmental conditions occasionally results in the phenomenon known as open-quotes cask weeping.close quotes We have postulated that contaminants in the storage pool adsorb onto the hydrous metal oxide surface of the passivated stainless steel and are subsequently released (by conversion from a fixed to a removable form) during transportation, due to varying environmental factors, such as humidity, road salt, dirt, and acid rain. It is well known that 304 stainless steel has a chromium enriched passive surface layer; thus its adsorption behavior should be similar to that of a mixed chromium/iron oxide. To help us interpret our studies of reversible binding of dissolved metals on stainless steel surfaces, we have studied the adsorption of Co +2 on Cr 2 O 3 . The data are interpreted using electrostatic surface complexation models. The FITEQL computer program was used to obtain the model binding constants and site densities from the experimental data. The MINTEQA2 computer speciation model was used, with the fitted constants, in an attempt to validate this approach

Metal Contamination of the Natural Environment in Norway from Long Range Atmospheric Transport

International Nuclear Information System (INIS)

Steinnes, E.

2001-01-01

Long range atmospheric transport is the most important source of contamination to the natural environment in Norway with many heavy metals. Investigations based on aerosol studies, bulk deposition measurements and moss analysis show that airborne transport from other parts of Europe is the major mode for supply of vanadium, zinc, arsenic, selenium, molybdenum, cadmium, tin,antimony, tellurium, thallium, lead, and bismuth, whereas metals such as chromium, nickel, and copper are mainly derived from point sources within Norway and in northwestern Russia close to the Norwegian border. Elements associated with long range transport show substantial enrichment in the humus horizon of natural soils in southern Norway, sometimes to levels suspected to cause effects on soil microbial processes. E.g. lead concentration values of 150-200 ppm are observed in the most contaminated areas in the south as compared to about 5 ppm in the far north. Elements such as lead and cadmium also show enrichment in some terrestrial food chains. These elements also show considerably elevated levels over background concentrations in the water and sediment of small lakes in the southern part of the country. Retrospective studies based on ombrogenous peatcores indicate that long range transport has been a significant source of heavy metal contamination in southern Norway for the last couple of centuries. The deposition of most heavy metals in Norway has been considerably reduced over the last 20 yr, with the exception of contributions in the north from Russian smelters

Fringe-controlled biodegradation under dynamic conditions: Quasi 2-D flow-through experiments and reactive-transport modeling

Science.gov (United States)

Eckert, Dominik; Kürzinger, Petra; Bauer, Robert; Griebler, Christian; Cirpka, Olaf A.

2015-01-01

Biodegradation in contaminated aquifers has been shown to be most pronounced at the fringe of contaminant plumes, where mixing of contaminated water and ambient groundwater, containing dissolved electron acceptors, stimulates microbial activity. While physical mixing of contaminant and electron acceptor by transverse dispersion has been shown to be the major bottleneck for biodegradation in steady-state plumes, so far little is known on the effect of flow and transport dynamics (caused, e.g., by a seasonally fluctuating groundwater table) on biodegradation in these systems. Towards this end we performed experiments in quasi-two-dimensional flow-through microcosms on aerobic toluene degradation by Pseudomonas putida F1. Plume dynamics were simulated by vertical alteration of the toluene plume position and experimental results were analyzed by reactive-transport modeling. We found that, even after disappearance of the toluene plume for two weeks, the majority of microorganisms stayed attached to the sediment and regained their full biodegradation potential within two days after reappearance of the toluene plume. Our results underline that besides microbial growth, also maintenance and dormancy are important processes that affect biodegradation performance under transient environmental conditions and therefore deserve increased consideration in future reactive-transport modeling.

CERES: a model of forest stand biomass dynamics for predicting trace contaminant, nutrient, and water effects. I. Model description

Energy Technology Data Exchange (ETDEWEB)

Dixon, K R; Luxmoore, R J; Begovich, C L

1978-06-01

CERES is a forest stand growth model which incorporates sugar transport in order to predict both short-term effects and long-term accumulation of trace contaminants and/or nutrients when coupled with the soil chemistry model (SCHEM), and models of solute uptake (DIFMAS and DRYADS) of the Unified Transport Model, UTM. An important feature of CERES is its ability to interface with the soil--plant--atmosphere water model (PROSPER) as a means of both predicting and studying the effects of plant water status on growth and solute transport. CERES considers the biomass dynamics of plants, standing dead and litter with plants divided into leaves, stems, roots, and fruits. The plant parts are divided further into sugar substrate, storage, and in the case of stems and roots, heartwood components. Each ecosystem omponent is described by a mass balance equation written as a first-order ordinary differential equation.

The effects of a perturbed source on contaminant transport near the Weldon Spring quarry

International Nuclear Information System (INIS)

Tomasko, D.

1989-03-01

The effects of a perturbed contamination source at the Weldon Spring quarry in St. Charles County, Missouri, on downstream solute concentrations were investigated using one-dimensional analytical solutions to an advection-dispersion equation developed for both constant-strength and multiple-stepped source functions. A sensitivity study using parameter base-case values and ranges consistent with the geologic conceptualization of the quarry area indicates that the parameters having the greatest effect on predicted concentrations are the distance from the quarry to the point of interest, the average linear groundwater velocity, the contaminant retardation coefficient, and the amplitude and duration of the source perturbation caused by response action activities. Use of base-case parameter value and realistic values for the amplitude and duration of the source perturbation produced a small effect on solute concentrations near the western extremity of the nearby municipal well field, as well as small uncertainties in the predicted results for the assumed model. The effect of simplifying assumptions made in deriving the analytic solution is unknown: use of a multidimensional flow and transport model and additional field work are needed to validate the model. 13 refs., 18 figs

RESEARCH ACTIVITIES AT U.S. GOVERNMENT AGENCIES IN SUBSURFACE REACTIVE TRANSPORT MODELING

Science.gov (United States)

The fate of contaminants in the environment is controlled by both chemical reactions and transport phenomena in the subsurface. Our ability to understand the significance of these processes over time requires an accurate conceptual model that incorporates the various mechanisms ...

Characterizing, for packaging and transport, large objects contaminated by radioactive material having a limited A2 value

International Nuclear Information System (INIS)

Pope, R.B.; Shappert, L.B.; Michelhaugh, R.D.; Cash, J.M.; Best, R.E.

1998-02-01

The International Atomic Energy Agency (IAEA) Regulations for the safe packaging and transportation of radioactive materials follow a graded approach to the requirements for both packaging and controls during transport. The concept is that, the lower the risk posed to the people and the environment by the contents, (1) the less demanding are the packaging requirements and (2) the smaller in number are the controls imposed on the transport of the material. There are likely to be a great number of situations arising in coming years when large objects, contaminated with radioactive material having unlimited A 2 values will result from various decommissioning and decontamination (D and D) activities and will then require shipment from the D and D site to a disposal site. Such situations may arise relatively frequently during the cleanup of operations involving mining, milling, feedstock, and uranium enrichment processing facilities. Because these objects are contaminated with materials having an unlimited A 2 value they present a low radiological risk to worker and public safety and to the environment during transport. However, when these radioactive materials reside on the surfaces of equipment and other large objects, where the equipment and objects themselves are not radioactive, the radioactive materials appear as surface contamination and, if the contaminated object is categorized as a surface contaminated object, it would need to be packaged for shipment according to the requirements of the Regulations for SCO. Despite this categorization, alternatives may be available which will allow these contaminants, when considered by themselves for packaging and transport, to be categorized as either (1) a limited quantity of radioactive material to be shipped in an excepted package or (2) low specific activity (LSA) materials to be shipped in an IP-1 package or possibly even shipped unpackaged. These options are discussed in this paper

Development of a resuspension model for contaminated soils. Application to the Palomares area

International Nuclear Information System (INIS)

Garcia-Olivares, A.

1993-01-01

A model is presented which has been used to simulate the wind resuspension and transport of contaminated soil in the area surrounding the Palomares village, in Southern Spain. The model uses site specific data and some generic parameters as resuspension rate and deposition velocity. The model is able to predict the order of magnitude of the observed air concentration of activity. Some lines of research are suggested which could improve the understanding of the phenomena involved. (Author) 20 refs

Development of a resupension model for contaminated soils: Application to the Palomares area

International Nuclear Information System (INIS)

Garcia-Olivares, A.

1993-01-01

A model is presented which has been used to simulate the wind resuspension and transport of contaminated soil in the area surrounding the Palomares village, in Southern Spain. The model uses site specific data and some generic parameters as resuspension rate and deposition velocity. The model is able to predict the order of magnitude of the observed air concentration of activity. Some lines of research are suggested which could improve the understanding of the phenomena involved. (author)

Contaminant Boundary at the Faultless Underground Nuclear Test

International Nuclear Information System (INIS)

Greg Pohll; Karl Pohlmann; Jeff Daniels; Ahmed Hassan; Jenny Chapman

2003-01-01

The U.S. Department of Energy (DOE) and the Nevada Division of Environmental Protection (NDEP) have reached agreement on a corrective action strategy applicable to address the extent and potential impact of radionuclide contamination of groundwater at underground nuclear test locations. This strategy is described in detail in the Federal Facility Agreement and Consent Order (FFACO, 2000). As part of the corrective action strategy, the nuclear detonations that occurred underground were identified as geographically distinct corrective action units (CAUs). The strategic objective for each CAU is to estimate over a 1,000-yr time period, with uncertainty quantified, the three-dimensional extent of groundwater contamination that would be considered unsafe for domestic and municipal use. Two types of boundaries (contaminant and compliance) are discussed in the FFACO that will map the three-dimensional extent of radionuclide contamination. The contaminant boundary will identify the region wi th 95 percent certainty that contaminants do not exist above a threshold value. It will be prepared by the DOE and presented to NDEP. The compliance boundary will be produced as a result of negotiation between the DOE and NDEP, and can be coincident with, or differ from, the contaminant boundary. Two different thresholds are considered for the contaminant boundary. One is based on the enforceable National Primary Drinking Water Regulations for radionuclides, which were developed as a requirement of the Safe Drinking Water Act. The other is a risk-based threshold considering applicable lifetime excess cancer-risk-based criteria The contaminant boundary for the Faultless underground nuclear test at the Central Nevada Test Area (CNTA) is calculated using a newly developed groundwater flow and radionuclide transport model that incorporates aspects of both the original three-dimensional model (Pohlmann et al., 1999) and the two-dimensional model developed for the Faultless data decision

Examination of the uncertainty in contaminant fate and transport modeling: a case study in the Venice Lagoon.

Science.gov (United States)

Sommerfreund, J; Arhonditsis, G B; Diamond, M L; Frignani, M; Capodaglio, G; Gerino, M; Bellucci, L; Giuliani, S; Mugnai, C

2010-03-01

A Monte Carlo analysis is used to quantify environmental parametric uncertainty in a multi-segment, multi-chemical model of the Venice Lagoon. Scientific knowledge, expert judgment and observational data are used to formulate prior probability distributions that characterize the uncertainty pertaining to 43 environmental system parameters. The propagation of this uncertainty through the model is then assessed by a comparative analysis of the moments (central tendency, dispersion) of the model output distributions. We also apply principal component analysis in combination with correlation analysis to identify the most influential parameters, thereby gaining mechanistic insights into the ecosystem functioning. We found that modeled concentrations of Cu, Pb, OCDD/F and PCB-180 varied by up to an order of magnitude, exhibiting both contaminant- and site-specific variability. These distributions generally overlapped with the measured concentration ranges. We also found that the uncertainty of the contaminant concentrations in the Venice Lagoon was characterized by two modes of spatial variability, mainly driven by the local hydrodynamic regime, which separate the northern and central parts of the lagoon and the more isolated southern basin. While spatial contaminant gradients in the lagoon were primarily shaped by hydrology, our analysis also shows that the interplay amongst the in-place historical pollution in the central lagoon, the local suspended sediment concentrations and the sediment burial rates exerts significant control on the variability of the contaminant concentrations. We conclude that the probabilistic analysis presented herein is valuable for quantifying uncertainty and probing its cause in over-parameterized models, while some of our results can be used to dictate where additional data collection efforts should focus on and the directions that future model refinement should follow. (c) 2009 Elsevier Inc. All rights reserved.

Contamination transfers during fuel transport cask loading. A concrete situation

International Nuclear Information System (INIS)

Fournel, B.; Turchet, J.P.; Faure, S.; Allinei, P.G.; Briquet, L.; Baubet, D.

2002-01-01

In 1998, a number of contamination cases detected during fuel shipments have been pointed out by the french nuclear safety authority. Wagon and casks external surfaces were partly contaminated upon arrival in Valognes railway terminal. Since then, measures taken by nuclear power plants operators in France and abroad solved the problem. In Germany, a report analyzing the situation in depth has been published in which correctives actions have been listed. In France, EDF launched a large cleanliness program (projet proprete radiologique) in order to better understand contamination transfers mechanisms during power plants exploitation and to list remediation actions to avoid further problems. In this context, CEA Department for Wastes Studies at Cadarache (CEA/DEN/DED) was in charge of a study about contamination transfers during fuel elements loading operations. It was decided to lead experiments for a concrete case. The loading of a transport cask at Tricastin-PWR-1 was followed in november 2000 and different analysis comprising water analysis and smear tests analysis were carried out and are detailed in this paper. Results are discussed and qualitatively compared to those obtained in Philippsburg-BWR, Germany for a similar set of tests. (authors)

A coupled reaction and transport model for assessing the injection, migration and fate of waste fluids

International Nuclear Information System (INIS)

Liu, X.; Ortoleva, P.

1996-01-01

The use of reaction-transport modeling for reservoir assessment and management in the context of deep well waste injection is evaluated. The study is based on CIRF.A (Chemical Interaction of Rock and Fluid), a fully coupled multiphase flow, contaminant transport, and fluid and mineral reaction model. Although SWIFT (Sandia Waste-Isolation Flow and Transport Model) is often the numerical model of choice, it can not account for chemical reactions involving rock, wastes, and formation fluids and their effects on contaminant transport, rock permeability and porosity, and the integrity of the reservoir and confining units. CIRF.A can simulate all these processes. Two field cases of waste injection were simulated by CIRF.A. Both observation data and simulation results show mineral precipitation in one case and rock dissolution in another case. Precipitation and dissolution change rock porosity and permeability, and hence the pattern of fluid migration. The model is shown to be invaluable in analyzing near borehole and reservoir-scale effects during waste injection and predicting the 10,000 year fate of the waste plume. The benefits of using underpressured compartments as waste repositories were also demonstrated by CIRF.A simulations

Modelling freight transport

NARCIS (Netherlands)

Tavasszy, L.A.; Jong, G. de

2014-01-01

Freight Transport Modelling is a unique new reference book that provides insight into the state-of-the-art of freight modelling. Focusing on models used to support public transport policy analysis, Freight Transport Modelling systematically introduces the latest freight transport modelling

Symposium on unsaturated flow and transport modeling

International Nuclear Information System (INIS)

Arnold, E.M.; Gee, G.W.; Nelson, R.W.

1982-09-01

This document records the proceedings of a symposium on flow and transport processes in partially saturated groundwater systems, conducted at the Battelle Seattle Research Center on March 22-24, 1982. The symposium was sponsored by the US Nuclear Regulatory Commission for the purpose of assessing the state-of-the-art of flow and transport modeling for use in licensing low-level nuclear waste repositories in partially saturated zones. The first day of the symposium centered around research in flow through partially saturated systems. Papers were presented with the opportunity for questions following each presentation. In addition, after all the talks, a formal panel discussion was held during which written questions were addressed to the panel of the days speakers. The second day of the Symposium was devoted to solute and contaminant transport in partially saturated media in an identical format. Individual papers are abstracted

Symposium on unsaturated flow and transport modeling

Energy Technology Data Exchange (ETDEWEB)

Arnold, E.M.; Gee, G.W.; Nelson, R.W. (eds.)

1982-09-01

This document records the proceedings of a symposium on flow and transport processes in partially saturated groundwater systems, conducted at the Battelle Seattle Research Center on March 22-24, 1982. The symposium was sponsored by the US Nuclear Regulatory Commission for the purpose of assessing the state-of-the-art of flow and transport modeling for use in licensing low-level nuclear waste repositories in partially saturated zones. The first day of the symposium centered around research in flow through partially saturated systems. Papers were presented with the opportunity for questions following each presentation. In addition, after all the talks, a formal panel discussion was held during which written questions were addressed to the panel of the days speakers. The second day of the Symposium was devoted to solute and contaminant transport in partially saturated media in an identical format. Individual papers are abstracted.

Transport of contaminants by Arctic sea ice and surface ocean currents

International Nuclear Information System (INIS)

Pfirman, S.

1995-01-01

Sea ice and ocean currents transport contaminants in the Arctic from source areas on the shelves, to biologically active regions often more than a thousand kilometers away. Coastal regions along the Siberian margin are polluted by discharges of agricultural, industrial and military wastes in river runoff, from atmospheric deposition and ocean dumping. The Kara Sea is of particular concern because of deliberate dumping of radioactive waste, as well as the large input of polluted river water. Contaminants are incorporated in ice during suspension freezing on the shelves, and by atmospheric deposition during drift. Ice releases its contaminant load through brine drainage, surface runoff of snow and meltwater, and when the floe disintegrates. The marginal ice zone, a region of intense biological activity, may also be the site of major contaminant release. Potentially contaminated ice from the Kara Sea is likely to influence the marginal ice zones of the Barents and Greenland seas. From studies conducted to date it appears that sea ice from the Kara Sea does not typically enter the Beaufort Gyre, and thus is unlikely to affect the northern Canadian and Alaskan margins

Selection of distribution coefficients for contaminant fate and transport calculations: Strontium as a case study

International Nuclear Information System (INIS)

Kaplan, D.I.; Krupka, K.M.; Serne, R.J.

1997-01-01

As part of an ongoing project funded by a cooperative effort involving the Office of Radiation and Indoor Air (ORIA) of the U.S. Environmental Protection Agency (EPA), the Office of Environmental Restoration (EM-40) of the Department of Energy (DOE), and the Nuclear Regulatory Agency (NRC), distribution coefficient (K d ) values are being compiled from the literature to develop provisional tables for cadmium, cesium, chromium, lead, plutonium, strontium, thorium, and uranium. The tables are organized according to important aqueous- and solid-phase parameters affecting the sorption of these contaminants. These parameters, which vary with contaminant, include pH and redox conditions; cation exchange capacity (CEC); presence of iron-oxide, aluminum-oxide, clay, and mica minerals; organic matter content; and solution concentrations of contaminants, competing ions, and complexing ligands. Sorption information compiled for strontium is used to illustrate our approach. The strontium data show how selected geochemical parameters (i.e., CEC, pH, and clay content) affect Strontium K d values and the selection of open-quote default close-quote K d values needed for modeling contaminant transport and risks at sites for which site specific data are lacking. Results of our evaluation may be used by site management and technical staff to assess contaminant fate, migration, and risk calculations in support of site remediation and waste management decisions

Classification of the Group Invariant Solutions for Contaminant Transport in Saturated Soils under Radial Uniform Water Flows

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.

Campylobacter genotypes from poultry transportation crates indicate a source of contamination and transmission.

Science.gov (United States)

Hastings, R; Colles, F M; McCarthy, N D; Maiden, M C J; Sheppard, S K

2011-01-01

Crates used to transport live poultry can be contaminated with Campylobacter, despite periodic sanitization, and are potential vectors for transmission between flocks. We investigated the microbial contamination of standard and silver ion containing crates in normal use and the genetic structure of associated Campylobacter populations. Bacteria from crates were enumerated by appropriate culture techniques, and multilocus sequence typing (MLST) was used to determine the genetic structure of Campylobacters isolated from standard and silver ion containing crates. Compared to standard crates, counts of bacteria, including Campylobacter, were consistently lower on silver ion containing crates throughout the decontamination process. In total, 16 different sequence types were identified from 89 Campylobacter jejuni isolates from crates. These were attributed to putative source population (chicken, cattle, sheep, the environment, wild bird) using the population genetic model, structure. Most (89%) were attributed to chicken, with 22% attribution to live chicken and 78% to retail poultry meat. MLST revealed a progressive shift in allele frequencies through the crate decontamination process. Campylobacter on crates survived for at least 3 h after sanitization, a period of time equivalent to the journey from the processing plant to the majority of farms in the catchment, showing the potential for involvement of crates in transmission. Inclusion of a silver ion biocide in poultry transportation crates to levels demonstrating acceptable antibacterial activity in vitro reduces the level of bacterial contamination during normal crate use compared to standard crates. Molecular analysis of Campylobacter isolates indicated a change in genetic structure of the population with respect to the poultry-processing plant sanitization practice. The application of a sustainable antimicrobial to components of poultry processing may contribute to reducing the levels of Campylobacter

Fringe-controlled biodegradation under dynamic conditions: quasi 2-D flow-through experiments and reactive-transport modeling.

Science.gov (United States)

Eckert, Dominik; Kürzinger, Petra; Bauer, Robert; Griebler, Christian; Cirpka, Olaf A

2015-01-01

Biodegradation in contaminated aquifers has been shown to be most pronounced at the fringe of contaminant plumes, where mixing of contaminated water and ambient groundwater, containing dissolved electron acceptors, stimulates microbial activity. While physical mixing of contaminant and electron acceptor by transverse dispersion has been shown to be the major bottleneck for biodegradation in steady-state plumes, so far little is known on the effect of flow and transport dynamics (caused, e.g., by a seasonally fluctuating groundwater table) on biodegradation in these systems. Towards this end we performed experiments in quasi-two-dimensional flow-through microcosms on aerobic toluene degradation by Pseudomonas putida F1. Plume dynamics were simulated by vertical alteration of the toluene plume position and experimental results were analyzed by reactive-transport modeling. We found that, even after disappearance of the toluene plume for two weeks, the majority of microorganisms stayed attached to the sediment and regained their full biodegradation potential within two days after reappearance of the toluene plume. Our results underline that besides microbial growth, also maintenance and dormancy are important processes that affect biodegradation performance under transient environmental conditions and therefore deserve increased consideration in future reactive-transport modeling. Copyright © 2014 Elsevier B.V. All rights reserved.

A compositional multiphase model for groundwater contamination by petroleum products: 1. Theoretical considerations

Science.gov (United States)

Corapcioglu, M. Yavuz; Baehr, Arthur L.

1987-01-01

A mathematical model is developed to describe the fate of hydrocarbon constituents of petroleum products introduced to soils as an immiscible liquid from sources such as leaking underground storage tanks and ruptured pipelines. The problem is one of multiphase transport (oil (immiscible), air, and water phases) of a reactive contaminant with constituents such as benzene, toluene, and xylene found in refined petroleum products like gasoline. In the unsaturated zone, transport of each constituent can occur as a solute in the water phase, vapor in the air phase, and as an unaltered constituent in the oil phase. Additionally, the model allows for adsorption. Molecular transformations, microbially mediated or abiotic, are incorporated as sink terms in the conservation of mass equations. An equilibrium approximation, applicable to any immiscible organic contaminant is applied to partition constituent mass between the air, oil, water, and adsorbed phases for points in the region where the oil phase exists. Outside the oil plume the equilibrium approximation takes on a simpler form to partition constituent mass between the air, water, and adsorbed phases only. Microbial degradation of petroleum products is first discussed in a general model, then the conservation of mass equation for oxygen is incorporated into the analysis which takes advantage of the key role played by oxygen in the metabolism of hydrocarbon utilizing microbes in soil environments. Approximations to two subproblems, oil plume establishment in the unsaturated zone, and solute and vapor transport subsequent to immiscible plume establishment are then developed from the general model.

A statistical model for deriving probability distributions of contamination for accidental releases

International Nuclear Information System (INIS)

ApSimon, H.M.; Davison, A.C.

1986-01-01

Results generated from a detailed long-range transport model, MESOS, simulating dispersal of a large number of hypothetical releases of radionuclides in a variety of meteorological situations over Western Europe have been used to derive a simpler statistical model, MESOSTAT. This model may be used to generate probability distributions of different levels of contamination at a receptor point 100-1000 km or so from the source (for example, across a frontier in another country) without considering individual release and dispersal scenarios. The model is embodied in a series of equations involving parameters which are determined from such factors as distance between source and receptor, nuclide decay and deposition characteristics, release duration, and geostrophic windrose at the source. Suitable geostrophic windrose data have been derived for source locations covering Western Europe. Special attention has been paid to the relatively improbable extreme values of contamination at the top end of the distribution. The MESOSTAT model and its development are described, with illustrations of its use and comparison with the original more detailed modelling techniques. (author)

Modelling multicomponent solute transport in structured soils

NARCIS (Netherlands)

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

Leaching and soil/groundwater transport of contaminants from coal combustion residues

International Nuclear Information System (INIS)

Hjelmar, O.; Hansen, E.A.; Larsen, F.; Thomassen, H.

1992-01-01

In this project the results of accelerated laboratory leaching tests on coal fly ash and flue gas desulfurization (FGD) products from the spray dryer absorption process (SDA) were evaluated by comparison to the results of large scale lysimeter leaching tests on the same residues. The mobility of chromium and molybdenum - two of the kev contaminants of coal combustion residue leachates - in various typical soil types was investigated by batch and column methods in the laboratory. Some of the results were confirmed by field observations at an old coal fly ash disposal site and by a lysimeter attenuation test with coal fly ash leachate on a clayed till. A large number of groundwater transport models and geochemical models were reviewed, and two of the models (Gove-Stollenwerk and CHMTRNS) were modified and adjusted and used to simulate column attenuation tests performed in the laboratory. One of the models (Grove-Stollenwerk) was used to illustrate a recommended method of environmental impact assessment, using lysimeter leaching data and laboratory column attenuation data to describe the emission and migration of Mo from a coal fly ash disposal site

GWSCREEN: A Semi-analytical Model for Assessment of the Groundwater Pathway from Surface or Buried Contamination, Theory and User's Manual, Version 2.5

Energy Technology Data Exchange (ETDEWEB)

Rood, Arthur South

1998-08-01

GWSCREEN was developed for assessment of the groundwater pathway from leaching of radioactive and non-radioactive substances from surface or buried sources. The code was designed for implementation in the Track I and Track II assessment of Comprehensive Environmental Response, Compensation, and Liability Act sites identified as low probability hazard at the Idaho National Engineering Laboratory. The code calculates 1) the limiting soil concentration such that, after leaching and transport to the aquifer regulatory contaminant levels in groundwater are not exceeded, 2) peak aquifer concentration and associated human health impacts, and 3) aquifer concentrations and associated human health impacts as a function of time and space. The code uses a mass conservation approach to model three processes: contaminant release from a source volume, vertical contaminant transport in the unsaturated zone, and 2D or 3D contaminant transport in the saturated zone. The source model considers the sorptive properties and solubility of the contaminant. In Version 2.5, transport in the unsaturated zone is described by a plug flow or dispersive solution model. Transport in the saturated zone is calculated with a semi-analytical solution to the advection dispersion equation in groundwater. Three source models are included; leaching from a surface or buried source, infiltration pond, or user-defined arbitrary release. Dispersion in the aquifer may be described by fixed dispersivity values or three, spatial-variable dispersivity functions. Version 2.5 also includes a Monte Carlo sampling routine for uncertainty/sensitivity analysis and a preprocessor to allow multiple input files and multiple contaminants to be run in a single simulation. GWSCREEN has been validated against other codes using similar algorithms and techniques. The code was originally designed for assessment and screening of the groundwater pathway when field data are limited. It was intended to simulate relatively simple

Evaluation of wastewater contaminant transport in surface waters using verified Lagrangian sampling

Science.gov (United States)

Antweiler, Ronald C.; Writer, Jeffrey H.; Murphy, Sheila F.

2014-01-01

Contaminants released from wastewater treatment plants can persist in surface waters for substantial distances. Much research has gone into evaluating the fate and transport of these contaminants, but this work has often assumed constant flow from wastewater treatment plants. However, effluent discharge commonly varies widely over a 24-hour period, and this variation controls contaminant loading and can profoundly influence interpretations of environmental data. We show that methodologies relying on the normalization of downstream data to conservative elements can give spurious results, and should not be used unless it can be verified that the same parcel of water was sampled. Lagrangian sampling, which in theory samples the same water parcel as it moves downstream (the Lagrangian parcel), links hydrologic and chemical transformation processes so that the in-stream fate of wastewater contaminants can be quantitatively evaluated. However, precise Lagrangian sampling is difficult, and small deviations – such as missing the Lagrangian parcel by less than 1 h – can cause large differences in measured concentrations of all dissolved compounds at downstream sites, leading to erroneous conclusions regarding in-stream processes controlling the fate and transport of wastewater contaminants. Therefore, we have developed a method termed “verified Lagrangian” sampling, which can be used to determine if the Lagrangian parcel was actually sampled, and if it was not, a means for correcting the data to reflect the concentrations which would have been obtained had the Lagrangian parcel been sampled. To apply the method, it is necessary to have concentration data for a number of conservative constituents from the upstream, effluent, and downstream sites, along with upstream and effluent concentrations that are constant over the short-term (typically 2–4 h). These corrections can subsequently be applied to all data, including non-conservative constituents. Finally, we

Evaluation of wastewater contaminant transport in surface waters using verified Lagrangian sampling.

Science.gov (United States)

Antweiler, Ronald C; Writer, Jeffrey H; Murphy, Sheila F

2014-02-01

Contaminants released from wastewater treatment plants can persist in surface waters for substantial distances. Much research has gone into evaluating the fate and transport of these contaminants, but this work has often assumed constant flow from wastewater treatment plants. However, effluent discharge commonly varies widely over a 24-hour period, and this variation controls contaminant loading and can profoundly influence interpretations of environmental data. We show that methodologies relying on the normalization of downstream data to conservative elements can give spurious results, and should not be used unless it can be verified that the same parcel of water was sampled. Lagrangian sampling, which in theory samples the same water parcel as it moves downstream (the Lagrangian parcel), links hydrologic and chemical transformation processes so that the in-stream fate of wastewater contaminants can be quantitatively evaluated. However, precise Lagrangian sampling is difficult, and small deviations - such as missing the Lagrangian parcel by less than 1h - can cause large differences in measured concentrations of all dissolved compounds at downstream sites, leading to erroneous conclusions regarding in-stream processes controlling the fate and transport of wastewater contaminants. Therefore, we have developed a method termed "verified Lagrangian" sampling, which can be used to determine if the Lagrangian parcel was actually sampled, and if it was not, a means for correcting the data to reflect the concentrations which would have been obtained had the Lagrangian parcel been sampled. To apply the method, it is necessary to have concentration data for a number of conservative constituents from the upstream, effluent, and downstream sites, along with upstream and effluent concentrations that are constant over the short-term (typically 2-4h). These corrections can subsequently be applied to all data, including non-conservative constituents. Finally, we show how data

Application of multiple tracers (SF6 and chloride) to identify the transport by characteristics of contaminant at two separate contaminated sites

Science.gov (United States)

Lee, K. K.; Lee, S. S.; Kim, H. H.; Koh, E. H.; Kim, M. O.; Lee, K.; Kim, H. J.

2016-12-01

Multiple tracers were applied for source and pathway detection at two different sites. CO2 gas injected in the subsurface for a shallow-depth CO2 injection and leak test can be regarded as a potential contaminant source. Therefore, it is necessary to identify the migration pattern of CO2 gas. Also, at a DNAPL contaminated site, it is important to figure out the characteristics of plume evolution from the source zone. In this study, multiple tracers (SF6 and chloride) were used to evaluate the applicability of volatile and non-volatile tracers and to identify the characteristics of contaminant transport at each CO2 injection and leak test site and DNAPL contaminated site. Firstly, at the CO2 test site, multiple tracers were used to perform the single well push-drift-pull tracer test at total 3 specific depth zones. As results of tests, volatile and non-volatile tracers showed different mass recovery percentage. Most of chloride mass was recovered but less than half of SF6 mass was recovered due to volatile property. This means that only gaseous SF6 leak out to unsaturated zone. However, breakthrough curves of both tracers indicated similar peak time, effective porosity, and regional groundwater velocity. Also, at both contaminated sites, natural gradient tracer tests were performed with multiple tracers. With the results of natural gradient tracer test, it was possible to confirm the applicability of multiple tracers and to understand the contaminant transport in highly heterogeneous aquifer systems through the long-term monitoring of tracers. Acknowledgement: financial support was provided by the R&D Project on Environmental Management of Geologic CO2 Storage)" from the KEITI (Project Number: 2014001810003) and Korea Ministry of Environment as "The GAIA project (2014000540010)".

Solute transport model for radioisotopes in layered soil

International Nuclear Information System (INIS)

Essel, P.

2010-01-01

The study considered the transport of a radioactive solute in solution from the surface of the earth down through the soil to the ground water when there is an accidental or intentional spillage of a radioactive material on the surface. The finite difference method was used to model the spatial and temporal profile of moisture content in a soil column using the θ-based Richard's equation leading to solution of the convective-dispersive equation for non-adsorbing solutes numerically. A matlab code has been generated to predict the transport of the radioactive contaminant, spilled on the surface of a vertically heterogeneous soil made up of two layers to determine the residence time of the solute in the unsaturated zone, the time it takes the contaminant to reach the groundwater and the amount of the solute entering the groundwater in various times and the levels of pollution in those times. The model predicted that, then there is a spillage of 7.2g of tritium, on the surface of the ground at the study area, it will take two years for the radionuclide to enter the groundwater and fifteen years to totally leave the unsaturated zone. There is therefore the need to try as much as possible to avoid intentional or accidental spillage of the radionuclide since it has long term effect. (au)

Rainfall-runoff model for prediction of waterborne viral contamination in a small river catchment

Science.gov (United States)

Gelati, E.; Dommar, C.; Lowe, R.; Polcher, J.; Rodó, X.

2013-12-01

We present a lumped rainfall-runoff model aimed at providing useful information for the prediction of waterborne viral contamination in small rivers. Viral contamination of water bodies may occur because of the discharge of sewage effluents and of surface runoff over areas affected by animal waste loads. Surface runoff is caused by precipitation that cannot infiltrate due to its intensity and to antecedent soil water content. It may transport animal feces to adjacent water bodies and cause viral contamination. We model streamflow by separating it into two components: subsurface flow, which is produced by infiltrated precipitation; and surface runoff. The model estimates infiltrated and non-infiltrated precipitation and uses impulse-response functions to compute the corresponding fractions of streamflow. The developed methodologies are applied to the Glafkos river, whose catchment extends for 102 km2 and includes the city of Patra. Streamflow and precipitation observations are available at a daily time resolution. Waterborne virus concentration measurements were performed approximately every second week from the beginning of 2011 to mid 2012. Samples were taken at several locations: in river water upstream of Patras and in the urban area; in sea water at the river outlet and approximately 2 km south-west of Patras; in sewage effluents before and after treatment. The rainfall-runoff model was calibrated and validated using observed streamflow and precipitation data. The model contribution to waterborne viral contamination prediction was benchmarked by analyzing the virus concentration measurements together with the estimated surface runoff values. The presented methodology may be a first step towards the development of waterborne viral contamination alert systems. Predicting viral contamination of water bodies would benefit sectors such as water supply and tourism.

Agriculture and groundwater nitrate contamination in the Seine basin. The STICS-MODCOU modelling chain

International Nuclear Information System (INIS)

Ledoux, E.; Gomez, E.; Monget, J.M.; Viavattene, C.; Viennot, P.; Ducharne, A.; Benoit, M.; Mignolet, C.; Schott, C.; Mary, B.

2007-01-01

A software package is presented here to predict the fate of nitrogen fertilizers and the transport of nitrate from the rooting zone of agricultural areas to surface water and groundwater in the Seine basin, taking into account the long residence times of water and nitrate in the unsaturated and aquifer systems. Information on pedological characteristics, land use and farming practices is used to determine the spatial units to be considered. These data are converted into input data for the crop model STICS which simulates the water and nitrogen balances in the soil-plant system with a daily time-step. A spatial application of STICS has been derived at the catchment scale which computes the water and nitrate fluxes at the bottom of the rooting zone. These fluxes are integrated into a surface and groundwater coupled model MODCOU which calculates the daily water balance in the hydrological system, the flow in the rivers and the piezometric variations in the aquifers, using standard climatic data (rainfall, PET). The transport of nitrate and the evolution of nitrate contamination in groundwater and to rivers is computed by the model NEWSAM. This modelling chain is a valuable tool to predict the evolution of crop productivity and nitrate contamination according to various scenarios modifying farming practices and/or climatic changes. Data for the period 1970-2000 are used to simulate the past evolution of nitrogen contamination. The method has been validated using available data bases of nitrate concentrations in the three main aquifers of the Paris basin (Oligocene, Eocene and chalk). The approach has then been used to predict the future evolution of nitrogen contamination up to 2015. A statistical approach allowed estimating the probability of transgression of different concentration thresholds in various areas in the basin. The model is also used to evaluate the cost of the damage resulting of the treatment of drinking water at the scale of a groundwater management

Agriculture and groundwater nitrate contamination in the Seine basin. The STICS-MODCOU modelling chain

Energy Technology Data Exchange (ETDEWEB)

Ledoux, E. [Centre de Geosciences, ENSMP, UMR Sisyphe, Fontainebleau (France)]. E-mail: emmanuel.ledoux@ensmp.fr; Gomez, E. [Centre de Geosciences, ENSMP, UMR Sisyphe, Fontainebleau (France); Monget, J.M. [Centre de Geosciences, ENSMP, UMR Sisyphe, Fontainebleau (France); Viavattene, C. [Centre de Geosciences, ENSMP, UMR Sisyphe, Fontainebleau (France); Viennot, P. [Centre de Geosciences, ENSMP, UMR Sisyphe, Fontainebleau (France); Ducharne, A. [Laboratoire Sisyphe, CNRS/Universite Pierre et Marie Curie, Paris (France); Benoit, M. [INRA, Station de Recherche SAD, 662 avenue Louis Buffet, 88500 Mirecourt (France); Mignolet, C. [INRA, Station de Recherche SAD, 662 avenue Louis Buffet, 88500 Mirecourt (France); Schott, C. [INRA, Station de Recherche SAD, 662 avenue Louis Buffet, 88500 Mirecourt (France); Mary, B. [INRA, Unite d' Agronomie Laon-Reims-Mons, Laon (France)

2007-04-01

A software package is presented here to predict the fate of nitrogen fertilizers and the transport of nitrate from the rooting zone of agricultural areas to surface water and groundwater in the Seine basin, taking into account the long residence times of water and nitrate in the unsaturated and aquifer systems. Information on pedological characteristics, land use and farming practices is used to determine the spatial units to be considered. These data are converted into input data for the crop model STICS which simulates the water and nitrogen balances in the soil-plant system with a daily time-step. A spatial application of STICS has been derived at the catchment scale which computes the water and nitrate fluxes at the bottom of the rooting zone. These fluxes are integrated into a surface and groundwater coupled model MODCOU which calculates the daily water balance in the hydrological system, the flow in the rivers and the piezometric variations in the aquifers, using standard climatic data (rainfall, PET). The transport of nitrate and the evolution of nitrate contamination in groundwater and to rivers is computed by the model NEWSAM. This modelling chain is a valuable tool to predict the evolution of crop productivity and nitrate contamination according to various scenarios modifying farming practices and/or climatic changes. Data for the period 1970-2000 are used to simulate the past evolution of nitrogen contamination. The method has been validated using available data bases of nitrate concentrations in the three main aquifers of the Paris basin (Oligocene, Eocene and chalk). The approach has then been used to predict the future evolution of nitrogen contamination up to 2015. A statistical approach allowed estimating the probability of transgression of different concentration thresholds in various areas in the basin. The model is also used to evaluate the cost of the damage resulting of the treatment of drinking water at the scale of a groundwater management

Impacts of Spatio-Variability of Source Morphology on Field-Scale Predictions of Subsurface Contaminant Transport

National Research Council Canada - National Science Library

Hatfield, Kirk

1998-01-01

... (organic immiscible liquids distribution and composition) and aquifer properties on predicting solute transport in saturated groundwater systems contaminated with residual Organic Immiscible Liquids (OIL's...

A compartmentalized solute transport model for redox zones in contaminated aquifers: 1. Theory and development

Science.gov (United States)

Abrams , Robert H.; Loague, Keith

2000-01-01

This paper, the first of two parts [see Abrams and Loague, this issue], takes the compartmentalized approach for the geochemical evolution of redox zones presented by Abrams et al. [1998] and embeds it within a solute transport framework. In this paper the compartmentalized approach is generalized to facilitate the description of its incorporation into a solute transport simulator. An equivalent formulation is developed which removes any discontinuities that may occur when switching compartments. Rate‐limited redox reactions are modeled with a modified Monod relationship that allows either the organic substrate or the electron acceptor to be the rate‐limiting reactant. Thermodynamic constraints are used to inhibit lower‐energy redox reactions from occurring under infeasible geochemical conditions without imposing equilibrium on the lower‐energy reactions. The procedure used allows any redox reaction to be simulated as being kinetically limited or thermodynamically limited, depending on local geochemical conditions. Empirical reaction inhibition methods are not needed. The sequential iteration approach (SIA), a technique which allows the number of solute transport equations to be reduced, is adopted to solve the coupled geochemical/solute transport problem. When the compartmentalized approach is embedded within the SIA, with the total analytical concentration of each component as the dependent variable in the transport equation, it is possible to reduce the number of transport equations even further than with the unmodified SIA. A one‐dimensional, coupled geochemical/solute transport simulation is presented in which redox zones evolve dynamically in time and space. The compartmentalized solute transport (COMPTRAN) model described in this paper enables the development of redox zones to be simulated under both kinetic and thermodynamic constraints. The modular design of COMPTRAN facilitates the use of many different, preexisting solute transport and

Experimental Study of Airborne Contaminant Migration in an Aircraft Cabin Model

Science.gov (United States)

Poussou, Stephane; Sojka, Paul; Plesniak, Michael

2007-11-01

The cabin air ventilation system in wide body jetliners is designed to provide a comfortable and controlled environment for passengers. Inside the cabin, the air flows continuously from overhead vents into sidewall exhausts, forming a circular pattern designed to minimize cross flow between adjacent seat rows. However, spreading of gaseous or particulate contaminants is possible when flight attendants or passengers walk along an aisle, perturbing the ventilation flow. Such unsteady flow perturbations have been found to alter the cabin air distribution and quality. A better fundamental understanding of the turbulent transport phenomena is needed to improve air quality monitoring and control systems and to validate numerical simulations. The velocity field in a 15:1 model of a simplified aircraft cabin is probed to investigate the wake of a rectangular body moving through a steady two-dimensional flow at a Reynolds number (based on body height) of the order of 50,000. Planar Laser Induced Fluorescence is used to visualize wake structure and scalar contaminant transport. The interaction between the wake and the ventilation flow is measured with PIV. The data are compared to numerical studies of cabin airflows in the literature.

Contamination of an arctic terrestrial food web with marine-derived persistent organic pollutants transported by breeding seabirds

International Nuclear Information System (INIS)

Choy, Emily S.; Kimpe, Linda E.; Mallory, Mark L.; Smol, John P.; Blais, Jules M.

2010-01-01

At Cape Vera, Devon Island (Nunavut, Canada), a colony of northern fulmars (Fulmarus glacialis) concentrates and releases contaminants through their guano to the environment. We determined whether persistent organic pollutants (POPs) from seabirds were transferred to coastal food webs. Snow buntings (Plectrophenax nivalis) were the most contaminated species, with ΣPCB and ΣDDT (mean: 168, 106 ng/g ww) concentrations surpassing environmental guidelines for protecting wildlife. When examined collectively, PCB congeners and DDT in jewel lichen (Xanthoria elegans) were lower in samples taken farther from the seabird colony, and increased with increasing δ 15 N values. However, only concentrations of p'p-DDE:ΣDDT and PCB-95 were significantly correlated inversely with distance from the seabird cliffs. Linkages between marine-derived POPs and their concentrations in terrestrial mammals were less clear. Our study provides novel contaminant data for these species and supports biovector transport as a source of organic contaminants to certain components of the terrestrial food web. - This study provides evidence of contaminant transport by seabirds to a coastal Arctic food web.

Contamination of an arctic terrestrial food web with marine-derived persistent organic pollutants transported by breeding seabirds

Energy Technology Data Exchange (ETDEWEB)

Choy, Emily S., E-mail: echoy087@uottawa.c [Program for Chemical and Environmental Toxicology, Department of Biology, University of Ottawa, Ottawa, ON, K1N 6N5 (Canada); Kimpe, Linda E., E-mail: linda.kimpe@uottawa.c [Program for Chemical and Environmental Toxicology, Department of Biology, University of Ottawa, Ottawa, ON, K1N 6N5 (Canada); Mallory, Mark L., E-mail: mark.mallory@ec.gc.c [Canadian Wildlife Service, Environment Canada, Iqaluit, NU, X0A 0H0 (Canada); Smol, John P., E-mail: smolj@queensu.c [Paleoecological Environmental Assessment and Research Lab (PEARL), Department of Biology, Queen' s University, Kingston, ON, K7L 3N6 (Canada); Blais, Jules M., E-mail: jules.blais@uottawa.c [Program for Chemical and Environmental Toxicology, Department of Biology, University of Ottawa, Ottawa, ON, K1N 6N5 (Canada)

2010-11-15

At Cape Vera, Devon Island (Nunavut, Canada), a colony of northern fulmars (Fulmarus glacialis) concentrates and releases contaminants through their guano to the environment. We determined whether persistent organic pollutants (POPs) from seabirds were transferred to coastal food webs. Snow buntings (Plectrophenax nivalis) were the most contaminated species, with {Sigma}PCB and {Sigma}DDT (mean: 168, 106 ng/g ww) concentrations surpassing environmental guidelines for protecting wildlife. When examined collectively, PCB congeners and DDT in jewel lichen (Xanthoria elegans) were lower in samples taken farther from the seabird colony, and increased with increasing {delta}{sup 15}N values. However, only concentrations of p'p-DDE:{Sigma}DDT and PCB-95 were significantly correlated inversely with distance from the seabird cliffs. Linkages between marine-derived POPs and their concentrations in terrestrial mammals were less clear. Our study provides novel contaminant data for these species and supports biovector transport as a source of organic contaminants to certain components of the terrestrial food web. - This study provides evidence of contaminant transport by seabirds to a coastal Arctic food web.

An analytical model for predicting transport in a coupled vadose/phreatic system

International Nuclear Information System (INIS)

Tomasko, D.

1997-05-01

A simple analytical model is presented for predicting the transport of a contaminant in both the unsaturated (vadose) and saturated (phreatic) zones following a surficial spill. The model incorporates advection, dispersion, adsorption, and first-order decay in both zones and couples the transport processes at the water table. The governing equation is solved by using the method of Laplace transforms, with numerical inversion of the Laplace space equation for concentration. Because of the complexity of the functional form for the Laplace space solution, a numerical methodology using the real and imaginary parts of a Fourier series was implemented. To reduce conservatism in the model, dilution at the water table was also included. Verification of the model is demonstrated by its ability to reproduce the source history at the surface and to replicate appropriate one-dimensional transport through either the vadose or phreatic zone. Because of its simplicity and lack of detailed input data requirements, the model is recommended for scoping calculations

CAirTOX, An inter-media transfer model for assessing indirect exposures to hazardous air contaminants

International Nuclear Information System (INIS)

McKone, T.E.

1994-01-01

Risk assessment is a quantitative evaluation of information on potential health hazards of environmental contaminants and the extent of human exposure to these contaminants. As applied to toxic chemical emissions to air, risk assessment involves four interrelated steps. These are (1) determination of source concentrations or emission characteristics, (2) exposure assessment, (3) toxicity assessment, and (4) risk characterization. These steps can be carried out with assistance from analytical models in order to estimate the potential risk associated with existing and future releases. CAirTOX has been developed as a spreadsheet model to assist in making these types of calculations. CAirTOX follows an approach that has been incorporated into the CalTOX model, which was developed for the California Department of Toxic Substances Control, With CAirTOX, we can address how contaminants released to an air basin can lead to contamination of soil, food, surface water, and sediments. The modeling effort includes a multimedia transport and transformation model, exposure scenario models, and efforts to quantify uncertainty in multimedia, multiple-pathway exposure assessments. The capacity to explicitly address uncertainty has been incorporated into the model in two ways. First, the spreadsheet form of the model makes it compatible with Monte-Carlo add-on programs that are available for uncertainty analysis. Second, all model inputs are specified in terms of an arithmetic mean and coefficient of variation so that uncertainty analyses can be carried out

Zero-tension lysimeters: An improved design to monitor colloid-facilitated contaminant transport in the vadose zone

International Nuclear Information System (INIS)

Thompson, M.L.; Scharf, R.L.; Shang, C.

1995-01-01

There is increasing evidence that mobile colloids facilitate the long-distance transport of contaminants. The mobility of fine particles and macromolecules has been linked to the movement of actinides, organic contaminants, and heavy metals through soil. Direct evidence for colloid mobility includes the presence of humic materials in deep aquifers as well as coatings of accumulated clay, organic matter, or sesquioxides on particle or aggregate surfaces in subsoil horizons of many soils. The potential for colloid-facilitated transport of contaminants from hazardous-waste sites requires adequate monitoring before, during, and after in-situ remediation treatments. Zero-tension lysimeters (ZTLs) are especially appropriate for sampling water as it moves through saturated soil, although some unsaturated flow events may be sampled as well. Because no ceramic barrier or fiberglass wick is involved to maintain tension on the water (as is the case with other lysimeters), particles suspended in the water as well as dissolved species may be sampled with ZTLs. In this report, a ZTL design is proposed that is more suitable for monitoring colloid-facilitated contaminant migration. The improved design consists of a cylinder made of polycarbonate or polytetrafluoroethylene (PTFE) that is placed below undisturbed soil material. In many soils, a hydraulically powered tube may be used to extract an undisturbed core of soil before placement of the lysimeter. In those cases, the design has significant advantages over conventional designs with respect to simplicity and speed of installation. Therefore, it will allow colloid-facilitated transport of contaminants to be monitored at more locations at a given site

Long Length Contaminated Equipment Retrieval System Receiver Trailer and Transport Trailer Operations and Maintenance Manual

International Nuclear Information System (INIS)

DALE, R.N.

2000-01-01

A system to accommodate the removal of long-length contaminated equipment (LLCE) from Hanford underground radioactive waste storage tanks was designed, procured, and demonstrated, via a project activity during the 1990s. The system is the Long Length Contaminated Equipment Removal System (LLCERS). LLCERS will be maintained and operated by Tank Farms Engineering and Operations organizations and other varied projects having a need for the system. The responsibility for the operation and maintenance of the LLCERS Receiver Trailer (RT) and Transport Trailer (TT) resides with the RPP Characterization Project Operations organization. The purpose of this document is to provide vendor supplied operating and maintenance (O and M) information for the RT and TT in a readily retrievable form. This information is provided this way instead of in a vendor information (VI) file to maintain configuration control of the operations baseline as described in RPP-6085, ''Configuration Management Plan for Long Length Contaminated Equipment Receiver and Transport Trailers''. Additional Operations Baseline documents are identified in RPP-6085

Modeling Aeolian Transport of Contaminated Sediments at Los Alamos National Laboratory, Technical Area 54, Area G: Sensitivities to Succession, Disturbance, and Future Climate

Energy Technology Data Exchange (ETDEWEB)

Whicker, Jeffrey J. [Los Alamos National Laboratory; Kirchner, Thomas B. [New Mexico State University; Breshears, David D. [University of Arizona; Field, Jason P. [University of Arizona

2012-03-27

The Technical Area 54 (TA-54) Area G disposal facility is used for the disposal of radioactive waste at Los Alamos National Laboratory (LANL). U.S. Department of Energy (DOE) Order 435.1 (DOE, 2001) requires that radioactive waste be managed in a manner that protects public health and safety and the environment. In compliance with that requirement, DOE field sites must prepare and maintain site-specific radiological performance assessments for facilities that receive waste after September 26, 1988. Sites are also required to conduct composite analyses for facilities that receive waste after this date; these analyses account for the cumulative impacts of all waste that has been (and will be) disposed of at the facilities and other sources of radioactive material that may interact with these facilities. LANL issued Revision 4 of the Area G performance assessment and composite analysis in 2008. In support of those analyses, vertical and horizontal sediment flux data were collected at two analog sites, each with different dominant vegetation characteristics, and used to estimate rates of vertical resuspension and wind erosion for Area G. The results of that investigation indicated that there was no net loss of soil at the disposal site due to wind erosion, and suggested minimal impacts of wind on the long-term performance of the facility. However, that study did not evaluate the potential for contaminant transport caused by the horizontal movement of soil particles over long time frames. Since that time, additional field data have been collected to estimate wind threshold velocities for initiating sediment transport due to saltation and rates of sediment transport once those thresholds are reached. Data such as these have been used in the development of the Vegetation Modified Transport (VMTran) model. This model is designed to estimate patterns and long-term rates of contaminant redistribution caused by winds at the site, taking into account the impacts of plant

Modeling Aeolian Transport of Contaminated Sediments at Los Alamos National Laboratory, Technical Area 54, Area G: Sensitivities to Succession, Disturbance, and Future Climate

International Nuclear Information System (INIS)

Whicker, Jeffrey J.; Kirchner, Thomas B.; Breshears, David D.; Field, Jason P.

2012-01-01

The Technical Area 54 (TA-54) Area G disposal facility is used for the disposal of radioactive waste at Los Alamos National Laboratory (LANL). U.S. Department of Energy (DOE) Order 435.1 (DOE, 2001) requires that radioactive waste be managed in a manner that protects public health and safety and the environment. In compliance with that requirement, DOE field sites must prepare and maintain site-specific radiological performance assessments for facilities that receive waste after September 26, 1988. Sites are also required to conduct composite analyses for facilities that receive waste after this date; these analyses account for the cumulative impacts of all waste that has been (and will be) disposed of at the facilities and other sources of radioactive material that may interact with these facilities. LANL issued Revision 4 of the Area G performance assessment and composite analysis in 2008. In support of those analyses, vertical and horizontal sediment flux data were collected at two analog sites, each with different dominant vegetation characteristics, and used to estimate rates of vertical resuspension and wind erosion for Area G. The results of that investigation indicated that there was no net loss of soil at the disposal site due to wind erosion, and suggested minimal impacts of wind on the long-term performance of the facility. However, that study did not evaluate the potential for contaminant transport caused by the horizontal movement of soil particles over long time frames. Since that time, additional field data have been collected to estimate wind threshold velocities for initiating sediment transport due to saltation and rates of sediment transport once those thresholds are reached. Data such as these have been used in the development of the Vegetation Modified Transport (VMTran) model. This model is designed to estimate patterns and long-term rates of contaminant redistribution caused by winds at the site, taking into account the impacts of plant

Review of hydrodynamic and transport models and data collected near the mid-Atlantic low-level radioactive waste disposal sites

International Nuclear Information System (INIS)

Onishi, Y.; Hibler, L.F.; Sherwood, C.R.

1987-08-01

The objectives of this study were to (1) briefly review and evaluate available simulation models that may be used to predict the distribution of low-level radioactive waste (LLW) from the 2800-m and 3800-m Low Level Radioactive Disposal Sites in the Mid-Atlantic Continental Slope and Rise on a regional (a few hundred kilometers square) scale, (2) identify pertinent physical, biological, and geological oceanographic data in or near those LLW disposal sites, and (3) determine minimum data requirements for regional modeling. With suitable model modifications such as turbulence closure, enhanced sediment transport, radionuclide transport, and/or curvilinear coordinate system setup, the FLESCOT model, the FLOWER model, and Blumberg's model would be appropriate candidates for regional radionuclide modeling to predict the transport and dispersion of LLW disposed in the 2800-m and 3800-m sites. Although the RMA10 model does not incorporate a turbulence closure scheme, this model, with some modifications, is also an appropriate candidate for regional radionuclide modeling. FLESCOT is currently the only one that solves distributions of flow, turbulence, salinity, water temperature, sediments, dissolved contaminants, and sediment-sorbed contaminants. Thus, the FLESCOT model is recommended to be applied to the 2800-m and 3800-m sites to predict the transport and accumulation of LLW on a regional scale

Contamination Analysis Tools

Science.gov (United States)

Brieda, Lubos

2015-01-01

This talk presents 3 different tools developed recently for contamination analysis:HTML QCM analyzer: runs in a web browser, and allows for data analysis of QCM log filesJava RGA extractor: can load in multiple SRS.ana files and extract pressure vs. time dataC++ Contamination Simulation code: 3D particle tracing code for modeling transport of dust particulates and molecules. Uses residence time to determine if molecules stick. Particulates can be sampled from IEST-STD-1246 and be accelerated by aerodynamic forces.

THE INTERPLAY BETWEEN GEOCHEMICAL REACTIONS AND ADVECTION-DISPERSION IN CONTAMINANT TRANSPORT AT A URANIUM MILL TAILINGS SITE

Science.gov (United States)

It is well known that the fate and transport of contaminants in the subsurface are controlled by complex processes including advection, dispersion-diffusion, and chemical reactions. However, the interplay between the physical transport processes and chemical reactions, and their...

Sources of Salmonella on broiler carcasses during transportation and processing: modes of contamination and methods of control.

Science.gov (United States)

Corry, Janet E L; Allen, V M; Hudson, W R; Breslin, M F; Davies, R H

2002-01-01

The prevalence and types of salmonella in broiler chickens during transportation and during slaughter and dressing were studied. This was part of a comprehensive investigation of salmonellas in two UK poultry companies, which aimed to find the origins and mechanisms of salmonella contamination. Salmonellas were isolated using cultural methods. Serovars of Salmonella detected during rearing were usually also found in a small proportion of birds on the day of slaughter and on the carcasses at various points during processing. There was little evidence of salmonellas spreading to large numbers of carcasses during processing. Many serovars found in the feedmills or hatcheries were also detected in the birds during rearing and/or slaughter. Transport crates were contaminated with salmonellas after washing and disinfection. Prevalence of salmonellas fell in the two companies during this survey. A small number of serovars predominated in the processing plants of each company. These serovars originated from the feed mills. Reasons for transport crate contamination were: (1) inadequate cleaning, resulting in residual faecal soiling; (2) disinfectant concentration and temperature of disinfectant too low; (3) contaminated recycled flume water used to soak the crates. Efforts to control salmonella infection in broilers need to concentrate on crate cleaning and disinfection and hygiene in the feed mills.

BLT-MS (Breach, Leach, and Transport -- Multiple Species) data input guide. A computer model for simulating release of contaminants from a subsurface low-level waste disposal facility

International Nuclear Information System (INIS)

Sullivan, T.M.; Kinsey, R.R.; Aronson, A.; Divadeenam, M.; MacKinnon, R.J.

1996-11-01

The BLT-MS computer code has been developed, implemented, and tested. BLT-MS is a two-dimensional finite element computer code capable of simulating the time evolution of concentration resulting from the time-dependent release and transport of aqueous phase species in a subsurface soil system. BLT-MS contains models to simulate the processes (water flow, container degradation, waste form performance, transport, and radioactive production and decay) most relevant to estimating the release and transport of contaminants from a subsurface disposal system. Water flow is simulated through tabular input or auxiliary files. Container degradation considers localized failure due to pitting corrosion and general failure due to uniform surface degradation processes. Waste form performance considers release to be limited by one of four mechanisms: rinse with partitioning, diffusion, uniform surface degradation, or solubility. Radioactive production and decay in the waste form are simulated. Transport considers the processes of advection, dispersion, diffusion, radioactive production and decay, reversible linear sorption, and sources (waste forms releases). To improve the usefulness of BLT-MS a preprocessor, BLTMSIN, which assists in the creation of input files, and a post-processor, BLTPLOT, which provides a visual display of the data have been developed. This document reviews the models implemented in BLT-MS and serves as a guide to creating input files for BLT-MS

BLT-MS (Breach, Leach, and Transport -- Multiple Species) data input guide. A computer model for simulating release of contaminants from a subsurface low-level waste disposal facility

Energy Technology Data Exchange (ETDEWEB)

Sullivan, T.M.; Kinsey, R.R.; Aronson, A.; Divadeenam, M. [Brookhaven National Lab., Upton, NY (United States); MacKinnon, R.J. [Brookhaven National Lab., Upton, NY (United States)]|[Ecodynamics Research Associates, Inc., Albuquerque, NM (United States)

1996-11-01

The BLT-MS computer code has been developed, implemented, and tested. BLT-MS is a two-dimensional finite element computer code capable of simulating the time evolution of concentration resulting from the time-dependent release and transport of aqueous phase species in a subsurface soil system. BLT-MS contains models to simulate the processes (water flow, container degradation, waste form performance, transport, and radioactive production and decay) most relevant to estimating the release and transport of contaminants from a subsurface disposal system. Water flow is simulated through tabular input or auxiliary files. Container degradation considers localized failure due to pitting corrosion and general failure due to uniform surface degradation processes. Waste form performance considers release to be limited by one of four mechanisms: rinse with partitioning, diffusion, uniform surface degradation, or solubility. Radioactive production and decay in the waste form are simulated. Transport considers the processes of advection, dispersion, diffusion, radioactive production and decay, reversible linear sorption, and sources (waste forms releases). To improve the usefulness of BLT-MS a preprocessor, BLTMSIN, which assists in the creation of input files, and a post-processor, BLTPLOT, which provides a visual display of the data have been developed. This document reviews the models implemented in BLT-MS and serves as a guide to creating input files for BLT-MS.

MaSTiS, microorganism and solute transport in streams, model documentation and user manual

Science.gov (United States)

In-stream fate and transport of solutes and microorganisms need to be understood to evaluate suitability of waters for agricultural, recreational, and household uses and eventually minimize surface water contamination. Concerns over safety of this water resulted in development of predictive models f...

ARSENIC CONTAMINATION IN GROUNDWATER: A STATISTICAL MODELING

Directory of Open Access Journals (Sweden)

Palas Roy

2013-01-01

Full Text Available High arsenic in natural groundwater in most of the tubewells of the Purbasthali- Block II area of Burdwan district (W.B, India has recently been focused as a serious environmental concern. This paper is intending to illustrate the statistical modeling of the arsenic contaminated groundwater to identify the interrelation of that arsenic contain with other participating groundwater parameters so that the arsenic contamination level can easily be predicted by analyzing only such parameters. Multivariate data analysis was done with the collected groundwater samples from the 132 tubewells of this contaminated region shows that three variable parameters are significantly related with the arsenic. Based on these relationships, a multiple linear regression model has been developed that estimated the arsenic contamination by measuring such three predictor parameters of the groundwater variables in the contaminated aquifer. This model could also be a suggestive tool while designing the arsenic removal scheme for any affected groundwater.

Phase I Contaminant Transport Parameters for the Groundwater Flow and Contaminant Transport Model of Corrective Action Unit 99: Rainier Mesa/Shoshone Mountain, Nevada Test Site, Nye County, Nevada, Revision 1

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.

Topsoil N-budget model in orchard farming to evaluate groundwater nitrate contamination

Science.gov (United States)

Wijayanti, Yureana; Budihardjo, Kadarwati; Sakamoto, Yasushi; Setyandito, Oki

2017-12-01

A small scale field research was conducted in an orchard farming area in Kofu, Japan, where nitrate contamination was found in groundwater. The purpose of assessing the leaching of nitrate in this study is to understand the transformation and transport process of N-source in topsoil that leads to nitrate contamination of groundwater. In order to calculate N-budget in the soil, the model was utilized to predict the nitrogen leaching. In this res earch, the N-budget model was modified to evaluate influence of precipitation and application pattern of fertilizer and manure compost. The result shows that at the time before the addition of manure compost and fertilizer, about 75% of fertilizer leach from topsoil. Every month, the average remaining nitrate in soil from fertilizer and manure compost are 22% and 50%, respectively. The accumulation of this monthly manure compost nitrate, which stored in soil, should be carefully monitored. It could become the potential source of nitrate leaching to groundwater in the future.

Impact of runoff infiltration on contaminant accumulation and transport in the soil/filter media of Sustainable Urban Drainage Systems: A literature review.

Science.gov (United States)

Tedoldi, Damien; Chebbo, Ghassan; Pierlot, Daniel; Kovacs, Yves; Gromaire, Marie-Christine

2016-11-01

The increasing use of Sustainable Urban Drainage Systems (SUDS) for stormwater management raises some concerns about the fate of ubiquitous runoff micropollutants in soils and their potential threat to groundwater. This question may be addressed either experimentally, by sampling and analyzing SUDS soil after a given operating time, or with a modeling approach to simulate the fate and transport of contaminants. After briefly reminding the processes responsible for the retention, degradation, or leaching of several urban-sourced contaminants in soils, this paper presents the state of the art about both experimental and modeling assessments. In spite of noteworthy differences in the sampling protocols, the soil parameters chosen as explanatory variables, and the methods used to evaluate the site-specific initial concentrations, most investigations undoubtedly evidenced a significant accumulation of metals and/or hydrocarbons in SUDS soils, which in the majority of the cases appears to be restricted to the upper 10 to 30cm. These results may suggest that SUDS exhibit an interesting potential for pollution control, but antinomic observations have also been made in several specific cases, and the inter-site concentration variability is still difficult to appraise. There seems to be no consensus regarding the level of complexity to be used in models. However, the available data deriving from experimental studies is generally limited to the contamination profiles and a few parameters of the soil, as a result of which "complex" models (including colloid-facilitated transport for example) appear to be difficult to validate before using them for predictive evaluations. Copyright © 2016 Elsevier B.V. All rights reserved.

Deterministic sensitivity analysis for the numerical simulation of contaminants transport; Analyse de sensibilite deterministe pour la simulation numerique du transfert de contaminants

Energy Technology Data Exchange (ETDEWEB)

Marchand, E

2007-12-15

The questions of safety and uncertainty are central to feasibility studies for an underground nuclear waste storage site, in particular the evaluation of uncertainties about safety indicators which are due to uncertainties concerning properties of the subsoil or of the contaminants. The global approach through probabilistic Monte Carlo methods gives good results, but it requires a large number of simulations. The deterministic method investigated here is complementary. Based on the Singular Value Decomposition of the derivative of the model, it gives only local information, but it is much less demanding in computing time. The flow model follows Darcy's law and the transport of radionuclides around the storage site follows a linear convection-diffusion equation. Manual and automatic differentiation are compared for these models using direct and adjoint modes. A comparative study of both probabilistic and deterministic approaches for the sensitivity analysis of fluxes of contaminants through outlet channels with respect to variations of input parameters is carried out with realistic data provided by ANDRA. Generic tools for sensitivity analysis and code coupling are developed in the Caml language. The user of these generic platforms has only to provide the specific part of the application in any language of his choice. We also present a study about two-phase air/water partially saturated flows in hydrogeology concerning the limitations of the Richards approximation and of the global pressure formulation used in petroleum engineering. (author)

A SCREENING MODEL FOR SIMULATING DNAPL FLOW AND TRANSPORT IN POROUS MEDIA: THEORETICAL DEVELOPMENT

Science.gov (United States)

There exists a need for a simple tool that will allow us to analyze a DNAPL contamination scenario from free-product release to transport of soluble constituents to downgradient receptor wells. The objective of this manuscript is to present the conceptual model and formulate the ...

Assessment of the contamination of drinking water supply wells by pesticides from surface water resources using a finite element reactive transport model and global sensitivity analysis techniques

DEFF Research Database (Denmark)

Malaguerra, Flavio; Albrechtsen, Hans-Jørgen; Binning, Philip John

2013-01-01

A reactive transport model is employed to evaluate the potential for contamination of drinking water wells by surface water pollution. The model considers various geologic settings, includes sorption and degradation processes and is tested by comparison with data from a tracer experiment where...... fluorescein dye injected in a river is monitored at nearby drinking water wells. Three compounds were considered: an older pesticide MCPP (Mecoprop) which is mobile and relatively persistent, glyphosate (Roundup), a newer biodegradable and strongly sorbing pesticide, and its degradation product AMPA. Global...... sensitivity analysis using the Morris method is employed to identify the dominant model parameters. Results show that the characteristics of clay aquitards (degree of fracturing and thickness), pollutant properties and well depths are crucial factors when evaluating the risk of drinking water well...

Fate and transport of mercury in soil systems : a numerical model in HP1 and sensitivity analysis

Science.gov (United States)

Leterme, Bertrand; Jacques, Diederik

2013-04-01

Mercury (Hg) poses threats for human health and the environment, notably due to its persistence and its ability to bioaccumulate in ecosystems. Anthropogenic activities are major contributors of mercury release to soils. Main sources of contamination include manufacturing (chlor-alkali plants, manometer spill), mine tailings from mercury, gold and silver mining industries, wood preservation. The objective of this study was to develop a reactive transport model for simulating mercury fate and transport in the unsaturated zone, and to gain insight in the fate and transport of Hg following anthropogenic soil contamination. The present work is done in the framework of the IMaHg project, which aims at providing recommendations to improve management of sites contaminated by mercury within the SNOWMAN funding framework. A model of mercury fate and transport in soil systems was developed using the reactive transport code HP1 (Jacques and Šimůnek, 2010). The geochemical database THERMODDEM (Blanc et al., 2012) is used, augmented with some speciation data from (Skyllberg, 2012). The main processes accounted for in the model are : Hg aqueous speciation (including complexation with dissolved organic matter (DOM) - humic and fulvic acids, and thiol groups), Hg sorption to solid organic matter (SOM), dissolution of solid phase Hg (e.g. cinnabar HgS(s)), dissolution of Hg non-aqueous liquid phase (NAPL), sunlight-driven Hg(II) reduction to Hg(0), Hg(0) diffusion in the gas phase and volatilization, DOM sorption to soil minerals. Colloid facilitated transport is implicitly accounted for by solute transport of Hg-DOM complexes. Because we focused on soil systems having a high Hg contamination, some processes showing relatively smaller Hg fluxes could be neglected such as vegetation uptake and atmospheric wet and dry deposition. NAPL migration and entrapment is not modelled, as pollution is assumed to be historical and only residual NAPL to be present. Mercury methylation and

Modeling subsurface contamination at Fernald

International Nuclear Information System (INIS)

Jones, B.W.; Flinn, J.C.; Ruwe, P.R.

1994-01-01

The Department of Energy's Fernald site is located about 20 miles northwest of Cincinnati. Fernald produced refined uranium metal products from ores between 1953 and 1989. The pure uranium was sent to other DOE sites in South Carolina, Tennessee, Colorado,and Washington in support of the nation's strategic defense programs. Over the years of large-scale uranium production, contamination of the site's soil and groundwater occurred.The contamination is of particular concern because the Fernald site is located over the Great Miami Aquifer, a designated sole-source drinking water aquifer. Contamination of the aquifer with uranium was found beneath the site, and migration of the contamination had occurred well beyond the site's southern boundary. As a result, Fernald was placed on the National Priorities (CERCLA/Superfund) List in 1989. Uranium production at the site ended in 1989,and Fernald's mission has been changed to one of environmental restoration. This paper presents information about computerized modeling of subsurface contamination used for the environmental restoration project at Fernald

Long Length Contaminated Equipment Retrieval System Receiver Trailer and Transport Trailer Operations and Maintenance Manual

Energy Technology Data Exchange (ETDEWEB)

DALE, R.N.

2000-05-01

A system to accommodate the removal of long-length contaminated equipment (LLCE) from Hanford underground radioactive waste storage tanks was designed, procured, and demonstrated, via a project activity during the 1990s. The system is the Long Length Contaminated Equipment Removal System (LLCERS). LLCERS will be maintained and operated by Tank Farms Engineering and Operations organizations and other varied projects having a need for the system. The responsibility for the operation and maintenance of the LLCERS Receiver Trailer (RT) and Transport Trailer (TT) resides with the RPP Characterization Project Operations organization. The purpose of this document is to provide vendor supplied operating and maintenance (O & M) information for the RT and TT in a readily retrievable form. This information is provided this way instead of in a vendor information (VI) file to maintain configuration control of the operations baseline as described in RPP-6085, ''Configuration Management Plan for Long Length Contaminated Equipment Receiver and Transport Trailers''. Additional Operations Baseline documents are identified in RPP-6085.

Modeling the potential role of a forest ecosystem in phytostabilization and phytoextraction of 90Sr at a contaminated watershed

International Nuclear Information System (INIS)

Garten, C.T. Jr.

1999-01-01

The behavior of 90 Sr at forest sites in the White Oak Creek watershed, near Oak Ridge, Tennessee, was simulated with a simple, site-specific, multicompartment model that linked biomass and element cycling dynamics. The model was used to predict the role of forest cover in mitigating hydrologic losses of 90 Sr from contaminated soils (i.e. phytostabilization) under conditions where contaminant transport is governed mainly by shallow subsurface flow. The model was also used to predict the removal of 90 Sr from soil (i.e. phytoextraction) through the growth and harvest of short rotation woody crops over a period of 30 years. Simulations with the model indicated that (1) forest preservation on the watershed is a form of phytostabilization because forest cover helps to minimize hydrologic losses of 90 Sr and (2) an attempt to significantly reduce amounts of 90 Sr in soil through phytoextraction would be unsuccessful. Over a period of 30 years, and under various management strategies, the model predicted that 90 Sr initially present in soil at a contaminated site was lost through hydrologic transport and <53% was lost by radioactive decay. Phytostabilization may be important in the management of radioactive land when issues like waste minimization and pollution prevention affect the selection of technologies to be used in environmental restoration. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

Application of HEC-RAS water quality model to estimate contaminant spreading in small stream

Energy Technology Data Exchange (ETDEWEB)

Halaj, Peter; Bárek, Viliam; Halajová, Anna Báreková; Halajová, Denisa [Slovak University of Agriculture in Nitra, Nitra (Slovakia)

2013-07-01

The paper presents study of some aspects of HEC-RAS water quality model connected to simulation of contaminant transport in small stream. Authors mainly focused on one of the key tasks in process of pollutant transport modelling in streams - determination of the dispersion characteristics represented by longitudinal dispersion coefficient D. Different theoretical and empirical formulas have been proposed for D value determination and they have revealed that the coefficient is variable parameter that depends on hydraulic and morphometric characteristics of the stream reaches. Authors compare the results of several methods of coefficient D assessment, assuming experimental data obtained by tracer studies and compare them with results optimized by HEC-RAS water quality model. The analyses of tracer study and computation outputs allow us to outline the important aspects of longitudinal dispersion coefficient set up in process of the HEC-RAS model use. Key words: longitudinal dispersion coefficient, HEC-RAS, water quality modeling.

Metropol: A computer code for the simulation of transport of contaminants with groundwater

International Nuclear Information System (INIS)

Sauter, F.J.; Hassanizadeh, S.M.; Leijnse, A.; Glasbergen, P.; Slot, A.F.M.

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 flow and transport are described as well as the mathematical techniques used to solve these equations. Pre-processing facilities for mesh generation and post-processing facilities such as particle tracking are also discussed. This work was part of the Community Mirage project Second phase, research area Calculation tools

A reactive transport modelling approach to assess the leaching potential of hydraulic fracturing fluids associated with coal seam gas extraction

Science.gov (United States)

Mallants, Dirk; Simunek, Jirka; Gerke, Kirill

2015-04-01

Coal Seam Gas production generates large volumes of "produced" water that may contain compounds originating from the use of hydraulic fracturing fluids. Such produced water also contains elevated concentrations of naturally occurring inorganic and organic compounds, and usually has a high salinity. Leaching of produced water from storage ponds may occur as a result of flooding or containment failure. Some produced water is used for irrigation of specific crops tolerant to elevated salt levels. These chemicals may potentially contaminate soil, shallow groundwater, and groundwater, as well as receiving surface waters. This paper presents an application of scenario modelling using the reactive transport model for variably-saturated media HP1 (coupled HYDRUS-1D and PHREEQC). We evaluate the fate of hydraulic fracturing chemicals and naturally occurring chemicals in soil as a result of unintentional release from storage ponds or when produced water from Coal Seam Gas operations is used in irrigation practices. We present a review of exposure pathways and relevant hydro-bio-geo-chemical processes, a collation of physico-chemical properties of organic/inorganic contaminants as input to a set of generic simulations of transport and attenuation in variably saturated soil profiles. We demonstrate the ability to model the coupled processes of flow and transport in soil of contaminants associated with hydraulic fracturing fluids and naturally occurring contaminants.

Techniques to better understand complex epikarst hydrogeology and contaminant transport in telogenetic karst settings

Science.gov (United States)

The movement of autogenic recharge through the shallow epikarstic zone in soil-mantled karst aquifers is important in understanding recharge areas and rates, groundwater storage, and contaminant transport processes. The groundwater flow in agricultural karst areas, such as Kentucky’s Pennyroyal Plat...

Conceptual model for transport processes in the Culebra Dolomite Member, Rustler Formation

International Nuclear Information System (INIS)

Holt, R.M.

1997-08-01

The Culebra Dolomite Member of the Rustler Formation represents a possible pathway for contaminants from the Waste Isolation Pilot Plant underground repository to the accessible environment. The geologic character of the Culebra is consistent with a double-porosity, multiple-rate model for transport in which the medium is conceptualized as consisting of advective porosity, where solutes are carried by the groundwater flow, and fracture-bounded zones of diffusive porosity, where solutes move through slow advection or diffusion. As the advective travel length or travel time increases, the nature of transport within a double-porosity medium changes. This behavior is important for chemical sorption, because the specific surface area per unit mass of the diffusive porosity is much greater than in the advective porosity. Culebra transport experiments conducted at two different length scales show behavior consistent with a multiple-rate, double-porosity conceptual model for Culebra transport. Tracer tests conducted on intact core samples from the Culebra show no evidence of significant diffusion, suggesting that at the core scale the Culebra can be modeled as a single-porosity medium where only the advective porosity participates in transport. Field tracer tests conducted in the Culebra show strong double-porosity behavior that is best explained using a multiple-rate model

Biochemical transport modeling, estimation, and detection in realistic environments

Science.gov (United States)

Ortner, Mathias; Nehorai, Arye

2006-05-01

Early detection and estimation of the spread of a biochemical contaminant are major issues for homeland security applications. We present an integrated approach combining the measurements given by an array of biochemical sensors with a physical model of the dispersion and statistical analysis to solve these problems and provide system performance measures. We approximate the dispersion model of the contaminant in a realistic environment through numerical simulations of reflected stochastic diffusions describing the microscopic transport phenomena due to wind and chemical diffusion using the Feynman-Kac formula. We consider arbitrary complex geometries and account for wind turbulence. Localizing the dispersive sources is useful for decontamination purposes and estimation of the cloud evolution. To solve the associated inverse problem, we propose a Bayesian framework based on a random field that is particularly powerful for localizing multiple sources with small amounts of measurements. We also develop a sequential detector using the numerical transport model we propose. Sequential detection allows on-line analysis and detecting wether a change has occurred. We first focus on the formulation of a suitable sequential detector that overcomes the presence of unknown parameters (e.g. release time, intensity and location). We compute a bound on the expected delay before false detection in order to decide the threshold of the test. For a fixed false-alarm rate, we obtain the detection probability of a substance release as a function of its location and initial concentration. Numerical examples are presented for two real-world scenarios: an urban area and an indoor ventilation duct.

Interaction of environmental contaminants with zebrafish organic anion transporting polypeptide, Oatp1d1 (Slco1d1)

Energy Technology Data Exchange (ETDEWEB)

Popovic, Marta; Zaja, Roko [Laboratory for Molecular Ecotoxicology, Division for Marine and Environmental Research, Rudjer Boskovic Institute, Bijenicka 54, 10 000 Zagreb (Croatia); Fent, Karl [University of Applied Sciences Northwestern Switzerland, School of Life Sciences, Gründenstrasse 40, CH-4132 Muttenz (Switzerland); Swiss Federal Institute of Technology (ETH Zürich), Department of Environmental System Sciences, Institute of Biogeochemistry and Pollution Dynamics, CH-8092 Zürich (Switzerland); Smital, Tvrtko, E-mail: smital@irb.hr [Laboratory for Molecular Ecotoxicology, Division for Marine and Environmental Research, Rudjer Boskovic Institute, Bijenicka 54, 10 000 Zagreb (Croatia)

2014-10-01

Polyspecific transporters from the organic anion transporting polypeptide (OATP/Oatp) superfamily mediate the uptake of a wide range of compounds. In zebrafish, Oatp1d1 transports conjugated steroid hormones and cortisol. It is predominantly expressed in the liver, brain and testes. In this study we have characterized the transport of xenobiotics by the zebrafish Oatp1d1 transporter. We developed a novel assay for assessing Oatp1d1 interactors using the fluorescent probe Lucifer yellow and transient transfection in HEK293 cells. Our data showed that numerous environmental contaminants interact with zebrafish Oatp1d1. Oatp1d1 mediated the transport of diclofenac with very high affinity, followed by high affinity towards perfluorooctanesulfonic acid (PFOS), nonylphenol, gemfibrozil and 17α-ethinylestradiol; moderate affinity towards carbaryl, diazinon and caffeine; and low affinity towards metolachlor. Importantly, many environmental chemicals acted as strong inhibitors of Oatp1d1. A strong inhibition of Oatp1d1 transport activity was found by perfluorooctanoic acid (PFOA), chlorpyrifos-methyl, estrone (E1) and 17β-estradiol (E2), followed by moderate to low inhibition by diethyl phthalate, bisphenol A, 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4 tetrahydronapthalene and clofibrate. In this study we identified Oatp1d1 as a first Solute Carrier (SLC) transporter involved in the transport of a wide range of xenobiotics in fish. Considering that Oatps in zebrafish have not been characterized before, our work on zebrafish Oatp1d1 offers important new insights on the understanding of uptake processes of environmental contaminants, and contributes to the better characterization of zebrafish as a model species. - Highlights: • We optimized a novel assay for determination of Oatp1d1 interactors • Oatp1d1 is the first SLC characterized fish xenobiotic transporter • PFOS, nonylphenol, diclofenac, EE2, caffeine are high affinity Oatp1d1substrates • PFOA, chlorpyrifos

Interaction of environmental contaminants with zebrafish organic anion transporting polypeptide, Oatp1d1 (Slco1d1)

International Nuclear Information System (INIS)

Popovic, Marta; Zaja, Roko; Fent, Karl; Smital, Tvrtko

2014-01-01

Polyspecific transporters from the organic anion transporting polypeptide (OATP/Oatp) superfamily mediate the uptake of a wide range of compounds. In zebrafish, Oatp1d1 transports conjugated steroid hormones and cortisol. It is predominantly expressed in the liver, brain and testes. In this study we have characterized the transport of xenobiotics by the zebrafish Oatp1d1 transporter. We developed a novel assay for assessing Oatp1d1 interactors using the fluorescent probe Lucifer yellow and transient transfection in HEK293 cells. Our data showed that numerous environmental contaminants interact with zebrafish Oatp1d1. Oatp1d1 mediated the transport of diclofenac with very high affinity, followed by high affinity towards perfluorooctanesulfonic acid (PFOS), nonylphenol, gemfibrozil and 17α-ethinylestradiol; moderate affinity towards carbaryl, diazinon and caffeine; and low affinity towards metolachlor. Importantly, many environmental chemicals acted as strong inhibitors of Oatp1d1. A strong inhibition of Oatp1d1 transport activity was found by perfluorooctanoic acid (PFOA), chlorpyrifos-methyl, estrone (E1) and 17β-estradiol (E2), followed by moderate to low inhibition by diethyl phthalate, bisphenol A, 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4 tetrahydronapthalene and clofibrate. In this study we identified Oatp1d1 as a first Solute Carrier (SLC) transporter involved in the transport of a wide range of xenobiotics in fish. Considering that Oatps in zebrafish have not been characterized before, our work on zebrafish Oatp1d1 offers important new insights on the understanding of uptake processes of environmental contaminants, and contributes to the better characterization of zebrafish as a model species. - Highlights: • We optimized a novel assay for determination of Oatp1d1 interactors • Oatp1d1 is the first SLC characterized fish xenobiotic transporter • PFOS, nonylphenol, diclofenac, EE2, caffeine are high affinity Oatp1d1substrates • PFOA, chlorpyrifos

Conceptual Site Model for Newark Bay—Hydrodynamics and Sediment Transport

Directory of Open Access Journals (Sweden)

Parmeshwar L. Shrestha

2014-02-01

Full Text Available A conceptual site model (CSM has been developed for the Newark Bay Study Area (NBSA as part of the Remedial Investigation/Feasibility Study (RI/FS for this New Jersey site. The CSM is an evolving document that describes the influence of physical, chemical and biological processes on contaminant fate and transport. The CSM is initiated at the start of a project, updated during site activities, and used to inform sampling and remediation planning. This paper describes the hydrodynamic and sediment transport components of the CSM for the NBSA. Hydrodynamic processes are influenced by freshwater inflows, astronomical forcing through two tidal straits, meteorological conditions, and anthropogenic activities such as navigational dredging. Sediment dynamics are driven by hydrodynamics, waves, sediment loading from freshwater sources and the tidal straits, sediment size gradation, sediment bed properties, and particle-to-particle interactions. Cohesive sediment transport is governed by advection, dispersion, aggregation, settling, consolidation, and erosion. Noncohesive sediment transport is governed by advection, dispersion, settling, armoring, and transport in suspension and along the bed. The CSM will inform the development and application of a numerical model that accounts for all key variables to adequately describe the NBSA’s historical, current, and future physical conditions.

Evidence for the 'grasshopper' effect and fractionation during long-range atmospheric transport of organic contaminants

International Nuclear Information System (INIS)

Gouin, T.; Mackay, D.; Jones, K.C.; Harner, T.; Meijer, S.N.

2004-01-01

Although there is indisputable evidence that long-range atmospheric transport (LRAT) of organic contaminants occurs on a global scale, uncertainties remain about the detailed mechanism and extent of this phenomenon as well as the physical-chemical properties which facilitate LRAT. In this study, we discuss how mass balance models and monitoring data can contribute to a fuller understanding of the mechanism and extent of LRAT. Specifically we address the issues of 'grasshopping' or 'hopping' (the extent to which molecules are subject to multiple hops as distinct from a single emission-deposition event) and 'global fractionation' (the differing behavior of chemicals as they are transported). It is shown that simple mass balance models can be used to assist the interpretation of monitoring data while also providing an instrument that can be used to assess the LRAT potential and the extent of hopping that organic substances may experience. The available evidence supports the notion that many persistent organic pollutants experience varying degrees of 'hopping' during their environmental journey and as a consequence become fractionated with distance from source. - Evidence for global scale fractionation and hopping of POPs is reviewed

Modelling the transuranic contamination in soils by using a generic model and systematic sampling

International Nuclear Information System (INIS)

Breitenecker, Katharina; Brandl, Alexander; Bock, Helmut; Villa, Mario

2008-01-01

Full text: In the course of the decommissioning the former ASTRA Research Reactor, the Seibersdorf site is to be surveyed for possible contamination by radioactive materials, including transuranium elements. To limit costs due to systematic sampling and time consuming laboratory analyses, a mathematical model that describes the migration of transuranium elements and that includes the local topography of the area where deposition has occurred, was established.The project basis is to find a mathematical function that determines the contamination by modelling the pathways of transuranium elements. The model approach chosen is cellular automata (CA). For this purpose, a hypothetical activity of transuranium elements is released on the ground in the centre of a simulated area. Under the assumption that migration of these elements only takes place by diffusion, transport and sorption, their equations are modelled in the CA-model by a simple discretization for the existing problem. To include local topography, most of the simulated area consists of a green corridor, where migration proceeds quite slowly; streets, where the migrational behaviour is different, and migration velocities in ditches are also modelled. The Migration of three different plutonium isotopes ( 238P u, 239+240P u, 241P u), the migration of one americium isotope ( 241A m), the radioactive decay of 241P u via 241A m to 237N p and the radioactive decay of 238P u to 234U were considered in this model. Due to the special modelling approach of CA, the physical necessity of conservation of the amount of substance is always fulfilled. The entire system was implemented in MATLAB. Systematic sampling onto a featured test site, followed by detailed laboratory analyses were done to compare the underlying CA-model to real data. On this account a nuclide vector with 241A m as the reference nuclide was established. As long as the initial parameters (e.g. meteorological data) are well known, the model describes the

Factors influencing aquatic-to-terrestrial contaminant transport to terrestrial arthropod consumers in a multiuse river system.

Science.gov (United States)

Alberts, Jeremy M; Sullivan, S Mažeika P

2016-06-01

Emerging aquatic insects are important vectors of contaminant transfer from aquatic to terrestrial food webs. However, the environmental factors that regulate contaminant body burdens in nearshore terrestrial consumers remain largely unexplored. We investigated the relative influences of riparian landscape composition (i.e., land use and nearshore vegetation structure) and contaminant flux via the emergent aquatic insect subsidy on selenium (Se) and mercury (Hg) body burdens of riparian ants (Formica subsericea) and spiders of the family Tetragnathidae along 11 river reaches spanning an urban-rural land-use gradient in Ohio, USA. Model-selection results indicated that fine-scale land cover (e.g., riparian zone width, shrub cover) in the riparian zone was positively associated with reach-wide body burdens of Se and Hg in both riparian F. subsericea and tetragnathid spiders (i.e., total magnitude of Hg and Se concentrations in ant and spider populations, respectively, for each reach). River distance downstream of Columbus, Ohio - where study reaches were impounded and flow through a large urban center - was also implicated as an important factor. Although stable-isotope analysis suggested that emergent aquatic insects were likely vectors of Se and Hg to tetragnathid spiders (but not to F. subsericea), emergent insect contaminant flux did not emerge as a significant predictor for either reach-wide body burdens of spider Hg or Se. Improved understanding of the pathways and influences that control aquatic-to-terrestrial contaminant transport will be critical for effective risk management and remediation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Contaminant Transport Parameters for the Groundwater Flow and Contaminant Transport Model of Corrective Action Units 101 and 102: Central and Western Pahute Mesa, Nye County, Nevada, Revision 0

Energy Technology Data Exchange (ETDEWEB)

Drici, Warda [International Technologies Corporation, Las Vegas, NV (United States)

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.

Experience with contamination protection of spent fuel transport packages in Germany since 2000/2001

International Nuclear Information System (INIS)

Krinninger, H.; Bach, R.; Seidel, J.; Jung, P.

2004-01-01

On April 30, 1998 just a few days before the PATRAM 1998 conference at Paris, the French Nuclear Installations Safety Directorate (DSIN now DGSNR) published a press release, that during the year before some 35% of the spent fuel transports to the reprocessing plant of COGEMA at La Hague have non-fixed surface contamination in excess of the regulatory standard. A few day in advance DSIN informed in French Ministries and the competent foreign authorities of the customer countries of COGEMA. The consequences of this publication were multi-fold and perceived by the public as an act negligence of the nuclear industry. Because of concerns about additional radiation exposure to the railway workers by the unions the French Railway company SNCF suspended all transports by May 6, 1998 until implementation of corrective measures. This decision of SNF interupted also the spent fuel transports from continental Europe to the reprocessing plant of BNFL at Sellafield all performed across France to the port of Dunkirk. Furthermore on May 25, 1998 the German Federal Ministry of Environment, Nature Protection and Nuclear Safety (BMU) imposed a transport ban for shipment of spent fuel from commercial power plants and for high active waste returned from La Hague to the Gorleben site. The conditions for resumption of these transports were outlined by NMU in a 10-point programme. In response to these publications on contamination findings competent German State and Federal Authorities commissioned investigations by independent experts dealing with the identification of the causes, the proposal of counter measures, the investigation of shortcomings in the transport system in general and recommendations for retification of it

Advanced transport modeling of toroidal plasmas with transport barriers

International Nuclear Information System (INIS)

Fukuyama, A.; Murakami, S.; Honda, M.; Izumi, Y.; Yagi, M.; Nakajima, N.; Nakamura, Y.; Ozeki, T.

2005-01-01

Transport modeling of toroidal plasmas is one of the most important issue to predict time evolution of burning plasmas and to develop control schemes in reactor plasmas. In order to describe the plasma rotation and rapid transition self-consistently, we have developed an advanced scheme of transport modeling based on dynamical transport equation and applied it to the analysis of transport barrier formation. First we propose a new transport model and examine its behavior by the use of conventional diffusive transport equation. This model includes the electrostatic toroidal ITG mode and the electromagnetic ballooning mode and successfully describes the formation of internal transport barriers. Then the dynamical transport equation is introduced to describe the plasma rotation and the radial electric field self-consistently. The formation of edge transport barriers is systematically studied and compared with experimental observations. The possibility of kinetic transport modeling in velocity space is also examined. Finally the modular structure of integrated modeling code for tokamaks and helical systems is discussed. (author)

Groundwater pumping effects on contaminant loading management in agricultural regions.

Science.gov (United States)

Park, Dong Kyu; Bae, Gwang-Ok; Kim, Seong-Kyun; Lee, Kang-Kun

2014-06-15

Groundwater pumping changes the behavior of subsurface water, including the location of the water table and characteristics of the flow system, and eventually affects the fate of contaminants, such as nitrate from agricultural fertilizers. The objectives of this study were to demonstrate the importance of considering the existing pumping conditions for contaminant loading management and to develop a management model to obtain a contaminant loading design more appropriate and practical for agricultural regions where groundwater pumping is common. Results from this study found that optimal designs for contaminant loading could be determined differently when the existing pumping conditions were considered. This study also showed that prediction of contamination and contaminant loading management without considering pumping activities might be unrealistic. Motivated by these results, a management model optimizing the permissible on-ground contaminant loading mass together with pumping rates was developed and applied to field investigation and monitoring data from Icheon, Korea. The analytical solution for 1-D unsaturated solute transport was integrated with the 3-D saturated solute transport model in order to approximate the fate of contaminants loaded periodically from on-ground sources. This model was further expanded to manage agricultural contaminant loading in regions where groundwater extraction tends to be concentrated in a specific period of time, such as during the rice-growing season, using a method that approximates contaminant leaching to a fluctuating water table. The results illustrated that the simultaneous management of groundwater quantity and quality was effective and appropriate to the agricultural contaminant loading management and the model developed in this study, which can consider time-variant pumping, could be used to accurately estimate and to reasonably manage contaminant loading in agricultural areas. Copyright © 2014 Elsevier Ltd. All

Coliform contamination of a coastal embayment: Sources and transport pathways

Science.gov (United States)

Weiskel, P.K.; Howes, B.L.; Heufelder, G.R.

1996-01-01

Fecal bacterial contamination of nearshore waters has direct economic impacts to coastal communities through the loss of shellfisheries and restrictions of recreational uses. We conducted seasonal measurements of fecal coliform (FC) sources and transport pathways contributing to FC contamination of Buttermilk Bay, a shallow embayment adjacent to Buzzards Bay, MA. Typical of most coastal embayments, there were no direct sewage discharges (i.e., outfalls), and fecal bacteria from human, domestic animal, and wildlife pools entered open waters primarily through direct deposition or after transport through surface waters or groundwaters. Direct fecal coliform inputs to bay waters occurred primarily in winter (December-March) from waterfowl, ~33 x 1012 FC yr-1 or ~67% of the total annual loading. Effects of waterfowl inputs on bay FC densities were mitigated by their seasonality, wide distribution across the bay surface, and the apparent limited dispersal from fecal pellets. On-site disposal of sewage by septic systems was the single largest FC source in the watershed-embayment system, 460 x 1012 FC yr-1, but due to attenuation during subsurface transport only a minute fraction, rain events with discharge concentrated in nearshore zones, wet-weather flows were found to have a disproportionately high impact on nearshore FC levels. Elution of FC from shoreline deposits of decaying vegetation (wrack) comprised an additional coliform source. Both laboratory and field experiments suggest significant elution of bacteria from wrack, ~3 x 1012 FC yr-1 on a bay-wide basis (6% of annual input), primarily by periodic tidal flooding and possibly by major rain events. Release of coliforms during resuspension of subtidal sediments was estimated to be a minor source in this system (<1.5 x 1012 FC yr-1 or < 3% of annual input), primarily associated with large storm events in the fall and winter. Based upon the relative source strengths and the spatial and temporal patterns of FC input

State-of-the-art in modeling solute and sediment transport in rivers

International Nuclear Information System (INIS)

Sayre, W.W.

1980-01-01

This overview is structured around a comprehensive general model based on the conservation of mass principle as applied to dissolved and particulate constituents in rivers, with a few restricted but more specific examples that illustrate the state-of-the-art in modeling typical physical, chemical, and biological processes undergone by selected constituents in rivers. These examples include: simplified one- and two-dimensional formulations focusing on the hydrodynamic advection and dispersion mechanisms; a two-dimensional biochemial oxygen demand-dissolved oxygen model; a one-dimensional polychlorinated biphenyl model that includes uptake and release of constituent by suspended sediment, and deposition and erosion of contaminated particles; and a one-dimensional sediment transport model that accounts for interactions between the flow and the bed, and is capable of tracking dispersing slugs of sediment through cycles of erosion, entrainment, transport in suspension and as bed load, and burial and storage in the bed

A Review of Removable Surface Contamination on Radioactive Materials Transportation Containers

Energy Technology Data Exchange (ETDEWEB)

Kennedy, Jr, W. E.; Watson, E. C.; Murphy, D. W.; Harrer, B. J.; Harty, R.; Aldrich, J. M.

1981-05-01

This report contains the results of a study sponsored by the U.S. Nuclear Regulatory Commission (NRC) of removable surface contamination on radioactive materials transportation containers. The purpose of the study is to provide information to the NRC during their review of existing regulations. Data was obtained from both industry and literature on three major topics: 1) radiation doses, 2) economic costs, and 3) contamination frequencies. Containers for four categories of radioactive materials are considered including radiopharmaceuticals, industrial sources, nuclear fuel cycle materials, and low-level radioactive waste. Assumptions made in this study use current information to obtain realistic yet conservative estimates of radiation dose and economic costs. Collective and individual radiation doses are presented for each container category on a per container basis. Total doses, to workers and the public, are also presented for spent fuel cask and low-level waste drum decontamination. Estimates of the additional economic costs incurred by lowering current limits by factors of 10 and 100 are presented. Current contamination levels for each category of container are estimated from the data collected. The information contained in this report is designed to be useful to the NRC in preparing their recommendations for new regulations.

Monitoring Potential Transport of Radioactive Contaminants in Shallow Ephemeral Channels: FY2017

Energy Technology Data Exchange (ETDEWEB)

Mizell, Steve A. [Desert Research Inst. (DRI), Las Vegas, NV (United States); Campbell, Scott A. [Desert Research Inst. (DRI), Las Vegas, NV (United States); McCurdy, Greg [Desert Research Inst. (DRI), Las Vegas, NV (United States); Miller, Julianne J. [Desert Research Inst. (DRI), Las Vegas, NV (United States)

2018-04-01

The Desert Research Institute (DRI) is conducting a field assessment of the potential for contaminated soil to be transported from the Smoky Site Contamination Area (CA) as a result of storm runoff. This activity supports U.S. Department of Energy (DOE) Environmental Management Nevada Program (EM-NV) efforts to establish post-closure monitoring plans for the Smoky Site Soils Corrective Action Unit (CAU) 550. The work is intended to confirm the likely mechanism of transport and determine the meteorological conditions that might cause the movement of contaminated soils, as well as determine the particle size fraction that is most closely associated with transported radionuclide-contaminated soils. These data will facilitate the design of the appropriate post-closure monitoring program. In 2011, DRI installed a meteorological monitoring station on the west side of the Smoky Site CA and a hydrologic (runoff) monitoring station within the CA, near the east side. Air temperature, wind speed, wind direction, relative humidity, precipitation, solar radiation, barometric pressure, soil temperature, and soil water content are collected at the meteorological station. The maximum, minimum, and average or total values (as appropriate) for each of these parameters are recorded for each 10-minute interval. The maximum, minimum, and average water depth in the flume installed at the hydrology station are also recorded for every 10-minute interval. This report presents data collected from these stations during fiscal year (FY) 2017. During the FY2017 reporting period, the warmest months were June, July, and August and the coldest were December and January. Solar radiation showed the same seasonal trend, although the months with the most solar radiation were May and June. Monthly mean wind speeds were highest in the spring (April and May). Winds were generally from the southwest during the summer and from the northwest throughout the remainder of the year. The monthly average

Hydrological model for the transport of radioisotope in surface water

International Nuclear Information System (INIS)

Adoboah, E.K.

2011-01-01

The use of radioisotopes has gained grounds in Ghana as a result of the numerous benefits that could be derived from it. In Ghana, radioisotope materials are used for various purposes in a number of institutions. However, improper disposal of the waste poses threat to the environment. To evaluate the environmental impact of radioisotope pollution, mathematical models play a major role in predicting the pollution level in any medium. This study is concerned with the hydrological model for the transport of radioactive material in the river. The model was composed by employing partial differential equations, describing relevant physical processes evolution (water level, velocities and dissolved substances concentrations) that occurs in water bodies. The mass conservation and momentum laws, state equation and state transport equations are equation system basis. The explicit central difference scheme in space and a forward difference method in time were used for the evaluation of the generalized transport equation, the Advection-Dispersion Equation. A Matlab code was developed to predict the concentration of the radioactive contaminant at any particular time along the river and in a reservoir. The model was able to simulate accurately the various levels of radionuclide concentration changes in the flowing rivers as the flows are augmented by tributary inflows. (au)

Modeling ground water flow and radioactive transport in a fractured aquifer

International Nuclear Information System (INIS)

Pohll, G.; Hassan, A.E.; Chapman, J.B.; Papelis, C.; Andricevic, R.

1999-01-01

Three-dimensional numerical modeling is used to characterize ground water flow and contaminant transport at the Shoal nuclear test site in north-central Nevada. The fractured rock aquifer at the site is modeled using an equivalent porous medium approach. Field data are used to characterize the fracture system into classes: large, medium, and no/small fracture zones. Hydraulic conductivities are assigned based on discrete interval measurements. Contaminants from the Shoal test are assumed to all be located within the cavity. Several challenging issues are addressed in this study. Radionuclides are apportioned between surface deposits and volume deposits in nuclear melt glass, based on their volatility and previous observations. Surface-deposited radionuclides are released hydraulically after equilibration of the cavity with the surrounding ground water system, and as a function of ground water flow through the higher-porosity cavity into the low-porosity surrounding aquifer. Processes that are modeled include the release functions, retardation, radioactive decay, prompt injection, and in growth of daughter products. Prompt injection of radionuclides away from the cavity is found to increase the arrival of mass at the control plane but is not found to significantly impact calculated concentrations due to increased spreading. Behavior of the other radionuclides is affected by the slow chemical release and retardation behavior. The transport calculations are sensitive to many flow and transport parameters. Most important are the heterogeneity of the flow field and effective porosity. The effect of porosity in radioactive decay is crucial and has not been adequately addressed in the literature. For reactive solutes, retardation and the glass dissolution rate are also critical

SUDOQU: a new dose model to derive criteria for surface contamination of non-food (consumer) goods, containers and conveyances

International Nuclear Information System (INIS)

Van Dillen, Teun

2015-01-01

The Fukushima nuclear accident (Japan, 11 March 2011) revealed the need for well-founded criteria for surface contamination and associated screening levels related to the import of non-food (consumer) goods, containers and conveyances. The only available European-harmonised criteria are those laid down in the IAEA transport regulations, but these criteria date back from the early 1960's and only apply to the safe transport of radioactive materials. The main problem is that a generic dose-assessment model for consumer products is missing. Therefore, RIVM (National Institute for Public Health and the Environment) developed a new methodology entitled SUDOQU (Surface Dose Quantification) to calculate the annual effective dose for both consumers and non-radiological workers, addressing issues of removability of surface contamination. The methodology can be used to derive criteria and screening levels for surface contamination and could serve as a useful tool for policy-makers and radiation-protection specialists. (authors)

Preliminary description of hydrologic characteristics and contaminant transport potential of rocks in the Pasco Basin, south-central Washington

International Nuclear Information System (INIS)

Deju, R.A.; Fecht, K.R.

1979-03-01

This report aims at consolidating existing data useful in defining the hydrologic characteristics of the Pasco Basin within south-central Washington. It also aims at compiling the properties required to evaluate contaminant transport potential within individual subsurface strata in this basin. The Pasco Basin itself is a tract of semi-arid land covering about 2,000 square miles in south-central Washington. The regional geology of this basin is dominated by tholeiitic flood basalts of the Columbia Plateau. The surface hydrology of the basin is dominated by the Yakima, Snake, and Columbia rivers. Short-lived ephemeral streams may flow for a short period of time after a heavy rainfall or snowmelt. The subsurface hydrology of the Pasco Basin is characterized by an unconfined aquifer carrying the bulk of the water discharged within the basin. This aquifer overlies a series of confined aquifers carrying progressively smaller amounts of groundwater as a function of depth. The hydraulic properties of the various aquifers and non-water-bearing strata are characterized and reported. A summary of the basic properties is tabulated. The hydrochemical data obtained are summarized. The contaminant transport properties of the rocks in the Pasco Basin are analyzed with emphasis on the dispersion and sorption coefficients and the characteristics of the potential reactions between emplaced waste and the surrounding medium. Some basic modeling considerations of the hydrogeologic systems in the basin with a brief discussion of model input requirements and their relationship to available data are presented

Mathematical modeling of heavy metals contamination from MSW landfill site in Khon Kaen, Thailand.

Science.gov (United States)

Tantemsapya, N; Naksakul, Y; Wirojanagud, W

2011-01-01

Kham Bon landfill site is one of many municipality waste disposal sites in Thailand which are in an unsanitary condition. The site has been receiving municipality wastes without separating hazardous waste since 1968. Heavy metals including, Pb, Cr and Cd are found in soil and groundwater around the site, posing a health risk to people living nearby. In this research, contamination transport modelling of Pb, Cr and Cd was simulated using MODFLOW for two periods, at the present (2010) and 20 years prediction (2030). Model results showed that heavy metals, especially Pb and Cr migrated toward the north-eastern and south-eastern direction. The 20 years prediction showed that, heavy metals tend to move from the top soil to the deeper aquifer. The migration would not exceed 500 m radius from the landfill centre in the next 20 years, which is considered to be a slow process. From the simulation model, it is recommended that a mitigation measure should be performed to reduce the risk from landfill contamination. Hazardous waste should be separated for proper management. Groundwater contamination in the aquifer should be closely monitored. Consumption of groundwater in a 500 m radius must be avoided. In addition, rehabilitation of the landfill site should be undertaken to prevent further mobilization of pollutants.

Toward a community coastal sediment transport modeling system: the second workshop

Science.gov (United States)

Sherwood, Christopher R.; Harris, Courtney K.; Geyer, W. Rockwell; Butman, Bradford

2002-01-01

Models for transport and the long-term fate of particles in coastal waters are essential for a variety of applications related to commerce, defense, public health, and the quality of the marine environment. Examples include: analysis of waste disposal and transport and the fate of contaminated materials; evaluation of burial rates for naval mines or archaeological artifacts; prediction of water-column optical properties; analysis of transport and the fate of biological particles; prediction of coastal flooding and coastal erosion; evaluation of impacts of sea-level or wave-climate changes and coastal development; planning for construction and maintenance of navigable waterways; evaluation of habitat for commercial fisheries; evaluation of impacts of natural or anthropogenic changes in coastal conditions on recreational activities; and design of intakes and outfalls for sewage treatment, cooling systems, and desalination plants.

UZ Colloid Transport Model

International Nuclear Information System (INIS)

McGraw, M.

2000-01-01

The UZ Colloid Transport model development plan states that the objective of this Analysis/Model Report (AMR) is to document the development of a model for simulating unsaturated colloid transport. This objective includes the following: (1) use of a process level model to evaluate the potential mechanisms for colloid transport at Yucca Mountain; (2) Provide ranges of parameters for significant colloid transport processes to Performance Assessment (PA) for the unsaturated zone (UZ); (3) Provide a basis for development of an abstracted model for use in PA calculations

Safety analysis report for packaging onsite long-length contaminated equipment transport system

International Nuclear Information System (INIS)

McCormick, W.A.

1997-01-01

This safety analysis report for packaging describes the components of the long-length contaminated equipment (LLCE) transport system (TS) and provides the analyses, evaluations, and associated operational controls necessary for the safe use of the LLCE TS on the Hanford Site. The LLCE TS will provide a standardized, comprehensive approach for the disposal of approximately 98% of LLCE scheduled to be removed from the 200 Area waste tanks

Safety analysis report for packaging, onsite, long-length contaminated equipment transport system

Energy Technology Data Exchange (ETDEWEB)

McCormick, W.A.

1997-05-09

This safety analysis report for packaging describes the components of the long-length contaminated equipment (LLCE) transport system (TS) and provides the analyses, evaluations, and associated operational controls necessary for the safe use of the LLCE TS on the Hanford Site. The LLCE TS will provide a standardized, comprehensive approach for the disposal of approximately 98% of LLCE scheduled to be removed from the 200 Area waste tanks.

Extended numerical modeling of impurity neoclassical transport in tokamak edge plasmas

International Nuclear Information System (INIS)

Inoue, H.; Yamoto, S.; Hatayama, A.; Homma, Y.

2016-01-01

Understanding of impurity transport in tokamaks is an important issue in order to reduce the impurity contamination in fusion core plasmas. Recently, a new kinetic numerical scheme of impurity classical/neoclassical transport has been developed. This numerical scheme makes it possible to include classical self-diffusion (CL SD), classical inward pinch (CL IWP), and classical temperature screening effect (CL TSE) of impurity ions. However, impurity neoclassical transport has been modeled only in the case where background plasmas are in the Pfirsch-Schluter (PS) regime. The purpose of this study is to extend our previous model to wider range of collisionality regimes, i.e., not only the PS regime, but also the plateau regime. As in the previous study, a kinetic model with Binary Collision Monte-Carlo Model (BMC) has been adopted. We focus on the modeling of the neoclassical self-diffusion (NC SD) and the neoclassical inward pinch (NC IWP). In order to simulate the neoclassical transport with the BCM, velocity distribution of background plasma ions has been modeled as a deformed Maxwell distribution which includes plasma density gradient. Some test simulations have been done. As for NC SD of impurity ions, our scheme reproduces the dependence on the collisionality parameter in wide range of collisionality regime. As for NC IWP, in cases where test impurity ions and background ions are in the PS and plateau regimes, parameter dependences have been reproduced. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Extended numerical modeling of impurity neoclassical transport in tokamak edge plasmas

Energy Technology Data Exchange (ETDEWEB)

Inoue, H.; Yamoto, S.; Hatayama, A. [Graduate School of Science and Technology, Keio University, Hiyoshi, Yokohama (Japan); Homma, Y. [Graduate School of Science and Technology, Keio University, Hiyoshi, Yokohama (Japan); Research Fellow of Japan Society for the Promotion of Science, Tokyo (Japan)

2016-08-15

Understanding of impurity transport in tokamaks is an important issue in order to reduce the impurity contamination in fusion core plasmas. Recently, a new kinetic numerical scheme of impurity classical/neoclassical transport has been developed. This numerical scheme makes it possible to include classical self-diffusion (CL SD), classical inward pinch (CL IWP), and classical temperature screening effect (CL TSE) of impurity ions. However, impurity neoclassical transport has been modeled only in the case where background plasmas are in the Pfirsch-Schluter (PS) regime. The purpose of this study is to extend our previous model to wider range of collisionality regimes, i.e., not only the PS regime, but also the plateau regime. As in the previous study, a kinetic model with Binary Collision Monte-Carlo Model (BMC) has been adopted. We focus on the modeling of the neoclassical self-diffusion (NC SD) and the neoclassical inward pinch (NC IWP). In order to simulate the neoclassical transport with the BCM, velocity distribution of background plasma ions has been modeled as a deformed Maxwell distribution which includes plasma density gradient. Some test simulations have been done. As for NC SD of impurity ions, our scheme reproduces the dependence on the collisionality parameter in wide range of collisionality regime. As for NC IWP, in cases where test impurity ions and background ions are in the PS and plateau regimes, parameter dependences have been reproduced. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Notification determining details of technical standards concerning transport of radioisotopes or goods contaminated by radioisotopes in works or enterprises

International Nuclear Information System (INIS)

1981-01-01

This rule is established under the provisions of the regulation for the execution of the law on the prevention of radiation injuries by radioisotopes. Terms are used in this rule for the same meanings as in the regulation. The limit of the concentration of radioisotopes in the goods contaminated by these isotopes which are not required to be sealed in containers defined by the Director General of the Science and Technology Agency is 1/10,000 of the value A 2 under the notification determining the details of technical standards concerning the transport of radioisotopes or the goods contaminated by radioisotopes outside works or enterprises. The application for the permission of transporting the goods which are highly difficult to be sealed in containers shall list names and addresses, the kinds, quantities, shapes and properties of the transported goods contaminated by radioisotopes, etc. The radiation dose rate of transported goods and vehicles under the regulation is 200 milli-rem an hour on the surfaces of these goods, vehicles and containers, and 10 milli-rem an hour at the distance of 1 meter from their surfaces. The permissible exposure dose of the persons engaging in transport is 1.5 rem a year. Dangerous goods, signs, and the application for the approval of special measures are specified, respectively. (Okada, K.)

Monte Carlo simulation of the turbulent transport of airborne contaminants

International Nuclear Information System (INIS)

Watson, C.W.; Barr, S.

1975-09-01

A generalized, three-dimensional Monte Carlo model and computer code (SPOOR) are described for simulating atmospheric transport and dispersal of small pollutant clouds. A cloud is represented by a large number of particles that we track by statistically sampling simulated wind and turbulence fields. These fields are based on generalized wind data for large-scale flow and turbulent energy spectra for the micro- and mesoscales. The large-scale field can be input from a climatological data base, or by means of real-time analyses, or from a separate, subjectively defined data base. We introduce the micro- and mesoscale wind fluctuations through a power spectral density, to include effects from a broad spectrum of turbulent-energy scales. The role of turbulence is simulated in both meander and dispersal. Complex flow fields and time-dependent diffusion rates are accounted for naturally, and shear effects are simulated automatically in the ensemble of particle trajectories. An important adjunct has been the development of computer-graphics displays. These include two- and three-dimensional (perspective) snapshots and color motion pictures of particle ensembles, plus running displays of differential and integral cloud characteristics. The model's versatility makes it a valuable atmospheric research tool that we can adapt easily into broader, multicomponent systems-analysis codes. Removal, transformation, dry or wet deposition, and resuspension of contaminant particles can be readily included

A Bayesian belief network approach for assessing uncertainty in conceptual site models at contaminated sites

DEFF Research Database (Denmark)

Thomsen, Nanna Isbak; Binning, Philip John; McKnight, Ursula S.

2016-01-01

the most important site-specific features and processes that may affect the contaminant transport behavior at the site. However, the development of a CSM will always be associated with uncertainties due to limited data and lack of understanding of the site conditions. CSM uncertainty is often found...... to be a major source of model error and it should therefore be accounted for when evaluating uncertainties in risk assessments. We present a Bayesian belief network (BBN) approach for constructing CSMs and assessing their uncertainty at contaminated sites. BBNs are graphical probabilistic models...... that are effective for integrating quantitative and qualitative information, and thus can strengthen decisions when empirical data are lacking. The proposed BBN approach facilitates a systematic construction of multiple CSMs, and then determines the belief in each CSM using a variety of data types and/or expert...

Transport and modeling of estrogenic hormones in a dairy farm effluent through undisturbed soil lysimeters.

Science.gov (United States)

Steiner, Laure D; Bidwell, Vincent J; Di, Hong J; Cameron, Keith C; Northcott, Grant L

2010-04-01

The presence of endocrine-disrupting chemicals, including estrone (E1) and 17beta-estradiol (E2), in surface waters has been associated with physiological dysfunction in a number of aquatic organisms. One source of surface and groundwater contamination with E1 and E2 is the land application of animal wastes. The processes involved in the transport of these hormones in the soil, when applied with animal wastes, are still unclear. Therefore, a field-transport experiment was carried out, where a dairy farm effluent spiked with E1 and E2 was applied on large (50 cm diameter and 70 cm depth) undisturbed soil lysimeters. The concentrations of E1 and E2 in the leachate were monitored over a 3-month period, during which irrigation was applied. The experimental data suggest that E1 and E2 were transported through preferential/macropore flow pathways. The data from the experiment also show that E1 and E2 are leached earlier than the inert tracer (bromide). This observation can be explained either by the presence of antecedent concentrations in the soil or by an enhanced transport of E1 and E2 through the soil. A state-space mixing-cell model was further developed in order to describe the transport of E1 and E2 by three transport processes in parallel. The inverse modeling of the leaching data did not support the hypothesis that antecedent concentrations of estrogens could be responsible for the observed breakthrough curves but confirmed that estrogens were transported mainly via preferential/macropore flow and also via an enhanced transport. The parameter values that characterized this enhanced transport strongly suggest that this enhanced transport is mediated by colloids. For the first time, the simultaneous transport of E1 and E2 was modeled under transient conditions, taking into account the advection-dispersion, preferential/macropore flow, and colloidal-enhanced transport processes as well as E1 and E2 dissipation in the soil. These findings have major implications in

Modeling contaminant transport in porous media in relation to nuclear-waste disposal: a review

International Nuclear Information System (INIS)

Grove, D.B.; Kipp, K.L.

1980-01-01

The modeling of solute transport in saturated porous media is reviewed as it is applied to the movement of radioactive waste in the subsurface. Those processes, both physical and chemical, that affect radionuclide movement are discussed and the references that best illustrate these processes listed. Movement is separated into convection, convection-dispersion, and convection-dispersion and chemical reactions. Solutions of equations describing such movement are divided into one-, two-, and three-dimensional analytical and numerical examples. Discussions of recent work in the area of stochastic modeling are followed by discussions of applications of the models to selected field sites

A multimedia fate and chemical transport modeling system for pesticides: II. Model evaluation

International Nuclear Information System (INIS)

Li Rong; Yang Fuquan; Sloan, James J; Trevor Scholtz, M

2011-01-01

Pesticides have adverse health effects and can be transported over long distances to contaminate sensitive ecosystems. To address problems caused by environmental pesticides we developed a multimedia multi-pollutant modeling system, and here we present an evaluation of the model by comparing modeled results against measurements. The modeled toxaphene air concentrations for two sites, in Louisiana (LA) and Michigan (MI), are in good agreement with measurements (average concentrations agree to within a factor of 2). Because the residue inventory showed no soil residues at these two sites, resulting in no emissions, the concentrations must be caused by transport; the good agreement between the modeled and measured concentrations suggests that the model simulates atmospheric transport accurately. Compared to the LA and MI sites, the measured air concentrations at two other sites having toxaphene soil residues leading to emissions, in Indiana and Arkansas, showed more pronounced seasonal variability (higher in warmer months); this pattern was also captured by the model. The model-predicted toxaphene concentration fraction on particles (0.5-5%) agrees well with measurement-based estimates (3% or 6%). There is also good agreement between modeled and measured dry (1:1) and wet (within a factor of less than 2) depositions in Lake Ontario. Additionally this study identified erroneous soil residue data around a site in Texas in a published US toxaphene residue inventory, which led to very low modeled air concentrations at this site. Except for the erroneous soil residue data around this site, the good agreement between the modeled and observed results implies that both the US and Mexican toxaphene soil residue inventories are reasonably good. This agreement also suggests that the modeling system is capable of simulating the important physical and chemical processes in the multimedia compartments.

A Process-Based Transport-Distance Model of Aeolian Transport

Science.gov (United States)

Naylor, A. K.; Okin, G.; Wainwright, J.; Parsons, A. J.

2017-12-01

We present a new approach to modeling aeolian transport based on transport distance. Particle fluxes are based on statistical probabilities of particle detachment and distributions of transport lengths, which are functions of particle size classes. A computational saltation model is used to simulate transport distances over a variety of sizes. These are fit to an exponential distribution, which has the advantages of computational economy, concordance with current field measurements, and a meaningful relationship to theoretical assumptions about mean and median particle transport distance. This novel approach includes particle-particle interactions, which are important for sustaining aeolian transport and dust emission. Results from this model are compared with results from both bulk- and particle-sized-specific transport equations as well as empirical wind tunnel studies. The transport-distance approach has been successfully used for hydraulic processes, and extending this methodology from hydraulic to aeolian transport opens up the possibility of modeling joint transport by wind and water using consistent physics. Particularly in nutrient-limited environments, modeling the joint action of aeolian and hydraulic transport is essential for understanding the spatial distribution of biomass across landscapes and how it responds to climatic variability and change.

Summary of ground water and surface water flow and contaminant transport computer codes used at the Idaho National Engineering Laboratory (INEL)

International Nuclear Information System (INIS)

Bandy, P.J.; Hall, L.F.

1993-03-01

This report presents information on computer codes for numerical and analytical models that have been used at the Idaho National Engineering Laboratory (INEL) to model ground water and surface water flow and contaminant transport. Organizations conducting modeling at the INEL include: EG ampersand G Idaho, Inc., US Geological Survey, and Westinghouse Idaho Nuclear Company. Information concerning computer codes included in this report are: agency responsible for the modeling effort, name of the computer code, proprietor of the code (copyright holder or original author), validation and verification studies, applications of the model at INEL, the prime user of the model, computer code description, computing environment requirements, and documentation and references for the computer code

A multimedia fate and chemical transport modeling system for pesticides: I. Model development and implementation

International Nuclear Information System (INIS)

Li Rong; Yang Fuquan; Sloan, James J; Scholtz, M Trevor

2011-01-01

We have combined the US EPA MM5/MCIP/SMOKE/CMAQ modeling system with a dynamic soil model, the pesticide emission model (PEM), to create a multimedia chemical transport model capable of describing the important physical and chemical processes involving pesticides in the soil, in the atmosphere, and on the surface of vegetation. These processes include: agricultural practices (e.g. soil tilling and pesticide application mode); advection and diffusion of pesticides, moisture, and heat in the soil; partitioning of pesticides between soil organic carbon and interstitial water and air; emissions from the soil to the atmosphere; gas-particle partitioning and transport in the atmosphere; and atmospheric chemistry and dry and wet deposition of pesticides to terrestrial and water surfaces. The modeling system was tested by simulating toxaphene in a domain that covers most of North America for the period from 1 January 2000 to 31 December 2000. The results show obvious transport of the pesticide from the heavily contaminated soils in the southern United States and Mexico to water bodies including the Atlantic Ocean, the Gulf of Mexico and the Great Lakes, leading to significant dry and wet deposition into these ecosystems. The spatial distributions of dry and wet depositions differ because of their different physical mechanisms; the former follows the distribution of air concentrations whereas the latter is more biased to the North East due to the effect of precipitation.

A multimedia fate and chemical transport modeling system for pesticides: I. Model development and implementation

Energy Technology Data Exchange (ETDEWEB)

Li Rong; Yang Fuquan; Sloan, James J [Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, ON N2L 3G1 (Canada); Scholtz, M Trevor, E-mail: sloanj@connect.uwaterloo.ca [ORTECH Environmental, 2395 Speakman Drive, Mississauga, ON L5K 1B3 (Canada)

2011-07-15

We have combined the US EPA MM5/MCIP/SMOKE/CMAQ modeling system with a dynamic soil model, the pesticide emission model (PEM), to create a multimedia chemical transport model capable of describing the important physical and chemical processes involving pesticides in the soil, in the atmosphere, and on the surface of vegetation. These processes include: agricultural practices (e.g. soil tilling and pesticide application mode); advection and diffusion of pesticides, moisture, and heat in the soil; partitioning of pesticides between soil organic carbon and interstitial water and air; emissions from the soil to the atmosphere; gas-particle partitioning and transport in the atmosphere; and atmospheric chemistry and dry and wet deposition of pesticides to terrestrial and water surfaces. The modeling system was tested by simulating toxaphene in a domain that covers most of North America for the period from 1 January 2000 to 31 December 2000. The results show obvious transport of the pesticide from the heavily contaminated soils in the southern United States and Mexico to water bodies including the Atlantic Ocean, the Gulf of Mexico and the Great Lakes, leading to significant dry and wet deposition into these ecosystems. The spatial distributions of dry and wet depositions differ because of their different physical mechanisms; the former follows the distribution of air concentrations whereas the latter is more biased to the North East due to the effect of precipitation.

A multimedia fate and chemical transport modeling system for pesticides: I. Model development and implementation

Science.gov (United States)

Li, Rong; Scholtz, M. Trevor; Yang, Fuquan; Sloan, James J.

2011-07-01

We have combined the US EPA MM5/MCIP/SMOKE/CMAQ modeling system with a dynamic soil model, the pesticide emission model (PEM), to create a multimedia chemical transport model capable of describing the important physical and chemical processes involving pesticides in the soil, in the atmosphere, and on the surface of vegetation. These processes include: agricultural practices (e.g. soil tilling and pesticide application mode); advection and diffusion of pesticides, moisture, and heat in the soil; partitioning of pesticides between soil organic carbon and interstitial water and air; emissions from the soil to the atmosphere; gas-particle partitioning and transport in the atmosphere; and atmospheric chemistry and dry and wet deposition of pesticides to terrestrial and water surfaces. The modeling system was tested by simulating toxaphene in a domain that covers most of North America for the period from 1 January 2000 to 31 December 2000. The results show obvious transport of the pesticide from the heavily contaminated soils in the southern United States and Mexico to water bodies including the Atlantic Ocean, the Gulf of Mexico and the Great Lakes, leading to significant dry and wet deposition into these ecosystems. The spatial distributions of dry and wet depositions differ because of their different physical mechanisms; the former follows the distribution of air concentrations whereas the latter is more biased to the North East due to the effect of precipitation.

Interactive 4D Visualization of Sediment Transport Models

Science.gov (United States)

Butkiewicz, T.; Englert, C. M.

2013-12-01

Coastal sediment transport models simulate the effects that waves, currents, and tides have on near-shore bathymetry and features such as beaches and barrier islands. Understanding these dynamic processes is integral to the study of coastline stability, beach erosion, and environmental contamination. Furthermore, analyzing the results of these simulations is a critical task in the design, placement, and engineering of coastal structures such as seawalls, jetties, support pilings for wind turbines, etc. Despite the importance of these models, there is a lack of available visualization software that allows users to explore and perform analysis on these datasets in an intuitive and effective manner. Existing visualization interfaces for these datasets often present only one variable at a time, using two dimensional plan or cross-sectional views. These visual restrictions limit the ability to observe the contents in the proper overall context, both in spatial and multi-dimensional terms. To improve upon these limitations, we use 3D rendering and particle system based illustration techniques to show water column/flow data across all depths simultaneously. We can also encode multiple variables across different perceptual channels (color, texture, motion, etc.) to enrich surfaces with multi-dimensional information. Interactive tools are provided, which can be used to explore the dataset and find regions-of-interest for further investigation. Our visualization package provides an intuitive 4D (3D, time-varying) visualization of sediment transport model output. In addition, we are also integrating real world observations with the simulated data to support analysis of the impact from major sediment transport events. In particular, we have been focusing on the effects of Superstorm Sandy on the Redbird Artificial Reef Site, offshore of Delaware Bay. Based on our pre- and post-storm high-resolution sonar surveys, there has significant scour and bedform migration around the

Method of processing dismantled products of radiation-contaminated equipments and transportation container therefor

International Nuclear Information System (INIS)

Komura, Shiro; Heki, Hideaki.

1991-01-01

In a method of decontaminating dismantled products of radiation-contaminated equipments removed at nuclear power facilities and classifying the dismantled products depending on their remaining radioactivity levels measured at a processing facility, the dismantled products are contained in a transportation container, to which decontamination liquids are injected and they are transferred to the processing facility. The decontaminated liquid wastes are drained from the transportation container, the dismantled products are washed while being contained in the transportation container as they are. Then, they are transferred to a step for measuring their remaining radioactivity level. This can shorten the time from the containment of the dismantled products to the transportation container to the completion of the decontamination, to improve the efficiency for the decontamination processing. Further, by separately containing the dismantled products on every kind of materials to respective containers, the processing time can be appropriately controlled respectively even if the dissolving efficiency to the decontamination liquids is different depending on the materials. (T.M.)

Dynamics of Coupled Contaminant and Microbial Transport in Heterogeneous Porous Media: Purdue Component

Energy Technology Data Exchange (ETDEWEB)

Cushman, J.H.; Madilyn Fletcher

2000-06-01

Dynamic microbial attachment/detachment occurs in subsurface systems in response to changing environmental conditions caused by contaminant movement and degradation. Understanding the environmental conditions and mechanisms by which anaerobic bacteria partition between aqueous and solid phases is a critical requirement for designing and evaluating in situ bioremediation efforts. This interdisciplinary research project, of which we report only the Purdue contribution, provides fundamental information on the attachment/detachment dynamics of bacteria in heterogeneous porous media. Fundamental results from the Purdue collaboration are: (a) development of a matched-index method for obtaining 3-D Lagrangian trajectories of microbial sized particles transporting within porous media or microflow cells, (b) application of advanced numerical methods to optimally design a microflow cell for studying anaerobic bacterial attachment/detachment phenomena, (c) development of two types of models for simulating bacterial movement and attachment/detachment in microflow cells and natural porous media, (d) application of stochastic analysis to upscale pore scale microbial attachment/detachment models to natural heterogeneous porous media, and (e) evaluation of the role nonlocality plays in microbial dynamics in heterogeneous porous media

Dynamics of Coupled Contaminant and Microbial Transport in Heterogeneous Porous Media: Purdue Component

Energy Technology Data Exchange (ETDEWEB)

Cushman, J.H.

2000-06-01

Dynamic microbial attachment/detachment occurs in subsurface systems in response to changing environmental conditions caused by contaminant movement and degradation. Understanding the environmental conditions and mechanisms by which anaerobic bacteria partition between aqueous and solid phases is a critical requirement for designing and evaluating in situ bioremediation efforts. This interdisciplinary research project, of which we report only the Purdue contribution, provides fundamental information on the attachment/detachment dynamics of bacteria in heterogeneous porous media. Fundamental results from the Purdue collaboration are: (a) development of a matched-index method for obtaining 3-D Lagrangian trajectories of microbial sized particles transporting within porous media or microflow cells, (b) application of advanced numerical methods to optimally design a microflow cell for studying anaerobic bacterial attachment/detachment phenomena, (c) development of two types of models for simulating bacterial movement and attachment/detachment in microflow cells and natural porous media, (d) application of stochastic analysis to upscale pore scale microbial attachment/detachment models to natural heterogeneous porous media, and (e) evaluation of the role nonlocality plays in microbial dynamics in heterogeneous porous media.

Isotope hydrology: Investigating groundwater contamination

International Nuclear Information System (INIS)

Dubinchuk, V.; Froehlich, K.; Gonfiantini, R.

1989-01-01

Groundwater quality has worsened in many regions, with sometimes serious consequences. Decontaminating groundwater is an extremely slow process, and sometimes impossible, because of the generally long residence time of the water in most geological formations. Major causes of contamination are poor groundwater management (often dictated by immediate social needs) and the lack of regulations and control over the use and disposal of contaminants. These types of problems have prompted an increasing demand for investigations directed at gaining insight into the behaviour of contaminants in the hydrological cycle. Major objectives are to prevent pollution and degradation of groundwater resources, or, if contamination already has occurred, to identify its origin so that remedies can be proposed. Environmental isotopes have proved to be a powerful tool for groundwater pollution studies. The IAEA has had a co-ordinated research programme since 1987 on the application of nuclear techniques to determine the transport of contaminants in groundwater. An isotope hydrology project is being launched within the framework of the IAEA's regional co-operative programme in Latin America (known as ARCAL). Main objectives are the application of environmental isotopes to problems of groundwater assessment and contamination in Latin America. In 1989, another co-ordinated research programme is planned under which isotopic and other tracers will be used for the validation of mathematical models in groundwater transport studies

Transport from diffuse sources of contamination and its application to a coupled unsaturated - saturated system

NARCIS (Netherlands)

Ommen, van H.C.

1988-01-01

A simple theory to predict groundwater quality upon contamination from diffuse sources was developed. It appeared that an analogy exists between the predominant transport phenomena and the reaction of a reservoir, in which perfect mixing takes place. Such an analogy enables a simple

Optimal Aquifer Pumping Policy to Reduce Contaminant Concentration

Directory of Open Access Journals (Sweden)

Ali Abaei

2012-01-01

Full Text Available Different sources of ground water contamination lead to non-uniform distribution of contaminant concentration in the aquifer. If elimination or containment of pollution sources was not possible, the distribution of contaminant concentrations could be modified in order to eliminate peak concentrations using optimal water pumping discharge plan. In the present investigation Visual MODFLOW model was used to simulate the flow and transport in a hypothetic aquifer. Genetic Algorithm (GA also was applied to optimize the location and pumping flow rate of wells in order to reduce contaminants peak concentrations in aquifer.

Complex relationship between groundwater velocity and concentration of radioactive contaminants

International Nuclear Information System (INIS)

Kaszeta, F.E.; Bond, F.W.

1980-01-01

This paper uses the results from the Multi-component Mass Transport model to examine the complex interrelationship between groundwater velocity and contaminant dispersion, decay, and retardation with regard to their influence on the contaminant concentration distribution as it travels through the geosphere to the biosphere. The rate of transport of contaminants through the geosphere is governed by groundwater velocity, leach rate, and contaminant retardation. The dominant characteristics of the contaminant concentration distribution are inherited during leaching and modified during transport by dilution, dispersion and decay. For a hypothetical non-decaying, non-dispersing contaminant with no retardation properties, the shape of the source term distribution is governed by the groundwater velocity (dilution) and leach rate. This distribution remains unchanged throughout transport. Under actual conditions, however, dispersion, decay and retardation modify the concentration distribution during both leaching and transport. The amount of dispersion is determined by the distance traveled, but it does have a greater peak-reducing influence on spiked distributions than square-shaped distributions. Decay acts as an overall scaling factor on the concentration distribution. Retardation alters the contaminant travel time and therefore indirectly influences the amount of dilution, dispersion and decay. Simple relationships between individual parameters and groundwater velocity as they influence peak concentration do not exist. For those cases where the source term is not solubility-limited and flow past the waste is independent of regional hydrologic conditions, a threshold concentration occurs at a specific groundwater velocity where the effects of dilution balance those of dispersion and decay

Catchment-scale contaminant transport under changing hydro-climatic conditions in the Aral Sea Drainage Basin, Central Asia

Science.gov (United States)

Jarsjö, Jerker; Törnqvist, Rebecka; Su, Ye

2013-04-01

Dependable projections of future water availability and quality are essential in the management of water resources. Changes in land use, water use and climate can have large impacts on water and contaminant flows across extensive catchments that may contain different administrative regions where shared water resources must be managed. We consider the extensive Aral Sea Drainage Basin (ASDB) and the Amu Darya River Delta in Central Asia, which are currently under severe water stress due to large-scale irrigation expansion. We interpret data on hydro-climatic conditions, main contaminants of surface water and shallow groundwater systems, location of rivers and canal networks, and groundwater flow directions. The data are used together with climate change projections from general circulation models (GCMs) as input to hydrological and (advective) transport modelling. The main goal is to assess how regional transport pathways and travel times have changed, and are likely to change further, in response to past and projected future hydro-climatic changes. More specifically, the hydrological modelling was based on temperature and precipitation change (ΔT and ΔP) results from 65 GCM projections of 21st century conditions (specifically considering time periods around 2025, 2050, and 2100), relative to reference conditions around 1975 (taken from the reference period 1961-1990). Whereas ΔT is robustly projected to increase with time, the projected magnitude of ΔP differs more among projections for the distant future (2100) than for the near future (2025), with uncertainty remaining even about the direction of change (i.e., positive or negative ΔP). However, mainly due to the projected temperature-driven increases in evapotranspiration, ensemble average results show that the Amu Darya river discharge Q in the downstream ASDB is likely to show a decreasing trend throughout the 21st century. Notably, projected changes in the upstream, mountainous regions have a relatively

Modelling of radionuclide transport in forests: Review and future perspectives

International Nuclear Information System (INIS)

Shaw, G.; Schell, W.; Linkov, I.

1997-01-01

Ecological modeling is a powerful tool which can be used to synthesize information on the dynamic processes which occur in ecosystems. Models of radionuclide transport in forests were first constructed in the mid-1960's, when the consequences of global fallout from nuclear weapons tests and waste disposal in the environment were of great concern. Such models were developed based on site-specific experimental data and were designed to address local needs. These models had a limited applicability in evaluating distinct ecosystems and deposition scenarios. Given the scarcity of information, the same experimental data sets were often used both for model calibration and validation, an approach which clearly constitutes a methodological error. Even though the carry modeling attempts were far from being faultless, they established a useful conceptual approach in that they tried to capture general processes in ecosystems and thus had a holistic nature. Later, radioecological modeling attempted to reveal ecosystem properties by separating the component parts from the whole system, as an approach to simplification. This method worked well for radionuclide transport in agricultural ecosystems, in which the biogeochemistry of radionuclide cycling is relatively well understood and can be influenced by fertilization. Several models have been successfully developed and applied to human dose evaluation and emergency response to contaminating events in agricultural lands

Analysis of TCE Fate and Transport in Karst Groundwater Systems Using Statistical Mixed Models

Science.gov (United States)

Anaya, A. A.; Padilla, I. Y.

2012-12-01

Karst groundwater systems are highly productive and provide an important fresh water resource for human development and ecological integrity. Their high productivity is often associated with conduit flow and high matrix permeability. The same characteristics that make these aquifers productive also make them highly vulnerable to contamination and a likely for contaminant exposure. Of particular interest are trichloroethylene, (TCE) and Di-(2-Ethylhexyl) phthalate (DEHP). These chemicals have been identified as potential precursors of pre-term birth, a leading cause of neonatal complications with a significant health and societal cost. Both of these contaminants have been found in the karst groundwater formations in this area of the island. The general objectives of this work are to: (1) develop fundamental knowledge and determine the processes controlling the release, mobility, persistence, and possible pathways of contaminants in karst groundwater systems, and (2) characterize transport processes in conduit and diffusion-dominated flow under base flow and storm flow conditions. The work presented herein focuses on the use of geo-hydro statistical tools to characterize flow and transport processes under different flow regimes, and their application in the analysis of fate and transport of TCE. Multidimensional, laboratory-scale Geo-Hydrobed models (GHM) were used for this purpose. The models consist of stainless-steel tanks containing karstified limestone blocks collected from the karst aquifer formation of northern Puerto Rico. The models integrates a network of sampling wells to monitor flow, pressure, and solute concentrations temporally and spatially. Experimental work entails injecting dissolved CaCl2 tracers and TCE in the upstream boundary of the GHM while monitoring TCE and tracer concentrations spatially and temporally in the limestone under different groundwater flow regimes. Analysis of the temporal and spatial concentration distributions of solutes

Transient modeling of non-Fickian transport and first-order reaction using continuous time random walk

Science.gov (United States)

Burnell, Daniel K.; Hansen, Scott K.; Xu, Jie

2017-09-01

Contaminants in groundwater may experience a broad spectrum of velocities and multiple rates of mass transfer between mobile and immobile zones during transport. These conditions may lead to non-Fickian plume evolution which is not well described by the advection-dispersion equation (ADE). Simultaneously, many groundwater contaminants are degraded by processes that may be modeled as first-order decay. It is now known that non-Fickian transport and reaction are intimately coupled, with reaction affecting the transport operator. However, closed-form solutions for these important scenarios have not been published for use in applications. In this paper, we present four new Green's function analytic solutions in the uncoupled, uncorrelated continuous time random walk (CTRW) framework for reactive non-Fickian transport, corresponding to the quartet of conservative tracer solutions presented by Kreft and Zuber (1978) for Fickian transport. These consider pulse injection for both resident and flux concentration combined with detection in both resident and flux concentration. A pair of solutions for resident concentration temporal pulses with detection in both flux and resident concentration is also presented. We also derive the relationship between flux and resident concentration for non-Fickian transport with first-order reaction for this CTRW formulation. An explicit discussion of employment of the new solutions to model transport with arbitrary upgradient boundary conditions as well as mobile-immobile mass transfer is then presented. Using the new solutions, we show that first-order reaction has no effect on the anomalous spatial spreading rate of concentration profiles, but produces breakthrough curves at fixed locations that appear to have been generated by Fickian transport. Under the assumption of a Pareto CTRW transition distribution, we present a variety of numerical simulations including results showing coherence of our analytic solutions and CTRW particle

A compositional multiphase model for groundwater contamination by petroleum products: 2. Numerical solution

Science.gov (United States)

Baehr, Arthur L.; Corapcioglu, M. Yavuz

1987-01-01

In this paper we develop a numerical solution to equations developed in part 1 (M. Y. Corapcioglu and A. L. Baehr, this issue) to predict the fate of an immiscible organic contaminant such as gasoline in the unsaturated zone subsequent to plume establishment. This solution, obtained by using a finite difference scheme and a method of forward projection to evaluate nonlinear coefficients, provides estimates of the flux of solubilized hydrocarbon constituents to groundwater from the portion of a spill which remains trapped in a soil after routine remedial efforts to recover the product have ceased. The procedure was used to solve the one-dimensional (vertical) form of the system of nonlinear partial differential equations defining the transport for each constituent of the product. Additionally, a homogeneous, isothermal soil with constant water content was assumed. An equilibrium assumption partitions the constituents between air, water, adsorbed, and immiscible phases. Free oxygen transport in the soil was also simulated to provide an upper bound estimate of aerobic biodgradation rates. Results are presented for a hypothetical gasoline consisting of eight groups of hydrocarbon constituents. Rates at which hydrocarbon mass is removed from the soil, entering either the atmosphere or groundwater, or is biodegraded are presented. A significant sensitivity to model parameters, particularly the parameters characterizing diffusive vapor transport, was discovered. We conclude that hydrocarbon solute composition in groundwater beneath a gasoline contaminated soil would be heavily weighted toward aromatic constituents like benzene, toluene, and xylene.

Health effects from long-range transported contaminants in Arctic top predators: An integrated review based on studies of polar bears and relevant model species.

Science.gov (United States)

Sonne, Christian

2010-07-01

The aim of this review is to provide a thorough overview of the health effects from the complexed biomagnified mixture of long-range transported industrial organochlorines (OCs), polybrominated diphenyl ethers (PBDEs), perfluorinated compounds (PFCs) and mercury (Hg) on polar bear (Ursus maritimus) health. Multiple scientific studies of polar bears indicate negative relationships between exposure to these contaminants and health parameters; however, these are all of a correlative nature and do not represent true cause-and-effects. Therefore, information from controlled studies of farmed Norwegian Arctic foxes (Vulpes lagopus) and housed East and West Greenland sledge dogs (Canis familiaris) were included as supportive weight of evidence in the clarification of contaminant exposure and health effects in polar bears. The review showed that hormone and vitamin concentrations, liver, kidney and thyroid gland morphology as well as reproductive and immune systems of polar bears are likely to be influenced by contaminant exposure. Furthermore, exclusively based on polar bear contaminant studies, bone density reduction and neurochemical disruption and DNA hypomethylation of the brain stem seemed to occur. The range of tissue concentration, at which these alterations were observed in polar bears, were ca. 1-70,000 ng/g lw for OCs (blood plasma concentrations of some PCB metabolites even higher), ca. 1-1000 ng/g lw for PBDEs and for PFCs and Hg 114-3052 ng/g ww and 0.1-50 microg/g ww, respectively. Similar concentrations were found in farmed foxes and housed sledge dogs while the lack of dose response designs did not allow an estimation of threshold levels for oral exposure and accumulated tissue concentrations. Nor was it possible to pinpoint a specific group of contaminants being more important than others nor analyze their interactions. For East Greenland polar bears the corresponding daily SigmaOC and SigmaPBDE oral exposure was estimated to be 35 and 0.34 microg/kg body

Residence-time framework for modeling multicomponent reactive transport in stream hyporheic zones

Science.gov (United States)

Painter, S. L.; Coon, E. T.; Brooks, S. C.

2017-12-01

Process-based models for transport and transformation of nutrients and contaminants in streams require tractable representations of solute exchange between the stream channel and biogeochemically active hyporheic zones. Residence-time based formulations provide an alternative to detailed three-dimensional simulations and have had good success in representing hyporheic exchange of non-reacting solutes. We extend the residence-time formulation for hyporheic transport to accommodate general multicomponent reactive transport. To that end, the integro-differential form of previous residence time models is replaced by an equivalent formulation based on a one-dimensional advection dispersion equation along the channel coupled at each channel location to a one-dimensional transport model in Lagrangian travel-time form. With the channel discretized for numerical solution, the associated Lagrangian model becomes a subgrid model representing an ensemble of streamlines that are diverted into the hyporheic zone before returning to the channel. In contrast to the previous integro-differential forms of the residence-time based models, the hyporheic flowpaths have semi-explicit spatial representation (parameterized by travel time), thus allowing coupling to general biogeochemical models. The approach has been implemented as a stream-corridor subgrid model in the open-source integrated surface/subsurface modeling software ATS. We use bedform-driven flow coupled to a biogeochemical model with explicit microbial biomass dynamics as an example to show that the subgrid representation is able to represent redox zonation in sediments and resulting effects on metal biogeochemical dynamics in a tractable manner that can be scaled to reach scales.