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...

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

    DEFF Research Database (Denmark)

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

    2002-01-01

    A biogeochemical transport code is used to simulate leachate attenuation. biogeochemical processes. and development of redox zones in a pollution plume downstream of the Vejen landfill in Denmark. Calibration of the degradation parameters resulted in a good agreement with the observed distribution...

  6. Reactive-Transport modeling as a technique for understanding coupled biogeochemical processes in surface and subsurface environments

    NARCIS (Netherlands)

    Regnier, P.; Jourabchi, P.; Slomp, C.P.

    2003-01-01

    Reactive-transport models contribute significantly to the field of modern geosciences. A general mathematical approach to solving models of complex biogeochemical systems is introduced. It is argued that even though mathematical models for reactive- transport simulations can be developed at various

  7. Variably saturated flow and multicomponent biogeochemical reactive transport modeling of a uranium bioremediation field experiment.

    Science.gov (United States)

    Yabusaki, Steven B; Fang, Yilin; Williams, Kenneth H; Murray, Christopher J; Ward, Andy L; Dayvault, Richard D; Waichler, Scott R; Newcomer, Darrell R; Spane, Frank A; Long, Philip E

    2011-11-01

    Three-dimensional, coupled variably saturated flow and biogeochemical reactive transport modeling of a 2008 in situ uranium bioremediation field experiment is used to better understand the interplay of transport and biogeochemical reactions controlling uranium behavior under pulsed acetate amendment, seasonal water table variation, spatially variable physical (hydraulic conductivity, porosity) and geochemical (reactive surface area) material properties. While the simulation of the 2008 Big Rusty acetate biostimulation field experiment in Rifle, Colorado was generally consistent with behaviors identified in previous field experiments at the Rifle IFRC site, the additional process and property detail provided several new insights. A principal conclusion from this work is that uranium bioreduction is most effective when acetate, in excess of the sulfate-reducing bacteria demand, is available to the metal-reducing bacteria. The inclusion of an initially small population of slow growing sulfate-reducing bacteria identified in proteomic analyses led to an additional source of Fe(II) from the dissolution of Fe(III) minerals promoted by biogenic sulfide. The falling water table during the experiment significantly reduced the saturated thickness of the aquifer and resulted in reactants and products, as well as unmitigated uranium, in the newly unsaturated vadose zone. High permeability sandy gravel structures resulted in locally high flow rates in the vicinity of injection wells that increased acetate dilution. In downgradient locations, these structures created preferential flow paths for acetate delivery that enhanced local zones of TEAP reactivity and subsidiary reactions. Conversely, smaller transport rates associated with the lower permeability lithofacies (e.g., fine) and vadose zone were shown to limit acetate access and reaction. Once accessed by acetate, however, these same zones limited subsequent acetate dilution and provided longer residence times that resulted

  8. Numerical modeling of watershed-scale radiocesium transport coupled with biogeochemical cycling in forests

    Science.gov (United States)

    Mori, K.; Tada, K.; Tawara, Y.; Tosaka, H.; Ohno, K.; Asami, M.; Kosaka, K.

    2015-12-01

    Since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, intensive monitoring and modeling works on radionuclide transfer in environment have been carried out. Although Cesium (Cs) concentration has been attenuating due to both physical and environmental half-life (i.e., wash-off by water and sediment), the attenuation rate depends clearly on the type of land use and land cover. In the Fukushima case, studying the migration in forest land use is important for predicting the long-term behavior of Cs because most of the contaminated region is covered by forests. Atmospheric fallout is characterized by complicated behavior in biogeochemical cycle in forests which can be described by biotic/abiotic interactions between many components. In developing conceptual and mathematical model on Cs transfer in forest ecosystem, defining the dominant components and their interactions are crucial issues (BIOMASS, 1997-2001). However, the modeling of fate and transport in geosphere after Cs exports from the forest ecosystem is often ignored. An integrated watershed modeling for simulating spatiotemporal redistribution of Cs that includes the entire region from source to mouth and surface to subsurface, has been recently developed. Since the deposited Cs can migrate due to water and sediment movement, the different species (i.e., dissolved and suspended) and their interactions are key issues in the modeling. However, the initial inventory as source-term was simplified to be homogeneous and time-independent, and biogeochemical cycle in forests was not explicitly considered. Consequently, it was difficult to evaluate the regionally-inherent characteristics which differ according to land uses, even if the model was well calibrated. In this study, we combine the different advantages in modeling of forest ecosystem and watershed. This enable to include more realistic Cs deposition and time series of inventory can be forced over the land surface. These processes are integrated

  9. Reactive transport modelling of biogeochemical processes and carbon isotope geochemistry inside a landfill leachate plume.

    Science.gov (United States)

    van Breukelen, Boris M; Griffioen, Jasper; Röling, Wilfred F M; van Verseveld, Henk W

    2004-06-01

    The biogeochemical processes governing leachate attenuation inside a landfill leachate plume (Banisveld, the Netherlands) were revealed and quantified using the 1D reactive transport model PHREEQC-2. Biodegradation of dissolved organic carbon (DOC) was simulated assuming first-order oxidation of two DOC fractions with different reactivity, and was coupled to reductive dissolution of iron oxide. The following secondary geochemical processes were required in the model to match observations: kinetic precipitation of calcite and siderite, cation exchange, proton buffering and degassing. Rate constants for DOC oxidation and carbonate mineral precipitation were determined, and other model parameters were optimized using the nonlinear optimization program PEST by means of matching hydrochemical observations closely (pH, DIC, DOC, Na, K, Ca, Mg, NH4, Fe(II), SO4, Cl, CH4, saturation index of calcite and siderite). The modelling demonstrated the relevance and impact of various secondary geochemical processes on leachate plume evolution. Concomitant precipitation of siderite masked the act of iron reduction. Cation exchange resulted in release of Fe(II) from the pristine anaerobic aquifer to the leachate. Degassing, triggered by elevated CO2 pressures caused by carbonate precipitation and proton buffering at the front of the plume, explained the observed downstream decrease in methane concentration. Simulation of the carbon isotope geochemistry independently supported the proposed reaction network. PMID:15134877

  10. 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.

  11. 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

  12. CLM4-BeTR, a generic biogeochemical transport and reaction module for CLM4: model development, evaluation, and application

    Directory of Open Access Journals (Sweden)

    J. Tang

    2012-09-01

    Full Text Available To improve regional and global biogeochemistry modeling and climate predictability, we have developed a generic reactive transport module for the land model CLM4 (called CLM4-BeTR (Biogeochemical Transport and Reactions. CLM4-BeTR represents the transport, interactions, and biotic and abiotic transformations of an arbitrary number of tracers (aka chemical species in an arbitrary number of phases (e.g. dissolved, gaseous, sorbed, aggregate. An operator splitting approach was employed and consistent boundary conditions were derived for each modeled sub-process. Tracer fluxes, associated with hydrological processes such as surface run-on and run-off, belowground drainage, and ice to liquid conversion were also computed consistently with the bulk water fluxes calculated by the soil physics module in CLM4. The transport code was evaluated and found be in good agreement with several analytical test cases. The model was then applied at the Harvard Forest site with a representation of depth-dependent belowground biogeochemistry. The results indicated that, at this site, (1 CLM4-BeTR was able to simulate soil-surface CO2 effluxes and soil CO2 profiles accurately; (2 the transient surface CO2 effluxes calculated based on the tracer transport mechanism were in general not equal to the belowground CO2 production rates and that their differences varied according to the seasonal cycle of soil physics and biogeochemistry; (3 losses of CO2 through processes other than surface gas efflux were less than 1% of the overall soil respiration; and (4 the contributions of root respiration and heterotrophic respiration have distinct temporal signals in surface CO2 effluxes and soil CO2 concentrations. The development of CLM4-BeTR will allow detailed comparisons between ecosystem observations and predictions and insights to the modeling of terrestrial biogeochemistry.

  13. Modeling the nitrogen fluxes in the Black Sea using a 3D coupled hydrodynamical-biogeochemical model: transport versus biogeochemical processes, exchanges across the shelf break and comparison of the shelf and deep sea ecodynamics

    NARCIS (Netherlands)

    Grégoire, M.; Beckers, J.M.

    2004-01-01

    A 6-compartment biogeochemical model of nitrogen cycling and plankton productivity has been coupled with a 3D general circulation model in an enclosed environment (the Black Sea) so as to quantify and compare, on a seasonal and annual scale, the typical internal biogeochemical functioning of the she

  14. CLM4-BeTR, a generic biogeochemical transport and reaction module for CLM4: model development, evaluation, and application

    Directory of Open Access Journals (Sweden)

    J. Y. Tang

    2013-01-01

    Full Text Available To improve regional and global biogeochemistry modeling and climate predictability, we have developed a generic reactive transport module for the land model CLM4 (called CLM4-BeTR (Biogeochemical Transport and Reactions. CLM4-BeTR represents the transport, interactions, and biotic and abiotic transformations of an arbitrary number of tracers (aka chemical species in an arbitrary number of phases (e.g., dissolved, gaseous, sorbed, aggregate. An operator splitting approach was employed and consistent boundary conditions were derived for each modeled sub-process. Aqueous tracer fluxes, associated with hydrological processes such as surface run-on and run-off, belowground drainage, and ice to liquid conversion were also computed consistently with the bulk water fluxes calculated by the soil physics module in CLM4. The transport code was evaluated and found in good agreement with several analytical test cases using a time step of 30 min. The model was then applied at the Harvard Forest site with a representation of depth-dependent belowground biogeochemistry. The results indicated that, at this site, (1 CLM4-BeTR was able to simulate soil–surface CO2 effluxes and soil CO2 profiles accurately; (2 the transient surface CO2 effluxes calculated based on the tracer transport mechanism were in general not equal to the belowground CO2 production rates with the magnitude of the difference being a function of averaging timescale and site conditions: differences were large (−20 ~ 20% on hourly, smaller (−5 ~ 5% at daily timescales, and persisted to the monthly timescales with a smaller magnitude (<4%; (3 losses of CO2 through processes other than surface gas efflux were less than 1% of the overall soil respiration; and (4 the contributions of root respiration and heterotrophic respiration have distinct temporal signals in surface CO2 effluxes and soil CO2 concentrations. The

  15. 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

  16. Modeling the nitrogen fluxes in the Black Sea using a 3D coupled hydrodynamical-biogeochemical model: transport versus biogeochemical processes, exchanges across the shelf break and comparison of the shelf and deep sea ecodynamics

    Directory of Open Access Journals (Sweden)

    J. M. Beckers

    2004-06-01

    Full Text Available A 6-compartment biogeochemical model of nitrogen cycling and plankton productivity has been coupled with a 3D general circulation model in an enclosed environment (the Black Sea so as to quantify and compare, on a seasonal and annual scale, the typical internal biogeochemical functioning of the shelf and of the deep sea as well as to estimate the nitrogen and water exchanges at the shelf break. Model results indicate that the annual nitrogen net export to the deep sea roughly corresponds to the annual load of nitrogen discharged by the rivers on the shelf. The model estimated vertically integrated gross annual primary production is 130 g C m-2yr-1 for the whole basin, 220 g C m-2yr-1 for the shelf and 40 g C m-2yr-1 for the central basin. In agreement with sediment trap observations, model results indicate a rapid and efficient recycling of particulate organic matter in the sub-oxic portion of the water column (60-80m of the open sea. More than 95% of the PON produced in the euphotic layer is recycled in the upper 100m of the water column, 87% in the upper 80 m and 67% in the euphotic layer. The model estimates the annual export of POC towards the anoxic layer to 4 1010mol yr-1. This POC is definitely lost for the system and represents 2% of the annual primary production of the open sea.

  17. 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.

  18. 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...... number of geochemical processes, allows the simulation of soil geochemical transformations when microbial by-products are released to surface water, and the consideration of non-linear feedbacks on bacterial growth and pollutant transformations. Sensitivity analysis is performed through Monte Carlo...

  19. Mapping pan-Arctic methane emissions at high spatial resolution using an adjoint atmospheric transport and inversion method and process-based wetland and lake biogeochemical models

    Directory of Open Access Journals (Sweden)

    Z. Tan

    2015-11-01

    Full Text Available Understanding methane emissions from the Arctic, a fast warming carbon reservoir, is important for projecting changes in the global methane cycle under future climate scenarios. Here we optimize Arctic methane emissions with a nested-grid high-resolution inverse model by assimilating both high-precision surface measurements and column-average SCIAMACHY satellite retrievals of methane mole fraction. For the first time, methane emissions from lakes are integrated into an atmospheric transport and inversion estimate, together with prior wetland emissions estimated by six different biogeochemical models. We find that, the global methane emissions during July 2004–June 2005 ranged from 496.4 to 511.5 Tg yr−1, with wetland methane emissions ranging from 130.0 to 203.3 Tg yr−1. The Arctic methane emissions during July 2004–June 2005 were in the range of 14.6–30.4 Tg yr−1, with wetland and lake emissions ranging from 8.8 to 20.4 Tg yr−1 and from 5.4 to 7.9 Tg yr−1 respectively. Canadian and Siberian lakes contributed most of the estimated lake emissions. Due to insufficient measurements in the region, Arctic methane emissions are less constrained in northern Russia than in Alaska, northern Canada and Scandinavia. Comparison of different inversions indicates that the distribution of global and Arctic methane emissions is sensitive to prior wetland emissions. Evaluation with independent datasets shows that the global and Arctic inversions improve estimates of methane mixing ratios in boundary layer and free troposphere. The high-resolution inversions provide more details about the spatial distribution of methane emissions in the Arctic.

  20. 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...

  1. 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.

  2. Biogeochemical processes controlling the mobility of major ions and trace metals in aquitard sediments beneath an oil sand tailing pond: laboratory studies and reactive transport modeling.

    Science.gov (United States)

    Holden, A A; Haque, S E; Mayer, K U; Ulrich, A C

    2013-08-01

    Increased production and expansion of the oil sand industry in Alberta are of great benefit to the economy, but they carry major environmental challenges. The volume of fluid fine tailings requiring storage is 840×10(6) m(3) and growing, making it imperative that we better understand the fate and transport of oil sand process-affected water (OSPW) seepage from these facilities. Accordingly, the current study seeks to characterize both a) the potential for major ion and trace element release, and b) the principal biogeochemical processes involved, as tailing pond OSPW infiltrates into, and interacts with, underlying glacial till sediments prior to reaching down gradient aquifers or surface waters. Objectives were addressed through a series of aqueous and solid phase experiments, including radial diffusion cells, an isotope analysis, X-ray diffraction, and sequential extractions. The diffusion cells were also simulated in a reactive transport framework to elucidate key reaction processes. The experiments indicate that the ingress and interaction of OSPW with the glacial till sediment-pore water system will result in: a mitigation of ingressing Na (retardation), displacement and then limited precipitation of exchangeable Ca and Mg (as carbonates), sulfate reduction and subsequent precipitation of the produced sulfides, as well as biodegradation of organic carbon. High concentrations of ingressing Cl (~375 mg L(-1)) and Na (~575 mg L(-1)) (even though the latter is delayed, or retarded) are expected to migrate through the till and into the underlying sand channel. Trace element mobility was influenced by ion exchange, oxidation-reduction, and mineral phase reactions including reductive dissolution of metal oxyhydroxides - in accordance with previous observations within sandy aquifer settings. Furthermore, although several trace elements showed the potential for release (Al, B, Ba, Cd, Mn, Pb, Si, Sr), large-scale mobilization is not supported. Thus, the present

  3. 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.

  4. 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...

  5. 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...

  6. 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

  7. 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

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. A Generic Biogeochemical Module for Earth System Models: Next Generation BioGeoChemical Module (NGBGC), Version 1.0

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Yilin; Huang, Maoyi; Liu, Chongxuan; Li, Hongyi; Leung, Lai-Yung R.

    2013-11-13

    Physical and biogeochemical processes regulate soil carbon dynamics and CO2 flux to and from 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 possible. 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 terrestrial ecosystems.

  14. 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.

  15. 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.

  16. 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

  17. Modeling biogeochemical processes in subterranean estuaries : Effect of flow dynamics and redox conditions on submarine groundwater discharge of nutrients

    NARCIS (Netherlands)

    Spiteri, C.; Slomp, C.P.; Tuncay, K.; Meile, C.

    2008-01-01

    A two-dimensional density-dependent reactive transport model, which couples groundwater flow and biogeochemical reactions, is used to investigate the fate of nutrients (NO3 −, NH4 +, and PO4) in idealized subterranean estuaries representing four end-members of oxic/anoxic aquifer and seawater redox

  18. Biogeochemical cycling in terrestrial ecosystems - Modeling, measurement, and remote sensing

    Science.gov (United States)

    Peterson, D. L.; Matson, P. A.; Lawless, J. G.; Aber, J. D.; Vitousek, P. M.

    1985-01-01

    The use of modeling, remote sensing, and measurements to characterize the pathways and to measure the rate of biogeochemical cycling in forest ecosystems is described. The application of the process-level model to predict processes in intact forests and ecosystems response to disturbance is examined. The selection of research areas from contrasting climate regimes and sites having a fertility gradient in that regime is discussed, and the sites studied are listed. The use of remote sensing in determining leaf area index and canopy biochemistry is analyzed. Nitrous oxide emission is investigated by using a gas measurement instrument. Future research projects, which include studying the influence of changes on nutrient cycling in ecosystems and the effect of pollutants on the ecosystems, are discussed.

  19. 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

    -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...... techniques, and 3) representation of hydrologic and biogeochemical phenomena in model development and practical application for natural resource management....

  20. 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...

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. Nutrient dynamics, transfer and retention along the aquatic continuum from land to ocean: towards integration of ecological and biogeochemical models

    Directory of Open Access Journals (Sweden)

    A. F. Bouwman

    2013-01-01

    Full Text Available In river basins, soils, groundwater, riparian zones and floodplains, streams, rivers, lakes and reservoirs act as successive filters in which the hydrology, ecology and biogeochemical processing are strongly coupled and together act to retain a significant fraction of the nutrients transported. This paper compares existing river ecology concepts with current approaches to describe river biogeochemistry, and assesses the value of these concepts and approaches for understanding the impacts of interacting global change disturbances on river biogeochemistry. Through merging perspectives, concepts, and modeling techniques, we propose integrated model approaches that encompass both aquatic and terrestrial components in heterogeneous landscapes. In this model framework, existing ecological and biogeochemical concepts are extended with a balanced approach for assessing nutrient and sediment delivery, on the one hand, and nutrient in-stream retention on the other hand.

  9. 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.

  10. 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.

  11. 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

  12. 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.

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

    DEFF Research Database (Denmark)

    Muchamad, Al Azhar

    The biogeochemical cycles of organic carbon, nutrients, oxygen, and sulfur in the oceans have been suggested to dominantly occur across the shelf–ocean transition over the continental margin, although this zone represents only a small percentage of the global ocean area. Coastal upwelling zones...... in eastern boundary upwelling systems is an example of the most productive ocean waters over continental margins where intense supply of nutrients occur from deeper ocean waters. Interesting questions arise related to the biogeochemical cycles in such upwelling systems; such as 1) how the recently observed...... these questions centering on shelf–ocean exchange and biogeochemical cycle in the coastal upwelling systems under oxic and anoxic conditions. Firstly, I developed a new biogeochemical model which resolves coupling between cycles of the elements nitrogen, oxygen, phosphate, and sulfur by considering several key...

  14. Mechanisms driving estuarine water quality: A 3D biogeochemical model for informed management

    Science.gov (United States)

    Wild-Allen, Karen; Skerratt, Jenny; Whitehead, Jason; Rizwi, Farhan; Parslow, John

    2013-12-01

    Estuaries are amongst the most productive marine ecosystems of the world but are also some of the most degraded due to coastal urban development. Sparse sampling of complex interactions between estuarine physics, sediment transport, chemistry, and biology limits understanding of the processes controlling estuarine water quality and confounds active management. We use a 3D coupled hydrodynamic, sediment and biogeochemical model to identify the key mechanisms driving fine-scale fluctuations in water quality in a temperate micro-tidal salt wedge estuary [Derwent Estuary, Tasmania]. Model results are dynamically consistent with relatively sparse monitoring data collected over a seasonal cycle and are considered to be a plausible hypothesis of sub-monitoring scale processes occurring in the estuary. The model shows enhanced mixing of nutrients across the pycnocline downstream of the salt wedge front that supports a persistent phytoplankton bloom. The length and flow regime of the estuary results in nutrient recycling and retention in the estuarine circulation driving a decline in bottom water dissolved oxygen in the mid- and upper-reaches. A budget analysis of modelled nitrogen suggests high levels of denitrification are critical to the maintenance of existing water quality. Active estuarine management focused on the improvement of bottom water dissolved oxygen for ecological health reasons must either concurrently reduce anthropogenic nitrogen loads or be sure to maintain high levels of microbial denitrification for net water quality improvement.

  15. Long-term controls on ocean phosphorus and oxygen in a global biogeochemical model

    NARCIS (Netherlands)

    Palastanga, V.; Slomp, C.P.; Heinze, C.

    2011-01-01

    In this study, we use a biogeochemical ocean general circulation model (HAMOCC), originally developed for the carbon and silicon cycles, and expand it with a description of the sedimentary phosphorus (P) cycle. The model simulates the release of reactive P by aerobic and anaerobic degradation of org

  16. Assimilation of Sea Color Data Into A Three Dimensional Biogeochemical Model: Sensitivity Experiments

    Science.gov (United States)

    Echevin, V.; Levy, M.; Memery, L.

    The assimilation of two dimensional sea color data fields into a 3 dimensional coupled dynamical-biogeochemical model is performed using a 4DVAR algorithm. The biogeochemical model includes description of nitrates, ammonium, phytoplancton, zooplancton, detritus and dissolved organic matter. A subset of the biogeochemical model poorly known parameters (for example,phytoplancton growth, mortality,grazing) are optimized by minimizing a cost function measuring misfit between the observations and the model trajectory. Twin experiments are performed with an eddy resolving model of 5 km resolution in an academic configuration. Starting from oligotrophic conditions, an initially unstable baroclinic anticyclone splits into several eddies. Strong vertical velocities advect nitrates into the euphotic zone and generate a phytoplancton bloom. Biogeochemical parameters are perturbed to generate surface pseudo-observations of chlorophyll,which are assimilated in the model in order to retrieve the correct parameter perturbations. The impact of the type of measurement (quasi-instantaneous, daily mean, weekly mean) onto the retrieved set of parameters is analysed. Impacts of additional subsurface measurements and of errors in the circulation are also presented.

  17. 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.

  18. 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

  19. 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

  20. 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

  1. Modelling freight transport

    NARCIS (Netherlands)

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

    2014-01-01

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

  2. 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

  3. 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.

  4. Modelling biogeochemical-stratigraphic dynamics of clinoform successions over geological timescales

    DEFF Research Database (Denmark)

    Legarth, Jens Jakob Fosselius; Bjerrum, Christian J.

    An understanding of the processes-dynamics governing the development of submarine fine grained clinoforms relies often on correlation of proxies (grain-size trends, spectral gamma, microfossils, TOC, d13C etc.) to more proximal settings where relative sea-level changes are more easily detected. R...... the dynamic biogeochemical-stratigraphic models to our global carbon-nutrient cycle model will permit investigation of how marine productivity indicators and d13C can be use to refine the interpretations of submarine clinoform development and as correlation tools....... are investigated with our novel dynamic biogeochemical-stratigraphic model which explicitly calculates sediment and biogeochemical tracer erosion and deposition over multi-kilo-years. In the model organic and uranium enrichment in the distal clinoform develops as a transgressive nature. As a result part...... of the sedimentary characteristics, traditionally interpreted as a maximum flooding surface, forms during eustatic low stand near the clinoform toe and during sea-level high stand near the clinoform rollover. Such a response may be further modified when considering global carbon and nutrient cycles. Thus coupling...

  5. Weathering Pathways and Limitations in Biogeochemical Models: Application to Earth System Evolution

    OpenAIRE

    Mills, Benjamin

    2012-01-01

    Current biogeochemical box models for Phanerozoic climate are reviewed and reduced to a robust, modular system, allowing application to the Precambrian. It is shown that stabilisation of climate following a Neoproterozoic snowball Earth should take more than 10(7) years, due to long-term geological limitation of global weathering rates. The timescale matches the observed gaps between extreme glaciations at this time, suggesting that the late Neoproterozoic system was oscillating around a s...

  6. Surface micro-topography causes hot spots of biogeochemical activity in wetland systems: A virtual modeling experiment

    Science.gov (United States)

    Frei, S.; Knorr, K. H.; Peiffer, S.; Fleckenstein, J. H.

    2012-12-01

    Wetlands provide important ecohydrological services by regulating fluxes of nutrients and pollutants to receiving waters, which can in turn mitigate adverse effects on water quality. Turnover of redox-sensitive solutes in wetlands has been shown to take place in distinct spatial and temporal patterns, commonly referred to as hot spots and hot moments. Despite the importance of such patterns for solute fluxes the mechanistic understanding of their formation is still weak and their existence is often explained by variations in soil properties and diffusive transport only. Here we show that surface micro-topography in wetlands can cause the formation of biogeochemical hot spots solely by the advective redistribution of infiltrating water as a result of complex subsurface flow patterns. Surface and subsurface flows are simulated for an idealized section of a riparian wetland using a fully integrated numerical code for coupled surface-subsurface systems. Biogeochemical processes and transport along advective subsurface flow paths are simulated kinetically using the biogeochemical code PHREEQC. Distinct patterns of biogeochemical activity (expressed as reaction rates) develop in response to micro-topography induced subsurface flow patterns. Simulated vertical pore water profiles for various redox-sensitive species resemble profiles observed in the field. This mechanistic explanation of hot spot formation complements the more static explanations that relate hot spots solely to spatial variability in soil characteristics and can account for spatial as well as temporal variability of biogeochemical activity, which is needed to assess future changes in the biogeochemical turnover of wetland systems.

  7. 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

  8. 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

  9. Implementation ambiguity: The fifth element long lost in uncertainty budgets for land biogeochemical modeling

    Science.gov (United States)

    Tang, J.; Riley, W. J.

    2015-12-01

    Previous studies have identified four major sources of predictive uncertainty in modeling land biogeochemical (BGC) processes: (1) imperfect initial conditions (e.g., assumption of preindustrial equilibrium); (2) imperfect boundary conditions (e.g., climate forcing data); (3) parameterization (type I equifinality); and (4) model structure (type II equifinality). As if that were not enough to cause substantial sleep loss in modelers, we propose here a fifth element of uncertainty that results from implementation ambiguity that occurs when the model's mathematical description is translated into computational code. We demonstrate the implementation ambiguity using the example of nitrogen down regulation, a necessary process in modeling carbon-climate feedbacks. We show that, depending on common land BGC model interpretations of the governing equations for mineral nitrogen, there are three different implementations of nitrogen down regulation. We coded these three implementations in the ACME land model (ALM), and explored how they lead to different preindustrial and contemporary land biogeochemical states and fluxes. We also show how this implementation ambiguity can lead to different carbon-climate feedback estimates across the RCP scenarios. We conclude by suggesting how to avoid such implementation ambiguity in ESM BGC models.

  10. 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.

  11. 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

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

    Science.gov (United States)

    Wu, Y.; Blodau, C.

    2013-08-01

    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.

  13. 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.

  14. Nutrient dynamics, transfer and retention along the aquatic continuum from land to ocean: Towards integration of ecological and biogeochemical models

    NARCIS (Netherlands)

    Bouwman, A.F.; Bierkens, M.F.P.; Griffioen, J.; Hefting, M.M.; Middelburg, J.J.; Middelkoop, H.; Slomp, C.P.

    2013-01-01

    In river basins, soils, groundwater, riparian zones and floodplains, streams, rivers, lakes and reservoirs act as successive filters in which the hydrology, ecology and biogeochemical processing are strongly coupled and together act to retain a significant fraction of the nutrients transported. This

  15. Modeling ocean circulation and biogeochemical variability in the Gulf of Mexico

    Science.gov (United States)

    Xue, Z.; He, R.; Fennel, K.; Cai, W.-J.; Lohrenz, S.; Hopkinson, C.

    2013-11-01

    A three-dimensional coupled physical-biogeochemical model is applied to simulate and examine temporal and spatial variability of circulation and biogeochemical cycling in the Gulf of Mexico (GoM). The model is driven by realistic atmospheric forcing, open boundary conditions from a data assimilative global ocean circulation model, and observed freshwater and terrestrial nitrogen input from major rivers. A 7 yr model hindcast (2004-2010) was performed, and validated against satellite observed sea surface height, surface chlorophyll, and in situ observations including coastal sea level, ocean temperature, salinity, and dissolved inorganic nitrogen (DIN) concentration. The model hindcast revealed clear seasonality in DIN, phytoplankton and zooplankton distributions in the GoM. An empirical orthogonal function analysis indicated a phase-locked pattern among DIN, phytoplankton and zooplankton concentrations. The GoM shelf nitrogen budget was also quantified, revealing that on an annual basis the DIN input is largely balanced by the removal through denitrification (an equivalent of ~ 80% of DIN input) and offshore exports to the deep ocean (an equivalent of ~ 17% of DIN input).

  16. Modeling ocean circulation and biogeochemical variability in the Gulf of Mexico

    Directory of Open Access Journals (Sweden)

    Z. Xue

    2013-05-01

    Full Text Available A three-dimensional coupled physical-biogeochemical model is applied to simulate and examine temporal and spatial variability of circulation and biogeochemical cycling in the Gulf of Mexico (GoM. The model is driven by realistic atmospheric forcing, open boundary conditions from a data assimilative global ocean circulation model, and observed freshwater and terrestrial nutrient input from major rivers. A 7 yr model hindcast (2004–2010 was performed, and validated against satellite observed sea surface height, surface chlorophyll, and in-situ observations including coastal sea-level, ocean temperature, salinity, and nutrient concentration. The model hindcast revealed clear seasonality in nutrient, phytoplankton and zooplankton distributions in the GoM. An Empirical Orthogonal Function analysis indicated a phase-locked pattern among nutrient, phytoplankton and zooplankton concentrations. The GoM shelf nutrient budget was also quantified, revealing that on an annual basis ~80% of nutrient input was denitrified on the shelf and ~17% was exported to the deep ocean.

  17. 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

  18. 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.

  19. UZ Colloid Transport Model

    Energy Technology Data Exchange (ETDEWEB)

    M. McGraw

    2000-04-13

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

  20. 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, ...

  1. A Thermodynamically-consistent FBA-based Approach to Biogeochemical Reaction Modeling

    Science.gov (United States)

    Shapiro, B.; Jin, Q.

    2015-12-01

    Microbial rates are critical to understanding biogeochemical processes in natural environments. Recently, flux balance analysis (FBA) has been applied to predict microbial rates in aquifers and other settings. FBA is a genome-scale constraint-based modeling approach that computes metabolic rates and other phenotypes of microorganisms. This approach requires a prior knowledge of substrate uptake rates, which is not available for most natural microbes. Here we propose to constrain substrate uptake rates on the basis of microbial kinetics. Specifically, we calculate rates of respiration (and fermentation) using a revised Monod equation; this equation accounts for both the kinetics and thermodynamics of microbial catabolism. Substrate uptake rates are then computed from the rates of respiration, and applied to FBA to predict rates of microbial growth. We implemented this method by linking two software tools, PHREEQC and COBRA Toolbox. We applied this method to acetotrophic methanogenesis by Methanosarcina barkeri, and compared the simulation results to previous laboratory observations. The new method constrains acetate uptake by accounting for the kinetics and thermodynamics of methanogenesis, and predicted well the observations of previous experiments. In comparison, traditional methods of dynamic-FBA constrain acetate uptake on the basis of enzyme kinetics, and failed to reproduce the experimental results. These results show that microbial rate laws may provide a better constraint than enzyme kinetics for applying FBA to biogeochemical reaction modeling.

  2. 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.

  3. 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?

  4. 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

  5. Spatial modeling of coupled hydrologic-biogeochemical processes for the Southern Sierra Critical Zone Observatory

    Science.gov (United States)

    Tague, C.

    2007-12-01

    One of the primary roles of modeling in critical zone research studies is to provide a framework for integrating field measurements and theory and for generalizing results across space and time. In the Southern Sierra Critical Zone Observatory (SCZO), significant spatial heterogeneity associated with mountainous terrain combined with high inter-annual and seasonal variation in climate, necessitates the use of spatial-temporal models for generating landscape scale understanding and predictions. Science questions related to coupled hydrologic and biogeochemical fluxes within the critical zone require a framework that can account for multiple and interacting processes. One of the core tools for the SCZO will be RHESSYs (Regional hydro-ecologic simulation system). RHESSys is an existing GIS-based model of hydrology and biogeochemical cycling. For the SCZO, we use RHESSys as an open-source, objected oriented model that can be extended to incorporate findings from field-based monitoring and analysis. We use the model as a framework for data assimilation, spatial-temporal interpolation, prediction, and scenario and hypothesis generation. Here we demonstrate the use of RHESSys as a hypothesis generation tool. We show how initial RHESSys predictions can be used to estimate when and where connectivity within the critical zone will lead to significant spatial or temporal gradients in vegetation carbon and moisture fluxes. We use the model to explore the potential implications of heterogeneity in critical zone controls on hydrologic processes at two scales: micro and macro. At the micro scale, we examine the role of preferential flowpaths. At the macro scale we consider the importance of upland-riparian zone connectivity. We show how the model can be used to design efficient field experiments by, a-priori providing quantitative estimate of uncertainty and highlighting when and where measurements might most effectively reduce that uncertainty.

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

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

    Directory of Open Access Journals (Sweden)

    O. Aumont

    2015-02-01

    Full Text Available PISCES-v2 is a biogeochemical model which simulates the lower trophic levels of marine ecosystem (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 twenty-four 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 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 silicium quotas are variable and 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 NEMO and 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.

  14. 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.

  15. Insights into biogeochemical cycling from a soil evolution model and long-term chronosequences

    Directory of Open Access Journals (Sweden)

    M. O. Johnson

    2014-04-01

    Full Text Available Despite the importance of soil processes for global biogeochemical cycles, our capability for predicting soil evolution over geological timescales is poorly constrained. We attempt to probe our understanding and predictive capability of this evolutionary process by developing a mechanistic soil evolution model, based on an existing model framework, and comparing the predictions with observations from soil chronosequences in Hawaii. Our soil evolution model includes the major processes of pedogenesis: mineral weathering, percolation of rainfall, leaching of solutes, surface erosion, bioturbation and vegetation interactions and can be applied to various bedrock compositions and climates. The specific properties the model simulates over timescales of tens to hundreds of thousand years are, soil depth, vertical profiles of elemental composition, soil solution pH and organic carbon distribution. We demonstrate with this model the significant role that vegetation plays in accelerating the rate of weathering and hence soil profile development. Comparisons with soils that have developed on Hawaiian basalts reveal a remarkably good agreement with Na, Ca and Mg profiles suggesting that the model captures well the key components of soil formation. Nevertheless, differences between modelled and observed K and P are substantial. The fact that these are important plant nutrients suggests that a process likely missing from our model is the active role of vegetation in selectively acquiring nutrients. This study therefore indirectly indicates the valuable role that vegetation can play in accelerating the weathering and thus release of these globally important nutrients into the biosphere.

  16. 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.

  17. 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.

  18. An integrated multi-level watershed-reservoir modeling system for examining hydrological and biogeochemical processes in small prairie watersheds.

    Science.gov (United States)

    Zhang, Hua; Huang, Guo H; Wang, Dunling; Zhang, Xiaodong; Li, Gongchen; An, Chunjiang; Cui, Zheng; Liao, Renfei; Nie, Xianghui

    2012-03-15

    Eutrophication of small prairie reservoirs presents a major challenge in water quality management and has led to a need for predictive water quality modeling. Studies are lacking in effectively integrating watershed models and reservoir models to explore nutrient dynamics and eutrophication pattern. A water quality model specific to small prairie water bodies is also desired in order to highlight key biogeochemical processes with an acceptable degree of parameterization. This study presents a Multi-level Watershed-Reservoir Modeling System (MWRMS) to simulate hydrological and biogeochemical processes in small prairie watersheds. It integrated a watershed model, a hydrodynamic model and an eutrophication model into a flexible modeling framework. It can comprehensively describe hydrological and biogeochemical processes across different spatial scales and effectively deal with the special drainage structure of small prairie watersheds. As a key component of MWRMS, a three-dimensional Willows Reservoir Eutrophication Model (WREM) is developed to addresses essential biogeochemical processes in prairie reservoirs and to generate 3D distributions of various water quality constituents; with a modest degree of parameterization, WREM is able to meet the limit of data availability that often confronts the modeling practices in small watersheds. MWRMS was applied to the Assiniboia Watershed in southern Saskatchewan, Canada. Extensive efforts of field work and lab analysis were undertaken to support model calibration and validation. MWRMS demonstrated its ability to reproduce the observed watershed water yield, reservoir water levels and temperatures, and concentrations of several water constituents. Results showed that the aquatic systems in the Assiniboia Watershed were nitrogen-limited and sediment flux played a crucial role in reservoir nutrient budget and dynamics. MWRMS can provide a broad context of decision support for water resources management and water quality

  19. 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.

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

    Science.gov (United States)

    Dutkiewicz, S.; Hickman, A. E.; Jahn, O.; Gregg, W. W.; Mouw, C. B.; Follows, M. J.

    2015-07-01

    We present a numerical model of the ocean that couples a three-stream radiative transfer component with a marine biogeochemical-ecosystem component in a dynamic three-dimensional physical framework. The radiative transfer component resolves the penetration of spectral irradiance as it is absorbed and scattered within the water column. We explicitly include the effect of several optically important water constituents (different phytoplankton functional types; 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 meridional 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 find that incorporating the different optically important constituents explicitly and including spectral irradiance was crucial to capture the variability in the depth of the subsurface chlorophyll a (Chl a) maximum. We conduct a series of sensitivity experiments to demonstrate, globally, the relative importance of each of the water constituents, as well as the crucial feedbacks between the light field, the relative fitness of phytoplankton types, and the biogeochemistry of the ocean. CDOM has proportionally more importance at attenuating light at short wavelengths and in more productive waters, phytoplankton absorption is relatively more important at the subsurface Chl a maximum, and water molecules have the greatest contribution when concentrations of other constituents are low, such as in the oligotrophic gyres. Scattering had less effect on attenuation, but since it is important for the amount and type of upwelling irradiance, it is crucial for setting sea surface reflectance. Strikingly, sensitivity experiments in which absorption by any of the

  1. 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

  2. STUDY OF CHLOROPHYLL-A DISTRIBUTIONS IN LOMBOK STRAIT USING BIOGEOCHEMICAL MODEL BASED ON REGIONAL OCEAN MODELLING SYSTEM (ROMS

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    KADEK ARY ANGGRAENI

    2015-06-01

    Full Text Available Regional Ocean Modelling System (ROMS has been intended to be a multi-purpose, multi-disciplinary oceanic modeling tool. The Biogeochemical model have coupled to ROMS consists of a system of seven coupled partial differential equations that include: nitrate, ammonium, small and large detritus, phytoplanJ..'ton, zooplankton, and a dynamic phytoplanJ..-ton carbon to chlorophyll ratio. The study of distribution patterns of chlorophyll-a in Lombok Strait (-7 °N - ·10 •sand 114 "E - 117 °E in 2006 was analyzed using the Biogeochemical model based on ROMS. The results show that low chlorophyll-a distributions (0.20 mgChl-a/m3 observed in Lombok Strait in ,January. Chlorophyll-a estimated around the southern part of Bali Strait and low chlorophyll-a distribution in upper layer of the Lomhok Strait. Chlorophyll-a of the booming (0.32 mgChl-a/m3 observed in August. The northeast current direction moves to the west and southern part of research area through Lombok Strait. The highest chlorophyll-a concentration estimated in the northern and southwestern part of Bali Tsland and also in the southern part of Lombok Island. During dry monsoon, southeasterly wind blow from Australia generates upwelling process (low temperature and nutrient-rich water near the surface also estimated from ROMS.

  3. Reconciling surface ocean productivity, export fluxes and sediment composition in a global biogeochemical ocean model

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    M. Gehlen

    2006-01-01

    Full Text Available This study focuses on an improved representation of the biological soft tissue pump in the global three-dimensional biogeochemical ocean model PISCES. We compare three parameterizations of particle dynamics: (1 the model standard version including two particle size classes, aggregation-disaggregation and prescribed sinking speed; (2 an aggregation-disaggregation model with a particle size spectrum and prognostic sinking speed; (3 a mineral ballast parameterization with no size classes, but prognostic sinking speed. In addition, the model includes a description of surface sediments and organic carbon early diagenesis. Model output is compared to data or data based estimates of ocean productivity, pe-ratios, particle fluxes, surface sediment bulk composition and benthic O2 fluxes. Model results suggest that different processes control POC fluxes at different depths. In the wind mixed layer turbulent particle coagulation appears as key process in controlling pe-ratios. Parameterization (2 yields simulated pe-ratios that compare well to observations. Below the wind mixed layer, POC fluxes are most sensitive to the intensity of zooplankton flux feeding, indicating the importance of zooplankton community composition. All model parameters being kept constant, the capability of the model to reproduce yearly mean POC fluxes below 2000 m and benthic oxygen demand does at first order not dependent on the resolution of the particle size spectrum. Aggregate formation appears essential to initiate an intense biological pump. At great depth the reported close to constant particle fluxes are most likely the result of the combined effect of aggregate formation and mineral ballasting.

  4. LiDAR-derived spatial models of hydrological and biogeochemical source areas to improve estimates of terrestrial-aquatic mercury export in northern forested landscapes

    Science.gov (United States)

    Richardson, M. C.; Mitchell, C. P.; Branfireun, B. A.; Kolka, R. K.; Fortin, M.

    2010-12-01

    Recent research on watershed mercury (Hg) and dissolved organic carbon (DOC) cycling in headwater research catchments in south-central Ontario, northwestern Ontario and northern Minnesota points to the critical role of discrete landscape elements in dictating rainfall-runoff response and the mobilization of DOC, Hg and methyl-mercury (MeHg) to downstream surface-waters. An overview of this research will be presented, emphasising two newly developed techniques used to extract hydrological and biogeochemical sources areas from airborne Light Detection and Ranging (LiDAR) surveys. First, hydrogeomorphic edge-detection was used to partition the landscape into discrete functional units based on local drainage conditions. From this initial landscape segmentation, forested wetlands and non-wetland saturation prone depressional areas were classified and extracted using classification and regression tree models based on LiDAR-derived geomorphic indices aggregated to the scale of individual landscape elements. Following this procedure, a characteristic morphology analysis was conducted from LiDAR bare-earth returns to quantitatively define the upland-peatland interfaces within all peatlands greater than 0.2 ha. These two terrain analysis techniques produced a number of functionally different landscape element classes that were subsequently used in the south-central Ontario study sites to test statistical models of terrestrial-aquatic fluxes of DOC, total Hg and MeHg over different time-scales. The regression models indicate that functional differences exist among landscape element classes with respect to their solute source-strengths and runoff generating potentials, and showed marked improvements over previous landscape models of hydrological and biogeochemical source areas in northern forested regions. LiDAR remote sensing can therefore be used to refine estimates of biogeochemical transformations and solute transport at the landscape scale, thus improving our

  5. 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Stegen, James C.; Konopka, Allan; McKinely, Jim; Murray, Christopher J.; Lin, Xueju; Miller, Micah D.; Kennedy, David W.; Miller, Erin A.; Resch, Charles T.; Fredrickson, Jim K.

    2016-07-29

    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, diversity, and community 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 diversity—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.

  7. 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

  8. Impact of satellite data assimilation in a coupled physical-biogeochemical model of the North Atlantic

    Science.gov (United States)

    Berline, L.; Brankart, J.-M.; Brasseur, P.

    The general objective of this work is to examine how the assimilation of data in a circulation model can improve the biological response simulated by a coupled physical-ecosystem model. In this work, the focus will be on the impact of altimetric, SST and SSS data assimilation in an eddy-permitting coupled model of the North Atlantic. The physical model is a z-coordinate, rigid lid, primitive-equation model based on the OPA code [Madec et al, 1998]. The horizontal resolution is 1/3° and there are 43 vertical levels with refinement near the surface. The biogeochemical model is the P3ZD biogeochemical model [Aumont et al., 1998] that describes the cycling of carbon, silica and calcium. The simulations are performed using realistic forcings during 1998. The assimilation method is based on a Kalman filter with reduced order error covariance matrix, known as the SEEK filter [ Pham et al., 1998]. The sequential scheme has been modified recently using the concept of "incremental analysis update" to enforce temporal continuity of the assimilation run. In order to evaluate how the assimilation can improve the representation of the biological fields, comparisons are made between free runs and simulations with assimilation. A first comparison with the assimilation run obtained using the scheme developed by Testut et al. [2003] indicates the excessive supply of nutrients in the euphotic zone through spurious mixing and advection mechanisms. This can be partly attributed to several factors, e.g. the statistical method which is unable to maintain the model constraint of hydrostatic stability, the discontinuous nature of the sequential algorithm, or the lack of consistent corrections between the physical and biological components of the state vector. Several variants of the assimilation algorithm are implemented in order to improve the representation of the model dynamics and its subsequent impact on the biological variables. A comparison between the assimilation runs obtained

  9. 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.

  10. Nutrient biogeochemical cycles in the Gulf of Riga: scaling up field studies with a mathematical model

    Science.gov (United States)

    Savchuk, Oleg P.

    2002-05-01

    A box model has been implemented to understand the large-scale biogeochemical cycles of nitrogen, phosphorus, and silicon in the Gulf of Riga. The large data sets collected within the international Gulf of Riga Project in 1993/1995 were used to validate the model. The comparison to data was useful in scaling up to the gulf-wide level and scrutinizing the conclusions based on short-term field surveys and experimental studies. The simulations indicate that the limiting role was passing from silicon to phosphorus to nitrogen over the seasons of organic production. However, on an annual scale, nutrient limitation was close to the "Redfield equilibrium". Mass balance considerations, based on modeled coupled fluxes, disagree with the conclusions on low sediment denitrification and high phosphorus retention in the pelagic system, which were derived from isolated measurements. Nutrient budgets constructed with the model revealed the high buffer capacity of the Gulf of Riga. The nutrient residence times span a range from 6 years for N to 70 years for Si. The buffering arises from intensive internal recycling in the water body and by the bottom sediments. The budgets indicate that the Gulf retains about two-thirds of external nitrogen and silicon inputs, while phosphorus retention is only 10%. A slow response to external perturbations is demonstrated with numerical experiments run for 15 years under 50% reductions of terrestrial nutrient inputs. These experiments imply that the most effective is the N+P reduction scenario, which resulted in a 20% decrease of primary production after 12 years. A reduction of P resulted in only a 6% decrease of primary production; however, it yielded an 80% drop in the amount of nitrogen fixation.

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

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    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.

  12. 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

  13. 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.

  14. High-resolution mineralogical characterization and biogeochemical modeling of uranium reaction pathways at the FRC

    Energy Technology Data Exchange (ETDEWEB)

    Chen Zhu

    2006-06-15

    High-Resolution Mineralogical Characterization and Biogeochemical Modeling of Uranium Reduction Pathways at the Oak Ridge Field-Research Center (FRC) Chen Zhu, Indiana University, David R. Veblen, Johns Hopkins University We have successfully completed a proof-of-concept, one-year grant on a three-year proposal from the former NABIR program, and here we seek additional two-year funding to complete and publish the research. Using a state-of-the-art 300-kV, atomic resolution, Field Emission Gun Transmission Electron Microscope (TEM), we have successfully identified three categories of mineral hosts for uranium in contaminated soils: (1) iron oxides; (2) mixed manganese-iron oxides; and (3) uranium phosphates. Method development using parallel electron energy loss spectroscopy (EELS) associated with the TEM shows great promise for characterizing the valence states of immobilized U during bioremediation. We have also collected 27 groundwater samples from two push-pull field biostimulation tests, which form two time series from zero to approximately 600 hours. The temporal evolution in major cations, anions, trace elements, and the stable isotopes 34S, 18O in sulfate, 15N in nitrate, and 13C in dissolved inorganic carbon (DIC) clearly show that biostimulation resulted in reduction of nitrate, Mn(IV), Fe(III), U(VI), sulfate, and Tc(VII), and these reduction reactions were intimately coupled with a complex network of inorganic reactions evident from alkalinity, pH, Na, K, Mg, and Ca concentrations. From these temporal trends, apparent zero order rates were regressed. However, our extensive suite of chemical and isotopic data sets, perhaps the first and only comprehensive data set available at the FRC, show that the derived rates from these field biostimulation experiments are composite and lump-sum rates. There were several reactions that were occurring at the same time but were masked by these pseudo-zero order rates. A reaction-path model comprising a total of nine

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

    Directory of Open Access Journals (Sweden)

    T. Arsouze

    2009-12-01

    Full Text Available The decoupled behaviour observed between Nd isotopic composition (Nd IC, also referred as εNd and Nd concentration cycles 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. This non-conservative behaviour is typical of nutrients affected by scavenging in surface waters and remineralisation at depth. In addition, recent studies suggest 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 do not simulate the input/output fluxes of Nd to the ocean, and therefore prevents from crucial information that limits our understanding of Nd decoupling. To investigate this paradox on a global scale, this study uses for the first time a fully prognostic coupled dynamical/biogeochemical model with an explicit representation of Nd sources and sinks to simulate the Nd oceanic cycle. Sources considered include dissolved river fluxes, atmospheric dusts and margin sediment re-dissolution. Sinks are scavenging by settling particles. This model simulates the global features of the Nd oceanic cycle well, and produces a realistic distribution of Nd concentration (correct order of magnitude, increase with depth and along the conveyor belt, 65% of the simulated values fit in the ±10 pmol/kg envelop when compared to the data and isotopic composition (inter-basin gradient, characterization of the main water-masses, more than 70% of the simulated values fit in the ±3 εNd envelop when compared to the data, though a slight overestimation of

  16. 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...

  17. 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.

  18. 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.

  19. 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...

  20. Nitrous oxide emissions from cropland: a procedure for calibrating the DayCent biogeochemical model using inverse modelling

    Science.gov (United States)

    Rafique, Rashad; Fienen, Michael N.; Parkin, Timothy B.; Anex, Robert P.

    2013-01-01

    DayCent is a biogeochemical model of intermediate complexity widely used to simulate greenhouse gases (GHG), soil organic carbon and nutrients in crop, grassland, forest and savannah ecosystems. Although this model has been applied to a wide range of ecosystems, it is still typically parameterized through a traditional “trial and error” approach and has not been calibrated using statistical inverse modelling (i.e. algorithmic parameter estimation). The aim of this study is to establish and demonstrate a procedure for calibration of DayCent to improve estimation of GHG emissions. We coupled DayCent with the parameter estimation (PEST) software for inverse modelling. The PEST software can be used for calibration through regularized inversion as well as model sensitivity and uncertainty analysis. The DayCent model was analysed and calibrated using N2O flux data collected over 2 years at the Iowa State University Agronomy and Agricultural Engineering Research Farms, Boone, IA. Crop year 2003 data were used for model calibration and 2004 data were used for validation. The optimization of DayCent model parameters using PEST significantly reduced model residuals relative to the default DayCent parameter values. Parameter estimation improved the model performance by reducing the sum of weighted squared residual difference between measured and modelled outputs by up to 67 %. For the calibration period, simulation with the default model parameter values underestimated mean daily N2O flux by 98 %. After parameter estimation, the model underestimated the mean daily fluxes by 35 %. During the validation period, the calibrated model reduced sum of weighted squared residuals by 20 % relative to the default simulation. Sensitivity analysis performed provides important insights into the model structure providing guidance for model improvement.

  1. 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...

  2. 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

  3. 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

  4. 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;

    2014-01-01

    convection cells capture living phytoplankton cells and recurrently expose them to sunlight. This study presents a parameterisation alled ‘phytoconvection’which focusses on the influence of convection on primary production. This parameterisationwas 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...

  5. 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.

  6. Integration of the DAYCENT Biogeochemical Model within a Multi-Model Framework

    Energy Technology Data Exchange (ETDEWEB)

    David Muth

    2012-07-01

    Agricultural residues are the largest near term source of cellulosic 13 biomass for bioenergy production, but removing agricultural residues sustainably 14 requires considering the critical roles that residues play in the agronomic system. 15 Determining sustainable removal rates for agricultural residues has received 16 significant attention and integrated modeling strategies have been built to evaluate 17 sustainable removal rates considering soil erosion and organic matter constraints. 18 However the current integrated model does not quantitatively assess soil carbon 19 and long term crop yields impacts of residue removal. Furthermore the current 20 integrated model does not evaluate the greenhouse gas impacts of residue 21 removal, specifically N2O and CO2 gas fluxes from the soil surface. The DAYCENT 22 model simulates several important processes for determining agroecosystem 23 performance. These processes include daily Nitrogen-gas flux, daily carbon dioxide 24 flux from soil respiration, soil organic carbon and nitrogen, net primary productivity, 25 and daily water and nitrate leaching. Each of these processes is an indicator of 26 sustainability when evaluating emerging cellulosic biomass production systems for 27 bioenergy. A potentially vulnerable cellulosic biomass resource is agricultural 28 residues. This paper presents the integration of the DAYCENT model with the 29 existing integration framework modeling tool to investigate additional environment 30 impacts of agricultural residue removal. The integrated model is extended to 31 facilitate two-way coupling between DAYCENT and the existing framework. The 32 extended integrated model is applied to investigate additional environmental 33 impacts from a recent sustainable agricultural residue removal dataset. The 34 integrated model with DAYCENT finds some differences in sustainable removal 35 rates compared to previous results for a case study county in Iowa. The extended 36 integrated model with

  7. Using satellite-derived backscattering coefficients in addition to chlorophyll data to constrain a simple marine biogeochemical model

    Directory of Open Access Journals (Sweden)

    H. Kettle

    2009-08-01

    Full Text Available Biogeochemical models of the ocean carbon cycle are frequently validated by, or tuned to, satellite chlorophyll data. However, ocean carbon cycle models are required to accurately model the movement of carbon, not chlorophyll, and due to the high variability of the carbon to chlorophyll ratio in phytoplankton, chlorophyll is not a robust proxy for carbon. Using inherent optical property (IOP inversion algorithms it is now possible to also derive the amount of light backscattered by the upper ocean (bb which is related to the amount of particulate organic carbon (POC present. Using empirical relationships between POC and bb, a 1-D marine biogeochemical model is used to simulate bb at 490 nm thereby allowing the model to be compared with both remotely-sensed chlorophyll or bb data. Here I investigate the possibility of using bb in conjunction with chlorophyll data to help constrain the parameters in a simple 1-D NPZD model. The parameters of the biogeochemical model are tuned with a genetic algorithm, so that the model is fitted to either chlorophyll data or to both chlorophyll and bb data at three sites in the Atlantic with very different characteristics. Several inherent optical property (IOP algorithms are available for estimating bb, three of which are used here. The effect of the different bb datasets on the behaviour of the tuned model is examined to ascertain whether the uncertainty in bb is significant. The results show that the addition of bb data does not consistently alter the same model parameters at each site and in fact can lead to some parameters becoming less well constrained, implying there is still much work to be done on the mechanisms relating chlorophyll to POC and bb within the model. However, this study does indicate that

  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. 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.

  10. Assessing biogeochemical effects and best management practice for a wheat–maize cropping system using the DNDC model

    Directory of Open Access Journals (Sweden)

    F. Cui

    2013-05-01

    Full Text Available Contemporary agriculture is shifting from a single-goal to a multi-goal strategy, which in turn requires choosing best management practice (BMP based on assessment of the biogeochemical effects of management alternatives. The bottleneck is the capacity of predicting the simultaneous effects of different management practice scenarios on multiple goals and choosing BMP among scenarios. The denitrification-decomposition (DNDC model may provide an opportunity to solve this problem. We validated the DNDC model (version 95 using the observations of soil moisture and temperature, crop yields, aboveground biomass and fluxes of net ecosystem exchange of carbon dioxide, methane, nitrous oxide (N2O, nitric oxide (NO and ammonia (NH3 from a wheat-maize cropping site in northern China. The model performed well for these variables. Then we used this model to simulate the effects of management practices on the goal variables of crop yields, NO emission, nitrate leaching, NH3 volatilization and net emission of greenhouse gases in the ecosystem (NEGE. Results showed that no-till and straw-incorporated practices had beneficial effects on crop yields and NEGE. Use of nitrification inhibitors decreased nitrate leaching and N2O and NO emissions, but they significantly increased NH3 volatilization. Irrigation based on crop demand significantly increased crop yield and decreased nitrate leaching and NH3 volatilization. Crop yields were hardly decreased if nitrogen dose was reduced by 15% or irrigation water amount was reduced by 25%. Two methods were used to identify BMP and resulted in the same BMP, which adopted the current crop cultivar, field operation schedules and full straw incorporation and applied nitrogen and irrigation water at 15% and 25% lower rates, respectively, than the current use. Our study indicates that the DNDC model can be used as a tool to assess biogeochemical effects of management alternatives and identify BMP.

  11. Goods Transport Modelling, Vol 1

    DEFF Research Database (Denmark)

    Petersen, Morten Steen (red.); Kristiansen, Jørgen

    The report is a study of data requirements and methodologies for goods transport. The study is intended to provide the basis for general discussion about the application of goods transport models in Denmark. The report provides an overview of different types of models and data availability....

  12. 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

  13. 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...

  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. 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

  16. Widespread euxinia in the aftermath of the Lomagundi event: insights from a modeling study of ocean biogeochemical dynamics

    Science.gov (United States)

    Ozaki, Kazumi; Tajika, Eiichi

    2015-04-01

    The emergence of strongly sulphidic oceanic waters (euxinia) during the Proterozoic may have affected biological turnover, extinction, and evolution, not only because of its toxicity to eukaryotes but also because of its fundamental role on bioessential trace metal availability. From this point of view, the evidence for euxinic environments in the Lomagundi-Jatuli event (LJE) aftermath (~2.08-2.05 billion years ago) in Gabon and Karelia are notable because their low δ98/95Mo values (less than 0.95o and 0.85o respectively) imply widespread euxinia at that time. The Francevillian Group in Gabon represents the oxic-anoxic/euxinic transitional sequence, implying a fluctuation in the atmospheric redox condition from oxic to relatively reducing, possibly due to the oxidation of substantial amount of organic matter deposited during the LJE. The large positive anomaly of sulphur isotopes and a substantial contraction of marine sulphate reservoir size through the latter part of the LJE also imply a fall in surface oxidation state. Variations of the oxygenation state of the Earth's surface would have caused substantial changes in oceanic chemical composition and, in turn, would surely have impacted the biosphere. However, the nature and dynamics of oceanic biogeochemical cycles for this interval are poorly understood. To unravel cause and effect of the variations of oceanic redox state in the Paleoproteorozoic, we improved the CANOPS model (a 1-D advection-diffusion-reaction marine biogeochemical cycle model), in which coupled C-N-O-P-S marine biogeochemical cycles and a series of redox reactions were adequately taken into account. Through systematic sensitivity experiments we show that a substantial drop in atmospheric oxygen level could cause a widespread euxinia for millions of years, which provides a theoretical explanation consistent with the geological records, such as large positive anomaly of δ34S, low δ98/95Mo, and a decrease in SO4 concentration, in the

  17. 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.

  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. Evaluating Southern Ocean biological production in two ocean biogeochemical models on daily to seasonal time-scales using satellite surface chlorophyll and O2/Ar observations

    Directory of Open Access Journals (Sweden)

    B. F. Jonsson

    2014-06-01

    Full Text Available We assess the ability of ocean biogeochemical models to represent seasonal structures in biomass and net community production (NCP in the Southern Ocean. Two models are compared to observations on daily to seasonal time scales in four different sections of the region. We use daily satellite fields of Chlorophyll (Chl as a proxy for biomass, and in-situ observations of O2 and Ar supersaturation (ΔO2Ar to estimate NCP. ΔO2Ar is converted to the flux of biologically generated O2 from sea to air ("O2 bioflux". All data are aggregated to a climatological year with a daily resolution. To account for potential regional differences within the Southern Ocean, we conduct separate analyses of sections south of South Africa, around the Drake Passage, south of Australia, and south of New Zealand. We find that the models simulate the upper range of Chl concentrations well, underestimate spring levels significantly, and show differences in skill between early and late parts of the growing season. While there is a great deal of scatter in the bioflux observations in general, the four sectors each have distinct patterns that the models pick up. Neither model exhibit a significant distinction between the Australian and New Zealand sectors, and between the Drake Passage and African sectors. South of 60° S, the models fail to predict the observed extent of biological O2 undersaturation. We suggest that this shortcoming may be due either to problems with the ecosystem dynamics or problems with the vertical transport of oxygen. Overall, the bioflux observations are in general agreement with the seasonal structures in satellite chlorophyll, suggesting that this seasonality represent changes in carbon biomass and not Chl : C ratios. This agreement is shared in the models and allows us to interpret the seasonal structure of satellite chlorophyll as qualitatively reflecting the integral of biological production over time for the purposes of model assessment.

  20. Transportation Modelling for Regional Evacuations

    NARCIS (Netherlands)

    Pel, A.J.

    2011-01-01

    Regional evacuation planning is complex and timely. These planning studies can be assisted by a transportation model. In this thesis, we investigate the requirements for such a model, and develop, implement, and test a new model, called EVAQ, which meets these requirements. Two case studies show how

  1. Development of a 3D Coupled Physical-Biogeochemical Model for the Marseille Coastal Area (NW Mediterranean Sea): What Complexity Is Required in the Coastal Zone?

    Science.gov (United States)

    Fraysse, Marion; Pinazo, Christel; Faure, Vincent Martin; Fuchs, Rosalie; Lazzari, Paolo; Raimbault, Patrick; Pairaud, Ivane

    2013-01-01

    Terrestrial inputs (natural and anthropogenic) from rivers, the atmosphere and physical processes strongly impact the functioning of coastal pelagic ecosystems. The objective of this study was to develop a tool for the examination of these impacts on the Marseille coastal area, which experiences inputs from the Rhone River and high rates of atmospheric deposition. Therefore, a new 3D coupled physical/biogeochemical model was developed. Two versions of the biogeochemical model were tested, one model considering only the carbon (C) and nitrogen (N) cycles and a second model that also considers the phosphorus (P) cycle. Realistic simulations were performed for a period of 5 years (2007–2011). The model accuracy assessment showed that both versions of the model were able of capturing the seasonal changes and spatial characteristics of the ecosystem. The model also reproduced upwelling events and the intrusion of Rhone River water into the Bay of Marseille well. Those processes appeared to greatly impact this coastal oligotrophic area because they induced strong increases in chlorophyll-a concentrations in the surface layer. The model with the C, N and P cycles better reproduced the chlorophyll-a concentrations at the surface than did the model without the P cycle, especially for the Rhone River water. Nevertheless, the chlorophyll-a concentrations at depth were better represented by the model without the P cycle. Therefore, the complexity of the biogeochemical model introduced errors into the model results, but it also improved model results during specific events. Finally, this study suggested that in coastal oligotrophic areas, improvements in the description and quantification of the hydrodynamics and the terrestrial inputs should be preferred over increasing the complexity of the biogeochemical model. PMID:24324589

  2. 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.

  3. 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...

  4. 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

    Science.gov (United States)

    Nickelsen, L.; Keller, D. P.; Oschlies, A.

    2014-12-01

    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.

  5. 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.

  6. Mathematical modeling of kidney transport.

    Science.gov (United States)

    Layton, Anita T

    2013-01-01

    In addition to metabolic waste and toxin excretion, the kidney also plays an indispensable role in regulating the balance of water, electrolytes, nitrogen, and acid-base. In this review, we describe representative mathematical models that have been developed to better understand kidney physiology and pathophysiology, including the regulation of glomerular filtration, the regulation of renal blood flow by means of the tubuloglomerular feedback mechanisms and of the myogenic mechanism, the urine concentrating mechanism, epithelial transport, and regulation of renal oxygen transport. We discuss the extent to which these modeling efforts have expanded our understanding of renal function in both health and disease.

  7. 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

  8. 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.

  9. 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...

  10. 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).

  11. 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.

  12. Biogeochemical modeling of CO2 and CH4 production in anoxic Arctic soil microcosms

    Science.gov (United States)

    Tang, Guoping; Zheng, Jianqiu; Xu, Xiaofeng; Yang, Ziming; Graham, David E.; Gu, Baohua; Painter, Scott L.; Thornton, Peter E.

    2016-09-01

    Soil organic carbon turnover to CO2 and CH4 is sensitive to soil redox potential and pH conditions. However, land surface models do not consider redox and pH in the aqueous phase explicitly, thereby limiting their use for making predictions in anoxic environments. Using recent data from incubations of Arctic soils, we extend the Community Land Model with coupled carbon and nitrogen (CLM-CN) decomposition cascade to include simple organic substrate turnover, fermentation, Fe(III) reduction, and methanogenesis reactions, and assess the efficacy of various temperature and pH response functions. Incorporating the Windermere Humic Aqueous Model (WHAM) enables us to approximately describe the observed pH evolution without additional parameterization. Although Fe(III) reduction is normally assumed to compete with methanogenesis, the model predicts that Fe(III) reduction raises the pH from acidic to neutral, thereby reducing environmental stress to methanogens and accelerating methane production when substrates are not limiting. The equilibrium speciation predicts a substantial increase in CO2 solubility as pH increases, and taking into account CO2 adsorption to surface sites of metal oxides further decreases the predicted headspace gas-phase fraction at low pH. Without adequate representation of these speciation reactions, as well as the impacts of pH, temperature, and pressure, the CO2 production from closed microcosms can be substantially underestimated based on headspace CO2 measurements only. Our results demonstrate the efficacy of geochemical models for simulating soil biogeochemistry and provide predictive understanding and mechanistic representations that can be incorporated into land surface models to improve climate predictions.

  13. 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

  14. 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

  15. 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

  16. 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.

  17. 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.

  18. 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

  19. Ecological controls on biogeochemical lfuxes in the western Antarctic Peninsula studied with an inverse foodweb model

    Institute of Scientific and Technical Information of China (English)

    Hugh W Ducklow; S C Doney; S F Sailley

    2015-01-01

    Sea ice in the western Antarctic Peninsula (WAP) region is both highly variable and rapidly changing. In the Palmer Station region, the ice season duration has decreased by 92 d since 1978. The sea-ice changes affect ocean stratification and freshwater balance and in turn impact every component of the polar marine ecosystem. Long-term observations from the WAP nearshore and offshore regions show a pattern of chlorophyll (Chl) variability with three to ifve years of negative Chl anomalies interrupted by one or two years of positive anomalies (high and low Chl regimes). Both ifeld observations and results from an inverse food-web model show that these high and low Chl regimes differed significantly from each other, with high primary productivity and net community production (NCP) and other rates associated with the high Chl years and low rates with low Chl years. Gross primary production rates (GPP) averaged 30 mmolC.m-2.d-1 in the low Chl years and 100 mmolC.m-2.d-1 in the high Chl years. Both large and small phytoplankton were more abundant and more productive in high Chl years than in low Chl years. Similarly, krill were more important as grazers in high Chl years, but did not differ from microzooplankton in high or low Chl years. Microzooplankton did not differ between high and low Chl years. Net community production differed signiifcantly between high and low Chl years, but mobilized a similar proportion of GPP in both high and low Chl years. The composition of the NCP was uniform in high and low Chl years. These results emphasize the importance of microbial components in the WAP plankton system and suggest that food webs dominated by small phytoplankton can have pathways that funnel production into NCP, and likely, export.

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

    Science.gov (United States)

    Nickelsen, L.; Keller, D. P.; Oschlies, A.

    2015-05-01

    Marine biological production as well as the associated biotic uptake of carbon in many ocean regions depends 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 sensitivity of the model to parameterized iron ligand concentrations, 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.

  1. Development of advanced process-based model towards evaluation of boundless biogeochemical cycles in terrestrial-aquatic continuum

    Science.gov (United States)

    Nakayama, Tadanobu; Maksyutov, Shamil

    2014-05-01

    Recent research shows inland water may play some role in continental biogeochemical cycling though its contribution has remained uncertain due to a paucity of data (Battin et al. 2009). The author has developed process-based National Integrated Catchment-based Eco-hydrology (NICE) model (Nakayama, 2008a-b, 2010, 2011a-b, 2012a-c, 2013; Nakayama and Fujita, 2010; Nakayama and Hashimoto, 2011; Nakayama and Shankman, 2013a-b; Nakayama and Watanabe, 2004, 2006, 2008a-b; Nakayama et al., 2006, 2007, 2010, 2012), which incorporates surface-groundwater interactions, includes up- and down-scaling processes between local, regional and global scales, and can simulate iteratively nonlinear feedback between hydrologic, geomorphic, and ecological processes. In this study, NICE was extended to evaluate global hydrologic cycle by using various global datasets. The simulated result agreed reasonably with that in the previous research (Fan et al., 2013) and extended to clarify further eco-hydrological process in global scale. Then, NICE was further developed to incorporate the biogeochemical cycle including the reaction between inorganic and organic carbons (DOC, POC, DIC, pCO2, etc.) in the biosphere (terrestrial and aquatic ecosystems including surface water and groundwater). The model simulated the carbon cycle, for example, CO2 evasion from inland water in global scale, which is relatively in good agreement in that estimated by empirical relation using the previous pCO2 data (Aufdenkampe et al., 2011; Global River Chemistry Database, 2013). This simulation system would play important role in identification of full greenhouse gas balance of the biosphere and spatio-temporal hot spots in boundless biogeochemical cycle (Cole et al. 2007; Frei et al. 2012). References; Aufdenkampe, A.K., et al., Front. Ecol. Environ., doi:10.1890/100014, 2011. Battin, T.J., et al., Nat. Geosci., 2, 598-600, 2009. Cole, J.J. et al., Ecosystems, doi:10.1007/s10021-006-9013-8, 2007. Fan, Y. et al

  2. Modelling of Transport Projects Uncertainties

    DEFF Research Database (Denmark)

    Salling, Kim Bang; Leleur, Steen

    2009-01-01

    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......-based graphs which function as risk-related decision support for the appraised transport infrastructure project....

  3. 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.

  4. Coupled transport in rotor models

    Science.gov (United States)

    Iubini, S.; Lepri, S.; Livi, R.; Politi, A.

    2016-08-01

    Steady nonequilibrium states are investigated in a one-dimensional setup in the presence of two thermodynamic currents. Two paradigmatic nonlinear oscillators models are investigated: an XY chain and the discrete nonlinear Schrödinger equation. Their distinctive feature is that the relevant variable is an angle in both cases. We point out the importance of clearly distinguishing between energy and heat flux. In fact, even in the presence of a vanishing Seebeck coefficient, a coupling between (angular) momentum and energy arises, mediated by the unavoidable presence of a coherent energy flux. Such a contribution is the result of the ‘advection’ induced by the position-dependent angular velocity. As a result, in the XY model, the knowledge of the two diagonal elements of the Onsager matrix suffices to reconstruct its transport properties. The analysis of the nonequilibrium steady states finally allows to strengthen the connection between the two models.

  5. 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

  6. 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

  7. 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

  8. 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.

  9. 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.

  10. 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

  11. 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....

  12. ParFlow.RT: Development and Verification of a New Reactive Transport Model

    Science.gov (United States)

    Beisman, J. J., III

    2015-12-01

    In natural subsurface systems, total elemental fluxes are often heavily influenced by areas of disproportionately high reaction rates. These pockets of high reaction rates tend to occur at interfaces, such as the hyporheic zone, where a hydrologic flowpath converges with either a chemically distinct hydrologic flowpath or a reactive substrate. Understanding the affects that these highly reactive zones have on the behavior of shallow subsurface systems is integral to the accurate quantification of nutrient fluxes and biogeochemical cycling. Numerical simulations of these systems may be able to offer some insight. To that end, we have developed a new reactive transport model, ParFlow.RT, by coupling the parallel flow and transport code ParFlow with the geochemical engines of both PFLOTRAN and CrunchFlow. The coupling was accomplished via the Alquimia biogeochemistry API, which provides a unified interface to several geochemical codes and allows a relatively simple implementation of advanced geochemical functionality in flow and transport codes. This model uses an operator-splitting approach, where the transport and reaction steps are solved separately. Here, we present the details of this new model, and the results of verification simulations and biogeochemical cycling simulations of the DOE's East River field site outside of Gothic, CO.

  13. 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

  14. Modeling energy transport in nanostructures

    Science.gov (United States)

    Pattamatta, Arvind

    Heat transfer in nanostructures differ significantly from that in the bulk materials since the characteristic length scales associated with heat carriers, i.e., the mean free path and the wavelength, are comparable to the characteristic length of the nanostructures. Nanostructure materials hold the promise of novel phenomena, properties, and functions in the areas of thermal management and energy conversion. Example of thermal management in micro/nano electronic devices is the use of efficient nanostructured materials to alleviate 'hot spots' in integrated circuits. Examples in the manipulation of heat flow and energy conversion include nanostructures for thermoelectric energy conversion, thermophotovoltaic power generation, and data storage. One of the major challenges in Metal-Oxide Field Effect Transistor (MOSFET) devices is to study the 'hot spot' generation by accurately modeling the carrier-optical phonon-acoustic phonon interactions. Prediction of hotspot temperature and position in MOSFET devices is necessary for improving thermal design and reliability of micro/nano electronic devices. Thermoelectric properties are among the properties that may drastically change at nanoscale. The efficiency of thermoelectric energy conversion in a material is measured by a non-dimensional figure of merit (ZT) defined as, ZT = sigmaS2T/k where sigma is the electrical conductivity, S is the Seebeck coefficient, T is the temperature, and k is the thermal conductivity. During the last decade, advances have been made in increasing ZT using nanostructures. Three important topics are studied with respect to energy transport in nanostructure materials for micro/nano electronic and thermoelectric applications; (1) the role of nanocomposites in improving the thermal efficiency of thermoelectric devices, (2) the interfacial thermal resistance for the semiconductor/metal contacts in thermoelectric devices and for metallic interconnects in micro/nano electronic devices, (3) the

  15. 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

  16. Cholesterol transport in model membranes

    Science.gov (United States)

    Garg, Sumit; Porcar, Lionel; Butler, Paul; Perez-Salas, Ursula

    2010-03-01

    Physiological processes distribute cholesterol unevenly within the cell. The levels of cholesterol are maintained by intracellular transport and a disruption in the cell's ability to keep these normal levels will lead to disease. Exchange rates of cholesterol are generally studied in model systems using labeled lipid vesicles. Initially donor vesicles have all the cholesterol and acceptor vesicles are devoid of it. They are mixed and after some time the vesicles are separated and cholesterol is traced in each vesicle. The studies performed up to date have significant scatter indicating that the methodologies are not consistent. The present work shows in-situ Time-Resolved SANS studies of cholesterol exchange rates in unsaturated PC lipid vesicles. Molecular dynamics simulations were done to investigate the energetic and kinetic behavior of cholesterol in this system. This synergistic approach will provide insight into our efforts to understand cholesterol traffic.

  17. 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.

  18. 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.

  19. Improving the parameters of a global ocean biogeochemical model via variational assimilation of in situ data at five time series stations

    Science.gov (United States)

    Kane, A.; Moulin, C.; Thiria, S.; Bopp, L.; Berrada, M.; Tagliabue, A.; CréPon, M.; Aumont, O.; Badran, F.

    2011-06-01

    The global ocean biogeochemical models that are used in order to assess the ocean role in the global carbon cycle and estimate the impact of the climate change on marine ecosystems are getting more and more sophisticated. They now often account for several phytoplankton functional types that play particular roles in marine food webs and the ocean carbon cycle. These phytoplankton functional types have specific physiological characteristics, which are usually poorly known and therefore add uncertainties to model results. Indeed, this evolution in model complexity is not accompanied by a similar increase in the number and diversity of in situ data sets necessary for model calibration and evaluation. Thus, it is of primary importance to develop new methods to improve model performance using existing biogeochemical data sets, despite their current limitations. In this paper, we have optimized 45 physiological parameters of the PISCES global model, using a variational optimal control method. In order to bypass a global 3-D ocean variational assimilation, which would require enormous computation and memory storage, we have simplified the estimation procedure by assimilating monthly climatological in situ observations at five contrasted oceanographic stations of the JGOFS program in a 1-D version of the PISCES model. We began by estimating the weight matrix in the cost function by using heuristic considerations. Then we used this matrix to estimate the 45 parameters of the 1-D version of the PISCES model by assimilating the different monthly profiles (observed profiles at the five stations) in the same variational procedure on a time window of 1 year. This set of optimized parameters was then used in the standard 3-D global PISCES version to perform a 500 year global simulation. The results of both the standard and the optimized versions of the model were compared to satellite-derived chlorophyll-a images, which are an independent and global data set, showing that our

  20. 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

  1. 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 ...

  2. 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.

  3. 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

  4. 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).

  5. 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.

  6. 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...

  7. 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

  8. 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

  9. 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

  10. 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.

  11. Modelling of Transport Projects Uncertainties

    DEFF Research Database (Denmark)

    Salling, Kim Bang; Leleur, Steen

    2012-01-01

    This paper proposes a new way of handling the uncertainties present in transport decision making based on infrastructure appraisals. The paper suggests to combine the principle of Optimism Bias, which depicts the historical tendency of overestimating transport related benefits and underestimating......-based graphs which functions as risk-related decision support for the appraised transport infrastructure project. The presentation of RSF is demonstrated by using an appraisal case concerning a new airfield in the capital of Greenland, Nuuk....

  12. Discrepant estimates of primary and export production from satellite algorithms, a biogeochemical model, and geochemical tracer measurements in the North Pacific Ocean

    Science.gov (United States)

    Palevsky, Hilary I.; Quay, Paul D.; Nicholson, David P.

    2016-08-01

    Estimates of primary and export production (PP and EP) based on satellite remote sensing algorithms and global biogeochemical models are widely used to provide year-round global coverage not available from direct observations. However, observational data to validate these approaches are limited. We find that no single satellite algorithm or model can reproduce seasonal and annual geochemically determined PP, export efficiency (EP/PP), and EP rates throughout the North Pacific basin, based on comparisons throughout the full annual cycle at time series stations in the subarctic and subtropical gyres and basin-wide regions sampled by container ship transects. The high-latitude regions show large PP discrepancies in winter and spring and strong effects of deep winter mixed layers on annual EP that cannot be accounted for in current satellite-based approaches. These results underscore the need to evaluate satellite- and model-based estimates using multiple productivity parameters measured over broad ocean regions throughout the annual cycle.

  13. 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

  14. The european Trans-Tools transport model

    NARCIS (Netherlands)

    Rooijen, T. van; Burgess, A.

    2008-01-01

    The paper presents the use of ArcGIS in the Transtools Transport Model, TRANS-TOOLS, created by an international consortium for the European Commission. The model describe passenger as well as freight transport in Europe with all medium and long distance modes (cars, vans, trucks, train, inland wate

  15. Inverse modeling of pan-Arctic methane emissions at high spatial resolution: what can we learn from assimilating satellite retrievals and using different process-based wetland and lake biogeochemical models?

    Science.gov (United States)

    Tan, Zeli; Zhuang, Qianlai; Henze, Daven K.; Frankenberg, Christian; Dlugokencky, Ed; Sweeney, Colm; Turner, Alexander J.; Sasakawa, Motoki; Machida, Toshinobu

    2016-10-01

    Understanding methane emissions from the Arctic, a fast-warming carbon reservoir, is important for projecting future changes in the global methane cycle. Here we optimized methane emissions from north of 60° N (pan-Arctic) regions using a nested-grid high-resolution inverse model that assimilates both high-precision surface measurements and column-average SCanning Imaging Absorption spectroMeter for Atmospheric CHartogrphY (SCIAMACHY) satellite retrievals of methane mole fraction. For the first time, methane emissions from lakes were integrated into an atmospheric transport and inversion estimate, together with prior wetland emissions estimated with six biogeochemical models. In our estimates, in 2005, global methane emissions were in the range of 496.4-511.5 Tg yr-1, and pan-Arctic methane emissions were in the range of 11.9-28.5 Tg yr-1. Methane emissions from pan-Arctic wetlands and lakes were 5.5-14.2 and 2.4-14.2 Tg yr-1, respectively. Methane emissions from Siberian wetlands and lakes are the largest and also have the largest uncertainty. Our results indicate that the uncertainty introduced by different wetland models could be much larger than the uncertainty of each inversion. We also show that assimilating satellite retrievals can reduce the uncertainty of the nested-grid inversions. The significance of lake emissions cannot be identified across the pan-Arctic by high-resolution inversions, but it is possible to identify high lake emissions from some specific regions. In contrast to global inversions, high-resolution nested-grid inversions perform better in estimating near-surface methane concentrations.

  16. 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.

  17. Uncertainty in tsunami sediment transport modeling

    Science.gov (United States)

    Jaffe, Bruce E.; Goto, Kazuhisa; Sugawara, Daisuke; Gelfenbaum, Guy R.; La Selle, SeanPaul M.

    2016-01-01

    Erosion and deposition from tsunamis record information about tsunami hydrodynamics and size that can be interpreted to improve tsunami hazard assessment. We explore sources and methods for quantifying uncertainty in tsunami sediment transport modeling. Uncertainty varies with tsunami, study site, available input data, sediment grain size, and model. Although uncertainty has the potential to be large, published case studies indicate that both forward and inverse tsunami sediment transport models perform well enough to be useful for deciphering tsunami characteristics, including size, from deposits. New techniques for quantifying uncertainty, such as Ensemble Kalman Filtering inversion, and more rigorous reporting of uncertainties will advance the science of tsunami sediment transport modeling. Uncertainty may be decreased with additional laboratory studies that increase our understanding of the semi-empirical parameters and physics of tsunami sediment transport, standardized benchmark tests to assess model performance, and development of hybrid modeling approaches to exploit the strengths of forward and inverse models.

  18. 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)

  19. Uncertainty calculation in transport models and forecasts

    DEFF Research Database (Denmark)

    Manzo, Stefano; Prato, Carlo Giacomo

    ) resources, hence resulting in socio-economic losses. Along with technical and decision-process related issues, such inaccuracy also originates from transport models’ inherent uncertainty, which in turns originates from the complexity of the systems generating both transport supply (e.g. services...... to 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...... investigated the effects of uncertainty in the volume-delay function parameters used in the Danish National Transport Model1. The results showed that some links in the modelled network have high sensitivity to the variability in the function parameters. In particular, the affected links mainly refer to short...

  20. 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

  1. 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.

  2. 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

  3. 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

  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. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Global changes in biogeochemical cycles in response to human activities

    Science.gov (United States)

    Moore, Berrien, III; Melillo, Jerry

    1994-01-01

    The main objective of our research was to characterize biogeochemical cycles at continental and global scales in both terrestrial and aquatic ecosystems. This characterization applied to both natural ecosystems and those disturbed by human activity. The primary elements of interest were carbon and nitrogen and the analysis sought to quantify standing stocks and dynamic cycling processes. The translocation of major nutrients from the terrestrial landscape to the atmosphere (via trace gases) and to fluvial systems (via leaching, erosional losses, and point source pollution) were of particular importance to this study. Our aim was to develop the first generation of Earth System Models. Our research was organized around the construction and testing of component biogeochemical models which treated terrestrial ecosystem processes, aquatic nutrient transport through drainage basins, and trace gas exchanges at the continental and global scale. A suite of three complementary models were defined within this construct. The models were organized to operate at a 1/2 degree latitude by longitude level of spatial resolution and to execute at a monthly time step. This discretization afforded us the opportunity to understand the dynamics of the biosphere down to subregional scales, while simultaneously placing these dynamics into a global context.

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. Real time model for public transportation management

    Directory of Open Access Journals (Sweden)

    Ireneusz Celiński

    2014-03-01

    Full Text Available 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 transportation based on telemetric and telecommunication data. Emphasis was placed mainly on a general concept and not the manner in which data was collected by other researchers.  Results: The above model gave results in the form of a system for managing a fleet in real-time. The objective of the system is also to optimally utilize means of transportation at the disposal of service providers. Conclusions: The presented concept enables a new perspective on managing public transportation fleets. In case of implementation, the project would facilitate, among others, designing dynamic timetables, updated based on observed demand, and even designing dynamic points of access to public transportation lines. Further research should encompass so-called rerouting based on dynamic measurements of the characteristics of the transportation system.

  16. 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.)

  17. 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

  18. 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.

  19. System Convergence in Transport Modelling

    DEFF Research Database (Denmark)

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

    2010-01-01

    -of-successive-averages (MSA) have been proposed. Convergence of the MSA under fairly weak regularity conditions was shown in Robbins and Monro (1951). The iteration between demand and assignment ? the external equilibrium ? are in many models either decoupled or follow a very simple iteration pattern. However, as demand...

  20. 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.

  1. 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...... is 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....

  2. 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

  3. 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

  4. The ocean response to volcanic iron fertilisation after the eruption of Kasatochi volcano: a regional-scale biogeochemical ocean model study

    Directory of Open Access Journals (Sweden)

    A. Lindenthal

    2013-06-01

    Full Text Available In high-nutrient–low-chlorophyll regions, phytoplankton growth is limited by the availability of water-soluble iron. The eruption of Kasatochi volcano in August 2008 led to ash deposition into the iron-limited NE Pacific Ocean. Volcanic ash released iron upon contact with seawater and generated a massive phytoplankton bloom. Here we investigate this event with a one-dimensional ocean biogeochemical column model to illuminate the ocean response to iron fertilisation by volcanic ash. The results indicate that the added iron triggered a phytoplankton bloom in the summer of 2008. Associated with this bloom, macronutrient concentrations such as nitrate and silicate decline and zooplankton biomass is enhanced in the ocean mixed layer. The simulated development of the drawdown of carbon dioxide and increase of pH in surface seawater is in good agreement with available observations. Sensitivity studies with different supply dates of iron to the ocean emphasise the favourable oceanic conditions in the NE Pacific to generate massive phytoplankton blooms in particular during July and August in comparison to other months. By varying the amount of volcanic ash and associated bio-available iron supplied to the ocean, model results demonstrate that the NE Pacific Ocean has higher, but limited capabilities to consume CO2 after iron fertilisation than those observed after the volcanic eruption of Kasatochi.

  5. Calibration and validation of a one-dimensional complex marine biogeochemical flux model in different areas of the northern Adriatic shelf

    Directory of Open Access Journals (Sweden)

    M. Vichi

    Full Text Available In this paper we show results from numerical simulations carried out with a complex biogeochemical fluxes model coupled with a one-dimensional high-resolution hydrodynamical model and implemented at three different locations of the northern Adriatic shelf. One location is directly affected by the Po River influence, one has more open-sea characteristics and one is located in the Gulf of Trieste with an intermediate behavior; emphasis is put on the comparison with observations and on the functioning of the northern Adriatic ecosystem in the three areas. The work has been performed in a climatological context and has to be considered as preliminary to the development of three-dimensional numerical simulations. Biogeochemical model parameterizations have been ameliorated with a detailed description of bacterial substrate utilization associated with the quality of the dissolved organic matter (DOM, in order to improve the models capability in capturing the observed DOM dynamics in the basin. The coupled model has been calibrated and validated at the three locations by means of climatological data sets. Results show satisfactory model behavior in simulating local seasonal dynamics in the limit of the available boundary conditions and the one-dimensional implementation. Comparisons with available measurements of primary and bacterial production and bacterial abundances have been performed in all locations. Model simulated rates and bacterial dynamics are in the same order of magnitude of observations and show a qualitatively correct time evolution. The importance of temperature as a factor controlling bacteria efficiency is investigated with sensitivity experiments on the model parameterizations.

    The different model behavior and pelagic ecosystem structure developed by the model at the three locations can be attributed to the local hydrodynamical features and interactions with external inputs of nutrients. The onset

  6. 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.

  7. 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.

  8. 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)

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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; 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 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. Finally, 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

  14. A mass-conserving advection scheme for offline simulation of scalar transport in coastal ocean models

    Science.gov (United States)

    Gillibrand, P. A.; Herzfeld, M.

    2016-05-01

    We present a flux-form semi-Lagrangian (FFSL) advection scheme designed for offline scalar transport simulation with coastal ocean models using curvilinear horizontal coordinates. The scheme conserves mass, overcoming problems of mass conservation typically experienced with offline transport models, and permits long time steps (relative to the Courant number) to be used by the offline model. These attributes make the method attractive for offline simulation of tracers in biogeochemical or sediment transport models using archived flow fields from hydrodynamic models. We describe the FFSL scheme, and test it on two idealised domains and one real domain, the Great Barrier Reef in Australia. For comparison, we also include simulations using a traditional semi-Lagrangian advection scheme for the offline simulations. We compare tracer distributions predicted by the offline FFSL transport scheme with those predicted by the original hydrodynamic model, assess the conservation of mass in all cases and contrast the computational efficiency of the schemes. We find that the FFSL scheme produced very good agreement with the distributions of tracer predicted by the hydrodynamic model, and conserved mass with an error of a fraction of one percent. In terms of computational speed, the FFSL scheme was comparable with the semi-Lagrangian method and an order of magnitude faster than the full hydrodynamic model, even when the latter ran in parallel on multiple cores. The FFSL scheme presented here therefore offers a viable mass-conserving and computationally-efficient alternative to traditional semi-Lagrangian schemes for offline scalar transport simulation in coastal models.

  15. Equilibrium models in multimodal container transport systems

    NARCIS (Netherlands)

    Corman, F.; Viti, F.; Negenborn, R.R.

    2015-01-01

    Optimizing the performance of multimodal freight transport networks involves adequately balancing the interplay between costs, volumes, times of departure and arrival, and times of travel. In order to study this interplay, we propose an assignment model that is able to efficiently determine flows an

  16. A depth integrated model for suspended transport

    NARCIS (Netherlands)

    Galappatti, R.

    1983-01-01

    A new depth averaged model for suspended sediment transport in open channels has been developed based on an asymptotic solution to the two dimensional convection-diffusion equation in the vertical plane. The solution for the depth averaged concentration is derived from the bed boundary condition and

  17. 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

  18. 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.

  19. 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Tammer Barkouki; Brian Martinez; Brina Mortensen; Tess Weathers; Jason DeJong; Nic Spycher; Tim Ginn; Yoshiko Fujita; Robert Smith

    2009-09-01

    Microbial ureolysis-induced calcite precipitation may offer an in situ remediation for heavy metal and radionuclide contamination, as well as an alternative to traditional soil strengthening techniques. A microbially mediated calcite precipitation model was built in TOUGHREACT v2 and calibrated to batch and columnar experimental data. Kinetic ureolysis and calcite precipitation-rate expressions were parameterized by coupling TOUCHREACT with UCODE.

  1. 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.

  2. 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.

  3. 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

  4. 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...

  5. Quantifying metabolic rates in submarine hydrothermal vent chimneys: A reaction transport model

    Science.gov (United States)

    LaRowe, D.; Dale, A.; Aguilera, D.; Amend, J. P.; Regnier, P.

    2012-12-01

    The fluids emanating from active submarine hydrothermal vent chimneys provide a window into subseafloor processes and, through mixing with seawater, are responsible for steep thermal and compositional gradients that provide the energetic basis for diverse biological communities. Although several models have been developed to better understand the dynamic interplay of seawater, hydrothermal fluid, minerals and microorganisms inside chimney walls, none provide a fully integrated approach to quantifying the biogeochemistry of these hydrothermal systems. In an effort to remedy this, a fully coupled biogeochemical reaction transport model of a hydrothermal vent chimney has been developed that explicitly quantifies the rate of microbial catalysis while taking into account geochemical processes such as fluid flow, solute transport and oxidation-reduction reactions associated with fluid mixing as a function of temperature. Methanogenesis, hydrogen oxidation by oxygen and sulfate, sulfide oxidation by oxygen and methane oxidation by oxygen and sulfate are the metabolisms included in the reaction network. Model results indicate that microbial catalysis is fastest in the hottest habitable portion of the vent chimney except for methane oxidation by oxygen, which peaks near the seawater-side of the chimney at 20 nmol /cm^3 yr. The dominant metabolisms in the chimney are hydrogen oxidation by sulfate and oxygen and sulfide oxidation at peak rates 3200 , 300 and 900 nmol /cm^3 yr, respectively. The maximum rate of hydrogenotrophic methanogensis is just under 0.07 nmol /cm^3 yr, the slowest of the metabolisms considered. Due to thermodynamic inhibition, there is no anaerobic oxidation of methane by sulfate (AOM). The model developed here provides a quantitative approach to understanding the rates of biogeochemical transformations in hydrothermal systems and can be used to better understand the role of microbial activity in the deep subsurface.

  6. 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

  7. 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.

  8. European initiatives for modeling emissions from transport

    DEFF Research Database (Denmark)

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

    1998-01-01

    covered are the composition of the vehicle fleets, emission factors, driving statistics and the modeling approach. Many of the European initiatives aim also at promoting further cooperation between national laboratories and at defining future research needs. An assessment of these future needs......In Europe there have been many cooperative studies into transport emission inventories since the late 80s. These cover the scope of CORINAIR program involving experts from seven European Community laboratories addressing only road transport emissions at national level. These also include the latest...

  9. Evolution models for mass transportation problems

    CERN Document Server

    Buttazzo, Giuseppe

    2012-01-01

    We present a survey on several mass transportation problems, in which a given mass dynamically moves from an initial configuration to a final one. The approach we consider is the one introduced by Benamou and Brenier in [5], where a suitable cost functional $F(\\rho,v)$, depending on the density $\\rho$ and on the velocity $v$ (which fulfill the continuity equation), has to be minimized. Acting on the functional $F$ various forms of mass transportation problems can be modeled, as for instance those presenting congestion effects, occurring in traffic simulations and in crowd motions, or concentration effects, which give rise to branched structures.

  10. Characterization of Biogeochemical Variability in a Tidal Estuary Using High Resolution Optical Measurements

    Science.gov (United States)

    Chang, G.; Jones, C.; Martin, T.

    2015-12-01

    The Berry's Creek Study Area (BCSA) is a tidal estuary located in New Jersey. Several chemicals of potential concern (COPCs) are present in the BCSA waterway and marshes, including mercury, methyl mercury, and polychlorinated biphenyls. Concentrations of COPCs and suspended solids in the BCSA vary temporally and spatially due to tidal variability, freshwater flow events, and interaction of marsh, waterway, and sediment bed materials. This system-wide variability confounds evaluation of COPC sources and transport mechanisms when using conventional laboratory-based analysis of discrete water column samples. Therefore, an optically-based biogeochemical monitoring program was conducted using near-continuous measurements of optical properties and an optical-biogeochemical partial least-squares regression model pioneered by B. Bergamaschi (USGS) and colleagues. The objective of the study was to characterize COPC concentration dynamics in the BCSA water column and relate the analysis to sediment bed processes. Optical-biogeochemical model results indicated that, in general, measured optical properties were sufficient for predicting COPC concentrations to within 10% of the accuracy of laboratory-based analytical measurements. The continuous, high temporal resolution time series of COPC concentrations determined by the optical-biogeochemical model enabled evaluation of the sediment bed dynamics and variability of COPCs in the surface water of the BCSA. Results indicate that tidally-induced resuspension of waterway sediment bed particulates is the primary mechanism for transport of COPCs to surface water. Waterway-marsh tidal exchange shows a net mass flux of particulate COPCs from waterway to marsh, indicating that particulate COPCs are retained and accumulate in the marshes with relatively little net export of dissolved COPCs from the marshes to the waterway.

  11. 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

  12. 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.

  13. 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

  14. 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)

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. Biogeochemical Cycles in Degraded Lands

    Science.gov (United States)

    Davidson, Eric A.; Vieira, Ima Celia G.; ReisdeCarvalho, Claudio Jose; DeanedeAbreuSa, Tatiana; deSouzaMoutinho, Paulo R.; Figueiredo, Ricardo O.; Stone, Thomas A.

    2004-01-01

    The objectives of this project were to define and describe the types of landscapes that fall under the broad category of "degraded lands" and to study biogeochemical cycles across this range of degradation found in secondary forests. We define degraded land as that which has lost part of its capacity of renovation of a productive ecosystem, either in the context of agroecosystems or as native communities of vegetation. This definition of degradation permits evaluation of biogeochemical constraints to future land uses.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Effects of soil data and simulation unit resolution on quantifying changes of soil organic carbon at regional scale with a biogeochemical process model.

    Directory of Open Access Journals (Sweden)

    Liming Zhang

    Full Text Available Soil organic carbon (SOC models were often applied to regions with high heterogeneity, but limited spatially differentiated soil information and simulation unit resolution. This study, carried out in the Tai-Lake region of China, defined the uncertainty derived from application of the DeNitrification-DeComposition (DNDC biogeochemical model in an area with heterogeneous soil properties and different simulation units. Three different resolution soil attribute databases, a polygonal capture of mapping units at 1:50,000 (P5, a county-based database of 1:50,000 (C5 and county-based database of 1:14,000,000 (C14, were used as inputs for regional DNDC simulation. The P5 and C5 databases were combined with the 1:50,000 digital soil map, which is the most detailed soil database for the Tai-Lake region. The C14 database was combined with 1:14,000,000 digital soil map, which is a coarse database and is often used for modeling at a national or regional scale in China. The soil polygons of P5 database and county boundaries of C5 and C14 databases were used as basic simulation units. Results project that from 1982 to 2000, total SOC change in the top layer (0-30 cm of the 2.3 M ha of paddy soil in the Tai-Lake region was +1.48 Tg C, -3.99 Tg C and -15.38 Tg C based on P5, C5 and C14 databases, respectively. With the total SOC change as modeled with P5 inputs as the baseline, which is the advantages of using detailed, polygon-based soil dataset, the relative deviation of C5 and C14 were 368% and 1126%, respectively. The comparison illustrates that DNDC simulation is strongly influenced by choice of fundamental geographic resolution as well as input soil attribute detail. The results also indicate that improving the framework of DNDC is essential in creating accurate models of the soil carbon cycle.

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

    Directory of Open Access Journals (Sweden)

    M. Chen

    2011-09-01

    Full Text Available 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 Pg C yr−1 and net primary production (NPP ranges from 3.81 to 4.38 Pg C yr−1 and net ecosystem production (NEP varies within 0.08–0.73 Pg C yr−1 over the period 2000–2005 for the conterminous United States. The uncertainty due to parameterization is 0.34, 0.65 and 0.18 Pg C yr−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.

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

    Directory of Open Access Journals (Sweden)

    M. Chen

    2011-03-01

    Full Text Available 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 generally captured the expected temporal and spatial patterns of regional carbon dynamics. We estimate that regional GPP is between 7.02 and 7.78 Pg C yr−1 and Net Primary Production (NPP ranges from 3.81 to 4.38 Pg C yr−1 and Net Ecosystem Production (NEP varies within 0.08–0.73 Pg C yr−1 over the period 2000–2005 for the conterminous United States. The uncertainty due to parameterization is 0.34, 0.65 and 0.18 Pg C yr−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.

  11. 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.

  12. 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

  13. 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...

  14. 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.

  15. 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.

  16. 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

  17. 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)

  18. 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.)

  19. 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.)

  20. Meeting in Turkey: WASP Transport Modeling and WASP Ecological Modeling

    Science.gov (United States)

    A combination of lectures, demonstrations, and hands-on excercises will be used to introduce pollutant transport modeling with the U.S. EPA's general water quality model, WASP (Water Quality Analysis Simulation Program). WASP features include a user-friendly Windows-based interfa...

  1. 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.

  2. 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.

  3. Extracellular Electron Transport Coupling Biogeochemical Processes Centimeters

    DEFF Research Database (Denmark)

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

    2010-01-01

    Recent observations in marine sediment have revealed  conductive networks transmitting electrons from oxidation processes in the anoxic zone to oxygen reduction in the oxiczone [1]. The electrochemical processes and conductors seem to be biologically controlled and may account for more than half...... 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 electron...

  4. Regional CO2 flux estimates from estuarine environments: a reactive-transport modeling approach

    Science.gov (United States)

    Goossens, Nicolas; Laruelle, Goulven G.; Arndt, Sandra; Regnier, Pierre

    2013-04-01

    Estuaries are key components of the land-ocean continuum and play an important role in the global carbon cycle. Large amounts of terrestrial carbon are channelled through estuaries before reaching the ocean. During estuarine transit, numerous biogeochemical processes transform the carbon flux, resulting in a significant CO2 evasion flux to the atmosphere. The global estuarine CO2 outgassing is evaluated at 0.25±0.25 PgC yr-1. Yet, these estimates rely on the extrapolation of local measurements and the scarcity of such measurements conducts to large uncertainties. Furthermore, the global quantification is biased towards anthropogenically impacted estuarine systems located in industrialized countries. Here we provide a first assessment of the estuarine carbon budget and, in particular, CO2 evasion fluxes using a generic and effective reactive-transport model (RTM) approach that is applicable at the regional scale. The new approach is based on the mutual dependency between estuarine geometry and hydrodynamics and uses idealized estuarine geometries. Global river databases (GLORICH) and watershed model outputs (GlobalNEWS) are used to quantify input fluxes for the generic estuarine model. The new modeling approach provides not only a quantification of the estuarine carbon budget, but also allows disentangling the relative contributions of biogeochemical and physical processes to estuarine CO2 emissions. Preliminary results are presented for the North Eastern coast of the US. Model results are consistent with observations and indicate that the net heterotrophy of these systems is the major contributor to estuarine CO2 fluxes (>50%), followed by outgassing of supersaturated riverine waters and nitrification. Results also highlight the strong seasonality in the biogeochemical dynamics. In addition, significant heterogeneity is observed across different estuaries due to spatial heterogeneities in climate forcing, estuarine geometry or riverine input fluxes. The proposed

  5. Io Volcanism: Modeling Vapor And Heat Transport

    Science.gov (United States)

    Allen, Daniel R.; Howell, R. R.

    2010-10-01

    Loki is a large, active volcanic source on Jupiter's moon, Io, whose overall temperatures are well explained by current cooling models, but there are unexplainable subtleties. Using the SO2 atmospheric models of Ingersoll (1989) as a starting point, we are investigating how volatiles, specifically sulfur, are transported on the surface and how they modify the temperatures at Loki and other volcanoes. Voyager images reveal light colored deposits, colloquially called "sulfur bergs,” on Loki's dark patera floor that may be sulfur fumaroles. Galileo images show the presence of red short-chain sulfur deposits around the patera. We are investigating the mechanisms that lead to these features. The light deposits are a few kilometers across. Calculations of the mean free paths for day time conditions on Io indicate lengths on the order of 0.1 km while poorly constrained night time conditions indicate mean free paths about 100 times greater, on the order of what is needed to produce the deposits under ballistic conditions. Preliminary calculations reveal horizontal transport length scales for diffuse transport in a collisional atmosphere of approximately 30 km for sublimating S8 sulfur at 300 K. These length scales would be sufficient to move the sulfur from the warm patera floor to the locations of the red sulfur deposits. At a typical Loki temperature of 300 K, the sublimation/evaporation rate of S8 is a few tens of microns/day. It then requires just a few days to deposit an optically thick 100 µm layer of material. Preliminary length scales and sublimation rates are thus of sufficient scale to produce the deposits. Investigations into the sulfur transport and its effect on temperature are ongoing.

  6. 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

  7. 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.

  8. 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

  9. 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...

  10. 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.

  11. Hydrological Perturbations Drive Biogeochemical Processes in Experimental Soil Columns from the Norman Landfill Site

    Science.gov (United States)

    Arora, B.; Mohanty, B. P.; McGuire, J. T.

    2010-12-01

    Fate and transport of contaminants in saturated and unsaturated zones is governed by biogeochemical processes that are complex and non-linearly coupled to each other. A fundamental understanding of the interactions between transport and reaction processes is essential to better characterize contaminant movement in the subsurface. The objectives of this study are to: i) develop quantitative relationships between hydrological (initial and boundary conditions, hydraulic conductivity ratio, and soil layering), geochemical (mineralogy, surface area, redox potential, and organic matter) and microbiological factors (MPN) that alter the biogeochemical processes, and ii) characterize the effect of hydrologic perturbations on coupled processes occurring at the column scale. The perturbations correspond to rainfall intensity, duration of wet and dry conditions, and water chemistry (pH). Soils collected from two locations with significantly different geochemistry at the Norman landfill site are used in this study. Controlled flow experiments were conducted on: i) two homogeneous soil columns, ii) a layered soil column, iii) a soil column with embedded clay lenses, and iv) a soil column with embedded clay lenses and one central macropore. Experimental observations showed enhanced biogeochemical activity at the interface of the layered and lensed columns over the texturally homogeneous soil columns. Multivariate statistical analysis showed that the most important processes were microbial reduction of Fe(III) and SO42-, and oxidation of reduced products in the columns. Modeling results from HP1 indicate least redox activity in the homogeneous sand column while the structurally heterogeneous columns utilize oxygen and nitrate from recharge as well as iron sulfide minerals already present in the columns as electron acceptors. Furthermore, the interface of the layered and lensed soil columns acts as a hotspot of biogeochemical activity due to increased transport timescale as a

  12. 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)

  13. Risk management model in road transport systems

    Science.gov (United States)

    Sakhapov, R. L.; Nikolaeva, R. V.; Gatiyatullin, M. H.; Makhmutov, M. M.

    2016-08-01

    The article presents the results of a study of road safety indicators that influence the development and operation of the transport system. Road safety is considered as a continuous process of risk management. Authors constructed a model that relates the social risks of a major road safety indicator - the level of motorization. The model gives a fairly accurate assessment of the level of social risk for any given level of motorization. Authors calculated the dependence of the level of socio-economic costs of accidents and injured people in them. The applicability of the concept of socio-economic damage is caused by the presence of a linear relationship between the natural and economic indicators damage from accidents. The optimization of social risk is reduced to finding the extremum of the objective function that characterizes the economic effect of the implementation of measures to improve safety. The calculations make it possible to maximize the net present value, depending on the costs of improving road safety, taking into account socio-economic damage caused by accidents. The proposed econometric models make it possible to quantify the efficiency of the transportation system, allow to simulate the change in road safety indicators.

  14. Modeling charge transport in organic photovoltaic materials.

    Science.gov (United States)

    Nelson, Jenny; Kwiatkowski, Joe J; Kirkpatrick, James; Frost, Jarvist M

    2009-11-17

    The performance of an organic photovoltaic cell depends critically on the mobility of charge carriers within the constituent molecular semiconductor materials. However, a complex combination of phenomena that span a range of length and time scales control charge transport in disordered organic semiconductors. As a result, it is difficult to rationalize charge transport properties in terms of material parameters. Until now, efforts to improve charge mobilities in molecular semiconductors have proceeded largely by trial and error rather than through systematic design. However, recent developments have enabled the first predictive simulation studies of charge transport in disordered organic semiconductors. This Account describes a set of computational methods, specifically molecular modeling methods, to simulate molecular packing, quantum chemical calculations of charge transfer rates, and Monte Carlo simulations of charge transport. Using case studies, we show how this combination of methods can reproduce experimental mobilities with few or no fitting parameters. Although currently applied to material systems of high symmetry or well-defined structure, further developments of this approach could address more complex systems such anisotropic or multicomponent solids and conjugated polymers. Even with an approximate treatment of packing disorder, these computational methods simulate experimental mobilities within an order of magnitude at high electric fields. We can both reproduce the relative values of electron and hole mobility in a conjugated small molecule and rationalize those values based on the symmetry of frontier orbitals. Using fully atomistic molecular dynamics simulations of molecular packing, we can quantitatively replicate vertical charge transport along stacks of discotic liquid crystals which vary only in the structure of their side chains. We can reproduce the trends in mobility with molecular weight for self-organizing polymers using a cheap, coarse

  15. 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

  16. 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

    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...... is localized to account for potential pore size limitations on microbial entry to the clay matrix. The model is used to assess the distribution of TCE and its daughter products in the clay matrix and the concentration of the different compounds at the outlet of the fracture. The time frame for complete cleanup...... 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...

  17. A disaggregate freight transport model of transport chain and shipment size choice

    NARCIS (Netherlands)

    Windisch, E.; De Jong, G.C.; Van Nes, R.; Hoogendoorn, S.P.

    2010-01-01

    The field of freight transport modelling is relatively young compared to passenger transport modelling. However, some key issues in freight policy, like growing freight shares on the road, advanced logistics concepts or emerging strict freight transport regulations, have been creating increasing dem

  18. 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

  19. 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)

  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. 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.

  2. 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.

  3. The Operation Models of Municipal Companies of Local Public Transport

    OpenAIRE

    Wąsowicz, Krzysztof

    2015-01-01

    The economic and legal circumstances of the operation of local public transport are a set of framework guidelines, which form the image of the sphere of transport activity of local governments. The purpose of this paper is to analyze the economic and legal circumstances of the organization and operation of the transport system. This paper presents models of solutions for the organization and operation of the local public transport system: the current model and the new market model. Individual...

  4. 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

  5. Biogeochemical budgets for Tapi Estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Bapardekar, M.V.; DeSousa, S.N.; Zingde, M.D.

    Guidelines were followed to calculate the biogeochemical budges for water, salt and nutrients (DIN and DIP) utilizing the above data. For this purpose, the estuary was split into two boxes based on the salinity gradient. The outer box had an average salinity...

  6. A biogeochemical cycle for aluminium?

    Science.gov (United States)

    Exley, Christopher

    2003-09-15

    The elaboration of biogeochemical cycles for elements which are known to be essential for life has enabled a broad appreciation of the homeostatic mechanisms which underlie element essentiality. In particular they can be used effectively to identify any part played by human activities in element cycling and to predict how such activities might impact upon the lithospheric and biospheric availability of an element in the future. The same criteria were the driving force behind the construction of a biogeochemical cycle for aluminium, a non-essential element which is a known ecotoxicant and a suspected health risk in humans. The purpose of this exercise was to examine the concept of a biogeochemical cycle for aluminium and not to review the biogeochemistry of this element. The cycle as presented is rudimentary and qualitative though, even in this nascent form, it is informative and predictive and, for these reasons alone, it is deserving of future quantification. A fully fledged biogeochemical cycle for aluminium should explain the biospheric abundance of this element and whether we should expect its (continued) active involvement in biochemical evolution.

  7. 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

  8. 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)

  9. 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)

  10. 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)

  11. Numerical Modelling Approaches for Sediment Transport in Sewer Systems

    DEFF Research Database (Denmark)

    Mark, Ole

    constitute the basic modelling system necessary to give a discription of the most dominant physical transport processes concerning particles and dissolved matter in sewer systems: A surface model. An advection-dispersion model. A sediment transport model.......A study of the sediment transport processes in sewers has been carried out. Based on this study a mathematical modelling system has been developed to describe the transport processes of sediments and dissolved matter in sewer systems. The modelling system consists of three sub-models which...

  12. Modeling Transport of Flushed Reservoir Sediment

    Science.gov (United States)

    Dubinski, I. M.

    2014-12-01

    Drawdown flushing of a reservoir is often part of a reservoir sediment management program. Flushing can deliver higher than normal sediment loads to the river channel located downstream of a reservoir. The flushed sediment may contain a higher proportion of finer sediment than what was delivered to a channel prior to the presence of the reservoir. The extent of long-term impacts caused by the flushed sediment on the channel morphology and habitat will in part depend on the residence time of the sediment within the channel. In this study we used MIKE 21C to model the fate of flushed sediment through a river channel where the bed material consists of an armoring layer of gravels overlying finer sediment. MIKE 21C is a two-dimensional curvilinear morphological model for rivers developed by DHI. Curvilinear means that the model grid may curve to better follow the channel and flow direction, for example in a meandering channel. Multiple bed material layers are included in the model to represent the armoring and underlying layers existing in the bed separately from the overlying flushed sediment. These layers may also mix. The nature of the interactions between these two layers helps regulate transport and deposition of the flushed sediment, thus are critical to assessing the fate of the flushed sediment and associated potential impacts.

  13. Signal Processing Model for Radiation Transport

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, D H

    2008-07-28

    This note describes the design of a simplified gamma ray transport model for use in designing a sequential Bayesian signal processor for low-count detection and classification. It uses a simple one-dimensional geometry to describe the emitting source, shield effects, and detector (see Fig. 1). At present, only Compton scattering and photoelectric absorption are implemented for the shield and the detector. Other effects may be incorporated in the future by revising the expressions for the probabilities of escape and absorption. Pair production would require a redesign of the simulator to incorporate photon correlation effects. The initial design incorporates the physical effects that were present in the previous event mode sequence simulator created by Alan Meyer. The main difference is that this simulator transports the rate distributions instead of single photons. Event mode sequences and other time-dependent photon flux sequences are assumed to be marked Poisson processes that are entirely described by their rate distributions. Individual realizations can be constructed from the rate distribution using a random Poisson point sequence generator.

  14. Complexities in coastal sediment transport studies by numerical modelling

    Digital Repository Service at National Institute of Oceanography (India)

    Ilangovan, D.; ManiMurali, R.

    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...

  15. 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...

  16. 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.

  17. 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...

  18. 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....

  19. 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.

  20. 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.

  1. 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)

  2. 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.

  3. Biogeochemical controls of uranium bioavailability from the dissolved phase

    Science.gov (United States)

    Croteau, Marie-Noele; Fuller, Christopher C.; Cain, Daniel J.; Campbell, Kate M.; Aiken, George R.

    2016-01-01

    To gain insights into the risks associated with uranium (U) mining and processing, we investigated the biogeochemical controls of U bioavailability in the model freshwater speciesLymnaea stagnalis (Gastropoda). Bioavailability of dissolved U(VI) was characterized in controlled laboratory experiments over a range of water hardness, pH, and in the presence of complexing ligands in the form of dissolved natural organic matter (DOM). Results show that dissolved U is bioavailable under all the geochemical conditions tested. Uranium uptake rates follow first order kinetics over a range encompassing most environmental concentrations. Uranium uptake rates in L. stagnalis ultimately demonstrate saturation uptake kinetics when exposure concentrations exceed 100 nM, suggesting uptake via a finite number of carriers or ion channels. The lack of a relationship between U uptake rate constants and Ca uptake rates suggest that U does not exclusively use Ca membrane transporters. In general, U bioavailability decreases with increasing pH, increasing Ca and Mg concentrations, and when DOM is present. Competing ions did not affect U uptake rates. Speciation modeling that includes formation constants for U ternary complexes reveals that the aqueous concentration of dicarbonato U species (UO2(CO3)2–2) best predicts U bioavailability to L. stagnalis, challenging the free-ion activity model postulate

  4. 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)

  5. 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

  6. 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.

  7. 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

    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...... 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...

  8. 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

  9. 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.

  10. 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.

  11. 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

  12. Fluid transport processes within sea ice: towards physically derived models

    Science.gov (United States)

    Wells, A. J.; Wettlaufer, J. S.; Orszag, S.

    2012-12-01

    Rather than being an impermeable solid barrier, young sea ice forms a porous matrix of ice crystals through which the interstitial brine can flow. Gravity drainage of dense brine is of particular importance in young sea ice, with the resulting fluid flow redistributing heat, salt, and passive tracers through the ice and controlling exchanges with the ocean. Hence, an understanding of this buoyancy-driven flow is critical for quantifying ice-ocean tracer fluxes, biogeochemical cycles, and evolution of the salinity-dependent material properties of ice that influence growth and decay. We use mushy layer theory, which describes the thermodynamics of the relevant multiphase flow, simulations and analogue experiments to provide insight into these processes. The approach provides a structure to evaluate ad-hoc parameterizations of brine drainage for consistency with the underlying physics. The resulting theoretical framework points towards a bottom-up approach to deriving models via a homogenization of the underlying physical processes.

  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. Combinatorial model of solute transport in porous media

    Institute of Scientific and Technical Information of China (English)

    张妙仙; 张丽萍

    2004-01-01

    Modeling of solute transport is a key issue in the area of soil physics and hydrogeology. The most common approach (the convection-dispersion equation) considers an average convection flow rate and Fickian-like dispersion. Here,we propose a solute transport model in porous media of continuously expanding scale, according to the combinatorics principle. The model supposed actual porous media as a combinative body of many basic segments. First, we studied the solute transport process in each basic segment body, and then deduced the distribution of pore velocity in each basic segment body by difference approximation, finally assembled the solute transport process of each basic segment body into one of the combinative body. The simulation result coincided with the solute transport process observed in test. The model provides useful insight into the solute transport process of the non-Fickian dispersion in continuously expanding scale.

  15. Towards Biogeochemical Modeling of Anaerobic Oxidation of Methane: Characterization of Microbial Communities in Methane-bearing North American Continental Margin Sediments

    Science.gov (United States)

    Graw, M. F.; Solomon, E. A.; Chrisler, W.; Krause, S.; Treude, T.; Ruppel, C. D.; Pohlman, J.; Colwell, F. S.

    2015-12-01

    Methane advecting through continental margin sediments may enter the water column and potentially contribute to ocean acidification and increase atmospheric methane concentrations. Anaerobic oxidation of methane (AOM), mediated by syntrophic consortia of anaerobic methanotrophic archaea and sulfate-reducing bacteria (ANME-SRB), consumes nearly all dissolved methane in methane-bearing sediments before it reaches the sediment-water interface. Despite the significant role ANME-SRB play in carbon cycling, our knowledge of these organisms and their surrounding microbial communities is limited. Our objective is to develop a metabolic model of ANME-SRB within methane-bearing sediments and to couple this to a geochemical reaction-transport model for these margins. As a first step towards this goal, we undertook fluorescent microscopic imaging, 16S rRNA gene deep-sequencing, and shotgun metagenomic sequencing of sediments from the US Pacific (Washington) and northern Atlantic margins where ANME-SRB are present. A successful Illumina MiSeq sequencing run yielded 106,257 bacterial and 857,834 archaeal 16S rRNA gene sequences from 12 communities from the Washington Margin using both universal prokaryotic and archaeal-specific primer sets. Fluorescent microscopy confirmed the presence of cells of the ANME-2c lineage in the sequenced communities. Microbial community characterization was coupled with measurements of sediment physical and geochemical properties and, for samples from the US Atlantic margin, 14C-based measurements of AOM rates and 35S-based measurements of sulfate reduction rates. These findings have the potential to increase understanding of ANME-SRB, their surrounding microbial communities, and their role in carbon cycling within continental margins. In addition, they pave the way for future efforts at developing a metabolic model of ANME-SRB and coupling it to geochemical models of the US Washington and Atlantic margins.

  16. Biogeochemical cycling and remote sensing

    Science.gov (United States)

    Peterson, D. L.

    1985-01-01

    Research is underway at the NASA Ames Research Center that is concerned with aspects of the nitrogen cycle in terrestrial ecosystems. An interdisciplinary research group is attempting to correlate nitrogen transformations, processes, and productivity with variables that can be remotely sensed. Recent NASA and other publications concerning biogeochemical cycling at global scales identify attributes of vegetation that could be related or explain the spatial variation in biologically functional variables. These functional variables include net primary productivity, annual nitrogen mineralization, and possibly the emission rate of nitrous oxide from soils.

  17. 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.

  18. 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...

  19. 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.

  20. Spatio-temporal evolution of biogeochemical processes at a landfill site

    Science.gov (United States)

    Arora, B.; Mohanty, B. P.; McGuire, J. T.

    2011-12-01

    Predictions of fate and transport of contaminants are strongly dependent on spatio-temporal variability of soil hydraulic and geochemical properties. This study focuses on time-series signatures of hydrological and geochemical properties at different locations within the Norman landfill site. Norman Landfill is a closed municipal landfill site with prevalent organic contamination. Monthly data at the site include specific conductance, δ18O, δ2H, dissolved organic carbon (DOC) and anions (chloride, sulfate, nitrate) from 1998-2006. Column scale data on chemical concentrations, redox gradients, and flow parameters are also available on daily and hydrological event (infiltration, drainage, etc.) scales. Since high-resolution datasets of contaminant concentrations are usually unavailable, Wavelet and Fourier analyses were used to infer the dominance of different biogeochemical processes at different spatio-temporal scales and to extract linkages between transport and reaction processes. Results indicate that time variability controls the progression of reactions affecting biodegradation of contaminants. Wavelet analysis suggests that iron-sulfide reduction reactions had high seasonal variability at the site, while fermentation processes dominated at the annual time scale. Findings also suggest the dominance of small spatial features such as layered interfaces and clay lenses in driving biogeochemical reactions at both column and landfill scales. A conceptual model that caters to increased understanding and remediating structurally heterogeneous variably-saturated media is developed from the study.

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

    OpenAIRE

    Picone, Rico A. R.; Garbini, Joseph L.; Sidles, John A.

    2013-01-01

    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 fo...

  2. 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

  3. 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

  4. 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.

  5. 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

  6. Mathematical Modelling of Cation Transport and Regulation in Yeast.

    Science.gov (United States)

    Kahm, Matthiasé; Kschischo, Maik

    2016-01-01

    Mathematical modelling of ion transport is a strategy to understand the complex interplay between various ionic species and their transporters. Such models should provide new insights and suggest new interesting experiments. Two essential variables in models for ion transport and control are the membrane potential and the intracellular pH, which generates an additional layer of complexity absent from many other models of biochemical reaction pathways. The aim of this text is to introduce the reader to the basic principles and assumptions of modelling in this field. A simplified model of potassium transport will be used as an example and will be derived in a step by step manner. This forms the basis for understanding the advantages and limitations of more complex models. These are briefly reviewed at the end of this chapter.

  7. Implementation of Gravity Model to Estimation of Transportation Market Shares

    Science.gov (United States)

    Krata, Przemysław

    2010-03-01

    The theoretical consideration presented in the paper is inspired by market gravity models, as an interesting attitude towards operations research on a market. The transportation market issues are emphasized. The mathematical model of relations, taking place between transportation companies and their customers on the market, which is applied in the course of the research is based on continuous functions characteristics. This attitude enables the use of the field theory notions. The resultant vector-type utility function facilitates obtaining of competitive advantage areas for all transportation companies located on the considered transportation market.

  8. 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

  9. 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.

  10. 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

  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.

  12. 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...

  13. Reduced Fast Ion Transport Model For The Tokamak Transport Code TRANSP

    Energy Technology Data Exchange (ETDEWEB)

    Podesta,, Mario; Gorelenkova, Marina; White, Roscoe

    2014-02-28

    Fast ion transport models presently implemented in the tokamak transport code TRANSP [R. J. Hawryluk, in Physics of Plasmas Close to Thermonuclear Conditions, CEC Brussels, 1 , 19 (1980)] are not capturing important aspects of the physics associated with resonant transport caused by instabilities such as Toroidal Alfv en Eigenmodes (TAEs). This work describes the implementation of a fast ion transport model consistent with the basic mechanisms of resonant mode-particle interaction. The model is formulated in terms of a probability distribution function for the particle's steps in phase space, which is consistent with the MonteCarlo approach used in TRANSP. The proposed model is based on the analysis of fast ion response to TAE modes through the ORBIT code [R. B. White et al., Phys. Fluids 27 , 2455 (1984)], but it can be generalized to higher frequency modes (e.g. Compressional and Global Alfv en Eigenmodes) and to other numerical codes or theories.

  14. 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.

  15. Particle Tracking Model and Abstraction of Transport Processes

    Energy Technology Data Exchange (ETDEWEB)

    B. Robinson

    2004-10-21

    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.

  16. 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

  17. Paving the road from transport models to “new mobilities” models

    DEFF Research Database (Denmark)

    Wind, Simon; Jensen, Ole B.; Kaplan, Sigal;

    2012-01-01

    For half a century, tremendous efforts have been invested in developing transport models as a decision aid for policy makers in designing effective policy interventions and deciding among costly public projects for the benefit of the population. Transport and activity-based models are often...... the traditional transport modeling approach and “new mobilities” research by suggesting a model framework that considers non-instrumental transport rationales, personal latent traits and intra-household decision dynamics....

  18. Mathematical modeling of sediment transport jn estuaries and coastal regions

    Institute of Scientific and Technical Information of China (English)

    窦国仁; 董凤舞; 窦希萍; 李禔来

    1995-01-01

    Based on the suspended sediment transport equation and transport capacity formula under the action of tidal currents and wind waves, a horizontal 2-D mathematical model of suspended sediment transport for estuaries and coastal regions is established. The verification of calculations shows that the sediment concentration distribution and sea bed deformation in the estuaries and coastal regions can be successfully simulated. Therefore, a new method for studying and solving the sediment problems in the estuarine and coastal engineering is presented.

  19. 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

  20. Logistics chains in freight transport modelling

    NARCIS (Netherlands)

    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, w

  1. Entropy based transportation model: A geometric programming approach

    Directory of Open Access Journals (Sweden)

    Samanta Bablu

    2007-01-01

    Full Text Available The entropy model has attached a good deal of attention in transportation analysis, urban and regional planning as well as in other areas. This paper shows the equivalence of entropy maximization models to geometric programs. To provide a better understanding of this entropy based transportation model they are analyzed by geometric programming. Dual mathematical programs and algorithms are also obtained and are supported by an illustrative example. .

  2. Integration of Genome-Scale Metabolic Nodels of Iron-Reducing Bacteria With Subsurface Flow and Geochemical Reactive Transport Models

    Science.gov (United States)

    Scheibe, T. D.; Mahadevan, R.; Fang, Y.; Garg, S.; Long, P. E.; Lovley, D. M.

    2008-12-01

    Several field and laboratory experiments have demonstrated that the growth and activity of iron-reducing bacteria can be stimulated in many subsurface environments by amendment of groundwater with a soluble electron donor. Under strong iron-reducing conditions, these organisms mediate reactions that can impact a wide range of subsurface contaminants including chlorinated hydrocarbons, metals, and radionuclides. Therefore there is strong interest in in-situ bioremediation as a potential technology for cleanup of contaminated aquifers. To evaluate and design bioremediation systems, as well as to evaluate the viability of monitored natural attenuation as an alternative, quantitative models of biogeochemically reactive transport are needed. To date, most such models represent microbial activity in terms of kinetic rate (e.g., Monod- type) formulations. Such models do not account for fundamental changes in microbial functionality (such as utilization of alternative respiratory pathways) that occur as the result of spatial and temporal variations in the geochemical environment experienced by microorganisms. Constraint-based genome-scale in silico models of microbial metabolism present an alternative to simplified rate formulations that provide flexibility to account for changes in microbial function in response to local geochemical conditions. We have developed and applied a methodology for coupling a constraint-based in silico model of Geobacter sulfurreducens with a conventional model of groundwater flow, transport, and geochemical reaction. Two uses of the in silico model are tested: 1) incorporation of modified microbial growth yield coefficients based on the in silico model, and 2) variation of reaction rates in a reactive transport model based on in silico modeling of a range of local geochemical conditions. Preliminary results from this integrated model will be presented.

  3. 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

    to steady state versus transient flow conditions and to the amount of hydraulic and solute data used is investigated. The flow parameters, transmissivity and leakage factor, are estimated simultaneously with the transport parameters: source strength, porosity, and longitudinal dispersivity. This paper...... and transport simulation model is combined with nonlinear least squares multiple regression. The U.S. Geological Survey method of characteristics model is used to simulate flow and transport, and the optimization part is solved using a Levenberg-Marquardt algorithm. The sensitivity of the optimization approach...

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. Modeling Quantum Transport in Nanoscale Vertical SOI nMOSFET

    Institute of Scientific and Technical Information of China (English)

    TONG Jian-nong; ZOU Xue-chang; SHEN Xu-bang

    2004-01-01

    The electron transports in micro-architecture semiconductor are simulated using vertical SOI nMOSFET with different models. Some details in transport can be presented by changing channel length, channel thickness and drain voltage. An interesting phenomenon similar to collimation effect in mesoscopic system is observed. This may suggest the quite intriguing possibility that scattering may open new channel in sufficiently narrow devices.

  12. Diel biogeochemical processes in terrestrial waters

    Science.gov (United States)

    Compiled and Edited by Nimick, David A.; Gammons, Christopher H.

    2011-01-01

    scientists typically do not encompass the wide diversity and range of processes that produce diel cycles, and (3) the logistics of making field measurements for 24-h periods has limited recognition and understanding of these important cycles. Thus, the topical session brought together hydrologists, biologists, geochemists, and ecologists to discuss field studies, laboratory experiments, theoretical modeling, and measurement techniques related to diel cycling. Hopefully with the cross-disciplinary synergy developed at the session as well as by this special issue, a more comprehensive understanding of the interrelationships between the diel processes will be developed. Needless to say, understanding diel processes is critical for regulatory agencies and the greater scientific community. And perhaps more importantly, expanded knowledge of biogeochemical cycling may lead to better predictions of how aquatic ecosystems might react to changing conditions of contaminant loading, eutrophication, climate change, drought, industrialization, development, and other variables.

  13. Using Transport Diagnostics to Understand Chemistry Climate Model Ozone Simulations

    Science.gov (United States)

    Strahan, S. E.; Douglass, A. R.; Stolarski, R. S.; Akiyoshi, H.; Bekki, S.; Braesicke, P.; Butchart, N.; Chipperfield, M. P.; Cugnet, D.; Dhomse, S.; Frith, S. M.; Gettleman, A.; Hardiman, S. C.; Kinnison, D. E.; Lamarque, J.-F.; Mancini, E.; Marchand, M.; Michou, M.; Morgenstern, O.; Nakamura, T.; Olivie, D.; Pawson, S.; Pitari, G.; Plummer, D. A.; Pyle, J. A.

    2010-01-01

    We demonstrate how observations of N2O and mean age in the tropical and midlatitude lower stratosphere (LS) can be used to identify realistic transport in models. The results are applied to 15 Chemistry Climate Models (CCMs) participating in the 2010 WMO assessment. Comparison of the observed and simulated N2O/mean age relationship identifies models with fast or slow circulations and reveals details of model ascent and tropical isolation. The use of this process-oriented N2O/mean age diagnostic identifies models with compensating transport deficiencies that produce fortuitous agreement with mean age. We compare the diagnosed model transport behavior with a model's ability to produce realistic LS O3 profiles in the tropics and midlatitudes. Models with the greatest tropical transport problems show the poorest agreement with observations. Models with the most realistic LS transport agree more closely with LS observations and each other. We incorporate the results of the chemistry evaluations in the SPARC CCMVal Report (2010) to explain the range of CCM predictions for the return-to-1980 dates for global (60 S-60 N) and Antarctic column ozone. Later (earlier) Antarctic return dates are generally correlated to higher (lower) vortex Cl(sub y) levels in the LS, and vortex Cl(sub y) is generally correlated with the model's circulation although model Cl(sub y) chemistry or Cl(sub y) conservation can have a significant effect. In both regions, models that have good LS transport produce a smaller range of predictions for the return-to-1980 ozone values. This study suggests that the current range of predicted return dates is unnecessarily large due to identifiable model transport deficiencies.

  14. Biogeochemical and Hydrological Heterogeneity and Emergent Archetypical Catchment Response Patterns

    Science.gov (United States)

    Jawitz, J. W.; Gall, H. E.; Rao, P. S.

    2014-12-01

    What can stream hydrologic and biogeochemical signals tell us about interactions among spatially heterogeneous hydrological and biogeochemical processes at the catchment-scale? We seek to understand how the spatial structure of solute sources coupled with both stationary and nonstationary hydroclimatic drivers affect observed archetypes of concentration-discharge (C-Q) patterns. These response patterns are the spatially integrated expressions of the spatiotemporal structure of solutes exported from managed catchments, and can provide insight into likely ecological consequences of receiving water bodies (e.g., wetlands, rivers, lakes, and coastal waters). We investigated the following broad questions: (1) How does the spatial correlation between the structure of flow-generating areas and biogeochemical source areas across a catchment evolve under stochastic hydro-climatic forcing? (2) What are the feasible hydrologic and biogeochemical responses that lead to the emergence of archetypical C-Q patterns? and; (3) What implications do these coupled dynamics have for catchment monitoring and implementation of management practices? We categorize the observed temporal signals into three archetypical C-Q patterns: dilution; accretion, and constant concentration. We applied a parsimonious stochastic model of heterogeneous catchments, which act as hydrologic and biogeochemical filters, to examine the relationship between spatial heterogeneity and temporal history of solute export signals. The core concept of the modeling framework is considering the type and degree of spatial correlation between solute source zones and flow generating zones, and activation of different portions of the catchments during rainfall events. Our overarching hypothesis is that each archetype C-Q pattern can be generated by explicitly linking landscape-scale hydrologic responses and spatial distributions of solute source properties within a catchment. We compared observed multidecadal data to

  15. 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

  16. Modelling Transition Towards Sustainable Transportation Sector

    DEFF Research Database (Denmark)

    Dominkovic, Dominik Franjo; Bačeković, I.; Mýrdal, Jón Steinar Garðarsson;

    2016-01-01

    fuels, biofuels, hydrogen and synthetic fuels utilizing excess intermittentelectricity generation. Results showed that the 72.3% of the fossil fuel demand in transportationsector of the European Union (EU) can be replaced by electricity demand, reducing final energydemand in transportation sector for 50...... equal to 3,069 TWh, which is extremely challenging tomeet in the future in a sustainable way. In the case of synthetic fuel production as an alternative,additional electricity demand was calculated to be 2,775 TWh, which is approximately 90% of thetotal electricity demand of the EU for the year 2013.......6% or 2,051 TWh. All the alternatives for the non-electrifiedpart of transportation suffer from the low well-to-wheel efficiency, resulting in a significant amountof additional resources needed. Replacing remaining part of the fossil fuels by biofuels led to theincreased demand for biomass on EU level...

  17. Hybrid Multiscale Simulation of Hydrologic and Biogeochemical Processes in the River-Groundwater Interaction Zone

    Science.gov (United States)

    Yang, X.; Scheibe, T. D.; Chen, X.; Hammond, G. E.; Song, X.

    2015-12-01

    The zone in which river water and groundwater mix plays an important role in natural ecosystems as it regulates the mixing of nutrients that control biogeochemical transformations. Subsurface heterogeneity leads to local hotspots of microbial activity that are important to system function yet difficult to resolve computationally. To address this challenge, we are testing a hybrid multiscale approach that couples models at two distinct scales, based on field research at the U. S. Department of Energy's Hanford Site. The region of interest is a 400 x 400 x 20 m macroscale domain that intersects the aquifer and the river and contains a contaminant plume. However, biogeochemical activity is high in a thin zone (mud layer, hybrid multiscale approach is used to efficiently and accurately predict flow and reactive transport at both scales. In our simulations, models at both scales are simulated using the PFLOTRAN code. Multiple microscale simulations in dynamically defined sub-domains (fine resolution, complex reaction network) are executed and coupled with a macroscale simulation over the entire domain (coarse resolution, simpler reaction network). The objectives of the research include: 1) comparing accuracy and computing cost of the hybrid multiscale simulation with a single-scale simulation; 2) identifying hot spots of microbial activity; and 3) defining macroscopic quantities such as fluxes, residence times and effective reaction rates.

  18. Fluid transport and ion fluxes in mammalian kidney proximal tubule: a model analysis of isotonic transport

    DEFF Research Database (Denmark)

    Larsen, Erik Hviid; Møbjerg, N.; Sørensen, J. N.

    2006-01-01

    Aim: By mathematical modelling, we analyse conditions for near-isotonic and isotonic transport by mammalian kidney proximal tubule. Methods: The model comprises compliant lateral intercellular space (lis) and cells, and infinitely large luminal and peritubular compartments with diffusible species......: Na+, K+, Cl- and an intracellular non-diffusible anion. Unknown model variables are solute concentrations, electrical potentials, volumes and hydrostatic pressures in cell and lis, and transepithelial potential. We used data mainly from rat proximal tubule to model epithelial cells and interspace...... transport similar to rat proximal tubule. Na+ recirculation is required for truly isotonic transport. The tonicity of the absorbate and the recirculation flux depend critically on ion permeabilities of interspace basement membrane. Conclusion: Our model based on solute-solvent coupling in lateral space...

  19. Modeling Reactive Transport in Coupled Groundwater-Conduit Systems

    Science.gov (United States)

    Spiessl, S. M.; Sauter, M.; Zheng, C.; Viswanathan, H. S.

    2002-05-01

    Modeling reactive transport in coupled groundwater-conduit systems requires consideration of two transport time scales in the flow and transport models. Consider for example a subsurface mine consisting of a network of highly conductive shafts, drifts or ventilation raises (i.e., conduits) within the considerably less permeable ore material (i.e., matrix). In the conduits, potential contaminants can travel much more rapidly than in the background aquifer (matrix). Since conduits cannot necessarily be regarded as a continuum, double continuum models are only of limited use for simulation of contaminant transport in such coupled groundwater-conduit systems. This study utilizes a "hybrid" flow and transport model in which contaminants can in essence be transported at a slower time scale in the matrix and at a faster time scale in the conduits. The hybrid flow model uses an approach developed by Clemens et al. (1996), which is based on the modelling of flow in a discrete pipe network, coupled to a continuum representing the low-permeability inter-conduit matrix blocks. Laminar or turbulent flow can be simulated in the different pipes depending on the flow conditions in the model domain. The three-dimensional finite-difference groundwater flow model MODFLOW (Harbaugh and McDonald, 1996) is used to simulate flow in the continuum. Contaminant transport within the matrix is simulated with a continuum approach using the three-dimensional multi-species solute transport model MT3DMS (Zheng and Wang, 1999), while that in the conduit system is simulated with a one-dimensional advective transport model. As a first step for reactive transport modeling in such systems, only equilibrium reactions among multiple species are considered by coupling the hybrid transport model to a geochemical speciation package. An idealized mine network developed by Viswanathan and Sauter (2001) is used as a test problem in this study. The numerical experiment is based on reference date collected from

  20. Metal transport across biomembranes: emerging models for a distinct chemistry.

    Science.gov (United States)

    Argüello, José M; Raimunda, Daniel; González-Guerrero, Manuel

    2012-04-20

    Transition metals are essential components of important biomolecules, and their homeostasis is central to many life processes. Transmembrane transporters are key elements controlling the distribution of metals in various compartments. However, due to their chemical properties, transition elements require transporters with different structural-functional characteristics from those of alkali and alkali earth ions. Emerging structural information and functional studies have revealed distinctive features of metal transport. Among these are the relevance of multifaceted events involving metal transfer among participating proteins, the importance of coordination geometry at transmembrane transport sites, and the presence of the largely irreversible steps associated with vectorial transport. Here, we discuss how these characteristics shape novel transition metal ion transport models.

  1. 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...

  2. 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...

  3. 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

  4. 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.)

  5. Modelling sediment transport processes in macro-tidal estuary

    Institute of Scientific and Technical Information of China (English)

    Rauen; William; B.

    2009-01-01

    This paper outlines a numerical modeling study to predict the sediment transport processes in a macro-tidal estuary, namely the Mersey Estuary, UK. An integrated numerical model study is conducted to investigate the interaction between the hydrodynamic, morphological and sediment transport processes occurring in the estuary. The numerical model widely used in environmental sediment transport studies worldwide, namely ECOMSED is used to simulate flow and sediment transport in estuary. A wetting and drying scheme is proposed and applied to the model, which defines "dry" cells as regions with a thin film of fluid O (cm). The primitive equations are solved in the thin film as well as in other regular wet cells. A model for the bed load transport is included in the code to account for the dynamics of the mobile bed boundary. The bed evolution due to bed load transport which is calculated according to van Rijn (1984a) is obtained by solving the sediment mass-balance equation. An estuary-related laboratory flume experiment is used to verify the model. Six sets of field measured hydrodynamic data are used to verify the corresponding predictions of the model, with the model-predicted water elevations and salinity levels generally agreeing well with the field measurements. The numerical model results show that in the Mersey Estuary both the tidal level and river discharge affect significantly the sediment transport. Reasonable agreement between the model results and field data has been obtained, indicating that the model can be used as computer-based tool for the environment management of estuarine system.

  6. 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.

  7. 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

  8. Modelling of hydrodynamics and mecury transport in lake Velenje. Part 2, Modelling and model verification

    OpenAIRE

    Kotnik, Jože; ŽAGAR, Dušan; Rajar, Rudi; Horvat, Milena

    2004-01-01

    PCFLOW3D - a three-dimensional mathematical model that was developed at the Chair of Fluid Mechanics of the Faculty of Civil and Geodetic Engineering, University of Ljubljana, was used for hydrodynamic and Hg transport simulations in Lake Velenje. The model is fully non-linear and computes three velocity components, water elevation and pressure. Transport-dispersion equations for salinity and heat (and/or any pollutant) are further used to compute the distributions of these par...

  9. 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.

  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. Electron transport model of dielectric charging

    Science.gov (United States)

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

    1979-01-01

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

  12. 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.

  13. 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

  14. 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...

  15. 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)

  16. Probabilistic transport models for plasma transport in the presence of critical thresholds: Beyond the diffusive paradigma)

    Science.gov (United States)

    Sánchez, R.; van Milligen, B. Ph.; Carreras, B. A.

    2005-05-01

    It is argued that the modeling of plasma transport in tokamaks may benefit greatly from extending the usual local paradigm to accommodate scale-free transport mechanisms. This can be done by combining Lévy distributions and a nonlinear threshold condition within the continuous time random walk concept. The advantages of this nonlocal, nonlinear extension are illustrated by constructing a simple particle density transport model that, as a result of these ideas, spontaneously exhibits much of nondiffusive phenomenology routinely observed in tokamaks. The fluid limit of the system shows that the kind of equations that are appropriate to capture these dynamics are based on fractional differential operators. In them, effective diffusivities and pinch velocities are found that are dynamically set by the system in response to the specific characteristics of the fueling source and external perturbations. This fact suggests some dramatic consequences for the extrapolation of these transport properties to larger size systems.

  17. Transport modelling in coastal waters using stochastic differential equations

    NARCIS (Netherlands)

    Charles, W.M.

    2007-01-01

    In this thesis, the particle model that takes into account the short term correlation behaviour of pollutants dispersion has been developed. An efficient particle model for sediment transport has been developed. We have modified the existing particle model by adding extra equations for the suspensio

  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. 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)

  1. Economic model of pipeline transportation systems

    Energy Technology Data Exchange (ETDEWEB)

    Banks, W. F.

    1977-07-29

    The objective of the work reported here was to develop a model which could be used to assess the economic effects of energy-conservative technological innovations upon the pipeline industry. The model is a dynamic simulator which accepts inputs of two classes: the physical description (design parameters, fluid properties, and financial structures) of the system to be studied, and the postulated market (throughput and price) projection. The model consists of time-independent submodels: the fluidics model which simulates the physical behavior of the system, and the financial model which operates upon the output of the fluidics model to calculate the economics outputs. Any of a number of existing fluidics models can be used in addition to that developed as a part of this study. The financial model, known as the Systems, Science and Software (S/sup 3/) Financial Projection Model, contains user options whereby pipeline-peculiar characteristics can be removed and/or modified, so that the model can be applied to virtually any kind of business enterprise. The several dozen outputs are of two classes: the energetics and the economics. The energetics outputs of primary interest are the energy intensity, also called unit energy consumption, and the total energy consumed. The primary economics outputs are the long-run average cost, profit, cash flow, and return on investment.

  2. Mineral dust aerosols over the Sahara: Meteorological controls on emission and transport and implications for modeling

    Science.gov (United States)

    Knippertz, Peter; Todd, Martin C.

    2012-02-01

    Atmospheric mineral dust has recently become an important research field in Earth system science because of its impacts on radiation, clouds, atmospheric dynamics and chemistry, air quality, and biogeochemical cycles. Studying and modeling dust emission and transport over the world's largest source region, the Sahara, is particularly challenging because of the complex meteorology and a very sparse observational network. Recent advances in satellite retrievals together with ground- and aircraft-based field campaigns have fostered our understanding of the spatiotemporal variability of the dust aerosol and its atmospheric drivers. We now have a more complete picture of the key processes in the atmosphere associated with dust emission. These cover a range of scales from (1) synoptic scale cyclones in the northern sector of the Sahara, harmattan surges and African easterly waves, through (2) low-level jets and cold pools of mesoscale convective systems (particularly over the Sahel), to (3) microscale dust devils and dusty plumes, each with its own pronounced diurnal and seasonal characteristics. This paper summarizes recent progress on monitoring and analyzing the dust distribution over the Sahara and discusses implications for numerical modeling. Among the key challenges for the future are a better quantification of the relative importance of single processes and a more realistic representation of the effects of the smaller-scale meteorological features in dust models. In particular, moist convection has been recognized as a major limitation to our understanding because of the inability of satellites to observe dust under clouds and the difficulties of numerical models to capture convective organization.

  3. 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

  4. 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 ...

  5. 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...... in 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...... classes of chemicals and nanoparticles for comparisons across chemical structures as well as different test systems. Our test systems are based on human material to bypass the extrapolation from animal data. By combining data from our two test systems, we are able to rank and compare the transport...

  6. Collisional broadening of angular correlations in a multiphase transport model

    CERN Document Server

    Edmonds, Terrence; Wang, Fuqiang

    2016-01-01

    Systematic comparisons of jetlike correlation data to radiative and collisional energy loss model calculations are essential to extract transport properties of the quark-gluon medium created in relativistic heavy ion collisions. This paper presents a transport study of collisional broadening of jetlike correlations, by following parton-parton collision history in a multiphase transport (AMPT) model. The correlation shape is studied as a function of the number of parton-parton collisions suffered by a high transverse momentum probe parton ($N_{\\rm coll}$) and the azimuth of the probe relative to the reaction plane ($\\phi_{\\rm fin.}^{\\rm probe}$). Correlation is found to broaden with increasing $N_{\\rm coll}$ and $\\phi_{\\rm fin.}^{\\rm probe}$ from in- to out-of-plane direction. This study provides a transport model benchmark for future jet-medium interaction studies.

  7. 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.

  8. 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

  9. 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))

  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. 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.

  12. 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.

  13. Model prodrugs for the intestinal oligopeptide transporter

    DEFF Research Database (Denmark)

    Nielsen, C U; Andersen, R; Brodin, Birger;

    2001-01-01

    (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......-moieties for 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...... media. The release rates of all the investigated model drug molecules followed first-order kinetics and were dependent on buffer concentration, pH, ionic strength, and model drug electronegativity. The electronegativity of the model drug influenced acid, water and base catalyzed release from D...

  14. 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.

  15. 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.

  16. A quasi-linear gyrokinetic transport model for tokamak plasmas

    CERN Document Server

    Casati, Alessandro

    2012-01-01

    The development of a quasi-linear gyrokinetic transport model for tokamak plasmas, ultimately designed to provide physically comprehensive predictions of the time evolution of the thermodynamic relevant quantities, is a task that requires tight links among theoretical, experimental and numerical studies. The framework of the model here proposed, which operates a reduction of complexity on the nonlinear self-organizing plasma dynamics, allows in fact multiple validations of the current understanding of the tokamak micro-turbulence. The main outcomes of this work stem from the fundamental steps involved by the formulation of such a reduced transport model, namely: (1) the verification of the quasi-linear plasma response against the nonlinearly computed solution, (2) the improvement of the turbulent saturation model through an accurate validation of the nonlinear codes against the turbulence measurements, (3) the integration of the quasi-linear model within an integrated transport solver.

  17. Examining an important urban transportation management tool: subarea modeling

    Directory of Open Access Journals (Sweden)

    Xueming CHEN

    2009-12-01

    Full Text Available At present, customized subarea models have been widely used in local transportation planning throughout the United States. The biggest strengths of a subarea model lie in its more detailed and accurate modeling outputs which better meet local planning requirements. In addition, a subarea model can substantially reduce database size and model running time. In spite of these advantages, subarea models remain quite weak in maintaining consistency with a regional model, modeling transit projects, smart growth measures, air quality conformity, and other areas. Both opportunities and threats exist for subarea modeling. In addition to examining subarea models, this paper introduces the decision-making process in choosing a proper subarea modeling approach (windowing versus focusing and software package. This study concludes that subarea modeling will become more popular in the future. More GIS applications, travel surveys, transit modeling, microsimulation software utilization, and other modeling improvements are expected to be incorporated into the subarea modeling process.

  18. 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.

  19. 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.

  20. 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.

  1. 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)

  2. 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

  3. 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)

  4. 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.

  5. A Coupled Chemical and Mass Transport Model for Concrete Durability

    DEFF Research Database (Denmark)

    Jensen, Mads Mønster; Johannesson, Björn; Geiker, Mette Rica

    2012-01-01

    In this paper a general continuum theory is used to evaluate the service life of cement based materials, in terms of mass transport processes and chemical degradation of the solid matrix. The model established is a reactive mass transport model, based on an extended version of the Poisson...... curves which is established from a set of mathematical criteria. The chemical degradation is modelled with the geochemical code iphreeqc, which provides a general tool for evaluating different paste compositions. The governing system of equations is solved by the finite element method with a Newton...... simulation. The relative simple test cases show that sorption hysteresis cannot be neglected in a mass transport model for cement based materials and a description of the chemical degradation is crucial for long term simulation of service life prediction....

  6. Sediment Transport and Water Quality Model of Cedar Lake, Indiana

    Science.gov (United States)

    James, S. C.; Jones, C. A.; Roberts, J. D.; Ahlmann, M.; Bucaro, D. A.

    2006-12-01

    The EPA-supported Environmental Fluid Dynamics Code, EFDC, is used to model hydrodynamics, sediment transport, and water quality in coastal regions, estuaries, rivers, and lakes. However, the empirical formulations used for sediment transport are not always adequate to accurately characterize cohesive sediment erosion and transport. New sediment transport subroutines have been incorporated into EFDC and the new model is called SNL-EFDC. The updated model provides an improved, coupled hydrodynamics, sediment transport, and water quality framework. The newly incorporated sediment transport subroutines facilitate direct use of measured erosion rate data from the Sediment Erosion with Depth Flume (SEDflume). Erosion rates are included as functions of both depth within the sediment bed and applied shear stresses. This bypasses problems associated with empirical erosion formulations often based on disaggregated particle size. Restoration alternatives are under consideration for Cedar Lake in Indiana and SNL-EFDC models its hydrodynamics, sediment transport, and water quality. The water quality model as implemented on Cedar Lake tracks algae, oxygen, temperature, carbon, phosphorous, and nitrogen kinetics, as well as, sediment bed diagenesis. Environmental conditions, wind, temperature, rainfall, and sunlight, were based on data collected in 2005. Tributary loading was modeled using L-THIA and provided influxes of water, nutrients (phosphorous, nitrogen, etc.), and sediments. The calibrated model was used to simulate a nine month period from March to November 2005. Results suggest that the model simulates sediments transport and associated water quality correctly. The calibrated model is being used to evaluate several restoration measures throughout the lake and watershed and their effect on water quality. Because Cedar Lake is a nitrogen limited lake, changes in the level of eutrophication from each measure are being tracked by calculating the Carlson trophic state index

  7. 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.

  8. 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

  9. MODELS FOR THE COUNTER-GRADIENT TRANSPORT PHENOMENA

    Institute of Scientific and Technical Information of China (English)

    蒋剑波; 卢志明; 刘晓明; 刘宇陆

    2001-01-01

    The counter gradient transport phenomena on momentum, energy and passive scalar in turbulent flows were studied by use of the single response function for TSDIA. As a result, models that can describe qualitatively the phenomena are obtained. Then the results are simplified by use of the inertial range theory, and the results for lower degrees agree with results of predecessor. Finally the counter gradient-transport phenomena in channel flow and circular wake flow are analyzed.

  10. Genetics of traffic assignment models for strategic transport planning

    NARCIS (Netherlands)

    Bliemer, M.C.J.; Raadsen, M.; Brederode, L.; Bell, M.; Wismans, L.J.J.; Smith, M.

    2016-01-01

    This paper presents a review and classification of traffic assignment models for strategic transport planning purposes by using concepts analogous to genetics in biology. Traffic assignment models share the same theoretical framework (DNA), but differ in capability (genes). We argue that all traffic

  11. On the Economic Order Quantity Model With Transportation Costs

    NARCIS (Netherlands)

    S.I. Birbil (Ilker); K. Bulbul; J.B.G. Frenk (Hans); H.M. Mulder (Henry)

    2009-01-01

    textabstractWe consider an economic order quantity type model with unit out-of-pocket holding costs, unit opportunity costs of holding, fixed ordering costs and general transportation costs. For these models, we analyze the associated optimization problem and derive an easy procedure for determining

  12. 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.

  13. 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

  14. Modelling of electron transport and of sawtooth activity in tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Angioni, C

    2001-10-01

    Transport phenomena in tokamak plasmas strongly limit the particle and energy confinement and represent a crucial obstacle to controlled thermonuclear fusion. Within the vast framework of transport studies, three topics have been tackled in the present thesis: first, the computation of neoclassical transport coefficients for general axisymmetric equilibria and arbitrary collisionality regime; second, the analysis of the electron temperature behaviour and transport modelling of plasma discharges in the Tokamak a configuration Variable (TCV); third, the modelling and simulation of the sawtooth activity with different plasma heating conditions. The work dedicated to neoclassical theory has been undertaken in order to first analytically identify a set of equations suited for implementation in existing Fokker-Planck codes. Modifications of these codes enabled us to compute the neoclassical transport coefficients considering different realistic magnetic equilibrium configurations and covering a large range of variation of three key parameters: aspect ratio, collisionality, and effective charge number. A comparison of the numerical results with an analytical limit has permitted the identification of two expressions for the trapped particle fraction, capable of encapsulating the geometrical effects and thus enabling each transport coefficient to be fitted with a single analytical function. This has allowed us to provide simple analytical formulae for all the neoclassical transport coefficients valid for arbitrary aspect ratio and collisionality in general realistic geometry. This work is particularly useful for a correct evaluation of the neoclassical contribution in tokamak scenarios with large bootstrap cur- rent fraction, or improved confinement regimes with low anomalous transport and for the determination of the plasma current density profile, since the plasma conductivity is usually assumed neoclassical. These results have been included in the plasma transport code

  15. 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

  16. Modeling Saharan dust emissions, transport, deposition, and optical properties

    Science.gov (United States)

    Colarco, Peter Richard

    We simulate Saharan dust emissions, transport, and removal with a three-dimensional aerosol transport model driven by assimilated meteorology. We explore dust distributions and optical properties for model runs over the tropical North Atlantic for time periods covering the ACE-2 (summer 1997, Canary Islands) and PRIDE (summer 2000, Puerto Rico) field experiments. Modeled dust fields are compared to ground-based, in situ, and satellite observations. Dust imaginary refractive index and single scatter albedo at UV wavelengths are inferred near source regions by computing the TOMS Aerosol Index from modeled dust fields. Our results indicate a dust aerosol that is considerably less absorbing than previous estimates. The timing of downwind dust events is generally uncorrelated with the details of the dust source process, indicating the dust exists in a persistent reservoir over source regions and the timing of its transport to remote regions is most strongly controlled by the transporting dynamics. Our model simulates the complicated vertical distributions of dust observed over Puerto Rico. The dust vertical distribution is controlled by sedimentation of dust particles and a general descending air motion over the tropical North Atlantic. Low-level dust can be transported directly from source regions, but the majority of it is efficiently eroded away in transit by wet removal processes. Our computed estimates of iron deposition fluxes into the North Atlantic are in reasonable agreement with estimates based on station data.

  17. 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.

  18. 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...

  19. 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)

  20. 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.

  1. A Data-Driven Approach for Upscaling Solute Transport Models

    Science.gov (United States)

    Hill, D. J.

    2004-12-01

    The goal of this study is to use a machine learning tool, genetic programming (GP), a domain independent model generator, to search for an upscaled hydrologic model. The development of upscaled models of hydrologic processes has long been a concern of researchers, because computational limitations prevent the use of high-resolution models capable of resolving all of the spatial variability of model domains. In particular, researchers have struggled for decades to develop upscaled numerical models for solute transport in porous media, where the scale of variability can range from the order of a few meters in the horizontal direction but only ten to twenty centimeters in the vertical direction. A wide variety of methods have been employed to develop upscaled solute transport models, including stochastic analysis, spatial filtering, and homogenization. However, these methods all rely upon various simplifying assumptions (e.g. small conductivity variance, a grid-scale significantly larger than the largest scale of heterogeneity). Moreover, these methods usually make additional assumptions about the physics of the sub-grid processes. This study examines the use of GP to search for an upscaled model of transport of a solute pulse by horizontal flow in a perfectly stratified aquifer. GP was chosen because it creates mathematical models of input data from which information about the underlying physical processes can be extracted. This type of transport system was selected as the first application of the proposed upscaling method, because it has been extensively studied in the literature, and thus will allow for a direct comparison that will demonstrate the efficacy of the data-driven upscaling method. It has been suggested that if the upscaled model domain of this type of system is a depth averaged representation of the aquifer, the plume evolution can be modeled in a Lagrangian coordinate system as a Fickian dispersive process with a time dependent dispersion coefficient

  2. Modelling vapour transport in Surtseyan bombs

    Science.gov (United States)

    McGuinness, Mark J.; Greenbank, Emma; Schipper, C. Ian

    2016-05-01

    We address questions that arise if a slurry containing liquid water is enclosed in a ball of hot viscous vesicular magma ejected as a bomb in the context of a Surtseyan eruption. We derive a mathematical model for transient changes in temperature and pressure due to flashing of liquid water to vapour inside the bomb. The magnitude of the transient pressure changes that are typically generated are calculated together with their dependence on material properties. A single criterion to determine whether the bomb will fragment as a result of the pressure changes is derived. Timescales for ejection of water vapour from a bomb that remains intact are also revealed.

  3. 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...

  4. 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.

  5. 3D contaminant migration model with consolidation dependent transport coefficients

    Institute of Scientific and Technical Information of China (English)

    Lu Huang; Cheng-Gang Zhao; Yan Liu; Guo-Qing Cai

    2012-01-01

    Soil consolidation would induce variations of its transport coefficients such as hydraulic conductivity and diffusion coefficient. This paper presents a study of the influence of barrier consolidation on transport coefficients,and a 3D transport model based on mixture theory is proposed for describing the liners that involve circular defects in the geomembrane.The elastoplastic ALPHA model is revised by using the spatially mobilized plane (SMP) criterion for simulating the deformation of the soils.Then,the 3D model coupling the nonlinear consolidation and contaminant advection-diffusion is solved using the finite element software ABAQUS.The results show that the importance of reducing the defect size in the geomembrane and the liner porosity to control the contaminant concentration increase.

  6. 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.

  7. 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

  8. 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.

  9. Creating transport models that matter: A strategic view on governance of transport models and road maps for innovation

    NARCIS (Netherlands)

    Tavasszy, L.A.; Duijnisveld, M; Hofman, F.; Pronk van Hoogeveen, S.; Schmorak, N.; Van de Berg, M.; Francke, J.; Van de Riet, O.; Van der Waard, J.; Poot, H.; Reiding, E.

    2010-01-01

    The basic use of transport models is that they help to increase our understanding of the mobility system. In more operational terms, they can be a basis for developing quantitative insights in the past and current state of the system or scenarios about the future. Models are also useful as impact as

  10. Groundwater transport modeling with nonlinear sorption and intraparticle diffusion

    Science.gov (United States)

    Singh, Anshuman; Allen-King, Richelle M.; Rabideau, Alan J.

    2014-08-01

    Despite recent advances in the mechanistic understanding of sorption in groundwater systems, most contaminant transport models provide limited support for nonideal sorption processes such as nonlinear isotherms and/or diffusion-limited sorption. However, recent developments in the conceptualization of "dual mode" sorption for hydrophobic organic contaminants have provided more realistic and mechanistically sound alternatives to the commonly used Langmuir and Freundlich models. To support the inclusion of both nonlinear and diffusion-limited sorption processes in groundwater transport models, this paper presents two numerical algorithms based on the split operator approach. For the nonlinear equilibrium scenario, the commonly used two-step split operator algorithm has been modified to provide a more robust treatment of complex multi-parameter isotherms such as the Polanyi-partitioning model. For diffusion-limited sorption, a flexible three step split-operator procedure is presented to simulate intraparticle diffusion in multiple spherical particles with different sizes and nonlinear isotherms. Numerical experiments confirmed the accuracy of both algorithms for several candidate isotherms. However, the primary advantages of the algorithms are: (1) flexibility to accommodate any isotherm equation including "dual mode" and similar expressions, and (2) ease of adapting existing grid-based transport models of any dimensionality to include nonlinear sorption and/or intraparticle diffusion. Comparisons are developed for one-dimensional transport scenarios with different isotherms and particle configurations. Illustrative results highlight (1) the potential influence of isotherm model selection on solute transport predictions, and (2) the combined effects of intraparticle diffusion and nonlinear sorption on the plume transport and flushing for both single-particle and multi-particle scenarios.

  11. AN ELECTRIC MODEL OF A CITY TRANSPORT NETWORK

    Directory of Open Access Journals (Sweden)

    Antoniadi G. D.

    2015-10-01

    Full Text Available The main characteristics of a transport network are the intensity of the traffic flow, speed and density of its traffic. Comfortable driver's traffic density is determined by the rule of the traffic police, which is "clearance between cars on the road should be a tenth of the speed of movement." We have built a reference curve of the density function of the flow of vehicles on its speed, which is basic when simulating a traffic flow. The article describes a model of electrical city transport networks, allowing calculating traffic flows, their speed, the density and the number of traffic lanes by means of laws of electrical engineering. We have also compared electrical concepts (current, resistance, electro-motive force, etc. and transportation (of intensity-flow lane road, transport driving force, etc.. For the transport network there are methods of calculation of electrical circuits - a method of Kirchhoff's laws, loop currents, etc. We have confirmed the correctness of electric models and the possibility of its use for the calculation of transport networks; as well as we have presented an example of the calculation

  12. 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 ...

  13. 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 (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.

  14. 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

  15. A coupled energy transport and hydrological model for urban canopies

    Science.gov (United States)

    Wang, Z.; Bou-Zeid, E.; Smith, J. A.

    2011-12-01

    Urban land-atmosphere interaction has been attracting more research efforts in order to understand the complex physics of flow and mass and heat transport in urban surfaces and the lower urban atmosphere. In this work, we developed and implemented a new physically-based single-layer urban canopy model, coupling the surface exchange of energy and the subsurface transport of water/soil moisture. The new model incorporates sub-facet heterogeneity for each urban surface (roof, wall or ground). This better simulates the energy transport in urban canopy layers, especially over low-intensity built (suburban type) terrains that include a significant fraction of vegetated surfaces. We implemented detailed urban hydrological models for both natural terrains (bare soil and vegetation) and porous engineered materials with water-holding capacity (concrete, gravel, etc). The skill of the new scheme was tested against experimental data collected through a wireless sensor network deployed over the campus of Princeton University. The model performance was found to be robust and insensitive to changes in weather conditions or seasonal variability. Predictions of the volumetric soil water content were also in good agreement with field measurements, highlighting the model capability of capturing subsurface water transport for urban lawns. The new model was also applied to a case study assessing different strategies, i.e. white versus green roofs, in the mitigation of urban heat island effect.

  16. 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.

  17. Computer-based modelling and optimization in transportation

    CERN Document Server

    Rossi, Riccardo

    2014-01-01

    This volume brings together works resulting from research carried out by members of the EURO Working Group on Transportation (EWGT) and presented during meetings and workshops organized by the Group under the patronage of the Association of European Operational Research Societies in 2012 and 2013. The main targets of the EWGT include providing a forum to share research information and experience, encouraging joint research and the development of both theoretical methods and applications, and promoting cooperation among the many institutions and organizations which are leaders at national level in the field of transportation and logistics. The primary fields of interest concern operational research methods, mathematical models and computation algorithms, to solve and sustain solutions to problems mainly faced by public administrations, city authorities, public transport companies, service providers and logistic operators. Related areas of interest are: land use and transportation planning, traffic control and ...

  18. Simulation model for the WIPP transportation and delivery system

    Energy Technology Data Exchange (ETDEWEB)

    Sharif, F. [Westinghouse Electric Corp., Carlsbad, NM (United States); Lippis, J. [USDOE Albuquerque Operations Office, Carlsbad, NM (United States). Waste Isolation Pilot Plant Project Office; Quinn, D. [Systems Modeling Corp., Sewickley, PA (United States)

    1992-12-31

    The United States Department of Energy`s (DOE`s) Waste Isolation Pilot Plant (WIPP) is a first of its kind repository designed to demonstrate safe disposal of transuranic (TRU) waste in bedded salt 2150 feet underground. Contact-handled (CH) TRU waste, waste with low beta or gamma emitting radionuclides that can be handled without protective clothing or additional shielding, will be transported to WIPP in Nuclear Regulatory Commission (NRC) certified containers known as TRUPACT-IIs. The TRUPACT-II is the cornerstone of a transportation system designed for extraordinarily safe transport of TRU waste from ten DOE production and research sites to WIPP. This paper describes the complexities of the transportation system and discusses how a simulation model can be utilized as a tool to develop economical operating parameters for the system.

  19. Continuous Modeling of Calcium Transport Through Biological Membranes

    Science.gov (United States)

    Jasielec, J. J.; Filipek, R.; Szyszkiewicz, K.; Sokalski, T.; Lewenstam, A.

    2016-08-01

    In this work an approach to the modeling of the biological membranes where a membrane is treated as a continuous medium is presented. The Nernst-Planck-Poisson model including Poisson equation for electric potential is used to describe transport of ions in the mitochondrial membrane—the interface which joins mitochondrial matrix with cellular cytosis. The transport of calcium ions is considered. Concentration of calcium inside the mitochondrion is not known accurately because different analytical methods give dramatically different results. We explain mathematically these differences assuming the complexing reaction inside mitochondrion and the existence of the calcium set-point (concentration of calcium in cytosis below which calcium stops entering the mitochondrion).

  20. Cuttings Transport Models and Experimental Visualization of Underbalanced Horizontal Drilling

    Directory of Open Access Journals (Sweden)

    Na Wei

    2013-01-01

    Full Text Available Aerated underbalanced horizontal drilling technology has become the focus of the drilling industry at home and abroad, and one of the engineering core issues is the horizontal borehole cleaning. Therefore, calculating the minimum injection volume of gas and liquid accurately is essential for the construction in aerated underbalanced horizontal drilling. This paper establishes a physical model of carrying cuttings and borehole cleaning in wellbore of horizontal well and a critical transport mathematical model according to gas-liquid-solid flow mechanism and large plane dunes particle transport theory.

  1. Introduction to stochastic models of transportation flows. Part I

    CERN Document Server

    Malyshev, V A

    2011-01-01

    We consider here probabilistic models of transportation flows. The main goal of this introduction is rather not to present various techniques for problem solving but to present some intuition to invent adequate and natural models having visual simplicity and simple (but rigorous) formulation, the main objects being cars not abstract flows. The papers consists of three parts. First part considers mainly linear flows on short time scale - dynamics of the flow due to changing driver behavior. Second part studies linear flow on longer time scales - individual car trajectory from entry to exit from the road. Part three considers collective car movement in complex transport networks.

  2. A novel adaptive biogeochemical model, and its 3-D application for a decadal hindcast simulation of the biogeochemistry of the southern North Sea

    Science.gov (United States)

    Kerimoglu, Onur; Hofmeister, Richard; Wirtz, Kai

    2016-04-01

    Adaptation and acclimation processes are often ignored in ecosystem-scale model implementations, despite the long-standing recognition of their importance. Here we present a novel adaptive phytoplankton growth model where acclimation of the community to the changes in external resource ratios is accounted for, using optimality principles and dynamic physiological traits. We show that the model can reproduce the internal stoichiometries obtained at marginal supply ratios in chemostat experiments. The model is applied in a decadal hindcast simulation of the southern North Sea, where it is coupled to a 2-D benthic model and a 3-D hydrodynamic model in an approximately 1.5km horizontal resolution at the German Bight coast. The model is shown to have good skill in capturing the steep, coastal gradients in the German Bight, suggested by the match between the estimated and observed dissolved nutrient and chlorophyll concentrations. We then analyze the differential sensitivity of the coastal and off-shore zones to major drivers of the system, such as riverine nutrient loads. We demonstrate that the relevance of phytoplankton acclimation varies across coastal gradients and can become particularly significant in terms of summer nutrient depletion.

  3. Reactive Transport Modeling of Vadose Zone Contamination: Feedback between Reactions and Gas-Phase Transport

    Science.gov (United States)

    Molins, S.; Mayer, K.

    2007-05-01

    The unsaturated zone acts as a buffer zone for contaminants on their way to the water table but can also attenuate the emission of contaminants leaving the subsurface environment through the gas phase. A reactive transport model that includes multicomponent gas transport has been developed to investigate the processes that contribute to the generation and attenuation of contaminants in the unsaturated zone. In particular, the model is suitable to study the feedback processes between advective-diffusive gas transport and geochemical reactions. The model is also able to estimate diffusive and advective contributions to gas transport in multicomponent systems. Two model applications are presented that investigate gas transport and reactions in mine tailings and at a site with organic contamination. In mine tailings, atmospheric oxygen transported into the sediment column is consumed in the oxidation of sulfide minerals. Gas volume loss caused by the consumption of atmospheric oxygen drives advective fluxes. In the absence of carbonate minerals, the advective component accounts for 16 % of the net oxygen flux into the column, while, in a carbonate-rich system, advection accounts for 10 % of the net oxygen flux. Dissolution of carbonate minerals has a moderating effect on advective gas transport since carbon dioxide can partially compensate for the depletion of oxygen. At an oil spill site, volatilization and degradation of organic contaminants cause advective and diffusive fluxes of organic vapors away from the source zone. At early stages, volatilization dominates and oxidation of these organic vapors attenuates the emission of contaminants to the atmosphere. The contribution of advection to organic vapor fluxes is significant initially but decreases with time. At later stages, the oil source becomes depleted of its most volatile fraction, and anaerobic degradation of aromatic compounds and heavier n-alkanes results in the production of methane. Up to 15 % of methane

  4. 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...

  5. Green Transport Balanced Scorecard Model with Analytic Network Process Support

    Directory of Open Access Journals (Sweden)

    David Staš

    2015-11-01

    Full Text Available In recent decades, the performance of economic and non-economic activities has required them to be friendly with the environment. Transport is one of the areas having considerable potential within the scope. The main assumption to achieve ambitious green goals is an effective green transport evaluation system. However, these systems are researched from the industrial company and supply chain perspective only sporadically. The aim of the paper is to design a conceptual framework for creating the Green Transport (GT Balanced Scorecard (BSC models from the viewpoint of industrial companies and supply chains using an appropriate multi-criteria decision making method. The models should allow green transport performance evaluation and support of an effective implementation of green transport strategies. Since performance measures used in Balanced Scorecard models are interdependent, the Analytic Network Process (ANP was used as the appropriate multi-criteria decision making method. The verification of the designed conceptual framework was performed on a real supply chain of the European automotive industry.

  6. Intelligent Transportation and Evacuation Planning A Modeling-Based Approach

    CERN Document Server

    Naser, Arab

    2012-01-01

    Intelligent Transportation and Evacuation Planning: A Modeling-Based Approach provides a new paradigm for evacuation planning strategies and techniques. Recently, evacuation planning and modeling have increasingly attracted interest among researchers as well as government officials. This interest stems from the recent catastrophic hurricanes and weather-related events that occurred in the southeastern United States (Hurricane Katrina and Rita). The evacuation methods that were in place before and during the hurricanes did not work well and resulted in thousands of deaths. This book offers insights into the methods and techniques that allow for implementing mathematical-based, simulation-based, and integrated optimization and simulation-based engineering approaches for evacuation planning. This book also: Comprehensively discusses the application of mathematical models for evacuation and intelligent transportation modeling Covers advanced methodologies in evacuation modeling and planning Discusses principles a...

  7. A mathematical model of inter-terminal transportation

    DEFF Research Database (Denmark)

    Tierney, Kevin; Voß, Stefan; Stahlbock, Robert

    2014-01-01

    We present a novel integer programming model for analyzing inter-terminal transportation (ITT) in new and expanding sea ports. ITT is the movement of containers between terminals (sea, rail or otherwise) within a port. ITT represents a significant source of delay for containers being transshipped...... contains special structures to model the long term loading and unloading of vehicles, and our model is general enough to model a number of important real-world aspects of ITT, such as traffic congestion, penalized late container delivery, multiple ITT transportation modes, and port infrastructure...... modifications. We show that our model can scale to real-world sizes and provide ports with important information for their long term decision making....

  8. Analytical modelling of hydrogen transport in reactor containments

    International Nuclear Information System (INIS)

    A versatile computational model of hydrogen transport in nuclear plant containment buildings is developed. The background and significance of hydrogen-related nuclear safety issues are discussed. A computer program is constructed that embodies the analytical models. The thermofluid dynamic formulation spans a wide applicability range from rapid two-phase blowdown transients to slow incompressible hydrogen injection. Detailed ancillary models of molecular and turbulent diffusion, mixture transport properties, multi-phase multicomponent thermodynamics and heat sink modelling are addressed. The numerical solution of the continuum equations emphasizes both accuracy and efficiency in the employment of relatively coarse discretization and long time steps. Reducing undesirable numerical diffusion is addressed. Problem geometry options include lumped parameter zones, one dimensional meshs, two dimensional Cartesian or axisymmetric coordinate systems and three dimensional Cartesian or cylindrical regions. An efficient lumped nodal model is included for simulation of events in which spatial resolution is not significant. Several validation calculations are reported

  9. Validation of transport models in ASDEX Upgrade current ramps

    International Nuclear Information System (INIS)

    In order to prepare adequate ramp up and down scenarios for ITER, understanding the physics of transport during the current ramps is essential. The aim of the work was to assess the capability of several transport models to reproduce the experimental data during the current ramps. For this purpose, the calculated temperature profiles from different transport models, i.e. Coppi-Tang, Neo-Alcator, Bohm-Gyrobohm, critical gradient model and H98/2 scaling-based are compared to experimental temperature profiles under different conditions. The strong variation of the experimental electron temperature profiles are partly reproduced by the models. The importance of central and edge radiation will be emphasized, as well as the main transport properties of the models, especially in the case of strong local electron heating (ECRH). To investigate the control capabilities of a Tokamak, particularly with regard to ITER, the impact on global plasma parameters like the internal inductance and the stored energy is also investigated.

  10. Aggregation–fragmentation model of vesicular transport in neurons

    International Nuclear Information System (INIS)

    We develop a mathematical model of the motor-based transport and delivery of vesicles to synaptic targets of an axon. Our model incorporates the ‘stop-and-go’ nature of bidirectional motor transport (which can be modeled in terms of advection–diffusion) and the reversible exchange of vesicles between motors and targets, both of which have been observed experimentally. Since motor-target interactions are reversible, it is necessary to keep track of the cluster size of vesicles bound to each motor-complex. This naturally leads to a modified version of the Becker–Doring model of aggregation–fragmentation processes. We analyze steady-state solutions of the transport model and obtain an explicit solution that supports a uniform distribution of synaptic resources along an axon. We thus establish a possible mechanism for the democratic distribution of synaptic resources along the length of an axon, based on reversible motor-target interactions. In the irreversible case, one finds that the motor-driven transport of newly synthesized proteins from the soma to presynaptic targets along the axon tends to favor the delivery of resources to more proximal synapses. (paper)

  11. Incorporating transportation network modeling tools within transportation economic impact studies of disasters

    Directory of Open Access Journals (Sweden)

    Yi Wen

    2014-08-01

    Full Text Available Transportation system disruption due to a disaster results in "ripple effects" throughout the entire transportation system of a metropolitan region. Many researchers have focused on the economic costs of transportation system disruptions in transportation-related industries, specifïcally within commerce and logistics, in the assessment of the regional economic costs. However, the foundation of an assessment of the regional economic costs of a disaster needs to include the evaluation of consumer surplus in addition to the direct cost for reconstruction of the regional transportation system. The objective of this study is to propose a method to estimate the regional consumer surplus based on indirect economic costs of a disaster on intermodal transportation systems in the context of diverting vehicles and trains. The computational methods used to assess the regional indirect economic costs sustained by the highway and railroad system can utilize readily available state departments of transportation (DOTs and metropolitan planning organizations (MPOs traffic models allowing prioritization of regional recovery plans after a disaster and strengthening of infrastructure before a disaster. Hurricane Katrina is one of the most devastating hurricanes in the history of the United States. Due to the significance of Hurricane Katrina, a case study is presented to evaluate consumer surplus in the Gulf Coast Region of Mississippi. Results from the case study indicate the costs of rerouting and congestion delays in the regional highway system and the rent costs of right-of-way in the regional railroad system are major factors of the indirect costs in the consumer surplus.

  12. Coupling Sediment Transport with the Integrated Hydrologic Model (PIHM)

    Science.gov (United States)

    Li, S.; Duffy, C. J.; Qu, Y.

    2006-12-01

    Penn State Integrated Hydrologic Model (PIHM) was developed by Qu and Duffy (2004) for multi-process simulation. As a further work, a physically-based non-equilibrium non-uniform sediment transport modeling component is developed and coupled with PIHM. It combines the hillslope and channel processes, and accounts for sediment yield as well as morphological evolution. For hillslope, the rain splash erosion, hydraulic erosion, and sediment transport by overland flow are simulated; for channel, it takes into account the hydraulic detachment and sediment transport by channel flow. An algorithm for bed armoring is proposed and incorporated in the component. And it also includes a river bank erosion submodel which is modified from Darby et al. (2002). The coupling system is solved using a semi-discrete finite volume approach. It is being tested based on three types of flow routing schemes: dynamic wave, diffusion wave and kinematic wave using different scales of watershed data.

  13. Dissipative particle dynamics model for colloid transport in porous media

    Energy Technology Data Exchange (ETDEWEB)

    Pan, W.; Tartakovsky, A. M.

    2013-08-01

    We present that the transport of colloidal particles in porous media can be effectively modeled with a new formulation of dissipative particle dynamics, which augments standard DPD with non-central dissipative shear forces between particles while preserving angular momentum. Our previous studies have demonstrated that the new formulation is able to capture accurately the drag forces as well as the drag torques on colloidal particles that result from the hydrodynamic retardation effect. In the present work, we use the new formulation to study the contact efficiency in colloid filtration in saturated porous media. Note that the present model include all transport mechanisms simultaneously, including gravitational sedimentation, interception and Brownian diffusion. Our results of contact efficiency show a good agreement with the predictions of the correlation equation proposed by Tufenkji and EliMelech, which also incorporate all transport mechanisms simultaneously without the additivity assumption.

  14. A new turbulence-based model for sand transport

    Science.gov (United States)

    Mayaud, Jerome; Wiggs, Giles; Bailey, Richard

    2016-04-01

    Knowledge of the changing rate of sediment flux in space and time is essential for quantifying surface erosion and deposition in desert landscapes. While many aeolian studies have relied on time-averaged parameters such as wind velocity (U) and wind shear velocity (u*) to determine sediment flux, there is increasing evidence that high-frequency turbulence is an important driving force behind the entrainment and transport of sand. However, turbulence has yet to be incorporated into a functional sand transport model that can be used for predictive purposes. In this study we present a new transport model (the 'turbulence model') that accounts for high-frequency variations in the horizontal (u) and vertical (w) components of wind flow. The turbulence model is fitted to wind velocity and sediment transport data from a field experiment undertaken in Namibia's Skeleton Coast National Park, and its performance at three temporal resolutions (10 Hz, 1 Hz, 1 min) is compared to two existing models that rely on time-averaged wind velocity data (Radok, 1977; Dong et al., 2003). The validity of the three models is analysed under a variety of saltation conditions, using a 2-hour (1 Hz measurement resolution) dataset from the Skeleton Coast and a 5-hour (1 min measurement resolution) dataset from the southwestern Kalahari Desert. The turbulence model is shown to outperform the Radok and Dong models when predicting total saltation count over the three experimental periods. For all temporal resolutions presented in this study (10 Hz-10 min), the turbulence model predicted total saltation count to within at least 0.34%, whereas the Radok and Dong models over- or underestimated total count by up to 5.50% and 20.53% respectively. The strong performance of the turbulence model can be attributed to a lag in mass flux response built into its formulation, which can be adapted depending on the temporal resolution of investigation. This accounts for the inherent lag within the physical

  15. 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.

  16. Kinetic models for nucleocytoplasmic transport of messenger RNA.

    Science.gov (United States)

    Schröder, H C; Müller, W E; Agutter, P S

    1995-05-21

    Much is known about the mechanism by which mRNAs cross the nuclear envelope (the translocation stage of nucleocytoplasmic transport), but far less is known about the preceding (intranuclear migration/release) and succeeding (cytoplasmic binding) stages. Therefore, existing information suffices for articulating detailed kinetic models of translocation, but not models for the overall mRNA transport process. In this paper, we show that simple kinetic models of translocation can (i) accommodate data about nucleocytoplasmic distributions of endogenous transcripts; (ii) predict the overall effects on these distributions of effectors such as insulin and epidermal growth factor; (iii) throw some light on the mechanism(s) of action of the HIV-1 protein Rev and produce experimentally testable predictions about this mechanism; and (iv) account for the action of influenza virus NS1 protein. However, the simplest forms of translocation models apparently fail to account for some properties of viral regulators such as HIV Rev and adenovirus E1B-E4 complex. To elucidate these topics, less narrowly focused models of mRNA transport are required, describing intranuclear binding/release as well as translocation. On the basis of our examination of translocation models, we suggest some criteria that the requisite broadly based models must satisfy.

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

    DEFF Research Database (Denmark)

    Fugleberg, S; Graff, J; Joffe, P;

    1994-01-01

    and lymphatic convective solute transport. The validation procedure included an assessment of theoretical (a priori) and practical (a posteriori) identifiability, goodness of fit, residual error analysis and plausibility of parameter estimates. The results of the validation procedure demonstrate that the model...

  18. Electron thermal transport barriers in RTP: experiment and modelling

    NARCIS (Netherlands)

    Schilham, A.M.R.; Hogeweij, G. M. D.; Cardozo, N. J. L.

    2001-01-01

    Experiments in which very localized electron cyclotron heating (ECH) is scanned through the RTP plasma show sharp transitions, in which the electron temperature profile abruptly changes shape. The phenomenology-the profiles shapes, the sharp transitions-can be reproduced with a transport model which

  19. Transport of Pathogen Surrogates in Soil Treatment Units: Numerical Modeling

    Directory of Open Access Journals (Sweden)

    Ivan Morales

    2014-04-01

    Full Text Available Segmented mesocosms (n = 3 packed with sand, sandy loam or clay loam soil were used to determine the effect of soil texture and depth on transport of two septic tank effluent (STE-borne microbial pathogen surrogates—green fluorescent protein-labeled E. coli (GFPE and MS-2 coliphage—in soil treatment units. HYDRUS 2D/3D software was used to model the transport of these microbes from the infiltrative surface. Mesocosms were spiked with GFPE and MS-2 coliphage at 105 cfu/mL STE and 105–106 pfu/mL STE, respectively. In all soils, removal rates were >99.99% at 25 cm. The transport simulation compared (1 optimization; and (2 trial-and-error modeling approaches. Only slight differences between the transport parameters were observed between these approaches. Treating both the die-off rates and attachment/detachment rates as variables resulted in an overall better model fit, particularly for the tailing phase of the experiments. Independent of the fitting procedure, attachment rates computed by the model were higher in sandy and sandy loam soils than clay, which was attributed to unsaturated flow conditions at lower water content in the coarser-textured soils. Early breakthrough of the bacteria and virus indicated the presence of preferential flow in the system in the structured clay loam soil, resulting in faster movement of water and microbes through the soil relative to a conservative tracer (bromide.

  20. Renormalized transport equations for the bistable potential model

    Science.gov (United States)

    Weidlich, Wolfgang; Grabert, Hermann

    1980-09-01

    Renormalized transport equations for general Fokker-Planck systems are derived and applied to the bistable potential model. The exact equation for the expectation value t can be evaluated in both domains ∈ x ± and ∈ D 0 outside and between the potential minima, leading to drastic differences of the dynamics prevailing in D ± and D 0, respectively.

  1. Modeling subsurface contaminant reactions and transport at the watershed scale

    Energy Technology Data Exchange (ETDEWEB)

    Gwo, J.P.; Jardine, P.M.; D`Azevedo, E.F. [Oak Ridge National Lab., TN (United States); Wilson, G.V. [Desert Research Inst., Las Vegas, NV (United States). Water Resources Center

    1997-12-01

    The objectives of this research are: (1) to numerically examine the multiscale effects of physical and chemical mass transfer processes on watershed scale, variably saturated subsurface contaminant transport, and (2) to conduct numerical simulations on watershed scale reactive solute transport and evaluate their implications to uncertainty characterization and cost benefit analysis. Concurrent physical and chemical nonequilibrium