WorldWideScience

Sample records for biogeochemical transport model

  1. Biogeochemical Transport and Reaction Model (BeTR) v1

    Energy Technology Data Exchange (ETDEWEB)

    2016-04-18

    The Biogeochemical Transport and Reaction Model (BeTR) is a F90 code that enables reactive transport modeling in land modules of earth system models (e.g. CESM, ACME). The code adopts the Objective-Oriented-Design, and allows users to plug in their own biogeochemical (BGC) formulations/codes, and compare them to other existing BGC codes in those ESMs. The code takes information of soil physics variables, such as variables, such as temperature, moisture, soil density profile; water flow, etc., from a land model to track the movement of different chemicals in presence of biogeochemical reactions.

  2. Hyporheic flow and transport processes: mechanisms, models, and biogeochemical implications

    Science.gov (United States)

    Boano, Fulvio; Harvey, Judson W.; Marion, Andrea; Packman, Aaron I.; Revelli, Roberto; Ridolfi, Luca; Anders, Wörman

    2014-01-01

    Fifty years of hyporheic zone research have shown the important role played by the hyporheic zone as an interface between groundwater and surface waters. However, it is only in the last two decades that what began as an empirical science has become a mechanistic science devoted to modeling studies of the complex fluid dynamical and biogeochemical mechanisms occurring in the hyporheic zone. These efforts have led to the picture of surface-subsurface water interactions as regulators of the form and function of fluvial ecosystems. Rather than being isolated systems, surface water bodies continuously interact with the subsurface. Exploration of hyporheic zone processes has led to a new appreciation of their wide reaching consequences for water quality and stream ecology. Modern research aims toward a unified approach, in which processes occurring in the hyporheic zone are key elements for the appreciation, management, and restoration of the whole river environment. In this unifying context, this review summarizes results from modeling studies and field observations about flow and transport processes in the hyporheic zone and describes the theories proposed in hydrology and fluid dynamics developed to quantitatively model and predict the hyporheic transport of water, heat, and dissolved and suspended compounds from sediment grain scale up to the watershed scale. The implications of these processes for stream biogeochemistry and ecology are also discussed."

  3. Modelling of transport and biogeochemical processes in pollution plumes: Literature review of model development

    DEFF Research Database (Denmark)

    Brun, A.; Engesgaard, Peter Knudegaard

    2002-01-01

    A literature survey shows how biogeochemical (coupled organic and inorganic reaction processes) transport models are based on considering the complete biodegradation process as either a single- or as a two-step process. It is demonstrated that some two-step process models rely on the Partial Equi...... second paper [J. Hydrol. 256 (2002) 230-249], reports the application of the model to a field study of biogeochemical transport processes in a landfill plume in Denmark (Vejen). (C) 2002 Elsevier Science B.V. All rights reserved....

  4. Technical Note: Simple formulations and solutions of the dual-phase diffusive transport for biogeochemical modeling

    Directory of Open Access Journals (Sweden)

    J. Y. Tang

    2014-01-01

    Full Text Available Representation of gaseous diffusion in variably saturated near-surface soils is becoming more common in land biogeochemical models, yet the formulations and numerical solution algorithms applied vary widely. We present three different but equivalent formulations of the dual-phase (gaseous and aqueous tracer diffusion transport problem that is relevant to a wide class of volatile tracers in land biogeochemical models. Of these three formulations (i.e., the gas-primary, aqueous-primary, and bulk tracer based formulations, we contend the gas-primary formulation is the most convenient for modeling tracer dynamics in biogeochemical models. We then provide finite volume approximation to the gas-primary equation and evaluate its accuracy against three analytical models: one for steady-state soil CO2 dynamics, one for steady-state soil CO2 dynamics, and one for transient tracer diffusion from a constant point source into two different sequentially aligned medias. All evaluations demonstrated good accuracy of the numerical approximation. We expect our result will standardize an efficient mechanistic numerical method for solving relatively simple, multi-phase, one-dimensional diffusion problems in land models.

  5. HYDROBIOGEOCHEM: A coupled model of HYDROlogic transport and mixed BIOGEOCHEMical kinetic/equilibrium reactions in saturated-unsaturated media

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, G.T.; Salvage, K.M. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Civil and Environmental Engineering; Gwo, J.P. [Oak Ridge National Lab., TN (United States); Zachara, J.M.; Szecsody, J.E. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-07-01

    The computer program HYDROBIOGEOCHEM is a coupled model of HYDROlogic transport and BIOGEOCHEMical kinetic and/or equilibrium reactions in saturated/unsaturated media. HYDROBIOGEOCHEM iteratively solves the two-dimensional transport equations and the ordinary differential and algebraic equations of mixed biogeochemical reactions. The transport equations are solved for all aqueous chemical components and kinetically controlled aqueous species. HYDROBIOGEOCHEM is designed for generic application to reactive transport problems affected by both microbiological and geochemical reactions in subsurface media. Input to the program includes the geometry of the system, the spatial distribution of finite elements and nodes, the properties of the media, the potential chemical and microbial reactions, and the initial and boundary conditions. Output includes the spatial distribution of chemical and microbial concentrations as a function of time and space, and the chemical speciation at user-specified nodes.

  6. A biogeochemical transport model to simulate the attenuation of chlorinated hydrocarbon contaminant fluxes across the groundwater-surface water interface

    DEFF Research Database (Denmark)

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

    because of the occurrence of redox gradients, strongly reductive conditions and high biological activity. In order to meet the expectations of the EU Water Framework Directive, an evaluation of the impact of such plumes on surface water is needed. The aim of this work is to develop a groundwater transport...... and biogeochemical transformation model of the discharge of a TCE plume into a stream, and to determine which parameters most strongly affect pollutant discharge concentrations. Here biological kinetics and the interaction with the soil matrix are implemented in PHREEQC. The ability of PHREEQC to deal...

  7. Modeling greenhouse gas emissions and nutrient transport in managed arable soils with a fully coupled hydrology-biogeochemical modeling system

    Science.gov (United States)

    Haas, Edwin; Klatt, Steffen; Kiese, Ralf; Butterbach-Bahl, Klaus; Kraft, Philipp; Breuer, Lutz

    2015-04-01

    The use of mineral nitrogen fertilizer sustains the global food production and therefore the livelihood of human kind. The rise in world population will put pressure on the global agricultural system to increase its productivity leading most likely to an intensification of mineral nitrogen fertilizer use. The fate of excess nitrogen and its distribution within landscapes is manifold. Process knowledge on the site scale has rapidly grown in recent years and models have been developed to simulate carbon and nitrogen cycling in managed ecosystems on the site scale. Despite first regional studies, the carbon and nitrogen cycling on the landscape or catchment scale is not fully understood. In this study we present a newly developed modelling approach by coupling the fully distributed hydrology model CMF (catchment modelling framework) to the process based regional ecosystem model LandscapeDNDC for the investigation of hydrological processes and carbon and nitrogen transport and cycling, with a focus on nutrient displacement and resulting greenhouse gas emissions in various virtual landscapes / catchment to demonstrate the capabilities of the modelling system. The modelling system was applied to simulate water and nutrient transport at the at the Yanting Agro-ecological Experimental Station of Purple Soil, Sichuan province, China. The catchment hosts cypress forests on the outer regions, arable fields on the sloping croplands cultivated with wheat-maize rotations and paddy rice fields in the lowland. The catchment consists of 300 polygons vertically stratified into 10 soil layers. Ecosystem states (soil water content and nutrients) and fluxes (evapotranspiration) are exchanged between the models at high temporal scales (hourly to daily) forming a 3-dimensional model application. The water flux and nutrients transport in the soil is modelled using a 3D Richards/Darcy approach for subsurface fluxes with a kinematic wave approach for surface water runoff and the

  8. A biogeochemical transport model to simulate the attenuation of chlorinated hydrocarbon contaminant fluxes across the groundwater-surface water interface

    DEFF Research Database (Denmark)

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

    2009-01-01

    Chlorinated hydrocarbons originating from point sources are amongst the most prevalent contaminants of ground water and surface water resources. Riparian zones may play an important role in the attenuation of contaminant concentrations when contaminant plumes flow from groundwater to surface water...... because of the occurrence of redox gradients, strongly reductive conditions and high biological activity. In order to meet the expectations of the EU Water Framework Directive, an evaluation of the impact of such plumes on surface water is needed. The aim of this work is to develop a groundwater transport...... and biogeochemical transformation model of the discharge of a TCE plume into a stream, and to determine which parameters most strongly affect pollutant discharge concentrations. Here biological kinetics and the interaction with the soil matrix are implemented in PHREEQC. The ability of PHREEQC to deal...

  9. Addressing numerical challenges in introducing a reactive transport code into a land surface model: a biogeochemical modeling proof-of-concept with CLM-PFLOTRAN 1.0

    Science.gov (United States)

    Tang, Guoping; Yuan, Fengming; Bisht, Gautam; Hammond, Glenn E.; Lichtner, Peter C.; Kumar, Jitendra; Mills, Richard T.; Xu, Xiaofeng; Andre, Ben; Hoffman, Forrest M.; Painter, Scott L.; Thornton, Peter E.

    2016-03-01

    We explore coupling to a configurable subsurface reactive transport code as a flexible and extensible approach to biogeochemistry in land surface models. A reaction network with the Community Land Model carbon-nitrogen (CLM-CN) decomposition, nitrification, denitrification, and plant uptake is used as an example. We implement the reactions in the open-source PFLOTRAN (massively parallel subsurface flow and reactive transport) code and couple it with the CLM. To make the rate formulae designed for use in explicit time stepping in CLMs compatible with the implicit time stepping used in PFLOTRAN, the Monod substrate rate-limiting function with a residual concentration is used to represent the limitation of nitrogen availability on plant uptake and immobilization. We demonstrate that CLM-PFLOTRAN predictions (without invoking PFLOTRAN transport) are consistent with CLM4.5 for Arctic, temperate, and tropical sites.Switching from explicit to implicit method increases rigor but introduces numerical challenges. Care needs to be taken to use scaling, clipping, or log transformation to avoid negative concentrations during the Newton iterations. With a tight relative update tolerance (STOL) to avoid false convergence, an accurate solution can be achieved with about 50 % more computing time than CLM in point mode site simulations using either the scaling or clipping methods. The log transformation method takes 60-100 % more computing time than CLM. The computing time increases slightly for clipping and scaling; it increases substantially for log transformation for half saturation decrease from 10-3 to 10-9 mol m-3, which normally results in decreasing nitrogen concentrations. The frequent occurrence of very low concentrations (e.g. below nanomolar) can increase the computing time for clipping or scaling by about 20 %, double for log transformation. Overall, the log transformation method is accurate and robust, and the clipping and scaling methods are efficient. When the

  10. PFLOTRAN: Recent Developments Facilitating Massively-Parallel Reactive Biogeochemical Transport

    Science.gov (United States)

    Hammond, G. E.

    2015-12-01

    With the recent shift towards modeling carbon and nitrogen cycling in support of climate-related initiatives, emphasis has been placed on incorporating increasingly mechanistic biogeochemistry within Earth system models to more accurately predict the response of terrestrial processes to natural and anthropogenic climate cycles. PFLOTRAN is an open-source subsurface code that is specialized for simulating multiphase flow and multicomponent biogeochemical transport on supercomputers. The object-oriented code was designed with modularity in mind and has been coupled with several third-party simulators (e.g. CLM to simulate land surface processes and E4D for coupled hydrogeophysical inversion). Central to PFLOTRAN's capabilities is its ability to simulate tightly-coupled reactive transport processes. This presentation focuses on recent enhancements to the code that enable the solution of large parameterized biogeochemical reaction networks with numerous chemical species. PFLOTRAN's "reaction sandbox" is described, which facilitates the implementation of user-defined reaction networks without the need for a comprehensive understanding of PFLOTRAN software infrastructure. The reaction sandbox is written in modern Fortran (2003-2008) and leverages encapsulation, inheritance, and polymorphism to provide the researcher with a flexible workspace for prototyping reactions within a massively parallel flow and transport simulation framework. As these prototypical reactions mature into well-accepted implementations, they can be incorporated into PFLOTRAN as native biogeochemistry capability. Users of the reaction sandbox are encouraged to upload their source code to PFLOTRAN's main source code repository, including the addition of simple regression tests to better ensure the long-term code compatibility and validity of simulation results.

  11. Addressing numerical challenges in introducing a reactive transport code into a land surface model: a biogeochemical modeling proof-of-concept with CLM–PFLOTRAN 1.0

    OpenAIRE

    Tang, Guoping; Yuan, Fengming; Bisht, Gautam; Hammond, Glenn E.; Lichtner, Peter C.; Kumar, Jitendra; Mills, Richard T.; XU, XIAOFENG; Andre, Ben; Hoffman, Forrest M; Painter, Scott L.; Thornton, Peter E

    2016-01-01

    We explore coupling to a configurable subsurface reactive transport code as a flexible and extensible approach to biogeochemistry in land surface models. A reaction network with the Community Land Model carbon–nitrogen (CLM-CN) decomposition, nitrification, denitrification, and plant uptake is used as an example. We implement the reactions in the open-source PFLOTRAN (massively parallel subsurface flow and reactive transport) code and couple it with the CLM. To make the r...

  12. Subsurface Uranium Fate and Transport: Integrated Experiments and Modeling of Coupled Biogeochemical Mechanisms of Nanocrystalline Uraninite Oxidation by Fe(III)-(hydr)oxides - Project Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Peyton, Brent M. [Montana State Univ., Bozeman, MT (United States); Timothy, Ginn R. [Univ. of California, Davis, CA (United States); Sani, Rajesh K. [South Dakota School of Mines and Technology, Rapid City, SD (United States)

    2013-08-14

    citrate. To complement to these laboratory studies, we collected U-bearing samples from a surface seep at the Rifle field site and have measured elevated U concentrations in oxic iron-rich sediments. To translate experimental results into numerical analysis of U fate and transport, a reaction network was developed based on Sani et al. (2004) to simulate U(VI) bioreduction with concomitant UO2 reoxidation in the presence of hematite or ferrihydrite. The reduction phase considers SRB reduction (using lactate) with the reductive dissolution of Fe(III) solids, which is set to be microbially mediated as well as abiotically driven by sulfide. Model results show the oxidation of HS– by Fe(III) directly competes with UO2 reoxidation as Fe(III) oxidizes HS– preferentially over UO2. The majority of Fe reduction is predicted to be abiotic, with ferrihydrite becoming fully consumed by reaction with sulfide. Predicted total dissolved carbonate concentrations from the degradation of lactate are elevated (log(pCO2) ~ –1) and, in the hematite system, yield close to two orders-of-magnitude higher U(VI) concentrations than under initial carbonate concentrations of 3 mM. Modeling of U(VI) bioreduction with concomitant reoxidation of UO2 in the presence of ferrihydrite was also extended to a two-dimensional field-scale groundwater flow and biogeochemically reactive transport model for the South Oyster site in eastern Virginia. This model was developed to simulate the field-scale immobilization and subsequent reoxidation of U by a biologically mediated reaction network.

  13. Modelling benthic biophysical drivers of ecosystem structure and biogeochemical response

    Science.gov (United States)

    Stephens, Nicholas; Bruggeman, Jorn; Lessin, Gennadi; Allen, Icarus

    2016-04-01

    The fate of carbon deposited at the sea floor is ultimately decided by biophysical drivers that control the efficiency of remineralisation and timescale of carbon burial in sediments. Specifically, these drivers include bioturbation through ingestion and movement, burrow-flushing and sediment reworking, which enhance vertical particulate transport and solute diffusion. Unfortunately, these processes are rarely satisfactorily resolved in models. To address this, a benthic model that explicitly describes the vertical position of biology (e.g., habitats) and biogeochemical processes is presented that includes biological functionality and biogeochemical response capturing changes in ecosystem structure, benthic-pelagic fluxes and biodiversity on inter-annual timescales. This is demonstrated by the model's ability to reproduce temporal variability in benthic infauna, vertical pore water nutrients and pelagic-benthic solute fluxes compared to in-situ data. A key advance is the replacement of bulk parameterisation of bioturbation by explicit description of the bio-physical processes responsible. This permits direct comparison with observations and determination of key parameters in experiments. Crucially, the model resolves the two-way interaction between sediment biogeochemistry and ecology, allowing exploration of the benthic response to changing environmental conditions, the importance of infaunal functional traits in shaping benthic ecological structure and the feedback the resulting bio-physical processes exert on pore water nutrient profiles. The model is actively being used to understand shelf sea carbon cycling, the response of the benthos to climatic change, food provision and other societal benefits.

  14. C-GEM (v 1.0): a new, cost-efficient biogeochemical model for estuaries and its application to a funnel-shaped system

    OpenAIRE

    Volta, C.; Arndt, S; H. H. G. Savenije; G. G. Laruelle; Regnier, P.

    2014-01-01

    Reactive transport models (RTMs) are powerful tools for disentangling the complex process interplay that drives estuarine biogeochemical dynamics, for assessing the quantitative role of estuaries in global biogeochemical cycles and for predicting their response to anthropogenic disturbances (land-use change, climate change and water management). Nevertheless, the application of RTMs for a regional or global estimation of estuarine biogeochemical transformations and fluxes is...

  15. DiaTrans – A Multi-Component Model for Density-Driven Flow, Transport and Biogeochemical Reaction Processes in the Subsurface

    OpenAIRE

    Schankat, Mirko

    2009-01-01

    Der Schwerpunkt der Arbeit liegt in der Verbesserung des Prozessverständnisses für den Interaktionsbereich Untergrund und freier Wassersäule und darauf aufbauend in einer verbesserten Quantifizierung von Stoffflüssen, welche beispielsweise für ökologische Fragestellungen in Küstengebieten erforderlich ist. Dazu wurde DiaTrans (diagenetic transport), ein mehrdimensionales, voll gekoppeltes Ein-Phasen/Mehr-Komponenten-Modell zur Simulation von dichtegetriebenen Strömungs-, Transport- und biogeo...

  16. Biogeographic validation of a global ocean biogeochemical model

    OpenAIRE

    Vichi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Allen, J. I.; PML; Hardman-Mountford, N.; PML, UK

    2008-01-01

    Currently biogeochemical models of the global ocean focus on simulating the coupling between prevalent physical conditions and the biogeochemical processes with the underlying assumption that coherent biological properties are a direct (or modulated) response to physics. This is one possible biogeographic characterisation of the pelagic environment, since biogeochemistry represents only one aspect of marine ecosystems. Several models are currently capable of simulating the chlorophyll distrib...

  17. A generic biogeochemical module for earth system models

    Directory of Open Access Journals (Sweden)

    Y. Fang

    2013-06-01

    Full Text Available Physical and biogeochemical processes regulate soil carbon dynamics and CO2 flux to and from the atmosphere, influencing global climate changes. Integration of these processes into earth system models (e.g. community land models – CLM, however, currently faces three major challenges: (1 extensive efforts are required to modify modeling structures and to rewrite computer programs to incorporate new or updated processes as new knowledge is being generated, (2 computational cost is prohibitively expensive to simulate biogeochemical processes in land models due to large variations in the rates of biogeochemical processes, and (3 various mathematical representations of biogeochemical processes exist to incorporate different aspects of fundamental mechanisms, but systematic evaluation of the different mathematical representations is difficult, if not impossible. To address these challenges, we propose a new computational framework to easily incorporate physical and biogeochemical processes into land models. The new framework consists of a new biogeochemical module with a generic algorithm and reaction database so that new and updated processes can be incorporated into land models without the need to manually set up the ordinary differential equations to be solved numerically. The reaction database consists of processes of nutrient flow through the terrestrial ecosystems in plants, litter and soil. This framework facilitates effective comparison studies of biogeochemical cycles in an ecosystem using different conceptual models under the same land modeling framework. The approach was first implemented in CLM and benchmarked against simulations from the original CLM-CN code. A case study was then provided to demonstrate the advantages of using the new approach to incorporate a phosphorus cycle into the CLM model. To our knowledge, the phosphorus-incorporated CLM is a new model that can be used to simulate phosphorus limitation on the productivity of

  18. Modeling greenhouse gas emissions (CO2, N2O, CH4) from managed arable soils with a fully coupled hydrology-biogeochemical modeling system simulating water and nutrient transport and associated carbon and nitrogen cycling at catchment scale

    Science.gov (United States)

    Klatt, Steffen; Haas, Edwin; Kraus, David; Kiese, Ralf; Butterbach-Bahl, Klaus; Kraft, Philipp; Plesca, Ina; Breuer, Lutz; Zhu, Bo; Zhou, Minghua; Zhang, Wei; Zheng, Xunhua; Wlotzka, Martin; Heuveline, Vincent

    2014-05-01

    The use of mineral nitrogen fertilizer sustains the global food production and therefore the livelihood of human kind. The rise in world population will put pressure on the global agricultural system to increase its productivity leading most likely to an intensification of mineral nitrogen fertilizer use. The fate of excess nitrogen and its distribution within landscapes is manifold. Process knowledge on the site scale has rapidly grown in recent years and models have been developed to simulate carbon and nitrogen cycling in managed ecosystems on the site scale. Despite first regional studies, the carbon and nitrogen cycling on the landscape or catchment scale is not fully understood. In this study we present a newly developed modelling approach by coupling the fully distributed hydrology model CMF (catchment modelling framework) to the process based regional ecosystem model LandscapeDNDC for the investigation of hydrological processes and carbon and nitrogen transport and cycling, with a focus on nutrient displacement and resulting greenhouse gas emissions in a small catchment at the Yanting Agro-ecological Experimental Station of Purple Soil, Sichuan province, China. The catchment hosts cypress forests on the outer regions, arable fields on the sloping croplands cultivated with wheat-maize rotations and paddy rice fields in the lowland. The catchment consists of 300 polygons vertically stratified into 10 soil layers. Ecosystem states (soil water content and nutrients) and fluxes (evapotranspiration) are exchanged between the models at high temporal scales (hourly to daily) forming a 3-dimensional model application. The water flux and nutrients transport in the soil is modelled using a 3D Richards/Darcy approach for subsurface fluxes with a kinematic wave approach for surface water runoff and the evapotranspiration is based on Penman-Monteith. Biogeochemical processes are modelled by LandscapeDNDC, including soil microclimate, plant growth and biomass allocation

  19. Stoichiometries of remineralisation and denitrification in global biogeochemical ocean models

    Directory of Open Access Journals (Sweden)

    A. Paulmier

    2009-05-01

    Full Text Available Since the seminal paper of Redfield (1934, constant stoichiometric elemental ratios linking biotic carbon and nutrient fluxes are often assumed in marine biogeochemistry, and especially in coupled biogeochemical circulation models, to couple the global oxygen, carbon and nutrient cycles. However, when looking in more detail, some deviations from the classical Redfield stoichiometry have been reported, in particular with respect to remineralization of organic matter changing with depth or with ambient oxygen levels. We here compare the assumptions about the stoichiometry of organic matter and its remineralization that are used explicitly and implicitly in common biogeochemical ocean models. We find that the implicit assumptions made about the hydrogen content of organic matter can lead to inconsistencies in the modeled remineralization and denitrification stoichiometries. It is suggested that future marine biogeochemical models explicitly state the chemical composition assumed for the organic matter, including its oxygen and hydrogen content.

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

    Science.gov (United States)

    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.

  1. Coupling a Terrestrial Biogeochemical Model to the Common Land Model

    Institute of Scientific and Technical Information of China (English)

    SHI Xiaoying; MAd Jiafu; WANG Yingping; DAI Yongjiu; TANG Xuli

    2011-01-01

    A terrestrial biogeochemical model (CASACNP) was coupled to a land surtace model (the Common Land Model,CoLM) to simulate the dynamics of carbon substrate in soil and its limitation on soil respiration.The combined model,CoLM_CASACNP,was able to predict long-term carbon sources and sinks that CoLM alone could not.The coupled model was tested using measurenents of belowground respiration and surface fluxes from two forest ecosystems.The combined model simulated reasonably well the diurnal and seasonal variations of net ecosystem carbon exchange,as well as seasonal variation in the soil respiration rate of both the forest sites chosen for this study.However,the agreement between model simulations and actual measurements was poorer under dry conditions.The model should be tested against more measurements before being applied globally to investigate the feedbacks between the carbon cycle and climate change.

  2. Biogeochemical reactive-transport modelling of the interactions of medium activity long-lived nuclear waste in fractured argillite and the effect on redox conditions

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. The role of anaerobic microbial processes in mediating gas generation and redox reactions in organic (cellulose) containing low level activity nuclear wastes (LLW) is well established through monitoring of operational near-surface LLW disposal sites and municipal waste disposal sites. Modelling approaches based on Monod kinetic growth models to represent the complex suite of anaerobic processes have been developed and these models are able to reproduce the evolving biogeochemistry and gas generation of large scale and long term (10 year) experiments on cellulose waste degradation. In the case of geological disposal of medium activity long-lived nuclear waste (MAVL) microbial processes have the potential to exploit metabolic energy sources present in the waste, engineered barriers and host geological formation and as a consequence influence redox potential. Several electron donors and electron acceptors may be present in MAVL. Electron donors include; hydrogen (resulting from radiolysis and anaerobic corrosion of metals), and hydrolysis products of organic waste materials. Sulphate, nitrate and Fe(III) containing minerals and corrosion products are examples of electron acceptors present in intermediate level wastes. Significant amounts of organic matter, sulphate and iron minerals may also be present in host geological formations and have the potential to act as microbial energy sources once the system is perturbed by electron donors/acceptors from the waste. The construction of a geological disposal facility will physically disturb the host formation, potentially causing fracturing of the excavation damage zone (EDZ). The EDZ may thus provide environmental conditions, such as space and free water that together with nutrient and energy sources to promote microbial activity. In this study the Generalised Repository Model (GRM) developed to simulate the coupled microbiological, chemical and transport processes in near

  3. What sea-ice biogeochemical modellers need from observers

    Directory of Open Access Journals (Sweden)

    Nadja Steiner

    2016-02-01

    Full Text Available Abstract Numerical models can be a powerful tool helping to understand the role biogeochemical processes play in local and global systems and how this role may be altered in a changing climate. With respect to sea-ice biogeochemical models, our knowledge is severely limited by our poor confidence in numerical model parameterisations representing those processes. Improving model parameterisations requires communication between observers and modellers to guide model development and improve the acquisition and presentation of observations. In addition to more observations, modellers need conceptual and quantitative descriptions of the processes controlling, for example: primary production and diversity of algal functional types in sea ice, ice algal growth, release from sea ice, heterotrophic remineralisation, transfer and emission of gases (e.g., DMS, CH4, BrO, incorporation of seawater components in growing sea ice (including Fe, organic and inorganic carbon, and major salts and subsequent release; CO2 dynamics (including CaCO3 precipitation, flushing and supply of nutrients to sea-ice ecosystems; and radiative transfer through sea ice. These issues can be addressed by focused observations, as well as controlled laboratory and field experiments that target specific processes. The guidelines provided here should help modellers and observers improve the integration of measurements and modelling efforts and advance toward the common goal of understanding biogeochemical processes in sea ice and their current and future impacts on environmental systems.

  4. Stoichiometries of remineralisation and denitrification in global biogeochemical ocean models

    Directory of Open Access Journals (Sweden)

    A. Paulmier

    2009-02-01

    Full Text Available Since the seminal paper of Redfield (1934, constant stoichiometric elemental ratios linking biotic carbon and nutrient fluxes are often assumed in marine biogeochemistry, and especially in coupled biogeochemical circulation models to link the global oxygen, carbon and nutrient cycles. However, when looking in more detail, some deviations from the classical Redfield stoichiometry have been reported, in particular with respect to remineralization of organic matter changing with depth or with ambient oxygen levels. We here compare the assumptions about the stoichiometry of organic matter and its remineralization that are used explicitly and implicitly in common biogeochemical ocean models. We find that the implicit assumptions made about the hydrogen content of organic matter can lead to inconsistencies in the modeled remineralization and denitrification stoichiometries. It is suggested that models explicitly state the chemical composition assumed for the organic matter, including its oxygen and hydrogen content.

  5. Modelling physical and biogeochemical state of the Mediterranean Sea under contemporary and future climate

    Science.gov (United States)

    Solidoro, Cosimo; Lazzari, Paolo; Cossarini, Gianpiero; Melaku Canu, Donata; Lovato, Tomas; Vichi, Marcello

    2014-05-01

    A validated 3D coupled transport-biogeochemical model is used to assess the impact of future climatic and management scenarios on biogeochemical and ecological properties of the Mediterranean Sea. Results are discussed in term of temporal and spatial distribution of parameters and indicators related to the carbonate system and the cycles of carbon and inorganic nutrients through dissolved and particulate phases, as simulated by a multi nutrient multi plankton numerical model under current and future conditions. Simulations span the period 2000-2040 and are performed by forcing a three-dimensional off-line coupled eco-hydrodynamical model (BFM and OPA-tracer model, http://bfm-community.eu/) with marine circulation fields produced by ad hoc implementation of the NEMO modelling system and with river input of nutrient and freshwater computed in recent European fp7 projects. The model properly describes available experimental information on contemporary seasonal dynamic and spatial distribution at the basin and sub-basin scale of major biogeochemical parameters, as well as primary production and carbon fluxes at the air-ocean interface. Model projections suggest that future Mediterranean sea will be globally warmer, more productive, and more acidic, but with significant space variability. The relative importance of different biotic and abiotic parameters in defining such a change is explored through several numerical experiments. Potential implications in terms of ecological and higher trophic level organisms dynamics are explored as well, by integrating niche properties of selected organisms and suggestions provided by food web models.

  6. Geomorphic and substrate controls on spatial variability in river solute transport and biogeochemical cycling

    Science.gov (United States)

    Blaen, Phillip; Kurz, Marie; Knapp, Julia; Mendoza-Lera, Clara; Lee-Cullin, Joe; Klaar, Megan; Drummond, Jen; Jaeger, Anna; Zarnetske, Jay; Lewandowski, Joerg; Marti, Eugenia; Ward, Adam; Fleckenstein, Jan; Datry, Thibault; Larned, Scott; Krause, Stefan

    2016-04-01

    Nutrient concentrations in surface waters and groundwaters are increasing in many agricultural catchments worldwide as a result of anthropogenic activities. Increasing geomorphological heterogeneity in river channels may help to attenuate nutrient pollution by facilitating water exchange fluxes with the hyporheic zone; a site of intense microbial activity where biogeochemical transformation rates (e.g. denitrification) can be high. However, the controls on spatial variability in biogeochemical cycling, particularly at scales relevant for river managers, are not well understood. Here, we aimed to assess: 1) how differences in geomorphological heterogeneity control river solute transport and rates of biogeochemical cycling at sub-reach scales (102 m); and 2) the relative magnitude of these differences versus those relating to reach scale substrate variability (103 m). We used the reactive 'smart' tracer resazurin (Raz), a weakly fluorescent dye that transforms to highly fluorescent resorufin (Rru) under mildly reducing conditions, as a proxy to assess rates of biogeochemical cycling in a lowland river in southern England. Solute tracer tests were conducted in two reaches with contrasting substrates: one sand-dominated and the other gravel-dominated. Each reach was divided into sub-reaches that varied in geomorphic complexity (e.g. by the presence of pool-riffle sequences or the abundance of large woody debris). Slug injections of Raz and the conservative tracer fluorescein were conducted in each reach during baseflow conditions (Q ≈ 80 L/s) and breakthrough curves monitored using in-situ fluorometers. Preliminary results indicate overall Raz:Rru transformation rates in the gravel-dominated reach were more than 50% higher than those in the sand-dominated reach. However, high sub-reach variability in Raz:Rru transformation rates and conservative solute transport parameters suggests small-scale targeted management interventions to alter geomorphic heterogeneity may be

  7. Traceable components of terrestrial carbon storage capacity in biogeochemical models.

    Science.gov (United States)

    Xia, Jianyang; Luo, Yiqi; Wang, Ying-Ping; Hararuk, Oleksandra

    2013-07-01

    Biogeochemical models have been developed to account for more and more processes, making their complex structures difficult to be understood and evaluated. Here, we introduce a framework to decompose a complex land model into traceable components based on mutually independent properties of modeled biogeochemical processes. The framework traces modeled ecosystem carbon storage capacity (Xss ) to (i) a product of net primary productivity (NPP) and ecosystem residence time (τE ). The latter τE can be further traced to (ii) baseline carbon residence times (τ'E ), which are usually preset in a model according to vegetation characteristics and soil types, (iii) environmental scalars (ξ), including temperature and water scalars, and (iv) environmental forcings. We applied the framework to the Australian Community Atmosphere Biosphere Land Exchange (CABLE) model to help understand differences in modeled carbon processes among biomes and as influenced by nitrogen processes. With the climate forcings of 1990, modeled evergreen broadleaf forest had the highest NPP among the nine biomes and moderate residence times, leading to a relatively high carbon storage capacity (31.5 kg cm(-2) ). Deciduous needle leaf forest had the longest residence time (163.3 years) and low NPP, leading to moderate carbon storage (18.3 kg cm(-2) ). The longest τE in deciduous needle leaf forest was ascribed to its longest τ'E (43.6 years) and small ξ (0.14 on litter/soil carbon decay rates). Incorporation of nitrogen processes into the CABLE model decreased Xss in all biomes via reduced NPP (e.g., -12.1% in shrub land) or decreased τE or both. The decreases in τE resulted from nitrogen-induced changes in τ'E (e.g., -26.7% in C3 grassland) through carbon allocation among plant pools and transfers from plant to litter and soil pools. Our framework can be used to facilitate data model comparisons and model intercomparisons via tracking a few traceable components for all terrestrial carbon

  8. Modelling Estuarine Biogeochemical Dynamics: From the Local to the Global Scale

    OpenAIRE

    Regnier, Pierre; Arndt, Sandra; Goossens, Nicolas; Volta, Chiara; Laruelle, Goulven G.; Lauerwald, Ronny; Hartmann, Jens

    2013-01-01

    Estuaries act as strong carbon and nutrient filters and are relevant contributors to the atmospheric CO2 budget. They thus play an important, yet poorly constrained, role for global biogeochemical cycles and climate. This manuscript reviews recent developments in the modelling of estuarine biogeochemical dynamics. The first part provides an overview of the dominant physical and biogeochemical processes that control the transformations and fluxes of carbon and nutrients along the estuarine gra...

  9. Biogeochemical modelling of the Mont Terri in situ bitumen-nitrate-clay interaction experiment

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. The Bitumen-Nitrate-Clay Interaction experiment (BN) currently being performed at the Mont Terri Rock Laboratory (Switzerland) provides an in situ examination of redox reactions expected between nitrate containing wastes and mineral and organic electron donors present in clay host rocks and as degradation products of organic wastes. The BN experiment has been designed to examine the fate of nitrate that is present in the form of soluble salts within a bitumen matrix; they are part of intermediate-level long-lived radioactive waste (ILW) manufactured in France and Belgium and planned for disposal in deep geological clay formations. The nitrate component of this bituminized waste form, as well as that present in other ILW, has the potential to affect the chemical conditions and the speciation and transport behaviour of redox sensitive radionuclides (e.g. Se, Tc, U, Np, Pu) in the near field and in host rocks with initially reducing conditions. A sequence of tests undertaken in the BN experiment will examine the reactions of nitrate with the Opalinus Clay together with acetate as a reference bitumen degradation product. The BN experiment includes comprehensive chemical and microbial characterisation of samples recovered during the nitrate injection tests that record the phases of microbial denitrification and other biogeochemical processes. As such the BN experiment provides an insight into the potential biogeochemical processes that may occur in the excavation and chemically disturbed zones (EDZ/CDZ) of a deep geological repository. In this paper the results of the BN experiment are modelled using the Generalised Repository Model (GRM) originally developed in the UK to examine biogeochemical processes occurring in cellulose containing low-level waste disposed in a near surface facility. The GRM simulation of the BN experiment provides further interpretation of the BN data. In addition, the study is aimed at building

  10. Biogeochemical modeling of tundra recovery following thermal erosion of permafrost

    Science.gov (United States)

    Pearce, A. R.; Rastetter, E. B.; Bowden, W. B.

    2011-12-01

    We simulate the biogeochemical recovery of tundra from a thermal erosion disturbance using the Multiple Element Limitation model (MEL) and compare model results with soil organic matter and nutrient chemistry measurements collected across a chronosequence of thermal erosion features. Thermal erosion of permafrost initially depletes the tundra of much of its vegetation and shallow soil organic matter. However, several decades later, there is often little distinguishing these scars from the surrounding undisturbed tundra. As thermal erosion features become more abundant on the arctic landscape, we desire to understand how the pools of carbon and nutrients rebuild after these disturbances. MEL is a plot-scale, process-based model that optimizes the acquisition of eight resources (light, water, CO2, PO4, NH4, NO3, DON and N-fixation) by vegetation based on how much of each is required and the effort needed to acquire it. Model output includes pool sizes of carbon, nitrogen and phosphorus in vegetation, litter, young soil organic matter and old soil organic matter and the fluxes among these pools over time. This calibration of MEL, operating on a daily timestep, was created with published data collected at or near the Toolik Field Station (Toolik Lake, AK, USA) from moist acidic tussock tundra sites. We corroborate our calibration with data from plot manipulations (N and P fertilization, greenhouse, and shade house) performed as part of the NSF Arctic LTER project. The initial conditions for the recovery simulations reflect post-failure observations of some of the variation in soil organic matter, and soil and water nutrient chemistry. With sufficient nutrients from residual soil or supplied in soil water from upslope, the model indicates that vegetation can recover within several decades, but recovery of C and nutrients lost from soils may take hundreds of years.

  11. Vadose zone attenuation of organic compounds at a crude oil spill site - Interactions between biogeochemical reactions and multicomponent gas transport

    Science.gov (United States)

    Molins, S.; Mayer, K.U.; Amos, R.T.; Bekins, B.A.

    2010-01-01

    Contaminant attenuation processes in the vadose zone of a crude oil spill site near Bemidji, MN have been simulated with a reactive transport model that includes multicomponent gas transport, solute transport, and the most relevant biogeochemical reactions. Dissolution and volatilization of oil components, their aerobic and anaerobic degradation coupled with sequential electron acceptor consumption, ingress of atmospheric O2, and the release of CH4 and CO2 from the smear zone generated by the floating oil were considered. The focus of the simulations was to assess the dynamics between biodegradation and gas transport processes in the vadose zone, to evaluate the rates and contributions of different electron accepting processes towards vadose zone natural attenuation, and to provide an estimate of the historical mass loss. Concentration distributions of reactive (O2, CH4, and CO2) and non-reactive (Ar and N2) gases served as key constraints for the model calibration. Simulation results confirm that as of 2007, the main degradation pathway can be attributed to methanogenic degradation of organic compounds in the smear zone and the vadose zone resulting in a contaminant plume dominated by high CH4 concentrations. In accordance with field observations, zones of volatilization and CH4 generation are correlated to slightly elevated total gas pressures and low partial pressures of N2 and Ar, while zones of aerobic CH4 oxidation are characterized by slightly reduced gas pressures and elevated concentrations of N2 and Ar. Diffusion is the most significant transport mechanism for gases in the vadose zone; however, the simulations also indicate that, despite very small pressure gradients, advection contributes up to 15% towards the net flux of CH4, and to a more limited extent to O2 ingress. Model calibration strongly suggests that transfer of biogenically generated gases from the smear zone provides a major control on vadose zone gas distributions and vadose zone carbon

  12. Nitrous Oxide Emissions from Biofuel Crops and Parameterization in the EPIC Biogeochemical Model

    Science.gov (United States)

    This presentation describes year 1 field measurements of N2O fluxes and crop yields which are used to parameterize the EPIC biogeochemical model for the corresponding field site. Initial model simulations are also presented.

  13. Parameter estimation and uncertainty quantification in a biogeochemical model using optimal experimental design methods

    Science.gov (United States)

    Reimer, Joscha; Piwonski, Jaroslaw; Slawig, Thomas

    2016-04-01

    , location and tracer. The high computational effort of a model evaluation was encountered by using the transport matrix method with spatial parallelization, advanced derivative-based optimization algorithms and a cost saving approximation of the derivative. Globalization techniques were used to overcome local minima. Due to a special software interface, coupling of arbitrary water-column biogeochemical models is possible. In the talk, we present the used methods together with results for this exemplary model.

  14. Biogeochemical consequences of vertical and lateral transport of particulate organic matter in the southern North Sea: A multiproxy approach

    NARCIS (Netherlands)

    Le Guitton, M.; Soetaert, K.; Sinninghe Damsté, J.S.; Middelburg, J.J.

    2015-01-01

    Vertical and lateral transports are of importance in continental shelf systems such as the North Sea andplay a major role in the processing of organic matter. We investigated the biogeochemical consequencesof these transports on particulate organic matter at the molecular level in the southern North

  15. New HYDRUS Modules for Simulating Preferential Flow, Colloid-Facilitated Contaminant Transport, and Various Biogeochemical Processes in Soils

    Science.gov (United States)

    Simunek, J.; Sejna, M.; Jacques, D.; Langergraber, G.; Bradford, S. A.; van Genuchten, M. Th.

    2012-04-01

    We have dramatically expanded the capabilities of the HYDRUS (2D/3D) software package by developing new modules to account for processes not available in the standard HYDRUS version. These new modules include the DualPerm, C-Hitch, HP2/3, Wetland, and Unsatchem modules. The dual-permeability modeling approach of Gerke and van Genuchten [1993] simulating preferential flow and transport is implemented into the DualPerm module. Colloid transport and colloid-facilitated solute transport, the latter often observed for many contaminants, such as heavy metals, radionuclides, pharmaceuticals, pesticides, and explosives [Šimůnek et al., 2006] are implemented into the C-Hitch module. HP2 and HP3 are the two and three-dimensional alternatives of the HP1 module, currently available with HYDRUS-1D [Jacques and Šimůnek, 2005], that couple HYDRUS flow and transport routines with the generic geochemical model PHREEQC of Parkhurst and Appelo [1999]. The Wetland module includes two alternative approaches (CW2D of Langergraber and Šimůnek [2005] and CWM1 of Langergraber et al. [2009]) for modeling aerobic, anaerobic, and anoxic biogeochemical processes in natural and constructed wetlands. Finally, the Unsatchem module simulates the transport and reactions of major ions in a soil profile. Brief descriptions and an application of each module will be presented. Except for HP3, all modules simulate flow and transport processes in two-dimensional transport domains. All modules are fully supported by the HYDRUS graphical user interface. Further development of these modules, as well as of several other new modules (such as Overland), is still envisioned. Continued feedback from the research community is encouraged.

  16. Inconsistent Strategies to Spin up Models in CMIP5: Implications for Ocean Biogeochemical Model Performance Assessment

    Science.gov (United States)

    Seferian, Roland; Gehlen, Marion; Bopp, Laurent; Resplandy, Laure; Orr, James C.; Marti, Olivier; Dunne, John P.; Christian, James R.; Doney, Scott C.; Ilyina, Tatiana; Romanou, Anastasia

    2015-01-01

    During the fifth phase of the Coupled Model Intercomparison Project (CMIP5) substantial efforts were made to systematically assess the skill of Earth system models. One goal was to check how realistically representative marine biogeochemical tracer distributions could be reproduced by models. In routine assessments model historical hindcasts were compared with available modern biogeochemical observations. However, these assessments considered neither how close modeled biogeochemical reservoirs were to equilibrium nor the sensitivity of model performance to initial conditions or to the spin-up protocols. Here, we explore how the large diversity in spin-up protocols used for marine biogeochemistry in CMIP5 Earth system models (ESMs) contributes to model-to-model differences in the simulated fields. We take advantage of a 500-year spin-up simulation of IPSL-CM5A-LR to quantify the influence of the spin-up protocol on model ability to reproduce relevant data fields. Amplification of biases in selected biogeochemical fields (O2, NO3, Alk-DIC) is assessed as a function of spin-up duration. We demonstrate that a relationship between spin-up duration and assessment metrics emerges from our model results and holds when confronted with a larger ensemble of CMIP5 models. This shows that drift has implications for performance assessment in addition to possibly aliasing estimates of climate change impact. Our study suggests that differences in spin-up protocols could explain a substantial part of model disparities, constituting a source of model-to- model uncertainty. This requires more attention in future model intercomparison exercises in order to provide quantitatively more correct ESM results on marine biogeochemistry and carbon cycle feedbacks.

  17. Inconsistent strategies to spin up models in CMIP5: implications for ocean biogeochemical model performance assessment

    Science.gov (United States)

    Séférian, Roland; Gehlen, Marion; Bopp, Laurent; Resplandy, Laure; Orr, James C.; Marti, Olivier; Dunne, John P.; Christian, James R.; Doney, Scott C.; Ilyina, Tatiana; Lindsay, Keith; Halloran, Paul R.; Heinze, Christoph; Segschneider, Joachim; Tjiputra, Jerry; Aumont, Olivier; Romanou, Anastasia

    2016-05-01

    During the fifth phase of the Coupled Model Intercomparison Project (CMIP5) substantial efforts were made to systematically assess the skill of Earth system models. One goal was to check how realistically representative marine biogeochemical tracer distributions could be reproduced by models. In routine assessments model historical hindcasts were compared with available modern biogeochemical observations. However, these assessments considered neither how close modeled biogeochemical reservoirs were to equilibrium nor the sensitivity of model performance to initial conditions or to the spin-up protocols. Here, we explore how the large diversity in spin-up protocols used for marine biogeochemistry in CMIP5 Earth system models (ESMs) contributes to model-to-model differences in the simulated fields. We take advantage of a 500-year spin-up simulation of IPSL-CM5A-LR to quantify the influence of the spin-up protocol on model ability to reproduce relevant data fields. Amplification of biases in selected biogeochemical fields (O2, NO3, Alk-DIC) is assessed as a function of spin-up duration. We demonstrate that a relationship between spin-up duration and assessment metrics emerges from our model results and holds when confronted with a larger ensemble of CMIP5 models. This shows that drift has implications for performance assessment in addition to possibly aliasing estimates of climate change impact. Our study suggests that differences in spin-up protocols could explain a substantial part of model disparities, constituting a source of model-to-model uncertainty. This requires more attention in future model intercomparison exercises in order to provide quantitatively more correct ESM results on marine biogeochemistry and carbon cycle feedbacks.

  18. Biogeochemical Impact of Long-Range Transported Dust over Northern South China Sea

    Science.gov (United States)

    Tsay, Si-Chee; Wang, S. H.; Hsu, N. C.

    2011-01-01

    Transpacific transport and impact of Asian dust aerosols have been well documented (e.g., results from ACE-Asia and regional follow-on campaigns), but little is known about dust invasion to the South China Sea (SCS). On 19-21 March 2010, a fierce Asian dust storm affected large areas from the Gobi deserts to the West Pacific, including Taiwan and Hong Kong. As a pilot study of the 7-SEAS (Seven South East Asian Studies) in the northern SCS, detailed characteristics of long-range transported dust aerosols were first observed by a comprehensive set of ground-based instruments deployed at the Dongsha islands (20deg42'52" N, 116deg43'51" E). Aerosol measurements such as particle mass concentrations, size distribution, optical properties, hygroscopicity, and vertical profiles help illustrate the evolution of this dust outbreak. Our results indicate that these dust particles were mixed with anthropogenic and marine aerosols, and transported near the surface. Satellite assessment of biogeochemical impact of dust deposition into open oceans is hindered by our current inability in retrieving areal dust properties and ocean colors over an extensive period of time, particularly under the influence of cloudy conditions. In this paper, we analyze the changes of retrieved Chlorophyll-a (Chl-a) concentration over the northern SCS, considered as oligotophic waters in the spring, from long-term SeaWiFS measurements since 1997. Over the past decade, six long-range transported dust events are identified based on spatiotemporal evolutions of PM10 measurements from regional monitoring stations, with the aid of trajectory analysis. Multi-year composites of Chl-a imagery for dust event and non-dust background during March-April are applied to overcome insufficient retrievals of Chl-a due to cloudy environment. Due to anthropogenic modification within a shallow boundary layer off the densely populated and industrial southeast coast of China, the iron ion activation of deliquescent dust

  19. Past and present of sediment and carbon biogeochemical cycling models

    Directory of Open Access Journals (Sweden)

    F. T. Mackenzie

    2004-01-01

    Full Text Available The global carbon cycle is part of the much more extensive sedimentary cycle that involves large masses of carbon in the Earth's inner and outer spheres. Studies of the carbon cycle generally followed a progression in knowledge of the natural biological, then chemical, and finally geological processes involved, culminating in a more or less integrated picture of the biogeochemical carbon cycle by the 1920s. However, knowledge of the ocean's carbon cycle behavior has only within the last few decades progressed to a stage where meaningful discussion of carbon processes on an annual to millennial time scale can take place. In geologically older and pre-industrial time, the ocean was generally a net source of CO2 emissions to the atmosphere owing to the mineralization of land-derived organic matter in addition to that produced in situ and to the process of CaCO3 precipitation. Due to rising atmospheric CO2 concentrations because of fossil fuel combustion and land use changes, the direction of the air-sea CO2 flux has reversed, leading to the ocean as a whole being a net sink of anthropogenic CO2. The present thickness of the surface ocean layer, where part of the anthropogenic CO2 emissions are stored, is estimated as of the order of a few hundred meters. The oceanic coastal zone net air-sea CO2 exchange flux has also probably changed during industrial time. Model projections indicate that in pre-industrial times, the coastal zone may have been net heterotrophic, releasing CO2 to the atmosphere from the imbalance between gross photosynthesis and total respiration. This, coupled with extensive CaCO3 precipitation in coastal zone environments, led to a net flux of CO2 out of the system. During industrial time the coastal zone ocean has tended to reverse its trophic status toward a non-steady state situation of net autotrophy, resulting in net uptake of anthropogenic CO2 and storage of carbon in the coastal ocean, despite the significant calcification

  20. Transport modeling

    Institute of Scientific and Technical Information of China (English)

    R.E. Waltz

    2007-01-01

    @@ There has been remarkable progress during the past decade in understanding and modeling turbulent transport in tokamaks. With some exceptions the progress is derived from the huge increases in computational power and the ability to simulate tokamak turbulence with ever more fundamental and physically realistic dynamical equations, e.g.

  1. Simulation of land-atmosphere gaseous exchange using a coupled land surface-biogeochemical model

    Science.gov (United States)

    Gu, C.; Riley, W. J.; Perez, T. J.; Pan, L.

    2009-12-01

    It is important to develop and evaluate biogeochemical models that on the one hand represent vegetation and soil dynamics and on the other hand provide energy and water fluxes in a temporal resolution suitable for biogeochemical processes. In this study, we present a consistent coupling between a common land surface model (CLM3.0) and a recently developed biogeochemical model (TOUGHREACT-N). The model TOUGHREACT-N (TR-N) is one of the few process-based models that simulate green house gases fluxes by using an implicit scheme to solve the diffusion equations governing soil heat and water fluxes. By coupling with CLM3.0, we have significantly improved TR-N by including realistic representations of surface water, energy, and momentum exchanges, through the use of improved formulations for soil evaporation, plant transpiration, vegetation growth, and plant nitrogen uptake embedded in CLM3.0. The coupled CLMTR-N model is a first step for a full coupling of land surface and biogeochemical processes. The model is evaluated with measurements of soil temperature, soil water content, and N2O and N2 gaseous emission data from fallow, corn, and forest sites in Venezuela. The results demonstrate that the CLMTR-N model simulates realistic diurnal variation of soil temperature, soil water content, and N gaseous fluxes. For example, mean differences between predicted and observed midday near-surface soil water content were 8, 11, and 4 % in July, August, and September. The sensitivity of the biogeochemical processes and resulting N emissions to variation in environmental drivers is high, which indicates the need to calculate biogeochemical processes in, at least, two hourly time steps using dynamically updated (rather than daily averaged) soil environmental conditions. The development in CLMTR-N of such a complex representation of processes will allow us to characterize relevant processes and simplifications appropriate for regional to global-scale coupled biogeochemical and

  2. Three-dimensional approach using two coupled models for description of hydrological and biogeochemical processes at the catchment scale

    Science.gov (United States)

    Plesca, Ina; Kraft, Philipp; Haas, Edwin; Klatt, Steffen; Butterbach-Bahl, Klaus; Frede, Hans-Georg; Breuer, Lutz

    2014-05-01

    Hydrological and biogeochemical transport through changing landscapes has been well described during the past years in literature. However, the uncertainties of combined water quality and water quantity models are still challenging, both due to a lack in process understanding as well to spatiotemporal heterogeneity of environmental conditions driving the processes. In order to reduce the uncertainty in water quality and runoff predictions at the catchment scale, a variety of different model approaches from empirical-conceptual to fully physical and process based models have been developed. In this study we present a new modelling approach for the investigation of hydrological processes and nutrient cycles, with a focus on nitrogen in a small catchment from Hessen, Germany. A hydrological model based on the model toolbox Catchment Modelling Framework (CMF) has been coupled with the process based biogeochemical model LandscapeDNDC. States, fluxes and parameters are exchanged between the models at high temporal and spatial resolution using the Python scripting language in order to obtain a 3-dimensional model application. The transport of water and nutrients through the catchment is modelled using a 3D Richards/Darcy approach for subsurface fluxes, a kinematic wave approach for surface runoff and a Penman-Monteith based calculation of evapotranspiration. Biogeochemical processes are modelled by Landscape-DNDC, including plant growth and biomass allocation, organic matter mineralisation, nitrification, denitrification and associated nitrous oxide emissions. The interactions and module connectivity between the two coupled models, as well as the model application on a 3.7 km² catchment with the runoff results and nitrogen quantification will be presented in this study.

  3. Towards coupled physical-biogeochemical models of the ocean carbon cycle

    Science.gov (United States)

    Rintoul, Stephen R.

    1992-01-01

    The purpose of this review is to discuss the critical gaps in our knowledge of ocean dynamics and biogeochemical cycles. It is assumed that the ultimate goal is the design of a model of the earth system that can predict the response to changes in the external forces driving climate.

  4. Modeling anticipated climate change impact on biogeochemical cycles of an acidified headwater catchment

    Czech Academy of Sciences Publication Activity Database

    Benčoková, A.; Hruška, Jakub; Krám, P.

    2011-01-01

    Roč. 26, S (2011), S6-S8. ISSN 0883-2927 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0073 Institutional research plan: CEZ:AV0Z60870520 Keywords : modeling anticipated * climate change * biogeochemical cycles * acidified headwater catchment Subject RIV: DD - Geochemistry Impact factor: 2.176, year: 2011

  5. A Unified Multi-scale Model for Cross-Scale Evaluation and Integration of Hydrological and Biogeochemical Processes

    Science.gov (United States)

    Liu, C.; Yang, X.; Bailey, V. L.; Bond-Lamberty, B. P.; Hinkle, C.

    2013-12-01

    Mathematical representations of hydrological and biogeochemical processes in soil, plant, aquatic, and atmospheric systems vary with scale. Process-rich models are typically used to describe hydrological and biogeochemical processes at the pore and small scales, while empirical, correlation approaches are often used at the watershed and regional scales. A major challenge for multi-scale modeling is that water flow, biogeochemical processes, and reactive transport are described using different physical laws and/or expressions at the different scales. For example, the flow is governed by the Navier-Stokes equations at the pore-scale in soils, by the Darcy law in soil columns and aquifer, and by the Navier-Stokes equations again in open water bodies (ponds, lake, river) and atmosphere surface layer. This research explores whether the physical laws at the different scales and in different physical domains can be unified to form a unified multi-scale model (UMSM) to systematically investigate the cross-scale, cross-domain behavior of fundamental processes at different scales. This presentation will discuss our research on the concept, mathematical equations, and numerical execution of the UMSM. Three-dimensional, multi-scale hydrological processes at the Disney Wilderness Preservation (DWP) site, Florida will be used as an example for demonstrating the application of the UMSM. In this research, the UMSM was used to simulate hydrological processes in rooting zones at the pore and small scales including water migration in soils under saturated and unsaturated conditions, root-induced hydrological redistribution, and role of rooting zone biogeochemical properties (e.g., root exudates and microbial mucilage) on water storage and wetting/draining. The small scale simulation results were used to estimate effective water retention properties in soil columns that were superimposed on the bulk soil water retention properties at the DWP site. The UMSM parameterized from smaller

  6. Dynamic modeling of nitrogen losses in river networks unravels the coupled effects of hydrological and biogeochemical processes

    Science.gov (United States)

    Alexander, R.B.; Böhlke, J.K.; Boyer, E.W.; David, M.B.; Harvey, J.W.; Mulholland, P.J.; Seitzinger, S.P.; Tobias, C.R.; Tonitto, C.; Wollheim, W.M.

    2009-01-01

    The importance of lotic systems as sinks for nitrogen inputs is well recognized. A fraction of nitrogen in streamflow is removed to the atmosphere via denitrification with the remainder exported in streamflow as nitrogen loads. At the watershed scale, there is a keen interest in understanding the factors that control the fate of nitrogen throughout the stream channel network, with particular attention to the processes that deliver large nitrogen loads to sensitive coastal ecosystems. We use a dynamic stream transport model to assess biogeochemical (nitrate loadings, concentration, temperature) and hydrological (discharge, depth, velocity) effects on reach-scale denitrification and nitrate removal in the river networks of two watersheds having widely differing levels of nitrate enrichment but nearly identical discharges. Stream denitrification is estimated by regression as a nonlinear function of nitrate concentration, streamflow, and temperature, using more than 300 published measurements from a variety of US streams. These relations are used in the stream transport model to characterize nitrate dynamics related to denitrification at a monthly time scale in the stream reaches of the two watersheds. Results indicate that the nitrate removal efficiency of streams, as measured by the percentage of the stream nitrate flux removed via denitrification per unit length of channel, is appreciably reduced during months with high discharge and nitrate flux and increases during months of low-discharge and flux. Biogeochemical factors, including land use, nitrate inputs, and stream concentrations, are a major control on reach-scale denitrification, evidenced by the disproportionately lower nitrate removal efficiency in streams of the highly nitrate-enriched watershed as compared with that in similarly sized streams in the less nitrate-enriched watershed. Sensitivity analyses reveal that these important biogeochemical factors and physical hydrological factors contribute nearly

  7. DRINK: a biogeochemical source term model for low level radioactive waste disposal sites.

    Science.gov (United States)

    Humphreys, P; McGarry, R; Hoffmann, A; Binks, P

    1997-07-01

    Interactions between element chemistry and the ambient geochemistry play a significant role in the control of radionuclide migration in the geosphere. These same interactions influence radionuclide release from near surface, low level radioactive waste, disposal sites once physical containment has degraded. In situations where LLW contains significant amounts of metal and organic materials such as cellulose, microbial degradation in conjunction with corrosion can significantly perturb the ambient geochemistry. These processes typically produce a transition from oxidising to reducing conditions and can influence radionuclide migration through changes in both the dominant radionuclide species and mineral phases. The DRINK (DRIgg Near field Kinetic) code is a biogeochemical transport code designed to simulate the long term evolution of the UK low level radioactive waste disposal site at Drigg. Drigg is the UK's principal solid low level radioactive waste disposal site and has been receiving waste since 1959. The interaction between microbial activity, the ambient geochemistry and radionuclide chemistry is central to the DRINK approach with the development of the ambient pH, redox potential and bulk geochemistry being directly influenced by microbial activity. This paper describes the microbial aspects of the code, site data underpinning the microbial model, the microbiology/chemistry interface and provides an example of the code in action. PMID:9340003

  8. Hydrological and biogeochemical controls on watershed dissolved organic matter transport: pulse-shunt concept.

    Science.gov (United States)

    Raymond, Peter A; Saiers, James E; Sobczak, William V

    2016-01-01

    Hydrological precipitation and snowmelt events trigger large "pulse" releases of terrestrial dissolved organic matter (DOM) into drainage networks due to an increase in DOM concentration with discharge. Thus, low-frequency large events, which are predicted to increase with climate change, are responsible for a significant percentage of annual terrestrial DOM input to drainage networks. These same events are accompanied by marked and rapid increases in headwater stream velocity; thus they also "shunt" a large proportion of the pulsed DOM to downstream, higher-order rivers and aquatic ecosystems geographically removed from the DOM source of origin. Here we merge these ideas into the "pulse-shunt concept" (PSC) to explain and quantify how infrequent, yet major hydrologic events may drive the timing, flux, geographical dispersion, and regional metabolism of terrestrial DOM. The PSC also helps reconcile long-standing discrepancies in C cycling theory and provides a robust framework for better quantifying its highly dynamic role in the global C cycle. The PSC adds a critical temporal dimension to linear organic matter removal dynamics postulated by the river continuum concept. It also can be represented mathematically through a model that is based on stream scaling approaches suitable for quantifying the important role of streams and rivers in the global C cycle. Initial hypotheses generated by the PSC include: (1) Infrequent large storms and snowmelt events account for a large and underappreciated percentage of the terrestrial DOM flux to drainage networks at annual and decadal time scales and therefore event statistics are equally important to total discharge when determining terrestrial fluxes. (2) Episodic hydrologic events result in DOM bypassing headwater streams and being metabolized in large rivers and exported to coastal systems. We propose that the PSC provides a framework for watershed biogeochemical modeling and predictions and discuss implications to

  9. High resolution modelling of the biogeochemical processes in the eutrophic Loire River (France)

    Science.gov (United States)

    Minaudo, Camille; Moatar, Florentina; Curie, Florence; Gassama, Nathalie; Billen, Gilles

    2016-04-01

    A biogeochemical model was developed, coupling a physically based water temperature model (T-NET) with a semi-mechanistic biogeochemical model (RIVE, used in ProSe and Riverstrahler models) in order to assess at a fine temporal and spatial resolution the biogeochemical processes in the eutrophic Middle Loire hydrosystem (≈10 000 km², 3361 river segments). The code itself allows parallelized computing, which decreased greatly the calculation time (5 hours for simulating 3 years hourly). We conducted a daily survey during the period 2012-2014 at 2 sampling stations located in the Middle Loire of nutrients, chlorophyll pigments, phytoplankton and physic-chemical variables. This database was used as both input data (upstream Loire boundary) and validation data of the model (basin outlet). Diffuse and non-point sources were assessed based on a land cover analysis and WWTP datasets. The results appeared very sensible to the coefficients governing the dynamic of suspended solids and of phosphorus (sorption/desorption processes) within the model and some parameters needed to be estimated numerically. Both the Lagrangian point of view and fluxes budgets at the seasonal and event-based scale evidenced the biogeochemical functioning of the Loire River. Low discharge levels set up favorable physical conditions for phytoplankton growth (long water travel time, limited water depth, suspended particles sedimentation). Conversely, higher discharge levels highly limited the phytoplankton biomass (dilution of the colony, washing-out, limited travel time, remobilization of suspended sediments increasing turbidity), and most biogeochemical species were basically transferred downstream. When hydrological conditions remained favorable for phytoplankton development, P-availability was the critical factor. However, the model evidenced that most of the P in summer was recycled within the water body: on one hand it was assimilated by the algae biomass, and on the other hand it was

  10. Modeling Nitrogen Leaching With A Biogeochemical Model Coupled With Soil Hydrology Model

    Science.gov (United States)

    Barman, R.; Yang, X.; Jain, A.; Post, W. M.; Sivapalan, M.

    2008-12-01

    Land use changes for cropland, excessive application of fertilizers in agriculture, and increase in anthropogenic activities such as fossil fuel burning have lead to widespread increases in anthropogenic production of reactive N and NH3 emissions, and N deposition rates. An important consequence of these processes is intensification of soil nutrient leaching activities, leading to serious ground water contamination problems. The current study focuses on the issue of nitrogen (nitrate and ammonium) leaching due to land cover changes for cropland, excess N fertilizer application, and atmospheric nitrogen deposition on nitrogen leaching at a global scale. Simulations of nitrogen leaching require integration of processes involving soil hydrology and biogeochemical cycles. An existing terrestrial coupled carbon-nitrogen cycle model, Integrated Science Assessment Model (ISAM), was used to estimate nitrogen leaching. The N-cycle in ISAM includes the major processes associated with nitrogen (immobilization, mineralization, nitrification, denitrification, leaching, nitrogen fixation, and vegetation nitrogen uptake). ISAM also considers how carbon and nitrogen dynamics are influenced by the effects of human perturbations to the N cycle including atmospheric deposition and fertilizer application, and the fate of N in land use activities, i.e., deforestation and agricultural harvest. In this study, the ISAM soil hydrology was extended and improved with CLM 3.5 hydrology processes and algorithms, which extended the modeling capabilities to consider the prediction of nitrogen leaching. The model performance was evaluated with flow and nutrient data at several locations within the Upper Sangamon River Basin in Illinois, and flow data in contrasting watersheds in Oklahoma. This talk will focus on describing the results of a series of modeling experiments examining the influence of land management changes for cropland and nitrogen deposition on nitrogen leaching at a global scale

  11. Modelling biogeochemical cycles in forest ecosystems: a Bayesian approach

    OpenAIRE

    Bagnara, Maurizio

    2015-01-01

    Forest models are tools for explaining and predicting the dynamics of forest ecosystems. They simulate forest behavior by integrating information on the underlying processes in trees, soil and atmosphere. Bayesian calibration is the application of probability theory to parameter estimation. It is a method, applicable to all models, that quantifies output uncertainty and identifies key parameters and variables. This study aims at testing the Bayesian procedure for calibration to different t...

  12. Use of a coastal biogeochemical model to select environmental monitoring sites

    Science.gov (United States)

    Wild-Allen, Karen; Thompson, Peter A.; Volkman, John K.; Parslow, John

    2011-10-01

    A method for the spatial selection of sites for a coastal environmental monitoring system is described. The study was completed in southeastern Tasmania, Australia, but the method can be applied in all regions with validated biogeochemical models. A 3-dimensional coupled hydrodynamic, sediment and biogeochemical model with high spatial and temporal resolution was validated against observations collected throughout 2002 and found to capture the essential features of the biogeochemical dynamics of the system. The model was used to predict the possible quantitative environmental impact of a projected increase in fish farming activity in the region. Integrated impacts of fish farm waste on labile nitrogen, phosphorus, chlorophyll and dissolved oxygen concentrations in the water column were spatially ranked to identify the most likely places to detect environmental change due to fish farming activities. Priority sites were found to be grouped in the Huon Estuary and northern part of the D'Entrecasteaux Channel consistent with the residual northward current in the region. The final monitoring program synthesized model and field understanding to ensure adequate spatial and temporal sampling of the region.

  13. Integrating remotely sensed land cover observations and a biogeochemical model for estimating forest ecosystem carbon dynamics

    Science.gov (United States)

    Liu, J.; Liu, S.; Loveland, T.R.; Tieszen, L.L.

    2008-01-01

    Land cover change is one of the key driving forces for ecosystem carbon (C) dynamics. We present an approach for using sequential remotely sensed land cover observations and a biogeochemical model to estimate contemporary and future ecosystem carbon trends. We applied the General Ensemble Biogeochemical Modelling System (GEMS) for the Laurentian Plains and Hills ecoregion in the northeastern United States for the period of 1975-2025. The land cover changes, especially forest stand-replacing events, were detected on 30 randomly located 10-km by 10-km sample blocks, and were assimilated by GEMS for biogeochemical simulations. In GEMS, each unique combination of major controlling variables (including land cover change history) forms a geo-referenced simulation unit. For a forest simulation unit, a Monte Carlo process is used to determine forest type, forest age, forest biomass, and soil C, based on the Forest Inventory and Analysis (FIA) data and the U.S. General Soil Map (STATSGO) data. Ensemble simulations are performed for each simulation unit to incorporate input data uncertainty. Results show that on average forests of the Laurentian Plains and Hills ecoregion have been sequestrating 4.2 Tg C (1 teragram = 1012 gram) per year, including 1.9 Tg C removed from the ecosystem as the consequences of land cover change. ?? 2008 Elsevier B.V.

  14. Assessing the utility of frequency dependent nudging for reducing biases in biogeochemical models

    Science.gov (United States)

    Lagman, Karl B.; Fennel, Katja; Thompson, Keith R.; Bianucci, Laura

    2014-09-01

    Bias errors, resulting from inaccurate boundary and forcing conditions, incorrect model parameterization, etc. are a common problem in environmental models including biogeochemical ocean models. While it is important to correct bias errors wherever possible, it is unlikely that any environmental model will ever be entirely free of such errors. Hence, methods for bias reduction are necessary. A widely used technique for online bias reduction is nudging, where simulated fields are continuously forced toward observations or a climatology. Nudging is robust and easy to implement, but suppresses high-frequency variability and introduces artificial phase shifts. As a solution to this problem Thompson et al. (2006) introduced frequency dependent nudging where nudging occurs only in prescribed frequency bands, typically centered on the mean and the annual cycle. They showed this method to be effective for eddy resolving ocean circulation models. Here we add a stability term to the previous form of frequency dependent nudging which makes the method more robust for non-linear biological models. Then we assess the utility of frequency dependent nudging for biological models by first applying the method to a simple predator-prey model and then to a 1D ocean biogeochemical model. In both cases we only nudge in two frequency bands centered on the mean and the annual cycle, and then assess how well the variability in higher frequency bands is recovered. We evaluate the effectiveness of frequency dependent nudging in comparison to conventional nudging and find significant improvements with the former.

  15. Simulation of glacial ocean biogeochemical tracer and isotope distributions based on the PMIP3 suite of climate models

    Science.gov (United States)

    Khatiwala, Samar; Muglia, Juan; Kvale, Karin; Schmittner, Andreas

    2016-04-01

    In the present climate system, buoyancy forced convection at high-latitudes together with internal mixing results in a vigorous overturning circulation whose major component is North Atlantic Deep Water. One of the key questions of climate science is whether this "mode" of circulation persisted during glacial periods, and in particular at the Last Glacial Maximum (LGM; 21000 years before present). Resolving this question is both important for advancing our understanding of the climate system, as well as a critical test of numerical models' ability to reliably simulate different climates. The observational evidence, based on interpreting geochemical tracers archived in sediments, is conflicting, as are simulations carried out with state-of-the-art climate models (e.g., as part of the PMIP3 suite), which, due to the computational cost involved, do not by and large include biogeochemical and isotope tracers that can be directly compared with proxy data. Here, we apply geochemical observations to evaluate the ability of several realisations of an ocean model driven by atmospheric forcing from the PMIP3 suite of climate models to simulate global ocean circulation during the LGM. This results in a wide range of circulation states that are then used to simulate biogeochemical tracer and isotope (13C, 14C and Pa/Th) distributions using an efficient, "offline" computational scheme known as the transport matrix method (TMM). One of the key advantages of this approach is the use of a uniform set of biogeochemical and isotope parameterizations across all the different circulations based on the PMIP3 models. We compare these simulated distributions to both modern observations and data from LGM ocean sediments to identify similarities and discrepancies between model and data. We find, for example, that when the ocean model is forced with wind stress from the PMIP3 models the radiocarbon age of the deep ocean is systematically younger compared with reconstructions. Changes in

  16. Biogeochemical Processes Responsible for the Enhanced Transport of Plutonium Under transient Unsaturated Ground Water Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Fred J. Molz, III

    2010-05-28

    To better understand longer-term vadose zone transport in southeastern soils, field lysimeter experiments were conducted at the Savannah River Site (SRS) near Aiken, SC, in the 1980s. Each of the three lysimeters analyzed herein contained a filter paper spiked with different Pu solutions, and they were left exposed to natural environmental conditions (including the growth of annual weed grasses) for 11 years. The resulting Pu activity measurements from each lysimeter core showed anomalous activity distributions below the source, with significant migration of Pu above the source. Such results are not explainable by adsorption phenomena alone. A transient variably saturated flow model with root water uptake was developed and coupled to a soil reactive transport model. Somewhat surprisingly, the fully transient analysis showed results nearly identical to those of a much simpler steady flow analysis performed previously. However, all phenomena studied were unable to produce the upward Pu transport observed in the data. This result suggests another transport mechanism such as Pu uptake by roots and upward transport due to transpiration. Thus, the variably saturated flow and reactive transport model was extended to include uptake and transport of Pu within the root xylem, along with computational methodology and results. In the extended model, flow velocity in the soil was driven by precipitation input along with transpiration and drainage. Water uptake by the roots determined the flow velocity in the root xylem, and this along with uptake of Pu in the transpiration stream drove advection and dispersion of the two Pu species in the xylem. During wet periods with high potential evapotranspiration, maximum flow velocities through the xylem would approached 600 cm/hr, orders of magnitude larger that flow velocities in the soil. Values for parameters and the correct conceptual viewpoint for Pu transport in plant xylem was uncertain. This motivated further experiments devoted

  17. Biogeochemical Processes Responsible for the Enhanced Transport of Plutonium Under transient Unsaturated Ground Water Conditions

    International Nuclear Information System (INIS)

    To better understand longer-term vadose zone transport in southeastern soils, field lysimeter experiments were conducted at the Savannah River Site (SRS) near Aiken, SC, in the 1980s. Each of the three lysimeters analyzed herein contained a filter paper spiked with different Pu solutions, and they were left exposed to natural environmental conditions (including the growth of annual weed grasses) for 11 years. The resulting Pu activity measurements from each lysimeter core showed anomalous activity distributions below the source, with significant migration of Pu above the source. Such results are not explainable by adsorption phenomena alone. A transient variably saturated flow model with root water uptake was developed and coupled to a soil reactive transport model. Somewhat surprisingly, the fully transient analysis showed results nearly identical to those of a much simpler steady flow analysis performed previously. However, all phenomena studied were unable to produce the upward Pu transport observed in the data. This result suggests another transport mechanism such as Pu uptake by roots and upward transport due to transpiration. Thus, the variably saturated flow and reactive transport model was extended to include uptake and transport of Pu within the root xylem, along with computational methodology and results. In the extended model, flow velocity in the soil was driven by precipitation input along with transpiration and drainage. Water uptake by the roots determined the flow velocity in the root xylem, and this along with uptake of Pu in the transpiration stream drove advection and dispersion of the two Pu species in the xylem. During wet periods with high potential evapotranspiration, maximum flow velocities through the xylem would approached 600 cm/hr, orders of magnitude larger that flow velocities in the soil. Values for parameters and the correct conceptual viewpoint for Pu transport in plant xylem was uncertain. This motivated further experiments devoted

  18. Parameter sensitivity study of the biogeochemical model in the China coastal seas

    Institute of Scientific and Technical Information of China (English)

    JI Xuanliang; LIU Guimei; GAO Shan; WANG Hui

    2015-01-01

    In order to develop a coupled basin scale model of ocean circulation and biogeochemical cycling, we present a biogeochemical model including 12 components to study the ecosystem in the China coastal seas (CCS). The formulation of phytoplankton mortality and zooplankton growth are modified according to biological characteristics of CCS.The four sensitivity biological parameters, zooplankton assimilation efficiency rate (ZooAE_N), zooplankton basal metabolism rate (ZooBM), maximum specific growth rate of zooplankton (μ20) and maximum chlorophyll to carbon ratio (Chl2C_m) are obtained in sensitivity experiments for the phytoplankton, and experiments about the parameterμ20, half-saturation for phytoplankton NO3 uptake ( KNO3 ) and remineralization rate of small detritusN (SDeRRN) are conducted. The results demonstrate that the biogeochemical model is quite sensitive to the zooplankton grazing parameter when it ranges from 0.1 to 1.2 d–1. The KNO3 and SDeRRN also play an important role in determining the nitrogen cycle within certain ranges.The sensitive interval of KNO3 is from 0.1 to 1.5 (mmol/m3)–1, and interval of SEdRRN is from 0.01 and 0.1 d–1. The observational data from September 1998 to July 2000 obtained at SEATS station are used to validate the performance of biological model after parameters optimization. The results show that the modified model has a good capacity to reveal the biological process features, and the sensitivity analysis can save computational resources greatly during the model simulation.

  19. Benthic-Pelagic Coupling in Biogeochemical and Climate Models: Existing Approaches, Recent developments and Roadblocks

    Science.gov (United States)

    Arndt, Sandra

    2016-04-01

    Marine sediments are key components in the Earth System. They host the largest carbon reservoir on Earth, provide the only long term sink for atmospheric CO2, recycle nutrients and represent the most important climate archive. Biogeochemical processes in marine sediments are thus essential for our understanding of the global biogeochemical cycles and climate. They are first and foremost, donor controlled and, thus, driven by the rain of particulate material from the euphotic zone and influenced by the overlying bottom water. Geochemical species may undergo several recycling loops (e.g. authigenic mineral precipitation/dissolution) before they are either buried or diffuse back to the water column. The tightly coupled and complex pelagic and benthic process interplay thus delays recycling flux, significantly modifies the depositional signal and controls the long-term removal of carbon from the ocean-atmosphere system. Despite the importance of this mutual interaction, coupled regional/global biogeochemical models and (paleo)climate models, which are designed to assess and quantify the transformations and fluxes of carbon and nutrients and evaluate their response to past and future perturbations of the climate system either completely neglect marine sediments or incorporate a highly simplified representation of benthic processes. On the other end of the spectrum, coupled, multi-component state-of-the-art early diagenetic models have been successfully developed and applied over the past decades to reproduce observations and quantify sediment-water exchange fluxes, but cannot easily be coupled to pelagic models. The primary constraint here is the high computation cost of simulating all of the essential redox and equilibrium reactions within marine sediments that control carbon burial and benthic recycling fluxes: a barrier that is easily exacerbated if a variety of benthic environments are to be spatially resolved. This presentation provides an integrative overview of

  20. A Coupled Land Surface-Subsurface Biogeochemical Model for Aqueous and Gaseous Nitrogen Losses

    Science.gov (United States)

    Gu, C.; Maggi, F.; Riley, W.; Pan, L.; Xu, T.; Oldenburg, C.; Miller, N.

    2008-12-01

    In recent years concern has grown over the contribution of nitrogen (N) fertilizers to nitrate (NOB3PB-P) water pollution and atmospheric pollution of nitrous oxide (NB2BO), nitric oxide (NO), and ammonia (NHB3B). Characterizing the amount and species of N losses is therefore essential in developing a strategy to estimate and mitigate N leaching and emission to the atmosphere. Indeed, transformations of nitrogen depend strongly on water content, soil temperature, and nitrogen concentration. Land surface processes therefore have to be taken into account to properly characterize N biogeochemical cycling. However, most current nitrogen biogeochemical models take the land surface as the upper boundary by lumping the complex processes above the surface as known boundary conditions. In this study, an extant subsurface mechanistic N cycle model (TOUGHREACT-N) was coupled with the community land model (CLM). The resulting coupled model extends the modeling capability of TOUGHREACT-N to include the important energy, momentum, and moisture dynamics provided by CLM. The coupled model showed a significant impact of land-surface diurnal forcing on soil temperature and moisture and on nitrogen fluxes. We also discuss field applications of the model and discuss how temporal dynamics of nitrogen fluxes are affected by land surface processes.

  1. PEATBOG: a biogeochemical model for analyzing coupled carbon and nitrogen dynamics in northern peatlands

    Directory of Open Access Journals (Sweden)

    Y. Wu

    2013-03-01

    Full Text Available Elevated nitrogen deposition and climate change alter the vegetation communities and carbon (C and nitrogen (N cycling in peatlands. To address this issue we developed a new process-oriented biogeochemical model (PEATBOG for analyzing coupled carbon and nitrogen dynamics in northern peatlands. The model consists of four submodels, which simulate: (1 daily water table depth and depth profiles of soil moisture, temperature and oxygen levels; (2 competition among three plants functional types (PFTs, production and litter production of plants; (3 decomposition of peat; and (4 production, consumption, diffusion and export of dissolved C and N species in soil water. The model is novel in the integration of the C and N cycles, the explicit spatial resolution belowground, the consistent conceptualization of movement of water and solutes, the incorporation of stoichiometric controls on elemental fluxes and a consistent conceptualization of C and N reactivity in vegetation and soil organic matter. The model was evaluated for the Mer Bleue Bog, near Ottawa, Ontario, with regards to simulation of soil moisture and temperature and the most important processes in the C and N cycles. Model sensitivity was tested for nitrogen input, precipitation, and temperature, and the choices of the most uncertain parameters were justified. A simulation of nitrogen deposition over 40 yr demonstrates the advantages of the PEATBOG model in tracking biogeochemical effects and vegetation change in the ecosystem.

  2. Monitoring strategies and scale appropriate hydrologic and biogeochemical modelling for natural resource management

    DEFF Research Database (Denmark)

    Bende-Michl, Ulrike; Volk, Martin; Harmel, Daren;

    2011-01-01

    This short communication paper presents recommendations for developing scale-appropriate monitoring and modelling strategies to assist decision making in natural resource management (NRM). These ideas presented here were discussed in the session (S5) ‘Monitoring strategies and scale......-appropriate hydrologic and biogeochemical modelling for natural resource management’ session at the 2008 International Environmental Modelling and Simulation Society conference, Barcelona, Spain. The outcomes of the session and recent international studies exemplify the need for a stronger collaboration and...... communication between researcher and model developer on the one side, and natural resource managers and the model users on the other side to increase knowledge in: 1) the limitations and uncertainties of current monitoring and modelling strategies, 2) scale-dependent linkages between monitoring and modelling...

  3. Investigating the initial stages of soil formation in glacier forefields using the new biogeochemical model: SHIMMER

    Science.gov (United States)

    Bradley, James; Anesio, Alexandre; Arndt, Sandra; Sabacka, Marie; Barker, Gary; Benning, Liane; Blacker, Joshua; Singarayer, Joy; Tranter, Martyn; Yallop, Marian

    2016-04-01

    Glaciers and ice sheets in Polar and alpine regions are retreating in response to recent climate warming, exposing terrestrial ecosystems that have been locked under the ice for thousands of years. Exposed soils exhibit successional characteristics that can be characterised using a chronosequence approach. Decades of empirical research in glacier forefields has shown that soils are quickly colonised by microbes which drive biogeochemical cycling of elements and affect soil properties including nutrient concentrations, carbon fluxes and soil stability (Bradley et al, 2014). The characterisation of these soils is important for our understanding of the cycling of organic matter under extreme environmental and nutrient limiting conditions, and their potential contribution to global biogeochemical cycles. This is particularly important as these new areas will become more geographically expansive with continued ice retreat. SHIMMER (Soil biogeocHemIcal Model of Microbial Ecosystem Response) (Bradley et al, 2015) is a new mathematical model that simulates biogeochemical and microbial dynamics in glacier forefields. The model captures, explores and predicts the growth of different microbial groups (classified by function), and the associated cycling of carbon, nitrogen and phosphorus along a chronosequence. SHIMMER improves typical soil model formulations by including explicit representation of microbial dynamics, and those processes which are shown to be important for glacier forefields. For example, we categorise microbial groups by function to represent the diversity of soil microbial communities, and include the different metabolic needs and physiological pathways of microbial organisms commonly found in glacier forefields (e.g. microbes derived from underneath the glacier, typical soil bacteria, and microbes that can fix atmospheric nitrogen and assimilate soil nitrogen). Here, we present data from a study where we integrated modelling using SHIMMER with empirical

  4. A new biogeochemical model to simulate regional scale carbon emission from lakes, ponds and wetlands

    Science.gov (United States)

    Bayer, Tina; Brakebusch, Matthias; Gustafsson, Erik; Beer, Christian

    2016-04-01

    Small aquatic systems are receiving increasing attention for their role in global carbon cycling. For instance, lakes and ponds in permafrost are net emitters of carbon to the atmosphere, and their capacity to process and emit carbon is significant on a landscape scale, with a global flux of 8-103 Tg methane per year which amounts to 5%-30% of all natural methane emissions (Bastviken et al 2011). However, due to the spatial and temporal highly localised character of freshwater methane emissions, fluxes remain poorly qualified and are difficult to upscale based on field data alone. While many models exist to model carbon cycling in individual lakes and ponds, we perceived a lack of models that can work on a larger scale, over a range of latitudes, and simulate regional carbon emission from a large number of lakes, ponds and wetlands. Therefore our objective was to develop a model that can simulate carbon dioxide and methane emission from freshwaters on a regional scale. Our resulting model provides an additional tool to assess current aquatic carbon emissions as well as project future responses to changes in climatic drivers. To this effect, we have combined an existing large-scale hydrological model (the Variable Infiltration Capacity Macroscale Hydrologic Model (VIC), Liang & Lettenmaier 1994), an aquatic biogeochemical model (BALTSEM, Savchuk et al., 2012; Gustafsson et al., 2014) and developed a new methane module for lakes. The resulting new process-based biogeochemical model is designed to model aquatic carbon emission on a regional scale, and to perform well in high-latitude environments. Our model includes carbon, oxygen and nutrient cycling in lake water and sediments, primary production and methanogenesis. Results of calibration and validation of the model in two catchments (Torne-Kalix in Northern Sweden and of a large arctic river catchment) will be presented.

  5. Biogeochemical modeling of phosphorus cycling in the ocean: response to long-term perturbations

    Science.gov (United States)

    Palastanga, Virginia; Slomp, Caroline; Heinze, Christoph; Winguth, Arne

    2010-05-01

    Phosphorus (P) is likely the limiting nutrient for marine primary productivity on geological time scales. Therefore, insight into the mechanisms that control P cycling and burial in marine sediments is of importance for our understanding of global biogeochemical cycling and climate. Here, we use a version of the Hamburg Oceanic Carbon Cycle biogeochemical ocean model (HAMOCC2) expanded with the sedimentary P cycle, i.e. burial of organic P and formation and burial of Fe-oxide bound P and authigenic Ca-P minerals. We also include anaerobic degradation of organic matter in the sediment and a description of the oceanic Fe cycle which takes into account aeolian input and scavenging of iron onto sinking particles. For present-day climate forcing, the model predictions for the solid forms of sediment P and benthic P fluxes are compared to observations from global surface sediments. In a sensitivity study, the relationships between primary productivity, nutrient cycling, and organic C and P burial are analyzed for scenarios of increased input of P from rivers as well as for changes in aeolian deposition and circulation forcing that represent Last Glacial Maximum conditions.

  6. Empirical approaches to more accurately predict benthic-pelagic coupling in biogeochemical ocean models

    Science.gov (United States)

    Dale, Andy; Stolpovsky, Konstantin; Wallmann, Klaus

    2016-04-01

    The recycling and burial of biogenic material in the sea floor plays a key role in the regulation of ocean chemistry. Proper consideration of these processes in ocean biogeochemical models is becoming increasingly recognized as an important step in model validation and prediction. However, the rate of organic matter remineralization in sediments and the benthic flux of redox-sensitive elements are difficult to predict a priori. In this communication, examples of empirical benthic flux models that can be coupled to earth system models to predict sediment-water exchange in the open ocean are presented. Large uncertainties hindering further progress in this field include knowledge of the reactivity of organic carbon reaching the sediment, the importance of episodic variability in bottom water chemistry and particle rain rates (for both the deep-sea and margins) and the role of benthic fauna. How do we meet the challenge?

  7. Carbon sequestration by patch fertilization: A comprehensive assessment using coupled physical-ecological-biogeochemical models

    Energy Technology Data Exchange (ETDEWEB)

    Sarmiento, Jorge L. [Princeton Univ., NJ (United States); Gnanadesikan, Anand [Princeton Univ., NJ (United States); Gruber, Nicolas [Univ. of California, Los Angeles, CA (United States); Jin, Xin [Univ. of California, Los Angeles, CA (United States); Armstrong, Robert [State Univ. of New York (SUNY), Plattsburgh, NY (United States)

    2007-06-21

    This final report summarizes research undertaken collaboratively between Princeton University, the NOAA Geophysical Fluid Dynamics Laboratory on the Princeton University campus, the State University of New York at Stony Brook, and the University of California, Los Angeles between September 1, 2000, and November 30, 2006, to do fundamental research on ocean iron fertilization as a means to enhance the net oceanic uptake of CO2 from the atmosphere. The approach we proposed was to develop and apply a suite of coupled physical-ecological-biogeochemical models in order to (i) determine to what extent enhanced carbon fixation from iron fertilization will lead to an increase in the oceanic uptake of atmospheric CO2 and how long this carbon will remain sequestered (efficiency), and (ii) examine the changes in ocean ecology and natural biogeochemical cycles resulting from iron fertilization (consequences). The award was funded in two separate three-year installments: September 1, 2000 to November 30, 2003, for a project entitled “Ocean carbon sequestration by fertilization: An integrated biogeochemical assessment.” A final report was submitted for this at the end of 2003 and is included here as Appendix 1; and, December 1, 2003 to November 30, 2006, for a follow-on project under the same grant number entitled “Carbon sequestration by patch fertilization: A comprehensive assessment using coupled physical-ecological-biogeochemical models.” This report focuses primarily on the progress we made during the second period of funding subsequent to the work reported on in Appendix 1. When we began this project, we were thinking almost exclusively in terms of long-term fertilization over large regions of the ocean such as the Southern Ocean, with much of our focus being on how ocean circulation and biogeochemical cycling would interact to control the response to a given fertilization scenario. Our research on these types of scenarios, which was carried out largely during the

  8. Biogeochemical mass balances in a turbid tropical reservoir. Field data and modelling approach

    Science.gov (United States)

    Phuong Doan, Thuy Kim; Némery, Julien; Gratiot, Nicolas; Schmid, Martin

    2014-05-01

    The turbid tropical Cointzio reservoir, located in the Trans Mexican Volcanic Belt (TMVB), behaves as a warm monomictic water body (area = 6 km2, capacity 66 Mm3, residence time ~ 1 year). It is strategic for the drinking water supply of the city of Morelia, capital of the state of Michoacán, and for downstream irrigation during the dry season. This reservoir is a perfect example of a human-impacted system since its watershed is mainly composed of degraded volcanic soils and is subjected to high erosion processes and agricultural loss. The reservoir is threatened by sediment accumulation and nutrients originating from untreated waters in the upstream watershed. The high content of very fine clay particles and the lack of water treatment plants lead to serious episodes of eutrophication (up to 70 μg chl. a L-1), high levels of turbidity (Secchi depth initial storage capacity since its construction in 1940. Nutrient mass balances showed that 50 % and 46 % of incoming P and N were retained by sedimentation, and mainly eliminated through denitrification respectively. Removal of C by 30 % was also observed both by sedimentation and through gas emission. To complete field data analyses we examined the ability of vertical one dimensional (1DV) numerical models (Aquasim biogeochemical model coupled with k-ɛ mixing model) to reproduce the main biogeochemical cycles in the Cointzio reservoir. The model can describe all the mineralization processes both in the water column and in the sediment. The values of the entire mass balance of nutrients and of the mineralization rates (denitrification and aerobic benthic mineralization) calculated from the model fitted well to the field measurements. Furthermore, this analysis indicates that the benthic mineralizations are the dominant processes involved in the nutrients release. This is the first implementation of a biogeochemical model applied to a highly productive reservoir in the TMVB in order to estimate nutrients release from

  9. Biotic Interactions in Microbial Communities as Modulators of Biogeochemical Processes: Methanotrophy as a Model System

    Science.gov (United States)

    Ho, Adrian; Angel, Roey; Veraart, Annelies J.; Daebeler, Anne; Jia, Zhongjun; Kim, Sang Yoon; Kerckhof, Frederiek-Maarten; Boon, Nico; Bodelier, Paul L. E.

    2016-01-01

    Microbial interaction is an integral component of microbial ecology studies, yet the role, extent, and relevance of microbial interaction in community functioning remains unclear, particularly in the context of global biogeochemical cycles. While many studies have shed light on the physico-chemical cues affecting specific processes, (micro)biotic controls and interactions potentially steering microbial communities leading to altered functioning are less known. Yet, recent accumulating evidence suggests that the concerted actions of a community can be significantly different from the combined effects of individual microorganisms, giving rise to emergent properties. Here, we exemplify the importance of microbial interaction for ecosystem processes by analysis of a reasonably well-understood microbial guild, namely, aerobic methane-oxidizing bacteria (MOB). We reviewed the literature which provided compelling evidence for the relevance of microbial interaction in modulating methane oxidation. Support for microbial associations within methane-fed communities is sought by a re-analysis of literature data derived from stable isotope probing studies of various complex environmental settings. Putative positive interactions between active MOB and other microbes were assessed by a correlation network-based analysis with datasets covering diverse environments where closely interacting members of a consortium can potentially alter the methane oxidation activity. Although, methanotrophy is used as a model system, the fundamentals of our postulations may be applicable to other microbial guilds mediating other biogeochemical processes. PMID:27602021

  10. Marine regime shifts in ocean biogeochemical models: a case study in the Gulf of Alaska

    Science.gov (United States)

    Beaulieu, Claudie; Cole, Harriet; Henson, Stephanie; Yool, Andrew; Anderson, Tom; de Mora, Lee; Buitenhuis, Erik T.; Butenschön, Momme; Totterdell, Ian J.; Icarus Allen, J.

    2016-08-01

    Regime shifts have been reported in many marine ecosystems, and are often expressed as an abrupt change occurring in multiple physical and biological components of the system. In the Gulf of Alaska, a regime shift in the late 1970s was observed, indicated by an abrupt increase in sea surface temperature and major shifts in the catch of many fish species. A thorough understanding of the extent and mechanisms leading to such regime shifts is challenged by data paucity in time and space. We investigate the ability of a suite of ocean biogeochemistry models of varying complexity to simulate regime shifts in the Gulf of Alaska by examining the presence of abrupt changes in time series of physical variables (sea surface temperature and mixed-layer depth), nutrients and biological variables (chlorophyll, primary productivity and plankton biomass) using change-point analysis. Our results show that some ocean biogeochemical models are capable of simulating the late 1970s shift, manifested as an abrupt increase in sea surface temperature followed by an abrupt decrease in nutrients and biological productivity. Models from low to intermediate complexity simulate an abrupt transition in the late 1970s (i.e. a significant shift from one year to the next) while the transition is smoother in higher complexity models. Our study demonstrates that ocean biogeochemical models can successfully simulate regime shifts in the Gulf of Alaska region. These models can therefore be considered useful tools to enhance our understanding of how changes in physical conditions are propagated from lower to upper trophic levels.

  11. A mercury transport and fate model (LM2-mercury) for mass budget assessment of mercury cycling in Lake Michigan

    Science.gov (United States)

    LM2-Mercury, a mercury mass balance model, was developed to simulate and evaluate the transport, fate, and biogeochemical transformations of mercury in Lake Michigan. The model simulates total suspended solids (TSS), disolved organic carbon (DOC), and total, elemental, divalent, ...

  12. A model of biogeochemical cycling of phosphorus, nitrogen, oxygen, and sulphur in the ocean: One step toward a global climate model

    Science.gov (United States)

    Shaffer, Gary

    1989-02-01

    An ocean model has been developed which, for prescribed physics, deals with interrelationships between chemical distributions, biogeochemical sinks and sources, chemical reactions at redox fronts, and transports across the air-sea and sediment-water interfaces. In its first application here, the model focuses on biogeochemical cycling of phosphorus, nitrogen, oxygen, and sulphur in an ocean forced by river input of nutrients. This is a natural starting point for a global climate model since ocean circulation and biology determine atmospheric CO2 concentrations for a given inventory of inorganic C and oceanic production is controlled mainly by the availability of inorganic P and/or N. A general approach is taken to look at oxic versus anoxic conditions, P versus N limitation of primary production, with or without inorganic removal of phosphate to the sediments. As demanded by this approach, the model is nonlinear and continuous in a vertical coordinate. To focus on the biogeochemical aspects, ocean physics are kept as simple as possible. Cold, oxygen-rich water sinks at high latitudes and is upwelled with a constant velocity. Turbulent mixing is parameterized with a constant, vertical diffusion coefficient. The biogeochemical processes considered are new production, burial, nitrogen fixation, phosphorite formation, and three types of organic decomposition: oxidation with O2, denitrification, and sulphate reduction. Organic matter is taken to consist of a high- and a low-reactive fraction. The chemical species considered explicitly are PO43--P, NO3--N, O2, NH4+-N and H2S-S. Results indicate that a change from oxic to weakly anoxic conditions at middepths in a P-limited ocean would lead to strong local denitrification and low nitrate concentrations throughout the water column. New production would also become dominated by nitrogen fixers. Geological evidence implies that anoxic conditions in the water column have been rare in the Phanerozoic ocean. Both phosphorite

  13. Biogeochemical Cycling

    Science.gov (United States)

    Bebout, Brad; Fonda, Mark (Technical Monitor)

    2002-01-01

    This lecture will introduce the concept of biogeochemical cycling. The roles of microbes in the cycling of nutrients, production and consumption of trace gases, and mineralization will be briefly introduced.

  14. Modeling the fate of nitrogen on the catchment scale using a spatially explicit hydro-biogeochemical simulation system

    Science.gov (United States)

    Klatt, S.; Butterbach-Bahl, K.; Kiese, R.; Haas, E.; Kraus, D.; Molina-Herrera, S. W.; Kraft, P.

    2015-12-01

    The continuous growth of the human population demands an equally growing supply for fresh water and food. As a result, available land for efficient agriculture is constantly diminishing which forces farmers to cultivate inferior croplands and intensify agricultural practices, e.g., increase the use of synthetic fertilizers. This intensification of marginal areas in particular will cause a dangerous rise in nitrate discharge into open waters or even drinking water resources. In order to reduce the amount of nitrate lost by surface runoff or lateral subsurface transport, bufferstrips have proved to be a valuable means. Current laws, however, promote rather static designs (i.e., width and usage) even though a multitude of factors, e.g., soil type, slope, vegetation and the nearby agricultural management, determines its effectiveness. We propose a spatially explicit modeling approach enabling to assess the effects of those factors on nitrate discharge from arable lands using the fully distributed hydrology model CMF coupled to the complex biogeochemical model LandscapeDNDC. Such a modeling scheme allows to observe the displacement of dissolved nutrients in both vertical and horizontal directions and serves to estimate both their uptake by the vegetated bufferstrip and loss to the environment. First results indicate a significant reduction of nitrate loss in the presence of a bufferstrip (2.5 m). We show effects induced by various buffer strip widths and plant cover on the nitrate retention.

  15. Parameterization of biogeochemical sediment-water fluxes using in situ measurements and a diagenetic model

    Science.gov (United States)

    Laurent, A.; Fennel, K.; Wilson, R.; Lehrter, J.; Devereux, R.

    2016-01-01

    Diagenetic processes are important drivers of water column biogeochemistry in coastal areas. For example, sediment oxygen consumption can be a significant contributor to oxygen depletion in hypoxic systems, and sediment-water nutrient fluxes support primary productivity in the overlying water column. Moreover, nonlinearities develop between bottom water conditions and sediment-water fluxes due to loss of oxygen-dependent processes in the sediment as oxygen becomes depleted in bottom waters. Yet, sediment-water fluxes of chemical species are often parameterized crudely in coupled physical-biogeochemical models, using simple linear parameterizations that are only poorly constrained by observations. Diagenetic models that represent sediment biogeochemistry are available, but rarely are coupled to water column biogeochemical models because they are computationally expensive. Here, we apply a method that efficiently parameterizes sediment-water fluxes of oxygen, nitrate and ammonium by combining in situ measurements, a diagenetic model and a parameter optimization method. As a proof of concept, we apply this method to the Louisiana Shelf where high primary production, stimulated by excessive nutrient loads from the Mississippi-Atchafalaya River system, promotes the development of hypoxic bottom waters in summer. The parameterized sediment-water fluxes represent nonlinear feedbacks between water column and sediment processes at low bottom water oxygen concentrations, which may persist for long periods (weeks to months) in hypoxic systems such as the Louisiana Shelf. This method can be applied to other systems and is particularly relevant for shallow coastal and estuarine waters where the interaction between sediment and water column is strong and hypoxia is prone to occur due to land-based nutrient loads.

  16. Marine regime shifts in ocean biogeochemical models: a case study in the Gulf of Alaska

    Science.gov (United States)

    Beaulieu, C.; Cole, H.; Henson, S.; Yool, A.; Anderson, T. R.; de Mora, L.; Buitenhuis, E. T.; Butenschön, M.; Totterdell, I. J.; Allen, J. I.

    2015-08-01

    Regime shifts have been reported in many marine ecosystems, and are often expressed as an abrupt change occurring in multiple physical and biological components of the system. In the Gulf of Alaska, a regime shift in the late 1970s was observed, indicated by an abrupt increase in sea surface temperature and major shifts in the catch of many fish species. This late 1970s regime shift in the Gulf of Alaska was followed by another shift in the late 1980s, not as pervasive as the 1977 shift, but which nevertheless did not return to the prior state. A thorough understanding of the extent and mechanisms leading to such regime shifts is challenged by data paucity in time and space. We investigate the ability of a suite of ocean biogeochemistry models of varying complexity to simulate regime shifts in the Gulf of Alaska by examining the presence of abrupt changes in time series of physical variables (sea surface temperature and mixed layer depth), nutrients and biological variables (chlorophyll, primary productivity and plankton biomass) using change-point analysis. Our study demonstrates that ocean biogeochemical models are capable of simulating the late 1970s shift, indicating an abrupt increase in sea surface temperature forcing followed by an abrupt decrease in nutrients and biological productivity. This predicted shift is consistent among all the models, although some of them exhibit an abrupt transition (i.e. a significant shift from one year to the next), whereas others simulate a smoother transition. Some models further suggest that the late 1980s shift was constrained by changes in mixed layer depth. Our study demonstrates that ocean biogeochemical can successfully simulate regime shifts in the Gulf of Alaska region, thereby providing better understanding of how changes in physical conditions are propagated from lower to upper trophic levels through bottom-up controls.

  17. Technical Note: A generic law-of-the-minimum flux limiter for simulating substrate limitation in biogeochemical models

    Directory of Open Access Journals (Sweden)

    J. Y. Tang

    2015-08-01

    Full Text Available We present a generic flux limiter to account for mass limitations from an arbitrary number of substrates in a biogeochemical reaction network. The flux limiter is based on the observation that substrate (e.g., nitrogen, phosphorus limitation in biogeochemical models can be represented as to ensure mass conservative and non-negative numerical solutions to the governing ordinary differential equations. Application of the flux limiter includes two steps: (1 formulate the biogeochemical processes with a matrix of stoichiometric coefficients and (2 apply Liebig's law of the minimum using the dynamic stoichiometric relationship of the reactants. This approach contrasts with the ad hoc down-regulation approaches that are implemented in many existing models (such as CLM4.5 and the ACME (Accelerated Climate Modeling for Energy Land Model (ALM of carbon and nutrient interactions, which are error prone when adding new processes, even for experienced modelers. Through an example implementation with a Century-like decomposition model that includes carbon, nitrogen, and phosphorus, we show that our approach (1 produced almost identical results to that from the ad hoc down-regulation approaches under non-limiting nutrient conditions; and (2 properly resolved the negative solutions under substrate-limited conditions where the simple clipping approach failed; and (3 successfully avoided the potential conceptual ambiguities that are implied by those ad hoc down-regulation approaches. We expect our approach will make future biogeochemical models easier to improve and more robust.

  18. Technical Note: A generic law-of-the-minimum flux limiter for simulating substrate limitation in biogeochemical models

    Science.gov (United States)

    Tang, J. Y.; Riley, W. J.

    2016-02-01

    We present a generic flux limiter to account for mass limitations from an arbitrary number of substrates in a biogeochemical reaction network. The flux limiter is based on the observation that substrate (e.g., nitrogen, phosphorus) limitation in biogeochemical models can be represented as to ensure mass conservative and non-negative numerical solutions to the governing ordinary differential equations. Application of the flux limiter includes two steps: (1) formulation of the biogeochemical processes with a matrix of stoichiometric coefficients and (2) application of Liebig's law of the minimum using the dynamic stoichiometric relationship of the reactants. This approach contrasts with the ad hoc down-regulation approaches that are implemented in many existing models (such as CLM4.5 and the ACME (Accelerated Climate Modeling for Energy) Land Model (ALM)) of carbon and nutrient interactions, which are error prone when adding new processes, even for experienced modelers. Through an example implementation with a CENTURY-like decomposition model that includes carbon, nitrogen, and phosphorus, we show that our approach (1) produced almost identical results to that from the ad hoc down-regulation approaches under non-limiting nutrient conditions, (2) properly resolved the negative solutions under substrate-limited conditions where the simple clipping approach failed, (3) successfully avoided the potential conceptual ambiguities that are implied by those ad hoc down-regulation approaches. We expect our approach will make future biogeochemical models easier to improve and more robust.

  19. Sensitivity of pelagic CaCO3 dissolution to ocean acidification in an ocean biogeochemical model

    Directory of Open Access Journals (Sweden)

    A. Regenberg

    2013-07-01

    Full Text Available In ocean biogeochemical models pelagic CaCO3 dissolution is usually calculated as R = k * Sn, where k is the dissolution rate constant transforming S, the degree of (under- saturation of seawater with respect to CaCO3, into a time dependent rate R, and n is the reaction rate order. Generally, there are two ways to define the saturation state of seawater with respect to CaCO3: (1 Δ[CO32−], which reflects the difference between the in-situ carbonate ion concentration and the saturation concentration, and (2 Ω, which is approximated by the ratio of in-situ carbonate ion concentration over the saturation concentration. Although describing the same phenomenon, the deviation from equilibrium, both expressions are not equally applicable for the calculation of CaCO3 dissolution in the ocean across pressure gradients, as they differ in their sensitivity to ocean acidification (change of [CO32−] over depth. In the present study we use a marine biogeochemical model to test the sensitivity of pelagic CaCO3 dissolution to ocean acidification (1–4 × CO2 + stabilization, exploring the possible parameter space for CaCO3 dissolution kinetics as given in the literature. We find that at the millennial time scale there is a wide range of CaCO3 particle flux attenuation into the ocean interior (e.g. a reduction of −55 to −85% at 1000 m depth, which means that there are significant differences in the impact on particle ballasting, depending on the kinetic expression applied.

  20. Small pores in soils: Is the physico-chemical environment accurately reflected in biogeochemical models ?

    Science.gov (United States)

    Weber, Tobias K. D.; Riedel, Thomas

    2015-04-01

    Free water is a prerequesite to chemical reactions and biological activity in earth's upper crust essential to life. The void volume between the solid compounds provides space for water, air, and organisms that thrive on the consumption of minerals and organic matter thereby regulating soil carbon turnover. However, not all water in the pore space in soils and sediments is in its liquid state. This is a result of the adhesive forces which reduce the water activity in small pores and charged mineral surfaces. This water has a lower tendency to react chemically in solution as this additional binding energy lowers its activity. In this work, we estimated the amount of soil pore water that is thermodynamically different from a simple aqueous solution. The quantity of soil pore water with properties different to liquid water was found to systematically increase with increasing clay content. The significance of this is that the grain size and surface area apparently affects the thermodynamic state of water. This implies that current methods to determine the amount of water content, traditionally determined from bulk density or gravimetric water content after drying at 105°C overestimates the amount of free water in a soil especially at higher clay content. Our findings have consequences for biogeochemical processes in soils, e.g. nutrients may be contained in water which is not free which could enhance preservation. From water activity measurements on a set of various soils with 0 to 100 wt-% clay, we can show that 5 to 130 mg H2O per g of soil can generally be considered as unsuitable for microbial respiration. These results may therefore provide a unifying explanation for the grain size dependency of organic matter preservation in sedimentary environments and call for a revised view on the biogeochemical environment in soils and sediments. This could allow a different type of process oriented modelling.

  1. MOPS-1.0: towards a model for the regulation of the global oceanic nitrogen budget by marine biogeochemical processes

    Directory of Open Access Journals (Sweden)

    I. Kriest

    2015-09-01

    Analysis of the model misfit with respect to observed biogeochemical tracer distributions and fluxes suggests a particle flux profile close to the one suggested by Martin et al. (1987. Simulated pelagic denitrification best agrees with the lower values between 59 and 84 Tg N yr−1 recently estimated by other authors.

  2. Performance and results of the high-resolution biogeochemical model PELAGOS025 within NEMO

    Directory of Open Access Journals (Sweden)

    I. Epicoco

    2015-12-01

    Full Text Available The present work aims at evaluating the scalability performance of a high-resolution global ocean biogeochemistry model (PELAGOS025 on massive parallel architectures and the benefits in terms of the time-to-solution reduction. PELAGOS025 is an on-line coupling between the physical ocean model NEMO and the BFM biogeochemical model. Both the models use a parallel domain decomposition along the horizontal dimension. The parallelisation is based on the message passing paradigm. The performance analysis has been done on two parallel architectures, an IBM BlueGene/Q at ALCF (Argonne Leadership Computing Facilities and an IBM iDataPlex with Sandy Bridge processors at CMCC (Euro Mediterranean Center on Climate Change. The outcome of the analysis demonstrated that the lack of scalability is due to several factors such as the I/O operations, the memory contention, the load unbalancing due to the memory structure of the BFM component and, for the BlueGene/Q, the absence of a hybrid parallelisation approach.

  3. A Hydrological Concept including Lateral Water Flow Compatible with the Biogeochemical Model ForSAFE

    Directory of Open Access Journals (Sweden)

    Giuliana Zanchi

    2016-03-01

    Full Text Available The study presents a hydrology concept developed to include lateral water flow in the biogeochemical model ForSAFE. The hydrology concept was evaluated against data collected at Svartberget in the Vindeln Research Forest in Northern Sweden. The results show that the new concept allows simulation of a saturated and an unsaturated zone in the soil as well as water flow that reaches the stream comparable to measurements. The most relevant differences compared to streamflow measurements are that the model simulates a higher base flow in winter and lower flow peaks after snowmelt. These differences are mainly caused by the assumptions made to regulate the percolation at the bottom of the simulated soil columns. The capability for simulating lateral flows and a saturated zone in ForSAFE can greatly improve the simulation of chemical exchange in the soil and export of elements from the soil to watercourses. Such a model can help improve the understanding of how environmental changes in the forest landscape will influence chemical loads to surface waters.

  4. Reconstructing the Nd oceanic cycle using a coupled dynamical – biogeochemical model

    Directory of Open Access Journals (Sweden)

    T. Arsouze

    2009-06-01

    Full Text Available The decoupling of behaviour observed between Nd isotopic composition (Nd IC, also referred as εNd and Nd concentration has led to the notion of a "Nd paradox". While εNd behaves in a quasi-conservative way in the open ocean, leading to its broad use as a water-mass tracer, Nd concentration displays vertical profiles that increase with depth together with a deep water enrichment along the global thermohaline circulation, non-conservative behaviour typical of nutrients affected by scavenging in surface waters and remineralisation at depth. In addition, recent studies suggested that the only way to reconcile both concentration and Nd IC oceanic budgets, is to invoke a "Boundary Exchange" process (BE, defined as the co-occurrence of transfer of elements from the margin to the sea with removal of elements from the sea by Boundary Scavenging as a source-sink term. However, these studies did not simulates the real input/output fluxes of Nd to the ocean, and therefore did prevent from crucial information to apprehend the "Nd paradox". In this study, we investigate this paradox on a global scale using for the first time a fully prognostic coupled dynamical/biogeochemical model and an explicit representation of the sources and sinks to simulate the Nd oceanic cycle. Sources considered are dissolved river fluxes, atmospheric dusts and margin sediment re-dissolution. Sinks are scavenging by settling particles. This model satisfyingly simulate the global Nd oceanic cycle, and produces realistic distribution of Nd concentration and isotopic composition, though a slight overestimation of Nd concentrations in the deep Pacific Ocean, likely revealing an underestimation of the particle fields by the biogeochemical model. Our results underlines that 1 vertical cycling (scavenging/remineralisation is absolutely necessary to satisfyingly simulate both concentration and εNd, and 2 BE is the dominant Nd source

  5. Capturing optically important constituents and properties in a marine biogeochemical and ecosystem model

    Directory of Open Access Journals (Sweden)

    S. Dutkiewicz

    2015-02-01

    Full Text Available We present a numerical model of the ocean that couples a three-stream radiative transfer component with a marine biogeochemical-ecosystem in a dynamic three-dimensional physical framework. The radiative transfer component resolves spectral irradiance as it is absorbed and scattered within the water column. We explicitly include the effect of several optically important water constituents (the phytoplankton community, detrital particles, and coloured dissolved organic matter, CDOM. The model is evaluated against in situ observed and satellite derived products. In particular we compare to concurrently measured biogeochemical, ecosystem and optical data along a north–south transect of the Atlantic Ocean. The simulation captures the patterns and magnitudes of these data, and estimates surface upwelling irradiance analogous to that observed by ocean colour satellite instruments. We conduct a series of sensitivity experiments to demonstrate, globally, the relative importance of each of the water constituents, and the crucial feedbacks between the light field and the relative fitness of phytoplankton types, and the biogeochemistry of the ocean. CDOM has proportionally more importance at short wavelengths and in more productive waters, phytoplankton absorption is especially important at the deep chlorophyll a (Chl a maximum, and absorption by water molecules is relatively most important in the highly oligotrophic gyres. Sensitivity experiments in which absorption by any of the optical constituents was increased led to a decrease in the size of the oligotrophic regions of the subtropical gyres: lateral nutrient supplies were enhanced as a result of decreasing high latitude productivity. Scattering does not as strongly affect the ecosystem and biogeochemistry fields within the water column but is important for setting the surface upwelling irradiance, and hence sea surface reflectance. Having a model capable of capturing bio-optical feedbacks will be

  6. Coupling among Microbial Communities, Biogeochemistry, and Mineralogy across Biogeochemical Facies.

    Science.gov (United States)

    Stegen, James C; Konopka, Allan; McKinley, James P; Murray, Chris; Lin, Xueju; Miller, Micah D; Kennedy, David W; Miller, Erin A; Resch, Charles T; Fredrickson, Jim K

    2016-01-01

    Physical properties of sediments are commonly used to define subsurface lithofacies and these same physical properties influence subsurface microbial communities. This suggests an (unexploited) opportunity to use the spatial distribution of facies to predict spatial variation in biogeochemically relevant microbial attributes. Here, we characterize three biogeochemical facies-oxidized, reduced, and transition-within one lithofacies and elucidate relationships among facies features and microbial community biomass, richness, and composition. Consistent with previous observations of biogeochemical hotspots at environmental transition zones, we find elevated biomass within a biogeochemical facies that occurred at the transition between oxidized and reduced biogeochemical facies. Microbial richness-the number of microbial taxa-was lower within the reduced facies and was well-explained by a combination of pH and mineralogy. Null modeling revealed that microbial community composition was influenced by ecological selection imposed by redox state and mineralogy, possibly due to effects on nutrient availability or transport. As an illustrative case, we predict microbial biomass concentration across a three-dimensional spatial domain by coupling the spatial distribution of subsurface biogeochemical facies with biomass-facies relationships revealed here. We expect that merging such an approach with hydro-biogeochemical models will provide important constraints on simulated dynamics, thereby reducing uncertainty in model predictions. PMID:27469056

  7. SHIMMER (1.0): a novel mathematical model for microbial and biogeochemical dynamics in glacier forefield ecosystems

    Science.gov (United States)

    Bradley, J. A.; Anesio, A. M.; Singarayer, J. S.; Heath, M. R.; Arndt, S.

    2015-08-01

    SHIMMER (Soil biogeocHemIcal Model for Microbial Ecosystem Response) is a new numerical modelling framework which is developed as part of an interdisciplinary, iterative, model-data based approach fully integrating fieldwork and laboratory experiments with model development, testing, and application. SHIMMER is designed to simulate the establishment of microbial biomass and associated biogeochemical cycling during the initial stages of ecosystem development in glacier forefield soils. However, it is also transferable to other extreme ecosystem types (such as desert soils or the surface of glaciers). The model mechanistically describes and predicts transformations in carbon, nitrogen and phosphorus through aggregated components of the microbial community as a set of coupled ordinary differential equations. The rationale for development of the model arises from decades of empirical observation on the initial stages of soil development in glacier forefields. SHIMMER enables a quantitative and process focussed approach to synthesising the existing empirical data and advancing understanding of microbial and biogeochemical dynamics. Here, we provide a detailed description of SHIMMER. The performance of SHIMMER is then tested in two case studies using published data from the Damma Glacier forefield in Switzerland and the Athabasca Glacier in Canada. In addition, a sensitivity analysis helps identify the most sensitive and unconstrained model parameters. Results show that the accumulation of microbial biomass is highly dependent on variation in microbial growth and death rate constants, Q10 values, the active fraction of microbial biomass, and the reactivity of organic matter. The model correctly predicts the rapid accumulation of microbial biomass observed during the initial stages of succession in the forefields of both the case study systems. Simulation results indicate that primary production is responsible for the initial build-up of substrate that subsequently

  8. SHIMMER (1.0: a novel mathematical model for microbial and biogeochemical dynamics in glacier forefield ecosystems

    Directory of Open Access Journals (Sweden)

    J. A. Bradley

    2015-08-01

    Full Text Available SHIMMER (Soil biogeocHemIcal Model for Microbial Ecosystem Response is a new numerical modelling framework which is developed as part of an interdisciplinary, iterative, model-data based approach fully integrating fieldwork and laboratory experiments with model development, testing, and application. SHIMMER is designed to simulate the establishment of microbial biomass and associated biogeochemical cycling during the initial stages of ecosystem development in glacier forefield soils. However, it is also transferable to other extreme ecosystem types (such as desert soils or the surface of glaciers. The model mechanistically describes and predicts transformations in carbon, nitrogen and phosphorus through aggregated components of the microbial community as a set of coupled ordinary differential equations. The rationale for development of the model arises from decades of empirical observation on the initial stages of soil development in glacier forefields. SHIMMER enables a quantitative and process focussed approach to synthesising the existing empirical data and advancing understanding of microbial and biogeochemical dynamics. Here, we provide a detailed description of SHIMMER. The performance of SHIMMER is then tested in two case studies using published data from the Damma Glacier forefield in Switzerland and the Athabasca Glacier in Canada. In addition, a sensitivity analysis helps identify the most sensitive and unconstrained model parameters. Results show that the accumulation of microbial biomass is highly dependent on variation in microbial growth and death rate constants, Q10 values, the active fraction of microbial biomass, and the reactivity of organic matter. The model correctly predicts the rapid accumulation of microbial biomass observed during the initial stages of succession in the forefields of both the case study systems. Simulation results indicate that primary production is responsible for the initial build-up of substrate that

  9. Improving National Capability in Biogeochemical Flux Modelling: the UK Environmental Virtual Observatory (EVOp)

    Science.gov (United States)

    Johnes, P.; Greene, S.; Freer, J. E.; Bloomfield, J.; Macleod, K.; Reaney, S. M.; Odoni, N. A.

    2012-12-01

    The best outcomes from watershed management arise where policy and mitigation efforts are underpinned by strong science evidence, but there are major resourcing problems associated with the scale of monitoring needed to effectively characterise the sources rates and impacts of nutrient enrichment nationally. The challenge is to increase national capability in predictive modelling of nutrient flux to waters, securing an effective mechanism for transferring knowledge and management tools from data-rich to data-poor regions. The inadequacy of existing tools and approaches to address these challenges provided the motivation for the Environmental Virtual Observatory programme (EVOp), an innovation from the UK Natural Environment Research Council (NERC). EVOp is exploring the use of a cloud-based infrastructure in catchment science, developing an exemplar to explore N and P fluxes to inland and coastal waters in the UK from grid to catchment and national scale. EVOp is bringing together for the first time national data sets, models and uncertainty analysis into cloud computing environments to explore and benchmark current predictive capability for national scale biogeochemical modelling. The objective is to develop national biogeochemical modelling capability, capitalising on extensive national investment in the development of science understanding and modelling tools to support integrated catchment management, and supporting knowledge transfer from data rich to data poor regions, The AERC export coefficient model (Johnes et al., 2007) has been adapted to function within the EVOp cloud environment, and on a geoclimatic basis, using a range of high resolution, geo-referenced digital datasets as an initial demonstration of the enhanced national capacity for N and P flux modelling using cloud computing infrastructure. Geoclimatic regions are landscape units displaying homogenous or quasi-homogenous functional behaviour in terms of process controls on N and P cycling

  10. Glacial-interglacial variability in ocean oxygen and phosphorus in a global biogeochemical model

    Directory of Open Access Journals (Sweden)

    V Palastanga

    2013-02-01

    Full Text Available Increased transfer of particulate matter from continental shelves to the open ocean during glacials may have had a major impact on the biogeochemistry of the ocean. Here, we assess the response of the coupled oceanic cycles of oxygen, carbon, phosphorus, and iron to the input of particulate organic carbon and reactive phosphorus from shelves. We use a biogeochemical ocean model and specifically focus on the Last Glacial Maximum (LGM. When compared to an interglacial reference run, our glacial scenario with shelf input shows major increases in ocean productivity and phosphorus burial, while mean deep-water oxygen concentrations decline. There is a downward expansion of the oxygen minimum zones (OMZs in the Atlantic and Indian Ocean, while the extension of the OMZ in the Pacific is slightly reduced. Oxygen concentrations below 2000 m also decline but bottom waters do not become anoxic. The model simulations show when shelf input of particulate organic matter and particulate reactive P is considered, low oxygen areas in the glacial ocean expand, but concentrations are not low enough to generate wide scale changes in sediment biogeochemistry and sedimentary phosphorus recycling. Increased reactive phosphorus burial in the open ocean during the LGM in the model is related to dust input, notably over the southwest Atlantic and northwest Pacific, whereas input of material from shelves explains higher burial fluxes in continental slope and rise regions. Our model results are in qualitative agreement with available data and reproduce the strong spatial differences in the response of phosphorus burial to glacial-interglacial change. Our model results also highlight the need for additional sediment core records from all ocean basins to allow further insight into changes in phosphorus, carbon and oxygen dynamics in the ocean on glacial-interglacial timescales.

  11. Beyond The Blueprint: Development Of Genome-Informed Trait-Based Models For Prediction Of Microbial Dynamics And Biogeochemical Rates

    Science.gov (United States)

    Brodie, E.; King, E.; Molins, S.; Karaoz, U.; Johnson, J. N.; Bouskill, N.; Hug, L. A.; Thomas, B. C.; Castelle, C. J.; Beller, H. R.; Banfield, J. F.; Steefel, C. I.

    2014-12-01

    In soils and sediments microorganisms perform essential ecosystem services through their roles in regulating the stability of carbon and the flux of nutrients, and the purification of water. But these are complex systems with the physical, chemical and biological components all intimately connected. Components of this complexity are gradually being uncovered and our understanding of the extent of microbial functional diversity in particular has been enhanced greatly with the development of cultivation independent approaches. However we have not moved far beyond a descriptive and correlative use of this powerful resource. As the ability to reconstruct thousands of genomes from microbial populations using metagenomic techniques gains momentum, the challenge will be to develop an understanding of how these metabolic blueprints serve to influence the fitness of organisms within these complex systems and how populations emerge and impact the physical and chemical properties of their environment. In the presentation we will discuss the development of a trait-based model of microbial activity that simulates coupled guilds of microorganisms that are parameterized including traits extracted from large-scale metagenomic data. Using a reactive transport framework we simulate the thermodynamics of coupled electron donor and acceptor reactions to predict the energy available for respiration, biomass development and exo-enzyme production. Each group within a functional guild is parameterized with a unique combination of traits governing organism fitness under dynamic environmental conditions. This presentation will address our latest developments in the estimation of trait values related to growth rate and the identification and linkage of key fitness traits associated with respiratory and fermentative pathways, macromolecule depolymerization enzymes and nitrogen fixation from metagenomic data. We are testing model sensitivity to initial microbial composition and intra

  12. Quantification of terrestrial ecosystem carbon dynamics in the conterminous United States combining a process-based biogeochemical model and MODIS and AmeriFlux data

    Science.gov (United States)

    Satellite remote sensing provides continuous temporal and spatial information of terrestrial ecosystems. Using these remote sensing data and eddy flux measurements and biogeochemical models, such as the Terrestrial Ecosystem Model (TEM), should provide a more adequate quantification of carbon dynami...

  13. MOPS-1.0: towards a model for the regulation of the global oceanic nitrogen budget by marine biogeochemical processes

    Science.gov (United States)

    Kriest, I.; Oschlies, A.

    2015-09-01

    Global models of the oceanic nitrogen cycle are subject to many uncertainties regarding the representation of the relevant biogeochemical processes and of the feedbacks between nitrogen sources and sinks that determine space- and timescales on which the global nitrogen budget is regulated. We investigate these aspects using a global model of ocean biogeochemistry that explicitly considers phosphorus and nitrogen, including pelagic denitrification and nitrogen fixation as sink and source terms of fixed nitrogen, respectively. The model explores different parameterizations of organic matter sinking speed, oxidant affinity of oxic and suboxic remineralization, and regulation of nitrogen fixation by temperature and different stoichiometric ratios. Examination of the initial transient behavior of different model setups initialized from observed biogeochemical tracer distributions reveal changes in simulated nitrogen inventories and fluxes particularly during the first centuries. Millennial timescales have to be resolved in order to bring all biogeochemical and physical processes into a dynamically consistent steady state. Analysis of global properties suggests that not only particularly particle sinking speed but also the parameterization of denitrification determine the extent of oxygen minimum zones, global nitrogen fluxes, and hence the oceanic nitrogen inventory. However, the ways and directions in which different parameterizations of particle sinking, nitrogen fixation, and denitrification affect the global diagnostics are different suggesting that these may, in principle, be constrained independently from each other. Analysis of the model misfit with respect to observed biogeochemical tracer distributions and fluxes suggests a particle flux profile close to the one suggested by Martin et al. (1987). Simulated pelagic denitrification best agrees with the lower values between 59 and 84 Tg N yr-1 recently estimated by other authors.

  14. SHIMMER (1.0): a novel mathematical model for microbial and biogeochemical dynamics in glacier forefield ecosystems

    Science.gov (United States)

    Bradley, J. A.; Anesio, A. M.; Singarayer, J. S.; Heath, M. R.; Arndt, S.

    2015-10-01

    SHIMMER (Soil biogeocHemIcal Model for Microbial Ecosystem Response) is a new numerical modelling framework designed to simulate microbial dynamics and biogeochemical cycling during initial ecosystem development in glacier forefield soils. However, it is also transferable to other extreme ecosystem types (such as desert soils or the surface of glaciers). The rationale for model development arises from decades of empirical observations in glacier forefields, and enables a quantitative and process focussed approach. Here, we provide a detailed description of SHIMMER, test its performance in two case study forefields: the Damma Glacier (Switzerland) and the Athabasca Glacier (Canada) and analyse sensitivity to identify the most sensitive and unconstrained model parameters. Results show that the accumulation of microbial biomass is highly dependent on variation in microbial growth and death rate constants, Q10 values, the active fraction of microbial biomass and the reactivity of organic matter. The model correctly predicts the rapid accumulation of microbial biomass observed during the initial stages of succession in the forefields of both the case study systems. Primary production is responsible for the initial build-up of labile substrate that subsequently supports heterotrophic growth. However, allochthonous contributions of organic matter, and nitrogen fixation, are important in sustaining this productivity. The development and application of SHIMMER also highlights aspects of these systems that require further empirical research: quantifying nutrient budgets and biogeochemical rates, exploring seasonality and microbial growth and cell death. This will lead to increased understanding of how glacier forefields contribute to global biogeochemical cycling and climate under future ice retreat.

  15. PISCES-v2: an ocean biogeochemical model for carbon and ecosystem studies

    Directory of Open Access Journals (Sweden)

    O. Aumont

    2015-08-01

    of marine ecosystems (phytoplankton, microzooplankton and mesozooplankton and the biogeochemical cycles of carbon and of the main nutrients (P, N, Fe, and Si. The model is intended to be used for both regional and global configurations at high or low spatial resolutions as well as for short-term (seasonal, interannual and long-term (climate change, paleoceanography analyses. There are 24 prognostic variables (tracers including two phytoplankton compartments (diatoms and nanophytoplankton, two zooplankton size classes (microzooplankton and mesozooplankton and a description of the carbonate chemistry. Formulations in PISCES-v2 are based on a mixed Monod–quota formalism. On the one hand, stoichiometry of C / N / P is fixed and growth rate of phytoplankton is limited by the external availability in N, P and Si. On the other hand, the iron and silicon quotas are variable and the growth rate of phytoplankton is limited by the internal availability in Fe. Various parameterizations can be activated in PISCES-v2, setting, for instance, the complexity of iron chemistry or the description of particulate organic materials. So far, PISCES-v2 has been coupled to the Nucleus for European Modelling of the Ocean (NEMO and Regional Ocean Modeling System (ROMS systems. A full description of PISCES-v2 and of its optional functionalities is provided here. The results of a quasi-steady-state simulation are presented and evaluated against diverse observational and satellite-derived data. Finally, some of the new functionalities of PISCES-v2 are tested in a series of sensitivity experiments.

  16. Introducing dynamic benthic fluxes in 3D biogeochemical model : an application on the Black Sea North-Western shelf

    OpenAIRE

    Capet, Arthur; MEYSMAN, Filip; Soetaert, Karline; Grégoire, Marilaure

    2013-01-01

    While benthic and sediment processes are now recognized as major components of the shelf iogeochemical budget, their representation in 3D biogeochemical model has for long been oversimplified [Soetaert et al., 2000]. These oversimplified formulations of the bottom boundary onditions prevent to account for the response of diagenetic processes to the environment. The onsequent absence of spatial and temporal variability of benthic/pelagic fluxes may lead to mis- valuation of important terms ...

  17. A new post-processing tool for the source-related element tracing in biogeochemical models: A case study for the North Sea

    Science.gov (United States)

    Große, Fabian; Kreus, Markus; Pätsch, Johannes

    2015-04-01

    The mitigation of eutrophication and its concomitants, like harmful algal blooms or deoxygenation of bottom waters, is one of the major aspects of the ecological management of coastal marine ecosystems. In the past, biogeochemical models helped to significantly improve the understanding of the interaction of the physical and biological processes behind eutrophication. Nevertheless, the quantification of the influence of source-related nutrient inputs to eutrophication in a specific region remains an important issue, since it is as crucial for an efficient management as it is difficult to obtain. About a decade ago, a method applicable to biogeochemical models had been developed allowing for the tracing of elements from different sources, e.g. phosphorus and/or nitrogen from two different rivers, throughout the whole process chain of the applied model. This tracing method - often referred to as 'trans-boundary nutrient transport' (TBNT) - provides additional information about the contributions from different sources to the overall amount ('bulk') of an element in each part of the model domain. This information constitutes the basis for the quantification, evaluation and optimisation of nutrient reduction targets for the tributaries of a marine ecosystem. In the meantime, the TBNT method has been applied to a variety of different biogeochemical models, e.g. to quantify the influence of nutrient loads from different rivers or atmospheric deposition on phytoplankton blooms or to determine the source-related composition of total nitrogen in different parts of an ecosystem. However, for all of these applications the method was directly implemented into the considered model, and thus was model-dependent and required an individual solution to deal with the model specifics like grid structure, programming language etc. For the application of the TBNT method to the ECOHAM model (ECOlogical model HAMburg), we further developed the approach by creating a post

  18. Iron-light colimitation in a global ocean biogeochemical model and the sensitivity of oceanic CO2 uptake to dust deposition

    Science.gov (United States)

    Nickelsen, L.; Oschlies, A.

    2012-12-01

    The iron hypothesis of glacial-interglacial cycles states that glacial increases in the deposition of dust enhanced the concentrations of the micronutrient iron in the ocean where it triggered phytoplankton growth and thus CO2 uptake. Indeed, iron fertilization experiments find that phytoplankton needs iron in particular for nitrate uptake, light harvesting, synthesis of chlorophyll and in the electron transport chain of photosynthesis. Previous global biogeochemical models used to extrapolate results from local culture and field experiments have suggested that the sensitivity of ocean biogeochemistry to changes in dust deposition is too low to account for the observed glacial-interglacial changes of atmospheric CO2 concentrations. Here we show that this sensitivity is increased significantly when iron-light colimitation, i.e. the impact of iron on light harvesting capabilities and chlorophyll synthesis, is explicitly considered in a global biogeochemical ocean model. Iron-light colimitation increases the shift of export production to higher latitudes at high dust deposition and amplifies iron limitation at low dust deposition. Our results suggest that iron fertilization by increased dust deposition may explain a substantially larger portion of the observed past CO2 variability than thought previously. Our results emphasize the role of iron as a key limiting nutrient for phytoplankton in the ocean, with a high potential for changes in oceanic iron supply affecting the global carbon cycle and climate.

  19. Assessment of the GHG reduction potential from energy crops using a combined LCA and biogeochemical process models: a review.

    Science.gov (United States)

    Jiang, Dong; Hao, Mengmeng; Fu, Jingying; Wang, Qiao; Huang, Yaohuan; Fu, Xinyu

    2014-01-01

    The main purpose for developing biofuel is to reduce GHG (greenhouse gas) emissions, but the comprehensive environmental impact of such fuels is not clear. Life cycle analysis (LCA), as a complete comprehensive analysis method, has been widely used in bioenergy assessment studies. Great efforts have been directed toward establishing an efficient method for comprehensively estimating the greenhouse gas (GHG) emission reduction potential from the large-scale cultivation of energy plants by combining LCA with ecosystem/biogeochemical process models. LCA presents a general framework for evaluating the energy consumption and GHG emission from energy crop planting, yield acquisition, production, product use, and postprocessing. Meanwhile, ecosystem/biogeochemical process models are adopted to simulate the fluxes and storage of energy, water, carbon, and nitrogen in the soil-plant (energy crops) soil continuum. Although clear progress has been made in recent years, some problems still exist in current studies and should be addressed. This paper reviews the state-of-the-art method for estimating GHG emission reduction through developing energy crops and introduces in detail a new approach for assessing GHG emission reduction by combining LCA with biogeochemical process models. The main achievements of this study along with the problems in current studies are described and discussed. PMID:25045736

  20. Simulating anchovy's full life cycle in the northern Aegean Sea (eastern Mediterranean): A coupled hydro-biogeochemical-IBM model

    Science.gov (United States)

    Politikos, D.; Somarakis, S.; Tsiaras, K. P.; Giannoulaki, M.; Petihakis, G.; Machias, A.; Triantafyllou, G.

    2015-11-01

    A 3-D full life cycle population model for the North Aegean Sea (NAS) anchovy stock is presented. The model is two-way coupled with a hydrodynamic-biogeochemical model (POM-ERSEM). The anchovy life span is divided into seven life stages/age classes. Embryos and early larvae are passive particles, but subsequent stages exhibit active horizontal movements based on specific rules. A bioenergetics model simulates the growth in both the larval and juvenile/adult stages, while the microzooplankton and mesozooplankton fields of the biogeochemical model provide the food for fish consumption. The super-individual approach is adopted for the representation of the anchovy population. A dynamic egg production module, with an energy allocation algorithm, is embedded in the bioenergetics equation and produces eggs based on a new conceptual model for anchovy vitellogenesis. A model simulation for the period 2003-2006 with realistic initial conditions reproduced well the magnitude of population biomass and daily egg production estimated from acoustic and daily egg production method (DEPM) surveys, carried out in the NAS during June 2003-2006. Model simulated adult and egg habitats were also in good agreement with observed spatial distributions of acoustic biomass and egg abundance in June. Sensitivity simulations were performed to investigate the effect of different formulations adopted for key processes, such as reproduction and movement. The effect of the anchovy population on plankton dynamics was also investigated, by comparing simulations adopting a two-way or a one-way coupling of the fish with the biogeochemical model.

  1. Shelf/Offshore interactions in the Benguela upwelling system using a 3-D coupled physical/biogeochemical model

    OpenAIRE

    Gutknecht, E.

    2011-01-01

    The main objective of this PhD thesis is the study of the shelf/offshore interactions in the Benguela upwelling system, off South African and Namibian coasts, using a numerical model as well as satellite and in-situ data. A Biogeochemical model adapted for the Benguela Upwelling System (BioBUS), taking into account the main processes linked with eastern boundary upwelling systems and associated oxygen minimum zones, has been developed and coupled with the ROMS hydrodynamical model, in order t...

  2. FORWARD AND INVERSE BIO-GEOCHEMICAL MODELING OF MICROBIALLY INDUCED PRECIPITATION IN 0.5M COLUMNAR EXPERIMENTS

    Science.gov (United States)

    Barkouki, T. H.; Martinez, B.; Mortensen, B.; Dejong, J.; Weathers, T. S.; Spycher, N.; Ginn, T. R.; Fujita, Y.; Smith, R. W.

    2009-12-01

    Subsurface contamination by metals and radionuclides threatens water supplies and ecosystem health at sites worldwide. One potential solution is immobilization in calcite where mineral precipitation is induced in situ by microbially-mediated ureolysis. Specifically, immobile aerobic biophases (cells or enzymes) mediate the conversion of urea to ammonium and carbonate, raising pH and promoting calcite precipitation. Divalent species such as strontium (including 90Sr, a common radionuclide contaminant) can co-precipitate, resulting in in situ immobilization. In waters that are saturated with respect to calcite, this represents a long-term sequestration mechanism. Calcite precipitation also enables control of mechanical properties of the medium through the cementation of particles thus increasing the shear strength and stiffness, while decreasing the permeability and compressibility. Challenges in application include design of the injectate aqueous chemistry (e.g., calcium, carbonate, urea, pH buffer, microbial nutrients) and selection of injection rates in order to control the timing and rate of calcite precipitation to generate the desired spatial distribution. Modeling ultimately requires incorporation of comprehensive reaction networks into transport simulators for non-uniform flow. To develop and validate the reaction network for use in both contaminant co-precipitation and subsurface structural modification applications, multicomponent biogeochemical modeling (TOUGHREACT v2) was applied in analyses of laboratory batch and column investigations of microbially-mediated calcite precipitation using Sporosarcina pasteurii. Column experiments included continuous and repeat pulse-flows, with cumulative flux equal in both cases. Aqueous chemistry and calcite distribution were monitored, as well as seismic shear waves that correlate to the stiffness of the column and thus to precipitation extent. TOUGHREACT was coupled with the inversion code UCODE to invert on observed

  3. Reconstructing the Nd oceanic cycle using a coupled dynamical - biogeochemical model

    OpenAIRE

    T. Arsouze; Dutay, J.-C; Lacan, F.; Jeandel, C.

    2009-01-01

    ISI Document Delivery No.: 536QY Times Cited: 37 Cited Reference Count: 73 Cited References: Amakawa H, 2004, GEOCHIM COSMOCHIM AC, V68, P715, DOI 10.1016/S0016-7037(03)00501-5 ANDERSON RF, 1990, EARTH PLANET SC LETT, V96, P287, DOI 10.1016/0012-821X(90)90008-L Arsouze T, 2007, CHEM GEOL, V239, P165, DOI 10.1016/j.chemgeo.2006.12.006 Arsouze T, 2008, CLIM PAST, V4, P191 Aumont O, 2003, GLOBAL BIOGEOCHEM CY, V17, DOI 10.1029/2001GB001745 Aumont O, 2006, GLOBAL BIOGEOCHEM CY, V20, DOI 10.1029/2...

  4. Coupled physical/biogeochemical modeling including O2-dependent processes in the Eastern Boundary Upwelling Systems: application in the Benguela

    Directory of Open Access Journals (Sweden)

    E. Gutknecht

    2013-06-01

    Full Text Available The Eastern Boundary Upwelling Systems (EBUS contribute to one fifth of the global catches in the ocean. Often associated with Oxygen Minimum Zones (OMZs, EBUS represent key regions for the oceanic nitrogen (N cycle. Important bioavailable N loss due to denitrification and anammox processes as well as greenhouse gas emissions (e.g, N2O occur also in these EBUS. However, their dynamics are currently crudely represented in global models. In the climate change context, improving our capability to properly represent these areas is crucial due to anticipated changes in the winds, productivity, and oxygen content. We developed a biogeochemical model (BioEBUS taking into account the main processes linked with EBUS and associated OMZs. We implemented this model in a 3-D realistic coupled physical/biogeochemical configuration in the Namibian upwelling system (northern Benguela using the high-resolution hydrodynamic ROMS model. We present here a validation using in situ and satellite data as well as diagnostic metrics and sensitivity analyses of key parameters and N2O parameterizations. The impact of parameter values on the OMZ off Namibia, on N loss, and on N2O concentrations and emissions is detailed. The model realistically reproduces the vertical distribution and seasonal cycle of observed oxygen, nitrate, and chlorophyll a concentrations, and the rates of microbial processes (e.g, NH4+ and NO2− oxidation, NO3− reduction, and anammox as well. Based on our sensitivity analyses, biogeochemical parameter values associated with organic matter decomposition, vertical sinking, and nitrification play a key role for the low-oxygen water content, N loss, and N2O concentrations in the OMZ. Moreover, the explicit parameterization of both steps of nitrification, ammonium oxidation to nitrate with nitrite as an explicit intermediate, is necessary to improve the representation of microbial activity linked with the OMZ. The simulated minimum oxygen

  5. Coupled physical/biogeochemical modeling including O2-dependent processes in the Eastern Boundary Upwelling Systems: application in the Benguela

    Directory of Open Access Journals (Sweden)

    A. Paulmier

    2012-10-01

    Full Text Available The Eastern Boundary Upwelling Systems (EBUS contribute to one fifth of the global catches in the ocean. Often associated with Oxygen Minimum Zones (OMZs, EBUS represent key regions for the oceanic nitrogen (N cycle. Important bioavailable N loss due to denitrification and anammox processes as well as greenhouse gas emissions (e.g, N2O occur also in these EBUS. However, their dynamics are currently crudely represented in global models. In the climate change context, improving our capability to properly represent these areas is crucial, due to anticipated changes in the winds, productivity, and oxygen content. We developed a biogeochemical model (BioEBUS taking into account the main processes linked with EBUS and associated OMZs. We implemented this model in a 3-D realistic coupled physical/biogeochemical configuration in the Namibian upwelling system (Northern Benguela using the high-resolution hydrodynamical model ROMS. We present here a validation using in situ and satellite data as well as diagnostic metrics, and sensitivity analyses of key parameters and N2O parameterizations. The impact of parameter values on the OMZ off Namibia, on N loss, and on N2O concentrations and emissions is detailed. The model realistically reproduces the vertical distribution and seasonal cycle of observed oxygen, nitrate and Chl a concentrations, and the rates of microbial processes (e.g. NH4+ and NO2− oxidation, NO3− reduction and anammox as well. Based on our sensitivity analyses, biogeochemical parameter values associated with organic matter decomposition, vertical sinking and nitrification play a key role for the low-oxygen water content, N loss and N2O concentrations in the OMZ. Moreover, the importance of both steps of nitrification, ammonium oxidation to nitrate with nitrite as an explicit intermediate, is highlighted to improve the representation of microbial activity linked with OMZ. The simulated minimum oxygen concentrations are driven by the

  6. Groupage Cargo Transportation Model

    OpenAIRE

    Aleksejevs Ruslans; Guseinovs Raufs; Medvedev Alexander N.; Guseynov Sharif E.

    2016-01-01

    In this work we consider a specific problem of optimal planning of maritime transportation of multiproduct cargo by ships of one (corporate strategy) or several (partially corporate strategy) companies: the core of the problem consists of the existence of the network of intermediate seaports (i.e. transitional seaports), where for every ship arrived the cargo handling is done, and which are situated between the starting and the finishing seaports. In this work, there are mathematical models b...

  7. Biogeochemical modelling of anaerobic vs. aerobic methane oxidation in a meromictic crater lake (Lake Pavin, France)

    International Nuclear Information System (INIS)

    Methane is a powerful greenhouse gas and its concentration in the atmosphere has increased over the past decades. Methane produced by methanogenic Archae can be consumed through aerobic and anaerobic oxidation pathways. In anoxic conditions found in freshwater environments such as meromictic lakes, CH4 oxidation pathways involving different terminal electron acceptors such as NO3-, SO42-, and oxides of Fe and Mn are thermodynamically possible. In this study, a reactive transport model was developed to assess the relative significance of the different pathways of CH4 consumption in the water column of Lake Pavin. In most cases, the model reproduced experimental data collected from the field from June 2006 to June 2007. Although the model and the field measurements suggest that anaerobic CH4 oxidation may contribute to CH4 consumption in the water column of Lake Pavin, aerobic oxidation remains the major sink of CH4 in this lake.

  8. Biogeochemical Modeling of Wetland Carbon Sequestration and Greenhouse Gas Emission Factors for the U.S. Temperate Prairie Ecoregions

    Science.gov (United States)

    Abdul-Aziz, O.; WU, Y.; Liu, S.; Grangaard, L.; Liu, J.

    2011-12-01

    Wetlands are known to play a critical role in carbon sequestration and major greenhouse gas (GHG) emissions. They are important depositional systems interfacing the terrestrial and aquatic ecosystems. We included a wetland component into the well-known terrestrial soil organic carbon dynamics model, CENTURY IV to simulate/predict carbon sequestration and emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from wetland ecosystems. The CENTURY-Wetland package was incorporated into a generalized ensemble biogeochemical modeling system (GEMS) to develop a regional-scale wetland biogeochemical model. We applied the regional CENTURY-Wetland to simulate major GHG emissions and carbon sequestration of the wetlands in the U.S. Temperate Prairie Ecoregions (i.e., US EPA Level II Ecoregion 9.2). The simulations are analyzed to develop regional emissions factors of wetland CO2, CH4, and N2O under historical, as well as different land use/cover and IPCC climate change scenarios. This research is a part of the USGS efforts to quantify 'biological' carbon sequestrations under a changing climate, land use/cover, and policy scenarios. The CENTURY-Wetland will be applied to other U.S. ecoregions for quantifying the wetland carbon sequestration and GHG emissions from the continental United States.

  9. Groupage Cargo Transportation Model

    Directory of Open Access Journals (Sweden)

    Aleksejevs Ruslans

    2016-03-01

    Full Text Available In this work we consider a specific problem of optimal planning of maritime transportation of multiproduct cargo by ships of one (corporate strategy or several (partially corporate strategy companies: the core of the problem consists of the existence of the network of intermediate seaports (i.e. transitional seaports, where for every ship arrived the cargo handling is done, and which are situated between the starting and the finishing seaports. In this work, there are mathematical models built from scratch in the form of multicriteria optimization problem; then the goal attainment method of Gembicki is used for reducing the built models to a one-criterion problem of linear programming.

  10. Testing of a near-field biogeochemical model against data from a large-scale gas generation experiment

    International Nuclear Information System (INIS)

    A biogeochemical model that represents processes of metal corrosion, microbial degradation of cellulosic waste and mass transfer within a heterogeneous system has been used to represent processes of gas generation in a large-scale (20m3) experiment that has studied degradation of typical nuclear reactor operating waste. The experiment has been in operation for a period of about eight years and has established a pattern of methanogenic gas generation. A 'blind testing' approach has been used to develop the model of the experiment using independently derived kinetic data for corrosion and microbial processes. The model correctly represents the anaerobic conditions leading to methane generation during the course of the experiment. The overall rate of gas generation of the experiment is well represented, as is the composition of evolved gases and geochemistry of sampled liquids. The experiment and the model together build confidence in the ability to simulate processes of gas generation and variation in chemical conditions in heterogeneous repository environments. (author)

  11. Useless arithmetic or useful scientific tools? Evaluation of the current state and future perspectives of aquatic biogeochemical modeling

    Science.gov (United States)

    Arhonditsis, G.

    2009-04-01

    What is the capacity of the current models to simulate the dynamics of environmental systems? How carefully do modelers develop their models? Which model features primarily determine our decision to utilize a specific model? How rigorously do we assess what a model can or cannot predict? The first part of my presentation is to answer some of these questions by reviewing the state of aquatic biogeochemical modeling; a research tool that has been extensively used for understanding and quantitatively describing aquatic ecosystems. Mechanistic aquatic biogeochemical models have form the scientific basis for environmental management decisions by providing a predictive link between management actions and ecosystem response; they have provided an important tool for elucidating the interactions between climate variability and plankton communities, and thus for addressing questions regarding the pace and impacts of climate change. The sizable number of aquatic ecosystem modeling studies which successfully passed the scrutiny of the peer-review process along with the experience gained from addressing a breadth of management problems can objectively reveal the systematic biases, methodological inconsistencies, and common misconceptions characterizing the modeling practice in environmental science. My arguments are that (i) models are not always developed in a consistent manner, clearly stated purpose, and predetermined acceptable model performance level, (ii) the potential "customers" select models without properly assessing their technical value, and (iii) oceanic modeling is a dynamic area of the current modeling practice whereas, model application for addressing environmental management issues on a local scale faces challenges as a scientific tool. The second part of my presentation argues that (i) the development of novel methods for rigorously assessing the uncertainty underlying model predictions should be a top priority of the modeling community, and (ii) the model

  12. An Analytical Particle Biogeochemical Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Evaluation of the technical and scientific feasibility of developing a model and sensor for the analytical optical determination of particle biogeochemical...

  13. The influence of winter convection on primary production: A parameterisation using a hydrostatic three-dimensional biogeochemical model

    DEFF Research Database (Denmark)

    Grosse, Fabian; Lindemann, Christian; Pätch, Johannes; Backhaus, Jan O.

    2014-01-01

    simulation using the new parameterisation showed good agreement with observation data recorded during winter, whereas the reference simulation did not capture the observed phytoplankton concentrations. The new parameterisation had a strong influence on the carbon export through the sinking of particulate......–biogeochemical model and applied to the Northwestern European Continental Shelf and areas of the adjacent Northeast Atlantic. The simulation was compared to a ‘conventional’ parameterisation with respect to its influence on phytoplankton concentrations during the annual cycle and its effect on the carbon cycle. The...... organic carbon. The carbon export during late winter/early spring significantly exceeded the export of the reference run. Furthermore, a non-hydrostatic convection model was used to evaluate the major assumption of the presented parameterisation which implies the matching of the mixed layer depth with the...

  14. The influence of winter convection on primary production: a parameterisation using a hydrostatic three-dimensional biogeochemical model

    CERN Document Server

    Große, Fabian; Pätsch, Johannes; Backhaus, Jan O

    2014-01-01

    In the recent past observational and modelling studies have shown that the vertical displacement of water parcels, and therefore, phytoplankton particles in regions of deep-reaching convection plays a key role in late winter/early spring primary production. The underlying mechanism describes how convection cells capture living phytoplankton cells and recurrently expose them to sunlight. This study presents a parameterisation called `phytoconvection' which focuses on the influence of convection on primary production. This parameterisation was implemented into a three-dimensional physical-biogeochemical model and applied to the Northwestern European Continental Shelf and areas of the adjacent Northeast Atlantic. The simulation was compared to a `conventional' parameterisation with respect to its influence on phytoplankton concentrations during the annual cycle and its effect on the carbon cycle. The simulation using the new parameterisation showed good agreement with observation data recorded during winter, whe...

  15. Division of Biogeochemical Ecology FY-1985 highlights

    International Nuclear Information System (INIS)

    The primary goal of the Division is to understand the various biogeochemical processes, both in aquatic and terrestrial systems, that occur in the southeastern United States, including the Savannah River Plant. Both applied and basic approaches are being used to enhance understanding of the biogeochemical cycles of certain elements and trace contaminants, either in inorganic or organic states, and in stable or radioactive forms. Specific examples of studies conducted during the past year include: (1) ecosystem modeling and implementation of a computer model to predict the fate, behavior and transport of heavy metals and radionuclides in SRP streams, (2) laboratory and greenhouse studies on the environmental chemistry of an organo-borate in the soil-plant system, (3) research on the behavior and fate of actinide elements and other long-lived radioisotopes in terrestrial and aquatic ecosystems, and (4) responses of pine plantations to organic waste fertilization. Major findings of these studies are summarized. The chemical speciation-transport model MEXAMS (Metal Exposure Analysis Modeling System) was implemented to provide predictive capabilities for the transport of heavy metals and radionuclides in SRP aquatic systems. The basic components of the model are the geochemical model MINTEQ, and an aquatic exposure assessment model, EXAMS. The interfacing of these two models provides information on the complex chemistry and behavior of metals, as well as the transport processes influencing their migration and ultimate fate in aquatic systems. Test simulations for Cd, Cu, and Ni speciation in various SRP streams were conducted. The results indicated that the MEXAMS model will be a useful tool in predicting the transport and fate of metals in SRP streams

  16. Methane emissions from wetlands: biogeochemical, microbial, and modeling perspectives from local to global scales.

    Science.gov (United States)

    Bridgham, Scott D; Cadillo-Quiroz, Hinsby; Keller, Jason K; Zhuang, Qianlai

    2013-05-01

    Understanding the dynamics of methane (CH4 ) emissions is of paramount importance because CH4 has 25 times the global warming potential of carbon dioxide (CO2 ) and is currently the second most important anthropogenic greenhouse gas. Wetlands are the single largest natural CH4 source with median emissions from published studies of 164 Tg yr(-1) , which is about a third of total global emissions. We provide a perspective on important new frontiers in obtaining a better understanding of CH4 dynamics in natural systems, with a focus on wetlands. One of the most exciting recent developments in this field is the attempt to integrate the different methodologies and spatial scales of biogeochemistry, molecular microbiology, and modeling, and thus this is a major focus of this review. Our specific objectives are to provide an up-to-date synthesis of estimates of global CH4 emissions from wetlands and other freshwater aquatic ecosystems, briefly summarize major biogeophysical controls over CH4 emissions from wetlands, suggest new frontiers in CH4 biogeochemistry, examine relationships between methanogen community structure and CH4 dynamics in situ, and to review the current generation of CH4 models. We highlight throughout some of the most pressing issues concerning global change and feedbacks on CH4 emissions from natural ecosystems. Major uncertainties in estimating current and future CH4 emissions from natural ecosystems include the following: (i) A number of important controls over CH4 production, consumption, and transport have not been, or are inadequately, incorporated into existing CH4 biogeochemistry models. (ii) Significant errors in regional and global emission estimates are derived from large spatial-scale extrapolations from highly heterogeneous and often poorly mapped wetland complexes. (iii) The limited number of observations of CH4 fluxes and their associated environmental variables loosely constrains the parameterization of process-based biogeochemistry

  17. Realistic primary and new productions in a 3D global biogeochemical model: biological complexity or physical forcing?

    Science.gov (United States)

    Popova, E. E.; Coward, A. C.

    2003-04-01

    A nitrogen-based, five compartment biological model has been coupled to a one degree OCCAM (Ocean Circulation and Climate Advanced Modelling Project) model with a KPP ("K profile parameterisation") of the vertical mixing. The biological model state variables are Phytoplankton, Zooplankton, Detritus, Nitrate, and Ammonium. A comparison of the solution with global satellite ocean colour shows that the model is capable of a realistic description of the main seasonal and regional patterns of the surface chlorophyll. Agreement is also good for satellite derived estimates of primary production. In situ data available from local study sites (such as BATS, NABE, India, Papa) are used for the detailed comparison of the model output with the observed ecosystem dynamics in different biological provinces. We discuss performance of the physical and biological model in contrasting areas of the World Ocean. In spite of the biological model being a very simple one, we are able to reproduce the major differences between ecosystem dynamics of these areas. We believe that the success of any global biogeochemical model is dependent first of all on the correct representation of the upper mixed layer (UML) dynamics. Without being able to reproduce contrasting UML regimes in different areas of the World Ocean (such as difference between the North Atlantic and Southern Ocean, or North Atlantic and North Pacific), increased complexity biological models are in danger of producing the right results by the wrong reason.

  18. A high-resolution hydrodynamic-biogeochemical coupled model of the Gulf of Cadiz – Alboran Sea region.

    Directory of Open Access Journals (Sweden)

    D. M. MACIAS

    2015-01-01

    Full Text Available The southern Iberia regional seas comprise the Gulf of Cadiz and the Alboran Sea sub-basins connected by the narrow Strait of Gibraltar. Both basins are very different in their hydrological and biological characteristics but are, also, tightly connected to each other. Integrative studies of the whole regional oceanic system are scarce and difficult to perform due to the relative large area to cover and the different relevant time-scales of the main forcings in each sub-basin. Here we propose, for the first time, a fully coupled, 3D, hydrodynamic-biogeochemical model that covers, in a single domain (~2km resolution both marine basins for a 20 years simulation (1989-2008. Model performance is assessed against available data in terms of spatial and temporal distributions of biological variables. In general, the proposed model is able to represent the climatological distributions of primary and secondary producers and also the main seasonality of primary production in the different sub-regions of the analyzed basins. Potential causes of the observed mismatches between model and data are identified and some solutions are proposed for future model development. We conclude that most of these mismatches could be attributed to the missing tidal forcing in the actual model configuration. This model is a first step to obtain a meaningful tool to study past and future oceanographic conditions in this important marine region constituting the unique connection of the Mediterranean Sea with the open world’s ocean.

  19. Abiotic/biotic coupling in the rhizosphere: a reactive transport modeling analysis

    Science.gov (United States)

    Lawrence, Corey R.; Steefel, Carl; Maher, Kate

    2014-01-01

    A new generation of models is needed to adequately simulate patterns of soil biogeochemical cycling in response changing global environmental drivers. For example, predicting the influence of climate change on soil organic matter storage and stability requires models capable of addressing complex biotic/abiotic interactions of rhizosphere and weathering processes. Reactive transport modeling provides a powerful framework simulating these interactions and the resulting influence on soil physical and chemical characteristics. Incorporation of organic reactions in an existing reactive transport model framework has yielded novel insights into soil weathering and development but much more work is required to adequately capture root and microbial dynamics in the rhizosphere. This endeavor provides many advantages over traditional soil biogeochemical models but also many challenges.

  20. Stochastic models of intracellular transport

    KAUST Repository

    Bressloff, Paul C.

    2013-01-09

    The interior of a living cell is a crowded, heterogenuous, fluctuating environment. Hence, a major challenge in modeling intracellular transport is to analyze stochastic processes within complex environments. Broadly speaking, there are two basic mechanisms for intracellular transport: passive diffusion and motor-driven active transport. Diffusive transport can be formulated in terms of the motion of an overdamped Brownian particle. On the other hand, active transport requires chemical energy, usually in the form of adenosine triphosphate hydrolysis, and can be direction specific, allowing biomolecules to be transported long distances; this is particularly important in neurons due to their complex geometry. In this review a wide range of analytical methods and models of intracellular transport is presented. In the case of diffusive transport, narrow escape problems, diffusion to a small target, confined and single-file diffusion, homogenization theory, and fractional diffusion are considered. In the case of active transport, Brownian ratchets, random walk models, exclusion processes, random intermittent search processes, quasi-steady-state reduction methods, and mean-field approximations are considered. Applications include receptor trafficking, axonal transport, membrane diffusion, nuclear transport, protein-DNA interactions, virus trafficking, and the self-organization of subcellular structures. © 2013 American Physical Society.

  1. Modelling Ballast Water Transport

    Digital Repository Service at National Institute of Oceanography (India)

    Jayakumar, S.; Babu, M.T.; Vethamony, P.

    Ballast water discharges in the coastal environs have caused a great concern over the recent periods as they account for transporting marine organisms from one part of the world to the other. The movement of discharged ballast water as well...

  2. The influence of winter convection on primary production: A parameterisation using a hydrostatic three-dimensional biogeochemical model

    Science.gov (United States)

    Große, Fabian; Lindemann, Christian; Pätsch, Johannes; Backhaus, Jan O.

    2015-07-01

    In the recent past observational and modelling studies have shown that the vertical displacement of water parcels, and therefore, phytoplankton particles in regions of deep-reaching convection plays a key role in late winter/early spring primary production. The underlying mechanism describes how convection cells capture living phytoplankton cells and recurrently expose them to sunlight. This study presents a parameterisation called 'phytoconvection' which focusses on the influence of convection on primary production. This parameterisation was implemented into a three-dimensional physical-biogeochemical model and applied to the Northwestern European Continental Shelf and areas of the adjacent Northeast Atlantic. The simulation was compared to a 'conventional' parameterisation with respect to its influence on phytoplankton concentrations during the annual cycle and its effect on the carbon cycle. The simulation using the new parameterisation showed good agreement with observation data recorded during winter, whereas the reference simulation did not capture the observed phytoplankton concentrations. The new parameterisation had a strong influence on the carbon export through the sinking of particulate organic carbon. The carbon export during late winter/early spring significantly exceeded the export of the reference run. Furthermore, a non-hydrostatic convection model was used to evaluate the major assumption of the presented parameterisation which implies the matching of the mixed layer depth with the convective mixing depth. The applied mixed layer depth criterion principally overestimates the actual convective mixing depth. However, the results showed that this assumption is reasonable during late winter, while indicating a mismatch during spring.

  3. Biogeochemical Modeling of In Situ U(VI) Reduction and Immobilization with Emulsified Vegetable Oil as the Electron Donor at a Field Site in Oak Ridge, Tennessee

    Science.gov (United States)

    Tang, G.; Parker, J.; Wu, W.; Schadt, C. W.; Watson, D. B.; Brooks, S. C.; Orifrc Team

    2011-12-01

    A comprehensive biogeochemical model was developed to quantitatively describe the coupled hydrologic, geochemical and microbiological processes that occurred following injection of emulsified vegetable oil (EVO) as the electron donor to immobilize U(VI) at the Oak Ridge Integrated Field Research Challenge site (ORIFRC) in Tennessee. The model couples the degradation of EVO, production and oxidation of long-chain fatty acids (LCFA), glycerol, hydrogen and acetate, reduction of nitrate, manganese, ferrous iron, sulfate and uranium, and methanoganesis with growth of multiple microbial groups. The model describes the evolution of geochemistry and microbial populations not only in the aqueous phase as typically observed, but also in the mineral phase and therefore enables us to evaluate the applicability of rates from the literature for field scale assessment, estimate the retention and degradation rates of EVO and LCFA, and assess the influence of the coupled processes on fate and transport of U(VI). Our results suggested that syntrophic bacteria or metal reducers might catalyze LCFA oxidation in the downstream locations when sulfate was consumed, and competition between methanogens and others for electron donors and slow growth of methanogen might contribute to the sustained reducing condition. Among the large amount of hydrologic, geochemical and microbiological parameter values, the initial biomass, and the interactions (e.g., inhibition) of the microbial functional groups, and the rate and extent of Mn and Fe oxide reduction appear as the major sources of uncertainty. Our model provides a platform to conduct numerical experiments to study these interactions, and could be useful for further iterative experimental and modeling investigations into the bioreductive immobiliztion of radionuclide and metal contaminants in the subsurface.

  4. [Seasonal evolution of the biogeochemical cycle in the southwest lagoon of New Caledonia. Application of a compartmental model].

    Science.gov (United States)

    Bujan, S; Grenz, C; Fichez, R; Douillet, P

    2000-02-01

    A biogeochemical box model describing the south-west lagoon of New-Caledonia was developed in order to simulate the seasonal cycle of carbon and nitrogen. We used fluxes generated by a 3D hydrodynamic model to simulate horizontal exchanges between boxes and added freshwater influxes as nitrogen sources from the land. Average residence time proved to be less than 11 days for the lagoon as a whole. Standard simulations showed baseline values of chlorophyll a between 0.2 and 0.4 microgram.L-1. Influences of freshwater influxes proved to be significant (increases up to 1 microgram.L-1) only in shallow areas protected from wind exposure and during short periods of heavy rainfall (tropical depressions). Tropical climatic events have reduced impact in space and time and long-term simulations over decades with increased nutrient inputs did not show any significant process of eutrophication. Hydrodynamics seemed to be one of the major control factors with respect to organic matter cycling in the lagoon. PMID:10763441

  5. Modeling Biogeochemical-Physical Interactions and Carbon Flux in the Sargasso Sea (Bermuda Atlantic Time-series Study site)

    Science.gov (United States)

    Signorini, Sergio R.; McClain, Charles R.; Christian, James R.

    2001-01-01

    An ecosystem-carbon cycle model is used to analyze the biogeochemical-physical interactions and carbon fluxes in the Bermuda Atlantic Time-series Study (BATS) site for the period of 1992-1998. The model results compare well with observations (most variables are within 8% of observed values). The sea-air flux ranges from -0.32 to -0.50 mol C/sq m/yr, depending upon the gas transfer algorithm used. This estimate is within the range (-0.22 to -0.83 mol C/sq m/yr) of previously reported values which indicates that the BATS region is a weak sink of atmospheric CO2. The overall carbon balance consists of atmospheric CO2 uptake of 0.3 Mol C/sq m/yr, upward dissolved inorganic carbon (DIC) bottom flux of 1.1 Mol C/sq m/yr, and carbon export of 1.4 mol C/sq m/yr via sedimentation. Upper ocean DIC levels increased between 1992 and 1996 at a rate of approximately 1.2 (micro)mol/kg/yr, consistent with observations. However, this trend was reversed during 1997-1998 to -2.7 (micro)mol/kg/yr in response to hydrographic changes imposed by the El Nino-La Nina transition, which were manifested in the Sargasso Sea by the warmest SST and lowest surface salinity of the period (1992-1998).

  6. Calibration of a biome-biogeochemical cycles model for modeling the net primary production of teak forests through inverse modeling of remotely sensed data

    Science.gov (United States)

    Imvitthaya, Chomchid; Honda, Kiyoshi; Lertlum, Surat; Tangtham, Nipon

    2011-01-01

    In this paper, we present the results of a net primary production (NPP) modeling of teak (Tectona grandis Lin F.), an important species in tropical deciduous forests. The biome-biogeochemical cycles or Biome-BGC model was calibrated to estimate net NPP through the inverse modeling approach. A genetic algorithm (GA) was linked with Biome-BGC to determine the optimal ecophysiological model parameters. The Biome-BGC was calibrated by adjusting the ecophysiological model parameters to fit the simulated LAI to the satellite LAI (SPOT-Vegetation), and the best fitness confirmed the high accuracy of generated ecophysioligical parameter from GA. The modeled NPP, using optimized parameters from GA as input data, was evaluated using daily NPP derived by the MODIS satellite and the annual field data in northern Thailand. The results showed that NPP obtained using the optimized ecophysiological parameters were more accurate than those obtained using default literature parameterization. This improvement occurred mainly because the model's optimized parameters reduced the bias by reducing systematic underestimation in the model. These Biome-BGC results can be effectively applied in teak forests in tropical areas. The study proposes a more effective method of using GA to determine ecophysiological parameters at the site level and represents a first step toward the analysis of the carbon budget of teak plantations at the regional scale.

  7. A dynamic marine iron cycle module coupled to the University of Victoria Earth System Model: the Kiel Marine Biogeochemical Model 2 (KMBM2 for UVic 2.9

    Directory of Open Access Journals (Sweden)

    L. Nickelsen

    2014-12-01

    Full Text Available Marine biological production and the associated biotic uptake of carbon in many ocean regions depend on the availability of nutrients in the euphotic zone. While large areas are limited by nitrogen and/or phosphorus, the micronutrient iron is considered the main limiting nutrient in the North Pacific, equatorial Pacific and Southern Ocean. Changes in iron availability via changes in atmospheric dust input are discussed to play an important role in glacial/interglacial cycles via climate feedbacks caused by changes in biological ocean carbon sequestration. Although many aspects of the iron cycle remain unknown, its incorporation into marine biogeochemical models is needed to test our current understanding and better constrain its role in the Earth system. In the University of Victoria Earth System Climate Model (UVic iron limitation in the ocean was, until now, simulated pragmatically with an iron concentration masking scheme that did not allow a consistent interactive response to perturbations of ocean biogeochemistry or iron cycling sensitivity studies. Here, we replace the iron masking scheme with a dynamic iron cycle and compare the results to available observations and the previous marine biogeochemical model. Sensitivity studies are also conducted with the new model to test the importance of considering the variable solubility of iron in dust deposition, the importance of considering high resolution bathymetry for the sediment release of iron, the effect of scaling the sedimentary iron release with temperature and the sensitivity of the iron cycle to a climate change scenario.

  8. Compilation of a global N{sub 2}O emission inventory for tropical rainforest soils using a detailed biogeochemical model

    Energy Technology Data Exchange (ETDEWEB)

    Werner, C.

    2007-09-15

    Nitrous oxide (N{sub 2}O) is a potent trace gas contributing to approximately 6% to the observed anthropogenic global warming. Soils have been identified to be the major source of atmospheric N{sub 2}O and tropical rainforest soils are thought to account for the largest part. Furthermore, various studies have shown that the magnitude of N{sub 2}O emissions from tropical rainforest soil is highly variable on spatial and temporal scales. Detailed, process-based models coupled to Geographic Information Systems (GIS) are considered promising tools for the calculation of N{sub 2}O emission inventories. This methodology explicitly accounts for the governing microbial processes as well as the environmental controls. Moreover, mechanistic biogeochemical models operating in daily time-steps (e.g. ForestDNDC-tropica) have been shown to capture the observed intra- and inter-annual variations of N{sub 2}O emissions. However, detailed N{sub 2}O emission datasets are required for model calibration and testing, but are currently few in numbers. In this study an automated measurement system was used to derive detailed datasets of N{sub 2}O, methane (CH{sub 4}) and carbon dioxide (CO{sub 2}) soil-atmosphere exchange and important environmental parameters from tropical rainforest soils in Kenya and Southwest China. Distinct differences were identified in the magnitude of the C and N soil-atmosphere exchange at the investigated sites and forest types. However, common features such as N{sub 2}O pulse emissions after dry season or the pronounced soil moisture dependency of N{sub 2}O emissions were observed at both sites. The derived datasets are unique for these tropical regions as so far no information about the source strength of these regions was available and, for the first time, the N{sub 2}O, CH{sub 4} and CO{sub 2} soil-atmosphere exchange was recorded in sub-daily resolution. The datasets were utilized in conjunction with available high-resolution datasets from Australian

  9. The Effects of Chlorophyll Assimilation on Carbon Fluxes in a Global Biogeochemical Model. [Technical Report Series on Global Modeling and Data Assimilation

    Science.gov (United States)

    Koster, Randal D. (Editor); Rousseaux, Cecile Severine; Gregg, Watson W.

    2014-01-01

    In this paper, we investigated whether the assimilation of remotely-sensed chlorophyll data can improve the estimates of air-sea carbon dioxide fluxes (FCO2). Using a global, established biogeochemical model (NASA Ocean Biogeochemical Model, NOBM) for the period 2003-2010, we found that the global FCO2 values produced in the free-run and after assimilation were within -0.6 mol C m(sup -2) y(sup -1) of the observations. The effect of satellite chlorophyll assimilation was assessed in 12 major oceanographic regions. The region with the highest bias was the North Atlantic. Here the model underestimated the fluxes by 1.4 mol C m(sup -2) y(sup -1) whereas all the other regions were within 1 mol C m(sup -2) y(sup -1) of the data. The FCO2 values were not strongly impacted by the assimilation, and the uncertainty in FCO2 was not decreased, despite the decrease in the uncertainty in chlorophyll concentration. Chlorophyll concentrations were within approximately 25% of the database in 7 out of the 12 regions, and the assimilation improved the chlorophyll concentration in the regions with the highest bias by 10-20%. These results suggest that the assimilation of chlorophyll data does not considerably improve FCO2 estimates and that other components of the carbon cycle play a role that could further improve our FCO2 estimates.

  10. A coupled hydrologic and biogeochemical model for assessing watershed responses to climate and land use

    Science.gov (United States)

    This seminar for Oregon State University’s Water Resources Graduate Program will describe the use of a spatially-distributed ecohydrological model, VELMA, for quantifying how alternative land use and climate scenarios affect tradeoffs among important ecosystem services. Sp...

  11. Subsurface Biogeochemical Research FY11 Second Quarter Performance Measure

    Energy Technology Data Exchange (ETDEWEB)

    Scheibe, Timothy D.

    2011-03-31

    The Subsurface Biogeochemical Research (SBR) Long Term Measure for 2011 under the Performance Assessment Rating Tool (PART) measure is to "Refine subsurface transport models by developing computational methods to link important processes impacting contaminant transport at smaller scales to the field scale." The second quarter performance measure is to "Provide a report on computational methods linking genome-enabled understanding of microbial metabolism with reactive transport models to describe processes impacting contaminant transport in the subsurface." Microorganisms such as bacteria are by definition small (typically on the order of a micron in size), and their behavior is controlled by their local biogeochemical environment (typically within a single pore or a biofilm on a grain surface, on the order of tens of microns in size). However, their metabolic activity exerts strong influence on the transport and fate of groundwater contaminants of significant concern at DOE sites, in contaminant plumes with spatial extents of meters to kilometers. This report describes progress and key findings from research aimed at integrating models of microbial metabolism based on genomic information (small scale) with models of contaminant fate and transport in aquifers (field scale).

  12. Quantification of sediment-water interactions in a polluted tropical river through biogeochemical modeling

    Science.gov (United States)

    Trinh, Anh Duc; Meysman, Filip; Rochelle-Newall, Emma; Bonnet, Marie Paule

    2012-09-01

    Diagenetic modeling presents an interesting and robust way to understand sediment-water column processes. Here we present the application of such a model to the Day River in Northern Vietnam, a system that is subject to high levels of domestic wastewater inputs from the Hanoi metropolitan area. Experimental data from three areas of different water and sediment quality, combined with some additional data from the river, are used to set up and calibrate a diagenetic model. The model was used to determine the role of the sediments as a sink for carbon and nutrients and shows that in the dry season, 27% of nitrogen, 25% of carbon, and 38% of phosphorus inputs into the river system are stored in sediments. The corresponding numbers during the rainy season are 15%, 10%, and 20%, respectively. The diagenetic model was then used to test the impact of an improvement in the treatment of Hanoi's municipal wastewater. We show that improved wastewater treatment could reduce by about 17.5% the load of organic matter to the sediment. These results are the first to highlight the importance of sediments as a potential removal mechanism of organic matter and nutrients from the water column in this type of highly impacted tropical urban river, further demonstrating that rivers need to be considered as reaction sites and not just as inert conduits.

  13. Modelling shelf-ocean exchange and its biogeochemical consequences in coastal upwelling systems

    DEFF Research Database (Denmark)

    Muchamad, Al Azhar

    remineralization associated with nitrate reduction to nitrite. Secondly, the coupled model was used to simulate upwelling and iogeochemical cycles associated with different continental shelf geometries. In particular the generalized effect of shelf width was investigated. Anoxic/euxinic conditions in bottom waters...... active but cryptic sulfur cycle possibly is coupled to the nitrogen cycle in an oxygen-minimum-zone (OMZ), 2) what is the relation between the shelf–ocean exchange, continental shelf width and development of the observed bottom water anoxia/euxinia associated with different configurations of continental...... calibrated to reproduce the observed coupling between nitrogen and sulfur cycles in OMZ of the northern Chile upwelling systems. The model results show that sulfate reduction contribute significantly to organic matter remineralization in the OMZ water depths, along with nitrate reduction. In the model...

  14. Biogeochemical factors affecting the distribution, speciation, and transport of Hg species in the Deûle and Lys Rivers (Northern France).

    Science.gov (United States)

    Daye, Mirna; Kadlecova, Milada; Ouddane, Baghdad

    2015-02-01

    The Deûle River is a highly polluted River by heavy metals caused by the historical discharges of ore minerals from the former ore smelter "Metaleurop." The potential mercury (Hg) pollution in the Deûle River implicates the importance of Hg distribution study in the river. As well as to configure the different biogeochemical factors that control the distribution and the potential transport of Hg to distant places. Four different sites were studied as follows: D-A (Deûle River, a site located upstream the river), D-B (Deûle River, a site located near a Zn, Pb, Cu, and Ni smelter that closed in 2003), L-C (Lys River, a site located upstream the confluence of the Deûle River with Lys River), and L-D (downstream the rivers confluence). Different Hg analyses were performed including total mercury in sediment (HgTS), methylmercury (MeHg) in sediment, total mercury in pore water (HgTPW), total mercury in surface water (HgTD), and total suspended particulate Hg in water (HgTP). HgTS decreases downstream from the Deûle River sites with a mean value of 11 ± 0.34 mg/kg to Lys River site (L-D) with a mean value of 0.53 ± 0.02 mg/kg at the confluence. The unaffected side of the Lys River, localized before the confluence (L-C), is characterized by low HgTS of an average value of 0.042 ± 0.003 mg/kg and high % MeHg reaching 4.2 %. Whereas, the highly contaminated Deûle sites are designated by low % MeHg with an average value of 0.053 %. Low pristine environments like that found in L-C site with more favorable biogeochemical conditions of lower concentrations of HgTS, sulfides, and Corg host more active biotic methylation than that of the highly polluted Deûle sites with high concentrations of HgTS and sulfides concentrations. Methylation in D-B (the closet site to Metaleurop smelter) is an old and recent methylation activity that has contributed to MeHg accumulation in the sediments as opposed to the exclusive recent events of methylation in Lys sites. Me

  15. A Hierarchical Bayesian Model for Estimating Remediation-induced Biogeochemical Transformations Using Spectral Induced Polarization Data: Development and Application to the Contaminated DOE Rifle (CO) Site

    Science.gov (United States)

    Chen, J.; Hubbard, S. S.; Williams, K. H.; Tuglus, C.; Flores-Orozco, A.; Kemna, A.

    2010-12-01

    Although in-situ bioremediation is often considered as a key approach for subsurface environmental remediation, monitoring induced biogeochemical processes, needed to evaluate the efficacy of the treatments, is challenging over field relevant scales. In this study, we develop a hierarchical Bayesian model that builds on our previous framework for estimating biogeochemical transformations using geochemical and geophysical data obtained from laboratory column experiments. The new Bayesian model treats the induced biogeochemical transformations as both spatial and temporal (rather than just temporal) processes and combines time-lapse borehole ‘point’ geochemical measurements with inverted surface- or crosshole-based spectral induced polarization (SIP) data. This model consists of three levels of statistical sub-models: (1) data model (or likelihood function), which provides links between the biogeochemical end-products and geophysical attributes, (2) process model, which describes the spatial and temporal variability of biogeochemical properties in the disturbed subsurface systems, and (3) parameter model, which describes the prior distributions of various parameters and initial conditions. The joint posterior probability distribution is explored using Markov Chain Monte Carlo sampling methods to obtain the spatial and temporal distribution of the hidden parameters. We apply the developed Bayesian model to the datasets collected from the uranium-contaminated DOE Rifle site for estimating the spatial and temporal distribution of remediation-induced end products. The datasets consist of time-lapse wellbore aqueous geochemical parameters (including Fe(II), sulfate, sulfide, acetate, uranium, chloride, and bromide concentrations) and surface SIP data collected over 13 frequencies (ranging from 0.065Hz to 256Hz). We first perform statistical analysis on the multivariate data to identify possible patterns (or ‘diagnostic signatures’) of bioremediation, and then we

  16. Capturing optically important constituents and properties in a marine biogeochemical and ecosystem model

    Directory of Open Access Journals (Sweden)

    S. Dutkiewicz

    2015-07-01

    This new model that captures bio-optical feedbacks will be important for improving our understanding of the role of light and optical constituents on ocean biogeochemistry, especially in a changing environment. Further, resolving surface upwelling irradiance will make it easier to connect to satellite-derived products in the future.

  17. Probabilistic Downscaling of Remote Sensing Data with Applications for Multi-Scale Biogeochemical Flux Modeling

    OpenAIRE

    Stoy, Paul C.; Quaife, Tristan

    2015-01-01

    Upscaling ecological information to larger scales in space and downscaling remote sensing observations or model simulations to finer scales remain grand challenges in Earth system science. Downscaling often involves inferring subgrid information from coarse-scale data, and such ill-posed problems are classically addressed using regularization. Here, we apply two-dimensional Tikhonov Regularization (2DTR) to simulate subgrid surface patterns for ecological applications. Specifically, we test t...

  18. Reconstructing paleo-ocean silicon chemistry and ecology during Last Glacial Maximum, a biogeochemical cycle modeling approach

    Science.gov (United States)

    Li, D. D.; Lerman, A.; Mackenzie, F. T.

    2012-12-01

    It has been established by a number of investigators that opal content and Si-C isotope studies in the marine sediments reveal information about paleooceanography and the impact on silicic acid utilization by marine autotrophes (diatoms, silicoflagellates) and heterotrophes (radiolarians) during the Last Glacial Maximum (LGM). Opal, as an amorphous form of SiO2, formed by marine Si-secreting organisms, has been used as a proxy to indicate chemical ocean evolution, paleoproductivity and temperature variations in the paleoenvironment and regional ocean water biogeochemical studies, both on million- and thousand-year scales. Here, we are using a model of the global silicon biogeochemical cycle to understand and reconstruct evolutionary history of the paleobiogeochemical cycle and paleoenvironment since LGM. The model is process-driven, temperature-driven, and land-ocean-sediment coupled with specific marine Si-secreting organisms that represent different trophic levels and physiological mechanisms. Specifically, Si utilization by marine silicoflagellates and radiolarians are each about 5% of that of ubiquitous marine diatoms. Available marine reactive Si is controlled by variation of diatom bioproduction that represents 5% of the total marine primary productivity (Si/C Redfield ratio in the marine organic matter is ~0.13, which is an order of magnitude higher than ratio in land organic matter). River input of Si is controlled by chemical weathering of silicate rocks and biocyling of land plant phytoliths. Decreasing dissolved and particulate Si input from land and less favorable climatic condition into LGM diminished the primary production of marine diatoms. However, because radiolarians favor deep-water habitat, where a higher level of DSi is found and that is less affected by temperature changes, a peak of relative abundance is usually observed in sedimentary record during LGM. Given that opal formation fractionated seawater δ30Si (1‰) and enriched seawater with

  19. Soil Biogeochemical Properties and Erosion Source Prediction Model Summary for the Buffalo Bayou Watershed, Houston, Texas

    Science.gov (United States)

    Ahmed, I.

    2015-12-01

    We draw conclusions on the research output and findings from a 4-year multidisciplinary USDA-CBG collaborative program in sustainable integrated monitoring of soil organic carbon (SOC) loss prediction via erosion. The underlying method uses the state-of-the-art stable isotope science of sediment tracing under uncertain hydrologic influences. The research finds are rooted in the (i) application of Bayesian Markov Chain Monte Carlo statistical models to assess the relationship between rainfall-runoff and soil erosion in space and time, (ii) capture of the episodic nature of rainfall events and its role in the spatial distribution of SOC loss from water erosion, (iii) stable isotope composition guided fingerprinting (source and quantity) of eroded soil, and (iv) the creation of an integrated watershed scale statistical soil loss monitoring model driven by spatial and temporal correlation of flow and stable isotope composition. The research theme was successfully applied on the urbanized Buffalo Bayou Watershed in Houston, Texas. The application brought to light novel future research conceptual outlines which will also be discussed in this deliverable to the AGU meeting. These include but not limited to: regional rainfall cluster research, physics of muddy river-bank soil and suspended sediment interaction, and friction & mobility that together make up the plasticity of soil aggregates that control erosion processes and landscape changes in a riparian corridor. References: Ahmed, I., Karim, A., Boutton, T.W., and Strom, K.B. (2013a). "Monitoring Soil Organic Carbon Loss from Erosion Using Stable Isotopes." Proc., Soil Carbon Sequestration, International Conference, May 26-29, Reykjavik, Iceland. Ahmed, I, Bouttom, T.W., Strom, K. B., Karim, A., and Irvin-Smith, N. (2013b). "Soil carbon distribution and loss monitoring in the urbanized Buffalo Bayou watershed, Houston, Texas." Proc., 4th Annual All Investigators Meeting of the North American Carbon Program, February 4

  20. Modeling physical and biogeochemical controls over carbon accumulation in a boreal forest soil

    Science.gov (United States)

    Carrasco, J.J.; Neff, J.C.; Harden, J.W.

    2006-01-01

    Boreal soils are important to the global C cycle owing to large C stocks, repeated disturbance from fire, and the potential for permafrost thaw to expose previously stable, buried C. To evaluate the primary mechanisms responsible for both short- and long-term C accumulation in boreal soils, we developed a multi-isotope (12,14C) Soil C model with dynamic soil layers that develop through time as soil organic matter burns and reaccumulates. We then evaluated the mechanisms that control organic matter turnover in boreal regions including carbon input rates, substrate recalcitrance, soil moisture and temperature, and the presence of historical permafrost to assess the importance of these factors in boreal C accumulation. Results indicate that total C accumulation is controlled by the rate of carbon input, decomposition rates, and the presence of historical permafrost. However, unlike more temperate ecosystems, one of the key mechanisms involved in C preservation in boreal soils examined here is the cooling of subsurface soil layers as soil depth increases rather than increasing recalcitrance in subsurface soils. The propagation of the 14C bomb spike into soils also illustrates the importance of historical permafrost and twentieth century warming in contemporary boreal soil respiration fluxes. Both 14C and total C simulation data also strongly suggest that boreal SOM need not be recalcitrant to accumulate; the strong role of soil temperature controls on boreal C accumulation at our modeling test site in Manitoba, Canada, indicates that carbon in the deep organic soil horizons is probably relatively labile and thus subject to perturbations that result from changing climatic conditions in the future. Copyright 2006 by the American Geophysical Union.

  1. Quantification of nitrate leaching from German forest ecosystems by use of a process oriented biogeochemical model

    International Nuclear Information System (INIS)

    Simulations with the process oriented Forest-DNDC model showed reasonable to good agreement with observations of soil water contents of different soil layers, annual amounts of seepage water and approximated rates of nitrate leaching at 79 sites across Germany. Following site evaluation, Forest-DNDC was coupled to a GIS to assess nitrate leaching from German forest ecosystems for the year 2000. At national scale leaching rates varied in a range of 0->80 kg NO3-N ha-1 yr-1 (mean 5.5 kg NO3-N ha-1 yr-1). A comparison of regional simulations with the results of a nitrate inventory study for Bavaria showed that measured and simulated percentages for different nitrate leaching classes (0-5 kg N ha-1 yr-1:66% vs. 74%, 5-15 kg N ha-1 yr-1:20% vs. 20%, >15 kg N ha-1 yr-1:14% vs. 6%) were in good agreement. Mean nitrate concentrations in seepage water ranged between 0 and 23 mg NO3-N l-1. - Highlights: → Forest-DNDC was successfully tested for prediction of annual NO3 leaching rates. → Coupled to GIS it generated regional estimates of NO3 leaching for German forests. → At national scale rates varied in a range of 0->80 (mean 5.5) kg NO3-N ha-1 yr-1. → Mean NO3 concentrations in seepage water were between 0 and 23 mg NO3-N l-1. → Indication of potential risk for groundwater pollution and plant biodiversity. - The Forest-DNDC model is tested on observations at nearly 80 sites and then used to quantify nitrate leaching from German forest ecosystems

  2. Next Generation Transport Phenomenology Model

    Science.gov (United States)

    Strickland, Douglas J.; Knight, Harold; Evans, J. Scott

    2004-01-01

    This report describes the progress made in Quarter 3 of Contract Year 3 on the development of Aeronomy Phenomenology Modeling Tool (APMT), an open-source, component-based, client-server architecture for distributed modeling, analysis, and simulation activities focused on electron and photon transport for general atmospheres. In the past quarter, column emission rate computations were implemented in Java, preexisting Fortran programs for computing synthetic spectra were embedded into APMT through Java wrappers, and work began on a web-based user interface for setting input parameters and running the photoelectron and auroral electron transport models.

  3. THE SEASONAL CYCLE OF SURFACE CHLOROPHYLL ALONG THE PERUVIAN COAST: COMPARISON BETWEEN SEAWIFS SATELLITE OBSERVATIONS AND DYNAMICAL/BIOGEOCHEMICAL COUPLED MODEL SIMULATIONS

    Directory of Open Access Journals (Sweden)

    Vincent Echevin

    2004-01-01

    Full Text Available The seasonal cycle of surface chlorophyll along the Peruvian coasts is studied with SeaWiFS satellite observations and coupled dynamical/biogeochemical ORCA/PISCES model simulations. The observed mean spatial structure of surface chlorophyll is shown to be in good agreement with that of the model. However the seasonal cycles contrast: whereas the model produces a spring bloom consistent with maximum upwelling and deepest mixed layer in the winter season, the observed seasonal cycle shows two distinct blooms one in late spring-early summer and other in fall. Several hypotheses are suggested to explain the fall bloom and its non-occurrence in the model

  4. Probabilistic Downscaling of Remote Sensing Data with Applications for Multi-Scale Biogeochemical Flux Modeling.

    Science.gov (United States)

    Stoy, Paul C; Quaife, Tristan

    2015-01-01

    Upscaling ecological information to larger scales in space and downscaling remote sensing observations or model simulations to finer scales remain grand challenges in Earth system science. Downscaling often involves inferring subgrid information from coarse-scale data, and such ill-posed problems are classically addressed using regularization. Here, we apply two-dimensional Tikhonov Regularization (2DTR) to simulate subgrid surface patterns for ecological applications. Specifically, we test the ability of 2DTR to simulate the spatial statistics of high-resolution (4 m) remote sensing observations of the normalized difference vegetation index (NDVI) in a tundra landscape. We find that the 2DTR approach as applied here can capture the major mode of spatial variability of the high-resolution information, but not multiple modes of spatial variability, and that the Lagrange multiplier (γ) used to impose the condition of smoothness across space is related to the range of the experimental semivariogram. We used observed and 2DTR-simulated maps of NDVI to estimate landscape-level leaf area index (LAI) and gross primary productivity (GPP). NDVI maps simulated using a γ value that approximates the range of observed NDVI result in a landscape-level GPP estimate that differs by ca 2% from those created using observed NDVI. Following findings that GPP per unit LAI is lower near vegetation patch edges, we simulated vegetation patch edges using multiple approaches and found that simulated GPP declined by up to 12% as a result. 2DTR can generate random landscapes rapidly and can be applied to disaggregate ecological information and compare of spatial observations against simulated landscapes. PMID:26067835

  5. Modelling of reactive gas transport

    OpenAIRE

    Sundelöf, Erik

    2003-01-01

    A rather general microscopic model for reactive gastransport in porous media is developed and applied to twodifferent processes in powder metal technology: carburization,and reduction of surface oxides. The carburization model is developed from the kinetic modelproposed by Grabke and applied to a 2-D porous geometryobtained from images. The effect of pore geometry on convectiveand diffusive transport is discussed by model problems andaveraging. The exercise demonstrates the capacity of theFEM...

  6. A Windowed Transportation Planning Model

    OpenAIRE

    David Levinson; Yuanlin Huang

    1997-01-01

    This research develops and applies a transportation planning model that integrates regional and local area forecasting approaches. While regional models have the scope to model the interaction of demand and congestion, they lack the spatial detail of a local approach. Local approaches typically do not consider the feedback between new project traffic and existing levels of traffic. Using a window, which retains the regional trip distribution information and the consistency between travel dema...

  7. Modelling of transport and biogeochemical processes in pollution plumes: Vejen landfill, Denmark

    DEFF Research Database (Denmark)

    Brun, A.; Engesgaard, Peter Knudegaard; Christensen, Thomas Højlund; Rosbjerg, Dan

    in the plume of a number of species. such as dissolved organic carbon (DOC), Fe2+, NO3-, HCO3-, SO42-, CH4, and pH. The simulated redox zones agree with observations confirming that the Fe-reducing zone played an important role in the attenuation of the DOC plume. Effective first-order rate constants...

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

    Science.gov (United States)

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

  9. PHT3D-UZF: A Reactive Transport Model for Variably-Saturated Porous Media.

    Science.gov (United States)

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

    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. PMID:25628017

  10. Energy-transport models for spin transport in ferromagnetic semiconductors

    OpenAIRE

    Jüngel, Ansgar; Shpartko, Polina; Zamponi, Nicola

    2016-01-01

    Explicit energy-transport equations for the spinorial carrier transport in ferromagnetic semiconductors are calculated from a general spin energy-transport system that was derived by Ben Abdallah and El Hajj from a spinorial Boltzmann equation. The novelty of our approach are the simplifying assumptions leading to explicit models which extend both spin drift-diffusion and semiclassical energy-transport equations. The explicit models allow us to examine the interplay between the spin and charg...

  11. MEDUSA-2.0: an intermediate complexity biogeochemical model of the marine carbon cycle for climate change and ocean acidification studies

    Directory of Open Access Journals (Sweden)

    A. Yool

    2013-02-01

    Full Text Available MEDUSA-1.0 (Model of Ecosystem Dynamics, nutrient Utilisation, Sequestration and Acidification was developed as an "intermediate complexity" plankton ecosystem model to study the biogeochemical response, and especially that of the so-called "biological pump", to anthropogenically-driven change in the World Ocean (Yool et al., 2011. The base currency in this model was nitrogen from which fluxes of organic carbon, including export to the deep ocean, were calculated by invoking fixed C:N ratios in phytoplankton, zooplankton and detritus. Since the beginning of the industrial era, the atmospheric concentration of carbon dioxide (CO2 has significantly increased above its natural, inter-glacial background concentration. Simulating and predicting the carbon cycle in the ocean in its entirety, including ventilation of CO2 with the atmosphere and the resulting impact of ocean acidification on marine ecosystems, therefore requires that both organic and inorganic carbon be afforded a full representation in the model specification. Here, we introduce MEDUSA-2.0, an expanded successor model which includes additional state variables for dissolved inorganic carbon, alkalinity, dissolved oxygen and detritus carbon (permitting variable C:N in exported organic matter, as well as a simple benthic formulation and extended parameterisations of phytoplankton growth, calcification and detritus remineralisation. A full description of MEDUSA-2.0, including its additional functionality, is provided and a multi-decadal hindcast simulation described (1860–2005, to evaluate the biogeochemical performance of the model.

  12. Performance and results of the high-resolution biogeochemical model PELAGOS025 v1.0 within NEMO v3.4

    Science.gov (United States)

    Epicoco, Italo; Mocavero, Silvia; Macchia, Francesca; Vichi, Marcello; Lovato, Tomas; Masina, Simona; Aloisio, Giovanni

    2016-06-01

    The present work aims at evaluating the scalability performance of a high-resolution global ocean biogeochemistry model (PELAGOS025) on massive parallel architectures and the benefits in terms of the time-to-solution reduction. PELAGOS025 is an on-line coupling between the Nucleus for the European Modelling of the Ocean (NEMO) physical ocean model and the Biogeochemical Flux Model (BFM) biogeochemical model. Both the models use a parallel domain decomposition along the horizontal dimension. The parallelisation is based on the message passing paradigm. The performance analysis has been done on two parallel architectures, an IBM BlueGene/Q at ALCF (Argonne Leadership Computing Facilities) and an IBM iDataPlex with Sandy Bridge processors at the CMCC (Euro Mediterranean Center on Climate Change). The outcome of the analysis demonstrated that the lack of scalability is due to several factors such as the I/O operations, the memory contention, the load unbalancing due to the memory structure of the BFM component and, for the BlueGene/Q, the absence of a hybrid parallelisation approach.

  13. System Convergence in Transport Modelling

    DEFF Research Database (Denmark)

    Rich, Jeppe; Nielsen, Otto Anker; Cantarella, Guilio E.

    2010-01-01

    level-of-service attributes (e.g., travel time and cost) offered to travellers. An important source of complexity is the congestion, which causes increasing demand to affect travel time in a non-linear way. Transport models most often involve separate models for traffic assignment and demand modelling....... As a result, two different equilibrium mechanisms are involved, (i) the internal traffic assignment equilibrium, and (ii) the external equilibrium loop between the assignment model and the demand model. Traditionally, there has been much research focus on the internal assignment equilibrium, which...... involves iterating between a route-choice (demand) model and a time-flow (supply) model. It is generally recognised that a simple iteration scheme where the level-of-service level is fed directly to the route-choice and vice versa may exhibit an unstable pattern and lead to cyclic unstable solutions. It...

  14. Anisotropic Mesoscale Eddy Transport in Ocean General Circulation Models

    Science.gov (United States)

    Reckinger, S. J.; Fox-Kemper, B.; Bachman, S.; Bryan, F.; Dennis, J.; Danabasoglu, G.

    2014-12-01

    Modern climate models are limited to coarse-resolution representations of large-scale ocean circulation that rely on parameterizations for mesoscale eddies. The effects of eddies are typically introduced by relating subgrid eddy fluxes to the resolved gradients of buoyancy or other tracers, where the proportionality is, in general, governed by an eddy transport tensor. The symmetric part of the tensor, which represents the diffusive effects of mesoscale eddies, is universally treated isotropically in general circulation models. Thus, only a single parameter, namely the eddy diffusivity, is used at each spatial and temporal location to impart the influence of mesoscale eddies on the resolved flow. However, the diffusive processes that the parameterization approximates, such as shear dispersion, potential vorticity barriers, oceanic turbulence, and instabilities, typically have strongly anisotropic characteristics. Generalizing the eddy diffusivity tensor for anisotropy extends the number of parameters to three: a major diffusivity, a minor diffusivity, and the principal axis of alignment. The Community Earth System Model (CESM) with the anisotropic eddy parameterization is used to test various choices for the newly introduced parameters, which are motivated by observations and the eddy transport tensor diagnosed from high resolution simulations. Simply setting the ratio of major to minor diffusivities to a value of five globally, while aligning the major axis along the flow direction, improves biogeochemical tracer ventilation and reduces global temperature and salinity biases. These effects can be improved even further by parameterizing the anisotropic transport mechanisms in the ocean.

  15. Biogeochemical investigations on processes affecting the transport behaviour of trace elements in the tidal Elbe River; Biogeochemische Prozessuntersuchungen zum Transportverhalten von Spurenelementen in der Tide-Elbe

    Energy Technology Data Exchange (ETDEWEB)

    Hennies, K. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Gewaesserphysik

    1997-12-31

    This work concentrates on distribution and transport of micropollutants in anthropogenically affected estuary systems. Choosing the tidal Elbe River as an example, the influence of microlagae on two important partial processes of the transport regime, the remobilization (a) from undisturbed sediments and (b) from suspended particulate matter, was simulated and quantified in the laboratory. Benthic and planktonic release of Cd, Cu, Pb and Zn into the dissolved phase of the river pelagial were estimated and comparatively evaluated for summer/late summer situation. During that season natural decomposition of suspended particulate matter in the water column thus represents the quantitatively most significant mobilization pathway for particle bound heavy metals in the river section between Hamburg and Glueckstadt. Knowing the composition and heavy metal load of suspended particulate matter, rich in algae, mobilization rates can consequently be calculated for the water column with regard to conditions typical for estuaries. The prognosis of the differing transport behaviour of single heavy metals for greater sections of estuaries is also possible if these rates are implemented into transport-reaction models. (orig.) [Deutsch] Die vorliegende Arbeit befasst sich mit Verteilung und Transport von Spurenschadstoffen in anthropogen belasteten Aestuarsystemen. Am Beispiel der Tide-Elbe wurde der Einfluss von Mikroalgen auf zwei wichtige Teilprozesse des Transportregimes, die Remobilisierung (a) aus ungestoerten Sedimenten und (b) aus suspendierten Schwebstoffen, im Labor simuliert und quantifiziert. Benthische und planktische Freisetzung von Cd, Cu, Pb und Zn in die Loesungsphase des Flusspelagials der Tide-Elbe wurden fuer die Sommer-/Spaetsommer-Situation abgeschaetzt und vergleichend bewertet. Der natuerliche Schwebstoff-Abbau in der Wassersaeule stellt demnach in dieser Jahreszeit im Stromabschnitt zwischen Hamburg und Glueckstadt den quantitativ bedeutsamsten

  16. Linking spatially distributed biogeochemical data with a two-host life-cycle pathogen:A model of whirling disease dynamics in salmonid fishes in the Intermountain West

    Science.gov (United States)

    Fytilis, N.; Lamb, R.; Stevens, L.; Morrissey, L. A.; Kerans, B.; Rizzo, D. M.

    2010-12-01

    Fish diseases are often caused by waterborne parasites, making them ideal systems for modeling the non-linear relationships between biogeochemical features and disease dynamics. Myxobolus cerebralis, the causative agent of whirling disease, has been a major contributor to the loss of wild rainbow trout populations in numerous streams within the Intermountain West (Colorado, Idaho, Montana, Utah, Wyoming). The parasite alternates between an invertebrate and vertebrate host, being transmitted between the sediment feeding worm T.Tubifex and salmonid fishes. A greater understanding of the linkage between biological stream integrity, geomorphic features, water quality parameters and whirling disease risk is needed to improve current management techniques. Biodiversity and abundance of the worm communities are influenced by biogeochemical features and linked to disease severity in fish. We collected and identified ~700 worms from eight sites using molecular genetic probes and a taxonomic key. Additionally, ~1700 worms were identified using only a taxonomic key. Our work examines the links between worm community structure and biogeochemical features. We use a modified Self-Organizing-Map (SOM), which is a non-parametric clustering method based on an artificial neural network (ANN). Clustering methods are particularly attractive for exploratory data analyses because they do not require either the target number of groupings or the data structure be specified at the outset. ANN clustering methods have been shown to be more robust and to account for more data variability than traditional methods when applied to clustering geo-hydrochemical and microbiological datasets. The SOM highlights spatial variation of worm community structure between sites; and is used in tandem with expert knowledge (Lamb and Kerans) of local worm communities and a Madison River, MT physiochemical dataset (GIS-derived layers, water quality parameters). We iteratively clustered the physiochemical data

  17. Evaluating the ocean biogeochemical components of earth system models using atmospheric potential oxygen (APO and ocean color data

    Directory of Open Access Journals (Sweden)

    C. D. Nevison

    2014-06-01

    Full Text Available The observed seasonal cycles in atmospheric potential oxygen (APO at a range of mid to high latitude surface monitoring sites are compared to those inferred from the output of 6 Earth System Models participating in the fifth phase of the Coupled Model Intercomparison Project (CMIP5. The simulated air–sea O2 fluxes are translated into APO seasonal cycles using a matrix method that takes into account atmospheric transport model (ATM uncertainty among 13 different ATMs. Half of the ocean biogeochemistry models tested are able to reproduce the observed APO cycles at most sites, to within the current large ATM uncertainty, while the other half generally are not. Net Primary Production (NPP and net community production (NCP, as estimated from satellite ocean color data, provide additional constraints, albeit more with respect to the seasonal phasing of ocean model productivity than the overall magnitude. The present analysis suggests that, of the tested ocean biogeochemistry models, CESM and GFDL ESM2M are best able to capture the observed APO seasonal cycle at both Northern and Southern Hemisphere sites. In the northern oceans, the comparison to observed APO suggests that most models tend to underestimate NPP or deep ventilation or both.

  18. Nitrogen transfers off Walvis Bay: a 3-D coupled physical/biogeochemical modeling approach in the Namibian upwelling system

    Directory of Open Access Journals (Sweden)

    E. Gutknecht

    2013-06-01

    Full Text Available Eastern boundary upwelling systems (EBUS are regions of high primary production often associated with oxygen minimum zones (OMZs. They represent key regions for the oceanic nitrogen (N cycle. By exporting organic matter (OM and nutrients produced in the coastal region to the open ocean, EBUS can play an important role in sustaining primary production in subtropical gyres. However, losses of fixed inorganic N through denitrification and anammox processes take place in oxygen depleted environments such as EBUS, and can potentially mitigate the role of these regions as a source of N to the open ocean. EBUS can also represent a considerable source of nitrous oxide (N2O to the atmosphere, affecting the atmospheric budget of N2O. In this paper a 3-D coupled physical/biogeochemical model (ROMS/BioEBUS is used to investigate the N budget in the Namibian upwelling system. The main processes linked to EBUS and associated OMZs are taken into account. The study focuses on the northern part of the Benguela upwelling system (BUS, especially the Walvis Bay area (between 22° S and 24° S where the OMZ is well developed. Fluxes of N off the Walvis Bay area are estimated in order to understand and quantify (1 the total N offshore export from the upwelling area, representing a possible N source that sustains primary production in the South Atlantic subtropical gyre; (2 export production and subsequent losses of fixed N via denitrification and anammox under suboxic conditions (O2 2 m−3; and (3 the N2O emission to the atmosphere in the upwelling area. In the mixed layer, the total N offshore export is estimated as 8.5 ± 3.9 × 1010 mol N yr−1 at 10° E off the Walvis Bay area, with a mesoscale contribution of 20%. Extrapolated to the whole BUS, the coastal N source for the subtropical gyre corresponds to 0.1 ± 0.04 mol N m−2 yr−1. This N flux represents a major source of N for the gyre compared with other N sources, and contributes 28% of the new primary

  19. Nitrogen transfers off Walvis Bay: a 3-D coupled physical/biogeochemical modeling approach in the Namibian upwelling system

    Science.gov (United States)

    Gutknecht, E.; Dadou, I.; Marchesiello, P.; Cambon, G.; Le Vu, B.; Sudre, J.; Garçon, V.; Machu, E.; Rixen, T.; Kock, A.; Flohr, A.; Paulmier, A.; Lavik, G.

    2013-06-01

    Eastern boundary upwelling systems (EBUS) are regions of high primary production often associated with oxygen minimum zones (OMZs). They represent key regions for the oceanic nitrogen (N) cycle. By exporting organic matter (OM) and nutrients produced in the coastal region to the open ocean, EBUS can play an important role in sustaining primary production in subtropical gyres. However, losses of fixed inorganic N through denitrification and anammox processes take place in oxygen depleted environments such as EBUS, and can potentially mitigate the role of these regions as a source of N to the open ocean. EBUS can also represent a considerable source of nitrous oxide (N2O) to the atmosphere, affecting the atmospheric budget of N2O. In this paper a 3-D coupled physical/biogeochemical model (ROMS/BioEBUS) is used to investigate the N budget in the Namibian upwelling system. The main processes linked to EBUS and associated OMZs are taken into account. The study focuses on the northern part of the Benguela upwelling system (BUS), especially the Walvis Bay area (between 22° S and 24° S) where the OMZ is well developed. Fluxes of N off the Walvis Bay area are estimated in order to understand and quantify (1) the total N offshore export from the upwelling area, representing a possible N source that sustains primary production in the South Atlantic subtropical gyre; (2) export production and subsequent losses of fixed N via denitrification and anammox under suboxic conditions (O2 area. In the mixed layer, the total N offshore export is estimated as 8.5 ± 3.9 × 1010 mol N yr-1 at 10° E off the Walvis Bay area, with a mesoscale contribution of 20%. Extrapolated to the whole BUS, the coastal N source for the subtropical gyre corresponds to 0.1 ± 0.04 mol N m-2 yr-1. This N flux represents a major source of N for the gyre compared with other N sources, and contributes 28% of the new primary production estimated for the South Atlantic subtropical gyre. Export production (16

  20. An integrated water system model considering hydrological and biogeochemical processes at basin scale: model construction and application

    OpenAIRE

    Y. Y. Zhang; Q. X. Shao; A. Z. Ye; H. T. Xing

    2014-01-01

    Integrated water system modeling is a reasonable approach to provide scientific understanding and possible solutions to tackle the severe water crisis faced over the world and to promote the implementation of integrated river basin management. Such a modeling practice becomes more feasible nowadays due to better computing facilities and available data sources. In this study, the process-oriented water system model (HEXM) is developed by integrating multiple ...

  1. MEDUSA-2.0: an intermediate complexity biogeochemical model of the marine carbon cycle for climate change and ocean acidification studies

    Directory of Open Access Journals (Sweden)

    A. Yool

    2013-10-01

    Full Text Available MEDUSA-1.0 (Model of Ecosystem Dynamics, nutrient Utilisation, Sequestration and Acidification was developed as an "intermediate complexity" plankton ecosystem model to study the biogeochemical response, and especially that of the so-called "biological pump", to anthropogenically driven change in the World Ocean (Yool et al., 2011. The base currency in this model was nitrogen from which fluxes of organic carbon, including export to the deep ocean, were calculated by invoking fixed C:N ratios in phytoplankton, zooplankton and detritus. However, due to anthropogenic activity, the atmospheric concentration of carbon dioxide (CO2 has significantly increased above its natural, inter-glacial background. As such, simulating and predicting the carbon cycle in the ocean in its entirety, including ventilation of CO2 with the atmosphere and the resulting impact of ocean acidification on marine ecosystems, requires that both organic and inorganic carbon be afforded a more complete representation in the model specification. Here, we introduce MEDUSA-2.0, an expanded successor model which includes additional state variables for dissolved inorganic carbon, alkalinity, dissolved oxygen and detritus carbon (permitting variable C:N in exported organic matter, as well as a simple benthic formulation and extended parameterizations of phytoplankton growth, calcification and detritus remineralisation. A full description of MEDUSA-2.0, including its additional functionality, is provided and a multi-decadal spin-up simulation (1860–2005 is performed. The biogeochemical performance of the model is evaluated using a diverse range of observational data, and MEDUSA-2.0 is assessed relative to comparable models using output from the Coupled Model Intercomparison Project (CMIP5.

  2. MEDUSA-2.0: an intermediate complexity biogeochemical model of the marine carbon cycle for climate change and ocean acidification studies

    Science.gov (United States)

    Yool, A.; Popova, E. E.; Anderson, T. R.

    2013-10-01

    MEDUSA-1.0 (Model of Ecosystem Dynamics, nutrient Utilisation, Sequestration and Acidification) was developed as an "intermediate complexity" plankton ecosystem model to study the biogeochemical response, and especially that of the so-called "biological pump", to anthropogenically driven change in the World Ocean (Yool et al., 2011). The base currency in this model was nitrogen from which fluxes of organic carbon, including export to the deep ocean, were calculated by invoking fixed C:N ratios in phytoplankton, zooplankton and detritus. However, due to anthropogenic activity, the atmospheric concentration of carbon dioxide (CO2) has significantly increased above its natural, inter-glacial background. As such, simulating and predicting the carbon cycle in the ocean in its entirety, including ventilation of CO2 with the atmosphere and the resulting impact of ocean acidification on marine ecosystems, requires that both organic and inorganic carbon be afforded a more complete representation in the model specification. Here, we introduce MEDUSA-2.0, an expanded successor model which includes additional state variables for dissolved inorganic carbon, alkalinity, dissolved oxygen and detritus carbon (permitting variable C:N in exported organic matter), as well as a simple benthic formulation and extended parameterizations of phytoplankton growth, calcification and detritus remineralisation. A full description of MEDUSA-2.0, including its additional functionality, is provided and a multi-decadal spin-up simulation (1860-2005) is performed. The biogeochemical performance of the model is evaluated using a diverse range of observational data, and MEDUSA-2.0 is assessed relative to comparable models using output from the Coupled Model Intercomparison Project (CMIP5).

  3. Modelling of radon transport in porous media

    NARCIS (Netherlands)

    van der Graaf, E.R.; de Meijer, R.J.; Katase, A; Shimo, M

    1998-01-01

    This paper aims to describe the state of the art of modelling radon transport in soil on basis of multiphase radon transport equations. Emphasis is given to methods to obtain a consistent set of input parameters needed For such models. Model-measurement comparisons with the KVI radon transport Facil

  4. Transport Properties for Combustion Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Brown, N.J.; Bastein, L.; Price, P.N.

    2010-02-19

    This review examines current approximations and approaches that underlie the evaluation of transport properties for combustion modeling applications. Discussed in the review are: the intermolecular potential and its descriptive molecular parameters; various approaches to evaluating collision integrals; supporting data required for the evaluation of transport properties; commonly used computer programs for predicting transport properties; the quality of experimental measurements and their importance for validating or rejecting approximations to property estimation; the interpretation of corresponding states; combination rules that yield pair molecular potential parameters for unlike species from like species parameters; and mixture approximations. The insensitivity of transport properties to intermolecular forces is noted, especially the non-uniqueness of the supporting potential parameters. Viscosity experiments of pure substances and binary mixtures measured post 1970 are used to evaluate a number of approximations; the intermediate temperature range 1 < T* < 10, where T* is kT/{var_epsilon}, is emphasized since this is where rich data sets are available. When suitable potential parameters are used, errors in transport property predictions for pure substances and binary mixtures are less than 5 %, when they are calculated using the approaches of Kee et al.; Mason, Kestin, and Uribe; Paul and Warnatz; or Ern and Giovangigli. Recommendations stemming from the review include (1) revisiting the supporting data required by the various computational approaches, and updating the data sets with accurate potential parameters, dipole moments, and polarizabilities; (2) characterizing the range of parameter space over which the fit to experimental data is good, rather than the current practice of reporting only the parameter set that best fits the data; (3) looking for improved combining rules, since existing rules were found to under-predict the viscosity in most cases; (4

  5. Methods for testing transport models

    International Nuclear Information System (INIS)

    Work to date includes construction of a ''stratified'' regression method which treats both measurement errors and machine-to-machine calibration differences, and using the results of an optimized predictive simulation code interpolator/approximator to estimate turbulence saturation levels using an entire set of available data. We have also set up semiempirical and theory-based models of an ARIES commercial reactor, incorporating a simple current drive source for studies of radiofrequency current drive in the BALDUR equilibrium transport code and trained ARIES personnel in the use of these tools

  6. An integrated water system model considering hydrological and biogeochemical processes at basin scale: model construction and application

    Directory of Open Access Journals (Sweden)

    Y. Y. Zhang

    2014-08-01

    Full Text Available Integrated water system modeling is a reasonable approach to provide scientific understanding and possible solutions to tackle the severe water crisis faced over the world and to promote the implementation of integrated river basin management. Such a modeling practice becomes more feasible nowadays due to better computing facilities and available data sources. In this study, the process-oriented water system model (HEXM is developed by integrating multiple water related processes including hydrology, biogeochemistry, environment and ecology, as well as the interference of human activities. The model was tested in the Shaying River Catchment, the largest, highly regulated and heavily polluted tributary of Huai River Basin in China. The results show that: HEXM is well integrated with good performance on the key water related components in the complex catchments. The simulated daily runoff series at all the regulated and less-regulated stations matches observations, especially for the high and low flow events. The average values of correlation coefficient and coefficient of efficiency are 0.81 and 0.63, respectively. The dynamics of observed daily ammonia-nitrogen (NH4N concentration, as an important index to assess water environmental quality in China, are well captured with average correlation coefficient of 0.66. Furthermore, the spatial patterns of nonpoint source pollutant load and grain yield are also simulated properly, and the outputs have good agreements with the statistics at city scale. Our model shows clear superior performance in both calibration and validation in comparison with the widely used SWAT model. This model is expected to give a strong reference for water system modeling in complex basins, and provide the scientific foundation for the implementation of integrated river basin management all over the world as well as the technical guide for the reasonable regulation of dams and sluices and environmental improvement in river

  7. Up-gradient transport in a probabilistic transport model

    DEFF Research Database (Denmark)

    Gavnholt, J.; Juul Rasmussen, J.; Garcia, O.E.;

    2005-01-01

    The transport of particles or heat against the driving gradient is studied by employing a probabilistic transport model with a characteristic particle step length that depends on the local concentration or heat gradient. When this gradient is larger than a prescribed critical value, the standard....... These results supplement recent works by van Milligen [Phys. Plasmas 11, 3787 (2004)], which applied Levy distributed step sizes in the case of supercritical gradients to obtain the up-gradient transport. (c) 2005 American Institute of Physics....

  8. Genome-Enabled Modeling of Biogeochemical Processes Predicts Metabolic Dependencies that Connect the Relative Fitness of Microbial Functional Guilds

    Science.gov (United States)

    Brodie, E.; King, E.; Molins, S.; Karaoz, U.; Steefel, C. I.; Banfield, J. F.; Beller, H. R.; Anantharaman, K.; Ligocki, T. J.; Trebotich, D.

    2015-12-01

    Pore-scale processes mediated by microorganisms underlie a range of critical ecosystem services, regulating carbon stability, nutrient flux, and the purification of water. Advances in cultivation-independent approaches now provide us with the ability to reconstruct thousands of genomes from microbial populations from which functional roles may be assigned. With this capability to reveal microbial metabolic potential, the next step is to put these microbes back where they belong to interact with their natural environment, i.e. the pore scale. At this scale, microorganisms communicate, cooperate and compete across their fitness landscapes with communities emerging that feedback on the physical and chemical properties of their environment, ultimately altering the fitness landscape and selecting for new microbial communities with new properties and so on. We have developed a trait-based model of microbial activity that simulates coupled functional guilds that are parameterized with unique combinations of traits that govern fitness under dynamic conditions. Using a reactive transport framework, we simulate the thermodynamics of coupled electron donor-acceptor reactions to predict energy available for cellular maintenance, respiration, biomass development, and enzyme production. From metagenomics, we directly estimate some trait values related to growth and identify the linkage of key traits associated with respiration and fermentation, macromolecule depolymerizing enzymes, and other key functions such as nitrogen fixation. Our simulations were carried out to explore abiotic controls on community emergence such as seasonally fluctuating water table regimes across floodplain organic matter hotspots. Simulations and metagenomic/metatranscriptomic observations highlighted the many dependencies connecting the relative fitness of functional guilds and the importance of chemolithoautotrophic lifestyles. Using an X-Ray microCT-derived soil microaggregate physical model combined

  9. Business Models For Transport eBusiness

    OpenAIRE

    Dragan Cisic; Ivan Franciskovic; Ana Peric

    2003-01-01

    In this paper authors are presenting expectations from electronic commerce and its connotations on transport logistics. Based on trends, the relations between the companies in the international transport have to be strengthened using Internet business models. In the paper authors are investigating e-business information models for usage in transport

  10. ANEMONA: multiassembly neutron transport modeling

    Energy Technology Data Exchange (ETDEWEB)

    Jevremovic, T.; Ito, T. E-mail: t-itoh@nfi.co.jp; Inaba, Y

    2002-11-01

    A new feature of the general geometry neutron transport code, ANEMONA, the modeling of multi-assembly geometries in 2D, is developed and presented in this paper. The new module is called the ANEMULT code. In addition, the two acceleration techniques are added: (a) the ANEMONA's original geometry independent ray tracer (GIT), now utilizes the, so called, virtual bounding volume concept that importantly speeds up the ray tracing, and (b) the flux solver is accelerated using the Chebyshev polynomials. A whole core configuration run by ANEMULT is generated linking assemblies through the boundary edges' flux. All geometrical data are prepared in advance running the ANEMONA code (independently for geometrically different assemblies only). In this paper, two numerical benchmarks are presented: a single BWR MOX fuel assembly and a 6x6 assembly geometry (each assembly is of BWR 9x9 type). The results compared with the Monte Carlo code, GMVP, show a very good agreement.

  11. Transportation System Modeling in the Silistra Region

    OpenAIRE

    Mihailov, B.

    1980-01-01

    The transportation system has many different components and it represents in itself a large-scale system. For this reason the solving of the problem concerning the modeling of the internal transportation links within a unified transportation system will not only help to solve an unsolved (to date) problem, but will also give us the possibility of incorporating the transportation in the system of models for integrated regional development. That is why the pursued goal here at this stage is lim...

  12. SATURATED ZONE FLOW AND TRANSPORT MODEL ABSTRACTION

    Energy Technology Data Exchange (ETDEWEB)

    B.W. ARNOLD

    2004-10-27

    The purpose of the saturated zone (SZ) flow and transport model abstraction task is to provide radionuclide-transport simulation results for use in the total system performance assessment (TSPA) for license application (LA) calculations. This task includes assessment of uncertainty in parameters that pertain to both groundwater flow and radionuclide transport in the models used for this purpose. This model report documents the following: (1) The SZ transport abstraction model, which consists of a set of radionuclide breakthrough curves at the accessible environment for use in the TSPA-LA simulations of radionuclide releases into the biosphere. These radionuclide breakthrough curves contain information on radionuclide-transport times through the SZ. (2) The SZ one-dimensional (I-D) transport model, which is incorporated in the TSPA-LA model to simulate the transport, decay, and ingrowth of radionuclide decay chains in the SZ. (3) The analysis of uncertainty in groundwater-flow and radionuclide-transport input parameters for the SZ transport abstraction model and the SZ 1-D transport model. (4) The analysis of the background concentration of alpha-emitting species in the groundwater of the SZ.

  13. SATURATED ZONE FLOW AND TRANSPORT MODEL ABSTRACTION

    International Nuclear Information System (INIS)

    The purpose of the saturated zone (SZ) flow and transport model abstraction task is to provide radionuclide-transport simulation results for use in the total system performance assessment (TSPA) for license application (LA) calculations. This task includes assessment of uncertainty in parameters that pertain to both groundwater flow and radionuclide transport in the models used for this purpose. This model report documents the following: (1) The SZ transport abstraction model, which consists of a set of radionuclide breakthrough curves at the accessible environment for use in the TSPA-LA simulations of radionuclide releases into the biosphere. These radionuclide breakthrough curves contain information on radionuclide-transport times through the SZ. (2) The SZ one-dimensional (I-D) transport model, which is incorporated in the TSPA-LA model to simulate the transport, decay, and ingrowth of radionuclide decay chains in the SZ. (3) The analysis of uncertainty in groundwater-flow and radionuclide-transport input parameters for the SZ transport abstraction model and the SZ 1-D transport model. (4) The analysis of the background concentration of alpha-emitting species in the groundwater of the SZ

  14. Modeling seawater intrusion and the associated reactive solute transport in fractured coastal aquifers

    Science.gov (United States)

    Nick, Hamid M.; Regnier, Pierre; Thullner, Martin

    2013-04-01

    In coastal aquifers seawater and terrestrial water get into contact and the reactive mixing between these water bodies controls the water quality of submarine groundwater discharge. The rates of such mixing controlled reactions are depending not only on the properties of the reactive species but also on the density driven flow dynamics and the resulting transport patterns. A prediction of these flow and transport processes and thus of the fate of reactive species is specifically challenged in fracture aquifers as it depends on the focusing of the flow and the local balance of viscous and gravitational forces. To study the influence of fractures on mixing and reactive transport in coastal aquifers we present a reactive discrete fracture and matrix (DFM) model using unstructured spatially adaptively refined finite-element meshes. This model is developed by coupling the Complex System Modelling Platform (CSMP++) utilizing a hybrid FEFV scheme, and a Biogeochemical Reaction Network Simulator (BRNS) capable of solving for kinetically and thermodynamically constrained biogeochemical reactions [1]. The model is applied to simulate the reactive transport in fracture networks embedded in a permeable rock matrix. For virtual coastal aquifers, different fracture data sets are employed to study the effect of fractures and their characteristics on the reactive mixing between fresh water and seawater in coastal aquifers. Obtained results show that the presence of fractures enhances reactive mixing for most cases due to the combined effect of fracture induced flow channeling and dispersion. The magnitude of this effect depends highly on fracture density, spacing and orientation. Furthermore the results indicate that reactive mixing in fractured aquifers is not well described using an effective parameterization of a homogeneous aquifer setup. This suggests that structural information on the fracture network is needed for a sufficient description of reactive transport processes in

  15. RADIONUCLIDE TRANSPORT MODELS UNDER AMBIENT CONDITIONS

    Energy Technology Data Exchange (ETDEWEB)

    S. Magnuson

    2004-11-01

    The purpose of this model report is to document the unsaturated zone (UZ) radionuclide transport model, which evaluates, by means of three-dimensional numerical models, the transport of radioactive solutes and colloids in the UZ, under ambient conditions, from the repository horizon to the water table at Yucca Mountain, Nevada.

  16. RADIONUCLIDE TRANSPORT MODELS UNDER AMBIENT CONDITIONS

    International Nuclear Information System (INIS)

    The purpose of this model report is to document the unsaturated zone (UZ) radionuclide transport model, which evaluates, by means of three-dimensional numerical models, the transport of radioactive solutes and colloids in the UZ, under ambient conditions, from the repository horizon to the water table at Yucca Mountain, Nevada

  17. Coal supply and transportation model (CSTM)

    International Nuclear Information System (INIS)

    The Coal Supply and Transportation Model (CSTM) forecasts annual coal supply and distribution to domestic and foreign markets. The model describes US coal production, national and international coal transportation industries. The objective of this work is to provide a technical description of the current version of the model

  18. Logistics and Transport - a conceptual model

    DEFF Research Database (Denmark)

    Jespersen, Per Homann; Drewes, Lise

    2004-01-01

    This paper describes how the freight transport sector is influenced by logistical principles of production and distribution. It introduces new ways of understanding freight transport as an integrated part of the changing trends of mobility. By introducing a conceptual model for understanding the...... interaction between logistics and transport, it points at ways to over-come inherent methodological difficulties when studying this relation...

  19. Modeling activity transport in the CANDU heat transport system

    International Nuclear Information System (INIS)

    The release and transport of corrosion products from the surfaces of primary coolant system components is a serious concern for all water-cooled nuclear power plants. The consequences of high levels of corrosion product transport are twofold: a) increased corrosion product (crud) deposition on fuel cladding surfaces, leading to reduced heat transfer and the possibility of fuel failures, and b) increased production of radioactive species by neutron activation, resulting in increased out-of-core radiation fields and worker dose. In recent years, a semi-empirical activity transport model has been successfully developed to predict the deposition of radionuclides, including 60Co, 95Zr, 124Sb and fission products, around the CANDU® primary Heat Transport System (HTS), and to predict radiation fields at the steam generators and reactor face. The model links corrosion of the carbon steel outlet feeders to magnetite and radionuclide deposition on steam generator and inlet piping surfaces. This paper will describe the model development, key assumptions, required inputs, and model validation. The importance of reactor artefact characterization in the model development will be highlighted, and some key results will be presented, including oxide morphology and loadings, and radionuclide distributions within the oxide. The predictive capabilities of the model will also be described, including predictions of oxide thickness and the effects of changes in chemistry parameters such as alkalinity. While the model was developed primarily for the CANDU® HTS, the information gained during model development regarding corrosion product and radionuclide transport and deposition can also provide insights into activity transport in other water-cooled reactor systems. (author)

  20. Using model reduction to predict the soil-surface C18OO flux: an example of representing complex biogeochemical dynamics in a computationally efficient manner

    Directory of Open Access Journals (Sweden)

    W. J. Riley

    2013-03-01

    Full Text Available Earth system models (ESMs must calculate large-scale interactions between the land and atmosphere while accurately characterizing fine-scale spatial heterogeneity in water, carbon, and other nutrient dynamics. We present here a high-dimension model representation (HDMR approach that allows detailed process representation of a coupled carbon and water tracer (the δ18O value of the soil-surface CO2 flux (δ Fs in a computationally tractable manner. δ Fs depends on the δ18O value of soil water, soil moisture and temperature, and soil CO2 production (all of which are depth dependent, and the δ18O value of above-surface CO2. We tested the HDMR approach over a growing season in a C4-dominated pasture using two vertical soil discretizations. The difference between the HDMR approach and the full model solution in the three-month integrated isoflux was less than 0.2% (0.5 mol m−2 ‰, and the approach is up to 100 times faster than the full numerical solution. This type of model reduction approach allows representation of complex coupled biogeochemical processes in regional and global climate models and can be extended to characterize subgrid-scale spatial heterogeneity.

  1. Using model reduction to predict the soil-surface C18OO flux: an example of representing complex biogeochemical dynamics in a computationally efficient manner

    Science.gov (United States)

    Riley, W. J.

    2013-03-01

    Earth system models (ESMs) must calculate large-scale interactions between the land and atmosphere while accurately characterizing fine-scale spatial heterogeneity in water, carbon, and other nutrient dynamics. We present here a high-dimension model representation (HDMR) approach that allows detailed process representation of a coupled carbon and water tracer (the δ18O value of the soil-surface CO2 flux (δ Fs)) in a computationally tractable manner. δ Fs depends on the δ18O value of soil water, soil moisture and temperature, and soil CO2 production (all of which are depth dependent), and the δ18O value of above-surface CO2. We tested the HDMR approach over a growing season in a C4-dominated pasture using two vertical soil discretizations. The difference between the HDMR approach and the full model solution in the three-month integrated isoflux was less than 0.2% (0.5 mol m-2 ‰), and the approach is up to 100 times faster than the full numerical solution. This type of model reduction approach allows representation of complex coupled biogeochemical processes in regional and global climate models and can be extended to characterize subgrid-scale spatial heterogeneity.

  2. Using model reduction to predict the soil-surface C18OO flux: an example of representing complex biogeochemical dynamics in a computationally efficient manner

    Directory of Open Access Journals (Sweden)

    W. J. Riley

    2012-11-01

    Full Text Available Earth System Models (ESMs must calculate large-scale interactions between the land and atmosphere while accurately characterizing fine-scale spatial heterogeneity in water, carbon, and nutrient dynamics. We present here a high-dimensional model representation (HDMR approach that allows detailed process representation of a coupled carbon and water tracer (the δ18O value of the soil-surface CO2 flux (δFs in a computationally tractable manner. δFs depends on the δ18O value of soil water, soil moisture, soil temperature, and soil CO2 production (all of which are depth-dependent, and the δ18O value of above-surface CO2. We tested the HDMR approach over a growing season in a C4-dominated pasture using two vertical soil discretizations. The difference between the HDMR approach and the full model solution in the three-month integrated isoflux was less than 0.2% (0.5 mol m−2‰, and the approach is up to 100 times faster than the full numerical solution. This type of model reduction approach allows representation of complex coupled biogeochemical processes in regional and global climate models and can be extended to characterize subgrid-scale spatial heterogeneity.

  3. New Insights into Fluvial Carbon Responses to Future Forest Management and Climate Change Obtained from Multi-Scale Modelling of Biogeochemical Processes

    Science.gov (United States)

    Oni, S. K.; Tiwari, T.; Futter, M. N.; Agren, A.; Teutschbein, C.; Ledesma, J.; Schelker, J.; Laudon, H.

    2014-12-01

    The boreal ecozone covers 2x107 km2 of the northern circumpolar region and includes 29% of the world's forests. The boreal consists of mosaic of forest/wetland landscape elements and stores about 500 Gt3 carbon (C) with a delicate sink-source C balance. Dissolved organic carbon (DOC) is the main form of C exported from boreal landscapes and is fundamental to global C cycling. This northern ecosystem is vulnerable to global climate change, and increasing demands for forest products threaten its surface water resources. So far, there have been no attempts to assess the combined impacts of climate change and forest management on the future DOC fluxes from boreal surface waters. While differences in model assumptions may have negligible effects on present day simulations, these differences could be amplified when projecting the future climate and land use change conditions. Here we use an ensemble of regional climate models and multi-scale models of biogeochemical processes to gain insights into uncertainties associated with climate change and forest management on C and runoff dynamics in boreal landscape. While there are significant uncertainties associated with model projections, our results show that climate change will be the main driver of long term DOC dynamics in meso- to large boreal catchments in the future. However, forestry intensifies hydrological processes and can lead to large DOC fluxes at the headwater scales.

  4. Optimal transportation networks models and theory

    CERN Document Server

    Bernot, Marc; Morel, Jean-Michel

    2009-01-01

    The transportation problem can be formalized as the problem of finding the optimal way to transport a given measure into another with the same mass. In contrast to the Monge-Kantorovitch problem, recent approaches model the branched structure of such supply networks as minima of an energy functional whose essential feature is to favour wide roads. Such a branched structure is observable in ground transportation networks, in draining and irrigation systems, in electrical power supply systems and in natural counterparts such as blood vessels or the branches of trees. These lectures provide mathematical proof of several existence, structure and regularity properties empirically observed in transportation networks. The link with previous discrete physical models of irrigation and erosion models in geomorphology and with discrete telecommunication and transportation models is discussed. It will be mathematically proven that the majority fit in the simple model sketched in this volume.

  5. Pitfalls in compartment modelling of transport processes. The influence of model structure

    International Nuclear Information System (INIS)

    Compartment models are generally used in radioecological modelling because they have a realistic chance to cope with complex biogeochemical processes. Often these compartment models include a description of transport processes in aquatic system. This study shows that care must be taken when selecting the number of compartments for the spatial representation of such aquatic systems, to get a correct representation of solute transport. A field tracer experiment was performed in an artificial dam at Ekeby wetland in Sweden. Tritium was used as tracer and injected as a pulse. The experimental residence time distribution (RTD) was evaluated with an analytical solution based on compartment models with only one mass transfer rate between compartments known as 'tank-in-series' model. The analytical solution applies for an initial mass release in the first tank in the series. To explore the impact of model structure, a variable number of compartments was used and compared with the observations. When four compartments were used in the model, the simulated RTD could fit the measured data relatively well. The RTD simulated by the model with one compartment deviates significantly more from the observations. With a continuous injection the RTDs simulated by one and four compartments will be the same after a long time. Analysis was made by superposing the RTDs with a time shift to simulate a continuous injection. The results show that after a time scale of about 10 days the RTDs obtained by one and four compartments reach equilibrium. The difference between the two RTDs is initially significant. Further analyses show that the times reaching equilibrium increase with an increase of RTDs. Since RTD for certain radionuclide in ecosystems can be in an order of several hundred years or even longer, care should be taken when one selects the model structure to describe the transport process. (author)

  6. Full uncertainty quantification of a regional N2O, NO, NH3 emission and NO3 leaching inventory using the biogeochemical model LandscapeDNDC

    Science.gov (United States)

    Santabarbara, Ignacio; Haas, Edwin

    2016-04-01

    Numerical simulation models are increasingly used to estimate greenhouse gas emissions at site to regional / national scale and are outlined as the most advanced methodology (Tier 3) in the framework of UNFCCC reporting. Process-based models incorporate the major processes of the carbon and nitrogen cycle of terrestrial ecosystems and are thus thought to be widely applicable at various spatial scales. Regional inventories require high spatial resolution input data on soil properties, climate drivers and management information. The acceptance of model based inventory calculations depends on the assessment of the inventory's uncertainty (model structure, initial condition data and parameter induced uncertainties). In this study we fully quantify uncertainty in regional simulation of the N cycle in arable, grassland and forest soils of Saxony (Germany) using the biogeochemical model LandscapeDNDC. We address model structural uncertainty (MU) by contrasting with Bayes factors two different soil biogeochemistry modules within LandscapeDNDC, the DNDC versus the MeTrx biogeochemistry process description. Initial conditions induced uncertainty (IU) was addressed with the parameter distribution obtained by a Bayesian calibration of soil properties, climate drivers and management practices. The parameter induced uncertainty (PU) was assessed by using a joint parameter distribution for key parameters describing microbial C and N turnover processes as obtained also by a Bayesian calibration study. Once the representative sample size from all parameters, initial conditions and model selection is set, we sampled the different configurations and used these to calculate individual realizations of the regional inventory. The ecosystems considered in this study (forest, arable and grasslands) are given spatially discretized into 8858 polygons (16058 km-2), each representing a unique land use and homogenous soil properties. For the overall uncertainty quantification we calculated

  7. A new multicomponent variably saturated flow and transport model

    International Nuclear Information System (INIS)

    The migration of many naturally occurring elements and contaminants in soil and sediments is affected by a multitude of complex, interactive physical, chemical, mineralogical, and biological processes. Computer simulation of the interaction of these processes requires a coupled reactive transport code that integrates the physical processes of water flow and advective-dispersive solute transport with a range of biogeochemical processes. Such coupled codes are necessary tools for evaluating waste management and pollution control scenarios. The objective is to develop, test, and apply a new reactive transport code that is the result of coupling two existing codes: the water flow and solute transport code HYDRUS-1D and the geochemical code PHREEQC-2. This new code, called HP1, expands significantly the possible applications of the individual codes by integrating water flow, solute transport, heat transport and biogeochemical reactions. The advantage of such coupled codes is that for example, relationships between changing flow conditions (from saturated to unsaturated flow and vice versa) and chemical conditions (from reducing to oxidising, or from low to high pH and vice versa) are accounted for. This allows a more accurate description

  8. Spatio-temporal dynamics of growth and survival of Lesser Sandeel early life-stages in the North Sea: Predictions from a coupled individual-based and hydrodynamic-biogeochemical model

    DEFF Research Database (Denmark)

    Gurkan, Zeren; Christensen, Asbjørn; Maar, Marie; Møller, Eva Friis; Madsen, Kristine Skovgaard; Munk, Peter; Mosegaard, Henrik

    2013-01-01

    Accounting for the individual variability and regional variations are important when predicting recruitment in fish species. Spatially explicit descriptions for recruitment in sandeels are necessary and sandeel growth and survival depend locally on zooplankton prey. We investigate the responses of...... larval and early juvenile Lesser Sandeel (Ammodytes marinus) in the North Sea to local feeding conditions by an adapted version of a generic bioenergetic individual-based model for larval fish describing growth and survival. Prey encounter and physiological processes are described explicitly in the model......, which allows analyzing the influence of prey on the growth and survival of sandeel. The model is coupled to a hydrodynamic-biogeochemical model with physical and prey fields and implemented in temporal and three-dimensional spatial settings. Zooplankton biomass simulated by the biogeochemical model is...

  9. Effect of Biogeochemical Redox Processes on the Fate and Transport of As and U at an Abandoned Uranium Mine Site: an X-ray Absorption Spectroscopy Study

    Energy Technology Data Exchange (ETDEWEB)

    Troyer, Lyndsay D.; Stone, James J.; Borch, Thomas

    2014-01-28

    Although As can occur in U ore at concentrations up to 10 wt-%, the fate and transport of both U and As at U mine tailings have not been previously investigated at a watershed scale. The major objective of this study was to determine primary chemical and physical processes contributing to transport of both U and As to a down gradient watershed at an abandoned U mine site in South Dakota. Uranium is primarily transported by erosion at the site, based on decreasing concentrations in sediment with distance from the tailings. equential extractions and U X-ray absorption near-edge fine structure (XANES) fitting indicate that U is immobilised in a near-source sedimentation pond both by prevention of sediment transport and by reduction of UVI to UIV. In contrast to U, subsequent release of As to the watershed takes place from the pond partially due to reductive dissolution of Fe oxy(hydr)oxides. However, As is immobilised by adsorption to clays and Fe oxy(hydr)oxides in oxic zones and by formation of As–sulfide mineral phases in anoxic zones down gradient, indicated by sequential extractions and As XANES fitting. This study indicates that As should be considered during restoration of uranium mine sites in order to prevent transport.

  10. Towards tracer-aided spatially distributed models of catchment storage and mixing to predict non-stationary hydrologic and biogeochemical response

    Science.gov (United States)

    Soulsby, Chris; van Huijgevoort, Marjolein; Dick, Jonathan; Birkel, Christian; Tetzlaff, Doerthe

    2016-04-01

    To develop a spatially distributed understanding of the linkages between storage dynamics, mixing processes and non-stationary watershed response we have used diverse, intensive data sets collected in a small montane catchment to both inform and test hydrological and water quality models. At the core of these efforts has been the use of ~6 years of daily isotope data in precipitation and stream flow to inform the calibration and testing of coupled flow-tracer models that constrain storage estimates, mixing processes and hydrologic fluxes in the dominant landscape units as well as simulating discharge and stream isotopes. LiDAR surveys have been used to extend this approach using a high resolution DTM to facilitate a Spatially distributed Tracer-Aided Rainfall-Runoff model (STARR). This provides a flexible, generic approach that allows us to track and visualise aggregated storage changes, mixing processes, and the fluxes and age distribution of water across spatio-temporal scales. The modelling framework provides a basis for assessing the effects of hydroclimatic variability on the non-stationary nature of catchment hydrological function by simulating the spatial variation in tracer composition of different source waters and flow paths. This is tested against extensive (over 120 sites) synoptic surveys of multiple-tracers in soil water, groundwater and stream water repeated under contrasting states of catchment storage when different flow paths are activated. The modelling approach can reproduce the major spatio-temporal differences in isotopes, dissolved organic (DOC) and alkalinity reasonably well and thus, has potential to be adapted for biogeochemical modelling. This potential is explored in relation to daily DOC simulations over prolonged (2 year) periods. The transferability of the modelling approach to other sites is also tested.

  11. Final Report Coupling in silico microbial models with reactive transport models to predict the fate of contaminants in the subsurface.

    Energy Technology Data Exchange (ETDEWEB)

    Lovley, Derek R.

    2012-10-31

    This project successfully accomplished its goal of coupling genome-scale metabolic models with hydrological and geochemical models to predict the activity of subsurface microorganisms during uranium bioremediation. Furthermore, it was demonstrated how this modeling approach can be used to develop new strategies to optimize bioremediation. The approach of coupling genome-scale metabolic models with reactive transport modeling is now well enough established that it has been adopted by other DOE investigators studying uranium bioremediation. Furthermore, the basic principles developed during our studies will be applicable to much broader investigations of microbial activities, not only for other types of bioremediation, but microbial metabolism in diversity of environments. This approach has the potential to make an important contribution to predicting the impact of environmental perturbations on the cycling of carbon and other biogeochemical cycles.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-11-01

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

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

    International Nuclear Information System (INIS)

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

  14. Generic reactive transport codes as flexible tools to integrate soil organic matter degradation models with water, transport and geochemistry in soils

    Science.gov (United States)

    Jacques, Diederik; Gérard, Fréderic; Mayer, Uli; Simunek, Jirka; Leterme, Bertrand

    2016-04-01

    A large number of organic matter degradation, CO2 transport and dissolved organic matter models have been developed during the last decades. However, organic matter degradation models are in many cases strictly hard-coded in terms of organic pools, degradation kinetics and dependency on environmental variables. The scientific input of the model user is typically limited to the adjustment of input parameters. In addition, the coupling with geochemical soil processes including aqueous speciation, pH-dependent sorption and colloid-facilitated transport are not incorporated in many of these models, strongly limiting the scope of their application. Furthermore, the most comprehensive organic matter degradation models are combined with simplified representations of flow and transport processes in the soil system. We illustrate the capability of generic reactive transport codes to overcome these shortcomings. The formulations of reactive transport codes include a physics-based continuum representation of flow and transport processes, while biogeochemical reactions can be described as equilibrium processes constrained by thermodynamic principles and/or kinetic reaction networks. The flexibility of these type of codes allows for straight-forward extension of reaction networks, permits the inclusion of new model components (e.g.: organic matter pools, rate equations, parameter dependency on environmental conditions) and in such a way facilitates an application-tailored implementation of organic matter degradation models and related processes. A numerical benchmark involving two reactive transport codes (HPx and MIN3P) demonstrates how the process-based simulation of transient variably saturated water flow (Richards equation), solute transport (advection-dispersion equation), heat transfer and diffusion in the gas phase can be combined with a flexible implementation of a soil organic matter degradation model. The benchmark includes the production of leachable organic matter

  15. Polar auxin transport: models and mechanisms

    NARCIS (Netherlands)

    Berkel, van K.; Boer, de R.J.; Scheres, B.; Tusscher, ten K.

    2013-01-01

    Spatial patterns of the hormone auxin are important drivers of plant development. The observed feedback between the active, directed transport that generates auxin patterns and the auxin distribution that influences transport orientation has rendered this a popular subject for modelling studies. Her

  16. A biogeochemical model of Lake Pusiano (North Italy and its use in the predictability of phytoplankton blooms: first preliminary results

    Directory of Open Access Journals (Sweden)

    Alessandro OGGIONI

    2006-02-01

    Full Text Available This study reports the first preliminary results of the DYRESM-CAEDYM model application to a mid size sub-alpine lake (Lake Pusiano North Italy. The in-lake modelling is a part of a more general project called Pusiano Integrated Lake/Catchment project (PILE whose final goal is to understand the hydrological and trophic relationship between lake and catchment, supporting the restoration plan of the lake through field data analysis and numerical models. DYRESM is a 1D-3D hydrodynamics model for predicting the vertical profile of temperature, salinity and density. CAEDYM is multi-component ecological model, used here as a phytoplankton-zooplankton processes based model, which includes algorithms to simulate the nutrient cycles within the water column as well as the air-water gas exchanges and the water-sediments fluxes. The first results of the hydrodynamics simulations underline the capability of the model to accurately simulate the surface temperature seasonal trend and the thermal gradient whereas, during summer stratification, the model underestimates the bottom temperature of around 2 °C. The ecological model describes the epilimnetic reactive phosphorus (PO4 depletion (due to the phytoplankton uptake and the increase in PO4 concentrations in the deepest layers of the lake (due to the mineralization processes and the sediments release. In terms of phytoplankton dynamics the model accounts for the Planktothrix rubescens dominance during the whole season, whereas it seems to underestimate the peak in primary production related to both the simulated algal groups (P. rubescens and the rest of the other species aggregated in a single class. The future aims of the project are to complete the model parameterization and to connect the in-lake and the catchment modelling in order to gain an integrated view of the lake-catchment ecosystem as well as to develop a three dimensional model of the lake.

  17. Comparison of Greenhouse Gas Emissions between Two Dairy Farm Systems (Conventional vs. Organic Management) in New Hampshire Using the Manure DNDC Biogeochemical Model

    Science.gov (United States)

    Dorich, C.; Contosta, A.; Li, C.; Brito, A.; Varner, R. K.

    2013-12-01

    Agriculture contributes 20 to 25 % of the total anthropogenic greenhouse gas (GHG) emissions globally. These agricultural emissions are primarily in the form of methane (CH4) and nitrous oxide (N2O) with these GHG accounting for roughly 40 and 80 % of the total anthropogenic emissions of CH4 and N2O, respectively. Due to varied management and the complexities of agricultural ecosystems, it is difficult to estimate these CH4 and N2O emissions. The IPCC emission factors can be used to yield rough estimates of CH4 and N2O emissions but they are often based on limited data. Accurate modeling validated by measurements is needed in order to identify potential mitigation areas, reduce GHG emissions from agriculture, and improve sustainability of farming practices. The biogeochemical model Manure DNDC was validated using measurements from two dairy farms in New Hampshire, USA in order to quantify GHG emissions under different management systems. One organic and one conventional dairy farm operated by the University of New Hampshire's Agriculture Experiment Station were utilized as the study sites for validation of Manure DNDC. Compilation of management records started in 2011 to provide model inputs. Model results were then compared to field collected samples of soil carbon and nitrogen, above-ground biomass, and GHG fluxes. Fluxes were measured in crop, animal, housing, and waste management sites on the farms in order to examine the entire farm ecosystem and test the validity of the model. Fluxes were measured by static flux chambers, with enteric fermentation measurements being conducted by the SF6 tracer test as well as a new method called Greenfeeder. Our preliminary GHG flux analysis suggests higher emissions than predicted by IPCC emission factors and equations. Results suggest that emissions from manure management is a key concern at the conventional dairy farm while bedded housing at the organic dairy produced large quantities of GHG.

  18. Integrated water system simulation by considering hydrological and biogeochemical processes: model development, with parameter sensitivity and autocalibration

    Science.gov (United States)

    Zhang, Y. Y.; Shao, Q. X.; Ye, A. Z.; Xing, H. T.; Xia, J.

    2016-02-01

    Integrated water system modeling is a feasible approach to understanding severe water crises in the world and promoting the implementation of integrated river basin management. In this study, a classic hydrological model (the time variant gain model: TVGM) was extended to an integrated water system model by coupling multiple water-related processes in hydrology, biogeochemistry, water quality, and ecology, and considering the interference of human activities. A parameter analysis tool, which included sensitivity analysis, autocalibration and model performance evaluation, was developed to improve modeling efficiency. To demonstrate the model performances, the Shaying River catchment, which is the largest highly regulated and heavily polluted tributary of the Huai River basin in China, was selected as the case study area. The model performances were evaluated on the key water-related components including runoff, water quality, diffuse pollution load (or nonpoint sources) and crop yield. Results showed that our proposed model simulated most components reasonably well. The simulated daily runoff at most regulated and less-regulated stations matched well with the observations. The average correlation coefficient and Nash-Sutcliffe efficiency were 0.85 and 0.70, respectively. Both the simulated low and high flows at most stations were improved when the dam regulation was considered. The daily ammonium-nitrogen (NH4-N) concentration was also well captured with the average correlation coefficient of 0.67. Furthermore, the diffuse source load of NH4-N and the corn yield were reasonably simulated at the administrative region scale. This integrated water system model is expected to improve the simulation performances with extension to more model functionalities, and to provide a scientific basis for the implementation in integrated river basin managements.

  19. Investigating the interactions between biogeophysical and biogeochemical processes in the northern high latitudes using a land surface model; feedbacks and climatic impacts

    Science.gov (United States)

    Barman, R.; Jain, A.; Liang, M.; McGuire, A. D.

    2010-12-01

    The dynamics of carbon fluxes in the permafrost region is likely to have tremendous impacts for the future global climate. Recently, several ecosystem and land surface models have demonstrated improved permafrost modeling capabilities by incorporating deep soil layers, organic soils, and parameterizing the effects of wind compaction and depth hoar formations, which influence high latitude soil biogeophysics. However, no global study has yet incorporated the combined effects of these biogeophysical improvements. Additionally, the primary focus has been on modeling biogeophysical fluxes rather than on how biogeochemical processes and feedbacks are impacted. In this study, we evaluate how biogeochemistry (carbon and nitrogen dynamics) responds to improved biogeophysics in the high latitudes. We employ a land surface model, the Integrated Science Assessment Model (ISAM), to model the fluxes of water, energy and carbon, as well as the change in active layer depths during the historical period. The ISAM represents fully prognostic carbon and nitrogen cycles, coupled with biogeophysics schemes adapted selectively from other land surface models such as the Community Land Model (CLM3.5) and the Common Land Model (CoLM). The soil decomposition module in the ISAM was calibrated with field experiment data, which includes representation of nitrogen mineralization processes. Additionally, biogeophysical improvements such as the inclusion of deep soils, organic soils, wind compaction and depth hoar formation effects, which are critical for high-latitude soil thermal dynamics, have been incorporated into the model. The performance of the model is evaluated using observations for active layer depths and carbon fluxes, together with recent estimates for total soil carbon amount in the permafrost region. This is one of the first studies to explore the combined effects of improvements in biogeophysics, coupled with a detailed model of soil carbon and nitrogen dynamics, for the entire

  20. Concept Layout Model of Transportation Terminals

    Directory of Open Access Journals (Sweden)

    Li-ya Yao

    2012-01-01

    Full Text Available Transportation terminal is the key node in transport systems. Efficient terminals can improve operation of passenger transportation networks, adjust the layout of public transportation networks, provide a passenger guidance system, and regulate the development of commercial forms, as well as optimize the assembly and distribution of modern logistic modes, among others. This study aims to clarify the relationship between the function and the structure of transportation terminals and establish the function layout design. The mapping mechanism of demand, function, and structure was analyzed, and a quantitative relationship between function and structure was obtained from a design perspective. Passenger demand and terminal structure were decomposed into several demand units and structural elements following the principle of reverse engineering. The relationship maps between these two kinds of elements were then analyzed. Function-oriented concept layout model of transportation terminals was established using the previous method. Thus, a technique in planning and design of transportation structures was proposed. Meaningful results were obtained from the optimization of transportation terminal facilities, which guide the design of the functional layout of transportation terminals and improve the development of urban passenger transportation systems.

  1. Highway and interline transportation routing models

    International Nuclear Information System (INIS)

    The potential impacts associated with the transportation of hazardous materials are important issues to shippers, carriers, and the general public. Since transportation routes are a central characteristic in most of these issues, the prediction of likely routes is the first step toward the resolution of these issues. In addition, US Department of Transportation requirements (HM-164) mandate specific routes for shipments of highway controlled quantities of radioactive materials. In response to these needs, two routing models have been developed at Oak Ridge National Laboratory under the sponsorship of the U.S. Department of Energy (DOE). These models have been designated by DOE's Office of Environmental Restoration and Waste Management, Transportation Management Division (DOE/EM) as the official DOE routing models. Both models, HIGHWAY and INTERLINE, are described

  2. Studying Uncertainties in Climate-Terrestrial Biogeochemical Feedbacks in the Northern High Latitudes using a Flexible Earth System Modeling Framework

    Science.gov (United States)

    Barman, R.; Hoffman, F. M.; Lawrence, D. M.; Song, Y.; Meiyappan, P.; Jain, A. K.; Jacob, R. L.; Vertenstein, M.

    2011-12-01

    Uncertainties in the representation of terrestrial biogeochemistry in land surface models (LSMs), together with their long spin-up time requirements, contribute to the many challenges inherent in coupled Earth system models (ESMs). Here we present a recently developed ESM framework, designed to incorporate multiple LSMs into an existing ESM. This ISAM-CESM framework provides an alternative LSM, the Integrated Science Assessment Model (ISAM), coupled to the NCAR Community Earth System Model (CESM1). The purpose of this general modeling framework is to carry out equivalent climate simulations using multiple LSMs with the rest of the component models being the same, allowing a more direct comparison of the effects of different land surface representations on corresponding feedbacks to climate change. In this presentation, we will analyze the role of different biogeochemistry representations and the effects of different land surface processes on climate-carbon cycle feedbacks using the ISAM and the NCAR Community Land Model (CLM4), the two LSMs currently available in the ISAM-CESM framework. Both ISAM and CLM4 contain fully prognostic, coupled carbon-nitrogen models, integrated with detailed representation of terrestrial biogeophysics. Biogeophysical schemes in the ISAM have been adapted from the CLM4, its precursor CLM3.5, and the Common Land Model (CoLM); however, the representation of the biogeochemistry of carbon nitrogen cycles are structurally different in the two models, making them suitable for inter-comparison. The aim of this study is to understand those differences and better attribute their roles in varying responses of the land surface to future climate change. We will compare the 20th century predictions of gross primary productivity (GPP) and annual cycle of CO2 from offline land simulations of ISAM and CLM4, using the newly available CRU-NCEP climate forcing data, in the CESM1 modeling framework to study the response of alternate land surface models

  3. Mathematical modeling plasma transport in tokamaks

    International Nuclear Information System (INIS)

    In this work, the author applied a systematic calibration, validation and application procedure based on the methodology of mathematical modeling to international thermonuclear experimental reactor (ITER) ignition studies. The multi-mode plasma transport model used here includes a linear combination of drift wave branch and ballooning branch instabilities with two a priori uncertain constants to account for anomalous plasma transport in tokamaks. A Bayesian parameter estimation method is used including experimental calibration error/model offsets and error bar rescaling factors to determine the two uncertain constants in the transport model with quantitative confidence level estimates for the calibrated parameters, which gives two saturation levels of instabilities. This method is first tested using a gyroBohm multi-mode transport model with a pair of DIII-D discharge experimental data, and then applied to calibrating a nominal multi-mode transport model against a broad database using twelve discharges from seven different tokamaks. The calibrated transport model is then validated on five discharges from JT-60 with no adjustable constants. The results are in a good agreement with experimental data. Finally, the resulting class of multi-mode tokamak plasma transport models is applied to the transport analysis of the ignition probability in a next generation machine, ITER. A reference simulation of basic ITER engineering design activity (EDA) parameters shows that a self-sustained thermonuclear burn with 1.5 GW output power can be achieved provided that impurity control makes radiative losses sufficiently small at an average plasma density of 1.2 X 1020/m3 with 50 MW auxiliary heating. The ignition probability of ITER for the EDA parameters, can be formally as high as 99.9% in the present context. The same probability for concept design activity (CDA) parameters of ITER, which has smaller size and lower current, is only 62.6%

  4. Hybrid models of transport in crowded environments

    OpenAIRE

    Battiato, Ilenia

    2010-01-01

    This dissertation deals with multi-scale, multi-physics descriptions of flow and transport in crowded environments forming porous media. Such phenomena can be described by employing either pore-scale or continuum-scale (Darcy- scale) models. Continuum-scale formulations are largely phenomenological, but often provide accurate and efficient representations of flow and transport. In the first part of the dissertation, we employ such a model to describe fluid flow through carbon nanotube (CNT) f...

  5. Microbial Metagenomics Reveals Climate-Relevant Subsurface Biogeochemical Processes.

    Science.gov (United States)

    Long, Philip E; Williams, Kenneth H; Hubbard, Susan S; Banfield, Jillian F

    2016-08-01

    Microorganisms play key roles in terrestrial system processes, including the turnover of natural organic carbon, such as leaf litter and woody debris that accumulate in soils and subsurface sediments. What has emerged from a series of recent DNA sequencing-based studies is recognition of the enormous variety of little known and previously unknown microorganisms that mediate recycling of these vast stores of buried carbon in subsoil compartments of the terrestrial system. More importantly, the genome resolution achieved in these studies has enabled association of specific members of these microbial communities with carbon compound transformations and other linked biogeochemical processes-such as the nitrogen cycle-that can impact the quality of groundwater, surface water, and atmospheric trace gas concentrations. The emerging view also emphasizes the importance of organism interactions through exchange of metabolic byproducts (e.g., within the carbon, nitrogen, and sulfur cycles) and via symbioses since many novel organisms exhibit restricted metabolic capabilities and an associated extremely small cell size. New, genome-resolved information reshapes our view of subsurface microbial communities and provides critical new inputs for advanced reactive transport models. These inputs are needed for accurate prediction of feedbacks in watershed biogeochemical functioning and their influence on the climate via the fluxes of greenhouse gases, CO2, CH4, and N2O. PMID:27156744

  6. Simulation of annual biogeochemical cycles of nutrient balance, phytoplankton bloom(s), and DO in Puget Sound using an unstructured grid model

    Energy Technology Data Exchange (ETDEWEB)

    Khangaonkar, Tarang; Sackmann, Brandon S.; Long, Wen; Mohamedali, Teizeen; Roberts, Mindy

    2012-08-14

    Nutrient pollution from rivers, nonpoint source runoff, and nearly 100 wastewater discharges is a potential threat to the ecological health of Puget Sound with evidence of hypoxia in some basins. However, the relative contributions of loads entering Puget Sound from natural and anthropogenic sources, and the effects of exchange flow from the Pacific Ocean are not well understood. Development of a quantitative model of Puget Sound is thus presented to help improve our understanding of the annual biogeochemical cycles in this system using the unstructured grid Finite Volume Coastal Ocean Model (FVCOM) framework and the Integrated Compartment Model (CE QUAL-ICM) water quality kinetics. Results based on 2006 data show that phytoplankton growth and die-off, succession between two species of algae, nutrient dynamics, and dissolved oxygen in Puget Sound are strongly tied to seasonal variation of temperature, solar radiation, and the annual exchange and flushing induced by upwelled Pacific Ocean waters. Concentrations in the mixed outflow surface layer occupying approximately 5−20 m of the upper water column show strong effects of eutrophication from natural and anthropogenic sources, spring and summer algae blooms, accompanied by depleted nutrients but high dissolved oxygen levels. The bottom layer reflects dissolved oxygen and nutrient concentrations of upwelled Pacific Ocean water modulated by mixing with biologically active surface outflow in the Strait of Juan De Fuca prior to entering Puget Sound over the Admiralty Inlet. The effect of reflux mixing at the Admiralty Inlet sill resulting in lower nutrient and higher dissolved oxygen levels in bottom waters of Puget Sound than the incoming upwelled Pacific Ocean water is reproduced. By late winter, with the reduction in algal activity, water column constituents of interest, were renewed and the system appeared to reset with cooler temperature, higher nutrient, and higher dissolved oxygen waters from the Pacific Ocean.

  7. Potential environmental impact of tidal energy extraction in the Pentland Firth at large spatial scales: results of a biogeochemical model

    Science.gov (United States)

    van der Molen, Johan; Ruardij, Piet; Greenwood, Naomi

    2016-05-01

    A model study was carried out of the potential large-scale (> 100 km) effects of marine renewable tidal energy generation in the Pentland Firth, using the 3-D hydrodynamics-biogeochemistry model GETM-ERSEM-BFM. A realistic 800 MW scenario and a high-impact scenario with massive expansion of tidal energy extraction to 8 GW scenario were considered. The realistic 800 MW scenario suggested minor effects on the tides, and undetectable effects on the biogeochemistry. The massive-expansion 8 GW scenario suggested effects would be observed over hundreds of kilometres away with changes of up to 10 % in tidal and ecosystem variables, in particular in a broad area in the vicinity of the Wash. There, waters became less turbid, and primary production increased with associated increases in faunal ecosystem variables. Moreover, a one-off increase in carbon storage in the sea bed was detected. Although these first results suggest positive environmental effects, further investigation is recommended of (i) the residual circulation in the vicinity of the Pentland Firth and effects on larval dispersal using a higher-resolution model and (ii) ecosystem effects with (future) state-of-the-art models if energy extraction substantially beyond 1 GW is planned.

  8. Potential environmental impact of tidal energy extraction in the Pentland Firth at large spatial scales: results of a biogeochemical model

    Directory of Open Access Journals (Sweden)

    J. van der Molen

    2015-12-01

    Full Text Available A model study was carried out of the potential large-scale (> 100 km effects of marine renewable tidal energy generation in the Pentland Firth, using the 3-D hydrodynamics-biogeochemistry model GETM-ERSEM-BFM. A realistic 800 MW scenario and an exaggerated academic 8 GW scenario were considered. The realistic 800 MW scenario suggested minor effects on the tides, and undetectable effects on the biogeochemistry. The academic 8 GW scenario suggested effects would be observed over hundreds of kilometres away with changes of up to 10 % in tidal and ecosystem variables, in particular in a broad area in the vicinity of The Wash. There, waters became less turbid, and primary production increased with associated increases in faunal ecosystem variables. Moreover, a one-off increase in carbon storage in the sea bed was detected. Although these first results suggest positive environmental effects, further investigation is recommended of: (i the residual circulation in the vicinity of the Pentland Firth and effects on larval dispersal using a higher resolution model, (ii ecosystem effects with (future state-of-the-art models if energy extraction substantially beyond 1 GW is planned.

  9. Geophysical Characterization and Reactive Transport Modeling to Quantify Plume Behavior

    Science.gov (United States)

    Hubbard, S. S.; Wainwright, H.; Bea, S. A.; Spycher, N.; Li, L.; Sassen, D.; Chen, J.

    2012-12-01

    transport over field-relevant scales as is needed for predicting the plume behavior. The second approach focuses on identifying diagnostic signatures of critical system transitions. We develop a data-driven statistical approach in which we assume the biogeochemical process can be classified into several states that can be characterized using Hidden Markov models. We use a Bayesian approach to estimate the probability of being in each state over time and space by conditioning to the time-series of the measured borehole geochemical data and geophysical time-lapse data. We apply the developed method to the Rifle DOE field study site using data collected during a bioremediation experiment (including time-lapse surface spectral induced polarization data) to estimate critical redox transitions that influence uranium mobility. We compare the complementary nature of the data-driven approach with mechanistic reactive transport models in understanding and predicting critical system transitions and as a step towards development of autonomous monitoring and assimilation approaches needed to assess long-term plume behavior.

  10. Quantifying methane emissions from rice paddies in Northeast China by integrating remote sensing mapping with a biogeochemical model

    Directory of Open Access Journals (Sweden)

    Y. Zhang

    2011-01-01

    Full Text Available The Sanjiang Plain located in Northeastern China is one of the major rice producing regions in the country. However, differing from the majority rice regions in Southern China, the Sanjinag Plain possesses a much cooler weather. Could the rice paddies in this domain be an important source of global methane? To answer this question, we calculated methane (CH4 emissions from the region by integrating remote sensing mapping with a process-based biogeochemistry model, Denitrification and Decomposition or DNDC. To quantify regional CH4 emissions from the plain, we first tested the model against a two-year dataset of CH4 fluxes measured at a typical rice field within the domian. A sensitivity test was conducted to find out the most sensitive factors affecting CH4 emissions in the region. Based on the understanding gained from the validation and sensitivity tests, a geographic information system (GIS database was constructed to hold the spatially differentiated input information to drive DNDC for its regional simulations. The GIS database included a rice map derived from the Landsat TM images, which provided crucial information about the spatial distribution of the rice fields within the domain of 10.93 million hectares. The modeled results showed that the total 1.44 million ha of rice paddies in the plain emitted 0.43–0.58 Tg CH4-C per year with spatially differentiated annual emission rates ranging between 100–800 kg CH4-C/ha, which are comparable with that observed in Southern China. The modeled data indicated that the high SOC contents, long crop season and high rice biomass enhanced CH4 production in the cool paddies. The modeled results proved that the northern wetland agroecosystems could make important contributions to global greenhouse gas inventory.

  11. Calibration of Daycent biogeochemical model for rice paddies in three agro-ecological zones in Peninsular India to optimize cropping practices and predict GHG emissions

    Science.gov (United States)

    Rajan, S.; Kritee, K.; Keough, C.; Parton, W. J.; Ogle, S. M.

    2014-12-01

    Rice is a staple for nearly half of the world population with irrigated and rainfed lowland rice accounting for about 80% of the worldwide harvested rice area. Increased atmospheric CO2 and rising temperatures are expected to adversely affect rice yields by the end of the 21st century. In addition, different crop management practices affect methane and nitrous oxide emissions from rice paddies antagonistically warranting a review of crop management practices such that farmers can adapt to the changing climate and also help mitigate climate change. The Daily DayCent is a biogeochemical model that operates on a daily time step, driven by four ecological drivers, i.e. climate, soil, vegetation, and management practices. The model is widely used to simulate daily fluxes of various gases, plant productivity, nutrient availability, and other ecosystem parameters in response to changes in land management and climate. We employed the DayCent model as a tool to optimize rice cropping practices in Peninsular India so as to develop a set of farming recommendations to ensure a triple win (i.e. higher yield, higher profit and lower GHG emissions). We applied the model to simulate both N2O and CH4 emissions, and crop yields from four rice paddies in three different agro-ecological zones under different management practices, and compared them with measured GHG and yield data from these plots. We found that, like all process based models, the biggest constraint in using the model was input data acquisition. Lack of accurate documentation of historic land use and management practices, missing historical daily weather data, and difficulty in obtaining digital records of soil and crop/vegetation parameters related to our experimental plots came in the way of our execution of this model. We will discuss utilization of estimates based on available literature, or knowledge-based values in lieu of missing measured parameters in our simulations with DayCent which could prove to be a

  12. Phytoplankton versus macrophyte contribution to primary production and biogeochemical cycles of a coastal mesotidal system. A modelling approach

    Science.gov (United States)

    Plus, M.; Auby, I.; Maurer, D.; Trut, G.; Del Amo, Y.; Dumas, F.; Thouvenin, B.

    2015-11-01

    This study presents an assessment of the contributions of various primary producers to the global annual production and N/P cycles of a coastal system, namely the Arcachon Bay, by means of a numerical model. This 3D model fully couples hydrodynamic with ecological processes and simulates nitrogen, silicon and phosphorus cycles as well as phytoplankton, macroalgae and seagrasses. Total annual production rates for the different components were calculated for different years (2005, 2007 and 2009) during a time period of drastic reduction in seagrass beds since 2005. The total demand of nitrogen and phosphorus was also calculated and discussed with regards to the riverine inputs. Moreover, this study presents the first estimation of particulate organic carbon export to the adjacent open ocean. The calculated annual net production for the Arcachon Bay (except microphytobenthos, not included in the model) ranges between 22,850 and 35,300 tons of carbon. The main producers are seagrasses in all the years considered with a contribution ranging from 56% to 81% of global production. According to our model, the -30% reduction in seagrass bed surface between 2005 and 2007, led to an approximate 55% reduction in seagrass production, while during the same period of time, macroalgae and phytoplankton enhanced their productions by about +83% and +46% respectively. Nonetheless, the phytoplankton production remains about eightfold higher than the macroalgae production. Our results also highlight the importance of remineralisation inside the Bay, since riverine inputs only fulfill at maximum 73% nitrogen and 13% phosphorus demands during the years 2005, 2007 and 2009. Calculated advection allowed a rough estimate of the organic matter export: about 10% of the total production in the bay was exported, originating mainly from the seagrass compartment, since most of the labile organic matter was remineralised inside the bay.

  13. Effects of light and phosphorus on summer DMS dynamics in subtropical waters using a global ocean biogeochemical model

    OpenAIRE

    Masotti, I; S. Belviso; Bopp, L.; A. Tagliabue; Bucciarelli, Eva

    2016-01-01

    Environmental context Models are needed to predict the importance of the changes in marine emissions of dimethylsulfide (DMS) in response to ocean warming, increased stratification and acidification, and to evaluate the potential effects on the Earth's climate. We use complementary simulations to further our understanding of the marine cycle of DMS in subtropical waters, and show that a lack of phosphorus may exert a more important control on surface DMS concentrations than an excess of light...

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

    Science.gov (United States)

    Molins, S.; Mayer, K. U.

    2007-05-01

    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.

  15. Quantifying methane emissions from rice paddies in Northeast China by integrating remote sensing mapping with a biogeochemical model

    Directory of Open Access Journals (Sweden)

    Y. Zhang

    2011-05-01

    Full Text Available The Sanjiang Plain located in Northeastern China is one of the major rice producing regions in the country. However, differing from the majority rice regions in Southern China, the Sanjinag Plain possesses a much cooler climate. Could the rice paddies in this domain be an important source of global methane? To answer this question, methane (CH4 emissions from the region were calculated by integrating remote sensing mapping with a process-based biogeochemistry model, Denitrification and Decomposition or DNDC. To quantify regional CH4 emissions from the plain, the model was first tested against a two-year dataset of CH4 fluxes measured at a typical rice field within the domain. A sensitivity test was conducted to find out the most sensitive factors affecting CH4 emissions in the region. Based on the understanding gained from the validation and sensitivity tests, a geographic information system (GIS database was constructed to hold the spatially differentiated input information to drive DNDC for its regional simulations. The GIS database included a rice map derived from the Landsat TM images acquired in 2006, which provided crucial information about the spatial distribution of the rice fields within the domain of 10.93 million ha. The modeled results showed that the total 1.44 million ha of rice paddies in the plain emitted 0.48–0.58 Tg CH4-C in 2006 with spatially differentiated annual emission rates ranging between 38.6–943.9 kg CH4-C ha−1, which are comparable with that observed in Southern China. The modeled data indicated that the high SOC contents, long crop season and high rice biomass enhanced CH4 production in the cool paddies. The modeled results proved that the northern wetland agroecosystems could make important contributions to global greenhouse gas inventory.

  16. Mechanistic site-based emulation of a global ocean biogeochemical model (MEDUSA 1.0 for parametric analysis and calibration: an application of the Marine Model Optimization Testbed (MarMOT 1.1

    Directory of Open Access Journals (Sweden)

    J. C. P. Hemmings

    2015-03-01

    Full Text Available Biogeochemical ocean circulation models used to investigate the role of plankton ecosystems in global change rely on adjustable parameters to capture the dominant biogeochemical dynamics of a complex biological system. In principle, optimal parameter values can be estimated by fitting models to observational data, including satellite ocean colour products such as chlorophyll that achieve good spatial and temporal coverage of the surface ocean. However, comprehensive parametric analyses require large ensemble experiments that are computationally infeasible with global 3-D simulations. Site-based simulations provide an efficient alternative but can only be used to make reliable inferences about global model performance if robust quantitative descriptions of their relationships with the corresponding 3-D simulations can be established. The feasibility of establishing such a relationship is investigated for an intermediate complexity biogeochemistry model (MEDUSA coupled with a widely used global ocean model (NEMO. A site-based mechanistic emulator is constructed for surface chlorophyll output from this target model as a function of model parameters. The emulator comprises an array of 1-D simulators and a statistical quantification of the uncertainty in their predictions. The unknown parameter-dependent biogeochemical environment, in terms of initial tracer concentrations and lateral flux information required by the simulators, is a significant source of uncertainty. It is approximated by a mean environment derived from a small ensemble of 3-D simulations representing variability of the target model behaviour over the parameter space of interest. The performance of two alternative uncertainty quantification schemes is examined: a direct method based on comparisons between simulator output and a sample of known target model "truths" and an indirect method that is only partially reliant on knowledge of the target model output. In general, chlorophyll

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

    DEFF Research Database (Denmark)

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

    2010-01-01

    Clayey tills contaminated with chlorinated solvents are a threat to groundwater and are difficult to remediate. A numerical model is developed for assessing leaching processes and for simulating the remediation via enhanced anaerobic dechlorination. The model simulates the transport...... to the physical processes, mainly diffusion in the matrix, than to the biogeochemical processes, when dechlorination is assumed to take place in a limited reaction zone only. The inclusion of sequential dechlorination in clay fracture transport models is crucial, as the contaminant flux to the aquifer...... of a contaminant in a single fracture-clay matrix system coupled with a reactive model for anaerobic dechlorination. The model takes into account microbially driven anaerobic dechlorination, where sequential Monod kinetics with competitive inhibition is used to model the reaction rates, and degradation...

  18. Uncertainty associated with selected environmental transport models

    International Nuclear Information System (INIS)

    A description is given of the capabilities of several models to predict accurately either pollutant concentrations in environmental media or radiological dose to human organs. The models are discussed in three sections: aquatic or surface water transport models, atmospheric transport models, and terrestrial and aquatic food chain models. Using data published primarily by model users, model predictions are compared to observations. This procedure is infeasible for food chain models and, therefore, the uncertainty embodied in the models input parameters, rather than the model output, is estimated. Aquatic transport models are divided into one-dimensional, longitudinal-vertical, and longitudinal-horizontal models. Several conclusions were made about the ability of the Gaussian plume atmospheric dispersion model to predict accurately downwind air concentrations from releases under several sets of conditions. It is concluded that no validation study has been conducted to test the predictions of either aquatic or terrestrial food chain models. Using the aquatic pathway from water to fish to an adult for 137Cs as an example, a 95% one-tailed confidence limit interval for the predicted exposure is calculated by examining the distributions of the input parameters. Such an interval is found to be 16 times the value of the median exposure. A similar one-tailed limit for the air-grass-cow-milk-thyroid for 131I and infants was 5.6 times the median dose. Of the three model types discussed in this report,the aquatic transport models appear to do the best job of predicting observed concentrations. However, this conclusion is based on many fewer aquatic validation data than were availaable for atmospheric model validation

  19. Modeling of collisional transport in ergodic region

    International Nuclear Information System (INIS)

    In recent tokamak experiments it is found that so-called stochastic diffusion theory based on the 'field line diffusion' overestimates the radial energy transport in collisionless edge plasma affected by resonant magnetic perturbations, though the perturbations induce chaotic behavior of the field lines. These results imply that the conventional modeling of the edge transport should be reconsidered for covering the range from lower to higher collisionalities. It is required to construct the modeling extracting information contributing to the transport in macro-scale from kinetic motions in micro-scale. A simulation study of collisional transport in the ergodic region is attempted for estimating the transport coefficients according to the modeling. By using a drift kinetic equation solver without the assumption of nested flux surfaces (the KEATS code), it is possible to execute the estimation. In this paper, we report the modeling constructed from the viewpoint of stochastic approach and the simulation study of the ion transport in the ergodic region under the assumption of neglecting effects of an electric field and neutrals. (author)

  20. Transport modelling to study ICRH with internal transport barriers

    International Nuclear Information System (INIS)

    Certain conditions in an auxiliary heated tokamak fusion plasma can give rise to a so called Internal Transport Barrier (ITB). Inside the radius of the barrier heat diffusion is greatly reduced. A much higher plasma temperature and core energy confinement time than normal can therefore be reached. An increased core temperature and corresponding temperature gradient can however affect the auxiliary power deposition profiles. This can reduce the amount of power deposited inside the ITB, which in turn reduces the achievable temperature. To investigate how the appearance of an ITB affects the auxiliary heating, especially Ion Cyclotron Resonance Heating (ICRH), a one-dimensional heat transport code has been developed. It uses a semi-empirical diffusivity model and calculates the evolution of the temperature profiles by means of Finite Element Methods. By iteratively taking power deposition profiles from an ICRH code and feeding temperature profiles back, the effect of the ITB on the ICRH can be established

  1. Transport properties site descriptive model. Guidelines for evaluation and modelling

    International Nuclear Information System (INIS)

    This report describes a strategy for the development of Transport Properties Site Descriptive Models within the SKB Site Investigation programme. Similar reports have been produced for the other disciplines in the site descriptive modelling (Geology, Hydrogeology, Hydrogeochemistry, Rock mechanics, Thermal properties, and Surface ecosystems). These reports are intended to guide the site descriptive modelling, but also to provide the authorities with an overview of modelling work that will be performed. The site descriptive modelling of transport properties is presented in this report and in the associated 'Strategy for the use of laboratory methods in the site investigations programme for the transport properties of the rock', which describes laboratory measurements and data evaluations. Specifically, the objectives of the present report are to: Present a description that gives an overview of the strategy for developing Site Descriptive Models, and which sets the transport modelling into this general context. Provide a structure for developing Transport Properties Site Descriptive Models that facilitates efficient modelling and comparisons between different sites. Provide guidelines on specific modelling issues where methodological consistency is judged to be of special importance, or where there is no general consensus on the modelling approach. The objectives of the site descriptive modelling process and the resulting Transport Properties Site Descriptive Models are to: Provide transport parameters for Safety Assessment. Describe the geoscientific basis for the transport model, including the qualitative and quantitative data that are of importance for the assessment of uncertainties and confidence in the transport description, and for the understanding of the processes at the sites. Provide transport parameters for use within other discipline-specific programmes. Contribute to the integrated evaluation of the investigated sites. The site descriptive modelling of

  2. Uncertainty calculation in transport models and forecasts

    DEFF Research Database (Denmark)

    Manzo, Stefano; Prato, Carlo Giacomo

    Transport projects and policy evaluations are often based on transport model output, i.e. traffic flows and derived effects. However, literature has shown that there is often a considerable difference between forecasted and observed traffic flows. This difference causes misallocation of (public...... represent the complex system in a deterministic way. By modelling complex systems, transport models are subject to uncertainty. The main consequence of such uncertainty is that point estimates of modelled traffic flows, and their derived measures, only represent one of the possible outputs generated by the...... refer to short, mid-distance road types potentially hosting commuting traffic. Any assessment of projects potentially affecting traffic flow on those links should then take into consideration this sensitivity and integrate uncertainty analysis in the decision process. The second paper analysed the...

  3. Activity transport models for PWR primary circuits

    International Nuclear Information System (INIS)

    The corrosion products activated in the primary circuit form a major source of occupational radiation dose in the PWR reactors. Transport of corrosion activity is a complex process including chemistry, reactor physics, thermodynamics and hydrodynamics. All the mechanisms involved are not known and there is no comprehensive theory for the process, so experimental test loops and plant data are very important in research efforts. Several activity transport modelling attempts have been made to improve the water chemistry control and to minimise corrosion in PWR's. In this research report some of these models are reviewed with special emphasis on models designed for Soviet VVER type reactors. (51 refs., 16 figs., 4 tabs.)

  4. Modelling of Transport Projects Uncertainties

    DEFF Research Database (Denmark)

    Salling, Kim Bang; Leleur, Steen

    2012-01-01

    investment costs, with a quantitative risk analysis based on Monte Carlo simulation and to make use of a set of exploratory scenarios. The analysis is carried out by using the CBA-DK model representing the Danish standard approach to socio-economic cost-benefit analysis. Specifically, the paper proposes to...... supplement Optimism Bias and the associated Reference Class Forecasting (RCF) technique with a new technique that makes use of a scenario-grid. We tentatively introduce and refer to this as Reference Scenario Forecasting (RSF). The final RSF output from the CBA-DK model consists of a set of scenario...

  5. Modelling of Transport Projects Uncertainties

    DEFF Research Database (Denmark)

    Salling, Kim Bang; Leleur, Steen

    investment costs, with a quantitative risk analysis based on Monte Carlo simulation and to make use of a set of exploratory scenarios. The analysis is carried out by using the CBA-DK model representing the Danish standard approach to socio-economic cost-benefit analysis. Specifically, the paper proposes to...... supplement Optimism Bias and the associated Reference Class Forecasting (RCF) technique with a new technique that makes use of a scenario-grid. We tentatively introduce and refer to this as Reference Scenario Forecasting (RSF). The final RSF output from the CBA-DK model consists of a set of scenario...

  6. A Sediment Transport Model for Sewers

    DEFF Research Database (Denmark)

    Mark, Ole; Larsson, Johan; Larsen, Torben

    1993-01-01

    This paper describes a mathematical model for transport processes in sewers. The model consists of three sub models, a surface model for the description of the buildup and the washoff of sediment particles from the surface area, a morphological model and an advection-dispersion model. The model i...... being developed as a part of a study being carried out at the University of Aalborg, Denmark and VBB VIAK, Sweden. The project is funded by the Swedish Water and Waste Water Works Association and the Nordic Industrial Foundation....

  7. Congestion Effects in Transport Modelling and Forecasting

    OpenAIRE

    West, Jens

    2015-01-01

    Transport investments and policies are increasingly turned towards dealing with transport congestion rather than with shortening the potential free flow travel time. However, appraisal methodologies for projects meant to reduce congestion are relatively less well developed compared to methodologies for projects aiming to reduce travel times. Static assignment models are for instance incapable of predicting the build-up and dissipation of traffic queues and capturing the experienced crowding c...

  8. MODELLING PRODUCTIONS AND ATTRACTIONS OF FREIGHT TRANSPORT

    OpenAIRE

    Zibelnik, Klemen

    2011-01-01

    This diploma thesis addresses the theoretical bases of the regression analysis, identifies the data necessary for the performance of the analysis and modelling of productions and freight transport attractions and examines dependence of European states’ export and import respectively on socio-economic indicators of the states. The focus was limited to the EU Member States and candidate countries for the entry into the EU as well as the available railway and road transport data a...

  9. Regional transport model of atmospheric sulfates

    International Nuclear Information System (INIS)

    As part of the Sulfate Regional Experiment (SURE) Design Project, a regional transport model of atmospheric sulfates has been developed. This quasi-Lagrangian three-dimensional grid numerical model uses a detailed SO2 emission inventory of major anthropogenic sources in the Eastern U.S. region, and observed meteorological data during an episode as inputs. The model accounts for advective transport and turbulent diffusion of the pollutants. The chemical transformation of SO2 and SO4/sup =/ and the deposition of the species at the earth's surface are assumed to be linear processes at specified constant rates. The numerical model can predict the daily average concentrations of SO2 and SO4/sup =/ at all receptor locations in the grid region during the episode. Because of the spatial resolution of the grid, this model is particularly suited to investigate the effect of tall stacks in reducing the ambient concentration levels of sulfur pollutants. This paper presents the formulations and assumptions of the regional sulfate transport model. The model inputs and results are discussed. Isopleths of predicted SO2 and SO4/sup =/ concentrations are compared with the observed ground level values. The bulk of the information in this paper is directed to air pollution meteorologists and environmental engineers interested in the atmospheric transport modeling studies of sulfur oxide pollutants

  10. Radionuclide Transport Models Under Ambient Conditions

    International Nuclear Information System (INIS)

    The purpose of Revision 00 of this Analysis/Model Report (AMR) is to evaluate (by means of 2-D semianalytical and 3-D numerical models) the transport of radioactive solutes and colloids in the unsaturated zone (UZ) under ambient conditions from the potential repository horizon to the water table at Yucca Mountain (YM), Nevada

  11. Radionuclide Transport Models Under Ambient Conditions

    Energy Technology Data Exchange (ETDEWEB)

    G. Moridis; Q. Hu

    2001-12-20

    The purpose of Revision 00 of this Analysis/Model Report (AMR) is to evaluate (by means of 2-D semianalytical and 3-D numerical models) the transport of radioactive solutes and colloids in the unsaturated zone (UZ) under ambient conditions from the potential repository horizon to the water table at Yucca Mountain (YM), Nevada.

  12. Modeling biogeochemical processes in sediments from the Rhône River prodelta area (NW Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    L. Pastor

    2011-05-01

    Full Text Available In situ oxygen microprofiles, sediment organic carbon content, and pore-water concentrations of nitrate, ammonium, iron, manganese, and sulfides obtained in sediments from the Rhône River prodelta and its adjacent continental shelf were used to constrain a numerical diagenetic model. Results showed that (1 the organic matter from the Rhône River is composed of a fraction of fresh material associated to high first-order degradation rate constants (11–33 yr−1; (2 the burial efficiency (burial/input ratio in the Rhône prodelta (within 3 km of the river outlet can be up to 80 %, and decreases to ~20 % on the adjacent continental shelf 10–15 km further offshore; (3 there is a large contribution of anoxic processes to total mineralization in sediments near the river mouth, certainly due to large inputs of fresh organic material combined with high sedimentation rates; (4 diagenetic by-products originally produced during anoxic organic matter mineralization are almost entirely precipitated (>97 % and buried in the sediment, which leads to (5 a low contribution of the re-oxidation of reduced products to total oxygen consumption. Consequently, total carbon mineralization rates as based on oxygen consumption rates and using Redfield stoichiometry can be largely underestimated in such River-dominated Ocean Margins (RiOMar environments.

  13. Impact of vegetation and ecosystems on chlorine(-36) cycling and its modeling: from simplified approaches towards more complex biogeochemical tools

    Science.gov (United States)

    Thiry, Yves; Redon, Paul-Olivier; Gustafsson, Malin; Marang, Laura; Bastviken, David

    2013-04-01

    Chlorine is very soluble at a global scale with chloride (Cl-), the dominating form. Because of its high mobility, chlorine is usually perceived as a good conservative tracer in hydrological studies and by analogy as little reactive in biosphere. Since 36Cl can be considered to have the same behaviour than stable Cl, a good knowledge of chlorine distribution between compartments of terrestrial ecosystems is sufficient to calibrate a specific activity model which supposes rapid dilution of 36Cl within the large pool of stable Cl and isotopic equilibrium between compartments. By assuming 36Cl redistribution similar to that of stable Cl at steady-state, specific activity models are simplified interesting tools for regulatory purposes in environmental safety assessment, especially in case of potential long term chronic contamination of agricultural food chain (IAEA, 2010). In many other more complex scenarios (accidental acute release, intermediate time frame, and contrasted natural ecosystems), new information and tools are necessary for improving (radio-)ecological realism, which entails a non-conservative behavior of chlorine. Indeed observed dynamics of chlorine in terrestrial ecosystems is far from a simple equilibrium notably because of natural processes of organic matter (SOM) chlorination mainly occurring in surface soils (Öberg, 1998) and mediated by microbial activities on a large extent (Bastviken et al. 2007). Our recent studies have strengthened the view that an organic cycle for chlorine should now be recognized, in addition to its inorganic cycle. Major results showed that: organochlorine (Clorg) formation occurs in all type of soils and ecosystems (culture, pasture, forest), leading to an average fraction of the total Cl pool in soil of about 80 % (Redon et al., 2012), chlorination in more organic soils over time leads to a larger Clorg pool and in turn to a possible high internal supply of inorganic chlorine (Clin) upon dechlorination. (Gustafsson et

  14. Radionuclide Transport Models Under Ambient Conditions

    International Nuclear Information System (INIS)

    The purpose of this Analysis/Model Report (AMR) is to evaluate (by means of 2-D semianalytical and 3-D numerical models) the transport of radioactive solutes and colloids in the unsaturated zone (UZ) under ambient conditions from the potential repository horizon to the water table at Yucca Mountain (YM), Nevada. This is in accordance with the ''AMR Development Plan U0060, Radionuclide Transport Models Under Ambient Conditions'' (CRWMS M and O 1999a). This AMR supports the UZ Flow and Transport Process Model Report (PMR). This AMR documents the UZ Radionuclide Transport Model (RTM). This model considers: the transport of radionuclides through fractured tuffs; the effects of changes in the intensity and configuration of fracturing from hydrogeologic unit to unit; colloid transport; physical and retardation processes and the effects of perched water. In this AMR they document the capabilities of the UZ RTM, which can describe flow (saturated and/or unsaturated) and transport, and accounts for (a) advection, (b) molecular diffusion, (c) hydrodynamic dispersion (with full 3-D tensorial representation), (d) kinetic or equilibrium physical and/or chemical sorption (linear, Langmuir, Freundlich or combined), (e) first-order linear chemical reaction, (f) radioactive decay and tracking of daughters, (g) colloid filtration (equilibrium, kinetic or combined), and (h) colloid-assisted solute transport. Simulations of transport of radioactive solutes and colloids (incorporating the processes described above) from the repository horizon to the water table are performed to support model development and support studies for Performance Assessment (PA). The input files for these simulations include transport parameters obtained from other AMRs (i.e., CRWMS M and O 1999d, e, f, g, h; 2000a, b, c, d). When not available, the parameter values used are obtained from the literature. The results of the simulations are used to evaluate the transport of radioactive solutes and colloids, and

  15. Radionuclide Transport Models Under Ambient Conditions

    Energy Technology Data Exchange (ETDEWEB)

    G. Moridis; Q. Hu

    2000-03-12

    The purpose of this Analysis/Model Report (AMR) is to evaluate (by means of 2-D semianalytical and 3-D numerical models) the transport of radioactive solutes and colloids in the unsaturated zone (UZ) under ambient conditions from the potential repository horizon to the water table at Yucca Mountain (YM), Nevada. This is in accordance with the ''AMR Development Plan U0060, Radionuclide Transport Models Under Ambient Conditions'' (CRWMS M and O 1999a). This AMR supports the UZ Flow and Transport Process Model Report (PMR). This AMR documents the UZ Radionuclide Transport Model (RTM). This model considers: the transport of radionuclides through fractured tuffs; the effects of changes in the intensity and configuration of fracturing from hydrogeologic unit to unit; colloid transport; physical and retardation processes and the effects of perched water. In this AMR they document the capabilities of the UZ RTM, which can describe flow (saturated and/or unsaturated) and transport, and accounts for (a) advection, (b) molecular diffusion, (c) hydrodynamic dispersion (with full 3-D tensorial representation), (d) kinetic or equilibrium physical and/or chemical sorption (linear, Langmuir, Freundlich or combined), (e) first-order linear chemical reaction, (f) radioactive decay and tracking of daughters, (g) colloid filtration (equilibrium, kinetic or combined), and (h) colloid-assisted solute transport. Simulations of transport of radioactive solutes and colloids (incorporating the processes described above) from the repository horizon to the water table are performed to support model development and support studies for Performance Assessment (PA). The input files for these simulations include transport parameters obtained from other AMRs (i.e., CRWMS M and O 1999d, e, f, g, h; 2000a, b, c, d). When not available, the parameter values used are obtained from the literature. The results of the simulations are used to evaluate the transport of radioactive

  16. Simulating Carbon Sequestration and GHGs Emissions in Abies fabric Forest on the Gongga Mountains Using a Biogeochemical Process Model Forest-DNDC

    Institute of Scientific and Technical Information of China (English)

    LU Xuyang; CHENG Genwei; XIAO Feipeng; HUO Changfu

    2008-01-01

    The process-oriented model Forest-DNDC describing biogeochemical cycling of C and N and GHGs (greenhouse gases) fluxes (CO2, NO and N2O) in forest ecosystems was applied to simulate carbon sequestration and GHGs emissions in Abies fabric forest of the Gongga Mountains at southeastern edge of the Tibetan Plateau. The results indicated that the simulated gross primary production (GPP) of Abies fabric forest was strongly affected by temperature. The annual total GPP was 24,245.3 kg C ha-1 yr-1 for 2005 and 26,318.8 kg C ha-1 yr-1 for 2006, respectively. The annual total net primary production (NPP) was 5,935.5 and 4,882.2 kg C ha-1 yr-1 for 2005 and 2006, and the annual total net ecosystem production (NEP) was 4,815.4 and 3,512.8 kg C ha-1 yr-1 for 2005 and 2006, respectively. The simulated seasonal variation in CO2 emissions generally followed the seasonal variations in temperature and precipitation. The annual total CO2 emissions were 3,109.0 and 4,821.0 kg C ha-1 yr-1 for 2005 and 2006, the simulated annual total N2O emissions from forest soil were 1.47 and 1.36 kg N ha-1 yr-1 for 2005 and 2006, and the annual total NO emissions were 0.09 and 0.12 kg N ha-1 yr-1 for 2005 and 2006, respectively.

  17. Hydrologic and biogeochemical functioning of intensively managed catchments: A synthesis of top-down analyses

    Science.gov (United States)

    Basu, Nandita B.; Thompson, Sally E.; Rao, P. Suresh C.

    2011-10-01

    This paper synthesizes a 3-year collaborative effort to characterize the biogeochemical and hydrological features of intensively managed agricultural catchments by combining data analysis, modeling, and preliminary hypothesis testing. The specific focus was on the Midwestern region of the United States. The results suggest that: (1) water management, specifically the homogenization of evapotranspiration losses driven by mono-cultural vegetation cover, and the homogenization of runoff generation driven by artificial drainage, has created engineered, predictable hydrologic systems; (2) nutrient and pesticide management, specifically their regular applications have created two kinds of biogeochemical export regimes: chemostatic (low variability in concentration as exhibited by nitrate) and episodic (high variability in concentration as exhibited by pesticides); (3) coupled mass-balance models for water and solutes reproduce these two regimes as a function of chemical rate constants. Phosphorus transport regimes were found to be episodic at smaller spatial scales, but chemostatic at larger scales. Chemostatic response dominates in transport-limited catchments that have internal sources of the solute to buffer the periodicity in episodic inputs, while episodic response dominates in source-limited catchments. The shift from episodic nitrate export in pristine catchments to chemostatic regimes in managed watersheds was attributed to legacy stores of nitrogen (built from continued fertilizer applications) that buffer interannual variations in biogeochemical processing. Fast degradation kinetics of pesticides prevents the build-up of legacy sources, and leads to episodic export. Analytical expressions were derived for the probability density functions of solute delivery ratio as a function of the stochastics of rainfall-runoff events and biogeochemical controls.

  18. Development and testing of conceptual models describing plutonium subsurface transport (Invited)

    Science.gov (United States)

    Powell, B. A.

    2009-12-01

    , a conceptual model describing the effects of plutonium redox cycling on subsurface transport was developed. This model accurately described downward movement of plutonium in a series of field lysimeters. Research related to these lysimeters has continued using a combination of long-term field observations, laboratory measurements, and computer modeling which have provided a unique and detailed conceptual and quantitative model describing plutonium subsurface transport. Field and laboratory experiments indicate that biogeochemical processes such as ligand complexation and redox cycling profoundly influence plutonium subsurface transport. This presentation will focus on laboratory efforts to develop these conceptual models and provide a quantitative framework for reactive transport modeling efforts.

  19. Quantification of Terrestrial Ecosystem Carbon Dynamics in the Conterminous United States Combining a Process-Based Biogeochemical Model and MODIS and AmeriFlux data

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Min; Zhuang, Qianlai; Cook, David R.; Coulter, Richard L.; Pekour, Mikhail S.; Scott, Russell L.; Munger, J. W.; Bible, Ken

    2011-09-21

    Satellite remote sensing provides continuous temporal and spatial information of terrestrial 24 ecosystems. Using these remote sensing data and eddy flux measurements and biogeochemical 25 models, such as the Terrestrial Ecosystem Model (TEM), should provide a more adequate 26 quantification of carbon dynamics of terrestrial ecosystems. Here we use Moderate Resolution 27 Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI), Land Surface Water Index 28 (LSWI) and carbon flux data of AmeriFlux to conduct such a study. We first modify the gross primary 29 production (GPP) modeling in TEM by incorporating EVI and LSWI to account for the effects of the 30 changes of canopy photosynthetic capacity, phenology and water stress. Second, we parameterize and 31 verify the new version of TEM with eddy flux data. We then apply the model to the conterminous 32 United States over the period 2000-2005 at a 0.05o ×0.05o spatial resolution. We find that the new 33 version of TEM generally captured the expected temporal and spatial patterns of regional carbon 34 dynamics. We estimate that regional GPP is between 7.02 and 7.78 Pg C yr-1 and net primary 35 production (NPP) ranges from 3.81 to 4.38 Pg C yr-1 and net ecosystem production (NEP) varies 36 within 0.08-0.73 Pg C yr-1 over the period 2000-2005 for the conterminous United States. The 37 uncertainty due to parameterization is 0.34, 0.65 and 0.18 Pg C yr-1 for the regional estimates of GPP, 38 NPP and NEP, respectively. The effects of extreme climate and disturbances such as severe drought in 39 2002 and destructive Hurricane Katrina in 2005 were captured by the model. Our study provides a 40 new independent and more adequate measure of carbon fluxes for the conterminous United States, 41 which will benefit studies of carbon-climate feedback and facilitate policy-making of carbon 42 management and climate.

  20. Quantification of terrestrial ecosystem carbon dynamics in the conterminous United States combining a process-based biogeochemical model and MODIS and AmeriFlux data

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Min; Zhuang, Qianlai; Cook, D.; Coulter, Richard L.; Pekour, Mikhail S.; Scott, Russell L.; Munger, J. W.; Bible, Ken

    2011-08-31

    Satellite remote sensing provides continuous temporal and spatial information of terrestrial ecosystems. Using these remote sensing data and eddy flux measurements and biogeochemical models, such as the Terrestrial Ecosystem Model (TEM), should provide a more adequate quantification of carbon dynamics of terrestrial ecosystems. Here we use Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI), Land Surface Water Index (LSWI) and carbon flux data of AmeriFlux to conduct such a study. We first modify the gross primary production (GPP) modeling in TEM by incorporating EVI and LSWI to account for the effects of the changes of canopy photosynthetic capacity, phenology and water stress. Second, we parameterize and verify the new version of TEM with eddy flux data. We then apply the model to the conterminous United States over the period 2000-2005 at a 0.05-0.05 spatial resolution. We find that the new version of TEM made improvement over the previous version and generally captured the expected temporal and spatial patterns of regional carbon dynamics. We estimate that regional GPP is between 7.02 and 7.78 PgC yr{sup -1} and net primary production (NPP) ranges from 3.81 to 4.38 Pg Cyr{sup -1} and net ecosystem production (NEP) varies within 0.08- 0.73 PgC yr{sup -1} over the period 2000-2005 for the conterminous United States. The uncertainty due to parameterization is 0.34, 0.65 and 0.18 PgC yr{sup -1} for the regional estimates of GPP, NPP and NEP, respectively. The effects of extreme climate and disturbances such as severe drought in 2002 and destructive Hurricane Katrina in 2005 were captured by the model. Our study provides a new independent and more adequate measure of carbon fluxes for the conterminous United States, which will benefit studies of carbon-climate feedback and facilitate policy-making of carbon management and climate.

  1. Diffusion Dominant Solute Transport Modelling In Deep Repository Under The Effect of Emplacement Media Degradation - 13285

    International Nuclear Information System (INIS)

    Deep geologic disposal of high activity and long-lived radioactive waste is being actively considered and pursued in many countries, where low permeability geological formations are used to provide long term waste contaminant with minimum impact to the environment and risk to the biosphere. A multi-barrier approach that makes use of both engineered and natural barriers (i.e. geological formations) is often used to further enhance the containment performance of the repository. As the deep repository system subjects to a variety of thermo-hydro-chemo-mechanical (THCM) effects over its long 'operational' lifespan (e.g. 0.1 to 1.0 million years, the integrity of the barrier system will decrease over time (e.g. fracturing in rock or clay)). This is broadly referred as media degradation in the present study. This modelling study examines the effects of media degradation on diffusion dominant solute transport in fractured media that are typical of deep geological environment. In particular, reactive solute transport through fractured media is studied using a 2-D model, that considers advection and diffusion, to explore the coupled effects of kinetic and equilibrium chemical processes, while the effects of degradation is studied using a pore network model that considers the media diffusivity and network changes. Model results are presented to demonstrate the use of a 3D pore-network model, using a novel architecture, to calculate macroscopic properties of the medium such as diffusivity, subject to pore space changes as the media degrade. Results from a reactive transport model of a representative geological waste disposal package are also presented to demonstrate the effect of media property change on the solute migration behaviour, illustrating the complex interplay between kinetic biogeochemical processes and diffusion dominant transport. The initial modelling results demonstrate the feasibility of a coupled modelling approach (using pore-network model and reactive

  2. DAC 22 High Speed Civil Transport Model

    Science.gov (United States)

    1992-01-01

    Between tests, NASA research engineer Dave Hahne inspects a tenth-scale model of a supersonic transport model in the 30- by 60-Foot Tunnel at NASA Langley Research Center, Hampton, Virginia. The model is being used in support of NASA's High-Speed Research (HSR) program. Langley researchers are applying advance aerodynamic design methods to develop a wing leading-edge flap system which significantly improves low-speed fuel efficiency and reduces noise generated during takeoff operation. Langley is NASA's lead center for the agency's HSR program, aimed at developing technology to help U.S. industry compete in the rapidly expanding trans-oceanic transport market. A U.S. high-speed civil transport is expected to fly in about the year 2010. As envisioned, it would fly 300 passengers across the Pacific in about four hours at Mach 2.4 (approximately 1,600 mph/1950 kph) for a modest increase over business class fares.

  3. GEOS-5 Chemistry Transport Model User's Guide

    Science.gov (United States)

    Kouatchou, J.; Molod, A.; Nielsen, J. E.; Auer, B.; Putman, W.; Clune, T.

    2015-01-01

    The Goddard Earth Observing System version 5 (GEOS-5) General Circulation Model (GCM) makes use of the Earth System Modeling Framework (ESMF) to enable model configurations with many functions. One of the options of the GEOS-5 GCM is the GEOS-5 Chemistry Transport Model (GEOS-5 CTM), which is an offline simulation of chemistry and constituent transport driven by a specified meteorology and other model output fields. This document describes the basic components of the GEOS-5 CTM, and is a user's guide on to how to obtain and run simulations on the NCCS Discover platform. In addition, we provide information on how to change the model configuration input files to meet users' needs.

  4. Modelling activity transport behavior in PWR plant

    International Nuclear Information System (INIS)

    The activation and transport of corrosion products around a PWR circuit is a major concern to PWR plant operators as these may give rise to high personnel doses. The understanding of what controls dose rates on ex-core surfaces and shutdown releases has improved over the years but still several questions remain unanswered. For example the relative importance of particle and soluble deposition in the core to activity levels in the plant is not clear. Wide plant to plant and cycle to cycle variations are noted with no apparent explanations why such variations are observed. Over the past few years this group have been developing models to simulate corrosion product transport around a PWR circuit. These models form the basis for the latest version of the BOA code and simulate the movement of Fe and Ni around the primary circuit. Part of this development is to include the activation and subsequent transport of radioactive species around the circuit and this paper describes some initial modelling work in this area. A simple model of activation, release and deposition is described and then applied to explain the plant behaviour at Sizewell B and Vandellos II. This model accounts for activation in the core, soluble and particulate activity movement around the circuit and for activity capture ex-core on both the inner and outer oxides. The model gives a reasonable comparison with plant observations and highlights what controls activity transport in these plants and importantly what factors can be ignored. (authors)

  5. Modeling biologically reactive transport in porous media

    International Nuclear Information System (INIS)

    A one-dimensional biofilm-based reactive transport model is developed to simulate biologically mediated substrate metabolism and contaminant destruction in saturated porous media. The resulting equations are solved by a finite-difference based, three-level, operator-split approach. The numerical solution procedure is stable, easy-to-code, and computationally efficient. As an example problem, biological denitrification and fortuitous CT destruction processes in one-dimensional porous media is studied. The simulation results of the example problem show that the present model can be successfully used to predict biological processes and nutrient/contaminant transport in saturated porous media

  6. The chemical transport model Oslo CTM3

    Directory of Open Access Journals (Sweden)

    O. A. Søvde

    2012-06-01

    Full Text Available We present here the global chemical transport model Oslo CTM3, an update of the Oslo CTM2. The update comprises a faster transport scheme, an improved wet scavenging scheme for large scale rain, updated photolysis rates and a new lightning parameterization. Oslo CTM3 is better parallelized and allows for stable, large time steps for advection, enabling more complex or high resolution simulations. Thorough comparisons between the Oslo CTM3, Oslo CTM2 and measurements are performed, and in general the Oslo CTM3 is found to reproduce measurements well. Inclusion of tropospheric sulfur chemistry and nitrate aerosols in CTM3 is shown to be important to reproduce tropospheric O3, OH and the CH4 lifetime well. Using the same meteorology to drive the two models, shows that some features related to transport are better resolved by the CTM3, such as polar cap transport, while features like transport close to the vortex edge are resolved better in the Oslo CTM2 due to its required shorter transport time step. The longer transport time steps in CTM3 result in larger errors e.g. near the jets, and when necessary, this can be remedied by using a shorter time step. An additional, more accurate and time consuming, treatment of polar cap transport is presented, however, both perform acceptably. A new treatment of the horizontal distribution of lightning is presented and found to compare well with measurements. Vertical distributions of lighting are updated, and tested against the old vertical distribution. The new profiles are found to produce more NOx in the tropical middle troposphere, and less at the surface and at high altitudes.

  7. Reactive transport models and simulation with ALLIANCES

    International Nuclear Information System (INIS)

    Many chemical processes influence the evolution of nuclear waste storage. As a result, simulations based only upon transport and hydraulic processes fail to describe adequately some industrial scenarios. We need to take into account complex chemical models (mass action laws, kinetics...) which are highly non-linear. In order to simulate the coupling of these chemical reactions with transport, we use a classical Sequential Iterative Approach (SIA), with a fixed point algorithm, within the mainframe of the ALLIANCES platform. This approach allows us to use the various transport and chemical modules available in ALLIANCES, via an operator-splitting method based upon the structure of the chemical system. We present five different applications of reactive transport simulations in the context of nuclear waste storage: 1. A 2D simulation of the lixiviation by rain water of an underground polluted zone high in uranium oxide; 2. The degradation of the steel envelope of a package in contact with clay. Corrosion of the steel creates corrosion products and the altered package becomes a porous medium. We follow the degradation front through kinetic reactions and the coupling with transport; 3. The degradation of a cement-based material by the injection of an aqueous solution of zinc and sulphate ions. In addition to the reactive transport coupling, we take into account in this case the hydraulic retroaction of the porosity variation on the Darcy velocity; 4. The decalcification of a concrete beam in an underground storage structure. In this case, in addition to the reactive transport simulation, we take into account the interaction between chemical degradation and the mechanical forces (cracks...), and the retroactive influence on the structure changes on transport; 5. The degradation of the steel envelope of a package in contact with a clay material under a temperature gradient. In this case the reactive transport simulation is entirely directed by the temperature changes and

  8. Modelling of activity transport in PHWR

    International Nuclear Information System (INIS)

    The modelling of mass and activity transport in PHWR is of importance in predicting the build up of radiation field in and around the Primary Heat Transport system which will consequently help in planning the Dilute Chemical Decontamination and man rem budgeting. Modeling also helps in understanding the different parameters controlling the transport behaviour. Some of the important parameters include coolant chemistry like pH, physical parameters like temperature, the nature of the corrosion film and hence the effect of passivation techniques. VVER code for activity transport uses six nodes for the primary system and is essentially devised for stainless steel system. In the present work though based on this model, major modifications have been incorporated to suit the PHWR conditions. In the code, the PHT system of PHWR is suitably divided into 14 nodes, 5 in-core and 9 out of core nodes based on material and heat transfer properties. This paper describes the mechanisms involved in the various processes like generation of corrosion products, their release as well as their transport into the primary coolant, the activation of inactive corrosion product nuclides and the build up of radiation field due to 60Co around the PHT system. (author)

  9. Numerical models of groundwater flow and transport

    International Nuclear Information System (INIS)

    This chapter reviews the state-of-the-art in deterministic modeling of groundwater flow and transport processes, which can be used for interpretation of isotope data through groundwater flow analyses. Numerical models which are available for this purpose are described and their applications to complex field problems are discussed. The theoretical bases of deterministic modeling are summarized, and advantages and limitations of numerical models are described. The selection of models for specific applications and their calibration procedures are described, and results of a few illustrative case study type applications are provided. (author). 145 refs, 17 figs, 2 tabs

  10. Linear transport models for adsorbing solutes

    Science.gov (United States)

    Roth, K.; Jury, W. A.

    1993-04-01

    A unified linear theory for the transport of adsorbing solutes through soils is presented and applied to analyze movement of napropamide through undisturbed soil columns. The transport characteristics of the soil are expressed in terms of the travel time distribution of the mobile phase which is then used to incorporate local interaction processes. This approach permits the analysis of all linear transport processes, not only the small subset for which a differential description is known. From a practical point of view, it allows the direct use of measured concentrations or fluxes of conservative solutes to characterize the mobile phase without first subjecting them to any model. For complicated flow regimes, this may vastly improve the identification of models and estimation of their parameters for the local adsorption processes.

  11. Radon transport: laboratory and model study

    International Nuclear Information System (INIS)

    In order to exploit radon profiles for geophysical purposes and also to estimate its entry indoors, it is necessary to study its transport through porous soils. The great number of involved parameters and processes affecting the emanation of radon from the soil grains and its transport in the source medium has led to many theoretical and/or laboratory studies. The authors report the first results of a laboratory study carried out at the Radioactivity Laboratory of the Department of Physics and Astronomy (University of Catania) by means of a facility for measuring radon concentrations in the sample pores at various depths under well-defined and controlled conditions of physical parameters. In particular, radon concentration vertical profiles extracted in low-moisture samples for different advective fluxes and temperatures were compared with expected concentrations, according to a three-phase transport model developed by Andersen (Risoe National Laboratory, Denmark), showing, in general, a good agreement between measurements and model calculations. (authors)

  12. Silicon isotopic chemistry in the Changjiang Estuary and coastal regions: Impacts of physical and biogeochemical processes on the transport of riverine dissolved silica

    Science.gov (United States)

    Zhang, A. Y.; Zhang, J.; Hu, J.; Zhang, R. F.; Zhang, G. S.

    2015-10-01

    The dissolved silica (DSi) concentration and silicon isotopic composition (δ30Si) of surface water samples from the Changjiang Estuary was measured in summer and winter to study the behavior of DSi fluvial inputs into the estuary. The DSi concentration decreased away from the estuary and had a linear relationship with salinity, suggesting that mixing between river water and seawater is the dominant effect on DSi levels in the study area. Measured δ30Si in the Changjiang Estuary ranged from +1.48‰ to +2.35‰ in summer, and from +1.54‰ to +1.95‰ in winter. As a result of low light levels and abundant DSi riverine inputs, DSi remains relatively unaffected by biological utilization and fractionation in the near-shore region, and the isotopic imprint of water from the Changjiang can still be detected up to a salinity level of 20 in summer. An obvious increase in δ30Si was observed beyond this salinity level, indicating a significant increase in biological utilization and fractionation of DSi in high salinity waters. Lower water temperatures and light levels that prevail over the winter lead to the reduced fractionation of DSi compared with that in summer. The fractionation factor (30ɛ) was estimated using a steady state model to the high salinity waters, yielding a value of -0.95‰, which is in agreement with previous results obtained for Skeletonema costatum in cultivation experiments. The results of this study suggest that silicon isotopes can be used to identify the impact of biological utilization on the behavior of DSi in highly dynamic estuarine environments.

  13. Biogeochemical weathering under ice: Size matters

    Science.gov (United States)

    Wadham, J. L.; Tranter, M.; Skidmore, M.; Hodson, A. J.; Priscu, J.; Lyons, W. B.; Sharp, M.; Wynn, P.; Jackson, M.

    2010-09-01

    The basal regions of continental ice sheets are gaps in our current understanding of the Earth's biosphere and biogeochemical cycles. We draw on existing and new chemical data sets for subglacial meltwaters to provide the first comprehensive assessment of sub-ice sheet biogeochemical weathering. We show that size of the ice mass is a critical control on the balance of chemical weathering processes and that microbial activity is ubiquitous in driving dissolution. Carbonate dissolution fueled by sulfide oxidation and microbial CO2 dominate beneath small valley glaciers. Prolonged meltwater residence times and greater isolation characteristic of ice sheets lead to the development of anoxia and enhanced silicate dissolution due to calcite saturation. We show that sub-ice sheet environments are highly geochemically reactive and should be considered in regional and global solute budgets. For example, calculated solute fluxes from Antarctica (72-130 t yr-1) are the same order of magnitude as those from some of the world's largest rivers and rates of chemical weathering (10-17 t km-2 yr-1) are high for the annual specific discharge (2.3-4.1 × 10-3 m). Our model of chemical weathering dynamics provides important information on subglacial biodiversity and global biogeochemical cycles and may be used to design strategies for the first sampling of Antarctic Subglacial Lakes and other sub-ice sheet environments for the next decade.

  14. Dimensionless Numbers For Morphological, Thermal And Biogeochemical Controls Of Hyporheic Processes

    Science.gov (United States)

    Bellin, Alberto; Marzadri, Alessandra; Tonina, Daniele

    2013-04-01

    Transport of solutes and heat within the hyporheic zone are interface processes that gained growing attention in the last decade, when several modelling strategies have been proposed, mainly at the local or reach scale. We propose to upscale local hyporheic biogeochemical processes to reach and network scales by means of a Lagrangian modelling framework, which allows to consider the impact of the flow structure on the processes modelled. This analysis shows that geochemical processes can be parametrized through two new Damköhler numbers, DaO, and DaT. DaO = ?up,50-?lim is defined as the ratio between the median hyporheic residence time, ?up,50 and the time of consuming dissolved oxygen to a prescribed threshold concentration, ?lim, below which reductive reactions are activated. It quantifies the biogeochemical status of the hyporheic zone and could be a metric for upscaling local hyporheic biogeochemical processes to reach and river-network scale processes. In addition, ?up,50 is the time scale of hyporheic advection; while ?lim is the representative time scale of biogeochemical reactions and indicates the distance along the streamline, measured as the time needed to travel that distance, that a particle of water travels before the dissolved oxygen concentration declines to [DO]lim, the value at which denitrification is activated. We show that DaO is representative of the redox status and indicates whether the hyporheic zone is a source or a sink of nitrate. Values of DaO larger than 1 indicate prevailing anaerobic conditions, whereas values smaller than 1 prevailing aerobic conditions. Similarly, DaT quantifies the importance of the temperature daily oscillations of the stream water on the hyporheic environment. It is defined as the ratio between ?up,50, and the time limit at which the ratio between the amplitude of the temperature oscillation within the hyporheic zone (evaluated along the streamline) and in the stream water is smaller than e-1. We show that

  15. Logistics Chains in Freight Transport Modelling

    NARCIS (Netherlands)

    Davydenko, I.Y.

    2015-01-01

    The flow of trade is not equal to transport flows, mainly due to the fact that warehouses and distribution facilities are used as intermediary stops on the way from production locations to the points of consumption or further rework of goods. This thesis proposes a logistics chain model, which estim

  16. Cumulus parameterizations in chemical transport models

    Science.gov (United States)

    Mahowald, Natalie M.; Rasch, Philip J.; Prinn, Ronald G.

    1995-12-01

    Global three-dimensional chemical transport models (CTMs) are valuable tools for studying processes controlling the distribution of trace constituents in the atmosphere. A major uncertainty in these models is the subgrid-scale parametrization of transport by cumulus convection. This study seeks to define the range of behavior of moist convective schemes and point toward more reliable formulations for inclusion in chemical transport models. The emphasis is on deriving convective transport from meteorological data sets (such as those from the forecast centers) which do not routinely include convective mass fluxes. Seven moist convective parameterizations are compared in a column model to examine the sensitivity of the vertical profile of trace gases to the parameterization used in a global chemical transport model. The moist convective schemes examined are the Emanuel scheme [Emanuel, 1991], the Feichter-Crutzen scheme [Feichter and Crutzen, 1990], the inverse thermodynamic scheme (described in this paper), two versions of a scheme suggested by Hack [Hack, 1994], and two versions of a scheme suggested by Tiedtke (one following the formulation used in the ECMWF (European Centre for Medium-Range Weather Forecasting) and ECHAM3 (European Centre and Hamburg Max-Planck-Institut) models [Tiedtke, 1989], and one formulated as in the TM2 (Transport Model-2) model (M. Heimann, personal communication, 1992). These convective schemes vary in the closure used to derive the mass fluxes, as well as the cloud model formulation, giving a broad range of results. In addition, two boundary layer schemes are compared: a state-of-the-art nonlocal boundary layer scheme [Holtslag and Boville, 1993] and a simple adiabatic mixing scheme described in this paper. Three tests are used to compare the moist convective schemes against observations. Although the tests conducted here cannot conclusively show that one parameterization is better than the others, the tests are a good measure of the

  17. Transperitoneal transport of creatinine. A comparison of kinetic models

    DEFF Research Database (Denmark)

    Fugleberg, S; Graff, J; Joffe, P; Løkkegaard, H; Feldt-Rasmussen, B; Fogh-Andersen, N; Nielsen, S L

    1994-01-01

    Six kinetic models of transperitoneal creatinine transport were formulated and validated on the basis of experimental results obtained from 23 non-diabetic patients undergoing peritoneal dialysis. The models were designed to elucidate the presence or absence of diffusive, non-lymphatic convective...... the model including all three forms of transport is superior to other models. We conclude that the best model of transperitoneal creatinine transport includes diffusion, non-lymphatic convective transport and lymphatic convective transport....

  18. Variational multiscale models for charge transport

    OpenAIRE

    Wei, Guo-Wei; Zheng, Qiong; Chen, Zhan; Xia, Kelin

    2012-01-01

    This work presents a few variational multiscale models for charge transport in complex physical, chemical and biological systems and engineering devices, such as fuel cells, solar cells, battery cells, nanofluidics, transistors and ion channels. An essential ingredient of the present models, introduced in an earlier paper (Bulletin of Mathematical Biology, 72, 1562-1622, 2010), is the use of differential geometry theory of surfaces as a natural means to geometrically separate the macroscopic ...

  19. Modelling soil transport by wind in drylands

    International Nuclear Information System (INIS)

    Understanding the movement of windblown soil particles and the resulting formation of complex surface features are among the most intriguing problems in dryland research. This understanding can only be achieved trough physical and mathematical modelling and must also involve observational data and laboratory experiments. Some current mathematical models that have contributed to the basic understanding of the transportation and deposition of soil particles by wind are presented and solved in these notes. (author). 26 refs, 5 figs

  20. Stochastic models for convective momentum transport

    OpenAIRE

    Majda, Andrew J; Stechmann, Samuel N.

    2008-01-01

    The improved parameterization of unresolved features of tropical convection is a central challenge in current computer models for long-range ensemble forecasting of weather and short-term climate change. Observations, theory, and detailed smaller-scale numerical simulations suggest that convective momentum transport (CMT) from the unresolved scales to the resolved scales is one of the major deficiencies in contemporary computer models. Here, a combination of mathematical and physical reasonin...

  1. Observation of different phytoplankton groups and biomass using Differential Optical Absorption Spectroscopy on SCIAMACHY data and comparisons to in-situ, NASA biogeochemical Model and MERIS

    OpenAIRE

    Bracher, Astrid; Taylor, Bettina; M. Vountas; Dinter, Tilman; J. P. Burrows; R. Röttgers; Peeken, Ilka

    2008-01-01

    In order to understand the marine phytoplanktons role in the global marine ecosystem and biogeochemical cycles it is necessary to derive global information on the distribution of major functional phytoplankton types (PFT) in the world oceans. In our study we use instead of the common ocean color sensors such as CZCS, SeaWiFS, MODIS, MERIS, with rather low spectral resolution, the Differential Optical Absorption Spectroscopy (DOAS) to study the retrieval of phytoplankton distribution and absor...

  2. Subdiffusive transport in model disordered media

    International Nuclear Information System (INIS)

    We study the transport properties of two models of disordered media. In both cases we consider the motion of a particle which is not in thermal equilibrium with the environment.The first example is a hopping process in a one-dimensional lattice with random spacing, the second one is a random telegraph process is a random potential. We show, by computing the average stationary flux for a finite segment of the system, that the transport is sub diffusive if the temperature of the particle is lower than the temperature of the medium. (author). 7 refs

  3. Delft Mass Transport model DMT-2

    Science.gov (United States)

    Ditmar, Pavel; Hashemi Farahani, Hassan; Inacio, Pedro; Klees, Roland; Zhao, Qile; Guo, Jing; Liu, Xianglin; Sun, Yu; Riva, Ricardo; Ran, Jiangjun

    2013-04-01

    Gravity Recovery And Climate Experiment (GRACE) satellite mission has enormously extended our knowledge of the Earth's system by allowing natural mass transport of various origin to be quantified. This concerns, in particular, the depletion and replenishment of continental water stocks; shrinking of polar ice sheets; deformation of the Earth's crust triggered by large earthquakes, and isostatic adjustment processes. A number of research centers compute models of temporal gravity field variations and mass transport, using GRACE data as input. One of such models - Delft Mass Transport model - is being produced at the Delft University of Technology in collaboration with the GNSS Research Center of Wuhan University. A new release of this model, DMT-2, has been produced on the basis of a new (second) release of GRACE level-1b data. This model consists of a time-series of monthly solutions spanning a time interval of more than 8 years, starting from Feb. 2003. Each solution consists of spherical harmonic coefficients up to degree 120. Both unconstrained and optimally filtered solutions are obtained. The most essential improvements of the DMT-2 model, as compared to its predecessors (DMT-1 and DMT-1b), are as follows: (i) improved estimation and elimination of low-frequency noise in GRACE data, so that strong mass transport signals are not damped; (ii) computation of accurate stochastic models of data noise for each month individually with a subsequent application of frequency-dependent data weighting, which allows statistically optimal solutions to be compiled even if data noise is colored and gradually changes in time; (iii) optimized estimation of accelerometer calibration parameters; (iv) incorporation of degree 1 coefficients estimated with independent techniques; (v) usage of state-of-the-art background models to de-alias GRACE data from rapid mass transport signals (this includes the EOT11a model of ocean tides and the latest release of the AOD1B product describing

  4. Numerical modelling of ion transport in flames

    KAUST Repository

    Han, Jie

    2015-10-20

    This paper presents a modelling framework to compute the diffusivity and mobility of ions in flames. The (n, 6, 4) interaction potential is adopted to model collisions between neutral and charged species. All required parameters in the potential are related to the polarizability of the species pair via semi-empirical formulas, which are derived using the most recently published data or best estimates. The resulting framework permits computation of the transport coefficients of any ion found in a hydrocarbon flame. The accuracy of the proposed method is evaluated by comparing its predictions with experimental data on the mobility of selected ions in single-component neutral gases. Based on this analysis, the value of a model constant available in the literature is modified in order to improve the model\\'s predictions. The newly determined ion transport coefficients are used as part of a previously developed numerical approach to compute the distribution of charged species in a freely propagating premixed lean CH4/O2 flame. Since a significant scatter of polarizability data exists in the literature, the effects of changes in polarizability on ion transport properties and the spatial distribution of ions in flames are explored. Our analysis shows that changes in polarizability propagate with decreasing effect from binary transport coefficients to species number densities. We conclude that the chosen polarizability value has a limited effect on the ion distribution in freely propagating flames. We expect that the modelling framework proposed here will benefit future efforts in modelling the effect of external voltages on flames. Supplemental data for this article can be accessed at http://dx.doi.org/10.1080/13647830.2015.1090018. © 2015 Taylor & Francis.

  5. Terrestrial ecosystems and the global biogeochemical silica cycle

    Science.gov (United States)

    Conley, Daniel J.

    2002-12-01

    Most research on the global Si cycle has focused nearly exclusively on weathering or the oceanic Si cycle and has not explored the complexity of the terrestrial biogeochemical cycle. The global biogeochemical Si cycle is of great interest because of its impact on global CO2 concentrations through the combined processes of weathering of silicate minerals and transfer of CO2 from the atmosphere to the lithosphere. A sizable pool of Si is contained as accumulations of amorphous silica, or biogenic silica (BSi), in living tissues of growing plants, known as phytoliths, and, after decomposition of organic material, as remains in the soil. The annual fixation of phytolith silica ranges from 60-200 Tmol yr-1 and rivals that fixed in the oceanic biogeochemical cycle (240 Tmol yr-1). Internal recycling of the phytolith pool is intense with riverine fluxes of dissolved silicate to the oceans buffered by the terrestrial biogeochemical Si cycle, challenging the ability of weathering models to predict rates of weathering and consequently, changes in global climate. Consideration must be given to the influence of the terrestrial BSi pool on variations in the global biogeochemical Si cycle over geologic time and the influence man has had on modifying both the terrestrial and aquatic biogeochemical cycles.

  6. Extracellular Electron Transport Coupling Biogeochemical Processes Centimeters

    DEFF Research Database (Denmark)

    Risgaard-Petersen, Nils; Fossing, Henrik; Christensen, Peter Bondo;

    2010-01-01

    the oxygen uptake in laboratory incubations of initially homogenized and stabilized sediment. Using microsensors and process rate measurements we further investigated the effect of the electric currents on sediment biogeochemistry. Dissolved sulfide readily donated electrons to the networks and could...... sediment confirmed the depth range of the electric communication and indicated donation of electrons directly from organotrophic bacteria. The separation of oxidation and reduction processes created steep pH gradients eventually causing carbonate precipitation at the surface. The results indicate that...

  7. Molecular modeling of auxin transport inhibitors

    Energy Technology Data Exchange (ETDEWEB)

    Gardner, G.; Black-Schaefer, C.; Bures, M.G. (Abbott Labs, North Chicago, IL (USA))

    1990-05-01

    Molecular modeling techniques have been used to study the chemical and steric properties of auxin transport inhibitors. These bind to a specific site on the plant plasma membrane characterized by its affinity for N-1-naphthylphthalamic acid (NPA). A three-dimensional model was derived from critical features of ligands for the NPA receptor, and a suggested binding conformation is proposed. This model, along with three-dimensional structural searching techniques, was then used to search the Abbott corporate database of chemical structures. Of the 467 compounds that satisfied the search criteria, 77 representative molecules were evaluated for their ability to compete for ({sup 3}H)NPA binding to corn microsomal membranes. Nineteen showed activity that ranged from 16 to 85% of the maximum NPA binding. Four of the most active of these, from chemical classes not included in the original compound set, also inhibited polar auxin transport through corn coleoptile sections.

  8. Symposium on unsaturated flow and transport modeling

    Energy Technology Data Exchange (ETDEWEB)

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

    1982-09-01

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

  9. PAT-2 (Plutonium Air Transportable Model 2)

    International Nuclear Information System (INIS)

    The PAT-2 (Plutonium Air Transportable Model 2) package is designed for the safe transport of plutonium and/or uranium in small quantities, especially as used in international safeguards activities, and especially as transported by air. The PAT-2 package is resistant to severe accidents, including that of a high-speed jet aircraft crash, and is designed to withstand such environments as extreme impact, crushing, puncturing and slashing loads, severe hydrocarbon-fueled fires, and deep underwater immersion, with no escape of contents. The accident environments may be imposed upon the package singly or seqentially. The package meets the requirements of 10 CFR 71 for Fissile Class I packages with a cargo of 15 grams of Pu-239, or other isotopic forms described herein, not to exceed 2 watts of thermal activity. Packaging, operational features, and contents of package, are discussed

  10. DIVIMP Modeling of Impurity Transport in EAST

    International Nuclear Information System (INIS)

    Simulations of carbon impurity transport in SOL/divertor plasmas with Ohmic heating on EAST tokamak were performed using the two-dimensional (2D) Monte Carlo impurity transport code DIVIMP. The background plasmas for DIVIMP simulations were externally taken from B2.5/Eirene calculation. Besides the basic output of DIVIMP, the 2D density distributions of the carbon impurity with different ionization states and neutral carbon atoms were obtained, the 2D distributions of CII and CIII emissivities from C+1 and C+2 radiation respectively were also calculated. Comparison between the measured and calculated CIII emissivities showed favorable agreement, indicating that the impurity physics transport models, as implemented in the DIVIMP code, are suitable for the EAST tokamak plasma condition. (magnetically confined plasma)

  11. DIVIMP Modeling of Impurity Transport in EAST

    Science.gov (United States)

    Wang, Fuqiong; Chen, Yiping; Hu, Liqun

    2014-07-01

    Simulations of carbon impurity transport in SOL/divertor plasmas with Ohmic heating on EAST tokamak were performed using the two-dimensional (2D) Monte Carlo impurity transport code DIVIMP. The background plasmas for DIVIMP simulations were externally taken from B2.5/Eirene calculation. Besides the basic output of DIVIMP, the 2D density distributions of the carbon impurity with different ionization states and neutral carbon atoms were obtained, the 2D distributions of CII and CIII emissivities from C+1 and C+2 radiation respectively were also calculated. Comparison between the measured and calculated CIII emissivities showed favorable agreement, indicating that the impurity physics transport models, as implemented in the DIVIMP code, are suitable for the EAST tokamak plasma condition.

  12. Symposium on unsaturated flow and transport modeling

    International Nuclear Information System (INIS)

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

  13. Mesoscopic Modeling of Reactive Transport Processes

    Science.gov (United States)

    Kang, Q.; Chen, L.; Deng, H.

    2012-12-01

    Reactive transport processes involving precipitation and/or dissolution are pervasive in geochemical, biological and engineered systems. Typical examples include self-assembled patterns such as Liesegang rings or bands, cones of stalactites in limestones caves, biofilm growth in aqueous environment, formation of mineral deposits in boilers and heat exchangers, uptake of toxic metal ions from polluted water by calcium carbonate, and mineral trapping of CO2. Compared to experimental studies, a numerical approach enables a systematic study of the reaction kinetics, mass transport, and mechanisms of nucleation and crystal growth, and hence provides a detailed description of reactive transport processes. In this study, we enhance a previously developed lattice Boltzmann pore-scale model by taking into account the nucleation process, and develop a mesoscopic approach to simulate reactive transport processes involving precipitation and/or dissolution of solid phases. The model is then used to simulate the formation of Liesegang precipitation patterns and investigate the effects of gel on the morphology of the precipitates. It is shown that this model can capture the porous structures of the precipitates and can account for the effects of the gel concentration and material. A wide range of precipitation patterns is predicted under different gel concentrations, including regular bands, treelike patterns, and for the first time with numerical models, transition patterns from regular bands to treelike patterns. The model is also applied to study the effect of secondary precipitate on the dissolution of primary mineral. Several types of dissolution and precipitation processes are identified based on the morphology and structures of the precipitates and on the extent to which the precipitates affect the dissolution of the primary mineral. Finally the model is applied to study the formation of pseudomorph. It is demonstrated for the first time by numerical simulation that a

  14. A comprehensive theory-based transport model

    International Nuclear Information System (INIS)

    A new theory based transport model with comprehensive physics (trapping, general toroidal geometry, finite beta, collisions) has been developed. The core of the model is the new trapped-gyro-Landau-fluid (TGLF) equations which provide a fast and accurate approximation to the linear eigenmodes for gyrokinetic drift-wave instabilities (trapped ion and electron modes, ion and electron temperature gradient modes and kinetic ballooning modes). This new TGLF transport model removes the limitation of its predecessor GLF23 and is valid for the same conditions as the gyrokinetic equations. A theory-based philosophy is used in the model construction. The closure coefficients of the TGLF equations are fit to local kinetic theory to give accurate linear eigenmodes. The saturation model is fit to non-linear turbulence simulations. No fitting to experiment is done so applying the model to experiments is a true test of the theory it is approximating. The TGLF model unifies trapped and passing particles in a single set of gyrofluid equations. A model for the averaging of the Landau resonance by the trapped particles makes the equations work seamlessly over the whole drift-wave wavenumber range from trapped ion modes to electron temperature gradient modes. A fast eigenmode solution method enables unrestricted magnetic geometry. Electron-ion collisions and full electromagnetic fluctuations round out the physics. The linear eigenmodes have been benchmarked against comprehensive physics gyrokinetic calculations over a large range of plasma parameters. The deviation between the gyrokinetic and TGLF linear growth rates averages 11.4% in shifted circle geometry. The transport model uses the TGLF eigenmodes to compute quasilinear fluxes of energy and particles. A model for the saturated amplitude of the turbulence completes the calculation. The saturation model is constructed to fit a large set of nonlinear gyrokinetic turbulence simulations. The TGLF model is valid in new physical

  15. A comprehensive theory-based transport model

    International Nuclear Information System (INIS)

    Full text: A new theory based transport model with comprehensive physics (trapping, general toroidal geometry, finite beta, collisions) has been developed. The core of the model is the new trapped-gyro- Landau-fluid (TGLF) equations which provide a fast and accurate approximation to the linear eigenmodes for gyrokinetic drift-wave instabilities (trapped ion and electron modes, ion and electron temperature gradient modes and kinetic ballooning modes). This new TGLF transport model removes the limitation of its predecessor GLF23 and is valid for the same conditions as the gyrokinetic equations. A theory-based philosophy is used in the model construction. The closure coefficients of the TGLF equations are fit to local kinetic theory to give accurate linear eigenmodes. The saturation model is fit to non-linear turbulence simulations. No fitting to experiment is done so applying the model to experiments is a true test of the theory it is approximating. The TGLF model unifies trapped and passing particles in a single set of gyrofluid equations. A model for the averaging of the Landau resonance by the trapped particles makes the equations work seamlessly over the whole drift-wave wavenumber range from trapped ion modes to electron temperature gradient modes. A fast eigenmode solution method enables unrestricted magnetic geometry. Electron-ion collisions and full electromagnetic fluctuations round out the physics. The linear eigenmodes have been benchmarked against comprehensive physics gyrokinetic calculations over a large range of plasma parameters. The deviation between the gyrokinetic and TGLF linear growth rates averages 11.4% in shifted circle geometry. The transport model uses the TGLF eigenmodes to compute quasilinear fluxes of energy and particles. A model for the saturated amplitude of the turbulence completes the calculation. The saturation model is constructed to fit a large set of nonlinear gyrokinetic turbulence simulations. The TGLF model is valid in new

  16. Porting marine ecosystem model spin-up using transport matrices to GPUs

    Directory of Open Access Journals (Sweden)

    E. Siewertsen

    2012-07-01

    Full Text Available We have ported an implementation of the spin-up for marine ecosystem models based on the "Transport Matrix Method" to graphics processing units (GPUs. The original implementation was designed for distributed-memory architectures and uses the PETSc library that is based on the "Message Passing Interface (MPI" standard. The spin-up computes a steady seasonal cycle of the ecosystem tracers with climatological ocean circulation data as forcing. Since the transport is linear with respect to the tracers, the resulting operator is represented in so-called "transport matrices". Each iteration of the spin-up involves two matrix-vector multiplications and the evaluation of the used biogeochemical model. The original code was written in C and Fortran. On the GPU, we use the CUDA standard, a specialized version of the PETSc toolkit and a CUDA Fortran compiler. We describe the extensions to PETSc and the modifications of the original C and Fortran codes that had to be done. Here we make use of freely available libraries for the GPU. We analyze the computational effort of the main parts of the spin-up for two exemplary ecosystem models and compare the overall computational time to those necessary on different CPUs. The results show that a consumer GPU can beat a significant number of cluster CPUs without further code optimization.

  17. Empirical particle transport model for tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Petravic, M.; Kuo-Petravic, G.

    1986-08-01

    A simple empirical particle transport model has been constructed with the purpose of gaining insight into the L- to H-mode transition in tokamaks. The aim was to construct the simplest possible model which would reproduce the measured density profiles in the L-regime, and also produce a qualitatively correct transition to the H-regime without having to assume a completely different transport mode for the bulk of the plasma. Rather than using completely ad hoc constructions for the particle diffusion coefficient, we assume D = 1/5 chi/sub total/, where chi/sub total/ approx. = chi/sub e/ is the thermal diffusivity, and then use the kappa/sub e/ = n/sub e/chi/sub e/ values derived from experiments. The observed temperature profiles are then automatically reproduced, but nontrivially, the correct density profiles are also obtained, for realistic fueling rates and profiles. Our conclusion is that it is sufficient to reduce the transport coefficients within a few centimeters of the surface to produce the H-mode behavior. An additional simple assumption, concerning the particle mean-free path, leads to a convective transport term which reverses sign a few centimeters inside the surface, as required by the H-mode density profiles.

  18. Modeling the highway transportation of spent fuel

    International Nuclear Information System (INIS)

    There will be a substantial increase in the number of spent fuel shipments on the nation's highway system in the next thirty years. Most of the spent fuel will be moving from reactors to a spent fuel repository. This study develops two models that evaluate the risk and cost of moving the spent fuel. The Minimum Total Transport Risk Model (MTTRM) seeks an efficient solution for this problem by finding the minimum risk path through the network and sending all the spent fuel shipments over this one path. The Equilibrium Transport Risk Model (ETRM) finds an equitable solution by distributing the shipments over a number of paths in the network. This model decreases the risk along individual paths, but increases society's risk because the spent fuel shipments are traveling over more links in the network. The study finds that there is a trade off between path risk and societal risk. As path risk declines, societal risk rises. The cost of shipping also increases as the number of paths expand. The cost and risk of shipping spent fuel from ten reactors to four potential repository sites are evaluated using the MTTRM. The temporary monitored retrievable storage (MRS) facility in Tennessee is found to be the minimum cost and minimum risk solution. When direct shipment to the permanent sites is considered, Deaf Smith, Texas is the least cost and least incident free transport risk location. Yucca Mountain, Nevada is the least risk location when the focus is placed on the potential consequences of an accident

  19. Modelling an Ammonium Transporter with SCLS

    Directory of Open Access Journals (Sweden)

    Angelo Troina

    2009-10-01

    Full Text Available The Stochastic Calculus of Looping Sequences (SCLS is a recently proposed modelling language for the representation and simulation of biological systems behaviour. It has been designed with the aim of combining the simplicity of notation of rewrite systems with the advantage of compositionality. It also allows a rather simple and accurate description of biological membranes and their interactions with the environment.In this work we apply SCLS to model a newly discovered ammonium transporter. This transporter is believed to play a fundamental role for plant mineral acquisition, which takes place in the arbuscular mycorrhiza, the most wide-spread plant-fungus symbiosis on earth. Due to its potential application in agriculture this kind of symbiosis is one of the main focuses of the BioBITs project. In our experiments the passage of NH3 / NH4+ from the fungus to the plant has been dissected in known and hypothetical mechanisms; with the model so far we have been able to simulate the behaviour of the system under different conditions. Our simulations confirmed some of the latest experimental results about the LjAMT2;2 transporter. The initial simulation results of the modelling of the symbiosis process are promising and indicate new directions for biological investigations.

  20. Biogeochemical and isotopic gradients in a BTEX/PAH contaminant plume: Model-based interpretation of a high-resolution field data set

    DEFF Research Database (Denmark)

    Prommer, H.; Anneser, B.; Rolle, Massimo;

    2009-01-01

    A high spatial resolution data set documenting carbon and sulfur isotope fractionation at a tar oil-contaminated, sulfate-reducing field site was analyzed with a reactive transport model. Within a comprehensive numerical model, the study links the distinctive observed isotope depth profiles with...... isotope signature of toluene, which is the most rapidly degrading compound and the most important reductant at the site. The resulting depth profiles at the observation well show distinct differences between the small isotopic enrichment in the contaminant plume core and the much stronger enrichment of up...

  1. Evaluating Conceptual Site Models with Multicomponent Reactive Transport Modeling

    Science.gov (United States)

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

    2005-05-01

    Modeling ground-water flow and multicomponent reactive chemical transport is a useful approach for testing conceptual site models and assessing the design of monitoring networks. A graded approach with three conceptual site models is presented here with a field case of tetrachloroethene (PCE) transport and biodegradation near Charleston, SC. The first model assumed a one-layer homogeneous aquifer structure with semi-infinite boundary conditions, in which an analytical solution of the reactive solute transport can be obtained with BIOCHLOR (Aziz et al., 1999). Due to the over-simplification of the aquifer structure, this simulation cannot reproduce the monitoring data. In the second approach we used GMS to develop the conceptual site model, a layer-cake multi-aquifer system, and applied a numerical module (MODFLOW and RT3D within GMS) to solve the flow and reactive transport problem. The results were better than the first approach but still did not fit the plume well because the geological structures were still inadequately defined. In the third approach we developed a complex conceptual site model by interpreting log and seismic survey data with Petra and PetraSeis. We detected a major channel and a younger channel, through the PCE source area. These channels control the local ground-water flow direction and provide a preferential chemical transport pathway. Results using the third conceptual site model agree well with the monitoring concentration data. This study confirms 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). Numerical modeling in this case provides key insight into the hydrogeology and geochemistry of the field site for predicting contaminant transport in the future. Finally, critical monitoring points and performance indicator parameters are selected for future monitoring to confirm system

  2. Global environmental transport models for tritium

    International Nuclear Information System (INIS)

    In this paper we discuss some of the obstacles to the construction of credible models of global tritium transport for use in dose assessments. We illustrate these difficulties by comparing model predictions of environmental tritium levels with measurements. Monitoring of tritium has shown that specific activities in precipitation over land are typically higher by a factor of three to four than those in precipitation over the oceans. Experience with modeling CO2 turnover in the oceans has led to the conclusion that two-box reservoir models of the ocean often give unsatisfactory representations of transient solutions. Failure to consider these factors in global models can lead to distorted estimates of collective dose and create difficulties in validation of the model against real data. We illustrate these problems with a seven-box model recommended by the National Council on Radiation Protection and Measurements in which we forced the atmospheric compartment to reproduce an exogenous function based on historic observations of HTO in precipitation at 500N. The fresh water response underestimates data from the Ottawa River by a factor of about five, and the ocean surface response overestimates tritium data from the surface waters of the Northern Pacific by nearly an order of magnitude. Revision of the model to include (1) separate over-land and over-ocean compartments of the atmosphere and (2) a box-diffusion model of the subsurface ocean brings the discrepant responses into good agreement with the environmental data. In a second exercise, we used a latitudinally disaggregated model and replaced a tropospheric compartment in the northern hemisphere by historic precipitation data. The model's response greatly underestimates the tritium specific activity in the southern hemisphere. These exercises lead us to doubt that a proper global transport model for tritium is available at present for collective dose assessment. 12 refs., 3 figs

  3. Flow and transport modeling and isotope monitoring of a dug well SAT prototype in Shafdan, Israel

    Science.gov (United States)

    Kloppmann, Wolfram; Pettenati, Marie; Chikurel, Haim; Picot, Géraldine; Guttmann, Joseph; Aharoni, Avi

    2010-05-01

    of freshwaters derived from treated sewage, both for short term tracer tests and for long term monitoring of artificial recharge, even if in aquifers with higher clay contents, sorption-linked isotope fractionation cannot be excluded. Redox conditions were addressed through a 1D vertical unsaturated and 1D horizontal saturated reactive transport model. This model combines kinetics of microbiological degradation of organic matter (Monod kinetics), kinetic control of electron acceptors, with water-mineral interactions (dissolution-precipitation reactions). It was possible to reproduce the observed redox sequence in the Shafdan system even if this example demonstrates the limits of current bio-geochemical concepts, in particular for an element like Mn for which no stable oxidised (MnIV) aqueous species exists. Clearly, the consideration of bacterially catalysed, non-equilibrium reactions, and, simultaneously, of water-mineral equilibria through coherent bio-geochemical models is currently one of the major challenges in modelling such complex systems as are MAR systems using reclaimed water. Such models are a prerequisite for risk assessment in the field of MAR, to go beyond the use of bulk parameters like sorption isotherms and biodegradation half lifes when looking on the behaviour of organic contaminants. A thorough understanding of biogeochemical reactions occurring both in the unsaturated and the saturated zone is needed to develop predictive tools that are able to address and foresee potential drawbacks of MAR systems like pollutant breakthrough, release of trace contaminants from the aquifer material and mineral precipitations leading to a degradation of the hydraulic properties of the receiving reservoir.

  4. Resistive Plate Chambers: electron transport and modeling

    International Nuclear Information System (INIS)

    We study the electron transport in gas mixtures used by Resistive Plate Chambers (RPCs) in high energy physics experiments at CERN. Calculations are performed using a multi term theory for solving the Boltzmann equation. We identify the effects induced by non-conservative nature of electron attachment, including attachment heating of electrons and negative differential conductivity (NDC). NDC was observed only in the bulk component of drift velocity. Using our Monte Carlo technique, we calculate the spatially resolved transport properties in order to investigate the origin of these effects. We also present our microscopic approach to modeling of RPCs which is based on Monte Carlo method. Calculated results for a timing RPC show good agreement with an analytical model and experimental data. Different cross section sets for electron scattering in C2H2F4 are used for comparison and analysis

  5. Kinetic modeling of microbially-driven redox chemistry of radionuclides in subsurface environments: Coupling transport, microbial metabolism and geochemistry

    International Nuclear Information System (INIS)

    Microbial degradation of organic matter is a driving force in many subsurface geochemical systems, and therefore may have significant impacts on the fate of radionuclides released into subsurface environments. In this paper, the authors present a general reaction-transport model for microbial metabolism, redox chemistry, and radionuclide migration in subsurface systems. The model explicitly accounts for biomass accumulation and the coupling of radionuclide redox reactions with major biogeochemical processes. Based on the consideration that the biomass accumulation in subsurface environments is likely to achieve a quasi-steady state, they have accordingly modified the traditional microbial growth kinetic equation. They justified the use of the biogeochemical models without the explicit representation of biomass accumulation, if the interest of modeling is in the net impact of microbial reactions on geochemical processes. They then applied their model to a scenario in which an oxic water flow containing both uranium and completing organic ligands is recharged into an oxic aquifer in a carbonate formation. The model simulation shows that uranium can be reduced and therefore immobilized in the anoxic zone created by microbial degradation

  6. USMC tactical motor transport lift requirements model

    OpenAIRE

    Allen, Scott Andrew

    1995-01-01

    This thesis concentrates on developing a spreadable model that can be used by Marine logisticians in computing sustainment requirements and the resulting tactical motor transport lift requirements necessary to keep a notional sized maneuver element supported on a daily basis in the Marine Corps projected maneuver warfare environment. Sustainment computations are limited to resupplying the maneuver element with food, water, fuel, and ammunition. Using an "add-in" simulation package the plannin...

  7. Dynamic modeling for designing transportation packaging components

    International Nuclear Information System (INIS)

    Soft impact limiters, such as polyurethane foams and aluminium honeycombs, were studied to assist the Sandia National Laboratories' Transportation Base Technology Program. The aim of this research was to study the mechanical behavior of these materials, which are being used as impact absorbers in nuclear waste transportation containers. A series of tests was performed along various loading paths. Different densities of polyurethane foams, aluminium honeycombs, and corrugated aluminium honeycombs were tested in different orientations. Static tests included uniaxial tension, uniaxial compression, triaxial compression, hydrostatic compression, and fracture toughness testing. The purpose of using different loading paths was to generate extensive test data, which is being used to develop constitutive models for these materials. Dynamic tests were conducted at strain rates of 100/s., to generate experimental data relevant to accident situations. Results of these tests were subsequently used to conduct scale-model tests of transportation cask of different industrial designers. Continuum damage constitutive models was used to predict material response. The primary focus was to capture the effect of progressive cell collapse and to be able to eventually predict the orientation and propagation of such a localized feature under a multi-axial state of stress. (author) 17 figs., 2 tabs., 28 refs

  8. Natural analogues and radionuclide transport model validation

    International Nuclear Information System (INIS)

    In this paper, some possible roles for natural analogues are discussed from the point of view of those involved with the development of mathematical models for radionuclide transport and with the use of these models in repository safety assessments. The characteristic features of a safety assessment are outlined in order to address the questions of where natural analogues can be used to improve our understanding of the processes involved and where they can assist in validating the models that are used. Natural analogues have the potential to provide useful information about some critical processes, especially long-term chemical processes and migration rates. There is likely to be considerable uncertainty and ambiguity associated with the interpretation of natural analogues, and thus it is their general features which should be emphasized, and models with appropriate levels of sophistication should be used. Experience gained in modelling the Koongarra uranium deposit in northern Australia is drawn upon. (author)

  9. Energy transport modelling including ergodic effects

    Energy Technology Data Exchange (ETDEWEB)

    McTaggart, N.; Bonnin, X.; Runov, A.; Schneider, R. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Wendelsteinstrasse 1, D-17491 Greifswald (Germany); Zagorski, R. [Institute of Plasma Physics and Laser Microfusion, P.O.Box 49, Warsaw (Poland)

    2004-04-01

    The effect of ergodization (either by additional coils like in TEXTOR-DED or by intrinsic plasma effects like in W7-X) defines the need for transport models being able to describe this properly. A prerequisite for this is the concept of local magnetic coordinates allowing a correct discretization with minimized numerical errors. For these coordinates the full respective metric tensor has to be known. To study the energy transport in complex edge geometries (in particular for W7-X) we use a finite difference discretization of the transport equations on a custom-tailored grid in local magnetic coordinates. This grid is generated by field line tracing to guarantee an exact discretization of the dominant parallel transport (this also minimizes the numerical diffusion problem). The perpendicular fluxes are interpolated on cross-sectional planes (toroidal cuts), where a quasi-isotropic problem is solved by a constrained Delaunay triangulation (preserving magnetic surfaces where they exist), and discretization. All terms involving toroidal terms are discretized by finite differences. The first tests for W7X and NCSX were successfully performed. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Energy transport modelling including ergodic effects

    International Nuclear Information System (INIS)

    The effect of ergodization (either by additional coils like in TEXTOR-DED or by intrinsic plasma effects like in W7-X) defines the need for transport models being able to describe this properly. A prerequisite for this is the concept of local magnetic coordinates allowing a correct discretization with minimized numerical errors. For these coordinates the full respective metric tensor has to be known. To study the energy transport in complex edge geometries (in particular for W7-X) we use a finite difference discretization of the transport equations on a custom-tailored grid in local magnetic coordinates. This grid is generated by field line tracing to guarantee an exact discretization of the dominant parallel transport (this also minimizes the numerical diffusion problem). The perpendicular fluxes are interpolated on cross-sectional planes (toroidal cuts), where a quasi-isotropic problem is solved by a constrained Delaunay triangulation (preserving magnetic surfaces where they exist), and discretization. All terms involving toroidal terms are discretized by finite differences. The first tests for W7X and NCSX were successfully performed. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Discrete element modelling of bedload transport

    Science.gov (United States)

    Loyer, A.; Frey, P.

    2011-12-01

    Discrete element modelling (DEM) has been widely used in solid mechanics and in granular physics. In this type of modelling, each individual particle is taken into account and intergranular interactions are modelled with simple laws (e.g. Coulomb friction). Gravity and contact forces permit to solve the dynamical behaviour of the system. DEM is interesting to model configurations and access to parameters not directly available in laboratory experimentation, hence the term "numerical experimentations" sometimes used to describe DEM. DEM was used to model bedload transport experiments performed at the particle scale with spherical glass beads in a steep and narrow flume. Bedload is the larger material that is transported on the bed on stream channels. It has a great geomorphic impact. Physical processes ruling bedload transport and more generally coarse-particle/fluid systems are poorly known, arguably because granular interactions have been somewhat neglected. An existing DEM code (PFC3D) already computing granular interactions was used. We implemented basic hydrodynamic forces to model the fluid interactions (buoyancy, drag, lift). The idea was to use the minimum number of ingredients to match the experimental results. Experiments were performed with one-size and two-size mixtures of coarse spherical glass beads entrained by a shallow turbulent and supercritical water flow down a steep channel with a mobile bed. The particle diameters were 4 and 6mm, the channel width 6.5mm (about the same width as the coarser particles) and the channel inclination was typically 10%. The water flow rate and the particle rate were kept constant at the upstream entrance and adjusted to obtain bedload transport equilibrium. Flows were filmed from the side by a high-speed camera. Using image processing algorithms made it possible to determine the position, velocity and trajectory of both smaller and coarser particles. Modelled and experimental particle velocity and concentration depth

  12. Thermal Transport Model for Heat Sink Design

    Science.gov (United States)

    Chervenak, James A.; Kelley, Richard L.; Brown, Ari D.; Smith, Stephen J.; Kilbourne, Caroline a.

    2009-01-01

    A document discusses the development of a finite element model for describing thermal transport through microcalorimeter arrays in order to assist in heat-sinking design. A fabricated multi-absorber transition edge sensor (PoST) was designed in order to reduce device wiring density by a factor of four. The finite element model consists of breaking the microcalorimeter array into separate elements, including the transition edge sensor (TES) and the silicon substrate on which the sensor is deposited. Each element is then broken up into subelements, whose surface area subtends 10 10 microns. The heat capacity per unit temperature, thermal conductance, and thermal diffusivity of each subelement are the model inputs, as are the temperatures of each subelement. Numerical integration using the Finite in Time Centered in Space algorithm of the thermal diffusion equation is then performed in order to obtain a temporal evolution of the subelement temperature. Thermal transport across interfaces is modeled using a thermal boundary resistance obtained using the acoustic mismatch model. The document concludes with a discussion of the PoST fabrication. PoSTs are novel because they enable incident x-ray position sensitivity with good energy resolution and low wiring density.

  13. User manual of the multicompenent variably - saturated flow and transport model HP1

    International Nuclear Information System (INIS)

    This report describes a new comprehensive simulation tool HP1 (HYDRUS1D-PHREEQC) that was obtained by coupling the HYDRUS-1D one-dimensional variably-saturated water flow and solute transport model with the PHREEQC geochemical code. The HP1 code incorporates modules simulating (1) transient water flow in variably-saturated media, (2) transport of multiple components, and (3) mixed equilibrium/kinetic geochemical reactions. The program numerically solves the Richards equation for variably-saturated water flow and advection-dispersion type equations for heat and solute transport. The flow equation incorporates a sink term to account for water uptake by plant roots. The heat transport equation considers transport due to conduction and convection with flowing water. The solute transport equations consider advective-dispersive transport in the liquid phase. The program can simulate a broad range of low-temperature biogeochemical reactions in water, soil and ground water systems including interactions with minerals, gases, exchangers, and sorption surfaces, based on thermodynamic equilibrium, kinetics, or mixed equilibrium-kinetic reactions. The program may be used to analyze water and solute movement in unsaturated, partially saturated, or fully saturated porous media. The flow region may be composed of nonuniform soils or sediments. Flow and transport can occur in the vertical, horizontal, or a generally inclined direction. The water flow part of the model can deal with prescribed head and flux boundaries, boundaries controlled by atmospheric conditions, as well as free drainage boundary conditions. The governing flow and transport equations were solved numerically using Galerkin-type linear finite element schemes. To test the accuracy of the coupling procedures implemented in HP1, simulation results were compared with (i) HYDRUS-1D for transport problems of multiple components subject to sequential first-order decay, (ii) PHREEQC for steady-state flow conditions, and

  14. Simulations of N2O concentrations for France using ecosystem models, emission databases and an atmospheric transport model

    Science.gov (United States)

    Massad, R. S.; Prieur, V.; Thompson, R.; Schultz, M.; Pison, I.; Bousquet, P.; Schmidt, M.; Lopez, M.; Boukari, E.; Lehuger, S.; Chaumartin, F.; Gabrielle, B.

    2012-04-01

    Soils are responsible for a major, although highly uncertain, share of the global emissions of nitrous oxide (N2O). N2O fluxes are strongly correlated to soil properties, soil management and local climatic conditions. These controlling factors interact at different temporal and spatial scales making it challenging to asses emissions at a regional level both with measurement and modeling. We used two biogeochemical simulation models CERES-EGC and O-CN to estimate N2O fluxes from agricultural soils over France, and compared them into the regional atmospheric chemistry-transport model CHIMERE (0.25°x0.25° for France). Comparisons between modelled and observed mixing ratios give insights on the quality of the emission scenarios used as input to the model, assuming small transport errors. The maps were tested by comparing CHIMERE simulations with time series of N2O atmospheric mixing ratios measured continuously in two locations over France during the year 2007. In an inverse mode, N2O emissions scenarios are used combination with N2O observed mixing ratios and an atmospheric transport model, to produce optimized emission scenarios. The model used is a global model (LMDZ-INCA, 3.75°x2.5° resolution with a 1°x1° zoom over Europe). For France the O-CN model which only accounts for crops and managed grassland emissions simulates total emissions of 95 Gg N-N2O/yr which are larger than total fluxes inferred from inversions (75 Gg N-N2O/yr). Inverted fluxes are 30% larger when compared to the prior emissions. Concerning CERES-EGC which only accounts for crops, the total emissions for 2007 sum-up to 20.4 Gg N-N2O/yr and are smaller than the total inverted flux.

  15. Model for radionuclide transport in running waters

    International Nuclear Information System (INIS)

    Two sites in Sweden are currently under investigation by SKB for their suitability as places for deep repository of radioactive waste, the Forsmark and Simpevarp/Laxemar area. As a part of the safety assessment, SKB has formulated a biosphere model with different sub-models for different parts of the ecosystem in order to be able to predict the dose to humans following a possible radionuclide discharge from a future deep repository. In this report, a new model concept describing radionuclide transport in streams is presented. The main difference from the previous model for running water used by SKB, where only dilution of the inflow of radionuclides was considered, is that the new model includes parameterizations also of the exchange processes present along the stream. This is done in order to be able to investigate the effect of the retention on the transport and to be able to estimate the resulting concentrations in the different parts of the system. The concentrations determined with this new model could later be used for order of magnitude predictions of the dose to humans. The presented model concept is divided in two parts, one hydraulic and one radionuclide transport model. The hydraulic model is used to determine the flow conditions in the stream channel and is based on the assumption of uniform flow and quasi-stationary conditions. The results from the hydraulic model are used in the radionuclide transport model where the concentration is determined in the different parts of the stream ecosystem. The exchange processes considered are exchange with the sediments due to diffusion, advective transport and sedimentation/resuspension and uptake of radionuclides in biota. Transport of both dissolved radionuclides and sorbed onto particulates is considered. Sorption kinetics in the stream water phase is implemented as the time scale of the residence time in the stream water probably is short in comparison to the time scale of the kinetic sorption. In the sediment

  16. Model for radionuclide transport in running waters

    Energy Technology Data Exchange (ETDEWEB)

    Jonsson, Karin; Elert, Mark [Kemakta Konsult AB, Stockholm (Sweden)

    2005-11-15

    Two sites in Sweden are currently under investigation by SKB for their suitability as places for deep repository of radioactive waste, the Forsmark and Simpevarp/Laxemar area. As a part of the safety assessment, SKB has formulated a biosphere model with different sub-models for different parts of the ecosystem in order to be able to predict the dose to humans following a possible radionuclide discharge from a future deep repository. In this report, a new model concept describing radionuclide transport in streams is presented. The main difference from the previous model for running water used by SKB, where only dilution of the inflow of radionuclides was considered, is that the new model includes parameterizations also of the exchange processes present along the stream. This is done in order to be able to investigate the effect of the retention on the transport and to be able to estimate the resulting concentrations in the different parts of the system. The concentrations determined with this new model could later be used for order of magnitude predictions of the dose to humans. The presented model concept is divided in two parts, one hydraulic and one radionuclide transport model. The hydraulic model is used to determine the flow conditions in the stream channel and is based on the assumption of uniform flow and quasi-stationary conditions. The results from the hydraulic model are used in the radionuclide transport model where the concentration is determined in the different parts of the stream ecosystem. The exchange processes considered are exchange with the sediments due to diffusion, advective transport and sedimentation/resuspension and uptake of radionuclides in biota. Transport of both dissolved radionuclides and sorbed onto particulates is considered. Sorption kinetics in the stream water phase is implemented as the time scale of the residence time in the stream water probably is short in comparison to the time scale of the kinetic sorption. In the sediment

  17. Understanding transport in model water desalination membranes

    Science.gov (United States)

    Chan, Edwin

    Polyamide based thin film composites represent the the state-of-the-art nanofiltration and reverse osmosis membranes used in water desalination. The performance of these membranes is enabled by the ultrathin (~100 nm) crosslinked polyamide film in facilitating the selective transport of water over salt ions. While these materials have been refined over the last several decades, understanding the relationships between polyamide structure and membrane performance remains a challenge because of the complex and heterogeneous nature of the polyamide film. In this contribution, we present our approach to addressing this challenge by studying the transport properties of model polyamide membranes synthesized via molecular layer-by-layer (mLbL) assembly. First, we demonstrate that mLbL can successfully construct polyamide membranes with well-defined nanoscale thickness and roughness using a variety of monomer formulations. Next, we present measurement tools for characterizing the network structure and transport of these model polyamide membranes. Specifically, we used X-ray and neutron scattering techniques to characterize their structure as well as a recently-developed indentation based poromechanics approach to extrapolate their water diffusion coefficient. Finally, we illustrate how these measurements can provide insight into the original problem by linking the key polyamide network properties, i.e. water-polyamide interaction parameter and characteristic network mesh size, to the membrane performance.

  18. COMPANY STRUCTURE MODEL FOR PUBLIC COLLECTIVE TRANSPORT

    Directory of Open Access Journals (Sweden)

    CARLOS ALBERTO MONCADA ARISTIZÁBAL

    2005-10-01

    Full Text Available The operation scheme of the collective public transport in Bogotá (Colombia has not suffered a big transformationin its general structure during the last seventy years. It is well known that the companies of collective public transportfor passengers operated by buses has not worked like managers of the vehicles, rather they worked like companies forvehicles affiliation.The operation base for the companies in the model of affiliation (as the Bogotá case, is the same for all the citieswith public transport around Colombia: there are owners and drivers of the vehicles in charge of the maintenance,control and service offers.This document presents a formulation of a theoretical model of company structure, remarked in the particularpolicies and operating conditions that transformed the service of public transport since 2003 in Bogotá city. The modelinvolves the operative, organizational and financial aspects, looking forward for a new collective public transportcompany which manage the vehicles fleet in an efficient way and for a better service to the users.

  19. Multimodal Transport Operator Liability Insurance Model

    OpenAIRE

    Zelenika, Ratko; Lotrič, Tomaž; Bužan, Ervin

    2011-01-01

    Multimodal transportation means transporting goods from a pickup point, where the operator receives the goods, all the way to the delivery location, using at least two different means of transportation, covered under the same multimodal transport contract and by only one document, regardless of the number or type of transportation vehicles used. The key factor to the optimal operation of multimodal transportation is the multimodal transport operator. It is up to this individual to compensate ...

  20. Model for tritiated water transport in soil

    International Nuclear Information System (INIS)

    Chemical forms of tritium released from nuclear facilities are mostly water (HTO) and hydrogen (HT, TT). Elemental tritium is inert in vegetation and superior animals, but the microorganisms from soil oxidize HT to HTO. After an atmospheric HT emission, in short time an equivalent quantity of HTO is re-emitted from soil. In the vicinity of a tritium source the spatial and temporary distribution of HTO is dependent on the chemical form of tritium releases. During routine tritium releases (continuously and constant releases), the local distribution of tritium reaches equilibrium, and specific activities of tritium in environmental compartments are almost equal. The situation is very different after an accidental emission. Having in view, harmful effects of tritium when it is incorporated into the body several models were developed for environmental tritium transport and dose assessment. The tritium transport into the soil is an important part of the environmental tritium behavior, but, unfortunately, in spite of the importance of this problem the corresponding modeling is unsatisfactory. The aim of this paper was the improvement of the TRICAIAP model, and the application of the model to BIOMOVS scenario. The BIOMOVS scenario predicts HTO concentrations in soil during 30 days, after one hour atmospheric HTO emission. The most important conclusions of the paper are: the principal carrier of tritium into the soil is water; the transfer processes are the reactions of water in soil and the diffusion due to concentration gradient; atmosphere-soil transport is dependent of surface characteristics (granulation, humidity, roughness, etc.); the conversion rate of HT to HTO is not well known and is dependent on active microorganism concentration in soil and on soil humidity. More experimental data are needed to decrease the uncertainty of transfer parameter, for the definition of the influence of vegetation, etc. (authors)

  1. Applying computationally efficient schemes for biogeochemical cycles (ACES4BGC)

    Energy Technology Data Exchange (ETDEWEB)

    Vertenstein, Mariana [Univ. Corporation For Atmospheric Research, Boulder, CO (United States)

    2016-01-11

    NCAR contributed to the ACES4BGC project through software engineering work on aerosol model implementation, build system and script changes, coupler enhancements for biogeochemical tracers, improvements to the Community Land Model (CLM) code and testing infrastructure, and coordinating and integrating code changes from the various project participants.

  2. Multidimensional boron transport modeling in subchannel approach

    International Nuclear Information System (INIS)

    The main objective of this study is to implement a solute tracking model into the subchannel code CTF for simulations of boric acid transients. Previously, three different boron tracking models have been implemented into CTF and based on the applied analytical and nodal sensitivity studies the Modified Godunov Scheme approach with a physical diffusion term has been selected as the most accurate and best estimate solution. This paper will present the implementation of a multidimensional boron transport modeling with Modified Godunov Scheme within a thermal-hydraulic code based on a subchannel approach. Based on the cross flow mechanism in a multiple-subchannel rod bundle geometry, heat transfer and lateral pressure drop effects will be discussed in deboration and boration case studies. (author)

  3. Porting marine ecosystem model spin-up using transport matrices to GPUs

    Directory of Open Access Journals (Sweden)

    E. Siewertsen

    2013-01-01

    Full Text Available We have ported an implementation of the spin-up for marine ecosystem models based on transport matrices to graphics processing units (GPUs. The original implementation was designed for distributed-memory architectures and uses the Portable, Extensible Toolkit for Scientific Computation (PETSc library that is based on the Message Passing Interface (MPI standard. The spin-up computes a steady seasonal cycle of ecosystem tracers with climatological ocean circulation data as forcing. Since the transport is linear with respect to the tracers, the resulting operator is represented by matrices. Each iteration of the spin-up involves two matrix-vector multiplications and the evaluation of the used biogeochemical model. The original code was written in C and Fortran. On the GPU, we use the Compute Unified Device Architecture (CUDA standard, a customized version of PETSc and a commercial CUDA Fortran compiler. We describe the extensions to PETSc and the modifications of the original C and Fortran codes that had to be done. Here we make use of freely available libraries for the GPU. We analyze the computational effort of the main parts of the spin-up for two exemplar ecosystem models and compare the overall computational time to those necessary on different CPUs. The results show that a consumer GPU can compete with a significant number of cluster CPUs without further code optimization.

  4. Modeling of capacitated transportation systems for integral scheduling

    OpenAIRE

    Ebben, Mark; Heijden, van der, J.; Hurink, Johann; Schutten, Marco

    2003-01-01

    Motivated by a planned automated cargo transportation network, we consider transportation problems in which the finite capacity of resources has to be taken nto account. We present a flexible modeling methodology which allows to construct, evaluate, and improve feasible solutions. The modeling is evaluated on instances stemming from a simulation model of the planned cargo transportation system.

  5. Reactive-Transport Model of Buffer Cementation

    Energy Technology Data Exchange (ETDEWEB)

    Arthur, Randy; Wei Zhou [Monitor Scientific LLC, Denver, CO (United States)

    2005-10-15

    Thermal gradients during the early, non-isothermal period of near-field evolution in a KBS-3 repository for spent nuclear fuel could alter the mineralogy of the bentonite buffer and cause the constituent clay particles to become cemented together by mineral precipitates. Cementation is a potential concern because it could alter the ductility, mechanical strength and swelling pressure of the buffer, thereby possibly adversely affecting the primary performance function of this key barrier to provide a stable diffusional transport pathway between the canister and rock. The present study uses the TOUGHREACT computer program to simulate reactive-transport processes that are thought to control buffer cementation. TOUGHREACT is generally applicable to problems involving non-isothermal, multiphase reactive transport in variably saturated media. For cementation problems, the modeling approach must account specifically for the temperature dependence of equilibrium and kinetic constraints on dissolution/precipitation reactions involving the primary smectite clays and accessory phases in bentonite, and for diffusive transport of aqueous reactants and products along concentration gradients that are aligned with, or in opposition to, the direction of decreasing temperatures across the near field. The modeling approach was evaluated in two stages. A conceptual model of buffer cementation was first calibrated using observations from field tests carried out at the Stripa mine and Aespoe HRL (LOT pilot experiments). The calibrated model was then used to simulate the geochemical evolution of the KBS-3 buffer during the non-isothermal period of repository evolution. This model accounts for the imbibition of groundwater from a granitic host rock into initially unsaturated buffer materials under capillary and hydraulic pressure gradients, and uses realistic time-temperature constraints on the thermal evolution of the near-field. Preliminary results suggest that the total extent of

  6. Reactive-Transport Model of Buffer Cementation

    International Nuclear Information System (INIS)

    Thermal gradients during the early, non-isothermal period of near-field evolution in a KBS-3 repository for spent nuclear fuel could alter the mineralogy of the bentonite buffer and cause the constituent clay particles to become cemented together by mineral precipitates. Cementation is a potential concern because it could alter the ductility, mechanical strength and swelling pressure of the buffer, thereby possibly adversely affecting the primary performance function of this key barrier to provide a stable diffusional transport pathway between the canister and rock. The present study uses the TOUGHREACT computer program to simulate reactive-transport processes that are thought to control buffer cementation. TOUGHREACT is generally applicable to problems involving non-isothermal, multiphase reactive transport in variably saturated media. For cementation problems, the modeling approach must account specifically for the temperature dependence of equilibrium and kinetic constraints on dissolution/precipitation reactions involving the primary smectite clays and accessory phases in bentonite, and for diffusive transport of aqueous reactants and products along concentration gradients that are aligned with, or in opposition to, the direction of decreasing temperatures across the near field. The modeling approach was evaluated in two stages. A conceptual model of buffer cementation was first calibrated using observations from field tests carried out at the Stripa mine and Aespoe HRL (LOT pilot experiments). The calibrated model was then used to simulate the geochemical evolution of the KBS-3 buffer during the non-isothermal period of repository evolution. This model accounts for the imbibition of groundwater from a granitic host rock into initially unsaturated buffer materials under capillary and hydraulic pressure gradients, and uses realistic time-temperature constraints on the thermal evolution of the near-field. Preliminary results suggest that the total extent of

  7. A model of morphogen transport II

    OpenAIRE

    Małogrosz, Marcin

    2014-01-01

    A model of morphogen transport consisting of two evolutionary PDEs of reaction-diffusion type and three ODEs posed on a rectangular domain is analysed. We prove that the problem is globally well-posed and that the corresponding solutions converge, as the width of the rectangle tends to zero, to the unique solution of the one dimensional system which was analyzed in the first paper of the series. Main difficulties in the analysis stem from the presence of a singular source term - a Dirac Delta...

  8. Modeling in transport phenomena a conceptual approach

    CERN Document Server

    Tosun, Ismail

    2007-01-01

    Modeling in Transport Phenomena, Second Edition presents and clearly explains with example problems the basic concepts and their applications to fluid flow, heat transfer, mass transfer, chemical reaction engineering and thermodynamics. A balanced approach is presented between analysis and synthesis, students will understand how to use the solution in engineering analysis. Systematic derivations of the equations and the physical significance of each term are given in detail, for students to easily understand and follow up the material. There is a strong incentive in science and engineering to

  9. Coupling of transport and geochemical models

    International Nuclear Information System (INIS)

    This contract stipulated separate pieces of work to consider mass transport in the far-field of a repository, and more detailed geochemical modelling of the groundwater in the near-field. It was envisaged that the far-field problem would be tackled by numerical solutions to the classical advection-diffusion equation obtained by the finite element method. For the near-field problem the feasibility of coupling existing geochemical equilibrium codes to the three dimensional groundwater flow codes was to be investigated. This report is divided into two sections with one part devoted to each aspect of this contract. (author)

  10. Conceptual and Numerical Models for UZ Flow and Transport

    International Nuclear Information System (INIS)

    The purpose of this Analysis/Model Report (AMR) is to document the conceptual and numerical models used for modeling of unsaturated zone (UZ) fluid (water and air) flow and solute transport processes. This is in accordance with ''AMR Development Plan for U0030 Conceptual and Numerical Models for Unsaturated Zone (UZ) Flow and Transport Processes, Rev 00''. The conceptual and numerical modeling approaches described in this AMR are used for models of UZ flow and transport in fractured, unsaturated rock under ambient and thermal conditions, which are documented in separate AMRs. This AMR supports the UZ Flow and Transport Process Model Report (PMR), the Near Field Environment PMR, and the following models: Calibrated Properties Model; UZ Flow Models and Submodels; Mountain-Scale Coupled Processes Model; Thermal-Hydrologic-Chemical (THC) Seepage Model; Drift Scale Test (DST) THC Model; Seepage Model for Performance Assessment (PA); and UZ Radionuclide Transport Models

  11. Benchmarking reactive transport models at a hillslope scale

    Science.gov (United States)

    Kalbacher, T.; He, W.; Nixdorf, E.; Jang, E.; Fleckenstein, J. H.; Kolditz, O.

    2015-12-01

    The hillslope scale is an important transition between the field scale and the catchment scale. The water flow in the unsaturated zone of a hillslope can be highly dynamic, which can lead to dynamic changes of groundwater flow or stream outflow. Additionally, interactions among host rock formation, soil properties and recharge water from precipitation or anthropogenic activities (mining, agriculture etc.) can influence the water quality of groundwater and stream in the long term. To simulate reactive transport processes at such a scale is a challenging task. On the one hand, simulation of water flow in a coupled soil-aquifer system often involves solving of highly non-linear PDEs such as Richards equation; on the other hand, one has to consider complicated biogeochemical reactions (e.g. water-rock interactions, biological degradation, redox reactions). Both aspects are computationally expensive and have high requirements on the numerical precision and stabilities of the employed code. The primary goals of this study are as follows: i) Identify the bottlenecks and quantitatively analyse their influence on simulation of biogeochemical reactions at a hillslope scale; ii) find or suggest practical strategies to deal with these bottlenecks, thus to provide detailed hints for future improvements of reactive transport simulators. To achieve these goals, the parallelized reactive transport simulator OGS#IPhreeqc has been applied to simulate two benchmark examples. The first example is about uranium leaching based on Šimůnek et al. (2012), which considers the leaching of uranium from a mill tailing and accompanied mineral dissolution/precipitation. The geochemical system is then extended to include redox reactions in the second example. Based on these examples, the numerical stability and parallel performance of the tool is analysed. ReferenceŠimůnek, J., Jacques, D., Šejna, M., van Genuchten, M. T.: The HP2 program for HYDRUS (2D/3D), A coupled code for simulating two

  12. Model of reversible vesicular transport with exclusion

    Science.gov (United States)

    Bressloff, Paul C.; Karamched, Bhargav R.

    2016-08-01

    A major question in neurobiology concerns the mechanics behind the motor-driven transport and delivery of vesicles to synaptic targets along the axon of a neuron. Experimental evidence suggests that the distribution of vesicles along the axon is relatively uniform and that vesicular delivery to synapses is reversible. A recent modeling study has made explicit the crucial role that reversibility in vesicular delivery to synapses plays in achieving uniformity in vesicle distribution, so called synaptic democracy (Bressloff et al 2015 Phys. Rev. Lett. 114 168101). In this paper we generalize the previous model by accounting for exclusion effects (hard-core repulsion) that may occur between molecular motor-cargo complexes (particles) moving along the same microtubule track. The resulting model takes the form of an exclusion process with four internal states, which distinguish between motile and stationary particles, and whether or not a particle is carrying vesicles. By applying a mean field approximation and an adiabatic approximation we reduce the system of ODEs describing the evolution of occupation numbers of the sites on a 1D lattice to a system of hydrodynamic equations in the continuum limit. We find that reversibility in vesicular delivery allows for synaptic democracy even in the presence of exclusion effects, although exclusion does exacerbate nonuniform distributions of vesicles in an axon when compared with a model without exclusion. We also uncover the relationship between our model and other models of exclusion processes with internal states.

  13. Reactive transport modeling of Li isotope fractionation

    Science.gov (United States)

    Wanner, C.; Sonnenthal, E. L.

    2013-12-01

    The fractionation of Li isotopes has been used as a proxy for interaction processes between silicate rocks and any kind of fluids. In particular, Li isotope measurements are powerful because Li is almost exclusively found in silicate minerals. Moreover, the two stable Li isotopes, 6Li and 7Li, differ by 17% in mass introducing a large mass dependent isotope fractionation even at high temperature. Typical applications include Li isotope measurements along soil profiles and of river waters to track silicate weathering patterns and Li isotope measurements of geothermal wells and springs to assess water-rock interaction processes in geothermal systems. For this contribution we present a novel reactive transport modeling approach for the simulation of Li isotope fractionation using the code TOUGHREACT [1]. It is based on a 6Li-7Li solid solution approach similar to the one recently described for simulating Cr isotope fractionation [2]. Model applications include the simulation of granite weathering along a 1D flow path as well as the simulation of a column experiment related to an enhanced geothermal system. Results show that measured δ7Li values are mainly controlled by (i) the degree of interaction between Li bearing primary silicate mineral phases (e.g., micas, feldspars) and the corresponding fluid, (ii) the Li isotope fractionation factor during precipitation of secondary mineral phases (e.g., clays), (iii) the Li concentration in primary and secondary Li bearing mineral phases and (iv) the proportion of dissolved Li that adsorbs to negatively charged surfaces (e.g., clays, Fe/Al-hydroxides). To date, most of these parameters are not very well constrained. Reactive transport modeling thus currently has to rely on many assumptions. Nevertheless, such models are powerful because they are the only viable option if individual contributions of all potential processes on the resulting (i.e., measured) Li isotopic ratio have to be quantitatively assessed. Accordingly, we

  14. Modeling the quasistatic energy transport between nanoparticles.

    Science.gov (United States)

    Panasyuk, George Y; Yerkes, Kirk L

    2015-12-01

    We consider phononic energy transport between nanoparticles mediated by a quantum particle. The nanoparticles are considered as thermal reservoirs described by ensembles of finite numbers of harmonic oscillators within the Drude-Ullersma model having, in general, unequal mode spacings Δ(1) and Δ(2), which amount to different numbers of atoms in the nanoparticles. The quasistatic energy transport between the nanoparticles on the time scale t∼1/Δ(1,2) is investigated using the generalized quantum Langevin equation. We find that double degeneracy of system's eigenfrequencies, which occurs in the case of identical nanoparticles, is removed when the mode spacings become unequal. The equations describing the dynamics of the averaged eigenmode energies are derived and solved, and the resulting expression for the energy current between the nanoparticles is obtained and explored. Unlike the case when the thermodynamic limit is assumed resulting in time-independent energy current, finite-size effects result in temporal behavior of the energy current that evinces reversibility features combined with decay and possesses peculiarities at time moments t=2πn/Δ(1)+2πm/Δ(2) for non-negative integers n and m. When Δ(1,2)→0, an expression for the heat current obtained previously under assumption of the thermodynamic limit is reproduced. The energy current between two platinum nanoparticles mediated by a carbon oxide molecule is considered as an application of the developed model. PMID:26764663

  15. Documentation of TRU biological transport model (BIOTRAN)

    International Nuclear Information System (INIS)

    Inclusive of Appendices, this document describes the purpose, rationale, construction, and operation of a biological transport model (BIOTRAN). This model is used to predict the flow of transuranic elements (TRU) through specified plant and animal environments using biomass as a vector. The appendices are: (A) Flows of moisture, biomass, and TRU; (B) Intermediate variables affecting flows; (C) Mnemonic equivalents (code) for variables; (D) Variable library (code); (E) BIOTRAN code (Fortran); (F) Plants simulated; (G) BIOTRAN code documentation; (H) Operating instructions for BIOTRAN code. The main text is presented with a specific format which uses a minimum of space, yet is adequate for tracking most relationships from their first appearance to their formulation in the code. Because relationships are treated individually in this manner, and rely heavily on Appendix material for understanding, it is advised that the reader familiarize himself with these materials before proceeding with the main text

  16. Documentation of TRU biological transport model (BIOTRAN)

    Energy Technology Data Exchange (ETDEWEB)

    Gallegos, A.F.; Garcia, B.J.; Sutton, C.M.

    1980-01-01

    Inclusive of Appendices, this document describes the purpose, rationale, construction, and operation of a biological transport model (BIOTRAN). This model is used to predict the flow of transuranic elements (TRU) through specified plant and animal environments using biomass as a vector. The appendices are: (A) Flows of moisture, biomass, and TRU; (B) Intermediate variables affecting flows; (C) Mnemonic equivalents (code) for variables; (D) Variable library (code); (E) BIOTRAN code (Fortran); (F) Plants simulated; (G) BIOTRAN code documentation; (H) Operating instructions for BIOTRAN code. The main text is presented with a specific format which uses a minimum of space, yet is adequate for tracking most relationships from their first appearance to their formulation in the code. Because relationships are treated individually in this manner, and rely heavily on Appendix material for understanding, it is advised that the reader familiarize himself with these materials before proceeding with the main text.

  17. Formulation of two-dimensional transport modeling in tokamak plasmas

    International Nuclear Information System (INIS)

    A two-dimensional transport modeling applicable to a whole tokamak plasma is proposed. The model is derived from the multi-fluid equations and Maxwell's equations and the moment approach of neoclassical transport is employed as fluid closures. The multi-fluid equations consist of the equations for particle density, momentum, energy and total heat flux transport for each plasma species. The expressions of the parallel viscosity and heat viscosity are extended in order to be applicable to both inside and outside of the last closed flux surface. It is confirmed that our neoclassical transport model is consistent with the ordinary flux-surface-averaged one-dimensional neoclassical transport model. Our transport equations are coupled with the electromagnetic equations in order to describe the time evolution of tokamak plasmas. The procedure for coupling a transport solver based on our transport model with an equilibrium solver is also briefly described. (author)

  18. Ecosystem element transport model for Lake Eckarfjaerden

    Energy Technology Data Exchange (ETDEWEB)

    Konovalenko, L.; Bradshaw, C. [The Department of Ecology, Environment and Plant Sciences, Stockholm University (Sweden); Andersson, E.; Kautsky, U. [Swedish Nuclear Fuel and Waste Management Co. - SKB (Sweden)

    2014-07-01

    The ecosystem transport model of elements was developed for Lake Eckarfjaerden located in the Forsmark area in Sweden. Forsmark has currently a low level repository (SFR) and a repository for spent fuel is planned. A large number of data collected during site-investigation program 2002-2009 for planning the repository were available for the creation of the compartment model based on carbon circulation, physical and biological processes (e.g. primary production, consumption, respiration). The model is site-specific in the sense that the food web model is adapted to the actual food web at the site, and most estimates of biomass and metabolic rates for the organisms and meteorological data originate from site data. The functional organism groups of Lake Eckarfjaerden were considered as separate compartments: bacterio-plankton, benthic bacteria, macro-algae, phytoplankton, zooplankton, fish, benthic fauna. Two functional groups of bacteria were taken into account for the reason that they have the highest biomass of all functional groups during the winter, comprising 36% of the total biomass. Effects of ecological parameters, such as bacteria and algae biomass, on redistribution of a hypothetical radionuclide release in the lake were examined. The ecosystem model was used to estimate the environmental transfer of several elements (U, Th, Ra) and their isotopes (U-238, U-234,Th-232, Ra-226) to various aquatic organisms in the lake, using element-specific distribution coefficients for suspended particle and sediment. Results of chemical analyses of the water, sediment and biota were used for model validation. The model gives estimates of concentration factors for fish based on modelling rather on in situ measurement, which reduces the uncertainties for many radionuclides with scarce of data. Document available in abstract form only. (authors)

  19. Ecosystem element transport model for Lake Eckarfjaerden

    International Nuclear Information System (INIS)

    The ecosystem transport model of elements was developed for Lake Eckarfjaerden located in the Forsmark area in Sweden. Forsmark has currently a low level repository (SFR) and a repository for spent fuel is planned. A large number of data collected during site-investigation program 2002-2009 for planning the repository were available for the creation of the compartment model based on carbon circulation, physical and biological processes (e.g. primary production, consumption, respiration). The model is site-specific in the sense that the food web model is adapted to the actual food web at the site, and most estimates of biomass and metabolic rates for the organisms and meteorological data originate from site data. The functional organism groups of Lake Eckarfjaerden were considered as separate compartments: bacterio-plankton, benthic bacteria, macro-algae, phytoplankton, zooplankton, fish, benthic fauna. Two functional groups of bacteria were taken into account for the reason that they have the highest biomass of all functional groups during the winter, comprising 36% of the total biomass. Effects of ecological parameters, such as bacteria and algae biomass, on redistribution of a hypothetical radionuclide release in the lake were examined. The ecosystem model was used to estimate the environmental transfer of several elements (U, Th, Ra) and their isotopes (U-238, U-234,Th-232, Ra-226) to various aquatic organisms in the lake, using element-specific distribution coefficients for suspended particle and sediment. Results of chemical analyses of the water, sediment and biota were used for model validation. The model gives estimates of concentration factors for fish based on modelling rather on in situ measurement, which reduces the uncertainties for many radionuclides with scarce of data. Document available in abstract form only. (authors)

  20. Modelling of sediment transport at Muria peninsula coastal, Jepara

    International Nuclear Information System (INIS)

    Modelling of transport sediment modelling at Muria Peninsula have been done. In this study we had been used mathematical model that consist of hydrodynamics and sediment transport . Data input for modelling has been used tidal, monsoon wind, and river debit. Simulation result of sediment transport modelling showed that tides pattern and seasonal variations are the main causes of variations in the suspended sediment distribution in Muria Peninsula. (author)

  1. Concept Layout Model of Transportation Terminals

    OpenAIRE

    Li-ya Yao; Li-shan Sun; Wu-hong Wang; Hui Xiong

    2012-01-01

    Transportation terminal is the key node in transport systems. Efficient terminals can improve operation of passenger transportation networks, adjust the layout of public transportation networks, provide a passenger guidance system, and regulate the development of commercial forms, as well as optimize the assembly and distribution of modern logistic modes, among others. This study aims to clarify the relationship between the function and the structure of transportation terminals and establish ...

  2. Terrestrial biogeochemical cycles: global interactions with the atmosphere and hydrology

    OpenAIRE

    Schimel, David S.; KITTEL, TIMOTHY G. F.; William J Parton

    2011-01-01

    Ecosystem scientists have developed a body of theory to predict the behaviour of biogeochemical cycles when exchanges with other ecosystems are small or prescribed. Recent environmental changes make it clear that linkages between ecosystems via atmospheric and hydrological transport have large effects on ecosystem dynamics when considered over time periods of a decade to a century, time scales relevant to contemporary humankind. Our ability to predict behaviour of ecosystems coupled by transp...

  3. Terrestrial biogeochemical cycles: global interactions with the atmosphere and hydrology

    OpenAIRE

    Schimel, David S.; KITTEL, TIMOTHY G. F.; William J Parton

    2011-01-01

    Ecosystem scientists have developed a body of theory to predict the behavior of biogeochemical cycles when exchanges with other ecosystems are small or prescribed. Recent environmental changes make it clear that linkages between ecosystems via atmospheric and hydrological transport have large effects on ecosystem dynamics when considered over time periods of a decade to a century, time scales relevant to contemporary humankind. Our ability to predict behavior of ecosystems coupled by transpor...

  4. Modeling reactive geochemical transport of concentrated aqueous solutions in variably saturated media

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Guoxiang; Zheng, Zuoping; Wan, Jiamin

    2004-01-28

    Concentrated aqueous solutions (CAS) have unique thermodynamic and physical properties. Chemical components in CAS are incompletely dissociated, especially those containing divalent or polyvalent ions. The problem is further complicated by the interaction between CAS flow processes and the naturally heterogeneous sediments. As the CAS migrates through the porous media, the composition may be altered subject to fluid-rock interactions. To effectively model reactive transport of CAS, we must take into account ion-interaction. A combination of the Pitzer ion-interaction and the ion-association model would be an appropriate way to deal with multiple-component systems if the Pitzer' parameters and thermodynamic data of dissolved components and the related minerals are available. To quantify the complicated coupling of CAS flow and transport, as well as the involved chemical reactions in natural and engineered systems, we have substantially extended an existing reactive biogeochemical transport code, BIO-CORE{sup 2D}{copyright}, by incorporating a comprehensive Pitzer ion-interaction model. In the present paper, the model, and two test cases against measured data were briefly introduced. Finally we present an application to simulate a laboratory column experiment studying the leakage of the high alkaline waste fluid stored in Hanford (a site of the U.S. Department of Energy, located in Washington State, USA). With the Pitzer ion-interaction ionic activity model, our simulation captures measured pH evolution. The simulation indicates that all the reactions controlling the pH evolution, including cation exchanges, mineral precipitation and dissolution, are coupled.

  5. Simulation of anthropogenic CO2 uptake in the CCSM3.1 ocean circulation-biogeochemical model: comparison with data-based estimates

    Directory of Open Access Journals (Sweden)

    S. Khatiwala

    2012-04-01

    Full Text Available The global ocean has taken up a large fraction of the CO2 released by human activities since the industrial revolution. Quantifying the oceanic anthropogenic carbon (Cant inventory and its variability is important for predicting the future global carbon cycle. The detailed comparison of data-based and model-based estimates is essential for the validation and continued improvement of our prediction capabilities. So far, three global estimates of oceanic Cant inventory that are "data-based" and independent of global ocean circulation models have been produced: one based on the Δ C* method, and two that are based on constraining surface-to-interior transport of tracers, the TTD method and a maximum entropy inversion method (GF. The GF method, in particular, is capable of reconstructing the history of Cant inventory through the industrial era. In the present study we use forward model simulations of the Community Climate System Model (CCSM3.1 to estimate the Cant inventory and compare the results with the data-based estimates. We also use the simulations to test several assumptions of the GF method, including the assumption of constant climate and circulation, which is common to all the data-based estimates. Though the integrated estimates of global Cant inventories are consistent with each other, the regional estimates show discrepancies up to 50 %. The CCSM3 model underestimates the total Cant inventory, in part due to weak mixing and ventilation in the North Atlantic and Southern Ocean. Analyses of different simulation results suggest that key assumptions about ocean circulation and air-sea disequilibrium in the GF method are generally valid on the global scale, but may introduce errors in Cant estimates on regional scales. The GF method should also be used with caution when predicting future oceanic anthropogenic carbon uptake.

  6. Simulation of anthropogenic CO2 uptake in the CCSM3.1 ocean circulation-biogeochemical model: comparison with data-based estimates

    Directory of Open Access Journals (Sweden)

    F. W. Primeau

    2011-11-01

    Full Text Available The global ocean has taken up a large fraction of the CO2 released by human activities since the industrial revolution. Quantifying the oceanic anthropogenic carbon (Cant inventory and its variability is important for predicting the future global carbon cycle. The detailed comparison of data-based and model-based estimates is essential for the validation and continued improvement of our prediction capabilities. So far, three global estimates of oceanic Cant inventory that are "data-based" and independent of global ocean circulation models have been produced: one based on the ΔC* method, and two are based on reconstructions of the Green function for the surface-to-interior transport, the TTD method and the maximum entropy inversion method (KPH. The KPH method, in particular, is capable of reconstructing the history of Cant inventory through the industrial era. In the present study we use forward model simulations of the Community Climate System Model (CCSM3.1 to estimate the Cant inventory and compare the results with the data-based estimates. We also use the simulations to test several assumptions of the KPH method, including the assumption of constant climate and circulation, which is common to all the data-based estimates. Though the integrated estimates of global Cant inventories are consistent with each other, the regional estimates show discrepancies up to 50 %. The CCSM3 model underestimates the total Cant inventory, in part due to weak mixing and ventilation in the North Atlantic and Southern Ocean. Analyses of different simulation results suggest that key assumptions about ocean circulation and air-sea disequilibrium in the KPH method are generally valid on the global scale, but may introduce significant errors in Cant estimates on regional scales. The KPH method should also be used with caution when predicting future oceanic anthropogenic carbon uptake.

  7. Modelling the Global Transportation Systems for the Hydrogen Economy

    Energy Technology Data Exchange (ETDEWEB)

    Krzyzanowski, D.A.; Kypreos, S.

    2004-03-01

    A modelling analysis of the transportation system is described, focused on the market penetration of different transportation technologies (including Learning-by-Doing) until the year 2050. A general outline of the work and first preliminary results are presented. (author)

  8. Heterogeneous Chemistry in Global Chemistry Transport Models

    Science.gov (United States)

    Stadtler, Scarlet; Simpson, David; Schultz, Martin; Bott, Andreas

    2016-04-01

    The impact of six tropospheric heterogeneous reactions on ozone and nitrogen species was studied using two chemical transport models EMEP MSC-W and ECHAM6-HAMMOZ. Since heterogeneous reactions depend on reactant concentrations (in this study these are N_2O_5, NO_3, NO_2, O_3, HNO_3, HO_2) and aerosol surface area S_a, the modeled surface area of both models was compared to a satellite product retrieving the surface area. This comparison shows a good agreement in global pattern and especially the capability of both models to capture the extreme aerosol loadings in East Asia. Further, the impact of the heterogeneous reactions was evaluated by the simulation of a reference run containing all heterogeneous reactions and several sensitivity runs. One reaction was turned off in each sensitivity run to compare it with the reference run. As previously shown, the analysis of the sensitivity runs shows that the globally most important heterogeneous reaction is the one of N_2O_5. Nevertheless, NO_2, NO_3, HNO3 and HO2 heterogeneous reactions gain relevance particular in East China due to presence of high NOx concentrations and high Sa in the same region. The heterogeneous reaction of O3 itself on dust is compared to the other heterogeneous reactions of minor relevance. Evaluation of the models with northern hemispheric ozone surface observations yields a better agreement of the models with observations when the heterogeneous reactions are incorporated. Impacts of emission changes on the importance of the heterogeneous chemistry will be discussed.

  9. Modeling transportation of efavirenz: inference on possibility of mixed modes of transportation and kinetic solubility

    OpenAIRE

    Nemaura, Tafireyi

    2015-01-01

    Understanding drug transportation mechanisms in the human body is of paramount importance in modeling Pharmacokinetic-Pharmacodynamic relationships. This work gives a novel general model of efavirenz transportation projections based on concentrations simulated from patients on a dose of 600 mg. The work puts forward a proposition that transportation can wholly be modeled by concentration and time in a uniform volumetric space. Furthermore, movement entities are used to inform the state of “ki...

  10. ab initio Electronic Transport Model with Explicit Solution to the Linearized Boltzmann Transport Equation

    OpenAIRE

    Faghaninia, Alireza; Ager III, Joel W.; Lo, Cynthia S.

    2015-01-01

    Accurate models of carrier transport are essential for describing the electronic properties of semiconductor materials. To the best of our knowledge, the current models following the framework of the Boltzmann transport equation (BTE) either rely heavily on experimental data (i.e., semi-empirical), or utilize simplifying assumptions, such as the constant relaxation time approximation (BTE-cRTA). While these models offer valuable physical insights and accurate calculations of transport propert...

  11. Model for Estimation Urban Transportation Supply-Demand Ratio

    OpenAIRE

    Chaoqun Wu; Yulong Pei; Jingpeng Gao

    2015-01-01

    The paper establishes an estimation model of urban transportation supply-demand ratio (TSDR) to quantitatively describe the conditions of an urban transport system and to support a theoretical basis for transport policy-making. This TSDR estimation model is supported by the system dynamic principle and the VENSIM (an application that simulates the real system). It was accomplished by long-term observation of eight cities’ transport conditions and by analyzing the estimated results of TSDR fr...

  12. The transport exponent in percolation models with additional loops

    Science.gov (United States)

    Babalievski, F.

    1994-10-01

    Several percolation models with additional loops were studied. The transport exponents for these models were estimated numerically by means of a transfer-matrix approach. It was found that the transport exponent has a drastically changed value for some of the models. This result supports some previous numerical studies on the vibrational properties of similar models (with additional loops).

  13. Numerical Modelling of Sediment Transport in Combined Sewer Systems

    DEFF Research Database (Denmark)

    Schlütter, Flemming

    A conceptual sediment transport model has been developed. Through a case study a comparison with other numerical models is performed.......A conceptual sediment transport model has been developed. Through a case study a comparison with other numerical models is performed....

  14. Modeling Biodegradation and Reactive Transport: Analytical and Numerical Models

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Y; Glascoe, L

    2005-06-09

    The computational modeling of the biodegradation of contaminated groundwater systems accounting for biochemical reactions coupled to contaminant transport is a valuable tool for both the field engineer/planner with limited computational resources and the expert computational researcher less constrained by time and computer power. There exists several analytical and numerical computer models that have been and are being developed to cover the practical needs put forth by users to fulfill this spectrum of computational demands. Generally, analytical models provide rapid and convenient screening tools running on very limited computational power, while numerical models can provide more detailed information with consequent requirements of greater computational time and effort. While these analytical and numerical computer models can provide accurate and adequate information to produce defensible remediation strategies, decisions based on inadequate modeling output or on over-analysis can have costly and risky consequences. In this chapter we consider both analytical and numerical modeling approaches to biodegradation and reactive transport. Both approaches are discussed and analyzed in terms of achieving bioremediation goals, recognizing that there is always a tradeoff between computational cost and the resolution of simulated systems.

  15. Modelling the transport system in China and evaluating the current strategies towards the sustainable transport development

    DEFF Research Database (Denmark)

    Liu, W.; Lund, H.; Mathiesen, B.V.

    2013-01-01

    Transport is one of the most challenge sectors when addressing energy security and climate change due to its high reliance on oil products and lack of the alternative fuels. This paper explores the ability of three transport strategies to contribute to the development of a sustainable transport...... in China. With this purpose in mind, a Chinese transport model has been created and three current transport strategies which are high speed railway (HSR), urban rail transit (URT) and electric vehicle (EV) were evaluated together with a reference transport system in 2020. As conservative results, 13...

  16. Modeling Oxygen Transport in the Human Placenta

    Science.gov (United States)

    Serov, Alexander; Filoche, Marcel; Salafia, Carolyn; Grebenkov, Denis

    Efficient functioning of the human placenta is crucial for the favorable pregnancy outcome. We construct a 3D model of oxygen transport in the placenta based on its histological cross-sections. The model accounts for both diffusion and convention of oxygen in the intervillous space and allows one to estimate oxygen uptake of a placentone. We demonstrate the existence of an optimal villi density maximizing the uptake and explain it as a trade-off between the incoming oxygen flow and the absorbing villous surface. Calculations performed for arbitrary shapes of fetal villi show that only two geometrical characteristics - villi density and the effective villi radius - are required to predict fetal oxygen uptake. Two combinations of physiological parameters that determine oxygen uptake are also identified: maximal oxygen inflow of a placentone and the Damköhler number. An automatic image analysis method is developed and applied to 22 healthy placental cross-sections demonstrating that villi density of a healthy human placenta lies within 10% of the optimal value, while overall geometry efficiency is rather low (around 30-40%). In a perspective, the model can constitute the base of a reliable tool of post partum oxygen exchange efficiency assessment in the human placenta. Also affiliated with Department of Chemistry and Biochemistry, UCLA, Los Angeles, CA 90095, USA.

  17. Carbon sequestration by patch fertilization: A comprehensive assessment using coupled physical-ecological-biogeochemical models: FINAL REPORT of grant Grant No. DE-FG02-04ER63726

    Energy Technology Data Exchange (ETDEWEB)

    Sarmiento, Jorge L; Gnanadesikan, Anand; Gruber, Nicolas

    2007-06-21

    This final report summarizes research undertaken collaboratively between Princeton University, the NOAA Geophysical Fluid Dynamics Laboratory on the Princeton University campus, the State University of New York at Stony Brook, and the University of California, Los Angeles between September 1, 2000, and November 30, 2006, to do fundamental research on ocean iron fertilization as a means to enhance the net oceanic uptake of CO2 from the atmosphere. The approach we proposed was to develop and apply a suite of coupled physical-ecologicalbiogeochemical models in order to (i) determine to what extent enhanced carbon fixation from iron fertilization will lead to an increase in the oceanic uptake of atmospheric CO2 and how long this carbon will remain sequestered (efficiency), and (ii) examine the changes in ocean ecology and natural biogeochemical cycles resulting from iron fertilization (consequences). The award was funded in two separate three-year installments: • September 1, 2000 to November 30, 2003, for a project entitled “Ocean carbon sequestration by fertilization: An integrated biogeochemical assessment.” A final report was submitted for this at the end of 2003 and is included here as Appendix 1. • December 1, 2003 to November 30, 2006, for a follow-on project under the same grant number entitled “Carbon sequestration by patch fertilization: A comprehensive assessment using coupled physical-ecological-biogeochemical models.” This report focuses primarily on the progress we made during the second period of funding subsequent to the work reported on in Appendix 1. When we began this project, we were thinking almost exclusively in terms of long-term fertilization over large regions of the ocean such as the Southern Ocean, with much of our focus being on how ocean circulation and biogeochemical cycling would interact to control the response to a given fertilization scenario. Our research on these types of scenarios, which was carried out largely during

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

    DEFF Research Database (Denmark)

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

    1996-01-01

    An application of an inverse flow and transport model to a contaminated aquifer is presented. The objective of the study is to identify physical and nonreactive flow and transport parameters through an optimization approach. The approach can be classified as a statistical procedure, where a flow ...... paper is the first in a two-paper series describing contaminant transport at a waste residue site. III the second paper, reactive transport at the site is investigated....

  19. Development of integrated transport analysis suite for LHD plasmas towards transport model validation and increased predictability

    International Nuclear Information System (INIS)

    In this study, the integrated transport analysis suite, TASK3D-a, was developed to enhance the physics understanding and accurate discussion of the Large Helical Device (LHD) experiment toward facilitating transport model validation. Steady-state and dynamic (transient) transport analyses of NBI (neutral-beam-injection)-heated LHD plasmas have been greatly facilitated by this suite. This will increase the predictability of the transport properties of LHD plasmas toward reactor-relevant regimes and reactor-scale plasmas. (author)

  20. Total maximum allocated load calculation of nitrogen pollutants by linking a 3D biogeochemical-hydrodynamic model with a programming model in Bohai Sea

    Science.gov (United States)

    Dai, Aiquan; Li, Keqiang; Ding, Dongsheng; Li, Yan; Liang, Shengkang; Li, Yanbin; Su, Ying; Wang, Xiulin

    2015-12-01

    The equal percent removal (EPR) method, in which pollutant reduction ratio was set as the same in all administrative regions, failed to satisfy the requirement for water quality improvement in the Bohai Sea. Such requirement was imposed by the developed Coastal Pollution Total Load Control Management. The total maximum allocated load (TMAL) of nitrogen pollutants in the sea-sink source regions (SSRs) around the Bohai Rim, which is the maximum pollutant load of every outlet under the limitation of water quality criteria, was estimated by optimization-simulation method (OSM) combined with loop approximation calculation. In OSM, water quality is simulated using a water quality model and pollutant load is calculated with a programming model. The effect of changes in pollutant loads on TMAL was discussed. Results showed that the TMAL of nitrogen pollutants in 34 SSRs was 1.49×105 ton/year. The highest TMAL was observed in summer, whereas the lowest in winter. TMAL was also higher in the Bohai Strait and central Bohai Sea and lower in the inner area of the Liaodong Bay, Bohai Bay and Laizhou Bay. In loop approximation calculation, the TMAL obtained was considered satisfactory for water quality criteria as fluctuation of concentration response matrix with pollutant loads was eliminated. Results of numerical experiment further showed that water quality improved faster and were more evident under TMAL input than that when using the EPR method

  1. Diffusion Dominant Solute Transport Modelling in Fractured Media Under Deep Geological Environment - 12211

    International Nuclear Information System (INIS)

    Deep geologic disposal of high activity and long-lived radioactive waste is gaining increasing support in many countries, where suitable low permeability geological formation in combination with engineered barriers are used to provide long term waste contaminant and minimise the impacts to the environment and risk to the biosphere. This modelling study examines the solute transport in fractured media under low flow velocities that are relevant to a deep geological environment. In particular, reactive solute transport through fractured media is studied using a 2-D model, that considers advection and diffusion, to explore the coupled effects of kinetic and equilibrium chemical processes. The effects of water velocity in the fracture, matrix porosity and diffusion on solute transport are investigated and discussed. Some illustrative modelled results are presented to demonstrate the use of the model to examine the effects of media degradation on solute transport, under the influences of hydrogeological (diffusion dominant) and microbially mediated chemical processes. The challenges facing the prediction of long term degradation such as cracks evolution, interaction and coalescence are highlighted. The potential of a novel microstructure informed modelling approach to account for these effects is discussed, particularly with respect to investigating multiple phenomena impact on material performance. The GRM code is used to examine the effects of media degradation for a geological waste disposal package, under the combined hydrogeological (diffusion dominant) and chemical effects in low groundwater flow conditions that are typical of deep geological disposal systems. An illustrative reactive transport modelling application demonstrates the use of the code to examine the interplay of kinetic controlled biogeochemical reactive processes with advective and diffusive transport, under the influence of media degradation. The initial model results are encouraging which show the

  2. Kinetic approach in magnetospheric plasma transport modeling

    International Nuclear Information System (INIS)

    The need for a kinetic approach in magnetospheric plasma transport problems is reviewed, as are the trends in its recent applications. The need for kinetic modeling is particularly obvious when confronted with the astonishing variety of magnetospheric particle measurements that display compelling energy and pitch angle-related spatial and/or temporal dispersion, and various types of highly non-Maxwellian features in the distribution functions. Global problems in which the kinetic approach has recently been applied include solar wind plasma injection and dispersion over the cusp, substorm particle injection near synchronous orbit, synergistic energization of ionospheric ions into ring current populations by waves and induced electric field-driven convection, and ionospheric outflow from restricted source regions into the magnetosphere. Kinetic modeling can include efforts ranging from test-particle techniques to particle-in-cell studies, and this range is considered here. There are some areas where fluid and kinetic approaches have been combined or patched together, and these will be briefly discussed. 131 references

  3. PLUME FORMATION, TRANSPORT AND MODELING, PRESENTED IN RENO, NEVADA

    Science.gov (United States)

    This presentation presents information on plume formation, transport and modeling. The outline for the presentation is: conceptualization of hydrocarbon releases; factors affecting plume length and concentration; modeling considerations; and uncertainty in model calculations.

  4. Modeling flow and solute transport in irrigation furrows

    Science.gov (United States)

    This paper presents an internally coupled flow and solute transport model for free-draining irrigation furrows. Furrow hydraulics is simulated with a numerical zero-inertia model and solute transport is computed with a model based on a numerical solution of the cross-section averaged advection-dispe...

  5. Transport threshold model of subsonic neoclassical tearing modes in tokamaks

    International Nuclear Information System (INIS)

    A transport threshold model of subsonic neoclassical tearing modes (NTMs) in tokamaks is developed. The basic procedure is to include the velocity-dependent term into the single-fluid heat-conductivity equation and to complement this equation with the single-fluid parallel plasma motion equation. These equations permit the determination of the perturbed plasma temperature and the bootstrap current drive of NTMs, for both strong and weak perpendicular heat transport, which is the precondition for developing the above model. It is shown that the subsonic NTMs transport threshold model can be more realistic than the standard transport model of NTMs suggested by Fitzpatrick [Phys. Plasmas 2, 825 (1995)

  6. Real time model for public transportation management

    OpenAIRE

    Ireneusz Celiński; Grzegorz Sierpiński

    2014-01-01

    Background: The article outlines managing a public transportation fleet in the dynamic aspect. There are currently many technical possibilities of identifying demand in the transportation network. It is also possible to indicate legitimate basis of estimating and steering demand. The article describes a general public transportation fleet management concept based on balancing demand and supply. Material and methods: The presented method utilizes a matrix description of demand for transpo...

  7. Modeling and analysis of transport in the mammary glands

    International Nuclear Information System (INIS)

    The transport of three toxins moving from the blood stream into the ducts of the mammary glands is analyzed in this work. The model predictions are compared with experimental data from the literature. The utility of the model lies in its potential to improve our understanding of toxin transport as a pre-disposing factor to breast cancer. This work is based on a multi-layer transport model to analyze the toxins present in the breast milk. The breast milk in comparison with other sampling strategies allows us to understand the mass transport of toxins once inside the bloodstream of breastfeeding women. The multi-layer model presented describes the transport of caffeine, DDT and cimetidine. The analysis performed takes into account the unique transport mechanisms for each of the toxins. Our model predicts the movement of toxins and/or drugs within the mammary glands as well as their bioaccumulation in the tissues. (paper)

  8. Modeling and analysis of transport in the mammary glands

    Science.gov (United States)

    Quezada, Ana; Vafai, Kambiz

    2014-08-01

    The transport of three toxins moving from the blood stream into the ducts of the mammary glands is analyzed in this work. The model predictions are compared with experimental data from the literature. The utility of the model lies in its potential to improve our understanding of toxin transport as a pre-disposing factor to breast cancer. This work is based on a multi-layer transport model to analyze the toxins present in the breast milk. The breast milk in comparison with other sampling strategies allows us to understand the mass transport of toxins once inside the bloodstream of breastfeeding women. The multi-layer model presented describes the transport of caffeine, DDT and cimetidine. The analysis performed takes into account the unique transport mechanisms for each of the toxins. Our model predicts the movement of toxins and/or drugs within the mammary glands as well as their bioaccumulation in the tissues.

  9. Modeling transport in toroidal plasmas: Status and issues

    International Nuclear Information System (INIS)

    The scope and detail of physics contained in computational models for fluid (density, momentum, energy) transport in toroidal plasmas have steadily increased during the past two decades. There has been considerable success in the development and verification of models for sources and sinks of particles, energy, momentum, and magnetic flux. Transport codes have collectively become very useful tools in interpreting experimental data and in providing guidance for new experiments. However, a more thorough understanding of the fundamental transport processes of magnetically confined plasmas and development of improved computational models are needed to enhance the predictive capabilities of transport codes. It is argued that fluid transport modeling by itself cannot lead to a complete understanding of transport---there must be a very strong collaboration among theory, experiment, and modeling on both the fluid and kinetic levels

  10. Final Project Report - Coupled Biogeochemical Process Evaluation for Conceptualizing Trichloriethylene Co-Metabolism: Co-Metabolic Enzyme Activity Probes and Modeling Co-Metabolism and Attenuation

    Energy Technology Data Exchange (ETDEWEB)

    Starr, Robert C; Orr, Brennon R; Lee, M Hope; Delwiche, Mark

    2010-02-26

    Trichloroethene (TCE) (also known as trichloroethylene) is a common contaminant in groundwater. TCE is regulated in drinking water at a concentration of 5 µg/L, and a small mass of TCE has the potential to contaminant large volumes of water. The physical and chemical characteristics of TCE allow it to migrate quickly in most subsurface environments, and thus large plumes of contaminated groundwater can form from a single release. The migration and persistence of TCE in groundwater can be limited by biodegradation. TCE can be biodegraded via different processes under either anaerobic or aerobic conditions. Anaerobic biodegradation is widely recognized, but aerobic degradation is less well recognized. Under aerobic conditions, TCE can be oxidized to non hazardous conditions via cometabolic pathways. This study applied enzyme activity probes to demonstrate that cometabolic degradation of TCE occurs in aerobic groundwater at several locations, used laboratory microcosm studies to determine aerobic degradation rates, and extrapolated lab-measured rates to in situ rates based on concentrations of microorganisms with active enzymes involved in cometabolic TCE degradation. Microcosms were constructed using basalt chips that were inoculated with microorganisms to groundwater at the Idaho National Laboratory Test Area North TCE plume by filling a set of Flow-Through In Situ Reactors (FTISRs) with chips and placing the FTISRs into the open interval of a well for several months. A parametric study was performed to evaluate predicted degradation rates and concentration trends using a competitive inhibition kinetic model, which accounts for competition for enzyme active sites by both a growth substrate and a cometabolic substrate. The competitive inhibition kinetic expression was programmed for use in the RT3D reactive transport package. Simulations of TCE plume evolution using both competitive inhibition kinetics and first order decay were performed.

  11. Progress in transport modelling of internal transport barrier plasmas in JET

    International Nuclear Information System (INIS)

    This paper will report on the recent progress in transport modelling of Internal Transport Barrier (ITB) plasmas. Two separate issues will be covered, fully predictive transport modelling of ITBs in the multi-tokamak database, including micro-stability analyses of ITBs, and predictive closed-loop (i.e. real-time control) transport simulations of the q-profile and ITBs. For the first time, the predictive capabilities of the mixed Bohm/GyroBohm and Weiland transport models are investigated with discharges from the ITPA ITB database by fully predictive transport simulations. The predictive transport simulations with the Bohm/GyroBohm model agree very well with experimental results from JET and JT-60U. In order to achieve a good agreement in DIII-D, the stabilisation had to be included into the model, showing the significant role played by the stabilisation in governing the physics of the ITBs. The significant role of the stabilisation is also emphasised by the gyrokinetic analysis. The Weiland transport model shows only limited agreement between the model predictions and experimental results with respect to the formation and location of the ITB. The fully predictive closed-loop simulations with real-time control of the q-profile and ITB show that it is possible to reach various set-point profiles for q and ITB and control them for longer than a current diffusion time in JET using the same real-time control technique as in the experiments. (author)

  12. Modelling multicomponent solute transport in structured soils

    NARCIS (Netherlands)

    Beinum, van G.W.

    2007-01-01

    The mobility of contaminants in soil is an important factor in determining their ability to spread into the wider environment. For non-volatile substances, transport within the soil is generally dominated by transport of dissolved fractions in the soil water phase, via either diffusion or convection

  13. Modeling of Anomalous Transport in Tokamaks with FACETS code

    Science.gov (United States)

    Pankin, A. Y.; Batemann, G.; Kritz, A.; Rafiq, T.; Vadlamani, S.; Hakim, A.; Kruger, S.; Miah, M.; Rognlien, T.

    2009-05-01

    The FACETS code, a whole-device integrated modeling code that self-consistently computes plasma profiles for the plasma core and edge in tokamaks, has been recently developed as a part of the SciDAC project for core-edge simulations. A choice of transport models is available in FACETS through the FMCFM interface [1]. Transport models included in FMCFM have specific ranges of applicability, which can limit their use to parts of the plasma. In particular, the GLF23 transport model does not include the resistive ballooning effects that can be important in the tokamak pedestal region and GLF23 typically under-predicts the anomalous fluxes near the magnetic axis [2]. The TGLF and GYRO transport models have similar limitations [3]. A combination of transport models that covers the entire discharge domain is studied using FACETS in a realistic tokamak geometry. Effective diffusivities computed with the FMCFM transport models are extended to the region near the separatrix to be used in the UEDGE code within FACETS. 1. S. Vadlamani et al. (2009) %First time-dependent transport simulations using GYRO and NCLASS within FACETS (this meeting).2. T. Rafiq et al. (2009) %Simulation of electron thermal transport in H-mode discharges Submitted to Phys. Plasmas.3. C. Holland et al. (2008) %Validation of gyrokinetic transport simulations using %DIII-D core turbulence measurements Proc. of IAEA FEC (Switzerland, 2008)

  14. Modelling the transport system in China and evaluating the current strategies towards the sustainable transport development

    International Nuclear Information System (INIS)

    Transport is one of the most challenge sectors when addressing energy security and climate change due to its high reliance on oil products and lack of the alternative fuels. This paper explores the ability of three transport strategies to contribute to the development of a sustainable transport in China. With this purpose in mind, a Chinese transport model has been created and three current transport strategies which are high speed railway (HSR), urban rail transit (URT) and electric vehicle (EV) were evaluated together with a reference transport system in 2020. As conservative results, 13% of the energy saving and 12% of the CO2 emission reduction can be attained by accomplishing three strategies compared with the reference transport system. However, the energy demand of transport in 2020 with the implementation of three strategies will be about 1.7 times as much as today. The three strategies show the potential of drawing the transport demand to the more energy efficient vehicles; however, more initiatives are needed if the sustainable transport is the long term objective, such as the solutions to stabilise the private vehicle demands, to continuously improve the vehicle efficiency and to boost the alternative fuels produced from the renewable energy sources. - Highlights: • A Chinese transport model was created and three transport strategies were evaluated • Transport is the biggest driver of the oil demand in China not the industry • The energy demand of transport in 2020 will be twice as much as today • Strategies contribute 13% energy saving and 12% CO2 emission reduction • More initiatives are needed if a sustainable transport is the long-term objective

  15. From one-body to collective transport models

    International Nuclear Information System (INIS)

    In a recent work, an extension of one-body transport model has been proposed by Ayik and Gregoire by incorporating dynamical fluctuations into the equation of motion for single-particle density. In addition to its various applications at intermediate energies, this model provides a microscopic and numerically tractable description for dissipation and fluctuation properties of large amplitude collective motion at low energies. This is illustrated by projecting the one-body transport equation into a collective subspace which yields a collective transport model known from phenomenological studies of damped nuclear collisions and induced fission, and provides an explicit calculation of transport coefficients with memory effects. (orig.)

  16. Suspended Particles: Their Role in Estuarine Biogeochemical Cycles

    Science.gov (United States)

    Turner, A.; Millward, G. E.

    2002-12-01

    Suspended particles are instrumental in controlling the reactivity, transport and biological impacts of substances in aquatic environments, and provide a crucial link for chemical constituents between the water column, bed sediment and food chain. This article reviews the role of suspended particles in the chemical and biological cycling of trace constituents (trace metals, organo-metallic compounds and hydrophobic organic micropollutants; HOMs) in estuaries, with particular emphasis on the effects of and changes to particle reactivity and composition. The partitioning (or distribution coefficient, KD ) and bioavailability of chemical constituents, and assimilation efficiency (AE) of such by bivalve suspension feeders, are identified as key parameters requiring definition for accurate biogeochemical modelling, and the discussion centres around the determination of and controls on these parameters. Particle-water interactions encompass a variety of physical, biological, electrostatic and hydrophobic effects, and are largely dependent on the character and concentration of suspended particles and salinity. The salinity-dependence results from the competing and complexing effects of seawater ions for trace metals, and the compression of water in the presence of dissolved seawater ions and consequent salting out of neutral solute (HOMs, organo-metallic compounds and some trace metal complexes). The extent of biological solubilization of chemical constituents from suspended particles is dependent on the nature of chemical components of the gastro-intestinal environment and their interactions with ingested particles, and the physiological (e.g. gut passage time) and chemical (e.g. redox conditions and pH) constraints imposed on these interactions. Generally, chemicals that associate with fine, organic-rich particles (or, for some HOMs, fine inorganic particles), and desorb at pH 5-6 and/or complex with digestive enzymes or surfactants are most readily solubilized in the

  17. Morphological, hydrological, biogeochemical and ecological changes and challenges in river restoration - the Thur River case study

    Science.gov (United States)

    Schirmer, M.; Luster, J.; Linde, N.; Perona, P.; Mitchell, E. A. D.; Barry, D. A.; Hollender, J.; Cirpka, O. A.; Schneider, P.; Vogt, T.; Radny, D.; Durisch-Kaiser, E.

    2014-06-01

    River restoration can enhance river dynamics, environmental heterogeneity and biodiversity, but the underlying processes governing the dynamic changes need to be understood to ensure that restoration projects meet their goals, and adverse effects are prevented. In particular, we need to comprehend how hydromorphological variability quantitatively relates to ecosystem functioning and services, biodiversity as well as ground- and surface water quality in restored river corridors. This involves (i) physical processes and structural properties, determining erosion and sedimentation, as well as solute and heat transport behavior in surface water and within the subsurface; (ii) biogeochemical processes and characteristics, including the turnover of nutrients and natural water constituents; and (iii) ecological processes and indicators related to biodiversity and ecological functioning. All these aspects are interlinked, requiring an interdisciplinary investigation approach. Here, we present an overview of the recently completed RECORD (REstored CORridor Dynamics) project in which we combined physical, chemical, and biological observations with modeling at a restored river corridor of the perialpine Thur River in Switzerland. Our results show that river restoration, beyond inducing morphologic changes that reshape the river bed and banks, triggered complex spatial patterns of bank infiltration, and affected habitat type, biotic communities and biogeochemical processes. We adopted an interdisciplinary approach of monitoring the continuing changes due to restoration measures to address the following questions: How stable is the morphological variability established by restoration? Does morphological variability guarantee an improvement in biodiversity? How does morphological variability affect biogeochemical transformations in the river corridor? What are some potential adverse effects of river restoration? How is river restoration influenced by catchment-scale hydraulics

  18. On EOQ cost models with arbitrary purchase and transportation costs

    OpenAIRE

    Birbil, Ş. İlker; Birbil, S. Ilker; Bülbül, Kerem; Bulbul, Kerem; Frenk, Hans; Mulder, H.M.

    2015-01-01

    We analyze an economic order quantity cost model with unit out-of-pocket holding costs, unit opportunity costs of holding, fixed ordering costs, and general purchase-transportation costs. We identify the set of purchase-transportation cost functions for which this model is easy to solve and related to solving a one-dimensional convex minimization problem. For the remaining purchase-transportation cost functions, when this problem becomes a global optimization problem, we propose a Lipschitz o...

  19. Modelling Domestic Air Transport Demand and Evaluating under Scenarios

    OpenAIRE

    Cenk OZAN; Özgür BAŞKAN; Haldenbilen, Soner; Ceylan, Halim

    2014-01-01

    The lack of balance and integration between transportation modes in Turkey is one of the main problems. In this study, domestic air transport demand is modeled and evaluated under scenarios. For this purpose, indexing method which is able to indicate observed monthly and seasonal variations in demand is used. Proposals are suggested in order to overcome the lack of balance between transportation modes. In modeling, purchasing power parity and jet fuel prices as independent variables are used....

  20. Modeling Nonequilibrium Flow and Transport Processes Using HYDRUS

    Science.gov (United States)

    Accurate process-based modeling of nonequilibrium water flow and solute transport remains a major challenge in vadose zone hydrology. The objective of this paper is to describe a wide range of nonequilibrium flow and transport modeling approaches available within the latest version of the HYDRUS-1D ...

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

    Science.gov (United States)

    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

  2. Symmetrization of mathematical model of charge transport in semiconductors

    Directory of Open Access Journals (Sweden)

    Alexander M. Blokhin

    2002-11-01

    Full Text Available A mathematical model of charge transport in semiconductors is considered. The model is a quasilinear system of differential equations. A problem of finding an additional entropy conservation law and system symmetrization are solved.

  3. Making Transporter Models for Drug-Drug Interaction Prediction Mobile.

    Science.gov (United States)

    Ekins, Sean; Clark, Alex M; Wright, Stephen H

    2015-10-01

    The past decade has seen increased numbers of studies publishing ligand-based computational models for drug transporters. Although they generally use small experimental data sets, these models can provide insights into structure-activity relationships for the transporter. In addition, such models have helped to identify new compounds as substrates or inhibitors of transporters of interest. We recently proposed that many transporters are promiscuous and may require profiling of new chemical entities against multiple substrates for a specific transporter. Furthermore, it should be noted that virtually all of the published ligand-based transporter models are only accessible to those involved in creating them and, consequently, are rarely shared effectively. One way to surmount this is to make models shareable or more accessible. The development of mobile apps that can access such models is highlighted here. These apps can be used to predict ligand interactions with transporters using Bayesian algorithms. We used recently published transporter data sets (MATE1, MATE2K, OCT2, OCTN2, ASBT, and NTCP) to build preliminary models in a commercial tool and in open software that can deliver the model in a mobile app. In addition, several transporter data sets extracted from the ChEMBL database were used to illustrate how such public data and models can be shared. Predicting drug-drug interactions for various transporters using computational models is potentially within reach of anyone with an iPhone or iPad. Such tools could help prioritize which substrates should be used for in vivo drug-drug interaction testing and enable open sharing of models. PMID:26199424

  4. A mesoscale chemical transport model (MEDIUM) nested in a global chemical transport model (MEDIANTE)

    Energy Technology Data Exchange (ETDEWEB)

    Claveau, J.; Ramaroson, R. [Office National d`Etudes et de Recherches Aerospatiales (ONERA), 92 - Chatillon (France)

    1997-12-31

    The lower stratosphere and upper troposphere (UT-LS) are frequently subject to mesoscale or local scale exchange of air masses occurring along discontinuities. This exchange (e.g. downward) can constitute one of the most important source of ozone from the stratosphere down to the middle troposphere where strong mixing dilutes the air mass and competing the non-linear chemistry. The distribution of the chemical species in the troposphere and the lower stratosphere depends upon various source emissions, e.g. from polluted boundary layer or from aircraft emissions. Global models, as well as chemical transport models describe the climatological state of the atmosphere and are not able to describe correctly the stratosphere and troposphere exchange. Mesoscale models go further in the description of smaller scales and can reasonably include a rather detailed chemistry. They can be used to assess the budget of NO{sub x} from aircraft emissions in a mesoscale domain. (author) 4 refs.

  5. Transport Model of Underground Sediment in Soils

    OpenAIRE

    Sun Jichao; Wang Guangqian

    2013-01-01

    Studies about sediment erosion were mainly concentrated on the river channel sediment, the terrestrial sediment, and the underground sediment. The transport process of underground sediment is studied in the paper. The concept of the flush potential sediment is founded. The transport equation with stable saturated seepage is set up, and the relations between the flush potential sediment and water sediment are discussed. Flushing of underground sediment begins with small particles, and large pa...

  6. Logistics chains in freight transport modelling

    OpenAIRE

    Davydenko, I.

    2015-01-01

    The research presented in this PhD thesis has been motivated by the fact that the Netherlands, and the Randstad region in particular, are affected by the large transport flows and extensive operations of the logistics sector. These operations create welfare for those people who work in the sector, who own the companies, and for the Dutch and European societies as the whole. The strong transport and logistics sector has also negative impact on the public infrastructure, air pollution, greenhou...

  7. Review of petroleum transport network models and their applicability to a national refinery model

    Energy Technology Data Exchange (ETDEWEB)

    Hooker, J. N.

    1982-04-01

    This report examines four petroleum transport network models to determine whether parts of them can be incorporated into the transportation component of a national refinery model. Two questions in particular are addressed. (a) How do the models under examination represent the oil transport network, estimate link capacities, and calculate transport costs. (b) Are any of these network representations, capacity estimates, or cost functions suitable for inclusion in a linear programming model of oil refinery and primary distribution in the US. Only pipeline and waterway transport is discussed. The models examined are the Department of Energy's OILNET model, the Department of Transportation's Freight Energy Model, the Federal Energy Administration Petroleum Transportation Network Model, and an Oak Ridge National Laboratory oil pipeline energy model. Link capacity and cost functions are recommended for each transport mode. The coefficients of the recommended pipeline cost functions remain to be estimated.

  8. Modeling atmospheric deposition using a stochastic transport model

    International Nuclear Information System (INIS)

    An advanced stochastic transport model has been modified to include the removal mechanisms of dry and wet deposition. Time-dependent wind and turbulence fields are generated with a prognostic mesoscale numerical model and are used to advect and disperse individually released particles that are each assigned a mass. These particles are subjected to mass reduction in two ways depending on their physical location. Particles near the surface experience a decrease in mass using the concept of a dry deposition velocity, while the mass of particles located within areas of precipitation are depleted using a scavenging coefficient. Two levels of complexity are incorporated into the particle model. The simple case assumes constant values of dry deposition velocity and scavenging coefficient, while the more complex case varies the values according to meteorology, surface conditions, release material, and precipitation intensity. Instantaneous and cumulative dry and wet deposition are determined from the mass loss due to these physical mechanisms. A useful means of validating the model results is with data available from a recent accidental release of Cesium-137 from a steel-processing furnace in Algeciras, Spain in May, 1998. This paper describes the deposition modeling technique, as well as a comparison of simulated concentration and deposition with measurements taken for the Algeciras release

  9. The DOE National Transportation Program Cost-Estimating Model

    International Nuclear Information System (INIS)

    The United States Department of Energy (DOE) carries out a significant amount of transportation each year, including waste remediation activities at the sites for which it is responsible. In future years, the amount of material transported is expected to increase, and the costs of this transportation are expected to be large. To support the assessment of such costs, a cost-estimating model was developed in 1996, peer-reviewed against other available packaging and transportation cost data, and used to calculate the costs for a significant number of shipping campaigns of radioactive waste. This cost-estimating model, known as the Ten-year Plan Transportation Model (TEPTRAM), served as the cost-estimating model for radioactive material shipments in developing the DOE Office of Environmental Management's Ten Year Plan. The TEPTRAM model considered costs for recovery and processing of the wastes, packaging of the wastes for transport, carriage of the waste and a rough estimate of labor costs associated with preparing and undertaking the shipments. At the user's direction, the model could also include the cost for DOE's interaction with its external stakeholders (e.g., state and local governments and tribal entities) and the cost associated with tracking and communication (e.g., use of the DOE TRANSCOM system). By considering all of these sources of costs, it provided a mechanism for assessing and comparing the costs of various waste processing and shipping campaign alternatives to help guide decision-making. Recognizing that a more user-friendly version of a cost-estimating model would be more useful to the DOE packaging and transportation community, the National Transportation Program sponsored an update of the TEPTRAM model. The new Transportation Cost Estimating Model (TRANSCOST) was developed to fulfill this need. TRANSCOST utilizes a series of input and output screens to facilitate information flow, and a number of new features were added on the basis of features

  10. Enhanced biogeochemical cycling and subsequent reduction of hydraulic conductivity associated with soil-layer interfaces in the vadose zone.

    Science.gov (United States)

    Hansen, David J; McGuire, Jennifer T; Mohanty, Binayak P

    2011-01-01

    Biogeochemical dynamics in the vadose zone are poorly understood due to the transient nature of chemical and hydrologic conditions but are nonetheless critical to understanding chemical fate and transport. This study explored the effects of a soil layer on linked geochemical, hydrological, and microbiological processes. Three laboratory soil columns were constructed: a homogenized medium-grained sand, a homogenized organic-rich loam, and a sand-over-loam layered column. Upward and downward infiltration of water was evaluated during experiments to simulate rising water table and rainfall events, respectively. In situ collocated probes measured soil water content, matric potential, and Eh. Water samples collected from the same locations were analyzed for Br, Cl, NO, SO, NH, Fe, and total sulfide. Compared with homogeneous columns, the presence of a soil layer altered the biogeochemistry and water flow of the system considerably. Enhanced biogeochemical cycling was observed in the layered column over the texturally homogeneous soil columns. Enumerations of iron- and sulfate-reducing bacteria showed 1 to 2 orders of magnitude greater community numbers in the layered column. Mineral and soil aggregate composites were most abundant near the soil-layer interface, the presence of which likely contributed to an observed order-of-magnitude decrease in hydraulic conductivity. These findings show that quantifying coupled hydrologic-biogeochemical processes occurring at small-scale soil interfaces is critical to accurately describing and predicting chemical changes at the larger system scale. These findings also provide justification for considering soil layering in contaminant fate and transport models because of its potential to increase biodegradation or to slow the rate of transport of contaminants. PMID:22031578

  11. Modeling oil weathering and transport in sea ice.

    Science.gov (United States)

    Afenyo, Mawuli; Khan, Faisal; Veitch, Brian; Yang, Ming

    2016-06-15

    This paper presents a model of oil weathering and transport in sea ice. It contains a model formulation and scenario simulation to test the proposed model. The model formulation is based on state-of-the-art models for individual weathering and transport processes. The approach incorporates the dependency of weathering and transport processes on each other, as well as their simultaneous occurrence after an oil spill in sea ice. The model is calibrated with available experimental data. The experimental data and model prediction show close agreement. A sensitivity analysis is conducted to determine the most sensitive parameters in the model. The model is useful for contingency planning of a potential oil spill in sea ice. It is suitable for coupling with a level IV fugacity model, to estimate the concentration and persistence of hydrocarbons in air, ice, water and sediments for risk assessment purposes. PMID:27130467

  12. A transport-rate model of wind-blown sand

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Sand transport by wind plays an important role in environmental problems.Formulating the sand-transport rate model has been of continuing significance,because the majority of the existing models relate sand-transport rate to the wind-shear velocity.However,the wind-shear velocity readapted to blown sand is difficult to determine from the measured wind profiles when sand movement occurs,especially at high wind velocity.Detailed wind tunnel tests were carried out to reformulate the sand-transport rate model,followed by attempts to relate sand-transport rate to parameters of wind velocity,threshold shear-velocity,and grain size.Finally,we validated the model based on the data from field observations.

  13. Principles and practice of reactive transport modeling

    International Nuclear Information System (INIS)

    This paper presents a review of the principles underlying a continuum formulation of reactive transport in a porous medium. Partial differential equations representing conservation of mass are derived for transport by advection, diffusion, and electrochemical migration combined with chemical reaction of aqueous species and solids. Several examples are presented to illustrate the general theory. These include weathering along a narrow crevice, electrochemical migration in a dilute NaCl solution, secondary pyrite formation mediated through intermediate sulfur oxidation states, and a description of a uranium roll-front deposit. Numerical techniques which take advantage of the quasi-stationary state approximation, based on the much longer time scale involved in mineral alteration compared to that characterizing changes in the aqueous phase, permit solving the reactive transport equations over geologic time scales

  14. Advanced transport systems analysis, modeling, and evaluation of performances

    CERN Document Server

    Janić, Milan

    2014-01-01

    This book provides a systematic analysis, modeling and evaluation of the performance of advanced transport systems. It offers an innovative approach by presenting a multidimensional examination of the performance of advanced transport systems and transport modes, useful for both theoretical and practical purposes. Advanced transport systems for the twenty-first century are characterized by the superiority of one or several of their infrastructural, technical/technological, operational, economic, environmental, social, and policy performances as compared to their conventional counterparts. The advanced transport systems considered include: Bus Rapid Transit (BRT) and Personal Rapid Transit (PRT) systems in urban area(s), electric and fuel cell passenger cars, high speed tilting trains, High Speed Rail (HSR), Trans Rapid Maglev (TRM), Evacuated Tube Transport system (ETT), advanced commercial subsonic and Supersonic Transport Aircraft (STA), conventionally- and Liquid Hydrogen (LH2)-fuelled commercial air trans...

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

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Y.; Ajo-Franklin, J.B.; Spycher, N.; Hubbard, S.S.; Zhang, G.; Williams, K.H.; Taylor, J.; Fujita, Y.; Smith, R.

    2011-07-15

    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 NH{sub 4}{sup

  16. Geophysical Monitoring and Reactive Transport Modeling of Ureolytically-Driven Calcium Carbonate Precipitation

    Energy Technology Data Exchange (ETDEWEB)

    Yuxin Wu; Jonathan B. Ajo-Franklin; Nicolas Spycher; Susan S. Hubbard; Guoxiang Zhang; Kenneth H. Williams; Joanna Taylor; Yoshiko Fujita; Robert Smith

    2011-09-01

    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

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

    Science.gov (United States)

    Wu, Yuxin; Ajo-Franklin, Jonathan B; Spycher, Nicolas; Hubbard, Susan S; Zhang, Guoxiang; Williams, Kenneth H; Taylor, Joanna; Fujita, Yoshiko; Smith, Robert

    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

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

    Directory of Open Access Journals (Sweden)

    Taylor Joanna

    2011-09-01

    Full Text Available Abstract 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

  19. European initiatives for modeling emissions from transport

    DEFF Research Database (Denmark)

    Joumard, Robert; Hickman, A. John; Samaras, Zissis;

    1998-01-01

    COST 319 action bringing together about 80 active scientists from the whole of Europe and considering all modes of transport and all inventory levels. The paper briefly presents the history of the various multilateral and EC initiatives and discusses the latest in more detail, from the collection of...... the raw data to the design of the inventory tools. The paper also considers the structures and the main assumptions of the current inventory methods for the various transport modes and various areas of application, including reference to work currently in progress or planned for the near future...

  20. Particle Tracking Model and Abstraction of Transport Processes

    International Nuclear Information System (INIS)

    The purpose of this report is to document the abstraction model being used in total system performance assessment (TSPA) model calculations for radionuclide transport in the unsaturated zone (UZ). The UZ transport abstraction model uses the particle-tracking method that is incorporated into the finite element heat and mass model (FEHM) computer code (Zyvoloski et al. 1997 [DIRS 100615]) to simulate radionuclide transport in the UZ. This report outlines the assumptions, design, and testing of a model for calculating radionuclide transport in the UZ at Yucca Mountain. In addition, methods for determining and inputting transport parameters are outlined for use in the TSPA for license application (LA) analyses. Process-level transport model calculations are documented in another report for the UZ (BSC 2004 [DIRS 164500]). Three-dimensional, dual-permeability flow fields generated to characterize UZ flow (documented by BSC 2004 [DIRS 169861]; DTN: LB03023DSSCP9I.001 [DIRS 163044]) are converted to make them compatible with the FEHM code for use in this abstraction model. This report establishes the numerical method and demonstrates the use of the model that is intended to represent UZ transport in the TSPA-LA. Capability of the UZ barrier for retarding the transport is demonstrated in this report, and by the underlying process model (BSC 2004 [DIRS 164500]). The technical scope, content, and management of this report are described in the planning document ''Technical Work Plan for: Unsaturated Zone Transport Model Report Integration'' (BSC 2004 [DIRS 171282]). Deviations from the technical work plan (TWP) are noted within the text of this report, as appropriate. The latest version of this document is being prepared principally to correct parameter values found to be in error due to transcription errors, changes in source data that were not captured in the report, calculation errors, and errors in interpretation of source data

  1. Model for Estimation Urban Transportation Supply-Demand Ratio

    Directory of Open Access Journals (Sweden)

    Chaoqun Wu

    2015-01-01

    Full Text Available The paper establishes an estimation model of urban transportation supply-demand ratio (TSDR to quantitatively describe the conditions of an urban transport system and to support a theoretical basis for transport policy-making. This TSDR estimation model is supported by the system dynamic principle and the VENSIM (an application that simulates the real system. It was accomplished by long-term observation of eight cities’ transport conditions and by analyzing the estimated results of TSDR from fifteen sets of refined data. The estimated results indicate that an urban TSDR can be classified into four grades representing four transport conditions: “scarce supply,” “short supply,” “supply-demand balance,” and “excess supply.” These results imply that transport policies or measures can be quantified to facilitate the process of ordering and screening them.

  2. Ocean fronts drive marine fishery production and biogeochemical cycling.

    Science.gov (United States)

    Woodson, C Brock; Litvin, Steven Y

    2015-02-10

    Long-term changes in nutrient supply and primary production reportedly foreshadow substantial declines in global marine fishery production. These declines combined with current overfishing, habitat degradation, and pollution paint a grim picture for the future of marine fisheries and ecosystems. However, current models forecasting such declines do not account for the effects of ocean fronts as biogeochemical hotspots. Here we apply a fundamental technique from fluid dynamics to an ecosystem model to show how fronts increase total ecosystem biomass, explain fishery production, cause regime shifts, and contribute significantly to global biogeochemical budgets by channeling nutrients through alternate trophic pathways. We then illustrate how ocean fronts affect fishery abundance and yield, using long-term records of anchovy-sardine regimes and salmon abundances in the California Current. These results elucidate the fundamental importance of biophysical coupling as a driver of bottom-up vs. top-down regulation and high productivity in marine ecosystems. PMID:25624488

  3. Modelling passenger flows in public transport facilities

    NARCIS (Netherlands)

    Daamen, W.

    2004-01-01

    This thesis describes the developement of a new type of simulation tool for the assessment of designs of public transport facilities (stations, airports) and other public spaces with intensive pedestrian flows. Since the available space for such facilities is increasingly under pressure, the space e

  4. Biogeochemical processes in forest riparian zones

    OpenAIRE

    Ledesma, José L. J.

    2016-01-01

    The area of interaction between terrestrial and aquatic environments, i.e. the riparian zone (RZ), has long been recognized as an important landscape feature from both scientific and management perspectives. Surface water quality is to a great extent regulated by substances exported from RZs. Boreal forest RZs are characterized by high organic matter content, which drives important biogeochemical processes. The overall objective of this thesis was to develop the understanding of RZ biogeochem...

  5. Biogeochemical aspects of aquifer thermal energy storage.

    OpenAIRE

    Brons, H.J.

    1992-01-01

    During the process of aquifer thermal energy storage the in situ temperature of the groundwater- sediment system may fluctuate significantly. As a result the groundwater characteristics can be considerably affected by a variety of chemical, biogeochemical and microbiological reactions. The interplay of these reactions may have a negative influence on the operational performance of ATES-systems. The objective of this thesis was to investigate bacterial clogging processes and the biogeochemical...

  6. Experience of biogeochemical researches around Digmai tailings

    International Nuclear Information System (INIS)

    The experience of works on the biogeochemical approbation executed from 1991 to 2007 is generalized in the article. It is shown that results of approbation are characterizing the behaviour of polluting substances in the tailing-soil-plant. The function reflecting a system condition during the various periods of time is offered. The conclusion is drawn on necessity of biogeochemical approbation to the general monitoring systems tailings-surrounding environment. (author)

  7. Modeling spin magnetization transport in a spatially varying magnetic field

    International Nuclear Information System (INIS)

    We present a framework for modeling the transport of any number of globally conserved quantities in any spatial configuration and apply it to obtain a model of magnetization transport for spin-systems that is valid in new regimes (including high-polarization). The framework allows an entropy function to define a model that explicitly respects the laws of thermodynamics. Three facets of the model are explored. First, it is expressed as nonlinear partial differential equations that are valid for the new regime of high dipole-energy and polarization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield (1975) [1]. Differences among the three forms of the model are illustrated by numerical solution with parameters corresponding to a magnetic resonance force microscopy (MRFM) experiment (Degen et al., 2009 [2]; Kuehn et al., 2008 [3]; Sidles et al., 2003 [4]; Dougherty et al., 2000 [5]). A family of analytic, steady-state solutions to the nonlinear equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. Finally, we analyze the separative quality of magnetization transport, and a steady-state solution for the magnetization is shown to be compatible with Fenske's separative mass transport equation (Fenske, 1932 [6]). - Highlights: • A framework for modeling the transport of conserved magnetic and thermodynamic quantities in any spatial configuration. • A thermodynamically grounded model of spin magnetization transport valid in new regimes, including high-polarization. • Analysis of the separative quality of

  8. Modeling spin magnetization transport in a spatially varying magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Picone, Rico A.R., E-mail: rpicone@stmartin.edu [Department of Mechanical Engineering, University of Washington, Seattle (United States); Garbini, Joseph L. [Department of Mechanical Engineering, University of Washington, Seattle (United States); Sidles, John A. [Department of Orthopædics, University of Washington, Seattle (United States)

    2015-01-15

    We present a framework for modeling the transport of any number of globally conserved quantities in any spatial configuration and apply it to obtain a model of magnetization transport for spin-systems that is valid in new regimes (including high-polarization). The framework allows an entropy function to define a model that explicitly respects the laws of thermodynamics. Three facets of the model are explored. First, it is expressed as nonlinear partial differential equations that are valid for the new regime of high dipole-energy and polarization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield (1975) [1]. Differences among the three forms of the model are illustrated by numerical solution with parameters corresponding to a magnetic resonance force microscopy (MRFM) experiment (Degen et al., 2009 [2]; Kuehn et al., 2008 [3]; Sidles et al., 2003 [4]; Dougherty et al., 2000 [5]). A family of analytic, steady-state solutions to the nonlinear equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. Finally, we analyze the separative quality of magnetization transport, and a steady-state solution for the magnetization is shown to be compatible with Fenske's separative mass transport equation (Fenske, 1932 [6]). - Highlights: • A framework for modeling the transport of conserved magnetic and thermodynamic quantities in any spatial configuration. • A thermodynamically grounded model of spin magnetization transport valid in new regimes, including high-polarization. • Analysis of the separative quality of

  9. Modeling of titration experiments by a reactive transport model

    Institute of Scientific and Technical Information of China (English)

    Ma Hongyun; Samper Javier; Xin Xin

    2011-01-01

    Acid mine drainage (AMD) is commonly treated by neutralization with alkaline substances. This treatment is supported by titration experiments that illustrate the buffering mechanisms and estimate the base neutralization capacity (BNC) of the AMD. Detailed explanation of titration curves requires modeling with a hydro-chemical model. In this study the titration curves of water samples from the drainage of the As Pontes mine and the corresponding dumps have been investigated and six buffers are selected by analyzing those curves. Titration curves have been simulated by a reactive transport model to discover the detailed buffering mechanisms. These simulations show seven regions involving different buffering mechanism. The BNC is primarily from buffers of dissolved Fe, Al and hydrogen sulfate. The BNC can be approximated by: BNC = 3(CFe + CAl) + 0.05Csulfate, where the units are mol/L. The BNC of the sample from the mine is 9.25 × 10-3 mol/L and that of the dumps sample is 1.28 × 10-2 mol/L.

  10. Preface to: Indian Ocean biogeochemical processes and ecological variability

    Digital Repository Service at National Institute of Oceanography (India)

    Hood, R.R.; Naqvi, S.W.A.; Wiggert, J.D.

    -1 PREFACE Although there have been significant advances in our ability to describe and model the oceanic environment, our understanding of the physical, biogeochemical, and eco logical dynamics of the Indian Ocean is still rudimentary in many respects.... This is partly because the Indian Ocean re mains substantially under sampled, in both space and time, compared to the Atlantic and Pacific oceans. The situation is compounded by the Indian Ocean being a dynamically complex and highly variable system under...

  11. Computational Modeling of Transport Limitations in Li-Air Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Ryan, Emily M.; Ferris, Kim F.; Tartakovsky, Alexandre M.; Khaleel, Mohammad A.

    2013-02-22

    In this paper we investigate transport limitations in the electrodes of lithium-air batteries through computational modeling. We use meso-scale models to consider the effects of dendrites on the current and potential at the anode surface, and to investigate the effects of reaction and transport parameters on the formation of precipitates in the cathode. The formation of dendrites on the anode surface during cycling reduces the transport of ions and can lead to short circuits in the cell. Growth of precipitates in the cathode reduces the specific capacity of the cell due to surface passivation and pore clogging. Both of these degradation mechanisms depend on meso-scale phenomena, such as the pore-scale reactive transport in the cathode. To understand the effects of the meso-scale transport and precipitation on the performance and lifetime of Li-air batteries, meso-scale modeling is needed that is able to resolve the electrodes and their microstructures.

  12. In vitro placental model optimization for nanoparticle transport studies

    DEFF Research Database (Denmark)

    Cartwright, Laura; Poulsen, Marie Sønnegaard; Nielsen, Hanne Mørck;

    2012-01-01

    ’s exposure to nanoparticles could have significant effects on the fetus developing in the womb. Therefore, the purpose of this study is to optimize an in vitro model for characterizing the transport of nanoparticles across human placental trophoblast cells. Methods: The growth of BeWo (clone b30) human...... transport. Following the determination of nontoxic concentrations of fluorescent polystyrene nanoparticles, the cellular uptake and transport of 50 nm and 100 nm diameter particles was measured using the in vitro BeWo cell model. Results: Particle size measurements, fluorescence readings, and confocal...... membranes (3.0 µm pore size) was four times higher for the 50 nm particles compared with the 100 nm particles. Conclusion: The BeWo cell line has been optimized and shown to be a valid in vitro model for studying the transplacental transport of nanoparticles. Fluorescent polystyrene nanoparticle transport...

  13. IOT technology application model research of transportation industry in China

    Institute of Scientific and Technical Information of China (English)

    Lai Mingyong; Zhou Tang; Liu Zhengchi

    2013-01-01

    The paper studied the connection between intemet of things (IOT) technology and transportation industry.Meanwhile,the definition of IOT in transportation was given.Concerning that many problems occurred during the process of traditional intelligent transportation system,the paper proposed a promising model of IOT in transportation.The advantage of the information utilization model from information to function was confirmed through comparative study.Finally,the model presented that a real interconnection of transportation would be achieved based on the unified information collection.It can greatly save cost on technology transfer,exploit potential value of information,and promote the emergence of a sustainable information service market and the industrial upgrade.

  14. Avalanches properties in a self-organized critical transport model

    International Nuclear Information System (INIS)

    We have proposed a one-dimensional transport model based on critical-gradient fluctuation dynamics to describe some of the properties of plasma turbulence induced transport. This model has the characteristic properties of a self-organized critical (SOC) system. In this model, the flux is self-regulated by the stability properties of the fluctuations. A high-gradient edge region emerges where transport dynamics is close to marginal stability. The core remains at the subcritical gradient that is typical of a SOC system. Avalanches are quasi-periodic events triggered mostly near the edge region. (author)

  15. Modelling of human transplacental transport as performed in Copenhagen, Denmark

    DEFF Research Database (Denmark)

    Mathiesen, Line; Mørck, Thit Aarøe; Zuri, Giuseppina;

    2014-01-01

    Placenta perfusion models are very effective when studying the placental mechanisms in order to extrapolate to real-life situations. The models are most often used to investigate the transport of substances between mother and foetus, including the potential metabolism of these. We have studied the...... vitro with an established human monolayer trophoblast cell culture model. Results from our studies distinguish placental transport of substances by physicochemical properties, adsorption to placental tissue, binding to transport and receptor proteins and metabolism. We have collected data from different...

  16. Finite difference methods for coupled flow interaction transport models

    Directory of Open Access Journals (Sweden)

    Shelly McGee

    2009-04-01

    Full Text Available Understanding chemical transport in blood flow involves coupling the chemical transport process with flow equations describing the blood and plasma in the membrane wall. In this work, we consider a coupled two-dimensional model with transient Navier-Stokes equation to model the blood flow in the vessel and Darcy's flow to model the plasma flow through the vessel wall. The advection-diffusion equation is coupled with the velocities from the flows in the vessel and wall, respectively to model the transport of the chemical. The coupled chemical transport equations are discretized by the finite difference method and the resulting system is solved using the additive Schwarz method. Development of the model and related analytical and numerical results are presented in this work.

  17. Olkiluoto surface hydrological modelling: Update 2012 including salt transport modelling

    Energy Technology Data Exchange (ETDEWEB)

    Karvonen, T. [WaterHope, Helsinki (Finland)

    2013-11-15

    Posiva Oy is responsible for implementing a final disposal program for spent nuclear fuel of its owners Teollisuuden Voima Oyj and Fortum Power and Heat Oy. The spent nuclear fuel is planned to be disposed at a depth of about 400-450 meters in the crystalline bedrock at the Olkiluoto site. Leakages located at or close to spent fuel repository may give rise to the upconing of deep highly saline groundwater and this is a concern with regard to the performance of the tunnel backfill material after the closure of the tunnels. Therefore a salt transport sub-model was added to the Olkiluoto surface hydrological model (SHYD). The other improvements include update of the particle tracking algorithm and possibility to estimate the influence of open drillholes in a case where overpressure in inflatable packers decreases causing a hydraulic short-circuit between hydrogeological zones HZ19 and HZ20 along the drillhole. Four new hydrogeological zones HZ056, HZ146, BFZ100 and HZ039 were added to the model. In addition, zones HZ20A and HZ20B intersect with each other in the new structure model, which influences salinity upconing caused by leakages in shafts. The aim of the modelling of long-term influence of ONKALO, shafts and repository tunnels provide computational results that can be used to suggest limits for allowed leakages. The model input data included all the existing leakages into ONKALO (35-38 l/min) and shafts in the present day conditions. The influence of shafts was computed using eight different values for total shaft leakage: 5, 11, 20, 30, 40, 50, 60 and 70 l/min. The selection of the leakage criteria for shafts was influenced by the fact that upconing of saline water increases TDS-values close to the repository areas although HZ20B does not intersect any deposition tunnels. The total limit for all leakages was suggested to be 120 l/min. The limit for HZ20 zones was proposed to be 40 l/min: about 5 l/min the present day leakages to access tunnel, 25 l/min from

  18. Olkiluoto surface hydrological modelling: Update 2012 including salt transport modelling

    International Nuclear Information System (INIS)

    Posiva Oy is responsible for implementing a final disposal program for spent nuclear fuel of its owners Teollisuuden Voima Oyj and Fortum Power and Heat Oy. The spent nuclear fuel is planned to be disposed at a depth of about 400-450 meters in the crystalline bedrock at the Olkiluoto site. Leakages located at or close to spent fuel repository may give rise to the upconing of deep highly saline groundwater and this is a concern with regard to the performance of the tunnel backfill material after the closure of the tunnels. Therefore a salt transport sub-model was added to the Olkiluoto surface hydrological model (SHYD). The other improvements include update of the particle tracking algorithm and possibility to estimate the influence of open drillholes in a case where overpressure in inflatable packers decreases causing a hydraulic short-circuit between hydrogeological zones HZ19 and HZ20 along the drillhole. Four new hydrogeological zones HZ056, HZ146, BFZ100 and HZ039 were added to the model. In addition, zones HZ20A and HZ20B intersect with each other in the new structure model, which influences salinity upconing caused by leakages in shafts. The aim of the modelling of long-term influence of ONKALO, shafts and repository tunnels provide computational results that can be used to suggest limits for allowed leakages. The model input data included all the existing leakages into ONKALO (35-38 l/min) and shafts in the present day conditions. The influence of shafts was computed using eight different values for total shaft leakage: 5, 11, 20, 30, 40, 50, 60 and 70 l/min. The selection of the leakage criteria for shafts was influenced by the fact that upconing of saline water increases TDS-values close to the repository areas although HZ20B does not intersect any deposition tunnels. The total limit for all leakages was suggested to be 120 l/min. The limit for HZ20 zones was proposed to be 40 l/min: about 5 l/min the present day leakages to access tunnel, 25 l/min from

  19. Reactive Transport Modeling of the Yucca Mountain Site, Nevada

    International Nuclear Information System (INIS)

    The Yucca Mountain site has a dry climate and deep water table, with the repository located in the middle of an unsaturated zone approximately 600 m thick. Radionuclide transport processes from the repository to the water table are sensitive to the unsaturated zone flow field, as well as to sorption, matrix diffusion, radioactive decay, and colloid transport mechanisms. The unsaturated zone flow and transport models are calibrated against both physical and chemical data, including pneumatic pressure, liquid saturation, water potential, temperature, chloride, and calcite. The transport model predictions are further compared with testing specific to unsaturated zone transport: at Alcove 1 in the Exploratory Studies Facility (ESF), at Alcove 8 and Niche 3 of the ESF, and at the Busted Butte site. The models are applied to predict the breakthroughs at the water table for nonsorbing and sorbing radionuclides, with faults shown as the important paths for radionuclide transport. Daughter products of some important radionuclides, such as 239Pu and 241Am, have faster transport than the parents and must be considered in the unsaturated zone transport model. Colloid transport is significantly affected by colloid size, but only negligibly affected by lunetic declogging (reverse filtering) mechanisms. Unsaturated zone model uncertainties are discussed, including the sensitivity of breakthrough to the active fracture model parameter, as an example of uncertainties related to detailed flow characteristics and fracture-matrix interaction. It is expected that additional benefits from the unsaturated zone barrier for transport can be achieved by full implementation of the shadow zone concept immediately below the radionuclide release points in the waste emplacement drifts

  20. Physics and modelling of scrape-off layer transport

    International Nuclear Information System (INIS)

    We present studies of three schemes for reducing the peak heat flux on divertor plates, divertor biasing, impurity injection (''radiative divertor'') and neutral gas injection (''gas target divertor''). We report on theoretical analysis of a likely source of turbulent transport in the SOL and incorporation of the resultant transport coefficients into self-consistent models

  1. Modelling heat transport through completely positive maps

    CERN Document Server

    Wichterich, H; Gemmer, J; Henrich, M J; Michel, M; Breuer, Heinz-Peter; Gemmer, Jochen; Henrich, Markus J.; Michel, Mathias; Wichterich, Hannu

    2007-01-01

    We investigate heat transport in a spin-1/2 Heisenberg chain, coupled locally to independent thermal baths of different temperature. The analysis is carried out within the framework of the theory of open systems by means of appropriate quantum master equations. The standard microscopic derivation of the weak-coupling Lindblad equation in the secular approximation is considered, and shown to be inadequate for the description of stationary nonequilibrium properties like a non-vanishing energy current. Furthermore, we derive an alternative master equation that is capable to describe a stationary energy current and, at the same time, leads to a completely positive dynamical map. This paves the way for efficient numerical investigations of heat transport in larger systems based on Monte Carlo wave function techniques.

  2. Modeling heat transport through completely positive maps

    OpenAIRE

    Wichterich, Hannu; Henrich, Markus J.; Breuer, Heinz-Peter; Gemmer, Jochen; Michel, Mathias

    2007-01-01

    We investigate heat transport in a spin-1/2 Heisenberg chain, coupled locally to independent thermal baths of different temperature. The analysis is carried out within the framework of the theory of open systems by means of appropriate quantum master equations. The standard microscopic derivation of the weak-coupling Lindblad equation in the secular approximation is considered, and shown to be inadequate for the description of stationary nonequilibrium properties like a non-vanishing energy c...

  3. On quantum hydrodynamic and quantum energy transport models

    OpenAIRE

    Degond, Pierre; Gallego, Samy; Mehats, Florian

    2007-01-01

    In this paper, we consider two recently derived models: the Quantum Hydrodynamic model (QHD) and the Quantum Energy Transport model (QET). We propose different equivalent formulations of these models and we use a commutator formula for stating new properties of the models. A gauge invariance lemma permits to simplify the QHD model for irrotational flows. We finish by considering the special case of a slowly varying temperature and we discuss possible approximations which will b...

  4. System convergence in transport models: algorithms efficiency and output uncertainty

    DEFF Research Database (Denmark)

    Rich, Jeppe; Nielsen, Otto Anker

    2015-01-01

    Transport models most often involve separate models for traffic assignment and demand. As a result, two different equilibrium mechanisms are involved, (i) the internal traffic assignment equilibrium, and (ii) the external equilibrium between the assignment model and the demand model. The objective...... of this paper is to analyse convergence performance for the external loop and to illustrate how an improper linkage between the converging parts can lead to substantial uncertainty in the final output. Although this loop is crucial for the performance of large-scale transport models it has not been......-scale in the Danish National Transport Model (DNTM). It is revealed that system convergence requires that either demand or supply is without random noise but not both. In that case, if MSA is applied to the model output with random noise, it will converge effectively as the random effects are gradually...

  5. VERIFICATION OF A TOXIC ORGANIC SUBSTANCE TRANSPORT AND BIOACCUMULATION MODEL

    Science.gov (United States)

    A field verification of the Toxic Organic Substance Transport and Bioaccumulation Model (TOXIC) was conducted using the insecticide dieldrin and the herbicides alachlor and atrazine as the test compounds. The test sites were two Iowa reservoirs. The verification procedure include...

  6. Plasma transport simulation modelling for helical confinement systems

    International Nuclear Information System (INIS)

    New empirical and theoretical transport models for helical confinement systems are developed on the basis of the neoclassical transport theory, including the effect of the radial electric field and of multi-helicity magnetic components as well as the drift wave turbulence transport for electrostatic and electromagnetic modes or the anomalous semi-empirical transport. These electron thermal diffusivities are compared with experimental data from the Compact Helical System which indicate that the central transport coefficient of a plasma with electron cyclotron heating agrees with neoclassical axisymmetric value and the transport outside the half-radius is anomalous. On the other hand, the transport of plasmas with neutral beam injection heating is anomalous in the whole plasma region. This anomaly is not explained by the electrostatic drift wave turbulence models in these discharges with flat density profiles. For a detailed prediction of the plasma parameters in the Large Helical Device (LHD), 3-D equilibrium/1-D transport simulations including empirical or drift wave turbulence models are performed which suggest that the global confinement time of the LHD is determined mainly by the electron anomalous transport in the plasma edge region rather than by the helical ripple transport in the core region. Even if the ripple loss can be eliminated, the increase in global confinement is 10%. However, the rise in the central ion temperature is more than 20%. If the anomalous loss can be reduced to half of the value used in the present scaling, as is the case in the H-mode of tokamak discharges, the neoclassical ripple loss through the ion channel becomes important even in the plasma core. The 5% radial inward shift of the plasma column with respect to the major radius improves the plasma confinement and increases the fusion product by more than 50% by reducing the neoclassical asymmetric ion transport loss and increasing the plasma radius (10%). (author). 32 refs, 7 figs

  7. Plasma transport simulation modeling for helical confinement systems

    International Nuclear Information System (INIS)

    New empirical and theoretical transport models for helical confinement systems are developed based on the neoclassical transport theory including the effect of radial electric field and multi-helicity magnetic components, and the drift wave turbulence transport for electrostatic and electromagnetic modes, or the anomalous semi-empirical transport. These electron thermal diffusivities are compared with CHS (Compact Helical System) experimental data, which indicates that the central transport coefficient of the ECH plasma agrees with the neoclassical axi-symmetric value and the transport outside the half radius is anomalous. On the other hand, the transport of NBI-heated plasmas is anomalous in the whole plasma region. This anomaly is not explained by the electrostatic drift wave turbulence models in these flat-density-profile discharges. For the detailed prediction of plasma parameters in LHD (Large Helical Device), 3-D(dimensional) equilibrium/1-D transport simulations including empirical or drift wave turbulence models are carried out, which suggests that the global confinement time of LHD is determined mainly by the electron anomalous transport near the plasma edge region rather than the helical ripple transport in the core region. Even if the ripple loss can be eliminated, the increase of the global confinement is 10%. However, the rise in the central ion temperature is more than 20%. If the anomalous loss can be reduced to the half level of the present scaling, like so-called 'H-mode' of the tokamak discharge, the neoclassical ripple loss through the ion channel becomes important even in the plasma core. The 5% radial inward shift of the plasma column with respect to the major radius is effective for improving plasma confinement and raising more than 50% of the fusion product by reducing this neoclassical asymmetric ion transport loss and increasing 10% in the plasma radius. (author)

  8. Modeling of pollutant emissions from road transport; Modelisation des emissions de polluants par le transport routier

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2003-07-01

    COPERT III (computer programme to calculate emissions from road transport) is the third version of an MS Windows software programme aiming at the calculation of air pollutant emissions from road transport. COPERT estimates emissions of all regulated air pollutants (CO, NO{sub x}, VOC, PM) produced by different vehicle categories as well as CO{sub 2} emissions on the basis of fuel consumption. This research seminar was organized by the French agency of environment and energy mastery (Ademe) around the following topics: the uncertainties and sensitiveness analysis of the COPERT III model, the presentation of case studies that use COPERT III for the estimation of road transport emissions, and the future of the modeling of road transport emissions: from COPERT III to ARTEMIS (assessment and reliability of transport emission models and inventory systems). This document is a compilation of 8 contributions to this seminar and dealing with: the uncertainty and sensitiveness analysis of the COPERT III model; the road mode emissions of the ESCOMPTE program: sensitivity study; the sensitivity analysis of the spatialized traffic at the time-aggregation level: application in the framework of the INTERREG project (Alsace); the road transport aspect of the regional air quality plan of Bourgogne region: exhaustive consideration of the road network; intercomparison of tools and methods for the inventory of emissions of road transport origin; evolution of the French park of vehicles by 2025: new projections; application of COPERT III to the French context: a new version of IMPACT-ADEME; the European ARTEMIS project: new structural considerations for the modeling of road transport emissions. (J.S.)

  9. Atmospheric & Oceanic Applications of Eulerian and Lagrangian Transport Modelling

    OpenAIRE

    Kjellsson, Joakim

    2014-01-01

    This thesis presents several ways to understand transports of air and water masses in the atmosphere and ocean, and the transports of energy that they imply. It presents work using various kinds of observations as well as computer simulations of the atmosphere and oceans. One of the main focuses is to identify similarities and differences between models and observations, as well as between different models. The first half of the thesis applies Lagrangian methods to study flows in the atmosphe...

  10. Complexities in coastal sediment transport studies by numerical modeling

    OpenAIRE

    Dandayudapani, I.; M. Murali

    2013-01-01

    Marine environmental studies related to erosion, accretion, pollution transport, dredge disposal, location of seawater intake, effluent disposal, etc., involve sediment transport studies. Numerical models use set of well linked mathematical equations arrived based on scientific principles as all natural phenomena are governed by certain rules which can be explained by scientific principles. Efficiency of numerical modeling greatly depends on quality of input parameters. When input parameters ...

  11. Quantum Model of Energy Transport in Collagen Molecules

    Institute of Scientific and Technical Information of China (English)

    XIAO Yi; LIN Xian-Zhe

    2001-01-01

    A semi-quantum model for energy transport in collagen molecules is presented. Soliton-like dynamics of this model is investigated numerically without and with the temperature effect taking into account. It is found that in both the cases energy can transport for a long distance along the collagen chain. This indicates that collagen molecules can be taken as a candidate for the acupuncture channel.

  12. Ab initio electronic transport model with explicit solution to the linearized Boltzmann transport equation

    Science.gov (United States)

    Faghaninia, Alireza; Ager, Joel W.; Lo, Cynthia S.

    2015-06-01

    Accurate models of carrier transport are essential for describing the electronic properties of semiconductor materials. To the best of our knowledge, the current models following the framework of the Boltzmann transport equation (BTE) either rely heavily on experimental data (i.e., semiempirical), or utilize simplifying assumptions, such as the constant relaxation time approximation (BTE-cRTA). While these models offer valuable physical insights and accurate calculations of transport properties in some cases, they often lack sufficient accuracy—particularly in capturing the correct trends with temperature and carrier concentration. We present here a transport model for calculating low-field electrical drift mobility and Seebeck coefficient of n -type semiconductors, by explicitly considering relevant physical phenomena (i.e., elastic and inelastic scattering mechanisms). We first rewrite expressions for the rates of elastic scattering mechanisms, in terms of ab initio properties, such as the band structure, density of states, and polar optical phonon frequency. We then solve the linear BTE to obtain the perturbation to the electron distribution—resulting from the dominant scattering mechanisms—and use this to calculate the overall mobility and Seebeck coefficient. Therefore, we have developed an ab initio model for calculating mobility and Seebeck coefficient using the Boltzmann transport (aMoBT) equation. Using aMoBT, we accurately calculate electrical transport properties of the compound n -type semiconductors, GaAs and InN, over various ranges of temperature and carrier concentration. aMoBT is fully predictive and provides high accuracy when compared to experimental measurements on both GaAs and InN, and vastly outperforms both semiempirical models and the BTE-cRTA. Therefore, we assert that this approach represents a first step towards a fully ab initio carrier transport model that is valid in all compound semiconductors.

  13. Electronic transport in VO2—Experimentally calibrated Boltzmann transport modeling

    International Nuclear Information System (INIS)

    Materials that undergo metal-insulator transitions (MITs) are under intense study, because the transition is scientifically fascinating and technologically promising for various applications. Among these materials, VO2 has served as a prototype due to its favorable transition temperature. While the physical underpinnings of the transition have been heavily investigated experimentally and computationally, quantitative modeling of electronic transport in the two phases has yet to be undertaken. In this work, we establish a density-functional-theory (DFT)-based approach with Hubbard U correction (DFT + U) to model electronic transport properties in VO2 in the semiconducting and metallic regimes, focusing on band transport using the Boltzmann transport equations. We synthesized high quality VO2 films and measured the transport quantities across the transition, in order to calibrate the free parameters in the model. We find that the experimental calibration of the Hubbard correction term can efficiently and adequately model the metallic and semiconducting phases, allowing for further computational design of MIT materials for desirable transport properties

  14. Electronic transport in VO{sub 2}—Experimentally calibrated Boltzmann transport modeling

    Energy Technology Data Exchange (ETDEWEB)

    Kinaci, Alper; Rosenmann, Daniel; Chan, Maria K. Y., E-mail: debasish.banerjee@toyota.com, E-mail: mchan@anl.gov [Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Kado, Motohisa [Higashifuji Technical Center, Toyota Motor Corporation, Susono, Shizuoka 410-1193 (Japan); Ling, Chen; Zhu, Gaohua; Banerjee, Debasish, E-mail: debasish.banerjee@toyota.com, E-mail: mchan@anl.gov [Materials Research Department, Toyota Motor Engineering and Manufacturing North America, Inc., Ann Arbor, Michigan 48105 (United States)

    2015-12-28

    Materials that undergo metal-insulator transitions (MITs) are under intense study, because the transition is scientifically fascinating and technologically promising for various applications. Among these materials, VO{sub 2} has served as a prototype due to its favorable transition temperature. While the physical underpinnings of the transition have been heavily investigated experimentally and computationally, quantitative modeling of electronic transport in the two phases has yet to be undertaken. In this work, we establish a density-functional-theory (DFT)-based approach with Hubbard U correction (DFT + U) to model electronic transport properties in VO{sub 2} in the semiconducting and metallic regimes, focusing on band transport using the Boltzmann transport equations. We synthesized high quality VO{sub 2} films and measured the transport quantities across the transition, in order to calibrate the free parameters in the model. We find that the experimental calibration of the Hubbard correction term can efficiently and adequately model the metallic and semiconducting phases, allowing for further computational design of MIT materials for desirable transport properties.

  15. Models of coupled salt and water transport across leaky epithelia.

    Science.gov (United States)

    Weinstein, A M; Stephenson, J L

    1981-05-15

    A general formulation is presented for the verification of isotonic transport and for the assignment of a degree of osmotic coupling in any epithelial model. In particular, it is shown that the concentration of the transported fluid in the presence of exactly equal bathing media is, in general, not a sufficient calculation by which to decide the issue of isotonicity of transport. Within this framework, two epithelial models are considered: (1) A nonelectrolyte compartment model of the lateral intercellular space is presented along with its linearization about the condition of zero flux. This latter approximate model is shown to be useful in the estimation of deviation from isotonicity, intraepithelial solute polarization effects, and the capacity to transport water against a gradient. In the case of uphill water transport, some limitations of a model of fixed geometry are indicated and the advantage of modeling a compliant interspace is suggested. (2) A comprehensive model of cell and channel is described which includes the major electrolytes and the possible presence of intraepithelial gradients. The general approach to verification of isotonicity is illustrated for this numerical model. In addition, the insights about parameter dependence gained from the linear compartment model are shown to be applicable to understanding this large simulation. PMID:6264088

  16. Comparison of biogeochemical dynamics in two time-series sites of a North Atlantic Ocean site (PAP and BATS): a modeling approach.

    Science.gov (United States)

    Ibello, Valeria; Butenschon, Momme; Salihoglu, Baris; Erkan Kideys, Ahmet

    2013-04-01

    Plankton functional type (PFT) models are highly complex ecosystem models. Indeed, the large number of processes and plankton functional groups represented in these models make the network of interactions extremely complicated. Slight differences in parameterization or formulation of single processes, therefore, may drive these models to respond in a very different way to perturbations of the system. An evaluation of such a different responses can be very useful to understand the processes regulating the functioning of the ecosystem. In this study we analyze the sensitivity of the biological parameters in a PFT model (European Regional Seas Ecosystem Model, ERSEM) in respect to primary production and detrital export. The tests are done on a subset of key parameters that control ocean ecosystem growth in a 1-D formulation of ERSEM coupled with a turbulence model (General Ocean Turbulence Model, GOTM). Results are compared with observed data from two time-series sites Bermuda Atlantic Time-Series (BATS, 32.16 N 64.5 W) and Porcupine Abyssal Plain (PAP, 49 N 16 W). A particular focus on factors determining the timing and intensity of the bloom is also presented on the base of literature review and on 1D(GOTM-ERSEM)-3D(NEMO-ERSEM) model simulations comparison. The different processes evaluated are: i). winter convective mixing, ii) lateral advection: mesoscale and sub-mesoscale eddies, iii) turbolent mixing iv) decoupling between euphotic zone and mixed layer depth. The study presented here is carried out in the framework of the European project EURO-BASIN (European Basin-scale Analysis, Synthesis and Integration), where long term 3D simulation aimed to evaluate the variability of primary production and carbon export are planned. Parameterization in use by the 3D NEMO-ERSEM is referring to the global ocean, while simulations are planned for the North North Atlantic. This study aims to contribute to fulfill the development of a specific parameterization for the North

  17. Peristaltic Transport through Eccentric Cylinders: Mathematical Model

    Directory of Open Access Journals (Sweden)

    Kh. S. Mekheimer

    2013-01-01

    Full Text Available This paper discusses the effect of peristaltic transport on the fluid flow in the gap between two eccentric tubes (eccentric-annulus flows. The inner tube is uniform, rigid, while the outer tube has a sinusoidal wave traveling down its wall. The flow analysis has been developed for low Reynolds number and long wave length approximation. The velocity and the pressure gradient have been obtained in terms of the dimensionless flow rate Q¯, time t, azimuthal coordinate θ and eccentricity parameter ϵ (the parameter that controls of the eccentricity of the inner tube position. The results show that there is a significant deference between eccentric and concentric annulus flows.

  18. Fokker-Planck/Transport model for neutral beam driven tokamaks

    International Nuclear Information System (INIS)

    The application of nonlinear Fokker-Planck models to the study of beam-driven plasmas is briefly reviewed. This evolution of models has led to a Fokker-Planck/Transport (FPT) model for neutral-beam-driven Tokamaks, which is described in detail. The FPT code has been applied to the PLT, PDX, and TFTR Tokamaks, and some representative results are presented

  19. A theoretical model for suspended sediment transport in river bends

    NARCIS (Netherlands)

    Talmon, A.M.

    1989-01-01

    A two dimensional depth-averaged model for the concentration field of suspended sediment in river bend flow is formulated. Transport of suspended sediment in horizontal and vertical directions is modelled. Convection by the main and secondary flow and turbulent diffusion are incorporated. The model

  20. Cost damping and functional form in transport models

    DEFF Research Database (Denmark)

    Rich, Jeppe; Mabit, Stefan Lindhard

    2015-01-01

    Transport models allowing for cost damping are characterised by marginally decreasing cost sensitivities in demand. As a result, cost damping is a model extension of the simple linear-in-cost model requiring an appropriate non-linear link function between utility and cost. The link function may t...

  1. Simulation model for the WIPP transportation and delivery system

    International Nuclear Information System (INIS)

    Simulation modelling is a powerful analysis tool used to evaluate complex systems or processes. The modeling concept was utilized to evaluate the performance of the Waste Isolation Pilot Plant (WIPP) transportation and delivery system. The model will assist in analyzing the responsiveness of the components in the system to the variations in waste generation schedule, system failures, and material handling options. (author)

  2. Using model reduction to predict the soil-surface C18OO flux: an example of representing complex biogeochemical dynamics in a computationally efficient manner

    OpenAIRE

    W. J. Riley

    2013-01-01

    Earth system models (ESMs) must calculate large-scale interactions between the land and atmosphere while accurately characterizing fine-scale spatial heterogeneity in water, carbon, and other nutrient dynamics. We present here a high-dimension model representation (HDMR) approach that allows detailed process representation of a coupled carbon and water tracer (the δ18O value of the soil-surface CO2 flux (δ Fs)) in a computationally tractable manner. δ Fs depends on the &delt...

  3. Evaluating changes of transport properties of chemically degrading concrete using a coupled reactive transport model

    International Nuclear Information System (INIS)

    This paper presents a model to simulate chemical degradation of concrete due to leaching. The model considers simultaneously the multi-scale nature of concrete, a thermodynamic description of cement phases, and time-variable transport properties. It is implemented in the generic simulator HP1, which simulates the reactive transport in variably-saturated porous media. To illustrate the capabilities of the program, we simulate diffusive transport through concrete in contact with waters of different solution compositions (i.e., concentrations of major cations and anions and inorganic carbon contents) and use a homogenization scheme for up-scaling tortuosity. The simulations show the coupled effects between geochemical state variables, transport properties, and durability criteria for cementitious materials used in near-surface radioactive waste disposal facilities. (authors)

  4. The thermoballistic transport model a novel approach to charge carrier transport in semiconductors

    CERN Document Server

    Lipperheide, Reinhard

    2014-01-01

    The book presents a comprehensive survey of the thermoballistic approach to charge carrier transport in semiconductors. This semi-classical approach, which the authors have developed over the past decade, bridges the gap between the opposing drift-diffusion and ballistic  models of carrier transport. While incorporating basic features of the latter two models, the physical concept underlying the thermoballistic approach constitutes a novel, unifying scheme. It is based on the introduction of "ballistic configurations" arising from a random partitioning of the length of a semiconducting sample into ballistic transport intervals. Stochastic averaging of the ballistic carrier currents over the ballistic configurations results in a position-dependent thermoballistic current, which is the key element of the thermoballistic concept and forms  the point of departure for the calculation of all relevant transport properties. In the book, the thermoballistic concept and its implementation are developed in great detai...

  5. Modeling of PAH transport in soils and groundwater

    OpenAIRE

    Bour, Olivier; Rollin, Claire; Baroudi, Hafid; Garcia, Michel; Emonet, Annelise; Bues, Michel A.; Le Thiez, Pierre; Blondel, T.; Schwartz, Jackie; Ben Slimane, Férid; Guyonnet, Dominique

    2003-01-01

    Risk assessment for groundwater resources requires most of the time the use of numerical models. These models are used to describe the migration and the transport of pollutants and to predict the contaminant evolution. the models and their parameters selection depend on the extension and the quality of the diagnosis data. the modeller has to know the limits of application of the modelling approach to improve the quality of the assessment. the research program TRANSPOL was undertaken in order ...

  6. ATTILA - Atmospheric Tracer Transport In a Langrangian Model

    Energy Technology Data Exchange (ETDEWEB)

    Reithmeier, C.; Sausen, R.

    2000-07-01

    The Lagrangian model ATTILA (atmospheric tracer transport in a Lagrangian model) has been developed to treat the global-scale transport of passive trace species in the atmosphere within the framework of a general circulation model (GCM). ATTILA runs online within the GCM ECHAM4 and uses the GCM produced wind field to advect the centrois of 80.000 to 180.000 constant mass air parcels into which the model atmosphere is divided. Each trace constituent is thereby represented by a mass mixing ratio in each parcel. ATTILA contains state-of-the-art parameterizations of convection, turbulent boundary layer mixing, and interparcel transport and provides an algorithm to map the tracer concentrations from the trajectories to the ECHAM model grid. We use two experiments to evaluate the transport characteristics of ATTILA against observations and the standard semiLagrangian transport scheme of ECHAM. In the first experiment we simulate the distribution of the short-lived tracer Radon ({sup 222}Rn) in order to examine fast vertical transport over continents, and long-range transport from the continents to remote areas. In the second experiment, we simulate the distribution of radiocarbon ({sup 14}C) that was injected into the northern stratosphere during the nuclear weapon tests in the early 60ties, in order to examine upper tropospheric and stratospheric transport characteristics. ATTILA compares well to the observations and in many respects to the semiLagrangian scheme. However, contrary to the semiLagrangian scheme, ATTILA shows a greatly reduced meridional transport in the upper troposphere and lower stratosphere, and a reduced downward flux from the stratosphere to the troposphere, especially in midlatitudes. Since both transport schemes use the same model meteorology, we conclude that the often cited enhanced meridional transport and overestimated downward flux in ECHAM as described above is rather due to the numerical properties of the semiLagrangian scheme than due to an

  7. Interfacial and Wall Transport Models for SPACE-CAP Code

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Soon Joon; Choo, Yeon Joon; Han, Tae Young; Hwang, Su Hyun; Lee, Byung Chul [FNC Tech., Seoul (Korea, Republic of); Choi, Hoon; Ha, Sang Jun [Korea Electric Power Research Institute, Daejeon (Korea, Republic of)

    2009-10-15

    The development project for the domestic design code was launched to be used for the safety and performance analysis of pressurized light water reactors. And CAP (Containment Analysis Package) code has been also developed for the containment safety and performance analysis side by side with SPACE. The CAP code treats three fields (gas, continuous liquid, and dispersed drop) for the assessment of containment specific phenomena, and is featured by its multidimensional assessment capabilities. Thermal hydraulics solver was already developed and now under testing of its stability and soundness. As a next step, interfacial and wall transport models was setup. In order to develop the best model and correlation package for the CAP code, various models currently used in major containment analysis codes, which are GOTHIC, CONTAIN2.0, and CONTEMPT-LT, have been reviewed. The origins of the selected models used in these codes have also been examined to find out if the models have not conflict with a proprietary right. In addition, a literature survey of the recent studies has been performed in order to incorporate the better models for the CAP code. The models and correlations of SPACE were also reviewed. CAP models and correlations are composed of interfacial heat/mass, and momentum transport models, and wall heat/mass, and momentum transport models. This paper discusses on those transport models in the CAP code.

  8. Chemical Kinetic Modeling of Advanced Transportation Fuels

    Energy Technology Data Exchange (ETDEWEB)

    PItz, W J; Westbrook, C K; Herbinet, O

    2009-01-20

    Development of detailed chemical kinetic models for advanced petroleum-based and nonpetroleum based fuels is a difficult challenge because of the hundreds to thousands of different components in these fuels and because some of these fuels contain components that have not been considered in the past. It is important to develop detailed chemical kinetic models for these fuels since the models can be put into engine simulation codes used for optimizing engine design for maximum efficiency and minimal pollutant emissions. For example, these chemistry-enabled engine codes can be used to optimize combustion chamber shape and fuel injection timing. They also allow insight into how the composition of advanced petroleum-based and non-petroleum based fuels affect engine performance characteristics. Additionally, chemical kinetic models can be used separately to interpret important in-cylinder experimental data and gain insight into advanced engine combustion processes such as HCCI and lean burn engines. The objectives are: (1) Develop detailed chemical kinetic reaction models for components of advanced petroleum-based and non-petroleum based fuels. These fuels models include components from vegetable-oil-derived biodiesel, oil-sand derived fuel, alcohol fuels and other advanced bio-based and alternative fuels. (2) Develop detailed chemical kinetic reaction models for mixtures of non-petroleum and petroleum-based components to represent real fuels and lead to efficient reduced combustion models needed for engine modeling codes. (3) Characterize the role of fuel composition on efficiency and pollutant emissions from practical automotive engines.

  9. Seasonal fluxes and temperature-dependent accumulation of persistent organic pollutants in lakes: The role of internal biogeochemical cycling

    International Nuclear Information System (INIS)

    A dynamic flux model for lakes taking into account the interactions between atmospheric depositional and biogeochemical processes (BIODEP model) was used to assess the importance of internal cycling and biogeochemical processes with respect to accumulation of four different polychlorinated biphenyls (PCBs) (congeners 28, 52, 101 and 153) in Lake Redo, a high-altitude lake in the Spanish Pyrenees. To investigate the effect of temperature on sediment accumulation, the model was run at different temperatures and corresponding sediment inventories were plotted vs. reciprocal temperature. In line with measurements from a previous study looking at sediment inventories of 19 European high-altitude lakes (MOLAR study), we found a stronger temperature dependence of lake sediment concentrations for the less volatile/less soluble PCBs. Seasonal and annual mass balances were investigated and highlighted the importance of internal lake processes controlling the differences in sediment accumulation for the different PCB congeners. For example, the higher temperature dependence of sediment inventories for the high chlorinated congeners is due to the fast dynamics of water-to-sediment transport in comparison to atmospheric deposition processes. - A dynamic flux model was used to assess the importance of internal lake processes in controlling sediment accumulation for different PCB congeners.

  10. Inter-annual variability of the atmospheric carbon dioxide concentrations as simulated with global terrestrial biosphere models and an atmospheric transport model

    International Nuclear Information System (INIS)

    Seasonal and inter-annual variations of atmospheric CO2 for the period from 1961 to 1997 have been simulated using a global tracer transport model driven by a new version of the Biome BioGeochemical Cycle model (Biome-BGC). Biome-BGC was forced by daily temperature and precipitation from the NCEP reanalysis dataset, and the calculated monthly-averaged CO2 fluxes were used as input to the global transport model. Results from an inter-comparison with the Carnegie-Ames-Stanford Approach model (CASA) and the Simulation model of Carbon CYCLE in Land Ecosystems (Sim-CYCLE) model are also reported. The phase of the seasonal cycle in the Northern Hemisphere was reproduced generally well by Biome-BGC, although the amplitude was smaller compared to the observations and to the other biosphere models. The CO2 time series simulated by Biome-BGC were compared to the global CO2 concentration anomalies from the observations at Mauna Loa and the South Pole. The modeled concentration anomalies matched the phase of the inter-annual variations in the atmospheric CO2 observations; however, the modeled amplitude was lower than the observed value in several cases. The result suggests that a significant part of the inter-annual variability in the global carbon cycle can be accounted for by the terrestrial biosphere models. Simulations performed with another climate-based model, Sim-CYCLE, produced a larger amplitude of inter-annual variability in atmospheric CO2, making the amplitude closer to the observed range, but with a more visible phase mismatch in a number of time periods. This may indicate the need to increase the Biome-BGC model sensitivity to seasonal and inter-annual changes in temperature and precipitation

  11. Transportation Sector Model of the National Energy Modeling System. Volume 2 -- Appendices: Part 1

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-01-01

    This volume contains input data and parameters used in the model of the transportation sector of the National Energy Modeling System. The list of Transportation Sector Model variables includes parameters for the following: Light duty vehicle modules (fuel economy, regional sales, alternative fuel vehicles); Light duty vehicle stock modules; Light duty vehicle fleet module; Air travel module (demand model and fleet efficiency model); Freight transport module; Miscellaneous energy demand module; and Transportation emissions module. Also included in these appendices are: Light duty vehicle market classes; Maximum light duty vehicle market penetration parameters; Aircraft fleet efficiency model adjustment factors; and List of expected aircraft technology improvements.

  12. Transport modeling and advanced computer techniques

    International Nuclear Information System (INIS)

    A workshop was held at the University of Texas in June 1988 to consider the current state of transport codes and whether improved user interfaces would make the codes more usable and accessible to the fusion community. Also considered was the possibility that a software standard could be devised to ease the exchange of routines between groups. It was noted that two of the major obstacles to exchanging routines now are the variety of geometrical representation and choices of units. While the workshop formulated no standards, it was generally agreed that good software engineering would aid in the exchange of routines, and that a continued exchange of ideas between groups would be worthwhile. It seems that before we begin to discuss software standards we should review the current state of computer technology --- both hardware and software to see what influence recent advances might have on our software goals. This is done in this paper

  13. Fast algorithms for transport models. Final report

    International Nuclear Information System (INIS)

    This project has developed a multigrid in space algorithm for the solution of the SN equations with isotropic scattering in slab geometry. The algorithm was developed for the Modified Linear Discontinuous (MLD) discretization in space which is accurate in the thick diffusion limit. It uses a red/black two-cell μ-line relaxation. This relaxation solves for all angles on two adjacent spatial cells simultaneously. It takes advantage of the rank-one property of the coupling between angles and can perform this inversion in O(N) operations. A version of the multigrid in space algorithm was programmed on the Thinking Machines Inc. CM-200 located at LANL. It was discovered that on the CM-200 a block Jacobi type iteration was more efficient than the block red/black iteration. Given sufficient processors all two-cell block inversions can be carried out simultaneously with a small number of parallel steps. The bottleneck is the need for sums of N values, where N is the number of discrete angles, each from a different processor. These are carried out by machine intrinsic functions and are well optimized. The overall algorithm has computational complexity O(log(M)), where M is the number of spatial cells. The algorithm is very efficient and represents the state-of-the-art for isotropic problems in slab geometry. For anisotropic scattering in slab geometry, a multilevel in angle algorithm was developed. A parallel version of the multilevel in angle algorithm has also been developed. Upon first glance, the shifted transport sweep has limited parallelism. Once the right-hand-side has been computed, the sweep is completely parallel in angle, becoming N uncoupled initial value ODE's. The author has developed a cyclic reduction algorithm that renders it parallel with complexity O(log(M)). The multilevel in angle algorithm visits log(N) levels, where shifted transport sweeps are performed. The overall complexity is O(log(N)log(M))

  14. Mathematical Model of Ion Transport in Electrodialysis Process

    Directory of Open Access Journals (Sweden)

    F.S. Rohman

    2010-10-01

    Full Text Available Mathematical models of ion transport in electrodialysis process is reviewed and their basics concept is discussed. Three scales of ion transport reviewed are: 1 ion transport in the membrane, where two approaches are used, the irreversible thermodynamics and modeling of the membrane material; 2 ion transport in a three-layer system composed of a membrane with two adjoining diffusion layers; and 3 coupling with hydraulic flow system in an electrodialysis 2D and 3D cell, where the differential equation of convectivediffusion is used. Most of the work carried out in the past implemented NP equations since relatively easily coupled with other equations describing hydrodynamic conditions and ion transport in the surrounding solutions, chemical reactions in the solutions and the membrane, boundary and other conditions. However, it is limited to point ionic transport in homogenous and uniformly - grainy phases of structure. © 2008 BCREC UNDIP. All rights reserved.[Received: 21 January 2008, Accepted: 10 March 2008][How to Cite: F.S. Rohman, N. Aziz (2008. Mathematical Model of Ion Transport in Electrodialysis Process. Bulletin of Chemical Reaction Engineering and Catalysis, 3(1-3: 3-8. doi:10.9767/bcrec.3.1-3.7122.3-8][How to Link/DOI: http://dx.doi.org/10.9767/bcrec.3.1-3.7122.3-8 || or local: http://ejournal.undip.ac.id/index.php/bcrec/article/view/7122 ] 

  15. Modelling Domestic Air Transport Demand and Evaluating under Scenarios

    Directory of Open Access Journals (Sweden)

    Cenk Ozan

    2014-09-01

    Full Text Available The lack of balance and integration between transportation modes in Turkey is one of the main problems. In this study, domestic air transport demand is modeled and evaluated under scenarios. For this purpose, indexing method which is able to indicate observed monthly and seasonal variations in demand is used. Proposals are suggested in order to overcome the lack of balance between transportation modes. In modeling, purchasing power parity and jet fuel prices as independent variables are used. Results showed that the developed model using indexing method is substantially sensitive to observed monthly and seasonal variations in domestic air transport demand. Furthermore, in the event that there are optimistic an increase in the income level and a crawl in the jet fuel prices, domestic air transport can rival with railways for second place in the transportation modes behind highways. For this reason, it is considered regulation on wages policy and tax of jet fuel prices necessary to support development of domestic air transport demand.

  16. UNCERTAINTY SUPPLY CHAIN MODEL AND TRANSPORT IN ITS DEPLOYMENTS

    Directory of Open Access Journals (Sweden)

    Fabiana Lucena Oliveira

    2014-05-01

    Full Text Available This article discusses the Model Uncertainty of Supply Chain, and proposes a matrix with their transportation modes best suited to their chains. From the detailed analysis of the matrix of uncertainty, it is suggested transportation modes best suited to the management of these chains, so that transport is the most appropriate optimization of the gains previously proposed by the original model, particularly when supply chains are distant from suppliers of raw materials and / or supplies.Here we analyze in detail Agile Supply Chains, which is a result of Uncertainty Supply Chain Model, with special attention to Manaus Industrial Center. This research was done at Manaus Industrial Pole, which is a model of industrial agglomerations, based in Manaus, State of Amazonas (Brazil, which contemplates different supply chains and strategies sharing same infrastructure of transport, handling and storage and clearance process and uses inbound for suppliers of raw material.  The state of art contemplates supply chain management, uncertainty supply chain model, agile supply chains, Manaus Industrial Center (MIC and Brazilian legislation, as a business case, and presents concepts and features, of each one. The main goal is to present and discuss how transport is able to support Uncertainty Supply Chain Model, in order to complete management model. The results obtained confirms the hypothesis of integrated logistics processes are able to guarantee attractivity for industrial agglomerations, and open discussions when the suppliers are far from the manufacturer center, in a logistics management.

  17. Multi-fluid plasma modeling with Braginskii collisional transport processes

    Science.gov (United States)

    Ho, A.; Shumlak, U.; Miller, S. T.

    2015-11-01

    Magnetohydrodynamics (MHD) works well where transport processes are primarily advective. Extensions of the MHD model are capable of capturing some collisional phenomena such as electrical resistivity, which are important in systems with mean free paths less than the characteristic length. However, MHD models have difficulties resolving systems where the Debye length cannot be assumed to approach zero. These systems arise in low density, hot plasmas. By modeling the ions and electrons as distinct fluids, the 5-moment multi-fluid plasma model is able to capture these short-range transport processes that are not accounted for in MHD. To model the transport processes the Braginskii transport terms are added to the 5-moment model, which introduces viscosity, heat conduction, and binary species interactions. These transport properties are affected by strong magnetic fields, resulting in anisotropic collisional effects. The multi-fluid equations are evolved explicitly and are coupled with Maxwell's equations. This research extends the University of Washington's WARPXM code to include the Braginskii terms with the 5-moment multi-fluid plasma model. The implementation is validated against theoretical results from a Hartmann flow benchmark problem. This work is supported by a grant from the United States Air Force Office of Scientific Research.

  18. Neutron Transport Models and Methods for HZETRN and Coupling to Low Energy Light Ion Transport

    Science.gov (United States)

    Blattnig, S.R.; Slaba, T.C.; Heinbockel, J.H.

    2008-01-01

    Exposure estimates inside space vehicles, surface habitats, and high altitude aircraft exposed to space radiation are highly influenced by secondary neutron production. The deterministic transport code HZETRN has been identified as a reliable and efficient tool for such studies, but improvements to the underlying transport models and numerical methods are still necessary. In this paper, the forward-backward (FB) and directionally coupled forward-backward (DC) neutron transport models are derived, numerical methods for the FB model are reviewed, and a computationally efficient numerical solution is presented for the DC model. Both models are compared to the Monte Carlo codes HETCHEDS and FLUKA, and the DC model is shown to agree closely with the Monte Carlo results. Finally, it is found in the development of either model that the decoupling of low energy neutrons from the light ion (A<4) transport procedure adversely affects low energy light ion fluence spectra and exposure quantities. A first order correction is presented to resolve the problem, and it is shown to be both accurate and efficient.

  19. Factors driving the biogeochemical budget of the Amazon River and its statistical modelling Facteurs denext term contrôle du bilan biogéochimique previous termdenext term l'Amazone et modélisation statistique associée

    OpenAIRE

    Bustillo, Vincent; Victoria, Reynaldo Luiz; Sousa De Moura, Jose Mauro; De Castro Victoria, Daniel; Toledo, Andrade; Collicchio, Erich

    2011-01-01

    The seasonal and interannual fluctuations of the biogeochemical budget (solutes, suspended matter, isotopes) of the Amazon River basin were analyzed, with a special focus on 44 physicochemical parameters monitored over the period 1982-1984 during the Carbon in the AMazon River Experiment (CAMREX) project. The relevant factors driving this variability were identified and sorted through the implementation of a statistical-regressive model coupled to variance analysis. Basically, the composition...

  20. Using Coupled Models to Study the Effects of River Discharge on Biogeochemical Cycling and Hypoxia in the Northern Gulf of Mexico

    Science.gov (United States)

    Penta, Bradley; Ko, D.; Gould, Richard W.; Arnone, Robert A.; Greene, R.; Lehrter, J.; Hagy, James; Schaeffer, B.; Murrell, M.; Kurtz, J.; Herchenroder, B.; Green, R.; Eldridge, P.

    2009-01-01

    We describe emerging capabilities to understand physical processes and biogeoehemical cycles in coastal waters through the use of satellites, numerical models, and ship observations. Emerging capabilities provide significantly improved ability to model ecological systems and the impact of environmental management actions on them. The complex interaction of physical and biogeoehemical processes responsible for hypoxic events requires an integrated approach to research, monitoring, and modeling in order to fully define the processes leading to hypoxia. Our efforts characterizes the carbon cycle associated with river plumes and the export of organic matter and nutrients form coastal Louisiana wetlands and embayments in a spatially and temporally intensive manner previously not possible. Riverine nutrients clearly affect ecosystems in the northern Gulf of Mexico as evidenced in the occurrence of regional hypoxia events. Less known and largely unqualified is the export of organic matter and nutrients from the large areas of disappearing coastal wetlands and large embayments adjacent to the Louisiana Continental Shelf. This project provides new methods to track the river plume along the shelf and to estimate the rate of export of suspended inorganic and organic paniculate matter and dissolved organic matter form coastal habitats of south Louisiana.

  1. Dynamic Modeling of the Electric Transportation Network

    CERN Document Server

    Scir`e, A; Eguiluz, V M; Scir\\`{e}, Alessandro; Tuval, Id\\'an

    2005-01-01

    We introduce a model for the dynamic self-organization of the electric grid. The model is characterized by a conserved magnitude, energy, that can travel following the links of the network to satisfy nodes' load. The load fluctuates in time causing local overloads that drive the dynamic evolution of the network topology. Our model displays a transition from a fully connected network to a configuration with a non-trivial topology and where global failures are suppressed. The most efficient topology is characterized by an exponential degree distribution, in agreement with the topology of the real electric grid. The model intrinsically presents self-induced break-down events, which can be thought as representative of real black-outs.

  2. Models of transport processes in concrete

    International Nuclear Information System (INIS)

    An approach being considered by the US Nuclear Regulatory Commission for disposal of low-level radioactive waste is to place the waste forms in concrete vaults buried underground. The vaults would need a service life of 500 years. Approaches for predicting the service life of concrete of such vaults include the use of mathematical models. Mathematical models are presented in this report for the major degradation processes anticipated for the concrete vaults, which are corrosion of steel reinforcement, sulfate attack, acid attack, and leaching. The models mathematically represent rate controlling processes including diffusion, convection, and reaction and sorption of chemical species. These models can form the basis for predicting the life of concrete under in-service conditions. 33 refs., 6 figs., 7 tabs

  3. Benchmarking of a Markov multizone model of contaminant transport.

    Science.gov (United States)

    Jones, Rachael M; Nicas, Mark

    2014-10-01

    A Markov chain model previously applied to the simulation of advection and diffusion process of gaseous contaminants is extended to three-dimensional transport of particulates in indoor environments. The model framework and assumptions are described. The performance of the Markov model is benchmarked against simple conventional models of contaminant transport. The Markov model is able to replicate elutriation predictions of particle deposition with distance from a point source, and the stirred settling of respirable particles. Comparisons with turbulent eddy diffusion models indicate that the Markov model exhibits numerical diffusion in the first seconds after release, but over time accurately predicts mean lateral dispersion. The Markov model exhibits some instability with grid length aspect when turbulence is incorporated by way of the turbulent diffusion coefficient, and advection is present. However, the magnitude of prediction error may be tolerable for some applications and can be avoided by incorporating turbulence by way of fluctuating velocity (e.g. turbulence intensity). PMID:25143517

  4. Aeolian Sediment Transport Integration in General Stratigraphic Forward Modeling

    Directory of Open Access Journals (Sweden)

    T. Salles

    2011-01-01

    Full Text Available A large number of numerical models have been developed to simulate the physical processes involved in saltation, and, recently to investigate the interaction between soil vegetation cover and aeolian transport. These models are generally constrained to saltation of monodisperse particles while natural saltation occurs over mixed soils. We present a three-dimensional numerical model of steady-state saltation that can simulate aeolian erosion, transport and deposition for unvegetated mixed soils. Our model simulates the motion of saltating particles using a cellular automata algorithm. A simple set of rules is used and takes into account an erosion formula, a transport model, a wind exposition function, and an avalanching process. The model is coupled to the stratigraphic forward model Sedsim that accounts for a larger number of geological processes. The numerical model predicts a wide range of typical dune shapes, which have qualitative correspondence to real systems. The model reproduces the internal structure and composition of the resulting aeolian deposits. It shows the complex formation of dune systems with cross-bedding strata development, bounding surfaces overlaid by fine sediment and inverse grading deposits. We aim to use it to simulate the complex interactions between different sediment transport processes and their resulting geological morphologies.

  5. Assessment of the sea-ice carbon pump: Insights from a three-dimensional ocean-sea-ice biogeochemical model (NEMO-LIM-PISCES

    Directory of Open Access Journals (Sweden)

    Sébastien Moreau

    2016-08-01

    Full Text Available Abstract The role of sea ice in the carbon cycle is minimally represented in current Earth System Models (ESMs. Among potentially important flaws, mentioned by several authors and generally overlooked during ESM design, is the link between sea-ice growth and melt and oceanic dissolved inorganic carbon (DIC and total alkalinity (TA. Here we investigate whether this link is indeed an important feature of the marine carbon cycle misrepresented in ESMs. We use an ocean general circulation model (NEMO-LIM-PISCES with sea-ice and marine carbon cycle components, forced by atmospheric reanalyses, adding a first-order representation of DIC and TA storage and release in/from sea ice. Our results suggest that DIC rejection during sea-ice growth releases several hundred Tg C yr−1 to the surface ocean, of which < 2% is exported to depth, leading to a notable but weak redistribution of DIC towards deep polar basins. Active carbon processes (mainly CaCO3 precipitation but also ice-atmosphere CO2 fluxes and net community production increasing the TA/DIC ratio in sea-ice modified ocean-atmosphere CO2 fluxes by a few Tg C yr−1 in the sea-ice zone, with specific hemispheric effects: DIC content of the Arctic basin decreased but DIC content of the Southern Ocean increased. For the global ocean, DIC content increased by 4 Tg C yr−1 or 2 Pg C after 500 years of model run. The simulated numbers are generally small compared to the present-day global ocean annual CO2 sink (2.6 ± 0.5 Pg C yr−1. However, sea-ice carbon processes seem important at regional scales as they act significantly on DIC redistribution within and outside polar basins. The efficiency of carbon export to depth depends on the representation of surface-subsurface exchanges and their relationship with sea ice, and could differ substantially if a higher resolution or different ocean model were used.

  6. Modeling passenger flows in public transport stations

    Directory of Open Access Journals (Sweden)

    Cem Kırlangıçoğlu

    2015-06-01

    Full Text Available There are many architectural design parameters for public transport stations which include urban and station level studies. Each station must be designed in accordance with the basic passenger requirements such as accessibility, safety, comfort, satisfaction and etc. Circulation spaces must be formed and sized to meet the minimum movement needs of passengers. For an underground station; main entrance region, position of gates, location and number of turnstiles, escalators, stairs, ramps, passageways, intermediate concourses and platforms must be arranged to minimize walking distances and to prevent congestion. In this study, circulation of passengers is simulated in a quantitatively verifiable manner, taking into account how individuals interact with each other and with the physical obstacles in their environment in a metro station. Virtual experiments are performed to see the continuity and density of pedestrian flow at different levels of Haram Area East Metro Station of the first metro line of Madinah Al-Munawwarah, Saudi Arabia. According to the predictions, more than 40.000 passengers are expected to use this station in one hour after a Friday prayer during Ramadan period in the year of 2040. That means a critically high travel demand and it is really significant to design the most convenient underground station for these passengers to fulfil the necessary requirements.

  7. Development of interfacial area transport equation - modeling and experimental benchmark

    International Nuclear Information System (INIS)

    A dynamic treatment of interfacial area concentration has been studied over the last decade by employing the interfacial area transport equation. When coupled with the two-fluid model, the interfacial area transport equation replaces the flow regime dependent correlations for interfacial area concentration and eliminates potential artificial bifurcation or numerical oscillations stemming from these static correlations. An extensive database has been established to evaluate the model under various two-phase flow conditions. These include adiabatic and heated conditions, vertical and horizontal flow orientations, round, rectangular, annulus and 8×8 rod bundle channel geometries, and normal-gravity and simulated reduced-gravity conditions. This paper reviews the current state-of-the-art in the development of the interfacial area transport equation, available experimental databases and 1D and 3D benchmarking work of the interfacial area transport equation. (author)

  8. Model prodrugs for the intestinal oligopeptide transporter

    DEFF Research Database (Denmark)

    Nielsen, C U; Andersen, R; Brodin, Birger;

    2001-01-01

    benzyl alcohol have been shown to have affinity for hPepT1. Furthermore, in aqueous solution at pH 5.5 to 10, the release of the model drug seems to be controlled by a specific base-catalyzed hydrolysis, indicating that the compounds may remain relatively stable in the upper small intestinal lumen with a...... physico-chemical properties such as electronegativity, solubility, and log P of the drug molecule may also have an influence on the potential of these kinds of prodrugs. The purpose of the present study is to investigate whether the model drug electronegativity, estimated as Taft substitution parameter...... (sigma*) may influence the acid, water or base catalyzed model drug release rates, when released from series of D-Glu-Ala and D-Asp-Ala pro-moieties. Release rates were investigated in both aqueous solutions with varying pH, ionic strength, and buffer concentrations as well as in in vitro biological...

  9. Transport modeling of sorbing tracers in artificial fractures

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-02-01

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

  10. UTEX modeling of radioxenon isotopic fractionation resulting from subsurface transport

    International Nuclear Information System (INIS)

    The underground transport of environmental xenon (UTEX) model is a finite-difference code that was developed at the University of Texas at Austin to simulate the transport of radioxenon from an underground nuclear detonation to the surface. UTEX handles a time dependent source term and includes the effects of radioactive decay to determine isotopic signatures of the various radioxenon species as a function of release time. The model shows that significant perturbations in the isotopic signatures are possible under some geologic conditions. Transport of radioxenon gas in UTEX is driven in large part by atmospheric pumping. A study was undertaken to characterize the dependence of resulting isotopic signatures on the various geologic and physical parameters that define the system model. Additionally, the model was used to roughly simulate isotopic measurements at various depths and position; the potential dependence of isotopic radioxenon fractionation on sampling depth and lateral position between fractures was examined. (author)

  11. Unsaturated zone transport modeling of the Greater Confinement Disposal Site

    International Nuclear Information System (INIS)

    Unsaturated zone transport modeling is being conducted as part of the performance assessment of the Greater Confinement Disposal (GCD) facility which is located on the Nevada Test Site. This performance assessment is based on an iterative process of modeling and data collection to assess the likelihood the site will meet the US Environmental Protection Agency's containment, individual protection and groundwater protection requirements for the disposal of transuranic wastes, high-level wastes and spent fuel. The current iteration of the performance assessment evaluates the potential impact of future events on the transport system. The future events included in this analysis are subsidence, bioturbation, erosion, climate change, irrigated farming and drilling. This paper presents the unsaturated transport model, how it fits into the performance assessment and how the future events are incorporated in the model

  12. Water Transport Models of Moisture Absorption and Sweat Discharge Yarns

    Institute of Scientific and Technical Information of China (English)

    WANG Fa-ming; ZHOU Xiao-hong; WANG Shan-yuan

    2008-01-01

    An important property of moisture absorption and sweat discharge yams is their water transport property. In the paper, two water transport models of moisture absorption and sweat discharge yams were developed to investigate the influence factors on their wicking rate. In parallel Column Pores Model, wicking rate is determined by the equivalent capillary radius R and length of the capillary tube L. In Pellets Accumulation Model, wicking rate is decided by the capillary radius r and length of the fiber unit assemble L0.

  13. Evaluation of cloud convection and tracer transport in a three-dimensional chemical transport model

    Directory of Open Access Journals (Sweden)

    W. Feng

    2011-06-01

    Full Text Available We investigate the performance of cloud convection and tracer transport in a global off-line 3-D chemical transport model. Various model simulations are performed using different meteorological (reanalyses (ERA-40, ECMWF operational and ECMWF Interim to diagnose the updraft mass flux, convective precipitation and cloud top height.

    The diagnosed upward mass flux distribution from TOMCAT agrees quite well with the ECMWF reanalysis data (ERA-40 and ERA-Interim below 200 hPa. Inclusion of midlevel convection improves the agreement at mid-high latitudes. However, the reanalyses show strong convective transport up to 100 hPa, well into the tropical tropopause layer (TTL, which is not captured by TOMCAT. Similarly, the model captures the spatial and seasonal variation of convective cloud top height although the mean modelled value is about 2 km lower than observed.

    The ERA-Interim reanalyses have smaller archived upward convective mass fluxes than ERA-40, and smaller convective precipitation, which is in better agreement with satellite-based data. TOMCAT captures these relative differences when diagnosing convection from the large-scale fields. The model also shows differences in diagnosed convection with the version of the operational analyses used, which cautions against using results of the model from one specific time period as a general evaluation.

    We have tested the effect of resolution on the diagnosed modelled convection with simulations ranging from 5.6° × 5.6° to 1° × 1°. Overall, in the off-line model, the higher model resolution gives stronger vertical tracer transport, however, it does not make a large change to the diagnosed convective updraft mass flux (i.e., the model results using the convection scheme fail to capture the strong convection transport up to 100 hPa as seen in the archived convective mass fluxes. Similarly, the resolution of the forcing winds in the higher resolution CTM does not make a

  14. Modeling of water and pesticide transport in andisols

    Czech Academy of Sciences Publication Activity Database

    Pavelková, Helena; Dušek, J.; Vogel, T.

    Bratislava : Slovenská akadémia vied, 2005, s. 423-431. ISBN 80-85754-13-4. [XIII. posterový deň s medzinárodnou účasťou "Transport vody, chemikálií a enrgie v systéme poda-rastlina-atmosféra". Bratislava (SK), 10.11.2005] Keywords : pesticide transport * and isols * modeling Subject RIV: DA - Hydrology ; Limnology

  15. Parallel Processing for Modeling Reactive Transport in Groundwater

    OpenAIRE

    Wright, Jennifer

    2006-01-01

    Natural attenuation and biotransformation are processes that can potentially control the transport and enhance the remediation of contaminants in groundwater. It is necessary to develop computer simulations that not only model the physical transport (advection and dispersion) of contaminants, but that can also accurately depict chemical reactions and some of these more complex processes, in order to determine the type and extent of contaminant plumes and to analyze potential remediation stra...

  16. Dynamic Traffic Models in Transportation Science (Dagstuhl Seminar 15412)

    OpenAIRE

    Correa, José R; Harks, Tobias; Nagel, Kai; Peis, Britta; Skutella, Martin

    2016-01-01

    Traffic assignment models are crucial for traffic planners to be able to predict traffic distributions, especially, in light of possible changes of the infrastructure, e.g., road constructions, traffic light controls, etc. The starting point of the seminar was the observation that there is a trend in the transportation community (science as well as industry) to base such predictions on complex computer-based simulations that are capable of resolving many elements of a real transportation syst...

  17. A model for radionuclide transport in the Cooling Water System

    International Nuclear Information System (INIS)

    A radionuclide transport model developed to assess radiological levels in the K-reactor Cooling Water System (CWS) in the event of an inadvertent process water (PW) leakage to the cooling water (CW) in the heat exchangers (HX) is described. During and following a process water leak, the radionuclide transport model determines the time-dependent release rates of radionuclide from the cooling water system to the environment via evaporation to the atmosphere and blow-down to the Savannah River. The developed model allows for delay times associated with the transport of the cooling water radioactivity through cooling water system components. Additionally, this model simulates the time-dependent behavior of radionuclides levels in various CWS components. The developed model is incorporated into the K-reactor Cooling Tower Activity (KCTA) code. KCTA allows the accident (heat exchanger leak rate) and the cooling tower blow-down and evaporation rates to be described as time-dependent functions. Thus, the postulated leak and the consequence of the assumed leak can be modelled realistically. This model is the first of three models to be ultimately assembled to form a comprehensive Liquid Pathway Activity System (LPAS). LPAS will offer integrated formation, transport, deposition, and release estimates for radionuclides formed in a SRS facility. Process water and river water modules are forthcoming as input and downstream components, respectively, for KCTA

  18. Validation of 1-D transport and sawtooth models for ITER

    International Nuclear Information System (INIS)

    In this paper the authors describe progress on validating a number of local transport models by comparing their predictions with relevant experimental data from a range of tokamaks in the ITER profile database. This database, the testing procedure and results are discussed. In addition a model for sawtooth oscillations is used to investigate their effect in an ITER plasma with alpha-particles

  19. A transport model for prediction of wildfire behavior

    Energy Technology Data Exchange (ETDEWEB)

    Linn, R.R.

    1997-07-01

    Wildfires are a threat to human life and property, yet they are an unavoidable part of nature. In the past people have tried to predict wildfire behavior through the use of point functional models but have been unsuccessful at adequately predicting the gross behavior of the broad spectrum of fires that occur in nature. The majority of previous models do not have self-determining propagation rates. The author uses a transport approach to represent this complicated problem and produce a model that utilizes a self-determining propagation rate. The transport approach allows one to represent a large number of environments including transition regions such as those with nonhomogeneous vegetation and terrain. Some of the most difficult features to treat are the imperfectly known boundary conditions and the fine scale structure that is unresolvable, such as the specific location of the fuel or the precise incoming winds. The author accounts for the microscopic details of a fire with macroscopic resolution by dividing quantities into mean and fluctuating parts similar to what is done in traditional turbulence modelling. The author develops a complicated model that includes the transport of multiple gas species, such as oxygen and volatile hydrocarbons, and tracks the depletion of various fuels and other stationary solids and liquids. From this model the author also forms a simplified local burning model with which he performs a number of simulations for the purpose of demonstrating the properties of a self-determining transport-based wildfire model.

  20. Unsaturated moisture and radionuclide transport: laboratory analysis and modeling

    International Nuclear Information System (INIS)

    This report describes several laboratory procedures and computer model simulations used to evaluate the transport of water and radionuclides through unsaturated Hanford soils. The unsaturated hydraulic conductivity was measured using the steady state methods of Klute and the transient state method of Rose. These experimental data were compared to other conductivity models. Good agreement was found between all methods in the wet range; however, disagreement was found in the dry range. None of the conductivity models explicity addresses the water vapor component of the conductivity. This may explain the under prediction of the hydraulic conductivity in the dry range where vapor transport is important. Radionuclide transport through unsaturated media was investigated by using two solute transport models to describe the transport of tritium and strontium-85 in laboratory columns. A two parameter convective-dispersive model was compared with a four parameter mobile-immobile water model. Both models adequately described the movement of tritium and strontium through small (5 cm x 27.5 cm) columns and the movement of tritium and strontium through a large (0.5 m x 1.7) column. The dispersion coefficient was found to be sensitive to changes in both velocity and column length. The mobile-immoble water equations were not as sensitive to changes in experimental scales as the convective-dispersive equation. Both models were relatively successful in describing the rapid flush of strontium-85 from a column initially leached with a low salt solution followed by a high salt solution, a phenomona called the snow plow effect. The four parameter mobile-immobile water model predicted the initial release of the strontium more accurately than the two parameter convective-dispersive model. Both models confirm enhanced mobility of strontium-85 with leaching solutions of increased salt concentration

  1. Second-order modeling of arsenite transport in soils

    Science.gov (United States)

    Zhang, Hua; Magdi Selim, H.

    2011-11-01

    Rate limited processes including kinetic adsorption-desorption can greatly impact the fate and behavior of toxic arsenic compounds in heterogeneous soils. In this study, miscible displacement column experiments were carried out to investigate the extent of reactivity during transport of arsenite in soils. Arsenite breakthrough curves (BTCs) of Olivier and Windsor soils exhibited strong retardation with diffusive effluent fronts followed by slow release or tailing during leaching. Such behavior is indicative of the dominance of kinetic retention reactions for arsenite transport in the soil columns. Sharp decrease or increase in arsenite concentration in response to flow interruptions (stop-flow) further verified that non-equilibrium conditions are dominant. After some 40-60 pore volumes of continued leaching, 30-70% of the applied arsenite was retained by the soil in the columns. Furthermore, continued arsenite slow release for months was evident by the high levels of residual arsenite concentrations observed during leaching. In contrast, arsenite transport in a reference sand material exhibited no retention where complete mass recovery in the effluent solution was attained. A second-order model (SOM) which accounts for equilibrium, reversible, and irreversible retention mechanisms was utilized to describe arsenite transport results from the soil columns. Based on inverse and predictive modeling results, the SOM model successfully depicted arsenite BTCs from several soil columns. Based on inverse and predictive modeling results, a second-order model which accounts for kinetic reversible and irreversible reactions is recommended for describing arsenite transport in soils.

  2. Contaminant transport modeling studies of Russian sites

    International Nuclear Information System (INIS)

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

  3. Modeling of transport in the two-dimensional atmospheric transport and kinetics codes SPHERNEW and TRACER

    Energy Technology Data Exchange (ETDEWEB)

    Edwards, A.

    1976-07-23

    The report describes how transport by the wind is modeled in the 2-D atmospheric transport and chemical kinetics codes SPHERNEW and TRACER. The description includes the equations for transport by a specified velocity field, the eddy diffusion approximation for short-term fluctuations in the velocity, other simplifying approximations, the geometric grid, the difference equations, and the coefficient matrix of the grid. The assumption of a constant vertical density distribution was used to derive mass-consistent forms of the difference equations. These forms eliminate the instabilities and unrealistic solutions associated with specified wind fields which are not exactly mass-consistent. An option is allowed for variable weighting between central (second-order) and upstream (first-order) forms of the spatial differencing of the advection terms, to modulate phase and amplitude errors in the advection model.

  4. Modeling spin magnetization transport in a spatially varying magnetic field

    Science.gov (United States)

    Picone, Rico A. R.; Garbini, Joseph L.; Sidles, John A.

    2015-01-01

    We present a framework for modeling the transport of any number of globally conserved quantities in any spatial configuration and apply it to obtain a model of magnetization transport for spin-systems that is valid in new regimes (including high-polarization). The framework allows an entropy function to define a model that explicitly respects the laws of thermodynamics. Three facets of the model are explored. First, it is expressed as nonlinear partial differential equations that are valid for the new regime of high dipole-energy and polarization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield (1975) [1]. Differences among the three forms of the model are illustrated by numerical solution with parameters corresponding to a magnetic resonance force microscopy (MRFM) experiment (Degen et al., 2009 [2]; Kuehn et al., 2008 [3]; Sidles et al., 2003 [4]; Dougherty et al., 2000 [5]). A family of analytic, steady-state solutions to the nonlinear equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. Finally, we analyze the separative quality of magnetization transport, and a steady-state solution for the magnetization is shown to be compatible with Fenske's separative mass transport equation (Fenske, 1932 [6]).

  5. Modeling tracer transport in randomly heterogeneous porous media by nonlocal moment equations: Anomalous transport

    Science.gov (United States)

    Morales-Casique, E.; Lezama-Campos, J. L.; Guadagnini, A.; Neuman, S. P.

    2013-05-01

    Modeling tracer transport in geologic porous media suffers from the corrupt characterization of the spatial distribution of hydrogeologic properties of the system and the incomplete knowledge of processes governing transport at multiple scales. Representations of transport dynamics based on a Fickian model of the kind considered in the advection-dispersion equation (ADE) fail to capture (a) the temporal variation associated with the rate of spreading of a tracer, and (b) the distribution of early and late arrival times which are often observed in field and/or laboratory scenarios and are considered as the signature of anomalous transport. Elsewhere we have presented exact stochastic moment equations to model tracer transport in randomly heterogeneous aquifers. We have also developed a closure scheme which enables one to provide numerical solutions of such moment equations at different orders of approximations. The resulting (ensemble) average and variance of concentration fields were found to display a good agreement against Monte Carlo - based simulation results for mildly heterogeneous (or well-conditioned strongly heterogeneous) media. Here we explore the ability of the moment equations approach to describe the distribution of early arrival times and late time tailing effects which can be observed in Monte-Carlo based breakthrough curves (BTCs) of the (ensemble) mean concentration. We show that BTCs of mean resident concentration calculated at a fixed space location through higher-order approximations of moment equations display long tailing features of the kind which is typically associated with anomalous transport behavior and are not represented by an ADE model with constant dispersive parameter, such as the zero-order approximation.

  6. A community firn densification and gas transport model

    Science.gov (United States)

    Stevens, C.; Lundin, J.; Harris, P.; Leahy, W.; Waddington, E. D.

    2012-12-01

    Gas bubbles trapped in ice preserve a record of Earth's climate history. Interpretation of ice-core records is complicated by the difference in age (called delta age) between the gas trapped in bubbles and the ice enclosing the gas. Determining delta age requires understanding both densification of polar firn and gas transport through the firn. Independent models of firn densification and firn gas transport have been developed in the past by individual research groups. We are developing a web-based model of firn densification and gas transport that combines the best features of those models and is freely accessible to research teams. Users input site-specific data, and the model provides depth-density-age and delta-age results. In addition to the web-based model, state-of-the-art transient firn-densification and gas-transport models are in development. These models allow physical properties to evolve, which results in more accurate delta-age approximations at times of rapid climate change in the past. These community models will be downloadable as open-source code. They will provide a baseline to make intercomparisons between datasets or other models. The models are modular, allowing users to choose preferred physical models and physical processes to include, based on available pre-coded options. Alternatively, users can adapt the code to include new or different physics. Here, we present results from the web-based model and early stages of the transient models and compare with known firn-density and gas-concentration profiles.

  7. Development and applications of reactive transport models in the framework of the reactive transport consortium (PGT)

    International Nuclear Information System (INIS)

    Full text of publication follows: Reactive transport models permit the simulation of hydrodynamic migration of reactive chemicals through different types of media. They have proven to be highly effective tools to better understand and predict the long-term evolution of geo-materials and the fate of hazardous substances in hydrodynamic systems via a wide variety of applications in different domains and at different scales. In an attempt to correctly represent a large number of simultaneously occurring processes, instances of these models tend to become increasingly complex. Accordingly, the efforts to develop, test and validate the model largely exceed the scope of a single laboratory and the timescale of a Ph.D. thesis. The Reactive Transport Consortium (PGT or 'Pole Geochimie-Transport') is a national research project with the objective of creating a long-term framework for the development of reactive transport models, reference studies and new application domains. Already operational for several years, the collaborative efforts within the PGT have allowed considerable progress to be made in the domain of reactive transport modelling, including generalized kinetics, reactive processes in unsaturated medium, complex boundary conditions, code parallelization and strong coupling between geochemistry, porosity and hydrodynamic parameters. The resulting code is applied to a wide variety of domains at different scales. This paper outlines the objectives, structure, operation mode and main results of the PGT. Model performance will be illustrated by simulations with a focus on subsystems of a radioactive waste repository, i.e. the waste glass, clay-concrete interface and excavation damaged zone (EDZ). (authors)

  8. GIS-Based Analytical Tools for Transport Planning: Spatial Regression Models for Transportation Demand Forecast

    Directory of Open Access Journals (Sweden)

    Simone Becker Lopes

    2014-04-01

    Full Text Available Considering the importance of spatial issues in transport planning, the main objective of this study was to analyze the results obtained from different approaches of spatial regression models. In the case of spatial autocorrelation, spatial dependence patterns should be incorporated in the models, since that dependence may affect the predictive power of these models. The results obtained with the spatial regression models were also compared with the results of a multiple linear regression model that is typically used in trips generation estimations. The findings support the hypothesis that the inclusion of spatial effects in regression models is important, since the best results were obtained with alternative models (spatial regression models or the ones with spatial variables included. This was observed in a case study carried out in the city of Porto Alegre, in the state of Rio Grande do Sul, Brazil, in the stages of specification and calibration of the models, with two distinct datasets.

  9. Physics models in the toroidal transport code PROCTR

    Energy Technology Data Exchange (ETDEWEB)

    Howe, H.C.

    1990-08-01

    The physics models that are contained in the toroidal transport code PROCTR are described in detail. Time- and space-dependent models are included for the plasma hydrogenic-ion, helium, and impurity densities, the electron and ion temperatures, the toroidal rotation velocity, and the toroidal current profile. Time- and depth-dependent models for the trapped and mobile hydrogenic particle concentrations in the wall and a time-dependent point model for the number of particles in the limiter are also included. Time-dependent models for neutral particle transport, neutral beam deposition and thermalization, fusion heating, impurity radiation, pellet injection, and the radial electric potential are included and recalculated periodically as the time-dependent models evolve. The plasma solution is obtained either in simple flux coordinates, where the radial shift of each elliptical, toroidal flux surface is included to maintain an approximate pressure equilibrium, or in general three-dimensional torsatron coordinates represented by series of helical harmonics. The detailed coupling of the plasma, scrape-off layer, limiter, and wall models through the neutral transport model makes PROCTR especially suited for modeling of recycling and particle control in toroidal plasmas. The model may also be used in a steady-state profile analysis mode for studying energy and particle balances starting with measured plasma profiles.

  10. Physics models in the toroidal transport code PROCTR

    International Nuclear Information System (INIS)

    The physics models that are contained in the toroidal transport code PROCTR are described in detail. Time- and space-dependent models are included for the plasma hydrogenic-ion, helium, and impurity densities, the electron and ion temperatures, the toroidal rotation velocity, and the toroidal current profile. Time- and depth-dependent models for the trapped and mobile hydrogenic particle concentrations in the wall and a time-dependent point model for the number of particles in the limiter are also included. Time-dependent models for neutral particle transport, neutral beam deposition and thermalization, fusion heating, impurity radiation, pellet injection, and the radial electric potential are included and recalculated periodically as the time-dependent models evolve. The plasma solution is obtained either in simple flux coordinates, where the radial shift of each elliptical, toroidal flux surface is included to maintain an approximate pressure equilibrium, or in general three-dimensional torsatron coordinates represented by series of helical harmonics. The detailed coupling of the plasma, scrape-off layer, limiter, and wall models through the neutral transport model makes PROCTR especially suited for modeling of recycling and particle control in toroidal plasmas. The model may also be used in a steady-state profile analysis mode for studying energy and particle balances starting with measured plasma profiles

  11. Model development for transport studies in negative shear modes

    International Nuclear Information System (INIS)

    This study develops a simple transport model which can be used predictively for tokamak negative central shear (NCS) modes, with the assistance of Lawrence Livermore National Laboratory's core plasma simulation code, CORSICA. The results show that the the Rebut-Lallia-Watkins Critical Electron Temperature Gradient Model, coupled with an NCS transport model and TRANSP data, renders a reasonably close match to experimental temperature profiles. Additionally, this research offers the first benchmark calculation indicating that the CORSICA code itself, when given transport coefficients from the analysis of experimental data, replicates the experimental profiles, indicating that both TRANSP and CORSICA together are consistent in their analysis of the plasma evolution. This means CORSICA is working properly and has no known major internal flaws. 14 refs., 12 figs

  12. Macroscopic Modeling of In Vivo Drug Transport in Electroporated Tissue.

    Science.gov (United States)

    Boyd, Bradley; Becker, Sid

    2016-03-01

    This study develops a macroscopic model of mass transport in electroporated biological tissue in order to predict the cellular drug uptake. The change in the macroscopic mass transport coefficient is related to the increase in electrical conductivity resulting from the applied electric field. Additionally, the model considers the influences of both irreversible electroporation (IRE) and the transient resealing of the cell membrane associated with reversible electroporation. Two case studies are conducted to illustrate the applicability of this model by comparing transport associated with two electrode arrangements: side-by-side arrangement and the clamp arrangement. The results show increased drug transmission to viable cells is possible using the clamp arrangement due to the more uniform electric field. PMID:26720199

  13. Catalog of selected heavy duty transport energy management models

    Science.gov (United States)

    Colello, R. G.; Boghani, A. B.; Gardella, N. C.; Gott, P. G.; Lee, W. D.; Pollak, E. C.; Teagan, W. P.; Thomas, R. G.; Snyder, C. M.; Wilson, R. P., Jr.

    1983-01-01

    A catalog of energy management models for heavy duty transport systems powered by diesel engines is presented. The catalog results from a literature survey, supplemented by telephone interviews and mailed questionnaires to discover the major computer models currently used in the transportation industry in the following categories: heavy duty transport systems, which consist of highway (vehicle simulation), marine (ship simulation), rail (locomotive simulation), and pipeline (pumping station simulation); and heavy duty diesel engines, which involve models that match the intake/exhaust system to the engine, fuel efficiency, emissions, combustion chamber shape, fuel injection system, heat transfer, intake/exhaust system, operating performance, and waste heat utilization devices, i.e., turbocharger, bottoming cycle.

  14. Detailed Radiative Transport Modeling of a Radiative Divertor

    CERN Document Server

    Wan, A S; Scott, H A; Post, D; Rognlien, T D

    1995-01-01

    An effective radiative divertor maximizes the utilization of atomic processes to spread out the energy deposition to the divertor chamber walls and to reduce the peak heat flux. Because the mixture of neutral atoms and ions in the divertor can be optically thick to a portion of radiated power, it is necessary to accurately model the magnitude and distribution of line radiation in this complex region. To assess their importance we calculate the effects of radiation transport using CRETIN, a multi-dimensional, non-local thermodynamic equilibrium simulation code that includes the atomic kinetics and radiative transport processes necessary to model the complex environment of a radiative divertor. We also include neutral transport to model radiation from recycling neutral atoms. This paper presents a case study of a high-recycling radiative divertor with a typical large neutral pressure at the divertor plate to estimate the impact of H line radiation on the overall power balance in the divertor region with conside...

  15. A self-organized criticality model for plasma transport

    International Nuclear Information System (INIS)

    Many models of natural phenomena manifest the basic hypothesis of self-organized criticality (SOC). The SOC concept brings together the self-similarity on space and time scales that is common to many of these phenomena. The application of the SOC modelling concept to the plasma dynamics near marginal stability opens new possibilities of understanding issues such as Bohm scaling, profile consistency, broad band fluctuation spectra with universal characteristics and fast time scales. A model realization of self-organized criticality for plasma transport in a magnetic confinement device is presented. The model is based on subcritical resistive pressure-gradient-driven turbulence. Three-dimensional nonlinear calculations based on this model show the existence of transport under subcritical conditions. This model that includes fluctuation dynamics leads to results very similar to the running sandpile paradigm

  16. Multiscale modeling for fluid transport in nanosystems.

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jonathan W.; Jones, Reese E.; Mandadapu, Kranthi Kiran; Templeton, Jeremy Alan; Zimmerman, Jonathan A.

    2013-09-01

    Atomistic-scale behavior drives performance in many micro- and nano-fluidic systems, such as mircrofludic mixers and electrical energy storage devices. Bringing this information into the traditionally continuum models used for engineering analysis has proved challenging. This work describes one such approach to address this issue by developing atomistic-to-continuum multi scale and multi physics methods to enable molecular dynamics (MD) representations of atoms to incorporated into continuum simulations. Coupling is achieved by imposing constraints based on fluxes of conserved quantities between the two regions described by one of these models. The impact of electric fields and surface charges are also critical, hence, methodologies to extend finite-element (FE) MD electric field solvers have been derived to account for these effects. Finally, the continuum description can have inconsistencies with the coarse-grained MD dynamics, so FE equations based on MD statistics were derived to facilitate the multi scale coupling. Examples are shown relevant to nanofluidic systems, such as pore flow, Couette flow, and electric double layer.

  17. Modelling intercontinental transport of atmospheric sulphur in the northern hemisphere

    OpenAIRE

    Tarrasón, L; Iversen, T.

    2011-01-01

    Intercontinental exchange of sulphur in major parts of the northern hemisphere has been studied with a 3-dimensional Eulerian transport model that resolves regional scale variability. Model results for 1988 have been evaluated against daily observations of sulphur dioxide and particulate sulphate in Europe and North America and show that the model reproduces the episodic character of oxidised sulphur in air. Yearly averages agree with the observations within a factor of 2, at over 75% of the ...

  18. Transport of nutrients from land to sea: Global modeling approaches and uncertainty analyses (Utrecht Studies in Earth Sciences 058)

    NARCIS (Netherlands)

    Beusen, A.H.W.

    2014-01-01

    This thesis presents four examples of global models developed as part of the Integrated Model to Assess the Global Environment (IMAGE). They describe different components of global biogeochemical cycles of the nutrients nitrogen (N), phosphorus (P) and silicon (Si), with a focus on approaches to ana

  19. Radon transport in fractured soil. Laboratory experiments and modelling

    International Nuclear Information System (INIS)

    Radon (Rn-222) transport in fractured soil has been investigated by laboratory experiments and by modelling. Radon transport experiments have been performed with two sand columns (homogeneous and inhomogeneous) and one undisturbed clayey till column containing a net of preferential flow paths (root holes). A numerical model (the finite-element model FRACTRAN) and an analytic model (a pinhole model) have been applied in simulations if soil gas and radon transport in fractured soil. Experiments and model calculations are included in a discussion of radon entry rates into houses placed on fractured soil. The main conclusion is, that fractures does not in general alter transport of internally generated radon out of soil, when the pressure and flow conditions in the soil is comparable to the conditions prevailing under a house. This indicates the important result, that fractures in soil have no impact on radon entry into a house beyond that of an increased gas permeability, but a more thorough investigation of this subject is needed. Only in the case where the soil is exposed to large pressure gradients, relative to gradients induced by a house, may it be possible to observe effects of radon exchange between fractures and matrix. (au) 52 tabs., 60 ill., 5 refs

  20. A transport model for computer simulation of wildfires

    Energy Technology Data Exchange (ETDEWEB)

    Linn, R. [Los Alamos National Lab., NM (United States)

    1997-12-31

    Realistic self-determining simulation of wildfires is a difficult task because of a large variety of important length scales (including scales on the size of twigs or grass and the size of large trees), imperfect data, complex fluid mechanics and heat transfer, and very complicated chemical reactions. The author uses a transport approach to produce a model that exhibits a self-determining propagation rate. The transport approach allows him to represent a large number of environments such as those with nonhomogeneous vegetation and terrain. He accounts for the microscopic details of a fire with macroscopic resolution by dividing quantities into mean and fluctuating parts similar to what is done in traditional turbulence modeling. These divided quantities include fuel, wind, gas concentrations, and temperature. Reaction rates are limited by the mixing process and not the chemical kinetics. The author has developed a model that includes the transport of multiple gas species, such as oxygen and volatile hydrocarbons, and tracks the depletion of various fuels and other stationary solids and liquids. From this model he develops a simplified local burning model with which he performs a number of simulations that demonstrate that he is able to capture the important physics with the transport approach. With this simplified model he is able to pick up the essence of wildfire propagation, including such features as acceleration when transitioning to upsloping terrain, deceleration of fire fronts when they reach downslopes, and crowning in the presence of high winds.

  1. Radon transport in fractured soil. Laboratory experiments and modelling

    Energy Technology Data Exchange (ETDEWEB)

    Hoff, A.

    1997-10-01

    Radon (Rn-222) transport in fractured soil has been investigated by laboratory experiments and by modelling. Radon transport experiments have been performed with two sand columns (homogeneous and inhomogeneous) and one undisturbed clayey till column containing a net of preferential flow paths (root holes). A numerical model (the finite-element model FRACTRAN) and an analytic model