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1

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

SciTech Connect

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 to what extent sinking particles are further broken down in the underlying waters of the Twilight Zone.

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

2008-02-25

2

Coupled Surface–Subsurface Solute Transport Model for Irrigation Borders and Basins. II. Model Evaluation  

Microsoft Academic Search

The development of a coupled surface-subsurface solute transport model for surface fertigation management is presented in a companion paper Part I. This paper discusses an evaluation of the coupled model. The numerical solution for pure advection of solute in the surface stream was evaluated using test problems with steep concentration gradients. The result shows that the model can simulate advection

D. Zerihun; C. A. Sanchez; A. Furman; A. W. Warrick

2005-01-01

3

A Process-Based, Distributed Hydrologic Model Based on a Large-Scale Method for Surface - Subsurface Coupling  

NASA Astrophysics Data System (ADS)

We present a novel physically-based hydrologic model, PAWS (Process-based Adaptive Watershed Simulator) which is based on a large-scale method for surface-subsurface coupling. The model solves the governing equations for major hydrologic processes with remarkable computational efficiency so that large scale applications become relevant. PAWS evaluates the integrated hydrologic response of the surface-subsurface system using a non-iterative method that couples runoff and groundwater flow to vadose zone processes approximating the 3D Richards equation. Numerical test cases indicate that the method is able to reproduce the essential dynamics of the 3D equation efficiently. PAWS uses public databases as input, possesses full capability to interact with GIS datasets and has the ability to link to current land surface models. The model was applied to two medium-sized watersheds in Michigan , verified using streamflow data, spatio-temporal data for groundwater heads and other observations and was found to offer useful insights into key hydrologic processes of the two watersheds.

Shen, C.; Phanikumar, M. S.

2010-12-01

4

A Process-Based, Distributed Hydrologic Model Based on a Large-Scale Method for Surface - Subsurface Coupling  

NASA Astrophysics Data System (ADS)

We present a novel physically-based hydrologic model, PAWS (Process-based Adaptive Watershed Simulator) based on a large-scale method for surface-subsurface coupling. The model solves the governing equations for major hydrologic processes with remarkable computational efficiency so that large scale applications become relevant. PAWS evaluates the integrated hydrologic response of the surface-subsurface system using a non-iterative method that couples runoff and groundwater flow to vadose zone processes approximating the 3D Richards equation. Numerical test cases indicate that the method is able to reproduce the essential dynamics of the 3D equation efficiently. PAWS uses public databases as input, possesses full capability to interact with GIS datasets and has the ability to link to current land surface models. The model was applied to two medium-sized watersheds in Michigan , verified using streamflow data, spatio-temporal data for groundwater heads and other observations and was found to offer useful insights into key hydrologic processes of the two watersheds.

Phanikumar, M. S.; Shen, C.

2010-12-01

5

A particle-tracking scheme for simulating pathlines in coupled surface-subsurface flows  

NASA Astrophysics Data System (ADS)

A Lagrangian particle tracking scheme has been extended to simulate advective transport through coupled surface and subsurface flows. This extended scheme assumes a two-dimensional flow field for the overland domain and a three-dimensional flow field for the subsurface domain. Moreover it is assumed that the flow fields are simulated by a cell centered finite difference method. Pathlines in both the subsurface and the overland domain are simulated by classical particle tracking methods. Exchange of particles between the two domains is simulated by newly-developed algorithms presented in this study. Different algorithms are used depending on the direction of the exchange across the interface between the two domains. In the subsurface domain knowledge about a particle's pathline is enough to detect a transfer to the surface domain and the solution is straightforward. However, in the two-dimensional overland domain pathlines are parallel to the land surface. Therefore the velocity field in the overland domain alone cannot be used to detect a transfer to the subsurface. We propose a relatively simple algorithm to estimate the probability of transfer to the subsurface domain. It is shown that this algorithm can also be used to handle the transfer from the overland domain to the atmosphere domain. The algorithm to estimate the transfer probabilities is based on the mass balance of water on a streamtube aligned with the particle's pathline. This newly developed technique ensures that transit time distributions can be simulated accurately. These new relationships are implemented in an existing particle tracking code and are verified using analytical solutions for transit times.

de Rooij, Rob; Graham, Wendy; Maxwell, Reed M.

2013-02-01

6

Coupling a terrestrial biogeochemical model to the common land model  

Microsoft Academic Search

A terrestrial biogeochemical model (CASACNP) was coupled to a land surface model (the Common Land Model, CoLM) to simulate\\u000a the dynamics of carbon substrate in soil and its limitation on soil respiration. The combined model, CoLM_CASACNP, was able\\u000a to predict long-term carbon sources and sinks that CoLM alone could not. The coupled model was tested using measurements of\\u000a belowground respiration

Xiaoying Shi; Jiafu Mao; Yingping Wang; Yongjiu Dai; Xuli Tang

2011-01-01

7

Measuring groundwater flow at the Sanford Laboratory with coupled surface/subsurface time-lapse gravity measurements  

NASA Astrophysics Data System (ADS)

Limited options exist to measure groundwater processes, particularly at large depths. Coupled time-lapse gravity measurements at the surface and underground are one possibility, but despite recent advances in borehole instruments, no repeat underground gravity measurements of water-mass change have been reported. At the Sanford Laboratory-located at the Homestake Mine in Lead, South Dakota, and site of the proposed Deep Underground Science and Engineering Laboratory (DUSEL)-the U.S. Geological Survey has established a network of 19 surface and 5 underground gravity stations to monitor groundwater-storage change over the projected 20-year existence of the underground laboratory. Continuous pumping is planned to dewater the mine to a depth of 2,500 m; the current pumping regime began in 2007 and current water levels (2011) are at a depth of about 1,700 m. Measurements using a field-portable A-10 absolute gravimeter have been made approximately annually at surface stations since 2007. Underground stations forming a vertical profile along the Ross Shaft on the 300, 800, 2000, 4100, and 4850 levels (numbers indicate approximate depth in feet) were established in 2011, and it is expected all stations will be surveyed annually. To date, surface time-lapse measurements show gravity increases of 50 to 100 nm/s^2 (10 nm/s^2 = 1 microgal) at some stations and equivalent decreases at others, indicating little evidence of water-mass change from pumping. Preliminary modeling, in which the dewatered zone is represented by a series of horizontal prisms that undergo mass change equal to the porosity (assumed 0.005, an average of rock porosity and mined-out voids), indicates that this is the expected result. At pumping rates required to maintain drawdown to a depth of 2,500 m, however, the expected gravity change increases from about 50 nm/s^2 at the surface to 250 nm/s^2 at the 4850 level. Gravity stations in the subsurface are advantageous because they are both closer to the water-mass change from pumping and removed from water-mass change at the surface caused by inter-annual climate variability. Furthermore, the predicted gravity response varies along the vertical profile depending on the distribution of water-mass change in the deep subsurface, indicating the subsurface measurements will be useful for calibrating and validating a groundwater flow model. A tunnel on the 300 level that traverses beneath a forested hillslope and exits at the land surface is a significant future opportunity for monitoring hydrologic processes; concurrent surface and subsurface gravity profiles above and below this hillslope, combined with other measurements, would likely lead to new advances in hillslope-scale hydrology.

Kennedy, J.; Murdoch, L.; Long, A. J.; Koth, K.

2011-12-01

8

Revisiting "nutrient trapping" in global coupled biogeochemical ocean circulation models  

NASA Astrophysics Data System (ADS)

We analyze an extensive set of global coupled biogeochemical ocean circulation models. The focus is on the equatorial Pacific. In all simulations, which are consistent with observed standing stocks of relevant biogeochemical species at the surface, we find spuriously enhanced (reduced) macronutrient (oxygen) concentrations in the deep eastern equatorial Pacific. This modeling problem, apparently endemic to global coupled biogeochemical ocean circulation models, was coined "nutrient trapping" by Najjar et al. (1992). In contrast to Aumont et al. (1999), we argue that "nutrient trapping" is still a persistent problem, even in eddy-permitting models and, further, that the scale of the problem retards model projections of nitrogen cycling. In line with previous work, our results indicate that a deficient circulation is at the core of the problem rather than an admittedly poor quantitative understanding of biogeochemical cycles. More specifically, we present indications that "nutrient trapping" in models is a result of a spuriously damped Equatorial Intermediate (zonal) Current System and Equatorial Deep Jets—phenomenon which await a comprehensive understanding and have, to date, not been successfully simulated.

Dietze, H.; Loeptien, U.

2013-04-01

9

Biogeochemical carbon coupling influences global precipitation in geoengineering experiments  

NASA Astrophysics Data System (ADS)

Abstract Climate model studies in which CO2-induced global warming is offset by engineered decreases of incoming solar radiation are generally robust in their prediction of reduced amounts of global precipitation. While this precipitation response has been explained on the basis of changes in net radiation controlling evaporative processes at the surface, there has been relatively little consideration of the relative role of <span class="hlt">biogeochemical</span> carbon-cycle interactions. To address this issue, we employ an Earth System Model that includes oceanic and terrestrial carbon components to isolate the impact of <span class="hlt">biogeochemical</span> carbon <span class="hlt">coupling</span> on the precipitation response in geoengineering experiments for two types of solar radiation management. We show that carbon <span class="hlt">coupling</span> is responsible for a large fraction of the global precipitation reduction in such geoengineering experiments and that the primary effect comes from reduced transpiration through the leaves of plants and trees in the terrestrial component of the carbon cycle due to elevated CO2. Our results suggest that <span class="hlt">biogeochemical</span> interactions are as important as changes in net radiation and that climate models that do not account for such carbon <span class="hlt">coupling</span> may significantly underestimate precipitation reductions in a geoengineered world.</p> <div class="credits"> <p class="dwt_author">Fyfe, J. C.; Cole, J. N. S.; Arora, V. K.; Scinocca, J. F.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-02-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">10</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/52973617"> <span id="translatedtitle">Characterising <span class="hlt">Surface-Subsurface</span> Hydrologic Interactions in Headwater Streams</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary"><span class="hlt">Surface-subsurface</span> interactions can have important influences on thermal regime, <span class="hlt">biogeochemical</span> cycling and habitat conditions in headwater streams. Different methods can be used to provide information on specific processes at different spatial scales. Constant-rate salt injection to steady-state along an entire reach can aid in characterising the spatial pattern of inflow, and can also be used to characterise advection, dispersion and</p> <div class="credits"> <p class="dwt_author">R. Moore; T. Gomi; A. Story; E. Mellina</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">11</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/893216"> <span id="translatedtitle">Characterization of <span class="hlt">Coupled</span> Hydrologic-<span class="hlt">Biogeochemical</span> Processes Using Geophysical Data</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary"><span class="hlt">Biogeochemical</span> and hydrological processes are naturally <span class="hlt">coupled</span> 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 <span class="hlt">coupled</span> 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.</p> <div class="credits"> <p class="dwt_author">Hubbard, Susan</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-06-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">12</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/1030623"> <span id="translatedtitle"><span class="hlt">Coupling</span> a terrestrial <span class="hlt">biogeochemical</span> model to the common land model</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">A terrestrial <span class="hlt">biogeochemical</span> model (CASACNP) was <span class="hlt">coupled</span> to a land surface model (the Common Land Model, CoLM) to simulate the dynamics of carbon substrate in soil and its limitation on soil respiration. The combined model, CoLM-CASACNP, was able to predict long-term carbon sources and sinks that CoLM alone could not. The <span class="hlt">coupled</span> model was tested using measurements of belowground respiration and surface fluxes from two forest ecosystems. The combined model simulated reasonably well the diurnal and seasonal variations of net ecosystem carbon exchange, as well as seasonal variation in the soil respiration rate of both the forest sites chosen for this study. However, the agreement between model simulations and actual measurements was poorer under dry conditions. The model should be tested against more measurements before being applied globally to investigate the feedbacks between the carbon cycle and climate change.</p> <div class="credits"> <p class="dwt_author">Shi, Xiaoying [ORNL; Mao, Jiafu [ORNL; Wang, Yingping [ORNL; Dai, Yongjiu [Beijing Normal University; Tang, Xuli [Chinese Academy of Sciences</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">13</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/894507"> <span id="translatedtitle"><span class="hlt">Coupled</span> <span class="hlt">Biogeochemical</span> Process Evaluation for Conceptualizing Trichloroethylene Co-Metabolism</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Chlorinated solvent wastes (e.g., trichloroethene or TCE) often occur as diffuse subsurface plumes in complex geological environments where <span class="hlt">coupled</span> 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 <span class="hlt">coupled</span> <span class="hlt">biogeochemical</span> 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 <span class="hlt">coupling</span> 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.</p> <div class="credits"> <p class="dwt_author">Colwell, Frederick; Radtke, Corey; Newby, Deborah; Delwiche, Mark; Crawf, Ronald L.; Paszczynski, Andrzej; Strap, Janice; Conrad, Mark; Brodic, Eoin; Starr, Robert; Lee, Hope</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-04-05</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">14</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/896426"> <span id="translatedtitle"><span class="hlt">Coupled</span> <span class="hlt">Biogeochemical</span> Process Evaluation for Conceptualizing Trichloroethylene Co-Metabolism</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Chlorinated solvent wastes (e.g., trichloroethene or TCE) often occur as diffuse subsurface plumes in complex geological environments where <span class="hlt">coupled</span> 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 different ?lines of evidence? indicating that the wastes are effectively destroyed. We are studying the <span class="hlt">coupled</span> <span class="hlt">biogeochemical</span> processes that dictate the rate of TCE co-metabolism first in the medial zone (TCE concentration: 1,000 to 20,000 ?g/L) of a plume at the Idaho National Laboratory?s Test Area North (TAN) site and then at Paducah or the Savannah River Site. We will use flow-through in situ reactors (FTISR) to investigate the rate of methanotrophic co-metabolism of TCE and the <span class="hlt">coupling</span> of the responsible biological processes with the dissolved methane flux and groundwater flow velocity. TCE co-metabolic rates at TAN are being assessed and interpreted 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 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 co-metabolism relative to other natural attenuation processes. This research will strengthen our ability to forecast the viability of MNA at DOE and other sites contaminated with chlorinated hydrocarbons.</p> <div class="credits"> <p class="dwt_author">Rick Colwell; Corey Radtke; Mark Delwiche; Deborah Newby; Lynn Petzke; Mark Conrad; Eoin Brodie; Hope Lee; Bob Starr; Dana Dettmers; Ron Crawford; Andrzej Paszczynski; Nick Bernardini; Ravi Paidisetti; Tonia Green</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">15</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012EGUGA..14.6641M"> <span id="translatedtitle"><span class="hlt">Surface-subsurface</span> model intercomparison: A first set of benchmark results to diagnose integrated hydrology and feedbacks.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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 <span class="hlt">coupled</span> to land-surface energy balances, <span class="hlt">biogeochemical</span> 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 <span class="hlt">surface-subsurface</span> models. The study is based on a series of benchmark problems, and the simulation results from seven <span class="hlt">coupled</span> 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 <span class="hlt">coupled</span> equations, including global implicit, sequential iterative, and asynchronous linking. Various strategies are used to enforce flux and pressure continuity at the <span class="hlt">surface--subsurface</span> 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.</p> <div class="credits"> <p class="dwt_author">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.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">16</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://quercus.igpp.ucla.edu/~frenzel/pub/CG27_2001GwoEtAl.pdf"> <span id="translatedtitle">HBGC123D: a high-performance computer model of <span class="hlt">coupled</span> hydrogeological and <span class="hlt">biogeochemical</span> processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Groundwater flow and transport models have been used to assist management of subsurface water resources and water quality. The needs of more efficient use of technical and financial resources have recently motivated the development of more effective remediation techniques and complex models of <span class="hlt">coupled</span> hydrogeological and <span class="hlt">biogeochemical</span> processes. We present a high-performance computer model of the <span class="hlt">coupled</span> processes, HBGC123D. The</p> <div class="credits"> <p class="dwt_author">Jin P. Gwo; Eduardo F D’Azevedo; Hartmut Frenzel; Melanie Mayes; Gour-Tsyh Yeh; Philip M. Jardine; Karen M. Salvagee; Forrest M. Hoffman</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">17</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2006AdWR...29..161O"> <span id="translatedtitle">Field exploration of <span class="hlt">coupled</span> hydrological and <span class="hlt">biogeochemical</span> catchment responses and a unifying perceptual model</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">This work presents the details of a focused field experiment carried out to understand the <span class="hlt">coupled</span> processes of runoff generation and <span class="hlt">biogeochemical</span> cycling in an agricultural catchment in Western Australia, with a particular focus on NO3- cycling and transport. Detailed hydrometric, chemical, and geochemical data corresponding to a shallow perched aquifer along a topo-sequence in the hillslope helped identify the existence of two hydrologically and chemically distinct landscape units, i.e., upland and riparian zones. Riparian zones control the catchment storm response while upland zones can be considered as storage units, controlling the base flow component of streamflow. The <span class="hlt">biogeochemical</span> role and functioning of these landscape units are also clear. Upland zones constitute the sources of NO3- and participate in down-slope transport, while riparian areas act as sinks for NO3- and are responsible for its depletion. The experimental results highlighted the critical role of the shallow perched aquifer whose space time dynamics governed the periodic connection and disconnection between riparian and upland zones, which have a significant impact on the catchment’s hydrological and hydrochemical responses. The role of topography was also highlighted, as different mechanisms of NO3- attenuation in the riparian zones are possible depending on the steepness of the hillslope, with differences in slope leading to different velocities and flow rates and impacting on relative dominance of the different mechanisms of NO3- depletion. These detailed analyses have helped us to develop a “unifying perceptual model” of the <span class="hlt">coupled</span> hydrological and <span class="hlt">biogeochemical</span> response of Susannah Brook catchment, which will advance our ability to generalize these results to other hillslopes, and eventually to other catchments in the region.</p> <div class="credits"> <p class="dwt_author">Ocampo, Carlos J.; Sivapalan, Murugesu; Oldham, Carolyn E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-02-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">18</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010EGUGA..12.6174J"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> cycle in the Arctic with a global <span class="hlt">coupled</span> sea ice-ocean-ecosystem model</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In the Arctic Ocean, both phytoplankton and sea ice algae are important contributors to the primary production and modulators of <span class="hlt">biogeochemical</span> cycle. A global <span class="hlt">coupled</span> ice-ocean-ecosystem model was established to investigate ice-ocean <span class="hlt">biogeochemical</span> cycle and the ice-ocean ecosystem modules are fully <span class="hlt">coupled</span> in the physical model POP-CICE (Parallel Ocean Program- Los Alamos Sea Ice Model). The model results are compared with various observations and the focus here are on the perspectives of the ice and ocean primary production and nutrients cycling in the Arctic Regions. The modeled sea ice algal carbon production shows reasonable seasonal successions of blooms from the subarctic toward the central Arctic and is in the comparable ranges of observations in the Chukchi Sea and the total amount in the pan-Arctic Regions. The phytoplankton blooms in the ocean starts with ice-edge blooms in the marginal ice zone, especially on shelf regions where nutrients concentrations are high. The ocean primary production is one order higher than the ice algal production in the subarctic seas and the shelf regions of the Arctic, while both are low in the central arctic due to nutrient limitation. The model reproduced the spatial distribution of the annual carbon production levels in the upper 100m of the Arctic Ocean. The DMS and DMSP concentrations are calculated in both sea ice and ocean, and preliminary results of the seasonal cycle of DMS, DMSP concentrations and fluxes at the air-sea interface are shown.</p> <div class="credits"> <p class="dwt_author">Jin, Meibing; Deal, Clara; Elliott, Scott; Hunke, Elizabeth; Maltrud, Mathew</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">19</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013JMS...117...81D"> <span id="translatedtitle">Stochastic estimation of <span class="hlt">biogeochemical</span> parameters from Globcolour ocean colour satellite data in a North Atlantic 3D ocean <span class="hlt">coupled</span> physical-<span class="hlt">biogeochemical</span> model</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary"><span class="hlt">Biogeochemical</span> parameters remain a major source of uncertainty in <span class="hlt">coupled</span> physical-<span class="hlt">biogeochemical</span> models of the ocean. In a previous study (Doron et al., 2011), a stochastic estimation method was developed to estimate a subset of <span class="hlt">biogeochemical</span> model parameters from surface phytoplankton observations. The concept was tested in the context of idealised twin experiments performed with a 1/4° resolution model of the North Atlantic ocean. The method was based on ensemble simulations describing the model response to parameter uncertainty. The statistical estimation process relies on nonlinear transformations of the estimated space to cope with the non-Gaussian behaviour of the resulting joint probability distribution of the model state variables and parameters. In the present study, the same method is applied to real ocean colour observations, as delivered by the sensors SeaWiFS, MERIS and MODIS embarked on the satellites OrbView-2, Envisat and Aqua respectively. The main outcome of the present experiments is a set of regionalised <span class="hlt">biogeochemical</span> parameters. The benefit is quantitatively assessed with an objective norm of the misfits, which automatically adapts to the different ecological regions. The chlorophyll concentration simulated by the model with this set of optimally derived parameters is closer to the observations than the reference simulation using uniform values of the parameters. In addition, the interannual and seasonal robustness of the estimated parameters is tested by repeating the same analysis using ocean colour observations from several months and several years. The results show the overall consistency of the ensemble of estimated parameters, which are also compared to the results of an independent study.</p> <div class="credits"> <p class="dwt_author">Doron, Maéva; Brasseur, Pierre; Brankart, Jean-Michel; Losa, Svetlana N.; Melet, Angélique</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">20</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013GMD.....6.1173W"> <span id="translatedtitle">PEATBOG: a <span class="hlt">biogeochemical</span> model for analyzing <span class="hlt">coupled</span> carbon and nitrogen dynamics in northern peatlands</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Elevated nitrogen deposition and climate change alter the vegetation communities and carbon (C) and nitrogen (N) cycling in peatlands. To address this issue we developed a new process-oriented <span class="hlt">biogeochemical</span> model (PEATBOG) for analyzing <span class="hlt">coupled</span> carbon and nitrogen dynamics in northern peatlands. The model consists of four submodels, which simulate: (1) daily water table depth and depth profiles of soil moisture, temperature and oxygen levels; (2) competition among three plants functional types (PFTs), production and litter production of plants; (3) decomposition of peat; and (4) production, consumption, diffusion and export of dissolved C and N species in soil water. The model is novel in the integration of the C and N cycles, the explicit spatial resolution belowground, the consistent conceptualization of movement of water and solutes, the incorporation of stoichiometric controls on elemental fluxes and a consistent conceptualization of C and N reactivity in vegetation and soil organic matter. The model was evaluated for the Mer Bleue Bog, near Ottawa, Ontario, with regards to simulation of soil moisture and temperature and the most important processes in the C and N cycles. Model sensitivity was tested for nitrogen input, precipitation, and temperature, and the choices of the most uncertain parameters were justified. A simulation of nitrogen deposition over 40 yr demonstrates the advantages of the PEATBOG model in tracking <span class="hlt">biogeochemical</span> effects and vegetation change in the ecosystem.</p> <div class="credits"> <p class="dwt_author">Wu, Y.; Blodau, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-08-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_1");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> 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href="#">7</a> <a onClick='return showDiv("page_8");' href="#">8</a> <a onClick='return showDiv("page_9");' href="#">9</a> <a onClick='return showDiv("page_10");' href="#">10</a> <a onClick='return showDiv("page_11");' href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_3");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">21</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010JGRF..115.4017W"> <span id="translatedtitle">Hydro-<span class="hlt">biogeochemical</span> <span class="hlt">coupling</span> beneath a large polythermal Arctic glacier: Implications for subice sheet biogeochemistry</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We analyze the interannual chemical and isotopic composition of runoff from a large, high Arctic valley glacier over a 5 year period, during which drainage evolved from a long-residence-time drainage system feeding an artesian subglacial upwelling (SGU) at the glacier terminus to a shorter-residence-time drainage system feeding an ice-marginal channel (IMC). Increased icemelt inputs to the SGU are thought to have triggered this evolution. This sequence of events provides a unique opportunity to identify <span class="hlt">coupling</span> between subglacial hydrology and <span class="hlt">biogeochemical</span> processes within drainage systems of differing residence time. The biogeochemistry of the SGU is consistent with prolonged contact between meltwaters and subglacial sediments, in which silicate dissolution is enhanced, anoxic processes (e.g., sulphate reduction) prevail, and microbially generated CO2 and sulphide oxidation drive mineral dissolution. Solute in the IMC was mainly derived from moraine pore waters which are added to the channel via extraglacial streams. These pore waters acquire solute predominantly via sulphide oxidation <span class="hlt">coupled</span> to carbonate/silicate dissolution. We present the first evidence that microbially mediated processes may contribute a substantial proportion (80% in this case) of the total glacial solute flux, which includes <span class="hlt">coupling</span> between microbial CO2-generation and silicate/carbonate dissolution. The latter suggests the presence of biofilms in subglacial/ice-marginal sediments, where local perturbation of the geochemical environment by release of protons, organic acids, and ligands stimulates mineral dissolution. These data enable inferences to be made regarding <span class="hlt">biogeochemical</span> processes in longer-residence-time glacial systems, with implications for the future exploration of Antarctic subglacial lakes and other wet-based ice sheet environments.</p> <div class="credits"> <p class="dwt_author">Wadham, J. L.; Tranter, M.; Hodson, A. J.; Hodgkins, R.; Bottrell, S.; Cooper, R.; Raiswell, R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">22</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/895884"> <span id="translatedtitle">Multi-scale Characterization and Prediction of <span class="hlt">Coupled</span> Subsurface <span class="hlt">Biogeochemical</span>-Hydrological Processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">To advance solutions needed for remediation of DOE contaminated sites, approaches are needed that can elucidate and predict reactions associated with <span class="hlt">coupled</span> 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 <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Hubbard, Susan; Williams, Ken; Steefel, Carl; Banfield, Jill; Long, Phil; Slater, Lee; Pride, Steve; Jinsong Chen</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">23</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=DE94009815"> <span id="translatedtitle">Hierarchical framework for <span class="hlt">coupling</span> a <span class="hlt">biogeochemical</span> trace gas model to a general circulation model.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">A scheme is described for the computation of terrestrial <span class="hlt">biogeochemical</span> trace gas fluxes in the context of a general circulation model. This hierarchical system flux scheme (HSFS) incorporates five major components: (1) a general circulation model (GCM), ...</p> <div class="credits"> <p class="dwt_author">N. L. Miller I. T. Foster</p> <p class="dwt_publisher"></p> <p class="publishDate">1994-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">24</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008AGUFM.B31I..06B"> <span id="translatedtitle">Modeling Nitrogen Leaching With A <span class="hlt">Biogeochemical</span> Model <span class="hlt">Coupled</span> With Soil Hydrology Model</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Land use changes for cropland, excessive application of fertilizers in agriculture, and increase in anthropogenic activities such as fossil fuel burning have lead to widespread increases in anthropogenic production of reactive N and NH3 emissions, and N deposition rates. An important consequence of these processes is intensification of soil nutrient leaching activities, leading to serious ground water contamination problems. The current study focuses on the issue of nitrogen (nitrate and ammonium) leaching due to land cover changes for cropland, excess N fertilizer application, and atmospheric nitrogen deposition on nitrogen leaching at a global scale. Simulations of nitrogen leaching require integration of processes involving soil hydrology and <span class="hlt">biogeochemical</span> cycles. An existing terrestrial <span class="hlt">coupled</span> carbon-nitrogen cycle model, Integrated Science Assessment Model (ISAM), was used to estimate nitrogen leaching. The N-cycle in ISAM includes the major processes associated with nitrogen (immobilization, mineralization, nitrification, denitrification, leaching, nitrogen fixation, and vegetation nitrogen uptake). ISAM also considers how carbon and nitrogen dynamics are influenced by the effects of human perturbations to the N cycle including atmospheric deposition and fertilizer application, and the fate of N in land use activities, i.e., deforestation and agricultural harvest. In this study, the ISAM soil hydrology was extended and improved with CLM 3.5 hydrology processes and algorithms, which extended the modeling capabilities to consider the prediction of nitrogen leaching. The model performance was evaluated with flow and nutrient data at several locations within the Upper Sangamon River Basin in Illinois, and flow data in contrasting watersheds in Oklahoma. This talk will focus on describing the results of a series of modeling experiments examining the influence of land management changes for cropland and nitrogen deposition on nitrogen leaching at a global scale. These experiments were conducted based on the measured activities of land use and nitrogen deposition over the last century.</p> <div class="credits"> <p class="dwt_author">Barman, R.; Yang, X.; Jain, A.; Post, W. M.; Sivapalan, M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">25</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.H52D..03M"> <span id="translatedtitle">Modeling Nitrogen Cycle at the <span class="hlt">Surface-Subsurface</span> Water Interface</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Anthropogenic activities, primarily food and energy production, have altered the global nitrogen cycle, increasing reactive dissolved inorganic nitrogen, Nr, chiefly ammonium NH4+ and nitrate NO3-, availability in many streams worldwide. Increased Nr promotes biological activity often with negative consequences such as water body eutrophication and emission of nitrous oxide gas, N2O, an important greenhouse gas as a by-product of denitrification. The hyporheic zone may play an important role in processing Nr and returning it to the atmosphere. Here, we present a process-based three-dimensional semi-analytical model, which <span class="hlt">couples</span> hyporheic hydraulics with <span class="hlt">biogeochemical</span> reactions and transport equations. Transport is solved by means of particle tracking with negligible local dispersion and <span class="hlt">biogeochemical</span> reactions modeled by linearized Monod's kinetics with temperature dependant reaction rate coefficients. Comparison of measured and predicted N2O emissions from 7 natural stream shows a good match. We apply our model to gravel bed rivers with alternate bar morphology to investigate the role of hyporheic hydraulic, depth of alluvium, relative availability of stream concentration of NO3- and NH4+ and water temperature on nitrogen gradients within the sediment. Our model shows complex concentration dynamics, which depend on hyporheic residence time distribution and consequently on streambed morphology, within the hyporheic zone. Nitrogen gas emissions from the hyporheic zone increase with alluvium depth in large low-gradient streams but not in small steep streams. On the other hand, hyporheic water temperature influences nitrification/denitrification processes mainly in small-steep than large low-gradient streams, because of the long residence times, which offset the slow reaction rates induced by low temperatures in the latter stream. The overall conclusion of our analysis is that river morphology has a major impact on <span class="hlt">biogeochemical</span> processes such as nitrification and denitrification with a direct impact on the stream nutrient removal and transport.</p> <div class="credits"> <p class="dwt_author">Marzadri, A.; Tonina, D.; Bellin, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">26</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012JGRG..117.0N12F"> <span id="translatedtitle">Surface micro-topography causes hot spots of <span class="hlt">biogeochemical</span> activity in wetland systems: A virtual modeling experiment</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> 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 <span class="hlt">coupled</span> <span class="hlt">surface-subsurface</span> systems. <span class="hlt">Biogeochemical</span> processes and transport along advective subsurface flow paths are simulated kinetically using the <span class="hlt">biogeochemical</span> code PHREEQC. Distinct patterns of <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> activity, which is needed to assess future changes in the <span class="hlt">biogeochemical</span> turnover of wetland systems.</p> <div class="credits"> <p class="dwt_author">Frei, S.; Knorr, K. H.; Peiffer, S.; Fleckenstein, J. H.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">27</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.agu.org/journals/wr/wr0803/2007WR006108/2007WR006108.pdf"> <span id="translatedtitle">Probabilistic dynamics of soil nitrate: <span class="hlt">Coupling</span> of ecohydrological and <span class="hlt">biogeochemical</span> processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">In this paper we analyze the probabilistic dynamics resulting from a simplified model of soil moisture and nitrate mass in relatively arid environments, which accounts for relevant hydrologic and <span class="hlt">biogeochemical</span> processes and for the random characters of rainfall. The soil nitrate balance includes uptake through transpiration, mineralization, nitrification, and denitrification. To allow an exact mathematical treatment, all nitrate fluxes are</p> <div class="credits"> <p class="dwt_author">G. Botter; E. Daly; A. Porporato; I. Rodriguez-Iturbe; A. Rinaldo</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">28</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2006AGUFM.B21C1035S"> <span id="translatedtitle">Estimating Stream Chemistry During the Snowmelt Pulse Using Remotely Sensed Snow Observations and a <span class="hlt">Coupled</span> Snowmelt and <span class="hlt">Biogeochemical</span> Modeling Approach</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The use of robust physically based models should improve the predictions made by <span class="hlt">biogeochemical</span> models across a range of ecosystems. While a widely held belief this statement has not been supported by that many integrated modeling studies. In this paper we will present our efforts to integrate a physically robust snowmelt model with a detailed <span class="hlt">biogeochemical</span> model of alpine ecosystems. Time series of fractional snow covered area (SCA) estimates from aerial photography were combined with a spatially distributed snowmelt model to reconstruct snow water equivalent (SWE) and snowmelt in the Green Lakes Valley, Colorado. In this reconstruction approach, modeled snowmelt over each pixel is integrated over the time of aircraft-observed snow cover to estimate SWE and pixel-specific snowmelt. The spatially explicit snowmelt estimates were then used as forcings in the Alpine Hydrochemical Model. Model runs for the 1996 snowmelt season showed that R2 increased from 0.6 to 0.75 when comparing observed NO3- concentrations to modeled estimates without and with <span class="hlt">coupling</span> to the distributed snowmelt model, respectively. In addition to the improved representation of source water input obtained under this research, results indicate that better representation of flow routing is also needed. Additionally the <span class="hlt">coupled</span> modeling allows isolation of these flow routing problems and thus an improvement in the hypothesis testing capabilities of the integrated model. The <span class="hlt">coupled</span>, spatially explicit modeling approach has implications for realizing feedbacks between hydrological processes and nitrogen fluxes and for identifying the sensitivity of these processes and feedbacks to climate variability.</p> <div class="credits"> <p class="dwt_author">Sickman, J.; Molotch, N. P.; Meixner, T.; Williams, M.; Painter, T.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">29</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010EGUGA..1210448V"> <span id="translatedtitle">Study of the Tagus estuarine plume using <span class="hlt">coupled</span> hydro and <span class="hlt">biogeochemical</span> models</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Plumes of buoyant water produced by inflow from rivers and estuaries are common on the continental shelf. Buoyancy associated with estuarine waters is a key mediating factor in the transport and transformation of dissolved and particulate materials in coastal margins. The offshore displacement of the plume is influenced greatly by the local alongshore wind, which will tend to advect the plume either offshore or onshore, consistently with the Ekman transport. Other factor affecting the propagation of an estuarine plume is the freshwater inflow on the landward boundary. In this paper, a <span class="hlt">coupled</span> three-dimensional ocean circulation and <span class="hlt">biogeochemical</span> model with realistic high and low frequency forcing is used to get insight on how the Tagus River plume responds to wind and freshwater discharge during winter and spring. A nesting approach based on the MOHID numerical system was implemented for the Tagus estuary near shelf. Realistic hindcast simulations were performed, covering a period from January to June 2007. Model results were evaluated using in-situ and satellite imagery data. The numerical model was implemented using a three level nesting model. The model domain includes the whole Portuguese coast, the Tagus estuary near shelf and the Tagus River estuary, using a realistic coastline and bottom topography. River discharge and wind forcing are considered as landward and surface boundary conditions, respectively. Initial ocean stratification is from the MERCATOR solution. Ambient shelf conditions include tidal motion. As a prior validation, models outputs of salinity and water temperature were compared to available data (January 30th and May 30th, 2007) and were found minor differences between model outputs and data. On January 30th, outside the estuary, the model results reveal a stratified water column, presenting salinity stratification of the order of 3-4. The model also reproduces the hydrography for the May 30th observations. In May, near the Tagus mouth, measurements show low salinity stratification (when compared to the January observations). During this month, stratification is mainly due to water temperature. In general, the correlation between water temperature from the model and satellite data, reveals values higher than 0.5 (significant values) for the whole simulation period, presenting high correlations (about 0.8) in January and February, when the plume propagation is mainly controlled by the estuarine discharge. The correlation between the model results of suspended sediments and the satellite data (suspended matter) presents significant values (higher than 0.5) for almost the whole simulation period. On the shelf, near the Tagus mouth, the export of estuarine waters forms a plume which is highly influenced by the geography of the coastline, inducing a plume trajectory very close to shore. Northern winds events cause a displacement of the coastally trapped plume, driving a new offshore plume. The relaxation of the northern wind regime pushes back the coastal jet toward the coast, propagating estuarine water to the north along the coastline. The model was also able to reproduce the effect of the estuary plume over the coastal surface chlorophyll patterns observed remotely and the in situ chlorophyll and nutrient profiles, especially in the periods of low wind intensity. In periods of persistent Northerly winds the effect of the Sintra Mountains Ridge over the wind field tend to be underestimated. This leads to a southerly transport by the model slightly more intense than the one observed remotely.</p> <div class="credits"> <p class="dwt_author">Vaz, Nuno; Leitão, Paulo C.; Juliano, Manuela; Mateus, Marcos; Dias, João. Miguel; Neves, Ramiro</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">30</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2007AGUFM.B11B0410H"> <span id="translatedtitle"><span class="hlt">Coupled</span> Hydrological and <span class="hlt">Biogeochemical</span> Controls on Methylmercury Production and Export from a Boreal Wetland</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Through long-term addition of a mercury (Hg) stable isotope to a wetland, we have begun to unravel the complexity of Hg and methylmercury (MeHg) cycling in a Boreal wetland. As part of the METAALICUS project being conducted at the Experimental Lakes Area, the lake 658 wetland was annually amended from 2001-2006 with a mercury isotope at a level approximately 5 times the annual anthropogenic deposition. However, wetlands not only receive Hg directly from atmospheric deposition, but also from upland runoff and from adjacent water bodies during periods of inundation. As METAALICUS is a whole watershed experiment, both the adjacent lake and uplands were each amended with a different mercury isotope. This has allowed us to study the cycling of Hg within the wetland in a watershed context. What is clear from this integrated approach is Hg cycling is dependent on the complex interplay of hydrodynamic and <span class="hlt">biogeochemical</span> factors which will form the focus of this presentation. The Lake 658 wetland is classified as a basin oligotrophic swamp, and is surrounded on three sides by steeply sloping uplands and on the fourth by a lake. The morphology of the wetland causes large portions of the wetland to be hydrologically disconnected for long periods during dry periods in the summer and by ice in winter. When flow occurs, it is along defined channels rather than by sheet flow, which is partially an artifact of the basin morphology. Thus, wetland form influences the wetland volume that contributes to Hg and MeHg export. The majority of the Hg isotope added to the wetland has been retained in the vegetation and upper few centimeters of peat, with less than 1% exported despite the substantial export of both inorganic ambient Hg and MeHg. As little newly deposited Hg, represented by the amended isotope has been exported, we hypothesize that Hg export from wetlands is strongly <span class="hlt">coupled</span> to decomposition and the fate of dissolved organic carbon which binds both Hg and MeHg. While MeHg is found throughout the wetland, MeHg concentrations and potentials (measured by short-term assays) were greatest in areas that are hydrologically connected to the lake or upland. These methylation assays correlate well with sulfate reduction and methane production. However, high concentrations of MeHg can be present in areas of the wetland when methylation assays reveal no measurable activity suggesting a pool of recalcitrant MeHg exists in wetlands. We hypothesize that the hydrologically interconnected areas of the wetland are most important in producing and exporting MeHg. However, the slow release of Hg isotope from the 658 wetland indicates Hg retention, thus response to changes in Hg deposition, is at least on the order of years and probably decades.</p> <div class="credits"> <p class="dwt_author">Heyes, A.; Krabbenhoft, D. P.; Branfireun, B. A.; Gilmour, C. C.; Mitchell, C. P.; Tate, M. T.; Richardson, M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">31</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013BGeo...10.3559G"> <span id="translatedtitle"><span class="hlt">Coupled</span> physical/<span class="hlt">biogeochemical</span> modeling including O2-dependent processes in the Eastern Boundary Upwelling Systems: application in the Benguela</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Eastern Boundary Upwelling Systems (EBUS) contribute to one fifth of the global catches in the ocean. Often associated with Oxygen Minimum Zones (OMZs), EBUS represent key regions for the oceanic nitrogen (N) cycle. Important bioavailable N loss due to denitrification and anammox processes as well as greenhouse gas emissions (e.g, N2O) occur also in these EBUS. However, their dynamics are currently crudely represented in global models. In the climate change context, improving our capability to properly represent these areas is crucial due to anticipated changes in the winds, productivity, and oxygen content. We developed a <span class="hlt">biogeochemical</span> model (BioEBUS) taking into account the main processes linked with EBUS and associated OMZs. We implemented this model in a 3-D realistic <span class="hlt">coupled</span> physical/<span class="hlt">biogeochemical</span> configuration in the Namibian upwelling system (northern Benguela) using the high-resolution hydrodynamic ROMS model. We present here a validation using in situ and satellite data as well as diagnostic metrics and sensitivity analyses of key parameters and N2O parameterizations. The impact of parameter values on the OMZ off Namibia, on N loss, and on N2O concentrations and emissions is detailed. The model realistically reproduces the vertical distribution and seasonal cycle of observed oxygen, nitrate, and chlorophyll a concentrations, and the rates of microbial processes (e.g, NH4+ and NO2- oxidation, NO3- reduction, and anammox) as well. Based on our sensitivity analyses, <span class="hlt">biogeochemical</span> parameter values associated with organic matter decomposition, vertical sinking, and nitrification play a key role for the low-oxygen water content, N loss, and N2O concentrations in the OMZ. Moreover, the explicit parameterization of both steps of nitrification, ammonium oxidation to nitrate with nitrite as an explicit intermediate, is necessary to improve the representation of microbial activity linked with the OMZ. The simulated minimum oxygen concentrations are driven by the poleward meridional advection of oxygen-depleted waters offshore of a 300 m isobath and by the <span class="hlt">biogeochemical</span> activity inshore of this isobath, highlighting a spatial shift of dominant processes maintaining the minimum oxygen concentrations off Namibia. In the OMZ off Namibia, the magnitude of N2O outgassing and of N loss is comparable. Anammox contributes to about 20% of total N loss, an estimate lower than currently assumed (up to 50%) for the global ocean.</p> <div class="credits"> <p class="dwt_author">Gutknecht, E.; Dadou, I.; Le Vu, B.; Cambon, G.; Sudre, J.; Garçon, V.; Machu, E.; Rixen, T.; Kock, A.; Flohr, A.; Paulmier, A.; Lavik, G.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-06-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">32</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/6578324708841n37.pdf"> <span id="translatedtitle">A physically-based integrated numerical model for flow, upland erosion, and contaminant transport in <span class="hlt">surface-subsurface</span> systems</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">This paper presents a physically-based integrated hydrologic model that can simulate the rainfall-induced 2D surface water\\u000a flow, 3D variably saturated subsurface flow, upland soil erosion and transport, and contaminant transport in the <span class="hlt">surface-subsurface</span>\\u000a system of a watershed. The model <span class="hlt">couples</span> surface and subsurface flows based on the assumption of continuity conditions of\\u000a pressure head and exchange flux at the ground,</p> <div class="credits"> <p class="dwt_author">ZhiGuo He; WeiMing Wu</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">33</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010DSRII..57.1762L"> <span id="translatedtitle">Seasonal variation of primary productivity in the East China Sea: A numerical study based on <span class="hlt">coupled</span> physical-<span class="hlt">biogeochemical</span> model</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The seasonal variation of phytoplankton growth in the East China Sea (ECS) is simulated with a three-dimensional <span class="hlt">coupled</span> physical-<span class="hlt">biogeochemical</span> model, which includes discharges from Changjiang (Yangtze River). The purpose is to determine the main control on the seasonality of primary productivity in the ECS shelf, which nurtures rich biological resources. The model has a horizontal resolution of 1/6° in the domain from 23°N to 41°N and from 116°E to 134°E, excluding the Japan/East Sea, and 33 layers in the vertical. The nitrogen-based <span class="hlt">biogeochemical</span> model has four compartments: dissolved inorganic nitrogen (DIN), phytoplankton, zooplankton and detritus. The chlorophyll to phytoplankton ratio depends on light and DIN availability. The model is driven by monthly climatological winds with the sea-surface temperature, salinity and DIN relaxed towards the climatological mean values. It successfully reproduces the observed seasonal variation of primary productivity over the ECS shelf with a strong peak in later spring and summer. The modeled annual mean primary production (PP) over the entire ECS shelf is 441 mg C m -2 d -1, which falls within the reported range of 390-529 mg C m -2 d -1. It also reproduces the marked seaward gradient of DIN that decreases away from the Changjiang plume. Strong dependency on the amount of photosynthetically active radiation (PAR) is demonstrated for primary production. For 1% change in PAR 0.7% change in PP is effected. Numerical experiments show that the strong summer peak of DIN load from Changjiang cannot generate the seasonality of PP without the seasonal cycle of PAR. On the other hand, the model can still produces the seasonal pattern with Changjiang nutrient load set to zero, indicating light availability as the major control. Yet the Changjiang DIN load induces a PP increase of 77 mg C m -2 d -1, which represents 13-20% of the observation based estimates of PP. It is noted that the increase in nitrogen uptake associated with PP is 2.7 times the DIN provided by the Changjiang discharge, implying efficient recycling of the riverine nutrients in the shelf water. The model needs improvement on the sluggish dispersion of the Changjiang plume and insufficient vertical mixing. It also needs a more complicated <span class="hlt">biogeochemical</span> model with more size classes of organisms, multiple-nutrient schemes and additional geochemical processes.</p> <div class="credits"> <p class="dwt_author">Liu, Kon-Kee; Chao, Shenn-Yu; Lee, Hung-Jen; Gong, Gwo-Ching; Teng, Yi-Cheng</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-10-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">34</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..15.3976L"> <span id="translatedtitle">Autonomous Studies of <span class="hlt">Coupled</span> Physical-<span class="hlt">Biogeochemical</span> Processes- Lessons from NAB08 and Prospects for the Future</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Motivated by the increasing application of autonomous sensors to physical, biological and <span class="hlt">biogeochemical</span> 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 <span class="hlt">coupled</span> 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 <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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 70% NCP occurred steadily throughout the main bloom, while respiration, rather than sinking, drove the rapid drop in POC at bloom termination. Sensor networks require proper intercalibration to support quantitative use of the measurements, but calibration efforts become increasingly difficult as the number of independent sensors grows. NAB08 offers a suitable model for modest networks, but alternative approaches will be required for larger arrays.</p> <div class="credits"> <p class="dwt_author">Lee, Craig; D'Asaro, Eric; Perry, Mary Jane</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">35</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2007AGUFM.B11B0411M"> <span id="translatedtitle">A <span class="hlt">Coupled</span> <span class="hlt">Biogeochemical</span> Reactive Transport Model in Bed Sediments and Water Column of Riverine Systems</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">ABSTRACT: A multi-scale, quasi-two-dimensional, <span class="hlt">biogeochemical</span> reactive theoretical and numerical model is presented, able to simulating sediment associated transport and transformations of contaminants in the water column and bed sediments of riverine systems as a result of sediment associated transport, as well as resuspension, deposition and burial. The model considers contaminant mass exchange between sediments and aqueous phase both in benthic sediments and water column as a kinetically controlled process. It also takes into account the effect of microbially-mediated redox reactions affecting the speciation of chemicals. Transport of species in the sediments is modeled using a set of vertical one-dimensional sub-models which take into account the reactive transport of chemicals, burial, sorption/desorption to/from the solid phase, and diffusive transport of aqueous species. An innovative multi-time step approach is used to model the fully kinetic nonlinear reaction terms using a non-iterative explicit method. This approach enables the model to handle fast and near- equilibrium reactions without a significant increase in computational burden. Ongoing and planned applications of this multiscale modeling strategy to two cases, multiple metal transport in Lake Coeur d'Alene, Idaho, and Mercury Cycling in Walker Creek, California, are discussed.</p> <div class="credits"> <p class="dwt_author">Massoudieh, A.; Bombardelli, F. A.; Sengor, S. S.; Ginn, T. R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">36</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/60792454"> <span id="translatedtitle">Multi-scale Characterization and Prediction of <span class="hlt">Coupled</span> Subsurface <span class="hlt">Biogeochemical</span>-Hydrological Processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">To advance solutions needed for remediation of DOE contaminated sites, approaches are needed that can elucidate and predict reactions associated with <span class="hlt">coupled</span> 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</p> <div class="credits"> <p class="dwt_author">Susan Hubbard; Ken Williams; Carl Steefel; Jill Banfield; Phil Long; Lee Slater; Steve Pride; Jinsong Chen</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">37</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010GeCoA..74.2811P"> <span id="translatedtitle">Aggregate-scale spatial heterogeneity in reductive transformation of ferrihydrite resulting from <span class="hlt">coupled</span> <span class="hlt">biogeochemical</span> and physical processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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 <span class="hlt">coupling</span> of physical and <span class="hlt">biogeochemical</span> 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-section and interior at low lactate concentration (0.3 mM) after 30 d of reaction. Under high lactate (3 mM) concentration, magnetite was observed only as a transitory phase, and rather goethite/lepidocrocite and siderite were the dominant secondary mineralization products. Our results illustrate the importance of slow diffusive transport of both electron donor and metabolites concentrations and concomitant <span class="hlt">biogeochemical</span> reactions within soils and sediments, giving rise to heterogeneous products over small spatial (?m) scale.</p> <div class="credits"> <p class="dwt_author">Pallud, C.; Masue-Slowey, Y.; Fendorf, S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">38</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.agu.org/journals/gc/gc0901/2008GC002291/2008GC002291.pdf"> <span id="translatedtitle">Influence of particle size and type on 231Pa and 230Th simulation with a global <span class="hlt">coupled</span> <span class="hlt">biogeochemical</span>-ocean general circulation model: A first approach</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The oceanic distributions of 231Pa and 230Th are simulated with the global <span class="hlt">coupled</span> <span class="hlt">biogeochemical</span>-ocean general circulation model NEMO-PISCES. These natural nonconservative tracers, which are removed from the water column by reversible scavenging processes onto particles, have been used to study modern and past ocean circulation. Our model includes three different types of particles: particulate organic matter (POM), calcium carbonate (CaCO3),</p> <div class="credits"> <p class="dwt_author">J.-C. Dutay; F. Lacan; M. Roy-Barman; L. Bopp</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">39</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010OcSci...6..247B"> <span id="translatedtitle">Characterization of mixing errors in a <span class="hlt">coupled</span> physical <span class="hlt">biogeochemical</span> model of the North Atlantic: implications for nonlinear estimation using Gaussian anamorphosis</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In <span class="hlt">biogeochemical</span> models <span class="hlt">coupled</span> to ocean circulation models, vertical mixing is an important physical process which governs the nutrient supply and the plankton residence in the euphotic layer. However, vertical mixing is often poorly represented in numerical simulations because of approximate parameterizations of sub-grid scale turbulence, wind forcing errors and other mis-represented processes such as restratification by mesoscale eddies. Getting a sufficient knowledge of the nature and structure of these errors is necessary to implement appropriate data assimilation methods and to evaluate if they can be controlled by a given observation system. In this paper, Monte Carlo simulations are conducted to study mixing errors induced by approximate wind forcings in a three-dimensional <span class="hlt">coupled</span> physical-<span class="hlt">biogeochemical</span> model of the North Atlantic with a 1/4° horizontal resolution. An ensemble forecast involving 200 members is performed during the 1998 spring bloom, by prescribing perturbations of the wind forcing to generate mixing errors. The <span class="hlt">biogeochemical</span> response is shown to be rather complex because of nonlinearities and threshold effects in the <span class="hlt">coupled</span> model. The response of the surface phytoplankton depends on the region of interest and is particularly sensitive to the local stratification. In addition, the statistical relationships computed between the various physical and <span class="hlt">biogeochemical</span> variables reflect the signature of the non-Gaussian behaviour of the system. It is shown that significant information on the ecosystem can be retrieved from observations of chlorophyll concentration or sea surface temperature if a simple nonlinear change of variables (anamorphosis) is performed by mapping separately and locally the ensemble percentiles of the distributions of each state variable on the Gaussian percentiles. The results of idealized observational updates (performed with perfect observations and neglecting horizontal correlations) indicate that the implementation of this anamorphosis method into sequential assimilation schemes can substantially improve the accuracy of the estimation with respect to classical computations based on the Gaussian assumption.</p> <div class="credits"> <p class="dwt_author">Béal, D.; Brasseur, P.; Brankart, J.-M.; Ourmières, Y.; Verron, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-02-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">40</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/1015726"> <span id="translatedtitle">Numerical modeling of <span class="hlt">coupled</span> fluid flow and thermal and reactive <span class="hlt">biogeochemical</span> transport in porous and fractured media</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Subsurface contamination problems of metals and radionuclides are ubiquitous. Metals and radionuclides may exist in the solute phase or may be bound to soil particles and interstitial portions of the geologic matrix. Accurate tools to reliably predict the migration and transformation of these metals and radionuclides in the subsurface environment enhance the ability of environmental scientists, engineers, and decision makers to analyze their impact and to evaluate the efficacy of alternative remediation techniques prior to incurring expense in the field. A mechanistic-based numerical model could provide such a tool. This paper communicates the development and verification of a mechanistically <span class="hlt">coupled</span> fluid-flow thermal-reactive <span class="hlt">biogeochemical</span>-transport model where both fast and slow reactions occur in porous and fractured media. Theoretical bases, numerical implementations, and numerical experiments using the model are described. A definition of the rates of fast/equilibrium reactions is presented to come up with a consistent set of governing equations. Two example problems are presented. The first one is a reactive transport problem which elucidates the non-isothermal effects on heterogeneous reactions. It also demonstrates that the rates of fast/equilibrium reactions are not necessarily greater than that of slow/kinetic reactions in the context of reactive transport. The second example focuses on a complicated but realistic advective dispersive reactive transport problem. This example exemplifies the need for innovative numerical algorithms to solve problems involving stiff geochemical reactions. It also demonstrates that rates of all fast/equilibrium reactions are finite and definite. Furthermore, it is noted that a species-versus-time curve cannot be used to characterize the rate of homogeneous fast/equilibrium reaction in a reactive transport system even if one and only one such reaction is responsible for the production of this species.</p> <div class="credits"> <p class="dwt_author">Yeh, Gour-Tsyh [University of Central Florida, Orlando; Fang, Yilin [Pacific Northwest National Laboratory (PNNL); Zhang, Fan [ORNL; Sun, Jiangtao [Engineering and Applied Science, Inc., Tampa, FL; Li, Yuan [Ayres Associates, Tampa, FL; Li, Ming-Hsu [National Central University, Taiwan; Siegel, Malcolm D [Sandia National Laboratories (SNL)</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' 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class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/974948"> <span id="translatedtitle">Numerical modeling of <span class="hlt">coupled</span> fluid flow and thermal and reactive <span class="hlt">biogeochemical</span> transport in porous and fractured media</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Subsurface contamination problems of metals and radionuclides are ubiquitous. Metals and radionuclides may exist in the solute phase or may be bound to soil particles and interstitial portions of the geologic matrix. Accurate tools to reliably predict the migration and transformation of these metals and radionuclides in the subsurface environment enhance the ability of environmental scientists, engineers, and decision makers to analyze their impact and to evaluate the efficacy of alternative remediation techniques prior to incurring expense in the field. A mechanistic-based numerical model could provide such a tool. This paper communicates the development and verification of a mechanistically <span class="hlt">coupled</span> fluid-flow thermal-reactive <span class="hlt">biogeochemical</span>-transport model where both fast and slow reactions occur in porous and fractured media. Theoretical bases, numerical implementations, and numerical experiments using the model are described. A definition of the "rates" of fast/equilibrium reactions is presented to come up with a consistent set of governing equations. Two example problems are presented. The first one is a reactive transport problem which elucidates the non-isothermal effects on heterogeneous reactions. It also demonstrates that the rates of fast/equilibrium reactions are not necessarily greater than that of slow/kinetic reactions in the context of reactive transport. The second example focuses on a complicated but realistic advective-dispersive-reactive transport problem. This example exemplifies the need for innovative numerical algorithms to solve problems involving stiff geochemical reactions. It also demonstrates that rates of all fast/equilibrium reactions are finite and definite. Furthermore, it is noted that a species-versus-time curve cannot be used to characterize the rate of homogeneous fast/equilibrium reaction in a reactive transport system even if one and only one such reaction is responsible for the production of this species.</p> <div class="credits"> <p class="dwt_author">Yeh, Gour T.; Fang, Yilin; Zhang, Fan; Sun, Jiangtao; Li, Yuan; Li, Ming-Hsu; Siegel, Malcolm D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">42</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=ADA084009"> <span id="translatedtitle">Arithmetic Architecture for <span class="hlt">Surface/Subsurface</span> Bearing - Only Radar Tracking by Microcomputer.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">Passive localization and tracking techniques are of interest in a variety of microcomputer based <span class="hlt">surface/subsurface</span> radar applications. Because a significant portion of the cost of building or maintaining a warship is the electronics in its sensor and wea...</p> <div class="credits"> <p class="dwt_author">F. Erdogdu</p> <p class="dwt_publisher"></p> <p class="publishDate">1979-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">43</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://dx.doi.org/10.1007/s10533-008-9274-8"> <span id="translatedtitle">Dynamic modeling of nitrogen losses in river networks unravels the <span class="hlt">coupled</span> effects of hydrological and <span class="hlt">biogeochemical</span> processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> (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. <span class="hlt">Biogeochemical</span> 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 <span class="hlt">biogeochemical</span> factors and physical hydrological factors contribute nearly equally to seasonal and stream-size related variations in the percentage of the stream nitrate flux removed in each watershed. ?? 2008 The Author(s).</p> <div class="credits"> <p class="dwt_author">Alexander, R. B.; Bohlke, 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.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">44</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008RMRE...41..421S"> <span id="translatedtitle">Optimal Underground Extraction of Coal at Shallow Cover Beneath <span class="hlt">Surface/Subsurface</span> Objects: Indian Practices</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Considering ground instability problems of underground coal mines at shallow covers, this paper reviews and describes problems of optimal extraction of coal stuck below <span class="hlt">surface/subsurface</span> constraints at Indian coal fields. Importance of thickness and quality of inter-burden between the working horizon and <span class="hlt">surface/subsurface</span> constraints is discussed from a ground movement point of view during optimisation of coal recovery by underground mining beneath the constraints. A CIMFR, formerly CMRI idea, known as Wide Stall Method, was found suitable to overcome the limitations of non-effective-width based optimisation of recovery of coal, trapped in pillars below <span class="hlt">surface/subsurface</span> objects, at shallow cover. The involved rock mechanics concept and three successful field trials of the Wide Stall Method under three different geo-mining conditions of the country are also briefly given in this paper.</p> <div class="credits"> <p class="dwt_author">Singh, Rajendra; Mandal, P. K.; Singh, A. K.; Kumar, R.; Sinha, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">45</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/895940"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> <span class="hlt">Coupling</span> of Fe and Tc Speciation in Subsurface Sediments: Implications to Long-Term Tc Immobilization</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Jim K. Fredrickson; C. I. Steefel; R. K. Kukkadapu; S. M. Heald</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-06-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">46</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://groundwater-ecology.univ-lyon1.fr/pdf/Malardetal.pdf"> <span id="translatedtitle">A landscape perspective of <span class="hlt">surface-subsurface</span> hydrological exchanges in river corridors</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">SUMMARY 1. River corridors can be visualised as a three-dimensional mosaic of <span class="hlt">surface-subsurface</span> exchange patches over multiple spatial scales. Along major flow paths, surface water downwells into the sediment, travels for some distance beneath or along the stream, eventually mixes with ground water, and then returns to the stream. 2. Spatial variations in bed topography and sediment permeability result in</p> <div class="credits"> <p class="dwt_author">FLORIAN M ALARD; K LEMENT T OCKNER; M ARIE-JOSEDOLE-OLIVIER; J. V. W ARD</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">47</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/w22711542l055730.pdf"> <span id="translatedtitle">Simulating complex flow and transport dynamics in an integrated <span class="hlt">surface-subsurface</span> modeling framework</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A fully-integrated <span class="hlt">surface-subsurface</span> flow and transport model is applied to a 17 km2 subcatchment of the Laurel Creek Watershed within the Grand River basin in Southern Ontario, Canada. Through past and ongoing\\u000a field studies, the subcatchment is reasonably well characterized and is being monitored on an ongoing basis. In addition to\\u000a diverse land-usage and surface cover and more than 65</p> <div class="credits"> <p class="dwt_author">Edward A. Sudicky; Jon P. Jones; Young-Jin Park; Andrea E. Brookfield; Dennis Colautti</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">48</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008AGUFM.B53A0472L"> <span id="translatedtitle">French Guiana Fluidized Muds: Predominant Sulfur Transformation Pathways and Prokaryotic Players in a <span class="hlt">Coupled</span> System of Carbon-Sulfur-Metal <span class="hlt">Biogeochemical</span> Cycling.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The fluidized mud ecosystem off French Guiana coast is a unique and globally important sedimentary environment characterized by intense physical reworking and rapid turnover of major <span class="hlt">biogeochemical</span> elements. Here we assess the major pathways of carbon cycling focusing on the transformation of sulfur species and major prokaryotic participants. The depth distribution of organic carbon oxidation rates was determined for ~100 cm long cores collected off the French Guiana coast. Total organic carbon oxidation rates inferred from accumulation of inorganic carbon during a 3-6 month incubation series were elevated at the surface and decreased with depth. A similar incubation approach was applied for estimation of ferric reduction|oxidation rates. Short- chain fatty acid degradation rates and dark carbon dioxide rates were determined with 14C radiolabeled acetate and carbon dioxide, respectively, which both decreased with depth. The rates for sulfate and elemental sulfur transformation pathways were determined using 35S radiolabeled sulfur species with and without the presence of molybdate. Proposed microbially-mediated <span class="hlt">biogeochemical</span> pathways were confirmed by MPN measurements of sulfate-, sulfur- and iron-reducing heterotrophic bacteria. Autotrophic bacteria were less numerous and their numbers did not directly correlate with rates of specific <span class="hlt">biogeochemical</span> pathways. With most carbon oxidation accounted for by sulfur species - and ferric iron respiration, corresponding microbial groups may play a significant role in regulation of the net balance of organic carbon mineralization. Experimental results imply that auto- and heterotrophy likely coexist simultaneously and, thus participate in the internal carbon cycling in this environment.</p> <div class="credits"> <p class="dwt_author">Luzan, T.; Chistoserdov, A. Y.; Aller, J. Y.; Aller, R. C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">49</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/958945"> <span id="translatedtitle">Simulating temporal variations of nitrogen losses in river networks with a dynamic transport model unravels the <span class="hlt">coupled</span> effects of hydrological and <span class="hlt">biogeochemical</span> processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> (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. <span class="hlt">Biogeochemical</span> 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 <span class="hlt">biogeochemical</span> factors and physical hydrological factors contribute nearly equally to seasonal and stream-size related variations in the percentage of the stream nitrate flux removed in each watershed.</p> <div class="credits"> <p class="dwt_author">Mulholland, Patrick J [ORNL; Alexander, Richard [U.S. Geological Survey; Bohlke, John [U.S. Geological Survey; Boyer, Elizabeth [Pennsylvania State University; Harvey, Judson [U.S. Geological Survey; Seitzinger, Sybil [Rutgers University; Tobias, Craig [University of North Carolina, Wilmington; Tonitto, Christina [Cornell University; Wollheim, Wilfred [University of New Hampshire</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">50</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFM.H31D1035N"> <span id="translatedtitle">Colloid Transport and <span class="hlt">Surface-Subsurface</span> Exchange in an Acid Mine Drainage-Impacted Stream</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Colloidal particles may provide an important control on the mobility of contaminants of concern; e.g., metals introduced into a stream from an acid mine drainage. In order to examine colloidal transport and <span class="hlt">surface-subsurface</span> exchange, we injected synthesized ferrihydrite colloids along with a conservative tracer, bromide, into Lefthand Creek, a stream contaminated by acid mine drainage in northwestern Boulder County, Colorado. The ferrihydrite colloids were co-precipitated with yttrium to form yttrium-labelled colloids so that we could differentiate them from environmental colloids. Yttrium was measured in samples collected from the surface water and the hyporheic zone. The hyporheic zone samples were collected from a series of mini-piezometers embedded up to 1 m in depth and over a 61 m reach of the stream. A one-dimensional transient storage model (OTIS-P) was used to quantify parameters describing the transport of the conservative tracer and the colloids. Approximately 20% of the colloidal mass was lost over the 61 m reach. The loss of colloids is attributed to deposition in the shallow hyporheic zone. Laboratory column experiments demonstrated that the stream bed sediments effectively remove colloids from suspension at the pH, ionic strength, and dissolved organic matter concentration conditions occurring in Lefthand Creek.</p> <div class="credits"> <p class="dwt_author">Norvell, A. S.; Ryan, J. N.; Ren, J.; McKnight, D. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">51</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://serc.carleton.edu/NAGTWorkshops/hydrogeo/HSG2013/activities/71648.html"> <span id="translatedtitle">Soil <span class="hlt">Biogeochemical</span> Cycles</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">This group activity charges students with teaching their colleagues about the <span class="hlt">biogeochemical</span> cycle of one key soil element (e.g., either C, N, S, P, Ca, or Fe). Students are given a single class period to summarize their knowledge and to develop a lesson that includes (1) an organized, 5-8 minute oral presentation, (2) a graphical, conceptual model of their assigned element's soil-<span class="hlt">biogeochemical</span> cycle, and (3) a list of discussion questions with which to engage their colleagues on the other teams. A second class session is used to refine and to expand upon the submitted models as necessary.</p> <div class="credits"> <p class="dwt_author">Robins, Colin</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">52</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/21112074"> <span id="translatedtitle">Improving <span class="hlt">surface-subsurface</span> water budgeting using high resolution satellite imagery applied on a brownfield.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The estimation of <span class="hlt">surface-subsurface</span> water interactions is complex and highly variable in space and time. It is even more complex when it has to be estimated in urban areas, because of the complex patterns of the land-cover in these areas. In this research a modeling approach with integrated remote sensing analysis has been developed for estimating water fluxes in urban environments. The methodology was developed with the aim to simulate fluxes of contaminants from polluted sites. Groundwater pollution in urban environments is linked to patterns of land use and hence it is essential to characterize the land cover in a detail. An object-oriented classification approach applied on high-resolution satellite data has been adopted. To assign the image objects to one of the land-cover classes a multiple layer perceptron approach was adopted (Kappa of 0.86). Groundwater recharge has been simulated using the spatially distributed WetSpass model and the subsurface water flow using MODFLOW in order to identify and budget water fluxes. The developed methodology is applied to a brownfield case site in Vilvoorde, Brussels (Belgium). The obtained land use map has a strong impact on the groundwater recharge, resulting in a high spatial variability. Simulated groundwater fluxes from brownfield to the receiving River Zenne were independently verified by measurements and simulation of groundwater-surface water interaction based on thermal gradients in the river bed. It is concluded that in order to better quantify total fluxes of contaminants from brownfields in the groundwater, remote sensing imagery can be operationally integrated in a modeling procedure. PMID:21112074</p> <div class="credits"> <p class="dwt_author">Dujardin, J; Batelaan, O; Canters, F; Boel, S; Anibas, C; Bronders, J</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-11-26</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">53</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.cavebiogeo/"> <span id="translatedtitle">Cave Formation: <span class="hlt">Biogeochemical</span> Cycles</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">This video explores the role of <span class="hlt">biogeochemical</span> cycles in the formation of caves. It discusses a radical new theory that identifies sulfuric acid as a cave-forming agent. The video, adapted from a NOVA broadcast, identifies the source of the sulfuric acid, which, unlike carbonic acid, the typical cave-forming agent, does not readily form in nature. The segment is 5 minutes and forty seconds in length.</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">54</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009BGeo....6..739Z"> <span id="translatedtitle">Quantifying methane emissions from rice fields in the Taihu Lake region, China by <span class="hlt">coupling</span> a detailed soil database with <span class="hlt">biogeochemical</span> model</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">As China has approximately 22% of the world's rice paddies, the regional quantification of CH4 emissions from these paddies is important in determining their contribution to the global greenhouse gas effect. This paper reports the use of a <span class="hlt">biogeochemical</span> model (DeNitrification and DeComposition or DNDC) for quantifying CH4 emissions from rice fields in the Taihu Lake region of China. For this application, the DNDC model was linked to a 1:50 000 soil database derived from 1107 paddy soil profiles compiled during the Second National Soil Survey of China in the 1980s-1990s. The simulated results showed that the 2.3 Mha of paddy rice fields in the Taihu Lake region emitted the equivalent of 5.7 Tg C from 1982-2000, with the average CH4 flux ranging from 114 to 138 kg C ha-1 y-1. As for soil subgroups, the highest emission rate (660 kg C ha-1 y-1) was linked to gleyed paddy soils accounting for about 4.4% of the total area of paddy soils. The lowest emission rate (91 kg C ha-1 y-1) was associated with degleyed paddy soils accounting for about 18% of the total area of paddy soils. The most common soil in the area was hydromorphic paddy soils, which accounted for about 53% of the total area of paddy soils with a CH4 flux of 106 kg C ha-1 y-1. On a regional basis, the annual averaged CH4 flux in the Taihu Lake plain soil region and alluvial plain soil region were higher than that in the low mountainous and hilly soil region and the polder soil region. The model simulation was conducted with two databases using polygons or counties as the basic units. The county-based database contained soil information coarser than the polygon system built based on the 1:50 000 soil database. The modeled results with the two databases found similar spatial patterns of CH4 emissions in the Taihu Lake region. However, discrepancies exist between the results from the two methods. The total CH4 emissions generated from the polygon-based database is 2.6 times the minimum CH4 emissions generated from the county-based database, and is 0.98 times the maximum CH4 emissions generated from the county-based database. The average value of the relative deviation ranged from -20% to 98% for most counties, which indicates that a more precise soil database is necessary to better simulate CH4 emissions from rice fields in the Taihu Lake region using the DNDC model.</p> <div class="credits"> <p class="dwt_author">Zhang, L.; Yu, D.; Shi, X.; Weindorf, D.; Zhao, L.; Ding, W.; Wang, H.; Pan, J.; Li, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">55</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..15.9661M"> <span id="translatedtitle">Impact of resolved scales on global marine <span class="hlt">biogeochemical</span> models</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The global marine <span class="hlt">biogeochemical</span> system is an integral part of the Earth system and carbon cycle. Like many other fields, as computer power improves so also has the trend towards using higher resolution in an effort to capture a greater proportion of the real world in the models. In the framework of the EU-FP7 GreenSeas project we examine this approach by performing two simulations of the global marine <span class="hlt">biogeochemical</span> system, one at 2 degree resolution (LO-res), and the other at 1/4 degree resolution (HI-res) using the PELAGOS model, a <span class="hlt">coupling</span> between NEMO and the BFM. Both the LO-res and HI-res simulations are set up with the same initial conditions, forcing and <span class="hlt">biogeochemical</span> parameterizations, allowing us to perform a direct inter-comparison of the two, with a special focus on the Atlantic ocean. We examine how resolving more of the physical features affects the <span class="hlt">biogeochemical</span> system, in particular how differences in the resolved horizontal, vertical motions and the mixed layer depth are reflected in the plankton biomass, the nutrient availability and community structure. While the global large-scale oceanographic features (fronts, gyres, etc) are captured in both the LO-res and HI-res simulations, differences in the mesoscale flow structures, and in particular the resolved vertical physics in the HI-res simulation, drive very different behaviour in the <span class="hlt">biogeochemical</span> system. These differences in the physics drive what is a spun-up <span class="hlt">biogeochemical</span> system in the LO-res simulation into a new regime in the HI-res simulation, where overall there is greater nutrient availability and much higher total primary production. Overall this approach identify the importance of resolving the vertical dynamics in marine <span class="hlt">biogeochemical</span> models and opens up the question of the sensitivity of the parameterizations to the resolved scales. Keywords: Atlantic ocean, resolution, <span class="hlt">biogeochemical</span>, models</p> <div class="credits"> <p class="dwt_author">McKiver, William; Vichi, Marcello; Lovato, Tomas; Storto, Andrea; Masina, Simona</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">56</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013AdAtS..30..983Q"> <span id="translatedtitle">Incorporating groundwater dynamics and <span class="hlt">surface/subsurface</span> runoff mechanisms in regional climate modeling over river basins in China</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">To improve the capability of numerical modeling of climate-groundwater interactions, a groundwater component and new <span class="hlt">surface/subsurface</span> runoff schemes were incorporated into the regional climate model RegCM3, renamed RegCM3_Hydro. 20-year simulations from both models were used to investigate the effects of groundwater dynamics and <span class="hlt">surface/subsurface</span> runoff parameterizations on regional climate over seven river basins in China. A comparison of results shows that RegCM3_Hydro reduced the positive biases of annual and summer (June, July, August) precipitation over six river basins, while it slightly increased the bias over the Huaihe River Basin in eastern China. RegCM3_Hydro also reduced the cold bias of surface air temperature from RegCM3 across years, especially for the Haihe and the Huaihe river basins, with significant bias reductions of 0.80°C and 0.88°C, respectively. The spatial distribution and seasonal variations of water table depth were also well captured. With the new surface and subsurface runoff schemes, RegCM3_Hydro increased annual surface runoff by 0.11-0.62 mm d-1 over the seven basins. Though previous studies found that incorporating a groundwater component tends to increase soil moisture due to the consideration of upward groundwater recharge, our present work shows that the modified runoff schemes cause less infiltration, which outweigh the recharge from groundwater and result in drier soil, and consequently cause less latent heat and more sensible heat over most of the basins.</p> <div class="credits"> <p class="dwt_author">Qin, Peihua; Xie, Zhenghui; Yuan, Xing</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-07-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">57</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/39322052"> <span id="translatedtitle">Field Testing of an Integrated <span class="hlt">Surface\\/Subsurface</span> Modeling Technique for Planetary Exploration</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">While there has been much interest in developing ground-penetrating radar (GPR) technology for rover-based planetary exploration, relatively little work has been done on the data collection process. Starting from the manual method, we fully automate GPR data collection using only sensors typically found on a rover. Further, we produce two novel data products: (1) a three-dimensional, photorealistic surface model <span class="hlt">coupled</span></p> <div class="credits"> <p class="dwt_author">Paul Timothy Furgale; Timothy D. Barfoot; Nadeem Ghafoor; Kevin Williams; Gordon Osinski</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">58</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.gulfbase.org/project/view.php?pid=nwbdn"> <span id="translatedtitle">National Wetlands <span class="hlt">Biogeochemical</span> Database (NWBD)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">The National Wetland <span class="hlt">Biogeochemical</span> Database (NWBD) is "an effort to locate, collect and compile existing <span class="hlt">biogeochemical</span> information on wetlands of the United States including Hawaii and Alaska." Funded in part by the Environmental Protection Agency (EPA), the database will be used to develop a Nutrient Criteria Technical Guidance Manual for US Wetlands -- for use in assessing potential nutrient-related trophic state impairment and pollution problems. Presently focused on water column and soil <span class="hlt">biogeochemical</span> parameters (e.g., N, P, C, Metals, temp., DO, pH, etc.), the completed NWBD will act as a reference data set for <span class="hlt">biogeochemical</span> parameters at different regional, community, and temporal scales. Data contributors are invited to participate using NWBD's on-site contact information.</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">59</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://treesearch.fs.fed.us/pubs/39107"> <span id="translatedtitle"><span class="hlt">Coupling</span> <span class="hlt">biogeochemical</span> cycles in urban environments ...</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.treesearch.fs.fed.us/">Treesearch</a></p> <p class="result-summary">Jun 5, 2012... Publications, Recreational Activities, Research and Development ... to offset greenhouse-gas (GHG) emissions, remove air and water pollutants, ... stormwater runoff mitigation, and improvements in air quality and health.</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">60</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.treesearch.fs.fed.us/pubs/39107"> <span id="translatedtitle"><span class="hlt">Coupling</span> <span class="hlt">biogeochemical</span> cycles in urban environments ...</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.treesearch.fs.fed.us/">Treesearch</a></p> <p class="result-summary">Forest Service National Links, Forest Service Home, Employment, Fire and Aviation ... In some cases the environmental benefits of this infrastructure have been well ... stormwater runoff mitigation, and improvements in air quality and health. ... page and attach it to the printout of the article, to retain the full citation information.</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_2");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" 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showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_5");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">61</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/10117660"> <span id="translatedtitle">A hierarchical framework for <span class="hlt">coupling</span> surface fluxes to atompsheric general circulation models: The homogeneity test</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The atmosphere and the biosphere are inherently <span class="hlt">coupled</span> to one another. Atmospheric surface state variables such as temperature, winds, water vapor, precipitation, and radiation control biophysical, <span class="hlt">biogeochemical</span>, and ecological processes at the surface and subsurface. At the same time, surface fluxes of momentum, moisture, heat, and trace gases act as time-dependent boundary conditions providing feedback on atmospheric processes. To understand such phenomena, a <span class="hlt">coupled</span> set of interactive models is required. Costs are still prohibitive for computing <span class="hlt">surface/subsurface</span> fluxes directly for medium-resolution atmospheric general circulation models (AGCMs), but a technique has been developed for testing large-scale homogeneity and accessing surface parameterizations and models to reduce this computational cost and maintain accuracy. This modeling system potentially bridges the observed spatial and temporal ranges yet allows the incorporation of necessary details about individual ecological community types or biomes and simulates the net momentum, heat, moisture, and trace gas fluxes. This suite of <span class="hlt">coupled</span> models is defined here as the hierarchical systems flux scheme (HSFS).</p> <div class="credits"> <p class="dwt_author">Miller, N.L.</p> <p class="dwt_publisher"></p> <p class="publishDate">1993-12-31</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">62</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/6663622"> <span id="translatedtitle">A hierarchical framework for <span class="hlt">coupling</span> surface fluxes to atompsheric general circulation models: The homogeneity test</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The atmosphere and the biosphere are inherently <span class="hlt">coupled</span> to one another. Atmospheric surface state variables such as temperature, winds, water vapor, precipitation, and radiation control biophysical, <span class="hlt">biogeochemical</span>, and ecological processes at the surface and subsurface. At the same time, surface fluxes of momentum, moisture, heat, and trace gases act as time-dependent boundary conditions providing feedback on atmospheric processes. To understand such phenomena, a <span class="hlt">coupled</span> set of interactive models is required. Costs are still prohibitive for computing <span class="hlt">surface/subsurface</span> fluxes directly for medium-resolution atmospheric general circulation models (AGCMs), but a technique has been developed for testing large-scale homogeneity and accessing surface parameterizations and models to reduce this computational cost and maintain accuracy. This modeling system potentially bridges the observed spatial and temporal ranges yet allows the incorporation of necessary details about individual ecological community types or biomes and simulates the net momentum, heat, moisture, and trace gas fluxes. This suite of <span class="hlt">coupled</span> models is defined here as the hierarchical systems flux scheme (HSFS).</p> <div class="credits"> <p class="dwt_author">Miller, N.L.</p> <p class="dwt_publisher"></p> <p class="publishDate">1993-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">63</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008AGUFM.H33F1066S"> <span id="translatedtitle">Discharge-nitrate data clustering for characterizing <span class="hlt">surface-subsurface</span> flow interaction and calibration of a hydrologic model</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Concentration of reactive chemicals has different chemical signatures in baseflow and surface runoff. Previous studies on nitrate export from a catchment indicate that the transport processes are driven by subsurface flow. Therefore nitrate signature can be used for understanding the event and pre-event contributions to streamflow and <span class="hlt">surface-subsurface</span> flow interactions. The study uses flow and nitrate concentration time series data for understanding the relationship between these two variables. Unsupervised artificial neural network based learning method called self organizing map is used for the identification of clusters in the datasets. Based on the cluster results, five different pattern in the datasets are identified which correspond to (i) baseflow, (ii) subsurface flow increase, (iii) surface runoff increase, (iv) surface runoff recession, and (v) subsurface flow decrease regions. The cluster results in combination with a hydrologic model are used for discharge separation. For this purpose, a multi-objective optimization tool NSGA-II is used, where violation of cluster results is used as one of the objective functions. The results show that the use of cluster results as supplementary information for the calibration of a hydrologic model gives a plausible simulation of subsurface flow as well total runoff at the catchment outlet. The study is undertaken using data from the Weida catchment in the North-Eastern Germany, which is a sub-catchment of the Weisse Elster river in the Elbe river basin.</p> <div class="credits"> <p class="dwt_author">Shrestha, R. R.; Rode, M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">64</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2004EOSTr..85..469S"> <span id="translatedtitle">The Role of Coastal Zones in Global <span class="hlt">Biogeochemical</span> Cycles</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The unique and dynamic coastal ocean is a significant source and sink of a multitude of atmospheric species of importance to global <span class="hlt">biogeochemical</span> cycles and climate. The transition zone between land and ocean, including the atmosphere as a medium for the exchange of matter and energy, is characterized by a strong physical-<span class="hlt">biogeochemical</span> <span class="hlt">coupling</span>, resulting in an inherently complex system. Important <span class="hlt">biogeochemical</span> exchanges occurring in the coastal zone involve water, nutrients (e.g., nitrogen, phosphorous, iron, and silica), salts (e.g., chlorine, bromine, and iodine), carbon (e.g., dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), particulate organic carbon (POC), carbon dioxide (CO2)), reactive organic trace gases (e.g., nitrogenous, halogenated, and sulfurous hydrocarbons), and inorganic trace gases (e.g., nitrous oxide, N2O). Coastal zones are of particular importance to humans, as they are characterized by high per area productivity and are responsible for the majority of the world's fish catch. In addition, coastal ecosystems play an important role in the global carbon cycle as large fluxes of carbon and carbon-related tracers move between the land, ocean, and atmosphere in these regions. Most of the world's population lives near coastal zones, and anthropogenic changes and related climate change in these regions can pose serious consequences not only for fisheries but also for global <span class="hlt">biogeochemical</span> cycles.</p> <div class="credits"> <p class="dwt_author">Siefert, Ronald; Plattner, Gian-Kasper</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-11-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">65</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/51666968"> <span id="translatedtitle">Indian Ocean <span class="hlt">Biogeochemical</span> Processes and Ecological Variability</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> 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 <span class="hlt">Biogeochemical</span> Processes and Ecological</p> <div class="credits"> <p class="dwt_author">Leslie Ofori</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">66</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2005PrOce..65..176W"> <span id="translatedtitle">Monsoon-driven <span class="hlt">biogeochemical</span> processes in the Arabian Sea</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Although it is nominally a tropical locale, the semiannual wind reversals associated with the Monsoon system of the Arabian Sea result annually in two distinct periods of elevated biological activity. While in both cases monsoonal forcing drives surface layer nutrient enrichment that supports increased rates of primary productivity, fundamentally different entrainment mechanisms are operating in summer (Southwest) and winter (Northeast) Monsoons. Moreover, the intervening intermonsoon periods, during which the region relaxes toward oligotrophic conditions more typical of tropical environments, provide a stark contrast to the dynamic <span class="hlt">biogeochemical</span> activity of the monsoons. The resulting spatial and temporal variability is great and provides a significant challenge for ship-based surveys attempting to characterize the physical and <span class="hlt">biogeochemical</span> environments of the region. This was especially true for expeditions in the pre-satellite era. Here, we present an overview of the dynamical response to seasonal monsoonal forcing and the characteristics of the physical environment that fundamentally drive regional <span class="hlt">biogeochemical</span> variability. We then review past observations of the biological distributions that provided our initial insights into the pelagic system of the Arabian Sea. These evolved through the 1980s as additional methodologies, in particular the first synoptic ocean color distributions gathered by the Coastal Zone Color Scanner, became available. Through analyses of these observations and the first large-scale physical <span class="hlt">biogeochemical</span> modeling attempts, a pre-JGOFS understanding of the Arabian Sea emerged. During the 1990s, the in situ and remotely sensed observational databases were significantly extended by regional JGOFS activities and the onset of Sea-viewing Wide Field-of-View Sensor ocean color measurements. Analyses of these new data and <span class="hlt">coupled</span> physical <span class="hlt">biogeochemical</span> models have already advanced our understanding and have led to either an amplification or revision of the pre-JGOFS paradigms. Our understanding of this complex and variable ocean region is still evolving. Nonetheless, we have a much better understanding of time space variability of <span class="hlt">biogeochemical</span> properties in the Arabian Sea and much deeper insights about the physical and biological factors that drive them, as well as a number of challenging new directions to pursue.</p> <div class="credits"> <p class="dwt_author">Wiggert, J. D.; Hood, R. R.; Banse, K.; Kindle, J. C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">67</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2002GBioC..16.1072P"> <span id="translatedtitle">Global <span class="hlt">biogeochemical</span> cycle of boron</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The global Boron (B) cycle is primarily driven by a large flux (1.44 Tg B/yr) through the atmosphere derived from seasalt aerosols. Other significant sources of atmospheric boron include emissions during the combustion of biomass (0.26-0.43 Tg B/yr) and coal, which adds 0.20 Tg B/yr as an anthropogenic contribution. These known inputs to the atmosphere cannot account for the boron removed from the atmosphere during rainfall (3.0 Tg B/yr) and estimated dry deposition (1.3-2.7 Tg B/yr). In addition to atmospheric deposition, rock weathering is a source of boron (0.19 Tg B/yr) for terrestrial ecosystems, and humans mine about 0.31 Tg B/yr from the Earth's crust. More than 4.8 Tg B/yr circulates in the <span class="hlt">biogeochemical</span> cycle of land plants, and about 0.53-0.63 Tg B/yr is carried from land to sea by rivers. The <span class="hlt">biogeochemical</span> cycle of boron in the sea includes 4.4 Tg B/yr circulating in the marine biosphere, and an annual loss of 0.47 Tg B/yr to the oceanic crust via a variety of sedimentary processes that collectively remove only a small fraction of the total annual inputs to the oceans. Thus with our current understanding of the global biogeochemistry of B, the atmospheric budget shows outputs > inputs, while the marine compartments show inputs > outputs. Despite these uncertainties, it is clear that the human perturbation of the global B cycle has more than doubled the mobilization of B from the crust and contributes significantly to the B transport in rivers.</p> <div class="credits"> <p class="dwt_author">Park, Haewon; Schlesinger, William H.</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">68</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1991TellA..43..188S"> <span id="translatedtitle">Terrestrial <span class="hlt">biogeochemical</span> cycles: global interactions with the atmosphere and hydrology</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Ecosystem scientists have developed a body of theory to predict the behaviour of <span class="hlt">biogeochemical</span> cycles when exchanges with other ecosystems are small or prescribed. Recent environmental changes make it clear that linkages between ecosystems via atmospheric and hydrological transport have large effects on ecosystem dynamics when considered over time periods of a decade to a century, time scales relevant to contemporary humankind. Our ability to predict behaviour of ecosystems <span class="hlt">coupled</span> by transport is limited by our ability (1) to extrapolate biotic function to large spatial scales and (2) to measure and model transport. We review developments in ecosystem theory, remote sensing, and geographical information systems (GIS) that support new efforts in spatial modeling. A paradigm has emerged to predict behaviour of ecosystems based on understanding responses to multiple resources (e.g., water, nutrients, light). Several ecosystem models <span class="hlt">couple</span> primary production to decomposition and nutrient availability using the above paradigm. These models require a fairly small set of environmental variables to simulate spatial and temporal variation in rates of <span class="hlt">biogeochemical</span> cycling. Simultaneously, techniques for inferring ecosystem behaviour from remotely measured canopy light interception are improving our ability to infer plant activity from satellite observations. Efforts have begun to <span class="hlt">couple</span> models of transport in air and water to models of ecosystem function. Preliminary work indicates that <span class="hlt">coupling</span> of transport and ecosystem processes alters the behaviour of earth system components (hydrology, terrestrial ecosystems, and the atmosphere) from that of an uncoupled mode.</p> <div class="credits"> <p class="dwt_author">Schimel, David S.; Kittel, Timothy G. F.; Parton, William J.</p> <p class="dwt_publisher"></p> <p class="publishDate">1991-08-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">69</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3619314"> <span id="translatedtitle">Proterozoic ocean redox and <span class="hlt">biogeochemical</span> stasis</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">The partial pressure of oxygen in Earth’s atmosphere has increased dramatically through time, and this increase is thought to have occurred in two rapid steps at both ends of the Proterozoic Eon (?2.5–0.543 Ga). However, the trajectory and mechanisms of Earth’s oxygenation are still poorly constrained, and little is known regarding attendant changes in ocean ventilation and seafloor redox. We have a particularly poor understanding of ocean chemistry during the mid-Proterozoic (?1.8–0.8 Ga). Given the <span class="hlt">coupling</span> between redox-sensitive trace element cycles and planktonic productivity, various models for mid-Proterozoic ocean chemistry imply different effects on the <span class="hlt">biogeochemical</span> cycling of major and trace nutrients, with potential ecological constraints on emerging eukaryotic life. Here, we exploit the differing redox behavior of molybdenum and chromium to provide constraints on seafloor redox evolution by <span class="hlt">coupling</span> a large database of sedimentary metal enrichments to a mass balance model that includes spatially variant metal burial rates. We find that the metal enrichment record implies a Proterozoic deep ocean characterized by pervasive anoxia relative to the Phanerozoic (at least ?30–40% of modern seafloor area) but a relatively small extent of euxinic (anoxic and sulfidic) seafloor (less than ?1–10% of modern seafloor area). Our model suggests that the oceanic Mo reservoir is extremely sensitive to perturbations in the extent of sulfidic seafloor and that the record of Mo and chromium enrichments through time is consistent with the possibility of a Mo–N colimited marine biosphere during many periods of Earth’s history.</p> <div class="credits"> <p class="dwt_author">Reinhard, Christopher T.; Planavsky, Noah J.; Robbins, Leslie J.; Partin, Camille A.; Gill, Benjamin C.; Lalonde, Stefan V.; Bekker, Andrey; Konhauser, Kurt O.; Lyons, Timothy W.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">70</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/15016262"> <span id="translatedtitle">A generic reaction-based <span class="hlt">biogeochemical</span> simulator</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">This paper presents a generic <span class="hlt">biogeochemical</span> simulator, <span class="hlt">BIOGEOCHEM</span>. 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. <span class="hlt">BIOGEOCHEM</span> 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 <span class="hlt">BIOGEOCHEM</span> 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.</p> <div class="credits"> <p class="dwt_author">Fang, Yilin; Yabusaki, Steven B.; Yeh, Gour T.; C.T. Miller, M.W. Farthing, W.G. Gray, and G.F. Pinder</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-06-17</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">71</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008cosp...37..379B"> <span id="translatedtitle">Development of assimilative <span class="hlt">biogeochemical</span> ocean models for operational and research applications</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Green-Mercator project (2007-2009, http://mercator-vert.ipsl.jussieu.fr/) aims at implementing the marine <span class="hlt">biogeochemical</span> model PISCES at global scale into the MERCATOR operational monitoring and forecasting system. Besides the development of the model system itself, this project relies on two major research activities to improve <span class="hlt">biogeochemical</span> simulations: (1) the refinement of process resolution to investigate the impact of the transition between eddy permitting to eddy resolving on <span class="hlt">biogeochemical</span> simulations at global scale, and (2) the assimilation of physical and <span class="hlt">biogeochemical</span> data (such as ocean color) into the model. The project also includes research activities to demonstrate the potential of an operational <span class="hlt">biogeochemical</span> model for regional downscaling and extension towards marine resources. In this talk, we will focus on developments achieved in the framework of the E.U. MERSEA project (2004-2008) to assimilate satellite and in situ data into <span class="hlt">coupled</span> models. Experiments using the SEEK filter in a North Atlantic prototype at 1/4° resolution illustrate the feasability of the approach. The results show that traditional methods such as the Kalman filter may lead to physical inconsistencies originating from the gaussian nature of the KF analysis scheme. A new scheme based on truncated gaussian pdfs is therefore developed (TGF) to integrate inequality constraints during the assimilation process. This new scheme represents a major step toward the assimilation of a variety of satellite data, such as sea-ice thickness and ocean colour data, into <span class="hlt">coupled</span> models.</p> <div class="credits"> <p class="dwt_author">Brasseur, Pierre</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">72</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://earth.geology.yale.edu/~ajs/1999/07-09.1999.11Ver.pdf"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> responses of the carbon cycle to natural and human perturbations: Past, present, and future</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">In the past three centuries, human perturbations of the environment have affected the <span class="hlt">biogeochemical</span> behavior of the global carbon cycle and that of the other three nutrient elements closely <span class="hlt">coupled</span> to carbon: nitrogen, phosphorus, and sulfur. The partitioning of anthropogenic COâ among its various sinks in the past, for the present, and for projections into the near future is controlled</p> <div class="credits"> <p class="dwt_author">LEAH MAY B. VER; FRED T. MACKENZIE; ABRAHAM LERMAN</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">73</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/42062512"> <span id="translatedtitle">A GEOCLIM simulation of climatic and <span class="hlt">biogeochemical</span> consequences of Pangea breakup</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Large fluctuations in continental configuration occur throughout the Mesozoic. While it has long been recognized that paleogeography may potentially influence atmospheric CO2 via the continental silicate weathering feedback, no numerical simulations have been done, because of the lack of a spatially resolved climate-carbon model. GEOCLIM, a <span class="hlt">coupled</span> numerical model of the climate and global <span class="hlt">biogeochemical</span> cycles, is used to investigate</p> <div class="credits"> <p class="dwt_author">Y. Donnadieu; Y. Goddéris; R. Pierrehumbert; G. Dromart; F. Fluteau; R. Jacob</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">74</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/54665952"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Process Comparison of the Five USGS Water, Energy, and <span class="hlt">Biogeochemical</span> Budget (WEBB) Sites</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Input - output budgets (in wet deposition and streamwater) have been constructed for water and major solutes at the five USGS Water, Energy, and <span class="hlt">Biogeochemical</span> 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 <span class="hlt">biogeochemical</span> processes, as influenced by the strong physical and biological contrasts</p> <div class="credits"> <p class="dwt_author">J. B. Shanley; N. E. Peters; B. T. Aulenbach; A. E. Blum; D. H. Campbell; D. W. Clow; M. C. Larsen; M. A. Mast; R. F. Stallard; J. W. Troester; J. F. Walker; R. M. Webb; A. F. White</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">75</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2006Natur.441..964M"> <span id="translatedtitle">The Southern Ocean <span class="hlt">biogeochemical</span> divide</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Marinov, I.; Gnanadesikan, A.; Toggweiler, J. R.; Sarmiento, J. L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-06-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">76</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=ADA465321"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Consequences of Infaunal Activities.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">Activities of sedimentary infauna have significant consequences on overall sedimentary diagenesis. Infauna directly participate in sedimentary processes by organic matter metabolization <span class="hlt">coupled</span> to aerobic respiration and metabolite excretion. In addition,...</p> <div class="credits"> <p class="dwt_author">Y. Furukawa</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">77</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012EOSTr..93..476W"> <span id="translatedtitle">Reconstructing the <span class="hlt">biogeochemical</span> consequences of disturbances</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Paleo Reconstructions of <span class="hlt">Biogeochemical</span> Environments (PROBE) Workshop;Manhattan, Kansas; 19-21 April 2012 Disturbances—discrete events that reduce plant biomass—commonly regulate material and energy flow in terrestrial ecosystems. Recent studies document an increase in the size and/or severity of disturbances such as native bark beetle outbreaks and large fires compared to the recent past. However, scientists cannot evaluate the potential consequences of these events for ecosystem dynamics without decadal to multimillennial records of disturbances and ecosystem response. The Paleo Reconstructions of <span class="hlt">Biogeochemical</span> Environments (PROBE) workshop brought together ecosystem ecologists and paleoecologists for a 3-day workshop at the Konza Prairie Biological Station in Manhattan, Kansas. The focus of the meeting was the reconstruction of the <span class="hlt">biogeochemical</span> consequences of disturbances (e.g., beetle outbreaks, wildfires, windstorms, and droughts) on different timescales, the assessment of the state of current knowledge, and identification of challenges and opportunities for future research.</p> <div class="credits"> <p class="dwt_author">Williams, Joseph; Morris, Jesse; Perakis, Steven</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">78</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010EOSTr..91..409O"> <span id="translatedtitle">Indian Ocean <span class="hlt">Biogeochemical</span> Processes and Ecological Variability</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> 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 <span class="hlt">Biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Ofori, Leslie</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-11-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">79</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/1096278"> <span id="translatedtitle">Managing <span class="hlt">biogeochemical</span> cycles to reduce greenhouse gases</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">This special issue focuses on terrestrial <span class="hlt">biogeochemical</span> 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) <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Post, Wilfred M [ORNL; Venterea, Rodney [United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Soil and Water</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">80</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/20000681"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> redox processes and their impact on contaminant dynamics.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Life and element cycling on Earth is directly related to electron transfer (or redox) reactions. An understanding of <span class="hlt">biogeochemical</span> redox processes is crucial for predicting and protecting environmental health and can provide new opportunities for engineered remediation strategies. Energy can be released and stored by means of redox reactions via the oxidation of labile organic carbon or inorganic compounds (electron donors) by microorganisms <span class="hlt">coupled</span> to the reduction of electron acceptors including humic substances, iron-bearing minerals, transition metals, metalloids, and actinides. Environmental redox processes play key roles in the formation and dissolution of mineral phases. Redox cycling of naturally occurring trace elements and their host minerals often controls the release or sequestration of inorganic contaminants. Redox processes control the chemical speciation, bioavailability, toxicity, and mobility of many major and trace elements including Fe, Mn, C, P, N, S, Cr, Cu, Co, As, Sb, Se, Hg, Tc, and U. Redox-active humic substances and mineral surfaces can catalyze the redox transformation and degradation of organic contaminants. In this review article, we highlight recent advances in our understanding of <span class="hlt">biogeochemical</span> redox processes and their impact on contaminant fate and transport, including future research needs. PMID:20000681</p> <div class="credits"> <p class="dwt_author">Borch, Thomas; Kretzschmar, Ruben; Kappler, Andreas; Cappellen, Philippe Van; Ginder-Vogel, Matthew; Voegelin, Andreas; Campbell, Kate</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_3");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return 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id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_4");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' href="#">4</a> <a style="font-weight: bold;">5</a> <a onClick='return showDiv("page_6");' href="#">6</a> <a onClick='return showDiv("page_7");' href="#">7</a> <a onClick='return showDiv("page_8");' href="#">8</a> <a onClick='return 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showDiv("page_6");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">81</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/22370419"> <span id="translatedtitle">Soil property control of <span class="hlt">biogeochemical</span> processes beneath two subtropical stormwater infiltration basins.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Substantially different <span class="hlt">biogeochemical</span> 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 ?N and ?O 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 <span class="hlt">surface/subsurface</span> 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. PMID:22370419</p> <div class="credits"> <p class="dwt_author">O'Reilly, Andrew M; Wanielista, Martin P; Chang, Ni-Bin; Harris, Willie G; Xuan, Zhemin</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">82</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/22742948"> <span id="translatedtitle">Nutrient removal using biosorption activated media: preliminary <span class="hlt">biogeochemical</span> assessment of an innovative stormwater infiltration basin.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">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. <span class="hlt">Biogeochemical</span> 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 <span class="hlt">surface/subsurface</span> 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 groundwater indicate predominantly minor increases and decreases in PO(4)(3-) with the exception of one summer sample that indicated a 50% loss. Differences in nutrient variations between the unsaturated zone and shallow groundwater may be the result of the intensity and duration of nutrient removal processes and mixing ratios with water that had undergone little <span class="hlt">biogeochemical</span> transformation. Observed nitrogen and phosphorus losses demonstrate the potential, as well as the future research needs to improve performance, of the innovative stormwater infiltration basin using BAM for providing passive, economical, stormwater nutrient-treatment technology to support green infrastructure. PMID:22742948</p> <div class="credits"> <p class="dwt_author">O'Reilly, Andrew M; Wanielista, Martin P; Chang, Ni-Bin; Xuan, Zhemin; Harris, Willie G</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-06-26</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">83</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/g016272v52324552.pdf"> <span id="translatedtitle">Seasonality of Hydrological and <span class="hlt">Biogeochemical</span> Fluxes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">\\u000a This chapter summarizes current knowledge on the seasonality of forest hydrological and <span class="hlt">biogeochemical</span> fluxes and suggests\\u000a future research directions within this field. Seasonal changes in water availability strongly influence forest growth and\\u000a phenology. Inversely, temporal patterns in canopy structure, meteorological conditions and atmospheric air concentrations\\u000a influence the interaction between soil, vegetation and atmosphere. Environmental factors such as precipitation, radiation\\u000a and</p> <div class="credits"> <p class="dwt_author">Jeroen Staelens; Mathias Herbst; Dirk Hölscher; An De Schrijver</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">84</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012EGUGA..1413738R"> <span id="translatedtitle">Solving the equation for the Iberian upwelling <span class="hlt">biogeochemical</span> dynamics: an optimization experience</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Trying to find a set of parameters to properly reproduce the <span class="hlt">biogeochemical</span> dynamics of the region of study is a major concern in <span class="hlt">biogeochemical</span> ocean modelling. Model parameters are constant values introduced in the equations that calculate the time and space evolution of the state variables of the <span class="hlt">biogeochemical</span> model. A good set of parameters allows for a better representation of the biological and chemical processes in the system, and thus to model results more approximated to reality. However, it is not a straightforward task, because many parameters are not well constrained in the literature, or they may be unknown or vary considerably between different regions. Usually, the approach to find the appropriate values is running several simulations, after some sensitivity test to individual parameters, until a satisfactory result is obtained. This may be very time consuming and quite subjective. A more systematic way to find this set of parameters has arisen over the last years by using mathematical optimization techniques. The basic principle under optimization is to minimize the difference between an observed and a simulated data series by using a cost function. We have applied an optimization technique to find an appropriate set of parameters for modelling the <span class="hlt">biogeochemical</span> dynamics of the western Iberian shelf, off the Atlantic coast of Portugal and Galicia (NW Spain), which is characterized by a conspicuous seasonal upwelling. The ocean model is a high resolution 3D regional configuration of ROMS <span class="hlt">coupled</span> to a N2PZD2 <span class="hlt">biogeochemical</span> model. Results using the a priori parameters and the optimized parameters are compared and discussed. The study is the result of a multidisciplinary collaborative effort between the University of Aveiro ocean modelling group (Portugal), the ETHZ (Switzerland) and the IIM-CSIC Vigo oceanography group (Spain).</p> <div class="credits"> <p class="dwt_author">Reboreda, R.; Santaren, D.; Castro, C. G.; Alvarez-Salgado, X. A.; Nolasco, R.; Queiroga, H.; Dubert, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">85</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/46773728"> <span id="translatedtitle">A continuous\\/discontinuous Galerkin framework for modeling <span class="hlt">coupled</span> subsurface and surface water flow</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We consider conjunctive <span class="hlt">surface-subsurface</span> flow modeling, where surface water flow is described by the shallow water equations\\u000a and ground water flow by Richards’ equation for the vadose zone. <span class="hlt">Coupling</span> between the models is based on the continuity of\\u000a flux and water pressure. Numerical approximation of the <span class="hlt">coupled</span> model using the framework of discontinuous Galerkin (DG) methods\\u000a is formulated. In the</p> <div class="credits"> <p class="dwt_author">Clint Dawson</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">86</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/895388"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Controls on Technetium Mobility in <span class="hlt">Biogeochemical</span> Controls on Technetium Mobility in FRC Sediments</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Technetium-99 is a priority pollutant at numerous DOE sites, due to its long half-life (2.1 x 10{sup 5} years), high mobility as Tc(VII) in oxic waters, and bioavailability as a sulfate analog. {sup 99}Tc is far less mobile under anaerobic conditions, forming insoluble Tc(IV) precipitates. As anaerobic microorganisms can reduce soluble Tc(VII) to insoluble Tc(IV), microbial metabolism may have the potential to treat sediments and waters contaminated with Tc. Baseline studies of fundamental mechanisms of Tc(VII) bioreduction and precipitation (reviewed by Lloyd et al, 2002) have generally used pure cultures of metal-reducing bacteria, in order to develop conceptual models for the <span class="hlt">biogeochemical</span> cycling of Tc. There is, however, comparatively little known about interactions of metal-reducing bacteria with environmentally relevant trace concentrations of Tc, against a more complex <span class="hlt">biogeochemical</span> background provided by mixed microbial communities in the subsurface. The objective of this new NABIR project is to probe the site specific <span class="hlt">biogeochemical</span> conditions that control the mobility of Tc at the FRC (Oak Ridge, TN). This information is required for the rational design of in situ bioremediation strategies for technetium-contaminated subsurface environments. We will use a combination of geochemical, mineralogical, microbiological and spectroscopic techniques to determine the solubility and phase associations of Tc in FRC sediments, and characterize the underpinning <span class="hlt">biogeochemical</span> controls. A key strength of this project is that many of the techniques we are using have already been optimized by our research team, who are also studying the <span class="hlt">biogeochemical</span> controls on Tc mobility in marine and freshwater sediments in the UK in a NERC funded companion study.</p> <div class="credits"> <p class="dwt_author">Lloyd, J.R.; McBeth, J.M.; Livens, F.R.; Bryan, N.D.; Ellis, B.; Sharma, H.; Burke, I.T.; Morris, K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-03-17</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">87</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/42053017"> <span id="translatedtitle">Terrestrial ecosystems and the global <span class="hlt">biogeochemical</span> silica cycle</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> cycle. The global <span class="hlt">biogeochemical</span> 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</p> <div class="credits"> <p class="dwt_author">Daniel J. Conley</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">88</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2007AGUFM.B51B0364A"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Reactions Under Simulated Europa Ocean Conditions</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Galileo data have demonstrated the probable presence of a liquid water ocean on Europa, and existence of salts and carbon dioxide in the satellite's surface ice (e.g., Carr et al., 1998; McCord et al., 1999, Pappalardo et al., 1999; Kivelson et al., 2000). Subsequently, the discovery of chemical signatures of extinct or extant life in Europa's ocean and on its surface became a distinct possibility. Moreover, understanding of Europa's potential habitability is now one of the major goals of the Europa Orbiter Flagship mission. It is likely, that in the early stages of Europa's ocean formation, moderately alkaline oceanic sulfate-carbonate species and a magnetite-silicate mantel could have participated in low-temperature <span class="hlt">biogeochemical</span> sulfur, iron and carbon cycles facilitated by primitive organisms (Zolotov and Shock, 2004). If periodic supplies of fresh rock and sulfate-carbonate ions are available in Europa's ocean, then an exciting prospect exists that life may be present in Europa's ocean today. In our laboratory, we began the study of the plausible <span class="hlt">biogeochemical</span> reactions under conditions appropriate to Europa's ocean using barophilic psychrophilic organisms that thrive under anaerobic conditions. In the near absence of abiotic synthetic pathways due to low Europa's temperatures, the biotic synthesis may present a viable opportunity for the formation of the organic and inorganic compounds under these extreme conditions. This work is independent of assumptions regarding hydrothermal vents at Europa's ocean floor or surface-derived oxidant sources. For our studies, we have fabricated a high-pressure (5,000 psi) reaction vessel that simulates aqueous conditions on Europa. We were also successful at reviving barophilic psychrophilic strains of Shewanella bacterium, which serve as test organisms in this investigation. Currently, facultative barophilic psychrophilic stains of Shewanella are grown in the presence of ferric food source; the strains exhibiting iron reduction capability will be later selected and used to facilitate <span class="hlt">biogeochemical</span> reduction of iron under simulated temperature and pressure of Europa's ocean. The results of this work will enable us to ascertain whether Europa's cold, high-pressure ocean is capable of supporting life. In addition, the data from this study will help in generating a list of organic and inorganic target molecules for future remote sensing and in situ exploration missions.</p> <div class="credits"> <p class="dwt_author">Amashukeli, X.; Connon, S. A.; Gleeson, D. F.; Kowalczyk, R. S.; Pappalardo, R. T.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">89</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2001AGUFM.B52A..02S"> <span id="translatedtitle">Synthesizing the Global <span class="hlt">Biogeochemical</span> Cycle of Boron</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">To understand human impacts on earth system function, we must develop internally consistent models for the <span class="hlt">biogeochemical</span> cycle of major elements. We will show approaches to this challenge using, as an example, our recent attempt to synthesize the global boron cycle, using the few data currently available. The global B cycle is primarily driven by a large flux (1.38 TgB/yr) through the atmosphere derived from seasalt aerosols. Other significant sources of atmospheric boron include emissions during the combustion of biomass (0.26-0.43 TgB/yr) and coal, which adds 0.19 TgB/yr as an anthropogenic contribution. These known inputs to the atmosphere cannot account for the boron removed from the atmosphere in rainfall (3.8 TgB/yr), estimated dry deposition (0.8 to 2.2 TgB/yr) and the gaseous absorption of B by the oceans (1.2 TgB/yr). In addition to atmospheric deposition, rock weathering is a source of boron (0.19 TgB/yr) for terrestrial ecosystems, and humans mine about 0.31 TgB/yr from the Earth's crust. More than 4.8 TgB/yr circulates in the <span class="hlt">biogeochemical</span> cycle of land plants, and about 0.51 to 0.61 TgB/yr is carried from land to sea by rivers. The <span class="hlt">biogeochemical</span> cycle of boron in the sea includes 4.4 TgB/yr circulating in the marine biosphere, and an annual loss of 0.47 TgB/yr to the oceanic crust via a variety of sedimentary processes that collectively remove only a small fraction of the total annual inputs to the oceans. Thus, with our current understanding of the global biogeochemistry of B, the atmospheric budget shows outputs>inputs, while the marine compartments show inputs>outputs. Despite these uncertainties, it is clear that the human perturbation of the global B cycle has more than doubled the mobilization of B from the crust and contributes significantly to the B transport in rivers.</p> <div class="credits"> <p class="dwt_author">Schlesinger, W. H.; Park, H.</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">90</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUFM.H13D1000Z"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Filtering of Solute Signals Explored as a Function of Transport and Reaction Time Scales</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Catchment <span class="hlt">biogeochemical</span> responses are the result of superposition of diverse dynamic components, which can be related to climate forcing, water flow, and <span class="hlt">biogeochemical</span> reactions. The interactions among these components are highly non-linear and contribute to the generation of emergent patterns at multiple spatial and temporal scales. The aim of this work is to explore the following <span class="hlt">biogeochemical</span> signatures arising from such interactions: (1) the relationship between contaminant loads (L) and discharge (Q) at the annual timescale, leading to an apparent chemostatic relationship (i.e., linear L-Q plots) for different contaminants and at different spatial scales; (2) spatial patterns in the slope and the scatter of the L-Q relationships; and (3) correlation between the intra-annual flow duration curves (FDC) and the load duration curves (LDC). Exploring this relationship necessitates the use of a parsimonious model, with few spatially uniform time constants, that can generate synthetic time series of load and flow at the outlet of river basins. The Mass Response Functions (MRF) approach (Rinaldo et al., 2006), lends itself suitable for the purpose since it relies on the assumption that the evolution of solute concentration in the water pulses depends only on the residence time, and not on its trajectory - thus space is replaced by time. The model simulates the episodic delivery of water and contaminant pulses from the hillslopes to the stream network in response to temporally random but spatially uniform effective rainfall patterns. The domain is described by an immobile source zone in which first order <span class="hlt">biogeochemical</span> reactions (degradation rate constant ke) alter the solute mass, while multiple mobile rainfall pulses exchange mass with the source zone following linear kinetics (mass transfer rate constant ?). The <span class="hlt">biogeochemical</span> module of MRF, that was originally written to simulate non-reactive tracer and nitrate transport, was modified to include the more complex biogeochemistry of pesticides. We calibrated and validated the model against nitrate and atrazine data collected in the Little Vermillion River basin (~400 km2; Illinois, IN). Comparison with data showed an excellent agreement of the model outputs with the observed hydrographs and chemographs. The model was then used to explore the effect of time constants on <span class="hlt">biogeochemical</span> signatures. Four time constants were used to characterize the <span class="hlt">coupling</span> of hydrologic and <span class="hlt">biogeochemical</span> processes considered in the model: 1) mean rainfall frequency; 2) mean residence time; 3) mass-transfer rate constant; 4) degradation rate constant. The effect of the four temporal constants on the hillslope <span class="hlt">biogeochemical</span> response was explored through a sesnsitivity analyses. We hypothesize that a single dimensionless number, a combination of all four temporal constants, could explain the observed patterns. Because this dimensionless number embeds all of the relevant time scales, relative significance of the hydrologic and <span class="hlt">biogeochemical</span> processes can be examined.</p> <div class="credits"> <p class="dwt_author">Zanardo, S.; Basu, N. B.; Rao, P. C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">91</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/21141668"> <span id="translatedtitle">Oceanographic and <span class="hlt">biogeochemical</span> insights from diatom genomes.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> 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. PMID:21141668</p> <div class="credits"> <p class="dwt_author">Bowler, Chris; Vardi, Assaf; Allen, Andrew E</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">92</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/19022498"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> cycling in the Strait of Georgia.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The papers in this special issue present the results of a five-year project to study sedimentary <span class="hlt">biogeochemical</span> 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</p> <div class="credits"> <p class="dwt_author">Johannessen, S C; Macdonald, R W; Burd, B; van Roodselaar, A</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-10-11</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">93</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010ARMS....2..333B"> <span id="translatedtitle">Oceanographic and <span class="hlt">Biogeochemical</span> Insights from Diatom Genomes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Bowler, Chris; Vardi, Assaf; Allen, Andrew E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">94</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012Ocgy...52..335L"> <span id="translatedtitle">Carbohydrates as indicators of <span class="hlt">biogeochemical</span> processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">A method is presented to study the carbohydrate composition of marine objects involved into sedimento- and diagenesis (plankton, particulate matter, benthos, and bottom sediments). The analysis of the carbohydrates is based upon the consecutive separation of their fractions with different solvents (water, alkali, and acid). The ratio of the carbohydrate fractions allows one to evaluate the lability of the carbohydrate complex. It is also usable as an indicator of the <span class="hlt">biogeochemical</span> processes in the ocean, as well of the genesis and the degree of conversion of organic matter in the bottom sediments and nodules. The similarity in the monosaccharide composition is shown for dissolved organic matter and aqueous and alkaline fractions of seston and particulate matter.</p> <div class="credits"> <p class="dwt_author">Lazareva, E. V.; Romankevich, E. A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">95</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://dx.doi.org/10.1016/j.apgeochem.2007.06.003"> <span id="translatedtitle">Centimeter-scale characterization of <span class="hlt">biogeochemical</span> gradients at a wetland-aquifer interface using capillary electrophoresis</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">Steep <span class="hlt">biogeochemical</span> gradients were measured at mixing interfaces in a wetland-aquifer system impacted by landfill leachate in Norman, Oklahoma. The system lies within a reworked alluvial plain and is characterized by layered low hydraulic conductivity wetland sediments interbedded with sandy aquifer material. Using cm-scale passive diffusion samplers, "peepers", water samples were collected in a depth profile to span interfaces between surface water and a sequence of deeper sedimentary layers. Geochemical indicators including electron acceptors, low-molecular-weight organic acids, base cations, and NH4+ were analyzed by capillary electrophoresis (CE) and field techniques to maximize the small sample volumes available from the centimeter-scale peepers. Steep concentration gradients of <span class="hlt">biogeochemical</span> indicators were observed at various interfaces including those created at sedimentary boundaries and boundaries created by heterogeneities in organic C and available electron acceptors. At the sediment-water interface, chemical profiles with depth suggest that SO42 - and Fe reduction dominate driven by inputs of organic C from the wetland and availability of electron acceptors. Deeper in the sediments (not associated with a lithologic boundary), a steep gradient of organic acids (acetate maximum 8.8 mM) and NH4+ (maximum 36 mM) is observed due to a localized source of organic matter <span class="hlt">coupled</span> with the lack of electron acceptor inputs. These findings highlight the importance of quantifying the redox reactions occurring in small interface zones and assessing their role on <span class="hlt">biogeochemical</span> cycling at the system scale. ?? 2007 Elsevier Ltd. All rights reserved.</p> <div class="credits"> <p class="dwt_author">Baez-Cazull, S.; McGuire, J. T.; Cozzarelli, I. M.; Raymond, A.; Welsh, L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">96</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011WRR....47.0J15B"> <span id="translatedtitle">Hydrologic and <span class="hlt">biogeochemical</span> functioning of intensively managed catchments: A synthesis of top-down analyses</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">This paper synthesizes a 3-year collaborative effort to characterize the <span class="hlt">biogeochemical</span> and hydrological features of intensively managed agricultural catchments by combining data analysis, modeling, and preliminary hypothesis testing. The specific focus was on the Midwestern region of the United States. The results suggest that: (1) water management, specifically the homogenization of evapotranspiration losses driven by mono-cultural vegetation cover, and the homogenization of runoff generation driven by artificial drainage, has created engineered, predictable hydrologic systems; (2) nutrient and pesticide management, specifically their regular applications have created two kinds of <span class="hlt">biogeochemical</span> export regimes: chemostatic (low variability in concentration as exhibited by nitrate) and episodic (high variability in concentration as exhibited by pesticides); (3) <span class="hlt">coupled</span> mass-balance models for water and solutes reproduce these two regimes as a function of chemical rate constants. Phosphorus transport regimes were found to be episodic at smaller spatial scales, but chemostatic at larger scales. Chemostatic response dominates in transport-limited catchments that have internal sources of the solute to buffer the periodicity in episodic inputs, while episodic response dominates in source-limited catchments. The shift from episodic nitrate export in pristine catchments to chemostatic regimes in managed watersheds was attributed to legacy stores of nitrogen (built from continued fertilizer applications) that buffer interannual variations in <span class="hlt">biogeochemical</span> processing. Fast degradation kinetics of pesticides prevents the build-up of legacy sources, and leads to episodic export. Analytical expressions were derived for the probability density functions of solute delivery ratio as a function of the stochastics of rainfall-runoff events and <span class="hlt">biogeochemical</span> controls.</p> <div class="credits"> <p class="dwt_author">Basu, Nandita B.; Thompson, Sally E.; Rao, P. Suresh C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-10-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">97</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFM.H52B..07A"> <span id="translatedtitle">Hydrological Perturbations Drive <span class="hlt">Biogeochemical</span> Processes in Experimental Soil Columns from the Norman Landfill Site</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Fate and transport of contaminants in saturated and unsaturated zones is governed by <span class="hlt">biogeochemical</span> processes that are complex and non-linearly <span class="hlt">coupled</span> 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 <span class="hlt">biogeochemical</span> processes, and ii) characterize the effect of hydrologic perturbations on <span class="hlt">coupled</span> 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 <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> activity due to increased transport timescale as a result of reduced hydraulic conductivity of loam and clay in these columns. Although the <span class="hlt">coupled</span> HP1 model was able to effectively capture redox dynamics in the experimental soil columns, findings suggest the need to incorporate: i) reduction in hydraulic conductivity due to the formation of iron sulfide precipitates, and ii) transport of aqueous iron sulfide clusters observed in all columns except homogeneous sand in such contaminant fate and transport models. Results indicate that textural differences across the layered, lensed, and macropore columns were directly responsible for redox gradient across these interfaces. Also, quantitative relationships observed between pH and total carbon, pe and redox <span class="hlt">couples</span>, etc. are most significantly affected by wetting and drying cycles of the soil moisture regime for the different soil columns.</p> <div class="credits"> <p class="dwt_author">Arora, B.; Mohanty, B. P.; McGuire, J. T.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">98</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2007AGUFM.U52A..08R"> <span id="translatedtitle">Temporal Scaling of <span class="hlt">Biogeochemical</span> Reaction Rates</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In at least two disparate areas of organic and inorganic geochemistry---the microbial degradation of detritus and the dissolution of minerals in sediments and soils---apparent rate constants k have been observed to diminish with the "age" t of the substrate like k(t) ~eq a t-b, where a ~eq 0.2 and b ~eq 1.0. Published reports display up to ten orders of magnitude in time [1,2]. Because the accuracy of <span class="hlt">biogeochemical</span> models typically depends crucially on the specification of such rates, an understanding of this scaling law has important implications for predicting the evolution of <span class="hlt">biogeochemical</span> cycles, especially the cycles of carbon and oxygen. The power-law decay of rates likely derives from a combination of chemical and physical heterogeneity. In a purely chemical scenario, an intrinsically heterogeneous substrate (e.g., a mixture of organic matter ranging from "labile" to "recalcitrant") is assumed to produce the observed slowdown of k(t). In contrast, a physical model assumes a homogeneous substrate in which rates nevertheless vary microscopically due to spatially varying physical constraints. Here we consider the extreme case of a purely physical origin and test its consistency with observations [3]. We first show how a diffusion-limited reaction-diffusion system leads to a logarithmic decay of the substrate. We then show how the power-law for k(t) derives from this logarithmic decay. We obtain not only the correct exponent b=1 but also a good approximation of the prefactor a. By constructing an extensive database of previously published measurements, we show that observations compare well to predictions. The particular way in which diffusion-limitation manifests itself varies from problem to problem. In the case of detrital decay in sediments, we suggest that rates are limited by contact of substrate with extracellular enzymes [3]. Mechanisms in soils are likely similar. For mineral dissolution is sediments, we suggest that rates are limited by diffusion of reactants from the seafloor. [1] J.~J.~Middelburg, Geochim.~Cosmochim.~Acta 53, 1577 (1989). [2] K.~Maher, D.~J.~DePaolo, J.~C.-F.~Lin, Geochim.~Cosmochim.~Acta 68, 4629. [3] D.~H.~Rothman and D.~C.~Forney, Science 316, 1325 (2004).</p> <div class="credits"> <p class="dwt_author">Rothman, D. H.; Forney, D. C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">99</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=PB254577T"> <span id="translatedtitle">Molybdenum-Infiltrated <span class="hlt">Biogeochemical</span> Provinces (Biogeokhimicheskie Provintsii, Obogashchennie Molibdenom).</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">The regions in Armenia that were studied are <span class="hlt">biogeochemical</span> provinces infiltrated by molybdenum. The content of molybdenum in the soils, waters, and living organisms in these provinces exceed the usual concentration of this element in other regions. Maxim...</p> <div class="credits"> <p class="dwt_author">V. V. Kovalskii G. A. Yarovaya</p> <p class="dwt_publisher"></p> <p class="publishDate">1966-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">100</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://treesearch.fs.fed.us/pubs/20140"> <span id="translatedtitle">Effects of hydrologic conditions on <span class="hlt">biogeochemical</span> processes and ...</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.treesearch.fs.fed.us/">Treesearch</a></p> <p class="result-summary">The goals were to: (1) determine the effects of static (flooded, drained) vs. ... on <span class="hlt">biogeochemical</span> processes and organic pollutant degradation in salt marsh sediments. In: Proceedings of a Conference on Sustainability of Wetlands and Water ...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_4");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' 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src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">101</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=248231"> <span id="translatedtitle">Climate change effects on watershed hydrological and <span class="hlt">biogeochemical</span> processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> processes will likely play out over many decades and spatial sc...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">102</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2705790"> <span id="translatedtitle">Understanding Oceanic Migrations with Intrinsic <span class="hlt">Biogeochemical</span> Markers</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Migratory marine vertebrates move annually across remote oceanic water masses crossing international borders. Many anthropogenic threats such as overfishing, bycatch, pollution or global warming put millions of marine migrants at risk especially during their long-distance movements. Therefore, precise knowledge about these migratory movements to understand where and when these animals are more exposed to human impacts is vital for addressing marine conservation issues. Because electronic tracking devices suffer from several constraints, mainly logistical and financial, there is emerging interest in finding appropriate intrinsic markers, such as the chemical composition of inert tissues, to study long-distance migrations and identify wintering sites. Here, using tracked pelagic seabirds and some of their own feathers which were known to be grown at different places and times within the annual cycle, we proved the value of <span class="hlt">biogeochemical</span> analyses of inert tissue as tracers of marine movements and habitat use. Analyses of feathers grown in summer showed that both stable isotope signatures and element concentrations can signal the origin of breeding birds feeding in distinct water masses. However, only stable isotopes signalled water masses used during winter because elements mainly accumulated during the long breeding period are incorporated into feathers grown in both summer and winter. Our findings shed new light on the simple and effective assignment of marine organisms to distinct oceanic areas, providing new opportunities to study unknown migration patterns of secretive species, including in relation to human-induced mortality on specific populations in the marine environment.</p> <div class="credits"> <p class="dwt_author">Ramos, Raul; Gonzalez-Solis, Jacob; Croxall, John P.; Oro, Daniel</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">103</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/9469887"> <span id="translatedtitle">Lichens as a tool for <span class="hlt">biogeochemical</span> prospecting.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The heavy metal content in lichens and vascular plants from abandoned copper mining areas, Gerakario (Kilkis) and Megali Panagia (Chalkidiki), have been compared with metal content in soil in order to assess their efficiency to accumulate five metals (Cu, Mn, Pb, Zn, and Cr). The average metal content in the mineralized soil of Gerakario was, in descending order, Cu, Mn, Pb, Zn, and Cr, and in Chalkidiki it was Cu, Mn, Cr, Pb, and Zn. The epilithic lichens (Neophuscelia pulla) accumulated the highest amount of Cu and Pb, and Xanthoparmelia taractica accumulated the highest amount of Zn. All the lichens revealed significant (P < 0.05) correlation between Cu content in soil and that in thalli. Out of five metals studied, four (Cu, Pb, Mn, and Cr) in the epigeic lichen Cladonia convoluta, two (Cu and Mn) in both epilithic lichen N. pulla and X. taractica, and one (Pb) in vascular plant Minuartia (root) were significantly (P < 0.05) correlated between their metal content in plant tissue and in soil. Further, discoloration of C. convoluta with higher Cu concentrations adds a visible clue for <span class="hlt">biogeochemical</span> exploration. Thus, lichens along with other symptomatic species will help in locating mining areas. PMID:9469887</p> <div class="credits"> <p class="dwt_author">Chettri, M K; Sawidis, T; Karataglis, S</p> <p class="dwt_publisher"></p> <p class="publishDate">1997-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">104</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2001AGUFM.B31B0099D"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Characterization of Constructed Wetland Functions</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Agricultural productions areas of the Midwestern United States are recognized as significant contributors of nonpoint source pollution and influence many aspects of water quality at both local and regional scales. In addition, ambitious land "improvement" programs stemming back to the mid-1800s have resulted in widespread loss of wetlands throughout the U.S., including heavy losses in agricultural production areas of the Mississippi River Basin. The combination of these two factors has been directly implicated as a contributing factor to high-profile environmental problems such as exacerbation of the zone of hypoxia in the Gulf of Mexico. Constructed wetlands are recognized for their potential to help mitigate the effects of agricultural nonpoint source pollution and previous loss of wetlands. The vast majority of previous studies of constructed wetlands have focused on the bulk movement of water quality constituents such as nitrogen, phosphorus, total carbon and sediment. While insightful, these studies do not address more detailed aspects of wetland function as it pertains to carbon flux and storage. In this study, we present results from <span class="hlt">biogeochemical</span> analyses of influent and effluent of an experimental wetland constructed near row crop and animal production facilities in North-central Indiana. Cross flow utrafiltration and chemolytic techniques were used to collect and characterize organic components of wetland influent and effluent. Biomarker molecules were used to describe functions of the constructed wetland.</p> <div class="credits"> <p class="dwt_author">Dalzell, B. J.; Parker, G. R.; Filley, T. R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">105</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/19623244"> <span id="translatedtitle">Understanding oceanic migrations with intrinsic <span class="hlt">biogeochemical</span> markers.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Migratory marine vertebrates move annually across remote oceanic water masses crossing international borders. Many anthropogenic threats such as overfishing, bycatch, pollution or global warming put millions of marine migrants at risk especially during their long-distance movements. Therefore, precise knowledge about these migratory movements to understand where and when these animals are more exposed to human impacts is vital for addressing marine conservation issues. Because electronic tracking devices suffer from several constraints, mainly logistical and financial, there is emerging interest in finding appropriate intrinsic markers, such as the chemical composition of inert tissues, to study long-distance migrations and identify wintering sites. Here, using tracked pelagic seabirds and some of their own feathers which were known to be grown at different places and times within the annual cycle, we proved the value of <span class="hlt">biogeochemical</span> analyses of inert tissue as tracers of marine movements and habitat use. Analyses of feathers grown in summer showed that both stable isotope signatures and element concentrations can signal the origin of breeding birds feeding in distinct water masses. However, only stable isotopes signalled water masses used during winter because elements mainly accumulated during the long breeding period are incorporated into feathers grown in both summer and winter. Our findings shed new light on the simple and effective assignment of marine organisms to distinct oceanic areas, providing new opportunities to study unknown migration patterns of secretive species, including in relation to human-induced mortality on specific populations in the marine environment. PMID:19623244</p> <div class="credits"> <p class="dwt_author">Ramos, Raül; González-Solís, Jacob; Croxall, John P; Oro, Daniel; Ruiz, Xavier</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-07-22</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">106</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/876838"> <span id="translatedtitle">A General Simulator for Reaction-Based <span class="hlt">Biogeochemical</span> Processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">As more complex <span class="hlt">biogeochemical</span> situations are being investigated (e.g., evolving reactivity, passivation of reactive surfaces, dissolution of sorbates), there is a growing need for <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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 <span class="hlt">BIOGEOCHEM</span> <span class="hlt">biogeochemical</span> simulator, is then compiled and linked into the <span class="hlt">BIOGEOCHEM</span> 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 <span class="hlt">biogeochemical</span> reaction networks and eliminates opportunities for mistakes in preparing input files and coding errors. Test problems are used to demonstrate the features of the procedure.</p> <div class="credits"> <p class="dwt_author">Fang, Yilin; Yabusaki, Steven B.; Yeh, George</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-02-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">107</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013GMDD....6.3211F"> <span id="translatedtitle">A generic <span class="hlt">biogeochemical</span> module for earth system models</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Physical and <span class="hlt">biogeochemical</span> processes regulate soil carbon dynamics and CO2 flux to and from the atmosphere, influencing global climate changes. Integration of these processes into earth system models (e.g. community land models - CLM), however, currently faces three major challenges: (1) extensive efforts are required to modify modeling structures and to rewrite computer programs to incorporate new or updated processes as new knowledge is being generated, (2) computational cost is prohibitively expensive to simulate <span class="hlt">biogeochemical</span> processes in land models due to large variations in the rates of <span class="hlt">biogeochemical</span> processes, and (3) various mathematical representations of <span class="hlt">biogeochemical</span> processes exist to incorporate different aspects of fundamental mechanisms, but systematic evaluation of the different mathematical representations is difficult, if not impossible. To address these challenges, we propose a new computational framework to easily incorporate physical and <span class="hlt">biogeochemical</span> processes into land models. The new framework consists of a new <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Fang, Y.; Huang, M.; Liu, C.; Li, H.-Y.; Leung, L. R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-06-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">108</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..1510618V"> <span id="translatedtitle">A cost-efficient <span class="hlt">biogeochemical</span> model for estuaries: a case-study of a funnel-shaped system</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The hydrodynamics exerts an important influence on the <span class="hlt">biogeochemical</span> functioning of estuarine systems. Comparative studies have long recognized this tight <span class="hlt">coupling</span> and, for instance, have attempted to correlate key estuarine <span class="hlt">biogeochemical</span> processes to simple hydrodynamic properties, such as the residence time or the tidal forcing. Yet, these correlations fail to resolve the estuarine spatio-temporal variability and do not provide powerful means to disentangle the complex interplay of multiple reaction and transport processes. In this context, reaction-transport models (RTMs) are useful tools to resolve the variability inherent to the estuarine environment. They ideally complement field observations, because their integrative power provides the required extrapolation means for a system-scale analysis over the entire spectrum of changing forcing conditions, including the long-term response to land-use and climate changes. However, RTM simulations are associated with high computational costs, especially when the <span class="hlt">biogeochemical</span> dynamics are to be resolved on a regional or global scale. Furthermore, specific data requirements, such as boundary conditions or bathymetric and geometric information may limit their applicability. Here, a generic one-dimensional RTM approach which relies on idealized geometries to support the estuarine physics is used to quantify the <span class="hlt">biogeochemical</span> dynamics. The model is cost-efficient and requires only a limited number of readily available input data. The approach is applied to a case-study of a funnel-shaped estuary (The Scheldt, BE/NL) and is tested by comparing integrative measures of the estuarine <span class="hlt">biogeochemical</span> functioning (e.g. Net Ecosystem Metabolism, integrated CO2 fluxes) with those derived from observations (Frankignoulle et al., 1996, 1998) and highly-resolved model simulations (Vanderborght et al., 2002; Arndt et al., 2009). The method provides a robust quantitative tool to carry sensitivity and uncertainty analyses and to investigate the estuarine biogeochemistry at the regional scale.</p> <div class="credits"> <p class="dwt_author">Volta, Chiara; Arndt, Sandra; Regnier, Pierre</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">109</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUFM.H13D0999Y"> <span id="translatedtitle">Predictability of <span class="hlt">Biogeochemical</span> Responses in Engineered Watersheds</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Examining the impacts of large-scale human modifications of watersheds (e.g., land-use intensification for food production; hydrologic modification through extensive tile-drainage, etc.) on the hydrologic and <span class="hlt">biogeochemical</span> responses, and ecological impacts at various scales has been the focus of monitoring and modeling studies over the past two decades. Complex interactions between hydrology and biogeochemistry and the need to predict responses across scales has led to the development of detailed process-based models that are computationally intensive and calibration-dependent. Our overall hypothesis is that human modifications and intensive management of these watersheds have led to more predictable responses, which are typical of engineered, less-complex systems rather than natural, complex systems. We examined monitoring data for nitrogen, phosphorous, silica and chloride in 25 large watersheds (10,000 km2 to 500,000 km2) in the Mississippi River Basin. This sparse dataset was complemented with nitrogen cycling and hydrology output from a whole-basin terrestrial and aquatic modeling system (IBIS-THMB). These sub-basins have diverse land uses, although agriculture still dominates (from ~30% to ~80%). Despite diversity in soils, geology, rainfall patterns, and land use, a linear relationship was observed between the annual cumulative discharge (Q; m3/yr) and the measured nitrate load (L; kg/yr). The slopes of these linear L-Q plots represent the flow-weighted annual average concentrations (Cf), and a linear L-Q relationship indicates an apparent “chemostatic” response of these large watersheds. Analysis of Mississippi River monitoring data for nitrate and IBIS-THMB simulations revealed that Cf is a strong function of land-use (eg, percent corn) that defines the chemical input function. The scatter around the L-Q plots was small for “endogenous” (generated from internal sources) solutes (eg, silica), intermediate for “hybrid” (contributions from both endogenous and exogenous sources) solutes (eg, nitrate), and maximum for exogenous (introduced from external sources) solutes (e.g., pesticides).</p> <div class="credits"> <p class="dwt_author">Yaeger, M. A.; Voepel, H. E.; Basu, N. B.; Rao, P. C.; Donner, S. D.; Packman, A. I.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">110</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUFM.H41D0928A"> <span id="translatedtitle">Quantifying Linkages between <span class="hlt">Biogeochemical</span> Processes in a Contaminated Aquifer-Wetland System Using Multivariate Statistics and HP1</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Fate and transport of contaminants in saturated and unsaturated zones in the subsurface is controlled by complex <span class="hlt">biogeochemical</span> processes such as precipitation, sorption-desorption, ion-exchange, redox, etc. In dynamic systems such as wetlands and anaerobic aquifers, these processes are <span class="hlt">coupled</span> and can interact non-linearly with each other. Variability in measured hydrological, geochemical and microbiological parameters thus corresponds to multiple processes simultaneously. To infer the contributing processes, it is important to eliminate correlations and to identify inter-linkages between factors. The objective of this study is to 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 <span class="hlt">biogeochemical</span> processes at the column scale. Data used in this study were collected from controlled flow experiments in: 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. The soil columns represent increasing level of soil structural heterogeneity to better mimic the Norman Landfill research site. The Norman Landfill is a closed municipal facility with prevalent organic contamination. The sources of variation in the dataset were explored using multivariate statistical techniques and dominant <span class="hlt">biogeochemical</span> processes were obtained using principal component analysis (PCA). Furthermore, artificial neural networks (ANN) <span class="hlt">coupled</span> with HP1 was used to develop mathematical rules identifying different combinations of factors that trigger, sustain, accelerate/decelerate, or discontinue the <span class="hlt">biogeochemical</span> processes. Experimental observations show that infiltrating water triggers <span class="hlt">biogeochemical</span> processes in all soil columns. Similarly, slow release of water from low permeability clay lenses sustain <span class="hlt">biogeochemical</span> cycling for a longer period of time than in homogeneous soil columns. Preliminary results indicate: i) certain variables (anion, cation concentrations, etc.) do not follow normal or lognormal distributions even at the column scale, ii) strong correlations exist between parameters related to redox geochemistry (pH with S2- concentrations), and iii) PCA can identify dominant processes (e.g. iron and sulfate reduction) occurring in the system by grouping together causative variables (e.g. dominant TEAPs).</p> <div class="credits"> <p class="dwt_author">Arora, B.; Mohanty, B. P.; McGuire, J. T.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">111</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013BGeo...10....1B"> <span id="translatedtitle">Nutrient dynamics, transfer and retention along the aquatic continuum from land to ocean: towards integration of ecological and <span class="hlt">biogeochemical</span> models</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In river basins, soils, groundwater, riparian zones and floodplains, streams, rivers, lakes and reservoirs act as successive filters in which the hydrology, ecology and <span class="hlt">biogeochemical</span> processing are strongly <span class="hlt">coupled</span> and together act to retain a significant fraction of the nutrients transported. This paper compares existing river ecology concepts with current approaches to describe river biogeochemistry, and assesses the value of these concepts and approaches for understanding the impacts of interacting global change disturbances on river biogeochemistry. Through merging perspectives, concepts, and modeling techniques, we propose integrated model approaches that encompass both aquatic and terrestrial components in heterogeneous landscapes. In this model framework, existing ecological and <span class="hlt">biogeochemical</span> concepts are extended with a balanced approach for assessing nutrient and sediment delivery, on the one hand, and nutrient in-stream retention on the other hand.</p> <div class="credits"> <p class="dwt_author">Bouwman, A. F.; Bierkens, M. F. P.; Griffioen, J.; Hefting, M. M.; Middelburg, J. J.; Middelkoop, H.; Slomp, C. P.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">112</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/22076375"> <span id="translatedtitle">Aerosol indirect effect on <span class="hlt">biogeochemical</span> cycles and climate.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The net effect of anthropogenic aerosols on climate is usually considered the sum of the direct radiative effect of anthropogenic aerosols, plus the indirect effect of these aerosols through aerosol-cloud interactions. However, an additional impact of aerosols on a longer time scale is their indirect effect on climate through <span class="hlt">biogeochemical</span> feedbacks, largely due to changes in the atmospheric concentration of CO(2). Aerosols can affect land and ocean <span class="hlt">biogeochemical</span> cycles by physical forcing or by adding nutrients and pollutants to ecosystems. The net <span class="hlt">biogeochemical</span> effect of aerosols is estimated to be equivalent to a radiative forcing of -0.5 ± 0.4 watts per square meter, which suggests that reaching lower carbon targets will be even costlier than previously estimated. PMID:22076375</p> <div class="credits"> <p class="dwt_author">Mahowald, Natalie</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-11-11</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">113</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011Sci...334..794M"> <span id="translatedtitle">Aerosol Indirect Effect on <span class="hlt">Biogeochemical</span> Cycles and Climate</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The net effect of anthropogenic aerosols on climate is usually considered the sum of the direct radiative effect of anthropogenic aerosols, plus the indirect effect of these aerosols through aerosol-cloud interactions. However, an additional impact of aerosols on a longer time scale is their indirect effect on climate through <span class="hlt">biogeochemical</span> feedbacks, largely due to changes in the atmospheric concentration of CO2. Aerosols can affect land and ocean <span class="hlt">biogeochemical</span> cycles by physical forcing or by adding nutrients and pollutants to ecosystems. The net <span class="hlt">biogeochemical</span> effect of aerosols is estimated to be equivalent to a radiative forcing of -0.5 ± 0.4 watts per square meter, which suggests that reaching lower carbon targets will be even costlier than previously estimated.</p> <div class="credits"> <p class="dwt_author">Mahowald, Natalie</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">114</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/885405"> <span id="translatedtitle">Modeling Interactions of <span class="hlt">Surface-Subsurface</span> Flow Using a Free-Surface Overland Flow Boundary Condition in a Parallel Flow Simulator</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Models incorporating interactions between surface and subsurface flow are commonly based on the conductance concept that presumes a distinct interface at the land surface, separating the surface from the subsurface domain. In these models the subsurface and surface domains are linked via an exchange flux that depends upon the magnitude and direction of the hydraulic gradient across the interface and a proportionality constant (a measure of the hydraulic connectivity). Because experimental evidence of such a distinct interface is often lacking in the field, a more general <span class="hlt">coupled</span> modeling approach would be preferable. We present a more general approach that incorporates a two-dimensional overland flow simulator into the parallel three-dimensional variably saturated subsurface flow code ParFlow developed at LLNL. This overland flow simulator takes the form of an upper, free-surface boundary condition and is, thus, fully integrated without relying on the conductance concept. Another advantage of this approach is the efficient parallelism of ParFlow, which is exploited by the overland flow simulator. Several verification and simulation examples are presented that focus on the two main processes of runoff production: excess infiltration and saturation. The usefulness of our approach is demonstrated in an application of the model to an urban watershed. The influence of heterogeneity of the shallow subsurface on overland flow and transport is also examined. The results show the uncertainty in flow and transport predictions due to heterogeneity. This is important in determining, for example, total maximum daily loads of surface water systems.</p> <div class="credits"> <p class="dwt_author">Kollet, S J; Maxwell, R M</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-10-25</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">115</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2005AGUFM.B22A..02S"> <span id="translatedtitle">Modeling <span class="hlt">Biogeochemical</span> Cycling of Heavy Metals in Lake Coeur d'Alene Sediments</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Mining of precious metals since the late 1800's have left Lake Coeur d'Alene (LCdA) sediments heavily enriched with toxic metals, including Cd, Cu, Pb, and Zn. Indigenous microbes however are capable of catalyzing reactions that detoxify the benthic and aqueous lake environments, and thus constitute an important driving component in the <span class="hlt">biogeochemical</span> cycles of these metals. Here we report on the development of a quantitative model of transport, fate, exposure and effects of toxic compounds on benthic microbial communities at LCdA. First, chemical data from the LCdA area have been compiled from multiple sources to investigate trends in chemical occurrence, as well as to define model boundary conditions. The model is structured as 1-D diffusive reactive transport model to simulate spatial and temporal distribution of metals through the benthic sediments. Inorganic reaction processes included in the model are aqueous speciation, surface complexation, mineral precipitation/dissolution and abiotic redox reactions. Simulations with and without surface complexation are carried out to evaluate the effect of sorption and the conservative behaviour of metals within the benthic sediments under abiotic and purely diffusive transport. The 1-D inorganic diffusive transport model is then <span class="hlt">coupled</span> to a biotic reaction network including consortium biodegradation kinetics with multiple electron acceptors, product toxicity, and energy partitioning. Multiyear simulations are performed, with water column chemistry established as a boundary condition from extant data, to explore the role of <span class="hlt">biogeochemical</span> dynamics on benthic fluxes of metals in the long term.</p> <div class="credits"> <p class="dwt_author">Sengor, S. S.; Spycher, N.; Belding, E.; Curthoys, K.; Ginn, T. R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">116</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2001AGUFM.H41A0259S"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Process Comparison of the Five USGS Water, Energy, and <span class="hlt">Biogeochemical</span> Budget (WEBB) Sites</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Input - output budgets (in wet deposition and streamwater) have been constructed for water and major solutes at the five USGS Water, Energy, and <span class="hlt">Biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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 weathered subtropical and tropical soils. At Sleepers River, net SO4 export occurs as a result of weathering of sulfide minerals in the bedrock, and correspondingly limited soil SO4 adsorption capacity. A small net export of SO4 occurs at Allequash Creek and Andrews Creek, but the SO4 may be in balance if dry deposition were added to the inputs. All sites except Icacos River retain NO3. At Andrews Creek and Sleepers River, net export of NO3 occurs during the peak snowmelt months, as soils are flushed during a time of low biological uptake. Additional analysis will be performed to evaluate the relative importance of temperature (affecting weathering rates and biological uptake) and water yield (i.e., the amount of water flushing through a catchment) in controlling solute fluxes.</p> <div class="credits"> <p class="dwt_author">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.</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">117</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.treesearch.fs.fed.us/pubs/14129"> <span id="translatedtitle">Effects of urban land-use change on <span class="hlt">biogeochemical</span> cycles</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.treesearch.fs.fed.us/">Treesearch</a></p> <p class="result-summary">... Employment, Fire and Aviation, International Forestry, Just for Kids, Maps and Brochures ... Title: Effects of urban land-use change on <span class="hlt">biogeochemical</span> cycles ... than half of the global population is expected to live in urban areas (United Nations 2004). Yet, urban settlements and surrounding areas are complex ecological ...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">118</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/48909171"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> investigations of marine methane seeps, Hydrate Ridge, Oregon</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A series of <span class="hlt">biogeochemical</span> studies were conducted at the southern summit of Hydrate Ridge, offshore Oregon. Using the submersible DSV Alvin, sediment push cores were collected from two distinct seep environments characterized by the presence of clam fields (CF) or microbial mats (MM) at the sediment-water interface; samples were also collected from a nearby reference site characterized by a barren</p> <div class="credits"> <p class="dwt_author">David L. Valentine; Miriam Kastner; George D. Wardlaw; Xuchen Wang; Alexandra Purdy; Douglas H. Bartlett</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">119</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.soest.hawaii.edu/oceanography/courses/OCN621/Spring2010/Falko%20et%20al%201998.pdf"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Controls and Feedbacks on Ocean Primary Production</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Changes in oceanic primary production, linked to changes in the network of global <span class="hlt">biogeochemical</span> cycles, have profoundly influenced the geochemistry of Earth for over 3 billion years. In the contemporary ocean, photosynthetic carbon fixation by marine phytoplankton leads to formation of ;45 gigatons of organic carbon per annum, of which 16 gigatons are ex- ported to the ocean interior. Changes</p> <div class="credits"> <p class="dwt_author">Paul G. Falkowski; Richard T. Barber; Victor Smetacek</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">120</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.lifesciences.napier.ac.uk/research/Envbiofiles/Tett&Wilson.pdf"> <span id="translatedtitle">From <span class="hlt">biogeochemical</span> to ecological models of marine microplankton</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Models must simplify the complexity of real marine pelagic ecosystems. How much simplicity is needed? A series of increasing numbers of state variables is used to illuminate this issue and to illustrate <span class="hlt">biogeochemical</span> (element-conserving) and ecological (semi-freely dynamically interacting) models of the marine microplankton, defined as all organisms less than 200 ?m. The models are those of Riley [Riley, 1946.</p> <div class="credits"> <p class="dwt_author">Paul Tett; Hilary Wilson</p> <p class="dwt_publisher"></p> <p class="publishDate">2000-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_5");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' 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id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_6");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' href="#">4</a> <a onClick='return showDiv("page_5");' href="#">5</a> <a onClick='return showDiv("page_6");' href="#">6</a> <a style="font-weight: bold;">7</a> <a onClick='return showDiv("page_8");' href="#">8</a> <a onClick='return showDiv("page_9");' href="#">9</a> <a onClick='return showDiv("page_10");' 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src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">121</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ag.arizona.edu/research/archer/reprints/Hibbard_etal_2001_Ecology.pdf"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Changes Accompanying Woody Plant Encroachment in a Subtropical Savanna</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Ecosystem properties of surficial (0-10 cm) soils in remnant herbaceous patches were compared to those of contrasting woody plant patch types (upland discrete cluster, upland grove, and lowland woodland) where shifting land cover is known to have occurred over the past 50-77 yr. The purpose of this study was to evaluate and quantify the <span class="hlt">biogeochemical</span> consequences and subsequent developmental rates</p> <div class="credits"> <p class="dwt_author">K. A. Hibbard; S. Archer; D. S. Schimel; D. W. Valentine</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">122</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://sfbay.wr.usgs.gov/publications/pdf/oremland_1988_microbial.pdf"> <span id="translatedtitle">Microbial and <span class="hlt">biogeochemical</span> processes in Big Soda Lake, Nevada</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">SUMMA R Y : Meromictic, alkaline lakes represent modern-day analogues of lacustrine source rock depositional environments. In order to further our understanding of how these lakes function in terms of limnological and <span class="hlt">biogeochemical</span> processes, we have conducted an interdisciplinary study of Big Soda Lake. Annual mixolimnion productivity (ca. 500 g m-') is dominated by a winter diatom bloom (60% of</p> <div class="credits"> <p class="dwt_author">R. S. Oremland; J. E. Cloern; R. L. Smith; C. W. Culbertson; J. Zehr; L. Miller; B. Cole; R. Harvey; Z. Sofer; N. Iversen; M. Klug; D. J. Des Marais; G. Rau</p> <p class="dwt_publisher"></p> <p class="publishDate">1988-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">123</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/59174908"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> cycling of methyl bromide in the surface ocean</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The <span class="hlt">biogeochemical</span> cycling of methyl bromide in the oceans is investigated through the determination of production and removal rates. Since atmospheric methyl bromide has been determined to contribute to the destruction of stratospheric ozone, phase-out of the production of methyl bromide has been proposed (Montreal Protocol and U.S. Clean Air Act). However, the large uncertainty associated with the budget and</p> <div class="credits"> <p class="dwt_author">Daniel Barry King</p> <p class="dwt_publisher"></p> <p class="publishDate">1997-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">124</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=48590"> <span id="translatedtitle">EFFECTS OF INCREASED SOLAR ULTRAVIOLET RADIATION ON <span class="hlt">BIOGEOCHEMICAL</span> CYCLES</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p class="result-summary">Increases in solar UV radiation could affect terrestrial and aquatic <span class="hlt">biogeochemical</span> cycles thus altering both sources and sinks of greenhouse and chemically important trace gases (e.g., carbon dioxide (CO2), carbon monoxide (CO), carbonyl sulfide (COS)). n terrestrial ecosystems,...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">125</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=60995"> <span id="translatedtitle">PHOTOREACTIONS IN SURFACE WATERS AND THEIR ROLE IN <span class="hlt">BIOGEOCHEMICAL</span> CYCLES</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p class="result-summary">During the past decade significant interest has developed in the influence of photochemical reactions on <span class="hlt">biogeochemical</span> cycles in surface waters of lakes and the sea. A major portion of recent research on these photoreactions has focused on the colored component of dissolved org...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">126</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/42313641"> <span id="translatedtitle">Cokriging of Heavy Metals as an Aid to <span class="hlt">Biogeochemical</span> Mapping</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary"><span class="hlt">Biogeochemical</span> maps determined from the distribution of sparsely sampled cadmium have been improved by the incorporation of more densely sampled zinc with which it is correlated and by the application of cokriging. The inherent variability of both elements, together with their correlation with each other, can be accounted for in terms both of multivariate statistics and spatial position using the</p> <div class="credits"> <p class="dwt_author">Michael S. Rosenbaum; Mats Söderström</p> <p class="dwt_publisher"></p> <p class="publishDate">1996-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">127</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/54406551"> <span id="translatedtitle">Ecosystem <span class="hlt">biogeochemical</span> function and services in an urbanizing desert region</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Ecosystem services derive from underlying ecosystem processes but are distinguished by their benefits to society. Among ecosystem services, those associated with <span class="hlt">biogeochemical</span> cycling and regulation of water, air, and soil quality are relatively unrecognized by the public, although concentrations of some materials are regulated by local, state and national laws. The disconnection between their importance and the degree to which</p> <div class="credits"> <p class="dwt_author">N. B. Grimm; E. M. Cook; S. Earl; R. L. Hale; S. J. Hall; H. E. Hartnett; D. Iwaniec; E. K. Larson; M. McHale; R. A. Sponseller</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">128</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010OcDyn..60.1061Z"> <span id="translatedtitle"><span class="hlt">Coupled</span> assimilation for an intermediated <span class="hlt">coupled</span> ENSO prediction model</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The value of <span class="hlt">coupled</span> assimilation is discussed using an intermediate <span class="hlt">coupled</span> model in which the wind stress is the only atmospheric state which is slavery to model sea surface temperature (SST). In the <span class="hlt">coupled</span> assimilation analysis, based on the <span class="hlt">coupled</span> wind-ocean state covariance calculated from the <span class="hlt">coupled</span> state ensemble, the ocean state is adjusted by assimilating wind data using the ensemble Kalman filter. As revealed by a series of assimilation experiments using simulated observations, the <span class="hlt">coupled</span> assimilation of wind observations yields better results than the assimilation of SST observations. Specifically, the <span class="hlt">coupled</span> assimilation of wind observations can help to improve the accuracy of the surface and subsurface currents because the correlation between the wind and ocean currents is stronger than that between SST and ocean currents in the equatorial Pacific. Thus, the <span class="hlt">coupled</span> assimilation of wind data can decrease the initial condition errors in the <span class="hlt">surface/subsurface</span> currents that can significantly contribute to SST forecast errors. The value of the <span class="hlt">coupled</span> assimilation of wind observations is further demonstrated by comparing the prediction skills of three 12-year (1997-2008) hindcast experiments initialized by the ocean-only assimilation scheme that assimilates SST observations, the <span class="hlt">coupled</span> assimilation scheme that assimilates wind observations, and a nudging scheme that nudges the observed wind stress data, respectively. The prediction skills of two assimilation schemes are significantly better than those of the nudging scheme. The prediction skills of assimilating wind observations are better than assimilating SST observations. Assimilating wind observations for the 2007/2008 La Niña event triggers better predictions, while assimilating SST observations fails to provide an early warning for that event.</p> <div class="credits"> <p class="dwt_author">Zheng, Fei; Zhu, Jiang</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-10-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">129</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008AGUFM.H13I..06A"> <span id="translatedtitle">Modeling the Effects of Hydrological and <span class="hlt">Biogeochemical</span> Processes on Denitrification and Stream Nitrogen Losses in River Networks</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Nitrogen flux in streams is the cumulative result of <span class="hlt">biogeochemical</span> and hydrological processes that control the supply and transport of nitrogen in terrestrial and aquatic ecosystems. These processes include the effects of denitrification on stream nitrogen removal, which influence the quantities of nitrogen delivered to downstream coastal waters, where increases in nitrogen flux have contributed to eutrophication and hypoxic conditions globally in recent decades. Despite progress in measuring and modeling stream denitrification, few studies have attempted to unravel the <span class="hlt">coupled</span> effects of <span class="hlt">biogeochemical</span> (nitrate loadings, concentration, temperature) and hydrological (streamflow, depth, velocity) factors on denitrification and stream nitrogen losses in river networks over space and time. We apply a dynamic nitrogen transport model to assess <span class="hlt">biogeochemical</span> vs. hydrological effects on seasonal nitrate removal by denitrification in the river networks of two watersheds. The watershed streams have widely differing levels of nitrate concentrations, but similar flows. Unique to our model is the nonlinear dependence of stream denitrification on nitrate concentration, streamflow, and temperature, as determined by regression relations estimated from more than 300 published field measurements available for a variety of U.S. streams. We use these empirical relations to parameterize the nitrogen transport model, which was then applied to the first- through fourth-order stream reaches of the two watersheds. The model results indicate that in-stream nitrate removal by denitrification becomes less efficient as nitrate concentrations and flows increase. This is denoted by the appreciably low percentage of the in-stream nitrate flux (expressed per unit length of stream channel) that is removed in reaches during the highest nitrate concentration and flow months (Feb. to June). The importance of <span class="hlt">biogeochemical</span> factors (which includes effects of anthropogenic nitrogen loadings, land use, and in-stream <span class="hlt">biogeochemical</span> factors) is demonstrated as a major control on reach-scale denitrification and in-stream nitrate removal, as evidenced by the disproportionately lower nitrate removal efficiency in stream reaches of the highly nitrate-enriched watershed as compared with that in similarly sized reaches in the less nitrate-enriched watershed. Furthermore, results from model sensitivity analyses confirm the importance of <span class="hlt">biogeochemical</span> factors (principally nitrate concentration), but suggest that hydrological factors contribute nearly equally to temporal and spatial variations in the percentage of the stream nitrate flux removed in the reaches of each watershed, with water depth indicated as a more important hydrological factor than water velocity.</p> <div class="credits"> <p class="dwt_author">Alexander, R. B.; Bohlke, 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.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">130</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..15.8300B"> <span id="translatedtitle">The value of automated high-frequency nutrient monitoring in inference of <span class="hlt">biogeochemical</span> processes, temporal variability and trends</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Stream water quality signals integrate catchment-scale processes responsible for delivery and <span class="hlt">biogeochemical</span> 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 <span class="hlt">coupling</span> of catchment-scale, in-stream, riparian and hyporheic <span class="hlt">biogeochemical</span> cycles. The synergistic effect of physical (temperature-driven, the hyporheic exchange controlled by diffusion) and <span class="hlt">biogeochemical</span> 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 and understanding reach-scale in-stream <span class="hlt">biogeochemical</span> processes. In this paper we discuss the advantages and limitations of the in-situ high-frequency nutrient monitoring, the challenges related to data analysis and process inference and the integration of the short-term <span class="hlt">biogeochemical</span> behaviour with the long-term trends. Finally the potential for integration of the long-term high-temporal resolution datasets with the predictions of reach- and catchment-scale <span class="hlt">biogeochemical</span> models and observations from coarse-sampling monitoring strategies has been discussed.</p> <div class="credits"> <p class="dwt_author">Bieroza, Magdalena; Heathwaite, Louise</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">131</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFM.H21C1055C"> <span id="translatedtitle">Development of interactive graphic user interfaces for modeling reaction-based <span class="hlt">biogeochemical</span> processes in batch systems with <span class="hlt">BIOGEOCHEM</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The <span class="hlt">BIOGEOCHEM</span> numerical model (Yeh and Fang, 2002; Fang et al., 2003) was developed with FORTRAN for simulating reaction-based geochemical and biochemical processes with mixed equilibrium and kinetic reactions in batch systems. A complete suite of reactions including aqueous complexation, adsorption/desorption, ion-exchange, redox, precipitation/dissolution, acid-base reactions, and microbial mediated reactions were embodied in this unique modeling tool. Any reaction can be treated as fast/equilibrium or slow/kinetic reaction. An equilibrium reaction is modeled with an implicit finite rate governed by a mass action equilibrium equation or by a user-specified algebraic equation. A kinetic reaction is modeled with an explicit finite rate with an elementary rate, microbial mediated enzymatic kinetics, or a user-specified rate equation. None of the existing models has encompassed this wide array of scopes. To ease the input/output learning curve using the unique feature of <span class="hlt">BIOGEOCHEM</span>, an interactive graphic user interface was developed with the Microsoft Visual Studio and .Net tools. Several user-friendly features, such as pop-up help windows, typo warning messages, and on-screen input hints, were implemented, which are robust. All input data can be real-time viewed and automated to conform with the input file format of <span class="hlt">BIOGEOCHEM</span>. A post-processor for graphic visualizations of simulated results was also embedded for immediate demonstrations. By following data input windows step by step, errorless <span class="hlt">BIOGEOCHEM</span> input files can be created even if users have little prior experiences in FORTRAN. With this user-friendly interface, the time effort to conduct simulations with <span class="hlt">BIOGEOCHEM</span> can be greatly reduced.</p> <div class="credits"> <p class="dwt_author">Chang, C.; Li, M.; Yeh, G.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">132</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6533302"> <span id="translatedtitle">Global <span class="hlt">biogeochemical</span> cycling estimates with CZCS satellite data and general circulation models</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Computed geophysical fields from a 3-D general circulation model are <span class="hlt">coupled</span> with the Coastal Zone Color Scanner (CZCS) satellite data on chlorophyll content of surface ocean waters. The CZCS satellite data on chlorophyll content of surface ocean waters are used to estimate the photochemical lability of dissolved organic matter in the surface ocean. Monthly estimates are made of the global ocean to atmosphere flux of a <span class="hlt">biogeochemically</span> important gas, carbonyl sulfide (OCS), with 2.8[degree] [times] 2.8[degree] latitude-longitude spatial resolution. This novel technique provides a conceptual and computational method for integrating data collected as part of future satellite measurement campaigns, such as the Earth Observing System (EOS) and Sea-viewing Wide-field-of view Sensor (SeaWiFS), with 3-D chemistry-climate prediction models. 15 refs., 2 figs.</p> <div class="credits"> <p class="dwt_author">Erickson, D.J. III; Eaton, B.E.</p> <p class="dwt_publisher"></p> <p class="publishDate">1993-02-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">133</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2005GeoRL..3217603P"> <span id="translatedtitle">Differential eddy diffusion of <span class="hlt">biogeochemical</span> tracers</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The marine ecosystem dynamics in the subtropical regions is controlled by the availability of nutrients. Their supply depends on lateral transport from higher latitudes, which is affected by the characteristics of the oceanic mesoscale turbulence. In many cases turbulent transport is parameterized in terms of eddy diffusion. We here test the validity of this approach in a mesoscale turbulence model <span class="hlt">coupled</span> to a simple ecosystem model. We show that the parameterization can be profitably used, provided that an effective eddy diffusion coefficient that depends on the reaction time scale of the transported tracers is used. If the diffusion coefficient valid for conservative tracers is used to express diffusion of nutrients and plankton, turbulent transport and biological productivity can be significantly overestimated.</p> <div class="credits"> <p class="dwt_author">Pasquero, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">134</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/893406"> <span id="translatedtitle">Novel Imaging Techniques, Integrated with Mineralogical, Geochemical and Microbiological Characterization to Determine the <span class="hlt">Biogeochemical</span> Controls....</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Tc(VII) will be reduced and precipitated in FRC sediments under anaerobic conditions in batch experiments (progressive microcosms). The complementary microcosm experiments using low pH/nigh nitrate sediments from 3 (near FW 009) are imminent, with the sediment cores already shipped to Manchester. HYPOTHESIS 2. Tc(VII) reduction and precipitation can be visualized in discrete <span class="hlt">biogeochemical</span> zones in sediment columns using 99mTc and a gamma-camera. Preliminary experiments testing the use of 99mTc as a radiotracer to address hypotheses 2 and 3 have suggested that the 99mTc associates with Fe(II)-bearing sediments in microcosms and stratified columns containing FRC sediments. Initial proof of concept microcosms containing Fe(II)-bearing, microbially-reduced FRC sediments were spiked with 99mTc and imaged using a gamma-camera. In comparison with oxic controls, 99mTc was significantly partitioned in the solid phase in Fe(III)-reducing sediments in batch experiments. Column experiments using FRC background area soil with stratified <span class="hlt">biogeochemical</span> zones after stimulation of anaerobic processes through nutrient supplementation, suggested that 99mTc transport was retarded through areas of Fe(III) reduction. HYPOTHESIS 3. Sediment-bound reduced 99mTc can be solubilized by perturbations including oxidation <span class="hlt">coupled</span> to biological nitrate reduction, and mobilization visualized in real-time using a gamma-camera. Significant progress has been made focusing on the impact of nitrate on the <span class="hlt">biogeochemical</span> behavior of technetium. Additions of 100 mM nitrate to FRC sediment microcosms, which could potentially compete for electrons during metal reduction, inhibited the reduction of both Fe(III) and Tc(VII) completely. Experiments have also addressed the impact of high nitrate concentrations on Fe(II) and Tc(IV) in pre-reduced sediments, showing no significant resolubilization of Tc with the addition of 25 mM nitrate. A parallel set of experiments addressing the impact of aerobic conditions on the stability/solubility of Fe(II) and Tc(IV), found 80 % resolubilization of the Tc. Column experiments exploring this behavior are being planned. HYPOTHESIS 4 The mobility of 99mTc in the sediment columns can be modeled using a <span class="hlt">coupled</span> speciation and transport code. Microbiological and geochemical characterization of the column experiments is ongoing and transport and geochemical modeling experiments are being planned.</p> <div class="credits"> <p class="dwt_author">Lloyd, Jonathan R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">135</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.B13E0613R"> <span id="translatedtitle">Microbial activity and <span class="hlt">biogeochemical</span> cycling in first-order Russian Arctic streams</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Global climate change is strongly impacting Arctic ecosystems and is predicted to lead to thawing of permafrost soils. These soils are rich in organic matter and other nutrients and influence <span class="hlt">biogeochemical</span> cycling in terrestrial and aquatic ecosystems. Small arctic streams are likely to be the first aquatic ecosystems to receive materials exported as soils warm. These first-order streams are characterized by strong interactions between the water column and stream bottom and have the potential to affect nutrient flux. Previous studies suggest that phosphorous availability limits biological productivity in many first-order arctic streams, however, they remain understudied, particularly in the Russian Arctic. Our objective was to assess microbial activity and <span class="hlt">biogeochemical</span> cycling among arctic streams. We used three approaches to meet our objectives, including a survey of 9 streams, intensive longitudinal sampling in 5 streams, and nutrient pulse addition experiments in 4 streams, designed to assess the potential for limitation by N or P. We measured pH, temperature, dissolved oxygen, NH4, SRP, DOC, and TDN at all sampling sites. We also conducted biological oxygen demand (BOD) incubations designed to assess DOC lability, and correlated these measurements with background nutrient concentrations. We found a strong positive linear correlation between BOD and phosphate concentration, suggesting P limitation of production and/or consumption of labile DOC. To complement ambient stream measurements, we conducted whole stream nutrient addition experiments to calculate N and P uptake lengths, which we then used to infer whether N or P is more likely to limit biological processes, and the degree of <span class="hlt">coupling</span> between N and P cycling. Results from the nutrient addition experiments suggest both N and P limitation among streams depending on stream location and characteristics. In addition, these experiments suggest a significant, but complex interaction between N and P cycles, with evidence that co-addition of N and P reduced P uptake rates over measurements made with addition of P alone. Because carbon degradation may be constrained by nutrient availability, we need a better understanding of the degree of <span class="hlt">coupling</span> between element cycles, and the influence of small streams on <span class="hlt">biogeochemical</span> cycling. Our findings show that first order streams have diverse impacts on nutrient flux and should be considered when modeling Arctic ecosystem response to climate change.</p> <div class="credits"> <p class="dwt_author">Rhoades, R. E.; Lynch, L. M.; Ortega, J. C.; Holmes, R. M.; Mann, P. J.; Vonk, J. E.; Schade, J. D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">136</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70019236"> <span id="translatedtitle">Polychlorinated Biphenyls as Probes of <span class="hlt">Biogeochemical</span> Processes in Rivers</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">A field study was conducted to investigate the use of PCB (polychlorinated biphenyl) congener and homolog assemblages as tracers of <span class="hlt">biogeochemical</span> 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. <span class="hlt">Biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Fitzgerald, S. A.; Steuer, J. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">1997-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">137</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/hxcxkw6lqfq43xmd.pdf"> <span id="translatedtitle">Aquifer\\/aquitard interfaces: mixing zones that enhance <span class="hlt">biogeochemical</span> reactions</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">.   Several important <span class="hlt">biogeochemical</span> reactions are known to occur near the interface between aquifer and aquitard sediments.\\u000a These reactions include O2 reduction; denitrification; and Fe3+, SO4\\u000a 2–, and CO2 (methanogenesis) reduction. In some settings, these reactions occur on the aquitard side of the interface as electron acceptors\\u000a move from the aquifer into the electron-donor-enriched aquitard. In other settings, these reactions</p> <div class="credits"> <p class="dwt_author">P. B. McMahon</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">138</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/57710293"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> reduction processes in a hyperalkaline affected leachate soil profile</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Hyperalkaline surface environments can occur naturally or because of contamination by hydroxide-rich wastes. The high pH produced in these areas has the potential to lead to highly specialised microbial communities and unusual <span class="hlt">biogeochemical</span> processes. This paper reports an investigation into the geochemical processes that are occurring in a buried, saturated, organic–rich soil layer at pH 12.3. The soil has been</p> <div class="credits"> <p class="dwt_author">Ian T. Burke; Robert J. G. Mortimer; Shanmugam Palani; Robert A. Whittleston; Cindy L. Lockwood; David J. Ashley; Douglas I. Stewart</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">139</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011JGRC..11612043C"> <span id="translatedtitle">Can ocean color assimilation improve <span class="hlt">biogeochemical</span> hindcasts in shelf seas?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The objective of this paper is to investigate if the assimilation of ocean color data into a complex marine ecosystem model can improve the hindcast of key <span class="hlt">biogeochemical</span> variables in shelf seas. A localized Ensemble Kalman filter was used to make a yearlong assimilation of weekly satellite chlorophyll data into a three-dimensional ecosystem model of the western English Channel. The skill of assimilation was evaluated with respect to non assimilated in situ data using twelve time series of <span class="hlt">biogeochemical</span> observations collected weekly at the monitoring station L4. It was found that the assimilation scheme reduced the root mean square error and increased the correlation with the spatial distributions of the assimilated chlorophyll data, with respect to the reference run. More significantly, the skill metrics for non assimilated variables indicate that the hindcast of the mean data values at L4 was improved; however improvements in the short term forecast were not discernable. On the basis of our application, we provide general recommendations for the successful application of ocean color assimilation to hindcast key <span class="hlt">biogeochemical</span> variables in shelf seas.</p> <div class="credits"> <p class="dwt_author">Ciavatta, Stefano; Torres, Ricardo; Saux-Picart, Stephane; Allen, Julian Icarus</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">140</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011JCHyd.126..271Y"> <span id="translatedtitle">Variably saturated flow and multicomponent <span class="hlt">biogeochemical</span> reactive transport modeling of a uranium bioremediation field experiment</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Three-dimensional, <span class="hlt">coupled</span> variably saturated flow and <span class="hlt">biogeochemical</span> reactive transport modeling of a 2008 in situ uranium bioremediation field experiment is used to better understand the interplay of transport and <span class="hlt">biogeochemical</span> reactions controlling uranium behavior under pulsed acetate amendment, seasonal water table variation, spatially variable physical (hydraulic conductivity, porosity) and geochemical (reactive surface area) material properties. While the simulation of the 2008 Big Rusty acetate biostimulation field experiment in Rifle, Colorado was generally consistent with behaviors identified in previous field experiments at the Rifle IFRC site, the additional process and property detail provided several new insights. A principal conclusion from this work is that uranium bioreduction is most effective when acetate, in excess of the sulfate-reducing bacteria demand, is available to the metal-reducing bacteria. The inclusion of an initially small population of slow growing sulfate-reducing bacteria identified in proteomic analyses led to an additional source of Fe(II) from the dissolution of Fe(III) minerals promoted by biogenic sulfide. The falling water table during the experiment significantly reduced the saturated thickness of the aquifer and resulted in reactants and products, as well as unmitigated uranium, in the newly unsaturated vadose zone. High permeability sandy gravel structures resulted in locally high flow rates in the vicinity of injection wells that increased acetate dilution. In downgradient locations, these structures created preferential flow paths for acetate delivery that enhanced local zones of TEAP reactivity and subsidiary reactions. Conversely, smaller transport rates associated with the lower permeability lithofacies (e.g., fine) and vadose zone were shown to limit acetate access and reaction. Once accessed by acetate, however, these same zones limited subsequent acetate dilution and provided longer residence times that resulted 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 <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">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.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-11-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_6");' href="#" 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showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_9");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">141</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008AGUFM.H24B..02L"> <span id="translatedtitle">Effects of Physical and Chemical Heterogeneities on <span class="hlt">Biogeochemical</span> Processes Associated With Uranium Bioremediation at Rifle, Colorado</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Natural porous media are inherently heterogeneous at multiple spatial scales, which can have profound impacts on <span class="hlt">biogeochemical</span> reactions in the subsurface. In this work, we aim to understand the effects of physical and chemical heterogeneities on various <span class="hlt">biogeochemical</span> reaction processes associated with a field- scale uranium bioremediation experiment at Rifle, Colorado. Numerical experiments were designed to mimic the field biostimulation experiment: acetate was injected into the subsurface as the electron donor to stimulate the growth of bacteria and the microbially-mediated reduction of uranium, iron, and sulfate. The field measurements were used to estimate the initial physical property distribution and to infer a relationship between physical and chemical properties. The reactive transport model CrunchFlow <span class="hlt">couples</span> the geochemical, transport, and microbial processes, and explicitly keeps track of the evolution of microbial community structures and their impact on reaction rates. The simulation results, which were validated using field monitoring well datasets, suggested that the physical heterogeneity, essentially the spatial variation in permeability, determines how the injected acetate is distributed, while the chemical heterogeneity, including the spatial distribution of iron hydroxide, determines where and how much iron reduction occurs. Because uranium is reduced by iron reducers, the chemical heterogeneities also determine where and how much uranium reduction occurs. The physical and chemical heterogeneities together determine the level of accessibility of acetate to iron hydroxide in the field. As a result, with different levels of spatial variation in Fe-hydroxide content, the efficacy of uranium bioremediation can differ by a factor of more than two. In contrast, for sulfate reduction, the effects of heterogeneities are much less significant because sulfate is uniformly distributed in the groundwater and is continuously replenished by upgradient groundwater flow. As a result, sulfate is mostly consumed close to the injection wells, leading to the accumulation of large amounts of sulfate reducers in these locations that can be order of magnitude larger than elsewhere. Because of the large spatial variations in the biomass, the rates of <span class="hlt">biogeochemical</span> reactions vary significantly over time and space. As a result, the rate laws that do not take such spatial and temporal evolution of biomass into account cannot match the breakthrough curves of chemical species in the field. In addition, because of the possibility of pore clogging and the associated flow path changes due to precipitates and biomass accumulation, the characteristics of physical and chemical heterogeneities can also evolve with time, which can have profound impacts on the efficacy and sustainability of in situ bioremediation strategies.</p> <div class="credits"> <p class="dwt_author">Li, L.; Steefel, C. I.; Kowalsky, M. B.; Englert, A. L.; Hubbard, S. S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">142</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFM.H53F1129M"> <span id="translatedtitle">Seasonal <span class="hlt">biogeochemical</span> profiling of an unlined landfill in rural Victoria (Australia): implications for stream and groundwater contamination</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Unlined landfills and waste transfer stations lack collection systems to prevent groundwater pollution. Unmonitored leakage into shallow groundwater can lead to eutrophication of freshwater ecosystems. Such sites are fairly common in rural Australia, and seven years of groundwater and leachate <span class="hlt">biogeochemical</span> data taken near a rural landfill in Beaufort (Victoria) Australia, showed that interacting <span class="hlt">biogeochemical</span> cycles (i.e. C, N, S, Fe) influenced contaminant transport into groundwaters seasonally. Reductive dissolution of iron oxyhydroxides <span class="hlt">coupled</span> with alkalinity spikes was <span class="hlt">coupled</span> to higher carbon turnover rates within a methanogenic landfill cell. This process appeared to occur mainly during summers and less during winters. Dissolved trace metal concentrations (Co, Cu, Ni, Zn) alternated with increases in dissolved iron, but with less frequency during the winter months. Nitrate and sulphate however seasonally alternated with high nitrate/low sulphate during the winter, and low nitrate/high sulphate during the summer, within the landfill cell. The seasonal variability of nitrate and sulphate in landfill leachate was also reflected in the down-flow groundwater chemistry.</p> <div class="credits"> <p class="dwt_author">Minard, A.; Moreau, J. W.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">143</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=204214"> <span id="translatedtitle">Operator-splitting errors in <span class="hlt">coupled</span> reactive transport codes for flow and transport under atmospheric boundary conditions or layered soil profiles</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p class="result-summary">One possible way of integrating subsurface flow and transport processes with (<span class="hlt">bio)geochemical</span> reactions is to <span class="hlt">couple</span> by means of an operator-splitting approach two completely separate codes, one for variably-saturated flow and solute transport and one for equilibrium and kinetic <span class="hlt">biogeochemical</span> react...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">144</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010GeoRL..3723404B"> <span id="translatedtitle">Nutrient loads exported from managed catchments reveal emergent <span class="hlt">biogeochemical</span> stationarity</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Complexity of heterogeneous catchments poses challenges in predicting <span class="hlt">biogeochemical</span> responses to human alterations and stochastic hydro-climatic drivers. Human interferences and climate change may have contributed to the demise of hydrologic stationarity, but our synthesis of a large body of observational data suggests that anthropogenic impacts have also resulted in the emergence of effective <span class="hlt">biogeochemical</span> stationarity in managed catchments. Long-term monitoring data from the Mississippi-Atchafalaya River Basin (MARB) and the Baltic Sea Drainage Basin (BSDB) reveal that inter-annual variations in loads (LT) for total-N (TN) and total-P (TP), exported from a catchment are dominantly controlled by discharge (QT) leading inevitably to temporal invariance of the annual, flow-weighted concentration, $\\overline{Cf = (LT/QT). Emergence of this consistent pattern across diverse managed catchments is attributed to the anthropogenic legacy of accumulated nutrient sources generating memory, similar to ubiquitously present sources for geogenic constituents that also exhibit a linear LT-QT relationship. These responses are characteristic of transport-limited systems. In contrast, in the absence of legacy sources in less-managed catchments, $\\overline{Cf values were highly variable and supply limited. We offer a theoretical explanation for the observed patterns at the event scale, and extend it to consider the stochastic nature of rainfall/flow patterns at annual scales. Our analysis suggests that: (1) expected inter-annual variations in LT can be robustly predicted given discharge variations arising from hydro-climatic or anthropogenic forcing, and (2) water-quality problems in receiving inland and coastal waters would persist until the accumulated storages of nutrients have been substantially depleted. The finding has notable implications on catchment management to mitigate adverse water-quality impacts, and on acceleration of global <span class="hlt">biogeochemical</span> cycles.</p> <div class="credits"> <p class="dwt_author">Basu, Nandita B.; Destouni, Georgia; Jawitz, James W.; Thompson, Sally E.; Loukinova, Natalia V.; Darracq, Amélie; Zanardo, Stefano; Yaeger, Mary; Sivapalan, Murugesu; Rinaldo, Andrea; Rao, P. Suresh C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">145</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2005AGUFM.B31A0979B"> <span id="translatedtitle">Rivers and Stable Isotopes as Indicators of <span class="hlt">Biogeochemical</span> Gradients</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Consideration of processes on very small (microbe) to large (catchment) scales become increasingly important in <span class="hlt">biogeochemical</span> gradient work. In this context, rivers are ideal indicators of <span class="hlt">biogeochemical</span> gradients for large continental scales when geochemical- and discharge data are combined for flux evaluations. If these are further combined with isotope measurements, sources and turnover of water and dissolved constituents can be quantified. An example study is the combination of GIS-, discharge- and water stable isotope data on the in Clyde River basin in Scotland. Here we determined transpiration with an annual average of 0.489 km3 a-1. When combining this rate with the water use efficiency, the CO2 uptake of the entire basin yielded an annual net primary production (NPP) of 185.2 g C m-2. Compared to other temperate areas this is about half the NPP than expected, which is most likely caused by the predominant cover of grasslands. Therefore, agricultural and forest vegetation schemes could influence continental water balances on time scales of years to decades. In another study on the Lagan River in N. Ireland, stable isotope methods were applied to evaluate the role of carbonate versus silicate dissolution. Of these two types of weathering only silicate dissolution withdraws atmospheric CO2 to be stored in the continental crust over long time periods. A downstream evolution with increasing pH- and ?13CDIC values revealed carbonate dissolution despite their minor abundance in the catchment of less than 5 %. This dominant carbonate signal on the riverine carbon cycle outlines the capacity of buffering anthropogenic influences and CO2 turnover. It should be even more pronounced in other rivers where carbonates usually occupy a larger proportion of the basin geology. Future <span class="hlt">biogeochemical</span> gradient work on rivers should apply particulate and dissolved organic constituent fluxes. This includes more refined compound specific isotope work on selected pollutants such as TCE, PAH, PCB as well as riverine microbiological considerations. Such expansions meet the challenge of measuring much smaller concentrations compared to groundwater contaminant plumes. Further combinations of stable N, H, O, and S isotope systems would also help to resolve overlapping trends when only carbon isotopes are measured. Apart from combining traditional light stable isotope systems, addition of newly accessible isotope groups by multicollector ICP-MS (i.e. Fe, Cr, Zn) and radioisotope techniques can provide innovative tools for resolving gradients and their <span class="hlt">biogeochemical</span> cycling within rivers.</p> <div class="credits"> <p class="dwt_author">Barth, J. A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">146</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=554001"> <span id="translatedtitle">Remote analysis of biological invasion and <span class="hlt">biogeochemical</span> change</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">We used airborne imaging spectroscopy and photon transport modeling to determine how biological invasion altered the chemistry of forest canopies across a Hawaiian montane rain forest landscape. The nitrogen-fixing tree Myrica faya doubled canopy nitrogen concentrations and water content as it replaced native forest, whereas the understory herb Hedychium gardnerianum reduced nitrogen concentrations in the forest overstory and substantially increased aboveground water content. This remote sensing approach indicates the geographic extent, intensity, and <span class="hlt">biogeochemical</span> impacts of two distinct invaders; its wider application could enhance the role of remote sensing in ecosystem analysis and management.</p> <div class="credits"> <p class="dwt_author">Asner, Gregory P.; Vitousek, Peter M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">147</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/23968989"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> classification of South Florida's estuarine and coastal waters.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">South Florida's watersheds have endured a century of urban and agricultural development and disruption of their hydrology. Spatial characterization of South Florida's estuarine and coastal waters is important to Everglades' restoration programs. We applied Factor Analysis and Hierarchical Clustering of water quality data in tandem to characterize and spatially subdivide South Florida's coastal and estuarine waters. Segmentation rendered forty-four <span class="hlt">biogeochemically</span> distinct water bodies whose spatial distribution is closely linked to geomorphology, circulation, benthic community pattern, and to water management. This segmentation has been adopted with minor changes by federal and state environmental agencies to derive numeric nutrient criteria. PMID:23968989</p> <div class="credits"> <p class="dwt_author">Briceño, Henry O; Boyer, Joseph N; Castro, Joffre; Harlem, Peter</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-08-19</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">148</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011DSRI...58.1175M"> <span id="translatedtitle">Atmospheric-induced variability of hydrological and <span class="hlt">biogeochemical</span> signatures in the NW Alboran Sea. Consequences for the spawning and nursery habitats of European anchovy</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The north-western Alboran Sea is a highly dynamic region in which the hydrological processes are mainly controlled by the entrance of the Atlantic Jet (AJ) through the Strait of Gibraltar. The biological patterns of the area are also related to this variability in which atmospheric pressure distributions and wind intensity and direction play major roles. In this work, we studied how changes in atmospheric forcing (from high atmospheric pressure over the Mediterranean to low atmospheric pressure) induced alterations in the physical and <span class="hlt">biogeochemical</span> environment by re-activating coastal upwelling on the Spanish shore. The nursery area of European anchovy ( Engraulis encrasicolus) in the NW Alboran Sea, confirmed to be the very coastal band around Malaga Bay, did not show any drastic change in its <span class="hlt">biogeochemical</span> characteristics, indicating that this coastal region is somewhat isolated from the rest of the basin. Our data also suggests that anchovy distribution is tightly <span class="hlt">coupled</span> to the presence of microzooplankton rather than mesozooplankton. Finally, we use detailed physical and biological information to evaluate a hydrological-<span class="hlt">biogeochemical</span> <span class="hlt">coupled</span> model with a specific hydrological configuration to represent the Alboran basin. This model is able to reproduce the general circulation patterns in the region forced by the AJ movements only including two variable external forcings; atmospheric pressure over the western Mediterranean and realistic wind fields.</p> <div class="credits"> <p class="dwt_author">Macías, D.; Catalán, I. A.; Solé, J.; Morales-Nin, B.; Ruiz, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">149</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.H54C..06R"> <span id="translatedtitle">A hybrid continuum-scale model with pore-scale refinements for <span class="hlt">biogeochemical</span> processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Fate and transport of contaminants in aquifers are influenced by geochemical reactions (precipitation/dissolution) and biological activities (biofilm development). If simulations and observations of contaminant behavior are at a large-scale (continuum-scale), processes leading to their degradation occur at a small-scale (pore-scale). In terms of modeling, the complexity of these last processes requires to represent them at their natural scale and to consider computational limitations for large domain simulations. As classical methods for transferring information between scales are not relevant for strongly <span class="hlt">coupled</span> processes, we aim at creating a new modeling approach combining different representation concepts over different sub-domains. The different models run simultaneously over the different sub-domains and are <span class="hlt">coupled</span> at the sub-domains interfaces by defining boundary fluxes for each model. Where <span class="hlt">biogeochemical</span> processes are determinant, a pore-scale representation will be used to describe the involved processes. For the rest of the domain, a continuum representation will be preferred with a level of complexity adapted to the processes characteristics. By optimizing the balance between computational efficiency and representation accuracy, this new approach for modeling contaminant behavior at their trajectory-scale promises the possibility of large domain simulations with an adequate representation of degradation processes.</p> <div class="credits"> <p class="dwt_author">Roubinet, D.; Tartakovsky, D. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">150</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2003AGUFMOS52D..03V"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Investigations of Methane Seepage, Hydrate Ridge, OR.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">During July, 2002 we conducted a series of <span class="hlt">biogeochemical</span> studies at the southern summit of Hydrate Ridge, OR. Using the DSV Alvin we collected sediment push cores from 2 distinct types of seep environments (clam beds and microbial mats) and from control sites (bare sediment). Samples from each setting were analyzed for the depth distributions of microbial abundance, most probable number counts for methanogenic archaea, volatile organic acids, dissolved organic carbon (including ? 13C), total organic carbon (including ? 13C and ? 14C), sulfate, alkalinity (including ? 13C-DIC), ? 13C-CH4, as well as the distribution of bacterial and archaeal 16S rDNA genes. These distributions provide the basis for a comparative analysis of the distinct seep environments and of <span class="hlt">biogeochemical</span> controls on methane hydrate. Primary production in the seeps appears to be driven by anaerobic methane oxidation in the sediments and sulfide oxidation at the sediment-water interface. However, results indicate distinctive microbial habitats in the different seep settings. Results further indicate a vigorous, secondary microbial community living off the wastes of the primary producers. High levels (up to 4%) of 13C-depleted ( ˜-45‰ ) organic carbon in the seeps and high C:N ratios (as high as 50:1) indicate a buildup of CH4-derived organic carbon, and raise the possibility of nitrogen limitation impacting seep communities.</p> <div class="credits"> <p class="dwt_author">Valentine, D. L.; Solem, R. C.; Kastner, M.; Wardlaw, G. D.; Boone, D. R.; Kendall, M.; Wang, X.; Hill, T. M.; Purdy, A.; Bartlett, D. H.</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">151</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/942130"> <span id="translatedtitle"><span class="hlt">BIOGEOCHEMICAL</span> GRADIENTS AS A FRAMEWORK FOR UNDERSTANDING WASTE SITE EVOLUTION</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The migration of <span class="hlt">biogeochemical</span> gradients is a useful framework for understanding the evolution of <span class="hlt">biogeochemical</span> conditions in groundwater at waste sites contaminated with metals and radionuclides. This understanding is critical to selecting sustainable remedies and evaluating sites for monitored natural attenuation, because most attenuation mechanisms are sensitive to geochemical conditions such as pH and redox potential. Knowledge of how gradients in these parameters evolve provides insights into the behavior of contaminants with time and guides characterization, remedy selection, and monitoring efforts. An example is a seepage basin site at the Savannah River Site in South Carolina where low-level acidic waste has seeped into groundwater. The remediation of this site relies, in part, on restoring the natural pH of the aquifer by injecting alkaline solutions. The remediation will continue until the pH up-flow of the treatment zone increases to an acceptable value. The time required to achieve this objective depends on the time it takes the trailing pH gradient, the gradient separating the plume from influxing natural groundwater, to reach the treatment zone. Predictions of this length of time will strongly influence long-term remedial decisions.</p> <div class="credits"> <p class="dwt_author">Denham, M; Karen Vangelas, K</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-10-17</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">152</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFMOS43E..08I"> <span id="translatedtitle">Long-term <span class="hlt">biogeochemical</span> impacts of liming the ocean</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Fossil fuel CO2 emissions result in large-scale long-term perturbations in seawater chemistry. Oceans take up atmospheric CO2, and several geo-engineering approaches have been suggested to mitigate impacts of CO2 emissions and resulting ocean acidification that are based on this property. One of them is to enhance weathering processes to remove atmospheric CO2. This method involves dissolving rocks (i.e. limestone) or adding strong bases (i.e. calcium hydroxide) in the upper ocean and is termed as liming the oceans. The net effect of this approach is to increase ocean alkalinity, thereby increasing the oceanic capacity to store anthropogenic CO2. Another effect of adding alkalinity would be to drive seawater to higher pH values and thus counteract the ongoing ocean acidification. However, whereas adding bases only alter alkalinity of seawater, dissolution of carbonates perturb both, alkalinity and dissolved inorganic carbon budgets. Thus, on longer time scales, these two methods will likely have different <span class="hlt">biogeochemical</span> effects in the ocean. Here we test enduring implications of the two approaches for marine carbon cycle using the global ocean <span class="hlt">biogeochemical</span> model HAMOCC. In our model scenarios we add alkalinity in the amounts proportional to fossil fuel emissions. We compare the long-term effectiveness of the two geo-engineering approaches to decrease atmospheric CO2.</p> <div class="credits"> <p class="dwt_author">Ilyina, T.; Wolf-Gladrow, D.; Munhoven, G.; Heinze, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">153</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/1018157"> <span id="translatedtitle">Subsurface <span class="hlt">Biogeochemical</span> Research FY11 Second Quarter Performance Measure</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The Subsurface <span class="hlt">Biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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).</p> <div class="credits"> <p class="dwt_author">Scheibe, Timothy D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-03-31</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">154</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/896239"> <span id="translatedtitle">Aqueous complexation reactions governing the rate and extent of <span class="hlt">biogeochemical</span> U(VI) reduction</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The proposed research will elucidate the principal <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> reduction of uranium in subsurface environments.</p> <div class="credits"> <p class="dwt_author">Kemner, K.M.; Kelly, S.D.; Brooks, Scott C.; Dong, Wenming; Carroll, Sue; Fredrickson, James K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">155</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/48896612"> <span id="translatedtitle">Scaling hyporheic exchange and its influence on <span class="hlt">biogeochemical</span> reactions in aquatic ecosystems</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Hyporheic exchange and <span class="hlt">biogeochemical</span> reactions are difficult to quantify because of the range in fluid-flow and sediment conditions inherent to streams, wetlands, and nearshore marine ecosystems. Field measurements of <span class="hlt">biogeochemical</span> reactions in aquatic systems are impeded by the difficulty of measuring hyporheic flow simultaneously with chemical gradients in sediments. Simplified models of hyporheic exchange have been developed using Darcy's law</p> <div class="credits"> <p class="dwt_author">Ben L. O'Connor; Judson W. Harvey</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">156</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=163405"> <span id="translatedtitle">INTERACTIVE EFFECTS OF SOLAR UV RADIATION AND CLIMATE CHANGE ON <span class="hlt">BIOGEOCHEMICAL</span> CYCLING</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p class="result-summary">This paper assesses research on the interactions of UV radiation (280-400 nm) and global climate change with global <span class="hlt">biogeochemical</span> cycles at the Earth's surface. The effects of UV-B (280-315 nm), which are dependent on the stratospheric ozone layer, on <span class="hlt">biogeochemical</span> cycles are o...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">157</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/55683613"> <span id="translatedtitle">Effects of Physical and Chemical Heterogeneities on <span class="hlt">Biogeochemical</span> Processes Associated With Uranium Bioremediation at Rifle, Colorado</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Natural porous media are inherently heterogeneous at multiple spatial scales, which can have profound impacts on <span class="hlt">biogeochemical</span> reactions in the subsurface. In this work, we aim to understand the effects of physical and chemical heterogeneities on various <span class="hlt">biogeochemical</span> reaction processes associated with a field- scale uranium bioremediation experiment at Rifle, Colorado. Numerical experiments were designed to mimic the field biostimulation</p> <div class="credits"> <p class="dwt_author">L. Li; C. I. Steefel; M. B. Kowalsky; A. L. Englert; S. S. Hubbard</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">158</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/14607476"> <span id="translatedtitle">Trimethylbenzoic acids as metabolite signatures in the <span class="hlt">biogeochemical</span> evolution of an aquifer contaminated with jet fuel hydrocarbons.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Evolution of trimethylbenzoic acids in the KC-135 aquifer at the former Wurtsmith Air Force Base (WAFB), Oscoda, MI was examined to determine the functionality of trimethylbenzoic acids as key metabolite signatures in the <span class="hlt">biogeochemical</span> evolution of an aquifer contaminated with JP-4 fuel hydrocarbons. Changes in the composition of trimethylbenzoic acids and the distribution and concentration profiles exhibited by 2,4,6- and 2,3,5-trimethylbenzoic acids temporally and between multilevel wells reflect processes indicative of an actively evolving contaminant plume. The concentration levels of trimethylbenzoic acids were 3-10 orders higher than their tetramethylbenzene precursors, a condition attributed to slow metabolite turnover under sulfidogenic conditions. The observed degradation of tetramethylbenzenes into trimethylbenzoic acids obviates the use of these alkylbenzenes as non-labile tracers for other degradable aromatic hydrocarbons, but provides rare field evidence on the range of high molecular weight alkylbenzenes and isomeric assemblages amenable to anaerobic degradation in situ. The <span class="hlt">coupling</span> of actual tetramethylbenzene loss with trimethylbenzoic acid production and the general decline in the concentrations of these compounds demonstrate the role of microbially mediated processes in the natural attenuation of hydrocarbons and may be a key indicator in the overall rate of hydrocarbon degradation and the <span class="hlt">biogeochemical</span> evolution of the KC-135 aquifer. PMID:14607476</p> <div class="credits"> <p class="dwt_author">Namocatcat, J A; Fang, J; Barcelona, M J; Quibuyen, A T O; Abrajano, T A</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">159</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFM.H14B..04E"> <span id="translatedtitle">Investigating Plot and Watershed Scale Hydrologic and <span class="hlt">Biogeochemical</span> Responses</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">While there are numerous water quality studies at either the plot-, field- or watershed-scale, there are very few studies that integrate the hydrologic and <span class="hlt">biogeochemical</span> responses across scales. A review of the literature reveals seemingly contradictory responses at the plot and watershed scales, e.g., in some cases pollutant concentrations decrease with increasing discharge at plot scales but increase with discharge at watershed scales. We investigate the <span class="hlt">biogeochemical</span> responses of several plots and at a watershed outlet in a small mixed-use watershed in New York State. Runoff plots established along a gradient in topographic position and land use types distributed throughout the watershed were monitored for a seven year period and runoff, dissolved and particulate phosphorus (DP and PP, respectively) and sediment (TSS) were collected from storm 213 events. Flow, sediment, and phosphorus (P) were also measured at the watershed outlet for the same period and events. The watershed outlet response for DP, PP and sediment were characterized by a linear increases in concentration [mg/L] with increasing runoff [mm] (DP = 0.002(runoff) + 0.019, PP = 0.006(runoff) +0.006, and TSS = 1.055(runoff) + 2.389) while plot scale responses for DP, PP and TSS showed decreasing concentrations with increasing runoff losses. The specific runoff-concentration relationships varied but were generally characterized by a negative power-function-type decline with increasing runoff, although some landcover types (fertilized lawns) and constituents (esp. DP) exhibited more linear declines with increasing runoff, presumably a result of greater easily transported P at the soil surface. These plot scale results show the classical first flush response typical of bound pollutants (DP, PP, TSS), while the watershed clearly exhibits a concentrating effect with higher flows. However, these seemingly contradictory responses can be explained by considering the hydrologic spatio-temporal variability in the watershed. Plots located in hydrologically active areas, which produce more frequent and greater quantities of runoff with generally smaller average concentrations, explain the small runoff events with smaller concentrations at the watershed scale; areas with few runoff events and smaller runoff volumes with generally greater average concentrations were associated with large runoff events and correspond to higher concentrations at the watershed scale. These results show that the hydrologic and <span class="hlt">biogeochemical</span> response can vary substantially at various scales, but are in fact related. This points towards a more parsimonious, accurate means of initializing watershed models and increasing their applicability by combining field monitoring with modeling in non-traditional ways.</p> <div class="credits"> <p class="dwt_author">Easton, Z. M.; Walter, M. T.; Steenhuis, T. S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">160</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/1033841"> <span id="translatedtitle">Variably Saturated Flow and Multicomponent <span class="hlt">Biogeochemical</span> Reactive Transport Modeling of a Uranium Bioremediation Field Experiment</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Field experiments at a former uranium mill tailings site have identified the potential for stimulating indigenous bacteria to catalyze the conversion of aqueous uranium in the +6 oxidation state to immobile solid-associated uranium in the +4 oxidation state. This effectively removes uranium from solution resulting in groundwater concentrations below actionable standards. Three-dimensional, <span class="hlt">coupled</span> variably-saturated flow and <span class="hlt">biogeochemical</span> reactive transport modeling of a 2008 in situ uranium bioremediation field experiment is used to better understand the interplay of transport rates and <span class="hlt">biogeochemical</span> reaction rates that determine the location and magnitude of key reaction products. A comprehensive reaction network, developed largely through previous 1-D modeling studies, was used to simulate the impacts on uranium behavior of pulsed acetate amendment, seasonal water table variation, spatially-variable physical (hydraulic conductivity, porosity) and geochemical (reactive surface area) material properties. A principal challenge is the mechanistic representation of biologically-mediated terminal electron acceptor process (TEAP) reactions whose products significantly alter geochemical controls on uranium mobility through increases in pH, alkalinity, exchangeable cations, and highly reactive reduction products. In general, these simulations of the 2008 Big Rusty acetate biostimulation field experiment in Rifle, Colorado confirmed previously identified behaviors including (1) initial dominance by iron reducing bacteria that concomitantly reduce aqueous U(VI), (2) sulfate reducing bacteria that become dominant after {approx}30 days and outcompete iron reducers for the acetate electron donor, (3) continuing iron-reducer activity and U(VI) bioreduction during dominantly sulfate reducing conditions, and (4) lower apparent U(VI) removal from groundwater during dominantly sulfate reducing conditions. New knowledge on simultaneously active metal and sulfate reducers has been 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 <span class="hlt">coupled</span> process models for multiple <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">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.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-11-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_7");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" 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onClick='return showDiv("page_6");' href="#">6</a> <a onClick='return showDiv("page_7");' href="#">7</a> <a onClick='return showDiv("page_8");' href="#">8</a> <a style="font-weight: bold;">9</a> <a onClick='return showDiv("page_10");' href="#">10</a> <a onClick='return showDiv("page_11");' href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_10");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">161</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010NatGe...3..675B"> <span id="translatedtitle">The <span class="hlt">biogeochemical</span> cycle of iron in the ocean</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Advances in iron biogeochemistry have transformed our understanding of the oceanic iron cycle over the past three decades: multiple sources of iron to the ocean were discovered, including dust, coastal and shallow sediments, sea ice and hydrothermal fluids. This new iron is rapidly recycled in the upper ocean by a range of organisms; up to 50% of the total soluble iron pool is turned over weekly in this way in some ocean regions. For example, bacteria dissolve particulate iron and at the same time release compounds - iron-binding ligands - that complex with iron and therefore help to keep it in solution. Sinking particles, on the other hand, also scavenge iron from solution. The balance between these supply and removal processes determines the concentration of dissolved iron in the ocean. Whether this balance, and many other facets of the <span class="hlt">biogeochemical</span> cycle, will change as the climate warms remains to be seen.</p> <div class="credits"> <p class="dwt_author">Boyd, P. W.; Ellwood, M. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-10-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">162</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70042424"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> evolution of a landfill leachate plume, Norman, Oklahoma</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">Leachate from municipal landfills can create groundwater contaminant plumes that may last for decades to centuries. The fate of reactive contaminants in leachate-affected aquifers depends on the sustainability of <span class="hlt">biogeochemical</span> processes affecting contaminant transport. Temporal variations in the configuration of redox zones downgradient from the Norman Landfill were studied for more than a decade. The leachate plume contained elevated concentrations of nonvolatile dissolved organic carbon (NVDOC) (up to 300 mg/L), methane (16 mg/L), ammonium (650 mg/L as N), iron (23 mg/L), chloride (1030 mg/L), and bicarbonate (4270 mg/L). Chemical and isotopic investigations along a 2D plume transect revealed consumption of solid and aqueous electron acceptors in the aquifer, depleting the natural attenuation capacity. Despite the relative recalcitrance of NVDOC to biodegradation, the center of the plume was depleted in sulfate, which reduces the long-term oxidation capacity of the leachate-affected aquifer. Ammonium and methane were attenuated in the aquifer relative to chloride by different processes: ammonium transport was retarded mainly by physical interaction with aquifer solids, whereas the methane plume was truncated largely by oxidation. Studies near plume boundaries revealed temporal variability in constituent concentrations related in part to hydrologic changes at various time scales. The upper boundary of the plume was a particularly active location where redox reactions responded to recharge events and seasonal water-table fluctuations. Accurately describing the <span class="hlt">biogeochemical</span> processes that affect the transport of contaminants in this landfill-leachate-affected aquifer required understanding the aquifer's geologic and hydrodynamic framework.</p> <div class="credits"> <p class="dwt_author">Isabelle M Cozzarelli;Johnkarl F Bohlke;Jason R Masoner;George N Breit;Michelle M Lorah;Michele L Tuttle;Jeanne B Jaeschke</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">163</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/22926879"> <span id="translatedtitle">Impact of climate change on ecological quality indicators and <span class="hlt">biogeochemical</span> fluxes in the Baltic sea: a multi-model ensemble study.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Multi-model ensemble simulations using three <span class="hlt">coupled</span> physical-<span class="hlt">biogeochemical</span> models were performed to calculate the combined impact of projected future climate change and plausible nutrient load changes on <span class="hlt">biogeochemical</span> cycles in the Baltic Sea. Climate projections for 1961-2099 were combined with four nutrient load scenarios ranging from a pessimistic business-as-usual to a more optimistic case following the Helsinki Commission's (HELCOM) Baltic Sea Action Plan (BSAP). The model results suggest that in a future climate, water quality, characterized by ecological quality indicators like winter nutrient, summer bottom oxygen, and annual mean phytoplankton concentrations as well as annual mean Secchi depth (water transparency), will be deteriorated compared to present conditions. In case of nutrient load reductions required by the BSAP, water quality is only slightly improved. Based on the analysis of <span class="hlt">biogeochemical</span> fluxes, we find that in warmer and more anoxic waters, internal feedbacks could be reinforced. Increased phosphorus fluxes out of the sediments, reduced denitrification efficiency and increased nitrogen fixation may partly counteract nutrient load abatement strategies. PMID:22926879</p> <div class="credits"> <p class="dwt_author">Meier, H E Markus; Müller-Karulis, Bärbel; Andersson, Helén C; Dieterich, Christian; Eilola, Kari; Gustafsson, Bo G; Höglund, Anders; Hordoir, Robinson; Kuznetsov, Ivan; Neumann, Thomas; Ranjbar, Zohreh; Savchuk, Oleg P; Schimanke, Semjon</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">164</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011CRGeo.343..261B"> <span id="translatedtitle">Factors driving the <span class="hlt">biogeochemical</span> budget of the Amazon River and its statistical modelling</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The seasonal and interannual fluctuations of the <span class="hlt">biogeochemical</span> budget (solutes, suspended matter, isotopes) of the Amazon River basin were analyzed, with a special focus on 44 physicochemical parameters monitored over the period 1982-1984 during the Carbon in the AMazon River Experiment (CAMREX) project. The relevant factors driving this variability were identified and sorted through the implementation of a statistical-regressive model <span class="hlt">coupled</span> to variance analysis. Basically, the compositional fluctuations in the Amazon River are related (1) to the variable contribution of major tributaries (variable regional source) to the river flow but also (2) to the variable contribution of hydrological sources, (3) to river processes, i.e. in-stream diagenesis and sediment dynamics and (4) to the hydrological budget of the floodplains. Their respective contributions to the variability of chemical signals observed in the stream waters depend on which parameter was investigated but their combination explains on average 85% of the observed variability. The variability related to regional sources was captured by the compared measures of flow discharge and <span class="hlt">biogeochemical</span> fluxes at the outlet of the major tributaries. The variability of hydrological sources was described by the variable contribution of three runoffs of distinct but constant composition: forwarded direct runoff, delayed floodplain runoff and baseflow. Several methods were tested to depict the seasonal and interannual variations of their individual discharges. Biologically-mediated processes were related to a hydrobiological index IBIO = [O 2]-[CO 2] which allows tracking the nature of the dominant ecological regime (autotrophy vs. heterotrophy). The alteration of chemical signals related to the intermittent discharge of the floodplains (where specific processes occur such as: gas exchanges at the air-water interface, sorption of dissolved organic matter, chemical weathering, deposition vs. remobilization of sediments, etc.) was simulated by taking into account the default of hydrological balance between inflows and outflows, used as a marker of floodplains discharge. This analysis shows that the chemical baseline observed in the waters of the Amazon River is mostly acquired upstream from the junction of major tributaries with the Amazon main reach.</p> <div class="credits"> <p class="dwt_author">Bustillo, Vincent; Victoria, Reynaldo Luiz; Moura, Jose Mauro Sousa de; Victoria, Daniel de Castro; Toledo, Andre Marcondes Andrade; Collicchio, Erich</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">165</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/895942"> <span id="translatedtitle">Aqueous Complexation Reactions Governing the Rate and Extent of <span class="hlt">Biogeochemical</span> U(VI) Reduction</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The proposed research will elucidate the principal <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Scott C. Brooks; Wenming Dong; Sue Carroll; Jim Fredrickson; Ken Kemner; Shelly Kelly</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-06-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">166</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/896202"> <span id="translatedtitle">Aqueous Complexation Reactions Governing the Rate and Extent of <span class="hlt">Biogeochemical</span> U(VI) Reduction</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The proposed research will elucidate the principal <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Scott C. Brooks; Wenming Dong; Sue Carroll; James K. Fredrickson; Kenneth M. Kemner; Shelly D. Kelly</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">167</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012BGD.....9.8733B"> <span id="translatedtitle">Nutrient dynamics, transfer and retention along the aquatic continuum from land to ocean: towards integration of ecological and <span class="hlt">biogeochemical</span> models</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In river basins, soils, groundwater, riparian zones, streams, rivers, lakes and reservoirs act as successive filters in which the hydrology, ecology and <span class="hlt">biogeochemical</span> processing are strongly <span class="hlt">coupled</span> and together act to retain a significant fraction of the nutrients transported. This paper compares existing river ecology concepts with current approaches to describe river biogeochemistry, and assesses the value of these concepts and approaches for understanding the impacts of interacting global change disturbances on river biogeochemistry. Through merging perspectives, concepts, modeling techniques, we propose integrated model approaches that encompass both aquatic and terrestrial components in heterogeneous landscapes. In this model framework, existing ecological and biogeochemistry concepts are extended with a balanced approach for assessing nutrient and sediment delivery on the one hand, and nutrient in-stream retention on the other hand.</p> <div class="credits"> <p class="dwt_author">Bouwman, A. F.; Bierkens, M. F. P.; Griffioen, J.; Hefting, M. M.; Middelburg, J. J.; Middelkoop, H.; Slomp, C. P.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-07-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">168</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2002ECSS...55..857T"> <span id="translatedtitle">Suspended Particles: Their Role in Estuarine <span class="hlt">Biogeochemical</span> Cycles</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Suspended particles are instrumental in controlling the reactivity, transport and biological impacts of substances in aquatic environments, and provide a crucial link for chemical constituents between the water column, bed sediment and food chain. This article reviews the role of suspended particles in the chemical and biological cycling of trace constituents (trace metals, organo-metallic compounds and hydrophobic organic micropollutants; HOMs) in estuaries, with particular emphasis on the effects of and changes to particle reactivity and composition. The partitioning (or distribution coefficient, KD ) and bioavailability of chemical constituents, and assimilation efficiency (AE) of such by bivalve suspension feeders, are identified as key parameters requiring definition for accurate <span class="hlt">biogeochemical</span> modelling, and the discussion centres around the determination of and controls on these parameters. Particle-water interactions encompass a variety of physical, biological, electrostatic and hydrophobic effects, and are largely dependent on the character and concentration of suspended particles and salinity. The salinity-dependence results from the competing and complexing effects of seawater ions for trace metals, and the compression of water in the presence of dissolved seawater ions and consequent salting out of neutral solute (HOMs, organo-metallic compounds and some trace metal complexes). The extent of biological solubilization of chemical constituents from suspended particles is dependent on the nature of chemical components of the gastro-intestinal environment and their interactions with ingested particles, and the physiological (e.g. gut passage time) and chemical (e.g. redox conditions and pH) constraints imposed on these interactions. Generally, chemicals that associate with fine, organic-rich particles (or, for some HOMs, fine inorganic particles), and desorb at pH 5-6 and/or complex with digestive enzymes or surfactants are most readily solubilized in the gut. The extent of assimilation of solubilized chemical is then determined by its ability to pass the gut lining and partition into cytosolic material. In practice, KD and AE are determined experimentally by means of radiotracers added to contained suspensions or mesocosms, while operational measurement of bioavailability relies on in vitro chemical or biological (enzymatic) extraction of particles. What is lacking, however, and is identified as an ultimate goal of future research, is the ability to predict these parameters from theoretical principles and thermodynamic constants. Since many of the inherent interactions and mechanisms are controlled by particle composition and reactivity, a more immediate objective would be better characterization of the <span class="hlt">biogeochemical</span> properties of suspended particles themselves. This includes chemical resolution of the bulk organic matter, definition of the abundance and synergistic effects of component sorbent phases, and determination of the effects of particle-seawater ion interactions on the reactivity of the particle surface.</p> <div class="credits"> <p class="dwt_author">Turner, A.; Millward, G. E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2002-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">169</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/16996577"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> value of managed realignment, Humber estuary, UK.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">We outline a plausible, albeit extreme, managed realignment scenario ('Extended Deep Green' scenario) for a large UK estuary to demonstrate the maximum possible <span class="hlt">biogeochemical</span> effects and economic outcomes of estuarine management decisions. Our interdisciplinary approach aims to better inform the policy process, by combining <span class="hlt">biogeochemical</span> and socioeconomic components of managed realignment schemes. Adding 7494 ha of new intertidal area to the UK Humber estuary through managed realignment leads to the annual accumulation of a 1.2 x 10(5) t of 'new' sediment and increases the current annual sink of organic C and N, and particle reactive P in the estuary by 150%, 83% and 50%, respectively. The increase in intertidal area should also increase denitrification. However, this positive outcome is offset by the negative effect of enhanced greenhouse gas emissions in new marshes in the low salinity region of the estuary. Short-term microbial reactions decrease the potential benefits of CO(2) sequestration through gross organic carbon burial by at least 50%. Net carbon storage is thus most effective where oxidation and denitrification reactions are reduced. In the Humber this translates to wet, saline marshes at the seaward end of estuaries. Cost-benefit analysis (CBA) was used to determine the economic efficiency of the Extended Deep Green managed realignment. When compared to a 'Hold-the-Line' future scenario, i.e. the present state/extent of sea defences in the estuary, the CBA shows that managed realignment is cost effective when viewed on >25 year timescales. This is because capital costs are incurred in the first years, whereas the benefits from habitat creation, carbon sequestration and reduced maintenance costs build up over time. Over 50- and 100-year timescales, the Extended Deep Green managed realignment scenario is superior in efficiency terms. The increased sediment accumulation is also likely to enhance storage of contaminant metals. In the case of Cu, a metal that currently causes significant water quality issues, Cu removal due to burial of suspended sediment in realigned areas translates to a value of approximately pounds sterling 1000 a(-1) (avoided clean up costs). Although this is not formally included in the CBA it illustrates another likely positive economic outcome of managed realignment. Although we focus on the Humber, the history of reclamation and its biogeochemistry is common to many estuaries in northern Europe. PMID:16996577</p> <div class="credits"> <p class="dwt_author">Andrews, J E; Burgess, D; Cave, R R; Coombes, E G; Jickells, T D; Parkes, D J; Turner, R K</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-09-25</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">170</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=67340"> <span id="translatedtitle">SEASONAL VARIATION IN THE <span class="hlt">BIOGEOCHEMICAL</span> CYCLING OF SESTON IN GRAND TRAVERSE BAY, LAKE MICHIGAN. (R825151)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p class="result-summary">This study describes the <span class="hlt">biogeochemical</span> cycling of seston in Grand Traverse Bay, Lake Michigan. Seston was characterized by carbon and nitrogen elemental and isotopic abundances. Fluorescence, temperature, light transmittance, and concentrations of dissolved inorganic nitrogen we...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">171</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=DE96743142"> <span id="translatedtitle">Possible impacts of global warming on tundra and boreal forest ecosystems - comparison of some <span class="hlt">biogeochemical</span> models.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">Global warming affects the magnitude of carbon, water, and nitrogen fluxes between biosphere and atmosphere as well as the distribution of vegetation types. <span class="hlt">Biogeochemical</span> models, global as well as patch models, can be used to estimate the differences bet...</p> <div class="credits"> <p class="dwt_author">M. Ploechl W. Cramer</p> <p class="dwt_publisher"></p> <p class="publishDate">1995-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">172</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=ADA529172"> <span id="translatedtitle">Generic Reaction-Based <span class="hlt">BioGeoChemical</span> Simulator (RBBGCS), Version 1.0.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">This report presents a generic reaction-based <span class="hlt">biogeochemical</span> simulator (RBBGCS) that was developed as part of the advancement of the subsurface reactive transport capability in the Adaptive Hydrology/Hydraulics (ADH) model. RBBGCS has been incorporated in...</p> <div class="credits"> <p class="dwt_author">C. J. McGrath H. Cheng J. C. Cheng M. W. Farthing S. E. Howington</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">173</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=N20070027283"> <span id="translatedtitle">Comprehensive Plan for the Long-Term Calibration and Validation of Oceanic <span class="hlt">Biogeochemical</span> Satellite Data.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">The primary objective of this planning document is to establish a long-term capability and validating oceanic <span class="hlt">biogeochemical</span> satellite data. It is a pragmatic solution to a practical problem based primarily o the lessons learned from prior satellite missi...</p> <div class="credits"> <p class="dwt_author">A. Mannino C. R. McClain S. B. Hooker</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">174</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=182865"> <span id="translatedtitle">CALIBRATION OF SUBSURFACE BATCH AND REACTIVE-TRANSPORT MODELS INVOLVING COMPLEX <span class="hlt">BIOGEOCHEMICAL</span> PROCESSES</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p class="result-summary">In this study, the calibration of subsurface batch and reactive-transport models involving complex <span class="hlt">biogeochemical</span> processes was systematically evaluated. Two hypothetical nitrate biodegradation scenarios were developed and simulated in numerical experiments to evaluate the perfor...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">175</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=DE93003464"> <span id="translatedtitle">Terrestrial <span class="hlt">biogeochemical</span> cycling and vegetation response to climate in an earth system model.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">We are developing (1) a seasonal model of terrestrial productivity and <span class="hlt">biogeochemical</span> cycling (TERRA) and (2) a model of vegetation response to climate (HABITAT). Both of these models are designed to be components of an Earth System Model being developed ...</p> <div class="credits"> <p class="dwt_author">J. R. Kercher M. C. Axelrod M. C. MacCracken J. Q. Chambers</p> <p class="dwt_publisher"></p> <p class="publishDate">1992-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">176</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFM.B31E0348B"> <span id="translatedtitle">Quantifying the effects of mountain pine beetle infestation on water and <span class="hlt">biogeochemical</span> cycles at multiple spatial and temporal scales</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Unprecedented levels of bark beetle infestation over the last decade have radically altered forest structure across millions of hectares of Western U.S. montane environments. The widespread extent of this disturbance presents a major challenge for governments and resource managers who lack a predictive understanding of how water and <span class="hlt">biogeochemical</span> cycles will respond to this disturbance over various temporal and spatial scales. There is a widespread perception, largely based on hydrological responses to fire or logging, that a reduction in both transpiration and interception following tree death will increase soil water availability and catchment water yield. However, few studies have directly addressed the effects of insect-induced forest decline on water and <span class="hlt">biogeochemical</span> cycling. We address this knowledge gap using observations and modeling at scales from 100 to 109 m2 across study sites in CO and WY that vary in the intensity and timing of beetle infestation and tree death. Our focus on multiple sites with different levels of impact allows us to address two broad, organizing questions: How do changes in vegetation structure associated with MPB alter the partitioning of energy and water? And How do these changes in energy and water availability affect local to regional scale water and <span class="hlt">biogeochemical</span> cycles? This presentation will focus primarily on energy balance and water partitioning, providing context for ongoing <span class="hlt">biogeochemical</span> work. During the growing season, stand-scale transpiration declines rapidly and soil moisture increases following infestation, consistent with streamflow data from regional catchments that shows an increase in baseflow following widespread attack. During the winter and spring, stand scale snow surveys and continuous snow depth sensors suggested that the variability in snow cover decreased as the severity of beetle impact increases, but there were no significant stand-scale differences in snow depth among levels of impact. This is due both to an increase in snow under the canopies of dead trees and a decrease in snow cover in canopy gaps. For example, mean snow depth under the canopy was 86cm (CV 0.02) in unimpacted sites and 95cm (CV 0.05) in heavily impacted sites. In canopy gaps however, mean snow depth was 117cm (CV 0.11) in unimpacted sites but only 93cm (CV 0.07) in heavily impacted sites. At the watershed scale, bark beetle infestation was more likely to decrease the amount of both snowmelt and annual runoff, suggesting that the opening of the canopy increases sublimation and evaporation of the snow cover. These data suggest that the disturbance due to bark beetle infestation is both quantitatively and qualitatively different than either fire or logging. Using these observations, we develop a conceptual model for evaluating how biotic and abiotic processes <span class="hlt">couple</span> water and <span class="hlt">biogeochemical</span> cycles in forest ecosystems.</p> <div class="credits"> <p class="dwt_author">Brooks, P. D.; Harpold, A. A.; Somor, A. J.; Troch, P. A.; Gochis, D. J.; Ewers, B. E.; Pendall, E.; Biederman, J. A.; Reed, D.; Barnard, H. R.; Whitehouse, F.; Aston, T.; Borkhuu, B.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">177</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/52304328"> <span id="translatedtitle">Study of the Tagus estuarine plume using <span class="hlt">coupled</span> hydro and <span class="hlt">biogeochemical</span> models</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Plumes of buoyant water produced by inflow from rivers and estuaries are common on the continental shelf. Buoyancy associated with estuarine waters is a key mediating factor in the transport and transformation of dissolved and particulate materials in coastal margins. The offshore displacement of the plume is influenced greatly by the local alongshore wind, which will tend to advect the</p> <div class="credits"> <p class="dwt_author">Nuno Vaz; Paulo C. Leitão; Manuela Juliano; Marcos Mateus; João. Miguel Dias; Ramiro Neves</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">178</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ocw.um.es/ciencias/ecologia/ejercicios-proyectos-y-casos-1/dahm-03.pdf"> <span id="translatedtitle"><span class="hlt">Coupled</span> <span class="hlt">biogeochemical</span> and hydrological responses of streams and rivers to drought</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">SUMMARY 1. Severe or extreme droughts occurred about 10% of the time over a 105-year record from central New Mexico, U.S.A., based on the Palmer Drought Severity Index. 2. Drought lowers water tables, creating extensive areas of groundwater recharge and fragmenting reaches of streams and rivers. Deeper groundwater inputs predominate as sources of surface flows during drought. Nutrient inputs to</p> <div class="credits"> <p class="dwt_author">CLIFFORD N. D AHM; M ICHELLE A. B AKER; DOUGLAS I. M OORE; J AMES R. T HIBAULT</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">179</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008CorRe..27..123W"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> responses following coral mass spawning on the Great Barrier Reef: pelagic-benthic <span class="hlt">coupling</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">This study quantified how the pulse of organic matter from the release of coral gametes triggered a chain of pelagic and benthic processes during an annual mass spawning event on the Australian Great Barrier Reef. Particulate organic matter (POM) concentrations in reef waters increased by threefold to 11-fold the day after spawning and resulted in a stimulation of pelagic oxygen consumption rates that lasted for at least 1 week. Water column microbial communities degraded the organic carbon of gametes of the broadcast-spawning coral Acropora millepora at a rate of >15% h-1, which is about three times faster than the degradation rate measured for larvae of the brooding coral Stylophora pistillata. Stable isotope signatures of POM in the water column reflected the fast transfer of organic matter from coral gametes into higher levels of the food chain, and the amount of POM reaching the seafloor immediately increased after coral spawning and then tailed-off in the next 2 weeks. Short-lasting phytoplankton blooms developed within a few days after the spawning event, indicating a prompt recycling of nutrients released through the degradation of spawning products. These data show the profound effects of coral mass spawning on the reef community and demonstrate the tight recycling of nutrients in this oligotrophic ecosystem.</p> <div class="credits"> <p class="dwt_author">Wild, C.; Jantzen, C.; Struck, U.; Hoegh-Guldberg, O.; Huettel, M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">180</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/42027382"> <span id="translatedtitle">A state-space Bayesian framework for estimating <span class="hlt">biogeochemical</span> transformations using time-lapse geophysical data</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We develop a state-space Bayesian framework to combine time-lapse geophysical data with other types of information for quantitative estimation of <span class="hlt">biogeochemical</span> parameters during bioremediation. We consider characteristics of end products of <span class="hlt">biogeochemical</span> transformations as state vectors, which evolve under constraints of local environments through evolution equations, and consider time-lapse geophysical data as available observations, which could be linked to the</p> <div class="credits"> <p class="dwt_author">Jinsong Chen; Susan S. Hubbard; Kenneth H. Williams; Steve Pride; Li Li; Carl Steefel; Lee Slater</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_8");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> 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onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_11");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">181</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/52926091"> <span id="translatedtitle">A new InterRidge Working Group : <span class="hlt">Biogeochemical</span> Interactions at Deep-sea Vents</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A new Working Group on `<span class="hlt">Biogeochemical</span> Interactions at deep-sea vents' has been created at the initiative of the InterRidge programme. This interdisciplinary group comprises experts in chemistry, geochemistry, biogeochemistry, and microbial ecology addressing questions of <span class="hlt">biogeochemical</span> interactions in different MOR and BAB environments. The past decade has raised major issues concerning the interactions between biotic and abiotic compartments of deep-sea</p> <div class="credits"> <p class="dwt_author">N. Le Bris; A. Boetius; M. K. Tivey; G. W. Luther; C. R. German; F. Wenzhoefer; J. Charlou; W. E. Seyfried; D. Fortin; G. Ferris; K. Takai; J. A. Baross</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">182</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008AGUFM.H11B0747K"> <span id="translatedtitle">Effect of Vertical Flow Exchange on <span class="hlt">Biogeochemical</span> Processes in Hyporheic Zones</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary"><span class="hlt">Biogeochemical</span> processes in hyporheic zones are of great interest because they make the hyporheic zones highly productive and complex environments. When contaminants or polluted water pass through hyporheic zones, in particular, <span class="hlt">biogeochemical</span> processes play an important role in removing contaminants or attenuating contamination under certain conditions. The study site, a reach of Munsan stream (Paju-si, South Korea), exhibits severe contamination of surface water by nitrate released from Water Treatment Plant (WTP) nearby. The objectives of this study are to investigate the hydrologic and <span class="hlt">biogeochemical</span> processes at the riparian area of the site which may contribute to natural attenuation of surface water driven nitrate, and analyze the effect of vertical (hyporheic) flow exchange on the <span class="hlt">biogeochemical</span> processes in the area. To examine hydraulic mixing or dilution processes, vertical hydraulic gradients were measured at several depth levels using minipiezometers, and then soil temperatures were measured by using i-buttons installed inside the minipiezometers. The microbial analyses by means of polymerase chain reaction (PCR)-cloning methods were also done in order to identify the denitrification process in soil samples. In addition, correlation between vertical flow exchange, temperature data, and denitrifying bacteria activity was also investigated so as to examine the effects on one another. The results showed that there were significant effects of vertical flow exchange and hyporheic soil temperature on the <span class="hlt">biogeochemical</span> processes of the site. This study found strong support for the idea that the <span class="hlt">biogeochemical</span> function of hyporheic zone is a predictable outcome of the interaction between microbial activity and flow exchange.</p> <div class="credits"> <p class="dwt_author">Kim, H.; Lee, S.; Shin, D.; Hyun, Y.; Lee, K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">183</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.sciencedirect.com/science/article/pii/S0009254110002962@displayLabeldoi@noteDIGITAL+OBJECT+IDENTIFIER#texthttp://dx.doi.org/10.1038/286118a0"> <span id="translatedtitle">Diel <span class="hlt">biogeochemical</span> processes and their effect on the aqueous chemistry of streams: A review</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">This review summarizes <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> cycles are interrelated because the cyclical variations produced by one <span class="hlt">biogeochemical</span> process commonly affect another. Thus, understanding <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Nimick, David A.; Gammons, Christopher H.; Parker, Stephen R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">184</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2002EGSGA..27.3603G"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Functionality of A Restored Wetland (basque Country, Spain).</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Wetlands in the quaternary aquifer of Vitoria-Gasteiz have tended to disappear due to changes in the land uses and agriculture intensification. Recent actions to restore natural spaces in the peri-urban area have led to its restoration by closing main ditches and the resulting elevation of the piezometric level. This is the case of the Zurbano's wetland. This restoration allows its <span class="hlt">biogeochemical</span> function in the reduction of nitrate from water to be show. NO3- contents are higher than 50 mg/l in groundwater enter- ing into the wetland and less than 10 mg/l in their way out. Conditions near wetland are favourable to denitrification: dissolved oxygen less than 1 mg/l and COD higher than 3 mg/l in groundwater, very low hydraulic gradients, organic matter rich soil and clay presence allow a local semiconfined flow. Nitrate content of Alegria River is in- fluenced by the discharge of the wetland, decreasing NO3- contents when discharge is high.</p> <div class="credits"> <p class="dwt_author">García, C.; Martínez, M.; Antigüedad, I.; Sánchez, J. M.; Aizpurua, A.</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">185</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/22318304"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> conditions determine virulence of black band disease in corals.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The microenvironmental dynamics of the microbial mat of black band disease (BBD) and its less virulent precursor, cyanobacterial patch (CP), were extensively profiled using microsensors under different light intensities with respect to O(2), pH and H(2)S. BBD mats exhibited vertical stratification into an upper phototrophic and lower anoxic and sulphidic zone. At the progression front of BBD lesions, high sulphide levels up to 4977??M were measured in darkness along with lower than ambient levels of pH (7.43±0.20). At the base of the coral-BBD microbial mat, conditions were hypoxic or anoxic depending on light intensity exposure. In contrast, CP mats did not exhibit strong microchemical stratification with mostly supersaturated oxygen conditions throughout the mats at all light intensities and with levels of pH generally higher than in BBD. Two of three replicate CP mats were devoid of sulphide, while the third replicate showed only low levels of sulphide (up to 42??M) present in darkness and at intermediate light levels. The level of oxygenation and sulphide correlated well with lesion migration rates, that is virulence of the mats, which were greater in BBD than in CP. The results suggest that <span class="hlt">biogeochemical</span> microgradients of BBD shaped by the complex microbial community, rather than a defined pathogen, are the major trigger for high virulence and the associated derived coral mortality of this disease. PMID:22318304</p> <div class="credits"> <p class="dwt_author">Glas, Martin S; Sato, Yui; Ulstrup, Karin E; Bourne, David G</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-02-09</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">186</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/23824266"> <span id="translatedtitle">Biovolatilisation: a poorly studied pathway of the arsenic <span class="hlt">biogeochemical</span> cycle.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">It has been known for over a hundred years that microorganisms can produce volatile arsenic (As) species, termed "arsines". However, this topic has received relatively little attention compared to As behaviour in soils and biotransformation through the trophic level in the marine and terrestrial environment. We believe this is due to long-standing misconceptions regarding volatile As stability and transport as well as an absence, until recently, of appropriate sampling methods. First and foremost, an attempt is made to unify arsines' designations, notations and formulas, taking into account all the different terms used in the literature. Then, the stability of As volatile species is discussed and new analytical developments are explored. Further, the special cases of diffuse low-level emissions (e.g. soil and sediment biovolatilisation), and point sources with high-level emissions (geothermal environments, landfills, and natural gas) are comprehensively reviewed. In each case, future possible areas of research and unknown mechanisms are identified and their importance towards the global As <span class="hlt">biogeochemical</span> cycle is explored. This review gathers new information regarding mechanisms, stability, transport and sampling of the very elusive arsines and shows that more research should be conducted on this important process. PMID:23824266</p> <div class="credits"> <p class="dwt_author">Mestrot, Adrien; Planer-Friedrich, Britta; Feldmann, Jörg</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">187</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/18721996"> <span id="translatedtitle">Nitrate attenuation in groundwater: a review of <span class="hlt">biogeochemical</span> controlling processes.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary"><span class="hlt">Biogeochemical</span> 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. PMID:18721996</p> <div class="credits"> <p class="dwt_author">Rivett, Michael O; Buss, Stephen R; Morgan, Philip; Smith, Jonathan W N; Bemment, Chrystina D</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-07-23</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">188</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008AGUFM.B33A0391M"> <span id="translatedtitle">Applications of Geostatistics to Data Assimilation in <span class="hlt">Biogeochemical</span> Models</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The field of geostatistics offers a rich set of tools for analyzing parameters that display spatial and/or temporal autocorrelation. Historically, these methods have been used primarily for interpolating sparse measurements of in situ data. More recently, however, methods based on geostatistical framework have used in an increasing numbers of areas of earth science. This presentation will discuss a number of recent developments in geostatistics relevant to data assimilation in <span class="hlt">biogeochemical</span> models. The overall goal of the presentation is to emphasize the need to explicitly account for spatial and temporal covariance in sampled data, and the need to translate available data between relevant spatial and temporal scales. The emphasis will be on presenting a common framework that can be used to develop problem-specific approaches. The presented examples will include (i) the identification of environmental parameters controlling observed variability in eddy covariance flux measurements, (ii) downscaling and upscaling observed spatial variability across spatial scales, (iii) geostatistical inverse modeling for constraining carbon fluxes at fine spatial resolutions, and (iv) merging of flux data and atmospheric concentration measurements for constraining parameters in biospheric models.</p> <div class="credits"> <p class="dwt_author">Michalak, A. M.; Mueller, K. L.; Yadav, V.; Alkhaled, A. A.; Zhou, Y.; Gourdji, S. M.; Huntzinger, D. N.; Hirsch, A. I.; Andrews, A. E.; Wofsy, S. C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">189</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/895281"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Processes Controlling Microbial Reductive Precipitation of Radionuclides</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">This project is focused on elucidating the principal <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Fredrickson, James K.; Brooks, Scott C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-03-17</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">190</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/17593723"> <span id="translatedtitle">In-stream <span class="hlt">biogeochemical</span> processes of a temporary river.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">A reach at the estuary of Krathis River in Greece was used to assess how in-stream processes alter its hydrologic and <span class="hlt">biogeochemical</span> regime. Krathis River exhibited high annual flow variability and its transmission losses become significant, especially during the dry months. These transmission losses are enhanced in chemistry due to release of nutrients from river sediments. These fluxes are significant because they correspond to 11% of the dissolved inorganic nitrogen flux of the river. Release of nitrogen species was influenced by temperature, while release of phosphate was not because phosphate levels were below the equilibrium concentration. There is a significant amount of sediments with fine composition that create "hot spot" areas in the river reach. These sediments are mobilized during the first flush events in the fall carrying with them a significant load of nutrient and suspended matter to the coastal zone. The nutrient organic content of sediments was also significant and it was studied in terms of its mineralization capacity. The capacity for mineralization was influenced by soil moisture, exhibiting significant capacity even at moisture levels of 40%. Temporary rivers are sensitive ecosystems, vulnerable to climate changes. In-stream processes play a significant role in altering the hydrology and biogeochemistry of the water and its impacts to the coastal zone. PMID:17593723</p> <div class="credits"> <p class="dwt_author">Tzoraki, Ourania; Nikolaidis, Nikolaos P; Amaxidis, Yorgos; Skoulikidis, Nikolaos Th</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-02-15</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">191</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/962957"> <span id="translatedtitle">Feedbacks between hydrological heterogeneity and bioremediation induced <span class="hlt">biogeochemical</span> transformations</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> transformations at the field scale, particularly the development of precipitates that may cause clogging and flow rerouting.</p> <div class="credits"> <p class="dwt_author">Englert, A.; Hubbard, S.S.; Williams, K.H.; Li, L.; Steefel, C.I.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-04-15</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">192</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..15.8361G"> <span id="translatedtitle">The role of estuarine discharges on the <span class="hlt">biogeochemical</span> characteristics of the nearby continental shelf ecosystem. The Guadalquivir-Gulf of Cadiz case study</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The hydrodynamics and <span class="hlt">biogeochemical</span> conditions of the Gulf of Cadiz (SW Iberian peninsula) is strongly influenced by the input of fresh, warm and nutrient-rich water from the main estuary in the region, the Guadalquivir River. This sea-river interaction favors the generation of surface retention structures that encompasses highly productive waters throughout the year constituting and ideal place for fish spawning and nursery. The biological productivity of the Gulf and its high fisheries yields are, thus, heavily forced by the Guadalquivir River discharges which are conditioned by the freshwater inputs from the upstream sections of the river and by the tidal mixing dynamics in the lower reaches of the estuary. In this work we use a <span class="hlt">coupled</span> hydrological-<span class="hlt">biogeochemical</span> 3D model of the Gulf of Cadiz, Strait of Gibraltar and Alboran Sea (a regional application of the Regional Ocean Model System) connected to a virtual estuary representing the Guadalquivir River. With this <span class="hlt">coupled</span> model we quantify the relative importance of each process (freshwater discharges and tidal mixing) for creating the special conditions of the nearby continental shelf. We found that freshwater input is only relevant during fall and winter when precipitation are important in the river catchment area. Tidal mixing, on the other hand, is more constant throughout the entire year and provides a nutrient input to the marine ecosystem of the same order of magnitude as the freshwater runoff. We also run the model with and without the river input and quantify, for the first time, the exact role of this external forcing on the <span class="hlt">biogeochemical</span> conditions of the continental shelf ecosystem.</p> <div class="credits"> <p class="dwt_author">Guerreiro, Catarina; Macías, Diego; Peliz, Alvaro; Prieto, Laura; Ruiz, Javier</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">193</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUFM.H53J..02H"> <span id="translatedtitle">Assessing Feedbacks between Remediation-Induced <span class="hlt">Biogeochemical</span> Transformations and Flow Characteristics using Multi-Scale Geophysical Approaches (Invited)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Although in situ strategies are frequently considered for environmental remediation, the impact of feedbacks between induced <span class="hlt">biogeochemical</span> transformations and hydrological characteristics on remediation efficacy is not well understood. In situ remediation approaches that strongly perturb subsurface systems (such as chemical oxidation, pH manipulation, redox manipulation or biostimulation) typically lead to <span class="hlt">biogeochemical</span> end-products, which form at grain-fluid boundaries, within pore spaces, and across pore throats. Our recent research has suggested that the evolution of these remediation-induced microscale end-products is significant enough to impact flow characteristics at the field scale. This feedback between <span class="hlt">biogeochemical</span> transformations and flow characteristics may render it challenging to introduce additional amendments into the subsurface or may alter the hydrobiogeochemical conditions favorable for sustained treatment. Our research focuses on exploring how geophysical signatures change as a function of remediation-induced biotic and abiotic transformations, including the evolution of electrically conductive (e.g., FeS) and non-conductive (e.g., calcite) precipitates, gases, biofilms, TDS, and electroactive ions. Using numerical, theoretical, and experimental approaches, our nested investigations span from several microns to the field scale. Our research is aligned with biostimulation experiments that are ongoing at the Uranium-contaminated Rifle, Colorado DOE Site, where stimulation of iron- and sulfate-reducing microorganisms accompanying acetate injection has been shown to promote uranium removal, presumably as insoluble mineral precipitates. To explore these transformations and their impact on flow characteristics, we are performing research along five different fronts: 1) dynamic synchrotron tomography studies to explore the evolution in pore geometry and precipitate morphology due to remediation treatments; (2) laboratory column experiments to develop an understanding about geophysical (complex resistivity, seismic, and radar) attributes to remediation-induced end-products and to develop petrophysical relationships; (3) stochastic approaches that permit integration of the disparate geophysical, geochemical, and petrophysical datasets to quantify end-product attributes (i.e., volume fraction, mean radius, and distribution of evolved precipitates) as well as their impact on permeability; (4) <span class="hlt">Coupled</span> imaging/inversion studies to explore the ability and resolution of geophysical methods for quantifying remediation-induced transformations at the field scale; and (5) iteration with reactive transport modeling to improve understanding of geophysical signatures as well as field-scale phenomena. This presentation will review advances in all of these research fronts and will discuss existing challenges for exploring complex system feedbacks using geophysical methods.</p> <div class="credits"> <p class="dwt_author">Hubbard, S. S.; Wu, Y.; Chen, J.; Ajo Franklin, J. B.; Li, L.; Tuglus, C.; Williams, K. H.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">194</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/56352143"> <span id="translatedtitle">Land Cover Change Effects on Hydrological and <span class="hlt">Biogeochemical</span> Functions in the Mekong River Basin: Insights From MacroScale Hydrologic and <span class="hlt">Biogeochemical</span> Models</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Concerns with the high rates of deforestation in the tropics include the possible impacts on species diversity, hydrologic response, <span class="hlt">biogeochemical</span> cycles and water quality, topsoil erosion, atmosphere chemistry, and land surface-atmosphere interactions affecting climate. Our work is concerned with hydrologic response and stream biogeochemistry under the monsoonal climate of Southeast Asia. How are the different components of the terrestrial hydrological</p> <div class="credits"> <p class="dwt_author">M. C. Costa-Cabral; J. E. Richey; G. Goteti; D. P. Lettenmaier; A. Snidvongs</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">195</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/883644"> <span id="translatedtitle">High-resolution mineralogical characterization and <span class="hlt">biogeochemical</span> modeling of uranium reaction pathways at the FRC</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">High-Resolution Mineralogical Characterization and <span class="hlt">Biogeochemical</span> Modeling of Uranium Reduction Pathways at the Oak Ridge Field-Research Center (FRC) Chen Zhu, Indiana University, David R. Veblen, Johns Hopkins University We have successfully completed a proof-of-concept, one-year grant on a three-year proposal from the former NABIR program, and here we seek additional two-year funding to complete and publish the research. Using a state-of-the-art 300-kV, atomic resolution, Field Emission Gun Transmission Electron Microscope (TEM), we have successfully identified three categories of mineral hosts for uranium in contaminated soils: (1) iron oxides; (2) mixed manganese-iron oxides; and (3) uranium phosphates. Method development using parallel electron energy loss spectroscopy (EELS) associated with the TEM shows great promise for characterizing the valence states of immobilized U during bioremediation. We have also collected 27 groundwater samples from two push-pull field biostimulation tests, which form two time series from zero to approximately 600 hours. The temporal evolution in major cations, anions, trace elements, and the stable isotopes 34S, 18O in sulfate, 15N in nitrate, and 13C in dissolved inorganic carbon (DIC) clearly show that biostimulation resulted in reduction of nitrate, Mn(IV), Fe(III), U(VI), sulfate, and Tc(VII), and these reduction reactions were intimately <span class="hlt">coupled</span> with a complex network of inorganic reactions evident from alkalinity, pH, Na, K, Mg, and Ca concentrations. From these temporal trends, apparent zero order rates were regressed. However, our extensive suite of chemical and isotopic data sets, perhaps the first and only comprehensive data set available at the FRC, show that the derived rates from these field biostimulation experiments are composite and lump-sum rates. There were several reactions that were occurring at the same time but were masked by these pseudo-zero order rates. A reaction-path model comprising a total of nine redox <span class="hlt">couples</span> (NO3–/NH4+, MnO2(s)/Mn2+, Fe(OH)3(s) /Fe2+, TcO4–/TcO2(s), UO22+/UO2(s), SO42–/HS–, CO2/CH4, ethanol/acetate, and H+/H2.) is used to simulate the temporal <span class="hlt">biogeochemical</span> evolution observed in the field tests. Preliminary results show that the models based on thermodynamics and more complex rate laws can generate the apparent zero order rates when several concurrent or competing reactions occur. Professor Alex Halliday of Oxford University, UK, and his postdoctoral associates are measuring the uranium isotopes in our groundwater samples. Newly developed state-of-the-art analytical techniques in measuring variability in 235U/238U offer the potential to distinguish biotic and abiotic uranium reductive mechanisms.</p> <div class="credits"> <p class="dwt_author">Chen Zhu</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-06-15</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">196</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2007AGUFM.B23G..04R"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Cycling of Iron Isotopes at Loihi Seamount</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">It is now well recognized that seafloor hydrothermal systems support diverse and unique biological communities capable of using dissolved chemical species, such as Iron (Fe), as well as mineral substrates as sources of metabolic energy. Deep-sea hydrothermal systems such as the Loihi Seamount hydrothermal field are important examples of environments where both chemical and biological oxidation of Fe can occur simultaneously and provide an ideal system in which to test hypotheses on biotic vs. abiotic origin of iron-oxide formation. Here, we applied Fe isotope systematics of hydrothermal fluids and Fe-oxide precipitates to study <span class="hlt">biogeochemical</span> cycling of iron and the formation of microbial mats at Loihi seamount. Warm hydrothermal fluids (<60°C) and iron oxide precipitates were recovered using the DSV Jason II during FeMO 2006 cruise. Fe-isotope composition of warm hydrothermal fluids yielded ?56Fe values near 0.1‰ and are indistinguishable from basalt values defined at 0.09‰. Suspended iron oxide particles in the fluids and seafloor iron oxide sediments (microbial mats) recovered in the vicinity of the vents yielded systematically positive ?56Fe values. The enrichment in heavy isotopes between 1.05 to 1.43‰ relative to Fe(II) in vent fluids is slightly higher than those obtained for abiotic Fe oxidation (around 0.9‰) and slightly lower than for bacterial Fe oxidation at circum neutral pH (around 1.5‰). Mass balance considerations also imply that the extent of Fe(II) oxidation is very limited in the vicinity of the vents (<20%) and that most Fe(II) is oxidized later in the water column. These results are consistent with the low oxygen content of seawater (i.e. summit of Loihi is located in the OMZ) and resultant slow kinetics of abiotic Fe oxidation. In contrast, mats supported by very diffuse fluids recovered at the base of the Loihi Seamount (~ 5000m depth) have distinctly negative Fe-isotope values between -0.3 to -1.5‰. These negative values are best explained by near-complete oxidation of isotopically light Fe(II) source. Negative ?56Fe values in the source fluid are likely generated by subsurface precipitation of isotopically heavy Fe-oxides during partial Fe(II) oxidation. These results, together with the significant enrichment in Mn-oxides relative to the warm mats, are consistent with the higher oxygen level in deep seawater and suggest extensive microbial Fe(II) oxidation below seafloor. Fe-isotope compositions of microbial mats at Loihi Seamount display a remarkable range between -1.2 to 1.6‰ which enlarges considerably the range of ?56Fe values for other hydrothermal Fe-oxide deposits at mid-oceanic ridges (?56Fe values between -0.8 to 0‰). This unique feature at Loihi indicates that Fe isotope compositions of hydrothermal Fe-oxide precipitates are particularly sensitive to oxygen levels in the local environment where they form, and are less sensitive to abiotic vs. biotic origins. The Loihi hydrothermal ecosystem provides an important modern analogue for testing hypotheses about the <span class="hlt">biogeochemical</span> cycling of Fe-isotopes on early Earth.</p> <div class="credits"> <p class="dwt_author">Rouxel, O. J.; Edwards, K. J.; Moyer, C. L.; Wheat, G.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">197</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2007ChJOL..25..157L"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> characteristics of nitrogen and phosphorus in Jiaozhou Bay sediments</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Sediment samples were cored from 3 locations representing the inner bay, the outer bay and the bay mouth of Jiaozhou Bay in September 2003 to study the source and <span class="hlt">biogeochemical</span> characteristics of nitrogen and phosphorus in the bay. The content and vertical distributions of total nitrogen (TN), total phosphorus (TP), organic nitrogen (ON), organic phosphorus (OP), inorganic nitrogen (IN), inorganic phosphorus (IP), the ratio of organic carbon and total nitrogen (OC/TN), and the ratio of total nitrogen and total phosphorus (TN/TP) in the sediments were analyzed. The results show that both TN and TP in surface sediments decrease from the inner bay to the outer bay. In general, ON occupies 50%-70% of TN and IP accounts for more than 60% of TP. In ratio of OC:TN, the nitrogen accumulated in the sediments from the inner bay and the bay mouth came mainly from terrestrial sources, and the portion of autogenetic nitrogen was 28.9% and 13.1%, respectively. However, in the outer bay, nitrogen was mainly autogenetic, accounting for 62.1% of TN, whereas phosphorus was mainly land-derived. The sedimentation fluxes of nitrogen and phosphorus varied spatially. The overall diagenesis rate of nitrogen was higher than that of phosphorus. Specifically, the diagenesis rate of OP was higher than that of IP. However, the diagenesis rate of ON was not always higher than that of IN. In species, the diagenesis rate of IN is sometimes much higher than that of the OC. In various environments, the diagenesis rate is, to some degree, affected by OC, pH, Eh, and Es.</p> <div class="credits"> <p class="dwt_author">Li, Xuegang; Song, Jinming; Yuan, Huamao; Dai, Jicui; Li, Ning</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">198</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/1006200"> <span id="translatedtitle">Microbial Reduction of Ferrous Arsenate: <span class="hlt">Biogeochemical</span> Implications for Arsenic Mobilization</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">In reduced aqueous environments, the presence of As in solution is a function of both biotic and abiotic mechanisms. Recent studies have demonstrated a significant release of As(III) through the microbial reduction of dissolved and mineral-bound As(V), which raises health concerns when the greater comparative mobility and toxicity of As(III) is considered. These release mechanisms do not operate in isolation but occur in concert with a number of removal processes, including secondary mineralization and sorption to other natural substrates. Thermodynamic and applied experimental studies have shown that ferrous arsenates, such as symplesite [Fe(II){sub 3}(As(V)O{sub 4}){sub 2} {center_dot} 8H{sub 2}O], may provide a significant sink for Fe(II) and As(V). In this study, the stability of a representative ferrous arsenate phase in the presence of the arsenate-reducing bacterium Shewanella sp. strain ANA-3 is examined. The reduction of ferrous arsenate by ANA-3 results in the release of aqueous As(III) and, subsequently, the progressive nucleation of a biogenic ferrous arsenite phase proximal to the microbial cells. The valence states of secondary solid-phase products were verified using X-ray absorption spectroscopy (XAS). Electron microscopy reveals that nucleation occurs on cellular exudates which may imply a role of extracellular reduction through c-type cytochromes as investigated in recent literature. These observations provide new insights into the reduction mechanisms of ANA-3 and the <span class="hlt">biogeochemical</span> cycling of As(III) in natural systems.</p> <div class="credits"> <p class="dwt_author">Babechuk, M.; Weisener, C.G.; Fryer, B.; Paktunc, D.; Maunders, C.; (Windsor); (CCM); (McMaster U.)</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-11-12</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">199</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..1513849K"> <span id="translatedtitle">Hotspots and hot moments of aquifer river exchange and <span class="hlt">biogeochemical</span> cyclinbg in the streambed of lowland rivers</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Exchange fluxes across aquifer-river interfaces can have a major impact on the <span class="hlt">biogeochemical</span> cycling in streambed environments. This paper presents integrated experimental and model-based investigations of physical drivers and chemical controls on streambed biogeochemcial cycling at two UK lowland rivers. It combines in-stream geophysical surveys, multi-level mini-piezometer networks and active and passive heat tracing methods for identifying spatial patterns and temporal dynamics of aquifer-river exchange fluxes with multi-scale hyporheic pore-water sampling and applications of reactive "smart-tracers". Hyporheic pore water analysis from nested multi-level piezometers and passive gel probe samplers revealed significant spatial variability in streambed nitrogen cycling in dependence of redox-conditions, dissolved oxygen and bio-available organic carbon concentrations. Hot spots of increased nitrate attenuation and anaerobic respiration were associated with semi-confining streambed peat lenses. The intensity of concentration changes underneath the confining peat layers correlated with the state of anoxia in the pore water as well as the supply of organic carbon and hyporheic residence times. In contrast, at locations where flow inhibiting peat layers were absent or disrupted - fast exchange between aquifer and river caused a break-through of nitrate without significant concentration changes along the hyporheic flow path. Fibre-optic Distributed Temperature Sensing was applied for identifying groundwater - surface water exchange flow patterns in dependency of streambed structural heterogeneity and support the identification of the location and extend of flow inhibiting structures as indicators of streambed reactivity hot spots. <span class="hlt">Coupled</span> groundwater-surface water model simulations supported the experimental results, indicating that hotspots of exchange fluxes and <span class="hlt">biogeochemical</span> activity were predominantly controlled by the spatial heterogeneous impact of streambed conductivity patterns on groundwater up-welling while surface driven processes as advective pumping had only marginal impacts.</p> <div class="credits"> <p class="dwt_author">Krause, Stefan; Munz, Mathias; Tecklenburg, Christina; Blume, Theresa; Binley, Andrew</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">200</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUFMPP23C1410G"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> changes in the eastern Mediterranean Sea during the early Holocene</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">During the early Holocene, a series of changes in the conditions of the Mediterranean hydrography, and corresponding its biogeochemistry, occurred. This led to the formation of sapropels, which are the result of an increased accumulation of organic matter that has been attributed to a better preservation of organic carbon due to oxygen depletion and/or to higher biological production that enhances the carbon flux to the seafloor. This study aims at a better understanding of the sensitivity of the Mediterranean Sea to high and low latitude climate forcing and to estimate the response to expected global change. For this purpose we set up a regional version of the general ocean circulation model MPI-OM for the Mediterranean (26 km horizontal resolution, 29 levels) <span class="hlt">coupled</span> to the <span class="hlt">biogeochemical</span> model HAMOCC. The model is forced with atmospheric data derived from equilibrium time slice simulations for pre-industrial conditions and 9000 B.P with the atmosphere-ocean-dynamical vegetation model ECHAM5/MPI-OM/LPJ. Diverse proxy records available from the marine cores are used for the validation of our simulations. Results show that the climate of the early Holocene led to changes in the spatial distribution and intensity of deep water formation in the eastern Mediterranean Sea. Sensitivity experiments concerning the opening of the Bosphorus inflow, the freshening of the Atlantic input due to melting ice sheets, as well as increasing riverine freshwater and nutrient input illustrate the evolution of stagnate deep water and a basin-wide shoaling of the pycnocline into the euphotic zone, both leading to an enhanced accumulation of organic material within the sediment.</p> <div class="credits"> <p class="dwt_author">Grimm, R.; Maier-Reimer, E. H.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_9");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' 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onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">201</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2006GGG.....711019D"> <span id="translatedtitle">A GEOCLIM simulation of climatic and <span class="hlt">biogeochemical</span> consequences of Pangea breakup</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Large fluctuations in continental configuration occur throughout the Mesozoic. While it has long been recognized that paleogeography may potentially influence atmospheric CO2 via the continental silicate weathering feedback, no numerical simulations have been done, because of the lack of a spatially resolved climate-carbon model. GEOCLIM, a <span class="hlt">coupled</span> numerical model of the climate and global <span class="hlt">biogeochemical</span> cycles, is used to investigate the consequences of the Pangea breakup. The climate module of the GEOCLIM model is the FOAM atmospheric general circulation model, allowing the calculation of the consumption of atmospheric CO2 through continental silicate weathering with a spatial resolution of 7.5°long × 4.5°lat. Seven time slices have been simulated. We show that the breakup of the Pangea supercontinent triggers an increase in continental runoff, resulting in enhanced atmospheric CO2 consumption through silicate weathering. As a result, atmospheric CO2 falls from values above 3000 ppmv during the Triassic down to rather low levels during the Cretaceous (around 400 ppmv), resulting in a decrease in global mean annual continental temperatures from about 20°C to 10°C. Silicate weathering feedback and paleogeography both act to force the Earth system toward a dry and hot world reaching its optimum over the last 260 Myr during the Middle-Late Triassic. In the super continent case, given the persistent aridity, the model generates high CO2 values to produce very warm continental temperatures. Conversely, in the fragmented case, the runoff becomes the most important contributor to the silicate weathering rate, hence producing a CO2 drawdown and a fall in continental temperatures. Finally, another unexpected outcome is the pronounced fluctuation in carbonate accumulation simulated by the model in response to the Pangea breakup. These fluctuations are driven by changes in continental carbonate weathering flux. Accounting for the fluctuations in area available for carbonate platforms, the simulated ratio of carbonate deposition between neritic and deep sea environments is in better agreement with available data.</p> <div class="credits"> <p class="dwt_author">Donnadieu, Y.; GoddéRis, Y.; Pierrehumbert, R.; Dromart, G.; Fluteau, F.; Jacob, R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">202</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010E%26PSL.298..125T"> <span id="translatedtitle">Iron isotopes constrain <span class="hlt">biogeochemical</span> redox cycling of iron and manganese in a Palaeoproterozoic stratified basin</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Hotazel Formation in the uppermost stratigraphic portion of the Neoarchaean-Palaeoproterozoic Transvaal Supergroup of southern Africa is an unusual sedimentary sequence of banded iron-formation (BIF) intercalated with three manganese-rich layers. As such, it is a succession that holds great potential to offer a unique view of one of the most dramatic transitions in early Earth history — the switch to a full oxidative cycle in shallow oceans at ca. 2.3 Ga. We present iron isotope results from BIF and Mn-rich samples collected across the entire Hotazel sequence, with a view to constraining processes of <span class="hlt">biogeochemical</span> redox cycling for both metals close to the transition from a reducing to an oxidizing ocean-atmosphere system. The recorded de-<span class="hlt">coupling</span> of Fe- and Mn reduction during anaerobic organic carbon cycling in the Hotazel strata, suggests that manganese became an important electron acceptor in stratified marine environments of the Palaeoproterozoic during periods of increased primary manganese precipitation relative to iron. Very low ?57Fe values registered across the entire Hotazel sequence and especially in manganese-rich samples (-2.4 to -3.5‰) signify deposition of iron and manganese in a terminal, stratified aqueous reservoir that was depleted in the heavy iron isotopes. These isotopic signatures, in conjunction with the unusual endowment of the Hotazel sequence in manganese, are interpreted to have evolved by Rayleigh distillation processes during protracted deposition of Mn-poor BIFs as preserved in the lower stratigraphic portion of the Transvaal Supergroup (Kuruman and Griquatown BIFs). The unique end-member geochemical and isotopic characteristics of the Hotazel rocks may therefore constitute a potential link between the widespread deposition of BIF during the Neoarchaean and Palaeoproterozoic, and the postulated rise in atmospheric oxygen levels around 2.3 Ga ago.</p> <div class="credits"> <p class="dwt_author">Tsikos, Harilaos; Matthews, Alan; Erel, Yigal; Moore, John M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">203</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFMOS31B1426Y"> <span id="translatedtitle">A Bay/Estuary Model to Simulated Hydrodynamics and <span class="hlt">Biogeochemical</span> Cycles</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">This talk presents the development of a numerical model to simulate integrated hydrodynamics and <span class="hlt">biogeochemical</span> cycles in /bays/estuaries/coastal waters. The hydrodynamic module solves three-dimensional, density-dependent Navier-Stokes and thermal, salinity, and sediment transport equations. The moving free surface is explicitly handled by solving the kinematic boundary condition equation using a node-repositioning algorithm. The <span class="hlt">biogeochemical</span> module considers the interaction of carbon, nitrogen, phosphorus, and oxygen cycles and biota kinetics. The interacting <span class="hlt">biogeochemical</span> cycles and biota kinetics were transformed into a reaction network, from which the transport equations of all <span class="hlt">biogeochemical</span> species and biota were set up automatically. These transport equations were then transformed into three subsets to decouple fast equilibrium reactions from slow kinetic reactions using a general paradigm of diagonalization. The first subset constitutes of transport equations of equilibrium variables. The second subset is made of transport equations of kinetic variables. Finally, the third subset composes transport equations of components for reaction invariance. The model was applied to the Loxahatchee Estuary river system. The computational domain includes the Loxahatchee estuary, Intracoastal Waterways, and three major tributaries of the river - the South Fork, North Fork, and Northwest Fork. The comparison between model simulations and field data is excellent for tides and adequate for salinities. To demonstrate the flexibility and generality of the <span class="hlt">biogeochemical</span> transport module, three widely used water quality models, WASP5, QUAL2E, and CE-QUAL-ICM, were recast in the mode of reaction networks of <span class="hlt">biogeochemical</span> processes. Simulations of QUAL2E and WASP5 using the model illustrated that they were treated simply as two examples in light of the general paradigm of modeling reactive <span class="hlt">biogeochemical</span> transport.</p> <div class="credits"> <p class="dwt_author">Yeh, G.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">204</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..15.7953P"> <span id="translatedtitle">Assessment of a global eddy-permitting <span class="hlt">biogeochemical</span> hindcast of the ocean colour era.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The combination of climate change and various anthropogenic drivers, such as e.g. changes in external nutrient inputs and exploitation of marine resources drive important changes in marine ecosystems. These changes occur against the background of natural variability. The retrospective analysis of global ocean <span class="hlt">biogeochemical</span> state holds promise for identifying the response of marine ecosystems and <span class="hlt">biogeochemical</span> fluxes to natural climate variability and, potentially, allows to detect trends driven by global climate change. Ideally, such a <span class="hlt">biogeochemical</span> hindcast simulation should resolve the mesoscale and span multiple decades. Here, we present a <span class="hlt">biogeochemical</span> simulation at 1/4° resolution for the period between 1994 to 2010 with NEMO/PISCES. The <span class="hlt">biogeochemical</span> model PISCES was forced off-line by weekly fields provided by a physical simulation at 1/4° resolution (orca025) over the same period. The model was initialized with global climatologies. The spin-up involved 20 years of <span class="hlt">biogeochemical</span> off-line simulation forced by a climatology of ocean physics. The inter-annual simulation (1994-2010) followed on the spin-up. The analysis of our spin-up strategy is presented with focus on the adjustment of model fields. The inter-annual simulation is evaluated by systematically comparing model fields to observations at global and regional scales. We draw on EOF (Empirical Orthogonal Functions) analysis to evaluate spatial/temporal variability. We focus on links between <span class="hlt">biogeochemical</span> and physical variables in order to identify underlying common modes of variability for multiple variables. Finally, to complete the assessment, we compare EOF modes for Globcolour chlorophyll estimates (a merged Seawifs-Meris-Modis product) and model output over the period of observations.</p> <div class="credits"> <p class="dwt_author">Perruche, Coralie; Gehlen, Marion; Daudin, Anne; El Moussaoui, Abdelali; Greiner, Eric; Ethe, Christian</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">205</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2003AnGeo..21..413V"> <span id="translatedtitle">Calibration and validation of a one-dimensional complex marine <span class="hlt">biogeochemical</span> flux model in different areas of the northern Adriatic shelf</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In this paper we show results from numerical simulations carried out with a complex <span class="hlt">biogeochemical</span> fluxes model <span class="hlt">coupled</span> with a one-dimensional high-resolution hydrodynamical model and implemented at three different locations of the northern Adriatic shelf. One location is directly affected by the Po River influence, one has more open-sea characteristics and one is located in the Gulf of Trieste with an intermediate behavior; emphasis is put on the comparison with observations and on the functioning of the northern Adriatic ecosystem in the three areas. The work has been performed in a climatological context and has to be considered as preliminary to the development of three-dimensional numerical simulations. <span class="hlt">Biogeochemical</span> model parameterizations have been ameliorated with a detailed description of bacterial substrate utilization associated with the quality of the dissolved organic matter (DOM), in order to improve the models capability in capturing the observed DOM dynamics in the basin. The <span class="hlt">coupled</span> model has been calibrated and validated at the three locations by means of climatological data sets. Results show satisfactory model behavior in simulating local seasonal dynamics in the limit of the available boundary conditions and the one-dimensional implementation. Comparisons with available measurements of primary and bacterial production and bacterial abundances have been performed in all locations. Model simulated rates and bacterial dynamics are in the same order of magnitude of observations and show a qualitatively correct time evolution. The importance of temperature as a factor controlling bacteria efficiency is investigated with sensitivity experiments on the model parameterizations.</p> <div class="credits"> <p class="dwt_author">Vichi, M.; Oddo, P.; Zavatarelli, M.; Coluccelli, A.; Coppini, G.; Celio, M.; Fonda Umani, S.; Pinardi, N.</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">206</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=DE2008913605"> <span id="translatedtitle">Hybrid Numerical Methods for Multiscale Simulations of Subsurface <span class="hlt">Biogeochemical</span> Processes.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">Many subsurface flow and transport problems of importance today involve <span class="hlt">coupled</span> non-linear flow, transport, and reaction in media exhibiting complex heterogeneity. In particular, problems involving biological mediation of reactions fall into this class of...</p> <div class="credits"> <p class="dwt_author">A. M. Tartakovsky D. M. Tartakovsky G. D. Redden M. Alexandre P. Meakin</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">207</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009ESRv...95...63P"> <span id="translatedtitle">A marine <span class="hlt">biogeochemical</span> perspective on black shale deposition</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Deposition of marine black shales has commonly been interpreted as having involved a high level of marine phytoplankton production that promoted high settling rates of organic matter through the water column and high burial fluxes on the seafloor or anoxic (sulfidic) water-column conditions that led to high levels of preservation of deposited organic matter, or a combination of the two processes. Here we review the hydrography and the budgets of trace metals and phytoplankton nutrients in two modern marine basins that have permanently anoxic bottom waters. This information is then used to hindcast the hydrography and <span class="hlt">biogeochemical</span> conditions of deposition of a black shale of Late Jurassic age (the Kimmeridge Clay Formation, Yorkshire, England) from its trace metal and organic carbon content. Comparison of the modern and Jurassic sediment compositions reveals that the rate of photic zone primary productivity in the Kimmeridge Sea, based on the accumulation rate of the marine fraction of Ni, was as high as 840 g organic carbon m - 2 yr -1. This high level was possibly tied to the maximum rise of sea level during the Late Jurassic that flooded this and other continents sufficiently to allow major open-ocean boundary currents to penetrate into epeiric seas. Sites of intense upwelling of nutrient-enriched seawater would have been transferred from the continental margins, their present location, onto the continents. This global flooding event was likely responsible for deposition of organic matter-enriched sediments in other marine basins of this age, several of which today host major petroleum source rocks. Bottom-water redox conditions in the Kimmeridge Sea, deduced from the V:Mo ratio in the marine fraction of the Kimmeridge Clay Formation, varied from oxic to anoxic, but were predominantly suboxic, or denitrifying. A high settling flux of organic matter, a result of the high primary productivity, supported a high rate of bacterial respiration that led to the depletion of O 2 in the bottom water. A high rate of burial of labile organic matter, albeit a low percentage of primary productivity, in turn promoted anoxic conditions in the sediment pore waters that enhanced retention of trace metals deposited from the water column.</p> <div class="credits"> <p class="dwt_author">Piper, D. Z.; Calvert, S. E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-06-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">208</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2003AGUFM.B31F..07M"> <span id="translatedtitle">Modeling <span class="hlt">Biogeochemical</span> Reactive Transport in Fractured Granites: Implications for the Performance of a Deep Geological Repository</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Several countries around the world are considering deep repositories in fractured granitic formations for the final disposal of high-level radioactive waste. Evaluating the long term safety of such repositories requires sound conceptual and numerical models which are being developed from data and knowledge gained from in situ experiments carried out at deep underground laboratories such as that of Žsp” in Sweden. One of the key aspects for performance assessment concerns to groundwater redox conditions because: (a) the presence of oxygen will affect to the corrosion of canisters, (b) possible production of hydrogen sulphide from sulphate reduction will also have a negative effect on these metallic containers, and (c) several long-lived radionuclides are much more soluble and mobile under oxidizing conditions. Several projects have been performed at Žsp” to investigate different aspects of the groundwater redox evolution. The vast amount of in situ-generated information has been used in this work to set up <span class="hlt">coupled</span> hydrobiogeochemical models. Numerical models account for saturated groundwater flow, solute transport by advection, dispersion and molecular diffusion, geochemical reactions involving both the liquid and solid phases, and microbially-catallyzed processes. For the Žsp” site, modelling results provide quantitative support for the following conclusions. (A) At the operational phase of the repository, shallow fresh groundwater could reach the depth of the underground facility. Shallow groundwaters loose dissolved oxygen during the infiltration through soil layers and then, respiration of dissolved organic matter is induced along the flow paths through the reduction of Fe(III)-bearing minerals of the fracture zones. Microbial anaerobic respiration of DOC provides additional reducing capacity at the depth of the tunnel. (B) After repository closure, atmospheric oxygen will remain trapped within the tunnel. Abiotic consumption of this oxygen has been computed to occur in a period of about 1,000 years as a result of diffusion-reaction processes. <span class="hlt">Coupled</span> <span class="hlt">biogeochemical</span> mechanisms, such as respiration of dissolved organic matter and aerobic methane oxidation, accelerate the oxygen uptake to less than a month.</p> <div class="credits"> <p class="dwt_author">Molinero, J.; Samper, J.; Pedersen, K.; Puigdomenech, I.</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">209</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2003WRR....39.1083F"> <span id="translatedtitle">A general paradigm to model reaction-based <span class="hlt">biogeochemical</span> processes in batch systems</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">This paper presents the development and illustration of a numerical model of reaction-based geochemical and biochemical processes with mixed equilibrium and kinetic reactions. The objective is to provide a general paradigm for modeling reactive chemicals in batch systems, with expectations that it is applicable to reactive chemical transport problems. The unique aspects of the paradigm are to simultaneously (1) facilitate the segregation (isolation) of linearly independent kinetic reactions and thus enable the formulation and parameterization of individual rates one reaction by one reaction when linearly dependent kinetic reactions are absent, (2) enable the inclusion of virtually any type of equilibrium expressions and kinetic rates users want to specify, (3) reduce problem stiffness by eliminating all fast reactions from the set of ordinary differential equations governing the evolution of kinetic variables, (4) perform systematic operations to remove redundant fast reactions and irrelevant kinetic reactions, (5) systematically define chemical components and explicitly enforce mass conservation, (6) accomplish automation in decoupling fast reactions from slow reactions, and (7) increase the robustness of numerical integration of the governing equations with species switching schemes. None of the existing models to our knowledge has included these scopes simultaneously. This model (<span class="hlt">BIOGEOCHEM</span>) is a general computer code to simulate <span class="hlt">biogeochemical</span> processes in batch systems from a reaction-based mechanistic standpoint, and is designed to be easily <span class="hlt">coupled</span> with transport models. To make the model applicable to a wide range of problems, programmed reaction types include aqueous complexation, adsorption-desorption, ion-exchange, oxidation-reduction, precipitation-dissolution, acid-base reactions, and microbial mediated reactions. In addition, user-specified reaction types can be programmed into the model. Any reaction can be treated as fast/equilibrium or slow/kinetic reaction. An equilibrium reaction is modeled with an infinite rate governed by a mass action equilibrium equation or by a user-specified algebraic equation. Programmed kinetic reaction rates include multiple Monod kinetics, nth order empirical, and elementary formulations. In addition, user-specified rate formulations can be programmed into the model. No existing models to our knowledge offer these simultaneous features. Furthermore, most available reaction-based models assume chemical components a priori so that reactions can be written in basic (canonical) forms and implicitly assume that fast equilibrium reactions occur only for homogeneous reactions. The decoupling of fast reactions from slow reactions lessens the stiffness typical of these systems. The explicit enforcement of mass conservation overcomes the mass conservation error due to numerical integration errors. The removal of redundant fast reactions alleviates the problem of singularity. The exclusion of irrelevant slow reactions eliminates the issue of exporting their problematic rate formulations/parameter estimations to different environment conditions. Taking the advantage of the nonuniqueness of components, a dynamic basis-species switching strategy is employed to make the model numerically robust. Backward basis switching allows components to freely change in the simulation of the chemistry module, while being recovered for transport simulation. Three example problems were selected to demonstrate the versatility and robustness of the model.</p> <div class="credits"> <p class="dwt_author">Fang, Yilin; Yeh, Gour-Tsyh; Burgos, William D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">210</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40283325"> <span id="translatedtitle">Operator-splitting errors in <span class="hlt">coupled</span> reactive transport codes for transient variably saturated flow and contaminant transport in layered soil profiles</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">One possible way of integrating subsurface flow and transport processes with (<span class="hlt">bio)geochemical</span> reactions is to <span class="hlt">couple</span> by means of an operator-splitting approach two completely separate codes, one for variably-saturated flow and solute transport and one for equilibrium and kinetic <span class="hlt">biogeochemical</span> reactions. This paper evaluates the accuracy of the operator-splitting approach for multicomponent systems for typical soil environmental problems involving transient</p> <div class="credits"> <p class="dwt_author">D. Jacques; J. Šim?nek; D. Mallants; M. Th. van Genuchten</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">211</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/5615759"> <span id="translatedtitle">Operator-splitting errors in <span class="hlt">coupled</span> reactive transport codes for transient variably saturated flow and contaminant transport in layered soil profiles</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Abstract One possible way of integrating subsurface flow and transport processes with (<span class="hlt">bio)geochemical</span> reactions is to <span class="hlt">couple</span> by means of an operator-splitting approach two completely separate codes, one for variably-saturated flow and solute transport and one for equilibrium and kinetic <span class="hlt">biogeochemical</span> reactions. This paper evaluates the accuracy of the operator-splitting approach for multicomponent systems for typical soil environmental problems involving</p> <div class="credits"> <p class="dwt_author">D. Jacques; J. šim?nek; D. Mallants; M. th. Van Genuchten</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">212</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2003AGUFM.H51C1070W"> <span id="translatedtitle">Use of the Water, Energy, and <span class="hlt">Biogeochemical</span> Model (WEBMOD) to Simulate Water Quality at Five U.S. Geological Survey Research Watersheds</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Water, Energy, and <span class="hlt">Biogeochemical</span> Model (WEBMOD) was developed as an aid to compare and contrast basic hydrologic and <span class="hlt">biogeochemical</span> processes active in the diverse hydroclimatic regions represented by the five U.S. Geological Survey (USGS) Water, Energy, and <span class="hlt">Biogeochemical</span> Budget (WEBB) sites: Loch Vale, Colorado; Trout Lake, Wisconsin; Sleepers River, Vermont; Panola Mountain, Georgia; and Luquillo Experimental Forest, Puerto Rico. WEBMOD simulates solute concentrations for vegetation canopy, snow pack, impermeable ground, leaf litter, unsaturated and saturated soil zones, riparian zones and streams using selected process modules <span class="hlt">coupled</span> within the USGS Modular Modeling System (MMS). Source codes for the MMS hydrologic modules include the USGS Precipitation Runoff Modeling System, the National Weather Service Hydro-17 snow model, and TOPMODEL. The hydrologic modules distribute precipitation and temperature to predict evapotranspiration, snow accumulation, snow melt, and streamflow. Streamflow generation mechanisms include infiltration excess, saturated overland flow, preferential lateral flow, and base flow. Input precipitation chemistry, and fluxes and residence times predicted by the hydrologic modules are input into the geochemical module where solute concentrations are computed for a series of discrete well-mixed reservoirs using calls to the geochemical engine PHREEQC. WEBMOD was used to better understand variations in water quality observed at the WEBB sites from October 1991 through September 1997. Initial calibrations were completed by fitting the simulated hydrographs with those measured at the watershed outlets. Model performance was then refined by comparing the predicted export of conservative chemical tracers such as chloride, with those measured at the watershed outlets. The model succeeded in duplicating the temporal variability of net exports of major ions from the watersheds.</p> <div class="credits"> <p class="dwt_author">Webb, R. M.; Leavesley, G. H.; Shanley, J. B.; Peters, N. E.; Aulenbach, B. T.; Blum, A. E.; Campbell, D. H.; Clow, D. W.; Mast, M. A.; Stallard, R. F.; Larsen, M. C.; Troester, J. W.; Walker, J. F.; White, A. F.</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">213</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/1035723"> <span id="translatedtitle">An offline unstructured <span class="hlt">biogeochemical</span> model (UBM) for complex estuarine and coastal environments</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Due to increased pollutant loads and water use from coastal development and population growth, occurrences of low-dissolved oxygen and "hypoxic zones" have increased. Reports of fish kills and water quality impairment are also becoming more frequent in many coastal waters. Water quality managers and regulatory agencies rely on numerical modeling tools to quantify the relative contributions of anthropogenic and "natural" pollutant loads (nutrients and biochemical oxygen demand) on dissolved oxygen levels and use the results for remedial activities and source control. The ability to conduct seasonlong simulations with sufficient nearshore resolution is therefore a key requirement. Mesh flexibility and the ability to increase site specific resolution without disturbing the larger domain setup and calibration are critical. The objective of this effort was to develop a robust <span class="hlt">biogeochemical</span> model suitable for simulation of water quality dynamics including dissolved oxygen in complex coastal environments with multiple tidal channels, tidal flats, and density-driven circulation using unstructured-grid formulation. This paper presents an offline unstructured <span class="hlt">biogeochemical</span> model that uses the Finite Volume Coastal Ocean Model (FVCOM) discretization of the study domain and the corresponding hydrodynamic solution to drive <span class="hlt">biogeochemical</span> kinetics based on a water quality model CE-QUAL-ICM. In this paper, the linkage between selected hydrodynamic and water quality models is subjected to several scalar transport and <span class="hlt">biogeochemical</span> module tests (plume transport and dilution, BOD/DO sag, and phytoplankton/nutrients reaction), and results are compared to their analytical solutions as part of model validation. A preliminary application of the <span class="hlt">biogeochemical</span> model with a year-long simulation of Hood Canal basin in Puget Sound, USA, is presented as an example and a test of the tool in a real estuary setting. The model reproduced the dynamics and seasonal variations in the <span class="hlt">biogeochemical</span> state variables and was used to test short-term wind-driven dynamics that could influence dissolved oxygen concentrations in Hood Canal.</p> <div class="credits"> <p class="dwt_author">Kim, Tae Yun; Khangaonkar, Tarang</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">214</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://dx.doi.org/10.1002/hyp.7279"> <span id="translatedtitle">First-order exchange coefficient <span class="hlt">coupling</span> for simulating surface water-groundwater interactions: Parameter sensitivity and consistency with a physics-based approach</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">Distributed hydrologic models capable of simulating fully-<span class="hlt">coupled</span> surface water and groundwater flow are increasingly used to examine problems in the hydrologic sciences. Several techniques are currently available to <span class="hlt">couple</span> the surface and subsurface; the two most frequently employed approaches are first-order exchange coefficients (a.k.a., the surface conductance method) and enforced continuity of pressure and flux at the <span class="hlt">surface-subsurface</span> boundary condition. The effort reported here examines the parameter sensitivity of simulated hydrologic response for the first-order exchange coefficients at a well-characterized field site using the fully <span class="hlt">coupled</span> Integrated Hydrology Model (InHM). This investigation demonstrates that the first-order exchange coefficients can be selected such that the simulated hydrologic response is insensitive to the parameter choice, while simulation time is considerably reduced. Alternatively, the ability to choose a first-order exchange coefficient that intentionally decouples the surface and subsurface facilitates concept-development simulations to examine real-world situations where the <span class="hlt">surface-subsurface</span> exchange is impaired. While the parameters comprising the first-order exchange coefficient cannot be directly estimated or measured, the insensitivity of the simulated flow system to these parameters (when chosen appropriately) combined with the ability to mimic actual physical processes suggests that the first-order exchange coefficient approach can be consistent with a physics-based framework. Copyright ?? 2009 John Wiley & Sons, Ltd.</p> <div class="credits"> <p class="dwt_author">Ebel, B. A.; Mirus, B. B.; Heppner, C. S.; VanderKwaak, J. E.; Loague, K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">215</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.agu.org/journals/gb/gb0703/2006GB002901/2006GB002901.pdf"> <span id="translatedtitle">Physical versus <span class="hlt">biogeochemical</span> interpretations of nitrogen and phosphorus attenuation in streams and its dependence on stream characteristics</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We investigate the influence of <span class="hlt">biogeochemical</span> nutrient attenuation rates versus physical solute travel times on nutrient transport and attenuation in streams with different characteristics. Comparative results indicate smaller <span class="hlt">biogeochemical</span> in-stream attenuation rate and greater decrease of this rate with stream depth for phosphorus than for nitrogen. Because physical solute travel times also decrease with stream depth, equally for both nutrients,</p> <div class="credits"> <p class="dwt_author">Amélie Darracq; Georgia Destouni</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">216</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/37958109"> <span id="translatedtitle">Correlating phospholipid fatty acids (PLFA) in a landfill leachate polluted aquifer with <span class="hlt">biogeochemical</span> factors by multivariate statistical methods</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Different multivariate statistical analyses were applied to phospholipid fatty acids representing the biomass composition and to different <span class="hlt">biogeochemical</span> parameters measured in 37 samples from a landfill contaminated aquifer at Grindsted Landfill (Denmark). Principal component analysis and correspondence analysis were used to identify groups of samples showing similar patterns with respect to <span class="hlt">biogeochemical</span> variables and phospholipid fatty acid composition. The principal</p> <div class="credits"> <p class="dwt_author">L Ludvigsen; H.-J Albrechtsen; H Holst; T. H Christensen</p> <p class="dwt_publisher"></p> <p class="publishDate">1997-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">217</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/vk67515r27537427.pdf"> <span id="translatedtitle">The evolution of saline lake waters: gradual and rapid <span class="hlt">biogeochemical</span> pathways in the Basotu Lake District, Tanzania</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The <span class="hlt">biogeochemical</span> evolution of solutes markedly alters the chemistry in the closed-basin maar lakes that comprise the Basotu Lake District (Tanzania, East Africa). Examination of 11 (out of 13) lakes in the Basotu Lake District identified two distinct evolutionary pathways: a gradual path and a rapid path. During the course of <span class="hlt">biogeochemical</span> evolution these waters follow either the gradual path</p> <div class="credits"> <p class="dwt_author">Peter Kilham; Paul L. Cloke</p> <p class="dwt_publisher"></p> <p class="publishDate">1990-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">218</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://groundwater.ucdavis.edu/Publications/Rains%20et%20al%20-%20Vernal%20pool%20connectivity%20-%20Hyd%20Proc%202006.pdf"> <span id="translatedtitle">The role of perched aquifers in hydrological connectivity and <span class="hlt">biogeochemical</span> processes in vernal pool landscapes, Central Valley, California</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Relatively little is known about the role of perched aquifers in hydrological, <span class="hlt">biogeochemical</span>, and biological processes of vernal pool landscapes. The objectives of this study are to introduce a perched aquifer concept for vernal pool formation and maintenance and to examine the resulting hydrological and <span class="hlt">biogeochemical</span> phenomena in a representative catchment with three vernal pools connected to one another and</p> <div class="credits"> <p class="dwt_author">Mark Cable Rains; Graham E. Fogg; Thomas Harter; Randy A. Dahlgren; Robert J. Williamson</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">219</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/q374327r74x7xgk1.pdf"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Budgets in a Mediterranean Catchment with High Rates of Atmospheric N Deposition – Importance of Scale and Temporal Asynchrony</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">In this study <span class="hlt">biogeochemical</span> export in a set of catchments that vary from 6 ha to almost 1500 ha is investigated. Studying catchments across this large range of scales enables us to investigate the scale dependence and fundamental processes controlling catchment <span class="hlt">biogeochemical</span> export that would not have been possible with a more limited data set. The Devil Canyon catchment, in the San</p> <div class="credits"> <p class="dwt_author">Thomas Meixner; Mark Fenn</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">220</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/60699298"> <span id="translatedtitle">Effects of solar UV radiation and climate change on <span class="hlt">biogeochemical</span> cycling: Interactions and feedbacks</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Solar UV radiation, climate and other drivers of global change are undergoing significant changes and models forecast that these changes will continue for the remainder of this century. Here we assess the effects of solar UV radiation on <span class="hlt">biogeochemical</span> cycles and the interactions of these effects with climate change, including feedbacks on climate. Such interactions occur in both terrestrial and</p> <div class="credits"> <p class="dwt_author">David J</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_10");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a 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href="#">10</a> <a onClick='return showDiv("page_11");' href="#">11</a> <a style="font-weight: bold;">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a onClick='return showDiv("page_18");' href="#">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_13");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">221</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/53110961"> <span id="translatedtitle">A new implementation of the <span class="hlt">Biogeochemical</span> Flux Model in sea ice</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The <span class="hlt">Biogeochemical</span> Flux Model (BFM) is a direct descendent of the European Regional Seas Ecosystem Model (ERSEM) and it has been widely used and validated among the scientific community. The BFM view of the of the marine ecosystem is based upon the recognition that the major ecological functions of producers, decomposers and consumers and their specific trophic interactions can be</p> <div class="credits"> <p class="dwt_author">L. Tedesco; M. Vichi</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">222</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40699871"> <span id="translatedtitle">Centimeter-scale characterization of <span class="hlt">biogeochemical</span> gradients at a wetland–aquifer interface using capillary electrophoresis</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Steep <span class="hlt">biogeochemical</span> gradients were measured at mixing interfaces in a wetland–aquifer system impacted by landfill leachate in Norman, Oklahoma. The system lies within a reworked alluvial plain and is characterized by layered low hydraulic conductivity wetland sediments interbedded with sandy aquifer material. Using cm-scale passive diffusion samplers, “peepers”, water samples were collected in a depth profile to span interfaces between</p> <div class="credits"> <p class="dwt_author">Susan Báez-Cazull; Jennifer T. McGuire; Isabelle M. Cozzarelli; Anne Raymond; Lisa Welsh</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">223</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/42725339"> <span id="translatedtitle">Multispectral video data for detecting <span class="hlt">biogeochemical</span> conditions at an Alabama oil field site</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Abstract. Multispectral video data were evaluated to determine their sensitivity to detect environmental conditions associated with hydrocarbon microseepage at the Pollard oil field. <span class="hlt">Biogeochemical</span> analysis of soil and tree leaves indicates that plants are extracting available heavy metals from the soil environment. Anomalous concentrations of Mn were found in plant tissue. Correlation analysis reveals statistically significant relationships between Mn concentrations</p> <div class="credits"> <p class="dwt_author">Gary J. Cwick; Michael P. Bishop; Robert C. Howe; Paul W. Mausel; James H. Everitt; David E. Escobar</p> <p class="dwt_publisher"></p> <p class="publishDate">1995-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">224</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/39930495"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> and hydrological controls on carbon export from a forested catchment in central Japan</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Here we review research on the links between hydrological processes and the <span class="hlt">biogeochemical</span> environment controlling the dynamics of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in temperate forested catchments. In addition, we present the results of original experiments. The spatial and temporal changes in DIC and DOC concentrations were investigated in tandem with observations of elementary belowground hydrological</p> <div class="credits"> <p class="dwt_author">Masatoshi Kawasaki; Nobuhito Ohte; Masanori Katsuyama</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">225</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.bios.edu/Labs/co2lab/reprints/bates2001.pdf"> <span id="translatedtitle">Interannual variability of oceanic CO and <span class="hlt">biogeochemical</span> properties in the Western North Atlantic subtropical gyre</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Understanding the relationship between Earth's climate and the oceanic carbon cycle requires an understanding of the time-variations of CO in the ocean, it's exchange with the atmosphere, and the rate of uptake of anthropogenic CO by the ocean. Since 1988, hydrographic and <span class="hlt">biogeochemical</span> data have been collected at the Bermuda Atlantic Time-Series Study (BATS) site in the Sargasso Sea, located</p> <div class="credits"> <p class="dwt_author">Nicholas R. Bates</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">226</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2002EGSGA..27.6565T"> <span id="translatedtitle">Inversion of Inherent Optical Properties To Infer <span class="hlt">Biogeochemical</span> Properties of Particles</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">With recent advances in sensing technology, measurements of inherent optical prop- erties (IOPs) are increasingly being used to infer <span class="hlt">biogeochemical</span> properties of sea- water, both in the particulate and dissolved fractions. One area of focus has been in the measurement of the volume scattering function (VSF) and its inversion to estimate characteristics of the particle population such as the size distribution and bulk refrac- tive index, i.e., properties describing the composition of the particle population. The link between spectral beam attenuation and the shape of the particle size distribution has also been investigated. Recent work into these issues will be discussed. Real-time, optical determinations of particle concentration, size distribution, and composition allows the study of <span class="hlt">biogeochemical</span> processes on fine temporal (order of several sam- ples per second) and spatial (order of centimeters) scales, that have not been resolved previously. This resolution is particularly important in understanding <span class="hlt">biogeochemical</span> fluxes in coastal regions where rapid time-space changes in particle composition are common. New methods of evaluating particle composition with VSF measurements also harbor potential for improving well established, but regionally specific, relation- ships between IOPs and certain <span class="hlt">biogeochemical</span> parameters (such as between beam attenuation and total suspended matter).</p> <div class="credits"> <p class="dwt_author">Twardowski, M. S.; Boss, E.</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">227</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=198888"> <span id="translatedtitle">Investigation of In-situ <span class="hlt">Biogeochemical</span> Reduction of Chlorinated Solvents in Groundwater by Reduced Iron Minerals</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p class="result-summary"><span class="hlt">Biogeochemical</span> transformation is a process in which chlorinated solvents are degraded abiotically by reactive minerals formed by, at least in part or indirectly from, anaerobic biological processes. Five mulch biowall and/or vegetable oil-based bioremediation applications for tr...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">228</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=230278"> <span id="translatedtitle">Catchment hydro-<span class="hlt">biogeochemical</span> response to climate change and future land-use</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p class="result-summary">The potential interacting effects of climate change and future land-use on hydrological and <span class="hlt">biogeochemical</span> dynamics rarely have been described at the catchment level and are difficult or impossible to capture through experimentation or observation alone. We apply a new model, Vi...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">229</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/49155820"> <span id="translatedtitle">The <span class="hlt">biogeochemical</span> reactivity of suspended particulate matter at nested sites in the Dee basin, NE Scotland</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Variation in the organic matter content associated with suspended particulate matter (SPM) is an often overlooked component of carbon cycling within freshwater riverine systems. The potential <span class="hlt">biogeochemical</span> reactivity of particulate organic carbon (POC) that affect its interactions and fate, i.e. respired and lost to the atmosphere along river continua or ultimately exported to estuarine and oceanic pools was assessed.Eleven contrasting</p> <div class="credits"> <p class="dwt_author">J. J. C. Dawson; Y. R. Adhikari; C. Soulsby; M. I. Stutter</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">230</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/22235429"> <span id="translatedtitle">Specifics of immunogenesis and metabolism in young hogs under <span class="hlt">biogeochemical</span> conditions of Chuvash Center.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Combined treatment of young hogs with Trepel food supplement and Polystim immunomodulator with consideration for specific <span class="hlt">biogeochemical</span> properties of Chuvash Center produced immunostimulating and metabolic effects and optimized the balance between free radical oxidation response and body antioxidant potential. PMID:22235429</p> <div class="credits"> <p class="dwt_author">Shukanov, R A; Lezhnina, M N; Shukanov, A A</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">231</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/42550863"> <span id="translatedtitle">Organic Carbon Degradation in Anoxic Organic-Rich Shelf Sediments: <span class="hlt">Biogeochemical</span> Rates and Microbial Abundance</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Identifying and explaining bottlenecks in organic carbon mineralization and the persistence of organic matter in marine sediments remain challenging. This study aims to illuminate the process of carbon flow between microorganisms involved in the sedimentary microbial food chain in anoxic, organic-rich sediments of the central Namibian upwelling system, using <span class="hlt">biogeochemical</span> rate measurements and abundances of Bacteroidetes, Gammaproteobacteria, and sulfate-reducing bacteria</p> <div class="credits"> <p class="dwt_author">Elsabé M. Julies; Bernhard M. Fuchs; Carol Arnosti; Volker Brüchert</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">232</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=232678"> <span id="translatedtitle">Effects of Solar UV Radiation and Climate Change on <span class="hlt">Biogeochemical</span> Cycling: Interactions and Feedbacks</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p class="result-summary">Solar UV radiation, climate and other drivers of global change are undergoing significant changes and models forecast that these changes will continue for the remainder of this century. Here we assess the effects of solar UV radiation on <span class="hlt">biogeochemical</span> cycles and the interactions...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">233</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/51248349"> <span id="translatedtitle">Evidence of linked <span class="hlt">biogeochemical</span> and hydrological processes in homogeneous and layered vadose zone systems</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Understanding chemical fate and transport in the vadose zone is critical to protect groundwater resources and preserve ecosystem health. However, prediction can be challenging due to the dynamic hydrologic and <span class="hlt">biogeochemical</span> nature of the vadose zone. Additional controls on hydrobiogeochemical processes are added by subsurface structural heterogeneity. This study uses repacked soil column experiments to quantify linkages between microbial activity,</p> <div class="credits"> <p class="dwt_author">J. T. McGuire; D. J. Hansen; B. P. Mohanty</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">234</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/52980643"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Cycles: A Computer-Interactive Study of Earth System Science and Global Change</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Global biogeochemistry is the discipline that links various aspects of biology, geology, and chemistry to investigate the surface environment of the Earth. The global <span class="hlt">biogeochemical</span> cycles of the elements lie at the very core of the subject and involve a myriad of processes that transform and transport various substances throughout the Earth's ecosphere, which consists of the atmosphere, hydrosphere, shallow</p> <div class="credits"> <p class="dwt_author">Fred T. Mackenzie</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">235</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=105290"> <span id="translatedtitle">INTERACTIVE EFFECTS OF OZONE DEPLETION AND CLIMATE CHANGE ON <span class="hlt">BIOGEOCHEMICAL</span> CYCLES</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p class="result-summary">The effects of ozone depletion on global <span class="hlt">biogeochemical</span> cycles, via increased UV-B radiation at the Earth's surface, have continued to be documented over the past 4 years. In this report we also document various effects of UV-B that interact with global climate change because the...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">236</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/5771873"> <span id="translatedtitle">NUTRIENT STOICHIOMETRIC RELATIONS AND <span class="hlt">BIOGEOCHEMICAL</span> NICHE IN COEXISTING PLANT SPECIES: EFFECT OF SIMULATED CLIMATE CHANGE</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">ABSTRACT: Here ,we define ,a “biogeo- chemical niche” characterized by the,species po- sition in the ,multivariate space generated ,by its content not only of macronutrients like N, P or K, but also of micronutrients such as Mo, Mg and Ca, and trace toxic elements such as Pb and As. We then ,hypothesize ,that the flexibility of the species “<span class="hlt">biogeochemical</span> niche”</p> <div class="credits"> <p class="dwt_author">Josep Peñuelas; Jordi Sardans; Romà Ogaya; Marc Estiarte</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">237</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/49596613"> <span id="translatedtitle">Numerical effects on organic-matter sedimentation and remineralization in <span class="hlt">biogeochemical</span> ocean models</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We investigate the effects of different vertical grid resolutions and algorithms for the calculation of particle sinking on the sedimentation and remineralization of particulate organic matter. Simulations carried out with an idealized 1D model of detritus sinking show that a coarse vertical resolution, such as used in many global <span class="hlt">biogeochemical</span> models, tends to enhance the particle flux through numerical mixing</p> <div class="credits"> <p class="dwt_author">I. Kriest; A. Oschlies</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">238</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012WRR....48.9533G"> <span id="translatedtitle">Residence time distributions in sinuosity-driven hyporheic zones and their <span class="hlt">biogeochemical</span> effects</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Hyporheic exchange plays a key role in the <span class="hlt">biogeochemical</span> 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 (?), valley slope (Jx), hydraulic conductivity (K), aquifer dispersivity (?L), and the <span class="hlt">biogeochemical</span> 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 ?, having a strong influence on the net <span class="hlt">biogeochemical</span> transformations within the HZ. Using BTSs proposed in previous studies and sensitivity analyses, we show the potential of ?, 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 <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Gomez, Jesus D.; Wilson, John L.; Cardenas, M. Bayani</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">239</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://wetlands.ifas.ufl.edu/publications/PDF-articles/300-1.pdf"> <span id="translatedtitle"><span class="hlt">BIOGEOCHEMICAL</span> INDICES OF PHOSPHORUS RETENTION AND RELEASE BY WETLAND SOILS AND ADJACENT STREAM SEDIMENTS</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Eutrophication is still a water quality problem within many watersheds. The Lake Okeechobee Basin, Florida, USA, like many watersheds is impacted by eutrophication caused by excess phosphorus (P). To meet water quality criteria to reduce this impairment, several levels of information on P dynamics within the Basin are required. The use of <span class="hlt">biogeochemical</span> indices to help determine P retention\\/release of</p> <div class="credits"> <p class="dwt_author">Ed J. Dunne; Ramesh Reddy; Mark W. Clark</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">240</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/57474819"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Processes on Tree Islands in the Greater Everglades: Initiating a New Paradigm</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Scientists’ understanding of the role of tree islands in the Everglades has evolved from a plant community of minor <span class="hlt">biogeochemical</span> 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</p> <div class="credits"> <p class="dwt_author">Paul R. Wetzel; Fred H. Sklar; Carlos A. Coronado; Tiffany G. Troxler; Steven L. Krupa; Pamela L. Sullivan; Sharon Ewe; René M. Price; Susan Newman; William H. Orem</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_11");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' 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onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">241</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/54020147"> <span id="translatedtitle">The effect of gold mining and processing on <span class="hlt">biogeochemical</span> cycles in Muteh area, Isfahan province, Iran</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The environmental impacts of gold mining and processing on geochemical and <span class="hlt">biogeochemical</span> 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</p> <div class="credits"> <p class="dwt_author">B. Keshavarzi; F. Moore</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">242</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/19864618"> <span id="translatedtitle">Particle methods for simulation of subsurface multiphase fluid flow and <span class="hlt">biogeochemical</span> processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A number of particle models that are suitable for simulating multiphase fluid flow and <span class="hlt">biogeochemical</span> 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</p> <div class="credits"> <p class="dwt_author">Paul Meakin; Alexandre Tartakovsky; Timothy D. Scheibe; Daniel Tartakovsky; George Redden; Philip E. Long; Scott C. Brooks; Zhijie Xu</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">243</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/48933630"> <span id="translatedtitle">Implications of the carbon cycle steady state assumption for <span class="hlt">biogeochemical</span> modeling performance and inverse parameter retrieval</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We analyze the impacts of the steady state assumption on inverse model parameter retrieval from <span class="hlt">biogeochemical</span> models. An inverse model parameterization study using eddy covariance CO2 flux data was performed with the Carnegie Ames Stanford Approach (CASA) model under conditions of strict and relaxed carbon cycle steady state assumption (CCSSA) in order to evaluate both the robustness of the model's</p> <div class="credits"> <p class="dwt_author">Nuno Carvalhais; Markus Reichstein; Júlia Seixas; G. James Collatz; João Santos Pereira; Paul Berbigier; Arnaud Carrara; André Granier; Leonardo Montagnani; Dario Papale; Serge Rambal; María José Sanz; Riccardo Valentini</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">244</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/53824620"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> controls on the bacterial population in the eastern Atlantic Ocean</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Little is known about bacterial dynamics in the oligotrophic ocean, particularly about its cultivable population. We examined the abundance of total and cultivable bacteria in relation to changes in <span class="hlt">biogeochemical</span> conditions in the eastern Atlantic Ocean with special regard to Vibrio spp., a group of bacteria that can cause diseases in human and aquatic organisms. Surface, deep water and plankton</p> <div class="credits"> <p class="dwt_author">S. B. Neogi; B. P. Koch; P. Schmitt-Kopplin; C. Pohl; G. Kattner; S. Yamasaki; R. J. Lara</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">245</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/53604569"> <span id="translatedtitle">On the <span class="hlt">biogeochemical</span> signature of the Lena River from its headwaters to the Arctic Ocean</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The Lena River integrates <span class="hlt">biogeochemical</span> signals from its vast drainage basin and its signal reaches far out over the Arctic Ocean. Transformation of riverine organic carbon into mineral carbon, and mineral carbon into the organic form in the Lena River watershed, can be considered a quasi-equilibrated processes. Increasing the Lena discharge causes opposite effects on total organic (TOC) and inorganic</p> <div class="credits"> <p class="dwt_author">I. P. Semiletov; I. I. Pipko; N. E. Shakhova; O. V. Dudarev; S. P. Pugach; A. N. Charkin; C. P. McRoy; D. Kosmach; O. Gustafsson</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">246</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/56404003"> <span id="translatedtitle">Estimating the Effects of Mountain Pine Beetle Outbreaks on Biophysical and <span class="hlt">Biogeochemical</span> Variables Using MODIS Products</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Insects such as mountain pine beetle (Dendroctonus ponderosae Hopkins) are major disturbances in forested ecosystems, affecting forest structure and function. In recent decades, mountain pine beetles have affected large forested areas in the United States and Canada. Insect disturbances impact biophysical variables important for atmosphere\\/ecosystem exchanges of mass, energy, and momentum as well as <span class="hlt">biogeochemical</span> processes, notably carbon cycling. Our</p> <div class="credits"> <p class="dwt_author">A. J. Meddens; J. A. Hicke</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">247</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2006AGUFMPP21B1674D"> <span id="translatedtitle">A GEOCLIM Simulation Of Climatic And <span class="hlt">Biogeochemical</span> Consequences Of Pangea Break Up</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Large fluctuations in continental configuration occur all along the Mesozoic times. While it has long been recognized that paleogeography may potentially influence atmospheric CO2 via the continental silicate weathering feedback, no numerical simulation have been done given the lack of a spatially resolved climate- carbon model. GEOCLIM, a <span class="hlt">coupled</span> numerical model of the climate and global <span class="hlt">biogeochemical</span> cycles, is used to investigate the consequences of the Pangea break up. The climate module of the GEOCLIM model is the FOAM atmospheric general circulation model, allowing the calculation of the consumption of atmospheric CO2 through continental silicate weathering with a spatial resolution of 7.5°long 4.5°lat. Seven time slices have been simulated. We show that the break up of the Pangea supercontinent triggers an increase in continental runoff, resulting in enhanced atmospheric CO2 consumption through silicate weathering. As a result, atmospheric CO2 falls from values above 3000 ppmv during the Triassic, down to rather low levels during the Cretaceous (around 400 ppmv), resulting in a decrease in continental temperatures from about 20°C to 10°C. Silicate weathering feedback and paleogeography both act to force the Earth system toward a dry and hot world reaching its optimum over the last 260 Ma during the Middle-Late Triassic. In the super continent case, given the relative aridity that cannot be climatically overwhelmed, the model generates high CO2 values to produce very warm continental temperatures compensating for the lack of continental humidity. Conversely, in the fragmented case, the runoff becomes the most important contributor to the silicate weathering rate, hence, producing a CO2 drawdown and a fall in continental temperatures. Finally, an other unexpected outcome is the pronounced fluctuations in carbonate accumulation simulated by the model in response to the Pangea break up. These fluctuations are driven by changes in continental carbonate weathering flux. Accounting for the fluctuations in area available for carbonate platforms, the simulated ratio of carbonate deposition between neritic and deep sea environments is in better agreement with available data.</p> <div class="credits"> <p class="dwt_author">Donnadieu, Y.; Godderis, Y.; Pierrehumbert, R.; Dromart, G.; Jacob, R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">248</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.H13C1220C"> <span id="translatedtitle">Hydrologic flowpaths and <span class="hlt">biogeochemical</span> cycles in the subalpine Como Creek catchment, Colorado Front Range, USA</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">An outstanding question for snowmelt-dominated watersheds of the western US are the responses of <span class="hlt">biogeochemical</span> processes to two major drivers of environmental change: directional changes in climate and increasing dissolved inorganic nitrogen (DIN) deposition in wetfall. In the Colorado Front Range, atmospheric deposition of DIN has increased several-fold in the last 25 years. In response, nitrate concentrations at the alpine Green Lakes 4 (GL4) catchment have increased from 1985 to 2009 by 0.27 ?eq L-1 yr-1. In contrast, we see no directional change in either nitrate concentrations or fluxes in the subalpine Como Creek catchment. We hypothesize that differences in surface/groundwater interactions result in the differing behavior of stream nitrate between the alpine and subalpine catchments that are receiving similar amounts of DIN from atmospheric deposition. For both basins we sampled precipitation, snowpack, snowmelt, surface water, and subsurface waters. All water samples are analyzed for geochemical, nutrient and isotopic (?18O, ?D) composition. Stream chemistry data from the last ten years at Como Creek show increases in nitrate concentration during baseflow conditions and then a sharp decline during snowmelt. In contrast, in the alpine basin there is sharp increase in surface water nitrate during snowmelt. Hydrograph separation at the alpine GL4 using end member mixing analysis (EMMA) shows that stream flow is a mixture of three components, groundwater, talus, and new snowmelt that each contribute to roughly a third of discharge, with talus flow supplying the majority of nitrate. In contrast, and somewhat surprisingly, EMMA shows that for the subalpine Como Creek basin, annual streamflow is a mixture of only two components, groundwater and new snowmelt. During snowmelt the groundwater and snow contributions are nearly equal and subsurface flows dominate the remainder of the year. Newly installed piezometers at Como Creek provide evidence that the basin is largely a losing reach during snowmelt, with water levels in the piezometers increasing 5-7 m. After peak snowmelt however, Como Creek becomes a gaining stream, with piezometer levels dropping. Thus, both EMMA and piezometers show that surface-groundwater interactions are tightly <span class="hlt">coupled</span> during snowmelt, with snowmelt at Como first replenishing the subsurface water deficit and increasing groundwater levels before contributing to discharge. Thus, in contrast to the alpine GL4 basin, DIN released in snowmelt is assimilated belowground as snowmelt infiltrates the subsurface in the subalpine basin. Interestingly, at the subalpine Como Creek basin, isotopic and geochemical solute concentrations undergo shifts during periods of winter baseflow prior to snowmelt. In winter much of the stream is frozen and we hypothesize that cryo-concentration of solutes and fractionation of isotopes may influence the concentrations of winter stream samples.</p> <div class="credits"> <p class="dwt_author">Cowie, R. M.; Williams, M. W.; Zeliff, M. M.; Parman, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">249</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=221777"> <span id="translatedtitle">MODELING <span class="hlt">COUPLED</span> HYDROLOGICAL AND CHEMICAL PROCESSES: LONG-TERM URANIUM TRANSPORT FOLLOWING PHOSPHOROUS-FERTILIZATION</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p class="result-summary">Contaminants in the vadose zone are affected by the physical processes of water flow, heat movement and multicomponent transport, as well as generally by a range of interacting <span class="hlt">biogeochemical</span> processes. <span class="hlt">Coupling</span> these various processes within one integrated numerical simulator provides a process-ba...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">250</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2003EAEJA.....1018M"> <span id="translatedtitle">Interanual and decadel variability of <span class="hlt">biogeochemical</span> ocean processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We have <span class="hlt">coupled</span> an ocean biology and carbon cycle model (HAMOCC4) to a physical ocean GCM (MPI-OM1, "C-HOPE") and a simple diffusive atmosphere. The grid has high resolution in the high latitude deep-water formation areas, and also meridionally enhanced resolution in the equatorial band. Using the NCEP reanalysis data as forcing fields, the model exhibits high variability in all variables, including the air-to-sea flux of carbon dioxide, on interannual and decadal timescales. We analyzed the processes, which drive the variability in the model, and have also compared the model with observed patterns.</p> <div class="credits"> <p class="dwt_author">Maier-Reimer, E.; Kriest, I.; Wetzel, P.</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">251</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/19853961"> <span id="translatedtitle">Vadose zone attenuation of organic compounds at a crude oil spill site - interactions between <span class="hlt">biogeochemical</span> reactions and multicomponent gas transport.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Contaminant attenuation processes in the vadose zone of a crude oil spill site near Bemidji, MN have been simulated with a reactive transport model that includes multicomponent gas transport, solute transport, and the most relevant <span class="hlt">biogeochemical</span> reactions. Dissolution and volatilization of oil components, their aerobic and anaerobic degradation <span class="hlt">coupled</span> with sequential electron acceptor consumption, ingress of atmospheric O(2), and the release of CH(4) and CO(2) from the smear zone generated by the floating oil were considered. The focus of the simulations was to assess the dynamics between biodegradation and gas transport processes in the vadose zone, to evaluate the rates and contributions of different electron accepting processes towards vadose zone natural attenuation, and to provide an estimate of the historical mass loss. Concentration distributions of reactive (O(2), CH(4), and CO(2)) and non-reactive (Ar and N(2)) gases served as key constraints for the model calibration. Simulation results confirm that as of 2007, the main degradation pathway can be attributed to methanogenic degradation of organic compounds in the smear zone and the vadose zone resulting in a contaminant plume dominated by high CH(4) concentrations. In accordance with field observations, zones of volatilization and CH(4) generation are correlated to slightly elevated total gas pressures and low partial pressures of N(2) and Ar, while zones of aerobic CH(4) oxidation are characterized by slightly reduced gas pressures and elevated concentrations of N(2) and Ar. Diffusion is the most significant transport mechanism for gases in the vadose zone; however, the simulations also indicate that, despite very small pressure gradients, advection contributes up to 15% towards the net flux of CH(4), and to a more limited extent to O(2) ingress. Model calibration strongly suggests that transfer of biogenically generated gases from the smear zone provides a major control on vadose zone gas distributions and vadose zone carbon balance. Overall, the model was successful in capturing the complex interactions between <span class="hlt">biogeochemical</span> reactions and multicomponent gas transport processes. However, despite employing a process-based modeling approach, honoring observed parameter ranges, and generally obtaining good agreement between field observations and model simulations, accurate quantification of natural attenuation rates remains difficult. The modeling results are affected by uncertainties regarding gas phase saturations, tortuosities, and the magnitude of CH(4) and CO(2) flux from the smear zone. These findings highlight the need to better delineate gas fluxes at the model boundaries, which will help constrain contaminant degradation rates, and ultimately source zone longevity. PMID:19853961</p> <div class="credits"> <p class="dwt_author">Molins, S; Mayer, K U; Amos, R T; Bekins, B A</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-09-20</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">252</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..15.5862G"> <span id="translatedtitle">On the physical and <span class="hlt">biogeochemical</span> processes driving the high frequency variability of CO2 fugacity at 6°S, 10°W : Potential role of the internal waves</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The availability of nutrients in the mixed layer is the main limitation to carbon biological production in the tropical regions. In this paper, we investigate the potential role of internal waves at promoting the development of biological activity on a PIRATA mooring at 6°S 10°W. This mooring is located above the Mid-Atlantic ridge where we observe strong internal waves. Using a one dimensional physical and <span class="hlt">biogeochemical</span> <span class="hlt">coupled</span> model, we show that it is possible to simulate dissolved inorganic carbon variations consistent with the biological production derived from the observations, provided that the vertical advection and diapycnal turbulent vertical diffusivity associated with the internal waves are taken into account. Not all the dissolved inorganic carbon (DIC) variations are simulated, likely because of uncertainties in initialization profiles. Nevertheless, our study strengthens the importance of taking into account correctly the effect of internal waves in tropical regions.</p> <div class="credits"> <p class="dwt_author">Gaelle, Parard; Jacqueline, Boutin; Cuypers, Yannis; Bourruet-Aubertot, Pascale; Caniaux, Guy</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">253</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/913605"> <span id="translatedtitle">Hybrid Numerical Methods for Multiscale Simulations of Subsurface <span class="hlt">Biogeochemical</span> Processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Many subsurface flow and transport problems of importance today involve <span class="hlt">coupled</span> non-linear flow, transport, and reaction in media exhibiting complex heterogeneity. In particular, problems involving biological mediation of reactions fall into this class of problems. Recent experimental research has revealed important details about the physical, chemical, and biological mechanisms involved in these processes at a variety of scales ranging from molecular to laboratory scales. However, it has not been practical or possible to translate detailed knowledge at small scales into reliable predictions of field-scale phenomena important for environmental management applications. A large assortment of numerical simulation tools have been developed, each with its own characteristic scale including molecular (e.g., molecular dynamics), microbial (e.g., cellular automata or particle individual-based models), pore (e.g., lattice-Boltzmann, pore network models, and discrete particle methods such as smoothed particle hydrodynamics) and continuum scales (e.g., traditional partial differential equations solved by finite difference or finite element methods). While many problems can be effectively addressed by one of these models at a single scale, some problems may require explicit integration of models across multiple scales. We are developing a hybrid multi-scale subsurface reactive transport modeling framework that integrates models with diverse representations of physics, chemistry and biology at different scales (sub-pore, pore and continuum). The modeling framework is being designed to take advantage of advanced computational technologies including parallel code components using the Common Component Architecture, parallel solvers, gridding, data and workflow management, and visualization. This paper describes the specific methods/codes being used at each scale, techniques used to directly and adaptively <span class="hlt">couple</span> across model scales, and preliminary results of application to a multi-scale model of mineral precipitation at a solute mixing interface.</p> <div class="credits"> <p class="dwt_author">Scheibe, Timothy D.; Tartakovsky, Alexandre M.; Tartakovsky, Daniel M.; Redden, George D.; Meakin, Paul</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-08-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">254</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012EGUGA..14.3689K"> <span id="translatedtitle">How important are <span class="hlt">biogeochemical</span> hotspots at aquifer-river interfaces for surface water and groundwater quality?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The mixing of groundwater (GW) and surface water (SW) can have substantial impact on the transformation of solutes transported between aquifer and river. The assessment of <span class="hlt">biogeochemical</span> cycling at reactivity hotspots as the aquifer-river interface and its implications for GW and SW quality require detailed understanding of the complex patterns of GW-SW exchange fluxes and residence time distributions in particular under changing climatic and landuse conditions. This study presents combined experimental and model-based investigations of the physical drivers and chemical controls of nutrient transport and transformation at the aquifer-river interfaces of two upland and lowland UK rivers. It combines the application of in-stream geophysical exploration techniques, multi-level mini-piezometer networks, active and passive heat tracing methods (including fibre-optic distributed temperature sensing - FO-DTS) for identifying hyporheic exchange fluxes and residence time distributions with multi-scale approaches of hyporheic pore-water sampling and reactive tracers for analysing the patterns of streambed redox conditions and chemical transformation rates. The analysis of hyporheic pore water from nested multi-level mini piezometers and passive gel probe samplers revealed significant spatial variability in streambed redox conditions and concentration changes of nitrogen species, dissolved oxygen and bio-available organic carbon. Hot spots of increased nitrate attenuation were identified beneath semi-confining peat lenses in the streambed of the investigated lowland river. The intensity of concentration changes underneath the confining peat pockets correlated with the state of anoxia in the pore water as well as the supply of organic carbon and hyporheic residence times. In contrast, at locations where flow inhibiting peat layers were absent or disrupted - fast exchange between aquifer and river caused a break-through of nitrate without significant concentration changes along the hyporheic flow path. Fibre-optic distributed temperature sensor networks and streambed electric resistivity tomography were applied for identifying exchange flow patterns between groundwater and surface water in dependency of streambed structural heterogeneity and for delineating the location and extend of flow inhibiting structures as indicators of streambed reactivity hot spots. Results of these surveys indicate that during summer, patterns of cold spots in the investigated streambed sediments can be attributed to fast groundwater up-welling in sandy and gravely sediments resulting in low hyporheic residence times. Contrasting conditions were found at warmer areas at the streambed surface where groundwater - surface water exchange was inhibited by the existence of peat or clay lenses within the streambed. Model simulations of <span class="hlt">coupled</span> groundwater and surface water flow indicated that ignoring the increased reactivity in hyporheic streambed hotspots would lead to substantial under- or over-prediction of nitrate fluxes between aquifer and stream with potentially critical implications for river management and restoration. The investigations supported the development of a conceptual model of aquifer-river exchange and hyporheic reactivity in lowland rivers including temperature traceable hyporheic exchange fluxes at multiple scales and highlighted the necessity to adequately reflect hyporheic hotspot reactivity in <span class="hlt">coupled</span> groundwater-surface water models for adequate water quality predictions.</p> <div class="credits"> <p class="dwt_author">Krause, S.; Blume, T.; Weatherill, J.; Munz, M.; Tecklenburg, C.; Angermann, L.; Cassidy, N. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">255</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=105435"> <span id="translatedtitle">EFFECT OF NUTRIENT LOADING ON <span class="hlt">BIOGEOCHEMICAL</span> AND MICROBIAL PROCESSES IN A NEW ENGLAND HIGH SALT MARSH, SPARTINA PATNES, (AITON MUHL)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> and microbial processes during the summer growing sea...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">256</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2004AGUSM.U22A..03C"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> susceptibility of Proterozoic oceans to extreme isotopic events</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">It has been suggested that Proterozoic oceans contained an unusually concentrated pool of dissolved and suspended organic carbon [1]. This high concentration is traced to its accumulation in the water column, prior to the evolutionary innovations that caused organic matter to sink. Oxidation of a small part of this large reservoir can create a large isotopic signal in the smaller inorganic pool, thereby explaining the large Neoproterozoic fluctuations in the isotopic composition of carbonate. Here we construct a simple continuous model to analyze the mechanisms by which such an organic-rich ocean can be created and investigate its stability with respect to oceanic circulation and evolutionary changes. Our model describes the biological, geochemical, and physical interactions of oceanic organic carbon, dissolved oxygen, and dissolved nutrients as a function of depth. It is formulated as <span class="hlt">coupled</span> advection-reaction-diffusion equations. We first verify that, in the presence of sinking organic matter, the model simulates modern depth profiles of oxygen, carbon, and nutrients such as phosphorus. We then explore the consequences of producing neutrally-buoyant organic matter. As expected, this case results in lower levels of oxygen at depth. We analyze the dynamic stability of this state, with particular emphasis on the effects of instability on the isotopic composition of carbonate. 1. Rothman D.H., Hayes J.M., Summons R.E. (2003) Dynamics of the Neoproterozoic carbon cycle. Proc. Nat. Acad. Sci., USA 100: 8124 - 8129.</p> <div class="credits"> <p class="dwt_author">Cohen, A. M.; Rothman, D. H.</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-05-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">257</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=207472"> <span id="translatedtitle"><span class="hlt">Surface-subsurface</span> flow linkage in a snowmelt environment</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p class="result-summary">In much of the inter-mountain western USA streamflow and water resources are driven by snowmelt. Hydrologic objectives for addressing water issues have generally revolved around predicting the timing and amount of snowmelt input and assessing the impact on streamflow. Groundwater is generally overlo...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">258</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009EGUGA..11.6646H"> <span id="translatedtitle">Testing methods for estimating physical and <span class="hlt">biogeochemical</span> uncertainty in GENIE-1</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Our goal is the simultaneous estimate of the uncertainty in physical and ocean <span class="hlt">biogeochemical</span> parameters in the intermediate complexity GENIE-1 model, which has an energy balance atmosphere and a 16 level frictional geostrophic ocean. Since the model is relatively cheap to run, it is also a good model for running large ensembles and testing new methods for parameter estimation. Here we have somewhat simplified our problem compared to previous work, performing an identical twin test and varying 4 physical and 4 <span class="hlt">biogeochemical</span> parameters. We use ensembles of several hundred members to improve the accuracy of the solution. Here we present the results generated to date by two different flavours of Iterative Importance Sampling.</p> <div class="credits"> <p class="dwt_author">Hargreaves, J. C.; Annan, J. D.; Ridgwell, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">259</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/946786"> <span id="translatedtitle">Novel imaging techniques, integrated with mineralogical, geochemical and microbiological characterizations to determine the <span class="hlt">biogeochemical</span> controls on technetium mobility in FRC sediments</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The objective of this research program was to take a highly multidisciplinary approach to define the <span class="hlt">biogeochemical</span> factors that control technetium (Tc) mobility in FRC sediments. The aim was to use batch and column studies to probe the <span class="hlt">biogeochemical</span> conditions that control the mobility of Tc at the FRC. Background sediment samples from Area 2 (pH 6.5, low nitrate, low {sup 99}Tc) and Area 3 (pH 3.5, high nitrate, relatively high {sup 99}Tc) of the FRC were selected (http://www.esd.ornl.gov/nabirfrc). For the batch experiments, sediments were mixed with simulated groundwater, modeled on chemical constituents of FRC waters and supplemented with {sup 99}Tc(VII), both with and without added electron donor (acetate). The solubility of the Tc was monitored, alongside other <span class="hlt">biogeochemical</span> markers (nitrate, nitrite, Fe(II), sulfate, acetate, pH, Eh) as the 'microcosms' aged. At key points, the microbial communities were also profiled using both cultivation-dependent and molecular techniques, and results correlated with the geochemical conditions in the sediments. The mineral phases present in the sediments were also characterized, and the solid phase associations of the Tc determined using sequential extraction and synchrotron techniques. In addition to the batch sediment experiments, where discrete microbial communities with the potential to reduce and precipitate {sup 99}Tc will be separated in time, we also developed column experiments where <span class="hlt">biogeochemical</span> processes were spatially separated. Experiments were conducted both with and without amendments proposed to stimulate radionuclide immobilization (e.g. the addition of acetate as an electron donor for metal reduction), and were also planned with and without competing anions at high concentration (e.g. nitrate, with columns containing Area 3 sediments). When the columns had stabilized, as determined by chemical analysis of the effluents, we used a spike of the short-lived gamma emitter {sup 99m}Tc (50-200 MBq; half life 6 hours) and its mobility was monitored using a {gamma}-camera. Incorporation of low concentrations of the long-lived 99Tc gave a tracer that can be followed by scintillation counting, should the metastable form of the radionuclide decay to below detection limits before the end of the experiment (complete immobilization or loss of the Tc from the column). After the Tc was reduced and immobilized, or passed through the system, the columns were dismantled carefully in an anaerobic cabinet and the pore water geochemistry and mineralogy of the columns profiled. Microbial community analysis was determined, again using molecular and culture-dependent techniques. Experimental results were also modeled using an established <span class="hlt">coupled</span> speciation and transport code, to develop a predictive tool for the mobility of Tc in FRC sediments. From this multidisciplinary approach, we hoped to obtain detailed information on the microorganisms that control the <span class="hlt">biogeochemical</span> cycling of key elements at the FRC, and we would also be able to determine the key factors that control the mobility of Tc at environmentally relevant concentrations at this site.</p> <div class="credits"> <p class="dwt_author">Jonathan R. Lloyd</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-02-03</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">260</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/899189"> <span id="translatedtitle"><span class="hlt">Coupling</span> TOUGH2 with CLM3: Developing a <span class="hlt">Coupled</span> Land Surface andSubsurface Model</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">An understanding of the hydrologic interactions among atmosphere, land surface, and subsurface is one of the keys to understanding the water cycling system that supports life on earth. The inherent <span class="hlt">coupled</span> processes and complex feedback structures among subsystems make such interactions difficult to simulate. In this paper, we present a model that simulates the land surface and subsurface hydrologic response to meteorological forcing. This model combines a state-of-the-art land-surface model, the NCAR Community Land Model version 3 (CLM3), with a variably saturated groundwater model, TOUGH2, through an internal interface that includes flux and state variables shared by the two submodels. Specifically, TOUGH2 uses infiltration, evaporation, and root-uptake rates, calculated by CLM3, as source/sink terms in its simulation; CLM3 uses saturation and capillary pressure profiles, calculated by TOUGH2, as state variables in its simulation. This new model, CLMT2, preserves the best aspects of both submodels: the state-of-the-art modeling capability of surface energy and hydrologic processes (including snow, runoff, freezing/melting, evapotranspiration, radiation, and biophysiological processes) from CLM3 and the more realistic physical-process-based modeling capability of subsurface hydrologic processes (including heterogeneity, three-dimensional flow, seamless combining of unsaturated and saturated zone, and water table) from TOUGH2. The preliminary simulation results show that the <span class="hlt">coupled</span> model greatly improved the predictions of the groundwater table, evapotranspiration, and surface temperature at a real watershed, as evaluated using 18 years of observed data. The new model is also ready to be <span class="hlt">coupled</span> with an atmospheric simulation model, to form one of the first top of the atmosphere to deep groundwater atmosphere-land-<span class="hlt">surface-subsurface</span> models.</p> <div class="credits"> <p class="dwt_author">Pan, Lehua; Jin, Jiming; Miller, Norman; Wu, Yu-Shu; Bodvarsson,Gudmundur</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-05-19</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_12");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" 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showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_15");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">261</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUSM.H31D..04R"> <span id="translatedtitle">Nutrient Cycling in Streams: Hydrologic and <span class="hlt">Biogeochemical</span> Controls on Intra-Annual Temporal Fluctuations</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Rapid changes in land use (e.g., shifts from agriculture to urban; intensification of agriculture) and projected impacts of global climate change (e.g., shifts in precipitation patterns) are expected to be reflected in shifts in the hydrologic cycles and the <span class="hlt">biogeochemical</span> cycles of nutrients and other contaminants, with an attendant spatial and temporal perturbations in aquatic ecosystem functions. Episodic nutrient loads to lotic systems occur via runoff events, with the advective transport along the river network moderated by <span class="hlt">biogeochemical</span> transformations, thus mitigating the likely impacts on downstream ecosystems. Exploring two types of patterns are of interest when examining nutrient cycling rates in river networks: (1) spatial patterns in temporally integrated (e.g., annual average) nutrient losses along the river networks, and (2) temporal patterns (e.g., intra- or inter-annual) in spatially integrated trends in nutrient losses at a given location within the network. The first type has received considerable attention over the past two decades in a series of field studies and modeling studies to interpret these data. However, studies focusing on temporal variations have only recently begun to receive attention. In examining nutrient losses along the stream/river networks, it is important to acknowledge the importance of: (1) the spatial patterns emerging from the hydrologic controls on <span class="hlt">biogeochemical</span> processes as the contributing drainage area increases; and (2) the temporal variations reflective of the short-term (intra- annual) and long-term (inter-annual) variations in climate-hillslope-vegetation interactions reflected in stream flow variations. We present here a conceptual framework of hierarchical levels of linked hydrologic and <span class="hlt">biogeochemical</span> controls, and then present a stochastic analytical approach to explicitly link such interactions to predict the intra-annual temporal variations in nutrient cycling in streams. Available data for nitrate cycling in stream networks is examined as the first case study for this approach.</p> <div class="credits"> <p class="dwt_author">Rao, P. C.; Basu, N. B.; Zanardo, S.; Botter, G.; Rinaldo, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">262</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://serc.carleton.edu/NAGTWorkshops/hydrogeo/HSG2013/activities/71641.html"> <span id="translatedtitle">How to read elemental soil profiles to investigate the <span class="hlt">biogeochemical</span> processes in Critical Zone?</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL National Science Digital Library</a></p> <p class="result-summary">In this exercise, students use elemental chemistry data in a soil profile to explore major <span class="hlt">biogeochemical</span> processes that dominate in critical zone. Data will be provided, and students calculate and graph the mass transfer coefficients as a function of depth using Excel. Based on these plots, student make generalized statements about how different elements behave in this soil profile and what processes dominate, e.g., depletion by rock-water interaction, addition by dust inputs or elemental loading by human activities etc.</p> <div class="credits"> <p class="dwt_author">Jin, Lixin</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">263</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/53065583"> <span id="translatedtitle">Spatial Scaling Patterns of C, N and P Loads in Engineered Watersheds: Hydrologic vs. <span class="hlt">Biogeochemical</span> Drivers</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Understanding nutrient dynamics in diverse ecosystems is critical in evaluating ecological impacts (e.g., eutrophication; coastal hypoxia) from increased loads of nitrogen (N), phosphorus (P), and carbon (C). The linkage between the hydrologic and the <span class="hlt">biogeochemical</span> cycles is crucial for predicting nutrient cycling in these ecosystems. Examining the impacts of large-scale human modifications of watersheds (e.g., land-use intensification for food production;</p> <div class="credits"> <p class="dwt_author">N. B. Basu; P. C. Rao; Z. S; S. Ye; G. Botter; M. Sivapalan; A. Rinaldo</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">264</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/47882979"> <span id="translatedtitle">Examining Human Impacts on Global <span class="hlt">Biogeochemical</span> Cycling Via the Coastal Zone and Ocean Margins</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">\\u000a <span class="hlt">Biogeochemical</span> cycling, like most earth system functions, is increasingly subject to human perturbation. Nowhere is this more\\u000a evident than in the coastal zone, the interphase domain between land, ocean, and atmosphere. The coast and its ecosystems,\\u000a including wetlands, estuaries, marshes, mangroves, seagrasses, and coral reefs, are continuously modified by human activities\\u000a through changing land and water uses, and increasing waste</p> <div class="credits"> <p class="dwt_author">Liana Talaue-McManus</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">265</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/48138803"> <span id="translatedtitle">Geological and <span class="hlt">biogeochemical</span> prerequisites for high Fe and Mn contents in the Amur River water</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The role of natural and anthropogenic factors in the seasonal dynamics of the Fe and Mn ion migration in the Amur River water\\u000a is examined. The contribution of the <span class="hlt">biogeochemical</span> processes in the migration of the Fe and Mn ions at the water-river bed\\u000a and groundwater-surface water contact zone is substantiated. The causes of the anomalously high Mn content in</p> <div class="credits"> <p class="dwt_author">V. V. Kulakov; L. M. Kondratyeva; Ye. M. Golubeva</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">266</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/41013383"> <span id="translatedtitle">Towards a classification of organic enrichment in marine sediments based on <span class="hlt">biogeochemical</span> indicators</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A nomogram is developed to show that pH, redox potentials (EhNHE) and measures of dissolved sulfides (H2S+HS?+S2?)(total free S2?) can be used to classify organic enrichment impacts in marine sediments. The <span class="hlt">biogeochemical</span> cycle of sulfur in marine sediments is described to show that changes in macrobenthic infauna community structure associated with high levels of organic matter supply result from stress</p> <div class="credits"> <p class="dwt_author">B. T. Hargrave; M. Holmer; C. P. Newcombe</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">267</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/41346355"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> cyclic activity of bacterial arsB in arsenic-contaminated mines</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary"><span class="hlt">Biogeochemical</span> cyclic activity of the ars (arsenic resistance system) operon is arsB influx\\/efflux encoded by the ecological of Pseudomonas putida. This suggests that studying arsenite-oxidizing bacteria may lead to a better understanding of molecular geomicrobiology, which can be applied to the bioremediation of arsenic-contaminated mines. This is the first report in which multiple arsB-binding mechanisms have been used on indigenous</p> <div class="credits"> <p class="dwt_author">Jin-Soo CHANG; Xianghao REN; Kyoung-Woong KIM</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">268</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009WRR....45.8420C"> <span id="translatedtitle">A state-space Bayesian framework for estimating <span class="hlt">biogeochemical</span> transformations using time-lapse geophysical data</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We develop a state-space Bayesian framework to combine time-lapse geophysical data with other types of information for quantitative estimation of <span class="hlt">biogeochemical</span> parameters during bioremediation. We consider characteristics of end products of <span class="hlt">biogeochemical</span> transformations as state vectors, which evolve under constraints of local environments through evolution equations, and consider time-lapse geophysical data as available observations, which could be linked to the state vectors through petrophysical models. We estimate the state vectors and their associated unknown parameters over time using Markov chain Monte Carlo sampling methods. To demonstrate the use of the state-space approach, we apply it to complex resistivity data collected during laboratory column biostimulation experiments that were poised to precipitate iron and zinc sulfides during sulfate reduction. We develop a petrophysical model based on sphere-shaped cells to link the sulfide precipitate properties to the time-lapse geophysical attributes and estimate volume fraction of the sulfide precipitates, fraction of the dispersed, sulfide-encrusted cells, mean radius of the aggregated clusters, and permeability over the course of the experiments. Results of the case study suggest that the developed state-space approach permits the use of geophysical data sets for providing quantitative estimates of end-product characteristics and hydrological feedbacks associated with <span class="hlt">biogeochemical</span> transformations. Although tested here on laboratory column experiment data sets, the developed framework provides the foundation needed for quantitative field-scale estimation of <span class="hlt">biogeochemical</span> parameters over space and time using direct, but often sparse wellbore data with indirect, but more spatially extensive geophysical data sets.</p> <div class="credits"> <p class="dwt_author">Chen, Jinsong; Hubbard, Susan S.; Williams, Kenneth H.; Pride, Steve; Li, Li; Steefel, Carl; Slater, Lee</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-08-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">269</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40779943"> <span id="translatedtitle">The hydromagnesite playas of Atlin, British Columbia, Canada: A <span class="hlt">biogeochemical</span> model for CO 2 sequestration</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Anthropogenic greenhouse gas emissions may be offset by sequestering carbon dioxide (CO2) through the carbonation of magnesium silicate minerals to form magnesium carbonate minerals. The hydromagnesite [Mg5(CO3)4(OH)2·4H2O] playas of Atlin, British Columbia, Canada provide a natural model to examine mineral carbonation on a watershed scale. At near surface conditions, CO2 is <span class="hlt">biogeochemically</span> sequestered by microorganisms that are involved in weathering</p> <div class="credits"> <p class="dwt_author">Ian M. Power; Siobhan A. Wilson; James M. Thom; Gregory M. Dipple; Janet E. Gabites; Gordon Southam</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">270</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/41182560"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> processes in Amazon shelf waters: chemical distributions and uptake rates of silicon, carbon and nitrogen</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary"><span class="hlt">Biogeochemical</span> processes in the Amazon River\\/ocean mixing zone were examined during four AmasSeds cruises between August 1989 and November 1991. On the Amazon shelf, the distributions of chlorophyll-a, oxygen supersaturation, pH and the biogenic-silica content of suspended matter all showed coherent patterns highlighting areas of high primary productivity. Phytoplankton blooms occurred seaward of the high-turbidity waters (suspended-solid concentration >10 mg</p> <div class="credits"> <p class="dwt_author">D. J. DeMaster; W. O. Smith; D. M. Nelson; J. Y. Aller</p> <p class="dwt_publisher"></p> <p class="publishDate">1996-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">271</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/57711568"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Reduction Processes in a HyperAlkaline Leachate Affected Soil Profile</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Hyperalkaline surface environments can occur naturally or because of contamination by hydroxide-rich wastes. The high pH produced in these areas has the potential to lead to highly specialized microbial communities and unusual <span class="hlt">biogeochemical</span> processes. This article reports an investigation into the geochemical processes that are occurring in a buried, saturated, organic-rich soil layer at pH 12.3. The soil has been</p> <div class="credits"> <p class="dwt_author">Ian T. Burke; Robert J. G. Mortimer; Shanmugam Palaniyandi; Robert A. Whittleston; Cindy L. Lockwood; David J. Ashley; Douglas I. Stewart</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">272</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/963651"> <span id="translatedtitle">A state-space Bayesian framework for estimating <span class="hlt">biogeochemical</span> transformations using time-lapse geophysical data</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">We develop a state-space Bayesian framework to combine time-lapse geophysical data with other types of information for quantitative estimation of <span class="hlt">biogeochemical</span> parameters during bioremediation. We consider characteristics of end-products of <span class="hlt">biogeochemical</span> transformations as state vectors, which evolve under constraints of local environments through evolution equations, and consider time-lapse geophysical data as available observations, which could be linked to the state vectors through petrophysical models. We estimate the state vectors and their associated unknown parameters over time using Markov chain Monte Carlo sampling methods. To demonstrate the use of the state-space approach, we apply it to complex resistivity data collected during laboratory column biostimulation experiments that were poised to precipitate iron and zinc sulfides during sulfate reduction. We develop a petrophysical model based on sphere-shaped cells to link the sulfide precipitate properties to the time-lapse geophysical attributes and estimate volume fraction of the sulfide precipitates, fraction of the dispersed, sulfide-encrusted cells, mean radius of the aggregated clusters, and permeability over the course of the experiments. Results of the case study suggest that the developed state-space approach permits the use of geophysical datasets for providing quantitative estimates of end-product characteristics and hydrological feedbacks associated with <span class="hlt">biogeochemical</span> transformations. Although tested here on laboratory column experiment datasets, the developed framework provides the foundation needed for quantitative field-scale estimation of <span class="hlt">biogeochemical</span> parameters over space and time using direct, but often sparse wellbore data with indirect, but more spatially extensive geophysical datasets.</p> <div class="credits"> <p class="dwt_author">Chen, J.; Hubbard, S.; Williams, K.; Pride, S.; Li, L.; Steefel, C.; Slater, L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-04-15</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">273</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40207410"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> behavior of Ampelozizyphus amazonicus Ducke in the Pitinga mining district, Amazon, Brazil</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The vegetal species Ampelozizyphus amazonicus Ducke (Rhamnaceae Family) was chosen as a sampling medium for the lateritic surfaces of the Pitinga Mine in the Amazon region,\\u000a in order to study the <span class="hlt">biogeochemical</span> behavior of this species and compare it with the chemical composition of a reference\\u000a plant. The Pitinga mining district is one of the largest producers of tin in</p> <div class="credits"> <p class="dwt_author">M. C. Lima e Cunha; V. P. Pereira; E. Menegotto; A. C. Bastos Neto; L. D. Oliveira; M. L. L. Formoso</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">274</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.aslo.org/lo/toc/vol_45/issue_2/0309.pdf"> <span id="translatedtitle">Continuous monitoring of surface optical properties across a geostrophic front: <span class="hlt">Biogeochemical</span> inferences</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A system was designed for the continuous surface monitoring of hydrological, bio-optical, and <span class="hlt">biogeochemical</span> properties in the vicinity of the Almeria-Oran jet-front system (Northwestern Mediterranean Sea). This system included a thermosalinograph, a fluorometer, an optical particle counter, and an absorbance-attenuance meter (AC9), allowing the estimation of the absorption (a(l), (m 21 )) and scattering (b(l), (m 21 )) coefficients at</p> <div class="credits"> <p class="dwt_author">Hervé Claustre; Frank Fell; Kadija Oubelkheir; Louis Prieur; Antoine Sciandra; Bernard Gentili; Marcel Babin</p> <p class="dwt_publisher"></p> <p class="publishDate">2000-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">275</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/7x8u96n156122x62.pdf"> <span id="translatedtitle">Rock-eating mycorrhizas: their role in plant nutrition and <span class="hlt">biogeochemical</span> cycles</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A decade ago, tunnels inside mineral grains were found that were likely formed by hyphae of ectomycorrhizal (EcM) fungi. This\\u000a observation implied that EcM fungi can dissolve mineral grains. The observation raised several questions on the ecology of\\u000a these “rock-eating” fungi. This review addresses the roles of these rock-eating EcM associations in plant nutrition, <span class="hlt">biogeochemical</span>\\u000a cycles and pedogenesis. Research approaches</p> <div class="credits"> <p class="dwt_author">Laura van Schöll; Thomas W. Kuyper; Mark M. Smits; Renske Landeweert; Ellis Hoffland; Nico van Breemen</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">276</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/41858701"> <span id="translatedtitle">Deepened snow increases late thaw <span class="hlt">biogeochemical</span> pulses in mesic low arctic tundra</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Pulses of plant-available nutrients to the soil solution are expected to occur during the dynamic winter–spring transition\\u000a in arctic tundra. Our aims were to quantify the magnitude of these potential nutrient pulses, to understand the sensitivity\\u000a of these pulses to winter conditions, and to characterize and integrate the environmental and <span class="hlt">biogeochemical</span> dynamics of this\\u000a period. To test the hypotheses that</p> <div class="credits"> <p class="dwt_author">Kate M. Buckeridge; Paul Grogan</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">277</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/51320275"> <span id="translatedtitle">Regional-Scale <span class="hlt">Biogeochemical</span> Modeling of Greenhouse Gas (GHG) Emissions from Wetland Ecosystems</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Wetlands can play an important role in carbon sequestration, greenhouse gas (GHG) emissions, and global warming. <span class="hlt">Biogeochemical</span> models are valuable tools to quantify emissions of major GHGs such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from wetland ecosystems. Although several models can be found in literature, most of them are mainly site-scale models and only few have</p> <div class="credits"> <p class="dwt_author">O. Abdul-Aziz; S. Liu; C. J. Young; S. Huang</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">278</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/22504424"> <span id="translatedtitle">Cyclic <span class="hlt">biogeochemical</span> processes and nitrogen fate beneath a subtropical stormwater infiltration basin.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">A stormwater infiltration basin in north-central Florida, USA, was monitored from 2007 through 2008 to identify subsurface <span class="hlt">biogeochemical</span> processes, with emphasis on N cycling, under the highly variable hydrologic conditions common in humid, subtropical climates. Cyclic variations in <span class="hlt">biogeochemical</span> 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 ?(15)N during prolonged basin flooding, and isotopically heavy ?(15)N and ?(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 <span class="hlt">biogeochemically</span> 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 <span class="hlt">biogeochemical</span> conditions under the observed basin. PMID:22504424</p> <div class="credits"> <p class="dwt_author">O'Reilly, Andrew M; Chang, Ni-Bin; Wanielista, Martin P</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-03-23</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">279</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2004AGUFM.B13A0211L"> <span id="translatedtitle">A new InterRidge Working Group : <span class="hlt">Biogeochemical</span> Interactions at Deep-sea Vents</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">A new Working Group on `<span class="hlt">Biogeochemical</span> Interactions at deep-sea vents' has been created at the initiative of the InterRidge programme. This interdisciplinary group comprises experts in chemistry, geochemistry, biogeochemistry, and microbial ecology addressing questions of <span class="hlt">biogeochemical</span> interactions in different MOR and BAB environments. The past decade has raised major issues concerning the interactions between biotic and abiotic compartments of deep-sea hydrothermal environments and the role they play in the microbial turnover of C, S, N, Fe, fluxes from the geosphere to hydrosphere, the formation of biominerals, the functioning of vent ecosystems and life in extreme environments, the deep-biosphere, and the origin of life. Recent multidisciplinary studies have provided some new insights to these issues. Results of some of these studies will be presented here. They point out the variability and complexity of geobiological systems at vents in space and time and highlight the need for interactions across the fields of chemistry, geochemistry, biogeochemistry, and microbial ecology of hydrothermal environments. Limitation for advances in these fields include the availability of seafloor observation/experimentation time, and of underwater instrumentation allowing quantitative, in situ measurements of chemical and biological fluxes, as well as physical and chemical sensing and sampling along small scale gradients and repeated observation of study sites. The aim of this new Working Group is to strengthen the scientific exchange among chemists, geochemists, biogeochemists and microbial ecologists to favor collaboration in field studies including intercomparison of methods and planning of integrated experiments. The <span class="hlt">Biogeochemical</span> Interactions working group will also foster development of underwater instrumentation for in situ <span class="hlt">biogeochemical</span> measurements and microscale sampling, and promote exchange and collaboration with students and scientists of neighboring disciplines, particularly with vent biologists, ecologists and geologists .</p> <div class="credits"> <p class="dwt_author">Le Bris, N.; Boetius, A.; Tivey, M. K.; Luther, G. W.; German, C. R.; Wenzhoefer, F.; Charlou, J.; Seyfried, W. E.; Fortin, D.; Ferris, G.; Takai, K.; Baross, J. A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">280</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/42550689"> <span id="translatedtitle">A Simple <span class="hlt">Biogeochemical</span> Process Removing Arsenic from a Mine Drainage Water</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Arsenic is a toxic element commonly found in mining environments. The present study aimed to determine the influence of the indigenous bacterial population on the <span class="hlt">biogeochemical</span> evolution of arsenic concentration in a mine drainage water. Biological As(III)-oxidizing activity was detected in diverse micro-environments along the water stream, from the source to the discharge point. Laboratory experiments showed that the bacterial</p> <div class="credits"> <p class="dwt_author">Fabienne Battaglia-Brunet; Yann Itard; Francis Garrido; Fabian Delorme; Catherine Crouzet; Catherine Greffié; Catherine Joulian</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_13");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" 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id="NextPageLink" onclick='return showDiv("page_16");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">281</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.B11F..07B"> <span id="translatedtitle">Hydrologic and <span class="hlt">Biogeochemical</span> Controls on Solute Export across Human Impact Gradients</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Intensively managed catchments are characterized by a dominance of human impacts and shifts in natural hydrological and <span class="hlt">biogeochemical</span> functioning. Concentration discharge relationships of geogenic (weathering derived) solutes and nutrients (nitrogen and phosphorus species) from pristine and agricultural basins were compared to explore anthropogenic impacts on <span class="hlt">biogeochemical</span> functioning. The results suggest that the export of nutrients shifts from episodic (highly variable concentration with minimal correlation between concentration and discharge) in pristine catchments to chemostatic (i.e. lower variability in concentration and strong correlation between concentration and discharge) in agricultural catchments. Chemostatic response was also characteristic of geogenic solutes in both pristine and managed systems. We hypothesized that chemostatic response dominates in transport-limited catchments that have internal sources of the solute to buffer the periodicity in episodic inputs, while episodic response dominates in source-limited catchments. The shift from episodic nitrate export in pristine catchments to chemostatic regimes in managed watersheds was attributed to legacy stores of nitrogen built from continued fertilizer applications. These sources buffer interannual variations in <span class="hlt">biogeochemical</span> processing, and make predictions of nitrate loads easier than in pristine systems.</p> <div class="credits"> <p class="dwt_author">Basu, N. B.; Rao, S.; Thompson, S. E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">282</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2005AGUFM.B52A..05W"> <span id="translatedtitle">Integrating Microbial Community Composition With <span class="hlt">Biogeochemical</span> Carbon and Nitrogen Dynamics: Examples From Lignin and Polyphenol Decomposition</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary"><span class="hlt">Biogeochemical</span> models conceptually utilize box and arrow diagrams to explain the rates of carbon cycling in soil. Within these models, labile, intermediate, and recalcitrant pools of carbon are linked to each other, to respiration, and dissolved organic carbon (DOC) flux using parameterized rate functions. These models have often been successful at predicting carbon cycling rates, but they often have to be parameterized to new environmental conditions. This may occur in part because <span class="hlt">biogeochemical</span> models do not explicitly include the underlying biological mechanisms controlling decomposition. <span class="hlt">Biogeochemical</span> models may be improved by advances in our understanding the distribution, biomass, and activity of decomposer functional groups. It is especially useful to understand the dynamics of decomposer functional groups and enzyme systems that breakdown recalcitrant soil carbon such as lignin and condensed polyphenolics. Quantitative PCR (QPCR) is an advance in molecular biology that can target decomposer functional groups and functional genes that holds promise for understanding the landscape-level variability in microbial communities controlling the flow and fate of carbon. Here we provide examples of how the abundance and distribution of soil fungi in grassland, temperate and boreal forests predicts the enzymatic capacity of the soil community to decompose recalcitrant soil C. Moreover, the abundance of soil fungi has important implications for the response of decomposers to soil N availability.</p> <div class="credits"> <p class="dwt_author">Waldrop, M.; Zak, D. R.; Blackwood, C.; Harden, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">283</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013BGeo...10.5651Q"> <span id="translatedtitle">Comparing soil <span class="hlt">biogeochemical</span> processes in novel and natural boreal forest ecosystems</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> processes between reconstructed soils and plants. In this study, we assessed key soil <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> attributes when comparing novel, anthropogenic ecosystems to the mature ecosystems that constitute ecological targets.</p> <div class="credits"> <p class="dwt_author">Quideau, S. A.; Swallow, M. J. B.; Prescott, C. E.; Grayston, S. J.; Oh, S.-W.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-08-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">284</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/20105035"> <span id="translatedtitle">Global <span class="hlt">biogeochemical</span> changes at both ends of the proterozoic: insights from phosphorites.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The distribution of major phosphate deposits in the Precambrian sedimentary rock record is restricted to periods that witnessed global <span class="hlt">biogeochemical</span> changes, but the cause of this distribution is unclear. The oldest known phosphogenic event occurred around 2.0 Ga and was followed, after more than 1.3 billion years, by an even larger phosphogenic event in the Neoproterozoic. Phosphorites (phosphate-rich sedimentary rocks that contain more than 15% P(2)O(5)) preserve a unique record of seawater chemistry, biological activity, and oceanographic changes. In an attempt to emphasize the potentially crucial significance of phosphorites in the evolution of Proterozoic <span class="hlt">biogeochemical</span> cycles, this contribution provides a review of some important Paleoproterozoic phosphate deposits and of models proposed for their origin. A new model is then presented for the spatial and temporal modes of occurrence of phosphorites along with possible connections to global changes at both ends of the Proterozoic. Central to the new model is that periods of atmospheric oxygenation may have been caused by globally elevated rates of primary productivity stimulated by high fluxes of phosphorus delivery to seawater as a result of increased chemical weathering of continental crust over geological timescales. The striking similarities in <span class="hlt">biogeochemical</span> evolution between the Paleo- and Neoproterozoic are discussed in light of the two oldest major phosphogenic events and their possible relation to the stepwise rise of atmospheric oxygen that ultimately resulted in significant leaps in biological evolution. PMID:20105035</p> <div class="credits"> <p class="dwt_author">Papineau, Dominic</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-03-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">285</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/48891963"> <span id="translatedtitle"><span class="hlt">Coupling</span> between geochemical reactions and multicomponent gas and solute transport in unsaturated media: A reactive transport modeling study</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The two-way <span class="hlt">coupling</span> that exists between <span class="hlt">biogeochemical</span> reactions and vadose zone transport processes, in particular gas phase transport, determines the composition of soil gas. To explore these feedback processes quantitatively, multicomponent gas diffusion and advection are implemented into an existing reactive transport model that includes a full suite of geochemical reactions. Multicomponent gas diffusion is described on the basis of</p> <div class="credits"> <p class="dwt_author">S. Molins; K. U. Mayer</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">286</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUFMEP33B0611M"> <span id="translatedtitle">Characterization of eco-hydraulic habitats for examining <span class="hlt">biogeochemical</span> processes in rivers</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Spatial variability in <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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 portions of the cobbley gravel channel sediments while fine benthic organic material was concentrated at channel margins, regardless of the underlying sediments. A high degree of spatial variability in hyporheic exchange potential was the result of the complex 2D nature of topography and hydraulics. However, sediment texture classifications did a reasonable job in characterizing variability in hyporheic exchange potential because sediment texture mapping incorporates qualitative aspects of bed shear stress and hydraulic conductivity that control hyporheic exchange. Together these variables greatly influenced point-metabolism measurements in different sediment texture habitats separated by only 1 to 2 m. Results from this study suggest that spatial variability and complex interactions between geomorphology, hydraulics, and biological communities generate eco-hydraulic habitats that control variability in <span class="hlt">biogeochemical</span> processes. The processes controlling variability are highly two-dimensional in nature and are not often accounted for in traditional one-dimensional analysis approaches of <span class="hlt">biogeochemical</span> processes.</p> <div class="credits"> <p class="dwt_author">McPhillips, L. E.; O'Connor, B. L.; Harvey, J. W.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">287</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012BGeo....9.1237M"> <span id="translatedtitle">Intra- versus inter-site macroscale variation in <span class="hlt">biogeochemical</span> properties along a paddy soil chronosequence</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In order to assess the intrinsic heterogeneity of paddy soils, a set of <span class="hlt">biogeochemical</span> soil parameters was investigated in five field replicates of seven paddy fields (50, 100, 300, 500, 700, 1000, and 2000 yr of wetland rice cultivation), one flooded paddy nursery, one tidal wetland (TW), and one freshwater site (FW) from a coastal area at Hangzhou Bay, Zhejiang Province, China. All soils evolved from a marine tidal flat substrate due to land reclamation. The <span class="hlt">biogeochemical</span> parameters based on their properties were differentiated into (i) a group behaving conservatively (TC, TOC, TN, TS, magnetic susceptibility, soil lightness and colour parameters, ?13C, ?15N, lipids and n-alkanes) and (ii) one encompassing more labile properties or fast cycling components (Nmic, Cmic, nitrate, ammonium, DON and DOC). The macroscale heterogeneity in paddy soils was assessed by evaluating intra- versus inter-site spatial variability of <span class="hlt">biogeochemical</span> properties using statistical data analysis (descriptive, explorative and non-parametric). Results show that the intrinsic heterogeneity of paddy soil organic and minerogenic components per field is smaller than between study sites. The coefficient of variation (CV) values of conservative parameters varied in a low range (10% to 20%), decreasing from younger towards older paddy soils. This indicates a declining variability of soil <span class="hlt">biogeochemical</span> properties in longer used cropping sites according to progress in soil evolution. A generally higher variation of CV values (>20-40%) observed for labile parameters implies a need for substantially higher sampling frequency when investigating these as compared to more conservative parameters. Since the representativeness of the sampling strategy could be sufficiently demonstrated, an investigation of long-term carbon accumulation/sequestration trends in topsoils of the 2000 yr paddy chronosequence under wetland rice cultivation restricted was conducted. Observations cannot be extrapolated to global scale but with coastal paddy fields developed on marine tidal flat substrates after land reclamation in the Zhejiang Province represent a small fraction (<1%) of the total rice cropping area. The evolutionary trend showed that the <span class="hlt">biogeochemical</span> signatures characteristic for paddy soils were fully developed in less than 300 yr since onset of wetland rice cultivation. A six-fold increase of topsoil TOC suggests a substantial gain in CO2 sequestration potential when marine tidal wetland substrate developed to 2000 yr old paddy soil.</p> <div class="credits"> <p class="dwt_author">Mueller-Niggemann, C.; Bannert, A.; Schloter, M.; Lehndorff, E.; Schwark, L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">288</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011BGD.....810119M"> <span id="translatedtitle">Intra-versus inter-site macroscale variation in <span class="hlt">biogeochemical</span> properties along a paddy soil chronosequence</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In order to assess the intrinsic heterogeneity of paddy soils, a set of <span class="hlt">biogeochemical</span> soil parameters was investigated in five field replicates of seven paddy fields (50, 100, 300, 500, 700, 1000, and 2000 yr of wetland rice cultivation), one flooded paddy nursery, one tidal wetland (TW), and one freshwater site (FW) from a coastal area at Hangzhou Bay, Zhejiang Province, China. All soils evolved from a marine tidal flat substrate due to land reclamation. The <span class="hlt">biogeochemical</span> parameters based on their properties were differentiated into (i) a group behaving conservatively (TC, TOC, TN, TS, magnetic susceptibility, soil lightness and colour parameters, ?13C, ?15N, lipids and n-alkanes) and (ii) one encompassing more labile properties or fast cycling components (Nmic, Cmic, nitrate, ammonium, DON and DOC). The macroscale heterogeneity in paddy soils was assessed by evaluating intra- versus inter-site spatial variability of <span class="hlt">biogeochemical</span> properties using statistical data analysis (descriptive, explorative and non-parametric). Results show that the intrinsic heterogeneity of paddy soil organic and minerogenic components per field is smaller than between study sites. The coefficient of variation (CV) values of conservative parameters varied in a low range (10 % to 20 %), decreasing from younger towards older paddy soils. This indicates a declining variability of soil <span class="hlt">biogeochemical</span> properties in longer used cropping sites according to progress in soil evolution. A generally higher variation of CV values (>20-40 %) observed for labile parameters implies a need for substantially higher sampling frequency when investigating these as compared to more conservative parameters. Since the representativeness of the sampling strategy could be sufficiently demonstrated, an investigation of long-term carbon accumulation/sequestration trends in topsoils of the 2000 year paddy chronosequence under wetland rice cultivation was conducted. The evolutionary trend showed that the <span class="hlt">biogeochemical</span> signatures characteristic for paddy soils were fully developed in less than 300 yr since onset of wetland rice cultivation. A six-fold increase of topsoil TOC suggests a substantial gain in CO2 sequestration potential when marine tidal wetland substrate developed to 2000 year old paddy soil.</p> <div class="credits"> <p class="dwt_author">Mueller-Niggemann, C.; Bannert, A.; Schloter, M.; Lehndorff, E.; Schwark, L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-10-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">289</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..15.2595G"> <span id="translatedtitle">Simulating the early Holocene eastern Mediterranean sapropel formation using an ocean <span class="hlt">biogeochemical</span> model</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The early Holocene sapropel S1 is an organic-rich sediment layer deposited under oxygen depleted conditions below 1800 m between 10 to 6.5 kyr BP in the eastern Mediterranean Sea. Whereas this silled ocean basin is well-ventilated and has a low biological productivity today, the S1 formation indicates drastic changes in the deep water circulation and/or productivity. Commonly, both of these processes are attributed to an enhanced humidity over the broader Mediterranean area. In particular, an increase in the strength of the African monsoon during the African humid period (AHP) is thought to have provided enhanced Nile runoff and nutrient load. However, the exact mechanisms leading to S1 formation are still being debated. Here we apply a regional ocean general circulation model <span class="hlt">coupled</span> to a marine <span class="hlt">biogeochemical</span> model covering the entire Mediterranean Sea to explore some of the many published hypotheses on sapropel formation. With a set of simulations we show that S1 formation cannot be explained by either enhanced biological productivity fueled by increased riverine nutrient input, or by an AHP climatic induced stagnating deep water circulation combined with enhanced biological productivity. The main reasons are: (i) Enhanced biological productivity cannot overcome the effect of a continuous deep ventilation, so that a stagnating deep water circulation is a prerequisite for S1 formation. (ii) The pre-sapropel period is characterized by low particulate organic carbon (POC) sediment burial fluxes, implying that river induced eutrophication is not a viable scenario. (iii) The time span required for complete oxygen depletion within the stagnating deep water circulation exceeds the time span between the beginning of the AHP and the onset of the S1 oxygen deficiency, so that the enhanced Nile runoff fueled by the AHP climate is an unlikely trigger for deep water isolation that caused S1 formation. Available data suggest substantial freshening and warming of the Mediterranean upper ocean during the last glacial-interglacial transition that stabilized stratification and prevented deep water ventilation. Imposing the climatic signals of the last glacial-interglacial transition triggers a persistent (> 4 kyr) deep water stagnation in this simulation. The productivity regime in this simulation was assumed similar to the present-day oligotrophic regime, and the simulated POC burial fluxes agree with observed pre-sapropel burial fluxes in sediments. No deep water anoxia evolves in the short time frame of this simulation (4 kyr) relative to the temporal extent of the deglaciation period, which started at ~17.5 kyr BP. The trend of the modeled oxygen consumption suggests that it takes at least 6.5 kyr until deep water anoxia is established. The simulation also suggests that addition of freshwater is required to maintain the stratification in order to meet the reconstructed spatial extent and duration of the S1 deposition. An examination of records of epibenthic deep-sea foraminifera ?18O supports our findings, and indicates that the stagnation of the deep circulation started ~6 kyr before the onset of the S1 deposition.</p> <div class="credits"> <p class="dwt_author">Grimm, Rosina; Maier-Reimer, Ernst; Mikolajewicz, Uwe; Schmiedl, Gerhard; Adloff, Fanny; Emeis, Kay</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">290</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010GMS...188..409L"> <span id="translatedtitle">Chemosynthetic communities and <span class="hlt">biogeochemical</span> energy pathways along the Mid-Atlantic Ridge: The case of Bathymodiolus azoricus</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Hydrothermal vents fields from the Mid-Atlantic Ridge (MAR) are hosted in diverse geological contexts, resulting in contrasted end-member fluids. Despite this variability, the same animal species dominate the chemosynthetic fauna at almost all sites. Among these organisms, two Bathymodiolus mussel species occur. Both harbor similar sulfide- and methane-oxidizing endosymbionts in their gills. This dual symbiosis is thought to allow mussels to adapt to the different types of fluids encountered along the MAR. Distribution, abundances, and nutritional role of the two symbiont types tend to be correlated with end-member composition, but their variability cannot be fully explained without considering local influences. In this paper, the processes governing the environment of mussel aggregates in terms of available electron donors and energy sources are discussed. The properties of mixed fluids surrounding animals depart from those predicted from end-member conservative dilution. Both subsurface transformations and the influence of mussels on their own environment can significantly modify the relative availability of electron donors. Recent observations about mussel dual symbioses are summarized, leading to the assumption that flexible response of symbiont populations may be a key adaptation allowing mussels to colonize the diversified MAR vent habitats. As illustrated here, tools are becoming available to investigate both environment and symbiosis in detail. We advocate for a more integrative study of the <span class="hlt">biogeochemical</span> <span class="hlt">couplings</span> between fluids and chemosynthetic species at hydrothermal vents, using combined interdisciplinary approaches at the scale of organisms. Bathymodiolus azoricus from contrasted chemical environments appear as particularly relevant models for such studies.</p> <div class="credits"> <p class="dwt_author">Le Bris, N.; Duperron, S.</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">291</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=https://abstracts.congrex.com/scripts/jmevent/abstracts/fcxnl-09a02a-1728765-1-oo-cwp_claustre_biofloats_final.pdf"> <span id="translatedtitle">Bio-optical profiling floats as new observational tools for <span class="hlt">biogeochemical</span> and ecosystem studies: Potential synergies with ocean color remote sensing</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Profiling floats now represent a mature technology. In parallel with their emergence, the field of miniature, low power bio-optical and <span class="hlt">biogeochemical</span> sensors is rapidly evolving. Over recent years, the <span class="hlt">bio-geochemical</span> and bio-optical community has begun to benefit from the increase in observational capacities by developing profiling floats that allow the measurement of key biooptical variables and subsequent products of <span class="hlt">biogeochemical</span></p> <div class="credits"> <p class="dwt_author">Hervé Claustre; Jim Bishop; Emmanuel Boss; Stewart Bernard; Jean-François Berthon; Christine Coatanoan; Ken Johnson; A. Lotiker; O. Ulloa; M. J. Perry; F. DOrtenzio; O. H. F. Dandon; J. Uitz</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">292</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2007BGeo....4...87R"> <span id="translatedtitle">Marine geochemical data assimilation in an efficient Earth System Model of global <span class="hlt">biogeochemical</span> cycling</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We have extended the 3-D ocean based "Grid ENabled Integrated Earth system model" (GENIE-1) to help understand the role of ocean biogeochemistry and marine sediments in the long-term (~100 to 100 000 year) regulation of atmospheric CO2, and the importance of feedbacks between CO2 and climate. Here we describe the ocean carbon cycle, which in its first incarnation is based around a simple single nutrient (phosphate) control on biological productivity. The addition of calcium carbonate preservation in deep-sea sediments and its role in regulating atmospheric CO2 is presented elsewhere (Ridgwell and Hargreaves, 2007). We have calibrated the model parameters controlling ocean carbon cycling in GENIE-1 by assimilating 3-D observational datasets of phosphate and alkalinity using an ensemble Kalman filter method. The calibrated (mean) model predicts a global export production of particulate organic carbon (POC) of 8.9 PgC yr-1, and reproduces the main features of dissolved oxygen distributions in the ocean. For estimating biogenic calcium carbonate (CaCO3) production, we have devised a parameterization in which the CaCO3:POC export ratio is related directly to ambient saturation state. Calibrated global CaCO3 export production (1.2 PgC yr-1) is close to recent marine carbonate budget estimates. The GENIE-1 Earth system model is capable of simulating a wide variety of dissolved and isotopic species of relevance to the study of modern global <span class="hlt">biogeochemical</span> cycles as well as past global environmental changes recorded in paleoceanographic proxies. Importantly, even with 12 active <span class="hlt">biogeochemical</span> tracers in the ocean and including the calculation of feedbacks between atmospheric CO2 and climate, we achieve better than 1000 years per (2.4 GHz) CPU hour on a desktop PC. The GENIE-1 model thus provides a viable alternative to box and zonally-averaged models for studying global <span class="hlt">biogeochemical</span> cycling over all but the very longest (>1 000 000 year) time-scales.</p> <div class="credits"> <p class="dwt_author">Ridgwell, A.; Hargreaves, J. C.; Edwards, N. R.; Annan, J. D.; Lenton, T. M.; Marsh, R.; Yool, A.; Watson, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">293</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/966412"> <span id="translatedtitle">Afforestation alters the composition of functional genes in soil and <span class="hlt">biogeochemical</span> processes in South American grasslands</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Soil microbes are highly diverse and control most soil <span class="hlt">biogeochemical</span> reactions. We examined how microbial functional genes and <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Berthrong, Sean T [ORNL; Schadt, Christopher Warren [ORNL; Pineiro, Gervasio [Duke University; Jackson, Robert B [Duke University</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">294</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011CSR....31...S3H"> <span id="translatedtitle">An overview of physical and <span class="hlt">biogeochemical</span> processes and ecosystem dynamics in the Taiwan Strait</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Taiwan Strait is an important channel in the west Pacific Ocean transporting water and chemical constituents between the East China Sea and the South China Sea. Due to its complex bottom topography, alternating monsoon forcing and conjunction of several current systems [such as the Zhejiang-Fujian (Zhe-Min) Coastal Current, the Kuroshio intrusion and the extension of the South China Sea Warm Current], the physical and <span class="hlt">biogeochemical</span> processes and ecosystem dynamics in the Taiwan Strait vary significantly both in space and in time. Our recent interdisciplinary studies, combining in situ and remote sensing observations with numerical modeling, allow us to address several important issues concerning the Taiwan Strait. The temporal and spatial variation of circulation in the Taiwan Strait is modulated by strong monsoon forcing, complex topography and circulation in the northern South China Sea as well as coastal water input and the Kuroshio intrusion. The <span class="hlt">biogeochemical</span> processes of carbon and nutrients in the Taiwan Strait depend largely on the physical forcing (external input) and the community structure (internal cycling). The primary producers in the Taiwan Strait are dominated by nano- and pico-phytoplankton, and the contribution of the microbial food web to the traditional food web is estimated to be about 30%, implying the fundamental significance of the microbial food web in this subtropical region. Upwelling is a predominant feature in the Taiwan Strait and shows dynamic short-term, seasonal and interannual variations. Combined hydrographic and satellite-derived information provides evidence on the teleconnection between the Taiwan Strait upwelling variation and the El Nino-Southern Oscillation (ENSO) climate variability. Upwelling has a tremendous impact on <span class="hlt">biogeochemical</span> processes, biological productivity and ecosystem structure. Not only the biological productivity, but also dramatic changes in the phytoplankton community structure reveal the dynamic ecosystem responses to the variations in upwelling, which should have significant impact on the fishery resources. In this overview, we summarize the hydrographical features with an emphasis on upwelling, which is the key driver of <span class="hlt">biogeochemical</span> processes and ecosystem dynamics in the Taiwan Strait.</p> <div class="credits"> <p class="dwt_author">Hong, Huasheng; Chai, Fei; Zhang, Caiyun; Huang, Bangqin; Jiang, Yiwu; Hu, Jianyu</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">295</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009EGUGA..11.1085T"> <span id="translatedtitle">A new implementation of the <span class="hlt">Biogeochemical</span> Flux Model in sea ice</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The <span class="hlt">Biogeochemical</span> Flux Model (BFM) is a direct descendent of the European Regional Seas Ecosystem Model (ERSEM) and it has been widely used and validated among the scientific community. The BFM view of the of the marine ecosystem is based upon the recognition that the major ecological functions of producers, decomposers and consumers and their specific trophic interactions can be expressed in terms of material flows of basic elements. The concentration and characteristics of organic and inorganic compounds are thus seen under a stoichiometrical perspective. This functional approach brings to the definition of Chemical Functional Families (CFF) and Living Functional Groups (LFG). The BFM is thus a set of <span class="hlt">biogeochemical</span> equations describing the cycling of carbon, the macro-nutrients and oxygen through the lower trophic levels of marine ecosystems. A Sea-Ice system has now been implemented in the BFM and the new BFM-SI consists of three new LFG (sea ice algae, heterotrophic zooplankton, bacterioplankton), one new non-living organic functional group (sea ice DOM and POM) and two new inorganic functional groups: dissolved gases (sea ice CO2 and O2) and four nutrients (sea ice PO4, NH3, NO3 and SiO4). The innovative approach consists in simulating the biogeochemistry of the sea ice Biologically-Active-Layer (BAL), where the majority of the biomass (bottom communities) concentrates. The BFM-SI requires the physical properties of the BAL in order to be able to simulate the physiological and ecological response of the biological community to the physical environment. This is currently done by using an Enhanced 1-D thermo-halodynamic Sea Ice Model (ESIM2), developed to be suitable for <span class="hlt">biogeochemical</span> studies. Since the biogeochemistry of sea ice is largely unknown, the BFM-SI is a useful tool that allow us to test hypotheses on the functioning of the sea ice ecosystem. By initially setting the sea ice community as having the same characteristics than the pelagic community, it is possible to change many parametrizations of the model, such as the adaptation to the different environmental conditions (light, temperature and salinity) but also nutrient utilization and carbon-chlorophyll ratio. Elected experiments will be shown to elucidate some dynamics of sea ice ecosystems. Once <span class="hlt">biogeochemical</span> dynamics have been studied in local process studies, it will be possible to apply the new implementation of the model both regionally and globally in order to give a wider picture of the role and importance of the sea ice biogeochemistry in the global carbon cycle, also in view of climate change scenarios.</p> <div class="credits"> <p class="dwt_author">Tedesco, L.; Vichi, M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">296</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/896457"> <span id="translatedtitle"><span class="hlt">BIOGEOCHEMICAL</span> CYCLING AND ENVIRONMENTAL STABILITY OF PLUTONIUM RELEVANT TO LONG-TERM STEWARDSHIP OF DOE SITES.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">FRANCIS, A.J.; GILLOW, J.P.; DODGE, C.J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-11-16</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">297</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/896248"> <span id="translatedtitle"><span class="hlt">BIOGEOCHEMICAL</span> CYCLING AND ENVIRONMENTAL STABILITY OF PLUTONIUM RELEVANT TO LONG-TERM STEWARDSHIP OF DOE SITES</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Francis, A.J.; Gillow, J.B.; Dodge, C.J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-06-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">298</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013ESSDD...6..389M"> <span id="translatedtitle">Winter measurements of <span class="hlt">biogeochemical</span> parameters in the Rockall Trough (2009-2012)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">This paper describes the sampling and analysis of <span class="hlt">biogeochemical</span> parameters collected in the Rockall Trough in January/February of 2009, 2010, 2011 and 2012. Sampling was carried out across two transects, one southern and one northern transect each year. Samples for dissolved inorganic carbon (DIC) and total alkalinity (TA) were taken alongside salinity, dissolved oxygen and dissolved inorganic nutrients (total-oxidised nitrogen, nitrite, phosphate and silicate) to describe the chemical signatures of the various water masses in the region. These were taken at regular intervals through the water column. The 2009 and 2010 data are available on the CDIAC database.</p> <div class="credits"> <p class="dwt_author">McGrath, T.; Kivimäe, C.; McGovern, E.; Cave, R. R.; Joyce, E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-08-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">299</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFM.H44C..03B"> <span id="translatedtitle">Anthropogenic Signatures in Nutrient Loads Exported from Managed Catchments: Emergence of Effective <span class="hlt">Biogeochemical</span> Stationarity</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Examining the impacts of large-scale human modifications of watersheds (e.g., land-use intensification for food production; hydrologic modification though extensive tile-drainage, etc.) on the hydrologic and <span class="hlt">biogeochemical</span> responses, and ecological impacts at various scales has been the focus of monitoring and modeling studies over the past two decades. Complex interactions between hydrology and biogeochemistry and the need to predict responses across scales has led to the development of detailed process based models that are computation intensive and calibration dependent. Despite the perceived complexity, our overall hypothesis is that human modifications and intensive management of these watersheds have led to more predictable responses, typical of an engineered, less-complex system rather than natural, complex systems. Thus, simpler and more efficient approaches can be used in these systems for predicting hydrologic and <span class="hlt">biogeochemical</span> responses. It has been argued that human interferences and climate change may have contributed to the demise of hydrologic stationarity. However, our synthesis of observational data shows that anthropogenic impacts have also resulted in the emergence of effective <span class="hlt">biogeochemical</span> stationarity in managed catchments. Long-term monitoring data from the Mississippi-Atchafalaya River Basin (MARB) and the Baltic Sea Drainage Basin (BSDB) reveal that inter-annual variations in loads (LT) for total-N (TN) and total-P (TP), and for geogenic constituents exported from a catchment are linearly correlated to discharge (QT), leading to temporal invariance of the flow-weighted concentration, Cf = (LT/QT). Emergence of this consistent pattern across diverse catchments is attributed to the anthropogenic legacy of accumulated nutrient sources generating memory, similar to ubiquitously present sources for geogenic constituents. These responses are characteristic of transport-limited systems. In contrast, in the absence of legacy sources in less-managed catchments, Cf values were highly variable and supply limited. We offer a theoretical explanation for the observed patterns at the event scale, and extend it to consider the stochastic nature of rainfall/flow patterns at annual scales. Our analysis suggests that (1) expected inter-annual variations in nutrient loads can be robustly predicted given discharge variations from hydro-climatic or anthropogenic forcing, and (2) water quality problems in receiving inland and coastal waters would persist until the accumulated storages of nutrients have been substantially depleted. The synthesis bears notable implications on catchment management and on global <span class="hlt">biogeochemical</span> cycles.</p> <div class="credits"> <p class="dwt_author">Basu, N. B.; Destouni, G.; Jawitz, J. W.; Thompson, S. E.; Rinaldo, A.; Sivapalan, M.; Rao, P. C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">300</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/5424269"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> conditions and ice algal photosynthetic parameters in Weddell Sea ice during early spring</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Physical, <span class="hlt">biogeochemical</span> and photosynthetic parameters were measured in sea ice brine and ice core bottom samples in the north-western\\u000a Weddell Sea during early spring 2006. Sea ice brines collected from sackholes were characterised by cold temperatures (range\\u000a ?7.4 to ?3.8°C), high salinities (range 61.4–118.0), and partly elevated dissolved oxygen concentrations (range 159–413 ?mol kg?1) when compared to surface seawater. Nitrate (range 0.5–76.3 ?mol kg?1),</p> <div class="credits"> <p class="dwt_author">Klaus Martin Meiners; S. Papadimitriou; D. N. Thomas; L. Norman; G. S. Dieckmann</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_14");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' 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onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">301</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012GMDD....5.3469R"> <span id="translatedtitle">Using model reduction to predict the soil-surface C18OO flux: an example of representing complex <span class="hlt">biogeochemical</span> dynamics in a computationally efficient manner</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Earth System Models (ESMs) must calculate large-scale interactions between the land and atmosphere while accurately characterizing fine-scale spatial heterogeneity in water, carbon, and nutrient dynamics. We present here a high-dimensional model representation (HDMR) approach that allows detailed process representation of a <span class="hlt">coupled</span> carbon and water tracer (the ?18O value of the soil-surface CO2 flux (?Fs)) in a computationally tractable manner. ?Fs depends on the ?18O value of soil water, soil moisture, soil temperature, and soil CO2 production (all of which are depth-dependent), and the ?18O value of above-surface CO2. We tested the HDMR approach over a growing season in a C4-dominated pasture using two vertical soil discretizations. The difference between the HDMR approach and the full model solution in the three-month integrated isoflux was less than 0.2% (0.5 mol m-2‰), and the approach is up to 100 times faster than the full numerical solution. This type of model reduction approach allows representation of complex <span class="hlt">coupled</span> <span class="hlt">biogeochemical</span> processes in regional and global climate models and can be extended to characterize subgrid-scale spatial heterogeneity.</p> <div class="credits"> <p class="dwt_author">Riley, W. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">302</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2007AGUFM.B53C..07L"> <span id="translatedtitle">Methane concentrations and <span class="hlt">biogeochemical</span> gradients within acoustic wipe-out zones at a Gulf of Mexico cold seep</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The spatial distribution of methane concentrations and <span class="hlt">biogeochemical</span> gradients were assessed within surficial sediments overlying acoustic wipe-out zones at a cold seep, Mississippi Canyon 118, Gulf of Mexico. We hypothesized that the wipe-outs were caused from saturated methane entrained within upward fluxing hydrocarbon-rich fluids and, since these fluids have been shown to stimulate sulfate reduction, anaerobic oxidation of methane, and methanogenesis, we also hypothesized that we would observe steep <span class="hlt">biogeochemical</span> gradients, indicating high microbial activity, in sediments overlying these features. We tested these hypotheses by collecting thirty sediment gravity cores both within and outside the wipe-out zones and measuring resultant pore-fluids for dissolved methane and sulfate concentration gradients, methane and dissolved inorganic carbon isotope gradients, and organic matter chemical composition. Outside the wipe-outs, fifteen cores resulted in methane concentrations below 10 uM, limited down-core sulfate or methane concentration gradients, and down- core d13C-CH4 values averaging -52+/-2 ppt. While these background cores exhibited low microbial activity, the cores collected within the wipe-outs resulted in moderate to high activity. Moderate activity was exhibited in eight cores where methane concentrations reached 20 uM and had gentle sloping sulfate and methane concentration gradients. The d13C-CH4 values showed little change with depth and averaged -67+/-4 ppt while the d13C-DIC values decreased from -7ppt at the SWI to -32ppt at the bottom of the cores at a rate of 0.22ppt/cm. In stark contrast, high activity was seen in four cores collected within the wipe-outs. Methane concentrations reached above 4 mM, sulfate was depleted by ~50 cmbsf, and down-core profiles of d13C-CH4 and d13C-DIC were indicative of distinct depth zones of sulfate reduction <span class="hlt">coupled</span> to anaerobic methane oxidation and methanogenesis. Bulk organic matter analysis suggested that the high activity cores were being supported by a source that is enriched in carbon (C:N=15) and depleted in d15N and d13C compared to other activity groups, possibly due to petroleum influx or chemosynthetic carbon. In the high activity cores, the isotopic values of the DIC were similar to the authigenic carbonates whereas in the moderate activity cores they were not, suggesting not only spatial but temporal variability in microbial processes. While the wipe-outs were correlated with saturated methane and were indicators of active microbial processes, the cause of the wipe-outs was not solely methane saturated pore-fluids. This novel data set was then compiled into a seep characterization model to determine the relative upward fluid flux.</p> <div class="credits"> <p class="dwt_author">Lapham, L.; Chanton, J.; Martens, C.; Sleeper, K.; Woolsey, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">303</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.sfr.cas.psu.edu/boyerlab/pubs/alexander_etal_2009.pdf"> <span id="translatedtitle">Dynamic modeling of nitrogen losses in river networks unravels the <span class="hlt">coupled</span> effects of hydrological and <span class="hlt">biogeochemical</span> processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The importance of lotic systems as sinks for nitrogen inputs is well recognized. A fraction of nitrogen in streamflow is removed\\u000a to the atmosphere via denitrification with the remainder exported in streamflow as nitrogen loads. At the watershed scale,\\u000a there is a keen interest in understanding the factors that control the fate of nitrogen throughout the stream channel network,\\u000a with</p> <div class="credits"> <p class="dwt_author">Richard B. Alexander; John Karl Böhlke; Elizabeth W. Boyer; Mark B. David; Judson W. Harvey; Patrick J. Mulholland; Sybil P. Seitzinger; Craig R. Tobias; Christina Tonitto; Wilfred M. Wollheim</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">304</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/894677"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> <span class="hlt">Coupling</span> of Fe and Tc Speciation in Subsurface Sediments: Implications to Long-Term Tc Immobilization</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The overall project has been investigating the reactivity of pertechnetate [Tc(VII)] with Fe(II) forms in model mineral and mineral-microbe systems, and with sediments from the Oak Ridge FRC and the Hanford site. Past project results with Hanford and Oak Ridge sediments have been published in Fredrickson et al., (2004) and Kukkadapu et al., (2006). This poster summarizes a series of model system experiments that investigates whether microbes or biogenic Fe(II) were more important in the reduction of Tc(VII) in an anoxic suspension of ferrihydrite, Shewanella oneidensis MR-1, Tc(VII), and electron donor. Ferrihydrite is used to represent a bioavailable Fe(III) oxide present in small amounts in Oak Ridge and Hanford sediments. In order to address this overall goal, Tc(VII) reduction rates and redox products were studied in less complex systems where individual abiotic and biotic reactions were isolated for rigorous characterization. The specific objectives of the individual experiments in the series were as follows: (1) Identify the rates and products of the reaction of Tc(VII) with aqueous Fe(II) at circumneutral pH values (homogeneous reduction). (2) Identify the rates and products of the reaction of Tc(VII) with surface complexed Fe(II) on goethite and hematite in the circumneutral pH range (heterogeneous reduction). (3) Identify the rates and products of the reaction of Tc(VII) with MR-1 under anoxic conditions individually with hydrogen and lactate as electron donors (biologic reduction). (4) Use insights from the above experiments to determine which of the three above, potentially parallel reactions determine the final speciation of Tc in a mixture of ferrihydrite, respiring MR-1, and Tc(VII).</p> <div class="credits"> <p class="dwt_author">Zachara, John M.; Kukkadapu, Ravi K.; Heald, Steve M.; McKinley, James P.; Dohnalkova, Alice C.; Fredrickson, James K.; Byong-Hun Jeon</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-04-05</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">305</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1519506"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> processes governing exposure and uptake of organic pollutant compounds in aquatic organisms.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">This paper reviews current knowledge of <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Farrington, J W</p> <p class="dwt_publisher"></p> <p class="publishDate">1991-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">306</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.H31H..06A"> <span id="translatedtitle">Spatio-temporal evolution of <span class="hlt">biogeochemical</span> processes at a landfill site</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">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, ?18O, ?2H, 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 <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Arora, B.; Mohanty, B. P.; McGuire, J. T.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">307</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2001GeCoA..65.1629S"> <span id="translatedtitle">Molecular organic tracers of <span class="hlt">biogeochemical</span> processes in a saline meromictic lake (Ace Lake)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The chemical structures, distribution and stable carbon isotopic compositions of lipids in a sediment core taken in meromictic Ace Lake (Antarctica) were analyzed to trace past <span class="hlt">biogeochemical</span> cycling. Biomarkers from methanogenic archaea, methanotrophic bacteria and photosynthetic green sulfur bacteria were unambiguously assigned using organic geochemical understanding and by reference to what is known about the lake's present-day ecosystem. For instance, saturated and unsaturated 2,6,10,15,19-pentamethylicosane, archaeol and sn2-hydroxyarchaeol were derived from methanogenic archaea. Carotenoid analysis revealed chlorobactene and isorenieratene derived from the green-colored and brown-colored strains of the green sulfur bacteria (Chlorobiaceae); isotopic analyses showed that they were 13C-enriched. Phytenes appear to be derived from photoautotrophs that use the Calvin-Benson cycle, while phytane has a different source, possibly within the archaea. The most 13C-depleted compounds (ca. -55‰) identified were 4-methyl-5?-cholest-8(14)-en-3?-ol, identified using an authentic standard, and co-occurring 4-methylsteradienes: these originate from the aerobic methanotrophic bacterium Methylosphaera hansonii. Lipids of photoautotrophic origin, steranes and alkenones, are relatively depleted (ca. -28 to -36‰) whilst archaeal biomarkers are relatively enriched in 13C (ca. -17 to -25‰). The structural and carbon isotope details of sedimentary lipids thus revealed aspects of in situ <span class="hlt">biogeochemical</span> processes such as methane generation and oxidation and phototrophic sulfide oxidation.</p> <div class="credits"> <p class="dwt_author">Schouten, S.; Rijpstra, W. I. C.; Kok, M.; Hopmans, E. C.; Summons, R. E.; Volkman, J. K.; Sinninghe Damsté, J. S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">308</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/1023369"> <span id="translatedtitle">Terrestrial <span class="hlt">biogeochemical</span> feedbacks in the climate system: from past to future</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The terrestrial biosphere plays a major role in the regulation of atmospheric composition, and hence climate, through multiple interlinked <span class="hlt">biogeochemical</span> cycles (BGC). Ice-core and other palaeoenvironmental records show a fast response of vegetation cover and exchanges with the atmosphere to past climate change, although the phasing of these responses reflects spatial patterning and complex interactions between individual biospheric feedbacks. Modern observations show a similar responsiveness of terrestrial <span class="hlt">biogeochemical</span> cycles to anthropogenically-forced climate changes and air pollution, with equally complex feedbacks. For future conditions, although carbon cycle-climate interactions have been a major focus, other BGC feedbacks could be as important in modulating climate changes. The additional radiative forcing from terrestrial BGC feedbacks other than those conventionally attributed to the carbon cycle is in the range of 0.6 to 1.6 Wm{sup -2}; all taken together we estimate a possible maximum of around 3 Wm{sup -2} towards the end of the 21st century. There are large uncertainties associated with these estimates but, given that the majority of BGC feedbacks result in a positive forcing because of the fundamental link between metabolic stimulation and increasing temperature, improved quantification of these feedbacks and their incorporation in earth system models is necessary in order to develop coherent plans to manage ecosystems for climate mitigation.</p> <div class="credits"> <p class="dwt_author">Arneth, A.; Harrison, S. P.; Zaehle, S.; Tsigaridis, K; Menon, S; Bartlein, P.J.; Feichter, J; Korhola, A; Kulmala, M; O'Donnell, D; Schurgers, G; Sorvari, S; Vesala, T</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-05</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">309</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013ECSS..130....9H"> <span id="translatedtitle">Environmental and <span class="hlt">biogeochemical</span> changes following a decade's reclamation in the Dapeng (Tapong) Bay, southwestern Taiwan</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">This study examines the environmental and <span class="hlt">biogeochemical</span> changes in Dapeng (formerly spelled Tapong) Bay, a semi-enclosed coastal lagoon in southwestern Taiwan, after two major reclamation works performed between 1999 and 2010. The lagoon was largely occupied by oyster culture racks and fish farming cages before December, 2002. Substantial external inputs of nutrients and organic carbon and the fairly long water exchange time (?) (10 ± 2 days) caused the lagoon to enter a eutrophic state, particularly at the inner lagoon, which directly received nutrient inputs. However, the entire lagoon showed autotrophic, and the estimated net ecosystem production (NEP) during the first stage was 5.8 mol C m-2 yr-1. After January, 2003, the aquaculture structures were completely removed, and the ? decreased to 6 ± 2 days. The annual mean concentrations of dissolved oxygen increased, and nutrients decreased substantially, likely due to improved water exchange, absence of feeding and increased biological utilization. The NEP increased 37% to 7.7 mol C m-2 yr-1 after structure removal. The second reclamation work beginning from July, 2006, focused on establishing artificial wetlands for wastewater treatment and on dredging bottom sediment. Although the ? did not change significantly (8 ± 3 days), substantial decreases in nutrient concentrations and dissolved organic matter continued. The NEP (14.3 mol C m-2 yr-1) increased 85% compared to that in the second stage. The data suggest that the reclamations substantially improved water quality, carbon and nutrient <span class="hlt">biogeochemical</span> processes and budgets in this semi-enclosed ecosystem.</p> <div class="credits"> <p class="dwt_author">Hung, J.-J.; Huang, W.-C.; Yu, C.-S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">310</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2006HyPr...20.4269O"> <span id="translatedtitle">Hydrological versus <span class="hlt">biogeochemical</span> controls on catchment nitrate export: a test of the flushing mechanism</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Deciphering the connection between streamflows and nitrate (NO-3) discharge requires identification of the various water flow pathways within a catchment, and the different time-scales at which hydrological and <span class="hlt">biogeochemical</span> processes occur. Despite the complexity of the processes involved, many catchments around the world present a characteristic flushing response of NO-3 export. Yet the controls on the flushing response, and how they vary across space and time, are still not clearly understood. In this paper, the flushing response of NO-3 export from a rural catchment in Western Australia was investigated using isotopic (deuterium), chemical (chloride, NO-3), and hydrometric data across different antecedent conditions and time-scales. The catchment streamflow was at all time-scales dominated by a pre-event water source, and the NO-3 discharge was correlated with the magnitude of areas contributing to saturation overland flow. The NO-3 discharge also appeared related to the shallow groundwater dynamics. Thus, the antecedent moisture condition of the catchment at seasonal and interannual time-scales had a major impact on the NO-3 flushing response. In particular, the dynamics of the shallow ephemeral perched aquifer drove a shift from hydrological controls on NO-3 discharge during the early flushing stage to an apparent <span class="hlt">biogeochemical</span> control on NO-3 discharge during the steady decline stage of the flushing response. This temporally variable control hypothesis provides a new and alternative description of the mechanisms behind the commonly seen flushing response. Copyright</p> <div class="credits"> <p class="dwt_author">Ocampo, Carlos J.; Oldham, Carolyn E.; Sivapalan, Murugesu; Turner, Jeffrey V.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">311</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012OcMod..51...19G"> <span id="translatedtitle">An Isopycnal Box Model with predictive deep-ocean structure for <span class="hlt">biogeochemical</span> cycling applications</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">To simulate global ocean <span class="hlt">biogeochemical</span> tracer budgets a model must accurately determine both the volume and surface origins of each water-mass. Water-mass volumes are dynamically linked to the ocean circulation in General Circulation Models, but at the cost of high computational load. In computationally efficient Box Models the water-mass volumes are simply prescribed and do not vary when the circulation transport rates or water mass densities are perturbed. A new computationally efficient Isopycnal Box Model is presented in which the sub-surface box volumes are internally calculated from the prescribed circulation using a diffusive conceptual model of the thermocline, in which upwelling of cold dense water is balanced by a downward diffusion of heat. The volumes of the sub-surface boxes are set so that the density stratification satisfies an assumed link between diapycnal diffusivity, ?d, and buoyancy frequency, N: ?d = c/(N?), where c and ? are user prescribed parameters. In contrast to conventional Box Models, the volumes of the sub-surface ocean boxes in the Isopycnal Box Model are dynamically linked to circulation, and automatically respond to circulation perturbations. This dynamical link allows an important facet of ocean <span class="hlt">biogeochemical</span> cycling to be simulated in a highly computationally efficient model framework.</p> <div class="credits"> <p class="dwt_author">Goodwin, Philip</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-07-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">312</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2005AGUFM.B31A0971Y"> <span id="translatedtitle">In Situ Biostimulation at a Former Uranium Mill Tailings Site: Multicomponent <span class="hlt">Biogeochemical</span> Reactive Transport Modeling</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In situ biostimulation at a Former Uranium Mill Tailings Site: Multicomponent <span class="hlt">Biogeochemical</span> Reactive Transport Modeling Field experiments conducted at a former uranium mill tailings site in western Colorado are being used to investigate microbially mediated immobilization of uranium as a potential future remediation option for such sites. While the general principle of biostimulating microbial communities to reduce aqueous hexavalent uranium to immobile uraninite has been demonstrated in the laboratory and field, the ability to predictably engineer long lasting immobilization will require a more complete understanding of field-scale processes and properties. For this study, numerical simulation of the flow field, geochemical conditions, and micriobial communities is used to interpret field-scale <span class="hlt">biogeochemical</span> reactive transport observed during experiments performed in 2002 to 2004. One key issue is identifying bioavailable Fe(III) oxide, which is the principal electron acceptor utilized by the acetate- oxidizing Geobacter sp. These organisms are responsible for uranium bioreduction that results in the removal of sufficient U(VI) to lower uranium groundwater concentrations to at or near applicable standards. The depletion of bioavailable Fe(III) leads to succession by sulfate reducers that are considerably less effective at uranium bioreduction. An important modeling consideration are the abiotic reactions (e.g., mineral precipitation and dissolution, aqueous and surface complexation) involving the Fe(II) and sulfide produced during biostimulation. These components, strongly associated with the solid phases, may play an important role in the evolving reactivity of the mineral surfaces that are likely to impact long-term uranium immobilization.</p> <div class="credits"> <p class="dwt_author">Yabusaki, S.; Fang, Y.; Long, P.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">313</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009BGD.....6.6441D"> <span id="translatedtitle">The role of airborne volcanic ash for the surface ocean <span class="hlt">biogeochemical</span> iron-cycle: a review</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Iron is a key micronutrient for phytoplankton growth in the surface ocean. Yet the significance of volcanism for the marine <span class="hlt">biogeochemical</span> iron-cycle is poorly constrained. Recent studies, however, suggest that offshore deposition of airborne ash from volcanic eruptions is a way to inject significant amounts of bio-available iron into the surface ocean. Volcanic ash may be transported up to several tens of kilometres high into the atmosphere during large-scale eruptions and fine ash may encircle the globe for years, thereby reaching even the remotest and most iron-starved oceanic areas. Scientific ocean drilling demonstrates that volcanic ash layers and dispersed ash particles are frequently found in marine sediments and that therefore volcanic ash deposition and iron-injection into the oceans took place throughout much of the Earth's history. The data from geochemical and biological experiments, natural evidence and satellite techniques now available suggest that volcanic ash is a so far underestimated source for iron in the surface ocean, possibly of similar importance as aeolian dust. Here we summarise the development of and the knowledge in this fairly young research field. The paper covers a wide range of chemical and biological issues and we make recommendations for future directions in these areas. The review paper may thus be helpful to improve our understanding of the role of volcanic ash for the marine <span class="hlt">biogeochemical</span> iron-cycle, marine primary productivity and the ocean-atmosphere exchange of CO2 and other gases relevant for climate throughout the Earth's history.</p> <div class="credits"> <p class="dwt_author">Duggen, S.; Olgun, N.; Croot, P.; Hoffmann, L.; Dietze, H.; Teschner, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-07-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">314</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/893690"> <span id="translatedtitle">Novel Imaging Techniques, Integrated with Mineralogical, Geochemical and Microbiological Characterization to Determine the <span class="hlt">Biogeochemical</span> Controls....</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Aims and objectives Technetium-99 is a priority pollutant at numerous DOE sites, due to a combination of its long half life (2.1 x 105 years), high mobility as Tc(VII) (TcO4-; pertechnetate anion) in oxic waters, and bioavailability as a sulfate analog. Under anaerobic conditions, however, the radionuclide is far less mobile, forming insoluble Tc(IV) precipitates. As anaerobic microorganisms can reduce soluble Tc(VII) to insoluble Tc(IV), microbial metabolism may have the potential to treat sediments and waters contaminated with Tc. In previous studies we have focused on the fundamental mechanisms of Tc(VII) bioreduction and precipitation, and we have identified direct enzymatic (hydrogenase-mediated) mechanisms, and a range of potentially important indirect transformations catalyzed by biogenic Fe(II), U(IV) or sulfide. These baseline studies have generally used pure cultures of metal-reducing bacteria, in order to develop conceptual models for the <span class="hlt">biogeochemical</span> cycling of Tc. There is, however, comparatively little known about interactions of metal-reducing bacteria with environmentally relevant trace concentrations of Tc, against a more complex <span class="hlt">biogeochemical</span> background provided by mixed microbial communities in the subsurface.</p> <div class="credits"> <p class="dwt_author">Lloyd, Jonathan R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-06-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">315</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.B41H..04T"> <span id="translatedtitle">Approaches for Investigating Hydraulic and <span class="hlt">Biogeochemical</span> Gradients at Multiple Scales in Critical Zone Processes</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Transport and transformations of chemical species in soils and other near-surface terrestrial environments of Earth's critical zone reflect complex interactions among physical, chemical, and biological processes. Hydraulic and <span class="hlt">biogeochemical</span> gradients driving transport and reactions occur over multiple scales in the subsurface. Thus, bulk measurements that average across hydraulic, chemical, and/or microbiological gradients limit identification of basic processes. Over the decades, a variety of tools and experimental methods have been developed with capabilities to resolve very steep environmental gradients. Although most of these methods are laboratory-based, they can provide insights into critical zone processes, especially when field-relevant conditions are reasonably replicated. In this presentation, examples of some novel experimental methods are reviewed, suitable for characterizing properties and processes at scales ranging from meters down to about 10 nm. The larger scale experimental approaches address dynamic processes in soil profiles. Intermediate scale experimental approaches are compatible with investigating <span class="hlt">biogeochemical</span> dynamics within soil aggregates. Still finer scale techniques permit examination of heterogeneity within individual soil particles and micro-aggregates.</p> <div class="credits"> <p class="dwt_author">Tokunaga, T. K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">316</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40017219"> <span id="translatedtitle">Applications of a hydro-<span class="hlt">biogeochemical</span> model and long-term simulations of the effects of logging in forested watersheds</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We simulated hydrological and <span class="hlt">biogeochemical</span> responses to logging in a forested watershed to determine the vulnerability and\\/or\\u000a resiliency of the forest ecosystems in the Lake Shumarinai Basin in northern Hokkaido, Japan. We used a <span class="hlt">biogeochemical</span> model\\u000a (PnET-CN) and a rainfall–runoff model (HYCYMODEL) to predict ecosystem responses. The PnET-CN model simulated well the observed\\u000a NO3\\u000a ? concentrations in streamwater, particularly at</p> <div class="credits"> <p class="dwt_author">M. Katsuyama; H. Shibata; T. Yoshioka; T. Yoshida; A. Ogawa; N. Ohte</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">317</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/244057"> <span id="translatedtitle">Assimilation of surface data in a one-dimensional physical-<span class="hlt">biogeochemical</span> model of the surface ocean: 2. Adjusting a simple trophic model to chlorophyll, temperature, nitrate, and pCO{sub 2} data</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">This paper builds on a previous work which produced a constrained physical-<span class="hlt">biogeochemical</span> model of the carbon cycle in the surface ocean. Three issues are addressed: (1) the results of chlorophyll assimilation using a simpler trophic model, (2) adjustment of parameters using the simpler model and data other than surface chlorophyll concentrations, and (3) consistency of the main carbon fluxes derived by the simplified model with values from the more complex model. A one-dimensional vertical model <span class="hlt">coupling</span> the physics of the ocean mixed layer and a description of <span class="hlt">biogeochemical</span> processes with a simple trophic model was used to address these issues. Chlorophyll concentration, nitrate concentration, and temperature were used to constrain the model. The surface chlorophyll information was shown to be sufficient to constrain primary production within the photic layer. The simultaneous assimilation of chlorophyll, nitrate, and temperature resulted in a significant improvement of model simulation for the data used. Of the nine biological and physical parameters which resulted in significant variations of the simulated chlorophyll concentration, seven linear combinations of the mode parameters were constrained. The model fit was an improvement on independent surface chlorophyll and nitrate data. This work indicates that a relatively simple biological model is sufficient to describe carbon fluxes. Assimilation of satellite or climatological data coulc be used to adjust the parameters of the model for three-dimensional models. It also suggests that the main carbon fluxes driving the carbon cycle within surface waters could be derived regionally from surface information. 38 refs., 16 figs., 7 tabs.</p> <div class="credits"> <p class="dwt_author">Prunet, P.; Minster, J.F.; Echevin, V. [Laboratoire CNES-CNRS, Toulouse (France)] [and others</p> <p class="dwt_publisher"></p> <p class="publishDate">1996-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">318</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013QSRv...79..207V"> <span id="translatedtitle">Role of sea ice in global <span class="hlt">biogeochemical</span> cycles: emerging views and challenges</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Observations from the last decade suggest an important role of sea ice in the global <span class="hlt">biogeochemical</span> cycles, promoted by (i) active biological and chemical processes within the sea ice; (ii) fluid and gas exchanges at the sea ice interface through an often permeable sea ice cover; and (iii) tight physical, biological and chemical interactions between the sea ice, the ocean and the atmosphere. Photosynthetic micro-organisms in sea ice thrive in liquid brine inclusions encased in a pure ice matrix, where they find suitable light and nutrient levels. They extend the production season, provide a winter and early spring food source, and contribute to organic carbon export to depth. Under-ice and ice edge phytoplankton blooms occur when ice retreats, favoured by increasing light, stratification, and by the release of material into the water column. In particular, the release of iron – highly concentrated in sea ice – could have large effects in the iron-limited Southern Ocean. The export of inorganic carbon transport by brine sinking below the mixed layer, calcium carbonate precipitation in sea ice, as well as active ice-atmosphere carbon dioxide (CO2) fluxes, could play a central role in the marine carbon cycle. Sea ice processes could also significantly contribute to the sulphur cycle through the large production by ice algae of dimethylsulfoniopropionate (DMSP), the precursor of sulphate aerosols, which as cloud condensation nuclei have a potential cooling effect on the planet. Finally, the sea ice zone supports significant ocean–atmosphere methane (CH4) fluxes, while saline ice surfaces activate springtime atmospheric bromine chemistry, setting ground for tropospheric ozone depletion events observed near both poles. All these mechanisms are generally known, but neither precisely understood nor quantified at large scales. As polar regions are rapidly changing, understanding the large-scale polar marine <span class="hlt">biogeochemical</span> processes and their future evolution is of high priority. Earth system models should in this context prove essential, but they currently represent sea ice as biologically and chemically inert. Palaeoclimatic proxies are also relevant, in particular the sea ice proxies, inferring past sea ice conditions from glacial and marine sediment core records and providing analogues for future changes. Being highly constrained by marine biogeochemistry, sea ice proxies would not only contribute to but also benefit from a better understanding of polar marine <span class="hlt">biogeochemical</span> cycles.</p> <div class="credits"> <p class="dwt_author">Vancoppenolle, Martin; Meiners, Klaus M.; Michel, Christine; Bopp, Laurent; Brabant, Frédéric; Carnat, Gauthier; Delille, Bruno; Lannuzel, Delphine; Madec, Gurvan; Moreau, Sébastien; Tison, Jean-Louis; van der Merwe, Pier</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-11-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">319</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013DSRII..93...16L"> <span id="translatedtitle">Two decades and counting: 24-years of sustained open ocean <span class="hlt">biogeochemical</span> measurements in the Sargasso Sea</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The Bermuda Atlantic Time-series Study (BATS) program has sampled the northwestern Sargasso Sea on a biweekly (January to April) to monthly basis since October 1988. The primary objective of the core BATS program continues to be an improved understanding of the time-variable processes and mechanisms that control the <span class="hlt">biogeochemical</span> cycling of carbon and related elements in the surface ocean. With 24 years of measurements for most chemical, physical and biological variables, we have moved beyond descriptions of seasonal and interannual variability to examination of multi-year trends and potential controls, however there remain substantial gaps in our knowledge of the ecosystem mechanisms related to organic matter production, export and remineralization. While earlier BATS overviews have focused on describing seasonal and year-to-year variability, this overview provides new information on three long-standing <span class="hlt">biogeochemical</span> questions in Sargasso Sea biogeochemistry. First, why is there a discrepancy between biological (i.e., sediment trap) and geochemical estimates of carbon export production? Winter storms and mesoscale eddies have now been clearly shown to contribute to annual nutrient budgets and carbon export production. Recent information on phytoplankton natural isotopic nitrogen composition, and data from profiling floats suggests that small phytoplankton are important contributors to new production in summer despite the apparent absence of a mechanism to entrain nitrate into the euphotic zone. These findings aid in closing the gap between these two different estimates of carbon export production. Second, what supports the seasonal drawdown of carbon dioxide in the absence of detectable nutrients? The zooplankton timeseries at BATS highlights the importance of zooplankton as a conduit for carbon removal due to grazing and vertical migration. Although increases in cellular elemental stoichiometry to values greater than the canonical Redfield Ratio, and the seasonal (and interannual) accumulation of euphotic zone dissolved organic carbon (DOC) without accumulation of DON in the surface ocean are also important explanations. Lastly, what are the sources of the elevated nitrate to phosphate ratio in the seasonal thermocline (N:P>30 on average)? While generally accepted that nitrogen fixation is the source of the additional nitrogen, new research suggests that export and remineralization of non-diazotroph particulate matter enriched in nitrogen (alternatively viewed as depleted in phosphorus) may also make substantial contributions. In addition, the ratio of particulate nitrogen to phosphorus captured in sediment traps has decreased from 50-75 to <50, possibly due to enhanced nitrogen remineralization. These and other findings from the core BATS observational program contribute to our improved understanding of <span class="hlt">biogeochemical</span> cycles and ecosystem mechanisms in the subtropical North Atlantic Ocean and how they are changing over time.</p> <div class="credits"> <p class="dwt_author">Lomas, M. W.; Bates, N. R.; Johnson, R. J.; Knap, A. H.; Steinberg, D. K.; Carlson, C. A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-09-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">320</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/24147410"> <span id="translatedtitle">Beyond best management practices: pelagic <span class="hlt">biogeochemical</span> dynamics in urban stormwater ponds.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">Urban stormwater ponds are considered to be a best management practice for flood control and the protection of downstream aquatic ecosystems from excess suspended solids and other contaminants. Following this, urban ponds are assumed to operate as unreactive settling basins, whereby their overall effectiveness in water treatment is strictly controlled by physical processes. However, pelagic microbial <span class="hlt">biogeochemical</span> dynamics could be significant contributors to nutrient and carbon cycling in these small, constructed aquatic systems. In the present study, we examined pelagic <span class="hlt">biogeochemical</span> dynamics in 26 stormwater ponds located in southern Ontario, Canada, during late summer. Initially, we tested to see if total suspended solids (TSS) concentration, which provides a measure of catchment disturbance, landscape stability, and pond performance, could be used as an indirect predictor of plankton stocks in stormwater ponds. Structural equation modeling (SEM) using TSS as a surrogate for external loading suggested that TSS was an imperfect predictor. TSS masked plankton-nutrient relationships and appeared to reflect autochthonous production moreso than external forces. When TSS was excluded, the SEM model explained a large amount of the variation in dissolved organic matter (DOM) characteristics (55-75%) but a small amount of the variation in plankton stocks (3-38%). Plankton stocks were correlated positively with particulate nutrients and extracellular enzyme activities, suggesting rapid recycling of the fixed nutrient and carbon pool with consequential effects on DOM. DOM characteristics across the ponds were mainly of autochthonous origin. Humic matter from the watershed formed a larger part of the DOM pool only in ponds with low productivity and low dissolved organic carbon concentrations. Our results suggest that in these small, high nutrient systems internal processes might outweigh the impact of the landscape on carbon cycles. Hence, the overall benefit that constructed ponds serve to protect downstream environments must be weighed with the <span class="hlt">biogeochemical</span> processes that take place within the water body, which could offset pond water quality gains by supporting intense microbial metabolism. Finally, TSS did not provide a useful indication of stormwater pond biogeochemistry and was biased by autochthonous production, which could lead to erroneous TSS-based management conclusions regarding pond performance. PMID:24147410</p> <div class="credits"> <p class="dwt_author">Williams, Clayton J; Frost, Paul C; Xenopoulos, Marguerite A</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-09-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_15");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' 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src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">321</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2004AGUSM.H44A..03Z"> <span id="translatedtitle">Influence of <span class="hlt">Biogeochemical</span> Conditions on the Stability and Remobilization of Biogenic U(IV)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Uranium (U) is a common contaminant at the US Department of Energy (DOE) sites resulting from its central role in nuclear fuel cycle, and at U mine tailing sites associated with its production. U is present in the environment primarily as the hexavalent U(VI) and tetravalent U(IV). U(IV) is typically contained in insoluble precipitates, such as uraninite [UO2(s)], whereas U(VI) exists as uranyl ion, UO22+, and its complexes with various ligands. The mobility of U(VI) is a major concern in the subsurface environments. Under anoxic conditions, U(VI) can be reduced into U(IV) by some metal reducing bacteria, thus immobilizing U from groundwater. The reductive immobilization of U has been proposed as a remediation technology and under active studies at many US DOE sites. A key to the success of such immobilization technology is the maintenance of long term stability of the immobilized U when remediation completes and subsurface environments return to oxic conditions. This study investigated the influence of <span class="hlt">biogeochemical</span> conditions on the stability and remobilization of biogenic U(IV). The experiments were conducted in a batch system using sediments collected from the US DOE Field Research Center at Oak Ridge National Laboratory. Both sediments and U(VI) were first reduced by a dissimilatory metal reducing bacterium, Shewanella putrefaciens strain CN32, and then mixed in a solution containing 0.1 mM bicarbonate and 0.1 M NaNO3 in contact with atmospheric O2. Aqueous U(VI) in the suspensions were monitored as a function of time to determine the rates of U remobilization. The influence of <span class="hlt">biogeochemical</span> conditions in the initial suspensions including Fe(II) concentration, pH, and the aging of bio-reduced U was evaluated. The results demonstrated that the Fe(II) concentration and pH had significant effects on the rate of U remobilization, while aging had only minor influence. The immobilized U was the most stable under neutral pH condition and its stability increased with increasing Fe(II) concentration. The armoring of U(IV) by Fe(III) oxides precipitated from Fe(II) oxidation and strong U(VI) adsorption to iron oxides are two mechanisms potentially responsible for the decreased rate of U remobilization. Overall, this study demonstrated that the U remobilization rate may be controlled by manipulating <span class="hlt">biogeochemical</span> conditions</p> <div class="credits"> <p class="dwt_author">Zhong, L.; Liu, C.; Szecsody, J. E.; Zachara, J. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">322</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.H21A1070T"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Modeling of In Situ U(VI) Reduction and Immobilization with Emulsified Vegetable Oil as the Electron Donor at a Field Site in Oak Ridge, Tennessee</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">A comprehensive <span class="hlt">biogeochemical</span> model was developed to quantitatively describe the <span class="hlt">coupled</span> hydrologic, geochemical and microbiological processes that occurred following injection of emulsified vegetable oil (EVO) as the electron donor to immobilize U(VI) at the Oak Ridge Integrated Field Research Challenge site (ORIFRC) in Tennessee. The model <span class="hlt">couples</span> the degradation of EVO, production and oxidation of long-chain fatty acids (LCFA), glycerol, hydrogen and acetate, reduction of nitrate, manganese, ferrous iron, sulfate and uranium, and methanoganesis with growth of multiple microbial groups. The model describes the evolution of geochemistry and microbial populations not only in the aqueous phase as typically observed, but also in the mineral phase and therefore enables us to evaluate the applicability of rates from the literature for field scale assessment, estimate the retention and degradation rates of EVO and LCFA, and assess the influence of the <span class="hlt">coupled</span> processes on fate and transport of U(VI). Our results suggested that syntrophic bacteria or metal reducers might catalyze LCFA oxidation in the downstream locations when sulfate was consumed, and competition between methanogens and others for electron donors and slow growth of methanogen might contribute to the sustained reducing condition. Among the large amount of hydrologic, geochemical and microbiological parameter values, the initial biomass, and the interactions (e.g., inhibition) of the microbial functional groups, and the rate and extent of Mn and Fe oxide reduction appear as the major sources of uncertainty. Our model provides a platform to conduct numerical experiments to study these interactions, and could be useful for further iterative experimental and modeling investigations into the bioreductive immobiliztion of radionuclide and metal contaminants in the subsurface.</p> <div class="credits"> <p class="dwt_author">Tang, G.; Parker, J.; Wu, W.; Schadt, C. W.; Watson, D. B.; Brooks, S. C.; Orifrc Team</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">323</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012ECSS..115...63C"> <span id="translatedtitle">Dynamics of <span class="hlt">biogeochemical</span> properties in temperate coastal areas of freshwater influence: Lessons from the Northern Adriatic Sea (Gulf of Trieste)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">High spatial and temporal variabilities of <span class="hlt">biogeochemical</span> properties are prominent features of regions under freshwater influence as a result of multiple factors. Understanding the ecological functioning of these ecosystems, which provide important services for humans, is challenging since it requires adequate observational strategies and efforts. Multi-years (1999-2006) continuous observations in the northernmost part of the Adriatic Sea (Gulf of Trieste) allowed us to compute a climatological description of seasonal dynamics of <span class="hlt">biogeochemical</span> properties for three relevant sites: a coastal area directly influenced by a river, an off-shore area located in the centre of the Gulf and a coastal area located far from potential source of external nutrients. The analysis of the climatologies provides a quantitative corroboration of the conceptual scheme for <span class="hlt">biogeochemical</span> and ecological seasonal dynamics of temperate coastal areas under freshwater influence already proposed in literature, highlighting the role of river input, lateral transport, stratification regime and interaction with bottom environment as driving factors. While all areas follow a common pattern of succession of ecological processes, spatial variability accounts for a significant decrease of the absolute trophic state, and for a phase delay in <span class="hlt">biogeochemical</span> dynamics. Results show that spatial heterogeneity is an inherent structural feature of coastal ecosystems, suggesting that the evaluation of the quality status of coastal ecosystems should be made by using different reference terms for different sub-areas.</p> <div class="credits"> <p class="dwt_author">Cossarini, Gianpiero; Solidoro, Cosimo; Fonda Umani, Serena</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">324</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/52233035"> <span id="translatedtitle">Microbial communities of Hyper saline Lake Salda and Acigol, SW Turkey and Their effects on <span class="hlt">Biogeochemical</span> cycles</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The modern lakes Acigol and Salda, located in the ``Lake District'' of SW of Turkey, are known for the precipitation of sodium, magnesium, and potassium salts, and Mg-rich carbonate, respectively. As an analogue to extraterrestrial environments, these lakes provide opportunities to study microbe-mineral interactions in extreme environments, and in turn to better understand <span class="hlt">biogeochemical</span> conditions in such environments. Lake Salda</p> <div class="credits"> <p class="dwt_author">N. Balci; N. G. Karaguler; I. Ece; C. Romanek</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">325</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/41346954"> <span id="translatedtitle">Phosphorus release: A <span class="hlt">biogeochemical</span> insight from a restored lakeside wetland in the Yangtze-Huaihe region, China</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The heavy intensification of agriculture in East China since the 1980s caused the decrease of lake area and water storage capacity with impediment of regulation, lake eutrophication and frequent floods. Many restoration projects have been conducted. However, the knowledge of <span class="hlt">biogeochemical</span> factors that drive nutrient cycles during the early stage of restoration is still limited. We studied the effect of</p> <div class="credits"> <p class="dwt_author">Xiaoling Zhou; Baoqing Shan; Hong Zhang</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">326</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40700034"> <span id="translatedtitle">Integrated <span class="hlt">biogeochemical</span> and hydrologic processes driving arsenic release from shallow sediments to groundwaters of the Mekong delta</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Arsenic is contaminating the groundwater of Holocene aquifers throughout South and Southeast Asia. To examine the <span class="hlt">biogeochemical</span> and hydrological processes influencing dissolved concentrations and transport of As within soils\\/sediments in the Mekong River delta, a ?50km2 field site was established near Phnom Penh, Cambodia, where aqueous As concentrations are dangerously high and where groundwater retrieval for irrigation is minimal. Dissolved</p> <div class="credits"> <p class="dwt_author">Benjamin D. Kocar; Matthew L. Polizzotto; Shawn G. Benner; Samantha C. Ying; Mengieng Ung; Kagna Ouch; Sopheap Samreth; Bunseang Suy; Kongkea Phan; Michael Sampson; Scott Fendorf</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">327</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/57572512"> <span id="translatedtitle">Decomposition during autumn foliage leaf-fall in wetlands situated along a <span class="hlt">biogeochemical</span> gradient in Pennsylvania, USA</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Autumn leaf fall represents an important allochthonous organic input to inland, aquatic ecosystems, particularly those situated in mixed hardwood forests. We evaluated factors that influence leaf decomposition in wetlands situated along a strong <span class="hlt">biogeochemical</span> gradient spanning the ridge and valley region in the mid-Atlantic region in the United States. Leaf decomposition rates were estimated using mesh bags; at the same</p> <div class="credits"> <p class="dwt_author">Hunter J. Carrick; Kacey L. Dananay; Rebecca A. Eckert; Keith J. Price</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">328</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/53726605"> <span id="translatedtitle">Quantifying the effects of mountain pine beetle infestation on water and <span class="hlt">biogeochemical</span> cycles at multiple spatial and temporal scales</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Unprecedented levels of bark beetle infestation over the last decade have radically altered forest structure across millions of hectares of Western U.S. montane environments. The widespread extent of this disturbance presents a major challenge for governments and resource managers who lack a predictive understanding of how water and <span class="hlt">biogeochemical</span> cycles will respond to this disturbance over various temporal and spatial</p> <div class="credits"> <p class="dwt_author">P. D. Brooks; A. A. Harpold; A. J. Somor; P. A. Troch; D. J. Gochis; B. E. Ewers; E. Pendall; J. A. Biederman; D. Reed; H. R. Barnard; F. Whitehouse; T. Aston; B. Borkhuu</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">329</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40973429"> <span id="translatedtitle">Assessment of <span class="hlt">biogeochemical</span> trends in soil organic matter sequestration in Mediterranean calcimorphic mountain soils (Almería, Southern Spain)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Total soil organic matter levels and humic acid formation processes in mountain calcimorphic soils from Sierra María-Los Vélez Natural Park (Almería, Southern Spain) were found to differ depending on soil use (pine and oak forests, and cleared areas either cultivated or affected by bush encroachment). <span class="hlt">Biogeochemical</span> indicators such as the concentration of exchangeable cations, or the concentration of the different</p> <div class="credits"> <p class="dwt_author">Isabel Miralles; Raúl Ortega; Manuel Sánchez-Marañón; Miguel Soriano; Gonzalo Almendros</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">330</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/q25x536752823337.pdf"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> evolution of a sulfur-iron rich aquatic system in a reflooded wetland environment (Lake Agmon, northern Israel)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Major <span class="hlt">biogeochemical</span> processes in the newly created, shallow Lake Agmon (Hula Valley, northern Israel) were investigated from 1994 to 1996. Sediment cores, lake water and porewater were analyzed for chemical composition and spatial distribution. Sediment analyses revealed that Lake Agmon has two different sediment types: peat sediments in the northern and central parts, and marls in the southern part. The</p> <div class="credits"> <p class="dwt_author">D. Markel; E. Sass; B. Lazar; A. Bein</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">331</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/10053870"> <span id="translatedtitle">Long-term simulation of main <span class="hlt">biogeochemical</span> events in a coastal lagoon: Sacca Di Goro (Northern Adriatic Coast, Italy)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A <span class="hlt">biogeochemical</span> model for the Sacca di Goro Lagoon has been developed and partially validated with field data from 1989 to 1998. The model considers the nutrient cycles in the water column as well as in the sediments. Furthermore, phytoplankton, zooplankton, and Ulva sp. dynamics, as well as shellfish farming, are taken into account. Due to the recent anoxic crises</p> <div class="credits"> <p class="dwt_author">J. M. Zald??var; E. Cattaneo; M. Plus; C. N. Murray; G. Giordani; P. Viaroli</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">332</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/61384093"> <span id="translatedtitle">Detection of hydrocarbons and hydrocarbon microseepage in the Bighorn Basin, Wyoming using isotopic, <span class="hlt">biogeochemical</span>, and spectral reflectance techniques</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A stable isotope, <span class="hlt">biogeochemical</span>, and gebotanical reflectance study was conducted at five areas in the Bighorn Basin of Wyoming. Three of the areas are active hydrocarbon producing fields, including Little Buffalo Basin, Bonanza, and Enigma oil fields. One area contains no surface or subsurface hydrocarbons, the Cody Base area. One area, Trapper Canyon, is a surface tar sand deposit. In</p> <div class="credits"> <p class="dwt_author">Bammel</p> <p class="dwt_publisher"></p> <p class="publishDate">1992-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">333</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/52030361"> <span id="translatedtitle">Instream Attenuation of Nitrogen and Phosphorus in NonPoint Source Dominated Streams: Hydrologic and <span class="hlt">Biogeochemical</span> Controls</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Non-point source inputs of total nitrogen (TN) and total phosphorus (TP) in rivers are the leading causes of water quality degradation in the United States (Turner and Rabalais, 2003; Broussard and Turner, 2009). Yet it remains a challenge to adequately quantify the relative role and influence of physical hydrological processes versus <span class="hlt">biogeochemical</span> processes on the attenuation of TN and TP</p> <div class="credits"> <p class="dwt_author">E. N. Bray; X. Chen; A. A. Keller</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">334</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/55877669"> <span id="translatedtitle">Impact of long-term drainage on hydrogeological and <span class="hlt">biogeochemical</span> processes near a drainage ditch in a Canadian peatland</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Little is known about long-term effects of climate change on hydrogeological and <span class="hlt">biogeochemical</span> processes in northern peatlands. A drainage ditch in the Mer Bleue Bog, Canada which has been established around 100 years ago, was investigated as natural analogue for long-term drying due to climate change. To examine the effects of the hydrological manipulation, several piezometer nests were installed across</p> <div class="credits"> <p class="dwt_author">B. Kopp; J. Fleckenstein; C. Blodau</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">335</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/40249314"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> weathering in sedimentary chronosequences of the Rhône and Oberaar Glaciers (Swiss Alps): Rates and mechanisms of biotite weathering</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We analysed the composition of phyllosilicate minerals in sediments deposited by the Rhône and Oberaar glaciers (Swiss Alps), in order to identify processes and rates of <span class="hlt">biogeochemical</span> weathering in relation to glacial erosion. The investigated sediments are part of chronosequences consisting of (A) suspended, ”fresh” sediment in melt water; (B) terminal moraines from the Little Ice Age (LIA; approximately 1560–1850);</p> <div class="credits"> <p class="dwt_author">K. B. Föllmi; K. Arn; R. Hosein; T. Adatte; P. Steinmann</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">336</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://dx.doi.org/10.1029/2009GL038695"> <span id="translatedtitle">Geoelectrical measurement and modeling of <span class="hlt">biogeochemical</span> breakthrough behavior during microbial activity</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">We recorded bulk electrical conductivity (??b) along a soil column during microbially-mediated selenite oxyanion reduction. Effluent fluid electrical conductivity and early time ??b were modeled according to classic advectivedispersive transport of the nutrient medium. However, ??b along the column exhibited strongly bimodal breakthrough which cannot be explained by changes in the electrical conductivity of the pore fluid. We model the anomalous breakthrough by adding a conduction path in parallel with the fluid phase, with a time dependence described by a microbial population-dynamics model. We incorporate a delay time to show that breakthrough curves along the column satisfy the same growth model parameters and offer a possible explanation based on biomass-limited growth that is delayed with distance from influent of the nutrient medium. Although the mechanism causing conductivity enhancement in the presence of biomass is uncertain, our results strongly , suggest that <span class="hlt">biogeochemical</span> breakthrough curves have been captured in geoelectrical datasets. Copyright 2009 by the American Geophysical Union.</p> <div class="credits"> <p class="dwt_author">Slater, L. D.; Day-Lewis, F. D.; Ntarlagiannis, D.; O'Brien, M.; Yee, N.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">337</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/17344963"> <span id="translatedtitle">Interactive effects of solar UV radiation and climate change on <span class="hlt">biogeochemical</span> cycling.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">This report assesses research on the interactions of UV radiation (280-400 nm) and global climate change with global <span class="hlt">biogeochemical</span> cycles at the Earth's surface. The effects of UV-B (280-315 nm), which are dependent on the stratospheric ozone layer, on <span class="hlt">biogeochemical</span> cycles are often linked to concurrent exposure to UV-A radiation (315-400 nm), which is influenced by global climate change. These interactions involving UV radiation (the combination of UV-B and UV-A) are central to the prediction and evaluation of future Earth environmental conditions. There is increasing evidence that elevated UV-B radiation has significant effects on the terrestrial biosphere with implications for the cycling of carbon, nitrogen and other elements. The cycling of carbon and inorganic nutrients such as nitrogen can be affected by UV-B-mediated changes in communities of soil organisms, probably due to the effects of UV-B radiation on plant root exudation and/or the chemistry of dead plant material falling to the soil. In arid environments direct photodegradation can play a major role in the decay of plant litter, and UV-B radiation is responsible for a significant part of this photodegradation. UV-B radiation strongly influences aquatic carbon, nitrogen, sulfur and metals cycling that affect a wide range of life processes. UV-B radiation changes the biological availability of dissolved organic matter to microorganisms, and accelerates its transformation into dissolved inorganic carbon and nitrogen, including carbon dioxide and ammonium. The coloured part of dissolved organic matter (CDOM) controls the penetration of UV radiation into water bodies, but CDOM is also photodegraded by solar UV radiation. Changes in CDOM influence the penetration of UV radiation into water bodies with major consequences for aquatic <span class="hlt">biogeochemical</span> processes. Changes in aquatic primary productivity and decomposition due to climate-related changes in circulation and nutrient supply occur concurrently with exposure to increased UV-B radiation, and have synergistic effects on the penetration of light into aquatic ecosystems. Future changes in climate will enhance stratification of lakes and the ocean, which will intensify photodegradation of CDOM by UV radiation. The resultant increase in the transparency of water bodies may increase UV-B effects on aquatic biogeochemistry in the surface layer. Changing solar UV radiation and climate also interact to influence exchanges of trace gases, such as halocarbons (e.g., methyl bromide) which influence ozone depletion, and sulfur gases (e.g., dimethylsulfide) that oxidize to produce sulfate aerosols that cool the marine atmosphere. UV radiation affects the biological availability of iron, copper and other trace metals in aquatic environments thus potentially affecting metal toxicity and the growth of phytoplankton and other microorganisms that are involved in carbon and nitrogen cycling. Future changes in ecosystem distribution due to alterations in the physical and chemical climate interact with ozone-modulated changes in UV-B radiation. These interactions between the effects of climate change and UV-B radiation on <span class="hlt">biogeochemical</span> cycles in terrestrial and aquatic systems may partially offset the beneficial effects of an ozone recovery. PMID:17344963</p> <div class="credits"> <p class="dwt_author">Zepp, R G; Erickson, D J; Paul, N D; Sulzberger, B</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-02-06</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">338</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..15.4338S"> <span id="translatedtitle">Holocene climate dynamics, <span class="hlt">biogeochemical</span> cycles and ecosystem variability in the eastern Mediterranean Sea</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The past variability of <span class="hlt">biogeochemical</span> processes and marine ecosystems of the eastern Mediterranean Sea (EMS) is documented in the form of organic-rich sapropels that occurred at northern hemisphere insolation maxima. In order to understand the processes leading from deglacial and Holocene climate variability to the formation of sapropel S1 via changed <span class="hlt">biogeochemical</span> cycling in the EMS, we integrated results from global and regional Earth system model experiments with <span class="hlt">biogeochemical</span> and micropaleontological proxy records. Our results suggest a high spatiotemporal variability of deep-water oxygenation and <span class="hlt">biogeochemical</span> processes at the sea floor during the late glacial and early Holocene. Changes in trophic conditions of bathyal ecosystems along ocean margins are closely linked to the hydrology of the EMS borderlands; they reflect orbital and sub-orbital climate variations of the high northern latitudes and the African monsoon system. Local trophic conditions were particularly variable in the northern Aegean Sea as a response to changes in riverine runoff and Black Sea outflow. During the time of S1 deposition, average oxygen levels decreased exponentially with increasing water depth, suggesting a basin-wide shallowing of vertical convection superimposed by local signals. In the northernmost Aegean Sea, deep-water ventilation persisted during the early period of S1 formation, owing to temperature-driven local convection and the absence of low-salinity Black Sea outflow. At the same time, severe temporary dysoxia or even short anoxia occurred in the eastern Levantine basin at water depths as shallow as 900 m. This area was likely influenced by enhanced nutrient input of the Nile river that resulted in high organic matter fluxes and related high oxygen-consumption rates in the water column. In contrast, abyssal ecosystems of the Levantine and Ionian basins lack eutrophication during the early Holocene suggesting that enhanced productivity did not play a crucial role in basin-wide S1 formation. Instead, sapropel formation can be attributed to a long-term persistence of water column stratification. The modeled and observed trends of oxygen consumption rates and deep-water residence times date the initiation of stagnating deep-waters at the start of the deglacial period, thus several millennia prior to S1 deposition. Once oxygen levels fell below a critical threshold, bathyal and abyssal benthic ecosystems collapsed almost synchronously with onset of S1 deposition suggesting a rapid vertical propagation of the oxygen minimum layer. The recovery of bathyal deep-sea benthic ecosystems during the terminal phase of S1 formation is controlled by subsequently deeper convection and re-ventilation over a period of approximately 1500 years; the ultra-oligotrophic abyssal ecosystems reveal a considerably lower recovery potential. After the re-ventilation of the various sub-basins had been completed during the middle and late Holocene, deep-water renewal was more or less similar to recent rates. During that time, deep-sea ecosystem variability was driven by short-term changes in food quantity and quality as well as in seasonality, all of which are linked to millennial-scale changes in riverine runoff and associated nutrient input.</p> <div class="credits"> <p class="dwt_author">Schmiedl, Gerhard; Adloff, Fanny; Emeis, Kay; Grimm, Rosina; Maier-Reimer, Ernst; Mikolajewicz, Uwe; Möbius, Jürgen; Müller-Navarra, Katharina</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">339</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/servlets/purl/894937"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Cycling and Environmental Stability of Pu Relevant to Long-Term Stewardship of DOE Sites</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The overall objective of this research is to understand the <span class="hlt">biogeochemical</span> cycling of Pu in environments of interest to long-term DOE stewardship issues. Central to Pu cycling (transport initiation and immobilization) is the role of microorganisms. The hypothesis underlying this work is that microbial activity is the causative agent in initiating the mobilization of Pu in near-surface environments: through the transformation of Pu associated with solid phases, production of extracellular polymeric substances (EPS) carrier phases and the creation of microenvironments. Also, 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 Pu transport retardation.</p> <div class="credits"> <p class="dwt_author">Honeyman, Bruce D.; Francis, A.J.; Gillow, Jeffrey B.; Dodge, Cleveland J.; Santschi, Peter H.; Chin-Chang Hung; Diaz, Angelique; Tinnacher, Ruth; Roberts, Kimberly; Schwehr, Kathy</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-04-05</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">340</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009GeoRL..3614402S"> <span id="translatedtitle">Geoelectrical measurement and modeling of <span class="hlt">biogeochemical</span> breakthrough behavior during microbial activity</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">We recorded bulk electrical conductivity (? b ) along a soil column during microbially-mediated selenite oxyanion reduction. Effluent fluid electrical conductivity and early time ? b were modeled according to classic advective-dispersive transport of the nutrient medium. However, ? b along the column exhibited strongly bimodal breakthrough which cannot be explained by changes in the electrical conductivity of the pore fluid. We model the anomalous breakthrough by adding a conduction path in parallel with the fluid phase, with a time dependence described by a microbial population-dynamics model. We incorporate a delay time to show that breakthrough curves along the column satisfy the same growth model parameters and offer a possible explanation based on biomass-limited growth that is delayed with distance from influent of the nutrient medium. Although the mechanism causing conductivity enhancement in the presence of biomass is uncertain, our results strongly suggest that <span class="hlt">biogeochemical</span> breakthrough curves have been captured in geoelectrical datasets.</p> <div class="credits"> <p class="dwt_author">Slater, L. D.; Day-Lewis, F. D.; Ntarlagiannis, D.; O'Brien, M.; Yee, N.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-07-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_16");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous Page" /></a> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a onClick='return showDiv("page_2");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a 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href="#">11</a> <a onClick='return showDiv("page_12");' href="#">12</a> <a onClick='return showDiv("page_13");' href="#">13</a> <a onClick='return showDiv("page_14");' href="#">14</a> <a onClick='return showDiv("page_15");' href="#">15</a> <a onClick='return showDiv("page_16");' href="#">16</a> <a onClick='return showDiv("page_17");' href="#">17</a> <a style="font-weight: bold;">18</a> <a onClick='return showDiv("page_19");' href="#">19</a> <a onClick='return showDiv("page_20");' href="#">20</a> <a onClick='return showDiv("page_21");' href="#">21</a> <a onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_19");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">341</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1988OrLi...18..347L"> <span id="translatedtitle">The <span class="hlt">biogeochemical</span> cycle of the adsorbed template II: Selective adsorption of mononucleotides on adsorbed polynucleotide templates</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Experimental results are presented for the verification of the specific interaction step of the ‘adsorbed template’ <span class="hlt">biogeochemical</span> cycle, a simple model for a primitive prebiotic replication system. The experimental system consisted of gypsum as the mineral to which an oligonucleotide template attaches (Poly-C or Poly-U) and 5'-AMP, 5'-GMP, 5'-CMP and 5'-UMP as the interacting biomonomers. When Poly-C or Poly-U were used as adsorbed templates, 5'-GMP and 5'-AMP, respectively were observed to be the most strongly adsorbed species. Moreover, there exists a direct quantitative relationship between the quantity of cytidine or uracil residues in the adsorbed state and the amount of the complementary mononucleotide that is attached to it. NaCl added to the system in order to create conditions of high ionic strength seems to enhance the selectivity of the adsorption of the monmucleotides to these adsorbed templates.</p> <div class="credits"> <p class="dwt_author">Lazard, Daniel; Lahav, Noam; Orenberg, James B.</p> <p class="dwt_publisher"></p> <p class="publishDate">1988-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">342</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/22763326"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> malfunctioning in sediments beneath a deep-water fish farm.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">We investigated the environmental impact of a deep water fish farm (190 m). Despite deep water and low water currents, sediments underneath the farm were heavily enriched with organic matter, resulting in stimulated <span class="hlt">biogeochemical</span> cycling. During the first 7 months of the production cycle benthic fluxes were stimulated >29 times for CO(2) and O(2) and >2000 times for NH(4)(+), when compared to the reference site. During the final 11 months, however, benthic fluxes decreased despite increasing sedimentation. Investigations of microbial mineralization revealed that the sediment metabolic capacity was exceeded, which resulted in inhibited microbial mineralization due to negative feed-backs from accumulation of various solutes in pore water. Conclusions are that (1) deep water sediments at 8 °C can metabolize fish farm waste corresponding to 407 and 29 mmol m(-2) d(-1) POC and TN, respectively, and (2) siting fish farms at deep water sites is not a universal solution for reducing benthic impacts. PMID:22763326</p> <div class="credits"> <p class="dwt_author">Valdemarsen, Thomas; Bannister, Raymond J; Hansen, Pia K; Holmer, Marianne; Ervik, Arne</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-07-02</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">343</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.usgs.gov/pp/1134d/report.pdf"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> variability of plants at native and altered sites, San Juan Basin, New Mexico</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">The San Juan Basin is becoming a major energy resource region. The anticipated increase in strip mining for coal can be expected to alter the geochemical and <span class="hlt">biogeochemical</span> environment. because such activities destroy the native vegetation communities, rearrange the rock strata, and disrupt natural soil development. This study investigated the variability in the biogeochemistry of native plant species at both undisturbed and altered sites and assessed the importance of the observed differences. Three studies are involved in this investigation: Study 1, the <span class="hlt">biogeochemical</span> variability of native species found at sites throughout that part of the basin underlain by economically recoverable coal; Study 2, the <span class="hlt">biogeochemical</span> variability of native species growing on soils considered favorable for use in the topsoiling of spoil areas; and Study 3, the <span class="hlt">biogeochemical</span> variability of native species on rehabilitated sites at the San Juan coal mine. Summary statistics for concentrations of 35 elements (and ash yield) are reported in Study 1 for galleta grass, broom snakeweed, and fourwing saltbush. The concentrations of manganese, molybdenum, nickel, and uranium (and possibly iron and selenium) in galleta show regional patterns, with the highest values generally found in the south-central region and western edge of the study area. Differences in the concentration of elements between species was generally subtle (less than a factor of two) except for the following: ash yield of saltbush was two times that of the other plants; boron in snakeweed and saltbush was four times greater than in galleta; iron in galleta was two times greater than in saltbush; and, calcium, magnesium, potassium, phosphorus, and sulfur were generally highest in saltbush. Summary statistics (including the 95-percent expected range) for concentrations of 35 elements (and ash yield) are reported from Study 2 for galleta and broom snakeweed growing on the Sheppard, Shiprock, and Doak soil association. Significant regional (greater than 10 km) variation for aluminum, iron, sulfur, vanadium, and zirconium in galleta are reported; however, for most elements, a significant proportion of the variation in the data was measured locally (less than 0.1 km). This variation indicates that samples of galleta and snakeweed taken more than 10 km apart vary, in their element composition, little more than plants sampled as close together as 0.1 km. The concentrations of 35 elements (and ash yield) in alkali sacaton and fourwing saltbush, which were collected on a rehabilitation plot at the San Juan mine (Study 3), are compared with those of control samples of similar material from native sites from throughout the ,an Juan Basin. Concentrations of aluminum, arsenic, boron, cobalt, copper, fluorine, iron, lead, manganese, sodium, and uranium in samples of saltbush growing over spoil generally exceed the levels of these elements in control samples. For many elements, concentrations in mine samples are from two to five times higher 1 han concentrations in the control samples. Sodium concentrations i saltbush, however, were 100 times higher in mine samples than in control samples. This high concentration reflects a corresponding : OO-fold increase in the extractable sodium levels in spoil material s compared to C-horizon control samples. Sampled plants from the l1ine area, spaced relatively close together (5 m (meters) or less), vary greatly in their element compositions, apparently in response 1 J the heterogenous composition and element availability of the l1ine soils. Topsoiling to a depth of 20 cm (centimeters) does little to meliorate the uptake of elements from spoil by saltbush.</p> <div class="credits"> <p class="dwt_author">Gough, L. P.; Severson, R. C.</p> <p class="dwt_publisher"></p> <p class="publishDate">1981-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">344</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/7010104"> <span id="translatedtitle">A <span class="hlt">biogeochemical</span> study of the coccolithophore, Emiliania huxleyi, in the North Atlantic</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">Coccolithophores are a diverse group of marine phytoplankton that produce external plates, or coccoliths, of calcium carbonate. They are widely distributed in all oceans except polar waters, and are the major and often dominant component of calcite of marine sediments. Their ecology and physiology are poorly known. This paper reports on the first of two cruises to investigate the productivity and <span class="hlt">biogeochemical</span> significance of Emiliania huxleyi in the North Atlantic. This focused on optics and air-sea gas exchange and provides the general context for more detailed analyses of the observations on the CO2 system in surface waters and on the production of organic matter and calcium carbonate by coccolithophores. 74 refs., 13 figs., 1 tab.</p> <div class="credits"> <p class="dwt_author">Holligan, P.M.; Fernandez, E.; Aiken, J.; Burkill, P.H. (Plymouth Marine Lab., West Hoe (United Kingdom)); Balch, W.M. (Rosenstiel School of Marine and Atmospheric Sciences, Miami, FL (United States)); Boyd, P. (Queens Univ., Portaferry (United Kingdom)); Finch, M. (Univ. of Southampton (United Kingdom)); Groom, S.B. (Univ. of Plymouth (United Kingdom)); Malin, G. (Univ. of East Anglia, Norwich (United Kingdom)); Muller, K. (Univ. College of North Wales, Bangor (United Kingdom))</p> <p class="dwt_publisher"></p> <p class="publishDate">1993-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">345</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/1987EnMan..11..805P"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> cycling of selenium in the San Joaquin Valley, California, USA</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Subsurface agricultural drainage waters from western San Joaquin Valley, California, were found to contain elevated concentrations of the element selenium in the form of selenate. In 1978, these drainage waters began to replace previous input to Kesterson Reservoir, a pond system within Kesterson National Wildlife Refuge; this substitution was completed by 1982. In the 1983 nesting season, unusual rates of deformity and death in embryos and hatchlings of wild aquatic birds (up to 64% of eared grebe and American coot nests) occurred at the refuge and were attributed to selenium toxicosis. Features necessary for contamination to have taken place included geologic setting, climate, soil type, availability of imported irrigation water, type of irrigation, and the unique chemical properties of selenium. The mechanisms of <span class="hlt">biogeochemical</span> cycling raise questions about other ecosystems and human exposure.</p> <div class="credits"> <p class="dwt_author">Presser, Theresa S.; Ohlendorf, Harry M.</p> <p class="dwt_publisher"></p> <p class="publishDate">1987-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">346</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009JPhCS.155a2005B"> <span id="translatedtitle">Optical <span class="hlt">coupling</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">This paper describes contributions to the CMBpol Technology Study Workshop concerning optical <span class="hlt">coupling</span> structures. These are structures in or near the focal plane which convert the free space wave to a superconducting microstrip on a SI wafer, or to the waveguide input to a HEMT receiver. In addition to an introduction and conclusions by the editor, this paper includes independent contributions by Bock on 'Planar Antenna-<span class="hlt">Coupled</span> Bolometers for CMB Polarimetry', by Gunderson and Wollack on 'Millimeter-Wave Platlet Feeds', and by Lee on 'Multi-band Dual-Polarization Lens-<span class="hlt">coupled</span> Planar Antennas for Bolometric CMB polarimetry.'</p> <div class="credits"> <p class="dwt_author">Bock, J. J.; Gundersen, J.; Lee, A. T.; Richards, P. L.; Wollack, E.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-03-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">347</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/22209805"> <span id="translatedtitle">A <span class="hlt">biogeochemical</span> framework for bioremediation of plutonium(V) in the subsurface environment.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> framework for bioremediation of Pu(V)O(2) (+) in the subsurface environment. We implemented the framework in the <span class="hlt">biogeochemical</span> 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 ?M (the half-maximum toxicity value for bacteria able to reduce Pu(V) to Pu(III)PO(4(am))) or ?250 ?M (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). PMID:22209805</p> <div class="credits"> <p class="dwt_author">Deo, Randhir P; Rittmann, Bruce E</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">348</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/19666624"> <span id="translatedtitle">Physical and <span class="hlt">biogeochemical</span> modulation of ocean acidification in the central North Pacific.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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</p> <div class="credits"> <p class="dwt_author">Dore, John E; Lukas, Roger; Sadler, Daniel W; Church, Matthew J; Karl, David M</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-07-27</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">349</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/23780728"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> patterns in a river network along a land use gradient.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The Bode catchment (Germany) shows strong land use gradients from forested parts of the National Park (23 % of total land cover) to agricultural (70 %) and urbanised areas (7 %). It is part of the Terrestrial Environmental Observatories of the German Helmholtz association. We performed a <span class="hlt">biogeochemical</span> analysis of the entire river network. Surface water was sampled at 21 headwaters and at ten downstream sites, before (in early spring) and during the growing season (in late summer). Many parameters showed lower concentrations in headwaters than in downstream reaches, among them nutrients (ammonium, nitrate and phosphorus), dissolved copper and seston dry mass. Nitrate and phosphorus concentrations were positively related to the proportion of agricultural area within the catchment. Punctual anthropogenic loads affected some parameters such as chloride and arsenic. Chlorophyll a concentration and total phosphorus in surface waters were positively related. The concentration of dissolved organic carbon (DOC) was higher in summer than in spring, whereas the molecular size of DOC was lower in summer. The specific UV absorption at 254 nm, indicating the content of humic substances, was higher in headwaters than in downstream reaches and was positively related to the proportion of forest within the catchment. CO2 oversaturation of the water was higher downstream compared with headwaters and was higher in summer than in spring. It was correlated negatively with oxygen saturation and positively with DOC concentration but negatively with DOC quality (molecular size and humic content). A principle component analysis clearly separated the effects of site (44 %) and season (15 %), demonstrating the strong effect of land use on <span class="hlt">biogeochemical</span> parameters. PMID:23780728</p> <div class="credits"> <p class="dwt_author">Kamjunke, Norbert; Büttner, Olaf; Jäger, Christoph G; Marcus, Hanna; von Tümpling, Wolf; Halbedel, Susanne; Norf, Helge; Brauns, Mario; Baborowski, Martina; Wild, Romy; Borchardt, Dietrich; Weitere, Markus</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-06-19</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">350</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUFM.B13E..03P"> <span id="translatedtitle">Interactive Effects of Urban Land Use and Climate Change on <span class="hlt">Biogeochemical</span> Cycles (Invited)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Urban land-use change can affect <span class="hlt">biogeochemical</span> cycles through altered disturbance regimes, landscape management practices (e.g., irrigation and fertilization), built structures, and altered environments (heat island effect, pollution, introduction of non-native species, loss of native species). As a result, the conversion of native to urban ecological systems has been shown to significantly affect carbon, nitrogen, and water cycles at local, regional, and global scales. These changes have created novel habitats and ecosystems, which have no analogue in the history of life. Nonetheless, some of the environmental changes occurring in urban areas are analogous to the changes expected in climate by the end of the century, e.g. atmospheric increase in CO2 and an increase in air temperatures, which can be utilized as a “natural experiment” to investigate global change effects on large scale ecosystem processes. Moreover, as analogues of expected future environments, urban ecological systems may act as reservoirs of plant and animal species for adjoining landscapes that are expected to undergo relatively rapid climate changes in the next 100 years. Urban land-use change by itself may contribute to changes in regional weather patterns and long-term changes in global climate, which will depend on the net effect of converting native systems to urban systems and the comparison of per capita “footprints” between urban, suburban, and rural inhabitants. My objectives are to 1) assess the impact of changes in urban land-use on climate change and in turn how climate change may affect urban <span class="hlt">biogeochemical</span> cycles and 2) discuss the potential for urban ecosystems to mitigate green house gas emissions.</p> <div class="credits"> <p class="dwt_author">Pouyat, R. V.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">351</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010BGeo....7..827D"> <span id="translatedtitle">The role of airborne volcanic ash for the surface ocean <span class="hlt">biogeochemical</span> iron-cycle: a review</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Iron is a key micronutrient for phytoplankton growth in the surface ocean. Yet the significance of volcanism for the marine <span class="hlt">biogeochemical</span> iron-cycle is poorly constrained. Recent studies, however, suggest that offshore deposition of airborne ash from volcanic eruptions is a way to inject significant amounts of bio-available iron into the surface ocean. Volcanic ash may be transported up to several tens of kilometers high into the atmosphere during large-scale eruptions and fine ash may stay aloft for days to weeks, thereby reaching even the remotest and most iron-starved oceanic regions. Scientific ocean drilling demonstrates that volcanic ash layers and dispersed ash particles are frequently found in marine sediments and that therefore volcanic ash deposition and iron-injection into the oceans took place throughout much of the Earth's history. Natural evidence and the data now available from geochemical and biological experiments and satellite techniques suggest that volcanic ash is a so far underestimated source for iron in the surface ocean, possibly of similar importance as aeolian dust. Here we summarise the development of and the knowledge in this fairly young research field. The paper covers a wide range of chemical and biological issues and we make recommendations for future directions in these areas. The review paper may thus be helpful to improve our understanding of the role of volcanic ash for the marine <span class="hlt">biogeochemical</span> iron-cycle, marine primary productivity and the ocean-atmosphere exchange of CO2 and other gases relevant for climate in the Earth's history.</p> <div class="credits"> <p class="dwt_author">Duggen, S.; Olgun, N.; Croot, P.; Hoffmann, L.; Dietze, H.; Delmelle, P.; Teschner, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-03-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">352</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2716384"> <span id="translatedtitle">Physical and <span class="hlt">biogeochemical</span> modulation of ocean acidification in the central North Pacific</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p class="result-summary">Atmospheric carbon dioxide (CO2) is increasing at an accelerating rate, primarily due to fossil fuel combustion and land use change. A substantial fraction of anthropogenic CO2 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 <span class="hlt">biogeochemical</span> 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 CO2 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 <span class="hlt">biogeochemical</span> 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.</p> <div class="credits"> <p class="dwt_author">Dore, John E.; Lukas, Roger; Sadler, Daniel W.; Church, Matthew J.; Karl, David M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">353</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/17307120"> <span id="translatedtitle">Geomycology: <span class="hlt">biogeochemical</span> transformations of rocks, minerals, metals and radionuclides by fungi, bioweathering and bioremediation.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p class="result-summary">The study of the role that fungi have played and are playing in fundamental geological processes can be termed 'geomycology' and this article seeks to emphasize the fundamental importance of fungi in several key areas. These include organic and inorganic transformations and element cycling, rock and mineral transformations, bioweathering, mycogenic mineral formation, fungal-clay interactions, metal-fungal interactions, and the significance of such processes in the environment and their relevance to areas of environmental biotechnology such as bioremediation. Fungi are intimately involved in <span class="hlt">biogeochemical</span> transformations at local and global scales, and although such transformations occur in both aquatic and terrestrial habitats, it is the latter environment where fungi probably have the greatest influence. Within terrestrial aerobic ecosystems, fungi may exert an especially profound influence on <span class="hlt">biogeochemical</span> processes, particularly when considering soil, rock and mineral surfaces, and the plant root-soil interface. The geochemical transformations that take place can influence plant productivity and the mobility of toxic elements and substances, and are therefore of considerable socio-economic relevance, including human health. Of special significance are the mutualistic symbioses, lichens and mycorrhizas. Some of the fungal transformations discussed have beneficial applications in environmental biotechnology, e.g. in metal leaching, recovery and detoxification, and xenobiotic and organic pollutant degradation. They may also result in adverse effects when these processes are associated with the degradation of foodstuffs, natural products, and building materials, including wood, stone and concrete. It is clear that a multidisciplinary approach is essential to understand fully all the phenomena encompassed within geomycology, and it is hoped that this review will serve to catalyse further research, as well as stimulate interest in an area of mycology of global significance. PMID:17307120</p> <div class="credits"> <p class="dwt_author">Gadd, Geoffrey M</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">354</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=DE87005680"> <span id="translatedtitle">Axion <span class="hlt">Couplings</span>.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">A pedagogical derivation of the <span class="hlt">couplings</span> of the axion to quarks, leptons, photons, gluons and nucleons is given. The effective Lagrangian method is used throughout. The results are applicable to all axion models. (ERA citation 12:021526)</p> <div class="credits"> <p class="dwt_author">P. Sikivie</p> <p class="dwt_publisher"></p> <p class="publishDate">1986-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">355</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011E%26PSL.305..371F"> <span id="translatedtitle">Simulating the <span class="hlt">biogeochemical</span> effects of volcanic CO2 degassing on the oxygen-state of the deep ocean during the Cenomanian/Turonian Anoxic Event (OAE2)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Cretaceous anoxic events may have been triggered by massive volcanic CO2 degassing as large igneous provinces (LIPs) were emplaced on the seafloor. Here, we present a comprehensive modeling study to decipher the marine <span class="hlt">biogeochemical</span> consequences of enhanced volcanic CO2 emissions. A <span class="hlt">biogeochemical</span> box model has been developed for transient model runs with time-dependent volcanic CO2 forcing. The box model considers continental weathering processes, marine export production, degradation processes in the water column, the rain of particles to the seafloor, benthic fluxes of dissolved species across the seabed, and burial of particulates in marine sediments. The ocean is represented by twenty-seven boxes. To estimate horizontal and vertical fluxes between boxes, a <span class="hlt">coupled</span> ocean-atmosphere general circulation model (AOGCM) is run to derive the circulation patterns of the global ocean under Late Cretaceous boundary conditions. The AOGCM modeling predicts a strong thermohaline circulation and intense ventilation in the Late Cretaceous oceans under high pCO2 values. With an appropriate choice of parameter values such as the continental input of phosphorus, the model produces ocean anoxia at low to mid latitudes and changes in marine ?13C that are consistent with geological data such as the well established ?13C curve. The spread of anoxia is supported by an increase in riverine phosphorus fluxes under high pCO2 and a decrease in phosphorus burial efficiency in marine sediments under low oxygen conditions in ambient bottom waters. Here, we suggest that an additional mechanism might contribute to anoxia, an increase in the C:P ratio of marine plankton which is induced by high pCO2 values. According to our AOGCM model results, an intensively ventilated Cretaceous ocean turns anoxic only if the C:P ratio of marine organic particles exported into the deep ocean is allowed to increase under high pCO2 conditions. Being aware of the uncertainties such as diagenesis, this modeling study implies that potential changes in Redfield ratios might be a strong feedback mechanism to attain ocean anoxia via enhanced CO2 emissions. The formation of C-enriched marine organic matter may also explain the frequent occurrence of global anoxia during other geological periods characterized by high pCO2 values.</p> <div class="credits"> <p class="dwt_author">Flögel, S.; Wallmann, K.; Poulsen, C. J.; Zhou, J.; Oschlies, A.; Voigt, S.; Kuhnt, W.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">356</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFMPP11A1769F"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> effects of volcanic degassing on the oxygen-state of the oceans during the Cenomanian/Turonian Anoxic Event 2</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Cretaceous anoxic events may have been triggered by massive volcanic CO2 degassing as large igneous provinces (LIPs) were emplaced on the seafloor. Here, we present a comprehensive modeling study to decipher the marine <span class="hlt">biogeochemical</span> consequences of enhanced volcanic CO2 emissions. A <span class="hlt">biogeochemical</span> box model has been developed for transient model runs with time-dependent volcanic CO2 forcing. The box model considers continental weathering processes, marine export production, degradation processes in the water column, the rain of particles to the seafloor, benthic fluxes of dissolved species across the seabed, and burial of particulates in marine sediments. The ocean is represented by twenty-seven boxes. To estimate horizontal and vertical fluxes between boxes, a <span class="hlt">coupled</span> ocean-atmosphere general circulation model (AOGCM) is run to derive the circulation patterns of the global ocean under Late Cretaceous boundary conditions. The AOGCM modeling predicts a strong thermohaline circulation and intense ventilation in the Late Cretaceous oceans under high pCO2 values. With an appropriate choice of parameter values such as the continental input of phosphorus, the model produces ocean anoxia at low to mid latitudes and changes in marine ?13C that are consistent with geological data such as the well established ?13C curve. The spread of anoxia is supported by an increase in riverine phosphorus fluxes under high pCO2 and a decrease in phosphorus burial efficiency in marine sediments under low oxygen conditions in ambient bottom waters. Here, we suggest that an additional mechanism might contribute to anoxia, an increase in the C:P ratio of marine plankton which is induced by high pCO2 values. According to our AOGCM model results, an intensively ventilated Cretaceous ocean turns anoxic only if the C:P ratio of marine organic particles exported into the deep ocean is allowed to increase under high pCO2 conditions. Being aware of the uncertainties such as diagenesis, this modeling study implies that potential changes in Redfield ratios might be a strong feedback mechanism to attain ocean anoxia via enhanced CO2 emissions. The formation of C-enriched marine organic matter may also explain the frequent occurrence of global anoxia during other geological periods characterized by high pCO2 values.</p> <div class="credits"> <p class="dwt_author">Floegel, S.; Wallmann, K. J.; Poulsen, C. J.; Zhou, J.; Oschlies, A.; Voigt, S.; Kuhnt, W.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">357</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2007JMS....64...66L"> <span id="translatedtitle">Validation of the 3D <span class="hlt">biogeochemical</span> model MIRO&CO with field nutrient and phytoplankton data and MERIS-derived surface chlorophyll a images</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">This paper presents results obtained with MIRO&CO-3D, a <span class="hlt">biogeochemical</span> model dedicated to the study of eutrophication and applied to the Channel and Southern Bight of the North Sea (48.5°N 52.5°N). The model results from <span class="hlt">coupling</span> of the COHERENS-3D hydrodynamic model and the <span class="hlt">biogeochemical</span> model MIRO, which was previously calibrated in a multi-box implementation. MIRO&CO-3D is run to simulate the annual cycle of inorganic and organic carbon and nutrients (nitrogen, phosphorus and silica), phytoplankton (diatoms, nanoflagellates and Phaeocystis), bacteria and zooplankton (microzooplankton and copepods) with realistic forcing (meteorological conditions and river loads) for the period 1991 2003. Model validation is first shown by comparing time series of model concentrations of nutrients, chlorophyll a, diatom and Phaeocystis with in situ data from station 330 (51°26.00?N, 2°48.50?E) located in the centre of the Belgian coastal zone. This comparison shows the model's ability to represent the seasonal dynamics of nutrients and phytoplankton in Belgian waters. However the model fails to simulate correctly the dissolved silica cycle, especially during the beginning of spring, due to the late onset (in the model) of the early spring diatom bloom. As a general trend the chlorophyll a spring maximum is underestimated in simulations. A comparison between the seasonal average of surface winter nutrients and spring chlorophyll a concentrations simulated with in situ data for different stations is used to assess the accuracy of the simulated spatial distribution. At a seasonal scale, the spatial distribution of surface winter nutrients is in general well reproduced by the model with nevertheless a small overestimation for a few stations close to the Rhine/Meuse mouth and a tendency to underestimation in the coastal zone from Belgium to France. PO4 was simulated best; silica was simulated with less success. Spring chlorophyll a concentration is in general underestimated by the model. The accuracy of the simulated phytoplankton spatial distribution is further evaluated by comparing simulated surface chlorophyll a with that derived from the satellite sensor MERIS for the year 2003. Reasonable agreement is found between simulated and satellite-derived regions of high chlorophyll a with nevertheless discrepancies close to the boundaries.</p> <div class="credits"> <p class="dwt_author">Lacroix, Geneviève; Ruddick, Kevin; Park, Youngje; Gypens, Nathalie; Lancelot, Christiane</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">358</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2008AGUFMOS34B..06Y"> <span id="translatedtitle">Environmental Assessment for Potential Impacts of Ocean CO2 Storage on Marine <span class="hlt">Biogeochemical</span> Cycles</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Ocean CO2 storage that actively utilizes the ocean potential to dissolve extremely large amounts of CO2 is a useful option with the intent of diminishing atmospheric CO2 concentration. CO2 storage into sub-seabed geological formations is also considered as the option which has been already put to practical reconnaissance in some projects. Direct release of CO2 in the ocean storage and potential CO2 leakage from geological formations into the bottom water can alter carbonate system as well as pH of seawater. It is essential to examine to what direction and extent chemistry change of seawater induced by CO2 can affect the marine environments. Previous studies have shown direct and acute effects by increasing CO2 concentrations on physiology of marine organisms. It is also a serious concern that chemistry change can affect the rates of chemical, biochemical and microbial processes in seawater resulting in significant influences on marine <span class="hlt">biogeochemical</span> cycles of the bioelements including carbon, nutrients and trace metals. We, AIST, have conducted a series of basic researches to assess the potential impacts of ocean CO2 storage on marine <span class="hlt">biogeochemical</span> processes including CaCO3 dissolution, and bacterial and enzymatic decomposition of organic matter. By laboratory experiments using a special high pressure apparatus, the improved empirical equation was obtained for CaCO3 dissolution rate in the high CO2 concentrations. Based on the experimentally obtained kinetics with a numerical simulation for a practical scenario of oceanic CO2 sequestration where 50 Mton CO2 per year is continuously injected to 1,000-2,500 m depth within 100 x 333 km area for 30 years, we could illustrate precise 3-D maps for the predicted distributions of the saturation depth of CaCO3, in situ ? value and CaCO3 dissolution rate in the western North Pacific. The result showed no significant change in the bathypelagic CaCO3 flux due to chemistry change induced by ocean CO2 sequestration. Both bacteria and hydrolytic enzymes are known as the essential promoters for organic matter decomposition in marine ecosystems. Bacterial activity and metabolisms under various CO2 concentrations and pH were examined on total cell abundance, 3H-leucine incorporation rate, and viable cell abundance. Our in vitro experiments demonstrated that acute effect by high CO2 conditions was negligible on the activities of bathypelagic bacteria at pH 7 or higher. However, our results suggested that bacterial assemblage in some organic-rich "microbial hot-spots" in seawater such as organic aggregates sinking particles, exhibited high sensitivity to acidification. Furthermore, it was indicated that CO2 injection seems to be the trigger to alter the microbial community structure between Eubacteria and Archaea. The activities of five types of hydrolytic enzymes showed no significant change with acidification as those observed in the bacterial activity. As to acute effects on microbial and biochemical processes examined by our laboratory studies, no significant influence was exhibited in the simulated ocean CO2 storage on marine <span class="hlt">biogeochemical</span> cycling. Uncertainties in chronic and large-scale impacts, however, remain and should be addressed for more understanding the potential benefits and risks of the ocean storage.</p> <div class="credits"> <p class="dwt_author">Yamada, N.; Tsurushima, N.; Suzumura, M.; Shibamoto, Y.; Harada, K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">359</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUSM.H31D..07B"> <span id="translatedtitle">Spatial Scaling Patterns of C, N and P Loads in Engineered Watersheds: Hydrologic vs. <span class="hlt">Biogeochemical</span> Drivers</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Understanding nutrient dynamics in diverse ecosystems is critical in evaluating ecological impacts (e.g., eutrophication; coastal hypoxia) from increased loads of nitrogen (N), phosphorus (P), and carbon (C). The linkage between the hydrologic and the <span class="hlt">biogeochemical</span> cycles is crucial for predicting nutrient cycling in these ecosystems. Examining the impacts of large-scale human modifications of watersheds (e.g., land-use intensification for food production; hydrologic modification though extensive tile-drainage, etc.) on the hydrologic and <span class="hlt">biogeochemical</span> responses, and ecological impacts at various scales has been the focus of large-scale monitoring and modeling studies over the past two decades. Non-linear interactions between the climate (rainfall, evapotranspiration) and landscape are modified by the fractal river network to generate emergent scaling patterns of runoff that has been studied in considerable detail. The role of biogeochemistry as an additional non-linear filter that modifies the runoff signature to generate emergent patterns of nutrient loads has received much less attention. While scaling behavior of streamflow has been observed to be a function of the time scales of rainfall and catchment response, scaling patterns of nutrient loads would also be dependent on the time scales of the contaminant input function, and reaction time scales within various components of the system (hillslope, riparian zones, stream network). We examined the hydrologic and water-quality monitoring data available for the Mississippi River Basin, and found consistent linear relationships between area-normalized annual discharge (Q; L3L-2T-1) and area- normalized annual nutrient loads (ML-2T-1) at all spatial scales, ranging from first-order watersheds (~101 to 102 km2) to the entire river basin (~3x106 km2). By comparing the load-discharge data for conservative constituents (e.g., bicarbonate) with that for more-reactive constituents (nitrate, phosphate, pesticides), we estimated the effective attenuation rate constants at each spatial scale. We derived explicit analytical expressions for reproducing the reported scale-dependence of the nutrient attenuation rate constants. Finally, we used a simple hillslope-network model to investigate the spatial scaling patterns of nutrient loads as a function of the transport and reaction time scales. Implications of these results to predicting water quality impacts of land-use and climate change are discussed.</p> <div class="credits"> <p class="dwt_author">Basu, N. B.; Rao, P. C.; S, Z.; Ye, S.; Botter, G.; Sivapalan, M.; Rinaldo, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-05-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">360</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009DSRI...56.2115S"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> impact of a model western iron source in the Pacific Equatorial Undercurrent</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Trace element distributions in the source waters of the Pacific Equatorial Undercurrent (EUC) show the existence of elevated total acid-soluble iron concentrations. This region has been suggested to contribute enough bioavailable iron to regulate interannual and interglacial variability in biological productivity downstream in the high-nitrate low-chlorophyll upwelling zone of the eastern equatorial Pacific. We investigated the advection and first-order <span class="hlt">biogeochemical</span> impact of an imposed, data-based iron maximum in the western Pacific EUC using an ecosystem model forced by a global dynamical model. We imposed two source profiles of iron constrained by total acid-soluble iron measurements. Though the data for total acid-soluble iron included both dissolved and acid-soluble particulate iron species, we treated all of the total acid-soluble iron as if it was dissolved and bioavailable. A deeper (270 m) source was centered in the density horizon of the observed iron maximum and a shallower (180 m) source was located in the core of our model's EUC, where a dissolved iron maximum has been frequently postulated. These source runs were compared with a control run that contained no specific source of iron associated with the EUC. In the source runs elevated iron concentrations were simulated in the EUC across its entire zonal span, evident as a subsurface plume of dissolved iron slightly below the core of the EUC. In the control run there was no iron maximum associated with the EUC. Upwelling of iron-replete water in the central and eastern equatorial Pacific increased integrated primary productivity in the Wyrtki box (180°W:90°W, 5°S:5°N, 0:200 m) by 41% and 66% for the deeper and shallower iron perturbation, respectively. The source runs increased the realism of the zonal extent of HNLC conditions and the meridional distributions of biological productivity, relative to the control run. However, in the source simulations surface chlorophyll concentrations were too high by a factor of two and maximum surface nitrate concentrations were too low, relative to climatologies. The relative abundance of diatoms roughly doubled upon the input of additional iron, exceeding field observations. Though <span class="hlt">biogeochemical</span> data are limited and we did not adjust parameters to optimize the model fits to observations, these results suggest that acid-soluble particulate iron supplied to the EUC in the western equatorial Pacific is unlikely to be entirely bioavailable.</p> <div class="credits"> <p class="dwt_author">Slemons, Lia; Gorgues, Thomas; Aumont, Olivier; Menkes, Christophe; Murray, James W.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-12-01</p> </div> </div> </div> </div> <div id="filter_results_form" class="filter_results_form floatContainer" style="visibility: visible;"> <div style="width:100%" id="PaginatedNavigation" class="paginatedNavigationElement"> <a id="FirstPageLink" onclick='return showDiv("page_1");' href="#" title="First Page"> <img id="FirstPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.first.18x20.png" alt="First Page" /></a> <a id="PreviousPageLink" onclick='return showDiv("page_17");' 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onClick='return showDiv("page_22");' href="#">22</a> <a onClick='return showDiv("page_23");' href="#">23</a> <a onClick='return showDiv("page_24");' href="#">24</a> <a onClick='return showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_20");' href="#" title="Next Page"> <img id="NextPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.next.18x20.png" alt="Next Page" /></a> <a id="LastPageLink" onclick='return showDiv("page_25.0");' href="#" title="Last Page"> <img id="LastPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.last.18x20.png" alt="Last Page" /></a> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">361</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFMNH11A1102K"> <span id="translatedtitle">Study of Impact of Groundwater Cascading on <span class="hlt">Bio-Geochemical</span> Parameters of Lake Michigan</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Groundwater Cascading (GC) is a specific type of thermohaline circulation, in which dense water formed over the continental shelf descends down the continental slope to a greater depth. This process is a major component of ventilation of intermediate and abyssal waters, hence affecting thermohaline circulation and global climate. The resulting flows produce an irreversible exchange of oceanic and shelf waters and takes an important role in <span class="hlt">bio-geochemical</span> cycles by removal of phytoplankton, carbon and chlorophyll from productive areas. Because it can take decades or more for the subducted water to re-surface, water cascades contribute to long term climatic variability. It is common to consider formation of dense water by cooling, evaporation or freezing in the surface layer. GC can provide an alternative mechanism of dense water formation on the shelf. We are working on the estimation of the impact of GC on the <span class="hlt">bio-geochemical</span> parameters of Lake Michigan. GC and groundwater discharge (GD) through permeable sediments is an important pathway for fluid, solute, and energy transport including freshwater, nutrients, trace metals, bacteria, and other land based pollutants. Given the vast population, agriculture, and industry surrounding Lake Michigan including Chicago area, there is high potential that the groundwater exchange in this environment can significantly contribute dissolved nutrients, heavy metal contaminants and organic pollutants to the lake. These pollutants are likely to impact both water quality and ecosystem health and must be considered by area managers and ecosystem modelers in order to fully understand the water, nutrient, and metal budgets of the lake under influence of climate change. It is important to obtain reliable quantitative estimates of both in coming and outgoing fluxes of fresh cold waters. In situation that incoming groundwater is cold enough to occupy the lower part of the lake water column, transport processes in the bottom boundary layer dominate the removal of discharged water from the coastal zone. Physical mechanisms of such removal seem to be similar to the mechanisms of dense water cascades off the continental shelf over the shelf break. We investigate the physical mechanisms of the removal of groundwater from the coastal zone of Lake Michigan to try to get a quantification of off-shore fluxes and transport pathways for GD/GC and chemical species from the shelf through numerical modeling of the processes in the bottom boundary layer. We are using numerical modeling of the GD fluxes and transport pathways of dense water flow in the bottom boundary layer of Lake Michigan using a set of process oriented numerical models of GC. Some results of this study will be presented during the session.</p> <div class="credits"> <p class="dwt_author">Kontar, Y. A.; Stumpf, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">362</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2010AGUFM.B34A..01R"> <span id="translatedtitle">Sources and <span class="hlt">Biogeochemical</span> Cycling of Iron Isotopes in Coastal Environments (Invited)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Despite the great importance of Fe to global marine <span class="hlt">biogeochemical</span> cycles, many key questions remain unanswered about Fe sources, Fe sinks, and the biological processing of Fe. Recent measurements of Fe isotope compositions of modern and ancient marine sediments have shown startling variability in ? 56Fe values demonstrating some of the ways in which Fe isotopes may be used constrain both global and local Fe <span class="hlt">biogeochemical</span> cycling. In particular, it has been hypothesized that the light Fe isotope composition of ocean water may reflect a significant contribution of diagenetic shelf-derived iron to the open ocean. Here, I will test this hypothesis by presenting new results of Fe isotope signatures in marine environments, in particular: (1) riverine input to the ocean, which has been generally considered to have low ? 56Fe values (down to -1‰ ). Our recent study of two estuaries along USA East coast suggests that flocculation processes produce minimal Fe-isotope fractionation. However, we also found that dissolved Fe flux to the ocean may be characterized by more positive ? 56Fe values (up to 0.3‰ ) relative to the crust than previously reported; (2) redox cycling of Fe in substerranean estuaries and shelf sediments from Waquoit Bay (USA), which can result in very light Fe-isotope composition in surface pore waters (down to -5‰ ) and affecting Fe-isotope composition of coastal seawater; (3) atmospheric Fe sources to the open ocean, with crustal ? 56Fe values, as demonstrated by our recent time-series study of marine particulates from the Saragasso sea (sediment traps) yielding ? 56Fe =0.07±0.03‰ (1s, n=36); (4) new open seawater Fe-isotope analysis from the North Atlantic (BATS Station) and South Atlantic yielding ? 56Fe values that are close to - or above - atmospheric values (? 56Fe between 0.2 and 0.5‰ ). Based on those data, Fe isotopes could prove to be a sensitive tracer for shelf-derived iron vs. atmospheric deposition, both of which have been hypothesized to be important components for the global oceanic iron cycle. Further advances will focus on the distribution of Fe-isotopes throughout seafloor hydrothermal plumes and Pacific Oxygen Minimum Zone in order to provide new constraints on the Fe-isotopic mass balance in seawater.</p> <div class="credits"> <p class="dwt_author">Rouxel, O.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">363</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011BGeo....8.1745A"> <span id="translatedtitle">East Siberian Sea, an Arctic region of very high <span class="hlt">biogeochemical</span> activity</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Shelf seas are among the most active <span class="hlt">biogeochemical</span> marine environments and the East Siberian Sea is a prime example. This sea is supplied by seawater from both the Atlantic and Pacific Oceans and has a substantial input of river runoff. All of these waters contribute chemical constituents, dissolved and particulate, but of different signatures. Sea ice formation during the winter season and melting in the summer has a major impact on physical as well as <span class="hlt">biogeochemical</span> conditions. The internal circulation and water mass distribution is significantly influenced by the atmospheric pressure field. The western region is dominated by input of river runoff from the Laptev Sea and an extensive input of terrestrial organic matter. The microbial decay of this organic matter produces carbon dioxide (CO2) that oversaturates all waters from the surface to bottom relative to atmospheric level, even when primary production, inferred from low surface water nutrients, has occurred. The eastern surface waters were under-saturated with respect to CO2 illustrating the dominance of marine primary production. The drawdown of dissolved inorganic carbon equals a primary production of ~0.8 ± 2 mol C m-2, which when multiplied by half the area of the East Siberian Sea, ~500 000 km2, results in an annual primary production of 0.4 (± 1) × 1012 mol C or ~4 (± 10) × 1012 gC. Microbial decay occurs through much of the water column, but dominates at the sediment interface where the majority of organic matter ends up, thus more of the decay products are recycled to the bottom water. High nutrient concentrations and fugacity of CO2 and low oxygen and pH were observed in the bottom waters. Another signature of organic matter decomposition, methane (CH4), was observed in very high but variable concentrations. This is due to its seabed sources of glacial origin or modern production from ancient organic matter, becoming available due to sub-sea permafrost thaw and formation of so-called taliks. The decay of organic matter to CO2 as well as oxidation of CH4 to CO2 contribute to a natural ocean acidification making the saturation state of calcium carbonate low, resulting in under-saturation of all the bottom waters with respect to aragonite and large areas of under-saturation down to 50 % with respect to calcite. Hence, conditions for calcifying organisms are very unfavorable.</p> <div class="credits"> <p class="dwt_author">Anderson, L. G.; Björk, G.; Jutterström, S.; Pipko, I.; Shakhova, N.; Semiletov, I.; Wåhlström, I.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-06-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">364</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2013DSRII..93....2C"> <span id="translatedtitle">Sea change: Charting the course for <span class="hlt">biogeochemical</span> ocean time-series research in a new millennium</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Ocean time-series provide vital information needed for assessing ecosystem change. This paper summarizes the historical context, major program objectives, and future research priorities for three contemporary ocean time-series programs: The Hawaii Ocean Time-series (HOT), the Bermuda Atlantic Time-series Study (BATS), and the CARIACO Ocean Time-Series. These three programs operate in physically and <span class="hlt">biogeochemically</span> distinct regions of the world's oceans, with HOT and BATS located in the open-ocean waters of the subtropical North Pacific and North Atlantic, respectively, and CARIACO situated in the anoxic Cariaco Basin of the tropical Atlantic. All three programs sustain near-monthly shipboard occupations of their field sampling sites, with HOT and BATS beginning in 1988, and CARIACO initiated in 1996. The resulting data provide some of the only multi-disciplinary, decadal-scale determinations of time-varying ecosystem change in the global ocean. Facilitated by a scoping workshop (September 2010) sponsored by the Ocean Carbon Biogeochemistry (OCB) program, leaders of these time-series programs sought community input on existing program strengths and for future research directions. Themes that emerged from these discussions included: 1. Shipboard time-series programs are key to informing our understanding of the connectivity between changes in ocean-climate and biogeochemistry 2. The scientific and logistical support provided by shipboard time-series programs forms the backbone for numerous research and education programs. Future studies should be encouraged that seek mechanistic understanding of ecological interactions underlying the <span class="hlt">biogeochemical</span> dynamics at these sites. 3. Detecting time-varying trends in ocean properties and processes requires consistent, high-quality measurements. Time-series must carefully document analytical procedures and, where possible, trace the accuracy of analyses to certified standards and internal reference materials. 4. Leveraged implementation, testing, and validation of autonomous and remote observing technologies at time-series sites provide new insights into spatiotemporal variability underlying ecosystem changes. 5. The value of existing time-series data for formulating and validating ecosystem models should be promoted. In summary, the scientific underpinnings of ocean time-series programs remain as strong and important today as when these programs were initiated. The emerging data inform our knowledge of the ocean's biogeochemistry and ecology, and improve our predictive capacity about planetary change.</p> <div class="credits"> <p class="dwt_author">Church, Matthew J.; Lomas, Michael W.; Muller-Karger, Frank</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-09-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">365</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2009EGUGA..11..974K"> <span id="translatedtitle">The effect of gold mining and processing on <span class="hlt">biogeochemical</span> cycles in Muteh area, Isfahan province, Iran</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The environmental impacts of gold mining and processing on geochemical and <span class="hlt">biogeochemical</span> 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 content in all analysed samples is higher than the published standard levels. The most probable source for As contamination is the high concentration of this element in tap water and nutrients in all trophic levels. As content was also found to be high in livestock's wool and hair. Arsenic toxicity is probably the main reason for the observed hyperpigmentation and keratosis of palms and soles seen in the villagers. The high concentration of arsenic in various <span class="hlt">biogeochemical</span> cycles in the Muteh region is the result of the geological nature of the Muteh district enhanced by gold mining and processing which plays an active role in the remobilization of this elements.</p> <div class="credits"> <p class="dwt_author">Keshavarzi, B.; Moore, F.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-04-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">366</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://pubs.er.usgs.gov/publication/70029440"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> and metabolic responses to the flood pulse in a semiarid floodplain</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">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 <span class="hlt">biogeochemical</span> 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 <span class="hlt">biogeochemical</span> 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 flooding occurs in the connected forest, while inundation of the disconnected forest occurs only as the result of managed application of water. In semiarid floodplains, water is scarce except during the flood pulse. Ecosystem responses to the flood pulse are related to the IFI and other measures of flooding history that help describe spatial variation in ecosystem function.</p> <div class="credits"> <p class="dwt_author">Valett, H. M.; Baker, M. A.; Morrice, J. A.; Crawford, C. S.; Molles, Jr. , M. C.; Dahm, C. N.; Moyer, D. L.; Thibault, J. R.; Ellis, L. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">367</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/57898919"> <span id="translatedtitle">Lesbian <span class="hlt">Couples</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">This article focuses on the qualitative descriptions of love by 10 lesbian <span class="hlt">couples</span>, together for 10 to 24 years. The researcher approached the phenomenological and ethnographic study from a feminist perspective, and attended to contextual meaning, culture, and language. Four key themes of love emerged from this qualitative research project: foundation, expression, ritualization, and revitalization. This article provides examples of</p> <div class="credits"> <p class="dwt_author">Colleen M. Connolly</p> <p class="dwt_publisher"></p> <p class="publishDate">2004-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">368</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/50630186"> <span id="translatedtitle">WQM: A New Integrated Water Quality Monitoring Package for Long-Term In-Situ Observation of Physical and <span class="hlt">Biogeochemical</span> Parameters</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">We describe a collaborative effort to develop and implement a new integrated water quality monitoring package that provides continuous and simultaneous multi-parameter physical and <span class="hlt">biogeochemical</span> measurements, including: conductivity, temperature, pressure, dissolved oxygen, chlorophyll fluorescence, and turbidity. The \\</p> <div class="credits"> <p class="dwt_author">C. M. Orrico; C. Moore; D. Romanko; A. Derr; A. H. Barnard; C. Janzen; N. Larson; D. Murphy; R. Johnson; J. Bauman</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">369</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=273283"> <span id="translatedtitle">Quantification of terrestrial ecosystem carbon dynamics in the conterminous United States combining a process-based <span class="hlt">biogeochemical</span> model and MODIS and AmeriFlux data</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p class="result-summary">Satellite remote sensing provides continuous temporal and spatial information of terrestrial ecosystems. Using these remote sensing data and eddy flux measurements and <span class="hlt">biogeochemical</span> models, such as the Terrestrial Ecosystem Model (TEM), should provide a more adequate quantification of carbon dynami...</p> <div class="credits"> <p class="dwt_author"></p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">370</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=ADA580041"> <span id="translatedtitle">Physiological and <span class="hlt">Biogeochemical</span> Traits of Bleaching and Recovery in the Mounding Species of Coral Porites lobata: Implications for Resilience in Mounding Corals.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">Mounding corals survive bleaching events in greater numbers than branching corals. However, no study to date has determined the underlying physiological and <span class="hlt">biogeochemical</span> trait(s) that are responsible for mounding coral holobiont resilience to bleaching....</p> <div class="credits"> <p class="dwt_author">A. Hughes A. G. Grottoli C. L. Osburn S. J. Levas Y. Matsui</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">371</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012ECSS..113....1C"> <span id="translatedtitle">The MIRACLE Project: An integrated approach to understanding <span class="hlt">biogeochemical</span> cycling of mercury and its relationship with lagoon clam farming</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The "MIRACLE" Project was aimed at two specific issues: understanding Hg <span class="hlt">biogeochemical</span> cycling in the Marano and Grado Lagoon and testing the coexistence of clam farming with Hg contamination in the sediments. Mercury contamination was measured in several matrices (water, sediment, biota) and its mobility was tested along with its speciation in relation to <span class="hlt">biogeochemical</span> processes occurring in the lagoon environment, where bacterial communities have a primary role in converting Hg to its more toxic form, methylmercury (MeHg). Bioaccumulation of the Hg species was investigated on natural and seeded clams (Ruditapes philippinarum), the most important commercial bivalves in the Lagoon. The Editorial summarizes the main results obtained from this multidisciplinary study and reported in the Special Issue.</p> <div class="credits"> <p class="dwt_author">Covelli, Stefano</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-11-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">372</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2006AGUFM.A42B..01B"> <span id="translatedtitle">Earth System Modeling: <span class="hlt">Coupling</span> the physical, chemical, biological and social aspects.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">In the past, the scientific community has developed tools including complex models to predict the expected evolution of climate, weather, chemical composition, carbon cycle, etc. It is expected that, in the future, new types of questions will be posed by society, for example, by decision makers and planners. These more applied questions will focus on actions to be taken by society to maintain future environmental/climate changes below specified thresholds. Earth system models, needed to address these questions, will have to include a representation of climate as well as <span class="hlt">biogeochemical</span> processes, and will have to account for socio- economic aspects. The purpose of the paper is to describe requirements for future Earth system models, and to highlight specifically how to <span class="hlt">couple</span> climate and <span class="hlt">biogeochemical</span> aspects. Some thoughts about how to link the biophysical and social systems will be presented.</p> <div class="credits"> <p class="dwt_author">Brasseur, G. P.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-12-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">373</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.B13E0606H"> <span id="translatedtitle">Modeling <span class="hlt">coupled</span> element cycles in coastal plain wetlands subject to saltwater intrusion - linking sulfur dynamics with carbon and nitrogen cycling</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Interactions of sea-level rise and drought conditions drive salt water intrusion within historically freshwater coastal wetlands. As salt water intrusion increases, <span class="hlt">biogeochemical</span> cycling will likely shift dramatically, but the rate and shape of the changes are uncertain. To explore the potential implications of increased sulfate from saltwater intrusion on wetland <span class="hlt">biogeochemical</span> cycles, we incorporate sulfur cycling into an existing model of <span class="hlt">coupled</span> oxygen, carbon and nitrogen cycling. The model operates based on fundamental principles of stoichiometry and thermodynamics: microbial assemblages use the suite of metabolic pathways that maximize microbial growth, given the available electron donors/acceptors and the stoichiometric ratio of carbon and nitrogen required for building biomass. Using solute concentrations from a coastal wetland experiencing salt water intrusion, we implement the model with and without sulfur cycling, and also compare model results to preliminary assays of wetland soils. Incorporating sulfur cycling introduces interactions between sulfur and nitrogen cycling (e.g., sulfide oxidation with nitrate) and a new suite of metabolic pathways (e.g., sulfate reduction and sulfide oxidation). After a salt water intrusion event, sulfur pathways play a more dominant role in wetland biogeochemistry and change the distribution and magnitude of existing <span class="hlt">biogeochemical</span> pathways (e.g., denitrification, methanogenesis), which affects carbon and nitrogen cycling as well as trace gas emissions. This modeling approach will provide a tool for exploring hypotheses regarding complex wetland <span class="hlt">biogeochemical</span> dynamics under changing climatic conditions.</p> <div class="credits"> <p class="dwt_author">Helton, A. M.; Poole, G.; Bernhardt, E. S.; Payn, R.; Burgin, A. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-12-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">374</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/49271452"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> dynamics of perfluorinated alkyl acids and sulfonates in the River Seine (Paris, France) under contrasting hydrological conditions</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The <span class="hlt">biogeochemical</span> dynamics of 15 perfluorinated compounds (PFCs) were investigated in a heavily urbanised river (River Seine, Paris, France). The target compounds included C4-C10 sulfonates and C5-C14 acids; eleven PFCs were detected and ?PFCs ranged between 31 and 91 ng L?1 (median: 47 ng L?1). The molecular pattern was dominated by the perfluoroalkyl sulfonates PFHxS and PFOS (>54% of ?PFCs), which were the only</p> <div class="credits"> <p class="dwt_author">Pierre Labadie; Marc Chevreuil</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">375</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/205573j558t60170.pdf"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Stratification and Carbonate Dissolution-Precipitation in Hypersaline Microbial Mats (Salt Pond, San Salvador, The Bahamas)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">Microbial mat communities host complex <span class="hlt">biogeochemical</span> processes and play a role in the formation of most carbonate rocks by\\u000a influencing both carbonate precipitation and dissolution. In this study, the biogeochemistry of microbial mats from the hypersaline\\u000a Salt Pond, San Salvador, Bahamas are described using scanning electron microscopy, X-ray diffraction, microelectrode profiling,\\u000a fatty acid methyl esters, and carbon and nitrogen analyses.</p> <div class="credits"> <p class="dwt_author">Mary K. Puckett; Karen S. McNeal; Brenda L. Kirkland; Margaret E. Corley; John E. Ezell</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">376</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/49329486"> <span id="translatedtitle">The <span class="hlt">biogeochemical</span> cycle of dissolved cobalt in the Atlantic and the Southern Ocean south off the coast of South Africa</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The spatial distribution, <span class="hlt">biogeochemical</span> cycle and external sources of dissolved cobalt (DCo) were investigated in the southeastern Atlantic and the Southern Ocean between 33°58?S and 57°33?S along the Greenwich Meridian during the austral summer 2008 in the framework of the International Polar Year. DCo concentrations were measured by flow-injection analysis and chemiluminescence detection in filtered (0.2?m), acidified and UV-digested samples</p> <div class="credits"> <p class="dwt_author">Johann Bown; Marie Boye; Alexander Baker; Eric Duvieilbourg; François Lacan; Frédéric Le Moigne; Frédéric Planchon; Sabrina Speich; David M. Nelson</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">377</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://academic.research.microsoft.com/Publication/48170539"> <span id="translatedtitle">Impact of a flood event on the <span class="hlt">biogeochemical</span> behaviour of a mesotrophic alpine lake: Lake Bourget (Savoy)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">A flood event which occurred during the onset of thermal stratification and of algal growth (March 1996) was studied in mesotrophic\\u000a Lake Bourget (France). Both physical and <span class="hlt">biogeochemical</span> processes occurring during this episode were assessed. The dominant\\u000a effect was a decrease of nutrient concentrations along the river–lake ecotone. This phenomenon seemed mainly linked to biological\\u000a factors: stimulation of the spring</p> <div class="credits"> <p class="dwt_author">B. Vinçon-Leite; P.-E. Bournet; X. Gayte; D. Fontvieille; B. Tassin</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">378</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.springerlink.com/index/r74g18w139l62420.pdf"> <span id="translatedtitle">Importance of Extracellular Enzymes for <span class="hlt">Biogeochemical</span> Processes in Temporary River Sediments during Fluctuating Dry–Wet Conditions</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">\\u000a Climate change represents an emerging problem for temporary waters by increasing the frequency and duration of drought periods,\\u000a with potentially important effects on fluvial <span class="hlt">biogeochemical</span> processes. Although benthic microbial processes have been recognized\\u000a to have a most important role in carbon, nutrient and energy flux, few studies have documented the response to dry–wet cycles\\u000a in temporary waters. Data so far</p> <div class="credits"> <p class="dwt_author">Annamaria Zoppini; Jürgen Marxsen</p> <p class="dwt_publisher"></p> <p class="publishDate"></p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">379</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.agu.org/journals/gb/gb0504/2005GB002482/2005GB002482.pdf"> <span id="translatedtitle">Impact of phytoplankton on the <span class="hlt">biogeochemical</span> cycling of iron in subantarctic waters southeast of New Zealand during FeCycle</span></a>  </p> <div class="resu