Reactive transport simulation via combination of a multiphase-capable transport code for unstructured meshes with a Gibbs energy minimization solver of geochemical equilibria

NASA Astrophysics Data System (ADS)

Fowler, S. J.; Driesner, T.; Hingerl, F. F.; Kulik, D. A.; Wagner, T.

2011-12-01

We apply a new, C++-based computational model for hydrothermal fluid-rock interaction and scale formation in geothermal reservoirs. The model couples the Complex System Modelling Platform (CSMP++) code for fluid flow in porous and fractured media (Matthai et al., 2007) with the Gibbs energy minimization numerical kernel GEMS3K of the GEM-Selektor (GEMS3) geochemical modelling package (Kulik et al., 2010) in a modular fashion. CSMP++ includes interfaces to commercial file formats, accommodating complex geometry construction using CAD (Rhinoceros) and meshing (ANSYS) software. The CSMP++ approach employs finite element-finite volume spatial discretization, implicit or explicit time discretization, and operator splitting. GEMS3K can calculate complex fluid-mineral equilibria based on a variety of equation of state and activity models. A selection of multi-electrolyte aqueous solution models, such as extended Debye-Huckel, Pitzer (Harvie et al., 1984), EUNIQUAC (Thomsen et al., 1996), and the new ELVIS model (Hingerl et al., this conference), makes it well-suited for application to a wide range of geothermal conditions. An advantage of the GEMS3K solver is simultaneous consideration of complex solid solutions (e.g., clay minerals), gases, fluids, and aqueous solutions. Each coupled simulation results in a thermodynamically-based description of the geochemical and physical state of a hydrothermal system evolving along a complex P-T-X path. The code design allows efficient, flexible incorporation of numerical and thermodynamic database improvements. We demonstrate the coupled code workflow and applicability to compositionally and physically complex natural systems relevant to enhanced geothermal systems, where temporally and spatially varying chemical interactions may take place within diverse lithologies of varying geometry. Engesgaard, P. & Kipp, K. L. (1992). Water Res. Res. 28: 2829-2843. Harvie, C. E.; Møller, N. & Weare, J. H. (1984). Geochim. Cosmochim. Acta 48: 723-751. Kulik, D. A., Wagner, T., Dmytrieva S. V, et al. (2010). GEM-Selektor home page, Paul Scherrer Institut. Available at http://gems.web.psi.ch. Matthäi, S. K., Geiger, S., Roberts, S. G., Paluszny, A., Belayneh, M., Burri, A., Mezentsev, A., Lu, H., Coumou, D., Driesner, T. & Heinrich C. A. (2007). Geol. Soc. London, Spec. Publ. 292: 405-429. Thomsen, K. Rasmussen, P. & Gani, R. (1996). Chem. Eng. Sci. 51: 3675-3683.

Lagrangian simulation of mixing and reactions in complex geochemical systems

NASA Astrophysics Data System (ADS)

Engdahl, Nicholas B.; Benson, David A.; Bolster, Diogo

2017-04-01

Simulations of detailed geochemical systems have traditionally been restricted to Eulerian reactive transport algorithms. This note introduces a Lagrangian method for modeling multicomponent reaction systems. The approach uses standard random walk-based methods for the particle motion steps but allows the particles to interact with each other by exchanging mass of their various chemical species. The colocation density of each particle pair is used to calculate the mass transfer rate, which creates a local disequilibrium that is then relaxed back toward equilibrium using the reaction engine PhreeqcRM. The mass exchange is the only step where the particles interact and the remaining transport and reaction steps are entirely independent for each particle. Several validation examples are presented, which reproduce well-known analytical solutions. These are followed by two demonstration examples of a competitive decay chain and an acid-mine drainage system. The source code, entitled Complex Reaction on Particles (CRP), and files needed to run these examples are hosted openly on GitHub (https://github.com/nbengdahl/CRP), so as to enable interested readers to readily apply this approach with minimal modifications.

Solid phase evolution in the Biosphere 2 hillslope experiment as predicted by modeling of hydrologic and geochemical fluxes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dontsova, K.; Steefel, C.I.; Desilets, S.

2009-07-15

A reactive transport geochemical modeling study was conducted to help predict the mineral transformations occurring over a ten year time-scale that are expected to impact soil hydraulic properties in the Biosphere 2 (B2) synthetic hillslope experiment. The modeling sought to predict the rate and extent of weathering of a granular basalt (selected for hillslope construction) as a function of climatic drivers, and to assess the feedback effects of such weathering processes on the hydraulic properties of the hillslope. Flow vectors were imported from HYDRUS into a reactive transport code, CrunchFlow2007, which was then used to model mineral weathering coupled tomore » reactive solute transport. Associated particle size evolution was translated into changes in saturated hydraulic conductivity using Rosetta software. We found that flow characteristics, including velocity and saturation, strongly influenced the predicted extent of incongruent mineral weathering and neo-phase precipitation on the hillslope. Results were also highly sensitive to specific surface areas of the soil media, consistent with surface reaction controls on dissolution. Effects of fluid flow on weathering resulted in significant differences in the prediction of soil particle size distributions, which should feedback to alter hillslope hydraulic conductivities.« less

Simulating Donnan equilibria based on the Nernst-Planck equation

NASA Astrophysics Data System (ADS)

Gimmi, Thomas; Alt-Epping, Peter

2018-07-01

Understanding ion transport through clays and clay membranes is important for many geochemical and environmental applications. Ion transport is affected by electrostatic forces exerted by charged clay surfaces. Anions are partly excluded from pore water near these surfaces, whereas cations are enriched. Such effects can be modeled by the Donnan approach. Here we introduce a new, comparatively simple way to represent Donnan equilibria in transport simulations. We include charged surfaces as immobile ions in the balance equation and calculate coupled transport of all components, including the immobile charges, with the Nernst-Planck equation. This results in an additional diffusion potential that influences ion transport, leading to Donnan ion distributions while maintaining local charge balance. The validity of our new approach was demonstrated by comparing Nernst-Planck simulations using the reactive transport code Flotran with analytical solutions available for simple Donnan systems. Attention has to be paid to the numerical evaluation of the electrochemical migration term in the Nernst-Planck equation to obtain correct results for asymmetric electrolytes. Sensitivity simulations demonstrate the influence of various Donnan model parameters on simulated anion accessible porosities. It is furthermore shown that the salt diffusion coefficient in a Donnan pore depends on local concentrations, in contrast to the aqueous salt diffusion coefficient. Our approach can be easily implemented into other transport codes. It is versatile and facilitates, for instance, assessing the implications of different activity models for the Donnan porosity.

Interface COMSOL-PHREEQC (iCP), an efficient numerical framework for the solution of coupled multiphysics and geochemistry

NASA Astrophysics Data System (ADS)

Nardi, Albert; Idiart, Andrés; Trinchero, Paolo; de Vries, Luis Manuel; Molinero, Jorge

2014-08-01

This paper presents the development, verification and application of an efficient interface, denoted as iCP, which couples two standalone simulation programs: the general purpose Finite Element framework COMSOL Multiphysics® and the geochemical simulator PHREEQC. The main goal of the interface is to maximize the synergies between the aforementioned codes, providing a numerical platform that can efficiently simulate a wide number of multiphysics problems coupled with geochemistry. iCP is written in Java and uses the IPhreeqc C++ dynamic library and the COMSOL Java-API. Given the large computational requirements of the aforementioned coupled models, special emphasis has been placed on numerical robustness and efficiency. To this end, the geochemical reactions are solved in parallel by balancing the computational load over multiple threads. First, a benchmark exercise is used to test the reliability of iCP regarding flow and reactive transport. Then, a large scale thermo-hydro-chemical (THC) problem is solved to show the code capabilities. The results of the verification exercise are successfully compared with those obtained using PHREEQC and the application case demonstrates the scalability of a large scale model, at least up to 32 threads.

Reactive Fluid Flow and Applications to Diagenesis, Mineral Deposits, and Crustal Rocks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rye, Danny M.; Bolton, Edward W.

2002-11-04

The objective is to initiate new: modeling of coupled fluid flow and chemical reactions of geologic environments; experimental and theoretical studies of water-rock reactions; collection and interpretation of stable isotopic and geochemical field data at many spatial scales of systems involving fluid flow and reaction in environments ranging from soils to metamorphic rocks. Theoretical modeling of coupled fluid flow and chemical reactions, involving kinetics, has been employed to understand the differences between equilibrium, steady-state, and non-steady-state behavior of the chemical evolution of open fluid-rock systems. The numerical codes developed in this project treat multi-component, finite-rate reactions combined with advective andmore » dispersive transport in multi-dimensions. The codes incorporate heat, mass, and isotopic transfer in both porous and fractured media. Experimental work has obtained the kinetic rate laws of pertinent silicate-water reactions and the rates of Sr release during chemical weathering. Ab-initio quantum mechanical techniques have been applied to obtain the kinetics and mechanisms of silicate surface reactions and isotopic exchange between water and dissolved species. Geochemical field-based studies were carried out on the Wepawaug metamorphic schist, on the Irish base-metal sediment-hosted ore system, in the Dalradian metamorphic complex in Scotland, and on weathering in the Columbia River flood basalts. The geochemical and isotopic field data, and the experimental and theoretical rate data, were used as constraints on the numerical models and to determine the length and time scales relevant to each of the field areas.« less

Predictions of hydrothermal alteration within near-ridge oceanic crust from coordinated geochemical and fluid flow models

USGS Publications Warehouse

Wetzel, L.R.; Raffensperger, Jeff P.; Shock, E.L.

2001-01-01

Coordinated geochemical and hydrological calculations guide our understanding of the composition, fluid flow patterns, and thermal structure of near-ridge oceanic crust. The case study presented here illustrates geochemical and thermal changes taking place as oceanic crust ages from 0.2 to 1.0 Myr. Using a finite element code, we model fluid flow and heat transport through the upper few hundred meters of an abyssal hill created at an intermediate spreading rate. We use a reaction path model with a customized database to calculate equilibrium fluid compositions and mineral assemblages of basalt and seawater at 500 bars and temperatures ranging from 150 to 400??C. In one scenario, reaction path calculations suggest that volume increases on the order of 10% may occur within portions of the basaltic basement. If this change in volume occurred, it would be sufficient to fill all primary porosity in some locations, effectively sealing off portions of the oceanic crust. Thermal profiles resulting from fluid flow simulations indicate that volume changes along this possible reaction path occur primarily within the first 0.4 Myr of crustal aging. ?? 2001 Elsevier Science B.V. All rights reserved.

Analysis of a Complex Faulted CO 2 Reservoir Using a Three-dimensional Hydro-geochemical-Mechanical Approach

DOE PAGES

Nguyen, Ba Nghiep; Hou, Zhangshuan; Bacon, Diana H.; ...

2017-08-18

This work applies a three-dimensional (3D) multiscale approach recently developed to analyze a complex CO 2 faulted reservoir that includes some key geological features of the San Andreas and nearby faults. The approach couples the STOMP-CO2-R code for flow and reactive transport modeling to the ABAQUS ® finite element package for geomechanical analysis. The objective is to examine the coupled hydro-geochemical-mechanical impact on the risk of hydraulic fracture and fault slip in a complex and representative CO 2 reservoir that contains two nearly parallel faults. STOMP-CO2-R/ABAQUS ® coupled analyses of this reservoir are performed assuming extensional and compressional stress regimesmore » to predict evolutions of fluid pressure, stress and strain distributions as well as potential fault failure and leakage of CO 2 along the fault damage zones. The tendency for the faults to slip and pressure margin to fracture are examined in terms of stress regime, mineral composition, crack distributions in the fault damage zones and geomechanical properties. Here, this model in combination with a detailed description of the faults helps assess the coupled hydro-geochemical-mechanical effect.« less

Analysis of a Complex Faulted CO 2 Reservoir Using a Three-dimensional Hydro-geochemical-Mechanical Approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Ba Nghiep; Hou, Zhangshuan; Bacon, Diana H.

This work applies a three-dimensional (3D) multiscale approach recently developed to analyze a complex CO 2 faulted reservoir that includes some key geological features of the San Andreas and nearby faults. The approach couples the STOMP-CO2-R code for flow and reactive transport modeling to the ABAQUS ® finite element package for geomechanical analysis. The objective is to examine the coupled hydro-geochemical-mechanical impact on the risk of hydraulic fracture and fault slip in a complex and representative CO 2 reservoir that contains two nearly parallel faults. STOMP-CO2-R/ABAQUS ® coupled analyses of this reservoir are performed assuming extensional and compressional stress regimesmore » to predict evolutions of fluid pressure, stress and strain distributions as well as potential fault failure and leakage of CO 2 along the fault damage zones. The tendency for the faults to slip and pressure margin to fracture are examined in terms of stress regime, mineral composition, crack distributions in the fault damage zones and geomechanical properties. Here, this model in combination with a detailed description of the faults helps assess the coupled hydro-geochemical-mechanical effect.« less

Final Report: Molecular mechanisms and kinetics of microbial anaerobic nitrate-dependent U(IV) and Fe(II) oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Day, Peggy A.; Asta, Maria P.; Kanematsu, Masakazu

2015-02-27

In this project, we combined molecular genetic, spectroscopic, and microscopic techniques with kinetic and reactive transport studies to describe and quantify biotic and abiotic mechanisms underlying anaerobic, nitrate-dependent U(IV) and Fe(II) oxidation, which influences the long-term efficacy of in situ reductive immobilization of uranium at DOE sites. In these studies, Thiobacillus denitrificans, an autotrophic bacterium that catalyzes anaerobic U(IV) and Fe(II) oxidation, was used to examine coupled oxidation-reduction processes under either biotic (enzymatic) or abiotic conditions in batch and column experiments with biogenically produced UIVO2(s). Synthesis and quantitative analysis of coupled chemical and transport processes were done with the reactivemore » transport modeling code Crunchflow. Research focused on identifying the primary redox proteins that catalyze metal oxidation, environmental factors that influence protein expression, and molecular-scale geochemical factors that control the rates of biotic and abiotic oxidation.« less

Generic Procedure for Coupling the PHREEQC Geochemical Modeling Framework with Flow and Solute Transport Simulators

NASA Astrophysics Data System (ADS)

Wissmeier, L. C.; Barry, D. A.

2009-12-01

Computer simulations of water availability and quality play an important role in state-of-the-art water resources management. However, many of the most utilized software programs focus either on physical flow and transport phenomena (e.g., MODFLOW, MT3DMS, FEFLOW, HYDRUS) or on geochemical reactions (e.g., MINTEQ, PHREEQC, CHESS, ORCHESTRA). In recent years, several couplings between both genres of programs evolved in order to consider interactions between flow and biogeochemical reactivity (e.g., HP1, PHWAT). Software coupling procedures can be categorized as ‘close couplings’, where programs pass information via the memory stack at runtime, and ‘remote couplings’, where the information is exchanged at each time step via input/output files. The former generally involves modifications of software codes and therefore expert programming skills are required. We present a generic recipe for remotely coupling the PHREEQC geochemical modeling framework and flow and solute transport (FST) simulators. The iterative scheme relies on operator splitting with continuous re-initialization of PHREEQC and the FST of choice at each time step. Since PHREEQC calculates the geochemistry of aqueous solutions in contact with soil minerals, the procedure is primarily designed for couplings to FST’s for liquid phase flow in natural environments. It requires the accessibility of initial conditions and numerical parameters such as time and space discretization in the input text file for the FST and control of the FST via commands to the operating system (batch on Windows; bash/shell on Unix/Linux). The coupling procedure is based on PHREEQC’s capability to save the state of a simulation with all solid, liquid and gaseous species as a PHREEQC input file by making use of the dump file option in the TRANSPORT keyword. The output from one reaction calculation step is therefore reused as input for the following reaction step where changes in element amounts due to advection/dispersion are introduced as irreversible reactions. An example for the coupling of PHREEQC and MATLAB for the solution of unsaturated flow and transport is provided.

Investigating ebullition in a sand column using dissolved gas analysis and reactive transport modeling

USGS Publications Warehouse

Amos, Richard T.; Mayer, K. Ulrich

2006-01-01

Ebullition of gas bubbles through saturated sediments can enhance the migration of gases through the subsurface, affect the rate of biogeochemical processes, and potentially enhance the emission of important greenhouse gases to the atmosphere. To better understand the parameters controlling ebullition, methanogenic conditions were produced in a column experiment and ebullition through the column was monitored and quantified through dissolved gas analysis and reactive transport modeling. Dissolved gas analysis showed rapid transport of CH4 vertically through the column at rates several times faster than the bromide tracer and the more soluble gas CO2, indicating that ebullition was the main transport mechanism for CH4. An empirically derived formulation describing ebullition was integrated into the reactive transport code MIN3P allowing this process to be investigated on the REV scale in a complex geochemical framework. The simulations provided insights into the parameters controlling ebullition and show that, over the duration of the experiment, 36% of the CH4 and 19% of the CO2 produced were transported to the top of the column through ebullition.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Ba Nghiep; Hou, Zhangshuan; Bacon, Diana H.

This paper applies a multiscale hydro-geochemical-mechanical approach to analyze faulted CO 2 reservoirs using the STOMP-CO 2-R code that is coupled to the ABAQUS® finite element package. STOMP-CO 2-R models the reactive transport of CO 2 causing mineral volume fraction changes that are captured by an Eshelby-Mori-Tanka model implemented in ABAQUS®. A three-dimensional (3D) STOMP-CO 2-R model for a reservoir containing an inclined fault was built to analyze a formation containing a reaction network with 5 minerals: albite, anorthite, calcite, kaolinite and quartz. A 3D finite element mesh that exactly maps the STOMP-CO 2-R grid is developed for coupled hydro-geochemical-mechanicalmore » analyses. The model contains alternating sandstone and shale layers. The impact of reactive transport of CO 2 on the geomechanical properties of reservoir rocks and seals are studied in terms of mineral composition changes that affect their geomechanical responses. Simulations assuming extensional and compressional stress regimes with and without coupled geochemistry are performed to study the stress regime effect on the risk of hydraulic fracture. The tendency for the fault to slip is examined in terms of stress regime, geomechanical and geochemical-mechanical effects as well as fault inclination. The results show that mineralogical changes due to long-term injection of CO 2 reduce the permeability and elastic modulus of the reservoir, leading to increased risk of hydraulic fracture in the injection location and at the caprock seal immediately above the injection zone. Fault slip is not predicted to occur. However, fault inclination and stress regime have an important impact on the slip tendency factor.« less

VIRUS TRANSPORT IN PHYSICALLY AND GEOCHEMICALLY HETEROGENEOUS SUBSURFACE POROUS MEDIA. (R826179)

EPA Science Inventory

A two-dimensional model for virus transport in physically and geochemically heterogeneous subsurface porous media is presented. The model involves solution of the advection–dispersion equation, which additionally considers virus inactivation in the solution, as well as ...

How the Geothermal Community Upped the Game for Computer Codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

The Geothermal Technologies Office Code Comparison Study brought 11 research institutions together to collaborate on coupled thermal, hydrologic, geomechanical, and geochemical numerical simulators. These codes have the potential to help facilitate widespread geothermal energy development.

A COMSOL-GEMS interface for modeling coupled reactive-transport geochemical processes

NASA Astrophysics Data System (ADS)

Azad, Vahid Jafari; Li, Chang; Verba, Circe; Ideker, Jason H.; Isgor, O. Burkan

2016-07-01

An interface was developed between COMSOL MultiphysicsTM finite element analysis software and (geo)chemical modeling platform, GEMS, for the reactive-transport modeling of (geo)chemical processes in variably saturated porous media. The two standalone software packages are managed from the interface that uses a non-iterative operator splitting technique to couple the transport (COMSOL) and reaction (GEMS) processes. The interface allows modeling media with complex chemistry (e.g. cement) using GEMS thermodynamic database formats. Benchmark comparisons show that the developed interface can be used to predict a variety of reactive-transport processes accurately. The full functionality of the interface was demonstrated to model transport processes, governed by extended Nernst-Plank equation, in Class H Portland cement samples in high pressure and temperature autoclaves simulating systems that are used to store captured carbon dioxide (CO2) in geological reservoirs.

Reactive transport modeling at uranium in situ recovery sites: uncertainties in uranium sorption on iron hydroxides

USGS Publications Warehouse

Johnson, Raymond H.; Tutu, Hlanganani; Brown, Adrian; Figueroa, Linda; Wolkersdorfer, Christian

2013-01-01

Geochemical changes that can occur down gradient from uranium in situ recovery (ISR) sites are important for various stakeholders to understand when evaluating potential effects on surrounding groundwater quality. If down gradient solid-phase material consists of sandstone with iron hydroxide coatings (no pyrite or organic carbon), sorption of uranium on iron hydroxides can control uranium mobility. Using one-dimensional reactive transport models with PHREEQC, two different geochemical databases, and various geochemical parameters, the uncertainties in uranium sorption on iron hydroxides are evaluated, because these oxidized zones create a greater risk for future uranium transport than fully reduced zones where uranium generally precipitates.

Data Collection Handbook to Support Modeling Impacts of Radioactive Material in Soil and Building Structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Charley; Kamboj, Sunita; Wang, Cheng

2015-09-01

This handbook is an update of the 1993 version of the Data Collection Handbook and the Radionuclide Transfer Factors Report to support modeling the impact of radioactive material in soil. Many new parameters have been added to the RESRAD Family of Codes, and new measurement methodologies are available. A detailed review of available parameter databases was conducted in preparation of this new handbook. This handbook is a companion document to the user manuals when using the RESRAD (onsite) and RESRAD-OFFSITE code. It can also be used for RESRAD-BUILD code because some of the building-related parameters are included in this handbook.more » The RESRAD (onsite) has been developed for implementing U.S. Department of Energy Residual Radioactive Material Guidelines. Hydrogeological, meteorological, geochemical, geometrical (size, area, depth), crops and livestock, human intake, source characteristic, and building characteristic parameters are used in the RESRAD (onsite) code. The RESRAD-OFFSITE code is an extension of the RESRAD (onsite) code and can also model the transport of radionuclides to locations outside the footprint of the primary contamination. This handbook discusses parameter definitions, typical ranges, variations, and measurement methodologies. It also provides references for sources of additional information. Although this handbook was developed primarily to support the application of RESRAD Family of Codes, the discussions and values are valid for use of other pathway analysis models and codes.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 performancemore » 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.« less

Geochemical Fate and Transport of Diphenhydramine and Cetirizine in Soil

NASA Astrophysics Data System (ADS)

Wireman, R.; Rutherford, C. J.; Vulava, V. M.; Cory, W. C.

2015-12-01

Pharmaceuticals compounds presence in natural soils and water around the world has become a growing concern. These compounds are being discharged into the environment through treated wastewater or municipal sludge applications. The main goal of this study is determine their geochemical fate in natural soils. In this study we investigated sorption and transport behavior of diphenhydramine (DPH) and cetirizine (CTZ) in natural soils. These two commonly-used antihistamines are complex aromatic hydrocarbons with polar functional groups. Two clean acidic soils (pH~4.5) were used for these studies - an A-horizon soil that had higher organic matter content (OM, 7.6%) and a B-horizon soil that had lower OM (1.6%), but higher clay content (5.1%). Sorption isotherms were measured using batch reactor experiments. Data indicated that sorption was nonlinear and that it was stronger in clay-rich soils. The pKa's of DPH and CTZ are 8.98 and 8.27 respectively, i.e., these compounds are predominantly in cationic form at soil pH. In these forms, they preferentially sorb to negatively charged mineral surfaces (e.g., clay) present in the soils. Soil clay mineral characterization indicated that kaolinite was the dominant clay mineral present along with small amount of montmorillonite. The nonlinear sorption isotherms were fitted with Freundlich model. Transport behavior of both compounds was measured using glass chromatography columns. As expected both DPH and CTZ were strongly retained in the clay-rich soil as compared with OM-rich soil. The asymmetrical shape of the breakthrough curves indicated that there were likely two separate sorption sites in the soil, each with different reaction rates with each compound. A two-region advection-dispersion transport code was used to model the transport breakthrough curves. There was no evidence of transformation or degradation of the compounds during our sorption and transport studies.

Implementation of agronomical and geochemical modules into a 3D groundwater code for assessing nitrate storage and transport through unconfined Chalk aquifer

NASA Astrophysics Data System (ADS)

Picot-Colbeaux, Géraldine; Devau, Nicolas; Thiéry, Dominique; Pettenati, Marie; Surdyk, Nicolas; Parmentier, Marc; Amraoui, Nadia; Crastes de Paulet, François; André, Laurent

2016-04-01

Chalk aquifer is the main water resource for domestic water supply in many parts in northern France. In same basin, groundwater is frequently affected by quality problems concerning nitrates. Often close to or above the drinking water standards, nitrate concentration in groundwater is mainly due to historical agriculture practices, combined with leakage and aquifer recharge through the vadose zone. The complexity of processes occurring into such an environment leads to take into account a lot of knowledge on agronomy, geochemistry and hydrogeology in order to understand, model and predict the spatiotemporal evolution of nitrate content and provide a decision support tool for the water producers and stakeholders. To succeed in this challenge, conceptual and numerical models representing accurately the Chalk aquifer specificity need to be developed. A multidisciplinary approach is developed to simulate storage and transport from the ground surface until groundwater. This involves a new agronomic module "NITRATE" (NItrogen TRansfer for Arable soil to groundwaTEr), a soil-crop model allowing to calculate nitrogen mass balance in arable soil, and the "PHREEQC" numerical code for geochemical calculations, both coupled with the 3D transient groundwater numerical code "MARTHE". Otherwise, new development achieved on MARTHE code allows the use of dual porosity and permeability calculations needed in the fissured Chalk aquifer context. This method concerning the integration of existing multi-disciplinary tools is a real challenge to reduce the number of parameters by selecting the relevant equations and simplifying the equations without altering the signal. The robustness and the validity of these numerical developments are tested step by step with several simulations constrained by climate forcing, land use and nitrogen inputs over several decades. In the first time, simulations are performed in a 1D vertical unsaturated soil column for representing experimental nitrates vertical soil profiles (0-30m depth experimental measurements in Somme region). In the second time, this approach is used to simulate with a 3D model a drinking water catchment area in order to compared nitrate contents time series calculated and measured in the domestic water pumping well since 1995 (field in northern France - Avre Basin region). This numerical tool will help the decision-making in all activities in relation with water uses.

Field-Integrated Studies of Long-Term Sustainability of Chromium Bioreduction at Hanford 100H Site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long, Philip E.

2006-06-01

The objectives of the project are to investigate coupled hydraulic, geochemical, and microbial conditions, and to determine the critical biogeochemical parameters necessary to maximize the extent of Cr(VI) bioreduction and minimize Cr(III) reoxidation in groundwater. Specific goals of the project are as follows: (1) Field testing and monitoring of Cr(VI) bioreduction in ground water and its transformation into insoluble species of Cr(III) at the Hanford 100H site, to develop the optimal strategy of water sampling for chemical, microbial, stable isotope analyses, and noninvasive geophysical monitoring; (2) Bench-scale flow and transport investigations using columns of undisturbed sediments to obtain diffusion andmore » kinetic parameters needed for the development of a numerical model, predictions of Cr(VI) bioreduction, and potential of Cr(III) reoxidation; and (3) Development of a multiphase, multi-component 3D reactive transport model and a code, TOUGHREACT-BIO, to predict coupled biogeochemical-hydrological processes associated with bioremediation, and to calibrate and validate the developed code based on the results of bench-scale and field-scale Cr(VI) biostimulation experiments in ground water at the Hanford Site.« less

A 1-D evolutionary model for icy satellites, applied to Enceladus

NASA Astrophysics Data System (ADS)

Prialnik, Dina; Malamud, Uri

2015-11-01

A 1-D long-term evolution code for icy satellites is presented, which couples multiple processes: water migration, geochemical reactions, water and silicate phase transitions, crystallization, compaction by self-gravity, and ablation. The code takes into account various energy sources: tidal heating, radiogenic heating, geochemical energy released by serpentinization or absorbed by mineral dehydration, gravitational energy, and insolation. It includes heat transport by conduction, convection, and advection.The code is applied to Enceladus, by guessing the initial conditions that would render a structure compatible with present-day observations, and adopting a homogeneous initial structure. Assuming that the satellite has been losing water continually along its evolution, it follows that it was formed as a more massive, more ice-rich and more porous object, and gradually transformed into its present day state, due to sustained tidal heating. Several initial compositions and evolution scenarios are considered, and the evolution is simulated for the age of the Solar System. The results corresponding to the present configuration are confronted with the available observational constraints. The present configuration is shown to be differentiated into a pure icy mantle, several tens of km thick, overlying a rocky core, composed of dehydrated rock in the central part and hydrated rock in the outer part. Such a differentiated structure is obtained not only for Enceladus, but for other medium size ice-rich bodies as well.Predictions for Enceladus are a higher rock/ice mass ratio than previously assumed, and a thinner ice mantle, compatible with recent estimates based on gravity field measurements. Although, obviously, the 1-D model cannot be used to explain local phenomena, it sheds light on the internal structure invoked in explanations of localized features and activities.

Decreasing Kd uncertainties through the application of thermodynamic sorption models.

PubMed

Domènech, Cristina; García, David; Pękala, Marek

2015-09-15

Radionuclide retardation processes during transport are expected to play an important role in the safety assessment of subsurface disposal facilities for radioactive waste. The linear distribution coefficient (Kd) is often used to represent radionuclide retention, because analytical solutions to the classic advection-diffusion-retardation equation under simple boundary conditions are readily obtainable, and because numerical implementation of this approach is relatively straightforward. For these reasons, the Kd approach lends itself to probabilistic calculations required by Performance Assessment (PA) calculations. However, it is widely recognised that Kd values derived from laboratory experiments generally have a narrow field of validity, and that the uncertainty of the Kd outside this field increases significantly. Mechanistic multicomponent geochemical simulators can be used to calculate Kd values under a wide range of conditions. This approach is powerful and flexible, but requires expert knowledge on the part of the user. The work presented in this paper aims to develop a simplified approach of estimating Kd values whose level of accuracy would be comparable with those obtained by fully-fledged geochemical simulators. The proposed approach consists of deriving simplified algebraic expressions by combining relevant mass action equations. This approach was applied to three distinct geochemical systems involving surface complexation and ion-exchange processes. Within bounds imposed by model simplifications, the presented approach allows radionuclide Kd values to be estimated as a function of key system-controlling parameters, such as the pH and mineralogy. This approach could be used by PA professionals to assess the impact of key geochemical parameters on the variability of radionuclide Kd values. Moreover, the presented approach could be relatively easily implemented in existing codes to represent the influence of temporal and spatial changes in geochemistry on Kd values. Copyright © 2015 Elsevier B.V. All rights reserved.

Continuum-based DFN-consistent numerical framework for the simulation of oxygen infiltration into fractured crystalline rocks

NASA Astrophysics Data System (ADS)

Trinchero, Paolo; Puigdomenech, Ignasi; Molinero, Jorge; Ebrahimi, Hedieh; Gylling, Björn; Svensson, Urban; Bosbach, Dirk; Deissmann, Guido

2017-05-01

We present an enhanced continuum-based approach for the modelling of groundwater flow coupled with reactive transport in crystalline fractured rocks. In the proposed formulation, flow, transport and geochemical parameters are represented onto a numerical grid using Discrete Fracture Network (DFN) derived parameters. The geochemical reactions are further constrained by field observations of mineral distribution. To illustrate how the approach can be used to include physical and geochemical complexities into reactive transport calculations, we have analysed the potential ingress of oxygenated glacial-meltwater in a heterogeneous fractured rock using the Forsmark site (Sweden) as an example. The results of high-performance reactive transport calculations show that, after a quick oxygen penetration, steady state conditions are attained where abiotic reactions (i.e. the dissolution of chlorite and the homogeneous oxidation of aqueous iron(II) ions) counterbalance advective oxygen fluxes. The results show that most of the chlorite becomes depleted in the highly conductive deformation zones where higher mineral surface areas are available for reactions.

PhreeqcRM: A reaction module for transport simulators based on the geochemical model PHREEQC

USGS Publications Warehouse

Parkhurst, David L.; Wissmeier, Laurin

2015-01-01

PhreeqcRM is a geochemical reaction module designed specifically to perform equilibrium and kinetic reaction calculations for reactive transport simulators that use an operator-splitting approach. The basic function of the reaction module is to take component concentrations from the model cells of the transport simulator, run geochemical reactions, and return updated component concentrations to the transport simulator. If multicomponent diffusion is modeled (e.g., Nernst–Planck equation), then aqueous species concentrations can be used instead of component concentrations. The reaction capabilities are a complete implementation of the reaction capabilities of PHREEQC. In each cell, the reaction module maintains the composition of all of the reactants, which may include minerals, exchangers, surface complexers, gas phases, solid solutions, and user-defined kinetic reactants.PhreeqcRM assigns initial and boundary conditions for model cells based on standard PHREEQC input definitions (files or strings) of chemical compositions of solutions and reactants. Additional PhreeqcRM capabilities include methods to eliminate reaction calculations for inactive parts of a model domain, transfer concentrations and other model properties, and retrieve selected results. The module demonstrates good scalability for parallel processing by using multiprocessing with MPI (message passing interface) on distributed memory systems, and limited scalability using multithreading with OpenMP on shared memory systems. PhreeqcRM is written in C++, but interfaces allow methods to be called from C or Fortran. By using the PhreeqcRM reaction module, an existing multicomponent transport simulator can be extended to simulate a wide range of geochemical reactions. Results of the implementation of PhreeqcRM as the reaction engine for transport simulators PHAST and FEFLOW are shown by using an analytical solution and the reactive transport benchmark of MoMaS.

Geochemical Characterization Using Geophysical Data and Markov Chain Monte Carlo Methods

NASA Astrophysics Data System (ADS)

Chen, J.; Hubbard, S.; Rubin, Y.; Murray, C.; Roden, E.; Majer, E.

2002-12-01

Although the spatial distribution of geochemical parameters is extremely important for many subsurface remediation approaches, traditional characterization of those parameters is invasive and laborious, and thus is rarely performed sufficiently to describe natural hydrogeological variability at the field-scale. This study is an effort to jointly use multiple sources of information, including noninvasive geophysical data, for geochemical characterization of the saturated and anaerobic portion of the DOE South Oyster Bacterial Transport Site in Virginia. Our data set includes hydrogeological and geochemical measurements from five boreholes and ground-penetrating radar (GPR) and seismic tomographic data along two profiles that traverse the boreholes. The primary geochemical parameters are the concentrations of extractable ferrous iron Fe(II) and ferric iron Fe(III). Since iron-reducing bacteria can reduce Fe(III) to Fe(II) under certain conditions, information about the spatial distributions of Fe(II) and Fe(III) may indicate both where microbial iron reduction has occurred and in which zone it is likely to occur in the future. In addition, as geochemical heterogeneity influences bacterial transport and activity, estimates of the geochemical parameters provide important input to numerical flow and contaminant transport models geared toward bioremediation. Motivated by our previous research, which demonstrated that crosshole geophysical data could be very useful for estimating hydrogeological parameters, we hypothesize in this study that geochemical and geophysical parameters may be linked through their mutual dependence on hydrogeological parameters such as lithofacies. We attempt to estimate geochemical parameters using both hydrogeological and geophysical measurements in a Bayesian framework. Within the two-dimensional study domain (12m x 6m vertical cross section divided into 0.25m x 0.25m pixels), geochemical and hydrogeological parameters were considered as data if they were available from direct measurements or as variables otherwise. To estimate the geochemical parameters, we first assigned a prior model for each variable and a likelihood model for each type of data, which together define posterior probability distributions for each variable on the domain. Since the posterior probability distribution may involve hundreds of variables, we used a Markov Chain Monte Carlo (MCMC) method to explore each variable by generating and subsequently evaluating hundreds of realizations. Results from this case study showed that although geophysical attributes are not necessarily directly related to geochemical parameters, geophysical data could be very useful for providing accurate and high-resolution information about geochemical parameter distribution through their joint and indirect connections with hydrogeological properties such as lithofacies. This case study also demonstrated that MCMC methods were particularly useful for geochemical parameter estimation using geophysical data because they allow incorporation into the procedure of spatial correlation information, measurement errors, and cross correlations among different types of parameters.

Coupling ANIMO and MT3DMS for 3D regional-scale modeling of nutrient transport in soil and groundwater

NASA Astrophysics Data System (ADS)

Janssen, G.; Del Val Alonso, L.; Groenendijk, P.; Griffioen, J.

2012-12-01

We developed an on-line coupling between the 1D/quasi-2D nutrient transport model ANIMO and the 3D groundwater transport model code MT3DMS. ANIMO is a detailed, process-oriented model code for the simulation of nitrate leaching to groundwater, N- and P-loads on surface waters and emissions of greenhouse gasses. It is the leading nutrient fate and transport code in the Netherlands where it is used primarily for the evaluation of fertilization related legislation. In addition, the code is applied frequently in international research projects. MT3DMS is probably the most commonly used groundwater solute transport package worldwide. The on-line model coupling ANIMO-MT3DMS combines the state-of-the-art descriptions of the biogeochemical cycles in ANIMO with the advantages of using a 3D approach for the transport through the saturated domain. These advantages include accounting for regional lateral transport, considering groundwater-surface water interactions more explicitly, and the possibility of using MODFLOW to obtain the flow fields. An additional merit of the on-line coupling concept is that it preserves feedbacks between the saturated and unsaturated zone. We tested ANIMO-MT3DMS by simulating nutrient transport for the period 1970-2007 in a Dutch agricultural polder catchment covering an area of 118 km2. The transient groundwater flow field had a temporal resolution of one day and was calculated with MODFLOW-MetaSWAP. The horizontal resolution of the model grid was 100x100m and consisted of 25 layers of varying thickness. To keep computation times manageable, we prepared MT3DMS for parallel computing, which in itself is a relevant development for a large community of groundwater transport modelers. For the parameterization of the soil, we applied a standard classification approach, representing the area by 60 units with unique combinations of soil type, land use and geohydrological setting. For the geochemical parameterization of the deeper subsurface, however, we applied a novel geostatistical technique, which allocates reactivity parameters to the grid cells by sampling from these parameters' cumulative frequency distribution (CDF) functions. These CDF functions are derived for each relevant geohydrological unit present in the model domain, from datasets of groundwater and sediment analyses. The nutrient loads on the surface water system and the nutrient concentrations in groundwater, simulated by the transport model, are in fair agreement with field measurements. The experience with the test model constitutes a proof-of-concept, justifying further developments towards application of ANIMO-MT3DMS in actual regional decision-making processes.

Modeling the hydrothermal circulation and the hydrogen production at the Rainbow site with Cast3M

NASA Astrophysics Data System (ADS)

Perez, F.; Mügler, C.; Charlou, J.; Jean-baptiste, P.

2012-12-01

On the Mid-Atlantic Ridge, the Rainbow venting site is described as an ultramafic-hosted active hydrothermal site and releases high fluxes of methane and hydrogen [1, 2]. This behavior has first been interpreted as the result of serpentinization processes. But geochemical reactions involving olivine and plagioclase assemblages, and leading to chlorite, tremolite, talc and magnetite assemblages, could contribute to the observed characteristics of the exiting fluid [2]. The predominance of one of these geochemical reactions or their coexistence strongly depend on the hydrothermal fluid circulation. We developed and validated a 2D/3D numerical model using a Finite Volume method to simulate heat driven fluid flows in the framework of the Cast3M code [3, 4]. We also developed a numerical model for hydrogen production and transport that is based on experimental studies of the serpentinization processes [5-6]. This geochemical model takes into account the exothermic and water-consuming behavior of the serpentinization reaction and it can be coupled to our thermo-hydrogeological model. Our simulations provide temperatures, mass fluxes and venting surface areas very close to those estimated in-situ [7]. We showed that a single-path model [8] was necessary to simulate high values such as the in-situ measured temperatures and estimated water mass fluxes of the Rainbow site [7]. This single-path model will be used to model the production and transport of hydrogen at the Rainbow hydrothermal site. References [1]Charlou et al. (2010) AGU Monograph series. [2]Seyfried et al. (2011) Geochim. Cosmochim. Acta 75, 1574-1593. [3]http://www-cast3m.cea.fr. [4]Martin & Fyfe (1970) Chem. Geol. 6, 185-202. [5] Marcaillou et al. (2011) Earth and Planet. Sci. Lett. 303, 281-290. [6]Malvoisin et al. (2012) JGR, 117, B01104. [7]Perez et al. (2012) submited to Computational Geosciences. [8]Lowell & Germanovich (2004) AGU, Washington DC, USA.

Surrogate model approach for improving the performance of reactive transport simulations

NASA Astrophysics Data System (ADS)

Jatnieks, Janis; De Lucia, Marco; Sips, Mike; Dransch, Doris

2016-04-01

Reactive transport models can serve a large number of important geoscientific applications involving underground resources in industry and scientific research. It is common for simulation of reactive transport to consist of at least two coupled simulation models. First is a hydrodynamics simulator that is responsible for simulating the flow of groundwaters and transport of solutes. Hydrodynamics simulators are well established technology and can be very efficient. When hydrodynamics simulations are performed without coupled geochemistry, their spatial geometries can span millions of elements even when running on desktop workstations. Second is a geochemical simulation model that is coupled to the hydrodynamics simulator. Geochemical simulation models are much more computationally costly. This is a problem that makes reactive transport simulations spanning millions of spatial elements very difficult to achieve. To address this problem we propose to replace the coupled geochemical simulation model with a surrogate model. A surrogate is a statistical model created to include only the necessary subset of simulator complexity for a particular scenario. To demonstrate the viability of such an approach we tested it on a popular reactive transport benchmark problem that involves 1D Calcite transport. This is a published benchmark problem (Kolditz, 2012) for simulation models and for this reason we use it to test the surrogate model approach. To do this we tried a number of statistical models available through the caret and DiceEval packages for R, to be used as surrogate models. These were trained on randomly sampled subset of the input-output data from the geochemical simulation model used in the original reactive transport simulation. For validation we use the surrogate model to predict the simulator output using the part of sampled input data that was not used for training the statistical model. For this scenario we find that the multivariate adaptive regression splines (MARS) method provides the best trade-off between speed and accuracy. This proof-of-concept forms an essential step towards building an interactive visual analytics system to enable user-driven systematic creation of geochemical surrogate models. Such a system shall enable reactive transport simulations with unprecedented spatial and temporal detail to become possible. References: Kolditz, O., Görke, U.J., Shao, H. and Wang, W., 2012. Thermo-hydro-mechanical-chemical processes in porous media: benchmarks and examples (Vol. 86). Springer Science & Business Media.

PHT3D-UZF: A reactive transport model for variably-saturated porous media

USGS Publications Warehouse

Wu, Ming Zhi; Post, Vincent E. A.; Salmon, S. Ursula; Morway, Eric D.; Prommer, H.

2016-01-01

A modified version of the MODFLOW/MT3DMS-based reactive transport model PHT3D was developed to extend current reactive transport capabilities to the variably-saturated component of the subsurface system and incorporate diffusive reactive transport of gaseous species. Referred to as PHT3D-UZF, this code incorporates flux terms calculated by MODFLOW's unsaturated-zone flow (UZF1) package. A volume-averaged approach similar to the method used in UZF-MT3DMS was adopted. The PHREEQC-based computation of chemical processes within PHT3D-UZF in combination with the analytical solution method of UZF1 allows for comprehensive reactive transport investigations (i.e., biogeochemical transformations) that jointly involve saturated and unsaturated zone processes. Intended for regional-scale applications, UZF1 simulates downward-only flux within the unsaturated zone. The model was tested by comparing simulation results with those of existing numerical models. The comparison was performed for several benchmark problems that cover a range of important hydrological and reactive transport processes. A 2D simulation scenario was defined to illustrate the geochemical evolution following dewatering in a sandy acid sulfate soil environment. Other potential applications include the simulation of biogeochemical processes in variably-saturated systems that track the transport and fate of agricultural pollutants, nutrients, natural and xenobiotic organic compounds and micropollutants such as pharmaceuticals, as well as the evolution of isotope patterns.

Subsurface Transport Over Multiple Phases Demonstration Software

DOE Office of Scientific and Technical Information (OSTI.GOV)

2016-01-05

The STOMP simulator is a suite of numerical simulators developed by Pacific Northwest National Laboratory for addressing problems involving coupled multifluid hydrologic, thermal, geochemical, and geomechanical processes in the subsurface. The simulator has been applied to problems concerning environmental remediation, environmental stewardship, carbon sequestration, conventional petroleum production, and the production of unconventional hydrocarbon fuels. The simulator is copyrighted by Battelle Memorial Institute, and is available outside of PNNL via use agreements. To promote the open exchange of scientific ideas the simulator is provided as source code. A demonstration version of the simulator has been developed, which will provide potential newmore » users with an executable (not source code) implementation of the software royalty free. Demonstration versions will be offered via the STOMP website for all currently available operational modes of the simulator. The demonstration versions of the simulator will be configured with the direct banded linear system solver and have a limit of 1,000 active grid cells. This will provide potential new users with an opportunity to apply the code to simple problems, including many of the STOMP short course problems, without having to pay a license fee. Users will be required to register on the STOMP website prior to receiving an executable.« less

A reactive transport model for mercury fate in soil--application to different anthropogenic pollution sources.

PubMed

Leterme, Bertrand; Blanc, Philippe; Jacques, Diederik

2014-11-01

Soil systems are a common receptor of anthropogenic mercury (Hg) contamination. Soils play an important role in the containment or dispersion of pollution to surface water, groundwater or the atmosphere. A one-dimensional model for simulating Hg fate and transport for variably saturated and transient flow conditions is presented. The model is developed using the HP1 code, which couples HYDRUS-1D for the water flow and solute transport to PHREEQC for geochemical reactions. The main processes included are Hg aqueous speciation and complexation, sorption to soil organic matter, dissolution of cinnabar and liquid Hg, and Hg reduction and volatilization. Processes such as atmospheric wet and dry deposition, vegetation litter fall and uptake are neglected because they are less relevant in the case of high Hg concentrations resulting from anthropogenic activities. A test case is presented, assuming a hypothetical sandy soil profile and a simulation time frame of 50 years of daily atmospheric inputs. Mercury fate and transport are simulated for three different sources of Hg (cinnabar, residual liquid mercury or aqueous mercuric chloride), as well as for combinations of these sources. Results are presented and discussed with focus on Hg volatilization to the atmosphere, Hg leaching at the bottom of the soil profile and the remaining Hg in or below the initially contaminated soil layer. In the test case, Hg volatilization was negligible because the reduction of Hg(2+) to Hg(0) was inhibited by the low concentration of dissolved Hg. Hg leaching was mainly caused by complexation of Hg(2+) with thiol groups of dissolved organic matter, because in the geochemical model used, this reaction only had a higher equilibrium constant than the sorption reactions. Immobilization of Hg in the initially polluted horizon was enhanced by Hg(2+) sorption onto humic and fulvic acids (which are more abundant than thiols). Potential benefits of the model for risk management and remediation of contaminated sites are discussed.

Small-scale geochemical cycles and the distribution of uranium in central and north Florida organic deposits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bond, P.A.

1993-03-01

The global geochemical cycle for an element tracks its path from its various sources to its sinks via processes of weathering and transportation. The cycle may then be quantified in a necessarily approximate manner. The geochemical cycle (thus quantified) reveals constraints (known and unknown) on an element's behavior imposed by the various processes which act on it. In the context of a global geochemical cycle, a continent becomes essentially a source term. If, however, an element's behavior is examined in a local or regional context, sources and their related sinks may be identified. This suggests that small-scale geochemical cycles maymore » be superimposed on global geochemical cycles. Definition of such sub-cycles may clarify the distribution of an element in the earth's near-surface environment. In Florida, phosphate minerals of the Hawthorn Group act as a widely distributed source of uranium. Uranium is transported by surface- and ground-waters. Florida is the site of extensive wetlands and peatlands. The organic matter associated with these deposits adsorbs uranium and may act as a local sink depending on its hydrogeologic setting. This work examines the role of organic matter in the distribution of uranium in the surface and shallow subsurface environments of central and north Florida.« less

Analyzing legacy U.S. Geological Survey geochemical databases using GIS: applications for a national mineral resource assessment

USGS Publications Warehouse

Yager, Douglas B.; Hofstra, Albert H.; Granitto, Matthew

2012-01-01

This report emphasizes geographic information system analysis and the display of data stored in the legacy U.S. Geological Survey National Geochemical Database for use in mineral resource investigations. Geochemical analyses of soils, stream sediments, and rocks that are archived in the National Geochemical Database provide an extensive data source for investigating geochemical anomalies. A study area in the Egan Range of east-central Nevada was used to develop a geographic information system analysis methodology for two different geochemical datasets involving detailed (Bureau of Land Management Wilderness) and reconnaissance-scale (National Uranium Resource Evaluation) investigations. ArcGIS was used to analyze and thematically map geochemical information at point locations. Watershed-boundary datasets served as a geographic reference to relate potentially anomalous sample sites with hydrologic unit codes at varying scales. The National Hydrography Dataset was analyzed with Hydrography Event Management and ArcGIS Utility Network Analyst tools to delineate potential sediment-sample provenance along a stream network. These tools can be used to track potential upstream-sediment-contributing areas to a sample site. This methodology identifies geochemically anomalous sample sites, watersheds, and streams that could help focus mineral resource investigations in the field.

COTHERM: Modelling fluid-rock interactions in Icelandic geothermal systems

NASA Astrophysics Data System (ADS)

Thien, Bruno; Kosakowski, Georg; Kulik, Dmitrii

2014-05-01

Mineralogical alteration of reservoir rocks, driven by fluid circulation in natural or enhanced geothermal systems, is likely to influence the long-term performance of geothermal power generation. A key factor is the change of porosity due to dissolution of primary minerals and precipitation of secondary phases. Porosity changes will affect fluid circulation and solute transport, which, in turn, influence mineralogical alteration. This study is part of the Sinergia COTHERM project (COmbined hydrological, geochemical and geophysical modeling of geotTHERMal systems) that is an integrative research project aimed at improving our understanding of the sub-surface processes in magmatically-driven natural geothermal systems. We model the mineralogical and porosity evolution of Icelandic geothermal systems with 1D and 2D reactive transport models. These geothermal systems are typically high enthalphy systems where a magmatic pluton is located at a few kilometers depth. The shallow plutons increase the geothermal gradient and trigger the circulation of hydrothermal waters with a steam cap forming at shallow depth. We investigate two contrasting geothermal systems: Krafla, for which the water recharge consists of meteoritic water; and Reykjanes, for which the water recharge mainly consists of seawater. The initial rock composition is a fresh basalt. We use the GEM-Selektor geochemical modeling package [1] for calculation of kinetically controlled mineral equilibria between the rock and the ingression water. We consider basalt minerals dissolution kinetics according to Palandri & Kharaka [2]. Reactive surface areas are assumed to be geometric surface areas, and are corrected using a spherical-particle surface/mass relationship. For secondary minerals, we consider the partial equilibrium assuming that the primary mineral dissolution is slow, and the secondary mineral precipitation is fast. Comparison of our modeling results with the mineralogical assemblages observed in the field by Gudmundsson & Arnorsson [3] and by Icelandic partners of the COTHERM project suggests that the concept of partial equilibrium with instantaneous precipitation of secondary minerals is not sufficient to satisfactorily describe the experimental data. Considering kinetic controls also for secondary minerals appears as indispensable to properly describe the geothermal system evolution using a reactive transport modelling approach [4]. [1] Kulik D.A., Wagner T., Dmytrieva S.V., Kosakowski G., Hingerl F.F., Chudnenko K.V., Berner U., 2013. GEM-Selektor geochemical modeling package: revised algorithm and GEMS3K numerical kernel for coupled simulation codes. Computational Geosciences 17, 1-24. http://gems.web.psi.ch. [2] Palandri, J.L., Kharaka, Y.K., 2004. A compilation of rate parameters of water-mineral interaction kinetics for application to geochemical modelling. U.S.Geological Survey, Menlo Park, CA, pp. 1-64. [3] Gudmundsson B.T., Arnorsson S., 2005. Secondary mineral-fluid equilibria in the Krafla and Namafjall geothermal systems, Iceland. Applied Geochememistry 20, 1607-1625. [4] Kosakowski, G., & Watanabe, N., 2013. OpenGeoSys-Gem: A numerical tool for calculating geochemical and porosity changes in saturated and partially saturated media. Physics and Chemistry of the Earth, Parts A/B/C. doi:10.1016/j.pce.2013.11.008

Continuum-based DFN-consistent numerical framework for the simulation of oxygen infiltration into fractured crystalline rocks.

PubMed

Trinchero, Paolo; Puigdomenech, Ignasi; Molinero, Jorge; Ebrahimi, Hedieh; Gylling, Björn; Svensson, Urban; Bosbach, Dirk; Deissmann, Guido

2017-05-01

We present an enhanced continuum-based approach for the modelling of groundwater flow coupled with reactive transport in crystalline fractured rocks. In the proposed formulation, flow, transport and geochemical parameters are represented onto a numerical grid using Discrete Fracture Network (DFN) derived parameters. The geochemical reactions are further constrained by field observations of mineral distribution. To illustrate how the approach can be used to include physical and geochemical complexities into reactive transport calculations, we have analysed the potential ingress of oxygenated glacial-meltwater in a heterogeneous fractured rock using the Forsmark site (Sweden) as an example. The results of high-performance reactive transport calculations show that, after a quick oxygen penetration, steady state conditions are attained where abiotic reactions (i.e. the dissolution of chlorite and the homogeneous oxidation of aqueous iron(II) ions) counterbalance advective oxygen fluxes. The results show that most of the chlorite becomes depleted in the highly conductive deformation zones where higher mineral surface areas are available for reactions. Copyright © 2017 Elsevier B.V. All rights reserved.

The effects of sorting by aeolian processes on the geochemical characteristics of surface materials: a wind tunnel experiment

NASA Astrophysics Data System (ADS)

Wang, Xunming; Lang, Lili; Hua, Ting; Zhang, Caixia; Li, Hui

2018-03-01

The geochemical characteristics of aeolian and surface materials in potential source areas of dust are frequently employed in environmental reconstructions as proxies of past climate and as source tracers of aeolian sediments deposited in downwind areas. However, variations in the geochemical characteristics of these aeolian deposits that result from near-surface winds are currently poorly understood. In this study, we collected surface samples from the Ala Shan Plateau (a major potential dust source area in Central Asia) to determine the influence of aeolian processes on the geochemical characteristics of aeolian transported materials. Correlation analyses show that compared with surface materials, the elements in transported materials (e.g., Cu, As, Pb, Mn, Zn, Al, Ca, Fe, Ga, K, Mg, P, Rb, Co, Cr, Na, Nb, Si, and Zr) were subjected to significant sorting by aeolian processes, and the sorting also varied among different particle size fractions and elements. Variations in wind velocity were significantly correlated with the contents of Cr, Ga, Sr, Ca, Y, Nd, Zr, Nb, Ba, and Al, and with the Zr/Al, Zr/Rb, K/Ca, Sr/Ca, Rb/Sr, and Ca/Al ratios. Given the great variation in the geochemical characteristics of materials transported under different aeolian processes relative to those of the source materials, these results indicate that considerable uncertainty may be introduced to analyses by using surface materials to trace the potential source areas of aeolian deposits that accumulate in downwind areas.

Nonstationary porosity evolution in mixing zone in coastal carbonate aquifer using an alternative modeling approach.

PubMed

Laabidi, Ezzeddine; Bouhlila, Rachida

2015-07-01

In the last few decades, hydrogeochemical problems have benefited from the strong interest in numerical modeling. One of the most recognized hydrogeochemical problems is the dissolution of the calcite in the mixing zone below limestone coastal aquifer. In many works, this problem has been modeled using a coupling algorithm between a density-dependent flow model and a geochemical model. A related difficulty is that, because of the high nonlinearity of the coupled set of equations, high computational effort is needed. During calcite dissolution, an increase in permeability can be identified, which can induce an increase in the penetration of the seawater into the aquifer. The majority of the previous studies used a fully coupled reactive transport model in order to model such problem. Romanov and Dreybrodt (J Hydrol 329:661-673, 2006) have used an alternative approach to quantify the porosity evolution in mixing zone below coastal carbonate aquifer at steady state. This approach is based on the analytic solution presented by Phillips (1991) in his book Flow and Reactions in Permeable Rock, which shows that it is possible to decouple the complex set of equation. This equation is proportional to the square of the salinity gradient, which can be calculated using a density driven flow code and to the reaction rate that can be calculated using a geochemical code. In this work, this equation is used in nonstationary step-by-step regime. At each time step, the quantity of the dissolved calcite is quantified, the change of porosity is calculated, and the permeability is updated. The reaction rate, which is the second derivate of the calcium equilibrium concentration in the equation, is calculated using the PHREEQC code (Parkhurst and Apello 1999). This result is used in GEODENS (Bouhlila 1999; Bouhlila and Laabidi 2008) to calculate change of the porosity after calculating the salinity gradient. For the next time step, the same protocol is used but using the updated porosity and permeability distributions.

Seasonal Drivers of Dissolved Metal Transport During Infiltration of Road Runoff in an Urban Roadside Environment

NASA Astrophysics Data System (ADS)

Mullins, A.; Bain, D.

2017-12-01

Infiltration-based green infrastructure (GI) is being increasingly applied in urban areas, systems characterized by substantial legacy contamination and complicated hydrology. However, it is not clear how the application of green infrastructure changes the geochemistry of urban roadside environments. Most current research on GI focuses on small sets of chemical parameters (e.g. road salt, nitrogen and phosphorous species) over relatively short time periods, limiting comprehensive understanding of geochemical function. This work measures changes in groundwater infiltration rate and dissolved metal concentrations in two infiltration trenches in Pittsburgh, PA to evaluate function and measure dissolved metal transport from the system over time. Two distinct geochemical regimes seem to be driven by seasonality: road de-icer exchange and microbial driven summer reducing conditions. Interactions between these geochemical regimes and variability in infiltration rate control the flux of different metals, varying with metal chemistry. These findings suggest the adoption of infiltration based green infrastructure will likely create complicated patterns of legacy contamination transport to downstream receptors.

INEEL Subregional Conceptual Model Report Volume 2: Summary of Existing Knowledge of Geochemical Influences on the Fate and Transport of Contaminants in the Subsurface at the INEEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paul L. Wichlacz; Robert C. Starr; Brennon Orr

2003-09-01

This document summarizes previous descriptions of geochemical system conceptual models for the vadose zone and groundwater zone (aquifer) beneath the Idaho National Engineering and Environmental Laboratory (INEEL). The primary focus is on groundwater because contaminants derived from wastes disposed at INEEL are present in groundwater, groundwater provides a pathway for potential migration to receptors, and because geochemical characteristics in and processes in the aquifer can substantially affect the movement, attenuation, and toxicity of contaminants. The secondary emphasis is perched water bodies in the vadose zone. Perched water eventually reaches the regional groundwater system, and thus processes that affect contaminants inmore » the perched water bodies are important relative to the migration of contaminants into groundwater. Similarly, processes that affect solutes during transport from nearsurface disposal facilities downward through the vadose zone to the aquifer are relevant. Sediments in the vadose zone can affect both water and solute transport by restricting the downward migration of water sufficiently that a perched water body forms, and by retarding solute migration via ion exchange. Geochemical conceptual models have been prepared by a variety of researchers for different purposes. They have been published in documents prepared by INEEL contractors, the United States Geological Survey (USGS), academic researchers, and others. The documents themselves are INEEL and USGS reports, and articles in technical journals. The documents reviewed were selected from citation lists generated by searching the INEEL Technical Library, the INEEL Environmental Restoration Optical Imaging System, and the ISI Web of Science databases. The citation lists were generated using the keywords ground water, groundwater, chemistry, geochemistry, contaminant, INEL, INEEL, and Idaho. In addition, a list of USGS documents that pertain to the INEEL was obtained and manually searched. The documents that appeared to be the most pertinent were selected from further review. These documents are tabulated in the citation list. This report summarizes existing geochemical conceptual models, but does not attempt to generate a new conceptual model or select the ''right'' model. This document is organized as follows. Geochemical models are described in general in Section 2. Geochemical processes that control the transport and fate of contaminants introduced into groundwater are described in Section 3. The natural geochemistry of the Eastern Snake River Plain Aquifer (SRPA) is described in Section 4. The effect of waste disposal on the INEEL subsurface is described in Section 5. The geochemical behavior of the major contaminants is described in Section 6. Section 7 describes the site-specific geochemical models developed for various INEEL facilities.« less

Reactive transport and mass balance modeling of the Stimson sedimentary formation and altered fracture zones constrain diagenetic conditions at Gale crater, Mars

NASA Astrophysics Data System (ADS)

Hausrath, E. M.; Ming, D. W.; Peretyazhko, T. S.; Rampe, E. B.

2018-06-01

On a planet as cold and dry as present-day Mars, evidence of multiple aqueous episodes offers an intriguing view into very different past environments. Fluvial, lacustrine, and eolian depositional environments are being investigated by the Mars Science Laboratory Curiosity in Gale crater, Mars. Geochemical and mineralogical observations of these sedimentary rocks suggest diagenetic processes affected the sediments. Here, we analyze diagenesis of the Stimson formation eolian parent material, which caused loss of olivine and formation of magnetite. Additional, later alteration in fracture zones resulted in preferential dissolution of pyroxene and precipitation of secondary amorphous silica and Ca sulfate. The ability to compare the unaltered parent material with the reacted material allows constraints to be placed on the characteristics of the altering solutions. In this work we use a combination of a mass balance approach calculating the fraction of a mobile element lost or gained, τ, with fundamental geochemical kinetics and thermodynamics in the reactive transport code CrunchFlow to examine the characteristics of multiple stages of aqueous alteration at Gale crater, Mars. Our model results indicate that early diagenesis of the Stimson sedimentary formation is consistent with leaching of an eolian deposit by a near-neutral solution, and that formation of the altered fracture zones is consistent with a very acidic, high sulfate solution containing Ca, P and Si. These results indicate a range of past aqueous conditions occurring at Gale crater, Mars, with important implications for past martian climate and environments.

Small scale changes of geochemistry and flow field due to transient heat storage in aquifers

NASA Astrophysics Data System (ADS)

Bauer, S.; Boockmeyer, A.; Li, D.; Beyer, C.

2013-12-01

Heat exchangers in the subsurface are increasingly installed for transient heat storage due to the need of heating or cooling of buildings as well as the interim storage of heat to compensate for the temporally fluctuating energy production by wind or solar energy. For heat storage to be efficient, high temperatures must be achieved in the subsurface. Significant temporal changes of the soil and groundwater temperatures however effect both the local flow field by temperature dependent fluid parameters as well as reactive mass transport through temperature dependent diffusion coefficients, geochemical reaction rates and mineral equilibria. As the use of heat storage will be concentrated in urban areas, the use of the subsurface for (drinking) water supply and heat storage will typically coincide and a reliable prognosis of the processes occurring is needed. In the present work, the effects of a temporal variation of the groundwater temperature, as induced by a local heat exchanger introduced into a groundwater aquifer, are studied. For this purpose, the coupled non-isothermal groundwater flow, heat transport and reactive mass transport is simulated in the near filed of such a heat exchanger. By explicitly discretizing and incorporating the borehole, the borehole cementation and the heat exchanger tubes, a realistic geometrical and process representation is obtained. The numerical simulation code OpenGeoSys is used in this work, which incorporates the required processes of coupled groundwater flow, heat and mass transport as well as temperature dependent geochemistry. Due to the use of a Finite Element Method, a close representation of the geometric effects can be achieved. Synthetic scenario simulations for typical settings of salt water formations in northern Germany are used to investigate the geochemical effects arising from a high temperature heat storage by quantifying changes in groundwater chemistry and overall reaction rates. This work presents the simulation approach used and results obtained for the synthetic scenarios. The model simulations show that locally in the direct vicinity of the borehole heat exchanger the flow field is changed, causing a ground water convergence and thus a mixing of water in the case of high temperatures. Also, geochemical reactions are induced due to shifting of temperature dependent mineral equilibria. Due to the moving groundwater, the changes are not reversible, and small impacts remain downstream of the borehole heat exchanger. However, the changes depend strongly on the mineral composition of the formation and the formation water present.

Porosity Development in a Coastal Setting: A Reactive Transport Model to Assess the Influence of Heterogeneity of Hydrological, Geochemical and Lithological Conditions

NASA Astrophysics Data System (ADS)

Maqueda, A.; Renard, P.; Cornaton, F. J.

2014-12-01

Coastal karst networks are formed by mineral dissolution, mainly calcite, in the freshwater-saltwater mixing zone. The problem has been approached first by studying the kinetics of calcite dissolution and then coupling ion-pairing software with flow and mass transport models. Porosity development models require high computational power. A workaround to reduce computational complexity is to assume the calcite dissolution reaction is relatively fast, thus equilibrium chemistry can be used to model it (Sanford & Konikow, 1989). Later developments allowed the full coupling of kinetics and transport in a model. However kinetics effects of calcite dissolution were found negligible under the single set of assumed hydrological and geochemical boundary conditions. A model is implemented with the coupling of FeFlow software as the flow & transport module and PHREEQC4FEFLOW (Wissmeier, 2013) ion-pairing module. The model is used to assess the influence of heterogeneities in hydrological, geochemical and lithological boundary conditions on porosity evolution. The hydrologic conditions present in the karst aquifer of Quintana Roo coast in Mexico are used as a guide for generating inputs for simulations.

On mass transport in porosity waves

NASA Astrophysics Data System (ADS)

Jordan, Jacob S.; Hesse, Marc A.; Rudge, John F.

2018-03-01

Porosity waves arise naturally from the equations describing fluid migration in ductile rocks. Here, we show that higher-dimensional porosity waves can transport mass and therefore preserve geochemical signatures, at least partially. Fluid focusing into these high porosity waves leads to recirculation in their center. This recirculating fluid is separated from the background flow field by a circular dividing streamline and transported with the phase velocity of the porosity wave. Unlike models for one-dimensional chromatography in geological porous media, tracer transport in higher-dimensional porosity waves does not produce chromatographic separations between relatively incompatible elements due to the circular flow pattern. This may allow melt that originated from the partial melting of fertile heterogeneities or fluid produced during metamorphism to retain distinct geochemical signatures as they rise buoyantly towards the surface.

A kinetics database and scripts for PHREEQC

NASA Astrophysics Data System (ADS)

Hu, B.; Zhang, Y.; Teng, Y.; Zhu, C.

2017-12-01

Kinetics of geochemical reactions has been increasingly used in numerical models to simulate coupled flow, mass transport, and chemical reactions. However, the kinetic data are scattered in the literature. To assemble a kinetic dataset for a modeling project is an intimidating task for most. In order to facilitate the application of kinetics in geochemical modeling, we assembled kinetics parameters into a database for the geochemical simulation program, PHREEQC (version 3.0). Kinetics data were collected from the literature. Our database includes kinetic data for over 70 minerals. The rate equations are also programmed into scripts with the Basic language. Using the new kinetic database, we simulated reaction path during the albite dissolution process using various rate equations in the literature. The simulation results with three different rate equations gave difference reaction paths at different time scale. Another application involves a coupled reactive transport model simulating the advancement of an acid plume in an acid mine drainage site associated with Bear Creek Uranium tailings pond. Geochemical reactions including calcite, gypsum, and illite were simulated with PHREEQC using the new kinetic database. The simulation results successfully demonstrated the utility of new kinetic database.

Evaluation of the transport matrix method for simulation of ocean biogeochemical tracers

NASA Astrophysics Data System (ADS)

Kvale, Karin F.; Khatiwala, Samar; Dietze, Heiner; Kriest, Iris; Oschlies, Andreas

2017-06-01

Conventional integration of Earth system and ocean models can accrue considerable computational expenses, particularly for marine biogeochemical applications. Offline numerical schemes in which only the biogeochemical tracers are time stepped and transported using a pre-computed circulation field can substantially reduce the burden and are thus an attractive alternative. One such scheme is the transport matrix method (TMM), which represents tracer transport as a sequence of sparse matrix-vector products that can be performed efficiently on distributed-memory computers. While the TMM has been used for a variety of geochemical and biogeochemical studies, to date the resulting solutions have not been comprehensively assessed against their online counterparts. Here, we present a detailed comparison of the two. It is based on simulations of the state-of-the-art biogeochemical sub-model embedded within the widely used coarse-resolution University of Victoria Earth System Climate Model (UVic ESCM). The default, non-linear advection scheme was first replaced with a linear, third-order upwind-biased advection scheme to satisfy the linearity requirement of the TMM. Transport matrices were extracted from an equilibrium run of the physical model and subsequently used to integrate the biogeochemical model offline to equilibrium. The identical biogeochemical model was also run online. Our simulations show that offline integration introduces some bias to biogeochemical quantities through the omission of the polar filtering used in UVic ESCM and in the offline application of time-dependent forcing fields, with high latitudes showing the largest differences with respect to the online model. Differences in other regions and in the seasonality of nutrients and phytoplankton distributions are found to be relatively minor, giving confidence that the TMM is a reliable tool for offline integration of complex biogeochemical models. Moreover, while UVic ESCM is a serial code, the TMM can be run on a parallel machine with no change to the underlying biogeochemical code, thus providing orders of magnitude speed-up over the online model.

Coupling between geochemical reactions and multicomponent gas and solute transport in unsaturated media: A reactive transport modeling study

USGS Publications Warehouse

Molins, S.; Mayer, K.U.

2007-01-01

The two‐way coupling that exists between biogeochemical reactions and vadose zone transport processes, in particular gas phase transport, determines the composition of soil gas. To explore these feedback processes quantitatively, multicomponent gas diffusion and advection are implemented into an existing reactive transport model that includes a full suite of geochemical reactions. Multicomponent gas diffusion is described on the basis of the dusty gas model, which accounts for all relevant gas diffusion mechanisms. The simulation of gas attenuation in partially saturated landfill soil covers, methane production, and oxidation in aquifers contaminated by organic compounds (e.g., an oil spill site) and pyrite oxidation in mine tailings demonstrate that both diffusive and advective gas transport can be affected by geochemical reactions. Methane oxidation in landfill covers reduces the existing upward pressure gradient, thereby decreasing the contribution of advective methane emissions to the atmosphere and enhancing the net flux of atmospheric oxygen into the soil column. At an oil spill site, methane oxidation causes a reversal in the direction of gas advection, which results in advective transport toward the zone of oxidation both from the ground surface and the deeper zone of methane production. Both diffusion and advection contribute to supply atmospheric oxygen into the subsurface, and methane emissions to the atmosphere are averted. During pyrite oxidation in mine tailings, pressure reduction in the reaction zone drives advective gas flow into the sediment column, enhancing the oxidation process. In carbonate‐rich mine tailings, calcite dissolution releases carbon dioxide, which partly offsets the pressure reduction caused by O2 consumption.

Uranium transport in a crushed granodiorite: Experiments and reactive transport modeling

DOE PAGES

Dittrich, T. M.; Reimus, P. W.

2015-02-12

The primary objective of this study was to develop and demonstrate an experimental method to refine and better parameterize process models for reactive contaminant transport in aqueous subsurface environments and to reduce conservatism in such models without attempting to fully describe the geochemical system.

Modeling porosity reductions caused by mineral fouling in continuous-wall permeable reactive barriers.

PubMed

Li, Lin; Benson, Craig H; Lawson, Elizabeth M

2006-02-01

A study was conducted to assess key factors to include when modeling porosity reductions caused by mineral fouling in permeable reactive barriers (PRBs) containing granular zero valent iron. The public domain codes MODFLOW and RT3D were used and a geochemical algorithm was developed for RT3D to simulate geochemical reactions occurring in PRBs. Results of simulations conducted with the model show that the largest porosity reductions occur between the entrance and mid-plane of the PRB as a result of precipitation of carbonate minerals and that smaller porosity reductions occur between the mid-plane and exit face due to precipitation of ferrous hydroxide. These findings are consistent with field and laboratory observations, as well as modeling predictions made by others. Parametric studies were conducted to identify the most important variables to include in a model evaluating porosity reduction. These studies showed that three minerals (CaCO3, FeCO3, and Fe(OH)2 (am)) account for more than 99% of the porosity reductions that were predicted. The porosity reduction is sensitive to influent concentrations of HCO3-, Ca2+, CO3(2-), and dissolved oxygen, the anaerobic iron corrosion rate, and the rates of CaCO3 and FeCO3 formation. The predictions also show that porosity reductions in PRBs can be spatially variable and mineral forming ions penetrate deeper into the PRB as a result of flow heterogeneities, which reflects the balance between the rate of mass transport and geochemical reaction rates. Level of aquifer heterogeneity and the contrast in hydraulic conductivity between the aquifer and PRB are the most important hydraulic variables affecting porosity reduction. Spatial continuity of aquifer hydraulic conductivity is less significant.

Methods for geochemical analysis

USGS Publications Warehouse

Baedecker, Philip A.

1987-01-01

The laboratories for analytical chemistry within the Geologic Division of the U.S. Geological Survey are administered by the Office of Mineral Resources. The laboratory analysts provide analytical support to those programs of the Geologic Division that require chemical information and conduct basic research in analytical and geochemical areas vital to the furtherance of Division program goals. Laboratories for research and geochemical analysis are maintained at the three major centers in Reston, Virginia, Denver, Colorado, and Menlo Park, California. The Division has an expertise in a broad spectrum of analytical techniques, and the analytical research is designed to advance the state of the art of existing techniques and to develop new methods of analysis in response to special problems in geochemical analysis. The geochemical research and analytical results are applied to the solution of fundamental geochemical problems relating to the origin of mineral deposits and fossil fuels, as well as to studies relating to the distribution of elements in varied geologic systems, the mechanisms by which they are transported, and their impact on the environment.

Uranium plume persistence impacted by hydrologic and geochemical heterogeneity in the groundwater and river water interaction zone of Hanford site

NASA Astrophysics Data System (ADS)

Chen, X.; Zachara, J. M.; Vermeul, V. R.; Freshley, M.; Hammond, G. E.

2015-12-01

The behavior of a persistent uranium plume in an extended groundwater- river water (GW-SW) interaction zone at the DOE Hanford site is dominantly controlled by river stage fluctuations in the adjacent Columbia River. The plume behavior is further complicated by substantial heterogeneity in physical and geochemical properties of the host aquifer sediments. Multi-scale field and laboratory experiments and reactive transport modeling were integrated to understand the complex plume behavior influenced by highly variable hydrologic and geochemical conditions in time and space. In this presentation we (1) describe multiple data sets from field-scale uranium adsorption and desorption experiments performed at our experimental well-field, (2) develop a reactive transport model that incorporates hydrologic and geochemical heterogeneities characterized from multi-scale and multi-type datasets and a surface complexation reaction network based on laboratory studies, and (3) compare the modeling and observation results to provide insights on how to refine the conceptual model and reduce prediction uncertainties. The experimental results revealed significant spatial variability in uranium adsorption/desorption behavior, while modeling demonstrated that ambient hydrologic and geochemical conditions and heterogeneities in sediment physical and chemical properties both contributed to complex plume behavior and its persistence. Our analysis provides important insights into the characterization, understanding, modeling, and remediation of groundwater contaminant plumes influenced by surface water and groundwater interactions.

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

EPA Science Inventory

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...

Identification and characterization of tsunami deposits off southeast coast of India from the 2004 Indian Ocean tsunami: Rock magnetic and geochemical approach

NASA Astrophysics Data System (ADS)

Veerasingam, S.; Venkatachalapathy, R.; Basavaiah, N.; Ramkumar, T.; Venkatramanan, S.; Deenadayalan, K.

2014-06-01

The December 2004 Indian Ocean Tsunami (IOT) had a major impact on the geomorphology and sedimentology of the east coast of India. Estimation of the magnitude of the tsunami from its deposits is a challenging topic to be developed in studies on tsunami hazard assessment. Two core sediments (C1 and C2) from Nagapattinam, southeast coast of India were subjected to textural, mineral, geochemical and rock-magnetic measurements. In both cores, three zones (zone I, II and III) have been distinguished based on mineralogical, geochemical and magnetic data. Zone II is featured by peculiar rock-magnetic, textural, mineralogical and geochemical signatures in both sediment cores that we interpret to correspond to the 2004 IOT deposit. Textural, mineralogical, geochemical and rock-magnetic investigations showed that the tsunami deposit is featured by relative enrichment in sand, quartz, feldspar, carbonate, SiO 2, TiO 2, K 2O and CaO and by a depletion in clay and iron oxides. These results point to a dilution of reworked ferromagnetic particles into a huge volume of paramagnetic materials, similar to what has been described in other nearshore tsunami deposits (Font et al. 2010). Correlation analysis elucidated the relationships among the textural, mineral, geochemical and magnetic parameters, and suggests that most of the quartz-rich coarse sediments have been transported offshore by the tsunami wave. These results agreed well with the previously published numerical model of tsunami induced sediment transport off southeast coast of India and can be used for future comparative studies on tsunami deposits.

Integrating surrogate models into subsurface simulation framework allows computation of complex reactive transport scenarios

NASA Astrophysics Data System (ADS)

De Lucia, Marco; Kempka, Thomas; Jatnieks, Janis; Kühn, Michael

2017-04-01

Reactive transport simulations - where geochemical reactions are coupled with hydrodynamic transport of reactants - are extremely time consuming and suffer from significant numerical issues. Given the high uncertainties inherently associated with the geochemical models, which also constitute the major computational bottleneck, such requirements may seem inappropriate and probably constitute the main limitation for their wide application. A promising way to ease and speed-up such coupled simulations is achievable employing statistical surrogates instead of "full-physics" geochemical models [1]. Data-driven surrogates are reduced models obtained on a set of pre-calculated "full physics" simulations, capturing their principal features while being extremely fast to compute. Model reduction of course comes at price of a precision loss; however, this appears justified in presence of large uncertainties regarding the parametrization of geochemical processes. This contribution illustrates the integration of surrogates into the flexible simulation framework currently being developed by the authors' research group [2]. The high level language of choice for obtaining and dealing with surrogate models is R, which profits from state-of-the-art methods for statistical analysis of large simulations ensembles. A stand-alone advective mass transport module was furthermore developed in order to add such capability to any multiphase finite volume hydrodynamic simulator within the simulation framework. We present 2D and 3D case studies benchmarking the performance of surrogates and "full physics" chemistry in scenarios pertaining the assessment of geological subsurface utilization. [1] Jatnieks, J., De Lucia, M., Dransch, D., Sips, M.: "Data-driven surrogate model approach for improving the performance of reactive transport simulations.", Energy Procedia 97, 2016, p. 447-453. [2] Kempka, T., Nakaten, B., De Lucia, M., Nakaten, N., Otto, C., Pohl, M., Chabab [Tillner], E., Kühn, M.: "Flexible Simulation Framework to Couple Processes in Complex 3D Models for Subsurface Utilization Assessment.", Energy Procedia, 97, 2016 p. 494-501.

Measured solubilities and speciations of neptunium, plutonium, and americium in a typical groundwater (J-13) from the Yucca Mountain region; Milestone report 3010-WBS 1.2.3.4.1.3.1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nitsche, H.; Gatti, R.C.; Standifer, E.M.

1993-07-01

Solubility and speciation data are important in understanding aqueous radionuclide transport through the geosphere. They define the source term for transport retardation processes such as sorption and colloid formation. Solubility and speciation data are useful in verifying the validity of geochemical codes that are part of predictive transport models. Results are presented from solubility and speciation experiments of {sup 237}NpO{sub 2}{sup +}, {sup 239}Pu{sup 4+}, {sup 241}Am{sup 3+}/Nd{sup 3+}, and {sup 243}Am{sup 3+} in J-13 groundwater (from the Yucca Mountain region, Nevada, which is being investigated as a potential high-level nuclear waste disposal site) at three different temperatures (25{degree}, 60{degree},more » and 90{degree}C) and pH values (5.9, 7.0, and 8.5). The solubility-controlling steady-state solids were identified and the speciation and/or oxidation states present in the supernatant solutions were determined. The neptunium solubility decreased with increasing temperature and pH. Plutonium concentrations decreased with increasing temperature and showed no trend with pH. The americium solutions showed no clear solubility trend with increasing temperature and increasing pH.« less

Modelling of the physico-chemical behaviour of clay minerals with a thermo-kinetic model taking into account particles morphology in compacted material.

NASA Astrophysics Data System (ADS)

Sali, D.; Fritz, B.; Clément, C.; Michau, N.

2003-04-01

Modelling of fluid-mineral interactions is largely used in Earth Sciences studies to better understand the involved physicochemical processes and their long-term effect on the materials behaviour. Numerical models simplify the processes but try to preserve their main characteristics. Therefore the modelling results strongly depend on the data quality describing initial physicochemical conditions for rock materials, fluids and gases, and on the realistic way of processes representations. The current geo-chemical models do not well take into account rock porosity and permeability and the particle morphology of clay minerals. In compacted materials like those considered as barriers in waste repositories, low permeability rocks like mudstones or compacted powders will be used : they contain mainly fine particles and the geochemical models used for predicting their interactions with fluids tend to misjudge their surface areas, which are fundamental parameters in kinetic modelling. The purpose of this study was to improve how to take into account the particles morphology in the thermo-kinetic code KINDIS and the reactive transport code KIRMAT. A new function was integrated in these codes, considering the reaction surface area as a volume depending parameter and the calculated evolution of the mass balance in the system was coupled with the evolution of reactive surface areas. We made application exercises for numerical validation of these new versions of the codes and the results were compared with those of the pre-existing thermo-kinetic code KINDIS. Several points are highlighted. Taking into account reactive surface area evolution during simulation modifies the predicted mass transfers related to fluid-minerals interactions. Different secondary mineral phases are also observed during modelling. The evolution of the reactive surface parameter helps to solve the competition effects between different phases present in the system which are all able to fix the chemical elements mobilised by the water-minerals interaction processes. To validate our model we simulated the compacted bentonite (MX80) studied for engineered barriers for radioactive waste confinement and mainly composed of Na-Ca-montmorillonite. The study of particles morphology and reactive surfaces evolutions reveals that aqueous ions have a complex behaviour, especially when competitions between various mineral phases occur. In that case, our model predicts a preferential precipitation of finest particles, favouring smectites instead of zeolites. This work is a part of a PhD Thesis supported by Andra, the French Radioactive Waste Management Agency.

A Cloud Based Framework For Monitoring And Predicting Subsurface System Behaviour

NASA Astrophysics Data System (ADS)

Versteeg, R. J.; Rodzianko, A.; Johnson, D. V.; Soltanian, M. R.; Dwivedi, D.; Dafflon, B.; Tran, A. P.; Versteeg, O. J.

2015-12-01

Subsurface system behavior is driven and controlled by the interplay of physical, chemical, and biological processes which occur at multiple temporal and spatial scales. Capabilities to monitor, understand and predict this behavior in an effective and timely manner are needed for both scientific purposes and for effective subsurface system management. Such capabilities require three elements: Models, Data and an enabling cyberinfrastructure, which allow users to use these models and data in an effective manner. Under a DOE Office of Science funded STTR award Subsurface Insights and LBNL have designed and implemented a cloud based predictive assimilation framework (PAF) which automatically ingests, controls quality and stores heterogeneous physical and chemical subsurface data and processes these data using different inversion and modeling codes to provide information on the current state and evolution of subsurface systems. PAF is implemented as a modular cloud based software application with five components: (1) data acquisition, (2) data management, (3) data assimilation and processing, (4) visualization and result delivery and (5) orchestration. Serverside PAF uses ZF2 (a PHP web application framework) and Python and both open source (ODM2) and in house developed data models. Clientside PAF uses CSS and JS to allow for interactive data visualization and analysis. Client side modularity (which allows for a responsive interface) of the system is achieved by implementing each core capability of PAF (such as data visualization, user configuration and control, electrical geophysical monitoring and email/SMS alerts on data streams) as a SPA (Single Page Application). One of the recent enhancements is the full integration of a number of flow and mass transport and parameter estimation codes (e.g., MODFLOW, MT3DMS, PHT3D, TOUGH, PFLOTRAN) in this framework. This integration allows for autonomous and user controlled modeling of hydrological and geochemical processes. In our presentation we will discuss our software architecture and present the results of using these codes and the overall developed performance of our framework using hydrological, geochemical and geophysical data from the LBNL SFA2 Rifle field site.

Review of simulation techniques for Aquifer Thermal Energy Storage (ATES)

NASA Astrophysics Data System (ADS)

Mercer, J. W.; Faust, C. R.; Miller, W. J.; Pearson, F. J., Jr.

1981-03-01

The analysis of aquifer thermal energy storage (ATES) systems rely on the results from mathematical and geochemical models. Therefore, the state-of-the-art models relevant to ATES were reviewed and evaluated. These models describe important processes active in ATES including ground-water flow, heat transport (heat flow), solute transport (movement of contaminants), and geochemical reactions. In general, available models of the saturated ground-water environment are adequate to address most concerns associated with ATES; that is, design, operation, and environmental assessment. In those cases where models are not adequate, development should be preceded by efforts to identify significant physical phenomena and relate model parameters to measurable quantities.

Modeling biogechemical reactive transport in a fracture zone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Molinero, Jorge; Samper, Javier; Yang, Chan Bing, and Zhang, Guoxiang

2005-01-14

A coupled model of groundwater flow, reactive solute transport and microbial processes for a fracture zone of the Aspo site at Sweden is presented. This is the model of the so-called Redox Zone Experiment aimed at evaluating the effects of tunnel construction on the geochemical conditions prevailing in a fracture granite. It is found that a model accounting for microbially-mediated geochemical processes is able to reproduce the unexpected measured increasing trends of dissolved sulfate and bicarbonate. The model is also useful for testing hypotheses regarding the role of microbial processes and evaluating the sensitivity of model results to changes inmore » biochemical parameters.« less

Subsurface Reactive Transport Modelling of the Lateritic Ni mineralization in New Caledonia: A coupled Thermo-Hydro-Geochemical Approach

NASA Astrophysics Data System (ADS)

Myagkiy, Andrey; Golfier, Fabrice; Truche, Laurent; Cathelineau, Michel

2017-04-01

This research proposes a subsurface reactive geochemical transport modelling of the development of a nickel laterite profile in New Caledonia over the past few million years. Such a regolith formation from ultramafic bedrock was not yet modelled and gives new profound insights into the Ni vertical mobility, its retention processes in a soil profile and relative enrichment, that are still poorly studied. The downward progression of the lateritization front is allowed by the leaching of the soluble elements (Si, Mg and Ni) through drainage system, represented by porous column of peridotite. Particular emphasis is placed on the detailed understanding of Ni redistribution as a function of time and depth triggered by Ni-bearing silicate precipitation (i.e. garnierite) and by sorption or recrystallization process with goethite. Current work consists of the following models: i) 1-D calculations that are done at 25oC with the code PHREEQC associated with the llnl thermodynamic database and ii) 2-D model that handles coupled thermo-hydro-chemical processes and is calculated on the interface Comsol-Phreeqc (iCP, Nardi et al., 2014). The impact of i) fluid flow in fractures and ii) recharge rate along with iii) hydraulic and iv) geothermal gradients are considered here. While the first model gives profound insights into the vertical mobility of metals upon the formation of laterite (Myagkiy et al, submitted), the latter one additionally allows to describe heterogeneities of mineralizing distributions due to the influence of preferential pathways (fractures), convective flows and lateral transfers. Our long-term 1-D simulations (10 Ma) clearly demonstrate that the Ni enrichment and thickening of iron-rich zone are governed by the vertical progression of the pH front. At the same time 2-D modelling shows reactivation of Ni from oxide zone and it subsequent redistribution and concentration in saprolite. Such a model appears to be of importance in attempt of explanation Ni mineralization processes, revealing the main keys to understanding the trace elements mobility in ultramafic environment. Myagkiy A, Truche L, Cathelineau M, Golfier F. "Revealing the conditions of Ni mineralization in laterite profile of New Caledonia: insights from reactive geochemical transport modelling" Preprint submitted to Chemical Geology (September 28, 2016). Nardi A, Idiart A, Trinchero P, de Vries LM, and Molinero J. "Interface COMSOL-PHREEQC (iCP), an efficient numerical framework for the solution of coupled multiphysics and geochemistry."Computers & Geosciences 69 (2014): 10-21.

Geochemical Controls on the Partitioning and Hydrological Transport of Metals in a Human Impacted, Non-Acidic, River System

NASA Astrophysics Data System (ADS)

Thorslund, J.; Jarsjo, J.; Wällstedt, T.; Morth, C. M.; Lychagin, M.; Chalov, S.

2014-12-01

The knowledge of coupled processes controlling the spreading and fate of metals in non-acidic river systems is currently much more limited than the knowledge of metal behavior under acidic conditions (e.g., in acid mine drainage systems). Critical geochemical controls governing metal speciation may thus differ substantially between acidic and non-acidic hydrological systems. We here aim at expanding the knowledge of metals in non-acidic river systems, by considering a high pH river, influenced by mining by the largest gold mining area in the Mongolian part of the transboundary Lake Baikal drainage basin. The combined impact of geochemical and hydrological processes is investigated, to be able to understand the solubility of various heavy metals, their partitioning between particulate and dissolved phase and its impact on overall transport. We show, through site specific measurements and a geochemical modelling approach, that the combined effects of precipitation of ferrihydrite and gibbsite and associated sorption complexes of several metals can explain the high impact of suspended transport relative to total transport often seen under non-acidic conditions. Our results also identifies the phosphate mineral Hydroxyapatite as a potential key sorption site for many metals, which has both site specific and general relevance for metal partitioning under non-acidic conditions. However, an adsorption database, which is currently unavailable for hydroxyapatite, needs to be developed for appropriate sorption quantification. Furthermore, Cd, Fe, Pb and Zn were particularly sensitive to increasing DOC concentrations, which increased the solubility of these metals due to metal-organic complexation. Modeling the sensitivity to changes in geochemical parameters showed that decreasing pH and increasing DOC concentrations in downstream regions would increase the dissolution and hence the toxicity and bioavailability of many pollutants of concern in the downstream ecosystem. In general, this study suggests that in non-acidic hydrological systems, both seasonality of DOC concentrations (which could vary by several 100%), changing DOC concentrations (resulting from climate and land use changes) and potential phosphate solids can majorly influence on the spreading and toxicity of several metals.

Geophysical monitoring and reactive transport modeling of ureolytically-driven calcium carbonate precipitation

PubMed Central

2011-01-01

Ureolytically-driven calcium carbonate precipitation is the basis for a promising in-situ remediation method for sequestration of divalent radionuclide and trace metal ions. It has also been proposed for use in geotechnical engineering for soil strengthening applications. Monitoring the occurrence, spatial distribution, and temporal evolution of calcium carbonate precipitation in the subsurface is critical for evaluating the performance of this technology and for developing the predictive models needed for engineering application. In this study, we conducted laboratory column experiments using natural sediment and groundwater to evaluate the utility of geophysical (complex resistivity and seismic) sensing methods, dynamic synchrotron x-ray computed tomography (micro-CT), and reactive transport modeling for tracking ureolytically-driven calcium carbonate precipitation processes under site relevant conditions. Reactive transport modeling with TOUGHREACT successfully simulated the changes of the major chemical components during urea hydrolysis. Even at the relatively low level of urea hydrolysis observed in the experiments, the simulations predicted an enhanced calcium carbonate precipitation rate that was 3-4 times greater than the baseline level. Reactive transport modeling results, geophysical monitoring data and micro-CT imaging correlated well with reaction processes validated by geochemical data. In particular, increases in ionic strength of the pore fluid during urea hydrolysis predicted by geochemical modeling were successfully captured by electrical conductivity measurements and confirmed by geochemical data. The low level of urea hydrolysis and calcium carbonate precipitation suggested by the model and geochemical data was corroborated by minor changes in seismic P-wave velocity measurements and micro-CT imaging; the latter provided direct evidence of sparsely distributed calcium carbonate precipitation. Ion exchange processes promoted through NH4+ production during urea hydrolysis were incorporated in the model and captured critical changes in the major metal species. The electrical phase increases were potentially due to ion exchange processes that modified charge structure at mineral/water interfaces. Our study revealed the potential of geophysical monitoring for geochemical changes during urea hydrolysis and the advantages of combining multiple approaches to understand complex biogeochemical processes in the subsurface. PMID:21943229

Comparison of clast and matrix dispersal in till: Charlo-Atholville area, north-central New Brunswick

USGS Publications Warehouse

Dickson, M.L.; Broster, B.E.; Parkhill, M.A.

2004-01-01

Striations and dispersal patterns for till clasts and matrix geochemistry are used to define flow directions of glacial transport across an area of about 800km2 in the Charlo-Atholville area of north-central New Brunswick. A total of 170 clast samples and 328 till matrix samples collected for geochemical analysis across the region, were analyzed for a total of 39 elements. Major lithologic contacts used here to delineate till clast provenance were based on recent bedrock mapping. Eleven known mineral occurrences and a gossan are used to define point source targets for matrix geochemical dispersal trains and to estimate probable distance and direction of transport from unknown sources. Clast trains are traceable for distances of approximately 10 km, whereas till geochemical dispersal patterns are commonly lost within 5 km of transport. Most dispersal patterns reflect more than a single direction of glacial transport. These data indicate that a single till sheet, 1-4 m thick, was deposited as the dominant ice-flow direction fluctuated between southeastward, eastward, and northward over the study area. Directions of early flow represent changes in ice sheet dominance, first from the northwest and then from the west. Locally, eastward and northward flow represent the maximum erosive phases. The last directions of flow are likely due to late glacial ice sheet drawdown towards the valley outlet at Baie des Chaleurs.

Model simulations of a field experiment on cation exchange-affected multicomponent solute transport in a sandy aquifer

NASA Astrophysics Data System (ADS)

Bjerg, Poul L.; Ammentorp, Hans C.; Christensen, Thomas H.

1993-04-01

A large-scale and long-term field experiment on cation exchange in a sandy aquifer has been modelled by a three-dimensional geochemical transport model. The geochemical model includes cation-exchange processes using a Gaines-Thomas expression, the closed carbonate system and the effects of ionic strength. Information on geology, hydrogeology and the transient conservative solute transport behaviour was obtained from a dispersion study in the same aquifer. The geochemical input parameters were carefully examined. CEC and selectivity coefficients were determined on the actual aquifer material by batch experiments and by the composition of the cations on the exchange complex. Potassium showed a non-ideal exchange behaviour with KCa selectivity coefficients indicating dependency on equivalent fraction and K + concentration in the aqueous phase. The model simulations over a distance of 35 m and a period of 250 days described accurately the observed attenuation of Na and the expelled amounts of Ca and Mg. Also, model predictions of plateau zones, formed by interaction with the background groundwater, in general agreed satisfactorily with the observations. Transport of K was simulated over a period of 800 days due to a substantially attenuation in the aquifer. The observed and the predicted breakthrough curves showed a reasonable accordance taking the duration of the experiment into account. However, some discrepancies were observed probably caused by the revealed non-ideal exchange behaviour of K +.

Modeling Low-temperature Geochemical Processes

NASA Astrophysics Data System (ADS)

Nordstrom, D. K.

2003-12-01

Geochemical modeling has become a popular and useful tool for a wide number of applications from research on the fundamental processes of water-rock interactions to regulatory requirements and decisions regarding permits for industrial and hazardous wastes. In low-temperature environments, generally thought of as those in the temperature range of 0-100 °C and close to atmospheric pressure (1 atm=1.01325 bar=101,325 Pa), complex hydrobiogeochemical reactions participate in an array of interconnected processes that affect us, and that, in turn, we affect. Understanding these complex processes often requires tools that are sufficiently sophisticated to portray multicomponent, multiphase chemical reactions yet transparent enough to reveal the main driving forces. Geochemical models are such tools. The major processes that they are required to model include mineral dissolution and precipitation; aqueous inorganic speciation and complexation; solute adsorption and desorption; ion exchange; oxidation-reduction; or redox; transformations; gas uptake or production; organic matter speciation and complexation; evaporation; dilution; water mixing; reaction during fluid flow; reaction involving biotic interactions; and photoreaction. These processes occur in rain, snow, fog, dry atmosphere, soils, bedrock weathering, streams, rivers, lakes, groundwaters, estuaries, brines, and diagenetic environments. Geochemical modeling attempts to understand the redistribution of elements and compounds, through anthropogenic and natural means, for a large range of scale from nanometer to global. "Aqueous geochemistry" and "environmental geochemistry" are often used interchangeably with "low-temperature geochemistry" to emphasize hydrologic or environmental objectives.Recognition of the strategy or philosophy behind the use of geochemical modeling is not often discussed or explicitly described. Plummer (1984, 1992) and Parkhurst and Plummer (1993) compare and contrast two approaches for modeling groundwater chemistry: (i) "forward modeling," which predicts water compositions from hypothesized reactions and user assumptions and (ii) "inverse modeling," which uses water, mineral, and isotopic compositions to constrain hypothesized reactions. These approaches simply reflect the amount of information one has to work with. With minimal information on a site, a modeler is forced to rely on forward modeling. Optimal information would include detailed mineralogy on drill cores or well cuttings combined with detailed water analyses at varying depths and sufficient spatial distribution to follow geochemical reactions and mixing of waters along defined flow paths. With optimal information, a modeler will depend on inverse modeling.This chapter outlines the main concepts and key developments in the field of geochemical modeling for low-temperature environments and illustrates their use with examples. It proceeds with a short discussion of what modeling is, continues with concepts and definitions commonly used, and follows with a short history of geochemical models, a discussion of databases, the codes that embody models, and recent examples of how these codes have been used in water-rock interactions. An important new stage of development seems to have been reached in this field with questions of reliability and validity of models. Future work will be obligated to document ranges of certainty and sources of uncertainty, sensitivity of models and codes to parameter errors and assumptions, propagation of errors, and delineation of the range of applicability.

Modelling radionuclide transport in fractured media with a dynamic update of K d values

DOE PAGES

Trinchero, Paolo; Painter, Scott L.; Ebrahimi, Hedieh; ...

2015-10-13

Radionuclide transport in fractured crystalline rocks is a process of interest in evaluating long term safety of potential disposal systems for radioactive wastes. Given their numerical efficiency and the absence of numerical dispersion, Lagrangian methods (e.g. particle tracking algorithms) are appealing approaches that are often used in safety assessment (SA) analyses. In these approaches, many complex geochemical retention processes are typically lumped into a single parameter: the distribution coefficient (Kd). Usually, the distribution coefficient is assumed to be constant over the time frame of interest. However, this assumption could be critical under long-term geochemical changes as it is demonstrated thatmore » the distribution coefficient depends on the background chemical conditions (e.g. pH, Eh, and major chemistry). In this study, we provide a computational framework that combines the efficiency of Lagrangian methods with a sound and explicit description of the geochemical changes of the site and their influence on the radionuclide retention properties.« less

Connectivity clues from short-term variability in settlement and geochemical tags of mytilid mussels

NASA Astrophysics Data System (ADS)

Fodrie, F. Joel; Becker, Bonnie J.; Levin, Lisa A.; Gruenthal, Kristen; McMillan, Pat A.

2011-01-01

The use of geochemical tags in calcified structures of fish and invertebrates is an exciting tool for investigating larval population connectivity. Tag evaluation over relatively short intervals (weeks) may detect environmental and ecological variability at a temporal scale highly relevant to larval transport and settlement. We collected newly settled mussels ( Mytilus californianus and M. galloprovincialis) weekly during winter/spring of 2002 along the coast of San Diego, CA, USA, at sites on the exposed coast (SIO) and in a protected coastal bay (HI), to investigate temporal patterns of geochemical tags in mussel shells. Analyses of post-settlement shell via LA-ICP-MS revealed statistically significant temporal variability for all elements we examined (Mg, Mn, Cu, Sr, Cd, Ba, Pb and U). Despite this, our ability to distinguish multielemental signatures between sites was largely conserved. Throughout our 13-week study, SIO and HI mussels could be chemically distinguished from one another in 78-87% of all cases. Settlement varied between 2 and 27 settlers gram-byssus -1 week -1 at SIO and HI, and both sites were characterized by 2-3 weeks with "high" settlement. Geochemical tags recorded in early larval shell of newly settled mussels differed between "high" and "low" settlement weeks at both sites (MANOVA), driven by Mg and Sr at SIO (p = 0.013) and Sr, Cd, Ba and Pb at HI (p < 0.001). These data imply that shifts in larval sources or transport corridors were responsible for observed settlement variation, rather than increased larval production. In particular, increased settlement at HI was observed concurrent with the appearance of geochemical tags (e.g., elevated Cd), suggesting that those larvae were retained in upwelled water near the mouth of the bay. Such shifts may reflect short-term changes in connectivity among sites due to altered transport corridors, and influence the demography of local populations.

Coupling R and PHREEQC: an interactive and extensible environment for efficient programming of geochemical models

NASA Astrophysics Data System (ADS)

De Lucia, Marco; Kühn, Michael

2013-04-01

PHREEQC [1] is a widely used non-interactive open source software for speciation, batch-reactions, one-dimensional transport, and inverse geochemical caclulations. It represents the tool of choice for many researchers and practicioners for a broad set of geochemical problems, underground CO2 storage among others. Its open source nature, the flexibility to program arbitrary kinetic laws for the chemical reactions, as well as a thorough implementation of the Pitzer formalism explain its success and longevity. However, its non-interactive architecture make it cumbersome to couple PHREEQC to transport programs to achieve reactive transport simulations [2], but also to overcome the limitations of PHREEQC itself regarding the setup of large numbers of simulations - for example exploring wide ranges of conditions - and the graphical evaluation of the results. This has been the main motivation leading to the development of an interface with the high level language and environment for statistical computing and graphics GNU R [3]. The interface consists of minor modifications in PHREEQC's C source code, only affecting data I/O, plus on the R side a bunch of helper functions used to setup the simulations - basically automated manipulation of PHREEQC's input files, which are text files - and to collect and visualize the results. The most relevant subset of PHREEQC's capabilities and features are fully usable through the interface. Illustratory examples for the utility of this programmable interface were given in the framework of the research project this developement originated from: CLEAN [4], a project investigating the feasibility of enhanced gas recovery combined with CO2 storage. This interface allowed us to successfully and easily manipulate, compare and refit chemical databases, perform sensitivity analysis by combinatory variations of parameters, and all that in an environment which is both scriptable and interactive, with all results directly available for further manipulations and visualization in a powerful high level language, and benefiting from an enormous amount of third-party open source R extensions. The possibility to rapidly prototype complex algorithms involving geochemical modelling is in our opinion a huge advantage. A demonstration is given by the successful evaluation of a strategy to reduce the CPU-time needed to perform reactive transport simulations in a sequential coupling scheme. The idea is the "reduction" of the number of actual chemical simulations to perform at every time step, by searching for "duplicates" of each chemical simulations in the grid: such comparison involves typically a huge number of elements (one chemical simulation for grid element for time step) and a quite large number of variables (concentrations and mineral abundances). However, through the straightforward implementation of the prototype algorithm through the R/PHREEQC interface, we found out that the scan is extremely cost-effective in terms of CPU-time and typically allows a relevant speedup for simulations starting from a homogeneous or zone-homogeneous state. This speedup can even greatily exceed that of parallelization in some favorable but not unfrequent case. This feature should therefore be implemented in reactive transport simulators. References [1] Parkhurst D, Appelo C (1999) Users guide to PHREEQC (version 2). Tech. rep, U.S. Geological Survey. [2] Beyer C, Li D, De Lucia M, Kühn M, Bauer S (2012): Modelling CO2-induced fluid-rock interactions in the Altensalzwedel gas reservoir. Part II: coupled reactive transport simulation. Environ. Earth Sci., 67, 2, 573-588. [3] R Core Team (2012) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. ISBN 3-900051-07-0, URL http://www.R-project.org/. [4] Kühn M, Münch U (2012) CLEAN: CO2 Large-Scale Enhanced Gas Recovery. GEOTECHNOLOGIEN Science Report No. 19. Series: Advanced. Technologies in Earth Sciences, 199 p, ISBN 978-3-642-31676-0.

WATEQ4F - a personal computer Fortran translation of the geochemical model WATEQ2 with revised data base

USGS Publications Warehouse

Ball, J.W.; Nordstrom, D. Kirk; Zachmann, D.W.

1987-01-01

A FORTRAN 77 version of the PL/1 computer program for the geochemical model WATEQ2, which computes major and trace element speciation and mineral saturation for natural waters has been developed. The code (WATEQ4F) has been adapted to execute on an IBM PC or compatible microcomputer. Two versions of the code are available, one operating with IBM Professional FORTRAN and an 8087 or 89287 numeric coprocessor, and one which operates without a numeric coprocessor using Microsoft FORTRAN 77. The calculation procedure is identical to WATEQ2, which has been installed on many mainframes and minicomputers. Limited data base revisions include the addition of the following ions: AlHS04(++), BaS04, CaHS04(++), FeHS04(++), NaF, SrC03, and SrHCO3(+). This report provides the reactions and references for the data base revisions, instructions for program operation, and an explanation of the input and output files. Attachments contain sample output from three water analyses used as test cases and the complete FORTRAN source listing. U.S. Geological Survey geochemical simulation program PHREEQE and mass balance program BALANCE also have been adapted to execute on an IBM PC or compatible microcomputer with a numeric coprocessor and the IBM Professional FORTRAN compiler. (Author 's abstract)

PHREEQCI; a graphical user interface for the geochemical computer program PHREEQC

USGS Publications Warehouse

Charlton, Scott R.; Macklin, Clifford L.; Parkhurst, David L.

1997-01-01

PhreeqcI is a Windows-based graphical user interface for the geochemical computer program PHREEQC. PhreeqcI provides the capability to generate and edit input data files, run simulations, and view text files containing simulation results, all within the framework of a single interface. PHREEQC is a multipurpose geochemical program that can perform speciation, inverse, reaction-path, and 1D advective reaction-transport modeling. Interactive access to all of the capabilities of PHREEQC is available with PhreeqcI. The interface is written in Visual Basic and will run on personal computers under the Windows(3.1), Windows95, and WindowsNT operating systems.

Continuum-based DFN-consistent simulations of oxygen ingress in fractured crystalline rocks

NASA Astrophysics Data System (ADS)

Trinchero, P.; Puigdomenech, I.; Molinero, J.; Ebrahimi, H.; Gylling, B.; Svensson, U.; Bosbach, D.; Deissmann, G.

2016-12-01

The potential transient infiltration of oxygenated glacial meltwater into initially anoxic and reducing fractured crystalline rocks during glaciation events is an issue of concern for some of the prospected deep geological repositories for spent nuclear fuel. Here, this problem is assessed using reactive transport calculations. First, a novel parameterisation procedure is presented, where flow, transport and geochemical parameters (i.e. hydraulic conductivity, effective/kinetic porosity, and mineral specific surface and abundance) are defined on a finite volume numerical grid based on the (spatially varying) properties of an underlying Discrete Fracture Network (DFN). Second, using this approach, a realistic reactive transport model of Forsmark, i.e. the selected site for the proposed Swedish spent nuclear fuel repository, is implemented. The model consists of more than 70 million geochemical transport degrees of freedom and simulates the ingress of oxygen-rich water from the recharge area of the domain and its depletion due to reactions with the Fe(II) mineral chlorite. Third, the calculations are solved in the supercomputer JUQUEEN of the Jülich Supercomputing Centre. The results of the simulations show that oxygen infiltrates relatively quickly along fractures and deformation zones until a steady state profile is reached, where geochemical reactions counterbalance advective transport processes. Interestingly, most of the iron-bearing minerals are consumed in the highly conductive zones, where larger mineral surfaces are available for reactions. An analysis based on mineral mass balance shows that the considered rock medium has enough capacity to buffer oxygen infiltration for a long period of time (i.e. some thousand years).

Naval Research Laboratory Arctic Initiatives

DTIC Science & Technology

2011-06-01

Campaign Code 7420 Arctic Modeling Code 7320/7500/7600 In-situ NRL, CRREL NRL boreholes Strategy Remote Sensing Synergism −Collect in-situ...Navy and Marine Corps Corporate Laboratory An array of BMFCs being prepared for deployment. Each BMFC consists of a weighted anode laid flat onto...Gas CH4 E C D CO2 BGHS Free Methane Gas Hydrates HCO3- HCO3- Seismic and geochemical data to predict deep sediment hydrates Estimate spatial

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

PubMed Central

Paz-Garcia, Juan M.; Baek, Kitae; Alshawabkeh, Iyad D.; Alshawabkeh, Akram N.

2012-01-01

A generalized model applicable to soils contaminated with multiple species under enhanced boundary conditions during treatment by electric fields is presented. The partial differential equations describing species transport are developed by applying the law of mass conservation to their fluxes. Transport, due to migration, advection and diffusion, of each aqueous component and complex species are combined to produce one partial differential equation hat describes transport of the total analytical concentrations of component species which are the primary dependent variables. This transport couples 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. PMID:22242884

Contaminant source identification using semi-supervised machine learning

NASA Astrophysics Data System (ADS)

Vesselinov, Velimir V.; Alexandrov, Boian S.; O'Malley, Daniel

2018-05-01

Identification of the original groundwater types present in geochemical mixtures observed in an aquifer is a challenging but very important task. Frequently, some of the groundwater types are related to different infiltration and/or contamination sources associated with various geochemical signatures and origins. The characterization of groundwater mixing processes typically requires solving complex inverse models representing groundwater flow and geochemical transport in the aquifer, where the inverse analysis accounts for available site data. Usually, the model is calibrated against the available data characterizing the spatial and temporal distribution of the observed geochemical types. Numerous different geochemical constituents and processes may need to be simulated in these models which further complicates the analyses. In this paper, we propose a new contaminant source identification approach that performs decomposition of the observation mixtures based on Non-negative Matrix Factorization (NMF) method for Blind Source Separation (BSS), coupled with a custom semi-supervised clustering algorithm. Our methodology, called NMFk, is capable of identifying (a) the unknown number of groundwater types and (b) the original geochemical concentration of the contaminant sources from measured geochemical mixtures with unknown mixing ratios without any additional site information. NMFk is tested on synthetic and real-world site data. The NMFk algorithm works with geochemical data represented in the form of concentrations, ratios (of two constituents; for example, isotope ratios), and delta notations (standard normalized stable isotope ratios).

Contaminant source identification using semi-supervised machine learning

DOE PAGES

Vesselinov, Velimir Valentinov; Alexandrov, Boian S.; O’Malley, Dan

2017-11-08

Identification of the original groundwater types present in geochemical mixtures observed in an aquifer is a challenging but very important task. Frequently, some of the groundwater types are related to different infiltration and/or contamination sources associated with various geochemical signatures and origins. The characterization of groundwater mixing processes typically requires solving complex inverse models representing groundwater flow and geochemical transport in the aquifer, where the inverse analysis accounts for available site data. Usually, the model is calibrated against the available data characterizing the spatial and temporal distribution of the observed geochemical types. Numerous different geochemical constituents and processes may needmore » to be simulated in these models which further complicates the analyses. In this paper, we propose a new contaminant source identification approach that performs decomposition of the observation mixtures based on Non-negative Matrix Factorization (NMF) method for Blind Source Separation (BSS), coupled with a custom semi-supervised clustering algorithm. Our methodology, called NMFk, is capable of identifying (a) the unknown number of groundwater types and (b) the original geochemical concentration of the contaminant sources from measured geochemical mixtures with unknown mixing ratios without any additional site information. NMFk is tested on synthetic and real-world site data. Finally, the NMFk algorithm works with geochemical data represented in the form of concentrations, ratios (of two constituents; for example, isotope ratios), and delta notations (standard normalized stable isotope ratios).« less

Contaminant source identification using semi-supervised machine learning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vesselinov, Velimir Valentinov; Alexandrov, Boian S.; O’Malley, Dan

Identification of the original groundwater types present in geochemical mixtures observed in an aquifer is a challenging but very important task. Frequently, some of the groundwater types are related to different infiltration and/or contamination sources associated with various geochemical signatures and origins. The characterization of groundwater mixing processes typically requires solving complex inverse models representing groundwater flow and geochemical transport in the aquifer, where the inverse analysis accounts for available site data. Usually, the model is calibrated against the available data characterizing the spatial and temporal distribution of the observed geochemical types. Numerous different geochemical constituents and processes may needmore » to be simulated in these models which further complicates the analyses. In this paper, we propose a new contaminant source identification approach that performs decomposition of the observation mixtures based on Non-negative Matrix Factorization (NMF) method for Blind Source Separation (BSS), coupled with a custom semi-supervised clustering algorithm. Our methodology, called NMFk, is capable of identifying (a) the unknown number of groundwater types and (b) the original geochemical concentration of the contaminant sources from measured geochemical mixtures with unknown mixing ratios without any additional site information. NMFk is tested on synthetic and real-world site data. Finally, the NMFk algorithm works with geochemical data represented in the form of concentrations, ratios (of two constituents; for example, isotope ratios), and delta notations (standard normalized stable isotope ratios).« less

Probabilistic, sediment-geochemical parameterisation of the groundwater compartment of the Netherlands for spatially distributed, reactive transport modelling

NASA Astrophysics Data System (ADS)

Janssen, Gijs; Gunnink, Jan; van Vliet, Marielle; Goldberg, Tanya; Griffioen, Jasper

2017-04-01

Pollution of groundwater aquifers with contaminants as nitrate is a common problem. Reactive transport models are useful to predict the fate of such contaminants and to characterise the efficiency of mitigating or preventive measures. Parameterisation of a groundwater transport model on reaction capacity is a necessary step during building the model. Two Dutch, national programs are combined to establish a methodology for building a probabilistic model on reaction capacity of the groundwater compartment at the national scale: the Geological Survey program and the NHI Netherlands Hydrological Instrument program. Reaction capacity is considered as a series of geochemical characteristics that control acid/base condition, redox condition and sorption capacity. Five primary reaction capacity variables are characterised: 1. pyrite, 2. non-pyrite, reactive iron (oxides, siderite and glauconite), 3. clay fraction, 4. organic matter and 5. Ca-carbonate. Important reaction capacity variables that are determined by more than one solid compound are also deduced: 1. potential reduction capacity (PRC) by pyrite and organic matter, 2. cation-exchange capacity (CEC) by organic matter and clay content, 3. carbonate buffering upon pyrite oxidation (CPBO) by carbonate and pyrite. Statistical properties of these variables are established based on c. 16,000 sediment geochemical analyses. The first tens of meters are characterised based on 25 regions using combinations of lithological class and geological formation as strata. Because of both less data and more geochemical uniformity, the deeper subsurface is characterised in a similar way based on 3 regions. The statistical data is used as input in an algoritm that probabilistically calculates the reaction capacity per grid cell. First, the cumulative frequency distribution (cfd) functions are calculated from the statistical data for the geochemical strata. Second, all voxel cells are classified into the geochemical strata. Third, the cfd functions are used to put random reaction capacity variables into the hydrological voxel model. Here, the distribution can be conditioned on two variables. Two important variables are clay content and depth. The first is valid because more dense data is available for clay content than for geochemical variables as pyrite and probabilistic, lithological models are also built at TNO Geological Survey. The second is important to account for locally different depths at which the redox cline between NO3-rich and Fe(II)-rich groundwater occurs within the first tens of meters of the subsurface. An extensive data-set of groundwater quality analyses is used to derive criteria for depth variability of the redox cline. The result is a unique algoritm in order to obtain heterogeneous geochemical reaction capacity models of the entire groundwater compartment of the Netherlands.

Reactive alteration of Mt. Simon sandstone during CO2-rich brine injection: A coupled experimental and modeling study

NASA Astrophysics Data System (ADS)

Dávila Ordoñez, M. G.; Zahasky, C.; Crandall, D.; Druhan, J. L.

2017-12-01

Thus far, one million metric tons of CO2 have been injected into the lower Mt. Simon formation as part of the Decatur CO2 Capture and Storage Project. Micro-seismic events were observed within the CO2 plume both during and after pressurization associated with the primary injection. The Mt. Simon reservoir rock consists of 76.5 wt.% quartz, 2.1 wt.% calcite, 17.3 wt.% K-feldspar, 1.1 wt.% chlorite, 0.7 wt.% illite and lesser extents of siderite, kaolinite, dolomite and marcasite, and is thus anticipated to become geochemically altered by exposure to acidified CO2-rich brine. However, the extent to which the geochemical reactivity contributes to structural weakening is unknown. To explore relationships between the principle geochemical reactions, evolution of fluid transport properties and physical alteration, we performed a series of flow-through experiments using Mt. Simon core (5 cm diameter, ranging from 4.3 - 8.6 cm length) and fluids representative of acidified reservoir brine. Experiments were operated under P = 1450 bar, Pconfining = 1900 - 3000 bar and T = 53 ºC conditions, and flow rates varied from 0.08 to 5.00 mL h-1 over a period of 166 h. A 2D reactive transport code (Crunch-Tope) was used to simulate these experiments, constrained by measured time series aqueous concentrations of Ca, Mg, S, Si, K and Fe and pH during the CO2-rich brine interaction. The model domain was divided into 30 nodes in x at a spacing of 0.12 cm, and 40 nodes in y at a spacing of 0.22 cm, and initial permeability measured for the core was specified and allowed to evolve over the course of the simulation using measured flow rate as a constraint. All relevant kinetic and thermodynamic reaction parameters were obtained from the literature. Solute time series from both experiments and simulations indicated that the acidified brine introduced continuously into the column promoted dissolution of K-feldspar, chloride, illite, pyrite and calcite, and the precipitation of Ca-, Fe- and Si -bearing secondary phases, resulting in a net porosity increase at the inlet. Despite this opening of the inlet pore space, permeability decreased over the length of the column (kfinal/kinitial = 0.76), thus altering local resistance to fluid phase pressure gradients.

Matlab Geochemistry: An open source geochemistry solver based on MRST

NASA Astrophysics Data System (ADS)

McNeece, C. J.; Raynaud, X.; Nilsen, H.; Hesse, M. A.

2017-12-01

The study of geological systems often requires the solution of complex geochemical relations. To address this need we present an open source geochemical solver based on the Matlab Reservoir Simulation Toolbox (MRST) developed by SINTEF. The implementation supports non-isothermal multicomponent aqueous complexation, surface complexation, ion exchange, and dissolution/precipitation reactions. The suite of tools available in MRST allows for rapid model development, in particular the incorporation of geochemical calculations into transport simulations of multiple phases, complex domain geometry and geomechanics. Different numerical schemes and additional physics can be easily incorporated into the existing tools through the object-oriented framework employed by MRST. The solver leverages the automatic differentiation tools available in MRST to solve arbitrarily complex geochemical systems with any choice of species or element concentration as input. Four mathematical approaches enable the solver to be quite robust: 1) the choice of chemical elements as the basis components makes all entries in the composition matrix positive thus preserving convexity, 2) a log variable transformation is used which transfers the nonlinearity to the convex composition matrix, 3) a priori bounds on variables are calculated from the structure of the problem, constraining Netwon's path and 4) an initial guess is calculated implicitly by sequentially adding model complexity. As a benchmark we compare the model to experimental and semi-analytic solutions of the coupled salinity-acidity transport system. Together with the reservoir simulation capabilities of MRST the solver offers a promising tool for geochemical simulations in reservoir domains for applications in a diversity of fields from enhanced oil recovery to radionuclide storage.

Investigating the role of gas bubble formation and entrapment in contaminated aquifers: Reactive transport modelling

USGS Publications Warehouse

Amos, Richard T.; Mayer, K. Ulrich

2006-01-01

In many natural and contaminated aquifers, geochemical processes result in the production or consumption of dissolved gases. In cases where methanogenesis or denitrification occurs, the production of gases may result in the formation and growth of gas bubbles below the water table. Near the water table, entrapment of atmospheric gases during water table rise may provide a significant source of O2 to waters otherwise depleted in O2. Furthermore, the presence of bubbles will affect the hydraulic conductivity of an aquifer, resulting in changes to the groundwater flow regime. The interactions between physical transport, biogeochemical processes, and gas bubble formation, entrapment and release is complex and requires suitable analysis tools. The objective of the present work is the development of a numerical model capable of quantitatively assessing these processes. The multicomponent reactive transport code MIN3P has been enhanced to simulate bubble growth and contraction due to in-situ gas production or consumption, bubble entrapment due to water table rise and subsequent re-equilibration of the bubble with ambient groundwater, and permeability changes due to trapped gas phase saturation. The resulting formulation allows for the investigation of complex geochemical systems where microbially mediated redox reactions both produce and consume gases as well as affect solution chemistry, alkalinity, and pH. The enhanced model has been used to simulate processes in a petroleum hydrocarbon contaminated aquifer where methanogenesis is an important redox process. The simulations are constrained by data from a crude oil spill site near Bemidji, MN. Our results suggest that permeability reduction in the methanogenic zone due to in-situ formation of gas bubbles, and dissolution of entrapped atmospheric bubbles near the water table, both work to attenuate the dissolved gas plume emanating from the source zone. Furthermore, the simulations demonstrate that under the given conditions more than 50% of all produced CH4 partitions to the gas phase or is aerobically oxidised near the water table, suggesting that these processes should be accounted for when assessing the rate and extent of methanogenic degradation of hydrocarbons.

Investigating the role of gas bubble formation and entrapment in contaminated aquifers: Reactive transport modelling

NASA Astrophysics Data System (ADS)

Amos, Richard T.; Ulrich Mayer, K.

2006-09-01

In many natural and contaminated aquifers, geochemical processes result in the production or consumption of dissolved gases. In cases where methanogenesis or denitrification occurs, the production of gases may result in the formation and growth of gas bubbles below the water table. Near the water table, entrapment of atmospheric gases during water table rise may provide a significant source of O 2 to waters otherwise depleted in O 2. Furthermore, the presence of bubbles will affect the hydraulic conductivity of an aquifer, resulting in changes to the groundwater flow regime. The interactions between physical transport, biogeochemical processes, and gas bubble formation, entrapment and release is complex and requires suitable analysis tools. The objective of the present work is the development of a numerical model capable of quantitatively assessing these processes. The multicomponent reactive transport code MIN3P has been enhanced to simulate bubble growth and contraction due to in-situ gas production or consumption, bubble entrapment due to water table rise and subsequent re-equilibration of the bubble with ambient groundwater, and permeability changes due to trapped gas phase saturation. The resulting formulation allows for the investigation of complex geochemical systems where microbially mediated redox reactions both produce and consume gases as well as affect solution chemistry, alkalinity, and pH. The enhanced model has been used to simulate processes in a petroleum hydrocarbon contaminated aquifer where methanogenesis is an important redox process. The simulations are constrained by data from a crude oil spill site near Bemidji, MN. Our results suggest that permeability reduction in the methanogenic zone due to in-situ formation of gas bubbles, and dissolution of entrapped atmospheric bubbles near the water table, both work to attenuate the dissolved gas plume emanating from the source zone. Furthermore, the simulations demonstrate that under the given conditions more than 50% of all produced CH 4 partitions to the gas phase or is aerobically oxidised near the water table, suggesting that these processes should be accounted for when assessing the rate and extent of methanogenic degradation of hydrocarbons.

Impacts of CO2 Leakage on a Shallow Aquifer System: Laboratory Column Experiments and Reactive Transport Modeling

NASA Astrophysics Data System (ADS)

Ha, Jong Heon; Jeen, Sung-Wook

2017-04-01

Groundwater quality change due to the leakage of CO2 in a shallow aquifer system is an important aspect of environmental impact assessment in a carbon dioxide capture and storage (CCS) site. This study evaluated geochemical changes in a shallow aquifer system resulting from leakage of CO2 through laboratory column experiments and reactive transport modeling. In the column experiments, two columns were set up and filled with the sediment from the Environmental Impact Test (EIT) facility of the Korea CO2 Storage Environmental Management (K-COSEM) Research Center. Groundwater, also collected form the EIT site, was purged with CO2 or Ar gases, and was pumped into the columns with the pumping rates of 200-1000 mL day-1 (0.124-0.62 m day-1). Profile and time-series effluent samplings were conducted to evaluate the spatial and temporal geochemical changes in the aquifer materials upon contact with CO2. The experimental results showed that after injecting CO2-purged groundwater, the pH was decreased, and alkalinity, electrical conductivity (EC) and concentrations of major cations were increased. The spatial and temporal geochemical changes from the column experiments indicate that dissolution of aquifer materials in contact with dissolved CO2 is the major contributor to the changes in groundwater geochemistry. The reactive transport modeling has been conducted to reproduce these geochemical changes in the aquifer system by incorporating dissolution of the dominant aluminosilicate minerals in the aquifer such as microcline, anorthite, albite, and biotite. This study suggests that pH, alkalinity, EC and concentrations of major cations are important monitoring parameters for detecting CO2 leakage in a shallow groundwater aquifer system.

A compilation of rate parameters of water-mineral interaction kinetics for application to geochemical modeling

USGS Publications Warehouse

Palandri, James L.; Kharaka, Yousif K.

2004-01-01

Geochemical reaction path modeling is useful for rapidly assessing the extent of water-aqueous-gas interactions both in natural systems and in industrial processes. Modeling of some systems, such as those at low temperature with relatively high hydrologic flow rates, or those perturbed by the subsurface injection of industrial waste such as CO2 or H2S, must account for the relatively slow kinetics of mineral-gas-water interactions. We have therefore compiled parameters conforming to a general Arrhenius-type rate equation, for over 70 minerals, including phases from all the major classes of silicates, most carbonates, and many other non-silicates. The compiled dissolution rate constants range from -0.21 log moles m-2 s-1 for halite, to -17.44 log moles m-2 s-1 for kyanite, for conditions far from equilibrium, at 25 ?C, and pH near neutral. These data have been added to a computer code that simulates an infinitely well-stirred batch reactor, allowing computation of mass transfer as a function of time. Actual equilibration rates are expected to be much slower than those predicted by the selected computer code, primarily because actual geochemical processes commonly involve flow through porous or fractured media, wherein the development of concentration gradients in the aqueous phase near mineral surfaces, which results in decreased absolute chemical affinity and slower reaction rates. Further differences between observed and computed reaction rates may occur because of variables beyond the scope of most geochemical simulators, such as variation in grain size, aquifer heterogeneity, preferred fluid flow paths, primary and secondary mineral coatings, and secondary minerals that may lead to decreased porosity and clogged pore throats.

Hydraulic and geochemical framework of the Idaho National Engineering and Environmental Laboratory vadose zone

USGS Publications Warehouse

Nimmo, John R.; Rousseau, Joseph P.; Perkins, Kim S.; Stollenwerk, Kenneth G.; Glynn, Pierre D.; Bartholomay, Roy C.; Knobel, LeRoy L.

2004-01-01

Questions of major importance for subsurface contaminant transport at the Idaho National Engineering and Environmental Laboratory (INEEL) include (i) travel times to the aquifer, both average or typical values and the range of values to be expected, and (ii) modes of contaminant transport, especially sorption processes. The hydraulic and geochemical framework within which these questions are addressed is dominated by extreme heterogeneity in a vadose zone and aquifer consisting of interbedded basalts and sediments. Hydraulically, major issues include diverse possible types of flow pathways, extreme anisotropy, preferential flow, combined vertical and horizontal flow, and temporary saturation or perching. Geochemically, major issues include contaminant mobility as influenced by redox conditions, the concentration of organic and inorganic complexing solutes and other local variables, the interaction with infiltrating waters and with the contaminant source environment, and the aqueous speciation of contaminants such as actinides. Another major issue is the possibility of colloid transport, which inverts some of the traditional concepts of mobility, as sorbed contaminants on mobile colloids may be transported with ease compared with contaminants that are not sorbed. With respect to the goal of minimizing aquifer concentrations of contaminants, some characteristics of the vadose zone are essentially completely favorable. Examples include the great thickness (200 m) of the vadose zone, and the presence of substantial quantities of fine sediments that can retard contaminant transport both hydraulically and chemically. Most characteristics, however, have both favorable and unfavorable aspects. For example, preferential flow, as promoted by several notable features of the vadose zone at the INEEL, can provide fast, minimally sorbing pathways for contaminants to reach the aquifer easily, but it also leads to a wide dispersal of contaminants in a large volume of subsurface material, thus increasing the opportunity for dilution and sorption.

Energy-Constrained Recharge, Assimilation, and Fractional Crystallization (EC-RAχFC): A Visual Basic computer code for calculating trace element and isotope variations of open-system magmatic systems

NASA Astrophysics Data System (ADS)

Bohrson, Wendy A.; Spera, Frank J.

2007-11-01

Volcanic and plutonic rocks provide abundant evidence for complex processes that occur in magma storage and transport systems. The fingerprint of these processes, which include fractional crystallization, assimilation, and magma recharge, is captured in petrologic and geochemical characteristics of suites of cogenetic rocks. Quantitatively evaluating the relative contributions of each process requires integration of mass, species, and energy constraints, applied in a self-consistent way. The energy-constrained model Energy-Constrained Recharge, Assimilation, and Fractional Crystallization (EC-RaχFC) tracks the trace element and isotopic evolution of a magmatic system (melt + solids) undergoing simultaneous fractional crystallization, recharge, and assimilation. Mass, thermal, and compositional (trace element and isotope) output is provided for melt in the magma body, cumulates, enclaves, and anatectic (i.e., country rock) melt. Theory of the EC computational method has been presented by Spera and Bohrson (2001, 2002, 2004), and applications to natural systems have been elucidated by Bohrson and Spera (2001, 2003) and Fowler et al. (2004). The purpose of this contribution is to make the final version of the EC-RAχFC computer code available and to provide instructions for code implementation, description of input and output parameters, and estimates of typical values for some input parameters. A brief discussion highlights measures by which the user may evaluate the quality of the output and also provides some guidelines for implementing nonlinear productivity functions. The EC-RAχFC computer code is written in Visual Basic, the programming language of Excel. The code therefore launches in Excel and is compatible with both PC and MAC platforms. The code is available on the authors' Web sites http://magma.geol.ucsb.edu/and http://www.geology.cwu.edu/ecrafc) as well as in the auxiliary material.

Experimental Study of Cement - Sandstone/Shale - Brine - CO2 Interactions

PubMed Central

2011-01-01

Background Reactive-transport simulation is a tool that is being used to estimate long-term trapping of CO2, and wellbore and cap rock integrity for geologic CO2 storage. We reacted end member components of a heterolithic sandstone and shale unit that forms the upper section of the In Salah Gas Project carbon storage reservoir in Krechba, Algeria with supercritical CO2, brine, and with/without cement at reservoir conditions to develop experimentally constrained geochemical models for use in reactive transport simulations. Results We observe marked changes in solution composition when CO2 reacted with cement, sandstone, and shale components at reservoir conditions. The geochemical model for the reaction of sandstone and shale with CO2 and brine is a simple one in which albite, chlorite, illite and carbonate minerals partially dissolve and boehmite, smectite, and amorphous silica precipitate. The geochemical model for the wellbore environment is also fairly simple, in which alkaline cements and rock react with CO2-rich brines to form an Fe containing calcite, amorphous silica, smectite and boehmite or amorphous Al(OH)3. Conclusions Our research shows that relatively simple geochemical models can describe the dominant reactions that are likely to occur when CO2 is stored in deep saline aquifers sealed with overlying shale cap rocks, as well as the dominant reactions for cement carbonation at the wellbore interface. PMID:22078161

Calculation of individual isotope equilibrium constants for implementation in geochemical models

USGS Publications Warehouse

Thorstenson, Donald C.; Parkhurst, David L.

2002-01-01

Theory is derived from the work of Urey to calculate equilibrium constants commonly used in geochemical equilibrium and reaction-transport models for reactions of individual isotopic species. Urey showed that equilibrium constants of isotope exchange reactions for molecules that contain two or more atoms of the same element in equivalent positions are related to isotope fractionation factors by , where is n the number of atoms exchanged. This relation is extended to include species containing multiple isotopes, for example and , and to include the effects of nonideality. The equilibrium constants of the isotope exchange reactions provide a basis for calculating the individual isotope equilibrium constants for the geochemical modeling reactions. The temperature dependence of the individual isotope equilibrium constants can be calculated from the temperature dependence of the fractionation factors. Equilibrium constants are calculated for all species that can be formed from and selected species containing , in the molecules and the ion pairs with where the subscripts g, aq, l, and s refer to gas, aqueous, liquid, and solid, respectively. These equilibrium constants are used in the geochemical model PHREEQC to produce an equilibrium and reaction-transport model that includes these isotopic species. Methods are presented for calculation of the individual isotope equilibrium constants for the asymmetric bicarbonate ion. An example calculates the equilibrium of multiple isotopes among multiple species and phases.

Programming PHREEQC calculations with C++ and Python a comparative study

USGS Publications Warehouse

Charlton, Scott R.; Parkhurst, David L.; Muller, Mike

2011-01-01

The new IPhreeqc module provides an application programming interface (API) to facilitate coupling of other codes with the U.S. Geological Survey geochemical model PHREEQC. Traditionally, loose coupling of PHREEQC with other applications required methods to create PHREEQC input files, start external PHREEQC processes, and process PHREEQC output files. IPhreeqc eliminates most of this effort by providing direct access to PHREEQC capabilities through a component object model (COM), a library, or a dynamically linked library (DLL). Input and calculations can be specified through internally programmed strings, and all data exchange between an application and the module can occur in computer memory. This study compares simulations programmed in C++ and Python that are tightly coupled with IPhreeqc modules to the traditional simulations that are loosely coupled to PHREEQC. The study compares performance, quantifies effort, and evaluates lines of code and the complexity of the design. The comparisons show that IPhreeqc offers a more powerful and simpler approach for incorporating PHREEQC calculations into transport models and other applications that need to perform PHREEQC calculations. The IPhreeqc module facilitates the design of coupled applications and significantly reduces run times. Even a moderate knowledge of one of the supported programming languages allows more efficient use of PHREEQC than the traditional loosely coupled approach.

Description of Transport Codes for Space Radiation Shielding

NASA Technical Reports Server (NTRS)

Kim, Myung-Hee Y.; Wilson, John W.; Cucinotta, Francis A.

2011-01-01

This slide presentation describes transport codes and their use for studying and designing space radiation shielding. When combined with risk projection models radiation transport codes serve as the main tool for study radiation and designing shielding. There are three criteria for assessing the accuracy of transport codes: (1) Ground-based studies with defined beams and material layouts, (2) Inter-comparison of transport code results for matched boundary conditions and (3) Comparisons to flight measurements. These three criteria have a very high degree with NASA's HZETRN/QMSFRG.

Inferences from Microfractures and Geochemistry in Dynamic Shale-CO2 Packed Bed Experiments

NASA Astrophysics Data System (ADS)

Radonjic, M.; Olabode, A.

2016-12-01

Subsurface storage of large volumes of carbondioxide (CO2) is expected to have long term rock-fluid interactions impact on reservoir and seal rocks properties. Caprocks, particularly sedimentary types, are the ultimate hydraulic barrier in carbon sequestration. The mineralogical components of sedimentary rocks are geochemically active under enormous earth stresses, which generate high pressure and temperature conditions. It has been postulated that in-situ mineralization can lead to flow impedance in natural fractures in the presence of favorable geochemical and thermodynamic conditions. This experimental modelling research investigated the impact of in-situ geochemical precipitation on conductivity of fractures. Geochemical analyses were performed on four different samples of shale rocks, effluent fluids and recovered precipitates both before and after CO2-brine flooding of crushed shale rocks at moderately high temperature and pressure conditions. The results showed that most significant diagenetic changes in shale rocks after flooding with CO2-brine, reflected in the effluent fluid with predominantly calcium based minerals dissolving and precipitating under experimental conditions. Major and trace elements in the effluent (using ICP-OES analysis) indicated that multiple geochemical reactions are occurring with almost all of the constituent minerals participating. The geochemical composition of precipitates recovered after the experiments showed diagenetic carbonates and opal as the main constituents. The bulk rock showed little changes in composition except for sharper and more refined peaks on XRD analysis, suggesting that a significant portion of the amorphous content of the rocks have been removed via dissolution by the slightly acid CO2-brine fluid that was injected. Micro-indentation results captured slight reduction in the hardness of the shale rocks and this reduction appeared dependent on diagenetic quartz content. It can be inferred that convective reactive transport of dissolved minerals are involved in nanoscale precipitation-dissolution processes in shale. This reactive transport of dissolved minerals can occlude micro-fracture flow paths, thereby improving shale caprock seal integrity with respect to leakage risk under CO2 sequestration conditions.

An alternative to fully coupled reactive transport simulations for long-term prediction of chemical reactions in complex geological systems

NASA Astrophysics Data System (ADS)

De Lucia, Marco; Kempka, Thomas; Kühn, Michael

2014-05-01

Fully-coupled reactive transport simulations involving multiphase hydrodynamics and chemical reactions in heterogeneous settings are extremely challenging from a computational point of view. This often leads to oversimplification of the investigated system: coarse spatial discretization, to keep the number of elements in the order of few thousands; simplified chemistry, disregarding many potentially important reactions. A novel approach for coupling non-reactive hydrodynamic simulations with the outcome of single batch geochemical simulations was therefore introduced to assess the potential long-term mineral trapping at the Ketzin pilot site for underground CO2 storage in Germany [1],[2]. The advantage of the coupling is the ability to use multi-million grid non-reactive hydrodynamics simulations on one side and few batch 0D geochemical simulations on the other, so that the complexity of both systems does not need to be reduced. This contribution shows the approach which was taken to validate this simplified coupling scheme. The procedure involved batch simulations of the reference geochemical model, then performing both non-reactive and fully coupled 1D and 3D reactive transport simulations and finally applying the simplified coupling scheme based on the non-reactive and geochemical batch model. The TOUGHREACT/ECO2N [3] simulator was adopted for the validation. The degree of refinement of the spatial grid and the complexity and velocity of the mineral reactions, along with a cut-off value for the minimum concentration of dissolved CO2 allowed to originate precipitates in the simplified approach were found out to be the governing parameters for the convergence of the two schemes. Systematic discrepancies between the approaches are not reducible, simply because there is no feedback between chemistry and hydrodynamics, and can reach 20 % - 30 % in unfavourable cases. However, even such discrepancy is completely acceptable, in our opinion, given the amount of uncertainty underlying the geochemical models. References [1] Klein, E., De Lucia, M., Kempka, T. Kühn, M. 2013. Evaluation of longterm mineral trapping at the Ketzin pilot site for CO2 storage: an integrative approach using geochemical modelling and reservoir simulation. International Journal of Greenhouse Gas Control 19: 720-730, doi:10.1016/j.ijggc.2013.05.014 [2] Kempka, T., Klein, E., De Lucia, M., Tillner, E. Kühn, M. 2013. Assessment of Long-term CO2 Trapping Mechanisms at the Ketzin Pilot Site (Germany) by Coupled Numerical Modelling. Energy Procedia 37: 5419-5426, doi:10.1016/j.egypro.2013.06.460 [3] Xu, T., Spycher, N., Sonnenthal, E., Zhang, G., Zheng, L., Pruess, K. 2010. TOUGHREACT Version 2.0: A simulator for subsurface reactive transport under non-isothermal multiphase flow conditions, Computers & Geosciences 37(6), doi:10.1016/j.cageo.2010.10.007

Data collection handbook to support modeling the impacts of radioactive material in soil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, C.; Cheng, J.J.; Jones, L.G.

1993-04-01

A pathway analysis computer code called RESRAD has been developed for implementing US Department of Energy Residual Radioactive Material Guidelines. Hydrogeological, meteorological, geochemical, geometrical (size, area, depth), and material-related (soil, concrete) parameters are used in the RESRAD code. This handbook discusses parameter definitions, typical ranges, variations, measurement methodologies, and input screen locations. Although this handbook was developed primarily to support the application of RESRAD, the discussions and values are valid for other model applications.

Numerical investigation of coupled density-driven flow and hydrogeochemical processes below playas

NASA Astrophysics Data System (ADS)

Hamann, Enrico; Post, Vincent; Kohfahl, Claus; Prommer, Henning; Simmons, Craig T.

2015-11-01

Numerical modeling approaches with varying complexity were explored to investigate coupled groundwater flow and geochemical processes in saline basins. Long-term model simulations of a playa system gain insights into the complex feedback mechanisms between density-driven flow and the spatiotemporal patterns of precipitating evaporites and evolving brines. Using a reactive multicomponent transport model approach, the simulations reproduced, for the first time in a numerical study, the evaporite precipitation sequences frequently observed in saline basins ("bull's eyes"). Playa-specific flow, evapoconcentration, and chemical divides were found to be the primary controls for the location of evaporites formed, and the resulting brine chemistry. Comparative simulations with the computationally far less demanding surrogate single-species transport models showed that these were still able to replicate the major flow patterns obtained by the more complex reactive transport simulations. However, the simulated degree of salinization was clearly lower than in reactive multicomponent transport simulations. For example, in the late stages of the simulations, when the brine becomes halite-saturated, the nonreactive simulation overestimated the solute mass by almost 20%. The simulations highlight the importance of the consideration of reactive transport processes for understanding and quantifying geochemical patterns, concentrations of individual dissolved solutes, and evaporite evolution.

Los Alamos radiation transport code system on desktop computing platforms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Briesmeister, J.F.; Brinkley, F.W.; Clark, B.A.

The Los Alamos Radiation Transport Code System (LARTCS) consists of state-of-the-art Monte Carlo and discrete ordinates transport codes and data libraries. These codes were originally developed many years ago and have undergone continual improvement. With a large initial effort and continued vigilance, the codes are easily portable from one type of hardware to another. The performance of scientific work-stations (SWS) has evolved to the point that such platforms can be used routinely to perform sophisticated radiation transport calculations. As the personal computer (PC) performance approaches that of the SWS, the hardware options for desk-top radiation transport calculations expands considerably. Themore » current status of the radiation transport codes within the LARTCS is described: MCNP, SABRINA, LAHET, ONEDANT, TWODANT, TWOHEX, and ONELD. Specifically, the authors discuss hardware systems on which the codes run and present code performance comparisons for various machines.« less

NETPATH-WIN: an interactive user version of the mass-balance model, NETPATH

USGS Publications Warehouse

El-Kadi, A. I.; Plummer, Niel; Aggarwal, P.

2011-01-01

NETPATH-WIN is an interactive user version of NETPATH, an inverse geochemical modeling code used to find mass-balance reaction models that are consistent with the observed chemical and isotopic composition of waters from aquatic systems. NETPATH-WIN was constructed to migrate NETPATH applications into the Microsoft WINDOWS® environment. The new version facilitates model utilization by eliminating difficulties in data preparation and results analysis of the DOS version of NETPATH, while preserving all of the capabilities of the original version. Through example applications, the note describes some of the features of NETPATH-WIN as applied to adjustment of radiocarbon data for geochemical reactions in groundwater systems.

Garnets within geode-like serpentinite veins: Implications for element transport, hydrogen production and life-supporting environment formation

NASA Astrophysics Data System (ADS)

Plümper, Oliver; Beinlich, Andreas; Bach, Wolfgang; Janots, Emilie; Austrheim, Håkon

2014-09-01

Geochemical micro-environments within serpentinizing systems can abiotically synthesize hydrocarbons and provide the ingredients required to support life. Observations of organic matter in microgeode-like hydrogarnets found in Mid-Atlantic Ridge serpentinites suggest these garnets possibly represent unique nests for the colonization of microbial ecosystems within the oceanic lithosphere. However, little is known about the mineralogical and geochemical processes that allow such unique environments to form. Here we present work on outcrop-scale vein networks from an ultramafic massif in Norway that contain massive amounts of spherulitic garnets (andradite), which help to constrain such processes. Vein andradite spherulites are associated with polyhedral serpentine, brucite, Ni-Fe alloy (awaruite), and magnetite indicative of low temperature (<200 °C) alteration under low fO2 and low aSiO2,aq geochemical conditions. Together with the outcrop- and micro-scale analysis geochemical reaction path modeling shows that there was limited mass transport and fluid flow over a large scale. Once opened the veins remained isolated (closed system), forming non-equilibrium microenvironments that allowed, upon a threshold supersaturation, the rapid crystallization (seconds to weeks) of spherulitic andradite. The presence of polyhedral serpentine spheres indicates that veins were initially filled with a gel-like protoserpentine phase. In addition, massive Fe oxidation associated with andradite formation could have generated as much as 600 mmol H2,aq per 100 cm3 vein. Although no carboneous matter was detected, the vein networks fulfill the reported geochemical criteria required to generate abiogenic hydrocarbons and support microbial communities. Thus, systems similar to those investigated here are of prime interest when searching for life-supporting environments within the deep subsurface.

Produced water re-injection in a non-fresh water aquifer with geochemical reaction, hydrodynamic molecular dispersion and adsorption kinetics controlling: model development and numerical simulation

NASA Astrophysics Data System (ADS)

Obe, Ibidapo; Fashanu, T. A.; Idialu, Peter O.; Akintola, Tope O.; Abhulimen, Kingsley E.

2017-06-01

An improved produced water reinjection (PWRI) model that incorporates filtration, geochemical reaction, molecular transport, and mass adsorption kinetics was developed to predict cake deposition and injectivity performance in hydrocarbon aquifers in Nigeria oil fields. Thus, the improved PWRI model considered contributions of geochemical reaction, adsorption kinetics, and hydrodynamic molecular dispersion mechanism to alter the injectivity and deposition of suspended solids on aquifer wall resulting in cake formation in pores during PWRI and transport of active constituents in hydrocarbon reservoirs. The injectivity decline and cake deposition for specific case studies of hydrocarbon aquifers in Nigeria oil fields were characterized with respect to its well geometry, lithology, and calibrations data and simulated in COMSOL multiphysics software environment. The PWRI model was validated by comparisons to assessments of previous field studies based on data and results supplied by operator and regulator. The results of simulation showed that PWRI performance was altered because of temporal variations and declinations of permeability, injectivity, and cake precipitation, which were observed to be dependent on active adsorption and geochemical reaction kinetics coupled with filtration scheme and molecular dispersion. From the observed results and findings, transition time t r to cake nucleation and growth were dependent on aquifer constituents, well capacity, filtration coefficients, particle-to-grain size ratio, water quality, and more importantly, particle-to-grain adsorption kinetics. Thus, the results showed that injectivity decline and permeability damage were direct contributions of geochemical reaction, hydrodynamic molecular diffusion, and adsorption kinetics to the internal filtration mechanism, which are largely dependent on the initial conditions of concentration of active constituents of produced water and aquifer capacity.

A Sr-Nd isotopic study of sand-sized sediment provenance and transport for the San Francisco Bay coastal system

USGS Publications Warehouse

Rosenbauer, Robert J.; Foxgrover, Amy C.; Hein, James R.; Swarzenski, Peter W.; Barnard, P.L.; Jaffee, B.E.; Schoellhamer, D.H.

2013-01-01

A diverse suite of geochemical tracers, including 87Sr/86Sr and 143Nd/144Nd isotope ratios, the rare earth elements (REEs), and select trace elements were used to determine sand-sized sediment provenance and transport pathways within the San Francisco Bay coastal system. This study complements a large interdisciplinary effort (Barnard et al., 2012) that seeks to better understand recent geomorphic change in a highly urbanized and dynamic estuarine-coastal setting. Sand-sized sediment provenance in this geologically complex system is important to estuarine resource managers and was assessed by examining the geographic distribution of this suite of geochemical tracers from the primary sources (fluvial and rock) throughout the bay, adjacent coast, and beaches. Due to their intrinsic geochemical nature, 143Nd/144Nd isotopic ratios provide the most resolved picture of where sediment in this system is likely sourced and how it moves through this estuarine system into the Pacific Ocean. For example, Nd isotopes confirm that the predominant source of sand-sized sediment to Suisun Bay, San Pablo Bay, and Central Bay is the Sierra Nevada Batholith via the Sacramento River, with lesser contributions from the Napa and San Joaquin Rivers. Isotopic ratios also reveal hot-spots of local sediment accumulation, such as the basalt and chert deposits around the Golden Gate Bridge and the high magnetite deposits of Ocean Beach. Sand-sized sediment that exits San Francisco Bay accumulates on the ebb-tidal delta and is in part conveyed southward by long-shore currents. Broadly, the geochemical tracers reveal a complex story of multiple sediment sources, dynamic intra-bay sediment mixing and reworking, and eventual dilution and transport by energetic marine processes. Combined geochemical results provide information on sediment movement into and through San Francisco Bay and further our understanding of how sustained anthropogenic activities which limit sediment inputs to the system (e.g., dike and dam construction) as well as those which directly remove sediments from within the Bay, such as aggregate mining and dredging, can have long-lasting effects

A velocity-dependent anomalous radial transport model for (2-D, 2-V) kinetic transport codes

NASA Astrophysics Data System (ADS)

Bodi, Kowsik; Krasheninnikov, Sergei; Cohen, Ron; Rognlien, Tom

2008-11-01

Plasma turbulence constitutes a significant part of radial plasma transport in magnetically confined plasmas. This turbulent transport is modeled in the form of anomalous convection and diffusion coefficients in fluid transport codes. There is a need to model the same in continuum kinetic edge codes [such as the (2-D, 2-V) transport version of TEMPEST, NEO, and the code being developed by the Edge Simulation Laboratory] with non-Maxwellian distributions. We present an anomalous transport model with velocity-dependent convection and diffusion coefficients leading to a diagonal transport matrix similar to that used in contemporary fluid transport models (e.g., UEDGE). Also presented are results of simulations corresponding to radial transport due to long-wavelength ExB turbulence using a velocity-independent diffusion coefficient. A BGK collision model is used to enable comparison with fluid transport codes.

Geochemical Exploration Techniques Applicable in the Search for Copper Deposits

USGS Publications Warehouse

Chaffee, Maurice A.

1975-01-01

Geochemical exploration is an important part of copper-resource evaluation. A large number of geochemical exploration techniques, both proved and untried, are available to the geochemist to use in the search for new copper deposits. Analyses of whole-rock samples have been used in both regional and local geochemical exploration surveys in the search for copper. Analyses of mineral separates, such as biotite, magnetite, and sulfides, have also been used. Analyses of soil samples are widely used in geochemical exploration, especially for localized surveys. It is important to distinguish between residual and transported soil types. Orientation studies should always be conducted prior to a geochemical investigation in a given area in order to determine the best soil horizon and the best size of soil material for sampling in that area. Silty frost boils, caliche, and desert varnish are specialized types of soil samples that might be useful sampling media. Soil gas is a new and potentially valuable geochemical sampling medium, especially in exploring for buried mineral deposits in arid regions. Gaseous products in samples of soil may be related to base-metal deposits and include mercury vapor, sulfur dioxide, hydrogen sulfide, carbon oxysulfide, carbon dioxide, hydrogen, oxygen, nitrogen, the noble gases, the halogens, and many hydrocarbon compounds. Transported materials that have been used in geochemical sampling programs include glacial float boulders, glacial till, esker gravels, stream sediments, stream-sediment concentrates, and lake sediments. Stream-sediment sampling is probably the most widely used and most successful geochemical exploration technique. Hydrogeochemical exploration programs have utilized hot- and cold-spring waters and their precipitates as well as waters from lakes, streams, and wells. Organic gel found in lakes and at stream mouths is an unproved sampling medium. Suspended material and dissolved gases in any type of water may also be useful media. Samples of ice and snow have been used for limited geochemical surveys. Both geobotanical and biogeochemical surveys have been successful in locating copper deposits in many parts of the world. Micro-organisms, including bacteria and algae, are other unproved media that should be studied. Animals can be used in geochemical-prospecting programs. Dogs have been used quite successfully to sniff out hidden and exposed sulfide minerals. Tennite mounds are commonly composed of subsurface material, but have not as yet proved to be useful in locating buried mineral deposits. Animal tissue and waste products are essentially unproved but potentially valuable sampling media. Knowledge of the location of areas where trace-element-associated diseases in animals and man are endemic as well as a better understanding of these diseases, may aid in identifying regions that are enriched in or depleted of various elements, including copper. Results of analyses of gases in the atmosphere are proving valuable in mineral-exploration surveys. Studies involving metallic compounds exhaled by plants into the atmosphere, and of particulate matter suspended in the atmosphere are reviewed these methods may become important in the future. Remote-sensing techniques are useful for making indirect measurements of geochemical responses. Two techniques applicable to geochemical exploration are neutron-activation analysis and gamma-ray spectrometry. Aerial photography is especially useful in vegetation surveys. Radar imagery is an unproved but potentially valuable method for use in studies of vegetation in perpetually clouded regions. With the advent of modern computers, many new techniques, such as correlation analysis, regression analysis, discriminant analysis, factor analysis, cluster analysis, trend-surface analysis, and moving-average analysis can be applied to geochemical data sets. Selective use of these techniques can provide new insights into the interpretatio

SYMTRAN - A Time-dependent Symmetric Tandem Mirror Transport Code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hua, D; Fowler, T

2004-06-15

A time-dependent version of the steady-state radial transport model in symmetric tandem mirrors in Ref. [1] has been coded up and first tests performed. Our code, named SYMTRAN, is an adaptation of the earlier SPHERE code for spheromaks, now modified for tandem mirror physics. Motivated by Post's new concept of kinetic stabilization of symmetric mirrors, it is an extension of the earlier TAMRAC rate-equation code omitting radial transport [2], which successfully accounted for experimental results in TMX. The SYMTRAN code differs from the earlier tandem mirror radial transport code TMT in that our code is focused on axisymmetric tandem mirrorsmore » and classical diffusion, whereas TMT emphasized non-ambipolar transport in TMX and MFTF-B due to yin-yang plugs and non-symmetric transitions between the plugs and axisymmetric center cell. Both codes exhibit interesting but different non-linear behavior.« less

Comparison of space radiation calculations for deterministic and Monte Carlo transport codes

NASA Astrophysics Data System (ADS)

Lin, Zi-Wei; Adams, James; Barghouty, Abdulnasser; Randeniya, Sharmalee; Tripathi, Ram; Watts, John; Yepes, Pablo

For space radiation protection of astronauts or electronic equipments, it is necessary to develop and use accurate radiation transport codes. Radiation transport codes include deterministic codes, such as HZETRN from NASA and UPROP from the Naval Research Laboratory, and Monte Carlo codes such as FLUKA, the Geant4 toolkit and HETC-HEDS. The deterministic codes and Monte Carlo codes complement each other in that deterministic codes are very fast while Monte Carlo codes are more elaborate. Therefore it is important to investigate how well the results of deterministic codes compare with those of Monte Carlo transport codes and where they differ. In this study we evaluate these different codes in their space radiation applications by comparing their output results in the same given space radiation environments, shielding geometry and material. Typical space radiation environments such as the 1977 solar minimum galactic cosmic ray environment are used as the well-defined input, and simple geometries made of aluminum, water and/or polyethylene are used to represent the shielding material. We then compare various outputs of these codes, such as the dose-depth curves and the flux spectra of different fragments and other secondary particles. These comparisons enable us to learn more about the main differences between these space radiation transport codes. At the same time, they help us to learn the qualitative and quantitative features that these transport codes have in common.

Sensitivity analysis of tracer transport in variably saturated soils at USDA-ARS OPE3 field site

USDA-ARS?s Scientific Manuscript database

The objective of this study was to assess the effects of uncertainties in hydrologic and geochemical parameters on the results of simulations of the tracer transport in variably saturated soils at the USDA-ARS OPE3 field site. A tracer experiment with a pulse of KCL solution applied to an irrigatio...

Modeling anomalous radial transport in kinetic transport codes

NASA Astrophysics Data System (ADS)

Bodi, K.; Krasheninnikov, S. I.; Cohen, R. H.; Rognlien, T. D.

2009-11-01

Anomalous transport is typically the dominant component of the radial transport in magnetically confined plasmas, where the physical origin of this transport is believed to be plasma turbulence. A model is presented for anomalous transport that can be used in continuum kinetic edge codes like TEMPEST, NEO and the next-generation code being developed by the Edge Simulation Laboratory. The model can also be adapted to particle-based codes. It is demonstrated that the model with a velocity-dependent diffusion and convection terms can match a diagonal gradient-driven transport matrix as found in contemporary fluid codes, but can also include off-diagonal effects. The anomalous transport model is also combined with particle drifts and a particle/energy-conserving Krook collision operator to study possible synergistic effects with neoclassical transport. For the latter study, a velocity-independent anomalous diffusion coefficient is used to mimic the effect of long-wavelength ExB turbulence.

Pore-Scale Geochemical Reactivity Associated with CO2 Storage: New Frontiers at the Fluid-Solid Interface.

PubMed

Noiriel, Catherine; Daval, Damien

2017-04-18

The reactivity of carbonate and silicate minerals is at the heart of porosity and pore geometry changes in rocks injected with CO 2 , which ultimately control the evolution of flow and transport properties of fluids in porous and/or fractured geological reservoirs. Modeling the dynamics of CO 2 -water-rock interactions is challenging because of the resulting large geochemical disequilibrium, the reservoir heterogeneities, and the large space and time scales involved in the processes. In particular, there is a lack of information about how the macroscopic properties of a reservoir, e.g., the permeability, will evolve as a result of geochemical reactions at the molecular scale. Addressing this point requires a fundamental understanding of how the microstructures influence the macroscopic properties of rocks. The pore scale, which ranges from a few nanometers to centimeters, has stood out as an essential scale of observation of geochemical processes in rocks. Transport or surface reactivity limitations due to the pore space architecture, for instance, are best described at the pore scale itself. It can be also considered as a mesoscale for aggregating and increasing the gain of fundamental understanding of microscopic interfacial processes. Here we focus on the potential application of a combination of physicochemical measurements coupled with nanoscale and microscale imaging techniques during laboratory experiments to improve our understanding of the physicochemical mechanisms that occur at the fluid-solid interface and the dynamics of the coupling between the geochemical reactions and flow and transport modifications at the pore scale. Imaging techniques such as atomic force microscopy, vertical scanning interferometry, focused ion beam transmission electron microscopy, and X-ray microtomography, are ideal for investigating the reactivity dynamics of these complex materials. Minerals and mineral assemblages, i.e., rocks, exhibit heterogeneous and anisotropic reactivity, which challenges the continuum description of porous media and assumptions required for reactive transport modeling at larger scales. The conventional approach, which consists of developing dissolution rate laws normalized to the surface area, should be revisited to account for both the anisotropic crystallographic structure of minerals and the transport of chemical species near the interface, which are responsible for the intrinsic evolution of the mineral dissolution rate as the reaction progresses. In addition, the crystal morphology and the mineral assemblage composition, texture, and structural heterogeneities are crucial in determining whether the permeability and transport properties of the reservoir will be altered drastically or maintain the sealing properties required to ensure the safe sequestration of CO 2 for hundreds of years. Investigating the transport properties in nanometer- to micrometer-thick amorphous Si-rich surface layers (ASSLs), which develop at the fluid-mineral interface in silicates, provides future direction, as ASSLs may prevent contact between the dissolving solids and the pore fluid, potentially inhibiting the dissolution/carbonation process. Equally, at a larger scale, the growth of micrometer- to millimeter-thick alteration layers, which result from the difference in reactivity between silicates and carbonates, slows the transport in the vicinity of the fluid-solid interface in polymineralic rocks, thus limiting the global reactivity of the carbonate matrix. In contrast, in pure limestone, the global reactivity of the monomineralic rock decreases because the flow localization promotes the local reactivity within the forming channels, thus enhancing permeability changes compared with more homogeneous dissolution of the rock matrix. These results indicate that the transformation of the rock matrix should control the evolution of the transport properties in reservoirs injected with CO 2 to the same extent as the intrinsic chemical reactivity of the minerals and the reservoir hydrodynamics. This process, which is currently not captured by large-scale modeling of reactive transport, should benefit from the increasing capabilities of noninvasive and nondestructive characterization tools for pore-scale processes, ultimately constraining reactive transport modeling and improving the reliability of predictions.

User’s guide for GcClust—An R package for clustering of regional geochemical data

USGS Publications Warehouse

Ellefsen, Karl J.; Smith, David B.

2016-04-08

GcClust is a software package developed by the U.S. Geological Survey for statistical clustering of regional geochemical data, and similar data such as regional mineralogical data. Functions within the software package are written in the R statistical programming language. These functions, their documentation, and a copy of the user’s guide are bundled together in R’s unit of sharable code, which is called a “package.” The user’s guide includes step-by-step instructions showing how the functions are used to cluster data and to evaluate the clustering results. These functions are demonstrated in this report using test data, which are included in the package.

Reductive dissolution and reactive solute transport in a sewage-contaminated glacial outwash aquifer

USGS Publications Warehouse

Lee, R.W.; Bennett, P.C.

1998-01-01

Contamination of shallow ground water by sewage effluent typically contains reduced chemical species that consume dissolved oxygen, developing either a low oxygen geochemical environment or an anaerobic geochemical environment. Based on the load of reduced chemical species discharged to shallow ground water and the amounts of reactants in the aquifer matrix, it should be possible to determine chemical processes in the aquifer and compare observed results to predicted ones. At the Otis Air Base research site (Cape Cod, Massachusetts) where sewage effluent has infiltrated the shallow aquifer since 1936, bacterially mediated processes such as nitrification, denitrification, manganese reduction, and iron reduction have been observed in the contaminant plume. In specific areas of the plume, dissolved manganese and iron have increased significantly where local geochemical conditions are favorable for reduction and transport of these constituents from the aquifer matrix. Dissolved manganese and iron concentrations ranged from 0.02 to 7.3 mg/L, and 0.001 to 13.0 mg/L, respectively, for 21 samples collected from 1988 to 1989. Reduction of manganese and iron is linked to microbial oxidation of sewage carbon, producing bicarbonate and the dissolved metal ions as by-products. Calculated production and flux of CO2 through the unsaturated zone from manganese reduction in the aquifer was 0.035 g/m2/d (12% of measured CO2 flux during winter). Manganese is limited in the aquifer, however. A one-dimensional, reaction-coupled transport model developed for the mildly reducing conditions in the sewage plume nearest the source beds showed that reduction, transport, and removal of manganese from the aquifer sediments should result in iron reduction where manganese has been depleted.

Geochemical data package for the Hanford immobilized low-activity tank waste performance assessment (ILAW PA)

DOE Office of Scientific and Technical Information (OSTI.GOV)

DI Kaplan; RJ Serne

Lockheed Martin Hanford Company (LMHC) is designing and assessing the performance of disposal facilities to receive radioactive wastes that are stored in single- and double-shell tanks at the Hanford Site. The preferred method of disposing of the portion that is classified as low-activity waste is to vitrify the liquid/slurry and place the solid product in near-surface, shallow-land burial facilities. The LMHC project to assess the performance of these disposal facilities is the Hanford Immobilized Low-Activity Tank Waste (ILAW) Performance Assessment (PA) activity. The goal of this project is to provide a reasonable expectation that the disposal of the waste ismore » protective of the general public, groundwater resources, air resources, surface-water resources, and inadvertent intruders. Achieving this goal will require prediction of contaminant migration from the facilities. This migration is expected to occur primarily via the movement of water through the facilities, and the consequent transport of dissolved contaminants in the porewater of the vadose zone. Pacific Northwest National Laboratory assists LMHC in their performance assessment activities. One of the PNNL tasks is to provide estimates of the geochemical properties of the materials comprising the disposal facility, the disturbed region around the facility, and the physically undisturbed sediments below the facility (including the vadose zone sediments and the aquifer sediments in the upper unconfined aquifer). The geochemical properties are expressed as parameters that quantify the adsorption of contaminants and the solubility constraints that might apply for those contaminants that may exceed solubility constraints. The common parameters used to quantify adsorption and solubility are the distribution coefficient (K{sub d}) and the thermodynamic solubility product (K{sub sp}), respectively. In this data package, the authors approximate the solubility of contaminants using a more simplified construct, called the solution concentration limit, a constant value. In future geochemical data packages, they will determine whether a more rigorous measure of solubility is necessary or warranted based on the dose predictions emanating from the ILAW 2001 PA and reviewers' comments. The K{sub d}s and solution concentration limits for each contaminant are direct inputs to subsurface flow and transport codes used to predict the performance of the ILAW system. In addition to the best-estimate K{sub d}s, a reasonable conservative value and a range are provided. They assume that K{sub d} values are log normally distributed over the cited ranges. Currently, they do not give estimates for the range in solubility limits or their uncertainty. However, they supply different values for both the K{sub d}s and solution concentration limits for different spatial zones in the ILAW system and supply time-varying K{sub d}s for the concrete zone, should the final repository design include concrete vaults or cement amendments to buffer the system pH.« less

Reactive Transport of Petroleum Hydrocarbon Constituents in a Shallow Aquifer: Modeling Geochemical Interactions Between Organic and Inorganic Species

NASA Astrophysics Data System (ADS)

McNab, W. W.; Narasimhan, T. N.

1995-08-01

Dissolved organic contaminants such as petroleum hydrocarbon constituents are often observed to degrade in groundwater environments through biologically mediated transformation reactions into carbon dioxide, methane, or intermediate organic compounds. Such transformations are closely tied to local geochemical conditions. Favorable degradation pathways depend upon local redox conditions through thermodynamic constraints and the availability of appropriate mediating microbial populations. Conversely, the progress of the degradation reactions may affect the chemical composition of groundwater through changes in electron donor/acceptor speciation and pH, possibly inducing mineral precipitation/dissolution reactions. Transport of reactive organic and inorganic aqueous species through open systems may enhance the reaction process by mixing unlike waters and producing a state of general thermodynamic disequilibrium. In this study, field data from an aquifer contaminated by petroleum hydrocarbons have been analyzed using a mathematical model which dynamically couples equilibrium geochemistry of inorganic constituents, kinetically dominated sequential degradation of organic compounds, and advective-dispersive chemical transport. Simulation results indicate that coupled geochemical processes inferred from field data, such as organic biodegradation, iron reduction and dissolution, and methanogenesis, can be successfully modeled using a partial-redox-disequilibrium approach. The results of this study also suggest how the modeling approach can be used to study system sensitivity to various physical and chemical parameters, such as the effect of dispersion on the position of chemical fronts and the impact of alternative buffering mineral phases (e.g., goethite versus amorphous Fe(OH)3) on water chemistry.

An integrated monitoring network for hydrologic, geochemical, and sediment fluxes to characterize carbon-mineral fate in the Christina River Basin Critical Zone Observatory

NASA Astrophysics Data System (ADS)

Sawyer, A. H.; Karwan, D. L.; Lazareva, O.

2011-12-01

Organic carbon (C) -mineral complexation mechanism plays an important role in C sequestration within watersheds. The primary goal of the Christina River Basin Critical Zone Observatory in SE Pennsylvania and N Delaware, USA (one of six National Science Foundation-funded observatories) is to quantify net carbon sink or source due to mineral production and transport and its dependence on land use. This effort requires an interdisciplinary understanding of carbon and mineral fluxes across interfaces between soil, aquifer, floodplain, and river. We have established a monitoring network that targets hydrologic, geochemical, and sedimentological transport processes across channel-floodplain-aquifer interfaces within White Clay Creek Watershed. Within the channel, suspended material is sampled and analyzed for organic and mineral composition as well as geochemical fingerprints. Surface water and groundwater are analyzed for C, Fe, and Mn chemistry. Within the floodplain, in-situ sensors monitor soil moisture, pressure, temperature, conductivity, and redox potential. Integrated data analysis should yield estimates of water and solute fluxes between the vadose zone, riparian aquifer, and stream. Our preliminary data show that storm events are important for carbon and mineral fluxes-suspended material in surface water changes in source and composition throughout the storm. Meanwhile, the variation in stream stage drives surface water-groundwater exchange, facilitating changes in redox potential and providing opportunity for enhanced transport and reactions involving C, Fe, and Mn in the riparian aquifer.

Geochemical and hydrologic controls on phosphorus transport in a sewage-contaminated sand and gravel aquifer near Ashumet Pond, Cape Cod, Massachusetts

USGS Publications Warehouse

Walter, Donald A.; Rea, Brigid A.; Stollenwerk, Kenneth G.; Savoie, Jennifer G.

1996-01-01

Currently (1993), about 170 kg/yr of phosphorus discharges into Ashumet Pond on Cape Cod from a plume of sewage-contaminated ground water. Phosphorus in the plume is mobile in two distinct geochemical environments--an anoxic zone containing dissolved iron and a suboxic zone containing dissolved oxygen. Phosphorus mobility in the suboxic zone is due to saturation of available sorption sites. Phosphorus loading to Ashumet Pond may increase significantly after sewage disposal is stopped due to phosphorus desorption from sediment surfaces.

Coupled hydrological and geochemical process evolution at the Landscape Evolution Observatory

NASA Astrophysics Data System (ADS)

Troch, P. A. A.

2015-12-01

Predictions of hydrologic and biogeochemical responses to natural and anthropogenic forcing at the landscape scale are highly uncertain due to the effects of heterogeneity on the scaling of reaction, flow and transport phenomena. The physical, chemical and biological structures and processes controlling reaction, flow and transport in natural landscapes interact at multiple space and time scales and are difficult to quantify. The current paradigm of hydrological and geochemical theory is that process descriptions derived from observations at small scales in controlled systems can be applied to predict system response at much larger scales, as long as some 'equivalent' or 'effective' values of the scale-dependent parameters can be identified. Furthermore, natural systems evolve in time in a way that is hard to observe in short-run laboratory experiments or in natural landscapes with unknown initial conditions and time-variant forcing. The spatial structure of flow pathways along hillslopes determines the rate, extent and distribution of geochemical reactions (and biological colonization) that drive weathering, the transport and precipitation of solutes and sediments, and the further evolution of soil structure. The resulting evolution of structures and processes, in turn, produces spatiotemporal variability of hydrological states and flow pathways. There is thus a need for experimental research to improve our understanding of hydrology-biogeochemistry interactions and feedbacks at appropriate spatial scales larger than laboratory soil column experiments. Such research is complicated in real-world settings because of poorly constrained impacts of initial conditions, climate variability, ecosystems dynamics, and geomorphic evolution. The Landscape Evolution Observatory (LEO) at Biosphere 2 offers a unique research facility that allows real-time observations of incipient hydrologic and biogeochemical response under well-constrained initial conditions and climate forcing. The LEO allows to close the water, carbon and energy budgets at hillslope scales, thereby enabling elucidation of the tight coupling between the time water spends along subsurface flow paths and geochemical weathering reactions, including the feedbacks between flow and pedogenesis.

Effect of transient wave forcing on the behavior of arsenic in a sandy nearshore aquifer

NASA Astrophysics Data System (ADS)

Rakhimbekova, S.; O'Carroll, D. M.; Robinson, C. E.

2016-12-01

Waves cause large quantities of coastal water to recirculate across the groundwater-coastal water interface in addition to inducing complex groundwater flows in the nearshore aquifer. Due to the distinct chemical composition of recirculating coastal water compared with discharging terrestrial groundwater, wave-induced recirculations and flows can alter geochemical gradients in the nearshore aquifer which may subsequently affect the mobilization and transport of reactive pollutants (e.g., arsenic). The impact of seasonal geochemical and hydrological variability on the occurrence and mobility of arsenic near the groundwater-surface water interface has been shown previously in riverine settings, however, the impact of high frequency geochemical variations (e.g., varying wave conditions) on arsenic mobility in groundwater-surface water environments is unclear. The objective of the study was to assess the impact of intensified wave conditions on the behavior of arsenic in a nearshore aquifer to determine the factors regulating its mobility and transport to receiving coastal waters. Field investigations were conducted at a permeable beach on the Great Lakes during a period of intensified wave conditions (wave event). High spatial resolution pore water sampling captured the geochemical conditions in the nearshore aquifer prior to the wave event, immediately after the wave event and over a recovery period of 3 weeks following the wave event. Shifts in pH and redox potential (ORP) gradients in response to varying wave conditions caused shifts in the iron and arsenic distributions in the aquifer. Sediment analysis was combined with the pore water distributions to assess the release of sediment-bound arsenic in response to the varying wave conditions. Insight into the effect of transient forcing on arsenic mobility and transport in groundwater-surface water environments is important for evaluating the potential risks associated with this toxic metalloid. The findings of this study also have significant implications for the fate of other reactive constituents (heavy metals, nutrients) discharging through nearshore aquifers to coastal waters.

CRUNCH_PARALLEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shumaker, Dana E.; Steefel, Carl I.

The code CRUNCH_PARALLEL is a parallel version of the CRUNCH code. CRUNCH code version 2.0 was previously released by LLNL, (UCRL-CODE-200063). Crunch is a general purpose reactive transport code developed by Carl Steefel and Yabusake (Steefel Yabsaki 1996). The code handles non-isothermal transport and reaction in one, two, and three dimensions. The reaction algorithm is generic in form, handling an arbitrary number of aqueous and surface complexation as well as mineral dissolution/precipitation. A standardized database is used containing thermodynamic and kinetic data. The code includes advective, dispersive, and diffusive transport.

Uncertainty quantification and experimental design based on unsupervised machine learning identification of contaminant sources and groundwater types using hydrogeochemical data

NASA Astrophysics Data System (ADS)

Vesselinov, V. V.

2017-12-01

Identification of the original groundwater types present in geochemical mixtures observed in an aquifer is a challenging but very important task. Frequently, some of the groundwater types are related to different infiltration and/or contamination sources associated with various geochemical signatures and origins. The characterization of groundwater mixing processes typically requires solving complex inverse models representing groundwater flow and geochemical transport in the aquifer, where the inverse analysis accounts for available site data. Usually, the model is calibrated against the available data characterizing the spatial and temporal distribution of the observed geochemical species. Numerous geochemical constituents and processes may need to be simulated in these models which further complicates the analyses. As a result, these types of model analyses are typically extremely challenging. Here, we demonstrate a new contaminant source identification approach that performs decomposition of the observation mixtures based on Nonnegative Matrix Factorization (NMF) method for Blind Source Separation (BSS), coupled with a custom semi-supervised clustering algorithm. Our methodology, called NMFk, is capable of identifying (a) the number of groundwater types and (b) the original geochemical concentration of the contaminant sources from measured geochemical mixtures with unknown mixing ratios without any additional site information. We also demonstrate how NMFk can be extended to perform uncertainty quantification and experimental design related to real-world site characterization. The NMFk algorithm works with geochemical data represented in the form of concentrations, ratios (of two constituents; for example, isotope ratios), and delta notations (standard normalized stable isotope ratios). The NMFk algorithm has been extensively tested on synthetic datasets; NMFk analyses have been actively performed on real-world data collected at the Los Alamos National Laboratory (LANL) groundwater sites related to Chromium and RDX contamination.

Geochemical Data Package for Performance Assessment Calculations Related to the Savannah River Site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaplan, Daniel I.

The Savannah River Site (SRS) disposes of low-level radioactive waste (LLW) and stabilizes high-level radioactive waste (HLW) tanks in the subsurface environment. Calculations used to establish the radiological limits of these facilities are referred to as Performance Assessments (PA), Special Analyses (SA), and Composite Analyses (CA). The objective of this document is to revise existing geochemical input values used for these calculations. This work builds on earlier compilations of geochemical data (2007, 2010), referred to a geochemical data packages. This work is being conducted as part of the on-going maintenance program of the SRS PA programs that periodically updates calculationsmore » and data packages when new information becomes available. Because application of values without full understanding of their original purpose may lead to misuse, this document also provides the geochemical conceptual model, the approach used for selecting the values, the justification for selecting data, and the assumptions made to assure that the conceptual and numerical geochemical models are reasonably conservative (i.e., bias the recommended input values to reflect conditions that will tend to predict the maximum risk to the hypothetical recipient). This document provides 1088 input parameters for geochemical parameters describing transport processes for 64 elements (>740 radioisotopes) potentially occurring within eight subsurface disposal or tank closure areas: Slit Trenches (ST), Engineered Trenches (ET), Low Activity Waste Vault (LAWV), Intermediate Level (ILV) Vaults, Naval Reactor Component Disposal Areas (NRCDA), Components-in-Grout (CIG) Trenches, Saltstone Facility, and Closed Liquid Waste Tanks. The geochemical parameters described here are the distribution coefficient, Kd value, apparent solubility concentration, k s value, and the cementitious leachate impact factor.« less

A Deterministic Transport Code for Space Environment Electrons

NASA Technical Reports Server (NTRS)

Nealy, John E.; Chang, C. K.; Norman, Ryan B.; Blattnig, Steve R.; Badavi, Francis F.; Adamczyk, Anne M.

2010-01-01

A deterministic computational procedure has been developed to describe transport of space environment electrons in various shield media. This code is an upgrade and extension of an earlier electron code. Whereas the former code was formulated on the basis of parametric functions derived from limited laboratory data, the present code utilizes well established theoretical representations to describe the relevant interactions and transport processes. The shield material specification has been made more general, as have the pertinent cross sections. A combined mean free path and average trajectory approach has been used in the transport formalism. Comparisons with Monte Carlo calculations are presented.

EQ3NR, a computer program for geochemical aqueous speciation-solubility calculations: Theoretical manual, user`s guide, and related documentation (Version 7.0); Part 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolery, T.J.

1992-09-14

EQ3NR is an aqueous solution speciation-solubility modeling code. It is part of the EQ3/6 software package for geochemical modeling. It computes the thermodynamic state of an aqueous solution by determining the distribution of chemical species, including simple ions, ion pairs, and complexes, using standard state thermodynamic data and various equations which describe the thermodynamic activity coefficients of these species. The input to the code describes the aqueous solution in terms of analytical data, including total (analytical) concentrations of dissolved components and such other parameters as the pH, pHCl, Eh, pe, and oxygen fugacity. The input may also include a desiredmore » electrical balancing adjustment and various constraints which impose equilibrium with special pure minerals, solid solution end-member components (of specified mole fractions), and gases (of specified fugacities). The code evaluates the degree of disequilibrium in terms of the saturation index (SI = 1og Q/K) and the thermodynamic affinity (A = {minus}2.303 RT log Q/K) for various reactions, such as mineral dissolution or oxidation-reduction in the aqueous solution itself. Individual values of Eh, pe, oxygen fugacity, and Ah (redox affinity) are computed for aqueous redox couples. Equilibrium fugacities are computed for gas species. The code is highly flexible in dealing with various parameters as either model inputs or outputs. The user can specify modification or substitution of equilibrium constants at run time by using options on the input file.« less

A Geochemical Reaction Model for Titration of Contaminated Soil and Groundwater at the Oak Ridge Reservation

NASA Astrophysics Data System (ADS)

Zhang, F.; Parker, J. C.; Gu, B.; Luo, W.; Brooks, S. C.; Spalding, B. P.; Jardine, P. M.; Watson, D. B.

2007-12-01

This study investigates geochemical reactions during titration of contaminated soil and groundwater at the Oak Ridge Reservation in eastern Tennessee. The soils and groundwater exhibits low pH and high concentrations of aluminum, calcium, magnesium, manganese, various trace metals such as nickel and cobalt, and radionuclides such as uranium and technetium. The mobility of many of the contaminant species diminishes with increasing pH. However, base additions to increase pH are strongly buffered by various precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior and associated geochemical effects is thus critical to evaluate remediation performance of pH manipulation strategies. This study was undertaken to develop a practical but generally applicable geochemical model to predict aqueous and solid-phase speciation during soil and groundwater titration. To model titration in the presence of aquifer solids, an approach proposed by Spalding and Spalding (2001) was utilized, which treats aquifer solids as a polyprotic acid. Previous studies have shown that Fe and Al-oxyhydroxides strongly sorb dissolved Ni, U and Tc species. In this study, since the total Fe concentration is much smaller than that of Al, only ion exchange reactions associated with Al hydroxides are considered. An equilibrium reaction model that includes aqueous complexation, precipitation, ion exchange, and soil buffering reactions was developed and implemented in the code HydroGeoChem 5.0 (HGC5). Comparison of model results with experimental titration curves for contaminated groundwater alone and for soil- water systems indicated close agreement. This study is expected to facilitate field-scale modeling of geochemical processes under conditions with highly variable pH to develop practical methods to control contaminant mobility at geochemically complex sites.

Surface-sediment grain-size distribution and sediment transport in the subaqueous Mekong Delta, Vietnam

NASA Astrophysics Data System (ADS)

Nguyen, T. T.; Stattegger, K.; Nittrouer, C.; Phung, P. V.; Liu, P.; DeMaster, D. J.; Bui, D. V.; Le, A. D.; Nguyen, T. N.

2016-02-01

Collected surface-sediment samples in coastal water around Mekong Delta (from distributary channels to Ca Mau Peninsula) were analyzed to determine surface-sediment grain-size distribution and sediment-transport trend in the subaqueous Mekong Delta. The grain-size data set of 238 samples was obtained by using the laser instrument Mastersizer 2000 and LS Particle Size Analyzer. Fourteen samples were selected for geochemical analysis (total-organic and carbonate content). These geochemical results were used to assist in interpreting variations of granulometricparamenters along the cross-shore transects. Nine transects were examined from CungHau river mouth to Ca Mau Peninsula and six thematic maps on the whole study area were made. The research results indicate that: (1) generally, the sediment becomes finer from the delta front downwards to prodelta and becomes coarser again and poorer sorted on the adjacent inner shelf due to different sources of sediment; (2) sediment-granulometry parameters vary among sedimentary sub-environments of the underwater part of Mekong Delta, the distance from sediment source and hydrodynamic regime controlling each region; (3) the net sediment transport is southwest toward the Ca Mau Peninsula.

Geologic, hydrologic, and geochemical interpretations of mineral deposits as analogs for understanding transport of environmental contaminants

USGS Publications Warehouse

Wanty, R.B.; Berger, B.R.

2006-01-01

Base- and precious-metal mineral deposits comprise anomalous concentrations of metals and associated elements, which may be useful subjects for study as analogs for migration of environmental contaminants. In the geologic past, hydrothermal mineral deposits formed at the intersection of favorable geologic, hydrologic and geochemical gradients. In the present, weathering of these sulfide-rich deposits occurs as a result of the interplay between rates of oxygen supply versus rates of ground or surface-water flow. Transport and spatial dispersion of elements from a mineral deposit occurs as a function of competing rates of water flow versus rates of attenuation mechanisms such as adsorption, dilution, or (co)precipitation. In this paper we present several case studies from mineralized and altered sedimentary and crystalline aquifers in the western United States to illustrate the geologic control of ground-water flow and solute transport, and to demonstrate how this combined approach leads to a more complete understanding of the systems under study as well as facilitating some capability to predict major flow directions in aquifers.

Porosity development in coastal carbonate aquifers

USGS Publications Warehouse

Sanford, W.E.; Konikow, Leonard F.

1989-01-01

Combines geochemical mixing theory with the hydrodynamics of fresh-water-salt-water mixing zones in a coupled reaction-transport model. Results from the reaction-path model PHREEQE are used with a variable-density groundwater flow and solute-transport model to simulate an idealized cross section of a coastal carbonate aquifer. The dissolution process is sensitive to fresh-water chemistry, groundwater velocities, and sea-level movement. -from Authors

Predicting subsurface uranium transport: Mechanistic modeling constrained by experimental data

NASA Astrophysics Data System (ADS)

Ottman, Michael; Schenkeveld, Walter D. C.; Kraemer, Stephan

2017-04-01

Depleted uranium (DU) munitions and their widespread use throughout conflict zones around the world pose a persistent health threat to the inhabitants of those areas long after the conclusion of active combat. However, little emphasis has been put on developing a comprehensive, quantitative tool for use in remediation and hazard avoidance planning in a wide range of environments. In this context, we report experimental data on U interaction with soils and sediments. Here, we strive to improve existing risk assessment modeling paradigms by incorporating a variety of experimental data into a mechanistic U transport model for subsurface environments. 20 different soils and sediments from a variety of environments were chosen to represent a range of geochemical parameters that are relevant to U transport. The parameters included pH, organic matter content, CaCO3, Fe content and speciation, and clay content. pH ranged from 3 to 10, organic matter content from 6 to 120 g kg-1, CaCO3 from 0 to 700 g kg-1, amorphous Fe content from 0.3 to 6 g kg-1 and clay content from 4 to 580 g kg-1. Sorption experiments were then performed, and linear isotherms were constructed. Sorption experiment results show that among separate sets of sediments and soils, there is an inverse correlation between both soil pH and CaCO¬3 concentration relative to U sorptive affinity. The geological materials with the highest and lowest sorptive affinities for U differed in CaCO3 and organic matter concentrations, as well as clay content and pH. In a further step, we are testing if transport behavior in saturated porous media can be predicted based on adsorption isotherms and generic geochemical parameters, and comparing these modeling predictions with the results from column experiments. The comparison of these two data sets will examine if U transport can be effectively predicted from reactive transport modeling that incorporates the generic geochemical parameters. This work will serve to show whether a more mechanistic approach offers an improvement over statistical regression-based risk assessment models.

A geochemical transport model for redox-controlled movement of mineral fronts in groundwater flow systems: A case of nitrate removal by oxidation of pyrite

USGS Publications Warehouse

Engesgaard, Peter; Kipp, Kenneth L.

1992-01-01

A one-dimensional prototype geochemical transport model was developed in order to handle simultaneous precipitation-dissolution and oxidation-reduction reactions governed by chemical equilibria. Total aqueous component concentrations are the primary dependent variables, and a sequential iterative approach is used for the calculation. The model was verified by analytical and numerical comparisons and is able to simulate sharp mineral fronts. At a site in Denmark, denitrification has been observed by oxidation of pyrite. Simulation of nitrate movement at this site showed a redox front movement rate of 0.58 m yr−1, which agreed with calculations of others. It appears that the sequential iterative approach is the most practical for extension to multidimensional simulation and for handling large numbers of components and reactions. However, slow convergence may limit the size of redox systems that can be handled.

Comparison of Space Radiation Calculations from Deterministic and Monte Carlo Transport Codes

NASA Technical Reports Server (NTRS)

Adams, J. H.; Lin, Z. W.; Nasser, A. F.; Randeniya, S.; Tripathi, r. K.; Watts, J. W.; Yepes, P.

2010-01-01

The presentation outline includes motivation, radiation transport codes being considered, space radiation cases being considered, results for slab geometry, results from spherical geometry, and summary. ///////// main physics in radiation transport codes hzetrn uprop fluka geant4, slab geometry, spe, gcr,

Implementation of an anomalous radial transport model for continuum kinetic edge codes

NASA Astrophysics Data System (ADS)

Bodi, K.; Krasheninnikov, S. I.; Cohen, R. H.; Rognlien, T. D.

2007-11-01

Radial plasma transport in magnetic fusion devices is often dominated by plasma turbulence compared to neoclassical collisional transport. Continuum kinetic edge codes [such as the (2d,2v) transport version of TEMPEST and also EGK] compute the collisional transport directly, but there is a need to model the anomalous transport from turbulence for long-time transport simulations. Such a model is presented and results are shown for its implementation in the TEMPEST gyrokinetic edge code. The model includes velocity-dependent convection and diffusion coefficients expressed as a Hermite polynominals in velocity. The specification of the Hermite coefficients can be set, e.g., by specifying the ratio of particle and energy transport as in fluid transport codes. The anomalous transport terms preserve the property of no particle flux into unphysical regions of velocity space. TEMPEST simulations are presented showing the separate control of particle and energy anomalous transport, and comparisons are made with neoclassical transport also included.

A coupled THC model of the FEBEX in situ test with bentonite swelling and chemical and thermal osmosis.

PubMed

Zheng, Liange; Samper, Javier; Montenegro, Luis

2011-09-25

The performance assessment of a geological repository for radioactive waste requires quantifying the geochemical evolution of the bentonite engineered barrier. This barrier will be exposed to coupled thermal (T), hydrodynamic (H), mechanical (M) and chemical (C) processes. This paper presents a coupled THC model of the FEBEX (Full-scale Engineered Barrier EXperiment) in situ test which accounts for bentonite swelling and chemical and thermal osmosis. Model results attest the relevance of thermal osmosis and bentonite swelling for the geochemical evolution of the bentonite barrier while chemical osmosis is found to be almost irrelevant. The model has been tested with data collected after the dismantling of heater 1 of the in situ test. The model reproduces reasonably well the measured temperature, relative humidity, water content and inferred geochemical data. However, it fails to mimic the solute concentrations at the heater-bentonite and bentonite-granite interfaces because the model does not account for the volume change of bentonite, the CO(2)(g) degassing and the transport of vapor from the bentonite into the granite. The inferred HCO(3)(-) and pH data cannot be explained solely by solute transport, calcite dissolution and protonation/deprotonation by surface complexation, suggesting that such data may be affected also by other reactions. Published by Elsevier B.V.

PHAST--a program for simulating ground-water flow, solute transport, and multicomponent geochemical reactions

USGS Publications Warehouse

Parkhurst, David L.; Kipp, Kenneth L.; Engesgaard, Peter; Charlton, Scott R.

2004-01-01

The computer program PHAST simulates multi-component, reactive solute transport in three-dimensional saturated ground-water flow systems. PHAST is a versatile ground-water flow and solute-transport simulator with capabilities to model a wide range of equilibrium and kinetic geochemical reactions. The flow and transport calculations are based on a modified version of HST3D that is restricted to constant fluid density and constant temperature. The geochemical reactions are simulated with the geochemical model PHREEQC, which is embedded in PHAST. PHAST is applicable to the study of natural and contaminated ground-water systems at a variety of scales ranging from laboratory experiments to local and regional field scales. PHAST can be used in studies of migration of nutrients, inorganic and organic contaminants, and radionuclides; in projects such as aquifer storage and recovery or engineered remediation; and in investigations of the natural rock-water interactions in aquifers. PHAST is not appropriate for unsaturated-zone flow, multiphase flow, density-dependent flow, or waters with high ionic strengths. A variety of boundary conditions are available in PHAST to simulate flow and transport, including specified-head, flux, and leaky conditions, as well as the special cases of rivers and wells. Chemical reactions in PHAST include (1) homogeneous equilibria using an ion-association thermodynamic model; (2) heterogeneous equilibria between the aqueous solution and minerals, gases, surface complexation sites, ion exchange sites, and solid solutions; and (3) kinetic reactions with rates that are a function of solution composition. The aqueous model (elements, chemical reactions, and equilibrium constants), minerals, gases, exchangers, surfaces, and rate expressions may be defined or modified by the user. A number of options are available to save results of simulations to output files. The data may be saved in three formats: a format suitable for viewing with a text editor; a format suitable for exporting to spreadsheets and post-processing programs; or in Hierarchical Data Format (HDF), which is a compressed binary format. Data in the HDF file can be visualized on Windows computers with the program Model Viewer and extracted with the utility program PHASTHDF; both programs are distributed with PHAST. Operator splitting of the flow, transport, and geochemical equations is used to separate the three processes into three sequential calculations. No iterations between transport and reaction calculations are implemented. A three-dimensional Cartesian coordinate system and finite-difference techniques are used for the spatial and temporal discretization of the flow and transport equations. The non-linear chemical equilibrium equations are solved by a Newton-Raphson method, and the kinetic reaction equations are solved by a Runge-Kutta or an implicit method for integrating ordinary differential equations. The PHAST simulator may require large amounts of memory and long Central Processing Unit (CPU) times. To reduce the long CPU times, a parallel version of PHAST has been developed that runs on a multiprocessor computer or on a collection of computers that are networked. The parallel version requires Message Passing Interface, which is currently (2004) freely available. The parallel version is effective in reducing simulation times. This report documents the use of the PHAST simulator, including running the simulator, preparing the input files, selecting the output files, and visualizing the results. It also presents four examples that verify the numerical method and demonstrate the capabilities of the simulator. PHAST requires three input files. Only the flow and transport file is described in detail in this report. The other two files, the chemistry data file and the database file, are identical to PHREEQC files and the detailed description of these files is found in the PHREEQC documentation.

PHAST Version 2-A Program for Simulating Groundwater Flow, Solute Transport, and Multicomponent Geochemical Reactions

USGS Publications Warehouse

Parkhurst, David L.; Kipp, Kenneth L.; Charlton, Scott R.

2010-01-01

The computer program PHAST (PHREEQC And HST3D) simulates multicomponent, reactive solute transport in three-dimensional saturated groundwater flow systems. PHAST is a versatile groundwater flow and solute-transport simulator with capabilities to model a wide range of equilibrium and kinetic geochemical reactions. The flow and transport calculations are based on a modified version of HST3D that is restricted to constant fluid density and constant temperature. The geochemical reactions are simulated with the geochemical model PHREEQC, which is embedded in PHAST. Major enhancements in PHAST Version 2 allow spatial data to be defined in a combination of map and grid coordinate systems, independent of a specific model grid (without node-by-node input). At run time, aquifer properties are interpolated from the spatial data to the model grid; regridding requires only redefinition of the grid without modification of the spatial data. PHAST is applicable to the study of natural and contaminated groundwater systems at a variety of scales ranging from laboratory experiments to local and regional field scales. PHAST can be used in studies of migration of nutrients, inorganic and organic contaminants, and radionuclides; in projects such as aquifer storage and recovery or engineered remediation; and in investigations of the natural rock/water interactions in aquifers. PHAST is not appropriate for unsaturated-zone flow, multiphase flow, or density-dependent flow. A variety of boundary conditions are available in PHAST to simulate flow and transport, including specified-head, flux (specified-flux), and leaky (head-dependent) conditions, as well as the special cases of rivers, drains, and wells. Chemical reactions in PHAST include (1) homogeneous equilibria using an ion-association or Pitzer specific interaction thermodynamic model; (2) heterogeneous equilibria between the aqueous solution and minerals, ion exchange sites, surface complexation sites, solid solutions, and gases; and (3) kinetic reactions with rates that are a function of solution composition. The aqueous model (elements, chemical reactions, and equilibrium constants), minerals, exchangers, surfaces, gases, kinetic reactants, and rate expressions may be defined or modified by the user. A number of options are available to save results of simulations to output files. The data may be saved in three formats: a format suitable for viewing with a text editor; a format suitable for exporting to spreadsheets and postprocessing programs; and in Hierarchical Data Format (HDF), which is a compressed binary format. Data in the HDF file can be visualized on Windows computers with the program Model Viewer and extracted with the utility program PHASTHDF; both programs are distributed with PHAST.

Hiereachical Bayesian Model for Combining Geochemical and Geophysical Data for Environmental Applications Software

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Jinsong

2013-05-01

Development of a hierarchical Bayesian model to estimate the spatiotemporal distribution of aqueous geochemical parameters associated with in-situ bioremediation using surface spectral induced polarization (SIP) data and borehole geochemical measurements collected during a bioremediation experiment at a uranium-contaminated site near Rifle, Colorado. The SIP data are first inverted for Cole-Cole parameters including chargeability, time constant, resistivity at the DC frequency and dependence factor, at each pixel of two-dimensional grids using a previously developed stochastic method. Correlations between the inverted Cole-Cole parameters and the wellbore-based groundwater chemistry measurements indicative of key metabolic processes within the aquifer (e.g. ferrous iron, sulfate, uranium)more » were established and used as a basis for petrophysical model development. The developed Bayesian model consists of three levels of statistical sub-models: 1) data model, providing links between geochemical and geophysical attributes, 2) process model, describing the spatial and temporal variability of geochemical properties in the subsurface system, and 3) parameter model, describing prior distributions of various parameters and initial conditions. The unknown parameters are estimated using Markov chain Monte Carlo methods. By combining the temporally distributed geochemical data with the spatially distributed geophysical data, we obtain the spatio-temporal distribution of ferrous iron, sulfate and sulfide, and their associated uncertainity information. The obtained results can be used to assess the efficacy of the bioremediation treatment over space and time and to constrain reactive transport models.« less

HANDBOOK: GROUNDWATER - METHODOLOGY - VOL. 2

EPA Science Inventory

The subsurface environment of ground water is characterized by a complex interplay of physical, geochemical and biological forces that govern the release, transport and fate of a variety of chemical substances. There are literally as many varied hydrogeologic settings as there ar...

Biogeochemical Barriers: Redox Behavior of Metals and Metalloids

EPA Science Inventory

Redox conditions and pH are arguably the most important geochemical parameters that control contaminant transport and fate in groundwater systems. Oxidation-reduction (redox) reactions mediate the chemical behavior of both inorganic and organic chemical constituents by affecting...

Benchmarking NNWSI flow and transport codes: COVE 1 results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayden, N.K.

1985-06-01

The code verification (COVE) activity of the Nevada Nuclear Waste Storage Investigations (NNWSI) Project is the first step in certification of flow and transport codes used for NNWSI performance assessments of a geologic repository for disposing of high-level radioactive wastes. The goals of the COVE activity are (1) to demonstrate and compare the numerical accuracy and sensitivity of certain codes, (2) to identify and resolve problems in running typical NNWSI performance assessment calculations, and (3) to evaluate computer requirements for running the codes. This report describes the work done for COVE 1, the first step in benchmarking some of themore » codes. Isothermal calculations for the COVE 1 benchmarking have been completed using the hydrologic flow codes SAGUARO, TRUST, and GWVIP; the radionuclide transport codes FEMTRAN and TRUMP; and the coupled flow and transport code TRACR3D. This report presents the results of three cases of the benchmarking problem solved for COVE 1, a comparison of the results, questions raised regarding sensitivities to modeling techniques, and conclusions drawn regarding the status and numerical sensitivities of the codes. 30 refs.« less

Nevada Test and Training Range Depleted Uranium Target Disposal Environmental Assessment

DTIC Science & Technology

2005-03-01

to establish the probability and scope of such transport. Long-Term Fate of Depleted Uranium at Aberdeen and Yuma Proving Grounds Phase II: Human...1990. Long-Term Fate of Depleted Uranium at Aberdeen and Yuma Proving Grounds Final Report, Phase 1: Geochemical Transport and Modeling. Los...of Depleted Uranium at Aberdeen and Yuma Proving Grounds , Phase II: Human Health and Ecological Risk Assessments. Los Alamos National Laboratory

Geochemical Impacts of Carbon Dioxide, Brine, Trace Metal and Organic Leakage into an Unconfined, Oxidizing Limestone Aquifer

DOE PAGES

Bacon, Diana H.; Dai, Zhenxue; Zheng, Liange

2014-12-31

An important risk at CO2 storage sites is the potential for groundwater quality impacts. As part of a system to assess the potential for these impacts a geochemical scaling function has been developed, based on a detailed reactive transport model of CO2 and brine leakage into an unconfined, oxidizing carbonate aquifer. Stochastic simulations varying a number of geochemical parameters were used to generate a response surface predicting the volume of aquifer that would be impacted with respect to regulated contaminants. The brine was assumed to contain several trace metals and organic contaminants. Aquifer pH and TDS were influenced by CO2more » leakage, while trace metal concentrations were most influenced by the brine concentrations rather than adsorption or desorption on calcite. Organic plume sizes were found to be strongly influenced by biodegradation.« less

Measured solubilities and speciations from oversaturation experiments of neptunium, plutonium, and americium in UE-25p No. 1 well water from the Yucca Mountain region: Milestone report 3329-WBS1.2.3.4.1.3.1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nitsche, H.; Roberts, K.; Prussin, T.

1994-04-01

Solubility and speciation are important in understanding aqueous radionuclide transport through the geosphere. They define the source term for transport retardation processes such as sorption and colloid formation. Solubility and speciation data are useful in verifying the validity of geochemical codes that are a part of predictive transport models. Results are presented from solubility and speciation experiments of {sup 237}NpO{sub 2}{sup +}, {sup 239}Pu{sup 4+}, and {sup 241}Am{sup 3+}/Nd{sup 3+} in a modified UE-25p No. 1 groundwater (from the Yucca Mountain region, Nevada, which is being investigated as a potential high-level nuclear waste disposal site) at two different temperatures (25{degree}more » and 60{degree}C) and three pH values (6.0, 7.0, 8.5). The solubility-controlling steady-state solids were identified and the speciation and/or oxidation states present in the supernatant solutions were determined. The neptunium solubility decreased with increasing temperature and pH. Plutonium concentrations significantly decreased with increasing temperature at pH 6 and 7. The concentration at pH 8.5 hardly decreased at all with increasing temperature. At both temperatures the concentrations were highest at pH 8.5, lowest at pH 7, and in between at pH 6. For the americium/neodymium solutions, the solubility decreased significantly with increasing temperature and increased somewhat with increasing pH.« less

An open, object-based modeling approach for simulating subsurface heterogeneity

NASA Astrophysics Data System (ADS)

Bennett, J.; Ross, M.; Haslauer, C. P.; Cirpka, O. A.

2017-12-01

Characterization of subsurface heterogeneity with respect to hydraulic and geochemical properties is critical in hydrogeology as their spatial distribution controls groundwater flow and solute transport. Many approaches of characterizing subsurface heterogeneity do not account for well-established geological concepts about the deposition of the aquifer materials; those that do (i.e. process-based methods) often require forcing parameters that are difficult to derive from site observations. We have developed a new method for simulating subsurface heterogeneity that honors concepts of sequence stratigraphy, resolves fine-scale heterogeneity and anisotropy of distributed parameters, and resembles observed sedimentary deposits. The method implements a multi-scale hierarchical facies modeling framework based on architectural element analysis, with larger features composed of smaller sub-units. The Hydrogeological Virtual Reality simulator (HYVR) simulates distributed parameter models using an object-based approach. Input parameters are derived from observations of stratigraphic morphology in sequence type-sections. Simulation outputs can be used for generic simulations of groundwater flow and solute transport, and for the generation of three-dimensional training images needed in applications of multiple-point geostatistics. The HYVR algorithm is flexible and easy to customize. The algorithm was written in the open-source programming language Python, and is intended to form a code base for hydrogeological researchers, as well as a platform that can be further developed to suit investigators' individual needs. This presentation will encompass the conceptual background and computational methods of the HYVR algorithm, the derivation of input parameters from site characterization, and the results of groundwater flow and solute transport simulations in different depositional settings.

Beam-dynamics codes used at DARHT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ekdahl, Jr., Carl August

Several beam simulation codes are used to help gain a better understanding of beam dynamics in the DARHT LIAs. The most notable of these fall into the following categories: for beam production – Tricomp Trak orbit tracking code, LSP Particle in cell (PIC) code, for beam transport and acceleration – XTR static envelope and centroid code, LAMDA time-resolved envelope and centroid code, LSP-Slice PIC code, for coasting-beam transport to target – LAMDA time-resolved envelope code, LSP-Slice PIC code. These codes are also being used to inform the design of Scorpius.

Computer finds ore

NASA Astrophysics Data System (ADS)

Bell, Peter M.

Artificial intelligence techniques are being used for the first time to evaluate geophysical, geochemical, and geologic data and theory in order to locate ore deposits. After several years of development, an intelligent computer code has been formulated and applied to the Mount Tolman area in Washington state. In a project funded by the United States Geological Survey and the National Science Foundation a set of computer programs, under the general title Prospector, was used successfully to locate a previously unknown ore-grade porphyry molybdenum deposit in the vicinity of Mount Tolman (Science, Sept. 3, 1982).The general area of the deposit had been known to contain exposures of porphyry mineralization. Between 1964 and 1978, exploration surveys had been run by the Bear Creek Mining Company, and later exploration was done in the area by the Amax Corporation. Some of the geophysical data and geochemical and other prospecting surveys were incorporated into the programs, and mine exploration specialists contributed to a set of rules for Prospector. The rules were encoded as ‘inference networks’ to form the ‘expert system’ on which the artificial intelligence codes were based. The molybdenum ore deposit discovered by the test is large, located subsurface, and has an areal extent of more than 18 km2.

Modules based on the geochemical model PHREEQC for use in scripting and programming languages

USGS Publications Warehouse

Charlton, Scott R.; Parkhurst, David L.

2011-01-01

The geochemical model PHREEQC is capable of simulating a wide range of equilibrium reactions between water and minerals, ion exchangers, surface complexes, solid solutions, and gases. It also has a general kinetic formulation that allows modeling of nonequilibrium mineral dissolution and precipitation, microbial reactions, decomposition of organic compounds, and other kinetic reactions. To facilitate use of these reaction capabilities in scripting languages and other models, PHREEQC has been implemented in modules that easily interface with other software. A Microsoft COM (component object model) has been implemented, which allows PHREEQC to be used by any software that can interface with a COM server—for example, Excel®, Visual Basic®, Python, or MATLAB". PHREEQC has been converted to a C++ class, which can be included in programs written in C++. The class also has been compiled in libraries for Linux and Windows that allow PHREEQC to be called from C++, C, and Fortran. A limited set of methods implements the full reaction capabilities of PHREEQC for each module. Input methods use strings or files to define reaction calculations in exactly the same formats used by PHREEQC. Output methods provide a table of user-selected model results, such as concentrations, activities, saturation indices, and densities. The PHREEQC module can add geochemical reaction capabilities to surface-water, groundwater, and watershed transport models. It is possible to store and manipulate solution compositions and reaction information for many cells within the module. In addition, the object-oriented nature of the PHREEQC modules simplifies implementation of parallel processing for reactive-transport models. The PHREEQC COM module may be used in scripting languages to fit parameters; to plot PHREEQC results for field, laboratory, or theoretical investigations; or to develop new models that include simple or complex geochemical calculations.

Modules based on the geochemical model PHREEQC for use in scripting and programming languages

USGS Publications Warehouse

Charlton, S.R.; Parkhurst, D.L.

2011-01-01

The geochemical model PHREEQC is capable of simulating a wide range of equilibrium reactions between water and minerals, ion exchangers, surface complexes, solid solutions, and gases. It also has a general kinetic formulation that allows modeling of nonequilibrium mineral dissolution and precipitation, microbial reactions, decomposition of organic compounds, and other kinetic reactions. To facilitate use of these reaction capabilities in scripting languages and other models, PHREEQC has been implemented in modules that easily interface with other software. A Microsoft COM (component object model) has been implemented, which allows PHREEQC to be used by any software that can interface with a COM server-for example, Excel??, Visual Basic??, Python, or MATLAB??. PHREEQC has been converted to a C++ class, which can be included in programs written in C++. The class also has been compiled in libraries for Linux and Windows that allow PHREEQC to be called from C++, C, and Fortran. A limited set of methods implements the full reaction capabilities of PHREEQC for each module. Input methods use strings or files to define reaction calculations in exactly the same formats used by PHREEQC. Output methods provide a table of user-selected model results, such as concentrations, activities, saturation indices, and densities. The PHREEQC module can add geochemical reaction capabilities to surface-water, groundwater, and watershed transport models. It is possible to store and manipulate solution compositions and reaction information for many cells within the module. In addition, the object-oriented nature of the PHREEQC modules simplifies implementation of parallel processing for reactive-transport models. The PHREEQC COM module may be used in scripting languages to fit parameters; to plot PHREEQC results for field, laboratory, or theoretical investigations; or to develop new models that include simple or complex geochemical calculations. ?? 2011.

The Influence of Surface Coal Mining on Runoff Processes and Stream Chemistry in the Elk Valley, British Colubmbia, Canada

NASA Astrophysics Data System (ADS)

Carey, S. K.; Wellen, C. C.; Shatilla, N. J.

2015-12-01

Surface mining is a common method of accessing coal. In high-elevation environments, vegetation and soils are typically removed prior to the blasting of overburden rock, thereby allowing access to mineable ore. Following this, the removed overburden rock is deposited in adjacent valleys as waste rock spoils. Previous research has identified that areas downstream of surface coal mining have impaired water quality, yet there is limited information about the interaction of hydrology and geochemistry across a range of mining conditions, particularly at the headwater scale. Here, we provide an analysis of an extensive long-term data set of geochemistry and flows across a gradient of coal mining in the Elk Valley, British Columbia, Canada. This work is part of a broader R&D program examining the influence of surface coal mining on hydrological and water quality responses in the Elk Valley aimed at informing effective management responses. Results indicate that water from waste rock piles has an ionic profile distinct from unimpacted catchments. While the concentration of geochemicals increased with the degree of mine impact, the control of hydrological transport capacity over geochemical export did not vary with degree of mine impact. Geochemical export in mine-influenced catchments was limited more strongly by transport capacity than supply, implying that more water moving through the waste rock mobilized more geochemicals. Placement of waste rock within the catchment (headwaters or outlet) did not affect chemical concentrations but did alter the timing with which chemically distinct water mixed. This work advances on results reported earlier using empirical models of selenium loading and further highlights the importance of limiting water inputs into waste rock piles.

Nanostructures and radionuclide transport in clay formations (Invited)

NASA Astrophysics Data System (ADS)

Wang, Y.

2010-12-01

Nanostructures are widely present in geologic materials and are expected to directly affect the interactions of these materials with geologic fluids. The study of mineral-water interface chemistry as controlled by nanostructures is a necessary step to bridge the existing gap between the molecular level understanding of a geochemical process and the macro-scale laboratory and field observations. In this presentation, I will review the recent progresses in nanoscience and provide a perspective on how these progresses can potentially impact geochemical studies. My presentation will be focused the following areas: (1) the characterization of nanostructures in natural systems, (2) the study of water and chemical species in nanoconfinement, (3) the effects of nanopores on geochemical reaction and mass transfers, and (4) the use nanostructured materials for environmental remediation and cleanup. Specifically, I will demonstrate that the nanopore confinement can significantly modify geochemical reactions in porous geologic media. As the pore size is reduced to a few nanometers, the difference between surface acidity constants (pK2 - pK1) decreases, giving rise to a higher surface charge density on a nanopore surface than that on an unconfined mineral-water interface. The change in surface acidity constants results in a shift of ion sorption edges and enhances ion sorption on nanopore surfaces. This effect causes preferential enrichment of trace elements in nanopores and therefore directly impacts the bioavailability of these elements. The implication of these processes to radionuclide transport in clay formations will be discussed. This work was performed at Sandia National Laboratories, which is a multiprogram laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the DOE under contract DE-AC04-94AL8500.

Development and testing of a compartmentalized reaction network model for redox zones in contaminated aquifers

USGS Publications Warehouse

Abrams , Robert H.; Loague, Keith; Kent, Douglas B.

1998-01-01

The work reported here is the first part of a larger effort focused on efficient numerical simulation of redox zone development in contaminated aquifers. The sequential use of various electron acceptors, which is governed by the energy yield of each reaction, gives rise to redox zones. The large difference in energy yields between the various redox reactions leads to systems of equations that are extremely ill-conditioned. These equations are very difficult to solve, especially in the context of coupled fluid flow, solute transport, and geochemical simulations. We have developed a general, rational method to solve such systems where we focus on the dominant reactions, compartmentalizing them in a manner that is analogous to the redox zones that are often observed in the field. The compartmentalized approach allows us to easily solve a complex geochemical system as a function of time and energy yield, laying the foundation for our ongoing work in which we couple the reaction network, for the development of redox zones, to a model of subsurface fluid flow and solute transport. Our method (1) solves the numerical system without evoking a redox parameter, (2) improves the numerical stability of redox systems by choosing which compartment and thus which reaction network to use based upon the concentration ratios of key constituents, (3) simulates the development of redox zones as a function of time without the use of inhibition factors or switching functions, and (4) can reduce the number of transport equations that need to be solved in space and time. We show through the use of various model performance evaluation statistics that the appropriate compartment choice under different geochemical conditions leads to numerical solutions without significant error. The compartmentalized approach described here facilitates the next phase of this effort where we couple the redox zone reaction network to models of fluid flow and solute transport.

Modification and benchmarking of MCNP for low-energy tungsten spectra.

PubMed

Mercier, J R; Kopp, D T; McDavid, W D; Dove, S B; Lancaster, J L; Tucker, D M

2000-12-01

The MCNP Monte Carlo radiation transport code was modified for diagnostic medical physics applications. In particular, the modified code was thoroughly benchmarked for the production of polychromatic tungsten x-ray spectra in the 30-150 kV range. Validating the modified code for coupled electron-photon transport with benchmark spectra was supplemented with independent electron-only and photon-only transport benchmarks. Major revisions to the code included the proper treatment of characteristic K x-ray production and scoring, new impact ionization cross sections, and new bremsstrahlung cross sections. Minor revisions included updated photon cross sections, electron-electron bremsstrahlung production, and K x-ray yield. The modified MCNP code is benchmarked to electron backscatter factors, x-ray spectra production, and primary and scatter photon transport.

USING MOLECULAR PROBES TO STUDY INTERFACIAL REDOX REACTION AT FE-BEARING SMECTITES

EPA Science Inventory

The interfacial electron transfer of clay-water systems has a wide range of significance in geochemical and biogeochernical environments. However the mechanism of interfacial electron transport is poorly understood. The electron transfer mechanism at the solid-water interfaces of...

Workshop discusses community models for coastal sediment transport

NASA Astrophysics Data System (ADS)

Sherwood, Christopher R.; Signell, Richard P.; Harris, Courtney K.; Butman, Bradford

Numerical models of coastal sediment transport are increasingly used to address problems ranging from remediation of contaminated sediments, to siting of sewage outfalls and disposal sites, to evaluating impacts of coastal development. They are also used as a test bed for sediment-transport algorithms, to provide realistic settings for biological and geochemical models, and for a variety of other research, both fundamental and applied. However, there are few full-featured, publicly available coastal sediment-transport models, and fewer still that are well tested and have been widely applied.This was the motivation for a workshop in Woods Hole, Massachusetts, on June 22-23, 2000, that explored the establishment of community models for coastal sediment-transport processes.

76 FR 2744 - Disclosure of Code-Share Service by Air Carriers and Sellers of Air Transportation

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-14

... DEPARTMENT OF TRANSPORTATION Office of the Secretary Disclosure of Code-Share Service by Air Carriers and Sellers of Air Transportation AGENCY: Office of the Secretary, Department of Transportation..., their agents, and third party sellers of air transportation in view of recent amendments to 49 U.S.C...

Patterns and variability in geochemical signatures and microbial activity within and between diverse cold seep habitats along the lower continental slope, Northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Bowles, Marshall; Hunter, Kimberley S.; Samarkin, Vladimir; Joye, Samantha

2016-07-01

We collected 69 sediment cores from distinct ecological and geological settings along the deep slope in the Northern Gulf of Mexico to evaluate whether specific geochemical- or habitat-related factors correlated with rates of microbial processes and geochemical signatures. By collecting replicate cores from distinct habitats across multiple sites, we illustrate and quantify the heterogeneity of cold seep geochemistry and microbial activity. These data also document the factors driving unique aspects of the geochemistry of deep slope gas, oil and brine seeps. Surprisingly little variation was observed between replicate (n=2-5) cores within sites for most analytes (except methane), implying that the common practice of collecting one core for geochemical analysis can capture the signature of a habitat in most cases. Depth-integrated concentrations of methane, dissolved inorganic carbon (DIC), and calcium were the predominant geochemical factors that correlated with a site's ecological or geological settings. Pore fluid methane concentration was related to the phosphate and DIC concentration, as well as to rates of sulfate reduction. While distinctions between seep habitats were identified from geochemical signatures, habitat specific geochemistry varied little across sites. The relative concentration of dissolved inorganic nitrogen versus phosphorus suggests that phosphorus availability limits biomass production at cold seeps. Correlations between calcium, chloride, and phosphate concentrations were indicative of brine-associated phosphate transport, suggesting that in addition to the co-migration of methane, dissolved organic carbon, and ammonium with brine, phosphate delivery is also associated with brine advection.

Computer Code for Transportation Network Design and Analysis

DOT National Transportation Integrated Search

1977-01-01

This document describes the results of research into the application of the mathematical programming technique of decomposition to practical transportation network problems. A computer code called Catnap (for Control Analysis Transportation Network A...

A Comparison of Analytical and Numerical Methods for Modeling Dissolution and Other Reactions in Transport Limited Systems

NASA Astrophysics Data System (ADS)

Hochstetler, D. L.; Kitanidis, P. K.

2009-12-01

Modeling the transport of reactive species is a computationally demanding problem, especially in complex subsurface media, where it is crucial to improve understanding of geochemical processes and the fate of groundwater contaminants. In most of these systems, reactions are inherently fast and actual rates of transformations are limited by the slower physical transport mechanisms. There have been efforts to reformulate multi-component reactive transport problems into systems that are simpler and less demanding to solve. These reformulations include defining conservative species and decoupling of reactive transport equations so that fewer of them must be solved, leaving mostly conservative equations for transport [e.g., De Simoni et al., 2005; De Simoni et al., 2007; Kräutle and Knabner, 2007; Molins et al., 2004]. Complex and computationally cumbersome numerical codes used to solve such problems have also caused De Simoni et al. [2005] to develop more manageable analytical solutions. Furthermore, this work evaluates reaction rates and has reaffirmed that the mixing rate,▽TuD▽u, where u is a solute concentration and D is the dispersion tensor, as defined by Kitanidis [1994], is an important and sometimes dominant factor in determining reaction rates. Thus, mixing of solutions is often reaction-limiting. We will present results from analytical and computational modeling of multi-component reactive-transport problems. The results have applications to dissolution of solid boundaries (e.g., calcite), dissolution of non-aqueous phase liquids (NAPLs) in separate phases, and mixing of saltwater and freshwater (e.g. saltwater intrusion in coastal carbonate aquifers). We quantify reaction rates, compare numerical and analytical results, and analyze under what circumstances which approach is most effective for a given problem. References: DeSimoni, M., et al. (2005), A procedure for the solution of multicomponent reactive transport problems, Water Resources Research, 41(W11410). DeSimoni, M., et al. (2007), A mixing ratios-based formulation for multicomponent reactive transport, Water Resources Research, 43(W07419). Kitanidis, P. (1994), The Concept of the Dilution Index, Water Resources Research, 30(7), 2011-2026. Kräutle, S., and P. Knabner (2007), A reduction scheme for coupled multicomponent transport-reaction problems in porous media: Generalization to problems with heterogeneous equilibrium reactions Water Resources Research, 43. Molins, S., et al. (2004), A formulation for decoupling components in reactive transport porblems, Water Resources Research, 40, 13.

Numerical simulation of in-situ chemical oxidation (ISCO) and biodegradation of petroleum hydrocarbons using a coupled model for bio-geochemical reactive transport

NASA Astrophysics Data System (ADS)

Marin, I. S.; Molson, J. W.

2013-05-01

Petroleum hydrocarbons (PHCs) are a major source of groundwater contamination, being a worldwide and well-known problem. Formed by a complex mixture of hundreds of organic compounds (including BTEX - benzene, toluene, ethylbenzene and xylenes), many of which are toxic and persistent in the subsurface and are capable of creating a serious risk to human health. Several remediation technologies can be used to clean-up PHC contamination. In-situ chemical oxidation (ISCO) and intrinsic bioremediation (IBR) are two promising techniques that can be applied in this case. However, the interaction of these processes with the background aquifer geochemistry and the design of an efficient treatment presents a challenge. Here we show the development and application of BIONAPL/Phreeqc, a modeling tool capable of simulating groundwater flow, contaminant transport with coupled biological and geochemical processes in porous or fractured porous media. BIONAPL/Phreeqc is based on the well-tested BIONAPL/3D model, using a powerful finite element simulation engine, capable of simulating non-aqueous phase liquid (NAPL) dissolution, density-dependent advective-dispersive transport, and solving the geochemical and kinetic processes with the library Phreeqc. To validate the model, we compared BIONAPL/Phreeqc with results from the literature for different biodegradation processes and different geometries, with good agreement. We then used the model to simulate the behavior of sodium persulfate (NaS2O8) as an oxidant for BTEX degradation, coupled with sequential biodegradation in a 2D case and to evaluate the effect of inorganic geochemistry reactions. The results show the advantages of a treatment train remediation scheme based on ISCO and IBR. The numerical performance and stability of the integrated BIONAPL/Phreeqc model was also verified.

Preliminary Reactive Geochemical Transport Modeling Study on Changes in Water Chemistry Induced by CO2 Injection at Frio Pilot Test Site

NASA Astrophysics Data System (ADS)

Xu, T.; Kharaka, Y.; Benson, S.

2006-12-01

A total of 1600 tons of CO2 were injected into the Frio ~{!0~}C~{!1~} sandstone layer at a depth of 1500 m over a period of 10 days. The pilot, located near Dayton, Texas, employed one injection well and one observation well, separated laterally by about 30 m. Each well was perforated over 6 m in the upper portion of the 23-m thick sandstone. Fluid samples were taken from both wells before, during, and after the injection. Following CO2 breakthrough, observations indicate drops in pH (6.5 to 5.7), pronounced increases in concentrations of HCO3- (100 to 3000 mg/L), in Fe (30 to 1100), and dissolved organic carbon. Numerical modeling was used in this study to understand changes of aqueous HCO3- and Fe caused by CO2 injection. The general multiphase reactive geochemical transport simulator TOUGHREACT was used, which includes new fluid property module ECO2N with an accurate description of the thermophysical properties of mixtures of water, brine, and CO2 at conditions of interest for CO2 storage. A calibrated 1-D radial well flow model was employed for the present reactive geochemical transport simulations. Mineral composition used was taken from literatures relevant to Frio sandstone. Increases in HCO3- concentration were well reproduced by an initial simulation. Several scenarios were used to capture increases in Fe concentration including (1) dissolution of carbonate minerals, (2) dissolution of iron oxyhydroxides, (3) de-sorption of previously coated Fe. Future modeling, laboratory and field investigations are proposed to better understand the CO2-brine-mineral interactions at the Frio site. Results from this study could have broad implication for subsurface storage of CO2 and potential water quality impacts.

Conceptual Model of Uranium in the Vadose Zone for Acidic and Alkaline Wastes Discharged at the Hanford Site Central Plateau

DOE Office of Scientific and Technical Information (OSTI.GOV)

Truex, Michael J.; Szecsody, James E.; Qafoku, Nikolla

2014-09-01

Historically, uranium was disposed in waste solutions of varying waste chemistry at the Hanford Site Central Plateau. The character of how uranium was distributed in the vadose zone during disposal, how it has continued to migrate through the vadose zone, and the magnitude of potential impacts on groundwater are strongly influenced by geochemical reactions in the vadose zone. These geochemical reactions can be significantly influenced by the disposed-waste chemistry near the disposal location. This report provides conceptual models and supporting information to describe uranium fate and transport in the vadose zone for both acidic and alkaline wastes discharged at amore » substantial number of waste sites in the Hanford Site Central Plateau. The conceptual models include consideration of how co-disposed acidic or alkaline fluids influence uranium mobility in terms of induced dissolution/precipitation reactions and changes in uranium sorption with a focus on the conditions near the disposal site. This information, when combined with the extensive information describing uranium fate and transport at near background pH conditions, enables focused characterization to support effective fate and transport estimates for uranium in the subsurface.« less

Subsurface transport of orthophosphate in five agricultural watersheds, USA

USGS Publications Warehouse

Domagalski, Joseph L.; Johnson, Henry M.

2011-01-01

Concentrations of dissolved orthophosphate (ortho P) in the unsaturated zone, groundwater, tile drains, and groundwater/stream water interfaces were assessed in five agricultural watersheds to determine the potential for subsurface transport. Concentrations of iron oxides were measured in the aquifer material and adsorption of ortho P on oxide surfaces was assessed by geochemical modeling. Attenuation of ortho P in these aquifers was attributed primarily to sorption onto iron oxides, and in one location onto clay minerals. Only one location showed a clear indication of phosphorus transport to a stream from groundwater discharge, although groundwater did contribute to the stream load elsewhere. Subsurface ortho P movement at a site in California resulted in a plume down gradient from orchards, which was attenuated by a 200 m thick riparian zone with natural vegetation. Iron oxides had an effect on phosphorus movement and concentrations at all locations, and groundwater chemistry, especially pH, exerted a major control on the amount of phosphorus adsorbed. Groundwater pH at a site in Maryland was below 5 and that resulted in complete sequestration of phosphorus and no movement toward the stream. Geochemical modeling indicated that as the surfaces approached saturation, groundwater concentrations of ortho P rise rapidly.

Mineral paragenesis on Mars: The roles of reactive surface area and diffusion

PubMed Central

Gil‐Lozano, Carolina; Uceda, Esther R.; Losa‐Adams, Elisabeth; Davila, Alfonso F.; Gago‐Duport, Luis

2017-01-01

Abstract Geochemical models of secondary mineral precipitation on Mars generally assume semiopen systems (open to the atmosphere but closed at the water‐sediment interface) and equilibrium conditions. However, in natural multicomponent systems, the reactive surface area of primary minerals controls the dissolution rate and affects the precipitation sequences of secondary phases, and simultaneously, the transport of dissolved species may occur through the atmosphere‐water and water‐sediment interfaces. Here we present a suite of geochemical models designed to analyze the formation of secondary minerals in basaltic sediments on Mars, evaluating the role of (i) reactive surface areas and (ii) the transport of ions through a basalt sediment column. We consider fully open conditions, both to the atmosphere and to the sediment, and a kinetic approach for mineral dissolution and precipitation. Our models consider a geochemical scenario constituted by a basin (i.e., a shallow lake) where supersaturation is generated by evaporation/cooling and the starting point is a solution in equilibrium with basaltic sediments. Our results show that cation removal by diffusion, along with the input of atmospheric volatiles and the influence of the reactive surface area of primary minerals, plays a central role in the evolution of the secondary mineral sequences formed. We conclude that precipitation of evaporites finds more restrictions in basaltic sediments of small grain size than in basaltic sediments of greater grain size. PMID:29104844

Mineral paragenesis on Mars: The roles of reactive surface area and diffusion.

PubMed

Fairén, Alberto G; Gil-Lozano, Carolina; Uceda, Esther R; Losa-Adams, Elisabeth; Davila, Alfonso F; Gago-Duport, Luis

2017-09-01

Geochemical models of secondary mineral precipitation on Mars generally assume semiopen systems (open to the atmosphere but closed at the water-sediment interface) and equilibrium conditions. However, in natural multicomponent systems, the reactive surface area of primary minerals controls the dissolution rate and affects the precipitation sequences of secondary phases, and simultaneously, the transport of dissolved species may occur through the atmosphere-water and water-sediment interfaces. Here we present a suite of geochemical models designed to analyze the formation of secondary minerals in basaltic sediments on Mars, evaluating the role of (i) reactive surface areas and (ii) the transport of ions through a basalt sediment column. We consider fully open conditions, both to the atmosphere and to the sediment, and a kinetic approach for mineral dissolution and precipitation. Our models consider a geochemical scenario constituted by a basin (i.e., a shallow lake) where supersaturation is generated by evaporation/cooling and the starting point is a solution in equilibrium with basaltic sediments. Our results show that cation removal by diffusion, along with the input of atmospheric volatiles and the influence of the reactive surface area of primary minerals, plays a central role in the evolution of the secondary mineral sequences formed. We conclude that precipitation of evaporites finds more restrictions in basaltic sediments of small grain size than in basaltic sediments of greater grain size.

A coupled THC model of the FEBEX in situ test with bentonite swelling and chemical and thermal osmosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, L.; Samper, J.; Montenegro, L.

The performance assessment of a geological repository for radioactive waste requires quantifying the geochemical evolution of the bentonite engineered barrier. This barrier will be exposed to coupled thermal (T), hydrodynamic (H), mechanical (M) and chemical (C) processes. This paper presents a coupled THC model of the FEBEX (Full-scale Engineered Barrier EXperiment) in situ test which accounts for bentonite swelling and chemical and thermal osmosis. Model results attest the relevance of thermal osmosis and bentonite swelling for the geochemical evolution of the bentonite barrier while chemical osmosis is found to be almost irrelevant. The model has been tested with data collectedmore » after the dismantling of heater 1 of the in situ test. The model reproduces reasonably well the measured temperature, relative humidity, water content and inferred geochemical data. However, it fails to mimic the solute concentrations at the heater-bentonite and bentonite-granite interfaces because the model does not account for the volume change of bentonite, the CO{sub 2}(g) degassing and the transport of vapor from the bentonite into the granite. The inferred HCO{sub 3}{sup -} and pH data cannot be explained solely by solute transport, calcite dissolution and protonation/deprotonation by surface complexation, suggesting that such data may be affected also by other reactions.« less

Geochemical evolution of groundwater in the Culebra dolomite near the Waste Isolation Pilot Plant, southeastern New Mexico, USA

USGS Publications Warehouse

Siegel, M.D.; Anderholm, S.

1994-01-01

The Culebra Dolomite Member of the Rustler Formation, a thin (10 m) fractured dolomite aquifer, lies approximately 450 m above the repository horizon of the Waste Isolation Pilot Plant (WIPP) in southeastern New Mexico, USA. Salinities of water in the Culebra range roughly from 10,000 to 200,000 mg/L within the WIPP site. A proposed model for the post-Pleistocene hydrochemical evolution of the Culebra tentatively identifies the major sources and sinks for many of the groundwater solutes. Reaction-path simulations with the PHRQPITZ code suggest that the Culebra dolomite is a partial chemical equilibrium system whose composition is controlled by an irreversible process (dissolution of evaporites) and equilibrium with gypsum and calcite. Net geochemical reactions along postulated modern flow paths, calculated with the NETPATH code, include dissolution of halite, carbonate and evaporite salts, and ion exchange. R-mode principal component analysis revealed correlations among the concentrations of Si, Mg, pH, Li, and B that are consistent with several clay-water reactions. The results of the geochemical calculations and mineralogical data are consistent with the following hydrochemical model: 1. (1) solutes are added to the Culebra by dissolution of evaporite minerals 2. (2) the solubilities of gypsum and calcite increase as the salinity increases; these minerals dissolve as chemical equilibrium is maintained between them and the groundwater 3. (3) equilibrium is not maintained between the waters and dolomite; sufficient Mg is added to the waters by dissolution of accessory carnallite or polyhalite such that the degree of dolomite supersaturation increases with ionic strength 4. (4) clays within the fractures and rock matrix exert some control on the distribution of Li, B, Mg, and Si via sorption, ion exchange, and dissolution. ?? 1994.

User's manual for a material transport code on the Octopus Computer Network

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naymik, T.G.; Mendez, G.D.

1978-09-15

A code to simulate material transport through porous media was developed at Oak Ridge National Laboratory. This code has been modified and adapted for use at Lawrence Livermore Laboratory. This manual, in conjunction with report ORNL-4928, explains the input, output, and execution of the code on the Octopus Computer Network.

Simultaneous leaching of arsenite, arsenate, selenite and selenate, and their migration in tunnel-excavated sedimentary rocks: II. Kinetic and reactive transport modeling.

PubMed

Tabelin, Carlito Baltazar; Sasaki, Ryosuke; Igarashi, Toshifumi; Park, Ilhwan; Tamoto, Shuichi; Arima, Takahiko; Ito, Mayumi; Hiroyoshi, Naoki

2017-12-01

Predicting the fates of arsenic (As) and selenium (Se) in natural geologic media like rocks and soils necessitates the understanding of how their various oxyanionic species behave and migrate under dynamic conditions. In this study, geochemical factors and processes crucial in the leaching and transport of arsenite (As III ), arsenate (As V ), selenite (Se IV ) and selenate (Se VI ) in tunnel-excavated rocks of marine origin were investigated using microscopic/extraction techniques, column experiments, dissolution-precipitation kinetics and one-dimensional reactive transport modeling. The results showed that evaporite salts were important because aside from containing As and Se, they played crucial roles in the evolution of pH and concentrations of coexisting ions, both of which had strong effects on adsorption-desorption reactions of As and Se species with iron oxyhydroxide minerals/phases. The observed leaching trends of As V , As III , Se IV and Se VI were satisfactorily simulated by one-dimensional reactive transport models, which predict that preferential adsorptions of As V and Se IV were magnified by geochemical changes in the columns due to water flow. Moreover, our results showed that migrations of As III , Se IV and Se VI could be predicted adequately by 1D solute transport with simple activity-K' d approach, but surface complexation was more reliable to simulate adsorption-desorption behavior of As V . Copyright © 2017 Elsevier Ltd. All rights reserved.

An interactive code (NETPATH) for modeling NET geochemical reactions along a flow PATH, version 2.0

USGS Publications Warehouse

Plummer, Niel; Prestemon, Eric C.; Parkhurst, David L.

1994-01-01

NETPATH is an interactive Fortran 77 computer program used to interpret net geochemical mass-balance reactions between an initial and final water along a hydrologic flow path. Alternatively, NETPATH computes the mixing proportions of two to five initial waters and net geochemical reactions that can account for the observed composition of a final water. The program utilizes previously defined chemical and isotopic data for waters from a hydrochemical system. For a set of mineral and (or) gas phases hypothesized to be the reactive phases in the system, NETPATH calculates the mass transfers in every possible combination of the selected phases that accounts for the observed changes in the selected chemical and (or) isotopic compositions observed along the flow path. The calculations are of use in interpreting geochemical reactions, mixing proportions, evaporation and (or) dilution of waters, and mineral mass transfer in the chemical and isotopic evolution of natural and environmental waters. Rayleigh distillation calculations are applied to each mass-balance model that satisfies the constraints to predict carbon, sulfur, nitrogen, and strontium isotopic compositions at the end point, including radiocarbon dating. DB is an interactive Fortran 77 computer program used to enter analytical data into NETPATH, and calculate the distribution of species in aqueous solution. This report describes the types of problems that can be solved, the methods used to solve problems, and the features available in the program to facilitate these solutions. Examples are presented to demonstrate most of the applications and features of NETPATH. The codes DB and NETPATH can be executed in the UNIX or DOS1 environment. This report replaces U.S. Geological Survey Water-Resources Investigations Report 91-4078, by Plummer and others, which described the original release of NETPATH, version 1.0 (dated December, 1991), and documents revisions and enhancements that are included in version 2.0. 1 The use of trade, brand or product names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey.

Coulombic interactions during advection-dominated transport of ions in porous media

NASA Astrophysics Data System (ADS)

Muniruzzaman, Muhammad; Stolze, Lucien; Rolle, Massimo

2017-04-01

Solute transport of charged species in porous media is significantly affected by the electrochemical migration term resulting from the charge-induced interactions among dissolved ions and with solid surfaces. Therefore, the characterization of such Coulombic interactions and their effect on multicomponent ionic transport is of critical importance for assessing the fate of charged solutes in porous media. In this work we present a detailed investigation of the electrochemical effects during conservative multicomponent ionic transport in homogeneous and heterogeneous domains by means of laboratory bench-scale experiments and numerical simulations. The investigation aims at quantifying the key role of small-scale electrostatic interactions in flow-through systems, especially when advection is the dominant mass-transfer process. Considering dilute solutions of strong electrolytes (e.g., MgCl2 and NaBr) we report results showing the important role of Coulombic interactions in the lateral displacement of the different ionic species for steady-state transport scenarios in which the solutions are continuously injected through different portions of the flow-through chamber [1, 2]. Successively, we focus our attention on transient transport and pulse injection of the electrolytes. In these experiments high-resolution spatial and temporal monitoring of the ions' concentrations (600 samples; 1800 concentration measurements), at closely spaced outlet ports (5 mm), allowed us resolving the effects of charge interactions on the temporal breakthrough and spatial profiles of the cations and anions [3]. The interpretation of the experimental results requires a multicomponent modeling approach with an accurate description of local hydrodynamic dispersion, as well as the explicit quantification of the dispersive fluxes' cross-coupling due to the Coulombic interactions between the charged species. A new 2-D simulator [4], coupling the solution of the multicomponent ionic transport problem with the geochemical code PHREEQC has been developed and used to quantitatively interpret the experimental results. References [1] Rolle M., Muniruzzaman M., Haberer C.M. and P. Grathwohl (2013). Geochim. Cosmochim. Acta 120, 195-205. [2] Muniruzzaman M., Haberer C.M., Grathwohl P. and M. Rolle (2014). Geochim. Cosmochim. Acta 141, 656-669. [3] Muniruzzaman M. and M. Rolle (2017). Water Resour. Res. (in press). [4] Muniruzzaman M. and M. Rolle (2016). Adv. Water Resour. 98, 1-15.

Comparison of heavy-ion transport simulations: Collision integral in a box

NASA Astrophysics Data System (ADS)

Zhang, Ying-Xun; Wang, Yong-Jia; Colonna, Maria; Danielewicz, Pawel; Ono, Akira; Tsang, Manyee Betty; Wolter, Hermann; Xu, Jun; Chen, Lie-Wen; Cozma, Dan; Feng, Zhao-Qing; Das Gupta, Subal; Ikeno, Natsumi; Ko, Che-Ming; Li, Bao-An; Li, Qing-Feng; Li, Zhu-Xia; Mallik, Swagata; Nara, Yasushi; Ogawa, Tatsuhiko; Ohnishi, Akira; Oliinychenko, Dmytro; Papa, Massimo; Petersen, Hannah; Su, Jun; Song, Taesoo; Weil, Janus; Wang, Ning; Zhang, Feng-Shou; Zhang, Zhen

2018-03-01

Simulations by transport codes are indispensable to extract valuable physical information from heavy-ion collisions. In order to understand the origins of discrepancies among different widely used transport codes, we compare 15 such codes under controlled conditions of a system confined to a box with periodic boundary, initialized with Fermi-Dirac distributions at saturation density and temperatures of either 0 or 5 MeV. In such calculations, one is able to check separately the different ingredients of a transport code. In this second publication of the code evaluation project, we only consider the two-body collision term; i.e., we perform cascade calculations. When the Pauli blocking is artificially suppressed, the collision rates are found to be consistent for most codes (to within 1 % or better) with analytical results, or completely controlled results of a basic cascade code. In orderto reach that goal, it was necessary to eliminate correlations within the same pair of colliding particles that can be present depending on the adopted collision prescription. In calculations with active Pauli blocking, the blocking probability was found to deviate from the expected reference values. The reason is found in substantial phase-space fluctuations and smearing tied to numerical algorithms and model assumptions in the representation of phase space. This results in the reduction of the blocking probability in most transport codes, so that the simulated system gradually evolves away from the Fermi-Dirac toward a Boltzmann distribution. Since the numerical fluctuations are weaker in the Boltzmann-Uehling-Uhlenbeck codes, the Fermi-Dirac statistics is maintained there for a longer time than in the quantum molecular dynamics codes. As a result of this investigation, we are able to make judgements about the most effective strategies in transport simulations for determining the collision probabilities and the Pauli blocking. Investigation in a similar vein of other ingredients in transport calculations, like the mean-field propagation or the production of nucleon resonances and mesons, will be discussed in the future publications.

Chemical equilibria model of strontium-90 adsorption and transport in soil in response to dynamic alkaline conditions.

PubMed

Spalding, B P; Spalding, I R

2001-01-15

Strontium-90 is a major hazardous contaminant of radioactive wastewater and its processing sludges at many Department of Energy (DOE) facilities. In the past, such contaminated wastewater and sludge have been disposed in soil seepage pits, lagoons, or cribs often under highly perturbed alkaline conditions (pH > 12) where 90Sr solubility is low and its adsorption to surrounding soil is high. As natural weathering returns these soils to near-neutral or slightly acidic conditions, the adsorbed and precipitated calcium and magnesium phases, in which 90Sr is carried, change significantly in both nature and amounts. No comprehensive computational method has been formulated previously to quantitatively simulate the dynamics of 90Sr in the soil-groundwater environment under such dynamic and wide-ranging conditions. A computational code, the Hydrologic Utility Model for Demonstrating Integrated Nuclear Geochemical Environmental Responses (HUMDINGER), was composed to describe the changing equilibria of 90Sr in soil based on its causative chemical reactions including soil buffering, pH-dependent cation-exchange capacity, cation selectivity, and the precipitation/dissolution of calcium carbonate, calcium hydroxide, and magnesium hydroxide in response to leaching groundwater characteristics including pH, acid-neutralizing capacity, dissolved cations, and inorganic carbonate species. The code includes a simulation of one-dimensional transport of 90Sr through a soil column as a series of soil mixing cells where the equilibrium soluble output from one cell is applied to the next cell. Unamended soil leaching and highly alkaline soil treatments, including potassium hydroxide, sodium silicate, and sodium aluminate, were simulated and compared with experimental findings using large (10 kg) soil columns that were leached with 90Sr-contaminated groundwater after treatment. HUMDINGER's simulations were in good agreement with dynamic experimental observations of soil exchange capacity, exchangeable cations, total 90Sr, and pH values of layers within the soil columns and of column effluents.

Reduced transport potential of a palladium-doped zero valent iron nanoparticle in a water saturated loamy sand.

PubMed

Basnet, Mohan; Di Tommaso, Caroline; Ghoshal, Subhasis; Tufenkji, Nathalie

2015-01-01

Direct in situ injection of palladium-doped nanosized zero valent iron (Pd-NZVI) particles can contribute to remediation of various environmental contaminants. A major challenge encountered is rapid aggregation of Pd-NZVI and hence very limited mobility. To reduce aggregation and concurrently improve particle mobility, the surface of bare Pd-NZVI can be modified with stabilizing surface modifiers. Selected surface-modified Pd-NZVI has shown dramatically improved stability and transport. However, little is known regarding the effects of aquifer grain geochemical heterogeneity on the transport and deposition behavior of surface-modified Pd-NZVI. Herein, the mobility of surface stabilized Pd-NZVI in two granular matrices representative of model ground water environments (quartz sand and loamy sand) was assessed over a wide range of environmentally relevant ionic strengths (IS). Carboxymethyl cellulose (CMC), soybean flour and rhamnolipid biosurfactant were used as Pd-NZVI surface modifiers. Our results show that, both in quartz sand and loamy sand, an increase in solution IS results in reduced Pd-NZVI transport. Moreover, at a given water chemistry, Pd-NZVI transport is notably attenuated in loamy sand implying that geochemical heterogeneity associated with loamy sand is a key factor influencing Pd-NZVI transport potential. Experiments conducted at a higher Pd-NZVI particle concentration, to be more representative of field conditions, show that rhamnolipid and CMC are effective stabilizing agents even when 1 g/L Pd-NZVI is injected into quartz sand. Overall, this study emphasizes the extent to which variation in groundwater chemistry, coupled with changes in aquifer geochemistry, could dramatically alter the transport potential of Pd-NZVI in the subsurface environment.

Verification and benchmark testing of the NUFT computer code

NASA Astrophysics Data System (ADS)

Lee, K. H.; Nitao, J. J.; Kulshrestha, A.

1993-10-01

This interim report presents results of work completed in the ongoing verification and benchmark testing of the NUFT (Nonisothermal Unsaturated-saturated Flow and Transport) computer code. NUFT is a suite of multiphase, multicomponent models for numerical solution of thermal and isothermal flow and transport in porous media, with application to subsurface contaminant transport problems. The code simulates the coupled transport of heat, fluids, and chemical components, including volatile organic compounds. Grid systems may be cartesian or cylindrical, with one-, two-, or fully three-dimensional configurations possible. In this initial phase of testing, the NUFT code was used to solve seven one-dimensional unsaturated flow and heat transfer problems. Three verification and four benchmarking problems were solved. In the verification testing, excellent agreement was observed between NUFT results and the analytical or quasianalytical solutions. In the benchmark testing, results of code intercomparison were very satisfactory. From these testing results, it is concluded that the NUFT code is ready for application to field and laboratory problems similar to those addressed here. Multidimensional problems, including those dealing with chemical transport, will be addressed in a subsequent report.

On mass transport in magmatic porosity waves

NASA Astrophysics Data System (ADS)

Jordan, J.; Hesse, M. A.; Rudge, J. F.

2017-12-01

Geochemical analyses of oceanic basalts indicate the mantle is lithologically heterogenous and subject to partial melting. Here we show that porosity waves-which arise naturally in models of buoyancy driven melt migration-transport mass and preserve geochemical signatures, at least partially. Prior studies of tracer transport in one dimensional porosity waves conclude that porosity waves do not transfer mass. However, it is well known that one-dimensional porosity waves are unstable in two and three dimensions and break up into sets of cylindrical or spherical porosity waves. We show that tracer transport in higher dimensional porosity waves is dramatically different than in one dimension. Lateral melt focusing into these high porosity regions leads to melt recirculating in the center of the wave. Melt focusing and recirculation are not resolvable in one dimension where no sustained transport is observed in numerical experiments of solitary porosity waves. In two and three dimensions, the recirculating melt is separated from the background melt-flow field by a circular or spherical dividing streamline and transported with the phase velocity of the porosity wave. The amount of melt focusing that occurs within any given porosity wave, and thus, the extent of the dividing streamline, and resultant volume of transported melt is extremely sensitive to the selection of porosity-permeability and porosity-rheology relationships. Therefore, we present a regime diagram spanning common parameterizations that illustrates the minimum amplitude and phase velocity required for a solitary porosity wave to transport mass as a function of material properties and common parameters used in magma dynamics and mid-ocean ridge models. The realization that solitary waves are capable of sustaining melt transport may require the reinterpretation of previous studies. For example, transport in porosity waves may allow melts that originated from the partial melting of fertile heterogeneities to retain their incompatible trace element signatures as they rise through the mantle. Porosity waves may also provide a mechanism for mixing melts derived from heterogeneities with ambient melts derived from different depths in the mantle.

49 CFR Appendix C to Part 229 - FRA Locomotive Standards-Code of Defects

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 4 2013-10-01 2013-10-01 false FRA Locomotive Standards-Code of Defects C Appendix C to Part 229 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD LOCOMOTIVE SAFETY STANDARDS Pt. 229, App. C...

49 CFR Appendix C to Part 229 - FRA Locomotive Standards-Code of Defects

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 4 2014-10-01 2014-10-01 false FRA Locomotive Standards-Code of Defects C Appendix C to Part 229 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD LOCOMOTIVE SAFETY STANDARDS Pt. 229, App. C...

49 CFR Appendix C to Part 229 - FRA Locomotive Standards-Code of Defects

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 4 2010-10-01 2010-10-01 false FRA Locomotive Standards-Code of Defects C Appendix C to Part 229 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD LOCOMOTIVE SAFETY STANDARDS Pt. 229, App. C...

49 CFR Appendix C to Part 215 - FRA Freight Car Standards Defect Code

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 4 2013-10-01 2013-10-01 false FRA Freight Car Standards Defect Code C Appendix C... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD FREIGHT CAR SAFETY STANDARDS Pt. 215, App. C Appendix C to Part 215—FRA Freight Car Standards Defect Code The following defect code has been established for use...

49 CFR Appendix C to Part 215 - FRA Freight Car Standards Defect Code

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 4 2014-10-01 2014-10-01 false FRA Freight Car Standards Defect Code C Appendix C... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD FREIGHT CAR SAFETY STANDARDS Pt. 215, App. C Appendix C to Part 215—FRA Freight Car Standards Defect Code The following defect code has been established for use...

49 CFR Appendix C to Part 215 - FRA Freight Car Standards Defect Code

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 4 2012-10-01 2012-10-01 false FRA Freight Car Standards Defect Code C Appendix C... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD FREIGHT CAR SAFETY STANDARDS Pt. 215, App. C Appendix C to Part 215—FRA Freight Car Standards Defect Code The following defect code has been established for use...

49 CFR Appendix C to Part 215 - FRA Freight Car Standards Defect Code

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 4 2011-10-01 2011-10-01 false FRA Freight Car Standards Defect Code C Appendix C... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD FREIGHT CAR SAFETY STANDARDS Pt. 215, App. C Appendix C to Part 215—FRA Freight Car Standards Defect Code The following defect code has been established for use...

Methods of treating complex space vehicle geometry for charged particle radiation transport

NASA Technical Reports Server (NTRS)

Hill, C. W.

1973-01-01

Current methods of treating complex geometry models for space radiation transport calculations are reviewed. The geometric techniques used in three computer codes are outlined. Evaluations of geometric capability and speed are provided for these codes. Although no code development work is included several suggestions for significantly improving complex geometry codes are offered.

Comparisons of anomalous and collisional radial transport with a continuum kinetic edge code

NASA Astrophysics Data System (ADS)

Bodi, K.; Krasheninnikov, S.; Cohen, R.; Rognlien, T.

2009-05-01

Modeling of anomalous (turbulence-driven) radial transport in controlled-fusion plasmas is necessary for long-time transport simulations. Here the focus is continuum kinetic edge codes such as the (2-D, 2-V) transport version of TEMPEST, NEO, and the code being developed by the Edge Simulation Laboratory, but the model also has wider application. Our previously developed anomalous diagonal transport matrix model with velocity-dependent convection and diffusion coefficients allows contact with typical fluid transport models (e.g., UEDGE). Results are presented that combine the anomalous transport model and collisional transport owing to ion drift orbits utilizing a Krook collision operator that conserves density and energy. Comparison is made of the relative magnitudes and possible synergistic effects of the two processes for typical tokamak device parameters.

Hydro-geochemical modeling of the spatial and the temporal geochemical variations of the granitic Strengbach catchment springs (Vosges massif, France)

NASA Astrophysics Data System (ADS)

Ackerer, Julien; Chabaux, François; Lucas, Yann; Pierret, Marie Claire; Viville, Daniel; Fritz, Bertrand; Clement, Alain; Beaulieu, Emilie; Negrel, Philippe

2017-04-01

Regular analysis of the major element concentrations in waters from springs emerging on the Strengbach catchment is made for more than 20 years (OHGE, Observatoire Hydro-Géochimique de l'Environnement). These data confirm the spatial variability of geochemical characteristics of the Strengbach springs linked, at least partly, to the lithological variability of the substratum (Pierret et al., 2014). The data also indicate that at the first order, the geochemical fluxes exported from each spring are mainly linked to the spring discharges, without significant variations of the relationships linking these two parameters between 1990 and 2010. There is also no observation of significant variations for the dissolved silica and for most of the cationic concentrations with time. Only a significant decrease of the Ca concentrations is observed for the Strengbach springs from 1990 to 2010. Numerical simulations, performed with the KIRMAT hydro-geochemical code, show that such a decrease can be considered as the response in the "bedrock" of the water-rock interactions to the variations of the soil solution chemical compositions recorded over the last 20 years, marked by a significant increase of pH and decrease of Ca concentrations. In particular, the modeling results show that the Ca concentration decrease is controlled by the couple apatite/clays, and that significant modifications of the apatite dissolution rate and clay compositions occurred between 1990 and 2010. This study shows that the temporal evolution of the Strengbach spring chemistry cannot be explained by the only variations of the clay mineral compositions, i.e. a modification of the chemical composition of the precipitated clays or a modification of the ionic exchange capacity of the clay minerals, but that it is definitely the interrelations between the apatite and the clay minerals that are involved.

Modeling of dust deposition in central Asia

USDA-ARS?s Scientific Manuscript database

The deposition of dust particles has a significant influence on the global bio-geochemical cycle. Currently, the lack of spatiotemporal data creates great uncertainty in estimating the global dust budget. To improve our understanding of the fate, transport and cycling of airborne dust, there is a ne...

Light transport feature for SCINFUL.

PubMed

Etaati, G R; Ghal-Eh, N

2008-03-01

An extended version of the scintillator response function prediction code SCINFUL has been developed by incorporating PHOTRACK, a Monte Carlo light transport code. Comparisons of calculated and experimental results for organic scintillators exposed to neutrons show that the extended code improves the predictive capability of SCINFUL.

First ERO2.0 modeling of Be erosion and non-local transport in JET ITER-like wall

NASA Astrophysics Data System (ADS)

Romazanov, J.; Borodin, D.; Kirschner, A.; Brezinsek, S.; Silburn, S.; Huber, A.; Huber, V.; Bufferand, H.; Firdaouss, M.; Brömmel, D.; Steinbusch, B.; Gibbon, P.; Lasa, A.; Borodkina, I.; Eksaeva, A.; Linsmeier, Ch; Contributors, JET

2017-12-01

ERO is a Monte-Carlo code for modeling plasma-wall interaction and 3D plasma impurity transport for applications in fusion research. The code has undergone a significant upgrade (ERO2.0) which allows increasing the simulation volume in order to cover the entire plasma edge of a fusion device, allowing a more self-consistent treatment of impurity transport and comparison with a larger number and variety of experimental diagnostics. In this contribution, the physics-relevant technical innovations of the new code version are described and discussed. The new capabilities of the code are demonstrated by modeling of beryllium (Be) erosion of the main wall during JET limiter discharges. Results for erosion patterns along the limiter surfaces and global Be transport including incident particle distributions are presented. A novel synthetic diagnostic, which mimics experimental wide-angle 2D camera images, is presented and used for validating various aspects of the code, including erosion, magnetic shadowing, non-local impurity transport, and light emission simulation.

HZETRN: A heavy ion/nucleon transport code for space radiations

NASA Technical Reports Server (NTRS)

Wilson, John W.; Chun, Sang Y.; Badavi, Forooz F.; Townsend, Lawrence W.; Lamkin, Stanley L.

1991-01-01

The galactic heavy ion transport code (GCRTRN) and the nucleon transport code (BRYNTRN) are integrated into a code package (HZETRN). The code package is computer efficient and capable of operating in an engineering design environment for manned deep space mission studies. The nuclear data set used by the code is discussed including current limitations. Although the heavy ion nuclear cross sections are assumed constant, the nucleon-nuclear cross sections of BRYNTRN with full energy dependence are used. The relation of the final code to the Boltzmann equation is discussed in the context of simplifying assumptions. Error generation and propagation is discussed, and comparison is made with simplified analytic solutions to test numerical accuracy of the final results. A brief discussion of biological issues and their impact on fundamental developments in shielding technology is given.

Geomechanical/Geochemical Modeling Studies Conducted within theInternational DECOVALEX Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Birkholzer, J.T.; Rutqvist, J.; Sonnenthal, E.L.

2005-10-19

The DECOVALEX project is an international cooperative project initiated by SKI, the Swedish Nuclear Power Inspectorate, with participation of about 10 international organizations. The general goal of this project is to encourage multidisciplinary interactive and cooperative research on modeling coupled thermo-hydro-mechanical-chemical (THMC) processes in geologic formations in support of the performance assessment for underground storage of radioactive waste. One of the research tasks, initiated in 2004 by the U.S. Department of Energy (DOE), addresses the long-term impact of geomechanical and geochemical processes on the flow conditions near waste emplacement tunnels. Within this task, four international research teams conduct predictive analysismore » of the coupled processes in two generic repositories, using multiple approaches and different computer codes. Below, we give an overview of the research task and report its current status.« less

Geomechanical/ Geochemical Modeling Studies onducted Within the International DECOVALEX Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

J.T. Birkholzer; J. Rutqvist; E.L. Sonnenthal

2006-02-01

The DECOVALEX project is an international cooperative project initiated by SKI, the Swedish Nuclear Power Inspectorate, with participation of about 10 international organizations. The general goal of this project is to encourage multidisciplinary interactive and cooperative research on modeling coupled thermo-hydro-mechanical-chemical (THMC) processes in geologic formations in support of the performance assessment for underground storage of radioactive waste. One of the research tasks, initiated in 2004 by the U.S. Department of Energy (DOE), addresses the long-term impact of geomechanical and geochemical processes on the flow conditions near waste emplacement tunnels. Within this task, four international research teams conduct predictive analysismore » of the coupled processes in two generic repositories, using multiple approaches and different computer codes. Below, we give an overview of the research task and report its current status.« less

ITS version 5.0 : the integrated TIGER series of coupled electron/photon Monte Carlo transport codes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franke, Brian Claude; Kensek, Ronald Patrick; Laub, Thomas William

ITS is a powerful and user-friendly software package permitting state of the art Monte Carlo solution of linear time-independent couple electron/photon radiation transport problems, with or without the presence of macroscopic electric and magnetic fields of arbitrary spatial dependence. Our goal has been to simultaneously maximize operational simplicity and physical accuracy. Through a set of preprocessor directives, the user selects one of the many ITS codes. The ease with which the makefile system is applied combines with an input scheme based on order-independent descriptive keywords that makes maximum use of defaults and internal error checking to provide experimentalists and theoristsmore » alike with a method for the routine but rigorous solution of sophisticated radiation transport problems. Physical rigor is provided by employing accurate cross sections, sampling distributions, and physical models for describing the production and transport of the electron/photon cascade from 1.0 GeV down to 1.0 keV. The availability of source code permits the more sophisticated user to tailor the codes to specific applications and to extend the capabilities of the codes to more complex applications. Version 5.0, the latest version of ITS, contains (1) improvements to the ITS 3.0 continuous-energy codes, (2)multigroup codes with adjoint transport capabilities, and (3) parallel implementations of all ITS codes. Moreover the general user friendliness of the software has been enhanced through increased internal error checking and improved code portability.« less

IPOLE - semi-analytic scheme for relativistic polarized radiative transport

NASA Astrophysics Data System (ADS)

Mościbrodzka, M.; Gammie, C. F.

2018-03-01

We describe IPOLE, a new public ray-tracing code for covariant, polarized radiative transport. The code extends the IBOTHROS scheme for covariant, unpolarized transport using two representations of the polarized radiation field: In the coordinate frame, it parallel transports the coherency tensor; in the frame of the plasma it evolves the Stokes parameters under emission, absorption, and Faraday conversion. The transport step is implemented to be as spacetime- and coordinate- independent as possible. The emission, absorption, and Faraday conversion step is implemented using an analytic solution to the polarized transport equation with constant coefficients. As a result, IPOLE is stable, efficient, and produces a physically reasonable solution even for a step with high optical depth and Faraday depth. We show that the code matches analytic results in flat space, and that it produces results that converge to those produced by Dexter's GRTRANS polarized transport code on a complicated model problem. We expect IPOLE will mainly find applications in modelling Event Horizon Telescope sources, but it may also be useful in other relativistic transport problems such as modelling for the IXPE mission.

SOPHAEROS code development and its application to falcon tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lajtha, G.; Missirlian, M.; Kissane, M.

1996-12-31

One of the key issues in source-term evaluation in nuclear reactor severe accidents is determination of the transport behavior of fission products released from the degrading core. The SOPHAEROS computer code is being developed to predict fission product transport in a mechanistic way in light water reactor circuits. These applications of the SOPHAEROS code to the Falcon experiments, among others not presented here, indicate that the numerical scheme of the code is robust, and no convergence problems are encountered. The calculation is also very fast being three times longer on a Sun SPARC 5 workstation than real time and typicallymore » {approx} 10 times faster than an identical calculation with the VICTORIA code. The study demonstrates that the SOPHAEROS 1.3 code is a suitable tool for prediction of the vapor chemistry and fission product transport with a reasonable level of accuracy. Furthermore, the fexibility of the code material data bank allows improvement of understanding of fission product transport and deposition in the circuit. Performing sensitivity studies with different chemical species or with different properties (saturation pressure, chemical equilibrium constants) is very straightforward.« less

Intact coding region of the serotonin transporter gene in obsessive-compulsive disorder

DOE Office of Scientific and Technical Information (OSTI.GOV)

Altemus, M.; Murphy, D.L.; Greenberg, B.

1996-07-26

Epidemiologic studies indicate that obsessive-compulsive disorder is genetically transmitted in some families, although no genetic abnormalities have been identified in individuals with this disorder. The selective response of obsessive-compulsive disorder to treatment with agents which block serotonin reuptake suggests the gene coding for the serotonin transporter as a candidate gene. The primary structure of the serotonin-transporter coding region was sequenced in 22 patients with obsessive-compulsive disorder, using direct PCR sequencing of cDNA synthesized from platelet serotonin-transporter mRNA. No variations in amino acid sequence were found among the obsessive-compulsive disorder patients or healthy controls. These results do not support a rolemore » for alteration in the primary structure of the coding region of the serotonin-transporter gene in the pathogenesis of obsessive-compulsive disorder. 27 refs.« less

Petrographic and geochemical characterization of the granitic rocks of the Araguainha impact crater, Brazil

NASA Astrophysics Data System (ADS)

Silva, Dailto; Lana, Cristiano; Souza Filho, Carlos Roberto

2016-03-01

Petrographic and geochemical data obtained on the Araguainha impact crater (Goiás/Mato Grosso States, Brazil) indicate the existence of several molten products that originated during impact-induced congruent melting of an alkali-granite exposed in the inner part of the central uplift of the structure. Although previous studies have described these melts to some extent, there is no detailed discussion on the petrographic and geochemical variability in the granite and its impactogenic derivatives, and therefore, little is known about the geochemical behavior and mobility of trace elements during its fusion in the central part of the Araguainha crater. This paper demonstrates that the preserved granitoid exposed in the core of the structure is a magnesium-rich granite, similar to postcollisional, A-type granites, also found in terrains outside the Araguainha crater, in the Brasília orogenic belt. The molten products are texturally distinct and different from the original rock, but have very similar geochemical composition, making it difficult to separate these lithotypes based on concentrations of major and minor elements. This also applies for trace and rare earth elements (REE), thus indicating a high degree of homogenization during impact-induced congruent melting under high pressure and postshock temperature conditions. Petrographic observations, along with geochemical data, indicate that melting occurs selectively, where some of the elements are transported with the melt. Simultaneously, there is an effective dissolution of the rock (granite), which leads to entrainment of the most resistant solid phases (intact or partially molten minerals) into the melt. Minerals more resistant to melting, such as quartz and oxides, contribute substantially to a chemical balance between the preserved granite and the fusion products generated during the meteoritic impact.

Evolution of Structure and Composition in Saturn's Rings Due to Ballistic Transport of Micrometeoroid Impact Ejecta

NASA Astrophysics Data System (ADS)

Estrada, P. R.; Durisen, R. H.; Cuzzi, J. N.

2014-04-01

We introduce improved numerical techniques for simulating the structural and compositional evolution of planetary rings due to micrometeoroid bombardment and subsequent ballistic transport of impact ejecta. Our current, robust code, which is based on the original structural code of [1] and on the pollution transport code of [3], is capable of modeling structural changes and pollution transport simultaneously over long times on both local and global scales. We provide demonstrative simulations to compare with, and extend upon previous work, as well as examples of how ballistic transport can maintain the observed structure in Saturn's rings using available Cassini occultation optical depth data.

A computer program incorporating Pitzer's equations for calculation of geochemical reactions in brines

USGS Publications Warehouse

Plummer, Niel; Parkhurst, D.L.; Fleming, G.W.; Dunkle, S.A.

1988-01-01

The program named PHRQPITZ is a computer code capable of making geochemical calculations in brines and other electrolyte solutions to high concentrations using the Pitzer virial-coefficient approach for activity-coefficient corrections. Reaction-modeling capabilities include calculation of (1) aqueous speciation and mineral-saturation index, (2) mineral solubility, (3) mixing and titration of aqueous solutions, (4) irreversible reactions and mineral water mass transfer, and (5) reaction path. The computed results for each aqueous solution include the osmotic coefficient, water activity , mineral saturation indices, mean activity coefficients, total activity coefficients, and scale-dependent values of pH, individual-ion activities and individual-ion activity coeffients , and scale-dependent values of pH, individual-ion activities and individual-ion activity coefficients. A data base of Pitzer interaction parameters is provided at 25 C for the system: Na-K-Mg-Ca-H-Cl-SO4-OH-HCO3-CO3-CO2-H2O, and extended to include largely untested literature data for Fe(II), Mn(II), Sr, Ba, Li, and Br with provision for calculations at temperatures other than 25C. An extensive literature review of published Pitzer interaction parameters for many inorganic salts is given. Also described is an interactive input code for PHRQPITZ called PITZINPT. (USGS)

ENVIRONMENTAL RESEARCH BRIEF: SPATIAL HETEROGENEITY OF GEOCHEMICAL AND HYDROLOGIC PARAMETERS AFFECTING METAL TRANSPORT IN GROUND WATER

EPA Science Inventory

Reliable assessment of the hazards or risks arising from groundwater contamination and the design of effective means of rehabilitation of contaminated sites requires the capability to predict the movement and fate of dissolved solutes in groundwater. The modeling of metal transp...

ENVIRONMENTAL RESEARCH BRIEF: SPATIAL HETEROGENEITY OF GEOCHEMICAL AND HYDROLOGIC PARAMETERS AFFECTING METAL TRANSPORT IN GROUNDWATER

EPA Science Inventory

Reliable assessment of the hazards or risks arising from groundwater contamination and the design of effective means of rehabilitation of contaminated sites requires the capability to predict the movement and fate of dissolved solutes in groundwater. he modeling of metal transpor...

Dust deposition and ambient PM10 concentration in northwest China: Spatial and temporal variability

USDA-ARS?s Scientific Manuscript database

Aeolian dust transport and deposition are important geophysical processes which influence global bio-geochemical cycles. Currently, reliable continental deposition data are scarce in central Asia. Located in the eastern part of central Asia, Xinjiang Province of northwestern China has long played a ...

Comparing Turbulence Simulation with Experiment in DIII-D

NASA Astrophysics Data System (ADS)

Ross, D. W.; Bravenec, R. V.; Dorland, W.; Beer, M. A.; Hammett, G. W.; McKee, G. R.; Murakami, M.; Jackson, G. L.

2000-10-01

Gyrofluid simulations of DIII-D discharges with the GRYFFIN code(D. W. Ross et al.), Transport Task Force Workshop, Burlington, VT, (2000). are compared with transport and fluctuation measurements. The evolution of confinement-improved discharges(G. R. McKee et al.), Phys. Plasmas 7, 1870 (200) is studied at early times following impurity injection, when EXB rotational shear plays a small role. The ion thermal transport predicted by the code is consistent with the experimental values. Experimentally, changes in density profiles resulting from the injection of neon, lead to reduction in fluctuation levels and transport following the injection. This triggers subsequent changes in the shearing rate that further reduce the turbulence.(M. Murakami et al.), European Physical Society, Budapest (2000); M. Murakami et al., this meeting. Estimated uncertainties in the plasma profiles, however, make it difficult to simulate these reductions with the code. These cases will also be studied with the GS2 gyrokinetic code.

Gyrokinetic Particle Simulation of Turbulent Transport in Burning Plasmas (GPS - TTBP) Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chame, Jacqueline

2011-05-27

The goal of this project is the development of the Gyrokinetic Toroidal Code (GTC) Framework and its applications to problems related to the physics of turbulence and turbulent transport in tokamaks,. The project involves physics studies, code development, noise effect mitigation, supporting computer science efforts, diagnostics and advanced visualizations, verification and validation. Its main scientific themes are mesoscale dynamics and non-locality effects on transport, the physics of secondary structures such as zonal flows, and strongly coherent wave-particle interaction phenomena at magnetic precession resonances. Special emphasis is placed on the implications of these themes for rho-star and current scalings and formore » the turbulent transport of momentum. GTC-TTBP also explores applications to electron thermal transport, particle transport; ITB formation and cross-cuts such as edge-core coupling, interaction of energetic particles with turbulence and neoclassical tearing mode trigger dynamics. Code development focuses on major initiatives in the development of full-f formulations and the capacity to simulate flux-driven transport. In addition to the full-f -formulation, the project includes the development of numerical collision models and methods for coarse graining in phase space. Verification is pursued by linear stability study comparisons with the FULL and HD7 codes and by benchmarking with the GKV, GYSELA and other gyrokinetic simulation codes. Validation of gyrokinetic models of ion and electron thermal transport is pursed by systematic stressing comparisons with fluctuation and transport data from the DIII-D and NSTX tokamaks. The physics and code development research programs are supported by complementary efforts in computer sciences, high performance computing, and data management.« less

An approach to modeling coupled thermal-hydraulic-chemical processes in geothermal systems

USGS Publications Warehouse

Palguta, Jennifer; Williams, Colin F.; Ingebritsen, Steven E.; Hickman, Stephen H.; Sonnenthal, Eric

2011-01-01

Interactions between hydrothermal fluids and rock alter mineralogy, leading to the formation of secondary minerals and potentially significant physical and chemical property changes. Reactive transport simulations are essential for evaluating the coupled processes controlling the geochemical, thermal and hydrological evolution of geothermal systems. The objective of this preliminary investigation is to successfully replicate observations from a series of hydrothermal laboratory experiments [Morrow et al., 2001] using the code TOUGHREACT. The laboratory experiments carried out by Morrow et al. [2001] measure permeability reduction in fractured and intact Westerly granite due to high-temperature fluid flow through core samples. Initial permeability and temperature values used in our simulations reflect these experimental conditions and range from 6.13 × 10−20 to 1.5 × 10−17 m2 and 150 to 300 °C, respectively. The primary mineralogy of the model rock is plagioclase (40 vol.%), K-feldspar (20 vol.%), quartz (30 vol.%), and biotite (10 vol.%). The simulations are constrained by the requirement that permeability, relative mineral abundances, and fluid chemistry agree with experimental observations. In the models, the granite core samples are represented as one-dimensional reaction domains. We find that the mineral abundances, solute concentrations, and permeability evolutions predicted by the models are consistent with those observed in the experiments carried out by Morrow et al. [2001] only if the mineral reactive surface areas decrease with increasing clay mineral abundance. This modeling approach suggests the importance of explicitly incorporating changing mineral surface areas into reactive transport models.

Overview of Recent Radiation Transport Code Comparisons for Space Applications

NASA Astrophysics Data System (ADS)

Townsend, Lawrence

Recent advances in radiation transport code development for space applications have resulted in various comparisons of code predictions for a variety of scenarios and codes. Comparisons among both Monte Carlo and deterministic codes have been made and published by vari-ous groups and collaborations, including comparisons involving, but not limited to HZETRN, HETC-HEDS, FLUKA, GEANT, PHITS, and MCNPX. In this work, an overview of recent code prediction inter-comparisons, including comparisons to available experimental data, is presented and discussed, with emphases on those areas of agreement and disagreement among the various code predictions and published data.

Model-Based Analysis of the Role of Biological, Hydrological and Geochemical Factors Affecting Uranium Bioremediation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Jiao; Scheibe, Timothy D.; Mahadevan, Radhakrishnan

2011-01-24

Uranium contamination is a serious concern at several sites motivating the development of novel treatment strategies such as the Geobacter-mediated reductive immobilization of uranium. However, this bioremediation strategy has not yet been optimized for the sustained uranium removal. While several reactive-transport models have been developed to represent Geobacter-mediated bioremediation of uranium, these models often lack the detailed quantitative description of the microbial process (e.g., biomass build-up in both groundwater and sediments, electron transport system, etc.) and the interaction between biogeochemical and hydrological process. In this study, a novel multi-scale model was developed by integrating our recent model on electron capacitancemore » of Geobacter (Zhao et al., 2010) with a comprehensive simulator of coupled fluid flow, hydrologic transport, heat transfer, and biogeochemical reactions. This mechanistic reactive-transport model accurately reproduces the experimental data for the bioremediation of uranium with acetate amendment. We subsequently performed global sensitivity analysis with the reactive-transport model in order to identify the main sources of prediction uncertainty caused by synergistic effects of biological, geochemical, and hydrological processes. The proposed approach successfully captured significant contributing factors across time and space, thereby improving the structure and parameterization of the comprehensive reactive-transport model. The global sensitivity analysis also provides a potentially useful tool to evaluate uranium bioremediation strategy. The simulations suggest that under difficult environments (e.g., highly contaminated with U(VI) at a high migration rate of solutes), the efficiency of uranium removal can be improved by adding Geobacter species to the contaminated site (bioaugmentation) in conjunction with the addition of electron donor (biostimulation). The simulations also highlight the interactive effect of initial cell concentration and flow rate on U(VI) reduction.« less

A comparative study of space radiation organ doses and associated cancer risks using PHITS and HZETRN.

PubMed

Bahadori, Amir A; Sato, Tatsuhiko; Slaba, Tony C; Shavers, Mark R; Semones, Edward J; Van Baalen, Mary; Bolch, Wesley E

2013-10-21

NASA currently uses one-dimensional deterministic transport to generate values of the organ dose equivalent needed to calculate stochastic radiation risk following crew space exposures. In this study, organ absorbed doses and dose equivalents are calculated for 50th percentile male and female astronaut phantoms using both the NASA High Charge and Energy Transport Code to perform one-dimensional deterministic transport and the Particle and Heavy Ion Transport Code System to perform three-dimensional Monte Carlo transport. Two measures of radiation risk, effective dose and risk of exposure-induced death (REID) are calculated using the organ dose equivalents resulting from the two methods of radiation transport. For the space radiation environments and simplified shielding configurations considered, small differences (<8%) in the effective dose and REID are found. However, for the galactic cosmic ray (GCR) boundary condition, compensating errors are observed, indicating that comparisons between the integral measurements of complex radiation environments and code calculations can be misleading. Code-to-code benchmarks allow for the comparison of differential quantities, such as secondary particle differential fluence, to provide insight into differences observed in integral quantities for particular components of the GCR spectrum.

A comparative study of space radiation organ doses and associated cancer risks using PHITS and HZETRN

NASA Astrophysics Data System (ADS)

Bahadori, Amir A.; Sato, Tatsuhiko; Slaba, Tony C.; Shavers, Mark R.; Semones, Edward J.; Van Baalen, Mary; Bolch, Wesley E.

2013-10-01

NASA currently uses one-dimensional deterministic transport to generate values of the organ dose equivalent needed to calculate stochastic radiation risk following crew space exposures. In this study, organ absorbed doses and dose equivalents are calculated for 50th percentile male and female astronaut phantoms using both the NASA High Charge and Energy Transport Code to perform one-dimensional deterministic transport and the Particle and Heavy Ion Transport Code System to perform three-dimensional Monte Carlo transport. Two measures of radiation risk, effective dose and risk of exposure-induced death (REID) are calculated using the organ dose equivalents resulting from the two methods of radiation transport. For the space radiation environments and simplified shielding configurations considered, small differences (<8%) in the effective dose and REID are found. However, for the galactic cosmic ray (GCR) boundary condition, compensating errors are observed, indicating that comparisons between the integral measurements of complex radiation environments and code calculations can be misleading. Code-to-code benchmarks allow for the comparison of differential quantities, such as secondary particle differential fluence, to provide insight into differences observed in integral quantities for particular components of the GCR spectrum.

Assessment of Alternative Conceptual Models Using Reactive Transport Modeling with Monitoring Data

NASA Astrophysics Data System (ADS)

Dai, Z.; Price, V.; Heffner, D.; Hodges, R.; Temples, T.; Nicholson, T.

2005-12-01

Monitoring data proved very useful in evaluating alternative conceptual models, simulating contaminant transport behavior, and reducing uncertainty. A graded approach using three alternative conceptual site models was formulated to simulate a field case of tetrachloroethene (PCE) transport and biodegradation. These models ranged from simple to complex in their representation of subsurface heterogeneities. The simplest model was a single-layer homogeneous aquifer that employed an analytical reactive transport code, BIOCHLOR (Aziz et al., 1999). Due to over-simplification of the aquifer structure, this simulation could not reproduce the monitoring data. The second model consisted of a multi-layer conceptual model, in combination with numerical modules, MODFLOW and RT3D within GMS, to simulate flow and reactive transport. Although the simulation results from the second model were comparatively better than those from the simple model, they still did not adequately reproduce the monitoring well concentrations because the geological structures were still inadequately defined. Finally, a more realistic conceptual model was formulated that incorporated heterogeneities and geologic structures identified from well logs and seismic survey data using the Petra and PetraSeis software. This conceptual model included both a major channel and a younger channel that were detected in the PCE source area. In this model, these channels control the local ground-water flow direction and provide a preferential chemical transport pathway. Simulation results using this conceptual site model proved compatible with the monitoring concentration data. This study demonstrates that the bias and uncertainty from inadequate conceptual models are much larger than those introduced from an inadequate choice of model parameter values (Neuman and Wierenga, 2003; Meyer et al., 2004; Ye et al., 2004). This case study integrated conceptual and numerical models, based on interpreted local hydrogeologic and geochemical data, with detailed monitoring plume data. It provided key insights for confirming alternative conceptual site models and assessing the performance of monitoring networks. A monitoring strategy based on this graded approach for assessing alternative conceptual models can provide the technical bases for identifying critical monitoring locations, adequate monitoring frequency, and performance indicator parameters for performance monitoring involving ground-water levels and PCE concentrations.

Towards a new method for modeling multicomponent, multiphase flow and transport in porous media

NASA Astrophysics Data System (ADS)

Kong, X. Z.; Schaedle, P.; Leal, A. M. M.; Saar, M. O.

2016-12-01

The ability to computationally simulate multiphase-multicomponent fluid flow, coupled with geochemical reactions between fluid species and rock minerals, in porous and/or fractured subsurface systems is of major importance to a vast number of applications. These include (1) carbon dioxide storage in geologic formations, (2) geothermal energy extraction, (3) combinations of the latter two applications during CO2-Plume Geothermal energy extraction, (4) waste fluid and waste storage, as well as (5) groundwater and contaminant transport. Modeling these systems with such a wide variety of coupled physical and chemical processes is both challenging and computationally expensive. In this work we present a new approach to develop a simulator for multicomponent-multiphase flow and reactive transport in porous media by using state of the art numerical tools, namely FEniCS (fenicsproject.org) and Reaktoro (reaktoro.org). The governing partial differential equations for fluid flow and transport are solved using FEniCS, which enables fast and efficient implementation of computer codes for the simulation of complex physical phenomena using finite element methods on unstructured meshes. FEniCS supports a wide range of finite element schemes of special interest to porous media flow. In addition, FEniCS interfaces with many sparse linear solvers and provides convenient tools for adaptive mesh refinement and the capability of massively parallel calculations. A fundamental component of our contribution is the coupling of our FEniCS based flow and transport solver with our chemical reaction simulator, Reaktoro, which implements efficient, robust, and accurate methods for chemical equilibrium and kinetics calculations at every node of the mesh, at every time step. These numerical methods for reaction modeling have been especially developed for performance-critical applications such as reactive transport modeling. Furthermore, Reaktoro is also used for the calculation of thermodynamic properties of rock minerals and fluids. The proposed simulator can, however, be coupled with other back-ends for the calculation of both thermodynamic and thermophysical properties of rock minerals and fluids. We present several example applications of our new approach, demonstrating its capabilities and computation speed.

Geochemical evidence for diversity of dust sources in the southwestern United States

USGS Publications Warehouse

Reheis, M.C.; Budahn, J.R.; Lamothe, P.J.

2002-01-01

Several potential dust sources, including generic sources of sparsely vegetated alluvium, playa deposits, and anthropogenic emissions, as well as the area around Owens Lake, California, affect the composition of modern dust in the southwestern United States. A comparison of geochemical analyses of modern and old (a few thousand years) dust with samples of potential local sources suggests that dusts reflect four primary sources: (1) alluvial sediments (represented by Hf, K, Rb, Zr, and rare-earth elements, (2) playas, most of which produce calcareous dust (Sr, associated with Ca), (3) the area of Owens (dry) Lake, a human-induced playa (As, Ba, Li, Pb, Sb, and Sr), and (4) anthropogenic and/or volcanic emissions (As, Cr, Ni, and Sb). A comparison of dust and source samples with previous analyses shows that Owens (dry) Lake and mining wastes from the adjacent Cerro Gordo mining district are the primary sources of As, Ba, Li, and Pb in dusts from Owens Valley. Decreases in dust contents of As, Ba, and Sb with distance from Owens Valley suggest that dust from southern Owens Valley is being transported at least 400 km to the east. Samples of old dust that accumulated before European settlement are distinctly lower in As, Ba, and Sb abundances relative to modern dust, likely due to modern transport of dust from Owens Valley. Thus, southern Owens Valley appears to be an important, geochemically distinct, point source for regional dust in the southwestern United States. Copyright ?? 2002 Elsevier Science Ltd.

MILSTAMP TACs: Military Standard Transportation and Movement Procedures Transportation Account Codes. Volume 2

DTIC Science & Technology

1987-02-15

this chapter. NO - If shipment is not second des - tination transportation , obtain fund cite per yes response for question 2 above. 4. For Direct Support...return . . . . . . . . .0 . . . . . . . a. . .. A820 (8) LOGAIR/QUICKTRANS. Transportation Account Codes de - signed herein are applicable to the...oo~• na~- Transportation Tis Document Contains Tasotto Missing Page/s That Are Unavailable In The And Original Document Movement sdocument has boon

Approach for environmental baseline water sampling

USGS Publications Warehouse

Smith, K.S.

2011-01-01

Samples collected during the exploration phase of mining represent baseline conditions at the site. As such, they can be very important in forecasting potential environmental impacts should mining proceed, and can become measurements against which future changes are compared. Constituents in stream water draining mined and mineralized areas tend to be geochemically, spatially, and temporally variable, which presents challenges in collecting both exploration and baseline water-quality samples. Because short-term (daily) variations can complicate long-term trends, it is important to consider recent findings concerning geochemical variability of stream-water constituents at short-term timescales in designing sampling plans. Also, adequate water-quality information is key to forecasting potential ecological impacts from mining. Therefore, it is useful to collect baseline water samples adequate tor geochemical and toxicological modeling. This requires complete chemical analyses of dissolved constituents that include major and minor chemical elements as well as physicochemical properties (including pH, specific conductance, dissolved oxygen) and dissolved organic carbon. Applying chemical-equilibrium and appropriate toxicological models to water-quality information leads to an understanding of the speciation, transport, sequestration, bioavailability, and aquatic toxicity of potential contaminants. Insights gained from geochemical and toxicological modeling of water-quality data can be used to design appropriate mitigation and for economic planning for future mining activities.

Transport calculations and accelerator experiments needed for radiation risk assessment in space.

PubMed

Sihver, Lembit

2008-01-01

The major uncertainties on space radiation risk estimates in humans are associated to the poor knowledge of the biological effects of low and high LET radiation, with a smaller contribution coming from the characterization of space radiation field and its primary interactions with the shielding and the human body. However, to decrease the uncertainties on the biological effects and increase the accuracy of the risk coefficients for charged particles radiation, the initial charged-particle spectra from the Galactic Cosmic Rays (GCRs) and the Solar Particle Events (SPEs), and the radiation transport through the shielding material of the space vehicle and the human body, must be better estimated Since it is practically impossible to measure all primary and secondary particles from all possible position-projectile-target-energy combinations needed for a correct risk assessment in space, accurate particle and heavy ion transport codes must be used. These codes are also needed when estimating the risk for radiation induced failures in advanced microelectronics, such as single-event effects, etc., and the efficiency of different shielding materials. It is therefore important that the models and transport codes will be carefully benchmarked and validated to make sure they fulfill preset accuracy criteria, e.g. to be able to predict particle fluence, dose and energy distributions within a certain accuracy. When validating the accuracy of the transport codes, both space and ground based accelerator experiments are needed The efficiency of passive shielding and protection of electronic devices should also be tested in accelerator experiments and compared to simulations using different transport codes. In this paper different multipurpose particle and heavy ion transport codes will be presented, different concepts of shielding and protection discussed, as well as future accelerator experiments needed for testing and validating codes and shielding materials.

Validating the performance of correlated fission multiplicity implementation in radiation transport codes with subcritical neutron multiplication benchmark experiments

DOE PAGES

Arthur, Jennifer; Bahran, Rian; Hutchinson, Jesson; ...

2018-06-14

Historically, radiation transport codes have uncorrelated fission emissions. In reality, the particles emitted by both spontaneous and induced fissions are correlated in time, energy, angle, and multiplicity. This work validates the performance of various current Monte Carlo codes that take into account the underlying correlated physics of fission neutrons, specifically neutron multiplicity distributions. The performance of 4 Monte Carlo codes - MCNP®6.2, MCNP®6.2/FREYA, MCNP®6.2/CGMF, and PoliMi - was assessed using neutron multiplicity benchmark experiments. In addition, MCNP®6.2 simulations were run using JEFF-3.2 and JENDL-4.0, rather than ENDF/B-VII.1, data for 239Pu and 240Pu. The sensitive benchmark parameters that in this workmore » represent the performance of each correlated fission multiplicity Monte Carlo code include the singles rate, the doubles rate, leakage multiplication, and Feynman histograms. Although it is difficult to determine which radiation transport code shows the best overall performance in simulating subcritical neutron multiplication inference benchmark measurements, it is clear that correlations exist between the underlying nuclear data utilized by (or generated by) the various codes, and the correlated neutron observables of interest. This could prove useful in nuclear data validation and evaluation applications, in which a particular moment of the neutron multiplicity distribution is of more interest than the other moments. It is also quite clear that, because transport is handled by MCNP®6.2 in 3 of the 4 codes, with the 4th code (PoliMi) being based on an older version of MCNP®, the differences in correlated neutron observables of interest are most likely due to the treatment of fission event generation in each of the different codes, as opposed to the radiation transport.« less

Validating the performance of correlated fission multiplicity implementation in radiation transport codes with subcritical neutron multiplication benchmark experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arthur, Jennifer; Bahran, Rian; Hutchinson, Jesson

Historically, radiation transport codes have uncorrelated fission emissions. In reality, the particles emitted by both spontaneous and induced fissions are correlated in time, energy, angle, and multiplicity. This work validates the performance of various current Monte Carlo codes that take into account the underlying correlated physics of fission neutrons, specifically neutron multiplicity distributions. The performance of 4 Monte Carlo codes - MCNP®6.2, MCNP®6.2/FREYA, MCNP®6.2/CGMF, and PoliMi - was assessed using neutron multiplicity benchmark experiments. In addition, MCNP®6.2 simulations were run using JEFF-3.2 and JENDL-4.0, rather than ENDF/B-VII.1, data for 239Pu and 240Pu. The sensitive benchmark parameters that in this workmore » represent the performance of each correlated fission multiplicity Monte Carlo code include the singles rate, the doubles rate, leakage multiplication, and Feynman histograms. Although it is difficult to determine which radiation transport code shows the best overall performance in simulating subcritical neutron multiplication inference benchmark measurements, it is clear that correlations exist between the underlying nuclear data utilized by (or generated by) the various codes, and the correlated neutron observables of interest. This could prove useful in nuclear data validation and evaluation applications, in which a particular moment of the neutron multiplicity distribution is of more interest than the other moments. It is also quite clear that, because transport is handled by MCNP®6.2 in 3 of the 4 codes, with the 4th code (PoliMi) being based on an older version of MCNP®, the differences in correlated neutron observables of interest are most likely due to the treatment of fission event generation in each of the different codes, as opposed to the radiation transport.« less

Geochemical and Hydrologic Factors Controlling Subsurface Transport of Poly- and Perfluoroalkyl Substances, Cape Cod, Massachusetts.

PubMed

Weber, Andrea K; Barber, Larry B; LeBlanc, Denis R; Sunderland, Elsie M; Vecitis, Chad D

2017-04-18

Growing evidence that certain poly- and perfluoroalkyl substances (PFASs) are associated with negative human health effects prompted the U.S. Environmental Protection Agency to issue lifetime drinking water health advisories for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in 2016. Given that groundwater is a major source of drinking water, the main objective of this work was to investigate geochemical and hydrological processes governing the subsurface transport of PFASs at a former fire training area (FTA) on Cape Cod, Massachusetts, where PFAS-containing aqueous film-forming foams were used historically. A total of 148 groundwater samples and 4 sediment cores were collected along a 1200-m-long downgradient transect originating near the FTA and analyzed for PFAS content. The results indicate that unsaturated zones at the FTA and at hydraulically downgradient former domestic wastewater effluent infiltration beds both act as continuous PFAS sources to the groundwater despite 18 and 20 years of inactivity, respectively. Historically different PFAS sources are evident from contrasting PFAS composition near the water table below the FTA and wastewater-infiltration beds. Results from total oxidizable precursor assays conducted using groundwater samples collected throughout the plume suggest that some perfluoroalkyl acid precursors at this site are transporting with perfluoroalkyl acids.

Geochemical and hydrologic factors controlling subsurface transport of poly- and perfluoroalkyl substances, Cape Cod, Massachusetts

USGS Publications Warehouse

Weber, Andrea K.; Barber, Larry B.; LeBlanc, Denis R.; Sunderland, Elsie M.; Vecitis, Chad D.

2017-01-01

Growing evidence that certain poly- and perfluoroalkyl substances (PFASs) are associated with negative human health effects prompted the U.S. Environmental Protection Agency to issue lifetime drinking water health advisories for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in 2016. Given that groundwater is a major source of drinking water, the main objective of this work was to investigate geochemical and hydrological processes governing the subsurface transport of PFASs at a former fire training area (FTA) on Cape Cod, Massachusetts, where PFAS-containing aqueous film-forming foams were used historically. A total of 148 groundwater samples and 4 sediment cores were collected along a 1200-m-long downgradient transect originating near the FTA and analyzed for PFAS content. The results indicate that unsaturated zones at the FTA and at hydraulically downgradient former domestic wastewater effluent infiltration beds both act as continuous PFAS sources to the groundwater despite 18 and 20 years of inactivity, respectively. Historically different PFAS sources are evident from contrasting PFAS composition near the water table below the FTA and wastewater-infiltration beds. Results from total oxidizable precursor assays conducted using groundwater samples collected throughout the plume suggest that some perfluoroalkyl acid precursors at this site are transporting with perfluoroalkyl acids.

Full 3D visualization tool-kit for Monte Carlo and deterministic transport codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frambati, S.; Frignani, M.

2012-07-01

We propose a package of tools capable of translating the geometric inputs and outputs of many Monte Carlo and deterministic radiation transport codes into open source file formats. These tools are aimed at bridging the gap between trusted, widely-used radiation analysis codes and very powerful, more recent and commonly used visualization software, thus supporting the design process and helping with shielding optimization. Three main lines of development were followed: mesh-based analysis of Monte Carlo codes, mesh-based analysis of deterministic codes and Monte Carlo surface meshing. The developed kit is considered a powerful and cost-effective tool in the computer-aided design formore » radiation transport code users of the nuclear world, and in particular in the fields of core design and radiation analysis. (authors)« less

Radiation Transport Tools for Space Applications: A Review

NASA Technical Reports Server (NTRS)

Jun, Insoo; Evans, Robin; Cherng, Michael; Kang, Shawn

2008-01-01

This slide presentation contains a brief discussion of nuclear transport codes widely used in the space radiation community for shielding and scientific analyses. Seven radiation transport codes that are addressed. The two general methods (i.e., Monte Carlo Method, and the Deterministic Method) are briefly reviewed.

Comparison of Transport Codes, HZETRN, HETC and FLUKA, Using 1977 GCR Solar Minimum Spectra

NASA Technical Reports Server (NTRS)

Heinbockel, John H.; Slaba, Tony C.; Tripathi, Ram K.; Blattnig, Steve R.; Norbury, John W.; Badavi, Francis F.; Townsend, Lawrence W.; Handler, Thomas; Gabriel, Tony A.; Pinsky, Lawrence S.;

Microbial Community Composition and Functional Capacity in a Terrestrial Ferruginous, Sulfate-Depleted Mud Volcano

PubMed Central

Tu, Tzu-Hsuan; Wu, Li-Wei; Lin, Yu-Shih; Imachi, Hiroyuki; Lin, Li-Hung; Wang, Pei-Ling

2017-01-01

Terrestrial mud volcanoes (MVs) are an important natural source of methane emission. The role of microbial processes in methane cycling and organic transformation in such environments remains largely unexplored. In this study, we aim to uncover functional potentials and community assemblages across geochemical transitions in a ferruginous, sulfate-depleted MV of eastern Taiwan. Geochemical profiles combined with 16S rRNA gene abundances indicated that anaerobic oxidation of methane (AOM) mediated by ANME-2a group coincided with iron/manganese reduction by Desulfuromonadales at shallow depths deprived of sulfate. The activity of AOM was stimulated either by methane alone or by methane and a range of electron acceptors, such as sulfate, ferrihydrite, and artificial humic acid. Metagenomic analyses revealed that functional genes for AOM and metal reduction were more abundant at shallow intervals. In particular, genes encoding pili expression and electron transport through multi-heme cytochromes were prevalent, suggesting potential intercellular interactions for electron transport involved in AOM. For comparison, genes responsible for methanogenesis and degradation of chitin and plant-derived molecules were more abundant at depth. The gene distribution combined with the enhanced proportions of 16S rRNA genes related to methanogens and heterotrophs, and geochemical characteristics suggest that particulate organic matter was degraded into various organic entities that could further fuel in situ methanogenesis. Finally, genes responsible for aerobic methane oxidation were more abundant in the bubbling pool and near-surface sediments. These methane oxidizers account for the ultimate attenuation of methane discharge into the atmosphere. Overall, our results demonstrated that various community members were compartmentalized into stratified niches along geochemical gradients. These community members form a metabolic network that cascades the carbon transformation from the upstream degradation of recalcitrant organic carbon with fermentative production of labile organic entities and methane to downstream methane oxidation and metal reduction near the surface. Such a metabolic architecture enables effective methane removal under ferruginous, sulfate-depleted conditions in terrestrial MVs. PMID:29163423

Microbial Community Composition and Functional Capacity in a Terrestrial Ferruginous, Sulfate-Depleted Mud Volcano.

PubMed

Tu, Tzu-Hsuan; Wu, Li-Wei; Lin, Yu-Shih; Imachi, Hiroyuki; Lin, Li-Hung; Wang, Pei-Ling

2017-01-01

Terrestrial mud volcanoes (MVs) are an important natural source of methane emission. The role of microbial processes in methane cycling and organic transformation in such environments remains largely unexplored. In this study, we aim to uncover functional potentials and community assemblages across geochemical transitions in a ferruginous, sulfate-depleted MV of eastern Taiwan. Geochemical profiles combined with 16S rRNA gene abundances indicated that anaerobic oxidation of methane (AOM) mediated by ANME-2a group coincided with iron/manganese reduction by Desulfuromonadales at shallow depths deprived of sulfate. The activity of AOM was stimulated either by methane alone or by methane and a range of electron acceptors, such as sulfate, ferrihydrite, and artificial humic acid. Metagenomic analyses revealed that functional genes for AOM and metal reduction were more abundant at shallow intervals. In particular, genes encoding pili expression and electron transport through multi-heme cytochromes were prevalent, suggesting potential intercellular interactions for electron transport involved in AOM. For comparison, genes responsible for methanogenesis and degradation of chitin and plant-derived molecules were more abundant at depth. The gene distribution combined with the enhanced proportions of 16S rRNA genes related to methanogens and heterotrophs, and geochemical characteristics suggest that particulate organic matter was degraded into various organic entities that could further fuel in situ methanogenesis. Finally, genes responsible for aerobic methane oxidation were more abundant in the bubbling pool and near-surface sediments. These methane oxidizers account for the ultimate attenuation of methane discharge into the atmosphere. Overall, our results demonstrated that various community members were compartmentalized into stratified niches along geochemical gradients. These community members form a metabolic network that cascades the carbon transformation from the upstream degradation of recalcitrant organic carbon with fermentative production of labile organic entities and methane to downstream methane oxidation and metal reduction near the surface. Such a metabolic architecture enables effective methane removal under ferruginous, sulfate-depleted conditions in terrestrial MVs.

Monitoring Cosmic Radiation Risk: Comparisons between Observations and Predictive Codes for Naval Aviation

DTIC Science & Technology

2009-01-01

proton PARMA PHITS -based Analytical Radiation Model in the Atmosphere PCAIRE Predictive Code for Aircrew Radiation Exposure PHITS Particle and...radiation transport code utilized is called PARMA ( PHITS based Analytical Radiation Model in the Atmosphere) [36]. The particle fluxes calculated from the...same dose equivalent coefficient regulations from the ICRP-60 regulations. As a result, the transport codes utilized by EXPACS ( PHITS ) and CARI-6

Monitoring Cosmic Radiation Risk: Comparisons Between Observations and Predictive Codes for Naval Aviation

DTIC Science & Technology

2009-07-05

proton PARMA PHITS -based Analytical Radiation Model in the Atmosphere PCAIRE Predictive Code for Aircrew Radiation Exposure PHITS Particle and Heavy...transport code utilized is called PARMA ( PHITS based Analytical Radiation Model in the Atmosphere) [36]. The particle fluxes calculated from the input...dose equivalent coefficient regulations from the ICRP-60 regulations. As a result, the transport codes utilized by EXPACS ( PHITS ) and CARI-6 (PARMA

Moving from Batch to Field Using the RT3D Reactive Transport Modeling System

NASA Astrophysics Data System (ADS)

Clement, T. P.; Gautam, T. R.

2002-12-01

The public domain reactive transport code RT3D (Clement, 1997) is a general-purpose numerical code for solving coupled, multi-species reactive transport in saturated groundwater systems. The code uses MODFLOW to simulate flow and several modules of MT3DMS to simulate the advection and dispersion processes. RT3D employs the operator-split strategy which allows the code solve the coupled reactive transport problem in a modular fashion. The coupling between reaction and transport is defined through a separate module where the reaction equations are specified. The code supports a versatile user-defined reaction option that allows users to define their own reaction system through a Fortran-90 subroutine, known as the RT3D-reaction package. Further a utility code, known as BATCHRXN, allows the users to independently test and debug their reaction package. To analyze a new reaction system at a batch scale, users should first run BATCHRXN to test the ability of their reaction package to model the batch data. After testing, the reaction package can simply be ported to the RT3D environment to study the model response under 1-, 2-, or 3-dimensional transport conditions. This paper presents example problems that demonstrate the methods for moving from batch to field-scale simulations using BATCHRXN and RT3D codes. The first example describes a simple first-order reaction system for simulating the sequential degradation of Tetrachloroethene (PCE) and its daughter products. The second example uses a relatively complex reaction system for describing the multiple degradation pathways of Tetrachloroethane (PCA) and its daughter products. References 1) Clement, T.P, RT3D - A modular computer code for simulating reactive multi-species transport in 3-Dimensional groundwater aquifers, Battelle Pacific Northwest National Laboratory Research Report, PNNL-SA-28967, September, 1997. Available at: http://bioprocess.pnl.gov/rt3d.htm.

Influence of hydrological and geochemical processes on the transport of chelated metals and chromate in fractured shale bedrock

NASA Astrophysics Data System (ADS)

Jardine, P. M.; Mehlhorn, T. L.; Larsen, I. L.; Bailey, W. B.; Brooks, S. C.; Roh, Y.; Gwo, J. P.

2002-03-01

Field-scale processes governing the transport of chelated radionuclides in groundwater remain conceptually unclear for highly structured, heterogeneous environments. The objectives of this research were to provide an improved understanding and predictive capability of the hydrological and geochemical mechanisms that control the transport behavior of chelated radionuclides and metals in anoxic subsurface environments that are complicated by fracture flow and matrix diffusion. Our approach involved a long-term, steady-state natural gradient field experiment where nonreactive Br - and reactive 57Co(II)EDTA 2-, 109CdEDTA 2-, and 51Cr(VI) were injected into a fracture zone of a contaminated fractured shale bedrock. The spatial and temporal distribution of the tracer and solutes was monitored for 500 days using an array of groundwater sampling wells instrumented within the fast-flowing fracture regime and a slower flowing matrix regime. The tracers were preferentially transported along strike-parallel fractures coupled with the slow diffusion of significant tracer mass into the bedrock matrix. The chelated radionuclides and metals were significantly retarded by the solid phase with the mechanisms of retardation largely due to redox reactions and sorption coupled with mineral-induced chelate-radionuclide dissociation. The formation of significant Fe(III)EDTA - byproduct that accompanied the dissociation of the radionuclide-chelate complexes was believed to be the result of surface interactions with biotite which was the only Fe(III)-bearing mineral phase present in these Fe-reducing environments. These results counter current conceptual models that suggest chelated contaminants move conservatively through Fe-reducing environments since they are devoid of Fe-oxyhydroxides that are known to aggressively compete for chelates in oxic regimes. Modeling results further demonstrated that chelate-radionuclide dissociation reactions were most prevalent along fractures where accelerated weathering processes are expected to expose more primary minerals than the surrounding rock matrix. The findings of this study suggest that physical retardation mechanisms (i.e. diffusion) are dominant within the matrix regime, whereas geochemical retardation mechanisms are dominant within the fracture regime.

Mesoscale Eddies, Satellite Altimetry, and New Production in the Sargasso Sea

NASA Technical Reports Server (NTRS)

Siegel, David A.; McGillicuddy, Dennis J., Jr.; Fields, Erik A.

1999-01-01

Satellite altimetry and hydrographic observations are used to characterize the mesoscale eddy field in the Sargasso Sea near Bermuda and to address the role of physical processes on the supply of new nutrients to the euphotic zone. The observed sea level anomaly (SLA) field is dominated by the occurrence of westward propagating features with SLA signatures as large as 25 cm, Eulerian temporal scales of roughly a month, lifetimes of several months, spatial scales of approximately 200 km, and a propagation of approximately 5 cm/s. Hydrographic estimates of dynamic height anomaly (referenced to 4000 dbar) are well correlated with satellite SLA (r(exp 2) = 0.65), and at least 85% of the observed dynamic height variability is associated with the first baroclinic mode of motion. This allows us to apply the satellite observations to remotely sensed estimate isopycnal displacements and the flux of nutrients into the euphotic zone due to eddy pumping. Eddy pumping is the process by which mesoscale eddies induce isopycnal displacements that lift nutrient-replete waters into the euphotic zone, driving new primary production. A kinematic approach to the estimation of the eddy pumping results in a flux of 0.24 +/- 0.1 mol N/sq m (including a scale estimate for the small contribution due to 18 deg water eddies). This flux is more than an order of magnitude larger than the diapycnal diffusive flux as well as scale estimates for the vertical transport due to isopycnal mixing along sloping isopycnal surfaces. Eddy pumping and wintertime convection are the two dominant mechanisms transporting new nutrients into the euphotic zone, and the sum of all physical new nutrient supply fluxes effectively balances previous geochemical estimates of annual new production for this site. However, if biological transports (e.g., nitrogen fixation, etc.) are significant, the new nitrogen supply budget will be in excess of geochemical new production estimates. This suggests that the various physical and biological transport fluxes, as well as geochemical inferences of new production, still need to be reconciled and many outstanding questions remain.

Mesoscale Eddies, Satellite Altimetry, and New Production in the Sargasso Sea

NASA Technical Reports Server (NTRS)

Siegel, David A.; McGillicuddy, Dennis J., Jr.; Fields, Erik A.

1999-01-01

Satellite altimetry and hydrographic observations are used to characterize the mesoscale eddy field in the Sargasso Sea near Bermuda and to address the role of physical processes on the supply of new nutrients to the euphotic zone. The observed sea level anomaly (SLA) field is dominated by the occurrence of westward propagating features with SLA signatures as large as 25 cm, Eulerian temporal scales of roughly a month, lifetimes of several months, spatial scales of approximately 200 km, and a propagation of approximately 5 cm/s . Hydrographic estimates of dynamic height anomaly (referenced to 4000 dbar) are well correlated with satellite SLA (r(sup 2) = 0.65), and at least 85% of the observed dynamic height variability is associated with the first baroclinic mode of motion. This allows us to apply the satellite observations to remotely estimate isopycnal displacements and the flux of nutrients into the euphotic zone due to eddy pumping. Eddy pumping is the process by which mesoscale eddies induce isopycnal displacements that lift nutrient- replete waters into the euphotic zone, driving new primary production. A kinematic approach to the estimation of the eddy pumping results in a flux of 0.24+/-0.1 mol N/sq m/yr (including a scale estimate for the small contribution due to 18 deg water eddies). This flux is more than an order of magnitude larger than the diapycnal diffusive flux as well as scale estimates for the vertical transport due to isopycnal mixing along sloping isopycnal surfaces. Eddy pumping and wintertime convection are the two dominant mechanisms transporting new nutrients into the euphotic zone, and the sum of all physical new nutrient supply fluxes effectively balances previous geochemical estimates of annual new production for this site. However, if biological transports (e.g., nitrogen fixation, etc.) are significant, the new nitrogen supply budget will be in excess of geochemical new production estimates. This suggests that the various physical and biological transport fluxes, as well as geochemical inferences of new production, still need to be reconciled and many outstanding questions remain.

Interpreting stream sediment fingerprints against primary and secondary source signatures in agricultural catchments

NASA Astrophysics Data System (ADS)

Blake, Will H.; Haley, Steve; Smith, Hugh G.; Taylor, Alex; Goddard, Rupert; Lewin, Sean; Fraser, David

2013-04-01

Many sediment fingerprinting studies adopt a black box approach to source apportionment whereby the properties of downstream sediment are compared quantitatively to the geochemical fingerprints of potential catchment sources without consideration of potential signature development or modification during transit. Working within a source-pathway-receptor framework, this study aimed to undertake sediment source apportionment within 6 subcatchments of an agricultural river basin with specific attention to the potential role of contaminants (vehicle emissions and mine waste) in development of stream sediment signatures. Fallout radionuclide (FRN) and geochemical fingerprinting methods were adopted independently to establish source signatures for primary sediment sources of surface and subsurface soil materials under various land uses plus reworked mine and 'secondary' soil material deposited, in transit, along road networks. FRN data demonstrated expected variability between surface soil (137Cs = 14 ± 3 Bq kg-1; 210Pbxs = 40 ± 7 Bq kg-1) and channel bank materials (137Cs = 3 ± 1 Bq kg-1; 210Pbxs = 24 ± 5 Bq kg-1) but road transported soil material was considerably elevated in 210Pbxs (up to 673 ± 51 Bq kg-1) due to sediment interaction with pluvial surface water within the road network. Geochemical discrimination between surface and subsurface soil materials was dominated by alkaline earth and alkali metals e.g. Ba, Rb, Ca, K, Mg which are sensitive to weathering processes in soil. Magnetic susceptibility and heavy metals were important discriminators of road transported material which demonstrated transformation of the signatures of material transported via the road network. Numerical unmixing of stream sediment indicated that alongside channel bank erosion, road transported material was an important component in some systems in accord with FRN evidence. While mining spoil also ranked as a significant source in an affected catchment, perhaps related to legacy sediment, the potential role of dissolved metal leaching and subsequent sediment-water interaction within the channel on signature modification remained unclear. Consideration of sediment signature modification en route from primary source to stream elucidated important information regarding sediment transfer pathways and dynamics relevant to sediment management decisions. Further work on sediment-water interactions and potential for signature transformation in the channel environment is required.

Comparison of Field Groundwater Biostimulation Experiments Using Polylactate and Lactate Solutions at the Chromium-Contaminated Hanford 100-H Site

NASA Astrophysics Data System (ADS)

Hazen, T. C.; Faybishenko, B.; Beller, H. R.; Brodie, E. L.; Sonnenthal, E. L.; Steefel, C.; Larsen, J.; Conrad, M. E.; Bill, M.; Christensen, J. N.; Brown, S. T.; Joyner, D.; Borglin, S. E.; Geller, J. T.; Chakraborty, R.; Nico, P. S.; Long, P. E.; Newcomer, D. R.; Arntzen, E.

2011-12-01

The primary contaminant of concern in groundwater at the DOE Hanford 100 Area (Washington State) is hexavalent chromium [Cr(VI)] in Hanford coarse-grained sediments. Three lactate injections were conducted in March, August, and October 2010 at the Hanford 100-H field site to assess the efficacy of in situ Cr(VI) bioreductive immobilization. Each time, 55 gal of lactate solution was injected into the Hanford aquifer. To characterize the biogeochemical regimes before and after electron donor injection, we implemented a comprehensive plan of groundwater sampling for microbial, geochemical, and isotopic analyses. These tests were performed to provide evidence of transformation of toxic and soluble Cr(VI) into less toxic and poorly soluble Cr(III) by bioimmobilization, and to quantify critical and interrelated microbial metabolic and geochemical mechanisms affecting chromium in situ reductive immobilization and the long-term sustainability of chromium bioremediation. The results of lactate injections were compared with data from two groundwater biostimulation tests that were conducted in 2004 and 2008 by injecting Hydrogen Release Compound (HRC°), a slow-release glycerol polylactate, into the Hanford aquifer. In all HRC and lactate injection tests, 13C-labeled lactate was added to the injected solutions to track post-injection carbon pathways. Monitoring showed that despite a very low initial total microbial density (from <104 to 105 cells/mL), both HRC and lactate injections stimulated anaerobic microbial activity, which led to an increase in biomass to >107 cells/mL (including sulfate- and nitrate-reducing bacteria), resulting in a significant decrease in soluble Cr(VI) concentrations to below the MCL. In all tests, lactate was consumed nearly completely within the first week, much faster than HRC. Modeling of biogeochemical and isotope fractionation processes with the reaction-transport code TOUGHREACT captured the biodegradation of lactate, fermentative production of acetate and propionate, the evolution of 13C in bicarbonate, and the rate of sulfate reduction. In contrast to the slow-release HRC injections, no long-term effects of biostimulation and Cr bioreduction were observed in groundwater after the lactate injections. The presentation will address these patterns of the geochemical, δ13C of DIC, and biomass changes in groundwater before and after the polylactate and lactate injections.

49 CFR 171.25 - Additional requirements for the use of the IMDG Code.

Code of Federal Regulations, 2010 CFR

2010-10-01

...) Packages containing primary lithium batteries and cells that are transported in accordance with Special Provision 188 of the IMDG Code must be marked “PRIMARY LITHIUM BATTERIES—FORBIDDEN FOR TRANSPORT ABOARD PASSENGER AIRCRAFT” or “LITHIUM METAL BATTERIES—FORBIDDEN FOR TRANSPORT ABOARD PASSENGER AIRCRAFT.” This...

77 FR 18716 - Transportation Security Administration Postal Zip Code Change; Technical Amendment

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-28

... organizational changes and it has no substantive effect on the public. DATES: Effective March 28, 2012. FOR... No. 1572-9] Transportation Security Administration Postal Zip Code Change; Technical Amendment AGENCY: Transportation Security Administration, DHS. ACTION: Final rule. SUMMARY: This rule is a technical change to...

Surface water quality assessment of the Upper Illinois River basin in Illinois, Indiana, and Wisconsin : geochemical data for fine-fraction streambed sediment from high- and low-order streams, 1987

USGS Publications Warehouse

Colman, John A.; Sanzolone, R.F.

1991-01-01

Geochemical data are presented from a synoptic survey of 46 elements in fine-fraction streambed sediments of the Upper Illinois River Basin during the fall of 1987. The survey was a component study of the Illinois pilot project of the U.S. Geological Survey's National Water-Quality Assessment program. Most of the sampling sites were randomly chosen--135 on main stems of rivers and 238 on first- and second-order streams. In addition, 196 samples were collected for quality-assurance and special-study purposes. The report includes element concentration data and summary-statistics tables of percentiles, nested analysis of variance, and correlation coefficients. All concentration data are included in tabular form and can be selected by map reference number, latitude and longitude, or remark code indicating purpose for collecting sample.

Transport and transformation of genetic information in the critical zone: The case of antibiotic resistance genes

NASA Astrophysics Data System (ADS)

Zhu, Y. G.

2015-12-01

In addition to material and energy flows, the dynamics and functions of the Earth's critical zone are intensively mediated by biological actions performed by diverse organisms. These biological actions are modulated by the expression of functional genes and their translation into enzymes that catalyze geochemical reactions, such as nutrient turnover and pollutant biodegradation. Although geobiology, as an interdisciplinary research area, is playing and vital role in linking biological and geochemical processes at different temporal and spatial scales, the distribution and transport of functional genes have rarely been investigated from the Earth's critical zone perspectives. To illustrate the framework of studies on the transport and transformation of genetic information in the critical zone, antibiotic resistance is taken as an example. Antibiotic resistance genes are considered as a group of emerging contaminants, and their emergence and spread within the critical zone on one hand are induced by anthropogenic activities, and on other hand are threatening human health worldwide. The transport and transformation of antibiotic resistance genes are controlled by both horizontal gene transfer between bacterial cells and the movement of bacteria harboring antibiotic resistance genes. In this paper, the fate and behavior of antibiotic resistance genes will be discussed in the following aspects: 1) general overview of environmental antibiotic resistance; 2) high through quantification of the resistome in various environmental media; 3) pathways of resistance gene flow within the critical zone; and 4) potential strategies in mitigating antibiotic resistance, particularly from the critical zone perspectives.

GoPhast: a graphical user interface for PHAST

USGS Publications Warehouse

Winston, Richard B.

2006-01-01

GoPhast is a graphical user interface (GUI) for the USGS model PHAST. PHAST simulates multicomponent, reactive solute transport in three-dimensional, saturated, ground-water flow systems. PHAST can model both equilibrium and kinetic geochemical reactions. PHAST is derived from HST3D (flow and transport) and PHREEQC (geochemical calculations). The flow and transport calculations are restricted to constant fluid density and constant temperature. The complexity of the input required by PHAST makes manual construction of its input files tedious and error-prone. GoPhast streamlines the creation of the input file and helps reduce errors. GoPhast allows the user to define the spatial input for the PHAST flow and transport data file by drawing points, lines, or polygons on top, front, and side views of the model domain. These objects can have up to two associated formulas that define their extent perpendicular to the view plane, allowing the objects to be three-dimensional. Formulas are also used to specify the values of spatial data (data sets) both globally and for individual objects. Objects can be used to specify the values of data sets independent of the spatial and temporal discretization of the model. Thus, the grid and simulation periods for the model can be changed without respecifying spatial data pertaining to the hydrogeologic framework and boundary conditions. This report describes the operation of GoPhast and demonstrates its use with examples. GoPhast runs on Windows 2000, Windows XP, and Linux operating systems.

Microbial respiration and dissolution precipitation reactions of minerals: thermo-kinetics and reactive transport modelling

NASA Astrophysics Data System (ADS)

Azaroual, M. M.; Parmentier, M.; Andre, L.; Croiset, N.; Pettenati, M.; Kremer, S.

2010-12-01

Microbial processes interact closely with abiotic geochemical reactions and mineralogical transformations in several hydrogeochemical systems. Reactive transport models are aimed to analyze these complex mechanisms integrating as well as the degradation of organic matter as the redox reactions involving successive terminal electron acceptors (TEAPs) mediated by microbes through the continuum of unsaturated zone (soil) - saturated zone (aquifer). The involvement of microbial processes in reactive transport in soil and subsurface geologic greatly complicates the mastery of the major mechanisms and the numerical modelling of these systems. The introduction of kinetic constraints of redox reactions in aqueous phase requires the decoupling of equilibrium reactions and the redefinition of mass balance of chemical elements including the concept of basis species and secondary species of thermodynamic databases used in geochemical modelling tools. An integrated methodology for modelling the reactive transport has been developed and implemented to simulate the transfer of arsenic, denitrification processes and the role of metastable aqueous sulfur species with pyrite and organic matter as electron donors entities. A mechanistic rate law of microbial respiration in various geochemical environments was used to simulate reactive transport of arsenic, nitrate and organic matter combined to the generalized rate law of mineral dissolution - precipitation reactions derived from the transition state theory was used for dissolution - precipitation of silica, aluminosilicate, carbonate, oxyhydroxide, and sulphide minerals. The kinetic parameters are compiled from the literature measurements based on laboratory constrained experiments and field observations. Numerical simulations, using the geochemical software PHREEQC, were performed aiming to identify the key reactions mediated by microbes in the framework of in the first hand the concept of the unsaturated - saturated zones of an artificial recharge of deep aquifers system and in a second hand an acid mine drainage system. A large amount of data is available on the old mine site of Cheni (France). This field data on acid mine drainage are compared to a thermokinetic model including biological kinetics, precipitation-dissolution kinetics and surface complexation on ferrihydrite. The kinetic parameters are from literature and from a fitting on batch biological experiments. The integrated approach combining reaction kinetics and biogeochemical thermodynamic constraints is successfully applied to denitrification experiments in the presence of acetate and pyrite conducted in the laboratory for batch and column systems. The powerful of this coupled approach allows a fine description of the different transition species from nitrate to nitrogen. The fitted kinetic parameters established for modelling these laboratory results are thus extended to simulate the denitrification processes in a field case where organic matter and pyrite FeS2 are the electron donors and O2, NO3, Fe(OH)3, SO4 are the electron acceptors in the framework of a continuum UZ - SZ aiming to identify the stabilized redox zones of acid mine drainage. The detailed results obtained on two actual case studies will be presented.

Thermodynamic and transport properties of gaseous tetrafluoromethane in chemical equilibrium

NASA Technical Reports Server (NTRS)

Hunt, J. L.; Boney, L. R.

1973-01-01

Equations and in computer code are presented for the thermodynamic and transport properties of gaseous, undissociated tetrafluoromethane (CF4) in chemical equilibrium. The computer code calculates the thermodynamic and transport properties of CF4 when given any two of five thermodynamic variables (entropy, temperature, volume, pressure, and enthalpy). Equilibrium thermodynamic and transport property data are tabulated and pressure-enthalpy diagrams are presented.

High-fidelity plasma codes for burn physics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cooley, James; Graziani, Frank; Marinak, Marty

Accurate predictions of equation of state (EOS), ionic and electronic transport properties are of critical importance for high-energy-density plasma science. Transport coefficients inform radiation-hydrodynamic codes and impact diagnostic interpretation, which in turn impacts our understanding of the development of instabilities, the overall energy balance of burning plasmas, and the efficacy of self-heating from charged-particle stopping. Important processes include thermal and electrical conduction, electron-ion coupling, inter-diffusion, ion viscosity, and charged particle stopping. However, uncertainties in these coefficients are not well established. Fundamental plasma science codes, also called high-fidelity plasma codes, are a relatively recent computational tool that augments both experimental datamore » and theoretical foundations of transport coefficients. This paper addresses the current status of HFPC codes and their future development, and the potential impact they play in improving the predictive capability of the multi-physics hydrodynamic codes used in HED design.« less

Development of a 1.5D plasma transport code for coupling to full orbit runaway electron simulations

NASA Astrophysics Data System (ADS)

Lore, J. D.; Del Castillo-Negrete, D.; Baylor, L.; Carbajal, L.

2017-10-01

A 1.5D (1D radial transport + 2D equilibrium geometry) plasma transport code is being developed to simulate runaway electron generation, mitigation, and avoidance by coupling to the full-orbit kinetic electron transport code KORC. The 1.5D code solves the time-dependent 1D flux surface averaged transport equations with sources for plasma density, pressure, and poloidal magnetic flux, along with the Grad-Shafranov equilibrium equation for the 2D flux surface geometry. Disruption mitigation is simulated by introducing an impurity neutral gas `pellet', with impurity densities and electron cooling calculated from ionization, recombination, and line emission rate coefficients. Rapid cooling of the electrons increases the resistivity, inducing an electric field which can be used as an input to KORC. The runaway electron current is then included in the parallel Ohm's law in the transport equations. The 1.5D solver will act as a driver for coupled simulations to model effects such as timescales for thermal quench, runaway electron generation, and pellet impurity mixtures for runaway avoidance. Current progress on the code and details of the numerical algorithms will be presented. Work supported by the US DOE under DE-AC05-00OR22725.

Integrated Disposal Facility FY2010 Glass Testing Summary Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierce, Eric M.; Bacon, Diana H.; Kerisit, Sebastien N.

2010-09-30

Pacific Northwest National Laboratory was contracted by Washington River Protection Solutions, LLC to provide the technical basis for estimating radionuclide release from the engineered portion of the disposal facility (e.g., source term). Vitrifying the low-activity waste at Hanford is expected to generate over 1.6 × 105 m3 of glass (Puigh 1999). The volume of immobilized low-activity waste (ILAW) at Hanford is the largest in the DOE complex and is one of the largest inventories (approximately 0.89 × 1018 Bq total activity) of long-lived radionuclides, principally 99Tc (t1/2 = 2.1 × 105), planned for disposal in a low-level waste (LLW) facility.more » Before the ILAW can be disposed, DOE must conduct a performance assessement (PA) for the Integrated Disposal Facility (IDF) that describes the long-term impacts of the disposal facility on public health and environmental resources. As part of the ILAW glass testing program PNNL is implementing a strategy, consisting of experimentation and modeling, in order to provide the technical basis for estimating radionuclide release from the glass waste form in support of future IDF PAs. The purpose of this report is to summarize the progress made in fiscal year (FY) 2010 toward implementing the strategy with the goal of developing an understanding of the long-term corrosion behavior of low-activity waste glasses. The emphasis in FY2010 was the completing an evaluation of the most sensitive kinetic rate law parameters used to predict glass weathering, documented in Bacon and Pierce (2010), and transitioning from the use of the Subsurface Transport Over Reactive Multi-phases to Subsurface Transport Over Multiple Phases computer code for near-field calculations. The FY2010 activities also consisted of developing a Monte Carlo and Geochemical Modeling framework that links glass composition to alteration phase formation by 1) determining the structure of unreacted and reacted glasses for use as input information into Monte Carlo calculations, 2) compiling the solution data and alteration phases identified from accelerated weathering tests conducted with ILAW glass by PNNL and Viteous State Laboratory/Catholic University of America as well as other literature sources for use in geochemical modeling calculations, and 3) conducting several initial calculations on glasses that contain the four major components of ILAW-Al2O3, B2O3, Na2O, and SiO2.« less

Multiple component codes based generalized LDPC codes for high-speed optical transport.

PubMed

Djordjevic, Ivan B; Wang, Ting

2014-07-14

A class of generalized low-density parity-check (GLDPC) codes suitable for optical communications is proposed, which consists of multiple local codes. It is shown that Hamming, BCH, and Reed-Muller codes can be used as local codes, and that the maximum a posteriori probability (MAP) decoding of these local codes by Ashikhmin-Lytsin algorithm is feasible in terms of complexity and performance. We demonstrate that record coding gains can be obtained from properly designed GLDPC codes, derived from multiple component codes. We then show that several recently proposed classes of LDPC codes such as convolutional and spatially-coupled codes can be described using the concept of GLDPC coding, which indicates that the GLDPC coding can be used as a unified platform for advanced FEC enabling ultra-high speed optical transport. The proposed class of GLDPC codes is also suitable for code-rate adaption, to adjust the error correction strength depending on the optical channel conditions.

Development of a new version of the Vehicle Protection Factor Code (VPF3)

NASA Astrophysics Data System (ADS)

Jamieson, Terrance J.

1990-10-01

The Vehicle Protection Factor (VPF) Code is an engineering tool for estimating radiation protection afforded by armoured vehicles and other structures exposed to neutron and gamma ray radiation from fission, thermonuclear, and fusion sources. A number of suggestions for modifications have been offered by users of early versions of the code. These include: implementing some of the more advanced features of the air transport rating code, ATR5, used to perform the air over ground radiation transport analyses; allowing the ability to study specific vehicle orientations within the free field; implementing an adjoint transport scheme to reduce the number of transport runs required; investigating the possibility of accelerating the transport scheme; and upgrading the computer automated design (CAD) package used by VPF. The generation of radiation free field fluences for infinite air geometries as required for aircraft analysis can be accomplished by using ATR with the air over ground correction factors disabled. Analysis of the effects of fallout bearing debris clouds on aircraft will require additional modelling of VPF.

ab initio MD simulations of geomaterials with ~1000 atoms

NASA Astrophysics Data System (ADS)

Martin, G. B.; Kirtman, B.; Spera, F. J.

2009-12-01

In the last two decades, ab initio studies of materials using Density Functional Theory (DFT) have increased exponentially in popularity. DFT codes are now used routinely to simulate properties of geomaterials--mainly silicates and geochemically important metals such as Fe. These materials are ubiquitous in the Earth’s mantle and core and in terrestrial exoplanets. Because of computational limitations, most First Principles Molecular Dynamics (FPMD) calculations are done on systems of only ~100 atoms for a few picoseconds. While this approach can be useful for calculating physical quantities related to crystal structure, vibrational frequency, and other lattice-scale properties (especially in crystals), it is statistically marginal for duplicating physical properties of the liquid state like transport and structure. In MD simulations in the NEV ensemble, temperature (T), and pressure (P) fluctuations scale as N-1/2; small particle number (N) systems are therefore characterized by greater statistical state point location uncertainty than large N systems. Previous studies have used codes such as VASP where CPU time increases with N2, making calculations with N much greater than 100 impractical. SIESTA (Soler, et al. 2002) is a DFT code that enables electronic structure and MD computations on larger systems (N~103) by making some approximations, such as localized numerical orbitals, that would be useful in modeling some properties of geomaterials. Here we test the applicability of SIESTA to simulate geosilicates, both hydrous and anhydrous, in the solid and liquid state. We have used SIESTA for lattice calculations of brucite, Mg(OH)2, that compare very well to experiment and calculations using CRYSTAL, another DFT code. Good agreement between more classical DFT calculations and SIESTA is needed to justify study of geosilicates using SIESTA across a range of pressures and temperatures relevant to the Earth’s interior. Thus, it is useful to adjust parameters in SIESTA in accordance with calculations from CRYSTAL as a check on feasibility. Results are reported here that suggest SIESTA may indeed be useful to model silicate liquids at very high T and P.

A Monte Carlo Code for Relativistic Radiation Transport Around Kerr Black Holes

NASA Technical Reports Server (NTRS)

Schnittman, Jeremy David; Krolik, Julian H.

2013-01-01

We present a new code for radiation transport around Kerr black holes, including arbitrary emission and absorption mechanisms, as well as electron scattering and polarization. The code is particularly useful for analyzing accretion flows made up of optically thick disks and optically thin coronae. We give a detailed description of the methods employed in the code and also present results from a number of numerical tests to assess its accuracy and convergence.

Benchmarking of Neutron Production of Heavy-Ion Transport Codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Remec, Igor; Ronningen, Reginald M.; Heilbronn, Lawrence

Accurate prediction of radiation fields generated by heavy ion interactions is important in medical applications, space missions, and in design and operation of rare isotope research facilities. In recent years, several well-established computer codes in widespread use for particle and radiation transport calculations have been equipped with the capability to simulate heavy ion transport and interactions. To assess and validate these capabilities, we performed simulations of a series of benchmark-quality heavy ion experiments with the computer codes FLUKA, MARS15, MCNPX, and PHITS. We focus on the comparisons of secondary neutron production. Results are encouraging; however, further improvements in models andmore » codes and additional benchmarking are required.« less

Benchmarking of Heavy Ion Transport Codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Remec, Igor; Ronningen, Reginald M.; Heilbronn, Lawrence

Accurate prediction of radiation fields generated by heavy ion interactions is important in medical applications, space missions, and in designing and operation of rare isotope research facilities. In recent years, several well-established computer codes in widespread use for particle and radiation transport calculations have been equipped with the capability to simulate heavy ion transport and interactions. To assess and validate these capabilities, we performed simulations of a series of benchmark-quality heavy ion experiments with the computer codes FLUKA, MARS15, MCNPX, and PHITS. We focus on the comparisons of secondary neutron production. Results are encouraging; however, further improvements in models andmore » codes and additional benchmarking are required.« less

Treating voxel geometries in radiation protection dosimetry with a patched version of the Monte Carlo codes MCNP and MCNPX.

PubMed

Burn, K W; Daffara, C; Gualdrini, G; Pierantoni, M; Ferrari, P

2007-01-01

The question of Monte Carlo simulation of radiation transport in voxel geometries is addressed. Patched versions of the MCNP and MCNPX codes are developed aimed at transporting radiation both in the standard geometry mode and in the voxel geometry treatment. The patched code reads an unformatted FORTRAN file derived from DICOM format data and uses special subroutines to handle voxel-to-voxel radiation transport. The various phases of the development of the methodology are discussed together with the new input options. Examples are given of employment of the code in internal and external dosimetry and comparisons with results from other groups are reported.

Examining offshore sediment-hosted contaminant transport from Hurricane Katrina: Chapter 7A in Science and the storms-the USGS response to the hurricanes of 2005

USGS Publications Warehouse

Swarzenski, Peter W.; Campbell, Pamela L.; Poore, Richard Z.; Osterman, Lisa E.; Rosenbauer, Robert J.

2007-01-01

A rapid-response expedition was organized after the passage of Hurricane Katrina to investigate potential offshore environmental impacts and storm-induced sediment-transport processes. Both water-column and sediment samples were collected on the Louisiana shelf for a full complement of organic, inorganic, and geochronological tracers. Based on excess lead-210 (210Pb) inventories in cores collected before and after Katrina, the surface sediments and their associated geochemical signatures were considerably affected by the passage of this storm.

Development of Parallel Computing Framework to Enhance Radiation Transport Code Capabilities for Rare Isotope Beam Facility Design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kostin, Mikhail; Mokhov, Nikolai; Niita, Koji

A parallel computing framework has been developed to use with general-purpose radiation transport codes. The framework was implemented as a C++ module that uses MPI for message passing. It is intended to be used with older radiation transport codes implemented in Fortran77, Fortran 90 or C. The module is significantly independent of radiation transport codes it can be used with, and is connected to the codes by means of a number of interface functions. The framework was developed and tested in conjunction with the MARS15 code. It is possible to use it with other codes such as PHITS, FLUKA andmore » MCNP after certain adjustments. Besides the parallel computing functionality, the framework offers a checkpoint facility that allows restarting calculations with a saved checkpoint file. The checkpoint facility can be used in single process calculations as well as in the parallel regime. The framework corrects some of the known problems with the scheduling and load balancing found in the original implementations of the parallel computing functionality in MARS15 and PHITS. The framework can be used efficiently on homogeneous systems and networks of workstations, where the interference from the other users is possible.« less

Hawai'i and Gale Crater: A Mars Analogue Study of Igneous, Sedimentary, Weathering, and Alteration Trends in Geochemistry

NASA Technical Reports Server (NTRS)

Berger, J. A.; Flemming, R. L.; Schmidt, M. E.; Gellert, R.; Morris, R. V.; Ming, D. W.

2017-01-01

Sedimentary rocks in Gale Crater on Mars indicate a varied provenance with a range of alteration and weathering [1, 2]. Geochemical trends identified in basaltic and alkalic sedimentary rocks by the Alpha Particle X-ray Spectrometer (APXS) on the Mars rover Curiosity represent a complex interplay of igneous, sedimentary, weathering, and alteration processes. Assessing the relative importance of these processes is challenging with unknown compositions for parent sediment sources and with the constraints provided by Curiosity's instruments. We therefore look to Mars analogues on Earth where higher-resolution analyses and geologic context can constrain interpretations of Gale Crater geochemical observations. We selected Maunakea (AKA Mauna Kea) and Kohala volcanoes, Hawai'i, for an analogue study because they are capped by post-shield transitional basalts and alkalic lavas (hawaiites, mugearites) with compositions similar to Gale Crater [1, 3]. Our aim was to characterize Hawaiian geochemical trends associated with igneous processes, sediment transport, weathering, and alteration. Here, we present initial results and discuss implications for selected trends observed by APXS in Gale Crater.

Alchemy in the underworld - recent progress and future potential of organic geochemistry applied to speleothems.

NASA Astrophysics Data System (ADS)

Blyth, Alison

2016-04-01

Speleothems are well used archives for chemical records of terrestrial environmental change, and the integration of records from a range of isotopic, inorganic, and organic geochemical techniques offers significant power in reconstructing both changes in past climates and identifying the resultant response in the overlying terrestrial ecosystems. The use of organic geochemistry in this field offers the opportunity to recover new records of vegetation change (via biomarkers and compound specific isotopes), temperature change (via analysis of glycerol dialkyl glycerol tetraethers, a compound group derived from microbes and varying in structure in response to temperature and pH), and changes in soil microbial behaviour (via combined carbon isotope analysis). However, to date the use of organic geochemical techniques has been relatively limited, due to issues relating to sample size, concerns about contamination, and unanswered questions about the origins of the preserved organic matter and rates of transport. Here I will briefly review recent progress in the field, and present a framework for the future research needed to establish organic geochemical analysis in speleothems as a robust palaeo-proxy approach.

Solid phase studies and geochemical modelling of low-cost permeable reactive barriers.

PubMed

Bartzas, Georgios; Komnitsas, Kostas

2010-11-15

A continuous column experiment was carried out under dynamic flow conditions in order to study the efficiency of low-cost permeable reactive barriers (PRBs) to remove several inorganic contaminants from acidic solutions. A 50:50 w/w waste iron/sand mixture was used as candidate reactive media in order to activate precipitation and promote sorption and reduction-oxidation mechanisms. Solid phase studies of the exhausted reactive products after column shutdown, using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), confirmed that the principal Fe corrosion products identified in the reactive zone are amorphous iron (hydr)oxides (maghemite/magnetite and goethite), intermediate products (sulfate green rust), and amorphous metal sulfides such as amFeS and/or mackinawite. Geochemical modelling of the metal removal processes, including interactions between reactive media, heavy metal ions and sulfates, and interpretation of the ionic profiles was also carried out by using the speciation/mass transfer computer code PHREEQC-2 and the WATEQ4F database. Mineralogical characterization studies as well as geochemical modelling calculations also indicate that the effect of sulfate and silica sand on the efficiency of the reactive zone should be considered carefully during design and operation of low-cost field PRBs. Copyright © 2010 Elsevier B.V. All rights reserved.

Only pick the right grains: Modelling the bias due to subjective grain-size interval selection for chronometric and fingerprinting approaches.

NASA Astrophysics Data System (ADS)

Dietze, Michael; Fuchs, Margret; Kreutzer, Sebastian

2016-04-01

Many modern approaches of radiometric dating or geochemical fingerprinting rely on sampling sedimentary deposits. A key assumption of most concepts is that the extracted grain-size fraction of the sampled sediment adequately represents the actual process to be dated or the source area to be fingerprinted. However, these assumptions are not always well constrained. Rather, they have to align with arbitrary, method-determined size intervals, such as "coarse grain" or "fine grain" with partly even different definitions. Such arbitrary intervals violate principal process-based concepts of sediment transport and can thus introduce significant bias to the analysis outcome (i.e., a deviation of the measured from the true value). We present a flexible numerical framework (numOlum) for the statistical programming language R that allows quantifying the bias due to any given analysis size interval for different types of sediment deposits. This framework is applied to synthetic samples from the realms of luminescence dating and geochemical fingerprinting, i.e. a virtual reworked loess section. We show independent validation data from artificially dosed and subsequently mixed grain-size proportions and we present a statistical approach (end-member modelling analysis, EMMA) that allows accounting for the effect of measuring the compound dosimetric history or geochemical composition of a sample. EMMA separates polymodal grain-size distributions into the underlying transport process-related distributions and their contribution to each sample. These underlying distributions can then be used to adjust grain-size preparation intervals to minimise the incorporation of "undesired" grain-size fractions.

METHES: A Monte Carlo collision code for the simulation of electron transport in low temperature plasmas

NASA Astrophysics Data System (ADS)

Rabie, M.; Franck, C. M.

2016-06-01

We present a freely available MATLAB code for the simulation of electron transport in arbitrary gas mixtures in the presence of uniform electric fields. For steady-state electron transport, the program provides the transport coefficients, reaction rates and the electron energy distribution function. The program uses established Monte Carlo techniques and is compatible with the electron scattering cross section files from the open-access Plasma Data Exchange Project LXCat. The code is written in object-oriented design, allowing the tracing and visualization of the spatiotemporal evolution of electron swarms and the temporal development of the mean energy and the electron number due to attachment and/or ionization processes. We benchmark our code with well-known model gases as well as the real gases argon, N2, O2, CF4, SF6 and mixtures of N2 and O2.

STELLTRANS: A Transport Analysis Suite for Stellarators

NASA Astrophysics Data System (ADS)

Mittelstaedt, Joseph; Lazerson, Samuel; Pablant, Novimir; Weir, Gavin; W7-X Team

2016-10-01

The stellarator transport code STELLTRANS allows us to better analyze the power balance in W7-X. Although profiles of temperature and density are measured experimentally, geometrical factors are needed in conjunction with these measurements to properly analyze heat flux densities in stellarators. The STELLTRANS code interfaces with VMEC to find an equilibrium flux surface configuration and with TRAVIS to determine the RF heating and current drive in the plasma. Stationary transport equations are then considered which are solved using a boundary value differential equation solver. The equations and quantities considered are averaged over flux surfaces to reduce the system to an essentially one dimensional problem. We have applied this code to data from W-7X and were able to calculate the heat flux coefficients. We will also present extensions of the code to a predictive capacity which would utilize DKES to find neoclassical transport coefficients to update the temperature and density profiles.

Benchmark Problems of the Geothermal Technologies Office Code Comparison Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, Mark D.; Podgorney, Robert; Kelkar, Sharad M.

A diverse suite of numerical simulators is currently being applied to predict or understand the performance of enhanced geothermal systems (EGS). To build confidence and identify critical development needs for these analytical tools, the United States Department of Energy, Geothermal Technologies Office has sponsored a Code Comparison Study (GTO-CCS), with participants from universities, industry, and national laboratories. A principal objective for the study was to create a community forum for improvement and verification of numerical simulators for EGS modeling. Teams participating in the study were those representing U.S. national laboratories, universities, and industries, and each team brought unique numerical simulationmore » capabilities to bear on the problems. Two classes of problems were developed during the study, benchmark problems and challenge problems. The benchmark problems were structured to test the ability of the collection of numerical simulators to solve various combinations of coupled thermal, hydrologic, geomechanical, and geochemical processes. This class of problems was strictly defined in terms of properties, driving forces, initial conditions, and boundary conditions. Study participants submitted solutions to problems for which their simulation tools were deemed capable or nearly capable. Some participating codes were originally developed for EGS applications whereas some others were designed for different applications but can simulate processes similar to those in EGS. Solution submissions from both were encouraged. In some cases, participants made small incremental changes to their numerical simulation codes to address specific elements of the problem, and in other cases participants submitted solutions with existing simulation tools, acknowledging the limitations of the code. The challenge problems were based on the enhanced geothermal systems research conducted at Fenton Hill, near Los Alamos, New Mexico, between 1974 and 1995. The problems involved two phases of research, stimulation, development, and circulation in two separate reservoirs. The challenge problems had specific questions to be answered via numerical simulation in three topical areas: 1) reservoir creation/stimulation, 2) reactive and passive transport, and 3) thermal recovery. Whereas the benchmark class of problems were designed to test capabilities for modeling coupled processes under strictly specified conditions, the stated objective for the challenge class of problems was to demonstrate what new understanding of the Fenton Hill experiments could be realized via the application of modern numerical simulation tools by recognized expert practitioners.« less

HYDROGEOLOGICAL AND GEOCHEMICAL FACTORS INFLUENCING MERCURY FATE AND TRANSPORT AT THE SULPHUR BANK MERCURY MINE, LAKE COUNTY, CALIFORNIA

EPA Science Inventory

Clear Lake, located approximately 150 km north of San Francisco in Lake County, is one of the largest fresh water lakes in the California. Elevated mercury levels were first identified in fish from Clear Lake in the late 1970s and early 1980s. Although naturally occurring mercury...

Adaptive Multiscale Modeling of Geochemical Impacts on Fracture Evolution

NASA Astrophysics Data System (ADS)

Molins, S.; Trebotich, D.; Steefel, C. I.; Deng, H.

2016-12-01

Understanding fracture evolution is essential for many subsurface energy applications, including subsurface storage, shale gas production, fracking, CO2 sequestration, and geothermal energy extraction. Geochemical processes in particular play a significant role in the evolution of fractures through dissolution-driven widening, fines migration, and/or fracture sealing due to precipitation. One obstacle to understanding and exploiting geochemical fracture evolution is that it is a multiscale process. However, current geochemical modeling of fractures cannot capture this multi-scale nature of geochemical and mechanical impacts on fracture evolution, and is limited to either a continuum or pore-scale representation. Conventional continuum-scale models treat fractures as preferential flow paths, with their permeability evolving as a function (often, a cubic law) of the fracture aperture. This approach has the limitation that it oversimplifies flow within the fracture in its omission of pore scale effects while also assuming well-mixed conditions. More recently, pore-scale models along with advanced characterization techniques have allowed for accurate simulations of flow and reactive transport within the pore space (Molins et al., 2014, 2015). However, these models, even with high performance computing, are currently limited in their ability to treat tractable domain sizes (Steefel et al., 2013). Thus, there is a critical need to develop an adaptive modeling capability that can account for separate properties and processes, emergent and otherwise, in the fracture and the rock matrix at different spatial scales. Here we present an adaptive modeling capability that treats geochemical impacts on fracture evolution within a single multiscale framework. Model development makes use of the high performance simulation capability, Chombo-Crunch, leveraged by high resolution characterization and experiments. The modeling framework is based on the adaptive capability in Chombo which not only enables mesh refinement, but also refinement of the model-pore scale or continuum Darcy scale-in a dynamic way such that the appropriate model is used only when and where it is needed. Explicit flux matching provides coupling betwen the scales.

Yucca Mountain Area Saturated Zone Dissolved Organic Carbon Isotopic Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, James; Decker, David; Patterson, Gary

2007-06-25

Groundwater samples in the Yucca Mountain area were collected for chemical and isotopic analyses and measurements of water temperature, pH, specific conductivity, and alkalinity were obtained at the well or spring at the time of sampling. For this project, groundwater samples were analyzed for major-ion chemistry, deuterium, oxygen-18, and carbon isotopes of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC). The U.S. Geological Survey (USGS) performed all the fieldwork on this project including measurement of water chemistry field parameters and sample collection. The major ions dissolved in the groundwater, deuterium, oxygen-18, and carbon isotopes of dissolved inorganic carbon (DIC)more » were analyzed by the USGS. All preparation and processing of samples for DOC carbon isotopic analyses and geochemical modeling were performed by the Desert Research Institute (DRI). Analysis of the DOC carbon dioxide gas produced at DRI to obtain carbon-13 and carbon-14 values was conducted at the University of Arizona Accelerator Facility (a NSHE Yucca Mountain project QA qualified contract facility). The major-ion chemistry, deuterium, oxygen-18, and carbon isotopes of DIC were used in geochemical modeling (NETPATH) to determine groundwater sources, flow paths, mixing, and ages. The carbon isotopes of DOC were used to calculate groundwater ages that are independent of DIC model corrected carbon-14 ages. The DIC model corrected carbon-14 calculated ages were used to evaluate groundwater travel times for mixtures of water including water beneath Yucca Mountain. When possible, groundwater travel times were calculated for groundwater flow from beneath Yucca Mountain to down gradient sample sites. DOC carbon-14 groundwater ages were also calculated for groundwaters in the Yucca Mountain area. When possible, groundwater travel times were estimated for groundwater flow from beneath Yucca Mountain to down gradient groundwater sample sites using the DOC calculated groundwater ages. The DIC calculated groundwater ages were compared with DOC calculated groundwater ages and both of these ages were compared to travel times developed in ground-water flow and transport models. If nuclear waste is stored in Yucca Mountain, the saturated zone is the final barrier against the release of radionuclides to the environment. The most recent rendition of the TSPA takes little credit for the presence of the saturated zone and is a testament to the inadequate understanding of this important barrier. If radionuclides reach the saturated zone beneath Yucca Mountain, then there is a travel time before they would leave the Yucca Mountain area and flow down gradient to the Amargosa Valley area. Knowing how long it takes groundwater in the saturated zone to flow from beneath Yucca Mountain to down gradient areas is critical information for potential radionuclide transport. Radionuclide transport in groundwater may be the quickest pathway for radionuclides in the proposed Yucca Mountain repository to reach land surface by way of groundwater pumped in Amargosa Valley. An alternative approach to ground-water flow and transport models to determine the travel time of radionuclides from beneath Yucca Mountain to down gradient areas in the saturated zone is by carbon-14 dating of both inorganic and organic carbon dissolved in the groundwater. A standard method of determining ground-water ages is to measure the carbon-13 and carbon-14 of DIC in the groundwater and then correct the measured carbon-14 along a flow path for geochemical reactions that involve carbon containing phases. These geochemical reactions are constrained by carbon-13 and isotopic fractionations. Without correcting for geochemical reactions, the ground-water ages calculated from only the differences in carbon-14 measured along a flow path (assuming the decrease in carbon-14 is due strictly to radioactive decay) could be tens of thousands of years too old. The computer program NETPATH, developed by the USGS, is the best geochemical program for correcting carbon-14 activities for geochemical reactions. The DIC carbon-14 corrected ages can be further constrained by measuring the carbon isotopes of DOC. Because the only source of organic carbon in aquifers is almost always greater than 40,000 years old, any organic carbon that may be added to the groundwater would contain no carbon-14. Thus, ground-water ages determined by carbon isotopes of DOC should be maximum ages that can be used to constrain DIC corrected ages.« less

Electron transport model of dielectric charging

NASA Technical Reports Server (NTRS)

Beers, B. L.; Hwang, H. C.; Lin, D. L.; Pine, V. W.

1979-01-01

A computer code (SCCPOEM) was assembled to describe the charging of dielectrics due to irradiation by electrons. The primary purpose for developing the code was to make available a convenient tool for studying the internal fields and charge densities in electron-irradiated dielectrics. The code, which is based on the primary electron transport code POEM, is applicable to arbitrary dielectrics, source spectra, and current time histories. The code calculations are illustrated by a series of semianalytical solutions. Calculations to date suggest that the front face electric field is insufficient to cause breakdown, but that bulk breakdown fields can easily be exceeded.

Capabilities overview of the MORET 5 Monte Carlo code

NASA Astrophysics Data System (ADS)

Cochet, B.; Jinaphanh, A.; Heulers, L.; Jacquet, O.

2014-06-01

The MORET code is a simulation tool that solves the transport equation for neutrons using the Monte Carlo method. It allows users to model complex three-dimensional geometrical configurations, describe the materials, define their own tallies in order to analyse the results. The MORET code has been initially designed to perform calculations for criticality safety assessments. New features has been introduced in the MORET 5 code to expand its use for reactor applications. This paper presents an overview of the MORET 5 code capabilities, going through the description of materials, the geometry modelling, the transport simulation and the definition of the outputs.

Cyanazine, Atrazine, and Their Metabolites as Geochemical Indicators of Contaminant Transport in the Mississippi River

USGS Publications Warehouse

Meyer, M.T.; Thurman, E.M.; Goolsby, D.A.

1996-01-01

The geochemical transport of cyanazine and its metabolite cyanazine amide (CAM) was compared to atrazine and its metabolite deethylatrazine (DEA) at three sites in the Mississippi River basin during 1992 and six sites during 1993. The floods of 1993 caused an uninterrupted exponential decline in herbicide concentrations; whereas, in 1992 herbicide concentrations varied mostly in response to two discrete discharge pulses in the spring and midsummer and were stable during an extended period of summer low-flow. Concentration half-lives calculated from the 1993 data for atrazine were approximately twice those of cyanazine at all sites. The half-life for atrazine and cyanazine was shortest, 22 and 14 days, respectively at the Mississippi River at Clinton, Ill. - the farthest upstream site - and longest, 42 and 22 days, respectively, at the Baton Rouge, La. site - the farthest downstream site. The concentration of CAM exceeded the concentration of DEA through September at all sites where the mean ratio of atrazine-to-cyanazine (ACR) was less than 4.0. The ratio of CAM-to-cyanazine (CAMCR) increased from 0.2 to more than 1.0 and the ratio of DEA-to-atrazine (DAR) increased from less than 0.1 to 0.3 from application in May through early to mid-July. Temporal changes in the CAMCR were used to identify pre- and post-application "slugs" of water transported along the reaches of the Mississippi River.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aleman, S.E.

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.

Adaptive Nodal Transport Methods for Reactor Transient Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas Downar; E. Lewis

2005-08-31

Develop methods for adaptively treating the angular, spatial, and time dependence of the neutron flux in reactor transient analysis. These methods were demonstrated in the DOE transport nodal code VARIANT and the US NRC spatial kinetics code, PARCS.

The Athena Astrophysical MHD Code in Cylindrical Geometry

NASA Astrophysics Data System (ADS)

Skinner, M. A.; Ostriker, E. C.

2011-10-01

We have developed a method for implementing cylindrical coordinates in the Athena MHD code (Skinner & Ostriker 2010). The extension has been designed to alter the existing Cartesian-coordinates code (Stone et al. 2008) as minimally and transparently as possible. The numerical equations in cylindrical coordinates are formulated to maintain consistency with constrained transport, a central feature of the Athena algorithm, while making use of previously implemented code modules such as the eigensystems and Riemann solvers. Angular-momentum transport, which is critical in astrophysical disk systems dominated by rotation, is treated carefully. We describe modifications for cylindrical coordinates of the higher-order spatial reconstruction and characteristic evolution steps as well as the finite-volume and constrained transport updates. Finally, we have developed a test suite of standard and novel problems in one-, two-, and three-dimensions designed to validate our algorithms and implementation and to be of use to other code developers. The code is suitable for use in a wide variety of astrophysical applications and is freely available for download on the web.

Transport and equilibrium in field-reversed mirrors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyd, J.K.

Two plasma models relevant to compact torus research have been developed to study transport and equilibrium in field reversed mirrors. In the first model for small Larmor radius and large collision frequency, the plasma is described as an adiabatic hydromagnetic fluid. In the second model for large Larmor radius and small collision frequency, a kinetic theory description has been developed. Various aspects of the two models have been studied in five computer codes ADB, AV, NEO, OHK, RES. The ADB code computes two dimensional equilibrium and one dimensional transport in a flux coordinate. The AV code calculates orbit average integralsmore » in a harmonic oscillator potential. The NEO code follows particle trajectories in a Hill's vortex magnetic field to study stochasticity, invariants of the motion, and orbit average formulas. The OHK code displays analytic psi(r), B/sub Z/(r), phi(r), E/sub r/(r) formulas developed for the kinetic theory description. The RES code calculates resonance curves to consider overlap regions relevant to stochastic orbit behavior.« less

Benchmarking of neutron production of heavy-ion transport codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Remec, I.; Ronningen, R. M.; Heilbronn, L.

Document available in abstract form only, full text of document follows: Accurate prediction of radiation fields generated by heavy ion interactions is important in medical applications, space missions, and in design and operation of rare isotope research facilities. In recent years, several well-established computer codes in widespread use for particle and radiation transport calculations have been equipped with the capability to simulate heavy ion transport and interactions. To assess and validate these capabilities, we performed simulations of a series of benchmark-quality heavy ion experiments with the computer codes FLUKA, MARS15, MCNPX, and PHITS. We focus on the comparisons of secondarymore » neutron production. Results are encouraging; however, further improvements in models and codes and additional benchmarking are required. (authors)« less

Method for calculating internal radiation and ventilation with the ADINAT heat-flow code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butkovich, T.R.; Montan, D.N.

1980-04-01

One objective of the spent fuel test in Climax Stock granite (SFTC) is to correctly model the thermal transport, and the changes in the stress field and accompanying displacements from the application of the thermal loads. We have chosen the ADINA and ADINAT finite element codes to do these calculations. ADINAT is a heat transfer code compatible to the ADINA displacement and stress analysis code. The heat flow problem encountered at SFTC requires a code with conduction, radiation, and ventilation capabilities, which the present version of ADINAT does not have. We have devised a method for calculating internal radiation andmore » ventilation with the ADINAT code. This method effectively reproduces the results from the TRUMP multi-dimensional finite difference code, which correctly models radiative heat transport between drift surfaces, conductive and convective thermal transport to and through air in the drifts, and mass flow of air in the drifts. The temperature histories for each node in the finite element mesh calculated with ADINAT using this method can be used directly in the ADINA thermal-mechanical calculation.« less

Monte Carlo Modeling of the Initial Radiation Emitted by a Nuclear Device in the National Capital Region

DTIC Science & Technology

2013-07-01

also simulated in the models. Data was derived from calculations using the three-dimensional Monte Carlo radiation transport code MCNP (Monte Carlo N...32  B.  MCNP PHYSICS OPTIONS ......................................................................................... 33  C.  HAZUS...input deck’) for the MCNP , Monte Carlo N-Particle, radiation transport code. MCNP is a general-purpose code designed to simulate neutron, photon

Considerations of MCNP Monte Carlo code to be used as a radiotherapy treatment planning tool.

PubMed

Juste, B; Miro, R; Gallardo, S; Verdu, G; Santos, A

2005-01-01

The present work has simulated the photon and electron transport in a Theratron 780® (MDS Nordion)⁶⁰Co radiotherapy unit, using the Monte Carlo transport code, MCNP (Monte Carlo N-Particle). This project explains mainly the different methodologies carried out to speedup calculations in order to apply this code efficiently in radiotherapy treatment planning.

CTViz: A tool for the visualization of transport in nanocomposites.

PubMed

Beach, Benjamin; Brown, Joshua; Tarlton, Taylor; Derosa, Pedro A

2016-05-01

A visualization tool (CTViz) for charge transport processes in 3-D hybrid materials (nanocomposites) was developed, inspired by the need for a graphical application to assist in code debugging and data presentation of an existing in-house code. As the simulation code grew, troubleshooting problems grew increasingly difficult without an effective way to visualize 3-D samples and charge transport in those samples. CTViz is able to produce publication and presentation quality visuals of the simulation box, as well as static and animated visuals of the paths of individual carriers through the sample. CTViz was designed to provide a high degree of flexibility in the visualization of the data. A feature that characterizes this tool is the use of shade and transparency levels to highlight important details in the morphology or in the transport paths by hiding or dimming elements of little relevance to the current view. This is fundamental for the visualization of 3-D systems with complex structures. The code presented here provides these required capabilities, but has gone beyond the original design and could be used as is or easily adapted for the visualization of other particulate transport where transport occurs on discrete paths. Copyright © 2016 Elsevier Inc. All rights reserved.

Qualitatively Modeling solute fate and transport across scales in an agricultural catchment with diverse lithology

NASA Astrophysics Data System (ADS)

Wayman, C. R.; Russo, T. A.; Li, L.; Forsythe, B.; Hoagland, B.

2017-12-01

As part of the Susquehanna Shale Hills Critical Zone Observatory (SSHCZO) project, we have collected geochemical and hydrological data from several subcatchments and four monitoring sites on the main stem of Shaver's Creek, in Huntingon county, Pennsylvania. One subcatchment (0.43 km2) is under agricultural land use, and the monitoring locations on the larger Shaver's Creek (up to 163 km2) drain watersheds with 0 to 25% agricultural area. These two scales of investigation, coupled with advances made across the SSHCZO on multiple lithologies allow us to extrapolate from the subcatchment to the larger watershed. We use geochemical surface and groundwater data to estimate the solute and water transport regimes within the catchment, and to show how lithology and land use are major controls on ground and surface water quality. One area of investigation includes the transport of nutrients between interflow and regional groundwater, and how that connectivity may be reflected in local surface waters. Water and nutrient (Nitrogen) isotopes, will be used to better understand the relative contributions of local and regional groundwater and interflow fluxes into nearby streams. Following initial qualitative modeling, multiple hydrologic and nutrient transport models (e.g. SWAT and CYCLES/PIHM) will be evaluated from the subcatchment to large watershed scales. We will evaluate the ability to simulate the contributions of regional groundwater versus local groundwater, and also impacts of agricultural land management on surface water quality. Improving estimations of groundwater contributions to stream discharge will provide insight into how much agricultural development can impact stream quality and nutrient loading.

Path Toward a Unified Geometry for Radiation Transport

NASA Astrophysics Data System (ADS)

Lee, Kerry

The Direct Accelerated Geometry for Radiation Analysis and Design (DAGRAD) element of the RadWorks Project under Advanced Exploration Systems (AES) within the Space Technology Mission Directorate (STMD) of NASA will enable new designs and concepts of operation for radiation risk assessment, mitigation and protection. This element is designed to produce a solution that will allow NASA to calculate the transport of space radiation through complex CAD models using the state-of-the-art analytic and Monte Carlo radiation transport codes. Due to the inherent hazard of astronaut and spacecraft exposure to ionizing radiation in low-Earth orbit (LEO) or in deep space, risk analyses must be performed for all crew vehicles and habitats. Incorporating these analyses into the design process can minimize the mass needed solely for radiation protection. Transport of the radiation fields as they pass through shielding and body materials can be simulated using Monte Carlo techniques or described by the Boltzmann equation, which is obtained by balancing changes in particle fluxes as they traverse a small volume of material with the gains and losses caused by atomic and nuclear collisions. Deterministic codes that solve the Boltzmann transport equation, such as HZETRN (high charge and energy transport code developed by NASA LaRC), are generally computationally faster than Monte Carlo codes such as FLUKA, GEANT4, MCNP(X) or PHITS; however, they are currently limited to transport in one dimension, which poorly represents the secondary light ion and neutron radiation fields. NASA currently uses HZETRN space radiation transport software, both because it is computationally efficient and because proven methods have been developed for using this software to analyze complex geometries. Although Monte Carlo codes describe the relevant physics in a fully three-dimensional manner, their computational costs have thus far prevented their widespread use for analysis of complex CAD models, leading to the creation and maintenance of toolkit specific simplistic geometry models. The work presented here builds on the Direct Accelerated Geometry Monte Carlo (DAGMC) toolkit developed for use with the Monte Carlo N-Particle (MCNP) transport code. The work-flow for doing radiation transport on CAD models using MCNP and FLUKA has been demonstrated and the results of analyses on realistic spacecraft/habitats will be presented. Future work is planned that will further automate this process and enable the use of multiple radiation transport codes on identical geometry models imported from CAD. This effort will enhance the modeling tools used by NASA to accurately evaluate the astronaut space radiation risk and accurately determine the protection provided by as-designed exploration mission vehicles and habitats.

Identification of Trends into Dose Calculations for Astronauts through Performing Sensitivity Analysis on Calculational Models Used by the Radiation Health Office

NASA Technical Reports Server (NTRS)

Adams, Thomas; VanBaalen, Mary

2009-01-01

The Radiation Health Office (RHO) determines each astronaut s cancer risk by using models to associate the amount of radiation dose that astronauts receive from spaceflight missions. The baryon transport codes (BRYNTRN), high charge (Z) and energy transport codes (HZETRN), and computer risk models are used to determine the effective dose received by astronauts in Low Earth orbit (LEO). This code uses an approximation of the Boltzman transport formula. The purpose of the project is to run this code for various International Space Station (ISS) flight parameters in order to gain a better understanding of how this code responds to different scenarios. The project will determine how variations in one set of parameters such as, the point of the solar cycle and altitude can affect the radiation exposure of astronauts during ISS missions. This project will benefit NASA by improving mission dosimetry.

Geochemical evidence for mélange melting in global arcs

PubMed Central

Nielsen, Sune G.; Marschall, Horst R.

2017-01-01

In subduction zones, sediments and hydrothermally altered oceanic crust, which together form part of the subducting slab, contribute to the chemical composition of lavas erupted at the surface to form volcanic arcs. Transport of this material from the slab to the overlying mantle wedge is thought to involve discreet melts and fluids that are released from various portions of the slab. We use a meta-analysis of geochemical data from eight globally representative arcs to show that melts and fluids from individual slab components cannot be responsible for the formation of arc lavas. Instead, the data are compatible with models that first invoke physical mixing of slab components and the mantle wedge, widely referred to as high-pressure mélange, before arc magmas are generated. PMID:28435882

Geochemical evidence for mélange melting in global arcs.

PubMed

Nielsen, Sune G; Marschall, Horst R

2017-04-01

In subduction zones, sediments and hydrothermally altered oceanic crust, which together form part of the subducting slab, contribute to the chemical composition of lavas erupted at the surface to form volcanic arcs. Transport of this material from the slab to the overlying mantle wedge is thought to involve discreet melts and fluids that are released from various portions of the slab. We use a meta-analysis of geochemical data from eight globally representative arcs to show that melts and fluids from individual slab components cannot be responsible for the formation of arc lavas. Instead, the data are compatible with models that first invoke physical mixing of slab components and the mantle wedge, widely referred to as high-pressure mélange, before arc magmas are generated.

Sources and dispersal of land-based runoff from small Hawaiian drainages to a coral reef: Insights from geochemical signatures

NASA Astrophysics Data System (ADS)

Takesue, Renee K.; Storlazzi, Curt D.

2017-03-01

Land-based sediment and contaminant runoff is a major threat to coral reefs, and runoff reduction efforts would benefit from knowledge of specific runoff sources. Geochemical signatures of small drainage basins were determined in the fine fraction of soil and sediment, then used in the nearshore region of a coral reef-fringed urban embayment on southeast Oahu, Hawaii, to describe sources and dispersal of land-based runoff. The sedimentary rare earth element ratio (La/Yb)N showed a clear distinction between the two main rock types in the overall contributing area, tholeiitic and alkalic olivine basalt. Based on this geochemical signature it was apparent that the majority of terrigenous sediment on the reef flat originated from geologically old tholeiitic drainages. Sediment from one of five tholeiitic drainages had a distinct geochemical signature, and sediment with this signature was dispersed on the reef flat 2 km west and 150 m offshore of the contributing basin. Sediment and the anthropogenic metals Cd, Pb, and Zn were entrained in runoff from the most heavily urbanized region of the watershed. Although anthropogenic Cd and Zn had localized distributions close to shore, anthropogenic Pb was found associated with fine sediment on the westernmost part of the reef flat and 400 m offshore, illustrating how trade-wind-driven sediment transport can increase the scale of runoff impacts to nearshore communities. Our findings show that sediment geochemical signatures can provide insights about the source and dispersal of land-based runoff in shallow coastal environments. The application of such knowledge to watershed management and habitat remediation efforts can aid in the protection and restoration of runoff-impacted coastal ecosystems worldwide.

Sources and dispersal of land-based runoff from small Hawaiian drainages to a coral reef: Insights from geochemical signatures

USGS Publications Warehouse

Takesue, Renee K.; Storlazzi, Curt

2017-01-01

Land-based sediment and contaminant runoff is a major threat to coral reefs, and runoff reduction efforts would benefit from knowledge of specific runoff sources. Geochemical signatures of small drainage basins were determined in the fine fraction of soil and sediment, then used in the nearshore region of a coral reef-fringed urban embayment on southeast Oahu, Hawaii, to describe sources and dispersal of land-based runoff. The sedimentary rare earth element ratio (La/Yb)N showed a clear distinction between the two main rock types in the overall contributing area, tholeiitic and alkalic olivine basalt. Based on this geochemical signature it was apparent that the majority of terrigenous sediment on the reef flat originated from geologically old tholeiitic drainages. Sediment from one of five tholeiitic drainages had a distinct geochemical signature, and sediment with this signature was dispersed on the reef flat 2 km west and 150 m offshore of the contributing basin. Sediment and the anthropogenic metals Cd, Pb, and Zn were entrained in runoff from the most heavily urbanized region of the watershed. Although anthropogenic Cd and Zn had localized distributions close to shore, anthropogenic Pb was found associated with fine sediment on the westernmost part of the reef flat and 400 m offshore, illustrating how trade-wind-driven sediment transport can increase the scale of runoff impacts to nearshore communities. Our findings show that sediment geochemical signatures can provide insights about the source and dispersal of land-based runoff in shallow coastal environments. The application of such knowledge to watershed management and habitat remediation efforts can aid in the protection and restoration of runoff-impacted coastal ecosystems worldwide.

Nanogeochemistry: Size-dependent mineral-fluid interface chemistry

NASA Astrophysics Data System (ADS)

Wang, Y.

2012-12-01

Nanostructures and nanometer mineral phases, both widely present in geologic materials, can potentially affect many geochemical processes. It is known that at nanometer scales a material tends to exhibit chemical properties distinct from the corresponding bulk phase. Understanding of this size-dependent property change will help us to bridge the existing knowledge gap between the molecular level understanding and the macro-scale laboratory/field observations of a geochemical process. In this presentation, I will review of the recent progresses in nanoscience and provide a perspective on how these progresses can potentially impact geochemical studies. My presentation will be focused the following areas: (1) the characterization of nanostructures in natural systems, (2) the study of fluids and chemical species in nanoconfinement, (3) the effects of nanopores on geochemical reaction and mass transfers, and (4) the use nanostructured materials for environmental management. I will demonstrate that the nanopore confinement can significantly modify geochemical reactions in porous geologic media. As the pore size is reduced to a few nanometers, the difference between surface acidity constants of a mineral (pK2 - pK1) decreases, giving rise to a higher surface charge density on a nanopore surface than that on an unconfined mineral-water interface. The change in surface acidity constants results in a shift of ion sorption edges and enhances ion sorption on nanopore surfaces. This effect causes preferential enrichment of trace elements in nanopores. I will then discuss the implications of this emergent nanometer-scale property to radionuclide transport and carbon dioxide storage in geologic media. This work was performed at Sandia National Laboratories, which is a multiprogram laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the DOE under contract DE-AC04-94AL8500.

Simulations of neutron transport at low energy: a comparison between GEANT and MCNP.

PubMed

Colonna, N; Altieri, S

2002-06-01

The use of the simulation tool GEANT for neutron transport at energies below 20 MeV is discussed, in particular with regard to shielding and dose calculations. The reliability of the GEANT/MICAP package for neutron transport in a wide energy range has been verified by comparing the results of simulations performed with this package in a wide energy range with the prediction of MCNP-4B, a code commonly used for neutron transport at low energy. A reasonable agreement between the results of the two codes is found for the neutron flux through a slab of material (iron and ordinary concrete), as well as for the dose released in soft tissue by neutrons. These results justify the use of the GEANT/MICAP code for neutron transport in a wide range of applications, including health physics problems.

SHIELD and HZETRN comparisons of pion production cross sections

NASA Astrophysics Data System (ADS)

Norbury, John W.; Sobolevsky, Nikolai; Werneth, Charles M.

2018-03-01

A program of comparing American (NASA) and Russian (ROSCOSMOS) space radiation transport codes has recently begun, and the first paper directly comparing the NASA and ROSCOSMOS space radiation transport codes, HZETRN and SHIELD respectively has recently appeared. The present work represents the second time that NASA and ROSCOSMOS calculations have been directly compared, and the focus here is on models of pion production cross sections used in the two transport codes mentioned above. It was found that these models are in overall moderate agreement with each other and with experimental data. Disagreements that were found are discussed.

Evaluation and utilization of beam simulation codes for the SNS ion source and low energy beam transport developmenta)

NASA Astrophysics Data System (ADS)

Han, B. X.; Welton, R. F.; Stockli, M. P.; Luciano, N. P.; Carmichael, J. R.

2008-02-01

Beam simulation codes PBGUNS, SIMION, and LORENTZ-3D were evaluated by modeling the well-diagnosed SNS base line ion source and low energy beam transport (LEBT) system. Then, an investigation was conducted using these codes to assist our ion source and LEBT development effort which is directed at meeting the SNS operational and also the power-upgrade project goals. A high-efficiency H- extraction system as well as magnetic and electrostatic LEBT configurations capable of transporting up to 100mA is studied using these simulation tools.

On the Development of a Deterministic Three-Dimensional Radiation Transport Code

NASA Technical Reports Server (NTRS)

Rockell, Candice; Tweed, John

2011-01-01

Since astronauts on future deep space missions will be exposed to dangerous radiations, there is a need to accurately model the transport of radiation through shielding materials and to estimate the received radiation dose. In response to this need a three dimensional deterministic code for space radiation transport is now under development. The new code GRNTRN is based on a Green's function solution of the Boltzmann transport equation that is constructed in the form of a Neumann series. Analytical approximations will be obtained for the first three terms of the Neumann series and the remainder will be estimated by a non-perturbative technique . This work discusses progress made to date and exhibits some computations based on the first two Neumann series terms.

Accelerating execution of the integrated TIGER series Monte Carlo radiation transport codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, L.M.; Hochstedler, R.D.

1997-02-01

Execution of the integrated TIGER series (ITS) of coupled electron/photon Monte Carlo radiation transport codes has been accelerated by modifying the FORTRAN source code for more efficient computation. Each member code of ITS was benchmarked and profiled with a specific test case that directed the acceleration effort toward the most computationally intensive subroutines. Techniques for accelerating these subroutines included replacing linear search algorithms with binary versions, replacing the pseudo-random number generator, reducing program memory allocation, and proofing the input files for geometrical redundancies. All techniques produced identical or statistically similar results to the original code. Final benchmark timing of themore » accelerated code resulted in speed-up factors of 2.00 for TIGER (the one-dimensional slab geometry code), 1.74 for CYLTRAN (the two-dimensional cylindrical geometry code), and 1.90 for ACCEPT (the arbitrary three-dimensional geometry code).« less

Radiological performance assessment for the E-Area Vaults Disposal Facility. Appendices A through M

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cook, J.R.

1994-04-15

These document contains appendices A-M for the performance assessment. They are A: details of models and assumptions, B: computer codes, C: data tabulation, D: geochemical interactions, E: hydrogeology of the Savannah River Site, F: software QA plans, G: completeness review guide, H: performance assessment peer review panel recommendations, I: suspect soil performance analysis, J: sensitivity/uncertainty analysis, K: vault degradation study, L: description of naval reactor waste disposal, M: porflow input file. (GHH)

Conference on Early Mars: Geologic and Hydrologic Evolution, Physical and Chemical Environments, and the Implications for Life

NASA Technical Reports Server (NTRS)

Clifford, S. M. (Editor); Treiman, A. H. (Editor); Newsom, H. E. (Editor); Farmer, J. D. (Editor)

1997-01-01

Topics considered include: Geology alteration and life in an extreme environment; developing a chemical code to identify magnetic biominerals; effect of impacts on early Martin geologic evolution; spectroscopic identification of minerals in Hematite-bearing soils and sediments; exopaleontology and the search for a Fossil record on Mars; geochemical evolution of the crust of Mars; geological evolution of the early earth;solar-wind-induced erosion of the Mars atmosphere. Also included geological evolution of the crust of Mars.

Methods for Estimating Physicochemical Properties of Inorganic Chemicals of Environmental Concern. Volume 1

DTIC Science & Technology

1987-03-01

available. Kincaid et al. (221 provide an overview of the geochemical code history (up to 1983) in which they group models into four major families...plant. The *Ixample is adapted from a study by Morel ,’t al. 1291 for Los Angeles County. It is prv.ented in four ;ections: I ’ Problem statement, ý2...presents environmentally important priperty dJata for several groups of elements or compcui’ds. The data include, for Pxrimpie, precal- culated

Description of input and examples for PHREEQC version 3: a computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations

USGS Publications Warehouse

Parkhurst, David L.; Appelo, C.A.J.

2013-01-01

PHREEQC version 3 is a computer program written in the C and C++ programming languages that is designed to perform a wide variety of aqueous geochemical calculations. PHREEQC implements several types of aqueous models: two ion-association aqueous models (the Lawrence Livermore National Laboratory model and WATEQ4F), a Pitzer specific-ion-interaction aqueous model, and the SIT (Specific ion Interaction Theory) aqueous model. Using any of these aqueous models, PHREEQC has capabilities for (1) speciation and saturation-index calculations; (2) batch-reaction and one-dimensional (1D) transport calculations with reversible and irreversible reactions, which include aqueous, mineral, gas, solid-solution, surface-complexation, and ion-exchange equilibria, and specified mole transfers of reactants, kinetically controlled reactions, mixing of solutions, and pressure and temperature changes; and (3) inverse modeling, which finds sets of mineral and gas mole transfers that account for differences in composition between waters within specified compositional uncertainty limits. Many new modeling features were added to PHREEQC version 3 relative to version 2. The Pitzer aqueous model (pitzer.dat database, with keyword PITZER) can be used for high-salinity waters that are beyond the range of application for the Debye-Hückel theory. The Peng-Robinson equation of state has been implemented for calculating the solubility of gases at high pressure. Specific volumes of aqueous species are calculated as a function of the dielectric properties of water and the ionic strength of the solution, which allows calculation of pressure effects on chemical reactions and the density of a solution. The specific conductance and the density of a solution are calculated and printed in the output file. In addition to Runge-Kutta integration, a stiff ordinary differential equation solver (CVODE) has been included for kinetic calculations with multiple rates that occur at widely different time scales. Surface complexation can be calculated with the CD-MUSIC (Charge Distribution MUltiSIte Complexation) triple-layer model in addition to the diffuse-layer model. The composition of the electrical double layer of a surface can be estimated by using the Donnan approach, which is more robust and faster than the alternative Borkovec-Westall integration. Multicomponent diffusion, diffusion in the electrostatic double layer on a surface, and transport of colloids with simultaneous surface complexation have been added to the transport module. A series of keyword data blocks has been added for isotope calculations—ISOTOPES, CALCULATE_VALUES, ISOTOPE_ALPHAS, ISOTOPE_RATIOS, and NAMED_EXPRESSIONS. Solution isotopic data can be input in conventional units (for example, permil, percent modern carbon, or tritium units) and the numbers are converted to moles of isotope by PHREEQC. The isotopes are treated as individual components (they must be defined as individual master species) so that each isotope has its own set of aqueous species, gases, and solids. The isotope-related keywords allow calculating equilibrium fractionation of isotopes among the species and phases of a system. The calculated isotopic compositions are printed in easily readable conventional units. New keywords and options facilitate the setup of input files and the interpretation of the results. Keyword data blocks can be copied (keyword COPY) and deleted (keyword DELETE). Keyword data items can be altered by using the keyword data blocks with the _MODIFY extension and a simulation can be run with all reactants of a given index number (keyword RUN_CELLS). The definition of the complete chemical state of all reactants of PHREEQC can be saved in a file in a raw data format ( DUMP and _RAW keywords). The file can be read as part of another input file with the INCLUDE$ keyword. These keywords facilitate the use of IPhreeqc, which is a module implementing all PHREEQC version 3 capabilities; the module is designed to be used in other programs that need to implement geochemical calculations; for example, transport codes. Charting capabilities have been added to some versions of PHREEQC. Charting capabilities have been added to Windows distributions of PHREEQC version 3. (Charting on Linux requires installation of Wine.) The keyword data block USER_GRAPH allows selection of data for plotting and manipulation of chart appearance. Almost any results from geochemical simulations (for example, concentrations, activities, or saturation indices) can be retrieved by using Basic language functions and specified as data for plotting in USER_GRAPH. Results of transport simulations can be plotted against distance or time. Data can be added to a chart from tab-separated-values files. All input for PHREEQC version 3 is defined in keyword data blocks, each of which may have a series of identifiers for specific types of data. This report provides a complete description of each keyword data block and its associated identifiers. Input files for 22 examples that demonstrate most of the capabilities of PHREEQC version 3 are described and the results of the example simulations are presented and discussed.

AN OPEN-SOURCE NEUTRINO RADIATION HYDRODYNAMICS CODE FOR CORE-COLLAPSE SUPERNOVAE

DOE Office of Scientific and Technical Information (OSTI.GOV)

O’Connor, Evan, E-mail: evanoconnor@ncsu.edu; CITA, Canadian Institute for Theoretical Astrophysics, Toronto, M5S 3H8

2015-08-15

We present an open-source update to the spherically symmetric, general-relativistic hydrodynamics, core-collapse supernova (CCSN) code GR1D. The source code is available at http://www.GR1Dcode.org. We extend its capabilities to include a general-relativistic treatment of neutrino transport based on the moment formalisms of Shibata et al. and Cardall et al. We pay special attention to implementing and testing numerical methods and approximations that lessen the computational demand of the transport scheme by removing the need to invert large matrices. This is especially important for the implementation and development of moment-like transport methods in two and three dimensions. A critical component of neutrinomore » transport calculations is the neutrino–matter interaction coefficients that describe the production, absorption, scattering, and annihilation of neutrinos. In this article we also describe our open-source neutrino interaction library NuLib (available at http://www.nulib.org). We believe that an open-source approach to describing these interactions is one of the major steps needed to progress toward robust models of CCSNe and robust predictions of the neutrino signal. We show, via comparisons to full Boltzmann neutrino-transport simulations of CCSNe, that our neutrino transport code performs remarkably well. Furthermore, we show that the methods and approximations we employ to increase efficiency do not decrease the fidelity of our results. We also test the ability of our general-relativistic transport code to model failed CCSNe by evolving a 40-solar-mass progenitor to the onset of collapse to a black hole.« less

Integrating Hydrogeological, Microbiological, and Geochemical Data Using a Multi-Component Reactive Transport Model: Quantifying the Biogeochemical Evolution of Redox Zones in a Contaminated Aquifer

NASA Astrophysics Data System (ADS)

McGuire, J. T.; Phanikumar, M. S.; Long, D. T.; Hyndman, D. W.

2003-12-01

Hydrogeological, microbiological, and geochemical processes operating in a shallow sandy aquifer contaminated by waste fuels and chlorinated solvents were integrated using high-resolution mechanistic models. A 3-D, transient, reactive transport model was developed to quantitatively describe coupled processes via thermodynamic and kinetic arguments. The model was created by linking the hydrodynamic model MODFLOW (McDonald and Harbaugh, 1988), with advection, dispersion and user defined kinetic reactions based on RT3D 2.0, (Clement and Jones, 1998) and geochemical model PHREEQC (Parkhurst and Appelo, 1999). This model, BGTK3D 2.0, describes 1) the biodegradation of organic matter based on the influence of transport processes on microbial growth, 2) the complex suite of biogeochemical reactions operating in the aquifer, and 3) sharp chemical gradients. Some key features of this model are an ability to incorporate realistic solid phases to test hypotheses regarding mineral-water interactions, and an ability to accurately describe small-scale biogeochemical cycling (cm variability) observed in the field without oscillations or excessive numerical damping. BGTK3D was used to test hypotheses regarding the evolution of redox chemistry in a contaminated aquifer. The conceptual model that terminal electron accepting processes (TEAPs) distribute themselves sequentially into redox zones down flow path in aqueous systems is often used to interpret how and at what rates organic compounds will be degraded in the environment. Geochemical and microbiological data collected from a mixed contaminant plume at the former Wurtsmith AFB in Oscoda, Michigan suggests that under steady-state, mature plume conditions, traditional redox zonation may not be a realistic model of the distribution of TEAPs and therefore may not be the best model to evaluate the potential degradation of organic compounds. Based on these data, a conceptual model of TEAP evolution in contaminated systems was established. This model proposes that during initial plume development terminal electron acceptors O2, Fe3+, NO3, and SO4, are consumed sequentially based on thermodynamic arguments until a balance between organic degradation rates and source inputs and thus a stable plume length can be achieved. Once this "mature" state has been achieved, distinct redox zones can no longer be sustained and methanogenesis will dominate except in portions of the aquifer impacted by recharge water and diffusion of TEAs from all sides. Under these conditions, TEAPs will not proceed sequentially.

Scaling Effects of Cr(VI) Reduction Kinetics. The Role of Geochemical Heterogeneity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Li; Li, Li

2015-10-22

The natural subsurface is highly heterogeneous with minerals distributed in different spatial patterns. Fundamental understanding of how mineral spatial distribution patterns regulate sorption process is important for predicting the transport and fate of chemicals. Existing studies about the sorption was carried out in well-mixed batch reactors or uniformly packed columns, with few data available on the effects of spatial heterogeneities. As a result, there is a lack of data and understanding on how spatial heterogeneities control sorption processes. In this project, we aim to understand and develop modeling capabilities to predict the sorption of Cr(VI), an omnipresent contaminant in naturalmore » systems due to its natural occurrence and industrial utilization. We systematically examine the role of spatial patterns of illite, a common clay, in determining the extent of transport limitation and scaling effects associated with Cr(VI) sorption capacity and kinetics using column experiments and reactive transport modeling. Our results showed that the sorbed mass and rates can differ by an order of magnitude due to of the illite spatial heterogeneities and transport limitation. With constraints from data, we also developed the capabilities of modeling Cr(VI) in heterogeneous media. The developed model is then utilized to understand the general principles that govern the relationship between sorption and connectivity, a key measure of the spatial pattern characteristics. This correlation can be used to estimate Cr(VI) sorption characteristics in heterogeneous porous media. Insights gained here bridge gaps between laboratory and field application in hydrogeology and geochemical field, and advance predictive understanding of reactive transport processes in the natural heterogeneous subsurface. We believe that these findings will be of interest to a large number of environmental geochemists and engineers, hydrogeologists, and those interested in contaminant fate and transport, water quality and water composition, and natural attenuation processes in natural systems.« less

Developing a Robust Geochemical and Reactive Transport Model to Evaluate Possible Sources of Arsenic at the CO2 Sequestration Natural Analog Site in Chimayo, New Mexico

EPA Science Inventory

Migration of carbon dioxide (CO₂) from deep storage formations into shallow drinking water aquifers is a possible system failure related to geologic CO₂ sequestration. A CO₂ leak may cause mineral precipitation/dissolution reactions, changes in a...

Temporal variations in parameters reflecting terminal-electron-accepting processes in an aquifer contaminated with waste fuel and chlorinated solvents

USGS Publications Warehouse

McGuire, Jennifer T.; Smith, Erik W.; Long, David T.; Hyndman, David W.; Haack, Sheridan K.; Klug, Michael J.; Velbel, Michael A.

2000-01-01

A fundamental issue in aquifer biogeochemistry is the means by which solute transport, geochemical processes, and microbiological activity combine to produce spatial and temporal variations in redox zonation. In this paper, we describe the temporal variability of TEAP conditions in shallow groundwater contaminated with both waste fuel and chlorinated solvents. TEAP parameters (including methane, dissolved iron, and dissolved hydrogen) were measured to characterize the contaminant plume over a 3-year period. We observed that concentrations of TEAP parameters changed on different time scales and appear to be related, in part, to recharge events. Changes in all TEAP parameters were observed on short time scales (months), and over a longer 3-year period. The results indicate that (1) interpretations of TEAP conditions in aquifers contaminated with a variety of organic chemicals, such as those with petroleum hydrocarbons and chlorinated solvents, must consider additional hydrogen-consuming reactions (e.g., dehalogenation); (2) interpretations must consider the roles of both in situ (at the sampling point) biogeochemical and solute transport processes; and (3) determinations of microbial communities are often necessary to confirm the interpretations made from geochemical and hydrogeological measurements on these processes.

Sewage contamination in the upper Mississippi River as measured by the fecal sterol, coprostanol

USGS Publications Warehouse

Writer, J.H.; Leenheer, J.A.; Barber, L.B.; Amy, G.L.; Chapra, S.C.

1995-01-01

The molecular sewage indicator, coprostanol, was measured in bed sediments of the Mississippi River for the purpose of determining sewage contamination. Coprostanol is a non-ionic, non-polar, organic molecule that associates with sediments in surface waters, and concentrations of coprostanol in bed sediments provide an indication of long-term sewage loads. Because coprostanol concentrations are dependent on particle size and percent organic carbon, a ratio between coprostanol (sewage sources) and cholestanol + cholesterol (sewage and non-sewage sources) was used to remove the biases related to particle size and percent organic carbon. The dynamics of contaminant transport in the Upper Mississippi River are influenced by both hydrologic and geochemical parameters. A mass balance model incorporating environmental parameters such as river and tributary discharge, suspended sediment concentration, fraction of organic carbon, sedimentation rates, municipal discharges and coprostanol decay rates was developed that describes coprostanol concentrations and therefore, expected patterns of municipal sewage effects on the Upper Mississippi River. Comparison of the computed and the measured coprostanol concentrations provides insight into the complex hydrologic and geochemical processes of contaminant transport and the ability to link measured chemical concentrations with hydrologic characteristics of the Mississippi River.

Reactive transport codes for subsurface environmental simulation

DOE PAGES

Steefel, C. I.; Appelo, C. A. J.; Arora, B.; ...

2014-09-26

A general description of the mathematical and numerical formulations used in modern numerical reactive transport codes relevant for subsurface environmental simulations is presented. The formulations are followed by short descriptions of commonly used and available subsurface simulators that consider continuum representations of flow, transport, and reactions in porous media. These formulations are applicable to most of the subsurface environmental benchmark problems included in this special issue. The list of codes described briefly here includes PHREEQC, HPx, PHT3D, OpenGeoSys (OGS), HYTEC, ORCHESTRA, TOUGHREACT, eSTOMP, HYDROGEOCHEM, CrunchFlow, MIN3P, and PFLOTRAN. The descriptions include a high-level list of capabilities for each of themore » codes, along with a selective list of applications that highlight their capabilities and historical development.« less

Fractionation and risk assessment of Fe and Mn in surface sediments from coastal sites of Sonora, Mexico (Gulf of California).

PubMed

Jara-Marini, Martín E; García-Camarena, Raúl; Gómez-Álvarez, Agustín; García-Rico, Leticia

2015-07-01

The aim of this study was to evaluate Fe and Mn distribution in geochemical fractions of the surface sediment of four oyster culture sites in the Sonora coast, Mexico. A selective fractionation scheme to obtain five fractions was adapted for the microwave system. Surface sediments were analyzed for carbonates, organic matter contents, and Fe and Mn in geochemical fractions. The bulk concentrations of Fe ranged from 10,506 to 21,918 mg/kg (dry weight, dry wt), and the bulk concentrations of Mn ranged from 185.1 to 315.9 mg/kg (dry wt) in sediments, which was low and considered as non-polluted in all of the sites. The fractionation study indicated that the major geochemical phases for the metals were the residual, as well as the Fe and Mn oxide fractions. The concentrations of metals in the geochemical fractions had the following order: residual > Fe and Mn oxides > organic matter > carbonates > interchangeable. Most of the Fe and Mn were linked to the residual fraction. Among non-residual fractions, high percentages of Fe and Mn were linked to Fe and Mn oxides. The enrichment factors (EFs) for the two metals were similar in the four studied coasts, and the levels of Fe and Mn are interpreted as non-enrichment (EF < 1) because the metals concentrations were within the baseline concentrations. According to the environmental risk assessment codes, Fe and Mn posed no risk and low risk, respectively. Although the concentrations of Fe and Mn were linked to the residual fraction, the levels in non-residual fractions may significantly result in the transference of other metals, depending on several physico-chemical and biological factors.

Field Testing of Downgradient Uranium Mobility at an In-Situ Recovery Uranium Mine

NASA Astrophysics Data System (ADS)

Reimus, P. W.; Clay, J. T.; Rearick, M.; Perkins, G.; Brown, S. T.; Basu, A.; Chamberlain, K.

2015-12-01

In-situ recovery (ISR) mining of uranium involves the injection of O2 and CO2 (or NaHCO3) into saturated roll-front deposits to oxidize and solubilize the uranium, which is then removed by ion exchange at the surface and processed into U3O8. While ISR is economical and environmentally-friendly relative to conventional mining, one of the challenges of extracting uranium by this process is that it leaves behind a geochemically-altered aquifer that is exceedingly difficult to restore to pre-mining geochemical conditions, a regulatory objective. In this research, we evaluated the ability of the aquifer downgradient of an ISR mining area to attenuate the transport of uranium and other problem constituents that are mobilized by the mining process. Such an evaluation can help inform both regulators and the mining industry as to how much restoration of the mined ore zone is necessary to achieve regulatory compliance at various distances downgradient of the mining zone even if complete restoration of the ore zone proves to be difficult or impossible. Three single-well push-pull tests and one cross-well test were conducted in which water from an unrestored, previously-mined ore zone was injected into an unmined ore zone that served as a geochemical proxy for the downgradient aquifer. In all tests, non-reactive tracers were injected with the previously-mined ore zone water to allow the transport of uranium and other constituents to be compared to that of the nonreactive species. In the single-well tests, it was shown that the recovery of uranium relative to the nonreactive tracers ranged from 12-25%, suggesting significant attenuation capacity of the aquifer. In the cross-well test, selenate, molybdate and metavanadate were injected with the unrestored water to provide information on the transport of these potentially-problematic anionic constituents. In addition to the species-specific transport information, this test provided valuable constraints on redox conditions within the system, as redox couples involving these species collectively bracket the predicted transition redox potential for the U(VI)/U(IV) couple. Reduction should provide much longer-lasting immobilization of constituents than adsorption, especially given the inherent reducing characteristics of roll-front systems.

Anthropogenic Increase Of Soil Erosion In The Gangetic Plain Revealed By Geochemical Budget Of Erosion

NASA Astrophysics Data System (ADS)

Galy, V.; France-Lanord, C.; Galy, A.; Gaillardet, J.

2007-12-01

Tectonic and climatic factors are the key natural variables controlling the erosion through complex interactions. Nonetheless, over the last few hundred years, human activity also exerts a dominant control in response to extensive land use. The geochemical budget of erosion allows the balance between the different erosion processes to be quantified. The chemical composition of river sediment results from the chemical composition of the source rock modified by (1) weathering reactions occurring during erosion and (2) physical segregation during transport. If erosion is at steady state, the difference between the chemical composition of source rocks and that of river sediments must therefore be counterbalanced by the dissolved flux. However, climatic variations or anthropic impact can induce changes in the erosion distribution in a given basin resulting in non steady state erosion. Using a mass balance approach, the comparison of detailed geochemical data on river sediments with the current flux of dissolved elements allows the steady state hypothesis to be tested. In this study, we present a geochemical budget of weathering for the Ganga basin, one of the most densely populated basin in the world, based on detailed sampling of Himalayan rivers and of the Ganga in the delta. Sampling includes depth profile in the river, to assess the variability generated by transport processes. Himalayan river sediments are described by the dilution of an aluminous component (micas + clays + feldspars) by quartz. Ganga sediments on the other hand correspond to the mixing of bedload, similar to coarse Himalayan sediments, with an aluminous component highly depleted in alkaline elements. Compared with the dissolved flux, the depletion of alkaline elements in Ganga sediments shows that the alkaline weathering budget is imbalanced. This imbalance results from an overabundance of fine soil material in the Ganga sediment relative to other less weathered material directly derived from Himalaya. Based on the average composition of the suspended load and of floodplain soils, we estimate that 250x106 t/yr i.e. 5 t/ha/yr is eroded from soil surfaces of the Ganga floodplain. This enhanced soil erosion is likely triggered by intense deforestation and change in land use due to increasing human activity in the basin.

Dust-Particle Transport in Tokamak Edge Plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pigarov, A Y; Krasheninnikov, S I; Soboleva, T K

2005-09-12

Dust particulates in the size range of 10nm-100{micro}m are found in all fusion devices. Such dust can be generated during tokamak operation due to strong plasma/material-surface interactions. Some recent experiments and theoretical estimates indicate that dust particles can provide an important source of impurities in the tokamak plasma. Moreover, dust can be a serious threat to the safety of next-step fusion devices. In this paper, recent experimental observations on dust in fusion devices are reviewed. A physical model for dust transport simulation, and a newly developed code DUSTT, are discussed. The DUSTT code incorporates both dust dynamics due to comprehensivemore » dust-plasma interactions as well as the effects of dust heating, charging, and evaporation. The code tracks test dust particles in realistic plasma backgrounds as provided by edge-plasma transport codes. Results are presented for dust transport in current and next-step tokamaks. The effect of dust on divertor plasma profiles and core plasma contamination is examined.« less

Application of a flexible lattice Boltzmann method based simulation tool for modelling physico-chemical processes at different scales

NASA Astrophysics Data System (ADS)

Patel, Ravi A.; Perko, Janez; Jacques, Diederik

2017-04-01

Often, especially in the disciplines related to natural porous media, such as for example vadoze zone or aquifer hydrology or contaminant transport, the relevant spatial and temporal scales on which we need to provide information is larger than the scale where the processes actually occur. Usual techniques used to deal with these problems assume the existence of a REV. However, in order to understand the behavior on larger scales it is important to downscale the problem onto the relevant scale of the processes. Due to the limitations of resources (time, memory) the downscaling can only be made up to the certain lower scale. At this lower scale still several scales may co-exist - the scale which can be explicitly described and a scale which needs to be conceptualized by effective properties. Hence, models which are supposed to provide effective properties on relevant scales should therefor be flexible enough to represent complex pore-structure by explicit geometry on one side, and differently defined processes (e.g. by the effective properties) which emerge on lower scale. In this work we present the state-of-the-art lattice Boltzmann method based simulation tool applicable to advection-diffusion equation coupled to geochemical processes. The lattice Boltzmann transport solver can be coupled with an external geochemical solver which allows to account for a wide range of geochemical reaction networks through thermodynamic databases. The applicability to multiphase systems is ongoing. We provide several examples related to the calculation of an effective diffusion properties, permeability and effective reaction rate based on a continuum scale based on the pore scale geometry.

Direct coupling of a genome-scale microbial in silico model and a groundwater reactive transport model.

PubMed

Fang, Yilin; Scheibe, Timothy D; Mahadevan, Radhakrishnan; Garg, Srinath; Long, Philip E; Lovley, Derek R

2011-03-25

The activity of microorganisms often plays an important role in dynamic natural attenuation or engineered bioremediation of subsurface contaminants, such as chlorinated solvents, metals, and radionuclides. To evaluate and/or design bioremediated systems, quantitative reactive transport models are needed. State-of-the-art reactive transport models often ignore the microbial effects or simulate the microbial effects with static growth yield and constant reaction rate parameters over simulated conditions, while in reality microorganisms can dynamically modify their functionality (such as utilization of alternative respiratory pathways) in response to spatial and temporal variations in environmental conditions. Constraint-based genome-scale microbial in silico models, using genomic data and multiple-pathway reaction networks, have been shown to be able to simulate transient metabolism of some well studied microorganisms and identify growth rate, substrate uptake rates, and byproduct rates under different growth conditions. These rates can be identified and used to replace specific microbially-mediated reaction rates in a reactive transport model using local geochemical conditions as constraints. We previously demonstrated the potential utility of integrating a constraint-based microbial metabolism model with a reactive transport simulator as applied to bioremediation of uranium in groundwater. However, that work relied on an indirect coupling approach that was effective for initial demonstration but may not be extensible to more complex problems that are of significant interest (e.g., communities of microbial species and multiple constraining variables). Here, we extend that work by presenting and demonstrating a method of directly integrating a reactive transport model (FORTRAN code) with constraint-based in silico models solved with IBM ILOG CPLEX linear optimizer base system (C library). The models were integrated with BABEL, a language interoperability tool. The modeling system is designed in such a way that constraint-based models targeting different microorganisms or competing organism communities can be easily plugged into the system. Constraint-based modeling is very costly given the size of a genome-scale reaction network. To save computation time, a binary tree is traversed to examine the concentration and solution pool generated during the simulation in order to decide whether the constraint-based model should be called. We also show preliminary results from the integrated model including a comparison of the direct and indirect coupling approaches and evaluated the ability of the approach to simulate field experiment. Published by Elsevier B.V.

Study of no-man's land physics in the total-f gyrokinetic code XGC1

NASA Astrophysics Data System (ADS)

Ku, Seung Hoe; Chang, C. S.; Lang, J.

2014-10-01

While the ``transport shortfall'' in the ``no-man's land'' has been observed often in delta-f codes, it has not yet been observed in the global total-f gyrokinetic particle code XGC1. Since understanding the interaction between the edge and core transport appears to be a critical element in the prediction for ITER performance, understanding the no-man's land issue is an important physics research topic. Simulation results using the Holland case will be presented and the physics causing the shortfall phenomenon will be discussed. Nonlinear nonlocal interaction of turbulence, secondary flows, and transport appears to be the key.

Development of Safety Analysis Code System of Beam Transport and Core for Accelerator Driven System

NASA Astrophysics Data System (ADS)

Aizawa, Naoto; Iwasaki, Tomohiko

2014-06-01

Safety analysis code system of beam transport and core for accelerator driven system (ADS) is developed for the analyses of beam transients such as the change of the shape and position of incident beam. The code system consists of the beam transport analysis part and the core analysis part. TRACE 3-D is employed in the beam transport analysis part, and the shape and incident position of beam at the target are calculated. In the core analysis part, the neutronics, thermo-hydraulics and cladding failure analyses are performed by the use of ADS dynamic calculation code ADSE on the basis of the external source database calculated by PHITS and the cross section database calculated by SRAC, and the programs of the cladding failure analysis for thermoelastic and creep. By the use of the code system, beam transient analyses are performed for the ADS proposed by Japan Atomic Energy Agency. As a result, the rapid increase of the cladding temperature happens and the plastic deformation is caused in several seconds. In addition, the cladding is evaluated to be failed by creep within a hundred seconds. These results have shown that the beam transients have caused a cladding failure.

Use of FEC coding to improve statistical multiplexing performance for video transport over ATM networks

NASA Astrophysics Data System (ADS)

Kurceren, Ragip; Modestino, James W.

1998-12-01

The use of forward error-control (FEC) coding, possibly in conjunction with ARQ techniques, has emerged as a promising approach for video transport over ATM networks for cell-loss recovery and/or bit error correction, such as might be required for wireless links. Although FEC provides cell-loss recovery capabilities it also introduces transmission overhead which can possibly cause additional cell losses. A methodology is described to maximize the number of video sources multiplexed at a given quality of service (QoS), measured in terms of decoded cell loss probability, using interlaced FEC codes. The transport channel is modelled as a block interference channel (BIC) and the multiplexer as single server, deterministic service, finite buffer supporting N users. Based upon an information-theoretic characterization of the BIC and large deviation bounds on the buffer overflow probability, the described methodology provides theoretically achievable upper limits on the number of sources multiplexed. Performance of specific coding techniques using interlaced nonbinary Reed-Solomon (RS) codes and binary rate-compatible punctured convolutional (RCPC) codes is illustrated.

Clean Energy in City Codes: A Baseline Analysis of Municipal Codification across the United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cook, Jeffrey J.; Aznar, Alexandra; Dane, Alexander

Municipal governments in the United States are well positioned to influence clean energy (energy efficiency and alternative energy) and transportation technology and strategy implementation within their jurisdictions through planning, programs, and codification. Municipal governments are leveraging planning processes and programs to shape their energy futures. There is limited understanding in the literature related to codification, the primary way that municipal governments enact enforceable policies. The authors fill the gap in the literature by documenting the status of municipal codification of clean energy and transportation across the United States. More directly, we leverage online databases of municipal codes to develop nationalmore » and state-specific representative samples of municipal governments by population size. Our analysis finds that municipal governments with the authority to set residential building energy codes within their jurisdictions frequently do so. In some cases, communities set codes higher than their respective state governments. Examination of codes across the nation indicates that municipal governments are employing their code as a policy mechanism to address clean energy and transportation.« less

ITS Version 6 : the integrated TIGER series of coupled electron/photon Monte Carlo transport codes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franke, Brian Claude; Kensek, Ronald Patrick; Laub, Thomas William

2008-04-01

ITS is a powerful and user-friendly software package permitting state-of-the-art Monte Carlo solution of lineartime-independent coupled electron/photon radiation transport problems, with or without the presence of macroscopic electric and magnetic fields of arbitrary spatial dependence. Our goal has been to simultaneously maximize operational simplicity and physical accuracy. Through a set of preprocessor directives, the user selects one of the many ITS codes. The ease with which the makefile system is applied combines with an input scheme based on order-independent descriptive keywords that makes maximum use of defaults and internal error checking to provide experimentalists and theorists alike with a methodmore » for the routine but rigorous solution of sophisticated radiation transport problems. Physical rigor is provided by employing accurate cross sections, sampling distributions, and physical models for describing the production and transport of the electron/photon cascade from 1.0 GeV down to 1.0 keV. The availability of source code permits the more sophisticated user to tailor the codes to specific applications and to extend the capabilities of the codes to more complex applications. Version 6, the latest version of ITS, contains (1) improvements to the ITS 5.0 codes, and (2) conversion to Fortran 90. The general user friendliness of the software has been enhanced through memory allocation to reduce the need for users to modify and recompile the code.« less

The effect of a confining unit on the geochemical evolution of ground water in the Upper Floridan aquifer system

USGS Publications Warehouse

Wicks, C.M.; Herman, J.S.

1994-01-01

In west-central Florida, sections of the Upper Floridan aquifer system range in character from confined to leaky to unconfined. The confining unit is the Hawthorn Formation, a clay-rich sequence. The presence or absence of the Hawthorn Formation affects the geochemical evolution of the ground water in the Upper Floridan aquifer system. Mass-balance and mass-transfer models suggest that, in unconfined areas, the geochemical reactions are dolomite dissolution, ion exchange (Mg for Na, K), sulfate reduction, calcite dissolution, and CO2 exchange. In the areas in which the Hawthorn Formation is leaky, the evolution of the ground water is accounted for by ion exchange, sulfate reduction, calcite dissolution, and CO2 exchange. In the confined areas, no ion exchange and only limited sulfate reduction occur, and the chemical character of the ground water is consistent with dolomite and gypsum dissolution, calcite precipitation, and CO2 ingassing. The Hawthorn Formation acts both as a physical barrier to the transport of CO2 and organic matter and as a source of ion-exchange sites, but the carbonate-mineral reactions are largely unaffected by the extent of confinement of the Upper Floridan aquifer. ?? 1994.

Trace element geochemistry in archaeological sites.

PubMed

Jenkins, D A

1989-06-01

Man can leave a geochemical imprint on an archaeological site in several ways. In common with other components of the biosphere, there is a selective enrichment of elements in his body tissues which, upon death and burial, may lead to detectable anomalies. Of elements concentrated in this way P is the most obvious, but Sn could be another possibility worth further investigation. There has been particular geochemical impact due to the progressive use of such metals as Ag, Au, Cu, Pb and Zn during successive cultural stages. Anomalies may thus arise due to recognisable transported ore, slags or artefacts, although there has also often been cryptic redispersion of the metals within a site. Charcoal is one of the commoner finds during excavations, and it has the ability to adsorb and concentrate metals progressively from percolating solutions since the time of its burial: with careful interpretation its analysis may thus provide a valuable historical record, as is illustrated by material from several sites in North Wales. Providing care is taken to interpret results in their particular geochemical and pedochemical context, trace element analysis may thus offer a useful insight into the history of man's activities in an archaeological site.

Geochemical evolution of groundwater in southern Bengal Basin: The example of Rajarhat and adjoining areas, West Bengal, India

NASA Astrophysics Data System (ADS)

Sahu, Paulami; Sikdar, P. K.; Chakraborty, Surajit

2016-02-01

Detailed geochemical analysis of groundwater beneath 1223 km2 area in southern Bengal Basin along with statistical analysis on the chemical data was attempted, to develop a better understanding of the geochemical processes that control the groundwater evolution in the deltaic aquifer of the region. Groundwater is categorized into three types: `excellent', `good' and `poor' and seven hydrochemical facies are assigned to three broad types: `fresh', `mixed' and `brackish' waters. The `fresh' water type dominated with sodium indicates active flushing of the aquifer, whereas chloride-rich `brackish' groundwater represents freshening of modified connate water. The `mixed' type groundwater has possibly evolved due to hydraulic mixing of `fresh' and `brackish' waters. Enrichment of major ions in groundwater is due to weathering of feldspathic and ferro-magnesian minerals by percolating water. The groundwater of Rajarhat New Town (RNT) and adjacent areas in the north and southeast is contaminated with arsenic. Current-pumping may induce more arsenic to flow into the aquifers of RNT and Kolkata cities. Future large-scale pumping of groundwater beneath RNT can modify the hydrological system, which may transport arsenic and low quality water from adjacent aquifers to presently unpolluted aquifer.

Path Toward a Unifid Geometry for Radiation Transport

NASA Technical Reports Server (NTRS)

Lee, Kerry; Barzilla, Janet; Davis, Andrew; Zachmann

2014-01-01

The Direct Accelerated Geometry for Radiation Analysis and Design (DAGRAD) element of the RadWorks Project under Advanced Exploration Systems (AES) within the Space Technology Mission Directorate (STMD) of NASA will enable new designs and concepts of operation for radiation risk assessment, mitigation and protection. This element is designed to produce a solution that will allow NASA to calculate the transport of space radiation through complex computer-aided design (CAD) models using the state-of-the-art analytic and Monte Carlo radiation transport codes. Due to the inherent hazard of astronaut and spacecraft exposure to ionizing radiation in low-Earth orbit (LEO) or in deep space, risk analyses must be performed for all crew vehicles and habitats. Incorporating these analyses into the design process can minimize the mass needed solely for radiation protection. Transport of the radiation fields as they pass through shielding and body materials can be simulated using Monte Carlo techniques or described by the Boltzmann equation, which is obtained by balancing changes in particle fluxes as they traverse a small volume of material with the gains and losses caused by atomic and nuclear collisions. Deterministic codes that solve the Boltzmann transport equation, such as HZETRN [high charge and energy transport code developed by NASA Langley Research Center (LaRC)], are generally computationally faster than Monte Carlo codes such as FLUKA, GEANT4, MCNP(X) or PHITS; however, they are currently limited to transport in one dimension, which poorly represents the secondary light ion and neutron radiation fields. NASA currently uses HZETRN space radiation transport software, both because it is computationally efficient and because proven methods have been developed for using this software to analyze complex geometries. Although Monte Carlo codes describe the relevant physics in a fully three-dimensional manner, their computational costs have thus far prevented their widespread use for analysis of complex CAD models, leading to the creation and maintenance of toolkit-specific simplistic geometry models. The work presented here builds on the Direct Accelerated Geometry Monte Carlo (DAGMC) toolkit developed for use with the Monte Carlo N-Particle (MCNP) transport code. The workflow for achieving radiation transport on CAD models using MCNP and FLUKA has been demonstrated and the results of analyses on realistic spacecraft/habitats will be presented. Future work is planned that will further automate this process and enable the use of multiple radiation transport codes on identical geometry models imported from CAD. This effort will enhance the modeling tools used by NASA to accurately evaluate the astronaut space radiation risk and accurately determine the protection provided by as-designed exploration mission vehicles and habitats

Boltzmann Transport Code Update: Parallelization and Integrated Design Updates

NASA Technical Reports Server (NTRS)

Heinbockel, J. H.; Nealy, J. E.; DeAngelis, G.; Feldman, G. A.; Chokshi, S.

2003-01-01

The on going efforts at developing a web site for radiation analysis is expected to result in an increased usage of the High Charge and Energy Transport Code HZETRN. It would be nice to be able to do the requested calculations quickly and efficiently. Therefore the question arose, "Could the implementation of parallel processing speed up the calculations required?" To answer this question two modifications of the HZETRN computer code were created. The first modification selected the shield material of Al(2219) , then polyethylene and then Al(2219). The modified Fortran code was labeled 1SSTRN.F. The second modification considered the shield material of CO2 and Martian regolith. This modified Fortran code was labeled MARSTRN.F.

Magma transport and metasomatism in the mantle: a critical review of current geochemical models

USGS Publications Warehouse

Nielson, J.E.; Wilshire, H.G.

1993-01-01

Conflicting geochemical models of metasomatic interactions between mantle peridotite and melt all assume that mantle reactions reflect chromatographic processes. Examination of field, petrological, and compositional data suggests that the hypothesis of chromatographic fractionation based on the supposition of large-scale percolative processes needs review and revision. Well-constrained rock and mineral data from xenoliths indicate that many elements that behave incompatibly in equilibrium crystallization processes are absorbed immediately when melts emerge from conduits into depleted peridotite. After reacting to equilibrium with the peridotite, melt that percolates away from the conduit is largely depleted of incompatible elements. Continued addition of melts extends the zone of equilibrium farther from the conduit. Such a process resembles ion-exchange chromatography for H2O purification, rather than the model of chromatographic species separation. -from Authors

TRANSP: status and planning

NASA Astrophysics Data System (ADS)

Andre, R.; Carlsson, J.; Gorelenkova, M.; Jardin, S.; Kaye, S.; Poli, F.; Yuan, X.

2016-10-01

TRANSP is an integrated interpretive and predictive transport analysis tool that incorporates state of the art heating/current drive sources and transport models. The treatments and transport solvers are becoming increasingly sophisticated and comprehensive. For instance, the ISOLVER component provides a free boundary equilibrium solution, while the PT- SOLVER transport solver is especially suited for stiff transport models such as TGLF. TRANSP incorporates high fidelity heating and current drive source models, such as NUBEAM for neutral beam injection, the beam tracing code TORBEAM for EC, TORIC for ICRF, the ray tracing TORAY and GENRAY for EC. The implementation of selected components makes efficient use of MPI for speed up of code calculations. Recently the GENRAY-CQL3D solver for modeling of LH heating and current drive has been implemented and currently being extended to multiple antennas, to allow modeling of EAST discharges. Also, GENRAY+CQL3D is being extended to the use of EC/EBW and of HHFW for NSTX-U. This poster will describe present uses of the code worldwide, as well as plans for upgrading the physics modules and code framework. Work supported by the US Department of Energy under DE-AC02-CH0911466.

BRYNTRN: A baryon transport model

NASA Technical Reports Server (NTRS)

Wilson, John W.; Townsend, Lawrence W.; Nealy, John E.; Chun, Sang Y.; Hong, B. S.; Buck, Warren W.; Lamkin, S. L.; Ganapol, Barry D.; Khan, Ferdous; Cucinotta, Francis A.

1989-01-01

The development of an interaction data base and a numerical solution to the transport of baryons through an arbitrary shield material based on a straight ahead approximation of the Boltzmann equation are described. The code is most accurate for continuous energy boundary values, but gives reasonable results for discrete spectra at the boundary using even a relatively coarse energy grid (30 points) and large spatial increments (1 cm in H2O). The resulting computer code is self-contained, efficient and ready to use. The code requires only a very small fraction of the computer resources required for Monte Carlo codes.

ecode - Electron Transport Algorithm Testing v. 1.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franke, Brian C.; Olson, Aaron J.; Bruss, Donald Eugene

2016-10-05

ecode is a Monte Carlo code used for testing algorithms related to electron transport. The code can read basic physics parameters, such as energy-dependent stopping powers and screening parameters. The code permits simple planar geometries of slabs or cubes. Parallelization consists of domain replication, with work distributed at the start of the calculation and statistical results gathered at the end of the calculation. Some basic routines (such as input parsing, random number generation, and statistics processing) are shared with the Integrated Tiger Series codes. A variety of algorithms for uncertainty propagation are incorporated based on the stochastic collocation and stochasticmore » Galerkin methods. These permit uncertainty only in the total and angular scattering cross sections. The code contains algorithms for simulating stochastic mixtures of two materials. The physics is approximate, ranging from mono-energetic and isotropic scattering to screened Rutherford angular scattering and Rutherford energy-loss scattering (simple electron transport models). No production of secondary particles is implemented, and no photon physics is implemented.« less

MCNP capabilities for nuclear well logging calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forster, R.A.; Little, R.C.; Briesmeister, J.F.

The Los Alamos Radiation Transport Code System (LARTCS) consists of state-of-the-art Monte Carlo and discrete ordinates transport codes and data libraries. This paper discusses how the general-purpose continuous-energy Monte Carlo code MCNP ({und M}onte {und C}arlo {und n}eutron {und p}hoton), part of the LARTCS, provides a computational predictive capability for many applications of interest to the nuclear well logging community. The generalized three-dimensional geometry of MCNP is well suited for borehole-tool models. SABRINA, another component of the LARTCS, is a graphics code that can be used to interactively create a complex MCNP geometry. Users can define many source and tallymore » characteristics with standard MCNP features. The time-dependent capability of the code is essential when modeling pulsed sources. Problems with neutrons, photons, and electrons as either single particle or coupled particles can be calculated with MCNP. The physics of neutron and photon transport and interactions is modeled in detail using the latest available cross-section data.« less

Differential Cross Section Kinematics for 3-dimensional Transport Codes

NASA Technical Reports Server (NTRS)

Norbury, John W.; Dick, Frank

2008-01-01

In support of the development of 3-dimensional transport codes, this paper derives the relevant relativistic particle kinematic theory. Formulas are given for invariant, spectral and angular distributions in both the lab (spacecraft) and center of momentum frames, for collisions involving 2, 3 and n - body final states.

49 CFR 171.25 - Additional requirements for the use of the IMDG Code.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 176 of this subchapter. (3) Packages containing primary lithium batteries and cells that are transported in accordance with Special Provision 188 of the IMDG Code must be marked “PRIMARY LITHIUM BATTERIES—FORBIDDEN FOR TRANSPORT ABOARD PASSENGER AIRCRAFT” or “LITHIUM METAL BATTERIES—FORBIDDEN FOR...

49 CFR 171.25 - Additional requirements for the use of the IMDG Code.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 176 of this subchapter. (3) Packages containing primary lithium batteries and cells that are transported in accordance with Special Provision 188 of the IMDG Code must be marked “PRIMARY LITHIUM BATTERIES—FORBIDDEN FOR TRANSPORT ABOARD PASSENGER AIRCRAFT” or “LITHIUM METAL BATTERIES—FORBIDDEN FOR...

49 CFR 171.25 - Additional requirements for the use of the IMDG Code.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 176 of this subchapter. (3) Packages containing primary lithium batteries and cells that are transported in accordance with Special Provision 188 of the IMDG Code must be marked “PRIMARY LITHIUM BATTERIES—FORBIDDEN FOR TRANSPORT ABOARD PASSENGER AIRCRAFT” or “LITHIUM METAL BATTERIES—FORBIDDEN FOR...

Three-Dimensional Modeling of the Reactive Transport of CO2 and Its Impact on Geomechanical Properties of Reservoir Rocks and Seals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Ba Nghiep; Hou, Zhangshuan; Bacon, Diana H.

This article develops a novel multiscale modeling approach to analyze CO2 reservoirs using Pacific Northwest National Laboratory’s STOMP-CO2-R code that is interfaced with the ABAQUS® finite element package. The STOMP-CO2-R/ABAQUS® sequentially coupled simulator accounts for the reactive transport of CO2 causing mineral composition changes that modify the geomechanical properties of reservoir rocks and seals. Formation rocks’ elastic properties that vary during CO2 injection and govern the poroelastic behavior of rocks are modeled by an Eshelby-Mori-Tanka approach (EMTA) implemented in ABAQUS® via user-subroutines. The computational tool incorporates the change in rock permeability due to both geochemistry and geomechanics. A three-dimensional (3D)more » STOMP-CO2-R model for a model CO2 reservoir containing a vertical fault is built to analyze a formation containing a realistic geochemical reaction network with 5 minerals: albite, anorthite, calcite, kaolinite and quartz. A 3D ABAQUS® model that maps the above STOMP-CO2-R model is built for the analysis using STOMP-CO2-R/ABAQUS®. The results show that the changes in volume fraction of minerals include dissolution of anorthite, precipitation of calcite and kaolinite, with little change in the albite volume fraction. After a long period of CO2 injection the mineralogical and geomechanical changes significantly reduced the permeability and elastic modulus of the reservoir (between the base and caprock) in front of the fault leading to a reduction of the pressure margin to fracture at and beyond the injection location. The impact of reactive transport of CO2 on the geomechanical properties of reservoir rocks and seals are studied in terms of mineral composition changes that directly affect the rock stiffness, stress and strain distributions as well as the pressure margin to fracture.« less

Integrating Thermodynamic Models in Geodynamic Simulations: The Example of the Community Software ASPECT

NASA Astrophysics Data System (ADS)

Dannberg, J.; Heister, T.; Grove, R. R.; Gassmoeller, R.; Spiegelman, M. W.; Bangerth, W.

2017-12-01

Earth's surface shows many features whose genesis can only be understood through the interplay of geodynamic and thermodynamic models. This is particularly important in the context of melt generation and transport: Mantle convection determines the distribution of temperature and chemical composition, the melting process itself is then controlled by the thermodynamic relations and in turn influences the properties and the transport of melt. Here, we present our extension of the community geodynamics code ASPECT, which solves the equations of coupled magma/mantle dynamics, and allows to integrate different parametrizations of reactions and phase transitions: They may alternatively be implemented as simple analytical expressions, look-up tables, or computed by a thermodynamics software. As ASPECT uses a variety of numerical methods and solvers, this also gives us the opportunity to compare different approaches of modelling the melting process. In particular, we will elaborate on the spatial and temporal resolution that is required to accurately model phase transitions, and show the potential of adaptive mesh refinement when applied to melt generation and transport. We will assess the advantages and disadvantages of iterating between fluid dynamics and chemical reactions derived from thermodynamic models within each time step, or decoupling them, allowing for different time step sizes. Beyond that, we will expand on the functionality required for an interface between computational thermodynamics and fluid dynamics models from the geodynamics side. Finally, using a simple example of melting of a two-phase, two-component system, we compare different time-stepping and solver schemes in terms of accuracy and efficiency, in dependence of the time scales of fluid flow and chemical reactions relative to each other. Our software provides a framework to integrate thermodynamic models in high resolution, 3d simulations of coupled magma/mantle dynamics, and can be used as a tool to study links between physical processes and geochemical signals in the Earth.

Identifying functional zones of denitrification in heterogeneous aquifer systems by numerical simulations - a case study

NASA Astrophysics Data System (ADS)

Jang, E.; Kalbacher, T.; He, W.; Shao, H.; Schueth, C.; Kolditz, O.

2014-12-01

Nitrate contamination in shallow groundwater is still one of the common problems in many countries. Because of its high solubility and anionic nature, nitrate can easily leach through soil and persist in groundwater for decades. High nitrate concentration has been suggested as a major cause of accelerated eutrophication, methemoglobinemia and gastric cancer. There are several factors influencing the fate of nitrate in groundwater system, which is e.g. distribution of N- sources to soil and groundwater, distribution and amount of reactive substances maintaining denitrification, rate of nitrate degradation and its kinetics, and geological characteristics of the aquifer. Nitrate transport and redox transformation processes are closely linked to complex and spatially distributed physical and chemical interaction, therefore it is difficult to predict and quantify in the field and laboratory experiment. Models can play a key role in elucidation of nitrate reduction pathway in groundwater system and in the design and evaluation of field tests to investigate in situ remediation technologies as well. The goal of the current study is to predict groundwater vulnerability to nitrate, to identify functional zones of denitrification in heterogeneous aquifer systems and to describe the uncertainty of the predictions due to scale effects. For this aim, we developed a kinetic model using multi-component mass transport code OpenGeoSys coupling with IPhreeqc module of the geochemical solver PHREEQC. The developed model included sequential aerobic and nitrate-based respiration, multi-Monod kinetics, multi-species biogeochemical reactions, and geological characteristics of the groundwater aquifer. Moreover water-rock interaction such as secondary mineral precipitation was also included in this model. In this presentation, we focused on the general modelling approach and present the simulation results of nitrate transport simulation in a hypothetical aquifer systems based on data from Hessian Ried, an important groundwater resource for the densely populated Rhine-Main region in Germany.

Nonperturbative methods in HZE ion transport

NASA Technical Reports Server (NTRS)

Wilson, John W.; Badavi, Francis F.; Costen, Robert C.; Shinn, Judy L.

1993-01-01

A nonperturbative analytic solution of the high charge and energy (HZE) Green's function is used to implement a computer code for laboratory ion beam transport. The code is established to operate on the Langley Research Center nuclear fragmentation model used in engineering applications. Computational procedures are established to generate linear energy transfer (LET) distributions for a specified ion beam and target for comparison with experimental measurements. The code is highly efficient and compares well with the perturbation approximations.

Geochemistry and the Understanding of Groundwater Systems

NASA Astrophysics Data System (ADS)

Glynn, P. D.; Plummer, L. N.; Weissmann, G. S.; Stute, M.

2009-12-01

Geochemical techniques and concepts have made major contributions to the understanding of groundwater systems. Advances continue to be made through (1) development of measurement and characterization techniques, (2) improvements in computer technology, networks and numerical modeling, (3) investigation of coupled geologic, hydrologic, geochemical and biologic processes, and (4) scaling of individual observations, processes or subsystem models into larger coherent model frameworks. Many applications benefit from progress in these areas, such as: (1) understanding paleoenvironments, in particular paleoclimate, through the use of groundwater archives, (2) assessing the sustainability (recharge and depletion) of groundwater resources, and (3) their vulnerability to contamination, (4) evaluating the capacity and consequences of subsurface waste isolation (e.g. geologic carbon sequestration, nuclear and chemical waste disposal), (5) assessing the potential for mitigation/transformation of anthropogenic contaminants in groundwater systems, and (6) understanding the effect of groundwater lag times in ecosystem-scale responses to natural events, land-use changes, human impacts, and remediation efforts. Obtaining “representative” groundwater samples is difficult and progress in obtaining “representative” samples, or interpreting them, requires new techniques in characterizing groundwater system heterogeneity. Better characterization and simulation of groundwater system heterogeneity (both physical and geochemical) is critical to interpreting the meaning of groundwater “ages”; to understanding and predicting groundwater flow, solute transport, and geochemical evolution; and to quantifying groundwater recharge and discharge processes. Research advances will also come from greater use and progress (1) in the application of environmental tracers to ground water dating and in the analysis of new geochemical tracers (e.g. compound specific isotopic analyses, noble gas isotopes, analyses of natural organic tracers), (2) in inverse geochemical and hydrological modeling, (3) in the understanding and simulation of coupled biological, geological, geochemical and hydrological processes, and (4) in the description and quantification of processes occurring at the boundaries of groundwater systems (e.g. unsaturated zone processes, groundwater/surface water interactions, impacts of changing geomorphology and vegetation). Improvements are needed in the integration of widely diverse information. Better techniques are needed to construct coherent conceptual frameworks from individual observations, simulated or reconstructed information, process models, and intermediate scale models. Iterating between data collection, interpretation, and the application of forward, inverse, and statistical modeling tools is likely to provide progress in this area. Quantifying groundwater system processes by using an open-system thermodynamic approach in a common mass- and energy-flow framework will also facilitate comparison and understanding of diverse processes.

Geochemistry of groundwater in the Beaver and Camas Creek drainage basins, eastern Idaho

USGS Publications Warehouse

Rattray, Gordon W.; Ginsbach, Michael L.

2014-01-01

The U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy, is studying the fate and transport of waste solutes in the eastern Snake River Plain (ESRP) aquifer at the Idaho National Laboratory (INL) in eastern Idaho. This effort requires an understanding of the natural and anthropogenic geochemistry of groundwater at the INL and of the important physical and chemical processes controlling the geochemistry. In this study, the USGS applied geochemical modeling to investigate the geochemistry of groundwater in the Beaver and Camas Creek drainage basins, which provide groundwater recharge to the ESRP aquifer underlying the northeastern part of the INL. Data used in this study include petrology and mineralogy from 2 sediment and 3 rock samples, and water-quality analyses from 4 surface-water and 18 groundwater samples. The mineralogy of the sediment and rock samples was analyzed with X-ray diffraction, and the mineralogy and petrology of the rock samples were examined in thin sections. The water samples were analyzed for field parameters, major ions, silica, nutrients, dissolved organic carbon, trace elements, tritium, and the stable isotope ratios of hydrogen, oxygen, carbon, sulfur, and nitrogen. Groundwater geochemistry was influenced by reactions with rocks of the geologic terranes—carbonate rocks, rhyolite, basalt, evaporite deposits, and sediment comprised of all of these rocks. Agricultural practices near and south of Dubois and application of road anti-icing liquids on U.S. Interstate Highway 15 were likely sources of nitrate, chloride, calcium, and magnesium to groundwater. Groundwater geochemistry was successfully modeled in the alluvial aquifer in Camas Meadows and the ESRP fractured basalt aquifer using the geochemical modeling code PHREEQC. The primary geochemical processes appear to be precipitation or dissolution of calcite and dissolution of silicate minerals. Dissolution of evaporite minerals, associated with Pleistocene Lake Terreton, is an important contributor of solutes in the Mud Lake-Dubois area. Oxidation-reduction reactions are important influences on the chemistry of groundwater at Camas Meadows and the Camas National Wildlife Refuge. In addition, mixing of different groundwaters or surface water with groundwater appears to be an important physical process influencing groundwater geochemistry in much of the study area, and evaporation may be an important physical process influencing the groundwater geochemistry of the Camas National Wildlife Refuge. The mass-balance modeling results from this study provide an explanation of the natural geochemistry of groundwater in the ESRP aquifer northeast of the INL, and thus provide a starting point for evaluating the natural and anthropogenic geochemistry of groundwater at the INL.

Geochemical Identification of Windblown Dust Deposits in the Upper Permian Brushy Canyon Formation, Southern New Mexico

NASA Astrophysics Data System (ADS)

Tice, M. M.; Motanated, K.; Weiss, R.

2009-12-01

Windblown dust is a potentially important but difficult-to-quantify source of siliciclastics for sedimentary basins worldwide. Positively identifying windblown deposits requires distinguishing them from other low density suspension transport deposits. For instance, laminated very fine grained sandstones and siltstones of the Upper Permian Brushy Canyon Formation have been variously interpreted as 1) the deposits of slow-moving, low-density turbidity currents, 2) distal overbank deposits of turbidity currents, 3) the deposits of turbulent suspensions transported across a pycnocline (interflows), and 4) windblown dust. This facies forms the bulk of Brushy Canyon Formation slope deposits, so understanding its origin is critical to understanding the evolution of the basin as a whole. We use a geochemical mapping technique (x-ray fluorescence microscopy) to show that these rocks are up to two times enriched in very fine sand sized zircon and rutile grains relative to Bouma A divisions of interbedded turbidites, suggesting substantial turbulence during transport. However, in contrast with the A divisions, the laminated sandstones and siltstones never show evidence of scour or amalgamation, implying that flow turbulence did not interact with underlying beds. Moreover, proximal loess deposits are often characterized by elevated Zr/Al2O3. These observations are most consistent with windblown interpretations for Brushy Canyon Formation slope sediments, and suggest that evolution of this early deepwater slope system was controlled largely by short-distance aeolian transport of very fine sand and silt from the coast. Heavy mineral incorporation into Brushy Canyon Formation slope deposits as reflected in laminae-scale bulk Zr and Ti abundances may preserve a long-term record of local wind intensity during the Upper Permian.

User's guide to PHREEQC (Version 2) : a computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations

USGS Publications Warehouse

Parkhurst, David L.; Appelo, C.A.J.

1999-01-01

PHREEQC version 2 is a computer program written in the C programming language that is designed to perform a wide variety of low-temperature aqueous geochemical calculations. PHREEQC is based on an ion-association aqueous model and has capabilities for (1) speciation and saturation-index calculations; (2) batch-reaction and one-dimensional (1D) transport calculations involving reversible reactions, which include aqueous, mineral, gas, solid-solution, surface-complexation, and ion-exchange equilibria, and irreversible reactions, which include specified mole transfers of reactants, kinetically controlled reactions, mixing of solutions, and temperature changes; and (3) inverse modeling, which finds sets of mineral and gas mole transfers that account for differences in composition between waters, within specified compositional uncertainty limits.New features in PHREEQC version 2 relative to version 1 include capabilities to simulate dispersion (or diffusion) and stagnant zones in 1D-transport calculations, to model kinetic reactions with user-defined rate expressions, to model the formation or dissolution of ideal, multicomponent or nonideal, binary solid solutions, to model fixed-volume gas phases in addition to fixed-pressure gas phases, to allow the number of surface or exchange sites to vary with the dissolution or precipitation of minerals or kinetic reactants, to include isotope mole balances in inverse modeling calculations, to automatically use multiple sets of convergence parameters, to print user-defined quantities to the primary output file and (or) to a file suitable for importation into a spreadsheet, and to define solution compositions in a format more compatible with spreadsheet programs. This report presents the equations that are the basis for chemical equilibrium, kinetic, transport, and inverse-modeling calculations in PHREEQC; describes the input for the program; and presents examples that demonstrate most of the program's capabilities.

GEOCHEMICAL EVOLUTION OF GROUND WATER AND TRANSPORT OF MERCURY AT THE SULPHUR BANK MERCURY MINE SUPERFUND SITE IN NORTHERN CALIFORNIA, USA

EPA Science Inventory

The Sulphur Bank Mercury Mine, located on the shore of Clear Lake, Lake County, California, is a potential source for a modern-day mercury flux into the local aquatic ecosystem. Surface mining created the Herman Pit, a 9.3 ha open pit with a depth > 30 m, while overburden and pr...

Spatial patterns and controls of soil chemical weathering rates along a transient hillslope

USGS Publications Warehouse

Yoo, K.; Mudd, S.M.; Sanderman, J.; Amundson, Ronald; Blum, A.

2009-01-01

Hillslopes have been intensively studied by both geomorphologists and soil scientists. Whereas geomorphologists have focused on the physical soil production and transport on hillslopes, soil scientists have been concerned with the topographic variation of soil geochemical properties. We combined these differing approaches and quantified soil chemical weathering rates along a grass covered hillslope in Coastal California. The hillslope is comprised of both erosional and depositional sections. In the upper eroding section, soil production is balanced by physical erosion and chemical weathering. The hillslope then transitions to a depositional slope where soil accumulates due to a historical reduction of channel incision at the hillslope's base. Measurements of hillslope morphology and soil thickness were combined with the elemental composition of the soil and saprolite, and interpreted through a process-based model that accounts for both chemical weathering and sediment transport. Chemical weathering of the minerals as they moved downslope via sediment transport imparted spatial variation in the geochemical properties of the soil. Inverse modeling of the field and laboratory data revealed that the long-term soil chemical weathering rates peak at 5 g m- 2 yr- 1 at the downslope end of the eroding section and decrease to 1.5 g m- 2 yr- 1 within the depositional section. In the eroding section, soil chemical weathering rates appear to be primarily controlled by the rate of mineral supply via colluvial input from upslope. In the depositional slope, geochemical equilibrium between soil water and minerals appeared to limit the chemical weathering rate. Soil chemical weathering was responsible for removing 6% of the soil production in the eroding section and 5% of colluvial influx in the depositional slope. These were among the lowest weathering rates reported for actively eroding watersheds, which was attributed to the parent material with low amount of weatherable minerals and intense coating of the primary minerals by secondary clay and iron oxides. We showed that both the morphologic disequilibrium of the hillslope and the spatial heterogeneity of soil properties are due to spatial variations in the physical and chemical processes that removed mass from the soil. ?? 2009 Elsevier B.V.

Up-Scaling Geochemical Reaction Rates for Carbon Dioxide (CO2) in Deep Saline Aquifers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peters, Catherine A

2013-02-28

Geochemical reactions in deep subsurface environments are complicated by the consolidated nature and mineralogical complexity of sedimentary rocks. Understanding the kinetics of these reactions is critical to our ability to make long-term predictions about subsurface processes such as pH buffering, alteration in rock structure, permeability changes, and formation of secondary precipitates. In this project, we used a combination of experiments and numerical simulation to bridge the gap between our knowledge of these reactions at the lab scale and rates that are meaningful for modeling reactive transport at core scales. The focus is on acid-driven mineral dissolution, which is specifically relevantmore » in the context of CO2-water-rock interactions in geological sequestration of carbon dioxide. The project led to major findings in three areas. First, we modeled reactive transport in pore-network systems to investigate scaling effects in geochemical reaction rates. We found significant scaling effects when CO2 concentrations are high and reaction rates are fast. These findings indicate that the increased acidity associated with geological sequestration can generate conditions for which proper scaling tools are yet to be developed. Second, we used mathematical modeling to investigate the extent to which SO2, if co-injected with CO2, would acidify formation brines. We found that there exist realistic conditions in which the impact on brine acidity will be limited due to diffusion rate-limited SO2 dissolution from the CO2 phase, and the subsequent pH shift may also be limited by the lack of availability of oxidants to produce sulfuric acid. Third, for three Viking sandstones (Alberta sedimentary basin, Canada), we employed backscattered electron microscopy and energy dispersive X-ray spectroscopy to statistically characterize mineral contact with pore space. We determined that for reactive minerals in sedimentary consolidated rocks, abundance alone is not a good predictor of mineral accessible surface area, and should not be used in reactive transport modeling. Our work showed that reaction rates would be overestimated by three to five times.« less

To the bottom of carbon processing at the seafloor: towards integration of geological, geochemical and ecological concepts (Vladimir Ivanovich Vernadsky Medal Lecture)

NASA Astrophysics Data System (ADS)

Middelburg, Jack J.

2017-04-01

Marine sediments are a habitat for organisms, govern the partitioning of material being buried or recycled, and act as filter for the paleorecord. Processes in the surface sediment layer determine whether carbon is recycled within the biosphere (short-term cycle) or transferred to the geosphere (long-term cycle) and as such it function as key interface in the System Earth. Scientists from various disciplines with their own interests, paradigms and techniques have studied this pivotal role of the seafloor in processing material deposited. Marine geologists and paleoceanographers study sediments with the primary aim to extract information on past environmental conditions using down-core measurements of substances delivered to the seafloor and that have survived the processing at the seafloor. Biogeochemists quantify the fate of material delivered, in particular how much of the material is eventually buried and when and in what form is the remaining recycled to the water column, because recycling of key nutrients (e.g. N, P, Si, Fe) sustain primary production. Organic geochemists investigate how organic matter delivered to the seafloor is degraded, transformed or preserved using changes in the composition at the molecular level. Ecologists focus on the organisms, i.e. the actors consuming, producing and transporting the material deposited. Although these disciplines often study the same material, e.g. organic matter delivered to the seafloor, they focus on different aspect ignoring key concepts, findings and approaches from other disciplines. For example, ecologists and biogeochemist studying carbon flow at the seafloor normally ignore detailed molecular information available from organic geochemistry. Bioturbation, particle transport and mixing at the seafloor, is often ignored by paleocanographers, and biogeochemists have developed advanced transport-reaction models in which the actors, the animals, mix the particles but do so without consuming organic matter, their food. Here I present existing views on organic carbon processing at the seafloor, discuss where they agree and disagree and aim to arrive at an integrated view of carbon processing at the seafloor that is consistent with recent views within the organic geochemical, sediment geochemical, ecological and microbiological communities.

Suite of Benchmark Tests to Conduct Mesh-Convergence Analysis of Nonlinear and Non-constant Coefficient Transport Codes

NASA Astrophysics Data System (ADS)

Zamani, K.; Bombardelli, F. A.

2014-12-01

Verification of geophysics codes is imperative to avoid serious academic as well as practical consequences. In case that access to any given source code is not possible, the Method of Manufactured Solution (MMS) cannot be employed in code verification. In contrast, employing the Method of Exact Solution (MES) has several practical advantages. In this research, we first provide four new one-dimensional analytical solutions designed for code verification; these solutions are able to uncover the particular imperfections of the Advection-diffusion-reaction equation, such as nonlinear advection, diffusion or source terms, as well as non-constant coefficient equations. After that, we provide a solution of Burgers' equation in a novel setup. Proposed solutions satisfy the continuity of mass for the ambient flow, which is a crucial factor for coupled hydrodynamics-transport solvers. Then, we use the derived analytical solutions for code verification. To clarify gray-literature issues in the verification of transport codes, we designed a comprehensive test suite to uncover any imperfection in transport solvers via a hierarchical increase in the level of tests' complexity. The test suite includes hundreds of unit tests and system tests to check vis-a-vis the portions of the code. Examples for checking the suite start by testing a simple case of unidirectional advection; then, bidirectional advection and tidal flow and build up to nonlinear cases. We design tests to check nonlinearity in velocity, dispersivity and reactions. The concealing effect of scales (Peclet and Damkohler numbers) on the mesh-convergence study and appropriate remedies are also discussed. For the cases in which the appropriate benchmarks for mesh convergence study are not available, we utilize symmetry. Auxiliary subroutines for automation of the test suite and report generation are designed. All in all, the test package is not only a robust tool for code verification but it also provides comprehensive insight on the ADR solvers capabilities. Such information is essential for any rigorous computational modeling of ADR equation for surface/subsurface pollution transport. We also convey our experiences in finding several errors which were not detectable with routine verification techniques.

Integrated modelling framework for short pulse high energy density physics experiments

NASA Astrophysics Data System (ADS)

Sircombe, N. J.; Hughes, S. J.; Ramsay, M. G.

2016-03-01

Modelling experimental campaigns on the Orion laser at AWE, and developing a viable point-design for fast ignition (FI), calls for a multi-scale approach; a complete description of the problem would require an extensive range of physics which cannot realistically be included in a single code. For modelling the laser-plasma interaction (LPI) we need a fine mesh which can capture the dispersion of electromagnetic waves, and a kinetic model for each plasma species. In the dense material of the bulk target, away from the LPI region, collisional physics dominates. The transport of hot particles generated by the action of the laser is dependent on their slowing and stopping in the dense material and their need to draw a return current. These effects will heat the target, which in turn influences transport. On longer timescales, the hydrodynamic response of the target will begin to play a role as the pressure generated from isochoric heating begins to take effect. Recent effort at AWE [1] has focussed on the development of an integrated code suite based on: the particle in cell code EPOCH, to model LPI; the Monte-Carlo electron transport code THOR, to model the onward transport of hot electrons; and the radiation hydrodynamics code CORVUS, to model the hydrodynamic response of the target. We outline the methodology adopted, elucidate on the advantages of a robustly integrated code suite compared to a single code approach, demonstrate the integrated code suite's application to modelling the heating of buried layers on Orion, and assess the potential of such experiments for the validation of modelling capability in advance of more ambitious HEDP experiments, as a step towards a predictive modelling capability for FI.

The role of rock moisture on regulating hydrologic and solute fluxes in the critical zone

NASA Astrophysics Data System (ADS)

Rempe, D. M.; Druhan, J. L.; Hahm, W. J.; Wang, J.; Murphy, C.; Cargill, S.; Dietrich, W. E.; Tune, A. K.

2017-12-01

In environments where the vadose zone extends below the soil layer into underlying weathered bedrock, the water held in the weathering -generated pores can be an important source of moisture to vegetation. The heterogeneous distribution of pore space in weathered bedrock, furthermore, controls the subsurface water flowpaths that dictate how water is partitioned in the critical zone (CZ) and evolves geochemically. Here, we present the results of direct monitoring of the fluxes of water and solutes through the deep CZ using a novel vadose zone monitoring system (VMS) as well as geophysical logging and sampling in a network of deep wells across a steep hillslope in Northern California. At our study site (Eel River CZO), multi-year monitoring reveals that a significant fraction of incoming rainfall (up to 30%) is seasonally stored in the fractures and matrix of the upper 12 m of weathered bedrock as rock moisture. Intensive geochemical and geophysical observations distributed from the surface to the depth of unweathered bedrock indicate that the seasonal addition and depletion of rock moisture has key implications for hydrologic and geochemical processes. First, rock moisture storage provides an annually consistent water storage reservoir for use by vegetation during the summer, which buffers transpiration fluxes against variability in seasonal precipitation. Second, because the timing and magnitude of groundwater recharge and streamflow are controlled by the annual filling and drainage of the rock moisture, rock moisture regulates the partitioning of hydrologic fluxes. Third, we find that rock moisture dynamics—which influence the myriad geochemical and microbial processes that weather bedrock—strongly correspond with the observed vertical weathering profile. As a result of the coupling between chemical weathering reactions and hydrologic fluxes, the geochemical composition of groundwater and streamflow is influenced by the temporal dynamics of rock moisture. Our findings highlight the strong influence of water transport and storage dynamics in the weathered bedrock beneath the soil layer on catchment-scale hydrologic and geochemical fluxes, and underscore the need for further exploration of the fractured bedrock vadose zones common to many upland landscapes.

Muon simulation codes MUSIC and MUSUN for underground physics

NASA Astrophysics Data System (ADS)

Kudryavtsev, V. A.

2009-03-01

The paper describes two Monte Carlo codes dedicated to muon simulations: MUSIC (MUon SImulation Code) and MUSUN (MUon Simulations UNderground). MUSIC is a package for muon transport through matter. It is particularly useful for propagating muons through large thickness of rock or water, for instance from the surface down to underground/underwater laboratory. MUSUN is designed to use the results of muon transport through rock/water to generate muons in or around underground laboratory taking into account their energy spectrum and angular distribution.

Approximate Green's function methods for HZE transport in multilayered materials

NASA Technical Reports Server (NTRS)

Wilson, John W.; Badavi, Francis F.; Shinn, Judy L.; Costen, Robert C.

1993-01-01

A nonperturbative analytic solution of the high charge and energy (HZE) Green's function is used to implement a computer code for laboratory ion beam transport in multilayered materials. The code is established to operate on the Langley nuclear fragmentation model used in engineering applications. Computational procedures are established to generate linear energy transfer (LET) distributions for a specified ion beam and target for comparison with experimental measurements. The code was found to be highly efficient and compared well with the perturbation approximation.

TEMPEST code simulations of hydrogen distribution in reactor containment structures. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trent, D.S.; Eyler, L.L.

The mass transport version of the TEMPEST computer code was used to simulate hydrogen distribution in geometric configurations relevant to reactor containment structures. Predicted results of Battelle-Frankfurt hydrogen distribution tests 1 to 6, and 12 are presented. Agreement between predictions and experimental data is good. Best agreement is obtained using the k-epsilon turbulence model in TEMPEST in flow cases where turbulent diffusion and stable stratification are dominant mechanisms affecting transport. The code's general analysis capabilities are summarized.

14 CFR 257.6 - Effective and compliance dates.

Code of Federal Regulations, 2011 CFR

2011-01-01

... the selling carrier is not the transporting carrier and (ii) Of the transporting carrier's identity... transportation involving a code-share arrangement of the transporting carrier's corporate name and any other name...

14 CFR 257.6 - Effective and compliance dates.

Code of Federal Regulations, 2014 CFR

2014-01-01

... the selling carrier is not the transporting carrier and (ii) Of the transporting carrier's identity... transportation involving a code-share arrangement of the transporting carrier's corporate name and any other name...

14 CFR 257.6 - Effective and compliance dates.

Code of Federal Regulations, 2013 CFR

2013-01-01

... the selling carrier is not the transporting carrier and (ii) Of the transporting carrier's identity... transportation involving a code-share arrangement of the transporting carrier's corporate name and any other name...

14 CFR 257.6 - Effective and compliance dates.

Code of Federal Regulations, 2012 CFR

2012-01-01

... the selling carrier is not the transporting carrier and (ii) Of the transporting carrier's identity... transportation involving a code-share arrangement of the transporting carrier's corporate name and any other name...

PelePhysics

DOE Office of Scientific and Technical Information (OSTI.GOV)

2017-05-17

PelePhysics is a suite of physics packages that provides functionality of use to reacting hydrodynamics CFD codes. The initial release includes an interface to reaction rate mechanism evaluation, transport coefficient evaluation, and a generalized equation of state (EOS) facility. Both generic evaluators and interfaces to code from externally available tools (Fuego for chemical rates, EGLib for transport coefficients) are provided.

Analysis of JT-60SA operational scenarios

NASA Astrophysics Data System (ADS)

Garzotti, L.; Barbato, E.; Garcia, J.; Hayashi, N.; Voitsekhovitch, I.; Giruzzi, G.; Maget, P.; Romanelli, M.; Saarelma, S.; Stankiewitz, R.; Yoshida, M.; Zagórski, R.

2018-02-01

Reference scenarios for the JT-60SA tokamak have been simulated with one-dimensional transport codes to assess the stationary state of the flat-top phase and provide a profile database for further physics studies (e.g. MHD stability, gyrokinetic analysis) and diagnostics design. The types of scenario considered vary from pulsed standard H-mode to advanced non-inductive steady-state plasmas. In this paper we present the results obtained with the ASTRA, CRONOS, JINTRAC and TOPICS codes equipped with the Bohm/gyro-Bohm, CDBM and GLF23 transport models. The scenarios analysed here are: a standard ELMy H-mode, a hybrid scenario and a non-inductive steady state plasma, with operational parameters from the JT-60SA research plan. Several simulations of the scenarios under consideration have been performed with the above mentioned codes and transport models. The results from the different codes are in broad agreement and the main plasma parameters generally agree well with the zero dimensional estimates reported previously. The sensitivity of the results to different transport models and, in some cases, to the ELM/pedestal model has been investigated.

Improvements on non-equilibrium and transport Green function techniques: The next-generation TRANSIESTA

NASA Astrophysics Data System (ADS)

Papior, Nick; Lorente, Nicolás; Frederiksen, Thomas; García, Alberto; Brandbyge, Mads

2017-03-01

We present novel methods implemented within the non-equilibrium Green function code (NEGF) TRANSIESTA based on density functional theory (DFT). Our flexible, next-generation DFT-NEGF code handles devices with one or multiple electrodes (Ne ≥ 1) with individual chemical potentials and electronic temperatures. We describe its novel methods for electrostatic gating, contour optimizations, and assertion of charge conservation, as well as the newly implemented algorithms for optimized and scalable matrix inversion, performance-critical pivoting, and hybrid parallelization. Additionally, a generic NEGF "post-processing" code (TBTRANS/PHTRANS) for electron and phonon transport is presented with several novelties such as Hamiltonian interpolations, Ne ≥ 1 electrode capability, bond-currents, generalized interface for user-defined tight-binding transport, transmission projection using eigenstates of a projected Hamiltonian, and fast inversion algorithms for large-scale simulations easily exceeding 106 atoms on workstation computers. The new features of both codes are demonstrated and bench-marked for relevant test systems.

Morse Monte Carlo Radiation Transport Code System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Emmett, M.B.

1975-02-01

The report contains sections containing descriptions of the MORSE and PICTURE codes, input descriptions, sample problems, deviations of the physical equations and explanations of the various error messages. The MORSE code is a multipurpose neutron and gamma-ray transport Monte Carlo code. Time dependence for both shielding and criticality problems is provided. General three-dimensional geometry may be used with an albedo option available at any material surface. The PICTURE code provide aid in preparing correct input data for the combinatorial geometry package CG. It provides a printed view of arbitrary two-dimensional slices through the geometry. By inspecting these pictures one maymore » determine if the geometry specified by the input cards is indeed the desired geometry. 23 refs. (WRF)« less

Applications of the microdosimetric function implemented in the macroscopic particle transport simulation code PHITS.

PubMed

Sato, Tatsuhiko; Watanabe, Ritsuko; Sihver, Lembit; Niita, Koji

2012-01-01

Microdosimetric quantities such as lineal energy are generally considered to be better indices than linear energy transfer (LET) for expressing the relative biological effectiveness (RBE) of high charge and energy particles. To calculate their probability densities (PD) in macroscopic matter, it is necessary to integrate microdosimetric tools such as track-structure simulation codes with macroscopic particle transport simulation codes. As an integration approach, the mathematical model for calculating the PD of microdosimetric quantities developed based on track-structure simulations was incorporated into the macroscopic particle transport simulation code PHITS (Particle and Heavy Ion Transport code System). The improved PHITS enables the PD in macroscopic matter to be calculated within a reasonable computation time, while taking their stochastic nature into account. The microdosimetric function of PHITS was applied to biological dose estimation for charged-particle therapy and risk estimation for astronauts. The former application was performed in combination with the microdosimetric kinetic model, while the latter employed the radiation quality factor expressed as a function of lineal energy. Owing to the unique features of the microdosimetric function, the improved PHITS has the potential to establish more sophisticated systems for radiological protection in space as well as for the treatment planning of charged-particle therapy.

Geochemical Fate and Transport of Sildenafil and Vardenafil

NASA Astrophysics Data System (ADS)

Richter, L.; Boudinot, G.; Vulava, V. M.; Cory, W. C.

2015-12-01

The geochemical fate of pharmaceuticals and their degradation products is a developing environmental field. The geologic, chemical, and biological fate of these pollutants has become very relevant with the increase in human population and the resulting increase in pollutant concentrations in the environment. In this study, we focus on sildenafil (SDF) and vardenafil (VDF), active compounds in Viagra and Levitra, respectively, two commonly used erectile dysfunction drugs. The main objective is to determine the sorption potential and transport behavior of these two compounds in natural soils. Both SDF and VDF are complex organic molecules with multiple amine functional groups in their structures. Two types of natural acidic soils (pH≈4.5), an organic-rich soil (7.6% OM) and clay-rich soil (5.1% clay) were used in this study to determine which soil components influence sorption behavior of both compounds. Sorption isotherms measured using batch reactors were nearly linear, but sorption was stronger in soil that contained higher clay content. Both compounds have multiple pKas due to the amine functional groups, the relevant pKas of SDF are 5.97 and 7.27, and those of VDF's are 4.72 and 6.21. These values indicate that these compounds likely behave as cations in soil suspensions and hence were strongly sorbed to negatively-charged clay minerals present in both soils. The clay composition in both soils is predominantly kaolinite with smaller amount of montmorillonite, both of which have a predominantly negative surface charge. Transport experiments using glass chromatography columns indicated that both compounds were more strongly retarded in the clay-rich soils. Breakthrough curves from the transport experiments were modeled using convection-dispersion transport equations. The organic matter in the soil seemed to play a less dominant role in the geochemistry in this study, but is likely to transform both compounds into derivative compounds as seen in other studies.

ipole: Semianalytic scheme for relativistic polarized radiative transport

NASA Astrophysics Data System (ADS)

Moscibrodzka, Monika; Gammie, Charles F.

2018-04-01

ipole is a ray-tracing code for covariant, polarized radiative transport particularly useful for modeling Event Horizon Telescope sources, though may also be used for other relativistic transport problems. The code extends the ibothros scheme for covariant, unpolarized transport using two representations of the polarized radiation field: in the coordinate frame, it parallel transports the coherency tensor, and in the frame of the plasma, it evolves the Stokes parameters under emission, absorption, and Faraday conversion. The transport step is as spacetime- and coordinate- independent as possible; the emission, absorption, and Faraday conversion step is implemented using an analytic solution to the polarized transport equation with constant coefficients. As a result, ipole is stable, efficient, and produces a physically reasonable solution even for a step with high optical depth and Faraday depth.

3D unstructured-mesh radiation transport codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morel, J.

1997-12-31

Three unstructured-mesh radiation transport codes are currently being developed at Los Alamos National Laboratory. The first code is ATTILA, which uses an unstructured tetrahedral mesh in conjunction with standard Sn (discrete-ordinates) angular discretization, standard multigroup energy discretization, and linear-discontinuous spatial differencing. ATTILA solves the standard first-order form of the transport equation using source iteration in conjunction with diffusion-synthetic acceleration of the within-group source iterations. DANTE is designed to run primarily on workstations. The second code is DANTE, which uses a hybrid finite-element mesh consisting of arbitrary combinations of hexahedra, wedges, pyramids, and tetrahedra. DANTE solves several second-order self-adjoint forms of the transport equation including the even-parity equation, the odd-parity equation, and a new equation called the self-adjoint angular flux equation. DANTE also offers three angular discretization options:more » $$S{_}n$$ (discrete-ordinates), $$P{_}n$$ (spherical harmonics), and $$SP{_}n$$ (simplified spherical harmonics). DANTE is designed to run primarily on massively parallel message-passing machines, such as the ASCI-Blue machines at LANL and LLNL. The third code is PERICLES, which uses the same hybrid finite-element mesh as DANTE, but solves the standard first-order form of the transport equation rather than a second-order self-adjoint form. DANTE uses a standard $$S{_}n$$ discretization in angle in conjunction with trilinear-discontinuous spatial differencing, and diffusion-synthetic acceleration of the within-group source iterations. PERICLES was initially designed to run on workstations, but a version for massively parallel message-passing machines will be built. The three codes will be described in detail and computational results will be presented.« less

AN EXTENSION OF THE ATHENA++ CODE FRAMEWORK FOR GRMHD BASED ON ADVANCED RIEMANN SOLVERS AND STAGGERED-MESH CONSTRAINED TRANSPORT

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, Christopher J.; Stone, James M.; Gammie, Charles F.

2016-08-01

We present a new general relativistic magnetohydrodynamics (GRMHD) code integrated into the Athena++ framework. Improving upon the techniques used in most GRMHD codes, ours allows the use of advanced, less diffusive Riemann solvers, in particular HLLC and HLLD. We also employ a staggered-mesh constrained transport algorithm suited for curvilinear coordinate systems in order to maintain the divergence-free constraint of the magnetic field. Our code is designed to work with arbitrary stationary spacetimes in one, two, or three dimensions, and we demonstrate its reliability through a number of tests. We also report on its promising performance and scalability.

Common Errors in the Calculation of Aircrew Doses from Cosmic Rays

NASA Astrophysics Data System (ADS)

O'Brien, Keran; Felsberger, Ernst; Kindl, Peter

2010-05-01

Radiation doses to air crew are calculated using flight codes. Flight codes integrate dose rates over the aircraft flight path, which were calculated by transport codes or obtained by measurements from take off at a specific airport to landing at another. The dose rates are stored in various ways, such as by latitude and longitude, or in terms of the geomagnetic vertical cutoff. The transport codes are generally quite satisfactory, but the treatment of the boundary conditions is frequently incorrect. Both the treatment of solar modulation and of the effect of the geomagnetic field are often defective, leading to the systematic overestimate of the crew doses.

49 CFR 178.905 - Large Packaging identification codes.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Large Packaging identification codes. 178.905... FOR PACKAGINGS Large Packagings Standards § 178.905 Large Packaging identification codes. Large packaging code designations consist of: two numerals specified in paragraph (a) of this section; followed by...

Were Chloride-Bearing Lakes on Mars Fed by Deep-Sourced Groundwater?

NASA Astrophysics Data System (ADS)

Melwani Daswani, M.; Kite, E. S.

2016-12-01

Chloride (probably halite)-bearing deposits have been identified by orbital spectroscopy in paleolakes and other geological settings on Mars. The origin of the saline fluids that formed the deposits remains largely unconstrained; chloride-rich inverted channels suggest surface runoff-fed ponds, alternatively, the abundance of chloride ( 10-25 wt. %) and absence of associated evaporites (carbonates, sulfates) are consistent with late-stage groundwater upwelling. We use HiRISE DTMs and THEMIS decorrelation stretched images to map a set of chloride-bearing deposits and calculate their volume, and a geochemical reaction-transport modeling code (CHIM-XPT) to test possible sources of the chlorine: groundwater chlorine would derive from deep igneous chlorapatite in basalt, whereas chlorine in surface runoff would derive mainly from volcanic Cl-phases deposited on top of Mars soil/dust. For a short duration (< 1 Mars yr) warming event (above freezing point), chlorapatite dissolution cannot provide sufficient Cl- to satisfy mass balance. High water-to-rock ratios (W/R) are also ruled out because sulfates would be transported into the lakes and precipitate close to or with the chlorides. If the source of chlorine was the weathering of volcanic Cl-phases (e.g. perchlorate), long warm events are not required, since the volcanic Cl-phases only reside in the top-most meters of soil/dust. For a 1.4 ×1011 kg NaCl deposit near Miyamoto Crater in Meridiani Planum, surface water in equilibrium with a possible early Hesperian pHCl = 1.2 × 10-4 bar atmosphere would have been too dilute ( 4 × 10-3 g Cl L-1) to form the deposit. However, chlorapatite weathering across the 1.2 ×109 m2 basin could form the deposit but the depth of weathering required ( 15 m) would be inconsistent with seasonal melting.

Porosity evolution in Icelandic hydrothermal systems

NASA Astrophysics Data System (ADS)

Thien, B.; Kosakowski, G.; Kulik, D. A.

2014-12-01

Mineralogical alteration of reservoir rocks, driven by fluid circulation in natural or enhanced hydrothermal systems, is likely to influence the long-term performance of geothermal power generation. A key factor is the change of porosity due to dissolution of primary minerals and precipitation of secondary phases. Porosity changes will affect fluid circulation and solute transport, which, in turn, influence mineralogical alteration. This study is part of the Sinergia COTHERM project (COmbined hydrological, geochemical and geophysical modeling of geotTHERMal systems, grant number CRSII2_141843/1) that is an integrative research project aimed at improving our understanding of the sub-surface processes in magmatically-driven natural geothermal systems. These are typically high enthalphy systems where a magmatic pluton is located at a few kilometers depth. These shallow plutons increase the geothermal gradient and trigger the circulation of hydrothermal waters with a steam cap forming at shallow depth. Field observations suggest that active and fossil Icelandic hydrothermal systems are built from a superposition of completely altered and completely unaltered layers. With help of 1D and 2D reactive transport models (OpenGeoSys-GEM code), we investigate the reasons for this finding, by studying the mineralogical evolution of protoliths with different initial porosities at different temperatures and pressures, different leaching water composition and gas content, and different porosity geometries (i.e. porous medium versus fractured medium). From this study, we believe that the initial porosity of protoliths and volume changes due to their transformation into secondary minerals are key factors to explain the different alteration extents observed in field studies. We also discuss how precipitation and dissolution kinetics can influence the alteration time scales.

Controls on the geochemical evolution of Prairie Pothole Region lakes and wetlands over decadal time scales

USGS Publications Warehouse

Goldhaber, Martin B.; Mills, Christopher T.; Mushet, David M.; McCleskey, R. Blaine; Rover, Jennifer

2016-01-01

One hundred sixty-seven Prairie Pothole lakes, ponds and wetlands (largely lakes) previously analyzed chemically during the late 1960’s and early to mid-1970’s were resampled and reanalyzed in 2011–2012. The two sampling periods differed climatically. The earlier sampling took place during normal to slightly dry conditions, whereas the latter occurred during and immediately following exceptionally wet conditions. As reported previously in Mushet et al. (2015), the dominant effect was expansion of the area of these lakes and dilution of their major ions. However, within that context, there were significant differences in the evolutionary pathways of major ions. To establish these pathways, we employed the inverse modeling computer code NetpathXL. This code takes the initial and final lake composition and, using mass balance constrained by the composition of diluting waters, and input and output of phases, calculates plausible geochemical evolution pathways. Despite the fact that in most cases major ions decreased, a subset of the lakes had an increase in SO42−. This distinction is significant because SO42− is the dominant anion in a majority of Prairie Pothole Region wetlands and lakes. For lakes with decreasing SO42−, the proportion of original lake water required for mass balance was subordinate to rainwater and/or overland flow. In contrast, lakes with increasing SO42− between the two sampling episodes tended to be dominated by original lake water. This suite of lakes tended to be smaller and have lower initial SO42−concentrations such that inputs of sulfur from dissolution of the minerals gypsum or pyrite had a significant impact on the final sulfur concentration given the lower dilution factors. Thus, our study provides context for how Prairie Pothole Region water bodies evolve geochemically as climate changes. Because wetland geochemistry in turn controls the ecology of these water bodies, this research contributes to the prediction of the impact of climate change on this important complex of ecosystems.

Upscaling of U (VI) desorption and transport from decimeter‐scale heterogeneity to plume‐scale modeling

USGS Publications Warehouse

Curtis, Gary P.; Kohler, Matthias; Kannappan, Ramakrishnan; Briggs, Martin A.; Day-Lewis, Frederick D.

2015-01-01

Scientifically defensible predictions of field scale U(VI) transport in groundwater requires an understanding of key processes at multiple scales. These scales range from smaller than the sediment grain scale (less than 10 μm) to as large as the field scale which can extend over several kilometers. The key processes that need to be considered include both geochemical reactions in solution and at sediment surfaces as well as physical transport processes including advection, dispersion, and pore-scale diffusion. The research summarized in this report includes both experimental and modeling results in batch, column and tracer tests. The objectives of this research were to: (1) quantify the rates of U(VI) desorption from sediments acquired from a uranium contaminated aquifer in batch experiments;(2) quantify rates of U(VI) desorption in column experiments with variable chemical conditions, and(3) quantify nonreactive tracer and U(VI) transport in field tests.

Use of Existing CAD Models for Radiation Shielding Analysis

NASA Technical Reports Server (NTRS)

Lee, K. T.; Barzilla, J. E.; Wilson, P.; Davis, A.; Zachman, J.

2015-01-01

The utility of a radiation exposure analysis depends not only on the accuracy of the underlying particle transport code, but also on the accuracy of the geometric representations of both the vehicle used as radiation shielding mass and the phantom representation of the human form. The current NASA/Space Radiation Analysis Group (SRAG) process to determine crew radiation exposure in a vehicle design incorporates both output from an analytic High Z and Energy Particle Transport (HZETRN) code and the properties (i.e., material thicknesses) of a previously processed drawing. This geometry pre-process can be time-consuming, and the results are less accurate than those determined using a Monte Carlo-based particle transport code. The current work aims to improve this process. Although several Monte Carlo programs (FLUKA, Geant4) are readily available, most use an internal geometry engine. The lack of an interface with the standard CAD formats used by the vehicle designers limits the ability of the user to communicate complex geometries. Translation of native CAD drawings into a format readable by these transport programs is time consuming and prone to error. The Direct Accelerated Geometry -United (DAGU) project is intended to provide an interface between the native vehicle or phantom CAD geometry and multiple particle transport codes to minimize problem setup, computing time and analysis error.

Status and Plans for the TRANSP Interpretive and Predictive Simulation Code

NASA Astrophysics Data System (ADS)

Kaye, Stanley; Andre, Robert; Marina, Gorelenkova; Yuan, Xingqui; Hawryluk, Richard; Jardin, Steven; Poli, Francesca

2015-11-01

TRANSP is an integrated interpretive and predictive transport analysis tool that incorporates state of the art heating/current drive sources and transport models. The treatments and transport solvers are becoming increasingly sophisticated and comprehensive. For instance, the ISOLVER component provides a free boundary equilibrium solution, while the PT_SOLVER transport solver is especially suited for stiff transport models such as TGLF. TRANSP also incorporates such source models as NUBEAM for neutral beam injection, GENRAY, TORAY, TORBEAM, TORIC and CQL3D for ICRH, LHCD, ECH and HHFW. The implementation of selected components makes efficient use of MPI for speed up of code calculations. TRANSP has a wide international user-base, and it is run on the FusionGrid to allow for timely support and quick turnaround by the PPPL Computational Plasma Physics Group. It is being used as a basis for both analysis and development of control algorithms and discharge operational scenarios, including simulation of ITER plasmas. This poster will describe present uses of the code worldwide, as well as plans for upgrading the physics modules and code framework. Progress on implementing TRANSP as a component in the ITER IMAS will also be described. This research was supported by the U.S. Department of Energy under contracts DE-AC02-09CH11466.

Cosmic-ray propagation with DRAGON2: I. numerical solver and astrophysical ingredients

NASA Astrophysics Data System (ADS)

Evoli, Carmelo; Gaggero, Daniele; Vittino, Andrea; Di Bernardo, Giuseppe; Di Mauro, Mattia; Ligorini, Arianna; Ullio, Piero; Grasso, Dario

2017-02-01

We present version 2 of the DRAGON code designed for computing realistic predictions of the CR densities in the Galaxy. The code numerically solves the interstellar CR transport equation (including inhomogeneous and anisotropic diffusion, either in space and momentum, advective transport and energy losses), under realistic conditions. The new version includes an updated numerical solver and several models for the astrophysical ingredients involved in the transport equation. Improvements in the accuracy of the numerical solution are proved against analytical solutions and in reference diffusion scenarios. The novel features implemented in the code allow to simulate the diverse scenarios proposed to reproduce the most recent measurements of local and diffuse CR fluxes, going beyond the limitations of the homogeneous galactic transport paradigm. To this end, several applications using DRAGON2 are presented as well. This new version facilitates the users to include their own physical models by means of a modular C++ structure.

Laser Blow-Off Impurity Injection Experiments at the HSX Stellarator

NASA Astrophysics Data System (ADS)

Castillo, J. F.; Bader, A.; Likin, K. M.; Anderson, D. T.; Anderson, F. S. B.; Kumar, S. T. A.; Talmadge, J. N.

2017-10-01

Results from the HSX laser blow-off experiment are presented and compared to a synthetic diagnostic implemented in the STRAHL impurity transport modeling code in order to measure the impurity transport diffusivity and convective velocity. A laser blow-off impurity injection system is used to rapidly deposit a small, controlled quantity of aluminum into the confinement volume. Five AXUV photodiode arrays are used to take time-resolved measurements of the impurity radiation. The spatially one-dimensional impurity transport code STRAHL is used to calculate a time-dependent plasma emissivity profile. Modeled intensity signals calculated from a synthetic diagnostic code provide direct comparison between plasma simulation and experimental results. An optimization algorithm with impurity transport coefficients acting as free parameters is used to fit the model to experimental data. This work is supported by US DOE Grant DE-FG02-93ER54222.

Gas Hydrate Exploration, Mid Chilean Coast; Geochemical-Geophysical Survey

DTIC Science & Technology

2006-12-27

design for the piston core provided a more safe core delivery and retrieval protocol with changes in the messenger weight and triggering mechanism ...selection of samples that were analyzed onboard depended on key data needed to assist in sample station selection and the ability to transport and...weight and triggering mechanism . Through the cruise there were 17 piston coring attempts resulting in 15 successful cores. Failures in the core

Mineral dissolution and precipitation during CO 2 injection at the Frio-I Brine Pilot: Geochemical modeling and uncertainty analysis

DOE PAGES

Ilgen, A. G.; Cygan, R. T.

2015-12-07

During the Frio-I Brine Pilot CO 2 injection experiment in 2004, distinct geochemical changes in response to the injection of 1600 tons of CO 2 were recorded in samples collected from the monitoring well. Previous geochemical modeling studies have considered dissolution of calcite and iron oxyhydroxides, or release of adsorbed iron, as the most likely sources of the increased ion concentrations. We explore in this modeling study possible alternative sources of the increasing calcium and iron, based on the data from the detailed petrographic characterization of the Upper Frio Formation “C”. Particularly, we evaluate whether dissolution of pyrite andmore » oligoclase (anorthite component) can account for the observed geochemical changes. Due to kinetic limitations, dissolution of pyrite and anorthite cannot account for the increased iron and calcium concentrations on the time scale of the field test (10 days). However, dissolution of these minerals is contributing to carbonate and clay mineral precipitation on the longer time scales (1000 years). The one-dimensional reactive transport model predicts carbonate minerals, dolomite and ankerite, as well as clay minerals kaolinite, nontronite and montmorillonite, will precipitate in the Frio Formation “C” sandstone as the system progresses towards chemical equilibrium during a 1000-year period. Cumulative uncertainties associated with using different thermodynamic databases, activity correction models (Pitzer vs. B-dot), and extrapolating to reservoir temperature, are manifested in the difference in the predicted mineral phases. Furthermore, these models are consistent with regards to the total volume of mineral precipitation and porosity values which are predicted to within 0.002%.« less

Hydrogeochemical zonation in intertidal salt marsh sediments: evidence of positive plant-soil feedback?

NASA Astrophysics Data System (ADS)

Moffett, K. B.; Dittmar, J.; Seyfferth, A.; Fendorf, S.; Gorelick, S.

2012-12-01

Surface and subsurface environments are linked by the biogeochemical activity in near-surface sediment and by the hydrological fluxes that mobilize its reagents and products. A particularly dynamic and interesting setting to study near-surface hydrogeochemistry is the intertidal zone. Here, the very strong tidal hydraulic forcing is often thought to dominate water and solute transport. However, we demonstrated the importance of two additional subsurface drivers: groundwater flow and plant root water uptake. A high-resolution, coupled surface water-groundwater model of an intertidal salt marsh in San Francisco Bay, CA showed that these three drivers vary over different spatial scales: tidal flooding varies over 10's of meters; groundwater flow varies over meters, particularly within channel banks; and plant root water uptake varies in 3D at the sub-meter scale. Expanding on this third driver, we investigated whether the spatial variations in soil-water-plant hydraulic interactions that occur due to vegetation zonation also cause distinct geochemical zonation in salt marsh sediment pore waters. The existence of such geochemical zonation was verified and mapped by detailed field observations of the chemical composition of sediments, pore waters, surface waters, and vegetation. The field data and the coupled hydrologic model were then further analyzed to evaluate potential causal mechanisms for the geochemical zonation, including testing the hypothesis that the vegetation affects pore water geochemistry via a positive feedback beneficial to itself. If further supported by future studies, this geochemical feedback may complement known physical ecosystem engineering mechanisms to help stabilize and organize intertidal wetlands.

Electrical characterization of non‐Fickian transport in groundwater and hyporheic systems

USGS Publications Warehouse

Singha, Kamini; Pidlisecky, Adam; Day-Lewis, Frederick D.; Gooseff, Michael N.

2008-01-01

Recent work indicates that processes controlling solute mass transfer between mobile and less mobile domains in porous media may be quantified by combining electrical geophysical methods and electrically conductive tracers. Whereas direct geochemical measurements of solute preferentially sample the mobile domain, electrical geophysical methods are sensitive to changes in bulk electrical conductivity (bulk EC) and therefore sample EC in both the mobile and immobile domains. Consequently, the conductivity difference between direct geochemical samples and remotely sensed electrical geophysical measurements may provide an indication of mass transfer rates and mobile and immobile porosities in situ. Here we present (1) an overview of a theoretical framework for determining parameters controlling mass transfer with electrical resistivity in situ; (2) a review of a case study estimating mass transfer processes in a pilot‐scale aquifer storage recovery test; and (3) an example application of this method for estimating mass transfer in watershed settings between streams and the hyporheic corridor. We demonstrate that numerical simulations of electrical resistivity studies of the stream/hyporheic boundary can help constrain volumes and rates of mobile‐immobile mass transfer. We conclude with directions for future research applying electrical geophysics to understand field‐scale transport in aquifer and fluvial systems subject to rate‐limited mass transfer.

Solubility and transport of Cr(III) in a historically contaminated soil - Evidence of a rapidly reacting dimeric Cr(III) organic matter complex.

PubMed

Löv, Åsa; Sjöstedt, Carin; Larsbo, Mats; Persson, Ingmar; Gustafsson, Jon Petter; Cornelis, Geert; Kleja, Dan B

2017-12-01

Chromium is a common soil contaminant and, although it has been studied widely, questions about its speciation and dissolutions kinetics remain unanswered. We combined information from an irrigation experiment performed with intact soil columns with data from batch experiments to evaluate solubility and mobilization mechanisms of Cr(III) in a historically contaminated soil (>65 years). Particulate and colloidal Cr(III) forms dominated transport in this soil, but their concentrations were independent of irrigation intensity (2-20 mm h -1 ). Extended X-ray absorption fine structure (EXAFS) measurements indicated that Cr(III) associated with colloids and particles, and with the solid phase, mainly existed as dimeric hydrolyzed Cr(III) bound to natural organic matter. Dissolution kinetics of this species were fast (≤1 day) at low pH (<3) and slightly slower (≤5 days) at neutral pH. Furthermore, it proved possible to describe the solubility of the dimeric Cr(III) organic matter complex with a geochemical equilibrium model using only generic binding parameters, opening the way for use of geochemical models in risk assessments of Cr(III)-contaminated sites. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Validation of the WIMSD4M cross-section generation code with benchmark results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leal, L.C.; Deen, J.R.; Woodruff, W.L.

1995-02-01

The WIMSD4 code has been adopted for cross-section generation in support of the Reduced Enrichment for Research and Test (RERTR) program at Argonne National Laboratory (ANL). Subsequently, the code has undergone several updates, and significant improvements have been achieved. The capability of generating group-collapsed micro- or macroscopic cross sections from the ENDF/B-V library and the more recent evaluation, ENDF/B-VI, in the ISOTXS format makes the modified version of the WIMSD4 code, WIMSD4M, very attractive, not only for the RERTR program, but also for the reactor physics community. The intent of the present paper is to validate the procedure to generatemore » cross-section libraries for reactor analyses and calculations utilizing the WIMSD4M code. To do so, the results of calculations performed with group cross-section data generated with the WIMSD4M code will be compared against experimental results. These results correspond to calculations carried out with thermal reactor benchmarks of the Oak Ridge National Laboratory(ORNL) unreflected critical spheres, the TRX critical experiments, and calculations of a modified Los Alamos highly-enriched heavy-water moderated benchmark critical system. The benchmark calculations were performed with the discrete-ordinates transport code, TWODANT, using WIMSD4M cross-section data. Transport calculations using the XSDRNPM module of the SCALE code system are also included. In addition to transport calculations, diffusion calculations with the DIF3D code were also carried out, since the DIF3D code is used in the RERTR program for reactor analysis and design. For completeness, Monte Carlo results of calculations performed with the VIM and MCNP codes are also presented.« less

New Parallel computing framework for radiation transport codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kostin, M.A.; /Michigan State U., NSCL; Mokhov, N.V.

A new parallel computing framework has been developed to use with general-purpose radiation transport codes. The framework was implemented as a C++ module that uses MPI for message passing. The module is significantly independent of radiation transport codes it can be used with, and is connected to the codes by means of a number of interface functions. The framework was integrated with the MARS15 code, and an effort is under way to deploy it in PHITS. Besides the parallel computing functionality, the framework offers a checkpoint facility that allows restarting calculations with a saved checkpoint file. The checkpoint facility canmore » be used in single process calculations as well as in the parallel regime. Several checkpoint files can be merged into one thus combining results of several calculations. The framework also corrects some of the known problems with the scheduling and load balancing found in the original implementations of the parallel computing functionality in MARS15 and PHITS. The framework can be used efficiently on homogeneous systems and networks of workstations, where the interference from the other users is possible.« less

Hydrologic Responses to CO2 Injection in Basalts Based on Flow-through Experiments

NASA Astrophysics Data System (ADS)

Thomas, D.; Hingerl, F.; Garing, C.; Bird, D. K.; Benson, S. M.; Maher, K.

2015-12-01

Experimental studies of basalt-CO2 interactions have increased our ability to predict geochemical responses within a mafic reservoir during geologic CO2 sequestration. However, the lack of flow-through experiments prevents the use of coupled hydrologic-geochemical models to predict evolution of permeability and porosity, critical parameters for assessing storage feasibility. We present here results of three flow-through experiments on an intact basalt core during which we employed X-ray Computed Tomography (CT) to quantify porosity evolution and fluid flow. Using a single core of glassy basaltic tuff from the Snake River Plain (Menan Buttes complex), we performed tracer tests using a solution of NaI (~100,000 ppm) before and after injection of CO2-saturated water at reservoir conditions (90 bar, 50°C) to image porosity and flow path distribution. During the tracer tests, CT scans were taken at 2.5-minute intervals, and outlet fluid was discretely sampled at the same intervals and subsequently measured via ICP-MS, enabling interpretation of the tracer breakthrough curve through both imaging and geochemical analyses. Comparison of the porosity distribution from before and after injection of CO2 shows an overall decrease in core-averaged porosity from 34% to 31.1%. Permeability decreased exponentially from ~4.9x10-12 m2 to 1.18 x10-12 m2. The decrease in porosity and permeability suggests geochemical transformations in the mineral assemblage of the core, which we observe through petrographic analysis of an unaltered sample of the same lithology in contrast with the altered core. There is a significant increase in grain coatings, as well as reduction in the grain size, suggesting dissolution re-precipitation mechanisms. Finally, to develop a framework for the coupled geochemical and hydrologic responses observed experimentally, we have calibrated a reactive transport model at the core scale using the TOUGHREACT simulator [1]. [1] Xu et al. (2011) Comput. Geosci.

FLUKA: A Multi-Particle Transport Code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferrari, A.; Sala, P.R.; /CERN /INFN, Milan

2005-12-14

This report describes the 2005 version of the Fluka particle transport code. The first part introduces the basic notions, describes the modular structure of the system, and contains an installation and beginner's guide. The second part complements this initial information with details about the various components of Fluka and how to use them. It concludes with a detailed history and bibliography.

Adapting HYDRUS-1D to simulate overland flow and reactive transport during sheet flow deviations

USDA-ARS?s Scientific Manuscript database

The HYDRUS-1D code is a popular numerical model for solving the Richards equation for variably-saturated water flow and solute transport in porous media. This code was adapted to solve rather than the Richards equation for subsurface flow the diffusion wave equation for overland flow at the soil sur...

Modeling of boron species in the Falcon 17 and ISP-34 integral tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lazaridis, M.; Capitao, J.A.; Drossinos, Y.

1996-09-01

The RAFT computer code for aerosol formation and transport was modified to include boron species in its chemical database. The modification was necessary to calculate fission product transport and deposition in the FAL-17 and ISP-34 Falcon tests, where boric acid was injected. The experimental results suggest that the transport of cesium is modified in the presence of boron. The results obtained with the modified RAFT code are presented; they show good agreement with experimental results for cesium and partial agreement for boron deposition in the Falcon silica tube. The new version of the RAFT code predicts the same behavior formore » iodine deposition as the previous version, where boron species were not included.« less

Comparison of Stopping Power and Range Databases for Radiation Transport Study

NASA Technical Reports Server (NTRS)

Tai, H.; Bichsel, Hans; Wilson, John W.; Shinn, Judy L.; Cucinotta, Francis A.; Badavi, Francis F.

1997-01-01

The codes used to calculate stopping power and range for the space radiation shielding program at the Langley Research Center are based on the work of Ziegler but with modifications. As more experience is gained from experiments at heavy ion accelerators, prudence dictates a reevaluation of the current databases. Numerical values of stopping power and range calculated from four different codes currently in use are presented for selected ions and materials in the energy domain suitable for space radiation transport. This study of radiation transport has found that for most collision systems and for intermediate particle energies, agreement is less than 1 percent, in general, among all the codes. However, greater discrepancies are seen for heavy systems, especially at low particle energies.

Bibliography for acid-rock drainage and selected acid-mine drainage issues related to acid-rock drainage from transportation activities

USGS Publications Warehouse

Bradley, Michael W.; Worland, Scott C.

2015-01-01

Acid-rock drainage occurs through the interaction of rainfall on pyrite-bearing formations. When pyrite (FeS2) is exposed to oxygen and water in mine workings or roadcuts, the mineral decomposes and sulfur may react to form sulfuric acid, which often results in environmental problems and potential damage to the transportation infrastructure. The accelerated oxidation of pyrite and other sulfidic minerals generates low pH water with potentially high concentrations of trace metals. Much attention has been given to contamination arising from acid mine drainage, but studies related to acid-rock drainage from road construction are relatively limited. The U.S. Geological Survey, in cooperation with the Tennessee Department of Transportation, is conducting an investigation to evaluate the occurrence and processes controlling acid-rock drainage and contaminant transport from roadcuts in Tennessee. The basic components of acid-rock drainage resulting from transportation activities are described and a bibliography, organized by relevant categories (remediation, geochemical, microbial, biological impact, and secondary mineralization) is presented.

Statistical Analysis of CFD Solutions from the Third AIAA Drag Prediction Workshop

NASA Technical Reports Server (NTRS)

Morrison, Joseph H.; Hemsch, Michael J.

2007-01-01

The first AIAA Drag Prediction Workshop, held in June 2001, evaluated the results from an extensive N-version test of a collection of Reynolds-Averaged Navier-Stokes CFD codes. The code-to-code scatter was more than an order of magnitude larger than desired for design and experimental validation of cruise conditions for a subsonic transport configuration. The second AIAA Drag Prediction Workshop, held in June 2003, emphasized the determination of installed pylon-nacelle drag increments and grid refinement studies. The code-to-code scatter was significantly reduced compared to the first DPW, but still larger than desired. However, grid refinement studies showed no significant improvement in code-to-code scatter with increasing grid refinement. The third Drag Prediction Workshop focused on the determination of installed side-of-body fairing drag increments and grid refinement studies for clean attached flow on wing alone configurations and for separated flow on the DLR-F6 subsonic transport model. This work evaluated the effect of grid refinement on the code-to-code scatter for the clean attached flow test cases and the separated flow test cases.

Toward computational models of magma genesis and geochemical transport in subduction zones

NASA Astrophysics Data System (ADS)

Katz, R.; Spiegelman, M.

2003-04-01

The chemistry of material erupted from subduction-related volcanoes records important information about the processes that lead to its formation at depth in the Earth. Self-consistent numerical simulations provide a useful tool for interpreting this data as they can explore the non-linear feedbacks between processes that control the generation and transport of magma. A model capable of addressing such issues should include three critical components: (1) a variable viscosity solid flow solver with smooth and accurate pressure and velocity fields, (2) a parameterization of mass transfer reactions between the solid and fluid phases and (3) a consistent fluid flow and reactive transport code. We report on progress on each of these parts. To handle variable-viscosity solid-flow in the mantle wedge, we are adapting a Patankar-based FAS multigrid scheme developed by Albers (2000, J. Comp. Phys.). The pressure field in this scheme is the solution to an elliptic equation on a staggered grid. Thus we expect computed pressure fields to have smooth gradient fields suitable for porous flow calculations, unlike those of commonly used penalty-method schemes. Use of a temperature and strain-rate dependent mantle rheology has been shown to have important consequences for the pattern of flow and the temperature structure in the wedge. For computing thermal structure we present a novel scheme that is a hybrid of Crank-Nicholson (CN) and Semi-Lagrangian (SL) methods. We have tested the SLCN scheme on advection across a broad range of Peclet numbers and show the results. This scheme is also useful for low-diffusivity chemical transport. We also describe our parameterization of hydrous mantle melting [Katz et. al., G3, 2002 in review]. This parameterization is designed to capture the melting behavior of peridotite--water systems over parameter ranges relevant to subduction. The parameterization incorporates data and intuition gained from laboratory experiments and thermodynamic calculations yet it remains flexible and computationally efficient. Given accurate solid-flow fields, a parameterization of hydrous melting and a method for calculating thermal structure (enforcing energy conservation), the final step is to integrate these components into a consistent framework for reactive-flow and chemical transport in deformable porous media. We present preliminary results for reactive flow in 2-D static and upwelling columns and discuss possible mechanical and chemical consequences of open system reactive melting with application to arcs.

Reactive transport modeling of stable carbon isotope fractionation in a multi-phase multi-component system during carbon sequestration

DOE PAGES

Zhang, Shuo; DePaolo, Donald J.; Zheng, Liange; ...

2014-12-31

Carbon stable isotopes can be used in characterization and monitoring of CO 2 sequestration sites to track the migration of the CO 2 plume and identify leakage sources, and to evaluate the chemical reactions that take place in the CO 2-water-rock system. However, there are few tools available to incorporate stable isotope information into flow and transport codes used for CO 2 sequestration problems. We present a numerical tool for modeling the transport of stable carbon isotopes in multiphase reactive systems relevant to geologic carbon sequestration. The code is an extension of the reactive transport code TOUGHREACT. The transport modulemore » of TOUGHREACT was modified to include separate isotopic species of CO 2 gas and dissolved inorganic carbon (CO 2, CO 3 2-, HCO 3 -,…). Any process of transport or reaction influencing a given carbon species also influences its isotopic ratio. Isotopic fractionation is thus fully integrated within the dynamic system. The chemical module and database have been expanded to include isotopic exchange and fractionation between the carbon species in both gas and aqueous phases. The performance of the code is verified by modeling ideal systems and comparing with theoretical results. Efforts are also made to fit field data from the Pembina CO 2 injection project in Canada. We show that the exchange of carbon isotopes between dissolved and gaseous carbon species combined with fluid flow and transport, produce isotopic effects that are significantly different from simple two-component mixing. These effects are important for understanding the isotopic variations observed in field demonstrations.« less

Polarization-multiplexed rate-adaptive non-binary-quasi-cyclic-LDPC-coded multilevel modulation with coherent detection for optical transport networks.

PubMed

Arabaci, Murat; Djordjevic, Ivan B; Saunders, Ross; Marcoccia, Roberto M

2010-02-01

In order to achieve high-speed transmission over optical transport networks (OTNs) and maximize its throughput, we propose using a rate-adaptive polarization-multiplexed coded multilevel modulation with coherent detection based on component non-binary quasi-cyclic (QC) LDPC codes. Compared to prior-art bit-interleaved LDPC-coded modulation (BI-LDPC-CM) scheme, the proposed non-binary LDPC-coded modulation (NB-LDPC-CM) scheme not only reduces latency due to symbol- instead of bit-level processing but also provides either impressive reduction in computational complexity or striking improvements in coding gain depending on the constellation size. As the paper presents, compared to its prior-art binary counterpart, the proposed NB-LDPC-CM scheme addresses the needs of future OTNs, which are achieving the target BER performance and providing maximum possible throughput both over the entire lifetime of the OTN, better.

TDA : Transportation Development Act : statutes and California codes of regulations.

DOT National Transportation Integrated Search

2009-03-01

The Mills-Alquist-Deddeh Act (SB 325) was enacted by the California Legislature to improve : existing public transportation services and encourage regional transportation coordination. : Known as the Transportation Development Act (TDA) of 1971, this...

A Monte Carlo model system for core analysis and epithermal neutron beam design at the Washington State University Radiation Center

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burns, T.D. Jr.

1996-05-01

The Monte Carlo Model System (MCMS) for the Washington State University (WSU) Radiation Center provides a means through which core criticality and power distributions can be calculated, as well as providing a method for neutron and photon transport necessary for BNCT epithermal neutron beam design. The computational code used in this Model System is MCNP4A. The geometric capability of this Monte Carlo code allows the WSU system to be modeled very accurately. A working knowledge of the MCNP4A neutron transport code increases the flexibility of the Model System and is recommended, however, the eigenvalue/power density problems can be run withmore » little direct knowledge of MCNP4A. Neutron and photon particle transport require more experience with the MCNP4A code. The Model System consists of two coupled subsystems; the Core Analysis and Source Plane Generator Model (CASP), and the BeamPort Shell Particle Transport Model (BSPT). The CASP Model incorporates the S({alpha}, {beta}) thermal treatment, and is run as a criticality problem yielding, the system eigenvalue (k{sub eff}), the core power distribution, and an implicit surface source for subsequent particle transport in the BSPT Model. The BSPT Model uses the source plane generated by a CASP run to transport particles through the thermal column beamport. The user can create filter arrangements in the beamport and then calculate characteristics necessary for assessing the BNCT potential of the given filter want. Examples of the characteristics to be calculated are: neutron fluxes, neutron currents, fast neutron KERMAs and gamma KERMAs. The MCMS is a useful tool for the WSU system. Those unfamiliar with the MCNP4A code can use the MCMS transparently for core analysis, while more experienced users will find the particle transport capabilities very powerful for BNCT filter design.« less

hybrid\\scriptsize{{MANTIS}}: a CPU-GPU Monte Carlo method for modeling indirect x-ray detectors with columnar scintillators

NASA Astrophysics Data System (ADS)

Sharma, Diksha; Badal, Andreu; Badano, Aldo

2012-04-01

The computational modeling of medical imaging systems often requires obtaining a large number of simulated images with low statistical uncertainty which translates into prohibitive computing times. We describe a novel hybrid approach for Monte Carlo simulations that maximizes utilization of CPUs and GPUs in modern workstations. We apply the method to the modeling of indirect x-ray detectors using a new and improved version of the code \\scriptsize{{MANTIS}}, an open source software tool used for the Monte Carlo simulations of indirect x-ray imagers. We first describe a GPU implementation of the physics and geometry models in fast\\scriptsize{{DETECT}}2 (the optical transport model) and a serial CPU version of the same code. We discuss its new features like on-the-fly column geometry and columnar crosstalk in relation to the \\scriptsize{{MANTIS}} code, and point out areas where our model provides more flexibility for the modeling of realistic columnar structures in large area detectors. Second, we modify \\scriptsize{{PENELOPE}} (the open source software package that handles the x-ray and electron transport in \\scriptsize{{MANTIS}}) to allow direct output of location and energy deposited during x-ray and electron interactions occurring within the scintillator. This information is then handled by optical transport routines in fast\\scriptsize{{DETECT}}2. A load balancer dynamically allocates optical transport showers to the GPU and CPU computing cores. Our hybrid\\scriptsize{{MANTIS}} approach achieves a significant speed-up factor of 627 when compared to \\scriptsize{{MANTIS}} and of 35 when compared to the same code running only in a CPU instead of a GPU. Using hybrid\\scriptsize{{MANTIS}}, we successfully hide hours of optical transport time by running it in parallel with the x-ray and electron transport, thus shifting the computational bottleneck from optical to x-ray transport. The new code requires much less memory than \\scriptsize{{MANTIS}} and, as a result, allows us to efficiently simulate large area detectors.

Regional Atmospheric Transport Code for Hanford Emission Tracking (RATCHET). Hanford Environmental Dose Reconstruction Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramsdell, J.V. Jr.; Simonen, C.A.; Burk, K.W.

1994-02-01

The purpose of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate radiation doses that individuals may have received from operations at the Hanford Site since 1944. This report deals specifically with the atmospheric transport model, Regional Atmospheric Transport Code for Hanford Emission Tracking (RATCHET). RATCHET is a major rework of the MESOILT2 model used in the first phase of the HEDR Project; only the bookkeeping framework escaped major changes. Changes to the code include (1) significant changes in the representation of atmospheric processes and (2) incorporation of Monte Carlo methods for representing uncertainty in input data, model parameters,more » and coefficients. To a large extent, the revisions to the model are based on recommendations of a peer working group that met in March 1991. Technical bases for other portions of the atmospheric transport model are addressed in two other documents. This report has three major sections: a description of the model, a user`s guide, and a programmer`s guide. These sections discuss RATCHET from three different perspectives. The first provides a technical description of the code with emphasis on details such as the representation of the model domain, the data required by the model, and the equations used to make the model calculations. The technical description is followed by a user`s guide to the model with emphasis on running the code. The user`s guide contains information about the model input and output. The third section is a programmer`s guide to the code. It discusses the hardware and software required to run the code. The programmer`s guide also discusses program structure and each of the program elements.« less

Minerva: Cylindrical coordinate extension for Athena

NASA Astrophysics Data System (ADS)

Skinner, M. Aaron; Ostriker, Eve C.

2013-02-01

Minerva is a cylindrical coordinate extension of the Athena astrophysical MHD code of Stone, Gardiner, Teuben, and Hawley. The extension follows the approach of Athena's original developers and has been designed to alter the existing Cartesian-coordinates code as minimally and transparently as possible. The numerical equations in cylindrical coordinates are formulated to maintain consistency with constrained transport (CT), a central feature of the Athena algorithm, while making use of previously implemented code modules such as the Riemann solvers. Angular momentum transport, which is critical in astrophysical disk systems dominated by rotation, is treated carefully.

Geochemical and geological factors controlling the spatial distribution of sulfate-methane transition zone in the Ría de Vigo (NW Spain)

NASA Astrophysics Data System (ADS)

Martínez-Carreño, N.; García-Gil, S.; Cartelle, V.; de Blas, E.; Ramírez-Pérez, A. M.; Insua, T. L.

2017-05-01

High-resolution seismic profiles, gravity core analysis and radiocarbon data have been used to identify the factors behind the methane production and free gas accumulation in the Ría de Vigo. Lithological and geochemical parameters (sulfate and methane concentration) from seventeen gravity cores were analyzed to characterize the sediment of the ria. The distribution of methane-charged sediments is mainly controlled by the quantity and quality of organic matter. Geochemical analyses reveal minimum methane concentrations ranging between 1 μM and 1 mM in sediments located outside the acoustic gas field, while gas-bearing sediments, show methane concentrations up to 5 mM. A shallowing of the sulfate-methane transition zone (SMTZ) is observed from the outer to the inner area of the ria. The presence of methane in the sulfate reduction zone (SRZ) likely to reflect the existence of methylotropic methanogenesis and/or migration processes of deeper methane gas in the sediments of the Ría de Vigo. The presence of an 'anomalous' high-sulfate concentration layer below the SMTZ in the inner and middle area of the ria, is attributed to the intrusion of sulfate-rich waters from adjacent areas that could be transported laterally through more porous layers.

Reach-scale cation exchange controls on major ion chemistry of an Antarctic glacial meltwater stream

USGS Publications Warehouse

Gooseff, Michael N.; McKnight, Diane M.; Runkel, Robert L.

2004-01-01

McMurdo dry valleys of Antarctica represent the largest of the ice-free areas on the Antarctic continent, containing glaciers, meltwater streams, and closed basin lakes. Previous geochemical studies of dry valley streams and lakes have addressed chemical weathering reactions of hyporheic substrate and geochemical evolution of dry valley surface waters. We examine cation transport and exchange reactions during a stream tracer experiment in a dry valley glacial meltwater stream. The injection solution was composed of dissolved Li+, Na+, K+, and Cl-. Chloride behaved conservatively in this stream, but Li+, Na+, and K+ were reactive to varying degrees. Mass balance analysis indicates that relative to Cl-, Li+ and K+ were taken up in downstream transport and Na+ was released. Simulations of conservative and reactive (first-order uptake or generation) solute transport were made with the OTIS (one-dimensional solute transport with inflow and storage) model. Among the four experimental reaches of Green Creek, solute transport simulations reveal that Li+ was removed from stream water in all four reaches, K+ was released in two reaches, taken up in one reach, and Na+ was released in all four reaches. Hyporheic sediments appear to be variable with uptake of Li+ in two reaches, uptake of K+ in one reach, release of K+ in two reaches, and uptake of Na+ in one reach. Mass balances of the conservative and reactive simulations show that from 1.05 to 2.19 moles of Li+ was adsorbed per reach, but less than 0.3 moles of K+ and less than 0.9 moles of Na+ were released per reach. This suggests that either (1) exchange of another ion which was not analyzed in this experiment or (2) that both ion exchange and sorption control inorganic solute transport. The elevated cation concentrations introduced during the experiment are typical of initial flows in each flow season, which flush accumulated dry salts from the streambed. We propose that the bed sediments (which compose the hyporheic zone) modulate the flushing of these salts during initial flows each season, due to ion exchange and sorption reactions.

Solar Proton Transport within an ICRU Sphere Surrounded by a Complex Shield: Combinatorial Geometry

NASA Technical Reports Server (NTRS)

Wilson, John W.; Slaba, Tony C.; Badavi, Francis F.; Reddell, Brandon D.; Bahadori, Amir A.

2015-01-01

The 3DHZETRN code, with improved neutron and light ion (Z (is) less than 2) transport procedures, was recently developed and compared to Monte Carlo (MC) simulations using simplified spherical geometries. It was shown that 3DHZETRN agrees with the MC codes to the extent they agree with each other. In the present report, the 3DHZETRN code is extended to enable analysis in general combinatorial geometry. A more complex shielding structure with internal parts surrounding a tissue sphere is considered and compared against MC simulations. It is shown that even in the more complex geometry, 3DHZETRN agrees well with the MC codes and maintains a high degree of computational efficiency.

Verification of Three Dimensional Triangular Prismatic Discrete Ordinates Transport Code ENSEMBLE-TRIZ by Comparison with Monte Carlo Code GMVP

NASA Astrophysics Data System (ADS)

Homma, Yuto; Moriwaki, Hiroyuki; Ohki, Shigeo; Ikeda, Kazumi

2014-06-01

This paper deals with verification of three dimensional triangular prismatic discrete ordinates transport calculation code ENSEMBLE-TRIZ by comparison with multi-group Monte Carlo calculation code GMVP in a large fast breeder reactor. The reactor is a 750 MWe electric power sodium cooled reactor. Nuclear characteristics are calculated at beginning of cycle of an initial core and at beginning and end of cycle of equilibrium core. According to the calculations, the differences between the two methodologies are smaller than 0.0002 Δk in the multi-plication factor, relatively about 1% in the control rod reactivity, and 1% in the sodium void reactivity.

Shielding evaluation for solar particle events using MCNPX, PHITS and OLTARIS codes

NASA Astrophysics Data System (ADS)

Aghara, S. K.; Sriprisan, S. I.; Singleterry, R. C.; Sato, T.

2015-01-01

Detailed analyses of Solar Particle Events (SPE) were performed to calculate primary and secondary particle spectra behind aluminum, at various thicknesses in water. The simulations were based on Monte Carlo (MC) radiation transport codes, MCNPX 2.7.0 and PHITS 2.64, and the space radiation analysis website called OLTARIS (On-Line Tool for the Assessment of Radiation in Space) version 3.4 (uses deterministic code, HZETRN, for transport). The study is set to investigate the impact of SPEs spectra transporting through 10 or 20 g/cm2 Al shield followed by 30 g/cm2 of water slab. Four historical SPE events were selected and used as input source spectra particle differential spectra for protons, neutrons, and photons are presented. The total particle fluence as a function of depth is presented. In addition to particle flux, the dose and dose equivalent values are calculated and compared between the codes and with the other published results. Overall, the particle fluence spectra from all three codes show good agreement with the MC codes showing closer agreement compared to the OLTARIS results. The neutron particle fluence from OLTARIS is lower than the results from MC codes at lower energies (E < 100 MeV). Based on mean square difference analysis the results from MCNPX and PHITS agree better for fluence, dose and dose equivalent when compared to OLTARIS results.

High-temperature hydrothermal circulation in the lower oceanic crust at fast spreading ridges: Reconciling geophysical and geochemical constraints

NASA Astrophysics Data System (ADS)

Wilcock, W.

2003-04-01

Hydrothermal circulation is the dominant mechanism for cooling young oceanic crust and knowledge of its depth, extent and timing is critical for our understanding of crustal accretion. At fast-spreading ridges there is considerable controversy regarding the importance of this process in the lower crust. Geochemical data indicate that high-temperature hydrothermal fluids react with the lower crust but they also suggest that the reactions are limited to a narrow temperature interval and involve relatively small volumes of fluid. As a result many geochemical studies conclude that high-temperature hydrothermal circulation plays a relatively small role in heat transport in the lower crust and occurs in a closed system that is isolated from upper crustal hydrothermal cells. In contrast, seismic observations on the fast spreading East Pacific Rise show that the mid-crustal axial magma chamber is underlain by a low velocity zone which is no more than 5-8 km wide throughout the lower crust and is interpreted as a region of elevated temperatures containing relatively low average melt fractions. Irrespective of the style of lower crustal accretion, simple physical considerations suggest that this structure is only thermally feasible if the lower crust cools by extensive hydrothermal circulation. Modeling studies indicate that this requires the permeability of the lower crust to temporarily reach at least ~10-13 m2. In order to reconcile the geochemical and geophysical data it is important to recognize that the thermal constraints do not require pervasive seawater circulation in the lower crust and can be satisfied by focused flow through narrow permeable zones spaced as far as about 1 km apart. Widely spaced regions of flow might be difficult to find in the field especially if the sampling strategies focus on the freshest outcrops. There is a tendency to overestimate the volume of fluid that must circulate through an open single-pass system. The fluid-rock ratios (0.2 - 1) inferred from oxygen isotope studies are often cited as evidence of limited circulation but when interpreted physically they are actually sufficient to transport a substantial proportion of the heat required to solidify and cool the lower crust. Nevertheless the geophysical constraints are also compatible with circulation in a two-layer double diffusive system favored by many researchers, in which the lower crust is cooled by a recirculating brine cell.

NPSS Space Team

NASA Technical Reports Server (NTRS)

Lavelle, Tom

2003-01-01

The objective is to increase the usability of the current NPSS code/architecture by incorporating an advanced space transportation propulsion system capability into the existing NPSS code and begin defining advanced capabilities for NPSS and provide an enhancement for the NPSS code/architecture.

Validation of the WIMSD4M cross-section generation code with benchmark results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deen, J.R.; Woodruff, W.L.; Leal, L.E.

1995-01-01

The WIMSD4 code has been adopted for cross-section generation in support of the Reduced Enrichment Research and Test Reactor (RERTR) program at Argonne National Laboratory (ANL). Subsequently, the code has undergone several updates, and significant improvements have been achieved. The capability of generating group-collapsed micro- or macroscopic cross sections from the ENDF/B-V library and the more recent evaluation, ENDF/B-VI, in the ISOTXS format makes the modified version of the WIMSD4 code, WIMSD4M, very attractive, not only for the RERTR program, but also for the reactor physics community. The intent of the present paper is to validate the WIMSD4M cross-section librariesmore » for reactor modeling of fresh water moderated cores. The results of calculations performed with multigroup cross-section data generated with the WIMSD4M code will be compared against experimental results. These results correspond to calculations carried out with thermal reactor benchmarks of the Oak Ridge National Laboratory (ORNL) unreflected HEU critical spheres, the TRX LEU critical experiments, and calculations of a modified Los Alamos HEU D{sub 2}O moderated benchmark critical system. The benchmark calculations were performed with the discrete-ordinates transport code, TWODANT, using WIMSD4M cross-section data. Transport calculations using the XSDRNPM module of the SCALE code system are also included. In addition to transport calculations, diffusion calculations with the DIF3D code were also carried out, since the DIF3D code is used in the RERTR program for reactor analysis and design. For completeness, Monte Carlo results of calculations performed with the VIM and MCNP codes are also presented.« less

30 CFR 206.56 - Transportation allowances-general.

Code of Federal Regulations, 2010 CFR

2010-07-01

... oil has been determined under § 206.52 or § 206.53 of this subpart at a point (e.g., sales point or... sales type code may not exceed 50 percent of the value of the oil at the point of sale as determined under § 206.52 of this subpart. Transportation costs cannot be transferred between sales type codes or...

LLNL Mercury Project Trinity Open Science Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dawson, Shawn A.

The Mercury Monte Carlo particle transport code is used to simulate the transport of radiation through urban environments. These challenging calculations include complicated geometries and require significant computational resources to complete. In the proposed Trinity Open Science calculations, I will investigate computer science aspects of the code which are relevant to convergence of the simulation quantities with increasing Monte Carlo particle counts.

THC-MP: High performance numerical simulation of reactive transport and multiphase flow in porous media

NASA Astrophysics Data System (ADS)

Wei, Xiaohui; Li, Weishan; Tian, Hailong; Li, Hongliang; Xu, Haixiao; Xu, Tianfu

2015-07-01

The numerical simulation of multiphase flow and reactive transport in the porous media on complex subsurface problem is a computationally intensive application. To meet the increasingly computational requirements, this paper presents a parallel computing method and architecture. Derived from TOUGHREACT that is a well-established code for simulating subsurface multi-phase flow and reactive transport problems, we developed a high performance computing THC-MP based on massive parallel computer, which extends greatly on the computational capability for the original code. The domain decomposition method was applied to the coupled numerical computing procedure in the THC-MP. We designed the distributed data structure, implemented the data initialization and exchange between the computing nodes and the core solving module using the hybrid parallel iterative and direct solver. Numerical accuracy of the THC-MP was verified through a CO2 injection-induced reactive transport problem by comparing the results obtained from the parallel computing and sequential computing (original code). Execution efficiency and code scalability were examined through field scale carbon sequestration applications on the multicore cluster. The results demonstrate successfully the enhanced performance using the THC-MP on parallel computing facilities.

Investigation of Fluctuation-Induced Electron Transport in Hall Thrusters with a 2D Hybrid Code in the Azimuthal and Axial Coordinates

NASA Astrophysics Data System (ADS)

Fernandez, Eduardo; Borelli, Noah; Cappelli, Mark; Gascon, Nicolas

2003-10-01

Most current Hall thruster simulation efforts employ either 1D (axial), or 2D (axial and radial) codes. These descriptions crucially depend on the use of an ad-hoc perpendicular electron mobility. Several models for the mobility are typically invoked: classical, Bohm, empirically based, wall-induced, as well as combinations of the above. Experimentally, it is observed that fluctuations and electron transport depend on axial distance and operating parameters. Theoretically, linear stability analyses have predicted a number of unstable modes; yet the nonlinear character of the fluctuations and/or their contribution to electron transport remains poorly understood. Motivated by these observations, a 2D code in the azimuthal and axial coordinates has been written. In particular, the simulation self-consistently calculates the azimuthal disturbances resulting in fluctuating drifts, which in turn (if properly correlated with plasma density disturbances) result in fluctuation-driven electron transport. The characterization of the turbulence at various operating parameters and across the channel length is also the object of this study. A description of the hybrid code used in the simulation as well as the initial results will be presented.

Nonambipolar Transport and Torque in Perturbed Equilibria

NASA Astrophysics Data System (ADS)

Logan, N. C.; Park, J.-K.; Wang, Z. R.; Berkery, J. W.; Kim, K.; Menard, J. E.

2013-10-01

A new Perturbed Equilibrium Nonambipolar Transport (PENT) code has been developed to calculate the neoclassical toroidal torque from radial current composed of both passing and trapped particles in perturbed equilibria. This presentation outlines the physics approach used in the development of the PENT code, with emphasis on the effects of retaining general aspect-ratio geometric effects. First, nonambipolar transport coefficients and corresponding neoclassical toroidal viscous (NTV) torque in perturbed equilibria are re-derived from the first order gyro-drift-kinetic equation in the ``combined-NTV'' PENT formalism. The equivalence of NTV torque and change in potential energy due to kinetic effects [J-K. Park, Phys. Plas., 2011] is then used to showcase computational challenges shared between PENT and stability codes MISK and MARS-K. Extensive comparisons to a reduced model, which makes numerous large aspect ratio approximations, are used throughout to emphasize geometry dependent physics such as pitch angle resonances. These applications make extensive use of the PENT code's native interfacing with the Ideal Perturbed Equilibrium Code (IPEC), and the combination of these codes is a key step towards an iterative solver for self-consistent perturbed equilibrium torque. Supported by US DOE contract #DE-AC02-09CH11466 and the DOE Office of Science Graduate Fellowship administered by the Oak Ridge Institute for Science & Education under contract #DE-AC05-06OR23100.

The Initial Atmospheric Transport (IAT) Code: Description and Validation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morrow, Charles W.; Bartel, Timothy James

The Initial Atmospheric Transport (IAT) computer code was developed at Sandia National Laboratories as part of their nuclear launch accident consequences analysis suite of computer codes. The purpose of IAT is to predict the initial puff/plume rise resulting from either a solid rocket propellant or liquid rocket fuel fire. The code generates initial conditions for subsequent atmospheric transport calculations. The Initial Atmospheric Transfer (IAT) code has been compared to two data sets which are appropriate to the design space of space launch accident analyses. The primary model uncertainties are the entrainment coefficients for the extended Taylor model. The Titan 34Dmore » accident (1986) was used to calibrate these entrainment settings for a prototypic liquid propellant accident while the recent Johns Hopkins University Applied Physics Laboratory (JHU/APL, or simply APL) large propellant block tests (2012) were used to calibrate the entrainment settings for prototypic solid propellant accidents. North American Meteorology (NAM )formatted weather data profiles are used by IAT to determine the local buoyancy force balance. The IAT comparisons for the APL solid propellant tests illustrate the sensitivity of the plume elevation to the weather profiles; that is, the weather profile is a dominant factor in determining the plume elevation. The IAT code performed remarkably well and is considered validated for neutral weather conditions.« less

Transport studies in high-performance field reversed configuration plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, S., E-mail: sgupta@trialphaenergy.com; Barnes, D. C.; Dettrick, S. A.

2016-05-15

A significant improvement of field reversed configuration (FRC) lifetime and plasma confinement times in the C-2 plasma, called High Performance FRC regime, has been observed with neutral beam injection (NBI), improved edge stability, and better wall conditioning [Binderbauer et al., Phys. Plasmas 22, 056110 (2015)]. A Quasi-1D (Q1D) fluid transport code has been developed and employed to carry out transport analysis of such C-2 plasma conditions. The Q1D code is coupled to a Monte-Carlo code to incorporate the effect of fast ions, due to NBI, on the background FRC plasma. Numerically, the Q1D transport behavior with enhanced transport coefficients (butmore » with otherwise classical parametric dependencies) such as 5 times classical resistive diffusion, classical thermal ion conductivity, 20 times classical electron thermal conductivity, and classical fast ion behavior fit with the experimentally measured time evolution of the excluded flux radius, line-integrated density, and electron/ion temperature. The numerical study shows near sustainment of poloidal flux for nearly 1 ms in the presence of NBI.« less

Groundwater flow with energy transport and water-ice phase change: Numerical simulations, benchmarks, and application to freezing in peat bogs

USGS Publications Warehouse

McKenzie, J.M.; Voss, C.I.; Siegel, D.I.

2007-01-01

In northern peatlands, subsurface ice formation is an important process that can control heat transport, groundwater flow, and biological activity. Temperature was measured over one and a half years in a vertical profile in the Red Lake Bog, Minnesota. To successfully simulate the transport of heat within the peat profile, the U.S. Geological Survey's SUTRA computer code was modified. The modified code simulates fully saturated, coupled porewater-energy transport, with freezing and melting porewater, and includes proportional heat capacity and thermal conductivity of water and ice, decreasing matrix permeability due to ice formation, and latent heat. The model is verified by correctly simulating the Lunardini analytical solution for ice formation in a porous medium with a mixed ice-water zone. The modified SUTRA model correctly simulates the temperature and ice distributions in the peat bog. Two possible benchmark problems for groundwater and energy transport with ice formation and melting are proposed that may be used by other researchers for code comparison. ?? 2006 Elsevier Ltd. All rights reserved.

2006 Interregional Transportation Improvement Program.

DOT National Transportation Integrated Search

2006-01-01

The Department of Transportations (Department) five-year Interregional Transportation : Improvement Program (ITIP) is prepared pursuant to Government Code 14526 and : consists of projects funded from the interregional share, which is 25 percent of...

Comparison of EGS4 and MCNP Monte Carlo codes when calculating radiotherapy depth doses.

PubMed

Love, P A; Lewis, D G; Al-Affan, I A; Smith, C W

1998-05-01

The Monte Carlo codes EGS4 and MCNP have been compared when calculating radiotherapy depth doses in water. The aims of the work were to study (i) the differences between calculated depth doses in water for a range of monoenergetic photon energies and (ii) the relative efficiency of the two codes for different electron transport energy cut-offs. The depth doses from the two codes agree with each other within the statistical uncertainties of the calculations (1-2%). The relative depth doses also agree with data tabulated in the British Journal of Radiology Supplement 25. A discrepancy in the dose build-up region may by attributed to the different electron transport algorithims used by EGS4 and MCNP. This discrepancy is considerably reduced when the improved electron transport routines are used in the latest (4B) version of MCNP. Timing calculations show that EGS4 is at least 50% faster than MCNP for the geometries used in the simulations.

COBRA-SFS thermal-hydraulic analysis code for spent fuel storage and transportation casks: Models and methods

DOE PAGES

Michener, Thomas E.; Rector, David R.; Cuta, Judith M.

2017-09-01

COBRA-SFS, a thermal-hydraulics code developed for steady-state and transient analysis of multi-assembly spent-fuel storage and transportation systems, has been incorporated into the Used Nuclear Fuel-Storage, Transportation and Disposal Analysis Resource and Data System tool as a module devoted to spent fuel package thermal analysis. This paper summarizes the basic formulation of the equations and models used in the COBRA-SFS code, showing that COBRA-SFS fully captures the important physical behavior governing the thermal performance of spent fuel storage systems, with internal and external natural convection flow patterns, and heat transfer by convection, conduction, and thermal radiation. Of particular significance is themore » capability for detailed thermal radiation modeling within the fuel rod array.« less

COBRA-SFS thermal-hydraulic analysis code for spent fuel storage and transportation casks: Models and methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michener, Thomas E.; Rector, David R.; Cuta, Judith M.

COBRA-SFS, a thermal-hydraulics code developed for steady-state and transient analysis of multi-assembly spent-fuel storage and transportation systems, has been incorporated into the Used Nuclear Fuel-Storage, Transportation and Disposal Analysis Resource and Data System tool as a module devoted to spent fuel package thermal analysis. This paper summarizes the basic formulation of the equations and models used in the COBRA-SFS code, showing that COBRA-SFS fully captures the important physical behavior governing the thermal performance of spent fuel storage systems, with internal and external natural convection flow patterns, and heat transfer by convection, conduction, and thermal radiation. Of particular significance is themore » capability for detailed thermal radiation modeling within the fuel rod array.« less

DEVELOPMENT OF A GEOCHEMICAL MODEL FOR URANIUM TRANSPORT IN THE UNSATURATED AND SATURATED SEDIMENTS AT THE 200 WEST AREA OF THE US DEPARTMENT OF ENERGY HANFORD SITE WASHINGTON (SEPTEMBER 2004)

DOE Office of Scientific and Technical Information (OSTI.GOV)

ADAMS SC; PETERSEN SW

2010-03-24

Final Deliverable under GWP-HQ-LMT-02 contract for Hanford Sci. & Tech. Gp. to BHI. The scope of work covered laboratory analyses and gephysical logging for 299-W19-43 near the 200 West U Plant. Other isotopic analyses were conducted for holes around 216-U-1&2, including U-236.

Radiation Transport and Shielding for Space Exploration and High Speed Flight Transportation

NASA Technical Reports Server (NTRS)

Maung, Khin Maung; Trapathi, R. K.

1997-01-01

Transportation of ions and neutrons in matter is of direct interest in several technologically important and scientific areas, including space radiation, cosmic ray propagation studies in galactic medium, nuclear power plants and radiological effects that impact industrial and public health. For the proper assessment of radiation exposure, both reliable transport codes and accurate data are needed. Nuclear cross section data is one of the essential inputs into the transport codes. In order to obtain an accurate parametrization of cross section data, theoretical input is indispensable especially for processes where there is little or no experimental data available. In this grant period work has been done on the studies of the use of relativistic equations and their one-body limits. The results will be useful in choosing appropriate effective one-body equation for reaction calculations. Work has also been done to improve upon the data base needed for the transport codes used in the studies of radiation transport and shielding for space exploration and high speed flight transportation. A phenomenological model was developed for the total absorption cross sections valid for any system of charged and/or uncharged collision pairs for the entire energy range. The success of the model is gratifying. It is being used by other federal agencies, national labs and universities. A list of publications based on the work during the grant period is given below and copies are enclosed with this report.

DARTAB: a program to combine airborne radionuclide environmental exposure data with dosimetric and health effects data to generate tabulations of predicted health impacts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Begovich, C.L.; Eckerman, K.F.; Schlatter, E.C.

1981-08-01

The DARTAB computer code combines radionuclide environmental exposure data with dosimetric and health effects data to generate tabulations of the predicted impact of radioactive airborne effluents. DARTAB is independent of the environmental transport code used to generate the environmental exposure data and the codes used to produce the dosimetric and health effects data. Therefore human dose and risk calculations need not be added to every environmental transport code. Options are included in DARTAB to permit the user to request tabulations by various topics (e.g., cancer site, exposure pathway, etc.) to facilitate characterization of the human health impacts of the effluents.more » The DARTAB code was written at ORNL for the US Environmental Protection Agency, Office of Radiation Programs.« less

Transoptr — A second order beam transport design code with optimization and constraints

NASA Astrophysics Data System (ADS)

Heighway, E. A.; Hutcheon, R. M.

1981-08-01

This code was written initially to design an achromatic and isochronous reflecting magnet and has been extended to compete in capability (for constrained problems) with TRANSPORT. Its advantage is its flexibility in that the user writes a routine to describe his transport system. The routine allows the definition of general variables from which the system parameters can be derived. Further, the user can write any constraints he requires as algebraic equations relating the parameters. All variables may be used in either a first or second order optimization.

MPACT Standard Input User s Manual, Version 2.2.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collins, Benjamin S.; Downar, Thomas; Fitzgerald, Andrew

The MPACT (Michigan PArallel Charactistics based Transport) code is designed to perform high-fidelity light water reactor (LWR) analysis using whole-core pin-resolved neutron transport calculations on modern parallel-computing hardware. The code consists of several libraries which provide the functionality necessary to solve steady-state eigenvalue problems. Several transport capabilities are available within MPACT including both 2-D and 3-D Method of Characteristics (MOC). A three-dimensional whole core solution based on the 2D-1D solution method provides the capability for full core depletion calculations.

Programmers manual for a one-dimensional Lagrangian transport model

USGS Publications Warehouse

Schoellhamer, D.H.; Jobson, H.E.

1986-01-01

A one-dimensional Lagrangian transport model for simulating water-quality constituents such as temperature, dissolved oxygen , and suspended sediment in rivers is presented in this Programmers Manual. Lagrangian transport modeling techniques, the model 's subroutines, and the user-written decay-coefficient subroutine are discussed in detail. Appendices list the program codes. The Programmers Manual is intended for the model user who needs to modify code either to adapt the model to a particular need or to use reaction kinetics not provided with the model. (Author 's abstract)

Validation of MCNP6 Version 1.0 with the ENDF/B-VII.1 Cross Section Library for Uranium Metal, Oxide, and Solution Systems on the High Performance Computing Platform Moonlight

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chapman, Bryan Scott; MacQuigg, Michael Robert; Wysong, Andrew Russell

In this document, the code MCNP is validated with ENDF/B-VII.1 cross section data under the purview of ANSI/ANS-8.24-2007, for use with uranium systems. MCNP is a computer code based on Monte Carlo transport methods. While MCNP has wide reading capability in nuclear transport simulation, this validation is limited to the functionality related to neutron transport and calculation of criticality parameters such as k eff.

Thermodynamic properties of potassium chloride aqueous solutions

NASA Astrophysics Data System (ADS)

Zezin, Denis; Driesner, Thomas

2017-04-01

Potassium chloride is a ubiquitous salt in natural fluids, being the second most abundant dissolved salt in many geological aqueous solutions after sodium chloride. It is a simple solute and strong electrolyte easily dissociating in water, however the thermodynamic properties of KCl aqueous solutions were never correlated with sufficient accuracy for a wide range of physicochemical conditions. In this communication we propose a set of parameters for a Pitzer-type model which allows calculation of all necessary thermodynamic properties of KCl solution, namely excess Gibbs free energy and derived activity coefficient, apparent molar enthalpy, heat capacity and volume, as well as osmotic coefficient and activity of water in solutions. The system KCl-water is one of the best studied aqueous systems containing electrolytes. Although extensive experimental data were collected for thermodynamic properties of these solutions over the years, the accurate volumetric data became available only recently, thus making possible a complete thermodynamic formulation including a pressure dependence of excess Gibbs free energy and derived properties of the KCl-water liquids. Our proposed model is intended for calculation of major thermodynamic properties of KCl aqueous solutions at temperatures ranging from freezing point of a solution to 623 K, pressures ranging from saturated water vapor up to 150 MPa, and concentrations up to the salt saturation. This parameterized model will be further implemented in geochemical software packages and can facilitate the calculation of aqueous equilibrium for reactive transport codes.

Obtaining higher-accuracy estimates of water-rich rocks and water-poor sand dunes on Mars in active neutron experiments

NASA Astrophysics Data System (ADS)

Gabriel, T. S. J.; Hardgrove, C.; Litvak, M. L.; Nowicki, S.; Mitrofanov, I. G.; Boynton, W. V.; Fedosov, F.; Golovin, D.; Jun, I.; Mischna, M.; Tate, C. G.; Moersch, J.; Harshman, K.; Kozyrev, A.; Malakhov, A. V.; Mokrousov, M.; Nikiforov, S.; Sanin, A. B.; Vostrukhin, A.; Thompson, L. M.

2017-12-01

The Dynamic Albedo of Neutrons (DAN) experiment on the Mars Science Laboratory Curiosity Rover delivers high-energy (14.1 MeV) pulses of neutrons into the surface when operating in "active" mode. Neutrons are moderated in the subsurface and return to two detectors to provide a time-of-flight profile in 64 time-bins in epithermal and thermal energy ranges. Results are compared to simulations of the experiment in the Monte Carlo N-Particle Transport Code where several aspects are modeled including the DAN detectors, neutron source, rover components, and underlying rock. Models can be improved by increasing the fidelity of the rock geochemistry as informed by instruments including the Alpha Particle X-Ray Spectrometer (APXS). Furthermore, increasing the fidelity of the rock morphology in models is enabled by the suite of imaging instruments on the rover.To rapidly interpret DAN data a set of pre-simulated generic rock density and bulk geochemistry models are compared to several DAN active observations. While, to first order, this methodology provides an indication of significant geochemical changes in the subsurface, higher-fidelity models should be used to provide accurate constraints on water content, depth of geologic layers, or abundance of neutron absorbers. For example, in high-silicon, low-iron rocks observed along the rover's traverse, generic models can differ by several wt%H2O from models that use APXS measurements of nearby drill samples. Accurate measurements of high-silicon targets are necessary in outlining the extent of aqueous alteration and hydrothermal activity in Gale Crater. Additionally, we find that for DAN active experiments over sand dunes best-fit models can differ by greater than 0.5 wt%HO when the upper layer density is reduced by 0.6 g/cm3 to account for the low-bulk density of sand. In areas where the rock geochemistry differs little from generic models the difference in results is expectedly less disparate. We report refined wt%HO values for high-silicon, aqueously-altered rock and comparatively dry sand dunes along the rover traverse. We also outline the methodology for providing accurate geochemical and morphological constraints using DAN active measurements.

Physical model of a fumarolic system inferred from a high-resolution 3-D Resistivity image of Solfatara volcano

NASA Astrophysics Data System (ADS)

Gresse, Marceau; Vandemeulebrouck, Jean; Byrdina, Svetlana; Chiodini, Giovanni; Rinaldi, Antonio Pio; Johnson, Timothy C.; Ricci, Tullio; Petrillo, Zaccaria; Vilardo, Giuseppe; Lebourg, Thomas; Mangiacapra, Annarita

2017-04-01

Solfatara crater, located inside the Phlegrean Fields caldera, is showing a significant unrest activity since 10 years with a increase of ground deformation, degassing and heating. Electrical Resistivity Imaging was performed between 2012 and 2016 with the purpose of improving our knowledge of the shallow hydrothermal system. The complete dataset includes 43,432 D-C measurements inverted using the E4D code. This 3-D inversion was compared with the mappings of surface temperature, diffuse soil CO2 flux and self-potential in order to better constrain the interpretation of the observed resistivity structure in terms of lithological contrasts and hydrothermal signatures. For the first time, we highlighted in 3-D the main geological units: Monte Olibano lava dome and Solfatara crypto-dome appear as two relatively resistive bodies (50-100 Ω.m). Furthermore, the resistivity model clearly revealed the contrasting geometry of the hydrothermal circulation in the Solfatara crater. A channel-like conductive structure (7 Ω.m) represents the condensate that flows from the main fumarolic area down to the liquid-dominated Fangaia mud pool. This interpretation is consistent with the negative Self-Potential anomaly and with the surface observations. We imaged at a metric-resolution the two main fumaroles, Bocca Grande and Bocca Nuova, that have the following geochemical characteristics. Bocca Grande vent: 162°C, ˜150 t of CO2 released per day with a mass ratio CO2/H20 = 0.4 and Bocca Nuova vent: 148°C, ˜50 t of CO2 released per day with a mass ratio CO2/H20 = 0.45. The differences between these geochemical characteristics could lead one to believe that they are fed by two distinct sources at depth. On the contrary, our resistivity model shows that the two fumarolic vents are directly connected to a common resistive body (30-50 Ω.m) at a depth of 50 meters. This structure likely represents a single gas reservoir feeding the two fumaroles. Its depth corresponds indeed to a steam source at a pressure of 6 bar and at a temperature of least 165 °C. The geophysical images combined with the geochemical data allowed us to build up a multiphase fluid flow model of the Bocca Grande and and Bocca Nuova fumaroles using the TOUGH 2 code. Our results show that the distinct resistivity structure, temperature, and water content of the both fumaroles are due to the particular geometry of the condensate flow that intersects and contaminates the Bocca Nuova but not the Bocca Grande fumarole. These results indicate the necessity to combine geophysical and geochemical approaches in order to better apprehend the structure complexity and the dynamics of fumaroles and hydrothermal systems.

Radiation transport codes for potential applications related to radiobiology and radiotherapy using protons, neutrons, and negatively charged pions

NASA Technical Reports Server (NTRS)

Armstrong, T. W.

1972-01-01

Several Monte Carlo radiation transport computer codes are used to predict quantities of interest in the fields of radiotherapy and radiobiology. The calculational methods are described and comparisions of calculated and experimental results are presented for dose distributions produced by protons, neutrons, and negatively charged pions. Comparisons of calculated and experimental cell survival probabilities are also presented.

SQA of finite element method (FEM) codes used for analyses of pit storage/transport packages

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russel, E.

1997-11-01

This report contains viewgraphs on the software quality assurance of finite element method codes used for analyses of pit storage and transport projects. This methodology utilizes the ISO 9000-3: Guideline for application of 9001 to the development, supply, and maintenance of software, for establishing well-defined software engineering processes to consistently maintain high quality management approaches.

49 CFR Appendix C to Part 215 - FRA Freight Car Standards Defect Code

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 4 2010-10-01 2010-10-01 false FRA Freight Car Standards Defect Code C Appendix C... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD FREIGHT CAR SAFETY STANDARDS Pt. 215, App. C Appendix C to... 13/4″. (C)(1) Rim thickness is 11/16″ or less; (2) Rim thickness is 5/8″ or less; (3) Rim thickness...

Kinetically Controlled Alteration of the Chemical Record During Diagenesis: An Experimental Study on Hydrothermal Carbonate Replacement

NASA Astrophysics Data System (ADS)

Mueller, T.; Dohmen, R.; Jonas, L.; Immenhauser, A.

2016-12-01

The geological record stored in the geochemical composition of carbonates provides a direct source of information on the Earth systems. However, the robustness and accuracy of these key records can be compromised by post-depositional alteration of sediments, such as dolomitization during diagenesis or low temperature metamorphism. Hence, knowledge on the mechanisms and rates of these processes hold the key to evaluate the robustness of proxies or to evaluate the extent of geochemical alteration. Previously, we presented experimental results of hydrothermal alteration of single calcite crystals and aragonitic coral fragments leading to replacement of the original carbonate by a Ca-Mg carbonate phase of variable composition. The experiments revealed the formation of a multiphase reaction rim with multiple replacement fronts [1]. Here, the reaction rate as well as composition of the reaction products is controlled by element transport in the pore fluid. In this study we focus on the reaction path of the replacement reaction and its effect on the recorded Mg-isotope composition. XRD diffraction patterns suggest the initial precipitation of non-ordered protodolomite that is subsequently continuously recrystallizing over the duration of the experiments to form an ordered, albeit non-stoichiometric dolomite. These observations are in agreement with Mg-isotope composition measured of the bulk reaction rim showing a systematic evolution over time that cannot be explained by simple Rayleigh or equilibrium fractionation. We interpret these findings as additional, but delayed reaction fronts affecting the microstructure and chemical composition of the newly formed carbonate rim that are essentially decoupled from the initial replacement front. Our results highlight the need to quantitatively understand alteration processes during diagenesis in order to accurately interpret the preserved geochemical record stored in element and isotope ratios of carbonates. [1] Jonas L., Mueller T., Dohmen R., Baumgartner L., and Putlitz B. (2015): Transport-controlled hydrothermal replacement of calcite by Mg-carbonates, Geology, 43, 779-782.

Study of negative ion transport phenomena in a plasma source

NASA Astrophysics Data System (ADS)

Riz, D.; Paméla, J.

1996-07-01

NIETZSCHE (Negative Ions Extraction and Transport ZSimulation Code for HydrogEn species) is a negative ion (NI) transport code developed at Cadarache. This code calculates NI trajectories using a 3D Monte-Carlo technique, taking into account the main destruction processes, as well as elastic collisions (H-/H+) and charge exchanges (H-/H0). It determines the extraction probability of a NI created at a given position. According to the simulations, we have seen that in the case of volume production, only NI produced close to the plasma grid (PG) can be extracted. Concerning the surface production, we have studied how NI produced on the PG and accelerated by the plasma sheath backward into the source could be extracted. We demonstrate that elastic collisions and charge exchanges play an important role, which in some conditions dominates the magnetic filter effect, which acts as a magnetic mirror. NI transport in various conditions will be discussed: volume/surface production, high/low plasmas density, tent filter/transverse filter.

Cosmic-ray propagation with DRAGON2: I. numerical solver and astrophysical ingredients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evoli, Carmelo; Gaggero, Daniele; Vittino, Andrea

2017-02-01

We present version 2 of the DRAGON code designed for computing realistic predictions of the CR densities in the Galaxy. The code numerically solves the interstellar CR transport equation (including inhomogeneous and anisotropic diffusion, either in space and momentum, advective transport and energy losses), under realistic conditions. The new version includes an updated numerical solver and several models for the astrophysical ingredients involved in the transport equation. Improvements in the accuracy of the numerical solution are proved against analytical solutions and in reference diffusion scenarios. The novel features implemented in the code allow to simulate the diverse scenarios proposed tomore » reproduce the most recent measurements of local and diffuse CR fluxes, going beyond the limitations of the homogeneous galactic transport paradigm. To this end, several applications using DRAGON2 are presented as well. This new version facilitates the users to include their own physical models by means of a modular C++ structure.« less

A comparison of the COG and MCNP codes in computational neutron capture therapy modeling, Part I: boron neutron capture therapy models.

PubMed

Culbertson, C N; Wangerin, K; Ghandourah, E; Jevremovic, T

2005-08-01

The goal of this study was to evaluate the COG Monte Carlo radiation transport code, developed and tested by Lawrence Livermore National Laboratory, for neutron capture therapy related modeling. A boron neutron capture therapy model was analyzed comparing COG calculational results to results from the widely used MCNP4B (Monte Carlo N-Particle) transport code. The approach for computing neutron fluence rate and each dose component relevant in boron neutron capture therapy is described, and calculated values are shown in detail. The differences between the COG and MCNP predictions are qualified and quantified. The differences are generally small and suggest that the COG code can be applied for BNCT research related problems.

Influence of mineral colloids and humic substances on uranium(VI) transport in water-saturated geologic porous media

NASA Astrophysics Data System (ADS)

Wang, Qing; Cheng, Tao; Wu, Yang

2014-12-01

Mineral colloids and humic substances often co-exist in subsurface environment and substantially influence uranium (U) transport. However, the combined effects of mineral colloids and humic substances on U transport are not clear. This study is aimed at quantifying U transport and elucidating geochemical processes that control U transport when both mineral colloids and humic acid (HA) are present. U-spiked solutions/suspensions were injected into water-saturated sand columns, and U and colloid concentrations in column effluent were monitored. We found that HA promoted U transport via (i) formation of aqueous U-HA complexes, and (ii) competition against aqueous U for surface sites on transport media. Illite colloids had no influence on U transport at pH 5 in the absence of HA due to low mobility of the colloids. At pH 9, U desorbed from mobile illite and the presence of illite decreased U transport. At pH 5, high U transport occurred when both illite colloids and HA were present, which was attributed to enhanced U adsorption to illite colloids via formation of ternary illite-HA-U surface complexes, and enhanced illite transport due to HA attachment to illite and transport media. This study demonstrates that the combined effects of mineral colloids and HA on contaminant transport is different from simple addition of the individual effect.

Un-collided-flux preconditioning for the first order transport equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rigley, M.; Koebbe, J.; Drumm, C.

2013-07-01

Two codes were tested for the first order neutron transport equation using finite element methods. The un-collided-flux solution is used as a preconditioner for each of these methods. These codes include a least squares finite element method and a discontinuous finite element method. The performance of each code is shown on problems in one and two dimensions. The un-collided-flux preconditioner shows good speedup on each of the given methods. The un-collided-flux preconditioner has been used on the second-order equation, and here we extend those results to the first order equation. (authors)

Nuclide Depletion Capabilities in the Shift Monte Carlo Code

DOE PAGES

Davidson, Gregory G.; Pandya, Tara M.; Johnson, Seth R.; ...

2017-12-21

A new depletion capability has been developed in the Exnihilo radiation transport code suite. This capability enables massively parallel domain-decomposed coupling between the Shift continuous-energy Monte Carlo solver and the nuclide depletion solvers in ORIGEN to perform high-performance Monte Carlo depletion calculations. This paper describes this new depletion capability and discusses its various features, including a multi-level parallel decomposition, high-order transport-depletion coupling, and energy-integrated power renormalization. Several test problems are presented to validate the new capability against other Monte Carlo depletion codes, and the parallel performance of the new capability is analyzed.

Using Tidal Fluctuation-Induced Dynamics of Radium Isotopes (224Ra, 223Ra, and 228Ra) to Trace the Hydrodynamics and Geochemical Reactions in a Coastal Groundwater Mixing Zone

NASA Astrophysics Data System (ADS)

Liu, Yi; Jiao, Jiu Jimmy; Liang, Wenzhao; Luo, Xin

2018-04-01

The reactive transport of radium isotopes (224Ra, 223Ra, and 228Ra) in coastal groundwater mixing zones (CGMZs) is sensitive to shifts of redox conditions and geochemical reactions induced by tidal fluctuation. This study presents a spatial distribution and temporal variation of radium isotopes in the CGMZ for the first time. Results show that the activity of radium isotopes in the upper saline plume (USP) is comparatively low due to a short residence time and mixing loss induced by the infiltration of low radium seawater whereas the activity of radium isotopes in the salt wedge (SW) is comparatively high due to a long residence time in the aquifer. The spatial distribution of radium isotopes is determined by the partitioning of radium isotopes, groundwater residence time, and relative ingrowth rates of radium isotopes. In addition, the variation of radium isotopes in the USP lags slightly (˜0 h) whereas the fluctuation of radium isotopes in the SW lags significantly (˜12 h) behind sea level oscillation. Tidal fluctuation affects the partitioning of radium isotopes through controlling seawater infiltration and subsequently influences the dynamics of radium isotopes in the USP. Concurrently, seawater infiltration significantly affects geochemical processes such as the production of nutrients and total alkalinity. Therefore, radium dynamics in the USP have implications for these geochemical processes. The variation of radium isotopes in the USP also has potential implications for transformation of trace metals such as iron and manganese because of the close affinity of radium isotopes to manganese and iron oxides.

Geochemical investigation of UMTRAP designated site at Durango, Colorado

DOE Office of Scientific and Technical Information (OSTI.GOV)

Markos, G.; Bush, K.J.

1983-09-01

This report is the result of a geochemical investigation of the former uranium mill and tailings site at Durango, Colorado. This is one in a series of site specific geochemical investigations performed on the inactive uranium mill tailings included in the UMTRA Project. The objectives of the investigation are to characterize the geochemistry, to determine the contaminant distribution resulting from the former milling activities and tailings, and to infer chemical pathways and transport mechanisms from the contaminant distribution. The results will be used to model contaminant migration and to develop criteria for long-term containment media such as a cover systemmore » which is impermeable to contaminant migration. This report assumes a familiarity with the hydrologic conditions of the site and the geochemical concepts underlying the investigation. The results reported are based on a one-time sampling of waters and solid material from the background, the area adjacent to the site, and the site. The solid samples are water extracted remove easily soluble salts and acids extracted to remove cabonates and hydroxides. The water extracts and solid samples were analyzed for the major and trace elements. A limited number of samples were analyzed for radiological components. The report includes the methods of sampling, sample processing, analysis, and data interpretation. Three major conclusions are: (1) carbonate salts and low TDS characterize the tailings; (2) the adjacent area and raffinate ponds contain contaminants deposited by a single event of fluid permeation of the soils; and (3) the Animas River adjacent to the site has elevated gross alpha activity attributed to /sup 226/Ra in the sediments derived from the tailings or milling activities.« less

Depth-resolved microbial community analyses in two contrasting soil cores contaminated by antimony and arsenic.

PubMed

Xiao, Enzong; Krumins, Valdis; Xiao, Tangfu; Dong, Yiran; Tang, Song; Ning, Zengping; Huang, Zhengyu; Sun, Weimin

2017-02-01

Investigation of microbial communities of soils contaminated by antimony (Sb) and arsenic (As) is necessary to obtain knowledge for their bioremediation. However, little is known about the depth profiles of microbial community composition and structure in Sb and As contaminated soils. Our previous studies have suggested that historical factors (i.e., soil and sediment) play important roles in governing microbial community structure and composition. Here, we selected two different types of soil (flooded paddy soil versus dry corn field soil) with co-contamination of Sb and As to study interactions between these metalloids, geochemical parameters and the soil microbiota as well as microbial metabolism in response to Sb and As contamination. Comprehensive geochemical analyses and 16S rRNA amplicon sequencing were used to shed light on the interactions of the microbial communities with their environments. A wide diversity of taxonomical groups was present in both soil cores, and many were significantly correlated with geochemical parameters. Canonical correspondence analysis (CCA) and co-occurrence networks further elucidated the impact of geochemical parameters (including Sb and As contamination fractions and sulfate, TOC, Eh, and pH) on vertical distribution of soil microbial communities. Metagenomes predicted from the 16S data using PICRUSt included arsenic metabolism genes such as arsenate reductase (ArsC), arsenite oxidase small subunit (AoxA and AoxB), and arsenite transporter (ArsA and ACR3). In addition, predicted abundances of arsenate reductase (ArsC) and arsenite oxidase (AoxA and AoxB) genes were significantly correlated with Sb contamination fractions, These results suggest potential As biogeochemical cycling in both soil cores and potentially dynamic Sb biogeochemical cycling as well. Copyright © 2016 Elsevier Ltd. All rights reserved.

Natural and Human Influences on Water Quality in a Shallow Regional Unconsolidated Aquifer, Northern Atlantic Coastal Plain

USGS Publications Warehouse

Ator, Scott W.

2008-01-01

Data collected from more than 400 wells in the surficial unconfined aquifer in the Northern Atlantic Coastal Plain (New York through North Carolina) were compiled and analyzed to improve understanding of multiple natural and human influences on water quality in such shallow regional aquifers. Geochemical patterns were identified and described through principal components analysis on major ions, and correlation and logistic regression were used to relate observed concentrations of nitrate and selected pesticide compounds (atrazine, metolachlor, simazine, and deethylatrazine, an atrazine degradate) and volatile organic compounds (chloroform, 1,1,1-trichloroethane, tetrachlorethene, and methyl tert-butyl ether) to likely influences, such as observed geochemical patterns, land use, hydrogeology, and soils. Variability in major-ion concentrations is primarily related to ionic strength and redox condition. Concentrations of nitrate, pesticides, and volatile organic compounds are related to natural conditions, as well as the distribution of likely sources reflected in land use. Nitrate is most common in aerobic ground water and in relatively well-drained areas, for example; concentrations greater than 0.4 milligrams per liter may result from a variety of human activities, although concentrations greater than 3 milligrams per liter are more likely in agricultural areas. Atrazine, deethylatrazine, and metolachlor also are related to geochemical patterns, likely because ground-water geochemistry reflects hydrogeologic and soil conditions affecting pesticide transport to the water table. Results demonstrate the value of geochemical information along with the distribution of sources and other influences to understanding the regional occurrence of selected compounds in ground water. Such influences are not unique to the Northern Atlantic Coastal Plain, and thus observations and interpretations are relevant to broader areas.

MCNP (Monte Carlo Neutron Photon) capabilities for nuclear well logging calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forster, R.A.; Little, R.C.; Briesmeister, J.F.

The Los Alamos Radiation Transport Code System (LARTCS) consists of state-of-the-art Monte Carlo and discrete ordinates transport codes and data libraries. The general-purpose continuous-energy Monte Carlo code MCNP (Monte Carlo Neutron Photon), part of the LARTCS, provides a computational predictive capability for many applications of interest to the nuclear well logging community. The generalized three-dimensional geometry of MCNP is well suited for borehole-tool models. SABRINA, another component of the LARTCS, is a graphics code that can be used to interactively create a complex MCNP geometry. Users can define many source and tally characteristics with standard MCNP features. The time-dependent capabilitymore » of the code is essential when modeling pulsed sources. Problems with neutrons, photons, and electrons as either single particle or coupled particles can be calculated with MCNP. The physics of neutron and photon transport and interactions is modeled in detail using the latest available cross-section data. A rich collections of variance reduction features can greatly increase the efficiency of a calculation. MCNP is written in FORTRAN 77 and has been run on variety of computer systems from scientific workstations to supercomputers. The next production version of MCNP will include features such as continuous-energy electron transport and a multitasking option. Areas of ongoing research of interest to the well logging community include angle biasing, adaptive Monte Carlo, improved discrete ordinates capabilities, and discrete ordinates/Monte Carlo hybrid development. Los Alamos has requested approval by the Department of Energy to create a Radiation Transport Computational Facility under their User Facility Program to increase external interactions with industry, universities, and other government organizations. 21 refs.« less

Roles of Nano- and Micro-Scale Subsurface Geochemical Reactions on Environmentally Sustainable Geologic Carbon Dioxide Sequestration

NASA Astrophysics Data System (ADS)

Hu, Yandi

Geologic CO2 sequestration (GCS) is a promising approach to reduce anthropogenic CO2 emissions into the atmosphere. At GCS sites, injected CO2 is kept in formation rock by an overlying low permeability caprock. During and after CO2 injection, geochemical reactions can affect the porosity, permeability, and pollutant transport in aquifers. Despite their importance, nano- and micro-scale subsurface geochemical reactions are far from well-understood. Clay mobilization has been reported to decrease aquifer permeability during water flooding, and clay minerals are abundant in caprock. Thus, we studied CO2-brine-clay interactions under varied conditions relevant to different GCS sites (at 35-95°C and under 35-120 atm CO2, in water, NaCl, MgCl2, or CaCl2 solutions). Biotite, Fe-bearing mica, was used as a model clay mineral. We observed numerous fibrous illite precipitates on mica after reaction for only 3 h, which had not been previously reported. A few hours later, the mica surface cracked and fibrous illite detached. The mobilization of fibrous illite can decrease the aquifer's permeability greatly and affect the safety and efficiency of GCS. Mechanisms related to ion exchange, mica swelling, and CO2 intercalation were explored. Oriented aggregation of illite nanoparticles forming the fibrous illite was directly observed, suggesting a new mechanism for fibrous illite formation. Interestingly, besides the pH effect, aqueous CO2 enhances mica cracking over N2. These findings can help to achieve safer subsurface operations. At GCS field sites, Fe concentration increased near the injection sites and originally adsorbed pollutants were released. As the brine flows, Fe re-precipitated because of pH increase. To better predict the fate and transport of aqueous pollutants, the nucleation and growth of Fe(III) (hydr)oxides were studied. New information about sizes and volumes of the Fe(III) (hydr)oxide nanoparticles precipitated in solution and on quartz, mica, and sapphire were provided using small angle X-ray scattering, in the presence of different ions (Al 3+, Cl-, NO3-, and SO 42-). Using complementary techniques, the controlling mechanisms related to surface charge, bond formation, and interfacial energies were explored. These new findings can help better predict pollutant transport in aquifers not only at GCS sites, but also in managed aquifer recharge and acid mine drainage sites.

Track-structure simulations for charged particles.

PubMed

Dingfelder, Michael

2012-11-01

Monte Carlo track-structure simulations provide a detailed and accurate picture of radiation transport of charged particles through condensed matter of biological interest. Liquid water serves as a surrogate for soft tissue and is used in most Monte Carlo track-structure codes. Basic theories of radiation transport and track-structure simulations are discussed and differences compared to condensed history codes highlighted. Interaction cross sections for electrons, protons, alpha particles, and light and heavy ions are required input data for track-structure simulations. Different calculation methods, including the plane-wave Born approximation, the dielectric theory, and semi-empirical approaches are presented using liquid water as a target. Low-energy electron transport and light ion transport are discussed as areas of special interest.

Shielding evaluation for solar particle events using MCNPX, PHITS and OLTARIS codes.

PubMed

Aghara, S K; Sriprisan, S I; Singleterry, R C; Sato, T

2015-01-01

Detailed analyses of Solar Particle Events (SPE) were performed to calculate primary and secondary particle spectra behind aluminum, at various thicknesses in water. The simulations were based on Monte Carlo (MC) radiation transport codes, MCNPX 2.7.0 and PHITS 2.64, and the space radiation analysis website called OLTARIS (On-Line Tool for the Assessment of Radiation in Space) version 3.4 (uses deterministic code, HZETRN, for transport). The study is set to investigate the impact of SPEs spectra transporting through 10 or 20 g/cm(2) Al shield followed by 30 g/cm(2) of water slab. Four historical SPE events were selected and used as input source spectra particle differential spectra for protons, neutrons, and photons are presented. The total particle fluence as a function of depth is presented. In addition to particle flux, the dose and dose equivalent values are calculated and compared between the codes and with the other published results. Overall, the particle fluence spectra from all three codes show good agreement with the MC codes showing closer agreement compared to the OLTARIS results. The neutron particle fluence from OLTARIS is lower than the results from MC codes at lower energies (E<100 MeV). Based on mean square difference analysis the results from MCNPX and PHITS agree better for fluence, dose and dose equivalent when compared to OLTARIS results. Copyright © 2015 The Committee on Space Research (COSPAR). All rights reserved.

Aerothermo-Structural Analysis of Low Cost Composite Nozzle/Inlet Components

NASA Technical Reports Server (NTRS)

Shivakumar, Kuwigai; Challa, Preeli; Sree, Dave; Reddy, D.

1999-01-01

This research is a cooperative effort among the Turbomachinery and Propulsion Division of NASA Glenn, CCMR of NC A&T State University, and the Tuskegee University. The NC A&T is the lead center and Tuskegee University is the participating institution. Objectives of the research were to develop an integrated aerodynamic, thermal and structural analysis code for design of aircraft engine components, such as, nozzles and inlets made of textile composites; conduct design studies on typical inlets for hypersonic transportation vehicles and setup standards test examples and finally manufacture a scaled down composite inlet. These objectives are accomplished through the following seven tasks: (1) identify the relevant public domain codes for all three types of analysis; (2) evaluate the codes for the accuracy of results and computational efficiency; (3) develop aero-thermal and thermal structural mapping algorithms; (4) integrate all the codes into one single code; (5) write a graphical user interface to improve the user friendliness of the code; (6) conduct test studies for rocket based combined-cycle engine inlet; and finally (7) fabricate a demonstration inlet model using textile preform composites. Tasks one, two and six are being pursued. Selected and evaluated NPARC for flow field analysis, CSTEM for in-depth thermal analysis of inlets and nozzles and FRAC3D for stress analysis. These codes have been independently verified for accuracy and performance. In addition, graphical user interface based on micromechanics analysis for laminated as well as textile composites was developed. Demonstration of this code will be made at the conference. A rocket based combined cycle engine was selected for test studies. Flow field analysis of various inlet geometries were studied. Integration of codes is being continued. The codes developed are being applied to a candidate example of trailblazer engine proposed for space transportation. A successful development of the code will provide a simpler, faster and user-friendly tool for conducting design studies of aircraft and spacecraft engines, applicable in high speed civil transport and space missions.

Recent Progress in the Development of a Multi-Layer Green's Function Code for Ion Beam Transport

NASA Technical Reports Server (NTRS)

Tweed, John; Walker, Steven A.; Wilson, John W.; Tripathi, Ram K.

2008-01-01

To meet the challenge of future deep space programs, an accurate and efficient engineering code for analyzing the shielding requirements against high-energy galactic heavy radiation is needed. To address this need, a new Green's function code capable of simulating high charge and energy ions with either laboratory or space boundary conditions is currently under development. The computational model consists of combinations of physical perturbation expansions based on the scales of atomic interaction, multiple scattering, and nuclear reactive processes with use of the Neumann-asymptotic expansions with non-perturbative corrections. The code contains energy loss due to straggling, nuclear attenuation, nuclear fragmentation with energy dispersion and downshifts. Previous reports show that the new code accurately models the transport of ion beams through a single slab of material. Current research efforts are focused on enabling the code to handle multiple layers of material and the present paper reports on progress made towards that end.

A comment on the use of flushing time, residence time, and age as transport time scales

USGS Publications Warehouse

Monsen, N.E.; Cloern, J.E.; Lucas, L.V.; Monismith, Stephen G.

2002-01-01

Applications of transport time scales are pervasive in biological, hydrologic, and geochemical studies yet these times scales are not consistently defined and applied with rigor in the literature. We compare three transport time scales (flushing time, age, and residence time) commonly used to measure the retention of water or scalar quantities transported with water. We identify the underlying assumptions associated with each time scale, describe procedures for computing these time scales in idealized cases, and identify pitfalls when real-world systems deviate from these idealizations. We then apply the time scale definitions to a shallow 378 ha tidal lake to illustrate how deviations between real water bodies and the idealized examples can result from: (1) non-steady flow; (2) spatial variability in bathymetry, circulation, and transport time scales; and (3) tides that introduce complexities not accounted for in the idealized cases. These examples illustrate that no single transport time scale is valid for all time periods, locations, and constituents, and no one time scale describes all transport processes. We encourage aquatic scientists to rigorously define the transport time scale when it is applied, identify the underlying assumptions in the application of that concept, and ask if those assumptions are valid in the application of that approach for computing transport time scales in real systems.

Fully-kinetic Ion Simulation of Global Electrostatic Turbulent Transport in C-2U

NASA Astrophysics Data System (ADS)

Fulton, Daniel; Lau, Calvin; Bao, Jian; Lin, Zhihong; Tajima, Toshiki; TAE Team

2017-10-01

Understanding the nature of particle and energy transport in field-reversed configuration (FRC) plasmas is a crucial step towards an FRC-based fusion reactor. The C-2U device at Tri Alpha Energy (TAE) achieved macroscopically stable plasmas and electron energy confinement time which scaled favorably with electron temperature. This success led to experimental and theoretical investigation of turbulence in C-2U, including gyrokinetic ion simulations with the Gyrokinetic Toroidal Code (GTC). A primary objective of TAE's new C-2W device is to explore transport scaling in an extended parameter regime. In concert with the C-2W experimental campaign, numerical efforts have also been extended in A New Code (ANC) to use fully-kinetic (FK) ions and a Vlasov-Poisson field solver. Global FK ion simulations are presented. Future code development is also discussed.

Simulations of 4D edge transport and dynamics using the TEMPEST gyro-kinetic code

NASA Astrophysics Data System (ADS)

Rognlien, T. D.; Cohen, B. I.; Cohen, R. H.; Dorr, M. R.; Hittinger, J. A. F.; Kerbel, G. D.; Nevins, W. M.; Xiong, Z.; Xu, X. Q.

2006-10-01

Simulation results are presented for tokamak edge plasmas with a focus on the 4D (2r,2v) option of the TEMPEST continuum gyro-kinetic code. A detailed description of a variety of kinetic simulations is reported, including neoclassical radial transport from Coulomb collisions, electric field generation, dynamic response to perturbations by geodesic acoustic modes, and parallel transport on open magnetic-field lines. Comparison is made between the characteristics of the plasma solutions on closed and open magnetic-field line regions separated by a magnetic separatrix, and simple physical models are used to qualitatively explain the differences observed in mean flow and electric-field generation. The status of extending the simulations to 5D turbulence will be summarized. The code structure used in this ongoing project is also briefly described, together with future plans.

Statistical Analysis of the AIAA Drag Prediction Workshop CFD Solutions

NASA Technical Reports Server (NTRS)

Morrison, Joseph H.; Hemsch, Michael J.

2007-01-01

The first AIAA Drag Prediction Workshop (DPW), held in June 2001, evaluated the results from an extensive N-version test of a collection of Reynolds-Averaged Navier-Stokes CFD codes. The code-to-code scatter was more than an order of magnitude larger than desired for design and experimental validation of cruise conditions for a subsonic transport configuration. The second AIAA Drag Prediction Workshop, held in June 2003, emphasized the determination of installed pylon-nacelle drag increments and grid refinement studies. The code-to-code scatter was significantly reduced compared to the first DPW, but still larger than desired. However, grid refinement studies showed no significant improvement in code-to-code scatter with increasing grid refinement. The third AIAA Drag Prediction Workshop, held in June 2006, focused on the determination of installed side-of-body fairing drag increments and grid refinement studies for clean attached flow on wing alone configurations and for separated flow on the DLR-F6 subsonic transport model. This report compares the transonic cruise prediction results of the second and third workshops using statistical analysis.

A Quantitative Geochemical, Mineralogical and Physical Study of Some Selected Rock Weathering Profiles from Brazil

DTIC Science & Technology

1977-08-17

weather to gibbsite (plus or minus iron oxides) in well-drained, and smectite in poorly-drained, environments. Kaolinite found in the vicinity of quartz...rock and completely weathered saprolite. Quartz-rich rock types exhibit wide, gradational weathered zones and usually form kaolinite or halloysite in...free rocks is either formed by re-silication of gibbsite , or is of secondary origin (transported). Texture of the rock (aphanitic vs. phaneric) has

Review of Hybrid (Deterministic/Monte Carlo) Radiation Transport Methods, Codes, and Applications at Oak Ridge National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wagner, John C; Peplow, Douglas E.; Mosher, Scott W

2011-01-01

This paper provides a review of the hybrid (Monte Carlo/deterministic) radiation transport methods and codes used at the Oak Ridge National Laboratory and examples of their application for increasing the efficiency of real-world, fixed-source Monte Carlo analyses. The two principal hybrid methods are (1) Consistent Adjoint Driven Importance Sampling (CADIS) for optimization of a localized detector (tally) region (e.g., flux, dose, or reaction rate at a particular location) and (2) Forward Weighted CADIS (FW-CADIS) for optimizing distributions (e.g., mesh tallies over all or part of the problem space) or multiple localized detector regions (e.g., simultaneous optimization of two or moremore » localized tally regions). The two methods have been implemented and automated in both the MAVRIC sequence of SCALE 6 and ADVANTG, a code that works with the MCNP code. As implemented, the methods utilize the results of approximate, fast-running 3-D discrete ordinates transport calculations (with the Denovo code) to generate consistent space- and energy-dependent source and transport (weight windows) biasing parameters. These methods and codes have been applied to many relevant and challenging problems, including calculations of PWR ex-core thermal detector response, dose rates throughout an entire PWR facility, site boundary dose from arrays of commercial spent fuel storage casks, radiation fields for criticality accident alarm system placement, and detector response for special nuclear material detection scenarios and nuclear well-logging tools. Substantial computational speed-ups, generally O(102-4), have been realized for all applications to date. This paper provides a brief review of the methods, their implementation, results of their application, and current development activities, as well as a considerable list of references for readers seeking more information about the methods and/or their applications.« less

Quantifying the Benthic Source of Nutrients to the Water Column of Upper Klamath Lake, Oregon

USGS Publications Warehouse

Kuwabara, James S.; Lynch, Dennis D.; Topping, Brent R.; Murphy, Fred; Carter, James L.; Simon, Nancy S.; Parcheso, Francis; Wood, Tamara M.; Lindenberg, Mary K.; Wiese, Katryn; Avanzino, Ronald J.

2007-01-01

Executive Summary Five sampling trips were coordinated in April, May and August 2006, and May and July 2007 to sample the water column and benthos of Upper Klamath Lake, OR (Fig. 1; Table 1), before, during and after the annual cyanophyte bloom of Aphanizomenon flos-aquae (AFA). A pore-water profiler was designed and fabricated to obtain the first high-resolution (centimeter-scale) estimates of the vertical concentration gradients for diffusive-flux determinations. Estimates based on molecular diffusion may underestimate benthic flux because solute transport across the sediment-water interface can be enhanced by processes including bioturbation, bioirrigation and ground-water advection. Water-column and benthic samples were also collected to help interpret spatial and temporal trends in diffusive-flux estimates. Data from these samples complement geochemical analyses of bottom-sediments taken from Upper Klamath Lake (UKL) in 2005. This ongoing study provides information necessary for developing process-interdependent solute-transport models for the watershed (that is, models integrating physical, geochemical and biological processes), and supports efforts to evaluate remediation or load-allocation strategies. To augment studies funded by the U.S. Bureau of Reclamation (USBR), the Department of Interior supported an additional full deployment of pore-water profilers in July 2007, during the summer AFA bloom. Results from this recent field trip are not fully completed. Data not presented herein will be included in a subsequent publication, scheduled for March 2009.

Subsurface conditions in hydrothermal vents inferred from diffuse flow composition, and models of reaction and transport

NASA Astrophysics Data System (ADS)

Larson, B. I.; Houghton, J. L.; Lowell, R. P.; Farough, A.; Meile, C. D.

2015-08-01

Chemical gradients in the subsurface of mid-ocean ridge hydrothermal systems create an environment where minerals precipitate and dissolve and where chemosynthetic organisms thrive. However, owing to the lack of easy access to the subsurface, robust knowledge of the nature and extent of chemical transformations remains elusive. Here, we combine measurements of vent fluid chemistry with geochemical and transport modeling to give new insights into the under-sampled subsurface. Temperature-composition relationships from a geochemical mixing model are superimposed on the subsurface temperature distribution determined using a heat flow model to estimate the spatial distribution of fluid composition. We then estimate the distribution of Gibb's free energies of reaction beneath mid oceanic ridges and by combining flow simulations with speciation calculations estimate anhydrite deposition rates. Applied to vent endmembers observed at the fast spreading ridge at the East Pacific Rise, our results suggest that sealing times due to anhydrite formation are longer than the typical time between tectonic and magmatic events. The chemical composition of the neighboring low temperature flow indicates relatively uniform energetically favorable conditions for commonly inferred microbial processes such as methanogenesis, sulfate reduction and numerous oxidation reactions, suggesting that factors other than energy availability may control subsurface microbial biomass distribution. Thus, these model simulations complement fluid-sample datasets from surface venting and help infer the chemical distribution and transformations in subsurface flow.

Validation of the BASALT model for simulating off-axis hydrothermal circulation in oceanic crust

NASA Astrophysics Data System (ADS)

Farahat, Navah X.; Archer, David; Abbot, Dorian S.

2017-08-01

Fluid recharge and discharge between the deep ocean and the porous upper layer of off-axis oceanic crust tends to concentrate in small volumes of rock, such as seamounts and fractures, that are unimpeded by low-permeability sediments. Basement structure, sediment burial, heat flow, and other regional characteristics of off-axis hydrothermal systems appear to produce considerable diversity of circulation behaviors. Circulation of seawater and seawater-derived fluids controls the extent of fluid-rock interaction, resulting in significant geochemical impacts. However, the primary regional characteristics that control how seawater is distributed within upper oceanic crust are still poorly understood. In this paper we present the details of the two-dimensional (2-D) BASALT (Basement Activity Simulated At Low Temperatures) numerical model of heat and fluid transport in an off-axis hydrothermal system. This model is designed to simulate a wide range of conditions in order to explore the dominant controls on circulation. We validate the BASALT model's ability to reproduce observations by configuring it to represent a thoroughly studied transect of the Juan de Fuca Ridge eastern flank. The results demonstrate that including series of narrow, ridge-parallel fractures as subgrid features produces a realistic circulation scenario at the validation site. In future projects, a full reactive transport version of the validated BASALT model will be used to explore geochemical fluxes in a variety of off-axis hydrothermal environments.

Modeling the Hydrogeochemical Transport of Radionuclides through Engineered Barriers System in the Proposed LLW Disposal Site of Taiwan - 12082

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Wen-Sheng; Liu, Chen-Wuing; Tsao, Jui-Hsuan

2012-07-01

A proposed site for final disposal of low-level radioactive waste located in Daren Township of Taitung County along the southeastern coast has been on the selected list in Taiwan. The geology of the Daren site consists of argillite and meta-sedimentary rocks. A mined cavern design with a tunnel system of 500 m below the surface is proposed. Concrete is used as the main confinement material for the engineered barrier. To investigate the hydrogeochemical transport of radionuclides through engineered barriers system, HYDROGEOCHEM5.0 model was applied to simulate the complex chemical interactions among radionuclides, the cement minerals of the concrete, groundwater flow,more » and transport in the proposed site. The simulation results showed that the engineered barriers system with the side ditch efficiently drained the ground water and lowered the concentration of the concrete degradation induced species (e.g., hydrogen ion, sulfate, and chloride). The velocity of groundwater observed at side ditch gradually decreased with time due to the fouling of pore space by the mineral formation of ettringite and thaumasite. The short half-life of Co-60, Sr-90 and Cs-137 significantly reduced the concentrations, whereas the long half-life of I-129(1.57x10{sup 7} years) and Am-241(432 years) remain stable concentrations at the interface of waste canister and concrete barrier after 300 years. The mineral saturation index (SI) was much less than zero due to the low aqueous concentration of radionuclide, so that the precipitation formation of Co-60, Sr-90, I-129, Cs-137 and Am-241 related minerals were not found. The effect of adsorption/desorption (i.e., surface complexation model) could be a crucial geochemical mechanism for the modeling of liquid-solid phase behavior of radionuclide in geochemically dynamic environments. Moreover, the development of advanced numerical models that are coupled with hydrogeochemical transport and dose assessment of radionuclide is required in the future. (authors)« less

Wind Transport of Radionuclide- Bearing Dust, Peña Blanca, Chihuahua, Mexico

NASA Astrophysics Data System (ADS)

Velarde, R.; Goodell, P. C.; Gill, T. E.; Arimoto, R.

2007-05-01

This investigation evaluates radionuclide fractionation during wind erosion of high-grade uranium ore storage piles at Peña Blanca (50km north of Chihuahua City), Chihuahua, Mexico. The aridity of the local environment promotes dust resuspension by high winds. Although active operations ceased in 1983, the Peña Blanca mining district is one of Mexico`s most important uranium ore reserves. The study site contains piles of high grade ore, left loose on the surface, and separated by the specific deposits from which they were derived (Margaritas, Nopal I, and Puerto I). Similar locations do not exist in the United States, since uranium mining sites in the USA have been reclaimed. The Peña Blanca site serves as an analog for the Yucca Mountain project. Dust deposition is collected at Peña Blanca with BSNE sediment catchers (Fryrear, 1986) and marble dust traps (Reheis, 1999). These devices capture windblown sediment; subsequently, the sample data will help quantify potentially radioactive short term field sediment loss from the repository surface and determine sediment flux. Aerosols and surface materials will be analyzed and radioactivity levels established utilizing techniques such as gamma spectroscopy. As a result, we will be able to estimate how much radionuclide contaminated dust is being transported or attached geochemically to fine grain soils or minerals (e.g., clays or iron oxides). The high-grade uranium-bearing material is at secular equilibrium, thus the entire decay series is present. Of resulting interest is not only the aeolian transport of uranium, but also of the other daughter products. These studies will improve our understanding of geochemical cycling of radionuclides with respect to sources, transport, and deposition. The results may also have important implications for the geosciences and homeland security, and potential applications to public health. Funding for this project is provided in part via a NSF grant to Arimoto.

Going the distance: Mapping mobility in the Kalahari Desert during the Middle Stone Age through multi-site geochemical provenancing of silcrete artefacts.

PubMed

Nash, David J; Coulson, Sheila; Staurset, Sigrid; Ullyott, J Stewart; Babutsi, Mosarwa; Smith, Martin P

2016-07-01

This study utilises geochemical provenancing of silcrete raw materials, in combination with chaîne opératoire analyses, to explore lithic procurement and behavioural patterns in the northern Kalahari Desert during the Middle Stone Age (MSA). New data from the sites of Rhino Cave, Corner Cave, and ≠Gi in northwest Botswana, combined with earlier results from White Paintings Shelter, reveal that the long distance transport of silcrete for stone tool manufacture was a repeated and extensively used behaviour in this region. Silcrete was imported over distances of up to 295 km to all four sites, from locations along the Boteti River and around Lake Ngami. Significantly, closer known sources of silcrete of equivalent quality were largely bypassed. Silcrete artefacts were transported at various stages of production (as partially and fully prepared cores, blanks, and finished tools) and, with the exception of ≠Gi, in large volumes. The import occurred despite the abundance of locally available raw materials, which were also used to manufacture the same tool types. On the basis of regional palaeoenvironmental data, the timing of the majority of silcrete import from the Boteti River and Lake Ngami is constrained to regionally drier periods of the MSA. The results of our investigation challenge key assumptions underlying predictive models of human mobility that use distance-decay curves and drop-off rates. Middle Stone Age peoples in the Kalahari appear to have been more mobile than anticipated, and repeatedly made costly choices with regard to both raw material selection and items to be transported. We conclude that (i) base transport cost has been overemphasised as a restrictive factor in predictive models, and (ii) factors such as source availability and preference, raw material quality, and potential sociocultural influences significantly shaped prehistoric landscape use choices. Copyright © 2016 Elsevier Ltd. All rights reserved.

Prompt Radiation Protection Factors

DTIC Science & Technology

2018-02-01

dimensional Monte-Carlo radiation transport code MCNP (Monte Carlo N-Particle) and the evaluation of the protection factors (ratio of dose in the open to...radiation was performed using the three dimensional Monte- Carlo radiation transport code MCNP (Monte Carlo N-Particle) and the evaluation of the protection...by detonation of a nuclear device have placed renewed emphasis on evaluation of the consequences in case of such an event. The Defense Threat

Modelling of clay diagenesis using a combined approach of crystalchemistry and thermochemistry: a case study in the smectite illitization.

NASA Astrophysics Data System (ADS)

Geloni, Claudio; Previde Massara, Elisabetta; Di Paola, Eleonora; Ortenzi, Andrea; Gherardi, Fabrizio; Blanc, Philippe

2017-04-01

Diagenetic transformations occurring in clayey and arenaceous sediments is investigated in a number of hydrocarbon reservoirs with an integrated approach that combines mineralogical analysis, crystalchemistry, estimation of thermochemical parameters of clay minerals, and geochemical modelling. Because of the extremely variable crystalchemistry of clays, especially in the smectite - illite compositional range, the estimation of thermochemical parameters of site-specific clay-rich rocks is crucial to investigate water-rock equilibria and to predict mineralogical evolutionary patterns at the clay-sandstone interface. The task of estimating the thermochemical properties of clay minerals and predicting diagenetic reactions in natural reservoirs is accomplished through the implementation of an informatized, procedure (IP) that consists of: (i) laboratory analysis of smectite, illite and mixed layers (I/S) for the determination of their textural characteristics and chemical composition; (ii) estimation of the thermodynamic and structural parameters (enthalpy, entropy, and free energy of formation, thermal capacity, molar volume, molar weight) with a MS Excel tool (XLS) specifically developed at the French Bureau of Geological and Mining Researches (BRGM); (iii) usage of the SUPCRT (Johnson et al., 1992) software package (thereinafter, SSP) to derive log K values to be incorporated in thermodynamic databases of the standard geochemical codes; (iv) check of the consistency of the stability domains calculated with these log K values with relevant predominance diagrams; (v) final application of geochemical and reactive transport models to investigate the reactive mechanisms under different thermal conditions (40-150°C). All the simulations consider pore waters having roughly the same chemical composition of reservoir pore waters, and are performed with The Geochemist Workbench (Bethke and Yeakel, 2015), PHREEQC (Parkhurst, 1999) and TOUGHREACT (Xu, 2006). The overall procedure benefits from: (i) (minor) improvements of the I/O structure of the SSP; (ii) the development of a suite of python scripts to automate the steps needed to augment the thermodynamic database by integrating the external information provided by potential users with the XLS tool and the SSP; (iii) the creation of specific outputs to allow for more convenient handling and inspection of computed parameters of the thermodynamic database. A case study focused on non-isothermal smectite-illite transformation is presented to show the capability of our numerical models to account for clay compaction under 1D geometry conditions. This model considers fluid flow driven by the compaction of a clay layer, and chemistry-fluid flow mutual feedback with the underlying sandstone during the advancement of the diagenesis. Due to this complex interaction, as a result of the smectite-illite transformation in the clays, significant quartz cementation affects the sandstone adjacent to the compacting clay.

Space Radiation Transport Codes: A Comparative Study for Galactic Cosmic Rays Environment

NASA Astrophysics Data System (ADS)

Tripathi, Ram; Wilson, John W.; Townsend, Lawrence W.; Gabriel, Tony; Pinsky, Lawrence S.; Slaba, Tony

For long duration and/or deep space human missions, protection from severe space radiation exposure is a challenging design constraint and may be a potential limiting factor. The space radiation environment consists of galactic cosmic rays (GCR), solar particle events (SPE), trapped radiation, and includes ions of all the known elements over a very broad energy range. These ions penetrate spacecraft materials producing nuclear fragments and secondary particles that damage biological tissues, microelectronic devices, and materials. In deep space missions, where the Earth's magnetic field does not provide protection from space radiation, the GCR environment is significantly enhanced due to the absence of geomagnetic cut-off and is a major component of radiation exposure. Accurate risk assessments critically depend on the accuracy of the input information as well as radiation transport codes used, and so systematic verification of codes is necessary. In this study, comparisons are made between the deterministic code HZETRN2006 and the Monte Carlo codes HETC-HEDS and FLUKA for an aluminum shield followed by a water target exposed to the 1977 solar minimum GCR spectrum. Interaction and transport of high charge ions present in GCR radiation environment provide a more stringent constraint in the comparison of the codes. Dose, dose equivalent and flux spectra are compared; details of the comparisons will be discussed, and conclusions will be drawn for future directions.

Upscaling of U(VI) Desorption and Transport from Decimeter-Scale Heterogeneity to Plume-Scale Modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Curtis, Gary P.; Kohler, Matthias; Kannappan, Ramakrishnan

2015-02-24

Scientifically defensible predictions of field scale U(VI) transport in groundwater requires an understanding of key processes at multiple scales. These scales range from smaller than the sediment grain scale (less than 10 μm) to as large as the field scale which can extend over several kilometers. The key processes that need to be considered include both geochemical reactions in solution and at sediment surfaces as well as physical transport processes including advection, dispersion, and pore-scale diffusion. The research summarized in this report includes both experimental and modeling results in batch, column and tracer tests. The objectives of this research weremore » to: (1) quantify the rates of U(VI) desorption from sediments acquired from a uranium contaminated aquifer in batch experiments;(2) quantify rates of U(VI) desorption in column experiments with variable chemical conditions, and(3) quantify nonreactive tracer and U(VI) transport in field tests.« less

Transportation fuel research and development : statistically validated codes and standards

DOT National Transportation Integrated Search

2007-08-28

The recent establishment of the National University Transportation Center at MST under the "Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users," expands the research and education activities to include alternative tr...

14 CFR 257.3 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... this part: (a) Air transportation means foreign air transportation or interstate air transportation as defined in 49 U.S.C. 40102 (a)(23) and (25) respectively. (b) Carrier means any air carrier or foreign air... scheduled passenger air transportation, including by wet lease. (c) Code-sharing arrangement means an...

Extension of the BRYNTRN code to monoenergetic light ion beams

NASA Technical Reports Server (NTRS)

Cucinotta, Francis A.; Wilson, John W.; Badavi, Francis F.

1994-01-01

A monoenergetic version of the BRYNTRN transport code is extended to beam transport of light ions (H-2, H-3, He-3, and He-4) in shielding materials (thick targets). The redistribution of energy in nuclear reactions is included in transport solutions that use nuclear fragmentation models. We also consider an equilibrium target-fragment spectrum for nuclei with mass number greater than four to include target fragmentation effects in the linear energy transfer (LET) spectrum. Illustrative results for water and aluminum shielding, including energy and LET spectra, are discussed for high-energy beams of H-2 and He-4.

Green's function methods in heavy ion shielding

NASA Technical Reports Server (NTRS)

Wilson, John W.; Costen, Robert C.; Shinn, Judy L.; Badavi, Francis F.

1993-01-01

An analytic solution to the heavy ion transport in terms of Green's function is used to generate a highly efficient computer code for space applications. The efficiency of the computer code is accomplished by a nonperturbative technique extending Green's function over the solution domain. The computer code can also be applied to accelerator boundary conditions to allow code validation in laboratory experiments.

A Green's function method for heavy ion beam transport

NASA Technical Reports Server (NTRS)

Shinn, J. L.; Wilson, J. W.; Schimmerling, W.; Shavers, M. R.; Miller, J.; Benton, E. V.; Frank, A. L.; Badavi, F. F.

1995-01-01

The use of Green's function has played a fundamental role in transport calculations for high-charge high-energy (HZE) ions. Two recent developments have greatly advanced the practical aspects of implementation of these methods. The first was the formulation of a closed-form solution as a multiple fragmentation perturbation series. The second was the effective summation of the closed-form solution through nonperturbative techniques. The nonperturbative methods have been recently extended to an inhomogeneous, two-layer transport media to simulate the lead scattering foil present in the Lawrence Berkeley Laboratories (LBL) biomedical beam line used for cancer therapy. Such inhomogeneous codes are necessary for astronaut shielding in space. The transport codes utilize the Langley Research Center atomic and nuclear database. Transport code and database evaluation are performed by comparison with experiments performed at the LBL Bevalac facility using 670 A MeV 20Ne and 600 A MeV 56Fe ion beams. The comparison with a time-of-flight and delta E detector measurement for the 20Ne beam and the plastic nuclear track detectors for 56Fe show agreement up to 35%-40% in water and aluminium targets, respectively.

A Conference on Spacecraft Charging Technology - 1978, held at U.S. Air Force Academy, Colorado Springs, Colorado, October 31 - November 2, 1978.

DTIC Science & Technology

1978-01-01

complex, applications of the code . NASCAP CODE DESCRIPTION The NASCAP code is a finite-element spacecraft-charging simulation that is written in FORTRAN ...transport code POEM (ref. 1), is applicable to arbitrary dielectrics, source spectra, and current time histories. The code calculations are illustrated by...iaxk ’. Vlbouced _DstributionL- 9TNA Availability Codes %ELECTEf Nationa Aeronautics and Dist. Spec al TAvalland/or. MAY 2 21980 Space Administration

The atmospheric transport of iodine-129 from Fukushima to British Columbia, Canada and its deposition and transport into groundwater

NASA Astrophysics Data System (ADS)

Herod, Matt N.; Suchy, Martin; Cornett, R. Jack; Kieser, W. E.; Clark, Ian D.; Graham, Gwyn

2015-12-01

The Fukushima-Daiichi nuclear accident (FDNA) released iodine-129 (15.7 million year half-life) and other fission product radionuclides into the environment in the spring and summer of 2011. 129I is recognized as a useful tracer for the short-lived radiohazard 131I, which has a mobile geochemical behavior with potential to contaminate water resources. To trace 129I released by the FDNA reaching Canada, pre-accident and post-accident rain samples collected in Vancouver, on Saturna Island and from the National Atmospheric Deposition Program in Washington State were measured. Groundwater from the Abbotsford-Sumas Aquifer was sampled to determine the fate of 129I that infiltrates below the root zone. Modeling of vadose zone transport was performed to constrain the travel time and retardation of 129I. The mean pre-accident 129I concentration in rain was 31 × 106 atoms/L (n = 4). Immediately following the FDNA, 129I values increased to 211 × 106 atoms/L and quickly returned to near-background levels. However, pulses of elevated 129I continued for several months. The increases in 129I concentrations from both Vancouver and Saturna Island were synchronized, and occurred directly after the initial release from the FDNA. The 129I in shallow (3H/3He age <1.4 years) Wassenaar et al. (2006) groundwater showed measurable variability through March 2013 with an average of 3.2 × 106 atoms/L (n = 32) that was coincident with modeled travel times for Fukushima 129I. The groundwater response and the modeling results suggest that 129I was partially attenuated in soil, which is consistent with its geochemical behavior; however, we conclude that the measured variability may be due to Fukushima 129I entering groundwater.

Groundwater assessment and environmental impact in the abandoned mine of Kettara (Morocco).

PubMed

Moyé, Julien; Picard-Lesteven, Tanguy; Zouhri, Lahcen; El Amari, Khalid; Hibti, Mohamed; Benkaddour, Abdelfattah

2017-12-01

Many questions about the soil pollution due to mining activities have been analyzed by numerous methods which help to evaluate the dispersion of the Metallic Trace Elements (MTE) in the soil and stream sediments of the abandoned mine of Kettara (Morocco). The transport of these MTE could have an important role in the degradation of groundwater and the health of people who are living in the vicinity. The present paper aims to evaluate the groundwater samples from 15 hydrogeological wells. This evaluation concerns the hydrogeological parameters, pH, Electrical conductivity, temperature and the groundwater level, and the geochemical assessment of Mg, Ca, Ti, Cr, Mn, Fe, Co, Ni, Zn, Cu, As, Se, Cd, Sb, Tl and Pb. Furthermore, the Metallic Trace Elements are transported in the saturated zone via the fractures network. The groundwater flow is from the north-east to south-west. The spatial distribution of As, Fe, Zn and Mn is very heterogeneous, with high values observed in the north, upstream, of the mine site. This distribution is maybe related to: i) the existence of hydrogeological structures (dividing and drainage axes); ii) the individualization of the fractures network that affects the shaly lithostratigraphical formation; iii) the transport of the contaminants from the soil towards groundwater; and iv) interaction water/rocks. Some MTE anomalies are linked to the lithology and the fracturation system of the area. Therefore, the groundwater contamination by Arsenic is detected in the hydrogeological wells (E1 and E2). This pollution which is higher than guideline standards of Moroccan drinking water could affect the public health. The hydrogeological and geochemical investigations favor the geological origin (mafic rocks) of this contamination rather than mining activities. Copyright © 2017. Published by Elsevier Ltd.

Altered volcanic ash layers of the Late Cretaceous San Felipe Formation, Sierra Madre Oriental (Northeastern Mexico): Usbnd Pb geochronology, provenance and tectonic setting

NASA Astrophysics Data System (ADS)

Velasco-Tapia, Fernando; Martínez-Paco, Margarita; Iriondo, Alexander; Ocampo-Díaz, Yam Zul Ernesto; Cruz-Gámez, Esther María; Ramos-Ledezma, Andrés; Andaverde, Jorge Alberto; Ostrooumov, Mikhail; Masuch, Dirk

2016-10-01

A detailed petrographic, geochemical, and Usbnd Pb geochronological study of altered volcanic ash layers, collected in eight outcrops of the Late Cretaceous San Felipe Formation (Sierra Madre Oriental, Northeastern Mexico), has been carried out. The main objectives have been: (1) to establish a deposit period, and (2) to propose a reliable provenance-transport-deposit-diagenetic model. These volcano-sedimentary strata represent the altered remains of vitreous-crystalline ash (main grains: quartz + K-feldspar (sanidine) + Na-plagioclase + zircon + biotite; groundmass: glass + calcite + clinochlore + illite) deposited and preserved in a shallow, relatively large in area, open platform environment. Major and trace element geochemistry indicate that parent volcanism was mainly rhyodacitic to rhyolitic in composition. Discrimination diagrams suggest a link to continental arc transitional to extension tectonic setting. Usbnd Pb geochronology in zircon has revealed that the volcanic ash was released from their sources approximately during the range 84.6 ± 0.8 to 73.7 ± 0.3 Ma, being transported to the depocenters. Burial diagenesis process was marked by: (a) a limited recycling, (b) the partial loss of original components (mainly K-feldspar, plagioclase, biotite and glass), and (c) the addition of quartz, calcite, illite and clinochlore. The location of the source area remains uncertain, although the lack of enrichment in Zr/Sc ratio suggests that ashes were subjected to relatively fast and short-distance transport process. El Peñuelo intrusive complex, at 130-170 km west of the depocenters, is the nearest known zone of active magmatism during the Upper Cretaceous. This intermediate to felsic pluton, characterized by a geochemical affinity to post-orogenic tectonic setting, could be linked to the volcanic sources.

Characterization of Magma-Driven Hydrothermal Systems at Oceanic Spreading Centers

NASA Astrophysics Data System (ADS)

Farough, A.; Lowell, R. P.; Corrigan, R.

2012-12-01

Fluid circulation in high-temperature hydrothermal systems involves complex water-rock chemical reactions and phase separation. Numerical modeling of reactive transport in multi-component, multiphase systems is required to obtain a full understanding of the characteristics and evolution of hydrothermal vent systems. We use a single-pass parameterized model of high-temperature hydrothermal circulation at oceanic spreading centers constrained by observational parameters such as vent temperature, heat output, and vent field area, together with surface area and depth of the sub-axial magma chamber, to deduce fundamental hydrothermal parameters such as mass flow rate, bulk permeability, conductive boundary layer thickness at the base of the system, magma replenishment rate, and residence time in the discharge zone. All of these key subsurface characteristics are known for fewer than 10 sites out of 300 known hydrothermal systems. The principal limitations of this approach stem from the uncertainty in heat output and vent field area. For systems where data are available on partitioning of heat and chemical output between focused and diffuse flow, we determined the fraction of high-temperature vent fluid incorporated into diffuse flow using a two-limb single pass model. For EPR 9°50` N and ASHES, the diffuse flow temperatures calculated assuming conservative mixing are nearly equal to the observed temperatures indicating that approximately 80%-90% of the hydrothermal heat output occurs as high-temperature flow derived from magmatic heat even though most of the heat output appears as low-temperature diffuse discharge. For the Main Endeavour Field and Lucky Strike, diffuse flow fluids show significant conductive cooling and heating respectively. Finally, we calculate the transport of various geochemical constituents in focused and diffuse flow at the vent field scale and compare the results with estimates of geochemical transports from the Rainbow hydrothermal field where diffuse flow is absent.

Reduced order models for prediction of groundwater quality impacts from CO₂ and brine leakage

DOE PAGES

Zheng, Liange; Carroll, Susan; Bianchi, Marco; ...

2014-12-31

A careful assessment of the risk associated with geologic CO₂ storage is critical to the deployment of large-scale storage projects. A potential risk is the deterioration of groundwater quality caused by the leakage of CO₂ and brine leakage from deep subsurface reservoirs. In probabilistic risk assessment studies, numerical modeling is the primary tool employed to assess risk. However, the application of traditional numerical models to fully evaluate the impact of CO₂ leakage on groundwater can be computationally complex, demanding large processing times and resources, and involving large uncertainties. As an alternative, reduced order models (ROMs) can be used as highlymore » efficient surrogates for the complex process-based numerical models. In this study, we represent the complex hydrogeological and geochemical conditions in a heterogeneous aquifer and subsequent risk by developing and using two separate ROMs. The first ROM is derived from a model that accounts for the heterogeneous flow and transport conditions in the presence of complex leakage functions for CO₂ and brine. The second ROM is obtained from models that feature similar, but simplified flow and transport conditions, and allow for a more complex representation of all relevant geochemical reactions. To quantify possible impacts to groundwater aquifers, the basic risk metric is taken as the aquifer volume in which the water quality of the aquifer may be affected by an underlying CO₂ storage project. The integration of the two ROMs provides an estimate of the impacted aquifer volume taking into account uncertainties in flow, transport and chemical conditions. These two ROMs can be linked in a comprehensive system level model for quantitative risk assessment of the deep storage reservoir, wellbore leakage, and shallow aquifer impacts to assess the collective risk of CO₂ storage projects.« less

Microfluidic Experiments Studying Pore Scale Interactions of Microbes and Geochemistry

NASA Astrophysics Data System (ADS)

Chen, M.; Kocar, B. D.

2016-12-01

Understanding how physical phenomena, chemical reactions, and microbial behavior interact at the pore-scale is crucial to understanding larger scale trends in groundwater chemistry. Recent studies illustrate the utility of microfluidic devices for illuminating pore-scale physical-biogeochemical processes and their control(s) on the cycling of iron, uranium, and other important elements 1-3. These experimental systems are ideal for examining geochemical reactions mediated by microbes, which include processes governed by complex biological phenomenon (e.g. biofilm formation, etc.)4. We present results of microfluidic experiments using a model metal reducing bacteria and varying pore geometries, exploring the limitations of the microorganisms' ability to access tight pore spaces, and examining coupled biogeochemical-physical controls on the cycling of redox sensitive metals. Experimental results will provide an enhanced understanding of coupled physical-biogeochemical processes transpiring at the pore-scale, and will constrain and compliment continuum models used to predict and describe the subsurface cycling of redox-sensitive elements5. 1. Vrionis, H. A. et al. Microbiological and geochemical heterogeneity in an in situ uranium bioremediation field site. Appl. Environ. Microbiol. 71, 6308-6318 (2005). 2. Pearce, C. I. et al. Pore-scale characterization of biogeochemical controls on iron and uranium speciation under flow conditions. Environ. Sci. Technol. 46, 7992-8000 (2012). 3. Zhang, C., Liu, C. & Shi, Z. Micromodel investigation of transport effect on the kinetics of reductive dissolution of hematite. Environ. Sci. Technol. 47, 4131-4139 (2013). 4. Ginn, T. R. et al. Processes in microbial transport in the natural subsurface. Adv. Water Resour. 25, 1017-1042 (2002). 5. Scheibe, T. D. et al. Coupling a genome-scale metabolic model with a reactive transport model to describe in situ uranium bioremediation. Microb. Biotechnol. 2, 274-286 (2009).

Arsenic transport between surface and groundwater in a moderately reducing zone: Geochemical approach

NASA Astrophysics Data System (ADS)

Khaska, Mahmoud; Le Gal La Salle, Corinne; Verdoux, Patrick

2015-04-01

Arsenic contamination represents a major risk to human health as one of the most prominent environmental causes of cancer mortality. Mining activities, particularly those involving arsenic rich ores have an impact on the environment and on human health that may persist for many decades after mine closure. The relationships between As released from alluvial aquifer in the vicinity of the sulfide-rich mine dumps was demonstrated with geochemical and isotopic tracers (major and traces elements, 87Sr/86Sr, 18O, 2H). Strontium isotopes were used to trace the transport of As downstream from a As rich tailing dam. Increasing As and Fe concentrations in surface water are explained by As release associated with alluvial groundwater discharge to the stream. This process occurs in a moderately reduced section of the stream downgradient from the sulfide-rich tailing dam. High As, total Fe and low Eh in groundwater confirm the discharge of alluvial groundwater and explain its impact on surface water. Transport of As between surface and groundwater can be described as follows: 1- Subsurface moderately reducing conditions prevail in groundwater downgradient from the tailing dams. This suggests a flux of reduced water from sulfide-rich tailing dams which is characterized by its high As and Fe content resulting from the reduction of Fe-sulfides. 2- Upon mixing with surface water, oxidizing conditions prevails and precipitate as Fe hydroxide on the stream bed. As and Sr subsequently adsorbed on the Fe -oxyhydroxide surface. This process contributes to the immobilization of As in surface water. Remaining dissolved As in surface water can be re-introduced in alluvial groundwater downstream of the reducing zone.

Fate of arsenic, phosphate and ammonium plumes in a coastal aquifer affected by saltwater intrusion.

PubMed

Colombani, N; Mastrocicco, M; Prommer, H; Sbarbati, C; Petitta, M

2015-08-01

A severe groundwater contamination with extensive plumes of arsenic, phosphate and ammonium was found in a coastal aquifer beneath a former fertilizer production plant. The implementation of an active groundwater remediation strategy, based on a comprehensive pump and treat scheme, now prevents the migration of the dissolved contaminants into the marine environment. However, due to the site's proximity to the coastline, a seawater wedge was induced by the pumping scheme. Additionally the groundwater flow and salinity patterns were also strongly affected by leakage from the site's sewer system and from a seawater-fed cooling canal. The objective of this study was to elucidate the fate of arsenic and its co-contaminants over the site's history under the complex, coupled hydrodynamic and geochemical conditions that prevail at the site. A detailed geochemical characterisation of samples from sediment cores and hydrochemical data provided valuable high-resolution information. The obtained data were used to develop various conceptual models and to constrain the development and calibration of a reactive transport model. The reactive transport simulations were performed for a sub-domain (two-dimensional transect) of an earlier developed three-dimensional flow and variable density solute transport model. The results suggest that in the upper sub-oxic zone the influx of oxygenated water promoted As attenuation via co-precipitation with Al and Fe oxides and copper hydroxides. In contrast, in the deeper aquifer zone, iron reduction, associated with the release of adsorbed As and the dissolution of As bearing phases, provided and still provides to date a persistent source for groundwater pollution. The presented monitoring and modelling approach could be broadly applied to coastal polluted sites by complex contaminant mixture containing As. Copyright © 2015 Elsevier B.V. All rights reserved.

Numerical modeling of coupled variably saturated fluid flow and reactive transport with fast and slow chemical reactions

NASA Astrophysics Data System (ADS)

Yeh, Gour-Tsyh (George); Siegel, Malcolm D.; Li, Ming-Hsu

2001-02-01

The couplings among chemical reaction rates, advective and diffusive transport in fractured media or soils, and changes in hydraulic properties due to precipitation and dissolution within fractures and in rock matrix are important for both nuclear waste disposal and remediation of contaminated sites. This paper describes the development and application of LEHGC2.0, a mechanistically based numerical model for simulation of coupled fluid flow and reactive chemical transport, including both fast and slow reactions in variably saturated media. Theoretical bases and numerical implementations are summarized, and two example problems are demonstrated. The first example deals with the effect of precipitation/dissolution on fluid flow and matrix diffusion in a two-dimensional fractured media. Because of the precipitation and decreased diffusion of solute from the fracture into the matrix, retardation in the fractured medium is not as large as the case wherein interactions between chemical reactions and transport are not considered. The second example focuses on a complicated but realistic advective-dispersive-reactive transport problem. This example exemplifies the need for innovative numerical algorithms to solve problems involving stiff geochemical reactions.

Linear energy transfer in water phantom within SHIELD-HIT transport code

NASA Astrophysics Data System (ADS)

Ergun, A.; Sobolevsky, N.; Botvina, A. S.; Buyukcizmeci, N.; Latysheva, L.; Ogul, R.

2017-02-01

The effect of irradiation in tissue is important in hadron therapy for the dose measurement and treatment planning. This biological effect is defined by an equivalent dose H which depends on the Linear Energy Transfer (LET). Usually, H can be expressed in terms of the absorbed dose D and the quality factor K of the radiation under consideration. In literature, various types of transport codes have been used for modeling and simulation of the interaction of the beams of protons and heavier ions with tissue-equivalent materials. In this presentation we used SHIELD-HIT code to simulate decomposition of the absorbed dose by LET in water for 16O beams. A more detailed description of capabilities of the SHIELD-HIT code can be found in the literature.

Overview of Edge Simulation Laboratory (ESL)

NASA Astrophysics Data System (ADS)

Cohen, R. H.; Dorr, M.; Hittinger, J.; Rognlien, T.; Umansky, M.; Xiong, A.; Xu, X.; Belli, E.; Candy, J.; Snyder, P.; Colella, P.; Martin, D.; Sternberg, T.; van Straalen, B.; Bodi, K.; Krasheninnikov, S.

2006-10-01

The ESL is a new collaboration to build a full-f electromagnetic gyrokinetic code for tokamak edge plasmas using continuum methods. Target applications are edge turbulence and transport (neoclassical and anomalous), and edge-localized modes. Initially the project has three major threads: (i) verification and validation of TEMPEST, the project's initial (electrostatic) edge code which can be run in 4D (neoclassical and transport-timescale applications) or 5D (turbulence); (ii) design of the next generation code, which will include more complete physics (electromagnetics, fluid equation option, improved collisions) and advanced numerics (fully conservative, high-order discretization, mapped multiblock grids, adaptivity), and (iii) rapid-prototype codes to explore the issues attached to solving fully nonlinear gyrokinetics with steep radial gradiens. We present a brief summary of the status of each of these activities.

Geochemical modeling of reactions and partitioning of trace metals and radionuclides during titration of contaminated acidic sediments.

PubMed

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

2008-11-01

Many geochemical reactions that control aqueous metal concentrations are directly affected by solution pH. However, changes in solution pH are strongly buffered by various aqueous phase and solid phase precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior of the soil-solution system is thus critical to predict metal transport under variable pH conditions. This studywas undertaken to develop a practical generic geochemical modeling approach to predict aqueous and solid phase concentrations of metals and anions during conditions of acid or base additions. The method of Spalding and Spalding was utilized to model soil buffer capacity and pH-dependent cation exchange capacity by treating aquifer solids as a polyprotic acid. To simulate the dynamic and pH-dependent anion exchange capacity, the aquifer solids were simultaneously treated as a polyprotic base controlled by mineral precipitation/ dissolution reactions. An equilibrium reaction model that describes aqueous complexation, precipitation, sorption and soil buffering with pH-dependent ion exchange was developed using HydroGeoChem v5.0 (HGC5). Comparison of model results with experimental titration data of pH, Al, Ca, Mg, Sr, Mn, Ni, Co, and SO4(2-) for contaminated sediments indicated close agreement suggesting that the model could potentially be used to predictthe acid-base behavior of the sediment-solution system under variable pH conditions.

Snowmelt induced hydrologic perturbations drive dynamic microbiological and geochemical behaviors across a shallow riparian aquifer

NASA Astrophysics Data System (ADS)

Danczak, Robert; Yabusaki, Steven; Williams, Kenneth; Fang, Yilin; Hobson, Chad; Wilkins, Michael

2016-05-01

Shallow riparian aquifers represent hotspots of biogeochemical activity in the arid western US. While these environments provide extensive ecosystem services, little is known of how natural environmental perturbations influence subsurface microbial communities and associated biogeochemical processes. Over a six-month period we tracked the annual snowmelt-driven incursion of groundwater into the vadose zone of an aquifer adjacent to the Colorado River, leading to increased dissolved oxygen (DO) concentrations in the normally suboxic saturated zone. Strong biogeochemical heterogeneity was measured across the site, with abiotic reactions between DO and sulfide minerals driving rapid DO consumption and mobilization of redox active species in reduced aquifer regions. Conversely, extensive DO increases were detected in less reduced sediments. 16S rRNA gene surveys tracked microbial community composition within the aquifer, revealing strong correlations between increases in putative oxygen-utilizing chemolithoautotrophs and heterotrophs and rising DO concentrations. The gradual return to suboxic aquifer conditions favored increasing abundances of 16S rRNA sequences matching members of the Microgenomates (OP11) and Parcubacteria (OD1) that have been strongly implicated in fermentative processes. Microbial community stability measurements indicated that deeper aquifer locations were relatively less affected by geochemical perturbations, while communities in shallower locations exhibited the greatest change. Reactive transport modeling of the geochemical and microbiological results supported field observations, suggesting that a predictive framework can be applied to develop a greater understanding of such environments.

Quantifying reactive transport processes governing arsenic mobility in a Bengal Delta aquifer

NASA Astrophysics Data System (ADS)

Rawson, Joey; Neidhardt, Harald; Siade, Adam; Berg, Michael; Prommer, Henning

2017-04-01

Over the last few decades significant progress has been made to characterize the extent and severity of groundwater arsenic pollution in S/SE Asia, and to understand the underlying geochemical processes. However, comparably little effort has been made to merge the findings from this research into quantitative frameworks that allow for a process-based quantitative analysis of observed arsenic behavior and predictions of its future fate. Therefore, this study developed and tested field-scale numerical modelling approaches to represent the primary and secondary geochemical processes associated with the reductive dissolution of Fe-oxy(hydr)oxides and the concomitant release of sorbed arsenic. We employed data from an in situ field experiment in the Bengal Delta Plain, which investigated the influence of labile organic matter (sucrose) on the mobility of Fe, Mn, and As. The data collected during the field experiment were used to guide our model development and to constrain the model parameterisation. Our results show that sucrose oxidation coupled to the reductive dissolution of Fe-oxy(hydr)oxides was accompanied by multiple secondary geochemical reactions that are not easily and uniquely identifiable and quantifiable. Those secondary reactions can explain the disparity between the observed Fe and As behavior. Our modelling results suggest that a significant fraction of the released As is scavenged through (co-)precipitation with newly formed Fe-minerals, specifically magnetite, rather than through sorption to pre-existing and freshly precipitated iron minerals.

Geomorphic and geochemical controls on leaf wax biomarker transport and preservation in alluvial river systems: Rio Bermejo, Argentina

NASA Astrophysics Data System (ADS)

Repasch, M. N.; Sachse, D.; Hovius, N.; Scheingross, J. S.; Szupiany, R. N.

2017-12-01

Rivers are the primary conduits for organic carbon (OC) transfer from vegetation-rich uplands to long-term sinks, and thus are responsible for significant fluxes among different reservoirs of the carbon cycle. Fluxes of terrestrial OC out of river systems are generally less than fluxes into the systems, indicating loss of OC either during active fluvial transport, during residence in the active channel belt, or in older deposits outside of the active channel belt. Sedimentary biomarkers can be used to elucidate the mechanisms of transport, preservation, and/or transformation of OC during its passage from source to sink. In this study we evaluate the influence of fluvial sediment transport on preservation of terrestrial leaf wax n-alkanes. Our natural laboratory is the Rio Bermejo in northern Argentina, which transports sediment and organic matter from the central Andes over 700 km across the foreland basin without input of foreign material from tributaries. Rapid channel migration rates in a region of flexural foreland basin uplift (the forebulge) are responsible for remobilization of floodplain sediment and terrestrial OC. By sampling suspended sediment, river bank sediment, and soil from several locations along the length of the Rio Bermejo, and analyzing the dissolved chemistry, biomarker composition, and compound-specific stable isotopes, we can evaluate the geomorphic and geochemical processes that act to influence the preservation of terrestrial biomarkers through the river system. Data suggest that concentrations of long-chain terrestrial (C25-C33) alkanes decrease downstream, while concentrations of short-chain (C15-C19) alkanes increase. This trend is corroborated by a downstream increase in suspended sediment δ13C values, suggesting a replacement of terrestrial OC by microbial OC. It is likely that microbial degradation is responsible for loss of terrestrial biomarkers as their residence time in the river system increases. Controlled laboratory experiments and analysis of modern and aged river bank sediment samples will determine where and over what timescales leaf wax alkanes are oxidized by microorganisms. With these data, we will be able to quantify the loss of OC during fluvial transit and determine the mechanisms responsible, enabling carbon cycle models to account for these losses.

Benchmarking Heavy Ion Transport Codes FLUKA, HETC-HEDS MARS15, MCNPX, and PHITS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ronningen, Reginald Martin; Remec, Igor; Heilbronn, Lawrence H.

Powerful accelerators such as spallation neutron sources, muon-collider/neutrino facilities, and rare isotope beam facilities must be designed with the consideration that they handle the beam power reliably and safely, and they must be optimized to yield maximum performance relative to their design requirements. The simulation codes used for design purposes must produce reliable results. If not, component and facility designs can become costly, have limited lifetime and usefulness, and could even be unsafe. The objective of this proposal is to assess the performance of the currently available codes PHITS, FLUKA, MARS15, MCNPX, and HETC-HEDS that could be used for designmore » simulations involving heavy ion transport. We plan to access their performance by performing simulations and comparing results against experimental data of benchmark quality. Quantitative knowledge of the biases and the uncertainties of the simulations is essential as this potentially impacts the safe, reliable and cost effective design of any future radioactive ion beam facility. Further benchmarking of heavy-ion transport codes was one of the actions recommended in the Report of the 2003 RIA R&D Workshop".« less

Application of a Java-based, univel geometry, neutral particle Monte Carlo code to the searchlight problem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Charles A. Wemple; Joshua J. Cogliati

2005-04-01

A univel geometry, neutral particle Monte Carlo transport code, written entirely in the Java programming language, is under development for medical radiotherapy applications. The code uses ENDF-VI based continuous energy cross section data in a flexible XML format. Full neutron-photon coupling, including detailed photon production and photonuclear reactions, is included. Charged particle equilibrium is assumed within the patient model so that detailed transport of electrons produced by photon interactions may be neglected. External beam and internal distributed source descriptions for mixed neutron-photon sources are allowed. Flux and dose tallies are performed on a univel basis. A four-tap, shift-register-sequence random numbermore » generator is used. Initial verification and validation testing of the basic neutron transport routines is underway. The searchlight problem was chosen as a suitable first application because of the simplicity of the physical model. Results show excellent agreement with analytic solutions. Computation times for similar numbers of histories are comparable to other neutron MC codes written in C and FORTRAN.« less

Using Modern C++ Idiom for the Discretisation of Sets of Coupled Transport Equations in Numerical Plasma Physics

NASA Astrophysics Data System (ADS)

van Dijk, Jan; Hartgers, Bart; van der Mullen, Joost

2006-10-01

Self-consistent modelling of plasma sources requires a simultaneous treatment of multiple physical phenomena. As a result plasma codes have a high degree of complexity. And with the growing interest in time-dependent modelling of non-equilibrium plasma in three dimensions, codes tend to become increasingly hard to explain-and-maintain. As a result of these trends there has been an increased interest in the software-engineering and implementation aspects of plasma modelling in our group at Eindhoven University of Technology. In this contribution we will present modern object-oriented techniques in C++ to solve an old problem: that of the discretisation of coupled linear(ized) equations involving multiple field variables on ortho-curvilinear meshes. The `LinSys' code has been tailored to the transport equations that occur in transport physics. The implementation has been made both efficient and user-friendly by using modern idiom like expression templates and template meta-programming. Live demonstrations will be given. The code is available to interested parties; please visit www.dischargemodelling.org.

Herbicide Metabolites in Surface Water and Groundwater: Introduction and Overview

USGS Publications Warehouse

Thurman, E.M.; Meyer, M.T.

1996-01-01

Several future research topics for herbicide metabolites in surface and ground water are outlined in this chapter. They are herbicide usage, chemical analysis of metabolites, and fate and transport of metabolites in surface and ground water. These three ideas follow the themes in this book, which are the summary of a symposium of the American Chemical Society on herbicide metabolites in surface and ground water. First, geographic information systems allow the spatial distribution of herbicide-use data to be combined with geochemical information on fate and transport of herbicides. Next these two types of information are useful in predicting the kinds of metabolites present and their probable distribution in surface and ground water. Finally, methods development efforts may be focused on these specific target analytes. This chapter discusses these three concepts and provides an introduction to this book on the analysis, chemistry, and fate and transport of herbicide metabolites in surface and ground water.

Thermal impact of magmatism in subduction zones

NASA Astrophysics Data System (ADS)

Rees Jones, David W.; Katz, Richard F.; Tian, Meng; Rudge, John F.

2018-01-01

Magmatism in subduction zones builds continental crust and causes most of Earth's subaerial volcanism. The production rate and composition of magmas are controlled by the thermal structure of subduction zones. A range of geochemical and heat flow evidence has recently converged to indicate that subduction zones are hotter at lithospheric depths beneath the arc than predicted by canonical thermomechanical models, which neglect magmatism. We show that this discrepancy can be resolved by consideration of the heat transported by magma. In our one- and two-dimensional numerical models and scaling analysis, magmatic transport of sensible and latent heat locally alters the thermal structure of canonical models by ∼300 K, increasing predicted surface heat flow and mid-lithospheric temperatures to observed values. We find the advection of sensible heat to be larger than the deposition of latent heat. Based on these results we conclude that thermal transport by magma migration affects the chemistry and the location of arc volcanoes.

Reactive solute transport in acidic streams

USGS Publications Warehouse

Broshears, R.E.

1996-01-01

Spatial and temporal profiles of Ph and concentrations of toxic metals in streams affected by acid mine drainage are the result of the interplay of physical and biogeochemical processes. This paper describes a reactive solute transport model that provides a physically and thermodynamically quantitative interpretation of these profiles. The model combines a transport module that includes advection-dispersion and transient storage with a geochemical speciation module based on MINTEQA2. Input to the model includes stream hydrologic properties derived from tracer-dilution experiments, headwater and lateral inflow concentrations analyzed in field samples, and a thermodynamic database. Simulations reproduced the general features of steady-state patterns of observed pH and concentrations of aluminum and sulfate in St. Kevin Gulch, an acid mine drainage stream near Leadville, Colorado. These patterns were altered temporarily by injection of sodium carbonate into the stream. A transient simulation reproduced the observed effects of the base injection.

One-dimensional model for biogeochemical interactions and permeability reduction in soils during leachate permeation.

PubMed

Singhal, Naresh; Islam, Jahangir

2008-02-19

This paper uses the findings from a column study to develop a reactive model for exploring the interactions occurring in leachate-contaminated soils. The changes occurring in the concentrations of acetic acid, sulphate, suspended and attached biomass, Fe(II), Mn(II), calcium, carbonate ions, and pH in the column are assessed. The mathematical model considers geochemical equilibrium, kinetic biodegradation, precipitation-dissolution reactions, bacterial and substrate transport, and permeability reduction arising from bacterial growth and gas production. A two-step sequential operator splitting method is used to solve the coupled transport and biogeochemical reaction equations. The model gives satisfactory fits to experimental data and the simulations show that the transport of metals in soil is controlled by multiple competing biotic and abiotic reactions. These findings suggest that bioaccumulation and gas formation, compared to chemical precipitation, have a larger influence on hydraulic conductivity reduction.

Serpentinization as a reactive transport process: The brucite silicification reaction

NASA Astrophysics Data System (ADS)

Tutolo, Benjamin M.; Luhmann, Andrew J.; Tosca, Nicholas J.; Seyfried, William E.

2018-02-01

Serpentinization plays a fundamental role in the biogeochemical and tectonic evolution of the Earth and perhaps many other rocky planetary bodies. Yet, geochemical models still fail to produce accurate predictions of the various modes of serpentinization, which limits our ability to predict a variety of related geological phenomena over many spatial and temporal scales. Here, we use kinetic and reactive transport experiments to parameterize the brucite silicification reaction and provide fundamental constraints on SiO2 transport during serpentinization. We show that, at temperatures characteristic of the sub-seafloor at the serpentinite-hosted Lost City Hydrothermal Field (150 °C), the assembly of Si tetrahedra onto MgOH2 (i.e., brucite) surfaces is a rate-limiting elementary reaction in the production of serpentine and/or talc from olivine. Moreover, this reaction is exponentially dependent on the activity of aqueous silica (a SiO2 (aq)), such that it can be calculated according to the rate law:

22 CFR 228.22 - Air transportation.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 22 Foreign Relations 1 2013-04-01 2013-04-01 false Air transportation. 228.22 Section 228.22... § 228.22 Air transportation. The Fly America Act, Title 49 of the United States Code, Subtitle VII, part A, subpart I, Chapter 401, 40118—Government-Financed Air Transportation, is applicable to all...

22 CFR 228.22 - Air transportation.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 22 Foreign Relations 1 2014-04-01 2014-04-01 false Air transportation. 228.22 Section 228.22... § 228.22 Air transportation. The Fly America Act, Title 49 of the United States Code, Subtitle VII, part A, subpart I, Chapter 401, 40118—Government-Financed Air Transportation, is applicable to all...

22 CFR 228.22 - Air transportation.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 22 Foreign Relations 1 2012-04-01 2012-04-01 false Air transportation. 228.22 Section 228.22... § 228.22 Air transportation. The Fly America Act, Title 49 of the United States Code, Subtitle VII, part A, subpart I, Chapter 401, 40118—Government-Financed Air Transportation, is applicable to all...

Modeling of ion orbit loss and intrinsic toroidal rotation with the COGENT code

NASA Astrophysics Data System (ADS)

Dorf, M.; Dorr, M.; Cohen, R.; Rognlien, T.; Hittinger, J.

2014-10-01

We discuss recent advances in cross-separatrix neoclassical transport simulations with COGENT, a continuum gyro-kinetic code being developed by the Edge Simulation Laboratory (ESL) collaboration. The COGENT code models the axisymmetric transport properties of edge plasmas including the effects of nonlinear (Fokker-Planck) collisions and a self-consistent electrostatic potential. Our recent work has focused on studies of ion orbit loss and the associated toroidal rotation driven by this mechanism. The results of the COGENT simulations are discussed and analyzed for the parameters of the DIII-D experiment. Work performed for USDOE at LLNL under Contract DE-AC52-07NA27344.

Development of the V4.2m5 and V5.0m0 Multigroup Cross Section Libraries for MPACT for PWR and BWR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Kang Seog; Clarno, Kevin T.; Gentry, Cole

2017-03-01

The MPACT neutronics module of the Consortium for Advanced Simulation of Light Water Reactors (CASL) core simulator is a 3-D whole core transport code being developed for the CASL toolset, Virtual Environment for Reactor Analysis (VERA). Key characteristics of the MPACT code include (1) a subgroup method for resonance selfshielding and (2) a whole-core transport solver with a 2-D/1-D synthesis method. The MPACT code requires a cross section library to support all the MPACT core simulation capabilities which would be the most influencing component for simulation accuracy.

9 CFR 355.25 - Canning with heat processing and hermetically sealed containers; closures; code marking; heat...

Code of Federal Regulations, 2013 CFR

2013-01-01

... hermetically sealed containers; closures; code marking; heat processing; incubation. 355.25 Section 355.25... processing and hermetically sealed containers; closures; code marking; heat processing; incubation. (a... storage and transportation as evidenced by the incubation test. (h) Lots of canned products shall be...

9 CFR 355.25 - Canning with heat processing and hermetically sealed containers; closures; code marking; heat...

Code of Federal Regulations, 2012 CFR

2012-01-01

... hermetically sealed containers; closures; code marking; heat processing; incubation. 355.25 Section 355.25... processing and hermetically sealed containers; closures; code marking; heat processing; incubation. (a... storage and transportation as evidenced by the incubation test. (h) Lots of canned products shall be...