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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

A Coupled Surface/Subsurface Model for Hydrological Drought Investigations  

NASA Astrophysics Data System (ADS)

Hydrological droughts occur when storage in the ground and surface-water bodies falls below statistical average. Due to the inclusion of regional groundwater, hydrological droughts evolve relatively slowly. The atmospheric and surface components of the hydrological cycle have been widely studied, are well understood, and their prognoses are fairly accurate. In large-scale land surface models on the other hand, subsurface (groundwater) flow processes are usually assumed unidirectional and limited to the vertically-downward percolation and the horizontal runoffs. The vertical feedback from groundwater to the unsaturated zone as well as the groundwater recharge from surface waters are usually misrepresented, resulting in poor model performance during low-flow periods. The feedback is important during meteorological droughts because it replenishes soil moisture from ground- and surface water, thereby delaying the onset of agricultural droughts. If sustained for long periods however, the depletion can significantly reduce surface and subsurface storage and lead to severe hydrological droughts. We hypothesise that an explicit incorporation of the groundwater component into an existing land surface model would lead to better representation of low flows, which is critical for drought analyses. It would also improve the model performance during low-flow periods. For this purpose, we coupled the process-based mHM surface model (Samaniego et al. 2010) with MODFLOW (Harbaugh 2005) to analyse droughts in the Unstrut catchment, one of the tributaries of the Elbe. The catchment is located in one of the most drought-prone areas of Germany. We present results for stand-alone and coupled mHM simulations for the period 1970-2000. References Arlen W. Harbaugh. MODFLOW-2005, The U.S. Geological Survey Modular Ground-water Model-the Ground-water Flow Process, chapter Modelling techniques, sec. A. Ground water, pages 1:1-9:62. USGS, 2005. Luis Samaniego, Rohini Kumar, and Sabine Attinger. Multiscale parameter regionalization of a grid-based hydrologic model at the mesoscale. Water Resour. Res., 46(W05523), 2010. doi: 10.1029/2008WR007327.

Musuuza, J. L.; Kumar, R.; Samaniego, L. E.; Fischer, T.; Kolditz, O.; Attinger, S.

2013-12-01

3

Ensemble Kalman filter versus particle filter for a physically-based coupled surface-subsurface model  

NASA Astrophysics Data System (ADS)

The ensemble Kalman filter (EnKF) and sequential importance resampling (SIR) are two Monte Carlo-based sequential data assimilation (DA) methods developed to solve the filtering problem in nonlinear systems. Both methods present drawbacks when applied to physically-based nonlinear models: the EnKF update is affected by the inherent Gaussian approximation, while SIR may require a large number of Monte Carlo realizations to ensure consistent updates. In this work we implemented EnKF and SIR into a physically-based coupled surface-subsurface flow model and applied it to a synthetic test case that considers a uniform soil v-shaped catchment subject to rainfall and evaporation events. After a sensitivity analysis on the number of Monte Carlo realizations and the correlation time of the atmospheric forcing, the comparison between the two filters is done on the basis of different simulation scenarios varying observations (outlet streamflow and/or pressure head), assimilation frequency, and type of bias (atmospheric forcing or initial conditions). The results demonstrate that both EnKF and SIR are suitable DA methods for detailed physically-based hydrological modeling using the same, relatively small, ensemble size. We highlight that the Gaussian approximation in the EnKF updates leads to a state estimation that can be not consistent with the physics of the model, resulting in a slowdown of the numerical solver. SIR instead duplicates physically consistent realizations, but can display difficulties in updates when the realizations are far from the true state. We propose and test a modification of the SIR algorithm to overcome this issue and preserve assimilation efficiency.

Pasetto, Damiano; Camporese, Matteo; Putti, Mario

2012-10-01

4

Insights into three-dimensional simulation of coastal flow dynamics using a fully coupled surface-subsurface approach  

NASA Astrophysics Data System (ADS)

Coastal aquifers are complex hydrologic systems because many physical processes interact: (i) variably saturated flow, (ii) spatial-temporal fluid density variations, (iii) tidal fluctuations, (iv) storm surges overtopping dykes, and (v) surface runoff of storm water. The HydroGeoSphere model is used to numerically simulate coastal flow dynamics, assuming a fully coupled surface-subsurface approach, accounting for all processes listed above. The diffusive wave approximation of the St. Venant equation is used to describe surface flow. Surface flow and salt transport are fully coupled with subsurfacial variably saturated, variable-density flow and salt transport through mathematical terms that represent exchange of fluid mass and solute mass, respectively. Tides and storm surges induce a time-variant head that is applied to nodes of the surface domain. The approach is applied to real cases of tide and storm surge events of the coastal catchment area of Unterweser, Northern Germany (ca. 2500 km2). To optimize the simulation and to reduce CPU cost, the actual simulation domain is only a part of the total catchment area: We selected a narrow strip of about 10 km width parallel to the coastline. The catchment area outside of that strip is not affected by saltwater intrusion and does therefore not need to be included in the numerical model. The seaside boundary condition of the reduced simulation domain is obtained from a 3D hydrodynamic-numerical flow model where changes in sea level are being simulated. The landside boundary condition is obtained from a 3D steady-state flow model of the total catchment area. The 3D model is calibrated using field data previously gathered at the study site. Results indicate that the fully coupled approach with a reduced simulation domain is effective in the simulation of 3D coastal flow dynamics.

Yang, Jie; Graf, Thomas

2013-04-01

5

Ensemble Kalman Filter vs Particle Filter in a Physically Based Coupled Model of Surface-Subsurface Flow (Invited)  

NASA Astrophysics Data System (ADS)

Data assimilation (DA) has recently received growing interest by the hydrological modeling community due to its capability to merge observations into model prediction. Among the many DA methods available, the Ensemble Kalman Filter (EnKF) and the Particle Filter (PF) are suitable alternatives for applications to detailed physically-based hydrological models. For each assimilation period, both methods use a Monte Carlo approach to approximate the state probability distribution (in terms of mean and covariance matrix) by a finite number of independent model trajectories, also called particles or realizations. The two approaches differ in the way the filtering distribution is evaluated. EnKF implements the classical Kalman filter, optimal only for linear dynamics and Gaussian error statistics. Particle filters, instead, use directly the recursive formula of the sequential Bayesian framework and approximate the posterior probability distributions by means of appropriate weights associated to each realization. We use the Sequential Importance Resampling (SIR) technique, which retains only the most probable particles, in practice the trajectories closest in a statistical sense to the observations, and duplicates them when needed. In contrast to EnKF, particle filters make no assumptions on the form of the prior distribution of the model state, and convergence to the true state is ensured for large enough ensemble size. In this study EnKF and PF have been implemented in a physically based catchment simulator that couples a three-dimensional finite element Richards equation solver with a finite difference diffusion wave approximation based on a digital elevation data for surface water dynamics. We report on the retrieval performance of the two schemes using a three-dimensional tilted v-catchment synthetic test case in which multi-source observations are assimilated (pressure head, soil moisture, and streamflow data). The comparison between the results of the two approaches allows to discuss some of the strengths and weaknesses, both physical and numerical, of EnKF and PF and to learn the implications related to the choice of the statistics used to build the ensemble of realizations.

Putti, M.; Camporese, M.; Pasetto, D.

2010-12-01

6

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

7

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">8</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 odd" lang="en"> <div class="resultNumber element">9</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">10</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/2014EGUGA..1614215H"> <span id="translatedtitle">Physical/<span class="hlt">biogeochemical</span> <span class="hlt">coupled</span> model : impact of an offline vs online strategy</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">Mercator-Ocean, the French ocean forecasting center, has been developing several operational forecasting systems and reanalysis of the physical and <span class="hlt">biogeochemical</span> 3D-Ocean. Here we study the impact of an offline vs online strategy to <span class="hlt">couple</span> the physical (OPA) and <span class="hlt">biogeochemical</span> (PISCES) modules included in the NEMO platform. For this purpose, we perform global one-year long simulations at 1° resolution. The model was initialized with global climatologies. The spin-up involved 10 years of <span class="hlt">biogeochemical</span> off-line simulation forced by a climatology of ocean physics. The online mode consists in running physical and <span class="hlt">biogeochemical</span> models simultaneously whereas in the offline mode, the <span class="hlt">biogeochemical</span> model is launched alone, forced by averaged physical forcing (1 day, 7 days,… ). The Mercator operational <span class="hlt">biogeochemical</span> system is currently using the offline mode with a weekly physical forcing. A special treatment is applied to the vertical diffusivity coefficient (Kz): as it varies of several orders of magnitude, we compute the mean of the LOG10 of Kz. Moreover, a threshold value is applied to remove the highest values corresponding to enhanced convection. To improve this system, 2 directions are explored. First, 3 physical forcing frequencies are compared to quantify errors due to the offline mode: 1 hour (online mode), 1 day and 1 week (offline modes). Secondly, sensitivity tests to the threshold value applied to Kz are performed. The simulations are evaluated by systematically comparing model fields to observations (Globcolour product and World Ocean Atlas 2005) at global and regional scales. We show first that offline simulations are in good agreement with online simulation. As expected, the lower the physical forcing frequency is, the closer to the online solution is the offline simulation. The threshold value on the vertical diffusivity coefficient manages the mixing strength within the mixed layer. A value of 1 m2.s-1 appears to be a good compromise to approach the online solution. Our sensitivity tests show that increasing the temporal resolution of the forcing induces a temporal shift in the surface chlorophyll seasonal cycle: less chlorophyll in winter and a stronger spring bloom in offline mode. We attribute this behavior to the entrainment/detrainment process of chlorophyll and nutrients at the bottom of the mixed layer during winter.</p> <div class="credits"> <p class="dwt_author">Hameau, Angélique; Perruche, Coralie; Bricaud, Clément; Gutknecht, Elodie; Reffray, Guillaume</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</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://adsabs.harvard.edu/abs/2008AGUFM.H41E0913K"> <span id="translatedtitle"><span class="hlt">Coupled</span> <span class="hlt">Biogeochemical</span> and Hydrologic Processes Governing Arsenic Mobility Within Sediments of Southeast Asia</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">Weathering of As-bearing rocks in the Himalayas has resulted in the transport of sediments down major river systems such as the Brahmaputra, Ganges, Red, Irrawaddy, and Mekong. Groundwater in these river basins commonly has As concentrations exceeding the World Health Organization's recommended drinking water limit (10 ?g L-1) by more than an order of magnitude. <span class="hlt">Coupling</span> of hydrology and <span class="hlt">biogeochemical</span> processes underlies the elevated concentrations of As in these aquifers, necessitating studies that allow their deconvolution. Furthermore, to fully elucidate the <span class="hlt">biogeochemical</span> mechanisms of sedimentary As release, the thermodynamic favorability of controlling <span class="hlt">biogeochemical</span> reactions must be considered. We therefore used a combination of spectroscopic and wet chemical measurements to resolve the dominant processes controlling As release and transport in surficial soils/sediments within an As-afflicted field area of the Mekong delta. Based on these measurements, we assess the thermodynamic potential for As, Fe, and S reduction to transpire--major processes influencing As release and mobility. Our results illustrate that clay (0-12m deep) underlying oxbow and wetland environments are subjected to continuously reducing conditions due to ample carbon input and saturated conditions. Ensuing reductive mobilization of As from As-bearing Fe (hydr)oxides results in its migration to the underlying sandy aquifer (>12 m deep). Reactive transport modeling using PHREEQC and MIN3P, constrained with chemical and hydrologic field measurements, provides a calibrated illustration of As release and transport occurring within the clays underlying organic-rich, permanently inundated locations. These areas provide sufficient As to the aqueous phase for widespread contamination of the aquifer, and release is predicted to occur for several thousand years prior to depletion of As from the solid phase.</p> <div class="credits"> <p class="dwt_author">Kocar, B. D.; Polizzotto, M. L.; Ying, S. C.; Benner, S. G.; Sampson, M.; Fendorf, 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">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.ncbi.nlm.nih.gov/pubmed/23872182"> <span id="translatedtitle">A <span class="hlt">coupled</span> <span class="hlt">biogeochemical</span>-Dynamic Energy Budget model as a tool for managing fish production 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">The sustainability of semi-intensive aquaculture relies on management practices that simultaneously improve production efficiency and minimize the environmental impacts of this activity. The purpose of the present work was to develop a mathematical model that reproduced the dynamics of a semi-intensive fish earth pond, to simulate different management scenarios for optimizing fish production. The modeling approach consisted of <span class="hlt">coupling</span> a <span class="hlt">biogeochemical</span> model that simulated the dynamics of the elements that are more likely to affect fish production and cause undesirable environmental impacts (nitrogen, phosphorus and oxygen) to a fish growth model based on the Dynamic Energy Budget approach. The <span class="hlt">biogeochemical</span> sub-model successfully simulated most water column and sediment variables. A good model fit was also found between predicted and observed white seabream (Diplodus sargus) growth data over a production cycle. In order to optimize fish production, different management scenarios were analysed with the model (e.g. increase stocking densities, decrease/increase water exchange rates, decrease/increase feeding rates, decrease phosphorus content in fish feeds, increase food assimilation efficiency and decrease pellets sinking velocity) to test their effects on the pond environment as well as on fish yields and effluent nutrient discharges. Scenarios were quantitatively evaluated and compared using the Analytical Hierarchical Process (AHP) methodology. The best management options that allow the maximization of fish production while maintaining a good pond environment and minimum impacts on the adjacent coastal system were to double standard stocking densities and to improve food assimilation efficiency. PMID:23872182</p> <div class="credits"> <p class="dwt_author">Serpa, Dalila; Pousão-Ferreira, Pedro; Caetano, Miguel; Cancela da Fonseca, Luís; Dinis, Maria Teresa; Duarte, Pedro</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-10-01</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://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">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/908925"> <span id="translatedtitle">Carbon sequestration by patch fertilization: A comprehensive assessment using <span class="hlt">coupled</span> physical-ecological-<span class="hlt">biogeochemical</span> 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">This final report summarizes research undertaken collaboratively between Princeton University, the NOAA Geophysical Fluid Dynamics Laboratory on the Princeton University campus, the State University of New York at Stony Brook, and the University of California, Los Angeles between September 1, 2000, and November 30, 2006, to do fundamental research on ocean iron fertilization as a means to enhance the net oceanic uptake of CO2 from the atmosphere. The approach we proposed was to develop and apply a suite of <span class="hlt">coupled</span> physical-ecological-<span class="hlt">biogeochemical</span> models in order to (i) determine to what extent enhanced carbon fixation from iron fertilization will lead to an increase in the oceanic uptake of atmospheric CO2 and how long this carbon will remain sequestered (efficiency), and (ii) examine the changes in ocean ecology and natural <span class="hlt">biogeochemical</span> cycles resulting from iron fertilization (consequences). The award was funded in two separate three-year installments: • September 1, 2000 to November 30, 2003, for a project entitled “Ocean carbon sequestration by fertilization: An integrated <span class="hlt">biogeochemical</span> assessment.” A final report was submitted for this at the end of 2003 and is included here as Appendix 1. • December 1, 2003 to November 30, 2006, for a follow-on project under the same grant number entitled “Carbon sequestration by patch fertilization: A comprehensive assessment using <span class="hlt">coupled</span> physical-ecological-<span class="hlt">biogeochemical</span> models.” This report focuses primarily on the progress we made during the second period of funding subsequent to the work reported on in Appendix 1. When we began this project, we were thinking almost exclusively in terms of long-term fertilization over large regions of the ocean such as the Southern Ocean, with much of our focus being on how ocean circulation and <span class="hlt">biogeochemical</span> cycling would interact to control the response to a given fertilization scenario. Our research on these types of scenarios, which was carried out largely during the first three years of our project, led to several major new insights on the interaction between ocean biogeochemistry and circulation. This work, which is described in the following Section II on “Large scale fertilization,” has continued to appear in the literature over the past few years, including two high visibility papers in Nature. Early on in the first three years of our project, it became clear that small "patch-scale" fertilizations over limited regions of order 100 km diameter were much more likely than large scale fertilization, and we carried out a series of idealized patch fertilization simulations reported on in Gnanadesikan et al. (2003). Based on this paper and other results we had obtained by the end of our first three-year grant, we identified a number of important issues that needed to be addressed in the second three-year period of this grant. Section III on “patch fertilization” discusses the major findings of this phase of our research, which is described in two major manuscripts that will be submitted for publication in the near future. This research makes use of new more realistic ocean ecosystem and iron cycling models than our first paper on this topic. We have several major new insights into what controls the efficiency of iron fertilization in the ocean. Section IV on “model development” summarizes a set of papers describing the progress that we made on improving the ecosystem models we use for our iron fertilization simulations.</p> <div class="credits"> <p class="dwt_author">Jorge L. Sarmiento - Princeton PI, Anand Gnanadesikan - Princeton Co-I, Nicolas Gruber - UCLA PI, Xin Jin - UCLA PostDoc, Robert Armstrong - SUNY /Stony Brook Consultant</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-06-21</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://www.osti.gov/scitech/servlets/purl/677000"> <span id="translatedtitle">HYDROBIOGEOCHEM: A <span class="hlt">coupled</span> model of HYDROlogic transport and mixed <span class="hlt">BIOGEOCHEMical</span> kinetic/equilibrium reactions in saturated-unsaturated 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">The computer program HYDROBIOGEOCHEM is a <span class="hlt">coupled</span> model of HYDROlogic transport and <span class="hlt">BIOGEOCHEMical</span> kinetic and/or equilibrium reactions in saturated/unsaturated media. HYDROBIOGEOCHEM iteratively solves the two-dimensional transport equations and the ordinary differential and algebraic equations of mixed <span class="hlt">biogeochemical</span> reactions. The transport equations are solved for all aqueous chemical components and kinetically controlled aqueous species. HYDROBIOGEOCHEM is designed for generic application to reactive transport problems affected by both microbiological and geochemical reactions in subsurface media. Input to the program includes the geometry of the system, the spatial distribution of finite elements and nodes, the properties of the media, the potential chemical and microbial reactions, and the initial and boundary conditions. Output includes the spatial distribution of chemical and microbial concentrations as a function of time and space, and the chemical speciation at user-specified nodes.</p> <div class="credits"> <p class="dwt_author">Yeh, G.T.; Salvage, K.M. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Civil and Environmental Engineering] [Pennsylvania State Univ., University Park, PA (United States). Dept. of Civil and Environmental Engineering; Gwo, J.P. [Oak Ridge National Lab., TN (United States)] [Oak Ridge National Lab., TN (United States); Zachara, J.M.; Szecsody, J.E. [Pacific Northwest National Lab., Richland, WA (United States)] [Pacific Northwest National Lab., Richland, WA (United States)</p> <p class="dwt_publisher"></p> <p class="publishDate">1998-07-01</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://adsabs.harvard.edu/abs/2011AGUFM.B23D..01W"> <span id="translatedtitle">Prospecting for natural attenuation: <span class="hlt">Coupled</span> geophysical-<span class="hlt">biogeochemical</span> studies at DOE's Rifle IFRC 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">Research activities at the Rifle Integrated Field Research Challenge (IFRC) site in Rifle, Colorado (USA) are designed to integrate geochemical, biological, and hydrological studies to enhance our understanding of subsurface uranium mobility. While much of the research activities at the site have focused on stimulating subsurface microbial activity through acetate amendment, there is growing interest in the role that natural <span class="hlt">biogeochemical</span> processes play in constraining uranium mobility in the aquifer. Such processes constitute a form of natural uranium attenuation in the subsurface and are inferred to result from elevated concentrations of natural organic matter associated with alluvial sediments. Referred to as naturally reduced zones (NRZ's), they are characterized by the presence of reduced and/or magnetic mineral phases (e.g. FeS, FeS2, and Fe3O4), elevated Fe(II), and refractory organic carbon compounds (e.g. roots, twigs, and cones). Elevated rates of microbial activity associated with NRZ's and their mineralogical makeup act to sequester uranium from groundwater at levels higher that background alluvium. Their unique composition within a matrix of relatively oxidized, low-bioactivity sediments constitutes a potential target for a variety of exploration geophysical techniques, such as induced polarization and magnetic susceptibility. Both methods have been successfully applied at the Rifle IFRC site to delineate the ubiquity and extent of NRZ's across the floodplain. Sediments recovered from drilling targets identified through the use of exploration geophysical techniques have identified elevated uranium concentrations associated with both magnetite and framboid pyrite; however, the extent to which such minerals are the direct product of in situ microbial activity remains unknown. While diverse, the microbial community composition of NRZ's suggest dominance by fermentative organisms capable of degrading lignitic carbon to low molecular weight organic compounds and molecular hydrogen, the oxidation of which may be <span class="hlt">coupled</span> to the reductive immobilization of aqueous uranium by a variety of indigenous microorganism (e.g. Geobacter sp.). The ability to utilize geophysical techniques to assess a site's prospects for natural attenuation thus constitutes an exciting new development in the emerging field of biogeophysics.</p> <div class="credits"> <p class="dwt_author">Williams, K. H.; Kukkadapu, R. K.; Long, P. E.; Flores Orozco, A.; Kemna, A.</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">17</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/57615987"> <span id="translatedtitle">Seasonal variability of surface phytoplankton in the Northern South China Sea: A one-dimensional <span class="hlt">coupled</span> physical-<span class="hlt">biogeochemical</span> 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 South China Sea is an oligotrophic marginal sea located in the tropical-subtropical Northwestern Pacific Ocean. Under the influences of monsoon winds, both the physical and <span class="hlt">biogeochemical</span> processes exhibit distinct seasonal variability in the upper waters. In order to study the seasonal variations of surface phytoplankton, a one-dimensional <span class="hlt">coupled</span> physical-<span class="hlt">biogeochemical</span> model was developed and applied to the deep basins of</p> <div class="credits"> <p class="dwt_author">Bingxu Geng; Shiyu Li; Dongxiao Wang; Jiatang Hu; Lin Luo; Siying Wang</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">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/2014EGUGA..1612904P"> <span id="translatedtitle">Three-dimensional approach using two <span class="hlt">coupled</span> models for description of hydrological and <span class="hlt">biogeochemical</span> processes at the catchment scale</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">Hydrological and <span class="hlt">biogeochemical</span> transport through changing landscapes has been well described during the past years in literature. However, the uncertainties of combined water quality and water quantity models are still challenging, both due to a lack in process understanding as well to spatiotemporal heterogeneity of environmental conditions driving the processes. In order to reduce the uncertainty in water quality and runoff predictions at the catchment scale, a variety of different model approaches from empirical-conceptual to fully physical and process based models have been developed. In this study we present a new modelling approach for the investigation of hydrological processes and nutrient cycles, with a focus on nitrogen in a small catchment from Hessen, Germany. A hydrological model based on the model toolbox Catchment Modelling Framework (CMF) has been <span class="hlt">coupled</span> with the process based <span class="hlt">biogeochemical</span> model LandscapeDNDC. States, fluxes and parameters are exchanged between the models at high temporal and spatial resolution using the Python scripting language in order to obtain a 3-dimensional model application. The transport of water and nutrients through the catchment is modelled using a 3D Richards/Darcy approach for subsurface fluxes, a kinematic wave approach for surface runoff and a Penman-Monteith based calculation of evapotranspiration. <span class="hlt">Biogeochemical</span> processes are modelled by Landscape-DNDC, including plant growth and biomass allocation, organic matter mineralisation, nitrification, denitrification and associated nitrous oxide emissions. The interactions and module connectivity between the two <span class="hlt">coupled</span> models, as well as the model application on a 3.7 km² catchment with the runoff results and nitrogen quantification will be presented in this study.</p> <div class="credits"> <p class="dwt_author">Plesca, Ina; Kraft, Philipp; Haas, Edwin; Klatt, Steffen; Butterbach-Bahl, Klaus; Frede, Hans-Georg; Breuer, Lutz</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</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/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">20</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/10141724"> <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.osti.gov/scitech">SciTech Connect</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), which provides a medium-resolution (i.e., 1{degrees} by 1{degrees}) simulation of the atmospheric circulation; (2) a procedure for identifying regions of defined homogeneity of surface type within GCM grid cells; (3) a set of surface process models, to be run within each homogeneous region, which include a biophysical model, the Biosphere Atmospheric Transfer Scheme (BATS), and a <span class="hlt">biogeochemical</span> model (BGCM); (4) an interpolation/integration system that transfers information between the GCM and surface process models with finer resolution; and (5) an interactive data array based on a geographic information system (GIS), which provides land characteristic information via the interpolator. The goals of this detailed investigation are to compute the local and global sensitivities of trace gas fluxes to GCM and BATS variables, the effects of trace gas fluxes on global climate, and the effects of global climate on specific biomes.</p> <div class="credits"> <p class="dwt_author">Miller, N.L.; Foster, I.T.</p> <p class="dwt_publisher"></p> <p class="publishDate">1994-04-01</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" 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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 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://ntrs.nasa.gov/search.jsp?R=20000112962&hterms=general+increment+density+cu+first+transition+series&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dgeneral%2Bincrement%2Bdensity%2Bcu%2Bfirst%2Btransition%2Bseries"> <span id="translatedtitle">A <span class="hlt">Coupled</span> Ocean General Circulation, <span class="hlt">Biogeochemical</span>, and Radiative Model of the Global Oceans: Seasonal Distributions of Ocean Chlorophyll and Nutrients</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">A <span class="hlt">coupled</span> ocean general circulation, <span class="hlt">biogeochemical</span>, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. <span class="hlt">Biogeochemical</span> processes in the model are determined from the influences of circulation and turbulence dynamics, irradiance availability. and the interactions among three functional phytoplankton groups (diatoms. chlorophytes, and picoplankton) and three nutrients (nitrate, ammonium, and silicate). Basin scale (greater than 1000 km) model chlorophyll results are in overall agreement with CZCS pigments in many global regions. Seasonal variability observed in the CZCS is also represented in the model. Synoptic scale (100-1000 km) comparisons of imagery are generally in conformance although occasional departures are apparent. Model nitrate distributions agree with in situ data, including seasonal dynamics, except for the equatorial Atlantic. The overall agreement of the model with satellite and in situ data sources indicates that the model dynamics offer a reasonably realistic simulation of phytoplankton and nutrient dynamics on synoptic scales. This is especially true given that initial conditions are homogenous chlorophyll fields. The success of the model in producing a reasonable representation of chlorophyll and nutrient distributions and seasonal variability in the global oceans is attributed to the application of a generalized, processes-driven approach as opposed to regional parameterization and the existence of multiple phytoplankton groups with different physiological and physical properties. These factors enable the model to simultaneously represent many aspects of the great diversity of physical, biological, chemical, and radiative environments encountered in the global oceans.</p> <div class="credits"> <p class="dwt_author">Gregg, Watson W.; Busalacchi, Antonio (Technical Monitor)</p> <p class="dwt_publisher"></p> <p class="publishDate">2000-01-01</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://adsabs.harvard.edu/abs/2014GMD.....7.2393K"> <span id="translatedtitle">Methods to evaluate CaCO3 cycle modules in <span class="hlt">coupled</span> global <span class="hlt">biogeochemical</span> ocean 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 marine CaCO3 cycle is an important component of the oceanic carbon system and directly affects the cycling of natural and the uptake of anthropogenic carbon. In numerical models of the marine carbon cycle, the CaCO3 cycle component is often evaluated against the observed distribution of alkalinity. Alkalinity varies in response to the formation and remineralization of CaCO3 and organic matter. However, it also has a large conservative component, which may strongly be affected by a deficient representation of ocean physics (circulation, evaporation, and precipitation) in models. Here we apply a global ocean <span class="hlt">biogeochemical</span> model run into preindustrial steady state featuring a number of idealized tracers, explicitly capturing the model's CaCO3 dissolution, organic matter remineralization, and various preformed properties (alkalinity, oxygen, phosphate). We compare the suitability of a variety of measures related to the CaCO3 cycle, including alkalinity (TA), potential alkalinity and TA*, the latter being a measure of the time-integrated imprint of CaCO3 dissolution in the ocean. TA* can be diagnosed from any data set of TA, temperature, salinity, oxygen and phosphate. We demonstrate the sensitivity of total and potential alkalinity to the differences in model and ocean physics, which disqualifies them as accurate measures of <span class="hlt">biogeochemical</span> processes. We show that an explicit treatment of preformed alkalinity (TA0) is necessary and possible. In our model simulations we implement explicit model tracers of TA0 and TA*. We find that the difference between modelled true TA* and diagnosed TA* was below 10% (25%) in 73% (81%) of the ocean's volume. In the Pacific (and Indian) Oceans the RMSE of A* is below 3 (4) mmol TA m-3, even when using a global rather than regional algorithms to estimate preformed alkalinity. Errors in the Atlantic Ocean are significantly larger and potential improvements of TA0 estimation are discussed. Applying the TA* approach to the output of three state-of-the-art ocean carbon cycle models, we demonstrate the advantage of explicitly taking preformed alkalinity into account for separating the effects of <span class="hlt">biogeochemical</span> processes and circulation on the distribution of alkalinity. In particular, we suggest to use the TA* approach for CaCO3 cycle model evaluation.</p> <div class="credits"> <p class="dwt_author">Koeve, W.; Duteil, O.; Oschlies, A.; Kähler, P.; Segschneider, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-10-01</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://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 " 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://www.ncbi.nlm.nih.gov/pubmed/25141147"> <span id="translatedtitle">Nutrient limitation and physiology mediate the fine-scale (de)<span class="hlt">coupling</span> of <span class="hlt">biogeochemical</span> cycles.</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">Nutrients in the environment are <span class="hlt">coupled</span> over broad timescales (days to seasons) when organisms add or withdraw multiple nutrients simultaneously and in ratios that are roughly constant. But at finer timescales (seconds to days), nutrients become decoupled if physiological traits such as nutrient storage limits, circadian rhythms, or enzyme kinetics cause one nutrient to be processed faster than another. To explore the interactions among these <span class="hlt">coupling</span> and decoupling mechanisms, we introduce a model in which organisms process resources via uptake, excretion, growth, respiration, and mortality according to adjustable trait parameters. The model predicts that uptake can <span class="hlt">couple</span> the input of one nutrient to the export of another in a ratio reflecting biological demand stoichiometry, but <span class="hlt">coupling</span> occurs only when the input nutrient is limiting. Temporal nutrient <span class="hlt">coupling</span> may, therefore, be a useful indicator of ecosystem limitation status. Fine-scale patterns of nutrient <span class="hlt">coupling</span> are further modulated by, and potentially diagnostic of, physiological traits governing growth, uptake, and internal nutrient storage. Together, limitation status and physiological traits create a complex and informative relationship between nutrient inputs and exports. Understanding the mechanisms behind that relationship could enrich interpretations of fine-scale time-series data such as those now emerging from in situ solute sensors. PMID:25141147</p> <div class="credits"> <p class="dwt_author">Appling, Alison P; Heffernan, James B</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-09-01</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/2012AGUFM.B23D0494L"> <span id="translatedtitle"><span class="hlt">Coupled</span> <span class="hlt">biogeochemical</span> cycles in riparian zones with contrasting hydrogeomorphic characteristics in the US Midwest</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 study we aims to understand what drives the fate and transport of multiple contaminants sensitive to soil redox condition across hydrogeomorphic (HGM) gradient and evaluate overall <span class="hlt">biogeochemical</span> functions of riparian zones regarding those contaminants. We conducted monthly field work for 19 consecutive months from November 2009 to May 2011 at three study sites representative for main HGM types at the US Midwest. We collected the parameters from different sources which include field parameters, such as topography, water table depth, oxidation reduction potential (ORP) and dissolved oxygen (DO), and groundwater chemistry, such as NH4+, NO3-, PO43-, SO42-, CI- , and Hg and MeHg. Our results demonstrated that seasonal water table fluctuations and groundwater flows characteristics at three sites are strongly affected by their HGM setting. Specifically, the convergence of quick rise of water table, high ORP and sharp decrease in concentrations of NO3- and SO42 from field edge to stream edge (60-90% at LWD and 90% at WR) in spring after snowmelt and early May, which could be explained by that snow melt and early summer rainfall are major drivers of fluctuations of water table, variations of ORP and transport and transformation of contaminants. Riparian zones removed NO3- and SO42- during high water table but released Mercury in summer at both LWD and WR, and sulfate reduction, ammonia production and MeHg production all occurred when ORP and water tables were low in summer. These results might reflect the strong ORP control on these processes at landscape scale. These findings supported our hypothesis. Other findings however contrast to our hypothesis. For instances, unusual high concentrations of nitrate and Hg at WR suggest that the transport and fate of multiple contaminants relate not only to HGM settings but geographic location and land use. Negligible variations of P concentration in groundwater indicate that the transformation of P is not sensitive to soil redox condition, while relatively higher P concentration in surface water suggests that surface runoff may be more responsible for the transport of P. Therefore, the value of this study is that it confirmed the connection of HGM and transport and fate of some contaminants, and also revealed that land use manner plays an important role in aquatic ecosystem sustainability and it should be considered in water resource management.</p> <div class="credits"> <p class="dwt_author">Liu, X.</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">26</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/51585875"> <span id="translatedtitle">A semi-evolutive partially local Kalman filter to assimilate ocean color data into a 3D <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://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">An advanced Kalman filter is used to assimilate pseudo color data into a three-dimensional <span class="hlt">coupled</span> physical-<span class="hlt">biogeochemical</span> model of the Cretan Sea. The model comprises the three-dimensional Princeton Model (POM) and the European Regional Seas Ecosystem Model (ERSEM). In this study, the Semi-Evolutive Partially Local Extended Kalman (SEPLEK) filter is introduced in order to reduce the computational burden and also to</p> <div class="credits"> <p class="dwt_author">I. Hoteit; G. Triantafyllou; G. Petihakis</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">27</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/70093912"> <span id="translatedtitle">Emergent biological patterns and <span class="hlt">surface-subsurface</span> interactions at landscape scales</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">In this chapter, we focus on emergent biological patterns in riverine ecosystems at landscape scales resulting from <span class="hlt">surface-subsurface</span> water interaction. Our objectives are to examine (1) how the balance of physical and chemical factors on the "natural" geologic template affects biological patterns, (2) how natural hydrothermal systems can be used as a model for understanding <span class="hlt">surface-subsurface</span> interactions and biological patterns in streams, and (3) how anthropogenic influences decouple the stream from the landscape by altering the nature of <span class="hlt">surface-subsurface</span> water interactions and affecting biological patterns. We conclude with a synthesis and recommendations for further studies.</p> <div class="credits"> <p class="dwt_author">Pringle, C. M.; Triska, F. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2000-01-01</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/2010AGUFM.B11D0391L"> <span id="translatedtitle">Global <span class="hlt">Biogeochemical</span> Cycle of Si: Its <span class="hlt">Coupling</span> to the Perturbed C-N-P cycles in Industrial Time</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 importance of silicon (Si) in global <span class="hlt">biogeochemical</span> cycles is demonstrated by its abundance in the land and aquatic biomass, where Si/C is 0.02 in land plants and 0.15 in marine organisms. Estimates show that Si-bioproduction accounts for ~1.5% of terrestrial primary production, and ~4.5% in the coastal ocean. Human land-use activities have substantially changed regional patterns of vegetation distribution, soil conditions, and nutrient fluxes via runoff to the coastal ocean. Anthropogenic chemical fertilization of the land has caused a significant increase in fluvial nitrogen (N) and phosphorus (P) transport, whereas land-use and vegetation mass changes have caused variations in the riverine Si input, all eventually affecting the cycling of nutrients in the marine environment. We developed a global <span class="hlt">biogeochemical</span> model of the Si cycle as <span class="hlt">coupled</span> to the global C-N-P cycle model, TOTEM II (Terrestrial-Ocean-aTmosphere-Ecosystem-Model). In the model analysis from year 1700, taken as the start of the Anthropocene, to 2050, the bioproduction of Si on land and in the ocean is <span class="hlt">coupled</span> to the bioproduction of C, perturbed by the atmospheric CO2 rise, land-use changes, and chemical fertilization. Also, temperature rise affects the Si cycling on land through bioproduction rates, terrestrial organic matter remineralization, and weathering, thereby affecting its delivery to the coastal zone. The results show that biouptake and subsequent release of Si on land strongly affect the Si river flux to the coastal ocean. During the 350-year period, Si river discharge has increased by ~10% until ~1940, decreasing since then to below its 1700 value and continuing to drop, under the current IPCC IS92 projections of CO2, temperature and other forcings. From 1700 to ~1950, land-use changes, associated with slash and burn of large areas of high-productivity land, caused a decrease of global land vegetation. Dissolution of Si in soil humus and weathering of silicate minerals are the main dissolved Si sources for rivers and groundwater. The decrease in Si uptake by land biomass made more Si available for river discharge, causing an increase in the Si river input until an increase in the land primary production reversed the process. Around 1950, the use of fertilizer on land, especially N and P, increased, driving the growth of coastal marine primary producers, including such Si organisms as diatoms, silicoflagellates, and sponge spicules, and thus causing a decrease of dissolved Si in the surface ocean. The percent decrease of coastal dissolved Si due to increased primary production is greater than that of surface open ocean due to the shorter residence time of Si in coastal water (~2.7 years) compared to that of surface open ocean (~10 years. The combination of the relatively small size and location of the coastal ocean at the junction of the land, atmosphere, and open ocean make it important to changes in water chemistry, in situ biological production, and sedimentary storage. Its buffer effect and fast response to perturbations are also shown in the results of this <span class="hlt">coupling</span> study of the C-N-P-Si cycles.</p> <div class="credits"> <p class="dwt_author">Lerman, A.; Li, D. D.; MacKenzie, F. T.</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">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/2014EGUGA..16.7433F"> <span id="translatedtitle">Control of mass balance error in a detailed model of <span class="hlt">surface-subsurface</span> flow interaction</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 process-based catchment-scale hydrologic models have been developed in recent years to describe the interactions and feedbacks between different components of the water cycle, but few studies have considered the sources of <span class="hlt">coupling</span> error in these models. In this work we analyze the sequential iterative <span class="hlt">coupling</span> scheme of the distributed model CATHY (CATchment HYdrology) in order to identify the different sources of mass balance error and to examine how these are influenced by topography, hydraulic properties, and atmospheric forcing. A pair of adimensional indices that quantify the degree of <span class="hlt">coupling</span> and of flux partitioning is presented. Our analysis shows that mass balance errors increase during the flood recession limb because of the exchange of information between surface and subsurface water flow. Surface water propagation is cell centered, while the subsurface flow equation is solved on the vertices of surface cells. Evaluation of surface pressure heads and exchange fluxes is critical on this staggered <span class="hlt">surface-subsurface</span> mesh, especially during transitions from unsaturated to saturated conditions and vice versa. A modified version of the flux exchange algorithm is introduced that considers the effective availability of water on surface cells. The performance of the model is also improved by introducing a heuristic procedure to control and adapt the time step interval. Starting from numerical stability and convergence constraints, this procedure varies the computational interval as a function of the rate of change of surface saturation via the <span class="hlt">coupling</span> degree index. A final improvement made to the sequential <span class="hlt">coupling</span> scheme in CATHY is to solve the surface routing equation after rather than before the subsurface module. We find that the modified version improves the water balance by more than 50% in most of the tests considered for a simple v-shaped catchment. The results so far obtained for the synthetic v-catchment indicate the need for a more comprehensive analysis including real catchments.</p> <div class="credits"> <p class="dwt_author">Fiorentini, Marcello; Orlandini, Stefano; Paniconi, Claudio; Putti, Mario</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</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://academic.research.microsoft.com/Publication/51622970"> <span id="translatedtitle">HydroSphere: Fully-Integrated, <span class="hlt">Surface\\/Subsurface</span> Numerical Model for Watershed Analysis of Hydrologic, Water Quality and Sedimentation 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 distributed, physically based and fully-<span class="hlt">coupled</span> <span class="hlt">surface\\/subsurface</span> numerical model, HydroSphere, has recently been developed for watershed analysis of hydrologic and water quality processes. It accounts for flow and transport in lateral two-dimensional surface water, one-dimensional tile drains and three-dimensional variably-saturated subsurface water. One-, two- and three-dimensional forms of the advection-dispersion equation are used to describe solute transport in the tile</p> <div class="credits"> <p class="dwt_author">G. B. Matanga; K. E. Nelson; E. Sudicky; R. Therrien; S. Panday; R. McLaren; D. Demarco; L. Gessford</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">31</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=3851166"> <span id="translatedtitle">Development of a 3D <span class="hlt">Coupled</span> Physical-<span class="hlt">Biogeochemical</span> Model for the Marseille Coastal Area (NW Mediterranean Sea): What Complexity Is Required in the Coastal Zone?</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">Terrestrial inputs (natural and anthropogenic) from rivers, the atmosphere and physical processes strongly impact the functioning of coastal pelagic ecosystems. The objective of this study was to develop a tool for the examination of these impacts on the Marseille coastal area, which experiences inputs from the Rhone River and high rates of atmospheric deposition. Therefore, a new 3D <span class="hlt">coupled</span> physical/<span class="hlt">biogeochemical</span> model was developed. Two versions of the <span class="hlt">biogeochemical</span> model were tested, one model considering only the carbon (C) and nitrogen (N) cycles and a second model that also considers the phosphorus (P) cycle. Realistic simulations were performed for a period of 5 years (2007–2011). The model accuracy assessment showed that both versions of the model were able of capturing the seasonal changes and spatial characteristics of the ecosystem. The model also reproduced upwelling events and the intrusion of Rhone River water into the Bay of Marseille well. Those processes appeared to greatly impact this coastal oligotrophic area because they induced strong increases in chlorophyll-a concentrations in the surface layer. The model with the C, N and P cycles better reproduced the chlorophyll-a concentrations at the surface than did the model without the P cycle, especially for the Rhone River water. Nevertheless, the chlorophyll-a concentrations at depth were better represented by the model without the P cycle. Therefore, the complexity of the <span class="hlt">biogeochemical</span> model introduced errors into the model results, but it also improved model results during specific events. Finally, this study suggested that in coastal oligotrophic areas, improvements in the description and quantification of the hydrodynamics and the terrestrial inputs should be preferred over increasing the complexity of the <span class="hlt">biogeochemical</span> model. PMID:24324589</p> <div class="credits"> <p class="dwt_author">Fraysse, Marion; Pinazo, Christel; Faure, Vincent Martin; Fuchs, Rosalie; Lazzari, Paolo; Raimbault, Patrick; Pairaud, Ivane</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">32</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/70034724"> <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.; Böhlke, J.K.; Boyer, E.W.; David, M.B.; Harvey, J.W.; Mulholland, P.J.; Seitzinger, S.P.; Tobias, C.R.; Tonitto, C.; Wollheim, W.M.</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://ntrs.nasa.gov/search.jsp?R=20010044959&hterms=astrobiology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dastrobiology"> <span id="translatedtitle">Europa <span class="hlt">Surface-Subsurface</span> Material Interchange: Astrobiology Implications of the Session</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">This paper will seek to identify key parameters, and critical measurements needed to determine exchange rates of <span class="hlt">surface-subsurface</span> materials of Europa and to anticipate their implications for the astrobiological studies NASA will plan. Additional information is contained in the original extended abstract.</p> <div class="credits"> <p class="dwt_author">Meyer, M. A.</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">34</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://repository.tamu.edu/handle/1969.1/ETD-TAMU-1992-THESIS-S274"> <span id="translatedtitle">Analysis of <span class="hlt">surface-subsurface</span> interaction of streamflow and salt loads</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">ANALYSIS OF <span class="hlt">SURFACE-SUBSURFACE</span> INTERACTION OF S~LOW AND SALT LOADS A Thesis by SUSAN LEE SAYGER Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER... 41 45 48 53 56 TABLE OF CONTENTS(CONTINUED) CHAPTER VI POSSUM KINGDOM TO DENNIS WATER BUDGET. Water Budget Fundamental Equation. . . . . . . . . Q, Prec, and LRO. Prec and DRO, Evap, and Del Sto. . . . . . . . . . . Possum Kingdom to Dennis...</p> <div class="credits"> <p class="dwt_author">Sayger, Susan Lee</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-06-07</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/2007AGUSM.H32B..03F"> <span id="translatedtitle">A Conceptual Model of <span class="hlt">Coupled</span> <span class="hlt">Biogeochemical</span> and Hydrogeological Processes Affected by In Situ Cr(VI) Bioreduction in Groundwater at Hanford 100H 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">The overall objective of this presentation is to demonstrate a conceptual multiscale, multidomain model of <span class="hlt">coupling</span> of <span class="hlt">biogeochemical</span> and hydrogeological processes during bioremediation of Cr(VI) contaminated groundwater at Hanford 100H site. A slow release polylactate, Hydrogen Release Compound (HRCTM), was injected in Hanford sediments to stimulate immobilization of Cr(VI). The HRC injection induced a 2-order-of- magnitude increase in biomass and the onset of reducing <span class="hlt">biogeochemical</span> conditions [e.g., redox potential decreased from +240 to -130 mV and dissolved oxygen (DO) was completely removed]. A three-well system, comprised of an injection well and upgradient and downgradient monitoring wells, was used for conducting the in situ biostimulation, one regional flow (no-pumping) tracer test, and five pumping tests along with the Br-tracer injection. Field measurements were conducted using a Br ion-selective electrode and a multiparameter flow cell to collect hourly data on temperature, pH, redox potential, electrical conductivity, and DO. Groundwater sampling was conducted by pumping through specially designed borehole water samplers. Cross-borehole radar tomography and seismic measurements were carried out to assess the site background lithological heterogeneity and the migration pathways of HRC byproducts through groundwater after the HRC injection. Several alternative approaches, including conventional and fractional advective dispersion equations and geostatistical analysis, were used to characterize hydraulic and <span class="hlt">biogeochemical</span> transport parameters. The results of a joint inversion of cross-borehole geophysical tomography and flow-rate measurements in boreholes indicate the presence of a bimodal distribution of hydraulic conductivity for Hanford sediments. The Br- concentration double-peak BTCs curves indicate that HRC injection caused an increase in the tracer travel time (mainly in the low-permeability zone) over the period of observations of about 2 years. This increase in the Br travel time could be explained by the decrease in the saturated hydraulic conductivity caused by the formation of CO2 and N2 gases, growth of biofilms, and precipitation of calcite and insoluble Cr(III) complexes. All these processes are known to cause partial blocking of flow pathways within heterogeneous media, and slowing of mobile-immobile-region mass transfer. The analysis of geophysical data was also used to delineate the temporal variations of the zone affected by byproducts of bioremediation. Our results also indicate the importance of combining in situ hydrogeological, geochemical (including stable isotope analysis), and geophysical measurements with microbiological analytical analyses of water samples and sediments. These measurements can be used for obtaining data to control and simulate both enforced biostimulation and long-term natural attenuation of metals in groundwater.</p> <div class="credits"> <p class="dwt_author">Faybishenko, B.; Long, P. E.; Hazen, T. C.; Hubbard, S. S.; Williams, K. H.; Peterson, J. E.; Chen, J.; Volkova, E. V.; Newcomer, D. R.; Resch, C. T.; Cantrell, K.; Conrad, M. S.; Brodie, E. L.; Joyner, D. C.; Borglin, S. E.; Chakraborty, R. C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-05-01</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://rocky.umeoce.maine.edu/docu/Lehodey-Chai-Hampton.pdf"> <span id="translatedtitle">Modelling climate-related variability of tuna populations from a <span class="hlt">coupled</span> ocean-<span class="hlt">biogeochemical</span>-populations dynamics model</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">fields from a 3D <span class="hlt">coupled</span> physical-biogechemical model. The hypothesis that the spatial dynamics of Marine Science, University of Maine, 5471 Libby Hall, Orono, Maine 04469-5741, USA (fchai populations, a spatial environmental population dynamic model (SEPODYM) has been developed (Bertignac et al</p> <div class="credits"> <p class="dwt_author">Maine, University of</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">37</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/919396"> <span id="translatedtitle">A Conceptual model of <span class="hlt">coupled</span> <span class="hlt">biogeochemical</span> and hydrogeologicalprocesses affected by in situ Cr(VI) bioreduction in groundwater atHanford 100H Site</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 presentation is to demonstratea conceptual multiscale, multidomain model of <span class="hlt">coupling</span> of biogeochemicaland hydrogeological processes during bioremediation of Cr(VI)contaminated groundwater at Hanford 100H site. A slow releasepolylactate, Hydrogen Release Compound (HRCTM), was injected in Hanfordsediments to stimulate immobilization of Cr(VI). The HRC injectioninduced a 2-order-of-magnitude increase in biomass and the onset ofreducing <span class="hlt">biogeochemical</span> conditions [e.g., redox potential decreased from+240 to -130 mV and dissolved oxygen (DO) was completely removed]. Athree-well system, comprised of an injection well and upgradient anddowngradient monitoring wells, was used for conducting the in situbiostimulation, one regional flow (no-pumping) tracer test, and fivepumping tests along with the Br-tracer injection. Field measurements wereconducted using a Br ion-selective electrode and a multiparameter flowcell to collect hourly data on temperature, pH, redox potential,electrical conductivity, and DO. Groundwater sampling was conducted bypumping through specially designed borehole water samplers.Cross-borehole radar tomography and seismic measurements were carried outto assess the site background lithological heterogeneity and themigration pathways of HRC byproducts through groundwater after the HRCinjection.</p> <div class="credits"> <p class="dwt_author">Faybishenko, B.; Long, P.E.; Hazen, T.C.; Hubbard, S.S.; Williams, K.H.; Peterson, J.E.; Chen, J.; Volkova, E.V.; Newcomer, D.R.; Resch, C.T.; Cantrell, K.; Conrad, M.S.; Brodie, E.L.; Joyner, D.C.; Borglin, S.E.; Chakraborty, R.C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-09-06</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://adsabs.harvard.edu/abs/2003EAEJA....10592H"> <span id="translatedtitle">A semi-evolutive partially local Kalman filter to assimilate ocean color data into a 3D <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">An advanced Kalman filter is used to assimilate pseudo color data into a three-dimensional <span class="hlt">coupled</span> physical-<span class="hlt">biogeochemical</span> model of the Cretan Sea. The model comprises the three-dimensional Princeton Model (POM) and the European Regional Seas Ecosystem Model (ERSEM). In this study, the Semi-Evolutive Partially Local Extended Kalman (SEPLEK) filter is introduced in order to reduce the computational burden and also to improve the performance of the standard Singular Evolutive Extended Kalman (SEEK) filter. The novel feature of the SEPLEK filter is its correction basis which is partially local in the sense that it consists of ``global (classical)'' and ``Local'' EOFs. The global EOFs, which can be let to evolve with the model dynamics, are used to represent the long range variability between all the ecosystem variables, while the local EOFs remain invariant and are computed in such a way to seperate the euphotic zone from the deep ocean. The filter is shown to be very efficient in the numerical experiments, leading to a continuous decreasing of the estimation error.</p> <div class="credits"> <p class="dwt_author">Hoteit, I.; Triantafyllou, G.; Petihakis, G.</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">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/2014JMS...139..139T"> <span id="translatedtitle">Quantifying the effects of nutrient loading on dissolved O2 cycling and hypoxia in Chesapeake Bay using a <span class="hlt">coupled</span> hydrodynamic-<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 Regional Ocean Modeling System (ROMS) was <span class="hlt">coupled</span> to a <span class="hlt">biogeochemical</span> model (RCA) to understand the controls on dissolved oxygen (O2) depletion in Chesapeake Bay. The model was calibrated to observational data in the year 2000 and subsequent simulations were performed for a 10-year period, where water-column state variables were validated against observations using multiple error metrics and model-simulated rate processes were compared to available measurements. ROMS-RCA captured observed seasonal and regional dynamics of water-column chlorophyll-a, dissolved O2, and nutrient concentrations, as well as sediment-water nutrient and oxygen fluxes and community respiration rates, but for the year 2000, the model over-predicted surface-water chlorophyll-a and bottom-water O2 in some regions. A series of model experiments were made using the physical regime for the year 2000 to understand ecosystem responses to altered loads of nitrogen and phosphorus and to quantify the spatial and temporal response of Chesapeake Bay to altered nutrient loading. Nutrient loading experiments revealed a non-linear response of hypoxia to nitrogen load, where hypoxic-volume-days maximized at nitrogen loads twice of that observed in the year 2000. O2 levels were more sensitive to nitrogen loads than phosphorus loads, consistent with the preponderance of nitrogen limitation in Chesapeake Bay in late spring and summer months. Expanded hypoxic volumes under higher nitrogen loads were associated with increases in water-column production and respiration in seaward regions of Chesapeake Bay during summer (June to August) months. Analysis of the 10-year model run with realistic hydrodynamics and nutrient loading revealed a similar pattern, emphasizing phytoplankton growth during summer in more nitrogen-limited, lower-Bay regions as a mechanism supporting elevated summer hypoxic volumes. This analysis (1) presents ROMS-RCA as a tool for investigating linked <span class="hlt">biogeochemical</span> processes in coastal ecosystems, (2) identifies phytoplankton growth in seaward Bay regions as a key link between nitrogen loading and hypoxic volume, and (3) suggests that given similar climatic conditions, nutrient load reductions will lead to reduced hypoxic volumes.</p> <div class="credits"> <p class="dwt_author">Testa, Jeremy M.; Li, Yun; Lee, Younjoo J.; Li, Ming; Brady, Damian C.; Di Toro, Dominic M.; Kemp, W. Michael; Fitzpatrick, James J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-11-01</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://adsabs.harvard.edu/abs/2010AGUFM.B11D0386P"> <span id="translatedtitle">A comparison of <span class="hlt">coupled</span> biogeophysical and <span class="hlt">biogeochemical</span> dynamics across a precipitation gradient in Oregon using data assimilation</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 present results from our <span class="hlt">coupled</span> biophysical - biochemical model data fusion (MDF) analysis across a climatic gradient in Oregon, USA, using data from a coast-range Douglas-fir (US-Fir; 2006-2008) and a semi-arid ponderosa pine (US-Me2; 2002-2008) AmeriFlux site. Our MDF scheme <span class="hlt">couples</span> the Ensemble Kalman Filter (EnKF) with the National Center for Atmospheric Research (NCAR) Community Land Model with Carbon-Nitrogen <span class="hlt">coupling</span> (CLM-CN, version 3.5). Assimilated data includes continuous eddy covariance measurements of forest-atmosphere CO2 (NEE, net ecosystem exchange) and water vapor fluxes (?E, latent heat flux), chamber-based soil respiratory flux, soil moisture and temperature, snow depth (US-Me2), MODIS-derived 8 day LAI, and carbon and nitrogen pools. We quantify the ecosystem carbon and nitrogen budgets, partition NEE and ?E fluxes, and thus increase confidence in multi-scale controls on CO2 and water vapor exchange. The MDF did a better job predicting NEE than ?E at both sites (r2 = 0.86 for NEE at both sites; ?E r2 = 0.65 and 0.63 at the US-ME2 and US-Fir sites, respectively) partly due to a weighting scheme we prescribed for NEE. The distribution of carbon and nitrogen differed significantly between sites, with total ecosystem carbon (vegetation, detritus, soil) of the US-Fir site being about 1.4 times higher than the US-Me2 site (35 kg C m-2 vs. 25 kg C m-2). Mean NEE over overlapping water years ‘07-‘08 was -495 gC m-2 at the US-Me2 site as opposed to -809 gC m-2 at the US-Fir site, nearly a two-fold difference in C uptake across this precipitation gradient. Average GPP and ecosystem respiration (Re) over these two water years were both ~1.7x greater at the US-Fir site, with 1712 gC m^-2 and 1217 gC m-2, respectively, at the US-Me2 site vs. 2841 gC m-2 and 2032 gC m-2 at the US-Fir. Autotrophic respiration contributed 79% and 72% to the Re flux at the US-Me2 and US-Fir sites, respectively, with total soil respiration contributing 53% and 58% to Re. While a comparison of observed and MDF environmental response functions suggests both root-zone soil moisture and leaf-to-air VPD photosynthetic controls at both sites, the MDF did not impose CLM-CN’s soil stress upon photosynthesis at the US-Fir site, suggesting the apparent soil moisture response arises from correlations with other driving variables such as VPD. In summary, we demonstrate that MDF analysis can help constrain <span class="hlt">coupled</span> ecosystem carbon and water dynamics by combining long-term ecosystem measurements by incorporating necessary measurement and model uncertainties.</p> <div class="credits"> <p class="dwt_author">Pettijohn, J. C.; Law, B. E.; Williams, M. D.; Stoekli, R.; Thornton, P. E.; Thomas, C. K.; Hudiburg, T. W.; Martin, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-12-01</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_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> <span id="PageLinks" class="pageLinks"> <span> <a onClick='return showDiv("page_1");' href="#">1</a> <a style="font-weight: bold;">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' href="#">4</a> <a 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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">41</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/2014RaSc...49..473L"> <span id="translatedtitle">Simulation of radar echoes from Mars' <span class="hlt">surface/subsurface</span> and inversion of surface media parameters</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">two-layer model of Mars' regolith/bedrock media with a cratered rough <span class="hlt">surface/subsurface</span> is presented for radar echo simulation of planetary exploration research. The numerical approach of geometric ray tracing for the scattering of rough surfaces, which is digitized by the triangulated network, is applied to the calculation of the scattering and imaging simulation of radar range echoes. Numerical simulations of a cratered rough surface generated by the Monte Carlo method are used to analyze the functional dependence of radar range echoes at 1-50 MHz center frequencies upon the <span class="hlt">surface/subsurface</span> feature and the parameters of the layering media, that is, layer depth and dielectric properties. The radar range echoes from two areas of the real Mars surface, which is described by digital elevation model data with a resolution of 1 m × 1 m and a vertical error of less than 1 m, are also simulated and analyzed. Based on these simulations, this study presents a numerical imaging test of radar sounder at center frequencies 1-50 MHz for exploration of different dielectric regolith and bedrock media. The channel 50 MHz with high resolution might be an optimal frequency. Finally, inversion of the dielectric constants of the two-layer media and the regolith layer thickness are developed.</p> <div class="credits"> <p class="dwt_author">Liu, Chuan; Ye, Hongxia; Jin, Ya-Qiu</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-07-01</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://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">43</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/2012AGUFM.H13C1356G"> <span id="translatedtitle"><span class="hlt">Coupled</span> in situ Ammonium and Nitrate analyses of a tidally dominated estuary: New developments from the Elkhorn Slough Land/Ocean <span class="hlt">Biogeochemical</span> Observatory network</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">For nearly nine years the Elkhorn Slough Land/Ocean <span class="hlt">Biogeochemical</span> Observatory (LOBO) network of moorings has been delivering freely available hourly data to the web in near real time. Each mooring hosts a suite of instruments including an ISUS nitrate sensor. In addition to providing valuable information on ecosystem scale processes, the moorings serve as ideal test platforms for novel in situ chemical sensors & analyzers developed by the Monterey Bay Aquarium Research Institute. The recent addition of a newly developed in situ NH4+ analyzer, the DigiScan-II, has provided additional insights into N cycling mechanisms within the slough. The analysis method estimates NH4+ concentration via base conversion to NH3 gas and diffusion across a membrane into an acid carrier stream with subsequent conductivity detection. Although this new NH4+ analyzer is reagent based, it was developed to be relatively cheap, robust, and configurable for a range of deployment options and requires minimal, infrequent maintenance that is ultimately governed by battery life. The fundamental DigiScan-II platform can also be used for other analyses of interest, such as PO4 or CT (total inorganic carbon), by swapping the necessary reagents and components and by making minor code modifications. For deployment in Elkhorn Slough, the NH4+ DigiScan-II was configured for mid-scale concentration detection with a linear calibration range of <0.2 to >30.0 ?M NH4+. The flux of different forms of bioavailable DIN through the system is driven by runoff inputs, tidal exchange, and biological processing. Large inputs of NO3- are sourced from the agriculturally influenced Old Salinas River (OSR), which enters the Slough near the estuary mouth and confluence with Monterey Bay. Rising ocean tides force this eutrophied water mass up into the slough where it is accessed by various biological communities during the course of the tidal period. Mass balance estimates suggest there is an imbalance between the amount of NO3- received by the slough and the amount that is released, with a net NO3- influx to the ecosystem. However, the slough ecosystem releases more NH4+ than it receives, resulting in a net efflux of NH4+ due to remineralization of organic matter (and potentially DNRA) in the slough. Although there is high variability among day to day flux estimates, the sign of the net flux term for NO3- and NH4+ are constant on a monthly scale and seasonal trends in flux magnitude are apparent. Excess N inputs to the slough ecosystem calculated from the LOBO data can serve to estimate productivity when <span class="hlt">coupled</span> with published estimates of sediment N flux. Published rates of denitrification in the system are few but generally very low. Using the LOBO nitrogen mass balance calculations and Redfield stoichiometry, we estimate that the nitrogen inputs from OSR and Monterey Bay support a net production of roughly 220 g C m-2 yr-1 in Elkhorn Slough, assuming no N is lost to denitrification. This estimate will be revised with detailed hydrological dynamics and available O2 data to provide more accurate estimates of net ecosystem metabolism and the relative influence of allochthonous inputs on ecosystem productivity.</p> <div class="credits"> <p class="dwt_author">Gibson, P. J.; Plant, J.; Johnson, K. S.</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">44</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.cccma.ec.gc.ca/papers/jchristian/PDF/christianetal2002_pt2.pdf"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> modelling of the tropical Pacific Ocean. II: Iron biogeochemistry</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">coupled</span> physical–<span class="hlt">biogeochemical</span> model of the tropical Pacific Ocean with simultaneous iron and nitrogen limitation was developed to study questions of iron biogeochemistry, its effects on upper ocean production, and ultimately the <span class="hlt">biogeochemical</span> cycles of the other elements. The model results suggest that iron limitation is ubiquitous in the equatorial Pacific, and extends further west than is generally believed unless</p> <div class="credits"> <p class="dwt_author">J. R. Christian; M. A. Verschell; R. Murtugudde; A. J. Busalacchi; C. R. McClain</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">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/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">46</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 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://ntrs.nasa.gov/search.jsp?R=20010119225&hterms=ecosystem&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Decosystem"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Processes in Microbial Ecosystems</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The hierarchical organization of microbial ecosystems determines process rates that shape Earth's environment, create the biomarker sedimentary and atmospheric signatures of life and define the stage upon which major evolutionary events occurred. In order to understand how microorganisms have shaped the global environment of Earth and potentially, other worlds, we must develop an experimental paradigm that links <span class="hlt">biogeochemical</span> processes with ever-changing temporal and spatial distributions of microbial population, and their metabolic properties. Photosynthetic microbial mats offer an opportunity to define holistic functionality at the millimeter scale. At the same time, their Biogeochemistry contributes to environmental processes on a planetary scale. These mats are possibly direct descendents of the most ancient biological communities; communities in which oxygenic photosynthesis might have been invented. Mats provide one of the best natural systems to study how microbial populations associate to control dynamic <span class="hlt">biogeochemical</span> gradients. These are self-sustaining, complete ecosystems in which light energy absorbed over a diel (24 hour) cycle drives the synthesis of spatially-organized, diverse biomass. Tightly-<span class="hlt">coupled</span> microorganisms in the mat have specialized metabolisms that catalyze transformations of carbon, nitrogen. sulfur, and a host of other elements.</p> <div class="credits"> <p class="dwt_author">DesMarais, David J.; DeVincenzi, Donald L. (Technical Monitor)</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">48</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/909151"> <span id="translatedtitle">Carbon sequestration by patch fertilization: A comprehensive assessment using <span class="hlt">coupled</span> physical-ecological-<span class="hlt">biogeochemical</span> models: FINAL REPORT of grant Grant No. DE-FG02-04ER63726</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 final report summarizes research undertaken collaboratively between Princeton University, the NOAA Geophysical Fluid Dynamics Laboratory on the Princeton University campus, the State University of New York at Stony Brook, and the University of California, Los Angeles between September 1, 2000, and November 30, 2006, to do fundamental research on ocean iron fertilization as a means to enhance the net oceanic uptake of CO2 from the atmosphere. The approach we proposed was to develop and apply a suite of <span class="hlt">coupled</span> physical-ecologicalbiogeochemical models in order to (i) determine to what extent enhanced carbon fixation from iron fertilization will lead to an increase in the oceanic uptake of atmospheric CO2 and how long this carbon will remain sequestered (efficiency), and (ii) examine the changes in ocean ecology and natural <span class="hlt">biogeochemical</span> cycles resulting from iron fertilization (consequences). The award was funded in two separate three-year installments: • September 1, 2000 to November 30, 2003, for a project entitled “Ocean carbon sequestration by fertilization: An integrated <span class="hlt">biogeochemical</span> assessment.” A final report was submitted for this at the end of 2003 and is included here as Appendix 1. • December 1, 2003 to November 30, 2006, for a follow-on project under the same grant number entitled “Carbon sequestration by patch fertilization: A comprehensive assessment using <span class="hlt">coupled</span> physical-ecological-<span class="hlt">biogeochemical</span> models.” This report focuses primarily on the progress we made during the second period of funding subsequent to the work reported on in Appendix 1. When we began this project, we were thinking almost exclusively in terms of long-term fertilization over large regions of the ocean such as the Southern Ocean, with much of our focus being on how ocean circulation and <span class="hlt">biogeochemical</span> cycling would interact to control the response to a given fertilization scenario. Our research on these types of scenarios, which was carried out largely during the first three years of our project, led to several major new insights on the interaction between ocean biogeochemistry and circulation. This work, which is described in 2 the following Section II on “Large scale fertilization,” has continued to appear in the literature over the past few years, including two high visibility papers in Nature. Early on in the first three years of our project, it became clear that small "patch-scale" fertilizations over limited regions of order 100 km diameter were much more likely than large scale fertilization, and we carried out a series of idealized patch fertilization simulations reported on in Gnanadesikan et al. (2003). Based on this paper and other results we had obtained by the end of our first three-year grant, we identified a number of important issues that needed to be addressed in the second three-year period of this grant. Section III on “patch fertilization” discusses the major findings of this phase of our research, which is described in two major manuscripts that will be submitted for publication in the near future. This research makes use of new more realistic ocean ecosystem and iron cycling models than our first paper on this topic. We have several major new insights into what controls the efficiency of iron fertilization in the ocean. Section IV on “model development” summarizes a set of papers describing the progress that we made on improving the ecosystem models we use for our iron fertilization simulations.</p> <div class="credits"> <p class="dwt_author">Sarmiento, Jorge L; Gnanadesikan, Anand; Gruber, Nicolas</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-06-21</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://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 " 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://academic.research.microsoft.com/Publication/52150946"> <span id="translatedtitle">Simulation of Marine Nitrogen Cycling as Function of Atmospheric Oxygen: Results of a <span class="hlt">Coupled</span> C,N,P,O,S <span class="hlt">Biogeochemical</span> Model Including d15N</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">Bioavailable nitrogen is a critical limiting nutrient in the modern marine biosphere. We expect that the rate of denitrification may have been higher in the geologic past due to decreased atmospheric O2 and expanded ocean anoxia. To examine the consequences of this idea, we present numerical simulations of <span class="hlt">coupled</span> carbon, nitrogen, phosphorus, oxygen, and sulfur cycling as a function of</p> <div class="credits"> <p class="dwt_author">S. J. Romaniello; L. A. Derry</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">51</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/2012AGUFM.H31O..04H"> <span id="translatedtitle">About the importance of small scale spatial variability in <span class="hlt">coupled</span> <span class="hlt">surface-subsurface</span> simulations and how it can be characterized.</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">Small scale spatial variability of soil and aquifer hydraulic properties exerts an important influence on flow and transport processes. Connected structures as present in fluvial aquifers, or macropores in soil, provide preferential flow paths for water and contaminants. Their characterization is therefore also important for management purposes. The importance of small scale spatial variability of riverbed hydraulic properties for exchange fluxes of water and solutes between a stream and the underlying subsurface is not so well studied. A few studies were dedicated to this topic and found that riverbed hydraulic properties might vary over many orders of magnitude and that most of the exchange fluxes might be centered at only a few spots. Next question is whether this spatial variability can be represented well with effective, uniform properties. In earlier work we found that effective, uniform parameters result in a biased estimation of stream-aquifer exchange fluxes, especially if the flow regime is very different from the flow regime in the calibration period. Given these results, the role of small-scale variability of riverbed hydraulic conductivity (K) (and its parameterization in a model) was investigated further by studying a 6km river section in the city of Zurich (Switzerland) in a transient finite elements model for variably saturated flow. It was also assessed whether the small-scale spatial variability can be characterized with stochastic realizations in combination with parameter estimation. Although the simulation example mimics the real-world case (Zurich) as much as possible and uses transient model forcings obtained from real data, synthetic experiments were conducted in order to verify the procedure in detail. Parameter estimation was done with help of the Ensemble Kalman Filter (EnKF), on the basis of an augmented state vector approach for estimating the unknown parameters. We used three different setups to generate synthetic realities, and for each setup 10 different synthetic realities were generated. For each synthetic reality 100 different stochastic realizations were generated and updated with EnKF. The set-ups had a moderately heterogeneous K of the riverbed, a strongly heterogeneous riverbed K with strong K contrasts between five different river sections, and a strongly heterogeneous riverbed K without a clear zonation. In all cases, EnKF was used to assimilate either zero (open loop), 10 or 100 time series of hydraulic head data to update either the riverbed K of all nodes (stochastic field approach) or only effective riverbed K for five, three or two zones. The results showed that the stochastic field approach outperforms the approaches where only a limited number of effective parameters is updated. This is especially the case for strongly heterogeneous realities and many measurement data. A zonation approach systematically underestimates net stream-aquifer exchange fluxes, but in case the position of the zones is well-known, also the zonation approach gives good results.</p> <div class="credits"> <p class="dwt_author">Hendricks Franssen, H.; Kurtz, W.; Brunner, P.; Vereecken, H.</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">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.osti.gov/scitech/servlets/purl/1089976"> <span id="translatedtitle">Subsurface Uranium Fate and Transport: Integrated Experiments and Modeling of <span class="hlt">Coupled</span> <span class="hlt">Biogeochemical</span> Mechanisms of Nanocrystalline Uraninite Oxidation by Fe(III)-(hydr)oxides - Project Final Report</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 bacteria including sulfate reducing bacteria (SRB) reduce soluble U(VI) to insoluble U(IV) with subsequent precipitation of UO2. We have shown that SRB reduce U(VI) to nanometer-sized UO2 particles (1-5 nm) which are both intra- and extracellular, with UO2 inside the cell likely physically shielded from subsequent oxidation processes. We evaluated the UO2 nanoparticles produced by Desulfovibrio desulfuricans G20 under growth and non-growth conditions in the presence of lactate or pyruvate and sulfate, thiosulfate, or fumarate, using ultrafiltration and HR-TEM. Results showed that a significant mass fraction of bioreduced U (35-60%) existed as a mobile phase when the initial concentration of U(VI) was 160 µM. Further experiments with different initial U(VI) concentrations (25 - 900 ?M) in MTM with PIPES or bicarbonate buffers indicated that aggregation of uraninite depended on the initial concentrations of U(VI) and type of buffer. It is known that under some conditions SRB-mediated UO2 nanocrystals can be reoxidized (and thus remobilized) by Fe(III)-(hydr)oxides, common constituents of soils and sediments. To elucidate the mechanism of UO2 reoxidation by Fe(III) (hydr)oxides, we studied the impact of Fe and U chelating compounds (citrate, NTA, and EDTA) on reoxidation rates. Experiments were conducted in anaerobic batch systems in PIPES buffer. Results showed EDTA significantly accelerated UO2 reoxidation with an initial rate of 9.5?M day-1 for ferrihydrite. In all cases, bicarbonate increased the rate and extent of UO2 reoxidation with ferrihydrite. The highest rate of UO2 reoxidation occurred when the chelator promoted UO2 and Fe(III) (hydr)oxide dissolution as demonstrated with EDTA. When UO2 dissolution did not occur, UO2 reoxidation likely proceeded through an aqueous Fe(III) intermediate as observed for both NTA and citrate. To complement to these laboratory studies, we collected U-bearing samples from a surface seep at the Rifle field site and have measured elevated U concentrations in oxic iron-rich sediments. To translate experimental results into numerical analysis of U fate and transport, a reaction network was developed based on Sani et al. (2004) to simulate U(VI) bioreduction with concomitant UO2 reoxidation in the presence of hematite or ferrihydrite. The reduction phase considers SRB reduction (using lactate) with the reductive dissolution of Fe(III) solids, which is set to be microbially mediated as well as abiotically driven by sulfide. Model results show the oxidation of HS– by Fe(III) directly competes with UO2 reoxidation as Fe(III) oxidizes HS– preferentially over UO2. The majority of Fe reduction is predicted to be abiotic, with ferrihydrite becoming fully consumed by reaction with sulfide. Predicted total dissolved carbonate concentrations from the degradation of lactate are elevated (log(pCO2) ~ –1) and, in the hematite system, yield close to two orders-of-magnitude higher U(VI) concentrations than under initial carbonate concentrations of 3 mM. Modeling of U(VI) bioreduction with concomitant reoxidation of UO2 in the presence of ferrihydrite was also extended to a two-dimensional field-scale groundwater flow and <span class="hlt">biogeochemically</span> reactive transport model for the South Oyster site in eastern Virginia. This model was developed to simulate the field-scale immobilization and subsequent reoxidation of U by a biologically mediated reaction network.</p> <div class="credits"> <p class="dwt_author">Peyton, Brent M. [Montana State University; Timothy, Ginn R. [University of California Davis; Sani, Rajesh K. [South Dakota School of Mines and Technology</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-08-14</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://adsabs.harvard.edu/abs/2014EGUGA..16..728R"> <span id="translatedtitle">The influence of the groundwater table dynamics on the land <span class="hlt">surface-subsurface</span> interactions</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 terrestrial hydrological cycle comprises complex processes in the subsurface, land surface and atmosphere. These processes interact at different space-time scales, resulting in a non-linear system behavior with two-way feedback between different compartments. In order to understand the overall mechanisms of the hydrological cycle, it is important to study the space-time variance of different processes and their influence on the mass and energy balance components of the <span class="hlt">coupled</span> water and energy cycles. In this study, the <span class="hlt">coupled</span> subsurface-land surface model ParFlow.CLM is applied over a ~28,000 km2 model domain encompassing the Rur catchment, Germany, to simulate the fluxes and states of the <span class="hlt">coupled</span> water and energy cycles. The model is forced by hourly atmospheric data from the COSMO-DE model (numerical weather prediction system of the German Weather Service) over the years 2009 and 2010. The space-time variability in different processes of the <span class="hlt">coupled</span> water and energy cycles over the Rur catchment has been studied previously using the same modeling platform. The simulation results demonstrate that the land surface is exposed to a dual boundary forcing of the atmosphere and the free groundwater transforming the spatial and temporal structures of both forcings, which is reflected in distinct patterns in the moisture and energy fluxes. In this study, we perform multiple model runs considering different temporal variations in the lower boundary condition (e.g., monthly, seasonally, and yearly) conserving the average spatial heterogeneity to study explicitly the influence of temporal groundwater table dynamics on the land surface mass and energy balance components. Analyzing the model results across different time scales using statistical, geostatistical, and wavelet transform techniques demonstrate that the temporal variation in the lower boundary condition influences the land surface mass and energy balance components, especially under moisture limited conditions. The lower boundary condition is influenced by the processes in the atmosphere, as the variance in the atmospheric forcing affects the groundwater table dynamics after being filtered for smaller scale variability by the land surface and subsurface. The time series analysis suggests that the variability in the lower boundary condition and land surface processes (e.g., evaportanspiration) are generally in phase for a shallow groundwater table, while a phase shift is evident for deeper water tables, which has been discussed in a number of previous studies. Utilizing multi-year simulation results, we test the hypothesis that for increasing phase shifts and amplitudes in water table fluctuations, seasonal impacts of groundwater dynamics on the land surface energy fluxes can be predicted quantitatively at the yearly time scale.</p> <div class="credits"> <p class="dwt_author">Rahman, Mostaquimur; Kollet, Stefan; Sulis, Mauro</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</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/2012AGUFM.H31N..04D"> <span id="translatedtitle">Incorporating atmospheric boundary layer processes in an integrated <span class="hlt">surface/subsurface</span> flow and transport 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">Traditional land surface-atmosphere models idealize variably-saturated subsurface flow by parameterizing the non-linear processes. Many previous models reduce the subsurface systems to either one-dimensional infiltration or constant-value boundary conditions. Consequently, the shortfalls of the currently available models constrain our ability to estimate the role of a spatially and temporally dynamic subsurface flow on atmospheric processes. In order to overcome these limitations, we developed a <span class="hlt">coupled</span> atmospheric boundary layer model, which is a zero-dimensional energy balance model, with HydroGeoSphere, a three-dimensional integrated surface/variably-saturated subsurface flow and energy transport model. The atmospheric boundary layer model calculates the net radiation, air temperature, moisture content, and precipitation in the atmosphere and relays the information directly to HydroGeoSphere to compute the water flow, land surface and subsurface temperatures, and evapotranspiration. As an illustration, the <span class="hlt">coupled</span> model is applied to land-use change in a Mediterranean climate transitioning from irrigated agriculture to urban communities to evaluate the variation in latent and sensible heat fluxes. Finally, our model's performance and results are compared to those of the traditional land surface models.</p> <div class="credits"> <p class="dwt_author">Davison, J. H.; Hwang, H.; Sudicky, E. A.; Lin, J. C.</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">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/2010AGUFM.B31H..01S"> <span id="translatedtitle">Planetary <span class="hlt">Biogeochemical</span> Stewardship (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">Many of today’s most pressing environmental problems have a basis in chemistry—that is human disruption of global <span class="hlt">biogeochemical</span> cycles. Humans have enhanced the movement of C, N, P, and S in the global cycle of these elements, with widespread consequences such as climate change, hypoxia and acid rain. Recent attempts to calculate thresholds of global vulnerability ignore ample evidence that human impacts on the Earth’s chemical environment yield progressive degradation of the biosphere, especially its species diversity. Our collect global impact now exceeds natural processes of planetary remediation—clearly an unsustainable path. I will attempt to provide a framework to evaluate suggested attempts to mitigate current human impact on global <span class="hlt">biogeochemical</span> cycles. Cap-and-trade systems are ideal for perturbations that involve a limited number of point sources that supplement a small background flux to the atmosphere, such as S. Better land management may be the most attractive way to mitigate human impacts to the Nitrogen cycle, where the potential for enhanced denitrification could respond to the order-of-magnitude of the current human perturbation. Impacts to the carbon cycle, seen through rising CO2 in Earth’s atmosphere, will require switching to energy that does not depend on fossil carbon.</p> <div class="credits"> <p class="dwt_author">Schlesinger, W. H.</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">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/2008AGUFMPP42A..06R"> <span id="translatedtitle">Simulation of Marine Nitrogen Cycling as Function of Atmospheric Oxygen: Results of a <span class="hlt">Coupled</span> C,N,P,O,S <span class="hlt">Biogeochemical</span> Model Including d15N</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">Bioavailable nitrogen is a critical limiting nutrient in the modern marine biosphere. We expect that the rate of denitrification may have been higher in the geologic past due to decreased atmospheric O2 and expanded ocean anoxia. To examine the consequences of this idea, we present numerical simulations of <span class="hlt">coupled</span> carbon, nitrogen, phosphorus, oxygen, and sulfur cycling as a function of atmospheric oxygen in an ocean with circulation similar to modern conditions. The model has been specifically developed to function over a wide range of ocean redox conditions and has been successfully tested in simulations of both the modern global ocean and Black Sea. Global rates of nitrogen fixation and pelagic denitrification, which are strongly <span class="hlt">coupled</span> in our default model, reach maximum rates between 25% and 50% of the present atmospheric level of O2 (PAL O2). At 40% PAL O2, the simulated steady-state pelagic denitrification rate is 82.1 Tmol/yr, and the N- fixation rate is 85.7 Tmol/yr. These rates are 8-15× greater than modern estimates. The maximum simulated rate of N-fixation is determined by the N flux required to entirely support export production. At mid- levels of atmospheric oxygen, large areas of the oceans are characterized by a suboxic to anoxic "oxygen minimum zone" between 100m and 1000m depth which is over- and underlain by oxic water. Under these conditions, denitrification in the upper water column is nearly complete, suppressing the ?15N isotopic signal for this process. To test the impact of limitation of N-fixation (e.g. by trace metals, light, temperature) we imposed a cap on the global N-fixation rate. In these simulations, limitation of N-fixation below 50% PAL O2 results in severe N limitation of primary production and low mean oceanic N:P. Our results imply that N limitation may have been chronic at intermediate levels of atmospheric O2. At the same time, low N:P conditions would create evolutionary pressure for efficient N-fixation pathways and high N use efficiency in non-fixing marine phytoplankton, testing the limits of plasticity in the Redfield ratio. If N-fixation were unable to keep up with high rates of denitrification at intermediate levels of atmospheric O2, intense N limitation of Proterozoic marine primary production may have strongly inhibited any further rise of atmospheric O2, thus stabilizing atmospheric O2 at <25% PAL.</p> <div class="credits"> <p class="dwt_author">Romaniello, S. J.; Derry, L. A.</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">57</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/2014EGUGA..16.5577S"> <span id="translatedtitle">Multi-constraint calibration of a <span class="hlt">surface-subsurface</span>-atmosphere model at the catchment scale</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 complex distributed numerical modelling framework including both groundwater- surface-water flow and heat flux exchange with the atmosphere, combined with a unique observational data set from the HOBE hydrological observatory in Western Denmark, enables a comprehensive application of multiple independent constraints to the model parameter optimization at the catchment scale (1050 km2). Five independent observational data sets consisting of stream discharge (8 stations), groundwater head (361 stations), latent heat flux (2 stations), soil moisture (28 stations) and remotely sensed land surface temperature (full spatial coverage on 28 days) are the basis for formulating 11 objective functions focussing on bias and RMSE of time series from multiple stations. In contrast to many multiple objective studies, where objective functions essentially originate from the same observational dataset (typically discharge time series), the dataset used in this study enables a truly multi-constraint evaluation of the states and fluxes simulated by the model. A preliminary sensitivity analysis of 35 model parameters reveals that even surface fluxes and states such as soil moisture, heat fluxes and land surface temperatures are highly sensitive to parameters that are typically associated with the groundwater components of the model. This indicates the importance of using fully <span class="hlt">coupled</span> modelling approaches also in detailed studies of the near surface-atmosphere exchanges. The model parameter optimization, conducted using the gradient based search algorithm in PEST, has been carried out for three separate assumptions of available evaluation data. The first calibration uses only traditional observations of stream discharge and groundwater head, the second uses observations associated mainly with the land surface component, specifically latent heat flux, soil moisture and remotely sensed surface temperature. As a third scenario the model is calibrated using all available observational data sets, and finally each of the calibrated models are evaluated against the observations that were not used during calibration and for all observations for a validation period. The results illustrate the importance of multiple constraints to complex <span class="hlt">coupled</span> models and the potential consequences of using model predictions of output that the model has not been constrained against. The study also highlights the need to develop spatial model calibration through new spatial performance metrics and new parameterisation and optimization frameworks that explicitly allow the models to improve their spatial pattern predictions while maintaining a reasonable number of free calibration parameters.</p> <div class="credits"> <p class="dwt_author">Stisen, Simon; Obel Sonnenborg, Torben; Refsgaard, Jens Christian; Koch, Julian; Bircher, Simone; Høgh Jensen, Karsten</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</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.osti.gov/scitech/servlets/purl/1096175"> <span id="translatedtitle">Final Report DE-EE0005380: Assessment of Offshore Wind Farm Effects on Sea <span class="hlt">Surface</span>, <span class="hlt">Subsurface</span> and Airborne Electronic Systems</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">Offshore wind energy is a valuable resource that can provide a significant boost to the US renewable energy portfolio. A current constraint to the development of offshore wind farms is the potential for interference to be caused by large wind farms on existing electronic and acoustical equipment such as radar and sonar systems for surveillance, navigation and communications. The US Department of Energy funded this study as an objective assessment of possible interference to various types of equipment operating in the marine environment where offshore wind farms could be installed. The objective of this project was to conduct a baseline evaluation of electromagnetic and acoustical challenges to sea <span class="hlt">surface</span>, <span class="hlt">subsurface</span> and airborne electronic systems presented by offshore wind farms. To accomplish this goal, the following tasks were carried out: (1) survey electronic systems that can potentially be impacted by large offshore wind farms, and identify impact assessment studies and research and development activities both within and outside the US, (2) engage key stakeholders to identify their possible concerns and operating requirements, (3) conduct first-principle modeling on the interactions of electromagnetic signals with, and the radiation of underwater acoustic signals from, offshore wind farms to evaluate the effect of such interactions on electronic systems, and (4) provide impact assessments, recommend mitigation methods, prioritize future research directions, and disseminate project findings. This report provides a detailed description of the methodologies used to carry out the study, key findings of the study, and a list of recommendations derived based the findings.</p> <div class="credits"> <p class="dwt_author">Ling, Hao [The University of Texas at Austin] [The University of Texas at Austin; Hamilton, Mark F. [The University of Texas at Austin Applied Research Laboratories] [The University of Texas at Austin Applied Research Laboratories; Bhalla, Rajan [Science Applications International Corporation] [Science Applications International Corporation; Brown, Walter E. [The University of Texas at Austin Applied Research Laboratories] [The University of Texas at Austin Applied Research Laboratories; Hay, Todd A. [The University of Texas at Austin Applied Research Laboratories] [The University of Texas at Austin Applied Research Laboratories; Whitelonis, Nicholas J. [The University of Texas at Austin] [The University of Texas at Austin; Yang, Shang-Te [The University of Texas at Austin] [The University of Texas at Austin; Naqvi, Aale R. [The University of Texas at Austin] [The University of Texas at Austin</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-09-30</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://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 " 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.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 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" 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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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.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 " 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://academic.research.microsoft.com/Publication/45904347"> <span id="translatedtitle">Eastern Mediterranean <span class="hlt">biogeochemical</span> flux model - Simulations of the pelagic ecosystem</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">During the second phase (2003-2006) of the Mediterranean ocean Forecasting System Project (MFS) named Toward Environmental Predictions (MFSTEP) one of the three major aims was the development of numerical forecasting systems. In this context a generic <span class="hlt">Biogeochemical</span> Flux Model (BFM) was developed and <span class="hlt">coupled</span> with hydrodynamic models already operating at basin scale as well as in regional areas. In the</p> <div class="credits"> <p class="dwt_author">G. Petihakis; G. Triantafyllou; K. Tsiaras; G. Korres; A. Pollani; I. Hoteit</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">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/2013AGUFM.H44B..07J"> <span id="translatedtitle">Emergent Archetype Hydrological-<span class="hlt">Biogeochemical</span> Response Patterns in Heterogeneous Catchments</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">What can spatiotemporally integrated patterns observed in stream hydrologic and <span class="hlt">biogeochemical</span> signals generated in response to transient hydro-climatic and anthropogenic forcing tell us about the interactions between spatially heterogeneous soil-mediated hydrological and <span class="hlt">biogeochemical</span> processes? We seek to understand how the spatial structure of solute sources <span class="hlt">coupled</span> with hydrologic responses affect observed concentration-discharge (C-Q) patterns. These patterns are expressions of the spatiotemporal structure of solute loads exported from managed catchments, and their likely ecological consequences manifested in receiving water bodies (e.g., wetlands, rivers, lakes, and coastal waters). We investigated the following broad questions: (1) How does the correlation between flow-generating areas and <span class="hlt">biogeochemical</span> source areas across a catchment evolve under stochastic hydro-climatic forcing? (2) What are the feasible hydrologic and <span class="hlt">biogeochemical</span> responses that lead to the emergence of the observed archetype C-Q patterns? and; (3) What implications do these <span class="hlt">coupled</span> dynamics have for catchment monitoring and implementation of management practices? We categorize the observed temporal signals into three archetypical C-Q patterns: dilution; accretion, and constant concentration. We introduce a parsimonious stochastic model of heterogeneous catchments, which act as hydrologic and <span class="hlt">biogeochemical</span> filters, to examine the relationship between spatial heterogeneity and temporal history of solute export signals. The core concept of the modeling framework is considering the types and degree of spatial correlation between solute source zones and flow generating zones, and activation of different portions of the catchments during rainfall events. Our overarching hypothesis is that each of the archetype C-Q patterns can be generated by explicitly linking landscape-scale hydrologic responses and spatial distributions of solute source properties within a catchment. The model simulations reproduce the three major C-Q patterns observed in published data, offering valuable insight into <span class="hlt">coupled</span> catchment processes. The findings have important implications for effective catchment management for water quality improvement, and stream monitoring strategies.</p> <div class="credits"> <p class="dwt_author">Jawitz, J. W.; Gall, H. E.; Rao, P.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-01</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://tracer.env.uea.ac.uk/esmg/papers/BergmanetalMay04AJS.pdf"> <span id="translatedtitle">COPSE: A new model of <span class="hlt">biogeochemical</span> cycling over Phanerozoic time</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 present a new model of <span class="hlt">biogeochemical</span> cycling over Phanerozoic time. This work <span class="hlt">couples</span> a feedback-based model of atmospheric O2 and ocean nutrients (Lenton and Watson, 2000a, 2000b) with a geochemical carbon cycle model (Berner, 1991, 1994), a simple sulfur cycle, and additional components. The resulting COPSE model (Carbon-Oxygen-Phosphorus-Sulfur-Evolution) represents the co- evolution of biotic and abiotic components of the</p> <div class="credits"> <p class="dwt_author">NOAM M. BERGMAN; TIMOTHY M. LENTON; ANDREW J. WATSON</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">65</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=20020002058&hterms=ecosystem&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Decosystem"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Processes in Microbial Ecosystems</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The hierarchical organization of microbial ecosystems determines process rates that shape Earth's environment, create the biomarker sedimentary and atmospheric signatures of life, and define the stage upon which major evolutionary events occurred. In order to understand how microorganisms have shaped the global environment of Earth and, potentially, other worlds, we must develop an experimental paradigm that links <span class="hlt">biogeochemical</span> processes with ever-changing temporal and spatial distributions of microbial populations and their metabolic properties. Additional information is contained in the original extended abstract.</p> <div class="credits"> <p class="dwt_author">DesMarais, David J.</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">66</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/40472129"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> processes in intensive zero-effluent marine fish culture with recirculating aerobic and anaerobic biofilters</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> processes that drive nutrient transformations and recycling in organic marine sediment–water environments were studied for 17 months in a zero-effluent intensive recirculating culture system. The system consisted of a 10 m3 gilthead seabream (Sparus aurata) tank <span class="hlt">coupled</span> to aerobic and anaerobic water treatment elements. Nutrients and alkalinity were measured in the system to quantify the main <span class="hlt">biogeochemical</span> processes. Fractions of</p> <div class="credits"> <p class="dwt_author">Amir Neori; Michael D. Krom; Jaap van Rijn</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">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/2014EGUGA..16.4487L"> <span id="translatedtitle">Parameterization of <span class="hlt">biogeochemical</span> sediment-water fluxes using in-situ measurements and a steady-state diagenetic 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">Sediment <span class="hlt">biogeochemical</span> processes are important drivers of water column biogeochemistry in coastal areas. For example, sediment oxygen consumption can be an important driver of bottom water oxygen depletion in hypoxic systems, and sediment-water nutrient fluxes support primary productivity in the overlying water column. Yet, <span class="hlt">biogeochemical</span> sediment-water fluxes are often parameterized crudely and only poorly constrained in <span class="hlt">coupled</span> physical-<span class="hlt">biogeochemical</span> models. Here, we present a method for parameterizing <span class="hlt">biogeochemical</span> sediment-water fluxes realistically and efficiently, using in-situ measurements and a steady state diagenetic model. We apply this method to the Louisiana Shelf where high primary production induced by excess nutrient loads from the Mississippi-Atchafalaya River system promotes the development of hypoxic bottom waters in summer. The implementation of the parameterizations in a <span class="hlt">coupled</span> circulation-<span class="hlt">biogeochemical</span> model of the northern Gulf of Mexico results in realistic sediment-water fluxes that enable a sediment-water column feedback at low bottom oxygen concentrations.</p> <div class="credits"> <p class="dwt_author">Laurent, Arnaud; Fennel, Katja; Wilson, Robin; Lehrter, John; Devereux, Richard</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</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://www.uta.edu/faculty/awinguth/Publications/WinguthGBC_YEARBOOK2006.pdf"> <span id="translatedtitle">Global <span class="hlt">Biogeochemical</span> Cycles Global <span class="hlt">biogeochemical</span> cycles can be defined as any of the natural circulation pathways</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Global <span class="hlt">Biogeochemical</span> Cycles Global <span class="hlt">biogeochemical</span> cycles can be defined as any of the natural) components of the biosphere and back to the nonliving again. Research on the <span class="hlt">biogeochemical</span> cycles focuses on seven of the major elements that make up more than 95% of all living species: hydrogen, carbon, sulfur</p> <div class="credits"> <p class="dwt_author">Winguth, Arne</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">69</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/2014JMS...139..348R"> <span id="translatedtitle">Modeling the <span class="hlt">biogeochemical</span> seasonal cycle in the Strait of Gibraltar</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 physical-biological <span class="hlt">coupled</span> model was used to estimate the effect of the physical processes at the Strait of Gibraltar over the <span class="hlt">biogeochemical</span> features of the Atlantic Inflow (AI) towards the Mediterranean Sea. This work was focused on the seasonal variation of the <span class="hlt">biogeochemical</span> patterns in the AI and the role of the Strait; including primary production and phytoplankton features. As the physical model is 1D (horizontal) and two-layer, different integration methods for the primary production in the <span class="hlt">Biogeochemical</span> Fluxes Model (BFM) have been evaluated. An approach based on the integration of a production-irradiance function was the chosen method. Using this Plankton Functional Type model (BFM), a simplified phytoplankton seasonal cycle in the AI was simulated. Main results included a principal bloom in spring dominated by nanoflagellates, whereas minimum biomass (mostly picophytoplankton) was simulated during summer. Physical processes occurring in the Strait could trigger primary production and raise phytoplankton biomass (during spring and autumn), mainly due to two combined effects. First, in the Strait a strong interfacial mixing (causing nutrient supply to the upper layer) is produced, and, second, a shoaling of the surface Atlantic layer occurs eastward. Our results show that these phenomena caused an integrated production of 105 g C m- 2 year- 1 in the eastern side of the Strait, and would also modify the proportion of the different phytoplankton groups. Nanoflagellates were favored during spring/autumn while picophytoplankton is more abundant in summer. Finally, AI could represent a relevant source of nutrients and biomass to Alboran Sea, fertilizing the upper layer of this area with 4.95 megatons nitrate year- 1 (79.83 gigamol year- 1) and 0.44 megatons C year- 1. A main advantage of this <span class="hlt">coupled</span> model is the capability of solving relevant high-resolution processes as the tidal forcing without expensive computing requirements, allowing to assess the effect of these phenomena on the <span class="hlt">biogeochemical</span> patterns at longer time scales.</p> <div class="credits"> <p class="dwt_author">Ramírez-Romero, E.; Vichi, M.; Castro, M.; Macías, J.; Macías, D.; García, C. M.; Bruno, M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-11-01</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://adsabs.harvard.edu/abs/2013EGUGA..15.5466W"> <span id="translatedtitle">Combining high resolution space- and air-borne data with borehole monitoring to investigate <span class="hlt">surface-subsurface</span> water relations in landslide-prone slopes</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">Water still seems to be a relatively little studied environmental factor in applications of multispectral space- and air-borne data to landslide investigations, even though stagnated drainage conditions have long been used as diagnostic elements for landslide recognition and mapping based on airphoto interpretation. Here we use both satellite imagery and airphotos, focusing on water as a critical factor of the recurrent instability of poorly drained slopes in a 15.6 km2 catchment area in the Apennine mountains (Italy) characterized by predominance of clay-rich flysch units and agricultural land use. We expand on our recent study (Wasowski et al., 2012) that exploited high resolution multispectral satellite imagery from early spring of 2006 for mapping active landslides, investigating their close association with seasonally wet zones (areas covered by free surface-water including ponds, migrating surface-water, seeps), and for inferring <span class="hlt">surface-subsurface</span> relationships in unstable slopes. In particular, we use sub-meter resolution multispectral orthophotos acquired in late winter of 2011 to map the distributions of active landslides and wet zones. Considerable spatial-temporal recurrence of these features is indicated from a comparison of the 2011 and 2006 inventories. Furthermore, using the extensive subsurface dataset from piezometer boreholes (ongoing monitoring since 2009) we show that a number of remotely sensed wet zones are indicative of sites with seasonally persistent very high groundwater levels within landslide-prone slopes and on intermittently active landslides. Where such <span class="hlt">surface-subsurface</span> water linkage can be established, the appearance of the wet zones (fully saturated ground/soil) resulting from groundwater discharge or seepage can be used as a forewarning signal of the increased susceptibility to landsliding, since the hillslopes with shallow groundwater tables are generally more prone to failure. However, the feasibility of retrieving reliable information about surface-water conditions from high resolution optical data, and the degree of its usefulness can be site-specific. This work suggests that useful results can be obtained in settings with similar topography (shallow slopes), lithology (clay-rich) and land use/land cover (agricultural soils with little woodland). A critical factor that will influence the results is the suitable timing of the imagery acquisition, in our case during wet season and early in vegetation period. Furthermore, acquisitions shortly after intense rainfall should be avoided if the focus is on wet zones indicative of shallow groundwater tables, that is those resulting from groundwater discharge and not just from accumulations of surface-water runoff. References Wasowski J., Lamanna C., Gigante G., Casarano D. 2012. High resolution satellite imagery analysis for inferring <span class="hlt">surface-subsurface</span> water relationships in unstable slopes. Remote Sensing of Environment, 124, 135-148. doi: 10.1016/j.rse.2012.05.007</p> <div class="credits"> <p class="dwt_author">Wasowski, Janusz; Lamanna, Caterina; Dipalma Lagreca, Marina; Pasquariello, Guido</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">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/2014JHyd..516...97Y"> <span id="translatedtitle">The role of macropores and multi-resolution soil survey datasets for distributed <span class="hlt">surface-subsurface</span> flow 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">Distributed watershed-scale modeling is often used as a framework for exploring the heterogeneity of runoff response and hydrologic performance of the catchment. The objective of this study is to apply this framework to characterizing the impacts of soil hydraulic properties at multiple scales on moisture storage and distributed runoff generation in a forested catchment. The physics-based and fully-<span class="hlt">coupled</span> Penn State Integrated Hydrologic Model (PIHM) is employed to test a priori and field-measured properties in the modeling of watershed hydrology. PIHM includes an approximate representation of macropore flow that preserves the water holding capacity of the soil matrix while still allowing rapid flow through the macroporous soil under wet conditions. Both phenomena are critical to the overall hydrologic performance of the catchment. Soils data at different scales were identified: Case I STATSGO soils data (uniform or single soil type), Case II STATSGO soils data with macropore effect, and Case III field-based hydropedologic experiment revised distributed soil hydraulic properties and macropore property estimation. Our results showed that the Case I had difficulties in simulating the timing and peakflow of the runoff responses. Case II performed satisfactorily for peakflow at the outlet and internal weir locations. The distributed soils data in Case III demonstrated the model ability of predicting groundwater levels. The analysis suggests the important role of macropore flow to setting the threshold for recharge and runoff response, while still preserving the water holding capability of the soil and plant water availability. The spatial variability in soil hydraulic properties represented by Case III introduces an additional improvement in distributed catchment flow modeling, especially as it relates to subsurface lateral flow. Comparison of the three cases suggests the value of high-resolution soil survey mapping combined with a macropore parameterization can improve distributed watershed models.</p> <div class="credits"> <p class="dwt_author">Yu, Xuan; Duffy, Christopher; Baldwin, Doug C.; Lin, Henry</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-08-01</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://www.ncbi.nlm.nih.gov/pubmed/23515332"> <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=pubmed">PubMed</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. PMID:23515332</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">2013-04-01</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://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 " 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://esd.lbl.gov/FILES/about/staff/susanhubbard/es071702s.pdf"> <span id="translatedtitle">Geophysical Monitoring of Hydrological and <span class="hlt">Biogeochemical</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Geophysical Monitoring of Hydrological and <span class="hlt">Biogeochemical</span> Transformations Associated with Cr explored the use of geophysical approaches for monitoring the spatiotemporal distribution of hydrological first integrated hydrological wellbore and geophysical tomographic data sets to estimate hydrological</p> <div class="credits"> <p class="dwt_author">Hubbard, Susan</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">75</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://lgmacweb.env.uea.ac.uk/ajw/Reprints/Bergman_Lenton_Watson_AmJSci_2004.pdf"> <span id="translatedtitle">American Journal of Science COPSE: A NEW MODEL OF <span class="hlt">BIOGEOCHEMICAL</span> CYCLING OVER</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">, 1994), a simple sulfur cycle, and additional components. The resulting COPSE model (Carbon-Oxygen-Phosphorus-Sulfur volume percent, provides the best combined pO2 and 13 C predictions. Sulfur cycle <span class="hlt">coupling</span> contributesAmerican Journal of Science MAY 2004 COPSE: A NEW MODEL OF <span class="hlt">BIOGEOCHEMICAL</span> CYCLING OVER PHANEROZOIC</p> <div class="credits"> <p class="dwt_author">Watson, Andrew</p> <p class="dwt_publisher"></p> <p class="publishDate"></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://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">77</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/40857072"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> marine ecosystem models I: IGBEM—a model of marine bay 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">The Integrated Generic Bay Ecosystem Model (IGBEM) is presented. It is a <span class="hlt">coupled</span> physical transport-<span class="hlt">biogeochemical</span> process model constructed as a basis to explore the effects of model structure and complexity. The foundations for the model are two existing models, the European Regional Seas Ecosystem Model II (ERSEM II) and the Port Phillip Bay Integrated Model (PPBIM). Additional functional groups (such</p> <div class="credits"> <p class="dwt_author">Elizabeth A Fulton; Anthony D. M Smith; Craig R Johnson</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">78</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://hal.archives-ouvertes.fr/docs/00/58/73/26/PDF/Bustillo-CRGA_oscience-2011.pdf"> <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://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Factors driving the <span class="hlt">biogeochemical</span> budget of the Amazon River and its statistical modelling the period 1982­1984 during the Carbon in the AMazon River Experiment (CAMREX) project. The relevant factors-regressive model <span class="hlt">coupled</span> to variance analysis. Basically, the compositional fluctuations in the Amazon River</p> <div class="credits"> <p class="dwt_author">Paris-Sud XI, Université de</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">79</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://math.unice.fr/~faugeras/Papiers/faugeras-jms-2003.pdf"> <span id="translatedtitle">Can <span class="hlt">biogeochemical</span> fluxes be recovered from nitrate and chlorophyll data? A case study assimilating data</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Can <span class="hlt">biogeochemical</span> fluxes be recovered from nitrate and chlorophyll data? A case study assimilating station (NW Mediterranean Sea), near-monthly nitrate and chlorophyll profiles and daily surface chlorophyll concentrations are assimilated in a <span class="hlt">coupled</span> dynamical­biological model using the tangent linear</p> <div class="credits"> <p class="dwt_author">Faugeras, Blaise</p> <p class="dwt_publisher"></p> <p class="publishDate"></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://adsabs.harvard.edu/abs/2010EGUGA..12.2293T"> <span id="translatedtitle">Linkages beyond boundaries between <span class="hlt">surface/subsurface</span> and land /ocean for better management of groundwater under the changing climate and society in Asia</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">Change in reliable water resources between groundwater and surface water occurred in many Asian cities depending on the development stage of urbanization and climate change. Although the subsurface water is connected with surface water in hydrological cycle, both waters were treated separately. Intensive field observations and data collections had been made in the basins including Tokyo, Osaka, Bangkok, Jakarta, Manila, Seoul, and Taipei, to evaluate the relationship between development stage of the city and various subsurface environments in Asia beyond the boundary between surface and subsurface environment under the condition of climate change. As a factor of separating water, energy and material at the earth surface into above and below the surface, land use/cover changes at three ages (1940's, 1970's and 2000's) in Asian 7 cities have been analyzed based on GIS with 0.5 km grid at seven targeted cities. Urbanization causes the decease in groundwater recharge rate and increase thermal energy transport into the subsurface. Global warming and heat island effects are also evaluated with in the cities and compared. Another boundary for water and material transports exists between land and ocean. Regarding material (contaminant) transports to the coast, direct groundwater discharge is recently recognized as a significant water and material pathway from land to ocean. Many Asian major cities are located in the coastal zone so material and contaminant transports by groundwater is a key to understanding the coastal water pollution and the effects on associated ecosystems. The exchanges of sea water and fresh water between the boundary were analyzed during the last 100 years in Asian coasts. In this paper, the importance of integrated treatments between <span class="hlt">surface/subsurface</span> and land/ocean will be shown for better understanding and management of subsurface environment including groundwater under the condition of climate variation.</p> <div class="credits"> <p class="dwt_author">Taniguchi, Makoto</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-05-01</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" 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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_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://adsabs.harvard.edu/abs/2011AIPC.1389...34S"> <span id="translatedtitle">Modelling Marine Biological and <span class="hlt">Biogeochemical</span> 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">In the environmental sciences, mathematic models are commonly applied to analyze ecological and <span class="hlt">biogeochemical</span> data. The technique where a model is used to interpret available measurements such as to retrieve unmeasured information on the system being observed is called "inverse modelling". In this paper we will discuss and give examples of two modeling techniques used to analyse ecological and <span class="hlt">biogeochemical</span> data. On the one hand are mechanistic mathematical models that are written as a set of non-linear differential equations. On the other hand are so-called linear inverse models (LIMs) that consist of a set of linear equations that need to be solved for the unknowns.</p> <div class="credits"> <p class="dwt_author">Soetaert, Karline; van Oevelen, Dick</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-09-01</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://pubs.er.usgs.gov/publication/70129606"> <span id="translatedtitle">Temporal dynamics of <span class="hlt">biogeochemical</span> processes at the Norman Landfill site</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 temporal variability observed in redox sensitive species in groundwater can be attributed to <span class="hlt">coupled</span> hydrological, geochemical, and microbial processes. These controlling processes are typically nonstationary, and distributed across various time scales. Therefore, the purpose of this study is to investigate <span class="hlt">biogeochemical</span> data sets from a municipal landfill site to identify the dominant modes of variation and determine the physical controls that become significant at different time scales. Data on hydraulic head, specific conductance, ?2H, chloride, sulfate, nitrate, and nonvolatile dissolved organic carbon were collected between 1998 and 2000 at three wells at the Norman Landfill site in Norman, OK. Wavelet analysis on this geochemical data set indicates that variations in concentrations of reactive and conservative solutes are strongly <span class="hlt">coupled</span> to hydrologic variability (water table elevation and precipitation) at 8 month scales, and to individual eco-hydrogeologic framework (such as seasonality of vegetation, surface-groundwater dynamics) at 16 month scales. Apart from hydrologic variations, temporal variability in sulfate concentrations can be associated with different sources (FeS cycling, recharge events) and sinks (uptake by vegetation) depending on the well location and proximity to the leachate plume. Results suggest that nitrate concentrations show multiscale behavior across temporal scales for different well locations, and dominant variability in dissolved organic carbon for a closed municipal landfill can be larger than 2 years due to its decomposition and changing content. A conceptual framework that explains the variability in chemical concentrations at different time scales as a function of hydrologic processes, site-specific interactions, and/or <span class="hlt">coupled</span> <span class="hlt">biogeochemical</span> effects is also presented.</p> <div class="credits"> <p class="dwt_author">Arora, Bhavna; Mohanty, Binayak P.; McGuire, Jennifer T.; Cozzarelli, Isabelle M.</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">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.ncbi.nlm.nih.gov/pubmed/25156418"> <span id="translatedtitle">Microbial diversity and <span class="hlt">biogeochemical</span> cycling in soda lakes.</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">Soda lakes contain high concentrations of sodium carbonates resulting in a stable elevated pH, which provide a unique habitat to a rich diversity of haloalkaliphilic bacteria and archaea. Both cultivation-dependent and -independent methods have aided the identification of key processes and genes in the microbially mediated carbon, nitrogen, and sulfur <span class="hlt">biogeochemical</span> cycles in soda lakes. In order to survive in this extreme environment, haloalkaliphiles have developed various bioenergetic and structural adaptations to maintain pH homeostasis and intracellular osmotic pressure. The cultivation of a handful of strains has led to the isolation of a number of extremozymes, which allow the cell to perform enzymatic reactions at these extreme conditions. These enzymes potentially contribute to biotechnological applications. In addition, microbial species active in the sulfur cycle can be used for sulfur remediation purposes. Future research should combine both innovative culture methods and state-of-the-art 'meta-omic' techniques to gain a comprehensive understanding of the microbes that flourish in these extreme environments and the processes they mediate. <span class="hlt">Coupling</span> the <span class="hlt">biogeochemical</span> C, N, and S cycles and identifying where each process takes place on a spatial and temporal scale could unravel the interspecies relationships and thereby reveal more about the ecosystem dynamics of these enigmatic extreme environments. PMID:25156418</p> <div class="credits"> <p class="dwt_author">Sorokin, Dimitry Y; Berben, Tom; Melton, Emily Denise; Overmars, Lex; Vavourakis, Charlotte D; Muyzer, Gerard</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-09-01</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/2014EGUGA..1615628D"> <span id="translatedtitle">Impact of model resolution on <span class="hlt">biogeochemical</span> tracers concentration in the tropical Atlantic 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">Representing correctly the distribution of <span class="hlt">biogeochemical</span> tracers in the interior ocean, such as oxygen or phosphate, is hampered by large biases in the representation of circulation in the coarse resolution models. Here we assess the oxygen and phosphate budget in two configurations of a <span class="hlt">coupled</span> circulation <span class="hlt">biogeochemical</span> model (NEMO - NPZD), focusing on the Atlantic Ocean. These two configurations have been integrated using realistic atmospheric forcings for the period 1948-2007. While a coarse (0.5°) configuration displays the common bias of too low oxygen associated with too high phosphate concentration, particularly at intermediate depth in the eastern side of the basin, the values are closer to the observations in an eddying (0.1°) configuration. The improvement in the representation of oxygen and phosphate is traced to a stronger transport by a more realistic representation of the equatorial and off-equatorial undercurrents. The <span class="hlt">biogeochemical</span> fluxes are less sensitive to the current strength as the phytoplankton growth is mainly limited by the available light in the two configurations. This study emphasizes the need of high resolution models to tackle <span class="hlt">coupled</span> <span class="hlt">biogeochemical</span> problematics, such as the extension of oxygen minimum zones or variability in the eastern boundary upwelling system productivity.</p> <div class="credits"> <p class="dwt_author">Duteil, Olaf; Boening, Claus; Oschlies, Andreas</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</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/59518346"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> aspects of aquifer thermal energy storage</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"><TT>During the process of aquifer thermal energy storage the in situ temperature of the groundwater- sediment system may fluctuate significantly. As a result the groundwater characteristics can be considerably affected by a variety of chemical, <span class="hlt">biogeochemical</span> and microbiological reactions. The interplay of these reactions may have a negative influence on the operational performance of ATES-systems. The objective of this thesis</p> <div class="credits"> <p class="dwt_author">H. J. Brons</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">86</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/46626279"> <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://academic.research.microsoft.com/">Microsoft Academic Search </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</p> <div class="credits"> <p class="dwt_author">Yilin Fang; Steven B. Yabusaki; Gour-Tsyh Yeh</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">87</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/70039049"> <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://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</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-1 and decreases in nitrate nitrogen (NO3-–N) from 2.7 mg L-1 to -1, followed by manganese and iron reduction, sulfate reduction, and methanogenesis. In contrast, beneath the basin with predominantly sandy soils (median, 2% silt+clay), aerobic conditions persisted from 2007 through 2009 (dissolved oxygen, 5.0–7.8 mg L-1), resulting in NO3-–N of 1.3 to 3.3 mg L-1 in shallow groundwater. Enrichment of d15N and d18O of NO3- combined with water chemistry data indicates denitrification beneath the clayey basin and relatively conservative NO3- transport beneath the sandy basin. Soil-extractable NO3-–N was significantly lower and the copper-containing nitrite reductase gene density was significantly higher beneath the clayey basin. Differences in moisture retention capacity between fine- and coarse-textured soils resulted in median volumetric gas-phase contents of 0.04 beneath the clayey basin and 0.19 beneath the sandy basin, inhibiting <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 NO3- impacts.</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">2012-01-01</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://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">2012-01-01</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/2013AGUFM.B51L..04E"> <span id="translatedtitle">The interaction between biogeophysical and <span class="hlt">biogeochemical</span> processes and their feedback on permafrost soil carbon stocks</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 current understanding of the full suite of processes and their responses to recent warming in terrestrial high-latitudes are far from complete. While continued research on development of more detailed Earth system models (ESMs) is essential to understand the interactions and feedbacks between vegetation, soils and climate change in the Northern high latitudes (NHL), one of the major challenges is the treatment of the biophysical and <span class="hlt">biogeochemical</span> processes and feedback in the ESM and their impact on soil organic carbon. We used a land surface model, the Integrated Science Assessment Model (ISAM), which <span class="hlt">coupled</span> carbon-nitrogen <span class="hlt">biogeochemical</span> and energy and hydrology biogeophysical processes, to investigate the effects of feedbacks between the <span class="hlt">biogeochemical</span> and biogeophysical processes on the model estimated soil organic carbon (SOC) for the NHL permafrost region. We not only focused on recent improvement in the ISAM biogeophysical processes that are deemed important for the high latitude soils/snow; such as deep soil column, modulation of soil thermal and hydrological properties, wind compaction of snow, and depth hoar formation; on permafrost SOC, but also <span class="hlt">biogeochemical</span> processes; such as dynamic phenology and root distribution, litter carbon decomposition rates and nitrogen amount remaining; on soil biogeochemistry. We selected multiple sites representative of different high latitude biomes to calibrate and evaluate the model. We then carried out several ISAM model simulations to study the effects of feedbacks between <span class="hlt">biogeochemical</span> and biogeophysical processes on SOC. Our model analysis shows that including the biogeophysical processes alone could increase modeled Northern high-latitude permafrost carbon by about 30% compared to measurements. Accounting for the biogeochmical processes further improve the NHL soil carbon. This study demonstrates that improvements in biogeophysical or <span class="hlt">biogeochemical</span> processes alone does not help to improve the modeled SOC, instead we emphasis on the importance of biogeophysical and biophysical processes and feedbacks between them in modeling permafrost carbon stocks.</p> <div class="credits"> <p class="dwt_author">ElMasri, B.; Barman, R.; Jain, A. K.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-01</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://ntrs.nasa.gov/search.jsp?R=20060015647&hterms=mab&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmab"> <span id="translatedtitle"><span class="hlt">BIOGEOCHEMICAL</span> STUDIES OF PHOTOSYNTHETIC MICROBIAL MATS AND THEIR BIOTA</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">Photosynthetic microbial mats offer an opportunity to define holistic functionality at the millimeter scale. At the same time. their biogeochemistry contributes to environmental processes on a planetary scale. These mats are possibly direct descendents of the most ancient biological communities; communities in which oxygenic photosynthesis might have been invented. Mats provide one of the best natural systems to study how microbial populations associate to control dynamic <span class="hlt">biogeochemical</span> gradients. These are self- sustaining, complete ecosystems in which light energy absorbed over a dial (24 hour) cycle drives the synthesis of spatially-organized, diverse biomass. Tightly-<span class="hlt">coupled</span> microorganisms in the mat have specialized metabolisms that catalyze transformations of carbon, nitrogen, sulfur, and a host of other elements.</p> <div class="credits"> <p class="dwt_author">DesMarais, David; Discipulo, M.; Turk, K.; Londry, K. L.</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">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/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">2012-08-15</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://academic.research.microsoft.com/Publication/10632798"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> modelling of the tropical Pacific Ocean. I: Seasonal and interannual 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">A <span class="hlt">coupled</span> physical–<span class="hlt">biogeochemical</span> model has been developed in order to study physical–biological interactions in the tropical Pacific Ocean on seasonal-to-interannual timescales. The model incorporates both iron- and nitrogen-limited phytoplankton growth, and succession of phytoplankton size classes in accordance with the “ecumenical” iron hypothesis. The model shows a strong El Niño–Southern Oscillation component to phytoplankton variability in the central equatorial Pacific</p> <div class="credits"> <p class="dwt_author">J. R. Christian; M. A. Verschell; R. Murtugudde; A. J. Busalacchi; C. R. McClaine</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">93</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/40283617"> <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://academic.research.microsoft.com/">Microsoft Academic Search </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 O2, and the</p> <div class="credits"> <p class="dwt_author">S. Molins; K. U. Mayer; R. T. Amos; B. A. Bekins</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://www.osti.gov/scitech/biblio/20062586"> <span id="translatedtitle">Coastal-zone <span class="hlt">biogeochemical</span> dynamics under global warming</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 coastal zone, consisting of the continental shelves to a depth of 200 meters, including bays, lagoons, estuaries, and near-shore banks, is an environment that is strongly affected by its <span class="hlt">biogeochemical</span> and physical interactions with reservoirs in the adjacent domains of land, atmosphere, open ocean, and marine sediments. Because the coastal zone is smaller in volume and area coverage relative to the open ocean, it traditionally has been studied as an integral part of the global oceans. In this paper, the authors show by numerical modeling that it is important to consider the coastal zone as an entity separate from the open ocean in any assessment of future Earth-system response under human perturbation. Model analyses for the early part of the 21st century suggest that the coastal zone plays a significant modifying role in the <span class="hlt">biogeochemical</span> dynamics of the carbon cycle and the nutrient cycles <span class="hlt">coupled</span> to it. This role is manifested in changes in primary production, storage, and/or export of organic matter, its remineralization, and calcium carbonate precipitation--all of which determine the state of the coastal zone with respect to exchange of CO{sub 2} with the atmosphere. Under a scenario of future reduced or complete cessation of the thermohaline circulation (THC) of the global oceans, coastal waters become an important sink for atmospheric CO{sub 2}, as opposed to the conditions in the past and present, when coastal waters are believed to be a source of CO{sub 2} to the atmosphere. Profound changes in coastal-zone primary productivity underscore the important role of phosphorus as a limiting nutrient. In addition, calculations indicate that the saturation state of coastal waters with respect to carbonate minerals will decline by {approximately}15% by the year 2030. Any future slowdown in the THC of the oceans will increase slightly the rate of decline in saturation state.</p> <div class="credits"> <p class="dwt_author">Mackenzie, F.T.; Ver, L.M.; Lerman, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2000-03-01</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://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 " 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/2009OcSci...5...29P"> <span id="translatedtitle">Eastern Mediterranean <span class="hlt">biogeochemical</span> flux model - Simulations of the pelagic ecosystem</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 second phase (2003-2006) of the Mediterranean ocean Forecasting System Project (MFS) named Toward Environmental Predictions (MFSTEP) one of the three major aims was the development of numerical forecasting systems. In this context a generic <span class="hlt">Biogeochemical</span> Flux Model (BFM) was developed and <span class="hlt">coupled</span> with hydrodynamic models already operating at basin scale as well as in regional areas. In the Eastern Mediterranean basin the BFM was <span class="hlt">coupled</span> with the Aegean Levantine Eddy Resolving MOdel (ALERMO). The BFM is a generic highly complex model based on ERSEM and although a detailed description of the model and its components is beyond the scope of this work, a short overview of the main processes, laying emphasis on the parameter values used is presented. In addition the performance of the model is evaluated with some preliminary results being qualitatively compared against field observations. The model in its present form is rather promising and reproduces all important major features although there are some slight inefficiencies mostly related to primary and bacterial productivity rates.</p> <div class="credits"> <p class="dwt_author">Petihakis, G.; Triantafyllou, G.; Tsiaras, K.; Korres, G.; Pollani, A.; Hoteit, I.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-02-01</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://www.mbari.org/chemsensor/Data/Monterey%20Bay/lobosFeNuts_web.xls"> <span id="translatedtitle">Monterey Bay Time Series <span class="hlt">Biogeochemical</span> Data</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 dataset includes a broad suite of <span class="hlt">biogeochemical</span> measurements, particularly dissolvable iron. The measurements span the time period from August 1998 to December 2004 and were taken at the most inshore station of a set of three which are maintained by the Monterey Bay Aquarium Research Institute (MBARI). The data show a large pulse of dissolvable iron consistently occurring during the first spring upwelling event of each year that is derived from resuspended sediment. Iron concentrations then drop rapidly at all three stations. During the summer months, only the most inshore station (C1) maintains iron concentrations in excess of nitrate.</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">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/2008AGUFM.H33G1099S"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Modeling of Ureolytically-Driven Calcium Carbonate Precipitation for Contaminant Immobilization</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">Radionuclide and metal contaminants such as strontium-90 are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center at the Idaho National Laboratory [INL]). Manipulation of in situ <span class="hlt">biogeochemical</span> conditions to induce immobilization of these contaminants is a promising remediation approach that could yield significant risk and cost benefits to DOE. However, the effective design and interpretation of such field remediation activities requires the availability of numerical tools to model the <span class="hlt">biogeochemical</span> processes underlying the remediation strategy. We are evaluating the use of microbial urea hydrolysis <span class="hlt">coupled</span> to calcite precipitation as a means for the cost effective in situ stabilization of trace inorganic contaminants in groundwater and vadose zone systems. The approach relies upon the activity of indigenous ureolytic bacteria to hydrolyze introduced urea and causing an increase in pH and alkalinity, thereby accelerating calcium carbonate precipitation. The precipitation reaction results in the co- precipitation of trace metals and is sustained by the release of cations (both calcium and trace metals) from the aquifer matrix via exchange reactions involving the ammonium ions produced by urea hydrolysis. We have developed and parameterized a mixed kinetic-equilibrium reaction model using the Geochemist's Workbench computer code. Simulation results based on laboratory- and field-scale studies demonstrate the importance of transient events in systems with geochemical fluxes as well as of the <span class="hlt">coupling</span> of <span class="hlt">biogeochemical</span> processes.</p> <div class="credits"> <p class="dwt_author">Smith, R. W.; Fujita, Y.; Taylor, J. L.</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">99</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/2014EGUGA..1613499S"> <span id="translatedtitle">Modelling physical and <span class="hlt">biogeochemical</span> state of the Mediterranean Sea under contemporary and future 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">A validated 3D <span class="hlt">coupled</span> transport-<span class="hlt">biogeochemical</span> model is used to assess the impact of future climatic and management scenarios on <span class="hlt">biogeochemical</span> and ecological properties of the Mediterranean Sea. Results are discussed in term of temporal and spatial distribution of parameters and indicators related to the carbonate system and the cycles of carbon and inorganic nutrients through dissolved and particulate phases, as simulated by a multi nutrient multi plankton numerical model under current and future conditions. Simulations span the period 2000-2040 and are performed by forcing a three-dimensional off-line <span class="hlt">coupled</span> eco-hydrodynamical model (BFM and OPA-tracer model, http://bfm-community.eu/) with marine circulation fields produced by ad hoc implementation of the NEMO modelling system and with river input of nutrient and freshwater computed in recent European fp7 projects. The model properly describes available experimental information on contemporary seasonal dynamic and spatial distribution at the basin and sub-basin scale of major <span class="hlt">biogeochemical</span> parameters, as well as primary production and carbon fluxes at the air-ocean interface. Model projections suggest that future Mediterranean sea will be globally warmer, more productive, and more acidic, but with significant space variability. The relative importance of different biotic and abiotic parameters in defining such a change is explored through several numerical experiments. Potential implications in terms of ecological and higher trophic level organisms dynamics are explored as well, by integrating niche properties of selected organisms and suggestions provided by food web models.</p> <div class="credits"> <p class="dwt_author">Solidoro, Cosimo; Lazzari, Paolo; Cossarini, Gianpiero; Melaku Canu, Donata; Lovato, Tomas; Vichi, Marcello</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</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://adsabs.harvard.edu/abs/2014EGUGA..1613522C"> <span id="translatedtitle">Reanalysis of <span class="hlt">biogeochemical</span> properties in the 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">In the 3D variational (3DVAR) assimilation approach the error covariance matrix can be decomposed in a series of operators. The decomposition makes the 3DVAR particularly suitable for marine biogeochemistry data assimilation, because of the reduced computational costs of the method and its modularity, which allows to define the covariance among the <span class="hlt">biogeochemical</span> variables in a specific operator. In the present work, the results of 3DVAR assimilation of surface chlorophyll concentration in a multi-annual simulation of the Mediterranean Sea biogeochemistry are presented. The assimilated chlorophyll concentrations are obtained from satellite observations (Volpe et al. 2012). The multi-annual simulation is carried out using the OPATM-BFM model (Lazzari et al. 2012), which describes the low trophic web dynamics and is offline <span class="hlt">coupled</span> with the MFS physical model (Oddo et al. 2009). In the OPATM-BFM four types of phytoplankton are simulated in terms of their content in carbon, nitrogen, phosphorous, silicon and chlorophyll. In the 3DVAR the error covariance matrix has been decomposed in three different operators, which account for the vertical, the horizontal and the <span class="hlt">biogeochemical</span> covariance (Teruzzi et al. 2014). The <span class="hlt">biogeochemical</span> operator propagates the result of the assimilation to the OPATM-BFM variables, providing innovation for the components of the four phytoplankton types. The <span class="hlt">biogeochemical</span> covariance has been designed supposing that the assimilation preserves the physiological status and the relative abundances of phytoplankton types. Practically, the assimilation preserves the internal quotas of the components for each phytoplankton as long as the optimal growth rate condition are maintained. The quotas preservation is not applied when the phytoplankton is in severe declining growth phase, and the correction provided by the assimilation is set equal to zero. Moreover, the relative abundances among the phytoplankton functional types are preserved. The 3DVAR has been applied to the Mediterranean Sea for the period 1999-2010 with weekly assimilation. The results of the multi-annual run show that the assimilation improves the model skill in terms of a better representation of the mean chlorophyll concentrations over the Mediterranean Sea sub-regions and also in terms of spatial and temporal definition of local bloom events. Furthermore, the comparison with nutrients climatology based on in situ measurements show that the non assimilated variables are consistent with observations. The application of the 3DVAR revealed that in specific cases the correction introduced by the assimilation is not maintained by the model dynamics. In these cases, the satellite observations are characterized by local patchy bloom events, which are not well captured by the model. It has been observed that, since the bloom events are strongly affected by the vertical mixing dynamics, which support nutrients to the surface layer, a possible source of error are the mixing conditions provided by the physical model. Oddo et al. 2009. Ocean Science, 5(4), 461-473, doi:10.5194/os-5-461-2009. Lazzari et al. 2012. Biogeosciences, 9(1), 217-233, doi:10.5194/bg-9-217-2012. Teruzzi et al. 2014. Journal of Geophysical Research, 119, 1-18, doi:10.1002/2013JC009277. Volpe et al. 2012. Ocean Science Discussions, 9(2), 1349-1385, doi:10.5194/osd-9-1349-2012.</p> <div class="credits"> <p class="dwt_author">Cossarini, Gianpiero; Teruzzi, Anna; Salon, Stefano; Solidoro, Cosimo</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</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_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 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showDiv("page_7");' 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">101</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=20030001107&hterms=sulfur+Isotope&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsulfur%2BIsotope"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Cycles of Carbon and Sulfur</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The elements carbon (C) and sulfur (S) interact with each other across a network of elemental reservoirs that are interconnected by an array of physical, chemical and biological processes. These networks are termed the <span class="hlt">biogeochemical</span> C and S cycles. The compounds of C are highly important, not only as organic matter, but also as atmospheric greenhouse gases, pH buffers in seawater, oxidation-reduction buffers virtually everywhere, and key magmatic constituents affecting plutonism and volcanism. The element S assumes important roles as an oxidation-reduction partner with C and Fe in biological systems, as a key constituent in magmas and volcanic gases, and as a major influence upon pH in certain environments. This presentation describes the modern <span class="hlt">biogeochemical</span> C and S cycles. Measurements are described whereby stable isotopes can help to infer the nature and quantitative significance of biological and geological processes involved in the C and S cycles. This lecture also summarizes the geological and climatologic aspects of the ancient C and S cycles, as well as the planetary and extraterrestrial processes that influenced their evolution over millions to billions of years.</p> <div class="credits"> <p class="dwt_author">DesMarais, David J.; DeVincenzi, D. (Technical Monitor)</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">102</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19840022596&hterms=marine+phosphorus+cycle+sulfate&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmarine%2Bphosphorus%2Bcycle%2Bsulfate"> <span id="translatedtitle">Global Biology Research Program: <span class="hlt">Biogeochemical</span> Processes in Wetlands</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The results of a workshop examining potential NASA contributions to research on wetland processes as they relate to global <span class="hlt">biogeochemical</span> cycles are summarized. A wetlands data base utilizing remotely sensed inventories, studies of wetland/atmosphere exchange processes, and the extrapolation of local measurements to global <span class="hlt">biogeochemical</span> cycling processes were identified as possible areas for NASA support.</p> <div class="credits"> <p class="dwt_author">Bartlett, D. S. (editor)</p> <p class="dwt_publisher"></p> <p class="publishDate">1984-01-01</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://water.usgs.gov/nrp/proj.bib/Publications/2011/cozzarelli_bohlke_etal_2011.pdf"> <span id="translatedtitle">Review Paper/ <span class="hlt">Biogeochemical</span> Evolution of a Landfill Leachate</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Review Paper/ <span class="hlt">Biogeochemical</span> Evolution of a Landfill Leachate Plume, Norman, Oklahoma by I Abstract Leachate from municipal landfills can create groundwater contaminant plumes that may last describing the <span class="hlt">biogeochemical</span> processes that affect the transport of contaminants in this landfill-leachate</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">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/2011JMS....88..267E"> <span id="translatedtitle">Evaluation of <span class="hlt">biogeochemical</span> cycles in an ensemble of three state-of-the-art numerical models of the Baltic 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">Three state-of-the-art <span class="hlt">coupled</span> physical-<span class="hlt">biogeochemical</span> models, the BAltic sea Long-Term large-Scale Eutrophication Model (BALTSEM), the Ecological Regional Ocean Model (ERGOM), and the Swedish Coastal and Ocean <span class="hlt">Biogeochemical</span> model <span class="hlt">coupled</span> to the Rossby Centre Ocean circulation model (RCO-SCOBI), are used to calculate changing nutrient and oxygen dynamics in the Baltic Sea. The models are different in that ERGOM and RCO-SCOBI are three-dimensional (3D) circulation models while BALTSEM resolves the Baltic Sea into 13 dynamically interconnected and horizontally integrated sub-basins. The aim is to assess the simulated long-term dynamics and to discuss the response of the <span class="hlt">coupled</span> physical-<span class="hlt">biogeochemical</span> models to changing physical conditions and nutrient loadings during the period 1970-2005. We compared the long-term seasonal and annual statistics of inorganic nitrogen, phosphorus, and oxygen from hindcast simulations with those estimated from observations. We also studied the extension of hypoxic bottom areas covered by waters with O 2 < 2 ml O 2 l - 1 and cod reproductive volumes comprising waters with salinity > 11 and O 2 > 2 ml O 2 l - 1 . The models reproduce much of the nutrient <span class="hlt">biogeochemical</span> cycling in the Baltic proper. However, biases are larger in the Bothnian Sea and Bothnian Bay. No model shows outstanding performance in all aspects but instead the ensemble mean results are better than or as good as the results of any of the individual models. Uncertainties are primarily related to differences in the bioavailable fractions of nutrient loadings from land and parameterizations of key processes like sediment fluxes that are presently not well known. Also the uncertainty related to the initialization of the models in the early 1960s influence the modeled <span class="hlt">biogeochemical</span> cycles during the investigated period.</p> <div class="credits"> <p class="dwt_author">Eilola, K.; Gustafsson, B. G.; Kuznetsov, I.; Meier, H. E. M.; Neumann, T.; Savchuk, O. P.</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-11-01</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://pubs.er.usgs.gov/publication/70039044"> <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://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p class="result-summary">Soil beneath a stormwater infiltration basin receiving runoff from a 22.7 ha predominantly residential watershed in 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 a prototype stormwater infiltration basin utilizing nutrient reduction and flood control sub-basins. Comparison of nitrate/chloride (NO3-/Cl-) ratios for the shallow groundwater indicate that prior to using BAM, NO3- concentrations were substantially influenced by nitrification or variations in NO3- input. In contrast, for the prototype basin utilizing BAM, NO3-/Cl- ratios indicate minor nitrification and NO3- 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 NO3- 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 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 (PO43-) 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 PO43-/Cl- ratios for shallow groundwater indicate predominantly minor increases and decreases in PO43- 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 not undergone significant chemical changes. Observed nitrogen and phosphorus losses demonstrate the potential, as well as future research needs to improve performance, of the prototype stormwater infiltration basin using BAM for providing passive, economical, stormwater nutrient-treatment technology to support green infrastructure.</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">2012-01-01</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.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">2008-12-01</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/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">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/2013HESSD..1010913S"> <span id="translatedtitle">River restoration: morphological, hydrological, <span class="hlt">biogeochemical</span> and ecological changes 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">River restoration is essential as a means to enhance river dynamics, environmental heterogeneity and biodiversity. The underlying processes governing the dynamic changes need to be understood thoroughly to ensure that restoration projects meet their goals. In particular, we need to understand quantitatively how hydromorphological variability relates to ecosystem functioning and services, biodiversity and (ground)water quality in restored river corridors. Here, we provide a short overview on the literature and present a study of a restored river corridor in Switzerland combining physical, chemical, and biological observations with modeling. The results show complex spatial patterns of bank infiltration, habitat-type, biotic communities and <span class="hlt">biogeochemical</span> processes. In particular, we found an increase in taxonomic and functional diversity for earthworms, testate amoebae and bacteria in the restored part of the river. This complexity is driven by river hydrology and morphodynamics, which are in turn actively <span class="hlt">coupled</span> to riparian vegetation processes. Given this complexity and the multiple constraints on the uses and management of floodplains, a multi-disciplinary approach is needed to monitor the success of restoration measures and to make recommendations for future restoration projects.</p> <div class="credits"> <p class="dwt_author">Schirmer, M.; Luster, J.; Linde, N.; Perona, P.; Mitchell, E. A. D.; Barry, D. A.; Cirpka, O. A.; Schneider, P.; Vogt, T.; Durisch-Kaiser, 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">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/2011JMS....88..120W"> <span id="translatedtitle">Use of a coastal <span class="hlt">biogeochemical</span> model to select environmental monitoring 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">A method for the spatial selection of sites for a coastal environmental monitoring system is described. The study was completed in southeastern Tasmania, Australia, but the method can be applied in all regions with validated <span class="hlt">biogeochemical</span> models. A 3-dimensional <span class="hlt">coupled</span> hydrodynamic, sediment and <span class="hlt">biogeochemical</span> model with high spatial and temporal resolution was validated against observations collected throughout 2002 and found to capture the essential features of the <span class="hlt">biogeochemical</span> dynamics of the system. The model was used to predict the possible quantitative environmental impact of a projected increase in fish farming activity in the region. Integrated impacts of fish farm waste on labile nitrogen, phosphorus, chlorophyll and dissolved oxygen concentrations in the water column were spatially ranked to identify the most likely places to detect environmental change due to fish farming activities. Priority sites were found to be grouped in the Huon Estuary and northern part of the D'Entrecasteaux Channel consistent with the residual northward current in the region. The final monitoring program synthesized model and field understanding to ensure adequate spatial and temporal sampling of the region.</p> <div class="credits"> <p class="dwt_author">Wild-Allen, Karen; Thompson, Peter A.; Volkman, John K.; Parslow, John</p> <p class="dwt_publisher"></p> <p class="publishDate">2011-10-01</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/2011WRR....47.1513S"> <span id="translatedtitle">Assessment of climate change impacts at the catchment scale with a detailed hydrological model of <span class="hlt">surface-subsurface</span> interactions and comparison with a land surface 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">A process-based model that incorporates hydrodynamic feedbacks between the land surface, soil, and groundwater zones is used to assess the sensitivity of the hydrological response (river discharge, aquifer recharge, and soil water storage) to future climate conditions. The analysis is based on the Intergovernmental Panel on Climate Change Special Report on Emissions Scenario A2 and the des Anglais catchment in southwestern Quebec (Canada). Application of the <span class="hlt">coupled</span> hydrological model (CATHY) to the study basin revealed significant spatiotemporal variations in the river discharge response to climate change owing to a different partitioning between the overland runoff and base flow components of the hydrograph, with the latter alleviating the marked decrease in discharge during the summer period. A spatial analysis of recharge patterns shows that the greatest variations are expected to occur, throughout the year, in the southern portion of the catchment, where the elevations are highest. Compared to river discharge and aquifer recharge, the soil water storage volumes are less sensitive to climate changes. From a spatial analysis of soil moisture variations it was possible to observe organizational patterns that follow the topographic and pedologic characteristics of the catchment. In addition to these analyses, we also compare predictions obtained with the land surface scheme (CLASS) that is <span class="hlt">coupled</span> to the regional climate model (CRCM) to those from the detailed catchment model for past and future climate change projections. An examination of the runoff revealed that CLASS produces higher estimates than CATHY of surface and subsurface runoff throughout the annual cycle for both past and future projections. For soil water storage, the two models are in general agreement in terms of the intra-annual variability of moisture content at shallower soil layers, whereas a larger difference is found for the deepest layer, with CATHY predicting wetter soil conditions over the entire simulation period and moisture fluctuations of much smaller amplitude.</p> <div class="credits"> <p class="dwt_author">Sulis, M.; Paniconi, C.; Rivard, C.; Harvey, R.; Chaumont, D.</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">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/2007JHyd..342...97R"> <span id="translatedtitle">Towards simulating <span class="hlt">biogeochemical</span> hot spots in the landscape: A geographic object-based 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">SummaryPhysically based models may offer a means to improve our understanding of how <span class="hlt">biogeochemical</span> hot spots form in the landscape, and a way to quantify the aggregated effects of their occurrences across scales [Burt, T.P., Pinay, G., 2005. Linking hydrology and biogeochemistry in complex landscapes. Progress in Physical Geography 29 (3), 297-316]. With this challenge in mind, a prototypical, geographic object-based simulation framework is presented to demonstrate methods for <span class="hlt">coupled</span> hydrological and <span class="hlt">biogeochemical</span> modelling. The framework integrates GIS-based spatial analysis and parameterization methods with object-oriented (OO) concepts and numerical methods for hydrological and <span class="hlt">biogeochemical</span> modelling. As proof-of-concept, the object-model is used to demonstrate saturated, lateral subsurface flood-wave and solute propagation, as well as hypothetical solute reaction hot spots whereby loss rates are controlled by solute concentration and hydrologic residence times using a modified 1st order decay mechanism. For the steady-state examples, the spatial patterns of hot spot formation are governed by 1st (global) and 2nd (local) order variations in subsurface topography which influence hydrologic residence time in sediments of varying thickness and depth variable saturated hydraulic conductivity. However, in these simplified scenarios overall reduction efficiencies are more strongly governed by the slope of the subsurface and hydrogeomorphic configuration than by 1st order variations in topography. The sample simulations support a claim for models that are more capable of handling the spatially and temporally complex hydrological-<span class="hlt">biogeochemical</span> linkages that drive the formation of hot spots in the landscape. Further development of this approach is advocated to provide a tool for exploratory analysis and hypothesis formulation and testing regarding landscape controls on hydrology and biogeochemistry.</p> <div class="credits"> <p class="dwt_author">Richardson, M. C.; Branfireun, B. A.; Robinson, V. B.; Graniero, P. A.</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">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.osti.gov/scitech/biblio/182825"> <span id="translatedtitle">IIASA`s climate-vegetation-<span class="hlt">biogeochemical</span> cycle module as a part of an integrated model for climate change</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 main objective of this study is the development of a hierarchy of <span class="hlt">coupled</span> climate biosphere models with a full description of the global <span class="hlt">biogeochemical</span> cycles. These models are planned for use as the core of a set of integrated models of climate change and they will incorporate the main elements of the Earth system (atmosphere, hydrosphere, pedosphere and biosphere) linked with each other (and eventually with the antroposphere) through the fluxes of heat, momentum, water and through the global <span class="hlt">biogeochemical</span> cycles of carbon and nitrogen. This set of integrated models can be considered to fill the gap between highly simplified integrated models of climate change and very sophisticated and computationally expensive <span class="hlt">coupled</span> models, developed on the basis of general circulation models (GCMs). It is anticipated that this range of integrated models will be an effective tool for investigating the broad spectrum of problems connected with the coexistence of human society and biosphere.</p> <div class="credits"> <p class="dwt_author">Ganopolski, A.V.; Jonas, M.; Krabec, J.; Olendrzynski, K.; Petoukhov, V.K.; Venevsky, S.V. [International Inst. for Applied Systems Analysis, Laxenburg (Austria)</p> <p class="dwt_publisher"></p> <p class="publishDate">1994-12-31</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/2013EGUGA..15.4605M"> <span id="translatedtitle">Plant Nitrogen Uptake in Terrestrial <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">Most terrestrial <span class="hlt">biogeochemical</span> models featured in the last Intergovernmental Panel on Climate Change (IPPC) Assessment Report highlight the importance of the terrestrial Carbon sequestration and feedbacks between the terrestrial Carbon cycle and the climate system. However, these models have been criticized for overestimating predicted Carbon sequestration and its potential climate feedback when calculating the rate of future climate change because they do not account for the Carbon sequestration constraints caused by nutrient limitation, particularly Nitrogen (N). This is particularly relevant considering the existence of a substantial deficit of Nitrogen for plants in most areas of the world. To date, most climate models assume that plants have access to as much Nitrogen as needed, but ignore the nutrient requirements for new vegetation growth. Determining the natural demand and acquisition for Nitrogen and its associated resource optimization is key when accounting for the Carbon sequestration constrains caused by nutrient limitation. The few climate models that include C-N dynamics have illustrated that the stimulation of plant growth over the coming century may be two to three times smaller than previously predicted. This reduction in growth is partially offset by an increase in the availability of nutrients resulting from an accelerated rate of decomposition of dead plants and other organic matter that occurring with a rise in temperature. However, this offset does not counterbalance the reduced level of plant growth calculated by natural nutrient limitations. Additionally, Nitrogen limitation is also expected to become more pronounced in some ecosystems as atmospheric CO2 concentration increases; resulting in less new growth and higher atmospheric CO2 concentrations than originally expected. This study compares alternative models of plant N uptake as found in different terrestrial <span class="hlt">biogeochemical</span> models against field measurements, and introduces a new N-uptake model to the Joint UK Land Environment Simulator (JULES).. Acknowledgements This work has been funded by the European Commission FP7-PEOPLE-ITN-2008 Marie Curie Action: "Greencycles II: FP7-PEOPLE-ITN-2008 Marie Curie Action: "Networks for Initial Training"</p> <div class="credits"> <p class="dwt_author">Marti, Alejandro; Cox, Peter; Sitch, Stephen; Jones, Chris; Liddicoat, spencer</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">114</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/2013AGUFM.B13D0532M"> <span id="translatedtitle">Plant Nitrogen Uptake in Terrestrial <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">Most terrestrial <span class="hlt">biogeochemical</span> models featured in the last Intergovernmental Panel on Climate Change (IPPC) Assessment Report highlight the importance of the terrestrial Carbon sequestration and feedbacks between the terrestrial Carbon cycle and the climate system. However, these models have been criticized for overestimating predicted Carbon sequestration and its potential climate feedback when calculating the rate of future climate change because they do not account for the Carbon sequestration constraints caused by nutrient limitation, particularly Nitrogen (N). This is particularly relevant considering the existence of a substantial deficit of Nitrogen for plants in most areas of the world. To date, most climate models assume that plants have access to as much Nitrogen as needed, but ignore the nutrient requirements for new vegetation growth. Determining the natural demand and acquisition for Nitrogen and its associated resource optimization is key when accounting for the Carbon sequestration constrains caused by nutrient limitation. The few climate models that include C-N dynamics have illustrated that the stimulation of plant growth over the coming century may be significantly smaller than previously predicted. However, models exhibit wide differences in their predictive accuracy and lead to widely diverging and inconsistent projections accounting for an uncertain Carbon sequestration decrease due to Nitrogen limitation ranging from 7 to 64%. This reduction in growth is partially offset by an increase in the availability of nutrients resulting from an accelerated rate of decomposition of dead plants and other organic matter that occurring with a rise in temperature. However, this offset does not counterbalance the reduced level of plant growth calculated by natural nutrient limitations. Additionally, Nitrogen limitation is also expected to become more pronounced in some ecosystems as atmospheric CO2 concentration increases; resulting in less new growth and higher atmospheric CO2 concentrations than originally expected. This study compares the differences in the predictions of alternative models of plant N uptake found in different terrestrial <span class="hlt">biogeochemical</span> models with the predictions from a new N-uptake model developed under the Joint UK Land Environment Simulator (JULES) framework. We implement a methodology for the construction, parameterization and evaluation of N uptake models to fully decompose all the N uptake component processes in terms of their parameter uncertainty and the accuracy of their predictions with respect to different empirical data sets. Acknowledgements This work has been funded by the European Commission FP7-PEOPLE-ITN-2008 Marie Curie Action: "Greencycles II: FP7-PEOPLE-ITN-2008 Marie Curie Action: "Networks for Initial Training"</p> <div class="credits"> <p class="dwt_author">Marti Donati, A.; Cox, P.; Smith, M. J.; Purves, D.; Sitch, S.; Jones, C. D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-01</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://www.soest.hawaii.edu/PubServices/2001pdfs/Mahadevan.pdf"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> variability in the upper ocean A. Mahadevan</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">carbon (DIC), nitrate, phosphate, ra- diocarbon and dissolved oxygen, have strong vertical concentration<span class="hlt">Biogeochemical</span> variability in the upper ocean A. Mahadevan Atmospheric and Environmental Research ocean forcing processes can lead to substantial differences in their patterns of variability</p> <div class="credits"> <p class="dwt_author">Cambridge, University of</p> <p class="dwt_publisher"></p> <p class="publishDate"></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/2010LPICo1538.5261P"> <span id="translatedtitle">Fried Phosphate and Organic Survival: Lightning in <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">Lightning is known to influence <span class="hlt">biogeochemical</span> processes. Here we discuss two studies on fulgurites, glasses formed by cloud-to-ground lightning. Lightning changes P redox state, and changes, but does not remove, carbon compounds.</p> <div class="credits"> <p class="dwt_author">Pasek, M. A.; Kee, T. P.; Carter, E. A.; Hargreaves, M. D.; Edwards, H. G. M.; Atlas, Z.</p> <p class="dwt_publisher"></p> <p class="publishDate">2010-04-01</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://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">118</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://dspace.mit.edu/handle/1721.1/69474"> <span id="translatedtitle">Organic geochemistry and stable isotope constraints on Precambrian <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/epsearch/">E-print Network</a></p> <p class="result-summary">Details of the <span class="hlt">biogeochemical</span> cycles and the dominant mechanisms present in Precambrian remain heavily debated topics. The events of the Late Proterozoic onset to glaciations and what types of early life existed in the ...</p> <div class="credits"> <p class="dwt_author">Thomas, Katherine S., S.M. Massachusetts Institute of Technology</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">119</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/45897662"> <span id="translatedtitle">Efficient data assimilation into a complex, 3-D physical-<span class="hlt">biogeochemical</span> model using partially-local Kalman filters</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">Advanced Kalman filtering techniques were used to assimilate pseudo ocean color and profile data into a complex, three-dimensional <span class="hlt">coupled</span> physical (POM)-<span class="hlt">biogeochemical</span> (ERSEM) model of the Cretan Sea ecosystem. The assimilation schemes, the Singular Evolutive Partially-Local Extended Kalman (SEPLEK) filter and its variant called SFPLEK, are based on the standard SEEK filter in which the Kalman correction is made along a</p> <div class="credits"> <p class="dwt_author">I. Hoteit; G. Triantafyllou; G. Petihakis</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-01-01</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://academic.research.microsoft.com/Publication/52079724"> <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://academic.research.microsoft.com/">Microsoft Academic Search </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 changes in environment (heat island effect, pollution, introduction of non-native species, loss of native species). These changes have created novel ecosystems, which have the potential to significantly affect <span class="hlt">biogeochemical</span> cycles at local, regional, and global scales. In this presentation</p> <div class="credits"> <p class="dwt_author">R. V. Pouyat; D. E. Pataki; K. T. Belt; P. M. Groffman; L. E. Band; J. Hom</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_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");' href="#">2</a> <a onClick='return showDiv("page_3");' href="#">3</a> <a onClick='return showDiv("page_4");' 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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_8");' 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">121</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=4217446"> <span id="translatedtitle">Redox chemistry in the phosphorus <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=pmc">PubMed Central</a></p> <p class="result-summary">The element phosphorus (P) controls growth in many ecosystems as the limiting nutrient, where it is broadly considered to reside as pentavalent P in phosphate minerals and organic esters. Exceptions to pentavalent P include phosphine—PH3—a trace atmospheric gas, and phosphite and hypophosphite, P anions that have been detected recently in lightning strikes, eutrophic lakes, geothermal springs, and termite hindguts. Reduced oxidation state P compounds include the phosphonates, characterized by C?P bonds, which bear up to 25% of total organic dissolved phosphorus. Reduced P compounds have been considered to be rare; however, the microbial ability to use reduced P compounds as sole P sources is ubiquitous. Here we show that between 10% and 20% of dissolved P bears a redox state of less than +5 in water samples from central Florida, on average, with some samples bearing almost as much reduced P as phosphate. If the quantity of reduced P observed in the water samples from Florida studied here is broadly characteristic of similar environments on the global scale, it accounts well for the concentration of atmospheric phosphine and provides a rationale for the ubiquity of phosphite utilization genes in nature. Phosphine is generated at a quantity consistent with thermodynamic equilibrium established by the disproportionation reaction of reduced P species. Comprising 10–20% of the total dissolved P inventory in Florida environments, reduced P compounds could hence be a critical part of the phosphorus <span class="hlt">biogeochemical</span> cycle, and in turn may impact global carbon cycling and methanogenesis. PMID:25313061</p> <div class="credits"> <p class="dwt_author">Pasek, Matthew A.; Sampson, Jacqueline M.; Atlas, Zachary</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</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://www.ncbi.nlm.nih.gov/pubmed/25313061"> <span id="translatedtitle">Redox chemistry in the phosphorus <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">The element phosphorus (P) controls growth in many ecosystems as the limiting nutrient, where it is broadly considered to reside as pentavalent P in phosphate minerals and organic esters. Exceptions to pentavalent P include phosphine-PH3-a trace atmospheric gas, and phosphite and hypophosphite, P anions that have been detected recently in lightning strikes, eutrophic lakes, geothermal springs, and termite hindguts. Reduced oxidation state P compounds include the phosphonates, characterized by C-P bonds, which bear up to 25% of total organic dissolved phosphorus. Reduced P compounds have been considered to be rare; however, the microbial ability to use reduced P compounds as sole P sources is ubiquitous. Here we show that between 10% and 20% of dissolved P bears a redox state of less than +5 in water samples from central Florida, on average, with some samples bearing almost as much reduced P as phosphate. If the quantity of reduced P observed in the water samples from Florida studied here is broadly characteristic of similar environments on the global scale, it accounts well for the concentration of atmospheric phosphine and provides a rationale for the ubiquity of phosphite utilization genes in nature. Phosphine is generated at a quantity consistent with thermodynamic equilibrium established by the disproportionation reaction of reduced P species. Comprising 10-20% of the total dissolved P inventory in Florida environments, reduced P compounds could hence be a critical part of the phosphorus <span class="hlt">biogeochemical</span> cycle, and in turn may impact global carbon cycling and methanogenesis. PMID:25313061</p> <div class="credits"> <p class="dwt_author">Pasek, Matthew A; Sampson, Jacqueline M; Atlas, Zachary</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-10-28</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://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. PMID:19623244</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 " 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://adsabs.harvard.edu/abs/2012EOSTr..93S.200B"> <span id="translatedtitle">Measuring <span class="hlt">biogeochemical</span> responses to pulses of water</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">Hydrologic pulses, temporary increases in water inputs such as bouts of precipitation, can affect <span class="hlt">biogeochemical</span> processes in ecosystems by providing water and nutrient resources. However, ecosystem responses to the water vary. Harms and Grimm conducted experiments to determine how hydrologic pulses and existing moisture conditions interact to affect the biogeochemistry of desert floodplains. During dry and monsoon seasons at their study site in the floodplains of the San Pedro River in Arizona, the researchers experimentally added pulses of water and then measured emissions of several trace gases that are indicators of biological processes. They found that the size of the added hydrologic pulse strongly interacted with existing soil moisture conditions in determining emissions of some trace gases. For instance, following dry conditions, pulses of water stimulated carbon dioxide, methane, and nitric oxide emissions, with larger water pulses stimulating more emissions. However, when soil was already wet, the addition of water pulses had less effect on the emission of these gases. (Journal of Geophysical Research-Biogeosciences, doi:10.1029/2011JG001775, 2012)</p> <div class="credits"> <p class="dwt_author">Balcerak, Ernie</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">125</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://rocky.umeoce.maine.edu/docu/JES-Liu-Chai-JMS-2008.pdf"> <span id="translatedtitle">Seasonal and interannual variation of physical and biological processes during 1994–2001 in the Sea of Japan\\/East Sea: A three-dimensional physical–<span class="hlt">biogeochemical</span> 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">A Pacific basin-wide physical–<span class="hlt">biogeochemical</span> model has been used to investigate the seasonal and interannual variation of physical and biological fields with analyses focusing on the Sea of Japan\\/East Sea (JES). The physical model is based on the Regional Ocean Model System (ROMS), and the <span class="hlt">biogeochemical</span> model is based on the Carbon, Si(OH)4, Nitrogen Ecosystem (CoSiNE) model. The <span class="hlt">coupled</span> ROMS–CoSiNE model</p> <div class="credits"> <p class="dwt_author">Guimei Liu; Fei Chai</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">126</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">127</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 " 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/2006CG.....32...64F"> <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://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</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 equilibria and kinetic rates (i.e., they are not defined in the format of the standardized database) are interpreted by the Maple V (Waterloo 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 governing equations, user-specified equilibrium expressions and rate laws. Matrix diagonalization eliminates the need to conceptualize the system of reactions as a tableau, which comprises a list of components, species, the stoichiometric matrix, and the formation equilibrium constant vector that forms the species from components ( Morel and Hering, 1993), 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, Gour-Tsyh</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">129</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/23744573"> <span id="translatedtitle">The impacts of climate change and human activities on <span class="hlt">biogeochemical</span> cycles on the Qinghai-Tibetan Plateau.</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">With a pace of about twice the observed rate of global warming, the temperature on the Qinghai-Tibetan Plateau (Earth's 'third pole') has increased by 0.2 °C per decade over the past 50 years, which results in significant permafrost thawing and glacier retreat. Our review suggested that warming enhanced net primary production and soil respiration, decreased methane (CH(4)) emissions from wetlands and increased CH(4) consumption of meadows, but might increase CH(4) emissions from lakes. Warming-induced permafrost thawing and glaciers melting would also result in substantial emission of old carbon dioxide (CO(2)) and CH(4). Nitrous oxide (N(2)O) emission was not stimulated by warming itself, but might be slightly enhanced by wetting. However, there are many uncertainties in such <span class="hlt">biogeochemical</span> cycles under climate change. Human activities (e.g. grazing, land cover changes) further modified the <span class="hlt">biogeochemical</span> cycles and amplified such uncertainties on the plateau. If the projected warming and wetting continues, the future <span class="hlt">biogeochemical</span> cycles will be more complicated. So facing research in this field is an ongoing challenge of integrating field observations with process-based ecosystem models to predict the impacts of future climate change and human activities at various temporal and spatial scales. To reduce the uncertainties and to improve the precision of the predictions of the impacts of climate change and human activities on <span class="hlt">biogeochemical</span> cycles, efforts should focus on conducting more field observation studies, integrating data within improved models, and developing new knowledge about <span class="hlt">coupling</span> among carbon, nitrogen, and phosphorus <span class="hlt">biogeochemical</span> cycles as well as about the role of microbes in these cycles. PMID:23744573</p> <div class="credits"> <p class="dwt_author">Chen, Huai; Zhu, Qiuan; Peng, Changhui; Wu, Ning; Wang, Yanfen; Fang, Xiuqing; Gao, Yongheng; Zhu, Dan; Yang, Gang; Tian, Jianqing; Kang, Xiaoming; Piao, Shilong; Ouyang, Hua; Xiang, Wenhua; Luo, Zhibin; Jiang, Hong; Song, Xingzhang; Zhang, Yao; Yu, Guirui; Zhao, Xinquan; Gong, Peng; Yao, Tandong; Wu, Jianghua</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-10-01</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://academic.research.microsoft.com/Publication/5441537"> <span id="translatedtitle">A singular evolutive interpolated Kalman filter for efficient data assimilation in a 3-D complex physical–<span class="hlt">biogeochemical</span> model of the Cretan Sea</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 singular evolutive interpolated Kalman (SEIK) filter is used to assimilate pseudo-observations via twin simulation experiments in a complex three-dimensional <span class="hlt">coupled</span> physical–<span class="hlt">biogeochemical</span> model of the Cretan Sea. The simulation system comprises two on-line <span class="hlt">coupled</span> sub-models: the three-dimensional Princeton Model and the European Regional Seas Ecosystem Model (ERSEM). In the SEIK filter, the estimation error is represented by an ensemble of</p> <div class="credits"> <p class="dwt_author">G. Triantafyllou; I. Hoteitsupbsu; G. Petihakis</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">131</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/1130678"> <span id="translatedtitle">A Generic <span class="hlt">Biogeochemical</span> Module for Earth System Models: Next Generation <span class="hlt">BioGeoChemical</span> Module (NGBGC), Version 1.0</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">Physical and <span class="hlt">biogeochemical</span> processes regulate soil carbon dynamics and CO2 flux to and from atmosphere, influencing global climate changes. Integration of these processes into earth system models (e.g., community land models (CLM)), however, currently faces three major challenges: 1) extensive efforts are required to modify modeling structures and to rewrite computer programs to incorporate new or updated processes as new knowledge is being generated, 2) computational cost is prohibitively expensive to simulate <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 possible. 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, Yilin; Huang, Maoyi; Liu, Chongxuan; Li, Hongyi; Leung, Lai-Yung R.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-11-13</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://adsabs.harvard.edu/abs/2014JSR....93...57F"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> drivers of phosphatase activity in salt marsh 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">Although nitrogen has become a major concern for wetlands scientists dealing with eutrophication problems, phosphorous represents another key element, and consequently its <span class="hlt">biogeochemical</span> cycling has a crucial role in eutrophication processes. Microbial communities are a central component in trophic dynamics and <span class="hlt">biogeochemical</span> processes on coastal systems, since most of the processes in sediments are microbial-mediated due to enzymatic action, including the mineralization of organic phosphorus carried out by acid phosphatase activity. In the present work, the authors investigate the <span class="hlt">biogeochemical</span> sediment drivers that control phosphatase activities. Authors also aim to assess <span class="hlt">biogeochemical</span> factors' influence on the enzyme-mediated phosphorous cycling processes in salt marshes. Plant rhizosediments and bare sediments were collected and <span class="hlt">biogeochemical</span> features, including phosphatase activities, inorganic and organic phosphorus contents, humic acids content and pH, were assessed. Acid phosphatase was found to give the highest contribution for total phosphatase activity among the three pH-isoforms present in salt marsh sediments, favored by acid pH in colonized sediments. Humic acids also appear to have an important role inhibiting phosphatase activity. A clear relation of phosphatase activity and inorganic phosphorous was also found. The data presented reinforces the role of phosphatase in phosphorous cycling.</p> <div class="credits"> <p class="dwt_author">Freitas, Joana; Duarte, Bernardo; Caçador, Isabel</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-10-01</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/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">134</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">135</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 " 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://adsabs.harvard.edu/abs/2010AGUFM.B24B..04P"> <span id="translatedtitle">A dynamical system view of rainfall-pulse propagation through <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">The episodic nature of water availability in semiarid ecosystems has significant consequences on belowground carbon and nutrient cycling with important repercussions on plant growth. Pulsed water events directly control belowground processes through soil wet-dry cycles. Rapid soil microbial response to incident moisture availability results in almost instantaneous C and N mineralization as well as in nitrate leaching events. The magnitude of the effect of water pulses on carbon and nutrient pools depends on the joint distribution of rainfall inputs (timing and amounts) and resource and soil-organism availability. We present a theoretical framework based on stochastically forced dynamical systems to analyze the propagation of these intermittent hydrologic inputs through the various compartments of the soil <span class="hlt">biogeochemical</span> cycles. In particular, we <span class="hlt">couple</span> a stochastic soil moisture model with a simple soil <span class="hlt">biogeochemical</span> cycling model where the water-stress response of microbial biomass is calibrated based on an extensive meta-analysis of literature data. We discuss the mechanisms responsible for their amplification, retardation or dampening and their eco-hydrological consequences.</p> <div class="credits"> <p class="dwt_author">Porporato, A. M.; Manzoni, S.; Austin, A.; Schimel, J.</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">137</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/2014EGUGA..1613183H"> <span id="translatedtitle">Modelling <span class="hlt">biogeochemical</span> tracer transport in sea ice due to gravity drainage</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">Sea ice is a porous material, formed of an evolving array of solid ice crystals bathed in liquid brine. The liquid-filled pore space provides a habitat for life within the ice, and, when the ice is permeable, provides a pathway for exchange of gases and other chemicals between the ice, ocean, and atmosphere. This <span class="hlt">coupling</span> between the physical, chemical, and biological evolution of sea ice has poorly constrained implications for <span class="hlt">biogeochemical</span> processes, such as the impact of sea ice on the carbon cycle. During winter ice growth, so-called gravity drainage drives a convective exchange of brine between the ocean and the porous interior of sea ice. Here, we use two-dimensional mushy-layer simulations of convective flow to provide insight into the resulting transport of passive <span class="hlt">biogeochemical</span> tracers through the ice. We quantify the chemical concentration in the liquid during periods of quasi-steady growth rate, and determine a scaling law for the total chemical tracer fluxes through the region of active convection inside the ice. Chemical concentrations show spatial heterogeneity, and our results predict enhanced chemical concentrations in the pore space near to brine channels. These results may provide useful insight for interpreting studies of sea-ice biogeochemistry, and offer a framework to develop models of physical, chemical, and biological interactions.</p> <div class="credits"> <p class="dwt_author">Hitchen, Joseph; Wells, Andrew</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</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://adsabs.harvard.edu/abs/2012EGUGA..1411461M"> <span id="translatedtitle">Modeling evapotranspiration based on plant hydraulic theory can predict spatial variability across an elevation gradient and link to <span class="hlt">biogeochemical</span> fluxes</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 woody plant systems transpiration is often the dominant component of total evapotranspiration, and so it is key to understanding water and energy cycles. Moreover, transpiration is tightly <span class="hlt">coupled</span> to carbon and nutrient fluxes, and so it is also vital to understanding spatial variability of <span class="hlt">biogeochemical</span> fluxes. However, the spatial variability of transpiration and its links to <span class="hlt">biogeochemical</span> fluxes, within- and among-ecosystems, has been a challenge to constrain because of complex feedbacks between physical and biological controls. Plant hydraulics provides an emerging theory with the rigor needed to develop testable hypotheses and build useful models for scaling these <span class="hlt">coupled</span> fluxes from individual plants to regional scales. This theory predicts that vegetative controls over water, energy, carbon, and nutrient fluxes can be determined from the limitation of plant water transport through the soil-xylem-stomata pathway. Limits to plant water transport can be predicted from measurable plant structure and function (e.g., vulnerability to cavitation). We present a next-generation <span class="hlt">coupled</span> transpiration-biogeochemistry model based on this emerging theory. The model, TREEScav, is capable of predicting transpiration, along with carbon and nutrient flows, constrained by plant structure and function. The model incorporates tightly <span class="hlt">coupled</span> mechanisms of the demand and supply of water through the soil-xylem-stomata system, with the feedbacks to photosynthesis and utilizable carbohydrates. The model is evaluated by testing it against transpiration and carbon flux data along an elevation gradient of woody plants comprising sagebrush steppe, mid-elevation lodgepole pine forests, and subalpine spruce/fir forests in the Rocky Mountains. The model accurately predicts transpiration and carbon fluxes as measured from gas exchange, sap flux, and eddy covariance towers. The results of this work demonstrate that credible spatial predictions of transpiration and related <span class="hlt">biogeochemical</span> fluxes will be possible at regional scales using relatively easily obtained vegetation structural and functional information.</p> <div class="credits"> <p class="dwt_author">Mackay, D. S.; Frank, J.; Reed, D.; Whitehouse, F.; Ewers, B. E.; Pendall, E.; Massman, W. J.; Sperry, J. S.</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">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/2007AGUFM.B43E1649B"> <span id="translatedtitle">Vesicomyid Clams Alter <span class="hlt">Biogeochemical</span> Processes at Pacific Methane Seeps</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 exists a close relationship between fluid flow, biogeochemistry, and biota in seep sediments. Upwelling of methane and sulfide-rich fluids supports abundant macrofauna species harboring thiotrophic or methanotrophic symbionts. Variations in fluid flow, thus supply of methane and sulfide, are considered key factors controlling benthic communities. Vesicomyid clams harbor thiotrophic symbionts in their gills, which are supplied with oxygen from the surrounding water and hydrogen sulfide from the sediment. The clams are capable of extending their foot into the sediment to tap sulfide sources in deeper layers, consequently affecting water-sediment solute exchange. Because seep fluids are generally depleted in sulfate compared to seawater, this bioturbation activity may enhance the supply of sulfate to otherwise sulfate-limited sediments, thus boosting microbial activity of sulfate reduction (SR) <span class="hlt">coupled</span> to anaerobic oxidation of methane (AOM). The goal of this study was to investigate the activity of three species of vesicomyid clams ( Calyptogena pacifica, C. kilmeri, C. gigas) from three methane seep habitats (Eel River Basin, Hydrate Ridge, Monterey Bay Canyon) and to evaluate its effect on <span class="hlt">biogeochemical</span> processes. Sediment cores and clams were collected using the submersible Alvin or the ROV Jason, during three cruises with the R/V Atlantis in July and October 2006 and July 2007 (AT 15-7, AT 15-11, and AT 15-20). We performed high-resolution measurements of geochemical gradients in intact sediment cores using microsensors (O2, H2S, pH, redox potential). The cores were then sliced (1 cm intervals) for detailed chemical and microbiological analyses. Parallel cores were used to determine microbial activity (AOM, SR) with radioactive tracers. For detailed laboratory investigations, clams were kept in narrow aquaria (15 cm x 20 cm x 5 cm) in the ship's cold room. The front of the aquaria was perforated with holes at 1 cm resolution. These silicone-filled holes served as sampling ports or for direct microsensor measurements. Vertical and horizontal microprofiles were measured, pore water samples were extracted, and small sediment cores were taken along the length of the aquaria for microbial rate measurements and chemical and microbiological analyses. We documented different bioturbation activity for the three species of vesicomyid clam that related to distinct geochemical gradients and differences in microbial activity. Sulfate reduction, thus sulfide production, was significantly enhanced in the presence of clams compared to the control.</p> <div class="credits"> <p class="dwt_author">Bertics, V. J.; Treude, T.; Ziebis, W.</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">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/2012AGUFMEP42D..06V"> <span id="translatedtitle">Developing <span class="hlt">biogeochemical</span> tracers of apatite weathering by ectomycorrhizal fungi</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">Chronic acid deposition has depleted calcium (Ca) from many New England forest soils, and intensive harvesting may reduce phosphorus (P) available to future rotations. Thin glacial till soils contain trace amounts of apatite, a primary calcium phosphate mineral, which may be an important long-term source of both P and Ca to ecosystems. The extent to which ECM fungi enhance the weathering rate of primary minerals in soil which contain growth-limiting nutrients remains poorly quantified, in part due to <span class="hlt">biogeochemical</span> tracers which are subsequently masked by within-plant fractionation. Rare earth elements (REEs) and Pb isotope ratios show some potential for revealing differences in soil apatite weathering rates across forest stands and silvicultural treatments. To test the utility of these tracers, we grew birch seedlings semi-hydroponically under controlled P-limited conditions, supplemented with mesh bags containing granite chips. Our experimental design included nonmycorrhizal (NM) as well as ectomycorrhizal cultures (Cortinarius or Leccinum). Resulting mycorrhizal roots and leachates of granite chips were analyzed for these tracers. REE concentrations in roots were greatly elevated in treatments with granite relative to those without granite, demonstrating uptake of apatite weathering products. Roots with different mycorrhizal fungi accumulated similar concentrations of REEs and were generally elevated compared to the NM cultures. Ammonium chloride leaches of granite chips grown in contact with mycorrhizal hyphae show elevated REE concentrations and significantly radiogenic Pb isotope signatures relative to bulk rock, also supporting enhanced apatite dissolution. Our results in culture are consistent with data from field-collected sporocarps from hardwood stands in the Bartlett Experimental Forest in New Hampshire, in which Cortinarius sporocarp Pb isotope ratios were more radiogenic than those of other ectomycorrhizal sporocarps. Taken together, the experimental and field results imply that the <span class="hlt">coupled</span> approach of REE and Pb isotopic values afford a means to quantify the degree to which primary mineral weathering inputs are contributing to ecosystem nutrient budgets and potentially the role of different types of ECM fungi in the weathering process.</p> <div class="credits"> <p class="dwt_author">Vadeboncoeur, M. A.; Bryce, J. G.; Hobbie, E. A.; Meana-Prado, M. F.; Blichert-Toft, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-12-01</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_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 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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_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://escholarship.org/uc/item/6c01g23r?query=(media+AND+dependency)"> <span id="translatedtitle">Subsurface <span class="hlt">Biogeochemical</span> Research (SBR) Contractor-Grantee Workshop--Abstracts</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">scales in porous media. The scale-dependency of uranyl [U(Dependency of Geochemical and <span class="hlt">Biogeochemical</span> Reaction Rates in Subsurface Porous Mediamedia; (2) investigate the effect of pore- and subpore- scale mass transfer/transport on the apparent rates and the scale-dependency</p> <div class="credits"> <p class="dwt_author">Hazen, Terry C.</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">142</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.bioone.org/perlserv/?request=get-document&doi=10.1641%2F0006-3568%282006%29056%5B0227%3APEEAAO%5D2.0.CO%3B2"> <span id="translatedtitle">Physical Ecosystem Engineers as Agents of <span class="hlt">Biogeochemical</span> Heterogeneity</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 peer-reviewed article form BioScience is about organisms that act as agents of <span class="hlt">biogeochemical</span> heterogeneity. Physical ecosystem engineers are organisms that physically modify the abiotic environment. They can affect <span class="hlt">biogeochemical</span> processing by changing the availability of resources for microbes (e.g., carbon, nutrients) or by changing abiotic conditions affecting microbial process rates (e.g., soil moisture or temperature). Physical ecosystem engineers can therefore create <span class="hlt">biogeochemical</span> heterogeneity in soils and sediments. They do so via general mechanisms influencing the flows of materials (i.e., modification of fluid dynamic properties, fluid pumping, and material transport) or the transfer of heat (i.e., modification of heat transfer properties, direct heat transfer, and convective forcing). The consequences of physical ecosystem engineering for <span class="hlt">biogeochemical</span> processes can be predicted by considering the resources or abiotic conditions that limit or promote a reaction, and the effect of physical ecosystem engineering on these resources or abiotic conditions via the control they exert on material flows and heat transfer.</p> <div class="credits"> <p class="dwt_author">JORGE L. GUTIÃÂÃÂRREZ and CLIVE G. JONES (;)</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-03-01</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.rsmas.miami.edu/groups/biogeochem/Hansell%20pdfs/78%20Hansell.pdf"> <span id="translatedtitle">Introduction to: ``Ecological and <span class="hlt">biogeochemical</span> interactions in the dark ocean''</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">.g., dissolved oxygen concentrations). Slowly occurring processes, which may happen throughout the ocean depthsEditorial Introduction to: ``Ecological and <span class="hlt">biogeochemical</span> interactions in the dark ocean of carbon, is the largest and least explored ecosystem on Earth (Fig. 1). At a time when the ocean</p> <div class="credits"> <p class="dwt_author">Hansell, Dennis</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://www.ag.unr.edu/nowak/NRES%20406/Spring%2011/GustinPresentation.pdf"> <span id="translatedtitle">The role of plants in the Hg <span class="hlt">biogeochemical</span> cycle</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary"><span class="hlt">Biogeochemical</span> Cycle Hg0RGM Hgp Sources Natural: · Soils G th l A ti Z Anthropogenic: · Coal fired power plants W ­ Anthropogenic emission sources and secondary formation by id ti f H 0oxidation of Hg0 · Particulate mercury (Hgp): ­ More common in fine fraction (formation</p> <div class="credits"> <p class="dwt_author">Nowak, Robert 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">145</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.gps.caltech.edu/users/jkirschvink/pdfs/Kopp2008_MagnetofossilReview.pdf"> <span id="translatedtitle">The identification and <span class="hlt">biogeochemical</span> interpretation of fossil magnetotactic bacteria</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">The identification and <span class="hlt">biogeochemical</span> interpretation of fossil magnetotactic bacteria Robert E. Available online 14 August 2007. Abstract Magnetotactic bacteria, which most commonly live within the oxic, specifically magnetite or greigite. The crystals cause the bacteria to orient themselves passively with respect</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">146</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://globalchange.mit.edu/files/document/MITJPSPGC_Reprint_13-10.pdf"> <span id="translatedtitle">Permafrost degradation and methane: low risk of <span class="hlt">biogeochemical</span> climate-</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Permafrost degradation and methane: low risk of <span class="hlt">biogeochemical</span> climate- warming feedback Xiang Gao. 8 (2013) 035014 (7pp) doi:10.1088/1748-9326/8/3/035014 Permafrost degradation and methane: low risk at stacks.iop.org/ERL/8/035014 Abstract Climate change and permafrost thaw have been suggested to increase</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">147</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">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/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">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/2013OcScD..10.1997H"> <span id="translatedtitle">Adapting to life: ocean <span class="hlt">biogeochemical</span> modelling and adaptive remeshing</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 problem in <span class="hlt">biogeochemical</span> modelling of the ocean is that many of the key processes occur intermittently at small scales, such as the sub-mesoscale, that are not well represented in global ocean models. As an example, state-of-the-art models give values of primary production approximately two orders of magnitude lower than those observed in the ocean's oligotrophic gyres, which cover a third of the Earth's surface. This is partly due to their failure to resolve sub-mesoscale phenomena, which play a significant role in nutrient supply. Simply increasing the resolution of the models may be an inefficient computational solution to this problem. An approach based on recent advances in adaptive mesh computational techniques may offer an alternative. Here the first steps in such an approach are described, using the example of a~simple vertical column (quasi 1-D) ocean <span class="hlt">biogeochemical</span> model. We present a novel method of simulating ocean <span class="hlt">biogeochemical</span> behaviour on a vertically adaptive computational mesh, where the mesh changes in response to the <span class="hlt">biogeochemical</span> and physical state of the system throughout the simulation. We show that the model reproduces the general physical and biological behaviour at three ocean stations (India, Papa and Bermuda) as compared to a high-resolution fixed mesh simulation and to observations. The simulations capture both the seasonal and inter-annual variations. The use of an adaptive mesh does not increase the computational error, but reduces the number of mesh elements by a factor of 2-3, so reducing computational overhead. We then show the potential of this method in two case studies where we change the metric used to determine the varying mesh sizes in order to capture the dynamics of chlorophyll at Bermuda and sinking detritus at Papa. We therefore demonstrate adaptive meshes may provide a~suitable numerical technique for simulating seasonal or transient <span class="hlt">biogeochemical</span> behaviour at high spatial resolution whilst minimising computational cost.</p> <div class="credits"> <p class="dwt_author">Hill, J.; Popova, E. E.; Ham, D. A.; Piggott, M. D.; Srokosz, M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-11-01</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/2014OcSci..10..323H"> <span id="translatedtitle">Adapting to life: ocean <span class="hlt">biogeochemical</span> modelling and adaptive remeshing</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 problem in <span class="hlt">biogeochemical</span> modelling of the ocean is that many of the key processes occur intermittently at small scales, such as the sub-mesoscale, that are not well represented in global ocean models. This is partly due to their failure to resolve sub-mesoscale phenomena, which play a significant role in vertical nutrient supply. Simply increasing the resolution of the models may be an inefficient computational solution to this problem. An approach based on recent advances in adaptive mesh computational techniques may offer an alternative. Here the first steps in such an approach are described, using the example of a simple vertical column (quasi-1-D) ocean <span class="hlt">biogeochemical</span> model. We present a novel method of simulating ocean <span class="hlt">biogeochemical</span> behaviour on a vertically adaptive computational mesh, where the mesh changes in response to the <span class="hlt">biogeochemical</span> and physical state of the system throughout the simulation. We show that the model reproduces the general physical and biological behaviour at three ocean stations (India, Papa and Bermuda) as compared to a high-resolution fixed mesh simulation and to observations. The use of an adaptive mesh does not increase the computational error, but reduces the number of mesh elements by a factor of 2-3. Unlike previous work the adaptivity metric used is flexible and we show that capturing the physical behaviour of the model is paramount to achieving a reasonable solution. Adding biological quantities to the adaptivity metric further refines the solution. We then show the potential of this method in two case studies where we change the adaptivity metric used to determine the varying mesh sizes in order to capture the dynamics of chlorophyll at Bermuda and sinking detritus at Papa. We therefore demonstrate that adaptive meshes may provide a suitable numerical technique for simulating seasonal or transient <span class="hlt">biogeochemical</span> behaviour at high vertical resolution whilst minimising the number of elements in the mesh. More work is required to move this to fully 3-D simulations.</p> <div class="credits"> <p class="dwt_author">Hill, J.; Popova, E. E.; Ham, D. A.; Piggott, M. D.; Srokosz, M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</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://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">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/2008Sci...320.1034F"> <span id="translatedtitle">The Microbial Engines That Drive Earth’s <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">Virtually all nonequilibrium electron transfers on Earth are driven by a set of nanobiological machines composed largely of multimeric protein complexes associated with a small number of prosthetic groups. These machines evolved exclusively in microbes early in our planet’s history yet, despite their antiquity, are highly conserved. Hence, although there is enormous genetic diversity in nature, there remains a relatively stable set of core genes coding for the major redox reactions essential for life and <span class="hlt">biogeochemical</span> cycles. These genes created and coevolved with <span class="hlt">biogeochemical</span> cycles and were passed from microbe to microbe primarily by horizontal gene transfer. A major challenge in the coming decades is to understand how these machines evolved, how they work, and the processes that control their activity on both molecular and planetary scales.</p> <div class="credits"> <p class="dwt_author">Falkowski, Paul G.; Fenchel, Tom; Delong, Edward F.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-05-01</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.ncbi.nlm.nih.gov/pubmed/3591164"> <span id="translatedtitle">Bioindicators and accumulators in geobotanical and <span class="hlt">biogeochemical</span> prospecting of metals.</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">Results of geobotanical and <span class="hlt">biogeochemical</span> studies carried out on the known lead-zinc deposits of Zawar Mines and Khetri Copper Deposits, India, are discussed. A wild variety of Impatiens balsamina was found to be the most characteristic species on lead-zinc metal dumps, which can be regarded as a local 'bioindicator' for these metals. A number of 'accumulators' for lead, zinc, copper with high BAC values, as well as some 'excluders' are also discussed. PMID:3591164</p> <div class="credits"> <p class="dwt_author">Aery, N C; Tiagi, Y D</p> <p class="dwt_publisher"></p> <p class="publishDate">1986-01-01</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://adsabs.harvard.edu/abs/2014EGUGA..16.6975P"> <span id="translatedtitle">Inorganic Carbon Cycling and the <span class="hlt">Biogeochemical</span> Processes in Hudson Bay</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">Coastal seas, like Hudson Bay, are <span class="hlt">biogeochemically</span> active areas with high primary productivity. High productivity can be expected to lead to fractionation of 13C/12C creating depletion of 12C isotope of Dissolved Inorganic Carbon (12CDIC) in the surface and enrichment of 12CDIC in deeper waters. The increase of anthropogenic CO2 concentration can have drastic impacts on the <span class="hlt">biogeochemical</span> properties of the ocean. Since the Arctic and coastal seas are primarily sensitive to these changes, assessing the carbon cycle of this area is very important for future studies. We present the carbon cycle and related data from the Arctic Net 2010 Cruise. We investigate and assess the processes governing the carbon cycle over the entire water column of Hudson Bay. We find that the deep waters of Hudson Bay are Pacifically derived and do not interact with Atlantic waters beyond the mouth of the Bay. River input greatly affect the waters of Hudson Bay. Also, the longer residence time of the deep Hudson Bay waters allows the accumulation of products due to various <span class="hlt">biogeochemical</span> and physical processes. These include respiration of organic matter, which causes greater DIC and lower del13C values at depth, and brine formation, which increases salinity, DIC and alkalinity. The eastern side of Hudson is observed to have greater DIC concentrations and is isotopically lighter in del13C than the western side.</p> <div class="credits"> <p class="dwt_author">Pengelly, Leah; Thomas, Helmuth; Burt, William; Papakyriakou, Tim; Miller, Lisa</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</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://adsabs.harvard.edu/abs/2014GBioC..28...71P"> <span id="translatedtitle">Estimating impacts of lichens and bryophytes on 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">Lichens and bryophytes may significantly affect global <span class="hlt">biogeochemical</span> cycles by fixation of nitrogen and biotic enhancement of surface weathering rates. Most of the studies suggesting these effects, however, are either conceptual or rely on upscaling of regional estimates to obtain global numbers. Here we use a different method, based on estimates of net carbon uptake, to quantify the impacts of lichens and bryophytes on <span class="hlt">biogeochemical</span> cycles at the global scale. We focus on three processes, namely, nitrogen fixation, phosphorus uptake, and chemical weathering. Our estimates have the form of potential rates, which means that we quantify the amount of nitrogen and phosphorus needed by the organisms to build up biomass, also accounting for resorption and leaching of nutrients. Subsequently, we use potential phosphorus uptake on bare ground to estimate chemical weathering by the organisms, assuming that they release weathering agents to obtain phosphorus. The predicted requirement for nitrogen ranges from 3.5 to 34 Tgyr-1 and for phosphorus it ranges from 0.46 to 4.6 Tgyr-1. Estimates of chemical weathering are between 0.058 and 1.1 km3 yr-1 of rock. These values seem to have a realistic order of magnitude, and they support the notion that lichens and bryophytes have the potential to play an important role for <span class="hlt">biogeochemical</span> cycles.</p> <div class="credits"> <p class="dwt_author">Porada, Philipp; Weber, Bettina; Elbert, Wolfgang; Pöschl, Ulrich; Kleidon, Axel</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-02-01</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://adsabs.harvard.edu/abs/2013AGUFM.B51B0274L"> <span id="translatedtitle">A Unified Multi-scale Model for Cross-Scale Evaluation and Integration 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://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Mathematical representations of hydrological and <span class="hlt">biogeochemical</span> processes in soil, plant, aquatic, and atmospheric systems vary with scale. Process-rich models are typically used to describe hydrological and <span class="hlt">biogeochemical</span> processes at the pore and small scales, while empirical, correlation approaches are often used at the watershed and regional scales. A major challenge for multi-scale modeling is that water flow, <span class="hlt">biogeochemical</span> processes, and reactive transport are described using different physical laws and/or expressions at the different scales. For example, the flow is governed by the Navier-Stokes equations at the pore-scale in soils, by the Darcy law in soil columns and aquifer, and by the Navier-Stokes equations again in open water bodies (ponds, lake, river) and atmosphere surface layer. This research explores whether the physical laws at the different scales and in different physical domains can be unified to form a unified multi-scale model (UMSM) to systematically investigate the cross-scale, cross-domain behavior of fundamental processes at different scales. This presentation will discuss our research on the concept, mathematical equations, and numerical execution of the UMSM. Three-dimensional, multi-scale hydrological processes at the Disney Wilderness Preservation (DWP) site, Florida will be used as an example for demonstrating the application of the UMSM. In this research, the UMSM was used to simulate hydrological processes in rooting zones at the pore and small scales including water migration in soils under saturated and unsaturated conditions, root-induced hydrological redistribution, and role of rooting zone <span class="hlt">biogeochemical</span> properties (e.g., root exudates and microbial mucilage) on water storage and wetting/draining. The small scale simulation results were used to estimate effective water retention properties in soil columns that were superimposed on the bulk soil water retention properties at the DWP site. The UMSM parameterized from smaller scale simulations were then used to simulate <span class="hlt">coupled</span> flow and moisture migration in soils in saturated and unsaturated zones, surface and groundwater exchange, and surface water flow in streams and lakes at the DWP site under dynamic precipitation conditions. Laboratory measurements of soil hydrological and <span class="hlt">biogeochemical</span> properties are used to parameterize the UMSM at the small scales, and field measurements are used to evaluate the UMSM.</p> <div class="credits"> <p class="dwt_author">Liu, C.; Yang, X.; Bailey, V. L.; Bond-Lamberty, B. P.; Hinkle, C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-01</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://adsabs.harvard.edu/abs/2011AGUFM.H23I..07W"> <span id="translatedtitle">Investigating the Impact of Pore Scale Microenvironments on Contaminant <span class="hlt">Biogeochemical</span> Reactive Transport</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">Microenvironments and transition zones dominate the subsurface <span class="hlt">biogeochemical</span> cycling of key contaminants, with strong effects resulting from the <span class="hlt">coupling</span> of chemical reactions, physical transport and microbiological processes. Understanding the impact of pore-scale environments (e.g. spatial heterogeneity, chemical gradients, and redox potential) is essential for modeling contaminant fate and transport in the subsurface. The driver for <span class="hlt">biogeochemical</span> processes at the pore scale changes from macroscopic advection to microscale diffusion, and this has a significant effect on the retention of soluble, highly mobile contaminants such as U(VI). Here, etched-silicon microfluidic models with defined chemistry, mineralogy, microbiology, and flow regimes are used for the incremental development of complex microenvironments that approach real-world systems. We demonstrate the colonization of such pore spaces by an anaerobic Fe(III)-reducing bacterium, the enzymatic reduction of a bioavailable Fe(III) phase within this environment, and the subsequent effects of both oxidized and reduced Fe phases on uranium biogeochemistry under flow conditions using both X-ray Microprobe (XMP) and X-ray Absorption Spectroscopy (XAS). Precipitated Fe(III) phases within the microfluidic model were most effectively reduced in the presence of an electron shuttle (e.g. AQDS), with Fe(II) ions adsorbing onto mineral precipitates and surfaces. In the absence of Fe, U(VI) was effectively reduced by the microbial population to insoluble U(IV), which was precipitated in discrete regions associated within biomass. In the presence of both oxidized and reduced Fe phases however, differing effects were observed with regards to U behavior; oxidized U(VI) was frequently adsorbed to poorly crystalline Fe(III), and reduced U(IV) associated with more reduced regions of the microscale flow cell. In the future, the flexibility in the design of the microfluidic models, in combination with advanced characterization techniques, will allow us to further probe a range of pore-structures with distinctive physical, chemical and biological properties to provide a better understanding of <span class="hlt">biogeochemical</span> redox processes occurring at the pore scale and their impact on contaminant transport.</p> <div class="credits"> <p class="dwt_author">Wilkins, M. J.; Pearce, C.; Zhang, C.; Heald, S.; Fredrickson, J. K.; Zachara, J. 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">158</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/2014EGUGA..16.5282P"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> mass balances in a turbid tropical reservoir. Field data and modelling 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 turbid tropical Cointzio reservoir, located in the Trans Mexican Volcanic Belt (TMVB), behaves as a warm monomictic water body (area = 6 km2, capacity 66 Mm3, residence time ~ 1 year). It is strategic for the drinking water supply of the city of Morelia, capital of the state of Michoacán, and for downstream irrigation during the dry season. This reservoir is a perfect example of a human-impacted system since its watershed is mainly composed of degraded volcanic soils and is subjected to high erosion processes and agricultural loss. The reservoir is threatened by sediment accumulation and nutrients originating from untreated waters in the upstream watershed. The high content of very fine clay particles and the lack of water treatment plants lead to serious episodes of eutrophication (up to 70 ?g chl. a L-1), high levels of turbidity (Secchi depth < 30 cm) and a long period of anoxia (from May to October). Based on intensive field measurements in 2009 (deposited sediment, benthic chamber, water vertical profiles, reservoir inflow and outflow) we determined suspended sediment (SS), carbon (C), nitrogen (N) and phosphorus (P) mass balances. Watershed SS yields were estimated at 35 t km2 y-1 of which 89-92 % were trapped in the Cointzio reservoir. As a consequence the reservoir has already lost 25 % of its initial storage capacity since its construction in 1940. Nutrient mass balances showed that 50 % and 46 % of incoming P and N were retained by sedimentation, and mainly eliminated through denitrification respectively. Removal of C by 30 % was also observed both by sedimentation and through gas emission. To complete field data analyses we examined the ability of vertical one dimensional (1DV) numerical models (Aquasim <span class="hlt">biogeochemical</span> model <span class="hlt">coupled</span> with k-? mixing model) to reproduce the main <span class="hlt">biogeochemical</span> cycles in the Cointzio reservoir. The model can describe all the mineralization processes both in the water column and in the sediment. The values of the entire mass balance of nutrients and of the mineralization rates (denitrification and aerobic benthic mineralization) calculated from the model fitted well to the field measurements. Furthermore, this analysis indicates that the benthic mineralizations are the dominant processes involved in the nutrients release. This is the first implementation of a <span class="hlt">biogeochemical</span> model applied to a highly productive reservoir in the TMVB in order to estimate nutrients release from sediments. It could be used for scenarios of reduction of eutrophication in the reservoir. This study provides a good example of the behavior of a small tropical reservoir under intense human pressure and it will help stakeholders to adopt appropriate strategies for the management of turbid tropical reservoirs.</p> <div class="credits"> <p class="dwt_author">Phuong Doan, Thuy Kim; Némery, Julien; Gratiot, Nicolas; Schmid, Martin</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</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/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 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://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 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" 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">161</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://etd.lib.umt.edu/theses/available/etd-01052012-145421/"> <span id="translatedtitle">Impacts of mountain pine beetle outbreak on <span class="hlt">biogeochemical</span> cycling in a high elevation whitebark pine ecosystem.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">??Ecological disturbances can significantly impact <span class="hlt">biogeochemical</span> cycles in terrestrial ecosystems, but the effects of the current widespread mountain pine beetle outbreak on ecosystem processes like… (more)</p> <div class="credits"> <p class="dwt_author">Keville, Megan</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">162</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 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/18597848"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> C and N cycles in urban soils.</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 percentage of urban population is projected to increase drastically. In 2030, 50.7 to 86.7% of the total population in Africa and Northern America may live in urban areas, respectively. The effects of the attendant increases in urban land uses on <span class="hlt">biogeochemical</span> C and N cycles are, however, largely unknown. <span class="hlt">Biogeochemical</span> cycles in urban ecosystems are altered directly and indirectly by human activities. Direct effects include changes in the biological, chemical and physical soil properties and processes in urban soils. Indirect effects of urban environments on <span class="hlt">biogeochemical</span> cycles may be attributed to the introductions of exotic plant and animal species and atmospheric deposition of pollutants. Urbanization may also affect the regional and global atmospheric climate by the urban heat island and pollution island effect. On the other hand, urban soils have the potential to store large amounts of soil organic carbon (SOC) and, thus, contribute to mitigating increases in atmospheric CO(2) concentrations. However, the amount of SOC stored in urban soils is highly variable in space and time, and depends among others on soil parent material and land use. The SOC pool in 0.3-m depth may range between 16 and 232 Mg ha(-1), and between 15 and 285 Mg ha(-1) in 1-m depth. Thus, depending on the soil replaced or disturbed, urban soils may have higher or lower SOC pools, but very little is known. This review provides an overview of the <span class="hlt">biogeochemical</span> cycling of C and N in urban soils, with a focus on the effects of urban land use and management on soil organic matter (SOM). In view of the increase in atmospheric CO(2) and reactive N concentrations as a result of urbanization, urban land use planning must also include strategies to sequester C in soil, and also enhance the N sink in urban soils and vegetation. This will strengthen soil ecological functions such as retention of nutrients, hazardous compounds and water, and also improve urban ecosystem services by promoting soil fertility. PMID:18597848</p> <div class="credits"> <p class="dwt_author">Lorenz, Klaus; Lal, Rattan</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">164</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/15894055"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> distinction of methane releases from two Amazon hydroreservoirs.</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> distinction of methane emissions to the atmosphere may essentially rely on the surface area and morphometry of Amazon hydroreservoirs. Tucurui (deep) and Samuel (shallow) reservoirs released in average 13.82+/-22.94 and 71.19+/-107.4 mg CH4 m(-2)d(-1), respectively. delta13C-CH4 values from the sediments to the atmosphere indicate that the deep reservoir has extended methanotrophic layer, oxidizing large quantities of light isotope methane coming from the sediments, while sediment-generated methane can easily evade the shallow reservoir. PMID:15894055</p> <div class="credits"> <p class="dwt_author">Lima, Ivan Bergier Tavares</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">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.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3809095"> <span id="translatedtitle">Enhanced <span class="hlt">biogeochemical</span> cycling and subsequent reduction of hydraulic conductivity associated with soil-layer interfaces in the vadose zone</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"><span class="hlt">Biogeochemical</span> dynamics in the vadose zone are poorly understood due to the transient nature of chemical and hydrologic conditions, but are nonetheless critical to understanding chemical fate and transport. This study explored the effects of a soil layer on linked geochemical, hydrological, and microbiological processes. Three laboratory soil columns were constructed: a homogenized medium-grained sand, a homogenized organic-rich loam, and a sand-over-loam layered column. Upward and downward infiltration of water was evaluated during experiments to simulate rising water table and rainfall events respectively. In-situ collocated probes measured soil water content, matric potential, and Eh while water samples collected from the same locations were analyzed for Br?, Cl?, NO3?, SO42?, NH4+, Fe2+, and total sulfide. Compared to homogenous columns, the presence of a soil layer altered the biogeochemistry and water flow of the system considerably. Enhanced <span class="hlt">biogeochemical</span> cycling was observed in the layered column over the texturally homogeneous soil columns. Enumerations of iron and sulfate reducing bacteria showed 1-2 orders of magnitude greater community numbers in the layered column. Mineral and soil aggregate composites were most abundant near the soil-layer interface; the presence of which, likely contributed to an observed order-of-magnitude decrease in hydraulic conductivity. These findings show that quantifying <span class="hlt">coupled</span> hydrologic-<span class="hlt">biogeochemical</span> processes occurring at small-scale soil interfaces is critical to accurately describing and predicting chemical changes at the larger system scale. Findings also provide justification for considering soil layering in contaminant fate and transport models because of its potential to increase biodegradation and/or slow the rate of transport of contaminants. PMID:22031578</p> <div class="credits"> <p class="dwt_author">Hansen, David J.; McGuire, Jennifer T.; Mohanty, Binayak 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">166</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.H51E0806M"> <span id="translatedtitle">Modeling Sediment-Water interactions and <span class="hlt">Biogeochemical</span> Reactive Contaminant Transport of Mercury Species in Estuarine/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">Sediments play a major role in fate and transport of mercury species in water bodies. Sediment-associated mercury can be released gradually due to leaching (aqueous diffusion <span class="hlt">coupled</span> with potentially kinetically controlled dissociation from solid phases),” or may be re-entrained in the watercolumn as a result of high flows or anthropogenic activities. The former controls chronic concentrations and the latter controls acute concentrations, that each lead to different exposure risks. In addition <span class="hlt">biogeochemical</span> transformations in the bed sediments control both the mobility and speciation (and thus toxicity) of mercury in the ecosystem. Therefore to quantify the fate and transport of mercury in water bodies, various processes ranging from hydrodynamic and sediment transport to <span class="hlt">biogeochemical</span> transformation of contaminants in the sediments need to be considered. Here, an integrated water column-benthic sediment, multi-scale, multi-component, and multiphase <span class="hlt">biogeochemical</span> reactive transport model is presented, with description of both theory and numerical implementation. The model includes four phases: aqueous water column, suspended sediment, aqueous bed porewater, and sediment bed, with associated contaminant transformation and transport within and between phases, as well as sediment resuspension, deposition and burial. The sediment bed domain is modeled using a set of vertical one-dimensional sub-models (“picket fence”) that take into account burial and compaction as well as diffusive-reactive transport of solutes. Reactions include speciation, sorption/desorption, and microbially-mediated multiple terminal-electron accepting processes as kinetically-controlled redox reactions. Applications of this multi-scale modeling strategy to mercury transport and transformations in water bodies in California, is also presented.</p> <div class="credits"> <p class="dwt_author">Massoudieh, A.; Ginn, T. R.; Bombardelli, F. A.; Cabrera, 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">167</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">168</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19940030179&hterms=Earth+System+Models&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3D%2522Earth%2BSystem%2BModels%2522"> <span id="translatedtitle">Global changes in <span class="hlt">biogeochemical</span> cycles in response to human activities</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The main objective of our research was to characterize <span class="hlt">biogeochemical</span> cycles at continental and global scales in both terrestrial and aquatic ecosystems. This characterization applied to both natural ecosystems and those disturbed by human activity. The primary elements of interest were carbon and nitrogen and the analysis sought to quantify standing stocks and dynamic cycling processes. The translocation of major nutrients from the terrestrial landscape to the atmosphere (via trace gases) and to fluvial systems (via leaching, erosional losses, and point source pollution) were of particular importance to this study. Our aim was to develop the first generation of Earth System Models. Our research was organized around the construction and testing of component <span class="hlt">biogeochemical</span> models which treated terrestrial ecosystem processes, aquatic nutrient transport through drainage basins, and trace gas exchanges at the continental and global scale. A suite of three complementary models were defined within this construct. The models were organized to operate at a 1/2 degree latitude by longitude level of spatial resolution and to execute at a monthly time step. This discretization afforded us the opportunity to understand the dynamics of the biosphere down to subregional scales, while simultaneously placing these dynamics into a global context.</p> <div class="credits"> <p class="dwt_author">Moore, Berrien, III; Melillo, Jerry</p> <p class="dwt_publisher"></p> <p class="publishDate">1994-01-01</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.osti.gov/scitech/biblio/20006255"> <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://www.osti.gov/scitech">SciTech Connect</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 CO{sub 2} among its various sinks in the past, for the present, and for projections into the near future is controlled by the interactions of these four elemental cycles within the major environmental domains of the land, atmosphere, coastal oceanic zone, and open ocean. The authors analyze the past, present, and future behavior of the global carbon cycle using the Terrestrial-Ocean-aTmosphere Ecosystem Model (TOTEM), a unique process-based model of the four global <span class="hlt">coupled</span> <span class="hlt">biogeochemical</span> cycles of carbon, nitrogen, phosphorus, and sulfur. They find that during the past 300 yrs, anthropogenic CO{sub 2} was mainly stored in the atmosphere and in the open ocean. Human activities on land caused an enhanced loss of mass from the terrestrial organic matter reservoirs (phytomass and humus) mainly through deforestation and consequently increased humus remineralization, erosion, and transport to the coastal margins by rivers and runoff. Photosynthetic uptake by the terrestrial phytomass was enhanced owing to fertilization by increasing atmospheric CO{sub 2} concentrations and supported by nutrients remineralized from organic matter. TOTEM results indicate that through most of the past 300 yrs, the loss of C from deforestation and other land-use activities was greater than the gain from the enhanced photosynthetic uptake. Since pre-industrial time (since 1700), the net flux of CO{sub 2} from the coastal waters has decreased by 40%, from 0.20 Gt C/yr to 0.12 Gt C/yr. TOTEM analyses of atmospheric CO{sub 2} concentrations for the 21st century were based on the fossil-fuel emission projections of IPCC (business as usual scenario) and of the more restrictive UN 1997 Kyoto Protocol. By the mid-21st century, the projected atmospheric CO{sub 2} concentrations range from about 550 ppmv (TOTEM, based on IPCC projected emissions) to 510 ppmv (IPCC projection) and to 460 ppmv (TOTEM, based on the Kyoto Protocol reduced emissions).</p> <div class="credits"> <p class="dwt_author">Ver, L.M.B.; Mackenzie, F.T.; Lerman, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-07-01</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://adsabs.harvard.edu/abs/2012EGUGA..14.1437Y"> <span id="translatedtitle">Simulation of a Storm Surge Event at the North Sea (Germany) Using a Fully <span class="hlt">Coupled</span> 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">Tidal fluctuation and storm surge events lead to saltwater intrusion into a coastal aquifer. Tidal fluctuation causes dynamic boundary conditions of the seaside boundary, where submerged zones are of Dirichlet-type, and where aerial zones are of Neumann type. In a storm surge event, saltwater will flow on the land surface towards the inland and cover parts of the land surface. Saltwater will eventually infiltrate the unsaturated soil and percolate downwards towards the groundwater table. To simulate that dynamic coastal flow system, a fully integrated approach based on the numerical "HydroGeoSphere" model is being developed, where the coastal zone is treated as a hydraulically <span class="hlt">coupled</span> <span class="hlt">surface-subsurface</span> system. That new approach will allow simulation of: (i) surface flow, (ii) variably saturated, density-dependent groundwater flow, (iii) salt transport in the surface and in the subsurface, and (iv) water and salt interaction between surface and subsurface. In the new approach, tide and storm surge events induce a time variant head that is applied to nodes of the surface domain thus tide or storm surge force will be applied to the system through surface domain. The hydraulic interaction between the surface domain and the subsurface domain simplify the flow and transport boundary conditions caused by tidal fluctuation and storm surge events. This newly proposed approach is the first conceptual model of a fully <span class="hlt">coupled</span> <span class="hlt">surface-subsurface</span> coastal flow domain. It allows simulation of tidal activity and storm surges at a heretofore impossible complexity.</p> <div class="credits"> <p class="dwt_author">Yang, J.; Graf, T.</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">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.lter.uaf.edu/pdf/1507_Yi_McGuire_2010.pdf"> <span id="translatedtitle">A dynamic organic soil <span class="hlt">biogeochemical</span> model for simulating the effects of wildfire on soil environmental</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">A dynamic organic soil <span class="hlt">biogeochemical</span> model for simulating the effects of wildfire on soil environmental conditions and carbon dynamics of black spruce forests Shuhua Yi,1 A. David McGuire,2 Eric, and <span class="hlt">biogeochemical</span> processes affect ecosystem dynamics in boreal forest ecosystems. In this study, we implemented</p> <div class="credits"> <p class="dwt_author">Wagner, Diane</p> <p class="dwt_publisher"></p> <p class="publishDate"></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.esd.ornl.gov/highlights/2008/johnson_%20Highlight_2008.pdf"> <span id="translatedtitle">Long-term Chronic Precipitation Change Did Not Modify <span class="hlt">Biogeochemical</span> Feedbacks in an Upland Oak Forest</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">to terrestrial <span class="hlt">biogeochemical</span> cycling models (e.g., deepg y g ( g , p rooting). 1 Managed by UT (TDE) was established on Walker Branch Watershed, Tennessee, in 1993. Three different throughfallLong-term Chronic Precipitation Change Did Not Modify <span class="hlt">Biogeochemical</span> Feedbacks in an Upland Oak</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">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.springerlink.com/index/r16p532p57447p25.pdf"> <span id="translatedtitle">A hierarchical approach to evaluating the significance of soil biodiversity to <span class="hlt">biogeochemical</span> cycling</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 significance of biodiversity to <span class="hlt">biogeochemical</span> cycling is viewed most directly through the specific <span class="hlt">biogeochemical</span> transformations that organisms perform. Although functional diversity in soils can be great, it is exceeded to a high degree by the richness of soil species. It is generally inferred from this richness that soil systems have a high level of functional redundancy. As such, indices</p> <div class="credits"> <p class="dwt_author">M. H. Beare; D. C. Coleman; D. A. Crossley; P. F. Hendrix; E. P. Odum</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">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=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">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.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4094194"> <span id="translatedtitle">Differential leaflet mortality may influence <span class="hlt">biogeochemical</span> cycling following tropical cyclones</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">Intensity of tropical cyclones is expected to increase in the coming century, and an improved understanding of their influence on <span class="hlt">biogeochemical</span> cycles would benefit ecologists and conservationists. We studied the November 2013 Typhoon Haiyan damage to observe that numerous examples of partial leaf necrosis on intact leaves of trees in the Cycadaceae and Arecaceae families resulted, leaving behind a copious amount of arboreal dead leaf material attached to live leaves. The decay process of this form of arboreal litter has not been previously studied. When compared with decay of ground litter or detached litter suspended in the canopy, we predict the decay process of this form of arboreal litter will include increased photooxidation, leaching, and comminution by detritivorous insects and mites; but decreased catabolism of organic molecules by saprophytic organisms. PMID:25083171</p> <div class="credits"> <p class="dwt_author">Marler, Thomas E; Ferreras, Ulysses</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</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://www.osti.gov/scitech/biblio/6245390"> <span id="translatedtitle">Sensitivity analysis of global terrestrial <span class="hlt">biogeochemical</span> cycling 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">We are developing a global model of terrestrial productivity and <span class="hlt">biogeochemical</span> cycling (TERRA) designed to be a component of an Earth System Model being developed at LLNL. An initial version of TERRA incorporating five state variables has been calibrated to 17 vegetation types. During sensitivity analysis, model parameters were individually varied by 10% and the model was run to steady-state. Total system response was found to be most sensitive to parameters affecting soil moisture which, in turn, affects soil respiration rate. Parameters describing optimum soil moisture for soil respiration rate, field capacity, pore volume, root depth and soil organic matter (SOM) decomposition rate, all exhibited significant sensitivity. These findings underscore the importance of the soil system in descriptions of ecosystems dynamics. Future versions of TERRA will divide the soil profile into a series of horizontal layers and include more detailed descriptions of SOM.</p> <div class="credits"> <p class="dwt_author">Chambers, J.Q.; Kercher, J.R. (Univ. of California, Santa Barbara (United States) Lawrence Livermore National Lab., CA (United States))</p> <p class="dwt_publisher"></p> <p class="publishDate">1993-06-01</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://adsabs.harvard.edu/abs/2013AGUFM.B11B0368M"> <span id="translatedtitle">Applications of synchrotron techniques in <span class="hlt">biogeochemical</span> and geomicrobiological research</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">Synchrotron methods are useful for examining the chemistry, speciation and distribution of elements such as Fe and Mn within environmental samples. Techniques such as x-ray absorption spectroscopy (XAS), x-ray diffraction (XRD), and x-ray fluorescence (XRF) are routinely used at synchrotrons worldwide, by both academic and industrial users. It can be a challenge for potential users to identify where these methods will be useful to them. Here, I will present an overview of techniques available for geomicrobiologists at the Canadian Light Source (CLS). I will provide examples of the use of synchrotron tools in geomicrobiological projects, as well as examples of where CLS scientists have worked with mining companies to use these tools to address challenges in the mining industry. An overview of the CLS Green Mining Program will also be provided; our research group is conducting <span class="hlt">biogeochemical</span> research that contributes to developing sustainable mining practices.</p> <div class="credits"> <p class="dwt_author">McBeth, J. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-01</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://www.ncbi.nlm.nih.gov/pubmed/25083171"> <span id="translatedtitle">Differential leaflet mortality may influence <span class="hlt">biogeochemical</span> cycling following tropical cyclones.</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">Intensity of tropical cyclones is expected to increase in the coming century, and an improved understanding of their influence on <span class="hlt">biogeochemical</span> cycles would benefit ecologists and conservationists. We studied the November 2013 Typhoon Haiyan damage to observe that numerous examples of partial leaf necrosis on intact leaves of trees in the Cycadaceae and Arecaceae families resulted, leaving behind a copious amount of arboreal dead leaf material attached to live leaves. The decay process of this form of arboreal litter has not been previously studied. When compared with decay of ground litter or detached litter suspended in the canopy, we predict the decay process of this form of arboreal litter will include increased photooxidation, leaching, and comminution by detritivorous insects and mites; but decreased catabolism of organic molecules by saprophytic organisms. PMID:25083171</p> <div class="credits"> <p class="dwt_author">Marler, Thomas E; Ferreras, Ulysses</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</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/2014BGD....1110513D"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> implications of comparative growth rates of Emiliania huxleyi and Coccolithus species</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">Coccolithophores are a diverse and <span class="hlt">biogeochemically</span> important group of phytoplankton in terms of the production and export of calcite, yet the comparative physiology and ecology of species other than the ubiquitous Emiliania huxleyi is poorly understood. Despite assumptions that Emiliania huxleyi is a fast growing species, we found it had comparable growth rates (0.16-0.85 d-1) with strains of Coccolithus pelagicus and Coccolithus braarudii when grown under identical temperature and light conditions. A recently isolated Arctic strain of C. pelagicus (RCC4092) exhibited only a 12% slower growth rate, on average, than a recently isolated Arctic strain of E. huxleyi (RCC3533), over a temperature range of 6-12 °C. Established temperate strains of E. huxleyi and C. braarudii (RCC1228 and RCC1198) exhibited a slightly larger difference in growth rates, with E. huxleyi growing 28% faster on average than C. braarudii over a temperature range of 12-19 °C. <span class="hlt">Coupled</span> with the 30-80 times higher cellular calcite content of C. pelagicus and C. braarudii compared to E. huxleyi, this suggests that Coccolithus species could be major calcite producers in mixed populations. The relative abundance of coccolithophore species is key for determining which species will dominate calcite production in mixed communities growing at similar rates. Field samples from the North Atlantic show that C. pelagicus is in a high enough relative abundance in 69% of samples collected in the spring and summer of 2010 to be a larger source of calcite production than E. huxleyi.</p> <div class="credits"> <p class="dwt_author">Daniels, C. J.; Sheward, R. M.; Poulton, A. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-07-01</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://adsabs.harvard.edu/abs/2012AGUFM.B43H0538P"> <span id="translatedtitle">Incorporating urban infrastructure into <span class="hlt">biogeochemical</span> assessment of urban tropical streams in Puerto Rico</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 development alters catchment hydrology and the subsequent delivery of solutes to streams and downstream ecosystems. The extent to which the impacts of urban development vary by biome is uncertain, and the impacts are poorly understood in tropical catchments. In a previous study (Helton et al. 2011), downstream changes in nitrogen (N) in the highly urbanized Rio Piedras catchment in Puerto Rico (42% urban land use) were found to be greater than predicted (23%) in a simple river network model that uses land use and in-stream N loss to predict spatial patterns in N fluxes. Here we evaluate the deviations of the <span class="hlt">biogeochemical</span> patterns in this urban catchment through synoptic sampling of hydrology and water quality collected annually at approximately 40 sites over 8 years (2004 - 2011) <span class="hlt">coupled</span> with spatial analysis of the urban infrastructure in the catchment. Results indicate that urbanization leads to an increase in most solute concentrations measured (DOC, DON, NH4, PO4), but not NO3. The lack of urban influence on NO3 is inconsistent with findings in other biomes, but consistent with previous studies in Puerto Rico. Conservative tracers (Cl and F) indicate that the source of the organic solutes increase is likely from sewage inputs. We suggest that stream nutrient cycling models that assume topographically driven flow accumulation need to be changed in urban catchments to include different delivery mechanisms such as sewer and water lines, especially in tropical regions where this infrastructure is often inadequate.</p> <div class="credits"> <p class="dwt_author">Potter, J.; McDowell, W. H.; Daley, M. L.; Helton, A. M.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-12-01</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_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> <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">181</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=272491"> <span id="translatedtitle">A <span class="hlt">coupled</span> hydrologic and <span class="hlt">biogeochemical</span> model for assessing watershed responses to climate and 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">This seminar for Oregon State University’s Water Resources Graduate Program will describe the use of a spatially-distributed ecohydrological model, VELMA, for quantifying how alternative land use and climate scenarios affect tradeoffs among important ecosystem services. Sp...</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">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/2014GMDD....7.6327H"> <span id="translatedtitle">Mechanistic site-based emulation of a global ocean <span class="hlt">biogeochemical</span> model for parametric analysis and calibration</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> ocean circulation models used to investigate the role of plankton ecosystems in global change rely on adjustable parameters to compensate for missing biological complexity. In principle, optimal parameter values can be estimated by fitting models to observational data, including satellite ocean colour products such as chlorophyll that achieve good spatial and temporal coverage of the surface ocean. However, comprehensive parametric analyses require large ensemble experiments that are computationally infeasible with global 3-D simulations. Site-based simulations provide an efficient alternative but can only be used to make reliable inferences about global model performance if robust quantitative descriptions of their relationships with the corresponding 3-D simulations can be established. The feasibility of establishing such a relationship is investigated for an intermediate complexity biogeochemistry model (MEDUSA) <span class="hlt">coupled</span> with a widely-used global ocean model (NEMO). A site-based mechanistic emulator is constructed for surface chlorophyll output from this target model as a function of model parameters. The emulator comprises an array of 1-D simulators and a statistical quantification of the uncertainty in their predictions. The unknown parameter-dependent <span class="hlt">biogeochemical</span> environment, in terms of initial tracer concentrations and lateral flux information required by the simulators, is a significant source of uncertainty. It is approximated by a mean environment derived from a small ensemble of 3-D simulations representing variability of the target model behaviour over the parameter space of interest. The performance of two alternative uncertainty quantification schemes is examined: a direct method based on comparisons between simulator output and a sample of known target model "truths" and an indirect method that is only partially reliant on knowledge of target model output. In general, chlorophyll records at a representative array of oceanic sites are well reproduced. The use of lateral flux information reduces the 1-D simulator error considerably, consistent with a major influence of advection at some sites. Emulator robustness is assessed by comparing actual error distributions with those predicted. With the direct uncertainty quantification scheme, the emulator is reasonably robust over all sites. The indirect uncertainty quantification scheme is less reliable at some sites but scope for improving its performance is identified. The results demonstrate the strong potential of the emulation approach to improve the effectiveness of site-based methods. This represents important progress towards establishing a robust site-based capability that will allow comprehensive parametric analyses to be achieved for improving global models and quantifying uncertainty in their predictions.</p> <div class="credits"> <p class="dwt_author">Hemmings, J. C. P.; Challenor, P. G.; Yool, A.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-09-01</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://adsabs.harvard.edu/abs/2008JMS....73..338C"> <span id="translatedtitle">Past, present and future state of the <span class="hlt">biogeochemical</span> Si cycle in the Baltic 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 Baltic Sea is one of many aquatic ecosystems that show long-term declines in dissolved silicate (DSi) concentrations due to anthropogenic alteration of the <span class="hlt">biogeochemical</span> Si cycle. Reductions in DSi in aquatic ecosystems have been <span class="hlt">coupled</span> to hydrological regulation reducing inputs, but also with eutrophication, although the relative significance of both processes remains unknown for the observed reductions in DSi concentrations. Here we combine present and historical data on water column DSi concentrations, together with estimates of present river DSi loads to the Baltic, the load prior to damming together with estimates of the long-term accumulation of BSi in sediments. In addition, a model has been used to evaluate the past, present and future state of the <span class="hlt">biogeochemical</span> Si cycle in the Baltic Sea. The present day DSi load to the Baltic Sea is 855 ktons y - 1 . Hydrological regulation and eutrophication of inland waters can account for a reduction of 420 ktons y - 1 less riverine DSi entering the Baltic Sea today. Using published data on basin-wide accumulation rates we estimate that 1074 ktons y - 1 of biogenic silica (BSi) is accumulating in the sediments, which is 36% higher than earlier estimates from the literature (791 ktons y - 1 ). The difference is largely due to the high reported sedimentation rates in the Bothnian Sea and the Bothnian Bay. Using river DSi loads and estimated BSi accumulation, our model was not able to estimate water column DSi concentrations as burial estimates exceeded DSi inputs. The model was then used to estimate the BSi burial from measured DSi concentrations and DSi load. The model estimate for the total burial of BSi in all three basins was 620 ktons y - 1 , 74% less than estimated from sedimentation rates and sediment BSi concentrations. The model predicted 20% less BSi accumulation in the Baltic Proper and 10% less in the Bothnian Bay than estimated, but with significantly less BSi accumulation in the Bothnian Sea by a factor of 3. The model suggests there is an overestimation of basin-wide sedimentation rates in the Bothnian Bay and the Bothnian Sea. In the Baltic Proper, modelling shows that historical DSi concentrations were 2.6 times higher at the turn of the last century (ca. 1900) than at present. Although the DSi decrease has leveled out and at present there are only restricted areas of the Baltic Sea with limiting DSi concentrations, further declines in DSi concentrations will lead to widespread DSi limitation of diatoms with severe implications for the food web.</p> <div class="credits"> <p class="dwt_author">Conley, Daniel J.; Humborg, Christoph; Smedberg, Erik; Rahm, Lars; Papush, Liana; Danielsson, Åsa; Clarke, Annemarie; Pastuszak, Marianna; Aigars, Juris; Ciuffa, Daniele; Mörth, Carl-Magnus</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-10-01</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/2011AGUFM.H43J1366K"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> and hydrological controls on fate and distribution of trace metals in oiled Gulf salt marshes</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">On April 20, 2010, the drilling rig Deepwater Horizon exploded in the Gulf of Mexico, resulting in the release of approximately 5 million barrels of crude oil into the environment. Oil and its associated trace metals have been demonstrated to have a detrimental effect on coastal wetland ecosystems. Wetlands are particularly susceptible to oil contamination because they are composed largely of fine-grained sediments, which have a high capacity to adsorb organic matter and metals. The <span class="hlt">biogeochemical</span> cycling of trace metals can be strongly influenced by microbial activity, specifically those of sulfate- and iron-reducing bacteria. Microbial activity may be enhanced by an increase in amounts of organic matter such as oil. This research incorporates an assessment of levels of trace metals and associated <span class="hlt">biogeochemical</span> changes from ten coastal marshes in Alabama, Mississippi, and Louisiana. These sampling sites range in their pollution levels from pristine to highly contaminated. A total digestion analysis of wetland sediments shows higher concentrations of certain trace metals (e.g., Ni, Cu, Pb, Zn, Sr, Co, V, Ba, Hg, As) in heavily-oiled areas compared to less-affected and pristine sites. Due to chemical complexation among organic compounds and metals, crude oils often contain elevated levels (up to hundreds of mg/kg) of trace metals At the heavily-oiled Louisiana sites (e.g., Bay Jimmy, Bayou Dulac, Bay Batiste), elevated levels of metals and total organic carbon have been found in sediments down to depths of 30 cm. Clearly the contamination is not limited to shallow sediments and oil, along with various associated metals, may be invading into deeper (pre-industrial) portions of the marsh sediments. Pore-waters extracted from contaminated sediments are characterized by very high levels of reduced sulfur (up to 80 mg/kg), in contrast to fairly low ferrous iron concentrations (<0.02 mg/kg). The influx of oil into the wetlands might provide the initial substrate and carbon source for stimulating sulfate-reducing bacteria. The high sulfur levels, <span class="hlt">coupled</span> with the low levels of iron, indicate that iron-reducing bacteria are outcompeted by sulfate reducers in oiled salt marshes. Moreover, pore-water pH values show a general increasing trend (ranging from 6.6 to 8.0) with depth, possibly reflecting the combined effects of bacterial sulfate reduction and saltwater intrusion at depth. Despite high levels of trace metals in bulk sediments, concentrations of trace metals dissolved in pore-waters are generally low. It is very likely that high organic matter content and bacterially-mediated sulfate reduction promote metal retention through the formation of sulfide solids. Framboidal pyrites, as well as other sulfides, have been identified, and are currently undergoing XRD, SEM, and EDAX analyses. Continued research is needed to monitor possible re-mobilization of trace metals in changing redox and <span class="hlt">biogeochemical</span> conditions.</p> <div class="credits"> <p class="dwt_author">Keevan, J.; Natter, M.; Lee, M.; Keimowitz, A.; Okeke, B.; Savrda, C.; Saunders, 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">185</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..185P"> <span id="translatedtitle">A Time Dependent Ecosystem Operational Tool For Pagasitikos Gulf. Part-ii. Simulation of <span class="hlt">Biogeochemical</span> Variables In Space and Time</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 system of Pagasitikos is highly influenced both by anthropogenic activities (in- flow of nutrients at the north and west parts) as well as by water exchange between the gulf and the Aegean Sea at its south part (Trikeri channel) resulting in the devel- opment of sub-areas within the gulf. Thus the inner part is characterised by eutrophic conditions with sporadic formation of harmful algal blooms while the central part acts as a buffer with mesotrophic characteristics influenced by the oligotrophic outer area. The aim of this study is to investigate the interactions between the physical and <span class="hlt">biogeochemical</span> systems in the Pagasitikos gulf by <span class="hlt">coupling</span> advanced hydrodynamic and ecological models. The simulation system comprises of two on-line <span class="hlt">coupled</span> sub- models: a three-dimensional hydrodynamic model based on Princeton Ocean Model (POM) and an ecological model adapted from the European Regional Seas Ecosystem Model (ERSEM) for the particular ecosystem. For the tuning and initialisation of the ecosystem parameters the one-dimensional version of the <span class="hlt">biogeochemical</span> model is used. After a model spin up period of ten years to reach a quasi steady state, the re- sults from an annual simulation are presented. Emphasis is given to understanding the relationship between physical forcing with the evolution and variability of the ecosys- tem along with other factors affecting the nutrient cycling and primary production. A cost function is used as validation method for the comparison of model results with field data. The estimated annual primary and bacteria production are found to be in the range of the reported values. Simulation results are in good agreement with in-situ data illustrating the role of the physical processes in determining the evolution and variability of the ecosystem as well as pointing out the significance of inputs in the functioning of this sensitive ecosystem. Highlighting thus the potential utility of the model as an operational tool to support environmental management decisions.</p> <div class="credits"> <p class="dwt_author">Petihakis, G.; Triantafyllou, G.; Theodorou, A.</p> <p class="dwt_publisher"></p> <p class="publishDate"></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://adsabs.harvard.edu/abs/2013AGUFM.H23F1341R"> <span id="translatedtitle">Spatial heterogeneity in <span class="hlt">biogeochemical</span> transport on Arctic hill slopes</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">Water tracks, saturated regions of the hill slope in permafrosted Arctic catchments, likely deliver the majority of water entering streams in these regions, and may play a central role in delivery of nutrients. Fate of dissolved nutrients and carbon as they are transported in water tracks has a substantial effect on stream ecosystems, as water tracks may cover up to 35% of the catchment land area. Water tracks are distinguished from adjacent areas of the hillslope by higher rates of hydrologic transport, greater woody biomass, and increased pools of nutrients. Substantial spatial heterogeneity within and between water tracks may influence their role in transfer of materials between the terrestrial and aquatic landscape. We examined spatial variability of hydrologic and chemical characteristics within and between water tracks in the Kuparuk Basin of northern Alaska to increase understanding of the factors influencing nutrient export from arctic catchments. We studied a sedge-dominated water track with perennial surface water flow with shrub-dominated water tracks containing intermittent surface flow. Nominal transit times of water in the perennial site was 5 hours, compared to 15.5 h in an ephemeral track over a 50 meter reach, indicating substantial variation in water residence time and opportunity for <span class="hlt">biogeochemical</span> reaction across sites. We evaluated spatial heterogeneity in <span class="hlt">biogeochemical</span> characteristics within 25-m reaches at each site with a grain size of 10 m. Dissolved CH4 concentration was elevated above atmospheric equilibrium only at the perennial water track, where CH4 concentration varied by more than 15-fold within the water track, indicating hot spots of anaerobic microbial activity. Dissolved CO2 concentration was 9 times greater on average at the perennial water track, compared to the ephemeral site, suggesting that continuous water flow supports more rapid microbial activity. CO2 concentration was also more variable in the perennial water track, with a CV of 64% compared to 11% in an ephemeral water track. Despite spatial heterogeneity in dissolved gas concentrations within the perennial site, NH4+ concentration in surface and soil water was less variable, with a CV of 38%. In contrast, NH4+ concentration was more variable (CV=41%) than dissolved gases within the ephemeral site, and mean concentration was 2 times greater than at the perennial site, suggesting less active biological retention of nitrogen at the ephemeral site. These differences in dissolved gases and nutrient concentrations among water tracks indicate that nutrient processing during hydrologic transport on hill slopes varies across the catchment, which will likely result in spatially heterogeneous responses of elemental cycles in response to permafrost loss.</p> <div class="credits"> <p class="dwt_author">Risser, R.; Harms, T.; Jones, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-01</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/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">2006-12-01</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/2003JMS....40..213T"> <span id="translatedtitle">A singular evolutive interpolated Kalman filter for efficient data assimilation in a 3-D complex physical <span class="hlt">biogeochemical</span> model of the Cretan 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">A singular evolutive interpolated Kalman (SEIK) filter is used to assimilate pseudo-observations via twin simulation experiments in a complex three-dimensional <span class="hlt">coupled</span> physical-<span class="hlt">biogeochemical</span> model of the Cretan Sea. The simulation system comprises two on-line <span class="hlt">coupled</span> sub-models: the three-dimensional Princeton Model and the European Regional Seas Ecosystem Model (ERSEM). In the SEIK filter, the estimation error is represented by an ensemble of state vectors, which are drawn randomly at every filtering step. In the twin experiments performed the predictions of the <span class="hlt">coupled</span> model were corrected every 2 days using synthetic measurements extracted from a model reference run according to a network of 23 stations in the Cretan Sea. The filter is shown to be very efficient, with the assimilation results exhibiting a continuous decrease of the estimation error during the experimental period.</p> <div class="credits"> <p class="dwt_author">Triantafyllou, G.; Hoteit, I.; Petihakis, G.</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">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.agu.org/journals/gb/gb1103/2010GB003827/2010GB003827.pdf"> <span id="translatedtitle">Long-term controls on ocean phosphorus and oxygen in a global <span class="hlt">biogeochemical</span> model</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">Sedimentary phosphorus dynamics are included in a global <span class="hlt">biogeochemical</span> modelIncreases in phosphorus river inputs promote the expansion of ocean suboxiaPreferential P regeneration enhances the expansion of ocean suboxia</p> <div class="credits"> <p class="dwt_author">V. Palastanga; C. P. Slomp; C. Heinze</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">190</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://repository.tamu.edu/handle/1969.1/ETD-TAMU-2011-08-9784"> <span id="translatedtitle">An Investigation of Linked Physical And <span class="hlt">Biogeochemical</span> Processes In Heterogeneous Soils In The Vadose Zone</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">university research groups to study hydrologic and <span class="hlt">biogeochemical</span> processes surrounding a leachate plume that has developed in the aquifer beneath the landfill (Báez-Cazull et al., 2007; Cozzarelli et al., 9 2000; Kneeshaw et al., 2007). The first soil... university research groups to study hydrologic and <span class="hlt">biogeochemical</span> processes surrounding a leachate plume that has developed in the aquifer beneath the landfill (Báez-Cazull et al., 2007; Cozzarelli et al., 9 2000; Kneeshaw et al., 2007). The first soil...</p> <div class="credits"> <p class="dwt_author">Hansen, David Joseph</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-10-19</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://adsabs.harvard.edu/abs/2009AGUFM.B33C0411S"> <span id="translatedtitle">The genomic potential of Marinobacter aquaeolei - A <span class="hlt">biogeochemical</span> opportunotroph</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 family of Marinobacter is one of the most ubiquitous in the ocean. Members of this genus are found throughout the water column, in the deep sea, and are often associated with hydrothermal plume particles and marine snow. They are known to degrade hydrocarbons and show some extremophilic lifestyles, such as pyschrophily, oligotrophy and halotolerance. This study has determined the genomic potential of one particular strain - Marinobacter aquaeolei VT8, which relies on a very large set of survival strategies. Isolated from an oil well in Southern Vietnam, M. aquaeolei was known to be a facultative anaerobe with the ability to utilize various carbon sources. Fitting with these observations, genome annotation has revealed: four variations of the TCA cycle, complete pathways of glycolysis and the degradation of more complex hydrocarbons (including octane oxidation and cyclohexanol degradation), alternative phosphorous and nitrogen sources, genes for the use of nitrate and sulfate as electron acceptors as well as complete pathways for sulfite oxidation, denitrification and iron oxidation. The versatility and interrelatedness of these metabolic potentials coin the opportunistic character of M. aquaeolei and help to more completely define the <span class="hlt">biogeochemical</span> niche of the genus.</p> <div class="credits"> <p class="dwt_author">Singer, E.; Webb, E.; Nelson, W.; Heidelberg, J.; Edwards, K. J.</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">192</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 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://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3400409"> <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=pmc">PubMed Central</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 O2, pH and H2S. 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">2012-01-01</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://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 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://adsabs.harvard.edu/abs/2012AGUFM.H24B..03B"> <span id="translatedtitle">Catchment Legacies and Trajectories: Understanding Time Lags in Catchment Response as a Function of 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://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">Increased nutrient loads delivered from watersheds due to agricultural intensification, industrialization, and urbanization have contributed globally to the persistence of large hypoxic zones in inland and coastal waters. Watershed management practices targeting these non-point source pollutants often lead to little or no improvement in water quality, even after extensive implementation of conservation measures or Best Management Practices (BMPs). The lag time between implementation of a conservation measure and resultant water quality benefits has recently been recognized as an important factor in the "apparent" failure of these BMPs. When conservation measures are implemented without explicit consideration of the lag time and with expectations that they will lead to immediate benefits, the resulting failure to meet such expectations can discourage vital restoration efforts. It is therefore important to quantify the lag times associated with watershed management efforts a priori and to implement restoration strategies targeted specifically at minimizing lag times and maximizing restoration benefits. The focus of this research is to develop a framework for understanding the time lags between land-use changes and stream water quality benefits. We hypothesize that such time lags arise from nutrient legacies building over decades of fertilizer application. For nitrogen (N), one can conceptualize this as either hydrologic legacy, in the form of dissolved nitrate that is delayed due to slow groundwater transport, or as <span class="hlt">biogeochemical</span> legacy, in the form of organic N, possibly in dissolved or readily mineralizable forms. Indeed, mass-balance studies across the Mississippi and Thames river basins indicate the possibility of missing N mass in these landscapes, with inputs being consistently greater than the outputs even when accounting for all possible pathways of nitrogen transformation. Historical soil data within the upper Mississippi River Basin (MRB) indicate that agriculture depletes organic N in surface soil, but leads to N accumulations deeper in the profile. Nitrogen accumulation estimates (approximately 2 million Mt/yr) based on the historical data are startlingly close to the deficit suggested by mass-balance studies of the MRB (3 million Mt/yr). Understanding the lag times associated with such <span class="hlt">biogeochemical</span> legacies requires quantification of this accumulation as a function of landscape attributes, climate, and management controls, as well as the rate of mineralization of accumulated N after implementation of management practices. Understanding hydrologic legacy requires a partitioning of flow along various pathways (e.g., overland flow, tile flow, or groundwater pathways), and the distribution of travel times along the pathways. Based on this framework, we developed a <span class="hlt">coupled</span> hydrologic and <span class="hlt">biogeochemical</span> model to quantify these legacies and predict landscape recovery times as a function of natural and anthropogenic controls.</p> <div class="credits"> <p class="dwt_author">Basu, N. B.; Van Meter, K. J.</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">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/2014EOSTr..95..316L"> <span id="translatedtitle">Expanding the Role of Reactive Transport Modeling in <span class="hlt">Biogeochemical</span> Sciences</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 systems are complex due to the intimate <span class="hlt">coupling</span> of physical, chemical, and biological processes in the subsurface. Field observation and data analysis have provided significant insights into the <span class="hlt">coupling</span> of these processes. However, mechanistic understanding often requires advanced modeling tools to quantify the role of individual processes while maintaining the process <span class="hlt">coupling</span> that determines the overall system behavior. As a result, reactive transport modeling (RTM) has been used extensively to interrogate complex subsurface processes relevant to energy and the environment. Existing work has shown the significant research and educational advantages of RTM in elucidating mechanisms, integrating large data sets, testing hypotheses, and guiding the stewardship and management of water and energy resources.</p> <div class="credits"> <p class="dwt_author">Li, Li; Maher, Katherine M.; Navarre-Sitchler, Alexis</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-09-01</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://ag.udel.edu/soilchem/Grafe03ICOBTE.pdf"> <span id="translatedtitle">SYM01or -Arsenic in Soil and Groundwater Environment:<span class="hlt">Biogeochemical</span> Interactions Proc. 7th Intern. Conf. on the <span class="hlt">Biogeochem</span>. of Trace Elements; Uppsala '03</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Intern. Conf. on the <span class="hlt">Biogeochem</span>. of Trace Elements; Uppsala '03 In-Situ Speciation of Arsenic cm (LM-B). Total elemental digests show that the As concentration was 883 mg As Kg-1 soil and determine elemental associations. Subsequently µ-XAFS data were collected on selected regions at the As K</p> <div class="credits"> <p class="dwt_author">Sparks, Donald L.</p> <p class="dwt_publisher"></p> <p class="publishDate"></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.ncbi.nlm.nih.gov/pubmed/24845674"> <span id="translatedtitle">Consequences of ecological, evolutionary and <span class="hlt">biogeochemical</span> uncertainty for coral reef responses to climatic stress.</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">Coral reefs are highly sensitive to the stress associated with greenhouse gas emissions, in particular ocean warming and acidification. While experiments show negative responses of most reef organisms to ocean warming, some autotrophs benefit from ocean acidification. Yet, we are uncertain of the response of coral reefs as systems. We begin by reviewing sources of uncertainty and complexity including the translation of physiological effects into demographic processes, indirect ecological interactions among species, the ability of coral reefs to modify their own chemistry, adaptation and trans-generational plasticity. We then incorporate these uncertainties into two simple qualitative models of a coral reef system under climate change. Some sources of uncertainty are far more problematic than others. Climate change is predicted to have an unambiguous negative effect on corals that is robust to several sources of uncertainty but sensitive to the degree of <span class="hlt">biogeochemical</span> <span class="hlt">coupling</span> between benthos and seawater. Macroalgal, zoanthid, and herbivorous fish populations are generally predicted to increase, but the ambiguity (confidence) of such predictions are sensitive to the source of uncertainty. For example, reversing the effect of climate-related stress on macroalgae from being positive to negative had no influence on system behaviour. By contrast, the system was highly sensitive to a change in the stress upon herbivorous fishes. Minor changes in competitive interactions had profound impacts on system behaviour, implying that the outcomes of mesocosm studies could be highly sensitive to the choice of taxa. We use our analysis to identify new hypotheses and suggest that the effects of climatic stress on coral reefs provide an exceptional opportunity to test emerging theories of ecological inheritance. PMID:24845674</p> <div class="credits"> <p class="dwt_author">Mumby, Peter J; van Woesik, Robert</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-19</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/2014GBioC..28..897M"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> control of marine productivity in the Mediterranean Sea during the last 50 years</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">temporal dynamics of <span class="hlt">biogeochemical</span> variables derived from a <span class="hlt">coupled</span> 3-D model of the Mediterranean Sea are evaluated for the last 50 years (1960-2010) against independent data on fisheries catch per unit effort (CPUE) for the same time period. Concordant patterns are found in the time series of all of the biological variables (from the model and from fisheries statistics), with low values at the beginning of the series, a later increase, with maximum levels reached at the end of the 1990s, and a posterior stabilization. Spectral analysis of the annual biological time series reveals coincident low-frequency signals in all of them. The first, more energetic signal peaks around the year 2000, while the second, less energetic signal peaks near 1982. Almost identical low-frequency signals are found in the nutrient loads of the rivers and in the integrated nutrient levels in the surface marine ecosystem. Nitrate concentration shows a maximum level in 1998, with a later stabilization to present-day values, coincident with the first low-frequency signal found in the biological series. Phosphate shows maximum concentrations around 1982 and a posterior sharp decline, in concordance with the second low-frequency signal observed in the biological series. That result seems to indicate that the control of marine productivity (plankton to fish) in the Mediterranean is principally mediated through bottom-up processes that could be traced back to the characteristics of riverine discharges. The high sensitivity of CPUE time series to environmental conditions might be another indicator of the overexploitation of this marine ecosystem.</p> <div class="credits"> <p class="dwt_author">Macias, Diego; Garcia-Gorriz, Elisa; Piroddi, Chiara; Stips, Adolf</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-08-01</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/2008AGUFM.B21B0359M"> <span id="translatedtitle">Development of Arsenic and Iron <span class="hlt">Biogeochemical</span> Gradients upon Anaerobiosis at Soil Aggregate Scale</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 aerated soils, As release is limited due to the strong interaction between As(V) and soil minerals. However, under anaerobic conditions, As desorption is stimulated by As(V) reduction to As(III) and reductive dissolution/transformation of Fe (hydr)oxides, common hosts of As. The effect of As(V) and Fe(III) reduction on As release has been extensively studied in laboratory batch and column systems; correlation of apparent Fe and As reduction, with concomitant release to pore water, has also been noted under field conditions. What remains unresolved is the <span class="hlt">coupling</span> of <span class="hlt">biogeochemical</span> and physical processes that ultimately control As transport within structured media such as soils. Soils are heterogeneous porous media that are comprised of individual aggregates having pores that are dominated by diffusive (aggregate interiors) or advective (aggregate exteriors) transport. As a consequence of physical and chemical differences in the interior and the exterior of aggregates, As(III,V) and Fe(II,III) chemical gradients develop. Here, we examine As release from constructed aggregates exposed to fluctuating redox conditions. Artificial aggregates were made with As(V) adsorbed ferrihydrite-coated sand homogeneously inoculated with Shewanella sp. ANA-3 (model As(V) and Fe(III) reducer) and then fused using an agarose binder into spheres. Aggregates were placed in a flow reactor and saturated flow of aerobic or anaerobic artificial groundwater media was initiated. Redox fluctuated in select systems to examine changes in chemical gradient under changing aeration status. Our results show that within aerated solutions, oxidized aggregate exteriors provide a "gprotective barrier"h against As release despite anoxia within diffusively constrained aggregate interiors. During a transition to anaerobic conditions in advective zones, however, As is released and transport is promoted. Our study illustrates the microscale variation in biogeoechemical processes within soils and the importance of appreciating the spatial connection between reaction and transport fronts.</p> <div class="credits"> <p class="dwt_author">Masue-Slowey, Y.; Pallud, C.; Bedore, P.; Tufano, K.; Fendorf, S.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-12-01</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" 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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_12");' 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">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/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 " 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://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1904194"> <span id="translatedtitle">The effect of tidal forcing on <span class="hlt">biogeochemical</span> processes in intertidal salt marsh sediments</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">Background Early diagenetic processes involved in natural organic matter (NOM) oxidation in marine sediments have been for the most part characterized after collecting sediment cores and extracting porewaters. These techniques have proven useful for deep-sea sediments where <span class="hlt">biogeochemical</span> processes are limited to aerobic respiration, denitrification, and manganese reduction and span over several centimeters. In coastal marine sediments, however, the concentration of NOM is so high that the spatial resolution needed to characterize these processes cannot be achieved with conventional sampling techniques. In addition, coastal sediments are influenced by tidal forcing that likely affects the processes involved in carbon oxidation. Results In this study, we used in situ voltammetry to determine the role of tidal forcing on early diagenetic processes in intertidal salt marsh sediments. We compare ex situ measurements collected seasonally, in situ profiling measurements, and in situ time series collected at several depths in the sediment during tidal cycles at two distinct stations, a small perennial creek and a mud flat. Our results indicate that the tides <span class="hlt">coupled</span> to the salt marsh topography drastically influence the distribution of redox geochemical species and may be responsible for local differences noted year-round in the same sediments. Monitoring wells deployed to observe the effects of the tides on the vertical component of porewater transport reveal that creek sediments, because of their confinements, are exposed to much higher hydrostatic pressure gradients than mud flats. Conclusion Our study indicates that iron reduction can be sustained in intertidal creek sediments by a combination of physical forcing and chemical oxidation, while intertidal mud flat sediments are mainly subject to sulfate reduction. These processes likely allow microbial iron reduction to be an important terminal electron accepting process in intertidal coastal sediments. PMID:17567893</p> <div class="credits"> <p class="dwt_author">Taillefert, Martial; Neuhuber, Stephanie; Bristow, Gwendolyn</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">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/2009AGUFM.U53C..09M"> <span id="translatedtitle">Subglacial (<span class="hlt">bio)geochemical</span> weathering and the unexplored Antarctic 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">Water exported from Alpine and polar glaciers is often concentrated in a range of major ions, and minor and trace elements, derived from the dissolution of subglacial rocks and minerals. The export of these species from subglacial environments to the oceans via subglacial hydrological systems appears to constitute an important global flux of biochemically essential species, such as Fe, potentially impacting upon plankton activity in the oceans and the associated consumption of CO2 on glacial-interglacial timescales. Recent studies have demonstrated the presence and activity of microorganisms in a range of subglacial environments, from Alpine glaciers, Arctic glaciers, and most recently in sub-Antarctic systems. Equally, isotopic studies at Alpine and Arctic glaciers provide evidence that microbe-mineral associations occur in subglacial environments, and account for the release and transformation of dissolved nutrients. However, the link between microbiological presence & activity, mineral weathering, ionic species transformations, and the configuration of the subglacial hydrological system, remains poorly understood. We will report on Whillans Ice Stream Subglacial Access Research Drilling (WISSARD), an NSF funded integrative study of ice sheet stability and life habitats in sub Antarctic aquatic environments. Direct sterile sampling from a subglacial Antarctic lake and grounding zone, will allow us for the first time to address these gaps in our knowledge, to determine the role of microbes on the weathering of rocks and the release and transport of nutrients in and from the unexplored sub-Antarctic environment. These data will yield seminal information on these systems and test the overarching hypothesis that active hydrological systems connect various subglacial environments and exert major control on geochemistry, metabolic and phylogenetic diversity, and <span class="hlt">biogeochemical</span> transformations, as well as ice sheet dynamics. This will provide a basis for understanding the importance of subglacial hydrological-geochemical-microbiological interactions in the past, and in the future, at glacial-interglacial timescales.</p> <div class="credits"> <p class="dwt_author">Mitchell, A. C.; Christner, B. C.; Mikucki, J.; Priscu, J. C.</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">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/2011AGUFM.C41B0403P"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> modeling of tundra recovery following thermal erosion of permafrost</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 simulate the <span class="hlt">biogeochemical</span> recovery of tundra from a thermal erosion disturbance using the Multiple Element Limitation model (MEL) and compare model results with soil organic matter and nutrient chemistry measurements collected across a chronosequence of thermal erosion features. Thermal erosion of permafrost initially depletes the tundra of much of its vegetation and shallow soil organic matter. However, several decades later, there is often little distinguishing these scars from the surrounding undisturbed tundra. As thermal erosion features become more abundant on the arctic landscape, we desire to understand how the pools of carbon and nutrients rebuild after these disturbances. MEL is a plot-scale, process-based model that optimizes the acquisition of eight resources (light, water, CO2, PO4, NH4, NO3, DON and N-fixation) by vegetation based on how much of each is required and the effort needed to acquire it. Model output includes pool sizes of carbon, nitrogen and phosphorus in vegetation, litter, young soil organic matter and old soil organic matter and the fluxes among these pools over time. This calibration of MEL, operating on a daily timestep, was created with published data collected at or near the Toolik Field Station (Toolik Lake, AK, USA) from moist acidic tussock tundra sites. We corroborate our calibration with data from plot manipulations (N and P fertilization, greenhouse, and shade house) performed as part of the NSF Arctic LTER project. The initial conditions for the recovery simulations reflect post-failure observations of some of the variation in soil organic matter, and soil and water nutrient chemistry. With sufficient nutrients from residual soil or supplied in soil water from upslope, the model indicates that vegetation can recover within several decades, but recovery of C and nutrients lost from soils may take hundreds of years.</p> <div class="credits"> <p class="dwt_author">Pearce, A. R.; Rastetter, E. B.; Bowden, W. B.</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">205</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/24894911"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> indicators of elevated nitrogen deposition in semiarid Mediterranean ecosystems.</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">Nitrogen (N) deposition has doubled the natural N inputs received by ecosystems through biological N fixation and is currently a global problem that is affecting the Mediterranean regions. We evaluated the existing relationships between increased atmospheric N deposition and <span class="hlt">biogeochemical</span> indicators related to soil chemical factors and cryptogam species across semiarid central, southern, and eastern Spain. The cryptogam species studied were the biocrust-forming species Pleurochaete squarrosa (moss) and Cladonia foliacea (lichen). Sampling sites were chosen in Quercus coccifera (kermes oak) shrublands and Pinus halepensis (Aleppo pine) forests to cover a range of inorganic N deposition representative of the levels found in the Iberian Peninsula (between 4.4 and 8.1 kg N ha(-1) year(-1)). We extended the ambient N deposition gradient by including experimental plots to which N had been added for 3 years at rates of 10, 20, and 50 kg N ha(-1) year(-1). Overall, N deposition (extant plus simulated) increased soil inorganic N availability and caused soil acidification. Nitrogen deposition increased phosphomonoesterase (PME) enzyme activity and PME/nitrate reductase (NR) ratio in both species, whereas the NR activity was reduced only in the moss. Responses of PME and NR activities were attributed to an induced N to phosphorus imbalance and to N saturation, respectively. When only considering the ambient N deposition, soil organic C and N contents were positively related to N deposition, a response driven by pine forests. The PME/NR ratios of the moss were better predictors of N deposition rates than PME or NR activities alone in shrublands, whereas no correlation between N deposition and the lichen physiology was observed. We conclude that integrative physiological measurements, such as PME/NR ratios, measured on sensitive species such as P. squarrosa, can provide useful data for national-scale biomonitoring programs, whereas soil acidification and soil C and N storage could be useful as additional corroborating ecosystem indicators of chronic N pollution. PMID:24894911</p> <div class="credits"> <p class="dwt_author">Ochoa-Hueso, Raúl; Arróniz-Crespo, María; Bowker, Matthew A; Maestre, Fernando T; Pérez-Corona, M Esther; Theobald, Mark R; Vivanco, Marta G; Manrique, Esteban</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-09-01</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://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 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://ntrs.nasa.gov/search.jsp?R=19910069342&hterms=Hydrology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DHydrology"> <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://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">A review is presented of developments in ecosystem theory, remote sensing, and geographic information systems that support new endeavors in spatial modeling. A paradigm has emerged to predict ecosystem behavior based on understanding responses to multiple resources. Ecosystem models <span class="hlt">couple</span> primary production to decomposition and nutrient availability utilizing this paradigm. It is indicated that <span class="hlt">coupling</span> of transport and ecosystem processes alters the behavior of earth system components (terrestrial ecosystems, hydrology, and the atmosphere) from that of an uncoupled model.</p> <div class="credits"> <p class="dwt_author">Schimel, David S.; Parton, William J.; Kittel, Timothy G. F.</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">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/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">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/2011AGUFM.B13E0623L"> <span id="translatedtitle">Extracellular enzyme activity and <span class="hlt">biogeochemical</span> cycling in restored prairies</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">Winter microbial activity in mid-latitude prairie ecosystems is thermally sensitive and significantly influenced by snow depth. Snow insulates the soil column facilitating microbial processing of complex organic substrates. Previous studies in forests and tundra ecosystems suggest patterns of substrate utilization and limitation are seasonal; above freezing, soil microbes access fresh litter inputs and sugar exudates from plant roots, while under frozen condition they recycle nutrients incorporated in microbial biomass. In order to liberate nutrients required for carbon degradation, soil microbes invest energy in the production of extracellular enzymes that cleave monomers from polymer bonds. The inverse relationship between relative enzyme abundance and substrate availability makes enzyme assays a useful proxy to assess changes in resources over time. Our objective in this study was to assess patterns in microbial biomass, nutrient availability, and extracellular enzyme activity in four snow exclosure sites over a seven-month period. Over the past three years, we have maintained a snow removal experiment on two restored prairies in central Minnesota. In each prairie, snow was continuously removed annually from two 4 x 4 m plots by shoveling after each snow event. Extractable C, N and P, and microbial C, N and P in soil samples were measured in samples collected from these snow removal plots, as well as in adjacent unmanipulated prairie control plots. Pools of C, N, and P were estimated using standard extraction protocols, and microbial pools were estimated using chloroform fumigation direct extraction (CFDE). We conducted fluorometric extracellular enzyme assays (EEA) to assess how the degradation potential of cellulose (cellobiohydrolase, CBH), protein (leucine aminopeptidase, LAP), and phosphate esters (phosphatase, PHOS) changed seasonally. Microbial C and N declined between October and June, while microbial P declined during the fall and winter, but increased during the spring. Microbial biomass C:N ratios increased from October to March, and decreased through the summer, while production of CBH, LAP and PHOS all showed the opposite pattern, decreasing through March and increasing in the summer. Following snowmelt, enzyme production preceded a recovery in microbial biomass, possibly as a result of increased competition for available resources between plant and microbial communities, or a shift to organic sources of C, N, and P which required a higher investment in enzymes. Due to their rapid growth rates and turnover, microbes are a particularly reactive component of terrestrial ecosystems and significantly influence <span class="hlt">biogeochemical</span> cycling. Because carbon degradation may be constrained by nutrient availability, understanding how extracellular enzyme production, decomposition rate, and nutrient flux change over time is essential if we are to anticipate ecosystem responses to environmental changes.</p> <div class="credits"> <p class="dwt_author">Lynch, L.; Hernandez, D.; 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">210</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.V13F..01N"> <span id="translatedtitle">The changing role of dust in <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">Dust emission and deposition have the potential to deplete and enrich ecosystems of mineral resources essential to life. In many parts of the world, and particularly in semi-arid settings, wind erosion of soils and the subsequent long-distance transport and deposition of mineral aerosols play a basic role in soil composition and processes, including the production of essential plant nutrients through weathering. Although the long-term role of dust in the development of soils is reasonably well understood, the effects of recent dust emission and deposition on ecosystems are not. Recent work on ecosystems around the world has highlighted the fundamental importance of contemporary wind erosion and dust deposition in <span class="hlt">biogeochemical</span> cycling. In the western U.S., studies of Sr and Nd isotopes, elemental concentrations, and magnetic properties elucidate the role of dust in recent soil development and soil loss by wind erosion related to land-use change. In the arid landscapes in and around Canyonlands National Park (Utah), these techniques provide insight into the development of soils in stable settings where human activities have been minimal but the loss of soil in areas affected by grazing and recreational activities. In stable settings of the central Colorado Plateau (Utah), dust deposition is responsible for a large proportion (as much as 20 percent) of surface soil mass and elemental content. In contrast, wind erosion is responsible for large losses of nutrients and surface soil of nearby, closely similar geomorphic settings disturbed by human activity. In the San Juan Mountains (Colorado) downwind of the Colorado Plateau, Nd and Sr isotopes in dust and lake sediments provide evidence for large increases in dust deposition during the 19th and 20th century compared to records from the middle to late Holocene. The recent enhancement in dust deposition is also responsible for increased loading of many elements, including essential nutrients that may influence ecological processes. In settings of continued dust accumulation over the past ca. 150 years, geochemical results point to changes in dust composition, particularly in some trace metals and P. The apparent, human-driven change in the amount and composition of emitted dusts has implications for both our understanding and prediction of mineralization processes across a range of landscapes.</p> <div class="credits"> <p class="dwt_author">Neff, J. C.; Reynolds, R. L.; Farmer, G. L.; Reheis, 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">211</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19940007992&hterms=factors+production&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dfactors%2Bproduction"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> factors which regulate the formation and fate of sulfide in wetlands</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">Coastal wetland areas occupy a small percentage of the terrestrial environment yet are extremely productive regions which support rapid rates of belowground bacterial activity. Wetlands appear to be significant as biogenic sources of gaseous sulfur, carbon, and nitrogen. These gases are important as tracers of man's activities, and they influence atmospheric chemistry. The interactions among wetland <span class="hlt">biogeochemical</span> processes regulate the anaerobic production of reduced gases and influence the fate of these volatiles. Therefore, spatial and temporal variations in hydrology, salinity, temperature and specification, and growth of vegetation affect the type and magnitude of gas emissions thus hindering predictive estimates of gas flux. Our research is divided into two major components, the first is the <span class="hlt">biogeochemical</span> characterization of a selected tidal wetland area in terms of factors likely to regulate sulfide flux; the second is a direct measurement of gaseous sulfur flux as related to changes in these <span class="hlt">biogeochemical</span> conditions. Presently, we are near completion of phase one.</p> <div class="credits"> <p class="dwt_author">Hines, Mark E.; Lyons, W. Berry; Gaudette, H. E.</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">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/2009GeoRL..3621601H"> <span id="translatedtitle">Decadal variability in <span class="hlt">biogeochemical</span> models: Comparison with a 50-year ocean colour dataset</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">Assessing the skill of <span class="hlt">biogeochemical</span> models to hindcast past variability is challenging, yet vital in order to assess their ability to predict <span class="hlt">biogeochemical</span> change. However, the validation of decadal variability is limited by the sparsity of consistent, long-term biological datasets. The Phytoplankton Colour Index (PCI) product from the Continuous Plankton Recorder survey, which has been sampling the North Atlantic since 1948, is an example of such a dataset. Converting the PCI to chlorophyll values using SeaWiFS data allows a direct comparison with model output. Here we validate decadal variability in chlorophyll from the GFDL TOPAZ model. The model demonstrates skill at reproducing interannual variability, but cannot simulate the regime shifts evident in the PCI data. Comparison of the model output, data and climate indices highlights under-represented processes that it may be necessary to include in future <span class="hlt">biogeochemical</span> models in order to accurately simulate decadal variability in ocean ecosystems.</p> <div class="credits"> <p class="dwt_author">Henson, Stephanie A.; Raitsos, Dionysios; Dunne, John P.; McQuatters-Gollop, Abigail</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-11-01</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://academic.research.microsoft.com/Publication/45904059"> <span id="translatedtitle">Eastern Mediterranean <span class="hlt">biogeochemical</span> flux model: simulations of the pelagic ecosystem</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">During the second phase (2003-2006) of the Mediterranean ocean Forecasting System Project (MFS) named Toward Environmental Predictions (MFSTEP) one of the three major aims was the development of numerical forecasting systems. In this context a generic Biochemical Flux Model (BFM) was developed and <span class="hlt">coupled</span> with hydrodynamic models already operating at basin scale as well as at regional areas. In the</p> <div class="credits"> <p class="dwt_author">G. Petihakis; G. Triantafyllou; G. Korres; A. Pollani; I. Hoteit</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">214</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 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://adsabs.harvard.edu/abs/2011AGUFM.B21L..07O"> <span id="translatedtitle">Sulfur and Methylmercury in the Florida Everglades - the <span class="hlt">Biogeochemical</span> Connection</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">Methylmercury (MeHg) is a serious environmental problem in aquatic ecosystems worldwide because of its toxicity and tendency to bioaccumulate. The Everglades receives some of the highest levels of atmospheric mercury deposition and has some of the highest levels of MeHg in fish in the USA, posing a threat to pisciverous wildlife and people through fish consumption. USGS studies show that a combination of <span class="hlt">biogeochemical</span> factors make the Everglades especially susceptible to MeHg production and bioaccumulation: (1) vast wetland area with anoxic soils supporting anaerobic microbial activity, (2) high rates of atmospheric mercury deposition, (3) high levels of dissolved organic carbon (DOC) that complexes and stabilizes mercury in solution for transport to sites of methylation, and (4) high sulfate loading in surface water that drives microbial sulfate reduction and mercury methylation. The high levels of sulfate in the Everglades represent an unnatural condition. Background sulfate levels are estimated to be <1 mg/L, but about 60% of the Everglades has surface water sulfate concentrations exceeding background. Highly sulfate-enriched marshes in the northern Everglades have average sulfate levels of 60 mg/L. Sulfate loading to the Everglades is principally a result of land and water management in south Florida. The highest concentrations of sulfate, averaging 60-70 mg/L, are in canal water in the Everglades Agricultural Area (EAA). Geochemical data and a preliminary sulfur mass balance for the EAA are consistent with sulfur currently used in agriculture, and sulfur released by oxidation of organic EAA soils (including legacy agricultural applications and natural sulfur) as the primary sources of sulfate enrichment to the canals and ecosystem. Sulfate loading increases microbial sulfate reduction and MeHg production in soils. The relationship between sulfate loading and MeHg production, however, is complex. Sulfate levels up to about 20-30 mg/L increase mercury methylation, but buildup of sulfide from microbial sulfate reduction begins to inhibit mercury methylation above this range. Sulfate from the EAA canals has primarily impacted the northern Everglades nearest the EAA, but recent evidence shows sulfate loading extending about 80 km further south into Everglades National Park. Current restoration plans to restore to deliver more water south to Everglades National Park may increase overall sulfur loads to the southern part of the ecosystem. A comprehensive Everglades restoration strategy should include reduction of sulfur loads as a goal because of the many detrimental impacts of sulfate on the ecosystem. Monitoring data show that the ecosystem response to changes in sulfate levels is rapid, and strategies for reducing sulfate loading may be effective in the near-term. A multifaceted approach employing best management practices for sulfur in agriculture, agricultural practices that minimize soil oxidation, and changes to stormwater treatment areas that increase sulfate retention, could help reduce sulfate loads to the Everglades, with resulting benefits.</p> <div class="credits"> <p class="dwt_author">Orem, W. H.; Gilmour, C. C.; Krabbenhoft, D. P.; Aiken, G.</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">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/51940799"> <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://academic.research.microsoft.com/">Microsoft Academic Search </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,</p> <div class="credits"> <p class="dwt_author">A. Minard; J. W. Moreau</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">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.b-ware.eu/content/project/publicaties/VanderWelle-Freshwater-Biology-2007.pdf"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> interactions between iron and sulphate in freshwater wetlands and their implications for interspecific competition between aquatic macrophytes</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. Wetlands are threatened by desiccation, eutrophication and changing water quality, generally leading to greatly altered <span class="hlt">biogeochemical</span> processes. Sulphate pollution can lead to severe eutrophication and sulphide toxicity, but may also interact with the availability of iron and other metals. 2. In the present study, we examined the <span class="hlt">biogeochemical</span> interactions between sulphate and iron availability, and their effects on</p> <div class="credits"> <p class="dwt_author">MARLIES E. W. V AN; W ELLE; J. P. S MOLDERS; HUUB J. M. O P D EN C AMP</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">218</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/939351"> <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 reactions 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. We are developing a hybrid multiscale modeling framework that combines discrete pore-scale models (which explicitly represent the geometry of grains and pores at a local scale) with continuum field-scale models (which conceptualize flow and transport in a porous medium without explicit pores and grains). At the pore scale, we have implemented a parallel three-dimensional Lagrangian model of flow and transport using the Smoothed Particle Hydrodynamics (SPH) method and performed test simulations using millions of computational particles on the supercomputer at the Environmental Molecular Sciences Laboratory (EMSL). We have also developed methods for gridding arbitrarily complex pore geometries and solution of pore-scale flow and transport using parallel implementations of grid-based computational fluid dynamics (CFD) methods. Within the multiscale hybrid framework, we have <span class="hlt">coupled</span> pore- and continuum-scale models to simulate <span class="hlt">coupled</span> diffusive mixing, reaction, and mineral precipitation, and compared the results with conventional continuum-only simulations. The hybrid multiscale modeling framework is being developed using a number of SciDAC enabling technologies including the Common Component Architecture (CCA), advanced solvers, grid technologies, scientific workflow tools, and visualization technologies.</p> <div class="credits"> <p class="dwt_author">Scheibe, Timothy D.; Tartakovsky, Alexandre M.; Tartakovsky, Daniel M.; Redden, George D.; Meakin, Paul; Palmer, Bruce J.; Schuchardt, Karen L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2008-08-18</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.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 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://repository.tamu.edu/handle/1969.1/ETD-TAMU-2520"> <span id="translatedtitle">Spatial and temporal controls on <span class="hlt">biogeochemical</span> indicators at the small-scale interface between a contaminated aquifer and wetland surface water</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">This high-resolution <span class="hlt">biogeochemical</span> study investigated spatial and temporal variability in the mixing interface zones within a wetland-aquifer system near a municipal landfill in the city of Norman, Oklahoma. Steep <span class="hlt">biogeochemical</span> gradients...</p> <div class="credits"> <p class="dwt_author">Baez-Cazull, Susan Enid</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-05-15</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 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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://adsabs.harvard.edu/abs/2010AGUFM.H13F1048K"> <span id="translatedtitle">Hydrogen and carbon isotope geochemistry of freshwater aquifers at the Mizunami Underground Research Laboratory: Implications for ongoing <span class="hlt">biogeochemical</span> processes in deep granitic rocks</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">Granite is one of major plutonic rocks and widely distributed in the terrestrial deep subsurface. Although many studies of <span class="hlt">biogeochemical</span> processes have been carried out for granitic aquifers associated with seawater in Scandinavian countries, there is not much knowledge of <span class="hlt">biogeochemical</span> processes mediated in those associated with freshwater. The Mizunami Underground Research Laboratory (MIU), which is located in Central Japan, provides us opportunities to investigate freshwater aquifers in granitic rocks. We collected groundwater samples from 200-m to 1150-m depths below ground level. We measured the concentration of methane, ethane, total inorganic carbon (TIC), molecular hydrogen, acetate, sulfate and ammonium, and the carbon and hydrogen isotopic compositions of methane and TIC. The concentration of methane increased with depth from 127 to 1164 ?M, and TIC decreased from 1300 to 50 ?M, respectively. The C1/C2+C3 ratios of >~800 indicated that methane might be biogenic. In contrast, the carbon and hydrogen isotopic composition of methane ranged from -42.6 to -26.9 ‰ and from -157 to -111 ‰, respectively, and the carbon isotopic composition of TIC ranged from -2.5 to -14.7 ‰. As the higher isotopic composition of methane and the difference in carbon isotopic composition between methane and TIC were around 30 ‰, the origin of main methane pool could be abiogenic. The concentration of hydrogen is the most sensitive indicator of ongoing <span class="hlt">biogeochemical</span> processes. The higher level of hydrogen was consistent with acetogenesis at a depth of 300-m (~100 nM), while the lower level was indicative of sulfate reduction at a depth of 200-m (~1.5 nM). The depletion of sulfate and the enrichment of acetate in the 300-m deep groundwater agreed with the hydrogen profile. Interestingly, this redox shift was associated with an increase in ammonia concentration. The depth profiles of sulfate and methane in which sulfate reduction is <span class="hlt">coupled</span> to methane oxidation have been obtained from the seawater granitic aquifers in Olkiluoto, Finland. Apparent lack of the profiles characterized by anaerobic methane oxidation in Mizunami groundwater might be attributed to the low level of sulfate. From our results, it is suggested that dominant <span class="hlt">biogeochemical</span> processes mediated in the deep granitic rocks differ significantly between freshwater and seawater aquifer systems. This study was supported by grants from the Nuclear and Industrial Safety Agency (NISA).</p> <div class="credits"> <p class="dwt_author">Konno, U.; Fukuda, A.; Kouduka, M.; Komatsu, D. D.; Tsunogai, U.; Aosai, D.; Mizuno, T.; Suzuki, Y.</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">222</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/2013AGUFMPP54B..02G"> <span id="translatedtitle">Implications of variance in <span class="hlt">biogeochemical</span> proxy records spanning Mesozoic Oceanic Anoxic 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">The cycling of key elements through the ocean and atmosphere varied widely in the Mesozoic in response to changes in primary productivity and organic carbon burial, volcanism, weathering, and evaporite burial. Many of these processes have been proposed as triggers for the discreet periods of widespread organic carbon production and/or preservation termed Ocean Anoxic Events or OAE's. Thus, it might be expected that similar patterns of elemental cycling would characterize most major OAE intervals and could be used to help elucidate the controls on initiation and/or termination of these events. Yet this is not the case. In this study we compare the variability of a series of geochemical proxies, focusing on sulfur (S) isotopes of marine sulfate and sulfide minerals, through a series of Mesozoic OAE's. The data set includes our own results from OAE1a (ca. 125Ma) and OAE2 (ca. 94Ma), as well as published data from other events. The results indicate that S cycling varied significantly among the events, despite many similarities in the behavior of carbon isotopes and geochemical indicators of oxygen deficiency. Specifically, S isotope compositions of seawater sulfate and pyrite are quite variable during OAE2 suggesting that a short-term increase in sulfate levels upon a low background occurred at the onset due to enhanced volcanism and/or weathering. In contrast, S isotope compositions of seawater sulfate and pyrite decrease dramatically through the OAE1a and are completely decoupled from the carbon cycle. We evaluate these trends using <span class="hlt">coupled</span> sulfur and carbon box models and show that patterns of S cycling during OAE1a were predominantly controlled by volcanism, whereas S cycling during OAE2 represents a stronger interplay between volcanic processes and linkage with the carbon cycle. An analysis of the differences in S cycling among events provides improved insight into the suite of processes that interacted to drive large-scale changes in environmental conditions during the Mesozoic. Major changes in <span class="hlt">biogeochemical</span> systems from one event to another likely contributed to low ecosystem resilience, which helped lay the foundation for significant levels of species turnover during Mesozoic OAE's.</p> <div class="credits"> <p class="dwt_author">Gomes, M. L.; Mills, J. V.; Hurtgen, M. T.; Sageman, B. B.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-01</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://www.geobotany.uaf.edu/cryoturbation/docs/Biocomplexity_prop.pdf"> <span id="translatedtitle">Biocomplexity associated with <span class="hlt">biogeochemical</span> cycles in arctic frost-boil ecosystems</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">i Biocomplexity associated with <span class="hlt">biogeochemical</span> cycles in arctic frost-boil ecosystems Principal CYCLES IN ARCTIC FROST-BOIL ECOSYSTEMS A PROJECT SUMMARY The central goal of this project to changing climate. We focus on frost-boils because: (1) The processes that are involved in the self</p> <div class="credits"> <p class="dwt_author">Wagner, Diane</p> <p class="dwt_publisher"></p> <p class="publishDate"></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://www.rsmas.miami.edu/groups/biogeochem/Hansell%20pdfs/79%20Hansell.pdf"> <span id="translatedtitle">The <span class="hlt">biogeochemical</span> fate of organic matter in the ocean is an important issue that must be</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">waters towards the seabed1 and the export of dissolved organic matter (DOM) from the euphotic zoneThe <span class="hlt">biogeochemical</span> fate of organic matter in the ocean is an important issue that must a series of processes through which CO2 is fixed as organic matter by photosynthesis and then transferred</p> <div class="credits"> <p class="dwt_author">Hansell, Dennis</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">225</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://people.eri.ucsb.edu/~davey/MyPapers/Swan_etal_DSR1_2009.pdf"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> and hydrographic controls on chromophoric dissolved organic matter distribution in the Pacific Ocean</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary"><span class="hlt">Biogeochemical</span> and hydrographic controls on chromophoric dissolved organic matter distribution Available online 19 September 2009 Keywords: CDOM AOU Pacific Water masses Hydrography Bio-optical a b s t r in diagnosing particulate organic matter (POM) remineralization rates within ocean basins. Relationships between</p> <div class="credits"> <p class="dwt_author">Siegel, David A.</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://www.liv.ac.uk/~ric/lfs/pdf/grl2003_mww.pdf"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> signatures of nitrogen fixation in the eastern North Claire Mahaffey,1</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary"><span class="hlt">Biogeochemical</span> signatures of nitrogen fixation in the eastern North Atlantic Claire Mahaffey,1 Received 30 October 2002; accepted 5 February 2003; published 22 March 2003. [1] Stable nitrogen isotopic in the upper thermocline, suggest that nitrogen fixation provides a local dominant supply of nitrogen</p> <div class="credits"> <p class="dwt_author">Williams, Ric</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://www.bnl.gov/envsci/pubs/pdf/2014/BNL-104903-2014-JA.pdf"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> changes at early stage after the closure of radioactive waste geological repository in South Korea</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Organic waste a b s t r a c t Permanent disposal of low- and intermediate-level radioactive wastes<span class="hlt">Biogeochemical</span> changes at early stage after the closure of radioactive waste geological repository e Korea Radioactive Waste Agency (KORAD), 111, Daedeok-daero 989 beon-gil, Yuseong-gu, Daejeon 305</p> <div class="credits"> <p class="dwt_author">Ohta, Shigemi</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://academic.research.microsoft.com/Publication/59741784"> <span id="translatedtitle">Winter flooding in Dutch stream valley floodplains: <span class="hlt">biogeochemical</span> effects and vegetation consequences</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">Winter flooding in Dutch stream valley floodplains: <span class="hlt">biogeochemical</span> effects and vegetation consequences Victor Beumer Climatic change has great impacts on stream catchments and their ecology. Expectations are that more extreme climate events will result in undesired flooding in stream catchments. In the Netherlands, former floodplains with a history of agricultural or semi natural land use are put into use again</p> <div class="credits"> <p class="dwt_author">V. Beumer</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">229</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/24449851"> <span id="translatedtitle">Gene-centric approach to integrating environmental genomics and <span class="hlt">biogeochemical</span> models.</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">Rapid advances in molecular microbial ecology have yielded an unprecedented amount of data about the evolutionary relationships and functional traits of microbial communities that regulate global geochemical cycles. <span class="hlt">Biogeochemical</span> models, however, are trailing in the wake of the environmental genomics revolution, and such models rarely incorporate explicit representations of bacteria and archaea, nor are they compatible with nucleic acid or protein sequence data. Here, we present a functional gene-based framework for describing microbial communities in <span class="hlt">biogeochemical</span> models by incorporating genomics data to provide predictions that are readily testable. To demonstrate the approach in practice, nitrogen cycling in the Arabian Sea oxygen minimum zone (OMZ) was modeled to examine key questions about cryptic sulfur cycling and dinitrogen production pathways in OMZs. Simulations support previous assertions that denitrification dominates over anammox in the central Arabian Sea, which has important implications for the loss of fixed nitrogen from the oceans. Furthermore, cryptic sulfur cycling was shown to attenuate the secondary nitrite maximum often observed in OMZs owing to changes in the composition of the chemolithoautotrophic community and dominant metabolic pathways. Results underscore the need to explicitly integrate microbes into <span class="hlt">biogeochemical</span> models rather than just the metabolisms they mediate. By directly linking geochemical dynamics to the genetic composition of microbial communities, the method provides a framework for achieving mechanistic insights into patterns and <span class="hlt">biogeochemical</span> consequences of marine microbes. Such an approach is critical for informing our understanding of the key role microbes play in modulating Earth's biogeochemistry. PMID:24449851</p> <div class="credits"> <p class="dwt_author">Reed, Daniel C; Algar, Christopher K; Huber, Julie A; Dick, Gregory J</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-02-01</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.princeton.edu/nitrogen/publications/pdfs/JayakumarEtal_2009_SIBERbooknirPhylogeny.pdf"> <span id="translatedtitle">Indian Ocean <span class="hlt">Biogeochemical</span> Processes and Ecological Variability Geophysical Monograph Series 185</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">) oxygen minimum zone (OMZ) is one of the largest pelagic low-oxygen environments in the open ocean is distinguished by very low dissolved oxygen (DO) concentration at depths between 150 and 1200 m, es- pecially187 Indian Ocean <span class="hlt">Biogeochemical</span> Processes and Ecological Variability Geophysical Monograph Series</p> <div class="credits"> <p class="dwt_author">Ward, Bess</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">231</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.montana.edu/lkbonney/DOCS/Publications/BarrettEtAl2007Stoichiometry.pdf"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> stoichiometry of Antarctic Dry Valley ecosystems J. E. Barrett,1,2</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary"><span class="hlt">Biogeochemical</span> stoichiometry of Antarctic Dry Valley ecosystems J. E. Barrett,1,2 R. A. Virginia,1 by availability of liquid water, they influence the chemical composition of their environment according that contemporary ecosystem stoichiometry of Antarctic Dry Valley soils, glaciers, streams, and lakes results from</p> <div class="credits"> <p class="dwt_author">Priscu, John C.</p> <p class="dwt_publisher"></p> <p class="publishDate"></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://climate.atmos.uiuc.edu/atuljain/publications/JainEtAl_GCBB_2010.pdf"> <span id="translatedtitle">An integrated <span class="hlt">biogeochemical</span> and economic analysis of bioenergy crops in the Midwestern United States</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">An integrated <span class="hlt">biogeochemical</span> and economic analysis of bioenergy crops in the Midwestern United-specific economic analysis of breakeven prices of bioenergy crop production to assess the biophysical and economic potential of biofuel production in the Midwestern United States. The bioenergy crops considered</p> <div class="credits"> <p class="dwt_author">Jain, Atul K.</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://adsabs.harvard.edu/abs/2009BGD.....6.9525Z"> <span id="translatedtitle">Rates of <span class="hlt">biogeochemical</span> phosphorus and copper redistribution in young floodplain soils</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">Nutrients and trace metals in river-floodplain systems may originate from anthropogenic activities and/or geogenic sources. Here, we analyze a soil chronosequence on a floodplain at the Danube River (Austria) to quantify the rates of P and Cu redistribution among <span class="hlt">biogeochemical</span> pools during 600 years of soil formation under temperate continental climate. While bulk and clay mineralogy remained unchanged over the studied age gradient, we found considerable (mostly non-linear) redistribution of P and Cu among <span class="hlt">biogeochemical</span> pools. The calcium-associated P and Cu pools decreased rapidly during the initial decades of soil formation. The dissolution of the calcium-associated pools was mirrored by marked accumulation of organic P, but was not accompanied by changes in organic matter-associated Cu. The dissolution rates of calcium-associated (primary mineral) P showed an exponential decrease with increasing soil age, and were almost an order of magnitude higher than rates reported for tropical environments. Our study demonstrates that on riverine floodplains, substantial <span class="hlt">biogeochemical</span> redistribution can occur within the first centuries of soil formation, and that, even under temperate climatic conditions, <span class="hlt">biogeochemical</span> transformation rates can be exceedingly high in these ecosystems.</p> <div class="credits"> <p class="dwt_author">Zehetner, F.; Lair, G. J.; Graf, M.; Gerzabek, M. H.</p> <p class="dwt_publisher"></p> <p class="publishDate">2009-10-01</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://www.agu.org/journals/jc/jc0607/2005JC003113/2005JC003113.pdf"> <span id="translatedtitle">Using inherent optical properties to investigate <span class="hlt">biogeochemical</span> dynamics in a tropical macrotidal coastal system</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 variability in the inherent optical properties along an estuary-coast-ocean continuum in tropical Australia has been studied. The study area, the Fitzroy Estuary and Keppel Bay system, is a shallow coastal environment (depth < 30 m) with highly turbid waters in the estuary and blue oceanic waters in the bay and subject to macrotides. <span class="hlt">Biogeochemical</span> and inherent optical properties (IOPs)</p> <div class="credits"> <p class="dwt_author">Kadija Oubelkheir; Lesley A. Clementson; Ian T. Webster; Phillip W. Ford; Arnold G. Dekker; Lynda C. Radke; Paul Daniel</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">235</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/11516911"> <span id="translatedtitle">Overview of the Water, Energy, <span class="hlt">Biogeochemical</span> Budgets Program of the U.S. Geological Survey</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">Small watershed studies serve as an important mechanism to understand changes in a broad range of hydrologic environments at a scale where multiple processes can be understood. The U. S. Geological Survey's (USGS) Water, Energy, and <span class="hlt">Biogeochemical</span> Budgets (WEBB) program was designed to understand processes in small watersheds located in geographically diverse environments that represent a range of hydrologic, ecologic,</p> <div class="credits"> <p class="dwt_author">Mary Jo Baedecker</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/54681269"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> factors affecting mercury methylation rate in two contaminated floodplain soils</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">An automated <span class="hlt">biogeochemical</span> microcosm system allowing controlled variation of redox potential (EH) in soil suspensions was used to assess the effect of various factors on the mobility of mercury (Hg) as well as on the methylation of Hg in two contaminated floodplain soils with different Hg concentrations (approximately 5 mg kg-1 Hg and >30 mg kg-1 Hg). The experiment was</p> <div class="credits"> <p class="dwt_author">T. Frohne; J. Rinklebe; U. Langer; G. Du Laing; S. Mothes; R. Wennrich</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">237</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">238</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://lmecol.evsc.virginia.edu/pubs/93-Gu_et_al__07WRR.pdf"> <span id="translatedtitle">Nitrate reduction in streambed sediments: Effects of flow and <span class="hlt">biogeochemical</span> kinetics</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Nitrate reduction in streambed sediments: Effects of flow and <span class="hlt">biogeochemical</span> kinetics Chuanhui Gu,1. The calibrated model successfully replicated the spatial profiles of nitrate under both steady and transient). At the study site, the Peclet number and the Damkohler numbers for both oxygen and nitrate are high (Pe = 25</p> <div class="credits"> <p class="dwt_author">Virginia, University of</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">239</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/2013AGUFM.H31L..06G"> <span id="translatedtitle">Comparing the <span class="hlt">Biogeochemical</span> Potential of Hyporheic Zones Driven by Different River Morphologies</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">Channel morphology controls the hydrodynamics of hyporheic exchange and its residence times. As a result, it also constrains the hyporheic zone's <span class="hlt">biogeochemical</span> processes that transform carbon, nutrients, metals, and contaminants and the hyporheic zone's net effect at the local, reach and watershed scales. Previous studies of different morphologies (e.g., meanders, bars, and smaller bedforms such as dunes) have mainly focused on the amount of exchange or, if biogeochemistry was involved, have been specific to a particular morphology. In this work, we present a quantitative intercomparison of the amount of exchange, residence time distributions (RTDs), and <span class="hlt">biogeochemical</span> potential for four channel morphologies: ripples, dunes, bars, and meander bends. To this end, simple two-dimensional conceptualizations and semi-analytical solutions for the hyporheic zone's flow and transport are used. In general, all morphologies are characterized by heavy-tail RTDs, implying long-term memory to solute inputs. We hypothesize that even though meander bends induce larger hyporheic exchange per unit length of channel and longer residence times, substrate limitations result in less <span class="hlt">biogeochemical</span> processing when compared with the cumulative effect of multiple bedforms. The models presented are a function of geometric and physical properties easily measured or constrained with field or remote sensing data. The simplicity of this approach allows for practical calculations of the hyporheic zone's exchange and <span class="hlt">biogeochemical</span> potential over a broad range of scenarios and morphologies, making it a useful tool for experimental design, sampling, and watershed scale assessment.</p> <div class="credits"> <p class="dwt_author">Gomez, J. D.; Harvey, J. W.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-01</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://www.glerl.noaa.gov/eegle/products/EEGLEoverview.pdf"> <span id="translatedtitle">The Impact of Episodic Events on the Nearshore-Offshore Transport and Transformation of <span class="hlt">Biogeochemically</span> Important</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">is the "unpredictable" tim- ing of the particular event. The onset of the annually recurrent southern Lake Michigan of <span class="hlt">Biogeochemically</span> Important Materials in the Great Lakes Episodic Events: Great Lakes Experiment Study Approach deployed in southern Lake Michigan to collect plume particles as they settle towards the lake bottom</p> <div class="credits"> <p class="dwt_author">NOAA Great Lakes Environmental Research Laboratory, Episodic Events</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_11");' href="#" title="Previous 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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_14");' 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">241</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.env.leeds.ac.uk/~ianburke/Burke%20et%20al%20(accepted).pdf"> <span id="translatedtitle">ForPeerReview <span class="hlt">Biogeochemical</span> reduction processes in a hyper-alkaline</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">ForPeerReview Only <span class="hlt">Biogeochemical</span> reduction processes in a hyper-alkaline affected leachate soil processes in a hyper-alkaline affected leachate soil profile1 2 Ian T. Burke1* , Robert J.G. Mortimer1 in a buried, saturated, organic­16 rich soil layer at pH 12.3. The soil has been trapped beneath calcite</p> <div class="credits"> <p class="dwt_author">Burke, Ian</p> <p class="dwt_publisher"></p> <p class="publishDate"></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://pubs.er.usgs.gov/publication/70015566"> <span id="translatedtitle">A tubular-coring device for use in <span class="hlt">biogeochemical</span> sampling of succulent and pulpy plants</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 hand-operated, tubular-coring device developed for use in <span class="hlt">biogeochemical</span> sampling of succulent and pulpy plants is described. The sampler weighs about 500 g (1.1 lb); and if 25 ?? 175 mm (1 ?? 7 in) screw-top test tubes are used as sample containers, the complete sampling equipment kit is easily portable, having both moderate bulk and weight. ?? 1986.</p> <div class="credits"> <p class="dwt_author">Campbell, W.L.</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">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/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">244</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=214116"> <span id="translatedtitle">Catchment hydro-<span class="hlt">biogeochemical</span> response to forest harvest intensity and spatial pattern</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">We apply a new model, Visualizing Ecosystems for Land Management Assessment (VELMA), to Watershed 10 (WS10) in the H.J. Andrews Experimental Forest to simulate the effects of harvest intensity and spatial pattern on catchment hydrological and <span class="hlt">biogeochemical</span> processes. Specificall...</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">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/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">246</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://science.whoi.edu/users/olga/eddies/eddies_proposal.pdf"> <span id="translatedtitle">Impacts of Eddies and Mixing on Plankton Community Structure and <span class="hlt">Biogeochemical</span> Cycling in the Sargasso Sea</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Impacts of Eddies and Mixing on Plankton Community Structure and <span class="hlt">Biogeochemical</span> Cycling of measurements that will document phyto- plankton physiological response, changes in community structure, export with an undulating towed instrument that includes a Video Plankton Recorder and a Fast Repetition Rate Fluorometer</p> <div class="credits"> <p class="dwt_author">Buesseler, Ken</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">247</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 " 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://moab.colorado.edu/Publications_files/carrasco002c-j.j.002c-j.c.-neff002c-and-j.w.-harden002c-002820060029..pdf"> <span id="translatedtitle">Modeling physical and <span class="hlt">biogeochemical</span> controls over carbon accumulation in a boreal forest soil</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">the physical and chemical properties of soils and the biophysical regu- lation of decomposition. Within boreal of these factors on C stabilization in boreal soils is essential to improving pre- dictions of how boreal soil CModeling physical and <span class="hlt">biogeochemical</span> controls over carbon accumulation in a boreal forest soil</p> <div class="credits"> <p class="dwt_author">Neff, Jason</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">249</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/41328870"> <span id="translatedtitle">A Linked Physical and Biological Framework to Assess <span class="hlt">Biogeochemical</span> Dynamics in a Shallow Estuarine Ecosystem</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 littoral zone of Chesapeake Bay contains a mosaic of shallow vegetated and nonvegetated habitats with biotic components that are sensitive to changes in biological and physical driving factors. Static and dynamic modelling frameworks provide an integrative way to study complex hydrodynamic and <span class="hlt">biogeochemical</span> processes in linked estuarine habitats. In this study we describe a spatial simulation model developed and</p> <div class="credits"> <p class="dwt_author">C. P Buzzelli; R. L Wetzel; M. B Meyers</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-01-01</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://www.people.fas.harvard.edu/~gbreed/gbreed_files/publications/Dagg_etal_2005.pdf"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Characteristics of the Lower Mississippi River, USA, During June 2003</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary"><span class="hlt">Biogeochemical</span> Characteristics of the Lower Mississippi River, USA, During June 2003 M. J. DAGG1, a period of mid level discharge (17,400 m23 s21 ), a parcel of water in the lower Mississippi River indicate there was little autotrophic or heterotrophic activity in the lower Mississippi River at this time</p> <div class="credits"> <p class="dwt_author">Breed, Greg 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">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.soest.hawaii.edu/oceanography/faculty/zeebe_files/Publications/WolfGladrowMarChem07.pdf"> <span id="translatedtitle">Total alkalinity: The explicit conservative expression and its application to <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/epsearch/">E-print Network</a></p> <p class="result-summary">carbon (DIC) which can be released in the form of CO2 by titration with a strong acid. The alkalinityTotal alkalinity: The explicit conservative expression and its application to <span class="hlt">biogeochemical</span> 2007 Abstract Total alkalinity (TA) is one of the few measurable quantities that can be used together</p> <div class="credits"> <p class="dwt_author">Zeebe, Richard E.</p> <p class="dwt_publisher"></p> <p class="publishDate"></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://www.biomedcentral.com/content/pdf/1467-4866-8-6.pdf"> <span id="translatedtitle">The effect of tidal forcing on <span class="hlt">biogeochemical</span> processes in intertidal salt marsh 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">BACKGROUND: Early diagenetic processes involved in natural organic matter (NOM) oxidation in marine sediments have been for the most part characterized after collecting sediment cores and extracting porewaters. These techniques have proven useful for deep-sea sediments where <span class="hlt">biogeochemical</span> processes are limited to aerobic respiration, denitrification, and manganese reduction and span over several centimeters. In coastal marine sediments, however, the concentration</p> <div class="credits"> <p class="dwt_author">Martial Taillefert; Stephanie Neuhuber; Gwendolyn Bristow</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">253</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/2006OcScD...3.1349P"> <span id="translatedtitle">Eastern Mediterranean <span class="hlt">biogeochemical</span> flux model: simulations of the pelagic ecosystem</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 second phase (2003-2006) of the Mediterranean ocean Forecasting System Project (MFS) named Toward Environmental Predictions (MFSTEP) one of the three major aims was the development of numerical forecasting systems. In this context a generic Biochemical Flux Model (BFM) was developed and <span class="hlt">coupled</span> with hydrodynamic models already operating at basin scale as well as at regional areas. In the Eastern Mediterranean basin the BFM was <span class="hlt">coupled</span> with the Aegean Levantine Eddy Resolving MOdel (ALERMO). The BFM is a generic highly complex model based on ERSEM and although a detailed description of the model and its sub models is beyond the scope of this work a short presentation of the main processes, paying emphasis on the parameter values used is presented. Additionally the performance of the model is evaluated with some preliminary results being qualitatively compared against field observations. The model at its present form is rather promising reproducing all major important features even though there are inefficiencies mostly related to primary and bacterial productivity rates.</p> <div class="credits"> <p class="dwt_author">Petihakis, G.; Triantafyllou, G.; Korres, G.; Pollani, A.; Hoteit, I.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-08-01</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/2001AGUSM...H31A15S"> <span id="translatedtitle">The Influence of Groundwater Seepage on Lakeshore <span class="hlt">Biogeochemical</span> Processes and Fluxes of Solutes Within 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"><span class="hlt">Biogeochemical</span> transformations occur at key interface zones within the landscape and dramatically alter water chemistry along hydrologic flowpaths. Past research has demonstrated that transformations at sediment and water interfaces are particularly important to changes of surface water chemistry within watersheds. However, past studies have rarely explored <span class="hlt">biogeochemical</span> transformations associated with seepage, the advective flux of water through sediments. Changes of the direction and magnitude of seepage influence the transport of gases, ions, and compounds through shoreline sediment profiles. Seepage could influence the availability and cycling of elements within lakeshore ecosystems because groundwater flowpaths converge at lake shorelines. <span class="hlt">Biogeochemical</span> transformations associated with seepage interfaces may be particularly important in the Adirondack Mountains region of New York, USA, where lakes are an important landscape feature and surface water has historically been influenced by atmospheric deposition. We investigated the influence of seepage on pore water biogeochemistry along three Adirondack lakeshores. Seepage meters were intensively monitored and pore water samples were collected over two summers and through spring snowmelt. The data indicated that the direction, magnitude, and variability of seepage fluxes influenced the fluxes and <span class="hlt">biogeochemical</span> cycling of base cations and trace metals (particularly zinc and iron) in pore waters. Seepage fluxes were temporally and spatially variable, but sites that had highly variable seepage fluxes disproportionately contributed to the flux of solutes both to and from the lakes. In contrast, <span class="hlt">biogeochemical</span> transformations at low flow areas altered pore water chemistry as seepage water passed through the sediment profile. Our findings suggest that temporal as well as spatial heterogeneity of seepage fluxes along lake shorelines must be quantified to understand the extent of chemical transformations that occur along groundwater flowpaths.</p> <div class="credits"> <p class="dwt_author">SEBESTYEN, S. D.; SCHNEIDER, R. L.</p> <p class="dwt_publisher"></p> <p class="publishDate">2001-05-01</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://www.ncbi.nlm.nih.gov/pubmed/24053722"> <span id="translatedtitle">Parameterizing soil emission and atmospheric oxidation-reduction in a model of the global <span class="hlt">biogeochemical</span> cycle of mercury.</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">Using the GEOS-Chem atmosphere-land-ocean <span class="hlt">coupled</span> mercury model, we studied the significances of two processes, soil emission and atmospheric oxidation-reduction, in the global <span class="hlt">biogeochemical</span> cycling of mercury and their parametrization to improve model performance. Implementing an empirical equation for soil emission flux (Esoil) including soil mercury concentration, solar radiation, and surface air temperature as parameters enabled the model to reproduce the observed seasonal variations of Esoil, whereas the default setting, which uses only the former two parameters, failed. The modified setting of Esoil also increased the model-simulated atmospheric concentration in the summertime surface layer of the lower- and midlatitudes and improved the model reproducibility for the observations in Japan and U.S. in the same period. Implementing oxidation of atmospheric gaseous elemental mercury (Hg(0)) by ozone with an updated rate constant, as well as the oxidation by bromine atoms (Br) in the default setting, improved the model reproducibility for the dry deposition fluxes observed in Japan. This setting, however, failed to reproduce the observed seasonal variations of atmospheric concentrations in the Arctic sites due to the imbalance between oxidation and reduction, whereas the model with Br as the sole Hg(0) oxidant in the polar atmosphere could capture the variations. PMID:24053722</p> <div class="credits"> <p class="dwt_author">Kikuchi, Tetsuro; Ikemoto, Hisatoshi; Takahashi, Katsuyuki; Hasome, Hisashi; Ueda, Hiromasa</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-11-01</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://pubs.er.usgs.gov/publication/70034593"> <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://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</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 O2, and the release of CH4 and CO2 from the smear zone generated by the floating oil were considered. The focus of the simulations was to assess the dynamics between biodegradation and gas transport processes in the vadose zone, to evaluate the rates and contributions of different electron accepting processes towards vadose zone natural attenuation, and to provide an estimate of the historical mass loss. Concentration distributions of reactive (O2, CH4, and CO2) and non-reactive (Ar and N2) gases served as key constraints for the model calibration. Simulation results confirm that as of 2007, the main degradation pathway can be attributed to methanogenic degradation of organic compounds in the smear zone and the vadose zone resulting in a contaminant plume dominated by high CH4 concentrations. In accordance with field observations, zones of volatilization and CH4 generation are correlated to slightly elevated total gas pressures and low partial pressures of N2 and Ar, while zones of aerobic CH4 oxidation are characterized by slightly reduced gas pressures and elevated concentrations of N2 and Ar. Diffusion is the most significant transport mechanism for gases in the vadose zone; however, the simulations also indicate that, despite very small pressure gradients, advection contributes up to 15% towards the net flux of CH4, and to a more limited extent to O2 ingress. Model calibration strongly suggests that transfer of biogenically generated gases from the smear zone provides a major control on vadose zone gas distributions and vadose zone carbon 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 CH4 and CO2 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. ?? 2009 Elsevier B.V.</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">2010-01-01</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://adsabs.harvard.edu/abs/2011AGUFMPP51B1845G"> <span id="translatedtitle">Ni <span class="hlt">biogeochemical</span> cycle through geological time: insights from Ni isotope variations in modern and ancient marine metallifereous deposits</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">Studies of isotopic composition of transition metals such as Fe, Cu, Zn, and Mo as <span class="hlt">biogeochemical</span> tracers became popular recently. Since Ni is ubiquitous in marine metallifereous deposits and its concentration in water column is <span class="hlt">coupled</span> to that of nutrients, it has a potential as a <span class="hlt">biogeochemical</span> tracer. Isotopic analyses were performed on a Neptune MC-ICP-MS using a double-spike correction method for instrumental mass bias. Deep-sea ferromanganese crusts have been used to establish a record of seawater over the last 60 Myr. Our results show that Fe-Mn crusts from both Atlantic and Pacific oceans are systematically enriched in heavy isotopes relative to Bulk Silicate Earth with ?60/58Ni values ranging from 0.30 to 1.80% (2se = 0.04%). In contrast, Iron Formations (IF) with ages ranging from 3.8 to 0.7 Gyr display a wider range of values with a striking negative Ni isotope excursion down to -2.46% (2se = 0.03%) in Neoproterozoic IF. Although correlation between Ni isotope compositions, Ni concentrations and BIFs ages seems to be lacking, several Ni isotope excursions to either positive or negative Ni isotope values are notable prior to 2.4 Gyr. Methanogens were likely abundant in Precambrian water column until they retreated to pore waters and local environments once the oceans were oxygenated after the Great Oxidation Event (GOE). They preferentially uptake light Ni isotopes leaving isotopically heavier Ni in oceans. Our Ni isotope record of Precambrian IF does not show a unidirectional change across the GOE implying that Ni isotope composition of the Archean oceans was not dominated by this metabolism. Preliminary Ni adsorption experiments on Fe-Mn oxy-hydroxides show a maximum fractionation factor between the mineral phase and aqueous solution of -1.00% (2se = 0.03%). Hence, isotopic variations in Fe-Mn crusts and IF cannot be simply explained by adsorption processes, but require changes in composition of either Ni sources (local or global) to seawater (e.g., rivers, atmosphere, and hydrothermal fluids) or sinks such as organic matter-rich sediments and Fe-Mn oxyhydroxides. Those results combined with our measurements of Ni isotope compositions of Fe-Mn crusts and IF indicate that recent and ancient seawaters were enriched in heavy Ni isotopes consistent with our initial results of Ni isotope composition of deep seawater.</p> <div class="credits"> <p class="dwt_author">Gueguen, B.; Rouxel, O.; Ponzevera, E.; Sorensen, J. V.; Toner, B.; Bekker, 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">258</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 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.ncbi.nlm.nih.gov/pubmed/24954648"> <span id="translatedtitle">Novel tracer method to measure isotopic labeled gas-phase nitrous acid (HO15NO) in <span class="hlt">biogeochemical</span> studies.</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">Gaseous nitrous acid (HONO), the protonated form of nitrite, contributes up to ?60% to the primary formation of hydroxyl radical (OH), which is a key oxidant in the degradation of most air pollutants. Field measurements and modeling studies indicate a large unknown source of HONO during daytime. Here, we developed a new tracer method based on gas-phase stripping-derivatization <span class="hlt">coupled</span> to liquid chromatography-mass spectrometry (LC-MS) to measure the 15N relative exceedance, ?(15N), of HONO in the gas-phase. Gaseous HONO is quantitatively collected and transferred to an azo dye, purified by solid phase extraction (SPE), and analyzed using high performance liquid chromatography <span class="hlt">coupled</span> to mass spectrometry (HPLC-MS). In the optimal working range of ?(15N)=0.2-0.5, the relative standard deviation of ?(15N) is <4%. The optimum pH and solvents for extraction by SPE and potential interferences are discussed. The method was applied to measure HO15NO emissions from soil in a dynamic chamber with and without spiking 15) labeled urea. The identification of HO15NO from soil with 15N urea addition confirmed biogenic emissions of HONO from soil. The method enables a new approach of studying the formation pathways of HONO and its role for atmospheric chemistry (e.g., ozone formation) and environmental tracer studies on the formation and conversion of gaseous HONO or aqueous NO2- as part of the <span class="hlt">biogeochemical</span> nitrogen cycle, e.g., in the investigation of fertilization effects on soil HONO emissions and microbiological conversion of NO2- in the hydrosphere. PMID:24954648</p> <div class="credits"> <p class="dwt_author">Wu, Dianming; Kampf, Christopher J; Pöschl, Ulrich; Oswald, Robert; Cui, Junfang; Ermel, Michael; Hu, Chunsheng; Trebs, Ivonne; Sörgel, Matthias</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-07-15</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://adsabs.harvard.edu/abs/2013JMS...109..S77H"> <span id="translatedtitle">A multi-decadal hindcast of a physical-<span class="hlt">biogeochemical</span> model and derived oceanographic indices in the Bay of Biscay</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">Multiple year oceanographic simulations (hindcast) are identified as a priority oceanography product for fisheries and environment studies since they provide a unique continuous long-term dataset allowing integrated assessment of the ocean state and evolution. We performed a 37 year (1972-2008) hindcast run with a <span class="hlt">coupled</span> physical-<span class="hlt">biogeochemical</span> model in the Bay of Biscay. The <span class="hlt">coupled</span> model and the hindcast configuration are described. A model skill assessment is performed with a large set of in-situ data. Average seasonal currents show major circulation patterns over the shelf. Among tracers, temperature and salinity have the best agreement, ahead of nitrates and silicates, chlorophyll, and finally phosphates and ammonium. For chlorophyll, improved pattern statistics are found when compared to monthly composites of satellite-derived chlorophyll data. From the hindcast, we derived indices related to mesoscale activity (eddies, plumes, fronts, stratification) and production (chlorophyll and primary production). They help characterise the evolution of the environment in a functional way, on both the seasonal and multi-decadal scales. From these indices, first, a multivariate analysis reveals an increasing number of years that deviate from the mean seasonal pattern. Second, we propose interpretations of the simulated increasing trends detected in several of them (temperature, thermocline depth and primary production). We also recommend further developments to confirm these simulated evolutions, from addition of open boundary forcing with a global circulation model, to the improvement of the dynamics of nutrient regeneration and of the seasonal variability of secondary production. As a perspective, we review the different applications made from our hindcast in relation to anchovy life cycle, a species of major interest in the Bay of Biscay.</p> <div class="credits"> <p class="dwt_author">Huret, Martin; Sourisseau, Marc; Petitgas, Pierre; Struski, Caroline; Léger, Fabien; Lazure, Pascal</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-01-01</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_12");' 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_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/2003EAEJA.....3454P"> <span id="translatedtitle">A time dependent ecosystem operational tool for Pagasitikos gulf. Simulation of <span class="hlt">biogeochemical</span> variables in space and time</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">Pagasitikos gulf is a semi-enclosed basin highly influenced both by anthropogenic activities (inflow of nutrients at the north and west parts) as well as by water exchange between the gulf and the Aegean Sea at its south part (Trikeri channel) resulting in the development of functional sub-areas within the gulf. Thus the inner part is characterised by eutrophic conditions with sporadic formation of harmful algal blooms while the central part acts as a buffer with mesotrophic characteristics influenced by the oligotrophic outer area. The aim of this study is to investigate the interactions between the physical and <span class="hlt">biogeochemical</span> systems in the Pagasitikos gulf by <span class="hlt">coupling</span> advanced hydrodynamic and ecological models. The simulation system comprises of two on-line <span class="hlt">coupled</span> sub-models: a three-dimensional hydrodynamic model based on Princeton Ocean Model (POM) and an ecological model adapted from the European Regional Seas Ecosystem Model (ERSEM) for the particular ecosystem. After a model spin up period of ten years to reach a quasi steady state, the results from an annual simulation are presented. Emphasis is given in the description of the spatial and temporal variability of the ecosystem parameters as well as in the relationship between physical forcing and the evolution of the ecosystem along with other factors affecting the nutrient cycling and primary production. A cost function is used as validation method for the comparison of model results with field data. The estimated annual primary and bacteria production are found to be in the range of the reported values. Simulation results are in good agreement with in-situ data illustrating the role of the physical processes in determining the evolution and variability of the ecosystem as well as pointing out the significance of inputs in the functioning of this sensitive ecosystem. Highlighting thus the potential utility of the model as an operational tool to support environmental management decisions.</p> <div class="credits"> <p class="dwt_author">Petihakis, G.; Triantafyllou, G.; Theodorou, A.</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">262</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/70019897"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> phosphorus mass balance for Lake Baikal, southeastern Siberia, Russia</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">Extensive data for Lake Baikal have been synthesized into a geochemical mass balance for phosphorus (P). Some of the P budget and internal cycling terms for Baikal have been compared to similar terms for oligotrophic Lake Superior, mesotrophic Lake Michigan and the Baltic Sea, and the Ocean. Lake Baikal has a large external source of fluvial P compared to the Laurentian upper Great Lakes and the Ocean. The major tributary to Lake Baikal has experienced substantial increases in organic P loading during the past 25 years. This, <span class="hlt">coupled</span> with potential P inputs from possible phosphorite mining, may threaten Baikal's oligotrophic status in the future. Water-column remineralization of particulate organic P is substantially greater in Lake Baikal than in the Laurentian Great Lakes. This is probably due to the great water depths of Lake Baikal. There is a gradient in P burial efficiency, with very high values (80%) for Lake Baikal and Lake Superior, lower values (50%) for Lake Michigan and the Baltic Sea, and a low value (13%) for the Ocean. The accumulation rate of P in Lake Baikal sediments is somewhat greater than that in the Laurentian upper Great Lakes and the Baltic Sea, and much greater than in the Ocean. Benthic regeneration rates are surprisingly similar for large lacustrine and marine environments and supply less than 10% of the P utilized for primary production in these aquatic environments.</p> <div class="credits"> <p class="dwt_author">Callender, E.; Granina, L.</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">263</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 " 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://www.lmd.jussieu.fr/~jldufres/publi/2002/Berthelot.Friedlingstein.ea-gbc-2002.pdf"> <span id="translatedtitle">Global response of the terrestrial biosphere to CO2 and climate change using a <span class="hlt">coupled</span> climate-carbon cycle model</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">feedback in the climate-carbon cycle system. INDEX TERMS: 0315 Atmospheric Composition and Structure: Impact phenomena; KEYWORDS: climate change impact, terrestrial carbon cycle Citation: Berthelot, M., P of the terrestrial biosphere to CO2 and climate change using a <span class="hlt">coupled</span> climate-carbon cycle model, Global <span class="hlt">Biogeochem</span></p> <div class="credits"> <p class="dwt_author">Dufresne, Jean-Louis</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://www.osti.gov/doepatents/biblio/6568536"> <span id="translatedtitle">Helix <span class="hlt">coupling</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p class="result-summary">A <span class="hlt">coupling</span> for connecting helix members in series, which consists of a pair of U-shaped elements, one of which is attached to each helix end with the U sections of the elements interlocked. The <span class="hlt">coupling</span> is particularly beneficial for interconnecting helical Nitinol elements utilized in thermal actuators or engines. Each <span class="hlt">coupling</span> half is attached to the associated helix at two points, thereby providing axial load while being easily removed from the helix, and reusable.</p> <div class="credits"> <p class="dwt_author">Ginell, W.S.</p> <p class="dwt_publisher"></p> <p class="publishDate">1982-03-17</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://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">267</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/2002JHyd..256..228B"> <span id="translatedtitle">Modelling of transport and <span class="hlt">biogeochemical</span> processes in pollution plumes: Vejen landfill, Denmark</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 <span class="hlt">biogeochemical</span> transport code is used to simulate leachate attenuation, <span class="hlt">biogeochemical</span> processes, and development of redox zones in a pollution plume downstream of the Vejen landfill in Denmark. Calibration of the degradation parameters resulted in a good agreement with the observed distribution in the plume of a number of species, such as dissolved organic carbon (DOC), Fe 2+, NO 3-, HCO 3-, SO 42-, CH 4, and pH. The simulated redox zones agree with observations confirming that the Fe-reducing zone played an important role in the attenuation of the DOC plume. Effective first-order rate constants for every redox zone were determined giving DOC half-lives ranging from 100 to 1-2 days going from the methanogenic to the aerobic zone. The order of decrease in DOC half-lives from the anaerobic to the aerobic zone corresponds to findings at other landfills.</p> <div class="credits"> <p class="dwt_author">Brun, Adam; Engesgaard, Peter; Christensen, Thomas H.; Rosbjerg, Dan</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">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/2012AGUFM.H42D..07F"> <span id="translatedtitle">Dynamic Landscape Connectivity, Threshold Behavior, and Scaling Frameworks for Hydrologic and <span class="hlt">Bio-geochemical</span> Fluxes</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 hydrologic connectivity of landscapes (the surface fluvial and non-fluvial flowpaths and the flowpaths in the sub-surface) is temporally and spatially changing as dictated by landscape features and precipitation. Developing simple conceptual frameworks for quantifying the response of a basin (hydrologic, sedimentologic, and <span class="hlt">bio-geochemical</span>) based on theories of network dynamics is still an open problem with slow progress. In this talk two issues will be addressed: (1) scaling of peak flows in response to space-time variable rainfall of duration smaller than the time of concentration of the basin, and (2) predictive modeling and scaling of <span class="hlt">bio-geochemical</span> fluxes using a spatially explicit model of light and nutrient availability, streamflow, and temperature on the connected network. Data from the Walnut Gulch watershed and the Eel river at Angelo Coast Range Reserve are used for model development and testing.</p> <div class="credits"> <p class="dwt_author">Foufoula, E.; Zanardo, S.; Danesh-Yazdi, M.; Zaliapin, I.; Power, M.; Dietrich, W.</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">269</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">270</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">271</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/ft5h576211t57586.pdf"> <span id="translatedtitle">Hydrologic and <span class="hlt">biogeochemical</span> controls on trace element export from northern Wisconsin wetlands</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 play an important role in determining the water quality of streams and are generally considered to act as a sink\\u000a for many reactive species. However, retention of chemical constituents varies seasonally and is affected by hydrologic and\\u000a <span class="hlt">biogeochemical</span> processes including water source, mineral weathering, DOC and SPM cycling, redox status, precipitation\\/dissolution\\/adsorption,\\u000a and seasonal events. Relatively little is known about</p> <div class="credits"> <p class="dwt_author">Sara C. Kerr; Martin M. Shafer; Joel Overdier; David E. Armstrong</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">272</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 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/48601310"> <span id="translatedtitle">Effect of nutrient loading on <span class="hlt">biogeochemical</span> processes in tropical tidal creeks</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 effect of increased nutrient loads on <span class="hlt">biogeochemical</span> processes in macrotidal, mangrove-lined creeks was studied in tropical\\u000a Darwin Harbour, Australia. This study uses an integrative approach involving multiple benthic and pelagic processes as measures\\u000a of ecosystem function, and provides a comparison of these processes in three tidal creeks receiving different loads of treated\\u000a sewage effluent. There were significant differences in</p> <div class="credits"> <p class="dwt_author">Jodie SmithMichele; Michele A. Burford; Andrew T. Revill; Ralf R. Haese; Julia Fortune</p> <p class="dwt_publisher"></p> <p class="publishDate"></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.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">2012-05-15</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://academic.research.microsoft.com/Publication/40205568"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> and environmental study of the chromite-rich ultramafic terrain of Malakand area, Pakistan</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> distribution of enzyme-bound metals in the plants and soil of the chromite-rich mineralized area of Malakand Agency and the non-mineralized area of Mardan (N.W.F.P., Pakistan) has been studied in regard to mineral prospecting and environmental pollution. Samples of lower plants accompanied with their associated soil samples were collected and analysed for copper, lead, zinc, nickel, chromium and cobalt.</p> <div class="credits"> <p class="dwt_author">Q. Kfayatullah; M. Tahir Shah; M. Arfan</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">276</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/u616q76p0057533x.pdf"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Contributions of Tree Islands to Everglades Wetland Landscape Nitrogen Cycling During Seasonal Inundation</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 Florida Everglades, tree islands are conspicuous heterogeneous elements in the herbaceous wetland landscape. We characterized\\u000a the <span class="hlt">biogeochemical</span> role of a seasonally flooded tree island during wet season inundation, specifically examining hydrologically\\u000a mediated flows of nitrogen (N) and N retention by the tree island. We estimated ecosystem N standing stocks and fluxes, soil\\u000a and litter N transformation rates, and</p> <div class="credits"> <p class="dwt_author">Tiffany G. Troxler; Daniel L. Childers</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/42052557"> <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://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p class="result-summary">The <span class="hlt">biogeochemical</span> properties of an extensive bloom (~250,000 km2) of the coccolithophore, EMiliania huxleyi, in the north east Atlantic Ocean were investigated in June 1991. Satellite (NOAA-AVHRR) imagery showed that the bloom was centered initially at 60°-63°N by 13°-28°W and lasted approximately 3 weeks. Spatial variations in satellite-measured reflectance were well correlated with surface measurements of the beam attenuation coefficient,</p> <div class="credits"> <p class="dwt_author">Patrick M. Holligan; Emilio Fernández; James Aiken; William M. Balch; Philip Boyd; Peter H. Burkill; Miles Finch; Stephen B. Groom; Gillian Malin; Kerstin Muller; Charles C. Trees; Suzanne M. Turner; Paul van der Wal</p> <p class="dwt_publisher"></p> <p class="publishDate">1993-01-01</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.osti.gov/scitech/biblio/678056"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> dynamics in zero-valent iron columns: Implications for permeable reactive barriers</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 impact of microbiological and geochemical processes has been a major concern for the long-term performance of permeable reactive barriers containing zero-valent iron (Fe{sup 0}). To evaluate potential <span class="hlt">biogeochemical</span> impacts, laboratory studies were performed over a 5-month period using columns containing a diverse microbial community. The conditions chosen for these experiments were designed to simulate high concentrations of bicarbonate and sulfate containing groundwater regimes. Groundwater chemistry was found to significantly affect corrosion rates of Fe{sup 0} filings and resulted in the formation of a suite of mineral precipitates. HCO{sub 3}{sup {minus}} ions in SO{sub 4}{sup 2{minus}}-containing water were particularly corrosive to Fe{sup 0}, resulting in the formation of ferrous carbonate and enhanced H{sub 2} gas generation that stimulated the growth of microbial populations and increased SO{sub 4}{sup 2{minus}} reduction. Major mineral precipitates identified included lepidocrocite, akaganeite, mackinawite, magnetite/maghemite, goethite, siderite, and amorphous ferrous sulfide. Sulfide was formed as a result of microbial reduction of SO{sub 4}{sup 2{minus}} that became significant after about 2 months of column operations. This study demonstrates that <span class="hlt">biogeochemical</span> influences on the performance and reaction of Fe{sup 0} may be minimal in the short term, necessitating longer-term operations to observe the effects of <span class="hlt">biogeochemical</span> reactions on the performance of Fe{sup 0} barriers. Although major failures of in-ground treatment barriers have not been problematic to date, the accumulation of iron oxyhydroxides, carbonates, and sulfides from <span class="hlt">biogeochemical</span> processes could reduce the reactivity and permeability of Fe{sup 0} beds, thereby decreasing treatment efficiency.</p> <div class="credits"> <p class="dwt_author">Gu, B.; Phelps, T.J.; Liang, L.; Palumbo, A.V.; Jacobs, G.K. [Oak Ridge National Lab., TN (United States). Environmental Sciences Div.] [Oak Ridge National Lab., TN (United States). Environmental Sciences Div.; Dickey, M.J.; Roh, Y.; Kinsall, B.L. [Oak Ridge Inst. for Science and Education, TN (United States)] [Oak Ridge Inst. for Science and Education, TN (United States)</p> <p class="dwt_publisher"></p> <p class="publishDate">1999-07-01</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://www.ncbi.nlm.nih.gov/pubmed/25360783"> <span id="translatedtitle">Defining mediterranean and black sea <span class="hlt">biogeochemical</span> subprovinces and synthetic ocean indicators using mesoscale oceanographic features.</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 Mediterranean and Black Seas are semi-enclosed basins characterized by high environmental variability and growing anthropogenic pressure. This has led to an increasing need for a bioregionalization of the oceanic environment at local and regional scales that can be used for managerial applications as a geographical reference. We aim to identify <span class="hlt">biogeochemical</span> subprovinces within this domain, and develop synthetic indices of the key oceanographic dynamics of each subprovince to quantify baselines from which to assess variability and change. To do this, we compile a data set of 101 months (2002-2010) of a variety of both "classical" (i.e., sea surface temperature, surface chlorophyll-a, and bathymetry) and "mesoscale" (i.e., eddy kinetic energy, finite-size Lyapunov exponents, and surface frontal gradients) ocean features that we use to characterize the surface ocean variability. We employ a k-means clustering algorithm to objectively define <span class="hlt">biogeochemical</span> subprovinces based on classical features, and, for the first time, on mesoscale features, and on a combination of both classical and mesoscale features. Principal components analysis is then performed on the oceanographic variables to define integrative indices to monitor the environmental changes within each resultant subprovince at monthly resolutions. Using both the classical and mesoscale features, we find five <span class="hlt">biogeochemical</span> subprovinces for the Mediterranean and Black Seas. Interestingly, the use of mesoscale variables contributes highly in the delineation of the open ocean. The first axis of the principal component analysis is explained primarily by classical ocean features and the second axis is explained by mesoscale features. <span class="hlt">Biogeochemical</span> subprovinces identified by the present study can be useful within the European management framework as an objective geographical framework of the Mediterranean and Black Seas, and the synthetic ocean indicators developed here can be used to monitor variability and long-term change. PMID:25360783</p> <div class="credits"> <p class="dwt_author">Nieblas, Anne-Elise; Drushka, Kyla; Reygondeau, Gabriel; Rossi, Vincent; Demarcq, Hervé; Dubroca, Laurent; Bonhommeau, Sylvain</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</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/48932063"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> simulation of nitrous oxide cycle based on the major nitrogen 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">We modeled the <span class="hlt">biogeochemical</span> nitrogen cycle with specific emphasis on N2O behavior to describe the global N2O cycle system quantitatively. Here all the major nitrogen cycle processes are included plus the processes directly related to N2O. The model includes 24 nitrogen reservoirs: 3 in the stratosphere (N2O, N2, and NOx), 4 in the troposphere (N2O, N2, NH3, and NOx), 7</p> <div class="credits"> <p class="dwt_author">Masao Sorai; Naohiro Yoshida; Masamichi Ishikawa</p> <p class="dwt_publisher"></p> <p class="publishDate">2007-01-01</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://pubs.er.usgs.gov/publication/70039045"> <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://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</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 O2 and NO3- showing similar temporal patterns. Reducing conditions in the subsurface evolved during prolonged flooding of the basin. At about the same time O2 and NO3- reduction concluded, Mn, Fe and SO42- reduction began, with the onset of methanogenesis one month later. Reducing conditions persisted up to six months, continuing into subsequent dry periods until the next major oxidizing infiltration event. Evidence of denitrification in shallow groundwater at the site is supported by median NO3-–N less than 0.016 mg L-1, excess N2 up to 3 mg L-1 progressively enriched in ?15N during prolonged basin flooding, and isotopically heavy ?15N and ?18O of NO3- (up to 25‰ and 15‰, respectively). Isotopic enrichment of newly infiltrated stormwater suggests denitrification was partially completed within two days. Soil and water chemistry data suggest that a <span class="hlt">biogeochemically</span> active zone exists in the upper 1.4 m of soil, where organic carbon was the likely electron donor supplied by organic matter in soil solids or dissolved in infiltrating stormwater. The cyclic nature of reducing conditions effectively controlled the N cycle, switching N fate beneath the basin from NO3- leaching to reduction in the shallow saturated zone. Results can inform design of functionalized soil amendments that could replace the native soil in a stormwater infiltration basin and mitigate potential NO3- leaching to groundwater by replicating the <span class="hlt">biogeochemical</span> conditions under the observed basin.</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">2012-01-01</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://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4216069"> <span id="translatedtitle">Defining Mediterranean and Black Sea <span class="hlt">Biogeochemical</span> Subprovinces and Synthetic Ocean Indicators Using Mesoscale Oceanographic Features</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 Mediterranean and Black Seas are semi-enclosed basins characterized by high environmental variability and growing anthropogenic pressure. This has led to an increasing need for a bioregionalization of the oceanic environment at local and regional scales that can be used for managerial applications as a geographical reference. We aim to identify <span class="hlt">biogeochemical</span> subprovinces within this domain, and develop synthetic indices of the key oceanographic dynamics of each subprovince to quantify baselines from which to assess variability and change. To do this, we compile a data set of 101 months (2002–2010) of a variety of both “classical” (i.e., sea surface temperature, surface chlorophyll-a, and bathymetry) and “mesoscale” (i.e., eddy kinetic energy, finite-size Lyapunov exponents, and surface frontal gradients) ocean features that we use to characterize the surface ocean variability. We employ a k-means clustering algorithm to objectively define <span class="hlt">biogeochemical</span> subprovinces based on classical features, and, for the first time, on mesoscale features, and on a combination of both classical and mesoscale features. Principal components analysis is then performed on the oceanographic variables to define integrative indices to monitor the environmental changes within each resultant subprovince at monthly resolutions. Using both the classical and mesoscale features, we find five <span class="hlt">biogeochemical</span> subprovinces for the Mediterranean and Black Seas. Interestingly, the use of mesoscale variables contributes highly in the delineation of the open ocean. The first axis of the principal component analysis is explained primarily by classical ocean features and the second axis is explained by mesoscale features. <span class="hlt">Biogeochemical</span> subprovinces identified by the present study can be useful within the European management framework as an objective geographical framework of the Mediterranean and Black Seas, and the synthetic ocean indicators developed here can be used to monitor variability and long-term change. PMID:25360783</p> <div class="credits"> <p class="dwt_author">Nieblas, Anne-Elise; Drushka, Kyla; Reygondeau, Gabriel; Rossi, Vincent; Demarcq, Herve; Dubroca, Laurent; Bonhommeau, Sylvain</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</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://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 " 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://adsabs.harvard.edu/abs/2013EGUGA..1510011R"> <span id="translatedtitle">Toward a dynamic <span class="hlt">biogeochemical</span> division of the Mediterranean Sea in a context of global climate change</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 recent decades, it has been found useful to ecoregionalise the pelagic environment assuming that within each partition environmental conditions are distinguishable and unique. Indeed, each partition of the ocean that is proposed aimed to delineate the main oceanographical and ecological patterns to provide a geographical framework of marine ecosystems for ecological studies and management purposes. The aim of the present work is to integrate and process existing data on the pelagic environment of the Mediterranean Sea in order to define <span class="hlt">biogeochemical</span> regions. Open access databases including remote sensing observations, oceanographic campaign data and physical modeling simulations are used. These various dataset allow the multidisciplinary view required to understand the interactions between climate and Mediterranean marine ecosystems. The first step of our study has consisted in a statistical selection of a set of crucial environmental factors to propose the most parsimonious biogeographical approach that allows detecting the main oceanographic structure of the Mediterranean Sea. Second, based on the identified set of environmental parameters, both non-hierarchical and hierarchical clustering algorithms have been tested. Outputs from each methodology are then inter-compared to propose a robust map of the biotopes (unique range of environmental parameters) of the area. Each biotope was then modeled using a non parametric environmental niche method to infer a dynamic <span class="hlt">biogeochemical</span> partition. Last, the seasonal, inter annual and long term spatial changes of each <span class="hlt">biogeochemical</span> regions were investigated. The future of this work will be to perform a second partition to subdivide the <span class="hlt">biogeochemical</span> regions according to biotic features of the Mediterranean Sea (ecoregions). This second level of division will thus be used as a geographical framework to identify ecosystems that have been altered by human activities (i.e. pollution, fishery, invasive species) for the European project PERSEUS (Protecting EuRopean Seas and borders through the intelligence US of surveillance) and the French program MERMEX (Marine Ecosystems Response in the Mediterranean Experiment).</p> <div class="credits"> <p class="dwt_author">Reygondeau, Gabriel; Olivier Irisson, Jean; Guieu, Cecile; Gasparini, Stephane; Ayata, Sakina; Koubbi, Philippe</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">285</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/2013GBioC..27.1139L"> <span id="translatedtitle">The influence of mesoscale and submesoscale heterogeneity on ocean <span class="hlt">biogeochemical</span> reactions</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 oceanic circulation in the meso to submesoscale regime generates heterogeneity in the concentrations of <span class="hlt">biogeochemical</span> components over these scales, horizontally between 1 and 100 km. Due to nonlinearities in the <span class="hlt">biogeochemical</span> reactions, such as phytoplankton primary production and zooplankton grazing, this small-scale heterogeneity can lead to departure from the mean field approximation, whereby plankton reactions are evaluated from mean distributions at coarser scale. Here we explore the magnitude of these eddy reactions and compare their strength to those of the more widely studied eddy transports. We use the term eddy to denote effects arising from scales smaller than ˜ 100 km. This is done using a submesoscale permitting <span class="hlt">biogeochemical</span> model, representative of the seasonally varying subtropical and subpolar gyres. We found that the eddy reactions associated with primary production and grazing account for ±5-30% of productivity and grazing, respectively, depending on location and time of year, and are scale dependent: two thirds are due to heterogeneities at scales 30-100 km and one third to those at scales below 30 km. Moreover, eddy productivities are systematically negative, implying that production tends to be reduced by nonlinear interactions at the mesoscale and smaller. The opposite result is found for eddy grazing, which is generally positive. The contrasting effects result from vertical advection, which negatively correlates phytoplankton and nutrients and positively correlates phytoplankton and zooplankton in the meso to submesoscale range. Moreover, our results highlight the central role played by eddy reactions for ecological aspects and the distribution of organisms and by eddy transport for <span class="hlt">biogeochemical</span> aspects and nutrient budgets.</p> <div class="credits"> <p class="dwt_author">Levy, M.; Martin, A. P.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-01</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/2013EGUGA..1511532G"> <span id="translatedtitle">A bottom-up approach: using residence time distributions and characteristic <span class="hlt">biogeochemical</span> timescales to upscale multiphysics models of hyporheic exchange</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">Residence time distributions (RTDs) and characteristic <span class="hlt">biogeochemical</span> time scales (CBTSs) are integrated metrics that can be used to describe the <span class="hlt">biogeochemical</span> evolution of water within hydrologic systems. RTDs describe the time that water and solutes are in contact with the system and strongly depend on the forcing and geomorphic features driving exchange and the system's hydraulic properties. On the other hand, CBTSs describe the time necessary for a <span class="hlt">biogeochemical</span> transformation to take place and depend on the reaction type, solute concentrations entering the system, and chemical kinetics (or thermodynamics). Comparing RTDs and CBTSs allow us to evaluate the potential for transformation within the hydrologic system. In this work, we illustrate this approach with sinuosity-driven hyporheic zones; however, these concepts can be applied to other hydrologic systems. A two-dimensional, transient, numerical flow and transport model is used to illustrate the effect that dynamics, caused by deterministically generated flood events, has on flow fields and RTDs, and therefore on the character of the hyporheic zone as a <span class="hlt">biogeochemical</span> reactor. A simple analytical model is used to estimate the CBTSs associated to the degradation of dissolved organic carbon in these hydrologic systems, which are compared to numerically-modeled RTDs and used to estimate the <span class="hlt">biogeochemical</span> zonation within the HZ and its net <span class="hlt">biogeochemical</span> response. Additionally, we use a multispecies, reactive transport model to assess this approach, paying special attention to those portions of the system with intermittent hyporheic contributions. In particular, transient flow results in time-varying hot-spot for <span class="hlt">biogeochemical</span> reactions and induces the emergence of new modes on the dynamic RTDs, which are observed within the system and at the outlet. This parsimonious approach can be used as a predictive tool to quantify the potential of meanders as <span class="hlt">biogeochemical</span> reactors at the watershed scale with the aid of historic discharge data, remote sensing data, and GIS processing techniques.</p> <div class="credits"> <p class="dwt_author">Gomez, Jesus D.; Wilson, John L.</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">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/2006AGUSM.B32A..01M"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Cycling at Natural System Interfaces at the Norman Landfill, Norman, OK: Living on the Edge</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">Steep <span class="hlt">biogeochemical</span> gradients were observed at mixing interfaces in a wetland-aquifer system impacted by landfill leachate in Norman, Oklahoma. The system lies within the reworked alluvial plain of the Canadian River and is characterized by layered low hydraulic conductivity wetland sediments and interbedded sandy aquifer material. Using cm-scale passive diffusion samplers (peepers), water samples were collected to span the interfaces between surface water, wetland sediments, and sandy sediments. Geochemical indicators of terminal electron accepting processes, including low molecular weight fatty acids, were analyzed by capillary electrophoresis and field techniques to maximize low sample volumes. Iron reduction and sulfate reduction appear to coexist at the sediment-water interface. Maximum concentrations of other <span class="hlt">biogeochemical</span> indicators (ex. acetate (1.80mM, 8.8mM) and ammonium (13mM, 36mM)) were observed at the sediment/water, and wetland sediment/sand interfaces. Findings support the hypothesis that increased <span class="hlt">biogeochemical</span> cycling occurs at interfaces where limiting electron acceptors and donors mix. The linkages between geochemical gradients and microbiological cycling are being evaluated using in-situ experiments designed to collect microbiological and geochemical data at similar spatial and temporal scales within the aquifer-wetland system.</p> <div class="credits"> <p class="dwt_author">McGuire, J. T.; Baez-Cazull, S.; Cozzarelli, I. M.; Voytek, M. A.; Smith, E. W.; Kneeshaw, T. A.; Kirshstein, J. D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-05-01</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/2008AGUFM.H24D..07M"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Connectivity in a Semi-Arid River Basin: San Pedro River , Arizona, 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">Streams and rivers are closely connected to the groundwater that supplies their baseflow, but only episodically connected to the <span class="hlt">biogeochemically</span> diverse uplands that dominate catchment area. This disconnection with uplands is especially marked in semi-arid systems where full connection of the catchment to the drainage network is infrequent, occurring for only a few days each year. While these hydrologic connections are infrequent, they are critical for supplying the carbon and nitrogen that drive in and near stream biogeochemistry for non-flood periods in these systems. Here we discuss a conceptual model of river scale catchment biogeochemistry for the San Pedro River. An important element of <span class="hlt">biogeochemical</span> linkages in semi-arid river systems is that dissolved constituents are consumed during transport and thus upland contributions of dissolved materials decrease with travel distance and catchment size. Suspended and particulate export do not decrease with catchment size and thus represent large fluxes of nitrogen and carbon during flood flows in a river system. While some fraction of this suspended load is transported through a system a significant percentage remains in stream bed sediments. This sediment load represents a key resource for <span class="hlt">biogeochemical</span> processing and nutrient availability during non-flood periods. These resources are mobilized into the aquatic environment through groundwater flux into the surface water system, hyporheic exchange and diurnal ET pumping of the stream bank environment. Floods and the sediment and nutrients fluxes they transport thus represent a hot moment that later drives the hot spot of riparian systems on the landscape.</p> <div class="credits"> <p class="dwt_author">Meixner, T.; Brooks, P.; Hogan, J.</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">289</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=3546933"> <span id="translatedtitle">Invasive Fishes Generate <span class="hlt">Biogeochemical</span> Hotspots in a Nutrient-Limited System</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">Fishes can play important functional roles in the nutrient dynamics of freshwater systems. Aggregating fishes have the potential to generate areas of increased <span class="hlt">biogeochemical</span> activity, or hotspots, in streams and rivers. Many of the studies documenting the functional role of fishes in nutrient dynamics have focused on native fish species; however, introduced fishes may restructure nutrient storage and cycling freshwater systems as they can attain high population densities in novel environments. The purpose of this study was to examine the impact of a non-native catfish (Loricariidae: Pterygoplichthys) on nitrogen and phosphorus remineralization and estimate whether large aggregations of these fish generate measurable <span class="hlt">biogeochemical</span> hotspots within nutrient-limited ecosystems. Loricariids formed large aggregations during daylight hours and dispersed throughout the stream during evening hours to graze benthic habitats. Excretion rates of phosphorus were twice as great during nighttime hours when fishes were actively feeding; however, there was no diel pattern in nitrogen excretion rates. Our results indicate that spatially heterogeneous aggregations of loricariids can significantly elevate dissolved nutrient concentrations via excretion relative to ambient nitrogen and phosphorus concentrations during daylight hours, creating <span class="hlt">biogeochemical</span> hotspots and potentially altering nutrient dynamics in invaded systems. PMID:23342083</p> <div class="credits"> <p class="dwt_author">Capps, Krista A.; Flecker, Alexander S.</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">290</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/10.1080/10643389.2010.530908"> <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://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</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 where nutrients and salts accumulate under the head of a tree island during dry periods. Results also suggest accumulated salts and nutrients are flushed downstream by regional water flows during wet periods. That trees modulate their environment to create <span class="hlt">biogeochemical</span> hot spots and strong nutrient gradients is a significant ecological paradigm shift in the understanding of the <span class="hlt">biogeochemical</span> processes in the Everglades. In terms of island sustainability, this new paradigm suggests the need for distinct dry-wet cycles as well as a hydrologic regime that supports tree survival. Restoration of historic tree islands needs further investigation but the creation of functional tree islands is promising. Copyright ?? 2011 Taylor & Francis Group, LLC.</p> <div class="credits"> <p class="dwt_author">Wetzel, P. R.; Sklar, F. H.; Coronado, C. A.; Troxler, T. G.; Krupa, S. L.; Sullivan, P. L.; Ewe, S.; Price, R. M.; Newman, S.; Orem, W. H.</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">291</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....6.2949Z"> <span id="translatedtitle">Rates of <span class="hlt">biogeochemical</span> phosphorus and copper redistribution in young floodplain soils</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">Nutrients and trace metals in river-floodplain systems may originate from anthropogenic activities and/or geogenic sources. Here, we analyze a soil chronosequence (2 to approximately 600 years) on a floodplain at the Danube River (Austria) to quantify the rates of P and Cu redistribution among <span class="hlt">biogeochemical</span> pools during early soil formation under temperate continental climate. While bulk and clay mineralogy remained unchanged over the studied age gradient, we found considerable (mostly non-linear) redistribution of P and Cu among <span class="hlt">biogeochemical</span> pools. The calcium-associated P and Cu fractions decreased rapidly during the initial decades of soil formation. The dissolution of calcium-associated P was mirrored by marked accumulation of organic P. Copper incorporated within resistant minerals showed a relative enrichment with soil age. The mean dissolution rates of calcium-associated (primary mineral) P decreased exponentially with increasing soil age from ~1.6 g m-2 yr-1 over ~15 years to ~0.04 g m-2 yr-1 over ~550 years, and were almost an order of magnitude higher than rates reported for tropical environments. Our study demonstrates that on riverine floodplains, rapid <span class="hlt">biogeochemical</span> transformations can occur within the first centuries of soil formation under temperate climatic conditions.</p> <div class="credits"> <p class="dwt_author">Zehetner, F.; Lair, G. J.; Graf, M.; Gerzabek, M. 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">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/2014BGeo...11.3721T"> <span id="translatedtitle">Technical Note: Simple formulations and solutions of the dual-phase diffusive transport for <span class="hlt">biogeochemical</span> 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">Representation of gaseous diffusion in variably saturated near-surface soils is becoming more common in land <span class="hlt">biogeochemical</span> models, yet the formulations and numerical solution algorithms applied vary widely. We present three different but equivalent formulations of the dual-phase (gaseous and aqueous) tracer diffusion transport problem that is relevant to a wide class of volatile tracers in land <span class="hlt">biogeochemical</span> models. Of these three formulations (i.e., the gas-primary, aqueous-primary, and bulk-tracer-based formulations), we contend that the gas-primary formulation is the most convenient for modeling tracer dynamics in <span class="hlt">biogeochemical</span> models. We then provide finite volume approximation to the gas-primary equation and evaluate its accuracy against three analytical models: one for steady-state soil CO2 dynamics, one for steady-state soil CH4 dynamics, and one for transient tracer diffusion from a constant point source into two different sequentially aligned medias. All evaluations demonstrated good accuracy of the numerical approximation. We expect our result will standardize an efficient mechanistic numerical method for solving relatively simple, multi-phase, one-dimensional diffusion problems in land models.</p> <div class="credits"> <p class="dwt_author">Tang, J. Y.; Riley, W. J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-07-01</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://ntrs.nasa.gov/search.jsp?R=19930073170&hterms=salinity+plants&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dsalinity%2Bplants"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> factors which regulate the formation and fate of sulfide in wetlands</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">Coastal wetland areas occupy a small percentage of the terrestrial environment yet are extremely productive regions which support rapid rates of below ground bacterial activity. Wetlands appear to be significant as biogenic sources of gaseous sulfur, carbon, and nitrogen. These gases are important as tracers of man's activities, and they influence atmospheric chemistry. The interactions among wetland <span class="hlt">biogeochemical</span> processes regulate the anaerobic production of reduced gases and influence the fate of these volatiles. Therefore, spatial and temporal variations in hydrology, salinity, temperature, and speciation and growth of vegetation affect the type and magnitude of gas emissions thus hindering predictive estimates of gas flux. The research is divided into two major parts, the first is the <span class="hlt">biogeochemical</span> characterization of a selected tidal wetland area in terms of factors likely to regulate sulfide flux; the second is a direct measurement of gaseous sulfur flux as related to changes in these <span class="hlt">biogeochemical</span> conditions. Variant factors affecting sulfide flux include the wetlands' tidal range, seasonal salinity, and other hydrological conditions, grass species and plant growth, soil composition, and microbial activity.</p> <div class="credits"> <p class="dwt_author">Hines, Mark E.; Lyons, W. Berry; Gaudette, H. E.</p> <p class="dwt_publisher"></p> <p class="publishDate">1985-01-01</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/2013BGD....10.7521Q"> <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">2013-04-01</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/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">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.ncbi.nlm.nih.gov/pubmed/23342083"> <span id="translatedtitle">Invasive fishes generate <span class="hlt">biogeochemical</span> hotspots in a nutrient-limited system.</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">Fishes can play important functional roles in the nutrient dynamics of freshwater systems. Aggregating fishes have the potential to generate areas of increased <span class="hlt">biogeochemical</span> activity, or hotspots, in streams and rivers. Many of the studies documenting the functional role of fishes in nutrient dynamics have focused on native fish species; however, introduced fishes may restructure nutrient storage and cycling freshwater systems as they can attain high population densities in novel environments. The purpose of this study was to examine the impact of a non-native catfish (Loricariidae: Pterygoplichthys) on nitrogen and phosphorus remineralization and estimate whether large aggregations of these fish generate measurable <span class="hlt">biogeochemical</span> hotspots within nutrient-limited ecosystems. Loricariids formed large aggregations during daylight hours and dispersed throughout the stream during evening hours to graze benthic habitats. Excretion rates of phosphorus were twice as great during nighttime hours when fishes were actively feeding; however, there was no diel pattern in nitrogen excretion rates. Our results indicate that spatially heterogeneous aggregations of loricariids can significantly elevate dissolved nutrient concentrations via excretion relative to ambient nitrogen and phosphorus concentrations during daylight hours, creating <span class="hlt">biogeochemical</span> hotspots and potentially altering nutrient dynamics in invaded systems. PMID:23342083</p> <div class="credits"> <p class="dwt_author">Capps, Krista A; Flecker, Alexander S</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">297</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 " 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/1993DSRII..40..651F"> <span id="translatedtitle">Nitrogen <span class="hlt">biogeochemical</span> cycling in the northwestern Indian 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">The vertical distribution and fine scale structure of nitrate (NO 3), nitrite (NO 2), nitrous Oxide (N 2O), phosphate (PO 4), oxygen (O 2) and chlorophyll ? (chl ?) were determined in the North Western Indian Ocean (NWIO) along a meridional section (67°E) from the Equator to the Gulf of Oman using an Autoanalyser for micromolar levels of nutrients, and chemiluminescence and gas chromatographic methods for nanomolar levels of NO 3 and NO 2 and N 2O respectively. Three biogeochimically contrasting regimes were investigated: (1) the highly oligotrophic nutrient-depleted subtropical gyre; (2) the nonsoonal upwelling of nutrient-rich intermediate waters of the southeastern Arabian Coast; and (3) the denitrifying O 2-depleted zone (ODZ; ca 150-1200 m depth) in the Arabian Sea. Concentrations of NO 3 and NO 2 were severely depleted in surface oligotrophic waters from the equator (average 43 and 3.6 nM respectively) to the subtropical gyre (12-15°N; average 13.3 and 2.0 nM respectively) with similar levels in the more stratified Gulf of Oman. Upwelling waters off Southern Arabia had three orders of magnitude higher NO 3 levels, and throughout the NWIO, the calculated NO 3-fuelled primary production appeared to be regulated by NO 3 concentration. Existing Redfield ?O 2/?NO 3 regeneration ratios (=9.1) previously derived for the deep Indian Ocean were confirmed (= 9.35) within the oxic upper layers of the NWIO. The "NO"-potential temperature relationship ( BROECKER, 1974 Earth and Planetary Science Letters, 23, 100-107) needed for the derivation of expected NO 3 and NO 3-deficits within the denitrifying ODZ were refined using an isopycnal, binary mixing model along the ?? = 26.6%, density layer to take into account the inflowing contribution of NO 3-depleted Persian Gulf Water. Vertically integrated NO 3-deficits increased northwards from 0.8 mol NO 3-N m -2 at Sta. 2 (04°N), up to 6.49 mol NO 3-N m -2 at Sta. 9, at the mouth of the Gulf of Oman, then decreased to 4.10 moles NO 3-N m -2 toward Sta. 11, near the Straits of Hormuz. When averaged for the denitrification area of the Arabian Sea, this corresponds to a deficit of 118 Tg NO 3-N. Adopting a recent Freon-11 based estimate of water residence time of 10 years ( OLSONet al., 1993, Deep-Sea Research II, 40, 673-685) for the O 2-depleted layer, we calculate an annual net denitrification flux of 11.9 Tg N to the atmosphere or approximately 10% of the global water column denitrification rates. Supersaturated N 2O concentrations were found in both surface oxic and upwelling waters (up to 246%) and peaked at the base of the ODZ (up to 1264%) in the northern Arabian Sea. Both nitrification in oxic waters and denitrification in hypoxic layers can be invoked as sources of N 2O. The inventory of excess N 2O amounted to 2.55 ± 1.3 Tg N 2O-N, corresponding to annual production of 0.26 ± 0.13 Tg from denitrification. This is comparable to earlier ( LAW AND OWENS, 1990, Nature, 346, 826-828) estimates of the ventilation flux of N 2O (0.22-0.39 Tg yr -1) from the upwelling region of the Arabian Sea. The decadal response times for circulation, deoxygenation, denitrification and ventilation of the ODZ-derived N 2O and CO 2 greenhouse gases and their monsoonal <span class="hlt">coupling</span> implies the Arabian Sea is a sensitive oceanic recorder of global climate change.</p> <div class="credits"> <p class="dwt_author">Fauzi, R.; Mantoura, C.; Law, Clifford S.; Owens, Nicholas J. P.; Burkill, Peter H.; Woodward, E. Malcolm S.; Howland, Robin J. M.; Llewellyn, Carole 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">299</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/70118989"> <span id="translatedtitle">Nitrous oxide emissions from cropland: a procedure for calibrating the DayCent <span class="hlt">biogeochemical</span> model using inverse modelling</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">DayCent is a <span class="hlt">biogeochemical</span> model of intermediate complexity widely used to simulate greenhouse gases (GHG), soil organic carbon and nutrients in crop, grassland, forest and savannah ecosystems. Although this model has been applied to a wide range of ecosystems, it is still typically parameterized through a traditional “trial and error” approach and has not been calibrated using statistical inverse modelling (i.e. algorithmic parameter estimation). The aim of this study is to establish and demonstrate a procedure for calibration of DayCent to improve estimation of GHG emissions. We <span class="hlt">coupled</span> DayCent with the parameter estimation (PEST) software for inverse modelling. The PEST software can be used for calibration through regularized inversion as well as model sensitivity and uncertainty analysis. The DayCent model was analysed and calibrated using N2O flux data collected over 2 years at the Iowa State University Agronomy and Agricultural Engineering Research Farms, Boone, IA. Crop year 2003 data were used for model calibration and 2004 data were used for validation. The optimization of DayCent model parameters using PEST significantly reduced model residuals relative to the default DayCent parameter values. Parameter estimation improved the model performance by reducing the sum of weighted squared residual difference between measured and modelled outputs by up to 67 %. For the calibration period, simulation with the default model parameter values underestimated mean daily N2O flux by 98 %. After parameter estimation, the model underestimated the mean daily fluxes by 35 %. During the validation period, the calibrated model reduced sum of weighted squared residuals by 20 % relative to the default simulation. Sensitivity analysis performed provides important insights into the model structure providing guidance for model improvement.</p> <div class="credits"> <p class="dwt_author">Rafique, Rashad; Fienen, Michael N.; Parkin, Timothy B.; Anex, Robert 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">300</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/2005AnGeo..23.3171H"> <span id="translatedtitle">Efficient data assimilation into a complex, 3-D physical-<span class="hlt">biogeochemical</span> model using partially-local Kalman filters</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">Advanced Kalman filtering techniques were used to assimilate pseudo ocean color and profile data into a complex, three-dimensional <span class="hlt">coupled</span> physical (POM)-<span class="hlt">biogeochemical</span> (ERSEM) model of the Cretan Sea ecosystem. The assimilation schemes, the Singular Evolutive Partially-Local Extended Kalman (SEPLEK) filter and its variant called SFPLEK, are based on the standard SEEK filter in which the Kalman correction is made along a set of "global" and "local" directions, determined via a so-called "global-local EOF analysis". The global functions are used to represent the ecosystem large-scale variability. They are allowed to evolve in time in the SEPLEK filter to follow changes in the model dynamics, while they remain invariant in the SFPLEK filter. The local functions always remain invariant and are determined in such a way as to independently represent the different spatial regimes of the ecological model. This helps to improve the estimation of fine-scale variations while requiring significantly less computational time compared to the SEEK filter. <P style="line-height: 20px;"> Several assimilation experiments were performed to assess the relevance of the assimilation system and to study its sensitivity to different choices of global/local EOFs. The SFPLEK filter was used in all the sensitivity experiments in order to efficiently measure the representativeness of the different set of correction directions, as well as to save computational time. Assimilation results suggest that the use of global-local correction directions clearly enhances the filter's performance under different assimilation setups. The choice of the local directions should, however, be carefully considered, taking into account the model regional variability and the characteristics of the observational system.</p> <div class="credits"> <p class="dwt_author">Hoteit, I.; Triantafyllou, G.; Petihakis, G.</p> <p class="dwt_publisher"></p> <p class="publishDate">2005-11-01</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_14");' href="#" title="Previous Page"> <img id="PreviousPageLinkImage" class="Icon" src="http://www.science.gov/scigov/images/icon.previous.18x20.png" alt="Previous 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showDiv("page_25");' href="#">25</a> </span> </span> <a id="NextPageLink" onclick='return showDiv("page_17");' 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">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/2014JGRG..119.1520S"> <span id="translatedtitle">A <span class="hlt">coupled</span> geochemical and <span class="hlt">biogeochemical</span> approach to characterize the bioreactivity of dissolved organic matter from a headwater 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">bioreactivity or susceptibility of dissolved organic matter (DOM) to microbial degradation in streams and rivers is of critical importance to global change studies, but a comprehensive understanding of DOM bioreactivity has been elusive due, in part, to the stunningly diverse assemblages of organic molecules within DOM. We approach this problem by employing a range of techniques to characterize DOM as it flows through biofilm reactors: dissolved organic carbon (DOC) concentrations, excitation emission matrix spectroscopy (EEMs), and ultrahigh resolution mass spectrometry. The EEMs and mass spectral data were analyzed using a combination of multivariate statistical approaches. We found that 45% of stream water DOC was biodegraded by microorganisms, including 31-45% of the humic DOC. This bioreactive DOM separated into two different groups: (1) H/C centered at 1.5 with O/C 0.1-0.5 or (2) low H/C of 0.5-1.0 spanning O/C 0.2-0.7 that were positively correlated (Spearman ranking) with chromophoric and fluorescent DOM (CDOM and FDOM, respectively). DOM that was more recalcitrant and resistant to microbial degradation aligned tightly in the center of the van Krevelen space (H/C 1.0-1.5, O/C 0.25-0.6) and negatively correlated (Spearman ranking) with CDOM and FDOM. These findings were supported further by principal component analysis and 2-D correlation analysis of the relative magnitudes of the mass spectral peaks assigned to molecular formulas. This study demonstrates that our approach of processing stream water through bioreactors followed by EEMs and FTICR-MS analyses, in combination with multivariate statistical analysis, allows for precise, robust characterization of compound bioreactivity and associated molecular level composition.</p> <div class="credits"> <p class="dwt_author">Sleighter, Rachel L.; Cory, Rose M.; Kaplan, Louis A.; Abdulla, Hussain A. N.; Hatcher, Patrick G.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-08-01</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://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">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.ncbi.nlm.nih.gov/pubmed/23744637"> <span id="translatedtitle">Global patterns of nitrogen limitation: confronting two global <span class="hlt">biogeochemical</span> models with observations.</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">Projections of future changes in land carbon (C) storage using <span class="hlt">biogeochemical</span> models depend on accurately modeling the interactions between the C and nitrogen (N) cycles. Here, we present a framework for analyzing N limitation in global <span class="hlt">biogeochemical</span> models to explore how C-N interactions of current models compare to field observations, identify the processes causing model divergence, and identify future observation and experiment needs. We used a set of N-fertilization simulations from two global <span class="hlt">biogeochemical</span> models (CLM-CN and O-CN) that use different approaches to modeling C-N interactions. On the global scale, net primary productivity (NPP) in the CLM-CN model was substantially more responsive to N fertilization than in the O-CN model. The most striking difference between the two models occurred for humid tropical forests, where the CLM-CN simulated a 62% increase in NPP at high N addition levels (30 g N m(-2) yr(-1)), while the O-CN predicted a 2% decrease in NPP due to N fertilization increasing plant respiration more than photosynthesis. Across 35 temperate and boreal forest sites with field N-fertilization experiments, we show that the CLM-CN simulated a 46% increase in aboveground NPP in response to N, which exceeded the observed increase of 25%. In contrast, the O-CN only simulated a 6% increase in aboveground NPP at the N-fertilization sites. Despite the small response of NPP to N fertilization, the O-CN model accurately simulated ecosystem retention of N and the fate of added N to vegetation when compared to empirical (15) N tracer application studies. In contrast, the CLM-CN predicted lower total ecosystem N retention and partitioned more losses to volatilization than estimated from observed N budgets of small catchments. These results point to the need for model improvements in both models in order to enhance the accuracy with which global C-N cycle feedbacks are simulated. PMID:23744637</p> <div class="credits"> <p class="dwt_author">Thomas, R Quinn; Zaehle, Sönke; Templer, Pamela H; Goodale, Christine L</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-10-01</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://adsabs.harvard.edu/abs/2007AGUFMOS11A0198S"> <span id="translatedtitle">Validating a <span class="hlt">Biogeochemical</span> Watershed Disturbance and Climate Change Proxy: Tampa Bay. FL</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 Tampa Bay estuary and watershed have been impacted in the past century by residential and industrial development activities that have resulted in pollutant release via runoff and wastewater discharges. Mangrove forest loss, mining activities, accidental spills and nutrient loading have also decreased water quality in this aquatic environment. The primary goal of this project is to provide historical water quality and climate information by determining <span class="hlt">biogeochemical</span> properties of oyster shells and sediments collected from various locations throughout the Tampa Bay region including ancient Native American shell mounds. <span class="hlt">Biogeochemical</span> properties of shells collected from these middens will provide insight regarding historical water quality of Tampa Bay. It is expected that a pristine, pre-Columbian baseline may be revealed from the midden shells, and changes in the <span class="hlt">biogeochemical</span> record may be demonstrated over the recent past from the industrial age to modern day on a seasonal and yearly scale. In order to achieve the goal of this project, midden shells and sediments will be collected and compared from three stations in Tampa Bay that range from undisturbed to severely impacted; Emerson Point, Weedon Island, and Bayboro Harbor, respectively. Water and sediment samples have also been examined to provide additional information regarding radiogeochemical properties of the three study sites. Sediments will be dated using gamma spectrometry techniques (U/Th series). Standard ICP-OES methods are being utilized to determine concentrations of trace, minor and major elements in the oyster and sediment samples. This project is part of a larger on-going investigation. If successful, this investigation will ultimately yield a high-resolution tool for establishing the history of terrestrial land use and climate change.</p> <div class="credits"> <p class="dwt_author">Schwing, P. T.; Martinez, E.; Pyrtle, A. J.; Haynes, S.</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">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=3910581"> <span id="translatedtitle">Seasonal ITCZ migration dynamically controls the location of the (sub)tropical Atlantic <span class="hlt">biogeochemical</span> divide</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">Inorganic nitrogen depletion restricts productivity in much of the low-latitude oceans, generating a selective advantage for diazotrophic organisms capable of fixing atmospheric dinitrogen (N2). However, the abundance and activity of diazotrophs can in turn be controlled by the availability of other potentially limiting nutrients, including phosphorus (P) and iron (Fe). Here we present high-resolution data (?0.3°) for dissolved iron, aluminum, and inorganic phosphorus that confirm the existence of a sharp north–south <span class="hlt">biogeochemical</span> boundary in the surface nutrient concentrations of the (sub)tropical Atlantic Ocean. Combining satellite-based precipitation data with results from a previous study, we here demonstrate that wet deposition in the region of the intertropical convergence zone acts as the major dissolved iron source to surface waters. Moreover, corresponding observations of N2 fixation and the distribution of diazotrophic Trichodesmium spp. indicate that movement in the region of elevated dissolved iron as a result of the seasonal migration of the intertropical convergence zone drives a shift in the latitudinal distribution of diazotrophy and corresponding dissolved inorganic phosphorus depletion. These conclusions are consistent with the results of an idealized numerical model of the system. The boundary between the distinct <span class="hlt">biogeochemical</span> systems of the (sub)tropical Atlantic thus appears to be defined by the diazotrophic response to spatial–temporal variability in external Fe inputs. Consequently, in addition to demonstrating a unique seasonal cycle forced by atmospheric nutrient inputs, we suggest that the underlying <span class="hlt">biogeochemical</span> mechanisms would likely characterize the response of oligotrophic systems to altered environmental forcing over longer timescales. PMID:24367112</p> <div class="credits"> <p class="dwt_author">Schlosser, Christian; Klar, Jessica K.; Wake, Bronwyn D.; Snow, Joseph T.; Honey, David J.; Woodward, E. Malcolm S.; Lohan, Maeve C.; Achterberg, Eric P.; Moore, C. Mark</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</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/2012GeCoA..87..267N"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> characterization of a lithified paleosol: Implications for the interpretation of ancient Critical 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">Modern soils are characterized by an array of physical, chemical, mineralogical, and biological laboratory analyses of samples taken from horizons of pedogenic profiles. In contrast, fossil soils (paleosols) are typically characterized from assays of whole-rock molecular oxides because of sample lithification where element sources are unconstrained. Here we for the first time subject a lithified paleosol to an array of modern soil analytical techniques and new pedotransfer functions, providing a glimpse into the colloidal world of an ancient Critical Zone as an analog to research conducted on a network of modern Critical Zones. This methodology provides a framework for decoding a previously unknown archive of terrestrial <span class="hlt">biogeochemical</span> information at multiple temporal and spatial scales. Application to a paleosol within an early Paleocene Critical Zone reveals that many <span class="hlt">biogeochemical</span> properties have been preserved since burial that are similar to modern clay-rich, Vertisols. The measured and calculated physical properties of this paleosol include clay content and mineralogy, bulk density and water retention, available water capacity, and coefficient of linear extensibility (shrink-swell potential). The chemical properties include cation exchange capacity, exchangeable cations, base saturation, and exchangeable sodium percentage. The solution properties electrical conductivity and pH seem reasonable, but are interpreted with less confidence because of their greater vulnerability to alteration from fluid flow. New pedotransfer functions to reconstruct pre-burial organic carbon and nitrogen contents provide invaluable information of organically-derived nutrient content. The sum of the measured properties of the early Paleocene paleosol in context of reconstructed regional environmental conditions indicate the presence of a mid-successional hardwood forest in a humid climate with high water holding capacity, high nutrient retention, and rapid flux of elements through <span class="hlt">biogeochemical</span> cycling.</p> <div class="credits"> <p class="dwt_author">Nordt, Lee C.; Hallmark, Charles T.; Driese, Steven G.; Dworkin, Steven I.; Atchley, Stacy C.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-06-01</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://www.ncbi.nlm.nih.gov/pubmed/21945186"> <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://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</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 sites draining nested catchments (5-1837 km(2)) in the River Dee basin, NE Scotland were sampled during summer 2008 to evaluate spatio-temporal variations in quantity and quality (<span class="hlt">biogeochemical</span> reactivity) of SPM during relatively low flow conditions. Mean SPM concentrations increased from 0.21 to 1.22 mg L(-1) between the uppermost and lowest mainstem sites. Individually, POC concentrations ranged from 0.08 to 0.55 mg L(-1) and accounted for ca. 3-15% of total aqueous organic carbon transported. The POC content was partitioned into autotrophic (2.78-73.0 mg C g(-1) SPM) and detrital (119-388 mg C g(-1) SPM) biomass carbon content. The particulate respired CO(2)-C as a % of the total carbon associated with SPM, measured by MicroResp™ over 18 h, varied in recalcitrance from 0.49% at peat-dominated sites to 3.20% at the lowermost mainstem site. Significant (p<0.05) relationships were observed between SPM <span class="hlt">biogeochemical</span> reactivity measures (% respired CO(2)-C; chlorophyll ?; bioavailable-phosphorus) and arable and improved grassland area, associated with increasing biological productivity downstream. Compositional characteristics and in-stream processing of SPM appear to be related to contributory land use pressures, that influence SPM characteristics and biogeochemistry (C:N:P stoichiometry) of its surrounding aqueous environment. As moorland influences declined, nutrient inputs from arable and improved grasslands increasingly affected the <span class="hlt">biogeochemical</span> content and reactivity of both dissolved and particulate matter. This increases the potential for recycling of the organic matter that is either transported from upstream or entering further along the riverine continuum. PMID:21945186</p> <div class="credits"> <p class="dwt_author">Dawson, J J C; Adhikari, Y R; Soulsby, C; Stutter, M I</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-09-15</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://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 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://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 " 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://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 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/2012AGUFMPP33B2121L"> <span id="translatedtitle">Reconstructing paleo-ocean silicon chemistry and ecology during Last Glacial Maximum, a <span class="hlt">biogeochemical</span> cycle 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">It has been established by a number of investigators that opal content and Si-C isotope studies in the marine sediments reveal information about paleooceanography and the impact on silicic acid utilization by marine autotrophes (diatoms, silicoflagellates) and heterotrophes (radiolarians) during the Last Glacial Maximum (LGM). Opal, as an amorphous form of SiO2, formed by marine Si-secreting organisms, has been used as a proxy to indicate chemical ocean evolution, paleoproductivity and temperature variations in the paleoenvironment and regional ocean water <span class="hlt">biogeochemical</span> studies, both on million- and thousand-year scales. Here, we are using a model of the global silicon <span class="hlt">biogeochemical</span> cycle to understand and reconstruct evolutionary history of the paleobiogeochemical cycle and paleoenvironment since LGM. The model is process-driven, temperature-driven, and land-ocean-sediment <span class="hlt">coupled</span> with specific marine Si-secreting organisms that represent different trophic levels and physiological mechanisms. Specifically, Si utilization by marine silicoflagellates and radiolarians are each about 5% of that of ubiquitous marine diatoms. Available marine reactive Si is controlled by variation of diatom bioproduction that represents 5% of the total marine primary productivity (Si/C Redfield ratio in the marine organic matter is ~0.13, which is an order of magnitude higher than ratio in land organic matter). River input of Si is controlled by chemical weathering of silicate rocks and biocyling of land plant phytoliths. Decreasing dissolved and particulate Si input from land and less favorable climatic condition into LGM diminished the primary production of marine diatoms. However, because radiolarians favor deep-water habitat, where a higher level of DSi is found and that is less affected by temperature changes, a peak of relative abundance is usually observed in sedimentary record during LGM. Given that opal formation fractionated seawater ?30Si (1‰) and enriched seawater with heavier 30Si, the sediment isotope records of ?30Si variations have been found to support the suppressed diatom Si biological bump. Since the LGM, the temperature increased about 5°C and contributed to almost 50% of land bio-productivity rise. On the other hand, warming climate and enhanced hydrological cycle drove the chemical weathering of continental silicate rocks and soil phytoliths remineralization that increased riverine input of dissolved Si, that promoted the Si utilization of diatom in the surface waters. We present a history of species-specific Si utilization due to the environmental and hydrological changes on land and in the ocean. We also use and compare available data of opal sedimentation, Si and C isotope records, as well as temperature history to better quantify the biogeochemistry of the Si cycle during LGM and in later time. The results provide insight into paleoproductivity of Si-C cycles in the ocean and assist the Si model in its projections of future environmental changes.</p> <div class="credits"> <p class="dwt_author">Li, D. D.; Lerman, A.; Mackenzie, F. T.</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">312</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/19870647"> <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://academic.research.microsoft.com/">Microsoft Academic Search </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</p> <div class="credits"> <p class="dwt_author">J. J. Bock; J. Gundersen; A. T. Lee; P. L. Richards; E. Wollack</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">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/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">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.bioone.org/perlserv/?request=get-document&doi=10.1641%2F0006-3568%282006%29056%5B0407%3ABABRTC%5D2.0.CO%3B2"> <span id="translatedtitle">Biophysical and <span class="hlt">Biogeochemical</span> Responses to Climate Change Depend on Dispersal and Migration</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 peer- reviewed article from BioScience looks at the effects of dispersal and migration on biophysical and <span class="hlt">biogeochemical</span> responses to climate change. Different species, populations, and individuals disperse and migrate at different rates. The rate of movement that occurs in response to changes in climate, whether fast or slow, will shape the distribution of natural ecosystems in the decades to come. Moreover, land-use patterns associated with urban, suburban, rural, and agricultural development will complicate ecosystem adaptation to climate change by hindering migration. Here we examine how vegetation's capacity to disperse and migrate may affect the biophysical and <span class="hlt">biogeochemical</span> characteristics of the land surface under anthropogenic climate change. We demonstrate that the effectiveness of plant migration strongly influences carbon storage, evapotranspiration, and the absorption of solar radiation by the land surface. As a result, plant migration affects the magnitude, and in some cases the sign, of feedbacks from the land surface to the climate system. We conclude that future climate projections depend on much better understanding of and accounting for dispersal and migration.</p> <div class="credits"> <p class="dwt_author">PAUL A. T. HIGGINS and JOHN HARTE (;)</p> <p class="dwt_publisher"></p> <p class="publishDate">2006-05-01</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://www.ncbi.nlm.nih.gov/pubmed/19843187"> <span id="translatedtitle">Not so old Archaea - the antiquity of <span class="hlt">biogeochemical</span> processes in the archaeal domain of life.</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">Since the archaeal domain of life was first recognized, it has often been assumed that Archaea are ancient, and harbor primitive traits. In fact, the names of the major archaeal lineages reflect our assumptions regarding the antiquity of their traits. Ancestral state reconstruction and relaxed molecular clock analyses using newly articulated oxygen age constraints show that although the archaeal domain itself is old, tracing back to the Archean eon, many clades and traits within the domain are not ancient or primitive. Indeed many clades and traits, particularly in the Euryarchaeota, were inferred to be Neoproterozoic or Phanerozoic in age. Both Eury- and Crenarchaeota show increasing metabolic and physiological diversity through time. Early archaeal microbial communities were likely limited to sulfur reduction and hydrogenotrophic methanogenesis, and were confined to high-temperature geothermal environments. However, after the appearance of atmospheric oxygen, nodes containing a wide variety of traits (sulfate and thiosulfate reduction, sulfur oxidation, sulfide oxidation, aerobic respiration, nitrate reduction, mesophilic methanogenesis in sedimentary environments) appear, first in environments containing terrestrial Crenarchaeota in the Meso/Neoproterozoic followed by environments containing marine Euryarchaeota in the Neoproterozoic and Phanerozoic. This provides phylogenetic evidence for increasing complexity in the <span class="hlt">biogeochemical</span> cycling of C, N, and S through geologic time, likely as a consequence of microbial evolution and the gradual oxygenation of various compartments within the biosphere. This work has implications not only for the large-scale evolution of microbial communities and <span class="hlt">biogeochemical</span> processes, but also for the interpretation of microbial biosignatures in the ancient rock record. PMID:19843187</p> <div class="credits"> <p class="dwt_author">Blank, Carrine E</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">316</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/23734151"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> implications of the ubiquitous colonization of marine habitats and redox gradients by Marinobacter species.</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 Marinobacter genus comprises widespread marine bacteria, found in localities as diverse as the deep ocean, coastal seawater and sediment, hydrothermal settings, oceanic basalt, sea-ice, sand, solar salterns, and oil fields. Terrestrial sources include saline soil and wine-barrel-decalcification wastewater. The genus was designated in 1992 for the Gram-negative, hydrocarbon-degrading bacterium Marinobacter hydrocarbonoclasticus. Since then, a further 31 type strains have been designated. Nonetheless, the metabolic range of many Marinobacter species remains largely unexplored. Most species have been classified as aerobic heterotrophs, and assessed for limited anaerobic pathways (fermentation or nitrate reduction), whereas studies of low-temperature hydrothermal sediments, basalt at oceanic spreading centers, and phytoplankton have identified species that possess a respiratory repertoire with significant <span class="hlt">biogeochemical</span> implications. Notable physiological traits include nitrate-dependent Fe(II)-oxidation, arsenic and fumarate redox cycling, and Mn(II) oxidation. There is also evidence for Fe(III) reduction, and metal(loid) detoxification. Considering the ubiquity and metabolic capabilities of the genus, Marinobacter species may perform an important and underestimated role in the <span class="hlt">biogeochemical</span> cycling of organics and metals in varied marine habitats, and spanning aerobic-to-anoxic redox gradients. PMID:23734151</p> <div class="credits"> <p class="dwt_author">Handley, Kim M; Lloyd, Jonathan R</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">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.ncbi.nlm.nih.gov/pubmed/22325634"> <span id="translatedtitle">A Chloroflexi bacterium dechlorinates polychlorinated biphenyls in marine sediments under in situ-like <span class="hlt">biogeochemical</span> conditions.</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 reductive dechlorination of Aroclor 1254 PCBs by a coplanar PCB-dechlorinating microbial community enriched from an actual site contaminated marine sediment of the Venice lagoon in sterile slurry microcosms of the same sediment suspended in its site water, i.e., under <span class="hlt">biogeochemical</span> conditions that closely mime those occurring in situ. The culture dechlorinated more than 75% of the penta- through hepta-chlorinated biphenyls to tri- and tetra-chlorinated congeners in 30 weeks. The dechlorination rate was reduced by the addition of H(2) and short chain fatty acids, which stimulated sulfate-reduction and methane production, and markedly increased by the presence of vancomycin or ampicillin. DGGE analysis of 16S rRNA genes on PCB-spiked and PCB-free cultures ruled out sulfate-reducing and methanogenic bacteria and revealed the presence of a single Chloroflexi phylotype closely related to the uncultured bacteria m-1 and SF1 associated to PCB dechlorination. These findings suggest that a single dechlorinator is responsible for the observed extensive dechlorination of Aroclor 1254 and that a Chloroflexi species similar to those already detected in freshwater and estuarine contaminated sediments mediates PCB dechlorination in the marine sediment adopted in this study under <span class="hlt">biogeochemical</span> conditions resembling those occurring in situ in the Brentella Canal of Venice Lagoon. PMID:22325634</p> <div class="credits"> <p class="dwt_author">Zanaroli, Giulio; Balloi, Annalisa; Negroni, Andrea; Borruso, Luigimaria; Daffonchio, Daniele; Fava, Fabio</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-03-30</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/2013JGRG..118..974B"> <span id="translatedtitle">Effects of bark beetle-caused tree mortality on <span class="hlt">biogeochemical</span> and biogeophysical MODIS products</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">affect forest-atmosphere exchanges of carbon, water, and energy, thereby influencing weather and climate. Bark beetle outbreaks are one such disturbance type that alters <span class="hlt">biogeochemical</span> and biogeophysical processes in forests. Few studies have documented bark beetle impacts to leaf area index (LAI), gross primary productivity (GPP), evapotranspiration (ET), land surface temperature (LST), and surface albedo with satellite observations. Our objective was to use Landsat-derived estimates of bark beetle-caused tree mortality and Moderate Resolution Imaging Spectroradiometer (MODIS) land surface products to estimate beetle-caused changes in LAI, GPP, ET, LST, and surface albedo in northern Colorado. Following bark beetle-caused tree mortality, decreases occurred in LAI (0.02-0.80 m2m-2, 1-40%), annual GPP (50-248 gC m-2 yr-1, (5-26%), and daily summer ET (0.20-0.70 mm day-1, 13-44%), whereas increases occurred in August LST (1-3.9 K) and February albedo (0.03-0.09, 19-52%). We found greater responses of these variables in areas of greater mortality severity. The extent and severity of tree mortality in northern Colorado caused substantial changes in land surface variables (9-23%) when averaged across all forested areas of our study area. Our results demonstrate that land surface variables are sensitive to bark beetle-caused tree mortality and that bark beetle outbreaks can significantly impact <span class="hlt">biogeochemical</span> and biogeophysical processes.</p> <div class="credits"> <p class="dwt_author">Bright, Benjamin C.; Hicke, Jeffrey A.; Meddens, Arjan J. H.</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">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/1995RvGeo..33.1271D"> <span id="translatedtitle">Ocean <span class="hlt">biogeochemical</span> fluxes: New production and export of organic matter from the upper 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">Studies of ocean <span class="hlt">biogeochemical</span> fluxes have been energized in this decade, by the urgency of our need to understand and predict the effects of continued CO2 accumulation in the atmosphere, by the global perspectives offered by satellite views of ocean color and related physical fields (McClain et al. 1991; Yoder et al. 1992; Mitchell 1994), and by the successful implementation of the Joint Global Ocean Flux Study (JGOFS; Bowles and Livingston, 1993). In this review, I focus on oceanic new production, originally defined as the fraction of primary production supported by inputs of `new' nitrogen from outside the euphotic zone. With a growing appreciation of the role of this fundamental <span class="hlt">biogeochemical</span> flux in the global carbon cycle, it has become more common to refer interchangeably to new production so defined, and to the export of organic matter from the upper ocean (e.g.. Sarmiento and Siegenthaler 1992). New production, the driving process of the ocean carbon cycle, is responsible for maintaining over half the vertical gradient in total inorganic carbon. In this review I refer to nitrate-based new production in the open sea, and not to new production supported by other N compounds as observed in the coastal zone. Eppley (1992) gives a personal view of the modern formulation of the concept of equivalence between new production and upper ocean export. This review is dedicated to the memory of John Martin, a friend, colleague, leader and teacher who contributed mightily to our field.</p> <div class="credits"> <p class="dwt_author">Ducklow, Hugh W.</p> <p class="dwt_publisher"></p> <p class="publishDate">1995-07-01</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/1904812"> <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=pubmed">PubMed</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. PMID:1904812</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 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");' href="#">2</a> <a onClick='return 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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/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">322</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/24803372"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> impacts of wildfires over four millennia in a Rocky Mountain subalpine watershed.</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">Wildfires can significantly alter forest carbon (C) storage and nitrogen (N) availability, but the long-term <span class="hlt">biogeochemical</span> legacy of wildfires is poorly understood. We obtained a lake-sediment record of fire and biogeochemistry from a subalpine forest in Colorado, USA, to examine the nature, magnitude, and duration of decadal-scale, fire-induced ecosystem change over the past c. 4250 yr. The high-resolution record contained 34 fires, including 13 high-severity events within the watershed. High-severity fires were followed by increased sedimentary N stable isotope ratios (?15N) and bulk density, and decreased C and N concentrations--reflecting forest floor destruction, terrestrial C and N losses, and erosion. Sustained low sediment C : N c. 20-50 yr post-fire indicates reduced terrestrial organic matter subsidies to the lake. Low sedimentary ?15N c. 50-70 yr post-fire, coincident with C and N recovery, suggests diminishing terrestrial N availability during stand development. The magnitude of post-fire changes generally scaled directly with inferred fire severity. Our results support modern studies of forest successional C and N accumulation and indicate pronounced, long-lasting <span class="hlt">biogeochemical</span> impacts of wildfires in subalpine forests. However, even repeated high-severity fires over millennia probably did not deplete C or N stocks, because centuries between high-severity fires allowed for sufficient biomass recovery. PMID:24803372</p> <div class="credits"> <p class="dwt_author">Dunnette, Paul V; Higuera, Philip E; McLauchlan, Kendra K; Derr, Kelly M; Briles, Christy E; Keefe, Margaret H</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-08-01</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/2012JHyd..428..104S"> <span id="translatedtitle">Elucidating temperature effects on seasonal variations of <span class="hlt">biogeochemical</span> turnover rates during riverbank filtration</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">SummaryRiverbank filtration (RBF) is a mechanism by which undesired substances contained in infiltrating surface waters are attenuated during their passage across the riverbed and its underlying aquifer towards production wells. In this study, multi-component reactive transport modeling was used to analyze the <span class="hlt">biogeochemical</span> processes that occur during subsurface passage at an existing RBF system - the Flehe Waterworks located along the Rhine River in Düsseldorf, Germany. The reactive transport model was established on the base of a conservative solute transport model for which temperature and chloride data served as calibration constraints. The model results showed that seasonal temperature changes superimposed by changes in residence time strongly affected the extent of the redox reactions along the flow path. The observed temporal, especially seasonal, changes in the breakthrough of dissolved oxygen were found to be best reproduced by the model when the temperature dependency of the <span class="hlt">biogeochemical</span> processes was explicitly considered. High floods in the Rhine drastically reduced the travel time to the RBF well from an average travel time of 25-40 days to less than 8 days. On the other hand, low flow conditions increased the subsurface residence times between the Rhine River and the RBF well to about 60 days. The model results revealed that short term changes in the terminal electron acceptor consumption (biodegrdation extent) were solely attributed to fluctuations in residence time, while more gradual changes in biodegradation extent were due to both seasonal variations of the river water temperature and gradual changes in residence time.</p> <div class="credits"> <p class="dwt_author">Sharma, Laxman; Greskowiak, Janek; Ray, Chittaranjan; Eckert, Paul; Prommer, Henning</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">324</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/2014OcMod..81...25L"> <span id="translatedtitle">Assessing the utility of frequency dependent nudging for reducing biases 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">Bias errors, resulting from inaccurate boundary and forcing conditions, incorrect model parameterization, etc. are a common problem in environmental models including <span class="hlt">biogeochemical</span> ocean models. While it is important to correct bias errors wherever possible, it is unlikely that any environmental model will ever be entirely free of such errors. Hence, methods for bias reduction are necessary. A widely used technique for online bias reduction is nudging, where simulated fields are continuously forced toward observations or a climatology. Nudging is robust and easy to implement, but suppresses high-frequency variability and introduces artificial phase shifts. As a solution to this problem Thompson et al. (2006) introduced frequency dependent nudging where nudging occurs only in prescribed frequency bands, typically centered on the mean and the annual cycle. They showed this method to be effective for eddy resolving ocean circulation models. Here we add a stability term to the previous form of frequency dependent nudging which makes the method more robust for non-linear biological models. Then we assess the utility of frequency dependent nudging for biological models by first applying the method to a simple predator-prey model and then to a 1D ocean <span class="hlt">biogeochemical</span> model. In both cases we only nudge in two frequency bands centered on the mean and the annual cycle, and then assess how well the variability in higher frequency bands is recovered. We evaluate the effectiveness of frequency dependent nudging in comparison to conventional nudging and find significant improvements with the former.</p> <div class="credits"> <p class="dwt_author">Lagman, Karl B.; Fennel, Katja; Thompson, Keith R.; Bianucci, Laura</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-09-01</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://adsabs.harvard.edu/abs/2010AGUFMGC21E..04U"> <span id="translatedtitle">Global <span class="hlt">Biogeochemical</span> Fluxes Program for the Ocean Observatories Initiative: A Proposal. (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">The overarching emphasis of the Global <span class="hlt">Biogeochemical</span> Flux Ocean Observatories Initiative <GBF-OOI: http://www.whoi.edu/whitepaper/GBF-OOI/> is to assess the role of oceanic carbon, both living and non-, in the Earth climate system. Modulation of atmospheric CO2 and its influence on global climate is a function of the quantitative capacity of the oceans to sequester organic carbon into deep waters. Critical to our understanding of the role of the oceans in the global cycling of carbon are the quantitative dynamics in both time and space of the fixation of CO2 into organic matter by surface ocean primary production and removal of this carbon to deep waters via the “biological pump”. To take the next major step forward in advancing our understanding of the oceanic biological pump, a global observation program is required that: (i) greatly improves constraints on estimates of global marine primary production (PP), a critical factor in understanding the global CO2 cycle and for developing accurate estimates of export production (EP); (ii) explores the spatiotemporal links between PP, EP and the <span class="hlt">biogeochemical</span> processes that attenuate particulate organic carbon (POC) flux; (iii) characterizes microbial community structure and dynamics both in the surface and deep ocean; (iv) develops a comprehensive picture of the chemical and biological processes that take place from the surface ocean to the sea floor; (v) provides unique time-series samples for detailed laboratory-based chemical and biological characterization and tracer studies that will enable connections to be made between the operation of the biological pump at present and in the geologic past. The primary goal is to provide high quality biological and <span class="hlt">biogeochemical</span> observational data for the modeling and prediction efforts of the global CO2 cycle research community. Crucial to the realization of the GBF-OOI is the development of reliable, long-term, time-series ocean observation platforms capable of precise and controlled placement of sophisticated <span class="hlt">biogeochemical</span> sensors/samplers, and in situ experimental systems at a wide range of depths, including close proximity to the sea surface. Significant opportunities exist to exploit sensor miniaturization in combination with recent exponential improvements in “omics” technologies for measurement of nucleic acids, proteins and metabolites with unprecedented throughput and resolution. We will discuss the goals, philosophy, principal experimental and technical approaches and operational challenges. We will outline proposed mooring systems as well as means for accurate, spatiotemporal assessment of: (i) primary production, (ii) constraint of POC export flux with season and depth, (iii) assessment of microbial and zooplankton community structure/function throughout the water column, and (iv) collection and preservation of particulate and water samples for land-based examination of temporal and vertical variability of specific tracers, isotopes, nutrients, DOC and related substances for even more precise measurements of environmental <span class="hlt">biogeochemical</span> properties. The GBF-OOI will become our Hubble for the sea.</p> <div class="credits"> <p class="dwt_author">Ulmer, K. M.; Taylor, 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">326</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://esd.lbl.gov/FILES/about/staff/terryhazen/1999Fractured%20Rock%20Proceedings.pdf"> <span id="translatedtitle">Proceedings Dynamics of Fluids in Fractured Rocks. LBNL-42718, Berkeley, CA February 1999 Critical <span class="hlt">Biogeochemical</span> Parameters Used for In Situ Bioremediation of Solvents in</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Critical <span class="hlt">Biogeochemical</span> Parameters Used for In Situ Bioremediation of Solvents in Fractured Rock Terry C-scale demonstrations of in situ bioremediation via biosparging/bioventing illustrate the critical <span class="hlt">biogeochemical</span> parameters for in situ bioremediation of solvents in fractured rock. Both sites were in Virginia</p> <div class="credits"> <p class="dwt_author">Hazen, Terry</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">327</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.rsmas.miami.edu/assets/syllabi/mac510.pdf"> <span id="translatedtitle">MAC 510: <span class="hlt">Biogeochemical</span> Exploration of the Major Ocean Basins Course Description: This course will have students explore the basic hydrography and</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">and major water masses; <span class="hlt">biogeochemical</span> features) 14) The Arctic Ocean ((general circulation and major water3/31/2008 Syllabus MAC 510: <span class="hlt">Biogeochemical</span> Exploration of the Major Ocean Basins Course Description: This course will have students explore the basic hydrography and biogeochemistry of the major ocean basins</p> <div class="credits"> <p class="dwt_author">Miami, University of</p> <p class="dwt_publisher"></p> <p class="publishDate"></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/42052647"> <span id="translatedtitle">The role of the vertical fluxes of particulate organic matter and calcite in the oceanic carbon cycle: Studies using an ocean <span class="hlt">biogeochemical</span> general circulation model</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">Distributions of chemical tracers in the world ocean are well reproduced in an ocean general circulation model which includes <span class="hlt">biogeochemical</span> processes (<span class="hlt">biogeochemical</span> general circulation model, B-GCM). The difference in concentration of tracers between the surface and the deep water depends not only on the export production but also on the remineralization depth. Case studies changing the vertical profile of particulate</p> <div class="credits"> <p class="dwt_author">Yasuhiro Yamanaka; Eiichi Tajika</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">329</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] [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">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.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 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://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 " 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://adsabs.harvard.edu/abs/2014EGUGA..1615766B"> <span id="translatedtitle">Oceanic <span class="hlt">biogeochemical</span> characteristic maps identified with holistic use of satellite, model and 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">Ocean province level plankton community exhibit heterogeneity across Arctic, Nordic, Atlantic Gyre and Southern Ocean provinces. GreenSeas research is an international FP7 consortium that includes Arctic, Atlantic and Southern Ocean based research teams who are analysing the planktonic ecosystem. We are looking at how the planktonic ecosystem responds to environmental and climate change. Using Earth Observation monitoring data we report new results on identifying generic plankton characteristics observable at a province level, and also touch on spatial and temporal trends that are evident using a holistic analysis framework. Using advanced statistical methods this framework compares and combines Earth Observation information together with an in-situ Oceanic plankton Analytical Database and up to 40 year ocean general circulation <span class="hlt">biogeochemical</span> model (OGCBM) time series of the equivalent plankton and sea-state measures of this system. Specifically, we outline the use of the GreenSeas Analytical Database, which is a harmonised set of Oceanic in-situ plankton and sea-state measures covering different cruises and time periods. The Analytical Database information ranges from plankton community,primary production, nutrient cycling to physical sea state temperature and salinity measures. The combined analysis utilises current, 10 year+ Earth Observations of ocean colour and sea surface temperature metrics and interprets these together with <span class="hlt">biogeochemical</span> model outputs from PELAGOS, ERSEM & NORWECOM model runs to help identify planktonic based biomes. Generic planktonic characteristic maps that are equivalently observable in both the Earth Observations and numerical models are reported on. Both ocean surface and sub-surface signals are analysed together with relevant Analytical Database biome extracts. We present the current results of this inter-comparison & discuss challenges of identifying the province level plankton dominance with the satellite, model and data. In particular we discuss the strategic importance of systematically analysing the knowledge present in the existing key long term Oceanic observation platforms through such holistic analysis frameworks. These maps help to enhance and improve current <span class="hlt">biogeochemical</span> models, our understanding of the plankton community structure and predictions used for future assessment of climate change.</p> <div class="credits"> <p class="dwt_author">Bruun, John; Allen, Icarus; Vichi, Marcello; Somerfield, Paul; Samuelsen, Annette; Racault, Marie-Fanny; Waldron, Howard; Monteiro, Pedro; McKiver, William; Bellerby, Richard; Thomalla, Sandy; Lygre, Kjetil; Moiseev, Denis; Johannessen, Johnny; Brewin, Robert; Butenschön, Momme; Jeansson, Emil; Vines, Aleksander; Heard, Jessica</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-05-01</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://adsabs.harvard.edu/abs/2014JMS...139..460V"> <span id="translatedtitle">A <span class="hlt">biogeochemical</span> model for phosphorus and nitrogen cycling in the Eastern Mediterranean Sea. Part 1. Model development, initialization and sensitivity</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 Mediterranean Sea (EMS) is the largest marine basin whose annual primary productivity is limited by phosphorus (P) rather than nitrogen (N). The basin is nearly entirely land-locked and receives substantial external nutrient fluxes, comparable for instance to those of the Baltic Sea. The biological productivity of the EMS, however, is among the lowest observed in the oceans. The water column exhibits very low P and N concentrations with N:P ratios in excess of the Redfield value. These unique <span class="hlt">biogeochemical</span> features are analyzed using a mass balance model of the <span class="hlt">coupled</span> P and N cycles in the EMS. The present paper describes the conceptual basis, quantitative implementation and sensitivity of the model. The model is initialized for the year 1950, that is, prior to the large increase in anthropogenic nutrient loading experienced by the EMS during the second half of the 20th century. In the companion paper, the model is used to simulate the P and N cycles during the period 1950-2000. The 1950 model set-up and sensitivity analyses support the following conclusions.<ce:list Phosphorus-limited primary production in the EMS is most sensitive to the P exchanges with the Western Mediterranean Sea (WMS) associated with the anti-estuarine circulation of the EMS. The supply of P through the Straits of Sicily is mainly under the form of dissolved organic P (DOP), while dissolved inorganic P (PO4) is primarily exported to the WMS. The efficient export of PO4 to the WMS maintains the EMS in its ultra-oligotrophic state. Inorganic molar N:P ratios in excess of the 16:1 Redfield value observed in the water column reflect higher-than-Redfield N:P ratios of the external inputs, combined with negligible denitrification. Model simulations imply that the denitrification flux would have to increase by at least a factor of 14, relative to the 1950 flux, in order for the inorganic N:P ratio of the deep waters to approach the Redfield value. The higher-than-Redfield N:P ratios of dissolved and particulate organic matter in the EMS further imply the preferential regeneration of P relative to N during organic matter decomposition.</p> <div class="credits"> <p class="dwt_author">Van Cappellen, P.; Powley, H. R.; Emeis, K.-C.; Krom, M. D.</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-11-01</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://adsabs.harvard.edu/abs/2005GBioC..19.4021K"> <span id="translatedtitle">Modeling the primary and secondary productions of the southern Benguela upwelling system: A comparative study through two <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">A three-dimensional primitive equation model, the Regional Ocean Modeling Systems (ROMS), <span class="hlt">coupled</span> to two <span class="hlt">biogeochemical</span> configurations (NPZD and N2P2Z2D2) was used to study the dynamics of the first trophic levels of the pelagic food web in the southern Benguela upwelling system. The domain extends from the Agulhas Bank bordered by the Agulhas Current to 27°S on the west coast of South Africa. The circulation is driven by monthly climatologies of atmospheric forcing fields. The NPZD ecosystem model consists of four state variables: nutrient (nitrate), phytoplankton, zooplankton and detritus. In the N2P2Z2D2 model, ammonium has been added and the three other variables have been divided into small and large organisms or detritus. Both models are able to reproduce the spatio-temporal phytoplankton distribution. Along the west coast, chlorophyll concentrations maxima are associated to surface waters. Westward dominating winds generate the lowest chlorophyll concentrations encountered in winter. The small phytoplankton organisms simulated by the N2P2Z2D2 model are responsible for a weaker chlorophyll inshore/offshore gradient, in closer agreement with observations. Transitions from a regime dominated by new production (high f ratio) to one dominated by regenerated production (low f ratio) happen to be abrupt, underlying the constant competition between small and large organisms with regard to upwelling induced nutrient inputs. On the Agulhas Bank, the summer enrichment is associated with subsurface maxima, while in winter, mixing by storms results in a homogeneous phytoplankton distribution in the water column. Regenerated production plays an important role in maintaining the total phytoplankton growth. Zooplankton biomass reflects the overall patterns of chlorophyll a concentrations with differences between the west coast and the Agulhas Bank, consistent with data, and its distribution exhibits a clear seasonal contrast. The seasonality of small and large zooplankton in the N2P2Z2D2 model is quite distinct, which allows, from the Agulhas Bank to St. Helena Bay, a food continuum for fish larvae. This was not achieved with the simpler NPZD model, emphasizing the importance of representing the appropriate level of complexity to characterize food availability for higher trophic levels.</p> <div class="credits"> <p class="dwt_author">Koné, V.; Machu, E.; Penven, P.; Andersen, V.; GarçOn, V.; FréOn, P.; Demarcq, H.</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">335</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://fizz.phys.dal.ca/~atmos/publications/Nowlan2014gbc.pdf"> <span id="translatedtitle">GLOBAL <span class="hlt">BIOGEOCHEMICAL</span> CYCLES, VOL. ???, XXXX, DOI:10.1029/, Global Dry Deposition of Nitrogen Dioxide and1</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">, these trace gases contribute reactive nitrogen and sulfur to soil, water and28 vegetation. Enhanced nitrogen nitrogen and sulfur deposition may acidify soil and30 water and influence climate by perturbing carbonGLOBAL <span class="hlt">BIOGEOCHEMICAL</span> CYCLES, VOL. ???, XXXX, DOI:10.1029/, Global Dry Deposition of Nitrogen</p> <div class="credits"> <p class="dwt_author">Martin, Randall</p> <p class="dwt_publisher"></p> <p class="publishDate"></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://www-paoc.mit.edu/paoc/papers/Verdy_etal_GBCpreprint.pdf"> <span id="translatedtitle">in press, Global <span class="hlt">Biogeochemical</span> Cycles, April 18, 2007 Carbon dioxide and oxygen fluxes in the Southern Ocean</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">of the two gases. 1. Introduction Deep waters in the Southern Ocean are rich in dissolved inorganic carbonin press, Global <span class="hlt">Biogeochemical</span> Cycles, April 18, 2007 Carbon dioxide and oxygen fluxes in the Southern Ocean: mechanisms of interannual variability A. Verdy1 , S. Dutkiewicz2 , M. J. Follows2 , J</p> <div class="credits"> <p class="dwt_author">Marshall, John</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">337</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://web.bio.utk.edu/wilhelm/Wilhelm%20lab%20papers/boyd%20et%20al.%202005.pdf"> <span id="translatedtitle">FeCycle: Attempting an iron <span class="hlt">biogeochemical</span> budget from a mesoscale SF6 tracer experiment in unperturbed low iron waters</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">FeCycle: Attempting an iron <span class="hlt">biogeochemical</span> budget from a mesoscale SF6 tracer experiment in unperturbed low iron waters P. W. Boyd,1 C. S. Law,2 D. A. Hutchins,3 E. R. Abraham,2 P. L. Croot,4 M. Ellwood December 2005. [1] An improved knowledge of iron biogeochemistry is needed to better understand key</p> <div class="credits"> <p class="dwt_author">Wilhelm, Steven W.</p> <p class="dwt_publisher"></p> <p class="publishDate"></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://people.ibest.uidaho.edu/~lforney/pdf/2004/LifeAtColdSeeps.pdf"> <span id="translatedtitle">Life at cold seeps: a synthesis of <span class="hlt">biogeochemical</span> and ecological data from Kazan mud volcano, eastern Mediterranean Sea</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/epsearch/">E-print Network</a></p> <p class="result-summary">Life at cold seeps: a synthesis of <span class="hlt">biogeochemical</span> and ecological data from Kazan mud volcano, especially the anaerobic oxidation of methane (AOM), associated with ascending fluids on Kazan mud volcano heterogeneity of mud volcano environments. Results from pore water geochemistry and modeling efforts indicate</p> <div class="credits"> <p class="dwt_author">Forney, Larry J.</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">339</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/60681501"> <span id="translatedtitle">U.S. Department of Energy (DOE)Surface <span class="hlt">Biogeochemical</span> Research (SBR) 6th Annual PI Meeting: Abstracts</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">On behalf of the Subsurface <span class="hlt">Biogeochemical</span> Research (SBR) program managers in the Climate and Environmental Sciences Division (CESD), Office of Biological and Environmental Research (BER), welcome to the 2011 SBR Principal Investigators meeting. Thank you in advance for your attendance and your presentations at this year's meeting. As the events in Japan continue to unfold, we are all reminded that</p> <div class="credits"> <p class="dwt_author">Hazen Ed</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">340</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/55125766"> <span id="translatedtitle">Carbon cycle dynamics in the geologic record: Speleothems as a source for new <span class="hlt">biogeochemical</span> and paleoclimate information</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">Many of the key outstanding questions in paleoclimate and <span class="hlt">biogeochemical</span> cycles involve terrestrial ecosystems. Caves provide an important depositional environment for sedimentary archives of past and present terrestrial environmental changes. Until recently, the tools available to the research community have been appropriate for coarse resolution studies, but have been inadequate to address other important questions such as: 1. How have</p> <div class="credits"> <p class="dwt_author">A. Frappier; D. Sahagian</p> <p class="dwt_publisher"></p> <p class="publishDate">2003-01-01</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_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 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">341</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 " 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://pubs.er.usgs.gov/publication/cir837"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> evidence for subsurface hydrocarbon occurrence, Recluse oil field, Wyoming; preliminary results</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">Anomalously high manganese-to-iron ratios occurring in pine needles and sage leaves over the Recluse oil field, Wyoming, suggest effects of petroleum microseepage on the plants. This conclusion is supported by iron and manganese concentrations in soils and carbon and oxygen isotope ratios in rock samples. Seeping hydrocarbons provided reducing conditions sufficient to enable divalent iron and manganese to be organically complexed or adsorbed on solids in the soils. These bound or adsorped elements in the divalent state are essential to plants, and the plants readily assimilate them. The magnitude of the plant anomalies, combined with the supportive isotopic and chemical evidence confirming petroleum leakage, makes a strong case for the use of plants as a <span class="hlt">biogeochemical</span> prospecting tool.</p> <div class="credits"> <p class="dwt_author">Dalziel, Mary C.; Donovan, Terrence J.</p> <p class="dwt_publisher"></p> <p class="publishDate">1980-01-01</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.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">2012-11-01</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/2009NIMPA.603..128A"> <span id="translatedtitle">Synchrotron X-ray fluorescent analysis application in <span class="hlt">biogeochemical</span> investigations in Yakutia</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 possibilities of synchrotron X-ray fluorescent analysis (SR-XRFA), along with the simple preparation of biological samples, allowed us to carry out valuable <span class="hlt">biogeochemical</span> investigations in Yakutia during the years 2002-2008. New data on the accumulation of macroelements K, Ca, Fe, Mn, biophilic microelements Cu, Zn, Mo, chalcophilous Ni, Pb, Ag, As, Sb, rare lithophilous Rb, Sr, Zr, Y, Nb, scattered chalcophilous Ga, Ge, Se, Cd, Te, Tl in the tissues of larch (Larix cajanderi Mayr.), mosses and lichens (Cladina genus, Dicranum genus, Hylocomium) were obtained. A connection between the elemental composition of larch tissues and the composition of bed rocks was revealed; a comparison with the elemental composition of mosses and lichens was carried out.</p> <div class="credits"> <p class="dwt_author">Artamonova, S. Yu.; Kolmogorov, Yu. P.</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">346</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=20040191782&hterms=Carbon+cycle&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DCarbon%2Bcycle"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> Cycles of Carbon and Sulfur on Early Earth (and on Mars?)</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The physical and chemical interactions between the atmosphere, hydrosphere, geosphere and biosphere can be examined for elements such as carbon (C) and sulfur (S) that have played central roles for both life and the environment. The compounds of C are highly important, not only as organic matter, but also as atmospheric greenhouse gases, pH buffers in seawater, oxidation-reduction buffers virtually everywhere, and key magmatic constituents affecting plutonism and volcanism. S assumes important roles as an oxidation-reduction partner with C and Fe in biological systems, as a key constituent in magmas and volcanic gases, and as a major influence upon pH in certain environments. These multiple roles of C and S interact across a network of elemental reservoirs interconnected by physical, chemical and biological processes. These networks are termed <span class="hlt">biogeochemical</span> C and S cycles.</p> <div class="credits"> <p class="dwt_author">DesMarais, D. J.</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">347</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 " 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://pubs.er.usgs.gov/publication/5220781"> <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://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</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, T.S.; Ohlendorf, H.M.</p> <p class="dwt_publisher"></p> <p class="publishDate">1987-01-01</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://adsabs.harvard.edu/abs/2013ESSD....5..375M"> <span id="translatedtitle">Winter measurements of oceanic <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 along 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-oxidized 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 data are available on the CDIAC database, <a href="http://cdiac.ornl.gov/ftp/oceans/Rockall_Trough/"target="_blank">http://cdiac.ornl.gov/ftp/oceans/Rockall_Trough/</a>.</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">2013-12-01</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://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3434959"> <span id="translatedtitle">Ocean viruses and their effects on microbial communities and <span class="hlt">biogeochemical</span> cycles</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">Viruses are the most abundant life forms on Earth, with an estimated 1031 total viruses globally. The majority of these viruses infect microbes, whether bacteria, archaea or microeukaryotes. Given the importance of microbes in driving global <span class="hlt">biogeochemical</span> cycles, it would seem, based on numerical abundances alone, that viruses also play an important role in the global cycling of carbon and nutrients. However, the importance of viruses in controlling host populations and ecosystem functions, such as the regeneration, storage and export of carbon and other nutrients, remains unresolved. Here, we report on advances in the study of ecological effects of viruses of microbes. In doing so, we focus on an area of increasing importance: the role that ocean viruses play in shaping microbial population sizes as well as in regenerating carbon and other nutrients. PMID:22991582</p> <div class="credits"> <p class="dwt_author">Wilhelm, Steven W.</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">351</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/225495"> <span id="translatedtitle">Sensitivity studies on uranium mobilization using the <span class="hlt">biogeochemical</span> transport code DRINK</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 sensitivity of uranium mobilization from LLW to cellulose degradation rates and the solubility of any uranium oxide (UO{sub 2}) precipitated, was investigated in a generic study using the <span class="hlt">biogeochemical</span> transport code DRINK. Three arbitrary degradation rates were employed, corresponding to cellulose half lives of 6.6, 66 and 660 years. At all degradation rates reducing conditions were generated due to microbial consumption of the available oxygen. At the shortest half life oxidizing condition were re-established due to the majority of cellulose being degraded. Under reducing conditions uranium mobilization was controlled by the solubility Of UO{sub 2} precipitate whereas under oxidizing conditions it was strongly K{sub d} dependent.</p> <div class="credits"> <p class="dwt_author">Johnstone, T.; Humphreys, P.N.; Trivedi, D.; Hoffmann, A. [British Nuclear Fuels plc, Risley (United Kingdom). Environmental Services</p> <p class="dwt_publisher"></p> <p class="publishDate">1995-12-31</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.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">2007-03-01</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://adsabs.harvard.edu/abs/2013EGUGA..15.3552S"> <span id="translatedtitle"><span class="hlt">Biogeochemical</span> cycles of Chernobyl-born radionuclides in the contaminated forest ecosystems: long-term dynamics of the migration 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"><span class="hlt">Biogeochemical</span> migration is a dominant factor of the radionuclide transport through the biosphere. In the early XX century, V.I. Vernadskii, a Russian scientist known, noted about a special role living things play in transport and accumulation of natural radionuclide in various environments. The role of <span class="hlt">biogeochemical</span> processes in migration and redistribution of technogenic radionuclides is not less important. In Russia, V. M. Klechkovskii and N.V. Timofeev-Ressovskii showed some important <span class="hlt">biogeochemical</span> aspects of radionuclide migration by the example of global fallout and Kyshtym accident. Their followers, R.M. Alexakhin, M.A. Naryshkin, N.V. Kulikov, F.A. Tikhomirov, E.B. Tyuryukanova, and others also contributed a lot to biogeochemistry of radionuclides. In the post-Chernobyl period, this area of knowledge received a lot of data that allowed building the radioactive element balance and flux estimation in various <span class="hlt">biogeochemical</span> cycles [Shcheglov et al., 1999]. Regrettably, many of recent radioecological studies are only focused on specific radionuclide fluxes or pursue some applied tasks, missing the holistic approach. Most of the studies consider <span class="hlt">biogeochemical</span> fluxes of radioactive isotopes in terms of either dose estimation or radionuclide migration rates in various food chains. However, to get a comprehensive picture and develop a reliable forecast of environmental, ecological, and social consequences of radioactive pollution in a vast contaminated area, it is necessary to investigate all the radionuclide fluxes associated with the <span class="hlt">biogeochemical</span> cycles in affected ecosystems. We believe such an integrated approach would be useful to study long-term environmental consequences of the Fukushima accident as well. In our long-term research, we tried to characterize the flux dynamics of the Chernobyl-born radionuclides in the contaminated forest ecosystems and landscapes as a part of the integrated <span class="hlt">biogeochemical</span> process. Our field studies were started in June of 1986 (less than two months after the accident) and have been continued up to now, focused on the most common forest ecosystems scattered over the contaminated areas of Russian Federation and Ukraine. A comprehensive analysis of the 137Cs and 90Sr <span class="hlt">biogeochemical</span> fluxes shows that downward radionuclide fluxes (those directed from tree crowns to the soil) dominated over the upward fluxes (from the soil to forest vegetation) in the first years after the accident. Currently, the biological cycle in the contaminated ecosystems is a main factor impeding further vertical migration of long-lived radionuclides from upper soil layers to the ground water. The role of biota as a retardation factor depends on landscape type as well. In accumulative landscapes (with positive material balance), biota plays leading role in radionuclide retardation, while in eluvial landscapes (with the negative balance) soil absorbing complex serves as the dominant barrier for radionuclides leaching down the soil profile. The manifestation of both soil- and biota-driven factors depends on the radionuclide chemical speciation in the initial fallout. The latter factor is most important for 137Cs, yet less manifested for 90Sr. Among the biota components, fungi and forest vegetation are of particular importance for 137Cs and 90Sr accumulation, respectively. In summary, <span class="hlt">biogeochemical</span> cycles of 137Cs and 90Sr in the investigated forest ecosystems serve as main factors impeding the radionuclide migration from the fallout to ground water. Larger-scale landscape factors determine the radionuclide flux intensity in the <span class="hlt">biogeochemical</span> cycles and affect the radionuclide spatial variability in the contaminated biota components.</p> <div class="credits"> <p class="dwt_author">Shcheglov, Alexey; Tsvetnova, Ol'ga; Klyashtorin, Alexey</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">354</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.H33G0962K"> <span id="translatedtitle">Hydro-<span class="hlt">biogeochemical</span> functions of a riparian wetland in a forested catchment</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">Riparian wetland, one of a landscape in a forested catchment, has a distinctive hydro-<span class="hlt">biogeochemical</span> functions from the unsaturated hillslope because it is continuously saturated. Mountain rivers in Japan generally have steep channel and there are many check dams to prevent from the severe soil erosion resulted from the overuse of forest. Sediments are deposited and riparian wetlands are formed in the area upslope from the dam. In this study, we observed the flow dynamics and chemical characteristics of the surface- and groundwater in such a wetland. Depending on sediment depositional patterns, soil material is sandy in upstream and lower layer of downstream of the wetland and clayey in upper layer of downstream. The results of piezometric observation showed the spatially heterogeneous flowpath of the groundwater; the flow concentrated to the lower layer of downstream, and the hyporheic exchange flow was hardly observed at the upper layer of downstream. The seasonal variability of the groundwater chemistry showed that the wetland was reduced more in summer. It was highly reduced in the clayey soil through the year. On the other hand, the reduced condition was moderated during winter in the sandy soil. These variations are result from the hydrological processes. The groundwater flow through the sandy soil easily supplies the oxygen. The degrees of effects of these hydrochemical processes on the streamwater depended on the precipitation amount. As the surface water less contacted to the wetland in a pluvial year, the effects weakened. These results suggest that the spatio-temporal heterogeneity of the hydrological processes are reflected on the <span class="hlt">biogeochemical</span> characteristics in the forested catchment.</p> <div class="credits"> <p class="dwt_author">Katsuyama, M.; Hayamizu, K.; Itoh, M.; Ohte, N.; Tani, M.</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">355</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">356</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/25201817"> <span id="translatedtitle">Tracing <span class="hlt">biogeochemical</span> and microbial variability over a complete oil sand mining and recultivation process.</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">Recultivation of disturbed oil sand mining areas is an issue of increasing importance. Nevertheless only little is known about the fate of organic matter, cell abundances and microbial community structures during oil sand processing, tailings management and initial soil development on reclamation sites. Thus the focus of this work is on <span class="hlt">biogeochemical</span> changes of mined oil sands through the entire process chain until its use as substratum for newly developing soils on reclamation sites. Therefore, oil sand, mature fine tailings (MFTs) from tailings ponds and drying cells and tailings sand covered with peat-mineral mix (PMM) as part of land reclamation were analyzed. The sample set was selected to address the question whether changes in the above-mentioned <span class="hlt">biogeochemical</span> parameters can be related to oil sand processing or biological processes and how these changes influence microbial activities and soil development. GC-MS analyses of oil-derived biomarkers reveal that these compounds remain unaffected by oil sand processing and biological activity. In contrast, changes in polycyclic aromatic hydrocarbon (PAH) abundance and pattern can be observed along the process chain. Especially naphthalenes, phenanthrenes and chrysenes are altered or absent on reclamation sites. Furthermore, root-bearing horizons on reclamation sites exhibit cell abundances at least ten times higher (10(8) to 10(9)cellsg(-1)) than in oil sand and MFT samples (10(7)cellsg(-1)) and show a higher diversity in their microbial community structure. Nitrate in the pore water and roots derived from the PMM seem to be the most important stimulants for microbial growth. The combined data show that the observed compositional changes are mostly related to biological activity and the addition of exogenous organic components (PMM), whereas oil extraction, tailings dewatering and compaction do not have significant influences on the evaluated compounds. Microbial community composition remains relatively stable through the entire process chain. PMID:25201817</p> <div class="credits"> <p class="dwt_author">Noah, Mareike; Lappé, Michael; Schneider, Beate; Vieth-Hillebrand, Andrea; Wilkes, Heinz; Kallmeyer, Jens</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-11-15</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/2008AGUFMPP31C1507O"> <span id="translatedtitle">Condition for Global Ocean Anoxia Obtained From a One Dimensional Ocean <span class="hlt">Biogeochemical</span> Cycle 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">Ocean anoxic events (OAEs) have occurred sporadically during the Phanerozoic. Previous studies proposed several oxygen-depleted mechanisms, such as stagnant ocean circulation, high primary productivity in surface ocean, sea level change, and low atmospheric oxygen level. There is a possibility that OAEs may have been caused by combination of these factors. There are however very few quantitative studies which examine the effects of these mechanisms. In this study, we constructed a vertical one-dimensional ocean <span class="hlt">biogeochemical</span> cycle model to investigate conditions for the occurrence of anoxia in the ocean. In addition to the <span class="hlt">biogeochemical</span> processes in oxic environments, this model includes decomposition processes of particulate organic matter due to nitrate and sulfate and oxidation processes of ammonium and hydrogen sulfide in aerobic water column. We divided the ocean anoxic conditions into "intermediate water anoxia" and "deep water anoxia" based on the vertical profile of dissolved oxygen in the water column. We investigate these two conditions systematically with respect to the two critical parameters, that is, ocean ventilation intensity and riverine nutrient (phosphorus) supply rate, which have been proposed as promising candidates for the mechanisms of ocean anoxic events. The effect of the redox condition on reactive phosphorus burial in seafloor sediments and the reduced solubility of oxygen due to increased sea surface temperature are also examined. Because of the characteristic behaviors of marine phosphorus cycle under the anoxic ocean condition, we found that primary production can be enhanced in spite of stagnant ocean circulation. Our results also suggest that the positive feedback between oxygen concentration, phosphorus regeneration, and primary productivity plays an important role in controlling the oceanic redox conditions.</p> <div class="credits"> <p class="dwt_author">Ozaki, K.; Tajika, E.</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">358</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. CO? 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">2013-11-01</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/2013AGUFM.B32A..04C"> <span id="translatedtitle">Sea Level Rise Modifies <span class="hlt">Biogeochemical</span> Cycles in Winyah Bay, South Carolina Wetlands</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">Rising sea level along the relatively flat southeastern US coastal plain significantly changes both vegetation composition and salinity of coastal wetlands, eventually modifying ecosystem functions and <span class="hlt">biogeochemical</span> processes of these wetlands. We conducted a two-year study to evaluate the dynamics and relationships among aboveground productivity, greenhouse and halocarbon gas emissions, nutrients, and dissolved organic matter of a freshwater forested wetland, a salt-impacted and degraded forested wetland, and a salt marsh in Winyah Bay, South Carolina, representing the salinity gradient and the transition from freshwater forested wetland to salt marsh due to sea level rise. The degraded forested wetland had significantly lower above-ground productivity with annual stem growth of 102 g/m^2/yr and litterfall of 392 g/m^2/yr compared to the freshwater forested wetland (230 and 612 g/m^2/yr, respectively). High methane emission [> 50 mmol/m2/day, n = 4] was only observed in the freshwater-forested wetland but there was a strong smell of sulfide noticed in the salt marsh, suggesting that different redox processes control the decomposition of natural organic matter along the salinity gradient. In addition, the largest CHCl3 [209 × 183 nmol/m2/day, n = 4] emission was observed in the degraded forested wetland, but net CH3Cl [257 × 190 nmol/m2/day, n = 4] and CH3Br [28 × 20 nmol/m2/day, n = 4] emissions were only observed in the salt marsh, suggesting different mechanisms in response to salt intrusion at that sites. The highest DOC concentration (28 - 42 mg/L) in monthly water samples was found in degraded forest wetland, followed by the freshwater forested wetland (19 - 38 mg/L) and salt marsh (9 - 18 mg/L). Results demonstrate that the salt-impacted degraded wetland has unique <span class="hlt">biogeochemical</span> cycles that differ from unaltered freshwater forested wetland and salt marsh.</p> <div class="credits"> <p class="dwt_author">Chow, A. T.; Conner, W.; Rhew, R. C.; Suhre, D.; Wang, J.</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-12-01</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/2014JMS...139..183S"> <span id="translatedtitle">Sedimentological, <span class="hlt">biogeochemical</span> and mineralogical facies of Northern and Central Western Adriatic 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 aim of this work was to identify sedimentary facies, i.e. facies having similar <span class="hlt">biogeochemical</span>, mineralogical and sedimentological properties, in present and recent fine sediments of the Northern and Central Adriatic Sea with their spatial and temporal variations. Further aims were to identify the transportation, dispersion and sedimentation processes and provenance areas of sediments belonging to the facies. A Q-mode factor analysis of mineralogical, granulometric, geochemical (major and trace elements) and biochemical (organic carbon and total nitrogen) properties of surficial and sub-surficial sediments sampled in the PRISMA 1 Project has been used to identify the sedimentary facies. On the whole, four facies were identified: 1) Padanic Facies, made up of fine siliciclastic sediments which reach the Adriatic Sea mainly from the Po River and are distributed by the Adriatic hydrodynamic in a parallel belt off the Italian coast. Southward, this facies gradually mixes with sediments from the Apennine rivers and with biogenic autochthonous particulate; 2) Dolomitic Facies, made up of dolomitic sediments coming from the eastern Alps. This facies is predominant north of the Po River outfalls and it mixes with Padanic Facies sediments in front of the Po River delta; 3) Mn-carbonate Facies, made up of very fine sediments, rich in coccolithophores and secondary Mn-oxy-hydroxides resulting from the reworking of surficial fine sediments in shallow areas and subsequent deposition in deeper areas; 4) Residual Facies, made up of coarse siliciclastic sediments and heavy minerals resulting from the action of waves and coastal currents; this facies is present mainly in inshore areas. The zoning of the facies, resulting from this study, will make possible the identification, through further investigation, on a greater scale, of more accurate facies borders and the recognition of sub-facies, resulting from secondary or weaker <span class="hlt">biogeochemical</span> processes.</p> <div class="credits"> <p class="dwt_author">Spagnoli, Federico; Dinelli, Enrico; Giordano, Patrizia; Marcaccio, Marco; Zaffagnini, Fabio; Frascari, Franca</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-11-01</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 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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://dx.doi.org/10.1023/B:WAFO.0000028363.48348.a4"> <span id="translatedtitle">A <span class="hlt">biogeochemical</span> comparison of two well-buffered catchments with contrasting histories of acid deposition</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">Much of the <span class="hlt">biogeochemical</span> cycling research in catchments in the past 25 years has been driven by acid deposition research funding. This research has focused on vulnerable base-poor systems; catchments on alkaline lithologies have received little attention. In regions of high acid loadings, however, even well-buffered catchments are susceptible to forest decline and episodes of low alkalinity in streamwater. As part of a collaboration between the Czech and U.S. Geological Surveys, we compared <span class="hlt">biogeochemical</span> patterns in two well-studied, well-buffered catchments: Pluhuv Bor in the western Czech Republic, which has received high loading of atmospheric acidity, and Sleepers River Research Watershed in Vermont, U.S.A., where acid loading has been considerably less. Despite differences in lithology, wetness, forest type, and glacial history, the catchments displayed similar patterns of solute concentrations and flow. At both catchments, base cation and alkalinity diluted with increasing flow, whereas nitrate and dissolved organic carbon increased with increasing flow. Sulfate diluted with increasing flow at Sleepers River, while at Pluhuv Bor the sulfate-flow relation shifted from positive to negative as atmospheric sulfur (S) loadings decreased and soil S pools were depleted during the 1990s. At high flow, alkalinity decreased to near 100 ??eq L-1 at Pluhuv Bor compared to 400 ??eq L-1 at Sleepers River. Despite the large amounts of S flushed from Pluhuv Bor soils, these alkalinity declines were caused solely by dilution, which was greater at Pluhuv Bor relative to Sleepers River due to greater contributions from shallow flow paths at high flow. Although the historical high S loading at Pluhuv Bor has caused soil acidification and possible forest damage, it has had little effect on the acid/base status of streamwater in this well-buffered catchment. ?? 2004 Kluwer Academic Publishers.</p> <div class="credits"> <p class="dwt_author">Shanley, J. B.; Kram, P.; Hruska, J.; Bullen, T. D.</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">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/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">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/2013BGD....1010685N"> <span id="translatedtitle">Saltwater intrusion into tidal freshwater marshes alters the <span class="hlt">biogeochemical</span> processing of orga