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Sample records for biogeochemical subsurface processes

  1. A Reactive Transport Simulator for Biogeochemical Processes in Subsurface System

    2003-04-01

    BIOGEOCHEM is a Fortran code that mumerically simulates the coupled processes of solute transport, microbial population dynamics, microbial metabolism, and geochemical reactions. The potential applications of the code include, but not limited to, (a) sensitivity and uncertainty analyses for assessing the impact of microbial activity on subsurface geochemical systems; (b) extraction of biogeochemical parameter values from field observations or laboratory measurements, (c) helping to design and optimize laboratory biogeochemical experiments, and (d) data integration. Methodmore » of Solution: A finite difference method and a Newton-Raphson technique are used to solve a set of coupled nonlinear partial differential equations and algebraic equations. Practical Application: Environmental analysis, bioremediation performance assessments of radioactive or non-radioactive wase disposal, and academic research.« less

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

    PubMed

    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.

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

    PubMed

    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

  4. CALIBRATION OF SUBSURFACE BATCH AND REACTIVE-TRANSPORT MODELS INVOLVING COMPLEX BIOGEOCHEMICAL PROCESSES

    EPA Science Inventory

    In this study, the calibration of subsurface batch and reactive-transport models involving complex biogeochemical processes was systematically evaluated. Two hypothetical nitrate biodegradation scenarios were developed and simulated in numerical experiments to evaluate the perfor...

  5. Biogeochemical Processes In Ethanol Stimulated Uranium Contaminated Subsurface Sediments

    SciTech Connect

    Mohanty, Santosh R.; Kollah, Bharati; Hedrick, David B.; Peacock, Aaron D.; Kukkadapu, Ravi K.; Roden, Eric E.

    2008-06-15

    A laboratory incubation experiment was conducted with uranium contaminated subsurface sediment to assess the geochemical and microbial community response to ethanol amendment. A classical sequence of TEAPs was observed in ethanol-amended slurries, with NO3- reduction, Fe(III) reduction, SO4 2- reduction, and CH4 production proceeding in sequence until all of the added 13C-ethanol (9 mM) was consumed. Approximately 60% of the U(VI) content of the sediment was reduced during the period of Fe(III) reduction. No additional U(VI) reduction took place during the sulfate-reducing and methanogenic phases of the experiment. Only gradual reduction of NO3 -, and no reduction of U(VI), took place in ethanol-free slurries. Stimulation of additional Fe(III) or SO4 2- reduction in the ethanol-amended slurries failed to promote further U(VI) reduction. Reverse transcribed 16S rRNA clone libraries revealed major increases in the abundance of organisms related to Dechloromonas, Geobacter, and Oxalobacter in the ethanolamended slurries. PLFAs indicative of Geobacter showed a distinct increase in the amended slurries, and analysis of PLFA 13C/12C ratios confirmed the incorporation of ethanol into these PLFAs. A increase in the abundance of 13C-labeled PLFAs indicative of Desulfobacter, Desulfotomaculum, and Desulfovibrio took place during the brief period of sulfate reduction which followed the Fe(III) reduction phase. Our results show that major redox processes in ethanol-amended sediments can be reliably interpreted in terms of standard conceptual models of TEAPs in sediments. However, the redox speciation of uranium is complex and cannot be explained based on simplified thermodynamic considerations.

  6. Multi-scale Characterization and Prediction of Coupled Subsurface Biogeochemical-Hydrological Processes

    SciTech Connect

    Hubbard, Susan; Williams, Ken; Steefel, Carl; Banfield, Jill; Long, Phil; Slater, Lee; Pride, Steve; Jinsong Chen

    2006-06-01

    To advance solutions needed for remediation of DOE contaminated sites, approaches are needed that can elucidate and predict reactions associated with coupled biological, geochemical, and hydrological processes over a variety of spatial scales and in heterogeneous environments. Our previous laboratory experimental experiments, which were conducted under controlled and homogeneous conditions, suggest that geophysical methods have the potential for elucidating system transformations that often occur during remediation. Examples include tracking the onset and aggregation of precipitates associated with sulfate reduction using seismic and complex resistivity methods (Williams et al., 2005; Ntarlagiannis et al., 2005) as well as estimating the volume of evolved gas associated with denitrification using radar velocity. These exciting studies illustrated that geophysical responses correlated with biogeochemical changes, but also that multiple factors could impact the geophysical signature and thus a better understanding as well as integration tools were needed to advance the techniques to the point where they can be used to provide quantitative estimates of system transformations.

  7. Subsurface Biogeochemical Research FY11 Second Quarter Performance Measure

    SciTech Connect

    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).

  8. Biogeochemical Processes in Microbial Ecosystems

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.

    2001-01-01

    The hierarchical organization of microbial ecosystems determines process rates that shape Earth's environment, create the biomarker sedimentary and atmospheric signatures of life, and define the stage upon which major evolutionary events occurred. In order to understand how microorganisms have shaped the global environment of Earth and, potentially, other worlds, we must develop an experimental paradigm that links biogeochemical processes with ever-changing temporal and spatial distributions of microbial populations and their metabolic properties. Additional information is contained in the original extended abstract.

  9. Deep subsurface microbial processes

    USGS Publications Warehouse

    Lovley, D.R.; Chapelle, F.H.

    1995-01-01

    Information on the microbiology of the deep subsurface is necessary in order to understand the factors controlling the rate and extent of the microbially catalyzed redox reactions that influence the geophysical properties of these environments. Furthermore, there is an increasing threat that deep aquifers, an important drinking water resource, may be contaminated by man's activities, and there is a need to predict the extent to which microbial activity may remediate such contamination. Metabolically active microorganisms can be recovered from a diversity of deep subsurface environments. The available evidence suggests that these microorganisms are responsible for catalyzing the oxidation of organic matter coupled to a variety of electron acceptors just as microorganisms do in surface sediments, but at much slower rates. The technical difficulties in aseptically sampling deep subsurface sediments and the fact that microbial processes in laboratory incubations of deep subsurface material often do not mimic in situ processes frequently necessitate that microbial activity in the deep subsurface be inferred through nonmicrobiological analyses of ground water. These approaches include measurements of dissolved H2, which can predict the predominant microbially catalyzed redox reactions in aquifers, as well as geochemical and groundwater flow modeling, which can be used to estimate the rates of microbial processes. Microorganisms recovered from the deep subsurface have the potential to affect the fate of toxic organics and inorganic contaminants in groundwater. Microbial activity also greatly influences 1 the chemistry of many pristine groundwaters and contributes to such phenomena as porosity development in carbonate aquifers, accumulation of undesirably high concentrations of dissolved iron, and production of methane and hydrogen sulfide. Although the last decade has seen a dramatic increase in interest in deep subsurface microbiology, in comparison with the study of

  10. Biogeochemical Processes in Microbial Ecosystems

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.; DeVincenzi, Donald L. (Technical Monitor)

    2001-01-01

    The hierarchical organization of microbial ecosystems determines process rates that shape Earth's environment, create the biomarker sedimentary and atmospheric signatures of life and define the stage upon which major evolutionary events occurred. In order to understand how microorganisms have shaped the global environment of Earth and potentially, other worlds, we must develop an experimental paradigm that links biogeochemical processes with ever-changing temporal and spatial distributions of microbial population, and their metabolic properties. Photosynthetic microbial mats offer an opportunity to define holistic functionality at the millimeter scale. At the same time, their Biogeochemistry contributes to environmental processes on a planetary scale. These mats are possibly direct descendents of the most ancient biological communities; communities in which oxygenic photosynthesis might have been invented. Mats provide one of the best natural systems to study how microbial populations associate to control dynamic biogeochemical gradients. These are self-sustaining, complete ecosystems in which light energy absorbed over a diel (24 hour) cycle drives the synthesis of spatially-organized, diverse biomass. Tightly-coupled microorganisms in the mat have specialized metabolisms that catalyze transformations of carbon, nitrogen. sulfur, and a host of other elements.

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

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

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

  12. Indian Ocean Biogeochemical Processes and Ecological Variability

    NASA Astrophysics Data System (ADS)

    Ofori, Leslie

    2010-11-01

    The Sustained Indian Ocean Biogeochemistry and Ecosystem Research (SIBER) conference was held in 2006 in Goa, India. The goals of the workshop were to assess the known facts about basin-wide biogeochemical and ecological dynamics of the Indian Ocean, to answer major questions, and to draw a road map for future research. The AGU monograph Indian Ocean Biogeochemical Processes and Ecological Variability, edited by Jerry D. Wiggert, Raleigh R. Hood, S. Wajih A. Naqvi, Kenneth H. Brink, and Sharon L. Smith, synthesizes the talks that were presented at this conference. In this interview, Eos talks with Jerry Wiggert, assistant professor of marine science at University of Southern Mississippi, Hattiesburg.

  13. Electric shortcuts of biogeochemical processes

    NASA Astrophysics Data System (ADS)

    Nielsen, Lars Peter; Risgaard-Petersen, Nils; Fossing, Henrik; Christensen, Peter Bondo; Sayama, Mikio

    2010-05-01

    Recent observations in marine sediment have revealed conductive networks transmitting electrons from oxidation processes in the anoxic zone to oxygen reduction in the oxic zone. The involved electrochemical processes seem to be biologically catalyzed and may account for more than half of the oxygen uptake in laboratory incubations of initially homogenized and stabilized sediment. Using microsensors and process rate measurements we further investigated the effect of the electric currents on sediment biogeochemistry. Dissolved sulfide readily donated electrons to the networks and could be depleted below detection limit in a several cm thick layer below the oxic zone. Subsequent dissolution of iron sulphide was indicated by mobilization of ferrous iron being precipitated again as ferric iron at the oxic-anoxic interface. Lowered sulphate reduction rates in the upper centimeters of the sediment confirmed the depth range of the electric communication and indicated donation of electrons directly from organotrophic bacteria. The separation of oxidation and reduction processes created steep pH gradients eventually causing carbonate precipitation at the surface and probably also carbonate dissolution at depth. We suggest that the electric currents allowing reactions between compounds far from one another have significant effects in natural marine sediments as well as other environments with redox gradients.

  14. Using NMR, SIP, and MS measurements for monitoring subsurface biogeochemical reactions at the Rifle IFRC site

    NASA Astrophysics Data System (ADS)

    Rosier, C. L.; Keating, K.; Williams, K. H.; Robbins, M.; Ntarlagiannis, D.; Grunewald, E.; Walsh, D. O.

    2013-12-01

    The Rifle Integrated Field Research Challenge (IFRC) site is located on a former uranium ore-processing facility in Rifle, Colorado (USA). Although removal of tailings and contaminated surface materials was completed in 1996, residual uranium contamination of groundwater and subsurface sediments remains. Since 2002, research at the site has primarily focused on quantifying uranium mobility associated with stimulated and natural biogeochemical processes. Uranium mobility at the Rifle IFRC site is typically quantified through direct sampling of groundwater; however, direct sampling does not provide information about the solid phase material outside of the borehole and continuous measurements are not always possible due to multiple constraints. Geophysical methods have been suggested as a minimally invasive alternative approach for long term monitoring of biogeochemical reactions associated with uranium remediation. In this study, nuclear magnetic resonance (NMR), spectral induced polarization (SIP), and magnetic susceptibility (MS) are considered as potential geophysical methods for monitoring the biogeochemical reactions occurring at the Rifle IFRC site. Additionally, a pilot field study using an NMR borehole-logging tool was carried out at the Rifle IFRC site. These methods are sensitive to changes in the chemical and physical subsurface properties that occur as a result of bioremediation efforts; specifically, changes in the redox state and chemical form of iron, production of iron sulfide minerals, production of the magnetic mineral magnetite, and associated changes in the pore geometry. Laboratory experiments consisted of monitoring changes in the NMR, SIP and MS response of an acetate-amended columns packed with sediments from the Rifle IFRC site over the course of two months. The MS values remained relatively stable throughout the course of the experiment suggesting negligible production of magnetic phases (e.g. magnetite, pyrrhotite) as a result of enhanced

  15. Biogeochemical Coupling of Fe and Tc Speciation in Subsurface Sediments: Implications to Long-Term Tc Immobilization

    SciTech Connect

    Jim K. Fredrickson; C. I. Steefel; R. K. Kukkadapu; S. M. Heald

    2006-06-01

    The project has been focused on biochemical processes in subsurface sediments involving Fe that control the valence state, solubility, and effective mobility of 99Tc. Our goal has been to understand the Tc biogeochemistry as it may occur in suboxic and biostimulated subsurface environments. Two objectives have been pursued: (1) To determine the relative reaction rates of 99Tc(VII)O2(aq) with metal reducing bacteria and biogenic Fe(II); and to characterize the identity, structure, and molecular speciation of Tc(IV) products formed through reaction with both biotic and abiotic reductants. (2) To quantify the biogeochemical factors controlling the reaction rate of O2 with Tc(IV)O2?nH2O in sediment resulting from the direct enzymatic reduction of Tc(VII) by DIRB and/or the reaction of Tc(VII) with the various types of biogenic Fe(II) produced by DIRB.

  16. Diel biogeochemical processes in terrestrial waters

    USGS Publications Warehouse

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

    2011-01-01

    Many biogeochemical processes in rivers and lakes respond to the solar photocycle and produce persistent patterns of measureable phenomena that exhibit a day-night, or 24-h, cycle. Despite a large body of recent literature, the mechanisms responsible for these diel fluctuations are widely debated, with a growing consensus that combinations of physical, chemical, and biological processes are involved. These processes include streamflow variation, photosynthesis and respiration, plant assimilation, and reactions involving photochemistry, adsorption and desorption, and mineral precipitation and dissolution. Diel changes in streamflow and water properties such as temperature, pH, and dissolved oxygen concentration have been widely recognized, and recently, diel studies have focused more widely by considering other constituents such as dissolved and particulate trace metals, metalloids, rare earth elements, mercury, organic matter, dissolved inorganic carbon (DIC), and nutrients. The details of many diel processes are being studied using stable isotopes, which also can exhibit diel cycles in response to microbial metabolism, photosynthesis and respiration, or changes in phase, speciation, or redox state. In addition, secondary effects that diel cycles might have, for example, on biota or in the hyporheic zone are beginning to be considered. This special issue is composed primarily of papers presented at the topical session "Diurnal Biogeochemical Processes in Rivers, Lakes, and Shallow Groundwater" held at the annual meeting of the Geological Society of America in October 2009 in Portland, Oregon. This session was organized because many of the growing number of diel studies have addressed just a small part of the full range of diel cycling phenomena found in rivers and lakes. This limited focus is understandable because (1) fundamental aspects of many diel processes are poorly understood and require detailed study, (2) the interests and expertise of individual

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

    USGS Publications Warehouse

    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."

  18. Hyporheic flow and transport processes: Mechanisms, models, and biogeochemical implications

    NASA Astrophysics Data System (ADS)

    Boano, F.; Harvey, J. W.; Marion, A.; Packman, A. I.; Revelli, R.; Ridolfi, L.; Wörman, A.

    2014-12-01

    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.

  19. Nitrate attenuation in groundwater: a review of biogeochemical controlling processes.

    PubMed

    Rivett, Michael O; Buss, Stephen R; Morgan, Philip; Smith, Jonathan W N; Bemment, Chrystina D

    2008-10-01

    Biogeochemical processes controlling nitrate attenuation in aquifers are critically reviewed. An understanding of the fate of nitrate in groundwater is vital for managing risks associated with nitrate pollution, and to safeguard groundwater supplies and groundwater-dependent surface waters. Denitrification is focused upon as the dominant nitrate attenuation process in groundwater. As denitrifying bacteria are essentially ubiquitous in the subsurface, the critical limiting factors are oxygen and electron donor concentration and availability. Variability in other environmental conditions such as nitrate concentration, nutrient availability, pH, temperature, presence of toxins and microbial acclimation appears to be less important, exerting only secondary influences on denitrification rates. Other nitrate depletion mechanisms such as dissimilatory nitrate reduction to ammonium and assimilation of nitrate into microbial biomass are unlikely to be important in most subsurface settings relative to denitrification. Further research is recommended to improve current understanding on the influence of organic carbon, sulphur and iron electron donors, physical restrictions on microbial activity in dual porosity aquifers, influences of environmental condition (e.g. pH in poorly buffered environments and salinity in coastal or salinized soil settings), co-contaminant influences (particularly the contrasting inhibitory and electron donor influences of pesticides) and improved quantification of denitrification rates in the laboratory and field.

  20. A biogeochemical framework for bioremediation of plutonium(V) in the subsurface environment.

    PubMed

    Deo, Randhir P; Rittmann, Bruce E

    2012-07-01

    Accidental release of plutonium (Pu) from storage facilities in the subsurface environment is a concern for the safety of human beings and the environment. Given the complexity of the subsurface environment and multivalent state of Pu, we developed a quantitative biogeochemical framework for bioremediation of Pu(V)O(2) (+) in the subsurface environment. We implemented the framework in the biogeochemical model CCBATCH by expanding its chemical equilibrium for aqueous complexation of Pu and its biological sub-models for including Pu's toxicity and reduction reactions. The quantified framework reveals that most of the Pu(V) is speciated as free Pu(V)O(2) (+) ((aq)), which is a problem if the concentration of free Pu(V)O(2) (+) is ≥28 μM (the half-maximum toxicity value for bacteria able to reduce Pu(V) to Pu(III)PO(4(am))) or ≥250 μM (the full-toxicity value that takes the bioreduction rate to zero). The framework includes bioreduction of Fe(3+) to Fe(2+), which abiotically reduces Pu(V)O(2) (+) to Pu(IV) and then to Pu(III). Biotic (enzymatic) reduction of Pu(V)O(2) (+) directly to Pu(III) by Shewanella alga (S. alga) is also included in the framework. Modeling results also reveal that for formation of Pu(III)PO(4(am)), the desired immobile product, the concentration of coexisting model strong ligand-nitrilotriacetic acid (NTA)-should be less than or equal to the concentration of total Pu(III).

  1. Global Biology Research Program: Biogeochemical Processes in Wetlands

    NASA Technical Reports Server (NTRS)

    Bartlett, D. S. (Editor)

    1984-01-01

    The results of a workshop examining potential NASA contributions to research on wetland processes as they relate to global biogeochemical cycles are summarized. A wetlands data base utilizing remotely sensed inventories, studies of wetland/atmosphere exchange processes, and the extrapolation of local measurements to global biogeochemical cycling processes were identified as possible areas for NASA support.

  2. Biogeochemical Process Comparison of the Five USGS Water, Energy, and Biogeochemical Budget (WEBB) Sites

    NASA Astrophysics Data System (ADS)

    Shanley, J. B.; Peters, N. E.; Aulenbach, B. T.; Blum, A. E.; Campbell, D. H.; Clow, D. W.; Larsen, M. C.; Mast, M. A.; Stallard, R. F.; Troester, J. W.; Walker, J. F.; Webb, R. M.; White, A. F.

    2001-12-01

    Input - output budgets (in wet deposition and streamwater) have been constructed for water and major solutes at the five USGS Water, Energy, and Biogeochemical Budget (WEBB) sites for the period 1992-97 (Peters et al., 2000). In this poster we interpret the net chemical fluxes to identify the controlling biogeochemical processes, as influenced by the strong physical and biological contrasts (climate, geology, physiography, and vegetation types) in the five diverse environments. The five sites are: Allequash Creek, Wisconsin (low-relief humid continental forest); Andrews Creek, Colorado (cold alpine, taiga/tundra, and subalpine boreal forest); Icacos River, Puerto Rico (lower montane, wet tropical forest); Panola Mountain, Georgia (humid subtropical piedmont forest); and Sleepers River, Vermont (humid northern hardwood forest). Base cations and Si produced by chemical weathering displayed a net export at each site. The magnitude and stoichiometry of export reflects mineralogy, climate (temperature and rainfall), and water residence time in the subsurface. The lowest and highest mass export generally was for Andrews Creek and Icacos River, respectively, consistent with their extreme mean annual temperatures (0/degC in Colorado to 21/degC in Puerto Rico) and the limited residence time of meltwater at Andrews Creek. Calcite in bedrock at the three coldest watersheds caused somewhat higher relative export of Ca, especially at Sleepers River where calcite weathering is a dominant control on stream chemistry. In contrast, the high Mg content of the volcaniclastic rocks at Icacos River and glacial deposits at Allequash Creek caused disproportionately high Mg export relative to the other sites. Relatively high Na export at Panola Mountain and K export at Sleepers River are probably caused by plagioclase and biotite weathering, respectively. SO4 is retained at the two warmest sites, Panola Mountain and Icacos River. SO4 adsorption is known to limit SO4- export in highly

  3. Modeling the Impact of Biogeochemical Hotspots and Hot Moments on Subsurface Carbon Fluxes from a Flood Plain Site

    NASA Astrophysics Data System (ADS)

    Arora, B.; Spycher, N.; Steefel, C. I.; King, E.; Conrad, M. E.

    2015-12-01

    Biogeochemical hotspots and hot moments are known to account for a high percentage of carbon and nutrient cycling within flood plain environments. To quantify the impact of these hotspots and hot moments on the carbon cycle, a 2D reactive transport model was developed for the saturated-unsaturated zone of a flood plain site in Rifle, CO. Previous studies have identified naturally reduced zones (NRZs) in the saturated zone of the Rifle site to be hotspots and important regions for subsurface biogeochemical cycling. Wavelet analysis of geochemical concentrations at the site suggested that hydrologic and temperature variations are hot moments and exert an important control on biogeochemical conditions in the Rifle aquifer. Here, we describe the development of a reactive transport model that couples hydrologic and biogeochemical processes to microbial functional distributions inferred from site-specific 'omic' data. The model includes microbial contributions from heterotrophic and chemolithoautotrophic processes. We use Monod based formulations to represent biomass formation and consider energy partitioning between catabolic and anabolic processes. We use this model to explore community emergence at the Rifle site and further constrain the extent and rates of nutrient uptake as well as abiotic and biotic reactions using stable carbon isotopes. Results from 2D model simulations with only abiotic reactions predict lower CO2 partial pressures in the unsaturated zone and severely underpredict (~200%) carbon fluxes to the river compared to simulations with chemolithoautotrophic pathways. δ13C-CO2 profiles also point to biotic sources for the locally observed high CO2 concentrations above NRZs. Results further indicate that groundwater carbon fluxes from the Rifle site to the river are underestimated by almost 180% (to 3.3 g m-2 d-1) when temperature fluctuations are ignored in the simulations. Preliminary results demonstrate the emergence of denitrifiers at specific depths

  4. Climate change effects on watershed hydrological and biogeochemical processes

    EPA Science Inventory

    Projected changes in climate are widely expected to alter watershed processes. However, the extent of these changes is difficult to predict because complex interactions among affected hydrological and biogeochemical processes will likely play out over many decades and spatial sc...

  5. Coupling of hydrodynamic and biogeochemical processes at aquatic interfaces

    NASA Astrophysics Data System (ADS)

    Lewandowski, Jörg; Krause, Stefan

    2015-04-01

    The overall aim of this contribution is a general conceptual framework for aquatic interfaces that is applicable to a wide range of systems, scales and processes. Aquatic interfaces are characterized by steep physical, chemical and biological gradients due to the contrast between the two adjacent environments. Investigating the spatially heterogeneous and temporally variable hydrodynamic and biogeochemical processes requires innovative monitoring technologies and sophisticated measurement techniques that can cope with different spatial scales. Although enhanced biogeochemical processing rates are inherent to aquatic interfaces due to their steep biogeochemical gradients and their intensive structural and compositional heterogeneity, the effective turnover depends strongly on the residence time distribution along the flow paths with their particular biogeochemical milieus and reaction kinetics. Thus, identification and characterization of the highly complex flow patterns in and across aquatic interfaces are crucial to understand biogeochemical processing along exchange flow paths and to quantify transport across aquatic interfaces; i.e. hydrodynamic and biogeochemical processes are closely interlinked. But interface processing rates are not only enhanced compared to the adjacent compartments that they connect; also completely different reactions might occur if certain thresholds are exceeded or the biogeochemical milieu differs significantly from the adjacent environments. Single events, temporal variability and spatial heterogeneity might increase overall processing rates of aquatic interfaces and thus, should not be neglected when studying aquatic interfaces. Aquatic interfaces are key zones relevant for the ecological state of the entire ecosystem and thus, understanding interface functioning and controls is paramount for ecosystem management.

  6. Microbial processes and subsurface contaminants

    NASA Astrophysics Data System (ADS)

    Molz, Fred J.

    A Chapman Conference entitled “Microbial Processes in the Transport, Fate, and In Situ Treatment of Subsurface Contaminants” was held in Snowbird, Utah, October 1-3, 1986. Members of the program committee and session chairmen were Lenore Clesceri (Rensselaer Polytechnic Institute, Troy, N.Y.), David Gibson (University of Texas, Austin), James Mercer (GeoTrans, Inc., Herndon , Va.), Donald Michelsen (Virginia Polytechnic Institute and State University, Blacksburg), Fred Molz (Auburn University, Auburn, Ala.), Bruce Rittman (University of Illinois, Urbana), Gary Sayler (University of Tennessee, Knoxville), and John T. Wilson (U.S. Environmental Protection Agency, Ada, Okla.). The following report attempts to highlight the six sessions that constituted the conference. For additional information, including a bound summary and abstracts, contact Fred J. Molz, Civil Engineering Department, Auburn University, AL 36849 (telephone: 205-826-4321).

  7. 2500 high-quality genomes reveal that the biogeochemical cycles of C, N, S and H are cross-linked by metabolic handoffs in the terrestrial subsurface

    NASA Astrophysics Data System (ADS)

    Anantharaman, K.; Brown, C. T.; Hug, L. A.; Sharon, I.; Castelle, C. J.; Shelton, A.; Bonet, B.; Probst, A. J.; Thomas, B. C.; Singh, A.; Wilkins, M.; Williams, K. H.; Tringe, S. G.; Beller, H. R.; Brodie, E.; Hubbard, S. S.; Banfield, J. F.

    2015-12-01

    Microorganisms drive the transformations of carbon compounds in the terrestrial subsurface, a key reservoir of carbon on earth, and impact other linked biogeochemical cycles. Our current knowledge of the microbial ecology in this environment is primarily based on 16S rRNA gene sequences that paint a biased picture of microbial community composition and provide no reliable information on microbial metabolism. Consequently, little is known about the identity and metabolic roles of the uncultivated microbial majority in the subsurface. In turn, this lack of understanding of the microbial processes that impact the turnover of carbon in the subsurface has restricted the scope and ability of biogeochemical models to capture key aspects of the carbon cycle. In this study, we used a culture-independent, genome-resolved metagenomic approach to decipher the metabolic capabilities of microorganisms in an aquifer adjacent to the Colorado River, near Rifle, CO, USA. We sequenced groundwater and sediment samples collected across fifteen different geochemical regimes. Sequence assembly, binning and manual curation resulted in the recovery of 2,542 high-quality genomes, 27 of which are complete. These genomes represent 1,300 non-redundant organisms comprising both abundant and rare community members. Phylogenetic analyses involving ribosomal proteins and 16S rRNA genes revealed the presence of up to 34 new phyla that were hitherto unknown. Less than 11% of all genomes belonged to the 4 most commonly represented phyla that constitute 93% of all currently available genomes. Genome-specific analyses of metabolic potential revealed the co-occurrence of important functional traits such as carbon fixation, nitrogen fixation and use of electron donors and electron acceptors. Finally, we predict that multiple organisms are often required to complete redox pathways through a complex network of metabolic handoffs that extensively cross-link subsurface biogeochemical cycles.

  8. Coupled Biogeochemical Process Evaluation for Conceptualizing Trichloroethylene Co-Metabolism

    SciTech Connect

    Colwell, Frederick; Radtke, Corey; Newby, Deborah; Delwiche, Mark; Crawf, Ronald L.; Paszczynski, Andrzej; Strap, Janice; Conrad, Mark; Brodic, Eoin; Starr, Robert; Lee, Hope

    2006-04-05

    Chlorinated solvent wastes (e.g., trichloroethene or TCE) often occur as diffuse subsurface plumes in complex geological environments where coupled processes must be understood in order to implement remediation strategies. Monitored natural attenuation (MNA) warrants study as a remediation technology because it minimizes worker and environment exposure to the wastes and because it costs less than other technologies. However, to be accepted MNA requires 'lines of evidence' indicating that the wastes are effectively destroyed. Our research will study the coupled biogeochemical processes that dictate the rate of TCE co-metabolism in contaminated aquifers first at the Idaho National Laboratory and then at Paducah or the Savannah River Site, where natural attenuation of TCE is occurring. We will use flow-through in situ reactors to investigate the rate of methanotrophic co-metabolism of TCE and the coupling of the responsible biological processes with the dissolved methane flux and groundwater flow velocity. We will use new approaches (e.g., stable isotope probing, enzyme activity probes, real-time reverse transcriptase polymerase chain reaction, proteomics) to assay the TCE co-metabolic rates, and interpret these rates in the context of enzyme activity, gene expression, and cellular inactivation related to intermediates of TCE co-metabolism. By determining the rate of TCE co-metabolism at different methane concentrations and groundwater flow velocities, we will derive key modeling parameters for the computational simulations that describe the attenuation, and thereby refine such models while assessing the contribution of microbial relative to other natural attenuation processes. This research will strengthen our ability to forecast the viability of MNA at DOE and other sites that are contaminated with chlorinated hydrocarbons.

  9. Cyclic biogeochemical processes and nitrogen fate beneath a subtropical stormwater infiltration basin

    USGS Publications Warehouse

    O'Reilly, Andrew M.; Chang, Ni-Bin; Wanielista, Martin P.

    2012-01-01

    A stormwater infiltration basin in north–central Florida, USA, was monitored from 2007 through 2008 to identify subsurface biogeochemical processes, with emphasis on N cycling, under the highly variable hydrologic conditions common in humid, subtropical climates. Cyclic variations in biogeochemical processes generally coincided with wet and dry hydrologic conditions. Oxidizing conditions in the subsurface persisted for about one month or less at the beginning of wet periods with dissolved O2 and NO3- showing similar temporal patterns. Reducing conditions in the subsurface evolved during prolonged flooding of the basin. At about the same time O2 and NO3- reduction concluded, Mn, Fe and SO42- reduction began, with the onset of methanogenesis one month later. Reducing conditions persisted up to six months, continuing into subsequent dry periods until the next major oxidizing infiltration event. Evidence of denitrification in shallow groundwater at the site is supported by median NO3-–N less than 0.016 mg L-1, excess N2 up to 3 mg L-1 progressively enriched in δ15N during prolonged basin flooding, and isotopically heavy δ15N and δ18O of NO3- (up to 25‰ and 15‰, respectively). Isotopic enrichment of newly infiltrated stormwater suggests denitrification was partially completed within two days. Soil and water chemistry data suggest that a biogeochemically active zone exists in the upper 1.4 m of soil, where organic carbon was the likely electron donor supplied by organic matter in soil solids or dissolved in infiltrating stormwater. The cyclic nature of reducing conditions effectively controlled the N cycle, switching N fate beneath the basin from NO3- leaching to reduction in the shallow saturated zone. Results can inform design of functionalized soil amendments that could replace the native soil in a stormwater infiltration basin and mitigate potential NO3- leaching to groundwater by replicating the biogeochemical conditions under the observed basin.

  10. Cyclic biogeochemical processes and nitrogen fate beneath a subtropical stormwater infiltration basin.

    PubMed

    O'Reilly, Andrew M; Chang, Ni-Bin; Wanielista, Martin P

    2012-05-15

    A stormwater infiltration basin in north-central Florida, USA, was monitored from 2007 through 2008 to identify subsurface biogeochemical processes, with emphasis on N cycling, under the highly variable hydrologic conditions common in humid, subtropical climates. Cyclic variations in biogeochemical processes generally coincided with wet and dry hydrologic conditions. Oxidizing conditions in the subsurface persisted for about one month or less at the beginning of wet periods with dissolved O(2) and NO(3)(-) showing similar temporal patterns. Reducing conditions in the subsurface evolved during prolonged flooding of the basin. At about the same time O(2) and NO(3)(-) reduction concluded, Mn, Fe and SO(4)(2-) reduction began, with the onset of methanogenesis one month later. Reducing conditions persisted up to six months, continuing into subsequent dry periods until the next major oxidizing infiltration event. Evidence of denitrification in shallow groundwater at the site is supported by median NO(3)(-)-N less than 0.016 mg L(-1), excess N(2) up to 3 mg L(-1) progressively enriched in δ(15)N during prolonged basin flooding, and isotopically heavy δ(15)N and δ(18)O of NO(3)(-) (up to 25‰ and 15‰, respectively). Isotopic enrichment of newly infiltrated stormwater suggests denitrification was partially completed within two days. Soil and water chemistry data suggest that a biogeochemically active zone exists in the upper 1.4m of soil, where organic carbon was the likely electron donor supplied by organic matter in soil solids or dissolved in infiltrating stormwater. The cyclic nature of reducing conditions effectively controlled the N cycle, switching N fate beneath the basin from NO(3)(-) leaching to reduction in the shallow saturated zone. Results can inform design of functionalized soil amendments that could replace the native soil in a stormwater infiltration basin and mitigate potential NO(3)(-) leaching to groundwater by replicating the biogeochemical

  11. Quantifying the surface-subsurface biogeochemical coupling during the VERTIGO ALOHA and K2 studies

    SciTech Connect

    Boyd, P.W.; Gall, M.P.; Silver, M.W.; Bishop, J.K.B.; Coale, Susan L.; Bidigare, Robert R.

    2008-02-25

    A central question addressed by the VERTIGO (VERtical Transport In the Global Ocean) study was 'What controls the efficiency of particle export between the surface and subsurface ocean'? Here, we present data from sites at ALOHA (N Central Pacific Gyre) and K2 (NW subarctic Pacific) on phytoplankton processes, and relate them via a simple planktonic foodweb model, to subsurface particle export (150-500 m). Three key factors enable quantification of the surface-subsurface coupling: a sampling design to overcome the temporal lag and spatial displacement between surface and subsurface processes; data on the size-partitioning of Net Primary Production (NPP) and subsequent transformations prior to export; estimates of the ratio of algal- to faecal-mediated vertical export flux. At ALOHA, phytoplankton were characterized by low stocks, NPP, F{sub v}/F{sub m} (N-limited), and were dominated by picoplankton. The HNLC waters at K2 were characterized by both two-fold changes in NPP and floristic shifts (high to low proportion of diatoms) between deployment 1 and 2. Prediction of export exiting the euphotic zone was based on size-partitioning of NPP, a copepod-dominated foodweb and a ratio of 0.2 (ALOHA) and 0.1 (K2) for algal:faecal particle flux. Predicted export was 20-22 mg POC m{sup -2} d{sup -1} at ALOHA (i.e. 10-11% NPP (0-125 m); 1.1-1.2 x export flux at 150 m (E{sub 150}). At K2, export was 111 mg C m{sup -2} d{sup -1} (21% NPP (0-50 m); 1.8 x E{sub 150}) and 33 mg POC m{sup -2} d{sup -1} (11% NPP, 0-55 m); 1.4 x E{sub 150}) for deployments 1 and 2, respectively. This decrease in predicted export at K2 matches the observed trend for E{sub 150}. Also, the low attenuation of export flux from 60 to 150 m is consistent with that between 150 to 500 m. This strong surface-subsurface coupling suggests that phytoplankton productivity and floristics play a key role at K2 in setting export flux, and moreover that pelagic particle transformations by grazers strongly influence

  12. Quantifying the surface subsurface biogeochemical coupling during the VERTIGO ALOHA and K2 studies

    NASA Astrophysics Data System (ADS)

    Boyd, Philip W.; Gall, Mark P.; Silver, Mary W.; Coale, Susan L.; Bidigare, Robert R.; Bishop, James L. K. B.

    2008-07-01

    A central question addressed by the VERtical Transport In the Global Ocean (VERTIGO) study was 'What controls the efficiency of particle export between the surface and subsurface ocean'? Here, we present data from sites at ALOHA (N Central Pacific Gyre) and K2 (NW subarctic Pacific) on phytoplankton processes, and relate them via a simple planktonic foodweb model, to subsurface particle export (150-500 m). Three key factors enable quantification of the surface-subsurface coupling: a sampling design to overcome the temporal lag and spatial displacement between surface and subsurface processes; data on the size partitioning of net primary production (NPP) and subsequent transformations prior to export; estimates of the ratio of algal- to faecal-mediated vertical export flux. At ALOHA, phytoplankton were characterized by low stocks, NPP, Fv/ Fm (N-limited), and were dominated by picoplankton. The HNLC waters at K2 were characterized by both two-fold changes in NPP and floristic shifts (high to low proportion of diatoms) between deployment 1 and 2. Prediction of export exiting the euphotic zone was based on size partitioning of NPP, a copepod-dominated foodweb and a ratio of 0.2 (ALOHA) and 0.1 (K2) for algal:faecal particle flux. Predicted export was 20-22 mg POC m -2 d -1 at ALOHA (i.e. 10-11% NPP (0-125 m); 1.1-1.2×export flux at 150 m ( E150). At K2, export was 111 mg C m -2 d -1 (21% NPP (0-50 m); 1.8× E150) and 33 mg POC m -2 d -1 (11% NPP, 0-55 m); 1.4× E150) for deployments 1 and 2, respectively. This decrease in predicted export at K2 matches the observed trend for E150. Also, the low attenuation of export flux from 60 to 150 m is consistent with that between 150 and 500 m. This strong surface-subsurface coupling suggests that phytoplankton productivity and floristics play a key role at K2 in setting export flux, and moreover that pelagic particle transformations by grazers strongly influence to what extent sinking particles are further broken down in the

  13. A General Simulator for Reaction-Based Biogeochemical Processes

    SciTech Connect

    Fang, Yilin; Yabusaki, Steven B.; Yeh, George

    2006-02-01

    As more complex biogeochemical situations are being investigated (e.g., evolving reactivity, passivation of reactive surfaces, dissolution of sorbates), there is a growing need for biogeochemical simulators to flexibly and facilely address new reaction forms and rate laws. This paper presents an approach that accommodates this need to efficiently simulate general biogeochemical processes, while insulating the user from additional code development. The approach allows for the automatic extraction of fundamental reaction stoichiometry and thermodynamics from a standard chemistry database, and the symbolic entry of arbitrarily complex user-specified reaction forms, rate laws, and equilibria. The user-specified equilibrium and kinetic reactions (i.e., reactions not defined in the format of the standardized database) are interpreted by the Maple symbolic mathematical software package. FORTRAN 90 code is then generated by Maple for (1) the analytical Jacobian matrix (if preferred over the numerical Jacobian matrix) used in the Newton-Raphson solution procedure, and (2) the residual functions for user-specified equilibrium expressions and rate laws. Matrix diagonalization eliminates the need to conceptualize the system of reactions as a tableau, while identifying a minimum rank set of basis species with enhanced numerical convergence properties. The newly generated code, which is designed to operate in the BIOGEOCHEM biogeochemical simulator, is then compiled and linked into the BIOGEOCHEM executable. With these features, users can avoid recoding the simulator to accept new equilibrium expressions or kinetic rate laws, while still taking full advantage of the stoichiometry and thermodynamics provided by an existing chemical database. Thus, the approach introduces efficiencies in the specification of biogeochemical reaction networks and eliminates opportunities for mistakes in preparing input files and coding errors. Test problems are used to demonstrate the features of

  14. Hydrologic and biogeochemical controls of river subsurface solutes under agriculturally enhanced ground water flow

    USGS Publications Warehouse

    Wildman, R.A.; Domagalski, J.L.; Hering, J.G.

    2009-01-01

    The relative influences of hydrologic processes and biogeochemistry on the transport and retention of minor solutes were compared in the riverbed of the lower Merced River (California, USA). The subsurface of this reach receives ground water discharge and surface water infiltration due to an altered hydraulic setting resulting from agricultural irrigation. Filtered ground water samples were collected from 30 drive point locations in March, June, and October 2004. Hydrologic processes, described previously, were verified by observations of bromine concentrations; manganese was used to indicate redox conditions. The separate responses of the minor solutes strontium, barium, uranium, and phosphorus to these influences were examined. Correlation and principal component analyses indicate that hydrologic processes dominate the distribution of trace elements in the ground water. Redox conditions appear to be independent of hydrologic processes and account for most of the remaining data variability. With some variability, major processes are consistent in two sampling transects separated by 100 m. Copyright ?? 2009 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

  15. Polychlorinated Biphenyls as Probes of Biogeochemical Processes in Rivers

    USGS Publications Warehouse

    Fitzgerald, S.A.; Steuer, J.J.

    1997-01-01

    A field study was conducted to investigate the use of PCB (polychlorinated biphenyl) congener and homolog assemblages as tracers of biogeochemical processes in the Milwaukee and Manitowoc Rivers in southeastern Wisconsin from 1993 to 1995. PCB congeners in the dissolved and suspended particle phases, along with various algal indicators (algal carbon and pigments), were quantitated in the water seasonally. In addition, PCB congener assemblages were determined seasonally in surficial bed sediments. Biogeochemical processes investigated included: determination of the source of suspended particles and bottom sediments by comparison with known Aroclor mixtures, water-solid partitioning, and algal uptake of PCBs. Seasonal differences among the PCB assemblages were observed mainly in the dissolved phase, somewhat less in the suspended particulate phase, and not at all in the bed sediments.

  16. Biogeochemical Stability of Contaminants in the Subsurface Following In Situ Treatment

    EPA Science Inventory

    In recent years, innovative treatment technologies have emerged to meet groundwater cleanup goals. In many cases these methods take advantage of the redox behavior of contaminant species. For example, remedial technologies that strategically manipulate subsurface redox conditio...

  17. Implementing high-latitude biogeochemical processes into Earth System Models

    NASA Astrophysics Data System (ADS)

    Brovkin, Victor; Kleinen, Thomas; Cresto-Aleina, Fabio; Kloster, Silvia; Ilyina, Tatiana

    2016-04-01

    Projections of future climate changes suggest that air temperatures in the Arctic could rise to the levels unprecedented in the last million years. Sensitivity of carbon storages on land and shelves to climate change of that scale is highly uncertain. Earth System models (ESMs), consisting of atmosphere, ocean, land, and cryosphere components are the main tools to understand interactions between carbon cycle and climate. However, ESM representation of ecological and biogeochemical processes in the Arctic is extremely simplistic. For example, all ESMs agree that tree cover in the future warming scenarios will move northwards to the Arctic coast, but they ignore interactions between vegetation, permafrost, and disturbances such as fires, which are critical for vegetation dynamics in this region. Improving modeling of interactions between model components and their evaluation against growing observational evidence is a promising research area. The first attempts to account for the permafrost carbon dynamics in the ESM framework suggest that CO2 and CH4 emissions from high-latitude regions in the 21st century are relatively small, but they become much more significant afterwards due to committed climate changes. Therefore, extension of ESM simulations beyond 2100 is essential to estimate a proper scale of frozen carbon pool response to human-induced climate change. Additionally, inclusion of sub-sea permafrost component into ESMs is an active research area that brings together terrestrial and marine biogeochemical communities, as well as geologists analyzing climate proxies on glacial timescales. Another challenging aspect of biogeochemical interactions in Arctic is an extreme land surface heterogeneity. A mixture of wetlands, lakes, and vegetation-covered surfaces on fine local scale is not properly reflected in the model structure. A promising approach of dealing with scaling gaps in modeling high-latitude biogeochemical processes in ESMs will be presented.

  18. Biogeochemical Processes Controlling Microbial Reductive Precipitation of Radionuclides

    SciTech Connect

    Fredrickson, James K.; Brooks, Scott C.

    2004-03-17

    This project is focused on elucidating the principal biogeochemical reactions that govern the concentrations, chemical speciation, and distribution of the redox sensitive contaminants uranium (U) and technetium (Tc) between the aqueous and solid phases. The research is designed to provide new insights into the under-explored areas of competing geochemical and microbiological oxidation-reduction reactions that govern the fate and transport of redox sensitive contaminants and to generate fundamental scientific understanding of the identity and stoichiometry of competing microbial reduction and geochemical oxidation reactions. These goals and objectives are met through a series of hypothesis-driven tasks that focus on (1) the use of well-characterized microorganisms and synthetic and natural mineral oxidants, (2) advanced spectroscopic and microscopic techniques to monitor redox transformations of U and Tc, and (3) the use of flow-through experiments to more closely approximate groundwater environments. The results are providing an improved understanding and predictive capability of the mechanisms that govern the redox dynamics of radionuclides in subsurface environments. For purposes of this poster, the results are divided into three sections: (1) influence of Ca on U(VI) bioreduction; (2) localization of biogenic UO{sub 2} and TcO{sub 2}; and (3) reactivity of Mn(III/IV) oxides.

  19. Biogeochemical evidence for subsurface hydrocarbon occurrence, Recluse oil field, Wyoming; preliminary results

    USGS Publications Warehouse

    Dalziel, Mary C.; Donovan, Terrence J.

    1980-01-01

    Anomalously high manganese-to-iron ratios occurring in pine needles and sage leaves over the Recluse oil field, Wyoming, suggest effects of petroleum microseepage on the plants. This conclusion is supported by iron and manganese concentrations in soils and carbon and oxygen isotope ratios in rock samples. Seeping hydrocarbons provided reducing conditions sufficient to enable divalent iron and manganese to be organically complexed or adsorbed on solids in the soils. These bound or adsorped elements in the divalent state are essential to plants, and the plants readily assimilate them. The magnitude of the plant anomalies, combined with the supportive isotopic and chemical evidence confirming petroleum leakage, makes a strong case for the use of plants as a biogeochemical prospecting tool.

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

    NASA Astrophysics Data System (ADS)

    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

  1. Temporal dynamics of biogeochemical processes at the Norman Landfill site

    NASA Astrophysics Data System (ADS)

    Arora, Bhavna; Mohanty, Binayak P.; McGuire, Jennifer T.; Cozzarelli, Isabelle M.

    2013-10-01

    The temporal variability observed in redox sensitive species in groundwater can be attributed to coupled hydrological, geochemical, and microbial processes. These controlling processes are typically nonstationary, and distributed across various time scales. Therefore, the purpose of this study is to investigate biogeochemical data sets from a municipal landfill site to identify the dominant modes of variation and determine the physical controls that become significant at different time scales. Data on hydraulic head, specific conductance, δ2H, chloride, sulfate, nitrate, and nonvolatile dissolved organic carbon were collected between 1998 and 2000 at three wells at the Norman Landfill site in Norman, OK. Wavelet analysis on this geochemical data set indicates that variations in concentrations of reactive and conservative solutes are strongly coupled to hydrologic variability (water table elevation and precipitation) at 8 month scales, and to individual eco-hydrogeologic framework (such as seasonality of vegetation, surface-groundwater dynamics) at 16 month scales. Apart from hydrologic variations, temporal variability in sulfate concentrations can be associated with different sources (FeS cycling, recharge events) and sinks (uptake by vegetation) depending on the well location and proximity to the leachate plume. Results suggest that nitrate concentrations show multiscale behavior across temporal scales for different well locations, and dominant variability in dissolved organic carbon for a closed municipal landfill can be larger than 2 years due to its decomposition and changing content. A conceptual framework that explains the variability in chemical concentrations at different time scales as a function of hydrologic processes, site-specific interactions, and/or coupled biogeochemical effects is also presented.

  2. Temporal dynamics of biogeochemical processes at the Norman Landfill site

    USGS Publications Warehouse

    Arora, Bhavna; Mohanty, Binayak P.; McGuire, Jennifer T.; Cozzarelli, Isabelle M.

    2013-01-01

    The temporal variability observed in redox sensitive species in groundwater can be attributed to coupled hydrological, geochemical, and microbial processes. These controlling processes are typically nonstationary, and distributed across various time scales. Therefore, the purpose of this study is to investigate biogeochemical data sets from a municipal landfill site to identify the dominant modes of variation and determine the physical controls that become significant at different time scales. Data on hydraulic head, specific conductance, δ2H, chloride, sulfate, nitrate, and nonvolatile dissolved organic carbon were collected between 1998 and 2000 at three wells at the Norman Landfill site in Norman, OK. Wavelet analysis on this geochemical data set indicates that variations in concentrations of reactive and conservative solutes are strongly coupled to hydrologic variability (water table elevation and precipitation) at 8 month scales, and to individual eco-hydrogeologic framework (such as seasonality of vegetation, surface-groundwater dynamics) at 16 month scales. Apart from hydrologic variations, temporal variability in sulfate concentrations can be associated with different sources (FeS cycling, recharge events) and sinks (uptake by vegetation) depending on the well location and proximity to the leachate plume. Results suggest that nitrate concentrations show multiscale behavior across temporal scales for different well locations, and dominant variability in dissolved organic carbon for a closed municipal landfill can be larger than 2 years due to its decomposition and changing content. A conceptual framework that explains the variability in chemical concentrations at different time scales as a function of hydrologic processes, site-specific interactions, and/or coupled biogeochemical effects is also presented.

  3. Characterization of Coupled Hydrologic-Biogeochemical Processes Using Geophysical Data

    SciTech Connect

    Hubbard, Susan

    2005-06-01

    Biogeochemical and hydrological processes are naturally coupled and variable over a wide range of spatial and temporal scales. Many remediation approaches also induce dynamic transformations in natural systems, such as the generation of gases, precipitates and biofilms. These dynamic transformations are often coupled and can reduce the hydraulic conductivity of the geologic materials, making it difficult to introduce amendments or to perform targeted remediation. Because it is difficult to predict these transformations, our ability to develop effective and sustainable remediation conditions at contaminated sites is often limited. Further complicating the problem is the inability to collect the necessary measurements at a high enough spatial resolution yet over a large enough volume for understanding field-scale transformations.

  4. Critical biogeochemical functions in the subsurface are associated with bacteria from new phyla and little studied lineages

    DOE PAGES

    Hug, Laura A.; Thomas, Brian C.; Sharon, Itai; Brown, Christopher T.; Sharma, Ritin; Hettich, Robert L.; Wilkins, Michael J.; Williams, Kenneth H.; Singh, Andrea; Banfield, Jillian F.

    2015-07-22

    Nitrogen, sulfur and carbon fluxes in the terrestrial subsurface are determined by the intersecting activities of microbial community members, yet the organisms responsible are largely unknown. Metagenomic methods can identify organisms and functions, but genome recovery is often precluded by data complexity. To address this limitation, we developed subsampling assembly methods to re-construct high-quality draft genomes from complex samples. Here, we applied these methods to evaluate the interlinked roles of the most abundant organisms in biogeochemical cycling in the aquifer sediment. Community proteomics confirmed these activities. The eight most abundant organisms belong to novel lineages, and two represent phyla withmore » no previously sequenced genome. Four organisms are predicted to fix carbon via the Calvin Benson Bassham, Wood Ljungdahl or 3-hydroxyproprionate/4-hydroxybutarate pathways. The profiled organisms are involved in the network of denitrification, dissimilatory nitrate reduction to ammonia, ammonia oxidation and sulfate reduction/oxidation, and require substrates supplied by other community members. An ammonium-oxidizing Thaumarchaeote is the most abundant community member, despite low ammonium concentrations in the groundwater. Finally, this organism likely benefits from two other relatively abundant organisms capable of producing ammonium from nitrate, which is abundant in the groundwater. Overall, dominant members of the microbial community are interconnected through exchange of geochemical resources.« less

  5. Critical biogeochemical functions in the subsurface are associated with bacteria from new phyla and little studied lineages

    SciTech Connect

    Hug, Laura A.; Thomas, Brian C.; Sharon, Itai; Brown, Christopher T.; Sharma, Ritin; Hettich, Robert L.; Wilkins, Michael J.; Williams, Kenneth H.; Singh, Andrea; Banfield, Jillian F.

    2015-07-22

    Nitrogen, sulfur and carbon fluxes in the terrestrial subsurface are determined by the intersecting activities of microbial community members, yet the organisms responsible are largely unknown. Metagenomic methods can identify organisms and functions, but genome recovery is often precluded by data complexity. To address this limitation, we developed subsampling assembly methods to re-construct high-quality draft genomes from complex samples. Here, we applied these methods to evaluate the interlinked roles of the most abundant organisms in biogeochemical cycling in the aquifer sediment. Community proteomics confirmed these activities. The eight most abundant organisms belong to novel lineages, and two represent phyla with no previously sequenced genome. Four organisms are predicted to fix carbon via the Calvin Benson Bassham, Wood Ljungdahl or 3-hydroxyproprionate/4-hydroxybutarate pathways. The profiled organisms are involved in the network of denitrification, dissimilatory nitrate reduction to ammonia, ammonia oxidation and sulfate reduction/oxidation, and require substrates supplied by other community members. An ammonium-oxidizing Thaumarchaeote is the most abundant community member, despite low ammonium concentrations in the groundwater. Finally, this organism likely benefits from two other relatively abundant organisms capable of producing ammonium from nitrate, which is abundant in the groundwater. Overall, dominant members of the microbial community are interconnected through exchange of geochemical resources.

  6. Impacts of Hydrological and Biogeochemical Process Synchrony Transcend Scale

    NASA Astrophysics Data System (ADS)

    Spence, C.; Kokelj, S.; McCluskie, M.; Hedstrom, N.

    2015-12-01

    In portions of the circumpolar north, there are documented cases of increases in annual inorganic nitrogen loading. Confounding the explanation of this phenomenon is a lack of accompanying annual trends in streamflow, precipitation or atmospheric nitrogen deposition. Evidence from Canada's subarctic suggests this dichotomy could be due to three key non-linearities in the predominant biogeochemical and hydrological processes. Because snowfall changes to rainfall near the zero degree air temperature isotherm, there has been an increase in late autumn rainfall across the region due to earlier passage of precipitation generating cold fronts. Runoff generation in cold regions is often a storage threshold-mediated process, and the enhanced rainfall results in more common exceedance of these thresholds and higher winter streamflow. Finally, net mineralization rates in regional lakes peak in winter following the onset of ice cover. Subtle increases in monthly rainfall at specific times of the year can permit hydro-chemical process synchrony within watersheds that enhances annual inorganic nitrogen loading, implying that the impacts of process synchrony transcend scale. The presence of shifts in nitrogen export suggests that sustained regular process synchrony can modify system states. Sound understanding of system processes and interactions across scales will be needed to properly predict impacts and make sound decisions when managing watersheds and competing resource demands.

  7. The emergence of hydrogeophysics for improved understanding of subsurface processes over multiple scales

    SciTech Connect

    Binley, Andrew; Hubbard, Susan S.; Huisman, Johan A.; Revil, André; Robinson, David A.; Singha, Kamini; Slater, Lee D.

    2015-06-15

    Geophysics provides a multidimensional suite of investigative methods that are transforming our ability to see into the very fabric of the subsurface environment, and monitor the dynamics of its fluids and the biogeochemical reactions that occur within it. Here we document how geophysical methods have emerged as valuable tools for investigating shallow subsurface processes over the past two decades and offer a vision for future developments relevant to hydrology and also ecosystem science. The field of “hydrogeophysics” arose in the late 1990s, prompted, in part, by the wealth of studies on stochastic subsurface hydrology that argued for better field-based investigative techniques. These new hydrogeophysical approaches benefited from the emergence of practical and robust data inversion techniques, in many cases with a view to quantify shallow subsurface heterogeneity and the associated dynamics of subsurface fluids. Furthermore, the need for quantitative characterization stimulated a wealth of new investigations into petrophysical relationships that link hydrologically relevant properties to measurable geophysical parameters. Development of time-lapse approaches provided a new suite of tools for hydrological investigation, enhanced further with the realization that some geophysical properties may be sensitive to biogeochemical transformations in the subsurface environment, thus opening up the new field of “biogeophysics.” Early hydrogeophysical studies often concentrated on relatively small “plot-scale” experiments. More recently, however, the translation to larger-scale characterization has been the focus of a number of studies. In conclusion, geophysical technologies continue to develop, driven, in part, by the increasing need to understand and quantify key processes controlling sustainable water resources and ecosystem services.

  8. The emergence of hydrogeophysics for improved understanding of subsurface processes over multiple scales

    PubMed Central

    Hubbard, Susan S.; Huisman, Johan A.; Revil, André; Robinson, David A.; Singha, Kamini; Slater, Lee D.

    2015-01-01

    Abstract Geophysics provides a multidimensional suite of investigative methods that are transforming our ability to see into the very fabric of the subsurface environment, and monitor the dynamics of its fluids and the biogeochemical reactions that occur within it. Here we document how geophysical methods have emerged as valuable tools for investigating shallow subsurface processes over the past two decades and offer a vision for future developments relevant to hydrology and also ecosystem science. The field of “hydrogeophysics” arose in the late 1990s, prompted, in part, by the wealth of studies on stochastic subsurface hydrology that argued for better field‐based investigative techniques. These new hydrogeophysical approaches benefited from the emergence of practical and robust data inversion techniques, in many cases with a view to quantify shallow subsurface heterogeneity and the associated dynamics of subsurface fluids. Furthermore, the need for quantitative characterization stimulated a wealth of new investigations into petrophysical relationships that link hydrologically relevant properties to measurable geophysical parameters. Development of time‐lapse approaches provided a new suite of tools for hydrological investigation, enhanced further with the realization that some geophysical properties may be sensitive to biogeochemical transformations in the subsurface environment, thus opening up the new field of “biogeophysics.” Early hydrogeophysical studies often concentrated on relatively small “plot‐scale” experiments. More recently, however, the translation to larger‐scale characterization has been the focus of a number of studies. Geophysical technologies continue to develop, driven, in part, by the increasing need to understand and quantify key processes controlling sustainable water resources and ecosystem services. PMID:26900183

  9. The emergence of hydrogeophysics for improved understanding of subsurface processes over multiple scales

    NASA Astrophysics Data System (ADS)

    Binley, Andrew; Hubbard, Susan S.; Huisman, Johan A.; Revil, André; Robinson, David A.; Singha, Kamini; Slater, Lee D.

    2015-06-01

    Geophysics provides a multidimensional suite of investigative methods that are transforming our ability to see into the very fabric of the subsurface environment, and monitor the dynamics of its fluids and the biogeochemical reactions that occur within it. Here we document how geophysical methods have emerged as valuable tools for investigating shallow subsurface processes over the past two decades and offer a vision for future developments relevant to hydrology and also ecosystem science. The field of "hydrogeophysics" arose in the late 1990s, prompted, in part, by the wealth of studies on stochastic subsurface hydrology that argued for better field-based investigative techniques. These new hydrogeophysical approaches benefited from the emergence of practical and robust data inversion techniques, in many cases with a view to quantify shallow subsurface heterogeneity and the associated dynamics of subsurface fluids. Furthermore, the need for quantitative characterization stimulated a wealth of new investigations into petrophysical relationships that link hydrologically relevant properties to measurable geophysical parameters. Development of time-lapse approaches provided a new suite of tools for hydrological investigation, enhanced further with the realization that some geophysical properties may be sensitive to biogeochemical transformations in the subsurface environment, thus opening up the new field of "biogeophysics." Early hydrogeophysical studies often concentrated on relatively small "plot-scale" experiments. More recently, however, the translation to larger-scale characterization has been the focus of a number of studies. Geophysical technologies continue to develop, driven, in part, by the increasing need to understand and quantify key processes controlling sustainable water resources and ecosystem services.

  10. The emergence of hydrogeophysics for improved understanding of subsurface processes over multiple scales

    DOE PAGES

    Binley, Andrew; Hubbard, Susan S.; Huisman, Johan A.; Revil, André; Robinson, David A.; Singha, Kamini; Slater, Lee D.

    2015-06-15

    Geophysics provides a multidimensional suite of investigative methods that are transforming our ability to see into the very fabric of the subsurface environment, and monitor the dynamics of its fluids and the biogeochemical reactions that occur within it. Here we document how geophysical methods have emerged as valuable tools for investigating shallow subsurface processes over the past two decades and offer a vision for future developments relevant to hydrology and also ecosystem science. The field of “hydrogeophysics” arose in the late 1990s, prompted, in part, by the wealth of studies on stochastic subsurface hydrology that argued for better field-based investigativemore » techniques. These new hydrogeophysical approaches benefited from the emergence of practical and robust data inversion techniques, in many cases with a view to quantify shallow subsurface heterogeneity and the associated dynamics of subsurface fluids. Furthermore, the need for quantitative characterization stimulated a wealth of new investigations into petrophysical relationships that link hydrologically relevant properties to measurable geophysical parameters. Development of time-lapse approaches provided a new suite of tools for hydrological investigation, enhanced further with the realization that some geophysical properties may be sensitive to biogeochemical transformations in the subsurface environment, thus opening up the new field of “biogeophysics.” Early hydrogeophysical studies often concentrated on relatively small “plot-scale” experiments. More recently, however, the translation to larger-scale characterization has been the focus of a number of studies. In conclusion, geophysical technologies continue to develop, driven, in part, by the increasing need to understand and quantify key processes controlling sustainable water resources and ecosystem services.« less

  11. Identifying biogeochemical processes beneath stormwater infiltration ponds in support of a new best management practice for groundwater protection

    USGS Publications Warehouse

    O'Reilly, Andrew M.; Chang, Ni-Bin; Wanielista, Martin P.; Xuan, Zhemin; Schirmer, Mario; Hoehn, Eduard; Vogt, Tobias

    2011-01-01

     When applying a stormwater infiltration pond best management practice (BMP) for protecting the quality of underlying groundwater, a common constituent of concern is nitrate. Two stormwater infiltration ponds, the SO and HT ponds, in central Florida, USA, were monitored. A temporal succession of biogeochemical processes was identified beneath the SO pond, including oxygen reduction, denitrification, manganese and iron reduction, and methanogenesis. In contrast, aerobic conditions persisted beneath the HT pond, resulting in nitrate leaching into groundwater. Biogeochemical differences likely are related to soil textural and hydraulic properties that control surface/subsurface oxygen exchange. A new infiltration BMP was developed and a full-scale application was implemented for the HT pond. Preliminary results indicate reductions in nitrate concentration exceeding 50% in soil water and shallow groundwater beneath the HT pond.

  12. Pore-scale experimental study of multiphase flow relevant to CO2 sequestration and biogeochemical reactive transport relevant to contaminant fate in the subsurface

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Oostrom, M.; Liu, C.

    2012-12-01

    Pore-scale micromodel experiments are being conducted at EMSL PNNL to gain better understanding of i) fundamental interfacial processes that control multiphase flow relevant to CO2 sequestration, and ii) biogeochemical reactive transport that affect the fate of contaminants in the subsurface. During the main drainage process, unstable capillary and viscous fingering mechanisms were observed in a nearly homogeneous micromodel and a dual-permeability micromodel that affect supercritical CO2 (scCO2, 9 MPa, 41 degree C) displacement of water from the pore space. During primary imbibition, water flooding of a micromodel partially saturated with scCO2 resulted in preferential dissolution of scCO2 (i.e., dissolution fingering). Micromodel experiments were also performed to investigate kinetics of reductive dissolution of hematite coating on grain surfaces when coupled with pore diffusion. Results showed hematite reduction rate in micropores where transport is dominated by diffusion is 1 to 2 orders of magnitude lower than macropores where transport is controlled by advection.

  13. Advances in interpretation of subsurface processes with time-lapse electrical imaging

    SciTech Connect

    Singha, Kamini; Day-Lewis, Frederick D.; Johnson, Timothy C.; Slater, Lee D.

    2015-03-15

    Electrical geophysical methods, including electrical resistivity, time-domain induced polarization, and complex resistivity, have become commonly used to image the near subsurface. Here, we outline their utility for time-lapse imaging of hydrological, geochemical, and biogeochemical processes, focusing on new instrumentation, processing, and analysis techniques specific to monitoring. We review data collection procedures, parameters measured, and petrophysical relationships and then outline the state of the science with respect to inversion methodologies, including coupled inversion. We conclude by highlighting recent research focused on innovative applications of time-lapse imaging in hydrology, biology, ecology, and geochemistry, among other areas of interest.

  14. Evaluation of Boundless Biogeochemical Cycle through Development of Process-Based Eco-Hydrological and Biogeochemical Cycle Model to Incorporate Terrestrial-Aquatic Continuum

    NASA Astrophysics Data System (ADS)

    Nakayama, T.; Maksyutov, S. S.

    2014-12-01

    Inland water might act as important transport pathway for continental biogeochemical cycle although its contribution has remained uncertain yet 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-global scales, and can simulate iteratively nonlinear feedback between hydrologic-geomorphic-ecological processes. Because NICE incorporates 3-D groundwater sub-model and expands from previous 1- or 2-D or steady state, the model can simulate the lateral transport pronounced at steeper-slope or riparian/floodplain with surface-groundwater connectivity. River discharge and groundwater level simulated by NICE agreed reasonably with those in previous researches (Niu et al., 2007; Fan et al., 2013) and extended to clarify lateral subsurface also has important role on global hydrologic cycle (Nakayama, 2011b; Nakayama and Shankman, 2013b) though the resolution was coarser. NICE was further developed to incorporate biogeochemical cycle including reaction between inorganic and organic carbons in terrestrial and aquatic ecosystems. The missing role of carbon cycle simulated by NICE, for example, CO2 evasion from inland water (global total flux was estimated as about 1.0 PgC/yr), was relatively in good agreement in that estimated by empirical relation using previous pCO2 data (Aufdenkampe et al., 2011; Laruelle et al., 2013). The model would play important role in identification of greenhouse gas balance of the biosphere and spatio-temporal hot spots, and bridging gap between top-down and bottom-up approaches (Cole et al. 2007; Frei et al. 2012).

  15. South Florida wetlands ecosystem; biogeochemical processes in peat

    USGS Publications Warehouse

    Orem, William; ,

    1996-01-01

    The South Florida wetlands ecosystem is an environment of great size and ecological diversity (figs. 1 and 2). The landscape diversity and subtropical setting of this ecosystem provide a habitat for an abundance of plants and wildlife, some of which are unique to South Florida. South Florida wetlands are currently in crisis, however, due to the combined effects of agriculture, urbanization, and nearly 100 years of water management. Serious problems facing this ecosystem include (1) phosphorus contamination producing nutrient enrichment, which is causing changes in the native vegetation, (2) methylmercury contamination of fish and other wildlife, which poses a potential threat to human health, (3) changes in the natural flow of water in the region, resulting in more frequent drying of wetlands, loss of organic soils, and a reduction in freshwater flow to Florida Bay, (4) hypersalinity, massive algal blooms, and seagrass loss in parts of Florida Bay, and (5) a decrease in wildlife populations, especially those of wading birds. This U.S. Geological Survey (USGS) project focuses on the role of organic-rich sediments (peat) of South Florida wetlands in regulating the concentrations and impact of important chemical species in the environment. The cycling of carbon, nitrogen, phosphorus, and sulfur in peat is an important factor in the regulation of water quality in the South Florida wetlands ecosystem. These elements are central to many of the contamination issues facing South Florida wetlands, such as nutrient enrichment, mercury toxicity, and loss of peat. Many important chemical and biological reactions occur in peat and control the fate of chemical species in wetlands. Wetland scientists often refer to these reactions as biogeochemical processes, because they are chemical reactions usually mediated by microorganisms in a geological environment. An understanding of the biogeochemical processes in peat of South Florida wetlands will provide a basis for evaluating the

  16. Silicon biogeochemical processes in a large river (Cauvery, India)

    NASA Astrophysics Data System (ADS)

    Kameswari Rajasekaran, Mangalaa; Arnaud, Dapoigny; Jean, Riotte; Sarma Vedula, V. S. S.; Nittala, S. Sarma; Sankaran, Subramanian; Gundiga Puttojirao, Gurumurthy; Keshava, Balakrishna; Cardinal, Damien

    2016-04-01

    Silicon (Si), one of the key nutrients for diatom growth in ocean, is principally released during silicate weathering on continents and then exported by rivers. Phytoplankton composition is determined by the availability of Si relative to other nutrients, mainly N and P, which fluxes in estuarine and coastal systems are affected by eutrophication due to land use and industrialization. In order to understand the biogeochemical cycle of Si and its supply to the coastal ocean, we studied a tropical monsoonal river from Southern India (Cauvery) and compare it with other large and small rivers. Cauvery is the 7th largest river in India with a basin covering 85626 sq.km. The major part of the basin (˜66%) is covered by agriculture and inhabited by more than 30 million inhabitants. There are 96 dams built across the basin. As a consequence, 80% of the historical discharge is diverted, mainly for irrigation (Meunier et al. 2015). This makes the Cauvery River a good example of current anthropogenic pressure on silicon biogeochemical cycle. We measured amorphous silica contents (ASi) and isotopic composition of dissolved silicon (δ30Si-DSi) in the Cauvery estuary, including freshwater end-member and groundwater as well as along a 670 km transect along the river course. Other Indian rivers and estuaries have also been measured, including some less impacted by anthropogenic pressure. The average Cauvery δ30Si signature just upstream the estuary is 2.21±0.15 ‰ (n=3) which is almost 1‰ heavier than the groundwater isotopic composition (1.38±0.03). The δ30Si-DSi of Cauvery water is also almost 1‰ heavier than the world river supply to the ocean estimated so far and 0.4‰ heavier than other large Indian rivers like Ganges (Frings et al 2015) and Krishna. On the other hand, the smaller watersheds (Ponnaiyar, Vellar, and Penna) adjacent to Cauvery also display heavy δ30Si-DSi. Unlike the effect of silicate weathering, the heavy isotopic compositions in the river

  17. Southern Sierra Critical Zone Observatory: integrating water cycle and biogeochemical processes across the rain-snow transition

    NASA Astrophysics Data System (ADS)

    Bales, R.; Boyer, B.; Conklin, M.; Goulden, M.; Hopmans, J.; Hunsaker, C.; Johnson, D.; Kirchner, J.; Tague, C.

    2007-12-01

    The Southern Sierra Critical Zone Observatory (CZO) is establishing a rain-snow transition research platform for research by investigators from multiple disciplines and a research program aimed at yielding general knowledge and tools for understanding the interactions between water, atmosphere, ecosystems and landforms in the critical zone. A primary, overarching goal is to understand how critical zone processes control fluxes and stores of water across the landscape, and how the water cycle modulates (bio)geochemical, biological, geomorphological and soil processes in the critical zone. Five science questions define and focus the core measurement and research program: i) how do coupled hydrologic and biogeochemical fluxes vary across the rain-snow transition, ii) what is the role of extreme hydrologic events in water and biogeochemical balances, iii) to what extent does vegetation modulate or actively control the primary subsurface fluxes of water and nutrients, iv) over what time and space scales, and during what seasons, are short-circuit pathways dominant in the critical zone, and v) how does the presence of a seasonal snowpack affect the subsurface, critical zone, soils, geomorphology, biogeochemistry and hydrology, and how will the system respond as climate warms and snowpacks recede. Some unique features of the Sierra Nevada system as compared to more mesic sites include: i) hydrophobic soils, ii) islands of fertility in soils, iii) dominant role of catastrophic events, e.g. fire, and iv) spatial decoupling of decomposition from root uptake in soil profile. The rationale for measurement design, including the value of high-frequency data will be illustrated, as will the strategy for providing community data and information, and educational programs.

  18. Spatial patterns in soil biogeochemical process rates along a Louisiana wetland salinity gradient in the Barataria Bay estuarine system

    NASA Astrophysics Data System (ADS)

    Roberts, B. J.; Rich, M. W.; Sullivan, H. L.; Bledsoe, R.; Dawson, M.; Donnelly, B.; Marton, J. M.

    2014-12-01

    Louisiana has the highest rates of coastal wetland loss in the United States. In addition to being lost, Louisiana wetlands experience numerous other environmental stressors including changes in salinity regime (both increases from salt water intrusion and decreases from the creation of river diversions) and climate change induced changes in vegetation (e.g. the northward expansion of Avicennia germinans (black mangrove) into salt marshes). In this study, we examined how these changes might influence biogeochemical process rates important in regulating carbon balance and the cycling, retention, and removal of nutrients in Louisiana wetlands. Specifically, we measured net soil greenhouse gas fluxes and collected cores for the determination of rates of greenhouse gas production, denitrification potential, nitrification potential, iron reduction, and phosphorus sorption from surface (0-5cm) and subsurface (10-15cm) depths for three plots in each of 4 sites along the salinity gradient: a freshwater marsh site, a brackish (7 ppt) marsh site, a salt marsh (17 ppt), and a Avicennia germinans stand (17 ppt; adjacent to salt marsh site) in the Barataria Bay estuarine system. Most biogeochemical processes displayed similar spatial patterns with salt marsh rates being lower than rates in freshwater and/or brackish marsh sites and not having significantly different rates than in Avicennia germinans stands. Rates in surface soils were generally higher than in subsurface soils. These patterns were generally consistent with spatial patterns in soil properties with soil water content, organic matter quantity and quality, and extractable nutrients generally being higher in freshwater and brackish marsh sites than salt marsh and Avicennia germinans sites, especially in surface soils. These spatial patterns suggest that the ability of coastal wetlands to retain and remove nutrients might change significantly in response to future climate changes in the region and that these

  19. Biogeochemical dynamics of amino acids in deep-subsurface marine sediments: Constraints from compound-specific nitrogen isotopic composition and enantiomer ratio

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Y. T.; Chikaraishi, Y.; Takano, Y.; Ogawa, N. O.; Suga, H.; Yokoyama, Y.; Ohkouchi, N.

    2013-12-01

    Vast microbial populations exist in deep-subsurface marine sediments. Although amino acids in sediment pore waters are key compounds in metabolic activities of sedimentary microbes and in remineralization of carbon and nitrogen, to date little is known about their biogeochemical dynamics (e.g., sources and transformation processes) in deep-subsurface sediments. As a new approach to constrain the sources of dissolved amino acids in sediment pore waters, we analyzed compound-specific nitrogen isotopic composition (d15N) and enantiomer ratio (%D) of total hydrolysable amino acids (THAA) in sediment solid phase and dissolved hydrolysable amino acids (DHAA) in sediment pore waters from the same sediment samples. Enantiomer ratio can be an indicator of source organisms of amino acids, because specific D-amino acids (such as alanine, aspartic acid, glutamic acid, and serine) are commonly found in the cell wall complex of bacteria. Compound-specific d15N can be an indicator of microbial metabolism of amino acids, because biosynthesis and degradation of amino acids cause nitrogen isotopic fractionation. Samples were collected from deep-subsurface sediments (up to 172.9 m below seafloor) at the Sagami Trough (Northwestern Pacific) during D/V Chikyu cruise CK09-03. In the sediments deeper than 9 mbsf, %D values of DHAA were 25.9×2.8% in alanine, 24.8×2.1% in aspartic acid, 11.3×2.8% in serine, and 16.3×2.7% in glutamic acid, and %D changes from THAA were +15.3×2.1% in alanine, -0.4×2.4% in aspartic acid, -8.1×6.2% in serine, and 4.6×3.3% in glutamic acid. Compound-specific d15N analysis showed that d15N values of alanine are higher in DHAA than THAA and that d15N values of glycine and glutamic acid are similar between the two fractions (d15N of DHAA - d15N of THAA = +5.8×2.3 permill, +1.9×0.6 permill, -0.3×1.1 permill, respectively). The differences of d15N and %D signatures between DHAA and THAA suggest that the depolymerization of THAA is not the sole source of

  20. Diel biogeochemical processes and their effect on the aqueous chemistry of streams: A review

    USGS Publications Warehouse

    Nimick, David A.; Gammons, Christopher H.; Parker, Stephen R.

    2011-01-01

    This review summarizes biogeochemical processes that operate on diel, or 24-h, time scales in streams and the changes in aqueous chemistry that are associated with these processes. Some biogeochemical processes, such as those producing diel cycles of dissolved O2 and pH, were the first to be studied, whereas processes producing diel concentration cycles of a broader spectrum of chemical species including dissolved gases, dissolved inorganic and organic carbon, trace elements, nutrients, stable isotopes, and suspended particles have received attention only more recently. Diel biogeochemical cycles are interrelated because the cyclical variations produced by one biogeochemical process commonly affect another. Thus, understanding biogeochemical cycling is essential not only for guiding collection and interpretation of water-quality data but also for geochemical and ecological studies of streams. Expanded knowledge of diel biogeochemical cycling will improve understanding of how natural aquatic environments function and thus lead to better predictions of how stream ecosystems might react to changing conditions of contaminant loading, eutrophication, climate change, drought, industrialization, development, and other factors.

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

    NASA Astrophysics Data System (ADS)

    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.

  2. Cumulative Significance of Hyporheic Exchange and Biogeochemical Processing in River Networks

    NASA Astrophysics Data System (ADS)

    Harvey, J. W.; Gomez-Velez, J. D.

    2014-12-01

    Biogeochemical reactions in rivers that decrease excessive loads of nutrients, metals, organic compounds, etc. are enhanced by hydrologic interactions with microbially and geochemically active sediments of the hyporheic zone. The significance of reactions in individual hyporheic flow paths has been shown to be controlled by the contact time between river water and sediment and the intrinsic reaction rate in the sediment. However, little is known about how the cumulative effects of hyporheic processing in large river basins. We used the river network model NEXSS (Gomez-Velez and Harvey, submitted) to simulate hyporheic exchange through synthetic river networks based on the best available models of network topology, hydraulic geometry and scaling of geomorphic features, grain size, hydraulic conductivity, and intrinsic reaction rates of nutrients and metals in river sediment. The dimensionless reaction significance factor, RSF (Harvey et al., 2013) was used to quantify the cumulative removal fraction of a reactive solute by hyporheic processing. SF scales reaction progress in a single pass through the hyporheic zone with the proportion of stream discharge passing through the hyporheic zone for a specified distance. Reaction progress is optimal where the intrinsic reaction timescale in sediment matches the residence time of hyporheic flow and is less efficient in longer residence time hyporheic flow as a result of the decreasing proportion of river flow that is processed by longer residence time hyporheic flow paths. In contrast, higher fluxes through short residence time hyporheic flow paths may be inefficient because of the repeated surface-subsurface exchanges required to complete the reaction. Using NEXSS we found that reaction efficiency may be high in both small streams and large rivers, although for different reasons. In small streams reaction progress generally is dominated by faster pathways of vertical exchange beneath submerged bedforms. Slower exchange

  3. Deriving forest fire ignition risk with biogeochemical process modelling☆

    PubMed Central

    Eastaugh, C.S.; Hasenauer, H.

    2014-01-01

    Climate impacts the growth of trees and also affects disturbance regimes such as wildfire frequency. The European Alps have warmed considerably over the past half-century, but incomplete records make it difficult to definitively link alpine wildfire to climate change. Complicating this is the influence of forest composition and fuel loading on fire ignition risk, which is not considered by purely meteorological risk indices. Biogeochemical forest growth models track several variables that may be used as proxies for fire ignition risk. This study assesses the usefulness of the ecophysiological model BIOME-BGC's ‘soil water’ and ‘labile litter carbon’ variables in predicting fire ignition. A brief application case examines historic fire occurrence trends over pre-defined regions of Austria from 1960 to 2008. Results show that summer fire ignition risk is largely a function of low soil moisture, while winter fire ignitions are linked to the mass of volatile litter and atmospheric dryness. PMID:26109905

  4. The interaction between biogeophysical and biogeochemical processes and their feedback on permafrost soil carbon stocks

    NASA Astrophysics Data System (ADS)

    ElMasri, B.; Barman, R.; Jain, A. K.

    2013-12-01

    Our current understanding of the full suite of processes and their responses to recent warming in terrestrial high-latitudes are far from complete. While continued research on development of more detailed Earth system models (ESMs) is essential to understand the interactions and feedbacks between vegetation, soils and climate change in the Northern high latitudes (NHL), one of the major challenges is the treatment of the biophysical and biogeochemical processes and feedback in the ESM and their impact on soil organic carbon. We used a land surface model, the Integrated Science Assessment Model (ISAM), which coupled carbon-nitrogen biogeochemical and energy and hydrology biogeophysical processes, to investigate the effects of feedbacks between the biogeochemical and biogeophysical processes on the model estimated soil organic carbon (SOC) for the NHL permafrost region. We not only focused on recent improvement in the ISAM biogeophysical processes that are deemed important for the high latitude soils/snow; such as deep soil column, modulation of soil thermal and hydrological properties, wind compaction of snow, and depth hoar formation; on permafrost SOC, but also biogeochemical processes; such as dynamic phenology and root distribution, litter carbon decomposition rates and nitrogen amount remaining; on soil biogeochemistry. We selected multiple sites representative of different high latitude biomes to calibrate and evaluate the model. We then carried out several ISAM model simulations to study the effects of feedbacks between biogeochemical and biogeophysical processes on SOC. Our model analysis shows that including the biogeophysical processes alone could increase modeled Northern high-latitude permafrost carbon by about 30% compared to measurements. Accounting for the biogeochmical processes further improve the NHL soil carbon. This study demonstrates that improvements in biogeophysical or biogeochemical processes alone does not help to improve the modeled SOC

  5. Geomicrobial Processes and Biodiversity in the Deep Terrestrial Subsurface

    SciTech Connect

    Fredrickson, Jim K.; Balkwill, David L.

    2005-09-01

    The concept of a deep microbial biosphere has advanced over the past several decades from a hypothesis viewed with considerable skepticism to being widely accepted. Phylogenetically diverse prokaryotes have been cultured from or detected via characterization of directly-extracted nucleic acids from a wide range of deep terrestrial environments. Recent advances have linked the metabolic potential of these microorganisms, determined directly or inferred from phylogeny, to biogeochemical reactions determined via geochemical measurements and modeling. Buried organic matter or kerogen is an important source of energy for sustaining anaerobic heterotrophic microbial communities in deep sediments and sedimentary rock although rates of respiration are among the slowest rates measured on the planet. In contrast, Subsurface Lithoautotrophic Microbial Ecosystems based on H2 as the primary energy source appear to dominate in many crystalline rock environments. These photosynthesis-independent ecosystems remain an enigma due to the difficulty in accessing and characterizing appropriate samples. Deep mines and dedicated rock laboratories, however, may offer unprecedented opportunities for investigating subsurface microbial communities and their interactions with the geosphere.

  6. Soil property control of biogeochemical processes beneath two subtropical stormwater infiltration basins.

    PubMed

    O'Reilly, Andrew M; Wanielista, Martin P; Chang, Ni-Bin; Harris, Willie G; Xuan, Zhemin

    2012-01-01

    Substantially different biogeochemical processes affecting nitrogen fate and transport were observed beneath two stormwater infiltration basins in north-central Florida. Differences are related to soil textural properties that deeply link hydroclimatic conditions with soil moisture variations in a humid, subtropical climate. During 2008, shallow groundwater beneath the basin with predominantly clayey soils (median, 41% silt+clay) exhibited decreases in dissolved oxygen from 3.8 to 0.1 mg L and decreases in nitrate nitrogen (NO-N) from 2.7 mg L to <0.016 mg L, followed by manganese and iron reduction, sulfate reduction, and methanogenesis. In contrast, beneath the basin with predominantly sandy soils (median, 2% silt+clay), aerobic conditions persisted from 2007 through 2009 (dissolved oxygen, 5.0-7.8 mg L), resulting in NO-N of 1.3 to 3.3 mg L in shallow groundwater. Enrichment of δN and δO of NO combined with water chemistry data indicates denitrification beneath the clayey basin and relatively conservative NO transport beneath the sandy basin. Soil-extractable NO-N was significantly lower and the copper-containing nitrite reductase gene density was significantly higher beneath the clayey basin. Differences in moisture retention capacity between fine- and coarse-textured soils resulted in median volumetric gas-phase contents of 0.04 beneath the clayey basin and 0.19 beneath the sandy basin, inhibiting surface/subsurface oxygen exchange beneath the clayey basin. Results can inform development of soil amendments to maintain elevated moisture content in shallow soils of stormwater infiltration basins, which can be incorporated in improved best management practices to mitigate NO impacts.

  7. Soil property control of biogeochemical processes beneath two subtropical stormwater infiltration basins

    USGS Publications Warehouse

    O'Reilly, Andrew M.; Wanielista, Martin P.; Chang, Ni-Bin; Harris, Willie G.; Xuan, Zhemin

    2012-01-01

    Substantially different biogeochemical processes affecting nitrogen fate and transport were observed beneath two stormwater infiltration basins in north-central Florida. Differences are related to soil textural properties that deeply link hydroclimatic conditions with soil moisture variations in a humid, subtropical climate. During 2008, shallow groundwater beneath the basin with predominantly clayey soils (median, 41% silt+clay) exhibited decreases in dissolved oxygen from 3.8 to 0.1 mg L-1 and decreases in nitrate nitrogen (NO3-–N) from 2.7 mg L-1 to -1, followed by manganese and iron reduction, sulfate reduction, and methanogenesis. In contrast, beneath the basin with predominantly sandy soils (median, 2% silt+clay), aerobic conditions persisted from 2007 through 2009 (dissolved oxygen, 5.0–7.8 mg L-1), resulting in NO3-–N of 1.3 to 3.3 mg L-1 in shallow groundwater. Enrichment of d15N and d18O of NO3- combined with water chemistry data indicates denitrification beneath the clayey basin and relatively conservative NO3- transport beneath the sandy basin. Soil-extractable NO3-–N was significantly lower and the copper-containing nitrite reductase gene density was significantly higher beneath the clayey basin. Differences in moisture retention capacity between fine- and coarse-textured soils resulted in median volumetric gas-phase contents of 0.04 beneath the clayey basin and 0.19 beneath the sandy basin, inhibiting surface/subsurface oxygen exchange beneath the clayey basin. Results can inform development of soil amendments to maintain elevated moisture content in shallow soils of stormwater infiltration basins, which can be incorporated in improved best management practices to mitigate NO3- impacts.

  8. The Interactions between Biogeophysical and Biogeochemical Processes and their Feedbacks on Permafrost Soil Carbon Stocks

    NASA Astrophysics Data System (ADS)

    Jain, A. K.; El Masri, B.; Barman, R.; Shu, S.; Song, Y.

    2014-12-01

    One of the major challenges in more detailed Earth system models (ESMs) is the treatment of the biophysical and biogeochemical processes and feedbacks and their impact on soil organic carbon in the Northern high latitudes (NHL). We use a land surface model, the Integrated Science Assessment Model (ISAM) to investigate the effects of feedbacks between the biogeochemical and biogeophysical processes on the model estimated soil organic carbon (SOC) for the NHL permafrost region. We not only focus on recent model improvements in the biogeophysical processes that are deemed important for the high latitude soils/snow; such as deep soil column, modulation of soil thermal and hydrological properties, wind compaction of snow, and depth hoar formation; on permafrost SOC; but also biogeochemical processes; such as dynamic phenology and root distribution, litter carbon decomposition rates and nitrogen amount remaining; on soil biogeochemistry. We select multiple sites to evaluate the model. We then carried out several model simulations to study the effects of feedbacks between biogeochemical and biogeophysical processes on SOC. Our model analysis shows that including the biogeophysical processes alone could increase modeled NHL permafrost carbon by about 30% compared to measurements. Accounting for the biogeochmical processes further improve the NHL soil carbon.

  9. Fungal production of citric and oxalic acid: importance in metal speciation, physiology and biogeochemical processes.

    PubMed

    Gadd, G M

    1999-01-01

    The production of organic acids by fungi has profound implications for metal speciation, physiology and biogeochemical cycles. Biosynthesis of oxalic acid from glucose occurs by hydrolysis of oxaloacetate to oxalate and acetate catalysed by cytosolic oxaloacetase, whereas on citric acid, oxalate production occurs by means of glyoxylate oxidation. Citric acid is an intermediate in the tricarboxylic acid cycle, with metals greatly influencing biosynthesis: growth limiting concentrations of Mn, Fe and Zn are important for high yields. The metal-complexing properties of these organic acids assist both essential metal and anionic (e.g. phosphate) nutrition of fungi, other microbes and plants, and determine metal speciation and mobility in the environment, including transfer between terrestrial and aquatic habitats, biocorrosion and weathering. Metal solubilization processes are also of potential for metal recovery and reclamation from contaminated solid wastes, soils and low-grade ores. Such 'heterotrophic leaching' can occur by several mechanisms but organic acids occupy a central position in the overall process, supplying both protons and a metal-complexing organic acid anion. Most simple metal oxalates [except those of alkali metals, Fe(III) and Al] are sparingly soluble and precipitate as crystalline or amorphous solids. Calcium oxalate is the most important manifestation of this in the environment and, in a variety of crystalline structures, is ubiquitously associated with free-living, plant symbiotic and pathogenic fungi. The main forms are the monohydrate (whewellite) and the dihydrate (weddelite) and their formation is of significance in biomineralization, since they affect nutritional heterogeneity in soil, especially Ca, P, K and Al cycling. The formation of insoluble toxic metal oxalates, e.g. of Cu, may confer tolerance and ensure survival in contaminated environments. In semi-arid environments, calcium oxalate formation is important in the formation and

  10. Do antibiotics have environmental side-effects? Impact of synthetic antibiotics on biogeochemical processes.

    PubMed

    Roose-Amsaleg, Céline; Laverman, Anniet M

    2016-03-01

    Antibiotic use in the early 1900 vastly improved human health but at the same time started an arms race of antibiotic resistance. The widespread use of antibiotics has resulted in ubiquitous trace concentrations of many antibiotics in most environments. Little is known about the impact of these antibiotics on microbial processes or "non-target" organisms. This mini-review summarizes our knowledge of the effect of synthetically produced antibiotics on microorganisms involved in biogeochemical cycling. We found only 31 articles that dealt with the effects of antibiotics on such processes in soil, sediment, or freshwater. We compare the processes, antibiotics, concentration range, source, environment, and experimental approach of these studies. Examining the effects of antibiotics on biogeochemical processes should involve environmentally relevant concentrations (instead of therapeutic), chronic exposure (versus acute), and monitoring of the administered antibiotics. Furthermore, the lack of standardized tests hinders generalizations regarding the effects of antibiotics on biogeochemical processes. We investigated the effects of antibiotics on biogeochemical N cycling, specifically nitrification, denitrification, and anammox. We found that environmentally relevant concentrations of fluoroquinolones and sulfonamides could partially inhibit denitrification. So far, the only documented effects of antibiotic inhibitions were at therapeutic doses on anammox activities. The most studied and inhibited was nitrification (25-100 %) mainly at therapeutic doses and rarely environmentally relevant. We recommend that firm conclusions regarding inhibition of antibiotics at environmentally relevant concentrations remain difficult due to the lack of studies testing low concentrations at chronic exposure. There is thus a need to test the effects of these environmental concentrations on biogeochemical processes to further establish the possible effects on ecosystem functioning.

  11. Understanding Biogeochemical Transformations Of Trace Elements In Multi Metal-Rich Geomaterials Under Stimulated Redox Conditions

    EPA Science Inventory

    Natural and anthropogenic influences on hydrological conditions can induce periodic or long-term reduced conditions in geologic materials. Such conditions can cause significant impacts on biogeochemical processes of trace elements in subsurface or near surface environments. The...

  12. Estimating Hydrologic Processes from Subsurface Soil Displacements

    NASA Astrophysics Data System (ADS)

    Freeman, C. E.; Murdoch, L. C.; Germanovich, L.; MIller, S.

    2012-12-01

    Soil moisture and the processes that control it are important components of the hydrologic cycle, but measuring these processes remains challenging. We have developed a new measurement method that offers flexibility compared to existing technology. The approach is to measure small vertical displacements in the soil which responds proportionally to distributed surface load changes such as variation in the near-surface water content. The instrument may be installed at a depth of several meters to hundreds of meters below the surface. Because the measurement averaging region scales with the depth of the displacement measurements, this approach provides the means for estimating the soil moisture time series over tens of square meters to tens of thousands of square meters. The instrument developed for this application is called a Sand-X, which is short for Sand Extensometer. It is designed for applications in unconsolidated material, ranging from clay to sand. The instrument is simple and relatively inexpensive, and it can be installed in a boring made with a hand auger or with a small drill rig. Studies at the field scale are ongoing at a field site near Clemson, SC. The site is underlain by saprolite weathered primarily from biotite gneiss. Several Sand-X devices are installed at a field site that is instrumented for validating soil moisture, precipitation, and evapotranspiration estimates. These instruments are emplaced at a depth of 6 m and respond to the weight of a vehicle out to 18 m from the well. Calibration is performed by comparing precipitation measurements to the soil displacement response. For example, the coefficient for one installation is roughly 185 nm soil displacement/mm water content change. The resolution of the instrument is approximately 10 nm, so the Sand-X is capable of detecting changes of soil moisture on the order of tenths of one mm in compliant soils like saprolite. A typical soil displacement time series shows alternating periods of

  13. LRS data processing methods for detection of lunar subsurface echoes

    NASA Astrophysics Data System (ADS)

    Oshigami, Shoko; Mochizuki, Kengo; Watanabe, Shiho; Watanabe, Toshiki; Yamaguchi, Yasushi; Yamaji, Atsushi; Ono, Takayuki; Kumamoto, Atsushi; Nakagawa, Hiromu; Kobayashi, Takao; Kasahara, Yoshiya

    Lunar Radar Sounder (LRS) is an instrument for one of fifteen science missions of SE- LENE (KAGUYA). LRS is a ground-penetrating FM-CW radar system of HF-band. LRS detects echoes reflected from subsurface discontinuities where dielectric constants of the rocks change. The range resolution of LRS is 75 m in free space, whereas the sampling interval in the flight direction is about 75 m when the spacecraft altitude is 100 km. The primary objective of LRS is to investigate lunar subsurface structures. We plan to perform global soundings by LRS to contribute to studying the evolution of the Moon. In this presentation, we introduce the techniques to process LRS data to produce data products and to detect subsurface echoes. We have two standard data products of LRS under consideration. The time series data of ‘A-scope' which is a plot of signal power spectrum as a function of range derived from of the waveform data are called ‘B-scan'. Because LRS instruments change timing of data recording (measurement delay time) according to the predicted distance between KAGUYA spacecraft and lunar surface, observation range with respect to the spacecraft varies from pulse to pulse. In addition, flight altitude of KAGUYA changes in the range of several tens of kilometers. Therefore a trace of surface nadir echoes in unprocessed B-scan images does not correspond to actual lunar topography. We corrected variations of the measurement delay time and flight altitude of KAGUYA to produce a B-scan data product with the original spatial resolution (BScan high) and a reduced spatial resolution product (BScan low) both in the PDS format. The echo signals in A-scope data might be classified in the following categories; (1) a surface nadir echo, (2) surface off-nadir backscattering echoes, and (3) subsurface echoes. The most intense signal usually comes from the nadir point, when KAGUYA is flying over a level surface. The A-scope data also include various noises resulted from, for example

  14. Dynamic interactions of ecohydrological and biogeochemical processes in water-stressed environments

    NASA Astrophysics Data System (ADS)

    Wang, L.; Manzoni, S.; Ravi, S.; Riveros-Iregui, D. A.; Caylor, K. K.

    2015-12-01

    Water is the essential reactant, catalyst, or medium for many biogeochemical reactions and flows. The coupling between hydrological and biogeochemical processes is particularly evident in drylands, but also in areas with strong seasonal precipitation patterns or in mesic systems during droughts. Moreover, this coupling is apparent at all levels in the ecosystems - from soil microbial cells to whole plants to landscapes. A holistic approach is essential to fully understand function and processes in water-limited ecosystems and to predict their responses to environmental change. We examine some of the mechanisms responsible for microbial and vegetation responses to moisture inputs in water-limited ecosystems through a synthesis of existing literature and we also summarize the modeling advances in addressing these interactions. This paper focuses on three opportunities to advance coupled hydrological and biogeochemical research: (1) improved quantitative understanding of mechanisms linking hydrological and biogeochemical variations in drylands, (2) experimental and theoretical approaches that describe linkages between hydrology and biogeochemistry (particularly across scales), and (3) the use of these tools and insights to address critical dryland issues of societal relevance.

  15. U(VI) reduction at the nano, meso and meter scale: concomitant transition from simpler to more complex biogeochemical processes

    NASA Astrophysics Data System (ADS)

    Veeramani, H.; Hochella, M. F.

    2012-12-01

    Reduction of aqueous hexavalent U(VI) to the sparingly soluble nanoparticulate mineral uraninite [UO2] represents a promising strategy for the in situ immobilization of uranium in contaminated subsurface sediments and groundwater. Studies related to uranium reduction have been extensively carried out at various scales ranging from nano to meso to the meter scale with varying degrees of success. While nanoscale processes involving simple two-electron transfer reactions such as enzymatic microbial U(VI) reduction results in biogenic UO2 formation, mesoscale processes involving minerals and U(VI) are a step up in complexity and have shown varying results ranging from partial uranium reduction to the formation of mixed U(IV)/U(V) species. Although nano- and meso-scale biogeochemical processes have been helpful in predicting the contaminant dynamics at the meter scale, their occurrence is not necessarily apparent in soils and aquifers given the enormous volume of contaminated groundwater to be remediated, among other factors. The formation and long-term stability of biologically reduced uranium at the meter scale is also determined in addition by the complex interplay of aqueous geochemistry, hydrology, soil and sediment mineralogy and microbial community dynamics. For instance, indigenous subsurface microbes often encounter multiple electron acceptors in heterogeneous environments during biostimulation and can catalyze the formation of various reactive biogenic minerals. In such cases, abiotic interactions between U(VI) and reactive biogenic minerals is potentially important because the success of a remediation strategy is contingent upon the speciation of reduced uranium. This presentation will give an overview of uranium reduction ranging from simple nanoscale biological processes to increasingly complex meso and meter scale processes involving abiotic interactions between aqueous uranium and nano-biogenic minerals and the effect of mineralogy and aqueous

  16. Stormwater sediment and bioturbation influences on hydraulic functioning, biogeochemical processes, and pollutant dynamics in laboratory infiltration systems.

    PubMed

    Nogaro, Geraldine; Mermillod-Blondin, Florian

    2009-05-15

    Stormwater sediments that accumulate at the surface of infiltration basins reduce infiltration efficiencies by physical clogging and produce anoxification in the subsurface. The present study aimed to quantify the influence of stormwater sediment origin (urban vs industrial catchments) and the occurrence of bioturbators (tubificid worms) on the hydraulic functioning, aerobic/anaerobic processes, and pollutant dynamics in stormwater infiltration systems. In laboratory sediment columns, effects of stormwater sediments and tubificids were examined on hydraulic conductivity, microbial processes, and pollutant releases. Significant differences in physical (particle size distribution) and chemical characteristics betoveen the two stormwater sediments led to distinct effects of these sediments on hydraulic and biogeochemical processes. Bioturbation by tubificid worms could increase the hydraulic conductivity in stormwater infiltration columns, but this effect depended on the characteristics of the stormwater sediments. Bioturbation-driven increases in hydraulic conductivity stimulated aerobic microbial processes and enhanced vertical fluxes of pollutants in the sediment layer. Our results showed that control of hydraulic functioning by stormwater sediment characteristics and/ or biological activities (such as bioturbation) determined the dynamics of organic matter and pollutants in stormwater infiltration devices.

  17. 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

    SciTech Connect

    Peyton, Brent M.; Timothy, Ginn R.; Sani, Rajesh K.

    2013-08-14

    Subsurface bacteria including sulfate reducing bacteria (SRB) reduce soluble U(VI) to insoluble U(IV) with subsequent precipitation of UO2. We have shown that SRB reduce U(VI) to nanometer-sized UO2 particles (1-5 nm) which are both intra- and extracellular, with UO2 inside the cell likely physically shielded from subsequent oxidation processes. We evaluated the UO2 nanoparticles produced by Desulfovibrio desulfuricans G20 under growth and non-growth conditions in the presence of lactate or pyruvate and sulfate, thiosulfate, or fumarate, using ultrafiltration and HR-TEM. Results showed that a significant mass fraction of bioreduced U (35-60%) existed as a mobile phase when the initial concentration of U(VI) was 160 µM. Further experiments with different initial U(VI) concentrations (25 - 900 M) in MTM with PIPES or bicarbonate buffers indicated that aggregation of uraninite depended on the initial concentrations of U(VI) and type of buffer. It is known that under some conditions SRB-mediated UO2 nanocrystals can be reoxidized (and thus remobilized) by Fe(III)-(hydr)oxides, common constituents of soils and sediments. To elucidate the mechanism of UO2 reoxidation by Fe(III) (hydr)oxides, we studied the impact of Fe and U chelating compounds (citrate, NTA, and EDTA) on reoxidation rates. Experiments were conducted in anaerobic batch systems in PIPES buffer. Results showed EDTA significantly accelerated UO2 reoxidation with an initial rate of 9.5 M day-1 for ferrihydrite. In all cases, bicarbonate increased the rate and extent of UO2 reoxidation with ferrihydrite. The highest rate of UO2 reoxidation occurred when the chelator promoted UO2 and Fe(III) (hydr)oxide dissolution as demonstrated with EDTA. When UO2 dissolution did not occur, UO2 reoxidation likely proceeded through an aqueous Fe(III) intermediate as observed for both NTA and

  18. Biogeochemical processes driving mercury cycling in estuarine ecosystems

    NASA Astrophysics Data System (ADS)

    Schartup, A. T.

    2015-12-01

    Mercury (Hg) is a naturally occurring element that has been enriched in the environment through human activities, particularly in the coastal zone. Bioaccumulation of methylmercury (MeHg) in marine fishposes health risks for fish-consuming populations and is a worldwide health concern. A broader understanding of major environmental processes controlling Hg cycling and MeHg production and bioaccumulation in estuaries is therefore needed. Recent fieldwork and modeling show diverse sources of MeHg production in estuaries. We present geochemical modeling results for Hg and MeHg acrossmultiple estuaries with contrasting physical, chemical and biological characteristics. We report new measurements of water column and sediment mercury speciation and methylation data from the subarctic (Lake Melville, Labrador Canada) and temperate latitudes (Long Island Sound, Delaware Bay, Chesapeake Bay). We find that benthic sediment is a relatively small source of MeHg to the water column in all systems. Water column methylation drives MeHg levels in Lake Melville, whereas in more impacted shallow systems such as Chesapeake Bay and Long Island Sound, external inputs and sediment resuspension are more dominant. All systems are a net source of MeHg to the ocean through tidal exchange. In light of these inter-system differences, we will evaluate timescales of coastal ecosystem responses to changes in Hg loading that can help predict potential responses to future perturbations.

  19. Isotopic Tracers for Biogeochemical Processes and Contaminant Transport: Hanford, Washington

    SciTech Connect

    Donald J. DePaolo; John N. Christensen; Mark E. Conrad; and P. Evan Dresel

    2007-04-19

    Our goal is to use isotopic measurements to understand how contaminants are introduced to and stored in the vadose zone, and what processes control migration from the vadose zone to groundwater and then to surface water. We have been using the Hanford Site in south-central Washington as our field laboratory, and our investigations are often stimulated by observations made as part of the groundwater monitoring program and vadose zone characterization activities. Understanding the transport of contaminants at Hanford is difficult due to the presence of multiple potential sources within small areas, the long history of activities, the range of disposal methods, and the continuing evolution of the hydrological system. Observations often do not conform to simple models, and cannot be adequately understood with standard characterization approaches, even though the characterization activities are quite extensive. One of our objectives is to test the value of adding isotopic techniques to the characterization program, which has the immediate potential benefit of addressing specific remediation issues, but more importantly, it allows us to study fundamental processes at the scale and in the medium where they need to be understood. Here we focus on two recent studies at the waste management area (WMA) T-TX-TY, which relate to the sources and transport histories of vadose zone and groundwater contamination and contaminant fluid-sediment interaction. The WMA-T and WMA-TX-TY tank farms are located within the 200 West Area in the central portion of the Hanford Site (Fig. 2). They present a complicated picture of mixed groundwater plumes of nitrate, {sup 99}Tc, Cr{sup 6+}, carbon tetrachloride, etc. and multiple potential vadose zone sources such as tank leaks and disposal cribs (Fig. 3). To access potential vadose zone sources, we analyzed samples from cores C3832 near tank TX-104 and from C4104 near tank T-106. Tank T-106 was involved in a major event in 1973 in which 435,000 L

  20. Evidence of biogeochemical processes in iron duricrust formation

    NASA Astrophysics Data System (ADS)

    Levett, Alan; Gagen, Emma; Shuster, Jeremiah; Rintoul, Llew; Tobin, Mark; Vongsvivut, Jitraporn; Bambery, Keith; Vasconcelos, Paulo; Southam, Gordon

    2016-11-01

    Canga is a moderately hard iron-rich duricrust primarily composed of goethite as a result of the weathering of banded iron formations. Canga duricrusts lack a well-developed soil profile and consequently form an innate association with rupestrian plants that may become ferruginised, contributing to canga possessing macroscopic biological features. Examination of polished canga using a field emission scanning electron microscope (FE-SEM) revealed the biological textures associated with canga extended to the sub-millimetre scale in petrographic sections and polished blocks. Laminae that formed by abiotic processes and regions where goethite cements were formed in association with microorganisms were observed in canga. Biological cycling of iron within canga has resulted in two distinct forms of microbial fossilisation: permineralisation of multispecies biofilms and mineralisation of cell envelopes. Goethite permineralised biofilms frequently formed around goethite-rich kaolinite grains in close proximity to goethite bands and were composed of micrometre-scale rod-shaped, cocci and filamentous microfossils. In contrast, the cell envelopes immobilised by authigenic iron oxides were primarily of rod-shaped microorganisms, were not permineralised and occurred in pore spaces within canga. Complete mineralisation of intact rod-shaped casts and the absence of permineralisation suggested mineralised cell envelopes may represent fossilised iron-oxidising bacteria in the canga ecosystem. Replication of these iron-oxidising bacteria appeared to infill the porous regions within canga. Synchrotron-based Fourier transform infrared (FTIR) microspectroscopy demonstrated that organic biomarkers were poorly preserved with only weak bands indicative of aliphatic methylene (CH2) associated with permineralised microbial biofilms. High resolution imaging of microbial fossils in canga that had been etched with oxalic acid supported the poor preservation of organic biomarkers within canga

  1. Geo- and biogeochemical processes in a heliothermal hypersaline lake

    NASA Astrophysics Data System (ADS)

    Zachara, John M.; Moran, James J.; Resch, Charles T.; Lindemann, Stephen R.; Felmy, Andrew R.; Bowden, Mark E.; Cory, Alexandra B.; Fredrickson, James K.

    2016-05-01

    precipitation in the mixolimnion and metalimnion, but the absence of calcareous sediments at depth suggests dissolution and recycling during winter months. Dissolved carbon concentrations [dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC)] increased with depth, reaching ∼0.04 mol/L at the metalimnion-monimolimnion boundary. DIC concentrations were seasonally variable in the mixolimnion and metalimnion, and were influenced by calcium carbonate precipitation. DOC concentrations mimicked those of conservative salts (e.g., Na+-Cl-) in the mixolimnion and metalimnion, but decreased in the monimolimnion where mass loss by anaerobic microbial processes is implied. Biogenic reduced solutes originating in monimolimnion (H2S and CH4) were biologically oxidized in the metalimnion as they were not observed in more shallow lake waters. Multi-year solute inventory calculations indicated that Hot Lake is a stable, albeit seasonally and annually dynamic feature, with inorganic solutes cycled between lake waters and sediments depending on annual recharge, temperature, and lake water dilution state. With its extreme geochemical and thermal regime, Hot Lake functions as analog of early earth and extraterrestrial life environments.

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

    NASA Astrophysics Data System (ADS)

    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. Effects of plant root on hydraulic performance of clogging process in subsurface flow constructed wetland

    NASA Astrophysics Data System (ADS)

    Hua, Guofen; Zhao, Zhongwei; Zeng, Yitao

    2013-04-01

    Subsurface flow constructed wetlands (SFCWs) have proven to be an efficient ecological technology for the treatment of various kinds of wastewaters. The clogging issue is the main operational problem, which limits its wide application. Clogging is a complicated process with physical (such as physical filtration), biogeochemical and plant-related processes. It was generally stated that suspended solids accumulation and biofilm play dominant roles response for clogging. However, the role of plants in SFCWs clogging remains unclear and debatable. In this paper, the performance of plants in the whole clogging process was addressed based on the lab-experiments between planted and unplanted system by measuring effective porosity, coefficient of permeability of the substrate within different operation periods. Furthermore, flow pattern and transport properties of the clogging process in the planted and unplanted wetland systems were evaluated by hydraulic performance (e.g. mean residence time, short-circuiting, volumetric efficiency, number of continuously stirred tank reactors, hydraulic efficiency factor, etc.) with salt tracer experiments. Plants played different roles in different clogging stage. In the earlier clogging stage, there were no obvious different effects on clogging process between planted and unplanted system. The effective porosity and coefficient of permeability slightly decreased within the planted system, which indicated that plant root restricted the flow of water when the pore spaces were lager. In the middle and later clogging stage, especially, in the later stage, the effective porosity and the coefficient of permeability increased considerably in the plant root zone. Furthermore, the longer retention times and higher hydraulic efficiency factors were gained in the planted system compared to that of unplanted, which implied that growing roots might open the new pore spaces in the substrate. The results are expected to be useful in the design of

  4. Linking subsurface temperature and hillslope processes through geologic time

    NASA Astrophysics Data System (ADS)

    Barnhart, Katherine; Anderson, Robert

    2015-04-01

    Many periglacial hillslope processes - physical, chemical, and biological - depend on subsurface temperature and water availability. As the subsurface temperature field varies both in space and through time over many scales up to climate cycles, the dominant processes of mobile regolith production and transport and the rate at which they act will vary. These processes include the chemical weathering of minerals, cracking of rocks through frost action and tree roots, presence and impact of vegetation on soil cohesion, location and activity of burrowing and trampling animals, frost creep, and solifluction. In order to explore the interplay between these processes across a landscape over the geologic timescales on which such landscapes evolve, we explore the effects of slope, aspect, latitude, atmosphere, and time before present on the expected energy balance at the surface of the earth and the resulting subsurface temperature field. We begin by calculating top-of-atmosphere insolation at any time in the Quaternary, honoring the variations in orbit over Milankovitch timescales. We then incorporate spatial and temporal variations in incoming short-wave radiation on sub-daily timescales due to elevation, latitude, aspect, and shading. Outgoing long-wave radiation is taken to depend on the surface temperature and may be modified by allowing back-radiation from the atmosphere. We then solve for the subsurface temperature field using a numerical model that acknowledges depth-varying material properties, water content, and phase change. With these tools we target variations in regolith production and motion over the long timescales on which periglacial hillslopes evolve. We implement a basic parameterization of temperature-dependent chemical and physical weathering linked to mobile regolith generation. We incorporate multiple regolith transport processes including frost heave and creep. Our intention is not to parameterize all operative processes, but to include sufficient

  5. Early Earth rock analogues for Martian subsurface processes

    NASA Astrophysics Data System (ADS)

    Bishop, J. L.; Grosch, E. G.; Maturilli, A.; Helbert, J.

    2015-12-01

    Sub-surface mafic-ultramafic crustal and hydrothermal environments on early Earth and Mars may have been very similar [1]. Hydrogen production from low-temperature alteration of ultramafic and basaltic rocks has been proposed to support early microbial life in Earth's earliest subsurface environments [1]. Similarly, evidence for microbial sulphate reduction has been reported from early Archean metabasaltic pillow lavas [2]. As such, Archean terrestrial rock environments preserved in greenstone belts may play an important role in understanding early Martian subsurface environments, which in turn may have led to preservation of early traces of life. In this context, the rock sequences of the Paleoarchean Barberton greenstone belt of South Africa provide unique Martian analogues as these rocks are exceptionally well preserved and record early Earth (and perhaps Martian-type) subsurface processes. In-situ exploration by rovers, remote sensing studies, and meteorite evidence has indicated the presence of altered gabbros, olivine-/pyroxene-bearing basalts and possible felsic porphyries on Mars. In this study we present a range of relevant 3.5 billion year old Archean greenstone belt analogue samples that include altered tholeiitic basalts, basaltic komatiites, serpentinized ultramafic komatiites and a felsic tonalite. The petrography and mineralogy of the samples are presented in terms of relic igneous phases and clay mineral alteration. We are acquiring visible/near-infrared reflectance and mid-IR emission spectra on these early Archean samples with the aim of using the hyperspectral data for ground truthing remote sensing data and mineral identification/environments on Mars.[1]. Grosch et al. (2014). Microscale mapping of alteration conditions and potential biosignatures in basaltic-ultramafic rocks on early Earth and beyond, Astrobiology 14 (3), 216-228. [2]. McLoughlin et al. (2012) Sulfur isotope evidence for a Paleoarchean subseafloor biosphere, Barberton, South

  6. Characterization of eco-hydraulic habitats for examining biogeochemical processes in rivers

    NASA Astrophysics Data System (ADS)

    McPhillips, L. E.; O'Connor, B. L.; Harvey, J. W.

    2009-12-01

    Spatial variability in biogeochemical reaction rates in streams is often attributed to sediment characteristics such as particle size, organic material content, and biota attached to or embedded within the sediments. Also important in controlling biogeochemical reaction rates are hydraulic conditions, which influence mass transfer of reactants from the stream to the bed, as well as hyporheic exchange within near-surface sediments. This combination of physical and ecological variables has the potential to create habitats that are unique not only in sediment texture but also in their biogeochemical processes and metabolism rates. In this study, we examine the two-dimensional (2D) variability of these habitats in an agricultural river in central Iowa. The streambed substratum was assessed using a grid-based survey identifying dominant particle size classes, as well as aerial coverage of green algae, benthic organic material, and coarse woody debris. Hydraulic conditions were quantified using a calibrated 2D model, and hyporheic exchange was assessed using a scaling relationship based on sediment and hydraulic characteristics. Point-metabolism rates were inferred from measured sediment dissolved oxygen profiles using an effective diffusion model and compared to traditional whole-stream measurements of metabolism. The 185 m study reach had contrasting geomorphologic and hydraulic characteristics in the upstream and downstream portions of an otherwise relatively straight run of a meandering river. The upstream portion contained a large central gravel bar (50 m in length) flanked by riffle-run segments and the downstream portion contained a deeper, fairly uniform channel cross-section. While relatively high flow velocities and gravel sediments were characteristic of the study river, the upstream island bar separated channels that differed with sandy gravels on one side and cobbley gravels on the other. Additionally, green algae was almost exclusively found in riffle

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

    NASA Astrophysics Data System (ADS)

    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, <1 m thick) immediately adjacent to the river. This microscale domain is highly heterogeneous and requires fine spatial resolution to adequately represent the effects of local mixing on reactions. It is not computationally feasible to resolve the full macroscale domain at the fine resolution needed in the mud layer, and the reaction network needed in the mud layer is much more complex than that needed in the rest of the macroscale domain. Hence, a 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.

  8. Stochastic and Deterministic Assembly Processes in Subsurface Microbial Communities

    SciTech Connect

    Stegen, James C.; Lin, Xueju; Konopka, Allan; Fredrickson, Jim K.

    2012-03-29

    A major goal of microbial community ecology is to understand the forces that structure community composition. Deterministic selection by specific environmental factors is sometimes important, but in other cases stochastic or ecologically neutral processes dominate. Lacking is a unified conceptual framework aiming to understand why deterministic processes dominate in some contexts but not others. Here we work towards such a framework. By testing predictions derived from general ecological theory we aim to uncover factors that govern the relative influences of deterministic and stochastic processes. We couple spatiotemporal data on subsurface microbial communities and environmental parameters with metrics and null models of within and between community phylogenetic composition. Testing for phylogenetic signal in organismal niches showed that more closely related taxa have more similar habitat associations. Community phylogenetic analyses further showed that ecologically similar taxa coexist to a greater degree than expected by chance. Environmental filtering thus deterministically governs subsurface microbial community composition. More importantly, the influence of deterministic environmental filtering relative to stochastic factors was maximized at both ends of an environmental variation gradient. A stronger role of stochastic factors was, however, supported through analyses of phylogenetic temporal turnover. While phylogenetic turnover was on average faster than expected, most pairwise comparisons were not themselves significantly non-random. The relative influence of deterministic environmental filtering over community dynamics was elevated, however, in the most temporally and spatially variable environments. Our results point to general rules governing the relative influences of stochastic and deterministic processes across micro- and macro-organisms.

  9. EFFECT OF NUTRIENT LOADING ON BIOGEOCHEMICAL AND MICROBIAL PROCESSES IN A NEW ENGLAND HIGH SALT MARSH, SPARTINA PATNES, (AITON MUHL)

    EPA Science Inventory

    Coastal marshes represent an important transitional zone between uplands and estuaries and can assimilate nutrient inputs from uplands. We examined the effects of nitrogen (N) and phosphorus (P) fertilization on biogeochemical and microbial processes during the summer growing sea...

  10. Comparing soil biogeochemical processes in novel and natural boreal forest ecosystems

    NASA Astrophysics Data System (ADS)

    Quideau, S. A.; Swallow, M. J. B.; Prescott, C. E.; Grayston, S. J.; Oh, S.-W.

    2013-04-01

    Emulating the variability that exists in the natural landscape prior to disturbance should be a goal of soil reconstruction and land reclamation efforts following resource extraction. Long-term ecosystem sustainability within reclaimed landscapes can only be achieved with the re-establishment of biogeochemical processes between reconstructed soils and plants. In this study, we assessed key soil biogeochemical attributes (nutrient availability, organic matter composition, and microbial communities) in reconstructed, novel, anthropogenic ecosystems covering different reclamation treatments following open-cast mining for oil extraction. We compared the attributes to those present in a range of natural soils representative of mature boreal forest ecosystems in the same area of northern Alberta. Soil nutrient availability was determined in situ with resin probes, organic matter composition was described with 13C nuclear magnetic resonance spectroscopy and soil microbial community structure was characterized using phospholipid fatty acid analysis. Significant differences among natural ecosystems were apparent in nutrient availability and seemed more related to the dominant tree cover than to soil type. When analyzed together, all natural forests differed significantly from the novel ecosystems, in particular with respect to soil organic matter composition. However, there was some overlap between the reconstructed soils and some of the natural ecosystems in nutrient availability and microbial communities, but not in organic matter characteristics. Hence, our results illustrate the importance of considering the range of natural landscape variability, and including several soil biogeochemical attributes when comparing novel, anthropogenic ecosystems to the mature ecosystems that constitute ecological targets.

  11. Comparing soil biogeochemical processes in novel and natural boreal forest ecosystems

    NASA Astrophysics Data System (ADS)

    Quideau, S. A.; Swallow, M. J. B.; Prescott, C. E.; Grayston, S. J.; Oh, S.-W.

    2013-08-01

    Emulating the variability that exists in the natural landscape prior to disturbance should be a goal of soil reconstruction and land reclamation efforts following resource extraction. Long-term ecosystem sustainability within reclaimed landscapes can only be achieved with the re-establishment of biogeochemical processes between reconstructed soils and plants. In this study, we assessed key soil biogeochemical attributes (nutrient availability, organic matter composition, and microbial communities) in reconstructed, novel, anthropogenic ecosystems, covering different reclamation treatments following open-cast mining for oil extraction. We compared the attributes to those present in a range of natural soils representative of mature boreal forest ecosystems in the same area of Northern Alberta. Soil nutrient availability was determined in situ with resin probes, organic matter composition was described with 13C nuclear magnetic resonance spectroscopy and soil microbial community structure was characterized using phospholipid fatty acid analysis. Significant differences among natural ecosystems were apparent in nutrient availability and seemed more related to the dominant tree cover than to soil type. When analyzed together, all natural forests differed significantly from the novel ecosystems, in particular with respect to soil organic matter composition. However, there was some overlap between the reconstructed soils and some of the natural ecosystems in nutrient availability and microbial communities, but not in organic matter characteristics. Hence, our results illustrate the importance of considering the range of natural landscape variability and including several soil biogeochemical attributes when comparing novel, anthropogenic ecosystems to the mature ecosystems that constitute ecological targets.

  12. Biogeochemical processes on tree islands in the greater everglades: Initiating a new paradigm

    USGS Publications Warehouse

    Wetzel, P.R.; Sklar, Fred H.; Coronado, C.A.; Troxler, T.G.; Krupa, S.L.; Sullivan, P.L.; Ewe, S.; Price, R.M.; Newman, S.; Orem, W.H.

    2011-01-01

    Scientists' understanding of the role of tree islands in the Everglades has evolved from a plant community of minor biogeochemical importance to a plant community recognized as the driving force for localized phosphorus accumulation within the landscape. Results from this review suggest that tree transpiration, nutrient infiltration from the soil surface, and groundwater flow create a soil zone of confluence where nutrients and salts accumulate under the head of a tree island during dry periods. Results also suggest accumulated salts and nutrients are flushed downstream by regional water flows during wet periods. That trees modulate their environment to create biogeochemical hot spots and strong nutrient gradients is a significant ecological paradigm shift in the understanding of the biogeochemical processes in the Everglades. In terms of island sustainability, this new paradigm suggests the need for distinct dry-wet cycles as well as a hydrologic regime that supports tree survival. Restoration of historic tree islands needs further investigation but the creation of functional tree islands is promising. Copyright ?? 2011 Taylor & Francis Group, LLC.

  13. Tracing biogeochemical processes in stream water and groundwater using non-linear statistics

    NASA Astrophysics Data System (ADS)

    Lischeid, Gunnar; Bittersohl, Jochen

    2008-07-01

    SummaryStream water and groundwater solute concentration are subject to a multitude of biogeochemical processes that act at different scales and are often characterized by non-linear relationships and feedback loops. Different multivariate statistical methods were applied to investigate the interplay of different processes. The data set from the Lehstenbach catchment in South Germany comprised 2641 stream water and groundwater samples from 38 different sites in the catchment, where 13 different solutes had been determined. According to the correlation dimension analysis, the number of dominant processes was four. The first four components determined via principal component analysis comprised 88% of the total variance, whereas the non-linear isometric feature mapping explained 92% with the first four components. These components were ascribed to prevailing biogeochemical processes and were used to investigate spatial and temporal patterns. Redox processes and contamination by road salt explained 35% of the variance each. Another 13% were ascribed to near-surface runoff in the acidified topsoil, and 9% to the impact of contaminated filter gravel in some of the groundwater wells. The redox component exhibited clear seasonal patterns at most stream water and groundwater sampling sites, with the most reduced conditions in late summer, immediately before the onset of re-wetting. There was clear evidence that redox processes, especially denitrification, play an important role even in the oxic aquifer. During discharge peaks, stream water exhibited higher values of the near-surface runoff component. However, the associated lower values of the redox component pointed to near-surface runoff in the riparian wetlands as the predominating runoff generation process rather than to a contribution of upslope soil water. A series of major rain storms in fall 1998 altered groundwater and stream water solute concentration for months: stream water and groundwater became more oxic and

  14. [DNDC model, a model of biogeochemical processes: Research progress and applications].

    PubMed

    Guo, Jia-Wei; Zou, Yuan-Chun; Huo, Li-Li; Lü, Xian-Guo

    2013-02-01

    Denitrification-decomposition (DNDC) model can estimate the emission fluxes of soil trace gases such as carbon dioxide (CO2), methane (CH4) , and nitrous oxide (N2O) via the coupling of the denitrification and decomposition processes driven by soil environmental factors. At present, DNDC model is one of the most successful models in the world in simulating the terrestrial biogeochemical cycles. This paper mainly reviewed the development process of the DNDC model, its structure, model validation, and sensitive factor analysis, and summarized the hot fields in the applications of the model.

  15. Trees actively and directly influence biogeochemical processes in boreal forested watersheds

    NASA Astrophysics Data System (ADS)

    Högberg, Peter

    2010-05-01

    Trees actively and directly influence biogeochemical processes in boreal forested watersheds Peter Högberg, Dept. of Forest Ecology and Management, SLU, SE-901 83 Umeå, Sweden It is increasingly realized that trees are directly influencing soil processes, and thereby significantly also biogeochemical processes at the scale of watersheds. For example, it is now well established that recent photosynthesis supports on average around 50% of the soil respiratory activity. It takes only a few days from tree canopy photosynthesis to the use of that C by plant roots and soil microbes. Importantly, not only does this represent a significant and rapid return flux of CO2 back to the atmosphere, but it also relates to a range of important biogeochemical processes. These occur not only in the soil, but also in streams and lakes, e.g., in nutrient-poor boreal forests areas labile C compounds produced by tree roots and their associated microorganisms constitute an important C source for lake biota. Furthermore, the tree belowground C allocation is under strong physiological control and responds to the supply of nutrients, especially to the supply of nitrogen. When this is low, as in most boreal forests, the belowground C allocation to roots and mycorrhizal fungi is large. This explains the very large N retention capacity of these forests. However, after large additions of N, this belowground C flux is reduced and consequently also the N retention capacity of mycorrhizal fungi. When this occurs, bacteria, organisms with a much lower C/N ratio, become dominant; but as these are C-limited, their capacity to sequester N is much lower than that of fungi. As a consequence, the N cycle opens up, and N is lost through leaching of nitrate and denitrification. However, if the N-load is removed, the trees start to allocate more C belowground to their mycorrhizal fungi again, and this important N-trap is restored. Thus, there are many examples of how trees actively and directly (with short

  16. Technical note: Sampling and processing of mesocosm sediment trap material for quantitative biogeochemical analysis

    NASA Astrophysics Data System (ADS)

    Boxhammer, Tim; Bach, Lennart T.; Czerny, Jan; Riebesell, Ulf

    2016-05-01

    Sediment traps are the most common tool to investigate vertical particle flux in the marine realm. However, the spatial and temporal decoupling between particle formation in the surface ocean and particle collection in sediment traps at depth often handicaps reconciliation of production and sedimentation even within the euphotic zone. Pelagic mesocosms are restricted to the surface ocean, but have the advantage of being closed systems and are therefore ideally suited to studying how processes in natural plankton communities influence particle formation and settling in the ocean's surface. We therefore developed a protocol for efficient sample recovery and processing of quantitatively collected pelagic mesocosm sediment trap samples for biogeochemical analysis. Sedimented material was recovered by pumping it under gentle vacuum through a silicon tube to the sea surface. The particulate matter of these samples was subsequently separated from bulk seawater by passive settling, centrifugation or flocculation with ferric chloride, and we discuss the advantages and efficiencies of each approach. After concentration, samples were freeze-dried and ground with an easy to adapt procedure using standard lab equipment. Grain size of the finely ground samples ranged from fine to coarse silt (2-63 µm), which guarantees homogeneity for representative subsampling, a widespread problem in sediment trap research. Subsamples of the ground material were perfectly suitable for a variety of biogeochemical measurements, and even at very low particle fluxes we were able to get a detailed insight into various parameters characterizing the sinking particles. The methods and recommendations described here are a key improvement for sediment trap applications in mesocosms, as they facilitate the processing of large amounts of samples and allow for high-quality biogeochemical flux data.

  17. Technical Note: Sampling and processing of mesocosm sediment trap material for quantitative biogeochemical analysis

    NASA Astrophysics Data System (ADS)

    Boxhammer, T.; Bach, L. T.; Czerny, J.; Riebesell, U.

    2015-11-01

    Sediment traps are the most common tool to investigate vertical particle flux in the marine realm. However, the spatial decoupling between particle formation and collection often handicaps reconciliation of these two processes even within the euphotic zone. Pelagic mesocosms have the advantage of being closed systems and are therefore ideally suited to study how processes in natural plankton communities influence particle formation and settling in the ocean's surface. We therefore developed a protocol for efficient sample recovery and processing of quantitatively collected pelagic mesocosm sediment trap samples. Sedimented material was recovered by pumping it under gentle vacuum through a silicon tube to the sea surface. The particulate matter of these samples was subsequently concentrated by passive settling, centrifugation or flocculation with ferric chloride and we discuss the advantages of each approach. After concentration, samples were freeze-dried and ground with an easy to adapt procedure using standard lab equipment. Grain size of the finely ground samples ranges from fine to coarse silt (2-63 μm), which guarantees homogeneity for representative subsampling, a widespread problem in sediment trap research. Subsamples of the ground material were perfectly suitable for a variety of biogeochemical measurements and even at very low particle fluxes we were able to get a detailed insight on various parameters characterizing the sinking particles. The methods and recommendations described here are a key improvement for sediment trap applications in mesocosms, as they facilitate processing of large amounts of samples and allow for high-quality biogeochemical flux data.

  18. Biogeochemical Considerations

    NASA Technical Reports Server (NTRS)

    Delwiche, C. C.

    1984-01-01

    Some questions relating to biogeochemical cycles and the nature of the biosphere driving them is best approached by means of remote (satellite) monitoring. Important among these are the distribution of various ecosystems and the boundaries between them, the extent and rate of modification of ecosystems by human or other factors, and various climatic and physical factors affecting ecosystem performance as influenced by human or natural processes.

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

    PubMed Central

    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.

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

    PubMed Central

    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

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

  4. Can spectroscopic analysis improve our understanding of biogeochemical processes in agricultural streams?

    NASA Astrophysics Data System (ADS)

    Bieroza, Magdalena; Heathwaite, Ann Louise

    2015-04-01

    In agricultural catchments diffuse fluxes of nutrients, mainly nitrogen (N) and phosphorus (P) from arable land and livestock are responsible for pollution of receiving waters and their eutrophication. Organic matter (OM) can play an important role in mediating a range of biogeochemical processes controlling diffuse pollution in streams and at their interface with surrounding land in the riparian and hyporheic zones. Thus, a holistic and simultaneous monitoring of N, P and OM fractions can help to improve our understanding of biogeochemical functioning of agricultural streams. In this study we build on intensive in situ monitoring of diffuse pollution in a small agricultural groundwater-fed stream in NW England carried out since 2009. The in situ monitoring unit captures high-frequency (15 minutes to hourly) responses of water quality parameters including total phosphorus, total reactive phosphorus and nitrate-nitrogen to changing flow conditions. For two consecutive hydrological years we have carried out additional spectroscopic water analyses to characterise organic matter components and their interactions with nutrient fractions. Automated and grab water samples have been analysed using ultraviolet-visible (UV-Vis) absorbance and excitation-emission (EEM) fluorescence spectroscopy. In addition, a tryptophan sensor was trialled to capture in situ fluorescence dynamics. Our paper evaluates patterns in nutrient and OM responses to baseflow and storm flow conditions and provides an assessment of storage-related changes of automated samples and temperature and turbidity effects on in situ tryptophan measurements. The paper shows the value of spectroscopic measurements to understand biogeochemical and hydrological nutrient dynamics and quantifies analytical uncertainty associated with both laboratory-based and in situ spectroscopic measurements.

  5. Characterizing biogeochemical processes in the hyporheic zone using flume experiments and reactive transport modeling

    NASA Astrophysics Data System (ADS)

    Quick, A. M.; Reeder, W. J.; Farrell, T. B.; Feris, K. P.; Tonina, D.; Benner, S. G.

    2015-12-01

    The hyporheic zones of streams are hotspots of biogeochemical cycling, where reactants from surface water and groundwater are continually brought into contact with microbial populations on the surfaces of stream sediments and reaction products are removed by hyporheic flow and degassing. Using large flume experiments we have documented the complex redox dynamics associated with dune-scale hyporheic flow. Observations, coupled with reactive transport modeling, provide insight into how flow dictates spatio-temporal distribution of redox reactions and the associated consumption and production of reactants and products. Dune hyporheic flow was experimentally produced by maintaining control over flow rates, slopes, sediment grain size, bedform geomorphology, and organic carbon content. An extensive in-situ monitoring array combined with sampling events over time elucidated redox-sensitive processes including constraints on the spatial distribution and magnitude of aerobic respiration, organic carbon consumption, sulfide deposition, and denitrification. Reactive transport modeling reveals further insight into the influence of system geometry and reaction rate. As an example application of the model, the relationship between residence times and reaction rates may be used to generate Damköhler numbers that are related to biogeochemical processes, such as the potential of streambed morphology and nitrate loading to influence production of the greenhouse gas nitrous oxide via incomplete denitrification.

  6. Integrating turbulent flow, biogeochemical, and poromechanical processes in rippled coastal sediment (Invited)

    NASA Astrophysics Data System (ADS)

    Cardenas, M. B.; Cook, P. L.; Jiang, H.; Traykovski, P.

    2010-12-01

    Coastal sediments are the locus of multiple coupled processes. Turbulent flow associated with waves and currents induces porewater flow through sediment leading to fluid exchange with the water column. This porewater flow is determined by the hydraulic and elastic properties of the sediment. Porewater flow also ultimately controls biogeochemical reactions in the sediment whose rates depend on delivery of reactants and export of products. We present results from numerical modeling studies directed at integrating these processes with the goal of shedding light on these complex environments. We show how denitrification rates inside ripples are largest at intermediate permeability which represents the optimal balance of reactant delivery and anoxic conditions. It is clear that nutrient cycling and distribution within the sediment is strongly dependent on the character of the multidimensional flow field inside of sediment. More recent studies illustrate the importance of the elastic properties of the saturated sediment on modulating fluid exchange between the water column and the sediment when pressure fluctuations along the sediment-water interface occur at the millisecond scale. Pressure fluctuations occur at this temporal scale due to turbulence and associated shedding of vortices due to the ripple geometry. This suggests that biogeochemical cycling may also be affected by these high-frequency elastic effects. Future studies should be directed towards this and should take advantage of modeling tools such as those we present.

  7. Aggregate-scale spatial heterogeneity in reductive transformation of ferrihydrite resulting from coupled biogeochemical and physical processes

    NASA Astrophysics Data System (ADS)

    Pallud, C.; Masue-Slowey, Y.; Fendorf, S.

    2010-05-01

    Iron (hydr)oxides are ubiquitous in soils and sediments and play a dominant role in the geochemistry of surface and subsurface environments. Their fate depends on local environmental conditions, which in structured soils may vary significantly over short distances due to mass-transfer limitations on solute delivery and metabolite removal. In the present study, artificial soil aggregates were used to investigate the coupling of physical and biogeochemical processes affecting the spatial distribution of iron (Fe) phases resulting from reductive transformation of ferrihydrite. Spherical aggregates made of ferrihydrite-coated sand were inoculated with the dissimilatory Fe-reducing bacterium Shewanella putrefaciens strain CN-32, and placed into a flow reactor, the reaction cell simulates a diffusion-dominated soil aggregate surrounded by an advective flow domain. The spatial and temporal evolution of secondary mineralization products resulting from dissimilatory Fe reduction of ferrihydrite were followed within the aggregates in response to a range of flow rates and lactate concentrations. Strong radial variations in the distribution of secondary phases were observed owing to diffusively controlled delivery of lactate and efflux of Fe(II) and bicarbonate. In the aggregate cortex, only limited formation of secondary Fe phases were observed over 30 d of reaction, despite high rates of ferrihydrite reduction. Under all flow conditions tested, ferrihydrite transformation was limited in the cortex (70-85 mol.% Fe remained as ferrihydrite) because metabolites such as Fe(II) and bicarbonate were efficiently removed in outflow solutes. In contrast, within the inner fractions of the aggregate, limited mass-transfer results in metabolite (Fe(II) and bicarbonate) build-up and the consummate transformation of ferrihydrite - only 15-40 mol.% Fe remained as ferrihydrite after 30 d of reaction. Goethite/lepidocrocite, and minor amounts of magnetite, formed in the aggregate mid

  8. Tracing biogeochemical and microbial variability over a complete oil sand mining and recultivation process.

    PubMed

    Noah, Mareike; Lappé, Michael; Schneider, Beate; Vieth-Hillebrand, Andrea; Wilkes, Heinz; Kallmeyer, Jens

    2014-11-15

    Recultivation of disturbed oil sand mining areas is an issue of increasing importance. Nevertheless only little is known about the fate of organic matter, cell abundances and microbial community structures during oil sand processing, tailings management and initial soil development on reclamation sites. Thus the focus of this work is on biogeochemical changes of mined oil sands through the entire process chain until its use as substratum for newly developing soils on reclamation sites. Therefore, oil sand, mature fine tailings (MFTs) from tailings ponds and drying cells and tailings sand covered with peat-mineral mix (PMM) as part of land reclamation were analyzed. The sample set was selected to address the question whether changes in the above-mentioned biogeochemical parameters can be related to oil sand processing or biological processes and how these changes influence microbial activities and soil development. GC-MS analyses of oil-derived biomarkers reveal that these compounds remain unaffected by oil sand processing and biological activity. In contrast, changes in polycyclic aromatic hydrocarbon (PAH) abundance and pattern can be observed along the process chain. Especially naphthalenes, phenanthrenes and chrysenes are altered or absent on reclamation sites. Furthermore, root-bearing horizons on reclamation sites exhibit cell abundances at least ten times higher (10(8) to 10(9) cells g(-1)) than in oil sand and MFT samples (10(7) cells g(-1)) and show a higher diversity in their microbial community structure. Nitrate in the pore water and roots derived from the PMM seem to be the most important stimulants for microbial growth. The combined data show that the observed compositional changes are mostly related to biological activity and the addition of exogenous organic components (PMM), whereas oil extraction, tailings dewatering and compaction do not have significant influences on the evaluated compounds. Microbial community composition remains relatively

  9. Tracing biogeochemical and microbial variability over a complete oil sand mining and recultivation process.

    PubMed

    Noah, Mareike; Lappé, Michael; Schneider, Beate; Vieth-Hillebrand, Andrea; Wilkes, Heinz; Kallmeyer, Jens

    2014-11-15

    Recultivation of disturbed oil sand mining areas is an issue of increasing importance. Nevertheless only little is known about the fate of organic matter, cell abundances and microbial community structures during oil sand processing, tailings management and initial soil development on reclamation sites. Thus the focus of this work is on biogeochemical changes of mined oil sands through the entire process chain until its use as substratum for newly developing soils on reclamation sites. Therefore, oil sand, mature fine tailings (MFTs) from tailings ponds and drying cells and tailings sand covered with peat-mineral mix (PMM) as part of land reclamation were analyzed. The sample set was selected to address the question whether changes in the above-mentioned biogeochemical parameters can be related to oil sand processing or biological processes and how these changes influence microbial activities and soil development. GC-MS analyses of oil-derived biomarkers reveal that these compounds remain unaffected by oil sand processing and biological activity. In contrast, changes in polycyclic aromatic hydrocarbon (PAH) abundance and pattern can be observed along the process chain. Especially naphthalenes, phenanthrenes and chrysenes are altered or absent on reclamation sites. Furthermore, root-bearing horizons on reclamation sites exhibit cell abundances at least ten times higher (10(8) to 10(9) cells g(-1)) than in oil sand and MFT samples (10(7) cells g(-1)) and show a higher diversity in their microbial community structure. Nitrate in the pore water and roots derived from the PMM seem to be the most important stimulants for microbial growth. The combined data show that the observed compositional changes are mostly related to biological activity and the addition of exogenous organic components (PMM), whereas oil extraction, tailings dewatering and compaction do not have significant influences on the evaluated compounds. Microbial community composition remains relatively

  10. Advances in Coupling of Kinetics and Molecular Scale Tools to Shed Light on Soil Biogeochemical Processes

    SciTech Connect

    Sparks, Donald

    2014-09-02

    Biogeochemical processes in soils such as sorption, precipitation, and redox play critical roles in the cycling and fate of nutrients, metal(loid)s and organic chemicals in soil and water environments. Advanced analytical tools enable soil scientists to track these processes in real-time and at the molecular scale. Our review focuses on recent research that has employed state-of-the-art molecular scale spectroscopy, coupled with kinetics, to elucidate the mechanisms of nutrient and metal(loid) reactivity and speciation in soils. We found that by coupling kinetics with advanced molecular and nano-scale tools major advances have been made in elucidating important soil chemical processes including sorption, precipitation, dissolution, and redox of metal(loids) and nutrients. Such advances will aid in better predicting the fate and mobility of nutrients and contaminants in soils and water and enhance environmental and agricultural sustainability.

  11. Plant impact on the biogeochemical cycle of silicon and related weathering processes

    NASA Astrophysics Data System (ADS)

    Alexandre, Anne; Meunier, Jean-Dominique; Colin, Fabrice; Koud, Jean-Mathias

    1997-02-01

    The contribution of plants to the biogeochemical cycle of Si and related weathering processes was studied in an equatorial rainforest ecosystem (Congo) where the biologic turnover of Si is high (58 to 76 kg/ha/y). Litterfall leaves, a soil profile and groundwaters were analysed. Phytoliths and organic matter have a similar distribution with depth in the soil profile. The model of a bicompartmental distribution of organic matter is applied to phytolith distribution and shows that about 92% of the biogenic silica input is rapidly recycled while about 8% of the biogenic silica input supplies a stable pool of phytoliths, with a lower turnover. Reprecipitation of silica was observed at the base of the soil profile, indicating a local geochemical environment that is oversaturated with respect to amorphous silica. A balance in biogeochemical cycle of Si requires that the vegetation absorb dissolved silicon released from weathering of minerals, which otherwise would be available for mineral neoformation or export from the profile towards regional drainages. Plant uptake of Si increases the chemical weathering rate without increasing the denudation rate. This study shows that the uptake, storage, and release of Si by the vegetation have to be taken into account when using dissolved Si for tracing chemical weathering dynamics.

  12. Compound-specific isotopic analyses: a novel tool for reconstruction of ancient biogeochemical processes

    NASA Technical Reports Server (NTRS)

    Hayes, J. M.; Freeman, K. H.; Popp, B. N.; Hoham, C. H.

    1990-01-01

    Patterns of isotopic fractionation in biogeochemical processes are reviewed and it is suggested that isotopic fractionations will be small when substrates are large. If so, isotopic compositions of biomarkers will reflect those of their biosynthetic precursors. This prediction is tested by consideration of results of analyses of geoporphyrins and geolipids from the Greenhorn Formation (Cretaceous, Western Interior Seaway of North America) and the Messel Shale (Eocene, lacustrine, southern Germany). It is shown (i) that isotopic compositions of porphyrins that are related to a common source, but which have been altered structurally, cluster tightly and (ii) that isotopic differences between geolipids and porphyrins related to a common source are equal to those observed in modern biosynthetic products. Both of these observations are consistent with preservation of biologically controlled isotopic compositions during diagenesis. Isotopic compositions of individual compounds can thus be interpreted in terms of biogeochemical processes in ancient depositional environments. In the Cretaceous samples, isotopic compositions of n-alkanes are covariant with those of total organic carbon, while delta values for pristane and phytane are covariant with those of porphyrins. In this unit representing an open marine environment, the preserved acyclic polyisoprenoids apparently derive mainly from primary material, while the extractable, n-alkanes derive mainly from lower levels of the food chain. In the Messel Shale, isotopic compositions of individual biomarkers range from -20.9 to -73.4% vs PDB. Isotopic compositions of specific compounds can be interpreted in terms of origin from methylotrophic, chemautotrophic, and chemolithotrophic microorganisms as well as from primary producers that lived in the water column and sediments of this ancient lake.

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

    NASA Astrophysics Data System (ADS)

    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.

  14. Spatial dynamics of biogeochemical processes in the St. Louis River freshwater estuary

    EPA Science Inventory

    In the Great Lakes, river-lake transition zones within freshwater estuaries are hydrologically and biogeochemically dynamic areas that regulate nutrient and energy fluxes between rivers and Great Lakes. The goal of our study was to characterize the biogeochemical properties of th...

  15. Isotope biogeochemical assessment of natural biodegradation processes in open cast pit mining landscapes

    NASA Astrophysics Data System (ADS)

    Jeschke, Christina; Knöller, Kay; Koschorreck, Matthias; Ussath, Maria; Hoth, Nils

    2014-05-01

    In Germany, a major share of the energy production is based on the burning of lignite from open cast pit mines. The remediation and re-cultivation of the former mining areas in the Lusatian and Central German lignite mining district is an enormous technical and economical challenge. After mine closures, the surrounding landscapes are threatened by acid mine drainage (AMD), i.e. the acidification and mineralization of rising groundwater with metals and inorganic contaminants. The high content of sulfur (sulfuric acid, sulfate), nitrogen (ammonium) and iron compounds (iron-hydroxides) deteriorates the groundwater quality and decelerates sustainable development of tourism in (former) mining landscapes. Natural biodegradation or attenuation (NA) processes of inorganic contaminants are considered to be a technically low impact and an economically beneficial solution. The investigations of the stable isotope compositions of compounds involved in NA processes helps clarify the dynamics of natural degradation and provides specific informations on retention processes of sulfate and nitrogen-compounds in mine dump water, mine dump sediment, and residual pit lakes. In an active mine dump we investigated zones where the process of bacterial sulfate reduction, as one very important NA process, takes place and how NA can be enhanced by injecting reactive substrates. Stable isotopes signatures of sulfur and nitrogen components were examined and evaluated in concert with hydrogeochemical data. In addition, we delineated the sources of ammonium pollution in mine dump sediments and investigated nitrification by 15N-labeling techniques to calculate the limit of the conversion of harmful ammonium to nitrate in residual mining lakes. Ultimately, we provided an isotope biogeochemical assessment of natural attenuation of sulfate and ammonium at mine dump sites and mining lakes. Also, we estimated the risk potential for water in different compartments of the hydrological system. In

  16. Saltwater intrusion into tidal freshwater marshes alters the biogeochemical processing of organic carbon

    NASA Astrophysics Data System (ADS)

    Neubauer, S. C.; Franklin, R. B.; Berrier, D. J.

    2013-12-01

    Environmental perturbations in wetlands affect the integrated plant-microbial-soil system, causing biogeochemical responses that can manifest at local to global scales. The objective of this study was to determine how saltwater intrusion affects carbon mineralization and greenhouse gas production in coastal wetlands. Working with tidal freshwater marsh soils that had experienced ~ 3.5 yr of in situ saltwater additions, we quantified changes in soil properties, measured extracellular enzyme activity associated with organic matter breakdown, and determined potential rates of anaerobic carbon dioxide (CO2) and methane (CH4) production. Soils from the field plots treated with brackish water had lower carbon content and higher C : N ratios than soils from freshwater plots, indicating that saltwater intrusion reduced carbon availability and increased organic matter recalcitrance. This was reflected in reduced activities of enzymes associated with the hydrolysis of cellulose and the oxidation of lignin, leading to reduced rates of soil CO2 and CH4 production. The effects of long-term saltwater additions contrasted with the effects of short-term exposure to brackish water during three-day laboratory incubations, which increased rates of CO2 production but lowered rates of CH4 production. Collectively, our data suggest that the long-term effect of saltwater intrusion on soil CO2 production is indirect, mediated through the effects of elevated salinity on the quantity and quality of autochthonous organic matter inputs to the soil. In contrast, salinity, organic matter content, and enzyme activities directly influence CH4 production. Our analyses demonstrate that saltwater intrusion into tidal freshwater marshes affects the entire process of carbon mineralization, from the availability of organic carbon through its terminal metabolism to CO2 and/or CH4, and illustrate that long-term shifts in biogeochemical functioning are not necessarily consistent with short

  17. Saltwater intrusion into tidal freshwater marshes alters the biogeochemical processing of organic carbon

    NASA Astrophysics Data System (ADS)

    Neubauer, S. C.; Franklin, R. B.; Berrier, D. J.

    2013-07-01

    Environmental perturbations in wetlands affect the integrated plant-microbial-soil system, causing biogeochemical responses that can manifest at local to global scales. The objective of this study was to determine how saltwater intrusion affects carbon mineralization and greenhouse gas production in coastal wetlands. Working with tidal freshwater marsh soils that had experienced roughly 3.5 yr of in situ saltwater additions, we quantified changes in soil properties, measured extracellular enzyme activity associated with organic matter breakdown, and determined potential rates of anaerobic carbon dioxide (CO2) and methane (CH4) production. Soils from the field plots treated with brackish water had lower carbon content and higher C : N ratios than soils from freshwater plots, indicating that saltwater intrusion reduced carbon availability and increased organic matter recalcitrance. This was reflected in reduced activities of enzymes associated with the hydrolysis of cellulose and the oxidation of lignin, leading to reduced rates of soil CO2 and CH4 production. The effects of long-term saltwater additions contrasted with the effects of short-term exposure to brackish water during three-day laboratory incubations, which increased rates of CO2 production but lowered rates of CH4 production. Collectively, our data suggest that the long-term effect of saltwater intrusion on soil CO2 production is indirect, mediated through the effects of elevated salinity on the quantity and quality of autochthonous organic matter inputs to the soil. In contrast, salinity, organic matter content, and enzyme activities directly influence CH4 production. Our analyses demonstrate that saltwater intrusion into tidal freshwater marshes affects the entire process of carbon mineralization, from the availability of organic carbon through its terminal metabolism to CO2 and/or CH4, and illustrate that long-term shifts in biogeochemical functioning are not necessarily consistent with short

  18. Ozone and Nitrogen Deposition as Modifiers of Biogeochemical Fluxes and Processes in California Forests

    NASA Astrophysics Data System (ADS)

    Fenn, M. E.

    2011-12-01

    The combined effects of ozone and N deposition results in major perturbations of C and N cycling in forests of southern and central California. Increased shoot:root ratios of the major trees species, N-stimulation of aboveground growth, and premature foliar abscission result in greater aboveground C and N pools. Fire suppression exacerbates these perturbations and provides the opportunity for chronic N deposition to further increase the stand densification problem. Long-term litter decomposition rates are retarded by N enrichment which contributes further to litter accumulation in the forest floor. Stage 3 of N saturation in California mixed conifer forests occurs as chronic N deposition, in conjunction with co-occurring ozone effects, decreases fine root biomass, interferes with stomatal control, and increases the susceptibility of ponderosa pine trees to drought stress and bark beetle attack, leading to increased stand mortality. Hot moments of N transfers from canopy to the forest floor occur during precipitation events that follow long dry periods, but particularly during fog events. During initial soil wet up, pulses of NO and N2O emissions from the forest floor occur. Streamwater losses of nitrate are highest following storms preceded by dry periods, but also during peak runoff, typically in February and March. However, major losses of accumulated N occur during and after fire events. However, ecosystem N budgets, biogeochemical modeling studies and experimental burns in N-saturated chaparral catchments in southern California demonstrate that symptoms of N excess are not easily reversed by N release in and following fire. Even with decreased N deposition, momentum for elevated N losses from California forests would likely continue, driven by actively nitrifying soils and increased N content of litter and soil organic matter. Initial studies show that during peak runoff, as much as 20-40% of runoff nitrate in some catchments is throughput of unassimilated

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

    PubMed

    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

  20. Perirheic mixing and biogeochemical processing in flow-through and backwater floodplain wetlands

    NASA Astrophysics Data System (ADS)

    Jones, C. Nathan; Scott, Durelle T.; Edwards, Brandon L.; Keim, Richard F.

    2014-09-01

    Inundation hydrology and associated processes control biogeochemical processing in floodplains. To better understand how hydrologic connectivity, residence time, and intrafloodplain mixing vary in floodplain wetlands, we examined how water quality of two contrasting areas in the floodplain of the Atchafalaya River—a flow-through and a backwater wetland—responded to an annual flood pulse. Large, synoptic sampling campaigns occurred in both wetlands during the rising limb, peak, and falling limb of the hydrograph. Using a combination of conservative and reactive tracers, we inferred three dominant processes that occurred over the course of the flood pulse: flushing (rising limb), advective transport (peak), and organic matter accumulation (falling limb). Biogeochemistry of the two wetlands was similar during the peak while the river overflowed into both. However, during the rising and falling limbs, flow in the backwater wetland experienced much greater residence time. This led to the accumulation of dissolved organic matter and dissolved phosphorus. There were also elevated ratios of dissolved organic carbon to nitrate in the backwater wetland, suggesting nitrogen removal was limited by nitrate transported into the floodplain there. Collectively, our results suggest inclusion of a temporal component into the perirheic concept more fully describes inundation hydrology and biogeochemistry in large river floodplain. This article was corrected on 6 OCT 2014. See the end of the full text for details

  1. A flexible numerical component to simulate surface runoff transport and biogeochemical processes through dense vegetation

    NASA Astrophysics Data System (ADS)

    Munoz-Carpena, R.; Perez-Ovilla, O.

    2012-12-01

    Methods to estimate surface runoff pollutant removal using dense vegetation buffers (i.e. vegetative filter strips) usually consider a limited number of factors (i.e. filter length, slope) and are in general based on empirical relationships. When an empirical approach is used, the application of the model is limited to those conditions of the data used for the regression equations. The objective of this work is to provide a flexible numerical mechanistic tool to simulate dynamics of a wide range of surface runoff pollutants through dense vegetation and their physical, chemical and biological interactions based on equations defined by the user as part of the model inputs. A flexible water quality model based on the Reaction Simulation Engine (RSE) modeling component is coupled to a transport module based on the traditional Bubnov -Galerkin finite element method to solve the advection-dispersion-reaction equation using the alternating split-operator technique. This coupled transport-reaction model is linked to the VFSMOD-W (http://abe.ufl.edu/carpena/vfsmod) program to mechanistically simulate mobile and stabile pollutants through dense vegetation based on user-defined conceptual models (differential equations written in XML language as input files). The key factors to consider in the creation of a conceptual model are the components in the buffer (i.e. vegetation, soil, sediments) and how the pollutant interacts with them. The biogeochemical reaction component was tested successfully with laboratory and field scale experiments. One of the major advantages when using this tool is that the pollutant transport and removal thought dense vegetation is related to physical and biogeochemical process occurring within the filter. This mechanistic approach increases the range of use of the model to a wide range of pollutants and conditions without modification of the core model. The strength of the model relies on the mechanistic approach used for simulating the removal of

  2. The effect of gold mining and processing on biogeochemical cycles in Muteh area, Isfahan province, Iran

    NASA Astrophysics Data System (ADS)

    Keshavarzi, B.; Moore, F.

    2009-04-01

    The environmental impacts of gold mining and processing on geochemical and biogeochemical cycles in Muteh region located northwest of Esfahan province and northeast of Golpaygan city is investigated. For this purpose systematic sampling was carried out in, rock, soil, water, and sediment environments along with plant, livestocks and human hair samples. Mineralogical and Petrological studies show that ore mineral such as pyrite and arsenopyrite along with fluorine-bearing minerals like tremolite, actinolite, biotite and muscovite occur in green schist, amphibolite and lucogranitic rocks in the area. The hydrochemistry of the analysed water samples indicate that As and F display the highest concentrations among the analysed elements. Indeed arsenic has the highest concentration in both topsoil and subsoil samples when compared with other potentially toxic elements. Anthropogenic activity also have it s greatest effect on increasing arsenic concentration among the analysed samples. The concentration of the majority of the analysed elements in the shoots and leaves of two local plants of the region i.e Artemesia and Penagum is higher than their concentration in the roots. Generally speaking, Artemesia has a greater tendency for bioaccumulating heavy metals. The results of cyanide analysis in soil samples show that cyanide concentration in the soils near the newly built tailing dam is much higher than that in the vicinity of the old tailing dam. The high concentration of fluorine in the drinking water of the Muteh village is the main reason of the observed dental fluorosis symptoms seen in the inhabitants. One of the two drinking water wells which is located near the metamorphic complex and supplies part of the tap water in the village, probably has the greatest impact in this regard. A decreasing trend in fluorine concentration is illustrated with increasing distance from the metamorphic complex. Measurements of As concentration in human hair specimens indicate that As

  3. Caught in the flux net: disentangling error, uncertainty, heterogeneity, and spatial process in biogeochemical scaling

    NASA Astrophysics Data System (ADS)

    Dietze, M.

    2014-12-01

    Attempts to link observations across multiple scales, and in particular the problem of scaling up fine-scale observations to landscape and regional process, faces numerous theoretical, computational, and statistical challenges. This talk aims to link theoretical advances in the scaling of biotic heterogeneity, abiotic heterogeneity, and contagious disturbance with statistical advances for linking observations that integrate over different scales. Critical to this goal is the need to partition sources of uncertainty and variability. In particular, the variance you can calculate most readily is rarely the most important or relevant one to quantify. In community ecology, hierarchical Bayes (HB) latent-variable models that separate true variability in ecosystem processes from observation errors have challenged long-standing theory surrounding the maintenance of biodiversity, yet application of such approaches to regional-scale biogeochemical processes is just beginning. A special case of such models, focused on the change of support problem, deal specifically with linking observations that integrate over different spatial and temporal scales. Occurring in parallel with these statistical advances have been the development of new theories for the spatially-implicit scaling of biotic and abiotic heterogeneity, as well as contagious disturbances such as fire and pathogens, and the incorporation of such approaches into process-based ecosystem models. Such approaches upscale by integrating the probability distributions of system heterogeneity over the functional response of the ecosystem to such heterogeneity. We demonstrate that this approach can also be downscaled by conditioning on incomplete partial observation at a local scale, and can have lower uncertainty than brute-force spatially-explicit approaches. We also extend such approaches from integrating over observed heterogeneities to integrating the latent, high-dimensional variability in HB models. Finally, there is a

  4. Determination of dominant biogeochemical processes in a contaminated aquifer-wetland system using multivariate statistical analysis

    USGS Publications Warehouse

    Baez-Cazull, S. E.; McGuire, J.T.; Cozzarelli, I.M.; Voytek, M.A.

    2008-01-01

    Determining the processes governing aqueous biogeochemistry in a wetland hydrologically linked to an underlying contaminated aquifer is challenging due to the complex exchange between the systems and their distinct responses to changes in precipitation, recharge, and biological activities. To evaluate temporal and spatial processes in the wetland-aquifer system, water samples were collected using cm-scale multichambered passive diffusion samplers (peepers) to span the wetland-aquifer interface over a period of 3 yr. Samples were analyzed for major cations and anions, methane, and a suite of organic acids resulting in a large dataset of over 8000 points, which was evaluated using multivariate statistics. Principal component analysis (PCA) was chosen with the purpose of exploring the sources of variation in the dataset to expose related variables and provide insight into the biogeochemical processes that control the water chemistry of the system. Factor scores computed from PCA were mapped by date and depth. Patterns observed suggest that (i) fermentation is the process controlling the greatest variability in the dataset and it peaks in May; (ii) iron and sulfate reduction were the dominant terminal electron-accepting processes in the system and were associated with fermentation but had more complex seasonal variability than fermentation; (iii) methanogenesis was also important and associated with bacterial utilization of minerals as a source of electron acceptors (e.g., barite BaSO4); and (iv) seasonal hydrological patterns (wet and dry periods) control the availability of electron acceptors through the reoxidation of reduced iron-sulfur species enhancing iron and sulfate reduction. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

  5. Reservoir and contaminated sediments impacts in high-Andean environments: Morphodynamic interactions with biogeochemical processes

    NASA Astrophysics Data System (ADS)

    Escauriaza, C. R.; Contreras, M. T.; Müllendorff, D. A.; Pasten, P.; Pizarro, G. E.

    2014-12-01

    Rapid changes due to anthropic interventions in high-altitude environments, such as the Altiplano region in South America, require new approaches to understand the connections between physical and biogeochemical processes. Alterations of the water quality linked to the river morphology can affect the ecosystems and human development in the long-term. The future construction of a reservoir in the Lluta river, located in northern Chile, will change the spatial distribution of arsenic-rich sediments, which can have significant effects on the lower parts of the watershed. In this investigation we develop a coupled numerical model to predict and evaluate the interactions between morphodynamic changes in the Lluta reservoir, and conditions that can potentially desorb arsenic from the sediments. Assuming that contaminants are mobilized under anaerobic conditions, we calculate the oxygen concentration within the sediments to study the interactions of the delta progradation with the potential arsenic release. This work provides a framework for future studies aimed to analyze the complex connections between morphodynamics and water quality, when contaminant-rich sediments accumulate in a reservoir. The tool can also help to design effective risk management and remediation strategies in these extreme environments. Research has been supported by Fondecyt grant 1130940 and CONICYT/FONDAP Grant 15110017

  6. Biogeochemical processes controlling density stratification in an iron-meromictic lake

    NASA Astrophysics Data System (ADS)

    Nixdorf, E.; Boehrer, B.

    2015-06-01

    Biogeochemical processes and mixing regime of a lake can control each other mutually. The prominent case of iron meromixis is investigated in Waldsee near Doebern, a small lake that originated from surface mining of lignite. From a four years data set of monthly measured electrical conductivity profiles, we calculated summed conductivity as a quantitative variable reflecting the amount of electro-active substances in the entire lake. Seasonal variations followed changing chemocline height. Coinciding changes of electrical conductivities in the monimolimnion indicated that a considerable share of substances, precipitated by the advancing oxygenated epilimnion, re-dissolved in the remaining anoxic deep waters and contributed considerably to the density stratification. In addition, we constructed a lab experiment, in which aeration of monimolimnetic waters removed iron compounds and organic material. Precipitates could be identified by visual inspection. Introduced air bubbles ascended through the water column and formed a water mass similar to the mixolimnetic Waldsee water. The remaining less dense water remained floating on the nearly unchanged monimolimnetic water. In conclusion, iron meromixis as seen in Waldsee did not require two different sources of incoming waters, but the inflow of iron rich deep groundwater and the aeration through the lake surface were fully sufficient.

  7. Seasonal Variation in Floodplain Biogeochemical Processing in a Restored Headwater Stream.

    PubMed

    Jones, C Nathan; Scott, Durelle T; Guth, Christopher; Hester, Erich T; Hession, W Cully

    2015-11-17

    Stream and river restoration activities have recently begun to emphasize the enhancement of biogeochemical processing within river networks through the restoration of river-floodplain connectivity. It is generally accepted that this practice removes pollutants such as nitrogen and phosphorus because the increased contact time of nutrient-rich floodwaters with reactive floodplain sediments. Our study examines this assumption in the floodplain of a recently restored, low-order stream through five seasonal experiments. During each experiment, a floodplain slough was artificially inundated for 3 h. Both the net flux of dissolved nutrients and nitrogen uptake rate were measured during each experiment. The slough was typically a source of dissolved phosphorus and dissolved organic matter, a sink of NO3(-), and variable source/sink of ammonium. NO3(-) uptake rates were relatively high when compared to riverine uptake, especially during the spring and summer experiments. However, when scaled up to the entire 1 km restoration reach with a simple inundation model, less than 0.5-1.5% of the annual NO3(-) load would be removed because of the short duration of river-floodplain connectivity. These results suggest that restoring river-floodplain connectivity is not necessarily an appropriate best management practice for nutrient removal in low-order streams with legacy soil nutrients from past agricultural landuse. PMID:26463837

  8. Seasonal Variation in Floodplain Biogeochemical Processing in a Restored Headwater Stream.

    PubMed

    Jones, C Nathan; Scott, Durelle T; Guth, Christopher; Hester, Erich T; Hession, W Cully

    2015-11-17

    Stream and river restoration activities have recently begun to emphasize the enhancement of biogeochemical processing within river networks through the restoration of river-floodplain connectivity. It is generally accepted that this practice removes pollutants such as nitrogen and phosphorus because the increased contact time of nutrient-rich floodwaters with reactive floodplain sediments. Our study examines this assumption in the floodplain of a recently restored, low-order stream through five seasonal experiments. During each experiment, a floodplain slough was artificially inundated for 3 h. Both the net flux of dissolved nutrients and nitrogen uptake rate were measured during each experiment. The slough was typically a source of dissolved phosphorus and dissolved organic matter, a sink of NO3(-), and variable source/sink of ammonium. NO3(-) uptake rates were relatively high when compared to riverine uptake, especially during the spring and summer experiments. However, when scaled up to the entire 1 km restoration reach with a simple inundation model, less than 0.5-1.5% of the annual NO3(-) load would be removed because of the short duration of river-floodplain connectivity. These results suggest that restoring river-floodplain connectivity is not necessarily an appropriate best management practice for nutrient removal in low-order streams with legacy soil nutrients from past agricultural landuse.

  9. Linking Food Webs and Biogeochemical Processes in Wetlands: Insights From Sulfur Isotopes

    NASA Astrophysics Data System (ADS)

    Stricker, C. A.; Guntenspergen, G. R.; Rye, R. O.

    2005-05-01

    To better understand the transfer of nutrients into prairie wetland food webs we have investigated the cycling of S (via S isotope systematics and geochemistry) in a prairie wetland landscape by characterizing sources (ground water, interstitial water, surface water) and processes in a small catchment comprised of four wetlands in eastern South Dakota. We focused on S to derive process information that is not generally available from carbon isotopes alone. The wetlands chosen for study spanned a considerable range in SO4 concentration (0.1-13.6 mM), which corresponded with landscape position. Ground water δ34SSO4 values remained relatively constant (mean = -13.2 per mil) through time. However, δ34SSO4 values of wetland surface waters ranged from -2.9 to -30.0 per mil (CDT) and were negatively correlated with SO4 concentrations (p<0.05). The isotopic variability of surface water SO4 resulted from mixing with re-oxidized sulfides associated with recently flushed wetland soils. The δ34S signatures of wetland primary (Gastropoda: Stagnicola elodes) and secondary (Odonata: Anax sp.) consumers were significantly related to surface water δ34SSO4 values (p<0.05) suggesting that food web components were responding to changes in the isotopic composition of the S source. Both primary and secondary consumer δ34S signatures differed between wetlands (ANOVA, p<0.05). These data illustrate the complexity of S cycling in prairie wetlands and the influence of wetland hydrologic and biogeochemical processes on prairie wetland food webs. Additionally, this work has demonstrated that sulfur isotopes can provide unique source and process information that cannot be derived from traditional carbon and nitrogen isotope studies.

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

    NASA Astrophysics Data System (ADS)

    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.

  11. Anthropogenic forcing of estuarine hypoxic events in sub-tropical catchments: landscape drivers and biogeochemical processes.

    PubMed

    Wong, Vanessa N L; Johnston, Scott G; Burton, Edward D; Bush, Richard T; Sullivan, Leigh A; Slavich, Peter G

    2011-11-15

    Episodic hypoxic events can occur following summer floods in sub-tropical estuaries of eastern Australia. These events can cause deoxygenation of waterways and extensive fish mortality. Here, we present a conceptual model that links key landscape drivers and biogeochemical processes which contribute to post-flood hypoxic events. The model provides a framework for examining the nature of anthropogenic forcing. Modification of estuarine floodplain surface hydrology through the construction of extensive drainage networks emerges as a major contributing factor to increasing the frequency, magnitude and duration of hypoxic events. Forcing occurs in two main ways. Firstly, artificial drainage of backswamp wetlands initiates drier conditions which cause a shift in vegetation assemblages from wetland-dominant species to dryland-dominant species. These species, which currently dominate the floodplain, are largely intolerant of inundation and provide abundant labile substrate for decomposition following flood events. Decomposition of this labile carbon pool consumes oxygen in the overlying floodwaters, and results in anoxic conditions and waters with excess deoxygenation potential (DOP). Carbon metabolism can be strongly coupled with microbially-mediated reduction of accumulated Fe and Mn oxides, phases which are common on these coastal floodplain landscapes. Secondly, artificial drainage enhances discharge rates during the flood recession phase. Drains transport deoxygenated high DOP floodwaters rapidly from backswamp wetlands to the main river channel to further consume oxygen. This process effectively displaces the natural carbon metabolism processes from floodplain wetlands to the main channel. Management options to reduce the impacts of post-flood hypoxia include i) remodifying drainage on the floodplain to promote wetter conditions, thereby shifting vegetation assemblages towards inundation-tolerant species, and ii) strategic retention of floodwaters in the backswamp

  12. Biogeochemical processes and buffering capacity concurrently affect acidification in a seasonally hypoxic coastal marine basin

    NASA Astrophysics Data System (ADS)

    Hagens, M.; Slomp, C. P.; Meysman, F. J. R.; Seitaj, D.; Harlay, J.; Borges, A. V.; Middelburg, J. J.

    2014-11-01

    Coastal areas are impacted by multiple natural and anthropogenic processes and experience stronger pH fluctuations than the open ocean. These variations can weaken or intensify the ocean acidification signal induced by increasing atmospheric pCO2. The development of eutrophication-induced hypoxia intensifies coastal acidification, since the CO2 produced during respiration decreases the buffering capacity of the hypoxic bottom water. To assess the combined ecosystem impacts of acidification and hypoxia, we quantified the seasonal variation in pH and oxygen dynamics in the water column of a seasonally stratified coastal basin (Lake Grevelingen, the Netherlands). Monthly water column chemistry measurements were complemented with estimates of primary production and respiration using O2 light-dark incubations, in addition to sediment-water fluxes of dissolved inorganic carbon (DIC) and total alkalinity (TA). The resulting dataset was used to set up a proton budget on a seasonal scale. Temperature-induced seasonal stratification combined with a high community respiration was responsible for the depletion of oxygen in the bottom water in summer. The surface water showed strong seasonal variation in process rates (primary production, CO2 air-sea exchange), but relatively small seasonal pH fluctuations (0.46 units on the total hydrogen ion scale). In contrast, the bottom water showed less seasonality in biogeochemical rates (respiration, sediment-water exchange), but stronger pH fluctuations (0.60 units). This marked difference in pH dynamics could be attributed to a substantial reduction in the acid-base buffering capacity of the hypoxic bottom water in the summer period. Our results highlight the importance of acid-base buffering in the pH dynamics of coastal systems and illustrate the increasing vulnerability of hypoxic, CO2-rich waters to any acidifying process.

  13. Biogeochemical processes and buffering capacity concurrently affect acidification in a seasonally hypoxic coastal marine basin

    NASA Astrophysics Data System (ADS)

    Hagens, M.; Slomp, C. P.; Meysman, F. J. R.; Seitaj, D.; Harlay, J.; Borges, A. V.; Middelburg, J. J.

    2015-03-01

    Coastal areas are impacted by multiple natural and anthropogenic processes and experience stronger pH fluctuations than the open ocean. These variations can weaken or intensify the ocean acidification signal induced by increasing atmospheric pCO2. The development of eutrophication-induced hypoxia intensifies coastal acidification, since the CO2 produced during respiration decreases the buffering capacity in any hypoxic bottom water. To assess the combined ecosystem impacts of acidification and hypoxia, we quantified the seasonal variation in pH and oxygen dynamics in the water column of a seasonally stratified coastal basin (Lake Grevelingen, the Netherlands). Monthly water-column chemistry measurements were complemented with estimates of primary production and respiration using O2 light-dark incubations, in addition to sediment-water fluxes of dissolved inorganic carbon (DIC) and total alkalinity (TA). The resulting data set was used to set up a proton budget on a seasonal scale. Temperature-induced seasonal stratification combined with a high community respiration was responsible for the depletion of oxygen in the bottom water in summer. The surface water showed strong seasonal variation in process rates (primary production, CO2 air-sea exchange), but relatively small seasonal pH fluctuations (0.46 units on the total hydrogen ion scale). In contrast, the bottom water showed less seasonality in biogeochemical rates (respiration, sediment-water exchange), but stronger pH fluctuations (0.60 units). This marked difference in pH dynamics could be attributed to a substantial reduction in the acid-base buffering capacity of the hypoxic bottom water in the summer period. Our results highlight the importance of acid-base buffering in the pH dynamics of coastal systems and illustrate the increasing vulnerability of hypoxic, CO2-rich waters to any acidifying process.

  14. Biogeochemical cycles of Chernobyl-born radionuclides in the contaminated forest ecosystems: long-term dynamics of the migration processes

    NASA Astrophysics Data System (ADS)

    Shcheglov, Alexey; Tsvetnova, Ol'ga; Klyashtorin, Alexey

    2013-04-01

    Biogeochemical migration is a dominant factor of the radionuclide transport through the biosphere. In the early XX century, V.I. Vernadskii, a Russian scientist known, noted about a special role living things play in transport and accumulation of natural radionuclide in various environments. The role of biogeochemical processes in migration and redistribution of technogenic radionuclides is not less important. In Russia, V. M. Klechkovskii and N.V. Timofeev-Ressovskii showed some important biogeochemical aspects of radionuclide migration by the example of global fallout and Kyshtym accident. Their followers, R.M. Alexakhin, M.A. Naryshkin, N.V. Kulikov, F.A. Tikhomirov, E.B. Tyuryukanova, and others also contributed a lot to biogeochemistry of radionuclides. In the post-Chernobyl period, this area of knowledge received a lot of data that allowed building the radioactive element balance and flux estimation in various biogeochemical cycles [Shcheglov et al., 1999]. Regrettably, many of recent radioecological studies are only focused on specific radionuclide fluxes or pursue some applied tasks, missing the holistic approach. Most of the studies consider biogeochemical fluxes of radioactive isotopes in terms of either dose estimation or radionuclide migration rates in various food chains. However, to get a comprehensive picture and develop a reliable forecast of environmental, ecological, and social consequences of radioactive pollution in a vast contaminated area, it is necessary to investigate all the radionuclide fluxes associated with the biogeochemical cycles in affected ecosystems. We believe such an integrated approach would be useful to study long-term environmental consequences of the Fukushima accident as well. In our long-term research, we tried to characterize the flux dynamics of the Chernobyl-born radionuclides in the contaminated forest ecosystems and landscapes as a part of the integrated biogeochemical process. Our field studies were started in June of

  15. The value of automated high-frequency nutrient monitoring in inference of biogeochemical processes, temporal variability and trends

    NASA Astrophysics Data System (ADS)

    Bieroza, Magdalena; Heathwaite, Louise

    2013-04-01

    Stream water quality signals integrate catchment-scale processes responsible for delivery and biogeochemical transformation of the key biotic macronutrients (N, C, P). This spatial and temporal integration is particularly pronounced in the groundwater-dominated streams, as in-stream nutrient dynamics are mediated by the processes occurring within riparian and hyporheic ecotones. In this paper we show long-term high-frequency in-stream macronutrient dynamics from a small agricultural catchment located in the North West England. Hourly in-situ measurements of total and reactive phosphorus (Systea, IT), nitrate (Hach Lange, DE) and physical water quality parameters (turbidity, specific conductivity, dissolved oxygen, temperature, pH; WaterWatch, UK) were carried out on the lowland, gaining reach of the River Leith. High-frequency data show complex non-linear nutrient concentration-discharge relationships. The dominance of hysteresis effects suggests the presence of a temporally varying apportionment of allochthonous and autochthonous nutrient sources. Varying direction, magnitude and dynamics of the hysteretic responses between storm events is driven by the variation in the contributing source areas and shows the importance of the coupling of catchment-scale, in-stream, riparian and hyporheic biogeochemical cycles. The synergistic effect of physical (temperature-driven, the hyporheic exchange controlled by diffusion) and biogeochemical drivers (stream and hyporheic metabolism) on in-stream nutrient concentrations manifests itself in observed diurnal patterns. As inferred from the high-frequency nutrient monitoring, the diurnal dynamics are of the greatest importance under baseflow conditions. Understanding the role and relative importance of these processes can be difficult due to spatial and temporal heterogeneity of the key mechanisms involved. This study shows the importance of in-situ, fine temporal resolution, automated monitoring approaches in providing evidence

  16. The "Point Zero": Monitoring of biogeochemical patterns and processes in an initial ecosystem (Lusatia, Germany)

    NASA Astrophysics Data System (ADS)

    Veste, M.; Biemelt, D.; Fischer, A.; Gerwin, W.; Schaaf, W.

    2009-04-01

    .), soil water (TDR, tensiometers), hydrology (stream flow, groundwater, water quality, etc.), erosion, and limnology (water quality). Furthermore, the establishment of higher vegetation (species, pattern) and soil fauna (species, abundance) are investigated and will be related to the physical-chemical soil development. The gathered data are the basis for the calculation of water and element fluxes in the ecosystem and their interactions with the formation of observed structures. A special focus will be on the interactions of the biogeochemical processes on different scales. First results will be presented and discussed.

  17. Significant differences in biogeochemical processes between a glaciated and a permafrost dominated catchment

    NASA Astrophysics Data System (ADS)

    Hindshaw, Ruth; Heaton, Tim; Boyd, Eric; Lang, Susan; Tipper, Ed

    2014-05-01

    It is increasingly recognised that microbially mediated processes have a significant impact on chemical fluxes from glaciated catchments. One important reaction is the oxidation of pyrite since the production of sulphuric acid facilitates the dissolution of minerals without the need for acidity generated by dissolved atmospheric CO2. Thus weathering processes can still continue even when isolated from the atmosphere, as is thought to occur under large ice masses. However, as a glacier melts, it is expected that the microbial community will change with knock-on effects on the stream water chemistry. Understanding the difference in solute generation processes between glaciated and un-glaciated terrain is key to understanding how glacial-interglacial cycles affect atmospheric CO2 consumption by chemical weathering. In order to investigate whether biogeochemical processes differ between glaciated and un-glaciated terrain we collected stream water samples from two small catchments (each approximately 3 km2) in Svalbard. One catchment is glaciated and the other catchment is un-glaciated but is affected by permafrost and a seasonal snow-pack. The two catchments are situated next to each other with identical bedrock (shale with minor siltstone and sandstone). The proximity of the catchments to each other ensures that meteorological variables such as temperature and precipitation are very similar. Sampling was conducted early in the melt-season when there was still significant snow-cover and in mid-summer when most of the seasonal snow-pack had melted. The water samples were analysed for δ34S-SO4, δ18O-SO4, δ18O-H2O, δ13C-DIC and δ13C-DOC, together with major anions and cations. Despite the nominally identical lithology, there were significant differences in the stream water chemistry between the two catchments. For example, sulphate was the dominant anion in the un-glaciated catchment whereas bicarbonate was the dominant anion in the glaciated catchment. Pyrite

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

    PubMed

    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. [Biogeochemical processes of methane cycle in the soils, swamps and lakes of Western Siberia].

    PubMed

    Gal'chenko, V F; Dulov, L E; Cramer, B; Konova, N I; Barysheva, S V

    2001-01-01

    The biogeochemical processes of methane production and oxidation were studied in the upper horizons of tundra and taiga soils and of raised bogs and lake bottom sediments nearby the Tarkosalinsk gas field in western Siberia. Both in dry and water-logged soils, the total methane concentration (in soil particles and gaseous phase) was an order of magnitude higher than in the soil gaseous phase alone (22 and 1.1 nl/cm3, respectively). In bogs and lake bottom sediments, methane concentration was as high as 11 microliters/cm3. Acetate was the major precursor of the newly formed methane. The rate of aceticlastic methanogenesis reached 55 ng C/(cm3 day), whereas that of autotrophic methanogenesis was an order of magnitude lower. The most active methane production and oxidation were observed in bogs and lake sediments where the delta 13C values of CO2 were inversely related to the intensity of bacterial methane oxidation. Methane diffusing from bogs and lake bottom sediments showed delta 13C values ranging from -78 to -47@1000, whereas the delta 13C value of carbon dioxide ranged from -18 to -6@1000. In these ecosystems, methane emission comprised from 3 to 206 mg CH4/(m2 day). Conversely, the dry and water-logged soils of tundra and taiga took up atmospheric methane at a rate varying from 0.3 to 5.3 mg CH4/(m2 day). Methane consumption in soils was of biological rather than of adsorptive nature. This was confirmed by the radioisotopic method and chamber experiments, in which weighting of methane carbon was observed (the delta 13C value changed from -51 to -41@1000). PMID:11386054

  20. Assessment of the GHG Reduction Potential from Energy Crops Using a Combined LCA and Biogeochemical Process Models: A Review

    PubMed Central

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  2. Bacterial Communities Associated with Subsurface Geochemical Processes in Continental Serpentinite Springs

    PubMed Central

    Morrill, Penny L.; Szponar, Natalie; Schrenk, Matthew O.

    2013-01-01

    Reactions associated with the geochemical process of serpentinization can generate copious quantities of hydrogen and low-molecular-weight organic carbon compounds, which may provide energy and nutrients to sustain subsurface microbial communities independently of the photosynthetically supported surface biosphere. Previous microbial ecology studies have tested this hypothesis in deep sea hydrothermal vents, such as the Lost City hydrothermal field. This study applied similar methods, including molecular fingerprinting and tag sequencing of the 16S rRNA gene, to ultrabasic continental springs emanating from serpentinizing ultramafic rocks. These molecular surveys were linked with geochemical measurements of the fluids in an interdisciplinary approach designed to distinguish potential subsurface organisms from those derived from surface habitats. The betaproteobacterial genus Hydrogenophaga was identified as a likely inhabitant of transition zones where hydrogen-enriched subsurface fluids mix with oxygenated surface water. The Firmicutes genus Erysipelothrix was most strongly correlated with geochemical factors indicative of subsurface fluids and was identified as the most likely inhabitant of a serpentinization-powered subsurface biosphere. Both of these taxa have been identified in multiple hydrogen-enriched subsurface habitats worldwide, and the results of this study contribute to an emerging biogeographic pattern in which Betaproteobacteria occur in near-surface mixing zones and Firmicutes are present in deeper, anoxic subsurface habitats. PMID:23584766

  3. Experimental study and steady-state simulation of biogeochemical processes in laboratory columns with aquifer material

    NASA Astrophysics Data System (ADS)

    Amirbahman, Aria; Schönenberger, René; Furrer, Gerhard; Zobrist, Jürg

    2003-07-01

    Packed bed laboratory column experiments were performed to simulate the biogeochemical processes resulting from microbially catalyzed oxidation of organic matter. These included aerobic respiration, denitrification, and Mn(IV), Fe(III) and SO 4 reduction processes. The effects of these reactions on the aqueous- and solid-phase geochemistry of the aquifer material were closely examined. The data were used to model the development of alkalinity and pH along the column. To study the independent development of Fe(III)- and SO 4-reducing environments, two columns were used. One of the columns (column 1) contained small enough concentrations of SO 4 in the influent to render the reduction of this species unimportant to the geochemical processes in the column. The rate of microbially catalyzed reduction of Mn(IV) changed with time as evidenced by the variations in the initial rate of Mn(II) production at the head of the column. The concentration of Mn in both columns was controlled by the solubility of rhodochrosite (MnCO 3(S)). In the column where significant SO 4 reduction took place (column 2), the concentration of dissolved Fe(II) was controlled by the solubility of FeS. In column 1, where SO 4 reduction was not important, maximum dissolved Fe(II) concentrations were controlled by the solubility of siderite (FeCO 3(S)). Comparison of solid-phase and aqueous-phase data suggests that nearly 20% of the produced Fe(II) precipitates as siderite in column 1. The solid-phase analysis also indicates that during the course of experiment, approximately 20% of the total Fe(III) hydroxides and more than 70% of the amorphous Fe(III) hydroxides were reduced by dissimilatory iron reduction. The most important sink for dissolved S(-II) produced by the enzymatic reduction of SO 4 was its direct reaction with solid-phase Fe(III) hydroxides leading initially to the formation of FeS. Compared to this pathway, precipitation as FeS did not constitute an important sink for S(-II) in column

  4. The genetic potential for key biogeochemical processes in Arctic frost flowers and young sea ice revealed by metagenomic analysis.

    PubMed

    Bowman, Jeff S; Berthiaume, Chris T; Armbrust, E Virginia; Deming, Jody W

    2014-08-01

    Newly formed sea ice is a vast and biogeochemically active environment. Recently, we reported an unusual microbial community dominated by members of the Rhizobiales in frost flowers at the surface of Arctic young sea ice based on the presence of 16S gene sequences related to these strains. Here, we use metagenomic analysis of two samples, from a field of frost flowers and the underlying young sea ice, to explore the metabolic potential of this surface ice community. The analysis links genes for key biogeochemical processes to the Rhizobiales, including dimethylsulfide uptake, betaine glycine turnover, and halocarbon production. Nodulation and nitrogen fixation genes characteristic of terrestrial root-nodulating Rhizobiales were generally lacking from these metagenomes. Non-Rhizobiales clades at the ice surface had genes that would enable additional biogeochemical processes, including mercury reduction and dimethylsulfoniopropionate catabolism. Although the ultimate source of the observed microbial community is not known, considerations of the possible role of eolian deposition or transport with particles entrained during ice formation favor a suspended particle source for this microbial community.

  5. Introduction: SIPEX-2: A study of sea-ice physical, biogeochemical and ecosystem processes off East Antarctica during spring 2012

    NASA Astrophysics Data System (ADS)

    Meiners, Klaus M.; Golden, Ken M.; Heil, Petra; Lieser, Jan L.; Massom, Rob; Meyer, Bettina; Williams, Guy D.

    2016-09-01

    This editorial introduces a suite of articles resulting from the second Sea Ice Physics and Ecosystems eXperiment (SIPEX-2) voyage by presenting some background information on the study area and Antarctic sea-ice conditions, and summarising the key findings from the project. Using the Australian icebreaker RV Aurora Australis, SIPEX-2 was conducted in the area between 115-125°E and 62-66°S off East Antarctica during September to November 2012. This region had been sampled during two previous experiments, i.e. ARISE in 2003 (Massom et al., 2006a) and SIPEX in 2007 (Worby et al., 2011a). The 2012 voyage combined traditional and newly developed sampling methods with satellite and other data to measure sea-ice physical properties and processes on large scales, which provided context for biogeochemical and ecological case studies. The specific goals of the SIPEX-2 project were to: (i) measure the spatial variability in sea-ice and snow-cover properties over small- to regional-length scales; (ii) improve understanding of sea-ice kinematic processes; and (iii) advance knowledge of the links between sea-ice physical characteristics, sea-ice biogeochemical cycling and ice-associated food-web dynamics. Our field-based activities were designed to inform modelling approaches and to improve our capability to assess impacts of predicted changes in Antarctic sea ice on Southern Ocean biogeochemical cycles and ecosystem function.

  6. Inorganic carbon cycling and biogeochemical processes in an Arctic inland sea (Hudson Bay)

    NASA Astrophysics Data System (ADS)

    Burt, William J.; Thomas, Helmuth; Miller, Lisa A.; Granskog, Mats A.; Papakyriakou, Tim N.; Pengelly, Leah

    2016-08-01

    The distributions of carbonate system parameters in Hudson Bay, which not only receives nearly one-third of Canada's river discharge but is also subject to annual cycles of sea-ice formation and melt, indicate that the timing and magnitude of freshwater inputs play an important role in carbon biogeochemistry and acidification in this unique Arctic ecosystem. This study uses basin-wide measurements of dissolved inorganic carbon (DIC) and total alkalinity (TA), as well as stable isotope tracers (δ18O and δ13CDIC), to provide a detailed assessment of carbon cycling processes within the bay. Surface distributions of carbonate parameters reveal the particular importance of freshwater inputs in the southern portion of the bay. Based on TA, we surmise that the deep waters in the Hudson Bay are largely of Pacific origin. Riverine TA end-members vary significantly both regionally and with small changes in near-surface depths, highlighting the importance of careful surface water sampling in highly stratified waters. In an along-shore transect, large increases in subsurface DIC are accompanied by equivalent decreases in δ13CDIC with no discernable change in TA, indicating a respiratory DIC production on the order of 100 µmol kg-1 DIC during deep water circulation around the bay.

  7. Biogeochemical Cycling

    NASA Technical Reports Server (NTRS)

    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.

  8. A field evaluation of subsurface and surface runoff. II. Runoff processes

    USGS Publications Warehouse

    Pilgrim, D.H.; Huff, D.D.; Steele, T.D.

    1978-01-01

    Combined use of radioisotope tracer, flow rate, specific conductance and suspended-sediment measurements on a large field plot near Stanford, California, has provided more detailed information on surface and subsurface storm runoff processes than would be possible from any single approach used in isolation. Although the plot was surficially uniform, the runoff processes were shown to be grossly nonuniform, both spatially over the plot, and laterally and vertically within the soil. The three types of processes that have been suggested as sources of storm runoff (Horton-type surface runoff, saturated overland flow, and rapid subsurface throughflow) all occurred on the plot. The nonuniformity of the processes supports the partial- and variable-source area concepts. Subsurface storm runoff occurred in a saturated layer above the subsoil horizon, and short travel times resulted from flow through macropores rather than the soil matrix. Consideration of these observations would be necessary for physically realistic modeling of the storm runoff process. ?? 1978.

  9. Measurements of spectral optical properties and their relation to biogeochemical variables and processes in Crater Lake, Crater Lake National Park, OR

    USGS Publications Warehouse

    Boss, E.S.; Collier, R.; Larson, G.; Fennel, K.; Pegau, W.S.

    2007-01-01

    Spectral inherent optical properties (IOPs) have been measured at Crater Lake, OR, an extremely clear sub-alpine lake. Indeed Pure water IOPs are major contributors to the total IOPs, and thus to the color of the lake. Variations in the spatial distribution of IOPs were observed in June and September 2001, and reflect biogeochemical processes in the lake. Absorption by colored dissolved organic material increases with depth and between June and September in the upper 300 m. This pattern is consistent with a net release of dissolved organic materials from primary and secondary production through the summer and its photo-oxidation near the surface. Waters fed by a tributary near the lake's rim exhibited low levels of absorption by dissolved organic materials. Scattering is mostly dominated by organic particulate material, though inorganic material is found to enter the lake from the rim following a rain storm. Several similarities to oceanic oligotrophic regions are observed: (a) The Beam attenuation correlates well with particulate organic material (POM) and the relationship is similar to that observed in the open ocean. (b) The specific absorption of colored dissolved organic material has a value similar to that of open ocean humic material. (c) The distribution of chlorophyll with depth does not follow the distribution of particulate organic material due to photo-acclimation resulting in a subsurface pigment maximum located about 50 m below the POM maximum. ?? 2007 Springer Science+Business Media B.V.

  10. Using Bathymodiolus tissue stable isotope signatures to infer biogeochemical process at hydrocarbon seeps

    NASA Astrophysics Data System (ADS)

    Feng, D.; Kiel, S.; Qiu, J.; Yang, Q.; Zhou, H.; Peng, Y.; Chen, D.

    2015-12-01

    Here we use stable isotopes of carbon, nitrogen and sulfur in the tissue of two bathymodiolin mussel species with different chemotrophic symbionts (methanotrophs in B. platifrons and sulfide-oxidizers in B. aduloides) to gain insights into the biogeochemical processes at an active site in 1120 m depth on the Formosa Ridge, called Site F. Because mussels with methanotrophic symbionts acquire the isotope signature of the used methane, the average δ13C values of B. platifrons (-70.3‰; n=36) indicates a biogenic methane source at Site F, consistent with the measured carbon isotope signature of methane (-61.1‰ to -58.7‰) sampled 1.5 m above the mussel beds. The only small offset between the δ13C signatures of the ascending methane and the authigenic carbonate at site F (as low as -55.3‰) suggests only minor mixing of the pore water with marine bicarbonate, which in turn may be used as an indicator for advective rather than diffusive seepage at this site. B. aduloides has much higher average δ13C values of -34.4‰ (n=9), indicating inorganic carbon (DIC) dissolved in epibenthic bottom water as its main carbon source. The DIC was apparently marine bicarbonate with a small contribution of 13C-depleted carbon from locally oxidized methane. The δ34S values of the two mussel species indicate that they used two different sulfur sources. B. platifrons (average δ34S = +6.4±2.6‰; n=36) used seawater sulfate mixed with isotopically light re-oxidized sulfide from the sulfate-dependent anaerobic oxidation of methane (AOM), while the sulfur source of B. aduloides (δ34S = -8.0±3.1‰; n=9) was AOM-derived sulfide used by its symbionts. δ15N values differed between the mussels, with B. platifrons having a wider range of on average slightly lower values (mean = +0.5±0.7‰, n=36) than B. aduloides (mean = +1.1±0.0‰). These values are significantly lower than δ15N values of South China Sea deep-sea sediments (+5‰ to +6‰), indicating that the organic nitrogen

  11. Biogeochemical hotspots within forested landscapes: quantifying the functional role of vernal pools in ecosystem processes

    NASA Astrophysics Data System (ADS)

    Capps, K. A.; Rancatti, R.; Calhoun, A.; Hunter, M.

    2013-12-01

    Biogeochemical hotspots are characterized as small areas within a landscape matrix that show comparably high chemical reaction rates relative to surrounding areas. For small, natural features to generate biogeochemical hotspots within a landscape, their contribution to nutrient dynamics must be significant relative to nutrient demand of the surrounding landscape. In northeastern forests in the US, vernal pools are abundant, small features that typically fill in spring with snow melt and precipitation and dry by the end of the summer. Ephemeral flooding alters soil moisture and the depth of the oxic/anoxic boundary in the soil, which may affect leaf-litter decomposition rates and nutrient dynamics including denitrification. Additionally, pool-breeding organisms may influence nutrient dynamics via consumer-driven nutrient remineralization. We studied the effects of vernal pools on rates of leaf-litter decomposition and denitrification in forested habitats in Maine. Our results indicate leaf-litter decomposition and denitrification rates in submerged habitats of vernal pools were greater than in upland forest habitat. Our data also suggest pool-breeding organisms, such as wood frogs, may play an important role in nutrient dynamics within vernal pools. Together, the results suggest vernal pools may function as biogeochemical hotspots within forested landscapes.

  12. Potential effects of climate change and variability on watershed biogeochemical processes and water quality in Northeast Asia.

    PubMed

    Park, Ji-Hyung; Duan, Lei; Kim, Bomchul; Mitchell, Myron J; Shibata, Hideaki

    2010-02-01

    An overview is provided of the potential effects of climate change on the watershed biogeochemical processes and surface water quality in mountainous watersheds of Northeast (NE) Asia that provide drinking water supplies for large populations. We address major 'local' issues with the case studies conducted at three watersheds along a latitudinal gradient going from northern Japan through the central Korean Peninsula and ending in southern China. Winter snow regimes and ground snowpack dynamics play a crucial role in many ecological and biogeochemical processes in the mountainous watersheds across northern Japan. A warmer winter with less snowfall, as has been projected for northern Japan, will alter the accumulation and melting of snowpacks and affect hydro-biogeochemical processes linking soil processes to surface water quality. Soils on steep hillslopes and rich in base cations have been shown to have distinct patterns in buffering acidic inputs during snowmelt. Alteration of soil microbial processes in response to more frequent freeze-thaw cycles under thinner snowpacks may increase nutrient leaching to stream waters. The amount and intensity of summer monsoon rainfalls have been increasing in Korea over recent decades. More frequent extreme rainfall events have resulted in large watershed export of sediments and nutrients from agricultural lands on steep hillslopes converted from forests. Surface water siltation caused by terrestrial export of sediments from these steep hillslopes is emerging as a new challenge for water quality management due to detrimental effects on water quality. Climatic predictions in upcoming decades for southern China include lower precipitation with large year-to-year variations. The results from a four-year intensive study at a forested watershed in Chongquing province showed that acidity and the concentrations of sulfate and nitrate in soil and surface waters were generally lower in the years with lower precipitation, suggesting year

  13. Potential effects of climate change and variability on watershed biogeochemical processes and water quality in Northeast Asia.

    PubMed

    Park, Ji-Hyung; Duan, Lei; Kim, Bomchul; Mitchell, Myron J; Shibata, Hideaki

    2010-02-01

    An overview is provided of the potential effects of climate change on the watershed biogeochemical processes and surface water quality in mountainous watersheds of Northeast (NE) Asia that provide drinking water supplies for large populations. We address major 'local' issues with the case studies conducted at three watersheds along a latitudinal gradient going from northern Japan through the central Korean Peninsula and ending in southern China. Winter snow regimes and ground snowpack dynamics play a crucial role in many ecological and biogeochemical processes in the mountainous watersheds across northern Japan. A warmer winter with less snowfall, as has been projected for northern Japan, will alter the accumulation and melting of snowpacks and affect hydro-biogeochemical processes linking soil processes to surface water quality. Soils on steep hillslopes and rich in base cations have been shown to have distinct patterns in buffering acidic inputs during snowmelt. Alteration of soil microbial processes in response to more frequent freeze-thaw cycles under thinner snowpacks may increase nutrient leaching to stream waters. The amount and intensity of summer monsoon rainfalls have been increasing in Korea over recent decades. More frequent extreme rainfall events have resulted in large watershed export of sediments and nutrients from agricultural lands on steep hillslopes converted from forests. Surface water siltation caused by terrestrial export of sediments from these steep hillslopes is emerging as a new challenge for water quality management due to detrimental effects on water quality. Climatic predictions in upcoming decades for southern China include lower precipitation with large year-to-year variations. The results from a four-year intensive study at a forested watershed in Chongquing province showed that acidity and the concentrations of sulfate and nitrate in soil and surface waters were generally lower in the years with lower precipitation, suggesting year

  14. Afforestation alters the composition of functional genes in soil and biogeochemical processes in South American grasslands

    SciTech Connect

    Berthrong, Sean T; Schadt, Christopher Warren; Pineiro, Gervasio; Jackson, Robert B

    2009-01-01

    Soil microbes are highly diverse and control most soil biogeochemical reactions. We examined how microbial functional genes and biogeochemical pools responded to the altered chemical inputs accompanying land use change. We examined paired native grasslands and adjacent Eucalyptus plantations (previously grassland) in Uruguay, a region that lacked forests before European settlement. Along with measurements of soil carbon, nitrogen, and bacterial diversity, we analyzed functional genes using the GeoChip 2.0 microarray, which simultaneously quantified several thousand genes involved in soil carbon and nitrogen cycling. Plantations and grassland differed significantly in functional gene profiles, bacterial diversity, and biogeochemical pool sizes. Most grassland profiles were similar, but plantation profiles generally differed from those of grasslands due to differences in functional gene abundance across diverse taxa. Eucalypts decreased ammonification and N fixation functional genes by 11% and 7.9% (P < 0.01), which correlated with decreased microbial biomass N and more NH{sub 4}{sup +} in plantation soils. Chitinase abundance decreased 7.8% in plantations compared to levels in grassland (P = 0.017), and C polymer-degrading genes decreased by 1.5% overall (P < 0.05), which likely contributed to 54% (P < 0.05) more C in undecomposed extractable soil pools and 27% less microbial C (P < 0.01) in plantation soils. In general, afforestation altered the abundance of many microbial functional genes, corresponding with changes in soil biogeochemistry, in part through altered abundance of overall functional gene types rather than simply through changes in specific taxa. Such changes in microbial functional genes correspond with altered C and N storage and have implications for long-term productivity in these soils.

  15. Urban pollution of sediments: Impact on the physiology and burrowing activity of tubificid worms and consequences on biogeochemical processes.

    PubMed

    Pigneret, M; Mermillod-Blondin, F; Volatier, L; Romestaing, C; Maire, E; Adrien, J; Guillard, L; Roussel, D; Hervant, F

    2016-10-15

    In urban areas, infiltration basins are designed to manage stormwater runoff from impervious surfaces and allow the settling of associated pollutants. The sedimentary layer deposited at the surface of these structures is highly organic and multicontaminated (mainly heavy metals and hydrocarbons). Only few aquatic species are able to maintain permanent populations in such an extreme environment, including the oligochaete Limnodrilus hoffmeisteri. Nevertheless, the impact of urban pollutants on these organisms and the resulting influence on infiltration basin functioning remain poorly studied. Thus, the aim of this study was to determine how polluted sediments could impact the survival, the physiology and the bioturbation activity of L. hoffmeisteri and thereby modify biogeochemical processes occurring at the water-sediment interface. To this end, we conducted laboratory incubations of worms, in polluted sediments from infiltration basins or slightly polluted sediments from a stream. Analyses were performed to evaluate physiological state and burrowing activity (X-ray micro-tomography) of worms and their influences on biogeochemical processes (nutrient fluxes, CO2 and CH4 degassing rates) during 30-day long experiments. Our results showed that worms exhibited physiological responses to cope with high pollution levels, including a strong ability to withstand the oxidative stress linked to contamination with heavy metals. We also showed that the presence of urban pollutants significantly increased the burrowing activity of L. hoffmeisteri, demonstrating the sensitivity and the relevance of such a behavioural response as biomarker of sediment toxicity. In addition, we showed that X-ray micro-tomography was an adequate technique for accurate and non-invasive three-dimensional investigations of biogenic structures formed by bioturbators. The presence of worms induced stimulations of nutrient fluxes and organic matter recycling (between +100% and 200% of CO2 degassing rate

  16. Urban pollution of sediments: Impact on the physiology and burrowing activity of tubificid worms and consequences on biogeochemical processes.

    PubMed

    Pigneret, M; Mermillod-Blondin, F; Volatier, L; Romestaing, C; Maire, E; Adrien, J; Guillard, L; Roussel, D; Hervant, F

    2016-10-15

    In urban areas, infiltration basins are designed to manage stormwater runoff from impervious surfaces and allow the settling of associated pollutants. The sedimentary layer deposited at the surface of these structures is highly organic and multicontaminated (mainly heavy metals and hydrocarbons). Only few aquatic species are able to maintain permanent populations in such an extreme environment, including the oligochaete Limnodrilus hoffmeisteri. Nevertheless, the impact of urban pollutants on these organisms and the resulting influence on infiltration basin functioning remain poorly studied. Thus, the aim of this study was to determine how polluted sediments could impact the survival, the physiology and the bioturbation activity of L. hoffmeisteri and thereby modify biogeochemical processes occurring at the water-sediment interface. To this end, we conducted laboratory incubations of worms, in polluted sediments from infiltration basins or slightly polluted sediments from a stream. Analyses were performed to evaluate physiological state and burrowing activity (X-ray micro-tomography) of worms and their influences on biogeochemical processes (nutrient fluxes, CO2 and CH4 degassing rates) during 30-day long experiments. Our results showed that worms exhibited physiological responses to cope with high pollution levels, including a strong ability to withstand the oxidative stress linked to contamination with heavy metals. We also showed that the presence of urban pollutants significantly increased the burrowing activity of L. hoffmeisteri, demonstrating the sensitivity and the relevance of such a behavioural response as biomarker of sediment toxicity. In addition, we showed that X-ray micro-tomography was an adequate technique for accurate and non-invasive three-dimensional investigations of biogenic structures formed by bioturbators. The presence of worms induced stimulations of nutrient fluxes and organic matter recycling (between +100% and 200% of CO2 degassing rate

  17. Thousands of microbial genomes shed light on interconnected biogeochemical processes in an aquifer system

    PubMed Central

    Anantharaman, Karthik; Brown, Christopher T.; Hug, Laura A.; Sharon, Itai; Castelle, Cindy J.; Probst, Alexander J.; Thomas, Brian C.; Singh, Andrea; Wilkins, Michael J.; Karaoz, Ulas; Brodie, Eoin L.; Williams, Kenneth H.; Hubbard, Susan S.; Banfield, Jillian F.

    2016-01-01

    The subterranean world hosts up to one-fifth of all biomass, including microbial communities that drive transformations central to Earth's biogeochemical cycles. However, little is known about how complex microbial communities in such environments are structured, and how inter-organism interactions shape ecosystem function. Here we apply terabase-scale cultivation-independent metagenomics to aquifer sediments and groundwater, and reconstruct 2,540 draft-quality, near-complete and complete strain-resolved genomes that represent the majority of known bacterial phyla as well as 47 newly discovered phylum-level lineages. Metabolic analyses spanning this vast phylogenetic diversity and representing up to 36% of organisms detected in the system are used to document the distribution of pathways in coexisting organisms. Consistent with prior findings indicating metabolic handoffs in simple consortia, we find that few organisms within the community can conduct multiple sequential redox transformations. As environmental conditions change, different assemblages of organisms are selected for, altering linkages among the major biogeochemical cycles. PMID:27774985

  18. Biogeochemical processes governing exposure and uptake of organic pollutant compounds in aquatic organisms

    SciTech Connect

    Farrington, J.W. )

    1991-01-01

    This paper reviews current knowledge of biogeochemical cycles of pollutant organic chemicals in aquatic ecosystems with a focus on coastal ecosystems. There is a bias toward discussing chemical and geochemical aspects of biogeochemical cycles and an emphasis on hydrophobic organic compounds such as polynuclear aromatic hydrocarbons, polychlorinated biphenyls, and chlorinated organic compounds used as pesticides. The complexity of mixtures of pollutant organic compounds, their various modes of entering ecosystems, and their physical chemical forms are discussed. Important factors that influence bioavailability and disposition (e.g., organism-water partitioning, uptake via food, food web transfer) are reviewed. These factors included solubilities of chemicals; partitioning of chemicals between solid surfaces, colloids, and soluble phases; variables rates of sorption, desorption; and physiological status of organism. It appears that more emphasis on considering food as a source of uptake and bioaccumulation is important in benthic and epibenthic ecosystems when sediment-associated pollutants are a significant source of input to an aquatic ecosystem. Progress with mathematical models for exposure and uptake of contaminant chemicals is discussed briefly.

  19. Biogeochemical processes in the continental slope of Bay of Bengal: I. Bacterial solubilization of inorganic phosphate.

    PubMed

    Das, Surajit; Lyla, P S; Khan, S Ajmal

    2007-03-01

    Microorganisms play a vital role in the biogeochemical cycles of various marine environments, but studies on occurrence and distribution of such bacteria in the marine environment from India are meager. We studied the phosphate solubilizing property of bacteria from the deep sea sediment of Bay of Bengal, India, to understand their role in phosphorous cycle (and thereby the benthic productivity of the deep sea environment). Sediment samples were obtained from 33 stations between 10 degrees 36'N-20 degrees 01' N and 79 degrees 59' E-87 degrees 30' E along 11 transects at 3 different depths i.e. ca. 200 m, 500 m, 1000 m in each transect. Total heterotrophic bacterial (THB) counts ranged from 0.42 to 37.38 x 10(4) CFU g(-1) dry sediment weight. Of the isolates tested, 7.57% showed the phosphate solubilizing property. The phosphate solubilizing bacterial genera were Pseudomonas, Bacillus, Vibrio, Alcaligenes, Micrococcus, Corynebacterium and Flavobacterium. These strains are good solubilizers of phosphates which ultimately may play a major role in the biogeochemical cycle and the benthic productivity of the Exclusive Economic Zone (EEZ) of Bay of Bengal, because this enzyme is important for the slow, but steady regeneration of phosphate and organic carbon in the deep sea. PMID:18457109

  20. Biogeochemical processes governing exposure and uptake of organic pollutant compounds in aquatic organisms.

    PubMed Central

    Farrington, J W

    1991-01-01

    This paper reviews current knowledge of biogeochemical cycles of pollutant organic chemicals in aquatic ecosystems with a focus on coastal ecosystems. There is a bias toward discussing chemical and geochemical aspects of biogeochemical cycles and an emphasis on hydrophobic organic compounds such as polynuclear aromatic hydrocarbons, polychlorinated biphenyls, and chlorinated organic compounds used as pesticides. The complexity of mixtures of pollutant organic compounds, their various modes of entering ecosystems, and their physical chemical forms are discussed. Important factors that influence bioavailability and disposition (e.g., organism-water partitioning, uptake via food, food web transfer) are reviewed. These factors include solubilities of chemicals; partitioning of chemicals between solid surfaces, colloids, and soluble phases; variables rates of sorption, desorption; and physiological status of organism. It appears that more emphasis on considering food as a source of uptake and bioaccumulation is important in benthic and epibenthic ecosystems when sediment-associated pollutants are a significant source of input to an aquatic ecosystem. Progress with mathematical models for exposure and uptake of contaminant chemicals is discussed briefly. PMID:1904812

  1. Biogeochemical processes in the continental slope of Bay of Bengal: I. Bacterial solubilization of inorganic phosphate.

    PubMed

    Das, Surajit; Lyla, P S; Khan, S Ajmal

    2007-03-01

    Microorganisms play a vital role in the biogeochemical cycles of various marine environments, but studies on occurrence and distribution of such bacteria in the marine environment from India are meager. We studied the phosphate solubilizing property of bacteria from the deep sea sediment of Bay of Bengal, India, to understand their role in phosphorous cycle (and thereby the benthic productivity of the deep sea environment). Sediment samples were obtained from 33 stations between 10 degrees 36'N-20 degrees 01' N and 79 degrees 59' E-87 degrees 30' E along 11 transects at 3 different depths i.e. ca. 200 m, 500 m, 1000 m in each transect. Total heterotrophic bacterial (THB) counts ranged from 0.42 to 37.38 x 10(4) CFU g(-1) dry sediment weight. Of the isolates tested, 7.57% showed the phosphate solubilizing property. The phosphate solubilizing bacterial genera were Pseudomonas, Bacillus, Vibrio, Alcaligenes, Micrococcus, Corynebacterium and Flavobacterium. These strains are good solubilizers of phosphates which ultimately may play a major role in the biogeochemical cycle and the benthic productivity of the Exclusive Economic Zone (EEZ) of Bay of Bengal, because this enzyme is important for the slow, but steady regeneration of phosphate and organic carbon in the deep sea.

  2. Relationship Between Storm Hydrograph Components and Subsurface Flow Processes in a Hilly Headwater Basin, Toyota, Japan

    NASA Astrophysics Data System (ADS)

    Tsujimura, M.; Asai, K.; Takei, R.

    2001-05-01

    Temporal and spatial distribution of tracer elements and subsurface flow processes were investigated to study relationship between storm hydrograph components and behavior of subsurface water in a headwater catchment of Toyota Hill, Aichi prefecture, central Japan. The catchment has an area of 0.857 ha with an altitude of 60 to 100 m, and is underlain by granite. The soil depth revealed by sounding test ranges from 0.5 to 4.0 m. Rain, stream, soil and ground waters were sampled once in a week, and the stream water was sampled at 5 to 60 minute intervals during rainstorms. The pressure head of subsurface water was monitored using tensiometers and piezometers nests, and the stream flow was monitored using V-notch weir. The stable isotopic ratios of deuterium and oxygen 18 and inorganic ion concentrations were determined on all water samples. The oxygen 18 isotopic ratio in stream water decreased with rainfall during the rainstorms. The ratio of event water component to the total runoff water at the peak discharge ranged from 16 to 92 %, and the event water ratio correlated with the peak discharge rate and rainfall intensity. The tesiometric data showed that the shallow subsurface water with low isotopic ratios at the lower slope discharged directly to the stream during the heavy rainstorms. The shallow subsurface flow at the lower slope and overland flow on the raiparian zone contributed much to the stream water chemistry during heavy rainstorms.

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

    USGS Publications Warehouse

    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

  4. 3D Seismic Experimentation and Advanced Processing/Inversion Development for Investigations of the Shallow Subsurface

    SciTech Connect

    Levander, Alan Richard; Zelt, Colin A.

    2015-03-17

    The work plan for this project was to develop and apply advanced seismic reflection and wide-angle processing and inversion techniques to high resolution seismic data for the shallow subsurface to seismically characterize the shallow subsurface at hazardous waste sites as an aid to containment and cleanup activities. We proposed to continue work on seismic data that we had already acquired under a previous DoE grant, as well as to acquire additional new datasets for analysis. The project successfully developed and/or implemented the use of 3D reflection seismology algorithms, waveform tomography and finite-frequency tomography using compressional and shear waves for high resolution characterization of the shallow subsurface at two waste sites. These two sites have markedly different near-surface structures, groundwater flow patterns, and hazardous waste problems. This is documented in the list of refereed documents, conference proceedings, and Rice graduate theses, listed below.

  5. 3-D Seismic Experimentation and Advanced Processing/Inversion Development for Investigations of the Shallow Subsurface

    SciTech Connect

    Levander, Alan R.

    2004-12-01

    Under ER63662, 3-D Seismic Experimentation and Advanced Processing/Inversion Development for Investigations of the Shallow Subsurface, we have completed a number of subprojects associated with the Hill Air Force Base (HAFB) high resolution 3-D reflection/tomography dataset.

  6. Hydro-biogeochemical Controls on Geophysical Signatures (Invited)

    NASA Astrophysics Data System (ADS)

    Atekwana, E. A.

    2013-12-01

    Geophysical techniques such as seismic, magnetic and electrical techniques have historically played a major role in oil exploration. Their main use has been for delineation basin geometry, structures and hydrocarbon traps and for understanding the subsurface stratigraphy. Their use for investigating microbial processes has only recently been recognized over the last decade resulting in the development of biogeophysics as a frontier research area which bridges the fields of environmental microbiology, biogeochemistry, geomicrobiology. Recent biogeophysical studies have demonstrated the potential of geophysical technologies to (1) probe the presence of microbial cells and biofilms in subsurface geologic media, (2) investigate the interactions between microorganisms and subsurface geologic media, (3) assess biogeochemical transformations, biomineralization, and biogeochemical reaction rates, and (4) investigate the alteration of physical properties of subsurface geologic media induced by microorganisms. The unique properties of geophysical datasets (e.g. non-invasive data acquisition, spatially continuous properties retrieved) make them attractive for probing microbial processes affecting fate and transport of contaminants. This presentation will provide an updated understanding of major controls on geophysical signatures by highlighting some of the important advancements in biogeophysical studies at hydrocarbon contaminated environments. Important challenges that provide an opportunity for further research in this new field will also be examined.

  7. Riverine skin temperature response to subsurface processes in low wind speeds

    NASA Astrophysics Data System (ADS)

    Brumer, Sophia E.; Zappa, Christopher J.; Anderson, Steven P.; Dugan, John P.

    2016-03-01

    Both surface and subsurface processes modulate the surface thermal skin and as such the skin temperature may serve as an indicator for coastal, estuarine, and alluvial processes. Infrared (IR) imagery offers the unique tool to survey such systems, allowing not only to assess temperature variability of the thermal boundary layer, but also to derive surface flow fields through digital particle image velocimetry, optical flow techniques, or spectral methods. In this study, IR time-series imagery taken from a boat moored in the Hudson River estuary is used to determine surface flow, turbulent kinetic energy dissipation rate, and characteristic temperature and velocity length scales. These are linked to subsurface measurements provided by in situ instruments. Under the low wind conditions and weak stratification, surface currents and dissipation rate are found to reflect subsurface mean flow (r2 = 0.89) and turbulence (r2 = 0.75). For relatively low dissipation rates, better correlations are obtained by computing dissipation rates directly from wavenumber spectra rather than when having to assume the validity of the Taylor hypothesis. Furthermore, the subsurface dissipation rate scales with the surface length scales (L) and mean flow (U) using ɛ ∝ U3/L (r2 = 0.9). The surface length scale derived from the thermal fields is found to have a strong linear relationship (r2 = 0.88) to water depth (D) with (D/L) ˜ 13. Such a relation may prove useful for remote bathymetric surveys when no waves are present.

  8. Improvement of subsurface process in land surface modeling including lateral flow under unsaturated zone

    NASA Astrophysics Data System (ADS)

    Kim, J.; Mohanty, B.

    2013-12-01

    Lateral subsurface flow is an important component in local water budgets through its direct impact on soil moisture. However, most of the land surface models are one-dimensional considering only vertical interactions and neglecting the horizontal flow of water at the grid or sub-grid scales. Subsurface flow can be affected by surface topography and non-homogenous soil properties controlling the lateral flow of water. In this study, we improved the subsurface flow process in land surface model (Community Land Model, CLM) by considering the lateral flow based on topography and heterogeneous soil hydraulic properties in unsaturated zone. The changes in flow direction derived from topographic factor are used to consider the lateral movement of water at the near surface. Furthermore, vertical and horizontal hydraulic conductivities for each layer in unsaturated zone are estimated using different averaging methods and anisotropic factors. Based on the hydraulic conductivities of each layer for heterogeneous soil profiles we considered lateral flow of soil water between soil columns. These approaches were tested at several different sites (e.g. field and watershed scales). The results showed the appropriate vertical and horizontal hydraulic conductivities with depth for each site and the improved subsurface flow process by considering the lateral flow in land surface models.

  9. Interim report: Manipulation of natural subsurface processes: Field research and validation.

    SciTech Connect

    Fruchter, J.S.; Spane, F.A.; Amonette, J.E.

    1994-11-01

    Often the only alternative for treating deep subsurface contamination is in situ manipulation of natural processes to change the mobility or form of contaminants. However, the complex interactions of natural subsurface physical, chemical, and microbial processes limit the predictability of the system-wide impact of manipulation based on current knowledge. This report is a summary of research conducted to examine the feasibility of controlling the oxidation-reduction (redox) potential of the unconfined aquifer at the Hanford Site in southeastern Washington State by introducing chemical reagents and microbial nutrients. The experiment would allow the testing of concepts and hypotheses developed from fundamental research in the US Department of Energy`s (DOE`s) Subsurface Science Program. Furthermore, the achievement of such control is expected to have implications for in situ remediation of dispersed aqueous contaminants in the subsurface environment at DOE sites nationwide, and particularly at the Hanford Site. This interim report summarizes initial research that was conducted between July 1990 and October 1991.

  10. Treatment of oil and grease in produced water by a pilot-scale constructed wetland system using biogeochemical processes.

    PubMed

    Pardue, Michael J; Castle, James W; Rodgers, John H; Huddleston, George M

    2014-05-01

    Constructed wetland treatment systems (CWTSs) can effectively remove many constituents that limit beneficial use of oilfield produced water. The objectives of this investigation were: (1) to assess the effect of mass loadings of oil and grease (O & G) on treatment performance in pilot-scale subsurface flow and free water surface CWTS series having sequential reducing and oxidizing cells, and (2) to evaluate effects on treatment performance of adding a pilot-scale oil-water separator. Increase in O & G mass loading from 5 to 20 mg min(-1) caused decreases in both dissolved oxygen concentration and sediment redox potential, which affected treatment performance. Biogeochemical pathways for removal of O & G, iron, and manganese operate under oxidizing conditions, and removal rate coefficients for these constituents decreased (0.905-0.514 d(-1) for O & G, 0.773-0.452 d(-1) for iron, and 0.970-0.518 d(-1) for manganese) because greater mass loading of O & G promoted reducing conditions. With increased mass loading, removal rate coefficients for nickel and zinc increased from 0.074 to 0.565 d(-1) and from 0.196 to 1.08 d(-1), respectively. Although the sequential reducing and oxidizing cells in the CWTS were very effective in treating the targeted constituents, an oil-water separator was added prior to wetland cells to enhance O & G removal at high inflow concentration (100 mg L(-1)). The oil-water separator removed approximately 50% of the O & G, and removal extents and efficiencies approximated those observed at 50 mg L(-1) inflow concentration during treatment without an oil-water separator.

  11. Influence of cutting parameters on the depth of subsurface deformed layer in nano-cutting process of single crystal copper.

    PubMed

    Wang, Quanlong; Bai, Qingshun; Chen, Jiaxuan; Su, Hao; Wang, Zhiguo; Xie, Wenkun

    2015-12-01

    Large-scale molecular dynamics simulation is performed to study the nano-cutting process of single crystal copper realized by single-point diamond cutting tool in this paper. The centro-symmetry parameter is adopted to characterize the subsurface deformed layers and the distribution and evolution of the subsurface defect structures. Three-dimensional visualization and measurement technology are used to measure the depth of the subsurface deformed layers. The influence of cutting speed, cutting depth, cutting direction, and crystallographic orientation on the depth of subsurface deformed layers is systematically investigated. The results show that a lot of defect structures are formed in the subsurface of workpiece during nano-cutting process, for instance, stair-rod dislocations, stacking fault tetrahedron, atomic clusters, vacancy defects, point defects. In the process of nano-cutting, the depth of subsurface deformed layers increases with the cutting distance at the beginning, then decreases at stable cutting process, and basically remains unchanged when the cutting distance reaches up to 24 nm. The depth of subsurface deformed layers decreases with the increase in cutting speed between 50 and 300 m/s. The depth of subsurface deformed layer increases with cutting depth, proportionally, and basically remains unchanged when the cutting depth reaches over 6 nm.

  12. Autonomous Studies of Coupled Physical-Biogeochemical Processes- Lessons from NAB08 and Prospects for the Future

    NASA Astrophysics Data System (ADS)

    Lee, Craig; D'Asaro, Eric; Perry, Mary Jane

    2013-04-01

    Motivated by the increasing application of autonomous sensors to physical, biological and biogeochemical investigations at the submesoscale, we examine techniques developed during the 2008 North Atlantic Bloom Experiment (NAB08), review successes, failures, and lessons learned, and offer perspectives on how these approaches might evolve in response to near-term shifts in scientific goals and technological advances. NAB08 exploited the persistence of autonomous platforms coupled with the extensive capabilities of a ship-based sampling program to investigate the patch-scale physics, biogeochemistry and community dynamics of a spring phytoplankton bloom. Autonomous platforms (Seagliders following a heavily-instrumented Lagrangian float) collected measurements in a quasi-Lagrangian frame, beginning before bloom initiation and extending well past its demise. This system of autonomous instruments resolved variability at the patch scale while also providing the persistence needed to follow bloom evolution. Biological and biogeochemical measurements were conducted from R/V Knorr during the bloom. An aggressive protocol for sensor calibration and proxy building bridged the ship-based and autonomous efforts, leveraging the intensive but sparse ship-based measurements onto the much more numerous autonomous observations. The combination of sampling in the patch-following frame, persistent, autonomous surveys and focused, aggressive calibration and proxy building produced robust, quantitative estimates of physical and biogeochemical processes. For example, budgets of nitrate, dissolved oxygen and particulate organic carbon (POC) following the patch were used to estimate net community production (NCP) and apparent POC export. Net community production was 805 mmol C?m-2 during the main bloom, with apparent POC export of 564 mmol C?m-2 and 282 mmol C?m-2 lost due to net respiration (70%) and apparent export (30%) on the day following bloom termination. Thus, POC export of roughly

  13. Subsurface Biogeochemical Heterogeneity (Field-scale removal of U(VI) from groundwater in an alluvial aquifer by electron donor amendment)

    SciTech Connect

    Long, Philip E.; Lovley, Derek R.; N'Guessan, A. L.; Nevin, Kelly; Resch, C. T.; Arntzen, Evan; Druhan, Jenny; Peacock, Aaron; Baldwin, Brett; Dayvault, Dick; Holmes, Dawn; Williams, Ken; Hubbard, Susan; Yabusaki, Steve; Fang, Yilin; White, D. C.; Komlos, John; Jaffe, Peter

    2006-06-01

    Determine if biostimulation of alluvial aquifers by electron donor amendment can effectively remove U(VI) from groundwater at the field scale. Uranium contamination in groundwater is a significant problem at several DOE sites. In this project, the possibility of accelerating bioreduction of U(VI) to U(IV) as a means of decreasing U(VI) concentrations in groundwater is directly addressed by conducting a series of field-scale experiments. Scientific goals include demonstrating the quantitative linkage between microbial activity and U loss from groundwater and relating the dominant terminal electron accepting processes to the rate of U loss. The project is currently focused on understanding the mechanisms for unexpected long-term ({approx}2 years) removal of U after stopping electron donor amendment. Results obtained in the project successfully position DOE and others to apply biostimulation broadly to U contamination in alluvial aquifers.

  14. Regional scale hydrological and biogeochemical processes controlling high biodiversity of a groundwater fed alkaline fen

    NASA Astrophysics Data System (ADS)

    van der Zee, Sjoerd E. A. T. M.; (D. G.) Cirkel, Gijsbert; (J. P. M) witte, Flip

    2014-05-01

    The high floral biodiversity of groundwater fed fens and mesotrophic grasslands depends on the different chemical signatures of the shallow rainwater fed topsoil water and the slightly deeper geochemically affected groundwater. The relatively abrupt gradients between these two layers of groundwater enable the close proximity of plants that require quite different site factors and have different rooting depths. However, sulphur inflow into such botanically interesting areas is generally perceived as a major threat to biodiversity. Although in Europe atmospheric deposition of sulphur has decreased considerably over the last decades, groundwater pollution by sulphate may still continue due to pyrite oxidation in soil as a result of excessive fertilisation. Inflowing groundwater rich in sulphate can change biogeochemical cycling in nutrient-poor wetland ecosystems because of 'so called' internal eutrophication as well as the accumulation of dissolved sulphide, which is phytotoxic. Complementary to conventions, we propose that upwelling sulphate rich groundwater may, in fact, promote the conservation of rare and threatened alkaline fens: excessive fertilisation and pyrite oxidation also produces acidity, which invokes calcite dissolution, and increased alkalinity and hardness of the inflowing groundwater. For a very species-rich wetland nature reserve, we show that sulphate is reduced and effectively precipitated as iron sulphides, when this calcareous and sulphate rich groundwater flows upward through the organic soil of the investigated nature reserve. Also, we show that sulphate reduction occurs simultaneously with an increase in alkalinity production, which in our case results in active calcite precipitation in the soil. In spite of the occurring sulphate reduction, we found no evidence for internal eutrophication. Extremely low phosphorous concentration in the pore water could be attributed to a high C:P ratio of soil organic matter and co-precipitation with

  15. Biogeochemical and hydrologic processes controlling mercury cycling in Great Salt Lake, Utah

    NASA Astrophysics Data System (ADS)

    Naftz, D.; Kenney, T.; Angeroth, C.; Waddell, B.; Darnall, N.; Perschon, C.; Johnson, W. P.

    2006-12-01

    Great Salt Lake (GSL), in the Western United States, is a terminal lake with a highly variable surface area that can exceed 5,100 km2. The open water and adjacent wetlands of the GSL ecosystem support millions of migratory waterfowl and shorebirds from throughout the Western Hemisphere, as well as a brine shrimp industry with annual revenues exceeding 70 million dollars. Despite the ecologic and economic significance of GSL, little is known about the biogeochemical cycling of mercury (Hg) and no water-quality standards currently exist for this system. Whole water samples collected since 2000 were determined to contain elevated concentrations of total Hg (100 ng/L) and methyl Hg (33 ng/L). The elevated levels of methyl Hg are likely the result of high rates of SO4 reduction and associated Hg methylation in persistently anoxic areas of the lake at depths greater than 6.5 m below the water surface. Hydroacoustic equipment deployed in this anoxic layer indicates a "conveyor belt" flow system that can distribute methyl Hg in a predominantly southerly direction throughout the southern half of GSL (fig. 1, URL: http://users.o2wire.com/dnaftz/Dave/AGU-abs-figs- AUG06.pdf). Periodic and sustained wind events on GSL may result in transport of the methyl Hg-rich anoxic water and bottom sediments into the oxic and biologically active regions. Sediment traps positioned above the anoxic brine interface have captured up to 6 mm of bottom sediment during cumulative wind-driven resuspension events (fig. 2, URL:http://users.o2wire.com/dnaftz/Dave/AGU-abs-figs-AUG06.pdf). Vertical velocity data collected with hydroacoustic equipment indicates upward flow > 1.5 cm/sec during transient wind events (fig. 3, URL:http://users.o2wire.com/dnaftz/Dave/AGU-abs-figs-AUG06.pdf). Transport of methyl Hg into the oxic regions of GSL is supported by biota samples. The median Hg concentration (wet weight) in brine shrimp increased seasonally from the spring to fall time period and is likely a

  16. Characterization and monitoring of subsurface processes using parallel computing and electrical resistivity imaging

    SciTech Connect

    Johnson, Timothy C.; Truex, Michael J.; Wellman, Dawn M.; Marble, Justin

    2011-12-01

    This newsletter discusses recent advancement in subsurface resistivity characterization and monitoring capabilities. The BC Cribs field desiccation treatability test resistivity monitoring data is use an example to demonstrate near-real time 3D subsurface imaging capabilities. Electrical resistivity tomography (ERT) is a method of imaging the electrical resistivity distribution of the subsurface. An ERT data collection system consists of an array of electrodes, deployed on the ground surface or within boreholes, that are connected to a control unit which can access each electrode independently (Figure 1). A single measurement is collected by injecting current across a pair of current injection electrodes (source and sink), and measuring the resulting potential generated across a pair of potential measurement electrodes (positive and negative). An ERT data set is generated by collecting many such measurements using strategically selected current and potential electrode pairs. This data set is then processed using an inversion algorithm, which reconstructs an estimate (or image) of the electrical conductivity (i.e. the inverse of resistivity) distribution that gave rise to the measured data.

  17. Dissimilatory Iron Reduction by Microorganisms Under Hot Deep Subsurface Conditions

    NASA Astrophysics Data System (ADS)

    Ruper, S.; Sharma, A.; Scott, J. H.

    2010-04-01

    In subsurface environments the availability of terminal electron acceptors will be the major biogeochemical constraint, before temperature or pressure begin plays a role. Data is presented to show the impact of deep hot subsurface conditions on dissimilatory iron reduction.

  18. Progress Towards Coupled Simulation of Surface/Subsurface Hydrologic Processes and Terrestrial Ecosystem Dynamics Using the Community Models PFLOTRAN and CLM

    NASA Astrophysics Data System (ADS)

    Mills, R. T.; Bisht, G.; Karra, S.; Hoffman, F. M.; Hammond, G. E.; Kumar, J.; Painter, S.; Thornton, P. E.; Lichtner, P. C.

    2012-12-01

    in how the governing equations are solved, and we will compare different surface flow formulations as well as coupling strategies between the surface and subsurface domains. Additionally, for studies of hydrology in Arctic regions, we have added a three-phase ice model. We will present some demonstrations of this capability and discuss solver strategies for handling the strong nonlinearities that arise. To provide a unified treatment of the unsaturated and saturated zones and to enable lateral redistribution of soil moisture (and eventually surface water, heat, and nutrients) in regional climate models, we have developed an approach for coupling PFLOTRAN with CLM. CLM is the global land model component used within the Community Earth System Model (CESM) to simulate an extensive set of biogeophysical and biogeochemical processes occurring at or near the terrestrial surface. We will describe our approach for replacing the existing CLM hydrology using PFLOTRAN and present some preliminary simulations undertaken with the CLM-PFLOTRAN coupled model.

  19. Are Changes in Biogeochemical or Hydrologic Processes Responsible for Increasing DOC Concentrations in Headwater Streams of Northeastern North America?

    NASA Astrophysics Data System (ADS)

    Burns, D. A.; Murdoch, P. S.

    2005-12-01

    The recent recognition of widespread and significant upward trends in dissolved organic carbon (DOC) concentrations in surface waters of northeastern North America and Europe has stimulated research to understand the cause of these trends. Several factors have been offered to explain these DOC trends including climate warming, chronic atmospheric nitrogen deposition, decreasing atmospheric sulfur deposition, and increasing surface water pH. Changes in these factors have acted to either increase the solubility of DOC or increase the rates of biogeochemical processes that generate labile carbon in the soil. Additionally, it is well known that rain events and snowmelt increase DOC concentrations in many surface waters through flushing along shallow flow paths where most labile carbon is stored. Changes in hydrologic flushing rates have generally not been explored as a possible explanation of these widely reported upward trends in DOC concentrations. Biscuit Brook, a 9.9 km2 catchment in the Catskill Mountains of New York has shown a significant increasing trend in DOC concentrations since 1992, consistent with other streams in this region. Stream chemistry has been monitored at Biscuit Brook on a weekly basis supplemented with event samples since 1983, providing a detailed data set with which to examine the causes of changes in DOC concentrations. Here, we examine the relative roles of climate warming, decreasing sulfate (SO42-) and nitrate (NO3-) concentrations, and changes in the frequency and size of hydrologic events on the long-term temporal pattern (1992 to 2004) of DOC concentrations in Biscuit Brook. DOC concentrations increased significantly in weekly samples collected primarily during low flow conditions. No similar trend was apparent in the high flow samples. Mean annual SO42- plus NO3- concentrations showed a strong inverse relation (r2 = 0.91, p < 0.01) to DOC concentrations, but these concentrations were not related to stream pH nor to air temperature

  20. Non-conservative behaviors of chromophoric dissolved organic matter in a turbid estuary: Roles of multiple biogeochemical processes

    NASA Astrophysics Data System (ADS)

    Yang, Liyang; Guo, Weidong; Hong, Huasheng; Wang, Guizhi

    2013-11-01

    Chromophoric dissolved organic matter (CDOM) may show notable non-conservative behaviors in many estuaries due to a variety of biogeochemical processes. The partition between CDOM and chromophoric particulate organic matter (CPOM) was examined in the Jiulong Estuary (China) using absorption and fluorescence spectroscopy, which was also compared with microbial and photochemical degradations. The absorption coefficient of water-soluble CPOM (aCPOM(280)) at ambient Milli-Q water pH (6.1) ranged from 0.11 to 7.94 m-1 in the estuary and was equivalent to 5-101% of CDOM absorption coefficient. The aCPOM(280) correlated significantly with the concentration of suspended particulate matter and was highest in the bottom water of turbidity maximum zone. Absorption spectral slope (S275-295) and slope ratio (SR) correlated positively with salinity for both CPOM and CDOM, suggesting decreases in the average molecular weight with increasing salinity. The adsorption of CDOM to re-suspended sediments (at 500 mg L-1) within 2 h was equivalent to 4-26% of the initial aCDOM(280). The adsorption of CDOM to particles was less selective with respect to various CDOM constituents, while the microbial degradation resulted decreases in S275-295 and SR of CDOM and preferential removal of protein-like components. The partition between CPOM and CDOM represented a rapid and important process for the non-conservative behavior of CDOM in turbid estuaries.

  1. [Neutrophilic lithotrophic iron-oxidizing prokaryotes and their role in the biogeochemical processes of the iron cycle].

    PubMed

    Dubinina, G A; Sorokina, A Iu

    2014-01-01

    Biology of lithotrophic neutrophilic iron-oxidizing prokaryotes and their role in the processes of the biogeochemical cycle of iron are discussed. This group of microorganisms is phylogenetically, taxonomically, and physiologically heterogeneous, comprising three metabolically different groups: aerobes, nitrate-dependent anaerobes, and phototrophs; the latter two groups have been revealed relatively recently. Their taxonomy and metabolism are described. Materials on the structure and functioning of the electron transport chain in the course of Fe(II) oxidation by members of various physiological groups are discussed. Occurrence of iron oxidizers in freshwater and marine ecosystems, thermal springs, areas of hydrothermal activity, and underwater volcanic areas are considered. Molecular genetic techniques were used to determine the structure of iron-oxidizing microbial communities in various natural ecosystems. Analysis of stable isotope fractioning of 56/54Fe in pure cultures and model experiments revealed predominance of biological oxidation over abiotic ones in shallow aquatic habitats and mineral springs, which was especially pronounced under microaerobic conditions at the redox zone boundary. Discovery of anaerobic bacterial Fe(II) oxidation resulted in development of new hypotheses concerning the possible role of microorganisms and the mechanisms of formation of the major iron ore deposits in Precambrian and early Proterozoic epoch. Paleobiological data are presented on the microfossils and specific biomarkers retrieved from ancient ore samples and confirming involvement of anaerobic biogenic processes in their formation.

  2. [Neutrophilic lithotrophic iron-oxidizing prokaryotes and their role in the biogeochemical processes of the iron cycle].

    PubMed

    2014-01-01

    Biology of lithotrophic neutrophilic iron-oxidizing prokaryotes and their role in the processes of the biogeochemical cycle of iron are discussed. This group of microorganisms is phylogenetically, taxonomically, and physiologically heterogeneous, comprising three metabolically different groups: aerobes, nitrate-dependent anaerobes, and phototrophs; the latter two groups have been revealed relatively recently. Their taxonomy and metabolism are described. Materials on the structure and functioning of the electron transport chain in the course of Fe(II) oxidation by members of various physiological groups are discussed. Occurrence of iron oxidizers in freshwater and marine ecosystems, thermal springs, areas of hydrothermal activity, and underwater volcanic areas are considered. Molecular genetic techniques were used to determine the structure of iron-oxidizing microbial communities in various natural ecosystems. Analysis of stable isotope fractioning of 56/54Fe in pure cultures and model experiments revealed predominance of biological oxidation over abiotic ones in shallow aquatic habitats and mineral springs, which was especially pronounced under microaerobic conditions at the redox zone boundary. Discovery of anaerobic bacterial Fe(II) oxidation resulted in development of new hypotheses concerning the possible role of microorganisms and the mechanisms of formation of the major iron ore deposits in Precambrian and early Proterozoic epoch. Paleobiological data are presented on the microfossils and specific biomarkers retrieved from ancient ore samples and confirming involvement of anaerobic biogenic processes in their formation. PMID:25507440

  3. [Neutrophilic lithotrophic iron-oxidizing prokaryotes and their role in the biogeochemical processes of the iron cycle].

    PubMed

    Dubinina, G A; Sorokina, A Iu

    2014-01-01

    Biology of lithotrophic neutrophilic iron-oxidizing prokaryotes and their role in the processes of the biogeochemical cycle of iron are discussed. This group of microorganisms is phylogenetically, taxonomically, and physiologically heterogeneous, comprising three metabolically different groups: aerobes, nitrate-dependent anaerobes, and phototrophs; the latter two groups have been revealed relatively recently. Their taxonomy and metabolism are described. Materials on the structure and functioning of the electron transport chain in the course of Fe(II) oxidation by members of various physiological groups are discussed. Occurrence of iron oxidizers in freshwater and marine ecosystems, thermal springs, areas of hydrothermal activity, and underwater volcanic areas are considered. Molecular genetic techniques were used to determine the structure of iron-oxidizing microbial communities in various natural ecosystems. Analysis of stable isotope fractioning of 56/54Fe in pure cultures and model experiments revealed predominance of biological oxidation over abiotic ones in shallow aquatic habitats and mineral springs, which was especially pronounced under microaerobic conditions at the redox zone boundary. Discovery of anaerobic bacterial Fe(II) oxidation resulted in development of new hypotheses concerning the possible role of microorganisms and the mechanisms of formation of the major iron ore deposits in Precambrian and early Proterozoic epoch. Paleobiological data are presented on the microfossils and specific biomarkers retrieved from ancient ore samples and confirming involvement of anaerobic biogenic processes in their formation. PMID:25423717

  4. Designing and interpreting laboratory experiments for hydrodynamical, biogeochemical, and ecological processes in rivers (Invited)

    NASA Astrophysics Data System (ADS)

    Packman, A. I.

    2009-12-01

    In this talk, I will articulate a general philosophy for the design of laboratory experiments for fluvial processes; discuss important concepts of scaling, scale limitation, and process coupling that should be considered in designing experiments and interpreting experimental results; and provide concrete examples of how this approach can be used to probe river mechanics, sedimentary biogeochemistry, benthic/hyporheic ecology, and downstream migration of reactive solutes and particles. It is challenging to design laboratory experiments to probe fluvial processes because river systems show extremely strong interactions over a wide range of spatial and temporal scales. Biological and ecological processes are especially difficult to study in the laboratory because they are influenced by a wide range of system conditions, and we do not currently have a strong theoretical basis to quantitatively generalize experimental observations. Further, many seemingly basic and invariant chemical and biological properties - such as sorption coefficients, reaction rate constants, respiration rates, and nutrient uptake rates - change over space and time in fluvial systems because these environments are highly dynamic over a wide range of temporal scales, show strong longitudinal connectivity, and have strong heterogeneity in the surrounding and underlying sediments. Laboratory studies can be used to systematically investigate these effects, thereby providing considerable insight into generally important controlling mechanisms, with the caveat that larger-scale drivers and process interactions must be considered when translating the results to the field. Laboratory experiments can best be targeted to discriminate alternate hypotheses regarding important governing processes, and to independently test the effects of each important variable. Once this information is obtained, it should be codified in the form of quantitative, theoretical relationships that can be subsequently evaluated in

  5. Integrated Biogeochemical and Hydrologic Processes Driving Arsenic Release from Shallow Sediments to Groundwaters of the Mekong Delta

    SciTech Connect

    Kocar, Benjamin D.; Polizzotto, Matthew L.; Benner, Shawn G.; Ying, Samantha C.; Ung, Mengieng; Ouch, Kagna; Samreth, Sopheap; Suy, Bunseang; Phan, Kongkea; Sampson, Michael; Fendorf, Scott

    2008-11-01

    Arsenic is contaminating the groundwater of Holocene aquifers throughout South and Southeast Asia. To examine the biogeochemical and hydrological processes influencing dissolved concentrations and transport of As within soils/sediments in the Mekong River delta, a ~50 km₂ field site was established near Phnom Penh, Cambodia, where aqueous As concentrations are dangerously high and where groundwater retrieval for irrigation is minimal. Dissolved As concentrations vary spatially, ranging up to 1300 µg/L in aquifer groundwater and up to 600 µg/L in surficial clay pore water. Groundwaters with high As concentrations are reducing with negligible dissolved O₂ and high concentrations of Fe(II), NH⁺₄ , and dissolved organic C. Within near-surface environments, these conditions are most pronounced in sediments underlying permanent wetlands, often found within oxbow channels near the Mekong River. There, labile C, co-deposited with As-bearing Fe (hydr)oxides under reducing conditions, drives the reductive mobilization (inclusive of Fe and As reduction) of As. Here, conditions are described under which As is mobilized from these sediments, and near-surface As release is linked to aquifer contamination over long time periods (100s to 1000s of years). Site biogeochemistry is coupled with extensive hydrologic measurements, and, accordingly, a comprehensive interpretation of spatial As release and transport within a calibrated hydraulic flow-field is provided of an As-contaminated aquifer that is representative of those found throughout South and Southeast Asia.

  6. Hydrogen Utilization Potential in Subsurface Sediments.

    PubMed

    Adhikari, Rishi R; Glombitza, Clemens; Nickel, Julia C; Anderson, Chloe H; Dunlea, Ann G; Spivack, Arthur J; Murray, Richard W; D'Hondt, Steven; Kallmeyer, Jens

    2016-01-01

    Subsurface microbial communities undertake many terminal electron-accepting processes, often simultaneously. Using a tritium-based assay, we measured the potential hydrogen oxidation catalyzed by hydrogenase enzymes in several subsurface sedimentary environments (Lake Van, Barents Sea, Equatorial Pacific, and Gulf of Mexico) with different predominant electron-acceptors. Hydrogenases constitute a diverse family of enzymes expressed by microorganisms that utilize molecular hydrogen as a metabolic substrate, product, or intermediate. The assay reveals the potential for utilizing molecular hydrogen and allows qualitative detection of microbial activity irrespective of the predominant electron-accepting process. Because the method only requires samples frozen immediately after recovery, the assay can be used for identifying microbial activity in subsurface ecosystems without the need to preserve live material. We measured potential hydrogen oxidation rates in all samples from multiple depths at several sites that collectively span a wide range of environmental conditions and biogeochemical zones. Potential activity normalized to total cell abundance ranges over five orders of magnitude and varies, dependent upon the predominant terminal electron acceptor. Lowest per-cell potential rates characterize the zone of nitrate reduction and highest per-cell potential rates occur in the methanogenic zone. Possible reasons for this relationship to predominant electron acceptor include (i) increasing importance of fermentation in successively deeper biogeochemical zones and (ii) adaptation of H2ases to successively higher concentrations of H2 in successively deeper zones. PMID:26858697

  7. Hydrogen Utilization Potential in Subsurface Sediments

    PubMed Central

    Adhikari, Rishi R.; Glombitza, Clemens; Nickel, Julia C.; Anderson, Chloe H.; Dunlea, Ann G.; Spivack, Arthur J.; Murray, Richard W.; D'Hondt, Steven; Kallmeyer, Jens

    2016-01-01

    Subsurface microbial communities undertake many terminal electron-accepting processes, often simultaneously. Using a tritium-based assay, we measured the potential hydrogen oxidation catalyzed by hydrogenase enzymes in several subsurface sedimentary environments (Lake Van, Barents Sea, Equatorial Pacific, and Gulf of Mexico) with different predominant electron-acceptors. Hydrogenases constitute a diverse family of enzymes expressed by microorganisms that utilize molecular hydrogen as a metabolic substrate, product, or intermediate. The assay reveals the potential for utilizing molecular hydrogen and allows qualitative detection of microbial activity irrespective of the predominant electron-accepting process. Because the method only requires samples frozen immediately after recovery, the assay can be used for identifying microbial activity in subsurface ecosystems without the need to preserve live material. We measured potential hydrogen oxidation rates in all samples from multiple depths at several sites that collectively span a wide range of environmental conditions and biogeochemical zones. Potential activity normalized to total cell abundance ranges over five orders of magnitude and varies, dependent upon the predominant terminal electron acceptor. Lowest per-cell potential rates characterize the zone of nitrate reduction and highest per-cell potential rates occur in the methanogenic zone. Possible reasons for this relationship to predominant electron acceptor include (i) increasing importance of fermentation in successively deeper biogeochemical zones and (ii) adaptation of H2ases to successively higher concentrations of H2 in successively deeper zones. PMID:26858697

  8. Potential for real-time understanding of coupled hydrologic and biogeochemical processes in stream ecosystems: Future integration of telemetered data with process models for glacial meltwater streams

    NASA Astrophysics Data System (ADS)

    McKnight, Diane M.; Cozzetto, Karen; Cullis, James D. S.; Gooseff, Michael N.; Jaros, Christopher; Koch, Joshua C.; Lyons, W. Berry; Neupauer, Roseanna; Wlostowski, Adam

    2015-08-01

    While continuous monitoring of streamflow and temperature has been common for some time, there is great potential to expand continuous monitoring to include water quality parameters such as nutrients, turbidity, oxygen, and dissolved organic material. In many systems, distinguishing between watershed and stream ecosystem controls can be challenging. The usefulness of such monitoring can be enhanced by the application of quantitative models to interpret observed patterns in real time. Examples are discussed primarily from the glacial meltwater streams of the McMurdo Dry Valleys, Antarctica. Although the Dry Valley landscape is barren of plants, many streams harbor thriving cyanobacterial mats. Whereas a daily cycle of streamflow is controlled by the surface energy balance on the glaciers and the temporal pattern of solar exposure, the daily signal for biogeochemical processes controlling water quality is generated along the stream. These features result in an excellent outdoor laboratory for investigating fundamental ecosystem process and the development and validation of process-based models. As part of the McMurdo Dry Valleys Long-Term Ecological Research project, we have conducted field experiments and developed coupled biogeochemical transport models for the role of hyporheic exchange in controlling weathering reactions, microbial nitrogen cycling, and stream temperature regulation. We have adapted modeling approaches from sediment transport to understand mobilization of stream biomass with increasing flows. These models help to elucidate the role of in-stream processes in systems where watershed processes also contribute to observed patterns, and may serve as a test case for applying real-time stream ecosystem models.

  9. Isotopic order, biogeochemical processes, and earth history - Goldschmidt lecture, Davos, Switzerland, August 2002

    NASA Astrophysics Data System (ADS)

    Hayes, John M.

    2004-04-01

    The impetus to interpret carbon isotopic signals comes from an understanding of isotopic fractionations imposed by living organisms. That understanding rests in turn on studies of enzymatic isotope effects, on fruitful concepts of isotopic order, and on studies of the distribution of 13C both between and within biosynthetic products. In sum, these studies have shown that the isotopic compositions of biological products are governed by reaction kinetics and by pathways of carbon flow. Isotopic compositions of individual compounds can indicate specific processes or environments. Examples include biomarkers which record the isotopic compositions of primary products in aquatic communities, which indicate that certain bacteria have used methane as a carbon source, and which show that some portions of marine photic zones have been anaerobic. In such studies, the combination of structural and isotopic lines of evidence reveals relationships between compounds and leads to process-related thinking. These are large steps. Reconstruction of the sources and histories of molecular fossils redeems much of the early promise of organic geochemistry by resolving and clarifying paleoenviron-mental signals. In turn, contemplation of this new information is driving geochemists to study microbial ecology and evolution, oceanography, and sedimentology.

  10. Chilly Hilly - coupling models of landscape evolution and subsurface thermal processes

    NASA Astrophysics Data System (ADS)

    Barnhart, K. R.; Anderson, R. S.

    2014-12-01

    Many hillslope processes - physical, chemical, and biological - depend on subsurface temperature and water availability. As the subsurface temperature field varies both in space and through climate cycles, the dominant processes of mobile regolith production and transport and the rate at which they act will vary. These processes include the chemical weathering of minerals, cracking of rocks through frost action and tree roots, presence and impact of vegetation on soil cohesion, location and activity of burrowing and trampling animals, frost creep, and solifluction. In order to explore the interplay between these processes across a landscape and over geologic time, we develop a pseudo-three-dimensional subsurface thermal model within the Landlab landscape evolution modeling framework, driven by an associated spatially explicit radiative surface boundary condition. We begin with the analytical solution for conduction in a medium with uniform thermal properties and progress to a numerical model that acknowledges variable material properties, water content, and phase change. At the surface we incorporate spatial and temporal variations in incoming short-wave radiation due to elevation, latitude, aspect, shading and orbital variations. Outgoing long-wave radiation is taken to depend on the surface temperature and may be modified by allowing back-radiation from the atmosphere. With these tools we target variations in regolith production and motion over the long timescales on which hillslopes evolve. We implement a basic parameterization of temperature-dependent chemical and physical weathering linked to mobile regolith generation. We incorporate multiple regolith transport processes including heave, creep, solifluction, tree throw, and animal burrowing. We incorporate material tracking to trace the chemical evolution of regolith as it moves downslope. Our intention is not to parameterize all operative processes, but to include sufficient detail to identify how the

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

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  13. Physical and biogeochemical processes controlling particle fluxes variability and carbon export in the Southern Adriatic

    NASA Astrophysics Data System (ADS)

    Turchetto, M.; Boldrin, A.; Langone, L.; Miserocchi, S.

    2012-08-01

    In the framework of the Vector Project downward particle fluxes have been measured in a station located in the centre of the South Adriatic Pit from November 2006 to August 2008. Sediment trap samples were collected at two different depths, below the photic layer (168 m) and near the bottom (1174 m), and analysed for total mass flux, for total and organic carbon, total nitrogen, carbonate, stable isotope of organic carbon (δ13Corg) and biogenic silica contents. The results have been integrated and compared with data obtained from previous research projects, carried out in the Southern Adriatic area in 1994-1995 and 1997-1998. Fluxes of particulate matter showed high seasonal and interannual variability, with maximum values in late winter-spring season. The organic carbon flux, followed the same seasonal trend, with higher values below the photic zone, and peaks in spring, related to blooms of silica and/or carbonates phytoplankton organisms (e.g., diatoms, coccolithophorids). The organic carbon export from the photic layer was of 5.2 and 2.1 g C m-2 y-1 reached the bottom. Climatological cycles and, in particular, the maximum depth of the convective vertical mixing determined the high fluxes measured in 1998 and in 2008 springs. Total mass fluxes measured at the bottom trap were twofold those measured below the photic layer, and showed a high lithogenic fraction, highlighting the presence of advective processes that appear particularly active in the area. These processes can be correlated with the spreading of dense waters coming from the north and central Adriatic, generally observed in spring. The elemental and isotopic composition of bottom trap samples, resulted similar to that of samples collected in the south-western Adriatic slope, corroborating the assumption that lateral advection other than vertical input were contributing to bottom particle fluxes.

  14. Distinguishing biogeochemical processes influencing phosphorus dynamics in oxidizing and desiccating mud deposits from a freshwater wetland system

    NASA Astrophysics Data System (ADS)

    Saaltink, Rémon; Dekker, Stefan C.; Wassen, Martin J.; Griffioen, Jasper

    2015-04-01

    Focus and aim: Currently, lake Markermeer (680 km2) provides poor environmental conditions for the development of flora and fauna due to a thick fluffy layer that prevails at the lake's bed. To improve the conditions in the lake, large wetlands will be built from this fluffy layer, possibly mixed with sand or with the underlying Southern Sea deposit. The aim of this study is to distinguish biogeochemical processes influencing phosphorus dynamics in porewater during oxidation and desiccation of mud deposits from this lake. We focus on three important aspects that potentially influence these processes: granulometry, sediment type and modification by plants. Material and methods: A greenhouse experiment was conducted with three types of sediment that potentially will function as building material for the islands: fluffy mud (FM), sandy mud (SM) and Southern Sea deposit (SSD). Reed (Phragmites australis) was planted in half of the pots to distinguish influence by plants. For six months, the porewater-, soil- and plant quality was monitored to determine important biogeochemical processes. Variables measured from the porewater include: Cl-, NO2-, NO3-, PO43- and SO42- (IC); Ca, Fe, K, Mn, Na, P, Si, Sr (ICP-OES); as well as Fe2+, pH, alkalinity and EC. A phosphorus fractionation was carried out on the sediment to determine the phosphorus pools and the major elements of the sediments were determined following an aqua regia destruction using ICP-OES. Plant tissue was analysed for N, P, K and C content as well as the above- and belowground biomass. Results and discussion: It was found that sulfate production was the most important process influencing phosphorus availability in these soils. Due to oxidation processes in the mud, sulfate (SO42-) concentrations rose drastically in porewater from 100 ppm at the beginning of the experiment to well over 2000 ppm at the end of the experiment. This effect was strongest in SSD soils, likely due to higher presence of pyrite that gets

  15. Hydrogeophysical characterization of subsurface processes and properties in the critical zone

    NASA Astrophysics Data System (ADS)

    Vereecken, H.; Huisman, J. A.; Altdorf, D.; von Hebel, C.; Gueting, N.; Klotzsche, A.; Van Der Kruk, J.

    2015-12-01

    Hydrogeophysical methods are ideally suited to characterize subsurface hydrologic structures and processes within the critical zone. Recent improvements in the acquisition and inversion of Ground Penetrating Radar (GPR) and ElectroMagnetic Induction (EMI) data now enable to characterize the subsurface in terms of spatially distributed information on soil and hydrologic properties, and to monitor hydrological processes using time-lapse measurements. We will illustrate these new developments by presenting three example cases. The first case illustrates the potential of using GPR full-waveform inversion techniques to obtain detailed information on subsurface porosity. For this purpose, we used cross-borehole GPR measurements along a series of longitudinal and transversal transects at the test site Krauthausen. The obtained information is key for modelling flow and solute transport because the high resolution of the GPR inversion results allows to study the effect of hydraulic connectivity on solute transport. In the following two cases, we illustrate the potential of multi-receiver electromagnetic induction (EMI) sensors that enable the imaging of the soil at different depths. The second case deals with the mapping of peat land properties at the field scale. We used multi-coil offset EMI measurements to provide spatial estimates of SOC content, bulk density, and SOC stock. Together with laser scanning elevation and soil core reference data, regression equations were built predicting SOC content, bulk density, and SOC stocks. EMI-derived explanatory variables were shown to strongly determine the prediction quality of the regression equations. In the last example, we investigated the origin of observed leaf area index (LAI) patterns that indicate crop performance. Using multi-coil offset EMI, we obtained a moderate to excellent spatial consistency of ECa and LAI patterns. It was concluded from these EMI measurements that improved crop performance was related to a higher

  16. Surface and subsurface cleanup protocol for radionuclides, Gunnison, Colorado, UMTRA project processing site. Final [report

    SciTech Connect

    Not Available

    1993-09-01

    Surface and subsurface soil cleanup protocols for the Gunnison, Colorado, processing sits are summarized as follows: In accordance with EPA-promulgated land cleanup standards (40 CFR 192), in situ Ra-226 is to be cleaned up based on bulk concentrations not exceeding 5 and 15 pCi/g in 15-cm surface and subsurface depth increments, averaged over 100-m{sup 2} grid blocks, where the parent Ra-226 concentrations are greater than, or in secular equilibrium with, the Th-230 parent. A bulk interpretation of these EPA standards has been accepted by the Nuclear Regulatory Commission (NRC), and while the concentration of the finer-sized soil fraction less than a No. 4 mesh sieve contains the higher concentration of radioactivity, the bulk approach in effect integrates the total sample radioactivity over the entire sample mass. In locations where Th-230 has differentially migrated in subsoil relative to Ra-226, a Th-230 cleanup protocol has been developed in accordance with Supplemental Standard provisions of 40 CFR 192 for NRC/Colorado Department of Health (CDH) approval for timely implementation. Detailed elements of the protocol are contained in Appendix A, Generic Protocol from Thorium-230 Cleanup/Verification at UMTRA Project Processing Sites. The cleanup of other radionuclides or nonradiological hazards that pose a significant threat to the public and the environment will be determined and implemented in accordance with pathway analysis to assess impacts and the implications of ALARA specified in 40 CFR 192 relative to supplemental standards.

  17. Storms as agents of wetland elevation change: their impact on surface and subsurface sediment processes

    USGS Publications Warehouse

    Cahoon, D.R.

    2003-01-01

    Direct measures of the impact of major storms on wetland sediment elevation are rare. Recently developed techniques have enabled simultaneous, quantitative observations of surface and subsurface processes affecting sediment elevation. An analysis of ten wetland sites revealed the following patterns of sediment elevation change after storm passage: (1) elevation change equivalent to sediment accretion or erosion, (2) elevation loss in spite of sediment deposition, or in excess of erosion, and (3) elevation gain greater than the amount of sediment accretion. These observations suggest that storms influence sediment elevation not only by sediment deposition and erosion but also through subsurface processes of sediment compaction, root growth and decomposition, and water flux. Wetlands receiving a substantial deposit of sediment did not always realize an equivalent elevation gain. Some realized a net loss in elevation as a result of sediment compaction apparently caused by the weight of the sediment deposit or the tidal surge waters, or both. Sediment elevation collapsed in two mangrove forests with highly organic substrate when the storm killed the forest. In two marshes, elevation gain exceeded deposition apparently through increased sediment water storage or plant root growth via nutrient enrichment from storm sediment deposits. The elevation responses were either temporary or permanent on an ecological time scale (> 8 years). In one organic marsh substrate, compaction was followed by expansion, only to be compacted again by another storm. Thus the elevation response of coastal wetlands to major storms varied depending on local substrate conditions and degree of storm impact.

  18. The Precambrian Biogeochemical Carbon Isotopic Record: Contributions of Thermal Versus Biological Processes

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Superplumes offer a new approach for understanding global C cycles. Isotopes help to discern the impacts of geological, environmental and biological processes ujpun the evolution of these cycles. For example, C-13/C-12 values of coeval sedimentary organics and carbonates give global estimates of the fraction of C buried as organics (Forg), which today lies near 0.2. Before Oxygenic photosynthesis arose, our biosphere obtained reducing power for biosynthesis solely from thermal volatiles and rock alteration. Thus Forg was dominated by the mantle redox state, which has remained remarkably constant for greater than Gy. Recent data confirm that the long-term change in Forg had been small, indicating that the mantle redox buffer remains important even today. Oxygenic photosynthesis enabled life to obtain additional reducing power by splitting the water molecule. Accordingly, biological organic production rose above the level constrained by the mantle-derived flux of reduced species. For example, today, chemoautotrophs harvesting energy from hydrothermal emanations can synthesize at most between 0.2 x 10(exp 12) and 2x 10(exp 12) mol C yr-1 of organic C globally. In contrast, global photosynthetic productivity is estimated at 9000 x 10(exp 12) mol C yr-1. Occasionally photosynthetic productivity did contribute to dramatically -elevated Forg values (to 0.4 or more) as evidenced by very high carbonate C-13/C-12. The interplay between biological, tectonic and other environmental factors is illustrated by the mid-Archean to mid-Proterozoic isotopic record. The relatively constant C-13/C-12 values of Archean carbonates support the view that photosynthetically-driven Forg increases were not yet possible. In contrast, major excursions in C-13/C-12, and thus also in Forg, during the early Proterozoic confirmed the global importance of oxygenic photosynthesis by that time. Remarkably, the superplume event at 1.9 Ga did not trigger another major Forg increase, despite the

  19. Microbial Analysis of Australian Dry Lake Cores; Analogs For Biogeochemical Processes

    NASA Astrophysics Data System (ADS)

    Nguyen, A. V.; Baldridge, A. M.; Thomson, B. J.

    2014-12-01

    Lake Gilmore in Western Australia is an acidic ephemeral lake that is analogous to Martian geochemical processes represented by interbedded phyllosilicates and sulfates. These areas demonstrate remnants of a global-scale change on Mars during the late Noachian era from a neutral to alkaline pH to relatively lower pH in the Hesperian era that continues to persist today. The geochemistry of these areas could possibly be caused by small-scale changes such as microbial metabolism. Two approaches were used to determine the presence of microbes in the Australian dry lake cores: DNA analysis and lipid analysis. Detecting DNA or lipids in the cores will provide evidence of living or deceased organisms since they provide distinct markers for life. Basic DNA analysis consists of extraction, amplification through PCR, plasmid cloning, and DNA sequencing. Once the sequence of unknown DNA is known, an online program, BLAST, will be used to identify the microbes for further analysis. The lipid analysis approach consists of phospholipid fatty acid analysis that is done by Microbial ID, which will provide direct identification any microbes from the presence of lipids. Identified microbes are then compared to mineralogy results from the x-ray diffraction of the core samples to determine if the types of metabolic reactions are consistent with the variation in composition in these analog deposits. If so, it provides intriguing implications for the presence of life in similar Martian deposits.

  20. [Biogeochemical processes of the major ions and dissolved inorganic carbon in the Guijiang River].

    PubMed

    Tang, Wen-Kui; Tao, Zhen; Gao, Quan-Zhou; Mao, Hai-Ruo; Jiang, Guang-Hui; Jiao, Shu-Lin; Zheng, Xiong-Bo; Zhang, Qian-Zhu; Ma, Zan-Wen

    2014-06-01

    Within the drainage basin, information about natural processes and human activities can be recorded in the chemical composition of riverine water. The analysis of the Guijiang River, the first level tributary of the Xijiang River, demonstrated that the chemical composition of water in the Guijiang River was mainly influenced by the chemical weathering of carbonate rocks within the drainage basin, in which CO2 was the main erosion medium, and that the weathering of carbonate rock by H2SO4 had a remarkable impact on the water chemical composition in the Guijiang River. Precipitation, human activities, the weathering of carbonate rocks and silicate rocks accounted for 2.7%, 6.3%, 72.8% and 18.2% of the total dissolved load, respectively. The stable isotopic compositions of dissolved inorganic carbon (delta13C(DIC)) indicated that DIC in the Guijiang River had been assimilated by the phytoplankton in photosynthesis. The primary production of phytoplankton contributed to 22.3%-30.9% of particulate organic carbon (POC) in the Guijiang River, which implies that phytoplankton can transform DIC into POC by photosynthesis, and parts of POC will sink into the bottom of the river in transit, which leads into the formation of burial organic carbon.

  1. Benthic Communities as Indicators of Geological and Biogeochemical Processes in the Gulf of Papua

    NASA Astrophysics Data System (ADS)

    Aller, J. Y.; Dhir, S.; Chummar, J.; Dantzler, M. M.; Aller, R. C.

    2003-12-01

    Benthic communities inhabiting Gulf of Papua deposits play important roles in determining remineralization and material cycling processes at the seafloor. Faunal abundances, size-frequency distributions, functional groups, and vertical distributions reflect a spectrum of diagenetic depositional environments produced by variations in local sediment transport dynamics and coastal morphology. Thus faunal properties provide a basis for comparison of factors influencing sediment - overlying water interactions, elemental cycling, and material storage. During mid NW monsoon periods (Jan-Feb), macrofaunal densities at Gulf stations are generally low (260 to 1270 m{-2 }), large macroinfauna are absent in the upper ˜25 cm, and small (< 0.5 mm) surface deposit-feeding polychaetes and tubiculous amphipods dominate, reflecting a frequently destabilized seabed and high sedimentation / erosion rates. Although significant numbers of macrofauna have generally been found to be absent over large areas due to frequent physical disturbance, sedimentary structures demonstrate that many regions of the GoP deltaic complex are periodically extensively bioturbated by relatively large and deep-burrowing infauna. Additionally, faunal samples from February 2003 have significantly increased numbers of opportunistic polychaete and crustacean species relative to 1999 and 2000, indicating that there are periods of faunal colonization and community expansion. These changes may correlate with decreased riverine sediment input associated with El Niño conditions. While the macrofaunal community is relatively depauperate and apparently subject to inhibition by inhospitable physical conditions, the microbial community is highly active, diverse, and abundant throughout the upper ˜1m. The dominance of bacteria and microfauna rather than macrofauna in wet tropical environments like the GoP, contrasts with many reactive continental shelf mud deposits in temperate regions.

  2. Combined physical and biogeochemical processes control the mobility of arsenic in rivers of the Atacama desert, Northern Chile

    NASA Astrophysics Data System (ADS)

    Packman, A.; Gaillard, J.; Pasten, P.; Pizarro, G.; Alsina, M.; Vega, A.; Florenzano, A.; MacDonald, L.; Chen, C.

    2008-12-01

    Many watersheds are contaminated by arsenic (As) derived from natural weathering of earth-surface minerals. Some of the highest naturally occurring As concentrations in surface waters occur in the Atacama desert, Chile. Arsenic enters the Rio Loa and Rio Lluta watersheds from hydrothermal sources in the high Altiplano, producing substantial dissolved and particulate-phase As throughout both river systems. Further, occasional floods related to the ENSO cycle have produced substantial pulses of sediment-laden, As-rich water. Nonetheless, water scarcity in this extremely arid region causes the resident population to rely on these river systems for water supply, and this has historically led to substantial public health effects from chronic As exposure. Despite the scientific and practical significance of As in the rivers of northern Chile, little information is available on the processes that control As dynamics in these systems. Recently we have investigated the distribution and speciation of As in the Rio Loa and Rio Lluta river networks using a variety of new measurement methodologies in an attempt to understand how the interplay of physical and biogeochemical processes regulates As migration through these systems. The unusual chemistry associated with these volcanic, hyper-arid watersheds appears to make As more mobile in these systems than in other types of As-contaminated rivers, favoring rapid remobilization during high-flow events. Further, As transport is largely conservative under low-flow conditions, and its concentration is primarily regulated by dilution from uncontaminated sources and concentration due to the very high rates of evaporation that occur during downstream transport.

  3. New insights into biogeochemical processing gained from sub-daily river monitoring

    NASA Astrophysics Data System (ADS)

    Halliday, S. J.; Wade, A. J.; Skeffington, R. A.; Bowes, M.; Palmer-Felgate, E.; Loewenthal, M.; Jarvie, H.; Neal, C.; Reynolds, B.; Gozzard, E.; Newman, J.

    2012-12-01

    This talk will focus on the insights obtained from sub-daily hydrochemical monitoring for a sustained time periods (> 1 year), at multiple sites within a catchment and across different catchment types. Sub-daily instream hydrochemical dynamics were investigated, using non-stationary time-series analysis techniques, for two catchments representative of upland and lowland UK. The River Hafren at Plynlimon, mid-Wales drains an upland catchment where half the land cover is unmanaged moorland and the other half is first generation plantation forestry. The Hafren was monitored at two sites on a 7-hourly basis, between March 2007 and January 2009, using a Xian automatic sampler. The River Enborne, Berkshire, southeast England, is a rural lowland catchment, impacted by agricultural runoff, and septic tank and sewage treatment works discharges. The Enborne was monitored on an hourly basis between November 2009 and February 2012, using in situ field deployable analytical equipment to measure: Total Reactive Phosphorus (TRP: Systea Micromac C), Nitrate (Hach-Lange Nitratax), pH, dissolved oxygen, conductivity and water temperature (YSI 6600 Multi-parameter sonde). The results reveal complex diurnal patterns which exhibit seasonal changes in phase and amplitude, and are influenced by both flow conditions and nutrient sources. The comparison of the upland and lowland nitrate time series highlights how the different nitrogen sources within each system results in marked differences in the seasonal and diurnal dynamics, with a seasonal maximum in winter and a single peak diurnal cycle in the upland system, compared to a summer maximum and a two peak diurnal cycle in the lowland system. The analysis of TRP and nitrate concentrations in the Enborne catchment, in combination with flow, pH, dissolved oxygen, conductivity and water temperature, allowed the main processes controlling the observed sub-daily nutrient dynamics to be investigated. The different monitoring approaches adopted

  4. Microbiological, Geochemical and Hydrologic Processes Controlling Uranium Mobility: An Integrated Field Scale Subsurface Research Challenge Site at Rifle, Colorado, February 2011 to January 2012

    SciTech Connect

    Long, Philip E.; Banfield, Jill; Chandler, Darrell P.; Davis, James A.; Hettich, Bob; VerBerkmoes, Nathan; Jaffe, Peter R.; Kerkhof, Lee J.; Kukkadapu, Ravi K.; Lipton, Mary; Peacock, Aaron; Williams, Kenneth H.; Yabusaki, Steven B.

    2012-02-15

    The Rifle IFRC continued to make excellent progress during the last 12 months. As noted above, a key field experiment (Best Western) was performed during 2011 as a logical follow-on to the Super 8 field experiment preformed in 2010. In the Super 8 experiment, we successfully combined desorption and bioreduction and deployed a number of novel tracer techniques to enhance our ability to interpret the biogeochemistry of the experiment. In the Best Western experiment, we used the same experimental plot (Plot C) as was used for Super 8. The overarching objective of the Best Western field experiment was to compared the impacts of abiotic vs. biotic increases in alkalinity and to assess the mass of the sorbed pool of U(VI) at Rifle at the field scale. Both of these objectives were met. Preliminary analysis of the data indicate that the underlying biogeochemical data sets were obtained that will support a mechanistic understanding of the underlying processes, including remarkable insight into previously unrecognized microbial processes taking place during acetate amendment of the subsurface for a second time.

  5. Final Progress Report: Coupled Biogeochemical Process Evaluation for Conceptualizing Trichloroethylene Cometabolism

    SciTech Connect

    Crawford, Ronald L; Paszczynski, Andrzej J

    2010-02-19

    Our goal within the overall project is to demonstrate the presence and abundance of methane monooxygenases (MMOs) enzymes and their genes within the microbial community of the Idaho National Laboratory (INL) Test Area North (TAN) site. MMOs are thought to be the primary catalysts of natural attenuation of trichloroethylene (TCE) in contaminated groundwater at this location. The actual presence of the proteins making up MMO complexes would provide direct evidence for its participation in TCE degradation. The quantitative estimation of MMO genes and their translation products (sMMO and pMMO proteins) and the knowledge about kinetics and substrate specificity of MMOs will be used to develop mathematical models of the natural attenuation process in the TAN aquifer. The model will be particularly useful in prediction of TCE degradation rate in TAN and possibly in the other DOE sites. Bacteria known as methanotrophs produce a set of proteins that assemble to form methane monooxygenase complexes (MMOs), enzymes that oxidize methane as their natural substrate, thereby providing a carbon and energy source for the organisms. MMOs are also capable of co-metabolically transforming chlorinated solvents like TCE into nontoxic end products such as carbon dioxide and chloride. There are two known forms of methane monooxygenase, a membrane-bound particulate form (pMMO) and a cytoplasmic soluble form (sMMO). pMMO consists of two components, pMMOH (a hydroxylase comprised of 47-, 27-, and 24-kDa subunits) and pMMOR (a reductase comprised of 63 and 8-kDa subunits). sMMO consists of three components: a hydroxylase (protein A-250 kDa), a dimer of three subunits (α2β2γ2), a regulatory protein (protein B-15.8 kDa), and a reductase (protein C-38.6 kDa). All methanotrophs will produce a methanol dehydrogenase to channel the product of methane oxidation (methanol) into the central metabolite formaldehyde. University of Idaho (UI) efforts focused on proteomic analyses using mass

  6. Flexible simulation framework to couple processes in complex 3D models for subsurface utilization assessment

    NASA Astrophysics Data System (ADS)

    Kempka, Thomas; Nakaten, Benjamin; De Lucia, Marco; Nakaten, Natalie; Otto, Christopher; Pohl, Maik; Tillner, Elena; Kühn, Michael

    2016-04-01

    Utilization of the geological subsurface for production and storage of hydrocarbons, chemical energy and heat as well as for waste disposal requires the quantification and mitigation of environmental impacts as well as the improvement of georesources utilization in terms of efficiency and sustainability. The development of tools for coupled process simulations is essential to tackle these challenges, since reliable assessments are only feasible by integrative numerical computations. Coupled processes at reservoir to regional scale determine the behaviour of reservoirs, faults and caprocks, generally demanding for complex 3D geological models to be considered besides available monitoring and experimenting data in coupled numerical simulations. We have been developing a flexible numerical simulation framework that provides efficient workflows for integrating the required data and software packages to carry out coupled process simulations considering, e.g., multiphase fluid flow, geomechanics, geochemistry and heat. Simulation results are stored in structured data formats to allow for an integrated 3D visualization and result interpretation as well as data archiving and its provision to collaborators. The main benefits in using the flexible simulation framework are the integration of data geological and grid data from any third party software package as well as data export to generic 3D visualization tools and archiving formats. The coupling of the required process simulators in time and space is feasible, while different spatial dimensions in the coupled simulations can be integrated, e.g., 0D batch with 3D dynamic simulations. User interaction is established via high-level programming languages, while computational efficiency is achieved by using low-level programming languages. We present three case studies on the assessment of geological subsurface utilization based on different process coupling approaches and numerical simulations.

  7. Geophysical Monitoring of Coupled Microbial and Geochemical Processes During Stimulated Subsurface Bioremediation

    SciTech Connect

    Williams, Kenneth H.; Kemna, Andreas; Wilkins, Michael J.; Druhan, Jennifer L.; Arntzen, Evan V.; N'Guessan, A. Lucie; Long, Philip E.; Hubbard, Susan S.; Banfield, Jillian F.

    2009-08-05

    Understanding how microorganisms alter their physical and chemical environment during bioremediation is hindered by our inability to resolve subsurface microbial activity with high spatial resolution. Here we demonstrate the use of a minimally invasive geophysical technique to monitor stimulated microbial activity during acetate amendment in an aquifer near Rifle, Colorado. During electrical induced polarization (IP) measurements, spatiotemporal variations in the phase response between imposed electric current and the resultant electric field correlated with changes in groundwater geochemistry accompanying stimulated iron and sulfate reduction and sulfide mineral precipitation. The magnitude of the phase response varied with measurement frequency (0.125 and 1 Hz) andwasdependent upon the dominant metabolic process. The spectral effect was corroborated using a biostimulated column experiment containing Rifle sediments and groundwater. Fluids and sediments recovered from regions exhibiting an anomalous phase response were enriched in Fe(II), dissolved sulfide, and cell-associated FeS nanoparticles. The accumulation of mineral precipitates and electroactive ions altered the ability of pore fluids to conduct electrical charge, accounting for the anomalous IP response and revealing the usefulness of multifrequency IP measurements for monitoring mineralogical and geochemical changes accompanying stimulated subsurface bioremediation.

  8. Biogeochemical Processes Related to Metal Removal and Toxicity Reduction in the H-02 Constructed Wetland, Savannah River Site

    NASA Astrophysics Data System (ADS)

    Burgess, E. A.; Mills, G. L.; Harmon, M.; Samarkin, V.

    2011-12-01

    The H-02 wetland system was designed to treat building process water and storm water runoff from multiple sources associated with the Tritium Facility at the DOE-Savannah River Site, Aiken, SC. The wetland construction included the addition of gypsum (calcium sulfate) to foster a sulfate-reducing bacterial population. Conceptually, the wetland functions as follows: ? Cu and Zn initially bind to both dissolved and particulate organic detritus within the wetland. ? A portion of this organic matter is subsequently deposited into the surface sediments within the wetland. ? The fraction of Cu and Zn that is discharged in the wetland effluent is organically complexed, less bioavailable, and consequently, less toxic. ? The Cu and Zn deposited in the surface sediments are eventually sequestered into insoluble sulfide minerals in the wetland. Development of the H-02 system has been closely monitored; sampling began in August 2007, shortly after its construction. This monitoring has included the measurement of water quality parameters, Cu and Zn concentrations in surface water and sediments, as well as, characterization of the prokaryotic (e.g., bacterial) component of wetland biogeochemical processes. Since the beginning of the study, the mean influent Cu concentration was 31.5±12.1 ppb and the mean effluent concentration was 11.9±7.3 ppb, corresponding to an average Cu removal of 64%. Zn concentrations were more variable, averaging 39.2±13.8 ppb in the influent and 25.7±21.3 ppb in the effluent. Average Zn removal was 52%. The wetland also ameliorated high pH values associated with influent water to values similar to those measured at reference sites. Seasonal variations in DOC concentration corresponded to seasonal variations in Cu and Zn removal efficiency. The concentration of Cu and Zn in the surface layer of the sediments has increased over the lifetime of the wetland and, like removal efficiency, demonstrated seasonal variation. Within its first year, the H-02

  9. Synchronous DOM and dissolved phosphorus release in riparian soil waters: linking water table fluctuations and biogeochemical processes

    NASA Astrophysics Data System (ADS)

    Gruau, G.; Dupas, R.; Humbert, G.; GU, S.; Jeanneau, L.; Fovet, O.; Denis, M.; Gascuel-Odoux, C.; Jaffrezic, A.; Faucheux, M.; Gilliet, N.; Hamon, Y.; Petitjean, P.

    2015-12-01

    Riparian zones are often viewed as hot spots controlling N, C, P and Fe cycling and export in catchments. Groundwater and surface water flowpaths converge in these zones, and encounter the most reactive, organic-rich, uppermost soil horizons, while being at the same time zones in which soil moisture conditions temporarily fluctuate due to changes in water table depth, which can trigger biogeochemical processes. One well documented example is the process of denitrification which can remove N from riparian groundwater due to the anaerobic reduction of nitrate by soil organic matter. However, the role of riparian zones on the cycling of other nutrients such as dissolved organic matter (DOM) and dissolved P (DP) is much less well documented. In this study, we evaluated this role by using time series of DOM and DP concentrations obtained on the Kervidy-Naizin catchment, a temperate agricultural headwater catchment controlled by shallow groundwater. Over 2 years, groundwater DOM and DP were monitored fortnightly both in the riparian zones and at the bottom of hillslope domains. Two periods of synchronous DOM and DP release were evidenced, the first corresponding to the rise of the water table after the dry summer period, the second being concomitant of the installation of reducing conditions. The reductive dissolution of soil Fe oxyhydroxides initiated by the prolonged soil water saturation caused the second peak, a process which was, however, strongly temporarily and spatially variable at the catchment scale, being dependent on i) the local topographic slope and ii) the annual rainfall amount and frequency. As regard the first peak, it was due either to the flushing by the water table of DOM and DP accumulated during the summer period, or to the release of microbial DOM and DP due to microbial biomass killing by osmotic shock. This study argues for the existence of coupled and complex DOM and DP release processes in the riparian zones of shallow groundwater dominated

  10. Transpiration Driven Hydrologic Transport in vegetated shallow water environments: Implications on Diel and Seasonal Soil Biogeochemical Processes and System Management

    NASA Astrophysics Data System (ADS)

    Bachand, P.; Bachand, S. M.; Fleck, J.; Anderson, F.

    2011-12-01

    modified Peclet No. calculations, we quantified the relative importance of upward diffusion from the sediments and downward advection from transpiration as hydrologic transport mechanisms in the root zone. Transpiration driven infiltration moves water past the diffusive zone within 1 - 2 days in this system during the summer months. With the waning seasons, evapotranspiration diminishes until by winter diffusion dominates throughout the entire root zone. This model has great implications on the analyses of soil biogeochemical process in the root zone of shallow aquatic systems. Downward advection is a major transport mechanism into the root zone of shallow flooded aquatic systems and provides an important physical mechanism that drives variability in the seasonal and diel storage; release and cycling of COCs; and the creation of both a physical and chemical barrierd to upward diffusion of soil-borne COCs into the water column. Models that do not account for root zone interactions may not be able to capture diel and seasonal differences. Moreover, these interactions may lead to unanticipated environmental consequences as a result of cultural practices.

  11. ASSESSMENT OF SUBSURFACE FATE OF MONOETHANOLAMINE AT SOUR GAS PROCESSING PLANT SITES-PHASE III

    SciTech Connect

    James A. Sorensen

    1999-02-01

    Alkanolamines are commonly used by the natural gas industry to remove hydrogen sulfide, carbon dioxide, and other acid gases from the natural gas in which they occur (''sour'' gas if hydrogen sulfide is present). At sour gas-processing plants, as at all plants that use alkanolamines for acid gas removal (AGR), spills and on-site management of wastes containing alkanolamines and associated reaction products have occasionally resulted in subsurface contamination that is presently the focus of some environmental concern. In 1994, the Energy and Environmental Research Center (EERC) initiated a three-phase program to investigate the natural attenuation processes that control the subsurface transport and fate of the most commonly used alkanolamine in Canada, monoethanolamine (MEA). Funding for the MEA research program was provided by the U.S. Department of Energy (DOE), Canadian Association of Petroleum Producers (CAPP), Canadian Occidental Petroleum Ltd. (CanOxy), Gas Research Institute (GRI), Environment Canada, and the National Energy Board of Canada. The MEA research program focused primarily on examining the biodegradability of MEA and MEA-related waste materials in soils and soil-slurries under a variety of environmentally relevant conditions, evaluating the mobility of MEA in soil and groundwater and the effectiveness of bioremediation techniques for removing contaminants and toxicity from MEA-contaminated soil. The presently inactive Okotoks sour gas-processing plant, owned by CanOxy in Alberta, Canada, was the source of samples and field data for much of the laboratory-based experimental work and was selected to be the location for the field-based efforts to evaluate remediation techniques. The objective of the research program is to provide the natural gas industry with ''real world'' data and insights developed under laboratory and field conditions regarding the effective and environmentally sound use of biological methods for the remediation of soil

  12. Use of Zn isotopes as a probe of anthropogenic contamination and biogeochemical processes in the Seine River, France

    NASA Astrophysics Data System (ADS)

    Chen, J.; Gaillardet, J.; Louvat, P.; Birck, J.

    2009-05-01

    a whole river basin, showing Zn isotopes a powerful probe to trace contamination sources and biogeochemical processes in hydrologic systems.

  13. Deciphering the Role of Surface and Subsurface Processes on Solute Dynamics at the Catchment Scale

    NASA Astrophysics Data System (ADS)

    Scanlon, T. M.; Riscassi, A. L.; Ingram, S. M.

    2008-12-01

    Nitrate (NO3-) leakage from forested watersheds due to disturbance is a well-documented but not well- understood process that can contribute to the degradation of receiving waters through eutrophication. Several studies have shown large-scale defoliation events in small forested watersheds in the Eastern U.S. cause immediate and dramatic increases in NO3- flux to steams with large differences in recovery time. Here, we analyze water-quality and discharge data collected from the time period 1992-2004 following a large-scale gypsy moth defoliation in Shenandoah National Park, Virginia. Following the defoliation, groundwater NO3- concentrations declined exponentially with a distinct seasonal pattern. Initial NO3- groundwater concentrations were related to the magnitude of defoliation within each watershed. Surprisingly, no long-term trend or seasonal pattern were found for soil water NO3- concentrations, as inferred from a mixing model applied to individual storm events. By comparing decay constants associated with groundwater discharge with constants for nitrate recovery to background concentrations, we find a hydrological imprint on the recovery time. This was confirmed by performing similar analysis on data from Hubbard Brook and Coweeta, where more rapid recovery times are attributed to the distinct biogeochemical processes associated with deforestation or crown damage. Synoptic measurements of NO3- concentrations collected on eight occasions within a stream network during the period of recovery are used to fit a model designed to capture the observed spatial variability. We find that upland terrestrial processes, rather than in-stream processes, account for the greatest proportion of this variability.

  14. Effects of biogeochemical processes on magnesium isotope variations in a forested catchment in the Vosges Mountains (France)

    NASA Astrophysics Data System (ADS)

    Bolou-Bi, Emile B.; Vigier, Nathalie; Poszwa, Anne; Boudot, Jean-Pierre; Dambrine, Etienne

    2012-06-01

    This study investigates the potential of Mg isotopes as tracers of biogeochemical processes in a small-forested catchment located on sandstones extremely poor in Mg-bearing minerals. The average δ26Mg is -0.63 ± 0.12‰ and 0 ± 0.14‰ for local rainwater and bedrock, respectively. From the C horizon to the upper eluvial (E) horizon, soil δ26Mg (from 0.0 ± 0.14‰ to 0.25 ± 0.14‰) is close to the bedrock value, while more than 70% of Mg is lost, suggesting a small isotopic shift during illite dissolution. The surface soil horizon (Ah) δ26Mg is close to plant δ26Mg, and especially to the grass δ26Mg value (-0.49‰). The bulk δ26Mg of trees and grass (-0.32‰ and -0.41‰, respectively) are higher than the average δ26Mg values of the soil exchangeable fraction (-0.92‰ to -0.42‰), and of rainwater (-0.65‰). Within plants, roots are enriched in heavy isotopes, whereas light isotopes are preferentially translocated and stored in the above ground parts. In Norway spruce, the older needles, forming the annual litterfall, are isotopically lighter and strongly depleted in Mg compared to more recent needles. Soil solution δ26Mg shifts seasonally, from low values, lower than rainwater and close to litterfall during a high rainfall period in spring, to higher values, close to soil δ26Mg in dryer periods of winter or summer. At the watershed scale, streamwater δ26Mg varies between -0.85 ± 0.14‰ and -0.08 ± 0.14‰ and δ26Mg values decrease linearly with discharge. The high streamwater δ26Mg at low flow, close to bedrock δ26Mg, most likely reflects dissolution processes in the deep saprolite in relation to the very long water residence time. Conversely, we suggest that low stream level δ26Mg values are at least partly related to the contribution of surface flows from wet areas. Using a simple mass and isotopic balance approach, we compute that mineral dissolution rates in the soil (0.35 kg Mg ha-1 year-1) presently compensate for Mg losses from

  15. Advances in Understanding Sorption and Transport Processes Affecting the Fate of Environmental Pollutants in the Subsurface

    NASA Astrophysics Data System (ADS)

    Karapanagioti, H. K.; Werner, D.; Werth, C.

    2012-04-01

    The results of a call for a special issue that is now in press by the Journal of Contaminant Hydrology will be presented. This special issue is edited by the authors and is entitled "Sorption and Transport Processes Affecting the Fate of Environmental Pollutants in the Subsurface". A short abstract of each paper will be presented along with the most interesting results. Nine papers were accepted. Pollutants studied include: biocolloids, metals (arsenic, chromium, nickel), organic compounds such as hydrocarbons, chlorinated hydrocarbons, micropollutants (PAHs, PCBs), pesticides (glyphosate, 2,4-D). Findings presented in the papers include a modified batch reactor system to study equilibrium-reactive transport problems of metals. Column studies along with theoretical approximations evaluate the combined effects of grain size and pore water velocity on the transport in water saturated porous media of three biocolloids. A polluted sediment remediation method is evaluated considering site-specific conditions through monitoring results and modelling. A field study points to glogging and also sorption as mechanisms affecting the effectiveness of sub-surface flow constructed wetlands. A new isotherm model combining modified traditionally used isotherms is proposed that can be used to simulate pH-dependent metal adsorption. Linear free energy relationships (LFERs) demonstrate ability to predict slight isotope shifts into the groundwater due to sorption. Possible modifications that improve the reliability of kinetic models and parameter values during the evaluation of experiments that assess the sorption of pesticides on soils are tested. Challenges in selecting groundwater pollutant fate and transport models that account for the effect of grain-scale sorption rate limitations are evaluated based on experimental results and are discussed based on the Damköhler number. Finally, a thorough review paper presents the impact of mineral micropores on the transport and fate of

  16. Toward a better understanding of the complex geochemical processes governing subsurface contaminant transport

    SciTech Connect

    Puls, R.W.

    1991-07-01

    Identification and understanding of the chemical, physical, and biological processes controlling subsurface contaminant migration is essential for making accurate predictions on the fate and transport of these constituents. Remediation assessment requires these predictions where pollution from municipal and industrial activities has occurred, and for the responsible siting of waste isolation and storage facilities. Geochemical processes include ion-exchange, precipitation, organic partitioning, chemisorption, aqueous complexation, and colloidal stability and transport. Current approaches to quantify the effect of these processes on transport in a ground water system primarily involve laboratory techniques. These include the use of closed static systems (batch experiments) and dynamic systems (column experiments) where a larger segment of the aquifer is investigated by analyzing the breakthrough profiles of reactive and non-reactive species. The latter approach may be more representative of in situ conditions than the former, however, when compared to large-scale field experiments both are still constrained by: differences in scale, alteration of media during sample collection and use, and spatial variability. More field reactivity studies are needed to complement established laboratory approaches for the determination of retardation factors, scaling factors for laboratory versus field data, corroboration or confirmation of batch and column results, and for validation of sampling techniques.

  17. Effects of Subsurface Sampling & Processing on Martian Simulant Containing Varying Quantities of Water

    NASA Technical Reports Server (NTRS)

    Menard, J.; Sangillo, J.; Savain, A.; McNamara, K. M.

    2004-01-01

    The presence of water-ice in the Martian subsurface is a subject of much debate and excited speculation. Recent results from the gammaray spectrometer (GRS) on board NASA's Mars Odyssey spacecraft indicate the presence of large amounts of hydrogen in regions of predicted ice stability. The combination of chemistry, low gravitational field (3.71 m/s(exp 2)) and a surface pressure of about 6.36 mbar at the mean radius, place limits on the stability of H2O on the surface, however, results from the GRS indicate that the hydrogen rich phase may be present at a depth as shallow as one meter in some locations on Mars. The potential for water on Mars leads directly to the speculation that life may once have existed there, since liquid water is the unifying factor for environments known to support life on Earth. Lubricant-free drilling has been considered as a means of obtaining water-rich subsurface samples on Mars, and two recent white papers sponsored by the Mars Program have attempted to identify the problems associated with this goal. The two major issues identified were: the engineering challenges of drilling into a water-soil mixture where phase changes may occur; and the potential to compromise the integrity of in-situ scientific analysis due to contamination, volatilization, and mineralogical or chemical changes as a result of processing. This study is a first attempt to simulate lubricantfree drilling into JSC Mars-1 simulant containing up to 50% water by weight. The goal is to address the following: 1) Does sample processing cause reactions or changes in mineralogy which will compromise the interpretation of scientific measurements conducted on the surface? 2) Does the presence of water-ice in the sample complicate (1)? 3) Do lubricant-free drilling and processing leave trace contaminants which may compromise our understanding of sample composition? 4) How does the torque/power required for drilling change as a function of water content and does this lead to

  18. MRF Applications: Measurement of Process-dependent Subsurface Damage in Optical Materials using the MRF Wedge Technique

    SciTech Connect

    Menapace, J A; Davis, P J; Steele, W A; Wong, L L; Suratwala, T I; Miller, P E

    2005-11-02

    Understanding the behavior of fractures and subsurface damage in the processes used during optic fabrication plays a key role in determining the final quality of the optical surface finish. During the early stages of surface preparation, brittle grinding processes induce fractures at or near an optical surface whose range can extend from depths of a few mm to hundreds of mm depending upon the process and tooling being employed. Controlling the occurrence, structure, and propagation of these sites during subsequent grinding and polishing operations is highly desirable if one wishes to obtain high-quality surfaces that are free of such artifacts. Over the past year, our team has made significant strides in developing a diagnostic technique that combines magnetorheological finishing (MRF) and scanning optical microscopy to measure and characterize subsurface damage in optical materials. The technique takes advantage of the unique nature of MRF to polish a prescribed large-area wedge into the optical surface without propagating existing damage or introducing new damage. The polished wedge is then analyzed to quantify subsurface damage as a function of depth from the original surface. Large-area measurement using scanning optical microscopy provides for improved accuracy and reliability over methods such as the COM ball-dimple technique. Examples of the technique's use will be presented that illustrate the behavior of subsurface damage in fused silica that arises during a variety of intermediate optical fabrication process steps.

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

    PubMed

    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

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

    PubMed Central

    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

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

    NASA Astrophysics Data System (ADS)

    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.

    2016-07-01

    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.

  2. Subsurface Water Oceans on Icy Satellites: Chemical Composition and Exchange Processes

    NASA Astrophysics Data System (ADS)

    Sohl, Frank; Choukroun, Mathieu; Kargel, Jeffrey; Kimura, Jun; Pappalardo, Robert; Vance, Steve; Zolotov, Mikhail

    2010-06-01

    The state of knowledge about the structure and composition of icy satellite interiors has been significantly extended by combining direct measurements from spacecraft, laboratory experiments, and theoretical modeling. The existence of potentially habitable liquid water reservoirs on icy satellites is dependent on the radiogenic heating of the rock component, additional contributions such as the dissipation of tidal energy, the efficiency of heat transfer to the surface, and the presence of substances that deplete the freezing point of liquid water. This review summarizes the chemical evolution of subsurface liquid water oceans, taking into account a number of chemical processes occuring in aqueous environments and partly related to material exchange with the deep interior. Of interest are processes occuring at the transitions from the liquid water layer to the ice layers above and below, involving the possible formation of clathrate hydrates and high-pressure ices on large icy satellites. In contrast, water-rock exchange is important for the chemical evolution of the liquid water layer if the latter is in contact with ocean floor rock on small satellites. The composition of oceanic floor deposits depends on ambient physical conditions and ocean chemistry, and their evolutions through time. In turn, physical properties of the ocean floor affect the circulation of oceanic water and related thermal effects due to tidally-induced porous flow and aqueous alteration of ocean floor rock.

  3. Afforestation Alters the Composition of Functional Genes in Soil and Biogeochemical Processes in South American Grasslands▿ †

    PubMed Central

    Berthrong, Sean T.; Schadt, Christopher W.; Piñeiro, Gervasio; Jackson, Robert B.

    2009-01-01

    Soil microbes are highly diverse and control most soil biogeochemical reactions. We examined how microbial functional genes and biogeochemical pools responded to the altered chemical inputs accompanying land use change. We examined paired native grasslands and adjacent Eucalyptus plantations (previously grassland) in Uruguay, a region that lacked forests before European settlement. Along with measurements of soil carbon, nitrogen, and bacterial diversity, we analyzed functional genes using the GeoChip 2.0 microarray, which simultaneously quantified several thousand genes involved in soil carbon and nitrogen cycling. Plantations and grassland differed significantly in functional gene profiles, bacterial diversity, and biogeochemical pool sizes. Most grassland profiles were similar, but plantation profiles generally differed from those of grasslands due to differences in functional gene abundance across diverse taxa. Eucalypts decreased ammonification and N fixation functional genes by 11% and 7.9% (P < 0.01), which correlated with decreased microbial biomass N and more NH4+ in plantation soils. Chitinase abundance decreased 7.8% in plantations compared to levels in grassland (P = 0.017), and C polymer-degrading genes decreased by 1.5% overall (P < 0.05), which likely contributed to 54% (P < 0.05) more C in undecomposed extractable soil pools and 27% less microbial C (P < 0.01) in plantation soils. In general, afforestation altered the abundance of many microbial functional genes, corresponding with changes in soil biogeochemistry, in part through altered abundance of overall functional gene types rather than simply through changes in specific taxa. Such changes in microbial functional genes correspond with altered C and N storage and have implications for long-term productivity in these soils. PMID:19700539

  4. Biogeochemical processing of nutrients in groundwater-fed stream during baseflow conditions - the value of fluorescence spectroscopy and automated high-frequency nutrient monitoring

    NASA Astrophysics Data System (ADS)

    Bieroza, Magdalena; Heathwaite, Louise

    2014-05-01

    Recent research in groundwater-dominated streams indicates that organic matter plays an important role in nutrient transformations at the surface-groundwater interface known as the hyporheic zone. Mixing of water and nutrient fluxes in the hyporheic zone controls in-stream nutrients availability, dynamics and export to downstream reaches. In particular, benthic sediments can form adsorptive sinks for organic matter and reactive nutrients (nitrogen and phosphorus) that sustain a variety of hyporheic processes e.g. denitrification, microbial uptake. Thus, hyporheic metabolism can have an important effect on both quantity (concentration) and quality (labile vs. refractory character) of organic matter. Here high-frequency nutrient monitoring combined with spectroscopic analysis was used to provide insights into biogeochemical processing of a small, agricultural stream in the NE England subject to diffuse nutrient pollution. Biogeochemical data were collected hourly for a week at baseflow conditions when in-stream-hyporheic nutrient dynamics have the greatest impact on stream health. In-stream nutrients (total phosphorus, reactive phosphorus, nitrate nitrogen) and water quality parameters (turbidity, specific conductivity, pH, temperature, dissolved oxygen, redox potential) were measured in situ hourly by an automated bank-side laboratory. Concurrent hourly autosamples were retrieved daily and analysed for nutrients and fine sediments including spectroscopic analyses of dissolved organic matter - excitation-emission matrix (EEM) fluorescence spectroscopy and ultraviolet-visible (UV-Vis) absorbance spectroscopy. Our results show that organic matter can potentially be utilised as a natural, environmental tracer of the biogeochemical processes occurring at the surface-groundwater interface in streams. High-frequency spectroscopic characterisation of in-stream organic matter can provide useful quantitative and qualitative information on fluxes of reactive nutrients in

  5. Final Report: A Model Management System for Numerical Simulations of Subsurface Processes

    SciTech Connect

    Zachmann, David

    2013-10-07

    The DOE and several other Federal agencies have committed significant resources to support the development of a large number of mathematical models for studying subsurface science problems such as groundwater flow, fate of contaminants and carbon sequestration, to mention only a few. This project provides new tools to help decision makers and stakeholders in subsurface science related problems to select an appropriate set of simulation models for a given field application.

  6. Planetary Biogeochemical Stewardship (Invited)

    NASA Astrophysics Data System (ADS)

    Schlesinger, W. H.

    2010-12-01

    Many of today’s most pressing environmental problems have a basis in chemistry—that is human disruption of global biogeochemical cycles. Humans have enhanced the movement of C, N, P, and S in the global cycle of these elements, with widespread consequences such as climate change, hypoxia and acid rain. Recent attempts to calculate thresholds of global vulnerability ignore ample evidence that human impacts on the Earth’s chemical environment yield progressive degradation of the biosphere, especially its species diversity. Our collect global impact now exceeds natural processes of planetary remediation—clearly an unsustainable path. I will attempt to provide a framework to evaluate suggested attempts to mitigate current human impact on global biogeochemical cycles. Cap-and-trade systems are ideal for perturbations that involve a limited number of point sources that supplement a small background flux to the atmosphere, such as S. Better land management may be the most attractive way to mitigate human impacts to the Nitrogen cycle, where the potential for enhanced denitrification could respond to the order-of-magnitude of the current human perturbation. Impacts to the carbon cycle, seen through rising CO2 in Earth’s atmosphere, will require switching to energy that does not depend on fossil carbon.

  7. Quantifying the dynamic coupling of hydrologic and biogeochemical processes in stream ecosystems: examples from streams in the McMurdo Dry Valleys, Antarctica

    NASA Astrophysics Data System (ADS)

    McKnight, D. M.; Lyons, W. B.; Gooseff, M. N.; Koch, J. C.; Neupauer, R.; Cozzetto, K.; Bencala, K.; Cullis, J. D.

    2014-12-01

    While continuous monitoring of stream flow and stream temperature has been a widely used resource for some time, currently there is great potential to expand continuous monitoring to include important water quality parameters such as nutrients and dissolved organic material. In many systems distinguishing between watershed and stream ecosystem controls can be challenging, and the usefulness of such monitoring can be enhanced by application of quantitative models to interpret observed patterns. The glacial meltwater streams of the McMurdo Dry Valleys, Antarctica, are surrounded by large expanses of patterned ground devoid of plants. In contrast, many streams have thriving cyanobacterial mats that are freeze-dried through the winter and begin photosynthesis with the onset of flow. Thus, the daily signal in terms of biogeochemical processes controlling water quality is generated within the stream. As part of the McMurdo Dry Valleys Long Term Ecological Research project, we have conducted field experiments and developed coupled biogeochemical transport models for the role of hyporheic exchange in controlling weathering of major ions, microbial cycling of nitrogen species, and streams temperature regulation. We have also adapted modelling approaches from sediment transport to understand mobilization of stream biomass with increasing flows. These models are relevant to understanding the role of in-stream processes in diverse stream systems where watershed processes also contribute to observed patterns.

  8. Simulating temporal variations of nitrogen losses in river networks with a dynamic transport model unravels the coupled effects of hydrological and biogeochemical processes

    SciTech Connect

    Mulholland, Patrick J; Alexander, Richard; Bohlke, John; Boyer, Elizabeth; Harvey, Judson; Seitzinger, Sybil; Tobias, Craig; Tonitto, Christina; Wollheim, Wilfred

    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

  9. Microbial redox processes in deep subsurface environments and the potential application of (per)chlorate in oil reservoirs

    PubMed Central

    Liebensteiner, Martin G.; Tsesmetzis, Nicolas; Stams, Alfons J. M.; Lomans, Bartholomeus P.

    2014-01-01

    The ability of microorganisms to thrive under oxygen-free conditions in subsurface environments relies on the enzymatic reduction of oxidized elements, such as sulfate, ferric iron, or CO2, coupled to the oxidation of inorganic or organic compounds. A broad phylogenetic and functional diversity of microorganisms from subsurface environments has been described using isolation-based and advanced molecular ecological techniques. The physiological groups reviewed here comprise iron-, manganese-, and nitrate-reducing microorganisms. In the context of recent findings also the potential of chlorate and perchlorate [jointly termed (per)chlorate] reduction in oil reservoirs will be discussed. Special attention is given to elevated temperatures that are predominant in the deep subsurface. Microbial reduction of (per)chlorate is a thermodynamically favorable redox process, also at high temperature. However, knowledge about (per)chlorate reduction at elevated temperatures is still scarce and restricted to members of the Firmicutes and the archaeon Archaeoglobus fulgidus. By analyzing the diversity and phylogenetic distribution of functional genes in (meta)genome databases and combining this knowledge with extrapolations to earlier-made physiological observations we speculate on the potential of (per)chlorate reduction in the subsurface and more precisely oil fields. In addition, the application of (per)chlorate for bioremediation, souring control, and microbial enhanced oil recovery are addressed. PMID:25225493

  10. Source Process of the 2003 Bam, Iran, Earthquake: Subsurface Rupture that Generated Extreme Ground Motion

    NASA Astrophysics Data System (ADS)

    Poiata, N.; Miyake, H.; Koketsu, K.; Hikima, K.

    2008-12-01

    The Bam earthquake occurred on December 26, 2003 in southeast Iran. This moderate size event (Mw 6.5) caused heavy damage in the city of Bam and killed about 26,000 people. According to previous studies of geodetic data (e.g., Talebian et al., 2004; Wang et al., 2004) and aftershock distribution (Nakamura et al., 2005), the earthquake was caused by a rupture on a previously unknown strike-slip fault. The strong-motion station located inside the heavily damaged area of the city of Bam in vicinity of the fault recorded a PGA of 988 gal in the UD component and two pulses with a dominant frequency of 1 Hz in the horizontal components. This large PGA and the proportion of damage due to this event might be explained by the combination of source directivity effect and large speed of the rupture front over the fault (Bouchon et al., 2005). To estimate the slip pattern in the source rupture area, precise hypocentral depth, and rupture velocity along the fault, we applied the moment tensor analysis as well as the source inversion method developed by Kikuchi and Kanamori (1991) and Kikuchi et al. (2003) to the IRIS broadband teleseismic data. The result of the source inversion shows the slip distribution that confirms a single asperity, as suggested by Yamanaka (2003), with the rupture propagating in S-N direction along an almost vertical strike-slip fault with dimensions of 25 km in length by 20 km in width. The hypocentral depth for the best fit model is estimated to be 8 km. The maximum slip occurred around the hypocenter at depths of 4-10 km; no slip is associated at a shallower depth. This agrees with the result of subsurface rupture and 'shallow slip deficit' obtained from geodetic data by Fialko et al. (2005) and might explain the extreme ground motion observed at the Bam station as being the result of the subsurface faulting on the immature fault. We also determined the rupture velocity that minimizes the residuals between observed and synthetic waveforms to be 2.8 km

  11. Carbon Processing in the Marine Subsurface: What Are They Doing Down There?

    NASA Astrophysics Data System (ADS)

    Biddle, J.; Martino, A. J.; Russell, J. A., III; Christman, G.; House, C. H.

    2014-12-01

    The deep marine subsurface is a place where small amounts of carbon are deposited, yet the majority of microorganisms appear to have heterotrophic lifestyles and carbon accumulates on a global scale. In this enviroment, how are heterotrophic organisms gathering their carbon and utilizing it? This talk will utilize subsurface metagenomics and amplicon data to discuss the interactions of deep microorganisms with buried sedimentary carbon. We will compare the Peru, Iberian and Costa Rica Margins to the abyssopelagic Equatorial Pacific. Specific organisms and their anticipated functions will be discussed. Additionally, we will discuss the potential for small scale trophic levels to form between bacteria and eukaryotes in deep basalts.

  12. Up-scaling of process-based eco-hydrology model to global scale for identification of hot spots in boundless biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Nakayama, T.; Maksyutov, S. S.

    2013-12-01

    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 includes surface-groundwater interactions and down-scaling process from regional to local simulation with finer resolution, and can simulate iteratively nonlinear feedback between hydrologic, geomorphic, and ecological processes in east Asia. In this study, NICE was further extended to implement map factor and non-uniform grid through up-scaling process of coordinate transformation from rectangular to longitude-latitude system applicable to global scale. This improved model was applied to several basins in Eurasia to evaluate the impact of coordinate transformation on eco-hydrological changes. Simulated eco-hydrological process after up-scaling corresponded reasonably to that in the original there after evaluating the effect of different latitude. Then, the model was expanded 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. This simulation system would play important role in identification of spatio-temporal hot spots in boundless biogeochemical cycle along terrestrial-aquatic continuum for global environmental change (Cole et al. 2007; Battin et al. 2009; Frei et al. 2012).

  13. Seasonal evolution of Titan's polar caps: interaction between atmospheric and subsurface processes

    NASA Astrophysics Data System (ADS)

    Sotin, C.

    2012-12-01

    Titan is the only satellite of the solar system with a dense atmosphere. It is also the only object, besides Earth, with stable liquid bodies at its surface. The (P,T) conditions at Titan's surface suggest that methane and ethane are liquid. Ethane has been detected in the lakes [1] whereas the signature of liquid methane is hidden by that of atmospheric methane which is the second most abundant atmospheric component. Methane is irreversibly transformed into ethane by photolysis. Titan's atmosphere contains very little ethane, which suggests that it is present in the surface (lakes) or/and the subsurface. Lakes are mostly located in the polar areas with many more lakes on the North Pole than on the South Pole. Ethane clouds above the North Pole have been identified during the winter when the atmospheric circulation leads to the formation of downwellings at the North Pole. Remote sensing instruments onboard the Cassini spacecraft have recently witnessed the formation of the South Polar vortex after the equinox in August 2009. Ethane rain may now happen over the South Pole. Laboratory experiments show that ethane and methane can react with ice to form clathrates that are denser and more stable than pure ice. Laboratory experiments also suggest that ethane clathrates are more stable than methane clathrates. The atmosphere can be replenished in methane through the substitution of methane by ethane that rains and percolates into the subsurface [2]. Because ethane clathrates are denser than methane clathrates, such a process would lead to significant subsidence on geological time scales. It may explain why Titan's flattening is larger than that due to spin rate only [2]. The amount of ethane required to explain Titan's shape is in agreement with the a global resurfacing event that would have occurred between a few hundreds of Myrs and 1 Gyr as suggested by the density of impact craters [3] and the age of the atmospheric methane [4]. The Cassini observations and results

  14. Evaluation of Surface and Subsurface Processes in Permeable Pavement Infiltration Trenches

    EPA Science Inventory

    The hydrologic performance of permeable pavement systems can be affected by clogging of the pavement surface and/or clogging at the interface where the subsurface storage layer meets the underlying soil. As infiltration and exfiltration are the primary functional mechanisms for ...

  15. BIOGEOPHYSICS: THE EFFECTS OF MICROBIAL PROCESSES ON GEOPHYSICAL PROPERTIES OF THE SHALLOW SUBSURFACE

    EPA Science Inventory

    This chapter provides a brief review of how microbial interactions with the geologic media may translate to changes in the bulk physical properties of the subsurface

    which are potentially measurable by geophysical techniques. The results of select pioneering laboratory and...

  16. Coupled hydrological and biogeochemical processes controlling variability of nitrogen species in streamflow during autumn in an upland forest

    NASA Astrophysics Data System (ADS)

    Sebestyen, Stephen D.; Shanley, James B.; Boyer, Elizabeth W.; Kendall, Carol; Doctor, Daniel H.

    2014-02-01

    Autumn is a season of dynamic change in forest streams of the northeastern United States due to effects of leaf fall on both hydrology and biogeochemistry. Few studies have explored how interactions of biogeochemical transformations, various nitrogen sources, and catchment flow paths affect stream nitrogen variation during autumn. To provide more information on this critical period, we studied (1) the timing, duration, and magnitude of changes to stream nitrate, dissolved organic nitrogen (DON), and ammonium concentrations; (2) changes in nitrate sources and cycling; and (3) source areas of the landscape that most influence stream nitrogen. We collected samples at higher temporal resolution for a longer duration than typical studies of stream nitrogen during autumn. This sampling scheme encompassed the patterns and extremes that occurred during base flow and stormflow events of autumn. Base flow nitrate concentrations decreased by an order of magnitude from 5.4 to 0.7 µmol L-1 during the week when most leaves fell from deciduous trees. Changes to rates of biogeochemical transformations during autumn base flow explained the low nitrate concentrations; in-stream transformations retained up to 72% of the nitrate that entered a stream reach. A decrease of in-stream nitrification coupled with heterotrophic nitrate cycling were primary factors in the seasonal nitrate decline. The period of low nitrate concentrations ended with a storm event in which stream nitrate concentrations increased by 25-fold. In the ensuing weeks, peak stormflow nitrate concentrations progressively decreased over closely spaced, yet similarly sized events. Most stormflow nitrate originated from nitrification in near-stream areas with occasional, large inputs of unprocessed atmospheric nitrate, which has rarely been reported for nonsnowmelt events. A maximum input of 33% unprocessed atmospheric nitrate to the stream occurred during one event. Large inputs of unprocessed atmospheric nitrate show

  17. Coupled hydrological and biogeochemical processes controlling variability of nitrogen species in streamflow during autumn in an upland forest

    USGS Publications Warehouse

    Sebestyen, Stephen D.; Shanley, James B.; Boyer, Elizabeth W.; Kendall, Carol; Doctor, Daniel H.

    2014-01-01

    Autumn is a season of dynamic change in forest streams of the northeastern United States due to effects of leaf fall on both hydrology and biogeochemistry. Few studies have explored how interactions of biogeochemical transformations, various nitrogen sources, and catchment flow paths affect stream nitrogen variation during autumn. To provide more information on this critical period, we studied (1) the timing, duration, and magnitude of changes to stream nitrate, dissolved organic nitrogen (DON), and ammonium concentrations; (2) changes in nitrate sources and cycling; and (3) source areas of the landscape that most influence stream nitrogen. We collected samples at higher temporal resolution for a longer duration than typical studies of stream nitrogen during autumn. This sampling scheme encompassed the patterns and extremes that occurred during base flow and stormflow events of autumn. Base flow nitrate concentrations decreased by an order of magnitude from 5.4 to 0.7 µmol L−1 during the week when most leaves fell from deciduous trees. Changes to rates of biogeochemical transformations during autumn base flow explained the low nitrate concentrations; in-stream transformations retained up to 72% of the nitrate that entered a stream reach. A decrease of in-stream nitrification coupled with heterotrophic nitrate cycling were primary factors in the seasonal nitrate decline. The period of low nitrate concentrations ended with a storm event in which stream nitrate concentrations increased by 25-fold. In the ensuing weeks, peak stormflow nitrate concentrations progressively decreased over closely spaced, yet similarly sized events. Most stormflow nitrate originated from nitrification in near-stream areas with occasional, large inputs of unprocessed atmospheric nitrate, which has rarely been reported for nonsnowmelt events. A maximum input of 33% unprocessed atmospheric nitrate to the stream occurred during one event. Large inputs of unprocessed atmospheric nitrate

  18. Preferential flow and mixing process in the chemical recharge in subsurface catchments: observations and modeling

    NASA Astrophysics Data System (ADS)

    Gascuel-Odoux, C.; Rouxel, M.; Molenat, J.; Ruiz, L.; Aquilina, L.; Faucheux, M.; Labasque, T.; Sebilo, M.

    2012-04-01

    Shallow groundwater that develops on hillslopes is the main compartment in headwater catchments for flow and solute transport to rivers. Although spatial and temporal variations in its chemical composition are reported in the literature, there is no coherent description of the way these variations are organized, nor is there an accepted conceptual model for the recharge mechanisms and flows in the groundwater involved. We instrumented an intensive farming and subsurface dominant catchment located in Oceanic Western Europe (Kerbernez, Brittany, France), a headwater catchment included in the Observatory for Research on Environment AgrHyS (Agro-Hydro-System) and a part of the French Network of catchments for environmental research (SOERE RBV focused on the Critical Zone). These systems are strongly constrained by anthropogenic pressures (agriculture) and are characterized by a clear non-equilibrium status. A network of 42 nested piezometers was installed along a 200 m hillslope allowing water sampling along two transects in the permanent water table as well as in what we call the "fluctuating zone", characterized by seasonal alternance of saturated and unsaturated conditions. Water composition was monitored at high frequency (weekly) over a 3-year period for major anion composition and over a one year period for detailed 15N, CFC, SF6 and other dissolved gases. The results demonstrated that (i) the anionic composition in water table fluctuation zone varied significantly compared to deeper portions of the aquifer on the hillslope, confirming that this layer constitutes a main compartment for the mixing of new recharge water and old groundwater, (ii) seasonally, the variations of 15N and CFC are much higher during the recharge period than during the recession period, confirming the preferential flow during early recharge events, iii) variations of nitrate 15N and O18 composition was suggesting any significant denitrification process in the fluctuating zone, confirming

  19. Reappraisal of soil C storage processes. The controversy on structural diversity of humic substances as biogeochemical driver for soil C fluxes

    NASA Astrophysics Data System (ADS)

    Almendros, Gonzalo; Gonzalez-Vila, Francisco J.; Gonzalez-Perez, Jose Antonio; Knicker, Heike

    2016-04-01

    The functional relationships between the macromolecular structure of the humic substances (HS) and a series of biogeochemical processes related with the C sequestration performance in soils have been recently questioned. In this communication we collect recent data from a wide array of different ecosystems where the C storage in soils has been studied and explained as a possible cause-to-effect relationship or has been found significantly correlated (multivariate statistical models) with a series of structural characteristics of humic materials. The study of humic materials has methodological analytical limitations that are derived from its complex, chaotic and not completely understood structure, that reflects its manifold precursors as well as the local impact of environmental/depositional factors. In this work we attempt to design an exploratory, multiomic approach based on the information provided by the molecular characterization of the soil organic matter (SOM). Massive data harvesting was carried out of statistical variables, to infer biogeochemical proxies (spectroscopic, chromatographic, mass spectrometric quantitative descriptors). The experimental data were acquired from advanced instrumental methodologies, viz, analytical pyrolysis, compound-specific stable isotope analysis (CSIA), derivative infrared (FTIR) spectroscopy, solid-state C-13 and N-15 nuclear magnetic resonance (NMR) and mass spectrometry (MS) data after direct injection (thermoevaporation), previous pyrolysis, or ion averaging of specific m/z ranges from classical GC/MS chromatograms. In the transversal exploratory analysis of the multianalytical information, the data were coded for on-line processing in a stage in which there is no need for interpretation, in molecular or structural terms, of the quantitative data consisting of e.g., peak intensities, signal areas, chromatographic (GC) total abundances, etc. A series of forecasting chemometric approaches (aiming to express SOM

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

    NASA Astrophysics Data System (ADS)

    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-processing

  1. Seasonal baseline of nutrients and stable isotopes in a saline lake of Argentina: biogeochemical processes and river runoff effects.

    PubMed

    Kopprio, Germán A; Kattner, Gerhard; Freije, R Hugo; de Paggi, Susana José; Lara, Rubén J

    2014-05-01

    The seasonal variability of inorganic and organic nutrients and stable isotopes and their relations with plankton and environmental conditions were monitored in Lake Chasicó. Principal component analysis evidenced the strong influence of the river runoff on several biogeochemical variables. Silicate concentrations were controlled by diatom biomass and river discharge. Higher values of nitrate and soluble reactive phosphorus (SRP) indicated agricultural uses in the river basin. Elevated pH values (∼ 9) inhibiting nitrification in the lake explained partially the dominance of ammonium: ∼ 83 % of dissolved inorganic nitrogen (DIN). The low DIN/SRP ratio inferred nitrogen limitation, although the hypotheses of iron and CO2 limitation are relevant in alkaline lakes. Particulate organic matter (POM) and dissolved organic matter (DOM) were mainly of autochthonous origin. The main allochthonous input was imported by the river as POM owning to the arid conditions. Dissolved organic carbon was likely top-down regulated by the bacterioplankton grazer Brachionus plicatilis. The δ(13)C signature was a good indicator of primary production and its values were influenced probably by CO2 limitation. The δ(15)N did not evidence nitrogen fixation and suggested the effects of anthropogenic activities. The preservation of a good water quality in the lake is crucial for resource management.

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

    NASA Astrophysics Data System (ADS)

    Spiteri, Claudette; Slomp, Caroline P.; Tuncay, Kagan; Meile, Christof

    2008-02-01

    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 conditions. Results from the simplified model representations show that the prevalent flow characteristics and redox conditions in the freshwater-seawater mixing zone determine the extent of nutrient removal and the input of nitrogen and phosphorus to coastal waters. At low to moderate groundwater velocities, simultaneous nitrification and denitrification can lead to a reversal in the depth of freshwater NO3- and NH4+-PO4 plumes, compared to their original positions at the landward source. Model results suggest that autotrophic denitrification pathways with Fe2+ or FeS2 may provide an important, often overlooked link between nitrogen and phosphorus biogeochemistry through the precipitation of iron oxides and subsequent binding of phosphorus. Simulations also highlight that deviations of nutrient data from conservative mixing curves do not necessarily indicate nutrient removal.

  3. In-Situ Anaerobic Biosurfactant Production Process For Remediation Of DNAPL Contamination In Subsurface Aquifers

    NASA Astrophysics Data System (ADS)

    Albino, J. D.; Nambi, I. M.

    2009-12-01

    Microbial Enhanced Oil Recovery (MEOR) and remediation of aquifers contaminated with hydrophobic contaminants require insitu production of biosurfactants for mobilization of entrapped hydrophobic liquids. Most of the biosurfactant producing microorganisms produce them under aerobic condition and hence surfactant production is limited in subsurface condition due to lack of oxygen. Currently bioremediation involves expensive air sparging or excavation followed by exsitu biodegradation. Use of microorganisms which can produce biosurfactants under anaerobic conditions can cost effectively expedite the process of insitu bioremediation or mobilization. In this work, the feasibility of anaerobic biosurfactant production in three mixed anaerobic cultures prepared from groundwater and soil contaminated with chlorinated compounds and municipal sewage sludge was investigated. The cultures were previously enriched under complete anaerobic conditions in the presence of Tetrachloroethylene (PCE) for more than a year before they were studied for biosurfactant production. Biosurfactant production under anaerobic conditions was simulated using two methods: i) induction of starvation in the microbial cultures and ii) addition of complex fermentable substrates. Positive result for biosurfactant production was not observed when the cultures were induced with starvation by adding PCE as blobs which served as the only terminal electron acceptor. However, slight reduction in interfacial tension was noticed which was caused by the adherence of microbes to water-PCE interface. Biosurfactant production was observed in all the three cultures when they were fed with complex fermentable substrates and surface tension of the liquid medium was lowered below 35 mN/m. Among the fermentable substrates tested, vegetable oil yielded highest amount of biosurfactant in all the cultures. Complete biodegradation of PCE to ethylene at a faster rate was also observed when vegetable oil was amended to the

  4. A Conceptual Model of Coupled Biogeochemical and Hydrogeological Processes Affected by In Situ Cr(VI) Bioreduction in Groundwater at Hanford 100H Site

    NASA Astrophysics Data System (ADS)

    Faybishenko, B.; Long, P. E.; Hazen, T. C.; Hubbard, S. S.; Williams, K. H.; Peterson, J. E.; Chen, J.; Volkova, E. V.; Newcomer, D. R.; Resch, C. T.; Cantrell, K.; Conrad, M. S.; Brodie, E. L.; Joyner, D. C.; Borglin, S. E.; Chakraborty, R. C.

    2007-05-01

    The overall objective of this presentation is to demonstrate a conceptual multiscale, multidomain model of coupling of biogeochemical and hydrogeological processes during bioremediation of Cr(VI) contaminated groundwater at Hanford 100H site. A slow release polylactate, Hydrogen Release Compound (HRCTM), was injected in Hanford sediments to stimulate immobilization of Cr(VI). The HRC injection induced a 2-order-of- magnitude increase in biomass and the onset of reducing biogeochemical conditions [e.g., redox potential decreased from +240 to -130 mV and dissolved oxygen (DO) was completely removed]. A three-well system, comprised of an injection well and upgradient and downgradient monitoring wells, was used for conducting the in situ biostimulation, one regional flow (no-pumping) tracer test, and five pumping tests along with the Br-tracer injection. Field measurements were conducted using a Br ion-selective electrode and a multiparameter flow cell to collect hourly data on temperature, pH, redox potential, electrical conductivity, and DO. Groundwater sampling was conducted by pumping through specially designed borehole water samplers. Cross-borehole radar tomography and seismic measurements were carried out to assess the site background lithological heterogeneity and the migration pathways of HRC byproducts through groundwater after the HRC injection. Several alternative approaches, including conventional and fractional advective dispersion equations and geostatistical analysis, were used to characterize hydraulic and biogeochemical transport parameters. The results of a joint inversion of cross-borehole geophysical tomography and flow-rate measurements in boreholes indicate the presence of a bimodal distribution of hydraulic conductivity for Hanford sediments. The Br- concentration double-peak BTCs curves indicate that HRC injection caused an increase in the tracer travel time (mainly in the low-permeability zone) over the period of observations of about 2 years

  5. Impact of dust on biogeochemical processes in the East Mediterranean Sea, lessons from on-board microcosm and land-based mesocosm experiments

    NASA Astrophysics Data System (ADS)

    Herut, Barak; Pitta, Paraskevi; Mihalopoulos, Nikos; Tsagaraki, Tatiana; Rahav, Eyal; Berman-Frank, Ilana; Psarra, Stella; Giannakourou, Antonia; Tsiola, Anastasia; Shi, Zongbo; Tanaka, Tsuneo; Kocak, Mustafa; Yucel, Nebil; Liu, Hongbin; Louiza Pedrotti, Maria; Tsapakis, Manolis; Violaki, Kalliopi; Fernandez, MariLuz; Meador, Travis; Panagiotopoulos, Christos

    2014-05-01

    Recent on-board microcosm and land-based mesocosm experiments in the oligotrophic Eastern Mediterranean Sea (EMS) indicates a significant role of Mediterranean aerosols as a net supplier of macro and micro nutrients (N, P, Fe and other trace metals) to the Low Nutrient Low Chlorophyll EMS. In such ultra-oligotrophic environment the leachable nutrients from dry atmospheric inputs add significant quantities of nutrients and become rapidly (<2hrs) bioavailable influencing substantially biogeochemical processes. Experimental additions triggered an increase in several of the performed rate and state variables as bacterial production and abundance, primary production rates and chlorophyll a (or other phytopigments), abundance of certain pico and nanophytoplankton groups and nitrogen fixation rates. Understanding these relationships is important to follow the pathways of N, P (and C) into the EMS food web and the future climate- and human-induced changes in the EMS.

  6. Using complex resistivity imaging to infer biogeochemical processes associated with bioremediation of a uranium-contaminated aquifer

    SciTech Connect

    Orozco, A. Flores; Williams, K.H.; Long, P.E.; Hubbard, S.S.; Kemna, A.

    2011-04-01

    Experiments at the Department of Energy's Rifle Integrated Field Research Challenge (IFRC) site near Rifle, Colorado (USA) have demonstrated the ability to remove uranium from groundwater by stimulating the growth and activity of Geobacter species through acetate amendment. Prolonging the activity of these strains in order to optimize uranium bioremediation has prompted the development of minimally-invasive and spatially-extensive monitoring methods diagnostic of their in situ activity and the end products of their metabolism. Here we demonstrate the use of complex resistivity imaging for monitoring biogeochemical changes accompanying stimulation of indigenous aquifer microorganisms during and after a prolonged period (100+ days) of acetate injection. A thorough raw-data statistical analysis of discrepancies between normal and reciprocal measurements and incorporation of a new power-law phase-error model in the inversion were used to significantly improve the quality of the resistivity phase images over those obtained during previous monitoring experiments at the Rifle IRFC site. The imaging results reveal spatiotemporal changes in the phase response of aquifer sediments, which correlate with increases in Fe(II) and precipitation of metal sulfides (e.g., FeS) following the iterative stimulation of iron and sulfate reducing microorganism. Only modest changes in resistivity magnitude were observed over the monitoring period. The largest phase anomalies (>40 mrad) were observed hundreds of days after halting acetate injection, in conjunction with accumulation of Fe(II) in the presence of residual FeS minerals, reflecting preservation of geochemically reduced conditions in the aquifer - a prerequisite for ensuring the long-term stability of immobilized, redox-sensitive contaminants, such as uranium.

  7. Using complex resistivity imaging to infer biogeochemical processes associated with bioremediation of a uranium-contaminated aquifer

    SciTech Connect

    Flores-Orozco, Adrian; Williams, Kenneth H.; Long, Philip E.; Hubbard, Susan S.; Kemna, Andreas

    2011-07-07

    Experiments at the Department of Energy’s Rifle Integrated Field Research Challenge (IFRC) site near Rifle, Colorado (USA) have demonstrated the ability to remove uranium from groundwater by stimulating the growth and activity of Geobacter species through acetate amendment. Prolonging the activity of these strains in order to optimize uranium bioremediation has prompted the development of minimally-invasive and spatially-extensive monitoring methods diagnostic of their in situ activity and the end products of their metabolism. Here we demonstrate the use of complex resistivity imaging for monitoring biogeochemical changes accompanying stimulation of indigenous aquifer microorganisms during and after a prolonged period (100+ days) of acetate injection. A thorough raw-data statistical analysis of discrepancies between normal and reciprocal measurements and incorporation of a new power-law phase-error model in the inversion were used to significantly improve the quality of the resistivity phase images over those obtained during previous monitoring experiments at the Rifle IRFC site. The imaging results reveal spatiotemporal changes in the phase response of aquifer sediments, which correlate with increases in Fe(II) and precipitation of metal sulfides (e.g., FeS) following the iterative stimulation of iron and sulfate reducing microorganism. Only modest changes in resistivity magnitude were observed over the monitoring period. The largest phase anomalies (>40 mrad) were observed hundreds of days after halting acetate injection, in conjunction with accumulation of Fe(II) in the presence of residual FeS minerals, reflecting preservation of geochemically reduced conditions in the aquifer – a prerequisite for ensuring the long-term stability of immobilized, redox-sensitive contaminants, such as uranium.

  8. Using complex resistivity imaging to infer biogeochemical processes associated with bioremediation of an uranium-contaminated aquifer

    NASA Astrophysics Data System (ADS)

    Flores Orozco, AdriáN.; Williams, Kenneth H.; Long, Philip E.; Hubbard, Susan S.; Kemna, Andreas

    2011-09-01

    Experiments at the Department of Energy's Integrated Field Research Challenge (IFRC) site near Rifle, Colorado, have demonstrated the ability to remove uranium from groundwater by stimulating the growth and activity of Geobacter species through acetate amendment. Prolonging the activity of these strains in order to optimize uranium bioremediation has prompted the development of minimally invasive and spatially extensive monitoring methods diagnostic of their in situ activity and the end products of their metabolism. Here we demonstrate the use of complex resistivity imaging for monitoring biogeochemical changes accompanying stimulation of indigenous aquifer microorganisms during and after a prolonged period (100+ days) of acetate injection. A thorough raw data statistical analysis of discrepancies between normal and reciprocal measurements and incorporation of a new power law phase-error model in the inversion were used to significantly improve the quality of the resistivity phase images over those obtained during previous monitoring experiments at the Rifle IFRC site. The imaging results reveal spatiotemporal changes in the phase response of aquifer sediments, which correlate with increases in Fe(II) and precipitation of metal sulfides (e.g., FeS) following the iterative stimulation of iron and sulfate-reducing microorganisms. Only modest changes in resistivity magnitude were observed over the monitoring period. The largest phase anomalies (>40 mrad) were observed hundreds of days after halting acetate injection, in conjunction with accumulation of Fe(II) in the presence of residual FeS minerals, reflecting preservation of geochemically reduced conditions in the aquifer, a prerequisite for ensuring the long-term stability of immobilized, redox-sensitive contaminants such as uranium.

  9. Biogeochemical Processes leading to release of As and Mn in the groundwaters of Murshidabad District of West Bengal, India

    NASA Astrophysics Data System (ADS)

    Johannesson, K. H.; Datta, S.; Vega, M.; Berube, M.

    2015-12-01

    Elevated concentrations of both manganese (Mn) and arsenic (As) have been observed in the groundwaters of Murshidabad, in eastern India. Mn, a postulated neurotoxin is known to cause neuromuscular problems, inhibition of neurological development particularly in children. The health impacts from higher bioavailable proportions of As is well known in being a Class I carcinogen. The discovery of this additional contaminant in the already As afflicted regions of SE Asia poses serious implications for millions of inhabitants. The current study aims to address three objectives in understanding biogeochemical cycling of Mn and As in groundwaters: i) the occurrence and overall distribution (lateral and temporal) of groundwater Mn and As; ii) characterization of the dissolved organic matter and microbial content and the resultant effects that are imposed on dissolved As and Mn; and iii) the relationship between Mn, As, and various other inorganic constituents and their impact on the subsequent release of Mn, on top of As. A three year time series of chemical data for the dissolved constituents from six villages in Murshidabad will be presented. Hariharpara, Beldanga, Naoda villages contain reducing groundwaters (mean Mn: 0.93mg/L); Nabagram, Kandi, Khidirpore demonstrate oxidizing aquifers (Mn: 0.74mg/L). Eighty-three percent of the wells surveyed contain Mn levels that exceed the recommended WHO limit of 0.4 mg/L. Dissolved As within the same locations show a range from <10μg/L to ~4000 μg/L. DOC values demonstrate a positive correlation with Mn in reducing and a negative correlation in oxidizing environments. The reducing aquifers are also high in As and DOC, indicating that the microbially mediated reductive dissolution of As-sorbed onto Fe-Mn mineral phases is probable. Fluorescence analyses of dissolved OM, solidphase modeling of Mn speciation are being combined in this study for more insight into the mechanisms of Mn release and its relation if any to As release.

  10. Microbial abundance in the deep subsurface of the Chesapeake Bay impact crater: relationship to lithology and impact processes

    USGS Publications Warehouse

    Cockell, Charles S.; Gronstal, Aaron L.; Voytek, Mary A.; Kirshtein, Julie D.; Finster, Kai; Sanford, Ward E.; Glamoclija, Mihaela; Gohn, Gregroy S.; Powars, David S.; Horton, J. Wright

    2009-01-01

    Asteroid and comet impact events are known to cause profound disruption to surface ecosystems. The aseptic collection of samples throughout a 1.76-km-deep set of cores recovered from the deep subsurface of the Chesapeake Bay impact structure has allowed the study of the subsurface biosphere in a region disrupted by an impactor. Microbiological enumerations suggest the presence of three major microbiological zones. The upper zone (127–867 m) is characterized by a logarithmic decline in microbial abundance from the surface through the postimpact section of Miocene to Upper Eocene marine sediments and across the transition into the upper layers of the impact tsunami resurge sediments and sediment megablocks. In the middle zone (867–1397 m) microbial abundances are below detection. This zone is predominantly quartz sand, primarily composed of boulders and blocks, and it may have been mostly sterilized by the thermal pulse delivered during impact. No samples were collected from the large granite block (1096–1371 m). The lowest zone (below 1397 m) of increasing microbial abundance coincides with a region of heavily impact-fractured, hydraulically conductive suevite and fractured schist. These zones correspond to lithologies influenced by impact processes. Our results yield insights into the influence of impacts on the deep subsurface biosphere.

  11. Aqueous complexation reactions governing the rate and extent of biogeochemical U(VI) reduction

    SciTech Connect

    Kemner, K.M.; Kelly, S.D.; Brooks, Scott C.; Dong, Wenming; Carroll, Sue; Fredrickson, James K.

    2006-06-01

    The proposed research will elucidate the principal biogeochemical reactions that govern the concentration, chemical speciation, and reactivity of the redox-sensitive contaminant uranium. The results will provide an improved understanding and predictive capability of the mechanisms that govern the biogeochemical reduction of uranium in subsurface environments.

  12. Enhanced Geothermal Systems Research and Development: Models of Subsurface Chemical Processes Affecting Fluid Flow

    SciTech Connect

    Moller, Nancy; Weare J. H.

    2008-05-29

    Successful exploitation of the vast amount of heat stored beneath the earth’s surface in hydrothermal and fluid-limited, low permeability geothermal resources would greatly expand the Nation’s domestic energy inventory and thereby promote a more secure energy supply, a stronger economy and a cleaner environment. However, a major factor limiting the expanded development of current hydrothermal resources as well as the production of enhanced geothermal systems (EGS) is insufficient knowledge about the chemical processes controlling subsurface fluid flow. With funding from past grants from the DOE geothermal program and other agencies, we successfully developed advanced equation of state (EOS) and simulation technologies that accurately describe the chemistry of geothermal reservoirs and energy production processes via their free energies for wide XTP ranges. Using the specific interaction equations of Pitzer, we showed that our TEQUIL chemical models can correctly simulate behavior (e.g., mineral scaling and saturation ratios, gas break out, brine mixing effects, down hole temperatures and fluid chemical composition, spent brine incompatibilities) within the compositional range (Na-K-Ca-Cl-SO4-CO3-H2O-SiO2-CO2(g)) and temperature range (T < 350°C) associated with many current geothermal energy production sites that produce brines with temperatures below the critical point of water. The goal of research carried out under DOE grant DE-FG36-04GO14300 (10/1/2004-12/31/2007) was to expand the compositional range of our Pitzer-based TEQUIL fluid/rock interaction models to include the important aluminum and silica interactions (T < 350°C). Aluminum is the third most abundant element in the earth’s crust; and, as a constituent of aluminosilicate minerals, it is found in two thirds of the minerals in the earth’s crust. The ability to accurately characterize effects of temperature, fluid mixing and interactions between major rock-forming minerals and hydrothermal and

  13. BIOGEOCHEMICAL CYCLING AND ENVIRONMENTAL STABILITY OF PLUTONIUM RELEVANT TO LONG-TERM STEWARDSHIP OF DOE SITES.

    SciTech Connect

    FRANCIS, A.J.; GILLOW, J.P.; DODGE, C.J.

    2006-11-16

    Pu is generally considered to be relatively immobile in the terrestrial environment, with the exception of transport via airborne and erosion mechanisms. More recently the transport of colloidal forms of Pu is being studied as a mobilization pathway from subsurface contaminated soils and sediments. The overall objective of this research is to understand the biogeochemical cycling of Pu in environments of interest to long-term DOE stewardship issues. Microbial processes are central to the immobilization of Pu species, through the metabolism of organically complexed Pu species and Pu associated with extracellular carrier phases and the creation of environments favorable for retardation of Pu transport.

  14. BIOGEOCHEMICAL CYCLING AND ENVIRONMENTAL STABILITY OF PLUTONIUM RELEVANT TO LONG-TERM STEWARDSHIP OF DOE SITES

    SciTech Connect

    Francis, A.J.; Gillow, J.B.; Dodge, C.J.

    2006-06-01

    Pu is generally considered to be relatively immobile in the terrestrial environment, with the exception of transport via airborne and erosion mechanisms. More recently the transport of colloidal forms of Pu is being studied as a mobilization pathway from subsurface contaminated soils and sediments. The overall objective of this research is to understand the biogeochemical cycling of Pu in environments of interest to long-term DOE stewardship issues. Microbial processes are central to the immobilization of Pu species, through the metabolism of organically complexed Pu species and Pu associated with extracellular carrier phases and the creation of environments favorable for retardation of Pu transport.

  15. Quantifying shallow subsurface water and heat dynamics using coupled hydrological-thermal-geophysical inversion

    NASA Astrophysics Data System (ADS)

    Phuong Tran, Anh; Dafflon, Baptiste; Hubbard, Susan S.; Kowalsky, Michael B.; Long, Philip; Tokunaga, Tetsu K.; Williams, Kenneth H.

    2016-08-01

    Improving our ability to estimate the parameters that control water and heat fluxes in the shallow subsurface is particularly important due to their strong control on recharge, evaporation and biogeochemical processes. The objectives of this study are to develop and test a new inversion scheme to simultaneously estimate subsurface hydrological, thermal and petrophysical parameters using hydrological, thermal and electrical resistivity tomography (ERT) data. The inversion scheme - which is based on a nonisothermal, multiphase hydrological model - provides the desired subsurface property estimates in high spatiotemporal resolution. A particularly novel aspect of the inversion scheme is the explicit incorporation of the dependence of the subsurface electrical resistivity on both moisture and temperature. The scheme was applied to synthetic case studies, as well as to real datasets that were autonomously collected at a biogeochemical field study site in Rifle, Colorado. At the Rifle site, the coupled hydrological-thermal-geophysical inversion approach well predicted the matric potential, temperature and apparent resistivity with the Nash-Sutcliffe efficiency criterion greater than 0.92. Synthetic studies found that neglecting the subsurface temperature variability, and its effect on the electrical resistivity in the hydrogeophysical inversion, may lead to an incorrect estimation of the hydrological parameters. The approach is expected to be especially useful for the increasing number of studies that are taking advantage of autonomously collected ERT and soil measurements to explore complex terrestrial system dynamics.

  16. Quantifying shallow subsurface water and heat dynamics using coupled hydrological-thermal-geophysical inversion

    DOE PAGES

    Tran, Anh Phuong; Dafflon, Baptiste; Hubbard, Susan S.; Kowalsky, Michael B.; Long, Philip; Tokunaga, Tetsu K.; Williams, Kenneth H.

    2016-08-31

    Improving our ability to estimate the parameters that control water and heat fluxes in the shallow subsurface is particularly important due to their strong control on recharge, evaporation and biogeochemical processes. The objectives of this study are to develop and test a new inversion scheme to simultaneously estimate subsurface hydrological, thermal and petrophysical parameters using hydrological, thermal and electrical resistivity tomography (ERT) data. The inversion scheme – which is based on a nonisothermal, multiphase hydrological model – provides the desired subsurface property estimates in high spatiotemporal resolution. A particularly novel aspect of the inversion scheme is the explicit incorporation of themore » dependence of the subsurface electrical resistivity on both moisture and temperature. The scheme was applied to synthetic case studies, as well as to real datasets that were autonomously collected at a biogeochemical field study site in Rifle, Colorado. At the Rifle site, the coupled hydrological-thermal-geophysical inversion approach well predicted the matric potential, temperature and apparent resistivity with the Nash–Sutcliffe efficiency criterion greater than 0.92. Synthetic studies found that neglecting the subsurface temperature variability, and its effect on the electrical resistivity in the hydrogeophysical inversion, may lead to an incorrect estimation of the hydrological parameters. The approach is expected to be especially useful for the increasing number of studies that are taking advantage of autonomously collected ERT and soil measurements to explore complex terrestrial system dynamics.« less

  17. Identification and Quantification of Processes Affecting the Fate of Ethanol-Blended Fuel in the Subsurface

    NASA Astrophysics Data System (ADS)

    Devries, J. M.; Mayer, K. U.

    2015-12-01

    At present, the oil and gas industry distributes gasoline with an ethanol content of up to 10% (E10) to the consumer. However, ethanol advocates are promoting gasoline blends with higher ethanol content to be introduced into the market (e.g., E20, corresponding to an ethanol content of 20%). The likelihood of unintended fuel releases with elevated ethanol concentrations through surficial spills or from underground storage systems will therefore increase. A particular concern is the increased rate of CH4 and CO2 production as the spill biodegrades, which is believed to be associated with the increased ethanol content in the fuel. Consequently, high gas generation rates associated with ethanol-blended fuels may amplify the risk of vapor intrusion of CH4 and BTEX into basements or other subsurface structures that may be nearby. A comprehensive and comparative study on the fate of higher concentration ethanol-blended fuels in the subsurface has not been conducted to date. The present study focuses on determining the fate of ethanol blended fuels in the subsurface through a series of controlled and instrumented laboratory column experiments. The experiments compare the behavior of pure gasoline with that of ethanol-blended fuels for different soil types (sand and silt) in columns 2 meters tall and 30cm in diameter. The column experiments focus on the quantification of gas generation by volatilization and biodegradation and 1-D vertical fate and transport of CO2, CH4, benzene and toluene through the vadose zone. The fuel blends have been injected into the lower third of the columns and gas composition and fluxes within the column are being monitored over time. The goal of this study is to contribute to the scientific foundation that will allow gauging the level of risk and the need for remediation at fuel spill sites with higher ethanol blends.

  18. A porewater-based stable isotope approach for the investigation of subsurface hydrological processes

    NASA Astrophysics Data System (ADS)

    Garvelmann, J.; Külls, C.; Weiler, M.

    2012-02-01

    Predicting and understanding subsurface flowpaths is still a crucial issue in hydrological research. We present an experimental approach to reveal present and past subsurface flowpaths of water in the unsaturated and saturated zone. Two hillslopes in a humid mountainous catchment have been investigated. The H2O(liquid) - H2O(vapor) equilibration laser spectroscopy method was used to obtain high resolution δ2H vertical depth profiles of pore water at various points along two fall lines of a pasture hillslope in the southern Black Forest, Germany. The Porewater-based Stable Isotope Profile (PSIP) approach was developed to use the integrated information of several vertical depth profiles of deuterium along transects at the hillslope. Different shapes of depth profiles were observed in relation to hillslope position. The statistical variability (inter-quartile range and standard deviation) of each profile was used to characterize different types of depth profiles. The profiles upslope or with a weak affinity for saturation as indicated by a low topographic wetness index preserve the isotopic input signal by precipitation with a distinct seasonal variability. These observations indicate mainly vertical movement of soil water in the upper part of the hillslope before sampling. The profiles downslope or at locations with a strong affinity for saturation do not show a similar seasonal isotopic signal. The input signal is erased in the foothills and a large proportion of pore water samples are close to the isotopic values of δ2H in streamwater during base flow conditions indicating the importance of the groundwater component in the catchment. Near the stream indications for efficient mixing of water from lateral subsurface flow paths with vertical percolation are found.

  19. A porewater - based stable isotope approach for the investigation of subsurface hydrological processes

    NASA Astrophysics Data System (ADS)

    Garvelmann, J.; Külls, C.; Weiler, M.

    2011-10-01

    Predicting and understanding subsurface flowpaths is still a crucial issue in hydrological research. We present an experimental approach to reveal present and past subsurface flowpaths of water in the unsaturated and saturated zone. Two hillslopes in a humid moutainous catchment have been investigated. The H2O(liquid) - H2O(vapor) equilibration laser spectroscopy method was used to obtain high resolution δ2H vertical depth profiles of porewater at various points along a fall line of a pasture hillslope in the southern Black Forest, Germany. The Porewater Stable Isotope Profile (PSIP) approach was developed to use the integrated information of several vertical depth profiles of deuterium along two transects at the hillslopes. Different shapes of depth profiles were observed in relation to hillslope position. The statistical variability (inter-quartile range and standard deviation) of each profile was used to characterize different types of depth profiles. The profiles upslope or with a weak affinity for saturation as indicated by a low topographic wetness index preserve the isotopic input signal by precipitation with a distinct seasonal variability. These observations indicate mainly vertical movement of soil water in the upper part of the hillslope before sampling. The profiles downslope or at locations with a strong affinity for saturation do not show a similar seasonal isotopic signal. The input signal is erased in the foothills and a large proportion of pore water samples are close to the isotopic values of δ2H in stream water during base flow. Near the stream indications for efficient mixing of water from lateral subsurface flow paths with vertical percolation are found.

  20. Simulating transient subsurface thermal fields in support of geomorphic process research

    NASA Astrophysics Data System (ADS)

    Gruber, S.; Endrizzi, S.; Gubler, S.

    2012-12-01

    The analysis or up-scaling of thermal control on weathering, erosion or transport phenomena usually requires the ability to simulate subsurface thermal fields as a function of time, depth, topographic position or material type. Using air temperature or temperatures measured at only one location usually does not suffice in this context. Three examples will motivate this presentation: (a) frost cracking investigated by outdoor monitoring of acoustic emissions, temperature and moisture in rock, (b) rock fall triggering investigated by numerical experiments, and (c) kinematics of permafrost slopes and rock glaciers investigated by distributed continuous GPS and simulated subsurface conditions. Based on the data needs of these examples, a simulation strategy and system that has evolved from permafrost modeling over the last decade is introduced. The basic structure of the models used is shown and current success and challenges in simulations discussed. The sparse data available for validation as well as the strong extrapolations involved necessitate an increasing attention to model uncertainty and its effect on the products or conclusions based on simulated data.

  1. Automated permanent resistivity monitoring of charge and discharge processes of subsurface aquifer at the Membach station, Belgium

    NASA Astrophysics Data System (ADS)

    Deceuster, J.; Kaufmann, O.; van Camp, M. J.; Lecocq, T.

    2010-12-01

    Permanent monitoring of changes in soil properties is of increasing interest in many engineering applications such as management of groundwater contamination, landslide and sinkhole risks prevention, detection of saline water intrusion, comprehension of charge and discharge processes of subsurface aquifer. As geophysical investigations allow detecting contrasts in physical properties of the subsurface, field and lab experiments have been conducted for a few years to assess the reliability of these methods to monitor temporal changes in soil properties. Among the methods available, DC resistivity tomography is recognized as one of the most promising techniques. In order to assess the efficiency of electrical resistivity in monitoring charge and discharge processes of subsurface aquifer, and also to better model hydrological effects on the gravity measurements, an on-going field experiment is conducted at the Membach station located in the eastern part of Belgium. This geophysical station is equipped with an accelerometer, seismometers and a superconducting gravimeter, installed at the end of a 130 m long tunnel excavated in a low-porosity argillaceous sandstone mount at 48.5 m depth. Continuous gravimetric observations have been taken since August 1995. Since 2004 rainfall and soil moisture changes are measured in situ. In July 2010, an automated permanent geoelectrical acquisition system was installed to monitor subsurface resistivity variations during a test period of about 6 months. The aim of this experiment is to better understand charge and discharge processes of the subsurface aquifer, which are expected to be mainly due to rainfall variations. This aquifer is localized at the top of the weathered bedrock at a depth of 4 to 5 meters. The acquisition system consists in a straight profile of 48 buried electrodes (with a 2 meters spacing) connected to a Syscal R1 resistivimeter which is automatically controlled by a computer. Resistivity measurements are taken

  2. Pore-Scale Process Coupling and Effective Surface Reaction Rates in Heterogeneous Subsurface Materials

    SciTech Connect

    Liu, Chongxuan; Liu, Yuanyuan; Kerisit, Sebastien N.; Zachara, John M.

    2015-09-01

    This manuscript provides a review of pore-scale researches in literature including experimental and numerical approaches, and scale-dependent behavior of geochemical and biogeochemical reaction rates in heterogeneous porous media. A mathematical equation that can be used to predict the scale-dependent behavior of geochemical reaction rates in heterogeneous porous media has been derived. The derived effective rate expression explicitly links the effective reaction rate constant to the intrinsic rate constant, and to the pore-scale variations in reactant concentrations in porous media. Molecular simulations to calculate the intrinsic rate constants were provided. A few examples of pore-scale simulations were used to demonstrate the application of the equation to calculate effective rate constants in heterogeneous materials. The results indicate that the deviation of effective rate constant from the intrinsic rate in heterogeneous porous media is caused by the pore-scale distributions of reactants and their correlation, which are affected by the pore-scale coupling of reactions and transport.

  3. Effect of sulfidogenesis cycling on the biogeochemical process in arsenic-enriched aquifers in the Lanyang Plain of Taiwan: Evidence from a sulfur isotope study

    NASA Astrophysics Data System (ADS)

    Kao, Yu-Hsuan; Liu, Chen-Wuing; Wang, Pei-Ling; Liao, Chung-Min

    2015-09-01

    This study evaluated the biogeochemical interactions between arsenic (As) and sulfur (S) in groundwater to understand the natural and anthropogenic influences of S redox processes on As mobilization in the Lanyang Plain, Taiwan. Cl- and the sulfate isotopic composition (δ34S[SO4]) were selected as conservative tracers. River water and saline seawater were considered as end members in the binary mixing model. Thirty-two groundwater samples were divided into four types of groundwater (I, pyrite-oxidation; II, iron- and sulfate-reducing; III, sulfate-reducing; and IV, anthropogenic and others). The binary mixing model coupled with discriminant analysis was applied to yield a classification with 97% correctness, indicating that the DO/ORP values and δ34S[SO4] and Fe2+ concentrations are effective redox-sensitive indicators. Type I groundwater is mostly located in a mountainous recharge area where pyrite oxidation is the major geochemical process. A high 18O enrichment factor (ε[SO4-H2O]) and high 34S enrichment factor (ε34S[FeS2-SO4]) indicate that disproportionation and dissimilatory sulfate reduction are both involved in Type II and Type III groundwater. The process of bacterial sulfate reduction may coprecipitate and sequester As, a mechanism that is unlikely to occur in Type II groundwater. The presence of high As and Fe2+ concentrations and enriched δ34S[SO4] in Type II groundwater suggest that biogeochemical reactions occurred under anaerobic conditions. The reductive dissolution of As-bearing Fe oxyhydroxides together with microbial disproportionation of sulfur explains the substantial correlations among the high As concentration and enriched δ34S[SO4] and Fe2+ concentrations in the iron- and sulfate-reducing zone (Type II). The As concentration in Type III groundwater (sulfate-reducing) is lower than that in Type II groundwater because of bacterial sulfate reduction and coprecipitation with As. Furthermore, the dissolution of sulfate minerals is not the

  4. Nontoxic chemical process for in situ permeability enhancement and accelerated decontamination of fine-grain subsurface sediments

    DOEpatents

    Kansa, Edward J.; Wijesinghe, Ananda M.; Viani, Brian E.

    1997-01-01

    The remediation of heterogeneous subsurfaces is extremely time consuming and expensive with current and developing technologies. Although such technologies can adequately remove contaminants in the high hydraulic conductivity, coarse-grained sediments, they cannot access the contaminated low hydraulic conductivity fine-grained sediments. The slow bleed of contaminants from the fine-grained sediments is the primary reason why subsurface remediation is so time-consuming and expensive. This invention addresses the problem of remediating contaminated fine-grained sediments. It is intended that, in the future, a heterogeneous site be treated by a hybrid process that first remediates the high hydraulic conductivity, coarse-grained sediments, to be followed by the process, described in this invention, to treat the contaminated low hydraulic conductivity fine-grained sediments. The invention uses cationic flocculents and organic solvents to collapse the swelling negative double layer surrounding water saturated clay particles, causing a flocculated, cracked clay structure. The modification of the clay fabric in fine-grained sediments dramatically increases the hydraulic conductivity of previously very tight clays many orders of magnitude.

  5. Nontoxic chemical process for in situ permeability enhancement and accelerated decontamination of fine-grain subsurface sediments

    DOEpatents

    Kansa, E.J.; Wijesinghe, A.M.; Viani, B.E.

    1997-01-14

    The remediation of heterogeneous subsurfaces is extremely time consuming and expensive with current and developing technologies. Although such technologies can adequately remove contaminants in the high hydraulic conductivity, coarse-grained sediments, they cannot access the contaminated low hydraulic conductivity fine-grained sediments. The slow bleed of contaminants from the fine-grained sediments is the primary reason why subsurface remediation is so time-consuming and expensive. This invention addresses the problem of remediating contaminated fine-grained sediments. It is intended that, in the future, a heterogeneous site be treated by a hybrid process that first remediates the high hydraulic conductivity, coarse-grained sediments, to be followed by the process, described in this invention, to treat the contaminated low hydraulic conductivity fine-grained sediments. The invention uses cationic flocculants and organic solvents to collapse the swelling negative double layer surrounding water saturated clay particles, causing a flocculated, cracked clay structure. The modification of the clay fabric in fine-grained sediments dramatically increases the hydraulic conductivity of previously very tight clays many orders of magnitude. 8 figs.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  7. Incorporating 3-D Subsurface Hydrologic Processes within the Community Land Surface Model (CLM): Coupling PFLOTRAN and CLM

    NASA Astrophysics Data System (ADS)

    Bisht, G.; Mills, R. T.; Hoffman, F. M.; Thornton, P. E.; Lichtner, P. C.; Hammond, G. E.

    2011-12-01

    Numerous studies have shown a positive soil moisture-rainfall feedback through observational data, as well as, modeling studies. Spatial variability of topography, soils, and vegetation play a significant role in determining the response of land surface states (soil moisture) and fluxes (runoff, evapotranspirtiaon); but their explicit accounting within Land Surface Models (LSMs) is computa- tionally expensive. Additionally, anthropogenic climate change is altering the hydrologic cycle at global and regional scales. Characterizing the sensitivity of groundwater recharge is critical for understanding the effects of climate change on water resources. In order to explicitly represent lateral redistribution of soil moisture and unified treatment of the unsaturated-saturated zone in the subsurface within the CLM, we propose coupling PFLOTRAN and CLM. PFLOTRAN is a parallel multiphase-multicomponent subsurface reactive flow and transport code for modeling subsurface processes and has been devel- oped under a DOE SciDAC-2 project. PFLOTRAN is written in Fortran 90 using a modular, object-oriented approach. PFLOTRAN utilizes fully implicit time-stepping and is built on top of the Portable, Extensible Toolkit for Scientific Computation (PETSc). The PFLOTRAN model is capable of simulating fluid flow through porous media with fluid phases of air, water, and supercritical CO2. PFLOTRAN has been successfully employed on up to 131,072 cores on Jaguar, the massively parallel Cray XT4/XT5 at ORNL, for problems composed of up to 2 billion degrees of freedom. In this work, we will present a strategy of coupling the two models, CLM and PFLOTRAN, along with a few preliminary results obtained from the coupled model.

  8. Geomicrobiology and Metagenomics of Terrestrial Deep Subsurface Microbiomes.

    PubMed

    Itävaara, M; Salavirta, H; Marjamaa, K; Ruskeeniemi, T

    2016-01-01

    Fractures in the deep subsurface of Earth's crust are inhabited by diverse microbial communities that participate in biogeochemical cycles of the Earth. Life on Earth, which arose c. 3.5-4.0 billion years ago, reaches down at least 5 km in the crust. Deep mines, caves, and boreholes have provided scientists with opportunities to sample deep subsurface microbiomes and to obtain information on the species diversity and functions. A wide variety of bacteria, archaea, eukaryotes, and viruses are now known to reside in the crust, but their functions are still largely unknown. The crust at different depths has varying geological composition and hosts endemic microbiomes accordingly. The diversity is driven by geological formations and gases evolving from deeper depths. Cooperation among different species is still mostly unexplored, but viruses are known to restrict density of bacterial and archaeal populations. Due to the complex growth requirements of the deep subsurface microbiomes, the new knowledge about their diversity and functions is mostly obtained by molecular methods, eg, meta'omics'. Geomicrobiology is a multidisciplinary research area combining disciplines from geology, mineralogy, geochemistry, and microbiology. Geomicrobiology is concerned with the interaction of microorganisms and geological processes. At the surface of mineralogical or rock surfaces, geomicrobial processes occur mainly under aerobic conditions. In the deep subsurface, however, the environmental conditions are reducing and anaerobic. The present chapter describes the world of microbiomes in deep terrestrial geological environments as well as metagenomic and metatranscriptomic methods suitable for studies of these enigmatic communities. PMID:26917241

  9. Geomicrobiology and Metagenomics of Terrestrial Deep Subsurface Microbiomes.

    PubMed

    Itävaara, M; Salavirta, H; Marjamaa, K; Ruskeeniemi, T

    2016-01-01

    Fractures in the deep subsurface of Earth's crust are inhabited by diverse microbial communities that participate in biogeochemical cycles of the Earth. Life on Earth, which arose c. 3.5-4.0 billion years ago, reaches down at least 5 km in the crust. Deep mines, caves, and boreholes have provided scientists with opportunities to sample deep subsurface microbiomes and to obtain information on the species diversity and functions. A wide variety of bacteria, archaea, eukaryotes, and viruses are now known to reside in the crust, but their functions are still largely unknown. The crust at different depths has varying geological composition and hosts endemic microbiomes accordingly. The diversity is driven by geological formations and gases evolving from deeper depths. Cooperation among different species is still mostly unexplored, but viruses are known to restrict density of bacterial and archaeal populations. Due to the complex growth requirements of the deep subsurface microbiomes, the new knowledge about their diversity and functions is mostly obtained by molecular methods, eg, meta'omics'. Geomicrobiology is a multidisciplinary research area combining disciplines from geology, mineralogy, geochemistry, and microbiology. Geomicrobiology is concerned with the interaction of microorganisms and geological processes. At the surface of mineralogical or rock surfaces, geomicrobial processes occur mainly under aerobic conditions. In the deep subsurface, however, the environmental conditions are reducing and anaerobic. The present chapter describes the world of microbiomes in deep terrestrial geological environments as well as metagenomic and metatranscriptomic methods suitable for studies of these enigmatic communities.

  10. Modelling Water Flow, Heat Transport, Soil Freezing and Thawing, and Snow Processes in a Clayey, Subsurface Drained Agricultural Field

    NASA Astrophysics Data System (ADS)

    Warsta, L.; Turunen, M.; Koivusalo, H. J.; Paasonen-Kivekäs, M.; Karvonen, T.; Taskinen, A.

    2012-12-01

    Simulation of hydrological processes for the purposes of agricultural water management and protection in boreal environment requires description of winter time processes, including heat transport, soil freezing and thawing, and snow accumulation and melt. Finland is located north of the latitude of 60 degrees and has one third to one fourth of the total agricultural land area (2.3 milj. ha) on clay soils (> 30% of clay). Most of the clayey fields are subsurface drained to provide efficient drainage and to enable heavy machines to operate on the fields as soon as possible after the spring snowmelt. Generation of drainflow and surface runoff in cultivated fields leads to nutrient and sediment load, which forms the major share of the total load reaching surface waters at the national level. Water, suspended sediment, and soluble nutrients on clayey field surface are conveyed through the soil profile to the subsurface drains via macropore pathways as the clayey soil matrix is almost impermeable. The objective of the study was to develop the missing winter related processes into the FLUSH model, including soil heat transport, snow pack simulation and the effects of soil freezing and thawing on the soil hydraulic conductivity. FLUSH is an open source (MIT license), distributed, process-based model designed to simulate surface runoff and drainflow in clayey, subsurface drained agricultural fields. 2-D overland flow is described with the diffuse wave approximation of the Saint Venant equations and 3-D subsurface flow with a dual-permeability model. Both macropores and soil matrix are simulated with the Richards equation. Soil heat transport is described with a modified 3-D convection-diffusion equation. Runoff and groundwater data was available from different periods from January 1994 to April 1999 measured in a clayey, subsurface drained field section (3.6 ha) in southern Finland. Soil temperature data was collected in two locations (to a depth of 0.8 m) next to the

  11. Mapping pan-Arctic CH4 emissions using an adjoint method by integrating process-based wetland and lake biogeochemical models and atmospheric CH4 concentrations

    NASA Astrophysics Data System (ADS)

    Tan, Z.; Zhuang, Q.; Henze, D. K.; Frankenberg, C.; Dlugokencky, E. J.; Sweeney, C.; Turner, A. J.

    2015-12-01

    Understanding CH4 emissions from wetlands and lakes are critical for the estimation of Arctic carbon balance under fast warming climatic conditions. To date, our knowledge about these two CH4 sources is almost solely built on the upscaling of discontinuous measurements in limited areas to the whole region. Many studies indicated that, the controls of CH4 emissions from wetlands and lakes including soil moisture, lake morphology and substrate content and quality are notoriously heterogeneous, thus the accuracy of those simple estimates could be questionable. Here we apply a high spatial resolution atmospheric inverse model (nested-grid GEOS-Chem Adjoint) over the Arctic by integrating SCIAMACHY and NOAA/ESRL CH4 measurements to constrain the CH4 emissions estimated with process-based wetland and lake biogeochemical models. Our modeling experiments using different wetland CH4 emission schemes and satellite and surface measurements show that the total amount of CH4 emitted from the Arctic wetlands is well constrained, but the spatial distribution of CH4 emissions is sensitive to priors. For CH4 emissions from lakes, our high-resolution inversion shows that the models overestimate CH4 emissions in Alaskan costal lowlands and East Siberian lowlands. Our study also indicates that the precision and coverage of measurements need to be improved to achieve more accurate high-resolution estimates.

  12. An approach to quantify sources, seasonal change, and biogeochemical processes affecting metal loading in streams: Facilitating decisions for remediation of mine drainage

    USGS Publications Warehouse

    Kimball, B.A.; Runkel, R.L.; Walton-Day, K.

    2010-01-01

    Historical mining has left complex problems in catchments throughout the world. Land managers are faced with making cost-effective plans to remediate mine influences. Remediation plans are facilitated by spatial mass-loading profiles that indicate the locations of metal mass-loading, seasonal changes, and the extent of biogeochemical processes. Field-scale experiments during both low- and high-flow conditions and time-series data over diel cycles illustrate how this can be accomplished. A low-flow experiment provided spatially detailed loading profiles to indicate where loading occurred. For example, SO42 - was principally derived from sources upstream from the study reach, but three principal locations also were important for SO42 - loading within the reach. During high-flow conditions, Lagrangian sampling provided data to interpret seasonal changes and indicated locations where snowmelt runoff flushed metals to the stream. Comparison of metal concentrations between the low- and high-flow experiments indicated substantial increases in metal loading at high flow, but little change in metal concentrations, showing that toxicity at the most downstream sampling site was not substantially greater during snowmelt runoff. During high-flow conditions, a detailed temporal sampling at fixed sites indicated that Zn concentration more than doubled during the diel cycle. Monitoring programs must account for diel variation to provide meaningful results. Mass-loading studies during different flow conditions and detailed time-series over diel cycles provide useful scientific support for stream management decisions.

  13. Improving predictions of large scale soil carbon dynamics: Integration of fine-scale hydrological and biogeochemical processes, scaling, and benchmarking

    NASA Astrophysics Data System (ADS)

    Riley, W. J.; Dwivedi, D.; Ghimire, B.; Hoffman, F. M.; Pau, G. S. H.; Randerson, J. T.; Shen, C.; Tang, J.; Zhu, Q.

    2015-12-01

    Numerical model representations of decadal- to centennial-scale soil-carbon dynamics are a dominant cause of uncertainty in climate change predictions. Recent attempts by some Earth System Model (ESM) teams to integrate previously unrepresented soil processes (e.g., explicit microbial processes, abiotic interactions with mineral surfaces, vertical transport), poor performance of many ESM land models against large-scale and experimental manipulation observations, and complexities associated with spatial heterogeneity highlight the nascent nature of our community's ability to accurately predict future soil carbon dynamics. I will present recent work from our group to develop a modeling framework to integrate pore-, column-, watershed-, and global-scale soil process representations into an ESM (ACME), and apply the International Land Model Benchmarking (ILAMB) package for evaluation. At the column scale and across a wide range of sites, observed depth-resolved carbon stocks and their 14C derived turnover times can be explained by a model with explicit representation of two microbial populations, a simple representation of mineralogy, and vertical transport. Integrating soil and plant dynamics requires a 'process-scaling' approach, since all aspects of the multi-nutrient system cannot be explicitly resolved at ESM scales. I will show that one approach, the Equilibrium Chemistry Approximation, improves predictions of forest nitrogen and phosphorus experimental manipulations and leads to very different global soil carbon predictions. Translating model representations from the site- to ESM-scale requires a spatial scaling approach that either explicitly resolves the relevant processes, or more practically, accounts for fine-resolution dynamics at coarser scales. To that end, I will present recent watershed-scale modeling work that applies reduced order model methods to accurately scale fine-resolution soil carbon dynamics to coarse-resolution simulations. Finally, we

  14. 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

    NASA Astrophysics Data System (ADS)

    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 × 106 m3 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

  15. 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.

    PubMed

    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

  16. Biosphere frontiers of subsurface life in the sedimented hydrothermal system of Guaymas Basin.

    PubMed

    Teske, Andreas; Callaghan, Amy V; LaRowe, Douglas E

    2014-01-01

    Temperature is one of the key constraints on the spatial extent, physiological and phylogenetic diversity, and biogeochemical function of subsurface life. A model system to explore these interrelationships should offer a suitable range of geochemical regimes, carbon substrates and temperature gradients under which microbial life can generate energy and sustain itself. In this theory and hypothesis article, we make the case for the hydrothermally heated sediments of Guaymas Basin in the Gulf of California as a suitable model system where extensive temperature and geochemical gradients create distinct niches for active microbial populations in the hydrothermally influenced sedimentary subsurface that in turn intercept and process hydrothermally generated carbon sources. We synthesize the evidence for high-temperature microbial methane cycling and sulfate reduction at Guaymas Basin - with an eye on sulfate-dependent oxidation of abundant alkanes - and demonstrate the energetic feasibility of these latter types of deep subsurface life in previously drilled Guaymas Basin locations of Deep-Sea Drilling Project 64.

  17. Biogeochemical cycling and remote sensing

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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 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 basins.

  19. Modeling study on the surface morphology evolution during removing the optics surface/subsurface damage using atmospheric pressure plasma processing

    NASA Astrophysics Data System (ADS)

    Xin, Qiang; Su, Xing; Wang, Bo

    2016-09-01

    Plasma processing has been widely reported as an effective tool in relieving or removing surface/subsurface damage induced by previous mechanical machining process. However, the surface morphology evolution during removing the damage using plasma processing is rarely reported. In this research, this procedure is studied based on experiments and robust numerical models developed on the basis of Level Set Method (LSM). Even if some unique properties of plasma etching are observed, such as particle redistribution, the dominant role of isotropic etching of plasma processing is verified based on experiments and 2D LSM simulations. With 2D LSM models, the damage removal process under various damage characteristics is explored in detail. Corresponding peak-to-valley roughness evolution is investigated as well. Study on morphology evolution is also conducted through the comparison between experiments and 3D LSM computations. The modeling results and experiments show good agreement with each other. The trends of simulated roughness evolution agree with the experiments as well. It is revealed that the plasma processing may end up with a planar surface depending on the damage characteristics. The planarization procedure can be divided into four parts: crack opening and pit formation; pit coalescing and shallow pits subsumed by deep ones; morphology duplicate etching; and finally a planar and damage free surface.

  20. Best Practice -- Subsurface Investigations

    SciTech Connect

    Clark Scott

    2010-03-01

    These best practices for Subsurface Survey processes were developed at the Idaho National Laboratory (INL) and later shared and formalized by a sub-committee, under the Electrical Safety Committee of EFCOG. The developed best practice is best characterized as a Tier II (enhanced) survey process for subsurface investigations. A result of this process has been an increase in the safety and lowering of overall cost, when utility hits and their related costs are factored in. The process involves improving the methodology and thoroughness of the survey and reporting processes; or improvement in tool use rather than in the tools themselves. It is hoped that the process described here can be implemented at other sites seeking to improve their Subsurface Investigation results with little upheaval to their existing system.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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

  3. Biogeochemical and hydrological processes controlling the transport and fate of 1,2-dibromoethane (EDB) in soil and ground water, central Florida

    USGS Publications Warehouse

    Katz, Brian G.

    1993-01-01

    Widespread contamination of ground water in central Florida by 1,2-dibromoethane (EDB) has resulted because of its heavy usage as a soil fumigant during a 20-year period, its relatively high aqueous solubility, and the low sorption capacity of the highly permeable sandy soils lacking organic matter. Two models were used to improve understanding of biogeochemical and hydrological processes that control the transport and fate of EDB in soil and ground water. First, a mass-balance model was developed to estimate the max-imum concentration of EDB in ground water resulting from known application rates of EDB. Key processes that were quantified in the model included volatilization, diffusion of EDB vapor in soils, partitioning between aqueous and gaseous phases, sorption of EDB vapor on organic carbon and soil particles, chemical and biological degradation reactions, and nonreversible binding of EDB to soils. Model calculations using an EDB half-life of 0.65 year closely reproduced the maximum observed concentrations in ground water, 37 and 0.22 micrograms per liter, at downgradient sites in two study areas in central Florida. Maximum concentrations of EDB in ground water also were estimated in a second model that incorporated an analytical solution to the three-dimensional advection-dispersion equation for instantaneous point sources of EDB entering the flow systems in the two study areas. The model used an EDB half-life of 0.65 year (obtained from the mass-balance calculations), mean ground-water flow velocities of 0.6 to 1 meter per day, coefficients of longitudinal hydro-dynamic dispersion of 0.6 to 1.0 square meter per day, and coefficients of transverse hydrodynamic dispersion of 0.1 square meter per day. Peak concentrations of EDB in ground water calculated from the analytical model agreed closely with observed peak concentrations measured from 1983 through 1987.

  4. DayCent-Chem Simulations of Ecological and Biogeochemical Processes of Eight Mountain Ecosystems in the United States

    USGS Publications Warehouse

    Hartman, Melannie D.; Baron, Jill S.; Clow, David W.; Creed, Irena F.; Driscoll, Charles T.; Ewing, Holly A.; Haines, Bruce D.; Knoepp, Jennifer; Lajtha, Kate; Ojima, Dennis S.; Parton, William J.; Renfro, Jim; Robinson, R. Bruce; Van Miegroet, Helga; Weathers, Kathleen C.; Williams, Mark W.

    2009-01-01

    deposition as a result of dry and fog inputs. The uncertainties related to weathering reactions, deposition, soil cation exchange capacity, and groundwater contributions influenced how well the simulated acid neutralizing capacity (ANC) and pH estimates compared to observed values. Daily discharge was well represented by the model for most sites. The chapters of this report describe the parameterization for each site and summarize model results for ecosystem variables, stream discharge, and stream chemistry. This intersite comparison exercise provided insight about important and possibly not well understood processes.

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

    NASA Astrophysics Data System (ADS)

    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.

  6. Strong Seasonality of Biogeochemical Characteristics and Source Regions in Permafrost Watersheds

    NASA Astrophysics Data System (ADS)

    Douglas, T. A.

    2015-12-01

    High latitude watersheds experience a dramatic seasonality of up to nine months of cold, snow covered winter and a warm, bright, summer. Spring melt runoff is a dramatic two to three week period when up to 75% of the yearly precipitation runs off. Identifying sources and measuring fluxes of compounds out of Arctic rivers is difficult in large rivers because they represent the combined effect of innumerable plot-scale melt water sources, each coming from different soil and vegetation types, each experiencing a slightly different melt timing and evolution. Numerous studies have shown spring melt is characterized by an ionic pulse of solutes, dissolved organic carbon and other nutrients (ammonium, phosphate and nitrate) leached by snow melt water from surface vegetation and soils. Summer and fall flows are comprised largely of shallow to deepening sources from a downwardly expanding seasonally thawed ("active") layer. In late summer flowpaths deepen and the biogeochemical composition of surface waters may be sourced from an increasing mineral weathering zone representing landscape scale soil processes. The watershed biogeochemical response to precipitation may also yield insight into subsurface permafrost geomorphological characteristics and flowpaths through water tracks or other small depressions. Winter processes are the least studied or understood but overflow ice ("aufeis") provides access to deep, old waters. The deeper snow pack in depressions can provide protection against winter cold and feed back to deeper summer season thaw. This presentation will focus on using water stable isotopes, major ion concentrations, trace metals, nutrients, and permafrost delineation to identify biogeochemical sources in watersheds draining continuous and discontinuous permafrost in Alaska. Biogeochemical processes associated with scaling, meteorology, and climate warming will be discussed.

  7. Transport of contaminants from energy-process-waste leachates through subsurface soils and soil components: laboratory experiments

    SciTech Connect

    Wangen, L.E.; Stallings, E.A.; Walker, R.D.

    1982-08-01

    The subsurface transport and attenuation of inorganic contaminants common to a variety of energy process waste leachates are being studied using laboratory column methods. Anionic species currently being emphasized are As, B, Mo, and Se. Transport of the cations Cd and Ni is also being studied. The solid adsorbents consist of three soil mineral components (silica sand, kaolinite, and goethite), and four subsurface soils (a dunal sand, an oxidic sandy clay loam, an acidic clay loam, and an alkaline clay loam). Breakthrough patterns of these species from packed soil columns are followed by monitoring eluent concentrations vs time under carefully controlled laboratory conditions. This report describes the experimental methods being used, the results of preliminary batch adsorption studies, and the results of column experiments completed through calendar year 1981. Using column influent concentrations of about 10 mg/l, adsorption (mmoles/100 g) has been determined from the eluent volume corresponding to 50% breakthrough. On silica sand, kaolinite, dunal sand, and goethite, respectively, these are 2.0 x 10/sup -4/, 0.020, 0.013, and 0.31 for cadmium, 4.4 x 10/sup -4/, 0.039, 0.020, and 0.98 for nickel. On kaolinite, dunal sand, and goethite, respectively, adsorption values (mmoles/100 g) are As (0.24, 0.019, and 20.5), B (0.041, 0.0019, and 1.77), Mo (0.048, 0.0010, and 5.93), and Se (0.029, 0.00048, and 1.30). Arsenic is the most highly adsorbed contaminant species and goethite has the largest adsorption capacity of the adsorbents.

  8. Biogeochemical processes underpin ecosystem services

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Elemental cycling is critical to the function of ecosystems and delivery of key ecosystem services because many of these elements are essential nutrients or detrimental toxicants that directly affect the health of organisms and ecosystems. A team of authors from North Carolina State University and ...

  9. Cretaceous-Palaeogene experiments in Biogeochemical Resilience

    NASA Astrophysics Data System (ADS)

    Penman, D. E.; Henehan, M. J.; Hull, P. M.; Planavsky, N.; Schmidt, D. N.; Rae, J. W. B.; Thomas, E.; Huber, B. T.

    2015-12-01

    Human activity is altering biogeochemical cycles in the ocean. While ultimately anthropogenic forcings may be brought under control, it is still unclear whether tipping points may exist beyond which human-induced changes to biogeochemical cycles become irreversible. We use the Late Cretaceous and the Cretaceous-Palaeogene (K-Pg) boundary interval as an informative case study. Over this interval, two carbon cycle perturbations (gradual flood basalt volcanism and abrupt bolide impact) occurred within a short time window, allowing us to investigate the resilience of biogeochemical cycles to different pressures applied to the same initial boundary conditions on very different time scales. We demonstrate that relatively gradual emission of CO2 from the Deccan large igneous province was efficiently mitigated within the limits of existing biogeochemical processes. However, the rapid extinction of pelagic calcifying organisms at the K-Pg boundary due to the Chicxulub bolide impact had more profound effects, and caused lasting (> 1 million years) changes to biogeochemical cycles. By combining sedimentological observations with boron isotope-based pH reconstructions over these events, we document two potentially useful partial analogues for best and worst case scenarios for anthropogenic global change. We suggest that if current ocean acidification results in the mass extinction of marine pelagic calcifiers, we may cause profound changes to the Earth system that will persist for 100,000s to millions of years.

  10. Spatio-temporal dynamics of biogeochemical processes and air-sea CO2 fluxes in the Western English Channel based on two years of FerryBox deployment

    NASA Astrophysics Data System (ADS)

    Marrec, P.; Cariou, T.; Latimier, M.; Macé, E.; Morin, P.; Vernet, M.; Bozec, Y.

    2014-12-01

    From January 2011 to January 2013, a FerryBox system was installed on a Voluntary Observing Ship (VOS), which crossed the Western English Channel (WEC) between Roscoff (France) and Plymouth (UK) up to 3 times a day. The FerryBox continuously measured sea surface temperature (SST), sea surface salinity (SSS), dissolved oxygen (DO), fluorescence and partial pressure of CO2 (from April 2012) along the ferry track. Sensors were calibrated based on 714 bimonthly surface samplings with precisions of 0.016 for SSS, 3.3 μM for DO, 0.40 μg L- 1 for Chlorophyll-a (Chl-a) (based on fluorescence measurements) and 5.2 μatm for pCO2. Over the 2 years of deployment (900 crossings), we reported 9% of data lost due to technical issues and quality checked data was obtained to allow investigation of the dynamics of biogeochemical processes related to air-sea CO2 fluxes in the WEC. Based on this unprecedented high-frequency dataset, the physical structure of the WEC was assessed using SST anomalies and the presence of a thermal front was observed around the latitude 49.5°N, which divided the WEC in two main provinces: the seasonally stratified northern WEC (nWEC) and the all-year well-mixed southern WEC (sWEC). These hydrographical properties strongly influenced the spatial and inter-annual distributions of phytoplankton blooms, which were mainly limited by nutrients and light availability in the nWEC and the sWEC, respectively. Air-sea CO2 fluxes were also highly related to hydrographical properties of the WEC between late April and early September 2012, with the sWEC a weak source of CO2 to the atmosphere of 0.9 mmol m- 2 d- 1, whereas the nWEC acted as a sink for atmospheric CO2 of 6.9 mmol m- 2 d- 1. The study of short time-scale dynamics of air-sea CO2 fluxes revealed that an intense and short (less than 10 days) summer bloom in the nWEC contributed to 29% of the CO2 sink during the productive period, highlighting the necessity for high frequency observations in coastal

  11. 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.

    PubMed

    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

  12. Process for guidance, containment, treatment, and imaging in a subsurface environment utilizing ferro-fluids

    DOEpatents

    Moridis, George J.; Oldenburg, Curtis M.

    2001-01-01

    Disclosed are processes for monitoring and control of underground contamination, which involve the application of ferrofluids. Two broad uses of ferrofluids are described: (1) to control liquid movement by the application of strong external magnetic fields; and (2) to image liquids by standard geophysical methods.

  13. MICROBIAL PROCESSES AFFECTING MONITORED NATURAL ATTENUATION OF CONTAMINANTS IN THE SUBSURFACE

    EPA Science Inventory

    Among the alternatives considered for the remediation of soil and ground water at hazardous wastes sites are the use of natural processes to reduce or remove the contaminants of concern. Under favorable conditions, the use of natural attenuation can result in significant cost sa...

  14. Seasonal ERT monitoring of subsurface processes connected to freezing, thawing, snow accumulation and melt cycles

    NASA Astrophysics Data System (ADS)

    Krzeminska, Dominika; Starkloff, Torsten; Bloem, Esther; Stolte, Jannes

    2016-04-01

    For a better understanding of processes that influence snowmelt infiltration and runoff, and their consequences on soil erosion during spring periods, we established a long-term winter-spring ERT transect in the Gryteland catchment (Norway). The ERT transect is 71 m long, with 1 m spacing between the electrodes. It covers a depression with a north and south facing slope. The readings are collected once a week and, if needed, after a sudden change in weather conditions. Additionally, the soil transect is equipped with six TDR profiles, which register soil moisture and soil temperature every thirty minutes, at five depths (5, 10, 20, 30, 40 cm), for quantifying the ERT readings. The measurements performed during winter 2014/2015 gave promising results and showed the potential of ERT monitoring for understanding the soil thermal and hydraulic processes occurring during a winter and early spring. Moreover, there are visible differences in temporal trends and spatial variations in observed ERT patterns on the opposite facing slopes, which are of special interest. With the on-going experiment, we are aiming to understand the reoccurrence of the observed processes as well as to quantify soil moisture patterns. Herein, we would like to present the preliminary result of two ERT experiments (2014/2015 and 2015/2016) and discuss the advantages and limitations of our experiments. Moreover, we would like to stimulate the discussion about the potential of ERT for spatial and temporal monitoring of soil hydraulic and thermal processes and indirect measurements of soil water content.

  15. Particle methods for simulation of subsurface multiphase fluid flow and biogeological processes

    SciTech Connect

    Paul Meakin; Alexandre Tartakovsky; Tim Scheibe; Daniel Tartakovsky; Georgr Redden; Philip E. Long; Scott C. Brooks; Zhijie Xu

    2007-06-01

    A number of particle models that are suitable for simulating multiphase fluid flow and biogeological processes have been developed during the last few decades. Here we discuss three of them: a microscopic model - molecular dynamics; a mesoscopic model - dissipative particle dynamics; and a macroscopic model - smoothed particle hydrodynamics. Particle methods are robust and versatile, and it is relatively easy to add additional physical, chemical and biological processes into particle codes. However, the computational efficiency of particle methods is low relative to continuum methods. Multiscale particle methods and hybrid (particle–particle and particle–continuum) methods are needed to improve computational efficiency and make effective use of emerging computational capabilities. These new methods are under development.

  16. Subsurface sounders

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Airborne or spaceborne electromagnetic systems used to detect subsurface features are discussed. Data are given as a function of resistivity of ground material, magnetic permeability of free space, and angular frequency. It was noted that resistivities vary with the water content and temperature.

  17. Biogeochemical processes at the fringe of a landfill leachate pollution plume: potential for dissolved organic carbon, Fe(II), Mn(II), NH 4, and CH 4 oxidation

    NASA Astrophysics Data System (ADS)

    van Breukelen, Boris M.; Griffioen, Jasper

    2004-09-01

    Various redox reactions may occur at the fringe of a landfill leachate plume, involving oxidation of dissolved organic carbon (DOC), CH 4, Fe(II), Mn(II), and NH 4 from leachate and reduction of O 2, NO 3 and SO 4 from pristine groundwater. Knowledge on the relevance of these processes is essential for the simulation and evaluation of natural attenuation (NA) of pollution plumes. The occurrence of such biogeochemical processes was investigated at the top fringe of a landfill leachate plume (Banisveld, the Netherlands). Hydrochemical depth profiles of the top fringe were captured via installation of a series of multi-level samplers at 18, 39 and 58 m downstream from the landfill. Ten-centimeter vertical resolution was necessary to study NA within a fringe as thin as 0.5 m. Bromide appeared an equally well-conservative tracer as chloride to calculate dilution of landfill leachate, and its ratio to chloride was high compared to other possible sources of salt in groundwater. The plume fringe rose steadily from a depth of around 5 m towards the surface with a few meters in the period 1998-2003. The plume uplift may be caused by enhanced exfiltration to a brook downstream from the landfill, due to increased precipitation over this period and an artificial lowering of the water level of the brook. This rise invoked cation exchange including proton buffering, and triggered degassing of methane. The hydrochemical depth profile was simulated in a 1D vertical reactive transport model using PHREEQC-2. Optimization using the nonlinear optimization program PEST brought forward that solid organic carbon and not clay minerals controlled retardation of cations. Cation exchange resulted in spatial separation of Fe(II), Mn(II) and NH 4 fronts from the fringe, and thereby prevented possible oxidation of these secondary redox species. Degradation of DOC may happen in the fringe zone. Re-dissolution of methane escaped from the plume and subsequent oxidation is an explanation for absence

  18. The forensics of sub-surface processes on island volcanoes from integrated geodetic observations: results from Tenerife and Montserrat (Invited)

    NASA Astrophysics Data System (ADS)

    Gottsmann, J.

    2009-12-01

    Spatio-temporal variations in geodetic signals at active volcanoes provide important insight on governing subsurface processes. This contribution explores the phenomenology of volcanic unrest and eruptive activity from the perspective of both ground deformation and gravimetric investigations at an ocean island volcanic complex (Tenerife, Canary Islands) and an active andesitic arc volcano (Soufrière Hills volcano [SHV], Montserrat). Despite their marked differences in volcanic evolution and tectonic settings both volcanic systems show remarkable similarities in their subsurface processes. On Tenerife, during unrest in 2004-5, mass movement at depth was quantified by time-lapse gravimetric observations despite the absence of significant ground deformation. Shallow migration of hydrous fluids is identified as the main cause for the unrest marking the reactivation of the central volcanic complex after a century of quiescence. The combination of static and dynamic gravimetric data reveals a causality between the major structural building blocks of the island and the pattern of mass variations. Low density bodies underlie areas of maximum mass variations at the complex. Gravimetric data also indicate that the shallow plumbing system of the 3700 m tall Pico Teide/Pico Viejo composite volcano remained unaffected by the unrest. On Montserrat, time-lapse gravimetric data invoke the existence of a previously unrecognized fault zone beneath the centre of the island that is influenced by changes in stress distribution associated with volcanic activity at SHV. The fault zone either provides a trace for ground water flow or responds to a changed stress field via volcano-tectonic coupling with an elastic opening/closing of fractures. Continuous gravimetric (CG) data enabled the calibration of a new precision tidal model for the island resulting in a reduction of the signal-to-noise ratio by about one order of magnitude. Detided CG records reveal particular gravity perturbations

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

    SciTech Connect

    WANG,YIFENG; PAPENGUTH,HANS W.

    2000-05-04

    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.

  20. Residence time distributions in sinuosity-driven hyporheic zones and their biogeochemical effects

    NASA Astrophysics Data System (ADS)

    Gomez, Jesus D.; Wilson, John L.; Cardenas, M. Bayani

    2012-09-01

    Hyporheic exchange plays a key role in the biogeochemical evolution of water and in ecosystem functioning at the local, reach, and watershed scales. Residence time is a fundamental metric to describe the possible transformation taking place in this exchange zone. With this in mind, we use a simple conceptual model to explore the residence time distributions (RTDs) of sinuosity-driven hyporheic zones (HZs) and to discriminate the individual effect of sinuosity (σ), valley slope (Jx), hydraulic conductivity (K), aquifer dispersivity (αL), and the biogeochemical timescales (BTSs) that characterize the degradation of dissolved organic carbon in these hydrologic systems. We find that RTDs are characterized by one early mode and a late time power law behavior. For a given aquifer dispersivity, the shape of these distributions is stretched or compressed by changes in Jx, K, and σ, having a strong influence on the net biogeochemical transformations within the HZ. Using BTSs proposed in previous studies and sensitivity analyses, we show the potential of σ, Jx, and K to classify meander HZs as net sinks of nitrates or only modulators of the residence times in the subsurface where nitrate reduction is negligible. These findings can be used as predictive tools to quantify the potential of meanders as biogeochemical reactors at the watershed scale with the aid of remote sensing data and GIS processing techniques. These tools can guide experimental design, suggesting important locations to visit, sample, and/or instrument. Also, hyporheic restoration projects can use them for initial site selection and design of channel modifications.

  1. 129I/(127)I as a new environmental tracer or geochronometer for biogeochemical or hydrodynamic processes in the hydrosphere and geosphere: the central role of organo-iodine.

    PubMed

    Santschi, Peter H; Schwehr, Kathleen A

    2004-04-01

    Iodine is a biophilic element, with several short-lived isotopes (e.g. (131)I, t(1/2)=8 days), one long-lived isotope, (129)I (t(1/2)=15.6 million years) and one stable isotope, (127)I. The inventory of (129)I in surface environments has been overwhelmed by anthropogenic releases over the past 50 years. Iodine and its isotopes are important for a number of reasons: (1) The largest fraction of the short-term and long-term dose from accidental releases and fallout from atomic bomb tests was from iodine isotopes. (2) (129)I is one of the two long-lived nuclides with highest mobility in stored radioactive waste. (3) (129)I could provide the scientific community with a new geochemical tracer and new geochronological applications in environmental science. (4) A better assessment of iodine deficiency disorders, mineralization in exploration geochemistry, and the transfer of volatile organic greenhouse-active and ozone-destroying iodine species from the oceans to the atmosphere is needed. One of the most promising future applications for the (129)I/(127)I ratio is not only as a new geochronometer, but also as a new source tracer for terrestrial organic matter with ages of 50 years or less. This is especially attractive, since radiocarbon can be, at times, an ambiguous chronometer for the 50-year time-scale, whereas (129)I concentrations during this time are overwhelming previous levels by orders of magnitude. Iodine is to a significant extent involved in the cycle of organic matter in all surface environments. Its biophilic nature is demonstrated by a relative enrichment of iodine in seaweed and dissolved macromolecular organic matter. Because of the close coupling of iodine and organic carbon cycles, our understanding of the underlying molecular mechanisms of the processes regulating iodination reactions in aquatic systems is still limited. The binding of iodine by organic matter has the potential to modify the transport, bioavailability and transfer of iodine isotopes to

  2. Investigation of Integrated Subsurface Processing of Landfill Gas and Carbon Sequestration, Johnson County, Kansas

    SciTech Connect

    K. David Newell; Timothy R. Carr

    2007-03-31

    The Johnson County Landfill in Shawnee, KS is operated by Deffenbaugh Industries and serves much of metropolitan Kansas City. Refuse, which is dumped in large plastic-underlined trash cells covering several acres, is covered over with shale shortly after burial. The landfill waste, once it fills the cell, is then drilled by Kansas City LFG, so that the gas generated by anaerobic decomposition of the refuse can be harvested. Production of raw landfill gas from the Johnson County landfill comes from 150 wells. Daily production is approximately 2.2 to 2.5 mmcf, of which approximately 50% is methane and 50% is carbon dioxide and NMVOCs (non-methane volatile organic compounds). Heating value is approximately 550 BTU/scf. A upgrading plant, utilizing an amine process, rejects the carbon dioxide and NMVOCs, and upgrades the gas to pipeline quality (i.e., nominally a heating value >950 BTU/scf). The gas is sold to a pipeline adjacent to the landfill. With coal-bearing strata underlying the landfill, and carbon dioxide a major effluent gas derived from the upgrading process, the Johnson County Landfill is potentially an ideal setting to study the feasibility of injecting the effluent gas in the coals for both enhanced coalbed methane recovery and carbon sequestration. To these ends, coals below the landfill were cored and then were analyzed for their thickness and sorbed gas content, which ranged up to 79 scf/ton. Assuming 1 1/2 square miles of land (960 acres) at the Johnson County Landfill can be utilized for coalbed and shale gas recovery, the total amount of in-place gas calculates to 946,200 mcf, or 946.2 mmcf, or 0.95 bcf (i.e., 985.6 mcf/acre X 960 acres). Assuming that carbon dioxide can be imbibed by the coals and shales on a 2:1 ratio compared to the gas that was originally present, then 1682 to 1720 days (4.6 to 4.7 years) of landfill carbon dioxide production can be sequestered by the coals and shales immediately under the landfill. Three coal--the Bevier

  3. Removal processes of disinfection byproducts in subsurface-flow constructed wetlands treating secondary effluent.

    PubMed

    Chen, Yi; Wen, Yue; Tang, Zhiru; Li, Ling; Cai, Yanlong; Zhou, Qi

    2014-03-15

    The removal efficiencies and the kinetics of disinfection byproducts (DBPs) were studied in six greenhouse laboratory-scale SSF CWs. Cattail (Typha latifolia) and its litter (collected from the aboveground samples of cattail in autumn) were used as a potential phytoremediation technology and as a primary substrate, respectively, for DBP removal. Results showed that most of the 11 DBPs (except chloroform and 1, 1-dichloropropanone) were efficiently removed (>90%) in six SSF CWs with hydraulic retention time of 5 d and there were no significant differences among the systems. Under the batch mode, the removal of DBPs in SSF CWs followed first-order kinetics with half-lives of 1.0-770.2 h. As a primary DBP in wastewater effluent, removal efficiencies for chloroform were higher in planted systems than in unplanted ones and plant uptake accounted for more than 23.8% of the removal. Plant litter greatly enhanced the removal of trihalomethanes (THMs) by supplying primary substrates and reducing conditions, and the formation of dichloromethane supported the anaerobic biodegradation of THMs via reductive dechlorination in SSF CWs. Trichloroacetonitrile was completely removed within 10 h in each system and hydrolysis was considered to be the dominant process as there was a rapid formation of the hydrolysis byproduct, trichloroacetamide.

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

    SciTech Connect

    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.

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

    NASA Astrophysics Data System (ADS)

    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

  6. Subsurface Microbes Expanding the Tree of Life

    SciTech Connect

    Banfield, Jillian

    2015-05-11

    Jillian Banfield, Ph.D., UC Berkeley Professor and Berkeley Lab Earth Sciences Division staff scientist and long-time user of the DOE Joint Genome Institute’s resources shares her perspective on how the DOE JGI helps advance her research addressing knowledge gaps related to the roles of subsurface microbial communities in biogeochemical cycling. The video was filmed near the town of Rifle, Colorado at the primary field site for Phase I of the Subsurface Systems Scientific Focus Area 2.0 sponsored by the DOE Office of Biological and Environmental Research.

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

    PubMed

    Wang, Y; Papenguth, H W

    2001-02-01

    Microbial reactions play an important role in regulating pore water chemistry as well as secondary mineral distribution in many subsurface systems and, therefore, may directly impact radionuclide migration in those systems. This paper presents a general modeling approach to couple microbial metabolism, redox chemistry, and radionuclide transport in a subsurface environment. To account for the likely achievement of quasi-steady state biomass accumulations in subsurface environments, a modification to the traditional microbial growth kinetic equation is proposed. The conditions for using biogeochemical models with or without an explicit representation of biomass growth are clarified. Based on the general approach proposed in this paper, the couplings of uranium reactions with biogeochemical processes are incorporated into computer code BIORXNTRN Version 2.0. The code is then used to simulate a subsurface contaminant migration scenario, in which a water flow containing both uranium and a complexing organic ligand is recharged into an oxic carbonate aquifer. The model simulation shows that Mn and Fe oxyhydroxides may vary significantly along a flow path. The simulation also shows that uranium(VI) can be reduced and therefore immobilized in the anoxic zone created by microbial degradation.

  8. Geophysical monitoring of microbial activity during stimulated subsurface bioremediation

    NASA Astrophysics Data System (ADS)

    Williams, K. H.; Kemna, A.; Wilkins, M.; Druhan, J.; Arntzen, E.; N'guessan, L.; Long, P.; Hubbard, S.; Banfield, J.

    2007-12-01

    Understanding how microorganisms alter their physical and chemical environment during bioremediation is hindered by our inability to resolve subsurface microbial activity with high spatial resolution. Here we demonstrate the use of a minimally invasive geophysical technique to monitor microbe-mediated iron and sulfate reduction during acetate amendment of a uranium-contaminated aquifer near Rifle, CO. During induced polarization (IP) measurements, spatiotemporal variations in the phase response between applied and measured voltages correlated with changes in groundwater geochemistry indicative of microbial iron and sulfate reduction and sulfide mineral precipitation. The enhanced sensitivity of the high and low frequency phase responses to accumulated aqueous iron and sulfide, respectively, provide the ability to discriminate the dominant subsurface biogeochemical process. The spectral effect was verified and calibrated using a biostimulated column experiment containing Rifle sediments and groundwater. Sediments and fluids recovered from regions of the field site exhibiting an anomalous phase response were enriched in sorbed Fe(II) and cell-associated 2-4 nm diameter FeS nanoparticles. These mineral precipitates and accumulated electroactive ions altered the ability of pore fluids to conduct electrical charge, accounting for the IP response. The results reveal the usefulness of multi-frequency IP measurements for discriminating mineralogical and geochemical changes during stimulated subsurface bioremediation.

  9. Aqueous Complexation Reactions Governing the Rate and Extent of Biogeochemical U(VI) Reduction

    SciTech Connect

    Scott C. Brooks; Wenming Dong; Sue Carroll; James K. Fredrickson; Kenneth M. Kemner; Shelly D. Kelly

    2006-06-01

    The proposed research will elucidate the principal biogeochemical reactions that govern the concentration, chemical speciation, and reactivity of the redox-sensitive contaminant uranium. The results will provide an improved understanding and predictive capability of the mechanisms that govern the biogeochemical reduction of uranium in subsurface environments. In addition, the work plan is designed to: (1) Generate fundamental scientific understanding on the relationship between U(VI) chemical speciation and its susceptibility to biogeochemical reduction reactions. (2) Elucidate the controls on the rate and extent of contaminant reactivity. (3) Provide new insights into the aqueous and solid speciation of U(VI)/U(IV) under representative groundwater conditions.

  10. Aqueous Complexation Reactions Governing the Rate and Extent of Biogeochemical U(VI) Reduction

    SciTech Connect

    Scott C. Brooks; Wenming Dong; Sue Carroll; Jim Fredrickson; Ken Kemner; Shelly Kelly

    2006-06-01

    The proposed research will elucidate the principal biogeochemical reactions that govern the concentration, chemical speciation, and reactivity of the redox-sensitive contaminant uranium. The results will provide an improved understanding and predictive capability of the mechanisms that govern the biogeochemical reduction of uranium in subsurface environments. In addition, the work plan is designed to: (1) Generate fundamental scientific understanding on the relationship between U(VI) chemical speciation and its susceptibility to biogeochemical reduction reactions. ? Elucidate the controls on the rate and extent of contaminant reactivity. (2) Provide new insights into the aqueous and solid speciation of U(VI)/U(IV) under representative groundwater conditions.

  11. Conceptual Model of Iodine Behavior in the Subsurface at the Hanford Site

    SciTech Connect

    Truex, Michael J.; Lee, Brady D.; Johnson, Christian D.; Qafoku, Nikolla P.; Last, George V.; Lee, Michelle H.; Kaplan, Daniel I.

    2015-09-01

    The fate and transport of 129I in the environment and potential remediation technologies are currently being studied as part of environmental remediation activities at the Hanford Site. A conceptual model describing the nature and extent of subsurface contamination, factors that control plume behavior, and factors relevant to potential remediation processes is needed to support environmental remedy decisions. Because 129I is an uncommon contaminant, relevant remediation experience and scientific literature are limited. Thus, the conceptual model also needs to both describe known contaminant and biogeochemical process information and to identify aspects about which additional information needed to effectively support remedy decisions. this document summarizes the conceptual model of iodine behavior relevant to iodine in the subsurface environment at the Hanford site.

  12. Coupled Biogeochemical Processes Governing the Stability of Bacteriogenic Uraninite and Release of U(VI) in Heterogeneous Media: Molecular to Meter Scales

    SciTech Connect

    Bargar, John R.

    2006-11-15

    In-situ reductive biotransformation of subsurface U(VI) to U(IV) (as ?UO2?) has been proposed as a bioremediation method to immobilize uranium at contaminated DOE sites. The chemical stability of bacteriogenic ?UO2? is the seminal issue governing its success as an in-situ waste form in the subsurface. The structure and properties of chemically synthesized UO2+x have been investigated in great detail. It has been found to exhibit complex structural disorder, with nonstoichiometry being common, hence the designation ?UO2+x?, where 0 < x < 0.25. Little is known about the structures and properties of the important bacteriogenic analogs, which are believed to occur as nanoparticles in the environment. Chemically synthesized UO2+x exhibits an open fluorite structure and is known to accommodate significant doping of divalent cations. The extent to which bacteriogenic UO2+x incorporates common ground water cations (e.g., Ca2+) has not been investigated, and little is known about nonstoichiometry and structure defects in the bacteriogenic material. Particle size, nonstoichiometry, and doping may significantly alter the reactivity, and hence stability, of bacteriogenic UO2+x in the subsurface. The presence of associated sulfide minerals, and solid phase oxidants such as bacteriogenic Mn oxides may also affect the longevity of bacteriogenic UO2 in the subsurface.

  13. Evaluation of the giant reed (Arundo donax) in horizontal subsurface flow wetlands for the treatment of dairy processing factory wastewater.

    PubMed

    Idris, Shaharah Mohd; Jones, Paul L; Salzman, Scott A; Croatto, George; Allinson, Graeme

    2012-09-01

    Two emergent macrophytes, Arundo donax and Phragmites australis, were established in experimental horizontal subsurface flow (HSSF), gravel-based constructed wetlands (CWs) and challenged by treated dairy processing factory wastewater with a median electrical conductivity of 8.9 mS cm(-1). The hydraulic loading rate was tested at 3.75 cm day(-1). In general, the plants grew well during the 7-month study period, with no obvious signs of salt stress. The major water quality parameters monitored (biological oxygen demand (BOD), suspended solids (SS) and total nitrogen (TN) but not total phosphorus) were generally improved after the effluent had passed through the CWs. There was no significance different in removal efficiencies between the planted beds and unplanted gravel beds (p > 0.007), nor was there any significant difference in removal efficiencies between the A. donax and P. australis beds for most parameters. BOD, SS and TN removal in the A. donax and P. australis CWs was 69, 95 and 26 % and 62, 97 and 26 %, respectively. Bacterial removal was observed but only to levels that would allow reuse of the effluent for use on non-food crops under Victorian state regulations. As expected, the A. donax CWs produced considerably more biomass (37 ± 7.2 kg wet weight) than the P. australis CWs (11 ± 1.4 kg wet weight). This standing crop equates to approximately 179 and 68 tonnes ha(-1) year(-1) biomass (dry weight) for A. donax and P. australis, respectively (assuming a 250-day growing season and single-cut harvest). The performance similarity of the A. donax and P. australis planted CWs indicates that either may be used in HSSF wetlands treating dairy factory wastewater, although the planting of A. donax provides additional opportunities for secondary income streams through utilisation of the biomass produced. PMID:22573095

  14. Surface and subsurface cleanup protocol for radionuclides Gunnison, Colorado, UMTRA Project Processing Site. Revision 3, Final report

    SciTech Connect

    Not Available

    1994-05-01

    The supplemental standards provisions of Title 40, Code of Federal Regulations, Part 192 (40 CFR Part 192) require the cleanup of radionuclides other than radium-226 (Ra-226) to levels ``as low as reasonably achievable`` (ALARA), taking into account site-specific conditions, if sufficient quantities and concentrations are present to constitute a significant radiation hazard. In this context, thorium-230 (Th-230) at the Gunnison, Colorado, processing site will require remediation. However, a seasonally fluctuating groundwater table at the site significantly complicates conventional remedial action with respect to cleanup. Characterization data indicate that in the offpile areas, the removal of residual in situ bulk Ra-226 and Th-230 such that the 1000-year projected Ra-226 concentration (Ra-226 concentration in 1000 years due to the decay of in situ Ra-226 and the in-growth of Ra-226 from in situ Th-230) complies with the US Environmental Protection Agency (EPA) cleanup standard for in situ Ra-226 and the cleanup protocol for in situ Th-230 can be readily achieved using conventional excavation techniques for bulk contamination without encountering significant impacts due to groundwater. The EPA cleanup standard and criterion for Ra-226 and the 1000-year projected Ra-226 are 5 and 15 picocuries per gram (pCi/g) above background, respectively, averaged over 15-centimeter (cm) deep surface and subsurface intervals and 100-square-meter (m{sup 2}) grid areas. Significant differential migration of Th-230 relative to Ra-226 has occurred over 40 percent of the subpile area. To effectively remediate the site with respect to Ra-226 and Th-230, supplemental standard is proposed and discussed in this report.

  15. [Community Characteristics of ANAMMOX Bacteria in Subsurface Flow Constructed Wetland (SSFCW) for Processing of Aquaculture Waster Water].

    PubMed

    Zeng, Xian-lei; Liu, Xing-guo; Wu, Zong-fan; Shi, Xu; Lu, Shi-min

    2016-02-15

    Anaerobic ammonium oxidation (ANAMMOX) is one of the important functions in waste water treatment by subsurface flow constructed wetland (SSFCW), however, there are few studies on ANAMMOX in SSFCW environment at present. The community characteristics of ANAMMOX in the SSFCW of processing aquaculture waste water were explored in this study. In order to analyze the structure, diversity and abundance of ANAMMOX bacteria, several 16S rRNA clone libraries were constructed and real-time PCR targeting specific 16S rRNA genes together with diversity analysis was adopted. The obtained results showed that the SSFCW identified a total of three unknown clusters and two known clusters including Candidatus brocadia and Candidatus kuenenia. The dominant cluster was Candidatus brocadia. The highest diversity levels of ANAMMOX bacteria occurred in autumn (H', 1.21), while the lowest in spring (H', 0.64). The abundance of ANAMMOX bacteria in SSFCW environment ranged from 8.0 x 10(4) to 9.4 x 10(6) copies x g(-1) of fresh weight and the copy number of total bacterial 16S rRNA genes ranged from 7.3 x 10(9) to 9.1 x 10(10) copies x g(-1) of fresh weight during culture cycle. There were significant differences in the ANAMMOX bacteria abundances of different stratum and seasons in SSFCW environment, but the differences in total bacterial abundances were not obvious. In addition, the differences in ANAMMOX bacteria abundances in different stratum and seasons in SSFCW environment were irregular in different culture cycle. According to the distribution characteristics of ANAMMOX bacteria in the wetland, the denitrification effect of SSFCW could be improved by changing the supplying manners of aquaculture wastewater and adjusting the structure of wetland. The research results will provide reference for further optimizing the SSFCW and improving the efficiency of purification. PMID:27363152

  16. [Community Characteristics of ANAMMOX Bacteria in Subsurface Flow Constructed Wetland (SSFCW) for Processing of Aquaculture Waster Water].

    PubMed

    Zeng, Xian-lei; Liu, Xing-guo; Wu, Zong-fan; Shi, Xu; Lu, Shi-min

    2016-02-15

    Anaerobic ammonium oxidation (ANAMMOX) is one of the important functions in waste water treatment by subsurface flow constructed wetland (SSFCW), however, there are few studies on ANAMMOX in SSFCW environment at present. The community characteristics of ANAMMOX in the SSFCW of processing aquaculture waste water were explored in this study. In order to analyze the structure, diversity and abundance of ANAMMOX bacteria, several 16S rRNA clone libraries were constructed and real-time PCR targeting specific 16S rRNA genes together with diversity analysis was adopted. The obtained results showed that the SSFCW identified a total of three unknown clusters and two known clusters including Candidatus brocadia and Candidatus kuenenia. The dominant cluster was Candidatus brocadia. The highest diversity levels of ANAMMOX bacteria occurred in autumn (H', 1.21), while the lowest in spring (H', 0.64). The abundance of ANAMMOX bacteria in SSFCW environment ranged from 8.0 x 10(4) to 9.4 x 10(6) copies x g(-1) of fresh weight and the copy number of total bacterial 16S rRNA genes ranged from 7.3 x 10(9) to 9.1 x 10(10) copies x g(-1) of fresh weight during culture cycle. There were significant differences in the ANAMMOX bacteria abundances of different stratum and seasons in SSFCW environment, but the differences in total bacterial abundances were not obvious. In addition, the differences in ANAMMOX bacteria abundances in different stratum and seasons in SSFCW environment were irregular in different culture cycle. According to the distribution characteristics of ANAMMOX bacteria in the wetland, the denitrification effect of SSFCW could be improved by changing the supplying manners of aquaculture wastewater and adjusting the structure of wetland. The research results will provide reference for further optimizing the SSFCW and improving the efficiency of purification.

  17. Continuous monitoring of the lunar or Martian subsurface using on-board pattern recognition and neural processing of Rover geophysical data

    NASA Technical Reports Server (NTRS)

    Mcgill, J. W.; Glass, C. E.; Sternberg, B. K.

    1990-01-01

    The ultimate goal is to create an extraterrestrial unmanned system for subsurface mapping and exploration. Neural networks are to be used to recognize anomalies in the profiles that correspond to potentially exploitable subsurface features. The ground penetrating radar (GPR) techniques are likewise identical. Hence, the preliminary research focus on GPR systems will be directly applicable to seismic systems once such systems can be designed for continuous operation. The original GPR profile may be very complex due to electrical behavior of the background, targets, and antennas, much as the seismic record is made complex by multiple reflections, ghosting, and ringing. Because the format of the GPR data is similar to the format of seismic data, seismic processing software may be applied to GPR data to help enhance the data. A neural network may then be trained to more accurately identify anomalies from the processed record than from the original record.

  18. The Serpentinite Subsurface Microbiome

    NASA Astrophysics Data System (ADS)

    Schrenk, M. O.; Nelson, B. Y.; Brazelton, W. J.

    2011-12-01

    Microbial habitats hosted in ultramafic rocks constitute substantial, globally-distributed portions of the subsurface biosphere, occurring both on the continents and beneath the seafloor. The aqueous alteration of ultramafics, in a process known as serpentinization, creates energy rich, high pH conditions, with low concentrations of inorganic carbon which place fundamental constraints upon microbial metabolism and physiology. Despite their importance, very few studies have attempted to directly access and quantify microbial activities and distributions in the serpentinite subsurface microbiome. We have initiated microbiological studies of subsurface seeps and rocks at three separate continental sites of serpentinization in Newfoundland, Italy, and California and compared these results to previous analyses of the Lost City field, near the Mid-Atlantic Ridge. In all cases, microbial cell densities in seep fluids are extremely low, ranging from approximately 100,000 to less than 1,000 cells per milliliter. Culture-independent analyses of 16S rRNA genes revealed low-diversity microbial communities related to Gram-positive Firmicutes and hydrogen-oxidizing bacteria. Interestingly, unlike Lost City, there has been little evidence for significant archaeal populations in the continental subsurface to date. Culturing studies at the sites yielded numerous alkaliphilic isolates on nutrient-rich agar and putative iron-reducing bacteria in anaerobic incubations, many of which are related to known alkaliphilic and subsurface isolates. Finally, metagenomic data reinforce the culturing results, indicating the presence of genes associated with organotrophy, hydrogen oxidation, and iron reduction in seep fluid samples. Our data provide insight into the lifestyles of serpentinite subsurface microbial populations and targets for future quantitative exploration using both biochemical and geochemical approaches.

  19. Microbial Transport in the Subsurface

    SciTech Connect

    Ginn, Timothy R.; Camesano, Terri; Scheibe, Timothy D.; Nelson, Kirk B.; Clement, T. P.; Wood, Brian D.

    2005-12-01

    In this article we focus on the physical, chemical, and biological processes involved in the transport of bacteria in the saturated subsurface. We will first review conceptual models of bacterial phases in the subsurface, and then the processes controlling fate and transport on short (e.g., bioremediation) time scales. Finally we briefly review field bacterial transport experiments and discuss a number of issues that impact the application of current process descriptions and models at the field scale.

  20. Using Geochemical Indicators to Distinguish High Biogeochemical Activity in Sediments

    NASA Astrophysics Data System (ADS)

    Kenwell, A. M.; Navarre-Sitchler, A.; Prugue, R.; Spear, J. R.; Williams, K. H.; Maxwell, R. M.

    2014-12-01

    A better understanding of how microbial communities interact with their surroundings in physically and chemically heterogeneous subsurface environments will lead to improved quantification of biogeochemical reactions and associated nutrient cycling. This study develops a methodology to predict elevated rates of biogeochemical activity (microbial "hotspots") in subsurface environments by correlating microbial community structure with the spatial distribution of geochemical indicators in subsurface sediments. Statistical hierarchical cluster analyses (HCA) of X-ray fluorescence (XRF), simulated precipitation leachate, bioavailable Fe and Mn, total organic carbon (TOC), microbial community structure, grain size, bulk density and moisture content data were used to identify regions of the subsurface characterized by biogeochemical hotspots and sample characteristics indicative of these hotspots within fluvially-derived aquifer sediments. The methodology has been applied to (a) alluvial materials collected at a former uranium mill site near Rifle, Colorado and (b) relatively undisturbed floodplain deposits (soils and sediments) collected along the East River near Crested Butte, Colorado. At Rifle, 33 sediment samples were taken from 8 sediment cores and at the East River 33 soil/sediment samples were collected across and perpendicular to 3 active meanders. The East River watershed exhibits characteristic fluvial progression and serves as a representative example of many headwater catchments with the upper Colorado River basin. Initial clustering revealed that operationally defined hotspots were characterized by high organic carbon, bioavailable iron and dark colors but not necessarily low hydraulic conductivity. Applying the method to identify hotspots in both contaminated and natural floodplain deposits and their associated alluvial aquifers demonstrates the broad applicability of a geochemical indicator based approach.

  1. Terrestrial Subsurface Ecosystem

    SciTech Connect

    Wilkins, Michael J.; Fredrickson, Jim K.

    2015-10-15

    The Earth’s crust is a solid cool layer that overlays the mantle, with a varying thickness of between 30-50 km on continental plates, and 5-10 km on oceanic plates. Continental crust is composed of a variety of igneous, metamorphic, and sedimentary rocks that weather and re-form over geologic cycles lasting millions to billions of years. At the crust surface, these weathered minerals and organic material combine to produce a variety of soils types that provide suitable habitats and niches for abundant microbial diversity (see Chapter 4). Beneath this soil zone is the subsurface. Once thought to be relatively free of microorganisms, recent estimates have calculated that between 1016-1017 g C biomass (2-19% of Earth’s total biomass) may be present in this environment (Whitman et al., 1998;McMahon and Parnell, 2014). Microbial life in the subsurface exists across a wide range of habitats: in pores associated with relatively shallow unconsolidated aquifer sediments to fractures in bedrock formations that are more than a kilometer deep, where extreme lithostatic pressures and temperatures are encountered. While these different environments contain varying physical and chemical conditions, the absence of light is a constant. Despite this, diverse physiologies and metabolisms enable microorganisms to harness energy and carbon for growth in water-filled pore spaces and fractures. Carbon and other element cycles are driven by microbial activity, which has implications for both natural processes and human activities in the subsurface, e.g., bacteria play key roles in both hydrocarbon formation and degradation. Hydrocarbons are a major focus for human utilization of the subsurface, via oil and gas extraction and potential geologic CO2 sequestration. The subsurface is also utilized or being considered for sequestered storage of high-level radioactive waste from nuclear power generation and residual waste from past production of weapons grade nuclear materials. While our

  2. Microbial iron reduction under deep subsurface pressure conditions

    NASA Astrophysics Data System (ADS)

    Picard, A.; Daniel, I.; Testemale, D.; Hazemann, J.; Oger, P.

    2009-12-01

    The deep subsurface is characterized by hostile conditions in terms of temperature, pressure and nutrient availability. Our current view of the biosphere extension is restricted to depths shallower than the isotherm associated to the highest observed temperature for life, i.e. 122°C. At this temperature, depending on the geological setting, pressure varies between ambient pressure at geothermal springs and 350 MPa in cold subduction zones. In this high-pressure biosphere, biological iron reduction is an important process linked to carbon oxidation. Among the factors governing reaction rates and yields in the deep subsurface, pressure could be of importance due its effects on kinetic and equilibrium reactions. The understanding and modelling of Fe reduction in natural environments, especially in the subsurface, can be first comprehended thanks to studies of Fe reduction in pure cultures; indeed the study of the effects of high pressure on Fe-reducing bacteria in pure cultures can serve as a basic model for the effects of pressure on Fe reduction in the subsurface. We investigated the effects of pressure on the reduction of Fe(III) to Fe(II) by the bacterial model Shewanella oneidensis MR-1. This strain is a mesophilic and piezosensitive counterpart of the psychrophilic and piezophilic Shewanella representatives that have been frequently isolated from deep-sea environments. Kinetics of Fe(III) reduction to Fe(II) were monitored in situ by X-ray Absorption Spectroscopy (XAS) in an appropriate pressure vessel dedicated to in situ XAS measurements (Testemale et al. 2005). Measurements were performed at the BM30B beamline of the European Synchrotron Radiation Facilty (Grenoble, France). Experiments were conducted from 0.1 MPa to 100 MPa at MR-1 optimal temperature (30°C). Iron reduction was monitored until 100 MPa in cultures of MR-1 at a concentration of 10e8 cells/ml. This shows that the metabolic activity of a piezosensitive microbe extends far beyond its pressure

  3. Archaea in biogeochemical cycles.

    PubMed

    Offre, Pierre; Spang, Anja; Schleper, Christa

    2013-01-01

    Archaea constitute a considerable fraction of the microbial biomass on Earth. Like Bacteria they have evolved a variety of energy metabolisms using organic and/or inorganic electron donors and acceptors, and many of them are able to fix carbon from inorganic sources. Archaea thus play crucial roles in the Earth's global geochemical cycles and influence greenhouse gas emissions. Methanogenesis and anaerobic methane oxidation are important steps in the carbon cycle; both are performed exclusively by anaerobic archaea. Oxidation of ammonia to nitrite is performed by Thaumarchaeota. They represent the only archaeal group that resides in large numbers in the global aerobic terrestrial and marine environments on Earth. Sulfur-dependent archaea are confined mostly to hot environments, but metal leaching by acidophiles and reduction of sulfate by anaerobic, nonthermophilic methane oxidizers have a potential impact on the environment. The metabolisms of a large number of archaea, in particular those dominating the subsurface, remain to be explored.

  4. Biogeochemical processes in an urban, restored wetland of San Francisco Bay, California, 2007-2009; methods and data for plant, sediment and water parameters

    USGS Publications Warehouse

    Windham-Myers, Lisamarie; Marvin-DiPasquale, Mark C.; Agee, Jennifer L.; Kieu, Le H.; Kakouros, Evangelos; Erikson, Li H.; Ward, Kristen

    2010-01-01

    The restoration of 18 acres of historic tidal marsh at Crissy Field has had great success in terms of public outreach and visibility, but less success in terms of revegetated marsh sustainability. Native cordgrass (Spartina foliosa) has experienced dieback and has failed to recolonize following extended flooding events during unintended periodic closures of its inlet channel, which inhibits daily tidal flushing. We examined the biogeochemical impacts of these impoundment events on plant physiology and on sulfur and mercury chemistry to help the National Park Service land managers determine the relative influence of these inlet closures on marsh function. In this comparative study, we examined key pools of sulfur, mercury, and carbon compounds both during and between closure events. Further, we estimated the net hydrodynamic flux of methylmercury and total mercury to and from the marsh during a 24-hour diurnal cycle. This report documents the methods used and the data generated during the study.

  5. Biogeochemical Cycles in Degraded Lands

    NASA Technical Reports Server (NTRS)

    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.

  6. Biogeochemical Cycles in Degraded Lands

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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.

  7. Investigating the Impact of Pore Scale Microenvironments on Contaminant Biogeochemical Reactive Transport

    NASA Astrophysics Data System (ADS)

    Wilkins, M. J.; Pearce, C.; Zhang, C.; Heald, S.; Fredrickson, J. K.; Zachara, J. M.

    2011-12-01

    Microenvironments and transition zones dominate the subsurface biogeochemical cycling of key contaminants, with strong effects resulting from the coupling of chemical reactions, physical transport and microbiological processes. Understanding the impact of pore-scale environments (e.g. spatial heterogeneity, chemical gradients, and redox potential) is essential for modeling contaminant fate and transport in the subsurface. The driver for biogeochemical processes at the pore scale changes from macroscopic advection to microscale diffusion, and this has a significant effect on the retention of soluble, highly mobile contaminants such as U(VI). Here, etched-silicon microfluidic models with defined chemistry, mineralogy, microbiology, and flow regimes are used for the incremental development of complex microenvironments that approach real-world systems. We demonstrate the colonization of such pore spaces by an anaerobic Fe(III)-reducing bacterium, the enzymatic reduction of a bioavailable Fe(III) phase within this environment, and the subsequent effects of both oxidized and reduced Fe phases on uranium biogeochemistry under flow conditions using both X-ray Microprobe (XMP) and X-ray Absorption Spectroscopy (XAS). Precipitated Fe(III) phases within the microfluidic model were most effectively reduced in the presence of an electron shuttle (e.g. AQDS), with Fe(II) ions adsorbing onto mineral precipitates and surfaces. In the absence of Fe, U(VI) was effectively reduced by the microbial population to insoluble U(IV), which was precipitated in discrete regions associated within biomass. In the presence of both oxidized and reduced Fe phases however, differing effects were observed with regards to U behavior; oxidized U(VI) was frequently adsorbed to poorly crystalline Fe(III), and reduced U(IV) associated with more reduced regions of the microscale flow cell. In the future, the flexibility in the design of the microfluidic models, in combination with advanced

  8. Active Serpentinization and the Potential for a Diverse Subsurface Biosphere

    NASA Astrophysics Data System (ADS)

    Canovas, P. A.; Shock, E.

    2013-12-01

    The ubiquitous nature of serpentinization and the unique fluids it generates have major consequences for habitat generation, abiotic organic synthesis, and biosynthesis. The production of hydrogen from the anaerobic hydrolysis of ultramafic minerals sets the redox state of serpentinizing fluids to be thermodynamically favorable for these processes. Consequently, a host of specialized microbial populations and metabolisms can be sustained. Active low-temperature serpentinizing systems, such as the Samail ophiolite in Oman, offer an ideal opportunity to investigate biogeochemical processes during the alteration of ultramafic minerals. At the Samail ophiolite in particular, serpentinization may provide the potential for an active subsurface microbial community shielded from potentially unfavorable surface conditions. Support for this assertion comes from geochemical data including Mg, Ca, CH4 (aq), and H2 (aq) abundances indicating that methane is a product of serpentinization. To further investigate viable metabolic strategies, affinity calculations were performed on both the surface waters and the hyperalkaline springs, which may be considered as messengers of processes occurring in the subsurface. Almost all sites yield positive affinities (i.e., are thermodynamically favorable) for a diverse suite of serpentinization metabolisms including methanogenesis, anammox, and carbon monoxide, nitrate, and sulfate reduction with hydrogen, as well as anaerobic methanotrophy coupled to nitrate, nitrite, and sulfate reduction. Reaction path modeling was performed to ascertain the extent to which serpentinization and mixing of surface waters with hyperalkaline spring waters in the subsurface can generate suitable habitats. The serpentinization model simulates the reaction of pristine Oman harzburgite with surface water to quantify the redox state and generation of hyperalkaline spring water. Preliminary results show that water-rock ratios as high as 100 could effectively reduce

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

    SciTech Connect

    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.

  10. Biogeochemical weathering under ice: Size matters

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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

    in higher concentrations of TEAP reaction products when terminal electron donors and acceptors were not limiting. Finally, facies-based porosity and reactive surface area variations were shown to affect aqueous uranium concentration distributions with localized effects of the fine lithofacies having the largest impact on U(VI) surface complexation. The ability to model the comprehensive biogeochemical reaction network, and spatially and temporally variable processes, properties, and conditions controlling uranium behavior during engineered bioremediation in the naturally complex Rifle IFRC subsurface system required a subsurface simulator that could use the large memory and computational performance of a massively parallel computer. In this case, the eSTOMP simulator, operating on 128 processor cores for 12h, was used to simulate the 110-day field experiment and 50 days of post-biostimulation behavior.

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

    NASA Astrophysics Data System (ADS)

    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

    in higher concentrations of TEAP reaction products when terminal electron donors and acceptors were not limiting. Finally, facies-based porosity and reactive surface area variations were shown to affect aqueous uranium concentration distributions with localized effects of the fine lithofacies having the largest impact on U(VI) surface complexation. The ability to model the comprehensive biogeochemical reaction network, and spatially and temporally variable processes, properties, and conditions controlling uranium behavior during engineered bioremediation in the naturally complex Rifle IFRC subsurface system required a subsurface simulator that could use the large memory and computational performance of a massively parallel computer. In this case, the eSTOMP simulator, operating on 128 processor cores for 12 h, was used to simulate the 110-day field experiment and 50 days of post-biostimulation behavior.

  13. TOUGH2Biot - A simulator for coupled thermal-hydrodynamic-mechanical processes in subsurface flow systems: Application to CO2 geological storage and geothermal development

    NASA Astrophysics Data System (ADS)

    Lei, Hongwu; Xu, Tianfu; Jin, Guangrong

    2015-04-01

    Coupled thermal-hydrodynamic-mechanical processes have become increasingly important in studying the issues affecting subsurface flow systems, such as CO2 sequestration in deep saline aquifers and geothermal development. In this study, a mechanical module based on the extended Biot consolidation model was developed and incorporated into the well-established thermal-hydrodynamic simulator TOUGH2, resulting in an integrated numerical THM simulation program TOUGH2Biot. A finite element method was employed to discretize space for rock mechanical calculation and the Mohr-Coulomb failure criterion was used to determine if the rock undergoes shear-slip failure. Mechanics is partly coupled with the thermal-hydrodynamic processes and gives feedback to flow through stress-dependent porosity and permeability. TOUGH2Biot was verified against analytical solutions for the 1D Terzaghi consolidation and cooling-induced subsidence. TOUGH2Biot was applied to evaluate the thermal, hydrodynamic, and mechanical responses of CO2 geological sequestration at the Ordos CCS Demonstration Project, China and geothermal exploitation at the Geysers geothermal field, California. The results demonstrate that TOUGH2Biot is capable of analyzing change in pressure and temperature, displacement, stress, and potential shear-slip failure caused by large scale underground man-made activity in subsurface flow systems. TOUGH2Biot can also be easily extended for complex coupled process problems in fractured media and be conveniently updated to parallel versions on different platforms to take advantage of high-performance computing.

  14. Complex Systems Science for Subsurface Fate and Transport Report from the August 2009 Workshop

    SciTech Connect

    2010-03-01

    The subsurface environment, which encompasses the vadose and saturated zones, is a heterogeneous, geologically complex domain. Believed to contain a large percentage of Earth's biomass in the form of microorganisms, the subsurface is a dynamic zone where important biogeochemical cycles work to sustain life. Actively linked to the atmosphere and biosphere through the hydrologic and carbon cycles, the subsurface serves as a storage location for much of Earth's fresh water. Coupled hydrological, microbiological, and geochemical processes occurring within the subsurface environment cause the local and regional natural chemical fluxes that govern water quality. These processes play a vital role in the formation of soil, economically important fossil fuels, mineral deposits, and other natural resources. Cleaning up Department of Energy (DOE) lands impacted by legacy wastes and using the subsurface for carbon sequestration or nuclear waste isolation require a firm understanding of these processes and the documented means to characterize the vertical and spatial distribution of subsurface properties directing water, nutrient, and contaminant flows. This information, along with credible, predictive models that integrate hydrological, microbiological, and geochemical knowledge over a range of scales, is needed to forecast the sustainability of subsurface water systems and to devise ways to manage and manipulate dynamic in situ processes for beneficial outcomes. Predictive models provide the context for knowledge integration. They are the primary tools for forecasting the evolving geochemistry or microbial ecology of groundwater under various scenarios and for assessing and optimizing the potential effectiveness of proposed approaches to carbon sequestration, waste isolation, or environmental remediation. An iterative approach of modeling and experimentation can reveal powerful insights into the behavior of subsurface systems. State-of-science understanding codified in models

  15. 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

    NASA Astrophysics Data System (ADS)

    Tan, Z.; Zhuang, Q.; Henze, D. K.; Frankenberg, C.; Dlugokencky, E.; Sweeney, C.; Turner, A. J.

    2015-11-01

    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.

  16. Final Technical Report: Viral Infection of Subsurface Microorganisms and Metal/Radionuclide Transport

    SciTech Connect

    Weber, Karrie A.; Bender, Kelly S.; Li, Yusong

    2013-09-28

    Microbially mediated metabolisms have been identified as a significant factor either directly or indirectly impacting the fate and transport of heavy metal/radionuclide contaminants. To date microorganisms have been isolated from contaminated environments. Examination of annotated finished genome sequences of many of these subsurface isolates from DOE sites, revealed evidence of prior viral infection. To date the role that viruses play influencing microbial mortality and the resulting community structure which directly influences biogeochemical cycling in soils and sedimentary environments remains poorly understood. The objective of this exploratory study was to investigate the role of viral infection of subsurface bacteria and the formation of contaminant-bearing viral particles. This objective was approached by examining the following working hypotheses: (i) subsurface microorganisms are susceptible to viral infections by the indigenous subsurface viral community, and (ii) viral surfaces will adsorb heavy metals and radionuclides. Our results have addressed basic research needed to accomplish the BER Long Term Measure to provide sufficient scientific understanding such that DOE sites would be able to incorporate coupled physical, chemical and biological processes into decision making for environmental remediation or natural attenuation and long-term stewardship by establishing viral-microbial relationships on the subsequent fate and transport of heavy metals and radionuclides. Here we demonstrated that viruses play a significant role in microbial mortality and community structure in terrestrial subsurface sedimentary systems. The production of viral-like particles within subsurface sediments in response to biostimulation with dissolved organic carbon and a terminal electron acceptor resulted in the production of viral-like particles. Organic carbon alone did not result in significant viral production and required the addition of a terminal electron acceptor

  17. Biogeochemical controls on the product of microbial U(VI) reduction.

    PubMed

    Stylo, Malgorzata; Alessi, Daniel S; Shao, Paul PaoYun; Lezama-Pacheco, Juan S; Bargar, John R; Bernier-Latmani, Rizlan

    2013-01-01

    Biologically mediated immobilization of radionuclides in the subsurface is a promising strategy for the remediation of uranium-contaminated sites. During this process, soluble U(VI) is reduced by indigenous microorganisms to sparingly soluble U(IV). The crystalline U(IV) phase uraninite, or UO2, is the preferable end-product of bioremediation due to its relatively high stability and low solubility in comparison to biomass-associated nonuraninite U(IV) species that have been reported in laboratory and under field conditions. The goal of this study was to delineate the geochemical conditions that promote the formation of nonuraninite U(IV) versus uraninite and to decipher the mechanisms of its preferential formation. U(IV) products were prepared under varying geochemical conditions and characterized with X-ray absorption spectroscopy (XAS), scanning transmission X-ray microscopy (STXM), and various wet chemical methods. We report an increasing fraction of nonuraninite U(IV) species with decreasing initial U concentration. Additionally, the presence of several common groundwater solutes (sulfate, silicate, and phosphate) promote the formation of nonuraninite U(IV). Our experiments revealed that the presence of those solutes promotes the formation of bacterial extracellular polymeric substances (EPS) and increases bacterial viability, suggesting that the formation of nonuraninite U(IV) is due to a biological response to solute presence during U(VI) reduction. The results obtained from this laboratory-scale research provide insight into biogeochemical controls on the product(s) of uranium reduction during bioremediation of the subsurface.

  18. Microbial production and oxidation of methane in deep subsurface

    NASA Astrophysics Data System (ADS)

    Kotelnikova, Svetlana

    2002-10-01

    microbially to carbon dioxide. Microbial methane oxidation is a biogeochemical process that limits the release of methane, a greenhouse gas from anaerobic environments. Anaerobic methane oxidation plays an important role in marine sediments. Similar processes may take place in deep subsurface and thus fuel the deep microbial community. Organisms or consortia responsible for anaerobic methane oxidation have not yet been cultured, although diverse aerobic methanotrophs have been isolated from a variety of underground niches. The presence of aerobic methanotrophs in the anoxic subsurface remains to be explained. The presence of methane in the deep subsurface have been shown all over the world. The flux of gases between the deep subsurface and the atmosphere is driven by the concentration gradient from depth to the atmosphere. However, methane is consumed by methanotrophs on the way of its evolution in oxidized environments and is transformed to organic form, available for further microbial processing. When the impact of subsurface environments to global warming is estimated, it is necessary to take into account the activity of methane-producing Archaea and methane-oxidizing biofilters in groundwater. Microbial production and oxidation of methane is involved in the carbon cycle in the deep subsurface environments.

  19. Terrestrial ecosystems and the global biogeochemical silica cycle

    NASA Astrophysics Data System (ADS)

    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.

  20. Arsenic in New Jersey Coastal Plain streams, sediments, and shallow groundwater: effects from different geologic sources and anthropogenic inputs on biogeochemical and physical mobilization processes

    USGS Publications Warehouse

    Barringer, Julia L.; Reilly, Pamela A.; Eberl, Dennis D.; Mumford, Adam C.; Benzel, William M.; Szabo, Zoltan; Shourds, Jennifer L.; Young, Lily Y.

    2013-01-01

    With a history of agriculture in the New Jersey Coastal Plain, anthropogenic inputs of As, such as residues from former pesticide applications in soils, can amplify any geogenic As in runoff. Such inputs contribute to an increased total As load to a stream at high stages of flow. As a result of yet another anthropogenic influence, microbes that reduce and mobilize As beneath the streambeds are stimulated by inputs of dissolved organic carbon (DOC). Although DOC is naturally occurring, anthropogenic contributions from wastewater inputs may deliver increased levels of DOC to subsurface soils and ultimately groundwater. Arsenic concentrations may increase with the increases in pH of groundwater and stream water in developed areas receiving wastewater inputs, as As mobilization caused by pH-controlled sorption and desorption reactions are likely to occur in waters of neutral or alkaline pH (for example, Nimick and others, 1998; Barringer and others, 2007b). Because of the difference in As content of the geologic materials in the two sub-provinces of the Coastal Plain, the amount of As that is mobile in groundwater and stream water is, potentially, substantially greater in the Inner Coastal Plain than in the Outer Coastal Plain. In turn, streams within the Inner and Outer Coastal Plain can receive substantially more As in groundwater discharge from developed areas than from environments where DOC appears to be of natural origin.

  1. Biogeochemical drivers of phosphatase activity in salt marsh sediments

    NASA Astrophysics Data System (ADS)

    Freitas, Joana; Duarte, Bernardo; Caçador, Isabel

    2014-10-01

    Although nitrogen has become a major concern for wetlands scientists dealing with eutrophication problems, phosphorous represents another key element, and consequently its biogeochemical cycling has a crucial role in eutrophication processes. Microbial communities are a central component in trophic dynamics and biogeochemical processes on coastal systems, since most of the processes in sediments are microbial-mediated due to enzymatic action, including the mineralization of organic phosphorus carried out by acid phosphatase activity. In the present work, the authors investigate the biogeochemical sediment drivers that control phosphatase activities. Authors also aim to assess biogeochemical factors' influence on the enzyme-mediated phosphorous cycling processes in salt marshes. Plant rhizosediments and bare sediments were collected and biogeochemical features, including phosphatase activities, inorganic and organic phosphorus contents, humic acids content and pH, were assessed. Acid phosphatase was found to give the highest contribution for total phosphatase activity among the three pH-isoforms present in salt marsh sediments, favored by acid pH in colonized sediments. Humic acids also appear to have an important role inhibiting phosphatase activity. A clear relation of phosphatase activity and inorganic phosphorous was also found. The data presented reinforces the role of phosphatase in phosphorous cycling.

  2. Using Halogens (Cl, Br, F, I) and Stable Isotopes of Water (δ18O, δ2H) to Trace Hydrological and Biogeochemical Processes in Prairie Wetlands

    NASA Astrophysics Data System (ADS)

    Levy, Z. F.; Lu, Z.; Mills, C. T.; Goldhaber, M. B.; Rosenberry, D. O.; Mushet, D.; Siegel, D. I.; Fiorentino, A. J., II; Gade, M.; Spradlin, J.

    2014-12-01

    Prairie pothole wetlands are ubiquitous features of the Great Plains of North America, and important habitat for amphibians and migratory birds. The salinity of proximal wetlands varies highly due to groundwater-glacial till interactions, which influence wetland biota and associated ecosystem functions. Here we use halogens and stable isotopes of water to fingerprint hydrological and biogeochemical controls on salt cycling in a prairie wetland complex. We surveyed surface, well, and pore waters from a groundwater recharge wetland (T8) and more saline closed (P1) and open (P8) basin discharge wetlands in the Cottonwood Lake Study Area (ND) in August/October 2013 and May 2014. Halogen concentrations varied over a broad range throughout the study area (Cl = 2.2 to 170 mg/L, Br = 13 to 2000 μg/L, F = < 30 (MDL) to 740 μg/L, I = 1 to 538 μg/L). The Cl/Br molar ratios were higher (171 to 574) at the recharge wetland, indicating meteoric sources, and had a tighter and lower range (33 to 320) at the down-gradient sites. The Cl/I molar ratios of waters throughout the site had a wide range (32 to 26,000). Lowest values occurred at the upgradient shore of P1 (32 to 43) due to low Cl concentrations and the center of P1 (196 to 213) where pore water of weathered till underlying 1.2 m of organic-rich sediment and silty clay soil is enriched in I to ~500 µg/L. Stable isotopes of water showed that evaporation-enriched pond water (δ18O = -9.5 to -2.71 ‰) mixes with shallow groundwater in the top 0.6 m of fringing wetland soils and 1.2 m of the substrate in the center of P1. Our results suggest endogenous sources for Br and I within the prairie landscape that may be controlled by biological mechanisms or weathering of shale from glacial till.

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

    PubMed

    Zhang, Liming; Yu, Dongsheng; Shi, Xuezheng; Xu, Shengxiang; Xing, Shihe; Zhao, Yongcong

    2014-01-01

    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.

  4. Climate Variability and Change in a Eutrophic Great Lakes Freshwater Embayment: Shifting Hydrodynamics and the Potential for Indirect Impacts on Biogeochemical Processes, Carbon Cycling and Hypoxia

    NASA Astrophysics Data System (ADS)

    Klump, J. V.; Waples, J. T.

    2008-12-01

    Future changes in the climatic regime of the Great Lakes region have the potential to induce a variety of both direct (e.g. thermal) and indirect (e.g. biogeochemical) alterations in ecosystem function. In the case of the later, we have identified a statistically significant shift in wind direction of the average wind field over the Great Lakes basin that is consistent with a southward migration of the dominant summer storm track. In Green Bay (NW Lake Michigan), we have shown that the new wind field has most likely resulted in periods of decreased thermal stratification and an overall decrease in water mass exchange with Lake Michigan. In subsequent studies, aimed at determining the impact of these shifts in the physical climate regime, time series measurements of currents, turbidity, dissolved oxygen, and the Be-7 activity of particulates in bottom sediments, sediment traps, and suspended particulates have been made over a 3 year period. A tracer of short term particle dynamics, Be-7 (half life 53 d) is useful in estimating particle residence times in the water column, along with episodic sediment deposition and erosion rates, and the average number of deposition/erosion cycles a particle experiences prior to permanent burial in the sediments. Be-7 derived estimates of the age of particulate organic carbon cycling between surface sediments and the overlying waters are on the order of months, and are dependent upon resuspension frequency. Remineralization of organic carbon within this actively resuspended pool of material results in estimated decomposition rates for POC ranging 0.08 to 0.04% per day, a rate intermediate between the rapid remineralization of fresh algal material and post-depositional diagenesis. Comparisons between 1989-90 and 2004-06 show a decrease in resuspension frequency, possibly in response to shifts in regional climatic scale dynamics. This appears to result in an increase in the efficiency of trapping of organic matter in the bay and a

  5. Effects of Soil Data and Simulation Unit Resolution on Quantifying Changes of Soil Organic Carbon at Regional Scale with a Biogeochemical Process Model

    PubMed Central

    Zhang, Liming; Yu, Dongsheng; Shi, Xuezheng; Xu, Shengxiang; Xing, Shihe; Zhao, Yongcong

    2014-01-01

    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. PMID:24523922

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

    SciTech Connect

    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

    SciTech Connect

    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. A biogeochemical cycle for aluminium?

    PubMed

    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.

  9. Linking the Modern and Recent Record of Cabo Frio Upwelling with Local Climate and Biogeochemical Processes in Hypersaline Coastal Lagoons, Região dos Lagos, Rio de Janeiro, Brazil

    NASA Astrophysics Data System (ADS)

    McKenzie, J. A.; Nascimento, G. S.; Albuquerque, A. L.; Belem, A. L.; Carreira, R.; Eglinton, T. I.; Vasconcelos, C.

    2015-12-01

    A unique marine and lagoonal system along the coast east of Rio de Janeiro is being investigated to understand the impact of climatic variability on the South Atlantic carbon cycle and biomineralisation processes involved in carbonate precipitation in the hypersaline coastal lagoons. The region is dominated by a semi-arid microclimate attributed to the local coastal upwelling phenomenon near Cabo Frio. The intensity of the upwelling affects the hydrology of the annual water and biogeochemical cycles in the lagoons, as well as biogeochemical signals of environmental change recorded in both onshore and offshore sediments. Preliminary results of δ18O and δD values of water samples collected monthly in Lagoa Vermelha and Brejo do Espinho from 2011 to 2014 show lower values for waters corresponding to the wet season, reflecting increased input of meteoric water. The higher values for waters collected during the dry season reflect the greater amount of evaporation with increased seasonal aridity. Radiocarbon dating of Holocene marine and lagoonal cores indicates that Mg-carbonate precipitation in the lagoons is associated with high evaporation. Modern field observations for the last 3 years suggest that the amount of carbonate precipitation is correlated with evaporitic conditions associated with the upwelling phenomenon. A calibration study of hydrogen isotopic fractionation in the modern lagoons is underway to define a relationship between δDlipid of suspended particles and δDwater of associated water. This isotopic relationship will be applied to material obtained in cores from the lagoons. Offshore cores will be studied using well-tested paleotemperature proxies to evaluate the intensity of the upwelling during the Holocene. In summary, linking the coastal upwelling with the lagoonal hydrology has the potential to furnish important insights about the relationship between the local climate and paleoceanographic circulation associated with the regional carbon cycle.

  10. 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

    NASA Astrophysics Data System (ADS)

    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

  11. The Role of Groundwater and River water Interactions in Modulating Land Surface and Subsurface States and Fluxes: A Local-Scale Case Study along the Columbia River Shoreline

    NASA Astrophysics Data System (ADS)

    Huang, M.; Bisht, G.; Chen, X.; Hammond, G. E.; Zachara, J. M.; Riley, W. J.; Downs, J.; Liu, Y.

    2015-12-01

    Lateral flow and transport between groundwater and river water through the subsurface interaction zone (SIZ) is a major pathway for energy, water, solute, and gas transfer between terrestrial and aquatic systems. Groundwater - surface water exchange is significant at multiple scales, but is not adequately resolved in Earth System Models (ESMs). In this study, an integrated land surface and subsurface model enhanced with hydrologic exchange was assembled within the land component of an ESM (i.e., the Community Land Model (CLM) coupled with PFLOTRAN) to investigate how land surface and subsurface states and fluxes are influenced by the lateral flow and mixing of waters within the SIZ. The new model was applied to a domain including 400 m of the Columbia River shoreline where subsurface properties and processes have been well-characterized through sediment characterization, pump tests, tracer experiments, and field monitoring of river water intrusion events driven by river stage changes. Simulations of CLM-PFLOTRAN at multiple spatial resolutions were conducted using observed meteorological and river stage data under different climate and hydrologic conditions. The coupled model revealed the importance of interaction zone processes in regulating temporal and spatial variability in land surface and subsurface hydrological fluxes and state variables, indicating strong nonlinear coupling between hydrologic and biogeochemical processes in riparian zones. The simulations are validated against field measurements collected at the site. Our results provide a foundation for better understanding the spatial and temporal dynamics of biogeochemical cycling and biogenic gas generation in the SIZ, and their regulation by the changing water cycle and climate.

  12. Linking sediment structure, hydrological functioning and biogeochemical cycling in disturbed coastal saltmarshes and implications for vegetation development

    NASA Astrophysics Data System (ADS)

    Spencer, Kate; Harvey, Gemma; James, Tempest; Simon, Carr; Michelle, Morris

    2014-05-01

    Saltmarsh restoration undoubtedly provides environmental enhancement, with vegetation quickly re-establishing following the breach of sea walls and subsequent tidal inundation of previously defended areas. Yet evidence increasingly suggests that the restored saltmarshes do not have the same biological characteristics as their natural counterparts (Mossman et al. 2012) and this may be in part be due to physicochemical parameters at the site including anoxia and poor drainage. Hence, restored saltmarshes may not offer the range and quality of ecosystem services anticipated. These environments will have been 'disturbed' by previous land use and there is little understanding of the impacts of this disturbance on the wider hydrogeomorphic and biogeochemical functioning in restored saltmarshes and the implications for saltmarsh vegetation development. This study examines linkages between physical sediment characteristics, sediment structure (using X-ray microtomography), sub-surface hydrology (using pressure transducers and time series analysis), and sediment and porewater geochemistry (major and trace elements, major anions) in sediment cores collected from undisturbed saltmarshes and those restored by de-embankment. Sub-surface sediments in restored saltmarshes have lower organic matter content, lower moisture content and higher bulk density than undisturbed sites. Using X-ray tomography a clear horizon can be observed which separates relict agricultural soils at depth with less dense and structureless sediments deposited since de-embankment. Ratios of open to closed pore space suggest that while undisturbed saltmarshes have the highest porosity, restored saltmarshes have larger void spaces, but limited pore connectivity. Sub-surface hydrological response to tidal flooding was subdued in the restored compared to the undisturbed site, suggesting that porewater flow may be impeded. Time series analysis indicated that flow pathways differ in restored saltmarsh sediments

  13. Biogeochemical Cycles of Carbon and Sulfur

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.; DeVincenzi, D. (Technical Monitor)

    2002-01-01

    The elements carbon (C) and sulfur (S) interact with each other across a network of elemental reservoirs that are interconnected by an array of physical, chemical and biological processes. These networks are termed the biogeochemical C and S cycles. The compounds of C are highly important, not only as organic matter, but also as atmospheric greenhouse gases, pH buffers in seawater, oxidation-reduction buffers virtually everywhere, and key magmatic constituents affecting plutonism and volcanism. The element S assumes important roles as an oxidation-reduction partner with C and Fe in biological systems, as a key constituent in magmas and volcanic gases, and as a major influence upon pH in certain environments. This presentation describes the modern biogeochemical C and S cycles. Measurements are described whereby stable isotopes can help to infer the nature and quantitative significance of biological and geological processes involved in the C and S cycles. This lecture also summarizes the geological and climatologic aspects of the ancient C and S cycles, as well as the planetary and extraterrestrial processes that influenced their evolution over millions to billions of years.

  14. Factors Influencing Phosphorous Cycling in Biogeochemical 'Hot Spots'

    NASA Astrophysics Data System (ADS)

    Saia, S. M.; Walter, M. T.; Buda, A. R.; Carrick, H. J.; Regan, J. M.

    2015-12-01

    Anthropogenic alteration of the phosphorus (P) cycle has led to subsequent soil and water quality issues. For example, P build up in soils due to historic fertilizer application may become biologically available and exacerbate eutrophication and anoxia in nearby water bodies. In the humid Northeastern United States, storm runoff transports P and also stimulates biogeochemical processes, these locations are termed biogeochemical 'hot spots'. Many studies have looked at nitrogen and carbon cycling in biogeochemical hot spots but few have focused on P. We hypothesize the periodic wetting and drying of biogeochemical hot spots promotes a combination of abiotic and biotic processes that influence the mobility of P. To test this hypothesis, we took monthly soil samples (5 cm deep) from May to October in forest, pasture, and cropped land near Ithaca, NY. In-situ measurements taken with each sample included volumetric soil moisture and soil temperature. We also analyzed samples for 'runoff generated' phosphate, nitrate, and sulfate (from 0.01 M CaCl2 extraction), Fe(II), percent organic matter, pH, as well as oxalate extractable and total P, Al, and Fe. We used linear mixed effects models to test how runoff generated phosphate concentrations vary with soil moisture and whether other environmental factors strengthen/weaken this relationship. The knowledge gained from this study will improve our understanding of P cycling in biogeochemical hot spots and can be used to improve the effectiveness of agricultural management practices in the Northeastern United States.

  15. Biogeochemical modeling at mass extinction boundaries

    NASA Technical Reports Server (NTRS)

    Rampino, M. R.; Caldeira, K. G.

    1991-01-01

    The causes of major mass extinctions is a subject of considerable interest to those concerned with the history and evolution of life on earth. The primary objectives of the proposed plan of research are: (1) to develop quantitative time-dependent biogeochemical cycle models, coupled with an ocean atmosphere in order to improve the understanding of global scale physical, chemical, and biological processes that control the distribution of elements important for life at times of mass extinctions; and (2) to develop a comprehensive data base of the best available geochemical, isotopic, and other relevant geologic data from sections across mass extinction boundaries. These data will be used to constrain and test the biogeochemical model. These modeling experiments should prove useful in: (1) determining the possible cause(s) of the environmental changes seen at bio-event boundaries; (2) identifying and quantifying little-known feedbacks among the oceans, atmosphere, and biosphere; and (3) providing additional insights into the possible responses of the earth system to perturbations of various timescales. One of the best known mass extinction events marks the Cretaceous/Tertiary (K/T) boundary (66 Myr ago). Data from the K/T boundary are used here to constrain a newly developed time-dependent biogeochemical cycle model that is designed to study transient behavior of the earth system. Model results predict significant fluctuations in ocean alkalinity, atmospheric CO2, and global temperatures caused by extinction of calcareous plankton and reduction in the sedimentation rates of pelagic carbonates and organic carbon. Oxygen-isotome and other paleoclimatic data from K/T time provide some evidence that such climatic fluctuations may have occurred, but stabilizing feedbacks may have acted to reduce the ocean alkalinity and carbon dioxide fluctuations.

  16. Analysis of conservative tracer measurement results using the Frechet distribution at planted horizontal subsurface flow constructed wetlands filled with coarse gravel and showing the effect of clogging processes.

    PubMed

    Dittrich, Ernő; Klincsik, Mihály

    2015-11-01

    A mathematical process, developed in Maple environment, has been successful in decreasing the error of measurement results and in the precise calculation of the moments of corrected tracer functions. It was proved that with this process, the measured tracer results of horizontal subsurface flow constructed wetlands filled with coarse gravel (HSFCW-C) can be fitted more accurately than with the conventionally used distribution functions (Gaussian, Lognormal, Fick (Inverse Gaussian) and Gamma). This statement is true only for the planted HSFCW-Cs. The analysis of unplanted HSFCW-Cs needs more research. The result of the analysis shows that the conventional solutions (completely stirred series tank reactor (CSTR) model and convection-dispersion transport (CDT) model) cannot describe these types of transport processes with sufficient accuracy. These outcomes can help in developing better process descriptions of very difficult transport processes in HSFCW-Cs. Furthermore, a new mathematical process can be developed for the calculation of real hydraulic residence time (HRT) and dispersion coefficient values. The presented method can be generalized to other kinds of hydraulic environments.

  17. Microbiological, Geochemical and Hydrologic Processes Controlling Uranium Mobility: An Integrated Field-Scale Subsurface Research Challenge Site at Rifle, Colorado, Quality Assurance Project Plan

    SciTech Connect

    Fix, N. J.

    2008-01-07

    The U.S. Department of Energy (DOE) is cleaning up and/or monitoring large, dilute plumes contaminated by metals, such as uranium and chromium, whose mobility and solubility change with redox status. Field-scale experiments with acetate as the electron donor have stimulated metal-reducing bacteria to effectively remove uranium [U(VI)] from groundwater at the Uranium Mill Tailings Site in Rifle, Colorado. The Pacific Northwest National Laboratory and a multidisciplinary team of national laboratory and academic collaborators has embarked on a research proposed for the Rifle site, the object of which is to gain a comprehensive and mechanistic understanding of the microbial factors and associated geochemistry controlling uranium mobility so that DOE can confidently remediate uranium plumes as well as support stewardship of uranium-contaminated sites. This Quality Assurance Project Plan provides the quality assurance requirements and processes that will be followed by the Rifle Integrated Field-Scale Subsurface Research Challenge Project.

  18. A numerical study of EGS heat extraction process based on a thermal non-equilibrium model for heat transfer in subsurface porous heat reservoir

    NASA Astrophysics Data System (ADS)

    Chen, Jiliang; Jiang, Fangming

    2016-02-01

    With a previously developed numerical model, we perform a detailed study of the heat extraction process in enhanced or engineered geothermal system (EGS). This model takes the EGS subsurface heat reservoir as an equivalent porous medium while it considers local thermal non-equilibrium between the rock matrix and the fluid flowing in the fractured rock mass. The application of local thermal non-equilibrium model highlights the temperature-difference heat exchange process occurring in EGS reservoirs, enabling a better understanding of the involved heat extraction process. The simulation results unravel the mechanism of preferential flow or short-circuit flow forming in homogeneously fractured reservoirs of different permeability values. EGS performance, e.g. production temperature and lifetime, is found to be tightly related to the flow pattern in the reservoir. Thermal compensation from rocks surrounding the reservoir contributes little heat to the heat transmission fluid if the operation time of an EGS is shorter than 15 years. We find as well the local thermal equilibrium model generally overestimates EGS performance and for an EGS with better heat exchange conditions in the heat reservoir, the heat extraction process acts more like the local thermal equilibrium process.

  19. MODELING CONTAMINANT TRANSPORT THROUGH SUBSURFACE SYSTEMS

    EPA Science Inventory

    Modeling of contaminant transport through soil to groundwater to a receptor requires that consideration be given to the many processes which control the transport and fate of chemical constituents in the subsurface environment. These processes include volatilization, degradation,...

  20. Biosphere frontiers of subsurface life in the sedimented hydrothermal system of Guaymas Basin

    PubMed Central

    Teske, Andreas; Callaghan, Amy V.; LaRowe, Douglas E.

    2014-01-01

    Temperature is one of the key constraints on the spatial extent, physiological and phylogenetic diversity, and biogeochemical function of subsurface life. A model system to explore these interrelationships should offer a suitable range of geochemical regimes, carbon substrates and temperature gradients under which microbial life can generate energy and sustain itself. In this theory and hypothesis article, we make the case for the hydrothermally heated sediments of Guaymas Basin in the Gulf of California as a suitable model system where extensive temperature and geochemical gradients create distinct niches for active microbial populations in the hydrothermally influenced sedimentary subsurface that in turn intercept and process hydrothermally generated carbon sources. We synthesize the evidence for high-temperature microbial methane cycling and sulfate reduction at Guaymas Basin – with an eye on sulfate-dependent oxidation of abundant alkanes – and demonstrate the energetic feasibility of these latter types of deep subsurface life in previously drilled Guaymas Basin locations of Deep-Sea Drilling Project 64. PMID:25132832

  1. A Coupled Model of Multiphase Flow, Reactive Biogeochemical Transport, Thermal Transport and Geo-Mechanics.

    NASA Astrophysics Data System (ADS)

    Tsai, C. H.; Yeh, G. T.

    2015-12-01

    In this investigation, a coupled model of multiphase flow, reactive biogeochemical transport, thermal transport and geo-mechanics in subsurface media is presented. It iteratively solves the mass conservation equation for fluid flow, thermal transport equation for temperature, reactive biogeochemical transport equations for concentration distributions, and solid momentum equation for displacement with successive linearization algorithm. With species-based equations of state, density of a phase in the system is obtained by summing up concentrations of all species. This circumvents the problem of having to use empirical functions. Moreover, reaction rates of all species are incorporated in mass conservation equation for fluid flow. Formation enthalpy of all species is included in the law of energy conservation as a source-sink term. Finite element methods are used to discretize the governing equations. Numerical experiments are presented to examine the accuracy and robustness of the proposed model. The results demonstrate the feasibility and capability of present model in subsurface media.

  2. Endoscopic subsurface imaging in tissues

    SciTech Connect

    Demos, S G; Staggs, M; Radousky, H B

    2001-02-12

    The objective of this work is to develop endoscopic subsurface optical imaging technology that will be able to image different tissue components located underneath the surface of the tissue at an imaging depth of up to 1 centimeter. This effort is based on the utilization of existing technology and components developed for medical endoscopes with the incorporation of the appropriate modifications to implement the spectral and polarization difference imaging technique. This subsurface imaging technique employs polarization and spectral light discrimination in combination with image processing to remove a large portion of the image information from the outer layers of the tissue which leads to enhancement of the contrast and image quality of subsurface tissue structures.

  3. Scaling Hyporheic Flow and Biogeochemical Reactions across a Wide Range of Flow and Sediment Conditions in Aquatic Systems

    NASA Astrophysics Data System (ADS)

    Harvey, J. W.; O'Connor, B. L.

    2008-12-01

    Aquatic ecosystems are strongly influenced by advective transport from surface water into shallow sediments of the hyporheic zone. The delivery of energy and nutrient-rich materials to microbially and geochemically reactive sediment stimulates high rates of biogeochemical reactions that influence the overall metabolism of the ecosystem as well as influencing the chemistry of downstream receiving waters. Predicting hyporheic flow is difficult because of the potential involvement of many physical processes, including diffusion, shear, bedform-scale advective pumping, bed mobility and bioturbation, turbulence penetration, and head potential- driven groundwater exchange. We used published data from carefully controlled laboratory flume experiments to develop a scaling relationship that predicts hyporheic exchange based on physical descriptors (e.g. shear stress velocity, roughness height, and sediment permeability) that summarize fluid- flow and sediment characteristics. We tested the scaling relationship's predictions by comparing them with more time and labor intensive measurements of solute and reactive tracer transport made in situ in hyporheic zones. In situ measurements were acquired using the USGS MINIPOINT sampler, which allows detailed subsurface measurements without significant disturbance of sediment or the ambient surface or subsurface water fluxes. Fieldwork was undertaken in several streams that varied widely in surface water flow velocities, grain type, median grain size, sediment porosity, sediment organic content, sediment hydraulic conductivity, and groundwater specific discharge. The comparison generally supported the predictive capability of the scaling relationship in complex field settings. The value of the scaling relationship is also indicated for improving rate measurements of biogeochemical reactions in hyporheic zones (e.g. oxygen uptake, denitrification, and manganese oxidation), as well as for estimating the cumulative influence of

  4. The biogeochemical footprint of agricultural soil erosion

    NASA Astrophysics Data System (ADS)

    Govers, Gerard; Van Oost, Kristof; Wang, Zhengang

    2015-04-01

    Global biogeochemical cycles are a key component of the functioning of the Earth System: these cycles are all, to a varying extent, disturbed by human activities which not only has dramatic consequences for the global climate but also for the acidity of the world's oceans. It is only relatively recently that the role of lateral fluxes related to surface water movement and soil erosion and deposition (and the way those fluxes are modified by human action) is explicitly considered by the scientific community. In this paper we present an overview of our present-day understanding of the role of agricultural soil erosion in the global cycles of carbon, nitrogen, phosphorous and silica. We discuss the major processes through which erosion affects these global cycles and pay particular attention to the knowledge gaps that prevent us from accurately assessing the impact of soil erosion on global biogeochemical cycling at different temporal scales. Furthering our understanding (and better constraining our estimates) will require progress both in terms of model development and process understanding. Research needs can be most clearly identified with respect to soil organic carbon: (i) at present, large-scale soil erosion (and deposition) models are poorly constrained so that the amount of carbon mobilised by erosion (and its fate) cannot be accurately estimated and (ii) the fate of soil organic carbon buried by deposition or delivered to river network is poorly understood. Uncertainties for N, P and Si are larger than those for C as we have less information on the amount of these elements stored in agricultural soils and/or do not fully understand how these elements cycle through the soil/plant system. Agricultural soil erosion does not affect soil functioning through its effect on biogeochemical cycling. Erosion directly affects soil hydrological functioning and is likely to affect weathering processes and soil production. Addressing all these issues requires the

  5. Application of divided convective-dispersive transport model to simulate conservative transport processes in planted horizontal sub-surface flow constructed wetlands.

    PubMed

    Dittrich, Ernő; Klincsik, Mihály

    2015-11-01

    We have created a divided convective-dispersive transport (D-CDT) model that can be used to provide an accurate simulation of conservative transport processes in planted horizontal sub-surface flow constructed wetlands filled with coarse gravel (HSFCW-C). This model makes a fitted response curve from the sum of two independent CDT curves, which show the contributions of the main and side streams. The analytical solutions of both CDT curves are inverse Gaussian distribution functions. We used Fréchet distribution to provide a fast optimization mathematical procedure. As a result of our detailed analysis, we concluded that the most important role in the fast upward part of the tracer response curve is played by the main stream, with high porous velocity and dispersion. This gives the first inverse Gaussian distribution function. The side stream shows slower transport processes in the micro-porous system, and this shows the impact of back-mixing and dead zones, too. The significance of this new model is that it can simulate transport processes in this kind of systems more accurately than the conventionally used convective-dispersive transport (CDT) model. The calculated velocity and dispersion coefficients with the D-CDT model gave differences of 24-54% (of velocity) and 22-308% (of dispersion coeff.) from the conventional CDT model, and were closer to actual hydraulic behaviour.

  6. What an Arctic terrestrial MIP tells about changes and differences in Arctic subsurface hydrology

    NASA Astrophysics Data System (ADS)

    Saito, K.

    2015-12-01

    The spatial and temporal characteristics of Arctic hydrology have been investigated in the GTMIP activity (https://ads.nipr.ac.jp/gtmip/gtmip.html), conducted as a part of GRENE Arctic Climate Change Project in Japan. The activity has two stages, one on local and the other on the circum-Arctic scales. Stage 1 is site simulations for the period of 1980-2013 for four Arctic observation sites, i.e., Fairbanks/AK, Kevo/Finland, Yakutsuk and Tiksi in Siberia, focusing on process evaluations with observation. Stage 2 is pan-arctic simulations for 1850-2100 with 0.5x0.5 degree resolution, targeting at the responses of Arctic terrestrial to global climate change. At both stages multiple terrestrial models have been participating (16+ for Stage 1; 10 for Stage 2), ranging from physically-oriented process models to biogeochemical models to ESM-compatible ecosystem models. The results are delineating a) spatial variations and temporal changes in subsurface thermal and hydrological states, and subsequently the ecosystem in different climatic/ecosystem zones (e.g., Kevo is underlain by seasonally frozen ground while others by permafrost; Tiksi is in tundra whole others in taiga; these two sites are Arctic while the other two sub-Arctic), and b) the differences and similarities in the reproducibility among models with respect to the target of the models (e.g., physical, or biogeochemical) and to the complexity of implemented processes.

  7. Physical and biogeochemical modulation of ocean acidification in the central North Pacific.

    PubMed

    Dore, John E; Lukas, Roger; Sadler, Daniel W; Church, Matthew J; Karl, David M

    2009-07-28

    Atmospheric carbon dioxide (CO(2)) is increasing at an accelerating rate, primarily due to fossil fuel combustion and land use change. A substantial fraction of anthropogenic CO(2) emissions is absorbed by the oceans, resulting in a reduction of seawater pH. Continued acidification may over time have profound effects on marine biota and biogeochemical cycles. Although the physical and chemical basis for ocean acidification is well understood, there exist few field data of sufficient duration, resolution, and accuracy to document the acidification rate and to elucidate the factors governing its variability. Here we report the results of nearly 20 years of time-series measurements of seawater pH and associated parameters at Station ALOHA in the central North Pacific Ocean near Hawaii. We document a significant long-term decreasing trend of -0.0019 +/- 0.0002 y(-1) in surface pH, which is indistinguishable from the rate of acidification expected from equilibration with the atmosphere. Superimposed upon this trend is a strong seasonal pH cycle driven by temperature, mixing, and net photosynthetic CO(2) assimilation. We also observe substantial interannual variability in surface pH, influenced by climate-induced fluctuations in upper ocean stability. Below the mixed layer, we find that the change in acidification is enhanced within distinct subsurface strata. These zones are influenced by remote water mass formation and intrusion, biological carbon remineralization, or both. We suggest that physical and biogeochemical processes alter the acidification rate with depth and time and must therefore be given due consideration when designing and interpreting ocean pH monitoring efforts and predictive models. PMID:19666624

  8. Physical and biogeochemical modulation of ocean acidification in the central North Pacific.

    PubMed

    Dore, John E; Lukas, Roger; Sadler, Daniel W; Church, Matthew J; Karl, David M

    2009-07-28

    Atmospheric carbon dioxide (CO(2)) is increasing at an accelerating rate, primarily due to fossil fuel combustion and land use change. A substantial fraction of anthropogenic CO(2) emissions is absorbed by the oceans, resulting in a reduction of seawater pH. Continued acidification may over time have profound effects on marine biota and biogeochemical cycles. Although the physical and chemical basis for ocean acidification is well understood, there exist few field data of sufficient duration, resolution, and accuracy to document the acidification rate and to elucidate the factors governing its variability. Here we report the results of nearly 20 years of time-series measurements of seawater pH and associated parameters at Station ALOHA in the central North Pacific Ocean near Hawaii. We document a significant long-term decreasing trend of -0.0019 +/- 0.0002 y(-1) in surface pH, which is indistinguishable from the rate of acidification expected from equilibration with the atmosphere. Superimposed upon this trend is a strong seasonal pH cycle driven by temperature, mixing, and net photosynthetic CO(2) assimilation. We also observe substantial interannual variability in surface pH, influenced by climate-induced fluctuations in upper ocean stability. Below the mixed layer, we find that the change in acidification is enhanced within distinct subsurface strata. These zones are influenced by remote water mass formation and intrusion, biological carbon remineralization, or both. We suggest that physical and biogeochemical processes alter the acidification rate with depth and time and must therefore be given due consideration when designing and interpreting ocean pH monitoring efforts and predictive models.

  9. Using geochemical indicators to distinguish high biogeochemical activity in floodplain soils and sediments.

    PubMed

    Kenwell, Amy; Navarre-Sitchler, Alexis; Prugue, Rodrigo; Spear, John R; Hering, Amanda S; Maxwell, Reed M; Carroll, Rosemary W H; Williams, Kenneth H

    2016-09-01

    A better understanding of how microbial communities interact with their surroundings in physically and chemically heterogeneous subsurface environments will lead to improved quantification of biogeochemical reactions and associated nutrient cycling. This study develops a methodology to predict potential elevated rates of biogeochemical activity (microbial "hotspots") in subsurface environments by correlating microbial DNA and aspects of the community structure with the spatial distribution of geochemical indicators in subsurface sediments. Multiple linear regression models of simulated precipitation leachate, HCl and hydroxylamine extractable iron and manganese, total organic carbon (TOC), and microbial community structure were used to identify sample characteristics indicative of biogeochemical hotspots within fluvially-derived aquifer sediments and overlying soils. The method has been applied to (a) alluvial materials collected at a former uranium mill site near Rifle, Colorado and (b) relatively undisturbed floodplain deposits (soils and sediments) collected along the East River near Crested Butte, Colorado. At Rifle, 16 alluvial samples were taken from 8 sediment cores, and at the East River, 46 soil/sediment samples were collected across and perpendicular to 3 active meanders and an oxbow meander. Regression models using TOC and TOC combined with extractable iron and manganese results were determined to be the best fitting statistical models of microbial DNA (via 16S rRNA gene analysis). Fitting these models to observations in both contaminated and natural floodplain deposits, and their associated alluvial aquifers, demonstrates the broad applicability of the geochemical indicator based approach. PMID:27145490

  10. Carbon sources and biogeochemical processes in Monticchio maar lakes, Mt Vulture volcano (southern Italy): New geochemical constrains of active degassing of mantle derived fluids

    NASA Astrophysics Data System (ADS)

    Caracausi, A.; Nuccio, P. M.; Favara, R.; Grassa, F.

    2012-04-01

    Since the catastrophic releases of carbon dioxide from the African volcanic lakes Nyos and Monoun in the 1980s, the scientific community draw attention towards all those crater lakes able to accumulate massive amount of CO2, which could be catastrophically released following overturn of their deep waters. This implies a quantification of the gas accumulation rate into the lakes and the knowledge of recharge processes and their evolution in time. In fact the gaseous recharge in a lake occurs at alarming rates, when an active degassing of hazardous nature volatiles occurs into the lakes and the structure and dynamic of the lake permit the accumulation of gases into the water. The Monticchio lakes, LPM and LGM, occupies two maar craters formed during the last volcanic activity of Mt. Vulture occurred ˜ 140 000 years ago. LPM is a permanently stratified lake, with a thick deep volume of stagnant water and a shallower layer affected by seasonal overturn. On the contrary LGM is a monomittic lake with a complete overturn of the water during winter time. The major dissolved volatiles are methane and CO2. Dissolved helium is in trace amounts and its isotopic signature ranges between 6.1 and 5.3 Ra (Ra is the atmospheric 3He/4He isotopic ratio). These values are within the range of those measured in the olivine fluid inclusions (both of mantle xenoliths and dispersed in the pyroclastics) of LPM maar ejecta. During three years of investigations we observed that dissolved methane in the deep waters of LGM drastically decreases in wintertime as consequence of the complete overturn of the water. The isotopic signature of methane in the deepest portions of LGM (both sediment and water) is quite stable with time and highlights a biogenic origin, being produced both by acetate fermentation and by CO2-reduction in variable proportions. In contrast, a higher contribution of methane produced via CO2 reduction characterizes sediments at shallower depths. At LPM, there is a great

  11. The OpenGeoSys coupling concept for THMC processes in subsurface and the neighboring hydro-compartments

    NASA Astrophysics Data System (ADS)

    Kalbacher, T.; Delfs, J. O.; Shao, H.; Boettcher, N.; Walther, M.; Kolditz, O.

    2012-12-01

    State-of-the-art computational models used for integrated water resources management are rapidly developing instruments. Advances in computational mathematics have revolutionized the variety and the nature of the problems that can be addressed by environmental scientists and engineers. For each hydro-compartment, from precipitation and surface run-off to catchment water balance and groundwater interactions, there exist many excellent simulation codes. However, their development has been isolated within different disciplines. The OpenGeoSys (OGS) project is a scientific open source initiative for numerical simulation of thermo-hydro-mechanical-chemical (THMC) processes in porous and fractured media. The basic concept is to provide a flexible numerical framework (using primarily the Finite Element Method (FEM)) for solving multi-field problems in porous and fractured media for applications in geoscience and hydrology. To this purpose, OGS is based on an object-oriented FEM concept including a broad spectrum of interfaces for pre- and post-processing. The idea includes a web-based platform for community access, outfitted with professional software engineering tools such as platform-independent compiling and fully automated benchmarking. The second strategy is to utilize an additional coupling concept that enables OGS simulations to interact sequentially with other individual modeling software in order to address coupled processes in neighboring hydrologic compartments, which includes methods of coupling different physical processes and different geometric model complexities under consideration of the spatial and temporal scale change and the required computational resources. The IWAS ToolBox concept.

  12. Are all runoff processes the same? Numerical experiments comparing a Darcy-Richards solver to an overland flow-based approach for subsurface storm runoff simulation

    NASA Astrophysics Data System (ADS)

    Ameli, A. A.; Craig, J. R.; McDonnell, J. J.

    2015-12-01

    Hillslope runoff theory is based largely on the differentiation between infiltration excess overland flow, saturation excess overland flow, and subsurface stormflow. Here we explore to what extent a 2-D friction-based overland flow model is useful for predicting hillslope-scale subsurface stormflow, posited here as phenomenologically the same as infiltration excess at depth. We compare our results to a 3-D variably saturated Darcy-Richards subsurface solver for individual rainfall runoff events. We use field data from the well-studied Panola Mountain Experimental hillslope in Georgia USA. Our results show that the two models are largely indistinguishable in terms of their ability to simulate the hillslope hydrograph magnitude and timing for a range of slopes and rainfall depths. Furthermore, we find that the descriptive ability of the overland flow model is comparable to the variably saturated subsurface flow model in terms of its ability to represent the spatial distribution of subsurface stormflow and infiltration across the soil-bedrock interface. More importantly, these results imply that the physics of infiltration excess subsurface stormflow at the soil-bedrock interface is similar to infiltration excess overland flow at the soil surface, in terms of detention storage, loss along the lower boundary, and threshold-like activation at the larger hillslope scale. Given the phenomenological similarity of overland flow and subsurface stormflow and the fact that overland flow model predictions are considerably faster to run (particularly as slope and rainfall depth increase), these findings imply that new forms of hillslope-scale subsurface storm runoff predictions may be possible with the knowledge of bedrock permeability and limited soil information. Finally, this work suggests that the role of soil mantle vis-à-vis subsurface stormflow is mainly as a filter that delays the development of patches of saturation along the bedrock surface. Our model results show

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

    SciTech Connect

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

    2014-01-28

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

  14. Single cell genomics of subsurface microorganisms

    NASA Astrophysics Data System (ADS)

    Stepanauskas, R.; Onstott, T. C.; Lau, C.; Kieft, T. L.; Woyke, T.; Rinke, C.; Sczyrba, A.; van Heerden, E.

    2012-12-01

    Recent studies have revealed unexpected abundance and diversity of microorganisms in terrestrial and marine subsurface, providing new perspectives over their biogeochemical significance, evolution, and the limits of life. The now commonly used research tools, such as metagenomics and PCR-based gene surveys enabled cultivation-unbiased analysis of genes encoded by natural microbial communities. However, these methods seldom provide direct evidence for how the discovered genes are organized inside genomes and from which organisms do they come from. Here we evaluated the feasibility of an alternative, single cell genomics approach, in the analysis of subsurface microbial community composition, metabolic potential and microevolution at the Sanford Underground Research Facility (SURF), South Dakota, and the Witwaterstrand Basin, South Africa. We successfully recovered genomic DNA from individual microbial cells from multiple locations, including ultra-deep (down to 3,500 m) and low-biomass (down to 10^3 cells mL^-1) fracture water. The obtained single amplified genomes (SAGs) from SURF contained multiple representatives of the candidate divisions OP3, OP11, OD1 and uncharacterized archaea. By sequencing eight of these SAGs, we obtained the first genome content information for these phylum-level lineages that do not contain a single cultured representative. The Witwaterstrand samples were collected from deep fractures, biogeochemical dating of which suggests isolation from tens of thousands to tens of millions of years. Thus, these fractures may be viewed as "underground Galapagos", a natural, long-term experiment of microbial evolution within well-defined temporal and spatial boundaries. We are analyzing multiple SAGs from these environments, which will provide detailed information about adaptations to life in deep subsurface, mutation rates, selective pressures and gene flux within and across microbial populations.

  15. Biogeochemical processes involving dissolved CO2 and CH4 at Albano, Averno, and Monticchio meromictic volcanic lakes (Central-Southern Italy)

    NASA Astrophysics Data System (ADS)

    Cabassi, Jacopo; Tassi, Franco; Vaselli, Orlando; Fiebig, Jens; Nocentini, Matteo; Capecchiacci, Francesco; Rouwet, Dmitri; Bicocchi, Gabriele

    2013-01-01

    This paper focuses on the chemical and isotopic features of dissolved gases (CH4 and CO2) from four meromictic lakes hosted in volcanic systems of Central-Southern Italy: Lake Albano (Alban Hills), Lake Averno (Phlegrean Fields), and Monticchio Grande and Piccolo lakes (Mt. Vulture). Deep waters in these lakes are characterized by the presence of a significant reservoir of extra-atmospheric dissolved gases mainly consisting of CH4 and CO2. The δ13C-CH4 and δD-CH4 values of dissolved gas samples from the maximum depths of the investigated lakes (from -66.8 to -55.6 ‰ V-PDB and from -279 to -195 ‰ V-SMOW, respectively) suggest that CH4 is mainly produced by microbial activity. The δ13C-CO2 values of Lake Grande, Lake Piccolo, and Lake Albano (ranging from -5.8 to -0.4 ‰ V-PDB) indicate a significant CO2 contribution from sublacustrine vents originating from (1) mantle degassing and (2) thermometamorphic reactions involving limestone, i.e., the same CO2 source feeding the regional thermal and cold CO2-rich fluid emissions. In contrast, the relatively low δ13C-CO2 values (from -13.4 to -8.2 ‰ V-PDB) of Lake Averno indicate a prevalent organic CO2. Chemical and isotopic compositions of dissolved CO2 and CH4 at different depths are mainly depending on (1) CO2 inputs from external sources (hydrothermal and/or anthropogenic); (2) CO2-CH4 isotopic exchange; and (3) methanogenic and methanotrophic activity. In the epilimnion, vertical water mixing, free oxygen availability, and photosynthesis cause the dramatic decrease of both CO2 and CH4 concentrations. In the hypolimnion, where the δ13C-CO2 values progressively increase with depth and the δ13C-CH4 values show an opposite trend, biogenic CO2 production from CH4 using different electron donor species, such as sulfate, tend to counteract the methanogenesis process whose efficiency achieves its climax at the water-bottom sediment interface. Theoretical values, calculated on the basis of δ13C-CO2 values, and

  16. Mars organic molecules irradiation and evolution (MOMIE): Assessing the processes impacting organic matter at Mars surface and subsurface

    NASA Astrophysics Data System (ADS)

    Coll, P. J.; Szopa, C.; Poch, O.; Noblet, A.; Desboeufs, K.; Stalport, F.; Cottin, H.; Buch, A.

    2011-12-01

    The search for organic relics from the early Mars is one of the major science objectives of the next missions to Mars: NASA MSL 2011 and ESA ExoMars 2018. To fulfill these mission goals, the MOMIE project has been developed to study the processes which potentially drive the evolution of organics, and evaluate the stability of organic molecules under current environmental conditions at the Mars surface. An experimental set-up enabling to simulate various interactions encountered by organic matter on Mars is the heart of the project. For instance, the relative influence of hydrogen peroxide (H2O2) diffusion in the soil and of oxidants formed by UV-water ice or UV-minerals interactions can be studied by monitoring an organic sample with infrared spectroscopy. The more complex synergy of different processes will be the UV irradiation of an organic compound adsorbed on a mineral matrix in contact with water ice and/or oxidants.

  17. Effects of physical and biogeochemical processes on aquatic ecosystems at the groundwater-surface water interface: An evaluation of a sulfate-impacted wild rice stream in Minnesota (USA)

    NASA Astrophysics Data System (ADS)

    Ng, G. H. C.; Yourd, A. R.; Myrbo, A.; Johnson, N.

    2015-12-01

    Significant uncertainty and variability in physical and biogeochemical processes at the groundwater-surface water interface complicate how surface water chemistry affects aquatic ecosystems. Questions surrounding a unique 10 mg/L sulfate standard for wild rice (Zizania sp.) waters in Minnesota are driving research to clarify conditions controlling the geochemistry of shallow sediment porewater in stream- and lake-beds. This issue raises the need and opportunity to carry out in-depth, process-based analysis into how water fluxes and coupled C, S, and Fe redox cycles interact to impact aquatic plants. Our study builds on a recent state-wide field campaign that showed that accumulation of porewater sulfide from sulfate reduction impairs wild rice, an annual grass that grows in shallow lakes and streams in the Great Lakes region of North America. Negative porewater sulfide correlations with organic C and Fe quantities also indicated that lower redox rates and greater mineral precipitation attenuate sulfide. Here, we focus on a stream in northern Minnesota that receives high sulfate loading from iron mining activity yet maintains wild rice stands. In addition to organic C and Fe effects, we evaluate the degree to which streambed hydrology, and in particular groundwater contributions, accounts for the active biogeochemistry. We collect field measurements, spanning the surrounding groundwater system to the stream, to constrain a reactive-transport model. Observations from seepage meters, temperature probes, and monitoring wells delineate upward flow that may lessen surface water impacts below the stream. Geochemical analyses of groundwater, porewater, and surface water samples and of sediment extractions reveal distinctions among the different domains and stream banks, which appear to jointly control conditions in the streambed. A model based on field conditions can be used to evaluate the relative the importance and the spatiotemporal scales of diverse flux and

  18. Selenium source identification and biogeochemical processes controlling selenium in surface water and biota, Kendrick Reclamation Project, Wyoming, U.S.A.

    USGS Publications Warehouse

    Naftz, D.L.; See, R.B.; Ramirez, P.

    1993-01-01

    The major tributaries draining the Kendrick Reclamation Project (KRP) account for an average of 52% of the total Se load measured in the North Platte River downstream from Casper, Wyoming. The Casper Creek drainage basin contributed the largest Se load of the five tributary sites to the North Platte River. The 4-d average Se concentration in water samples from one site in the part of the North Platte River that receives irrigation return flows exceeded the 5 ??g/l U.S. Environmental Protection Agency's aquatic life criterion five time during a 50-d monitoring period in 1989. In agreement with the water-quality data, muscle and liver tissue rom rainbow trout collected from the same part of the North Platte River had Se concentrations exceeding levels known to cause reproductive failure and chronic Se poisoning. On the basis of Se: Cl, 18O/16O and D/H ratios in water from Goose and Rasmus Lee Lakes (closed-basin systems), the large Se concentrations in those lakes were derived by natural evaporation of irrigation water without leaching of soluble forms of Se from soil or rocks. Water samples from Thirtythree Mile Reservoir and Illco Pond (flow-through systems) showed considerable enrichment in Se over evaporative concentration, presumably due to leaching and desorption of Se from soil and rock. The Se: Cl ratios of irrigation drain water collected from the KRP indicate that leaching and desorption of soluble forms of Se from soils and rocks are the dominant processes in drain water. Results of a Wilcoxon matched-pairs test for 43 paired drain-water samples collected during June and August 1988, indicated there is a statistically larger concentration of Se (0.01 significance level) during the June sampling period. The larger concentrations of Se and other chemical constitutents during the early part of the irrigation season probably were due to dissolution of seleniferous salts that have accumulated in soils within the KRP since the last irrigation season. The large

  19. Oceanographic and Biogeochemical Insights from Diatom Genomes

    NASA Astrophysics Data System (ADS)

    Bowler, Chris; Vardi, Assaf; Allen, Andrew E.

    2010-01-01

    Diatoms are the most successful group of eukaryotic phytoplankton in the modern ocean and have risen to dominance relatively quickly over the last 100 million years. Recently completed whole genome sequences from two species of diatom, Thalassiosira pseudonana and Phaeodactylum tricornutum, have revealed a wealth of information about the evolutionary origins and metabolic adaptations that have led to their ecological success. A major finding is that they have incorporated genes both from their endosymbiotic ancestors and by horizontal gene transfer from marine bacteria. This unique melting pot of genes encodes novel capacities for metabolic management, for example, allowing the integration of a urea cycle into a photosynthetic cell. In this review we show how genome-enabled approaches are being leveraged to explore major phenomena of oceanographic and biogeochemical relevance, such as nutrient assimilation and life histories in diatoms. We also discuss how diatoms may be affected by climate change-induced alterations in ocean processes.

  20. Biogeochemical cycling in the Strait of Georgia.

    PubMed

    Johannessen, S C; Macdonald, R W; Burd, B; van Roodselaar, A

    2008-12-01

    The papers in this special issue present the results of a five-year project to study sedimentary biogeochemical processes in the Strait of Georgia, with special emphasis on the near-field of a large municipal outfall. Included in this special issue are overviews of the sedimentology, benthic biology, status of siliceous sponge reefs and distribution of organic carbon in the water column. Other papers address the cycling of contaminants (PCBs, PBDEs) and redox metals in the sediment, a method to map the extent of the influence of municipal effluent from staining on benthic bivalves, and the relationships among geochemical conditions and benthic abundance and diversity. The latter set of papers addresses the role of municipal effluent as a pathway of organic carbon and other contaminants into the Strait of Georgia and the effect of the effluent on benthic geochemistry and biology. PMID:19022498

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

    NASA Astrophysics Data System (ADS)

    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

  2. Data acquisition and processing system and method for investigating sub-surface features of a rock formation

    SciTech Connect

    Vu, Cung Khac; Nihei, Kurt; Johnson, Paul A; Guyer, Robert; Ten Cate, James A; Le Bas, Pierre-Yves; Larmat, Carene S

    2015-01-27

    A system and a method includes generating a first signal at a first frequency; and a second signal at a second frequency. Respective sources are positioned within the borehole and controllable such that the signals intersect in an intersection volume outside the borehole. A receiver detects a difference signal returning to the borehole generated by a non-linear mixing process within the intersection volume, and records the detected signal and stores the detected signal in a storage device and records measurement parameters including a position of the first acoustic source, a position of the second acoustic source, a position of the receiver, elevation angle and azimuth angle of the first acoustic signal and elevation angle and azimuth angle of the second acoustic signal.

  3. Relating sulfide mineral zonation and trace element chemistry to subsurface processes in the Reykjanes geothermal system, Iceland

    NASA Astrophysics Data System (ADS)

    Libbey, R. B.; Williams-Jones, A. E.

    2016-01-01

    The nature and distribution of sulfide minerals and their trace element chemistry in the seawater-dominated Reykjanes geothermal system was determined through the study of cuttings and core from wells that intersect different regions of the hydrothermal cell, from the near surface to depths of > 3000 m. The observed sulfide mineral zonation and trace element enrichment correlate well with the present-day thermal structure of the system. Isocubanite and pyrrhotite are confined to the deep, low permeability regions, whereas an assemblage of chalcopyrite and pyrite predominates in the main convective upflow path. The presence of marcasite in the uppermost regions of the system reflects weakly acidic conditions (pH < 5) marginal to the upflow, where outflow and downward percolating fluids have dissolved deeply exsolved CO2. The presence of "chalcopyrite disease" in sphalerite may be an indication that the system is experiencing a heating trend, following the logic of "zone-refining" in volcanogenic massive sulfide systems. Sulfide sulfur at all analyzed depths in the Reykjanes geothermal system was derived from a mixture of basaltic and reduced seawater sources. Petrographic evidence suggests that seawater-derived hydrothermal fluids have altered primary igneous sulfides in the host rocks, a process that has been proposed as a major control of aqueous sulfide production in mid-ocean ridge environments. Calculations show that igneous sulfides in the host basalts likely account for less than 5% of the total available ore metal budget in the system, however, their contribution to fluid metal budgets is probably significant because of their relatively high solubility. The processes documented by this study are likely analogous to those operating in the feeder and deep reaction zones of mid-ocean ridge seafloor hydrothermal systems. The results show that sulfide mineral zonation and trace element chemistry vary as a function of physicochemical parameters that are relevant

  4. KINETICS AND MECHANISMS OF SOIL BIOGEOCHEMICAL PROCESSES

    EPA Science Inventory

    The application of kinetic studies to soil chemistry is useful to determine reaction mechanisms and fate of nutrients and environmental contaminants. How deeply one wishes to query the mechanism depends on the detail sought. Reactions that involve chemical species in more than on...

  5. Biogeochemical cycling and remote sensing

    NASA Technical Reports Server (NTRS)

    Peterson, D. L.; Mouat, D. A.

    1984-01-01

    The present investigation is concerned with the role of remote sensing in the analysis of biochemical cycling. A general review is provided of the interest of NASA in biochemical cycling, taking into account an assessment of the state and dynamics of the pools and fluxes of four major elements (carbon, nitrogen, phosphorus, sulfur), an understanding of the coupling and interaction of the biosphere and the atmosphere, and an understanding of the biosphere and the oceans. Attention is given to biogeochemical cycling science issues, the potential remote sensing role, the vegetation type, aspects of vegetation structure, the leaf area index, the canopy height, functional relationships, environmental and soil variables, questions of experimental design, sampling sites and ground data, and radiometric data and analysis.

  6. Effects of Privately Owned Land Management Practices on Biogeochemical Cycling

    NASA Astrophysics Data System (ADS)

    Getson, J. M.; Hutyra, L.; Short, A. G.; Templer, P. H.; Kittredge, D.

    2014-12-01

    An increasing fraction of the global population lives in urban settings. Understanding how the human-natural system couple and decouple biogeochemical cycles across urbanization gradients is crucial for human health and environmental sustainability. Natural processes of nutrient deposition, export, uptake, and internal cycling can be disrupted by human activities. Residential landscape management (e.g. composting, leaf litter collection, fertilizer application) interrupts these natural biogeochemical cycles; therefore, it is key to characterize these practices and their impacts. This study looks at private land management practices along a rural to urban gradient in Boston, Massachusetts. We used a mail survey instrument coupled with biogeochemical measurements and remote sensing derived estimates of aboveground biomass to estimate biogeochemical modifications associated with residential landscape management practices. We find parcel size influences management behavior, management practices differ for leaf litter and lawn clippings, and fertilizer application is unrelated to parcel size or degree of urban-ness. These management practices result in nutrient redistribution that differs with residential characteristics.

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

    NASA Astrophysics Data System (ADS)

    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

  8. Surface-subsurface model intercomparison: A first set of benchmark results to diagnose integrated hydrology and feedbacks.

    NASA Astrophysics Data System (ADS)

    Maxwell, R. M.; Putti, M.; Meyerhoff, S.; Delfs, J.-O.; Ferguson, I. M.; Ivanov, V.; Kim, J.; Kolditz, O.; Kollet, S. J.; Kumar, M.; Paniconi, C.; Park, Y.-J.; Phanikumar, M. S.; Sudicky, E.; Sulis, M.

    2012-04-01

    There is a growing number of large scale, complex hydrologic models with fully 2D and 3D formulations that seek to combine surface and subsurface flow. Many of these models are coupled to land-surface energy balances, biogeochemical and ecological process models, and atmospheric models. Although they are being increasingly applied for hydrologic prediction and environmental understanding, no formal verification and/or benchmarking of these models has been performed. This presentation describes the results of a first intercomparison study of surface-subsurface models. The study is based on a series of benchmark problems, and the simulation results from seven coupled hydrologic models are presented. All the models simultaneously solve adapted forms of the Richards and shallow water equations, yet they span a range of approaches for the solution of the coupled equations, including global implicit, sequential iterative, and asynchronous linking. Various strategies are used to enforce flux and pressure continuity at the surface--subsurface interface. The simulation results show good agreement for the simpler test cases, while the more complicated test cases bring out some of the differences in physical process representations and numerical resolution approaches between the models. This project funded by the United States National Science Foundation (NSF) Grant EAR-1126761.

  9. Gaining a Better Understanding of Surface-Subsurface Reactive Transport using a High-Order Advection Approach

    NASA Astrophysics Data System (ADS)

    Beisman, J. J., III; Maxwell, R. M.; Navarre-Sitchler, A.; Steefel, C. I.

    2014-12-01

    Understanding the interactions between physical, geochemical, and biological processes in the shallow subsurface is prerequisite to the development of effective contamination remediation techniques, or the accurate quantification of nutrient fluxes and biogeochemical cycling. Here we present recent developments to the massively parallel reactive transport code ParCrunchFlow. This model, previously applicable only to steady-state, saturated subsurface flows, has been extended to transient, surface-subsurface systems. Proof-of-concept simulations detailing reactive transport processes in hillslope and floodplain settings will be presented. In order to reduce the numerical dispersion inherent in grid based advection schemes, which can lead to an over prediction of reaction rates, a weighted, essentially non-oscillatory (WENO) advection scheme has been implemented, providing formal fifth-order spatial and third-order temporal accuracy. We use a mass-conservative, positivity-preserving flux limiter while advecting solute concentrations to prevent non-physical solutions. The effects of advection schemes and their associated numerical dispersion on reaction rates are evaluated by comparing our scheme to a monotonic lower order scheme in a transverse mixing scenario. The work presented here allows a better understanding of nutrient cycling dynamics in watershed systems.

  10. Geophysical characterization of subsurface barriers

    SciTech Connect

    Borns, D.J.

    1995-08-01

    An option for controlling contaminant migration from plumes and buried waste sites is to construct a subsurface barrier of a low-permeability material. The successful application of subsurface barriers requires processes to verify the emplacement and effectiveness of barrier and to monitor the performance of a barrier after emplacement. Non destructive and remote sensing techniques, such as geophysical methods, are possible technologies to address these needs. The changes in mechanical, hydrologic and chemical properties associated with the emplacement of an engineered barrier will affect geophysical properties such a seismic velocity, electrical conductivity, and dielectric constant. Also, the barrier, once emplaced and interacting with the in situ geologic system, may affect the paths along which electrical current flows in the subsurface. These changes in properties and processes facilitate the detection and monitoring of the barrier. The approaches to characterizing and monitoring engineered barriers can be divided between (1) methods that directly image the barrier using the contrasts in physical properties between the barrier and the host soil or rock and (2) methods that reflect flow processes around or through the barrier. For example, seismic methods that delineate the changes in density and stiffness associated with the barrier represents a direct imaging method. Electrical self potential methods and flow probes based on heat flow methods represent techniques that can delineate the flow path or flow processes around and through a barrier.

  11. Searching for Biogeochemical Cycles on Mars

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.

    1997-01-01

    The search for life on Mars clearly benefits from a rigorous, yet broad, definition of life that compels us to consider all possible lines of evidence for a martian biosphere. Recent studies in microbial ecology illustrate that the classic definition of life should be expanded beyond the traditional definition of a living cell. The traditional defining characteristics of life are threefold. First, life is capable of metabolism, that is, it performs chemical reactions that utilize energy and also synthesize its cellular constituents. Second, life is capable of self-replication. Third, life can evolve in order to adapt to environmental changes. An expanded, ecological definition of life also recognizes that life is a community of organisms that must interact with their nonliving environment through processes called biogeochemical cycles. This regenerative processing maintains, in an aqueous conditions, a dependable supply of nutrients and energy for growth. In turn, life can significantly affect those processes that control the exchange of materials between the atmosphere, ocean, and upper crust. Because metabolic processes interact directly with the environment, they can alter their surroundings and thus leave behind evidence of life. For example, organic matter is produced from single-carbon-atom precursors for the biosynthesis of cellular constituents. This leads to a reservoir of reduced carbon in sediments that, in turn, can affect the oxidation state of the atmosphere. The harvesting of chemical energy for metabolism often employs oxidation-reduction reactions that can alter the chemistry and oxidation state of the redox-sensitive elements carbon, sulfur, nitrogen, iron, and manganese. Have there ever been biogeochemical cycles on Mars? Certain key planetary processes can offer clues. Active volcanism provides reduced chemical species that biota can use for organic synthesis. Volcanic carbon dioxide and methane can serve as greenhouse gases. Thus the

  12. Subsurface chlorophyll maximum layers: enduring enigma or mystery solved?

    PubMed

    Cullen, John J

    2015-01-01

    The phenomenon of subsurface chlorophyll maximum layers (SCMLs) is not a unique ecological response to environmental conditions; rather, a broad range of interacting processes can contribute to the formation of persistent layers of elevated chlorophyll a concentration (Chl) that are nearly ubiquitous in stratified surface waters. Mechanisms that contribute to the formation and maintenance of the SCMLs include a local maximum in phytoplankton growth rate near the nutricline, photoacclimation of pigment content that leads to elevated Chl relative to phytoplankton biomass at depth, and a range of physiologically influenced swimming behaviors in motile phytoplankton and buoyancy control in diatoms and cyanobacteria that can lead to aggregations of phytoplankton in layers, subject to grazing and physical control. A postulated typical stable water structure characterizes consistent patterns in vertical profiles of Chl, phytoplankton biomass, nutrients, and light across a trophic gradient structured by the vertical flux of nutrients and characterized by the average daily irradiance at the nutricline. Hypothetical predictions can be tested using a nascent biogeochemical global ocean observing system. Partial results to date are generally consistent with predictions based on current knowledge, which has strong roots in research from the twentieth century.

  13. Alquimia: Exposing mature biogeochemistry capabilities for easier benchmarking and development of next-generation subsurface codes

    NASA Astrophysics Data System (ADS)

    Johnson, J. N.; Molins, S.

    2015-12-01

    The complexity of subsurface models is increasing in order to address pressing scientific questions in hydrology and climate science. In particular, models that attempt to explore the coupling between microbial metabolic activity and hydrology at larger scales need an accurate representation of their underlying biogeochemical systems. These systems tend to be very complicated, and they result in large nonlinear systems that have to be coupled with flow and transport algorithms in reactive transport codes. The complexity inherent in implementing a robust treatment of biogeochemistry is a significant obstacle in the development of new codes. Alquimia is an open-source software library intended to help developers of these codes overcome this obstacle by exposing tried-and-true biogeochemical capabilities in existing software. It provides an interface through which a reactive transport code can access and evolve a chemical system, using one of several supported geochemical "engines." We will describe Alquimia's current capabilities, and how they can be used for benchmarking reactive transport codes. We will also discuss upcoming features that will facilitate the coupling of biogeochemistry to other processes in new codes.

  14. Modeling the influence of subsurface topography on spatial and temporal variability of subsurface stormflow

    NASA Astrophysics Data System (ADS)

    van Verseveld, W. J.; Tromp-van Meerveld, H. J.; Weiler, M.; McDonnell, J. J.

    2003-12-01

    Recent investigations of spatial patterns of soil depth, water table and subsurface flow response at the hillslope scale suggest that the variability in depth to bedrock (or to any other low permeable layer) may be a primary control on the space-time variability of subsurface stormflow. However, simulating or even predicting subsurface flow variability is still a challenge. Even more problematic is the fact that spatially explicit soil depth information is generally lacking at hillslope and catchment scales. We investigate how soil depth variability affects the spatial and temporal response of subsurface stormflow and propose a new way forward to defining these controls on sites without soil depth data. We used long-term data of spatially explicit subsurface flow measurements from a trenched hillslope at the Panola Mountain Research Watershed, as well as soil depth and soil property information, to calibrate and verify the HillVi hillslope model. Then we generated numerous realizations of the subsurface topography using geo-statistical information of the observed soil depth in the watershed. Subsurface flow variability was simulated based on these subsurface topography realizations. The spatial-temporal properties of the modeled flow were compared with the spatial and temporal variability of the observed flow. HillVi is a quasi 3D spatially explicit saturated and unsaturated water balance model and is well suited for this approach as it captures all major subsurface runoff generation processes (matrix and macropore flow and infiltration, lateral subsurface flow and pipe flow). We discuss the potentials and drawbacks of this approach to simulate spatially variable outflow from hillslopes and the general role of subsurface topography on the spatial and temporal patterns of subsurface flow.

  15. Prospecting for natural attenuation: Coupled geophysical-biogeochemical studies at DOE's Rifle IFRC site

    NASA Astrophysics Data System (ADS)

    Williams, K. H.; Kukkadapu, R. K.; Long, P. E.; Flores Orozco, A.; Kemna, A.

    2011-12-01

    Research activities at the Rifle Integrated Field Research Challenge (IFRC) site in Rifle, Colorado (USA) are designed to integrate geochemical, biological, and hydrological studies to enhance our understanding of subsurface uranium mobility. While much of the research activities at the site have focused on stimulating subsurface microbial activity through acetate amendment, there is growing interest in the role that natural biogeochemical processes play in constraining uranium mobility in the aquifer. Such processes constitute a form of natural uranium attenuation in the subsurface and are inferred to result from elevated concentrations of natural organic matter associated with alluvial sediments. Referred to as naturally reduced zones (NRZ's), they are characterized by the presence of reduced and/or magnetic mineral phases (e.g. FeS, FeS2, and Fe3O4), elevated Fe(II), and refractory organic carbon compounds (e.g. roots, twigs, and cones). Elevated rates of microbial activity associated with NRZ's and their mineralogical makeup act to sequester uranium from groundwater at levels higher that background alluvium. Their unique composition within a matrix of relatively oxidized, low-bioactivity sediments constitutes a potential target for a variety of exploration geophysical techniques, such as induced polarization and magnetic susceptibility. Both methods have been successfully applied at the Rifle IFRC site to delineate the ubiquity and extent of NRZ's across the floodplain. Sediments recovered from drilling targets identified through the use of exploration geophysical techniques have identified elevated uranium concentrations associated with both magnetite and framboid pyrite; however, the extent to which such minerals are the direct product of in situ microbial activity remains unknown. While diverse, the microbial community composition of NRZ's suggest dominance by fermentative organisms capable of degrading lignitic carbon to low molecular weight organic

  16. Feedbacks between hydrological heterogeneity and bioremediation induced biogeochemical transformations

    SciTech Connect

    Englert, A.; Hubbard, S.S.; Williams, K.H.; Li, L.; Steefel, C.I.

    2009-04-15

    For guiding optimal design and interpretation of in-situ treatments that strongly perturb subsurface systems, knowledge about the spatial and temporal patterns of mass transport and reaction intensities are important. Here, a procedure was developed and applied to time-lapse concentrations of a conservative tracer (bromide), an injected amendment (acetate) and reactive species (iron(II), uranium(VI) and sulfate) associated with two field scale biostimulation experiments, which were conducted successively at the same field location over two years. The procedure is based on a temporal moment analysis approach that relies on a streamtube approximation. The study shows that biostimulated reactions can be considerably influenced by subsurface hydrological and geochemical heterogeneities: the delivery of bromide and acetate and the intensity of the sulfate reduction is interpreted to be predominantly driven by the hydrological heterogeneity, while the intensity of the iron reduction is interpreted to be primarily controlled by the geochemical heterogeneity. The intensity of the uranium(VI) reduction appears to be impacted by both the hydrological and geochemical heterogeneity. Finally, the study documents the existence of feedbacks between hydrological heterogeneity and remediation-induced biogeochemical transformations at the field scale, particularly the development of precipitates that may cause clogging and flow rerouting.

  17. Ceramic subsurface marker prototypes

    SciTech Connect

    Lukens, C.E.

    1985-05-02

    The client submitted 5 sets of porcelain and stoneware subsurface (radioactive site) marker prototypes (31 markers each set). The following were determined: compressive strength, thermal shock resistance, thermal crazing resistance, alkali resistance, color retention, and chemical resistance.

  18. Subsurface Microbiology and Biogeochemistry

    SciTech Connect

    Fredrickson, Jim K.; Fletcher, Madilyn

    2001-05-01

    Jim contributed a chapter to this book, in addition to co-editing it with Madilyn Fletcher. Fredrickson, J. K., and M. Fletcher. (eds.) 2001 Subsurface Microbiology and Biogeochemistry. Wiley-Liss, Inc., New York.

  19. Electrical Subsurface Grounding Analysis

    SciTech Connect

    J.M. Calle

    2000-11-01

    The purpose and objective of this analysis is to determine the present grounding requirements of the Exploratory Studies Facility (ESF) subsurface electrical system and to verify that the actual grounding system and devices satisfy the requirements.

  20. Benthic exchange and biogeochemical cycling in permeable sediments.

    PubMed

    Huettel, Markus; Berg, Peter; Kostka, Joel E

    2014-01-01

    The sandy sediments that blanket the inner shelf are situated in a zone where nutrient input from land and strong mixing produce maximum primary production and tight coupling between water column and sedimentary processes. The high permeability of the shelf sands renders them susceptible to pressure gradients generated by hydrodynamic and biological forces that modulate spatial and temporal patterns of water circulation through these sediments. The resulting dynamic three-dimensional patterns of particle and solute distribution generate a broad spectrum of biogeochemical reaction zones that facilitate effective decomposition of the pelagic and benthic primary production products. The intricate coupling between the water column and sediment makes it challenging to quantify the production and decomposition processes and the resultant fluxes in permeable shelf sands. Recent technical developments have led to insights into the high biogeochemical and biological activity of these permeable sediments and their role in the global cycles of matter.

  1. Site Recommendation Subsurface Layout

    SciTech Connect

    C.L. Linden

    2000-06-28

    The purpose of this analysis is to develop a Subsurface Facility layout that is capable of accommodating the statutory capacity of 70,000 metric tons of uranium (MTU), as well as an option to expand the inventory capacity, if authorized, to 97,000 MTU. The layout configuration also requires a degree of flexibility to accommodate potential changes in site conditions or program requirements. The objective of this analysis is to provide a conceptual design of the Subsurface Facility sufficient to support the development of the Subsurface Facility System Description Document (CRWMS M&O 2000e) and the ''Emplacement Drift System Description Document'' (CRWMS M&O 2000i). As well, this analysis provides input to the Site Recommendation Consideration Report. The scope of this analysis includes: (1) Evaluation of the existing facilities and their integration into the Subsurface Facility design. (2) Identification and incorporation of factors influencing Subsurface Facility design, such as geological constraints, thermal loading, constructibility, subsurface ventilation, drainage control, radiological considerations, and the Test and Evaluation Facilities. (3) Development of a layout showing an available area in the primary area sufficient to support both the waste inventories and individual layouts showing the emplacement area required for 70,000 MTU and, if authorized, 97,000 MTU.

  2. Incorporating microbes into large-scale biogeochemical models

    NASA Astrophysics Data System (ADS)

    Allison, S. D.; Martiny, J. B.

    2008-12-01

    Micro-organisms, including Bacteria, Archaea, and Fungi, control major processes throughout the Earth system. Recent advances in microbial ecology and microbiology have revealed an astounding level of genetic and metabolic diversity in microbial communities. However, a framework for interpreting the meaning of this diversity has lagged behind the initial discoveries. Microbial communities have yet to be included explicitly in any major biogeochemical models in terrestrial ecosystems, and have only recently broken into ocean models. Although simplification of microbial communities is essential in complex systems, omission of community parameters may seriously compromise model predictions of biogeochemical processes. Two key questions arise from this tradeoff: 1) When and where must microbial community parameters be included in biogeochemical models? 2) If microbial communities are important, how should they be simplified, aggregated, and parameterized in models? To address these questions, we conducted a meta-analysis to determine if microbial communities are sensitive to four environmental disturbances that are associated with global change. In all cases, we found that community composition changed significantly following disturbance. However, the implications for ecosystem function were unclear in most of the published studies. Therefore, we developed a simple model framework to illustrate the situations in which microbial community changes would affect rates of biogeochemical processes. We found that these scenarios could be quite common, but powerful predictive models cannot be developed without much more information on the functions and disturbance responses of microbial taxa. Small-scale models that explicitly incorporate microbial communities also suggest that process rates strongly depend on microbial interactions and disturbance responses. The challenge is to scale up these models to make predictions at the ecosystem and global scales based on measurable

  3. A generic reaction-based biogeochemical simulator

    SciTech Connect

    Fang, Yilin; Yabusaki, Steven B.; Yeh, Gour T.; C.T. Miller, M.W. Farthing, W.G. Gray, and G.F. Pinder

    2004-06-17

    This paper presents a generic biogeochemical simulator, BIOGEOCHEM. The simulator can read a thermodynamic database based on the EQ3/EQ6 database. It can also read user-specified equilibrium and kinetic reactions (reactions not defined in the format of that in EQ3/EQ6 database) symbolically. BIOGEOCHEM is developed with a general paradigm. It overcomes the requirement in most available reaction-based models that reactions and rate laws be specified in a limited number of canonical forms. The simulator interprets the reactions, and rate laws of virtually any type for input to the MAPLE symbolic mathematical software package. MAPLE then generates Fortran code for the analytical Jacobian matrix used in the Newton-Raphson technique, which are compiled and linked into the BIOGEOCHEM executable. With this feature, the users are exempted from recoding the simulator to accept new equilibrium expressions or kinetic rate laws. Two examples are used to demonstrate the new features of the simulator.

  4. Subsurface Contamination Control

    SciTech Connect

    Y. Yuan

    2001-12-12

    There are two objectives of this report, ''Subsurface Contamination Control''. The first is to provide a technical basis for recommending limiting radioactive contamination levels (LRCL) on the external surfaces of waste packages (WP) for acceptance into the subsurface repository. The second is to provide an evaluation of the magnitude of potential releases from a defective WP and the detectability of the released contents. The technical basis for deriving LRCL has been established in ''Retrieval Equipment and Strategy for Wp on Pallet'' (CRWMS M and O 2000g, 6.3.1). This report updates the derivation by incorporating the latest design information of the subsurface repository for site recommendation. The derived LRCL on the external surface of WPs, therefore, supercede that described in CRWMS M and O 2000g. The derived LRCL represent the average concentrations of contamination on the external surfaces of each WP that must not be exceeded before the WP is to be transported to the subsurface facility for emplacement. The evaluation of potential releases is necessary to control the potential contamination of the subsurface repository and to detect prematurely failed WPs. The detection of failed WPs is required in order to provide reasonable assurance that the integrity of each WP is intact prior to MGR closure. An emplaced WP may become breached due to manufacturing defects or improper weld combined with failure to detect the defect, by corrosion, or by mechanical penetration due to accidents or rockfall conditions. The breached WP may release its gaseous and volatile radionuclide content to the subsurface environment and result in contaminating the subsurface facility. The scope of this analysis is limited to radioactive contaminants resulting from breached WPs during the preclosure period of the subsurface repository. This report: (1) documents a method for deriving LRCL on the external surfaces of WP for acceptance into the subsurface repository; (2) provides a

  5. Subsurface Contamination Control

    SciTech Connect

    Y. Yuan

    2001-11-16

    There are two objectives of this report, ''Subsurface Contamination Control''. The first is to provide a technical basis for recommending limiting radioactive contamination levels (LRCL) on the external surfaces of waste packages (WP) for acceptance into the subsurface repository. The second is to provide an evaluation of the magnitude of potential releases from a defective WP and the detectability of the released contents. The technical basis for deriving LRCL has been established in ''Retrieval Equipment and Strategy for Wp on Pallet'' (CRWMS M and O 2000g, 6.3.1). This report updates the derivation by incorporating the latest design information of the subsurface repository for site recommendation. The derived LRCL on the external surface of WPs, therefore, supercede that described in CRWMS M and O 2000g. The derived LRCL represent the average concentrations of contamination on the external surfaces of each WP that must not be exceeded before the WP is to be transported to the subsurface facility for emplacement. The evaluation of potential releases is necessary to control the potential contamination of the subsurface repository and to detect prematurely failed WPs. The detection of failed WPs is required in order to provide reasonable assurance that the integrity of each WP is intact prior to MGR closure. An emplaced WP may become breached due to manufacturing defects or improper weld combined with failure to detect the defect, by corrosion, or by mechanical penetration due to accidents or rockfall conditions. The breached WP may release its gaseous and volatile radionuclide content to the subsurface environment and result in contaminating the subsurface facility. The scope of this analysis is limited to radioactive contaminants resulting from breached WPs during the preclosure period of the subsurface repository. This report: (1) documents a method for deriving LRCL on the external surfaces of WP for acceptance into the subsurface repository; (2) provides a

  6. Seafloor surface processes and subsurface paleo-channel unconformities mapped using multi-channel seismic and multi-beam sonar data from the Galicia 3D seismic experiment.

    NASA Astrophysics Data System (ADS)

    Gibson, J. C.; Shillington, D. J.; Sawyer, D. S.; Jordan, B.; Morgan, J. K.; Ranero, C.; Reston, T. J.

    2015-12-01

    In this study we use geophysical methods, stratigraphic relationships, and coring/drilling leg results to assess possible controls on deep-sea channel formation in order to further constrain paleo-channel (PC) and associated unconformity timing/source processes. A series of cut and fill PC are mapped in 3D multi-channel seismic (MCS) data and compared with multi-beam (MB) sonar bathymetry/backscatter data collected during the Galicia 3D survey with the R/V Marcus G. Langseth (2013). The MCS data were collected using four 6 km streamers spaced at 200 m resulting in 25 m x 25 m common mid-point bins within the ~67 km x 20 km 3D volume. The MB data were collected at an average depth of ~4900 m with a constrained swath width of 4.5 km resulting in 11.25x overlap while enabling 25-m bathymetry and 10-m backscatter grids. The PC lie below the mouth of a submarine canyon at the edge of the Galicia abyssal plain and cut pre/syn-rift sediments; they are bound by a rift block to the north and paleo-levees to the south (maximum height of ~180m). From drilling results, the most recent PC is late Miocene in age. In this study, four PC are traced into the basin as unconformities. Several of the PC/unconformities are tentatively correlated with previously interpreted Pyrenean orogeny/compressional Miocene/Oligocene tectonic events. However, one PC/unconformity within this interval has not been previously interpreted. In order test the hypothesis that the unconformities are the result of a significant change in base level indicated by a low shale/sand (SS) ratio, we use seismic surface attributes to calculate the SS ratio and trace the horizontal extent of the unconformities. Additionally, the MB/MCS seafloor morphology reveals sedimentary waves outboard of the canyon mouth. We use backscatter data to compare the extent of recent processes (e.g., Pleistocene glaciation/de-glaciation) with the unconformities by mapping the surface/shallow subsurface SS ratio (volume scattering).

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

    NASA Astrophysics Data System (ADS)

    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.

  8. The Southern Ocean biogeochemical divide

    NASA Astrophysics Data System (ADS)

    Marinov, I.; Gnanadesikan, A.; Toggweiler, J. R.; Sarmiento, J. L.

    2006-06-01

    Modelling studies have demonstrated that the nutrient and carbon cycles in the Southern Ocean play a central role in setting the air-sea balance of CO2 and global biological production. Box model studies first pointed out that an increase in nutrient utilization in the high latitudes results in a strong decrease in the atmospheric carbon dioxide partial pressure (pCO2). This early research led to two important ideas: high latitude regions are more important in determining atmospheric pCO2 than low latitudes, despite their much smaller area, and nutrient utilization and atmospheric pCO2 are tightly linked. Subsequent general circulation model simulations show that the Southern Ocean is the most important high latitude region in controlling pre-industrial atmospheric CO2 because it serves as a lid to a larger volume of the deep ocean. Other studies point out the crucial role of the Southern Ocean in the uptake and storage of anthropogenic carbon dioxide and in controlling global biological production. Here we probe the system to determine whether certain regions of the Southern Ocean are more critical than others for air-sea CO2 balance and the biological export production, by increasing surface nutrient drawdown in an ocean general circulation model. We demonstrate that atmospheric CO2 and global biological export production are controlled by different regions of the Southern Ocean. The air-sea balance of carbon dioxide is controlled mainly by the biological pump and circulation in the Antarctic deep-water formation region, whereas global export production is controlled mainly by the biological pump and circulation in the Subantarctic intermediate and mode water formation region. The existence of this biogeochemical divide separating the Antarctic from the Subantarctic suggests that it may be possible for climate change or human intervention to modify one of these without greatly altering the other.

  9. The Southern Ocean biogeochemical divide.

    PubMed

    Marinov, I; Gnanadesikan, A; Toggweiler, J R; Sarmiento, J L

    2006-06-22

    Modelling studies have demonstrated that the nutrient and carbon cycles in the Southern Ocean play a central role in setting the air-sea balance of CO(2) and global biological production. Box model studies first pointed out that an increase in nutrient utilization in the high latitudes results in a strong decrease in the atmospheric carbon dioxide partial pressure (pCO2). This early research led to two important ideas: high latitude regions are more important in determining atmospheric pCO2 than low latitudes, despite their much smaller area, and nutrient utilization and atmospheric pCO2 are tightly linked. Subsequent general circulation model simulations show that the Southern Ocean is the most important high latitude region in controlling pre-industrial atmospheric CO(2) because it serves as a lid to a larger volume of the deep ocean. Other studies point out the crucial role of the Southern Ocean in the uptake and storage of anthropogenic carbon dioxide and in controlling global biological production. Here we probe the system to determine whether certain regions of the Southern Ocean are more critical than others for air-sea CO(2) balance and the biological export production, by increasing surface nutrient drawdown in an ocean general circulation model. We demonstrate that atmospheric CO(2) and global biological export production are controlled by different regions of the Southern Ocean. The air-sea balance of carbon dioxide is controlled mainly by the biological pump and circulation in the Antarctic deep-water formation region, whereas global export production is controlled mainly by the biological pump and circulation in the Subantarctic intermediate and mode water formation region. The existence of this biogeochemical divide separating the Antarctic from the Subantarctic suggests that it may be possible for climate change or human intervention to modify one of these without greatly altering the other.

  10. Biogeochemical dynamics of pollutants in Insitu groundwater remediation systems

    NASA Astrophysics Data System (ADS)

    Kumar, N.; Millot, R.; Rose, J.; Négrel, P.; Battaglia-Brunnet, F.; Diels, L.

    2010-12-01

    Insitu (bio) remediation of groundwater contaminants has been area of potential research interest in last few decades as the nature of contaminant encountered has also changed drastically. This gives tough challenge to researchers in finding a common solution for all contaminants together in one plume. Redox processes play significant role in pollutant dynamics and mobility in such systems. Arsenic particularly in reduced environments can get transformed into its reduced form (As3+), which is apparently more mobile and highly toxic. Also parallel sulfate reduction can lead to sulfide production and formation of thioarsenic species. On the other hand heavy metals (Zn, Fe, and Cd) in similar conditions will favour more stable metal sulfide precipitation. In the present work, we tested Zero Valent Iron (ZVI) in handling such issues and found promising results. Although it has been well known for contaminants like arsenic and chlorinated compounds but not much explored for heavy metals. Its high available surface area supports precipitation and co -precipitation of contaminants and its highly oxidizing nature and water born hydrogen production helps in stimulation of microbial activities in sediment and groundwater. These sulfate and Iron reducing bacteria can further fix heavy metals as stable metal sulfides by using hydrogen as potential electron donor. In the present study flow through columns (biotic and control) were set up in laboratory to understand the behaviour of contaminants in subsurface environments, also the impact of microbiology on performance of ZVI was studied. These glass columns (30 x 4cm) with intermediate sampling points were monitored over constant temperature (20°C) and continuous groundwater (up)flow at ~1ml/hr throughout the experiment. Simulated groundwater was prepared in laboratory containing sulfate, metals (Zn,Cd) and arsenic (AsV). While chemical and microbial parameters were followed regularly over time, solid phase has been

  11. The Microbial Engines That Drive Earth’s Biogeochemical Cycles

    NASA Astrophysics Data System (ADS)

    Falkowski, Paul G.; Fenchel, Tom; Delong, Edward F.

    2008-05-01

    Virtually all nonequilibrium electron transfers on Earth are driven by a set of nanobiological machines composed largely of multimeric protein complexes associated with a small number of prosthetic groups. These machines evolved exclusively in microbes early in our planet’s history yet, despite their antiquity, are highly conserved. Hence, although there is enormous genetic diversity in nature, there remains a relatively stable set of core genes coding for the major redox reactions essential for life and biogeochemical cycles. These genes created and coevolved with biogeochemical cycles and were passed from microbe to microbe primarily by horizontal gene transfer. A major challenge in the coming decades is to understand how these machines evolved, how they work, and the processes that control their activity on both molecular and planetary scales.

  12. The microbial engines that drive Earth's biogeochemical cycles.

    PubMed

    Falkowski, Paul G; Fenchel, Tom; Delong, Edward F

    2008-05-23

    Virtually all nonequilibrium electron transfers on Earth are driven by a set of nanobiological machines composed largely of multimeric protein complexes associated with a small number of prosthetic groups. These machines evolved exclusively in microbes early in our planet's history yet, despite their antiquity, are highly conserved. Hence, although there is enormous genetic diversity in nature, there remains a relatively stable set of core genes coding for the major redox reactions essential for life and biogeochemical cycles. These genes created and coevolved with biogeochemical cycles and were passed from microbe to microbe primarily by horizontal gene transfer. A major challenge in the coming decades is to understand how these machines evolved, how they work, and the processes that control their activity on both molecular and planetary scales.

  13. SUBSURFACE REPOSITORY INTEGRATED CONTROL SYSTEM DESIGN

    SciTech Connect

    D.C. Randle

    2000-01-07

    The primary purpose of this document is to develop a preliminary high-level functional and physical control system architecture for the potential repository at Yucca Mountain. This document outlines an overall control system concept that encompasses and integrates the many diverse process and communication systems being developed for the subsurface repository design. This document presents integrated design concepts for monitoring and controlling the diverse set of subsurface operations. The Subsurface Repository Integrated Control System design will be composed of a series of diverse process systems and communication networks. The subsurface repository design contains many systems related to instrumentation and control (I&C) for both repository development and waste emplacement operations. These systems include waste emplacement, waste retrieval, ventilation, radiological and air monitoring, rail transportation, construction development, utility systems (electrical, lighting, water, compressed air, etc.), fire protection, backfill emplacement, and performance confirmation. Each of these systems involves some level of I&C and will typically be integrated over a data communications network throughout the subsurface facility. The subsurface I&C systems will also interface with multiple surface-based systems such as site operations, rail transportation, security and safeguards, and electrical/piped utilities. In addition to the I&C systems, the subsurface repository design also contains systems related to voice and video communications. The components for each of these systems will be distributed and linked over voice and video communication networks throughout the subsurface facility. The scope and primary objectives of this design analysis are to: (1) Identify preliminary system-level functions and interfaces (Section 6.2). (2) Examine the overall system complexity and determine how and on what levels the engineered process systems will be monitored, controlled, and

  14. Nutrient removal using biosorption activated media: preliminary biogeochemical assessment of an innovative stormwater infiltration basin.

    PubMed

    O'Reilly, Andrew M; Wanielista, Martin P; Chang, Ni-Bin; Xuan, Zhemin; Harris, Willie G

    2012-08-15

    Soil beneath a stormwater infiltration basin receiving runoff from a 23 ha predominantly residential watershed in north-central Florida, USA, was amended using biosorption activated media (BAM) to study the effectiveness of this technology in reducing inputs of nitrogen and phosphorus to groundwater. The functionalized soil amendment BAM consists of a 1.0:1.9:4.1 mixture (by volume) of tire crumb (to increase sorption capacity), silt and clay (to increase soil moisture retention), and sand (to promote sufficient infiltration), which was applied to develop an innovative stormwater infiltration basin utilizing nutrient reduction and flood control sub-basins. Comparison of nitrate/chloride (NO(3)(-)/Cl(-)) ratios for the shallow groundwater indicates that prior to using BAM, NO(3)(-) concentrations were substantially influenced by nitrification or variations in NO(3)(-) input. In contrast, for the new basin utilizing BAM, NO(3)(-)/Cl(-) ratios indicate minor nitrification and NO(3)(-) losses with the exception of one summer sample that indicated a 45% loss. Biogeochemical indicators (denitrifier activity derived from real-time polymerase chain reaction and variations in major ions, nutrients, dissolved and soil gases, and stable isotopes) suggest that NO(3)(-) losses are primarily attributable to denitrification, whereas dissimilatory nitrate reduction to ammonium is a minor process. Denitrification was likely occurring intermittently in anoxic microsites in the unsaturated zone, which was enhanced by the increased soil moisture within the BAM layer and resultant reductions in surface/subsurface oxygen exchange that produced conditions conducive to increased denitrifier activity. Concentrations of total dissolved phosphorus and orthophosphate (PO(4)(3-)) were reduced by more than 70% in unsaturated zone soil water, with the largest decreases in the BAM layer where sorption was the most likely mechanism for removal. Post-BAM PO(4)(3-)/Cl(-) ratios for shallow

  15. Biogeochemical and hydrographic controls on chromophoric dissolved organic matter distribution in the Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Swan, Chantal M.; Siegel, David A.; Nelson, Norman B.; Carlson, Craig A.; Nasir, Elora

    2009-12-01

    Recent in situ observations of chromophoric dissolved organic material (CDOM) in the Pacific Ocean reveal the biogeochemical controls on CDOM and indicate predictive potential for open-ocean CDOM in diagnosing particulate organic matter (POM) remineralization rates within ocean basins. Relationships between CDOM and concentrations of dissolved oxygen, nutrients and inorganic carbon in the subthermocline waters of the Pacific reflect the relative influences of water mass ventilation and water-column oxidative remineralization. Apparent in situ oxygen utilization (AOU) accounts for 86% and 61% of variance in CDOM abundance, respectively, in Antarctic Intermediate Water and North Pacific Intermediate Water. In the deep waters of the Pacific below the zone of remineralization, AOU explains 26% of CDOM variability. The AOU-CDOM relationship results from competing biogeochemical and advective processes within the ocean interior. Dissolved organic carbon (DOC) is not statistically linked to the CDOM or AOU distributions, indicating that the majority of CDOM production occurs during the remineralization of sinking POM and thus potentially provides key information about carbon export. Once formed in the ocean interior, CDOM is relatively stable until it reaches the surface ocean where it is destroyed by solar bleaching. Susceptibility to bleaching confers an additional tracer-like quality for CDOM in water masses with active convection, such as mode waters that appear as subsurface CDOM minima. In the surface ocean, atypically low CDOM abundance highlights a region of unusually extreme oligotrophy: the subtropical South Pacific gyre. For these hyper-oligotrophic waters, the present CDOM observations are consistent with analysis of in situ radiometric observations of light attenuation and reflectance, demonstrating the accuracy of the CDOM spectrophotometric observations. Overall, we illustrate how CDOM abundance in the ocean interior can potentially diagnose rates of

  16. Possible biogeochemical consequences of ocean fertilization

    SciTech Connect

    Fuhrman, J.A. ); Capone, D.G. )

    1991-12-01

    The authors consider biogeochemical secondary effects that could arise from an increase in ocean productivity, such as may occur via fertilization with Fe. These processes and feedback loops are infrequently discussed in this context, yet are likely to be highly relevant to the understanding of global change in general. In particular, the authors suggest that increased productivity may increase the production and efflux of greenhouse gases, such as nitrous oxide (N{sub 2}O) and methane (CH{sub 4}) and that shifts in phytoplankton species and productivity may cause changes in another climate-related gas, dimethylsulfide (DMS). N{sub 2}O is also implicated in the destruction of stratospheric ozone. Factors contributing to amplified release include both increased nutrient cycling in general and possible development of low oxygen conditions from fertilization. It is also remotely possible that reduced oxygen from an initial fertilization could mobilize existing Fe pools, inducing uncontrolled self-fertilization. Although lack of relevant physiological and ecological data makes it difficult to provide quantitative limits on the extent of the undesired effects, rough calculations suggest that the enhanced release of N{sub 2}O alone could totally negate any potential benefit from fertilization and likely worsen global warming and ozone depletion.

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  18. Biogeochemical consequences of an oxygenated intrusion into an anoxic fjord

    PubMed Central

    2014-01-01

    Background This paper is based on the studies of the biogeochemical structure of the water column in the anoxic Fjord Hunnbunn (south-eastern Norway) performed in 2009, 2011 and 2012. This Fjord is an enclosed basin of brackish water separated by a narrow and shallow outlet to the sea with a permanently anoxic layer. We show how an oxygenated intrusion could lead to both positive and negative effects on the ecosystem state in Hunnbunn due to a change in the biogeochemical structure. Results During the stratified periods in 2009 and 2012 the anoxic layer amounted to approximately 10% of the total water volume in the Fjord, while dissolved oxygen (DO) was present in 80-90% of the water. In the autumn of 2011 the water chemistry structure observed in Fjord Hunnbunn was clearly affected by a recent oxygenated intrusion defined by abnormal salinity patterns. This led to a shift of the DO boundary position to shallower depths, resulting in a thicker anoxic layer comprising approximately 40% of the total water volume, with DO present only in approximately 60% of the water. The oxygenated water intrusions led to a twofold decrease of the concentrations of hydrogen sulphide, ammonia, phosphate and silicate in the deep layers with a simultaneous increase of these nutrients and a decrease of the pH level in the surface layers. The concentrations of manganese, iron, and mercury species changed dramatically and in particular revealed a significant supply of iron and methylmercury to the water column. Conclusions Oxic water intrusions into anoxic fjords could lead not only to the flushing of the bottom anoxia, but to a dispersal of sulphidic and low oxygen conditions to the larger bottom area. The elevation of the hydrogen sulphide to the shallower layers (that can be rapidly oxidized) is accompanied by the appearance in the subsurface water of methylmercury, which is easily accumulated by organisms and can be transported to the surrounding waters, affecting the ecosystem over a

  19. Estimating impacts of lichens and bryophytes on global biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Porada, Philipp; Weber, Bettina; Elbert, Wolfgang; Pöschl, Ulrich; Kleidon, Axel

    2014-02-01

    Lichens and bryophytes may significantly affect global biogeochemical cycles by fixation of nitrogen and biotic enhancement of surface weathering rates. Most of the studies suggesting these effects, however, are either conceptual or rely on upscaling of regional estimates to obtain global numbers. Here we use a different method, based on estimates of net carbon uptake, to quantify the impacts of lichens and bryophytes on biogeochemical cycles at the global scale. We focus on three processes, namely, nitrogen fixation, phosphorus uptake, and chemical weathering. Our estimates have the form of potential rates, which means that we quantify the amount of nitrogen and phosphorus needed by the organisms to build up biomass, also accounting for resorption and leaching of nutrients. Subsequently, we use potential phosphorus uptake on bare ground to estimate chemical weathering by the organisms, assuming that they release weathering agents to obtain phosphorus. The predicted requirement for nitrogen ranges from 3.5 to 34 Tgyr-1 and for phosphorus it ranges from 0.46 to 4.6 Tgyr-1. Estimates of chemical weathering are between 0.058 and 1.1 km3 yr-1 of rock. These values seem to have a realistic order of magnitude, and they support the notion that lichens and bryophytes have the potential to play an important role for biogeochemical cycles.

  20. Subsurface connection methods for subsurface heaters

    SciTech Connect

    Vinegar, Harold J.; Bass, Ronald Marshall; Kim, Dong Sub; Mason, Stanley Leroy; Stegemeier, George Leo; Keltner, Thomas Joseph; Carl, Jr., Frederick Gordon

    2010-12-28

    A system for heating a subsurface formation is described. The system includes a first elongated heater in a first opening in the formation. The first elongated heater includes an exposed metal section in a portion of the first opening. The portion is below a layer of the formation to be heated. The exposed metal section is exposed to the formation. A second elongated heater is in a second opening in the formation. The second opening connects to the first opening at or near the portion of the first opening below the layer to be heated. At least a portion of an exposed metal section of the second elongated heater is electrically coupled to at least a portion of the exposed metal section of the first elongated heater in the portion of the first opening below the layer to be heated.

  1. Biogeochemical and metabolic responses to the flood pulse in a semiarid floodplain

    USGS Publications Warehouse

    Valett, H.M.; Baker, M.A.; Morrice, J.A.; Crawford, C.S.; Molles, M.C.; Dahm, Clifford N.; Moyer, D.L.; Thibault, J.R.; Ellis, L.M.

    2005-01-01

    Flood pulse inundation of riparian forests alters rates of nutrient retention and organic matter processing in the aquatic ecosystems formed in the forest interior. Along the Middle Rio Grande (New Mexico, USA), impoundment and levee construction have created riparian forests that differ in their inter-flood intervals (IFIs) because some floodplains are still regularly inundated by the flood pulse (i.e., connected), while other floodplains remain isolated from flooding (i.e., disconnected). This research investigates how ecosystem responses to the flood pulse relate to forest IFI by quantifying nutrient and organic matter dynamics in the Rio Grande floodplain during three years of experimental flooding of the disconnected floodplain and during a single year of natural flooding of the connected floodplain. Surface and subsurface conditions in paired sites (control, flood) established in the two floodplain types were monitored to address metabolic and biogeochemical responses. Compared to dry controls, rates of respiration in the flooded sites increased by up to three orders of magnitude during the flood pulse. In the disconnected forest, month-long experimental floods produced widespread anoxia of four-week duration during each of the three years of flooding. In contrast, water in the connected floodplain remained well oxygenated (3-8 ppm). Material budgets for experimental floods showed the disconnected floodplain to be a sink for inorganic nitrogen and suspended solids, but a potential source of dissolved organic carbon (DOC). Compared to the main stem of the Rio Grande, flood-water on the connected floodplain contained less nitrate, but comparable concentrations of DOC, phosphate-phosphorus, and ammonium-nitrogen. Results suggest that floodplain IFI drives metabolic and biogeochemical responses during the flood pulse. Impoundment and fragmentation have altered floodplains from a mosaic of patches with variable IFI to a bimodal distribution. Relatively predictable

  2. SUBSURFACE EMPLACEMENT TRANSPORTATION SYSTEM

    SciTech Connect

    T. Wilson; R. Novotny

    1999-11-22

    The objective of this analysis is to identify issues and criteria that apply to the design of the Subsurface Emplacement Transportation System (SET). The SET consists of the track used by the waste package handling equipment, the conductors and related equipment used to supply electrical power to that equipment, and the instrumentation and controls used to monitor and operate those track and power supply systems. Major considerations of this analysis include: (1) Operational life of the SET; (2) Geometric constraints on the track layout; (3) Operating loads on the track; (4) Environmentally induced loads on the track; (5) Power supply (electrification) requirements; and (6) Instrumentation and control requirements. This analysis will provide the basis for development of the system description document (SDD) for the SET. This analysis also defines the interfaces that need to be considered in the design of the SET. These interfaces include, but are not limited to, the following: (1) Waste handling building; (2) Monitored Geologic Repository (MGR) surface site layout; (3) Waste Emplacement System (WES); (4) Waste Retrieval System (WRS); (5) Ground Control System (GCS); (6) Ex-Container System (XCS); (7) Subsurface Electrical Distribution System (SED); (8) MGR Operations Monitoring and Control System (OMC); (9) Subsurface Facility System (SFS); (10) Subsurface Fire Protection System (SFR); (11) Performance Confirmation Emplacement Drift Monitoring System (PCM); and (12) Backfill Emplacement System (BES).

  3. The distribution of subsurface damage in fused silica

    SciTech Connect

    Miller, P E; Suratwala, T I; Wong, L L; Feit, M D; Menapace, J A; Davis, P J; Steele, R A

    2005-11-21

    Managing subsurface damage during the shaping process and removing subsurface damage during the polishing process is essential in the production of low damage density optical components, such as those required for use on high peak power lasers. Removal of subsurface damage, during the polishing process, requires polishing to a depth which is greater than the depth of the residual cracks present following the shaping process. To successfully manage, and ultimately remove subsurface damage, understanding the distribution and character of fractures in the subsurface region introduced during fabrication process is important. We have characterized the depth and morphology of subsurface fractures present following fixed abrasive and loose abrasive grinding processes. At shallow depths lateral cracks and an overlapping series of trailing indentation fractures were found to be present. At greater depths, subsurface damage consists of a series of trailing indentation fractures. The area density of trailing fractures changes as a function of depth, however the length and shape of individual cracks remain nearly constant for a given grinding process. We have developed and applied a model to interpret the depth and crack length distributions of subsurface surface damage in terms of key variables including abrasive size and load.

  4. Micro-topography creates biogeochemical hot spots in wetlands

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Atreyee

    2012-10-01

    Interventions in wetlands could improve water quality, as wetlands regulate not only nutrients such as nitrogen and sulfur but also pollutants in the waters that flow through them. Biological and chemical processes maintain conditions for redox reactions in the wetlands that control the concentration of certain solutes, including nutrients and pollutants. But such biogeochemical processes are not evenly distributed and often are localized in “hot spots” or take place in bouts known as “hot moments.” How these hot spots or hot moments arise remains poorly understood and is often explained by simply evoking variations in soil properties in the wetlands.

  5. Variably Saturated Flow and Multicomponent Biogeochemical Reactive Transport Modeling of a Uranium Bioremediation Field Experiment

    SciTech Connect

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

    2011-11-01

    incorporated into the modeling. In this case, an initially small population of slow growing sulfate reducers is active from the initiation of biostimulation. Three-dimensional, variably saturated flow modeling was used to address impacts of a falling water table during acetate injection. These impacts included a significant reduction in aquifer saturated thickness and isolation of residual 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 in higher concentrations of TEAP products when terminal electron donors and acceptors were not limiting. Finally, facies-based porosity and reactive surface area variations were shown to affect aqueous uranium concentration distributions; however, the ranges were sufficiently small to preserve general trends. Large computer memory and high computational performance were required to simulate the detailed coupled process models for multiple biogeochemical components in highly resolved heterogeneous materials for the 110-day field experiment and 50 days of post-biostimulation behavior. In this case, a highly-scalable subsurface simulator operating on 128 processor cores for 12 hours was used to simulate each realization. An equivalent simulation without parallel processing would have taken 60 days, assuming sufficient memory was available.

  6. Mars penetrator: Subsurface science mission

    NASA Technical Reports Server (NTRS)

    Lumpkin, C. K.

    1974-01-01

    A penetrator system to emplace subsurface science on the planet Mars is described. The need for subsurface science is discussed, and the technologies for achieving successful atmospheric entry, Mars penetration, and data retrieval are presented.

  7. Lateral subsurface flow pathways in a semiarid Ponderosa pine hillslope

    NASA Astrophysics Data System (ADS)

    Newman, Brent D.; Campbell, Andrew R.; Wilcox, Bradford P.

    1998-12-01

    The mechanisms controlling lateral subsurface flow in semiarid environments have received relatively little attention despite the fact that lateral subsurface flow can be an important runoff process in these environments. The objective of the current study is to better understand lateral subsurface flow process in semiarid environments. Natural chloride, dissolved organic carbon, and stable isotope (δD and δ18O) tracers were used to investigate the lateral subsurface flow process and the chemical changes that occur as a result of lateral subsurface flow. Observed differences in chemistry between soil matrix water and lateral subsurface flow were large (for example, chloride concentrations in matrix soil water samples were >200 mg/L, compared with only 2 mg/L in lateral subsurface flow samples obtained at the same time). This difference in chemistry is indicative of a two-domain flow system in which macropores conduct lateral subsurface flow that is not in chemical or hydrological equilibrium with the soil matrix. The size of precipitation events appeared to have a strong influence on the variations in old/new water percentages, and examples of both old and new water dominated events were observed. There were also large variations in the chemistry of lateral subsurface flow with time. For example, chloride and dissolved organic carbon concentrations were 10 and 70 times greater, respectively, under saturated conditions than under unsaturated conditions.

  8. Managing biogeochemical cycles to reduce greenhouse gases

    SciTech Connect

    Post, Wilfred M; Venterea, Rodney

    2012-01-01

    This special issue focuses on terrestrial biogeochemical cycles as they relate to North America-wide budgeting and future projection of biogenic greenhouse gases (GHGs). Understanding the current magnitude and providing guidance on the future trajectories of atmospheric concentrations of these gases requires investigation of their (i) biogeochemical origins, (ii) response to climate feedbacks and other environmental factors, and (iii) susceptibility to management practices. This special issue provides a group of articles that present the current state of continental scale sources and sinks of biogenic GHGs and the potential to better manage them in the future.

  9. Coupled Monitoring and Inverse Modeling to Investigate Surface - Subsurface Hydrological and Thermal Dynamics in the Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Tran, A. P.; Dafflon, B.; Hubbard, S. S.; Bisht, G.; Peterson, J.; Ulrich, C.; Romanovsky, V. E.; Kneafsey, T. J.; Wu, Y.

    2015-12-01

    Quantitative characterization of the soil surface-subsurface hydrological and thermal processes is essential as they are primary factors that control the biogeochemical processes, ecological landscapes and greenhouse gas fluxes. In the Artic region, the surface-subsurface hydrological and thermal regimes co-interact and are both largely influenced by soil texture and soil organic content. In this study, we present a coupled inversion scheme that jointly inverts hydrological, thermal and geophysical data to estimate the vertical profiles of clay, sand and organic contents. Within this inversion scheme, the Community Land Model (CLM4.5) serves as a forward model to simulate the land-surface energy balance and subsurface hydrological-thermal processes. Soil electrical conductivity (from electrical resistivity tomography), temperature and water content are linked together via petrophysical and geophysical models. Particularly, the inversion scheme accounts for the influences of the soil organic and mineral content on both of the hydrological-thermal dynamics and the petrophysical relationship. We applied the inversion scheme to the Next Generation Ecosystem Experiments (NGEE) intensive site in Barrow, AK, which is characterized by polygonal-shaped arctic tundra. The monitoring system autonomously provides a suite of above-ground measurements (e.g., precipitation, air temperature, wind speed, short-long wave radiation, canopy greenness and eddy covariance) as well as below-ground measurements (soil moisture, soil temperature, thaw layer thickness, snow thickness and soil electrical conductivity), which complement other periodic, manually collected measurements. The preliminary results indicate that the model can well reproduce the spatiotemporal dynamics of the soil temperature, and therefore, accurately predict the active layer thickness. The hydrological and thermal dynamics are closely linked to the polygon types and polygon features. The results also enable the

  10. Restoration of biogeochemical function in mangrove forests

    USGS Publications Warehouse

    McKee, K.L.; Faulkner, P.L.

    2000-01-01

    Forest structure of mangrove restoration sites (6 and 14 years old) at two locations (Henderson Creek [HC] and Windstar [WS]) in southwest Florida differed from that of mixed-basin forests (>50 years old) with which they were once contiguous. However, the younger site (HC) was typical of natural, developing forests, whereas the older site (WS) was less well developed with low structural complexity. More stressful physicochemical conditions resulting from incomplete tidal flushing (elevated salinity) and variable topography (waterlogging) apparently affected plant survival and growth at the WS restoration site. Lower leaf fall and root production rates at the WS restoration site, compared with that at HC were partly attributable to differences in hydroedaphic conditions and structural development. However, leaf and root inputs at each restoration site were not significantly different from that in reference forests within the same physiographic setting. Macrofaunal consumption of tethered leaves also did not differ with site history, but was dramatically higher at HC compared with WS, reflecting local variation in leaf litter processing rates, primarily by snails (Melampus coffeus). Degradation of leaves and roots in mesh bags was slow overall at restoration sites, however, particularly at WS where aerobic decomposition may have been more limited. These findings indicate that local or regional factors such as salinity regime act together with site history to control primary production and turnover rates of organic matter in restoration sites. Species differences in senescent leaf nitrogen content and degradation rates further suggest that restoration sites dominated by Laguncularia racemosa and Rhizophora mangle should exhibit slower recycling of nutrients compared with natural basin forests where Avicennia germinans is more abundant. Structural development and biogeochemical functioning of restored mangrove forests thus depend on a number of factors, but site

  11. Subsurface Geotechnical Parameters Report

    SciTech Connect

    D. Rigby; M. Mrugala; G. Shideler; T. Davidsavor; J. Leem; D. Buesch; Y. Sun; D. Potyondy; M. Christianson

    2003-12-17

    The Yucca Mountain Project is entering a the license application (LA) stage in its mission to develop the nation's first underground nuclear waste repository. After a number of years of gathering data related to site characterization, including activities ranging from laboratory and site investigations, to numerical modeling of processes associated with conditions to be encountered in the future repository, the Project is realigning its activities towards the License Application preparation. At the current stage, the major efforts are directed at translating the results of scientific investigations into sets of data needed to support the design, and to fulfill the licensing requirements and the repository design activities. This document addresses the program need to address specific technical questions so that an assessment can be made about the suitability and adequacy of data to license and construct a repository at the Yucca Mountain Site. In July 2002, the U.S. Nuclear Regulatory Commission (NRC) published an Integrated Issue Resolution Status Report (NRC 2002). Included in this report were the Repository Design and Thermal-Mechanical Effects (RDTME) Key Technical Issues (KTI). Geotechnical agreements were formulated to resolve a number of KTI subissues, in particular, RDTME KTIs 3.04, 3.05, 3.07, and 3.19 relate to the physical, thermal and mechanical properties of the host rock (NRC 2002, pp. 2.1.1-28, 2.1.7-10 to 2.1.7-21, A-17, A-18, and A-20). The purpose of the Subsurface Geotechnical Parameters Report is to present an accounting of current geotechnical information that will help resolve KTI subissues and some other project needs. The report analyzes and summarizes available qualified geotechnical data. It evaluates the sufficiency and quality of existing data to support engineering design and performance assessment. In addition, the corroborative data obtained from tests performed by a number of research organizations is presented to reinforce

  12. Subsurface contaminants focus area

    SciTech Connect

    1996-08-01

    The US Department of Enregy (DOE) Subsurface Contaminants Focus Area is developing technologies to address environmental problems associated with hazardous and radioactive contaminants in soil and groundwater that exist throughout the DOE complex, including radionuclides, heavy metals; and dense non-aqueous phase liquids (DNAPLs). More than 5,700 known DOE groundwater plumes have contaminated over 600 billion gallons of water and 200 million cubic meters of soil. Migration of these plumes threatens local and regional water sources, and in some cases has already adversely impacted off-site rsources. In addition, the Subsurface Contaminants Focus Area is responsible for supplying technologies for the remediation of numerous landfills at DOE facilities. These landfills are estimated to contain over 3 million cubic meters of radioactive and hazardous buried Technology developed within this specialty area will provide efective methods to contain contaminant plumes and new or alternative technologies for development of in situ technologies to minimize waste disposal costs and potential worker exposure by treating plumes in place. While addressing contaminant plumes emanating from DOE landfills, the Subsurface Contaminants Focus Area is also working to develop new or alternative technologies for the in situ stabilization, and nonintrusive characterization of these disposal sites.

  13. Subsurface Characterization To Support Evaluation Of Radionuclide Transport And Attenuation

    EPA Science Inventory

    Remediation of ground water contaminated with radionuclides may be achieved using attenuation-based technologies. These technologies may rely on engineered processes (e.g., bioremediation) or natural processes (e.g., monitored natural attenuation) within the subsurface. In gene...

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

    NASA Astrophysics Data System (ADS)

    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, t