surface-subsurface biogeochemical coupling: Topics by Science.gov

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

NASA Astrophysics Data System (ADS)

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

2008-07-01

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stegen, James C.; Konopka, Allan; McKinely, Jim

Physical properties of sediments are commonly used to define subsurface lithofacies and these same physical properties influence subsurface microbial communities. This suggests an (unexploited) opportunity to use the spatial distribution of facies to predict spatial variation in biogeochemically relevant microbial attributes. Here, we characterize three biogeochemical facies—oxidized, reduced, and transition—within one lithofacies and elucidate relationships among facies features and microbial community biomass, diversity, and community composition. Consistent with previous observations of biogeochemical hotspots at environmental transition zones, we find elevated biomass within a biogeochemical facies that occurred at the transition between oxidized and reduced biogeochemical facies. Microbial diversity—the number ofmore » microbial taxa—was lower within the reduced facies and was well-explained by a combination of pH and mineralogy. Null modeling revealed that microbial community composition was influenced by ecological selection imposed by redox state and mineralogy, possibly due to effects on nutrient availability or transport. As an illustrative case, we predict microbial biomass concentration across a three-dimensional spatial domain by coupling the spatial distribution of subsurface biogeochemical facies with biomass-facies relationships revealed here. We expect that merging such an approach with hydro-biogeochemical models will provide important constraints on simulated dynamics, thereby reducing uncertainty in model predictions.« less
Integrated Coupling of Surface and Subsurface Flow with HYDRUS-2D

NASA Astrophysics Data System (ADS)

Hartmann, Anne; Šimůnek, Jirka; Wöhling, Thomas; Schütze, Niels

2016-04-01

Describing interactions between surface and subsurface flow processes is important to adequately define water flow in natural systems. Since overland flow generation is highly influenced by rainfall and infiltration, both highly spatially heterogeneous processes, overland flow is unsteady and varies spatially. The prediction of overland flow needs to include an appropriate description of the interactions between the surface and subsurface flow. Coupling surface and subsurface water flow is a challenging task. Different approaches have been developed during the last few years, each having its own advantages and disadvantages. A new approach by Weill et al. (2009) to couple overland flow and subsurface flow based on a generalized Richards equation was implemented into the well-known subsurface flow model HYDRUS-2D (Šimůnek et al., 2011). This approach utilizes the one-dimensional diffusion wave equation to model overland flow. The diffusion wave model is integrated in HYDRUS-2D by replacing the terms of the Richards equation in a pre-defined runoff layer by terms defining the diffusion wave equation. Using this approach, pressure and flux continuity along the interface between both flow domains is provided. This direct coupling approach provides a strong coupling of both systems based on the definition of a single global system matrix to numerically solve the coupled flow problem. The advantage of the direct coupling approach, compared to the loosely coupled approach, is supposed to be a higher robustness, when many convergence problems can be avoided (Takizawa et al., 2014). The HYDRUS-2D implementation was verified using a) different test cases, including a direct comparison with the results of Weill et al. (2009), b) an analytical solution of the kinematic wave equation, and c) the results of a benchmark test of Maxwell et al. (2014), that included several known coupled surface subsurface flow models. Additionally, a sensitivity analysis evaluating the effects
Coupling a three-dimensional subsurface flow model with a land surface model to simulate stream-aquifer-land interactions

NASA Astrophysics Data System (ADS)

Huang, M.; Bisht, G.; Zhou, T.; Chen, X.; Dai, H.; Hammond, G. E.; Riley, W. J.; Downs, J.; Liu, Y.; Zachara, J. M.

2016-12-01

A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5) and a massively-parallel multi-physics reactive tranport model (PFLOTRAN). The coupled model (CLM-PFLOTRAN) is applied to a 400m×400m study domain instrumented with groundwater monitoring wells in the Hanford 300 Area along the Columbia River. CLM-PFLOTRAN simulations are performed at three different spatial resolutions over the period 2011-2015 to evaluate the impact of spatial resolution on simulated variables. To demonstrate the difference in model simulations with and without lateral subsurface flow, a vertical-only CLM-PFLOTRAN simulation is also conducted for comparison. Results show that the coupled model is skillful in simulating stream-aquifer interactions, and the land-surface energy partitioning can be strongly modulated by groundwater-river water interactions in high water years due to increased soil moisture availability caused by elevated groundwater table. In addition, spatial resolution does not seem to impact the land surface energy flux simulations, although it is a key factor for accurately estimating the mass exchange rates at the boundaries and associated biogeochemical reactions in the aquifer. The coupled model developed in this study establishes a solid foundation for understanding co-evolution of hydrology and biogeochemistry along the river corridors under historical and future hydro-climate changes.
Using lagged dependence to identify (de)coupled surface and subsurface soil moisture values

NASA Astrophysics Data System (ADS)

Carranza, Coleen D. U.; van der Ploeg, Martine J.; Torfs, Paul J. J. F.

2018-04-01

Recent advances in radar remote sensing popularized the mapping of surface soil moisture at different spatial scales. Surface soil moisture measurements are used in combination with hydrological models to determine subsurface soil moisture values. However, variability of soil moisture across the soil column is important for estimating depth-integrated values, as decoupling between surface and subsurface can occur. In this study, we employ new methods to investigate the occurrence of (de)coupling between surface and subsurface soil moisture. Using time series datasets, lagged dependence was incorporated in assessing (de)coupling with the idea that surface soil moisture conditions will be reflected at the subsurface after a certain delay. The main approach involves the application of a distributed-lag nonlinear model (DLNM) to simultaneously represent both the functional relation and the lag structure in the time series. The results of an exploratory analysis using residuals from a fitted loess function serve as a posteriori information to determine (de)coupled values. Both methods allow for a range of (de)coupled soil moisture values to be quantified. Results provide new insights into the decoupled range as its occurrence among the sites investigated is not limited to dry conditions.
Linking Chaotic Advection with Subsurface Biogeochemical Processes

NASA Astrophysics Data System (ADS)

Mays, D. C.; Freedman, V. L.; White, S. K.; Fang, Y.; Neupauer, R.

2017-12-01

This work investigates the extent to which groundwater flow kinematics drive subsurface biogeochemical processes. In terms of groundwater flow kinematics, we consider chaotic advection, whose essential ingredient is stretching and folding of plumes. Chaotic advection is appealing within the context of groundwater remediation because it has been shown to optimize plume spreading in the laminar flows characteristic of aquifers. In terms of subsurface biogeochemical processes, we consider an existing model for microbially-mediated reduction of relatively mobile uranium(VI) to relatively immobile uranium(IV) following injection of acetate into a floodplain aquifer beneath a former uranium mill in Rifle, Colorado. This model has been implemented in the reactive transport code eSTOMP, the massively parallel version of STOMP (Subsurface Transport Over Multiple Phases). This presentation will report preliminary numerical simulations in which the hydraulic boundary conditions in the eSTOMP model are manipulated to simulate chaotic advection resulting from engineered injection and extraction of water through a manifold of wells surrounding the plume of injected acetate. This approach provides an avenue to simulate the impact of chaotic advection within the existing framework of the eSTOMP code.
Microbial Metagenomics Reveals Climate-Relevant Subsurface Biogeochemical Processes.

PubMed

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

2016-08-01

Microorganisms play key roles in terrestrial system processes, including the turnover of natural organic carbon, such as leaf litter and woody debris that accumulate in soils and subsurface sediments. What has emerged from a series of recent DNA sequencing-based studies is recognition of the enormous variety of little known and previously unknown microorganisms that mediate recycling of these vast stores of buried carbon in subsoil compartments of the terrestrial system. More importantly, the genome resolution achieved in these studies has enabled association of specific members of these microbial communities with carbon compound transformations and other linked biogeochemical processes-such as the nitrogen cycle-that can impact the quality of groundwater, surface water, and atmospheric trace gas concentrations. The emerging view also emphasizes the importance of organism interactions through exchange of metabolic byproducts (e.g., within the carbon, nitrogen, and sulfur cycles) and via symbioses since many novel organisms exhibit restricted metabolic capabilities and an associated extremely small cell size. New, genome-resolved information reshapes our view of subsurface microbial communities and provides critical new inputs for advanced reactive transport models. These inputs are needed for accurate prediction of feedbacks in watershed biogeochemical functioning and their influence on the climate via the fluxes of greenhouse gases, CO2, CH4, and N2O. Copyright © 2016 Elsevier Ltd. All rights reserved.
Biogeochemical Coupling between Ocean and Sea Ice

NASA Astrophysics Data System (ADS)

Wang, S.; Jeffery, N.; Maltrud, M. E.; Elliott, S.; Wolfe, J.

2016-12-01

Biogeochemical processes in ocean and sea ice are tightly coupled at high latitudes. Ongoing changes in Arctic and Antarctic sea ice domain likely influence the coupled system, not only through physical fields but also biogeochemical properties. Investigating the system and its changes requires representation of ocean and sea ice biogeochemical cycles, as well as their coupling in Earth System Models. Our work is based on ACME-HiLAT, a new offshoot of the Community Earth System Model (CESM), including a comprehensive representation of marine ecosystems in the form of the Biogeochemical Elemental Cycling Module (BEC). A full vertical column sea ice biogeochemical module has recently been incorporated into the sea ice component. We have further introduced code modifications to couple key growth-limiting nutrients (N, Si, Fe), dissolved and particulate organic matter, and phytoplankton classes that are important in polar regions between ocean and sea ice. The coupling of ocean and sea ice biology-chemistry will enable representation of key processes such as the release of important climate active constituents or seeding algae from melting sea ice into surface waters. Sensitivity tests suggest sea ice and ocean biogeochemical coupling influences phytoplankton competition, biological production, and the CO2 flux. Sea ice algal seeding plays an important role in determining phytoplankton composition of Arctic early spring blooms, since different groups show various responses to the seeding biomass. Iron coupling leads to increased phytoplankton biomass in the Southern Ocean, which also affects carbon uptake via the biological pump. The coupling of macronutrients and organic matter may have weaker influences on the marine ecosystem. Our developments will allow climate scientists to investigate the fully coupled responses of the sea ice-ocean BGC system to physical changes in polar climate.
Coupling a three-dimensional subsurface flow and transport model with a land surface model to simulate stream-aquifer-land interactions (CP v1.0)

NASA Astrophysics Data System (ADS)

Bisht, Gautam; Huang, Maoyi; Zhou, Tian; Chen, Xingyuan; Dai, Heng; Hammond, Glenn E.; Riley, William J.; Downs, Janelle L.; Liu, Ying; Zachara, John M.

2017-12-01

A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5) and a massively parallel multiphysics reactive transport model (PFLOTRAN). The coupled model, named CP v1.0, is applied to a 400 m × 400 m study domain instrumented with groundwater monitoring wells along the Columbia River shoreline. CP v1.0 simulations are performed at three spatial resolutions (i.e., 2, 10, and 20 m) over a 5-year period to evaluate the impact of hydroclimatic conditions and spatial resolution on simulated variables. Results show that the coupled model is capable of simulating groundwater-river-water interactions driven by river stage variability along managed river reaches, which are of global significance as a result of over 30 000 dams constructed worldwide during the past half-century. Our numerical experiments suggest that the land-surface energy partitioning is strongly modulated by groundwater-river-water interactions through expanding the periodically inundated fraction of the riparian zone, and enhancing moisture availability in the vadose zone via capillary rise in response to the river stage change. Meanwhile, CLM4.5 fails to capture the key hydrologic process (i.e., groundwater-river-water exchange) at the site, and consequently simulates drastically different water and energy budgets. Furthermore, spatial resolution is found to significantly impact the accuracy of estimated the mass exchange rates at the boundaries of the aquifer, and it becomes critical when surface and subsurface become more tightly coupled with groundwater table within 6 to 7 meters below the surface. Inclusion of lateral subsurface flow influenced both the surface energy budget and subsurface transport processes as a result of river-water intrusion into the
Coupling a three-dimensional subsurface flow and transport model with a land surface model to simulate stream–aquifer–land interactions (CP v1.0)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bisht, Gautam; Huang, Maoyi; Zhou, Tian

A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5) and a massively parallel multiphysics reactive transport model (PFLOTRAN). The coupled model, named CP v1.0, is applied to a 400 m × 400 m study domain instrumented with groundwater monitoring wells along the Columbia River shoreline. CP v1.0 simulations are performed at three spatial resolutions (i.e., 2, 10, and 20 m) over a 5-year period to evaluate themore » impact of hydroclimatic conditions and spatial resolution on simulated variables. Results show that the coupled model is capable of simulating groundwater–river-water interactions driven by river stage variability along managed river reaches, which are of global significance as a result of over 30 000 dams constructed worldwide during the past half-century. Our numerical experiments suggest that the land-surface energy partitioning is strongly modulated by groundwater–river-water interactions through expanding the periodically inundated fraction of the riparian zone, and enhancing moisture availability in the vadose zone via capillary rise in response to the river stage change. Meanwhile, CLM4.5 fails to capture the key hydrologic process (i.e., groundwater–river-water exchange) at the site, and consequently simulates drastically different water and energy budgets. Furthermore, spatial resolution is found to significantly impact the accuracy of estimated the mass exchange rates at the boundaries of the aquifer, and it becomes critical when surface and subsurface become more tightly coupled with groundwater table within 6 to 7 meters below the surface. Inclusion of lateral subsurface flow influenced both the surface energy budget and subsurface transport processes as a result of river
Coupling a three-dimensional subsurface flow and transport model with a land surface model to simulate stream–aquifer–land interactions (CP v1.0)

DOE PAGES

Bisht, Gautam; Huang, Maoyi; Zhou, Tian; ...

2017-01-01

A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5) and a massively parallel multiphysics reactive transport model (PFLOTRAN). The coupled model, named CP v1.0, is applied to a 400 m × 400 m study domain instrumented with groundwater monitoring wells along the Columbia River shoreline. CP v1.0 simulations are performed at three spatial resolutions (i.e., 2, 10, and 20 m) over a 5-year period to evaluate themore » impact of hydroclimatic conditions and spatial resolution on simulated variables. Results show that the coupled model is capable of simulating groundwater–river-water interactions driven by river stage variability along managed river reaches, which are of global significance as a result of over 30 000 dams constructed worldwide during the past half-century. Our numerical experiments suggest that the land-surface energy partitioning is strongly modulated by groundwater–river-water interactions through expanding the periodically inundated fraction of the riparian zone, and enhancing moisture availability in the vadose zone via capillary rise in response to the river stage change. Meanwhile, CLM4.5 fails to capture the key hydrologic process (i.e., groundwater–river-water exchange) at the site, and consequently simulates drastically different water and energy budgets. Furthermore, spatial resolution is found to significantly impact the accuracy of estimated the mass exchange rates at the boundaries of the aquifer, and it becomes critical when surface and subsurface become more tightly coupled with groundwater table within 6 to 7 meters below the surface. Inclusion of lateral subsurface flow influenced both the surface energy budget and subsurface transport processes as a result of river
Coupling a three-dimensional subsurface flow and transport model with a land surface model to simulate stream–aquifer–land interactions (CP v1.0)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bisht, Gautam; Huang, Maoyi; Zhou, Tian

A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5) and a massively parallel multiphysics reactive transport model (PFLOTRAN). The coupled model, named CP v1.0, is applied to a 400 m × 400 m study domain instrumented with groundwater monitoring wells along the Columbia River shoreline. CP v1.0 simulations are performed at three spatial resolutions (i.e., 2, 10, and 20 m) over a 5-year periodmore » to evaluate the impact of hydroclimatic conditions and spatial resolution on simulated variables. Results show that the coupled model is capable of simulating groundwater–river-water interactions driven by river stage variability along managed river reaches, which are of global significance as a result of over 30 000 dams constructed worldwide during the past half-century. Our numerical experiments suggest that the land-surface energy partitioning is strongly modulated by groundwater–river-water interactions through expanding the periodically inundated fraction of the riparian zone, and enhancing moisture availability in the vadose zone via capillary rise in response to the river stage change. Meanwhile, CLM4.5 fails to capture the key hydrologic process (i.e., groundwater–river-water exchange) at the site, and consequently simulates drastically different water and energy budgets. Furthermore, spatial resolution is found to significantly impact the accuracy of estimated the mass exchange rates at the boundaries of the aquifer, and it becomes critical when surface and subsurface become more tightly coupled with groundwater table within 6 to 7 meters below the surface. Inclusion of lateral subsurface flow influenced both the surface energy budget and subsurface transport processes as a result of river-water intrusion
Coupling a three-dimensional subsurface flow and transport model with a land surface model to simulate stream–aquifer–land interactions (CP v1.0)

DOE PAGES

Bisht, Gautam; Huang, Maoyi; Zhou, Tian; ...

2017-12-12

A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5) and a massively parallel multiphysics reactive transport model (PFLOTRAN). The coupled model, named CP v1.0, is applied to a 400 m × 400 m study domain instrumented with groundwater monitoring wells along the Columbia River shoreline. CP v1.0 simulations are performed at three spatial resolutions (i.e., 2, 10, and 20 m) over a 5-year periodmore » to evaluate the impact of hydroclimatic conditions and spatial resolution on simulated variables. Results show that the coupled model is capable of simulating groundwater–river-water interactions driven by river stage variability along managed river reaches, which are of global significance as a result of over 30 000 dams constructed worldwide during the past half-century. Our numerical experiments suggest that the land-surface energy partitioning is strongly modulated by groundwater–river-water interactions through expanding the periodically inundated fraction of the riparian zone, and enhancing moisture availability in the vadose zone via capillary rise in response to the river stage change. Meanwhile, CLM4.5 fails to capture the key hydrologic process (i.e., groundwater–river-water exchange) at the site, and consequently simulates drastically different water and energy budgets. Furthermore, spatial resolution is found to significantly impact the accuracy of estimated the mass exchange rates at the boundaries of the aquifer, and it becomes critical when surface and subsurface become more tightly coupled with groundwater table within 6 to 7 meters below the surface. Inclusion of lateral subsurface flow influenced both the surface energy budget and subsurface transport processes as a result of river-water intrusion
Quantifying Subsurface Water and Heat Distribution and its Linkage with Landscape Properties in Terrestrial Environment using Hydro-Thermal-Geophysical Monitoring and Coupled Inverse Modeling

NASA Astrophysics Data System (ADS)

Dafflon, B.; Tran, A. P.; Wainwright, H. M.; Hubbard, S. S.; Peterson, J.; Ulrich, C.; Williams, K. H.

2015-12-01

Quantifying water and heat fluxes in the subsurface is crucial for managing water resources and for understanding the terrestrial ecosystem where hydrological properties drive a variety of biogeochemical processes across a large range of spatial and temporal scales. Here, we present the development of an advanced monitoring strategy where hydro-thermal-geophysical datasets are continuously acquired and further involved in a novel inverse modeling framework to estimate the hydraulic and thermal parameter that control heat and water dynamics in the subsurface and further influence surface processes such as evapotranspiration and vegetation growth. The measured and estimated soil properties are also used to investigate co-interaction between subsurface and surface dynamics by using above-ground aerial imaging. The value of this approach is demonstrated at two different sites, one in the polygonal shaped Arctic tundra where water and heat dynamics have a strong impact on freeze-thaw processes, vegetation and biogeochemical processes, and one in a floodplain along the Colorado River where hydrological fluxes between compartments of the system (surface, vadose zone and groundwater) drive biogeochemical transformations. Results show that the developed strategy using geophysical, point-scale and aerial measurements is successful to delineate the spatial distribution of hydrostratigraphic units having distinct physicochemical properties, to monitor and quantify in high resolution water and heat distribution and its linkage with vegetation, geomorphology and weather conditions, and to estimate hydraulic and thermal parameters for enhanced predictions of water and heat fluxes as well as evapotranspiration. Further, in the Colorado floodplain, results document the potential presence of only periodic infiltration pulses as a key hot moment controlling soil hydro and biogeochemical functioning. In the arctic, results show the strong linkage between soil water content, thermal
CALIBRATION OF SUBSURFACE BATCH AND REACTIVE-TRANSPORT MODELS INVOLVING COMPLEX BIOGEOCHEMICAL PROCESSES

EPA Science Inventory

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

NASA Astrophysics Data System (ADS)

Alves Meira Neto, A.; Sengupta, A.; Wang, Y.; Volkmann, T.; Chorover, J.; Troch, P. A. A.

2017-12-01

Advances in the understanding of processes in the critical zone (CZ) are dependent on studies coupling the fields of hydrology, microbiology, geochemistry and soil development. At the same time, better insights are needed to integrate hydrologic information into biogeochemical analysis of subsurface environments. This study investigated potential hydrological indexes that help explaining spatiotemporal biogeochemical patterns. The miniLEO is a 2 m3, 10 degree sloping lysimeter located at Biosphere 2 - University of Arizona. The lysimeter was initially filled with pristine basaltic soil and subject to intermittent rainfall applications throughout the period of 18 months followed by its excavation, resulting in a grid-based sample collection at 324 locations. As a result, spatially distributed microbiological and geochemical patterns as well as soil physical properties were obtained. A hydrologic model was then developed in order to simulate the history of the system until the excavation. After being calibrated against sensor data to match its observed input-state-output behavior, the resulting distributed fields of flow velocities and moisture states were retrieved. These results were translated into several hydrological indexes to be used in with distributed microbiological and geochemical signatures. Our study attempts at conciliating sound hydrological modelling with an investigation of the subsurface biological signatures, thus providing a unique opportunity for understanding of fine-scale hydro-biological interactions.
Effects of ozone-vegetation coupling on surface ozone air quality via biogeochemical and meteorological feedbacks

NASA Astrophysics Data System (ADS)

Sadiq, Mehliyar; Tai, Amos P. K.; Lombardozzi, Danica; Martin, Maria Val

2017-02-01

Tropospheric ozone is one of the most hazardous air pollutants as it harms both human health and plant productivity. Foliage uptake of ozone via dry deposition damages photosynthesis and causes stomatal closure. These foliage changes could lead to a cascade of biogeochemical and biogeophysical effects that not only modulate the carbon cycle, regional hydrometeorology and climate, but also cause feedbacks onto surface ozone concentration itself. In this study, we implement a semi-empirical parameterization of ozone damage on vegetation in the Community Earth System Model to enable online ozone-vegetation coupling, so that for the first time ecosystem structure and ozone concentration can coevolve in fully coupled land-atmosphere simulations. With ozone-vegetation coupling, present-day surface ozone is simulated to be higher by up to 4-6 ppbv over Europe, North America and China. Reduced dry deposition velocity following ozone damage contributes to ˜ 40-100 % of those increases, constituting a significant positive biogeochemical feedback on ozone air quality. Enhanced biogenic isoprene emission is found to contribute to most of the remaining increases, and is driven mainly by higher vegetation temperature that results from lower transpiration rate. This isoprene-driven pathway represents an indirect, positive meteorological feedback. The reduction in both dry deposition and transpiration is mostly associated with reduced stomatal conductance following ozone damage, whereas the modification of photosynthesis and further changes in ecosystem productivity are found to play a smaller role in contributing to the ozone-vegetation feedbacks. Our results highlight the need to consider two-way ozone-vegetation coupling in Earth system models to derive a more complete understanding and yield more reliable future predictions of ozone air quality.
Biogeochemical carbon coupling influences global precipitation in geoengineering experiments

NASA Astrophysics Data System (ADS)

Fyfe, J. C.; Cole, J. N. S.; Arora, V. K.; Scinocca, J. F.

2013-02-01

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 biogeochemical 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 biogeochemical carbon coupling on the precipitation response in geoengineering experiments for two types of solar radiation management. We show that carbon coupling 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 biogeochemical interactions are as important as changes in net radiation and that climate models that do not account for such carbon coupling may significantly underestimate precipitation reductions in a geoengineered world. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1313253-quantifying-shallow-subsurface-water-heat-dynamics-using-coupled-hydrological-thermal-geophysical-inversion','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1313253-quantifying-shallow-subsurface-water-heat-dynamics-using-coupled-hydrological-thermal-geophysical-inversion">Quantifying shallow subsurface water and heat dynamics using coupled hydrological-thermal-geophysical inversion</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Tran, Anh Phuong; Dafflon, Baptiste; Hubbard, Susan S.; ... 2016-04-25 Improving our ability to estimate the parameters that control water and heat fluxes in the shallow subsurface is particularly important due to their strong control on recharge, evaporation and biogeochemical processes. The objectives of this study are to develop and test a new inversion scheme to simultaneously estimate subsurface hydrological, thermal and petrophysical parameters using hydrological, thermal and electrical resistivity tomography (ERT) data. The inversion scheme-which is based on a nonisothermal, multiphase hydrological model-provides the desired subsurface property estimates in high spatiotemporal resolution. A particularly novel aspect of the inversion scheme is the explicit incorporation of the dependence of themore » subsurface electrical resistivity on both moisture and temperature. The scheme was applied to synthetic case studies, as well as to real datasets that were autonomously collected at a biogeochemical field study site in Rifle, Colorado. At the Rifle site, the coupled hydrological-thermal-geophysical inversion approach well predicted the matric potential, temperature and apparent resistivity with the Nash-Sutcliffe efficiency criterion greater than 0.92. Synthetic studies found that neglecting the subsurface temperature variability, and its effect on the electrical resistivity in the hydrogeophysical inversion, may lead to an incorrect estimation of the hydrological parameters. The approach is expected to be especially useful for the increasing number of studies that are taking advantage of autonomously collected ERT and soil measurements to explore complex terrestrial system dynamics.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24211462','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24211462">A size selective porous silicon grating-coupled Bloch surface and sub-surface wave biosensor.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Rodriguez, Gilberto A; Ryckman, Judson D; Jiao, Yang; Weiss, Sharon M 2014-03-15 A porous silicon (PSi) grating-coupled Bloch surface and sub-surface wave (BSW/BSSW) biosensor is demonstrated to size selectively detect the presence of both large and small molecules. The BSW is used to sense large immobilized analytes at the surface of the structure while the BSSW that is confined inside but near the top of the structure is used to sensitively detect small molecules. Functionality of the BSW and BSSW modes is theoretically described by dispersion relations, field confinements, and simulated refractive index shifts within the structure. The theoretical results are experimentally verified by detecting two different small chemical molecules and one large 40 base DNA oligonucleotide. The PSi-BSW/BSSW structure is benchmarked against current porous silicon technology and is shown to have a 6-fold higher sensitivity in detecting large molecules and a 33% improvement in detecting small molecules. This is the first report of a grating-coupled BSW biosensor and the first report of a BSSW propagating mode. © 2013 Published by Elsevier B.V. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li class="active">1</li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_2" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li class="active">2</li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="21"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.H21K..06P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.H21K..06P">Robust Representation of Integrated Surface-subsurface Hydrology at Watershed Scales</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Painter, S. L.; Tang, G.; Collier, N.; Jan, A.; Karra, S. 2015-12-01 A representation of integrated surface-subsurface hydrology is the central component to process-rich watershed models that are emerging as alternatives to traditional reduced complexity models. These physically based systems are important for assessing potential impacts of climate change and human activities on groundwater-dependent ecosystems and water supply and quality. Integrated surface-subsurface models typically couple three-dimensional solutions for variably saturated flow in the subsurface with the kinematic- or diffusion-wave equation for surface flows. The computational scheme for coupling the surface and subsurface systems is key to the robustness, computational performance, and ease-of-implementation of the integrated system. A new, robust approach for coupling the subsurface and surface systems is developed from the assumption that the vertical gradient in head is negligible at the surface. This tight-coupling assumption allows the surface flow system to be incorporated directly into the subsurface system; effects of surface flow and surface water accumulation are represented as modifications to the subsurface flow and accumulation terms but are not triggered until the subsurface pressure reaches a threshold value corresponding to the appearance of water on the surface. The new approach has been implemented in the highly parallel PFLOTRAN (www.pflotran.org) code. Several synthetic examples and three-dimensional examples from the Walker Branch Watershed in Oak Ridge TN demonstrate the utility and robustness of the new approach using unstructured computational meshes. Representation of solute transport in the new approach is also discussed. Notice: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC0500OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JAMES..10...43D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JAMES..10...43D">Full Coupling Between the Atmosphere, Surface, and Subsurface for Integrated Hydrologic Simulation</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Davison, Jason Hamilton; Hwang, Hyoun-Tae; Sudicky, Edward A.; Mallia, Derek V.; Lin, John C. 2018-01-01 An ever increasing community of earth system modelers is incorporating new physical processes into numerical models. This trend is facilitated by advancements in computational resources, improvements in simulation skill, and the desire to build numerical simulators that represent the water cycle with greater fidelity. In this quest to develop a state-of-the-art water cycle model, we coupled HydroGeoSphere (HGS), a 3-D control-volume finite element surface and variably saturated subsurface flow model that includes evapotranspiration processes, to the Weather Research and Forecasting (WRF) Model, a 3-D finite difference nonhydrostatic mesoscale atmospheric model. The two-way coupled model, referred to as HGS-WRF, exchanges the actual evapotranspiration fluxes and soil saturations calculated by HGS to WRF; conversely, the potential evapotranspiration and precipitation fluxes from WRF are passed to HGS. The flexible HGS-WRF coupling method allows for unique meshes used by each model, while maintaining mass and energy conservation between the domains. Furthermore, the HGS-WRF coupling implements a subtime stepping algorithm to minimize computational expense. As a demonstration of HGS-WRF's capabilities, we applied it to the California Basin and found a strong connection between the depth to the groundwater table and the latent heat fluxes across the land surface. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B12A..04M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B12A..04M">Numerical modeling of watershed-scale radiocesium transport coupled with biogeochemical cycling in forests</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mori, K.; Tada, K.; Tawara, Y.; Tosaka, H.; Ohno, K.; Asami, M.; Kosaka, K. 2015-12-01 Since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, intensive monitoring and modeling works on radionuclide transfer in environment have been carried out. Although Cesium (Cs) concentration has been attenuating due to both physical and environmental half-life (i.e., wash-off by water and sediment), the attenuation rate depends clearly on the type of land use and land cover. In the Fukushima case, studying the migration in forest land use is important for predicting the long-term behavior of Cs because most of the contaminated region is covered by forests. Atmospheric fallout is characterized by complicated behavior in biogeochemical cycle in forests which can be described by biotic/abiotic interactions between many components. In developing conceptual and mathematical model on Cs transfer in forest ecosystem, defining the dominant components and their interactions are crucial issues (BIOMASS, 1997-2001). However, the modeling of fate and transport in geosphere after Cs exports from the forest ecosystem is often ignored. An integrated watershed modeling for simulating spatiotemporal redistribution of Cs that includes the entire region from source to mouth and surface to subsurface, has been recently developed. Since the deposited Cs can migrate due to water and sediment movement, the different species (i.e., dissolved and suspended) and their interactions are key issues in the modeling. However, the initial inventory as source-term was simplified to be homogeneous and time-independent, and biogeochemical cycle in forests was not explicitly considered. Consequently, it was difficult to evaluate the regionally-inherent characteristics which differ according to land uses, even if the model was well calibrated. In this study, we combine the different advantages in modeling of forest ecosystem and watershed. This enable to include more realistic Cs deposition and time series of inventory can be forced over the land surface. These processes are integrated </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1913886N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1913886N">Spectral induced polarization as a tool to map subsurface biogeochemical hot spots: a first laboratory evaluation in the Fe-S system</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Nordsiek, Sven; Gilfedder, Ben; Frei, Sven 2017-04-01 Zones of intense biogeochemical reactivity (hot spots) arise in the saturated subsurface at the interface between regions with oxidizing and reducing conditions. Hot spots are both sinks and sources of different chemical compounds, thus they are of particular importance for element cycling in the subsurface. However, the investigation of hot spot structures is difficult, because they are not directly identifiable from the surface and can only be investigated by invasive methods in the subsurface. Additionally, they often form in sensitive wetland ecosystems where only non-destructive measurements are applicable to avoid significant degradation of these sensitive environments. Under these circumstances, geophysical methods may provide useful tools to identify biogeochemically active regions. One of the most important biogeochemical reactions in wetlands is the reduction of sulphate and formation and accumulation of FexSy minerals (where x and y delineate mineral stoichiometry). These reactions only occur in specific hot spots where specific chemical and microbial conditions are met. Within a research project concerning biogeochemical transformations and turnover in wetlands, we investigate the applicability of the geoelectrical method of spectral induced polarization (SIP) to locate and monitor regions containing polarizing FexSy particles as indicator for biogeochemical hot spots. After developing and testing a sample holder and a set of non-polarizing electrodes for laboratory SIP measurements, we performed experiments on natural soil samples taken from the hyporheic zone of a local river channel. The collected material originates from a location known for biogeochemical activity. The sample contains a high percentage of dark grayish/black sediment interpreted as FexSy, and possibly pyrite (FeS2). The material was homogenized and split into four samples. The FexSy concentration was adjusted to three different levels by oxidation using H2O2. For all samples we </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.1225S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.1225S">Evaluation of SCS-CN method using a fully distributed physically based coupled surface-subsurface flow model</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shokri, Ali 2017-04-01 The hydrological cycle contains a wide range of linked surface and subsurface flow processes. In spite of natural connections between surface water and groundwater, historically, these processes have been studied separately. The current trend in hydrological distributed physically based model development is to combine distributed surface water models with distributed subsurface flow models. This combination results in a better estimation of the temporal and spatial variability of the interaction between surface and subsurface flow. On the other hand, simple lumped models such as the Soil Conservation Service Curve Number (SCS-CN) are still quite common because of their simplicity. In spite of the popularity of the SCS-CN method, there have always been concerns about the ambiguity of the SCS-CN method in explaining physical mechanism of rainfall-runoff processes. The aim of this study is to minimize these ambiguity by establishing a method to find an equivalence of the SCS-CN solution to the DrainFlow model, which is a fully distributed physically based coupled surface-subsurface flow model. In this paper, two hypothetical v-catchment tests are designed and the direct runoff from a storm event are calculated by both SCS-CN and DrainFlow models. To find a comparable solution to runoff prediction through the SCS-CN and DrainFlow, the variance between runoff predictions by the two models are minimized by changing Curve Number (CN) and initial abstraction (Ia) values. Results of this study have led to a set of lumped model parameters (CN and Ia) for each catchment that is comparable to a set of physically based parameters including hydraulic conductivity, Manning roughness coefficient, ground surface slope, and specific storage. Considering the lack of physical interpretation in CN and Ia is often argued as a weakness of SCS-CN method, the novel method in this paper gives a physical explanation to CN and Ia. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H43G1032S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H43G1032S">Exploring the Influence of Topography on Belowground C Processes Using a Coupled Hydrologic-Biogeochemical Model</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shi, Y.; Davis, K. J.; Eissenstat, D. M.; Kaye, J. P.; Duffy, C.; Yu, X.; He, Y. 2014-12-01 Belowground carbon processes are affected by soil moisture and soil temperature, but current biogeochemical models are 1-D and cannot resolve topographically driven hill-slope soil moisture patterns, and cannot simulate the nonlinear effects of soil moisture on carbon processes. Coupling spatially-distributed physically-based hydrologic models with biogeochemical models may yield significant improvements in the representation of topographic influence on belowground C processes. We will couple the Flux-PIHM model to the Biome-BGC (BBGC) model. Flux-PIHM is a coupled physically-based land surface hydrologic model, which incorporates a land-surface scheme into the Penn State Integrated Hydrologic Model (PIHM). The land surface scheme is adapted from the Noah land surface model. Because PIHM is capable of simulating lateral water flow and deep groundwater, Flux-PIHM is able to represent the link between groundwater and the surface energy balance, as well as the land surface heterogeneities caused by topography. The coupled Flux-PIHM-BBGC model will be tested at the Susquehanna/Shale Hills critical zone observatory (SSHCZO). The abundant observations, including eddy covariance fluxes, soil moisture, groundwater level, sap flux, stream discharge, litterfall, leaf area index, above ground carbon stock, and soil carbon efflux, make SSHCZO an ideal test bed for the coupled model. In the coupled model, each Flux-PIHM model grid will couple a BBGC cell. Flux-PIHM will provide BBGC with soil moisture and soil temperature information, while BBGC provides Flux-PIHM with leaf area index. Preliminary results show that when Biome- BGC is driven by PIHM simulated soil moisture pattern, the simulated soil carbon is clearly impacted by topography. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GBioC..32..226F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GBioC..32..226F">Biogeochemical Role of Subsurface Coherent Eddies in the Ocean: Tracer Cannonballs, Hypoxic Storms, and Microbial Stewpots?</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Frenger, Ivy; Bianchi, Daniele; Stührenberg, Carolin; Oschlies, Andreas; Dunne, John; Deutsch, Curtis; Galbraith, Eric; Schütte, Florian 2018-02-01 Subsurface eddies are known features of ocean circulation, but the sparsity of observations prevents an assessment of their importance for biogeochemistry. Here we use a global eddying (0.1°) ocean-biogeochemical model to carry out a census of subsurface coherent eddies originating from eastern boundary upwelling systems (EBUS) and quantify their biogeochemical effects as they propagate westward into the subtropical gyres. While most eddies exist for a few months, moving over distances of hundreds of kilometers, a small fraction (<5%) of long-lived eddies propagates over distances greater than 1,000 km, carrying the oxygen-poor and nutrient-rich signature of EBUS into the gyre interiors. In the Pacific, transport by subsurface coherent eddies accounts for roughly 10% of the offshore transport of oxygen and nutrients in pycnocline waters. This "leakage" of subsurface waters can be a significant fraction of the transport by nutrient-rich poleward undercurrents and may contribute to the well-known reduction of productivity by eddies in EBUS. Furthermore, at the density layer of their cores, eddies decrease climatological oxygen locally by close to 10%, thereby expanding oxygen minimum zones. Finally, eddies represent low-oxygen extreme events in otherwise oxygenated waters, increasing the area of hypoxic waters by several percent and producing dramatic short-term changes that may play an important ecological role. Capturing these nonlocal effects in global climate models, which typically include noneddying oceans, would require dedicated parameterizations. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20100002940&hterms=soil+layers&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsoil%2Blayers','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20100002940&hterms=soil+layers&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsoil%2Blayers">Role of Subsurface Physics in the Assimilation of Surface Soil Moisture Observations</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Reichle, R. H. 2010-01-01 Root zone soil moisture controls the land-atmosphere exchange of water and energy and exhibits memory that may be useful for climate prediction at monthly scales. Assimilation of satellite-based surface soil moisture observations into a land surface model is an effective way to estimate large-scale root zone soil moisture. The propagation of surface information into deeper soil layers depends on the model-specific representation of subsurface physics that is used in the assimilation system. In a suite of experiments we assimilate synthetic surface soil moisture observations into four different models (Catchment, Mosaic, Noah and CLM) using the Ensemble Kalman Filter. We demonstrate that identical twin experiments significantly overestimate the information that can be obtained from the assimilation of surface soil moisture observations. The second key result indicates that the potential of surface soil moisture assimilation to improve root zone information is higher when the surface to root zone coupling is stronger. Our experiments also suggest that (faced with unknown true subsurface physics) overestimating surface to root zone coupling in the assimilation system provides more robust skill improvements in the root zone compared with underestimating the coupling. When CLM is excluded from the analysis, the skill improvements from using models with different vertical coupling strengths are comparable for different subsurface truths. Finally, the skill improvements through assimilation were found to be sensitive to the regional climate and soil types. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.5316E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.5316E">Assimilation of Sea Color Data Into A Three Dimensional Biogeochemical Model: Sensitivity Experiments</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Echevin, V.; Levy, M.; Memery, L. The assimilation of two dimensional sea color data fields into a 3 dimensional coupled dynamical-biogeochemical model is performed using a 4DVAR algorithm. The biogeochemical model includes description of nitrates, ammonium, phytoplancton, zooplancton, detritus and dissolved organic matter. A subset of the biogeochemical model poorly known parameters (for example,phytoplancton growth, mortality,grazing) are optimized by minimizing a cost function measuring misfit between the observations and the model trajectory. Twin experiments are performed with an eddy resolving model of 5 km resolution in an academic configuration. Starting from oligotrophic conditions, an initially unstable baroclinic anticyclone splits into several eddies. Strong vertical velocities advect nitrates into the euphotic zone and generate a phytoplancton bloom. Biogeochemical parameters are perturbed to generate surface pseudo-observations of chlorophyll,which are assimilated in the model in order to retrieve the correct parameter perturbations. The impact of the type of measurement (quasi-instantaneous, daily mean, weekly mean) onto the retrieved set of parameters is analysed. Impacts of additional subsurface measurements and of errors in the circulation are also presented. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.2020R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.2020R">Soil Carbon Dioxide Production and Surface Fluxes: Subsurface Physical Controls</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Risk, D.; Kellman, L.; Beltrami, H. Soil respiration is a critical determinant of landscape carbon balance. Variations in soil temperature and moisture patterns are important physical processes controlling soil respiration which need to be better understood. Relationships between soil respi- ration and physical controls are typically addressed using only surface flux data but other methods also exist which permit more rigorous interpretation of soil respira- tion processes. Here we use a combination of subsurface CO_{2} concentrations, surface CO_{2} fluxes and detailed physical monitoring of the subsurface envi- ronment to examine physical controls on soil CO_{2} production at four climate observatories in Eastern Canada. Results indicate that subsurface CO_{2} produc- tion is more strongly correlated to the subsurface thermal environment than the surface CO_{2} flux. Soil moisture was also found to have an important influence on sub- surface CO_{2} production, particularly in relation to the soil moisture - soil profile diffusivity relationship. Non-diffusive profile CO_{2} transport appears to be im- portant at these sites, resulting in a de-coupling of summertime surface fluxes from subsurface processes and violating assumptions that surface CO_{2} emissions are the result solely of diffusion. These results have implications for the study of soil respiration across a broad range of terrestrial environments. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1914421L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1914421L">Toward the assimilation of biogeochemical data in the CMEMS BIOMER coupled physical-biogeochemical operational system</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lamouroux, Julien; Testut, Charles-Emmanuel; Lellouche, Jean-Michel; Perruche, Coralie; Paul, Julien 2017-04-01 The operational production of data-assimilated biogeochemical state of the ocean is one of the challenging core projects of the Copernicus Marine Environment Monitoring Service. In that framework - and with the April 2018 CMEMS V4 release as a target - Mercator Ocean is in charge of improving the realism of its global ¼° BIOMER coupled physical-biogeochemical (NEMO/PISCES) simulations, analyses and re-analyses, and to develop an effective capacity to routinely estimate the biogeochemical state of the ocean, through the implementation of biogeochemical data assimilation. Primary objectives are to enhance the time representation of the seasonal cycle in the real time and reanalysis systems, and to provide a better control of the production in the equatorial regions. The assimilation of BGC data will rely on a simplified version of the SEEK filter, where the error statistics do not evolve with the model dynamics. The associated forecast error covariances are based on the statistics of a collection of 3D ocean state anomalies. The anomalies are computed from a multi-year numerical experiment (free run without assimilation) with respect to a running mean in order to estimate the 7-day scale error on the ocean state at a given period of the year. These forecast error covariances rely thus on a fixed-basis seasonally variable ensemble of anomalies. This methodology, which is currently implemented in the "blue" component of the CMEMS operational forecast system, is now under adaptation to be applied to the biogeochemical part of the operational system. Regarding observations - and as a first step - the system shall rely on the CMEMS GlobColour Global Ocean surface chlorophyll concentration products, delivered in NRT. The objective of this poster is to provide a detailed overview of the implementation of the aforementioned data assimilation methodology in the CMEMS BIOMER forecasting system. Focus shall be put on (1) the assessment of the capabilities of this data </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B44B..01T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B44B..01T">AquaDiva: Understanding the Link between the Surface and Subsurface Biogeosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Trumbore, S.; Küsel, K.; Totsche, K. U.; Schwab, V.; Herrmann, M.; Nowak, M. E.; Gleixner, G. 2017-12-01 In the collaborative research project AquaDiva, we combine hydrogeochemical, metagemonic and biogeochemical tools to understand how the complex interactions between geologic setting and surface land use influence the function and biodiversity of the subsurface, especially ground water ecosystems. At the Hainich Critical Zone Exploratory in central Germany, we investigate soil and seepage waters in recharge areas and aquifers in a fractured limestone setting characterized by a dynamic water infiltration regime. Within the Exploratory, we have so far identified three distinct biogeochemical zones in which land use and lithologic differences combine to give rise to surprisingly different biotic communities and hydrogeochemical properties with different degrees of connection to the surface. Here we will focus on how we have combined carbon isotopic, organic biomarkers such as phospholipid fatty acids, and `omics' approaches to determine (i) how deep soil-borne microorganisms can be traced into the subsurface, and (ii) which energy sources sustain microbial life in oligotrophic limestone aquifers. With increasing travel distance to the surface, there is a decline in the abundance of microbes, with less than 5% of the taxa identified overlapping with those identified in the soils. Dissolved organic matter also is altered as it passes through soils, demonstrating an overall increase in molecular weight and a change in molecular makeup as well as radiocarbon content. Using the radiocarbon signature (corrected for the influence of carbonate dissolution), as a way to identify if organic C is being supplied recently by plants, atmosphere sources of energy for communities within the aquifer differ for the identified biogeochemical zones and include (i) dominance of inputs of fresh organic carbon from the surface feeding heterotrophy in oxygenic environments; (ii) CO2 fixation linked to nitrogen and sulfur cycling in anoxic environments and (iii) rock-derived organic matter </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMOS43C..03S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMOS43C..03S">The impact of multi-decadal sub-surface circulation changes on sea surface chlorophyll patterns in the tropical Pacific</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schollaert Uz, S.; Busalacchi, A. J.; Smith, T. M.; Evans, M. N.; Brown, C.; Hackert, E. C.; Wang, X. 2016-12-01 The tropical Pacific is a region of strong forcing where physical oceanography primarily controls biological variability over the seasonal to interannual time scales observed since dedicated ocean color satellite remote sensing began in 1997. To quantify how multi-decadal, climate-scale changes impact marine biological dynamics, we used the correlation with sea-surface temperature and height to reconstruct a 50-year time series of surface chlorophyll concentrations. The reconstruction demonstrates greatest skill away from the coast and within 10o of the equator where chlorophyll variance is greatest and primarily associated with El Niño Southern Oscillation (ENSO) dynamics and secondarily associated with decadal variability. We observe significant basin-wide differences between east and central Pacific events when the El Niño events are strong: chlorophyll increases with La Niña and decreases with El Niño, with larger declines east of 180o for remotely-forced east Pacific events and west of 180o for locally-forced central Pacific events. Chlorophyll variations also reflect the physical dynamics of Pacific decadal variability with small but significant differences between cool and warm eras: consistent with advection variability west of 180o and likely driven by subsurface changes in the nutricline depth between 110-140oW. Comparisons with output from a fully-coupled biogeochemical model support the hypothesis that this anomalous region is controlled by lower frequency changes in subsurface circulation patterns that transport nutrients to the surface. Basin-wide chlorophyll distributions exhibiting spatial heterogeneity in response to multi-decadal climate forcing imply similar long-term changes in phytoplankton productivity, with implications for the marine food web and the ocean's role as a carbon sink. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017HydJ...25..331B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017HydJ...25..331B">Coupled surface and subsurface flow modeling of natural hillslopes in the Aburrá Valley (Medellín, Colombia)</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Blessent, Daniela; Barco, Janet; Temgoua, André Guy Tranquille; Echeverrri-Ramirez, Oscar 2017-03-01 Numerical results are presented of surface-subsurface water modeling of a natural hillslope located in the Aburrá Valley, in the city of Medellín (Antioquia, Colombia). The integrated finite-element hydrogeological simulator HydroGeoSphere is used to conduct transient variably saturated simulations. The objective is to analyze pore-water pressure and saturation variation at shallow depths, as well as volumes of water infiltrated in the porous medium. These aspects are important in the region of study, which is highly affected by soil movements, especially during the high-rain seasons that occur twice a year. The modeling exercise considers rainfall events that occurred between October and December 2014 and a hillslope that is currently monitored because of soil instability problems. Simulation results show that rainfall temporal variability, mesh resolution, coupling length, and the conceptual model chosen to represent the heterogeneous soil, have a noticeable influence on results, particularly for high rainfall intensities. Results also indicate that surface-subsurface coupled modeling is required to avoid unrealistic increase in hydraulic heads when high rainfall intensities cause top-down saturation of soil. This work is a first effort towards fostering hydrogeological modeling expertise that may support the development of monitoring systems and early landslide warning in a country where the rainy season is often the cause of hydrogeological tragedies associated with landslides, mud flow or debris flow. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1917423S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1917423S">Insights in time dependent cross compartment sensitivities from ensemble simulations with the fully coupled subsurface-land surface-atmosphere model TerrSysMP</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schalge, Bernd; Rihani, Jehan; Haese, Barbara; Baroni, Gabriele; Erdal, Daniel; Haefliger, Vincent; Lange, Natascha; Neuweiler, Insa; Hendricks-Franssen, Harrie-Jan; Geppert, Gernot; Ament, Felix; Kollet, Stefan; Cirpka, Olaf; Saavedra, Pablo; Han, Xujun; Attinger, Sabine; Kunstmann, Harald; Vereecken, Harry; Simmer, Clemens 2017-04-01 Currently, an integrated approach to simulating the earth system is evolving where several compartment models are coupled to achieve the best possible physically consistent representation. We used the model TerrSysMP, which fully couples subsurface, land surface and atmosphere, in a synthetic study that mimicked the Neckar catchment in Southern Germany. A virtual reality run at a high resolution of 400m for the land surface and subsurface and 1.1km for the atmosphere was made. Ensemble runs at a lower resolution (800m for the land surface and subsurface) were also made. The ensemble was generated by varying soil and vegetation parameters and lateral atmospheric forcing among the different ensemble members in a systematic way. It was found that the ensemble runs deviated for some variables and some time periods largely from the virtual reality reference run (the reference run was not covered by the ensemble), which could be related to the different model resolutions. This was for example the case for river discharge in the summer. We also analyzed the spread of model states as function of time and found clear relations between the spread and the time of the year and weather conditions. For example, the ensemble spread of latent heat flux related to uncertain soil parameters was larger under dry soil conditions than under wet soil conditions. Another example is that the ensemble spread of atmospheric states was more influenced by uncertain soil and vegetation parameters under conditions of low air pressure gradients (in summer) than under conditions with larger air pressure gradients in winter. The analysis of the ensemble of fully coupled model simulations provided valuable insights in the dynamics of land-atmosphere feedbacks which we will further highlight in the presentation. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/869941','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/869941">Optical method and apparatus for detection of surface and near-subsurface defects in dense ceramics</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> Ellingson, William A.; Brada, Mark P. 1995-01-01 A laser is used in a non-destructive manner to detect surface and near-subsurface defects in dense ceramics and particularly in ceramic bodies with complex shapes such as ceramic bearings, turbine blades, races, and the like. The laser's wavelength is selected based upon the composition of the ceramic sample and the laser can be directed on the sample while the sample is static or in dynamic rotate or translate motion. Light is scattered off surface and subsurface defects using a preselected polarization. The change in polarization angle is used to select the depth and characteristics of surface/subsurface defects. The scattered light is detected by an optical train consisting of a charge coupled device (CCD), or vidicon, television camera which, in turn, is coupled to a video monitor and a computer for digitizing the image. An analyzing polarizer in the optical train allows scattered light at a given polarization angle to be observed for enhancing sensitivity to either surface or near-subsurface defects. Application of digital image processing allows subtraction of digitized images in near real-time providing enhanced sensitivity to subsurface defects. Storing known "feature masks" of identified defects in the computer and comparing the detected scatter pattern (Fourier images) with the stored feature masks allows for automatic classification of detected defects. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B51I1934G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B51I1934G">Multi `omics reveals role of phenotypic plasticity in governing biogeochemical hotspots within the groundwater-surface water (hyporheic) mixing zone</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Graham, E.; Tfaily, M. M.; Crump, A.; Arntzen, E.; Romero, E. B.; Goldman, A. E.; Resch, T.; Kennedy, D.; Nelson, W. C.; Stegen, J. 2017-12-01 Subsurface groundwater-surface water mixing zones (hyporheic zones) contain spatially heterogeneous hotspots of enhanced biogeochemical activity that contribute disproportionately to river corridor function. We have a poor understanding of the processes governing hotspots, but recent advances have enabled greater mechanistic understanding. We employ a suite of ultra-high resolution measurements to investigate the mechanisms underlying biogeochemical cycles in hyporheic zone hotspots. We use Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), metagenomic shotgun sequencing, and mass spectrometry of metaproteomes to characterize metabolite structure and metabolic transformations, microbiome structure and functional potential, and expressed microbiome functions in hyporheic sediments from the Columbia River in central Washington State. Surprisingly, microbiome structure and function in biogeochemical hotspots were indistinguishable from low-activity sediments. Metabolites were uncorrelated to protein expression but strongly related to aerobic respiration. Hotspot metabolites were distinguished by high molecular weight compounds and protein-, lignin-, and lipid-like molecules. Although the most common metabolic transformations were similar between hotspots and low-activity samples, hotspots contained a greater proportion of rare pathways, which in turn were correlated to metabolism. Our results contradicted our expectations that hotspots would be characterized by a unique microbiome with distinct physiology. Instead, our results indicate that microbial phenotypic plasticity underlies elevated hyporheic zone function, whereby the activity of rare pathways is stimulated by substrate availability. We therefore hypothesize that microbiome plasticity couples meso- (e.g., local root distribution) and macro-scale (e.g., landscape vegetation) resource heterogeneity to ecosystem-scale function. This indicates a need to mechanistically understand and </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/87733','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/biblio/87733">Optical method and apparatus for detection of surface and near-subsurface defects in dense ceramics</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> Ellingson, W.A.; Brada, M.P. 1995-06-20 A laser is used in a non-destructive manner to detect surface and near-subsurface defects in dense ceramics and particularly in ceramic bodies with complex shapes such as ceramic bearings, turbine blades, races, and the like. The laser`s wavelength is selected based upon the composition of the ceramic sample and the laser can be directed on the sample while the sample is static or in dynamic rotate or translate motion. Light is scattered off surface and subsurface defects using a preselected polarization. The change in polarization angle is used to select the depth and characteristics of surface/subsurface defects. The scattered light is detected by an optical train consisting of a charge coupled device (CCD), or vidicon, television camera which, in turn, is coupled to a video monitor and a computer for digitizing the image. An analyzing polarizer in the optical train allows scattered light at a given polarization angle to be observed for enhancing sensitivity to either surface or near-subsurface defects. Application of digital image processing allows subtraction of digitized images in near real-time providing enhanced sensitivity to subsurface defects. Storing known ``feature masks`` of identified defects in the computer and comparing the detected scatter pattern (Fourier images) with the stored feature masks allows for automatic classification of detected defects. 29 figs. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012OcMod..51...19G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012OcMod..51...19G">An Isopycnal Box Model with predictive deep-ocean structure for biogeochemical cycling applications</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Goodwin, Philip 2012-07-01 To simulate global ocean biogeochemical tracer budgets a model must accurately determine both the volume and surface origins of each water-mass. Water-mass volumes are dynamically linked to the ocean circulation in General Circulation Models, but at the cost of high computational load. In computationally efficient Box Models the water-mass volumes are simply prescribed and do not vary when the circulation transport rates or water mass densities are perturbed. A new computationally efficient Isopycnal Box Model is presented in which the sub-surface box volumes are internally calculated from the prescribed circulation using a diffusive conceptual model of the thermocline, in which upwelling of cold dense water is balanced by a downward diffusion of heat. The volumes of the sub-surface boxes are set so that the density stratification satisfies an assumed link between diapycnal diffusivity, κd, and buoyancy frequency, N: κd = c/(Nα), where c and α are user prescribed parameters. In contrast to conventional Box Models, the volumes of the sub-surface ocean boxes in the Isopycnal Box Model are dynamically linked to circulation, and automatically respond to circulation perturbations. This dynamical link allows an important facet of ocean biogeochemical cycling to be simulated in a highly computationally efficient model framework. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H53G1550L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H53G1550L">Linking Surface Topography Variations To Subsurface Mixing And Reaction Patterns</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Le Borgne, T.; Bandopadhyay, A.; Davy, P. 2017-12-01 Fluctuations in surface topography generate nested streamline patterns in the subsurface over scales ranging from millimeters to kilometers. Because solute residence times can be very different for each streamlines, these patterns exert a strong control on biogeochemical reactions. While this effect has been quantified in reactive transport models, solute transfer across streamlines has been generally neglected. Yet, this process can lead to significant solute dilution and may trigger reactions by mixing water with different chemical compositions. Considering topography-driven subsurface flow cells of different sizes, we show that the resulting streamline structures act as shear flows, with shear rates that can vary over orders of magnitude depending on scale, permeability and hydraulic head gradient. This leads to the formation of localized layers of enhanced dilution and reaction, where mixing rates can be orders of magnitude larger than diffusion limited rates (Bandopadhyay et al. under review). We develop a theoretical model that predicts the depth and magnitude of these mixing hotspots and quantifies the resulting exports of conservative and reactive chemical species at discharge locations. We discuss consequences of these findings by applying this model at hyporheic zone, hillslope, and catchment scales. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li class="active">2</li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_3" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active">3</li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="41"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1337208-influence-hydrological-biogeochemical-temperature-transients-subsurface-carbon-fluxes-flood-plain-environment','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1337208-influence-hydrological-biogeochemical-temperature-transients-subsurface-carbon-fluxes-flood-plain-environment">Influence of hydrological, biogeochemical and temperature transients on subsurface carbon fluxes in a flood plain environment</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Arora, Bhavna; Spycher, Nicolas F.; Steefel, Carl I. 2016-02-01 Flood plains play a potentially important role in the global carbon cycle. The accumulation of organic matter in flood plains often induces the formation of chemically reduced groundwater and sediments along riverbanks. In this study, our objective is to evaluate the cumulative impact of such reduced zones, water table fluctuations, and temperature gradients on subsurface carbon fluxes in a flood plain at Rifle, Colorado located along the Colorado River. 2-D coupled variably-saturated, non-isothermal flow and biogeochemical reactive transport modeling was applied to improve our understanding of the abiotic and microbially mediated reactions controlling carbon dynamics at the Rifle site. Modelmore » simulations considering only abiotic reactions (thus ignoring microbial reactions) underestimated CO2 partial pressures observed in the unsaturated zone and severely underestimated inorganic (and overestimated organic) carbon fluxes to the river compared to simulations with biotic pathways. Both model simulations and field observations highlighted the need to include microbial contributions from chemolithoautotrophic processes (e.g., Fe?2 and S-2 oxidation) to match locally-observed high CO2 concentrations above reduced zones. Observed seasonal variations in CO2 concentrations in the unsaturated zone could not be reproduced without incorporating temperature gradients in the simulations. Incorporating temperature fluctuations resulted in an increase in the annual groundwater carbon fluxes to the river by 170 % to 3.3 g m-2 d-1, while including water table variations resulted in an overall decrease in the simulated fluxes. We conclude that spatial microbial and redox zonation as well as temporal fluctuations of temperature and water table depth contribute significantly to subsurface carbon fluxes in flood plains and need to be represented appropriately in model simulations.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMOS32A..07K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMOS32A..07K">Molecular biogeochemical provinces in the Atlantic Surface Ocean</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Koch, B. P.; Flerus, R.; Schmitt-Kopplin, P.; Lechtenfeld, O. J.; Bracher, A.; Cooper, W.; Frka, S.; Gašparović, B.; Gonsior, M.; Hertkorn, N.; Jaffe, R.; Jenkins, A.; Kuss, J.; Lara, R. J.; Lucio, M.; McCallister, S. L.; Neogi, S. B.; Pohl, C.; Roettgers, R.; Rohardt, G.; Schmitt, B. B.; Stuart, A.; Theis, A.; Ying, W.; Witt, M.; Xie, Z.; Yamashita, Y.; Zhang, L.; Zhu, Z. Y.; Kattner, G. 2010-12-01 One of the most important aspects to understand marine organic carbon fluxes is to resolve the molecular mechanisms which convert fresh, labile biomolecules into semi-labile and refractory dissolved and particulate organic compounds in the ocean. In this interdisciplinary project, which was performed on a cruise with RV Polarstern, we carried out a detailed molecular characterisation of dissolved organic matter (DOM) on a North-South transect in the Atlantic surface ocean in order to relate the data to different biological, climatic, oceanographic, and meteorological regimes as well as to terrestrial input from riverine and atmospheric sources. Our goal was to achieve a high resolution data set for the biogeochemical characterisation of the sources and reactivity of DOM. We applied ultrahigh resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS), nutrient, trace element, amino acid, and lipid analyses and other biogeochemical measurements for 220 samples from the upper water column (0-200m) and eight deep profiles. Various spectroscopic techniques were applied continuously in a constant sample water flow supplied by a fish system and the moon pool. Radiocarbon dating enabled assessing DOC residence time. Bacterial abundance and production provided a metabolic context for the DOM characterization work and pCO2 concentrations. Combining molecular organic techniques and inductively coupled plasma mass spectrometry (ICP-MS) established an important link between organic and inorganic biogeochemical studies. Multivariate statistics, primarily based on FT-ICR-MS data for 220 samples, allowed identifying geographical clusters which matched ecological provinces proposed previously by Longhurst (2007). Our study demonstrated that marine DOM carries molecular information reflecting the “history” of ocean water masses. This information can be used to define molecular biogeochemical provinces and to improve our understanding of element fluxes in </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=216548&keyword=Two+AND+photon&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=216548&keyword=Two+AND+photon&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">Understanding Biogeochemical Transformations Of Trace Elements In Multi Metal-Rich Geomaterials Under Stimulated Redox Conditions</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Natural and anthropogenic influences on hydrological conditions can induce periodic or long-term reduced conditions in geologic materials. Such conditions can cause significant impacts on biogeochemical processes of trace elements in subsurface or near surface environments. The... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1095019','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1095019">Final Technical Report: Viral Infection of Subsurface Microorganisms and Metal/Radionuclide Transport</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Weber, Karrie A.; Bender, Kelly S.; Li, Yusong Microbially mediated metabolisms have been identified as a significant factor either directly or indirectly impacting the fate and transport of heavy metal/radionuclide contaminants. To date microorganisms have been isolated from contaminated environments. Examination of annotated finished genome sequences of many of these subsurface isolates from DOE sites, revealed evidence of prior viral infection. To date the role that viruses play influencing microbial mortality and the resulting community structure which directly influences biogeochemical cycling in soils and sedimentary environments remains poorly understood. The objective of this exploratory study was to investigate the role of viral infection of subsurface bacteria and themore » formation of contaminant-bearing viral particles. This objective was approached by examining the following working hypotheses: (i) subsurface microorganisms are susceptible to viral infections by the indigenous subsurface viral community, and (ii) viral surfaces will adsorb heavy metals and radionuclides. Our results have addressed basic research needed to accomplish the BER Long Term Measure to provide sufficient scientific understanding such that DOE sites would be able to incorporate coupled physical, chemical and biological processes into decision making for environmental remediation or natural attenuation and long-term stewardship by establishing viral-microbial relationships on the subsequent fate and transport of heavy metals and radionuclides. Here we demonstrated that viruses play a significant role in microbial mortality and community structure in terrestrial subsurface sedimentary systems. The production of viral-like particles within subsurface sediments in response to biostimulation with dissolved organic carbon and a terminal electron acceptor resulted in the production of viral-like particles. Organic carbon alone did not result in significant viral production and required the addition of a terminal electron </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1439194-influence-hydrological-biogeochemical-temperature-transients-subsurface-carbon-fluxes-flood-plain-environment','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1439194-influence-hydrological-biogeochemical-temperature-transients-subsurface-carbon-fluxes-flood-plain-environment">Influence of hydrological, biogeochemical and temperature transients on subsurface carbon fluxes in a flood plain environment</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Arora, Bhavna; Spycher, Nicolas F.; Steefel, Carl I.; ... 2016-02-12 Flood plains play a potentially important role in the global carbon cycle. The accumulation of organic matter in flood plains often induces the formation of chemically reduced groundwater and sediments along riverbanks. In this study, our objective is to evaluate the cumulative impact of such reduced zones, water table fluctuations, and temperature gradients on subsurface carbon fluxes in a flood plain at Rifle, Colorado located along the Colorado River. 2-D coupled variably-saturated, non-isothermal flow and biogeochemical reactive transport modeling was applied to improve our understanding of the abiotic and microbially mediated reactions controlling carbon dynamics at the Rifle site. Modelmore » simulations considering only abiotic reactions (thus ignoring microbial reactions) underestimated CO 2 partial pressures observed in the unsaturated zone and severely underestimated inorganic (and overestimated organic) carbon fluxes to the river compared to simulations with biotic pathways. Both model simulations and field observations highlighted the need to include microbial contributions from chemolithoautotrophic processes (e.g., Fe +2 and S -2 oxidation) to match locally-observed high CO 2 concentrations above reduced zones. Observed seasonal variations in CO 2 concentrations in the unsaturated zone could not be reproduced without incorporating temperature gradients in the simulations. Incorporating temperature fluctuations resulted in an increase in the annual groundwater carbon fluxes to the river by 170 % to 3.3 g m -2 d -1, while including water table variations resulted in an overall decrease in the simulated fluxes. We thus conclude that spatial microbial and redox zonation as well as temporal fluctuations of temperature and water table depth contribute significantly to subsurface carbon fluxes in flood plains and need to be represented appropriately in model simulations.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B11J0567A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B11J0567A">2500 high-quality genomes reveal that the biogeochemical cycles of C, N, S and H are cross-linked by metabolic handoffs in the terrestrial subsurface</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Anantharaman, K.; Brown, C. T.; Hug, L. A.; Sharon, I.; Castelle, C. J.; Shelton, A.; Bonet, B.; Probst, A. J.; Thomas, B. C.; Singh, A.; Wilkins, M.; Williams, K. H.; Tringe, S. G.; Beller, H. R.; Brodie, E.; Hubbard, S. S.; Banfield, J. F. 2015-12-01 Microorganisms drive the transformations of carbon compounds in the terrestrial subsurface, a key reservoir of carbon on earth, and impact other linked biogeochemical cycles. Our current knowledge of the microbial ecology in this environment is primarily based on 16S rRNA gene sequences that paint a biased picture of microbial community composition and provide no reliable information on microbial metabolism. Consequently, little is known about the identity and metabolic roles of the uncultivated microbial majority in the subsurface. In turn, this lack of understanding of the microbial processes that impact the turnover of carbon in the subsurface has restricted the scope and ability of biogeochemical models to capture key aspects of the carbon cycle. In this study, we used a culture-independent, genome-resolved metagenomic approach to decipher the metabolic capabilities of microorganisms in an aquifer adjacent to the Colorado River, near Rifle, CO, USA. We sequenced groundwater and sediment samples collected across fifteen different geochemical regimes. Sequence assembly, binning and manual curation resulted in the recovery of 2,542 high-quality genomes, 27 of which are complete. These genomes represent 1,300 non-redundant organisms comprising both abundant and rare community members. Phylogenetic analyses involving ribosomal proteins and 16S rRNA genes revealed the presence of up to 34 new phyla that were hitherto unknown. Less than 11% of all genomes belonged to the 4 most commonly represented phyla that constitute 93% of all currently available genomes. Genome-specific analyses of metabolic potential revealed the co-occurrence of important functional traits such as carbon fixation, nitrogen fixation and use of electron donors and electron acceptors. Finally, we predict that multiple organisms are often required to complete redox pathways through a complex network of metabolic handoffs that extensively cross-link subsurface biogeochemical cycles. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1014919','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/1014919">Insulated conductor temperature limited heater for subsurface heating coupled in a three-phase WYE configuration</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> Vinegar, Harold J.; Sandberg, Chester Ledlie 2010-11-09 A heating system for a subsurface formation is described. The heating system includes a first heater, a second heater, and a third heater placed in an opening in the subsurface formation. Each heater includes: an electrical conductor; an insulation layer at least partially surrounding the electrical conductor; and an electrically conductive sheath at least partially surrounding the insulation layer. The electrical conductor is electrically coupled to the sheath at a lower end portion of the heater. The lower end portion is the portion of the heater distal from a surface of the opening. The first heater, the second heater, and the third heater are electrically coupled at the lower end portions of the heaters. The first heater, the second heater, and the third heater are configured to be electrically coupled in a three-phase wye configuration. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.3956R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.3956R">Technical geothermal potential of urban subsurface influenced by land surface effects</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rivera, Jaime A.; Blum, Philipp; Bayer, Peter 2016-04-01 Changes in land use are probably one of the most notorious anthropogenic perturbations in urban environments. They significantly change the coupled thermal regime at the ground surface leading in most cases to increased ground surface temperatures (GST). The associated elevated vertical heat fluxes act at different scales and can influence the thermal conditions in several tens of meters in the subsurface. Urban subsurface thus often stores a higher amount of heat than less affected rural surroundings. The stored heat is regarded as a potential source of low-enthalpy geothermal energy to supply the heating energy demands in urban areas. In this work, we explore the technical geothermal potential of urban subsurface via ground coupled heat pumps with borehole heat exchangers (BHE). This is tackled by semi-analytical line-source equations. The commonly used response factors or g-functions are modified to include transient land surface effects. By including this additional source of heat, the new formulation allows to analyse the effect of pre-existing urban warming as well as different exploitation schemes fulfilling standard renewable and sustainable criteria. In our generalized reference scenario, it is demonstrated that energy gains for a single BHE may be up to 40 % when compared to non-urbanized conditions. For a scenario including the interaction of multiple BHEs, results indicate that it would be possible to supply between 6 % and 27 % of the heating demands in Central European urban settlements in a renewable way. The methodology is also applied to a study case of the city of Zurich, Switzerland, where the detailed evolution of land use is available. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.9289F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.9289F">Subsurface flow pathway dynamics in the active layer of coupled permafrost-hydrogeological systems under seasonal and annual temperature variability.</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Frampton, Andrew 2017-04-01 There is a need for improved understanding of the mechanisms controlling subsurface solute transport in the active layer in order to better understand permafrost-hydrological-carbon feedbacks, in particular with regards to how dissolved carbon is transported in coupled surface and subsurface terrestrial arctic water systems under climate change. Studying solute transport in arctic systems is also relevant in the context of anthropogenic pollution which may increase due to increased activity in cold region environments. In this contribution subsurface solute transport subject to ground surface warming causing permafrost thaw and active layer change is studied using a physically based model of coupled cryotic and hydrogeological flow processes combined with a particle tracking method. Changes in subsurface water flows and solute transport travel times are analysed for different modelled geological configurations during a 100-year warming period. Results show that for all simulated cases, the minimum and mean travel times increase non-linearly with warming irrespective of geological configuration and heterogeneity structure. The timing of the start of increase in travel time depends on heterogeneity structure, combined with the rate of permafrost degradation that also depends on material thermal and hydrogeological properties. These travel time changes are shown to depend on combined warming effects of increase in pathway length due to deepening of the active layer, reduced transport velocities due to a shift from horizontal saturated groundwater flow near the surface to vertical water percolation deeper into the subsurface, and pathway length increase and temporary immobilization caused by cryosuction-induced seasonal freeze cycles. The impact these change mechanisms have on solute and dissolved substance transport is further analysed by integrating pathway analysis with a Lagrangian approach, incorporating considerations for both dissolved organic and inorganic </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018MMTA..tmp.1484S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018MMTA..tmp.1484S">Defining the Post-Machined Sub-surface in Austenitic Stainless Steels</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Srinivasan, N.; Sunil Kumar, B.; Kain, V.; Birbilis, N.; Joshi, S. S.; Sivaprasad, P. V.; Chai, G.; Durgaprasad, A.; Bhattacharya, S.; Samajdar, I. 2018-04-01 Austenitic stainless steels grades, with differences in chemistry, stacking fault energy, and thermal conductivity, were subjected to vertical milling. Anodic potentiodynamic polarization was able to differentiate (with machining speed/strain rate) between different post-machined sub-surfaces in SS 316L and Alloy A (a Cu containing austenitic stainless steel: Sanicroe 28™), but not in SS 304L. However, such differences (in the post-machined sub-surfaces) were revealed in surface roughness, sub-surface residual stresses and misorientations, and in the relative presence of sub-surface Cr2O3 films. It was shown, quantitatively, that higher machining speed reduced surface roughness and also reduced the effective depths of the affected sub-surface layers. A qualitative explanation on the sub-surface microstructural developments was provided based on the temperature-dependent thermal conductivity values. The results herein represent a mechanistic understanding to rationalize the corrosion performance of widely adopted engineering alloys. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018MMTA...49.2281S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018MMTA...49.2281S">Defining the Post-Machined Sub-surface in Austenitic Stainless Steels</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Srinivasan, N.; Sunil Kumar, B.; Kain, V.; Birbilis, N.; Joshi, S. S.; Sivaprasad, P. V.; Chai, G.; Durgaprasad, A.; Bhattacharya, S.; Samajdar, I. 2018-06-01 Austenitic stainless steels grades, with differences in chemistry, stacking fault energy, and thermal conductivity, were subjected to vertical milling. Anodic potentiodynamic polarization was able to differentiate (with machining speed/strain rate) between different post-machined sub-surfaces in SS 316L and Alloy A (a Cu containing austenitic stainless steel: Sanicroe 28™), but not in SS 304L. However, such differences (in the post-machined sub-surfaces) were revealed in surface roughness, sub-surface residual stresses and misorientations, and in the relative presence of sub-surface Cr2O3 films. It was shown, quantitatively, that higher machining speed reduced surface roughness and also reduced the effective depths of the affected sub-surface layers. A qualitative explanation on the sub-surface microstructural developments was provided based on the temperature-dependent thermal conductivity values. The results herein represent a mechanistic understanding to rationalize the corrosion performance of widely adopted engineering alloys. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120007602','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120007602">Estimation of subsurface thermal structure using sea surface height and sea surface temperature</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Kang, Yong Q. (Inventor); Jo, Young-Heon (Inventor); Yan, Xiao-Hai (Inventor) 2012-01-01 A method of determining a subsurface temperature in a body of water is disclosed. The method includes obtaining surface temperature anomaly data and surface height anomaly data of the body of water for a region of interest, and also obtaining subsurface temperature anomaly data for the region of interest at a plurality of depths. The method further includes regressing the obtained surface temperature anomaly data and surface height anomaly data for the region of interest with the obtained subsurface temperature anomaly data for the plurality of depths to generate regression coefficients, estimating a subsurface temperature at one or more other depths for the region of interest based on the generated regression coefficients and outputting the estimated subsurface temperature at the one or more other depths. Using the estimated subsurface temperature, signal propagation times and trajectories of marine life in the body of water are determined. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70015494','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70015494">Subsurface temperatures and surface heat flow in the Michigan Basin and their relationships to regional subsurface fluid movement</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Vugrinovich, R. 1989-01-01 Linear regression of 405 bottomhole temperature (BHT) measurements vs. associated depths from Michigan's Lower Peninsula results in the following equation relating BHT and depth: BHT(??C) = 14.5 + 0.0192 ?? depth(m) Temperature residuals, defined as (BHT measured)-(BHT calculated), were determined for each of the 405 BHT's. Areas of positive temperature residuals correspond to areas of regional groundwater discharge (determined from maps of equipotential surface) while areas of negative temperature residuals correspond to areas of regional groundwater recharge. These relationships are observed in the principal aquifers in rocks of Devonian and Ordovician age and in a portion of the principal aquifer in rocks of Silurian age. There is a similar correspondence between high surface heat flow (determined using the silica geothermometer) and regional groundwater discharge areas and low surface heat flow and regional groundwater recharge areas. Post-Jurassic depositional and tectonic histories suggest that the observed coupling of subsurface temperature and groundwater flow systems may have persisted since Jurassic time. Thus the higher subsurface palaeotemperatures (and palaeogeothermal gradients) indicated by recent studies most likely pre-date the Jurassic. ?? 1989. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.B24C..06N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.B24C..06N">Development of Advanced Eco-hydrologic and Biogeochemical Coupling Model to Constrain Missing Role of Inland Waters on Boundless Biogeochemical Cycle</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Nakayama, T.; Maksyutov, S. S. 2016-12-01 Inland waters including rivers, lakes, and groundwater are suggested to act as a transport pathway for water and dissolved substances, and play some role in continental biogeochemical cycling (Cole et al., 2007; Battin et al., 2009). The authors have developed process-based National Integrated Catchment-based Eco-hydrology (NICE) model (Nakayama, 2014, 2015, etc.), which includes feedback between hydrologic-geomorphic-ecological processes. In this study, NICE was further developed to couple with various biogeochemical cycle models in biosphere, those for water quality in aquatic ecosystems, and those for carbon weathering, etc. (NICE-BGC) (Nakayama, accepted). The new model incorporates connectivity of the biogeochemical cycle accompanied by hydrologic cycle between surface water and groundwater, hillslopes and river networks, and other intermediate regions. The model also includes reaction between inorganic and organic carbons, and its relation to nitrogen and phosphorus in terrestrial-aquatic continuum. The model results of CO2 evasion to the atmosphere, sediment storage, and carbon transport to the ocean (DOC, POC, and DIC flux) were reasonably in good agreement with previous compiled data. The model also showed carbon budget in major river basins and in each continent in global scale. In order to decrease uncertainty about carbon cycle, it became clear the previous empirical estimation by compiled data should be extended to this process-oriented model and higher resolution data to further clarify mechanistic interplay between inorganic and organic carbon and its relationship to nitrogen and phosphorus in terrestrial-aquatic linkages. NICE-BGC would play important role to re-evaluate greenhouse gas budget of the biosphere, and to bridge gap between top-down and bottom-up approaches (Battin et al., 2009; Regnier et al., 2013). </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1653b0091Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1653b0091Q">Surface and subsurface cracks characteristics of single crystal SiC wafer in surface machining</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Qiusheng, Y.; Senkai, C.; Jisheng, P. 2015-03-01 Different machining processes were used in the single crystal SiC wafer machining. SEM was used to observe the surface morphology and a cross-sectional cleavages microscopy method was used for subsurface cracks detection. Surface and subsurface cracks characteristics of single crystal SiC wafer in abrasive machining were analysed. The results show that the surface and subsurface cracks system of single crystal SiC wafer in abrasive machining including radial crack, lateral crack and the median crack. In lapping process, material removal is dominated by brittle removal. Lots of chipping pits were found on the lapping surface. With the particle size becomes smaller, the surface roughness and subsurface crack depth decreases. When the particle size was changed to 1.5µm, the surface roughness Ra was reduced to 24.0nm and the maximum subsurface crack was 1.2µm. The efficiency of grinding is higher than lapping. Plastic removal can be achieved by changing the process parameters. Material removal was mostly in brittle fracture when grinding with 325# diamond wheel. Plow scratches and chipping pits were found on the ground surface. The surface roughness Ra was 17.7nm and maximum subsurface crack depth was 5.8 µm. When grinding with 8000# diamond wheel, the material removal was in plastic flow. Plastic scratches were found on the surface. A smooth surface of roughness Ra 2.5nm without any subsurface cracks was obtained. Atomic scale removal was possible in cluster magnetorheological finishing with diamond abrasive size of 0.5 µm. A super smooth surface eventually obtained with a roughness of Ra 0.4nm without any subsurface crack. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017DPS....4920301P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017DPS....4920301P">Surface Modification and Surface - Subsurface Exchange Processes on Europa</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Phillips, Cynthia B.; Molaro, Jamie; Hand, Kevin P. 2017-10-01 The surface of Jupiter’s moon Europa is modified by exogenic processes such as sputtering, gardening, radiolysis, sulfur ion implantation, and thermal processing, as well as endogenic processes including tidal shaking, mass wasting, and the effects of subsurface tectonic and perhaps cryovolcanic activity. New materials are created or deposited on the surface (radiolysis, micrometeorite impacts, sulfur ion implantation, cryovolcanic plume deposits), modified in place (thermal segregation, sintering), transported either vertically or horizontally (sputtering, gardening, mass wasting, tectonic and cryovolcanic activity), or lost from Europa completely (sputtering, plumes, larger impacts). Some of these processes vary spatially, as visible in Europa’s leading-trailing hemisphere brightness asymmetry.Endogenic geologic processes also vary spatially, depending on terrain type. The surface can be classified into general landform categories that include tectonic features (ridges, bands, cracks); disrupted “chaos-type” terrain (chaos blocks, matrix, domes, pits, spots); and impact craters (simple, complex, multi-ring). The spatial distribution of these terrain types is relatively random, with some differences in apex-antiapex cratering rates and latitudinal variation in chaos vs. tectonic features.In this work, we extrapolate surface processes and rates from the top meter of the surface in conjunction with global estimates of transport and resurfacing rates. We combine near-surface modification with an estimate of surface-subsurface (and vice versa) transport rates for various geologic terrains based on an average of proposed formation mechanisms, and a spatial distribution of each landform type over Europa’s surface area.Understanding the rates and mass balance for each of these processes, as well as their spatial and temporal variability, allows us to estimate surface - subsurface exchange rates over the average surface age (~50myr) of Europa. Quantifying the </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P52B..08P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P52B..08P">Surface Modification and Surface - Subsurface Exchange Processes on Europa</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Phillips, C. B.; Molaro, J.; Hand, K. P. 2017-12-01 The surface of Jupiter's moon Europa is modified by exogenic processes such as sputtering, gardening, radiolysis, sulfur ion implantation, and thermal processing, as well as endogenic processes including tidal shaking, mass wasting, and the effects of subsurface tectonic and perhaps cryovolcanic activity. New materials are created or deposited on the surface (radiolysis, micrometeorite impacts, sulfur ion implantation, cryovolcanic plume deposits), modified in place (thermal segregation, sintering), transported either vertically or horizontally (sputtering, gardening, mass wasting, tectonic and cryovolcanic activity), or lost from Europa completely (sputtering, plumes, larger impacts). Some of these processes vary spatially, as visible in Europa's leading-trailing hemisphere brightness asymmetry. Endogenic geologic processes also vary spatially, depending on terrain type. The surface can be classified into general landform categories that include tectonic features (ridges, bands, cracks); disrupted "chaos-type" terrain (chaos blocks, matrix, domes, pits, spots); and impact craters (simple, complex, multi-ring). The spatial distribution of these terrain types is relatively random, with some differences in apex-antiapex cratering rates and latitudinal variation in chaos vs. tectonic features. In this work, we extrapolate surface processes and rates from the top meter of the surface in conjunction with global estimates of transport and resurfacing rates. We combine near-surface modification with an estimate of surface-subsurface (and vice versa) transport rates for various geologic terrains based on an average of proposed formation mechanisms, and a spatial distribution of each landform type over Europa's surface area. Understanding the rates and mass balance for each of these processes, as well as their spatial and temporal variability, allows us to estimate surface - subsurface exchange rates over the average surface age ( 50myr) of Europa. Quantifying the timescale </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AdWR..116....1M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AdWR..116....1M">Modelling coupled microbial processes in the subsurface: Model development, verification, evaluation and application</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Masum, Shakil A.; Thomas, Hywel R. 2018-06-01 To study subsurface microbial processes, a coupled model which has been developed within a Thermal-Hydraulic-Chemical-Mechanical (THCM) framework is presented. The work presented here, focuses on microbial transport, growth and decay mechanisms under the influence of multiphase flow and bio-geochemical reactions. In this paper, theoretical formulations and numerical implementations of the microbial model are presented. The model has been verified and also evaluated against relevant experimental results. Simulated results show that the microbial processes have been accurately implemented and their impacts on porous media properties can be predicted either qualitatively or quantitatively or both. The model has been applied to investigate biofilm growth in a sandstone core that is subjected to a two-phase flow and variable pH conditions. The results indicate that biofilm growth (if not limited by substrates) in a multiphase system largely depends on the hydraulic properties of the medium. When the change in porewater pH which occurred due to dissolution of carbon dioxide gas is considered, growth processes are affected. For the given parameter regime, it has been shown that the net biofilm growth is favoured by higher pH; whilst the processes are considerably retarded at lower pH values. The capabilities of the model to predict microbial respiration in a fully coupled multiphase flow condition and microbial fermentation leading to production of a gas phase are also demonstrated. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JCHyd.203....9S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JCHyd.203....9S">Volume reduction outweighs biogeochemical processes in controlling phosphorus treatment in aged detention systems</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shukla, Asmita; Shukla, Sanjay; Annable, Michael D.; Hodges, Alan W. 2017-08-01 Stormwater detention areas (SDAs) play an important role in treating end-of-the-farm runoff in phosphorous (P) limited agroecosystems. Phosphorus transport from the SDAs, including those through subsurface pathways, are not well understood. The prevailing understanding of these systems assumes that biogeochemical processes play the primary treatment role and that subsurface losses can be neglected. Water and P fluxes from a SDA located in a row-crop farm were measured for two years (2009-2011) to assess the SDA's role in reducing downstream P loads. The SDA treated 55% (497 kg) and 95% (205 kg) of the incoming load during Year 1 (Y1, 09-10) and Year 2 (Y2, 10-11), respectively. These treatment efficiencies were similar to surface water volumetric retention (49% in Y1 and 84% in Y2) and varied primarily with rainfall. Similar water volume and P retentions indicate that volume retention is the main process controlling P loads. A limited role of biogeochemical processes was supported by low to no remaining soil P adsorption capacity due to long-term drainage P input. The fact that outflow P concentrations (Y1 = 368.3 μg L- 1, Y2 = 230.4 μg L- 1) could be approximated by using a simple mixing of rainfall and drainage P input further confirmed the near inert biogeochemical processes. Subsurface P losses through groundwater were 304 kg (27% of inflow P) indicating that they are an important source for downstream P. Including subsurface P losses reduces the treatment efficiency to 35% (from 61%). The aboveground biomass in the SDA contained 42% (240 kg) of the average incoming P load suggesting that biomass harvesting could be a cost-effective alternative for reviving the role of biogeochemical processes to enhance P treatment in aged, P-saturated SDAs. The 20-year present economic value of P removal through harvesting was estimated to be 341,000, which if covered through a cost share or a payment for P treatment services program could be a positive outcome for both </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApSS..404...82I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApSS..404...82I">Influence of Si wafer thinning processes on (sub)surface defects</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Inoue, Fumihiro; Jourdain, Anne; Peng, Lan; Phommahaxay, Alain; De Vos, Joeri; Rebibis, Kenneth June; Miller, Andy; Sleeckx, Erik; Beyne, Eric; Uedono, Akira 2017-05-01 Wafer-to-wafer three-dimensional (3D) integration with minimal Si thickness can produce interacting multiple devices with significantly scaled vertical interconnections. Realizing such a thin 3D structure, however, depends critically on the surface and subsurface of the remaining backside Si after the thinning processes. The Si (sub)surface after mechanical grinding has already been characterized fruitfully for a range of few dozen of μm. Here, we expand the characterization of Si (sub)surface to 5 μm thickness after thinning process on dielectric bonded wafers. The subsurface defects and damage layer were investigated after grinding, chemical mechanical polishing (CMP), wet etching and plasma dry etching. The (sub)surface defects were characterized using transmission microscopy, atomic force microscopy, and positron annihilation spectroscopy. Although grinding provides the fastest removal rate of Si, the surface roughness was not compatible with subsequent processing. Furthermore, mechanical damage such as dislocations and amorphous Si cannot be reduced regardless of Si thickness and thin wafer handling systems. The CMP after grinding showed excellent performance to remove this grinding damage, even though the removal amount is 1 μm. For the case of Si thinning towards 5 μm using grinding and CMP, the (sub)surface is atomic scale of roughness without vacancy. For the case of grinding + dry etch, vacancy defects were detected in subsurface around 0.5-2 μm. The finished surface after wet etch remains in the nm scale in the strain region. By inserting a CMP step in between grinding and dry etch it is possible to significantly reduce not only the roughness, but also the remaining vacancies at the subsurface. The surface of grinding + CMP + dry etching gives an equivalent mono vacancy result as to that of grinding + CMP. This combination of thinning processes allows development of extremely thin 3D integration devices with minimal roughness and vacancy surface. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active">3</li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_4" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active">4</li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="61"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24216435','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24216435">Nutrient loss in leachate and surface runoff from surface-broadcast and subsurface-banded broiler litter.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Lamba, Jasmeet; Srivastava, Puneet; Way, Thomas R; Sen, Sumit; Wood, C Wesley; Yoo, Kyung H 2013-09-01 Subsurface band application of poultry litter has been shown to reduce the transport of nutrients from fields in surface runoff compared with conventional surface broadcast application. Little research has been conducted to determine the effects of surface broadcast application and subsurface banding of litter on nutrients in leachate. Therefore, a field experiment was conducted to determine the effects of subsurface band application and surface broadcast application of poultry litter on nutrient losses in leachate. Zero-tension pan and passive capillary fiberglass wick lysimeters were installed in situ 50 cm beneath the soil surface of an established tall fescue ( Schreb.) pasture on a sandy loam soil. The treatments were surface broadcast and subsurface-banded poultry litter at 5 Mg ha and an unfertilized control. Results of the rainfall simulations showed that the concentrations of PO-P and total phosphorus (TP) in leachate were reduced by 96 and 37%, respectively, in subsurface-banded litter treatment compared with the surface-applied litter treatment. There was no significant difference in PO-P concentration between control and subsurface-banded litter treatment in leachate. The trend in the loading of nutrients in leachate was similar to the trend in concentration. Concentration and loading of the nutrients (TP, PO-P, NH-N, and NO-N) in runoff from the subsurface-banded treatment were significantly less than for the surface-applied treatment and were similar to those from control plots. These results show that, compared with conventional surface broadcast application of litter, subsurface band application of litter can greatly reduce loss of P in surface runoff and leachate. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1210029-mesh-infrastructure-coupled-multiprocess-geophysical-simulations','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1210029-mesh-infrastructure-coupled-multiprocess-geophysical-simulations">Mesh infrastructure for coupled multiprocess geophysical simulations</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Garimella, Rao V.; Perkins, William A.; Buksas, Mike W.; ... 2014-01-01 We have developed a sophisticated mesh infrastructure capability to support large scale multiphysics simulations such as subsurface flow and reactive contaminant transport at storage sites as well as the analysis of the effects of a warming climate on the terrestrial arctic. These simulations involve a wide range of coupled processes including overland flow, subsurface flow, freezing and thawing of ice rich soil, accumulation, redistribution and melting of snow, biogeochemical processes involving plant matter and finally, microtopography evolution due to melting and degradation of ice wedges below the surface. In addition to supporting the usual topological and geometric queries about themore » mesh, the mesh infrastructure adds capabilities such as identifying columnar structures in the mesh, enabling deforming of the mesh subject to constraints and enabling the simultaneous use of meshes of different dimensionality for subsurface and surface processes. The generic mesh interface is capable of using three different open source mesh frameworks (MSTK, MOAB and STKmesh) under the hood allowing the developers to directly compare them and choose one that is best suited for the application's needs. We demonstrate the results of some simulations using these capabilities as well as present a comparison of the performance of the different mesh frameworks.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814172A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814172A">Benthic-Pelagic Coupling in Biogeochemical and Climate Models: Existing Approaches, Recent developments and Roadblocks</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Arndt, Sandra 2016-04-01 Marine sediments are key components in the Earth System. They host the largest carbon reservoir on Earth, provide the only long term sink for atmospheric CO2, recycle nutrients and represent the most important climate archive. Biogeochemical processes in marine sediments are thus essential for our understanding of the global biogeochemical cycles and climate. They are first and foremost, donor controlled and, thus, driven by the rain of particulate material from the euphotic zone and influenced by the overlying bottom water. Geochemical species may undergo several recycling loops (e.g. authigenic mineral precipitation/dissolution) before they are either buried or diffuse back to the water column. The tightly coupled and complex pelagic and benthic process interplay thus delays recycling flux, significantly modifies the depositional signal and controls the long-term removal of carbon from the ocean-atmosphere system. Despite the importance of this mutual interaction, coupled regional/global biogeochemical models and (paleo)climate models, which are designed to assess and quantify the transformations and fluxes of carbon and nutrients and evaluate their response to past and future perturbations of the climate system either completely neglect marine sediments or incorporate a highly simplified representation of benthic processes. On the other end of the spectrum, coupled, multi-component state-of-the-art early diagenetic models have been successfully developed and applied over the past decades to reproduce observations and quantify sediment-water exchange fluxes, but cannot easily be coupled to pelagic models. The primary constraint here is the high computation cost of simulating all of the essential redox and equilibrium reactions within marine sediments that control carbon burial and benthic recycling fluxes: a barrier that is easily exacerbated if a variety of benthic environments are to be spatially resolved. This presentation provides an integrative overview of </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H31F1576S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H31F1576S">Influences of Coupled Hydrologic and Microbial Processes on River Corridor Biogeochemistry and Ecology</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Scheibe, T. D.; Song, H. S.; Stegen, J.; Graham, E.; Bao, J.; Goldman, A.; Zhou, T.; Crump, A.; Hou, Z.; Hammond, G. E.; Chen, X.; Huang, M.; Zhang, X.; Nelson, W. C.; Garayburu-Caruso, V. A. 2017-12-01 The exchange of water between rivers and surrounding subsurface environments (hydrologic exchange flows or HEFs) is a vital aspect of river ecology and watershed function. HEFs play a key role in water quality, nutrient cycling, and ecosystem health, and they modulate water temperatures and enhance exchange of terrestrial and aquatic nutrients, which lead to elevated biogeochemical activity. However, these coupled hydrologic and microbiological processes are not well understood, particularly in the context of large managed river systems with highly variable discharge, and are poorly represented in system-scale quantitative models. Using the 75 km Hanford Reach of the Columbia River as the research domain, we apply high-resolution flow simulations supported by field observations to understand how variable river discharge interacts with hydromorphic and hydrogeologic structures to generate HEFs and distributions of subsurface residence times. We combine this understanding of hydrologic processes with microbiological activity measurements and reactive transport models to elucidate the holistic impacts of variable discharge on river corridor (surface and subsurface) ecosystems. In particular, our project seeks to develop and test new conceptual and numerical models that explicitly incorporate i) the character (chemical speciation and thermodynamics) of natural organic matter as it varies along flow paths and through mixing of groundwater and surface water, and ii) the history-dependent response of microbial communities to varying time scales of inundation associated with fluctuations in river discharge. The results of these high-resolution mechanistic models are guiding formulation and parameterization of reduced-order models applicable at reach to watershed scales. New understanding of coupled hydrology and microbiology in the river corridor will play a key role in reduction of uncertainties associated with major Earth system biogeochemical fluxes, improving </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H43U..04Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H43U..04Z">Lateral, vertical, and longitudinal connectivity of runoff source areas drive stream hydro-biogeochemical signals across a low relief drainage network</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zimmer, M. A.; McGlynn, B. L. 2017-12-01 Our understanding of the balance between longitudinal, lateral, and vertical expansion and contraction of reactive flowpaths and source areas in headwater catchments is limited. To address this, we utilized an ephemeral-to-perennial stream network in the Piedmont region of North Carolina, USA to gain new understanding about critical zone mechanisms that drive runoff generation and biogeochemical signals in both groundwater and stream water. Here, we used chemical and hydrometric data collected from zero through second order catchments to characterize spatial and temporal runoff and overland, shallow soil, and deep subsurface flow across characteristic landscape positions. Our results showed that the active stream network was driven by two superimposed runoff generation regimes that produced distinct hydro-biogeochemical signals at the catchment outlet. The baseflow runoff generation regime expanded and contracted the stream network seasonally through the rise and fall of the seasonal water table. Superimposed on this, event-activated source area contributions were driven by surficial and shallow subsurface flowpaths. The subsurface critical zone stratigraphy in this landscape coupled with the precipitation regime activated these shallow flowpaths frequently. This drove an increase in dissolved organic carbon (DOC) concentrations with increases in runoff across catchment scales. DOC-runoff relationship variability and spread was driven by the balance between runoff regimes as well as a seasonal depletion of DOC from shallow subsurface flowpath activation and annual replenishment from litterfall. From this, we suggest that the hydro-biogeochemical signals at larger catchment outlets can be driven by a balance of longitudinal, lateral, and vertical source area contributions, critical zone structure, and complex hydrological processes. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=286539','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=286539">Nutrient loss in leachate and surface runoff from surface-broadcast and subsurface-banded broiler litter</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> Subsurface band application of poultry litter has been shown to reduce the transport of nutrients from fields in surface runoff, compared to the conventional surface broadcast application. Little in situ research has been conducted to determine effects of surface broadcast application and subsurfac... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018OcMod.126...13Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018OcMod.126...13Y">Insights on multivariate updates of physical and biogeochemical ocean variables using an Ensemble Kalman Filter and an idealized model of upwelling</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yu, Liuqian; Fennel, Katja; Bertino, Laurent; Gharamti, Mohamad El; Thompson, Keith R. 2018-06-01 Effective data assimilation methods for incorporating observations into marine biogeochemical models are required to improve hindcasts, nowcasts and forecasts of the ocean's biogeochemical state. Recent assimilation efforts have shown that updating model physics alone can degrade biogeochemical fields while only updating biogeochemical variables may not improve a model's predictive skill when the physical fields are inaccurate. Here we systematically investigate whether multivariate updates of physical and biogeochemical model states are superior to only updating either physical or biogeochemical variables. We conducted a series of twin experiments in an idealized ocean channel that experiences wind-driven upwelling. The forecast model was forced with biased wind stress and perturbed biogeochemical model parameters compared to the model run representing the "truth". Taking advantage of the multivariate nature of the deterministic Ensemble Kalman Filter (DEnKF), we assimilated different combinations of synthetic physical (sea surface height, sea surface temperature and temperature profiles) and biogeochemical (surface chlorophyll and nitrate profiles) observations. We show that when biogeochemical and physical properties are highly correlated (e.g., thermocline and nutricline), multivariate updates of both are essential for improving model skill and can be accomplished by assimilating either physical (e.g., temperature profiles) or biogeochemical (e.g., nutrient profiles) observations. In our idealized domain, the improvement is largely due to a better representation of nutrient upwelling, which results in a more accurate nutrient input into the euphotic zone. In contrast, assimilating surface chlorophyll improves the model state only slightly, because surface chlorophyll contains little information about the vertical density structure. We also show that a degradation of the correlation between observed subsurface temperature and nutrient fields, which has been an </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.H41D0928A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.H41D0928A">Quantifying Linkages between Biogeochemical Processes in a Contaminated Aquifer-Wetland System Using Multivariate Statistics and HP1</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Arora, B.; Mohanty, B. P.; McGuire, J. T. 2009-12-01 Fate and transport of contaminants in saturated and unsaturated zones in the subsurface is controlled by complex biogeochemical processes such as precipitation, sorption-desorption, ion-exchange, redox, etc. In dynamic systems such as wetlands and anaerobic aquifers, these processes are coupled 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 biogeochemical 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 biogeochemical processes were obtained using principal component analysis (PCA). Furthermore, artificial neural networks (ANN) coupled with HP1 was used to develop mathematical rules identifying different combinations of factors that trigger, sustain, accelerate/decelerate, or discontinue the biogeochemical processes. Experimental observations show that infiltrating water triggers biogeochemical processes in all soil columns. Similarly, slow release of water </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28595989','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28595989">Volume reduction outweighs biogeochemical processes in controlling phosphorus treatment in aged detention systems.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Shukla, Asmita; Shukla, Sanjay; Annable, Michael D; Hodges, Alan W 2017-08-01 Stormwater detention areas (SDAs) play an important role in treating end-of-the-farm runoff in phosphorous (P) limited agroecosystems. Phosphorus transport from the SDAs, including those through subsurface pathways, are not well understood. The prevailing understanding of these systems assumes that biogeochemical processes play the primary treatment role and that subsurface losses can be neglected. Water and P fluxes from a SDA located in a row-crop farm were measured for two years (2009-2011) to assess the SDA's role in reducing downstream P loads. The SDA treated 55% (497kg) and 95% (205kg) of the incoming load during Year 1 (Y1, 09-10) and Year 2 (Y2, 10-11), respectively. These treatment efficiencies were similar to surface water volumetric retention (49% in Y1 and 84% in Y2) and varied primarily with rainfall. Similar water volume and P retentions indicate that volume retention is the main process controlling P loads. A limited role of biogeochemical processes was supported by low to no remaining soil P adsorption capacity due to long-term drainage P input. The fact that outflow P concentrations (Y1=368.3μg L -1 , Y2=230.4μg L -1 ) could be approximated by using a simple mixing of rainfall and drainage P input further confirmed the near inert biogeochemical processes. Subsurface P losses through groundwater were 304kg (27% of inflow P) indicating that they are an important source for downstream P. Including subsurface P losses reduces the treatment efficiency to 35% (from 61%). The aboveground biomass in the SDA contained 42% (240kg) of the average incoming P load suggesting that biomass harvesting could be a cost-effective alternative for reviving the role of biogeochemical processes to enhance P treatment in aged, P-saturated SDAs. The 20-year present economic value of P removal through harvesting was estimated to be $341,000, which if covered through a cost share or a payment for P treatment services program could be a positive outcome for both </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H31B1500T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H31B1500T">Coupled Land Surface-Subsurface Hydrogeophysical Inverse Modeling to Estimate Soil Organic Carbon Content in an Arctic Tundra</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tran, A. P.; Dafflon, B.; Hubbard, S. 2017-12-01 Soil organic carbon (SOC) is crucial for predicting carbon climate feedbacks in the vulnerable organic-rich Arctic region. However, it is challenging to achieve this property due to the general limitations of conventional core sampling and analysis methods. In this study, we develop an inversion scheme that uses single or multiple datasets, including soil liquid water content, temperature and ERT data, to estimate the vertical profile of SOC content. Our approach relies on the fact that SOC content strongly influences soil hydrological-thermal parameters, and therefore, indirectly controls the spatiotemporal dynamics of soil liquid water content, temperature and their correlated electrical resistivity. The scheme includes several advantages. First, this is the first time SOC content is estimated by using a coupled hydrogeophysical inversion. Second, by using the Community Land Model, we can account for the land surface dynamics (evapotranspiration, snow accumulation and melting) and ice/liquid phase transition. Third, we combine a deterministic and an adaptive Markov chain Monte Carlo optimization algorithm to better estimate the posterior distributions of desired model parameters. Finally, the simulated subsurface variables are explicitly linked to soil electrical resistivity via petrophysical and geophysical models. We validate the developed scheme using synthetic experiments. The results show that compared to inversion of single dataset, joint inversion of these datasets significantly reduces parameter uncertainty. The joint inversion approach is able to estimate SOC content within the shallow active layer with high reliability. Next, we apply the scheme to estimate OC content along an intensive ERT transect in Barrow, Alaska using multiple datasets acquired in the 2013-2015 period. The preliminary results show a good agreement between modeled and measured soil temperature, thaw layer thickness and electrical resistivity. The accuracy of estimated SOC content </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19547587','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19547587">Subsurface damage in precision ground ULE(R) and Zerodur(R) surfaces.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Tonnellier, X; Morantz, P; Shore, P; Baldwin, A; Evans, R; Walker, D D 2007-09-17 The total process cycle time for large ULE((R)) and Zerodur((R))optics can be improved using a precise and rapid grinding process, with low levels of surface waviness and subsurface damage. In this paper, the amounts of defects beneath ULE((R)) and Zerodur((R) )surfaces ground using a selected grinding mode were compared. The grinding response was characterised by measuring: surface roughness, surface profile and subsurface damage. The observed subsurface damage can be separated into two distinct depth zones, which are: 'process' and 'machine dynamics' related. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006SPIE.6034..127Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006SPIE.6034..127Y">Surface/subsurface observation and removal mechanisms of ground reaction bonded silicon carbide</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yao, Wang; Zhang, Yu-Min; Han, Jie-cai; Zhang, Yun-long; Zhang, Jian-han; Zhou, Yu-feng; Han, Yuan-yuan 2006-01-01 Reaction Bonded Silicon Carbide (RBSiC) has long been recognized as a promising material for optical applications because of its unique combination of favorable properties and low-cost fabrication. Grinding of silicon carbide is difficult because of its high hardness and brittleness. Grinding often induces surface and subsurface damage, residual stress and other types of damage, which have great influence on the ceramic components for optical application. In this paper, surface integrity, subsurface damage and material removal mechanisms of RBSiC ground using diamond grinding wheel on creep-feed surface grinding machine are investigated. The surface and subsurface are studied with scanning electron microscopy (SEM) and optical microscopy. The effects of grinding conditions on surface and subsurface damage are discussed. This research links the surface roughness, surface and subsurface cracks to grinding parameters and provides valuable insights into the material removal mechanism and the dependence of grind induced damage on grinding conditions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.H33D1344P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.H33D1344P">Understanding the Impacts of Climate Change and Land Use Dynamics Using a Fully Coupled Hydrologic Feedback Model between Surface and Subsurface Systems</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Park, C.; Lee, J.; Koo, M. 2011-12-01 Climate is the most critical driving force of the hydrologic system of the Earth. Since the industrial revolution, the impacts of anthropogenic activities to the Earth environment have been expanded and accelerated. Especially, the global emission of carbon dioxide into the atmosphere is known to have significantly increased temperature and affected the hydrologic system. Many hydrologists have contributed to the studies regarding the climate change on the hydrologic system since the Intergovernmental Panel on Climate Change (IPCC) was created in 1988. Among many components in the hydrologic system groundwater and its response to the climate change and anthropogenic activities are not fully understood due to the complexity of subsurface conditions between the surface and the groundwater table. A new spatio-temporal hydrologic model has been developed to estimate the impacts of climate change and land use dynamics on the groundwater. The model consists of two sub-models: a surface model and a subsurface model. The surface model involves three surface processes: interception, runoff, and evapotranspiration, and the subsurface model does also three subsurface processes: soil moisture balance, recharge, and groundwater flow. The surface model requires various input data including land use, soil types, vegetation types, topographical elevations, and meteorological data. The surface model simulates daily hydrological processes for rainfall interception, surface runoff varied by land use change and crop growth, and evapotranspiration controlled by soil moisture balance. The daily soil moisture balance is a key element to link two sub-models as it calculates infiltration and groundwater recharge by considering a time delay routing through a vadose zone down to the groundwater table. MODFLOW is adopted to simulate groundwater flow and interaction with surface water components as well. The model is technically flexible to add new model or modify existing model as it is </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=60995&keyword=ocean+AND+climate+AND+changes&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=60995&keyword=ocean+AND+climate+AND+changes&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">PHOTOREACTIONS IN SURFACE WATERS AND THEIR ROLE IN BIOGEOCHEMICAL CYCLES</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> During the past decade significant interest has developed in the influence of photochemical reactions on biogeochemical 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... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018BGeo...15.2411R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018BGeo...15.2411R">Large- to submesoscale surface circulation and its implications on biogeochemical/biological horizontal distributions during the OUTPACE cruise (southwest Pacific)</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rousselet, Louise; de Verneil, Alain; Doglioli, Andrea M.; Petrenko, Anne A.; Duhamel, Solange; Maes, Christophe; Blanke, Bruno 2018-04-01 The patterns of the large-scale, meso- and submesoscale surface circulation on biogeochemical and biological distributions are examined in the western tropical South Pacific (WTSP) in the context of the OUTPACE cruise (February-April 2015). Multi-disciplinary original in situ observations were achieved along a zonal transect through the WTSP and their analysis was coupled with satellite data. The use of Lagrangian diagnostics allows for the identification of water mass pathways, mesoscale structures, and submesoscale features such as fronts. In particular, we confirmed the existence of a global wind-driven southward circulation of surface waters in the entire WTSP, using a new high-resolution altimetry-derived product, validated by in situ drifters, that includes cyclogeostrophy and Ekman components with geostrophy. The mesoscale activity is shown to be responsible for counter-intuitive water mass trajectories in two subregions: (i) the Coral Sea, with surface exchanges between the North Vanuatu Jet and the North Caledonian Jet, and (ii) around 170° W, with an eastward pathway, whereas a westward general direction dominates. Fronts and small-scale features, detected with finite-size Lyapunov exponents (FSLEs), are correlated with 25 % of surface tracer gradients, which reveals the significance of such structures in the generation of submesoscale surface gradients. Additionally, two high-frequency sampling transects of biogeochemical parameters and microorganism abundances demonstrate the influence of fronts in controlling the spatial distribution of bacteria and phytoplankton, and as a consequence the microbial community structure. All circulation scales play an important role that has to be taken into account not only when analysing the data from OUTPACE but also, more generally, for understanding the global distribution of biogeochemical components. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70034286','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70034286">First-order exchange coefficient coupling for simulating surface water-groundwater interactions: Parameter sensitivity and consistency with a physics-based approach</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Ebel, B.A.; Mirus, B.B.; Heppner, C.S.; VanderKwaak, J.E.; Loague, K. 2009-01-01 Distributed hydrologic models capable of simulating fully-coupled surface water and groundwater flow are increasingly used to examine problems in the hydrologic sciences. Several techniques are currently available to couple the surface and subsurface; the two most frequently employed approaches are first-order exchange coefficients (a.k.a., the surface conductance method) and enforced continuity of pressure and flux at the surface-subsurface boundary condition. The effort reported here examines the parameter sensitivity of simulated hydrologic response for the first-order exchange coefficients at a well-characterized field site using the fully coupled Integrated Hydrology Model (InHM). This investigation demonstrates that the first-order exchange coefficients can be selected such that the simulated hydrologic response is insensitive to the parameter choice, while simulation time is considerably reduced. Alternatively, the ability to choose a first-order exchange coefficient that intentionally decouples the surface and subsurface facilitates concept-development simulations to examine real-world situations where the surface-subsurface exchange is impaired. While the parameters comprising the first-order exchange coefficient cannot be directly estimated or measured, the insensitivity of the simulated flow system to these parameters (when chosen appropriately) combined with the ability to mimic actual physical processes suggests that the first-order exchange coefficient approach can be consistent with a physics-based framework. Copyright ?? 2009 John Wiley & Sons, Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.B33C0617O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.B33C0617O">Ground-based Remote Sensing for Quantifying Subsurface and Surface Co-variability to Scale Arctic Ecosystem Functioning</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Oktem, R.; Wainwright, H. M.; Curtis, J. B.; Dafflon, B.; Peterson, J.; Ulrich, C.; Hubbard, S. S.; Torn, M. S. 2016-12-01 Predicting carbon cycling in Arctic requires quantifying tightly coupled surface and subsurface processes including permafrost, hydrology, vegetation and soil biogeochemistry. The challenge has been a lack of means to remotely sense key ecosystem properties in high resolution and over large areas. A particular challenge has been characterizing soil properties that are known to be highly heterogeneous. In this study, we exploit tightly-coupled above/belowground ecosystem functioning (e.g., the correlations among soil moisture, vegetation and carbon fluxes) to estimate subsurface and other key properties over large areas. To test this concept, we have installed a ground-based remote sensing platform - a track-mounted tram system - along a 70 m transect in the ice-wedge polygonal tundra near Barrow, Alaska. The tram carries a suite of near-surface remote sensing sensors, including sonic depth, thermal IR, NDVI and multispectral sensors. Joint analysis with multiple ground-based measurements (soil temperature, active layer soil moisture, and carbon fluxes) was performed to quantify correlations and the dynamics of above/belowground processes at unprecedented resolution, both temporally and spatially. We analyzed the datasets with particular focus on correlating key subsurface and ecosystem properties with surface properties that can be measured by satellite/airborne remote sensing over a large area. Our results provided several new insights about system behavior and also opens the door for new characterization approaches. We documented that: (1) soil temperature (at >5 cm depth; critical for permafrost thaw) was decoupled from soil surface temperature and was influenced strongly by soil moisture, (2) NDVI and greenness index were highly correlated with both soil moisture and gross primary productivity (based on chamber flux data), and (3) surface deformation (which can be measured by InSAR) was a good proxy for thaw depth dynamics at non-inundated locations. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018WRR....54..995S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018WRR....54..995S">Upscaling the Coupled Water and Heat Transport in the Shallow Subsurface</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sviercoski, R. F.; Efendiev, Y.; Mohanty, B. P. 2018-02-01 Predicting simultaneous movement of liquid water, water vapor, and heat in the shallow subsurface has many practical interests. The demand for multidimensional multiscale models for this region is important given: (a) the critical role that these processes play in the global water and energy balances, (b) that more data from air-borne and space-borne sensors are becoming available for parameterizations of modeling efforts. On the other hand, numerical models that consider spatial variations of the soil properties, termed here as multiscale, are prohibitively expensive. Thus, there is a need for upscaled models that take into consideration these features, and be computationally affordable. In this paper, a multidimensional multiscale model coupling the water flow and heat transfer and its respective upscaled version are proposed. The formulation is novel as it describes the multidimensional and multiscale tensorial versions of the hydraulic conductivity and the vapor diffusivity, taking into account the tortuosity and porosity properties of the medium. It also includes the coupling with the energy balance equation as a boundary describing atmospheric influences at the shallow subsurface. To demonstrate the accuracy of both models, comparisons were made between simulation and field experiments for soil moisture and temperature at 2, 7, and 12 cm deep, during 11 days. The root-mean-square errors showed that the upscaled version of the system captured the multiscale features with similar accuracy. Given the good matching between simulated and field data for near-surface soil temperature, the results suggest that it can be regarded as a 1-D variable. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SurSc.640..190C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SurSc.640..190C">Stability of surface and subsurface hydrogen on and in Au/Ni near-surface alloys</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Celik, Fuat E.; Mavrikakis, Manos 2015-10-01 Periodic, self-consistent DFT-GGA (PW91) calculations were used to study the interaction of hydrogen atoms with the (111) surfaces of substitutional near-surface alloys (NSAs) of Au and Ni with different surface layer compositions and different arrangements of Au atoms in the surface layer. The effect of hydrogen adsorption on the surface and in the first and second subsurface layers of the NSAs was studied. Increasing the Au content in the surface layer weakens hydrogen binding on the surface, but strengthens subsurface binding, suggesting that the distribution of surface and subsurface hydrogen will be different than that on pure Ni(111). While the metal composition of the surface layer has an effect on the binding energy of hydrogen on NSA surfaces, the local composition of the binding site has a stronger effect. For example, fcc hollow sites consisting of three Ni atoms bind H nearly as strongly as on Ni(111), and fcc sites consisting of three Au atoms bind H nearly as weakly as on Au(111). Sites with one or two Au atoms show intermediate binding energies. The preference of hydrogen for three-fold Ni hollow sites alters the relative stabilities of different surface metal atom arrangements, and may provide a driving force for adsorbate-induced surface rearrangement. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H32D..01H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H32D..01H">Predictive Understanding of Mountainous Watershed Hydro-Biogeochemical Function and Response to Perturbations</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hubbard, S. S.; Williams, K. H.; Agarwal, D.; Banfield, J. F.; Beller, H. R.; Bouskill, N.; Brodie, E.; Maxwell, R. M.; Nico, P. S.; Steefel, C. I.; Steltzer, H.; Tokunaga, T. K.; Wainwright, H. M.; Dwivedi, D.; Newcomer, M. E. 2017-12-01 Recognizing the societal importance, vulnerability and complexity of mountainous watersheds, the `Watershed Function' project is developing a predictive understanding of how mountainous watersheds retain and release downgradient water, nutrients, carbon, and metals. In particular, the project is exploring how early snowmelt, drought, floods and other disturbances will influence mountainous watershed dynamics at seasonal to decadal timescales. Located in the 300km2 East River headwater catchment of the Upper Colorado River Basin, the project is guided by several constructs. First, the project considers the integrated role of surface and subsurface flow and biogeochemical reactions - from bedrock to the top of the vegetative canopy, from terrestrial through aquatic compartments, and from summit to receiving waters. The project takes a system-of-systems perspective, focused on developing new methods to quantify the cumulative watershed hydrobiogeochemical response to perturbations based on information from select subsystems within the watershed, each having distinct vegetation-subsurface biogeochemical-hydrological characteristics. A `scale-adaptive' modeling capability, in development using adaptive mesh refinement methods, serves as the organizing framework for the SFA. The scale-adaptive approach is intended to permit simulation of system-within-systems behavior - and aggregation of that behavior - from genome through watershed scales. This presentation will describe several early project discoveries and advances made using experimental, observational and numerical approaches. Among others, examples may include:quantiying how seasonal hydrological perturbations drive biogeochemical responses across critical zone compartments, with a focus on N and C transformations; metagenomic documentation of the spatial variability in floodplain meander microbial ecology; 3D reactive transport simulations of couped hydrological-biogeochemical behavior in the hyporheic zone; and </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active">4</li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_5" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active">5</li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="81"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H41H..02C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H41H..02C">A Method for Partitioning Surface and Subsurface Flow Using Rainfall Simulaton and Two-Dimensional Surface Electrical Resistivity Imaging</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Carey, A. M.; Paige, G. B.; Miller, S. N.; Carr, B. J.; Holbrook, W. S. 2014-12-01 In semi-arid rangeland environments understanding how surface and subsurface flow processes and their interactions are influenced by watershed and rainfall characteristics is critical. However, it is difficult to resolve the temporal variations between mechanisms controlling these processes and challenging to obtain field measurements that document their interactions. Better insight into how these complex systems respond hydrologically is necessary in order to refine hydrologic models and decision support tools. We are conducting field studies integrating high resolution, two-dimensional surface electrical resistivity imaging (ERI) with variable intensity rainfall simulation, to quantify real-time partitioning of rainfall into surface and subsurface response. These studies are being conducted at the hillslope scale on long-term runoff plots on four different ecological sites in the Upper Crow Creek Watershed in southeastern Wyoming. Variable intensity rainfall rates were applied using the Walnut Gulch Rainfall Simulator in which intensities were increased incrementally from 49 to 180 mm hr-1 and steady-state runoff rates for each intensity were measured. Two 13.5 m electrode arrays at 0.5 m spacing were positioned on the surface perpendicular to each plot and potentials were measured at given time intervals prior to, during and following simulations using a dipole-dipole array configuration. The configuration allows for a 2.47 m depth of investigation in which magnitude and direction of subsurface flux can be determined. We used the calculated steady state infiltration rates to quantify the variability in the partial area runoff response on the ecological sites. Coupling this information with time-lapse difference inversions of ERI data, we are able to track areas of increasing and decreasing resistivity in the subsurface related to localized areas of infiltration during and following rainfall events. We anticipate implementing this method across a variety of </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.G51B0743W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.G51B0743W">Surface and subsurface continuous gravimetric monitoring of groundwater recharge processes through the karst vadose zone at Rochefort Cave (Belgium)</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Watlet, A.; Van Camp, M. J.; Francis, O.; Poulain, A.; Hallet, V.; Triantafyllou, A.; Delforge, D.; Quinif, Y.; Van Ruymbeke, M.; Kaufmann, O. 2017-12-01 Ground-based gravimetry is a non-invasive and integrated tool to characterize hydrological processes in complex environments such as karsts or volcanoes. A problem in ground-based gravity measurements however concerns the lack of sensitivity in the first meters below the topographical surface, added to limited infiltration below the gravimeter building (umbrella effect). Such limitations disappear when measuring underground. Coupling surface and subsurface gravity measurements therefore allow isolating hydrological signals occurring in the zone between the two gravimeters. We present a coupled surface/subsurface continuous gravimetric monitoring of 2 years at the Rochefort Cave Laboratory (Belgium). The gravity record includes surface measurements of a GWR superconducting gravimeter and subsurface measurements of a Micro-g LaCoste gPhone gravimeter, installed in a cave 35 m below the surface station. The recharge of karstic aquifers is extremely complex to model, mostly because karst hydrological systems are composed of strongly heterogeneous flows. Most of the problem comes from the inadequacy of conventional measuring tools to correctly sample such heterogeneous media, and particularly the existence of a duality of flow types infiltrating the vadose zone: from rapid flows via open conduits to slow seepage through porous matrix. Using the surface/subsurface gravity difference, we were able to identify a significant seasonal groundwater recharge within the karst vadose zone. Seasonal or perennial perched reservoirs have already been proven to exist in several karst areas due to the heterogeneity of the porosity and permeability gradient in karstified carbonated rocks. Our gravimetric experiment allows assessing more precisely the recharge processes of such reservoirs. The gravity variations were also compared with surface and in-cave hydrogeological monitoring (i.e. soil moisture, in-cave percolating water discharges, water levels of the saturated zone). Combined </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.4427P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.4427P">Hyporheic zone as a bioreactor: sediment heterogeneity influencing biogeochemical processes</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Perujo, Nuria; Romani, Anna M.; Sanchez-Vila, Xavier 2017-04-01 Mediterranean fluvial systems are characterized by frequent periods of low flow or even drought. During low flow periods, water from wastewater treatment plants (WWTPs) is proportionally large in fluvial systems. River water might be vertically transported through the hyporheic zone, and then porous medium acts as a complementary treatment system since, as water infiltrates, a suite of biogeochemical processes occurs. Subsurface sediment heterogeneity plays an important role since it influences the interstitial fluxes of the medium and drives biomass growing, determining biogeochemical reactions. In this study, WWTP water was continuously infiltrated for 3 months through two porous medium tanks: one consisting of 40 cm of fine sediment (homogeneous); and another comprised of two layers of different grain size sediments (heterogeneous), 20 cm of coarse sediment in the upper part and 20 cm of fine one in the bottom. Several hydrological, physicochemical and biological parameters were measured periodically (weekly at the start of the experiment and biweekly at the end). Analysed parameters include dissolved nitrogen, phosphorus, organic carbon, and oxygen all measured at the surface, and at 5, 20 and 40 cm depth. Variations in hydraulic conductivity with time were evaluated. Sediment samples were also analysed at three depths (surface, 20 and 40 cm) to determine bacterial density, chlorophyll content, extracellular polymeric substances, and biofilm function (extracellular enzyme activities and carbon substrate utilization profiles). Preliminary results suggest hydraulic conductivity to be the main driver of the differences in the biogeochemical processes occurring in the subsurface. At the heterogeneous tank, a low nutrient reduction throughout the whole medium is measured. In this medium, high hydraulic conductivity allows for a large amount of infiltrating water, but with a small residence time. Since some biological processes are largely time-dependent, small water </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1407981-stability-surface-subsurface-hydrogen-au-ni-near-surface-alloys','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1407981-stability-surface-subsurface-hydrogen-au-ni-near-surface-alloys">Stability of surface and subsurface hydrogen on and in Au/Ni near-surface alloys</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Celik, Fuat E.; Mavrikakis, Manos 2015-01-12 Periodic, self-consistent DFT-GGA (PW91) calculations were used to study the interaction of hydrogen atoms with the (111) surfaces of substitutional near-surface alloys (NSAs) of Au and Ni with different surface layer compositions and different arrangements of Au atoms in the surface layer. The effect of hydrogen adsorption on the surface and in the first and second subsurface layers of the NSAs was studied. Increasing the Au content in the surface layer weakens hydrogen binding on the surface, but strengthens subsurface binding, suggesting that the distribution of surface and subsurface hydrogen will be different than that on pure Ni(111). While themore » metal composition of the surface layer has an effect on the binding energy of hydrogen on NSA surfaces, the local composition of the binding site has a stronger effect. For example, fcc hollow sites consisting of three Ni atoms bind H nearly as strongly as on Ni(111), and fcc sites consisting of three Au atoms bind H nearly as weakly as on Au(111). Sites with one or two Au atoms show intermediate binding energies. The preference of hydrogen for three-fold Ni hollow sites alters the relative stabilities of different surface metal atom arrangements, and may provide a driving force for adsorbate-induced surface rearrangement.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1222060-stability-surface-subsurface-hydrogen-au-ni-near-surface-alloys','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1222060-stability-surface-subsurface-hydrogen-au-ni-near-surface-alloys">Stability of Surface and Subsurface Hydrogen on and in Au/Ni Near-Surface Alloys</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Celik, Fuat E.; Mavrikakis, Manos 2015-10-01 Periodic, self-consistent DFT-GGA (PW91) calculations were used to study the interaction of hydrogen atoms with the (111) surfaces of substitutional near-surface alloys (NSAs) of Au and Ni with different surface layer compositions and different arrangements of Au atoms in the surface layer. The effect of hydrogen adsorption on the surface and in the first and second subsurface layers of the NSAs was studied. Increasing the Au content in the surface layer weakens hydrogen binding on the surface, but strengthens subsurface binding, suggesting that the distribution of surface and subsurface hydrogen will be different than that on pure Ni(111). While themore » metal composition of the surface layer has an effect on the binding energy of hydrogen on NSA surfaces, the local composition of the binding site has a stronger effect. For example, fcc hollow sites consisting of three Ni atoms bind H nearly as strongly as on Ni(111), and fcc sites consisting of three Au atoms bind H nearly as weakly as on Au(111). Sites with one or two Au atoms show intermediate binding energies. The preference of hydrogen for three-fold Ni hollow sites alters the relative stabilities of different surface metal atom arrangements, and may provide a driving force for adsorbate-induced surface rearrangement.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JHyd..542..101Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JHyd..542..101Z">A field study of colloid transport in surface and subsurface flows</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zhang, Wei; Tang, Xiang-Yu; Xian, Qing-Song; Weisbrod, Noam; Yang, Jae E.; Wang, Hong-Lan 2016-11-01 Colloids have been recognized to enhance the migration of strongly-sorbing contaminants. However, few field investigations have examined combined colloid transport via surface runoff and subsurface flows. In a headwater catchment of the upper Yangtze River, a 6 m (L) by 4 m (W) sloping (6°) farmland plot was built by cement walls to form no-flow side boundaries. The plot was monitored in the summer of 2014 for the release and transport of natural colloids via surface runoff and subsurface flows (i.e., the interflow from the soil-mudrock interface and fracture flow from the mudrock-sandstone interface) in response to rain events. The water sources of the subsurface flows were apportioned to individual rain events using a two end-member model (i.e., mobile pre-event soil water extracted by a suction-cup sampler vs. rainwater (event water)) based on δ18O measurements. For rain events with high preceding soil moisture, mobile pre-event soil water was the main contributor (generally >60%) to the fracture flow. The colloid concentration in the surface runoff was 1-2 orders of magnitude higher than that in the subsurface flows. The lowest colloid concentration was found in the subsurface interflow, which was probably the result of pore-scale colloid straining mechanisms. The rainfall intensity and its temporal variation govern the dynamics of the colloid concentrations in both surface runoff and subsurface flows. The duration of the antecedent dry period affected not only the relative contributions of the rainwater and the mobile pre-event soil water to the subsurface flows but also the peak colloid concentration, particularly in the fracture flow. The <10 μm fine colloid size fraction accounted for more than 80% of the total suspended particles in the surface runoff, while the colloid size distributions of both the interflow and the fracture flow shifted towards larger diameters. These results highlight the need to avoid the application of strongly </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.H41O..03R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.H41O..03R">Patterns in coupled water and energy cycle: Modeling, synthesis with observations, and assessing the subsurface-landsurface interactions</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rahman, A.; Kollet, S. J.; Sulis, M. 2013-12-01 In the terrestrial hydrological cycle, the atmosphere and the free groundwater table act as the upper and lower boundary condition, respectively, in the non-linear two-way exchange of mass and energy across the land surface. Identifying and quantifying the interactions among various atmospheric-subsurface-landsurface processes is complicated due to the diverse spatiotemporal scales associated with these processes. In this study, the coupled subsurface-landsurface model ParFlow.CLM was applied over a ~28,000 km2 model domain encompassing the Rur catchment, Germany, to simulate the fluxes of the coupled water and energy cycle. The model was forced by hourly atmospheric data from the COSMO-DE model (numerical weather prediction system of the German Weather Service) over one year. Following a spinup period, the model results were synthesized with observed river discharge, soil moisture, groundwater table depth, temperature, and landsurface energy flux data at different sites in the Rur catchment. It was shown that the model is able to reproduce reasonably the dynamics and also absolute values in observed fluxes and state variables without calibration. The spatiotemporal patterns in simulated water and energy fluxes as well as the interactions were studied using statistical, geostatistical and wavelet transform methods. While spatial patterns in the mass and energy fluxes can be predicted from atmospheric forcing and power law scaling in the transition and winter months, it appears that, in the summer months, the spatial patterns are determined by the spatially correlated variability in groundwater table depth. Continuous wavelet transform techniques were applied to study the variability of the catchment average mass and energy fluxes at varying time scales. From this analysis, the time scales associated with significant interactions among different mass and energy balance components were identified. The memory of precipitation variability in subsurface hydrodynamics </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014OptEn..53i2010C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014OptEn..53i2010C">Magnetorheological finishing for removing surface and subsurface defects of fused silica optics</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Catrin, Rodolphe; Neauport, Jerome; Taroux, Daniel; Cormont, Philippe; Maunier, Cedric; Lambert, Sebastien 2014-09-01 We investigate the capacity of magnetorheological finishing (MRF) process to remove surface and subsurface defects of fused silica optics. Polished samples with engineered surface and subsurface defects were manufactured and characterized. Uniform material removals were performed with a QED Q22-XE machine using different MRF process parameters in order to remove these defects. We provide evidence that whatever the MRF process parameters are, MRF is able to remove surface and subsurface defects. Moreover, we show that MRF induces a pollution of the glass interface similar to conventional polishing processes. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70193750','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70193750">Advances in interpretation of subsurface processes with time-lapse electrical imaging</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Singha, Kaminit; Day-Lewis, Frederick D.; Johnson, Tim B.; Slater, Lee D. 2015-01-01 Electrical geophysical methods, including electrical resistivity, time-domain induced polarization, and complex resistivity, have become commonly used to image the near subsurface. Here, we outline their utility for time-lapse imaging of hydrological, geochemical, and biogeochemical processes, focusing on new instrumentation, processing, and analysis techniques specific to monitoring. We review data collection procedures, parameters measured, and petrophysical relationships and then outline the state of the science with respect to inversion methodologies, including coupled inversion. We conclude by highlighting recent research focused on innovative applications of time-lapse imaging in hydrology, biology, ecology, and geochemistry, among other areas of interest. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1208765-advances-interpretation-subsurface-processes-time-lapse-electrical-imaging','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1208765-advances-interpretation-subsurface-processes-time-lapse-electrical-imaging">Advances in interpretation of subsurface processes with time-lapse electrical imaging</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Singha, Kamini; Day-Lewis, Frederick D.; Johnson, Timothy C. 2015-03-15 Electrical geophysical methods, including electrical resistivity, time-domain induced polarization, and complex resistivity, have become commonly used to image the near subsurface. Here, we outline their utility for time-lapse imaging of hydrological, geochemical, and biogeochemical processes, focusing on new instrumentation, processing, and analysis techniques specific to monitoring. We review data collection procedures, parameters measured, and petrophysical relationships and then outline the state of the science with respect to inversion methodologies, including coupled inversion. We conclude by highlighting recent research focused on innovative applications of time-lapse imaging in hydrology, biology, ecology, and geochemistry, among other areas of interest. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B13C0518C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B13C0518C">Active Serpentinization and the Potential for a Diverse Subsurface Biosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Canovas, P. A.; Shock, E. 2013-12-01 The ubiquitous nature of serpentinization and the unique fluids it generates have major consequences for habitat generation, abiotic organic synthesis, and biosynthesis. The production of hydrogen from the anaerobic hydrolysis of ultramafic minerals sets the redox state of serpentinizing fluids to be thermodynamically favorable for these processes. Consequently, a host of specialized microbial populations and metabolisms can be sustained. Active low-temperature serpentinizing systems, such as the Samail ophiolite in Oman, offer an ideal opportunity to investigate biogeochemical processes during the alteration of ultramafic minerals. At the Samail ophiolite in particular, serpentinization may provide the potential for an active subsurface microbial community shielded from potentially unfavorable surface conditions. Support for this assertion comes from geochemical data including Mg, Ca, CH4 (aq), and H2 (aq) abundances indicating that methane is a product of serpentinization. To further investigate viable metabolic strategies, affinity calculations were performed on both the surface waters and the hyperalkaline springs, which may be considered as messengers of processes occurring in the subsurface. Almost all sites yield positive affinities (i.e., are thermodynamically favorable) for a diverse suite of serpentinization metabolisms including methanogenesis, anammox, and carbon monoxide, nitrate, and sulfate reduction with hydrogen, as well as anaerobic methanotrophy coupled to nitrate, nitrite, and sulfate reduction. Reaction path modeling was performed to ascertain the extent to which serpentinization and mixing of surface waters with hyperalkaline spring waters in the subsurface can generate suitable habitats. The serpentinization model simulates the reaction of pristine Oman harzburgite with surface water to quantify the redox state and generation of hyperalkaline spring water. Preliminary results show that water-rock ratios as high as 100 could effectively reduce </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000JHyd..227..292H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000JHyd..227..292H">Reply to 'Comment on kinetic modeling of microbially-driven redox chemistry of subsurface environments: coupling transport, microbial metabolism and geochemistry' by J. Griffioen</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hunter, K. S.; Van Cappellen, P. 2000-01-01 Our paper, 'Kinetic modeling of microbially-driven redox chemistry of subsurface environments: coupling transport, microbial metabolism and geochemistry' (Hunter et al., 1998), presents a theoretical exploration of biogeochemical reaction networks and their importance to the biogeochemistry of groundwater systems. As with any other model, the kinetic reaction-transport model developed in our paper includes only a subset of all physically, biologically and chemically relevant processes in subsurface environments. It considers aquifer systems where the primary energy source driving microbial activity is the degradation of organic matter. In addition to the primary biodegradation pathways of organic matter (i.e. respiration and fermentation), the redox chemistry of groundwaters is also affected by reactions not directly involving organic matter oxidation. We refer to the latter as secondary reactions. By including secondary redox reactions which consume reduced reaction products (e.g., Mn2+, FeS, H2S), and in the process compete with microbial heterotrophic populations for available oxidants (i.e. O2, NO3-, Mn(IV), Fe(III), SO42-), we predict spatio-temporal distributions of microbial activity which differ significantly from those of models which consider only the biodegradation reactions. That is, the secondary reactions have a significant impact on the distributions of the rates of heterotrophic and chemolithotrophic metabolic pathways. We further show that secondary redox reactions, as well as non-redox reactions, significantly influence the acid-base chemistry of groundwaters. The distributions of dissolved inorganic redox species along flowpaths, however, are similar in simulations with and without secondary reactions (see Figs. 3(b) and 7(b) in Hunter et al., 1998), indicating that very different biogeochemical reaction dynamics may lead to essentially the same chemical redox zonation of a groundwater system. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.V51C0364M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.V51C0364M">The Lusi eruption site: insights from surface and subsurface investigations</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mazzini, A. 2017-12-01 The Indonesian Lusi eruption has been spewing boiling water, gas, and sediments since the 29th of May 2006. Initially, numerous aligned eruptions sites appeared along the Watukosek fault system (WFS) that was reactivated after the Yogyakarta earthquake occurring the 27th of May in the Java Island. Within weeks several villages were submerged by boiling mud. The most prominent eruption site was named Lusi. To date Lusi is still active and an area of 7 km2is covered by mud. Since its birth Lusi erupted with a pulsating behaviour. In the framework of the ERC grant "Lusi Lab" we conducted several years of monitoring and regional investigations coupling surface sampling and subsurface imaging in the region around Lusi. Ambient noise tomography studies, obtained with a local network of 31 stations, revealed for the first time subsurface images of the Lusi region and the adjacent Arjuno-Welirang (AW) volcanic complex. Results show that below the AW volcanic complex are present 5km deep magma chambers that are connected, through a defined corridor, with the roots of the Lusi eruption site. The Lusi subsurface shows the presence of a defined vertical hydrothermal plume that extends to at least 5km. Chemical analyses of the seeping fluids sampled from 1) the Lusi plume (using a specifically designed drone), 2) the region around Lusi, and 3) the fumaroles and the hydro thermal springs of AW, revealed striking similarities. More specifically a mantellic signature of the Lusi fluids confirms the scenario that Lusi represents a magmatic-driven hydrothermal system hosted in sedimentary basin. Seismic profiles interpretation, surface mapping, and fluid sampling show that the WFS, connecting AW and extending towards the NE of Java, acted as a preferential pathway for the igneous intrusion and fluids migration towards the subsurface. Petrography and dating of the clasts erupted at Lusi record high temperatures and indicate that the roots of the active conduit extend to at least 5km </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=86512&Lab=NRMRL&keyword=bio+AND+remediation&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=86512&Lab=NRMRL&keyword=bio+AND+remediation&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">GEOCHEMISTRY OF SUBSURFACE REACTIVE BARRIERS FOR REMEDIATION OF CONTAMINATED GROUND WATER</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Reactive barriers that couple subsurface fluid flow with a passive chemical treatment zone are emerging, cost effective approaches for in-situ remediation of contaminated groundwater. Factors such as the build-up of surface precipitates, bio-fouling, and changes in subsurface tr... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1439188-hierarchical-bayesian-method-mapping-biogeochemical-hot-spots-using-induced-polarization-imaging','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1439188-hierarchical-bayesian-method-mapping-biogeochemical-hot-spots-using-induced-polarization-imaging">Hierarchical Bayesian method for mapping biogeochemical hot spots using induced polarization imaging</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Wainwright, Haruko M.; Flores Orozco, Adrian; Bucker, Matthias; ... 2016-01-29 In floodplain environments, a naturally reduced zone (NRZ) is considered to be a common biogeochemical hot spot, having distinct microbial and geochemical characteristics. Although important for understanding their role in mediating floodplain biogeochemical processes, mapping the subsurface distribution of NRZs over the dimensions of a floodplain is challenging, as conventional wellbore data are typically spatially limited and the distribution of NRZs is heterogeneous. In this work, we present an innovative methodology for the probabilistic mapping of NRZs within a three-dimensional (3-D) subsurface domain using induced polarization imaging, which is a noninvasive geophysical technique. Measurements consist of surface geophysical surveys andmore » drilling-recovered sediments at the U.S. Department of Energy field site near Rifle, CO (USA). Inversion of surface time domain-induced polarization (TDIP) data yielded 3-D images of the complex electrical resistivity, in terms of magnitude and phase, which are associated with mineral precipitation and other lithological properties. By extracting the TDIP data values colocated with wellbore lithological logs, we found that the NRZs have a different distribution of resistivity and polarization from the other aquifer sediments. To estimate the spatial distribution of NRZs, we developed a Bayesian hierarchical model to integrate the geophysical and wellbore data. In addition, the resistivity images were used to estimate hydrostratigraphic interfaces under the floodplain. Validation results showed that the integration of electrical imaging and wellbore data using a Bayesian hierarchical model was capable of mapping spatially heterogeneous interfaces and NRZ distributions thereby providing a minimally invasive means to parameterize a hydrobiogeochemical model of the floodplain.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1615715S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1615715S">Linking sediment structure, hydrological functioning and biogeochemical cycling in disturbed coastal saltmarshes and implications for vegetation development</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Spencer, Kate; Harvey, Gemma; James, Tempest; Simon, Carr; Michelle, Morris 2014-05-01 Saltmarsh restoration undoubtedly provides environmental enhancement, with vegetation quickly re-establishing following the breach of sea walls and subsequent tidal inundation of previously defended areas. Yet evidence increasingly suggests that the restored saltmarshes do not have the same biological characteristics as their natural counterparts (Mossman et al. 2012) and this may be in part be due to physicochemical parameters at the site including anoxia and poor drainage. Hence, restored saltmarshes may not offer the range and quality of ecosystem services anticipated. These environments will have been 'disturbed' by previous land use and there is little understanding of the impacts of this disturbance on the wider hydrogeomorphic and biogeochemical functioning in restored saltmarshes and the implications for saltmarsh vegetation development. This study examines linkages between physical sediment characteristics, sediment structure (using X-ray microtomography), sub-surface hydrology (using pressure transducers and time series analysis), and sediment and porewater geochemistry (major and trace elements, major anions) in sediment cores collected from undisturbed saltmarshes and those restored by de-embankment. Sub-surface sediments in restored saltmarshes have lower organic matter content, lower moisture content and higher bulk density than undisturbed sites. Using X-ray tomography a clear horizon can be observed which separates relict agricultural soils at depth with less dense and structureless sediments deposited since de-embankment. Ratios of open to closed pore space suggest that while undisturbed saltmarshes have the highest porosity, restored saltmarshes have larger void spaces, but limited pore connectivity. Sub-surface hydrological response to tidal flooding was subdued in the restored compared to the undisturbed site, suggesting that porewater flow may be impeded. Time series analysis indicated that flow pathways differ in restored saltmarsh sediments </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1417492-situ-subsurface-soil-analyzer','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1417492-situ-subsurface-soil-analyzer">In-situ Subsurface Soil Analyzer</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Ulmer, Chris The Department of Energy’s (DOE’s) Terrestrial Ecosystem Science (TES) program is seeking improved sensor systems for monitoring hydro-biogeochemical processes in complex subsurface environments. The TES program is specifically interested in acquiring chemical and structural information regarding the type and nature of the hydration and redox states of subsurface chemical species. The technology should be able to perform on-site and real-time measurements to provide information not available using current sample acquisition and preservation processes. To address the needs of the DOE and the terrestrial science community, Physical Optics Corporation (POC) worked on the development of a new In-Situ Subsurface Soil Analyzermore » (ISSA) based on magnetic resonance technologies. Benchtop testing was performed to assess the feasibility of continuous wave electron pair resonance (CW-EPR) detection of chemical species in subsurface soil systems.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMEP53B1715L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMEP53B1715L">Linking Surface and Subsurface Processes: Implications for Seismic Hazards in Southern California</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lin, J. C.; Moon, S.; Yong, A.; Meng, L.; Martin, A. J.; Davis, P. M. 2017-12-01 Earth's surface and subsurface processes such as bedrock weathering, soil production, and river incision can influence and be influenced by spatial variations in the mechanical strength of surface material. Mechanically weakened rocks tend to have reduced seismic velocity, which can result in larger ground-motion amplification and greater potential for earthquake-induced damages. However, the influence and extent of surface and subsurface processes on the mechanical strength of surface material and seismic site conditions in southern California remain unclear. In this study, we examine whether physics-based models of surface and subsurface processes can explain the spatial variability and non-linearity of near-surface seismic velocity in southern California. We use geophysical measurements (Yong et al., 2013; Ancheta et al., 2014), consisting of shear-wave velocity (Vs) tomography data, Vs profiles, and the time-averaged Vs in the upper 30 m of the crust (Vs30) to infer lateral and vertical variations of surface material properties. Then, we compare Vs30 values with geologic and topographic attributes such as rock type, slope, elevation, and local relief, as well as metrics for surface processes such as soil production and bedrock weathering from topographic stress, frost cracking, chemical reactions, and vegetation presence. Results from this study will improve our understanding of physical processes that control subsurface material properties and their influences on local variability in seismic site conditions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017WRR....53.8698Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017WRR....53.8698Y">Multiscale Investigation on Biofilm Distribution and Its Impact on Macroscopic Biogeochemical Reaction Rates</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yan, Zhifeng; Liu, Chongxuan; Liu, Yuanyuan; Bailey, Vanessa L. 2017-11-01 Biofilms are critical locations for biogeochemical reactions in the subsurface environment. The occurrence and distribution of biofilms at microscale as well as their impacts on macroscopic biogeochemical reaction rates are still poorly understood. This paper investigated the formation and distributions of biofilms in heterogeneous sediments using multiscale models and evaluated the effects of biofilm heterogeneity on local and macroscopic biogeochemical reaction rates. Sediment pore structures derived from X-ray computed tomography were used to simulate the microscale flow dynamics and biofilm distribution in the sediment column. The response of biofilm formation and distribution to the variations in hydraulic and chemical properties was first examined. One representative biofilm distribution was then utilized to evaluate its effects on macroscopic reaction rates using nitrate reduction as an example. The results revealed that microorganisms primarily grew on the surfaces of grains and aggregates near preferential flow paths where both electron donor and acceptor were readily accessible, leading to the heterogeneous distribution of biofilms in the sediments. The heterogeneous biofilm distribution decreased the macroscopic rate of biogeochemical reactions as compared with those in homogeneous cases. Operationally considering the heterogeneous biofilm distribution in macroscopic reactive transport models such as using dual porosity domain concept can significantly improve the prediction of biogeochemical reaction rates. Overall, this study provided important insights into the biofilm formation and distribution in soils and sediments as well as their impacts on the macroscopic manifestation of reaction rates. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29634805','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29634805">Modeling Phosphorus Losses through Surface Runoff and Subsurface Drainage Using ICECREAM.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Qi, Hongkai; Qi, Zhiming; Zhang, T Q; Tan, C S; Sadhukhan, Debasis 2018-03-01 Modeling soil phosphorus (P) losses by surface and subsurface flow pathways is essential in developing successful strategies for P pollution control. We used the ICECREAM model to simultaneously simulate P losses in surface and subsurface flow, as well as to assess effectiveness of field practices in reducing P losses. Monitoring data from a mineral-P-fertilized clay loam field in southwestern Ontario, Canada, were used for calibration and validation. After careful adjustment of model parameters, ICECREAM was shown to satisfactorily simulate all major processes of surface and subsurface P losses. When the calibrated model was used to assess tillage and fertilizer management scenarios, results point to a 10% reduction in total P losses by shifting autumn tillage to spring, and a 25.4% reduction in total P losses by injecting fertilizer rather than broadcasting. Although the ICECREAM model was effective in simulating surface and subsurface P losses when thoroughly calibrated, further testing is needed to confirm these results with manure P application. As illustrated here, successful use of simulation models requires careful verification of model routines and comprehensive calibration to ensure that site-specific processes are accurately represented. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active">5</li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active">6</li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/1982/1044/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/1982/1044/report.pdf">A study of surface and subsurface ground motions at Calico Hills, Nevada Test Site</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> King, Kenneth W. 1982-01-01 A study of earthquake ground motions recorded at depth in a drill hole and at the ground surface has derived the surface to subsurface transfer functions such as might be expected at a potential nuclear waste repository in a similar setting. The site under investigation has small seismic velocity contrasts in the layers of rock between the surface and the subsurface seismometer location. The subsurface seismic motions were similar in spectral characteristics to the surface motions and were lower in amplitude across the recorded band-width by a factor of 1.5. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/379159-homology-between-genes-aromatic-hydrocarbon-degradation-surface-deep-subsurface-sphingomonas-strains','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/379159-homology-between-genes-aromatic-hydrocarbon-degradation-surface-deep-subsurface-sphingomonas-strains">Homology between genes for aromatic hydrocarbon degradation in surface and deep-subsurface sphingomonas strains</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Kim, E.; Aversano, P.J.; Zylstra, G.J. The cloned genes for aromatic hydrocarbon degradation from Sphingomonas yanoikuyae B1 were utilized in Southern hybridization experiments with Sphingomonas strains from the surface and deep-subsurface environments. One hybridization pattern was obtained with BamHI-digested genomic DNAs for two surface strains, while a differing pattern was seen for five deep-subsurface strains. The cross-hybridizing genes were located in the chromosomes of the surface strains and on plasmids in the deep-subsurface strains. 31 refs., 3 figs., 1 tab. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26917241','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26917241">Geomicrobiology and Metagenomics of Terrestrial Deep Subsurface Microbiomes.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Itävaara, M; Salavirta, H; Marjamaa, K; Ruskeeniemi, T 2016-01-01 Fractures in the deep subsurface of Earth's crust are inhabited by diverse microbial communities that participate in biogeochemical cycles of the Earth. Life on Earth, which arose c. 3.5-4.0 billion years ago, reaches down at least 5 km in the crust. Deep mines, caves, and boreholes have provided scientists with opportunities to sample deep subsurface microbiomes and to obtain information on the species diversity and functions. A wide variety of bacteria, archaea, eukaryotes, and viruses are now known to reside in the crust, but their functions are still largely unknown. The crust at different depths has varying geological composition and hosts endemic microbiomes accordingly. The diversity is driven by geological formations and gases evolving from deeper depths. Cooperation among different species is still mostly unexplored, but viruses are known to restrict density of bacterial and archaeal populations. Due to the complex growth requirements of the deep subsurface microbiomes, the new knowledge about their diversity and functions is mostly obtained by molecular methods, eg, meta'omics'. Geomicrobiology is a multidisciplinary research area combining disciplines from geology, mineralogy, geochemistry, and microbiology. Geomicrobiology is concerned with the interaction of microorganisms and geological processes. At the surface of mineralogical or rock surfaces, geomicrobial processes occur mainly under aerobic conditions. In the deep subsurface, however, the environmental conditions are reducing and anaerobic. The present chapter describes the world of microbiomes in deep terrestrial geological environments as well as metagenomic and metatranscriptomic methods suitable for studies of these enigmatic communities. Copyright © 2016 Elsevier Inc. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26413801','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26413801">Residues of endosulfan in surface and subsurface agricultural soil and its bioremediation.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Odukkathil, Greeshma; Vasudevan, Namasivayam 2016-01-01 The persistence of many hydrophobic pesticides has been reported by various workers in various soil environments and its bioremediation is a major concern due to less bioavailability. In the present study, the pesticide residues in the surface and subsurface soil in an area of intense agricultural activity in Pakkam Village of Thiruvallur District, Tamilnadu, India, and its bioremediation using a novel bacterial consortium was investigated. Surface (0-15 cm) and subsurface soils (15-30 cm and 30-40 cm) were sampled, and pesticides in different layers of the soil were analyzed. Alpha endosulfan and beta endosulfan concentrations ranged from 1.42 to 3.4 mg/g and 1.28-3.1 mg/g in the surface soil, 0.6-1.4 mg/g and 0.3-0.6 mg/g in the subsurface soil (15-30 cm), and 0.9-1.5 mg/g and 0.34-1.3 mg/g in the subsurface soil (30-40 cm) respectively. Residues of other persistent pesticides were also detected in minor concentrations. These soil layers were subjected to bioremediation using a novel bacterial consortium under a simulated soil profile condition in a soil reactor. The complete removal of alpha and beta endosulfan was observed over 25 days. Residues of endosulfate were also detected during bioremediation, which was subsequently degraded on the 30th day. This study revealed the existence of endosulfan in the surface and subsurface soils and also proved that the removal of such a ubiquitous pesticide in the surface and subsurface environment can be achieved in the field by bioaugumenting a biosurfactant-producing bacterial consortium that degrades pesticides. Copyright © 2015 Elsevier Ltd. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70131477','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70131477">Hyporheic flow and transport processes: mechanisms, models, and biogeochemical implications</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Boano, Fulvio; Harvey, Judson W.; Marion, Andrea; Packman, Aaron I.; Revelli, Roberto; Ridolfi, Luca; Anders, Wörman 2014-01-01 Fifty years of hyporheic zone research have shown the important role played by the hyporheic zone as an interface between groundwater and surface waters. However, it is only in the last two decades that what began as an empirical science has become a mechanistic science devoted to modeling studies of the complex fluid dynamical and biogeochemical mechanisms occurring in the hyporheic zone. These efforts have led to the picture of surface-subsurface water interactions as regulators of the form and function of fluvial ecosystems. Rather than being isolated systems, surface water bodies continuously interact with the subsurface. Exploration of hyporheic zone processes has led to a new appreciation of their wide reaching consequences for water quality and stream ecology. Modern research aims toward a unified approach, in which processes occurring in the hyporheic zone are key elements for the appreciation, management, and restoration of the whole river environment. In this unifying context, this review summarizes results from modeling studies and field observations about flow and transport processes in the hyporheic zone and describes the theories proposed in hydrology and fluid dynamics developed to quantitatively model and predict the hyporheic transport of water, heat, and dissolved and suspended compounds from sediment grain scale up to the watershed scale. The implications of these processes for stream biogeochemistry and ecology are also discussed." </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014RvGeo..52..603B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014RvGeo..52..603B">Hyporheic flow and transport processes: Mechanisms, models, and biogeochemical implications</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Boano, F.; Harvey, J. W.; Marion, A.; Packman, A. I.; Revelli, R.; Ridolfi, L.; Wörman, A. 2014-12-01 Fifty years of hyporheic zone research have shown the important role played by the hyporheic zone as an interface between groundwater and surface waters. However, it is only in the last two decades that what began as an empirical science has become a mechanistic science devoted to modeling studies of the complex fluid dynamical and biogeochemical mechanisms occurring in the hyporheic zone. These efforts have led to the picture of surface-subsurface water interactions as regulators of the form and function of fluvial ecosystems. Rather than being isolated systems, surface water bodies continuously interact with the subsurface. Exploration of hyporheic zone processes has led to a new appreciation of their wide reaching consequences for water quality and stream ecology. Modern research aims toward a unified approach, in which processes occurring in the hyporheic zone are key elements for the appreciation, management, and restoration of the whole river environment. In this unifying context, this review summarizes results from modeling studies and field observations about flow and transport processes in the hyporheic zone and describes the theories proposed in hydrology and fluid dynamics developed to quantitatively model and predict the hyporheic transport of water, heat, and dissolved and suspended compounds from sediment grain scale up to the watershed scale. The implications of these processes for stream biogeochemistry and ecology are also discussed. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24324589','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24324589">Development of a 3D coupled physical-biogeochemical model for the Marseille coastal area (NW Mediterranean Sea): what complexity is required in the coastal zone?</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Fraysse, Marion; Pinazo, Christel; Faure, Vincent Martin; Fuchs, Rosalie; Lazzari, Paolo; Raimbault, Patrick; Pairaud, Ivane 2013-01-01 Terrestrial inputs (natural and anthropogenic) from rivers, the atmosphere and physical processes strongly impact the functioning of coastal pelagic ecosystems. The objective of this study was to develop a tool for the examination of these impacts on the Marseille coastal area, which experiences inputs from the Rhone River and high rates of atmospheric deposition. Therefore, a new 3D coupled physical/biogeochemical model was developed. Two versions of the biogeochemical model were tested, one model considering only the carbon (C) and nitrogen (N) cycles and a second model that also considers the phosphorus (P) cycle. Realistic simulations were performed for a period of 5 years (2007-2011). The model accuracy assessment showed that both versions of the model were able of capturing the seasonal changes and spatial characteristics of the ecosystem. The model also reproduced upwelling events and the intrusion of Rhone River water into the Bay of Marseille well. Those processes appeared to greatly impact this coastal oligotrophic area because they induced strong increases in chlorophyll-a concentrations in the surface layer. The model with the C, N and P cycles better reproduced the chlorophyll-a concentrations at the surface than did the model without the P cycle, especially for the Rhone River water. Nevertheless, the chlorophyll-a concentrations at depth were better represented by the model without the P cycle. Therefore, the complexity of the biogeochemical model introduced errors into the model results, but it also improved model results during specific events. Finally, this study suggested that in coastal oligotrophic areas, improvements in the description and quantification of the hydrodynamics and the terrestrial inputs should be preferred over increasing the complexity of the biogeochemical model. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5877337','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5877337">Long-Term Cultivation and Metagenomics Reveal Ecophysiology of Previously Uncultivated Thermophiles Involved in Biogeochemical Nitrogen Cycle</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Kato, Shingo; Sakai, Sanae; Hirai, Miho; Tasumi, Eiji; Nishizawa, Manabu; Suzuki, Katsuhiko; Takai, Ken 2018-01-01 Many thermophiles thriving in a natural high-temperature environment remain uncultivated, and their ecophysiological functions in the biogeochemical cycle remain unclear. In the present study, we performed long-term continuous cultivation at 65°C and 70°C using a microbial mat sample, collected from a subsurface geothermal stream, as the inoculum, and reconstructed the whole genome of the maintained populations using metagenomics. Some metagenome-assembled genomes (MAGs), affiliated into phylum-level bacterial and archaeal clades without cultivated representatives, contained genes involved in nitrogen metabolism including nitrification and denitrification. Our results show genetic components and their potential interactions for the biogeochemical nitrogen cycle in a subsurface geothermal environment. PMID:29459499 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1818190C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1818190C">Skill assessment of the coupled physical-biogeochemical operational Mediterranean Forecasting System</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Cossarini, Gianpiero; Clementi, Emanuela; Salon, Stefano; Grandi, Alessandro; Bolzon, Giorgio; Solidoro, Cosimo 2016-04-01 The Mediterranean Monitoring and Forecasting Centre (Med-MFC) is one of the regional production centres of the European Marine Environment Monitoring Service (CMEMS-Copernicus). Med-MFC operatively manages a suite of numerical model systems (3DVAR-NEMO-WW3 and 3DVAR-OGSTM-BFM) that provides gridded datasets of physical and biogeochemical variables for the Mediterranean marine environment with a horizontal resolution of about 6.5 km. At the present stage, the operational Med-MFC produces ten-day forecast: daily for physical parameters and bi-weekly for biogeochemical variables. The validation of the coupled model system and the estimate of the accuracy of model products are key issues to ensure reliable information to the users and the downstream services. Product quality activities at Med-MFC consist of two levels of validation and skill analysis procedures. Pre-operational qualification activities focus on testing the improvement of the quality of a new release of the model system and relays on past simulation and historical data. Then, near real time (NRT) validation activities aim at the routinely and on-line skill assessment of the model forecast and relays on the NRT available observations. Med-MFC validation framework uses both independent (i.e. Bio-Argo float data, in-situ mooring and vessel data of oxygen, nutrients and chlorophyll, moored buoys, tide-gauges and ADCP of temperature, salinity, sea level and velocity) and semi-independent data (i.e. data already used for assimilation, such as satellite chlorophyll, Satellite SLA and SST and in situ vertical profiles of temperature and salinity from XBT, Argo and Gliders) We give evidence that different variables (e.g. CMEMS-products) can be validated at different levels (i.e. at the forecast level or at the level of model consistency) and at different spatial and temporal scales. The fundamental physical parameters temperature, salinity and sea level are routinely validated on daily, weekly and quarterly base </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.B31H0565S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.B31H0565S">Quantifying Hydro-biogeochemical Model Sensitivity in Assessment of Climate Change Effect on Hyporheic Zone Processes</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Song, X.; Chen, X.; Dai, H.; Hammond, G. E.; Song, H. S.; Stegen, J. 2016-12-01 The hyporheic zone is an active region for biogeochemical processes such as carbon and nitrogen cycling, where the groundwater and surface water mix and interact with each other with distinct biogeochemical and thermal properties. The biogeochemical dynamics within the hyporheic zone are driven by both river water and groundwater hydraulic dynamics, which are directly affected by climate change scenarios. Besides that, the hydraulic and thermal properties of local sediments and microbial and chemical processes also play important roles in biogeochemical dynamics. Thus for a comprehensive understanding of the biogeochemical processes in the hyporheic zone, a coupled thermo-hydro-biogeochemical model is needed. As multiple uncertainty sources are involved in the integrated model, it is important to identify its key modules/parameters through sensitivity analysis. In this study, we develop a 2D cross-section model in the hyporheic zone at the DOE Hanford site adjacent to Columbia River and use this model to quantify module and parametric sensitivity on assessment of climate change. To achieve this purpose, We 1) develop a facies-based groundwater flow and heat transfer model that incorporates facies geometry and heterogeneity characterized from a field data set, 2) derive multiple reaction networks/pathways from batch experiments with in-situ samples and integrate temperate dependent reactive transport modules to the flow model, 3) assign multiple climate change scenarios to the coupled model by analyzing historical river stage data, 4) apply a variance-based global sensitivity analysis to quantify scenario/module/parameter uncertainty in hierarchy level. The objectives of the research include: 1) identifing the key control factors of the coupled thermo-hydro-biogeochemical model in the assessment of climate change, and 2) quantify the carbon consumption in different climate change scenarios in the hyporheic zone. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AdWR..109...94M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AdWR..109...94M">Dynamic coupling of subsurface and seepage flows solved within a regularized partition formulation</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Marçais, J.; de Dreuzy, J.-R.; Erhel, J. 2017-11-01 Hillslope response to precipitations is characterized by sharp transitions from purely subsurface flow dynamics to simultaneous surface and subsurface flows. Locally, the transition between these two regimes is triggered by soil saturation. Here we develop an integrative approach to simultaneously solve the subsurface flow, locate the potential fully saturated areas and deduce the generated saturation excess overland flow. This approach combines the different dynamics and transitions in a single partition formulation using discontinuous functions. We propose to regularize the system of partial differential equations and to use classic spatial and temporal discretization schemes. We illustrate our methodology on the 1D hillslope storage Boussinesq equations (Troch et al., 2003). We first validate the numerical scheme on previous numerical experiments without saturation excess overland flow. Then we apply our model to a test case with dynamic transitions from purely subsurface flow dynamics to simultaneous surface and subsurface flows. Our results show that discretization respects mass balance both locally and globally, converges when the mesh or time step are refined. Moreover the regularization parameter can be taken small enough to ensure accuracy without suffering of numerical artefacts. Applied to some hundreds of realistic hillslope cases taken from Western side of France (Brittany), the developed method appears to be robust and efficient. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H44A..04C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H44A..04C">Cumulative effects of wetland drainage on watershed-scale subsurface hydrologic connectivity</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Creed, I. F.; Ameli, A. 2017-12-01 Subsurface hydrologic connectivity influences hydrological, biogeochemical and ecological responses within watersheds. However, information about the location, duration, and frequency of subsurface hydrologic connections within wetlandscapes and between wetlandscapes and streams is often not available. This leads to a lack of understanding of the potential effects of human modifications of the landscape, including wetland degradation and removal, on subsurface hydrologic connectivity and therefore watershed responses. Herein, we develop a computationally efficient, physically-based subsurface hydrologic connectivity model that explicitly characterizes the effects of wetland degradation and removal on the distribution, length, and timing of subsurface hydrologic connectivity within a wetland-dominated watershed in the Prairie Pothole Region of North America. We run the model using a time series of wetland inventories that reflect incremental wetland loss from 1962, to 1993, and to 2009. We also consider a potential future wetland loss scenario based on removal of all wetlands outside of the protected areas of the watershed. Our findings suggest that wetland degradation and removal over this period increased the average length, transit time, and frequency of subsurface hydrologic connections to the regional surface waters, resulting in decreased baseflow in the major river network. This study provides important insights that can be used by wetland managers and policy makers to support watershed-scale wetland protection and restoration plans to improve water resource management. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25803587','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25803587">Relating sub-surface ice features to physiological stress in a climate sensitive mammal, the American pika (Ochotona princeps).</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Wilkening, Jennifer L; Ray, Chris; Varner, Johanna 2015-01-01 The American pika (Ochotona princeps) is considered a sentinel species for detecting ecological effects of climate change. Pikas are declining within a large portion of their range, and ongoing research suggests loss of sub-surface ice as a mechanism. However, no studies have demonstrated physiological responses of pikas to sub-surface ice features. Here we present the first analysis of physiological stress in pikas living in and adjacent to habitats underlain by ice. Fresh fecal samples were collected non-invasively from two adjacent sites in the Rocky Mountains (one with sub-surface ice and one without) and analyzed for glucocorticoid metabolites (GCM). We also measured sub-surface microclimates in each habitat. Results indicate lower GCM concentration in sites with sub-surface ice, suggesting that pikas are less stressed in favorable microclimates resulting from sub-surface ice features. GCM response was well predicted by habitat characteristics associated with sub-surface ice features, such as lower mean summer temperatures. These results suggest that pikas inhabiting areas without sub-surface ice features are experiencing higher levels of physiological stress and may be more susceptible to changing climates. Although post-deposition environmental effects can confound analyses based on fecal GCM, we found no evidence for such effects in this study. Sub-surface ice features are key to water cycling and storage and will likely represent an increasingly important component of water resources in a warming climate. Fecal samples collected from additional watersheds as part of current pika monitoring programs could be used to further characterize relationships between pika stress and sub-surface ice features. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4372430','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4372430">Relating Sub-Surface Ice Features to Physiological Stress in a Climate Sensitive Mammal, the American Pika (Ochotona princeps)</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Wilkening, Jennifer L.; Ray, Chris; Varner, Johanna 2015-01-01 The American pika (Ochotona princeps) is considered a sentinel species for detecting ecological effects of climate change. Pikas are declining within a large portion of their range, and ongoing research suggests loss of sub-surface ice as a mechanism. However, no studies have demonstrated physiological responses of pikas to sub-surface ice features. Here we present the first analysis of physiological stress in pikas living in and adjacent to habitats underlain by ice. Fresh fecal samples were collected non-invasively from two adjacent sites in the Rocky Mountains (one with sub-surface ice and one without) and analyzed for glucocorticoid metabolites (GCM). We also measured sub-surface microclimates in each habitat. Results indicate lower GCM concentration in sites with sub-surface ice, suggesting that pikas are less stressed in favorable microclimates resulting from sub-surface ice features. GCM response was well predicted by habitat characteristics associated with sub-surface ice features, such as lower mean summer temperatures. These results suggest that pikas inhabiting areas without sub-surface ice features are experiencing higher levels of physiological stress and may be more susceptible to changing climates. Although post-deposition environmental effects can confound analyses based on fecal GCM, we found no evidence for such effects in this study. Sub-surface ice features are key to water cycling and storage and will likely represent an increasingly important component of water resources in a warming climate. Fecal samples collected from additional watersheds as part of current pika monitoring programs could be used to further characterize relationships between pika stress and sub-surface ice features. PMID:25803587 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70156316','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70156316">Identifying biogeochemical processes beneath stormwater infiltration ponds in support of a new best management practice for groundwater protection</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> O'Reilly, Andrew M.; Chang, Ni-Bin; Wanielista, Martin P.; Xuan, Zhemin; Schirmer, Mario; Hoehn, Eduard; Vogt, Tobias 2011-01-01 When applying a stormwater infiltration pond best management practice (BMP) for protecting the quality of underlying groundwater, a common constituent of concern is nitrate. Two stormwater infiltration ponds, the SO and HT ponds, in central Florida, USA, were monitored. A temporal succession of biogeochemical processes was identified beneath the SO pond, including oxygen reduction, denitrification, manganese and iron reduction, and methanogenesis. In contrast, aerobic conditions persisted beneath the HT pond, resulting in nitrate leaching into groundwater. Biogeochemical differences likely are related to soil textural and hydraulic properties that control surface/subsurface oxygen exchange. A new infiltration BMP was developed and a full-scale application was implemented for the HT pond. Preliminary results indicate reductions in nitrate concentration exceeding 50% in soil water and shallow groundwater beneath the HT pond. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50..571Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50..571Z">Influence of surface nudging on climatological mean and ENSO feedbacks in a coupled model</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zhu, Jieshun; Kumar, Arun 2018-01-01 Studies have suggested that surface nudging could be an efficient way to reconstruct the subsurface ocean variability, and thus a useful method for initializing climate predictions (e.g., seasonal and decadal predictions). Surface nudging is also the basis for climate models with flux adjustments. In this study, however, some negative aspects of surface nudging on climate simulations in a coupled model are identified. Specifically, a low-resolution version of the NCEP Climate Forecast System, version 2 (CFSv2L) is used to examine the influence of nudging on simulations of climatological mean and on the coupled feedbacks during ENSO. The effect on ENSO feedbacks is diagnosed following a heat budget analysis of mixed layer temperature anomalies. Diagnostics of the climatological mean state indicates that, even though SST biases in all ocean basins, as expected, are eliminated, the fidelity of climatological precipitation, surface winds and subsurface temperature (or the thermocline depth) could be highly ocean basin dependent. This is exemplified by improvements in the climatology of these variables in the tropical Atlantic, but degradations in the tropical Pacific. Furthermore, surface nudging also distorts the dynamical feedbacks during ENSO. For example, while the thermocline feedback played a critical role during the evolution of ENSO in a free simulation, it only played a minor role in the nudged simulation. These results imply that, even though the simulation of surface temperature could be improved in a climate model with surface nudging, the physics behind might be unrealistic. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/sciencecinema/biblio/1191224','SCIGOVIMAGE-SCICINEMA'); return false;" href="http://www.osti.gov/sciencecinema/biblio/1191224">Subsurface Microbes Expanding the Tree of Life</a> <a target="_blank" href="http://www.osti.gov/sciencecinema/">ScienceCinema</a> Banfield, Jillian 2018-02-14 Jillian Banfield, Ph.D., UC Berkeley Professor and Berkeley Lab Earth Sciences Division staff scientist and long-time user of the DOE Joint Genome Instituteâs resources shares her perspective on how the DOE JGI helps advance her research addressing knowledge gaps related to the roles of subsurface microbial communities in biogeochemical cycling. The video was filmed near the town of Rifle, Colorado at the primary field site for Phase I of the Subsurface Systems Scientific Focus Area 2.0 sponsored by the DOE Office of Biological and Environmental Research. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.T23C1938I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.T23C1938I">SURFACE FISSURE FORMATION ABOVE UNDERGROUND COALSEAM FIRES: DIMENSIONLESS RELATIONSHIPS BETWEEN SURFACE FISSURES AND SUBSURFACE SUBSIDENCE</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ide, T. S.; Pollard, D. D.; Orr, F. M. 2009-12-01 Coalbed fires are uncontrolled subsurface fires that occur around the world. These fires are believed to be significant contributors to annual CO2 emissions. Although many of these fires have been burning for decades, researchers have only recently begun to investigate physical mechanisms that control fire behavior. One aspect that is poorly characterized is the relationship between subsurface combustion and surface fissures. At the surface above many fires, long, wide fissures are observed. At a coalbed fire near Durango, Colorado, these fissures form systematic orthogonal patterns that align with regional joints in the Upper Cretaceous Fruitland Formation. Understanding the mechanisms that form and widen these fissures is important, as the fissures are believed to play vital roles in sustaining the combustion in the subsurface by acting as chimneys for the escaping gases and conduits for incoming oxygen. In some of the coalbed fire simulation models available today, these fissures are treated as fixed boundary conditions, but we argue, using field observations and simulation results, that there exists a relationship between the location and magnitude of subsidence caused by the fire and the opening of fissures. Four distinct types of fissures are observed over the coalbed fire near Durango, CO. These fissures are termed ‘molehill’, ‘plateau’, ‘gaping’, and ‘narrow’ based on their surface appearances. Molehill fissures are marked by surface depressions on either side, causing the strata around the opening to form an apex towards the center of the fissure. Plateau fissures show a steep vertical offset on only one side with minimal horizontal displacement. Gaping fissures and narrow fissures are predominantly opening with little evidence for vertical displacements. Gaping fissures are defined as fissures with wide apertures (0.3 ~ 1.5m), while narrow fissures have apertures on the order of centimeters. A boundary element method code was used to show </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27380087','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27380087">Phosphorus Release to Floodwater from Calcareous Surface Soils and Their Corresponding Subsurface Soils under Anaerobic Conditions.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Jayarathne, P D K D; Kumaragamage, D; Indraratne, S; Flaten, D; Goltz, D 2016-07-01 Enhanced phosphorus (P) release from soils to overlying water under flooded, anaerobic conditions has been well documented for noncalcareous and surface soils, but little information is available for calcareous and subsurface soils. We compared the magnitude of P released from 12 calcareous surface soils and corresponding subsurface soils to overlying water under flooded, anaerobic conditions and examined the reasons for the differences. Surface (0-15 cm) and subsurface (15-30 cm) soils were packed into vessels and flooded for 8 wk. Soil redox potential and concentrations of dissolved reactive phosphorus (DRP) and total dissolved Ca, Mg, Fe, and Mn in floodwater and pore water were measured weekly. Soil test P was significantly smaller in subsurface soils than in corresponding surface soils; thus, the P release to floodwater from subsurface soils was significantly less than from corresponding surface soils. Under anaerobic conditions, floodwater DRP concentration significantly increased in >80% of calcareous surface soils and in about 40% of subsurface soils. The increase in floodwater DRP concentration was 2- to 17-fold in surface soils but only 4- to 7-fold in subsurface soils. With time of flooding, molar ratios of Ca/P and Mg/P in floodwater increased, whereas Fe/P and Mn/P decreased, suggesting that resorption and/or reprecipitation of P took place involving Fe and Mn. Results indicate that P release to floodwater under anaerobic conditions was enhanced in most calcareous soils. Surface and subsurface calcareous soils in general behaved similarly in releasing P under flooded, anaerobic conditions, with concentrations released mainly governed by initial soil P concentrations. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3851166','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3851166">Development of a 3D Coupled Physical-Biogeochemical Model for the Marseille Coastal Area (NW Mediterranean Sea): What Complexity Is Required in the Coastal Zone?</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Fraysse, Marion; Pinazo, Christel; Faure, Vincent Martin; Fuchs, Rosalie; Lazzari, Paolo; Raimbault, Patrick; Pairaud, Ivane 2013-01-01 Terrestrial inputs (natural and anthropogenic) from rivers, the atmosphere and physical processes strongly impact the functioning of coastal pelagic ecosystems. The objective of this study was to develop a tool for the examination of these impacts on the Marseille coastal area, which experiences inputs from the Rhone River and high rates of atmospheric deposition. Therefore, a new 3D coupled physical/biogeochemical model was developed. Two versions of the biogeochemical model were tested, one model considering only the carbon (C) and nitrogen (N) cycles and a second model that also considers the phosphorus (P) cycle. Realistic simulations were performed for a period of 5 years (2007–2011). The model accuracy assessment showed that both versions of the model were able of capturing the seasonal changes and spatial characteristics of the ecosystem. The model also reproduced upwelling events and the intrusion of Rhone River water into the Bay of Marseille well. Those processes appeared to greatly impact this coastal oligotrophic area because they induced strong increases in chlorophyll-a concentrations in the surface layer. The model with the C, N and P cycles better reproduced the chlorophyll-a concentrations at the surface than did the model without the P cycle, especially for the Rhone River water. Nevertheless, the chlorophyll-a concentrations at depth were better represented by the model without the P cycle. Therefore, the complexity of the biogeochemical model introduced errors into the model results, but it also improved model results during specific events. Finally, this study suggested that in coastal oligotrophic areas, improvements in the description and quantification of the hydrodynamics and the terrestrial inputs should be preferred over increasing the complexity of the biogeochemical model. PMID:24324589 </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active">6</li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active">7</li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H43P..06D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H43P..06D">Critical Zone Co-dynamics: Quantifying Interactions between Subsurface, Land Surface, and Vegetation Properties Using UAV and Geophysical Approaches</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Dafflon, B.; Leger, E.; Peterson, J.; Falco, N.; Wainwright, H. M.; Wu, Y.; Tran, A. P.; Brodie, E.; Williams, K. H.; Versteeg, R.; Hubbard, S. S. 2017-12-01 Improving understanding and modelling of terrestrial systems requires advances in measuring and quantifying interactions among subsurface, land surface and vegetation processes over relevant spatiotemporal scales. Such advances are important to quantify natural and managed ecosystem behaviors, as well as to predict how watershed systems respond to increasingly frequent hydrological perturbations, such as droughts, floods and early snowmelt. Our study focuses on the joint use of UAV-based multi-spectral aerial imaging, ground-based geophysical tomographic monitoring (incl., electrical and electromagnetic imaging) and point-scale sensing (soil moisture sensors and soil sampling) to quantify interactions between above and below ground compartments of the East River Watershed in the Upper Colorado River Basin. We evaluate linkages between physical properties (incl. soil composition, soil electrical conductivity, soil water content), metrics extracted from digital surface and terrain elevation models (incl., slope, wetness index) and vegetation properties (incl., greenness, plant type) in a 500 x 500 m hillslope-floodplain subsystem of the watershed. Data integration and analysis is supported by numerical approaches that simulate the control of soil and geomorphic characteristic on hydrological processes. Results provide an unprecedented window into critical zone interactions, revealing significant below- and above-ground co-dynamics. Baseline geophysical datasets provide lithological structure along the hillslope, which includes a surface soil horizon, underlain by a saprolite layer and the fractured Mancos shale. Time-lapse geophysical data show very different moisture dynamics in various compartments and locations during the winter and growing season. Integration with aerial imaging reveals a significant linkage between plant growth and the subsurface wetness, soil characteristics and the topographic gradient. The obtained information about the organization and </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.P11C0704B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.P11C0704B">Organic and Inorganic Carbon in the Rio Tinto (Spain) Deep Subsurface System: a Possible Model for Subsurface Carbon and Lithoautotrophs on Mars.</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bonaccorsi, R.; Stoker, C. R.; MARTE Science Team 2007-12-01 The subsurface is the key environment for searching for life on planets lacking surface life. Subsurface ecosystems are of great relevance to astrobiology including the search for past/present life on Mars. Conditions on the Martian surface do not support biological activity but the subsurface might preserve organics and host subsurface life [1]. A key requirement for the analysis of subsurface samples on Mars is the ability to characterize organic vs. inorganic carbon pools. This information is needed to determine if the sample contains organic material of biological origin and/ or to establish if pools of inorganic carbon can support subsurface biospheres. The Mars Analog Rio Tinto Experiment (MARTE) performed deep drilling of cores i.e., down to 165-m depth, in a volcanically-hosted-massive-sulfide deposit at Rio Tinto, Spain, which is considered an important analog of the Sinus Meridiani site on Mars. Results from MARTE suggest the existence of a relatively complex subsurface life including aerobic and anaerobic chemoautotrophs, and strict anaerobic methanogens sustained by Fe and S minerals in anoxic conditions, which is an ideal model analog for a deep subsurface Martian environment. We report here on the distribution of organic (C-org: 0.01-0.3Wt% and inorganic carbon (IC = 0.01-7.0 Wt%) in a subsurface rock system including weathered/oxidized i.e., gossan, and unaltered pyrite stockwork. Cores were analyzed from 3 boreholes (BH-4, BH-7, and BH-8) that penetrated down to a depth of ~165 m into massive sulfide. Nearsurface phyllosilicate rich-pockets contain the highest amounts of organics (0.3Wt%) [2], while the deeper rocks contain the highest amount of carbonates. Assessing the amount of C pools available throughout the RT subsurface brings key insight on the type of trophic system sustaining its microbial ecosystem (i.e., heterotrophs vs. autotrophs) and the biogeochemical relationships that characterize a new type of subsurface biosphere at RT. This </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1324057-integrated-surface-subsurface-permafrost-thermal-hydrology-model-formulation-proof-concept-simulations','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1324057-integrated-surface-subsurface-permafrost-thermal-hydrology-model-formulation-proof-concept-simulations">Integrated surface/subsurface permafrost thermal hydrology: Model formulation and proof-of-concept simulations</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Painter, Scott L.; Coon, Ethan T.; Atchley, Adam L.; ... 2016-08-11 The need to understand potential climate impacts and feedbacks in Arctic regions has prompted recent interest in modeling of permafrost dynamics in a warming climate. A new fine-scale integrated surface/subsurface thermal hydrology modeling capability is described and demonstrated in proof-of-concept simulations. The new modeling capability combines a surface energy balance model with recently developed three-dimensional subsurface thermal hydrology models and new models for nonisothermal surface water flows and snow distribution in the microtopography. Surface water flows are modeled using the diffusion wave equation extended to include energy transport and phase change of ponded water. Variation of snow depth in themore » microtopography, physically the result of wind scour, is also modeled heuristically with a diffusion wave equation. The multiple surface and subsurface processes are implemented by leveraging highly parallel community software. Fully integrated thermal hydrology simulations on the tilted open book catchment, an important test case for integrated surface/subsurface flow modeling, are presented. Fine-scale 100-year projections of the integrated permafrost thermal hydrological system on an ice wedge polygon at Barrow Alaska in a warming climate are also presented. Finally, these simulations demonstrate the feasibility of microtopography-resolving, process-rich simulations as a tool to help understand possible future evolution of the carbon-rich Arctic tundra in a warming climate.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010SPIE.7739E..2EA','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010SPIE.7739E..2EA">Studies on evaluating and removing subsurface damage on the ground surface of CLEARCERAM-Z HS</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Akitaya, Hiroshi; Yamashita, Takuya; Ohshima, Norio; Iye, Masanori; Maihara, Toshinori; Tokoro, Hitoshi; Takahashi, Keisuke 2010-07-01 We evaluated depth of subsurface damage on a ground surface of the ultra low expansion glass-ceramics CLEARCERAMR®-Z HS (CC-Z HS) by Ohara Inc., which is one of the candidates for material for segmented mirrors of the Thirty Meter Telescope. We made polishing spots of Magnetorheological Finishing on the ground surface of CC-Z HS and measured exposed subsurface damage features on the spot surface. We also studied on hydrofluoric acid etching of the CC-Z HS ground surface, which is expected to be an effective method to remove a subsurface damage layer compared with time-consuming polishing. We etched small ground surfaces of CC-Z HS and evaluated its uniformity. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1980GeoRL...7..885M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1980GeoRL...7..885M">Sources of fatty acids in Lake Michigan surface microlayers and subsurface waters</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Meyers, Philip A.; Owen, Robert M. 1980-11-01 Fatty acid and organic carbon contents have been measured in the particulate and dissolved phases of surface microlayer and subsurface water samples collected from Lake Michigan. Concentrations are highest close to fluvial sources and lowest in offshore areas, yet surface/subsurface fractionation is lowest near river mouths and highest in open lake locations. These gradients plus accompanying fatty acid compositional changes indicate that river-borne organic materials are important constituents of coastal Lake Michigan microlayers and that sinking and turbulent resuspension of particulates affect surface film characteristics. Lake neuston and plankton contribute organic components which partially replace potamic materials removed by sinking. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOS.B44B0379X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOS.B44B0379X">Impacts of mesoscale eddies on biogeochemical cycles in the South China Sea</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Xiu, P.; Chai, F.; Guo, M. 2016-02-01 Biogeochemical cycles associated with mesoscale eddies in the South China Sea (SCS) are investigated by using satellite surface chlorophyll concentration, altimeter data, satellite sea surface temperature, and a coupled physical-biogeochemical Pacific Ocean model (ROMS-CoSiNE) simulation for the period from 1991 to 2007. Considering the annual mean, composite analysis reveals that cyclonic eddies are associated with higher concentrations of nutrients, phytoplankton and zooplankton while the anticyclonic eddies are with lower concentrations compared with surrounding waters, which is generally controlled by the eddy pumping mechanism. Dipole structures of vertical fluxes with net upward motion in cyclonic eddies and net downward motion in anticyclonic eddies are also revealed. During the lifetime of an eddy, the evolutions of physical, biological, and chemical structures are not linearly coupled at the eddy core where plankton grow and composition of the community depend not only on the physical and chemical processes but also on the adjustments by the predator-prey relationship. Considering the seasonal variability, we find eddy pumping mechanisms are generally dominant in winter and eddy advection effects are dominant in summer. Over the space, variability of chlorophyll to the west of Luzon Strait and off northwest of Luzon Island are mainly controlled by eddy pumping mechanism. In regions off the Vietnam coast, chlorophyll distributions are generally associated with horizontal eddy advection. This research highlights different mesoscale mechanisms affecting biological structures that can potentially disturb ocean biogeochemical cycling processes in the South China Sea. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20050109883&hterms=mining+topography&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmining%2Btopography','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20050109883&hterms=mining+topography&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmining%2Btopography">Lunar and Martian Sub-surface Habitat Structure Technology Development and Application</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Boston, Penelope J.; Strong, Janet D. 2005-01-01 NASA's human exploration initiative poses great opportunity and great risk for manned missions to the Moon and Mars. Subsidace structures such as caves and lava tubes offer readily available and existing in-situ habitat options. Sub-surface dwellings can provide complete radiation, micro-meteorite and exhaust plume shielding and a moderate and constant temperature environment; they are, therefore, excellent pre-existing habitat risk mitigation elements. Technical challenges to subsurface habitat structure development include surface penetration (digging and mining equipment), environmental pressurization, and psychological environment enhancement requirements. Lunar and Martian environments and elements have many beneficial similarities. This will allow for lunar testing and design development of subsurface habitat structures for Martian application; however, significant differences between lunar and Martian environments and resource elements will mandate unique application development. Mars is NASA's ultimate exploration goal and is known to have many very large lava tubes. Other cave types are plausible. The Moon has unroofed rilles and lava tubes, but further research will, in the near future, define the extent of Lunar and Martian differences and similarities. This paper will discuss Lunar and Martian subsurface habitation technology development challenges and opportunities. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.......223A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.......223A">Structural analyses of a rigid pavement overlaying a sub-surface void</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Adam, Fatih Alperen Pavement failures are very hazardous for public safety and serviceability. These failures in pavements are mainly caused by subsurface voids, cracks, and undulation at the slab-base interface. On the other hand, current structural analysis procedures for rigid pavement assume that the slab-base interface is perfectly planar and no imperfections exist in the sub-surface soil. This assumption would be violated if severe erosion were to occur due to inadequate drainage, thermal movements, and/or mechanical loading. Until now, the effect of erosion was only considered in the faulting performance model, but not with regards to transverse cracking at the mid-slab edge. In this research, the bottom up fatigue cracking potential, caused by the combined effects of wheel loading and a localized imperfection in the form of a void below the mid-slab edge, is studied. A robust stress and surface deflection analysis was also conducted to evaluate the influence of a sub-surface void on layer moduli back-calculation. Rehabilitative measures were considered, which included a study on overlay and fill remediation. A series regression of equations was proposed that provides a relationship between void size, layer moduli stiffness, and the overlay thickness required to reduce the stress to its original pre-void level. The effect of the void on 3D pavement crack propagation was also studied under a single axle load. The amplifications to the stress intensity was shown to be high but could be mitigated substantially if stiff material is used to fill the void and impede crack growth. The pavement system was modeled using the commercial finite element modeling program Abaqus RTM. More than 10,000 runs were executed to do the following analysis: stress analysis of subsurface voids, E-moduli back-calculation of base layer, pavement damage calculations of Beaumont, TX, overlay thickness estimations, and mode I crack analysis. The results indicate that the stress and stress intensity are, on </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050198846','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050198846">High-Frequency Focused Water-Coupled Ultrasound Used for Three-Dimensional Surface Depression Profiling</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Roth, Don J.; Whalen, Mike F.; Hendricks, J. Lynne; Bodis, James R. 2001-01-01 To interface with other solids, many surfaces are engineered via methods such as plating, coating, and machining to produce a functional surface ensuring successful end products. In addition, subsurface properties such as hardness, residual stress, deformation, chemical composition, and microstructure are often linked to surface characteristics. Surface topography, therefore, contains the signatures of the surface and possibly links to volumetric properties, and as a result serves as a vital link between surface design, manufacturing, and performance. Hence, surface topography can be used to diagnose, monitor, and control fabrication methods. At the NASA Glenn Research Center, the measurement of surface topography is important in developing high-temperature structural materials and for profiling the surface changes of materials during microgravity combustion experiments. A prior study demonstrated that focused air-coupled ultrasound at 1 MHz could profile surfaces with a 25-m depth resolution and a 400-m lateral resolution over a 1.4-mm depth range. In this work, we address the question of whether higher frequency focused water-coupled ultrasound can improve on these specifications. To this end, we employed 10- and 25-MHz focused ultrasonic transducers in the water-coupled mode. The surface profile results seen in this investigation for 25-MHz water-coupled ultrasound, in comparison to those for 1-MHz air-coupled ultrasound, represent an 8 times improvement in depth resolution (3 vs. 25 m seen in practice), an improvement of at least 2 times in lateral resolution (180 vs. 400 m calculated and observed in practice), and an improvement in vertical depth range of 4 times (calculated). </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B53H..01C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B53H..01C">Biogeochemical control points in a water-limited critical zone</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chorover, J.; Brooks, P. D.; Gallery, R. E.; McIntosh, J. C.; Olshansky, Y.; Rasmussen, C. 2017-12-01 The routing of water and carbon through complex terrain is postulated to control structure evolution in the sub-humid critical zone of the southwestern US. By combining measurements of land-atmosphere exchange, ecohydrologic partitioning, and subsurface biogeochemistry, we seek to quantify how a heterogeneous (in time and space) distribution of "reactants" impacts both short-term (sub-)catchment response (e.g., pore and surface water chemical dynamics) and long-term landscape evolution (e.g., soil geochemistry/morphology and regolith weathering depth) in watersheds underlain by rhyolite and schist. Instrumented pedons in convergent, planar, and divergent landscape positions show distinct depth-dependent responses to precipitation events. Wetting front propagation, dissolved carbon flux and associated biogeochemical responses (e.g., pulses of CO2 production, O2 depletion, solute release) vary with topography, revealing the influence of lateral subsidies of water and carbon. The impacts of these episodes on the evolution of porous media heterogeneity is being investigated by statistical analysis of pore water chemistry, chemical/spectroscopic studies of solid phase organo-mineral products, sensor-derived water characteristic curves, and quantification of co-located microbial community activity/composition. Our results highlight the interacting effects of critical zone structure and convergent hydrologic flows in the evolution of biogeochemical control points. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B11G1747M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B11G1747M">Can Surface Seeps Elucidate Carbon Cycling in Terrestrial Subsurface Ecosystems in Ophiolite-hosted Serpentinizing Fluids?</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Meyer-Dombard, D. R.; Cardace, D.; Woycheese, K. M.; Vallalar, B.; Arcilla, C. A. 2017-12-01 Serpentinization in ophiolite-hosted regimes produces highly reduced, high pH fluids that are often characterized as having copious H2 and CH4 gas, little/no inorganic carbon, and limited electron acceptors. Subsurface microbial biomes shift as deeply-sourced fluids reach the oxygenated surface environment, where organisms capable of metabolizing O2 thrive (Woycheese et al., 2015). The relationship, connection, and communication between surface expressions (such as fluid seeps) and the subsurface biosphere is still largely unexplored. Our work in the Zambales and Palawan ophiolites (Philippines) defines surface habitats with geochemistry, targeted culturing efforts, and community analysis (Cardace et al., 2015; Woycheese et al., 2015). Fluids in the spring sources are largely `typical' and fall in the pH range of 9-11.5 with measurable gas escaping from the subsurface (H2 and CH4 > 10uM, CO2 > 1 mM; Cardace et al., 2015). Outflow channels extend from the source pools. These surface data encourage prediction of the subsurface metabolic landscape. To understand how carbon cycling in the subsurface and surface environments might be related, we focus on community analysis, culturing, and the geochemical context of the ecosystem. Shotgun metagenomic analyses indicate carbon cycling is reliant on methanogenesis, acetogenesis, sulfate reduction, and H2 and CH4 oxidation. Methyl coenzyme M reductase, and formylmethanofuran dehydrogenase were detected, and relative abundance increased near the near-anoxic spring source. In this tropical climate, cellulose is also a likely carbon source, possibly even in the subsurface. Enrichment cultures [pH 8-12] and strains [pH 8-10] from Zambales springs show degradation of cellulose and production of cellulase. DIC, DOC, and 13C of solid substrates show mixed autotrophic/heterotrophic activity. Results indicate a metabolically flexible surface community, and suggest details about carbon cycling in the subsurface. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EurSS..50.1506Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EurSS..50.1506Z">Characteristics of Nitrogen Loss through Surface-Subsurface Flow on Red Soil Slopes of Southeast China</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zheng, Haijin; Liu, Zhao; Zuo, Jichao; Wang, Lingyun; Nie, Xiaofei 2017-12-01 Soil nitrogen (N) loss related to surface flow and subsurface flow (including interflow and groundwater flow) from slope lands is a global issue. A lysimetric experiment with three types of land cover (grass cover, GC; litter cover, LC; and bare land, BL) were carried out on a red soil slope land in southeast China. Total Nitrogen (TN) loss through surface flow, interflow and groundwater flow was observed under 28 natural precipitation events from 2015 to 2016. TN concentrations from subsurface flow on BL and LC plots were, on average, 2.7-8.2 and 1.5-4.4 times greater than TN concentrations from surface flow, respectively; the average concentration of TN from subsurface flow on GC was about 36-56% of that recorded from surface flow. Surface flow, interflow and groundwater flow contributed 0-15, 2-9 and 76-96%, respectively, of loss load of TN. Compared with BL, GC and LC intercepted 83-86% of TN loss through surface runoff; GC intercepted 95% of TN loss through subsurface flow while TN loss through subsurface flow on LC is 2.3 times larger than that on BL. In conclusion, subsurface flow especially groundwater flow is the dominant hydrological rout for N loss that is usually underestimated. Grass cover has the high retention of N runoff loss while litter mulch will increase N leaching loss. These findings provide scientific support to control N runoff loss from the red soil slope lands by using suitable vegetation cover and mulching techniques. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70039045','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70039045">Cyclic biogeochemical processes and nitrogen fate beneath a subtropical stormwater infiltration basin</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> O'Reilly, Andrew M.; Chang, Ni-Bin; Wanielista, Martin P. 2012-01-01 A stormwater infiltration basin in north–central Florida, USA, was monitored from 2007 through 2008 to identify subsurface biogeochemical processes, with emphasis on N cycling, under the highly variable hydrologic conditions common in humid, subtropical climates. Cyclic variations in biogeochemical processes generally coincided with wet and dry hydrologic conditions. Oxidizing conditions in the subsurface persisted for about one month or less at the beginning of wet periods with dissolved O2 and NO3- showing similar temporal patterns. Reducing conditions in the subsurface evolved during prolonged flooding of the basin. At about the same time O2 and NO3- reduction concluded, Mn, Fe and SO42- reduction began, with the onset of methanogenesis one month later. Reducing conditions persisted up to six months, continuing into subsequent dry periods until the next major oxidizing infiltration event. Evidence of denitrification in shallow groundwater at the site is supported by median NO3-–N less than 0.016 mg L-1, excess N2 up to 3 mg L-1 progressively enriched in δ15N during prolonged basin flooding, and isotopically heavy δ15N and δ18O of NO3- (up to 25‰ and 15‰, respectively). Isotopic enrichment of newly infiltrated stormwater suggests denitrification was partially completed within two days. Soil and water chemistry data suggest that a biogeochemically active zone exists in the upper 1.4 m of soil, where organic carbon was the likely electron donor supplied by organic matter in soil solids or dissolved in infiltrating stormwater. The cyclic nature of reducing conditions effectively controlled the N cycle, switching N fate beneath the basin from NO3- leaching to reduction in the shallow saturated zone. Results can inform design of functionalized soil amendments that could replace the native soil in a stormwater infiltration basin and mitigate potential NO3- leaching to groundwater by replicating the biogeochemical conditions under the observed basin. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.P21A2076R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.P21A2076R">Estimating Surface and Subsurface Ice Abundance on Mercury Using a Thermophysical Model</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rubanenko, L.; Mazarico, E.; Neumann, G. A.; Paige, D. A. 2016-12-01 The small obliquity of the Moon and Mercury causes some topographic features near their poles to cast permanent shadows for geologic time periods. In the past, these permanently shadowed regions (PSRs) were found to have low enough temperatures to trap surface and subsurface water ice. On Mercury, high normal albedo is correlated with maximum temperatures <100 m and high radar backscatter, possibly indicating the presence of surface ice. Areas with slightly higher maximum temperatures were measured to have a decreased albedo, postulated to contain of organic materials overlaying buried ice. We evaluate this theory by employing a thermophysical model that considers insolation, scattering, thermal emissions and subsurface conduction. We model the area fraction of surface and subsurface cold-traps on realistic topography at scales of ˜500 m , recorded by the Mercury Laster Altimeter (MLA) on board the MErcury Surface, Space ENviroment, GEochemistry and Ranging (MESSENGER) spacecraft. At smaller scales, below the instrument threshold, we consider a statistical description of the surface assuming a Gaussian slope distribution. Using the modeled cold-trap area fraction we calculate the expected surface albedo and compare it to MESSENGER's near-infrared surface reflectance data. Last, we apply our model to other airless small-obliquity planetary bodies such as the Moon and Ceres in order to explain other correlations between the maximum temperature and normal albedo. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70012525','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70012525">A field evaluation of subsurface and surface runoff. II. Runoff processes</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Pilgrim, D.H.; Huff, D.D.; Steele, T.D. 1978-01-01 Combined use of radioisotope tracer, flow rate, specific conductance and suspended-sediment measurements on a large field plot near Stanford, California, has provided more detailed information on surface and subsurface storm runoff processes than would be possible from any single approach used in isolation. Although the plot was surficially uniform, the runoff processes were shown to be grossly nonuniform, both spatially over the plot, and laterally and vertically within the soil. The three types of processes that have been suggested as sources of storm runoff (Horton-type surface runoff, saturated overland flow, and rapid subsurface throughflow) all occurred on the plot. The nonuniformity of the processes supports the partial- and variable-source area concepts. Subsurface storm runoff occurred in a saturated layer above the subsoil horizon, and short travel times resulted from flow through macropores rather than the soil matrix. Consideration of these observations would be necessary for physically realistic modeling of the storm runoff process. ?? 1978. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.3017K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.3017K">Study of the plankton ecosystem variability using a coupled hydrodynamics biogeochemical modelling in the Mediterranean Sea</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kessouri, Fayçal; Ulses, Caroline; Estournel, Claude; Marsaleix, Patrick 2015-04-01 The Mediterranean Sea presents a wide variety of trophic regimes since the large and intense spring bloom of the North-Western Mediterranean Sea (NWMS) that follows winter convection to the extreme oligotrophic regions of the South-eastern basin. The Mediterranean Sea displays a strong time variability revealing its high sensitivity to climate and anthropic pressures. In this context, it is crucial to develop tools allowing to understand the evolution of the Mediterranean hydrology and marine ecosystem as a response to external forcing. Numerical coupled hydrodynamic and biogeochemical modelling carefully calibrated in the different regions of the basin is the only tool that can answer this question. However, this important step of calibration is particularly difficult because of the lack of coherent sets of data describing the seasonal evolution of the main parameters characterizing the physical and biogeochemical environment in the different sub-basins. The chlorophyll satellite data from 4km MODIS products, a multiple in situ data from MerMEX MOOSE and DEWEX cruises and Bio-Argo floats from NAOS project are believed to be an opportunity to strongly improve the realism of ecosystem models. The model is a 3D coupled simulation using NemoMed12 for hydrodynamics and ECO 3MS for biogeochemistry and covers the whole Mediterranean Sea and runs at 1/12°. The relevant variables mentioned are phytoplankton, organic and inorganic matters faced to water masses dynamics, over ten years since summer 2003. After a short validation, we will expose two topics: First, through this coupling we quantify the nutrients fluxes across the Mediterranean straits over the years. For example, we found an annual net average around 150 Giga moles NO3 per year at Gibraltar, where we expect low annual fluctuations. In contrast, the Strait of Sicily shows greater annual variability going from 70 to 92 Giga moles NO3 per year. All the fluxes are resumed in a detailed diagram of the transport </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B53J..03Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B53J..03Y">Subsurface soil carbon losses offset surface carbon accumulation in abandoned agricultural fields</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yang, Y.; Knops, J. M. H. 2017-12-01 Soil carbon is widely understood to accumulate after agricultural abandonment. However, most of the studies have been focused on shallow depths (10 to 30 cm), and there is a lack of deeper soil carbon data. It was reported that in temperate grasslands, 58% of the soil organic carbon in the first meter was stored between 20 and 100 cm, and organic matter in deeper soil might also be susceptible to agricultural disturbance. We used repeated sampling in 2001 and 2014 to directly measure rates of soil carbon change in both surface and subsurface soil in 21 abandoned agricultural fields at Cedar Creek Ecosystem Science Reserve, MN. Congruent with many other studies, we found carbon accumulated 384.2 C g/m2 in surface soil (0 - 20 cm) over the 13 years. However, we also found carbon pool declined 688.1 C g/m2 in the subsurface soil (40-100 cm), which resulted in a net total loss of soil carbon. We investigated the ecosystem carbon pools and fluxes to explore the mechanisms of the observed soil carbon changes. We found root carbon was not significantly correlated with soil carbon in any of the depth. In situ soil incubation showed nitrogen mineralization rates in subsurface soil are lower than that of surface soil. However, the estimated nitrogen and carbon output through decomposition is higher than inputs from roots, therefore leading to carbon loss in subsurface soil. These results suggest that the decomposition of soil organic matter by microorganisms in subsurface soil is significant, and should be incorporated in ecosystem carbon budget models. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PrOce.138..399P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PrOce.138..399P">Simulating anchovy's full life cycle in the northern Aegean Sea (eastern Mediterranean): A coupled hydro-biogeochemical-IBM model</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Politikos, D.; Somarakis, S.; Tsiaras, K. P.; Giannoulaki, M.; Petihakis, G.; Machias, A.; Triantafyllou, G. 2015-11-01 A 3-D full life cycle population model for the North Aegean Sea (NAS) anchovy stock is presented. The model is two-way coupled with a hydrodynamic-biogeochemical model (POM-ERSEM). The anchovy life span is divided into seven life stages/age classes. Embryos and early larvae are passive particles, but subsequent stages exhibit active horizontal movements based on specific rules. A bioenergetics model simulates the growth in both the larval and juvenile/adult stages, while the microzooplankton and mesozooplankton fields of the biogeochemical model provide the food for fish consumption. The super-individual approach is adopted for the representation of the anchovy population. A dynamic egg production module, with an energy allocation algorithm, is embedded in the bioenergetics equation and produces eggs based on a new conceptual model for anchovy vitellogenesis. A model simulation for the period 2003-2006 with realistic initial conditions reproduced well the magnitude of population biomass and daily egg production estimated from acoustic and daily egg production method (DEPM) surveys, carried out in the NAS during June 2003-2006. Model simulated adult and egg habitats were also in good agreement with observed spatial distributions of acoustic biomass and egg abundance in June. Sensitivity simulations were performed to investigate the effect of different formulations adopted for key processes, such as reproduction and movement. The effect of the anchovy population on plankton dynamics was also investigated, by comparing simulations adopting a two-way or a one-way coupling of the fish with the biogeochemical model. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002ESASP.518..313E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002ESASP.518..313E">Robotic astrobiology - the need for sub-surface penetration of Mars</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ellery, A.; Ball, A.; Cockell, C.; Coste, P.; Dickensheets, D.; Edwards, H.; Hu, H.; Kolb, C.; Lammer, H.; Lorenz, R.; McKee, G.; Richter, L.; Winfield, A.; Welch, C. 2002-11-01 Recent interest in the astrobiological investigation of Mars has culminated in the only planned astrobiology-focussed robotic mission to Mars - the Beagle2 mission to be carried to Mars by the Mars Express spacecraft in 2003. Beagle2 will be primarily investigating the surface and near-surface environment of Mars. However, the results from the Viking Mars lander indicated that the Martian surface is saturated in peroxides and super-oxides which would rapidly degrade any organic material. Furthermore, recent models of gardening due to meteoritic impacts on the Martian surface suggest that the depth of this oxidising layer could extend to depths of 2-3m. Given that the discovery of organic fossilised residues will be the primary target for astrobiological investigation, this implies that future robotic astrobiology missions to Mars must penetrate to below these depths. The need to penetrate into the sub-surface of Mars has recently been given greater urgency with the discovery of extensive water ice-fields as little as 1m from the surface. We review the different technologies that make this penetration into the sub-surface a practical possibility on robotic missions. We further briefly present one such implementation of these technologies through the use of ground-penetrating moles - The Vanguard Mars mission proposal. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.H43D1473L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.H43D1473L">Effects of leaf area index on the coupling between water table, land surface energy fluxes, and planetary boundary layer at the regional scale</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lu, Y.; Rihani, J.; Langensiepen, M.; Simmer, C. 2013-12-01 Vegetation plays an important role in the exchange of moisture and energy at the land surface. Previous studies indicate that vegetation increases the complexity of the feedbacks between the atmosphere and subsurface through processes such as interception, root water uptake, leaf surface evaporation, and transpiration. Vegetation cover can affect not only the interaction between water table depth and energy fluxes, but also the development of the planetary boundary layer. Leaf Area Index (LAI) is shown to be a major factor influencing these interactions. In this work, we investigate the sensitivity of water table, surface energy fluxes, and atmospheric boundary layer interactions to LAI as a model input. We particularly focus on the role LAI plays on the location and extent of transition zones of strongest coupling and how this role changes over seasonal timescales for a real catchment. The Terrestrial System Modelling Platform (TerrSysMP), developed within the Transregional Collaborative Research Centre 32 (TR32), is used in this study. TerrSysMP consists of the variably saturated groundwater model ParFlow, the land surface model Community Land Model (CLM), and the regional climate and weather forecast model COSMO (COnsortium for Small-scale Modeling). The sensitivity analysis is performed over a range of LAI values for different vegetation types as extracted from the Moderate Resolution Imaging Spectroradiometer (MODIS) dataset for the Rur catchment in Germany. In the first part of this work, effects of vegetation structure on land surface energy fluxes and their connection to water table dynamics are studied using the stand-alone CLM and the coupled subsurface-surface components of TerrSysMP (ParFlow-CLM), respectively. The interconnection between LAI and transition zones of strongest coupling are investigated and analyzed through a subsequent set of subsurface-surface-atmosphere coupled simulations implementing the full TerrSysMP model system. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active">7</li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active">8</li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1328276-critical-biogeochemical-functions-subsurface-associated-bacteria-from-new-phyla-little-studied-lineages','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1328276-critical-biogeochemical-functions-subsurface-associated-bacteria-from-new-phyla-little-studied-lineages">Critical biogeochemical functions in the subsurface are associated with bacteria from new phyla and little studied lineages</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Hug, Laura A.; Thomas, Brian C.; Sharon, Itai; ... 2015-07-22 Nitrogen, sulfur and carbon fluxes in the terrestrial subsurface are determined by the intersecting activities of microbial community members, yet the organisms responsible are largely unknown. Metagenomic methods can identify organisms and functions, but genome recovery is often precluded by data complexity. To address this limitation, we developed subsampling assembly methods to re-construct high-quality draft genomes from complex samples. Here, we applied these methods to evaluate the interlinked roles of the most abundant organisms in biogeochemical cycling in the aquifer sediment. Community proteomics confirmed these activities. The eight most abundant organisms belong to novel lineages, and two represent phyla withmore » no previously sequenced genome. Four organisms are predicted to fix carbon via the Calvin Benson Bassham, Wood Ljungdahl or 3-hydroxyproprionate/4-hydroxybutarate pathways. The profiled organisms are involved in the network of denitrification, dissimilatory nitrate reduction to ammonia, ammonia oxidation and sulfate reduction/oxidation, and require substrates supplied by other community members. An ammonium-oxidizing Thaumarchaeote is the most abundant community member, despite low ammonium concentrations in the groundwater. Finally, this organism likely benefits from two other relatively abundant organisms capable of producing ammonium from nitrate, which is abundant in the groundwater. Overall, dominant members of the microbial community are interconnected through exchange of geochemical resources.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12708672','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12708672">Surface and subsurface geologic risk factors to ground water affecting brownfield redevelopment potential.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Kaufman, Martin M; Murray, Kent S; Rogers, Daniel T 2003-01-01 A model is created for assessing the redevelopment potential of brownfields. The model is derived from a space and time conceptual framework that identifies and measures the surface and subsurface risk factors present at brownfield sites. The model then combines these factors with a contamination extent multiplier at each site to create an index of redevelopment potential. Results from the application of the model within an urbanized watershed demonstrate clear differences between the redevelopment potential present within five different near-surface geologic units, with those units containing clay being less vulnerable to subsurface contamination. With and without the extent multiplier, the total risk present at the brownfield sites within all the geologic units is also strongly correlated to the actual costs of remediation. Thus, computing the total surface and subsurface risk within a watershed can help guide the remediation efforts at broad geographic scales, and prioritize the locations for redevelopment. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.H13L..03O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.H13L..03O">Mechanisms of Arsenic Mobilization and Attenuation in Subsurface Sediments</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> O'Day, P. A.; Illera, V.; Root, R.; Choi, S.; Vlassopoulos, D. 2007-12-01 This talk will review molecular mechanisms of As mobilization and attenuation in subsurface sediments using examples from recent field studies that represent a range in oxidation-redox (redox) potential. As a ubiquitous trace element in sediments, As speciation and fate is linked to the abundance and biogeochemical behavior of the generally more abundant redox-active elements Fe, S, and Mn. All four elements are subject to oxidation, reduction, and pH-dependent processes such as sorption, desorption, precipitation, and dissolution, and which may include both biotic and abiotic reaction steps. We have used spectroscopic interrogation and geochemical modeling to characterize As speciation in subsurface sediments in several contrasting environments, including high and low S and Fe settings. Aquifers most at risk for contamination by As include those that are rich in organic matter and nutrients, stimulating high rates of microbial reduction and creating anoxic conditions, but limited in labile or available S and/or Fe that remove As by precipitation or adsorption. In subsurface sediments with low labile S and Fe, laboratory experiments and spectroscopic studies suggest that sediment Mn minerals are important in the oxidation of sorbed As(III) to As(V), but that they have a limited oxidation capacity. Arsenic attenuation and mobilization in the subsurface are affected by seasonal variations when hydraulic conditions are influenced by surface infiltration, which may induce transitions from oxidized to reduced conditions (or vice versa) in porewater. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1711202H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1711202H">Modeling greenhouse gas emissions and nutrient transport in managed arable soils with a fully coupled hydrology-biogeochemical modeling system</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Haas, Edwin; Klatt, Steffen; Kiese, Ralf; Butterbach-Bahl, Klaus; Kraft, Philipp; Breuer, Lutz 2015-04-01 The use of mineral nitrogen fertilizer sustains the global food production and therefore the livelihood of human kind. The rise in world population will put pressure on the global agricultural system to increase its productivity leading most likely to an intensification of mineral nitrogen fertilizer use. The fate of excess nitrogen and its distribution within landscapes is manifold. Process knowledge on the site scale has rapidly grown in recent years and models have been developed to simulate carbon and nitrogen cycling in managed ecosystems on the site scale. Despite first regional studies, the carbon and nitrogen cycling on the landscape or catchment scale is not fully understood. In this study we present a newly developed modelling approach by coupling the fully distributed hydrology model CMF (catchment modelling framework) to the process based regional ecosystem model LandscapeDNDC for the investigation of hydrological processes and carbon and nitrogen transport and cycling, with a focus on nutrient displacement and resulting greenhouse gas emissions in various virtual landscapes / catchment to demonstrate the capabilities of the modelling system. The modelling system was applied to simulate water and nutrient transport at the at the Yanting Agro-ecological Experimental Station of Purple Soil, Sichuan province, China. The catchment hosts cypress forests on the outer regions, arable fields on the sloping croplands cultivated with wheat-maize rotations and paddy rice fields in the lowland. The catchment consists of 300 polygons vertically stratified into 10 soil layers. Ecosystem states (soil water content and nutrients) and fluxes (evapotranspiration) are exchanged between the models at high temporal scales (hourly to daily) forming a 3-dimensional model application. The water flux and nutrients transport in the soil is modelled using a 3D Richards/Darcy approach for subsurface fluxes with a kinematic wave approach for surface water runoff and the </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1430450-multiscale-investigation-biofilm-distribution-its-impact-macroscopic-biogeochemical-reaction-rates-biofilm-distribution-rate-scaling','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1430450-multiscale-investigation-biofilm-distribution-its-impact-macroscopic-biogeochemical-reaction-rates-biofilm-distribution-rate-scaling">Multiscale Investigation on Biofilm Distribution and Its Impact on Macroscopic Biogeochemical Reaction Rates: BIOFILM DISTRIBUTION AND RATE SCALING</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Yan, Zhifeng; Liu, Chongxuan; Liu, Yuanyuan Biofilms are critical locations for biogeochemical reactions in the subsurface environment. The occurrence and distribution of biofilms at microscale as well as their impacts on macroscopic biogeochemical reaction rates are still poorly understood. This paper investigated the formation and distributions of biofilms in heterogeneous sediments using multiscale models, and evaluated the effects of biofilm heterogeneity on local and macroscopic biogeochemical reaction rates. Sediment pore structures derived from X-ray computed tomography were used to simulate the microscale flow dynamics and biofilm distribution in the sediment column. The response of biofilm formation and distribution to the variations in hydraulic and chemical propertiesmore » was first examined. One representative biofilm distribution was then utilized to evaluate its effects on macroscopic reaction rates using nitrate reduction as an example. The results revealed that microorganisms primarily grew on the surfaces of grains and aggregates near preferential flow paths where both electron donor and acceptor were readily accessible, leading to the heterogeneous distribution of biofilms in the sediments. The heterogeneous biofilm distribution decreased the macroscopic rate of biogeochemical reactions as compared with those in homogeneous cases. Operationally considering the heterogeneous biofilm distribution in macroscopic reactive transport models such as using dual porosity domain concept can significantly improve the prediction of biogeochemical reaction rates. Overall, this study provided important insights into the biofilm formation and distribution in soils and sediments as well as their impacts on the macroscopic manifestation of reaction rates.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70019093','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70019093">Deep subsurface microbial processes</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Lovley, D.R.; Chapelle, F.H. 1995-01-01 Information on the microbiology of the deep subsurface is necessary in order to understand the factors controlling the rate and extent of the microbially catalyzed redox reactions that influence the geophysical properties of these environments. Furthermore, there is an increasing threat that deep aquifers, an important drinking water resource, may be contaminated by man's activities, and there is a need to predict the extent to which microbial activity may remediate such contamination. Metabolically active microorganisms can be recovered from a diversity of deep subsurface environments. The available evidence suggests that these microorganisms are responsible for catalyzing the oxidation of organic matter coupled to a variety of electron acceptors just as microorganisms do in surface sediments, but at much slower rates. The technical difficulties in aseptically sampling deep subsurface sediments and the fact that microbial processes in laboratory incubations of deep subsurface material often do not mimic in situ processes frequently necessitate that microbial activity in the deep subsurface be inferred through nonmicrobiological analyses of ground water. These approaches include measurements of dissolved H2, which can predict the predominant microbially catalyzed redox reactions in aquifers, as well as geochemical and groundwater flow modeling, which can be used to estimate the rates of microbial processes. Microorganisms recovered from the deep subsurface have the potential to affect the fate of toxic organics and inorganic contaminants in groundwater. Microbial activity also greatly influences 1 the chemistry of many pristine groundwaters and contributes to such phenomena as porosity development in carbonate aquifers, accumulation of undesirably high concentrations of dissolved iron, and production of methane and hydrogen sulfide. Although the last decade has seen a dramatic increase in interest in deep subsurface microbiology, in comparison with the study of </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/908925','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/908925">Carbon sequestration by patch fertilization: A comprehensive assessment using coupled physical-ecological-biogeochemical models</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Sarmiento, Jorge L.; Gnanadesikan, Anand; Gruber, Nicolas 2007-06-21 This final report summarizes research undertaken collaboratively between Princeton University, the NOAA Geophysical Fluid Dynamics Laboratory on the Princeton University campus, the State University of New York at Stony Brook, and the University of California, Los Angeles between September 1, 2000, and November 30, 2006, to do fundamental research on ocean iron fertilization as a means to enhance the net oceanic uptake of CO2 from the atmosphere. The approach we proposed was to develop and apply a suite of coupled physical-ecological-biogeochemical models in order to (i) determine to what extent enhanced carbon fixation from iron fertilization will lead to anmore » increase in the oceanic uptake of atmospheric CO2 and how long this carbon will remain sequestered (efficiency), and (ii) examine the changes in ocean ecology and natural biogeochemical cycles resulting from iron fertilization (consequences). The award was funded in two separate three-year installments: September 1, 2000 to November 30, 2003, for a project entitled “Ocean carbon sequestration by fertilization: An integrated biogeochemical assessment.” A final report was submitted for this at the end of 2003 and is included here as Appendix 1; and, December 1, 2003 to November 30, 2006, for a follow-on project under the same grant number entitled “Carbon sequestration by patch fertilization: A comprehensive assessment using coupled physical-ecological-biogeochemical models.” This report focuses primarily on the progress we made during the second period of funding subsequent to the work reported on in Appendix 1. When we began this project, we were thinking almost exclusively in terms of long-term fertilization over large regions of the ocean such as the Southern Ocean, with much of our focus being on how ocean circulation and biogeochemical cycling would interact to control the response to a given fertilization scenario. Our research on these types of scenarios, which was carried out largely </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2696352','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2696352">Fluorescence tomography characterization for sub-surface imaging with protoporphyrin IX</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Kepshire, Dax; Davis, Scott C.; Dehghani, Hamid; Paulsen, Keith D.; Pogue, Brian W. 2009-01-01 Optical imaging of fluorescent objects embedded in a tissue simulating medium was characterized using non-contact based approaches to fluorescence remittance imaging (FRI) and sub-surface fluorescence diffuse optical tomography (FDOT). Using Protoporphyrin IX as a fluorescent agent, experiments were performed on tissue phantoms comprised of typical in-vivo tumor to normal tissue contrast ratios, ranging from 3.5:1 up to 10:1. It was found that tomographic imaging was able to recover interior inclusions with high contrast relative to the background; however, simple planar fluorescence imaging provided a superior contrast to noise ratio. Overall, FRI performed optimally when the object was located on or close to the surface and, perhaps most importantly, FDOT was able to recover specific depth information about the location of embedded regions. The results indicate that an optimal system for localizing embedded fluorescent regions should combine fluorescence reflectance imaging for high sensitivity and sub-surface tomography for depth detection, thereby allowing more accurate localization in all three directions within the tissue. PMID:18545571 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AdWR..109..302M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AdWR..109..302M">Geophysical characterisation of the groundwater-surface water interface</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> McLachlan, P. J.; Chambers, J. E.; Uhlemann, S. S.; Binley, A. 2017-11-01 Interactions between groundwater (GW) and surface water (SW) have important implications for water quantity, water quality, and ecological health. The subsurface region proximal to SW bodies, the GW-SW interface, is crucial as it actively regulates the transfer of nutrients, contaminants, and water between GW systems and SW environments. However, geological, hydrological, and biogeochemical heterogeneity in the GW-SW interface makes it difficult to characterise with direct observations. Over the past two decades geophysics has been increasingly used to characterise spatial and temporal variability throughout the GW-SW interface. Geophysics is a powerful tool in evaluating structural heterogeneity, revealing zones of GW discharge, and monitoring hydrological processes. Geophysics should be used alongside traditional hydrological and biogeochemical methods to provide additional information about the subsurface. Further integration of commonly used geophysical techniques, and adoption of emerging techniques, has the potential to improve understanding of the properties and processes of the GW-SW interface, and ultimately the implications for water quality and environmental health. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24115624','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24115624">Patterns and drivers of bacterial α- and β-diversity across vertical profiles from surface to subsurface sediments.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Luna, Gian Marco; Corinaldesi, Cinzia; Rastelli, Eugenio; Danovaro, Roberto 2013-10-01 We investigated the patterns and drivers of bacterial α- and β-diversity, along with viral and prokaryotic abundance and the carbon production rates, in marine surface and subsurface sediments (down to 1 m depth) in two habitats: vegetated sediments (seagrass meadow) and non-vegetated sediments. Prokaryotic abundance and production decreased with depth in the sediment, but cell-specific production rates and the virus-to-prokaryote ratio increased, highlighting unexpectedly high activity in the subsurface. The highest diversity was observed in vegetated sediments. Bacterial β-diversity between sediment horizons was high, and only a minor number of taxa was shared between surface and subsurface layers. Viruses significantly contributed to explain α- and β-diversity patterns. Despite potential limitations due to the only use of fingerprinting techniques, this study indicates that the coastal subsurface host highly active and diversified bacterial assemblages, that subsurface cells are more active than expected and that viruses promote β-diversity and stimulate bacterial metabolism in subsurface layers. The limited number of taxa shared between habitats, and between surface and subsurface sediment horizons, suggests that future investigations of the shallow subsurface will provide insights into the census of bacterial diversity, and the comprehension of the patterns and drivers of prokaryotic diversity in marine ecosystems. © 2013 John Wiley & Sons Ltd and Society for Applied Microbiology. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19770025483','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19770025483">Drogue performance evaluation. Part 1: Data acquisition. [for accurate description of subsurface water circulation</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Johnson, R. E. 1975-01-01 Surface buoy/subsurface drogue drag coupling was investigated. Data acquisition methods and techniques derived from several experimental cruises on the Chesapeake Bay are presented. Four buoys were utilized: three coupled to steel plates rigidly attached to each other at right angles and at various depths; and one spar type that did not require drag plates. Data from these surface floats and the drogue depth combinations were processed. Errors in tracking the surface buoys are discussed. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018BGeo...15.1335L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018BGeo...15.1335L">Towards an assessment of riverine dissolved organic carbon in surface waters of the western Arctic Ocean based on remote sensing and biogeochemical modeling</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Le Fouest, Vincent; Matsuoka, Atsushi; Manizza, Manfredi; Shernetsky, Mona; Tremblay, Bruno; Babin, Marcel 2018-03-01 Future climate warming of the Arctic could potentially enhance the load of terrigenous dissolved organic carbon (tDOC) of Arctic rivers due to increased carbon mobilization within watersheds. A greater flux of tDOC might impact the biogeochemical processes of the coastal Arctic Ocean (AO) and ultimately its capacity to absorb atmospheric CO2. In this study, we show that sea-surface tDOC concentrations simulated by a physical-biogeochemical coupled model in the Canadian Beaufort Sea for 2003-2011 compare favorably with estimates retrieved by satellite imagery. Our results suggest that, over spring-summer, tDOC of riverine origin contributes to 35 % of primary production and that an equivalent of ˜ 10 % of tDOC is exported westwards with the potential of fueling the biological production of the eastern Alaskan nearshore waters. The combination of model and satellite data provides promising results to extend this work to the entire AO so as to quantify, in conjunction with in situ data, the expected changes in tDOC fluxes and their potential impact on the AO biogeochemistry at basin scale. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010OcDyn..60.1061Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010OcDyn..60.1061Z">Coupled assimilation for an intermediated coupled ENSO prediction model</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zheng, Fei; Zhu, Jiang 2010-10-01 The value of coupled assimilation is discussed using an intermediate coupled model in which the wind stress is the only atmospheric state which is slavery to model sea surface temperature (SST). In the coupled assimilation analysis, based on the coupled wind-ocean state covariance calculated from the coupled 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 coupled assimilation of wind observations yields better results than the assimilation of SST observations. Specifically, the coupled 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 coupled assimilation of wind data can decrease the initial condition errors in the surface/subsurface currents that can significantly contribute to SST forecast errors. The value of the coupled 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 coupled 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. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=199766&keyword=redox+AND+reaction&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=199766&keyword=redox+AND+reaction&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">Biogeochemical Stability of Contaminants in the Subsurface Following In Situ Treatment</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> In recent years, innovative treatment technologies have emerged to meet groundwater cleanup goals. In many cases these methods take advantage of the redox behavior of contaminant species. For example, remedial technologies that strategically manipulate subsurface redox conditio... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ISPAr62W1....1B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ISPAr62W1....1B">The Development of 3d Sub-Surface Mapping Scheme and its Application to Martian Lobate Debris Aprons</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Baik, H.; Kim, J. 2017-07-01 The Shallow Subsurface Radar (SHARAD), a sounding radar equipped on the Mars Reconnaissance Orbiter (MRO), has produced highly valuable information about the Martian subsurface. In particular, the complicated substructures of Mars such as polar deposit, pedestal crater and the other geomorphic features involving possible subsurface ice body has been successfully investigated by SHARAD. In this study, we established a 3D subsurface mapping strategy employing the multiple SHARAD profiles. A number of interpretation components of SHARAD signals were integrated into a subsurface mapping scheme using radargram information and topographic data, then applied over a few mid latitude Lobate Debris Aprons (LDAs). From the identified subsurface layers of LDA, and the GIS data base incorporating the other interpretation outcomes, we are expecting to trace the origin of LDAs. Also, the subsurface mapping scheme developed in this study will be further applied to other interesting Martian geological features such as inter crater structures, aeolian deposits and fluvial sediments. To achieve higher precision sub-surface mapping, the clutter simulation employing the high resolution topographic data and the upgraded clustering algorithms assuming multiple sub-surface layers will be also developed. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1170054-anticorrelation-between-surface-subsurface-point-defects-impact-redox-chemistry-tio2','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1170054-anticorrelation-between-surface-subsurface-point-defects-impact-redox-chemistry-tio2">Anticorrelation between Surface and Subsurface Point Defects and the Impact on the Redox Chemistry of TiO2(110)</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Yoon, Yeohoon; Du, Yingge; Garcia, Juan C. 2015-02-02 Using combination of STM, DFT and SIMS, we explored the interplay and relative impact of surface vs. subsurface defects on the surface chemistry of rutile TiO2. STM results show that surface O vacancies (VO’s) are virtually absent in the vicinity of positively-charged subsurface point-defects. This observation is consistent with DFT calculations of impact of subsurface defect proximity on VO formation energy. To monitor the influence of such lateral anticorrelation on surface redox chemistry, a test reaction of the dissociative adsorption of O2 is employed, which is observed to be suppressed around them. DFT results attribute this to a perceived absencemore » of the intrinsic (Ti) (and likely extrinsic) interstitials in the nearest subsurface layer beneath “inhibited” areas. We also postulate that the entire nearest subsurface region could be voided of any charged point-defects, whereas prevalent VO’s are largely responsible for mediation of the redox chemistry at reduced TiO2(110) surface.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3690036','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3690036">A Mobile Acoustic Subsurface Sensing (MASS) System for Rapid Roadway Assessment</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Lu, Yifeng; Zhang, Yi; Cao, Yinghong; McDaniel, J. Gregory; Wang, Ming L. 2013-01-01 Surface waves are commonly used for vibration-based nondestructive testing for infrastructure. Spectral Analysis of Surface Waves (SASW) has been used to detect subsurface properties for geologic inspections. Recently, efforts were made to scale down these subsurface detection approaches to see how they perform on small-scale structures such as concrete slabs and pavements. Additional efforts have been made to replace the traditional surface-mounted transducers with non-contact acoustic transducers. Though some success has been achieved, most of these new approaches are inefficient because they require point-to-point measurements or off-line signal analysis. This article introduces a Mobile Acoustic Subsurface Sensing system as MASS, which is an improved surface wave based implementation for measuring the subsurface profile of roadways. The compact MASS system is a 3-wheeled cart outfitted with an electromagnetic impact source, distance register, non-contact acoustic sensors and data acquisition/processing equipment. The key advantage of the MASS system is the capability to collect measurements continuously at walking speed in an automatic way. The fast scan and real-time analysis advantages are based upon the non-contact acoustic sensing and fast air-coupled surface wave analysis program. This integration of hardware and software makes the MASS system an efficient mobile prototype for the field test. PMID:23698266 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.1705G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.1705G">Equatorial Indian Ocean subsurface current variability in an Ocean General Circulation Model</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Gnanaseelan, C.; Deshpande, Aditi 2018-03-01 The variability of subsurface currents in the equatorial Indian Ocean is studied using high resolution Ocean General Circulation Model (OGCM) simulations during 1958-2009. February-March eastward equatorial subsurface current (ESC) shows weak variability whereas strong variability is observed in northern summer and fall ESC. An eastward subsurface current with maximum amplitude in the pycnocline is prominent right from summer to winter during strong Indian Ocean Dipole (IOD) years when air-sea coupling is significant. On the other hand during weak IOD years, both the air-sea coupling and the ESC are weak. This strongly suggests the role of ESC on the strength of IOD. The extension of the ESC to the summer months during the strong IOD years strengthens the oceanic response and supports intensification and maintenance of IODs through modulation of air sea coupling. Although the ESC is triggered by equatorial winds, the coupled air-sea interaction associated with IODs strengthens the ESC to persist for several seasons thereby establishing a positive feedback cycle with the surface. This suggests that the ESC plays a significant role in the coupled processes associated with the evolution and intensification of IOD events by cooling the eastern basin and strengthening thermocline-SST (sea surface temperature) interaction. As the impact of IOD events on Indian summer monsoon is significant only during strong IOD years, understanding and monitoring the evolution of ESC during these years is important for summer monsoon forecasting purposes. There is a westward phase propagation of anomalous subsurface currents which persists for a year during strong IOD years, whereas such persistence or phase propagation is not seen during weak IOD years, supporting the close association between ESC and strength of air sea coupling during strong IOD years. In this study we report the processes which strengthen the IOD events and the air sea coupling associated with IOD. It also unravels </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.B11D0391L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.B11D0391L">Global Biogeochemical Cycle of Si: Its Coupling to the Perturbed C-N-P cycles in Industrial Time</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lerman, A.; Li, D. D.; MacKenzie, F. T. 2010-12-01 The importance of silicon (Si) in global biogeochemical 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 biogeochemical model of the Si cycle as coupled 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 coupled 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 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ECSS..196..150P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ECSS..196..150P">Enzymatic activity in the surface microlayer and subsurface water in the harbour channel</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Perliński, Piotr; Mudryk, Zbigniew J.; Antonowicz, Józef 2017-09-01 Hydrolytic activity of eight extracellular enzymes was determined spectrofluorimetric method in the surface microlayer and subsurface water in the harbour channel in Ustka. The ranking order of the potential enzyme activity rates in the studied water layers was as follows: lipase > phosphatase > aminopeptidase > β-glucosidase > α-glucosidase > xylanase > cellulase > chitinase. The level of activity of all studied hydrolases was higher in the surface microlayer than subsurface water. No clear gradients in the level of enzymatic activity were determined along the horizontal profile of the studied channel. Activity of extracellular enzymes was strongly influenced by the season. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active">8</li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active">9</li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29715908','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29715908">In situ high temperature microwave microscope for nondestructive detection of surface and sub-surface defects.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Wang, Peiyu; Li, Zhencheng; Pei, Yongmao 2018-04-16 An in situ high temperature microwave microscope was built for detecting surface and sub-subsurface structures and defects. This system was heated with a self-designed quartz lamp radiation module, which is capable of heating to 800°C. A line scanning of a metal grating showed a super resolution of 0.5 mm (λ/600) at 1 GHz. In situ scanning detections of surface hole defects on an aluminium plate and a glass fiber reinforced plastic (GFRP) plate were conducted at different high temperatures. A post processing algorithm was proposed to remove the background noises induced by high temperatures and the 3.0 mm-spaced hole defects were clearly resolved. Besides, hexagonal honeycomb lattices were in situ detected and clearly resolved under a 1.0 mm-thick face panel at 20°C and 50°C, respectively. The core wall positions and bonding width were accurately detected and evaluated. In summary, this in situ microwave microscope is feasible and effective in sub-surface detection and super resolution imaging at different high temperatures. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26317241','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26317241">Surface-Activated Coupling Reactions Confined on a Surface.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Dong, Lei; Liu, Pei Nian; Lin, Nian 2015-10-20 Chemical reactions may take place in a pure phase of gas or liquid or at the interface of two phases (gas-solid or liquid-solid). Recently, the emerging field of "surface-confined coupling reactions" has attracted intensive attention. In this process, reactants, intermediates, and products of a coupling reaction are adsorbed on a solid-vacuum or a solid-liquid interface. The solid surface restricts all reaction steps on the interface, in other words, the reaction takes place within a lower-dimensional, for example, two-dimensional, space. Surface atoms that are fixed in the surface and adatoms that move on the surface often activate the surface-confined coupling reactions. The synergy of surface morphology and activity allow some reactions that are inefficient or prohibited in the gas or liquid phase to proceed efficiently when the reactions are confined on a surface. Over the past decade, dozens of well-known "textbook" coupling reactions have been shown to proceed as surface-confined coupling reactions. In most cases, the surface-confined coupling reactions were discovered by trial and error, and the reaction pathways are largely unknown. It is thus highly desirable to unravel the mechanisms, mechanisms of surface activation in particular, of the surface-confined coupling reactions. Because the reactions take place on surfaces, advanced surface science techniques can be applied to study the surface-confined coupling reactions. Among them, scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) are the two most extensively used experimental tools. The former resolves submolecular structures of individual reactants, intermediates, and products in real space, while the latter monitors the chemical states during the reactions in real time. Combination of the two methods provides unprecedented spatial and temporal information on the reaction pathways. The experimental findings are complemented by theoretical modeling. In particular, density </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4744786','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4744786">The emergence of hydrogeophysics for improved understanding of subsurface processes over multiple scales</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Hubbard, Susan S.; Huisman, Johan A.; Revil, André; Robinson, David A.; Singha, Kamini; Slater, Lee D. 2015-01-01 Abstract Geophysics provides a multidimensional suite of investigative methods that are transforming our ability to see into the very fabric of the subsurface environment, and monitor the dynamics of its fluids and the biogeochemical reactions that occur within it. Here we document how geophysical methods have emerged as valuable tools for investigating shallow subsurface processes over the past two decades and offer a vision for future developments relevant to hydrology and also ecosystem science. The field of “hydrogeophysics” arose in the late 1990s, prompted, in part, by the wealth of studies on stochastic subsurface hydrology that argued for better field‐based investigative techniques. These new hydrogeophysical approaches benefited from the emergence of practical and robust data inversion techniques, in many cases with a view to quantify shallow subsurface heterogeneity and the associated dynamics of subsurface fluids. Furthermore, the need for quantitative characterization stimulated a wealth of new investigations into petrophysical relationships that link hydrologically relevant properties to measurable geophysical parameters. Development of time‐lapse approaches provided a new suite of tools for hydrological investigation, enhanced further with the realization that some geophysical properties may be sensitive to biogeochemical transformations in the subsurface environment, thus opening up the new field of “biogeophysics.” Early hydrogeophysical studies often concentrated on relatively small “plot‐scale” experiments. More recently, however, the translation to larger‐scale characterization has been the focus of a number of studies. Geophysical technologies continue to develop, driven, in part, by the increasing need to understand and quantify key processes controlling sustainable water resources and ecosystem services. PMID:26900183 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.B23B0443P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.B23B0443P">Biofilm-induced calcium carbonate precipitation: application in the subsurface</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Phillips, A. J.; Eldring, J.; Lauchnor, E.; Hiebert, R.; Gerlach, R.; Mitchell, A. C.; Esposito, R.; Cunningham, A. B.; Spangler, L. 2012-12-01 We have investigated mitigation strategies for sealing high permeability regions, like fractures, in the subsurface. This technology has the potential to, for example, improve the long-term security of geologically-stored carbon dioxide (CO2) by sealing fractures in cap rocks or to mitigate leakage pathways to prevent contamination of overlying aquifers from hydraulic fracturing fluids. Sealing technologies using low-viscosity fluids are advantageous since they potentially reduce the necessary injection pressures and increase the radius of influence around injection wells. In this technology, aqueous solutions and suspensions are used to promote microbially-induced mineral precipitation which can be applied in subsurface environments. To this end, a strategy was developed to twice seal a hydraulically fractured, 74 cm (2.4') diameter Boyles Sandstone core, collected in North-Central Alabama, with biofilm-induced calcium carbonate (CaCO3) precipitates under ambient pressures. Sporosarcina pasteurii biofilms were established and calcium and urea containing reagents were injected to promote saturation conditions favorable for CaCO3 precipitation followed by growth reagents to resuscitate the biofilm's ureolytic activity. Then, in order to evaluate this process at relevant deep subsurface pressures, a novel high pressure test vessel was developed to house the 74 cm diameter core under pressures as high as 96 bar (1,400 psi). After determining that no impact to the fracture permeability occurred due to increasing overburden pressure, the fractured core was sealed under subsurface relevant pressures relating to 457 meters (1,500 feet) below ground surface (44 bar (650 psi) overburden pressure). After fracture sealing under both ambient and subsurface relevant pressure conditions, the sandstone core withstood three times higher well bore pressure than during the initial fracturing event, which occurred prior to biofilm-induced CaCO3 mineralization. These studies suggest </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1429750','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1429750"></a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Hammond, Glenn Edward; Yang, Xiaofan; Song, Xuehang The groundwater-surface water interaction zone (GSIZ) plays an important role in riverine and watershed ecosystems as the exchange of waters of variable composition and temperature (hydrologic exchange flows) stimulate microbial activity and associated biogeochemical reactions. Variable temporal and spatial scales of hydrologic exchange flows, heterogeneity of the subsurface environment, and complexity of biogeochemical reaction networks in the GSIZ present challenges to incorporation of fundamental process representations and model parameterization across a range of spatial scales (e.g. from pore-scale to field scale). This paper presents a novel hybrid multiscale simulation approach that couples hydrologic-biogeochemical (HBGC) processes between two distinct length scalesmore » of interest.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H12E..05N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H12E..05N">Evaluating the role of sulfur and hyporheic exchange in biogeochemical cycling in riparian wetlands</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ng, G. H. C.; O'Hara, P. A.; Santelli, C. M.; Rosenfeld, C.; Yourd, A. 2017-12-01 Although the mixing of surface water and groundwater is well-recognized to support hotspots of redox activities such as denitrification, few hyporheic zone studies have examined sulfur reactions. Because sulfate concentrations in wetlands, lake beds, and stream beds are low compared to in marine settings, the hierarchical redox tower dictates that sulfate reduction should play a substantially lesser role in biogeochemical cycling than nitrate or iron reduction when these sediments become anoxic. However, recent experiments challenge the classically held redox sequence by revealing "cryptic" sulfur cycling that can support unexpectedly high sulfate reduction rates and could be driving iron and carbon cycling through coupled reactions. Sulfur biogeochemical processes remain poorly understood in field settings, where little is known about the impact of hydrologic fluxes. Our study examines how hyporheic flux can "kick" forward cryptic sulfur cycling and related iron and carbon reactions by perturbing geochemical gradients to which microbial communities respond. We evaluate field-scale cycling of iron, sulfur, and carbon through a combination of hydrologic monitoring, microbial and geochemical analyses, and reactive-transport modeling at a riparian wetland site in northeastern Minnesota that is impacted by mining practices. In particular, we assess how varying fluxes between high sulfate concentration surface water and lower sulfate concentration groundwater over a season could be (1) facilitating intensified sulfur cycling coupled to abiotic iron reduction and (2) altering methane release possibly through anaerobic methane oxidation. Our findings can help clarify the importance of sulfur in non-marine biogeochemical cycling and provide better understanding of how anthropogenic activities can impact critical freshwater systems. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.H33F1066S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.H33F1066S">Discharge-nitrate data clustering for characterizing surface-subsurface flow interaction and calibration of a hydrologic model</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shrestha, R. R.; Rode, M. 2008-12-01 Concentration of reactive chemicals has different chemical signatures in baseflow and surface runoff. Previous studies on nitrate export from a catchment indicate that the transport processes are driven by subsurface flow. Therefore nitrate signature can be used for understanding the event and pre-event contributions to streamflow and surface-subsurface flow interactions. The study uses flow and nitrate concentration time series data for understanding the relationship between these two variables. Unsupervised artificial neural network based learning method called self organizing map is used for the identification of clusters in the datasets. Based on the cluster results, five different pattern in the datasets are identified which correspond to (i) baseflow, (ii) subsurface flow increase, (iii) surface runoff increase, (iv) surface runoff recession, and (v) subsurface flow decrease regions. The cluster results in combination with a hydrologic model are used for discharge separation. For this purpose, a multi-objective optimization tool NSGA-II is used, where violation of cluster results is used as one of the objective functions. The results show that the use of cluster results as supplementary information for the calibration of a hydrologic model gives a plausible simulation of subsurface flow as well total runoff at the catchment outlet. The study is undertaken using data from the Weida catchment in the North-Eastern Germany, which is a sub-catchment of the Weisse Elster river in the Elbe river basin. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1250473','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1250473">Final Report DE-SC0006997; PI Sharp; Coupled Biological and Micro-XAS/XRF Analysis of In Situ Uranium Biogeochemical Processes</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Sharp, Jonathan O. Project Overview: The impact of the original seed award was substantially increased by leveraging a postdoctoral fellowship (Marie Curie Postdoctoral Fellowship) and parallel funds from (A) synergistic project supported by NSF and (B) with DOE collaborators (PI’s Ranville and Williams) as well as no-cost extension that greatly increased the impact and publications associated with the project. In aligning with SBR priorities, the project’s focus was extended more broadly to explore coupled biogeochemical analysis of metal (im)mobilization processes beyond uranium with a foundation in integrating microbial ecology with geochemical analyses. This included investigations of arsenic and zinc during sulfate reducing conditionsmore » in addition to direct microbial reduction of metals. Complimentary work with NSF funding and collaborative DOE interactions further increased the project scope to investigate metal (im)mobilization coupled to biogeochemical perturbations in forest ecosystems with an emphasis on coupled carbon and metal biogeochemistry. In total, the project was highly impactful and resulted in 9 publications and directly supported salary/tuition for 3 graduate students at various stages of their academic careers as well as my promotion to Associate Professor. In going forward, findings provided inspiration for a two subsequent proposals with collaborators at Lawrence Berkeley Laboratory and others that are currently in review (as of March 2016).« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010IzAOP..46..482B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010IzAOP..46..482B">Surface manifestations of internal waves investigated by a subsurface buoyant jet: 3. Surface manifestations of internal waves</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bondur, V. G.; Grebenyuk, Yu. V.; Ezhova, E. V.; Kazakov, V. I.; Sergeev, D. A.; Soustova, I. A.; Troitskaya, Yu. I. 2010-08-01 In a large test reservoir at the Institute of Applied Physics, Russian Academy of Sciences, a series of experiments were performed to investigate the surface manifestations of internal waves radiated by a subsurface buoyant jet. The field of currents on the water surface of the reservoir was studied through the distribution of temperature with shallow thermocline. Using Particle Tracking Velocimetry (PTV), the velocity field of surface currents was measured. A theoretical model was developed to calculate the rates of disturbances on the surface. A comparison with experimental data indicated that the calculated data of the surface rate value are overestimated. This discrepancy was explained by the presence of a film of surface-active substances (SASs) with experimentally obtained parameters. Using scale modeling coefficients, we estimated the parameters of internal waves radiated by the subsurface wastewater system and the values of their surface manifestations in field conditions. We estimated the hydrodynamic contrasts in the field of surface waves, which can be caused by these inhomogeneous currents on the surface. For a wind velocity of 5 m/s, the magnitude of the contrast in the field of short waves can reach up to 10-25%, which is detected with confidence by remote-sensing methods. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013GMD.....6.1173W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013GMD.....6.1173W">PEATBOG: a biogeochemical model for analyzing coupled carbon and nitrogen dynamics in northern peatlands</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wu, Y.; Blodau, C. 2013-08-01 Elevated nitrogen deposition and climate change alter the vegetation communities and carbon (C) and nitrogen (N) cycling in peatlands. To address this issue we developed a new process-oriented biogeochemical model (PEATBOG) for analyzing coupled carbon and nitrogen dynamics in northern peatlands. The model consists of four submodels, which simulate: (1) daily water table depth and depth profiles of soil moisture, temperature and oxygen levels; (2) competition among three plants functional types (PFTs), production and litter production of plants; (3) decomposition of peat; and (4) production, consumption, diffusion and export of dissolved C and N species in soil water. The model is novel in the integration of the C and N cycles, the explicit spatial resolution belowground, the consistent conceptualization of movement of water and solutes, the incorporation of stoichiometric controls on elemental fluxes and a consistent conceptualization of C and N reactivity in vegetation and soil organic matter. The model was evaluated for the Mer Bleue Bog, near Ottawa, Ontario, with regards to simulation of soil moisture and temperature and the most important processes in the C and N cycles. Model sensitivity was tested for nitrogen input, precipitation, and temperature, and the choices of the most uncertain parameters were justified. A simulation of nitrogen deposition over 40 yr demonstrates the advantages of the PEATBOG model in tracking biogeochemical effects and vegetation change in the ecosystem. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013GMDD....6.1599W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013GMDD....6.1599W">PEATBOG: a biogeochemical model for analyzing coupled carbon and nitrogen dynamics in northern peatlands</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wu, Y.; Blodau, C. 2013-03-01 Elevated nitrogen deposition and climate change alter the vegetation communities and carbon (C) and nitrogen (N) cycling in peatlands. To address this issue we developed a new process-oriented biogeochemical model (PEATBOG) for analyzing coupled carbon and nitrogen dynamics in northern peatlands. The model consists of four submodels, which simulate: (1) daily water table depth and depth profiles of soil moisture, temperature and oxygen levels; (2) competition among three plants functional types (PFTs), production and litter production of plants; (3) decomposition of peat; and (4) production, consumption, diffusion and export of dissolved C and N species in soil water. The model is novel in the integration of the C and N cycles, the explicit spatial resolution belowground, the consistent conceptualization of movement of water and solutes, the incorporation of stoichiometric controls on elemental fluxes and a consistent conceptualization of C and N reactivity in vegetation and soil organic matter. The model was evaluated for the Mer Bleue Bog, near Ottawa, Ontario, with regards to simulation of soil moisture and temperature and the most important processes in the C and N cycles. Model sensitivity was tested for nitrogen input, precipitation, and temperature, and the choices of the most uncertain parameters were justified. A simulation of nitrogen deposition over 40 yr demonstrates the advantages of the PEATBOG model in tracking biogeochemical effects and vegetation change in the ecosystem. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPCM...28f4006D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPCM...28f4006D">Pd surface and Pt subsurface segregation in Pt1-c Pd c nanoalloys</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> De Clercq, A.; Giorgio, S.; Mottet, C. 2016-02-01 The structure and chemical arrangement of Pt1-c Pd c nanoalloys with the icosahedral and face centered cubic symmetry are studied using Monte Carlo simulations with a tight binding interatomic potential fitted to density-functional theory calculations. Pd surface segregation from the lowest to the highest coordinated sites is predicted by the theory together with a Pt enrichment at the subsurface, whatever the structure and the size of the nanoparticles, and which subsists when increasing the temperature. The onion-shell chemical configuration is found for both symmetries and is initiated from the Pd surface segregation. It is amplified in the icosahedral symmetry and small sizes but when considering larger sizes, the oscillating segregation profile occurs near the surface on about three to four shells whatever the structure. Pd segregation results from the significant lower cohesive energy of Pd as compared to Pt and the weak ordering tendency leads to the Pt subsurface segregation. The very weak size mismatch does not prevent the bigger atoms (Pt) from occupying subsurface sites which are in compression whereas the smaller ones (Pd) occupy the central site of the icosahedra where the compression is an order of magnitude higher. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=306294&Lab=NRMRL&keyword=pavement+AND+design&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=306294&Lab=NRMRL&keyword=pavement+AND+design&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">Evaluation of Surface and Subsurface Processes in Permeable Pavement Infiltration Trenches</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> The hydrologic performance of permeable pavement systems can be affected by clogging of the pavement surface and/or clogging at the interface where the subsurface storage layer meets the underlying soil. As infiltration and exfiltration are the primary functional mechanisms for ... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170001749','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170001749">Hydrogen Isotopic Constraints on the Evolution of Surface and Subsurface Water on Mars</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Usui, T.; Kurokawa, H.; Wang, J.; Alexander, C. M. O’D.; Simon, J. I.; Jones, J. H. 2017-01-01 The geology and geomorphology of Mars provide clear evidence for the presence of liquid water on its surface during the Noachian and Hesperien eras (i.e., >3 Ga). In contrast to the ancient watery environment, today the surface of Mars is relatively dry. The current desert-like surface conditions, however, do not necessarily indicate a lack of surface or near-surface water/ice. In fact, massive deposits of ground ice and/or icy sediments have been proposed based on subsurface radar sounder observations. Hence, accurate knowledge of both the evolution of the distribution of water and of the global water inventory is crucial to our understanding of the evolution of the climate and near-surface environments and the potential habitability of Mars. This study presents insights from hydrogen isotopes for the interactive evolution of Martian water reservoirs. In particular, based on our new measurement of the D/H ratio of 4 Ga-old Noachian water, we constrain the atmospheric loss and possible exchange of surface and subsurface water through time. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.H44B..07J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.H44B..07J">Emergent Archetype Hydrological-Biogeochemical Response Patterns in Heterogeneous Catchments</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Jawitz, J. W.; Gall, H. E.; Rao, P. 2013-12-01 What can spatiotemporally integrated patterns observed in stream hydrologic and biogeochemical signals generated in response to transient hydro-climatic and anthropogenic forcing tell us about the interactions between spatially heterogeneous soil-mediated hydrological and biogeochemical processes? We seek to understand how the spatial structure of solute sources coupled 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 biogeochemical source areas across a catchment evolve under stochastic hydro-climatic forcing? (2) What are the feasible hydrologic and biogeochemical responses that lead to the emergence of the observed archetype C-Q patterns? and; (3) What implications do these coupled dynamics have for catchment monitoring and implementation of management practices? We categorize the observed temporal signals into three archetypical C-Q patterns: dilution; accretion, and constant concentration. We introduce a parsimonious stochastic model of heterogeneous catchments, which act as hydrologic and biogeochemical filters, to examine the relationship between spatial heterogeneity and temporal history of solute export signals. The core concept of the modeling framework is considering the 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 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25982028','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25982028">Change in ocean subsurface environment to suppress tropical cyclone intensification under global warming.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Huang, Ping; Lin, I-I; Chou, Chia; Huang, Rong-Hui 2015-05-18 Tropical cyclones (TCs) are hazardous natural disasters. Because TC intensification is significantly controlled by atmosphere and ocean environments, changes in these environments may cause changes in TC intensity. Changes in surface and subsurface ocean conditions can both influence a TC's intensification. Regarding global warming, minimal exploration of the subsurface ocean has been undertaken. Here we investigate future subsurface ocean environment changes projected by 22 state-of-the-art climate models and suggest a suppressive effect of subsurface oceans on the intensification of future TCs. Under global warming, the subsurface vertical temperature profile can be sharpened in important TC regions, which may contribute to a stronger ocean coupling (cooling) effect during the intensification of future TCs. Regarding a TC, future subsurface ocean environments may be more suppressive than the existing subsurface ocean environments. This suppressive effect is not spatially uniform and may be weak in certain local areas. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4479036','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4479036">Change in ocean subsurface environment to suppress tropical cyclone intensification under global warming</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Huang, Ping; Lin, I. -I; Chou, Chia; Huang, Rong-Hui 2015-01-01 Tropical cyclones (TCs) are hazardous natural disasters. Because TC intensification is significantly controlled by atmosphere and ocean environments, changes in these environments may cause changes in TC intensity. Changes in surface and subsurface ocean conditions can both influence a TC's intensification. Regarding global warming, minimal exploration of the subsurface ocean has been undertaken. Here we investigate future subsurface ocean environment changes projected by 22 state-of-the-art climate models and suggest a suppressive effect of subsurface oceans on the intensification of future TCs. Under global warming, the subsurface vertical temperature profile can be sharpened in important TC regions, which may contribute to a stronger ocean coupling (cooling) effect during the intensification of future TCs. Regarding a TC, future subsurface ocean environments may be more suppressive than the existing subsurface ocean environments. This suppressive effect is not spatially uniform and may be weak in certain local areas. PMID:25982028 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1257339-emergence-hydrogeophysics-improved-understanding-subsurface-processes-over-multiple-scales','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1257339-emergence-hydrogeophysics-improved-understanding-subsurface-processes-over-multiple-scales">The emergence of hydrogeophysics for improved understanding of subsurface processes over multiple scales</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Binley, Andrew; Hubbard, Susan S.; Huisman, Johan A.; ... 2015-06-15 Geophysics provides a multidimensional suite of investigative methods that are transforming our ability to see into the very fabric of the subsurface environment, and monitor the dynamics of its fluids and the biogeochemical reactions that occur within it. Here we document how geophysical methods have emerged as valuable tools for investigating shallow subsurface processes over the past two decades and offer a vision for future developments relevant to hydrology and also ecosystem science. The field of “hydrogeophysics” arose in the late 1990s, prompted, in part, by the wealth of studies on stochastic subsurface hydrology that argued for better field-based investigativemore » techniques. These new hydrogeophysical approaches benefited from the emergence of practical and robust data inversion techniques, in many cases with a view to quantify shallow subsurface heterogeneity and the associated dynamics of subsurface fluids. Furthermore, the need for quantitative characterization stimulated a wealth of new investigations into petrophysical relationships that link hydrologically relevant properties to measurable geophysical parameters. Development of time-lapse approaches provided a new suite of tools for hydrological investigation, enhanced further with the realization that some geophysical properties may be sensitive to biogeochemical transformations in the subsurface environment, thus opening up the new field of “biogeophysics.” Early hydrogeophysical studies often concentrated on relatively small “plot-scale” experiments. More recently, however, the translation to larger-scale characterization has been the focus of a number of studies. In conclusion, geophysical technologies continue to develop, driven, in part, by the increasing need to understand and quantify key processes controlling sustainable water resources and ecosystem services.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1257339','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1257339">The emergence of hydrogeophysics for improved understanding of subsurface processes over multiple scales</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Binley, Andrew; Hubbard, Susan S.; Huisman, Johan A. Geophysics provides a multidimensional suite of investigative methods that are transforming our ability to see into the very fabric of the subsurface environment, and monitor the dynamics of its fluids and the biogeochemical reactions that occur within it. Here we document how geophysical methods have emerged as valuable tools for investigating shallow subsurface processes over the past two decades and offer a vision for future developments relevant to hydrology and also ecosystem science. The field of “hydrogeophysics” arose in the late 1990s, prompted, in part, by the wealth of studies on stochastic subsurface hydrology that argued for better field-based investigativemore » techniques. These new hydrogeophysical approaches benefited from the emergence of practical and robust data inversion techniques, in many cases with a view to quantify shallow subsurface heterogeneity and the associated dynamics of subsurface fluids. Furthermore, the need for quantitative characterization stimulated a wealth of new investigations into petrophysical relationships that link hydrologically relevant properties to measurable geophysical parameters. Development of time-lapse approaches provided a new suite of tools for hydrological investigation, enhanced further with the realization that some geophysical properties may be sensitive to biogeochemical transformations in the subsurface environment, thus opening up the new field of “biogeophysics.” Early hydrogeophysical studies often concentrated on relatively small “plot-scale” experiments. More recently, however, the translation to larger-scale characterization has been the focus of a number of studies. In conclusion, geophysical technologies continue to develop, driven, in part, by the increasing need to understand and quantify key processes controlling sustainable water resources and ecosystem services.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150003290','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150003290">Eddy Current Probe for Surface and Sub-Surface Inspection</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Wincheski, Russell A. (Inventor); Simpson, John W. (Inventor) 2014-01-01 An eddy current probe includes an excitation coil for coupling to a low-frequency alternating current (AC) source. A magneto-resistive sensor is centrally disposed within and at one end of the excitation coil to thereby define a sensing end of the probe. A tubular flux-focusing lens is disposed between the excitation coil and the magneto-resistive sensor. An excitation wire is spaced apart from the magneto-resistive sensor in a plane that is perpendicular to the sensor's axis of sensitivity and such that, when the sensing end of the eddy current probe is positioned adjacent to the surface of a structure, the excitation wire is disposed between the magneto-resistive sensor and the surface of the structure. The excitation wire is coupled to a high-frequency AC source. The excitation coil and flux-focusing lens can be omitted when only surface inspection is required. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active">9</li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active">10</li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C11A0755G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C11A0755G">Subsurface Scattered Photons: Friend or Foe? Improving visible light laser altimeter elevation estimates, and measuring surface properties using subsurface scattered photons</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Greeley, A.; Kurtz, N. T.; Neumann, T.; Cook, W. B.; Markus, T. 2016-12-01 Photon counting laser altimeters such as MABEL (Multiple Altimeter Beam Experimental Lidar) - a single photon counting simulator for ATLAS (Advanced Topographical Laser Altimeter System) - use individual photons with visible wavelengths to measure their range to target surfaces. ATLAS, the sole instrument on NASA's upcoming ICESat-2 mission, will provide scientists a view of Earth's ice sheets, glaciers, and sea ice with unprecedented detail. Precise calibration of these instruments is needed to understand rapidly changing parameters such as sea ice freeboard, and to measure optical properties of surfaces like snow covered ice sheets using subsurface scattered photons. Photons that travel through snow, ice, or water before scattering back to an altimeter receiving system travel farther than photons taking the shortest path between the observatory and the target of interest. These delayed photons produce a negative elevation bias relative to photons scattered directly off these surfaces. We use laboratory measurements of snow surfaces using a flight-tested laser altimeter (MABEL), and Monte Carlo simulations of backscattered photons from snow to estimate elevation biases from subsurface scattered photons. We also use these techniques to demonstrate the ability to retrieve snow surface properties like snow grain size. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15724756','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15724756">Effect of tray-based and trayless tooth whitening systems on microhardness of enamel surface and subsurface.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Teixeira, Erica C N; Ritter, André V; Thompson, Jeffrey Y; Leonard, Ralph H; Swift, Edward J 2004-12-01 To evaluate the effect of tray-based and trayless tooth whitening systems on surface and subsurface microhardness of human enamel. Enamel slabs were obtained from recently extracted human third molars. Specimens were randomly assigned to six groups according to tooth whitening treatment (n = 10): 6.0% hydrogen peroxide (HP) (Crest Whitestrips), 6.5% HP (Crest Professional Whitestrips), 7.5% HP (Day White Excel 3), 9.5% HP (Day White Excel 3), 10% carbamide peroxide (Opalescence), and a control group (untreated). Specimens were treated for 14 days following manufacturers' recommended protocols, and were immersed in artificial saliva between treatments. Enamel surface Knoop microhardness (KHN) was measured immediately before treatment, and at days 1, 7, and 14 of treatment. After treatment, subsurface microhardness was measured at depths of 50-500 microm. Data were analyzed for statistical significance using analysis of variance. Differences in microhardness for treated vs. untreated enamel surface were not statistically significant at any time interval. For 6.5% and 9.5% HP, there was a decrease in surface microhardness values during treatment, but at the end of treatment the microhardness values were not statistically different from the baseline values. For the enamel subsurface values, no differences were observed between treated vs. untreated specimens at each depth. Trayless and tray-based tooth whitening treatments do not significantly affect surface or subsurface enamel microhardness. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.B33B0595S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.B33B0595S">Using a spatially-distributed hydrologic biogeochemistry model to study the spatial variation of carbon processes in a Critical Zone Observatory</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shi, Y.; Eissenstat, D. M.; Davis, K. J.; He, Y. 2016-12-01 Forest carbon processes are affected by, among other factors, soil moisture, soil temperature, soil nutrients and solar radiation. Most of the current biogeochemical models are 1-D and represent one point in space. Therefore, they cannot resolve the topographically driven hill-slope land surface heterogeneity or the spatial pattern of nutrient availability. A spatially distributed forest ecosystem model, Flux-PIHM-BGC, has been developed by coupling a 1-D mechanistic biogeochemical model Biome-BGC (BBGC) with a spatially distributed land surface hydrologic model, Flux-PIHM. Flux-PIHM is a coupled physically based model, which incorporates a land-surface scheme into the Penn State Integrated Hydrologic Model (PIHM). The land surface scheme is adapted from the Noah land surface model. Flux-PIHM is able to represent the link between groundwater and the surface energy balance, as well as the land surface heterogeneities caused by topography. In the coupled Flux-PIHM-BGC model, each Flux-PIHM model grid couples a 1-D BBGC model, while soil nitrogen is transported among model grids via subsurface water flow. In each grid, Flux-PIHM provides BBGC with soil moisture, soil temperature, and solar radiation information, while BBGC provides Flux-PIHM with leaf area index. The coupled Flux-PIHM-BGC model has been implemented at the Susquehanna/Shale Hills critical zone observatory (SSHCZO). Model results suggest that the vegetation and soil carbon distribution is primarily constrained by nitorgen availability (affected by nitorgen transport via topographically driven subsurface flow), and also constrained by solar radiation and root zone soil moisture. The predicted vegetation and soil carbon distribution generally agrees with the macro pattern observed within the watershed. The coupled ecosystem-hydrologic model provides an important tool to study the impact of topography on watershed carbon processes, as well as the impact of climate change on water resources. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23616445','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23616445">Feasibility of correlation mapping optical coherence tomography (cmOCT) for anti-spoof sub-surface fingerprinting.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Zam, Azhar; Dsouza, Roshan; Subhash, Hrebesh M; O'Connell, Marie-Louise; Enfield, Joey; Larin, Kirill; Leahy, Martin J 2013-09-01 We propose the use of correlation mapping optical coherence tomography (cmOCT) to deliver additional biometrics associated with the finger that could complement existing fingerprint technology for law enforcement applications. The current study extends the existing fingerprint paradigm by measuring additional biometrics associated with sub-surface finger tissue such as sub-surface fingerprints, sweat glands, and the pattern of the capillary bed to yield a user-friendly cost effective and anti-spoof multi-mode biometric solution associated with the finger. To our knowledge no other method has been able to capture sub-surface fingerprint, papillary pattern and horizontal vessel pattern in a single scan or to show the correspondence between these patterns in live adult human fingertip. Unlike many current technologies this approach incorporates 'liveness' testing by default. The ultimate output is a biometric module which is difficult to defeat and complements fingerprint scanners that currently are used in border control and law enforcement applications. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22370421','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22370421">Field application of farmstead runoff to vegetated filter strips: surface and subsurface water quality assessment.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Larson, Rebecca A; Safferman, Steven I 2012-01-01 Farmstead runoff poses significant environmental impacts to ground and surface waters. Three vegetated filter strips were assessed for the treatment of dairy farmstead runoff at the soil surface and subsurface at 0.3- or 0. 46-m and 0. 76-m depths for numerous storm events. A medium-sized Michigan dairy was retrofitted with two filter strips on sandy loam soil and a third filter strip was implemented on a small Michigan dairy with sandy soil to collect and treat runoff from feed storage, manure storage, and other impervious farmstead areas. All filter strips were able to eliminate surface runoff via infiltration for all storm events over the duration of the study, eliminating pollutant contributions to surface water. Subsurface effluent was monitored to determine the contributing groundwater concentrations of numerous pollutants including chemical oxygen demand (COD), metals, and nitrates. Subsurface samples have an average reduction of COD concentrations of 20, 11, and 85% for the medium dairy Filter Strip 1 (FS1), medium dairy Filter Strip 2 (FS2), and the small Michigan dairy respectively, resulting in average subsurface concentrations of 355, 3960, and 718 mg L COD. Similar reductions were noted for ammonia and total Kjeldahl nitrogen (TKN) in the subsurface effluent. The small Michigan dairy was able to reduce the pollutant leachate concentrations of COD, TKN, and ammonia over a range of influent concentrations. Increased influent concentrations in the medium Michigan dairy filter strips resulted in an increase in COD, TKN, and ammonia concentrations in the leachate. Manganese was leached from the native soils at all filter strips as evidenced by the increase in manganese concentrations in the leachate. Nitrate concentrations were above standard drinking water limits (10 mg L), averaging subsurface concentrations of 11, 45, and 25 mg L NO-N for FS1, FS2, and the small Michigan dairy, respectively. Copyright © by the American Society of Agronomy, Crop Science </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhDT........23F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhDT........23F">A new high-resolution electromagnetic method for subsurface imaging</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Feng, Wanjie For most electromagnetic (EM) geophysical systems, the contamination of primary fields on secondary fields ultimately limits the capability of the controlled-source EM methods. Null coupling techniques were proposed to solve this problem. However, the small orientation errors in the null coupling systems greatly restrict the applications of these systems. Another problem encountered by most EM systems is the surface interference and geologic noise, which sometimes make the geophysical survey impossible to carry out. In order to solve these problems, the alternating target antenna coupling (ATAC) method was introduced, which greatly removed the influence of the primary field and reduced the surface interference. But this system has limitations on the maximum transmitter moment that can be used. The differential target antenna coupling (DTAC) method was proposed to allow much larger transmitter moments and at the same time maintain the advantages of the ATAC method. In this dissertation, first, the theoretical DTAC calculations were derived mathematically using Born and Wolf's complex magnetic vector. 1D layered and 2D blocked earth models were used to demonstrate that the DTAC method has no responses for 1D and 2D structures. Analytical studies of the plate model influenced by conductive and resistive backgrounds were presented to explain the physical phenomenology behind the DTAC method, which is the magnetic fields of the subsurface targets are required to be frequency dependent. Then, the advantages of the DTAC method, e.g., high-resolution, reducing the geologic noise and insensitive to surface interference, were analyzed using surface and subsurface numerical examples in the EMGIMA software. Next, the theoretical advantages, such as high resolution and insensitive to surface interference, were verified by designing and developing a low-power (moment of 50 Am 2) vertical-array DTAC system and testing it on controlled targets and scaled target coils. At last, a </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011epsc.conf.1125C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011epsc.conf.1125C">Ma_Miss Experiment: miniaturized imaging spectrometer for subsurface studies</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Coradini, A.; Ammannito, E.; Boccaccini, A.; de Sanctis, M. C.; di Iorio, T.; Battistelli, E.; Capanni, A. 2011-10-01 The study of the Martian subsurface will provide important constraints on the nature, timing and duration of alteration and sedimentation processes on Mars, as well as on the complex interactions between the surface and the atmosphere. A Drilling system, coupled with an in situ analysis package, is installed on the Exomars-Pasteur Rover to perform in situ investigations up to 2m in the Mars soil. Ma_Miss (Mars Multispectral Imager for Subsurface Studies) is a spectrometer devoted to observe the lateral wall of the borehole generated by the Drilling system. The instrument is fully integrated with the Drill and shares its structure and electronics. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSEC54A1302H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSEC54A1302H">Coupled Biogeochemical and Hydrodynamic Measurements over a Palauan Seagrass Bed: Can Seagrasses Mitigate Local Acidification Stress?</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hirsh, H.; Torres, W.; Shea, M. 2016-02-01 Interest in seagrass beds as a tool to locally mitigate ocean acidification is growing rapidly. Much of the interest in seagrasses is motivated by their root structure, which is able to sequester carbon over interannual and longer timescales. Far less is known about their biogeochemistry on shorter diel timescales, yet we know that diel cycle variation in CO2 chemistry on coral reefs can be quite substantial. Understanding short-term seagrass biogeochemistry is critical to evaluating if, and how, seagrasses may eventually be utilized to mitigate OA on coral reefs. We present the results of a high-resolution, 24-hour control volume experiment conducted in the Republic of Palau covering a 50m x 100m seagrass bed. Our dataset includes diel cycles of hydrodynamic (current profiles and turbulence), biogeochemical (pH, pCO2, TA, DIC, and O2), and environmental (temperature and salinity) parameters. We use these coupled hydrodynamic-biogeochemical measurements to estimate ecosystem metabolism and better quantify the capacity of seagrass to mitigate local acidification through the photosynthetic uptake of CO2. Combining our field observations with box model predictions allows us to gain better insight into the mechanisms that control seagrass metabolism and their ability to buffer CO2 for downstream corals. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=317540','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=317540">Tillage impact on herbicide loss by surface runoff and lateral subsurface flow</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> There is worldwide interest in conservation tillage practices because they can reduce surface runoff, agrichemical, and sediment loss from farm fields. Since these practices typically increase infiltration, their use may increase subsurface transport of water-soluble contaminants. Thus, to assess lo... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993JGR....98.3319Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993JGR....98.3319Z">A coupled subsurface-boundary layer model of water on Mars</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zent, A. P.; Haberle, R. M.; Houben, H. C.; Jakosky, B. M. 1993-02-01 A 1D numerical model of the exchange of H2O between the atmosphere and subsurface of Mars through the PBL is employed to explore the mechanisms of H2O exchange and to elucidate the role played by the regolith in the local H2O budget. The atmospheric model includes effects of Coriolis, pressure gradient, and frictional forces for momentum: radiation, sensible heat flux, and advection for heat. It is suggested that in most cases, the flux through the Martian surface reverses twice in the course of each sol. The effects of surface albedo, thermal inertia, solar declination, atmospheric optical depth, and regolith pore structure are explored. It is proposed that higher thermal inertia forces more H2O into the atmosphere because the regolith is warmer at depth. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP21E..01L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP21E..01L">Using coral Ba/Ca records to investigate seasonal to decadal scale biogeochemical cycling in the surface and intermediate ocean.</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> LaVigne, M.; Cobb, K. M.; DeLong, K. L.; Freiberger, M. M.; Grottoli, A. G.; Hill, T. M.; Miller, H. R.; Nurhati, I. S.; Richey, J. N.; Serrato Marks, G.; Sherrell, R. M. 2016-12-01 Dissolved barium (BaSW), a bio-intermediate element, is linked to several biogeochemical processes such as the cycling and export of nutrients, organic carbon (Corg), and barite in surface and intermediate oceans. Dynamic BaSW cycling has been demonstrated in the water column on short timescales (days-weeks) while sedimentary records have documented geologic-scale changes in barite preservation driven by export production. Our understanding of how seasonal-decadal scale climate variability impacts these biogeochemical processes currently lacks robust records. Ba/Ca calibrations in surface and deep sea corals suggest barium is incorporated via cationic substitution in both aragonite and calcite. Here we demonstrate the utility of Ba/Ca for reconstructing biogeochemical variability using examples of surface and deep sea coral records. Century-long deep sea coral records from the California Current System (bamboo corals: 900-1500m) record interannual variations in Ba/Ca, likely reflecting changes in barite formation via bacterial Corg respiration or barite saturation state. A surface Porites coral Ba/Ca record from Christmas Island (central equatorial Pacific: 1978-1995) shows maxima during low productivity El Niño warm periods, suggesting that variations in BaSW are driven by biological removal via direct cellular uptake or indirectly via barite precipitation with the decomposition of large phytoplankton blooms at this location. Similarly, a sixteen-year long Siderastera siderea surface coral record from Dry Tortugas, FL (Gulf of Mexico: 1991-2007) shows seasonal Ba/Ca cycles that align with annual chlorophyll and δ13C. Taken together, these records demonstrate the linkages among Corg, nutrient cycling and BaSW in the surface and intermediate ocean on seasonal to decadal timescales. Multi-proxy paleoceanographic reconstructions including Ba/Ca have the potential to elucidate the mechanisms linking past climate, productivity, nutrients, and BaSW cycling in the past. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70129606','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70129606">Temporal dynamics of biogeochemical processes at the Norman Landfill site</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Arora, Bhavna; Mohanty, Binayak P.; McGuire, Jennifer T.; Cozzarelli, Isabelle M. 2013-01-01 The temporal variability observed in redox sensitive species in groundwater can be attributed to coupled hydrological, geochemical, and microbial processes. These controlling processes are typically nonstationary, and distributed across various time scales. Therefore, the purpose of this study is to investigate biogeochemical data sets from a municipal landfill site to identify the dominant modes of variation and determine the physical controls that become significant at different time scales. Data on hydraulic head, specific conductance, δ2H, chloride, sulfate, nitrate, and nonvolatile dissolved organic carbon were collected between 1998 and 2000 at three wells at the Norman Landfill site in Norman, OK. Wavelet analysis on this geochemical data set indicates that variations in concentrations of reactive and conservative solutes are strongly coupled to hydrologic variability (water table elevation and precipitation) at 8 month scales, and to individual eco-hydrogeologic framework (such as seasonality of vegetation, surface-groundwater dynamics) at 16 month scales. Apart from hydrologic variations, temporal variability in sulfate concentrations can be associated with different sources (FeS cycling, recharge events) and sinks (uptake by vegetation) depending on the well location and proximity to the leachate plume. Results suggest that nitrate concentrations show multiscale behavior across temporal scales for different well locations, and dominant variability in dissolved organic carbon for a closed municipal landfill can be larger than 2 years due to its decomposition and changing content. A conceptual framework that explains the variability in chemical concentrations at different time scales as a function of hydrologic processes, site-specific interactions, and/or coupled biogeochemical effects is also presented. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRC..120.2973B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.2973B">Surface wave effects in the NEMO ocean model: Forced and coupled experiments</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Breivik, Øyvind; Mogensen, Kristian; Bidlot, Jean-Raymond; Balmaseda, Magdalena Alonso; Janssen, Peter A. E. M. 2015-04-01 The NEMO general circulation ocean model is extended to incorporate three physical processes related to ocean surface waves, namely the surface stress (modified by growth and dissipation of the oceanic wavefield), the turbulent kinetic energy flux from breaking waves, and the Stokes-Coriolis force. Experiments are done with NEMO in ocean-only (forced) mode and coupled to the ECMWF atmospheric and wave models. Ocean-only integrations are forced with fields from the ERA-Interim reanalysis. All three effects are noticeable in the extratropics, but the sea-state-dependent turbulent kinetic energy flux yields by far the largest difference. This is partly because the control run has too vigorous deep mixing due to an empirical mixing term in NEMO. We investigate the relation between this ad hoc mixing and Langmuir turbulence and find that it is much more effective than the Langmuir parameterization used in NEMO. The biases in sea surface temperature as well as subsurface temperature are reduced, and the total ocean heat content exhibits a trend closer to that observed in a recent ocean reanalysis (ORAS4) when wave effects are included. Seasonal integrations of the coupled atmosphere-wave-ocean model consisting of NEMO, the wave model ECWAM, and the atmospheric model of ECMWF similarly show that the sea surface temperature biases are greatly reduced when the mixing is controlled by the sea state and properly weighted by the thickness of the uppermost level of the ocean model. These wave-related physical processes were recently implemented in the operational coupled ensemble forecast system of ECMWF. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSPP14A0534K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSPP14A0534K">The Importance of Subsurface Production for Carbon Export - Evidence from Past Oceans</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kemp, A. E. S. 2016-02-01 The maxim of the geological concept of uniformitarianism is "the present is the key to the past", but in the context of our temporally and spatially minimal observational record of modern ocean biogeochemical processes, ancient ocean sediments may provide critical evidence of the key species involved in carbon flux. Specifically, laminated marine sediments that preserve the seasonal flux cycle represent "palaeo-sediment traps" that vastly expand our knowledge of the operations of the marine biological carbon pump. Several key subsurface-dwelling diatom taxa, hitherto thought to be biogeochemically insignificant, are dominant components of ancient marine sediments. For example, the sapropels and equivalent horizons that have accumulated in the Mediterranean over the past 5 million years, contain abundant rhizosolenid and hemiaulid diatoms. These deposits contain the highest concentrations of organic carbon and there is extensive evidence that this was produced by subsurface production in a deep chlorophyll maximum. The highly stratified conditions that led to this subsurface production and carbon flux are in contrast to prevailing views that have held upwelling systems as those with the highest potential for export in the global ocean. Similarly, studies of ancient "greenhouse" periods such as the Cretaceous, with highly stratified oceans and which are potential analogues for future climate change, show evidence for extensive subsurface production. Together with emerging evidence from stratified regions of the modern ocean, such as the subtropical gyres, insights from these ancient oceans suggest that a reappraisal is required of current views on key phytoplankton producers and their role the operation of the marine biological carbon pump. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.B51F..01W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.B51F..01W">Remote Sensing of Subsurface Microbial Transformations</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Williams, K. H.; Ntarlagiannis, D.; Slater, L.; Long, P.; Dohnalkova, A.; Hubbard, S. S.; Banfield, J. F. 2004-12-01 Understanding how microorganisms influence the physical and chemical properties of the subsurface is hindered by our inability to detect microbial dynamics in real time with high spatial resolution. Here we have used non-invasive geophysical methods to monitor biomineralization and related processes during biostimulation at both laboratory and field scales. Alterations in saturated sediment characteristics resulting from microbe-mediated transformations were concomitant with changes in complex resistivity, spontaneous potential, and acoustic wave signatures. Variability in complex resistivity and acoustic wave amplitudes appears tied to the nucleation, growth, and development of nanoparticulate precipitates along grain surfaces and within the pore space. In contrast, time-varying spontaneous potentials appear primarily sensitive to the electrochemical gradients resulting from metabolic pathways, such as iron- and sulfate-reduction. Furthermore, they enable us to track mobile fronts of active respiration that arise due to microbial chemotaxis. In this way, geophysical data may be used to image the distribution of mineral precipitates, biomass, and biogeochemical fronts evolving over time and suggest the ability to remotely monitor contaminated aquifers undergoing bioremediation. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018CG....116...74S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018CG....116...74S">Estimating habitat volume of living resources using three-dimensional circulation and biogeochemical models</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Smith, Katharine A.; Schlag, Zachary; North, Elizabeth W. 2018-07-01 Coupled three-dimensional circulation and biogeochemical models predict changes in water properties that can be used to define fish habitat, including physiologically important parameters such as temperature, salinity, and dissolved oxygen. However, methods for calculating the volume of habitat defined by the intersection of multiple water properties are not well established for coupled three-dimensional models. The objectives of this research were to examine multiple methods for calculating habitat volume from three-dimensional model predictions, select the most robust approach, and provide an example application of the technique. Three methods were assessed: the "Step," "Ruled Surface", and "Pentahedron" methods, the latter of which was developed as part of this research. Results indicate that the analytical Pentahedron method is exact, computationally efficient, and preserves continuity in water properties between adjacent grid cells. As an example application, the Pentahedron method was implemented within the Habitat Volume Model (HabVol) using output from a circulation model with an Arakawa C-grid and physiological tolerances of juvenile striped bass (Morone saxatilis). This application demonstrates that the analytical Pentahedron method can be successfully applied to calculate habitat volume using output from coupled three-dimensional circulation and biogeochemical models, and it indicates that the Pentahedron method has wide application to aquatic and marine systems for which these models exist and physiological tolerances of organisms are known. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.H23F1646Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.H23F1646Y">Hybrid Multiscale Simulation of Hydrologic and Biogeochemical Processes in the River-Groundwater Interaction Zone</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yang, X.; Scheibe, T. D.; Chen, X.; Hammond, G. E.; Song, X. 2015-12-01 The zone in which river water and groundwater mix plays an important role in natural ecosystems as it regulates the mixing of nutrients that control biogeochemical transformations. Subsurface heterogeneity leads to local hotspots of microbial activity that are important to system function yet difficult to resolve computationally. To address this challenge, we are testing a hybrid multiscale approach that couples models at two distinct scales, based on field research at the U. S. Department of Energy's Hanford Site. The region of interest is a 400 x 400 x 20 m macroscale domain that intersects the aquifer and the river and contains a contaminant plume. However, biogeochemical activity is high in a thin zone (mud layer, <1 m thick) immediately adjacent to the river. This microscale domain is highly heterogeneous and requires fine spatial resolution to adequately represent the effects of local mixing on reactions. It is not computationally feasible to resolve the full macroscale domain at the fine resolution needed in the mud layer, and the reaction network needed in the mud layer is much more complex than that needed in the rest of the macroscale domain. Hence, a hybrid multiscale approach is used to efficiently and accurately predict flow and reactive transport at both scales. In our simulations, models at both scales are simulated using the PFLOTRAN code. Multiple microscale simulations in dynamically defined sub-domains (fine resolution, complex reaction network) are executed and coupled with a macroscale simulation over the entire domain (coarse resolution, simpler reaction network). The objectives of the research include: 1) comparing accuracy and computing cost of the hybrid multiscale simulation with a single-scale simulation; 2) identifying hot spots of microbial activity; and 3) defining macroscopic quantities such as fluxes, residence times and effective reaction rates. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9866E..0OZ','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9866E..0OZ">Remote sensing based water-use efficiency evaluation in sub-surface irrigated wine grape vines</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zúñiga, Carlos Espinoza; Khot, Lav R.; Jacoby, Pete; Sankaran, Sindhuja 2016-05-01 Increased water demands have forced agriculture industry to investigate better irrigation management strategies in crop production. Efficient irrigation systems, improved irrigation scheduling, and selection of crop varieties with better water-use efficiencies can aid towards conserving water. In an ongoing experiment carried on in Red Mountain American Viticulture area near Benton City, Washington, subsurface drip irrigation treatments at 30, 60 and 90 cm depth, and 15, 30 and 60% irrigation were applied to satisfy evapotranspiration demand using pulse and continuous irrigation. These treatments were compared to continuous surface irrigation applied at 100% evapotranspiration demand. Thermal infrared and multispectral images were acquired using unmanned aerial vehicle during the growing season. Obtained results indicated no difference in yield among treatments (p<0.05), however there was statistical difference in leaf temperature comparing surface and subsurface irrigation (p<0.05). Normalized vegetation index obtained from the analysis of multispectral images showed statistical difference among treatments when surface and subsurface irrigation methods were compared. Similar differences in vegetation index values were observed, when irrigation rates were compared. Obtained results show the applicability of aerial thermal infrared and multispectral images to characterize plant responses to different irrigation treatments and use of such information in irrigation scheduling or high-throughput selection of water-use efficient crop varieties in plant breeding. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11.2089P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11.2089P">Coupled land surface-subsurface hydrogeophysical inverse modeling to estimate soil organic carbon content and explore associated hydrological and thermal dynamics in the Arctic tundra</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Phuong Tran, Anh; Dafflon, Baptiste; Hubbard, Susan S. 2017-09-01 Quantitative characterization of soil organic carbon (OC) content is essential due to its significant impacts on surface-subsurface hydrological-thermal processes and microbial decomposition of OC, which both in turn are important for predicting carbon-climate feedbacks. While such quantification is particularly important in the vulnerable organic-rich Arctic region, it is challenging to achieve due to the general limitations of conventional core sampling and analysis methods, and to the extremely dynamic nature of hydrological-thermal processes associated with annual freeze-thaw events. In this study, we develop and test an inversion scheme that can flexibly use single or multiple datasets - including soil liquid water content, temperature and electrical resistivity tomography (ERT) data - to estimate the vertical distribution of OC content. Our approach relies on the fact that OC content strongly influences soil hydrological-thermal parameters and, therefore, indirectly controls the spatiotemporal dynamics of soil liquid water content, temperature and their correlated electrical resistivity. We employ the Community Land Model to simulate nonisothermal surface-subsurface hydrological dynamics from the bedrock to the top of canopy, with consideration of land surface processes (e.g., solar radiation balance, evapotranspiration, snow accumulation and melting) and ice-liquid water phase transitions. For inversion, we combine a deterministic and an adaptive Markov chain Monte Carlo (MCMC) optimization algorithm to estimate a posteriori distributions of desired model parameters. For hydrological-thermal-to-geophysical variable transformation, the simulated subsurface temperature, liquid water content and ice content are explicitly linked to soil electrical resistivity via petrophysical and geophysical models. We validate the developed scheme using different numerical experiments and evaluate the influence of measurement errors and benefit of joint inversion on the </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70178260','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70178260">Biogeochemical redox processes and their impact on contaminant dynamics</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Borch, Thomas; Kretzschmar, Ruben; Kappler, Andreas; Van Cappellen, Philippe; Ginder-Vogel, Matthew; Campbell, Kate M. 2010-01-01 Life and element cycling on Earth is directly related to electron transfer (or redox) reactions. An understanding of biogeochemical redox processes is crucial for predicting and protecting environmental health and can provide new opportunities for engineered remediation strategies. Energy can be released and stored by means of redox reactions via the oxidation of labile organic carbon or inorganic compounds (electron donors) by microorganisms coupled to the reduction of electron acceptors including humic substances, iron-bearing minerals, transition metals, metalloids, and actinides. Environmental redox processes play key roles in the formation and dissolution of mineral phases. Redox cycling of naturally occurring trace elements and their host minerals often controls the release or sequestration of inorganic contaminants. Redox processes control the chemical speciation, bioavailability, toxicity, and mobility of many major and trace elements including Fe, Mn, C, P, N, S, Cr, Cu, Co, As, Sb, Se, Hg, Tc, and U. Redox-active humic substances and mineral surfaces can catalyze the redox transformation and degradation of organic contaminants. In this review article, we highlight recent advances in our understanding of biogeochemical redox processes and their impact on contaminant fate and transport, including future research needs. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active">10</li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active">11</li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19990092375','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990092375">Seasonal Distributions of Global Ocean Chlorophyll and Nutrients: Analysis with a Coupled Ocean General Circulation Biogeochemical, and Radiative Model</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Gregg, Watson W. 1999-01-01 A coupled general ocean circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. The model is driven by climatological meteorological conditions, cloud cover, and sea surface temperature. Biogeochemical 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, chorophytes, and picoplankton) and three nutrient groups (nitrate, ammonium, and silicate). Phytoplankton groups are initialized as homogeneous fields horizontally and vertically, and allowed to distribute themselves according to the prevailing conditions. Basin-scale model chlorophyll results are in very good agreement with CZCS pigments in virtually every global region. Seasonal variability observed in the CZCS is also well represented in the model. Synoptic scale (100-1000 km) comparisons of imagery are also in good conformance, although occasional departures are apparent. Agreement of nitrate distributions with in situ data is even better, including seasonal dynamics, except for the equatorial Atlantic. The good agreement of the model with satellite and in situ data sources indicates that the model dynamics realistically simulate 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 the great diversity of physical, biological </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29220820','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29220820">Application of an in-situ soil sampler for assessing subsurface biogeochemical dynamics in a diesel-contaminated coastal site during soil flushing operations.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Kwon, Man Jae; O'Loughlin, Edward J; Ham, Baknoon; Hwang, Yunho; Shim, Moojoon; Lee, Soonjae 2018-01-15 Subsurface biogeochemistry and contaminant dynamics during the remediation of diesel-contamination by in-situ soil flushing were investigated at a site located in a coastal region. An in-situ sampler containing diesel-contaminated soils separated into two size fractions (<0.063- and <2-mm) was utilized in two monitoring wells: DH1 (located close to the injection and extraction wells for in-situ soil flushing) and DH2 (located beyond sheet piles placed to block the transport of leaked diesel). Total petroleum hydrocarbon (TPH) concentrations and biogeochemical properties were monitored both in soil and groundwater for six months. A shift occurred in the groundwater type from Ca-HCO 3 to Na-Cl due to seawater intrusion during intense pumping, while the concentrations of Ni, Cu, Co, V, Cr, and Se increased substantially following surfactant (TWEEN 80) injection. The in-situ sampler with fine particles was more sensitive to variations in conditions during the remedial soil flushing process. In both wells, soil TPH concentrations in the <0.063-mm fraction were much higher than those in the <2-mm fraction. Increases in soil TPH in DH1 were consistent with the expected outcomes following well pumping and surfactant injection used to enhance TPH extraction. However, the number of diesel-degrading microorganisms decreased after surfactant injection. 16S-rRNA gene-based analysis also showed that the community composition and diversity depended on both particle size and diesel contamination. The multidisciplinary approach to the contaminated site assessments showed that soil flushing with surfactant enhanced diesel extraction, but negatively impacted in-situ diesel biodegradation as well as groundwater quality. The results also suggest that the in-situ sampler can be an effective monitoring tool for subsurface biogeochemistry as well as contaminant dynamics. Copyright © 2017 Elsevier Ltd. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940026113','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940026113">Towards coupled physical-biogeochemical models of the ocean carbon cycle</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Rintoul, Stephen R. 1992-01-01 The purpose of this review is to discuss the critical gaps in our knowledge of ocean dynamics and biogeochemical cycles. It is assumed that the ultimate goal is the design of a model of the earth system that can predict the response to changes in the external forces driving climate. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/803136','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/803136">Subsurface Contamination Control</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Y. Yuan There are two objectives of this report, ''Subsurface Contamination Control''. The first is to provide a technical basis for recommending limiting radioactive contamination levels (LRCL) on the external surfaces of waste packages (WP) for acceptance into the subsurface repository. The second is to provide an evaluation of the magnitude of potential releases from a defective WP and the detectability of the released contents. The technical basis for deriving LRCL has been established in ''Retrieval Equipment and Strategy for Wp on Pallet'' (CRWMS M and O 2000g, 6.3.1). This report updates the derivation by incorporating the latest design information of themore » subsurface repository for site recommendation. The derived LRCL on the external surface of WPs, therefore, supercede that described in CRWMS M and O 2000g. The derived LRCL represent the average concentrations of contamination on the external surfaces of each WP that must not be exceeded before the WP is to be transported to the subsurface facility for emplacement. The evaluation of potential releases is necessary to control the potential contamination of the subsurface repository and to detect prematurely failed WPs. The detection of failed WPs is required in order to provide reasonable assurance that the integrity of each WP is intact prior to MGR closure. An emplaced WP may become breached due to manufacturing defects or improper weld combined with failure to detect the defect, by corrosion, or by mechanical penetration due to accidents or rockfall conditions. The breached WP may release its gaseous and volatile radionuclide content to the subsurface environment and result in contaminating the subsurface facility. The scope of this analysis is limited to radioactive contaminants resulting from breached WPs during the preclosure period of the subsurface repository. This report: (1) documents a method for deriving LRCL on the external surfaces of WP for acceptance into the subsurface repository; (2 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.5399L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.5399L">Sorption of pathogens during sub-surface drip irrigation with wastewater</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Levi, Laillach; Gillerman Gillerman, Leonid; Kalavrouziotis, Ioannis; Oron, Gideon 2017-04-01 Water scarcity continues to be one of the major threats to human survival in many regions worldwide, such as Africa, the Mediterranean Basin, the State of California in the US. Due to a mixture of factors such as population growth, reduction in water resources availability and higher demand for high quality waters in these regions these countries face water shortage issues that stem from overuse, extensive extraction of groundwater, and frequent drought events. In addition, there are increases in environmental and health awareness that have led to intensive efforts in the treatment and reuse of nonconventional water sources, mainly wastewater and greywater. One approach to water shortages issues is to use wastewater as means to close the gap between supply and demand. However, the need to treat wastewater and to disinfect it forces additional economic burden on the users, primarily for agricultural irrigation. A possible solution might be to use the soil as a sorbent for the contained pathogens. Under sub-surface drip irrigation, not allowing the wastewater to reach the soil surface, the pathogens will remain in the soil. It was as well shown in field experiments that the opening size of roots will not allow pathogens to penetrate into the plants. Additional advantages such as water saving, protection of the pipe systems and others are also important. Field experiments in commercial fields just emphasize the main advantages of sub-surface drip irrigation. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11804141','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11804141">Treatment of laboratory wastewater in a tropical constructed wetland comparing surface and subsurface flow.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Meutia, A A 2001-01-01 Wastewater treatment by constructed wetland is an appropriate technology for tropical developing countries like Indonesia because it is inexpensive, easily maintained, and has environmentally friendly and sustainable characteristics. The aim of the research is to examine the capability of constructed wetlands for treating laboratory wastewater at our Center, to investigate the suitable flow for treatment, namely vertical subsurface or horizontal surface flow, and to study the effect of the seasons. The constructed wetland is composed of three chambered unplanted sedimentation tanks followed by the first and second beds, containing gravel and sand, planted with Typha sp.; the third bed planted with floating plant Lemna sp.; and a clarifier with two chambers. The results showed that the subsurface flow in the dry season removed 95% organic carbon (COD) and total phosphorus (T-P) respectively, and 82% total nitrogen (T-N). In the transition period from the dry season to the rainy season, COD removal efficiency decreased to 73%, T-N increased to 89%, and T-P was almost the same as that in the dry season. In the rainy season COD and T-N removal efficiencies increased again to 95% respectively, while T-P remained unchanged. In the dry season, COD and T-P concentrations in the surface flow showed that the removal efficiencies were a bit lower than those in the subsurface flow. Moreover, T-N removal efficiency was only half as much as that in the subsurface flow. However, in the transition period, COD removal efficiency decreased to 29%, while T-N increased to 74% and T-P was still constant, around 93%. In the rainy season, COD and T-N removal efficiencies increased again to almost 95%. On the other hand, T-P decreased to 76%. The results show that the constructed wetland is capable of treating the laboratory wastewater. The subsurface flow is more suitable for treatment than the surface flow, and the seasonal changes have effects on the removal efficiency. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.H51C0911G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.H51C0911G">Reactive Transport Modeling of Induced Calcite Precipitation Reaction Fronts in Porous Media Using A Parallel, Fully Coupled, Fully Implicit Approach</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Guo, L.; Huang, H.; Gaston, D.; Redden, G. D.; Fox, D. T.; Fujita, Y. 2010-12-01 Inducing mineral precipitation in the subsurface is one potential strategy for immobilizing trace metal and radionuclide contaminants. Generating mineral precipitates in situ can be achieved by manipulating chemical conditions, typically through injection or in situ generation of reactants. How these reactants transport, mix and react within the medium controls the spatial distribution and composition of the resulting mineral phases. Multiple processes, including fluid flow, dispersive/diffusive transport of reactants, biogeochemical reactions and changes in porosity-permeability, are tightly coupled over a number of scales. Numerical modeling can be used to investigate the nonlinear coupling effects of these processes which are quite challenging to explore experimentally. Many subsurface reactive transport simulators employ a de-coupled or operator-splitting approach where transport equations and batch chemistry reactions are solved sequentially. However, such an approach has limited applicability for biogeochemical systems with fast kinetics and strong coupling between chemical reactions and medium properties. A massively parallel, fully coupled, fully implicit Reactive Transport simulator (referred to as “RAT”) based on a parallel multi-physics object-oriented simulation framework (MOOSE) has been developed at the Idaho National Laboratory. Within this simulator, systems of transport and reaction equations can be solved simultaneously in a fully coupled, fully implicit manner using the Jacobian Free Newton-Krylov (JFNK) method with additional advanced computing capabilities such as (1) physics-based preconditioning for solution convergence acceleration, (2) massively parallel computing and scalability, and (3) adaptive mesh refinements for 2D and 3D structured and unstructured mesh. The simulator was first tested against analytical solutions, then applied to simulating induced calcium carbonate mineral precipitation in 1D columns and 2D flow cells as analogs </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040171203&hterms=BIO&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DBIO','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040171203&hterms=BIO&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DBIO">Habitat Inspection Scanner, Bio-Structure Scanner, and In Situ Sub-Surface Composition Sensor</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> VanSteenberg, Michael 2004-01-01 The extension of dielectric and inductive spectroscopy into in situ observations represents a significant exploration-enabling tool. This technology can be widely applied from microscopic to macroscopic. Dielectrometry and inductometry can measure sub-surface composition and its distribution. The primary environment that we cannot easily explored is the sub-surface of solid bodies. Weather as part of our equipment that we bring with us, or the locations we are exploring. These fundamental questions lie at the core of the exploration Initiative. To answer them we must use a whole host of complimentary tools including those that allow us to practically examine the sub-surface environment. A nondestructive approach offers significant advantages for both the initial identification of likely samples but also the monitoring of ecosystems and crew health. These include materials characterization, nondestructive inspection, and process quality control, damage monitoring, and hidden object detection and identification. The identification of natural resources such as water on the Moon or Mars is of great importance to the utilization of local resource in the support of human exploration crews. On the macroscopic scale, the understanding of what resources are available and how they are distributed is of primary importance to their productive utilization. Even if initial explorations do not require the use of local resources to succeed, eventual settlement and commercial development will. The routine examination of the structural integrity (micro cracks, leaks) of hi.inafi habitats in harsh envkmments ww!d also be enabled. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23987916','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23987916">Benthic exchange and biogeochemical cycling in permeable sediments.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Huettel, Markus; Berg, Peter; Kostka, Joel E 2014-01-01 The sandy sediments that blanket the inner shelf are situated in a zone where nutrient input from land and strong mixing produce maximum primary production and tight coupling between water column and sedimentary processes. The high permeability of the shelf sands renders them susceptible to pressure gradients generated by hydrodynamic and biological forces that modulate spatial and temporal patterns of water circulation through these sediments. The resulting dynamic three-dimensional patterns of particle and solute distribution generate a broad spectrum of biogeochemical reaction zones that facilitate effective decomposition of the pelagic and benthic primary production products. The intricate coupling between the water column and sediment makes it challenging to quantify the production and decomposition processes and the resultant fluxes in permeable shelf sands. Recent technical developments have led to insights into the high biogeochemical and biological activity of these permeable sediments and their role in the global cycles of matter. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1918854G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1918854G">Coupled charge migration and fluid mixing in reactive fronts</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ghosh, Uddipta; Bandopadhyay, Aditya; Jougnot, Damien; Le Borgne, Tanguy; Meheust, Yves 2017-04-01 Quantifying fluid mixing in subsurface environments and its consequence on biogeochemical reactions is of paramount importance owing to its role in processes such as contaminant migration, aquifer remediation, CO2 sequestration or clogging processes, to name a few (Dentz et al. 2011). The presence of strong velocity gradients in porous media is expected to lead to enhanced diffusive mixing and augmented reaction rates (Le Borgne et al. 2014). Accurate in situ imaging of subsurface reactive solute transport and mixing remains to date a challenging proposition: the opacity of the medium prevents optical imaging and field methods based on tracer tests do not provide spatial information. Recently developed geophysical methods based on the temporal monitoring of electrical conductivity and polarization have shown promises for mapping and monitoring biogeochemical reactions in the subsurface although it remains challenging to decipher the multiple sources of electrical signals (e.g. Knight et al. 2010). In this work, we explore the coupling between fluid mixing, reaction and charge migration in porous media to evaluate the potential of mapping reaction rates from electrical measurements. To this end, we develop a new theoretical framework based on a lamellar mixing model (Le Borgne et al. 2013) to quantify changes in electrical mobility induced by chemical reactions across mixing fronts. Electrical conductivity and induced polarization are strongly dependent on the concentration of ionic species, which in turn depend on the local reaction rates. Hence, our results suggest that variation in real and complex electrical conductivity may be quantitatively related to the mixing and reaction dynamics. Thus, the presented theory provides a novel upscaling framework for quantifying the coupling between mixing, reaction and charge migration in heterogeneous porous media flows. References: Dentz. et al., Mixing, spreading and reaction in heterogeneous media: A brief review J </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740026676','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740026676">Feasibility study of a swept frequency electromagnetic probe (SWEEP) using inductive coupling for the determination of subsurface conductivity of the earth and water prospecting in arid regions</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Latorraca, G. A.; Bannister, L. H. 1974-01-01 Techniques developed for electromagnetic probing of the lunar interior, and techniques developed for the generation of high power audio frequencies were combined to make practical a magnetic inductive coupling system for the rapid measurement of ground conductivity profiles which are helpful when prospecting for the presence and quality of subsurface water. A system which involves the measurement of the direction, intensity, and time phase of the magnetic field observed near the surface of the earth at a distance from a horizontal coil energized so as to create a field that penetrates the earth was designed and studied to deduce the conductivity and stratification of the subsurface. Theoretical studies and a rudimentary experiment in an arid region showed that the approach is conceptually valid and that this geophysical prospecting technique can be developed for the economical exploration of subterranean water resources. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.H13C1546K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.H13C1546K">Modeling the fate of nitrogen on the catchment scale using a spatially explicit hydro-biogeochemical simulation system</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Klatt, S.; Butterbach-Bahl, K.; Kiese, R.; Haas, E.; Kraus, D.; Molina-Herrera, S. W.; Kraft, P. 2015-12-01 The continuous growth of the human population demands an equally growing supply for fresh water and food. As a result, available land for efficient agriculture is constantly diminishing which forces farmers to cultivate inferior croplands and intensify agricultural practices, e.g., increase the use of synthetic fertilizers. This intensification of marginal areas in particular will cause a dangerous rise in nitrate discharge into open waters or even drinking water resources. In order to reduce the amount of nitrate lost by surface runoff or lateral subsurface transport, bufferstrips have proved to be a valuable means. Current laws, however, promote rather static designs (i.e., width and usage) even though a multitude of factors, e.g., soil type, slope, vegetation and the nearby agricultural management, determines its effectiveness. We propose a spatially explicit modeling approach enabling to assess the effects of those factors on nitrate discharge from arable lands using the fully distributed hydrology model CMF coupled to the complex biogeochemical model LandscapeDNDC. Such a modeling scheme allows to observe the displacement of dissolved nutrients in both vertical and horizontal directions and serves to estimate both their uptake by the vegetated bufferstrip and loss to the environment. First results indicate a significant reduction of nitrate loss in the presence of a bufferstrip (2.5 m). We show effects induced by various buffer strip widths and plant cover on the nitrate retention. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.H34A..05R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.H34A..05R">Plutonium Oxidation State Distribution under Aerobic and Anaerobic Subsurface Conditions for Metal-Reducing Bacteria</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Reed, D. T.; Swanson, J.; Khaing, H.; Deo, R.; Rittmann, B. 2009-12-01 The fate and potential mobility of plutonium in the subsurface is receiving increased attention as the DOE looks to cleanup the many legacy nuclear waste sites and associated subsurface contamination. Plutonium is the near-surface contaminant of concern at several DOE sites and continues to be the contaminant of concern for the permanent disposal of nuclear waste. The mobility of plutonium is highly dependent on its redox distribution at its contamination source and along its potential migration pathways. This redox distribution is often controlled, especially in the near-surface where organic/inorganic contaminants often coexist, by the direct and indirect effects of microbial activity. The redox distribution of plutonium in the presence of facultative metal reducing bacteria (specifically Shewanella and Geobacter species) was established in a concurrent experimental and modeling study under aerobic and anaerobic conditions. Pu(VI), although relatively soluble under oxidizing conditions at near-neutral pH, does not persist under a wide range of the oxic and anoxic conditions investigated in microbiologically active systems. Pu(V) complexes, which exhibit high chemical toxicity towards microorganisms, are relatively stable under oxic conditions but are reduced by metal reducing bacteria under anaerobic conditions. These facultative metal-reducing bacteria led to the rapid reduction of higher valent plutonium to form Pu(III/IV) species depending on nature of the starting plutonium species and chelating agents present in solution. Redox cycling of these lower oxidation states is likely a critical step in the formation of pseudo colloids that may lead to long-range subsurface transport. The CCBATCH biogeochemical model is used to explain the redox mechanisms and final speciation of the plutonium oxidation state distributions observed. These results for microbiologically active systems are interpreted in the context of their importance in defining the overall migration </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=241726','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=241726">Escherichia coli Transport from Surface-Applied Manure to Subsurface Drains through Artificial Biopores</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> Transport of pathogenic bacteria in soils primarily occurs through soil mesopores and macropores (e.g., biopores and cracks). Field research has demonstrated that biopores and subsurface drains can be hydraulically connected. This research was conducted to investigate the importance of surface conne... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H42E..03R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H42E..03R">Structure of peat soils and implications for biogeochemical processes and hydrological flow</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rezanezhad, F.; McCarter, C. P. R.; Gharedaghloo, B.; Kleimeier, C.; Milojevic, T.; Liu, H.; Weber, T. K. D.; Price, J. S.; Quinton, W. L.; Lenartz, B.; Van Cappellen, P. 2017-12-01 Permafrost peatlands contain globally important amounts of soil organic carbon and play major roles in global water, nutrient and biogeochemical cycles. The structure of peatland soils (i.e., peat) are highly complex with unique physical and hydraulic properties; where significant, and only partially reversible, shrinkage occurs during dewatering (including water table fluctuations), compression and/or decomposition. These distinct physical and hydraulic properties controls water flow, which in turn affect reactive and non-reactive solute transport (such as, sorption or degradation) and biogeochemical functions. Additionally, peat further attenuates solute migration through molecular diffusion into the inactive pores of Sphagnum dominated peat. These slow, diffusion-limited solute exchanges between the pore regions may give rise to pore-scale chemical gradients and heterogeneous distributions of microbial habitats and activity in peat soils. Permafrost peat plateaus have the same essential subsurface characteristics as other widely organic soil-covered peatlands, where the hydraulic conductivity is related to the degree of decomposition and soil compression. Increasing levels of decomposition correspond with a reduction of effective pore diameter and consequently restrict water and solute flow (by several orders of magnitude in hydraulic conductivity between the ground surface and a depth of 50 cm). In this presentation, we present the current knowledge of key physical and hydraulic properties related to the structure of globally available peat soils and discuss their implications for water storage, flow and the migration of solutes. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JCoPh.352....1D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JCoPh.352....1D">A multiscale fixed stress split iterative scheme for coupled flow and poromechanics in deep subsurface reservoirs</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Dana, Saumik; Ganis, Benjamin; Wheeler, Mary F. 2018-01-01 In coupled flow and poromechanics phenomena representing hydrocarbon production or CO2 sequestration in deep subsurface reservoirs, the spatial domain in which fluid flow occurs is usually much smaller than the spatial domain over which significant deformation occurs. The typical approach is to either impose an overburden pressure directly on the reservoir thus treating it as a coupled problem domain or to model flow on a huge domain with zero permeability cells to mimic the no flow boundary condition on the interface of the reservoir and the surrounding rock. The former approach precludes a study of land subsidence or uplift and further does not mimic the true effect of the overburden on stress sensitive reservoirs whereas the latter approach has huge computational costs. In order to address these challenges, we augment the fixed-stress split iterative scheme with upscaling and downscaling operators to enable modeling flow and mechanics on overlapping nonmatching hexahedral grids. Flow is solved on a finer mesh using a multipoint flux mixed finite element method and mechanics is solved on a coarse mesh using a conforming Galerkin method. The multiscale operators are constructed using a procedure that involves singular value decompositions, a surface intersections algorithm and Delaunay triangulations. We numerically demonstrate the convergence of the augmented scheme using the classical Mandel's problem solution. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMOS31C1734C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMOS31C1734C">Predictability of Subsurface Temperature and the AMOC</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chang, Y.; Schubert, S. D. 2013-12-01 GEOS 5 coupled model is extensively used for experimental decadal climate prediction. Understanding the limits of decadal ocean predictability is critical for making progress in these efforts. Using this model, we study the subsurface temperature initial value predictability, the variability of the Atlantic meridional overturning circulation (AMOC) and its impacts on the global climate. Our approach is to utilize the idealized data assimilation technology developed at the GMAO. The technique 'replay' allows us to assess, for example, the impact of the surface wind stresses and/or precipitation on the ocean in a very well controlled environment. By running the coupled model in replay mode we can in fact constrain the model using any existing reanalysis data set. We replay the model constraining (nudging) it to the MERRA reanalysis in various fields from 1948-2012. The fields, u,v,T,q,ps, are adjusted towards the 6-hourly analyzed fields in atmosphere. The simulated AMOC variability is studied with a 400-year-long segment of replay integration. The 84 cases of 10-year hindcasts are initialized from 4 different replay cycles. Here, the variability and predictability are examined further by a measure to quantify how much the subsurface temperature and AMOC variability has been influenced by atmospheric forcing and by ocean internal variability. The simulated impact of the AMOC on the multi-decadal variability of the SST, sea surface height (SSH) and sea ice extent is also studied. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/949153','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/949153">Project Work Plan: Sequestration of Strontium-90 Subsurface Contamination in the Hanford 100-N Area by Surface Infiltration of an Apatite Solution</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Szecsody, Jim E. 2006-04-30 We propose to develop an infiltration strategy that defines the precipitation rate of an apatite-forming solution and Sr-90 sequestration processes under variably saturated (low water content) conditions. We will develop this understanding through small-scale column studies, intermediate-scale two-dimensional (2-D) experiments, and numerical modeling to quantify individual and coupled processes associated with apatite formation and Sr-90 transport during and after infiltration of the Ca-citrate-PO4 solution. Development of capabilities to simulate these coupled biogeochemical processes during both injection and infiltration will be used to determine the most cost-effective means to emplace an in situ apatite barrier with a longevity of 300 yearsmore » to permanently sequester Sr-90 until it decays. Biogeochemical processes that will be investigated are citrate biodegradation and apatite precipitation rates at varying water contents as a function of water content. Coupled processes that will be investigated include the influence of apatite precipitation (which occupies pore space) on the hydraulic and transport properties of the porous media during infiltration.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1457147-role-subsurface-oxygen-cu-surfaces-co2-electrochemical-reduction','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1457147-role-subsurface-oxygen-cu-surfaces-co2-electrochemical-reduction">The Role of Subsurface Oxygen on Cu Surfaces for CO 2 Electrochemical Reduction</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Fields, Meredith; Hong, Xin; Norskov, Jens K.; ... 2018-06-12 Under ambient conditions, copper with oxygen near the surface displays strengthened CO 2 and CO adsorption energies. This finding is often used to rationalize differences seen in product distributions between Cu-oxide and pure Cu electrodes during electrochemical CO 2 reduction. However, little evidence exists to confirm the presence of oxygen within first few layers of the Cu matrix under relevant experimental reducing conditions. As a result, using density functional theory calculations, we discuss the stability of subsurface oxygen from thermodynamic and kinetic perspectives, and show that under reducing potentials, subsurface oxygen alone should have negligible effects on the activity ofmore » crystalline Cu.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1457147-role-subsurface-oxygen-cu-surfaces-co2-electrochemical-reduction','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1457147-role-subsurface-oxygen-cu-surfaces-co2-electrochemical-reduction">The Role of Subsurface Oxygen on Cu Surfaces for CO 2 Electrochemical Reduction</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Fields, Meredith; Hong, Xin; Norskov, Jens K. Under ambient conditions, copper with oxygen near the surface displays strengthened CO 2 and CO adsorption energies. This finding is often used to rationalize differences seen in product distributions between Cu-oxide and pure Cu electrodes during electrochemical CO 2 reduction. However, little evidence exists to confirm the presence of oxygen within first few layers of the Cu matrix under relevant experimental reducing conditions. As a result, using density functional theory calculations, we discuss the stability of subsurface oxygen from thermodynamic and kinetic perspectives, and show that under reducing potentials, subsurface oxygen alone should have negligible effects on the activity ofmore » crystalline Cu.« less </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active">11</li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active">12</li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000081769','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000081769">Significant Findings: Tracking the SeaWiFS Record with a Coupled Physical/Biogeochemical/Radiative Model of the Global Oceans</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Watson, Gregg W. 2000-01-01 The Sea-Viewing Wide Field-of-view Sensor (SeaWiFS) has observed 2.5 years of routine global chlorophyll observations from space. The mission was launched into a record El Nino event, which eventually gave way to one of the most intensive and longest-lasting La Nina events ever recorded. The SeaWiFS chlorophyll record captured the response of ocean phytoplankton to these significant events in the tropical Indo-Pacific basins, but also indicated significant interannual variability unrelated to the El Nino/La Nina events. This included large variability in the North Atlantic and Pacific basins, in the North Central and equatorial Atlantic, and milder patterns in the North Central Pacific. This SeaWiFS record was tracked with a coupled physical/biogeochemical/radiative model of the global oceans using near-real-time forcing data such as wind stresses, sea surface temperatures, and sea ice. This provided an opportunity to offer physically and biogeochemically meaningful explanations of the variability observed in the SeaWiFS data set, since the causal mechanisms and interrelationships of the model are completely understood. The coupled model was able to represent the seasonal distributions of chlorophyll during the SeaWiFS era, and was capable of differentiating among the widely different processes and dynamics occurring in the global oceans. The model was also reasonably successful in representing the interannual signal, especially when it was large, such as, the El Nino and La Nina events in the tropical Pacific and Indian Oceans. The model provided different phytoplankton group responses for the different events in these regions: diatoms were predominant in the tropical Pacific during the La Nina but other groups were predominant during El Nino. The opposite condition occurred in the tropical Indian Ocean. Both situations were due to the different responses of the basins to El Nino. The interannual variability in the North Atlantic, which was exhibited in Sea </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910042998&hterms=cement&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dcement','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910042998&hterms=cement&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dcement">A survey of surface structures and subsurface developments for lunar bases</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hypes, Warren D.; Wright, Robert L. 1990-01-01 Concepts proposed for lunar-base structures and shelters include those fabricated on earth, fabricated locally using lunar materials, and developed from subsurface features. Early bases may rely on evolutionary growth using Space Station modules and nodes covered with regolith for protection against thermal and radiative stresses. Expandable/inflatable shelters used alone on the surface or in conjunction with subselene (beneath the lunar surface) features and spent portions of the Space Shuttle's fuel tanks offer early alternatives. More mature lunar bases may need larger volumes provided by erectable buildings, hybrid inflatable/rigid spheres, modular concrete buildings using locally derived cement, or larger subselene developments. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70036943','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70036943">Hydrologic and biogeochemical controls of river subsurface solutes under agriculturally enhanced ground water flow</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Wildman, R.A.; Domagalski, Joseph L.; Hering, J.G. 2009-01-01 The relative influences of hydrologic processes and biogeochemistry on the transport and retention of minor solutes were compared in the riverbed of the lower Merced River (California, USA). The subsurface of this reach receives ground water discharge and surface water infiltration due to an altered hydraulic setting resulting from agricultural irrigation. Filtered ground water samples were collected from 30 drive point locations in March, June, and October 2004. Hydrologic processes, described previously, were verified by observations of bromine concentrations; manganese was used to indicate redox conditions. The separate responses of the minor solutes strontium, barium, uranium, and phosphorus to these influences were examined. Correlation and principal component analyses indicate that hydrologic processes dominate the distribution of trace elements in the ground water. Redox conditions appear to be independent of hydrologic processes and account for most of the remaining data variability. With some variability, major processes are consistent in two sampling transects separated by 100 m. Copyright ?? 2009 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/505265','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/505265">Demonstration of close-coupled barriers for subsurface containment of buried waste</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Dwyer, B.P. 1996-05-01 A close-coupled barrier is produced by first installing a conventional cement grout curtain followed by a thin inner lining of a polymer grout. The resultant barrier is a cement polymer composite that has economic benefits derived from the cement and performance benefits from the durable and resistant polymer layer. Close-coupled barrier technology is applicable for final, interim, or emergency containment of subsurface waste forms. Consequently, when considering the diversity of technology application, the construction emplacement and material technology maturity, general site operational requirements, and regulatory compliance incentives, the close-coupled barrier system provides an alternative for any hazardous or mixed wastemore » remediation plan. This paper discusses the installation of a close-coupled barrier and the subsequent integrity verification. The demonstration was installed at a benign site at the Hanford Geotechnical Test Facility, 400 Area, Hanford, Washington. The composite barrier was emplaced beneath a 7,500 liter tank. The tank was chosen to simulate a typical DOE Complex waste form. The stresses induced on the waste form were evaluated during barrier construction. The barrier was constructed using conventional jet grouting techniques. Drilling was completed at a 45{degree} angle to the ground, forming a conical shaped barrier with the waste form inside the cone. Two overlapping rows of cylindrical cement columns were grouted in a honeycomb fashion to form the secondary backdrop barrier layer. The primary barrier, a high molecular weight polymer manufactured by 3M Company, was then installed providing a relatively thin inner liner for the secondary barrier. The primary barrier was emplaced by panel jet grouting with a dual wall drill stem, two phase jet grouting system.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ISPAr.XL8..469S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ISPAr.XL8..469S">GIS based 3D visualization of subsurface and surface lineaments / faults and their geological significance, northern tamil nadu, India</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Saravanavel, J.; Ramasamy, S. M. 2014-11-01 The study area falls in the southern part of the Indian Peninsular comprising hard crystalline rocks of Archaeozoic and Proterozoic Era. In the present study, the GIS based 3D visualizations of gravity, magnetic, resistivity and topographic datasets were made and therefrom the basement lineaments, shallow subsurface lineaments and surface lineaments/faults were interpreted. These lineaments were classified as category-1 i.e. exclusively surface lineaments, category-2 i.e. surface lineaments having connectivity with shallow subsurface lineaments and category-3 i.e. surface lineaments having connectivity with shallow subsurface lineaments and basement lineaments. These three classified lineaments were analyzed in conjunction with known mineral occurrences and historical seismicity of the study area in GIS environment. The study revealed that the category-3 NNE-SSW to NE-SW lineaments have greater control over the mineral occurrences and the N-S, NNE-SSW and NE-SW, faults/lineaments control the seismicities in the study area. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814108V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814108V">Biogeochemical characteristics of mesoscale eddies in the generation zone off Valparaíso, Chile</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Villegas, Valerie; Cornejo, Marcela; Molina, Verónica; Silva, Nelson; Hormazábal, Samuel 2016-04-01 The coastal area off Valparaiso is characterized by an intense mesoscale activity associated with eddies, which transport highly productive-coastal waters to the oligotrophic areas of the Subtropical Gyre. Among these, the Intrathermocline Anticyclonic Eddies (ITE's) which are forming in the eastern South Pacific, transport low oxygen- and high nutrients- subsurface water of Equatorial Subsurface Water (ESSW). These eddies have been well characterized in terms of generation rate, direction, speed and water transport. However, biogeochemical conditions in their origin and its temporal variability are not well assessed. The present study aims to determine the variability, spatially and temporally, of the biogeochemical properties in the water column at the eddies generation zone, off Punta Ángeles, Valparaíso (33° S). For this, a monthly time series was conducted between January and August 2016 where a cross-shore transect with six-stations was deployed (from coast to 16 nm). Each station was sampled with CTD-OF, while only in station 5 (1300 m depth) was sampled in 16 depth for biogeochemical variables: nutrients (NO3-, NO2-, PO4-3, Si(OH)4), greenhouse gases (CO2, CH4 and N2O), chlorophyll a, stable isotopes in particulate organic material (13C, 15N), content of organic carbon and nitrogen in POM. The spatial and temporal distribution shows the presence of subsurface cores (100 - 300 m) with water with high salinity (> 34.7 psu) and low oxygen content (< 0.5 mLṡL-1), associated with mesoscale subsurface structures. The largest vertical and horizontal extension of these structures was observed in January 2015. These subsurface structures showed a significant deficit of reactive nitrogen (N* < -10 μM), nitrite accumulation (> 0.6 μM) and the highest supersaturations of CO2 (110 - 344%) and N2O (107 - 407%). Along with this, the eddies generation zone presented a temporal variability of air-sea gases fluxes with the highest in the austral summer and autumn </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880052848&hterms=Saunders&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D50%26Ntt%3DSaunders%252C%2BM','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880052848&hterms=Saunders&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D50%26Ntt%3DSaunders%252C%2BM">Evidence for highly reflecting materials on the surface and subsurface of Venus</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Jurgens, R. F.; Slade, M. A.; Saunders, R. S. 1988-01-01 Radar images at a 12.5-centimeter wavelength made with the Goldstone radar interferometer in 1980 and 1986, together with lunar radar images and recent Venera 15 and 16 data, indicate that material on the surface and subsurface of Venus has a Fresnel reflectivity in excess of 50 percent. Such high reflectivities have been reported on the surface in mountainous regions. Material of high reflectivity may also underlie lower reflectivity surficial materials of the plains regions, where it has been excavated by impact cratering in some areas. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.B24C..07O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.B24C..07O">Immobilization and Natural Attenuation of Arsenic in Surface and Subsurface Sediments</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> O'Day, P. A.; Illera, V.; Choi, S.; Vlassopoulos, D. 2008-12-01 Understanding of molecular-scale biogeochemical processes that control the mobilization and distribution of As and other oxyanions can be used to develop remediation strategies that take advantage of natural geochemical and hydrologic gradients. Arsenic and other toxic oxyanions can be mobilized at low bulk sediment concentrations (ppm range) and thus, treatment technologies are challenged by low contaminant concentrations, widespread sources, variable pH and Eh conditions, and inaccessibility of subsurface environments. In situ chemical amendments to soils and sediments can be used to decrease the mobility and bioaccessibility of As and oxyanions through sorption to, or precipitation with, stabilizing phases. At a site near San Francisco Bay (CA, USA), treatment of As-contaminated soils with sulfate-cement amendments has effectively immobilized As. Laboratory experiments with field soils and spectroscopic characterizations showed that in high pH cement-type treatments, As is precipitated in ettringite-type phases (Ca-Al sulfates), whereas in low pH ferrous sulfate treatments, As is associated with an iron-arsenate phase (angellelite). The presence of As-associated ettringite-type phases in field sediments amended more than a decade ago indicates long-term stability of these neophases, as long as environmental conditions are relatively constant. At sites of subsurface contamination, monitored natural attenuation (MNA) as a remediation approach for As is gaining interest and acceptance. Successful implementation of MNA requires a mechanistic understanding of As sequestration processes and of the subsurface conditions that may enhance or reduce long-term effectiveness. At a former military site (MA, USA), naturally occurring As was mobilized from sediments as a result of reducing conditions from addition of organic carbon as a biodegradation treatment of chlorinated solvents. Elevated As concentrations were not detected further than about 30 m downgradient of the </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA....12774B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA....12774B">Biogeochemistry of the coupled manganese-iron-sulfur cycles of intertidal surface sediments</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bosselmann, K.; Boettcher, M. E.; Billerbeck, M.; Walpersdorf, E.; Debeer, D.; Brumsack, H.-J.; Huettel, M.; Joergensen, B. B. 2003-04-01 The biogeochemistry of the coupled iron-manganese-sulfur-carbon cycles was studied in temperate intertidal surface sediments of the German Wadden Sea (North Sea). Coastal sampling sites include sand, mixed and mud flats with different organic matter and metal contents and permeability reflecting different hydrodynamic regimes. The field study focusses on the influence of temperature, organic matter load, and sediment types on the dynamics of biogeochemical reactions on different time scales (season, day-night, tidal cycles). One of the main interests was related to the cycling of metals (Mn, Fe) in relation to the activity of sulfate-reducing bacteria. Pore water profiles were investigated by sediment sectioning and high resolution gel sampling techniques. Microbial sulfate reduction rates were measured using radiolabeled sulfate with the whole core incubation technique and the spatial distribution of bacterial activity was visualised by using "2D-photoemulsion-monitoring technique". The biogeochemical sulfur cycle was additionally characterised by the stable isotope ratios (S,O) of different sulfur species (e.g., SO_4, AVS, pyrite). Element transfers (metals, nutrients) across the sediment-water interface were additionally quantified by the application of benthic flux chambers. Microbial sulfate reduction was generally highest in the suboxic zone of the surface sediments indicating its potential importance for the mobilization of iron and manganese. In organic matter poor permeable sediments tidal effects additionally influence the spatial and temporal distribution of dissolved redox-sensitive metals. In organic matter-rich silty and muddy sediments, temperature controlled the microbial sulfate reduction rates. Depth-integrated sulfate reduction rates in sandy sediments were much lower and controlled by both temperature and organic matter. Formation of anoxic sediment surfaces due to local enhanced organic matter load (so-called "black spots") may create windows </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.P11B2079K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.P11B2079K">The design of long wavelength planetary SAR sensor and its applications for monitoring shallow sub-surface of Moon and planets.</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kim, K. 2015-12-01 SAR observations over planetary surface have been conducted mainly in two ways. The first is the subsurface sounding, for example Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) and Shallow Surface Radar (SHARAD), using ground penetration capability of long wavelength electromagnetic waves. On the other hand, imaging SAR sensors using burst mode design have been employed to acquire surface observations in the presence of opaque atmospheres such as in the case of Venus and Titan. We propose a lightweight SAR imaging system with P/L band wavelength to cover the vertical observation gap of these planetary radar observation schemes. The sensor is for investigating prominent surface and near-subsurface geological structures and physical characteristics. Such measurements will support landers and rover missions as well as future manned missions. We evaluate required power consumption, and estimate mass and horizontal resolution, which can be as good as 3-7 meters. Initial specifications for P/L dual band SARs for the lunar case at 130 km orbital altitude were designed already based on a assumptions that sufficient size antenna (>3m width diameter or width about 3m and >10kg weight) can be equipped. Useful science measurements to be obtained include: (1) derivation of subsurface regolith depth; 2) Surface and shallow subsurface radar imaging, together with radar ranging techniques such as radargrammetry and inteferometry. The concepts in this study can be used as an important technical basis for the future solid plant/satellite missions and already proposed for the 2018 Korean Lunar mission. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SPIE.9036E..0VW','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SPIE.9036E..0VW">Registration of liver images to minimally invasive intraoperative surface and subsurface data</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wu, Yifei; Rucker, D. C.; Conley, Rebekah H.; Pheiffer, Thomas S.; Simpson, Amber L.; Geevarghese, Sunil K.; Miga, Michael I. 2014-03-01 Laparoscopic liver resection is increasingly being performed with results comparable to open cases while incurring less trauma and reducing recovery time. The tradeoff is increased difficulty due to limited visibility and restricted freedom of movement. Image-guided surgical navigation systems have the potential to help localize anatomical features to improve procedural safety and achieve better surgical resection outcome. Previous research has demonstrated that intraoperative surface data can be used to drive a finite element tissue mechanics organ model such that high resolution preoperative scans are registered and visualized in the context of the current surgical pose. In this paper we present an investigation of using sparse data as imposed by laparoscopic limitations to drive a registration model. Non-contact laparoscopicallyacquired surface swabbing and mock-ultrasound subsurface data were used within the context of a nonrigid registration methodology to align mock deformed intraoperative surface data to the corresponding preoperative liver model as derived from pre-operative image segmentations. The mock testing setup to validate the potential of this approach used a tissue-mimicking liver phantom with a realistic abdomen-port patient configuration. Experimental results demonstrates a range of target registration errors (TRE) on the order of 5mm were achieving using only surface swab data, while use of only subsurface data yielded errors on the order of 6mm. Registrations using a combination of both datasets achieved TRE on the order of 2.5mm and represent a sizeable improvement over either dataset alone. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/circ/1980/0837/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/circ/1980/0837/report.pdf">Biogeochemical evidence for subsurface hydrocarbon occurrence, Recluse oil field, Wyoming; preliminary results</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Dalziel, Mary C.; Donovan, Terrence J. 1980-01-01 Anomalously high manganese-to-iron ratios occurring in pine needles and sage leaves over the Recluse oil field, Wyoming, suggest effects of petroleum microseepage on the plants. This conclusion is supported by iron and manganese concentrations in soils and carbon and oxygen isotope ratios in rock samples. Seeping hydrocarbons provided reducing conditions sufficient to enable divalent iron and manganese to be organically complexed or adsorbed on solids in the soils. These bound or adsorped elements in the divalent state are essential to plants, and the plants readily assimilate them. The magnitude of the plant anomalies, combined with the supportive isotopic and chemical evidence confirming petroleum leakage, makes a strong case for the use of plants as a biogeochemical prospecting tool. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1089976','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1089976">Subsurface Uranium Fate and Transport: Integrated Experiments and Modeling of Coupled Biogeochemical Mechanisms of Nanocrystalline Uraninite Oxidation by Fe(III)-(hydr)oxides - Project Final Report</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Peyton, Brent M.; Timothy, Ginn R.; Sani, Rajesh K. 2013-08-14 Subsurface bacteria including sulfate reducing bacteria (SRB) reduce soluble U(VI) to insoluble U(IV) with subsequent precipitation of UO 2. We have shown that SRB reduce U(VI) to nanometer-sized UO 2 particles (1-5 nm) which are both intra- and extracellular, with UO 2 inside the cell likely physically shielded from subsequent oxidation processes. We evaluated the UO 2 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 phasemore » 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 UO 2 nanocrystals can be reoxidized (and thus remobilized) by Fe(III)-(hydr)oxides, common constituents of soils and sediments. To elucidate the mechanism of UO 2 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 UO 2 reoxidation with an initial rate of 9.5 M day-1 for ferrihydrite. In all cases, bicarbonate increased the rate and extent of UO 2 reoxidation with ferrihydrite. The highest rate of UO 2 reoxidation occurred when the chelator promoted UO 2 and Fe(III) (hydr)oxide dissolution as demonstrated with EDTA. When UO 2 dissolution did not occur, UO 2 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 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B33G..04Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B33G..04Y">Modeling Coupled Landscape Evolution and Soil Organic Carbon Dynamics in Intensively Management Landscapes</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yan, Q.; Kumar, P. 2017-12-01 Soil is the largest reservoir of carbon in the biosphere but in agricultural areas it is going through rapid erosion due disturbance arising from crop harvest, tillage, and tile drainage. Identifying whether the production of soil organic carbon (SOC) from the crops can compensate for the loss due to erosion is critical to ensure our food security and adapt to climate change. In the U.S. Midwest where large areas of land are intensively managed for agriculture practices, predicting soil quantity and quality are critical for maintaining crop yield and other Critical Zone services. This work focuses on modeling the coupled landscape evolutions soil organic carbon dynamics in agricultural fields. It couples landscape evolution, surface water runoff, organic matter transformation, and soil moisture dynamics to understand organic carbon gain and loss due to natural forcing and farming practices, such as fertilizer application and tillage. A distinctive feature of the model is the coupling of surface ad subsurface processes that predicts both surficial changes and transport along with the vertical transport and dynamics. Our results show that landscape evolution and farming practices play dominant roles in soil organic carbon (SOC) dynamics both above- and below-ground. Contrary to the common assumption that a vertical profile of SOC concentration decreases exponentially with depth, we find that in many situations SOC concentration below-ground could be higher than that at the surface. Tillage plays a complex role in organic matter dynamics. On one hand, tillage would accelerate the erosion rate, on the other hand, it would improve carbon storage by burying surface SOC into below ground. Our model consistently reproduces the observed above- and below-ground patterns of SOC in the field sites of Intensively Managed Landscapes Critical Zone Observatory (IMLCZO). This model bridges the gaps between the landscape evolution, below- and above-ground hydrologic cycle, and </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMOS43A1257B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMOS43A1257B">Impact of Sea Surface Salinity on Coupled Dynamics for the Tropical Indo Pacific</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Busalacchi, A. J.; Hackert, E. C. 2014-12-01 In this presentation we assess the impact of in situ and satellite sea surface salinity (SSS) observations on seasonal to interannual variability of tropical Indo-Pacific Ocean dynamics as well as on dynamical ENSO forecasts using a Hybrid Coupled Model (HCM) for 1993-2007 (cf., Hackert et al., 2011) and August 2011 until February 2014 (cf., Hackert et al., 2014). The HCM is composed of a primitive equation ocean model coupled with a SVD-based statistical atmospheric model for the tropical Indo-Pacific region. An Ensemble Reduced Order Kalman Filter (EROKF) is used to assimilate observations to constrain dynamics and thermodynamics for initialization of the HCM. Including SSS generally improves NINO3 sea surface temperature anomaly validation. Assimilating SSS gives significant improvement versus just subsurface temperature for all forecast lead times after 5 months. We find that the positive impact of SSS assimilation is brought about by surface freshening in the western Pacific warm pool that leads to increased barrier layer thickness (BLT) and shallower mixed layer depths. Thus, in the west the net effect of assimilating SSS is to increase stability and reduce mixing, which concentrates the wind impact of ENSO coupling. Specifically, the main benefit of SSS assimilation for 1993-2007 comes from improvement to the Spring Predictability Barrier (SPB) period. In the east, the impact of Aquarius satellite SSS is to induce more cooling in the NINO3 region as a result of being relatively more salty than in situ SSS in the eastern Pacific leading to increased mixing and entrainment. This, in turn, sets up an enhanced west to east SST gradient and intensified Bjerknes coupling. For the 2011-2014 period, consensus coupled model forecasts compiled by the IRI tend to erroneously predict NINO3 warming; SSS assimilation corrects this defect. Finally, we plan to update our analysis and report on the dynamical impact of including Aquarius SSS for the most-recent, ongoing 2014 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApSS..422..394C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApSS..422..394C">Adsorption, dissociation and diffusion of hydrogen on the ZrCo surface and subsurface: A comprehensive study using first principles approach</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chattaraj, D.; Kumar, Nandha; Ghosh, Prasenjit; Majumder, C.; Dash, Smruti 2017-11-01 With increasing demand for hydrogen economy driven world, the fundamental research of hydrogen-metal interactions has gained momentum. In this work we report a systematic theoretical study of the stability of different surfaces of intermetallic ZrCo that is a possible candidate as a getter bed for tritium. Our first principles ab initio thermodynamic calculations predict that amongst the (100), (110) and (111) surfaces, the stoichiometric (110) surface is the most stable one over a wide range of Co chemical potential. We have also studied adsorption, dissociation and diffusion of hydrogen on the (110) surface. On the basis of total energy, it is seen that adsorption of molecular hydrogen (H2) on the surface is much weaker than atomic hydrogen. The H2 decomposition on ZrCo surface can easily take place and the dissociation barrier is calculated to be 0.70 eV. The strength of binding of H atom on the surface is more or less independent of surface coverage till 1.0 ML of H. The thermodynamic stability of atomic H adsorbed on the surface, in subsurface and bulk decreases from surface to bulk to subsurface. Though the H atoms are mobile on the surface, their diffusion to the subsurface involves a barrier of about 0.79 eV. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRE..122.1951C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRE..122.1951C">Next Steps Forward in Understanding Martian Surface and Subsurface Chemistry</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Carrier, Brandi L. 2017-09-01 The presence of oxidants such as hydrogen peroxide (H2O2) and perchlorate (ClO4-), which have been detected on Mars, has significant implications for chemistry and astrobiology. These oxidants can increase the reactivity of the Martian soil, accelerate the decomposition of organic molecules, and depress the freezing point of water. The study by Crandall et al. "Can Perchlorates be Transformed to Hydrogen Peroxide Products by Cosmic Rays on the Martian Surface" reveals a new formation mechanism by which hydrogen peroxide and other potential oxidants can be generated via irradiation of perchlorate by cosmic rays. This study represents an important next step in developing a full understanding of Martian surface and subsurface chemistry, particularly with respect to degradation of organic molecules and potential biosignatures. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1143511-subsurface-failure-spherical-bodies-formation-scenario-linear-troughs-vestas-surface','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1143511-subsurface-failure-spherical-bodies-formation-scenario-linear-troughs-vestas-surface">Subsurface failure in spherical bodies. A formation scenario for linear troughs on Vesta’s surface</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Stickle, Angela M.; Schultz, P. H.; Crawford, D. A. 2014-10-13 Many asteroids in the Solar System exhibit unusual, linear features on their surface. The Dawn mission recently observed two sets of linear features on the surface of the asteroid 4 Vesta. Geologic observations indicate that these features are related to the two large impact basins at the south pole of Vesta, though no specific mechanism of origin has been determined. Furthermore, the orientation of the features is offset from the center of the basins. Experimental and numerical results reveal that the offset angle is a natural consequence of oblique impacts into a spherical target. We demonstrate that a set ofmore » shear planes develops in the subsurface of the body opposite to the point of first contact. Moreover, these subsurface failure zones then propagate to the surface under combined tensile-shear stress fields after the impact to create sets of approximately linear faults on the surface. Comparison between the orientation of damage structures in the laboratory and failure regions within Vesta can be used to constrain impact parameters (e.g., the approximate impact point and likely impact trajectory).« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22908256','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22908256">Impact of abrupt deglacial climate change on tropical Atlantic subsurface temperatures.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Schmidt, Matthew W; Chang, Ping; Hertzberg, Jennifer E; Them, Theodore R; Ji, Link; J, Link; Otto-Bliesner, Bette L 2012-09-04 Both instrumental data analyses and coupled ocean-atmosphere models indicate that Atlantic meridional overturning circulation (AMOC) variability is tightly linked to abrupt tropical North Atlantic (TNA) climate change through both atmospheric and oceanic processes. Although a slowdown of AMOC results in an atmospheric-induced surface cooling in the entire TNA, the subsurface experiences an even larger warming because of rapid reorganizations of ocean circulation patterns at intermediate water depths. Here, we reconstruct high-resolution temperature records using oxygen isotope values and Mg/Ca ratios in both surface- and subthermocline-dwelling planktonic foraminifera from a sediment core located in the TNA over the last 22 ky. Our results show significant changes in the vertical thermal gradient of the upper water column, with the warmest subsurface temperatures of the last deglacial transition corresponding to the onset of the Younger Dryas. Furthermore, we present new analyses of a climate model simulation forced with freshwater discharge into the North Atlantic under Last Glacial Maximum forcings and boundary conditions that reveal a maximum subsurface warming in the vicinity of the core site and a vertical thermal gradient change at the onset of AMOC weakening, consistent with the reconstructed record. Together, our proxy reconstructions and modeling results provide convincing evidence for a subsurface oceanic teleconnection linking high-latitude North Atlantic climate to the tropical Atlantic during periods of reduced AMOC across the last deglacial transition. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9799E..3SH','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9799E..3SH">Experimental validation of a sub-surface model of solar power for distributed marine sensor systems</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hahn, Gregory G.; Cantin, Heather P.; Shafer, Michael W. 2016-04-01 The capabilities of distributed sensor systems such as marine wildlife telemetry tags could be significantly enhanced through the integration of photovoltaic modules. Photovoltaic cells could be used to supplement the primary batteries for wildlife telemetry tags to allow for extended tag deployments, wherein larger amounts of data could be collected and transmitted in near real time. In this article, we present experimental results used to validate and improve key aspects of our original model for sub-surface solar power. We discuss the test methods and results, comparing analytic predictions to experimental results. In a previous work, we introduced a model for sub-surface solar power that used analytic models and empirical data to predict the solar irradiance available for harvest at any depth under the ocean's surface over the course of a year. This model presented underwater photovoltaic transduction as a viable means of supplementing energy for marine wildlife telemetry tags. The additional data provided by improvements in daily energy budgets would enhance the temporal and spatial comprehension of the host's activities and/or environments. Photovoltaic transduction is one method that has not been widely deployed in the sub-surface marine environments despite widespread use on terrestrial and avian species wildlife tag systems. Until now, the use of photovoltaic cells for underwater energy harvesting has generally been disregarded as a viable energy source in this arena. In addition to marine telemetry systems, photovoltaic energy harvesting systems could also serve as a means of energy supply for autonomous underwater vehicles (AUVs), as well as submersible buoys for oceanographic data collection. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active">12</li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active">13</li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18286003','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18286003">Effect of surface roughness and subsurface damage on grazing-incidence x-ray scattering and specular reflectance.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Lodha, G S; Yamashita, K; Kunieda, H; Tawara, Y; Yu, J; Namba, Y; Bennett, J M 1998-08-01 Grazing-incidence specular reflectance and near-specular scattering were measured at Al-K(alpha) (1.486-keV, 8.34-?) radiation on uncoated dielectric substrates whose surface topography had been measured with a scanning probe microscope and a mechanical profiler. Grazing-incidence specular reflectance was also measured on selected substrates at the Cu-K(alpha) (8.047-keV, 1.54-?) wavelength. Substrates included superpolished and conventionally polished fused silica; SiO(2) wafers; superpolished and precision-ground Zerodur; conventionally polished, float-polished, and precision-ground BK-7 glass; and superpolished and precision-ground silicon carbide. Roughnesses derived from x-ray specular reflectance and scattering measurements were in good agreement with topographic roughness values measured with a scanning probe microscope (atomic force microscope) and a mechanical profiler that included similar ranges of surface spatial wavelengths. The specular reflectance was also found to be sensitive to the density of polished surface layers and subsurface damage down to the penetration depth of the x rays. Density gradients and subsurface damage were found in the superpolished fused-silica and precision-ground Zerodur samples. These results suggest that one can nondestructively evaluate subsurface damage in transparent materials using grazing-incidence x-ray specular reflectance in the 1.5-8-keV range. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015OcDyn..65.1335G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015OcDyn..65.1335G">Impacts of mesoscale eddies in the South China Sea on biogeochemical cycles</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Guo, Mingxian; Chai, Fei; Xiu, Peng; Li, Shiyu; Rao, Shivanesh 2015-09-01 Biogeochemical cycles associated with mesoscale eddies in the South China Sea (SCS) were investigated. The study was based on a coupled physical-biogeochemical Pacific Ocean model (Regional Ocean Model System-Carbon, Silicate, and Nitrogen Ecosystem, ROMS-CoSiNE) simulation for the period from 1991 to 2008. A total of 568 mesoscale eddies with lifetime longer than 30 days were used in the analysis. Composite analysis revealed that the cyclonic eddies were associated with abundance of nutrients, phytoplankton, and zooplankton while the anticyclonic eddies depressed biogeochemical cycles, which are generally controlled by the eddy pumping mechanism. In addition, diatoms were dominant in phytoplankton species due to the abundance of silicate. Dipole structures of vertical fluxes with net upward motion in cyclonic eddies and net downward motion in anticyclonic eddies were revealed. During the lifetime of an eddy, the evolutions of physical, biological, and chemical structures were not linearly coupled at the eddy core where plankton grew, and composition of the community depended not only on the physical and chemical processes but also on the adjustments by the predator-prey relationship. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22218179','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22218179">Inputs and losses by surface runoff and subsurface leaching for pastures managed by continuous or rotational stocking.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Owens, L B; Barker, D J; Loerch, S C; Shipitalo, M J; Bonta, J V; Sulc, R M 2012-01-01 Pasture management practices can affect forage quality and production, animal health and production, and surface and groundwater quality. In a 5-yr study conducted at the North Appalachian Experimental Watershed near Coshocton, Ohio, we compared the effects of two contrasting grazing methods on surface and subsurface water quantity and quality. Four pastures, each including a small, instrumented watershed (0.51-1.09 ha) for surface runoff measurements and a developed spring for subsurface flow collection, received 112 kg N ha(-1) yr(-1) and were grazed at similar stocking rates (1.8-1.9 cows ha(-1)). Two pastures were continuously stocked; two were subdivided so that they were grazed with frequent rotational stocking (5-6 times weekly). In the preceding 5 yr, these pastures received 112 kg N ha(-1) yr(-1) after several years of 0 N fertilizer and were grazed with weekly rotational stocking. Surface runoff losses of N were minimal. During these two periods, some years had precipitation up to 50% greater than the long-term average, which increased subsurface flow and NO(3)-N transport. Average annual NO(3)-N transported in subsurface flow from the four watersheds during the two 5-yr periods ranged from 11.3 to 22.7 kg N ha(-1), which was similar to or less than the mineral-N received in precipitation. Flow and transport variations were greater among seasons than among watersheds. Flow-weighted seasonal NO(3)-N concentrations in subsurface flow did not exceed 7 mg L(-1). Variations in NO(3)-N leached from pastures were primarily due to variable precipitation rather than the effects of continuous, weekly rotational, or frequent rotational stocking practices. This suggests that there was no difference among these grazing practices in terms of NO(3)-N leaching. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B51B0274L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B51B0274L">A Unified Multi-scale Model for Cross-Scale Evaluation and Integration of Hydrological and Biogeochemical Processes</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Liu, C.; Yang, X.; Bailey, V. L.; Bond-Lamberty, B. P.; Hinkle, C. 2013-12-01 scale simulations were then used to simulate coupled 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 biogeochemical properties are used to parameterize the UMSM at the small scales, and field measurements are used to evaluate the UMSM. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018OcSci..14..259P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018OcSci..14..259P">Estimation of oceanic subsurface mixing under a severe cyclonic storm using a coupled atmosphere-ocean-wave model</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Prakash, Kumar Ravi; Nigam, Tanuja; Pant, Vimlesh 2018-04-01 A coupled atmosphere-ocean-wave model was used to examine mixing in the upper-oceanic layers under the influence of a very severe cyclonic storm Phailin over the Bay of Bengal (BoB) during 10-14 October 2013. The coupled model was found to improve the sea surface temperature over the uncoupled model. Model simulations highlight the prominent role of cyclone-induced near-inertial oscillations in subsurface mixing up to the thermocline depth. The inertial mixing introduced by the cyclone played a central role in the deepening of the thermocline and mixed layer depth by 40 and 15 m, respectively. For the first time over the BoB, a detailed analysis of inertial oscillation kinetic energy generation, propagation, and dissipation was carried out using an atmosphere-ocean-wave coupled model during a cyclone. A quantitative estimate of kinetic energy in the oceanic water column, its propagation, and its dissipation mechanisms were explained using the coupled atmosphere-ocean-wave model. The large shear generated by the inertial oscillations was found to overcome the stratification and initiate mixing at the base of the mixed layer. Greater mixing was found at the depths where the eddy kinetic diffusivity was large. The baroclinic current, holding a larger fraction of kinetic energy than the barotropic current, weakened rapidly after the passage of the cyclone. The shear induced by inertial oscillations was found to decrease rapidly with increasing depth below the thermocline. The dampening of the mixing process below the thermocline was explained through the enhanced dissipation rate of turbulent kinetic energy upon approaching the thermocline layer. The wave-current interaction and nonlinear wave-wave interaction were found to affect the process of downward mixing and cause the dissipation of inertial oscillations. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007LPICo1353.3084D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007LPICo1353.3084D">Long-Duration Orbit Exposure Experiment with Sub-Surface Microorganism from a Mars Terrestrial Analog</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Davila, A. F.; Lim, D.; Fairen, A. G.; Uceda, E. R.; Zavaleta, J.; McKay, C. 2007-07-01 Orbit Exposure Experiments (OEE) allow us to test the possibility of life transfer between planets and moons. Deep sub-surface microorganisms may be the best candidates to survive long-term exposure to space conditions. A long duration OEE is proposed to test our hypothesis. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920004382','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920004382">Subsurface microbial habitats on Mars</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Boston, P. J.; Mckay, C. P. 1991-01-01 We developed scenarios for shallow and deep subsurface cryptic niches for microbial life on Mars. Such habitats could have considerably prolonged the persistence of life on Mars as surface conditions became increasingly inhospitable. The scenarios rely on geothermal hot spots existing below the near or deep subsurface of Mars. Recent advances in the comparatively new field of deep subsurface microbiology have revealed previously unsuspected rich aerobic and anaerobic microbal communities far below the surface of the Earth. Such habitats, protected from the grim surface conditions on Mars, could receive warmth from below and maintain water in its liquid state. In addition, geothermally or volcanically reduced gases percolating from below through a microbiologically active zone could provide the reducing power needed for a closed or semi-closed microbial ecosystem to thrive. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA......305B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA......305B">Reconstruction of sub-surface archaeological remains from magnetic data using neural computing.</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bescoby, D. J.; Cawley, G. C.; Chroston, P. N. 2003-04-01 The remains of a former Roman colonial settlement, once part of the classical city of Butrint in southern Albania have been the subject of a high resolution magnetic survey using a caesium-vapour magnetometer. The survey revealed the surviving remains of an extensive planned settlement and a number of outlying buildings, today buried beneath over 0.5 m of alluvial deposits. The aim of the current research is to derive a sub-surface model from the magnetic survey measurements, allowing an enhanced archaeological interpretation of the data. Neural computing techniques are used to perform the non-linear mapping between magnetic data and corresponding sub-surface model parameters. The adoption of neural computing paradigms potentially holds several advantages over other modelling techniques, allowing fast solutions for complex data, while having a high tolerance to noise. A multi-layer perceptron network with a feed-forward architecture is trained to estimate the shape and burial depth of wall foundations using a series of representative models as training data. Parameters used to forward model the training data sets are derived from a number of trial trench excavations targeted over features identified by the magnetic survey. The training of the network was optimized by first applying it to synthetic test data of known source parameters. Pre-processing of the network input data, including the use of a rotationally invariant transform, enhanced network performance and the efficiency of the training data. The approach provides good results when applied to real magnetic data, accurately predicting the depths and layout of wall foundations within the former settlement, verified by subsequent excavation. The resulting sub-surface model is derived from the averaged outputs of a ‘committee’ of five networks, trained with individualized training sets. Fuzzy logic inference has also been used to combine individual network outputs through correlation with data from a second </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=163405&Lab=NERL&keyword=erickson&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=163405&Lab=NERL&keyword=erickson&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">INTERACTIVE EFFECTS OF SOLAR UV RADIATION AND CLIMATE CHANGE ON BIOGEOCHEMICAL CYCLING</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> This paper assesses research on the interactions of UV radiation (280-400 nm) and global climate change with global biogeochemical cycles at the Earth's surface. The effects of UV-B (280-315 nm), which are dependent on the stratospheric ozone layer, on biogeochemical cycles are o... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AIPC.1949r0004N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AIPC.1949r0004N">Photoacoustic microscopic imaging of surface and subsurface damages in CFRP</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Nakahata, Kazuyuki; Ogi, Keiji; Namita, Takeshi; Ohira, Katsumi; Maruyama, Masayuki; Shiina, Tsuyoshi 2018-04-01 Photoacoustic imaging comprises an optical excitation within a target zone and the detection of the ultrasonic wave so created. A pulsed laser illuminates the target zone, and this illumination causes rapid thermoelastic expansion that generates a broadband high-frequency ultrasonic wave (photoacoustic wave, PA). In this paper, we report proof-of-concept experiments for nondestructive testing of laminar materials using a PA microscope. A specimen containing carbon-fiber-reinforced plastic (CFRP) was used in this experiment and involved an artificial delamination. A 532-nm-wavelength laser irradiates the top surface of the specimen, and the resulting ultrasonic waves are received by a point-focusing immersion transducer on the same side. Our system estimated the depth and dimension of the subsurface delamination accurately. By coating a light-absorbing material on the surface, the amplitude of the PA wave increased. This finding shows that the signal-noise (S/N) ratio of the scattered wave from delaminations can be improved with the surface coatings. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.P21B2088K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.P21B2088K">Methane clathrate stability zone variations and gas transport in the Martian subsurface</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Karatekin, O.; Gloesener, E.; Dehant, V. M. A.; Temel, O. 2016-12-01 During the last years, several detections of methane in the atmosphere of Mars were reported from Earth-based and Mars orbit instruments with abundances ranging to tens of parts-per-billion by volume (ppbv). Recently, the Curiosity rover detected methane with background levels of 0.7 ppbv and episodic releases of 7 ppbv. Although the methane sources are still unknown, this gas may have been stored in reservoirs of clathrate hydrate in the Martian subsurface where thermodynamics conditions are favourable to their presence. Clathrate hydrates are crystalline compounds constituted by cages formed by hydrogen-bonded water molecules inside of which guest gas molecules are trapped. In this study, methane clathrate stability in the Martian subsurface are investigated and their temporal and spatial variations are studied. Present-day maps of methane clathrate stability zone are produced by coupling the stability conditions of methane clathrate with a subsurface model using the available observations such as the the thermal inertia derived from TES MGS data. Then, a gas transport model has been used to study the methane flux at the surface due to the diffusion of different plausible methane volumes released by clathrate hydrates at variable depths under the Martian surface. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6592609-evolution-cave-systems-from-surface-subsurface','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/6592609-evolution-cave-systems-from-surface-subsurface">The evolution of cave systems from the surface to subsurface</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Loucks, R.G.; Handford, C.R. 1996-01-01 Many carbonate reservoirs are the result of cave-forming processes. The origin and recognition of fractures, breccias, and sediment fills associated with paleocaves were determined through the study of modern and paleocaves systems. Cave formation and destruction are the products of near-surface processes. Near-surface processes include solutional excavation, clastic and chemical sedimentation, and collapse of cave walls and ceilings. Cave sediment is derived from inside and/or outside the system. Depositional mechanisms include suspension, tractional, mass-flow and rock-fall. Collapse of ceilings and walls from chaotic breakdown breccias. These piles can be tens of meters thick and contain large voids and variable amountsmore » of matrix. Cave-roof crackle breccia forms from stress-and tension-related fractures in cave-roof strata. As the cave-bearing strata subside into the subsurface, mechanical compaction increases and restructures the existing breccias and remaining cavities. Fracture porosity increases and breccia and vug porosity decreases. Large cavities collapse forming burial chaotic breakdown breccias. Differentially compacted strata over the collapsed chamber fracture and form burial cave-roof crackle breccias. Continued burial leads to more extensive mechanical compaction causing previously formed clasts to fracture and pack closer together. The resulting product is a rebrecciated chaotic breakdown breccia composed predominantly of small clasts. Rebrecciated blocks are often overprinted by crackling. Subsurface paleocave systems commonly have a complex history with several episodes of fracturing and brecciation. The resulting collapsed-paleocave reservoir targets are not single collapsed passages of tens of feet across, but are homogenized collapsed-cave systems hundreds to several thousand feet across.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/425697-evolution-cave-systems-from-surface-subsurface','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/425697-evolution-cave-systems-from-surface-subsurface">The evolution of cave systems from the surface to subsurface</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Loucks, R.G.; Handford, C.R. 1996-12-31 Many carbonate reservoirs are the result of cave-forming processes. The origin and recognition of fractures, breccias, and sediment fills associated with paleocaves were determined through the study of modern and paleocaves systems. Cave formation and destruction are the products of near-surface processes. Near-surface processes include solutional excavation, clastic and chemical sedimentation, and collapse of cave walls and ceilings. Cave sediment is derived from inside and/or outside the system. Depositional mechanisms include suspension, tractional, mass-flow and rock-fall. Collapse of ceilings and walls from chaotic breakdown breccias. These piles can be tens of meters thick and contain large voids and variable amountsmore » of matrix. Cave-roof crackle breccia forms from stress-and tension-related fractures in cave-roof strata. As the cave-bearing strata subside into the subsurface, mechanical compaction increases and restructures the existing breccias and remaining cavities. Fracture porosity increases and breccia and vug porosity decreases. Large cavities collapse forming burial chaotic breakdown breccias. Differentially compacted strata over the collapsed chamber fracture and form burial cave-roof crackle breccias. Continued burial leads to more extensive mechanical compaction causing previously formed clasts to fracture and pack closer together. The resulting product is a rebrecciated chaotic breakdown breccia composed predominantly of small clasts. Rebrecciated blocks are often overprinted by crackling. Subsurface paleocave systems commonly have a complex history with several episodes of fracturing and brecciation. The resulting collapsed-paleocave reservoir targets are not single collapsed passages of tens of feet across, but are homogenized collapsed-cave systems hundreds to several thousand feet across.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3437837','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3437837">Impact of abrupt deglacial climate change on tropical Atlantic subsurface temperatures</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Schmidt, Matthew W.; Chang, Ping; Hertzberg, Jennifer E.; Them, Theodore R.; Ji, Link; Otto-Bliesner, Bette L. 2012-01-01 Both instrumental data analyses and coupled ocean-atmosphere models indicate that Atlantic meridional overturning circulation (AMOC) variability is tightly linked to abrupt tropical North Atlantic (TNA) climate change through both atmospheric and oceanic processes. Although a slowdown of AMOC results in an atmospheric-induced surface cooling in the entire TNA, the subsurface experiences an even larger warming because of rapid reorganizations of ocean circulation patterns at intermediate water depths. Here, we reconstruct high-resolution temperature records using oxygen isotope values and Mg/Ca ratios in both surface- and subthermocline-dwelling planktonic foraminifera from a sediment core located in the TNA over the last 22 ky. Our results show significant changes in the vertical thermal gradient of the upper water column, with the warmest subsurface temperatures of the last deglacial transition corresponding to the onset of the Younger Dryas. Furthermore, we present new analyses of a climate model simulation forced with freshwater discharge into the North Atlantic under Last Glacial Maximum forcings and boundary conditions that reveal a maximum subsurface warming in the vicinity of the core site and a vertical thermal gradient change at the onset of AMOC weakening, consistent with the reconstructed record. Together, our proxy reconstructions and modeling results provide convincing evidence for a subsurface oceanic teleconnection linking high-latitude North Atlantic climate to the tropical Atlantic during periods of reduced AMOC across the last deglacial transition. PMID:22908256 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1033841-variably-saturated-flow-multicomponent-biogeochemical-reactive-transport-modeling-uranium-bioremediation-field-experiment','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1033841-variably-saturated-flow-multicomponent-biogeochemical-reactive-transport-modeling-uranium-bioremediation-field-experiment">Variably Saturated Flow and Multicomponent Biogeochemical Reactive Transport Modeling of a Uranium Bioremediation Field Experiment</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Yabusaki, Steven B.; Fang, Yilin; Williams, Kenneth H. 2011-11-01 has been incorporated into the modeling. In this case, an initially small population of slow growing sulfate reducers is active from the initiation of biostimulation. Three-dimensional, variably saturated flow modeling was used to address impacts of a falling water table during acetate injection. These impacts included a significant reduction in aquifer saturated thickness and isolation of residual reactants and products, as well as unmitigated uranium, in the newly unsaturated vadose zone. High permeability sandy gravel structures resulted in locally high flow rates in the vicinity of injection wells that increased acetate dilution. In downgradient locations, these structures created preferential flow paths for acetate delivery that enhanced local zones of TEAP reactivity and subsidiary reactions. Conversely, smaller transport rates associated with the lower permeability lithofacies (e.g., fine) and vadose zone were shown to limit acetate access and reaction. Once accessed by acetate, however, these same zones limited subsequent acetate dilution and provided longer residence times that resulted in higher concentrations of TEAP products when terminal electron donors and acceptors were not limiting. Finally, facies-based porosity and reactive surface area variations were shown to affect aqueous uranium concentration distributions; however, the ranges were sufficiently small to preserve general trends. Large computer memory and high computational performance were required to simulate the detailed coupled process models for multiple biogeochemical components in highly resolved heterogeneous materials for the 110-day field experiment and 50 days of post-biostimulation behavior. In this case, a highly-scalable subsurface simulator operating on 128 processor cores for 12 hours was used to simulate each realization. An equivalent simulation without parallel processing would have taken 60 days, assuming sufficient memory was available.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H42E..02Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H42E..02Y">Effect of Freeze-Thaw Cycles on Soil Nitrogen Reactive Transport in a Polygonal Arctic Tundra Ecosystem at Barrow AK Using 3-D Coupled ALM-PFLOTRAN</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yuan, F.; Wang, G.; Painter, S. L.; Tang, G.; Xu, X.; Kumar, J.; Bisht, G.; Hammond, G. E.; Mills, R. T.; Thornton, P. E.; Wullschleger, S. D. 2017-12-01 In Arctic tundra ecosystem soil freezing-thawing is one of dominant physical processes through which biogeochemical (e.g., carbon and nitrogen) cycles are tightly coupled. Besides hydraulic transport, freezing-thawing can cause pore water movement and aqueous species gradients, which are additional mechanisms for soil nitrogen (N) reactive-transport in Tundra ecosystem. In this study, we have fully coupled an in-development ESM(i.e., Advanced Climate Model for Energy, ACME)'s Land Model (ALM) aboveground processes with a state-of-the-art massively parallel 3-D subsurface thermal-hydrology and reactive transport code, PFLOTRAN. The resulting coupled ALM-PFLOTRAN model is a Land Surface Model (LSM) capable of resolving 3-D soil thermal-hydrological-biogeochemical cycles. This specific version of PFLOTRAN has incorporated CLM-CN Converging Trophic Cascade (CTC) model and a full and simple but robust soil N cycle. It includes absorption-desorption for soil NH4+ and gas dissolving-degasing process as well. It also implements thermal-hydrology mode codes with three newly-modified freezing-thawing algorithms which can greatly improve computing performance in regarding to numerical stiffness at freezing-point. Here we tested the model in fully 3-D coupled mode at the Next Generation Ecosystem Experiment-Arctic (NGEE-Arctic) field intensive study site at the Barrow Environmental Observatory (BEO), AK. The simulations show that: (1) synchronous coupling of soil thermal-hydrology and biogeochemistry in 3-D can greatly impact ecosystem dynamics across polygonal tundra landscape; and (2) freezing-thawing cycles can add more complexity to the system, resulting in greater mobility of soil N vertically and laterally, depending upon local micro-topography. As a preliminary experiment, the model is also implemented for Pan-Arctic region in 1-D column mode (i.e. no lateral connection), showing significant differences compared to stand-alone ALM. The developed ALM-PFLOTRAN coupling </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=305351','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=305351">Effect of replacing surface inlets with blind or gravel inlets on sediment and phosphorus subsurface drainage losses</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> Open surface inlets that connect to subsurface tile drainage systems provide a direct pathway for sediment, nutrients, and agrochemicals to surface waters. This study was conducted to determine whether modifying open inlets by burying them in gravel capped with 30 cm of sandy clay loam soil or in ve... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1245538','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1245538">Subsurface Conditions Controlling Uranium Incorporation in Iron Oxides: A Redox Stable Sink</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Fendorf, Scott 2016-04-05 Toxic metals and radionuclides throughout the U.S. Department of Energy Complex pose a serious threat to ecosystems and to human health. Of particular concern is the redox-sensitive radionuclide uranium, which is classified as a priority pollutant in soils and groundwaters at most DOE sites owing to its large inventory, its health risks, and its mobility with respect to primary waste sources. The goal of this research was to contribute to the long-term mission of the Subsurface Biogeochemistry Program by determining reactions of uranium with iron (hydr)oxides that lead to long-term stabilization of this pervasive contaminant. The research objectives of thismore » project were thus to (1) identify the (bio)geochemical conditions, including those of the solid-phase, promoting uranium incorporation in Fe (hydr)oxides, (2) determine the magnitude of uranium incorporation under a variety of relevant subsurface conditions in order to quantify the importance of this pathway when in competition with reduction or adsorption; (3) identify the mechanism(s) of U(VI/V) incorporation in Fe (hydr)oxides; and (4) determine the stability of these phases under different biogeochemical (inclusive of redox) conditions. Our research demonstrates that redox transformations are capable of achieving U incorporation into goethite at ambient temperatures, and that this transformation occurs within days at U and Fe(II) concentrations that are common in subsurface geochemical environments with natural ferrihydrites—inclusive of those with natural impurities. Increasing Fe(II) or U concentration, or initial pH, made U(VI) reduction to U(IV) a more competitive sequestration pathway in this system, presumably by increasing the relative rate of U reduction. Uranium concentrations commonly found in contaminated subsurface environments are often on the order of 1-10 μM, and groundwater Fe(II) concentrations can reach exceed 1 mM in reduced zones of the subsurface. The redox-driven U </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22739492','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22739492">Metabolic stratification driven by surface and subsurface interactions in a terrestrial mud volcano.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Cheng, Ting-Wen; Chang, Yung-Hsin; Tang, Sen-Lin; Tseng, Ching-Hung; Chiang, Pei-Wen; Chang, Kai-Ti; Sun, Chih-Hsien; Chen, Yue-Gau; Kuo, Hung-Chi; Wang, Chun-Ho; Chu, Pao-Hsuan; Song, Sheng-Rong; Wang, Pei-Ling; Lin, Li-Hung 2012-12-01 Terrestrial mud volcanism represents the prominent surface geological feature, where fluids and hydrocarbons are discharged along deeply rooted structures in tectonically active regimes. Terrestrial mud volcanoes (MVs) directly emit the major gas phase, methane, into the atmosphere, making them important sources of greenhouse gases over geological time. Quantification of methane emission would require detailed insights into the capacity and efficiency of microbial metabolisms either consuming or producing methane in the subsurface, and establishment of the linkage between these methane-related metabolisms and other microbial or abiotic processes. Here we conducted geochemical, microbiological and genetic analyses of sediments, gases, and pore and surface fluids to characterize fluid processes, community assemblages, functions and activities in a methane-emitting MV of southwestern Taiwan. Multiple lines of evidence suggest that aerobic/anaerobic methane oxidation, sulfate reduction and methanogenesis are active and compartmentalized into discrete, stratified niches, resembling those in marine settings. Surface evaporation and oxidation of sulfide minerals are required to account for the enhanced levels of sulfate that fuels subsurface sulfate reduction and anaerobic methanotrophy. Methane flux generated by in situ methanogenesis appears to alter the isotopic compositions and abundances of thermogenic methane migrating from deep sources, and to exceed the capacity of microbial consumption. This metabolic stratification is sustained by chemical disequilibria induced by the mixing between upward, anoxic, methane-rich fluids and downward, oxic, sulfate-rich fluids. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3504961','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3504961">Metabolic stratification driven by surface and subsurface interactions in a terrestrial mud volcano</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Cheng, Ting-Wen; Chang, Yung-Hsin; Tang, Sen-Lin; Tseng, Ching-Hung; Chiang, Pei-Wen; Chang, Kai-Ti; Sun, Chih-Hsien; Chen, Yue-Gau; Kuo, Hung-Chi; Wang, Chun-Ho; Chu, Pao-Hsuan; Song, Sheng-Rong; Wang, Pei-Ling; Lin, Li-Hung 2012-01-01 Terrestrial mud volcanism represents the prominent surface geological feature, where fluids and hydrocarbons are discharged along deeply rooted structures in tectonically active regimes. Terrestrial mud volcanoes (MVs) directly emit the major gas phase, methane, into the atmosphere, making them important sources of greenhouse gases over geological time. Quantification of methane emission would require detailed insights into the capacity and efficiency of microbial metabolisms either consuming or producing methane in the subsurface, and establishment of the linkage between these methane-related metabolisms and other microbial or abiotic processes. Here we conducted geochemical, microbiological and genetic analyses of sediments, gases, and pore and surface fluids to characterize fluid processes, community assemblages, functions and activities in a methane-emitting MV of southwestern Taiwan. Multiple lines of evidence suggest that aerobic/anaerobic methane oxidation, sulfate reduction and methanogenesis are active and compartmentalized into discrete, stratified niches, resembling those in marine settings. Surface evaporation and oxidation of sulfide minerals are required to account for the enhanced levels of sulfate that fuels subsurface sulfate reduction and anaerobic methanotrophy. Methane flux generated by in situ methanogenesis appears to alter the isotopic compositions and abundances of thermogenic methane migrating from deep sources, and to exceed the capacity of microbial consumption. This metabolic stratification is sustained by chemical disequilibria induced by the mixing between upward, anoxic, methane-rich fluids and downward, oxic, sulfate-rich fluids. PMID:22739492 </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active">13</li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active">14</li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002ESRv...58..367K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002ESRv...58..367K">Microbial production and oxidation of methane in deep subsurface</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kotelnikova, Svetlana 2002-10-01 The goal of this review is to summarize present studies on microbial production and oxidation of methane in the deep subterranean environments. Methane is a long-living gas causing the "greenhouse" effect in the planet's atmosphere. Earlier, the deep "organic carbon poor" subsurface was not considered as a source of "biogenic" methane. Evidence of active methanogenesis and presence of viable methanogens including autotrophic organisms were obtained for some subsurface environments including water-flooded oil-fields, deep sandy aquifers, deep sea hydrothermal vents, the deep sediments and granitic groundwater at depths of 10 to 2000 m below sea level. As a rule, the deep subterranean microbial populations dwell at more or less oligotrophic conditions. Molecular hydrogen has been found in a variety of subsurface environments, where its concentrations were significantly higher than in the tested surface aquatic environments. Chemolithoautotrophic microorganisms from deep aquifers that could grow on hydrogen and carbon dioxide can act as primary producers of organic carbon, initiating heterotrophic food chains in the deep subterranean environments independent of photosynthesis. "Biogenic" methane has been found all over the world. On the basis of documented occurrences, gases in reservoirs and older sediments are similar and have the isotopic character of methane derived from CO 2 reduction. Groundwater representing the methanogenic end member are characterized by a relative depletion of dissolved organic carbon (DOC) in combination with an enrichment in 13C in inorganic carbon, which is consistent with the preferential reduction of 12CO 2 by autotrophic methanogens or acetogens. The isotopic composition of methane formed via CO 2 reduction is controlled by the δ13C of the original CO 2 substrate. Literature data shows that CH 4 as heavy as -40‰ or -50‰ can be produced by the microbial reduction of isotopically heavy CO 2. Produced methane may be oxidized </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B31E2035N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B31E2035N">A subsurface Fe-silicate weathering microbiome</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Napieralski, S. A.; Buss, H. L.; Roden, E. E. 2017-12-01 Traditional models of microbially mediated weathering of primary Fe-bearing minerals often invoke organic ligands (e.g. siderophores) used for nutrient acquisition. However, it is well known that the oxidation of Fe(II) governs the overall rate of Fe-silicate mineral dissolution. Recent work has demonstrated the ability of lithtrophic iron oxidizing bacteria (FeOB) to grow via the oxidation of structural Fe(II) in biotite as a source of metabolic energy with evidence suggesting a direct enzymatic attack on the mineral surface. This process necessitates the involvement of dedicated outer membrane proteins that interact with insoluble mineral phases in a process known as extracellular electron transfer (EET). To investigate the potential role FeOB in a terrestrial subsurface weathering system, samples were obtained from the bedrock-saprolite interface (785 cm depth) within the Rio Icacos Watershed of the Luquillo Mountains in Puerto Rico. Prior geochemical evidence suggests the flux of Fe(II) from the weathering bedrock supports a robust lithotrophic microbial community at depth. Current work confirms the activity of microorganism in situ, with a marked increase in ATP near the bedrock-saprolite interface. Regolith recovered from the interface was used as inoculum to establish enrichment cultures with powderized Fe(II)-bearing minerals serving as the sole energy source. Monitoring of the Fe(II)/Fe(total) ratio and ATP generation suggests growth of microorganisms coupled to the oxidation of mineral bound Fe(II). Analysis of 16S rRNA gene and shotgun metagenomic libraries from in situ and enrichment culture samples lends further support to FeOB involvement in the weathering process. Multiple metagenomic bins related to known FeOB, including Betaproteobacteria genera, contain homologs to model EET systems, including Cyc2 and MtoAB. Our approach combining geochemistry and metagenomics with ongoing microbiological and genomic characterization of novel isolates obtained </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018CG....111...46A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018CG....111...46A">An innovative computationally efficient hydromechanical coupling approach for fault reactivation in geological subsurface utilization</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Adams, M.; Kempka, T.; Chabab, E.; Ziegler, M. 2018-02-01 Estimating the efficiency and sustainability of geological subsurface utilization, i.e., Carbon Capture and Storage (CCS) requires an integrated risk assessment approach, considering the occurring coupled processes, beside others, the potential reactivation of existing faults. In this context, hydraulic and mechanical parameter uncertainties as well as different injection rates have to be considered and quantified to elaborate reliable environmental impact assessments. Consequently, the required sensitivity analyses consume significant computational time due to the high number of realizations that have to be carried out. Due to the high computational costs of two-way coupled simulations in large-scale 3D multiphase fluid flow systems, these are not applicable for the purpose of uncertainty and risk assessments. Hence, an innovative semi-analytical hydromechanical coupling approach for hydraulic fault reactivation will be introduced. This approach determines the void ratio evolution in representative fault elements using one preliminary base simulation, considering one model geometry and one set of hydromechanical parameters. The void ratio development is then approximated and related to one reference pressure at the base of the fault. The parametrization of the resulting functions is then directly implemented into a multiphase fluid flow simulator to carry out the semi-analytical coupling for the simulation of hydromechanical processes. Hereby, the iterative parameter exchange between the multiphase and mechanical simulators is omitted, since the update of porosity and permeability is controlled by one reference pore pressure at the fault base. The suggested procedure is capable to reduce the computational time required by coupled hydromechanical simulations of a multitude of injection rates by a factor of up to 15. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.2270D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.2270D">Surface Geology of Europa: A Window to Subsurface Composition and Habitability</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Dalton, J. Brad; Shirley, James H.; Prockter, Louise M. 2010-05-01 Observations from the Galileo Near-Infrared Mapping Spectrometer (NIMS) provide a wealth of spectral information on the surface composition of Europa. Recent advances in the analysis of spacecraft observations, combined with newly available reference spectra of expected chemical compounds [Dalton et al., 2005], now permit investigation of composition for individual geologic units. Some of these units appear to represent low-viscosity cryovolcanic flows, presenting substantial evidence for subsurface origin. Subsequent processing by radiolysis and photolysis (chemistry driven by high-energy particle and ultraviolet radiation) has altered the composition of these deposits since their emplacement. It has been postulated that hydrated sulfate salts from the interior may have been converted to sulfuric acid hydrate by this exogenic processing [Carlson et al., 1999; McCord et al., 2002]. It has also been postulated that much of the observed sulfuric acid hydrate may be derived entirely from water ice and implanted sulfur ions from Jupiter's magnetosphere [Carlson et al., 2005]. Destruction of large molecules by the same radiation [Loeffler et al., 2010] however suggests that there may be an equilibrium between creation and destruction that varies based on sulfur content and radiation flux. Derivation of compositions for multiple exposures of individual surface units reveals a gradient in sulfuric acid abundance that increases from the leading hemisphere to the trailing hemisphere, which receives a higher radiogenic dose. Certain geologically young cryovolcanic flow surface units exhibit comparatively higher proportions of hydrated salts (with correspondingly lower abundance of sulfuric acid hydrate) than is found for older surface units of the same type, or for surface units of different geologic origin. Taken together these lines of evidence suggest that in at least some of these units, we are observing an intermediate stage of the conversion of endogenically </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4257577','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4257577">Evaluating the performance of parallel subsurface simulators: An illustrative example with PFLOTRAN</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Hammond, G E; Lichtner, P C; Mills, R T 2014-01-01 [1] To better inform the subsurface scientist on the expected performance of parallel simulators, this work investigates performance of the reactive multiphase flow and multicomponent biogeochemical transport code PFLOTRAN as it is applied to several realistic modeling scenarios run on the Jaguar supercomputer. After a brief introduction to the code's parallel layout and code design, PFLOTRAN's parallel performance (measured through strong and weak scalability analyses) is evaluated in the context of conceptual model layout, software and algorithmic design, and known hardware limitations. PFLOTRAN scales well (with regard to strong scaling) for three realistic problem scenarios: (1) in situ leaching of copper from a mineral ore deposit within a 5-spot flow regime, (2) transient flow and solute transport within a regional doublet, and (3) a real-world problem involving uranium surface complexation within a heterogeneous and extremely dynamic variably saturated flow field. Weak scalability is discussed in detail for the regional doublet problem, and several difficulties with its interpretation are noted. PMID:25506097 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25506097','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25506097">Evaluating the performance of parallel subsurface simulators: An illustrative example with PFLOTRAN.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Hammond, G E; Lichtner, P C; Mills, R T 2014-01-01 [1] To better inform the subsurface scientist on the expected performance of parallel simulators, this work investigates performance of the reactive multiphase flow and multicomponent biogeochemical transport code PFLOTRAN as it is applied to several realistic modeling scenarios run on the Jaguar supercomputer. After a brief introduction to the code's parallel layout and code design, PFLOTRAN's parallel performance (measured through strong and weak scalability analyses) is evaluated in the context of conceptual model layout, software and algorithmic design, and known hardware limitations. PFLOTRAN scales well (with regard to strong scaling) for three realistic problem scenarios: (1) in situ leaching of copper from a mineral ore deposit within a 5-spot flow regime, (2) transient flow and solute transport within a regional doublet, and (3) a real-world problem involving uranium surface complexation within a heterogeneous and extremely dynamic variably saturated flow field. Weak scalability is discussed in detail for the regional doublet problem, and several difficulties with its interpretation are noted. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=329858','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=329858">Surface and subsurface inspection of food safety and quality using a line-scan Raman system</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> This paper presents a line-scan Raman platform for food safety and quality research, which can be configured for Raman chemical imaging (RCI) mode for surface inspection and spatially offset Raman spectroscopy (SORS) mode for subsurface inspection. In the RCI mode, macro-scale imaging was achieved u... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.B22A..02S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.B22A..02S">Modeling Biogeochemical Cycling of Heavy Metals in Lake Coeur d'Alene Sediments</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sengor, S. S.; Spycher, N.; Belding, E.; Curthoys, K.; Ginn, T. R. 2005-12-01 Mining of precious metals since the late 1800's have left Lake Coeur d'Alene (LCdA) sediments heavily enriched with toxic metals, including Cd, Cu, Pb, and Zn. Indigenous microbes however are capable of catalyzing reactions that detoxify the benthic and aqueous lake environments, and thus constitute an important driving component in the biogeochemical cycles of these metals. Here we report on the development of a quantitative model of transport, fate, exposure and effects of toxic compounds on benthic microbial communities at LCdA. First, chemical data from the LCdA area have been compiled from multiple sources to investigate trends in chemical occurrence, as well as to define model boundary conditions. The model is structured as 1-D diffusive reactive transport model to simulate spatial and temporal distribution of metals through the benthic sediments. Inorganic reaction processes included in the model are aqueous speciation, surface complexation, mineral precipitation/dissolution and abiotic redox reactions. Simulations with and without surface complexation are carried out to evaluate the effect of sorption and the conservative behaviour of metals within the benthic sediments under abiotic and purely diffusive transport. The 1-D inorganic diffusive transport model is then coupled to a biotic reaction network including consortium biodegradation kinetics with multiple electron acceptors, product toxicity, and energy partitioning. Multiyear simulations are performed, with water column chemistry established as a boundary condition from extant data, to explore the role of biogeochemical dynamics on benthic fluxes of metals in the long term. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2803725','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2803725">Surface response of a fractional order viscoelastic halfspace to surface and subsurface sources</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Meral, F. Can; Royston, Thomas J.; Magin, Richard L. 2009-01-01 Previous studies by the second author published in this journal focused on low audible frequency (40–400 Hz) shear and surface wave motion in and on a viscoelastic material representative of biological tissue. Specific cases considered were that of surface wave motion on a halfspace caused by a finite rigid circular disk located on the surface and oscillating normal to it [Royston et al., J. Acoust. Soc. Am. 106, 3678–3686 (1999)] and compression, shear, and surface wave motion in a halfspace generated by a subsurface finite dipole [Royston et al., J. Acoust. Soc. Am. 113, 1109–1121 (2003)]. In both studies, a Voigt model of viscoelasticity was assumed in the theoretical treatment, which resulted in agreement between theoretical predictions and experimental measurements over a limited frequency range. In the present article, the linear viscoelastic assumption in these two prior works is revisited to consider a (still linear) fractional order Voigt model, where the rate-dependent damping component that is dependent on the first derivative of time is replaced with a component that is dependent on a fractional derivative of time. It is shown that in both excitation source configurations, the fractional order Voigt model assumption improves the match of theory to experiment over a wider frequency range (in some cases up to the measured range of 700 Hz). PMID:20000941 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010045102&hterms=Xxxii&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DXxxii','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010045102&hterms=Xxxii&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DXxxii">Chronology: An Important (and Potentially Accessible) Parameter in Understanding Europa Surface-Subsurface Material Interchange, Burial, and Resurfacing Processes</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Swindle, T. D. 2001-01-01 Time is an important parameter in understanding the interaction of the surface and subsurface of Europa. It should be possible to determine potassium-argon and cosmic ray exposure ages in situ on the surface of Europa. Additional information is contained in the original extended abstract. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSEC14A0956S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSEC14A0956S">Biogeochemical responses to meso- and submesoscale oceanic variability in the Kuroshio region</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Suzue, Y.; Uchiyama, Y.; Yamazaki, H. 2016-02-01 Influences of the Kuroshio and associated meso- and submesoscale variability due to frontally- and topographically-induced eddies on biogeochemical processes in the Kuroshio region off Japan are examined with a synoptic downscaling ocean modeling using the UCLA version of ROMS (Shchepetkin and McWilliams, 2005; 2008) coupled with an NPZD (nutrient, phyto/zooplanktons and detritus) nitrogen-based biogeochemical model (e.g., Fasham et al., 1990). The hydrodynamic model is initialized and forced by the JCOPE2 assimilative oceanic reanalysis (Miyazawa et al., 2009) with a horizontal grid resolution of 1/12o (dx ≈ 10 km) to convey the basin-scale information including the transient Kuroshio path though the parent ROMS-L1 model (dx = 3 km) and the child ROMS-L2 model (dx = 1 km) successively with the one-way offline nesting technique (Mason et al., 2011). The JMA GPV-MSM assimilative atmospheric reanalysis (dx = 6 km) is used to force both the ROMS models, while the NPZD model is configured according to Gruber et al. (2006). The model result is extensively compared with satellite (e.g., AVISO, MODIS/Aqua Chl.a) and in-situ data (e.g., the JMA's ship measurement) to confirm good agreement. The submesoscale eddy-resolving L2 output exhibits that intermediate water containing abundant nutrients occasionally surfaces by localized upwelling associated with cyclonic eddies, and that high Chl.a concentration appears around the Kuroshio Front. Furthermore, it is found that meso- and submesoscale eddies developed between the Kuroshio and the coastline also influence on the nearshore biogeochemical productivity. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70032307','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70032307">Scaling hyporheic exchange and its influence on biogeochemical reactions in aquatic ecosystems</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> O'Connor, Ben L.; Harvey, Judson W. 2008-01-01 Hyporheic exchange and biogeochemical reactions are difficult to quantify because of the range in fluid‐flow and sediment conditions inherent to streams, wetlands, and nearshore marine ecosystems. Field measurements of biogeochemical reactions in aquatic systems are impeded by the difficulty of measuring hyporheic flow simultaneously with chemical gradients in sediments. Simplified models of hyporheic exchange have been developed using Darcy's law generated by flow and bed topography at the sediment‐water interface. However, many modes of transport are potentially involved (molecular diffusion, bioturbation, advection, shear, bed mobility, and turbulence) with even simple models being difficult to apply in complex natural systems characterized by variable sediment sizes and irregular bed geometries. In this study, we synthesize information from published hyporheic exchange investigations to develop a scaling relationship for estimating mass transfer in near‐surface sediments across a range in fluid‐flow and sediment conditions. Net hyporheic exchange was quantified using an effective diffusion coefficient (De) that integrates all of the various transport processes that occur simultaneously in sediments, and dimensional analysis was used to scale De to shear stress velocity, roughness height, and permeability that describe fluid‐flow and sediment characteristics. We demonstrated the value of the derived scaling relationship by using it to quantify dissolved oxygen (DO) uptake rates on the basis of DO profiles in sediments and compared them to independent flux measurements. The results support a broad application of the De scaling relationship for quantifying coupled hyporheic exchange and biogeochemical reaction rates in streams and other aquatic ecosystems characterized by complex fluid‐flow and sediment conditions. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1224515','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1224515">Conceptual Model of Iodine Behavior in the Subsurface at the Hanford Site</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Truex, Michael J.; Lee, Brady D.; Johnson, Christian D. The fate and transport of 129I in the environment and potential remediation technologies are currently being studied as part of environmental remediation activities at the Hanford Site. A conceptual model describing the nature and extent of subsurface contamination, factors that control plume behavior, and factors relevant to potential remediation processes is needed to support environmental remedy decisions. Because 129I is an uncommon contaminant, relevant remediation experience and scientific literature are limited. Thus, the conceptual model also needs to both describe known contaminant and biogeochemical process information and to identify aspects about which additional information needed to effectively support remedy decisions.more » this document summarizes the conceptual model of iodine behavior relevant to iodine in the subsurface environment at the Hanford site.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010119225&hterms=global+biomarker&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dglobal%2Bbiomarker','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010119225&hterms=global+biomarker&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dglobal%2Bbiomarker">Biogeochemical Processes in Microbial Ecosystems</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> DesMarais, David J.; DeVincenzi, Donald L. (Technical Monitor) 2001-01-01 The hierarchical organization of microbial ecosystems determines process rates that shape Earth's environment, create the biomarker sedimentary and atmospheric signatures of life and define the stage upon which major evolutionary events occurred. In order to understand how microorganisms have shaped the global environment of Earth and potentially, other worlds, we must develop an experimental paradigm that links biogeochemical processes with ever-changing temporal and spatial distributions of microbial population, and their metabolic properties. Photosynthetic microbial mats offer an opportunity to define holistic functionality at the millimeter scale. At the same time, their Biogeochemistry contributes to environmental processes on a planetary scale. These mats are possibly direct descendents of the most ancient biological communities; communities in which oxygenic photosynthesis might have been invented. Mats provide one of the best natural systems to study how microbial populations associate to control dynamic biogeochemical gradients. These are self-sustaining, complete ecosystems in which light energy absorbed over a diel (24 hour) cycle drives the synthesis of spatially-organized, diverse biomass. Tightly-coupled microorganisms in the mat have specialized metabolisms that catalyze transformations of carbon, nitrogen. sulfur, and a host of other elements. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015WRR....51.6725M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015WRR....51.6725M">Potential for real-time understanding of coupled hydrologic and biogeochemical processes in stream ecosystems: Future integration of telemetered data with process models for glacial meltwater streams</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> McKnight, Diane M.; Cozzetto, Karen; Cullis, James D. S.; Gooseff, Michael N.; Jaros, Christopher; Koch, Joshua C.; Lyons, W. Berry; Neupauer, Roseanna; Wlostowski, Adam 2015-08-01 While continuous monitoring of streamflow and temperature has been common for some time, there is great potential to expand continuous monitoring to include water quality parameters such as nutrients, turbidity, oxygen, and dissolved organic material. In many systems, distinguishing between watershed and stream ecosystem controls can be challenging. The usefulness of such monitoring can be enhanced by the application of quantitative models to interpret observed patterns in real time. Examples are discussed primarily from the glacial meltwater streams of the McMurdo Dry Valleys, Antarctica. Although the Dry Valley landscape is barren of plants, many streams harbor thriving cyanobacterial mats. Whereas a daily cycle of streamflow is controlled by the surface energy balance on the glaciers and the temporal pattern of solar exposure, the daily signal for biogeochemical processes controlling water quality is generated along the stream. These features result in an excellent outdoor laboratory for investigating fundamental ecosystem process and the development and validation of process-based models. As part of the McMurdo Dry Valleys Long-Term Ecological Research project, we have conducted field experiments and developed coupled biogeochemical transport models for the role of hyporheic exchange in controlling weathering reactions, microbial nitrogen cycling, and stream temperature regulation. We have adapted modeling approaches from sediment transport to understand mobilization of stream biomass with increasing flows. These models help to elucidate the role of in-stream processes in systems where watershed processes also contribute to observed patterns, and may serve as a test case for applying real-time stream ecosystem models. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.U31B..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.U31B..07S">Polycyclic Aromatic Hydrocarbon Distribution and Modification in the Sub-surface Plume Near the Deepwater Horizon Wellhead</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shiller, A. M.; Joung, D.; Wade, T. 2011-12-01 A significant concern associated with oil spills is the toxicity associated with the polycyclic aromatic hydrocarbon (PAH) component. Ratios of various PAH's have also been used as indicators of oil sources. During a late May/early June cruise, 57 samples for PAH analysis were collected in the vicinity of the Deepwater Horizon wellhead. Most samples were from the previously reported sub-surface oil plume, centered near 1100 m depth. PAH concentrations ranged up to 117 μg/L and rapidly diminished in the subsurface with distance from the wellhead. The Macondo well oil was observed to be rich in naphthalenes. Within a few km of the wellhead, the percentage of methyl-naphthalenes in the sub-surface plume was generally higher than in the source, suggesting preferential solubilization of this low molecular weight fraction. However, the percentage rapidly decreased away from the well also suggesting rapid destruction or removal of the naphthalenes. The pyrogenic index (Wang et al.) was <0.05 for all samples, indicating a petroleum origin. For a few samples, some other PAH ratios (e.g., MP/P and P/A ratios) suggested a combustion origin. However, these ratios also tended to vary both with percent methyl-naphthalenes and distance from the wellhead, suggesting anomalous ratios originating from solubilization/degradation effects. We also obtained a more limited set of surface water samples, generally avoiding the most contaminated areas as well as areas of oil burning. For these surface water samples, similar trends were observed as at depth, probably resulting from selective volatilization and photo-degradation. Overall, the data illustrate how environmental factors lead both to reduced concentrations and fractionation of the PAH's. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.4869C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.4869C">Exploiting Soil Moisture, Precipitation, and Streamflow Observations to Evaluate Soil Moisture/Runoff Coupling in Land Surface Models</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Crow, W. T.; Chen, F.; Reichle, R. H.; Xia, Y.; Liu, Q. 2018-05-01 Accurate partitioning of precipitation into infiltration and runoff is a fundamental objective of land surface models tasked with characterizing the surface water and energy balance. Temporal variability in this partitioning is due, in part, to changes in prestorm soil moisture, which determine soil infiltration capacity and unsaturated storage. Utilizing the National Aeronautics and Space Administration Soil Moisture Active Passive Level-4 soil moisture product in combination with streamflow and precipitation observations, we demonstrate that land surface models (LSMs) generally underestimate the strength of the positive rank correlation between prestorm soil moisture and event runoff coefficients (i.e., the fraction of rainfall accumulation volume converted into stormflow runoff during a storm event). Underestimation is largest for LSMs employing an infiltration-excess approach for stormflow runoff generation. More accurate coupling strength is found in LSMs that explicitly represent subsurface stormflow or saturation-excess runoff generation processes. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JHyd..547..664A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JHyd..547..664A">Integrated surface-subsurface model to investigate the role of groundwater in headwater catchment runoff generation: A minimalist approach to parameterisation</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ala-aho, Pertti; Soulsby, Chris; Wang, Hailong; Tetzlaff, Doerthe 2017-04-01 Understanding the role of groundwater for runoff generation in headwater catchments is a challenge in hydrology, particularly so in data-scarce areas. Fully-integrated surface-subsurface modelling has shown potential in increasing process understanding for runoff generation, but high data requirements and difficulties in model calibration are typically assumed to preclude their use in catchment-scale studies. We used a fully integrated surface-subsurface hydrological simulator to enhance groundwater-related process understanding in a headwater catchment with a rich background in empirical data. To set up the model we used minimal data that could be reasonably expected to exist for any experimental catchment. A novel aspect of our approach was in using simplified model parameterisation and including parameters from all model domains (surface, subsurface, evapotranspiration) in automated model calibration. Calibration aimed not only to improve model fit, but also to test the information content of the observations (streamflow, remotely sensed evapotranspiration, median groundwater level) used in calibration objective functions. We identified sensitive parameters in all model domains (subsurface, surface, evapotranspiration), demonstrating that model calibration should be inclusive of parameters from these different model domains. Incorporating groundwater data in calibration objectives improved the model fit for groundwater levels, but simulations did not reproduce well the remotely sensed evapotranspiration time series even after calibration. Spatially explicit model output improved our understanding of how groundwater functions in maintaining streamflow generation primarily via saturation excess overland flow. Steady groundwater inputs created saturated conditions in the valley bottom riparian peatlands, leading to overland flow even during dry periods. Groundwater on the hillslopes was more dynamic in its response to rainfall, acting to expand the saturated area </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H14D..02S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H14D..02S">Using a spatially-distributed hydrologic biogeochemistry model with nitrogen transport to study the spatial variation of carbon stocks and fluxes in a Critical Zone Observatory</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shi, Y.; Eissenstat, D. M.; He, Y.; Davis, K. J. 2017-12-01 Most current biogeochemical models are 1-D and represent one point in space. Therefore, they cannot resolve topographically driven land surface heterogeneity (e.g., lateral water flow, soil moisture, soil temperature, solar radiation) or the spatial pattern of nutrient availability. A spatially distributed forest biogeochemical model with nitrogen transport, Flux-PIHM-BGC, has been developed by coupling a 1-D mechanistic biogeochemical model Biome-BGC (BBGC) with a spatially distributed land surface hydrologic model, Flux-PIHM, and adding an advection dominated nitrogen transport module. Flux-PIHM is a coupled physically based model, which incorporates a land-surface scheme into the Penn State Integrated Hydrologic Model (PIHM). The land surface scheme is adapted from the Noah land surface model, and is augmented by adding a topographic solar radiation module. Flux-PIHM is able to represent the link between groundwater and the surface energy balance, as well as land surface heterogeneities caused by topography. In the coupled Flux-PIHM-BGC model, each Flux-PIHM model grid couples a 1-D BBGC model, while nitrogen is transported among model grids via surface and subsurface water flow. In each grid, Flux-PIHM provides BBGC with soil moisture, soil temperature, and solar radiation, while BBGC provides Flux-PIHM with spatially-distributed leaf area index. The coupled Flux-PIHM-BGC model has been implemented at the Susquehanna/Shale Hills Critical Zone Observatory. The model-predicted aboveground vegetation carbon and soil carbon distributions generally agree with the macro patterns observed within the watershed. The importance of abiotic variables (including soil moisture, soil temperature, solar radiation, and soil mineral nitrogen) in predicting aboveground carbon distribution is calculated using a random forest. The result suggests that the spatial pattern of aboveground carbon is controlled by the distribution of soil mineral nitrogen. A Flux-PIHM-BGC simulation </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B11G1741A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B11G1741A">Deep subsurface life in Bengal Fan sediments (IODP Exp. 354)</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Adhikari, R. R.; Heuer, V. B.; Elvert, M.; Kallmeyer, J.; Kitte, J. A.; Wörmer, L.; Hinrichs, K. U. 2017-12-01 We collected Bengal Fan sediment samples along a 8°N transect during International Ocean Discovery Program Expedition 354 (February - March 2015, Singapore - Colombo, Sri Lanka) to study subseafloor life in this, as yet unstudied, area. Among other biogeochemical parameters, we quantified microbial biomass by analyzing prokaryotic cells using epifluorescence microscopy after detaching cells from the sediment, and bacterial endospores by analyzing the diagnostic biomarker dipicolinic acid (DPA) by detection of fluorescence of the terbium-DPA complex. To gain understanding of total microbial activity, we quantified hydrogen utilization potential of hydrogenase enzymes, which are ubiquitous in subsurface microorganisms, by using a tritium assay. We measured highest cell concentrations of ca. 108 cells g-1 in shallow sediments close to the seafloor. These concentrations are one to two orders of magnitude lower than in most marine continental margin settings [1]. Similar to the global trend [1], cell concentrations decreased with depth according to a power-law function. Endospore concentrations scattered between ca. 105 and 107 cells g-1 sediment at all sites and depths. We could not observe a clear relationship of endospore concentration and sediment depth; instead, it appears to be linked to lithology and total organic carbon content. Bulk Hydrogenase enzyme activity ranged from nmolar to μmolar range of H2 g-1d-1. Similar to previous observations [2], per-cell hydrogen utilization depends on vertical biogeochemical zones, which could be due to the differences in hydrogen utilization requirements/efficiency of the respective metabolic processes such as sulfate reduction, methanogenesis, fermentation etc. Bengal fan is highly dynamic due to channel and levee systems and the sediments are dominated by turbidites, thick sand layers and hemipelagic deposits, which may control biogeochemical zonation. Based on our microbial biomass and activity data, we suggest that the </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active">14</li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active">15</li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017CliPa..13..333R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017CliPa..13..333R">Holocene evolution of the North Atlantic subsurface transport</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Repschläger, Janne; Garbe-Schönberg, Dieter; Weinelt, Mara; Schneider, Ralph 2017-04-01 Previous studies suggested that short-term freshening events in the subpolar gyre can be counterbalanced by advection of saline waters from the subtropical gyre and thus stabilize the Atlantic Meridional Overturning Circulation (AMOC). However, little is known about the inter-gyre transport pathways. Here, we infer changes in surface and subsurface transport between the subtropical and polar North Atlantic during the last 11 000 years, by combining new temperature and salinity reconstructions obtained from combined δ18O and Mg / Ca measurements on surface and subsurface dwelling foraminifera with published foraminiferal abundance data from the subtropical North Atlantic, and with salinity and temperature data from the tropical and subpolar North Atlantic. This compilation implies an overall stable subtropical warm surface water transport since 10 ka BP. In contrast, subsurface warm water transport started at about 8 ka but still with subsurface heat storage in the subtropical gyre. The full strength of intergyre exchange was probably reached only after the onset of northward transport of warm saline subsurface waters at about 7 ka BP, associated with the onset of the modern AMOC mode. A critical evaluation of different potential forcing mechanisms leads to the assumption that freshwater supply from the Laurentide Ice Sheet was the main control on subtropical to subpolar ocean transport at surface and subsurface levels. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JVGR..321..171B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JVGR..321..171B">Sub-surface structure of La Soufrière of Guadeloupe lava dome deduced from a ground-based magnetic survey</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bouligand, Claire; Coutant, Olivier; Glen, Jonathan M. G. 2016-07-01 In this study, we present the analysis and interpretation of a new ground magnetic survey acquired at the Soufrière volcano on Guadeloupe Island. Observed short-wavelength magnetic anomalies are compared to those predicted assuming a constant magnetization within the sub-surface. The good correlation between modeled and observed data over the summit of the dome indicates that the shallow sub-surface displays relatively constant and high magnetization intensity. In contrast, the poor correlation at the base of the dome suggests that the underlying material is non- to weakly-magnetic, consistent with what is expected for a talus comprised of randomly oriented and highly altered and weathered boulders. The new survey also reveals a dipole anomaly that is not accounted for by a constant magnetization in the sub-surface and suggests the existence of material with decreased magnetization beneath the Soufrière lava dome. We construct simple models to constrain its dimensions and propose that this body corresponds to hydrothermally altered material within and below the dome. The very large inferred volume for such material may have implications on the stability of the dome. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B14D..02C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B14D..02C">Demonstrating the Value of Fine-resolution Optical Data for Minimising Aliasing Impacts on Biogeochemical Models of Surface Waters</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chappell, N. A.; Jones, T.; Young, P.; Krishnaswamy, J. 2015-12-01 There is increasing awareness that under-sampling may have resulted in the omission of important physicochemical information present in water quality signatures of surface waters - thereby affecting interpretation of biogeochemical processes. For dissolved organic carbon (DOC) and nitrogen this under-sampling can now be avoided using UV-visible spectroscopy measured in-situ and continuously at a fine-resolution e.g. 15 minutes ("real time"). Few methods are available to extract biogeochemical process information directly from such high-frequency data. Jones, Chappell & Tych (2014 Environ Sci Technol: 13289-97) developed one such method using optically-derived DOC data based upon a sophisticated time-series modelling tool. Within this presentation we extend the methodology to quantify the minimum sampling interval required to avoid distortion of model structures and parameters that describe fundamental biogeochemical processes. This shifting of parameters which results from under-sampling is called "aliasing". We demonstrate that storm dynamics at a variety of sites dominate over diurnal and seasonal changes and that these must be characterised by sampling that may be sub-hourly to avoid aliasing. This is considerably shorter than that used by other water quality studies examining aliasing (e.g. Kirchner 2005 Phys Rev: 069902). The modelling approach presented is being developed into a generic tool to calculate the minimum sampling for water quality monitoring in systems driven primarily by hydrology. This is illustrated with fine-resolution, optical data from watersheds in temperate Europe through to the humid tropics. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170002418','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170002418">Evidence for Surface and Subsurface Ice Inside Micro Cold-Traps on Mercury's North Pole</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Rubanenko, L.; Mazarico, E.; Neumann, G. A.; Paige, D. A. 2017-01-01 The small obliquity of Mercury causes topographic depressions located near its poles to cast persistent shadows. Many [1, 9, 15] have shown these permanently shadowed regions (PSRs) may trap water ice for geologic time periods inside cold-traps. More recently, direct evidence for the presence of water ice deposits inside craters was remotely sensed in RADAR [5] and visible imagery [3]. Albedo measurements (reflectence at 1064 nm) obtained by the MErcury Space ENviroment GEochemistry and Ranging Laser Altimeter (MLA) found unusually bright and dark areas next to Mercury's north pole [7]. Using a thermal illumination model, Paige et al. [8] found the bright deposits are correlated with surface cold-traps, and the dark deposits are correlated with subsurface cold-traps. They suggested these anomalous deposits were brought to the surface by comets and were processed by the magnetospheric radiation flux, removing hydrogen and mixing C-N-O-S atoms to form a variety of molecules which will darken with time. Here we use a thermal illumination model to find the link between the cold-trap area fraction of a rough surface and its albedo. Using this link and the measurements obtained by MESSENGER we derive a surface and a subsurface ice distribution map on Mercury's north pole below the MESSENGER spatial resolution, approximately 500 m. We find a large fraction of the polar ice on Mercury resides inside micro cold-traps (of scales 10 - 100 m) distributed along the inter-crater terrain. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=59558&keyword=diversity+AND+surface&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=59558&keyword=diversity+AND+surface&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">COMPONENTS OF SURFACE AND SUBSURFACE CONNECTIVITY IN A LARGE OREGON (USA) RIVER--WHAT CAN BE RESTORED?</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> We conducted research on the Willamette River in western Oregon (USA) to determine the ecological functions of off-channel habitats (OCH). OCHs have declined in our 70 km study reach of the active floodplain since European settlement. Surface and subsurface connectivity between... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=306710&Lab=NRMRL&keyword=urease&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=306710&Lab=NRMRL&keyword=urease&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">Processes of Ammonia Air-Surface Exchange in a Fertilized Zea Mays Canopy</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Recent incorporation of coupled soil biogeochemical and bi-directional NH3 air-surface exchange algorithms into regional air quality models holds promise for further reducing uncertainty in estimates of NH3 emissions from fertilized soils. While this advancement represents a sig... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70031337','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70031337">Centimeter-scale characterization of biogeochemical gradients at a wetland-aquifer interface using capillary electrophoresis</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Baez-Cazull, S.; McGuire, J.T.; Cozzarelli, I.M.; Raymond, A.; Welsh, L. 2007-01-01 Steep biogeochemical gradients were measured at mixing interfaces in a wetland-aquifer system impacted by landfill leachate in Norman, Oklahoma. The system lies within a reworked alluvial plain and is characterized by layered low hydraulic conductivity wetland sediments interbedded with sandy aquifer material. Using cm-scale passive diffusion samplers, "peepers", water samples were collected in a depth profile to span interfaces between surface water and a sequence of deeper sedimentary layers. Geochemical indicators including electron acceptors, low-molecular-weight organic acids, base cations, and NH4+ were analyzed by capillary electrophoresis (CE) and field techniques to maximize the small sample volumes available from the centimeter-scale peepers. Steep concentration gradients of biogeochemical indicators were observed at various interfaces including those created at sedimentary boundaries and boundaries created by heterogeneities in organic C and available electron acceptors. At the sediment-water interface, chemical profiles with depth suggest that SO42 - and Fe reduction dominate driven by inputs of organic C from the wetland and availability of electron acceptors. Deeper in the sediments (not associated with a lithologic boundary), a steep gradient of organic acids (acetate maximum 8.8 mM) and NH4+ (maximum 36 mM) is observed due to a localized source of organic matter coupled with the lack of electron acceptor inputs. These findings highlight the importance of quantifying the redox reactions occurring in small interface zones and assessing their role on biogeochemical cycling at the system scale. ?? 2007 Elsevier Ltd. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70182805','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70182805">Subsurface clade of Geobacteraceae that predominates in a diversity of Fe(III)-reducing subsurface environments</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Holmes, Dawn E.; O'Neil, Regina A.; Vrionis, Helen A.; N'Guessan, Lucie A.; Ortiz-Bernad, Irene; Larrahondo, Maria J.; Adams, Lorrie A.; Ward, Joy A.; Nicoll , Julie S.; Nevin, Kelly P.; Chavan, Milind A.; Johnson, Jessica P.; Long, Philip E.; Lovely, Derek R. 2007-01-01 There are distinct differences in the physiology of Geobacter species available in pure culture. Therefore, to understand the ecology of Geobacter species in subsurface environments, it is important to know which species predominate. Clone libraries were assembled with 16S rRNA genes and transcripts amplified from three subsurface environments in which Geobacter species are known to be important members of the microbial community: (1) a uranium-contaminated aquifer located in Rifle, CO, USA undergoing in situ bioremediation; (2) an acetate-impacted aquifer that serves as an analog for the long-term acetate amendments proposed for in situ uranium bioremediation and (3) a petroleum-contaminated aquifer in which Geobacter species play a role in the oxidation of aromatic hydrocarbons coupled with the reduction of Fe(III). The majority of Geobacteraceae 16S rRNA sequences found in these environments clustered in a phylogenetically coherent subsurface clade, which also contains a number of Geobacter species isolated from subsurface environments. Concatamers constructed with 43 Geobacter genes amplified from these sites also clustered within this subsurface clade. 16S rRNA transcript and gene sequences in the sediments and groundwater at the Rifle site were highly similar, suggesting that sampling groundwater via monitoring wells can recover the most active Geobacter species. These results suggest that further study of Geobacter species in the subsurface clade is necessary to accurately model the behavior of Geobacter species during subsurface bioremediation of metal and organic contaminants. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?direntryid=336803','PESTICIDES'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?direntryid=336803">Efforts to estimate pesticide degradation rates in subsurface ...</a> <a target="_blank" href="http://www.epa.gov/pesticides/search.htm">EPA Pesticide Factsheets</a> When pesticides are used in real-world settings, the objective is to be effective in pest eradication at the site of application, but also it is desired that the pesticide have minimal persistence and mobility as it migrates away from the application site. At the site of application, sorption on soil and surface-soil degradation rates both factor into the pesticides' persistence. But once it migrates to the subsurface vadose zone and/or aquifers, subsurface degradation rate is a factor as well. Unfortunately, numerous soil properties that might affect pesticide degradation rate vary by orders of magnitude in the subsurface environment, both spatially and temporally, e.g., organic-carbon concentration, oxygen concentration, redox conditions, pH and soil mineralogy. Consequently, estimation of subsurface pesticide degradation rates and, in tum, pesticide persistence and mobility in the environment, has remained a challenge. To address this intransigent uncertainty, we surveyed peer-reviewed literature to identify > 100 data pairs in which investigators reported pesticide degradation rates in both surface and subsurface soils, using internally consistent experimental methods. These > 100 data pairs represented >30 separate pesticides. When the > 100 subsurface half-lives were plotted against surface half-lives, a limiting line could be defined for which all subsurface half-lives but three fe ll below the line. Of the three data points plotting above the limiting li </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B13N0056L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B13N0056L">Carbon mineralization in surface and subsurface soils in a subtropical mixed forest in central China</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Liu, F.; Tian, Q. 2014-12-01 About a half of soil carbon is stored in subsurface soil horizons, their dynamics have the potential to significantly affect carbon balancing in terrestrial ecosystems. However, the main factors regulating subsurface soil carbon mineralization are poorly understood. As affected by mountain humid monsoon, the subtropical mountains in central China has an annual precipitation of about 2000 mm, which causes strong leaching of ions and nutrition. The objectives of this study were to monitor subsurface soil carbon mineralization and to determine if it is affected by nutrient limitation. We collected soil samples (up to 1 m deep) at three locations in a small watershed with three soil layers (0-10 cm, 10-30 cm, below 30 cm). For the three layers, soil organic carbon (SOC) ranged from 35.8 to 94.4 mg g-1, total nitrogen ranged from 3.51 to 8.03 mg g-1, microbial biomass carbon (MBC) ranged from 170.6 to 718.4 μg g-1 soil. We measured carbon mineralization with the addition of N (100 μg N/g soil), P (50 μg P/g soil), and liable carbon (glucose labeled by 5 atom% 13C, at five levels: control, 10% MBC, 50% MBC, 100% MBC, 200% MBC). The addition of N and P had negligible effects on CO2 production in surface soil layers; in the deepest soil layer, the addition of N and P decreased CO2 production from 4.32 to 3.20 μg C g-1 soil carbon h-1. Glucose addition stimulated both surface and subsurface microbial mineralization of SOC, causing priming effects. With the increase of glucose addition rate from 10% to 200% MBC, the primed mineralization rate increased from 0.19 to 3.20 μg C g-1 soil carbon h-1 (fifth day of glucose addition). The magnitude of priming effect increased from 28% to 120% as soil layers go deep compare to the basal CO2 production (fifth day of 200% MBC glucose addition, basal CO2 production rate for the surface and the deepest soil was 11.17 and 2.88 μg C g-1 soil carbon h-1). These results suggested that the mineralization of subsurface carbon is more </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110014708','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110014708">Subsurface Ice Probe</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hecht, Michael; Carsey, Frank 2005-01-01 The subsurface ice probe (SIPR) is a proposed apparatus that would bore into ice to depths as great as hundreds of meters by melting the ice and pumping the samples of meltwater to the surface. Originally intended for use in exploration of subsurface ice on Mars and other remote planets, the SIPR could also be used on Earth as an alternative to coring, drilling, and melting apparatuses heretofore used to sample Arctic and Antarctic ice sheets. The SIPR would include an assembly of instrumentation and electronic control equipment at the surface, connected via a tether to a compact assembly of boring, sampling, and sensor equipment in the borehole (see figure). Placing as much equipment as possible at the surface would help to attain primary objectives of minimizing power consumption, sampling with high depth resolution, and unobstructed imaging of the borehole wall. To the degree to which these requirements would be satisfied, the SIPR would offer advantages over the aforementioned ice-probing systems. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B51B0426S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B51B0426S">Coupled Spatiotemporal Dynamics of Microbial Community Ecology, Biogeochemistry, and Hydrologic Mixing</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Stegen, J.; Johnson, T. C.; Fredrickson, J.; Wilkins, M.; Konopka, A.; Nelson, W.; Arntzen, E.; Chrisler, W.; Chu, R. K.; Fansler, S.; Kennedy, D.; Resch, T.; Tfaily, M. M. 2015-12-01 The hyporheic zone (HZ) is a critical ecosystem component that links terrestrial, surface water, and groundwater ecosystems. A dominant feature of the HZ is groundwater-surface water mixing and the input of terrestrially—as well as aquatically—derived organic carbon. In many systems the HZ has a relatively small spatial extent, but in larger riverine systems groundwater-surface water mixing can occur 100s of meters beyond the surface water shoreline; we consider these more distal locations to be within the 'subsurface interaction zone' (SIZ) as they are beyond the traditional HZ. Microbial communities in the HZ and SIZ drive biogeochemical processes in these system components, yet relatively little is known about the ecological processes that drive HZ and SIZ microbial communities. Here, we applied ecological theory, aqueous biogeochemistry, DNA sequencing, and ultra-high resolution organic carbon profiling to field samples collected through space (400m spatial extent) and time (7 month temporal extent) within the Hanford Site 300 Area. These data streams were integrated to evaluate how the influence of groundwater-surface water mixing on microbial communities changes when moving from the HZ to the broader SIZ. Our results indicate that groundwater-surface water mixing (i) consistently stimulated heterotrophic respiration, but only above a threshold of surface water intrusion, (ii) did not stimulate denitrification, (iii) caused deterministic shifts in HZ microbial communities due to changes in organic carbon composition, and (iv) did not cause shifts in SIZ microbial communities. These results suggest that microbial communities and the biogeochemical processes they drive are impacted by groundwater-surface water mixing primarily in the HZ and to a lesser extent in the SIZ. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.H13L1582H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.H13L1582H">Predicting Mountainous Watershed Biogeochemical Dynamics, Including Response to Droughts and Early Snowmelt</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hubbard, S. S.; Williams, K. H.; Long, P.; Agarwal, D.; Banfield, J. F.; Beller, H. R.; Bouskill, N.; Brodie, E.; Maxwell, R. M.; Nico, P. S.; Steefel, C. I.; Steltzer, H.; Tokunaga, T. K.; Wainwright, H. M. 2016-12-01 Climate change, extreme weather, land-use change, and other perturbations are significantly reshaping interactions with in watersheds throughout the world. While mountainous watersheds are recognized as the water towers for the world, hydrological processes in watersheds also mediate biogeochemical processes that support all terrestrial life. Developing predictive understanding of watershed hydrological and biogeochemical functioning is challenging, as complex interactions occurring within a heterogeneous watershed can lead to a cascade of effects on downstream water availability and quality. Although these interactions can have significant implications for energy production, agriculture, water quality, and other benefits valued by society, uncertainty associated with predicting watershed function is high. The Watershed Function project aims to substantially reduce this uncertainty through developing a predictive understanding of how mountainous watersheds retain and release downgradient water, nutrients, carbon, and metals. In particular, the project is exploring how early snowmelt, drought, and other disturbances will influence mountainous watershed dynamics at seasonal to decadal timescales. The Watershed Function project is being carried out in a headwater mountainous catchment of the Upper Colorado River Basin, within a watershed characterized by significant gradients in elevation, vegetation and hydrogeology. A system-within system project perspective posits that the integrated watershed response to disturbances can be adequately predicted through consideration of interactions and feedbacks occurring within a limited number of subsystems, each having distinct vegetation-subsurface biogeochemical-hydrological characteristics. A key technological goal is the development of scale-adaptive simulation capabilities that can incorporate genomic information where and when it is useful for predicting the overall watershed response to disturbance. Through developing </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMGC43C1205R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMGC43C1205R">Sensitivity of land surface modeling to parameters: An uncertainty quantification method applied to the Community Land Model</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ricciuto, D. M.; Mei, R.; Mao, J.; Hoffman, F. M.; Kumar, J. 2015-12-01 Uncertainties in land parameters could have important impacts on simulated water and energy fluxes and land surface states, which will consequently affect atmospheric and biogeochemical processes. Therefore, quantification of such parameter uncertainties using a land surface model is the first step towards better understanding of predictive uncertainty in Earth system models. In this study, we applied a random-sampling, high-dimensional model representation (RS-HDMR) method to analyze the sensitivity of simulated photosynthesis, surface energy fluxes and surface hydrological components to selected land parameters in version 4.5 of the Community Land Model (CLM4.5). Because of the large computational expense of conducting ensembles of global gridded model simulations, we used the results of a previous cluster analysis to select one thousand representative land grid cells for simulation. Plant functional type (PFT)-specific uniform prior ranges for land parameters were determined using expert opinion and literature survey, and samples were generated with a quasi-Monte Carlo approach-Sobol sequence. Preliminary analysis of 1024 simulations suggested that four PFT-dependent parameters (including slope of the conductance-photosynthesis relationship, specific leaf area at canopy top, leaf C:N ratio and fraction of leaf N in RuBisco) are the dominant sensitive parameters for photosynthesis, surface energy and water fluxes across most PFTs, but with varying importance rankings. On the other hand, for surface ans sub-surface runoff, PFT-independent parameters, such as the depth-dependent decay factors for runoff, play more important roles than the previous four PFT-dependent parameters. Further analysis by conditioning the results on different seasons and years are being conducted to provide guidance on how climate variability and change might affect such sensitivity. This is the first step toward coupled simulations including biogeochemical processes, atmospheric processes </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1194283-hybrid-multiscale-framework-subsurface-flow-transport-simulations','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1194283-hybrid-multiscale-framework-subsurface-flow-transport-simulations">A Hybrid Multiscale Framework for Subsurface Flow and Transport Simulations</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Scheibe, Timothy D.; Yang, Xiaofan; Chen, Xingyuan; ... 2015-06-01 Extensive research efforts have been invested in reducing model errors to improve the predictive ability of biogeochemical earth and environmental system simulators, with applications ranging from contaminant transport and remediation to impacts of biogeochemical elemental cycling (e.g., carbon and nitrogen) on local ecosystems and regional to global climate. While the bulk of this research has focused on improving model parameterizations in the face of observational limitations, the more challenging type of model error/uncertainty to identify and quantify is model structural error which arises from incorrect mathematical representations of (or failure to consider) important physical, chemical, or biological processes, properties, ormore » system states in model formulations. While improved process understanding can be achieved through scientific study, such understanding is usually developed at small scales. Process-based numerical models are typically designed for a particular characteristic length and time scale. For application-relevant scales, it is generally necessary to introduce approximations and empirical parameterizations to describe complex systems or processes. This single-scale approach has been the best available to date because of limited understanding of process coupling combined with practical limitations on system characterization and computation. While computational power is increasing significantly and our understanding of biological and environmental processes at fundamental scales is accelerating, using this information to advance our knowledge of the larger system behavior requires the development of multiscale simulators. Accordingly there has been much recent interest in novel multiscale methods in which microscale and macroscale models are explicitly coupled in a single hybrid multiscale simulation. A limited number of hybrid multiscale simulations have been developed for biogeochemical earth systems, but they mostly utilize application </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991TellA..43..188S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991TellA..43..188S">Terrestrial biogeochemical cycles: global interactions with the atmosphere and hydrology</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schimel, David S.; Kittel, Timothy G. F.; Parton, William J. 1991-08-01 Ecosystem scientists have developed a body of theory to predict the behaviour of biogeochemical cycles when exchanges with other ecosystems are small or prescribed. Recent environmental changes make it clear that linkages between ecosystems via atmospheric and hydrological transport have large effects on ecosystem dynamics when considered over time periods of a decade to a century, time scales relevant to contemporary humankind. Our ability to predict behaviour of ecosystems coupled by transport is limited by our ability (1) to extrapolate biotic function to large spatial scales and (2) to measure and model transport. We review developments in ecosystem theory, remote sensing, and geographical information systems (GIS) that support new efforts in spatial modeling. A paradigm has emerged to predict behaviour of ecosystems based on understanding responses to multiple resources (e.g., water, nutrients, light). Several ecosystem models couple primary production to decomposition and nutrient availability using the above paradigm. These models require a fairly small set of environmental variables to simulate spatial and temporal variation in rates of biogeochemical cycling. Simultaneously, techniques for inferring ecosystem behaviour from remotely measured canopy light interception are improving our ability to infer plant activity from satellite observations. Efforts have begun to couple models of transport in air and water to models of ecosystem function. Preliminary work indicates that coupling of transport and ecosystem processes alters the behaviour of earth system components (hydrology, terrestrial ecosystems, and the atmosphere) from that of an uncoupled mode. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015A%26A...578A.137S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015A%26A...578A.137S">Seismic sensitivity to sub-surface solar activity from 18 yr of GOLF/SoHO observations</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Salabert, D.; García, R. A.; Turck-Chièze, S. 2015-06-01 Solar activity has significantly changed over the last two Schwabe cycles. After a long and deep minimum at the end of Cycle 23, the weaker activity of Cycle 24 contrasts with the previous cycles. In this work, the response of the solar acoustic oscillations to solar activity is used in order to provide insights into the structural and magnetic changes in the sub-surface layers of the Sun during this on-going unusual period of low activity. We analyze 18 yr of continuous observations of the solar acoustic oscillations collected by the Sun-as-a-star GOLF instrument on board the SoHO spacecraft. From the fitted mode frequencies, the temporal variability of the frequency shifts of the radial, dipolar, and quadrupolar modes are studied for different frequency ranges that are sensitive to different layers in the solar sub-surface interior. The low-frequency modes show nearly unchanged frequency shifts between Cycles 23 and 24, with a time evolving signature of the quasi-biennial oscillation, which is particularly visible for the quadrupole component revealing the presence of a complex magnetic structure. The modes at higher frequencies show frequency shifts that are 30% smaller during Cycle 24, which is in agreement with the decrease observed in the surface activity between Cycles 23 and 24. The analysis of 18 yr of GOLF oscillations indicates that the structural and magnetic changes responsible for the frequency shifts remained comparable between Cycle 23 and Cycle 24 in the deeper sub-surface layers below 1400 km as revealed by the low-frequency modes. The frequency shifts of the higher-frequency modes, sensitive to shallower regions, show that Cycle 24 is magnetically weaker in the upper layers of Sun. Appendices are available in electronic form at http://www.aanda.orgThe following 68 GOLF frequency tables are available and Table A.1 is also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013CSR....52...97C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013CSR....52...97C">Concentration and characterization of dissolved organic matter in the surface microlayer and subsurface water of the Bohai Sea, China</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chen, Yan; Yang, Gui-Peng; Wu, Guan-Wei; Gao, Xian-Chi; Xia, Qing-Yan 2013-01-01 A total of 19 sea-surface microlayer and corresponding subsurface samples collected from the Bohai Sea, China in April 2010 were analyzed for chlorophyll a, dissolved organic carbon (DOC) and its major compound classes including total dissolved carbohydrates (TDCHO, including monosaccharides, MCHO, and polysaccharides, PCHO) and total hydrolysable amino acids (THAA, including dissolved free, DFAA, and combined fraction, DCAA). The concentrations of DOC in the subsurface water ranged from 130.2 to 407.7 μM C, with an average of 225.9±75.4 μM C, while those in the surface microlayer varied between 140.1 and 330.9 μM C, with an average of 217.8±56.8 μM C. The concentrations of chlorophyll a, DOC, TDCHO and THAA in the microlayer were, respectively correlated with their subsurface water concentrations, implying that there was a strong exchange effect between the microlayer and subsurface water. The concentrations of DOC and TDCHO were negatively correlated with salinity, respectively, indicating that water mixing might play an important role in controlling the distribution of DOC and TDCHO in the water column. Major constituents of DCAA and DFAA present in the study area were glycine, alanine, glutamic acid, serine and histidine. Principal component analysis (PCA) was applied to examine the complex compositional differences that existed among the sampling sites. Our results showed that DFAA had higher mole percentages of glycine, valine and serine in the microlayer than in the subsurface water, while DCAA tended to have higher mole percentages of glutamic acid, aspartic acid, threonine, arginine, alanine, tyrosine, phenylalanine and leucine in the microlayer. The yields of TDCHO and THAA exhibited similar trends between the microlayer and subsurface water. Carbohydrate species displayed significant enrichment in the microlayer, whereas the DFAA and DCAA exhibited non-uniform enrichment in the microlayer. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1253864-groundwatersurface-water-mixing-shifts-ecological-assembly-processes-stimulates-organic-carbon-turnover','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1253864-groundwatersurface-water-mixing-shifts-ecological-assembly-processes-stimulates-organic-carbon-turnover">Groundwater–surface water mixing shifts ecological assembly processes and stimulates organic carbon turnover</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Stegen, James C.; Fredrickson, James K.; Wilkins, Michael J.; ... 2016-04-07 Environmental transition zones are associated with geochemical gradients that overcome energy limitations to microbial metabolism, resulting in biogeochemical hot spots and moments. Riverine systems where groundwater mixes with surface water (the hyporheic zone) are spatially complex and temporally dynamic, making development of predictive models challenging. Spatial and temporal variations in hyporheic zone microbial communities are a key, but understudied, component of riverine biogeochemical function. To investigate the coupling among groundwater-surface water mixing, microbial communities, and biogeochemistry we applied ecological theory, aqueous biogeochemistry, DNA sequencing, and ultra-high resolution organic carbon profiling to field samples collected across times and locations representing amore » broad range of mixing conditions. Mixing of groundwater and surface water resulted in a shift from transport-driven stochastic dynamics to a deterministic microbial structure associated with elevated biogeochemical rates. While the dynamics of the hyporheic make predictive modeling a challenge, we provide new knowledge that can improve the tractability of such models.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=64942&keyword=concept+AND+design&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=64942&keyword=concept+AND+design&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">INLAND DISSOLVED SALT CHEMISTRY: STATISTICAL EVALUATION OF BIVARIATE AND TERNARY DIAGRAM MODELS FOR SURFACE AND SUBSURFACE WATERS</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> We compared the use of ternary and bivariate diagrams to distinguish the effects of atmospheric precipitation, rock weathering, and evaporation on inland surface and subsurface water chemistry. The three processes could not be statistically differentiated using bivariate models e... </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active">15</li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active">16</li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25251268','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25251268">Subsurface chlorophyll maximum layers: enduring enigma or mystery solved?</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Cullen, John J 2015-01-01 The phenomenon of subsurface chlorophyll maximum layers (SCMLs) is not a unique ecological response to environmental conditions; rather, a broad range of interacting processes can contribute to the formation of persistent layers of elevated chlorophyll a concentration (Chl) that are nearly ubiquitous in stratified surface waters. Mechanisms that contribute to the formation and maintenance of the SCMLs include a local maximum in phytoplankton growth rate near the nutricline, photoacclimation of pigment content that leads to elevated Chl relative to phytoplankton biomass at depth, and a range of physiologically influenced swimming behaviors in motile phytoplankton and buoyancy control in diatoms and cyanobacteria that can lead to aggregations of phytoplankton in layers, subject to grazing and physical control. A postulated typical stable water structure characterizes consistent patterns in vertical profiles of Chl, phytoplankton biomass, nutrients, and light across a trophic gradient structured by the vertical flux of nutrients and characterized by the average daily irradiance at the nutricline. Hypothetical predictions can be tested using a nascent biogeochemical global ocean observing system. Partial results to date are generally consistent with predictions based on current knowledge, which has strong roots in research from the twentieth century. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JCHyd..89..174F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JCHyd..89..174F">A partially coupled, fraction-by-fraction modelling approach to the subsurface migration of gasoline spills</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Fagerlund, F.; Niemi, A. 2007-01-01 The subsurface spreading behaviour of gasoline, as well as several other common soil- and groundwater pollutants (e.g. diesel, creosote), is complicated by the fact that it is a mixture of hundreds of different constituents, behaving differently with respect to e.g. dissolution, volatilisation, adsorption and biodegradation. Especially for scenarios where the non-aqueous phase liquid (NAPL) phase is highly mobile, such as for sudden spills in connection with accidents, it is necessary to simultaneously analyse the migration of the NAPL and its individual components in order to assess risks and environmental impacts. Although a few fully coupled, multi-phase, multi-constituent models exist, such models are highly complex and may be time consuming to use. A new, somewhat simplified methodology for modelling the subsurface migration of gasoline while taking its multi-constituent nature into account is therefore introduced here. Constituents with similar properties are grouped together into eight fractions. The migration of each fraction in the aqueous and gaseous phases as well as adsorption is modelled separately using a single-constituent multi-phase flow model, while the movement of the free-phase gasoline is essentially the same for all fractions. The modelling is done stepwise to allow updating of the free-phase gasoline composition at certain time intervals. The output is the concentration of the eight different fractions in the aqueous, gaseous, free gasoline and solid phases with time. The approach is evaluated by comparing it to a fully coupled multi-phase, multi-constituent numerical simulator in the modelling of a typical accident-type spill scenario, based on a tanker accident in northern Sweden. Here the PCFF method produces results similar to those of the more sophisticated, fully coupled model. The benefit of the method is that it is easy to use and can be applied to any single-constituent multi-phase numerical simulator, which in turn may have </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSHI54B1873Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSHI54B1873Y">Where the oil from surface and subsurface plumes deposited during/after Deepwater Horizon oil spill?</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yan, B. 2016-02-01 The Deepwater Horizon (DwH) oil spill released an estimated 4.9 million barrels (about 200 million gallons) of crude oil into the Gulf of Mexico between April 20, 2010 and July 15, 2010. Though Valentine et al. has linked the elevated oil components in some sediments with the subsurface plume, the sites with fallout from the ocean surface plume has not been identified. This piece of information is critical not only for a comprehensive scientific understanding of the ecosystem response and fate of spill-related pollutants, but also for litigation purposes and future spill response and restoration planning. In this study we focus on testing the hypothesis that marine snow from the surface plume were deposited on the sea floor over a broad area. To do so, we use publicly available data generated as part of the ongoing Natural Resource Damage Assessment (NRDA) process to assess the spatial distribution of petroleum hydrocarbons in the water column and deep-ocean sediments of the Gulf of Mexico. Sensitive hydrocarbon markers are used to differentiate hydrocarbons from surface plume, deep subsurface plume, and in-situ burning. Preliminary results suggest the overlapping but different falling sites of these plumes and the sedimentation process was controlled by various biological, chemical, and physical factors. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29867150','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29867150">Role of subsurface ocean in decadal climate predictability over the South Atlantic.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Morioka, Yushi; Doi, Takeshi; Storto, Andrea; Masina, Simona; Behera, Swadhin K 2018-06-04 Decadal climate predictability in the South Atlantic is explored by performing reforecast experiments using a coupled general circulation model with two initialization schemes; one is assimilated with observed sea surface temperature (SST) only, and the other is additionally assimilated with observed subsurface ocean temperature and salinity. The South Atlantic is known to undergo decadal variability exhibiting a meridional dipole of SST anomalies through variations in the subtropical high and ocean heat transport. Decadal reforecast experiments in which only the model SST is initialized with the observation do not predict well the observed decadal SST variability in the South Atlantic, while the other experiments in which the model SST and subsurface ocean are initialized with the observation skillfully predict the observed decadal SST variability, particularly in the Southeast Atlantic. In-depth analysis of upper-ocean heat content reveals that a significant improvement of zonal heat transport in the Southeast Atlantic leads to skillful prediction of decadal SST variability there. These results demonstrate potential roles of subsurface ocean assimilation in the skillful prediction of decadal climate variability over the South Atlantic. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29336556','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29336556">Linking Spectral Induced Polarization (SIP) and Subsurface Microbial Processes: Results from Sand Column Incubation Experiments.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Mellage, Adrian; Smeaton, Christina M; Furman, Alex; Atekwana, Estella A; Rezanezhad, Fereidoun; Van Cappellen, Philippe 2018-02-20 Geophysical techniques, such as spectral induced polarization (SIP), offer potentially powerful approaches for in situ monitoring of subsurface biogeochemistry. The successful implementation of these techniques as monitoring tools for reactive transport phenomena, however, requires the deconvolution of multiple contributions to measured signals. Here, we present SIP spectra and complementary biogeochemical data obtained in saturated columns packed with alternating layers of ferrihydrite-coated and pure quartz sand, and inoculated with Shewanella oneidensis supplemented with lactate and nitrate. A biomass-explicit diffusion-reaction model is fitted to the experimental biogeochemical data. Overall, the results highlight that (1) the temporal response of the measured imaginary conductivity peaks parallels the microbial growth and decay dynamics in the columns, and (2) SIP is sensitive to changes in microbial abundance and cell surface charging properties, even at relatively low cell densities (<10 8 cells mL -1 ). Relaxation times (τ) derived using the Cole-Cole model vary with the dominant electron accepting process, nitrate or ferric iron reduction. The observed range of τ values, 0.012-0.107 s, yields effective polarization diameters in the range 1-3 μm, that is, 2 orders of magnitude smaller than the smallest quartz grains in the columns, suggesting that polarization of the bacterial cells controls the observed chargeability and relaxation dynamics in the experiments. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1919457P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1919457P">Application of a fully integrated surface-subsurface physically based flow model for evaluating groundwater recharge from a flash flood event</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Pino, Cristian; Herrera, Paulo; Therrien, René 2017-04-01 In many arid regions around the world groundwater recharge occurs during flash floods. This transient spatially and temporally concentrated flood-recharge process takes place through the variably saturated zone between surface and usually the deep groundwater table. These flood events are characterized by rapid and extreme changes in surface flow depth and velocity and soil moisture conditions. Infiltration rates change over time controlled by the hydraulic gradients and the unsaturated hydraulic conductivity at the surface-subsurface interface. Today is a challenge to assess the spatial and temporal distribution of groundwater recharge from flash flood events under real field conditions at different scales in arid areas. We apply an integrated surface-subsurface variably saturated physically-based flow model at the watershed scale to assess the recharge process during and after a flash flood event registered in an arid fluvial valley in Northern Chile. We are able to reproduce reasonably well observed groundwater levels and surface flow discharges during and after the flood with a calibrated model. We also investigate the magnitude and spatio-temporal distribution of recharge and the response of the system to variations of different surface and subsurface parameters, initial soil moisture content and groundwater table depths and surface flow conditions. We demonstrate how an integrated physically based model allows the exploration of different spatial and temporal system states, and that the analysis of the results of the simulations help us to improve our understanding of the recharge processes in similar type of systems that are common to many arid areas around the world. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMNS41B1682Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMNS41B1682Z">Numerical correction of the phase error due to electromagnetic coupling effects in 1D EIT borehole measurements</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zhao, Y.; Zimmermann, E.; Huisman, J. A.; Treichel, A.; Wolters, B.; van Waasen, S.; Kemna, A. 2012-12-01 Spectral Electrical Impedance Tomography (EIT) allows obtaining images of the complex electrical conductivity for a broad frequency range (mHz to kHz). It has recently received increased interest in the field of near-surface geophysics and hydrogeophysics because of the relationships between complex electrical properties and hydrogeological and biogeochemical properties and processes observed in the laboratory with Spectral Induced Polarization (SIP). However, these laboratory results have also indicated that a high phase accuracy is required for surface and borehole EIT measurements because many soils and sediments are only weakly polarizable and show phase angles between 1 and 20 mrad. In the case of borehole EIT measurements, long cables and electrode chains (>10 meters) are typically used, which leads to undesired inductive coupling between the electric loops for current injection and potential measurement and capacitive coupling between the electrically conductive cable shielding and the soil. Depending on the electrical properties of the subsurface and the measured transfer impedances, both coupling effects can cause large phase errors that have typically limited the frequency bandwidth of field EIT measurement to the mHz to Hz range. The aim of this study is i) to develop correction procedures for these coupling effects to extend the applicability of EIT to the kHz range and ii) to validate these corrections using controlled laboratory measurements and field measurements. In order to do so, the inductive coupling effect was modeled using electronic circuit models and the capacitive coupling effect was modeled by integrating discrete capacitances in the electrical forward model describing the EIT measurement process. The correction methods were successfully verified with measurements under controlled conditions in a water-filled rain barrel, where a high phase accuracy of 2 mrad in the frequency range up to 10 kHz was achieved. In a field demonstration using </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/20012','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/20012">Surface and subsurface sensor performance in acoustically detecting western drywood termites in naturally infested boards.</a> <a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a> V.R. Lewis; A.B. Power; M.I. Haverty 2004-01-01 Field-collected boards showing visual signs of damage by the western drywood termite, Incisitermes minor, were searched with a portable acoustic emission (AE) device. Depending on cross-sectional size, boards were either searched with a flat sensor that was hot-melt-glued to the wood surface or a subsurface sensor that wasthreaded 20 mm into the... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005SPIE.5715..110L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005SPIE.5715..110L">Surface morphology and subsurface damaged layer of various glasses machined by 193-nm ArF excimer laser</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Liao, Yunn-shiuan; Chen, Ying-Tung; Chao, Choung-Lii; Liu, Yih-Ming 2005-01-01 Owing to the high bonding energy, most of the glasses are removed by photo-thermal rather than photo-chemical effect when they are ablated by the 193 or 248nm excimer lasers. Typically, the machined surface is covered by re-deposited debris and the sub-surface, sometimes surface as well, is scattered with micro-cracks introduced by thermal stress generated during the process. This study aimed to investigate the nature and extent of the surface morphology and sub-surface damaged (SSD) layer induced by the laser ablation. The effects of laser parameters such as fluence, shot number and repetition rate on the morphology and SSD were discussed. An ArF excimer laser (193 nm) was used in the present study to machine glasses such as soda-lime, Zerodur and BK-7. It is found that the melt ejection and debris deposition tend to pile up higher and become denser in structure under a higher energy density, repetition rate and shot number. There are thermal stress induced lateral cracks when the debris covered top layer is etched away. Higher fluence and repetition rate tend to generate more lateral and median cracks which propagate into the substrate. The changes of mechanical properties of the SSD layer were also investigated. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMEP33A3617B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMEP33A3617B">Effects of Surface and Subsurface Bed Material Composition on Gravel Transport and Flow Competence Relations—Possibilities for Prediction</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bunte, K.; Abt, S. R.; Swingle, K. W.; Cenderelli, D. A.; Gaeuman, D. A. 2014-12-01 Bedload transport and flow competence relations are difficult to predict in coarse-bedded steep streams where widely differing sediment supply, bed stability, and complex flow hydraulics greatly affect amounts and sizes of transported gravel particles. This study explains how properties of bed material surface and subsurface size distributions are directly related to gravel transport and may be used for prediction of gravel transport and flow competence relations. Gravel transport, flow competence, and bed material size were measured in step-pool and plane-bed streams. Power functions were fitted to gravel transport QB=aQb and flow competence Dmax=cQd relations; Q is water discharge. Frequency distributions of surface FDsurf and subsurface FDsub bed material were likewise described by power functions FDsurf=hD j and FDsub=kDm fitted over six 0.5-phi size classes within 4 to 22.4 mm. Those gravel sizes are typically mobile even in moderate floods. Study results show that steeper subsurface bed material size distributions lead to steeper gravel transport and flow competence relations, whereas larger amounts of sediment contained in those 6 size bedmaterial classes (larger h and k) flatten the relations. Similarly, steeper surface size distributions decrease the coefficients of the gravel transport and flow competence relations, whereas larger amounts of sediment within the six bed material classes increase the intercepts of gravel transport and flow competence relations. Those relations are likely causative in streams where bedload stems almost entirely from the channel bed as opposed to direct (unworked) contributions from hillslopes and tributaries. The exponent of the subsurface bed material distribution m predicted the gravel transport exponent b with r2 near 0.7 and flow competence exponent d with r2 near 0.5. The intercept of bed surface distributions h increased the intercept a of gravel transport and c of the flow competence relations with r2 near 0.6. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.H52B..05B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.H52B..05B">Coupling of Groundwater Recharge and Biodegradation of Subsurface Crude-Oil Contamination (Invited)</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bekins, B. A.; Hostettler, F. D.; Delin, G. N.; Herkelrath, W. N.; Warren, E.; Campbell, P.; Rosenbauer, R. J.; Cozzarelli, I. 2010-12-01 Surface hydrologic properties controlling groundwater recharge can have a large effect on biodegradation rates in the subsurface. Two studies of crude oil contamination show that degradation rates are dramatically increased where recharge rates are enhanced. The first site, located near Bemidji, Minnesota, was contaminated in August, 1979 when oil from a pipeline rupture infiltrated into a surficial glacial outwash aquifer. Discrete oil phases form three separate pools at the water table, the largest of which is 25x75 m at a depth of 6-8 m. Gas and water concentrations and microbial community data show that methanogenic conditions prevail in this oil pool. There is extreme spatial dependence in the degradation rates such that most of the n-alkanes have been degraded in the upgradient end, but in the downgradient end n-alkane concentrations are nearly unaltered from the original spill. Recharge rates through the two ends of the oil body were estimated using a water table fluctuation method. In 2002, the more degraded end received 15.2 cm of recharge contrasted to 10.7 cm at the less degraded end. The enhanced recharge is caused by topographic focusing of runoff toward a local depression. Microbial data using the Most Probable Number method show that the methanogen concentrations are 10-100 times greater in the more degraded end of the oil body suggesting that a growth nutrient is supplied by recharge. A decrease in partial pressure of N2 compared to Ar in the soil gas indicates nitrogen fixation probably meets N requirements (Amos et al., 2005, WRR, doi:10.1029/2004WR003433). Organic phosphorus is the main form of P in infiltrating pore water and concentration decreases with depth. The second site is located 40 km southeast of the Bemidji site at an oil pipeline pumping station near Cass Lake, Minnesota. This site was contaminated by oil leaking from a pipe coupling for an unknown duration of time between 1971 and 2002. The oil body at this site lies under a fenced </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29710650','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29710650">Characterizing variable biogeochemical changes during the treatment of produced oilfield waste.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Hildenbrand, Zacariah L; Santos, Inês C; Liden, Tiffany; Carlton, Doug D; Varona-Torres, Emmanuel; Martin, Misty S; Reyes, Michelle L; Mulla, Safwan R; Schug, Kevin A 2018-09-01 At the forefront of the discussions about climate change and energy independence has been the process of hydraulic fracturing, which utilizes large amounts of water, proppants, and chemical additives to stimulate sequestered hydrocarbons from impermeable subsurface strata. This process also produces large amounts of heterogeneous flowback and formation waters, the subsurface disposal of which has most recently been linked to the induction of anthropogenic earthquakes. As such, the management of these waste streams has provided a newfound impetus to explore recycling alternatives to reduce the reliance on subsurface disposal and fresh water resources. However, the biogeochemical characteristics of produced oilfield waste render its recycling and reutilization for production well stimulation a substantial challenge. Here we present a comprehensive analysis of produced waste from the Eagle Ford shale region before, during, and after treatment through adjustable separation, flocculation, and disinfection technologies. The collection of bulk measurements revealed significant reductions in suspended and dissolved constituents that could otherwise preclude untreated produced water from being utilized for production well stimulation. Additionally, a significant step-wise reduction in pertinent scaling and well-fouling elements was observed, in conjunction with notable fluctuations in the microbiomes of highly variable produced waters. Collectively, these data provide insight into the efficacies of available water treatment modalities within the shale energy sector, which is currently challenged with improving the environmental stewardship of produced water management. Copyright © 2018 Elsevier B.V. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25612725','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25612725">Effect of gold subsurface layer on the surface activity and segregation in Pt/Au/Pt3M (where M = 3d transition metals) alloy catalyst from first-principles.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Kim, Chang-Eun; Lim, Dong-Hee; Jang, Jong Hyun; Kim, Hyoung Juhn; Yoon, Sung Pil; Han, Jonghee; Nam, Suk Woo; Hong, Seong-Ahn; Soon, Aloysius; Ham, Hyung Chul 2015-01-21 The effect of a subsurface hetero layer (thin gold) on the activity and stability of Pt skin surface in Pt3M system (M = 3d transition metals) is investigated using the spin-polarized density functional theory calculation. First, we find that the heterometallic interaction between the Pt skin surface and the gold subsurface in Pt/Au/Pt3M system can significantly modify the electronic structure of the Pt skin surface. In particular, the local density of states projected onto the d states of Pt skin surface near the Fermi level is drastically decreased compared to the Pt/Pt/Pt3M case, leading to the reduction of the oxygen binding strength of the Pt skin surface. This modification is related to the increase of surface charge polarization of outmost Pt skin atoms by the electron transfer from the gold subsurface atoms. Furthermore, a subsurface gold layer is found to cast the energetic barrier to the segregation loss of metal atoms from the bulk (inside) region, which can enhance the durability of Pt3M based catalytic system in oxygen reduction condition at fuel cell devices. This study highlights that a gold subsurface hetero layer can provide an additional mean to tune the surface activity toward oxygen species and in turn the oxygen reduction reaction, where the utilization of geometric strain already reaches its practical limit. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.H44B..01S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.H44B..01S">Hydrologic and Biogeochemical Connections between Uplands and Streams in Contrasting Landscapes</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shanley, J. B.; Webb, R. M.; Hjerdt, K. N.; Sebestyen, S. D.; Peters, N. E.; Burns, D. A.; Aulenbach, B. T.; Campbell, D. H.; Clow, D. W.; Mast, M. A.; Walker, J. F.; Hunt, R. J.; Troester, J. W.; Larsen, M. C. 2004-12-01 We used combinations of hydrometric, chemical, and isotopic evidence to evaluate linkages between upland and riparian zones at the 5 small watersheds of the U.S. Geological Survey Water Energy and Biogeochemical Budget (WEBB) program. These sites span a broad range of climate and topography. At Sleepers River, Vermont, snowmelt induced the water table on hillslopes to rise into the highly transmissive upper soil. The close timing of the groundwater and stream hydrographs suggests a large contribution of hillslope water to the stream. However, the chemistry of these upland groundwaters indicates that only limited areas of convergent groundwater flow directly contribute to streamflow. At Panola Mountain, Georgia, a thin saturated zone develops on the hillslope during large rainstorms. This hillslope groundwater is chemically distinct from riparian groundwater, and transits the riparian zone near land surface with little mixing. Based on chemical mixing analysis, the hillslope contributes up to 30% of the streamwater during moderate to large-sized rainstorms. The Trout Lake site in Wisconsin is a low-lying landscape in highly conductive sandy glacial outwash.Hillslope water chemistry is considerably more dilute (i.e. less evolved) than the regional groundwater that supplies baseflow. The lack of chemical response in streamwater during storms suggests that hillslope water makes a minimal contribution relative to regional groundwater flow. In the alpine/subalpine watershed of Loch Vale, Colorado, much of the subsurface flow occurs on steep slopes of talus. Water in the talus flow has a wide range of residence times. The talus deposits are biogeochemically active and play an important role in maintaining summer baseflow, regulating seasonal changes in streamwater chemistry, and exporting nitrogen from atmospheric deposition. The tropical Icacos watershed in the Luquillo mountains of Puerto Rico receives 4 meters of rainfall annually and has high physical and chemical </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.H53G..05G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.H53G..05G">Modeling Subsurface Behavior at the System Level: Considerations and a Path Forward</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Geesey, G. 2005-12-01 The subsurface is an obscure but essential resource to life on Earth. It is an important region for carbon production and sequestration, a source and reservoir for energy, minerals and metals and potable water. There is a growing need to better understand subsurface possesses that control the exploitation and security of these resources. Our best models often fail to predict these processes at the field scale because of limited understanding of 1) the processes and the controlling parameters, 2) how processes are coupled at the field scale 3) geological heterogeneities that control hydrological, geochemical and microbiological processes at the field scale and 4) lack of data sets to calibrate and validate numerical models. There is a need for experimental data obtained at scales larger than those obtained at the laboratory bench that take into account the influence of hydrodynamics, geochemical reactions including complexation and chelation/adsorption/precipitation/ion exchange/oxidation-reduction/colloid formation and dissolution, and reactions of microbial origin. Furthermore, the coupling of each of these processes and reactions needs to be evaluated experimentally at a scale that produces data that can be used to calibrate numerical models so that they accurately describe field scale system behavior. Establishing the relevant experimental scale for collection of data from coupled processes remains a challenge and will likely be process-dependent and involve iterations of experimentation and data collection at different intermediate scales until the models calibrated with the appropriate date sets achieve an acceptable level of performance. Assuming that the geophysicists will soon develop technologies to define geological heterogeneities over a wide range of scales in the subsurface, geochemists need to continue to develop techniques to remotely measure abiotic reactions, while geomicrobiologists need to continue their development of complementary technologies </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22293598-method-implementing-subsurface-solid-derived-concentration-guideline-levels-dcgl','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22293598-method-implementing-subsurface-solid-derived-concentration-guideline-levels-dcgl">Method for Implementing Subsurface Solid Derived Concentration Guideline Levels (DCGL) - 12331</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Lively, J.W. 2012-07-01 The U.S. Nuclear Regulatory Commission (NRC) and other federal agencies currently approve the Multi-Agency Radiation Site Survey and Investigation Manual (MARSSIM) as guidance for licensees who are conducting final radiological status surveys in support of decommissioning. MARSSIM provides a method to demonstrate compliance with the applicable regulation by comparing residual radioactivity in surface soils with derived concentration guideline levels (DCGLs), but specifically discounts its applicability to subsurface soils. Many sites and facilities undergoing decommissioning contain subsurface soils that are potentially impacted by radiological constituents. In the absence of specific guidance designed to address the derivation of subsurface soil DCGLs andmore » compliance demonstration, decommissioning facilities have attempted to apply DCGLs and final status survey techniques designed specifically for surface soils to subsurface soils. The decision to apply surface soil limits and surface soil compliance metrics to subsurface soils typically results in significant over-excavation with associated cost escalation. MACTEC, Inc. has developed the overarching concepts and principles found in recent NRC decommissioning guidance in NUREG 1757 to establish a functional method to derive dose-based subsurface soil DCGLs. The subsurface soil method developed by MACTEC also establishes a rigorous set of criterion-based data evaluation metrics (with analogs to the MARSSIM methodology) that can be used to demonstrate compliance with the developed subsurface soil DCGLs. The method establishes a continuum of volume factors that relate the size and depth of a volume of subsurface soil having elevated concentrations of residual radioactivity with its ability to produce dose. The method integrates the subsurface soil sampling regime with the derivation of the subsurface soil DCGL such that a self-regulating optimization is naturally sought by both the responsible party and </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMNS33B..06F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMNS33B..06F">Assessment of DInSAR Potential in Simulating Geological Subsurface Structure</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Fouladi Moghaddam, N.; Rudiger, C.; Samsonov, S. V.; Hall, M.; Walker, J. P.; Camporese, M. 2013-12-01 High resolution geophysical surveys, including seismic, gravity, magnetic, etc., provide valuable information about subsurface structuring but they are very costly and time consuming with non-unique and sometimes conflicting interpretations. Several recent studies have examined the application of DInSAR to estimate surface deformation, monitor possible fault reactivation and constrain reservoir dynamic behaviour in geothermal and groundwater fields. The main focus of these studies was to generate an elevation map, which represents the reservoir extraction induced deformation. This research study, however, will focus on developing methods to simulate subsurface structuring and identify hidden faults/hydraulic barriers using DInSAR surface observations, as an innovative and cost-effective reconnaissance exploration tool for planning of seismic acquisition surveys in geothermal and Carbon Capture and Sequestration regions. By direct integration of various DInSAR datasets with overlapping temporal and spatial coverage we produce multi-temporal ground deformation maps with high resolution and precision to evaluate the potential of a new multidimensional MSBAS technique (Samsonov & d'Oreye, 2012). The technique is based on the Small Baseline Subset Algorithm (SBAS) that is modified to account for variation in sensor parameters. It allows integration of data from sensors with different wave-band, azimuth and incidence angles, different spatial and temporal sampling and resolutions. These deformation maps then will be used as an input for inverse modelling to simulate strain history and shallow depth structure. To achieve the main objective of our research, i.e. developing a method for coupled InSAR and geophysical observations and better understanding of subsurface structuring, comparing DInSAR inverse modelling results with previously provided static structural model will result in iteratively modified DInSAR structural model for adequate match with in situ observations </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/7793','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/7793">Subsurface drainage processes and management impacts</a> <a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a> Elizabeth T. Keppeler; David Brown 1998-01-01 Storm-induced streamflow in forested upland watersheds is linked to rainfall by transient, variably saturated flow through several different flow paths. In the absence of exposed bedrock, shallow flow-restrictive layers, or compacted soil surfaces, virtually all of the infiltrated rainfall reaches the stream as subsurface flow. Subsurface runoff can occur within... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.H33G1099S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.H33G1099S">Biogeochemical Modeling of Ureolytically-Driven Calcium Carbonate Precipitation for Contaminant Immobilization</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Smith, R. W.; Fujita, Y.; Taylor, J. L. 2008-12-01 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 biogeochemical 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 biogeochemical processes underlying the remediation strategy. We are evaluating the use of microbial urea hydrolysis coupled 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 coupling of biogeochemical processes. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.P33B1574K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.P33B1574K">Tidal Response of Europa's Subsurface Ocean</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Karatekin, O.; Comblen, R.; Deleersnijder, E.; Dehant, V. M. 2010-12-01 Time-variable tides in the subsurface oceans of icy satellites cause large periodic surface displacements and tidal dissipation can become a major energy source that can affect long-term orbital and internal evolution. In the present study, we investigate the response of the subsurface ocean of Europa to a time-varibale tidal potential. Two-dimensional nonlinear shallow water equations are solved on a sphere by means of a finite element code. The resulting ocean tidal flow velocities,dissipation and surface displacements will be presented. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active">16</li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active">17</li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P12A..05E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P12A..05E">Using GNSS-R techniques to investigate the near sub-surface of Mars with the Deep Space Network</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Elliott, H. M.; Bell, D. J.; Jin, C.; Decrossas, E.; Asmar, S.; Lazio, J.; Preston, R. A.; Ruf, C. S.; Renno, N. O. 2017-12-01 Global Navigation Satellite Systems Reflectometry (GNSS-R) has shown that passive measurements using separate active sources can infer the soil moisture, snow pack depth and other quantities of scientific interest. Here, we expand upon this method and propose that a passive measurement of the sub-surface dielectric profile of Mars can be made by using multipath interference between reflections off the surface and subsurface dielectric discontinuities. This measurement has the ability to reveal changes in the soil water content, the depth of a layer of sand, thickness of a layer of ice, and even identify centimeter-scale layering which may indicate the presence of a sedimentary bed. We have created a numerical ray tracing model to understand the potential of using multipath interference techniques to investigate the sub-surface dielectric properties and structure of Mars. We have further verified this model using layered beds of sand and concrete in laboratory experiments and then used the model to extrapolate how this technique may be applied to future Mars missions. We will present new results demonstrating how to characterize a multipath interference patterns as a function of frequency and/or incidence angle to measure the thickness of a dielectric layer of sand or ice. Our results demonstrate that dielectric discontinuities in the subsurface can be measured using this passive sensing technique and it could be used to effectively measure the thickness of a dielectric layer in the proximity of a landed spacecraft. In the case of an orbiter, we believe this technique would be effective at measuring the seasonal thickness of CO2 ice in the Polar Regions. This is exciting because our method can produce similar results to traditional ground penetrating radars without the need to have an active radar transmitter in-situ. Therefore, it is possible that future telecommunications systems can serve as both a radio and a scientific instrument when used in conjunction with </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.6609C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.6609C">Detection of subsurface-intensified eddies from observations of the sea-surface: a case study for Mediterranean Water Eddies in a long-term high-resolution simulation</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ciani, Daniele; Carton, Xavier; Barbosa Aguiar, Ana Claudia; Peliz, Alvaro; Bashmachnikov, Igor; Ienna, Federico; Chapron, Bertrand 2017-04-01 Subsurface-intensified eddies are ubiquitous in the world ocean. They can be generated by exchanges of water masses between semi-enclosed evaporation basins and the open ocean or by deep convection. Past and recent studies have shown that these eddies are carriers of large amounts of heat and salt, that they are coherent over inter-annual timescales and that they can migrate for several thousands of miles from their origination areas towards the open ocean. Hence, subsurface-intensified eddies can influence the three-dimensional distribution of oceanic tracers at global scale. The synoptic knowledge of the eddies positions and mean pathways is then crucial for evaluating temperature and salinity budgets in the world ocean. At present day, satellite sensors constitute the ideal tool for the synoptic and global scale observations of the ocean. Since they only provide informations on the oceanic surface, we characterized the signatures that subsurface eddies generate at the sea-surface, to determine the extent to which they can be isolated from the surrounding surface turbulence and be considered as a trace of an underlying eddy. We studied the surface signature of subsurface-intensified anticyclones (Mediterranean Water Eddies - Meddies) in a realistic, long-term (20 years) and high resolution simulation (dx = 3 km) based on the ROMS model. The novelty and advantage of this approach is given by the simultaneous availability of the full 3D eddies characteristics, the ones of the background ocean and of the sea-surface (in terms of sea-surface height, temperature and salinity). This also allowed us to speculate on a synergy between different satellite observations for the automatic detection of subsurface eddies from space. The along trajectory properties and surface signatures of more than 90 long-lived Meddies were analyzed. We showed that the Meddies constantly generate positive anomalies in sea-surface height and that these anomalies are principally related to the </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=329136','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=329136">Line-scan Raman imaging and spectroscopy platform for surface and subsurface evaluation of food safety and quality</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> Both surface and subsurface food inspection is important since interesting safety and quality attributes can be at different sample locations. This paper presents a multipurpose line-scan Raman platform for food safety and quality research, which can be configured for Raman chemical imaging (RCI) mo... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23584766','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23584766">Bacterial communities associated with subsurface geochemical processes in continental serpentinite springs.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Brazelton, William J; Morrill, Penny L; Szponar, Natalie; Schrenk, Matthew O 2013-07-01 Reactions associated with the geochemical process of serpentinization can generate copious quantities of hydrogen and low-molecular-weight organic carbon compounds, which may provide energy and nutrients to sustain subsurface microbial communities independently of the photosynthetically supported surface biosphere. Previous microbial ecology studies have tested this hypothesis in deep sea hydrothermal vents, such as the Lost City hydrothermal field. This study applied similar methods, including molecular fingerprinting and tag sequencing of the 16S rRNA gene, to ultrabasic continental springs emanating from serpentinizing ultramafic rocks. These molecular surveys were linked with geochemical measurements of the fluids in an interdisciplinary approach designed to distinguish potential subsurface organisms from those derived from surface habitats. The betaproteobacterial genus Hydrogenophaga was identified as a likely inhabitant of transition zones where hydrogen-enriched subsurface fluids mix with oxygenated surface water. The Firmicutes genus Erysipelothrix was most strongly correlated with geochemical factors indicative of subsurface fluids and was identified as the most likely inhabitant of a serpentinization-powered subsurface biosphere. Both of these taxa have been identified in multiple hydrogen-enriched subsurface habitats worldwide, and the results of this study contribute to an emerging biogeographic pattern in which Betaproteobacteria occur in near-surface mixing zones and Firmicutes are present in deeper, anoxic subsurface habitats. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3697581','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3697581">Bacterial Communities Associated with Subsurface Geochemical Processes in Continental Serpentinite Springs</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Morrill, Penny L.; Szponar, Natalie; Schrenk, Matthew O. 2013-01-01 Reactions associated with the geochemical process of serpentinization can generate copious quantities of hydrogen and low-molecular-weight organic carbon compounds, which may provide energy and nutrients to sustain subsurface microbial communities independently of the photosynthetically supported surface biosphere. Previous microbial ecology studies have tested this hypothesis in deep sea hydrothermal vents, such as the Lost City hydrothermal field. This study applied similar methods, including molecular fingerprinting and tag sequencing of the 16S rRNA gene, to ultrabasic continental springs emanating from serpentinizing ultramafic rocks. These molecular surveys were linked with geochemical measurements of the fluids in an interdisciplinary approach designed to distinguish potential subsurface organisms from those derived from surface habitats. The betaproteobacterial genus Hydrogenophaga was identified as a likely inhabitant of transition zones where hydrogen-enriched subsurface fluids mix with oxygenated surface water. The Firmicutes genus Erysipelothrix was most strongly correlated with geochemical factors indicative of subsurface fluids and was identified as the most likely inhabitant of a serpentinization-powered subsurface biosphere. Both of these taxa have been identified in multiple hydrogen-enriched subsurface habitats worldwide, and the results of this study contribute to an emerging biogeographic pattern in which Betaproteobacteria occur in near-surface mixing zones and Firmicutes are present in deeper, anoxic subsurface habitats. PMID:23584766 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1429749','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1429749"></a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Hammond, Glenn Edward; Bao, J; Huang, M Hyporheic exchange is a critical mechanism shaping hydrological and biogeochemical processes along a river corridor. Recent studies on quantifying the hyporheic exchange were mostly limited to local scales due to field inaccessibility, computational demand, and complexity of geomorphology and subsurface geology. Surface flow conditions and subsurface physical properties are well known factors on modulating the hyporheic exchange, but quantitative understanding of their impacts on the strength and direction of hyporheic exchanges at reach scales is absent. In this study, a high resolution computational fluid dynamics (CFD) model that couples surface and subsurface flow and transport is employed to simulate hyporheicmore » exchanges in a 7-km long reach along the main-stem of the Columbia River. Assuming that the hyporheic exchange does not affect surface water flow conditions due to its negligible magnitude compared to the volume and velocity of river water, we developed a one-way coupled surface and subsurface water flow model using the commercial CFD software STAR-CCM+. The model integrates the Reynolds-averaged Navier-Stokes (RANS) equation solver with a realizable κ-ε two-layer turbulence model, a two-layer all y + wall treatment, and the volume of fluid (VOF) method, and is used to simulate hyporheic exchanges by tracking the free water-air interface as well as flow in the river and the subsurface porous media. The model is validated against measurements from acoustic Doppler current profiler (ADCP) in the stream water and hyporheic fluxes derived from a set of temperature profilers installed across the riverbed. The validated model is then employed to systematically investigate how hyporheic exchanges are influenced by surface water fluid dynamics strongly regulated by upstream dam operations, as well as subsurface structures (e.g. thickness of riverbed and subsurface formation layers) and hydrogeological properties (e.g. permeability). The results suggest </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JPhCS.842a2029T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JPhCS.842a2029T">Sub-surface defects detection of by using active thermography and advanced image edge detection</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tse, Peter W.; Wang, Gaochao 2017-05-01 Active or pulsed thermography is a popular non-destructive testing (NDT) tool for inspecting the integrity and anomaly of industrial equipment. One of the recent research trends in using active thermography is to automate the process in detecting hidden defects. As of today, human effort has still been using to adjust the temperature intensity of the thermo camera in order to visually observe the difference in cooling rates caused by a normal target as compared to that by a sub-surface crack exists inside the target. To avoid the tedious human-visual inspection and minimize human induced error, this paper reports the design of an automatic method that is capable of detecting subsurface defects. The method used the technique of active thermography, edge detection in machine vision and smart algorithm. An infrared thermo-camera was used to capture a series of temporal pictures after slightly heating up the inspected target by flash lamps. Then the Canny edge detector was employed to automatically extract the defect related images from the captured pictures. The captured temporal pictures were preprocessed by a packet of Canny edge detector and then a smart algorithm was used to reconstruct the whole sequences of image signals. During the processes, noise and irrelevant backgrounds exist in the pictures were removed. Consequently, the contrast of the edges of defective areas had been highlighted. The designed automatic method was verified by real pipe specimens that contains sub-surface cracks. After applying such smart method, the edges of cracks can be revealed visually without the need of using manual adjustment on the setting of thermo-camera. With the help of this automatic method, the tedious process in manually adjusting the colour contract and the pixel intensity in order to reveal defects can be avoided. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JHyd..557..613H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JHyd..557..613H">High spatial-temporal resolution and integrated surface and subsurface precipitation-runoff modelling for a small stormwater catchment</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hailegeorgis, Teklu T.; Alfredsen, Knut 2018-02-01 Reliable runoff estimation is important for design of water infrastructure and flood risk management in urban catchments. We developed a spatially distributed Precipitation-Runoff (P-R) model that explicitly represents the land cover information, performs integrated modelling of surface and subsurface components of the urban precipitation water cycle and flow routing. We conducted parameter calibration and validation for a small (21.255 ha) stormwater catchment in Trondheim City during Summer-Autumn events and season, and snow-influenced Winter-Spring seasons at high spatial and temporal resolutions of respectively 5 m × 5 m grid size and 2 min. The calibration resulted in good performance measures (Nash-Sutcliffe efficiency, NSE = 0.65-0.94) and acceptable validation NSE for the seasonal and snow-influenced periods. The infiltration excess surface runoff dominates the peak flows while the contribution of subsurface flow to the sewer pipes also augments the peak flows. Based on the total volumes of simulated flow in sewer pipes (Qsim) and precipitation (P) during the calibration periods, the Qsim/P ranges from 21.44% for an event to 56.50% for the Winter-Spring season, which are in close agreement with the observed volumes (Qobs/P). The lowest percentage of precipitation volume that is transformed to the total simulated runoff in the catchment (QT) is 79.77%. Computation of evapotranspiration (ET) indicated that the ET/P is less than 3% for the events and snow-influenced seasons while it is about 18% for the Summer-Autumn season. The subsurface flow contribution to the sewer pipes are markedly higher than the total surface runoff volume for some events and the Summer-Autumn season. The peakiest flow rates correspond to the Winter-Spring season. Therefore, urban runoff simulation for design and management purposes should include two-way interactions between the subsurface runoff and flow in sewer pipes, and snow-influenced seasons. The developed urban P-R model is </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811204S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811204S">Impact of atmospheric forcing on heat content variability in the sub-surface layer in the Japan/East Sea, 1948-2009</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Stepanov, Dmitry; Gusev, Anatoly; Diansky, Nikolay 2016-04-01 Based on numerical simulations the study investigates impact of atmospheric forcing on heat content variability of the sub-surface layer in Japan/East Sea (JES), 1948-2009. We developed a model configuration based on a INMOM model and atmospheric forcing extracted from the CORE phase II experiment dataset 1948-2009, which enables to assess impact of only atmospheric forcing on heat content variability of the sub-surface layer of the JES. An analysis of kinetic energy (KE) and total heat content (THC) in the JES obtained from our numerical simulations showed that the simulated circulation of the JES is being quasi-steady state. It was found that the year-mean KE variations obtained from our numerical simulations are similar those extracted from the SODA reanalysis. Comparison of the simulated THC and that extracted from the SODA reanalysis showed significant consistence between them. An analysis of numerical simulations showed that the simulated circulation structure is very similar that obtained from the PALACE floats in the intermediate and abyssal layers in the JES. Using empirical orthogonal function analysis we studied spatial-temporal variability of the heat content of the sub-surface layer in the JES. Based on comparison of the simulated heat content variations with those obtained from natural observations an assessment of the atmospheric forcing impact on the heat content variability was obtained. Using singular value decomposition analysis we considered relationships between the heat content variability and wind stress curl as well as sensible heat flux in winter. It was established the major role of sensible heat flux in decadal variability of the heat content of the sub-surface layer in the JES. The research was supported by the Russian Foundation for Basic Research (grant N 14-05-00255) and the Council on the Russian Federation President Grants (grant N MK-3241.2015.5) </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8731B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8731B">Wireless sensors for measuring sub-surface processes in firn</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bagshaw, Elizabeth; Karlsson, Nanna; Lishman, Ben; Bun Lok, Lai; Burrow, Stephen; Wadham, Jemma; Clare, Lindsay; Nicholls, Keith; Corr, Hugh; Brennan, Paul; Eisen, Olaf; Dahl-Jensson, Dorthe 2017-04-01 Subsurface processes exert controls on meltwater storage and densification within firn, which are, by their nature, challenging to measure. We present the results of proof-of-concept tests of wireless ETracer sensors with the East Greenland Ice Core Project (EGRIP) at the Northeast Greenland Ice Stream. ETracers equipped with temperature, pressure and electrical conductivity sensors were deployed in firn boreholes at the centre and the shear margins of the ice stream. Data were returned from a 60m deep test borehole, and continuously for 4 weeks from two 14m deep boreholes, to autonomous receivers at the surface. Two receivers were tested: a station using software radio and PC, and the BAS/UCL ApRES radar system. The sensors were used to track high resolution changes in temperature with depth, changes in densification rates in response to accumulation events and snow redistribution, and the presence of liquid water within the firn. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4658423','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4658423">Microbial Communities and Organic Matter Composition in Surface and Subsurface Sediments of the Helgoland Mud Area, North Sea</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Oni, Oluwatobi E.; Schmidt, Frauke; Miyatake, Tetsuro; Kasten, Sabine; Witt, Matthias; Hinrichs, Kai-Uwe; Friedrich, Michael W. 2015-01-01 The role of microorganisms in the cycling of sedimentary organic carbon is a crucial one. To better understand relationships between molecular composition of a potentially bioavailable fraction of organic matter and microbial populations, bacterial and archaeal communities were characterized using pyrosequencing-based 16S rRNA gene analysis in surface (top 30 cm) and subsurface/deeper sediments (30–530 cm) of the Helgoland mud area, North Sea. Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) was used to characterize a potentially bioavailable organic matter fraction (hot-water extractable organic matter, WE-OM). Algal polymer-associated microbial populations such as members of the Gammaproteobacteria, Bacteroidetes, and Verrucomicrobia were dominant in surface sediments while members of the Chloroflexi (Dehalococcoidales and candidate order GIF9) and Miscellaneous Crenarchaeota Groups (MCG), both of which are linked to degradation of more recalcitrant, aromatic compounds and detrital proteins, were dominant in subsurface sediments. Microbial populations dominant in subsurface sediments (Chloroflexi, members of MCG, and Thermoplasmata) showed strong correlations to total organic carbon (TOC) content. Changes of WE-OM with sediment depth reveal molecular transformations from oxygen-rich [high oxygen to carbon (O/C), low hydrogen to carbon (H/C) ratios] aromatic compounds and highly unsaturated compounds toward compounds with lower O/C and higher H/C ratios. The observed molecular changes were most pronounced in organic compounds containing only CHO atoms. Our data thus, highlights classes of sedimentary organic compounds that may serve as microbial energy sources in methanic marine subsurface environments. PMID:26635758 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22489342-guiding-bending-splitting-coupled-defect-surface-modes-surface-wave-photonic-crystal','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22489342-guiding-bending-splitting-coupled-defect-surface-modes-surface-wave-photonic-crystal">Guiding, bending, and splitting of coupled defect surface modes in a surface-wave photonic crystal</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Gao, Zhen; Gao, Fei; Zhang, Baile, E-mail: blzhang@ntu.edu.sg 2016-01-25 We experimentally demonstrate a type of waveguiding mechanism for coupled surface-wave defect modes in a surface-wave photonic crystal. Unlike conventional spoof surface plasmon waveguides, waveguiding of coupled surface-wave defect modes is achieved through weak coupling between tightly localized defect cavities in an otherwise gapped surface-wave photonic crystal, as a classical wave analogue of tight-binding electronic wavefunctions in solid state lattices. Wave patterns associated with the high transmission of coupled defect surface modes are directly mapped with a near-field microwave scanning probe for various structures including a straight waveguide, a sharp corner, and a T-shaped splitter. These results may find usemore » in the design of integrated surface-wave devices with suppressed crosstalk.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MS%26E..269a2071H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MS%26E..269a2071H">Analysis of Surface and Subsurface Damage Morphology in Rotary Ultrasonic Machining of BK7 Glass</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hong-xiang, Wang; Chu, Wang; Jun-liang, Liu; Shi, Gao; Wen-Jie, Zhai 2017-11-01 This paper investigates the formation process of surface/subsurface damage in the rotary ultrasonic machining of BK7 glass. The results show that during the milling using the end face of the tool, the cutting depth and the residual height between the abrasive grains constantly change with the high-frequency vibration, generating lots of cracks on both sides of the scratches. The high-frequency vibration accelerates the chips falling from the surface, so that the chips and thermal damage are reduced, causing the grinding surface quality better. A plastic deformation area is formed during the grinding, due to the non-uniform cutting force on the material surface, and the residual stress is produced in the deformation area, inducing the median/lateral cracks. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MS%26E...78a2033B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MS%26E...78a2033B">Isolation and Characterization of Surface and Subsurface Bacteria in Seawater of Mantanani Island, Kota Belud, Sabah by Direct and Enrichment Techniques</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Benard, L. D.; Tuah, P. M.; Suadin, E. G.; Jamian, N. 2015-04-01 The distribution of hydrocarbon-utilizing bacterial may vary between surface and subsurface of the seawater. One of the identified contributors is the Total Petroleum Hydrocarbon. The isolation and characterization of bacteria using Direct and Enrichment techniques helps in identifying dominant bacterial populations in seawater of Mantanani Island, Kota Belud, Sabah, potential of further investigation as hydrocarbon degrader. Crude oil (5% v/v) was added as the carbon source for bacteria in Enrichment technique. For surface seawater, the highest population of bacteria identified for both Direct and Enrichment technique were 2.60 × 107 CFU/mL and 3.84 × 106 CFU/mL respectively. Meanwhile, for subsurface seawater, the highest population of bacteria identified for both Direct and Enrichment technique were 5.21 × 106 CFU/mL and 8.99 × 107 CFU/mL respectively. Dominant species in surface seawater were characterized as Marinobacter hydrocarbonoclasticus-RMSF-C1 and RMSF-C2 and Alcanivorax borkumensis-RMSF-C3, RMSF-C4 and RMSF-C5. As for subsurface seawater, dominant species were characterized as Pseudomonas luteola-SSBR-W1, Burkholderia cepacia-SSBR-C1, Rhizobium radiobacter- SSBR-C3 and Leuconostoc-cremois -SSBR-C4. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.H51F0958S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.H51F0958S">Effects of cell surface characteristics and manure-application practices on Escherichia coli populations in the subsurface: A three-farm study</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Salvucci, A. E.; Elton, M.; Siler, J. D.; Zhang, W.; Richards, B. K.; Geohring, L. D.; Warnick, L. D.; Hay, A. G.; Steenhuis, T. 2010-12-01 The introduction of microbial pathogens into the environment from untreated manure represents a threat to water quality and human health. Thus, understanding the effect of manure management strategies is imperative to effectively mitigate the inadvertent release of pathogens, particularly in subsurface environments where they can be transported through macropores to the groundwater or through agricultural tile line to open water bodies. The production of cell-surface biomolecules is also suspected to play an important role in the environmental survival and transport of enterobacterial pathogens. This study collected Escherichia coli samples from three dairy farms with artificial tile drainage systems and active manure spreading in the Central New York region over a three-month period. Sampling targeted four potential source locations on each farm: (i) cow housing, (ii) manure storage facilities, (iii) field soil, and (iv) subsurface drainage effluent. Over 2800 E. coli isolates were recovered and consequently analyzed for the cell surface components, cellulose and curli, traits associated with increased environmental survival, altered transport and pathogenicity. The E. coli isolates from locations i-iii displayed highly variable curli and cellulose-producing communities, while isolates collected from subsurface runoff on each farm had stable curli and cellulose production communities over all sampling dates. Furthermore, the method of manure application to the fields influenced the population characteristics found in drainage effluent isolates. Incorporation of manure into the soil was correlated to isolate populations largely deficient of curli and cellulose; whereas farms that only surface-applied manure were correlated to isolate populations of high curli and cellulose production. The production of curli and cellulose has previously been shown to be a response to environmental stress on the cell. Therefore, incorporation of manure directly into the soil appears </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090009968','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090009968">Sub-Surface Windscreen for the Measurement of Outdoor Infrasound</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Shams, Qamar A.; Burkett, Cecil G., Jr.; Comeaux, Toby; Zuckerwar, Allan J.; Weistroffer, George R. 2008-01-01 A windscreen has been developed that features two advantages favorable for the measurement of outdoor infrasound. First, the sub-surface location, with the top of the windscreen flush with the ground surface, minimizes the mean velocity of the impinging wind. Secondly, the windscreen material (closed cell polyurethane foam) has a sufficiently low acoustic impedance (222 times that of air) and wall thickness (0.0127 m) to provide a transmission coefficient of nearly unity over the infrasonic frequency range (0-20 Hz). The windscreen, a tightly-sealed box having internal dimensions of 0.3048 x 0.3048 x 0.3556 m, contains a microphone, preamplifier, and a cable feed thru to an external power supply. Provisions are made for rain drainage and seismic isolation. A three-element array, configured as an equilateral triangle with 30.48 m spacing and operating continuously in the field, periodically receives highly coherent signals attributed to emissions from atmospheric turbulence. The time delays between infrasonic signals received at the microphones permit determination of the bearing and elevation of the sources, which correlate well with locations of pilot reports (PIREPS) within a 320 km radius about the array. The test results are interpreted to yield spectral information on infrasonic emissions from clear air turbulence. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70016134','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70016134">Oxidation of aromatic contaminants coupled to microbial iron reduction</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Lovley, D.R.; Baedecker, M.J.; Lonergan, D.J.; Cozzarelli, I.M.; Phillips, E.J.P.; Siegel, D.I. 1989-01-01 THE contamination of sub-surface water supplies with aromatic compounds is a significant environmental concern1,2. As these contaminated sub-surface environments are generally anaerobic, the microbial oxidation of aromatic compounds coupled to nitrate reduction, sulphate reduction and methane production has been studied intensively1-7. In addition, geochemical evidence suggests that Fe(III) can be an important electron acceptor for the oxidation of aromatic compounds in anaerobic groundwater. Until now, only abiological mechanisms for the oxidation of aromatic compounds with Fe(III) have been reported8-12. Here we show that in aquatic sediments, microbial activity is necessary for the oxidation of model aromatic compounds coupled to Fe(III) reduction. Furthermore, a pure culture of the Fe(III)-reducing bacterium GS-15 can obtain energy for growth by oxidizing benzoate, toluene, phenol or p-cresol with Fe(III) as the sole electron acceptor. These results extend the known physiological capabilities of Fe(III)-reducing organisms and provide the first example of an organism of any type which can oxidize an aromatic hydrocarbon anaerobically. ?? 1989 Nature Publishing Group. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ECSS..206...76S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ECSS..206...76S">Great differences in the critical erosion threshold between surface and subsurface sediments: A field investigation of an intertidal mudflat, Jiangsu, China</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shi, Benwei; Wang, Ya Ping; Wang, Li Hua; Li, Peng; Gao, Jianhua; Xing, Fei; Chen, Jing Dong 2018-06-01 Understanding of bottom sediment erodibility is necessary for the sustainable management and protection of coastlines, and is of great importance for numerical models of sediment dynamics and transport. To investigate the dependence of sediment erodibility on degree of consolidation, we measured turbidity, waves, tidal currents, intratidal bed-level changes, and sediment properties on an exposed macrotidal mudflat during a series of tidal cycles. We estimated the water content of surface sediments (in the uppermost 2 cm of sediment) and sub-surface sediments (at 2 cm below the sediment surface). Bed shear stress values due to currents (τc), waves (τw), and combined current-wave action (τcw) were calculated using a hydrodynamic model. In this study, we estimate the critical shear stress for erosion using two approaches and both of them give similar results. We found that the critical shear stress for erosion (τce) was 0.17-0.18 N/m2 in the uppermost 0-2 cm of sediment and 0.29 N/m2 in sub-surface sediment layers (depth, 2 cm), as determined by time series of τcw values and intratidal bed-level changes, and values of τce, obtained using the water content of bottom sediments, were 0.16 N/m2 in the uppermost 2 cm and 0.28 N/m2 in the sub-surface (depth, 2 cm) sediment. These results indicate that the value of τce for sub-surface sediments (depth, 2 cm) is much greater than that for the uppermost sediments (depth, 0-2 cm), and that the τce value is mainly related to the water content, which is determined by the extent of consolidation. Our results have implications for improving the predictive accuracy of models of sediment transport and morphological evolution, by introducing variable τce values for corresponding sediment layers, and can also provide a mechanistic understanding of bottom sediment erodibility at different sediment depths on intertidal mudflats, as related to differences in the consolidation time. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.S13C1452H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.S13C1452H">Calibration of Subsurface Amplification Factors Using Surface/Borehole Strong-motion Records from the KiK-net</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hayashida, T.; Tajima, F. 2007-12-01 The Real-time Earthquake Information System (REIS, Horiuchi et al., 2005) detects earthquakes and determines event parameters using the Hi-net (High-sensitivity seismograph network Japan) data in Japan. The system also predicts the arrival time and seismic intensity at a given site before ground motions arrive. Here, the seismic intensity is estimated based on the intensity magnitude which is derived from data of the Hi-net. As the Hi-net stations are located in the boreholes, intensity estimation on the ground surface is evaluated using a constant for subsurface amplification. But the estimated intensities based on the conventionally used amplification constants are not always in agreement with those observed at specific sites on the ground surface. The KiK-net (KIBAN Kyoshin network Japan) consists of strong motion instruments. Each station has two sets of accelerometers, one set is installed on the ground surface and the other one is co-located with a Hi-net station in the borehole. We use data recorded at the KiK-net stations to calibrate subsurface site amplification factors between the borehole and the ground surface. We selected data recorded for over 200 events during the period of 1997 to 2006 in Hiroshima prefecture and calculated the ratios of peak velocity amplitudes on the ground surface ( Asurf) to those in the borehole ( Abor). The subsurface amplification varies from station to station showing dependency on the propagation distance as well as on the incident direction of seismic waves. Results suggest that the site amplification factors shall be described as a function of distance and incident direction, and are not constants. Thus, we derived empirical amplification formulas between Asurf and the peak velocity amplitudes on the engineering bedrock ( Abed) as a function of distance in place of the conventionally used amplification constants. Here, the engineering bedrock is defined as the depth where the S- wave velocity is 600 m/s. The estimated </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSPP11A..01T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSPP11A..01T">Subsurface phytoplankton layers in the Arctic Ocean</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tremblay, J. E. 2016-02-01 Recent observations underscored the near-ubiquitous presence of subsurface chlorophyll maxima (SCM) and their potential importance for total primary production (PP) and pelagic food webs in perennially stratified waters of the Arctic Ocean. The contribution of SCM layers to annual PP is particularly important in oligotrophic areas, where modest nutrient supply to the upper euphotic zone results in weak or short-lived phytoplankton blooms near the surface. The large amount of nutrients present in the Pacific halocline relative to comparable depths in the Atlantic sector of the Arctic may also foster particularly productive SCM along the path of Pacific water. The association between strongly stratified conditions and the SCM in today's Arctic Ocean has broad relevance in providing a glimpse into the future of other oceans whose vertical stratification progressively rises with water temperature and freshwater content. In this regard, there is much to learn on the photosynthetic and nutritive ecology of SCM layers, whose biogeochemical significance depends on the extent to which they rely on allochthonous nitrogen (new production), their contribution to carbon biomass and their ability to influence air-sea CO2 exchange. Here we report on several years of eco-physiological investigations of SCM across the Arctic Ocean, with an aim to provide a basis of comparison with the ecology of SCM in other ocean areas. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active">17</li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active">18</li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29199291','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29199291">Geo-material surface modification of microchips using layer-by-layer (LbL) assembly for subsurface energy and environmental applications.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Zhang, Y Q; Sanati-Nezhad, A; Hejazi, S H 2018-01-16 A key constraint in the application of microfluidic technology to subsurface flow and transport processes is the surface discrepancy between microchips and the actual rocks/soils. This research employs a novel layer-by-layer (LbL) assembly technology to produce rock-forming mineral coatings on microchip surfaces. The outcome of the work is a series of 'surface-mimetic micro-reservoirs (SMMR)' that represent multi-scales and multi-types of natural rocks/soils. For demonstration, the clay pores of sandstones and mudrocks are reconstructed by representatively coating montmorillonite and kaolinite in polydimethylsiloxane (PDMS) microchips in a wide range of channel sizes (width of 10-250 μm, depth of 40-100 μm) and on glass substrates. The morphological and structural properties of mineral coatings are characterized using a scanning electron microscope (SEM), optical microscope and profilometer. The coating stability is tested by dynamic flooding experiments. The surface wettability is characterized by measuring mineral oil-water contact angles. The results demonstrate the formation of nano- to micro-scale, fully-covered and stable mineral surfaces with varying wetting properties. There is an opportunity to use this work in the development of microfluidic technology-based applications for subsurface energy and environmental research. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SuMi..102..259S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SuMi..102..259S">Modeling and analysis of sub-surface leakage current in nano-MOSFET under cutoff regime</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Swami, Yashu; Rai, Sanjeev 2017-02-01 The high leakage current in nano-meter regimes is becoming a significant portion of power dissipation in nano-MOSFET circuits as threshold voltage, channel length, and gate oxide thickness are scaled down to nano-meter range. Precise leakage current valuation and meticulous modeling of the same at nano-meter technology scale is an increasingly a critical work in designing the low power nano-MOSFET circuits. We present a specific compact model for sub-threshold regime leakage current in bulk driven nano-MOSFETs. The proposed logical model is instigated and executed into the latest updated PTM bulk nano-MOSFET model and is found to be in decent accord with technology-CAD simulation data. This paper also reviews various transistor intrinsic leakage mechanisms for nano-MOSFET exclusively in weak inversion, like drain-induced barricade lowering (DIBL), gate-induced drain leakage (GIDL), gate oxide tunneling (GOT) leakage etc. The root cause of the sub-surface leakage current is mainly due to the nano-scale short channel length causing source-drain coupling even in sub-threshold domain. Consequences leading to carriers triumphing the barricade between the source and drain. The enhanced model effectively considers the following parameter dependence in the account for better-quality value-added results like drain-to-source bias (VDS), gate-to-source bias (VGS), channel length (LG), source/drain junction depth (Xj), bulk doping concentration (NBULK), and operating temperature (Top). </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.3981V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.3981V">Shallow subsurface imaging of the Piano di Pezza active normal fault (central Italy) by high-resolution refraction and electrical resistivity tomography coupled with time domain electromagnetic data</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Villani, Fabio; Tulliani, Valerio; Fierro, Elisa; Sapia, Vincenzo; Civico, Riccardo 2015-04-01 The Piano di Pezza fault is the north-westernmost segment of the >20 km long Ovindoli-Pezza active normal fault-system (central Italy). Although existing paleoseismic data document high vertical Holocene slip rates (~1 mm/yr) and a remarkable seismogenic potential of this fault, its subsurface setting and Pleistocene cumulative displacement are still poorly known. We investigated for the first time by means of high-resolution seismic and electrical resistivity tomography coupled with time domain electromagnetic (TDEM) measurements the shallow subsurface of a key section of the Piano di Pezza fault. Our surveys cross a ~5 m-high fault scarp that was generated by repeated surface-rupturing earthquakes displacing some Late Holocene alluvial fans. We provide 2-D Vp and resistivity images which clearly show significant details of the fault structure and the geometry of the shallow basin infill material down to 50 m depth. We can estimate the dip (~50°) and the Holocene vertical displacement of the master fault (~10 m). We also recognize in the hangingwall some low-velocity/low-resistivity regions that we relate to packages of colluvial wedges derived from scarp degradation, which may represent the record of several paleo-earthquakes older than the Late Holocene events previously recognized by paleoseismic trenching. Conversely, due to the limited investigation depth of seismic and electrical tomography, the estimation of the cumulative amount of Pleistocene throw is hampered. Therefore, to increase the depth of investigation, we performed 7 TDEM measurements along the electrical profile using a 50 m loop size both in central and offset configuration. The recovered 1-D resistivity models show a good match with 2-D resistivity images in the near surface. Moreover, TDEM inversion results indicate that in the hangingwall, ~200 m away from the surface fault trace, the carbonate pre-Quaternary basement may be found at ~90-100 m depth. The combined approach of electrical and </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=331486','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=331486">Antibiotic resistance and community analysis of surface and subsurface drainage waters in the South Fork Iowa River watershed</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> The Midwest is a center for swine production leading to application of swine manure onto lands that have artificial subsurface drainage. Previous reports have indicated elevated levels of antibiotic resistance genes (ARGs) in surface water and groundwater around confined animal feeding operations w... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=341091','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=341091">Antibiotic resistance and community analysis of surface and subsurface drainage waters in the South Fork Iowa River watershed</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> The Midwest is a center for swine production leading to application of swine manure onto lands that have artificial subsurface drainage. Previous reports have indicated elevated levels of antibiotic resistance genes (ARGs) in surface water and groundwater around confined animal feeding operations wh... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1613522C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1613522C">Reanalysis of biogeochemical properties in the Mediterranean Sea</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Cossarini, Gianpiero; Teruzzi, Anna; Salon, Stefano; Solidoro, Cosimo 2014-05-01 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 biogeochemical 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 coupled 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 biogeochemical covariance (Teruzzi et al. 2014). The biogeochemical operator propagates the result of the assimilation to the OPATM-BFM variables, providing innovation for the components of the four phytoplankton types. The biogeochemical 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 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/898584','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/898584">Sub-surface mechanical damage distributions during grinding of fused silica</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Suratwala, T I; Wong, L L; Miller, P E 2005-11-28 The distribution and characteristics of surface cracking (i.e. sub-surface damage or SSD) formed during standard grinding processes has been investigated on fused silica glass. The SSD distributions of the ground surfaces were determined by: (1) creating a shallow (18-108 {micro}m) wedge/taper on the surface by magneto-rheological finishing; (2) exposing the SSD by HF acid etching; and (3) performing image analysis of the observed cracks from optical micrographs taken along the surface taper. The observed surface cracks are characterized as near-surface lateral and deeper trailing indent type fractures (i.e., chatter marks). The SSD depth distributions are typically described by a singlemore » exponential distribution followed by an asymptotic cutoff in depth (c{sub max}). The length of the trailing indent is strongly correlated with a given process. Using established fracture indentation relationships, it is shown that only a small fraction of the abrasive particles are being mechanically loaded and causing fracture, and it is likely the larger particles in the abrasive particle size distribution that bear the higher loads. The SSD depth was observed to increase with load and with a small amount of larger contaminant particles. Using a simple brittle fracture model for grinding, the SSD depth distribution has been related to the SSD length distribution to gain insight into ''effective'' size distribution of particles participating in the fracture. Both the average crack length and the surface roughness were found to scale linearly with the maximum SSD depth (c{sub max}). These relationships can serve as useful rules-of-thumb for nondestructively estimating SSD depth and to identify the process that caused the SSD. In certain applications such as high intensity lasers, SSD on the glass optics can serve as a reservoir for minute amounts of impurities that absorb the high intensity laser light and lead to subsequent laser-induced surface damage. Hence a more </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19171414','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19171414">Nutrient transport through a Vegetative Filter Strip with subsurface drainage.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Bhattarai, Rabin; Kalita, Prasanta Kumar; Patel, Mita Kanu 2009-04-01 The transport of nutrients and soil sediments in runoff has been recognized as a noteworthy environmental issue. Vegetative Filter Strips (VFS) have been used as one of the best management practices (BMPs) for retaining nutrients and sediments from surface runoff, thus preventing the pollutants from reaching receiving waters. However, the effectiveness of a VFS when combined with a subsurface drainage system has not been investigated previously. This study was undertaken to monitor the retention and transport of nutrients within a VFS that had a subsurface drainage system installed at a depth of 1.2 m below the soil surface. Nutrient concentrations of NO(3)-N (Nitrate Nitrogen), PO(-)(4) (Orthophosphorus), and TP (Total Phosphorus) were measured in surface water samples (entering and leaving the VFS), and subsurface outflow. Soil samples were collected and analyzed for plant available Phosphorus (Bray P1) and NO(3)-N concentrations. Results showed that PO(-)(4), NO(3)-N, and TP concentrations decreased in surface flow through the VFS. Many surface outflow water samples from the VFS showed concentration reductions of as much as 75% for PO(-)(4) and 70% for TP. For subsurface outflow water samples through the drainage system, concentrations of PO(-)(4) and TP decreased but NO(3)-N concentrations increased in comparison to concentrations in surface inflow samples. Soil samples that were collected from various depths in the VFS showed a minimal buildup of nutrients in the top soil profile but indicated a gradual buildup of nutrients at the depth of the subsurface drain. Results demonstrate that although a VFS can be very effective in reducing runoff and nutrients from surface flow, the presence of a subsurface drain underneath the VFS may not be environmentally beneficial. Such a combination may increase NO(3)-N transport from the VFS, thus invalidating the purpose of the BMP. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.P11E1621C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.P11E1621C">WISDOM, a polarimetric GPR for the shallow subsurface characterization</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ciarletti, V.; Plettemeier, D.; Hassen-Kodja, R.; Clifford, S. M.; Wisdom Team 2011-12-01 WISDOM (Water Ice and Subsurface Deposit Observations on Mars) is a polarimetric Ground Penetrating Radar (GPR) that has been selected to be part of the Pasteur payload onboard the Rover of the 2018 ExoMars mission. It will perform large-scale scientific investigations of the sub-surface of the landing site and provide precise information about the subsurface structure prior to drilling. WISDOM has been designed to provide accurate information on the sub-surface structure down to a depth in excess to 2 meters (commensurate to the drill capacities) with a vertical resolution of a several centimetres. It will give access to the geological structure, electromagnetic nature, and, possibly, to the hydrological state of the shallow subsurface by retrieving the layering and properties of the layers and buried reflectors. The data will also be used to determine the most promising locations to collect underground samples with the drilling system mounted on board the rover. Polarimetric measurements have been recently acquired on perfectly known targets as well as in natural environments. They demonstrated the ability to provide a better understanding of sub-surface structure and significantly reduce the ambiguity associated with identifying the location of off-nadir reflectors, relative to the rover path. This work describes the instrument and its operating modes with particular emphasis on its polarimetric capacities. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PrOce.122...30X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PrOce.122...30X">Connections between physical, optical and biogeochemical processes in the Pacific Ocean</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Xiu, Peng; Chai, Fei 2014-03-01 A new biogeochemical model has been developed and coupled to a three-dimensional physical model in the Pacific Ocean. With the explicitly represented dissolved organic pools, this new model is able to link key biogeochemical processes with optical processes. Model validation against satellite and in situ data indicates the model is robust in reproducing general biogeochemical and optical features. Colored dissolved organic matter (CDOM) has been suggested to play an important role in regulating underwater light field. With the coupled model, physical and biological regulations of CDOM in the euphotic zone are analyzed. Model results indicate seasonal variability of CDOM is mostly determined by biological processes, while the importance of physical regulation manifests in the annual mean terms. Without CDOM attenuating light, modeled depth-integrated primary production is about 10% higher than the control run when averaged over the entire basin, while this discrepancy is highly variable in space with magnitudes reaching higher than 100% in some locations. With CDOM dynamics integrated in physical-biological interactions, a new mechanism by which physical processes affect biological processes is suggested, namely, physical transport of CDOM changes water optical properties, which can further modify underwater light field and subsequently affect the distribution of phytoplankton chlorophyll. This mechanism tends to occur in the entire Pacific basin but with strong spatial variability, implying the importance of including optical processes in the coupled physical-biogeochemical model. If ammonium uptake is sufficient to permit utilization of DOM, that is, UB∗⩾-U{U}/{U}-{(1-r_b)}/{RB}, then bacteria uptake of DOM has the form of FB=(1-r_b){U}/{RB}, bacteria respiration, SB=r_b×U, remineralization by bacteria, EB=UC{UN}/{UC}-{(1-r_b)}/{RB}. If EB > 0, then UB = 0; otherwise, UB = -EB. If there is insufficient ammonium, that is, UB∗<-U{U}/{U}-{(1-r_b)}/{RB}, then </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110013399','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110013399">Lessons Learned from Assimilating Altimeter Data into a Coupled General Circulation Model with the GMAO Augmented Ensemble Kalman Filter</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Keppenne, Christian; Vernieres, Guillaume; Rienecker, Michele; Jacob, Jossy; Kovach, Robin 2011-01-01 Satellite altimetry measurements have provided global, evenly distributed observations of the ocean surface since 1993. However, the difficulties introduced by the presence of model biases and the requirement that data assimilation systems extrapolate the sea surface height (SSH) information to the subsurface in order to estimate the temperature, salinity and currents make it difficult to optimally exploit these measurements. This talk investigates the potential of the altimetry data assimilation once the biases are accounted for with an ad hoc bias estimation scheme. Either steady-state or state-dependent multivariate background-error covariances from an ensemble of model integrations are used to address the problem of extrapolating the information to the sub-surface. The GMAO ocean data assimilation system applied to an ensemble of coupled model instances using the GEOS-5 AGCM coupled to MOM4 is used in the investigation. To model the background error covariances, the system relies on a hybrid ensemble approach in which a small number of dynamically evolved model trajectories is augmented on the one hand with past instances of the state vector along each trajectory and, on the other, with a steady state ensemble of error estimates from a time series of short-term model forecasts. A state-dependent adaptive error-covariance localization and inflation algorithm controls how the SSH information is extrapolated to the sub-surface. A two-step predictor corrector approach is used to assimilate future information. Independent (not-assimilated) temperature and salinity observations from Argo floats are used to validate the assimilation. A two-step projection method in which the system first calculates a SSH increment and then projects this increment vertically onto the temperature, salt and current fields is found to be most effective in reconstructing the sub-surface information. The performance of the system in reconstructing the sub-surface fields is particularly </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70144442','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70144442">Coupled hydrological and biogeochemical processes controlling variability of nitrogen species in streamflow during autumn in an upland forest</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Sebestyen, Stephen D.; Shanley, James B.; Boyer, Elizabeth W.; Kendall, Carol; Doctor, Daniel H. 2014-01-01 Autumn is a season of dynamic change in forest streams of the northeastern United States due to effects of leaf fall on both hydrology and biogeochemistry. Few studies have explored how interactions of biogeochemical transformations, various nitrogen sources, and catchment flow paths affect stream nitrogen variation during autumn. To provide more information on this critical period, we studied (1) the timing, duration, and magnitude of changes to stream nitrate, dissolved organic nitrogen (DON), and ammonium concentrations; (2) changes in nitrate sources and cycling; and (3) source areas of the landscape that most influence stream nitrogen. We collected samples at higher temporal resolution for a longer duration than typical studies of stream nitrogen during autumn. This sampling scheme encompassed the patterns and extremes that occurred during base flow and stormflow events of autumn. Base flow nitrate concentrations decreased by an order of magnitude from 5.4 to 0.7 µmol L−1 during the week when most leaves fell from deciduous trees. Changes to rates of biogeochemical transformations during autumn base flow explained the low nitrate concentrations; in-stream transformations retained up to 72% of the nitrate that entered a stream reach. A decrease of in-stream nitrification coupled with heterotrophic nitrate cycling were primary factors in the seasonal nitrate decline. The period of low nitrate concentrations ended with a storm event in which stream nitrate concentrations increased by 25-fold. In the ensuing weeks, peak stormflow nitrate concentrations progressively decreased over closely spaced, yet similarly sized events. Most stormflow nitrate originated from nitrification in near-stream areas with occasional, large inputs of unprocessed atmospheric nitrate, which has rarely been reported for nonsnowmelt events. A maximum input of 33% unprocessed atmospheric nitrate to the stream occurred during one event. Large inputs of unprocessed atmospheric nitrate </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Nanot..26J5602B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Nanot..26J5602B">Surface-confined Ullmann coupling of thiophene substituted porphyrins</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Beggan, J. P.; Boyle, N. M.; Pryce, M. T.; Cafolla, A. A. 2015-09-01 The covalent coupling of (5,10,15,20-tetrabromothien-2-ylporphyrinato)zinc(II) (TBrThP) molecules on the Ag(111) surface has been investigated under ultra-high-vacuum conditions, using scanning tunnelling microscopy and x-ray photoelectron spectroscopy. The findings provide atomic-level insight into surface-confined Ullmann coupling of thiophene substituted porphyrins, analyzing the progression of organometallic intermediate to final coupled state. Adsorption of the TBrThP molecules on the Ag(111) surface at room temperature is found to result in the reductive dehalogenation of the bromothienyl substituents and the subsequent formation of single strand and crosslinked coordination networks. The coordinated substrate atoms bridge the proximal thienyl groups of the organometallic intermediate, while the cleaved bromine atoms are bound on the adjacent Ag(111) surface. The intermediate complex displays a thermal lability at ˜423 K that results in the dissociation of the proximal thienyl groups with the concomitant loss of the surface bound bromine. At the thermally induced dissociation of the intermediate complex the resultant thienylporphyrin derivatives covalently couple, leading to the formation of a polymeric network of thiophene linked and meso-meso fused porphyrins. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70029884','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70029884">Fractal topography and subsurface water flows from fluvial bedforms to the continental shield</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Worman, A.; Packman, A.I.; Marklund, L.; Harvey, J.W.; Stone, S.H. 2007-01-01 Surface-subsurface flow interactions are critical to a wide range of geochemical and ecological processes and to the fate of contaminants in freshwater environments. Fractal scaling relationships have been found in distributions of both land surface topography and solute efflux from watersheds, but the linkage between those observations has not been realized. We show that the fractal nature of the land surface in fluvial and glacial systems produces fractal distributions of recharge, discharge, and associated subsurface flow patterns. Interfacial flux tends to be dominated by small-scale features while the flux through deeper subsurface flow paths tends to be controlled by larger-scale features. This scaling behavior holds at all scales, from small fluvial bedforms (tens of centimeters) to the continental landscape (hundreds of kilometers). The fractal nature of surface-subsurface water fluxes yields a single scale-independent distribution of subsurface water residence times for both near-surface fluvial systems and deeper hydrogeological flows. Copyright 2007 by the American Geophysical Union. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.1659S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.1659S">Association between mean and interannual equatorial Indian Ocean subsurface temperature bias in a coupled model</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Srinivas, G.; Chowdary, Jasti S.; Gnanaseelan, C.; Prasad, K. V. S. R.; Karmakar, Ananya; Parekh, Anant 2018-03-01 In the present study the association between mean and interannual subsurface temperature bias over the equatorial Indian Ocean (EIO) is investigated during boreal summer (June through September; JJAS) in the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFSv2) hindcast. Anomalously high subsurface warm bias (greater than 3 °C) over the eastern EIO (EEIO) region is noted in CFSv2 during summer, which is higher compared to other parts of the tropical Indian Ocean. Prominent eastward current bias in the upper 100 m over the EIO region induced by anomalous westerly winds is primarily responsible for subsurface temperature bias. The eastward currents transport warm water to the EEIO and is pushed down to subsurface due to downwelling. Thus biases in both horizontal and vertical currents over the EIO region support subsurface warm bias. The evolution of systematic subsurface warm bias in the model shows strong interannual variability. These maximum subsurface warming episodes over the EEIO are mainly associated with La Niña like forcing. Strong convergence of low level winds over the EEIO and Maritime continent enhanced the westerly wind bias over the EIO during maximum warming years. This low level convergence of wind is induced by the bias in the gradient in the mean sea level pressure with positive bias over western EIO and negative bias over EEIO and parts of western Pacific. Consequently, changes in the atmospheric circulation associated with La Niña like conditions affected the ocean dynamics by modulating the current bias thereby enhancing the subsurface warm bias over the EEIO. It is identified that EEIO subsurface warming is stronger when La Niña co-occurred with negative Indian Ocean Dipole events as compared to La Niña only years in the model. Ocean general circulation model (OGCM) experiments forced with CFSv2 winds clearly support our hypothesis that ocean dynamics influenced by westerly winds bias is primarily </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.H33N..05B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.H33N..05B">Carbon Characteristics and Biogeochemical Processes of Uranium Accumulating Organic Matter Rich Sediments in the Upper Colorado River Basin</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Boye, K.; Noel, V.; Tfaily, M. M.; Dam, W. L.; Bargar, J.; Fendorf, S. E. 2015-12-01 Uranium plume persistence in groundwater aquifers is a problem on several former ore processing sites on floodplains in the upper Colorado River Basin. Earlier observations by our group and others at the Old Rifle Site, CO, have noted that U concentrations are highest in organic rich, fine-grained, and, therefore, diffusion limited sediment material. Due to the constantly evolving depositional environments of floodplains, surficial organic matter may become buried at various stages of decomposition, through sudden events such as overbank flooding and through the slower progression of river meandering. This creates a discontinuous subsurface distribution of organic-rich sediments, which are hotspots for microbial activity and thereby central to the subsurface cycling of contaminants (e.g. U) and biologically relevant elements (e.g. C, N, P, Fe). However, the organic matter itself is poorly characterized. Consequently, little is known about its relevance in driving biogeochemical processes that control U fate and transport in the subsurface. In an investigation of soil/sediment cores from five former uranium ore processing sites on floodplains distributed across the Upper Colorado River Basin we confirmed consistent co-enrichment of U with organic-rich layers in all profiles. However, using C K-edge X-ray Absorption Spectroscopy (XAS) coupled with Fourier-Transformed Ion-Cyclotron-Resonance Mass-Spectroscopy (FT-ICR-MS) on bulk sediments and density-separated organic matter fractions, we did not detect any chemical difference in the organic rich sediments compared to the surrounding coarser-grained aquifer material within the same profile, even though there were differences in organic matter composition between the 5 sites. This suggests that U retention and reduction to U(IV) is independent of C chemical composition on the bulk scale. Instead it appears to be the abundance of organic matter in combination with a limited O2 supply in the fine-grained material that </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000112962','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000112962">A Coupled Ocean General Circulation, Biogeochemical, and Radiative Model of the Global Oceans: Seasonal Distributions of Ocean Chlorophyll and Nutrients</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Gregg, Watson W.; Busalacchi, Antonio (Technical Monitor) 2000-01-01 A coupled ocean general circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. Biogeochemical 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. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.B51E0465X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.B51E0465X">Modeling biogeochemical responses of vegetation to ENSO: comparison and analysis on subgrid PFT patches</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Xu, M.; Hoffman, F. M. 2016-12-01 The El Niño Southern Oscillation (ENSO) is an important interannual climate variability and has significant consequences and impacts on the global biosphere. The responses of vegetation to ENSO are highly heterogeneous and generally depend on the biophysical and biochemical characteristics associated with model plant functional types (PFTs). The modeled biogeochemical variables from Earth System Models (ESMs) are generally grid averages consisting of several PFTs within a gridcell, which will lead to difficulties in directly comparing them with site observations and large uncertainties in studying their responses to large scale climate variability. In this study, we conducted a transient ENSO simulation for the previoustwo decades from 1995 to 2020 using the DOE ACME v0.3 model. It has a comprehensive terrestrial biogeochemistry model that is fully coupled with a sophisticated atmospheric model with an advanced spectral element dynamical core. The model was driven by the NOAA optimum interpolation sea surface temperature (SST) for contemporary years and CFS v2 nine-month seasonal predicted and reconstructed SST for future years till to 2020. We saved the key biogeochemical variables in the subgrid PFT patches and compared them with site observations directly. Furthermore, we studied the biogeochemical responses of terrestrial vegetation to two largest ENSO events (1997-1998 and 2015-2016) for different PFTs. Our results show that it is useful and meaningful to compare and analyze model simulations in subgrid patches. The comparison and analysis not only gave us the details of responses of terrestrial ecosystem to global climate variability under changing climate, but also the insightful view on the model performance on the PFT level. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.B33I..08M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.B33I..08M">Exploring the Deep Biosphere in Ophiolite-hosted Systems: What Can Metabolic Processes in Surface Seeps Tell Us About Subsurface Ecosystems in Serpentinizing Fluids?</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Meyer-Dombard, D. R.; Cardace, D.; Woycheese, K. M.; Vallalar, B.; Casar, C.; Simon, A.; Arcilla, C. A. 2016-12-01 Serpentinization in the subsurface produces highly reduced, high pH fluids that provide microbial habitats. It is assumed that these deep subsurface fluids contain copious H2 and CH4 gas, little/no inorganic carbon, and limited electron acceptors. As serpentinized fluids reach the oxygenated surface environment, microbial biomes shift and organisms capable of metabolizing O2 thrive (Woycheese et al., 2015). However, the relationship of microbial communities found in surface expressions of serpentinizing fluids to the subsurface biosphere is still a target of exploration. Our work in the Zambales ophiolite (Philippines) defines surface microbial habitats with geochemistry, targeted culturing efforts, and community analysis (Cardace et al., 2015; Woycheese et al., 2015). Springs range from pH 9-11.5, and contain 0.06-2 ppm DO, 0-3.7 ppm sulfide, 30-800 ppm silica. Gases include H2 and CH4 > 10uM, CO2 > 1 mM, and trace amounts of CO. These surface data allow prediction of the subsurface metabolic landscape. For example, Cardace et al., (2015) predicted that metabolism of iron is important in both biospheres. Growth media were designed to target iron reduction yielding heterotrophic and autotrophic iron reducers at high pH. Reduced iron minerals were produced in several cultures (Casar et al., sub.), and isolation efforts are underway. Shotgun metagenomic analysis shows the metabolic capacity for methanogenesis, suggesting microbial origins for some CH4 present. The enzymes methyl coenzyme M reductase, and formylmethanofuran dehydrogenase were detected, and relative abundance increased near the near-anoxic spring source. The metagenomes indicate carbon cycling at these sites is reliant on methanogenesis, acetogenesis, sulfate reduction, and H2 and CH4 oxidation. In this tropical climate, cellulose is also a likely carbon source; cellulose degrading isolates have been obtained. These results indicate a metabolically flexible community at the surface where serpentinizing </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27339740','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27339740">Wastewater injection, aquifer biogeochemical reactions, and resultant groundwater N fluxes to coastal waters: Kā'anapali, Maui, Hawai'i.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Fackrell, Joseph K; Glenn, Craig R; Popp, Brian N; Whittier, Robert B; Dulai, Henrietta 2016-09-15 We utilize N and C species concentration data along with δ(15)N values of NO3(-) and δ(13)C values of dissolved inorganic C to evaluate the stoichiometry of biogeochemical reactions (mineralization, nitrification, anammox, and denitrification) occurring within a subsurface wastewater plume that originates as treated wastewater injection and enters the coastal waters of Maui as submarine groundwater discharge. Additionally, we compare wastewater effluent time-series data, injection rates, and treatment history with submarine spring discharge time-series data. We find that heterotrophic denitrification is the primary mechanism of N loss within the groundwater plume and that chlorination for pathogen disinfection suppresses microbial activity in the aquifer responsible for N loss, resulting in increased coastal ocean N loading. Replacement of chlorination with UV disinfection may restore biogeochemical reactions responsible for N loss within the aquifer and return N-attenuating conditions in the effluent plume, reducing N loading to coastal waters. Copyright © 2016 Elsevier Ltd. All rights reserved. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active">18</li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active">19</li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015WRR....51.1158B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015WRR....51.1158B">Untangling the effects of urban development on subsurface storage in Baltimore</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bhaskar, Aditi S.; Welty, Claire; Maxwell, Reed M.; Miller, Andrew J. 2015-02-01 The impact of urban development on surface flow has been studied extensively over the last half century, but effects on groundwater systems are still poorly understood. Previous studies of the influence of urban development on subsurface storage have not revealed any consistent pattern, with results showing increases, decreases, and negligible change in groundwater levels. In this paper, we investigated the effects of four key features that impact subsurface storage in urban landscapes. These include reduced vegetative cover, impervious surface cover, infiltration and inflow (I&I) of groundwater and storm water into wastewater pipes, and other anthropogenic recharge and discharge fluxes including water supply pipe leakage and well and reservoir withdrawals. We applied the integrated groundwater-surface water-land surface model ParFlow.CLM to the Baltimore metropolitan area. We compared the base case (all four features) to simulations in which an individual urban feature was removed. For the Baltimore region, the effect of infiltration of groundwater into wastewater pipes had the greatest effect on subsurface storage (I&I decreased subsurface storage 11.1% relative to precipitation minus evapotranspiration after 1 year), followed by the impact of water supply pipe leakage and lawn irrigation (combined anthropogenic discharges and recharges led to a 7.4% decrease) and reduced vegetation (1.9% increase). Impervious surface cover led to a small increase in subsurface storage (0.56% increase) associated with decreased groundwater discharge as base flow. The change in subsurface storage due to infiltration of groundwater into wastewater pipes was largest despite the smaller spatial extent of surface flux modifications, compared to other features. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRG..122..966N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRG..122..966N">Development of an advanced eco-hydrologic and biogeochemical coupling model aimed at clarifying the missing role of inland water in the global biogeochemical cycle</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Nakayama, Tadanobu 2017-04-01 Recent research showed that inland water including rivers, lakes, and groundwater may play some role in carbon cycling, although its contribution has remained uncertain due to limited amount of reliable data available. In this study, the author developed an advanced model coupling eco-hydrology and biogeochemical cycle (National Integrated Catchment-based Eco-hydrology (NICE)-BGC). This new model incorporates complex coupling of hydrologic-carbon cycle in terrestrial-aquatic linkages and interplay between inorganic and organic carbon during the whole process of carbon cycling. The model could simulate both horizontal transports (export from land to inland water 2.01 ± 1.98 Pg C/yr and transported to ocean 1.13 ± 0.50 Pg C/yr) and vertical fluxes (degassing 0.79 ± 0.38 Pg C/yr, and sediment storage 0.20 ± 0.09 Pg C/yr) in major rivers in good agreement with previous researches, which was an improved estimate of carbon flux from previous studies. The model results also showed global net land flux simulated by NICE-BGC (-1.05 ± 0.62 Pg C/yr) decreased carbon sink a little in comparison with revised Lund-Potsdam-Jena Wetland Hydrology and Methane (-1.79 ± 0.64 Pg C/yr) and previous materials (-2.8 to -1.4 Pg C/yr). This is attributable to CO2 evasion and lateral carbon transport explicitly included in the model, and the result suggests that most previous researches have generally overestimated the accumulation of terrestrial carbon and underestimated the potential for lateral transport. The results further implied difference between inverse techniques and budget estimates suggested can be explained to some extent by a net source from inland water. NICE-BGC would play an important role in reevaluation of greenhouse gas budget of the biosphere, quantification of hot spots, and bridging the gap between top-down and bottom-up approaches to global carbon budget. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27888928','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27888928">Analytical prediction of sub-surface thermal history in translucent tissue phantoms during plasmonic photo-thermotherapy (PPTT).</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Dhar, Purbarun; Paul, Anup; Narasimhan, Arunn; Das, Sarit K 2016-12-01 Knowledge of thermal history and/or distribution in biological tissues during laser based hyperthermia is essential to achieve necrosis of tumour/carcinoma cells. A semi-analytical model to predict sub-surface thermal distribution in translucent, soft, tissue mimics has been proposed. The model can accurately predict the spatio-temporal temperature variations along depth and the anomalous thermal behaviour in such media, viz. occurrence of sub-surface temperature peaks. Based on optical and thermal properties, the augmented temperature and shift of the peak positions in case of gold nanostructure mediated tissue phantom hyperthermia can be predicted. Employing inverse approach, the absorption coefficient of nano-graphene infused tissue mimics is determined from the peak temperature and found to provide appreciably accurate predictions along depth. Furthermore, a simplistic, dimensionally consistent correlation to theoretically determine the position of the peak in such media is proposed and found to be consistent with experiments and computations. The model shows promise in predicting thermal distribution induced by lasers in tissues and deduction of therapeutic hyperthermia parameters, thereby assisting clinical procedures by providing a priori estimates. Copyright Â© 2016 Elsevier Ltd. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018BGeo...15.1579M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018BGeo...15.1579M">Coupling physics and biogeochemistry thanks to high-resolution observations of the phytoplankton community structure in the northwestern Mediterranean Sea</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Marrec, Pierre; Grégori, Gérald; Doglioli, Andrea M.; Dugenne, Mathilde; Della Penna, Alice; Bhairy, Nagib; Cariou, Thierry; Hélias Nunige, Sandra; Lahbib, Soumaya; Rougier, Gilles; Wagener, Thibaut; Thyssen, Melilotus 2018-03-01 Fine-scale physical structures and ocean dynamics strongly influence and regulate biogeochemical and ecological processes. These processes are particularly challenging to describe and understand because of their ephemeral nature. The OSCAHR (Observing Submesoscale Coupling At High Resolution) campaign was conducted in fall 2015 in which a fine-scale structure (1-10 km/1-10 days) in the northwestern Mediterranean Ligurian subbasin was pre-identified using both satellite and numerical modeling data. Along the ship track, various variables were measured at the surface (temperature, salinity, chlorophyll a and nutrient concentrations) with ADCP current velocity. We also deployed a new model of the CytoSense automated flow cytometer (AFCM) optimized for small and dim cells, for near real-time characterization of the surface phytoplankton community structure of surface waters with a spatial resolution of a few kilometers and an hourly temporal resolution. For the first time with this optimized version of the AFCM, we were able to fully resolve Prochlorococcus picocyanobacteria in addition to the easily distinguishable Synechococcus. The vertical physical dynamics and biogeochemical properties of the studied area were investigated by continuous high-resolution CTD profiles thanks to a moving vessel profiler (MVP) during the vessel underway associated with a high-resolution pumping system deployed during fixed stations allowing sampling of the water column at a fine resolution (below 1 m). The observed fine-scale feature presented a cyclonic structure with a relatively cold core surrounded by warmer waters. Surface waters were totally depleted in nitrate and phosphate. In addition to the doming of the isopycnals by the cyclonic circulation, an intense wind event induced Ekman pumping. The upwelled subsurface cold nutrient-rich water fertilized surface waters and was marked by an increase in Chl a concentration. Prochlorococcus and pico- and nano-eukaryotes were more </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=248341','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=248341">Investigation of the near subsurface using acoustic to seismic coupling</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> Agricultural, hydrological and civil engineering applications have realized a need for information of the near subsurface over large areas. In order to obtain this spatially distributed data over such scales, the measurement technique must be highly mobile with a short acquisition time. Therefore, s... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H41F1521H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H41F1521H">Characterization of Thermal Refugia and Biogeochemical Hotspots at Sleepers River Watershed, VT</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hwang, K.; Chandler, D. G.; Kelleher, C.; Shanley, J. B.; Shaw, S. B. 2017-12-01 During low flow, changes in the extent of the channel network in headwater catchments depend on groundwater-surface water interactions, and dictate thermal and biogeochemical heterogeneities. Channel reaches with low temperature may act as refugia for valued species such as brook trout, and warmer reaches with high dissolved organic matter may act as biogeochemical hotspots. Prior studies have found uniform scaling of hydrologic and biogeochemical processes above certain spatial thresholds but sizable heterogeneities in these processes below the threshold. We utilize high resolution measurements of water quality parameters including stream temperature, conductivity and fluorescent dissolved organic matter (fDOM) at tributaries in two catchments of Sleepers River Watershed, Vermont to investigate seasonal and spatial variation of water quality and scaling of stream chemistry within the intensive study area and the larger Sleepers River Watershed. This study leverages findings from various small scale regional studies to identify differences in headwater channel reach behavior in a similar climate across some dissimilar geomorphic units, to inform the identification of thermal refugia and biogeochemical hotspots. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=127523&Lab=NRMRL&keyword=technology+AND+electrical&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=127523&Lab=NRMRL&keyword=technology+AND+electrical&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">COUPLED IRON CORROSION AND CHROMATE REDUCTION: MECHANISMS FOR SUBSURFACE REMEDIATION</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> The reduction of chromium from the Cr(VI) to the Cr- (Ill) state by the presence of elemental, or zero-oxidation-state, iron metal was studied to evaluate the feasibility of such a process for subsurface chromate remediation. Reactions were studied in systems of natural aquifer m... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993PhDT........76H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993PhDT........76H">Physically-Based Models for the Reflection, Transmission and Subsurface Scattering of Light by Smooth and Rough Surfaces, with Applications to Realistic Image Synthesis</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> He, Xiao Dong This thesis studies light scattering processes off rough surfaces. Analytic models for reflection, transmission and subsurface scattering of light are developed. The results are applicable to realistic image generation in computer graphics. The investigation focuses on the basic issue of how light is scattered locally by general surfaces which are neither diffuse nor specular; Physical optics is employed to account for diffraction and interference which play a crucial role in the scattering of light for most surfaces. The thesis presents: (1) A new reflectance model; (2) A new transmittance model; (3) A new subsurface scattering model. All of these models are physically-based, depend on only physical parameters, apply to a wide range of materials and surface finishes and more importantly, provide a smooth transition from diffuse-like to specular reflection as the wavelength and incidence angle are increased or the surface roughness is decreased. The reflectance and transmittance models are based on the Kirchhoff Theory and the subsurface scattering model is based on Energy Transport Theory. They are valid only for surfaces with shallow slopes. The thesis shows that predicted reflectance distributions given by the reflectance model compare favorably with experiment. The thesis also investigates and implements fast ways of computing the reflectance and transmittance models. Furthermore, the thesis demonstrates that a high level of realistic image generation can be achieved due to the physically -correct treatment of the scattering processes by the reflectance model. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21520748','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21520748">Phosphorus runoff losses from subsurface-applied poultry litter on coastal plain soils.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Kibet, Leonard C; Allen, Arthur L; Kleinman, Peter J A; Feyereisen, Gary W; Church, Clinton; Saporito, Lou S; Way, Thomas R 2011-01-01 The application of poultry litter to soils is a water quality concern on the Delmarva Peninsula, as runoff contributes P to the eutrophic Chesapeake Bay. This study compared a new subsurface applicator for poultry litter with conventional surface application and tillage incorporation of litter on a Coastal Plain soil under no-till management. Monolith lysimeters (61 cm by 61 cm by 61 cm) were collected immediately after litter application and subjected to rainfall simulation (61 mm h(-1) 1 h) 15 and 42 d later. In the first rainfall event, subsurface application of litter significantly lowered total P losses in runoff (1.90 kg ha(-1)) compared with surface application (4.78 kg ha(-1)). Losses of P with subsurface application were not significantly different from disked litter or an unamended control. By the second event, total P losses did not differ significantly between surface and subsurface litter treatments but were at least twofold greater than losses from the disked and control treatments. A rising water table in the second event likely mobilized dissolved forms of P in subsurface-applied litter to the soil surface, enriching runoff water with P. Across both events, subsurface application of litter did not significantly decrease cumulative losses of P relative to surface-applied litter, whereas disking the litter into the soil did. Results confirm the short-term reduction of runoff P losses with subsurface litter application observed elsewhere but highlight the modifying effect of soil hydrology on this technology's ability to minimize P loss in runoff. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H23D1712K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H23D1712K">Surface-subsurface turbulent interaction at the interface of a permeable bed: influence of the wall permeability</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kim, T.; Blois, G.; Best, J.; Christensen, K. T. 2017-12-01 Coarse-gravel river beds possess a high degree of permeability. Flow interactions between surface and subsurface flow across the bed interface is key to a number of natural processes occurring in the hyporheic zone. In fact, it is increasingly recognized that these interactions drive mass, momentum and energy transport across the interface, and consequently control biochemical processes as well as stability of sediments. The current study explores the role of the wall permeability in surface and subsurface flow interaction under controlled experimental conditions on a physical model of a gravel bed. The present wall model was constructed by five layers of cubically arranged spheres (d=25.4mm, where d is a diameter) providing 48% of porosity. Surface topography was removed by cutting half of a diameter on the top layer of spheres to render the flow surface smooth and highlight the impact of the permeability on the overlying flow. An impermeable smooth wall was also considered as a baseline of comparison for the permeable wall flow. To obtain basic flow statistics, low-frame-rate high-resolution PIV measurements were performed first in the streamwise-wall-normal (x-y) plane and refractive-index matching was employed to optically access the flow within the permeable wall. Time-resolved PIV experiments in the same facility were followed to investigate the flow interaction across the wall interface in sptaio-temporal domain. In this paper, a detailed analysis of the first and second order velocity statistics as well as the amplitude modulation for the flow overlying the permeable smooth wall will be presented. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B53D1983H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B53D1983H">Multi-year coupled biogeochemical and biophysical impacts of restoring drained agricultural peatlands to wetlands across the Sacramento-San Joaquin Delta, California, USA.</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hemes, K. S.; Eichelmann, E.; Chamberlain, S.; Knox, S. H.; Oikawa, P.; Sturtevant, C.; Verfaillie, J. G.; Baldocchi, D. D. 2017-12-01 Globally, delta ecosystems are critical for human livelihoods, but are at increasingly greater risk of degradation. The Sacramento-San Joaquin River Delta (`Delta') has been subsiding dramatically, losing close to 100 Tg of carbon since the mid 19th century due in large part to agriculture-induced oxidation of the peat soils through drainage and cultivation. Efforts to re-wet the peat soils through wetland restoration are attractive as climate mitigation activities. While flooded wetland systems have the potential to sequester significant amounts of carbon as photosynthesis outpaces aerobic respiration, the highly-reduced conditions can result in significant methane emissions. This study will utilize three years (2014-2016) of continuous, gap-filled, CO2 and CH4 flux data from a mesonetwork of seven eddy covariance towers in the Delta to compute GHG budgets for the restored wetlands and agricultural baseline sites measured. Along with biogeochemical impacts of wetland restoration, biophysical impacts such as changes in reflectance, energy partitioning, and surface roughness, can have significant local to regional impacts on air temperature and heat fluxes. We hypothesize that despite flooded wetlands reducing albedo, wetland land cover will cool the near-surface air temperature due to increased net radiation being preferentially partitioned into latent heat flux and rougher canopy conditions allowing for more turbulent mixing with the atmosphere. This study will investigate the seasonal and diurnal patterns of turbulent energy fluxes and the surface properties that drive them. With nascent policy mechanisms set to compensate landowners and farmers for low emission land use practices beyond reforestation, it is essential that policy mechanisms take into consideration how the biophysical impacts of land use change could drive local to regional-scale climatic perturbations, enhancing or attenuating the biogeochemical impacts. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70185228','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70185228">Silica-coated titania and zirconia colloids for subsurface transport field experiments</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Ryan, Joseph N.; Elimelech, Menachem; Baeseman, Jenny L.; Magelky, Robin D. 2000-01-01 Silica-coated titania (TiO2) and zirconia (ZrO2) colloids were synthesized in two sizes to provide easily traced mineral colloids for subsurface transport experiments. Electrophoretic mobility measurements showed that coating with silica imparted surface properties similar to pure silica to the titania and zirconia colloids. Measurements of steady electrophoretic mobility and size (by dynamic light scattering) over a 90-day period showed that the silica-coated colloids were stable to aggregation and loss of coating. A natural gradient field experiment conducted in an iron oxide-coated sand and gravel aquifer also showed that the surface properties of the silica-coated colloids were similar. Colloid transport was traced at μg L-1 concentrations by inductively coupled plasma-atomic emission spectroscopy measurement of Ti and Zr in acidified samples. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020074590&hterms=cycling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D50%26Ntt%3Dcycling','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020074590&hterms=cycling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D50%26Ntt%3Dcycling">Biogeochemical Cycling</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Bebout, Brad; Fonda, Mark (Technical Monitor) 2002-01-01 This lecture will introduce the concept of biogeochemical cycling. The roles of microbes in the cycling of nutrients, production and consumption of trace gases, and mineralization will be briefly introduced. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016usc..confE..13S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016usc..confE..13S">Active Region Formation and Subsurface Structure</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Stein, F.; Nordlund, Robert A. 2016-10-01 We present results from emerging magnetic flux simulations showing how several different active regions form and their very different subsurface structures. The simulations assumed an infinite sheet of uniform, untwisted, horizontal field advected into the computational domain by inflows at a depth of 20 Mm. Results from two different horizontal field strengths, 1 and 5 kG, will be presented. Convective up and down flows buckle the horizontal field into Omega and U loops. Upflows and magnetic buoyancy carry the field toward the surface, while fast downflows pin down the field. Small (granular) convective motions, near the surface, shred the emerging field into fine filaments that emerge as the observed "pepper and salt" pattern. The large (supergranular) motions, at depth, keep the overall loop structure intact, so that as the overall omega-loop emerges through the surface the opposite polarity fields counter-stream into large unipolar flux concentrations producing first pores which then coalesce into spots. These tend to be located over the supergranular downflow lanes near the bottom of the domain. The pores and spots exhibit a great variety of subsurface field structures - from monolithic but twisted bundles to intertwined separate spaghetti sturctures. We will show movies of the surface evolution of the field and emergent continuum intensity and of the subsurface evolution of the magnetic field lines. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.5662S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.5662S">Modeling Coupled Movement of Water, Vapor, and Energy in Soils and at the Soil-Atmosphere Interface Using HYDRUS</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Simunek, Jiri; Brunetti, Giuseppe; Saito, Hirotaka; Bristow, Keith 2017-04-01 Mass and energy fluxes in the subsurface are closely coupled and cannot be evaluated without considering their mutual interactions. However, only a few numerical models consider coupled water, vapor and energy transport in both the subsurface and at the soil-atmosphere interface. While hydrological and thermal processes in the subsurface are commonly implemented in existing models, which often consider both isothermally and thermally induced water and vapor flow, the interactions at the soil-atmosphere interface are often simplified, and the effects of slope inclination, slope azimuth, variable surface albedo and plant shading on incoming radiation and spatially variable surface mass and energy balance, and consequently on soil moisture and temperature distributions, are rarely considered. In this presentation we discuss these missing elements and our attempts to implement them into the HYDRUS model. We demonstrate implications of some of these interactions and their impact on the spatial distributions of soil temperature and water content, and their effect on soil evaporation. Additionally, we will demonstrate the use of the HYDRUS model to simulate processes relevant to the ground source heat pump systems. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H23D1713P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H23D1713P">Residence-time framework for modeling multicomponent reactive transport in stream hyporheic zones</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Painter, S. L.; Coon, E. T.; Brooks, S. C. 2017-12-01 Process-based models for transport and transformation of nutrients and contaminants in streams require tractable representations of solute exchange between the stream channel and biogeochemically active hyporheic zones. Residence-time based formulations provide an alternative to detailed three-dimensional simulations and have had good success in representing hyporheic exchange of non-reacting solutes. We extend the residence-time formulation for hyporheic transport to accommodate general multicomponent reactive transport. To that end, the integro-differential form of previous residence time models is replaced by an equivalent formulation based on a one-dimensional advection dispersion equation along the channel coupled at each channel location to a one-dimensional transport model in Lagrangian travel-time form. With the channel discretized for numerical solution, the associated Lagrangian model becomes a subgrid model representing an ensemble of streamlines that are diverted into the hyporheic zone before returning to the channel. In contrast to the previous integro-differential forms of the residence-time based models, the hyporheic flowpaths have semi-explicit spatial representation (parameterized by travel time), thus allowing coupling to general biogeochemical models. The approach has been implemented as a stream-corridor subgrid model in the open-source integrated surface/subsurface modeling software ATS. We use bedform-driven flow coupled to a biogeochemical model with explicit microbial biomass dynamics as an example to show that the subgrid representation is able to represent redox zonation in sediments and resulting effects on metal biogeochemical dynamics in a tractable manner that can be scaled to reach scales. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Geomo.303..122P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Geomo.303..122P">Coupled three-layer model for turbulent flow over large-scale roughness: On the hydrodynamics of boulder-bed streams</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Pan, Wen-hao; Liu, Shi-he; Huang, Li 2018-02-01 This study developed a three-layer velocity model for turbulent flow over large-scale roughness. Through theoretical analysis, this model coupled both surface and subsurface flow. Flume experiments with flat cobble bed were conducted to examine the theoretical model. Results show that both the turbulent flow field and the total flow characteristics are quite different from that in the low gradient flow over microscale roughness. The velocity profile in a shallow stream converges to the logarithmic law away from the bed, while inflecting over the roughness layer to the non-zero subsurface flow. The velocity fluctuations close to a cobble bed are different from that of a sand bed, and it indicates no sufficiently large peak velocity. The total flow energy loss deviates significantly from the 1/7 power law equation when the relative flow depth is shallow. Both the coupled model and experiments indicate non-negligible subsurface flow that accounts for a considerable proportion of the total flow. By including the subsurface flow, the coupled model is able to predict a wider range of velocity profiles and total flow energy loss coefficients when compared with existing equations. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5549742','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5549742">Effects of rainfall patterns and land cover on the subsurface flow generation of sloping Ferralsols in southern China</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Yang, Jie; Tang, Chongjun; Chen, Lihua; Liu, Yaojun; Wang, Lingyun 2017-01-01 Rainfall patterns and land cover are two important factors that affect the runoff generation process. To determine the surface and subsurface flows associated with different rainfall patterns on sloping Ferralsols under different land cover types, observational data related to surface and subsurface flows from 5 m × 15 m plots were collected from 2010 to 2012. The experiment was conducted to assess three land cover types (grass, litter cover and bare land) in the Jiangxi Provincial Soil and Water Conservation Ecological Park. During the study period, 114 natural rainfall events produced subsurface flow and were divided into four groups using k-means clustering according to rainfall duration, rainfall depth and maximum 30-min rainfall intensity. The results showed that the total runoff and surface flow values were highest for bare land under all four rainfall patterns and lowest for the covered plots. However, covered plots generated higher subsurface flow values than bare land. Moreover, the surface and subsurface flows associated with the three land cover types differed significantly under different rainfall patterns. Rainfall patterns with low intensities and long durations created more subsurface flow in the grass and litter cover types, whereas rainfall patterns with high intensities and short durations resulted in greater surface flow over bare land. Rainfall pattern I had the highest surface and subsurface flow values for the grass cover and litter cover types. The highest surface flow value and lowest subsurface flow value for bare land occurred under rainfall pattern IV. Rainfall pattern II generated the highest subsurface flow value for bare land. Therefore, grass or litter cover are able to convert more surface flow into subsurface flow under different rainfall patterns. The rainfall patterns studied had greater effects on subsurface flow than on total runoff and surface flow for covered surfaces, as well as a greater effect on surface flows associated </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26960564','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26960564">Local control on precipitation in a fully coupled climate-hydrology model.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Larsen, Morten A D; Christensen, Jens H; Drews, Martin; Butts, Michael B; Refsgaard, Jens C 2016-03-10 The ability to simulate regional precipitation realistically by climate models is essential to understand and adapt to climate change. Due to the complexity of associated processes, particularly at unresolved temporal and spatial scales this continues to be a major challenge. As a result, climate simulations of precipitation often exhibit substantial biases that affect the reliability of future projections. Here we demonstrate how a regional climate model (RCM) coupled to a distributed hydrological catchment model that fully integrates water and energy fluxes between the subsurface, land surface, plant cover and the atmosphere, enables a realistic representation of local precipitation. Substantial improvements in simulated precipitation dynamics on seasonal and longer time scales is seen for a simulation period of six years and can be attributed to a more complete treatment of hydrological sub-surface processes including groundwater and moisture feedback. A high degree of local influence on the atmosphere suggests that coupled climate-hydrology models have a potential for improving climate projections and the results further indicate a diminished need for bias correction in climate-hydrology impact studies. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4785381','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4785381">Local control on precipitation in a fully coupled climate-hydrology model</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Larsen, Morten A. D.; Christensen, Jens H.; Drews, Martin; Butts, Michael B.; Refsgaard, Jens C. 2016-01-01 The ability to simulate regional precipitation realistically by climate models is essential to understand and adapt to climate change. Due to the complexity of associated processes, particularly at unresolved temporal and spatial scales this continues to be a major challenge. As a result, climate simulations of precipitation often exhibit substantial biases that affect the reliability of future projections. Here we demonstrate how a regional climate model (RCM) coupled to a distributed hydrological catchment model that fully integrates water and energy fluxes between the subsurface, land surface, plant cover and the atmosphere, enables a realistic representation of local precipitation. Substantial improvements in simulated precipitation dynamics on seasonal and longer time scales is seen for a simulation period of six years and can be attributed to a more complete treatment of hydrological sub-surface processes including groundwater and moisture feedback. A high degree of local influence on the atmosphere suggests that coupled climate-hydrology models have a potential for improving climate projections and the results further indicate a diminished need for bias correction in climate-hydrology impact studies. PMID:26960564 </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active">19</li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active">20</li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.B21A0339P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.B21A0339P">Biogeochemical Controls on Biodegradation of MC252 Oil:Sand Aggregates on a Rapidly Eroding Coastal Headland Beach</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Pardue, J.; Elango, V.; Urbano, M.; Lemelle, K. 2012-12-01 dramatically different in appearance and have a distinctive chemical signature indicative of different rates of weathering. Supratidal surface samples were depleted in n-alkanes and lower-molecular weight PAHs. Geochemically, aggregates located in these environments had low salinities (1.3-1.5 ppt), O2 at near saturation throughout the aggregates and nutrient concentrations (N and P) significantly lower than SSRBs deposited in the intertidal and subtidal. Intertidal and subtidal subsurface oil samples were characterized by elevated nutrient concentrations and salinities consistent with regular seawater inundation. Complete inundation leads to O2 consumption in the aggregates after several days. Despite the presence of elevated nutrients, PAHs and n-alkanes were comparatively unweathered in the subtidal subsurface samples consistent with O2 limitations. Sequences of known PAH degraders were isolated from the supratidal and intertidal aggregates. The results to be presented support the hypothesis that SSRBs deposited at different locations on the beach have different biogeochemical characteristics . These characteristics are due, in part, to their location on the landscape. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001JGR...10630923R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001JGR...10630923R">Importance of solar subsurface heating in ocean general circulation models</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rochford, Peter A.; Kara, A. Birol; Wallcraft, Alan J.; Arnone, Robert A. 2001-12-01 The importance of subsurface heating on surface mixed layer properties in an ocean general circulation model (OGCM) is examined using attenuation of solar irradiance with depth below the ocean surface. The depth-dependent attenuation of subsurface heating is given by global monthly mean fields for the attenuation of photosynthetically available radiation (PAR), kPAR. These global fields of kPAR are derived from Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data on the spectral diffuse attenuation coefficient at 490 nm (k490), and have been processed to have the smoothly varying and continuous coverage necessary for use in OGCM applications. These monthly fields provide the first complete global data sets of subsurface optical fields that can be used for OGCM applications of subsurface heating and bio-optical processes. The effect on global OGCM prediction of sea surface temperature (SST) and surface mixed layer depth (MLD) is examined when solar heating, as given by monthly mean kPAR and PAR fields, is included in the model. It is found that subsurface heating yields a marked increase in the SST predictive skill of the OGCM at low latitudes. No significant improvement in MLD predictive skill is obtained when including subsurface heating. Use of the monthly mean kPAR produces an SST decrease of up to 0.8°C and a MLD increase of up to only 4-5 m for climatological surface forcing, with this primarily confined to the equatorial regions. Remarkably, a constant kPAR value of 0.06 m-1, which is indicative of optically clear open ocean conditions, is found to serve very well for OGCM prediction of SST and MLD over most of the global ocean. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H13C1117R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H13C1117R">The influence of subsurface hydrodynamics on convective precipitation</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rahman, A. S. M. M.; Sulis, M.; Kollet, S. J. 2014-12-01 The terrestrial hydrological cycle comprises complex processes in the subsurface, land surface, and atmosphere, which are connected via complex non-linear feedback mechanisms. The influence of subsurface hydrodynamics on land surface mass and energy fluxes has been the subject of previous studies. Several studies have also investigated the soil moisture-precipitation feedback, neglecting however the connection with groundwater dynamics. The objective of this study is to examine the impact of subsurface hydrodynamics on convective precipitation events via shallow soil moisture and land surface processes. A scale-consistent Terrestrial System Modeling Platform (TerrSysMP) that consists of an atmospheric model (COSMO), a land surface model (CLM), and a three-dimensional variably saturated groundwater-surface water flow model (ParFlow), is used to simulate hourly mass and energy fluxes over days with convective rainfall events over the Rur catchment, Germany. In order to isolate the effect of groundwater dynamics on convective precipitation, two different model configurations with identical initial conditions are considered. The first configuration allows the groundwater table to evolve through time, while a spatially distributed, temporally constant groundwater table is prescribed as a lower boundary condition in the second configuration. The simulation results suggest that groundwater dynamics influence land surface soil moisture, which in turn affects the atmospheric boundary layer (ABL) height by modifying atmospheric thermals. It is demonstrated that because of this sensitivity of ABL height to soil moisture-temperature feedback, the onset and magnitude of convective precipitation is influenced by subsurface hydrodynamics. Thus, the results provide insight into the soil moisture-precipitation feedback including groundwater dynamics in a physically consistent manner by closing the water cycle from aquifers to the atmosphere. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990079376&hterms=use+remote+sensing&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Duse%2Bremote%2Bsensing','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990079376&hterms=use+remote+sensing&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Duse%2Bremote%2Bsensing">Use of Ocean Remote Sensing Data to Enhance Predictions with a Coupled General Circulation Model</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Rienecker, Michele M. 1999-01-01 Surface height, sea surface temperature and surface wind observations from satellites have given a detailed time sequence of the initiation and evolution of the 1997/98 El Nino. The data have beet complementary to the subsurface TAO moored data in their spatial resolution and extent. The impact of satellite observations on seasonal prediction in the tropical Pacific using a coupled ocean-atmosphere general circulation model will be presented. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780061111&hterms=abbott+lab&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dabbott%2Blab','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780061111&hterms=abbott+lab&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dabbott%2Blab">Orbital radar evidence for lunar subsurface layering in Maria Serenitatis and Crisium</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Peeples, W. J.; Sill, W. R.; May, T. W.; Ward, S. H.; Phillips, R. J.; Jordan, R. L.; Abbott, E. A.; Killpack, T. J. 1978-01-01 Data from the lunar-orbiting Apollo 17 radar sounding experiment (60-m wavelength) have been examined in both digital and holographic formats, and it is concluded that there are two subsurface radar reflectors below the surface in Mare Serenitatis and one reflector below the surface in Mare Crisium. The mean apparent depths of the reflectors below the surface of the former Mare are 0.9 and 1.6 km, while the reflector below the surface of the latter Mare has a mean depth of 1.4 km. These reflectors represent basin-wide subsurface interfaces. Techniques for reducing surface backscatter (clutter) in the data are described, and reasons for thinking that the distinct alignments in radar returns represent subsurface reflecting horizons are explained </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018SPIE10585E..0RV','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018SPIE10585E..0RV">Image-based overlay and alignment metrology through optically opaque media with sub-surface probe microscopy</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> van Es, Maarten H.; Mohtashami, Abbas; Piras, Daniele; Sadeghian, Hamed 2018-03-01 Nondestructive subsurface nanoimaging through optically opaque media is considered to be extremely challenging and is essential for several semiconductor metrology applications including overlay and alignment and buried void and defect characterization. The current key challenge in overlay and alignment is the measurement of targets that are covered by optically opaque layers. Moreover, with the device dimensions moving to the smaller nodes and the issue of the so-called loading effect causing offsets between between targets and product features, it is increasingly desirable to perform alignment and overlay on product features or so-called on-cell overlay, which requires higher lateral resolution than optical methods can provide. Our recently developed technique known as SubSurface Ultrasonic Resonance Force Microscopy (SSURFM) has shown the capability for high-resolution imaging of structures below a surface based on (visco-)elasticity of the constituent materials and as such is a promising technique to perform overlay and alignment with high resolution in upcoming production nodes. In this paper, we describe the developed SSURFM technique and the experimental results on imaging buried features through various layers and the ability to detect objects with resolution below 10 nm. In summary, the experimental results show that the SSURFM is a potential solution for on-cell overlay and alignment as well as detecting buried defects or voids and generally metrology through optically opaque layers. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.B51B0364A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.B51B0364A">Biogeochemical Reactions Under Simulated Europa Ocean Conditions</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Amashukeli, X.; Connon, S. A.; Gleeson, D. F.; Kowalczyk, R. S.; Pappalardo, R. T. 2007-12-01 Galileo data have demonstrated the probable presence of a liquid water ocean on Europa, and existence of salts and carbon dioxide in the satellite's surface ice (e.g., Carr et al., 1998; McCord et al., 1999, Pappalardo et al., 1999; Kivelson et al., 2000). Subsequently, the discovery of chemical signatures of extinct or extant life in Europa's ocean and on its surface became a distinct possibility. Moreover, understanding of Europa's potential habitability is now one of the major goals of the Europa Orbiter Flagship mission. It is likely, that in the early stages of Europa's ocean formation, moderately alkaline oceanic sulfate-carbonate species and a magnetite-silicate mantel could have participated in low-temperature biogeochemical sulfur, iron and carbon cycles facilitated by primitive organisms (Zolotov and Shock, 2004). If periodic supplies of fresh rock and sulfate-carbonate ions are available in Europa's ocean, then an exciting prospect exists that life may be present in Europa's ocean today. In our laboratory, we began the study of the plausible biogeochemical reactions under conditions appropriate to Europa's ocean using barophilic psychrophilic organisms that thrive under anaerobic conditions. In the near absence of abiotic synthetic pathways due to low Europa's temperatures, the biotic synthesis may present a viable opportunity for the formation of the organic and inorganic compounds under these extreme conditions. This work is independent of assumptions regarding hydrothermal vents at Europa's ocean floor or surface-derived oxidant sources. For our studies, we have fabricated a high-pressure (5,000 psi) reaction vessel that simulates aqueous conditions on Europa. We were also successful at reviving barophilic psychrophilic strains of Shewanella bacterium, which serve as test organisms in this investigation. Currently, facultative barophilic psychrophilic stains of Shewanella are grown in the presence of ferric food source; the strains exhibiting iron </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JCHyd.201...19C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JCHyd.201...19C">Long-term ERT monitoring of biogeochemical changes of an aged hydrocarbon contamination</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Caterina, David; Flores Orozco, Adrian; Nguyen, Frédéric 2017-06-01 Adequate management of contaminated sites requires information with improved spatio-temporal resolution, in particular to assess bio-geochemical processes, such as the transformation and degradation of contaminants, precipitation of minerals or changes in groundwater geochemistry occurring during and after remediation procedures. Electrical Resistivity Tomography (ERT), a geophysical method sensitive to pore-fluid and pore-geometry properties, permits to gain quasi-continuous information about subsurface properties in real-time and has been consequently widely used for the characterization of hydrocarbon-impacted sediments. However, its application for the long-term monitoring of processes accompanying natural or engineered bioremediation is still difficult due to the poor understanding of the role that biogeochemical processes play in the electrical signatures. For in-situ studies, the task is further complicated by the variable signal-to-noise ratio and the variations of environmental parameters leading to resolution changes in the electrical images. In this work, we present ERT imaging results for data collected over a period of two years on a site affected by a diesel fuel contamination and undergoing bioremediation. We report low electrical resistivity anomalies in areas associated to the highest contaminant concentrations likely due transformations of the contaminant due to microbial activity and accompanying release of metabolic products. We also report large seasonal variations of the bulk electrical resistivity in the contaminated areas in correlation with temperature and groundwater level fluctuations. However, the amplitude of bulk electrical resistivity variations largely exceeds the amplitude expected given existing petrophysical models. Our results suggest that the variations in electrical properties are mainly controlled by microbial activity which in turn depends on soil temperature and hydrogeological conditions. Therefore, ERT can be suggested as </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21244990','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21244990">High-spatial-resolution sub-surface imaging using a laser-based acoustic microscopy technique.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Balogun, Oluwaseyi; Cole, Garrett D; Huber, Robert; Chinn, Diane; Murray, Todd W; Spicer, James B 2011-01-01 Scanning acoustic microscopy techniques operating at frequencies in the gigahertz range are suitable for the elastic characterization and interior imaging of solid media with micrometer-scale spatial resolution. Acoustic wave propagation at these frequencies is strongly limited by energy losses, particularly from attenuation in the coupling media used to transmit ultrasound to a specimen, leading to a decrease in the depth in a specimen that can be interrogated. In this work, a laser-based acoustic microscopy technique is presented that uses a pulsed laser source for the generation of broadband acoustic waves and an optical interferometer for detection. The use of a 900-ps microchip pulsed laser facilitates the generation of acoustic waves with frequencies extending up to 1 GHz which allows for the resolution of micrometer-scale features in a specimen. Furthermore, the combination of optical generation and detection approaches eliminates the use of an ultrasonic coupling medium, and allows for elastic characterization and interior imaging at penetration depths on the order of several hundred micrometers. Experimental results illustrating the use of the laser-based acoustic microscopy technique for imaging micrometer-scale subsurface geometrical features in a 70-μm-thick single-crystal silicon wafer with a (100) orientation are presented. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.S53A0655C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.S53A0655C">Characterization of the Subsurface Using Vp, Vs, Vp/Vs, and Poisson's Ratio from Body and Surface Waves</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Catchings, R. 2017-12-01 P- and S-wave propagation differ in varying materials in the Earth's crust. As a result, combined measurements of P- and S-wave data can be used to infer properties of the shallow crust, including bulk composition, fluid saturation, faulting and fracturing, seismic velocities, reflectivity, and general structures. Ratios of P- to S-wave velocities and Poisson's ratio, which can be derived from the P- and S-wave data, can be particularly diagnostic of subsurface materials and their physical state. In field studies, S-wave data can be obtained directly with S-wave sources or from surface waves associated with P-wave sources. P- and S-wave data can be processed using reflection, refraction, and surface-wave-analysis methods. With the combined data, unconsolidated sediments, consolidated sediments, and rocks can be differentiated on the basis of seismic velocities and their ratios, as can saturated versus unsaturated sediments. We summarize studies where we have used combined P- and S-wave measurements to reliably map the top of ground water, prospect for minerals, locate subsurface faults, locate basement interfaces, determine basin shapes, and measure shear-wave velocities (with calculated Vs30), and other features of the crust that are important for hazards, engineering, and exploration purposes. When compared directly, we find that body waves provide more accurate measures than surface waves. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28612336','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28612336">Ammonia, phosphate, phenol, and copper(II) removal from aqueous solution by subsurface and surface flow constructed wetland.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Mojiri, Amin; Ahmad, Zakiah; Tajuddin, Ramlah Mohd; Arshad, Mohd Fadzil; Gholami, Ali 2017-07-01 Water pollution is a global problem. During current study, ammonia, phosphate, phenol, and copper(II) were removed from aqueous solution by subsurface and surface flow constructed wetland. In current investigation, distilled water was polluted with four contaminants including ammonia, phosphate, copper (Cu), and phenol. Response surface methodology and central composite design were applied to optimize pollutant removal during treatment by subsurface flow constructed wetland (SSFCW). Contact time (12 to 80 h) and initial pollutant concentration (20 to 85 mg/L) were selected as independent factors; some upper and lower ranges were also monitored for accuracy. In SSFCW, water hyacinth transplanted in two substrate layers, namely zeolite and cockle shell. SSFCW removed 87.7, 81.4, 74.7, and 54.9% of ammonia, phosphate, Cu, and phenol, respectively, at optimum contact time (64.5 h) and initial pollutant concentration (69.2 mg/L). Aqueous solution was moved to a surface flow constructed wetland (SFCW) after treating via SSFCW at optimum conditions. In SFCW, Typha was transplanted to a fixed powdered substrate layer, including bentonite, zeolite, and cockle shell. SFCW could develop performance of this combined system and could improve elimination efficacy of the four contaminants to 99.99%. So this combined CW showed a good performance in removing pollutants. Graphical abstract Wetlands arrangement for treating aqueous solution in current study. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/2015/1043/downloads/OFR2015-1043.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/2015/1043/downloads/OFR2015-1043.pdf">Surface and subsurface microgravity data in the vicinity of Sanford Underground Research Facility, Lead, South Dakota</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Kennedy, Jeffrey R.; Koth, Karl R.; Carruth, Rob 2015-01-01 Absolute gravity data were collected at 32 stations in the vicinity of the Sanford Underground Research Facility from 2007 through 2014 for the purpose of monitoring groundwater storage change during dewatering of the former Homestake gold mine in the Black Hills of South Dakota, the largest and deepest underground mine in North America. Eight underground stations are at depths from 300 feet below land surface to 4,850 feet below land surface. Surface stations were located using Global Positioning System observations, and subsurface stations were located on the basis of maps constructed from survey measurements made while the mine was in operation. Gravity varies widely at many stations; however, no consistent temporal trends are present across all stations during the 7-year period of data collection. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1712299H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1712299H">Extrapolating subsurface geometry by surface expressions in transpressional strike slip fault, deduced from analogue experiments with settings of rheology and convergence angle</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hsieh, Shang Yu; Neubauer, Franz 2015-04-01 The internal structure of major strike-slip faults is still poorly understood, particularly how to extrapolate subsurface structures by surface expressions. Series of brittle analogue experiments by Leever et al., 2011 resulted the convergence angle is the most influential factor for surface structures. Further analogue models with different ductile settings allow a better understanding in extrapolating surface structures to the subsurface geometry of strike-slip faults. Fifteen analogue experiments were constructed to represent strike-slip faults in nature in different geological settings. As key parameters investigated in this study include: (a) the angle of convergence, (b) the thickness of brittle layer, (c) the influence of a rheological weak layer within the crust, and (d) influence of a thick and rheologically weak layer at the base of the crust. The experiments are aimed to explain first order structures along major transcurrent strike-slip faults such as the Altyn, Kunlun, San Andrea and Greendale (Darfield earthquake 2010) faults. The preliminary results show that convergence angle significantly influences the overall geometry of the transpressional system with greater convergence angles resulting in wider fault zones and higher elevation. Different positions, densities and viscosities of weak rheological layers have not only different surface expressions but also affect the fault geometry in the subsurface. For instance, rheological weak material in the bottom layer results in stretching when experiment reaches a certain displacement and a buildup of a less segmented, wide positive flower structure. At the surface, a wide fault valley in the middle of the fault zone is the reflection of stretching along the velocity discontinuity at depth. In models with a thin and rheologically weaker layer in the middle of the brittle layer, deformation is distributed over more faults and the geometry of the fault zone below and above the weak zone shows significant </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PhRvB..82s5304R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhRvB..82s5304R">Generalized effective-mass theory of subsurface scanning tunneling microscopy: Application to cleaved quantum dots</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Roy, M.; Maksym, P. A.; Bruls, D.; Offermans, P.; Koenraad, P. M. 2010-11-01 An effective-mass theory of subsurface scanning tunneling microscopy (STM) is developed. Subsurface structures such as quantum dots embedded into a semiconductor slab are considered. States localized around subsurface structures match on to a tail that decays into the vacuum above the surface. It is shown that the lateral variation in this tail may be found from a surface envelope function provided that the effects of the slab surfaces and the subsurface structure decouple approximately. The surface envelope function is given by a weighted integral of a bulk envelope function that satisfies boundary conditions appropriate to the slab. The weight function decays into the slab inversely with distance and this slow decay explains the subsurface sensitivity of STM. These results enable STM images to be computed simply and economically from the bulk envelope function. The method is used to compute wave-function images of cleaved quantum dots and the computed images agree very well with experiment. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013GMD.....6.1977F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013GMD.....6.1977F">A generic biogeochemical module for Earth system models: Next Generation BioGeoChemical Module (NGBGC), version 1.0</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Fang, Y.; Huang, M.; Liu, C.; Li, H.; Leung, L. R. 2013-11-01 Physical and biogeochemical processes regulate soil carbon dynamics and CO2 flux to and from the atmosphere, influencing global climate changes. Integration of these processes into Earth system models (e.g., community land models (CLMs)), however, currently faces three major challenges: (1) extensive efforts are required to modify modeling structures and to rewrite computer programs to incorporate new or updated processes as new knowledge is being generated, (2) computational cost is prohibitively expensive to simulate biogeochemical processes in land models due to large variations in the rates of biogeochemical processes, and (3) various mathematical representations of biogeochemical processes exist to incorporate different aspects of fundamental mechanisms, but systematic evaluation of the different mathematical representations is difficult, if not impossible. To address these challenges, we propose a new computational framework to easily incorporate physical and biogeochemical processes into land models. The new framework consists of a new biogeochemical module, Next Generation BioGeoChemical Module (NGBGC), version 1.0, with a generic algorithm and reaction database so that new and updated processes can be incorporated into land models without the need to manually set up the ordinary differential equations to be solved numerically. The reaction database consists of processes of nutrient flow through the terrestrial ecosystems in plants, litter, and soil. This framework facilitates effective comparison studies of biogeochemical cycles in an ecosystem using different conceptual models under the same land modeling framework. The approach was first implemented in CLM and benchmarked against simulations from the original CLM-CN code. A case study was then provided to demonstrate the advantages of using the new approach to incorporate a phosphorus cycle into CLM. To our knowledge, the phosphorus-incorporated CLM is a new model that can be used to simulate phosphorus </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CG.....77....8L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CG.....77....8L">TOUGH2Biot - A simulator for coupled thermal-hydrodynamic-mechanical processes in subsurface flow systems: Application to CO2 geological storage and geothermal development</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lei, Hongwu; Xu, Tianfu; Jin, Guangrong 2015-04-01 Coupled thermal-hydrodynamic-mechanical processes have become increasingly important in studying the issues affecting subsurface flow systems, such as CO2 sequestration in deep saline aquifers and geothermal development. In this study, a mechanical module based on the extended Biot consolidation model was developed and incorporated into the well-established thermal-hydrodynamic simulator TOUGH2, resulting in an integrated numerical THM simulation program TOUGH2Biot. A finite element method was employed to discretize space for rock mechanical calculation and the Mohr-Coulomb failure criterion was used to determine if the rock undergoes shear-slip failure. Mechanics is partly coupled with the thermal-hydrodynamic processes and gives feedback to flow through stress-dependent porosity and permeability. TOUGH2Biot was verified against analytical solutions for the 1D Terzaghi consolidation and cooling-induced subsidence. TOUGH2Biot was applied to evaluate the thermal, hydrodynamic, and mechanical responses of CO2 geological sequestration at the Ordos CCS Demonstration Project, China and geothermal exploitation at the Geysers geothermal field, California. The results demonstrate that TOUGH2Biot is capable of analyzing change in pressure and temperature, displacement, stress, and potential shear-slip failure caused by large scale underground man-made activity in subsurface flow systems. TOUGH2Biot can also be easily extended for complex coupled process problems in fractured media and be conveniently updated to parallel versions on different platforms to take advantage of high-performance computing. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.9681S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.9681S">Seasonal re-emergence of North Atlantic subsurface ocean temperature anomalies and Northern hemisphere climate</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sinha, Bablu; Blaker, Adam; Duchez, Aurelie; Grist, Jeremy; Hewitt, Helene; Hirschi, Joel; Hyder, Patrick; Josey, Simon; Maclachlan, Craig; New, Adrian 2017-04-01 A high-resolution coupled ocean atmosphere model is used to study the effects of seasonal re-emergence of North Atlantic subsurface ocean temperature anomalies on northern hemisphere winter climate. A 50-member control simulation is integrated from September 1 to 28 February and compared with a similar ensemble with perturbed ocean initial conditions. The perturbation consists of a density-compensated subsurface (deeper than 180m) temperature anomaly corresponding to the observed subsurface temperature anomaly for September 2010, which is known to have re-emerged at the ocean surface in subsequent months. The perturbation is confined to the North Atlantic Ocean between the Equator and 65 degrees North. The model has 1/4 degree horizontal resolution in the ocean and the experiment is repeated for two atmosphere horizontal resolutions ( 60km and 25km) in order to determine whether the sensitivity of the atmosphere to re-emerging temperature anomalies is dependent on resolution. The ensembles display a wide range of reemergence behaviour, in some cases re-emergence occurs by November, in others it is delayed or does not occur at all. A wide range of amplitudes of the re-emergent temperature anomalies is observed. In cases where re-emergence occurs, there is a marked effect on both the regional (North Atlantic and Europe) and hemispheric surface pressure and temperature patterns. The results highlight a potentially important process whereby ocean memory of conditions up to a year earlier can significantly enhance seasonal forecast skill. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.7541L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.7541L">Revising Hydrology of a Land Surface Model</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Le Vine, Nataliya; Butler, Adrian; McIntyre, Neil; Jackson, Christopher 2015-04-01 Land Surface Models (LSMs) are key elements in guiding adaptation to the changing water cycle and the starting points to develop a global hyper-resolution model of the terrestrial water, energy and biogeochemical cycles. However, before this potential is realised, there are some fundamental limitations of LSMs related to how meaningfully hydrological fluxes and stores are represented. An important limitation is the simplistic or non-existent representation of the deep subsurface in LSMs; and another is the lack of connection of LSM parameterisations to relevant hydrological information. In this context, the paper uses a case study of the JULES (Joint UK Land Environmental Simulator) LSM applied to the Kennet region in Southern England. The paper explores the assumptions behind JULES hydrology, adapts the model structure and optimises the coupling with the ZOOMQ3D regional groundwater model. The analysis illustrates how three types of information can be used to improve the model's hydrology: a) observations, b) regionalized information, and c) information from an independent physics-based model. It is found that: 1) coupling to the groundwater model allows realistic simulation of streamflows; 2) a simple dynamic lower boundary improves upon JULES' stationary unit gradient condition; 3) a 1D vertical flow in the unsaturated zone is sufficient; however there is benefit in introducing a simple dual soil moisture retention curve; 4) regionalized information can be used to describe soil spatial heterogeneity. It is concluded that relatively simple refinements to the hydrology of JULES and its parameterisation method can provide a substantial step forward in realising its potential as a high-resolution multi-purpose model. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27052662','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27052662">Groundwater-surface water mixing shifts ecological assembly processes and stimulates organic carbon turnover.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Stegen, James C; Fredrickson, James K; Wilkins, Michael J; Konopka, Allan E; Nelson, William C; Arntzen, Evan V; Chrisler, William B; Chu, Rosalie K; Danczak, Robert E; Fansler, Sarah J; Kennedy, David W; Resch, Charles T; Tfaily, Malak 2016-04-07 Environmental transitions often result in resource mixtures that overcome limitations to microbial metabolism, resulting in biogeochemical hotspots and moments. Riverine systems, where groundwater mixes with surface water (the hyporheic zone), are spatially complex and temporally dynamic, making development of predictive models challenging. Spatial and temporal variations in hyporheic zone microbial communities are a key, but understudied, component of riverine biogeochemical function. Here, to investigate the coupling among groundwater-surface water mixing, microbial communities and biogeochemistry, we apply ecological theory, aqueous biogeochemistry, DNA sequencing and ultra-high-resolution organic carbon profiling to field samples collected across times and locations representing a broad range of mixing conditions. Our results indicate that groundwater-surface water mixing in the hyporheic zone stimulates heterotrophic respiration, alters organic carbon composition, causes ecological processes to shift from stochastic to deterministic and is associated with elevated abundances of microbial taxa that may degrade a broad suite of organic compounds. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=105006&keyword=redox+AND+reaction&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=105006&keyword=redox+AND+reaction&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">KINETIC CONTROL OF OXIDATION STATE AT THERMODYNAMICALLY BUFFERED POTENTIALS IN SUBSURFACE WATERS</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Dissolved oxygen (DO) and organic carbon (Corg) are among the highest- and lowest-potential reactants, respectively, of redox couples in natural waters. When DO and Corg are present in subsurface settings, other couples are drawn toward potentials imposed by them, generating a b... </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active">20</li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active">21</li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AcAau.147..445Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AcAau.147..445Y">Surface thermochemical effects on TPS-coupled aerothermodynamics in hypersonic Martian gas flow</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yang, Xiaofeng; Gui, Yewei; Tang, Wei; Du, Yanxia; Liu, Lei; Xiao, Guangming; Wei, Dong 2018-06-01 This paper deals with the surface thermochemical effects on TPS-coupled aerothermodynamics in hypersonic Martian gas flow. An interface condition with finite-rate thermochemistry was established to balance the three-dimensional Navier-Stokes solver and TPS thermal response solver, and a series of coupled simulations of chemical non-equilibrium aerothermodynamics and structure heat transfer with various surface catalycities were performed for hypersonic Mars entries. The analysis of surface thermochemistry reveals that the surface chemical reactions have great contribution to aerodynamic heating, and the temperature-dependence of finite-rate catalysis highly influences the evolution of the coupling aerodynamic heating in the coupling process. For fixed free stream parameters with proper catalytic excitation energy, a "leap" phenomenon of the TPS-coupled heat flux with the coupling time appears in the initial stage of the coupling process, due to the strong thermochemical effects on the TPS surface. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018WRR....54.2487W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018WRR....54.2487W">Estimating Surface/Subsurface Sediment Mixing in Karst Settings Using 7Be Isotopes</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wicks, C. M.; Paylor, R. L.; Bentley, S. J. 2018-03-01 This study shows that the cosmogenic radionuclide beryllium-7 can be used to track sediment movement through caves. The activities of beryllium-7 and cesium-137 were measured in two different karst settings at both surface and subsurface sites before and after storm runoff events. At one site, 7Be-enriched sediment was detected up to 1.5 km along a stream conduit after a moderate storm event; however, the activity of 137Cs was too variable to show a meaningful pattern. The percentages of surface sediment that was found ranged from 0 to 52% along the entire 3 km cave stream and from 33 to 52% along the upper 1.5 km. At the other site, as much as 96% of the sediment initially discharged at the spring during a storm event was fresh surface material that had traveled into and through the cave stream. Moreover, during the 4 day runoff event, approximately 23% of the total suspended sediment flux was estimated to originate from surface erosion with 78% being reworked sediment from within the cave. The data in this study show that cosmogenic radionuclides with multiyear half-lives are too long-lived to track sediment origins in the caves; whereas, 7Be with a 53.2 day half-life, can be used to track movement of sediment along cave streams. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1915619F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1915619F">Cross-compartment evaluation of a fully-coupled hydrometeorological modeling system using comprehensive observation data</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Fersch, Benjamin; Senatore, Alfonso; Kunstmann, Harald 2017-04-01 Fully-coupled hydrometeorological modeling enables investigations about the complex and often non-linear exchange mechanisms among subsurface, land, and atmosphere with respect to water and energy fluxes. The consideration of lateral redistribution of surface and subsurface water in such modeling systems is a crucial enhancement, allowing for a better representation of surface spatial patterns and providing also channel discharge predictions. However, the evaluation of fully-coupled simulations is difficult since the amount of physical detail along with feedback mechanisms leads to high degrees of freedom. Therefore, comprehensive observation data is required to obtain meaningful model configurations. We present a case study for a medium-sized river catchment in southern Germany that includes the calibration of the stand-alone and the evaluation of the fully-coupled WRF-Hydro modeling system with a horizontal resolution of 1 x 1 km2, for the period June to August 2015. ECMWF ERA-Interim reanalysis is used for model driving. Land-surface processes are represented by the Noah-MP land surface model. Land-cover is described by the EU CORINE data set. Observations for model evaluation are obtained from the TERENO Pre-Alpine observatory (http://www.imk-ifu.kit.edu/tereno.php) and are complemented by further measurements from the ScaleX campaign (http://scalex.imk-ifu.kit.edu) such as atmospheric profiles obtained from radiometer sounding and airborne systems as well as soil moisture and -temperature networks. We show how well water budgets and heat-fluxes are being reproduced by the stand-alone WRF, the stand-alone WRF-Hydro and the fully-coupled WRF-Hydro model. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.B53C0546K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.B53C0546K">Electrode Cultivation and Interfacial Electron Transport in Subsurface Microorganisms</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Karbelkar, A. A.; Jangir, Y.; Reese, B. K.; Wanger, G.; Anderson, C.; El-Naggar, M.; Amend, J. 2016-12-01 Continental subsurface environments can present significant energetic challenges to the resident microorganisms. While these environments are geologically diverse, potentially allowing energy harvesting by microorganisms that catalyze redox reactions, many of the abundant electron donors and acceptors are insoluble and therefore not directly bioavailable. Microbes can use extracellular electron transfer (EET) as a metabolic strategy to interact with redox active surfaces. This process can be mimicked on electrode surfaces and hence can lead to enrichment and quantification of subsurface microorganisms A primary bioelectrochemical enrichment with different oxidizing and reducing potentials set up in a single bioreactor was applied in situ to subsurface microorganisms residing in iron oxide rich deposits in the Sanford Underground Research Facility. Secondary enrichment revealed a plethora of classified and unclassified subsurface microbiota on both oxidizing and reducing potentials. From this enrichment, we have isolated a Gram-positive Bacillus along with Gram-negative Cupriavidus and Anaerospora strains (as electrode reducers) and Comamonas (as an electrode oxidizer). The Bacillus and Comamonas isolates were subjected to a detailed electrochemical characterization in half-reactors at anodic and cathodic potentials, respectively. An increase in cathodic current upon inoculation and cyclic voltammetry measurements confirm the hypothesis that Comamonas is capable of electron uptake from electrodes. In addition, measurements of Bacillus on anodes hint towards novel mechanisms that allow EET from Gram-positive bacteria. This study suggests that electrochemical approaches are well positioned to dissect such extracellular interactions that may be prevalent in the subsurface, while using physical electrodes to emulate the microhabitats, redox and geochemical gradients, and the spatially dependent interspecies interactions encountered in the subsurface. Electrochemical </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ThApC.tmp..211D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ThApC.tmp..211D">Impact of intra-seasonal oscillations of Indian summer monsoon on biogeochemical constituents of North Indian Ocean</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Das, D.; Chakrabarty, M.; Goswami, S.; Basu, D.; Chaudhuri, S. 2018-05-01 The intra-seasonal perturbations in the atmospheric weather are closely related to the variability in the ocean circulation. NASA Ocean Biogeochemical Model (NOBM) couples the oceanic general circulation and the radiative forcing. The NOBM model products of nitrate, total chlorophyll, and mixed layer depth (MLD) collected during the period from 1998 to 2007 as well as the sea surface temperature (SST), precipitation, outgoing long wave radiation (OLR), and wind are considered in this study to identify the influence of intra-seasonal oscillation (ISO) of Indian summer monsoon (ISM) on the biogeochemical constituents of Bay of Bengal (BOB) (6°-22° N; 80°-100° E) and Arabian Sea (AS) (3°-17° N; 55°-73.5° E) of North Indian Ocean (NIO). The active and break phases are the most significant components of ISO during ISM. The result of the study reveals that the upper ocean biology and chemistry significantly vary during the said phases of ISM. The nitrate, total chlorophyll, and MLD are observed to be strongly correlated with the ISO of ISM. The result shows that, during ISO of ISM, the concentration of nitrate and chlorophyll is strongly and positively correlated both in BOB and AS. However, the correlation is more in AS, endorsing that the Arabian Sea is more nutrient reach than Bay of Bengal. Nitrate and MLD, on the other hand, are strongly but negatively correlated in the said basins of North Indian Ocean (NIO). The forcing behind the variability of the biogeochemical constituents of BOB and AS during active and break phases of ISM is identified through the analyses of SST, precipitation, OLR, and wind. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=105290&keyword=ocean+AND+climate+AND+changes&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=105290&keyword=ocean+AND+climate+AND+changes&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">INTERACTIVE EFFECTS OF OZONE DEPLETION AND CLIMATE CHANGE ON BIOGEOCHEMICAL CYCLES</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> The effects of ozone depletion on global biogeochemical cycles, via increased UV-B radiation at the Earth's surface, have continued to be documented over the past 4 years. In this report we also document various effects of UV-B that interact with global climate change because the... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1916668Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1916668Z">Fronts and eddies: Engines for biogeochemical variability of the Central Red Sea during winter-spring periods</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zarokanellos, Nikolaos; Jones, Burton 2017-04-01 The central Red Sea (CRS) has been shown to be characterized by significant eddy activity throughout the year. In winter, weakened stratification may lead to enhanced vertical exchange contributing to physical and biogeochemical processes. In winter 2014-2015 we began an extended glider time series to monitor a region in the northern CRS where eddy activity is significant. Remote sensing and glider observations that include CTD, oxygen, CDOM and chlorophyll fluorescence, and multi-wavelength optical backscatter, have been used to characterize the effects of winter mixing and eddy activity in this region. During winter, deep mixing driven by surface cooling and strong winds combined with eddy features, can supply nutrients into the upper layer dramatically modifies the environment from its typically stratified conditions. These mixing events disperse the phytoplankton from the deep chlorophyll maximum throughout the upper mixed layer, and increase the chlorophyll signature detected by ocean color imagery. In addition to the mixing, cyclonic eddies in the region can enhance the vertical displacement of deeper, nutrient containing water toward the euphotic zone contributing to increased chlorophyll concentration and biological productivity. Remote sensing analyses indicate that these eddies also contribute to significant horizontal dispersion including the exchange between the open sea and coastal coral reef ecosystems. During the winter mixing periods, diel fluctuations in phytoplankton biomass have been observed indicative of solar driven plankton dynamics. The biogeochemical response to the subsurface physical processes provides a sensitive indicator to the processes that result from the mixing and eddy dynamics - processes that are not necessarily detectable via remote sensing. In order to understand the seasonal responses, but also the interannual influences on these processes, sustained in situ autonomous platform measurements are essential. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26461444','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26461444">Treatability of organic matter derived from surface and subsurface waters of drinking water catchments.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Awad, John; van Leeuwen, John; Liffner, Joel; Chow, Christopher; Drikas, Mary 2016-02-01 The treatability of NOM present in runoff and subsurface waters from discrete zero-order catchments (ZOCs) with three land management practices (Australian native vegetation, pine plantation, grasslands) on varying soil textures of a closed drinking water reservoir-catchment was investigated. Subsurface water samples were collected by lysimeters and shallow piezometers and surface waters by installation of barriers that diverted waters to collection devices. For small sample volumes collected, a 'micro' jar testing procedure was developed to assess the treatability of organics by enhanced coagulation using alum, under standardised conditions. DOM present in water samples was quantified by measurement of DOC and UV absorbance (at 254 nm) and characterized using these and F-EEM. The mean alum dose rate (mg alum per mg DOC removed or Al/DOC) was found to be lower for DOM from sandy soil ZOCs (21.1 ± 11.0 Al/DOC) than from clayey soil ZOCs (38.6 ± 27.7 Al/DOC). ZOCs with Pinus radiata had prominent litter layers (6.3 ± 2.6 cm), and despite differences in soil textures showed similarity in DOM character in subsurface waters, and in alum dose rates (22.2 ± 5.5 Al/DOC). For sandy soil ZOCs, the lowest alum dose rates (16.5 ± 10.6 Al/DOC) were for waters from native vegetation catchment while, for clayey soil ZOCs, waters from pine vegetation had the lowest alum dose rates (23.0 ± 5.0 Al/DOC). Where ZOCs have a prominent O horizon, soil minerals had no apparent influence on the treatability of DOM. Copyright © 2015 Elsevier Ltd. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1327190-terrestrial-subsurface-ecosystem','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1327190-terrestrial-subsurface-ecosystem">Terrestrial Subsurface Ecosystem</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Wilkins, Michael J.; Fredrickson, Jim K. 2015-10-15 The Earth’s crust is a solid cool layer that overlays the mantle, with a varying thickness of between 30-50 km on continental plates, and 5-10 km on oceanic plates. Continental crust is composed of a variety of igneous, metamorphic, and sedimentary rocks that weather and re-form over geologic cycles lasting millions to billions of years. At the crust surface, these weathered minerals and organic material combine to produce a variety of soils types that provide suitable habitats and niches for abundant microbial diversity (see Chapter 4). Beneath this soil zone is the subsurface. Once thought to be relatively free ofmore » microorganisms, recent estimates have calculated that between 1016-1017 g C biomass (2-19% of Earth’s total biomass) may be present in this environment (Whitman et al., 1998;McMahon and Parnell, 2014). Microbial life in the subsurface exists across a wide range of habitats: in pores associated with relatively shallow unconsolidated aquifer sediments to fractures in bedrock formations that are more than a kilometer deep, where extreme lithostatic pressures and temperatures are encountered. While these different environments contain varying physical and chemical conditions, the absence of light is a constant. Despite this, diverse physiologies and metabolisms enable microorganisms to harness energy and carbon for growth in water-filled pore spaces and fractures. Carbon and other element cycles are driven by microbial activity, which has implications for both natural processes and human activities in the subsurface, e.g., bacteria play key roles in both hydrocarbon formation and degradation. Hydrocarbons are a major focus for human utilization of the subsurface, via oil and gas extraction and potential geologic CO2 sequestration. The subsurface is also utilized or being considered for sequestered storage of high-level radioactive waste from nuclear power generation and residual waste from past production of weapons grade nuclear materials </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=314962','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=314962">Water and nitrogen requirements of subsurface drip irrigated pomegranate</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> Surface drip irrigation is a well-developed practice for both annual and perennial crops. The use of subsurface drip is a well-established practice in many annual row crops, e.g. tomatoes, strawberries, lettuce. However, the use of subsurface drip on perennial crops has been slow to develop. With th... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930051902&hterms=Silicide&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DSilicide','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930051902&hterms=Silicide&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DSilicide">Columnar and subsurface silicide growth with novel molecular beam epitaxy techniques</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Fathauer, R. W.; George, T.; Pike, W. T. 1992-01-01 We have found novel growth modes for epitaxial CoSi2 at high temperatures coupled with Si-rich flux ratios or low deposition rates. In the first of these modes, codeposition of metal and Si at 600-800 C with excess Si leads to the formation of epitaxial silicide columns surrounded by single-crystal Si. During the initial stages of the deposition, the excess Si grows homoepitaxially in between the silicide, which forms islands, so that the lateral growth of the islands is confined. Once a template layer is established by this process, columns of silicide form as a result of selective epitaxy of silicide on silicide and Si on Si. This growth process allows nanometer control over silicide particles in three dimensions. In the second of these modes, a columnar silicide seed layer is used as a template to nucleate subsurface growth of CoSi2. With a 100 nm Si layer covering CoSi2 seeds, Co deposited at 800C and 0.01 nm/s diffuses down to grow on the buried seeds rather than nucleating surface silicide islands. For thicker Si caps or higher deposition rates, the surface concentration of Co exceeds the critical concentration for nucleation of islands, preventing this subsurface growth mode from occurring. Using this technique, single-crystal layers of CoSi2 buried under single-crystal Si caps have been grown. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170006051&hterms=standard+model+physics&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dstandard%2Bmodel%2Bphysics','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170006051&hterms=standard+model+physics&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dstandard%2Bmodel%2Bphysics">Biogeochemical Protocols and Diagnostics for the CMIP6 Ocean Model Intercomparison Project (OMIP)</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Orr, James C.; Najjar, Raymond G.; Aumont, Olivier; Bopp, Laurent; Bullister, John L.; Danabasoglu, Gokhan; Doney, Scott C.; Dunne, John P.; Dutay, Jean-Claude; Graven, Heather; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20170006051'); toggleEditAbsImage('author_20170006051_show'); toggleEditAbsImage('author_20170006051_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20170006051_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20170006051_hide"> 2017-01-01 The Ocean Model Intercomparison Project (OMIP) focuses on the physics and biogeochemistry of the ocean component of Earth system models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6). OMIP aims to provide standard protocols and diagnostics for ocean models, while offering a forum to promote their common assessment and improvement. It also offers to compare solutions of the same ocean models when forced with reanalysis data (OMIP simulations) vs. when integrated within fully coupled Earth system models (CMIP6). Here we detail simulation protocols and diagnostics for OMIP's biogeochemical and inert chemical tracers. These passive-tracer simulations will be coupled to ocean circulation models, initialized with observational data or output from a model spin-up, and forced by repeating the 1948-2009 surface fluxes of heat, fresh water, and momentum. These so-called OMIP-BGC simulations include three inert chemical tracers (CFC-11, CFC-12, SF [subscript] 6) and biogeochemical tracers (e.g., dissolved inorganic carbon, carbon isotopes, alkalinity, nutrients, and oxygen). Modelers will use their preferred prognostic BGC model but should follow common guidelines for gas exchange and carbonate chemistry. Simulations include both natural and total carbon tracers. The required forced simulation (omip1) will be initialized with gridded observational climatologies. An optional forced simulation (omip1-spunup) will be initialized instead with BGC fields from a long model spin-up, preferably for 2000 years or more, and forced by repeating the same 62-year meteorological forcing. That optional run will also include abiotic tracers of total dissolved inorganic carbon and radiocarbon, CTabio and 14CTabio, to assess deep-ocean ventilation and distinguish the role of physics vs. biology. These simulations will be forced by observed atmospheric histories of the three inert gases and CO2 as well as carbon isotope ratios of CO2. OMIP-BGC simulation </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GMD....10.2169O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GMD....10.2169O">Biogeochemical protocols and diagnostics for the CMIP6 Ocean Model Intercomparison Project (OMIP)</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Orr, James C.; Najjar, Raymond G.; Aumont, Olivier; Bopp, Laurent; Bullister, John L.; Danabasoglu, Gokhan; Doney, Scott C.; Dunne, John P.; Dutay, Jean-Claude; Graven, Heather; Griffies, Stephen M.; John, Jasmin G.; Joos, Fortunat; Levin, Ingeborg; Lindsay, Keith; Matear, Richard J.; McKinley, Galen A.; Mouchet, Anne; Oschlies, Andreas; Romanou, Anastasia; Schlitzer, Reiner; Tagliabue, Alessandro; Tanhua, Toste; Yool, Andrew 2017-06-01 The Ocean Model Intercomparison Project (OMIP) focuses on the physics and biogeochemistry of the ocean component of Earth system models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6). OMIP aims to provide standard protocols and diagnostics for ocean models, while offering a forum to promote their common assessment and improvement. It also offers to compare solutions of the same ocean models when forced with reanalysis data (OMIP simulations) vs. when integrated within fully coupled Earth system models (CMIP6). Here we detail simulation protocols and diagnostics for OMIP's biogeochemical and inert chemical tracers. These passive-tracer simulations will be coupled to ocean circulation models, initialized with observational data or output from a model spin-up, and forced by repeating the 1948-2009 surface fluxes of heat, fresh water, and momentum. These so-called OMIP-BGC simulations include three inert chemical tracers (CFC-11, CFC-12, SF6) and biogeochemical tracers (e.g., dissolved inorganic carbon, carbon isotopes, alkalinity, nutrients, and oxygen). Modelers will use their preferred prognostic BGC model but should follow common guidelines for gas exchange and carbonate chemistry. Simulations include both natural and total carbon tracers. The required forced simulation (omip1) will be initialized with gridded observational climatologies. An optional forced simulation (omip1-spunup) will be initialized instead with BGC fields from a long model spin-up, preferably for 2000 years or more, and forced by repeating the same 62-year meteorological forcing. That optional run will also include abiotic tracers of total dissolved inorganic carbon and radiocarbon, CTabio and 14CTabio, to assess deep-ocean ventilation and distinguish the role of physics vs. biology. These simulations will be forced by observed atmospheric histories of the three inert gases and CO2 as well as carbon isotope ratios of CO2. OMIP-BGC simulation protocols are </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4597356','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4597356">Microplastics in Arctic polar waters: the first reported values of particles in surface and sub-surface samples</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Lusher, Amy L.; Tirelli, Valentina; O’Connor, Ian; Officer, Rick 2015-01-01 Plastic, as a form of marine litter, is found in varying quantities and sizes around the globe from surface waters to deep-sea sediments. Identifying patterns of microplastic distribution will benefit an understanding of the scale of their potential effect on the environment and organisms. As sea ice extent is reducing in the Arctic, heightened shipping and fishing activity may increase marine pollution in the area. Microplastics may enter the region following ocean transport and local input, although baseline contamination measurements are still required. Here we present the first study of microplastics in Arctic waters, south and southwest of Svalbard, Norway. Microplastics were found in surface (top 16 cm) and sub-surface (6 m depth) samples using two independent techniques. Origins and pathways bringing microplastic to the Arctic remain unclear. Particle composition (95% fibres) suggests they may either result from the breakdown of larger items (transported over large distances by prevailing currents, or derived from local vessel activity), or input in sewage and wastewater from coastal areas. Concurrent observations of high zooplankton abundance suggest a high probability for marine biota to encounter microplastics and a potential for trophic interactions. Further research is required to understand the effects of microplastic-biota interaction within this productive environment. PMID:26446348 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatSR...514947L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatSR...514947L">Microplastics in Arctic polar waters: the first reported values of particles in surface and sub-surface samples</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lusher, Amy L.; Tirelli, Valentina; O'Connor, Ian; Officer, Rick 2015-10-01 Plastic, as a form of marine litter, is found in varying quantities and sizes around the globe from surface waters to deep-sea sediments. Identifying patterns of microplastic distribution will benefit an understanding of the scale of their potential effect on the environment and organisms. As sea ice extent is reducing in the Arctic, heightened shipping and fishing activity may increase marine pollution in the area. Microplastics may enter the region following ocean transport and local input, although baseline contamination measurements are still required. Here we present the first study of microplastics in Arctic waters, south and southwest of Svalbard, Norway. Microplastics were found in surface (top 16 cm) and sub-surface (6 m depth) samples using two independent techniques. Origins and pathways bringing microplastic to the Arctic remain unclear. Particle composition (95% fibres) suggests they may either result from the breakdown of larger items (transported over large distances by prevailing currents, or derived from local vessel activity), or input in sewage and wastewater from coastal areas. Concurrent observations of high zooplankton abundance suggest a high probability for marine biota to encounter microplastics and a potential for trophic interactions. Further research is required to understand the effects of microplastic-biota interaction within this productive environment. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26446348','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26446348">Microplastics in Arctic polar waters: the first reported values of particles in surface and sub-surface samples.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Lusher, Amy L; Tirelli, Valentina; O'Connor, Ian; Officer, Rick 2015-10-08 Plastic, as a form of marine litter, is found in varying quantities and sizes around the globe from surface waters to deep-sea sediments. Identifying patterns of microplastic distribution will benefit an understanding of the scale of their potential effect on the environment and organisms. As sea ice extent is reducing in the Arctic, heightened shipping and fishing activity may increase marine pollution in the area. Microplastics may enter the region following ocean transport and local input, although baseline contamination measurements are still required. Here we present the first study of microplastics in Arctic waters, south and southwest of Svalbard, Norway. Microplastics were found in surface (top 16 cm) and sub-surface (6 m depth) samples using two independent techniques. Origins and pathways bringing microplastic to the Arctic remain unclear. Particle composition (95% fibres) suggests they may either result from the breakdown of larger items (transported over large distances by prevailing currents, or derived from local vessel activity), or input in sewage and wastewater from coastal areas. Concurrent observations of high zooplankton abundance suggest a high probability for marine biota to encounter microplastics and a potential for trophic interactions. Further research is required to understand the effects of microplastic-biota interaction within this productive environment. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2737403','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2737403">Radiative decay engineering 3. Surface plasmon-coupled directional emission</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Lakowicz, Joseph R. 2009-01-01 A new method of fluorescence detection that promises to increase sensitivity by 20- to 1000-fold is described. This method will also decrease the contribution of sample autofluorescence to the detected signal. The method depends on the coupling of excited fluorophores with the surface plasmon resonance present in thin metal films, typically silver and gold. The phenomenon of surface plasmon-coupled emission (SPCE) occurs for fluorophores 20–250 nm from the metal surface, allowing detection of fluorophores over substantial distances beyond the metal–sample interface. SPCE depends on interactions of the excited fluorophore with the metal surface. This interaction is independent of the mode of excitation; that is, it does not require evanescent wave or surface-plasmon excitation. In a sense, SPCE is the inverse process of the surface plasmon resonance absorption of thin metal films. Importantly, SPCE occurs over a narrow angular distribution, converting normally isotropic emission into easily collected directional emission. Up to 50% of the emission from unoriented samples can be collected, much larger than typical fluorescence collection efficiencies near 1% or less. SPCE is due only to fluorophores near the metal surface and may be regarded as emission from the induced surface plasmons. Autofluorescence from more distal parts of the sample is decreased due to decreased coupling. SPCE is highly polarized and autofluorescence can be further decreased by collecting only the polarized component or only the light propagating with the appropriate angle. Examples showing how simple optical configurations can be used in diagnostics, sensing, or biotechnology applications are presented. Surface plasmon-coupled emission is likely to find widespread applications throughout the biosciences. PMID:14690679 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/983226','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/983226">Characterization of microbial communities in subsurface nuclear blast cavities of the Nevada Test Site</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Moser, Duane P; Czerwinski, Ken; Russell, Charles E 2010-07-13 This US Department of Energy (DOE) Environmental Remediation Sciences Project (ERSP) was designed to test fundamental hypotheses concerning the existence and nature of indigenous microbial populations of Nevada Test Site subsurface nuclear test/detonation cavities. Now called Subsurface Biogeochemical Research (SBR), this program's Exploratory Research (ER) element, which funded this research, is designed to support high risk, high potential reward projects. Here, five cavities (GASCON, CHANCELLOR, NASH, ALEMAN, and ALMENDRO) and one tunnel (U12N) were sampled using bailers or pumps. Molecular and cultivation-based techniques revealed bacterial signatures at five sites (CHANCELLOR may be lifeless). SSU rRNA gene libraries contained diverse andmore » divergent microbial sequences affiliated with known metal- and sulfur-cycling microorganisms, organic compound degraders, microorganisms from deep mines, and bacteria involved in selenate reduction and arsenite oxidation. Close relatives of Desulforudis audaxviator, a microorganism thought to subsist in the terrestrial deep subsurface on H2 and SO42- produced by radiochemical reactions, was detected in the tunnel waters. NTS-specific media formulations were used to culture and quantify nitrate-, sulfate-, iron-reducing, fermentative, and methanogenic microorganisms. Given that redox manipulations mediated by microorganisms can impact the mobility of DOE contaminants, our results should have implications for management strategies at this and other DOE sites.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1415078','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1415078">Dispersal-Based Microbial Community Assembly Decreases Biogeochemical Function</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Graham, Emily B.; Stegen, James C. Ecological mechanisms influence relationships among microbial communities, which in turn impact biogeochemistry. In particular, microbial communities are assembled by deterministic (e.g., selection) and stochastic (e.g., dispersal) processes, and the relative balance of these two process types is hypothesized to alter the influence of microbial communities over biogeochemical function. We used an ecological simulation model to evaluate this hypothesis, defining biogeochemical function generically to represent any biogeochemical reaction of interest. We assembled receiving communities under different levels of dispersal from a source community that was assembled purely by selection. The dispersal scenarios ranged from no dispersal (i.e., selection-only) to dispersal ratesmore » high enough to overwhelm selection (i.e., homogenizing dispersal). We used an aggregate measure of community fitness to infer a given community’s biogeochemical function relative to other communities. We also used ecological null models to further link the relative influence of deterministic assembly to function. We found that increasing rates of dispersal decrease biogeochemical function by increasing the proportion of maladapted taxa in a local community. Niche breadth was also a key determinant of biogeochemical function, suggesting a tradeoff between the function of generalist and specialist species. Finally, we show that microbial assembly processes exert greater influence over biogeochemical function when there is variation in the relative contributions of dispersal and selection among communities. Taken together, our results highlight the influence of spatial processes on biogeochemical function and indicate the need to account for such effects in models that aim to predict biogeochemical function under future environmental scenarios.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1415078-dispersal-based-microbial-community-assembly-decreases-biogeochemical-function','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1415078-dispersal-based-microbial-community-assembly-decreases-biogeochemical-function">Dispersal-Based Microbial Community Assembly Decreases Biogeochemical Function</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Graham, Emily B.; Stegen, James C. 2017-11-01 Ecological mechanisms influence relationships among microbial communities, which in turn impact biogeochemistry. In particular, microbial communities are assembled by deterministic (e.g., selection) and stochastic (e.g., dispersal) processes, and the relative balance of these two process types is hypothesized to alter the influence of microbial communities over biogeochemical function. We used an ecological simulation model to evaluate this hypothesis, defining biogeochemical function generically to represent any biogeochemical reaction of interest. We assembled receiving communities under different levels of dispersal from a source community that was assembled purely by selection. The dispersal scenarios ranged from no dispersal (i.e., selection-only) to dispersal ratesmore » high enough to overwhelm selection (i.e., homogenizing dispersal). We used an aggregate measure of community fitness to infer a given community’s biogeochemical function relative to other communities. We also used ecological null models to further link the relative influence of deterministic assembly to function. We found that increasing rates of dispersal decrease biogeochemical function by increasing the proportion of maladapted taxa in a local community. Niche breadth was also a key determinant of biogeochemical function, suggesting a tradeoff between the function of generalist and specialist species. Finally, we show that microbial assembly processes exert greater influence over biogeochemical function when there is variation in the relative contributions of dispersal and selection among communities. Taken together, our results highlight the influence of spatial processes on biogeochemical function and indicate the need to account for such effects in models that aim to predict biogeochemical function under future environmental scenarios.« less </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active">21</li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active">22</li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26927965','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26927965">Integration of the subsurface and the surface sectors for a more holistic approach for sustainable redevelopment of urban brownfields.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Norrman, Jenny; Volchko, Yevheniya; Hooimeijer, Fransje; Maring, Linda; Kain, Jaan-Henrik; Bardos, Paul; Broekx, Steven; Beames, Alistair; Rosén, Lars 2016-09-01 This paper presents a holistic approach to sustainable urban brownfield redevelopment where specific focus is put on the integration of a multitude of subsurface qualities in the early phases of the urban redevelopment process, i.e. in the initiative and plan phases. Achieving sustainability in brownfield redevelopment projects may be constrained by a failure of engagement between two key expert constituencies: urban planners/designers and subsurface engineers, leading to missed opportunities and unintended outcomes in the plan realisation phase. A more integrated approach delivers greater benefits. Three case studies in the Netherlands, Belgium and Sweden were used to test different sustainability assessment instruments in terms of the possibility for knowledge exchange between the subsurface and the surface sectors and in terms of cooperative learning among experts and stakeholders. Based on the lessons learned from the case studies, a generic decision process framework is suggested that supports holistic decision making. The suggested framework focuses on stakeholder involvement, communication, knowledge exchange and learning and provides an inventory of instruments that can support these processes. Copyright © 2016 Elsevier B.V. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AdWR..111..381M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AdWR..111..381M">Efficient uncertainty quantification in fully-integrated surface and subsurface hydrologic simulations</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Miller, K. L.; Berg, S. J.; Davison, J. H.; Sudicky, E. A.; Forsyth, P. A. 2018-01-01 Although high performance computers and advanced numerical methods have made the application of fully-integrated surface and subsurface flow and transport models such as HydroGeoSphere common place, run times for large complex basin models can still be on the order of days to weeks, thus, limiting the usefulness of traditional workhorse algorithms for uncertainty quantification (UQ) such as Latin Hypercube simulation (LHS) or Monte Carlo simulation (MCS), which generally require thousands of simulations to achieve an acceptable level of accuracy. In this paper we investigate non-intrusive polynomial chaos for uncertainty quantification, which in contrast to random sampling methods (e.g., LHS and MCS), represents a model response of interest as a weighted sum of polynomials over the random inputs. Once a chaos expansion has been constructed, approximating the mean, covariance, probability density function, cumulative distribution function, and other common statistics as well as local and global sensitivity measures is straightforward and computationally inexpensive, thus making PCE an attractive UQ method for hydrologic models with long run times. Our polynomial chaos implementation was validated through comparison with analytical solutions as well as solutions obtained via LHS for simple numerical problems. It was then used to quantify parametric uncertainty in a series of numerical problems with increasing complexity, including a two-dimensional fully-saturated, steady flow and transient transport problem with six uncertain parameters and one quantity of interest; a one-dimensional variably-saturated column test involving transient flow and transport, four uncertain parameters, and two quantities of interest at 101 spatial locations and five different times each (1010 total); and a three-dimensional fully-integrated surface and subsurface flow and transport problem for a small test catchment involving seven uncertain parameters and three quantities of interest at </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.3039B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.3039B">Multi-scale controls on spatial variability in river biogeochemical cycling</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Blaen, Phillip; Kurz, Marie; Knapp, Julia; Mendoza-Lera, Clara; Lee-Cullin, Joe; Klaar, Megan; Drummond, Jennifer; Jaeger, Anna; Zarnetske, Jay; Lewandowski, Joerg; Marti, Eugenia; Ward, Adam; Fleckenstein, Jan; Datry, Thibault; Larned, Scott; Krause, Stefan 2016-04-01 Excessive nutrient concentrations are common in surface waters and groundwaters in agricultural catchments worldwide. Increasing geomorphological heterogeneity in river channels may help to attenuate nutrient pollution by facilitating water exchange fluxes with the hyporheic zone; a site of intense microbial activity where biogeochemical cycling rates can be high. However, the controls on spatial variability in biogeochemical cycling, particularly at scales relevant for river managers, are largely unknown. Here, we aimed to assess: 1) how differences in river geomorphological heterogeneity control solute transport and rates of biogeochemical cycling at sub-reach scales (102 m); and 2) the relative magnitude of these differences versus those relating to reach scale substrate variability (103 m). We used the reactive tracer resazurin (Raz), a weakly fluorescent dye that transforms to highly fluorescent resorufin (Rru) under mildly reducing conditions, as a proxy to assess rates of biogeochemical cycling in a lowland river in southern England. Solute tracer tests were conducted in two reaches with contrasting substrates: one sand-dominated and the other gravel-dominated. Each reach was divided into sub-reaches that varied in geomorphic complexity (e.g. by the presence of pool-riffle sequences or the abundance of large woody debris). Slug injections of Raz and the conservative tracer fluorescein were conducted in each reach during baseflow conditions (Q ≈ 80 L/s) and breakthrough curves monitored using in-situ fluorometers. Preliminary results indicate overall Raz:Rru transformation rates in the gravel-dominated reach were more than 50% higher than those in the sand-dominated reach. However, high sub-reach variability in Raz:Rru transformation rates and conservative solute transport parameters suggests small scale targeted management interventions to alter geomorphic heterogeneity may be effective in creating hotspots of river biogeochemical cycling and nutrient load </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018NucFu..58e6027K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018NucFu..58e6027K">Influence of sub-surface damage evolution on low-energy-plasma-driven deuterium permeation through tungsten</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kapser, Stefan; Balden, Martin; Fiorini da Silva, Tiago; Elgeti, Stefan; Manhard, Armin; Schmid, Klaus; Schwarz-Selinger, Thomas; von Toussaint, Udo 2018-05-01 Low-energy-plasma-driven deuterium permeation through tungsten at 300 K and 450 K has been investigated. Microstructural analysis by scanning electron microscopy, assisted by focused ion beam, revealed sub-surface damage evolution only at 300 K. This damage evolution was correlated with a significant evolution of the deuterium amount retained below the plasma-exposed surface. Although both of these phenomena were observed for 300 K exposure temperature only, the deuterium permeation flux at both exposure temperatures was indistinguishable within the experimental uncertainty. The permeation flux was used to estimate the maximum ratio of solute-deuterium to tungsten atoms during deuterium-plasma exposure at both temperatures and thus in the presence and absence of damage evolution. Diffusion-trapping simulations revealed the proximity of damage evolution to the implantation surface as the reason for an only insignificant decrease of the permeation flux. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T33A2645M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T33A2645M">Surface and Subsurface Fault Displacements from the September 2010 Darfield (Canterbury) Earthquake</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Meyers, B.; Furlong, K. P.; Hayes, G. P.; Herman, M. W.; Quigley, M. 2012-12-01 On September 3, 2010 a Magnitude 7.1 earthquake struck near Darfield, New Zealand. This was to be the first earthquake in an ongoing, damaging sequence near the city of Christchurch. The earthquake produced a surface rupture with measurable offsets of up to 5.3m along a 30km surface fault system. The spatial pattern of slip during this rupture has been determined by various groups using a range of approaches and several independent data sets. Surface fault rupture was measured in the field and fault slip at depth has been inferred from a seismologic finite fault model (FFM) and various geodetic observations including GPS and InSAR. Here we compare the observed segmented surface displacements with fault slip inferred from the other data. Measurements of the surface rupture show segmented faulting consistent with subsurface slip in the FFM. In the FFM, the main slip patch near the hypocenter can be directly correlated to the region of maximum surface displacement. The FFM and some evidence in the InSAR data also indicate that the Greendale fault system, the structure responsible for the bulk of the rupture, continues at depth closer towards Christchurch than is seen in surface rupture patterns. There is an additional 20km long patch with up to 3m of modeled slip seen in the eastern end of the inverted fault, offset to the south from the Greendale fault trace. This additional fault segment is consistent with a zone of aftershock activity of the main Darfield event, and with local patterns of strong motion. It thus appears that slip recorded at the surface does not describe the entire fault system. This eastward extension of the September rupture means that there is only a short segment of unruptured crust remaining along the entire fault system involved in the Canterbury earthquake sequence. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005PCE....30..598A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005PCE....30..598A">Mechanisms of surface runoff genesis on a subsurface drained soil affected by surface crusting: A field investigation</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Augeard, Bénédicte; Kao, Cyril; Chaumont, Cédric; Vauclin, Michel Artificial drainage has been subject to widespread criticism because of its impact on water quality and because there is suspicion that it may have detrimental effects on flood genesis. The present work aims at a better understanding of the mechanisms controlling infiltration and surface runoff genesis, particularly in soils with artificial drainage and affected by surface crusting. A field experiment was conducted during one drainage season (November 2003-March 2004) in the Brie region (80 km east of Paris, France) on a subsurface drained silty soil. Water table elevation and surface runoff were monitored above the drain and at midpoint between drains. Soil water pressure head was measured at various depths and locations between the midpoint and the drain. Soil surface characteristics (microtopography and degree of structural and sedimentary crust development) were recorded regularly on the experimental site and on other plots of various drainage intensities. The results show that the first surface runoff events were induced by high water table. However, runoff was higher at midpoint between the drains because water table reached the soil surface at that point, thus considerably reducing infiltration capacity compared to that above the drain. Comparing different plots, the area with older drainage installation (1948) yielded the most surface runoff. Wider drain spacing, smaller drain depth and possible plugging may have led to a greater area of saturated soil between drains. During the winter period, the impact of raindrops induced the formation of a structural crust on the soil surface. Furthermore, the development of the sedimentary crust, which was favored by water actually flowing on the soil surface during the high water table periods could be correlated with surface runoff volume. The formation of this crust had a significant impact on runoff occurrence at the end of the winter. Therefore, poorly drained fields presented more favorable conditions for both </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GMDD....8.6143B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GMDD....8.6143B">SHIMMER (1.0): a novel mathematical model for microbial and biogeochemical dynamics in glacier forefield ecosystems</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bradley, J. A.; Anesio, A. M.; Singarayer, J. S.; Heath, M. R.; Arndt, S. 2015-08-01 SHIMMER (Soil biogeocHemIcal Model for Microbial Ecosystem Response) is a new numerical modelling framework which is developed as part of an interdisciplinary, iterative, model-data based approach fully integrating fieldwork and laboratory experiments with model development, testing, and application. SHIMMER is designed to simulate the establishment of microbial biomass and associated biogeochemical cycling during the initial stages of ecosystem development in glacier forefield soils. However, it is also transferable to other extreme ecosystem types (such as desert soils or the surface of glaciers). The model mechanistically describes and predicts transformations in carbon, nitrogen and phosphorus through aggregated components of the microbial community as a set of coupled ordinary differential equations. The rationale for development of the model arises from decades of empirical observation on the initial stages of soil development in glacier forefields. SHIMMER enables a quantitative and process focussed approach to synthesising the existing empirical data and advancing understanding of microbial and biogeochemical dynamics. Here, we provide a detailed description of SHIMMER. The performance of SHIMMER is then tested in two case studies using published data from the Damma Glacier forefield in Switzerland and the Athabasca Glacier in Canada. In addition, a sensitivity analysis helps identify the most sensitive and unconstrained model parameters. Results show that the accumulation of microbial biomass is highly dependent on variation in microbial growth and death rate constants, Q10 values, the active fraction of microbial biomass, and the reactivity of organic matter. The model correctly predicts the rapid accumulation of microbial biomass observed during the initial stages of succession in the forefields of both the case study systems. Simulation results indicate that primary production is responsible for the initial build-up of substrate that subsequently </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25079404','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25079404">Hybrid constructed wetlands for highly polluted river water treatment and comparison of surface- and subsurface-flow cells.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Zheng, Yucong; Wang, Xiaochang; Xiong, Jiaqing; Liu, Yongjun; Zhao, Yaqian 2014-04-01 A series of large pilot constructed wetland (CW) systems were constructed near the confluence of an urban stream to a larger river in Xi'an, a northwestern megacity in China, for treating polluted stream water before it entered the receiving water body. Each CW system is a combination of surface-and subsurface-flow cells with local gravel, sand or slag as substrates and Phragmites australis and Typha orientalis as plants. During a one-year operation with an average surface loading of 0.053 m(3)/(m(2)·day), the overall COD, BOD, NH3-N, total nitrogen (TN) and total phosphorus (TP) removals were 72.7% ± 4.5%, 93.4% ± 2.1%, 54.0% ± 6.3%, 53.9% ± 6.0% and 69.4% ± 4.6%, respectively, which brought about an effective improvement of the river water quality. Surface-flow cells showed better NH3-N removal than their TN removal while subsurface-flow cells showed better TN removal than their NH3-N removal. Using local slag as the substrate, the organic and phosphorus removal could be much improved. Seasonal variation was also found in the removal of all the pollutants and autumn seemed to be the best season for pollutant removal due to the moderate water temperature and well grown plants in the CWs. Copyright © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013OcScD..10.1997H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013OcScD..10.1997H">Adapting to life: ocean biogeochemical modelling and adaptive remeshing</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hill, J.; Popova, E. E.; Ham, D. A.; Piggott, M. D.; Srokosz, M. 2013-11-01 An outstanding problem in biogeochemical 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 biogeochemical model. We present a novel method of simulating ocean biogeochemical behaviour on a vertically adaptive computational mesh, where the mesh changes in response to the biogeochemical 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 biogeochemical behaviour at high spatial resolution whilst minimising </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1615923K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1615923K">Modeling greenhouse gas emissions (CO2, N2O, CH4) from managed arable soils with a fully coupled hydrology-biogeochemical modeling system simulating water and nutrient transport and associated carbon and nitrogen cycling at catchment scale</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Klatt, Steffen; Haas, Edwin; Kraus, David; Kiese, Ralf; Butterbach-Bahl, Klaus; Kraft, Philipp; Plesca, Ina; Breuer, Lutz; Zhu, Bo; Zhou, Minghua; Zhang, Wei; Zheng, Xunhua; Wlotzka, Martin; Heuveline, Vincent 2014-05-01 The use of mineral nitrogen fertilizer sustains the global food production and therefore the livelihood of human kind. The rise in world population will put pressure on the global agricultural system to increase its productivity leading most likely to an intensification of mineral nitrogen fertilizer use. The fate of excess nitrogen and its distribution within landscapes is manifold. Process knowledge on the site scale has rapidly grown in recent years and models have been developed to simulate carbon and nitrogen cycling in managed ecosystems on the site scale. Despite first regional studies, the carbon and nitrogen cycling on the landscape or catchment scale is not fully understood. In this study we present a newly developed modelling approach by coupling the fully distributed hydrology model CMF (catchment modelling framework) to the process based regional ecosystem model LandscapeDNDC for the investigation of hydrological processes and carbon and nitrogen transport and cycling, with a focus on nutrient displacement and resulting greenhouse gas emissions in a small catchment at the Yanting Agro-ecological Experimental Station of Purple Soil, Sichuan province, China. The catchment hosts cypress forests on the outer regions, arable fields on the sloping croplands cultivated with wheat-maize rotations and paddy rice fields in the lowland. The catchment consists of 300 polygons vertically stratified into 10 soil layers. Ecosystem states (soil water content and nutrients) and fluxes (evapotranspiration) are exchanged between the models at high temporal scales (hourly to daily) forming a 3-dimensional model application. The water flux and nutrients transport in the soil is modelled using a 3D Richards/Darcy approach for subsurface fluxes with a kinematic wave approach for surface water runoff and the evapotranspiration is based on Penman-Monteith. Biogeochemical processes are modelled by LandscapeDNDC, including soil microclimate, plant growth and biomass allocation </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H43N..06I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H43N..06I">Evidence of weak land-atmosphere coupling under varying bare soil conditions: Are fully coupled Darcy/Navier-Stokes models necessary for simulating soil moisture dynamics?</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Illangasekare, T. H.; Trautz, A. C.; Howington, S. E.; Cihan, A. 2017-12-01 It is a well-established fact that the land and atmosphere form a continuum in which the individual domains are coupled by heat and mass transfer processes such as bare-soil evaporation. Soil moisture dynamics can be simulated at the representative elementary volume (REV) scale using decoupled and fully coupled Darcy/Navier-Stokes models. Decoupled modeling is an asynchronous approach in which flow and transport in the soil and atmosphere is simulated independently; the two domains are coupled out of time-step via prescribed flux parameterizations. Fully coupled modeling in contrast, solves the governing equations for flow and transport in both domains simultaneously with the use of coupling interface boundary conditions. This latter approach, while being able to provide real-time two-dimensional feedbacks, is considerably more complex and computationally intensive. In this study, we investigate whether fully coupled models are necessary, or if the simpler decoupled models can sufficiently capture soil moisture dynamics under varying land preparations. A series of intermediate-scale physical and numerical experiments were conducted in which soil moisture distributions and evaporation estimates were monitored at high spatiotemporal resolutions for different heterogeneous packing and soil roughness scenarios. All experimentation was conducted at the newly developed Center for Experimental Study of Subsurface Environmental Processes (CESEP) wind tunnel-porous media user test-facility at the Colorado School of. Near-surface atmospheric measurements made during the experiments demonstrate that the land-atmosphere coupling was relatively weak and insensitive to the applied edaphic and surface conditions. Simulations with a decoupled multiphase heat and mass transfer model similarly show little sensitivity to local variations in atmospheric forcing; a single, simple flux parameterization can sufficiently capture the soil moisture dynamics (evaporation and redistribution </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMOS33A1445C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMOS33A1445C">Greenland's glacial fjords and their role in regional biogeochemical dynamics.</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Crosby, J.; Arndt, S. 2017-12-01 Greenland's coastal fjords serve as important pathways that connect the Greenland Ice Sheet (GrIS) and the surrounding oceans. They export seasonal glacial meltwater whilst being significant sites of primary production. These fjords are home to some of the most productive ecosystems in the world and possess high socio-economic value via fisheries. A growing number of studies have proposed the GrIS as an underappreciated yet significant source of nutrients to surrounding oceans. Acting as both transfer routes and sinks for glacial nutrient export, fjords have the potential to act as significant biogeochemical processors, yet remain underexplored. Critically, an understanding of the quantitative contribution of fjords to carbon and nutrient budgets is lacking, with large uncertainties associated with limited availability of field data and the lack of robust upscaling approaches. To close this knowledge gap we developed a coupled 2D physical-biogeochemical model of the Godthåbsfjord system, a sub-Arctic sill fjord in southwest Greenland, to quantitatively assess the impact of nutrients exported from the GrIS on fjord primary productivity and biogeochemical dynamics. Glacial meltwater is found to be a key driver of fjord-scale circulation patterns, whilst tracer simulations reveal the relative nutrient contributions from meltwater-driven upwelling and meltwater export from the GrIS. Hydrodynamic circulation patterns and freshwater transit times are explored to provide a first understanding of the glacier-fjord-ocean continuum, demonstrating the complex pattern of carbon and nutrient cycling at this critical land-ocean interface. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H31A0591R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H31A0591R">The Effect of Subsurface Parameterizations on Modeled Flows in the Catchment Land Surface Model, Fortuna 2.5</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Roningen, J. M.; Eylander, J. B. 2014-12-01 Groundwater use and management is subject to economic, legal, technical, and informational constraints and incentives at a variety of spatial and temporal scales. Planned and de facto management practices influenced by tax structures, legal frameworks, and agricultural and trade policies that vary at the country scale may have medium- and long-term effects on the ability of a region to support current and projected agricultural and industrial development. USACE is working to explore and develop global-scale, physically-based frameworks to serve as a baseline for hydrologic policy comparisons and consequence assessment, and such frameworks must include a reasonable representation of groundwater systems. To this end, we demonstrate the effects of different subsurface parameterizations, scaling, and meteorological forcings on surface and subsurface components of the Catchment Land Surface Model Fortuna v2.5 (Koster et al. 2000). We use the Land Information System 7 (Kumar et al. 2006) to process model runs using meteorological components of the Air Force Weather Agency's AGRMET forcing data from 2006 through 2011. Seasonal patterns and trends are examined in areas of the Upper Nile basin, northern China, and the Mississippi Valley. We also discuss the relevance of the model's representation of the catchment deficit with respect to local hydrogeologic structures. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018OptCo.410..936G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018OptCo.410..936G">Study of gain-coupled distributed feedback laser based on high order surface gain-coupled gratings</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Gao, Feng; Qin, Li; Chen, Yongyi; Jia, Peng; Chen, Chao; Cheng, LiWen; Chen, Hong; Liang, Lei; Zeng, Yugang; Zhang, Xing; Wu, Hao; Ning, Yongqiang; Wang, Lijun 2018-03-01 Single-longitudinal-mode, gain-coupled distributed feedback (DFB) lasers based on high order surface gain-coupled gratings are achieved. Periodic surface metal p-contacts with insulated grooves realize gain-coupled mechanism. To enhance gain contrast in the quantum wells without the introduction of effective index-coupled effect, groove length and depth were well designed. Our devices provided a single longitudinal mode with the maximum CW output power up to 48.8 mW/facet at 971.31 nm at 250 mA without facet coating, 3dB linewidth (<3.2 pm) and SMSR (>39 dB). Optical bistable characteristic was observed with a threshold current difference. Experimentally, devices with different cavity lengths were contrasted on power-current and spectrum characteristics. Due to easy fabrication technique and stable performance, it provides a method of fabricating practical gain-coupled distributed feedback lasers for commercial applications. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.H43G1621B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.H43G1621B">Development of a 3D Soil-Plant-Atmosphere Continuum (SPAC) coupled to a Land Surface Model</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bisht, G.; Riley, W. J.; Lorenzetti, D.; Tang, J. 2015-12-01 Exchange of water between the atmosphere and biosphere via evapotranspiration (ET) influences global hydrological, energy, and biogeochemical cycles. Isotopic analysis has shown that evapotranspiration over the continents is largely dominated by transpiration. Water is taken up from soil by plant roots, transported through the plant's vascular system, and evaporated from the leaves. Yet current Land Surface Models (LSMs) integrated into Earth System Models (ESMs) treat plant roots as passive components. These models distribute the ET sink vertically over the soil column, neglect the vertical pressure distribution along the plant vascular system, and assume that leaves can directly access water from any soil layer within the root zone. Numerous studies have suggested that increased warming due to climate change will lead drought and heat-induced tree mortality. A more mechanistic treatment of water dynamics in the soil-plant-atmosphere continuum (SPAC) is essential for investigating the fate of ecosystems under a warmer climate. In this work, we describe a 3D SPAC model that can be coupled to a LSM. The SPAC model uses the variably saturated Richards equations to simulate water transport. The model uses individual governing equations and constitutive relationships for the various SPAC components (i.e., soil, root, and xylem). Finite volume spatial discretization and backward Euler temporal discretization is used to solve the SPAC model. The Portable, Extensible Toolkit for Scientific Computation (PETSc) is used to numerically integrate the discretized system of equations. Furthermore, PETSc's multi-physics coupling capability (DMComposite) is used to solve the tightly coupled system of equations of the SPAC model. Numerical results are presented for multiple test problems. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4829693','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4829693">Groundwater–surface water mixing shifts ecological assembly processes and stimulates organic carbon turnover</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Stegen, James C.; Fredrickson, James K.; Wilkins, Michael J.; Konopka, Allan E.; Nelson, William C.; Arntzen, Evan V.; Chrisler, William B.; Chu, Rosalie K.; Danczak, Robert E.; Fansler, Sarah J.; Kennedy, David W.; Resch, Charles T.; Tfaily, Malak 2016-01-01 Environmental transitions often result in resource mixtures that overcome limitations to microbial metabolism, resulting in biogeochemical hotspots and moments. Riverine systems, where groundwater mixes with surface water (the hyporheic zone), are spatially complex and temporally dynamic, making development of predictive models challenging. Spatial and temporal variations in hyporheic zone microbial communities are a key, but understudied, component of riverine biogeochemical function. Here, to investigate the coupling among groundwater–surface water mixing, microbial communities and biogeochemistry, we apply ecological theory, aqueous biogeochemistry, DNA sequencing and ultra-high-resolution organic carbon profiling to field samples collected across times and locations representing a broad range of mixing conditions. Our results indicate that groundwater–surface water mixing in the hyporheic zone stimulates heterotrophic respiration, alters organic carbon composition, causes ecological processes to shift from stochastic to deterministic and is associated with elevated abundances of microbial taxa that may degrade a broad suite of organic compounds. PMID:27052662 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20110012850&hterms=water&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26Nf%3DPublication-Date%257CBTWN%2B20110101%2B20111231%26N%3D0%26No%3D50%26Ntt%3Dwater','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20110012850&hterms=water&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26Nf%3DPublication-Date%257CBTWN%2B20110101%2B20111231%26N%3D0%26No%3D50%26Ntt%3Dwater">Hyperresolution Global Land Surface Modeling: Meeting a Grand Challenge for Monitoring Earth's Terrestrial Water</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Wood, Eric F.; Roundy, Joshua K.; Troy, Tara J.; van Beek, L. P. H.; Bierkens, Marc F. P.; 4 Blyth, Eleanor; de Roo, Ad; Doell. Petra; Ek, Mike; Famiglietti, James; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20110012850'); toggleEditAbsImage('author_20110012850_show'); toggleEditAbsImage('author_20110012850_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20110012850_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20110012850_hide"> 2011-01-01 Monitoring Earth's terrestrial water conditions is critically important to many hydrological applications such as global food production; assessing water resources sustainability; and flood, drought, and climate change prediction. These needs have motivated the development of pilot monitoring and prediction systems for terrestrial hydrologic and vegetative states, but to date only at the rather coarse spatial resolutions (approx.10-100 km) over continental to global domains. Adequately addressing critical water cycle science questions and applications requires systems that are implemented globally at much higher resolutions, on the order of 1 km, resolutions referred to as hyperresolution in the context of global land surface models. This opinion paper sets forth the needs and benefits for a system that would monitor and predict the Earth's terrestrial water, energy, and biogeochemical cycles. We discuss six major challenges in developing a system: improved representation of surface-subsurface interactions due to fine-scale topography and vegetation; improved representation of land-atmospheric interactions and resulting spatial information on soil moisture and evapotranspiration; inclusion of water quality as part of the biogeochemical cycle; representation of human impacts from water management; utilizing massively parallel computer systems and recent computational advances in solving hyperresolution models that will have up to 10(exp 9) unknowns; and developing the required in situ and remote sensing global data sets. We deem the development of a global hyperresolution model for monitoring the terrestrial water, energy, and biogeochemical cycles a grand challenge to the community, and we call upon the international hydrologic community and the hydrological science support infrastructure to endorse the effort. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011WRR....47.5301W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011WRR....47.5301W">Hyperresolution global land surface modeling: Meeting a grand challenge for monitoring Earth's terrestrial water</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wood, Eric F.; Roundy, Joshua K.; Troy, Tara J.; van Beek, L. P. H.; Bierkens, Marc F. P.; Blyth, Eleanor; de Roo, Ad; DöLl, Petra; Ek, Mike; Famiglietti, James; Gochis, David; van de Giesen, Nick; Houser, Paul; Jaffé, Peter R.; Kollet, Stefan; Lehner, Bernhard; Lettenmaier, Dennis P.; Peters-Lidard, Christa; Sivapalan, Murugesu; Sheffield, Justin; Wade, Andrew; Whitehead, Paul 2011-05-01 Monitoring Earth's terrestrial water conditions is critically important to many hydrological applications such as global food production; assessing water resources sustainability; and flood, drought, and climate change prediction. These needs have motivated the development of pilot monitoring and prediction systems for terrestrial hydrologic and vegetative states, but to date only at the rather coarse spatial resolutions (˜10-100 km) over continental to global domains. Adequately addressing critical water cycle science questions and applications requires systems that are implemented globally at much higher resolutions, on the order of 1 km, resolutions referred to as hyperresolution in the context of global land surface models. This opinion paper sets forth the needs and benefits for a system that would monitor and predict the Earth's terrestrial water, energy, and biogeochemical cycles. We discuss six major challenges in developing a system: improved representation of surface-subsurface interactions due to fine-scale topography and vegetation; improved representation of land-atmospheric interactions and resulting spatial information on soil moisture and evapotranspiration; inclusion of water quality as part of the biogeochemical cycle; representation of human impacts from water management; utilizing massively parallel computer systems and recent computational advances in solving hyperresolution models that will have up to 109 unknowns; and developing the required in situ and remote sensing global data sets. We deem the development of a global hyperresolution model for monitoring the terrestrial water, energy, and biogeochemical cycles a "grand challenge" to the community, and we call upon the international hydrologic community and the hydrological science support infrastructure to endorse the effort. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27310571','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27310571">In vivo measurement of skin surface strain and sub-surface layer deformation induced by natural tissue stretching.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Maiti, Raman; Gerhardt, Lutz-Christian; Lee, Zing S; Byers, Robert A; Woods, Daniel; Sanz-Herrera, José A; Franklin, Steve E; Lewis, Roger; Matcher, Stephen J; Carré, Matthew J 2016-09-01 Stratum corneum and epidermal layers change in terms of thickness and roughness with gender, age and anatomical site. Knowledge of the mechanical and tribological properties of skin associated with these structural changes are needed to aid in the design of exoskeletons, prostheses, orthotics, body mounted sensors used for kinematics measurements and in optimum use of wearable on-body devices. In this case study, optical coherence tomography (OCT) and digital image correlation (DIC) were combined to determine skin surface strain and sub-surface deformation behaviour of the volar forearm due to natural tissue stretching. The thickness of the epidermis together with geometry changes of the dermal-epidermal junction boundary were calculated during change in the arm angle, from flexion (90°) to full extension (180°). This posture change caused an increase in skin surface Lagrange strain, typically by 25% which induced considerable morphological changes in the upper skin layers evidenced by reduction of epidermal layer thickness (20%), flattening of the dermal-epidermal junction undulation (45-50% reduction of flatness being expressed as Ra and Rz roughness profile height change) and reduction of skin surface roughness Ra and Rz (40-50%). The newly developed method, DIC combined with OCT imaging, is a powerful, fast and non-invasive methodology to study structural skin changes in real time and the tissue response provoked by mechanical loading or stretching. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000115605','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000115605">Significant Findings: Seasonal Distributions of Global Ocean Chlorophyll and Nutrients With a Coupled Ocean General Circulation, Biogeochemical, and Radiative Model. 2; Comparisons With Satellite and In Situ Data</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Gregg, Watson W.; Busalacchi, Antonio (Technical Monitor) 2000-01-01 A coupled ocean general circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. Biogeochemical processes in the model were 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 (>1000 km) model chlorophyll seasonal distributions were statistically positively correlated with CZCS chlorophyll in 10 of 12 major oceanographic regions, and with SeaWiFS in all 12. Notable disparities in magnitudes occurred, however, in the tropical Pacific, the spring/summer bloom in the Antarctic, autumn in the northern high latitudes, and during the southwest monsoon in the North Indian Ocean. Synoptic scale (100-1000 km) comparisons of satellite and in situ data exhibited broad agreement, although occasional departures were apparent. Model nitrate distributions agreed 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 indicated that the model dynamics offer a reasonably realistic simulation of phytoplankton and nutrient dynamics on basin and synoptic scales. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active">22</li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active">23</li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMOS43B2055Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMOS43B2055Y">Multimillennium changes in dissolved oxygen under global warming: results from an AOGCM and offline ocean biogeochemical model</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yamamoto, A.; Abe-Ouchi, A.; Shigemitsu, M.; Oka, A.; Takahashi, K.; Ohgaito, R.; Yamanaka, Y. 2016-12-01 Long-term oceanic oxygen change due to global warming is still unclear; most future projections (such as CMIP5) are only performed until 2100. Indeed, few previous studies using conceptual models project oxygen change in the next thousands of years, showing persistent global oxygen reduction by about 30% in the next 2000 years, even after atmospheric carbon dioxide stops rising. Yet, these models cannot sufficiently represent the ocean circulation change: the key driver of oxygen change. Moreover, considering serious effect oxygen reduction has on marine life and biogeochemical cycling, long-term oxygen change should be projected for higher validity. Therefore, we used a coupled atmosphere-ocean general circulation model (AOGCM) and an offline ocean biogeochemical model, investigating realistic long-term changes in oceanic oxygen concentration and ocean circulation. We integrated these models for 2000 years under atmospheric CO2 doubling and quadrupling. After global oxygen reduction in the first 500 years, oxygen concentration in deep ocean globally recovers and overshoots, despite surface oxygen decrease and weaker Atlantic Meridional Overturning Circulation. Deep ocean convection in the Weddell Sea recovers and overshoots, after initial cessation. Thus, enhanced deep convection and associated Antarctic Bottom Water supply oxygen-rich surface waters to deep ocean, resulting global deep ocean oxygenation. We conclude that the change in ocean circulation in the Southern Ocean potentially drives millennial-scale oxygenation in the deep ocean; contrary to past reported long-term oxygen reduction and general expectation. In presentation, we will discuss the mechanism of response of deep ocean convection in the Weddell Sea and show the volume changes of hypoxic waters. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21112074','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21112074">Improving surface-subsurface water budgeting using high resolution satellite imagery applied on a brownfield.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Dujardin, J; Batelaan, O; Canters, F; Boel, S; Anibas, C; Bronders, J 2011-01-15 The estimation of surface-subsurface water interactions is complex and highly variable in space and time. It is even more complex when it has to be estimated in urban areas, because of the complex patterns of the land-cover in these areas. In this research a modeling approach with integrated remote sensing analysis has been developed for estimating water fluxes in urban environments. The methodology was developed with the aim to simulate fluxes of contaminants from polluted sites. Groundwater pollution in urban environments is linked to patterns of land use and hence it is essential to characterize the land cover in a detail. An object-oriented classification approach applied on high-resolution satellite data has been adopted. To assign the image objects to one of the land-cover classes a multiple layer perceptron approach was adopted (Kappa of 0.86). Groundwater recharge has been simulated using the spatially distributed WetSpass model and the subsurface water flow using MODFLOW in order to identify and budget water fluxes. The developed methodology is applied to a brownfield case site in Vilvoorde, Brussels (Belgium). The obtained land use map has a strong impact on the groundwater recharge, resulting in a high spatial variability. Simulated groundwater fluxes from brownfield to the receiving River Zenne were independently verified by measurements and simulation of groundwater-surface water interaction based on thermal gradients in the river bed. It is concluded that in order to better quantify total fluxes of contaminants from brownfields in the groundwater, remote sensing imagery can be operationally integrated in a modeling procedure. Copyright © 2010 Elsevier B.V. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014APS..DFDD19005A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014APS..DFDD19005A">Effects of Droplet Size on Intrusion of Sub-Surface Oil Spills</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Adams, Eric; Chan, Godine; Wang, Dayang 2014-11-01 We explore effects of droplet size on droplet intrusion and transport in sub-surface oil spills. Negatively buoyant glass beads released continuously to a stratified ambient simulate oil droplets in a rising multiphase plume, and distributions of settled beads are used to infer signatures of surfacing oil. Initial tests used quiescent conditions, while ongoing tests simulate currents by towing the source and a bottom sled. Without current, deposited beads have a Gaussian distribution, with variance increasing with decreasing particle size. Distributions agree with a model assuming first order particle loss from an intrusion layer of constant thickness, and empirically determined flow rate. With current, deposited beads display a parabolic distribution similar to that expected from a source in uniform flow; we are currently comparing observed distributions with similar analytical models. Because chemical dispersants have been used to reduce oil droplet size, our study provides one measure of their effectiveness. Results are applied to conditions from the `Deep Spill' field experiment, and the recent Deepwater Horizon oil spill, and are being used to provide ``inner boundary conditions'' for subsequent far field modeling of these events. This research was made possible by grants from Chevron Energy Technology Co., through the Chevron-MITEI University Partnership Program, and BP/The Gulf of Mexico Research Initiative, GISR. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=233567&keyword=acidification+AND+ocean&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=233567&keyword=acidification+AND+ocean&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">Acidification of subsurface coastal waters enhanced by eutrophication</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Uptake of fossil-fuel carbon dioxide (CO2) from the atmosphere has acidified the surface ocean by ~0.1 pH units and driven down the carbonate saturation state. Ocean acidification is a threat to marine ecosystems and may alter key biogeochemical cycles. Coastal oceans have also b... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.B53B0343J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.B53B0343J">A bioenergetics-kinetics coupled modeling study on subsurface microbial metabolism in a field biostimulation experiment</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Jin, Q.; Zheng, Z.; Zhu, C. 2006-12-01 Microorganisms in nature conserve energy by catalyzing various geochemical reactions. To build a quantitative relationship between geochemical conditions and metabolic rates, we propose a bioenergetics-kinetics coupled modeling approach. This approach describes microbial community as a metabolic network, i.e., fermenting microbes degrade organic substrates while aerobic respirer, nitrate reducer, metal reducer, sulfate reducer, and methanogen consume the fermentation products. It quantifies the control of substrate availability and biological energy conservation on the metabolic rates using thermodynamically consistent rate laws. We applied this simulation approach to study the progress of microbial metabolism during a field biostimulation experiment conducted in Oak Ridge, Tennessee. In the experiment, ethanol was injected into a monitoring well and groundwater was sampled to monitor changes in the chemistry. With time, concentrations of ethanol and SO42- decreased while those of NH4+, Fe2+, and Mn2+ increased. The simulation results fitted well to the observation, indicating simultaneous ethanol degradation and terminal electron accepting processes. The rates of aerobic respiration and denitrification were mainly controlled by substrate concentrations while those of ethanol degradation, sulfate reduction, and methanogenesis were controlled dominantly by the energy availability. The simulation results suggested two different microbial growth statuses in the subsurface. For the functional groups with significant growth, variations with time in substrate concentrations demonstrated a typical S curve. For the groups without significant growth, initial decreases in substrate concentrations were linear with time. Injecting substrates followed by monitoring environmental chemistry therefore provides a convenient approach to characterize microbial growth in the subsurface where methods for direct observation are currently unavailable. This research was funded by the </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.P51E..04B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.P51E..04B">Radar Imaging of Europa's Subsurface Properties and Processes: The View from Earth</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Blankenship, D. D.; Moore, W. B.; Young, D. A.; Peters, M. E. 2007-12-01 A primary objective of future Europa studies will be to characterize the distribution of shallow subsurface water as well as to identify any ice-ocean interface. Another objective will be to understand the formation of surface and subsurface features associated with interchange processes between any ocean and the surface. Achieving these objectives will require either direct or inferred knowledge of the position of any ice/water interfaces as well as any brine or layer pockets. We will review the hypothesized processes that control the thermal, compositional and structural (TCS) properties, and therefore the dielectric character, of the subsurface of Europa's icy shell. Our approach will be to extract the TCS properties for various subsurface processes thought to control the formation of major surface (e.g., ridges/bands, lenticulae, chaos, cratering...) and subsurface (e.g., rigid shell eutectics, diapirs, accretionary lenses ...) features on Europa. We will then assess the spectrum of analog processes and TCS properties represented by Earth's cryosphere including both Arctic and Antarctic ice sheets, ice shelves and valley glaciers. There are few complete analogs over the full TCS space but, because of the wide range of ice thickness, impurities and strain rates for Earth's cryosphere, there are many more analogs than many Earth and planetary researchers might imagine for significant portions of this space (e.g., bottom crevasses, marine ice shelf/subglacial lake accretion, surging polythermal glaciers...).Our ultimate objective is to use these Earth analog studies to define the radar imaging approach for Europa's subsurface that will be most useful for supporting/refuting the hypotheses for the formation of major surface/subsurface features as well as for "pure" exploration of Europa's icy shell and its interface with the underlying ocean. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015BGeo...12.1191M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015BGeo...12.1191M">Microbial colonization in diverse surface soil types in Surtsey and diversity analysis of its subsurface microbiota</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Marteinsson, V.; Klonowski, A.; Reynisson, E.; Vannier, P.; Sigurdsson, B. D.; Ólafsson, M. 2015-02-01 Colonization of life on Surtsey has been observed systematically since the formation of the island 50 years ago. Although the first colonisers were prokaryotes, such as bacteria and blue-green algae, most studies have been focused on the settlement of plants and animals but less on microbial succession. To explore microbial colonization in diverse soils and the influence of associated vegetation and birds on numbers of environmental bacteria, we collected 45 samples from different soil types on the surface of the island. Total viable bacterial counts were performed with the plate count method at 22, 30 and 37 °C for all soil samples, and the amount of organic matter and nitrogen (N) was measured. Selected samples were also tested for coliforms, faecal coliforms and aerobic and anaerobic bacteria. The subsurface biosphere was investigated by collecting liquid subsurface samples from a 181 m borehole with a special sampler. Diversity analysis of uncultivated biota in samples was performed by 16S rRNA gene sequences analysis and cultivation. Correlation was observed between nutrient deficits and the number of microorganisms in surface soil samples. The lowest number of bacteria (1 × 104-1 × 105 cells g-1) was detected in almost pure pumice but the count was significantly higher (1 × 106-1 × 109 cells g-1) in vegetated soil or pumice with bird droppings. The number of faecal bacteria correlated also to the total number of bacteria and type of soil. Bacteria belonging to Enterobacteriaceae were only detected in vegetated samples and samples containing bird droppings. The human pathogens Salmonella, Campylobacter and Listeria were not in any sample. Both thermophilic bacteria and archaea 16S rDNA sequences were found in the subsurface samples collected at 145 and 172 m depth at 80 and 54 °C, respectively, but no growth was observed in enrichments. The microbiota sequences generally showed low affiliation to any known 16S rRNA gene sequences. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014BGD....1113775M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014BGD....1113775M">Microbial colonisation in diverse surface soil types in Surtsey and diversity analysis of its subsurface microbiota</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Marteinsson, V.; Klonowski, A.; Reynisson, E.; Vannier, P.; Sigurdsson, B. D.; Ólafsson, M. 2014-09-01 Colonisation of life on Surtsey has been observed systematically since the formation of the island 50 years ago. Although the first colonisers were prokaryotes, such as bacteria and blue-green algae, most studies have been focusing on settlement of plants and animals but less on microbial succession. To explore microbial colonization in diverse soils and the influence of associate vegetation and birds on numbers of environmental bacteria, we collected 45 samples from different soils types on the surface of the island. Total viable bacterial counts were performed with plate count at 22, 30 and 37 °C for all soils samples and the amount of organic matter and nitrogen (N) was measured. Selected samples were also tested for coliforms, faecal coliforms aerobic and anaerobic bacteria. The deep subsurface biosphere was investigated by collecting liquid subsurface samples from a 182 m borehole with a special sampler. Diversity analysis of uncultivated biota in samples was performed by 16S rRNA gene sequences analysis and cultivation. Correlation was observed between N deficits and the number of microorganisms in surface soils samples. The lowest number of bacteria (1 × 104-1 × 105 g-1) was detected in almost pure pumice but the count was significant higher (1 × 106-1 × 109 g-1) in vegetated soil or pumice with bird droppings. The number of faecal bacteria correlated also to the total number of bacteria and type of soil. Bacteria belonging to Enterobacteriaceae were only detected in vegetated and samples containing bird droppings. The human pathogens Salmonella, Campylobacter and Listeria were not in any sample. Both thermophilic bacteria and archaea 16S rDNA sequences were found in the subsurface samples collected at 145 m and 172 m depth at 80 °C and 54 °C, respectively, but no growth was observed in enrichments. The microbiota sequences generally showed low affiliation to any known 16S rRNA gene sequences. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27541440','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27541440">A novel single-ended readout depth-of-interaction PET detector fabricated using sub-surface laser engraving.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Uchida, H; Sakai, T; Yamauchi, H; Hakamata, K; Shimizu, K; Yamashita, T 2016-09-21 We propose a novel scintillation detector design for positron emission tomography (PET), which has depth of interaction (DOI) capability and uses a single-ended readout scheme. The DOI detector contains a pair of crystal bars segmented using sub-surface laser engraving (SSLE). The two crystal bars are optically coupled to each other at their top segments and are coupled to two photo-sensors at their bottom segments. Initially, we evaluated the performance of different designs of single crystal bars coupled to photomultiplier tubes at both ends. We found that segmentation by SSLE results in superior performance compared to the conventional method. As the next step, we constructed a crystal unit composed of a 3 × 3 × 20 mm 3 crystal bar pair, with each bar containing four layers segmented using the SSLE. We measured the DOI performance by changing the optical conditions for the crystal unit. Based on the experimental results, we then assessed the detector performance in terms of the DOI capability by evaluating the position error, energy resolution, and light collection efficiency for various crystal unit designs with different bar sizes and a different number of layers (four to seven layers). DOI encoding with small position error was achieved for crystal units composed of a 3 × 3 × 20 mm 3 LYSO bar pair having up to seven layers, and with those composed of a 2 × 2 × 20 mm 3 LYSO bar pair having up to six layers. The energy resolution of the segment in the seven-layer 3 × 3 × 20 mm 3 crystal bar pair was 9.3%-15.5% for 662 keV gamma-rays, where the segments closer to the photo-sensors provided better energy resolution. SSLE provides high geometrical accuracy at low production cost due to the simplicity of the crystal assembly. Therefore, the proposed DOI detector is expected to be an attractive choice for practical small-bore PET systems dedicated to imaging of the </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.V43B3133P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.V43B3133P">Shallow Subsurface Structures of Volcanic Fissures</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Parcheta, C. E.; Nash, J.; Mitchell, K. L.; Parness, A. 2015-12-01 Volcanic fissure vents are a difficult geologic feature to quantify. They are often too thin to document in detail with seismology or remote geophysical methods. Additionally, lava flows, lava drain back, or collapsed rampart blocks typically conceal a fissure's surface expression. For exposed fissures, quantifying the surface (let along sub0surface) geometric expression can become an overwhelming and time-consuming task given the non-uniform distribution of wall irregularities, drain back textures, and the larger scale sinuosity of the whole fissure system. We developed (and previously presented) VolcanoBot to acquire robust characteristic data of fissure geometries by going inside accessible fissures after an eruption ends and the fissure cools off to <50 C. Data from VolcanoBot documents the fissure conduit geometry with a near-IR structured light sensor, and reproduces the 3d structures to cm-scale accuracy. Here we present a comparison of shallow subsurface structures (<30 m depth) within the Mauna Ulu fissure system and their counterpart features at the vent-to-ground-surface interface. While we have not mapped enough length of the fissure to document sinuosity at depth, we see a self-similar pattern of irregularities on the fissure walls throughout the entire shallow subsurface, implying a fracture mechanical origin similar to faults. These irregularities are, on average, 1 m across and protrude 30 cm into the drained fissure. This is significantly larger than the 10% wall roughness addressed in the engineering literature on fluid dynamics, and implies that magma fluid dynamics during fissure eruptions are probably not as passive nor as simple as previously thought. In some locations, it is possible to match piercing points across the fissure walls, where the dike broke the wall rock in order to propagate upwards, yet in other locations there are erosional cavities, again, implying complex fluid dynamics in the shallow sub-surface during fissure eruptions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.H52B..06M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.H52B..06M">Evidence of linked biogeochemical and hydrological processes in homogeneous and layered vadose zone systems</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> McGuire, J. T.; Hansen, D. J.; Mohanty, B. P. 2010-12-01 Understanding chemical fate and transport in the vadose zone is critical to protect groundwater resources and preserve ecosystem health. However, prediction can be challenging due to the dynamic hydrologic and biogeochemical nature of the vadose zone. Additional controls on hydrobiogeochemical processes are added by subsurface structural heterogeneity. This study uses repacked soil column experiments to quantify linkages between microbial activity, geochemical cycling and hydrologic flow. Three “short” laboratory soil columns were constructed to evaluate the effects of soil layering: a homogenized medium-grained sand, homogenized organic-rich loam, and a sand-over-loam layered column. In addition, two “long” columns were constructed using either gamma-irradiated (sterilized) or untreated sediments to evaluate the effects of both soil layers and the presence of microorganisms. The long columns were packed identically; a medium-grained sand matrix with two vertically separated and horizontally offset lenses of organic-rich loam. In all 5 columns, downward and upward infiltration of water was evaluated to simulate rainfall and rising water table events respectively. In-situ colocated probes were used to measure soil water content, matric potential, Eh, major anions, ammonium, Fe2+, and total sulfide. Enhanced biogeochemical cycling was observed in the short layered column versus the short, homogeneous columns, and enumerations of iron and sulfate reducing bacteria were 1-2 orders of magnitude greater. In the long columns, microbial activity caused mineral bands and produced insoluble gases that impeded water flow through the pores of the sediment. Capillary barriers, formed around the lenses due to soil textural differences, retarded water flow rates through the lenses. This allowed reducing conditions to develop, evidenced by the production of Fe2+ and S2-. At the fringes of the lenses, Fe2+ oxidized to form Fe(III)-oxide bands that further retarded water </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1105046','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1105046">MICROSCALE METABOLIC, REDOX AND ABIOTIC REACTIONS IN HANFORD 300 AREA SUBSURFACE SEDIMENTS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Beyenal, Haluk; McLEan, Jeff; Majors, Paul 2013-11-14 The Hanford 300 Area is a unique site due to periodic hydrologic influence of river water resulting in changes in groundwater elevation and flow direction. This area is also highly subject to uranium remobilization, the source of which is currently believed to be the region at the base of the vadose zone that is subject to period saturation due to the changes in the water levels in the Columbia River. We found that microbial processes and redox and abiotic reactions which operate at the microscale were critical to understanding factors controlling the macroscopic fate and transport of contaminants in themore » subsurface. The combined laboratory and field research showed how microscale conditions control uranium mobility and how biotic, abiotic and redox reactions relate to each other. Our findings extended the current knowledge to examine U(VI) reduction and immobilization using natural 300 Area communities as well as selected model organisms on redox-sensitive and redox-insensitive minerals. Using innovative techniques developed specifically to probe biogeochemical processes at the microscale, our research expanded our current understanding of the roles played by mineral surfaces, bacterial competition, and local biotic, abiotic and redox reaction rates on the reduction and immobilization of uranium.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.S34A..06S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.S34A..06S">From Ground Truth to Space: Surface, Subsurface and Remote Observations Associated with Nuclear Test Detection</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sussman, A. J.; Anderson, D.; Burt, C.; Craven, J.; Kimblin, C.; McKenna, I.; Schultz-Fellenz, E. S.; Miller, E.; Yocky, D. A.; Haas, D. 2016-12-01 Underground nuclear explosions (UNEs) result in numerous signatures that manifest on a wide range of temporal and spatial scales. Currently, prompt signals, such as the detection of seismic waves provide only generalized locations and the timing and amplitude of non-prompt signals are difficult to predict. As such, research into improving the detection, location, and identification of suspect events has been conducted, resulting in advancement of nuclear test detection science. In this presentation, we demonstrate the scalar variably of surface and subsurface observables, briefly discuss current capabilities to locate, detect and characterize potential nuclear explosion locations, and explain how emergent technologies and amalgamation of disparate data sets will facilitate improved monitoring and verification. At the smaller scales, material and fracture characterization efforts on rock collected from legacy UNE sites and from underground experiments using chemical explosions can be incorporated into predictive modeling efforts. Spatial analyses of digital elevation models and orthoimagery of both modern conventional and legacy nuclear sites show subtle surface topographic changes and damage at nearby outcrops. Additionally, at sites where such technology cannot penetrate vegetative cover, it is possible to use the vegetation itself as both a companion signature reflecting geologic conditions and showing subsurface impacts to water, nutrients, and chemicals. Aerial systems based on RGB imagery, light detection and ranging, and hyperspectral imaging can allow for combined remote sensing modalities to perform pattern recognition and classification tasks. Finally, more remote systems such as satellite based synthetic aperture radar and satellite imagery are other techniques in development for UNE site detection, location and characterization. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.P51D0961B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.P51D0961B">Aseptically Sampled Organics in Subsurface Rocks From the Mars Analog Rio Tinto Experiment: An Analog For The Search for Deep Subsurface Life on Mars.}</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bonaccorsi, R.; Stoker, C. R. 2005-12-01 The subsurface is the key environment for searching for life on planets lacking surface life. Subsurface ecosystems are of great relevance to astrobiology including the search for past/present life on Mars. The surface of Mars has conditions preventing current life but the subsurface might preserve organics and even host some life [1]. The Mars-Analog-Rio-Tinto-Experiment (MARTE) is performing a simulation of a Mars drilling experiment. This comprises conventional and robotic drilling of cores in a volcanically-hosted-massive-pyrite deposit [2] from the Iberian Pyritic Belt (IBP) and life detection experiments applying anti-contamination protocols (e.g., ATP Luminometry assay). The RT is considered an important analog of the Sinus Meridiani site on Mars and an ideal model analog for a deep subsurface Martian environment. Former results from MARTE suggest the existence of a relatively complex subsurface life including aerobic and anaerobic chemoautotrophs and strict anaerobic methanogens sustained by Fe and S minerals in anoxic conditions. A key requirement for the analysis of a subsurface sample on Mars is a set of simple tests that can help determine if the sample contains organic material of biological origin, and its potential for retaining definitive biosignatures. We report here on the presence of bulk organic matter Corg (0.03-0.05 Wt%), and Ntot (0.01-0.04 Wt%) and amount of measured ATP (Lightning MVP, Biocontrol) in weathered rocks (tuffs, gossan, pyrite stockwork from Borehole #8; >166m). This provides key insight on the type of trophic system sustaining the subsurface biosphere (i.e., heterotrophs vs. autotrophs) at RT. ATP data (Relative-Luminosity-Units, RLU) provide information on possible contamination and distribution of viable biomass with core depth (BH#8, and BH#7, ~3m). Avg. 153 RLU, i.e., surface vs. center of core, suggest that cleaness/sterility can be maintained when using a simple sterile protocol under field conditions. Results from this </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1136443','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1136443">Development of Enabling Scientific Tools to Characterize the Geologic Subsurface at Hanford</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Kenna, Timothy C.; Herron, Michael M. 2014-07-08 This final report to the Department of Energy provides a summary of activities conducted under our exploratory grant, funded through U.S. DOE Subsurface Biogeochemical Research Program in the category of enabling scientific tools, which covers the period from July 15, 2010 to July 14, 2013. The main goal of this exploratory project is to determine the parameters necessary to translate existing borehole log data into reservoir properties following scientifically sound petrophysical relationships. For this study, we focused on samples and Ge-based spectral gamma logging system (SGLS) data collected from wells located in the Hanford 300 Area. The main activities consistedmore » of 1) the analysis of available core samples for a variety of mineralogical, chemical and physical; 2) evaluation of selected spectral gamma logs, environmental corrections, and calibration; 3) development of algorithms and a proposed workflow that permits translation of log responses into useful reservoir properties such as lithology, matrix density, porosity, and permeability. These techniques have been successfully employed in the petroleum industry; however, the approach is relatively new when applied to subsurface remediation. This exploratory project has been successful in meeting its stated objectives. We have demonstrated that our approach can lead to an improved interpretation of existing well log data. The algorithms we developed can utilize available log data, in particular gamma, and spectral gamma logs, and continued optimization will improve their application to ERSP goals of understanding subsurface properties.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23848498','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23848498">The Mojave vadose zone: a subsurface biosphere analogue for Mars.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Abbey, William; Salas, Everett; Bhartia, Rohit; Beegle, Luther W 2013-07-01 If life ever evolved on the surface of Mars, it is unlikely that it would still survive there today, but as Mars evolved from a wet planet to an arid one, the subsurface environment may have presented a refuge from increasingly hostile surface conditions. Since the last glacial maximum, the Mojave Desert has experienced a similar shift from a wet to a dry environment, giving us the opportunity to study here on Earth how subsurface ecosystems in an arid environment adapt to increasingly barren surface conditions. In this paper, we advocate studying the vadose zone ecosystem of the Mojave Desert as an analogue for possible subsurface biospheres on Mars. We also describe several examples of Mars-like terrain found in the Mojave region and discuss ecological insights that might be gained by a thorough examination of the vadose zone in these specific terrains. Examples described include distributary fans (deltas, alluvial fans, etc.), paleosols overlain by basaltic lava flows, and evaporite deposits. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=80892&Lab=NRMRL&keyword=public+AND+relations&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=80892&Lab=NRMRL&keyword=public+AND+relations&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">THE HYDROLOGIC SYSTEM: GEOMORPHIC AND HYDROGEOLOGIC CONTROLS ON SURFACE AND SUBSURFACE FLOW REGIMES IN RIPARIAN MEADOW ECOSYSTEMS IN THE CENTRAL GREAT BASIN</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Riparian corridors in upland watersheds in the Great Basin of central Nevada contain the majority of the region's biodiversity. Water, in both surface and subsurface flow regimes, is an important resource sustaining these sensitive ecosystems and other similar riparian ecosystem... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=31952&Lab=ORD&keyword=bone&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=31952&Lab=ORD&keyword=bone&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">MORPHOLOGICAL AND CULTURAL COMPARISON OF MICROORGANISMS IN SURFACE SOIL AND SUBSURFACE SEDIMENTS AT A PRISTINE STUDY SITE IN OKLAHOMA (JOURNAL VERSION)</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Surface-soil and subsurface microfloras at the site of a shallow aquifer in Oklahoma were examined and compared with respect to (1) total and viable cell numbers, (2) colony and cell types that grew on various plating media, (3) cell morphologies seen in flotation films stripped ... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B53H..02M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B53H..02M">A soil-landscape framework for understanding spatial and temporal variability in biogeochemical processes in catchments</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> McGuire, K. J.; Bailey, S. W.; Ross, D. S. 2017-12-01 Heterogeneity in biophysical properties within catchments challenges how we quantify and characterize biogeochemical processes and interpret catchment outputs. Interactions between the spatiotemporal variability of hydrological states and fluxes and soil development can spatially structure catchments, leading to a framework for understanding patterns in biogeochemical processes. In an upland, glaciated landscape at the Hubbard Brook Experimental Forest (HBEF) in New Hampshire, USA, we are embracing the structure and organization of soils to understand the spatial relations between runoff production zones, distinct soil-biogeochemical environments, and solute retention and release. This presentation will use observations from the HBEF to demonstrate that a soil-landscape framework is essential in understanding the spatial and temporal variability of biogeochemical processes in this catchment. Specific examples will include how laterally developed soils reveal the location of active runoff production zones and lead to gradients in primary mineral dissolution and the distribution of weathering products along hillslopes. Soil development patterns also highlight potential carbon and nitrogen cycling hotspots, differentiate acidic conditions, and affect the regulation of surface water quality. Overall, this work demonstrates the importance of understanding the landscape-level structural organization of soils in characterizing the variation and extent of biogeochemical processes that occur in catchments. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23700443','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23700443">Pyrosequencing-based assessment of the bacteria diversity in surface and subsurface peat layers of a northern wetland, with focus on poorly studied phyla and candidate divisions.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Serkebaeva, Yulia M; Kim, Yongkyu; Liesack, Werner; Dedysh, Svetlana N 2013-01-01 Northern peatlands play a key role in the global carbon and water budget, but the bacterial diversity in these ecosystems remains poorly described. Here, we compared the bacterial community composition in the surface (0-5 cm depth) and subsurface (45-50 cm) peat layers of an acidic (pH 4.0) Sphagnum-dominated wetland, using pyrosequencing of 16S rRNA genes. The denoised sequences (37,229 reads, average length ∼430 bp) were affiliated with 27 bacterial phyla and corresponded to 1,269 operational taxonomic units (OTUs) determined at 97% sequence identity. Abundant OTUs were affiliated with the Acidobacteria (35.5±2.4% and 39.2±1.2% of all classified sequences in surface and subsurface peat, respectively), Alphaproteobacteria (15.9±1.7% and 25.8±1.4%), Actinobacteria (9.5±2.0% and 10.7±0.5%), Verrucomicrobia (8.5±1.4% and 0.6±0.2%), Planctomycetes (5.8±0.4% and 9.7±0.6%), Deltaproteobacteria (7.1±0.4% and 4.4%±0.3%), and Gammaproteobacteria (6.6±0.4% and 2.1±0.1%). The taxonomic patterns of the abundant OTUs were uniform across all the subsamples taken from each peat layer. In contrast, the taxonomic patterns of rare OTUs were different from those of the abundant OTUs and varied greatly among subsamples, in both surface and subsurface peat. In addition to the bacterial taxa listed above, rare OTUs represented the following groups: Armatimonadetes, Bacteroidetes, Chlamydia, Chloroflexi, Cyanobacteria, Elusimicrobia, Fibrobacteres, Firmicutes, Gemmatimonadetes, Spirochaetes, AD3, WS1, WS4, WS5, WYO, OD1, OP3, BRC1, TM6, TM7, WPS-2, and FCPU426. OTU richness was notably higher in the surface layer (882 OTUs) than in the anoxic subsurface peat (483 OTUs), with only 96 OTUs common to both data sets. Most members of poorly studied phyla, such as the Acidobacteria, Verrucomicrobia, Planctomycetes and the candidate division TM6, showed a clear preference for growth in either oxic or anoxic conditions. Apparently, the bacterial communities in surface and </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active">23</li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active">24</li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.T43D..04O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.T43D..04O">State-of-stress in magmatic rift zones: Predicting the role of surface and subsurface topography</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Oliva, S. J. C.; Ebinger, C.; Rivalta, E.; Williams, C. A. 2017-12-01 Continental rift zones are segmented along their length by large fault systems that form in response to extensional stresses. Volcanoes and crustal magma chambers cause fundamental changes to the density structure, load the plates, and alter the state-of-stress within the crust, which then dictates fracture orientation. In this study, we develop geodynamic models scaled to a < 7 My rift sector in the Eastern rift, East Africa where geophysical imaging provides tight constraints on subsurface structure, petrologic and thermodynamic studies constrain material densities, and seismicity and structural analyses constrain active and time-averaged kinematics. This area is an ideal test area because a 60º stress rotation is observed in time-averaged fault and magma intrusion, and in local seismicity, and because this was the site of a large volume dike intrusion and seismic sequence in 2007. We use physics-based 2D and 3D models (analytical and finite elements) constrained by data from active rift zones to quantify the effects of loading on state-of-stress. By modeling varying geometric arrangements, and density contrasts of topographic and subsurface loads, and with reasonable regional extensional forces, the resulting state-of-stress reveals the favored orientation for new intrusions. Although our models are generalized, they allow us to evaluate whether a magmatic system (surface and subsurface) can explain the observed stress rotation, and enable new intrusions, new faults, or fault reactivation with orientations oblique to the main border faults. Our results will improve our understanding of the different factors at play in these extensional regimes, as well as contribute to a better assessment of the hazards in the area. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70029440','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70029440">Biogeochemical and metabolic responses to the flood pulse in a semiarid floodplain</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Valett, H.M.; Baker, M.A.; Morrice, J.A.; Crawford, C.S.; Molles, M.C.; Dahm, Clifford N.; Moyer, D.L.; Thibault, J.R.; Ellis, L.M. 2005-01-01 Flood pulse inundation of riparian forests alters rates of nutrient retention and organic matter processing in the aquatic ecosystems formed in the forest interior. Along the Middle Rio Grande (New Mexico, USA), impoundment and levee construction have created riparian forests that differ in their inter-flood intervals (IFIs) because some floodplains are still regularly inundated by the flood pulse (i.e., connected), while other floodplains remain isolated from flooding (i.e., disconnected). This research investigates how ecosystem responses to the flood pulse relate to forest IFI by quantifying nutrient and organic matter dynamics in the Rio Grande floodplain during three years of experimental flooding of the disconnected floodplain and during a single year of natural flooding of the connected floodplain. Surface and subsurface conditions in paired sites (control, flood) established in the two floodplain types were monitored to address metabolic and biogeochemical responses. Compared to dry controls, rates of respiration in the flooded sites increased by up to three orders of magnitude during the flood pulse. In the disconnected forest, month-long experimental floods produced widespread anoxia of four-week duration during each of the three years of flooding. In contrast, water in the connected floodplain remained well oxygenated (3-8 ppm). Material budgets for experimental floods showed the disconnected floodplain to be a sink for inorganic nitrogen and suspended solids, but a potential source of dissolved organic carbon (DOC). Compared to the main stem of the Rio Grande, flood-water on the connected floodplain contained less nitrate, but comparable concentrations of DOC, phosphate-phosphorus, and ammonium-nitrogen. Results suggest that floodplain IFI drives metabolic and biogeochemical responses during the flood pulse. Impoundment and fragmentation have altered floodplains from a mosaic of patches with variable IFI to a bimodal distribution. Relatively predictable </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1430685-subsurface-oxygen-necessary-electrochemical-reduction-co2-copper','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1430685-subsurface-oxygen-necessary-electrochemical-reduction-co2-copper">Is Subsurface Oxygen Necessary for the Electrochemical Reduction of CO 2 on Copper?</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Garza, Alejandro J.; Bell, Alexis T.; Head-Gordon, Martin It has recently been proposed that subsurface oxygen is crucial for the adsorption and subsequent electroreduction of CO 2 on copper. Using density functional theory, we have studied the stability and diffusion of subsurface oxygen in single crystals of copper exposing (111) and (100) facets. Oxygen is at least 1.5 eV more stable on the surface than beneath it for both crystal orientations; interstitial sites are too small to accommodate oxygen. Here, the rate of atomic oxygen diffusion from one layer below a Cu(111) surface to the surface is 5 × 10 3 s –1. Oxygen can survive longer inmore » deeper layers, but it does not promote CO 2 adsorption there. Diffusion of subsurface oxygen is easier to the less-dense Cu(100) surface, even from lower layers (rate ≈ 1 × 107 s–1). Finally, once the applied voltage and dispersion forces are properly modeled, we find that subsurface oxygen is unnecessary for CO 2 adsorption on copper.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1430685-subsurface-oxygen-necessary-electrochemical-reduction-co2-copper','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1430685-subsurface-oxygen-necessary-electrochemical-reduction-co2-copper">Is Subsurface Oxygen Necessary for the Electrochemical Reduction of CO 2 on Copper?</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Garza, Alejandro J.; Bell, Alexis T.; Head-Gordon, Martin 2018-01-17 It has recently been proposed that subsurface oxygen is crucial for the adsorption and subsequent electroreduction of CO 2 on copper. Using density functional theory, we have studied the stability and diffusion of subsurface oxygen in single crystals of copper exposing (111) and (100) facets. Oxygen is at least 1.5 eV more stable on the surface than beneath it for both crystal orientations; interstitial sites are too small to accommodate oxygen. Here, the rate of atomic oxygen diffusion from one layer below a Cu(111) surface to the surface is 5 × 10 3 s –1. Oxygen can survive longer inmore » deeper layers, but it does not promote CO 2 adsorption there. Diffusion of subsurface oxygen is easier to the less-dense Cu(100) surface, even from lower layers (rate ≈ 1 × 107 s–1). Finally, once the applied voltage and dispersion forces are properly modeled, we find that subsurface oxygen is unnecessary for CO 2 adsorption on copper.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70125710','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70125710">MODFLOW-based coupled surface water routing and groundwater-flow simulation</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Hughes, Joseph D.; Langevin, Christian D.; White, Jeremy T. 2015-01-01 In this paper, we present a flexible approach for simulating one- and two-dimensional routing of surface water using a numerical surface water routing (SWR) code implicitly coupled to the groundwater-flow process in MODFLOW. Surface water routing in SWR can be simulated using a diffusive-wave approximation of the Saint-Venant equations and/or a simplified level-pool approach. SWR can account for surface water flow controlled by backwater conditions caused by small water-surface gradients or surface water control structures. A number of typical surface water control structures, such as culverts, weirs, and gates, can be represented, and it is possible to implement operational rules to manage surface water stages and streamflow. The nonlinear system of surface water flow equations formulated in SWR is solved by using Newton methods and direct or iterative solvers. SWR was tested by simulating the (1) Lal axisymmetric overland flow, (2) V-catchment, and (3) modified Pinder-Sauer problems. Simulated results for these problems compare well with other published results and indicate that SWR provides accurate results for surface water-only and coupled surface water/groundwater problems. Results for an application of SWR and MODFLOW to the Snapper Creek area of Miami-Dade County, Florida, USA are also presented and demonstrate the value of coupled surface water and groundwater simulation in managed, low-relief coastal settings. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=83027&keyword=Ford&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=83027&keyword=Ford&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">IMPACT OF REDOX DISEQUILIBRIA ON CONTAMINANT TRANSPORT AND REMEDIATION IN SUBSURFACE SYSTEMS</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Partitioning to mineral surfaces exerts significant control on inorganic contaminant transport in subsurface systems. Remedial technologies for in-situ treatment of subsurface contamination are frequently designed to optimize the efficiency of contaminant partitioning to solid s... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12387392','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12387392">Oceanic biogeochemical controls on global dynamics of persistent organic pollutants.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Dachs, Jordi; Lohmann, Rainer; Ockenden, Wendy A; Méjanelle, Laurence; Eisenreich, Steven J; Jones, Kevin C 2002-10-15 Understanding and quantifying the global dynamics and sinks of persistent organic pollutants (POPs) is important to assess their environmental impact and fate. Air-surface exchange processes, where temperature plays a central role in controlling volatilization and deposition, are of key importance in controlling global POP dynamics. The present study is an assessment of the role of oceanic biogeochemical processes, notably phytoplankton uptake and vertical fluxes of particles, on the global dynamics of POPs. Field measurements of atmospheric polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins (PCDDs), and furans (PCDFs) are combined with remote sensing estimations of oceanic temperature, wind speed, and chlorophyll, to model the interactions between air-water exchange, phytoplankton uptake, and export of organic matter and POPs out of the mixed surface ocean layer. Deposition is enhanced in the mid-high latitudes and is driven by sinking marine particulate matter, rather than by a cold condensation effect. However, the relative contribution of the biological pump is a function of the physical-chemical properties of POPs. It is concluded that oceanic biogeochemical processes play a critical role in controlling the global dynamics and the ultimate sink of POPs. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29044977','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29044977">Plasmon-Exciton Coupling Interaction for Surface Catalytic Reactions.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Wang, Jingang; Lin, Weihua; Xu, Xuefeng; Ma, Fengcai; Sun, Mengtao 2018-05-01 In this review, we firstly reveal the physical principle of plasmon-exciton coupling interaction with steady absorption spectroscopy, and ultrafast transition absorption spectroscopy, based on the pump-prop technology. Secondly, we introduce the fabrication of electro-optical device of two-dimensional semiconductor-nanostructure noble metals hybrid, based on the plasmon-exciton coupling interactions. Thirdly, we introduce the applications of plasmon-exciton coupling interaction in the field of surface catalytic reactions. Lastly, the perspective of plasmon-exciton coupling interaction and applications closed this review. © 2018 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JHyd..367..200G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JHyd..367..200G">A spatially explicit hydro-ecological modeling framework (BEPS-TerrainLab V2.0): Model description and test in a boreal ecosystem in Eastern North America</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Govind, Ajit; Chen, Jing Ming; Margolis, Hank; Ju, Weimin; Sonnentag, Oliver; Giasson, Marc-André 2009-04-01 SummaryA spatially explicit, process-based hydro-ecological model, BEPS-TerrainLab V2.0, was developed to improve the representation of ecophysiological, hydro-ecological and biogeochemical processes of boreal ecosystems in a tightly coupled manner. Several processes unique to boreal ecosystems were implemented including the sub-surface lateral water fluxes, stratification of vegetation into distinct layers for explicit ecophysiological representation, inclusion of novel spatial upscaling strategies and biogeochemical processes. To account for preferential water fluxes common in humid boreal ecosystems, a novel scheme was introduced based on laboratory analyses. Leaf-scale ecophysiological processes were upscaled to canopy-scale by explicitly considering leaf physiological conditions as affected by light and water stress. The modified model was tested with 2 years of continuous measurements taken at the Eastern Old Black Spruce Site of the Fluxnet-Canada Research Network located in a humid boreal watershed in eastern Canada. Comparison of the simulated and measured ET, water-table depth (WTD), volumetric soil water content (VSWC) and gross primary productivity (GPP) revealed that BEPS-TerrainLab V2.0 simulates hydro-ecological processes with reasonable accuracy. The model was able to explain 83% of the ET, 92% of the GPP variability and 72% of the WTD dynamics. The model suggests that in humid ecosystems such as eastern North American boreal watersheds, topographically driven sub-surface baseflow is the main mechanism of soil water partitioning which significantly affects the local-scale hydrological conditions. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=20186&Lab=NRMRL&keyword=land+AND+indigenous&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=20186&Lab=NRMRL&keyword=land+AND+indigenous&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">OVERVIEW -- SUBSURFACE PROTECTION AND REMEDIATION DIVISION</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> NRMRL's Subsurface Protection and Remediation Division located in Ada, Oklahoma, conducts EPA-investigator led laboratory and field research to provide the scientific basis to support the development of strategies and technologies to protect and restore ground and surface water q... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B11J0571L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B11J0571L">Insight from Genomics on Biogeochemical Cycles in a Shallow-Sea Hydrothermal System</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lu, G. S.; Amend, J. 2015-12-01 Shallow-sea hydrothermal ecosystems are dynamic, high-energy systems influenced by sunlight and geothermal activity. They provide accessible opportunities for investigating thermophilic microbial biogeochemical cycles. In this study, we report biogeochemical data from a shallow-sea hydrothermal system offshore Paleochori Bay, Milos, Greece, which is characterized by a central vent covered by white microbial mats with hydrothermally influenced sediments extending into nearby sea grass area. Geochemical analysis and deep sequencing provide high-resolution information on the geochemical patterns, microbial diversity and metabolic potential in a two-meter transect. The venting fluid is elevated in temperature (~70oC), low in pH (~4), and enriched in reduced species. The geochemical pattern shows that the profile is affected by not only seawater dilution but also microbial regulation. The microbial community in the deepest section of vent core (10-12 cm) is largely dominated by thermophilic archaea, including a methanogen and a recently described Crenarcheon. Mid-core (6-8 cm), the microbial community in the venting area switches to the hydrogen utilizer Aquificae. Near the sediment-water interface, anaerobic Firmicutes and Actinobacteria dominate, both of which are commonly associated with subsurface and hydrothermal sites. All other samples are dominated by diverse Proteobacteria. The sulfate profile is strongly correlated with the population size of delta- and episilon-proteobactia. The dramatic decrease in concentrations of As and Mn in pore fluids as a function of distance from the vent suggests that in addition to seawater dilution, microorganisms are likely transforming these and other ions through a combination of detoxification and catabolism. In addition, high concentrations of dissolved Fe are only measurable in the shallow sea grass area, suggesting that iron-transforming microorganisms are controlling Fe mobility, and promoting biomineralization. Taken </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28442237','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28442237">Long-term ERT monitoring of biogeochemical changes of an aged hydrocarbon contamination.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Caterina, David; Flores Orozco, Adrian; Nguyen, Frédéric 2017-06-01 Adequate management of contaminated sites requires information with improved spatio-temporal resolution, in particular to assess bio-geochemical processes, such as the transformation and degradation of contaminants, precipitation of minerals or changes in groundwater geochemistry occurring during and after remediation procedures. Electrical Resistivity Tomography (ERT), a geophysical method sensitive to pore-fluid and pore-geometry properties, permits to gain quasi-continuous information about subsurface properties in real-time and has been consequently widely used for the characterization of hydrocarbon-impacted sediments. However, its application for the long-term monitoring of processes accompanying natural or engineered bioremediation is still difficult due to the poor understanding of the role that biogeochemical processes play in the electrical signatures. For in-situ studies, the task is further complicated by the variable signal-to-noise ratio and the variations of environmental parameters leading to resolution changes in the electrical images. In this work, we present ERT imaging results for data collected over a period of two years on a site affected by a diesel fuel contamination and undergoing bioremediation. We report low electrical resistivity anomalies in areas associated to the highest contaminant concentrations likely due transformations of the contaminant due to microbial activity and accompanying release of metabolic products. We also report large seasonal variations of the bulk electrical resistivity in the contaminated areas in correlation with temperature and groundwater level fluctuations. However, the amplitude of bulk electrical resistivity variations largely exceeds the amplitude expected given existing petrophysical models. Our results suggest that the variations in electrical properties are mainly controlled by microbial activity which in turn depends on soil temperature and hydrogeological conditions. Therefore, ERT can be suggested as </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1013652','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/1013652">Low temperature monitoring system for subsurface barriers</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> Vinegar, Harold J [Bellaire, TX; McKinzie, II Billy John [Houston, TX 2009-08-18 A system for monitoring temperature of a subsurface low temperature zone is described. The system includes a plurality of freeze wells configured to form the low temperature zone, one or more lasers, and a fiber optic cable coupled to at least one laser. A portion of the fiber optic cable is positioned in at least one freeze well. At least one laser is configured to transmit light pulses into a first end of the fiber optic cable. An analyzer is coupled to the fiber optic cable. The analyzer is configured to receive return signals from the light pulses. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.1419B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.1419B">Improved global simulation of groundwater-ecosystem interactions via tight coupling of a dynamic global ecosystem model and a global hydrological model</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Braakhekke, Maarten; Rebel, Karin; Dekker, Stefan; Smith, Benjamin; Sutanudjaja, Edwin; van Beek, Rens; van Kampenhout, Leo; Wassen, Martin 2017-04-01 In up to 30% of the global land surface ecosystems are potentially influenced by the presence of a shallow groundwater table. In these regions upward water flux by capillary rise increases soil moisture availability in the root zone, which has a strong effect on evapotranspiration, vegetation dynamics, and fluxes of carbon and nitrogen. Most global hydrological models and several land surface models simulate groundwater table dynamics and their effects on land surface processes. However, these models typically have relatively simplistic representation of vegetation and do not consider changes in vegetation type and structure. Dynamic global vegetation models (DGVMs), describe land surface from an ecological perspective, combining detailed description of vegetation dynamics and structure, and biogeochemical processes and are thus more appropriate to simulate the ecological and biogeochemical effects of groundwater interactions. However, currently virtually all DGVMs ignore these effects, assuming that water tables are too deep to affect soil moisture in the root zone. We have implemented a tight coupling between the dynamic global ecosystem model LPJ-GUESS and the global hydrological model PCR-GLOBWB, which explicitly simulates groundwater dynamics. This coupled model allows us to explicitly account for groundwater effects on terrestrial ecosystem processes at global scale. Results of global simulations indicate that groundwater strongly influences fluxes of water, carbon and nitrogen, in many regions, adding up to a considerable effect at the global scale. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1175137','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/1175137">Visual probes and methods for placing visual probes into subsurface areas</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> Clark, Don T.; Erickson, Eugene E.; Casper, William L.; Everett, David M. 2004-11-23 Visual probes and methods for placing visual probes into subsurface areas in either contaminated or non-contaminated sites are described. In one implementation, the method includes driving at least a portion of a visual probe into the ground using direct push, sonic drilling, or a combination of direct push and sonic drilling. Such is accomplished without providing an open pathway for contaminants or fugitive gases to reach the surface. According to one implementation, the invention includes an entry segment configured for insertion into the ground or through difficult materials (e.g., concrete, steel, asphalt, metals, or items associated with waste), at least one extension segment configured to selectively couple with the entry segment, at least one push rod, and a pressure cap. Additional implementations are contemplated. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AREPS..46..521B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AREPS..46..521B">Role of Soil Erosion in Biogeochemical Cycling of Essential Elements: Carbon, Nitrogen, and Phosphorus</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Berhe, Asmeret Asefaw; Barnes, Rebecca T.; Six, Johan; Marín-Spiotta, Erika 2018-05-01 Most of Earth's terrestrial surface is made up of sloping landscapes. The lateral distribution of topsoil by erosion controls the availability, stock, and persistence of essential elements in the terrestrial ecosystem. Over the last two decades, the role of soil erosion in biogeochemical cycling of essential elements has gained considerable interest from the climate, global change, and biogeochemistry communities after soil erosion and terrestrial sedimentation were found to induce a previously unaccounted terrestrial sink for atmospheric carbon dioxide. More recent studies have highlighted the role of erosion in the persistence of organic matter in soil and in the biogeochemical cycling of elements beyond carbon . Here we synthesize available knowledge and data on how erosion serves as a major driver of biogeochemical cycling of essential elements. We address implications of erosion-driven changes in biogeochemical cycles on the availability of essential elements for primary production, on the magnitude of elemental exports downstream, and on the exchange of greenhouse gases from the terrestrial ecosystem to the atmosphere. Furthermore, we explore fates of eroded material and how terrestrial mass movement events play major roles in modifying Earth's climate. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3461276','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3461276">Mining the Salivary Proteome with Grating-Coupled Surface Plasmon Resonance Imaging and Surface Plasmon Coupled Emission Microarrays</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Molony, Ryan D.; Rice, James M.; Yuk, Jongseol; Shetty, Vivek; Dey, Dipak; Lawrence, David A.; Lynes, Michael A. 2012-01-01 Biological indicators have numerous and widespread utility in personalized medicine, but the measurement of these indicators also pose many technological and practical challenges. Blood/plasma has typically been used as the sample source with which to measure these indicators, but the invasiveness associated with procurement of samples has led to increased interest in saliva as an attractive alternative. However, there are unique issues associated with the measurement of saliva biomarkers. These issues are compounded by the imperfect correlation between saliva and plasma with respect to biomarker profiles. In this manuscript, we address the technical challenges associated with saliva biomarker quantification describe a high-content microarray assay that employs both grating-coupled surface plasmon resonance imaging surface plasmon coupled emission modalities in a highly sensitive assay that has a large dynamic range. This powerful approach provides the tools to map the proteome of saliva, which in turn should greatly enhance the utility of salivary biomarker profiles in personalized medicine. PMID:22896008 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19486458','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19486458">Confocal examination of subsurface cracking in ceramic materials.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Etman, Maged K 2009-10-01 The original ceramic surface finish and its microstructure may have an effect on crack propagation. The purpose of this study was to investigate the relation between crack propagation and ceramic microstructure following cyclic fatigue loading, and to qualitatively evaluate and quantitatively measure the surface and subsurface crack depths of three types of ceramic restorations with different microstructures using a Confocal Laser Scanning Microscope (CLSM) and Scanning Electron Microscope (SEM). Twenty (8 x 4 x 2 mm(3)) blocks of AllCeram (AC), experimental ceramic (EC, IPS e.max Press), and Sensation SL (SSL) were prepared, ten glazed and ten polished of each material. Sixty antagonist enamel specimens were made from the labial surfaces of permanent incisors. The ceramic abraders were attached to a wear machine, so that each enamel specimen presented at 45 degrees to the vertical movement of the abraders, and immersed in artificial saliva. Wear was induced for 80K cycles at 60 cycles/min with a load of 40 N and 2-mm horizontal deflection. The specimens were examined for cracks at baseline, 5K, 10K, 20K, 40K, and 80K cycles. Twenty- to 30-microm deep subsurface cracking appeared in SSL, with 8 to 10 microm in AC, and 7 microm close to the margin of the wear facets in glazed EC after 5K cycles. The EC showed no cracks with increasing wear cycles. Seventy-microm deep subsurface cracks were detected in SSL and 45 microm in AC after 80K cycles. Statistically, there was significant difference among the three materials (p < 0.05). Bonferroni multiple comparison of means test confirmed the ANOVA test and showed that there was no statistical difference (p > 0.05) in crack depth within the same ceramic material with different surface finishes. The ceramic materials with different microstructures showed different patterns of subsurface cracking. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PhRvB..81l5408T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhRvB..81l5408T">Electronic damping of anharmonic adsorbate vibrations at metallic surfaces</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tremblay, Jean Christophe; Monturet, Serge; Saalfrank, Peter 2010-03-01 The nonadiabatic coupling of an adsorbate close to a metallic surface leads to electronic damping of adsorbate vibrations and line broadening in vibrational spectroscopy. Here, a perturbative treatment of the electronic contribution to the lifetime broadening serves as a building block for a new approach, in which anharmonic vibrational transition rates are calculated from a position-dependent coupling function. Different models for the coupling function will be tested, all related to embedding theory. The first two are models based on a scattering approach with (i) a jellium-type and (ii) a density functional theory based embedding density, respectively. In a third variant a further refined model is used for the embedding density, and a semiempirical approach is taken in which a scaling factor is chosen to match harmonic, single-site, first-principles transition rates, obtained from periodic density functional theory. For the example of hydrogen atoms on (adsorption) and below (subsurface absorption) a Pd(111) surface, lifetimes of and transition rates between vibrational levels are computed. The transition rates emerging from different models serve as input for the selective subsurface adsorption of hydrogen in palladium starting from an adsorption site, by using sequences of infrared laser pulses in a laser distillation scheme. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1010281','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1010281">Characterization of Microbial Communities in Subsurface Nuclear Blast Cavities of the Nevada Test Site</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Moser, Duane P.; Bruckner, Jim; Fisher, Jen 2010-09-01 This U.S. Department of Energy (DOE) Environmental Remediation Sciences Project (ERSP) was designed to test fundamental hypotheses concerning the existence and nature of indigenous microbial populations of Nevada Test Site subsurface nuclear test/detonation cavities. Now called Subsurface Biogeochemical Research (SBR), this program’s Exploratory Research (ER) element, which funded this research, is designed to support high risk, high potential reward projects. Here, five cavities (GASCON, CHANCELLOR, NASH, ALEMAN, and ALMENDRO) and one tunnel (U12N) were sampled using bailers or pumps. Molecular and cultivation-based techniques revealed bacterial signatures at five sites (CHANCELLOR may be lifeless). SSU rRNA gene libraries contained diverse andmore » divergent microbial sequences affiliated with known metal- and sulfur-cycling microorganisms, organic compound degraders, microorganisms from deep mines, and bacteria involved in selenate reduction and arsenite oxidation. Close relatives of Desulforudis audaxviator, a microorganism thought to subsist in the terrestrial deep subsurface on H2 and SO42- produced by radiochemical reactions, was detected in the tunnel waters. NTS-specific media formulations were used to culture and quantify nitrate-, sulfate-, iron-reducing, fermentative, and methanogenic microorganisms. Given that redox manipulations mediated by microorganisms can impact the mobility of DOE contaminants, our results should have implications for management strategies at this and other DOE sites.« less </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active">24</li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active">25</li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.U13B..05T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.U13B..05T">Stress management skills in the subsurface: H2 stress on thermophilic heterotrophs and methanogens</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Topcuoglu, B. D.; Holden, J. F. 2017-12-01 Marine hyperthermophilic heterotrophs and methanogens belonging to the Thermococcales and Methanococcales are often found in subsurface environments such as coal and shale beds, marine sediments, and oil reservoirs where they encounter H2 stress conditions. It is important to study the H2 stress survival strategies of these organisms and their cooperation with one another for survival to better understand their biogeochemical impact in hot subsurface environments. In this study, we have shown that H2 inhibition changed the growth kinetics and the transcriptome of Thermococcus paralvinellae. We observed a significant decrease in batch phase growth rates and cell concentrations with high H2 background. Produced metabolite production measurements, RNA-seq analyses of differentially expressed genes and in silico experiments we performed with the T. paralvinellae metabolic model showed that T. paralvinellae produces formate by a formate hydrogenlyase to survive H2 inhibition. We have also shown that H2 limitation caused a significant decrease in batch phase growth rates and methane production rates of the methanogen, Methanocaldococcus jannaschii. H2 stress of both organisms can be ameliorated by syntrophic growth. H2 syntrophy was demonstrated in microcosm incubations for a natural assemblage of Thermococcus and hyperthermophilic methanogens present in hydrothermal fluid samples. This project aims to describe how a hyperthermophilic heterotroph and a hyperthermophilic methanogen eliminate H2 stress and explore cooperation among thermophiles in the hot subsurface. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17467138','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17467138">The efficacy of techniques for the disinfection of artificial sub-surface dentinal caries lesions and their effect on demineralization and remineralization in vitro.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Preston, K P; Higham, S M; Smith, P W 2007-06-01 The efficacy of three techniques for the disinfection of artificial sub-surface root caries lesions and their response to subsequent episodes of de- and remineralization was investigated quantitatively in vitro. Sub-surface dentinal lesions (n=20), cut into four experimental blocks and deliberately contaminated with Streptococcus mutans, were subject to either steam autoclaving (121 degrees C, 5min), gamma irradiation (4100Gy), immersion in 0.1% (w/v) thymol-distilled water solution (24h) or reserved as a control. Next, the lesions were incubated aerobically in sterile nutrient broth for 24h at 37 degrees C and resultant cultures plated onto blood agar and neutralisation agar. Ten blocks from each experimental group were then immersed in an acidic buffer solution or exposed to artificial saliva for 5 days. Baseline changes in the mineral content and distribution of the lesions were assessed by transverse microradiography (TMR). Micro-organisms were recovered from each control block and one block treated by gamma irradiation. Steam autoclaving and immersion in a thymol solution significantly decreased (p<0.05) the amount of mineral lost from the body of lesions subject to a further acid challenge. Mineral ion uptake by lesions exposed to artificial saliva was significantly increased (p<0.05) through disinfection by steam autoclaving. Gamma irradiation proved the most acceptable method for the disinfection of sub-surface root dentine lesions having the least adverse effect on demineralization and remineralization. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H41I1567D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H41I1567D">Subsurface Controls on Stream Intermittency in a Semi-Arid Landscape</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Dohman, J.; Godsey, S.; Thackray, G. D.; Hale, R. L.; Wright, K.; Martinez, D. 2017-12-01 Intermittent streams currently constitute 30% to greater than 50% of the global river network. In addition, the number of intermittent streams is expected to increase due to changes in land use and climate. These streams provide important ecosystem services, such as water for irrigation, increased biodiversity, and high rates of nutrient cycling. Many hydrological studies have focused on mapping current intermittent flow regimes or evaluating long-term flow records, but very few have investigated the underlying causes of stream intermittency. The disconnection and reconnection of surface flow reflects the capacity of the subsurface to accommodate flow, so characterizing subsurface flow is key to understanding stream drying. We assess how subsurface flow paths control local surface flows during low-flow periods, including intermittency. Water table dynamics were monitored in an intermittent reach of Gibson Jack Creek in southeastern Idaho. Four transects were delineated with a groundwater well located in the hillslope, riparian zone, and in the stream, for a total of 12 groundwater wells. The presence or absence of surface flow was determined by frequent visual observations as well as in situ loggers every 30m along the 200m study reach. The rate of surface water drying was measured in conjunction with temperature, precipitation, subsurface hydraulic conductivity, hillslope-riparian-stream connectivity and subsurface travel time. Initial results during an unusually wet year suggest different responses in reaches that were previously observed to occasionally cease flowing. Flows in the intermittent reaches had less coherent and lower amplitude diel variations during base flow periods than reaches that had never been observed to dry out. Our findings will help contribute to our understanding of mechanisms driving expansion and contraction cycles in intermittent streams, increase our ability to predict how land use and climate change will affect flow regimes, and </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21410603-trails-kilovolt-ions-created-subsurface-channeling','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21410603-trails-kilovolt-ions-created-subsurface-channeling">Trails of Kilovolt Ions Created by Subsurface Channeling</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Redinger, Alex; Standop, Sebastian; Michely, Thomas 2010-02-19 Using scanning tunneling microscopy, we observe the damage trails produced by keV noble-gas ions incident at glancing angles onto Pt(111). Surface vacancies and adatoms aligned along the ion trajectory constitute the ion trails. Atomistic simulations reveal that these straight trails are produced by nuclear (elastic) collisions with surface layer atoms during subsurface channeling of the projectiles. In a small energy window around 5 keV, Xe{sup +} ions create vacancy grooves that mark the ion trajectory with atomic precision. The asymmetry of the adatom production on the two sides of the projectile path is traced back to the asymmetry of themore » ion's subsurface channel.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24902965','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24902965">MODFLOW-Based Coupled Surface Water Routing and Groundwater-Flow Simulation.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Hughes, J D; Langevin, C D; White, J T 2015-01-01 In this paper, we present a flexible approach for simulating one- and two-dimensional routing of surface water using a numerical surface water routing (SWR) code implicitly coupled to the groundwater-flow process in MODFLOW. Surface water routing in SWR can be simulated using a diffusive-wave approximation of the Saint-Venant equations and/or a simplified level-pool approach. SWR can account for surface water flow controlled by backwater conditions caused by small water-surface gradients or surface water control structures. A number of typical surface water control structures, such as culverts, weirs, and gates, can be represented, and it is possible to implement operational rules to manage surface water stages and streamflow. The nonlinear system of surface water flow equations formulated in SWR is solved by using Newton methods and direct or iterative solvers. SWR was tested by simulating the (1) Lal axisymmetric overland flow, (2) V-catchment, and (3) modified Pinder-Sauer problems. Simulated results for these problems compare well with other published results and indicate that SWR provides accurate results for surface water-only and coupled surface water/groundwater problems. Results for an application of SWR and MODFLOW to the Snapper Creek area of Miami-Dade County, Florida, USA are also presented and demonstrate the value of coupled surface water and groundwater simulation in managed, low-relief coastal settings. Published 2014. This article is a U.S. Government work and is in the public domain in the USA. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040012617','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040012617">Biogeochemical Cycles in Degraded Lands</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Davidson, Eric A.; Vieira, Ima Celia G.; ReisdeCarvalho, Claudio Jose; DeanedeAbreuSa, Tatiana; deSouzaMoutinho, Paulo R.; Figueiredo, Ricardo O.; Stone, Thomas A. 2004-01-01 The objectives of this project were to define and describe the types of landscapes that fall under the broad category of "degraded lands" and to study biogeochemical cycles across this range of degradation found in secondary forests. We define degraded land as that which has lost part of its capacity of renovation of a productive ecosystem, either in the context of agroecosystems or as native communities of vegetation. This definition of degradation permits evaluation of biogeochemical constraints to future land uses. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SPIE10217E..06D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SPIE10217E..06D">Raman spectroscopy method for subsurface detection of food powders through plastic layers</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Dhakal, Sagar; Chao, Kuanglin; Qin, Jianwei; Schmidt, Walter F.; Kim, Moon S.; Chan, Diane E.; Bae, Abigail 2017-05-01 Proper chemical analyses of materials in sealed containers are important for quality control purpose. Although it is feasible to detect chemicals at top surface layer, it is relatively challenging to detect objects beneath obscuring surface. This study used spatially offset Raman spectroscopy (SORS) method to detect urea, ibuprofen and acetaminophen powders contained within one or more (up to eight) layers of gelatin capsules to demonstrate subsurface chemical detection and identification. A 785 nm point-scan Raman spectroscopy system was used to acquire spatially offset Raman spectra for an offset range of 0 to 10 mm from the surfaces of 24 encapsulated samples, using a step size of 0.1 mm to obtain 101 spectral measurements per sample. With increasing offset distance, the fraction of information from the deeper subsurface material increased compared to that from the top surface material. The series of measurements was analyzed to differentiate and identify the top surface and subsurface materials. Containing mixed contributions from the powder and capsule, the SORS of each sample was decomposed using self modeling mixture analysis (SMA) to obtain pure component spectra of each component and corresponding components were identified using spectral information divergence values. Results show that SORS technique together with SMA method has a potential for non-invasive detection of chemicals at deep subsurface layer. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1014221-thinking-outside-channel-modeling-nitrogen-cycling-networked-river-ecosystems','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1014221-thinking-outside-channel-modeling-nitrogen-cycling-networked-river-ecosystems">Thinking outside the channel: Modeling nitrogen cycling in networked river ecosystems</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Helton, Ashley; Poole, Geoffrey C.; Meyer, Judy 2011-01-01 Agricultural and urban development alters nitrogen and other biogeochemical cycles in rivers worldwide. Because such biogeochemical processes cannot be measured empirically across whole river networks, simulation models are critical tools for understanding river-network biogeochemistry. However, limitations inherent in current models restrict our ability to simulate biogeochemical dynamics among diverse river networks. We illustrate these limitations using a river-network model to scale up in situ measures of nitrogen cycling in eight catchments spanning various geophysical and land-use conditions. Our model results provide evidence that catchment characteristics typically excluded from models may control river-network biogeochemistry. Based on our findings, we identify importantmore » components of a revised strategy for simulating biogeochemical dynamics in river networks, including approaches to modeling terrestrial-aquatic linkages, hydrologic exchanges between the channel, floodplain/riparian complex, and subsurface waters, and interactions between coupled biogeochemical cycles.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.P33B1447S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.P33B1447S">Subsurface Tectonics and Pingos of Northern Alaska</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Skirvin, S.; Casavant, R.; Burr, D. 2008-12-01 We describe preliminary results of a two-phase study that investigated links between subsurface structural and stratigraphic controls, and distribution of hydrostatic pingos on the central coastal plain of Arctic Alaska. Our 2300 km2 study area is underlain by a complete petroleum system that supports gas, oil and water production from 3 of the largest oil fields in North America. In addition, gas hydrate deposits exist in this area within and just below the permafrost interval at depths of 600 to 1800 feet below sea level. Phase 1 of the study compared locations of subsurface faults and pingos for evidence of linkages between faulting and pingo genesis and distribution. Several hundred discrete fault features were digitized from published data and georeferenced in a GIS database. Fault types were determined by geometry and sense of slip derived from well log and seismic maps. More than 200 pingos and surface sediment type associated with their locations were digitized from regional surficial geology maps within an area that included wire line and seismic data coverage. Beneath the pingos lies an assemblage of high-angle normal and transtensional faults that trend NNE and NW; subsidiary trends are EW and NNW. Quaternary fault reactivation is evidenced by faults that displaced strata at depths exceeding 3000 meters below sea level and intersect near-surface units. Unpublished seismic images and cross-section analysis support this interpretation. Kinematics and distribution of reactivated faults are linked to polyphase deformational history of the region that includes Mesozoic rift events, succeeded by crustal shortening and uplift of the Brooks Range to the south, and differential subsidence and segmentation of a related foreland basin margin beneath the study area. Upward fluid migration, a normal process in basin formation and fault reactivation, may play yet unrecognized roles in the genesis (e.g. fluid charging) of pingos and groundwater hydrology. Preliminary </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/twri/twri6a6/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/twri/twri6a6/">A coupled surface-water and ground-water flow model (MODBRANCH) for simulation of stream-aquifer interaction</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Swain, Eric D.; Wexler, Eliezer J. 1996-01-01 Ground-water and surface-water flow models traditionally have been developed separately, with interaction between subsurface flow and streamflow either not simulated at all or accounted for by simple formulations. In areas with dynamic and hydraulically well-connected ground-water and surface-water systems, stream-aquifer interaction should be simulated using deterministic responses of both systems coupled at the stream-aquifer interface. Accordingly, a new coupled ground-water and surface-water model was developed by combining the U.S. Geological Survey models MODFLOW and BRANCH; the interfacing code is referred to as MODBRANCH. MODFLOW is the widely used modular three-dimensional, finite-difference ground-water model, and BRANCH is a one-dimensional numerical model commonly used to simulate unsteady flow in open- channel networks. MODFLOW was originally written with the River package, which calculates leakage between the aquifer and stream, assuming that the stream's stage remains constant during one model stress period. A simple streamflow routing model has been added to MODFLOW, but is limited to steady flow in rectangular, prismatic channels. To overcome these limitations, the BRANCH model, which simulates unsteady, nonuniform flow by solving the St. Venant equations, was restructured and incorporated into MODFLOW. Terms that describe leakage between stream and aquifer as a function of streambed conductance and differences in aquifer and stream stage were added to the continuity equation in BRANCH. Thus, leakage between the aquifer and stream can be calculated separately in each model, or leakages calculated in BRANCH can be used in MODFLOW. Total mass in the coupled models is accounted for and conserved. The BRANCH model calculates new stream stages for each time interval in a transient simulation based on upstream boundary conditions, stream properties, and initial estimates of aquifer heads. Next, aquifer heads are calculated in MODFLOW based on stream </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P43C2893W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P43C2893W">Implications of Surface Morphologies for the Distribution of Shallow Subsurface Ice in Arcadia Planitia, Mars</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Williams, N. R.; Hibbard, S. M.; Golombek, M. P. 2017-12-01 The plains of Arcadia Planitia on Mars at 40°N and 200°E straddle the southern boundary of a latitude-dependent mantle (LDM) of shallow water-ice that holds key records for the planet's climate. Ice is not stable at mid-latitude surfaces today, but is expected to have precipitated in the past during different obliquities and climatic conditions with remnant excess ice preserved in the subsurface under a veneer of soil partially isolating it from the atmosphere. Previous work has documented evidence for substantial ice in Arcadia using gamma ray spectrometry; ground-penetrating radar reflections and dielectric constants; and surface morphologies of lobate debris aprons, expanded secondary craters, terraced craters, and surface polygons. New high-resolution orbital images have been acquired that resolve meter-scale ice-related morphologies. In particular, Arcadia exhibits widespread polygonal patterned ground created by cryoturbation, and large areas of crenulated "brain coral" terrain for which the sinuous troughs have already undergone sublimation while the sinuous ridges are still ice-rich. We examined over 200 High Resolution Imaging Science Experiment (HiRISE) 25 cm/pixel images that resolve these morphologies indicating a complex transition of progressive ice loss at the edge of the LDM. HiRISE coverage is sparse across Arcadia; however, 6 m/pixel Context Camera (CTX) image coverage is nearly complete and fills in the gaps for terrain units with distinct textures. We find that crenulated terrain is restricted to a narrow latitude band at 38°N-43°N. Isolated shallow pits also occur northward of 40°N, and in many cases interconnect to form crenulations as part of a transitional morphologic continuum. Polygonal surface morphologies are ubiquitous farther north, but become increasingly sparse and more degraded farther south. These pits, crenulations, and polygons are sensitive to ice at depths of centimeters to a few meters, which could be easily accessible </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMEP21A1818Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMEP21A1818Z">Sedimentary silicon isotope indicates the Kuroshio subsurface upwelling in the East China Sea</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zhao, Y.; Yang, S.; Su, N. 2017-12-01 The Kuroshio as the western boundary current of the North Pacific subtropical circulation, originates from east of the Philippine Islands, and flows northeastward along the eastern coast of Taiwan. It's subsurface water intrudes the East China Sea (ECS) and forms a typical upwelling on the inner shelf, which may play an important role in the material and heat transport, biogeochemical process and marine ecosystem of the ECS.To date, most previous studies on the Kuroshio subsurface upwelling focuse on the seasonal and interannual variations, and few researches touch on the upwelling evolution in the geologic past. In this study, eight short sediment cores were taken along the ECS inner shelf (upwelling area), which allow us to reconstruct the upwelling history over the last several hundred years. Although conventional indexes of oceanographic changes, such as salinity, temperature and hydrogen and oxygen isotope, provide valuable constraints on the modern oceanic circulation and water mass movements, how to reconstruct them from geologic records is always a challenging work. In this contribution, we present the data of stable silicon isotope, biogenic opal, diatom assemblages, element geochemistry and stable carbon and nitrogen isotopes of these core sediments, and aim to decipher the Kuroshio subsurface upwelling history on the ECS shelf. We will also illustrate the difference in δ30Si signals between small (<30 um) and large (>150 um) diatom fractions, and test whether it is an effective indicator for paleo-upwelling intensity. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMEP43C0982M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMEP43C0982M">Biogeochemical patterns of intermittent streams over space and time as surface flows decrease</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> MacNeille, R. B.; Lohse, K. A.; Godsey, S.; McCorkle, E. P.; Parsons, S.; Baxter, C. 2016-12-01 Climate change in the western United States is projected to lead to earlier snowmelt, increasing fire risk and potentially transitioning perennial streams to intermittent ones. Differences between perennial and intermittent streams, especially the temporal and spatial patterns of carbon and nutrient dynamics during periods of drying, are understudied. We examined spatial and temporal patterns in surface water biogeochemistry in southwest Idaho and hypothesized that as streams dry, carbon concentrations would increase due to evapoconcentration and/or increased in-stream production. Furthermore, we expected that biogeochemical patterns of streams would become increasingly spatially heterogeneous with drying. Finally, we expected that these patterns would vary in response to fire. To test these hypotheses, we collected water samples every 50 meters from two intermittent streams, one burned and one unburned, in April, May and June, 2016 to determine surface water biogeochemistry. Results showed average concentrations of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) increased 3-fold from April to June in the burned site compared to the unburned site where concentrations remained relatively constant. Interestingly, average concentrations of total nitrogen (TN) dropped substantially for the burned site over these three months, but only decreased slightly for the unburned site over the same time period. We also assessed changes in spatial correlation between the burned and unburned site: carbon concentrations were less spatially correlated at the unburned site than at the burned site. Scatterplot matrices of DIC values indicated that at a lag distance of 300 m in April and June, the unburned site had r-values of 0.7416 and 0.5975, respectively, while the burned site had r-values of 0.9468 and 0.8783, respectively. These initial findings support our hypotheses that carbon concentrations and spatial heterogeneity increased over time. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70192572','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70192572">Dynamic modeling of nitrogen losses in river networks unravels the coupled effects of hydrological and biogeochemical processes</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Alexander, Richard B.; Böhlke, John Karl; Boyer, Elizabeth W.; David, Mark B.; Harvey, Judson W.; Mulholland, Patrick J.; Seitzinger, Sybil P.; Tobias, Craig R.; Tonitto, Christina; Wollheim, Wilfred M. 2009-01-01 The importance of lotic systems as sinks for nitrogen inputs is well recognized. A fraction of nitrogen in streamflow is removed to the atmosphere via denitrification with the remainder exported in streamflow as nitrogen loads. At the watershed scale, there is a keen interest in understanding the factors that control the fate of nitrogen throughout the stream channel network, with particular attention to the processes that deliver large nitrogen loads to sensitive coastal ecosystems. We use a dynamic stream transport model to assess biogeochemical (nitrate loadings, concentration, temperature) and hydrological (discharge, depth, velocity) effects on reach-scale denitrification and nitrate removal in the river networks of two watersheds having widely differing levels of nitrate enrichment but nearly identical discharges. Stream denitrification is estimated by regression as a nonlinear function of nitrate concentration, streamflow, and temperature, using more than 300 published measurements from a variety of US streams. These relations are used in the stream transport model to characterize nitrate dynamics related to denitrification at a monthly time scale in the stream reaches of the two watersheds. Results indicate that the nitrate removal efficiency of streams, as measured by the percentage of the stream nitrate flux removed via denitrification per unit length of channel, is appreciably reduced during months with high discharge and nitrate flux and increases during months of low-discharge and flux. Biogeochemical factors, including land use, nitrate inputs, and stream concentrations, are a major control on reach-scale denitrification, evidenced by the disproportionately lower nitrate removal efficiency in streams of the highly nitrate-enriched watershed as compared with that in similarly sized streams in the less nitrate-enriched watershed. Sensitivity analyses reveal that these important biogeochemical factors and physical hydrological factors contribute nearly </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMNS34A..03S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMNS34A..03S">Subsurface Ice Detection via Low Frequency Surface Electromagnetic Method</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Stillman, D. E.; Grimm, R. E.; Mcginnis, R. N. 2014-12-01 The geophysical detection of ice in the Cryosphere is typically conducted by measuring the absence of water. These interpretations can become non-unique in dry soils or in clay- and silt-rich soils that contain significant quantities of unfrozen water. Extensive laboratory measurements of electrical properties were made on permafrost samples as a function of frequency, temperature, and water content. These laboratory measurements show that the amount of ice can be uniquely obtained by measuring a frequency dependence of the electrical properties over a large frequency range (20 kHz - 10 Hz). In addition, the electrical properties of permafrost are temperature dependent, which can allow for an estimate of subsurface temperature. In order to test this approach in the field, we performed field surveys at four locations in Alaska. We used three low frequency electromagnetic methods: Spectral Induced Polarization (SIP: 20 kHz - 10 Hz), Capacively Coupled Resistivity (CCR: OhmMapper - 16.5 kHz), and DC Resistivity (Syscal ~ 8 Hz). At the Cold Regions Research and Engineering Laboratory permafrost tunnel near Fox, AK, we used SIP to measure the average ice concentration of 80 v% and determined the temperature to be -3±1°C by matching survey results to lab data. SIP data acquisition is very slow; therefore, at three sites near Tok, AK, we used CCR to perform reconnaissance of the area. Then SIP and DC resistivity were performed at anomalous areas. The three survey types give very similar absolute resistivity values. We found that while SIP gives the most quantitative results, the frequency dependence from the CCR and DC resistivity surveys is all that are needed to determine ice content in permafrost. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1412137Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1412137Z">Urban heat fluxes in the subsurface of Cologne, Germany</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zhu, K.; Bayer, P.; Blum, P. 2012-04-01 Urbanization during the last hundred years has led to both environmental and thermal impacts on the subsurface. The urban heat island (UHI) effect is mostly described as an atmospheric phenomenon, where the measured aboveground temperatures in cities are elevated in comparison to undisturbed rural regions. However, UHIs can be found below, as well as above ground. A large amount of anthropogenic heat migrates into the urban subsurface, which also raises the ground temperature and permanently changes the thermal conditions in shallow aquifers. The main objective of our work is to study and determine the urban heat fluxes in Cologne, Germany, and to improve our understanding of the dynamics of subsurface energy fluxes in UHIs. Ideally, our findings will contribute to strategic and more sustainable geothermal use in cities. For a quantitative analysis of the energy fluxes within the subsurface and across the atmospheric boundary, two and three-dimensional coupled numerical flow and heat transport models were developed. The simulation results indicate that during the past hundred years, an average vertical urban heat flux that ranges between 80 and 375 mW m-2 can be deduced. Thermal anomalies have migrated into the local urban aquifer system and they reach a depth of about 150 m. In this context, the influence of the regional groundwater flow on the subsurface heat transport and temperature development is comprehensively discussed. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PhDT........22E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PhDT........22E">Intracellular subsurface imaging using a hybrid shear-force feedback/scanning quantitative phase microscopy technique</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Edward, Kert Quantitative phase microscopy (QPM) allows for the imaging of translucent or transparent biological specimens without the need for exogenous contrast agents. This technique is usually applied towards the investigation of simple cells such as red blood cells which are typically enucleated and can be considered to be homogenous. However, most biological cells are nucleated and contain other interesting intracellular organelles. It has been established that the physical characteristics of certain subsurface structures such as the shape and roughness of the nucleus is well correlated with onset and progress of pathological conditions such as cancer. Although the acquired quantitative phase information of biological cells contains surface information as well as coupled subsurface information, the latter has been ignored up until now. A novel scanning quantitative phase imaging system unencumbered by 2pi ambiguities is hereby presented. This system is incorporated into a shear-force feedback scheme which allows for simultaneous phase and topography determination. It will be shown how subsequent image processing of these two data sets allows for the extraction of the subsurface component in the phase data and in vivo cell refractometry studies. Both fabricated samples and biological cells ranging from rat fibroblast cells to malaria infected human erythrocytes were investigated as part of this research. The results correlate quite well with that obtained via other microscopy techniques. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/946355-generalized-subsurface-flow-parameterization-considering-subgrid-spatial-variability-recharge-topography','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/946355-generalized-subsurface-flow-parameterization-considering-subgrid-spatial-variability-recharge-topography">A Generalized Subsurface Flow Parameterization Considering Subgrid Spatial Variability of Recharge and Topography</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Huang, Maoyi; Liang, Xu; Leung, Lai R. 2008-12-05 Subsurface flow is an important hydrologic process and a key component of the water budget, especially in humid regions. In this study, a new subsurface flow formulation is developed that incorporates spatial variability of both topography and recharge. It is shown through theoretical derivation and case studies that the power law and exponential subsurface flow parameterizations and the parameterization proposed by Woods et al.[1997] are all special cases of the new formulation. The subsurface flows calculated using the new formulation compare well with values derived from observations at the Tulpehocken Creek and Walnut Creek watersheds. Sensitivity studies show that whenmore » the spatial variability of topography or recharge, or both is increased, the subsurface flows increase at the two aforementioned sites and the Maimai hillslope. This is likely due to enhancement of interactions between the groundwater table and the land surface that reduce the flow path. An important conclusion of this study is that the spatial variability of recharge alone, and/or in combination with the spatial variability of topography can substantially alter the behaviors of subsurface flows. This suggests that in macroscale hydrologic models or land surface models, subgrid variations of recharge and topography can make significant contributions to the grid mean subsurface flow and must be accounted for in regions with large surface heterogeneity. This is particularly true for regions with humid climate and relatively shallow groundwater table where the combined impacts of spatial variability of recharge and topography are shown to be more important. For regions with arid climate and relatively deep groundwater table, simpler formulations, especially the power law, for subsurface flow can work well, and the impacts of subgrid variations of recharge and topography may be ignored.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020046350&hterms=warm&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dwarm','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020046350&hterms=warm&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dwarm">Is Europa's Subsurface Water Ocean Warm?</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Melosh, H. J.; Ekholm, A. G.; Showman, A. P.; Lorenz, R. D. 2002-01-01 Europa's subsurface water ocean may be warm: that is, at the temperature of water's maximum density. This provides a natural explanation of chaos melt-through events and leads to a correct estimate of the age of its surface. Additional information is contained in the original extended abstract. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMPP33E..01C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMPP33E..01C">Investigating the use of paired Uk'37 and TEX86 measurements to reconstruct past sea surface and subsurface (thermocline) temperatures (Invited)</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Castaneda, I. S.; Urann, B.; Phu, V. 2013-12-01 Two organic geochemical temperature proxies widely applied to marine sediments are the Uk'37 Index, based on long-chain alkenones produced by haptophyte algae, and TEX86, based on isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs), produced by Thaumarchaeota. At some locations, temperature reconstructions based on Uk'37 and TEX86 are in agreement within the calibration errors of each proxy, while at other sites absolute Uk'37 and TEX86 reconstructed temperatures differ but both proxies reveal similar overall trends (e.g. Caley et al., 2011). In contrast, at other locations Uk'37 and TEX86 temperature reconstructions from the same samples yield dramatically different overall trends. Differences observed between Uk'37 and TEX86 temperature reconstructions have been attributed to a variety of factors including seasonal production biases, differences in preservation and lateral transport, and differences related to the depth habitat of the source organisms. An increasing number of studies have provided evidence that TEX86 likely reflects a subsurface water temperature in certain areas of the world's oceans and have used paired Uk'37 and TEX86 measurements to simultaneously examine sea surface and subsurface (in some cases thermocline) temperature variability (e.g. Lopes dos Santos et al., 2010; Rommerskirchen et al., 2011; Li et al., 2013). In the tropical N Atlantic, a distinctive signature of Atlantic Meridional Overturning Circulation (AMOC) slowdown is anticorrelated variation between surface and subsurface water temperatures (e.g. Chang et al., 2008; Zhang et al., 2007) where sea surface temperature (SST) cooling is accompanied by shallow subsurface warming (e.g. Chang et al., 2008). Lopes dos Santos et al. (2010) examined a site in the tropical NE Atlantic where they showed that in the modern Uk'37 reflects SST while TEXH86 likely reflects a thermocline temperature. The authors noted several periods during the past 200 kyr when surface cooling and </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active">25</li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div class="footer-extlink text-muted" style="margin-bottom:1rem; text-align:center;">Some links on this page may take you to non-federal websites. 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Sample records for surface-subsurface biogeochemical coupling