Reactive Oxygen Species are Ubiquitous along Subsurface Redox Gradients

NASA Astrophysics Data System (ADS)

Nico, P. S.; Yuan, X.; Davis, J. A.; Dwivedi, D.; Williams, K. H.; Bhattacharyya, A.; Fox, P. M.

2016-12-01

Reactive oxygen species (hydroxyl radical, superoxide, hydrogen peroxide, etc.) are known to be important intermediates in many biological and earth system processes. They have been particularly well studied in the realms of atmospheric chemistry and aquatic photochemistry. However, recently there is increasing evidence that they are also present in impactful quantities in dark systems as a result of both biotic and abiotic reactions. Herein we will present a complementary suite of laboratory and field studies examining the presence and production of hydrogen peroxide under relevant subsurface conditions. The laboratory work examines the redox cycling between reduced organic matter, molecular oxygen, and Fe which results in not only the production of hydrogen peroxide and oxidation of organic functional groups but also the maintenance of steady-state concentration of Fe(II) under fully oxygenated aqueous conditions. The field studies involve three distinct locations, namely a shallow subsurface aquifer, a hyporheic zone redox gradient across a river meander, and a hillside shale seep. In all cases detectable quantities (tens of nanomolar) of hydrogen peroxide were measured. In general, concentrations peak under transitional redox conditions where there is the simultaneous presence of reduced Fe, organic matter, and at least trace dissolved oxygen. Many, but not all, of the observed dynamics in hydrogen peroxide production can be reproduced by a simple kinetic model representing the reactions between Fe, organic matter, and molecular oxygen, but many questions remain regarding the role of microorganisms and other redox active chemical species in determining the detected hydrogen peroxide concentrations. The consistent detection of hydrogen peroxide at these disparate locations supports the hypothesis that hydrogen peroxide, and by extension, the entire suite of reactive oxygen species are ubiquitous along subsurface redox gradients.

Examination of oxygen release from plants in constructed wetlands in different stages of wetland plant life cycle.

PubMed

Zhang, Jian; Wu, Haiming; Hu, Zhen; Liang, Shuang; Fan, Jinlin

2014-01-01

The quantification of oxygen release by plants in different stages of wetland plant life cycle was made in this study. Results obtained from 1 year measurement in subsurface wetland microcosms demonstrated that oxygen release from Phragmites australis varied from 108.89 to 404.44 mg O₂/m(2)/d during the different periods from budding to dormancy. Plant species, substrate types, and culture solutions had a significant effect on the capacity of oxygen release of wetland plants. Oxygen supply by wetland plants was estimated to potentially support a removal of 300.37 mg COD/m(2)/d or 55.87 mg NH₄-N/m(2)/d. According to oxygen balance analysis, oxygen release by plants could provide 0.43-1.12% of biochemical oxygen demand in typical subsurface-flow constructed wetlands (CWs). This demonstrates that oxygen release of plants may be a potential source for pollutants removal especially in low-loaded CWs. The results make it possible to quantify the role of plants in wastewater purification.

Bioremediation of contaminated groundwater

DOEpatents

Hazen, Terry C.; Fliermans, Carl B.

1995-01-01

An apparatus and method for in situ remediation of contaminated subsurface soil or groundwater contaminated by chlorinated hydrocarbons. A nutrient fluid is selected to stimulate the growth and reproduction of indigenous subsurface microorganisms that are capable of degrading the contaminants; an oxygenated fluid is selected to create a generally aerobic environment for these microorganisms to degrade the contaminants, leaving only pockets that are anaerobic. The nutrient fluid is injected periodically while the oxygenated fluid is injected continuously and both are extracted so that both are drawn across the plume. The nutrient fluid stimulates microbial colony growth; withholding it periodicially forces the larger, healthy colony of microbes to degrade the contaminants. Treatment is continued until the subsurface concentration of contaminants is reduced to an acceptable, preselected level. The nutrient fluid can be methane and the oxygenated fluid air for stimulating production of methanotrophs to break down chlorohydrocarbons, especially trichloroethylene (TCE) and tetrachloroethylene.

Bioremediation of contaminated groundwater

DOEpatents

Hazen, T.C.; Fliermans, C.B.

1995-01-24

An apparatus and method are described for in situ remediation of contaminated subsurface soil or groundwater contaminated by chlorinated hydrocarbons. A nutrient fluid is selected to stimulate the growth and reproduction of indigenous subsurface microorganisms that are capable of degrading the contaminants. An oxygenated fluid is selected to create a generally aerobic environment for these microorganisms to degrade the contaminants, leaving only pockets that are anaerobic. The nutrient fluid is injected periodically while the oxygenated fluid is injected continuously and both are extracted so that both are drawn across the plume. The nutrient fluid stimulates microbial colony growth. Withholding it periodically forces the larger, healthy colony of microbes to degrade the contaminants. Treatment is continued until the subsurface concentration of contaminants is reduced to an acceptable, preselected level. The nutrient fluid can be methane and the oxygenated fluid air for stimulating production of methanotrophs to break down chlorohydrocarbons, especially trichloroethylene (TCE) and tetrachloroethylene. 3 figures.

Large fluctuations of dissolved oxygen in the Indian and Pacific oceans during Dansgaard-Oeschger oscillations caused by variations of North Atlantic Deep Water subduction

NASA Astrophysics Data System (ADS)

Schmittner, Andreas; Galbraith, Eric D.; Hostetler, Steven W.; Pedersen, Thomas F.; Zhang, Rong

2007-09-01

Paleoclimate records from glacial Indian and Pacific oceans sediments document millennial-scale fluctuations of subsurface dissolved oxygen levels and denitrification coherent with North Atlantic temperature oscillations. Yet the mechanism of this teleconnection between the remote ocean basins remains elusive. Here we present model simulations of the oxygen and nitrogen cycles that explain how changes in deepwater subduction in the North Atlantic can cause large and synchronous variations of oxygen minimum zones throughout the Northern Hemisphere of the Indian and Pacific oceans, consistent with the paleoclimate records. Cold periods in the North Atlantic are associated with reduced nutrient delivery to the upper Indo-Pacific oceans, thereby decreasing productivity. Reduced export production diminishes subsurface respiration of organic matter leading to higher oxygen concentrations and less denitrification. This effect of reduced oxygen consumption dominates at low latitudes. At high latitudes in the Southern Ocean and North Pacific, increased mixed layer depths and steepening of isopycnals improve ocean ventilation and oxygen supply to the subsurface. Atmospheric teleconnections through changes in wind-driven ocean circulation modify this basin-scale pattern regionally. These results suggest that changes in the Atlantic Ocean circulation, similar to those projected by climate models to possibly occur in the centuries to come because of anthropogenic climate warming, can have large effects on marine ecosystems and biogeochemical cycles even in remote areas.

Thermal etching of silver: Influence of rolling defects

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

Ollivier, M., E-mail: o.maelig@imperial.ac.uk

2016-08-15

Silver is well known to be thermally etched in an oxygen-rich atmosphere and has been extensively studied in the laboratory to understand thermal etching and to limit its effect when this material is used as a catalyst. Yet, in many industrial applications the surface of rolled silver sheets is used without particular surface preparation. Here, it is shown by combining FIB-tomography, FIB-SIMS and analytical SEM that the kinetics of thermal etch pitting are significantly faster on rolled Ag surfaces than on polished surfaces. This occurs due to range of interacting phenomena including (i) the reaction of subsurface carbon-contamination with dissolvedmore » oxygen to form pores that grow to intersect the surface, (ii) surface reconstruction around corrosion pits and surface scratches, and (iii) sublimation at low pressure and high temperature. A method to identify subsurface pores is developed to show that the pores have (111) and (100) internal facets and may be filled with a gas coming from the chemical reaction of oxygen and carbon contamination. - Highlights: Thermal etching of industrial silver sheets vs. polished silver sheets Effect of annealing atmosphere on the thermal etching of silver: surface and subsurface characterization Link between etch pitting and defects induced by rolling. FIB-tomography coupled with EBSD for determining crystal planes of the facets of subsurface pores. FIB-SIMS characterization to probe the gas confined inside subsurface pores.« less

Use of Novel Whole Core Incubations to Measure the Fate of Fertilizer N in a Flooded Agricultural System

NASA Astrophysics Data System (ADS)

Penton, C. R.; Bruland, G. L.; Popp, B. N.; Engstrom, P.; Tiedje, J.; Brown, G. A.; Deenik, J. L.

2010-12-01

We developed a new whole-core perfusion technique for tracking the fate of 15NH4+ added to intact vegetated cores. Taro plants (Colocasia esculenta) were field-grown in (20 cm diameter) cores for three months, which allowed exchange with natural porewater, then harvested. Following core extraction, surface and porewater were removed and 15NH4+ labeled porewater was slowly re-introduced to the core through a perfusion cap in the laboratory. Mini porewater equilibrators were placed in 1 cm increments through the sediment profile for porewater extraction during incubation. We also independently tested the ability of taro roots to oxygenate the subsurface by growing plants in nutrient agar and measuring O2 flux with a microelectrode. In the agar experiment, diurnal O2 transport was monitored and the application of wind across the taro leaves was found necessary to develop an oxygenated zone at the root tips. Using this information, the harvested taro were incubated in growth chambers after perfusion using three treatments: Vegetated without wind, vegetated with wind, and a non-vegetated control. Porewater was analyzed for 29+30N2, 15NH4+, 15NO3-, and unlabeled nitrate and ammonium species. Plant uptake of 15NH4+ was also determined. Quantitative PCR was performed on the sediment profiles of functional genes involved in nitrogen cycling for correlation to N transformations. The major pathway of N loss was root-mediated nitrification/denitrification followed by a flow of 29+30N2 through the aerenchyma. The vegetated wind treatment exhibited the highest concentrations of labeled N2 in the subsurface during all time periods. In contrast, the vegetated no wind treatment had much higher aerenchyma 29+30N2 concentration, accounting for ~100% of the subsurface N2 accumulation by day three of the incubation. Surface water N2 concentrations were also highest in the no wind treatment. After nine days the 29+30N2 concentrations dropped by ~70%, with little difference remaining among the treatments, indicating limitation by 15NH4+ diffusion. These results indicate that N2 is preferentially transported through the aerenchyma in taro and probably other plants grown in flooded agricultural fields. However, increased wind stress reduced transport through the aerenchyma and resulted in greater N2 accumulation in the subsurface, which indicates the importance of mass flow transport of air and its effect on oxygenation at the root tips. The results indicate that the complexity of N cycling in flooded agricultural systems may confound attempts to estimate in-situ N losses through porewater modeling, ‘classic’ isotope pairing techniques, or N flux chambers. The whole-core technique presented here allows for the measurement of multiple N pools and fates while minimizing system disturbance and more accurately representing field conditions.

Large fluctuations of dissolved oxygen in the Indian and Pacific oceans during Dansgaard-Oeschger oscillations caused by variations of North Atlantic Deep Water subduction

USGS Publications Warehouse

Schmittner, A.; Galbraith, E.D.; Hostetler, S.W.; Pedersen, Thomas F.; Zhang, R.

2007-01-01

Paleoclimate records from glacial Indian and Pacific oceans sediments document millennial-scale fluctuations of subsurface dissolved oxygen levels and denitrification coherent with North Atlantic temperature oscillations. Yet the mechanism of this teleconnection between the remote ocean basins remains elusive. Here we present model simulations of the oxygen and nitrogen cycles that explain how changes in deepwater subduction in the North Atlantic can cause large and synchronous variations of oxygen minimum zones, throughout the Northern Hemisphere of the Indian and Pacific oceans, consistent with the paleoclimate records. Cold periods in the North Atlantic are associated with reduced nutrient delivery to the upper Indo-Pacific oceans, thereby decreasing productivity. Reduced export production diminishes subsurface respiration of organic matter leading to higher oxygen concentrations and less denitrification. This effect of reduced oxygen consumption dominates at low latitudes. At high latitudes in the Southern Ocean and North Pacific, increased mixed layer depths and steepening of isopycnals improve ocean ventilation and oxygen supply to the subsurface. Atmospheric teleconnections through changes in wind-driven ocean circulation modify this basin-scale pattern regionally. These results suggest that changes in the Atlantic Ocean circulation, similar to those projected by climate models to possibly occur in the centuries to come because of anthropogenic climate warming, can have large effects on marine ecosystems and biogeochemical cycles even in remote areas. Copyright 2007 by the American Geophysical Union.

BIOPLUME MODEL FOR CONTAMINANT TRANSPORT AFFECTED BY OXYGEN LIMITED BIODEGRADATION

EPA Science Inventory

Many of the organic pollutants entering ground water are potentially biodegradable in the subsurface. This potential has been demonstrated in aquifers contaminated by wood-creosoting process wastes. The persistence of many of these organic compounds in the subsurface indicated ...

Arabian Sea

Atmospheric Science Data Center

2013-04-16

... sometimes results in copious phytoplankton production and oxygen depletion of the subsurface waters. Although red phytoplankton fluorescences have been associated with the low oxygen concentrations in the intermediate and deep waters of the Arabian Sea, ...

Photosynthetic oxygen production in a warmer ocean: the Sargasso Sea as a case study.

PubMed

Richardson, Katherine; Bendtsen, Jørgen

2017-09-13

Photosynthetic O 2 production can be an important source of oxygen in sub-surface ocean waters especially in permanently stratified oligotrophic regions of the ocean where O 2 produced in deep chlorophyll maxima (DCM) is not likely to be outgassed. Today, permanently stratified regions extend across approximately 40% of the global ocean and their extent is expected to increase in a warmer ocean. Thus, predicting future ocean oxygen conditions requires a better understanding of the potential response of photosynthetic oxygen production to a warmer ocean. Based on our own and published observations of water column processes in oligotrophic regions, we develop a one-dimensional water column model describing photosynthetic oxygen production in the Sargasso Sea to quantify the importance of photosynthesis for the downward flux of O 2 and examine how it may be influenced in a warmer ocean. Photosynthesis is driven in the model by vertical mixing of nutrients (including eddy-induced mixing) and diazotrophy and is found to substantially increase the downward O 2 flux relative to physical-chemical processes alone. Warming (2°C) surface waters does not significantly change oxygen production at the DCM. Nor does a 15% increase in re-mineralization rate (assuming Q 10  = 2; 2°C warming) have significant effect on net sub-surface oxygen accumulation. However, changes in the relative production of particulate (POM) and dissolved organic material (DOM) generate relatively large changes in net sub-surface oxygen production. As POM/DOM production is a function of plankton community composition, this implies plankton biodiversity and food web structure may be important factors influencing O 2 production in a warmer ocean.This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'. © 2017 The Author(s).

Photosynthetic oxygen production in a warmer ocean: the Sargasso Sea as a case study

NASA Astrophysics Data System (ADS)

Richardson, Katherine; Bendtsen, Jørgen

2017-08-01

Photosynthetic O2 production can be an important source of oxygen in sub-surface ocean waters especially in permanently stratified oligotrophic regions of the ocean where O2 produced in deep chlorophyll maxima (DCM) is not likely to be outgassed. Today, permanently stratified regions extend across approximately 40% of the global ocean and their extent is expected to increase in a warmer ocean. Thus, predicting future ocean oxygen conditions requires a better understanding of the potential response of photosynthetic oxygen production to a warmer ocean. Based on our own and published observations of water column processes in oligotrophic regions, we develop a one-dimensional water column model describing photosynthetic oxygen production in the Sargasso Sea to quantify the importance of photosynthesis for the downward flux of O2 and examine how it may be influenced in a warmer ocean. Photosynthesis is driven in the model by vertical mixing of nutrients (including eddy-induced mixing) and diazotrophy and is found to substantially increase the downward O2 flux relative to physical-chemical processes alone. Warming (2°C) surface waters does not significantly change oxygen production at the DCM. Nor does a 15% increase in re-mineralization rate (assuming Q10 = 2; 2°C warming) have significant effect on net sub-surface oxygen accumulation. However, changes in the relative production of particulate (POM) and dissolved organic material (DOM) generate relatively large changes in net sub-surface oxygen production. As POM/DOM production is a function of plankton community composition, this implies plankton biodiversity and food web structure may be important factors influencing O2 production in a warmer ocean. This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'.

KINETIC CONTROL OF OXIDATION STATE AT THERMODYNAMICALLY BUFFERED POTENTIALS IN SUBSURFACE WATERS

EPA Science Inventory

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...

Intrinsic Gettering in Nitrogen-Doped and Hydrogen-Annealed Czochralski-Grown Silicon Wafers

NASA Astrophysics Data System (ADS)

Goto, Hiroyuki; Pan, Lian-Sheng; Tanaka, Masafumi; Kashima, Kazuhiko

2001-06-01

The properties of nitrogen-doped and hydrogen-annealed Czochralski-grown silicon (NHA-CZ-Si) wafers were investigated in this study. The quality of the subsurface was investigated by monitoring the generation lifetime of minority carriers, as measured by the capacitance-time measurements of a metal oxide silicon capacitor (MOS C-t). The intrinsic gettering (IG) ability was investigated by determining the nickel concentration on the surface and in the subsurface as measured by graphite furnace atomic absorption spectrometry (GFAAS) after the wafer was deliberately contaminated with nickel. From the results obtained, the generation lifetimes of these NHA-CZ-Si wafers were determined to be almost the same as, or a little longer than those of epitaxial wafers, and the IG ability was proportional to the total volume of oxygen precipitates [i.e., bulk micro defects (BMDs)], which was influenced by the oxygen and nitrogen concentrations in the wafers. Therefore, it is suggested that the subsurface of the NHA-CZ-Si wafers is of good quality and the IG capacity is controllable by the nitrogen and oxygen concentrations in the wafers.

Theoretical studies of positron states and annihilation characteristics at the oxidized Cu(100) surface

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Weiss, A. H.

2013-04-01

In this work we present the results of theoretical studies of positron surface and bulk states and annihilation probabilities of surface-trapped positrons with relevant core electrons at the oxidized Cu(100) surface under conditions of high oxygen coverage. An ab-initio study of the electronic properties of the Cu(100) missing row reconstructed surface at various on surface and sub-surface oxygen coverages has been performed on the basis of the density functional theory (DFT) using the Dmol3 code and the generalized gradient approximation (GGA). Surface structures in calculations have been constructed by adding oxygen atoms to various surface hollow and sub-surface octahedral sites of the 0.5 monolayer (ML) missing row reconstructed phase of the Cu(100) surface with oxygen coverages ranging from 0.5 to 1.5 ML. The charge redistribution at the surface and variations in atomic structure and chemical composition of the topmost layers associated with oxidation and surface reconstruction have been found to affect the spatial extent and localization of the positron surface state wave function and annihilation probabilities of surface trapped positrons with relevant core electrons. Theoretical results are compared with experimental data obtained from studies of oxidation of the Cu(100) surface using positron annihilation induced Auger electron spectroscopy (PAES). It has been shown that positron annihilation probabilities with Cu 3s and 3p core electrons decrease when total (on-surface and sub-surface) oxygen coverage of the Cu(100) surface increases up to 1 ML. The calculations show that for high oxygen coverage when total oxygen coverage is 1. 5 ML the positron is not bound to the surface.

Theoretical studies of positron states and annihilation characteristics at the oxidized Cu(100) surface

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

Fazleev, N. G.; Weiss, A. H.

2013-04-19

In this work we present the results of theoretical studies of positron surface and bulk states and annihilation probabilities of surface-trapped positrons with relevant core electrons at the oxidized Cu(100) surface under conditions of high oxygen coverage. An ab-initio study of the electronic properties of the Cu(100) missing row reconstructed surface at various on surface and sub-surface oxygen coverages has been performed on the basis of the density functional theory (DFT) using the Dmol3 code and the generalized gradient approximation (GGA). Surface structures in calculations have been constructed by adding oxygen atoms to various surface hollow and sub-surface octahedral sitesmore » of the 0.5 monolayer (ML) missing row reconstructed phase of the Cu(100) surface with oxygen coverages ranging from 0.5 to 1.5 ML. The charge redistribution at the surface and variations in atomic structure and chemical composition of the topmost layers associated with oxidation and surface reconstruction have been found to affect the spatial extent and localization of the positron surface state wave function and annihilation probabilities of surface trapped positrons with relevant core electrons. Theoretical results are compared with experimental data obtained from studies of oxidation of the Cu(100) surface using positron annihilation induced Auger electron spectroscopy (PAES). It has been shown that positron annihilation probabilities with Cu 3s and 3p core electrons decrease when total (on-surface and sub-surface) oxygen coverage of the Cu(100) surface increases up to 1 ML. The calculations show that for high oxygen coverage when total oxygen coverage is 1. 5 ML the positron is not bound to the surface.« less

The formation of a subsurface anticyclonic eddy in the Peru-Chile Undercurrent and its impact on the near-coastal salinity, oxygen, and nutrient distributions

NASA Astrophysics Data System (ADS)

Thomsen, Soeren; Kanzow, Torsten; Krahmann, Gerd; Greatbatch, Richard J.; Dengler, Marcus; Lavik, Gaute

2016-01-01

The formation of a subsurface anticyclonic eddy in the Peru-Chile Undercurrent (PCUC) in January and February 2013 is investigated using a multiplatform four-dimensional observational approach. Research vessel, multiple glider, and mooring-based measurements were conducted in the Peruvian upwelling regime near 12°30'S. The data set consists of >10,000 glider profiles and repeated vessel-based hydrography and velocity transects. It allows a detailed description of the eddy formation and its impact on the near-coastal salinity, oxygen, and nutrient distributions. In early January, a strong PCUC with maximum poleward velocities of ˜0.25 m/s at 100-200 m depth was observed. Starting on 20 January, a subsurface anticyclonic eddy developed in the PCUC downstream of a topographic bend, suggesting flow separation as the eddy formation mechanism. The eddy core waters exhibited oxygen concentration of <1 μmol/kg, an elevated nitrogen deficit of ˜17 μmol/L, and potential vorticity close to zero, which seemed to originate from the bottom boundary layer of the continental slope. The eddy-induced across-shelf velocities resulted in an elevated exchange of water masses between the upper continental slope and the open ocean. Small-scale salinity and oxygen structures were formed by along-isopycnal stirring, and indications of eddy-driven oxygen ventilation of the upper oxygen minimum zone were observed. It is concluded that mesoscale stirring of solutes and the offshore transport of eddy core properties could provide an important coastal open ocean exchange mechanism with potentially large implications for nutrient budgets and biogeochemical cycling in the oxygen minimum zone off Peru.

Water masses in the Humboldt Current System: Properties, distribution, and the nitrate deficit as a chemical water mass tracer for Equatorial Subsurface Water off Chile

NASA Astrophysics Data System (ADS)

Silva, Nelson; Rojas, Nora; Fedele, Aldo

2009-07-01

Three sections are used to analyze the physical and chemical characteristics of the water masses in the eastern South Pacific and their distributions. Oceanographic data were taken from the SCORPIO (May-June 1967), PIQUERO (May-June 1969), and KRILL (June 1974) cruises. Vertical sections of temperature, salinity, σ θ, dissolved oxygen, nitrate, nitrite, phosphate, and silicate were used to analyze the water column structure. Five water masses were identified in the zone through T- S diagrams: Subantarctic Water, Subtropical Water, Equatorial Subsurface Water, Antarctic Intermediate Water, and Pacific Deep Water. Their proportions in the sea water mixture are calculated using the mixing triangle method. Vertical sections were used to describe the geographical distributions of the water mass cores in the upper 1500 m. Several characteristic oceanographic features in the study area were analyzed: the shallow salinity minimum displacement towards the equator, the equatorial subsurface salinity maximum associated with a dissolved oxygen minimum zone and a high nutrient content displacement towards the south, and the equatorward intermediate Antarctic salinity minimum associated with a dissolved oxygen maximum. The nitrate deficit generated in the denitrification area off Peru and northern Chile is proposed as a conservative chemical tracer for the Equatorial Subsurface Waters off the coast of Chile, south of 25°S.

Accelerated aging studies of UHMWPE. II. Virgin UHMWPE is not immune to oxidative degradation.

PubMed

Edidin, A A; Villarraga, M L; Herr, M P; Muth, J; Yau, S S; Kurtz, S M

2002-08-01

In Part I of this series, we showed that aging at elevated oxygen pressure is more successful at increasing the depth to which degradation occurs although it, too, generally causes greater degradation at the surface than at the subsurface. Therefore we hypothesized that thermal degradation alone, in the absence of free radicals, could be sufficient to artificially age UHMWPE in a manner analogous to natural aging. In the present study, virgin and air-irradiated UHMWPE (extruded GUR 1050 and compression-molded 1900) were aged up to 4 weeks at elevated oxygen pressure, and the mechanical behavior at the surface and subsurface was examined. All the materials were substantially degraded following 4 weeks of aging, but the spatial variations in the nonirradiated materials more closely mimicked the previously observed subsurface peak of degradation seen in naturally aged UHMWPE following irradiation in air. This aged material could provide a more realistic model for subsurface mechanical degradation, making it suitable for further mechanical testing in venues such as wear simulation. Copyright 2002 Wiley Periodicals, Inc.

Constructed wetland as a low cost and sustainable solution for wastewater treatment adapted to rural settlements: the Chorfech wastewater treatment pilot plant.

PubMed

Ghrabi, Ahmed; Bousselmi, Latifa; Masi, Fabio; Regelsberger, Martin

2011-01-01

The paper presents the detailed design and some preliminary results obtained from a study regarding a wastewater treatment pilot plant (WWTPP), serving as a multistage constructed wetland (CW) located at the rural settlement of 'Chorfech 24' (Tunisia). The WWTPP implemented at Chorfech 24 is mainly designed as a demonstration of sustainable water management solutions (low-cost wastewater treatment), in order to prove the efficiency of these solutions working under real Tunisian conditions and ultimately allow the further spreading of the demonstrated techniques. The pilot activity also aims to help gain experience with the implemented techniques and to improve them when necessary to be recommended for wide application in rural settlements in Tunisia and similar situations worldwide. The selected WWTPP at Chorfech 24 (rural settlement of 50 houses counting 350 inhabitants) consists of one Imhoff tank for pre-treatment, and three stages in series: as first stage a horizontal subsurface flow CW system, as second stage a subsurface vertical flow CW system, and a third horizontal flow CW. The sludge of the Imhoff tank is treated in a sludge composting bed. The performances of the different components as well as the whole treatment system were presented based on 3 months monitoring. The results shown in this paper are related to carbon, nitrogen and phosphorus removal as well as to reduction of micro-organisms. The mean overall removal rates of the Chorfech WWTPP during the monitored period have been, respectively, equal to 97% for total suspended solids and biochemical oxygen demand (BOD5), 95% for chemical oxygen demand, 71% for total nitrogen and 82% for P-PO4. The removal of E. coli by the whole system is 2.5 log units.

Seasonal and interannual variability of dissolved oxygen around the Balearic Islands from hydrographic data

NASA Astrophysics Data System (ADS)

Balbín, R.; López-Jurado, J. L.; Aparicio-González, A.; Serra, M.

2014-10-01

Oceanographic data obtained between 2001 and 2011 by the Spanish Institute of Oceanography (IEO, Spain) have been used to characterise the spatial distribution and the temporal variability of the dissolved oxygen around the Balearic Islands (Mediterranean Sea). The study area includes most of the Western Mediterranean Sea, from the Alboran Sea to Cape Creus, at the border between France and Spain. Dissolved oxygen (DO) at the water surface is found to be in a state of equilibrium exchange with the atmosphere. In the spring and summer a subsurface oxygen supersaturation is observed due to the biological activity, above the subsurface fluorescence maximum. Minimum observed values of dissolved oxygen are related to the Levantine Intermediate Waters (LIW). An unusual minimum of dissolved oxygen concentrations was also recorded in the Alboran Sea Oxygen Minimum Zone. The Western Mediterranean Deep Waters (WMDW) and the Western Intermediate Waters (WIW) show higher values of dissolved oxygen than the Levantine Intermediate Waters due to their more recent formation. Using these dissolved oxygen concentrations it is possible to show that the Western Intermediate Waters move southwards across the Ibiza Channel and the deep water circulates around the Balearic Islands. It has also been possible to characterise the seasonal evolution of the different water masses and their dissolved oxygen content in a station in the Algerian sub-basin.

The stream subsurface: nitrogen cycling and the cleansing function of hyporheic zones

Treesearch

Rhonda Mazza; Steve Wondzell; Jay Zarnetske

2014-01-01

Nitrogen is an element essential to plant growth and ecosystem productivity. Excess nitrogen, however, is a common water pollutant. It can lead to algal blooms that deplete the water's dissolved oxygen, creating "dead zones" devoid of fish and aquatic insects.Previous research showed that the subsurface area of a stream, known as the hyporheic...

The genome of Geobacter bemidjiensis, exemplar for the subsurface clade of Geobacter species that predominate in Fe(III)-reducing subsurface environments

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

Aklujkar, Muktak; Young, Nelson D; Holmes, Dawn

2010-01-01

Background. Geobacter species in a phylogenetic cluster known as subsurface clade 1 are often the predominant microorganisms in subsurface environments in which Fe(III) reduction is the primary electron-accepting process. Geobacter bemidjiensis, a member of this clade, was isolated from hydrocarbon-contaminated subsurface sediments in Bemidji, Minnesota, and is closely related to Geobacter species found to be abundant at other subsurface sites. This study examines whether there are significant differences in the metabolism and physiology of G. bemidjiensis compared to non-subsurface Geobacter species. Results. Annotation of the genome sequence of G. bemidjiensis indicates several differences in metabolism compared to previously sequenced non-subsurfacemore » Geobacteraceae, which will be useful for in silico metabolic modeling of subsurface bioremediation processes involving Geobacter species. Pathways can now be predicted for the use of various carbon sources such as propionate by G. bemidjiensis. Additional metabolic capabilities such as carbon dioxide fixation and growth on glucose were predicted from the genome annotation. The presence of different dicarboxylic acid transporters and two oxaloacetate decarboxylases in G. bemidjiensis may explain its ability to grow by disproportionation of fumarate. Although benzoate is the only aromatic compound that G. bemidjiensis is known or predicted to utilize as an electron donor and carbon source, the genome suggests that this species may be able to detoxify other aromatic pollutants without degrading them. Furthermore, G. bemidjiensis is auxotrophic for 4-aminobenzoate, which makes it the first Geobacter species identified as having a vitamin requirement. Several features of the genome indicated that G. bemidjiensis has enhanced abilities to respire, detoxify and avoid oxygen. Conclusion. Overall, the genome sequence of G. bemidjiensis offers surprising insights into the metabolism and physiology of Geobacteraceae in subsurface environments, compared to non-subsurface Geobacter species, such as the ability to disproportionate fumarate, more efficient oxidation of propionate, enhanced responses to oxygen stress, and dependence on the environment for a vitamin requirement. Therefore, an understanding of the activity of Geobacter species in the subsurface is more likely to benefit from studies of subsurface isolates such as G. bemidjiensis than from the non-subsurface model species studied so far.« less

Subsurface Oxygen in Oxide-Derived Copper Electrocatalysts for Carbon Dioxide Reduction

DOE PAGES

Eilert, Andre; Cavalca, Filippo; Roberts, F. Sloan; ...

2016-12-16

Copper electrocatalysts derived from an oxide have shown extraordinary electrochemical properties for the carbon dioxide reduction reaction (CO 2RR). Using in situ ambient pressure X-ray photoelectron spectroscopy and quasi in situ electron energy-loss spectroscopy in a transmission electron microscope, we show that there is a substantial amount of residual oxygen in nanostructured, oxide-derived copper electrocatalysts but no residual copper oxide. On the basis of these findings in combination with density functional theory simulations, we propose that residual subsurface oxygen changes the electronic structure of the catalyst and creates sites with higher carbon monoxide binding energy. If such sites are stablemore » under the strongly reducing conditions found in CO 2RR, these findings would explain the high efficiencies of oxide-derived copper in reducing carbon dioxide to multicarbon compounds such as ethylene.« less

Theoretical aspects of studies of high coverage oxidation of the Cu(100) surface using low energy positrons

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Maddox, W. B.; Reed, J. A.

2011-03-01

The study of adsorption of oxygen on transition metal surface is important for the understanding of oxidation, heterogeneous catalysis, and metal corrosion. The structures formed on transition metal surfaces vary from simple adlayers of chemisorbed oxygen to more complex structures which results from diffusion of oxygen into the sub-surface regions. In this work we present the results of an ab-initio investigation of positron surface and bulk states and annihilation probabilities of surface-trapped positrons with relevant core electrons at the Cu(100) missing row reconstructed surface under conditions of high oxygen coverage. Calculations are performed for various surface and subsurface oxygen coverages ranging from 0.50 to 1.50 monolayers. Calculations are also performed for the on-surface adsorption of oxygen on the unreconstructed Cu(001) surface for coverages up to one monolayer to use for comparison. Estimates of the positron binding energy, positron work function, and annihilation characteristics reveal their sensitivity to atomic structure of the topmost layers of the surface and charge transfer. Theoretical results are compared with experimental data obtained from studies of oxidation of the Cu(100) surface using positron annihilation induced Auger electron spectroscopy.

BIOREMEDIATION OF BTEX, NAPTHALENE, AND PHENANTHRENE IN AQUIFER MATERIAL USING MIXED OXYGEN/NITRATE ELECTRON

EPA Science Inventory

The goal of the research described herein was to examine the feasibility of biodegradation of mono and polycyclic aromatic hydrocarbons typically present in a manufactured gas processing (MGP) site groundwater and subsurface sediments under mixed oxygen/denitrifying conditions. ...

Biological, Physical and Chemical Data From Gulf of Mexico Gravity and Box Core MRD05-04

USGS Publications Warehouse

Osterman, Lisa E.; Campbell, Pamela L.; Swarzenski, Peter W.; Ricardo, John P.

2010-01-01

This paper presents the benthic foraminiferal census data, magnetic susceptibility measurements, vanadium and organic geochemistry (carbon isotope, sterols, and total organic carbon) data from the MRD05-04 gravity and box cores. The MRD05-04 cores were obtained from the Louisiana continental shelf in an on-going initiative to examine the geographic and temporal extent of hypoxia, low-oxygen bottom-water content, and geochemical transport. The development of low-oxygen bottom water conditions in coastal waters is dependent upon a new source of bio-available nutrients introduced into a well-stratified water column. A number of studies have concluded that the development of the current seasonal hypoxia (dissolved oxygen < 2 mg L-1) in subsurface waters of the northern Gulf of Mexico is related to increased transport of nutrients (primarily nitrogen, but possibly also phosphorous) by the Mississippi River. However, the development of earlier episodes of seasonal low-oxygen subsurface water on the Louisiana shelf may be related to Mississippi River discharge.

Exploration of a Subsurface Biosphere in a Volcanic Massive Sulfide: Results of the Mars Analog Rio Tinto Drilling Experiment

NASA Astrophysics Data System (ADS)

Stoker, C. R.; Stevens, T.; Amils, R.; Fernandez, D.

2005-12-01

Biological systems on Earth require three key ingredients-- liquid water, an energy source, and a carbon source, that are found in very few extraterrestrial environments. Previous examples of independent subsurface ecosystems have been found only in basalt aquifers. Such lithotrophic microbial ecosystems (LME) have been proposed as models for steps in the early evolution of Earth's biosphere and for potential biospheres on other planets where the surface is uninhabitable, such as Mars and Europa.. The Mars Analog Rio Tinto Experiment (MARTE) has searched in a volcanic massive sulfide deposit in Rio Tinto Spain for a subsurface biosphere capable of living without sunlight or oxygen and found a subsurface ecosystem driven by the weathering of the massive sulfide deposit (VMS) in which the rock matrix provides sufficient resources to support microbial metabolism, including the vigorous production of H2 by water-rock interactions. Microbial production of methane and sulfate occurred in the sulfide orebody and microbial production of methane and hydrogen sulfide continued in an anoxic plume downgradient from the sulfide ore. Organic carbon concentrations in the parent rock were too low to support microbes. The Rio Tinto system thus represents a new type of subsurface ecosystem with strong relevance for exobiological studies. Commercial drilling was used to reach the aquifer system at 100 m depth and conventional laboratory techniques were used to identify and characterize the biosphere. Then, the life search strategy that led to successful identification of this biosphere was applied to the development of a robotic drilling, core handling, inspection, subsampling, and life detection system built on a prototype planetary lander that was deployed in Rio Tinto Spain in September 2005 to test the capability of a robotic drilling system to search for subsurface life. A remote science team directed the simulation and analyzed the data from the MARTE robotic drill. The results of this experiment have important implications for the strategy for searching for life on Mars.

COMPARISON OF METHODS TO DETERMINE OXYGEN DEMAND FOR BIOREMEDIATION OF A FUEL CONTAMINATED AQUIFER

EPA Science Inventory

Four analytical methods were compared for estimating concentrations of fuel contaminants in subsurface core samples. The methods were total organic carbon, chemical oxygen demand, oil and grease, and a solvent extraction of fuel hydrocarbons combined with a gas chromatographic te...

Simple technique for observing subsurface damage in machining of ceramics

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

Xu, H.H.K.; Jahanmir, S.

1994-05-01

A simple technique is proposed for directly observing subsurface damage in the machining of ceramics. The technique requires two polished specimens and an optical microscope with Nomarski illumination for examination. The subsurface damage created by the grinding of an alumina ceramic is investigated using this technique. The mode of damage is identified as intragrain twinning/slip, and intergranular and transgranular cracking. Chipping along the twinned planes and along the transgranular crack planes, and dislodgement of the intergranularly debonded grains are suggested to be the mechanisms of material removal in the machining of this alumina ceramic.

Leachate plume delineation and lithologic profiling using surface resistivity in an open municipal solid waste dumpsite, Sri Lanka.

PubMed

Wijesekara, Hasintha Rangana; De Silva, Sunethra Nalin; Wijesundara, Dharani Thanuja De Silva; Basnayake, Bendict Francis Antony; Vithanage, Meththika Suharshini

2015-01-01

This study presents the use of direct current resistivity techniques (DCRT) for investigation and characterization of leachate-contaminated subsurface environment of an open solid waste dumpsite at Kandy, Sri Lanka. The particular dumpsite has no liner and hence the leachate flows directly to the nearby river via subsurface and surface channels. For the identification of possible subsurface flow paths and the direction of the leachate, DCRT (two-dimensional, three-dimensional and vertical electrical sounding) have been applied. In addition, the physico-chemical parameters such as pH, electrical conductivity (EC), alkalinity, hardness, chloride, chemical oxygen demand (COD) and total organic carbon (TOC) of leachate collected from different points of the solid waste dumping area and leachate drainage channel were analysed. Resistivity data confirmed that the leachate flow is confined to the near surface and no separate plume is observed in the downstream area, which may be due to the contamination distribution in the shallow overburden thickness. The stratigraphy with leachate pockets and leachate plume movements was well demarcated inside the dumpsite via low resistivity zones (1-3 Ωm). The recorded EC, alkalinity, hardness and chloride contents in leachate were averaged as 14.13 mS cm⁻¹, 3236, 2241 and 320 mg L⁻¹, respectively, which confirmed the possible causes for low resistivity values. This study confirms that DCRT can be effectively utilized to assess the subsurface characteristics of the open dumpsites to decide on corridor placement and depth of permeable reactive barriers to reduce the groundwater contamination.

Experience in non-conventional wastewater treatment techniques used in the Czech Republic.

PubMed

Felberova, L; Kucera, J; Mlejnska, E

2007-01-01

Among the most common non-conventional wastewater treatment techniques used in the Czech Republic are waste stabilisation ponds (WSP), subsurface horizontal flow constructed wetlands (CW) and vertical flow groundfilters (GF). These extensive systems can be advantageously used for treatment of waters coming from sewerages where the ballast weighting commonly makes more than half of dry-weather flow. The monitoring was focused at 14 different extensive systems. Organics removal efficiencies were favourable (CW-82%; GF-88%); in the case of WSP only 57% due to the algal bloom. Total nitrogen removal efficiencies were 43 and 47% for WSP and GF; in the case of CW only 32% due to often occurring anaerobic conditions in filter beds. Total phosphorus removal efficiencies were 37, 35 and 22% for WSP, GF and CW, respectively. Often occurring problems are the ice-blockage of surface aerators at WSP during wintertimes, the pond duckweed-cover or the algal bloom at WSP during summers; a gradual colmatage of filter systems; and the oxygen deficiency in beds of subsurface horizontal flow constructed wetlands. Czech legal regulations do not allow treated wastewater disposal into underground waters. There is only an exception for individual family houses. Up to now, knowledge gained by monitoring of a village (which uses the infiltration upon a permission issued according to earlier legal regulations) have not shown an unacceptable groundwater quality deterioration into the infiltration areas.

High temperature methods for forming oxidizer fuel

DOEpatents

Bravo, Jose Luis [Houston, TX

2011-01-11

A method of treating a formation fluid includes providing formation fluid from a subsurface in situ heat treatment process. The formation fluid is separated to produce a liquid stream and a first gas stream. The first gas stream includes carbon dioxide, hydrogen sulfide, hydrocarbons, hydrogen or mixtures thereof. Molecular oxygen is separated from air to form a molecular oxygen stream comprising molecular oxygen. The first gas stream is combined with the molecular oxygen stream to form a combined stream comprising molecular oxygen and the first gas stream. The combined stream is provided to one or more downhole burners.

Control of grown-in defects and oxygen precipitates in silicon wafers with DZ-IG structure by ultrahigh-temperature rapid thermal oxidation

NASA Astrophysics Data System (ADS)

Maeda, Susumu; Sudo, Haruo; Okamura, Hideyuki; Nakamura, Kozo; Sueoka, Koji; Izunome, Koji

2018-04-01

A new control technique for achieving compatibility between crystal quality and gettering ability for heavy metal impurities was demonstrated for a nitrogen-doped Czochralski silicon wafer with a diameter of 300 mm via ultra-high temperature rapid thermal oxidation (UHT-RTO) processing. We have found that the DZ-IG structure with surface denuded zone and the wafer bulk with dense oxygen precipitates were formed by the control of vacancies in UHT-RTO process at temperature exceeding 1300 °C. It was also confirmed that most of the void defects were annihilated from the sub-surface of the wafer due to the interstitial Si atoms that were generated at the SiO2/Si interface. These results indicated that vacancies corresponded to dominant species, despite numerous interstitial silicon injections. We have explained these prominent features by the degree of super-saturation for the interstitial silicon due to oxidation and the precise thermal properties of the vacancy and interstitial silicon.

Seasonal isotope hydrology of Appalachian forest catchments

Treesearch

D. R. DeWalle; P. J. Edwards; B. R. Swistock; R. J. Drimmie; R. Aravena

1995-01-01

Seasonal hydrologic behavior of small forested catchments in the Appalachians was studied using oxygen-18 as a tracer. Oxygen-18 in samples of precipitation and streamflow were used to determine seasonal variations of subsurface water recharge and movement within two 30-40 ha forest catchments (Watershed 3 and 4) at the Fernow Experimental Forest in northcentral West...

Aerobic Denitrification as an Innovative Method for In-Situ Biological Remediation of Contaminated Subsurface Sites

DTIC Science & Technology

1989-01-01

presumed subsurface conditon; * more rapid mineralization of organics and secondary metabolites ; * decrease in the biochemical oxygen demand and the...additon of nitrate would result in the more rapid mineralization of organic carbon and secondary metabolites . This was illustrated in this study with...and water. The list is far from complete. Many denitrifying species, such as those from the genera Moraxella and Achromobacter , are commonly found in

Episodic subsurface injections in the oligotrophic North Pacific observed from BioArgo

NASA Astrophysics Data System (ADS)

Wilson, C.

2016-12-01

Summer blooms of chlorophyll often develop in the oligotrophic North Pacific Ocean in the region between Hawaii and 30°N. Episodic injections of subsurface nutrients have been hypothesized to fuel these blooms, but the exact mechanism is unknown. Here we examine oxygen data from 13 BioArgo floats deployed near Hawaii between September 2002 to April 2016 to look for evidence of subsurface mixing that could be driving the development of the surface chlorophyll features. Twelve injection events (defined as oxygen values < 2 standard deviations below the mean at 100 m depth) were observed. Nine (75%) of the events happened in winter (Dec-Mar), when surface chl blooms do not generally develop. While most of the events were short-lived (< 5 days), several events lasted a month or two. An event that began in August 2014, and lasted almost 2 months, is examined in detail. The start of the event preceded by a few days the development of a surface increase in chlorophyll in the surrounding area evident from satellite data.

Surface vacancies concentration of CeO2(1 1 1) using kinetic Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Mattiello, S.; Kolling, S.; Heiliger, C.

2016-01-01

Kinetic Monte Carlo simulations (kMC) are useful tools for the investigation of the dynamics of surface properties. Within this method we investigate the oxygen vacancy concentration of \\text{Ce}{{\\text{O}}2}(1 1 1) at ultra high vacuum conditions (UHV). In order to achieve first principles calculations the input for the simulations, i.e. energy barriers for the microscopic processes, we use density functional theory (DFT) results from literature. We investigate the possibility of ad- and desorption of oxygen on ceria as well as the diffusion of oxygen vacancies to and from the subsurface. In particular, we focus on the vacancy surface concentration as well as on the ratio of the number of subsurface vacancies to the number of vacancies at the surface. The comparison of our dynamically obtained results to the experimental findings leads to several issues. In conclusion, we can claim a substantial incompatibility of the experimental results and the dynamical calculation using DFT inputs.

Oxidation of trichloroethylene by the hydroxyl radicals produced from oxygenation of reduced nontronite.

PubMed

Liu, Xixiang; Yuan, Songhu; Tong, Man; Liu, Deng

2017-04-15

Reduction by Fe(II)-bearing silicate minerals has been proposed as an important mechanism for the attenuation of chlorinated hydrocarbons (CHCs) in anoxic subsurfaces. The redox condition of subsurface often changes from anoxic to oxic due to natural processes and human activities, but little is known about the transformation of CHCs induced by Fe(II)-bearing silicate minerals under oxic conditions. This study reveals that trichloroethylene (TCE) can be efficiently oxidized during the oxygenation of reduced nontronite at pH 7.5, whereas the reduction was negligible under anoxic conditions. The maximum oxidation of TCE (initially 1 mg/L) attained 89.6% for 3 h oxygenation of 2 g/L nontronite with 50% reduction extent. TCE oxidation is attributed to the strongly oxidizing hydroxyl radicals (OH) produced by the oxygenation of Fe(II) in nontronite. Fe(II) on the edges is preferentially oxygenated for OH production, and the interior Fe(II) serves as an electron pool to regenerate the Fe(II) on the edges. Oxidation of TCE could be sustainable through chemically or biologically reducing the oxidized silicate minerals. Our findings present a new mechanism for the transformation of CHCs and other redox-active substances in the redox-fluctuation environments. Copyright © 2017 Elsevier Ltd. All rights reserved.

SIRE: A MIMO Radar for Landmine/IED Detection

DTIC Science & Technology

2013-04-30

pursuit) for image formation. This technique has been used for subsurface imaging in the image domain, producing ’CLEANer’ images (where prior knowledge...Astronomy and Astrophysics Supplement 15 (1974). [22] Karpat, E., “CLEAN technique to classify and detect objects in subsurface imaging ,” International

Microbial Communities and Organic Matter Composition in Surface and Subsurface Sediments of the Helgoland Mud Area, North Sea

PubMed Central

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

Environmental Electrokinetics for a sustainable subsurface.

PubMed

Lima, A T; Hofmann, A; Reynolds, D; Ptacek, C J; Van Cappellen, P; Ottosen, L M; Pamukcu, S; Alshawabekh, A; O'Carroll, D M; Riis, C; Cox, E; Gent, D B; Landis, R; Wang, J; Chowdhury, A I A; Secord, E L; Sanchez-Hachair, A

2017-08-01

Soil and groundwater are key components in the sustainable management of the subsurface environment. Source contamination is one of its main threats and is commonly addressed using established remediation techniques such as in-situ chemical oxidation (ISCO), in-situ chemical reduction (ISCR; most notably using zero-valent iron [ZVI]), enhanced in-situ bioremediation (EISB), phytoremediation, soil-washing, pump-and-treat, soil vapour extraction (SVE), thermal treatment, and excavation and disposal. Decades of field applications have shown that these techniques can successfully treat or control contaminants in higher permeability subsurface materials such as sands, but achieve only limited success at sites where low permeability soils, such as silts and clays, prevail. Electrokinetics (EK), a soil remediation technique mostly recognized in in-situ treatment of low permeability soils, has, for the last decade, been combined with more conventional techniques and can significantly enhance the performance of several of these remediation technologies, including ISCO, ISCR, EISB and phytoremediation. Herein, we discuss the use of emerging EK techniques in tandem with conventional remediation techniques, to achieve improved remediation performance. Furthermore, we highlight new EK applications that may come to play a role in the sustainable treatment of the contaminated subsurface. Copyright © 2017 Elsevier Ltd. All rights reserved.

Remote sensing of subsurface water temperature by Raman scattering.

PubMed

Leonard, D A; Caputo, B; Hoge, F E

1979-06-01

The application of Raman scattering to remote sensing of subsurface water temperature and salinity is considered, and both theoretical and experimental aspects of the technique are discussed. Recent experimental field measurements obtained in coastal waters and on a trans-Atlantic/Mediterranean research cruise are correlated with theoretical expectations. It is concluded that the Raman technique for remote sensing of subsurface water temperature has been brought from theoretical and laboratory stages to the point where practical utilization can now be developed.

Efforts to estimate pesticide degradation rates in subsurface ...

EPA Pesticide Factsheets

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

Bacterial communities associated with subsurface geochemical processes in continental serpentinite springs.

PubMed

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.

Bacterial Communities Associated with Subsurface Geochemical Processes in Continental Serpentinite Springs

PubMed Central

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

2013-01-01

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

Density-functional theory study of the initial oxygen incorporation in Pd(111)

NASA Astrophysics Data System (ADS)

Todorova, Mira; Reuter, Karsten; Scheffler, Matthias

2005-05-01

Pd(111) has recently been shown to exhibit a propensity to form a subnanometer thin surface oxide film already well before a full monolayer coverage of adsorbed O atoms is reached on the surface. Aiming at an atomic-scale understanding of this finding, we study the initial oxygen incorporation into the Pd(111) surface using density-functional theory. We find that oxygen incorporation into the sub-surface region starts at essentially the same coverage as formation of the surface oxide. This implies that the role of sub-surface oxygen should be considered as that of a metastable precursor in the oxidation process of the surface. The mechanisms found to play a role towards the ensuing stabilization of an ordered oxidic structure with a mixed on-surface/sub-surface site occupation follow a clear trend over the late 4d transition metal series, as seen by comparing our data to previously published studies concerned with oxide formation at the basal surface of Ru, Rh, and Ag. The formation of a linearly aligned O-TM-O trilayered structure (TM=Ru,Rh,Pd,Ag) , together with an efficient coupling to the underlying substrate seem to be key ingredients in this respect.

Winery wastewater treatment using the land filter technique.

PubMed

Christen, E W; Quayle, W C; Marcoux, M A; Arienzo, M; Jayawardane, N S

2010-08-01

This study outlines a new approach to the treatment of winery wastewater by application to a land FILTER (Filtration and Irrigated cropping for Land Treatment and Effluent Reuse) system. The land FILTER system was tested at a medium size rural winery crushing approximately 20,000 tonnes of grapes. The approach consisted of a preliminary treatment through a coarse screening and settling in treatment ponds, followed by application to the land FILTER planted to pasture. The land FILTER system efficiently dealt with variable volumes and nutrient loads in the wastewater. It was operated to minimize pollutant loads in the treated water (subsurface drainage) and provide adequate leaching to manage salt in the soil profile. The land FILTER system was effective in neutralizing the pH of the wastewater and removing nutrient pollutants to meet EPA discharge limits. However, suspended solids (SS) and biological oxygen demand (BOD) levels in the subsurface drainage waters slightly exceeded EPA limits for discharge. The high organic content in the wastewater initially caused some soil blockage and impeded drainage in the land FILTER site. This was addressed by reducing the hydraulic loading rate to allow increased soil drying between wastewater irrigations. The analysis of soil characteristics after the application of wastewater found that there was some potassium accumulation in the profile but sodium and nutrients decreased after wastewater application. Thus, the wastewater application and provision of subsurface drainage ensured adequate leaching, and so was adequate to avoid the risk of soil salinisation. Crown Copyright 2010. Published by Elsevier Ltd. All rights reserved.

Subsurface Mapping: A Question of Position and Interpretation

ERIC Educational Resources Information Center

Kellie, Andrew C.

2009-01-01

This paper discusses the character and challenges inherent in the graphical portrayal of features in subsurface mapping. Subsurface structures are, by their nature, hidden and must be mapped based on drilling and/or geophysical data. Efficient use of graphical techniques is central to effectively communicating the results of expensive exploration…

Subsurface imaging and cell refractometry using quantitative phase/ shear-force feedback microscopy

NASA Astrophysics Data System (ADS)

Edward, Kert; Farahi, Faramarz

2009-10-01

Over the last few years, several novel quantitative phase imaging techniques have been developed for the study of biological cells. However, many of these techniques are encumbered by inherent limitations including 2π phase ambiguities and diffraction limited spatial resolution. In addition, subsurface information in the phase data is not exploited. We hereby present a novel quantitative phase imaging system without 2 π ambiguities, which also allows for subsurface imaging and cell refractometry studies. This is accomplished by utilizing simultaneously obtained shear-force topography information. We will demonstrate how the quantitative phase and topography data can be used for subsurface and cell refractometry analysis and will present results for a fabricated structure and a malaria infected red blood cell.

Deep Subsurface Life from North Pond: Enrichment, Isolation, Characterization and Genomes of Heterotrophic Bacteria

PubMed Central

Russell, Joseph A.; León-Zayas, Rosa; Wrighton, Kelly; Biddle, Jennifer F.

2016-01-01

Studies of subsurface microorganisms have yielded few environmentally relevant isolates for laboratory studies. In order to address this lack of cultivated microorganisms, we initiated several enrichments on sediment and underlying basalt samples from North Pond, a sediment basin ringed by basalt outcrops underlying an oligotrophic water-column west of the Mid-Atlantic Ridge at 22°N. In contrast to anoxic enrichments, growth was observed in aerobic, heterotrophic enrichments from sediment of IODP Hole U1382B at 4 and 68 m below seafloor (mbsf). These sediment depths, respectively, correspond to the fringes of oxygen penetration from overlying seawater in the top of the sediment column and upward migration of oxygen from oxic seawater from the basalt aquifer below the sediment. Here we report the enrichment, isolation, initial characterization and genomes of three isolated aerobic heterotrophs from North Pond sediments; an Arthrobacter species from 4 mbsf, and Paracoccus and Pseudomonas species from 68 mbsf. These cultivated bacteria are represented in the amplicon 16S rRNA gene libraries created from whole sediments, albeit at low (up to 2%) relative abundance. We provide genomic evidence from our isolates demonstrating that the Arthrobacter and Pseudomonas isolates have the potential to respire nitrate and oxygen, though dissimilatory nitrate reduction could not be confirmed in laboratory cultures. The cultures from this study represent members of abundant phyla, as determined by amplicon sequencing of environmental DNA extracts, and allow for further studies into geochemical factors impacting life in the deep subsurface. PMID:27242705

Subsurface low dissolved oxygen occurred at fresh- and saline-water intersection of the Pearl River estuary during the summer period.

PubMed

Li, Gang; Liu, Jiaxing; Diao, Zenghui; Jiang, Xin; Li, Jiajun; Ke, Zhixin; Shen, Pingping; Ren, Lijuan; Huang, Liangmin; Tan, Yehui

2018-01-01

Estuarine oxygen depletion is one of the worldwide problems, which is caused by the freshwater-input-derived severe stratification and high nutrients loading. In this study we presented the horizontal and vertical distributions of dissolved oxygen (DO) in the Pearl River estuary, together with temperature, salinity, chlorophyll a concentration and heterotrophic bacteria abundance obtained from two cruises during the summer (wet) and winter (dry) periods of 2015. In surface water, the DO level in the summer period was lower and varied greater, as compared to the winter period. The DO remained unsaturated in the summer period if salinity is <12 and saturated if salinity is >12; while in the winter period it remained saturated throughout the estuary. In subsurface (>5m) water, the DO level varied from 0.71 to 6.65mgL -1 and from 6.58 to 8.20mgL -1 in the summer and winter periods, respectively. Particularly, we observed an area of ~1500km 2 low DO zone in the subsurface water with a threshold of 4mgDOL -1 during this summer period, that located at the fresh- and saline-water intersection where is characterized with severe stratification and high heterotrophic bacteria abundance. In addition, our results indicate that spatial DO variability in surface water was contributed differently by biological and physio-chemical variables in the summer and winter periods, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

Deep Subsurface Life from North Pond: Enrichment, Isolation, Characterization and Genomes of Heterotrophic Bacteria.

PubMed

Russell, Joseph A; León-Zayas, Rosa; Wrighton, Kelly; Biddle, Jennifer F

2016-01-01

Studies of subsurface microorganisms have yielded few environmentally relevant isolates for laboratory studies. In order to address this lack of cultivated microorganisms, we initiated several enrichments on sediment and underlying basalt samples from North Pond, a sediment basin ringed by basalt outcrops underlying an oligotrophic water-column west of the Mid-Atlantic Ridge at 22°N. In contrast to anoxic enrichments, growth was observed in aerobic, heterotrophic enrichments from sediment of IODP Hole U1382B at 4 and 68 m below seafloor (mbsf). These sediment depths, respectively, correspond to the fringes of oxygen penetration from overlying seawater in the top of the sediment column and upward migration of oxygen from oxic seawater from the basalt aquifer below the sediment. Here we report the enrichment, isolation, initial characterization and genomes of three isolated aerobic heterotrophs from North Pond sediments; an Arthrobacter species from 4 mbsf, and Paracoccus and Pseudomonas species from 68 mbsf. These cultivated bacteria are represented in the amplicon 16S rRNA gene libraries created from whole sediments, albeit at low (up to 2%) relative abundance. We provide genomic evidence from our isolates demonstrating that the Arthrobacter and Pseudomonas isolates have the potential to respire nitrate and oxygen, though dissimilatory nitrate reduction could not be confirmed in laboratory cultures. The cultures from this study represent members of abundant phyla, as determined by amplicon sequencing of environmental DNA extracts, and allow for further studies into geochemical factors impacting life in the deep subsurface.

Subsurface flow and vegetation patterns in tidal environments

NASA Astrophysics Data System (ADS)

Ursino, Nadia; Silvestri, Sonia; Marani, Marco

2004-05-01

Tidal environments are characterized by a complex interplay of hydrological, geomorphic, and biological processes, and their understanding and modeling thus require the explicit description of both their biotic and abiotic components. In particular, the presence and spatial distribution of salt marsh vegetation (a key factor in the stabilization of the surface soil) have been suggested to be related to topographic factors and to soil moisture patterns, but a general, process-based comprehension of this relationship has not yet been achieved. The present paper describes a finite element model of saturated-unsaturated subsurface flow in a schematic salt marsh, driven by tidal fluctuations and evapotranspiration. The conditions leading to the establishment of preferentially aerated subsurface zones are studied, and inferences regarding the development and spatial distribution of salt marsh vegetation are drawn, with important implications for the overall ecogeomorphological dynamics of tidal environments. Our results show that subsurface water flow in the marsh induces complex water table dynamics, even when the tidal forcing has a simple sinusoidal form. The definition of a space-dependent aeration time is then proposed to characterize root aeration. The model shows that salt marsh subsurface flow depends on the distance from the nearest creek or channel and that the subsurface water movement near tidal creeks is both vertical and horizontal, while farther from creeks, it is primarily vertical. Moreover, the study shows that if the soil saturated conductivity is relatively low (10-6 m s-1, values quite common in salt marsh areas), a persistently unsaturated zone is present below the soil surface even after the tide has flooded the marsh; this provides evidence of the presence of an aerated layer allowing a prolonged presence of oxygen for aerobic root respiration. The results further show that plant transpiration increases the extent and persistence of the aerated layer, thereby introducing a strong positive feedback: Pioneer plants on marsh edges have the effect of increasing soil oxygen availability, thus creating the conditions for the further development of other plant communities.

Integrating spatial and temporal oxygen data to improve the quantification of in situ petroleum biodegradation rates.

PubMed

Davis, Gregory B; Laslett, Dean; Patterson, Bradley M; Johnston, Colin D

2013-03-15

Accurate estimation of biodegradation rates during remediation of petroleum impacted soil and groundwater is critical to avoid excessive costs and to ensure remedial effectiveness. Oxygen depth profiles or oxygen consumption over time are often used separately to estimate the magnitude and timeframe for biodegradation of petroleum hydrocarbons in soil and subsurface environments. Each method has limitations. Here we integrate spatial and temporal oxygen concentration data from a field experiment to develop better estimates and more reliably quantify biodegradation rates. During a nine-month bioremediation trial, 84 sets of respiration rate data (where aeration was halted and oxygen consumption was measured over time) were collected from in situ oxygen sensors at multiple locations and depths across a diesel non-aqueous phase liquid (NAPL) contaminated subsurface. Additionally, detailed vertical soil moisture (air-filled porosity) and NAPL content profiles were determined. The spatial and temporal oxygen concentration (respiration) data were modeled assuming one-dimensional diffusion of oxygen through the soil profile which was open to the atmosphere. Point and vertically averaged biodegradation rates were determined, and compared to modeled data from a previous field trial. Point estimates of biodegradation rates assuming no diffusion ranged up to 58 mg kg(-1) day(-1) while rates accounting for diffusion ranged up to 87 mg kg(-1) day(-1). Typically, accounting for diffusion increased point biodegradation rate estimates by 15-75% and vertically averaged rates by 60-80% depending on the averaging method adopted. Importantly, ignoring diffusion led to overestimation of biodegradation rates where the location of measurement was outside the zone of NAPL contamination. Over or underestimation of biodegradation rate estimates leads to cost implications for successful remediation of petroleum impacted sites. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Slow-Releasing Oxygen Source

EPA Science Inventory

Subsurface pollution is an environmental issue of great concern in the United States and around the world. Bioremediation has proven to be an effective and environmentally preferable treatment for biodegradable pollutants, such as methyl tertiary butyl ether, toluene, ethylbenze...

Bioremediation of contaminated groundwater

DOEpatents

Hazen, T.C.; Fliermans, C.B.

1994-01-01

Disclosed is an apparatus and method for in situ remediation of contaminated subsurface soil or groundwater contaminated by chlorinated hydrocarbons. A nutrient fluid (NF) is selected to simulated the growth and reproduction of indigenous subsurface microorganisms capable of degrading the contaminants; an oxygenated fluid (OF) is selected to create an aerobic environment with anaerobic pockets. NF is injected periodically while OF is injected continuously and both are extracted so that both are drawn across the plume. NF stimulates microbial colony growth; withholding it periodically forces the larger, healthy colony of microbes to degrade the contaminants. Treatment is continued until the subsurface concentration of contaminants is acceptable. NF can be methane and OF be air, for stimulating production of methanotrophs to break down chlorohydrocarbons, especially TCE and tetrachloroethylene.

Line-scan spatially offset Raman spectroscopy for inspecting subsurface food safety and quality

NASA Astrophysics Data System (ADS)

Qin, Jianwei; Chao, Kuanglin; Kim, Moon S.

2016-05-01

This paper presented a method for subsurface food inspection using a newly developed line-scan spatially offset Raman spectroscopy (SORS) technique. A 785 nm laser was used as a Raman excitation source. The line-shape SORS data was collected in a wavenumber range of 0-2815 cm-1 using a detection module consisting of an imaging spectrograph and a CCD camera. A layered sample, which was created by placing a plastic sheet cut from the original container on top of cane sugar, was used to test the capability for subsurface food inspection. A whole set of SORS data was acquired in an offset range of 0-36 mm (two sides of the laser) with a spatial interval of 0.07 mm. Raman spectrum from the cane sugar under the plastic sheet was resolved using self-modeling mixture analysis algorithms, demonstrating the potential of the technique for authenticating foods and ingredients through packaging. The line-scan SORS measurement technique provides a new method for subsurface inspection of food safety and quality.

Surface assessment of CaF2 deep-ultraviolet and vacuum-ultraviolet optical components by the quasi-Brewster angle technique.

PubMed

Wang, Jue; Maier, Robert L

2006-08-01

The requirements for optical components have drastically increased for the deep-ultraviolet and vacuum-ultraviolet spectral regions. Low optical loss, high laser damage threshold, and long lifetime fluoride optics are required for microlithographic applications. A nondestructive quasi-Brewster angle technique (qBAT) has been developed for evaluating the quality of optical surfaces including both top surface and subsurface information. By using effective medium approximation, the negative quasi-Brewster angle shift at wavelengths longer than 200 nm has been used to model the distribution of subsurface damage, whereas the positive quasi-Brewster angle shift for wavelengths shorter than 200 nm has been explained by subsurface contamination. The top surface roughness depicted by the qBAT is consistent with atomic force microscopy measurements. The depth and the microporous structure of the subsurface damage measured by the qBAT has been confirmed by magnetorheological finishing. The technique has been extended to evaluate both polished and antireflection-coated CaF(2) components.

Isolation and Characterization of Surface and Subsurface Bacteria in Seawater of Mantanani Island, Kota Belud, Sabah by Direct and Enrichment Techniques

NASA Astrophysics Data System (ADS)

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.

Marine biogeochemistry: Methylmercury manufacture

NASA Astrophysics Data System (ADS)

Cossa, Daniel

2013-10-01

The neurotoxin methylmercury can accumulate in marine food webs, contaminating seafood. An analysis of the isotopic composition of fish in the North Pacific suggests that much of the mercury that enters the marine food web originates from low-oxygen subsurface waters.

Multiple sulphur and oxygen isotopes reveal microbial sulphur cycling in spring waters in the Lower Engadin, Switzerland.

PubMed

Strauss, Harald; Chmiel, Hannah; Christ, Andreas; Fugmann, Artur; Hanselmann, Kurt; Kappler, Andreas; Königer, Paul; Lutter, Andreas; Siedenberg, Katharina; Teichert, Barbara M A

2016-01-01

Highly mineralized springs in the Scuol-Tarasp area of the Lower Engadin and in the Albula Valley near Alvaneu, Switzerland, display distinct differences with respect to the source and fate of their dissolved sulphur species. High sulphate concentrations and positive sulphur (δ(34)S) and oxygen (δ(18)O) isotopic compositions argue for the subsurface dissolution of Mesozoic evaporitic sulphate. In contrast, low sulphate concentrations and less positive or even negative δ(34)S and δ(18)O values indicate a substantial contribution of sulphate sulphur from the oxidation of sulphides in the crystalline basement rocks or the Jurassic sedimentary cover rocks. Furthermore, multiple sulphur (δ(34)S, Δ(33)S) isotopes support the identification of microbial sulphate reduction and sulphide oxidation in the subsurface, the latter is also evident through the presence of thick aggregates of sulphide-oxidizing Thiothrix bacteria.

Fibre optic confocal imaging (FOCI) for subsurface microscopy of the colon in vivo.

PubMed Central

Delaney, P M; King, R G; Lambert, J R; Harris, M R

1994-01-01

Fibre optic confocal imaging (FOCI) is a new type of microscopy which has been recently developed (Delaney et al. 1993). In contrast to conventional light microscopy, FOCI and other confocal techniques allow clear imaging of subsurface structures within translucent objects. However, unlike conventional confocal microscopes which are bulky (because of a need for accurate alignment of large components) FOCI allows the imaging end to be miniaturised and relatively mobile. FOCI is thus particularly suited for clear subsurface imaging of structures within living animals or subjects. The aim of the present study was to assess the suitability of using FOCI for imaging of subsurface structures within the colon, both in vitro (human and rat biopsies) and in vivo (in rats). Images were obtained in fluorescence mode (excitation 488 nm, detection above 515 nm) following topical application of fluorescein. By this technique the glandular structure of the colon was imaged. FOCI is thus suitable for subsurface imaging of the colon in vivo. Images Fig. 2 Fig. 3 PMID:8157487

Imaging of Subsurface Corrosion Using Gradient-Field Pulsed Eddy Current Probes with Uniform Field Excitation

PubMed Central

Ren, Shuting; Yan, Bei; Zainal Abidin, Ilham Mukriz; Wang, Yi

2017-01-01

A corrosive environment leaves in-service conductive structures prone to subsurface corrosion which poses a severe threat to the structural integrity. It is indispensable to detect and quantitatively evaluate subsurface corrosion via non-destructive evaluation techniques. Although the gradient-field pulsed eddy current technique (GPEC) has been found to be superior in the evaluation of corrosion in conductors, it suffers from a technical drawback resulting from the non-uniform field excited by the conventional pancake coil. In light of this, a new GPEC probe with uniform field excitation for the imaging of subsurface corrosion is proposed in this paper. The excited uniform field makes the GPEC signal correspond only to the field perturbation due to the presence of subsurface corrosion, which benefits the corrosion profiling and sizing. A 3D analytical model of GPEC is established to analyze the characteristics of the uniform field induced within a conductor. Following this, experiments regarding the imaging of subsurface corrosion via GPEC have been carried out. It has been found from the results that the proposed GPEC probe with uniform field excitation not only applies to the imaging of subsurface corrosion in conductive structures, but provides high-sensitivity imaging results regarding the corrosion profile and opening size. PMID:28758985

Imaging of Subsurface Corrosion Using Gradient-Field Pulsed Eddy Current Probes with Uniform Field Excitation.

PubMed

Li, Yong; Ren, Shuting; Yan, Bei; Zainal Abidin, Ilham Mukriz; Wang, Yi

2017-07-31

A corrosive environment leaves in-service conductive structures prone to subsurface corrosion which poses a severe threat to the structural integrity. It is indispensable to detect and quantitatively evaluate subsurface corrosion via non-destructive evaluation techniques. Although the gradient-field pulsed eddy current technique (GPEC) has been found to be superior in the evaluation of corrosion in conductors, it suffers from a technical drawback resulting from the non-uniform field excited by the conventional pancake coil. In light of this, a new GPEC probe with uniform field excitation for the imaging of subsurface corrosion is proposed in this paper. The excited uniform field makes the GPEC signal correspond only to the field perturbation due to the presence of subsurface corrosion, which benefits the corrosion profiling and sizing. A 3D analytical model of GPEC is established to analyze the characteristics of the uniform field induced within a conductor. Following this, experiments regarding the imaging of subsurface corrosion via GPEC have been carried out. It has been found from the results that the proposed GPEC probe with uniform field excitation not only applies to the imaging of subsurface corrosion in conductive structures, but provides high-sensitivity imaging results regarding the corrosion profile and opening size.

Final Technical Report

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

Sobecky, Patricia A; Taillefert, Martial

This final technical report describes results and findings from a research project to examine the role of microbial phosphohydrolase enzymes in naturally occurring subsurface microorganisms for the purpose of promoting the immobilization of the radionuclide uranium through the production of insoluble uranium phosphate minerals. The research project investigated the microbial mechanisms and the physical and chemical processes promoting uranium biomineralization and sequestration in oxygenated subsurface soils. Uranium biomineralization under aerobic conditions can provide a secondary biobarrier strategy to immobilize radionuclides should the metal precipitates formed by microbial dissimilatory mechanisms remobilize due to a change in redox state.

Probing the surface of γ-Al2O3 by oxygen-17 dynamic nuclear polarization enhanced solid-state NMR spectroscopy.

PubMed

Li, Wenzheng; Wang, Qiang; Xu, Jun; Aussenac, Fabien; Qi, Guodong; Zhao, Xingling; Gao, Pan; Wang, Chao; Deng, Feng

2018-06-14

γ-Al2O3 is an important catalyst and catalyst support of industrial interest. Its acid/base characteristics are correlated to the surface structure, which has always been an issue of concern. In this work, the complex (sub-)surface oxygen species on surface-selectively labelled γ-Al2O3 were probed by 17O dynamic nuclear polarization surface-enhanced NMR spectroscopy (DNP-SENS). Direct 17O MAS and indirect 1H-17O cross-polarization (CP)/MAS DNP experiments enable observation of the (sub-)surface bare oxygen species and hydroxyl groups. In particular, a two-dimensional (2D) 17O 3QMAS DNP spectrum was for the first time achieved for γ-Al2O3, in which two O(Al)4 and one O(Al)3 bare oxygen species were identified. The 17O isotropic chemical shifts (δcs) vary from 56.7 to 81.0 ppm and the quadrupolar coupling constants (CQ) range from 0.6 to 2.5 MHz for the three oxygen species. The coordinatively unsaturated O(Al)3 species is characterized by a higher field chemical shift (56.7 ppm) and the largest CQ value (2.5 MHz) among these oxygen sites. 2D 1H → 17O HETCOR DNP experiments allow us to discriminate three bridging (Aln)-μ2-OH and two terminal (Aln)-μ1-OH hydroxyl groups. The structural features of the bare oxygen species and hydroxyl groups are similar for the γ-Al2O3 samples isotopically labelled by 17O2 gas or H217O. The results presented here show that the combination of surface-selective labelling and DNP-SENS is an effective approach for characterizing oxides with complex surface species.

Deep subsurface life from North Pond: Enrichment, isolation, characterization and genomes of heterotrophic bacteria

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

Russell, Joseph A.; Leon-Zayas, Rosa; Wrighton, Kelly

Studies of subsurface microorganisms have yielded few environmentally relevant isolates for laboratory studies. In order to address this lack of cultivated microorganisms, we initiated several enrichments on sediment and underlying basalt samples from North Pond, a sediment basin ringed by basalt outcrops underlying an oligotrophic watercolumn west of the Mid-Atlantic Ridge at 22° N. In contrast to anoxic enrichments, growth was observed in aerobic, heterotrophic enrichments from sediment of IODP Hole U1382B at 4 and 68 m below seafloor (mbsf). These sediment depths, respectively, correspond to the fringes of oxygen penetration from overlying seawater in the top of the sedimentmore » column and upward migration of oxygen from oxic seawater from the basalt aquifer below the sediment. Here we report the enrichment, isolation, initial characterization and genomes of three isolated aerobic heterotrophs from North Pond sediments; an Arthrobacter species from 4 mbsf, and Paracoccus and Pseudomonas species from 68 mbsf. These cultivated bacteria are represented in the amplicon 16S rRNA gene libraries created from whole sediments, albeit at low (up to 2%) relative abundance. We provide genomic evidence from our isolates demonstrating that the Arthrobacter and Pseudomonas isolates have the potential to respire nitrate and oxygen, though dissimilatory nitrate reduction could not be confirmed in laboratory cultures. Furthermore, the cultures from this study represent members of abundant phyla, as determined by amplicon sequencing of environmental DNA extracts, and allow for further studies into geochemical factors impacting life in the deep subsurface.« less

Deep subsurface life from North Pond: Enrichment, isolation, characterization and genomes of heterotrophic bacteria

DOE PAGES

Russell, Joseph A.; Leon-Zayas, Rosa; Wrighton, Kelly; ...

2016-05-10

Studies of subsurface microorganisms have yielded few environmentally relevant isolates for laboratory studies. In order to address this lack of cultivated microorganisms, we initiated several enrichments on sediment and underlying basalt samples from North Pond, a sediment basin ringed by basalt outcrops underlying an oligotrophic watercolumn west of the Mid-Atlantic Ridge at 22° N. In contrast to anoxic enrichments, growth was observed in aerobic, heterotrophic enrichments from sediment of IODP Hole U1382B at 4 and 68 m below seafloor (mbsf). These sediment depths, respectively, correspond to the fringes of oxygen penetration from overlying seawater in the top of the sedimentmore » column and upward migration of oxygen from oxic seawater from the basalt aquifer below the sediment. Here we report the enrichment, isolation, initial characterization and genomes of three isolated aerobic heterotrophs from North Pond sediments; an Arthrobacter species from 4 mbsf, and Paracoccus and Pseudomonas species from 68 mbsf. These cultivated bacteria are represented in the amplicon 16S rRNA gene libraries created from whole sediments, albeit at low (up to 2%) relative abundance. We provide genomic evidence from our isolates demonstrating that the Arthrobacter and Pseudomonas isolates have the potential to respire nitrate and oxygen, though dissimilatory nitrate reduction could not be confirmed in laboratory cultures. Furthermore, the cultures from this study represent members of abundant phyla, as determined by amplicon sequencing of environmental DNA extracts, and allow for further studies into geochemical factors impacting life in the deep subsurface.« less

Surface states and annihilation characteristics of positrons trapped at the oxidized Cu(100) surface

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Weiss, A. H.

2013-06-01

In this work we present the results of theoretical studies of positron surface and bulk states and annihilation probabilities of surface-trapped positrons with relevant core electrons at the oxidized Cu(100) surface under conditions of high oxygen coverage. Oxidation of the Cu(100) surface has been studied by performing an ab-initio investigation of the stability and electronic structure of the Cu(100) missing row reconstructed surface at various on-surface and subsurface oxygen coverages ranging from 0.5 to 1.5 monolayers using density functional theory (DFT). All studied structures have been found to be energetically more favorable as compared to structures formed by purely on-surface oxygen adsorption. The observed decrease in the positron work function when oxygen atoms occupy on-surface and subsurface sites has been attributed to a significant charge redistribution within the first two layers, buckling effects within each layer and an interlayer expansion. The computed positron binding energy, positron surface state wave function, and annihilation probabilities of the surface trapped positrons with relevant core electrons demonstrate their sensitivity to oxygen coverage, atomic structure of the topmost layers of surfaces, and charge transfer effects. Theoretical results are compared with experimental data obtained from studies of oxidation of the Cu(100) surface using positron annihilation induced Auger electron spectroscopy (PAES). The results presented provide an explanation for the changes observed in the probability of annihilation of surface trapped positrons with Cu 3p core-level electrons as a function of annealing temperature.

Conceptual Model Evaluation using Advanced Parameter Estimation Techniques with Heat as a Tracer

NASA Astrophysics Data System (ADS)

Naranjo, R. C.; Morway, E. D.; Healy, R. W.

2016-12-01

Temperature measurements made at multiple depths beneath the sediment-water interface has proven useful for estimating seepage rates from surface-water channels and corresponding subsurface flow direction. Commonly, parsimonious zonal representations of the subsurface structure are defined a priori by interpretation of temperature envelopes, slug tests or analysis of soil cores. However, combining multiple observations into a single zone may limit the inverse model solution and does not take full advantage of the information content within the measured data. Further, simulating the correct thermal gradient, flow paths, and transient behavior of solutes may be biased by inadequacies in the spatial description of subsurface hydraulic properties. The use of pilot points in PEST offers a more sophisticated approach to estimate the structure of subsurface heterogeneity. This presentation evaluates seepage estimation in a cross-sectional model of a trapezoidal canal with intermittent flow representing four typical sedimentary environments. The recent improvements in heat as a tracer measurement techniques (i.e. multi-depth temperature probe) along with use of modern calibration techniques (i.e., pilot points) provides opportunities for improved calibration of flow models, and, subsequently, improved model predictions.

Study on nitrogen removal enhanced by shunt distributing wastewater in a constructed subsurface infiltration system under intermittent operation mode.

PubMed

Li, Yinghua; Li, Haibo; Sun, Tieheng; Wang, Xin

2011-05-15

Subsurface wastewater infiltration system is an efficient and economic technology in treating small scattered sewage. The removal rates are generally satisfactory in terms of COD, BOD(5), TP and SS removal; while nitrogen removal is deficient in most of the present operating SWIS due to the different requirements for the presence of oxygen for nitrification and denitrification processes. To study the enhanced nitrogen removal technologies, two pilot subsurface wastewater infiltration systems were constructed in a village in Shenyang, China. The filled matrix was a mixture of 5% activated sludge, 65% brown soil and 30% coal slag in volume ratio for both systems. Intermittent operation mode was applied in to supply sufficient oxygen to accomplish the nitrification; meanwhile sewage was supplemented as the carbon source to the lower part in to denitrify. The constructed subsurface wastewater infiltration systems worked successfully under wetting-drying ratio of 1:1 with hydraulic loading of 0.081 m(3)/(m(2)d) for over 4 months. Carbon source was supplemented with shunt ratio of 1:1 and shunt position at the depth of 0.5m. The experimental results showed that intermittent operation mode and carbon source supplementation could significantly enhance the nitrogen removal efficiency with little influence on COD and TP removal. The average removal efficiencies for NH(3)-N and TN were 87.7 ± 1.4 and 70.1 ± 1.0%, increased by 12.5 ± 1.0 and 8.6 ± 0.7%, respectively. Copyright © 2011 Elsevier B.V. All rights reserved.

Analysing the origin of rain- and subsurface water in seasonal wetlands of north-central Namibia

NASA Astrophysics Data System (ADS)

Hiyama, Tetsuya; Kanamori, Hironari; Kambatuku, Jack R.; Kotani, Ayumi; Asai, Kazuyoshi; Mizuochi, Hiroki; Fujioka, Yuichiro; Iijima, Morio

2017-03-01

We investigated the origins of rain- and subsurface waters of north-central Namibia’s seasonal wetlands, which are critical to the region’s water and food security. The region includes the southern part of the Cuvelai system seasonal wetlands (CSSWs) of the Cuvelai Basin, a transboundary river basin covering southern Angola and northern Namibia. We analysed stable water isotopes (SWIs) of hydrogen (HDO) and oxygen (H2 18O) in rainwater, surface water and shallow groundwater. Rainwater samples were collected during every rainfall event of the rainy season from October 2013 to April 2014. The isotopic ratios of HDO (δD) and oxygen H2 18O (δ 18O) were analysed in each rainwater sample and then used to derive the annual mean value of (δD, δ 18O) in precipitation weighted by each rainfall volume. Using delta diagrams (plotting δD vs. δ 18O), we showed that the annual mean value was a good indicator for determining the origins of subsurface waters in the CSSWs. To confirm the origins of rainwater and to explain the variations in isotopic ratios, we conducted atmospheric water budget analysis using Tropical Rainfall Measuring Mission (TRMM) multi-satellite precipitation analysis (TMPA) data and ERA-Interim atmospheric reanalysis data. The results showed that around three-fourths of rainwater was derived from recycled water at local-regional scales. Satellite-observed outgoing longwave radiation (OLR) and complementary satellite data from MODerate-resolution Imaging Spectroradiometer (MODIS) and Advanced Microwave Scanning Radiometer (AMSR) series implied that the isotopic ratios in rainwater were affected by evaporation of raindrops falling from convective clouds. Consequently, integrated SWI analysis of rain-, surface and subsurface waters, together with the atmospheric water budget analysis, revealed that shallow groundwater of small wetlands in this region was very likely to be recharged from surface waters originating from local rainfall, which was temporarily pooled in small wetlands. This was also supported by tritium (3H) counting of the current rain- and subsurface waters in the region. We highly recommend that shallow groundwater not be pumped intensively to conserve surface and subsurface waters, both of which are important water resources in the region.

Calibration of Complex Subsurface Reaction Models Using a Surrogate-Model Approach

EPA Science Inventory

Application of model assessment techniques to complex subsurface reaction models involves numerous difficulties, including non-trivial model selection, parameter non-uniqueness, and excessive computational burden. To overcome these difficulties, this study introduces SAMM (Simult...

Active-Passive Microwave Remote Sensing of Martian Permafrost and Subsurface Water

NASA Technical Reports Server (NTRS)

Raizer, V.; Linkin, V. M.; Ozorovich, Y. R.; Smythe, W. D.; Zoubkov, B.; Babkin, F.

2000-01-01

The investigation of permafrost formation global distribution and their appearance in h less than or equal 1 m thick subsurface layer would be investigated successfully by employment of active-passive microwave remote sensing techniques.

The combined effects of acidification and hypoxia on pH and aragonite saturation in the coastal waters of the California current ecosystem and the northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Feely, Richard A.; Okazaki, Remy R.; Cai, Wei-Jun; Bednaršek, Nina; Alin, Simone R.; Byrne, Robert H.; Fassbender, Andrea

2018-01-01

Inorganic carbon chemistry data from the surface and subsurface waters of the West Coast of North America have been compared with similar data from the northern Gulf of Mexico to demonstrate how future changes in CO2 emissions will affect chemical changes in coastal waters affected by respiration-induced hypoxia ([O2] ≤ 60 μmol kg-1). In surface waters, the percentage change in the carbon parameters due to increasing CO2 emissions are very similar for both regions even though the absolute decrease in aragonite saturation is much higher in the warmer waters of the Gulf of Mexico. However, in subsurface waters the changes are enhanced due to differences in the initial oxygen concentration and the changes in the buffer capacity (i.e., increasing Revelle Factor) with increasing respiration from the oxidation of organic matter, with the largest impacts on pH and CO2 partial pressure (pCO2) occurring in the colder West Coast waters. As anthropogenic CO2 concentrations begin to build up in subsurface waters, increased atmospheric CO2 will expose organisms to hypercapnic conditions (pCO2 >1000 μatm) within subsurface depths. Since the maintenance of the extracellular pH appears as the first line of defense against external stresses, many biological response studies have been focused on pCO2-induced hypercapnia. The extent of subsurface exposure will occur sooner and be more widespread in colder waters due to their capacity to hold more dissolved oxygen and the accompanying weaker acid-base buffer capacity. Under present conditions, organisms in the West Coast are exposed to hypercapnic conditions when oxygen concentrations are near 100 μmol kg-1 but will experience hypercapnia at oxygen concentrations of 260 μmol kg-1 by year 2100 under the highest elevated-CO2 conditions. Hypercapnia does not occur at present in the Gulf of Mexico but will occur at oxygen concentrations of 170 μmol kg-1 by the end of the century under similar conditions. The aragonite saturation horizon is currently above the hypoxic zone in the West Coast. With increasing atmospheric CO2, it is expected to shoal up close to surface waters under the IPCC Representative Concentration Pathway (RCP) 8.5 in West Coast waters, while aragonite saturation state will exhibit steeper gradients in the Gulf of Mexico. This study demonstrates how different biological thresholds (e.g., hypoxia, CaCO3 undersaturation, hypercapnia) will vary asymmetrically because of local initial conditions that are affected differently with increasing atmospheric CO2. The direction of change in amplitude of hypercapnia will be similar in both ecosystems, exposing both biological communities from the West Coast and Gulf of Mexico to intensification of stressful conditions. However, the region of lower Revelle factors (i.e., the Gulf of Mexico), currently provides an adequate refuge habitat that might no longer be the case under the most severe RCP scenarios.

Enhancement of subsurface geologic structure model based on gravity, magnetotelluric, and well log data in Kamojang geothermal field

NASA Astrophysics Data System (ADS)

Yustin Kamah, Muhammad; Armando, Adilla; Larasati Rahmani, Dinda; Paramitha, Shabrina

2017-12-01

Geophysical methods such as gravity and magnetotelluric methods commonly used in conventional and unconventional energy exploration, notably for exploring geothermal prospect. They used to identify the subsurface geology structures which is estimated as a path of fluid flow. This study was conducted in Kamojang Geothermal Field with the aim of highlighting the volcanic lineament in West Java, precisely in Guntur-Papandayan chain where there are three geothermal systems. Kendang Fault has predominant direction NE-SW, identified by magnetotelluric techniques and gravity data processing techniques. Gravity techniques such as spectral analysis, derivative solutions, and Euler deconvolution indicate the type and geometry of anomaly. Magnetotelluric techniques such as inverse modeling and polar diagram are required to know subsurface resistivity charactersitics and major orientation. Furthermore, the result from those methods will be compared to geology information and some section of well data, which is sufficiently suitable. This research is very useful to trace out another potential development area.

Density functional theory simulation of titanium migration and reaction with oxygen in the early stages of oxidation of equiatomic NiTi alloy.

PubMed

Nolan, Michael; Tofail, Syed A M

2010-05-01

The biocompatibility of NiTi shape memory alloys (SMA) has made possible applications in self-expandable cardio-vascular stents, stone extraction baskets, catheter guide wires and other invasive and minimally invasive biomedical devices. The NiTi intermetallic alloy spontaneously forms a thin passive layer of TiO(2), which provides its biocompatibility. The oxide layer is thought to form as the Ti in the alloy surface reacts with oxygen, resulting in a depletion of Ti in the subsurface region - experimental evidence indicates formation of a Ni-rich layer below the oxide film. In this paper, we study the initial stages of oxide growth on the (110) surface of the NiTi alloy to understand the formation of alloy/oxide interface. We initially adsorb atomic and molecular oxygen on the (110) surface and then successively add O(2) molecules, up to 2 monolayer of O(2). Oxygen adsorption always results in a large energy gain. With atomic oxygen, Ti is pulled out of the surface layer leaving behind a Ni-rich subsurface region. Molecular O(2), on the other hand adsorbs dissociatively and pulls a Ti atom farther out of the surface layer. The addition of further O(2) up to 1 monolayer is also dissociative and results in complete removal of Ti from the initial surface layer. When further O(2) is added up to 2 monolayer, Ti is pulled even further out of the surface and a single thin layer of composition O-Ti-O is formed. The electronic structure shows that the metallic character of the alloy is unaffected by interaction with oxygen and formation of the oxide layer, consistent with the oxide layer being a passivant. Copyright 2010 Elsevier Ltd. All rights reserved.

Applying model abstraction techniques to optimize monitoring networks for detecting subsurface contaminant transport

USDA-ARS?s Scientific Manuscript database

Improving strategies for monitoring subsurface contaminant transport includes performance comparison of competing models, developed independently or obtained via model abstraction. Model comparison and parameter discrimination involve specific performance indicators selected to better understand s...

Integral Analysis of Seismic Refraction and Ambient Vibration Survey for Subsurface Profile Evaluation

NASA Astrophysics Data System (ADS)

Hazreek, Z. A. M.; Kamarudin, A. F.; Rosli, S.; Fauziah, A.; Akmal, M. A. K.; Aziman, M.; Azhar, A. T. S.; Ashraf, M. I. M.; Shaylinda, M. Z. N.; Rais, Y.; Ishak, M. F.; Alel, M. N. A.

2018-04-01

Geotechnical site investigation as known as subsurface profile evaluation is the process of subsurface layer characteristics determination which finally used for design and construction phase. Traditionally, site investigation was performed using drilling technique thus suffers from several limitation due to cost, time, data coverage and sustainability. In order to overcome those problems, this study adopted surface techniques using seismic refraction and ambient vibration method for subsurface profile depth evaluation. Seismic refraction data acquisition and processing was performed using ABEM Terraloc and OPTIM software respectively. Meanwhile ambient vibration data acquisition and processing was performed using CityShark II, Lennartz and GEOPSY software respectively. It was found that studied area consist of two layers representing overburden and bedrock geomaterials based on p-wave velocity value (vp = 300 – 2500 m/s and vp > 2500 m/s) and natural frequency value (Fo = 3.37 – 3.90 Hz) analyzed. Further analysis found that both methods show some good similarity in term of depth and thickness with percentage accuracy at 60 – 97%. Consequently, this study has demonstrated that the application of seismic refractin and ambient vibration method was applicable in subsurface profile depth and thickness estimation. Moreover, surface technique which consider as non-destructive method adopted in this study was able to compliment conventional drilling method in term of cost, time, data coverage and environmental sustainaibility.

Total Internal Reflection Microscopy (TIRM) as a nondestructive surface damage assessment tool

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

Liao, Z.M.; Cohen, S.J.; Taylor, J.R.

1994-10-01

An easy to use, nondestructive, method for evaluating subsurface damage in polished substrates has been established at LLNL. Subsurface damage has been related to laser damage in coated optical components used in high power, high repetition rate laser systems. Total Internal Reflection Microscopy (TIRM) has been shown to be a viable nondestructive technique in analyzing subsurface damage in optical components. A successful TIRM system has been established for evaluating subsurface damage on fused silica components. Laser light scattering from subsurface damage sites is collected through a Nomarski microscope. These images are then captured by a CCD camera for analysis onmore » a computer. A variety of optics, including components with intentional subsurface damage due to grinding and polishing, have been analyzed and their TIRM images compared to an existing destructive etching method. Methods for quantitative measurement of subsurface damage are also discussed.« less

Infrared Photothermal Radiometry.

DTIC Science & Technology

1984-04-10

changes whenever the transmitted thermal wave crosses a void. This provides a means of nondestructive subsurface imaging of defects, and Busse found that...15 In the flash excitation, the excitation beam is modulated by a broad spectrum of Fourier modulation frequencies. In all cases of subsurface imaging , the...technique of Nordal and Kanstad 2 1t 23 is not only good for spectroscopic detection, but also for subsurface imaging applications as well. 2.4 Pulsed

Characterization and reclamation assessment for the Central Shops Diesel Storage Facility, Savannah River Site, Aiken, South Carolina

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

Fliermans, C.B.; Hazen, T.C.; Bledsoe, H.

1993-10-01

The contamination of subsurface terrestrial environments by organic contaminants is a global phenomenon. The remediation of such environments requires innovative assessment techniques and strategies for successful clean-ups. Central Shops Diesel Storage Facility at Savannah River Site was characterized to determine the extent of subsurface diesel fuel contamination using innovative approaches and effective bioremediation techniques for clean-up of the contaminant plume have been established.

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

NASA Technical Reports Server (NTRS)

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.

Applicability of radar subsurface profiling in estimating sidewalk undermining.

DOT National Transportation Integrated Search

1979-01-01

An evaluation was made of the applicability of the geophysical technique of radar subsurface profiling to estimating the extent of sidewalk undermining. It was found that there is a distinct difference between the observed radar echo patterns of a no...

Application of model abstraction techniques to simulate transport in soils

USDA-ARS?s Scientific Manuscript database

Successful understanding and modeling of contaminant transport in soils is the precondition of risk-informed predictions of the subsurface contaminant transport. Exceedingly complex models of subsurface contaminant transport are often inefficient. Model abstraction is the methodology for reducing th...

Fundamentals of ISCO Using Ozone

EPA Science Inventory

In situ chemical oxidation (ISCO) using ozone involves the introduction of ozone gas (O3) into the subsurface to degrade organic contaminants of concern. Ozone is tri-molecular oxygen (O2) that is a gas under atmospheric conditions and is a strong oxidant. Ozone may react with ...

PASSIVE TREATMENT OF ACID ROCK DRAINAGE FROM A SUBSURFACE MINE

EPA Science Inventory

Acidic, metal-contaminated drainages are a critical problem facing many areas of the world. Acid rock drainage results when metal sulfide minerals, particularly pyrite, are oxidized by exposure to oxygen and water. The deleterious effects of these drainages on receiving streams a...

The human gut and groundwater harbor non-photosynthetic bacteria belonging to a new candidate phylum sibling to Cyanobacteria

PubMed Central

Di Rienzi, Sara C; Sharon, Itai; Wrighton, Kelly C; Koren, Omry; Hug, Laura A; Thomas, Brian C; Goodrich, Julia K; Bell, Jordana T; Spector, Timothy D; Banfield, Jillian F; Ley, Ruth E

2013-01-01

Cyanobacteria were responsible for the oxygenation of the ancient atmosphere; however, the evolution of this phylum is enigmatic, as relatives have not been characterized. Here we use whole genome reconstruction of human fecal and subsurface aquifer metagenomic samples to obtain complete genomes for members of a new candidate phylum sibling to Cyanobacteria, for which we propose the designation ‘Melainabacteria’. Metabolic analysis suggests that the ancestors to both lineages were non-photosynthetic, anaerobic, motile, and obligately fermentative. Cyanobacterial light sensing may have been facilitated by regulators present in the ancestor of these lineages. The subsurface organism has the capacity for nitrogen fixation using a nitrogenase distinct from that in Cyanobacteria, suggesting nitrogen fixation evolved separately in the two lineages. We hypothesize that Cyanobacteria split from Melainabacteria prior or due to the acquisition of oxygenic photosynthesis. Melainabacteria remained in anoxic zones and differentiated by niche adaptation, including for symbiosis in the mammalian gut. DOI: http://dx.doi.org/10.7554/eLife.01102.001 PMID:24137540

Pulsed Photothermal Radiometry for Noncontact Spectroscopy, Material Testing and Inspection Measurement.

DTIC Science & Technology

1984-08-08

transmission PTR signal changes whenever the transmitted thermal wave crosses a void. This provides a means of nondestructive subsurface imaging of defects...and Busse and Renk( 2 2 ) have demonstrated a new stereoscopic subsurface imaging technique involving two adjacent modulated PT source for...modulation frequencies. In all cases of subsurface imaging , the authors preferred to use the shape or the phase of the PTR signal rather than the amplitude

Thermal-Wave Microscope

NASA Technical Reports Server (NTRS)

Jones, Robert E.; Kramarchuk, Ihor; Williams, Wallace D.; Pouch, John J.; Gilbert, Percy

1989-01-01

Computer-controlled thermal-wave microscope developed to investigate III-V compound semiconductor devices and materials. Is nondestructive technique providing information on subsurface thermal features of solid samples. Furthermore, because this is subsurface technique, three-dimensional imaging also possible. Microscope uses intensity-modulated electron beam of modified scanning electron microscope to generate thermal waves in sample. Acoustic waves generated by thermal waves received by transducer and processed in computer to form images displayed on video display of microscope or recorded on magnetic disk.

Evidence of remediation-induced alteration of subsurface poly- and perfluoroalkyl substance distribution at a former firefighter training area.

PubMed

McGuire, Meghan E; Schaefer, Charles; Richards, Trenton; Backe, Will J; Field, Jennifer A; Houtz, Erika; Sedlak, David L; Guelfo, Jennifer L; Wunsch, Assaf; Higgins, Christopher P

2014-06-17

Poly- and perfluoroalkyl substances (PFASs) are a class of fluorinated chemicals that are utilized in firefighting and have been reported in groundwater and soil at several firefighter training areas. In this study, soil and groundwater samples were collected from across a former firefighter training area to examine the extent to which remedial activities have altered the composition and spatial distribution of PFASs in the subsurface. Log Koc values for perfluoroalkyl acids (PFAAs), estimated from analysis of paired samples of groundwater and aquifer solids, indicated that solid/water partitioning was not entirely consistent with predictions based on laboratory studies. Differential PFAA transport was not strongly evident in the subsurface, likely due to remediation-induced conditions. When compared to the surface soil spatial distributions, the relative concentrations of perfluorooctanesulfonate (PFOS) and PFAA precursors in groundwater strongly suggest that remedial activities altered the subsurface PFAS distribution, presumably through significant pumping of groundwater and transformation of precursors to PFAAs. Additional evidence for transformation of PFAA precursors during remediation included elevated ratios of perfluorohexanesulfonate (PFHxS) to PFOS in groundwater near oxygen sparging wells.

Bacterial Oxidation of Iron in Olivine: Implications for the Subsurface Biosphere, Global Chemical Cycles, and Life on Mars

NASA Astrophysics Data System (ADS)

Fisk, M. R.; Popa, R.; Smith, A. R.; Popa, R.; Boone, J.

2011-12-01

We isolated 21 species of bacteria from subseafloor and terrestrial basalt environments and which thrive on olivine at neutral pH. Cell numbers increase four to five orders of magnitude over three weeks in media where the only metabolic energy comes from the oxidation of Fe(II) in olivine. The subseafloor bacteria were isolated from a borehole on the flank of Juan de Fuca Ridge in the northeast Pacific basin where the temperature ranged from 4 up to 64 °C over four years. Terrestrial isolates originated from the basalt-ice boundary in a lava tube on the flank of Newberry Caldera in the Cascades of Oregon. The borehole water was either seawater or seawater plus subseafloor formation water and the lava tube ice was frozen meteoric or ground water. Although microorganisms capable of oxidizing iron for growth are known, microbes that oxidize iron from silicate minerals at neutral pH have not previously been cultured. The 21 species in this study are the first neutrophilic, iron-oxidizing bacteria (nFeOB) to be isolated and cultured that grow on olivine. These nFeOB are primary producers and we believe that they are a widespread component of the subsurface biosphere. In addition to their ability use iron from olivine, these microbes assimilate carbon from bicarbonate in solution and can grow when oxygen pressures are low. They also use nitrate as an alternative electron acceptor to oxygen in anaerobiosis. Since basalt is the most common rock in the Earth's crust and iron is the fourth most abundant element in the crust, we believe nFeOB are likely to be a significant portion of the subsurface biosphere. They are likely to affect, and perhaps in some environments control, the weathering rate of olivine and possibly of pyroxene and basalt glass. Olivine is a component of Mars's surface and it is present on other rocky bodies in the solar system. The ability of these bacteria to use Fe(II) from olivine, to assimilate carbon, to grow at low temperature, and to use low levels of oxygen and nitrate as oxidants would allow them to survive below the surface of Mars. These cultured organisms, which are the first known to oxidize iron from olivine at neutral pH, may be a major component of the subsurface biosphere, may affect global chemical cycles of elements in basalt, and could potentially, live in the Martian subsurface.

Active microbial biofilms in deep poor porous continental subsurface rocks.

PubMed

Escudero, Cristina; Vera, Mario; Oggerin, Monike; Amils, Ricardo

2018-01-24

Deep continental subsurface is defined as oligotrophic environments where microorganisms present a very low metabolic rate. To date, due to the energetic cost of production and maintenance of biofilms, their existence has not been considered in poor porous subsurface rocks. We applied fluorescence in situ hybridization techniques and confocal laser scanning microscopy in samples from a continental deep drilling project to analyze the prokaryotic diversity and distribution and the possible existence of biofilms. Our results show the existence of natural microbial biofilms at all checked depths of the Iberian Pyrite Belt (IPB) subsurface and the co-occurrence of bacteria and archaea in this environment. This observation suggests that multi-species biofilms may be a common and widespread lifestyle in subsurface environments.

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

Goltz, M.N.; Kawakami, B.T.; McCarty, P.L.

A full-scale study of in-situ bioremediation is being planned for implementation at Edwards Air Force Base. The bioremediation system that is being proposed has been developed over 8 years of research and testing in the laboratory and at a pilot field site located at Moffett Naval Air Station in Mountain View, California. Studies conducted at the Moffett field site have demonstrated that trichloroethylene (TCE), the contaminant found at Edwards, can be effectively biodegraded cometabolically through the introduction into the subsurface of a primary substrate and an oxygen source to support the growth and energy requirements of a native population ofmore » microorganisms. One of the main questions that needs to be answered, prior to full-scale demonstration of this technology on the Edwards TCE plume, is how best to mix a primary substrate, an oxygen source, and TCE, and subsequently get the mixture to the microorganisms. At Moffett Field, mixing of these three components was accomplished above ground, with the mixture then introduced into the subsurface through an injection well. In the full-scale demonstration, the TCE will, of course, already be in the groundwater. A major objective of the demonstration will be to investigate how a primary substrate and an oxygen source can be efficiently mixed and transported to indigenous microorganisms, in order to promote cometabolic degradation of TCE.« less

Investigation of the near subsurface using acoustic to seismic coupling

USDA-ARS?s Scientific Manuscript database

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...

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

DOE PAGES

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

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

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

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

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

PubMed Central

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

2015-01-01

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

Oxidation behavior and area specific resistance of La, Cu and B alloyed Fe-22Cr ferritic steels for solid oxide fuel cell interconnects

NASA Astrophysics Data System (ADS)

Swaminathan, Srinivasan; Ko, Yoon Seok; Lee, Young-Su; Kim, Dong-Ik

2017-11-01

Two Fe-22 wt% Cr ferritic stainless steels containing varying concentrations of La (0.14 or 0.52 wt%), Cu (0.17 or 1.74 wt%) and B (48 or 109 ppm) are investigated with respect to oxidation behavior and high temperature area specific resistance (ASR) of the surface oxide scales. To determine the oxidation resistance of developed steels, continuous isothermal oxidation is carried out at 800 °C in air, for 2000 h, and their thermally grown oxide scale is characterized using dynamic SIMS, SEM/EDX, XRD and GI-XRD techniques. To assess their electrical performance, the ASR measurement by four-point probe method is conducted at 800 °C in air, for 400 h. In higher La content steel, the La-oxides at the scale/alloy interface promotes the oxygen transport which resulted in sub-surface oxidation of Mn, Cr, Ti and Al. Moreover, the inward growth of oxides contributes to increase of Fe-Cr alloy protrusions within the scale, which reduced the ASR. In contrast, sub-surface oxidation is reduced in high Cu-alloyed steel by segregated Cu at the scale/alloy interface. Thus, addition of Cu is effective to oxidation resistance and also to better electrical performance. However, no obvious impact of B on the scale sequence and/or ASR is observed.

Subsurface structures of buried features in the lunar Procellarum region

NASA Astrophysics Data System (ADS)

Wang, Wenrui; Heki, Kosuke

2017-07-01

The Gravity Recovery and Interior Laboratory (GRAIL) mission unraveled numbers of features showing strong gravity anomalies without prominent topographic signatures in the lunar Procellarum region. These features, located in different geologic units, are considered to have complex subsurface structures reflecting different evolution processes. By using the GRAIL level-1 data, we estimated the free-air and Bouguer gravity anomalies in several selected regions including such intriguing features. With the three-dimensional inversion technique, we recovered subsurface density structures in these regions.

EVALUATION OF GEOPHYSICAL METHODS FOR THE DETECTION OF SUBSURFACE TETRACHLOROETHYLENE IN CONTROLLED SPILL EXPERIMENTS

EPA Science Inventory

The purpose of the work was to determine the capability of various geophysical methods to detect PCE in the subsurface. Measurements were made with ten different geophysical techniques before, during, and after the PCE injection. This approach provided a clear identification of a...

Yield response and economics of shallow subsurface drip irrigation systems

USDA-ARS?s Scientific Manuscript database

Field tests were conducted using shallow subsurface drip irrigation (S3DI) on cotton (Gossypium hirsutum, L.), corn (Zea mays, L.), and peanut (Arachis hypogeae, L.) in rotation to investigate yield potential and economic sustainability of this irrigation system technique over a six year period. Dri...

SUBSURFACE CHARACTERIZATION AND MONITORING TECHNIQUES: A DESK REFERENCE GUIDE - VOLUME I: SOLIDS AND GROUND WATER - APPENDICES A AND B

EPA Science Inventory

Many EPA programs, including those under the Resource Conservation and Recovery Act (RCRA) and the Comprehensive Response, Compensation, and Liability Act (CERCLA), require subsurface characterization and monitoring to detect ground-water contamination and provide data to devel...

Research on subsurface defects of potassium dihydrogen phosphate crystals fabricated by single point diamond turning technique

NASA Astrophysics Data System (ADS)

Tie, Guipeng; Dai, Yifan; Guan, Chaoliang; Chen, Shaoshan; Song, Bing

2013-03-01

Potassium dihydrogen phosphate (KDP) crystals, which are widely used in high-power laser systems, are required to be free of defects on fabricated subsurfaces. The depth of subsurface defects (SSD) of KDP crystals is significantly influenced by the parameters used in the single point diamond turning technique. In this paper, based on the deliquescent magnetorheological finishing technique, the SSD of KDP crystals is observed and the depths under various cutting parameters are detected and discussed. The results indicate that no SSD is generated under small parameters and with the increase of cutting parameters, SSD appears and the depth rises almost linearly. Although the ascending trends of SSD depths caused by cutting depth and feed rate are much alike, the two parameters make different contributions. Taking the same material removal efficiency as a criterion, a large cutting depth generates shallower SSD depth than a large feed rate. Based on the experiment results, an optimized cutting procedure is obtained to generate defect-free surfaces.

Fiber Optic Bragg Grating Sensors for Thermographic Detection of Subsurface Anomalies

NASA Technical Reports Server (NTRS)

Allison, Sidney G.; Winfree, William P.; Wu, Meng-Chou

2009-01-01

Conventional thermography with an infrared imager has been shown to be an extremely viable technique for nondestructively detecting subsurface anomalies such as thickness variations due to corrosion. A recently developed technique using fiber optic sensors to measure temperature holds potential for performing similar inspections without requiring an infrared imager. The structure is heated using a heat source such as a quartz lamp with fiber Bragg grating (FBG) sensors at the surface of the structure to detect temperature. Investigated structures include a stainless steel plate with thickness variations simulated by small platelets attached to the back side using thermal grease. A relationship is shown between the FBG sensor thermal response and variations in material thickness. For comparison, finite element modeling was performed and found to agree closely with the fiber optic thermography results. This technique shows potential for applications where FBG sensors are already bonded to structures for Integrated Vehicle Health Monitoring (IVHM) strain measurements and can serve dual-use by also performing thermographic detection of subsurface anomalies.

Robust optode-based method for measuring in situ oxygen profiles in gravelly streambeds.

PubMed

Vieweg, Michael; Trauth, Nico; Fleckenstein, Jan H; Schmidt, Christian

2013-09-03

One of the key environmental conditions controlling biogeochemical reactions in aquatic sediments like streambeds is the distribution of dissolved oxygen. We present a novel approach for the in situ measurement of vertical oxygen profiles using a planar luminescence-based optical sensor. The instrument consists of a transparent acrylic tube with the oxygen-sensitive layer mounted on the outside. The luminescence is excited and detected by a moveable piston inside the acrylic tube. Since no moving parts are in contact with the streambed, the disturbance of the subsurface flow field is minimized. The precision of the distributed oxygen sensor (DOS) was assessed by a comparison with spot optodes. Although the precision of the DOS, expressed as standard deviation of calculated oxygen air saturation, is lower (0.2-6.2%) compared to spot optodes (<0.1-0.6%), variations of the oxygen content along the profile can be resolved. The uncertainty of the calculated oxygen is assessed with a Monte Carlo uncertainty assessment. The obtained vertical oxygen profiles of 40 cm in length reveal variations of the oxygen content reaching from 90% to 0% air saturation and are characterized by patches of low oxygen rather than a continuous decrease with depth.

Mechanisms and detectability of oxygen depletion in the North Atlantic

NASA Astrophysics Data System (ADS)

Tjiputra, J. F.; Goris, N.; Lauvset, S. K.; Schwinger, J.

2016-12-01

Dissolved oxygen is a key tracer in models used to represent the tight interaction between ocean biogeochemical cycle and circulation. Future ocean warming and stratification are projected, leading to a reduced oxygen concentration. Reduction in export production, in contrast, is projected to increase subsurface concentration by lowering the oxygen consumption during organic matter remineralization. In this exercise, we use a suite of CMIP5 models to study the oxygen evolution under the RCP8.5 scenario focusing on the North Atlantic, a region of rapid and steady circulation change. Most models agree with a large reduction in the deep North Atlantic (north of 40N), whereas an increase is projected in the upper subtropical ocean region. We attribute the former to weakening of the net primary production due to stronger stratification and the latter to less air-sea oxygen flux owing to less ventilation. The models also show that interior oxygen could provide earlier indicator of climate change than surface tracers. Sustained observation of oxygen is therefore crucial to reaffirm the ongoing circulation change due to global warming.

Performance of dentrification beds for removing nitrate from drainage water at cold temperatures

USDA-ARS?s Scientific Manuscript database

Transport of soluble nitrogen and phosphorus to water bodies has been a concern for many years due to human health issues, and is a major contributor to the formation of oxygen deficiency in aquatic ecosystems. Agricultural subsurface drainage is one pathway for transport of excess nutrients to surf...

Elucidating the fate of a mixed toluene, DHM, methanol, and i-propanol plume during in situ bioremediation

NASA Astrophysics Data System (ADS)

Verardo, E.; Atteia, O.; Prommer, H.

2017-06-01

Organic pollutants such as solvents or petroleum products are widespread contaminants in soil and groundwater systems. In-situ bioremediation is a commonly used remediation technology to clean up the subsurface to eliminate the risks of toxic substances to reach potential receptors in surface waters or drinking water wells. This study discusses the development of a subsurface model to analyse the performance of an actively operating field-scale enhanced bioremediation scheme. The study site was affected by a mixed toluene, dihydromyrcenol (DHM), methanol, and i-propanol plume. A high-resolution, time-series of data was used to constrain the model development and calibration. The analysis shows that the observed failure of the treatment system is linked to an inefficient oxygen injection pattern. Moreover, the model simulations also suggest that additional contaminant spillages have occurred in 2012. Those additional spillages and their associated additional oxygen demand resulted in a significant increase in contaminant fluxes that remained untreated. The study emphasises the important role that reactive transport modelling can play in data analyses and for enhancing remediation efficiency.

Low temperature alkaline pH hydrolysis of oxygen-free Titan tholins

NASA Astrophysics Data System (ADS)

Brassé, C.; Buch, A.; Raulin, F.; Coll, P.; Poch, O.; Ramirez, S.

2013-09-01

Titan, the largest moon of Saturn, is known for its dense and nitrogen-rich atmosphere. The organic aerosols which are produced in Titan's atmosphere are objects of astrobiological interest. In this paper we focus on their potential chemical evolution when they reach the surface and interact with putative ammonia-water cryomagma[1]. In this context we have studied the evolution of alkaline pH hydrolysis of Titan tholins (produced by an experimental setup using a plasma DC discharge named PLASMA) at ambient and low temperature. However, we identified oxygenated molecules in non-hydrolyzed tholins meaning that oxygen gets in the PLASMA reactor during the tholins synthesis [2]. Following this preliminary study the synthesis protocol has been improved by isolating the whole device in a specially designed glove box which protect the PLASMA experiment from the laboratory atmosphere. After confirming the non-presence of oxygen in tholins produced with this new experimental setup, the study of oxygen-free tholins' evolution has been carried out. A recent study shows that the subsurface ocean may contain a lower fraction of ammonia (about 5wt% or less [3]), as previously described by other teams [2,4]. Thus new hydrolysis experiments will take this lower value into account. Additionally, a new report [5] provides upper and lower limits for the bulk content of Titan's interior for various gas species. It also shows that most of them are likely stored and dissolved in the subsurface water ocean. But considering the plausible acido-alkaline properties of the ammonia-water ocean, additional species could be dissolved in the ocean and present in the magma. They were also included in our hydrolysis experiments. Taking into account these new data, four different hydrolysis have been applied to oxygen-free tholins. For each type of hydrolysis, we also follow the influence of the hydrolysis temperature on the organic molecules production. The preliminary qualitative and quantitative results of those experiments will be presented at EPSC.

Subsurface damage detection in non-ferrous systems using 3D synchronous magnetic inspection

NASA Astrophysics Data System (ADS)

Gray, David; Berry, David

2018-04-01

Prime Photonics is developing a non-destructive inspection (NDI) technology, 3-D synchronous magnetic imaging system (3-D SMIS), that uses synchronous detection of magnetic signatures resulting from ultrasonic excitation to measure both surface and subsurface flaws in conductive structures. 3-D SMIS is showing promise in a wide range of NDI/NDE uses including characterizing surface-breaking cracks in ferrous and non-ferrous materials, locating and characterizing subsurface cracks within nonferrous conductive materials (Ti 6-4 and carbon fiber composites), and characterization of subsurface residual stresses. The technology offers a non-contact, high resolution inspection technique that does not require austere environments, and can accommodate non-planar specimen geometries.

Sources of oxygen flux in groundwater during induced bank filtration at a site in Berlin, Germany

NASA Astrophysics Data System (ADS)

Kohfahl, Claus; Massmann, Gudrun; Pekdeger, Asaf

2009-05-01

The microbial degradation of pharmaceuticals found in surface water used for artificial recharge is strongly dependent on redox conditions of the subsurface. Furthermore the durability of production wells may decrease considerably with the presence of oxygen and ferrous iron due to the precipitation of trivalent iron oxides and subsequent clogging. Field measurements are presented for oxygen at a bank filtration site in Berlin, Germany, along with simplified calculations of different oxygen pathways into the groundwater. For a two-dimensional vertical cross-section, oxygen input has been calculated for six scenarios related to different water management strategies. Calculations were carried out in order to assess the amount of oxygen input due to (1) the infiltration of oxic lake water, (2) air entrapment as a result of water table oscillations, (3) diffusive oxygen flux from soil air and (4) infiltrating rainwater. The results show that air entrapment and infiltrating lake water during winter constitute by far the most important mechanism of oxygen input. Oxygen input by percolating rainwater and by diffusive delivery of oxygen in the gas phase is negligible. The results exemplify the importance of well management as a determining factor for water oscillations and redox conditions during artificial recharge.

Yield and economics of shallow subsurface drip irrigation (S3DI) and furrow diking

USDA-ARS?s Scientific Manuscript database

A shallow subsurface drip irrigation (S3DI) was installed yearly in conjunction with furrow diking to document yield and economic benefit of these techniques on peanut (Arachis hypogaea L.), cotton (Gossypium hirsutum L.), and corn (Zea mays L.). This research was conducted for three years from 2005...

SUBSURFACE CHARACTERIZATION AND MONITORING TECHNIQUES: A DESK REFERENCE GUIDE - VOLUME II: THE VADOSE ZONE, FIELD SCREENING AND ANALYTICAL METHODS - APPENDICES C AND D

EPA Science Inventory

Many EPA programs, including those under the Resource Conservation and Recovery Act (RCRA) and the Comprehensive Response, Compensation, and Liability Act (CERCLA), require subsurface characterization and monitoring to detect ground-water contamination and provide data to deve...

Estimating sedimentation rates and sources in a partially urbanized catchment using caesium-137

NASA Astrophysics Data System (ADS)

Ormerod, L. M.

1998-06-01

While there has been increased interest in determining sedimentation rates and sources in agricultural and forested catchments in recent years, there have been few studies dealing with urbanized catchments. A study of sedimentation rates and sources within channel and floodplain deposits of a partially urbanized catchment has been undertaken using the 137Cs technique. Results for sedimentation rates showed no particular downstream pattern. This may be partially explained by underestimation of sedimentation rates at some sites by failure to sample the full 137Cs profile, floodplain erosion and deliberate removal of sediment. Evidence of lateral increases in net sedimentation rates with distance from the channel may be explained by increased floodplain erosion at sites closer to the channel and floodplain formation by lateral deposition. Potential sediment sources for the catchment were considered to be forest topsoil, subsurface material and sediments derived from urban areas, which were found to be predominantly subsurface material. Tracing techniques showed an increase in subsurface material for downstream sites, confirming expectations that subsurface material would increase in the downstream direction in response to the direct and indirect effects of urbanization.

Radio Sounding Techniques for the Galilean Icy Moons and their Jovian Magnetospheric Environment

NASA Technical Reports Server (NTRS)

Green, James L.; Markus, Thursten; Fung, Shing F.; Benson, Robert F.; Reinich, Bodo W.; Song, Paul; Gogineni, S. Prasad; Cooper, John F.; Taylor, William W. L.; Garcia, Leonard

2004-01-01

Radio sounding of the Earth's topside ionosphere and magnetosphere is a proven technique from geospace missions such as the International Satellites for Ionospheric Studies (ISIS) and the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE). Application of this technique to Jupiter's icy moons and the surrounding Jovian magnetosphere will provide unique remote sensing observations of the plasma and magnetic field environments and the subsurface conductivities, of Europa, Ganymede, and Callisto. Spatial structures of ionospheric plasma above the surfaces of the moons vary in response to magnetic-field perturbations from (1) magnetospheric plasma flows, (2) ionospheric currents from ionization of sputtered surface material, and (3) induced electric currents in salty subsurface oceans and from the plasma flows and ionospheric currents themselves. Radio sounding from 3 kHz to 10 MHz can provide the global electron densities necessary for the extraction of the oceanic current signals and supplements in-situ plasma and magnetic field measurements. While radio sounding requires high transmitter power for subsurface sounding, little power is needed to probe the electron density and magnetic field intensity near the spacecraft. For subsurface sounding, reflections occur at changes in the dielectric index, e.g., at the interfaces between two different phases of water or between water and soil. Variations in sub-surface conductivity of the icy moons can be investigated by radio sounding in the frequency range from 10 MHz to 50 MHz, allowing the determination of the presence of density and solid-liquid phase boundaries associated with oceans and related structures in overlying ice crusts. The detection of subsurface oceans underneath the icy crusts of the Jovian moons is one of the primary objectives of the Jupiter Icy Moons Orbiter (JIMO) mission. Preliminary modeling results show that return signals are clearly distinguishable be&een an ice crust with a thickness of 7 km on 1) an ocean and 2) a layer of bedrock. Knowledge of the ionospheric contributions to the time delay of the low-frequency subsurface radar is shown to be important in obtaining accurate depth information.

Understanding Subsurface Colloid Behavior: A New Visualization Technique and the Application of Geo-Centrifuge Modeling

NASA Astrophysics Data System (ADS)

Yoon, J. S.; Culligan, P. J.; Germaine, J. T.

2003-12-01

Subsurface colloid behavior has recently drawn attention because colloids are suspected of enhancing contaminant transport in groundwater systems. To better understand the processes by which colloids move through the subsurface, and in particular the vadose zone, a new technique that enables real-time visualization of colloid particles as they move through a porous medium has been developed. This visualization technique involves the use of laser induced fluorescent particles and digital image processing to directly observe particles moving through a porous medium consisting of soda-lime glass beads and water in a transparent experimental box of 10.0cm\\x9D27.9cm\\x9D2.38cm. Colloid particles are simulated using commercially available micron sized particles that fluoresce under argon-ion laser light. The fluorescent light given off from the particles is captured through a camera filter, which lets through only the emitted wavelength of the colloid particles. The intensity of the emitted light is proportional to the colloid particle concentration. The images of colloid movement are captured by a MagnaFire digital camera; a cooled CCD digital camera produced by Optronics. This camera enables real-time capture of images to a computer, thereby allowing the images to be processed immediately. The images taken by the camera are analyzed by the ImagePro software from Media Cybernetics, which contains a range of counting, sizing, measuring, and image enhancement tools for image processing. Laboratory experiments using the new technique have demonstrated the existence of both irreversible and reversible sites for colloid entrapment during uniform saturated flow in a homogeneous porous medium. These tests have also shown a dependence of colloid entrapment on velocity. Models for colloid transport currently available in the literature have proven to be inadequate predictors for the experimental observations, despite the simplicity of the system studied. To further extend the work, the visualization technique has been developed for use on the geo-centrifuge. The advantage that the geo-centrifuge has for investigating subsurface colloid behavior, is the ability to simulate unsaturated transport mechanisms under well simulated field moisture profiles and in shortened periods of time. A series of tests to investigate colloid transport during uniform saturated flow is being used to examine basic scaling laws for colloid transport under enhanced gravity. The paper will describe the new visualization technique, its use in geo-centrifuge testing and observations on scaling relationships for colloid transport during geo-centrifuge experiments. Although the visualization technique has been developed for investigating subsurface colloid behavior, it does have application in other areas of investigation, including the investigation of microbial behavior in the subsurface.

Impact of abrupt deglacial climate change on tropical Atlantic subsurface temperatures

PubMed Central

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

Impact of abrupt deglacial climate change on tropical Atlantic subsurface temperatures.

PubMed

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.

Introduction of a Ground Penetrating Radar System for Subsurface Investigation in Balik Pulau, Penang Island

NASA Astrophysics Data System (ADS)

Teoh, YJ; Bruka, MA; Idris, NM; Ismail, NA; Muztaza, NM

2018-04-01

Ground penetrating radar (GPR) are non-invasive geophysical techniques that enhance studies of the shallow subsurface. The purposes of this work are to study the subsurface composition of Balik Pulau area in Penang Island and to identify shallow subsurface geology features. Data acquisition for GPR is by using 250 MHz antenna to cover 200m survey line at Jalan Tun Sardon, Balik Pulau. GPR survey was divided into ten sections at 20 m each. Results from GPR shows that there is low EM reflection along the first 40 m of the survey line. Intense EM reflections were recorded along the distance 40 m to 100 m. Less noticeable radar reflections recorded along 100 m to 200 m distance of the survey line. As a conclusion, clear signal of radar wave reflection indicates dry region of the subsurface. Meanwhile, low signal of radar wave reflection indicates highly weathered granitic soil or clay of the subsurface.

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

Ahnood, Arman, E-mail: arman.ahnood@unimelb.edu.au; Ganesan, Kumaravelu; Stacey, Alastair

Beyond conventional electrically-driven neuronal stimulation methods, there is a growing interest in optically-driven approaches. In recent years, nitrogen-doped ultrananocrystalline diamond (N-UNCD) has emerged as a strong material candidate for use in electrically-driven stimulation electrodes. This work investigates the electrochemical activity of N-UNCD in response to pulsed illumination, to assess its potential for use as an optically-driven stimulation electrode. Whilst N-UNCD in the as-grown state exhibits a weak photoresponse, the oxygen plasma treated film exhibits two orders of magnitude enhancement in its sub-bandgap open circuit photovoltage response. The enhancement is attributed to the formation of a dense network of oxygen-terminated diamondmore » nanocrystals at the N-UNCD surface. Electrically connected to the N-UNCD bulk via sub-surface graphitic grain boundaries, these diamond nanocrystals introduce a semiconducting barrier between the sub-surface graphitic semimetal and the electrolyte solution, leading to a photovoltage under irradiation with wavelengths of λ = 450 nm and shorter. Within the safe optical exposure limit of 2 mW mm{sup −2}, charge injection capacity of 0.01 mC cm{sup −2} is achieved using a 15 × 15 μm electrode, meeting the requirements for extracellular and intercellular stimulation. The nanoscale nature of processes presented here along with the diamond's biocompatibility and biostability open an avenue for the use of oxygen treated N-UNCD as optically driven stimulating electrodes.« less

Transient photoresponse of nitrogen-doped ultrananocrystalline diamond electrodes in saline solution

NASA Astrophysics Data System (ADS)

Ahnood, Arman; Simonov, Alexandr N.; Laird, Jamie S.; Maturana, Matias I.; Ganesan, Kumaravelu; Stacey, Alastair; Ibbotson, Michael R.; Spiccia, Leone; Prawer, Steven

2016-03-01

Beyond conventional electrically-driven neuronal stimulation methods, there is a growing interest in optically-driven approaches. In recent years, nitrogen-doped ultrananocrystalline diamond (N-UNCD) has emerged as a strong material candidate for use in electrically-driven stimulation electrodes. This work investigates the electrochemical activity of N-UNCD in response to pulsed illumination, to assess its potential for use as an optically-driven stimulation electrode. Whilst N-UNCD in the as-grown state exhibits a weak photoresponse, the oxygen plasma treated film exhibits two orders of magnitude enhancement in its sub-bandgap open circuit photovoltage response. The enhancement is attributed to the formation of a dense network of oxygen-terminated diamond nanocrystals at the N-UNCD surface. Electrically connected to the N-UNCD bulk via sub-surface graphitic grain boundaries, these diamond nanocrystals introduce a semiconducting barrier between the sub-surface graphitic semimetal and the electrolyte solution, leading to a photovoltage under irradiation with wavelengths of λ = 450 nm and shorter. Within the safe optical exposure limit of 2 mW mm-2, charge injection capacity of 0.01 mC cm-2 is achieved using a 15 × 15 μm electrode, meeting the requirements for extracellular and intercellular stimulation. The nanoscale nature of processes presented here along with the diamond's biocompatibility and biostability open an avenue for the use of oxygen treated N-UNCD as optically driven stimulating electrodes.

Near-Field Resonance Microwave Tomography and Holography

NASA Astrophysics Data System (ADS)

Gaikovich, K. P.; Smirnov, A. I.; Yanin, D. V.

2018-02-01

We develop the methods of electromagnetic computer near-field microwave tomography of distributed subsurface inhomogeneities of complex dielectric permittivity and of holography (shape retrieval) of internally homogeneous subsurface objects. The methods are based on the solution of the near-field inverse scattering problem from measurements of the resonance-parameter variations of microwave probes above the medium surface. The capabilities of the proposed diagnostic technique are demonstrated in the numerical simulation for sensors with a cylindrical capacitor as a probe element, the edge capacitance of which is sensitive to subsurface inhomogeneities.

Holographic Subsurface Radar Technique for Nondestructive Testing of Dielectric Structures

NASA Astrophysics Data System (ADS)

Ivashov, S. I.; Bugaev, A. S.; Zhuravlev, A. V.; Razevig, V. V.; Chizh, M. A.; Ivashov, A. I.

2018-02-01

Holographic subsurface radar method is compared with the conventional technology of impulse radars. Basic relationships needed for the reconstruction of complex microwave holograms are presented. Possible applications of the proposed technology are discussed. Diagnostics of polyurethane foam coatings of spacecrafts is used as an example of the efficiency of holographic subsurface radars. Results of reconstruction of complex and amplitude microwave holograms are compared. It is demonstrated that the image quality that results from reconstruction of complex microwave holograms is higher than the image quality obtained with the aid of amplitude holograms.

Can Surface Seeps Elucidate Carbon Cycling in Terrestrial Subsurface Ecosystems in Ophiolite-hosted Serpentinizing Fluids?

NASA Astrophysics Data System (ADS)

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.

Denitrifying Bacteria from the Genus Rhodanobacter Dominate Bacterial Communities in the Highly Contaminated Subsurface of a Nuclear Legacy Waste Site

PubMed Central

Green, Stefan J.; Prakash, Om; Jasrotia, Puja; Overholt, Will A.; Cardenas, Erick; Hubbard, Daniela; Tiedje, James M.; Watson, David B.; Schadt, Christopher W.; Brooks, Scott C.

2012-01-01

The effect of long-term mixed-waste contamination, particularly uranium and nitrate, on the microbial community in the terrestrial subsurface was investigated at the field scale at the Oak Ridge Integrated Field Research Challenge (ORIFRC) site in Oak Ridge, TN. The abundance, community composition, and distribution of groundwater microorganisms were examined across the site during two seasonal sampling events. At representative locations, subsurface sediment was also examined from two boreholes, one sampled from the most heavily contaminated area of the site and another from an area with low contamination. A suite of DNA- and RNA-based molecular tools were employed for community characterization, including quantitative PCR of rRNA and nitrite reductase genes, community composition fingerprinting analysis, and high-throughput pyrotag sequencing of rRNA genes. The results demonstrate that pH is a major driver of the subsurface microbial community structure and that denitrifying bacteria from the genus Rhodanobacter (class Gammaproteobacteria) dominate at low pH. The relative abundance of bacteria from this genus was positively correlated with lower-pH conditions, and these bacteria were abundant and active in the most highly contaminated areas. Other factors, such as the concentration of nitrogen species, oxygen level, and sampling season, did not appear to strongly influence the distribution of Rhodanobacter bacteria. The results indicate that these organisms are acid-tolerant denitrifiers, well suited to the acidic, nitrate-rich subsurface conditions, and pH is confirmed as a dominant driver of bacterial community structure in this contaminated subsurface environment. PMID:22179233

NONDESTRUCTIVE TESTING (NDT) TECHNIQUES TO DETECT CONTAINED SUBSURFACE HAZARDOUS WASTE

EPA Science Inventory

The project involves the detection of buried containers with NDT (remote-sensing) techniques. Seventeen techniques were considered and four were ultimately decided upon. They were: electromagnetic induction (EMI); metal detection (MD); magnetometer (MAG); and ground penetrating r...

The subsurface record for the Anthropocene based on the global analysis of deep wells

NASA Astrophysics Data System (ADS)

Rose, K.

2016-12-01

While challenges persist in the characterization of Earth's subsurface, over two centuries of exploration resulting in more than six million deep wellbores, offer insights into these systems. Characteristics of the subsurface vary and can be analyzed on a variety of spatial scales using geospatial tools and methods. Characterization and prediction of subsurface properties, such as depth, thickness, porosity, permeability, pressure and temperature, are important for models and interpretations of the subsurface. Subsurface studies contribute to insights and understanding of natural system but also enable predictions and assessments of subsurface resources and support environmental and geohazard assessments. As the geo-data science landscape shifts, becoming more open, there are increasing opportunities to fill knowledge gaps, mine large, interrelated datasets, and develop innovative methods to improve our understanding of the subsurface and the impacts of its exploration. In this study, a global dataset of more than 6,000,000 deep subsurface wells has been assembled using ArcGIS and Access, which reflects to a first order, the cumulative representation of over two centuries of drilling. Wellbore data, in general represent the only portal for direct measurement and characterization of deep subsurface properties. As human engineering of the subsurface evolves from a focus on hydrocarbon resource development to include subsurface waste product disposal (e.g. CO2, industrial waste, etc) and production of other deep subsurface resources, such as heat and water resources, there is the increasing need to improve characterization techniques and understand local and global ramifications of anthropogenic interaction with the subsurface. Data and geospatial analyses are reviewed to constrain the extent to which human interactions, not just with Earth's surface systems, atmospheric and geologic, but subsurface systems will result in an enduring signature of human influences on the planet. Specifically, the extent and enduring signature of subsurface interactions with the planet, utilizing the four-dimensional, spatial and temporal, record for known deep wellbores is utilized.

Using GNSS-R techniques to investigate the near sub-surface of Mars with the Deep Space Network

NASA Astrophysics Data System (ADS)

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 the Deep Space Network, a huge potential cost-savings for interplanetary missions.

Theoretical aspects of studies of high coverage oxidation of the Cu(100) surface using low energy positrons

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Maddox, W. B.

2010-10-01

The study of adsorption of oxygen on transition metal surface is important for the understanding of oxidation, heterogeneous catalysis, and metal corrosion. The structures formed on transition metal surfaces vary from simple adlayers of chemisorbed oxygen to oxygen diffusion into the sub-surface region and the formation of oxides. In this work we present the results of an ab-initio investigation of positron surface and bulk states and annihilation probabilities of surface-trapped positrons with relevant core electrons at the oxidized Cu(100) surface under conditions of high oxygen coverage. Calculations are performed for various high coverage missing row structures ranging between 0.50 and 1.50 ML oxygen coverage. Calculations are also performed for the on-surface adsorption of oxygen on the unreconstructed Cu(001) surface for coverages up to one monolayer to use for comparison. The geometry of the surfaces with adsorbed oxygen is fully optimized. Theoretical results are compared with experimental data obtained from studies of oxidation of the Cu(100) surface using positron annihilation induced Auger electron spectroscopy.

Intracellular subsurface imaging using a hybrid shear-force feedback/scanning quantitative phase microscopy technique

NASA Astrophysics Data System (ADS)

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.

Enhanced truncated-correlation photothermal coherence tomography with application to deep subsurface defect imaging and 3-dimensional reconstructions

NASA Astrophysics Data System (ADS)

Tavakolian, Pantea; Sivagurunathan, Koneswaran; Mandelis, Andreas

2017-07-01

Photothermal diffusion-wave imaging is a promising technique for non-destructive evaluation and medical applications. Several diffusion-wave techniques have been developed to produce depth-resolved planar images of solids and to overcome imaging depth and image blurring limitations imposed by the physics of parabolic diffusion waves. Truncated-Correlation Photothermal Coherence Tomography (TC-PCT) is the most successful class of these methodologies to-date providing 3-D subsurface visualization with maximum depth penetration and high axial and lateral resolution. To extend the depth range and axial and lateral resolution, an in-depth analysis of TC-PCT, a novel imaging system with improved instrumentation, and an optimized reconstruction algorithm over the original TC-PCT technique is developed. Thermal waves produced by a laser chirped pulsed heat source in a finite thickness solid and the image reconstruction algorithm are investigated from the theoretical point of view. 3-D visualization of subsurface defects utilizing the new TC-PCT system is reported. The results demonstrate that this method is able to detect subsurface defects at the depth range of ˜4 mm in a steel sample, which exhibits dynamic range improvement by a factor of 2.6 compared to the original TC-PCT. This depth does not represent the upper limit of the enhanced TC-PCT. Lateral resolution in the steel sample was measured to be ˜31 μm.

Analysis of chemical reaction kinetics of depredating organic pollutants from secondary effluent of wastewater treatment plant in constructed wetlands.

PubMed

Wang, Hao; Jiang, Dengling; Yang, Yong; Cao, Guoping

2013-01-01

Four subsurface constructed wetlands were built to treat the secondary effluent of a wastewater treatment plant in Tangshan, China. The chemical pollutant indexes of chemical oxygen demand (COD) were analyzed to evaluate the removal efficiency of organic pollutants from the secondary effluent of the wastewater treatment plant. In all cases, the subsurface constructed wetlands were efficient in treating organic pollutants. Under the same hydraulic loading condition, the horizontal flow wetlands exhibited better efficiency of COD removal than vertical flow wetlands: the removal rates in horizontal flow wetlands could be maintained at 68.4 ± 2.42% to 92.2 ± 1.61%, compared with 63.8 ± 1.19% to 85.0 ± 1.25% in the vertical flow wetlands. Meanwhile, the chemical reaction kinetics of organic pollutants was analyzed, and the results showed that the degradation courses of the four subsurface wetlands all corresponded with the first order reaction kinetics to a large extent.

Silver Nanoparticles with Surface-Bonded Oxygen for Highly Selective CO 2 Reduction

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

Jiang, Kun; Kharel, Priti; Peng, Yande

Here, the surface electronic structures of catalysts need to be carefully engineered in CO 2 reduction reaction (CO 2RR), where the hydrogen evolution side reaction usually takes over under a significant overpotential, and thus dramatically lows the reaction selectivity. Surface oxides can play a critical role in tuning the surface oxidation state of metal catalysts for a proper binding with CO 2RR reaction intermediates, which may significantly improve the catalyst activity and selectivity. Here, we demonstrate the importance of surface-bonded oxygen on silver nanoparticles in altering the reaction pathways and improving the CO 2RR performances. A comparative investigation on air-annealedmore » Ag (Air-Ag) catalyst with or without the post-treatment of H 2 thermal annealing (H 2-Ag) was performed. In Air-Ag, the subsurface chemically bonded O species (O-Ag δ+) was identified by angle resolved X-ray photoelectron spectroscopy and X-ray absorption spectroscopy techniques, and contributed to the improved CO selectivity rather than H 2 in CO 2RR electrolysis. As a result, while the maximal CO Faradaic efficiency of H 2-Ag is at ~ 30 %, the Air-Ag catalyst presented a high CO selectivity of more than 90 % under a current density of ~ 21 mA/cm 2.« less

Silver Nanoparticles with Surface-Bonded Oxygen for Highly Selective CO 2 Reduction

DOE PAGES

Jiang, Kun; Kharel, Priti; Peng, Yande; ...

2017-09-12

Here, the surface electronic structures of catalysts need to be carefully engineered in CO 2 reduction reaction (CO 2RR), where the hydrogen evolution side reaction usually takes over under a significant overpotential, and thus dramatically lows the reaction selectivity. Surface oxides can play a critical role in tuning the surface oxidation state of metal catalysts for a proper binding with CO 2RR reaction intermediates, which may significantly improve the catalyst activity and selectivity. Here, we demonstrate the importance of surface-bonded oxygen on silver nanoparticles in altering the reaction pathways and improving the CO 2RR performances. A comparative investigation on air-annealedmore » Ag (Air-Ag) catalyst with or without the post-treatment of H 2 thermal annealing (H 2-Ag) was performed. In Air-Ag, the subsurface chemically bonded O species (O-Ag δ+) was identified by angle resolved X-ray photoelectron spectroscopy and X-ray absorption spectroscopy techniques, and contributed to the improved CO selectivity rather than H 2 in CO 2RR electrolysis. As a result, while the maximal CO Faradaic efficiency of H 2-Ag is at ~ 30 %, the Air-Ag catalyst presented a high CO selectivity of more than 90 % under a current density of ~ 21 mA/cm 2.« less

Method for Implementing Subsurface Solid Derived Concentration Guideline Levels (DCGL) - 12331

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

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 regulator. This paper describes the concepts and basis used by MACTEC to develop the dose-based subsurface soil DCGL method. The paper will show how MACTEC's method can be used to demonstrate that higher concentrations of residual radioactivity in subsurface soils (as compared with surface soils) can meet the NRC's dose-based regulations. MACTEC's method has been used successfully to obtain the NRC's radiological release at a site with known radiological impacts to subsurface soils exceeding the surface soil DCGL, saving both time and cost. Having considered the current NRC guidance for consideration of residual radioactivity in subsurface soils during decommissioning, MACTEC has developed a technically based approach to the derivation of and demonstration of compliance with subsurface soil DCGLs for radionuclides. In fact, the process uses the already accepted concepts and metrics approved for surface soils as the foundation for deriving scaling factors used to calculate subsurface soil DCGLs that are at least equally protective of the decommissioning annual dose standard. Each of the elements identified for consideration in the current NRC guidance is addressed in this proposed method. Additionally, there is considerable conservatism built into the assumptions and techniques used to arrive at subsurface soil scaling factors and DCGLs. The degree of conservatism embodied in the approach used is such that risk managers and decision makers approving and using subsurface soil DCGLs derived in accordance with this method can be confident that the future exposures will be well below permissible and safe levels. The technical basis for the method can be applied to a broad variety of sites with residual radioactivity in subsurface soils. Given the costly nature of soil surveys, excavation, and disposal of soils as low-level radioactive waste, MACTEC's method for deriving and demonstrating compliance with subsurface soil DCGLs offers the possibility of significant cost savings over the traditional approach of applying surface soil DCGLs to subsurface soils. Furthermore, while yet untested, MACTEC believes that the concepts and methods embodied in this approach could readily be applied to other types of contamination found in subsurface soils. (author)« less

Line-scan spatially offset Raman spectroscopy for inspecting subsurface food safety and quality

USDA-ARS?s Scientific Manuscript database

This paper presented a method for subsurface food inspection using a newly developed line-scan spatially offset Raman spectroscopy (SORS) technique. A 785 nm laser was used as a Raman excitation source. The line-shape SORS data was collected in a wavenumber range of 0–2815 cm-1 using a detection mod...

Orbital radar evidence for lunar subsurface layering in Maria Serenitatis and Crisium

NASA Technical Reports Server (NTRS)

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

Detection of stiff nanoparticles within cellular structures by contact resonance atomic force microscopy subsurface nanomechanical imaging.

PubMed

Reggente, Melania; Passeri, Daniele; Angeloni, Livia; Scaramuzzo, Francesca Anna; Barteri, Mario; De Angelis, Francesca; Persiconi, Irene; De Stefano, Maria Egle; Rossi, Marco

2017-05-04

Detecting stiff nanoparticles buried in soft biological matrices by atomic force microscopy (AFM) based techniques represents a new frontier in the field of scanning probe microscopies, originally developed as surface characterization methods. Here we report the detection of stiff (magnetic) nanoparticles (NPs) internalized in cells by using contact resonance AFM (CR-AFM) employed as a potentially non-destructive subsurface characterization tool. Magnetite (Fe 3 O 4 ) NPs were internalized in microglial cells from cerebral cortices of mouse embryos of 18 days by phagocytosis. Nanomechanical imaging of cells was performed by detecting the contact resonance frequencies (CRFs) of an AFM cantilever held in contact with the sample. Agglomerates of NPs internalized in cells were visualized on the basis of the local increase in the contact stiffness with respect to the surrounding biological matrix. A second AFM-based technique for nanomechanical imaging, i.e., HarmoniX™, as well as magnetic force microscopy and light microscopy were used to confirm the CR-AFM results. Thus, CR-AFM was demonstrated as a promising technique for subsurface imaging of nanomaterials in biological samples.

Visualization of Au Nanoparticles Buried in a Polymer Matrix by Scanning Thermal Noise Microscopy.

PubMed

Yao, Atsushi; Kobayashi, Kei; Nosaka, Shunta; Kimura, Kuniko; Yamada, Hirofumi

2017-02-17

Several researchers have recently demonstrated visualization of subsurface features with a nanometer-scale resolution using various imaging schemes based on atomic force microscopy. Since all these subsurface imaging techniques require excitation of the oscillation of the cantilever and/or sample surface, it has been difficult to identify a key imaging mechanism. Here we demonstrate visualization of Au nanoparticles buried 300 nm into a polymer matrix by measurement of the thermal noise spectrum of a microcantilever with a tip in contact to the polymer surface. We show that the subsurface Au nanoparticles are detected as the variation in the contact stiffness and damping reflecting the viscoelastic properties of the polymer surface. The variation in the contact stiffness well agrees with the effective stiffness of a simple one-dimensional model, which is consistent with the fact that the maximum depth range of the technique is far beyond the extent of the contact stress field.

The Design and Implementation of Instruments for Low-Frequency Electromagnetic Sounding of the Martian Subsurface

NASA Technical Reports Server (NTRS)

Delory, G. T.; Grimm, R. E.

2003-01-01

Low-frequency electromagnetic soundings of the subsurface can identify liquid water at depths ranging from hundreds of meters to approx. 10 km in an environment such as Mars. Among the tools necessary to perform these soundings are low-frequency electric and magnetic field sensors capable of being deployed from a lander or rover such that horizontal and vertical components of the fields can be measured free of structural or electrical interference. Under a NASA Planetary Instrument Definition and Development Program (PIDDP), we are currently engaged in the prototype stages of low frequency sensor implementations that will enable this technique to be performed autonomously within the constraints of a lander platform. Once developed, this technique will represent both a complementary and alternative method to orbital radar sounding investigations, as the latter may not be able to identify subsurface water without significant ambiguities. Low frequency EM methods can play a crucial role as a ground truth measurement, performing deep soundings at sites identified as high priority areas by orbital radars. Alternatively, the penetration depth and conductivity discrimination of low-frequency methods may enable detection of subsurface water in areas that render radar methods ineffective. In either case, the sensitivity and depth of penetration inherent in low frequency EM exploration makes this tool a compelling candidate method to identify subsurface liquid water from a landed platform on Mars or other targets of interest.

A high frequency electromagnetic impedance imaging system

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

Tseng, Hung-Wen; Lee, Ki Ha; Becker, Alex

2003-01-15

Non-invasive, high resolution geophysical mapping of the shallow subsurface is necessary for delineation of buried hazardous wastes, detecting unexploded ordinance, verifying and monitoring of containment or moisture contents, and other environmental applications. Electromagnetic (EM) techniques can be used for this purpose since electrical conductivity and dielectric permittivity are representative of the subsurface media. Measurements in the EM frequency band between 1 and 100 MHz are very important for such applications, because the induction number of many targets is small and the ability to determine the subsurface distribution of both electrical properties is required. Earlier workers were successful in developing systemsmore » for detecting anomalous areas, but quantitative interpretation of the data was difficult. Accurate measurements are necessary, but difficult to achieve for high-resolution imaging of the subsurface. We are developing a broadband non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using an EM impedance approach similar to the MT exploration technique. Electric and magnetic sensors were tested to ensure that stray EM scattering is minimized and the quality of the data collected with the high-frequency impedance (HFI) system is good enough to allow high-resolution, multi-dimensional imaging of hidden targets. Additional efforts are being made to modify and further develop existing sensors and transmitters to improve the imaging capability and data acquisition efficiency.« less

Significant contribution of Archaea to extant biomass in marine subsurface sediments.

PubMed

Lipp, Julius S; Morono, Yuki; Inagaki, Fumio; Hinrichs, Kai-Uwe

2008-08-21

Deep drilling into the marine sea floor has uncovered a vast sedimentary ecosystem of microbial cells. Extrapolation of direct counts of stained microbial cells to the total volume of habitable marine subsurface sediments suggests that between 56 Pg (ref. 1) and 303 Pg (ref. 3) of cellular carbon could be stored in this largely unexplored habitat. From recent studies using various culture-independent techniques, no clear picture has yet emerged as to whether Archaea or Bacteria are more abundant in this extensive ecosystem. Here we show that in subsurface sediments buried deeper than 1 m in a wide range of oceanographic settings at least 87% of intact polar membrane lipids, biomarkers for the presence of live cells, are attributable to archaeal membranes, suggesting that Archaea constitute a major fraction of the biomass. Results obtained from modified quantitative polymerase chain reaction and slot-blot hybridization protocols support the lipid-based evidence and indicate that these techniques have previously underestimated archaeal biomass. The lipid concentrations are proportional to those of total organic carbon. On the basis of this relationship, we derived an independent estimate of amounts of cellular carbon in the global marine subsurface biosphere. Our estimate of 90 Pg of cellular carbon is consistent, within an order of magnitude, with previous estimates, and underscores the importance of marine subsurface habitats for global biomass budgets.

Patterns and drivers of bacterial α- and β-diversity across vertical profiles from surface to subsurface sediments.

PubMed

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.

Time-Lapse Electrical Resistivity Investigations for Imaging the Grouting Injection in Shallow Subsurface Cavities

PubMed Central

Farooq, Muhammad; Kim, Jung Ho; Song, Young Soo; Amjad Sabir, Mohammad; Umar, Muhammad; Tariq, Mohammad; Muhammad, Said

2014-01-01

The highway of Yongweol-ri, Muan-gun, south-western part of the South Korean Peninsula, is underlain by the abandoned of subsurface cavities, which were discovered in 2005. These cavities lie at shallow depths with the range of 5∼15 meters below the ground surface. Numerous subsidence events have repeatedly occurred in the past few years, damaging infrastructure and highway. As a result of continuing subsidence issues, the Korean Institute of Geosciences and Mineral Resources (KIGAM) was requested by local administration to resolve the issue. The KIGAM used geophysical methods to delineate subsurface cavities and improve more refined understanding of the cavities network in the study area. Cement based grouting has been widely employed in the construction industry to reinforce subsurface ground. In this research work, time-lapse electrical resistivity surveys were accomplished to monitor the grouting injection in the subsurface cavities beneath the highway, which have provided a quasi-real-time monitoring for modifying the subsurface cavities related to ground reinforcement, which would be difficult with direct methods. The results obtained from time-lapse electrical resistivity technique have satisfactory imaged the grouting injection experiment in the subsurface cavities beneath the highway. Furthermore, the borehole camera confirmed the presence of grouting material in the subsurface cavities, and hence this procedure increases the mechanical resistance of subsurface cavities below the highway. PMID:24578621

Time-lapse electrical resistivity investigations for imaging the grouting injection in shallow subsurface cavities.

PubMed

Farooq, Muhammad; Park, Samgyu; Kim, Jung Ho; Song, Young Soo; Amjad Sabir, Mohammad; Umar, Muhammad; Tariq, Mohammad; Muhammad, Said

2014-01-01

The highway of Yongweol-ri, Muan-gun, south-western part of the South Korean Peninsula, is underlain by the abandoned of subsurface cavities, which were discovered in 2005. These cavities lie at shallow depths with the range of 5∼15 meters below the ground surface. Numerous subsidence events have repeatedly occurred in the past few years, damaging infrastructure and highway. As a result of continuing subsidence issues, the Korean Institute of Geosciences and Mineral Resources (KIGAM) was requested by local administration to resolve the issue. The KIGAM used geophysical methods to delineate subsurface cavities and improve more refined understanding of the cavities network in the study area. Cement based grouting has been widely employed in the construction industry to reinforce subsurface ground. In this research work, time-lapse electrical resistivity surveys were accomplished to monitor the grouting injection in the subsurface cavities beneath the highway, which have provided a quasi-real-time monitoring for modifying the subsurface cavities related to ground reinforcement, which would be difficult with direct methods. The results obtained from time-lapse electrical resistivity technique have satisfactory imaged the grouting injection experiment in the subsurface cavities beneath the highway. Furthermore, the borehole camera confirmed the presence of grouting material in the subsurface cavities, and hence this procedure increases the mechanical resistance of subsurface cavities below the highway.

Studies of high coverage oxidation of the Cu(100) surface using low energy positrons

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Maddox, W. B.; Weiss, A. H.

2012-02-01

The study of oxidation of single crystal metal surfaces is important in understanding the corrosive and catalytic processes associated with thin film metal oxides. The structures formed on oxidized transition metal surfaces vary from simple adlayers of chemisorbed oxygen to more complex structures which result from the diffusion of oxygen into subsurface regions. In this work we present the results of theoretical studies of positron surface and bulk states and annihilation probabilities of surface-trapped positrons with relevant core electrons at the oxidized Cu(100) surface under conditions of high oxygen coverage. Calculations are performed for various high coverage missing row structures ranging between 0.50 and 1.50 ML oxygen coverage. The results of calculations of positron binding energy, positron work function, and annihilation characteristics of surface trapped positrons with relevant core electrons as function of oxygen coverage are compared with experimental data obtained from studies of oxidation of the Cu(100) surface using positron annihilation induced Auger electron spectroscopy (PAES).

Physics-based subsurface visualization of human tissue.

PubMed

Sharp, Richard; Adams, Jacob; Machiraju, Raghu; Lee, Robert; Crane, Robert

2007-01-01

In this paper, we present a framework for simulating light transport in three-dimensional tissue with inhomogeneous scattering properties. Our approach employs a computational model to simulate light scattering in tissue through the finite element solution of the diffusion equation. Although our model handles both visible and nonvisible wavelengths, we especially focus on the interaction of near infrared (NIR) light with tissue. Since most human tissue is permeable to NIR light, tools to noninvasively image tumors, blood vasculature, and monitor blood oxygenation levels are being constructed. We apply this model to a numerical phantom to visually reproduce the images generated by these real-world tools. Therefore, in addition to enabling inverse design of detector instruments, our computational tools produce physically-accurate visualizations of subsurface structures.

Evidence for iron-sulfate coupling in salt marsh sediments

NASA Astrophysics Data System (ADS)

Mills, Jennifer; Antler, Gilad; Turchyn, Alexandra

2014-05-01

Organic carbon burial in shallow marine sediments represents an important net sink in the global carbon cycle. Microbially mediated oxidation of organic matter in oxic, suboxic, and anoxic sediments however, prevents the ultimate burial of organic carbon and its removal from the surface of the planet. Although the subsurface transformations of organic carbon have been studied extensively, an enigmatic question remains: when organic matter is deposited, what determines whether it will be buried, reoxidized, or undergo methanogenesis? One hypothesis is that the sulfur cycle, due to the abundance of sulfate in many surface environments, dominates the subsurface oxidation or other fate of organic carbon. However, it has also been suggested that iron may in turn play a key role in determining the behavior of the sulfur cycle. To better understand the controls on these processes, we are using stable isotope and geochemical techniques to explore the microbially mediated oxidation of organic carbon in salt marsh sediments in North Norfolk, UK. In these sediments there is a high supply of organic carbon, iron, and sulfate (from diurnal tidal cycles). Thus these environments may provide insight into the nature of interactions between the carbon, iron, and sulfur cycles. A series of sampling missions was undertaken in the autumn and winter of 2013-2014. In subsurface fluid samples we observe very high ferrous iron concentrations (>1mM), indicative of extended regions of iron reduction (to over 30cm depth). Within these zones of iron reduction we would predict no sulfate reduction, and as expected δ34Ssulfate remains unchanged with depth. However, δ18Osulfate exhibits significant enrichments of up to 5 permil. This decoupling in the sulfur and oxygen isotopes of sulfate is suggestive of a sulfate recycling process in which sulfate is reduced to an intermediate sulfur species and subsequently reoxidized to sulfate. Taken together, these data suggest that microbial assemblages in these salt marsh sediments facilitate a cryptic cycling of sulfur, potentially mediated by iron species in the zone of iron reduction.

Subsurface ice and brine sampling using an ultrasonic/sonic gopher for life detection and characterization in the McMurdo Dry Valleys

NASA Technical Reports Server (NTRS)

Bar-Cohen, Y.; Sherrit, S.; Chang, Z.; Wessel, L.; Bao, X.; Doran, P. T.; Fritsen, C. H.; Kenig, F.; McKay, C. P.; Murray, A.;

Partitioning Tracer Test for Detection, Estimation, and Remediation Performance Assessment of Subsurface Nonaqueous Phase Liquids

NASA Astrophysics Data System (ADS)

Jin, Minquan; Delshad, Mojdeh; Dwarakanath, Varadarajan; McKinney, Daene C.; Pope, Gary A.; Sepehrnoori, Kamy; Tilburg, Charles E.; Jackson, Richard E.

1995-05-01

In this paper we present a partitioning interwell tracer test (PITT) technique for the detection, estimation, and remediation performance assessment of the subsurface contaminated by nonaqueous phase liquids (NAPLs). We demonstrate the effectiveness of this technique by examples of experimental and simulation results. The experimental results are from partitioning tracer experiments in columns packed with Ottawa sand. Both the method of moments and inverse modeling techniques for estimating NAPL saturation in the sand packs are demonstrated. In the simulation examples we use UTCHEM, a comprehensive three-dimensional, chemical flood compositional simulator developed at the University of Texas, to simulate a hypothetical two-dimensional aquifer with properties similar to the Borden site contaminated by tetrachloroethylene (PCE), and we show how partitioning interwell tracer tests can be used to estimate the amount of PCE contaminant before remedial action and as the remediation process proceeds. Tracer tests results from different stages of remediation are compared to determine the quantity of PCE removed and the amount remaining. Both the experimental (small-scale) and simulation (large-scale) results demonstrate that PITT can be used as an innovative and effective technique to detect and estimate the amount of residual NAPL and for remediation performance assessment in subsurface formations.

Partitioning tracer test for detection, estimation, and remediation performance assessment of subsurface nonaqueous phase liquids

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

Jin, M.; Delshad, M.; Dwarakanath, V.

1995-05-01

In this paper we present a partitioning interwell tracer test (PITT) technique for the detection, estimation, and remediation performance assessment of the subsurface contaminated by nonaqueous phase liquids (NAPLs). We demonstrate the effectiveness of this technique by examples of experimental and simulation results. The experimental results are from partitioning tracer experiments in columns packed with Ottawa sand. Both the method of moments and inverse modeling techniques for estimating NAPL saturation in the sand packs are demonstrated. In the simulation examples we use UTCHEM, a comprehensive three-dimensional, chemical flood compositional simulator developed at the University of Texas, to simulate a hypotheticalmore » two-dimensional aquifer with properties similar to the Borden site contaminated by tetrachloroethylene (PCE), and we show how partitioning interwell tracer tests can be used to estimate the amount of PCE contaminant before remedial action and as the remediation process proceeds. Tracer test results from different stages of remediation are compared to determine the quantity of PCE removed and the amount remaining. Both the experimental (small-scale) and simulation (large-scale) results demonstrate that PITT can be used as an innovative and effective technique to detect and estimate the amount of residual NAPL and for remediation performance assessment in subsurface formations. 43 refs., 10 figs., 1 tab.« less

Oxygen adsorption on the Al₉Co₂(001) surface: first-principles and STM study.

PubMed

Villaseca, S Alarcón; Loli, L N Serkovic; Ledieu, J; Fournée, V; Gille, P; Dubois, J-M; Gaudry, E

2013-09-04

Atomic oxygen adsorption on a pure aluminum terminated Al9Co2(001) surface is studied by first-principle calculations coupled with STM measurements. Relative adsorption energies of oxygen atoms have been calculated on different surface sites along with the associated STM images. The local electronic structure of the most favourable adsorption site is described. The preferential adsorption site is identified as a 'bridge' type site between the cluster entities exposed at the (001) surface termination. The Al-O bonding between the adsorbate and the substrate presents a covalent character, with s-p hybridization occurring between the states of the adsorbed oxygen atom and the aluminum atoms of the surface. The simulated STM image of the preferential adsorption site is in agreement with experimental observations. This work shows that oxygen adsorption generates important atomic relaxations of the topmost surface layer and that sub-surface cobalt atoms strongly influence the values of the adsorption energies. The calculated Al-O distances are in agreement with those reported in Al2O and Al2O3 oxides and for oxygen adsorption on Al(111).

Energy as a Constraint on Habitability in the Subsurface

NASA Astrophysics Data System (ADS)

Hoehler, T.

2008-12-01

All living things must obtain energy from the environment to grow, to maintain a metabolic steady state, or simply to preserve viability. The availability of energy sources in the environment thus represents a key factor in determining the size, distribution, and activity of biological populations, and ultimately constrains the possibility for life itself. Lacking the abundant energy provided by solar radiation or the products of oxygenic photosynthesis, life in subsurface environments may be limited by energy availability as much as any other factor. The biological requirement for energy is expressed in two dimensions - analogous to the power and voltage requirements of electrical devices - and consideration and quantification of these requirements establishes quantitative boundary conditions on subsurface habitability. The magnitude of these requirements depends significantly on physicochemical environment, as does the provision of biologically-accessible energy from subsurface sources. With this conceptual basis, we are developing an 'energy balance' model that is designed to ultimately predict the habitability of a given environment, with respect to a given metabolism, in quantitative terms (as 'biomass density potential'). The model will develop from conceptual to quantitative as experimental and observational work constrains and quantifies, in natural populations adapted to low energy conditions, the magnitude of the biological energy requirements and the impacts of physicochemical environmental conditions on energy demand and supply.

Metabolic activity of subseafloor microbes in the South Pacific Gyre

NASA Astrophysics Data System (ADS)

Morono, Y.; Ito, M.; Terada, T.; Inagaki, F.

2013-12-01

The South Pacific Gyre (SPG) is characterized as the most oligotrophic open ocean environment. The sediment is rich in oxygen but poor in energy-sources such as reduced organic matter, and hence harbors very low numbers of microbial cells in relatively shallow subseafloor sediment (D'Hondt et al., 2009; Kallmeyer et al., 2012). In such an energy-limited sedimentary habitat, a small size of microbial community persists living functions with extraordinary low oxygen-consumption rate (Røy et al., 2012). During IODP Expedition 329, a series of sediment samples were successfully recovered from 7 drill sites (U1365-1371) from the seafloor to basement in the SPG, providing an unprecedented opportunity to study metabolic activity of the aerobic subseafloor microbial communities. We initiated incubation onboard by adding stable isotope-labeled substrates to the freshly collected sediment sample, such as 13C and/or 15N-labeled bicarbonate, glucose, amino acids, acetate, and ammonium under the (micro-) aerobic condition. One of the technological challenges in this study is to harvest microbial cells from very low-biomass sediment samples for the analysis using nano-scale secondary ion mass spectrometry (NanoSIMS). To address the technical issue, we improved existing cell separation technique for the SPG sediment samples with small inorganic zeolitic grains. By monitoring cell recovery rates through an image-based cell enumeration technique (Morono et al., 2009), we found that cell recovery rates in the SPG sediment samples are generally lower than those in other oceanographic settings (i.e., organic-rich ocean margin sediments). To gain higher cell recovery ratio, we applied multiple density gradient layers, resulting in the cell recovery ratio up to around 80-95% (Morono et al., in press). Then, using the newly developed cell separation technique, we successfully sorted enough number of microbial cells in small spots on the membrane (i.e., 103 to 105 cells per spot). NanoSIMS analysis showed incorporation of the supplemented stable isotope-labeled substrates after 1.5 year-incubation. The substrate incorporation rates of individual microbial cell ranged in average from 1/10 to 1/2 of those values previously observed in an organic-rich ocean margin sediment (Morono et al., 2011). References S. D'Hondt et al., Subseafloor sedimentary life in the South Pacific Gyre. Proc Natl Acad Sci USA 106, 11651 (2009) J. Kallmeyeret al., Global distribution of microbial abundance and biomass in subseafloor sediment. Proc Natl Acad Sci USA 109, 16213 (2012) H. Røy et al., Aerobic microbial respiration in 86-million-year-old deep-sea red clay. Science 336, 922 (2012) Y. Morono et al. Discriminative detection and enumeration of microbial life in marine subsurface sediments. ISME J 3, 503 (2009) Y. Morono et al., An Improved Cell Separation Technique for Marine Subsurface Sediments: Applications for High-throughput Analysis Using Flow Cytometry and Cell Sorting. Environ Microbiol, (2013) Y. Morono et al., Carbon and nitrogen assimilation in deep subseafloor microbial cells. Proc Natl Acad Sci USA 108, 18295 (2011)

Nitrogen removal from wastewater by an aerated subsurface-flow constructed wetland in cold climates.

PubMed

Redmond, Eric D; Just, Craig L; Parkin, Gene F

2014-04-01

The objective of this study was to assess the role of cyclic aeration, vegetation, and temperature on nitrogen removal by subsurface-flow engineered wetlands. Aeration was shown to enhance total nitrogen and ammonia removal and to enhance removal of carbonaceous biochemical oxygen demand, chemical oxygen demand, and phosphorus. Effluent ammonia and total nitrogen concentrations were significantly lower in aerated wetland cells when compared with unaerated cells. There was no significant difference in nitrogen removal between planted and unplanted cells. Effluent total nitrogen concentrations ranged from 9 to 12 mg N/L in the aerated cells and from 23 to 24 mg N/L in unaerated cells. Effluent ammonia concentrations ranged from 3 to 7 mg N/L in aerated wetland cells and from 22 to 23 mg N/L in unaerated cells. For the conditions tested, temperature had only a minimal effect on effluent ammonia or total nitrogen concentrations. The tanks-in-series and the PkC models predicted the general trends in effluent ammonia and total nitrogen concentrations, but did not do well predicting short-term variability. Rate coefficients for aerated systems were 2 to 10 times greater than those for unaerated systems.

Treatment of landfill leachate using an aerated, horizontal subsurface-flow constructed wetland.

PubMed

Nivala, J; Hoos, M B; Cross, C; Wallace, S; Parkin, G

2007-07-15

A pilot-scale subsurface-flow constructed wetland was installed at the Jones County Municipal Landfill, near Anamosa, Iowa, in August 1999 to demonstrate the use of constructed wetlands as a viable low-cost treatment option for leachate generated at small landfills. The system was equipped with a patented wetland aeration process to aid in removal of organic matter and ammonia nitrogen. The high iron content of the leachate caused the aeration system to cease 2 years into operation. Upon the installation of a pretreatment chamber for iron removal and a new aeration system, treatment efficiencies dramatically improved. Seasonal performance with and without aeration is reported for 5-day biochemical oxygen demand (BOD(5)), chemical oxygen demand (COD), ammonia nitrogen (NH(4)-N), and nitrate nitrogen (NO(3)-N). Since winter air temperatures in Iowa can be very cold, a layer of mulch insulation was installed on top of the wetland bed to keep the system from freezing. When the insulation layer was properly maintained (either through sufficient litterfall or replenishing the mulch layer), the wetland sustained air temperatures of as low as -26 degrees C without freezing problems.

Vertical flow constructed wetlands: kinetics of nutrient and organic matter removal.

PubMed

Pérez, M M; Hernández, J M; Bossens, J; Jiménez, T; Rosa, E; Tack, F

2014-01-01

The kinetics of organic matter and nutrient removal in a pilot vertical subsurface wetland with red ferralitic soil as substrate were evaluated. The wetland (20 m(2)) was planted with Cyperus alternifolius. The domestic wastewater that was treated in the wetland had undergone a primary treatment consisting of a septic moat and a buffer tank. From the sixth week of operation, the performance of the wetland stabilized, and a significant reduction in pollutant concentration of the effluent wastewater was obtained. Also a significant increase of dissolved oxygen (5 mg/l) was obtained. The organic matter removal efficiency was greater than 85% and the nutrient removal efficiency was greater than 75% in the vertical subsurface wetland. Nitrogen and biochemical oxygen demand (BOD) removal could be described by a first-order model. The kinetic constants were 3.64 and 3.27 d(-1) for BOD and for total nitrogen, respectively. Data on the removal of phosphorus were adapted to a second-order model. The kinetic constant was 0.96 (mg/l)(-1) d(-1). The results demonstrated the potential of vertical flow constructed wetlands to clean treated domestic wastewater before discharge into the environment.

Effect of water depth on the removal of organic matter in horizontal subsurface flow constructed wetlands.

PubMed

Aguirre, Paula; Ojeda, Esther; García, Joan; Barragán, Jesús; Mujeriego, Rafael

2005-01-01

The objective of this article is to evaluate the effect of water depth on organic matter removal efficiency in horizontal subsurface flow constructed wetlands (SSFs). Experiments were carried out in a pilot plant comprising eight parallel SSF of almost equal surface area (54-56 m2 each) and treating urban wastewater. Each SSF differs from the others in the aspect ratio or the size of the granular medium or the water depth. During a period of two years, the shallow SSFs (0.27 m water depth) removed more chemical oxygen demand (COD) (72-81%), biochemical oxygen demand (BOD)5 (72-85%), ammonia (35-56%), and dissolved reactive phosphorus (DRP) (8-23%) than deep SSFs (0.5 m water depth) (59-64% for COD; 51-57% for BOD5; 18-29% for ammonia; and 0-7% for DRP). Experiments carried out during the summer indicated that sulphate reduction accounted for a clearly higher organic matter removal in the deep SSFs than in the shallow ones. Denitrification seemed to be a significant mechanism for organic matter removal to occur in shallow SSFs. The results suggest that the relative contribution of different metabolic pathways varies with depth.

Oxidation of a Commercial Nickel-Based Superalloy under Static Loading

NASA Astrophysics Data System (ADS)

Foss, B. J.; Hardy, M. C.; Child, D. J.; McPhail, D. S.; Shollock, B. A.

2014-12-01

The current demands of the aviation industry for increased gas-turbine efficiency necessitate higher turbine entry temperatures, requiring that alloys exhibit superior oxidation resistance. The synergistic effects of oxidation and mechanical stresses pose a complex issue. The purpose of the current research was to examine the effects of stress on the oxidation and oxygen transport in a commercial nickel-based superalloy. Fine grain RR1000 in both polished and shot-peened conditions was studied for classic (zero load) and statically loaded conditions using integrated two-stage isotopic tracing combined with focused-ion-beam secondary ion mass spectrometry (FIB-SIMS). Cr2O3 external oxide formed with semicontinuous TiO2 above and below. Preferential grain boundary Al2O3 internal oxide formation, γ'-dissolution, and recrystallization occurred subsurface. Oxidation mechanisms were dominated by anionic/cationic growth in the external oxide with inward oxygen transport, initially through the partially unprotective external oxide, then along internal oxide/alloy interfaces. Loading did not influence the oxidation products formed but did bring about expedited oxidation kinetics and changes to the oxide morphology. The oxygen diffusivity D {O/ * } (×10-13 cm2s-1) ranged from 0.39 for the polished alloy to 3.7 for the shot-peened condition under compressive stress. Arguably, the most significant effects took place in the subsurface regions. Increased oxidation kinetics were attributed to the development of fast cation diffusion paths as the alloy deformed by creep.

Image-based overlay measurement using subsurface ultrasonic resonance force microscopy

NASA Astrophysics Data System (ADS)

Tamer, M. S.; van der Lans, M. J.; Sadeghian, H.

2018-03-01

Image Based Overlay (IBO) measurement is one of the most common techniques used in Integrated Circuit (IC) manufacturing to extract the overlay error values. The overlay error is measured using dedicated overlay targets which are optimized to increase the accuracy and the resolution, but these features are much larger than the IC feature size. IBO measurements are realized on the dedicated targets instead of product features, because the current overlay metrology solutions, mainly based on optics, cannot provide sufficient resolution on product features. However, considering the fact that the overlay error tolerance is approaching 2 nm, the overlay error measurement on product features becomes a need for the industry. For sub-nanometer resolution metrology, Scanning Probe Microscopy (SPM) is widely used, though at the cost of very low throughput. The semiconductor industry is interested in non-destructive imaging of buried structures under one or more layers for the application of overlay and wafer alignment, specifically through optically opaque media. Recently an SPM technique has been developed for imaging subsurface features which can be potentially considered as a solution for overlay metrology. In this paper we present the use of Subsurface Ultrasonic Resonance Force Microscopy (SSURFM) used for IBO measurement. We used SSURFM for imaging the most commonly used overlay targets on a silicon substrate and photoresist. As a proof of concept we have imaged surface and subsurface structures simultaneously. The surface and subsurface features of the overlay targets are fabricated with programmed overlay errors of +/-40 nm, +/-20 nm, and 0 nm. The top layer thickness changes between 30 nm and 80 nm. Using SSURFM the surface and subsurface features were successfully imaged and the overlay errors were extracted, via a rudimentary image processing algorithm. The measurement results are in agreement with the nominal values of the programmed overlay errors.

Use of Large-Scale Multi-Configuration EMI Measurements to Characterize Subsurface Structures of the Vadose Zone.

NASA Astrophysics Data System (ADS)

Huisman, J. A.; Brogi, C.; Pätzold, S.; Weihermueller, L.; von Hebel, C.; Van Der Kruk, J.; Vereecken, H.

2017-12-01

Subsurface structures of the vadose zone can play a key role in crop yield potential, especially during water stress periods. Geophysical techniques like electromagnetic induction EMI can provide information about dominant shallow subsurface features. However, previous studies with EMI have typically not reached beyond the field scale. We used high-resolution large-scale multi-configuration EMI measurements to characterize patterns of soil structural organization (layering and texture) and their impact on crop productivity at the km2 scale. We collected EMI data on an agricultural area of 1 km2 (102 ha) near Selhausen (NRW, Germany). The area consists of 51 agricultural fields cropped in rotation. Therefore, measurements were collected between April and December 2016, preferably within few days after the harvest. EMI data were automatically filtered, temperature corrected, and interpolated onto a common grid of 1 m resolution. Inspecting the ECa maps, we identified three main sub-areas with different subsurface heterogeneity. We also identified small-scale geomorphological structures as well as anthropogenic activities such as soil management and buried drainage networks. To identify areas with similar subsurface structures, we applied image classification techniques. We fused ECa maps obtained with different coil distances in a multiband image and applied supervised and unsupervised classification methodologies. Both showed good results in reconstructing observed patterns in plant productivity and the subsurface structures associated with them. However, the supervised methodology proved more efficient in classifying the whole study area. In a second step, we selected hundred locations within the study area and obtained a soil profile description with type, depth, and thickness of the soil horizons. Using this ground truth data it was possible to assign a typical soil profile to each of the main classes obtained from the classification. The proposed methodology was effective in producing a high resolution subsurface model in a large and complex study area that extends well beyond the field scale.

Localized versus itinerant states created by multiple oxygen vacancies in SrTiO3

NASA Astrophysics Data System (ADS)

Jeschke, Harald O.; Shen, Juan; Valentí, Roser

2015-02-01

Oxygen vacancies in strontium titanate surfaces (SrTiO3) have been linked to the presence of a two-dimensional electron gas with unique behavior. We perform a detailed density functional theory study of the lattice and electronic structure of SrTiO3 slabs with multiple oxygen vacancies, with a main focus on two vacancies near a titanium dioxide terminated SrTiO3 surface. We conclude based on total energies that the two vacancies preferably inhabit the first two layers, i.e. they cluster vertically, while in the direction parallel to the surface, the vacancies show a weak tendency towards equal spacing. Analysis of the nonmagnetic electronic structure indicates that oxygen defects in the surface TiO2 layer lead to population of Ti {{t}2g} states and thus itinerancy of the electrons donated by the oxygen vacancy. In contrast, electrons from subsurface oxygen vacancies populate Ti eg states and remain localized on the two Ti ions neighboring the vacancy. We find that both the formation of a bound oxygen-vacancy state composed of hybridized Ti 3eg and 4p states neighboring the oxygen vacancy as well as the elastic deformation after extracting oxygen contribute to the stabilization of the in-gap state.

Field application of farmstead runoff to vegetated filter strips: surface and subsurface water quality assessment.

PubMed

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 Society of America, and Soil Science Society of America, Inc.

Adaptation of a canopy reflectance model for sub-aqueous vegetation: Definition and sensitivity analysis

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

Plummer, S.E.; Malthus, T.J.; Clark, C.D.

1997-06-01

Seagrass meadows are a key component of shallow coastal environments acting as a food resource, nursery and contributing to water oxygenation. Given the importance of these meadows and their susceptibility to anthropogenic disturbance, it is vital that the extent and growth of seagrass is monitored. Remote sensing techniques offer the potential to determine biophysical characteristics of seagrass. This paper presents observations on the development and testing of an invertible model of seagrass canopy reflectance. The model is an adaptation of a land surface reflectance model to incorporate the effects of attenuation and scattering of incoming radiative flux in water. Sensitivitymore » analysis reveals that the subsurface reflectance is strongly dependent on the water depth, vegetation amount, the parameter which we wish to determine, and turbidity respectively. By contrast the chlorophyll concentration of water and gelbstoff are relatively unimportant. Water depth and turbidity need to be known or accommodated in any inversion as free parameters.« less

Ocean Nitrogen Isotopic Change in the Early Eocene

NASA Astrophysics Data System (ADS)

Kast, E.; Stolper, D. A.; Higgins, J. A.; Ren, H. A.; Wang, X. T.; Sigman, D. M.

2017-12-01

The long term variability of the marine nitrogen (N) cycle is an open question. The Cenozoic provides a well-studied framework for investigating the marine N cycle over long time scales and across large climate transitions. However, only sparse bulk Cenozoic sediment δ15N data exist, the utility of which for reconstructing environmental conditions is unclear. We present a record of foraminifera-bound organic matter δ15N from the Paleocene to late Eocene. At three distant sites, foraminifera-bound δ15N decreases dramatically between 56 Ma and 50 Ma: from 14‰ to 2‰ in the northwest Pacific (ODP site 1209), from 12‰ to 4‰ in the southeast Atlantic (ODP site 1263), and from 9‰ to 4‰ in the northwest Atlantic (IODP site U1409). This foraminifera-bound δ15N change is on par, if not greater, than the largest changes that have been observed in bulk sediment δ15N over the last 600 million years. The shared change among the sites implies a change in mean δ15N of oceanic fixed N, which is thought to be sensitive to the ratio of water column to sedimentary denitrification, with a higher δ15N reflecting a greater proportion of denitrification occurring in the water column. Today, water column denitrification occurs in the shallow subsurface, in regions where these waters are suboxic. Thus, the δ15N decrease may reflect a slowing of water column denitrification, which can be generated by a decline in shallow subsurface suboxia. A key factor in the extent of shallow subsurface suboxia is the amount of "preformed oxygen," the initial concentration of dissolved O2 in the water that flows from the surface into the shallow subsurface: a decline in suboxia would require a rise in preformed oxygen from 56 to 50 Ma. The δ15N decline occurs before the onset of cooling in the Eocene, eliminating global temperature change as the driver of increased preformed oxygen. Instead we favor explanations that involve tectonically driven changes in continental configuration and shallow and mid-depth ocean bathymetry. Indeed, the δ15N decline appears coincident with the initiation of bathymetric effects from the collision of India with Asia. This category of explanation is consistent with the overlap of the δ15N decline with the previously identified increase in marine barite δ34S at 51 Ma.

Detection in subsurface air of radioxenon released from medical isotope production

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

Johnson, Christine; Biegalski, Steven; Haas, Derek

Abstract Under the Comprehensive Nuclear-Test-Ban Treaty, an On-Site Inspection (OSI) may be conducted to clarify whether a nuclear explosion has been carried out in violation of Article I of the Treaty. A major component of an OSI is the measurement of subsurface gases in order to detect radioactive noble gases that are produced in a nuclear explosion, particularly radioxenon and radioargon. In order to better understand potential backgrounds of these gases, a sampling campaign was performed near Canadian Nuclear Laboratories in the Ottawa River Valley, a major source of environmental radioxenon. First of their kind measurements of atmospheric radioxenon imprintedmore » into the shallow subsurface from an atmospheric pressure driven force were made using current OSI techniques to measure both atmospheric and subsurface gas samples which were analyzed for radioxenon. These measurements indicate that under specific sampling conditions, on the order of one percent of the atmospheric radioxenon concentration may be measured via subsurface sampling.« less

Synthetic seismic monitoring using reverse-time migration and Kirchhoff migration for CO2 sequestration in Korea

NASA Astrophysics Data System (ADS)

Kim, W.; Kim, Y.; Min, D.; Oh, J.; Huh, C.; Kang, S.

2012-12-01

During last two decades, CO2 sequestration in the subsurface has been extensively studied and progressed as a direct tool to reduce CO2 emission. Commercial projects such as Sleipner, In Salah and Weyburn that inject more than one million tons of CO2 per year are operated actively as well as test projects such as Ketzin to study the behavior of CO2 and the monitoring techniques. Korea also began the CCS (CO2 capture and storage) project. One of the prospects for CO2 sequestration in Korea is the southwestern continental margin of Ulleung basin. To monitor the behavior of CO2 underground for the evaluation of stability and safety, several geophysical monitoring techniques should be applied. Among various geophysical monitoring techniques, seismic survey is considered as the most effective tool. To verify CO2 migration in the subsurface more effectively, seismic numerical simulation is an essential process. Furthermore, the efficiency of the seismic migration techniques should be investigated for various cases because numerical seismic simulation and migration test help us accurately interpret CO2 migration. In this study, we apply the reverse-time migration and Kirchhoff migration to synthetic seismic monitoring data generated for the simplified model based on the geological structures of Ulleung basin in Korea. Synthetic seismic monitoring data are generated for various cases of CO2 migration in the subsurface. From the seismic migration images, we can investigate CO2 diffusion patterns indirectly. From seismic monitoring simulation, it is noted that while the reverse-time migration generates clear subsurface images when subsurface structures are steeply dipping, Kirchhoff migration has an advantage in imaging horizontal-layered structures such as depositional sediments appearing in the continental shelf. The reverse-time migration and Kirchhoff migration present reliable subsurface images for the potential site characterized by stratigraphical traps. In case of vertical CO2 migration at injection point, the reverse time migration yields better images than Kirchhoff migration does. On the other hand, Kirchhoff migration images horizontal CO2 migration clearer than the reverse time migration does. From these results, we can conclude that the reverse-time migration and Kirchhoff migration can complement with each other to describe the behavior of CO2 in the subsurface. Acknowledgement This work was financially supported by the Brain Korea 21 project of Energy Systems Engineering, the "Development of Technology for CO2 Marine Geological Storage" program funded by the Ministry of Land, Transport and Maritime Affairs (MLTM) of Korea and the Korea CCS R&D Center (KCRC) grant funded by the Korea government (Ministry of Education, Science and Technology) (No. 2012-0008926).

Fiber Optic Thermal Health Monitoring of Aerospace Structures and Materials

NASA Technical Reports Server (NTRS)

Wu, Meng-Chou; Winfree, William P.; Allison, Sidney G.

2009-01-01

A new technique is presented for thermographic detection of flaws in materials and structures by performing temperature measurements with fiber Bragg gratings. Individual optical fibers with multiple Bragg gratings employed as surface temperature sensors were bonded to the surfaces of structures with subsurface defects or thickness variations. Both during and following the application of a thermal heat flux to the surface, the individual Bragg grating sensors measured the temporal and spatial temperature variations. The investigated structures included a 10-ply composite specimen with subsurface delaminations of various sizes and depths. The data obtained from grating sensors were further analyzed with thermal modeling to reveal particular characteristics of the interested areas. These results were found to be consistent with those from conventional thermography techniques. Limitations of the technique were investigated using both experimental and numerical simulation techniques. Methods for performing in-situ structural health monitoring are discussed.

Fiber Optic Thermal Health Monitoring of Composites

NASA Technical Reports Server (NTRS)

Wu, Meng-Chou; Winfree, William P.; Moore, Jason P.

2010-01-01

A recently developed technique is presented for thermographic detection of flaws in composite materials by performing temperature measurements with fiber optic Bragg gratings. Individual optical fibers with multiple Bragg gratings employed as surface temperature sensors were bonded to the surfaces of composites with subsurface defects. The investigated structures included a 10-ply composite specimen with subsurface delaminations of various sizes and depths. Both during and following the application of a thermal heat flux to the surface, the individual Bragg grating sensors measured the temporal and spatial temperature variations. The data obtained from grating sensors were analyzed with thermal modeling techniques of conventional thermography to reveal particular characteristics of the interested areas. Results were compared with the calculations using numerical simulation techniques. Methods and limitations for performing in-situ structural health monitoring are discussed.

Spatial and temporal variation of residence time and storage volume of subsurface water evaluated by multi-tracers approach in mountainous headwater catchments

NASA Astrophysics Data System (ADS)

Tsujimura, Maki; Yano, Shinjiro; Abe, Yutaka; Matsumoto, Takehiro; Yoshizawa, Ayumi; Watanabe, Ysuhito; Ikeda, Koichi

2015-04-01

Headwater catchments in mountainous region are the most important recharge area for surface and subsurface waters, additionally time and stock information of the water is principal to understand hydrological processes in the catchments. However, there have been few researches to evaluate variation of residence time and storage volume of subsurface water in time and space at the mountainous headwaters especially with steep slope. We performed an investigation on age dating and estimation of storage volume using simple water budget model in subsurface water with tracing of hydrological flow processes in mountainous catchments underlain by granite, Paleozoic and Tertiary, Yamanashi and Tsukuba, central Japan. We conducted hydrometric measurements and sampling of spring, stream and ground waters in high-flow and low-flow seasons from 2008 through 2012 in the catchments, and CFCs, stable isotopic ratios of oxygen-18 and deuterium, inorganic solute constituent concentrations were determined on all water samples. Residence time of subsurface water ranged from 11 to 60 years in the granite catchments, from 17 to 32 years in the Paleozoic catchments, from 13 to 26 years in the Tertiary catchments, and showed a younger age during the high-flow season, whereas it showed an older age in the low-flow season. Storage volume of subsurface water was estimated to be ranging from 10 ^ 4 to 10 ^ 6 m3 in the granite catchments, from 10 ^ 5 to 10 ^ 7 m3 in the Paleozoic catchments, from 10 ^ 4 to 10 ^ 6 m3 in the Tertiary catchments. In addition, seasonal change of storage volume in the granite catchments was the highest as compared with those of the Paleozoic and the Tertiary catchments. The results suggest that dynamic change of hydrological process seems to cause a larger variation of the residence time and storage volume of subsurface water in time and space in the granite catchments, whereas higher groundwater recharge rate due to frequent fissures or cracks seems to cause larger storage volume of the subsurface water in the Paleozoic catchments though the variation is not so considerable. Also, numerical simulation results support these findings.

3D subsurface geological modeling using GIS, remote sensing, and boreholes data

NASA Astrophysics Data System (ADS)

Kavoura, Katerina; Konstantopoulou, Maria; Kyriou, Aggeliki; Nikolakopoulos, Konstantinos G.; Sabatakakis, Nikolaos; Depountis, Nikolaos

2016-08-01

The current paper presents the combined use of geological-geotechnical insitu data, remote sensing data and GIS techniques for the evaluation of a subsurface geological model. High accuracy Digital Surface Model (DSM), airphotos mosaic and satellite data, with a spatial resolution of 0.5m were used for an othophoto base map compilation of the study area. Geological - geotechnical data obtained from exploratory boreholes and the 1:5000 engineering geological maps were digitized and implemented in a GIS platform for a three - dimensional subsurface model evaluation. The study is located at the North part of Peloponnese along the new national road.

Laser-assisted focused He + ion beam induced etching with and without XeF 2 gas assist

DOE PAGES

Stanford, Michael G.; Mahady, Kyle; Lewis, Brett B.; ...

2016-10-04

Focused helium ion (He +) milling has been demonstrated as a high-resolution nanopatterning technique; however, it can be limited by its low sputter yield as well as the introduction of undesired subsurface damage. Here, we introduce pulsed laser- and gas-assisted processes to enhance the material removal rate and patterning fidelity. A pulsed laser-assisted He+ milling process is shown to enable high-resolution milling of titanium while reducing subsurface damage in situ. Gas-assisted focused ion beam induced etching (FIBIE) of Ti is also demonstrated in which the XeF 2 precursor provides a chemical assist for enhanced material removal rate. In conclusion, amore » pulsed laser-assisted and gas-assisted FIBIE process is shown to increase the etch yield by ~9× relative to the pure He+ sputtering process. These He + induced nanopatterning techniques improve material removal rate, in comparison to standard He + sputtering, while simultaneously decreasing subsurface damage, thus extending the applicability of the He + probe as a nanopattering tool.« less

Visualization of Au Nanoparticles Buried in a Polymer Matrix by Scanning Thermal Noise Microscopy

PubMed Central

Yao, Atsushi; Kobayashi, Kei; Nosaka, Shunta; Kimura, Kuniko; Yamada, Hirofumi

2017-01-01

Several researchers have recently demonstrated visualization of subsurface features with a nanometer-scale resolution using various imaging schemes based on atomic force microscopy. Since all these subsurface imaging techniques require excitation of the oscillation of the cantilever and/or sample surface, it has been difficult to identify a key imaging mechanism. Here we demonstrate visualization of Au nanoparticles buried 300 nm into a polymer matrix by measurement of the thermal noise spectrum of a microcantilever with a tip in contact to the polymer surface. We show that the subsurface Au nanoparticles are detected as the variation in the contact stiffness and damping reflecting the viscoelastic properties of the polymer surface. The variation in the contact stiffness well agrees with the effective stiffness of a simple one-dimensional model, which is consistent with the fact that the maximum depth range of the technique is far beyond the extent of the contact stress field. PMID:28210001

Laser-assisted focused He + ion beam induced etching with and without XeF 2 gas assist

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

Stanford, Michael G.; Mahady, Kyle; Lewis, Brett B.

Focused helium ion (He +) milling has been demonstrated as a high-resolution nanopatterning technique; however, it can be limited by its low sputter yield as well as the introduction of undesired subsurface damage. Here, we introduce pulsed laser- and gas-assisted processes to enhance the material removal rate and patterning fidelity. A pulsed laser-assisted He+ milling process is shown to enable high-resolution milling of titanium while reducing subsurface damage in situ. Gas-assisted focused ion beam induced etching (FIBIE) of Ti is also demonstrated in which the XeF 2 precursor provides a chemical assist for enhanced material removal rate. In conclusion, amore » pulsed laser-assisted and gas-assisted FIBIE process is shown to increase the etch yield by ~9× relative to the pure He+ sputtering process. These He + induced nanopatterning techniques improve material removal rate, in comparison to standard He + sputtering, while simultaneously decreasing subsurface damage, thus extending the applicability of the He + probe as a nanopattering tool.« less

Assessment of groundwater potentiality using geophysical techniques in Wadi Allaqi basin, Eastern Desert, Egypt - Case study

NASA Astrophysics Data System (ADS)

Helaly, Ahmad Sobhy

2017-12-01

Electrical resistivity surveying has been carried out for the determination of the thickness and resistivity of layered media in Wadi Allaqi, Eastern Desert, Egypt. That is widely used geophysical tool for the purpose of assessing the groundwater potential and siting the best locations for boreholes in the unconfined Nubian Sandstone aquifers within the study area. This has been done using thirteen 1D Vertical Electrical Sounding (VES) surveys. 1D-VES surveys provide only layered model structures for the subsurface and do not provide comprehensive information for interpreting the structure and extent of subsurface hydro-geological features. The integration of two-dimensional (2D) geophysical techniques for groundwater prospecting has been done to provide a more detailed identification for the subsurface hydro-geological features from which potential sites for successful borehole locations are recognized. In addition, five magnetic profiles were measured for basement depth determination, expected geological structures and thickness of sedimentary succession that could include some basins suitable for groundwater accumulation as groundwater aquifers.

An Overview on Measurement-While-Drilling Technique and its Scope in Excavation Industry

NASA Astrophysics Data System (ADS)

Rai, P.; Schunesson, H.; Lindqvist, P.-A.; Kumar, U.

2015-04-01

Measurement-while-drilling (MWD) aims at collecting accurate, speedy and high resolution information from the production blast hole drills with a target of characterization of highly variable rock masses encountered in sub-surface excavations. The essence of the technique rests on combining the physical drill variables in a manner to yield a fairly accurate description of the sub-surface rock mass much ahead of following downstream operations. In this light, the current paper presents an overview of the MWD by explaining the technique and its set-up, the existing drill-rock mass relationships and numerous on-going researches highlighting the real-time applications. Although the paper acknowledges the importance of concepts of specific energy, rock quality index and a couple of other indices and techniques for rock mass characterization, it must be distinctly borne in mind that the technique of MWD is highly site-specific, which entails derivation of site-specific calibration with utmost care.

Dual-Use Applications of Infrared Sensitive Materials

DTIC Science & Technology

1993-06-01

only limit to MCT-based detectors’ market potential is in price. Specialty systems for subsurface imaging (such as buried storage tanks, toxic wastes...and assessment of automotive paint damaged by rust or stone impacts. Since automotive paint is a multi-layered coating, it lends itself to subsurface ... imaging , as well as aerospace aluminum and epoxy composites. Another family of non-destructive evaluation techniques which could use infrared detectors

Implications of Polishing Techniques in Quantitative X-Ray Microanalysis

PubMed Central

Rémond, Guy; Nockolds, Clive; Phillips, Matthew; Roques-Carmes, Claude

2002-01-01

Specimen preparation using abrasives results in surface and subsurface mechanical (stresses, strains), geometrical (roughness), chemical (contaminants, reaction products) and physical modifications (structure, texture, lattice defects). The mechanisms involved in polishing with abrasives are presented to illustrate the effects of surface topography, surface and subsurface composition and induced lattice defects on the accuracy of quantitative x-ray microanalysis of mineral materials with the electron probe microanalyzer (EPMA). PMID:27446758

Microbial degradation of crude oil and some model hydrocarbons

USGS Publications Warehouse

Chang, Fu-Hsian; Noben, N.N.; Brand, Danny; Hult, Marc F.

1988-01-01

Research on microbial degradation of crude oil in the shallow subsurface at a spill site near Bemidji, Minn. (fig. C-l), began in 1983 (Hull, 1984; Chang and Ehrlich, 1984). The rate and extent of crude oil and model hydrocarbon biodegradation by the indigenous microbial community was measured in the laboratory at several concentrations of inorganic nutrients, conditions of oxygen availability, incubation temperatures, and incubation time.

Subsurface defects of fused silica optics and laser induced damage at 351 nm.

PubMed

Hongjie, Liu; Jin, Huang; Fengrui, Wang; Xinda, Zhou; Xin, Ye; Xiaoyan, Zhou; Laixi, Sun; Xiaodong, Jiang; Zhan, Sui; Wanguo, Zheng

2013-05-20

Many kinds of subsurface defects are always present together in the subsurface of fused silica optics. It is imperfect that only one kind of defects is isolated to investigate its impact on laser damage. Therefore it is necessary to investigate the impact of subsurface defects on laser induced damage of fused silica optics with a comprehensive vision. In this work, we choose the fused silica samples manufactured by different vendors to characterize subsurface defects and measure laser induced damage. Contamination defects, subsurface damage (SSD), optical-thermal absorption and hardness of fused silica surface are characterized with time-of-flight secondary ion mass spectrometry (TOF-SIMS), fluorescence microscopy, photo-thermal common-path interferometer and fully automatic micro-hardness tester respectively. Laser induced damage threshold and damage density are measured by 351 nm nanosecond pulse laser. The correlations existing between defects and laser induced damage are analyzed. The results show that Cerium element and SSD both have a good correlation with laser-induced damage thresholds and damage density. Research results evaluate process technology of fused silica optics in China at present. Furthermore, the results can provide technique support for improving laser induced damage performance of fused silica.

Contributions of oxygen vacancies and titanium interstitials to band-gap states of reduced titania

NASA Astrophysics Data System (ADS)

Li, Jingfeng; Lazzari, Rémi; Chenot, Stéphane; Jupille, Jacques

2018-01-01

The spectroscopic fingerprints of the point defects of titanium dioxide remain highly controversial. Seemingly indisputable experiments lead to conflicting conclusions in which oxygen vacancies and titanium interstitials are alternately referred to as the primary origin of the Ti 3 d band-gap states. We report on experiments performed by electron energy loss spectroscopy whose key is the direct annealing of only the very surface of rutile TiO2(110 ) crystals and the simultaneous measurement of its temperature via the Bose-Einstein loss/gain ratio. By surface preparations involving reactions with oxygen and water vapor, in particular, under electron irradiation, vacancy- and interstitial-related band-gap states are singled out. Off-specular measurements reveal that both types of defects contribute to a unique charge distribution that peaks in subsurface layers with a common dispersive behavior.

Roles of Mo Surface Dopants in Enhancing the ORR Performance of Octahedral PtNi Nanoparticles

DOE PAGES

Jia, Qingying; Zhao, Zipeng; Cao, Liang; ...

2017-12-22

Doping with a transition metal was recently shown to greatly boost the activity and durability of PtNi/C octahedral nanoparticles (NPs) for the oxygen reduction reaction (ORR), but its specific roles remain unclear. By combining electrochemistry, ex situ and in situ spectroscopic techniques, density functional theory calculations, and a newly developed kinetic Monte Carlo model, we showed that Mo atoms are preferentially located on the vertex and edge sites of Mo–PtNi/C in the form of oxides, which are stable within the wide potential window of the electrochemical cycle. These surface Mo oxides stabilize adjacent Pt sites, hereby stabilizing the octahedral shapemore » enriched with (111) facets, and lead to increased concentration of Ni in subsurface layers where they are protected against acid dissolution. Consequently, the favorable Pt 3Ni(111) structure for the ORR is stabilized on the surface of PtNi/C NPs in acid against voltage cycling. Significantly, the unusual potential-dependent oxygen coverage trend on Mo-doped PtNi/C NPs as revealed by the surface-sensitive Δμ analysis suggests that the Mo dopants may also improve the ORR kinetics by modifying the coordination environments of Pt atoms on the surface. Lastly, our studies point out a possible way to stabilize the favorable shape and composition established on conceptual catalytic models in practical nanoscale catalysts.« less

Roles of Mo Surface Dopants in Enhancing the ORR Performance of Octahedral PtNi Nanoparticles

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

Jia, Qingying; Zhao, Zipeng; Cao, Liang

Doping with a transition metal was recently shown to greatly boost the activity and durability of PtNi/C octahedral nanoparticles (NPs) for the oxygen reduction reaction (ORR), but its specific roles remain unclear. By combining electrochemistry, ex situ and in situ spectroscopic techniques, density functional theory calculations, and a newly developed kinetic Monte Carlo model, we showed that Mo atoms are preferentially located on the vertex and edge sites of Mo–PtNi/C in the form of oxides, which are stable within the wide potential window of the electrochemical cycle. These surface Mo oxides stabilize adjacent Pt sites, hereby stabilizing the octahedral shapemore » enriched with (111) facets, and lead to increased concentration of Ni in subsurface layers where they are protected against acid dissolution. Consequently, the favorable Pt 3Ni(111) structure for the ORR is stabilized on the surface of PtNi/C NPs in acid against voltage cycling. Significantly, the unusual potential-dependent oxygen coverage trend on Mo-doped PtNi/C NPs as revealed by the surface-sensitive Δμ analysis suggests that the Mo dopants may also improve the ORR kinetics by modifying the coordination environments of Pt atoms on the surface. Lastly, our studies point out a possible way to stabilize the favorable shape and composition established on conceptual catalytic models in practical nanoscale catalysts.« less

Baseline hydraulic performance of the Heathrow constructed wetlands subsurface flow system.

PubMed

Richter, K M; Margetts, J R; Saul, A J; Guymer, I; Worrall, P

2003-01-01

A constructed wetland treatment system has been commissioned by BAA (formerly the British Airports Authority) in order to attenuate airfield runoff contaminated with de-icant and other potentially polluting materials from Heathrow Airport. Airfield runoff containing de-icants has the potential to impose significant oxygen demands on water bodies. The site consists of a number of integrated treatment systems, including a 1 ha rafted reed bed canal system and a 2 ha sub-surface flow gravel reed bed. This research project is concerned with the performance of the subsurface flow reed beds, though attention will be paid in this paper to the operation of the whole system. Prior to the planting of the subsurface flow reed beds, flow-tracing experiments were carried out on the three different types of subsurface flow beds, so that the baseline performance of the system could be quantified. In association, data regarding the soil organic matter content was also collected prior to the planting of the beds. As expected, soil organic matter content is observed to be negligible within the bed, though a small amount of build up was observed in localised areas on the surface of the beds. This was attributed to the growth of algae in depressions where standing water persisted during the construction phase. Few studies exist which provide detailed measurements into the cause and effect of variations in hydraulic conductivity within an operational reed bed system. The data presented here form the baseline results for an ongoing study into the investigation of the change in hydraulic conductivity of an operational reed bed system.

Cultivation Of Deep Subsurface Microbial Communities

NASA Astrophysics Data System (ADS)

Obrzut, Natalia; Casar, Caitlin; Osburn, Magdalena R.

2018-01-01

The potential habitability of surface environments on other planets in our solar system is limited by exposure to extreme radiation and desiccation. In contrast, subsurface environments may offer protection from these stressors and are potential reservoirs for liquid water and energy that support microbial life (Michalski et al., 2013) and are thus of interest to the astrobiology community. The samples used in this project were extracted from the Deep Mine Microbial Observatory (DeMMO) in the former Homestake Mine at depths of 800 to 2000 feet underground (Osburn et al., 2014). Phylogenetic data from these sites indicates the lack of cultured representatives within the community. We used geochemical data to guide media design to cultivate and isolate organisms from the DeMMO communities. Media used for cultivation varied from heterotrophic with oxygen, nitrate or sulfate to autotrophic media with ammonia or ferrous iron. Environmental fluid was used as inoculum in batch cultivation and strains were isolated via serial transfers or dilution to extinction. These methods resulted in isolating aerobic heterotrophs, nitrate reducers, sulfate reducers, ammonia oxidizers, and ferric iron reducers. DNA sequencing of these strains is underway to confirm which species they belong to. This project is part of the NASA Astrobiology Institute Life Underground initiative to detect and characterize subsurface microbial life; by characterizing the intraterrestrials, the life living deep within Earth’s crust, we aim to understand the controls on how and where life survives in subsurface settings. Cultivation of terrestrial deep subsurface microbes will provide insight into the survival mechanisms of intraterrestrials guiding the search for these life forms on other planets.

Whole-stream metabolism of a perennial spring-fed aufeis field in Alaska, with coincident surface and subsurface flow

NASA Astrophysics Data System (ADS)

Hendrickson, P. J.; Gooseff, M. N.; Huryn, A. D.

2017-12-01

Aufeis (icings or naleds) are seasonal arctic and sub-arctic features that accumulate through repeated overflow and freeze events of river or spring discharge. Aufeis fields, defined as the substrate on which aufeis form and the overlaying ice, have been studied to mitigate impacts on engineering structures; however, ecological characteristics and functions of aufeis fields are poorly understood. The perennial springs that supply warm water to aufeis fields create unique fluvial habitats, and are thought to act as winter and summer oases for biota. To investigate ecosystem function, we measured whole-stream metabolism at the Kuparuk River Aufeis (North Slope, AK), a large ( 5 km2) field composed of cobble substrate and predominately subsurface flow dynamics. The single-station open channel diel oxygen method was utilized at several dissolved oxygen (DO) stations located within and downstream of the aufeis field. DO loggers were installed in August 2016, and data downloaded summer 2017. Daily ecosystem respiration (ER), gross primary production (GPP) and reaeration rates were modeled using BASE, a package freely available in the open-source software R. Preliminary results support net heterotrophy during a two-week period of DO measurements in the fall season when minimum ice extent is observed. GPP, ER, and net metabolism are greater at the upstream reach near the spring source (P/R = 0.53), and decrease as flow moves downstream. As flow exits the aufeis field, surface and subsurface flow are incorporated into the metabolism model, and indicate the stream system becomes dependent on autochthonous production (P/R = 0.91). Current work is directed towards spring and summer discharge and metabolic parameter estimation, which is associated with maximum ice extent and rapid melting of the aufeis feature.

Temperature and Redox Effect on Mineral Colonization in Juan de Fuca Ridge Flank Subsurface Crustal Fluids

PubMed Central

Baquiran, Jean-Paul M.; Ramírez, Gustavo A.; Haddad, Amanda G.; Toner, Brandy M.; Hulme, Samuel; Wheat, Charles G.; Edwards, Katrina J.; Orcutt, Beth N.

2016-01-01

To examine microbe-mineral interactions in subsurface oceanic crust, we evaluated microbial colonization on crustal minerals that were incubated in borehole fluids for 1 year at the seafloor wellhead of a crustal borehole observatory (IODP Hole U1301A, Juan de Fuca Ridge flank) as compared to an experiment that was not exposed to subsurface crustal fluids (at nearby IODP Hole U1301B). In comparison to previous studies at these same sites, this approach allowed assessment of the effects of temperature, fluid chemistry, and/or mineralogy on colonization patterns of different mineral substrates, and an opportunity to verify the approach of deploying colonization experiments at an observatory wellhead at the seafloor instead of within the borehole. The Hole U1301B deployment did not have biofilm growth, based on microscopy and DNA extraction, thereby confirming the integrity of the colonization design against bottom seawater intrusion. In contrast, the Hole U1301A deployment supported biofilms dominated by Epsilonproteobacteria (43.5% of 370 16S rRNA gene clone sequences) and Gammaproteobacteria (29.3%). Sequence analysis revealed overlap in microbial communities between different minerals incubated at the Hole U1301A wellhead, indicating that mineralogy did not separate biofilm structure within the 1-year colonization experiment. Differences in the Hole U1301A wellhead biofilm community composition relative to previous studies from within the borehole using similar mineral substrates suggest that temperature and the diffusion of dissolved oxygen through plastic components influenced the mineral colonization experiments positioned at the wellhead. This highlights the capacity of low abundance crustal fluid taxa to rapidly establish communities on diverse mineral substrates under changing environmental conditions such as from temperature and oxygen. PMID:27064928

The Prediction-Focused Approach: An opportunity for hydrogeophysical data integration and interpretation

NASA Astrophysics Data System (ADS)

Hermans, Thomas; Nguyen, Frédéric; Klepikova, Maria; Dassargues, Alain; Caers, Jef

2017-04-01

Hydrogeophysics is an interdisciplinary field of sciences aiming at a better understanding of subsurface hydrological processes. If geophysical surveys have been successfully used to qualitatively characterize the subsurface, two important challenges remain for a better quantification of hydrological processes: (1) the inversion of geophysical data and (2) their integration in hydrological subsurface models. The classical inversion approach using regularization suffers from spatially and temporally varying resolution and yields geologically unrealistic solutions without uncertainty quantification, making their utilization for hydrogeological calibration less consistent. More advanced techniques such as coupled inversion allow for a direct use of geophysical data for conditioning groundwater and solute transport model calibration. However, the technique is difficult to apply in complex cases and remains computationally demanding to estimate uncertainty. In a recent study, we investigate a prediction-focused approach (PFA) to directly estimate subsurface physical properties from geophysical data, circumventing the need for classic inversions. In PFA, we seek a direct relationship between the data and the subsurface variables we want to predict (the forecast). This relationship is obtained through a prior set of subsurface models for which both data and forecast are computed. A direct relationship can often be derived through dimension reduction techniques. PFA offers a framework for both hydrogeophysical "inversion" and hydrogeophysical data integration. For hydrogeophysical "inversion", the considered forecast variable is the subsurface variable, such as the salinity. An ensemble of possible solutions is generated, allowing uncertainty quantification. For hydrogeophysical data integration, the forecast variable becomes the prediction we want to make with our subsurface models, such as the concentration of contaminant in a drinking water production well. Geophysical and hydrological data are combined to derive a direct relationship between data and forecast. We illustrate the process for the design of an aquifer thermal energy storage (ATES) system. An ATES system can theoretically recover in winter the heat stored in the aquifer during summer. In practice, the energy efficiency is often lower than expected due to spatial heterogeneity of hydraulic properties combined to a non-favorable hydrogeological gradient. A proper design of ATES systems should consider the uncertainty of the prediction related to those parameters. With a global sensitivity analysis, we identify sensitive parameters for heat storage prediction and validate the use of a short term heat tracing experiment monitored with geophysics to generate informative data. First, we illustrate how PFA can be used to successfully derive the distribution of temperature in the aquifer from ERT during the heat tracing experiment. Then, we successfully integrate the geophysical data to predict medium-term heat storage in the aquifer using PFA. The result is a full quantification of the posterior distribution of the prediction conditioned to observed data in a relatively limited time budget.

Noninvasive imaging of human skin hemodynamics using a digital red-green-blue camera

NASA Astrophysics Data System (ADS)

Nishidate, Izumi; Tanaka, Noriyuki; Kawase, Tatsuya; Maeda, Takaaki; Yuasa, Tomonori; Aizu, Yoshihisa; Yuasa, Tetsuya; Niizeki, Kyuichi

2011-08-01

In order to visualize human skin hemodynamics, we investigated a method that is specifically developed for the visualization of concentrations of oxygenated blood, deoxygenated blood, and melanin in skin tissue from digital RGB color images. Images of total blood concentration and oxygen saturation can also be reconstructed from the results of oxygenated and deoxygenated blood. Experiments using tissue-like agar gel phantoms demonstrated the ability of the developed method to quantitatively visualize the transition from an oxygenated blood to a deoxygenated blood in dermis. In vivo imaging of the chromophore concentrations and tissue oxygen saturation in the skin of the human hand are performed for 14 subjects during upper limb occlusion at 50 and 250 mm Hg. The response of the total blood concentration in the skin acquired by this method and forearm volume changes obtained from the conventional strain-gauge plethysmograph were comparable during the upper arm occlusion at pressures of both 50 and 250 mm Hg. The results presented in the present paper indicate the possibility of visualizing the hemodynamics of subsurface skin tissue.

Deglacial changes in oxygen minimum zones - the roles of physics, phytoplankton and ... fish? (Invited)

NASA Astrophysics Data System (ADS)

Galbraith, E. D.; bianchi, D.

2013-12-01

A global network of marine multi-proxy sediment records has shown that during the last deglaciation, hypoxic waters of the northern Indo-Pacific expanded, the oxygen minimum zones intensified, and denitrification within the oxygen minima accelerated. These changes would have impacted the fish and zooplankton that migrate on a daily basis down to the upper margins of hypoxic, or even suboxic waters, presumably in order to hide from predators. But the reasons behind these observed changes remain uncertain. Physical circulation changes could have altered the supply rate of oxygen to the subsurface, simultaneously modifying the resupply of nutrients to the ocean surface, while changes in dust deposition could have changed the iron nutrition of phytoplankton, further modifying export fluxes. Changes in respiration patterns could also have played an important part, either by altering the sinking depth of organic particles, or - perhaps - through changes in the respiration patterns of migrating animals, which could have acted as a strong feedback on any of the other changes. We show model simulations that explore the possible roles of these different mechanisms in natural oceanic oxygenation changes of the Quaternary.

The production of oxidants in Europa's surface.

PubMed

Johnson, R E; Quickenden, T I; Cooper, P D; McKinley, A J; Freeman, C G

2003-01-01

The oxidants produced by radiolysis and photolysis in the icy surface of Europa may be necessary to sustain carbon-based biochemistry in Europa's putative subsurface ocean. Because the subduction of oxidants to the ocean presents considerable thermodynamic challenges, we examine the formation of oxygen and related species in Europa's surface ice with the goal of characterizing the chemical state of the irradiated material. Relevant spectral observations of Europa and the laboratory data on the production of oxygen and related species are first summarized. Since the laboratory data are incomplete, we examine the rate equations for formation of oxygen and its chemical precursors by radiolysis and photolysis. Measurements and simple rate equations are suggested that can be used to characterize the production of oxidants in Europa's surface material and the chemical environment produced by radiolysis. Possible precursor molecules and the role of radical trapping are examined. The possibility of oxygen reactions on grain surfaces in Europa's regolith is discussed, and the earlier estimates of the supply of O(2) to the atmosphere are increased.

The role of water exchange between a stream channel and its hyporheic zone in nitrogen cycling at the terrestrial-aquatic interface

USGS Publications Warehouse

Triska, F.J.; Duff, J.H.; Avanzino, R.J.

1993-01-01

The subsurface riparian zone was examined as an ecotone with two interfaces. Inland is a terrestrial boundary, where transport of water and dissolved solutes is toward the channel and controlled by watershed hydrology. Streamside is an aquatic boundary, where exchange of surface water and dissolved solutes is bi-directional and flux is strongly influenced by channel hydraulics. Streamside, bi-directional exchange of water was qualitatively defined using biologically conservative tracers in a third order stream. In several experiments, penetration of surface water extended 18 m inland. Travel time of water from the channel to bankside sediments was highly variable. Subsurface chemical gradients were indirectly related to the travel time. Sites with long travel times tended to be low in nitrate and DO (dissolved oxygen) but high in ammonium and DOC (dissolved organic carbon). Sites with short travel times tended to be high in nitrate and DO but low in ammonium and DOC. Ammonium concentration of interstitial water also was influenced by sorption-desorption processes that involved clay minerals in hyporheic sediments. Denitrification potential in subsurface sediments increased with distance from the channel, and was limited by nitrate at inland sites and by DO in the channel sediments. Conversely, nitrification potential decreased with distance from the channel, and was limited by DO at inland sites and by ammonium at channel locations. Advection of water and dissolved oxygen away from the channel resulted in an oxidized subsurface habitat equivalent to that previously defined as the hyporheic zone. The hyporheic zone is viewed as stream habitat because of its high proportion of surface water and the occurrence of channel organisms. Beyond the channel's hydrologic exchange zone, interstitial water is often chemically reduced. Interstitial water that has not previously entered the channel, groundwater, is viewed as a terrestrial component of the riparian ecotone. Thus, surface water habitats may extend under riparian vegetation, and terrestrial groundwater habitats may be found beneath the stream channel. ?? 1993 Kluwer Academic Publishers.

Immunological techniques as tools to characterize the subsurface microbial community at a trichloroethylene contaminated site

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

Fliermans, C.B.; Dougherty, J.M.; Franck, M.M.

Effective in situ bioremediation strategies require an understanding of the effects pollutants and remediation techniques have on subsurface microbial communities. Therefore, detailed characterization of a site`s microbial communities is important. Subsurface sediment borings and water samples were collected from a trichloroethylene (TCE) contaminated site, before and after horizontal well in situ air stripping and bioventing, as well as during methane injection for stimulation of methane-utilizing microorganisms. Subsamples were processed for heterotrophic plate counts, acridine orange direct counts (AODC), community diversity, direct fluorescent antibodies (DFA) enumeration for several nitrogen-transforming bacteria, and Biolog {reg_sign} evaluation of enzyme activity in collected water samples.more » Plate counts were higher in near-surface depths than in the vadose zone sediment samples. During the in situ air stripping and bioventing, counts increased at or near the saturated zone, remained elevated throughout the aquifer, but did not change significantly after the air stripping. Sporadic increases in plate counts at different depths as well as increased diversity appeared to be linked to differing lithologies. AODCs were orders of magnitude higher than plate counts and remained relatively constant with depth except for slight increases near the surface depths and the capillary fringe. Nitrogen-transforming bacteria, as measured by serospecific DFA, were greatly affected both by the in situ air stripping and the methane injection. Biolog{reg_sign} activity appeared to increase with subsurface stimulation both by air and methane. The complexity of subsurface systems makes the use of selective monitoring tools imperative.« less

Benthic foraminiferal micro-ecology and the geochemical environments they sample

NASA Astrophysics Data System (ADS)

Jacobsen, Brittani; Loubere, Paul; Yavorska, Iryna; Klitgaard-Kristensen, Dorthe; Jernas, Patrycja

2010-05-01

Benthic foraminifera inhabit, and are adapted to, microenvironments ranging from within the water column to centimeters into the sediments. These influence the geochemistry of the foraminiferal shell, and the paleoceanographic tracers we extract from that geochemistry. For a number of proxies it is important to know what geochemical environments the foraminifera are calcifying in, and whether species are consistent in the habitats they select for calcification. We examine these issues by sampling pore water chemistry and living species distributions on the microscale that the foraminifera themselves experience. We maintained cores from the Norwegian margin under in-situ conditions while measuring oxygen microprofiles and small scale sampling for foraminifera using rose Bengal and cell tracker green staining. In addition we sampled cores for porosity and pore water carbon isotopes using two extraction techniques so as to measure isotope profiles and degree of sediment irrigation via infaunal structures. The primary forcing variable we examined was changing labile organic carbon flux to the seabed. Under moderate to higher fluxes we found evidence for extensive bio-irrigation which influenced the composition of pore waters and microhabitats available to foraminifera. Macro-meiofaunal burrows and tubes produced a mosaic of pore water geochemical conditions rather than smooth gradients from the sediment-water interface. We found species adapted to particular conditions living at various subsurface depths, where their preferred conditions existed. We also found evidence that foraminiferal species responded to larger organism activities (feeding activities) and products (fecal deposits). It appears that taxa select for particular conditions rather than simply living at specific subsurface depths, recording whatever geochemistry happens to exist at that level.

3D Lifetime Tomography Reveals How CdCl 2 Improves Recombination Throughout CdTe Solar Cells

DOE PAGES

Barnard, Edward S.; Ursprung, Benedikt; Colegrove, Eric; ...

2016-11-15

When using two-photon tomography, carrier lifetimes are mapped in polycrystalline CdTe photovoltaic devices. These 3D maps probe subsurface carrier dynamics that are inaccessible with traditional optical techniques. They reveal that CdCl 2 treatment of CdTe solar cells suppresses nonradiative recombination and enhances carrier lifetimes throughout the film with substantial improvements particularly near subsurface grain boundaries and the critical buried p-n junction.

Characterization of Subsurface Defects in Ceramic Rods by Laser Scattering and Fractography

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

Zhang, J. M.; Sun, J. G.; Andrews, M. J.

2006-03-06

Silicon nitride ceramics are leading materials being evaluated for valve train components in diesel engine applications. The surface and subsurface defects and damage induced by surface machining can significantly affect component strength and lifetime. In this study, a nondestructive evaluation (NDE) technique based upon laser scattering has been utilized to analyze eight transversely ground silicon nitride cylindrical rods before fracture tests. The fracture origins (machining cracks or material-inherent flaws) identified by fractography after fracture testing were correlated with laser scattering images. The results indicate that laser scattering is able to identify possible fracture origin in the silicon nitride subsurface withoutmore » the need for destructive fracture tests.« less

A review of factors influencing the availability of dissolved oxygen to incubating salmonid embryos

NASA Astrophysics Data System (ADS)

Greig, S. M.; Sear, D. A.; Carling, P. A.

2007-01-01

Previous investigations into factors influencing incubation success of salmonid progeny have largely been limited to the development of empirical relationships between characteristics of the incubation environment and survival to emergence. It is suggested that adopting a process-based approach to assessing incubation success aids identification of the precise causes of embryonic mortalities, and provides a robust framework for developing and implementing managerial responses.Identifying oxygen availability within the incubation environment as a limiting factor, a comprehensive review of trends in embryonic respiration, and processes influencing the flux of oxygenated water through gravel riverbeds is provided. The availability of oxygen to incubating salmonid embryos is dependent on the exchange of oxygenated water with the riverbed, and the ability of the riverbed gravel medium to transport this water at a rate and concentration appropriate to support embryonic respiratory requirements. Embryonic respiratory trends indicate that oxygen consumption varies with stage of development, ambient water temperature and oxygen availability. The flux of oxygenated water through the incubation environment is controlled by a complex interaction of intragravel and extragravel processes and factors. The processes driving the exchange of channel water with gravel riverbeds include bed topography, bed permeability, and surface roughness effects. The flux of oxygenated water through riverbed gravels is controlled by gravel permeability, coupling of surface-subsurface flow and oxygen demands imposed by materials infiltrating riverbed gravels. Temporally and spatially variable inputs of groundwater can also influence the oxygen concentration of interstitial water. Copyright

FEASIBILITY OF HYDRAULIC FRACTURING OF SOILS TO IMPROVE REMEDIAL ACTIONS

EPA Science Inventory

Hydraulic fracturing, a method of increasing fluid flow within the subsurface, should improve the effectiveness of several remedial techniques, including pump and treat, vapor extraction, bio-remediation, and soil-flushing. he technique is widely used to increase the yields of oi...

PARTITIONING INTERWELL TRACER TEST FOR NAPL SOURCE CHARACTERIZATION: A GENERAL OVERVIEW

EPA Science Inventory

Innovative and nondestructive characterization techniques have been developed to locate and quantify nonaqueous phase liquids (NAPLs) in the vadose and saturated zones in the subsurface environment. One such technique is the partitioning interwell tracer test (PITT). The PITT i...

Growth of the acidophilic iron-sulfur bacterium Acidithiobacillus ferrooxidans under Mars-like geochemical conditions

NASA Astrophysics Data System (ADS)

Bauermeister, Anja; Rettberg, Petra; Flemming, Hans-Curt

2014-08-01

The question of life on Mars has been in focus of astrobiological research for several decades, and recent missions in orbit or on the surface of the planet are constantly expanding our knowledge on Martian geochemistry. For example, massive stratified deposits have been identified on Mars containing sulfate minerals and iron oxides, which suggest the existence of acidic aqueous conditions in the past, similar to acidic iron- and sulfur-rich environments on Earth. Acidophilic organisms thriving in such habitats could have been an integral part of a possibly widely extinct Martian ecosystem, but remains might possibly even exist today in protected subsurface niches. The chemolithoautotrophic strain Acidithiobacillus ferrooxidans was selected as a model organism to study the metabolic capacities of acidophilic iron-sulfur bacteria, especially regarding their ability to grow with in situ resources that could be expected on Mars. The experiments were not designed to accurately simulate Martian physical conditions (except when certain single parameters such as oxygen partial pressure were considered), but rather the geochemical environment that can be found on Mars. A. ferrooxidans could grow solely on the minerals contained in synthetic Mars regolith mixtures with no added nutrients, using either O2 as an external electron acceptor for iron oxidation, or H2 as an external electron donor for iron reduction, and thus might play important roles in the redox cycling of iron on Mars. Though the oxygen partial pressure of the Martian atmosphere at the surface was not sufficient for detectable iron oxidation and growth of A. ferrooxidans during short-term incubation (7 days), alternative chemical O2-generating processes in the subsurface might yield microhabitats enriched in oxygen, which principally are possible under such conditions. The bacteria might also contribute to the reductive dissolution of Fe3+-containing minerals like goethite and hematite, which are characterized by a high thermodynamic stability. Even in a desiccated environment, A. ferrooxidans survived for one week under simulated Martian shallow subsurface conditions (6 hPa, -20 °C, 0.13% O2) in the form of dried biofilms without loss of viability. Low temperature and low oxygen pressure were favorable to survival. Thus, the acidophilic iron-sulfur bacterium A. ferrooxidans may be considered a plausible candidate of a potential Martian food web based on its metabolic capacities. As an autotroph it would be located at the base of such a food web, providing organic carbon.

Long-term in situ oxidation of biogenic uraninite in an alluvial aquifer: impact of dissolved oxygen and calcium.

PubMed

Lezama-Pacheco, Juan S; Cerrato, José M; Veeramani, Harish; Alessi, Daniel S; Suvorova, Elena; Bernier-Latmani, Rizlan; Giammar, Daniel E; Long, Philip E; Williams, Kenneth H; Bargar, John R

2015-06-16

Oxidative dissolution controls uranium release to (sub)oxic pore waters from biogenic uraninite produced by natural or engineered processes, such as bioremediation. Laboratory studies show that uraninite dissolution is profoundly influenced by dissolved oxygen (DO), carbonate, and solutes such as Ca(2+). In complex and heterogeneous subsurface environments, the concentrations of these solutes vary in time and space. Knowledge of dissolution processes and kinetics occurring over the long-term under such conditions is needed to predict subsurface uranium behavior and optimize the selection and performance of uraninite-based remediation technologies over multiyear periods. We have assessed dissolution of biogenic uraninite deployed in wells at the Rifle, CO, DOE research site over a 22 month period. Uraninite loss rates were highly sensitive to DO, with near-complete loss at >0.6 mg/L over this period but no measurable loss at lower DO. We conclude that uraninite can be stable over decadal time scales in aquifers under low DO conditions. U(VI) solid products were absent over a wide range of DO values, suggesting that dissolution proceeded through complexation and removal of oxidized surface uranium atoms by carbonate. Moreover, under the groundwater conditions present, Ca(2+) binds strongly to uraninite surfaces at structural uranium sites, impacting uranium fate.

Hydraulische Optimierung des Reaktionsraumes um einen Infiltrationsbrunnen zur unterirdischen Enteisenung. Feldversuche und numerische Simulation zur Planung der optimalen Verfahrensergiebigkeit (Teil 1/2) Hydraulic optimization of the reaction zone around an injection well during subsurface iron removal

NASA Astrophysics Data System (ADS)

Ahrns, Johannes; Bartak, Rico; Grischek, Thomas; Pörschke, Richard

2017-11-01

In subsurface iron removal (SIR), oxygen-enriched water is injected into an aquifer to create a reaction zone. Aside from the hydraulic properties of the aquifer, groundwater quality often varies with depth so that in vertical wells the dissolved oxygen distribution (reaction zone) may not correspond to the dissolved iron concentration which may result in a lower efficiency coefficient. Therefore, measures to hydraulically optimize the formation of the reaction zone through a non-conventional injection were investigated. A high-resolution groundwater flow model was calibrated based on tracer and pump tests and used to plan the optimized injection for a SIR-pilot well with two screen segments. An optimized injection appears to be possible through the inactivation of well screen sections using packers. A doubling of the efficiency coefficient in comparison to a conventional injection was predicted when a packer, which remains evacuated inside the well while pumping, was used to seal 4/5 of the upper well screen length during injection. This scenario was used to plan the operating regime for a SIR field test, which is presented in Part 2.

Effects of a dual-pump crude-oil recovery system, Bemidji, Minnesota, USA

USGS Publications Warehouse

Delin, Geoffrey N.; Herkelrath, William N.

2014-01-01

A crude-oil spill occurred in 1979 when a pipeline burst near Bemidji, MN. In 1998, the pipeline company installed a dual-pump recovery system designed to remove crude oil remaining in the subsurface at the site. The remediation from 1999 to 2003 resulted in removal of about 115,000 L of crude oil, representing between 36% and 41% of the volume of oil (280,000 to 316,000 L) estimated to be present in 1998. Effects of the 1999 to 2003 remediation on the dissolved plume were evaluated using measurements of oil thicknesses in wells plus measurements of dissolved oxygen in groundwater. Although the recovery system decreased oil thicknesses in the immediate vicinity of the remediation wells, average oil thicknesses measured in wells were largely unaffected. Dissolved-oxygen measurements indicate that a secondary plume was caused by disposal of the pumped water in an upgradient infiltration gallery; this plume expanded rapidly immediately following the start of the remediation in 1999. The result was expansion of the anoxic zone of groundwater upgradient and beneath the existing natural attenuation plume. Oil-phase recovery at this site was shown to be challenging, and considerable volumes of mobile and entrapped oil remain in the subsurface despite remediation efforts.

[XPS analysis of beads formed by fuse breaking of electric copper wire].

PubMed

Wu, Ying; Meng, Qing-Shan; Wang, Xin-Ming; Gao, Wei; Di, Man

2010-05-01

The in-depth composition of beads formed by fuse breaking of the electric copper wire in different circumstances was studied by XPS with Ar+ ion sputtering. In addition, the measured Auger spectra and the calculated Auger parameters were compared for differentiation of the substances of Cu and Cu2O. Corresponding to the sputtering depth, the molten product on a bead induced directly by fuse breaking of the copper wire without cover may be distinguished as three portions: surface layer with a drastic decrease in carbon content; intermediate layer with a gentle change in oxygen content and gradually diminished carbon peak, and consisting of Cu2O; transition layer without Cu2O and with a rapid decrease in oxygen content. While the molten product on a bead formed by fuse breaking of the copper wire after its insulating cover had been burned out may be distinguished as two portions: surface layer with carbon content decreasing quickly; subsurface layer without Cu2O and with carbon and oxygen content decreasing gradually. Thus, it can be seen that there was an obvious interface between the layered surface product and the substrate for the first type of bead, while as to the second type of bead there was no interface. As a result, the presence of Cu2O and the quantitative results can be used to identify the molten product on a bead induced directly by fuse breaking of the copper wire without cover and the molten product on a bead formed by fuse breaking of the cupper wire after its insulating cover had been burned out, as a complementary technique for the judgments of fire cause.

Real rock-microfluidic flow cell: A test bed for real-time in situ analysis of flow, transport, and reaction in a subsurface reactive transport environment.

PubMed

Singh, Rajveer; Sivaguru, Mayandi; Fried, Glenn A; Fouke, Bruce W; Sanford, Robert A; Carrera, Martin; Werth, Charles J

2017-09-01

Physical, chemical, and biological interactions between groundwater and sedimentary rock directly control the fundamental subsurface properties such as porosity, permeability, and flow. This is true for a variety of subsurface scenarios, ranging from shallow groundwater aquifers to deeply buried hydrocarbon reservoirs. Microfluidic flow cells are now commonly being used to study these processes at the pore scale in simplified pore structures meant to mimic subsurface reservoirs. However, these micromodels are typically fabricated from glass, silicon, or polydimethylsiloxane (PDMS), and are therefore incapable of replicating the geochemical reactivity and complex three-dimensional pore networks present in subsurface lithologies. To address these limitations, we developed a new microfluidic experimental test bed, herein called the Real Rock-Microfluidic Flow Cell (RR-MFC). A porous 500μm-thick real rock sample of the Clair Group sandstone from a subsurface hydrocarbon reservoir of the North Sea was prepared and mounted inside a PDMS microfluidic channel, creating a dynamic flow-through experimental platform for real-time tracking of subsurface reactive transport. Transmitted and reflected microscopy, cathodoluminescence microscopy, Raman spectroscopy, and confocal laser microscopy techniques were used to (1) determine the mineralogy, geochemistry, and pore networks within the sandstone inserted in the RR-MFC, (2) analyze non-reactive tracer breakthrough in two- and (depth-limited) three-dimensions, and (3) characterize multiphase flow. The RR-MFC is the first microfluidic experimental platform that allows direct visualization of flow and transport in the pore space of a real subsurface reservoir rock sample, and holds potential to advance our understandings of reactive transport and other subsurface processes relevant to pollutant transport and cleanup in groundwater, as well as energy recovery. Copyright © 2017 Elsevier B.V. All rights reserved.

Band edge engineering of oxide photoanodes for photoelectrochemical water splitting: Integration of subsurface dipoles with atomic-scale control

DOE PAGES

Hikita, Yasuyuki; Nishio, Kazunori; Seitz, Linsey C.; ...

2016-01-22

One of the crucial parameters dictating the efficiency of photoelectrochemical water-splitting is the semiconductor band edge alignment with respect to hydrogen and oxygen redox potentials. Despite the importance of metal oxides in their use as photoelectrodes, studies to control the band edge alignment in aqueous solution have been limited predominantly to compound semiconductors with modulation ranges limited to a few hundred mV. The ability to modulate the flat band potential of oxide photoanodes by as much as 1.3 V, using the insertion of subsurface electrostatic dipoles near a Nb-doped SrTiO 3/aqueous electrolyte interface is reported. Lastly, the tunable range achievedmore » far exceeds previous reports in any semiconductor/aqueous electrolyte system and suggests a general design strategy for highly efficient oxide photoelectrodes.« less

Method for determination of .sup.18 O/.sup.16 O and .sup.2 H/.sup.1 H ratios and .sup.3 H (tritium) concentrations of xylem waters and subsurface waters using time series sampling

DOEpatents

Smith, Brian; Menchaca, Leticia

1999-01-01

A method for determination of .sup.18 O/.sup.16 O and .sup.2 H/.sup.1 H ratios and .sup.3 H concentrations of xylem and subsurface waters using time series sampling, insulating sampling chambers, and combined .sup.18 O/.sup.16 O, .sup.2 H/.sup.1 H and .sup.3 H concentration data on transpired water. The method involves collecting water samples transpired from living plants and correcting the measured isotopic compositions of oxygen (.sup.18 O/.sup.16 O) and hydrogen (.sup.2 H/.sup.1 H and/or .sup.3 H concentrations) to account for evaporative isotopic fractionation in the leafy material of the plant.

A Tower-based Prototype VHF/UHF Radar for Subsurface Sensing: System Description and Data Inversion Results

NASA Technical Reports Server (NTRS)

Moghaddam, Mahta; Pierce, Leland; Tabatabaeenejad, Alireza; Rodriguez, Ernesto

2005-01-01

Knowledge of subsurface characteristics such as permittivity variations and layering structure could provide a breakthrough in many terrestrial and planetary science disciplines. For Earth science, knowledge of subsurface and subcanopy soil moisture layers can enable the estimation of vertical flow in the soil column linking surface hydrologic processes with that in the subsurface. For planetary science, determining the existence of subsurface water and ice is regarded as one of the most critical information needs for the study of the origins of the solar system. The subsurface in general can be described as several near-parallel layers with rough interfaces. Each homogenous rough layer can be defined by its average thickness, permittivity, and rms interface roughness assuming a known surface spectral distribution. As the number and depth of layers increase, the number of measurements needed to invert for the layer unknowns also increases, and deeper penetration capability would be required. To nondestructively calculate the characteristics of the rough layers, a multifrequency polarimetric radar backscattering approach can be used. One such system is that we have developed for data prototyping of the Microwave Observatory of Subcanopy and Subsurface (MOSS) mission concept. A tower-mounted radar makes backscattering measurements at VHF, UHF, and L-band frequencies. The radar is a pulsed CW system, which uses the same wideband antenna to transmit and receive the signals at all three frequencies. To focus the beam at various incidence angles within the beamwidth of the antenna, the tower is moved vertically and measurements made at each position. The signals are coherently summed to achieve focusing and image formation in the subsurface. This requires an estimate of wave velocity profiles. To solve the inverse scattering problem for subsurface velocity profile simultaneously with radar focusing, we use an iterative technique based on a forward numerical solution of the layered rough surface problem. The layers are each defined in terms of a small number of unknown distributions as given above. An a priori estimate of the solution is first assumed, based on which the forward problem is solved for the backscattered measurements. This is compared with the measured data and using iterative techniques an update to the solution for the unknowns is calculated. The process continues until convergence is achieved. Numerical results will be shown using actual radar data acquired with the MOSS tower radar system in Arizona in Fall 2003, and compared with in-situ measurements.

Probing the critical zone using passive- and active-source estimates of subsurface shear-wave velocities

NASA Astrophysics Data System (ADS)

Callahan, R. P.; Taylor, N. J.; Pasquet, S.; Dueker, K. G.; Riebe, C. S.; Holbrook, W. S.

2016-12-01

Geophysical imaging is rapidly becoming popular for quantifying subsurface critical zone (CZ) architecture. However, a diverse array of measurements and measurement techniques are available, raising the question of which are appropriate for specific study goals. Here we compare two techniques for measuring S-wave velocities (Vs) in the near surface. The first approach quantifies Vs in three dimensions using a passive source and an iterative residual least-squares tomographic inversion. The second approach uses a more traditional active-source seismic survey to quantify Vs in two dimensions via a Monte Carlo surface-wave dispersion inversion. Our analysis focuses on three 0.01 km2 study plots on weathered granitic bedrock in the Southern Sierra Critical Zone Observatory. Preliminary results indicate that depth-averaged velocities from the two methods agree over the scales of resolution of the techniques. While the passive- and active-source techniques both quantify Vs, each method has distinct advantages and disadvantages during data acquisition and analysis. The passive-source method has the advantage of generating a three dimensional distribution of subsurface Vs structure across a broad area. Because this method relies on the ambient seismic field as a source, which varies unpredictably across space and time, data quality and depth of investigation are outside the control of the user. Meanwhile, traditional active-source surveys can be designed around a desired depth of investigation. However, they only generate a two dimensional image of Vs structure. Whereas traditional active-source surveys can be inverted quickly on a personal computer in the field, passive source surveys require significantly more computations, and are best conducted in a high-performance computing environment. We use data from our study sites to compare these methods across different scales and to explore how these methods can be used to better understand subsurface CZ architecture.

WISDOM : an UHF GPR on the Exomars Mission

NASA Astrophysics Data System (ADS)

Corbel, C.; Hamram, S.; Ney, R.; Plettemeier, D.; Dolon, F.; Jeangeot, A.; Ciarletti, V.; Berthelier, J.

2006-12-01

This paper describes the main technical features of WISDOM (Water Ice and Subsurface Deposit Observations on Mars) Ground Penetrating Radar. This radar has been selected on the PASTEUR payload of the ESA ExoMars rover. The launch is scheduled in 2011. The main objective of this mission is to acquire and analyze samples of the shallow subsurface and search for traces of extinct or extant life. The WISDOM GPR aims at providing observations of the structure and layering of the upper layers of the subsurface in order to retrieve geological information that are of prime interest to select optimal sites to drill. It will also localize buried obstacles (rocks, boulders, ?)in the underground that will make the delicate drilling operations safer. WISDOM will operate in the UHF range from 500 MHz to 3 GHz and probe the first few meters of the subsurface with a high resolution (a few centimeters). The large bandwidth requirement (2.5 GHz) led us to select a gated step frequency technique for WISDOM. The Step Frequency technique is based on the analysis of the system in the frequency domain. The phase and amplitude of the reflected signal are measured at about 200 different frequencies effectively measuring the transfer function of the sub-surface between the transmitter and receiver antenna. The impulse response and eventually the distance of the reflecting structures can be obtained by performing an inverse Fourier transform of the measured transfer function. The broad band antennas have been designed in order to have a wide radiation pattern into the sub-surface and to avoid the direct coupling and allow co and cross polar measurements. To decrease the direct signal between the transmitter and the receiver or strong reflections from the surface, hardware range gating is implemented. The performances of the instrument operated in well characterized conditions will be presented

Empirical Mode Decomposition of Geophysical Well-log Data of Bombay Offshore Basin, Mumbai, India

NASA Astrophysics Data System (ADS)

Siddharth Gairola, Gaurav; Chandrasekhar, Enamundram

2016-04-01

Geophysical well-log data manifest the nonlinear behaviour of their respective physical properties of the heterogeneous subsurface layers as a function of depth. Therefore, nonlinear data analysis techniques must be implemented, to quantify the degree of heterogeneity in the subsurface lithologies. One such nonlinear data adaptive technique is empirical mode decomposition (EMD) technique, which facilitates to decompose the data into oscillatory signals of different wavelengths called intrinsic mode functions (IMF). In the present study EMD has been applied to gamma-ray log and neutron porosity log of two different wells: Well B and Well C located in the western offshore basin of India to perform heterogeneity analysis and compare the results with those obtained by multifractal studies of the same data sets. By establishing a relationship between the IMF number (m) and the mean wavelength associated with each IMF (Im), a heterogeneity index (ρ) associated with subsurface layers can be determined using the relation, Im=kρm, where 'k' is a constant. The ρ values bear an inverse relation with the heterogeneity of the subsurface: smaller ρ values designate higher heterogeneity and vice-versa. The ρ values estimated for different limestone payzones identified in the wells clearly show that Well C has higher degree of heterogeneity than Well B. This correlates well with the estimated Vshale values for the limestone reservoir zone showing higher shale content in Well C than Well B. The ρ values determined for different payzones of both wells will be used to quantify the degree of heterogeneity in different wells. The multifractal behaviour of each IMF of both the logs of both the wells will be compared with one another and discussed on the lines of their heterogeneity indices.

Characterizing the deformation of reservoirs using interferometry, gravity, and seismic analyses

NASA Astrophysics Data System (ADS)

Schiek, Cara Gina

In this dissertation, I characterize how reservoirs deform using surface and subsurface techniques. The surface technique I employ is radar interferometry, also known as InSAR (Interferometric Synthetic Aperture Radar). The subsurface analyses I explore include gravity modeling and seismic techniques consisting of determining earthquake locations from a small-temporary seismic network of six seismometers. These techniques were used in two different projects to determine how reservoirs deform in the subsurface and how this deformation relates to its remotely sensed surface deformation. The first project uses InSAR to determine land subsidence in the Mimbres basin near Deming, NM. The land subsidence measurements are visually compared to gravity models in order to determine the influence of near surface faults on the subsidence and the physical properties of the aquifers in these basins. Elastic storage coefficients were calculated for the Mimbres basin to aid in determining the stress regime of the aquifers. In the Mimbres basin, I determine that it is experiencing elastic deformation at differing compaction rates. The west side of the Mimbres basin is deforming faster, 17 mm/yr, while the east side of the basin is compacting at a rate of 11 mm/yr. The second project focuses on San Miguel volcano, El Salvador. Here, I integrate InSAR with earthquake locations using surface deformation forward modeling to investigate the explosive volcanism in this region. This investigation determined the areas around the volcano that are undergoing deformation, and that could lead to volcanic hazards such as slope failure from a fractured volcano interior. I use the earthquake epicenters with field data to define the subsurface geometry of the deformation source, which I forward model to produce synthetic interferograms. Residuals between the synthetic and observed interferograms demonstrate that the observed deformation is a direct result of the seismic activity along the San Miguel Fracture Zone. Based on the large number of earthquakes concentrated in this region and the fracturing suggested by the earthquake location results, I conclude that the southwestern slope of San Miguel is the most susceptible to volcanic hazards such as landsliding and flank lava flows. Together these projects explore the dynamics of reservoir systems, both hydrologic and magmatic. They show the utility of geodetic remote sensing to constrain the relative importance of various, complex, subsurface processes, including faulting, fluid migration, and compaction.

Compositional and Textural Analysis of Maar-Diatreme Volcanic Deposits at Hopi Buttes Volcanic Field (AZ) Using GigaPan Panoramic and Thermal Infrared Imagery

NASA Astrophysics Data System (ADS)

Lee, R.; Graettinger, A. H.; Weinell, M.; Hughes, C. G.

2016-12-01

Basaltic maar-diatreme volcanoes are produced when rising magma interacts with groundwater and produces a maar crater at the ground surface. This crater is underlain by a diatreme, a downward-tapering conical structure filled with a mixture of fragments of intruded magma, fractured host rock, and clasts recycled through repeated discrete subsurface explosions. The debris of the diatreme records the mixing processes caused by subsurface explosions and is the source for ejected material that forms maar tephra rings. Determining the variable depths and lateral locations of these explosions and how energy is dissipated in the subsurface is critical to understanding how maar-diatreme eruptions progress. The Hopi Buttes Volcanic Field (HBVF) in the Navajo Nation, Arizona, USA, contains several diatremes and incised tephra rings with heterolithic clasts 10 mm - 10 m in size, and are well-exposed near-vertical to vertical outcrops. Our ability to measure the length scales and distribution of textures produced by subsurface explosions in these diatremes is limited by the physical accessibility of the exposures, due to both the verticality of the outcrops and the cultural sensitivity of the site. Quantifying the number and locations of explosions is dependent on our ability to investigate the full diatreme outcrop, and not just what can be accessed through traditional field observations. We present a novel field and computer-based technique for both quantitatively and qualitatively characterizing the composition and texture of maar-diatreme deposits in vertical outcrops. This technique uses a combination of field-collected multispectral thermal infrared (TIR) image data and visible wavelength GigaPan imagery to characterize the compositional and textural variations over a whole outcrop. To increase the spatial and spectral resolution of the TIR data, a super-resolution technique will be applied. The technique provides a simple and efficient method to augment the study of the maar-diatreme deposits at HBVF. In addition to contributing to a better understanding of the formation processes of maar-diatreme deposits around the world, the technique also shows great promise for studies involving other types of large outcrops and geologic structures.

Improving Vintage Seismic Data Quality through Implementation of Advance Processing Techniques

NASA Astrophysics Data System (ADS)

Latiff, A. H. Abdul; Boon Hong, P. G.; Jamaludin, S. N. F.

2017-10-01

It is essential in petroleum exploration to have high resolution subsurface images, both vertically and horizontally, in uncovering new geological and geophysical aspects of our subsurface. The lack of success may have been from the poor imaging quality which led to inaccurate analysis and interpretation. In this work, we re-processed the existing seismic dataset with an emphasis on two objectives. Firstly, to produce a better 3D seismic data quality with full retention of relative amplitudes and significantly reduce seismic and structural uncertainty. Secondly, to facilitate further prospect delineation through enhanced data resolution, fault definitions and events continuity, particularly in syn-rift section and basement cover contacts and in turn, better understand the geology of the subsurface especially in regard to the distribution of the fluvial and channel sands. By adding recent, state-of-the-art broadband processing techniques such as source and receiver de-ghosting, high density velocity analysis and shallow water de-multiple, the final results produced a better overall reflection detail and frequency in specific target zones, particularly in the deeper section.

In Situ Monitoring of Chemical Reactions at a Solid-Water Interface by Femtosecond Acoustics.

PubMed

Shen, Chih-Chiang; Weng, Meng-Yu; Sheu, Jinn-Kong; Yao, Yi-Ting; Sun, Chi-Kuang

2017-11-02

Chemical reactions at a solid-liquid interface are of fundamental importance. Interfacial chemical reactions occur not only at the very interface but also in the subsurface area, while existing monitoring techniques either provide limited spatial resolution or are applicable only for the outmost atomic layer. Here, with the aid of the time-domain analysis with femtosecond acoustics, we demonstrate a subatomic-level-resolution technique to longitudinally monitor chemical reactions at solid-water interfaces, capable of in situ monitoring even the subsurface area under atmospheric conditions. Our work was proven by monitoring the already-known anode oxidation process occurring during photoelectrochemical water splitting. Furthermore, whenever the oxide layer thickness equals an integer  number of the effective atomic layer thickness, the measured acoustic echo will show higher signal-to-noise ratios with reduced speckle noise, indicating the quantum-like behavior of this coherent-phonon-based technique.

A seismic refraction technique used for subsurface investigations at Meteor Crater, Arizona

NASA Technical Reports Server (NTRS)

Ackermann, H. D.; Godson, R. H.; Watkins, J. S.

1975-01-01

A seismic refraction technique for interpreting the subsurface shape and velocity distribution of an anomalous surface feature such as an impact crater is described. The method requires the existence of a relatively deep refracting horizon and combines data obtained from both standard shallow refraction spreads and distant offset shots by using the deep refractor as a source of initial arrivals. Results obtained from applying the technique to Meteor crater generally agree with the known structure of the crater deduced by other investigators and provide new data on an extensive fractured zone surrounding the crater. The breccia lens is computed to extend roughly 190 m below the crater floor, about 30 m less than the value deduced from early drilling data. Rocks around the crater are fractured as distant as 900 m from the rim crest and to a depth of at least 800 m beneath the crater floor.

Using Laser Ultrasound to Detect Subsurface Defects in Metal Laser Powder Bed Fusion Components

NASA Astrophysics Data System (ADS)

Everton, Sarah; Dickens, Phill; Tuck, Chris; Dutton, Ben

2018-03-01

Laser powder bed fusion offers many advantages over conventional manufacturing methods, such as the integration of multiple parts that can result in significant weight-savings. The increased design freedom that layer-wise manufacture allows has also been seen to enhance component performance at little or no added cost. For such benefits to be realized, however, the material quality must first be assured. Laser ultrasonic testing is a noncontact inspection technique that has been proposed as suitable for in situ monitoring of metal additive manufacturing processes. This article explores the current capability of this technique to detect manufactured, subsurface defects in Ti-6Al-4V samples, ex situ. The results are compared with x-ray computed tomography reconstructions and focus variation microscopy. Although laser ultrasound has been used to identify material discontinuities, further work is required before this technique could be implemented in situ.

Application of seismic-refraction techniques to hydrologic studies

USGS Publications Warehouse

Haeni, F.P.

1986-01-01

During the past 30 years, seismic-refraction methods have been used extensively in petroleum, mineral, and engineering investigations, and to some extent for hydrologic applications. Recent advances in equipment, sound sources, and computer interpretation techniques make seismic refraction a highly effective and economical means of obtaining subsurface data in hydrologic studies. Aquifers that can be defined by one or more high seismic-velocity surfaces, such as (1) alluvial or glacial deposits in consolidated rock valleys, (2) limestone or sandstone underlain by metamorphic or igneous rock, or (3) saturated unconsolidated deposits overlain by unsaturated unconsolidated deposits,are ideally suited for applying seismic-refraction methods. These methods allow the economical collection of subsurface data, provide the basis for more efficient collection of data by test drilling or aquifer tests, and result in improved hydrologic studies.This manual briefly reviews the basics of seismic-refraction theory and principles. It emphasizes the use of this technique in hydrologic investigations and describes the planning, equipment, field procedures, and intrepretation techniques needed for this type of study.Examples of the use of seismic-refraction techniques in a wide variety of hydrologic studies are presented.

Application of seismic-refraction techniques to hydrologic studies

USGS Publications Warehouse

Haeni, F.P.

1988-01-01

During the past 30 years, seismic-refraction methods have been used extensively in petroleum, mineral, and engineering investigations and to some extent for hydrologic applications. Recent advances in equipment, sound sources, and computer interpretation techniques make seismic refraction a highly effective and economical means of obtaining subsurface data in hydrologic studies. Aquifers that can be defined by one or more high-seismic-velocity surface, such as (1) alluvial or glacial deposits in consolidated rock valleys, (2) limestone or sandstone underlain by metamorphic or igneous rock, or (3) saturated unconsolidated deposits overlain by unsaturated unconsolidated deposits, are ideally suited for seismic-refraction methods. These methods allow economical collection of subsurface data, provide the basis for more efficient collection of data by test drilling or aquifer tests, and result in improved hydrologic studies. This manual briefly reviews the basics of seismic-refraction theory and principles. It emphasizes the use of these techniques in hydrologic investigations and describes the planning, equipment, field procedures, and interpretation techniques needed for this type of study. Further-more, examples of the use of seismic-refraction techniques in a wide variety of hydrologic studies are presented.

Microbial life in cold, hydrologically active oceanic crustal fluids

NASA Astrophysics Data System (ADS)

Meyer, J. L.; Jaekel, U.; Girguis, P. R.; Glazer, B. T.; Huber, J. A.

2012-12-01

It is estimated that at least half of Earth's microbial biomass is found in the deep subsurface, yet very little is known about the diversity and functional roles of these microbial communities due to the limited accessibility of subseafloor samples. Ocean crustal fluids, which may have a profound impact on global nutrient cycles given the large volumes of water moving through the crustal aquifer, are particularly difficult to sample. Access to uncontaminated ocean crustal fluids is possible with CORK (Circulation Obviation Retrofit Kit) observatories, installed through the Integrated Ocean Drilling Program (IODP). Here we present the first microbiological characterization of the formation fluids from cold, oxygenated igneous crust at North Pond on the western flank of the Mid Atlantic Ridge. Fluids were collected from two CORKs installed at IODP boreholes 1382A and 1383C and include fluids from three different depth horizons within oceanic crust. Collection of borehole fluids was monitored in situ using an oxygen optode and solid-state voltammetric electrodes. In addition, discrete samples were analyzed on deck using a comparable lab-based system as well as a membrane-inlet mass spectrometer to quantify all dissolved volatiles up to 200 daltons. The instruments were operated in parallel and both in situ and shipboard geochemical measurements point to a highly oxidized fluid, revealing an apparent slight depletion of oxygen in subsurface fluids (~215μM) relative to bottom seawater (~245μM). We were unable to detect reduced hydrocarbons, e.g. methane. Cell counts indicated the presence of roughly 2 x 10^4 cells per ml in all fluid samples, and DNA was extracted and amplified for the identification of both bacterial and archaeal community members. The utilization of ammonia, nitrate, dissolved inorganic carbon, and acetate was measured using stable isotopes, and oxygen consumption was monitored to provide an estimate of the rate of respiration per cell per day. These results provide the first dataset describing the diversity of microbes present in cold, oxygenated ocean crustal fluids and the biogeochemical processes they mediate in the subseafloor.

Storm event-scale nutrient attenuation in constructed wetlands experiencing a Mediterranean climate: A comparison of a surface flow and hybrid surface-subsurface flow system.

PubMed

Adyel, Tanveer M; Oldham, Carolyn E; Hipsey, Matthew R

2017-11-15

Among different Water Sensitive Urban Design options, constructed wetlands (CWs) are used to protect and restore downstream water quality by attenuating nutrients generated by stormwater runoff. This research compared the nutrient attenuation ability during a diverse population of storm events of two CWs: (a) a hybrid CW with multiple alternating surface flow (SF) and laterite-based subsurface flow (SSF) compartments, and (b) a single stage SF CW. Within-storm variability, nutrient concentrations were assessed at 2 to 3-h intervals at both the main inlet and outlet of each CW. Dissolved oxygen concentrations of the surface waters were also monitored at 10-min intervals using high frequency in situ sensors. Nutrient loads into the CWs were observed to be higher when a high rainfall event occurred, particularly after longer antecedent dry conditions. Longer hydraulic retention times promoted higher attenuation at both sites. However, the relative extent of nutrient attenuation differed between the CW types; the mean total nitrogen (TN) attenuation in the hybrid and SF CW was 45 and 48%, respectively. The hybrid CW attenuated 67% total phosphorus (TP) loads on average, while the SF CW acted as a net TP source. Periodic storm events transitioned the lentic CW into a lotic CW and caused riparian zone saturation; it was therefore hypothesized that such saturation of organic matter rich-riparian zones led to release of TP in the system. The hybrid CW attenuated the released TP in the downstream laterite-based SSF compartments. Diel oxygen metabolism calculated before and after the storm events was found to be strongly correlated with water temperature, solar exposure and antecedent dry condition during the pre-storm conditions. Furthermore, the SF CW showed a significant relationship between overall nutrient load attenuation and the change in oxygen metabolism during the storm perturbation, suggesting oxygen variation could be a useful proxy indicator of CW function. Copyright © 2017 Elsevier B.V. All rights reserved.

Frozen-Plug Technique for Liquid-Oxygen Plumbing

NASA Technical Reports Server (NTRS)

McCaskey, C. E. " Mac" ; Lobmeyer, Dennis; Nagy, Zoltan; Peltzer, Rich

2005-01-01

A frozen-plug technique has been conceived as a means of temporarily blocking the flow of liquid oxygen or its vapor through a tube or pipe. The technique makes it possible to perform maintenance, repair, or other work on downstream parts of the cryogenic system in which the oxygen is used, without having to empty an upstream liquid-oxygen reservoir and, hence, without wasting the stored liquid oxygen and without subjecting the reservoir to the stresses of thermal cycling.

Methylmercury Mass Budgets and Distribution Characteristics in the Western Pacific Ocean.

PubMed

Kim, Hyunji; Soerensen, Anne L; Hur, Jin; Heimbürger, Lars-Eric; Hahm, Doshik; Rhee, Tae Siek; Noh, Seam; Han, Seunghee

2017-02-07

Methylmercury (MeHg) accumulation in marine organisms poses serious ecosystem and human health risk, yet the sources of MeHg in the surface and subsurface ocean remain uncertain. Here, we report the first MeHg mass budgets for the Western Pacific Ocean estimated based on cruise observations. We found the major net source of MeHg in surface water to be vertical diffusion from the subsurface layer (1.8-12 nmol m -2  yr -1 ). A higher upward diffusion in the North Pacific (12 nmol m -2  yr -1 ) than in the Equatorial Pacific (1.8-5.7 nmol m -2  yr -1 ) caused elevated surface MeHg concentrations observed in the North Pacific. We furthermore found that the slope of the linear regression line for MeHg versus apparent oxygen utilization in the Equatorial Pacific was about 2-fold higher than that in the North Pacific. We suggest this could be explained by redistribution of surface water in the tropical convergence-divergence zone, supporting active organic carbon decomposition in the Equatorial Pacific Ocean. On the basis of this study, we predict oceanic regions with high organic carbon remineralization to have enhanced MeHg concentrations in both surface and subsurface waters.

A New Sensitive GC-MS-based Method for Analysis of Dipicolinic Acid and Quantifying Bacterial Endospores in Deep Marine Subsurface Sediment

NASA Astrophysics Data System (ADS)

Fang, J.

2015-12-01

Marine sediments cover more than two-thirds of the Earth's surface and represent a major part of the deep biosphere. Microbial cells and microbial activity appear to be widespread in these sediments. Recently, we reported the isolation of gram-positive anaerobic spore-forming piezophilic bacteria and detection of bacterial endospores in marine subsurface sediment from the Shimokita coalbed, Japan. However, the modern molecular microbiological methods (e.g., DNA-based microbial detection techniques) cannot detect bacterial endospore, because endospores are impermeable and are not stained by fluorescence DNA dyes or by ribosomal RNA staining techniques such as catalysed reporter deposition fluorescence in situ hybridization. Thus, the total microbial cell abundance in the deep biosphere may has been globally underestimated. This emphasizes the need for a new cultivation independent approach for the quantification of bacterial endospores in the deep subsurface. Dipicolinic acid (DPA, pyridine-2,6-dicarboxylic acid) is a universal and specific component of bacterial endospores, representing 5-15wt% of the dry spore, and therefore is a useful indicator and quantifier of bacterial endospores and permits to estimate total spore numbers in the subsurface biosphere. We developed a sensitive analytical method to quantify DPA content in environmental samples using gas chromatography-mass spectrometry. The method is sensitive and more convenient in use than other traditional methods. We applied this method to analyzing sediment samples from the South China Sea (obtained from IODP Exp. 349) to determine the abundance of spore-forming bacteria in the deep marine subsurface sediment. Our results suggest that gram-positive, endospore-forming bacteria may be the "unseen majority" in the deep biosphere.

Watershed scale fungal community characterization along a pH gradient in a subsurface environment co-contaminated with uranium and nitrate

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

Jasrotia, Puja; Green, Stefan; Canion, Andy

2014-01-01

The objective of this study was to characterize fungal communities in a subsurface environment co-contaminated with uranium and nitrate at the watershed scale, and to determine the potential contribution of fungi to contaminant transformation (nitrate attenuation). The abundance, distribution and diversity of fungi in subsurface groundwater samples were determined using quantitative and semi-quantitative molecular techniques, including quantitative PCR of eukaryotic SSU rRNA genes and pyrosequencing of fungal internal transcribed spacer (ITS) regions. Potential bacterial and fungal denitrification was assessed in sediment-groundwater slurries amended with antimicrobial compounds and in fungal pure cultures isolated from subsurface. Our results demonstrate that subsurface fungalmore » communities are dominated by members of the phylum Ascomycota, and a pronounced shift in fungal community composition occurs across the groundwater pH gradient at the field site, with lower diversity observed under acidic (pH < 4.5) conditions. Fungal isolates recovered from subsurface sediments were shown to reduce nitrate to nitrous oxide, including cultures of the genus Coniochaeta that were detected in abundance in pyrosequence libraries of site groundwater samples. Denitrifying fungal isolates recovered from the site were classified, and found to be distributed broadly within the phylum Ascomycota, and within a single genus within the Basidiomycota. Potential denitrification rate assays with sediment-groundwater slurries showed the potential for subsurface fungi to reduce nitrate to nitrous oxide under in situ acidic pH conditions.« less

Watershed-Scale Fungal Community Characterization along a pH Gradient in a Subsurface Environment Cocontaminated with Uranium and Nitrate

PubMed Central

Jasrotia, Puja; Green, Stefan J.; Canion, Andy; Overholt, Will A.; Prakash, Om; Wafula, Denis; Hubbard, Daniela; Watson, David B.; Schadt, Christopher W.; Brooks, Scott C.

2014-01-01

The objective of this study was to characterize fungal communities in a subsurface environment cocontaminated with uranium and nitrate at the watershed scale and to determine the potential contribution of fungi to contaminant transformation (nitrate attenuation). The abundance, distribution, and diversity of fungi in subsurface groundwater samples were determined using quantitative and semiquantitative molecular techniques, including quantitative PCR of eukaryotic small-subunit rRNA genes and pyrosequencing of fungal internal transcribed spacer (ITS) regions. Potential bacterial and fungal denitrification was assessed in sediment-groundwater slurries amended with antimicrobial compounds and in fungal pure cultures isolated from the subsurface. Our results demonstrate that subsurface fungal communities are dominated by members of the phylum Ascomycota, and a pronounced shift in fungal community composition occurs across the groundwater pH gradient at the field site, with lower diversity observed under acidic (pH <4.5) conditions. Fungal isolates recovered from subsurface sediments, including cultures of the genus Coniochaeta, which were detected in abundance in pyrosequence libraries of site groundwater samples, were shown to reduce nitrate to nitrous oxide. Denitrifying fungal isolates recovered from the site were classified and found to be distributed broadly within the phylum Ascomycota and within a single genus of the Basidiomycota. Potential denitrification rate assays with sediment-groundwater slurries showed the potential for subsurface fungi to reduce nitrate to nitrous oxide under in situ acidic pH conditions. PMID:24389927

Conclusions and Recommendations Regarding the Deep Sea Hybrid Power Systems Initial Study

DTIC Science & Technology

2010-06-01

proton-exchange membrane fuel cells ( PEMFC ) powered with hydrogen and oxygen, similar to that used on proven subsurface vessels; (2) fuel-cells...AND STORAGE OPTIONS CONSIDERED FOR INITIAL STUDY NO. NOMENCLATURE DESCRIPTION 1 PWR Nuclear Reactor + Battery 2 FC1 PEMFC + Line for surface O2...Wellhead Gas + Reformer + Battery 3 FC2 PEMFC + Stored O2 + Wellhead Gas + Reformer + Battery 4 SV1 PEMFC + Submersible Vehicle for O2 Transport

Cryogenic Collection of Complete Subsurface Samples for Molecular Biological Analysis

DTIC Science & Technology

2012-05-01

Nitrate was analyzed by ion chromatography ( Dionex IC25) and had a detection limit of 0.01 mg/L. Fluorescein was measured using a flow-through...dissolved oxygen (DO) with a flow through electrode, Nitrate by ion chromatography , and fluorescein with a flow through fluorometer. 1.9 LARGE...measured by headspace gas chromatography (HP 7694 Headspace Sampler attached to an HP 5890 GC with an FID detector). The GC method had a detection

Subsurface damage distribution in the lapping process.

PubMed

Wang, Zhuo; Wu, Yulie; Dai, Yifan; Li, Shengyi

2008-04-01

To systematically investigate the influence of lapping parameters on subsurface damage (SSD) depth and characterize the damage feature comprehensively, maximum depth and distribution of SSD generated in the optical lapping process were measured with the magnetorheological finishing wedge technique. Then, an interaction of adjacent indentations was applied to interpret the generation of maximum depth of SSD. Eventually, the lapping procedure based on the influence of lapping parameters on the material removal rate and SSD depth was proposed to improve the lapping efficiency.

Drogue performance evaluation. Part 1: Data acquisition. [for accurate description of subsurface water circulation

NASA Technical Reports Server (NTRS)

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.

Sedimentary silicon isotope indicates the Kuroshio subsurface upwelling in the East China Sea

NASA Astrophysics Data System (ADS)

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.

Underground Habitats in the Río Tinto Basin: A Model for Subsurface Life Habitats on Mars

NASA Astrophysics Data System (ADS)

Fernández-Remolar, David C.; Prieto-Ballesteros, Olga; Rodríguez, Nuria; Gómez, Felipe; Amils, Ricardo; Gómez-Elvira, Javier; Stoker, Carol R.

2008-10-01

A search for evidence of cryptic life in the subsurface region of a fractured Paleozoic volcanosedimentary deposit near the source waters of the Río Tinto River (Iberian pyrite belt, southwest Spain) was carried out by Mars Astrobiology Research and Technology Experiment (MARTE) project investigators in 2003 and 2004. This conventional deep-drilling experiment is referred to as the MARTE ground truth drilling project. Boreholes were drilled at three sites, and samples from extracted cores were analyzed with light microscopy, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy. Core leachates were analyzed with ion chromatography, and borehole fluids were analyzed with ion and gas chromatography. Key variables of the groundwater system (e.g. , pO2, pH, and salinity) exhibit huge ranges probably due to surficial oxygenation of overall reducing waters, physical mixing of waters, and biologically mediated water-rock interactions. Mineral distribution is mainly driven by the pH of subsurface solutions, which range from highly acidic to neutral. Borehole fluids contain dissolved gases such as CO2, CH4, and H2. SEM-EDS analyses of core samples revealed evidence of microbes attacking pyrite. The Río Tinto alteration mechanisms may be similar to subsurface weathering of the martian crust and provide insights into the possible (bio)geochemical cycles that may have accompanied underground habitats in extensive early Mars volcanic regions and associated sulfide ores.

Underground habitats in the Río Tinto basin: a model for subsurface life habitats on Mars.

PubMed

Fernández-Remolar, David C; Prieto-Ballesteros, Olga; Rodríguez, Nuria; Gómez, Felipe; Amils, Ricardo; Gómez-Elvira, Javier; Stoker, Carol R

2008-10-01

A search for evidence of cryptic life in the subsurface region of a fractured Paleozoic volcanosedimentary deposit near the source waters of the Río Tinto River (Iberian pyrite belt, southwest Spain) was carried out by Mars Astrobiology Research and Technology Experiment (MARTE) project investigators in 2003 and 2004. This conventional deep-drilling experiment is referred to as the MARTE ground truth drilling project. Boreholes were drilled at three sites, and samples from extracted cores were analyzed with light microscopy, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy. Core leachates were analyzed with ion chromatography, and borehole fluids were analyzed with ion and gas chromatography. Key variables of the groundwater system (e.g., pO(2), pH, and salinity) exhibit huge ranges probably due to surficial oxygenation of overall reducing waters, physical mixing of waters, and biologically mediated water-rock interactions. Mineral distribution is mainly driven by the pH of subsurface solutions, which range from highly acidic to neutral. Borehole fluids contain dissolved gases such as CO(2), CH(4), and H(2). SEM-EDS analyses of core samples revealed evidence of microbes attacking pyrite. The Río Tinto alteration mechanisms may be similar to subsurface weathering of the martian crust and provide insights into the possible (bio)geochemical cycles that may have accompanied underground habitats in extensive early Mars volcanic regions and associated sulfide ores.

Fate of leaf litter deposits and impacts on oxygen availability in bank filtration column studies.

PubMed

Bayarsaikhan, Uranchimeg; Filter, Josefine; Gernert, Ulrich; Jekel, Martin; Ruhl, Aki Sebastian

2018-07-01

Degradation of particulate organic carbon (POC) such as leaf litter might deplete dissolved oxygen within the upper layers of bank filtration, an efficient and robust barrier for pathogens and for various organic micro-pollutants (OMP) in water supply systems worldwide. The degradation of OMP during bank filtration depends on the redox conditions. The present study aimed at identifying the impacts and fates of different local leaves on the oxygen consumption and the possible biological degradation of indicator OMP. Oxygen concentrations initially decreased within the columns from around 8 mg/L in the influent to low concentrations indicating extensive consumption within a short travel distance. Still a substantial oxygen consumption was observed after 250 days. OMP concentrations were not significantly affected by the microbial processes. A layer of calcium carbonate crystallites was observed on the POC layer. Some leaf fragments appeared to be persistant towards degradation and the carbon content relative to nitrogen and sulfur contents decreased within 250 days. The results demonstrate that trees at bank filtration sites might have a strong long-term impact on the subsurface redox conditions. Copyright © 2018 Elsevier Inc. All rights reserved.

Investigation of the sensitivity of a cross-polarized light visualization system to detect subclinical erythema and dryness in women with vulvovaginitis.

PubMed

Farage, Miranda A; Singh, Mukul; Ledger, William J

2009-07-01

An enhanced visualization technique using polarized light (Syris v600 enhanced visualization system; Syris Scientific LLC, Gray, ME) detects surface and subsurface ( approximately 1 mm depth) inflammation. We sought to compare the Syris v600 system with unaided visual inspection and colposcopy of the female genitalia. Erythema and dryness of the vulva, introitus, vagina, and cervix were visualized and scored by each method in patients with and without vulvitis. Subsurface visualization was more sensitive in detecting genital erythema and dryness at all sites whether or not symptoms were present. Subsurface inflammation of the introitus, vagina, and cervix only was detected uniquely in women with vulvar vestibulitis syndrome (VVS). A subset of women presenting with VVS exhibited subclinical inflammation of the vulva vestibule and vagina (designated VVS/lichen sclerosus subgroup). Enhanced visualization of the genital epithelial subsurface with cross-polarized light may assist in diagnosing subclinical inflammation in vulvar conditions heretofore characterized as sensory syndromes.

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

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

Levander, Alan Richard; Zelt, Colin A.

2015-03-17

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

A locally conservative stabilized continuous Galerkin finite element method for two-phase flow in poroelastic subsurfaces

NASA Astrophysics Data System (ADS)

Deng, Q.; Ginting, V.; McCaskill, B.; Torsu, P.

2017-10-01

We study the application of a stabilized continuous Galerkin finite element method (CGFEM) in the simulation of multiphase flow in poroelastic subsurfaces. The system involves a nonlinear coupling between the fluid pressure, subsurface's deformation, and the fluid phase saturation, and as such, we represent this coupling through an iterative procedure. Spatial discretization of the poroelastic system employs the standard linear finite element in combination with a numerical diffusion term to maintain stability of the algebraic system. Furthermore, direct calculation of the normal velocities from pressure and deformation does not entail a locally conservative field. To alleviate this drawback, we propose an element based post-processing technique through which local conservation can be established. The performance of the method is validated through several examples illustrating the convergence of the method, the effectivity of the stabilization term, and the ability to achieve locally conservative normal velocities. Finally, the efficacy of the method is demonstrated through simulations of realistic multiphase flow in poroelastic subsurfaces.

Using electrokinetic phenomena and electrical resistance tomography to characterize the movement of subsurface fluids

DOEpatents

Ramirez, Abelardo L.; Cooper, John F.; Daily, William D.

1996-01-01

This invention relates generally to the remote detections of subsurface liquid contaminants using in combination a geophysical technique known as ERT and an EKS. Electrokinetic transport is used to enhance the ability of electrical resistance tomography (ERT) to detect position and movement of subsurface contaminant liquids, particles or ions. ERT images alone are difficult to interpret because of natural inhomogeneities in soil composition and electrical properties. By subtracting two or more ERT images obtained before and after field induced movement, a high contrast image of a plume of distinct electrokinetic properties can be seen. The invention is applicable to important subsurface characterization problems including, as examples, (1) detection of liquid-saturated plumes of contaminants such as those associated with leaks from underground storage tanks containing hazardous concentrated electrolytes, (2) detection and characterization of soils contaminated with organic pollutants such as droplets of gasoline; and (3) monitoring the progress of electrokinetic containment or clean up of underground contamination.

Using electrokinetic phenomena and electrical resistance tomography to characterize the movement of subsurface fluids

DOEpatents

Ramirez, A.L.; Cooper, J.F.; Daily, W.D.

1996-02-27

This invention relates generally to the remote detections of subsurface liquid contaminants using in combination a geophysical technique known as ERT and an EKS. Electrokinetic transport is used to enhance the ability of electrical resistance tomography (ERT) to detect position and movement of subsurface contaminant liquids, particles or ions. ERT images alone are difficult to interpret because of natural inhomogeneities in soil composition and electrical properties. By subtracting two or more ERT images obtained before and after field induced movement, a high contrast image of a plume of distinct electrokinetic properties can be seen. The invention is applicable to important subsurface characterization problems including, as examples, (1) detection of liquid-saturated plumes of contaminants such as those associated with leaks from underground storage tanks containing hazardous concentrated electrolytes, (2) detection and characterization of soils contaminated with organic pollutants such as droplets of gasoline; and (3) monitoring the progress of electrokinetic containment or clean up of underground contamination. 1 fig.

Geophysical characterization of the role of fault and fracture systems for recharging groundwater aquifers from surface water of Lake Nasser

NASA Astrophysics Data System (ADS)

Mansour, Khamis; Omar, Khaled; Ali, Kamal; Abdel Zaher, Mohamed

2018-06-01

The role of the fracture system is important for enhancing the recharge or discharge of fluids in the subsurface reservoir. The Lake Nasser is consider one of the largest artificial lakes all over the world and contains huge bulk of storage water. In this study, the influence of fracture zones on subsurface fluid flow in groundwater reservoirs is investigated using geophysical techniques including seismicity, geoelectric and gravity data. These data have been utilized for exploring structural structure in south west Lake Nasser, and subsurface discontinuities (joints or faults) notwithstanding its related fracture systems. Seismicity investigation gave us the comprehension of the dynamic geological structure sets and proposing the main recharging paths for the Nubian aquifer from Lake Nasser surface water. Processing and modelling of aerogravity data show that the greater thickness of sedimentary cover (700 m) is located eastward and northward while basement outcrops occur at Umm Shaghir and Al Asr areas. Sixty-nine vertical electrical soundings (VES's) were used to delineate the subsurface geoelectric layers along eight profiles that help to realize the subsurface geological structure behind the hydrogeological conditions of the studied area.

Investigation of tunneling current and local contact potential difference on the TiO2(110) surface by AFM/KPFM at 78 K.

PubMed

Wen, Huan Fei; Li, Yan Jun; Arima, Eiji; Naitoh, Yoshitaka; Sugawara, Yasuhiro; Xu, Rui; Cheng, Zhi Hai

2017-03-10

We propose a new multi-image method for obtaining the frequency shift, tunneling current and local contact potential difference (LCPD) on a TiO 2 (110) surface with atomic resolution. The tunneling current image reveals rarely observed surface oxygen atoms contrary to the conventional results. We analyze how the surface and subsurface defects affect the distribution of the LCPD. In addition, the subsurface defects are observed clearly in the tunneling current image, in contrast to a topographic image. To clarify the origin of the atomic contrast, we perform site-dependent spectroscopy as a function of the tip-sample distance. The multi-image method is expected to be widely used to investigate the charge transfer phenomena between the nanoparticles and surface sites, and it is useful for elucidating the mechanisms of catalytic reactions.

Eukaryotic opportunists dominate the deep-subsurface biosphere in South Africa

PubMed Central

Borgonie, G.; Linage-Alvarez, B.; Ojo, A. O.; Mundle, S.O.C.; Freese, L B.; Van Rooyen, C.; Kuloyo, O.; Albertyn, J.; Pohl, C.; Cason, E. D.; Vermeulen, J.; Pienaar, C.; Litthauer, D.; Van Niekerk, H.; Van Eeden, J.; Lollar, B. Sherwood.; Onstott, T. C.; Van Heerden, E.

2015-01-01

Following the discovery of the first Eukarya in the deep subsurface, intense interest has developed to understand the diversity of eukaryotes living in these extreme environments. We identified that Platyhelminthes, Rotifera, Annelida and Arthropoda are thriving at 1.4 km depths in palaeometeoric fissure water up to 12,300 yr old in South African mines. Protozoa and Fungi have also been identified; however, they are present in low numbers. Characterization of the different species reveals that many are opportunistic organisms with an origin due to recharge from surface waters rather than soil leaching. This is the first known study to demonstrate the in situ distribution of biofilms on fissure rock faces using video documentation. Calculations suggest that food, not dissolved oxygen is the limiting factor for eukaryal population growth. The discovery of a group of Eukarya underground has important implications for the search for life on other planets in our solar system. PMID:26597082

Eukaryotic opportunists dominate the deep-subsurface biosphere in South Africa.

PubMed

Borgonie, G; Linage-Alvarez, B; Ojo, A O; Mundle, S O C; Freese, L B; Van Rooyen, C; Kuloyo, O; Albertyn, J; Pohl, C; Cason, E D; Vermeulen, J; Pienaar, C; Litthauer, D; Van Niekerk, H; Van Eeden, J; Sherwood Lollar, B; Onstott, T C; Van Heerden, E

2015-11-24

Following the discovery of the first Eukarya in the deep subsurface, intense interest has developed to understand the diversity of eukaryotes living in these extreme environments. We identified that Platyhelminthes, Rotifera, Annelida and Arthropoda are thriving at 1.4 km depths in palaeometeoric fissure water up to 12,300 yr old in South African mines. Protozoa and Fungi have also been identified; however, they are present in low numbers. Characterization of the different species reveals that many are opportunistic organisms with an origin due to recharge from surface waters rather than soil leaching. This is the first known study to demonstrate the in situ distribution of biofilms on fissure rock faces using video documentation. Calculations suggest that food, not dissolved oxygen is the limiting factor for eukaryal population growth. The discovery of a group of Eukarya underground has important implications for the search for life on other planets in our solar system.

Subscale Validation of the Subsurface Active Filtration of Exhaust (SAFE) Approach to the NTP Ground Testing

NASA Technical Reports Server (NTRS)

Marshall, William M.; Borowski, Stanley K.; Bulman, Mel; Joyner, Russell; Martin, Charles R.

2015-01-01

Nuclear thermal propulsion (NTP) has been recognized as an enabling technology for missions to Mars and beyond. However, one of the key challenges of developing a nuclear thermal rocket is conducting verification and development tests on the ground. A number of ground test options are presented, with the Sub-surface Active Filtration of Exhaust (SAFE) method identified as a preferred path forward for the NTP program. The SAFE concept utilizes the natural soil characteristics present at the Nevada National Security Site to provide a natural filter for nuclear rocket exhaust during ground testing. A validation method of the SAFE concept is presented, utilizing a non-nuclear sub-scale hydrogen/oxygen rocket seeded with detectible radioisotopes. Additionally, some alternative ground test concepts, based upon the SAFE concept, are presented. Finally, an overview of the ongoing discussions of developing a ground test campaign are presented.

The atomic level structure of the TiO(2)-NiTi interface.

PubMed

Nolan, M; Tofail, S A M

2010-09-07

The biocompatibility of NiTi shape memory alloys (SMA) has made possible applications in invasive and minimally invasive biomedical devices. The NiTi intermetallic alloy spontaneously forms a thin passive layer of TiO(2), which provides its biocompatibility. The oxide layer is thought to form as Ti in the alloy reacts with oxygen. In this paper, we study the details of the oxide-alloy interface. The atomic model is the (110) NiTi surface interfaced with the (100) rutile TiO(2) surface; this combination provides the best lattice match of alloy and oxide. When the interface forms, static minimisations and molecular dynamics show that there is no migration of atoms between the alloy and the oxide. In the alloy there are some notable structural relaxations. We find that a columnar structure appears in which alternating long and short Ni-Ti bonds are present in each surface and subsurface plane into the fourth subsurface layer. The oxide undergoes some structural changes as a result of terminal oxygen coordinating to Ti in the NiTi surface. The electronic structure shows that Ti(3+) species are present at the interface, with Ti(4+) in the bulk of the oxide layer and that the metallic character of the alloy is unaffected by the interaction with oxygen, all of which is consistent with experiment. A thermodynamic analysis is used to examine the stability of different possible structures-a perfect interface and one with Ti and O vacancies. We find that under conditions typical of oxidation and shape memory treatments, the most stable interface structure is that with Ti vacancies in the alloy surface, leaving an Ni-rich layer, consistent with the experimental findings for this interface.

Respiratory Pathways Reconstructed by Multi-Omics Analysis in Melioribacter roseus, Residing in a Deep Thermal Aquifer of the West-Siberian Megabasin

PubMed Central

Gavrilov, Sergey; Podosokorskaya, Olga; Alexeev, Dmitry; Merkel, Alexander; Khomyakova, Maria; Muntyan, Maria; Altukhov, Ilya; Butenko, Ivan; Bonch-Osmolovskaya, Elizaveta; Govorun, Vadim; Kublanov, Ilya

2017-01-01

Melioribacter roseus, a representative of recently proposed Ignavibacteriae phylum, is a metabolically versatile thermophilic bacterium, inhabiting subsurface biosphere of the West-Siberian megabasin and capable of growing on various substrates and electron acceptors. Genomic analysis followed by inhibitor studies and membrane potential measurements of aerobically grown M. roseus cells revealed the activity of aerobic respiratory electron transfer chain comprised of respiratory complexes I and IV, and an alternative complex III. Phylogeny reconstruction revealed that oxygen reductases belonged to atypical cc(o/b)o3-type and canonical cbb3–type cytochrome oxidases. Also, two molybdoenzymes of M. roseus were affiliated either with Ttr or Psr/Phs clades, but not with typical respiratory arsenate reductases of the Arr clade. Expression profiling, both at transcripts and protein level, allowed us to assign the role of the terminal respiratory oxidase under atmospheric oxygen concentration for the cc(o/b)o3 cytochrome oxidase, previously proposed to serve for oxygen detoxification only. Transcriptomic analysis revealed the involvement of both molybdoenzymes of M. roseus in As(V) respiration, yet differences in the genomic context of their gene clusters allow to hypothesize about their distinct roles in arsenate metabolism with the ‘Psr/Phs’-type molybdoenzyme being the most probable candidate respiratory arsenate reductase. Basing on multi-omics data, the pathways for aerobic and arsenate respiration were proposed. Our results start to bridge the vigorously increasing gap between homology-based predictions and experimentally verified metabolic processes, what is especially important for understudied microorganisms of novel lineages from deep subsurface environments of Eurasia, which remained separated from the rest of the biosphere for several geological periods. PMID:28713355

Using rates of oxygen and nitrate reduction to map the subsurface distribution of groundwater denitrification

NASA Astrophysics Data System (ADS)

Kolbe, T.; De Dreuzy, J. R.; Abbott, B. W.; Aquilina, L.; Babey, T.; Green, C. T.; Fleckenstein, J. H.; Labasque, T.; Laverman, A.; Marçais, J.; Peiffer, S.; Thomas, Z.; Pinay, G.

2017-12-01

Widespread fertilizer application over the last 70 years has caused serious ecological and socioeconomic problems in aquatic and estuarine ecosystems. When surplus nitrogen leaches as nitrate (a major groundwater pollutant) to the aquifer, complex flow dynamics and naturally occurring degradation processes control its transport. Under the conditions of depleted oxygen and abundant electron donors, microorganisms reduce NO3- to N2 (denitrification). Denitrification rates vary over orders of magnitude among sites within the same aquifer, complicating estimation of denitrification capacity at the catchment scale. Because it is impractical or impossible to access the subsurface to directly quantify denitrification rates, reactivity is often assumed to occur continuous along flowlines, potentially resulting in substantial over- or underestimation of denitrification. Here we investigated denitrification in an unconfined crystalline aquifer in western France using a combination of common tracers (chlorofluorocarbons, O2, NO3-, and N2) measured in 16 wells to inform a time-based modeling approach. We found that spatially variable denitrification rates arise from the intersection of nitrate rich water with reactive zones defined by the abundance of electron donors (primarily pyrite). Furthermore, based on observed reaction rates of the sequential reduction of oxygen and nitrate, we present a general framework to estimate the location and intensity of the reactive zone in aquifers. Accounting for the vertical distribution of reaction rates results in large differences in estimations of net denitrification rates that assume homogeneous reactivity. This new framework provides a tractable approach for quantifying catchment and regional groundwater denitrification rates that could be used to improve estimation of groundwater resilience to nitrate pollution and develop more realistic management strategies.

Nitrogen fixation in denitrified marine waters.

PubMed

Fernandez, Camila; Farías, Laura; Ulloa, Osvaldo

2011-01-01

Nitrogen fixation is an essential process that biologically transforms atmospheric dinitrogen gas to ammonia, therefore compensating for nitrogen losses occurring via denitrification and anammox. Currently, inputs and losses of nitrogen to the ocean resulting from these processes are thought to be spatially separated: nitrogen fixation takes place primarily in open ocean environments (mainly through diazotrophic cyanobacteria), whereas nitrogen losses occur in oxygen-depleted intermediate waters and sediments (mostly via denitrifying and anammox bacteria). Here we report on rates of nitrogen fixation obtained during two oceanographic cruises in 2005 and 2007 in the eastern tropical South Pacific (ETSP), a region characterized by the presence of coastal upwelling and a major permanent oxygen minimum zone (OMZ). Our results show significant rates of nitrogen fixation in the water column; however, integrated rates from the surface down to 120 m varied by ∼30 fold between cruises (7.5±4.6 versus 190±82.3 µmol m(-2) d(-1)). Moreover, rates were measured down to 400 m depth in 2007, indicating that the contribution to the integrated rates of the subsurface oxygen-deficient layer was ∼5 times higher (574±294 µmol m(-2) d(-1)) than the oxic euphotic layer (48±68 µmol m(-2) d(-1)). Concurrent molecular measurements detected the dinitrogenase reductase gene nifH in surface and subsurface waters. Phylogenetic analysis of the nifH sequences showed the presence of a diverse diazotrophic community at the time of the highest measured nitrogen fixation rates. Our results thus demonstrate the occurrence of nitrogen fixation in nutrient-rich coastal upwelling systems and, importantly, within the underlying OMZ. They also suggest that nitrogen fixation is a widespread process that can sporadically provide a supplementary source of fixed nitrogen in these regions.

Effects of seasonal anoxia on the distribution of phosphorus fractions in the surface sediments of southeastern Arabian Sea shelf

NASA Astrophysics Data System (ADS)

Sudheesh, V.; Movitha, M.; Hatha, A. A. Mohamed; Renjith, K. R.; Resmi, P.; Rahiman, Mujeeb; Nair, S. M.

2017-11-01

The seasonal upwelling along the southeastern Arabian Sea (SEAS) brings cold, nutrient-rich low oxygen subsurface water to the continental shelf. The subsurface oxygen deficiency due to upwelling is severe in some years, the intensity of which could profoundly influence the nutrient cycling along the SEAS. Herein, we studied the effect of seasonal anoxia on fractionation of phosphorus during the peak upwelling period of August 2013. Abundance of five fractions of phosphorus (P), namely exchangeable or loosely sorbed P (Pads), iron-bound P (PFe), authigenic P (Paut), detrital apatite plus other inorganic P (Pdet) and organic P (Porg), in surface sediments of SEAS shelf has been studied using a sequential extraction procedure (SEDEX) to examine their distributions and sources. Total P (TP) concentrations ranged from 209 to 1081 μg g-1 with an average of 508 ± 256 μg g-1. Among the five P fractions, the authigenic P was the dominant species, representing about 60% of TP. The relative abundance of P fractions was in the order: Paut>Pdet>Porg>PFe> Pads. Multivariate analyses revealed that the P fractions were primarily associated with the organic constituents and fine sediments. The hypoxic bottom condition associated with summer monsoon upwelling significantly reduced the concentrations of PFe, Pads and Porg in the surface sediments. The enhanced release of organic bound and iron oxides bound P under low oxygen condition was evident from the enhanced C/P and N/P ratios and lower C/N ratio in the sediments. The intense biomineralization of organic matter and reduction of Fe-Mn oxides due to the periodic anoxia resulted in the transformations of their associated P fractions and enhanced accumulation as authigenic calcium phosphate mineral.

Image-based overlay and alignment metrology through optically opaque media with sub-surface probe microscopy

NASA Astrophysics Data System (ADS)

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.

Potential and timescales for oxygen depletion in coastal upwelling systems: A box-model analysis

NASA Astrophysics Data System (ADS)

Harrison, C. S.; Hales, B.; Siedlecki, S.; Samelson, R. M.

2016-05-01

A simple box model is used to examine oxygen depletion in an idealized ocean-margin upwelling system. Near-bottom oxygen depletion is controlled by a competition between flushing with oxygenated offshore source waters and respiration of particulate organic matter produced near the surface and retained near the bottom. Upwelling-supplied nutrients are consumed in the surface box, and some surface particles sink to the bottom where they respire, consuming oxygen. Steady states characterize the potential for hypoxic near-bottom oxygen depletion; this potential is greatest for faster sinking rates, and largely independent of production timescales except in that faster production allows faster sinking. Timescales for oxygen depletion depend on upwelling and productivity differently, however, as oxygen depletion can only be reached in meaningfully short times when productivity is rapid. Hypoxia thus requires fast production, to capture upwelled nutrients, and fast sinking, to deliver the respiration potential to model bottom waters. Combining timescales allows generalizations about tendencies toward hypoxia. If timescales of sinking are comparable to or smaller than the sum of those for respiration and flushing, the steady state will generally be hypoxic, and results indicate optimal timescales and conditions exist to generate hypoxia. For example, the timescale for approach to hypoxia lengthens with stronger upwelling, since surface particle and nutrient are shunted off-shelf, in turn reducing subsurface respiration and oxygen depletion. This suggests that if upwelling winds intensify with climate change the increased forcing could offer mitigation of coastal hypoxia, even as the oxygen levels in upwelled source waters decline.

Acetate: A better astrobiological indicator of life than methane?

NASA Astrophysics Data System (ADS)

Kanik, I.; Russell, M. J.; Hodyss, R. P.; Johnson, P. V.

2009-12-01

The emergence of life on the ocean floor of the early Earth has implications for life detection on other rocky planetary bodies having subsurface ocean or ground waters in our solar system. At bottom life hydrogenates carbon dioxide. This is true not only of oxygenic photosynthesis—a relatively late evolutionary invention—but also of autotrophic chemosynthesizers such as the acetogenic bacteria and the methanoarchaea; respectively probably the first and second organisms to have emerged on Earth. Both of these prokaryotes use the acetyl coenzyme-a pathway for biosynthesis, though the variant leading to methanogenesis is substantially more complicated and therefore more highly evolved. Yet serpentinization and volcanism can produce methane with facility—an ambiguity that confounds life detection. In contrast, hydrothermal vent experiments to date along with hot spring analyses have indicated that no significant concentrations of abiotic acetate were produced in spite of the simplicity of the biological pathway. It seems that the geochemical conditions that generate abiotic methane are generally too reducing to produce acetate. Thus, the generation of acetate is solely a biotic process. As there is every reason to believe that the same chemical and electrochemical tensions would occur on other wet rocky planets containing subsurface ocean or ground waters. This encourages us to look into chemical and spectroscopic methods of detecting of acetate (both remotely and in situ) which is a better indicator than methane for the past or present biological activity on planetary bodies such as Mars. We, at the Jet Propulsion Laboratory, have designed laboratory experiments to investigate the feasibility of detecting acetate using conventional chemical and spectroscopic methods. The results and applicability of these techniques for the future astrobiology missions will be discussed.

The efficacy of techniques for the disinfection of artificial sub-surface dentinal caries lesions and their effect on demineralization and remineralization in vitro.

PubMed

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.

Optimal Electromagnetic (EM) Geophysical Techniques to Map the Concentration of Subsurface Ice and Adsorbed Water on Mars and the Moon

NASA Astrophysics Data System (ADS)

Stillman, D. E.; Grimm, R. E.

2013-12-01

Water ice is ubiquitous in our Solar System and is a probable target for planetary exploration. Mapping the lateral and vertical concentration of subsurface ice from or near the surface could determine the origin of lunar and martian ice and quantify a much-needed resource for human exploration. Determining subsurface ice concentration on Earth is not trivial and has been attempted previously with electrical resistivity tomography (ERT), ground penetrating radar (GPR), airborne EM (AEM), and nuclear magnetic resonance (NMR). These EM geophysical techniques do not actually detect ice, but rather the absence of unfrozen water. This causes a non-unique interpretation of frozen and dry subsurface sediments. This works well in the arctic because most locations are not dry. However, for planetary exploration, liquid water is exceedingly rare and subsurface mapping must discriminate between an ice-rich and a dry subsurface. Luckily, nature has provided a unique electrical signature of ice: its dielectric relaxation. The dielectric relaxation of ice creates a temperature and frequency dependence of the electrical properties and varies the relative dielectric permittivity from ~3.1 at radar frequencies to >100 at low frequencies. On Mars, sediments smaller than silt size can hold enough adsorbed unfrozen water to complicate the measurement. This is because the presence of absorbed water also creates frequency-dependent electrical properties. The dielectric relaxation of adsorbed water and ice can be separated as they have different shapes and frequency ranges as long as a spectrum spanning the two relaxations is measured. The volume concentration of ice and adsorbed water is a function of the strength of their relaxations. Therefore, we suggest that capacitively-coupled dielectric spectroscopy (a.k.a. spectral induced polarization or complex resistivity) can detect the concentration of both ice and adsorbed water in the subsurface. To prove this concept we have collected dielectric spectroscopy at the Cold Regions Research and Engineering Laboratory (CRREL) permafrost tunnel in Fox, AK. We were able to detect the ice relaxation in the subsurface despite the considerable amount of subsurface unfrozen water due to the presence of montmorillonite clay and much warmer temperatures than Mars or permanently shadowed regions of the Moon. While dielectric spectroscopy can be used to determine ice and adsorbed water content it does not possess the high resolution mapping capability of a GPR. Moreover, GPR cannot detect subsurface ice content in ice-sediment mixtures as evidenced in the interpretation of the Medusae Fossae Formation. Orbital radar surveys show this unit has a low attenuation and a dielectric permittivity near 4. This allows the formation to be interpreted as ice-rich or a dry high-porosity volcanic tuff unit. Therefore, combining GPR and dielectric spectroscopy will enable high-resolution structural and volatile mapping of the subsurface. Furthermore, the addition of neutron spectroscopy would add total hydrogen abundance in the top meter. This could lead to the determination of how much hydrogen resides in ice, adsorbed water, and minerals.

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

Verbiest, G. J., E-mail: Verbiest@physik.rwth-aachen.de; Zalm, D. J. van der; Oosterkamp, T. H.

The application of ultrasound in an Atomic Force Microscope (AFM) gives access to subsurface information. However, no commercially AFM exists that is equipped with this technique. The main problems are the electronic crosstalk in the AFM setup and the insufficiently strong excitation of the cantilever at ultrasonic (MHz) frequencies. In this paper, we describe the development of an add-on that provides a solution to these problems by using a special piezo element with a lowest resonance frequency of 2.5 MHz and by separating the electronic connection for this high frequency piezo element from all other connections. In this sense, wemore » support researches with the possibility to perform subsurface measurements with their existing AFMs and hopefully pave also the way for the development of a commercial AFM that is capable of imaging subsurface features with nanometer resolution.« less

Comparison of multispectral remote-sensing techniques for monitoring subsurface drain conditions. [Imperial Valley, California

NASA Technical Reports Server (NTRS)

Goettelman, R. C.; Grass, L. B.; Millard, J. P.; Nixon, P. R.

1983-01-01

The following multispectral remote-sensing techniques were compared to determine the most suitable method for routinely monitoring agricultural subsurface drain conditions: airborne scanning, covering the visible through thermal-infrared (IR) portions of the spectrum; color-IR photography; and natural-color photography. Color-IR photography was determined to be the best approach, from the standpoint of both cost and information content. Aerial monitoring of drain conditions for early warning of tile malfunction appears practical. With careful selection of season and rain-induced soil-moisture conditions, extensive regional surveys are possible. Certain locations, such as the Imperial Valley, Calif., are precluded from regional monitoring because of year-round crop rotations and soil stratification conditions. Here, farms with similar crops could time local coverage for bare-field and saturated-soil conditions.

Study of the Vibrational Modes of Subsurface Oxygen on Al (111) Using Diode Laser Infrared Reflection-Absorption Spectroscopy.

DTIC Science & Technology

1987-10-15

apparent shift of this band to higher energy with increasing coverage, observed at lower resolution (but higher sensitivity) in electron energy loss...apparent shift of this band to higher energy with increasing coverage, observed at lower resolution (but higher sen- sitivity) in electron energy ...11 using high-resolution electron energy -loss spectroscopy (EELS), is especially intriguing. 02 dissociates on this surface to populate two types of

Characteristics of Nitrogen Loss through Surface-Subsurface Flow on Red Soil Slopes of Southeast China

NASA Astrophysics Data System (ADS)

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.

Comparative quantification of oxygen release by wetland plants: electrode technique and oxygen consumption model.

PubMed

Wu, Haiming; Liu, Jufeng; Zhang, Jian; Li, Cong; Fan, Jinlin; Xu, Xiaoli

2014-01-01

Understanding oxygen release by plants is important to the design of constructed wetlands for wastewater treatment. Lab-scale systems planted with Phragmites australis were studied to evaluate the amount of oxygen release by plants using electrode techniques and oxygen consumption model. Oxygen release rate (0.14 g O2/m(2)/day) measured using electrode techniques was much lower than that (3.94-25.20 gO2/m(2)/day) calculated using the oxygen consumption model. The results revealed that oxygen release by plants was significantly influenced by the oxygen demand for the degradation of pollutants, and the oxygen release rate increased with the rising of the concentration of degradable materials in the solution. The summary of the methods in qualifying oxygen release by wetland plants demonstrated that variations existed among different measuring methods and even in the same measuring approach. The results would be helpful for understanding the contribution of plants in constructed wetlands toward actual wastewater treatment.

AN EXPERIMENTAL ASSESSMENT OF THE IMPACTS OF PARTIAL DNAPL SOURCE ZONE DELETION USING SPARGING AS A REMEDIATION TECHNIQUE

EPA Science Inventory

The contamination of the subsurface environment by dense non-aqueous phase liquids (DNAPL) is a wide-spread problem that poses a significant threat to soil and groundwater quality. Implementing different remediation techniques can lead to the removal of a high fraction of the DNA...

Improved Pseudo-section Representation for CSAMT Data in Geothermal Exploration

NASA Astrophysics Data System (ADS)

Grandis, Hendra; Sumintadireja, Prihadi

2017-04-01

Controlled-Source Audio-frequency Magnetotellurics (CSAMT) is a frequency domain sounding technique employing typically a grounded electric dipole as the primary electromagnetic (EM) source to infer the subsurface resistivity distribution. The use of an artificial source provides coherent signals with higher signal-to-noise ratio and overcomes the problems with randomness and fluctuation of the natural EM fields used in MT. However, being an extension of MT, the CSAMT data still uses apparent resistivity and phase for data representation. The finite transmitter-receiver distance in CSAMT leads to a somewhat “distorted” response of the subsurface compared to MT data. We propose a simple technique to present CSAMT data as an apparent resistivity pseudo-section with more meaningful information for qualitative interpretation. Tests with synthetic and field CSAMT data showed that the simple technique is valid only for sounding curves exhibiting a transition from high - low - high resistivity (i.e. H-type) prevailing in data from a geothermal prospect. For quantitative interpretation, we recommend the use of the full-solution of CSAMT modelling since our technique is not valid for more general cases.

Subsurface Growth Of Silicide Structures In Silicon

NASA Technical Reports Server (NTRS)

Fathauer, Robert W.; George, Thomas; Pike, William T.; Schowalter, Leo

1993-01-01

Technique shows promise for fabrication of novel electronic, optoelectronic, and electro-optical devices. Experiments demonstrated feasibility of growing microscopic single-crystal CoSi2 structures beneath surfaces of Si substrates.

Integrated geophysical methods for geotechnical subsurface investigations : final report.

DOT National Transportation Integrated Search

2006-01-01

This report summarizes the New Hampshire Department of Transportations (NHDOTs) investigation of : geophysical techniques to supplement conventional test borings and other explorations on transportation projects. : The Departments geotechnic...

Non-local drivers of the summer hypoxia in the East China Sea off the Changjiang Estuary

NASA Astrophysics Data System (ADS)

Qian, Wei; Dai, Minhan; Xu, Min; Kao, Shuh-ji; Du, Chuanjun; Liu, Jinwen; Wang, Hongjie; Guo, Liguo; Wang, Lifang

2017-11-01

The East China Sea (ECS) off the Changjiang (Yangtze River) Estuary, located around the near field of the Changjiang plume (CJP) is a hot spot where phytoplankton blooms in the surface water and hypoxias in the subsurface/bottom waters are frequently observed. Based on field observations conducted in summer 2009 and 2011, we examined non-local drivers associated with the initial dissolved oxygen (DO) levels that had significant impact on the development of summer hypoxias in the ECS off the Changjiang Estuary. The bottom water mass therein could be traced isopycnally at 24.2 < σθ < 25.2 back to the vicinity of the Luzon Strait, ∼1300 km upstream, where subsurface Kuroshio water (∼220 m deep with ∼190 μmol DO kg-1) mixed with the South China Sea subsurface water (∼120 m deep with ∼130 μmol DO kg-1). Owing to the difference in DO of these two source water masses, their mixing ratio ultimately determined the initial DO supply to the ECS bottom water that eventually reached the hypoxic zone. This water mass mixture was also subject to biogeochemical alteration during its travel (∼60 days) after it intruded into the ECS at the northeastern tip of Taiwan. Along the pathway of the intruded bottom-hugging water, we found systematic increases in nutrient concentrations and apparent oxygen utilization, or drawdown in DO following Redfield stoichiometry as a result of marine organic matter decomposition. These non-local factors exerted a synergistic control on the initial DO of CJP bottom water promoting hypoxia formation, although the residence time of the CJP bottom water was relatively short (∼11 days). We contend that such far field drivers should be taken into account in order to better predict the future scenarios of coastal hypoxias in the context of global warming.

Spatially resolved, diffuse reflectance imaging for subsurface pattern visualization toward development of a lensless imaging platform: phantom experiments

NASA Astrophysics Data System (ADS)

Schelkanova, Irina; Pandya, Aditya; Saiko, Guennadi; Nacy, Lidia; Babar, Hannan; Shah, Duoaud; Lilge, Lothar; Douplik, Alexandre

2016-01-01

A portable, spatially resolved, diffuse reflectance lensless imaging technique based on the charge-coupled device or complementary metal-oxide semiconductor sensor directly coupled to the fiber optic bundle is proposed for visualization of subsurface structures such as superficial microvasculature in the epithelium. We discuss an experimental method for emulating a lensless imaging setup via raster scanning a single fiber-optic cable over a microfluidic phantom containing periodic hemoglobin absorption contrast. To evaluate the ability of the technique to recover information about the subsurface linear structures, scattering layers formed of the Sylgard® 184 Silicone Elastomer and titanium dioxide were placed atop the microfluidic phantom. Thickness of the layers ranged from 0.2 to 0.7 mm, and the values of the reduced scattering coefficient (μs‧) were between 0.85 and 4.25 mm-1. The results demonstrate that fiber-optic, lensless platform can be used for two-dimensional imaging of absorbing inclusions in diffuse reflectance mode. In these experiments, it was shown that diffuse reflectance imaging can provide sufficient spatial sampling of the phantom for differentiation of 30 μm structural features of the embedded absorbing pattern inside the scattering media.

Data Processing Methods for 3D Seismic Imaging of Subsurface Volcanoes: Applications to the Tarim Flood Basalt.

PubMed

Wang, Lei; Tian, Wei; Shi, Yongmin

2017-08-07

The morphology and structure of plumbing systems can provide key information on the eruption rate and style of basalt lava fields. The most powerful way to study subsurface geo-bodies is to use industrial 3D reflection seismological imaging. However, strategies to image subsurface volcanoes are very different from that of oil and gas reservoirs. In this study, we process seismic data cubes from the Northern Tarim Basin, China, to illustrate how to visualize sills through opacity rendering techniques and how to image the conduits by time-slicing. In the first case, we isolated probes by the seismic horizons marking the contacts between sills and encasing strata, applying opacity rendering techniques to extract sills from the seismic cube. The resulting detailed sill morphology shows that the flow direction is from the dome center to the rim. In the second seismic cube, we use time-slices to image the conduits, which corresponds to marked discontinuities within the encasing rocks. A set of time-slices obtained at different depths show that the Tarim flood basalts erupted from central volcanoes, fed by separate pipe-like conduits.

Landfill disposal systems.

PubMed

Slimak, K M

1978-12-01

The current status of landfill disposal of hazardous wastes in the United States is indicated by presenting descriptions of six operating landfills. These landfills illustrate the variety of techniques that exist in landfill disposal of hazardous wastes. Although some landfills more effectively isolate hazardous waste than others, all landfills must deal with the following problems. Leachate from hazardous waste landfills is generally highly polluted. Most landfills attempt to contain leachate at the site and prevent its discharge to surface or groundwaters. To retain leachate within a disposal area, subsurface barriers of materials such as concrete, asphalt, butyl rubber, vinyl, and clay are used. It is difficult to assure that these materials can seal a landfill indefinitely. When a subsurface barrier fails, the leachate enters the groundwater in a concentrated, narrow band which may bypass monitoring wells. Once a subsurface barrier has failed, repairs are time-consuming and costly, since the waste above the repair site may have to be removed. The central problem in landfill disposal is leachate control. Recent emphasis has been on developing subsurface barriers to contain the wastes and any leachate. Future emphasis should also be on techniques for removing water from hazardous wastes before they are placed in landfills, and on methods for preventing contact of the wastes with water during and after disposal operations. When leachate is eliminated, the problems of monitoring, and subsurface barrier failure and repair can be addressed, and a waste can be effectively isolated.A surface seal landfill design is recommended for maintaining the dry state of solid hazardous wastes and for controlling leachate. Any impervious liner is utilized over the top of the landfill to prevent surface water from seeping into the waste. The surface barrier is also the site where monitoring and maintenance activities are focused. Barrier failure can be detected by visual inspections and any repairs can be made without disturbing the waste. The surface seal landfill does not employ a subsurface barrier. The surface seal landfill successfully addresses each of the four environmental problems listed above, provided that this landfill design is utilized for dry wastes only and is located at a site which provides protection from groundwater and temporary perched water tables.

A stochastic approach for model reduction and memory function design in hydrogeophysical inversion

NASA Astrophysics Data System (ADS)

Hou, Z.; Kellogg, A.; Terry, N.

2009-12-01

Geophysical (e.g., seismic, electromagnetic, radar) techniques and statistical methods are essential for research related to subsurface characterization, including monitoring subsurface flow and transport processes, oil/gas reservoir identification, etc. For deep subsurface characterization such as reservoir petroleum exploration, seismic methods have been widely used. Recently, electromagnetic (EM) methods have drawn great attention in the area of reservoir characterization. However, considering the enormous computational demand corresponding to seismic and EM forward modeling, it is usually a big problem to have too many unknown parameters in the modeling domain. For shallow subsurface applications, the characterization can be very complicated considering the complexity and nonlinearity of flow and transport processes in the unsaturated zone. It is warranted to reduce the dimension of parameter space to a reasonable level. Another common concern is how to make the best use of time-lapse data with spatial-temporal correlations. This is even more critical when we try to monitor subsurface processes using geophysical data collected at different times. The normal practice is to get the inverse images individually. These images are not necessarily continuous or even reasonably related, because of the non-uniqueness of hydrogeophysical inversion. We propose to use a stochastic framework by integrating minimum-relative-entropy concept, quasi Monto Carlo sampling techniques, and statistical tests. The approach allows efficient and sufficient exploration of all possibilities of model parameters and evaluation of their significances to geophysical responses. The analyses enable us to reduce the parameter space significantly. The approach can be combined with Bayesian updating, allowing us to treat the updated ‘posterior’ pdf as a memory function, which stores all the information up to date about the distributions of soil/field attributes/properties, then consider the memory function as a new prior and generate samples from it for further updating when more geophysical data is available. We applied this approach for deep oil reservoir characterization and for shallow subsurface flow monitoring. The model reduction approach reliably helps reduce the joint seismic/EM/radar inversion computational time to reasonable levels. Continuous inversion images are obtained using time-lapse data with the “memory function” applied in the Bayesian inversion.

Watershed models for instructional films

Treesearch

Peter E. Black; Raymond E. Leonard

1970-01-01

Watershed models, with a special sponge material that simulates soil drainage, were used to make an instructional film on subsurface flow and stream flow. Construction of the models and filming techniques are described.

Biogeochemical characteristics of mesoscale eddies in the generation zone off Valparaíso, Chile

NASA Astrophysics Data System (ADS)

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 (from 67.64 to 9.12 mmolṡm-2ṡd-1, from 3.00 to 0.94 μmolṡm-2ṡd-1, and from 19.62 to 5.77 μmolṡm-2ṡd-1, for CO2, CH4 and N2O, respectively), while between June and August, the ocean-atmosphere flows were close to equilibrium (from 0.09 to -1.93 mmolṡm-2ṡd-1, from 0.40 to 0.03 μmolṡm-2ṡd-1, and from 0,29 to -0.02 μmolṡm-2ṡd-1, for CO2, CH4 and N2O, respectively). Acknowledgment: This work is part of the PIA 037.474 Project (PUCV) and the Instituto Milenio de Oceanografía (IMO-Chile).

Statistical analysis of iron geochemical data suggests limited late Proterozoic oxygenation

NASA Astrophysics Data System (ADS)

Sperling, Erik A.; Wolock, Charles J.; Morgan, Alex S.; Gill, Benjamin C.; Kunzmann, Marcus; Halverson, Galen P.; MacDonald, Francis A.; Knoll, Andrew H.; Johnston, David T.

2015-07-01

Sedimentary rocks deposited across the Proterozoic-Phanerozoic transition record extreme climate fluctuations, a potential rise in atmospheric oxygen or re-organization of the seafloor redox landscape, and the initial diversification of animals. It is widely assumed that the inferred redox change facilitated the observed trends in biodiversity. Establishing this palaeoenvironmental context, however, requires that changes in marine redox structure be tracked by means of geochemical proxies and translated into estimates of atmospheric oxygen. Iron-based proxies are among the most effective tools for tracking the redox chemistry of ancient oceans. These proxies are inherently local, but have global implications when analysed collectively and statistically. Here we analyse about 4,700 iron-speciation measurements from shales 2,300 to 360 million years old. Our statistical analyses suggest that subsurface water masses in mid-Proterozoic oceans were predominantly anoxic and ferruginous (depleted in dissolved oxygen and iron-bearing), but with a tendency towards euxinia (sulfide-bearing) that is not observed in the Neoproterozoic era. Analyses further indicate that early animals did not experience appreciable benthic sulfide stress. Finally, unlike proxies based on redox-sensitive trace-metal abundances, iron geochemical data do not show a statistically significant change in oxygen content through the Ediacaran and Cambrian periods, sharply constraining the magnitude of the end-Proterozoic oxygen increase. Indeed, this re-analysis of trace-metal data is consistent with oxygenation continuing well into the Palaeozoic era. Therefore, if changing redox conditions facilitated animal diversification, it did so through a limited rise in oxygen past critical functional and ecological thresholds, as is seen in modern oxygen minimum zone benthic animal communities.

Application of field geophysics in geomorphology: Advances and limitations exemplified by case studies

NASA Astrophysics Data System (ADS)

Schrott, Lothar; Sass, Oliver

2008-01-01

During the last decade, the use of geophysical techniques has become popular in many geomorphological studies. However, the correct handling of geophysical instruments and the subsequent processing of the data they yield are difficult tasks. Furthermore, the description and interpretation of geomorphological settings to which they apply can significantly influence the data gathering and subsequent modelling procedure ( e.g. achieving a maximum depth of 30 m requires a certain profile length and geophone spacing or a particular frequency of antenna). For more than three decades geophysical techniques have been successfully applied, for example, in permafrost studies. However, in many cases complex or more heterogeneous subsurface structures could not be adequately interpreted due to limited computer facilities and time consuming calculations. As a result of recent technical improvements, geophysical techniques have been applied to a wider spectrum of geomorphological and geological settings. This paper aims to present some examples of geomorphological studies that demonstrate the powerful integration of geophysical techniques and highlight some of the limitations of these techniques. A focus has been given to the three most frequently used techniques in geomorphology to date, namely ground-penetrating radar, seismic refraction and DC resistivity. Promising applications are reported for a broad range of landforms and environments, such as talus slopes, block fields, landslides, complex valley fill deposits, karst and loess covered landforms. A qualitative assessment highlights suitable landforms and environments. The techniques can help to answer yet unsolved questions in geomorphological research regarding for example sediment thickness and internal structures. However, based on case studies it can be shown that the use of a single geophysical technique or a single interpretation tool is not recommended for many geomorphological surface and subsurface conditions as this may lead to significant errors in interpretation. Because of changing physical properties of the subsurface material ( e.g. sediment, water content) in many cases only a combination of two or sometimes even three geophysical methods gives sufficient insight to avoid serious misinterpretation. A "good practice guide" has been framed that provides recommendations to enable the successful application of three important geophysical methods in geomorphology and to help users avoid making serious mistakes.

Electromagnetic geophysical leaching plume detection experiments - San Xavier Mine Facility, Tucson, Arizona

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

Lee, D.O.; Wayland, J.R.

1991-03-01

The objective of this work was to investigate whether a subsurface plume may be detected and followed using crosshole and surface-to-borehole electromagnetic geophysical techniques. both of these techniques were experimentally demonstrated to be feasible. The presence of the injected plume was easily detected with these methods but additional work must be done to refine the techniques. 5 refs., 15 figs., 1 tab.

Deglacial development of (sub) sea surface temperature and salinity in the subarctic northwest Pacific: Implications for upper-ocean stratification

NASA Astrophysics Data System (ADS)

Riethdorf, Jan-Rainer; Max, Lars; Nürnberg, Dirk; Lembke-Jene, Lester; Tiedemann, Ralf

2013-01-01

Based on models and proxy data, it has been proposed that salinity-driven stratification weakened in the subarctic North Pacific during the last deglaciation, which potentially contributed to the deglacial rise in atmospheric carbon dioxide. We present high-resolution subsurface temperature (TMg/Ca) and subsurface salinity-approximating (δ18Oivc-sw) records across the last 20,000 years from the subarctic North Pacific and its marginal seas, derived from combined stable oxygen isotopes and Mg/Ca ratios of the planktonic foraminiferal species Neogloboquadrina pachyderma (sin.). Our results indicate regionally differing changes of subsurface conditions. During the Heinrich Stadial 1 and the Younger Dryas cold phases, our sites were subject to reduced thermal stratification, brine rejection due to sea-ice formation, and increased advection of low-salinity water from the Alaskan Stream. In contrast, the Bølling-Allerød warm phase was characterized by strengthened thermal stratification, stronger sea-ice melting, and influence of surface waters that were less diluted by the Alaskan Stream. From direct comparison with alkenone-based sea surface temperature estimates (SSTUk'37), we suggest deglacial thermocline changes that were closely related to changes in seasonal contrasts and stratification of the mixed layer. The modern upper-ocean conditions seem to have developed only since the early Holocene.

Performance of the subsurface flow constructed wetlands for pretreatment of slightly polluted source water.

PubMed

Yang, Xu; Zhang, Xueping; Wang, Jifu; Zhao, Guangying; Wang, Baojian

2014-05-01

The slightly polluted source water of Yellow River was pretreated in a horizontal subsurface flow constructed wetland (HSFCW) and a lateral subsurface flow constructed wetland (LSFCW) in the Ji'nan city Reservoir, Shandong, China. During almost one years run, the results showed that at the hydraulic loading rate of 1 m/day, the removal efficiencies of chemical oxygen demand (COD), total nitrogen (TN), ammonium nitrogen (NH4 (+)-N) and total phosphorus (TP) in the HSFCW were 48.9, 51.4, 48.7 and 48.9 %, respectively, and the corresponding removal efficiencies in the LSFCW were 50.51, 53.12, 50.44 and 50.83 %, respectively. The HSFCW and LSFCW had a similar high potential for nutrients removal and LSFCW was slightly better. According to the China standard for surface water resources (GB3838-2002), mean effluent COD can reach the Class I (≤ 15 mg/L), and NH4 (+)-N and TP and TN can reach nearly the Class I (≤ 0.015 mg/L), the Class III (≤ 0.05 mg/L) and the Class IV (≤ 1.5 mg/L), respectively. It can be concluded that the slightly polluted source water from Reservoir was pretreated well by the constructed wetland.

Humic acids contribution to sedimentary organic matter on a shallow continental shelf (northern Adriatic Sea)

NASA Astrophysics Data System (ADS)

Giani, M.; Rampazzo, F.; Berto, D.

2010-12-01

The shallow northern Adriatic Sea receives large river runoff, predominantly from the Po River, which is the main allochthonous source of nutrients and organic matter. The origin and quality of organic matter deposited in the sediments can influence the degradation processes and oxygen consumption in the bottom waters as well as the fate of many pollutants. Therefore the humic acids (HA) were quantified in surface and sub-surface sediments collected in an area of the north-western Adriatic platform south of Po River. HA showed to have a relevant contribution to sedimentary organic matter. HA content in sediments were positively correlated with the organic carbon concentration and negatively with redox potential and pH, particularly in sub-surface reduced sediments, suggesting their important role in the diagenetic processes taking place in anoxic conditions. Elemental composition of HA extracted from surface and sub-surface sediments showed a wide range of variation of the C org/N ratios which could be due to a mixed (terrestrial and marine) origin and/or an elevated bacteria degradation of nitrogen during diagenesis processes in sediments. The spectroscopic ratios A 2/A 4 and A 4/A 6 of HA confirmed a mixed origin with a high degree of condensation of the HA extracted from sediments.

Component Activity Measurements in the Ti-Al-O System by Knudsen Cell Mass Spectrometry

NASA Technical Reports Server (NTRS)

Copland, Evan; Jacobson, Nathan S.

2003-01-01

Titanium-aluminides (containing (alpha)2-Ti3Al and gamma-TiAl intermetallic phases) have received continued research focus due to their potential as low-density materials for structural applications at intermediate temperatures. However their application above about 850C is hindered by poor oxidation resistance, characterized by the formation of a non-protective TiO2+Al2O3 scale and an oxygen-enriched subsurface zone. Consistent with this are measured titanium and aluminum activities in "oxygen-free" titanium-aluminides, which indicate Al2O3 is only stable for aluminum concentrations greater then 54 atom percent at 1373 K. However, the inability to form a protective Al2O3 scale is in apparent conflict with phase diagram studies, as experimental isothermal sections of the Ti-Al-O system show gamma-TiAl + alpha2-Ti3Al structures are in equilibrium only with Al2O3. The apparent resolution to this conflict lies in the inclusion of oxygen effects in the thermodynamic measurements

Techniques for Measuring Low Earth Orbital Atomic Oxygen Erosion of Polymers

NASA Technical Reports Server (NTRS)

deGroh, Kim K.; Banks, Bruce A.; Demko, Rikako

2002-01-01

Polymers such as polyimide Kapton and Teflon FEP (fluorinated ethylene propylene) are commonly used spacecraft materials due to their desirable properties such as flexibility, low density, and in the case of FEP, a low solar absorptance and high thermal emittance. Polymers on the exterior of spacecraft in the low Earth orbit (LEO) environment are exposed to energetic atomic oxygen. Atomic oxygen reaction with polymers causes erosion, which is a threat to spacecraft durability. It is therefore important to understand the atomic oxygen erosion yield (E, the volume loss per incident oxygen atom) of polymers being considered in spacecraft design. The most common technique for determining E is through mass loss measurements. For limited duration exposure experiments, such as shuttle experiments, where the atomic oxygen fluence is often so low that mass loss measurements can not produce acceptable uncertainties, recession measurements based on atomic force microscopy analyses can be used. Equally necessary to knowing the mass loss or recession depth for determining the erosion yield of polymers is the knowledge of the atomic oxygen fluence that the polymers were exposed to in space. This paper discusses the procedures and relevant issues for mass loss and recession depth measurements for passive atomic oxygen erosion yield characterization of polymers, along with techniques for active atomic oxygen fluence and erosion characterization. One active atomic oxygen erosion technique discussed is a new technique based on optical measurements. Details including the use of both semi-transparent and opaque polymers for active erosion measurement are reviewed.

Analysis of a PAH-degrading bacterial population in subsurface sediments on the Mid-Atlantic Ridge

NASA Astrophysics Data System (ADS)

Shao, Zongze; Cui, Zhisong; Dong, Chunming; Lai, Qiliang; Chen, Liang

2010-05-01

Little is known about the types and concentrations of polycyclic aromatic hydrocarbons (PAHs) existing in the deep-sea subsurface environment, which is believed to be cold, oligothrophic and of high static pressure. PAHs in the upper layers of the water column are unavoidably subjected to degradation while they are deposited to the sea floor and become embedded in the deep-sea sediment. In this report, a high concentration of PAHs was discovered in the sediment 2.7 m beneath the bottom surface at a water depth of 3962 m on the Mid-Atlantic Ridge (MAR). The total concentration of PAHs was 445 ng (g dry wt sediment) -1. Among the seven detected PAHs, the concentrations of phenanthrene (222 ng g -1) and fluorene (79 ng g -1) were relatively high. In addition, PAH-degrading bacteria were found within the sediments. As in a previously detected site on the MAR, in the PAH-enriched region of this site, a bacterium of the genus Cycloclasticus was found to be the predominant isolate detected by PCR-DGGE analysis. In addition, bacteria of the Halomonas, Marinobacter, Alcanivorax, Thalassospira and Maricaulis genera, were also included in the PAH-degrading community. In summary, a high concentration of PAHs was detected in the subsurface of the deep-sea sediment, and once again, the Cycloclasticus bacterium was confirmed to be a ubiquitous marine PAH degrader even in the subsurface marine environment. Considering the abundance of PAHs therein, biodegradation is thus thought to be inactive, probably because of the low temperature, limited oxygen and/or limited nutrients.

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

Eilert, Andre; Cavalca, Filippo; Roberts, F. Sloan

Copper electrocatalysts derived from an oxide have shown extraordinary electrochemical properties for the carbon dioxide reduction reaction (CO 2RR). Using in situ ambient pressure X-ray photoelectron spectroscopy and quasi in situ electron energy-loss spectroscopy in a transmission electron microscope, we show that there is a substantial amount of residual oxygen in nanostructured, oxide-derived copper electrocatalysts but no residual copper oxide. On the basis of these findings in combination with density functional theory simulations, we propose that residual subsurface oxygen changes the electronic structure of the catalyst and creates sites with higher carbon monoxide binding energy. If such sites are stablemore » under the strongly reducing conditions found in CO 2RR, these findings would explain the high efficiencies of oxide-derived copper in reducing carbon dioxide to multicarbon compounds such as ethylene.« less

Structural, electronic and optical properties of CO adsorbed on the defective anatase TiO2 (101) surface; a DFT study

NASA Astrophysics Data System (ADS)

Rafique, Muhammad; Shuai, Yong; Hassan, Muhammad

2017-08-01

This paper illustrates the study of stable structural, electronic and optical properties of carbon mono oxide (CO) molecule adsorbed on pure anatase TiO2 (101) surface and CO molecule adsorbed on defective anatase TiO2 (101) surface containing oxygen (O) atom subsurface vacancy using first-principles study calculations based on density functional theory (DFT) method. A foreign molecule CO was added in the interstitial space of anatase TiO2 (101) surface. It was observed that, adsorption of CO molecule is not favorable on pure anatase TiO2 (101) surface, however adsorption process is improved when subsurface contains O atom vacancy defect. In case of anatase TiO2 (101) surface containing subsurface vacancy, adsorption process is exothermic, resulting in stable structures. The adsorption energies calculated for CO molecules adsorbed at O2c site, at defect site and at Ti5c site of anatase surface containing subsurface O vacancy are 0.16 eV (at O2c), 0.32 eV (at defect site) and 0.43 eV (at Ti5c) site. DOS and PDOS plots are calculated for all the structures. Results indicated that CO molecule adsorption introduces surface states at the Fermi energy level (EF) as shown in partial density of states (PDOS) plots. The dielectric matrix and absorption coefficient (α) for defective anatase TiO2 (101) surface, CO adsorbed at O2c site, at defect site and at Ti5C site of anatase TiO2 (101) surface containing O atom subsurface vacancy has been calculated within the random phase approximation (RPA) using VASP (Vienna ab-initio simulation package) code. It was observed that upon CO adsorption at defective anatase surface, real and imaginary dielectric function peaks were shifted towards lower energy level and a small absorption peak was observed at 1.1 eV energy level which is not present in case of defective anatase (101) surface. CO adsorption produces a red shift in the absorption spectrum of anatase TiO2 (101) surface containing subsurface O atom vacancy.

Imaging lateral groundwater flow in the shallow subsurface using stochastic temperature fields

NASA Astrophysics Data System (ADS)

Fairley, Jerry P.; Nicholson, Kirsten N.

2006-04-01

Although temperature has often been used as an indication of vertical groundwater movement, its usefulness for identifying horizontal fluid flow has been limited by the difficulty of obtaining sufficient data to draw defensible conclusions. Here we use stochastic simulation to develop a high-resolution image of fluid temperatures in the shallow subsurface at Borax Lake, Oregon. The temperature field inferred from the geostatistical simulations clearly shows geothermal fluids discharging from a group of fault-controlled hydrothermal springs, moving laterally through the subsurface, and mixing with shallow subsurface flow originating from nearby Borax Lake. This interpretation of the data is supported by independent geochemical and isotopic evidence, which show a simple mixing trend between Borax Lake water and discharge from the thermal springs. It is generally agreed that stochastic simulation can be a useful tool for extracting information from complex and/or noisy data and, although not appropriate in all situations, geostatistical analysis may provide good definition of flow paths in the shallow subsurface. Although stochastic imaging techniques are well known in problems involving transport of species, e.g. delineation of contaminant plumes from soil gas survey data, we are unaware of previous applications to the transport of thermal energy for the purpose of inferring shallow groundwater flow.

Raman spectroscopy method for subsurface detection of food powders through plastic layers

NASA Astrophysics Data System (ADS)

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.

Zero source insertion technique to account for undersampling in GPR imaging

DOEpatents

Chambers, David H; Mast, Jeffrey E; Paglieroni, David W

2014-02-25

A method and system for detecting the presence of subsurface objects within a medium is provided. In some embodiments, the imaging and detection system operates in a multistatic mode to collect radar return signals generated by an array of transceiver antenna pairs that is positioned across the surface and that travels down the surface. The imaging and detection system pre-processes the return signal to suppress certain undesirable effects. The imaging and detection system then generates synthetic aperture radar images from real aperture radar images generated from the pre-processed return signal. The imaging and detection system then post-processes the synthetic aperture radar images to improve detection of subsurface objects. The imaging and detection system identifies peaks in the energy levels of the post-processed image frame, which indicates the presence of a subsurface object.

Prospects of passive radio detection of a subsurface ocean on Europa with a lander

NASA Astrophysics Data System (ADS)

Romero-Wolf, Andrew; Schroeder, Dustin M.; Ries, Paul; Bills, Bruce G.; Naudet, Charles; Scott, Bryan R.; Treuhaft, Robert; Vance, Steve

2016-09-01

We estimate the sensitivity of a lander-based instrument for the passive radio detection of a subsurface ocean beneath the ice shell of Europa, expected to be between 3 km and 30 km thick, using Jupiter's decametric radiation. A passive technique was previously studied for an orbiter. Using passive detection in a lander platform provides a point measurement with significant improvements due to largely reduced losses from surface roughness effects, longer integration times, and diminished dispersion due to ionospheric effects allowing operation at lower frequencies and a wider band. A passive sounder on-board a lander provides a low resource instrument sensitive to subsurface ocean at Europa up to depths of 6.9 km for high loss ice (16 dB/km two-way attenuation rate) and 69 km for pure ice (1.6 dB/km).

Modeling of Aircraft Deicing Fluid Induced Biochemical Oxygen Demand in Subsurface-Flow Constructed Treatment Wetlands

DTIC Science & Technology

2009-03-01

meters. The input and output control structures are modeled as sharp crested , rectangular weirs one meter in width. The elevation of the input weir is...manipulated by adjusting the width of both the input and output weirs and the crest height of the output weir . All of these adjustments were found to be...reduction of the weir crest height had an effect on the amount of storm water retained during low precipitation conditions, but not on the crest

Reconstruction of sub-surface archaeological remains from magnetic data using neural computing.

NASA Astrophysics Data System (ADS)

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 geophysical technique, allowing the integration of data from a separate series of measurements.

Air Force and Army Corps of Engineers Improperly Managed the Award of Contracts for the Blue Devil Block 2 Persistent Surveillance System

DTIC Science & Technology

2013-09-19

environments. This can include the development of new and/or improved analytical and numerical models, rapid data-processing techniques, and new subsurface ... imaging techniques that include active and passive sensor modalities in a variety of rural and urban terrains. Of particular interest is the broadband

Geophysical testing of rock and its relationships to physical properties

DOT National Transportation Integrated Search

2011-02-01

Testing techniques were designed to characterize spatial variability in geotechnical engineering physical parameters of : rock formations. Standard methods using seismic waves, which are routinely used for shallow subsurface : investigation, have lim...

Elementary surface chemistry during CuO/Al nanolaminate-thermite synthesis: copper and oxygen deposition on aluminum (111) surfaces.

PubMed

Lanthony, Cloé; Guiltat, Mathilde; Ducéré, Jean Marie; Verdier, Agnes; Hémeryck, Anne; Djafari-Rouhani, Mehdi; Rossi, Carole; Chabal, Yves J; Estève, Alain

2014-09-10

The surface chemistry associated with the synthesis of energetic nanolaminates controls the formation of the critical interfacial layers that dominate the performances of nanothermites. For instance, the interaction of Al with CuO films or CuO with Al films needs to be understood to optimize Al/CuO nanolaminates. To that end, the chemical mechanisms occurring during early stages of molecular CuO adsorption onto crystalline Al(111) surfaces are investigated using density functional theory (DFT) calculations, leading to the systematic determination of their reaction enthalpies and associated activation energies. We show that CuO undergoes dissociative chemisorption on Al(111) surfaces, whereby the Cu and O atoms tend to separate from each other. Both Cu and O atoms form islands with different properties. Copper islanding fosters Cu insertion (via surface site exchange mechanism) into the subsurface, while oxygen islands remain stable at the surface. Above a critical local oxygen coverage, aluminum atoms are extracted from the Al surface, leading to oxygen-aluminum intermixing and the formation of aluminum oxide (γ-alumina). For Cu and O co-deposition, copper promotes oxygen-aluminum interaction by oxygen segregation and separates the resulting oxide from the Al substrate by insertion into Al and stabilization below the oxide front, preventing full mixing of Al, Cu, and O species.

High Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring and Verification Efforts

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

Lee, Ki Ha; Becker, Alex; Framgos, William

1999-06-01

Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data can bemore » mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately imaging the electrical conductivity and dielectric permittivity of the shallow subsurface using the plane wave impedance approach. Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.« less

High-Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring and Verification Efforts

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

Lee, Ki Ha; Becker, Alex; Tseng, Hung-Wen

2002-11-20

Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic (EM) measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data canmore » be mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using the EM impedance approach (Frangos, 2001; Lee and Becker, 2001; Song et al., 2002). Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.« less

High-Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring, and Verification Efforts

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

Lee, Ki Ha; Becker, Alex

2000-06-01

Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data can bemore » mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately imaging the electrical conductivity and dielectric permittivity of the shallow subsurface using the plane wave impedance approach (Song et al., 1997). Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.« less

High-Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring and Verification Efforts

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

Lee, Ki Ha; Becker, Alex; Tseng, Hung-Wen

2001-06-10

Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic (EM) measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data canmore » be mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using the EM impedance approach (Frangos, 2001; Lee and Becker, 2001). Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.« less

Near Real-Time Prospecting for Lunar Volatiles: Demonstrating RESOLVE Science in the Field

NASA Astrophysics Data System (ADS)

Elphic, R. C.; Colaprete, A.; Heldmann, J. L.; Mattes, G.; Ennico, K.; Sanders, G. B.; Quinn, J.; Fritzler, E.; Marinova, M.; Roush, T. L.; Stoker, C.; Larson, W.; Picard, M.; McMurray, R.; Morse, S.

2012-12-01

The Regolith and Environment Science and Oxygen & Lunar Volatile Extraction (RESOLVE) project aims to demonstrate the utility of "in situ resource utilization". In situ resource utilization (ISRU) is a way to rebalance the economics of spaceflight by reducing or eliminating materials that must be brought up from Earth and placed on the surface of the Moon for human use. RESOLVE is developing a rover-borne payload that (1) can locate near subsurface volatiles, (2) excavate and analyze samples of the volatile-bearing regolith, and (3) demonstrate the form, extractability and usefulness of the materials. Such investigations are important not only for ISRU but are also critically important for understanding the scientific nature of these intriguing lunar polar volatile deposits. Temperature models and orbital data suggest near surface volatile concentrations may exist at briefly lit lunar polar locations outside persistently shadowed regions. A lunar rover could be remotely operated at some of these locations for the 4-7 days of expected sunlight at relatively low cost. In July 2012 the RESOLVE project conducted a full-scale field demonstration. In particular, the ability to perform the real-time measurement analysis necessary to search for volatiles and the ability to combine the various measurement techniques to meet the mission measurement and science goals. With help from the Pacific International Space Center for Exploration Systems (PISCES), a lunar rover prototype (provided by the Canadian Space Agency) was equipped with prospecting instruments (neutron spectrometer and near-infrared spectrometer), subsurface access and sampling tools, including both an auger and coring drill (provided by CSA) and subsurface sample analysis instrumentation, including a sample oven system, the Oxygen and Volatile Extraction Node (OVEN), and Gas Chromatograph / Mass Spectrometer system, the Lunar Advanced Volatile Analysis (LAVA) system. Given the relatively short time period this lunar mission is being designed to, prospecting needs to occur in near real-time. The two prospecting instruments are the neutron and NIR spectrometers. In the field demo a small radioactive source was provided the neutron flux. The NIR spectrometer, which includes its own light source, looks at surface reflectance for signatures of bound H2O/OH and general mineralogy. Once a "hot spot" was found by the prospecting instruments, the drill could either auger or core. The auger drill worked to a depth of 50 cm and is monitored with a drill camera and the NIR spectrometer. As cuttings are brought up the NIR spectra is monitored. If a particular location is considered of high-interest then the decision to core could be made. The coring drill (a push-tube) allowed a 1-meter sample to be acquired processed by the OVEN/LAVA sys-tem. This presentation will provide details as how these instruments worked together and how and if the planned measurements and science was obtained.

Near Real Time Prospecting for Lunar Volatiles: Demonstrating RESOLVE Science in the Field

NASA Technical Reports Server (NTRS)

Elphic, Richard; Colaprete, Anthony; Heldmann, Jennifer; Mattes, Gregory W.; Ennico, Kimberly; Sanders, Gerald; Quinn, Jacqueline; Tegnerud, Erin Leigh; Marinova, Margarita; Larson, William E.;

Evaluating the Impact of Changes in Oceanic Dissolved Oxygen on Marine Nitrous Oxide

NASA Astrophysics Data System (ADS)

Suntharalingam, Parvadha; Buitenhuis, Erik; Schmidtko, Sunke; Andrews, Oliver; LeQuere, Corinne

2013-04-01

Emissions of the greenhouse gas nitrous-oxide (N2O) from oceanic oxygen minimum zones (OMZs) in the Equatorial Pacific and Northwest Indian Ocean are believed to provide a significant portion of the global oceanic flux to the atmosphere. Mechanisms of marine N2O production and consumption in these regions display significant sensitivity to ambient oxygen, with high yields at low oxygen levels (O2 < 50 micromol/L), and N2O depletion via denitrification in anoxic zones. These OMZ regions display large gradients in sub-surface N2O, and high rates of N2O turnover that far exceed those observed in the open ocean. Recent studies have suggested that possible expansion of oceanic OMZs in a warming climate, could lead to significant changes in N2O emissions from these zones. In this analysis we employ a global ocean biogeochemistry model (NEMO-PlankTOM), which includes representation of the marine N2O cycle, to explore the impact of changes in dissolved oxygen on the ocean-atmosphere N2O flux. We focus on the period 1960-2000, and evaluate the impact of estimated changes in ocean oxygen from two alternative sources : (a) the observationally-based upper-ocean oxygen distributions and trends of Stramma et al. [2012]; (b) simulated oxygen distributions and temporal variations from a set of CMIP5 Earth System models. We will inter-compare the oceanic N2O estimates derived from these alternative scenarios of ocean de-oxygenation. We will also discuss the implications of our results for the ability to reliably predict changes in N2O emissions under potential expansion of oceanic OMZs, particularly in view of the recently noted discrepancies between observed and modeled trends in oceanic oxygen by Stramma et al. [2012].

Enamel subsurface damage due to tooth preparation with diamonds.

PubMed

Xu, H H; Kelly, J R; Jahanmir, S; Thompson, V P; Rekow, E D

1997-10-01

In clinical tooth preparation with diamond burs, sharp diamond particles indent and scratch the enamel, causing material removal. Such operations may produce subsurface damage in enamel. However, little information is available on the mechanisms and the extent of subsurface damage in enamel produced during clinical tooth preparation. The aim of this study, therefore, was to investigate the mechanisms of subsurface damage produced in enamel during tooth preparation by means of diamond burs, and to examine the dependence of such damage on enamel rod orientation, diamond particle size, and removal rate. Subsurface damage was evaluated by a bonded-interface technique. Tooth preparation was carried out on two enamel rod orientations, with four clinical diamond burs (coarse, medium, fine, and superfine) used in a dental handpiece. The results of this study showed that subsurface damage in enamel took the form of median-type cracks and distributed microcracks, extending preferentially along the boundaries between the enamel rods. Microcracks within individual enamel rods were also observed. The median-type cracks were significantly longer in the direction parallel to the enamel rods than perpendicular to the rods. Preparation with the coarse diamond bur produced cracks as deep as 84 +/- 30 microns in enamel. Finishing with fine diamond burs was effective in crack removal. The crack lengths in enamel were not significantly different when the removal rate was varied. Based on these results, it is concluded that subsurface damage in enamel induced by tooth preparation takes the form of median-type cracks as well as inter- and intra-rod microcracks, and that the lengths of these cracks are sensitive to diamond particle size and enamel rod orientation, but insensitive to removal rate.

3D Seismic Imaging over a Potential Collapse Structure

NASA Astrophysics Data System (ADS)

Gritto, Roland; O'Connell, Daniel; Elobaid Elnaiem, Ali; Mohamed, Fathelrahman; Sadooni, Fadhil

2016-04-01

The Middle-East has seen a recent boom in construction including the planning and development of complete new sub-sections of metropolitan areas. Before planning and construction can commence, however, the development areas need to be investigated to determine their suitability for the planned project. Subsurface parameters such as the type of material (soil/rock), thickness of top soil or rock layers, depth and elastic parameters of basement, for example, comprise important information needed before a decision concerning the suitability of the site for construction can be made. A similar problem arises in environmental impact studies, when subsurface parameters are needed to assess the geological heterogeneity of the subsurface. Environmental impact studies are typically required for each construction project, particularly for the scale of the aforementioned building boom in the Middle East. The current study was conducted in Qatar at the location of a future highway interchange to evaluate a suite of 3D seismic techniques in their effectiveness to interrogate the subsurface for the presence of karst-like collapse structures. The survey comprised an area of approximately 10,000 m2 and consisted of 550 source- and 192 receiver locations. The seismic source was an accelerated weight drop while the geophones consisted of 3-component 10 Hz velocity sensors. At present, we analyzed over 100,000 P-wave phase arrivals and performed high-resolution 3-D tomographic imaging of the shallow subsurface. Furthermore, dispersion analysis of recorded surface waves will be performed to obtain S-wave velocity profiles of the subsurface. Both results, in conjunction with density estimates, will be utilized to determine the elastic moduli of the subsurface rock layers.

Links between climate change, water-table depth, and water chemistry in a mineralized mountain watershed

USGS Publications Warehouse

Manning, Andrew H.; Verplanck, Philip L.; Caine, Jonathan S.; Todd, Andrew S.

2013-01-01

Recent studies suggest that climate change is causing rising solute concentrations in mountain lakes and streams. These changes may be more pronounced in mineralized watersheds due to the sensitivity of sulfide weathering to changes in subsurface oxygen transport. Specific causal mechanisms linking climate change and accelerated weathering rates have been proposed, but in general remain entirely hypothetical. For mineralized watersheds, a favored hypothesis is that falling water tables caused by declining recharge rates allow an increasing volume of sulfide-bearing rock to become exposed to air, thus oxygen. Here, we test the hypothesis that falling water tables are the primary cause of an increase in metals and SO4 (100-400%) observed since 1980 in the Upper Snake River (USR), Colorado. The USR drains an alpine watershed geologically and climatologically representative of many others in mineralized areas of the western U.S. Hydrologic and chemical data collected from 2005 to 2011 in a deep monitoring well (WP1) at the top of the USR watershed are utilized. During this period, both water table depths and groundwater SO4 concentrations have generally increased in the well. A numerical model was constructed using TOUGHREACT that simulates pyrite oxidation near WP1, including groundwater flow and oxygen transport in both saturated and unsaturated zones. The modeling suggests that a falling water table could produce an increase in metals and SO4 of a magnitude similar to that observed in the USR (up to 300%). Future water table declines may produce limited increases in sulfide weathering high in the watershed because of the water table dropping below the depth of oxygen penetration, but may continue to enhance sulfide weathering lower in the watershed where water tables are shallower. Advective air (oxygen) transport in the unsaturated zone caused by seasonally variable recharge and associated water table fluctuations was found to have little influence on pyrite oxidation rates near WP1. However, this mechanism could be important in the case of a shallow dynamic water table and more abundant/reactive sulfides in the shallow subsurface. Data from WP1 and numerical modeling results are thus consistent with the falling water table hypothesis, and illustrate fundamental processes linking climate and sulfide weathering in mineralized watersheds.

Assessment of DInSAR Potential in Simulating Geological Subsurface Structure

NASA Astrophysics Data System (ADS)

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. The newly developed and modified algorithm will then be applied in another part of the region where subsurface information is limited.

Anoxygenic photosynthesis modulated Proterozoic oxygen and sustained Earth's middle age

PubMed Central

Johnston, D. T.; Wolfe-Simon, F.; Pearson, A.; Knoll, A. H.

2009-01-01

Molecular oxygen (O2) began to accumulate in the atmosphere and surface ocean ca. 2,400 million years ago (Ma), but the persistent oxygenation of water masses throughout the oceans developed much later, perhaps beginning as recently as 580–550 Ma. For much of the intervening interval, moderately oxic surface waters lay above an oxygen minimum zone (OMZ) that tended toward euxinia (anoxic and sulfidic). Here we illustrate how contributions to primary production by anoxygenic photoautotrophs (including physiologically versatile cyanobacteria) influenced biogeochemical cycling during Earth's middle age, helping to perpetuate our planet's intermediate redox state by tempering O2 production. Specifically, the ability to generate organic matter (OM) using sulfide as an electron donor enabled a positive biogeochemical feedback that sustained euxinia in the OMZ. On a geologic time scale, pyrite precipitation and burial governed a second feedback that moderated sulfide availability and water column oxygenation. Thus, we argue that the proportional contribution of anoxygenic photosynthesis to overall primary production would have influenced oceanic redox and the Proterozoic O2 budget. Later Neoproterozoic collapse of widespread euxinia and a concomitant return to ferruginous (anoxic and Fe2+ rich) subsurface waters set in motion Earth's transition from its prokaryote-dominated middle age, removing a physiological barrier to eukaryotic diversification (sulfide) and establishing, for the first time in Earth's history, complete dominance of oxygenic photosynthesis in the oceans. This paved the way for the further oxygenation of the oceans and atmosphere and, ultimately, the evolution of complex multicellular organisms. PMID:19805080

Mass-specific respiration of mesozooplankton and its role in the maintenance of an oxygen-deficient ecological barrier (BEDOX) in the upwelling zone off Chile upon presence of a shallow oxygen minimum zone

NASA Astrophysics Data System (ADS)

Donoso, Katty; Escribano, Ruben

2014-01-01

A shallow oxygen minimum zone (OMZ) in the coastal upwelling zone off Chile may vertically confine most zooplankton to a narrow (< 50 m) upper layer. From laboratory experiments, we estimated oxygen consumption of the mesozooplankton community obtained in Bay of Mejillones, northern Chile (23°S) in May 2010, December 2010 and August 2011. Mass-specific respiration rates were in the range of 8.2-24.5 μmol O2 mg dry mass- 1 day- 1, at an average temperature of 12 °C. Estimates of the mesozooplankton biomass in the water column indicated that its aerobic respiration may remove daily a maximum of about 20% of oxygen available at the base of the oxycline. Since previous work indicates that zooplankton aggregate near the base of the oxycline, the impact of aerobic respiration on oxygen content might be even stronger at this depth. Mesozooplankton respiration, along with community respiration by microorganisms near the base of the oxycline and a strongly stratified condition (limiting vertical flux of O2), are suggested as being critical factors causing and maintaining a persistent subsurface oxygen-deficient ecological barrier (BEDOX) in the upwelling zone. This BEDOX layer can have a major role in affecting and regulating zooplankton distribution and their dynamics in the highly productive coastal upwelling zone of the Humboldt Current System.

Anoxygenic photosynthesis modulated Proterozoic oxygen and sustained Earth's middle age.

PubMed

Johnston, D T; Wolfe-Simon, F; Pearson, A; Knoll, A H

2009-10-06

Molecular oxygen (O(2)) began to accumulate in the atmosphere and surface ocean ca. 2,400 million years ago (Ma), but the persistent oxygenation of water masses throughout the oceans developed much later, perhaps beginning as recently as 580-550 Ma. For much of the intervening interval, moderately oxic surface waters lay above an oxygen minimum zone (OMZ) that tended toward euxinia (anoxic and sulfidic). Here we illustrate how contributions to primary production by anoxygenic photoautotrophs (including physiologically versatile cyanobacteria) influenced biogeochemical cycling during Earth's middle age, helping to perpetuate our planet's intermediate redox state by tempering O(2) production. Specifically, the ability to generate organic matter (OM) using sulfide as an electron donor enabled a positive biogeochemical feedback that sustained euxinia in the OMZ. On a geologic time scale, pyrite precipitation and burial governed a second feedback that moderated sulfide availability and water column oxygenation. Thus, we argue that the proportional contribution of anoxygenic photosynthesis to overall primary production would have influenced oceanic redox and the Proterozoic O(2) budget. Later Neoproterozoic collapse of widespread euxinia and a concomitant return to ferruginous (anoxic and Fe(2+) rich) subsurface waters set in motion Earth's transition from its prokaryote-dominated middle age, removing a physiological barrier to eukaryotic diversification (sulfide) and establishing, for the first time in Earth's history, complete dominance of oxygenic photosynthesis in the oceans. This paved the way for the further oxygenation of the oceans and atmosphere and, ultimately, the evolution of complex multicellular organisms.

[Microbes on the edge of global biosphere].

PubMed

Naganuma, T

2000-12-01

The search for life on the edge of global biosphere is a frontier to bridge conventional bio/ecology and exo/astrobiology. This communication reviews the foci of microbiological studies on the inhabitants of the selected "edges", i.e., deep-sea, deep subsurface and Antarctic habitats. The deep-sea is characterized as the no-light (non-photosynthetic) habitat, and the primary production is mostly due to the chemosynthetic autotrophy at the hydrothermal vents and methane-rich seeps. Formation of the chemosynthesis-dependent animal communities in the deep leads to the idea that such communities may be found in "ocean" of the Jovian satellite, Europa. The oxygen minimal layer (OML) in mid-water provides another field of deep-sea research. Modern OML is a relatively thin layer, found between the water depth of 200 and 1000 m, but was much thicker during the periods of oceanic anoxia events (OAEs) in the past. The history of oceanic biosphere is regarded as the cycle of OAE and non-OAE periods, and the remnants of the past OAEs may be seen in the modem OML. Anoxic (no-O2) condition is also characteristic of deep subsurface biosphere. Microorganisms in deep subsurface biosphere exploit every available oxidant, or terminal electron acceptor (TEA), for anaerobic respiration. Sulfate, nitrate, iron (III) and CO2 are the representative TEAs in the deep subsurface. Subsurface of hydrothermal vents, or sub-vent biosphere, may house brine (high salt) habitats and halophilic microorganisms. Some sub-vent halophiles were phylogenetically closely similar to the ones found in the Antarctic habitats which are extremely dry by the liophilizing climate. Below the 3000-4000 m-thick glacier on Antarctica, there have been >70 lakes with liquid water located. One of such sub-glacial lakes, Lake Vostok, has been a target of "life in extreme environments" and is about to be drill-penetrated for microbiological studies. These 'microbiological platforms' will provide new knowledge about the diversity and potential of the Earth's life and facilitate the capability of astrobiologial exploration.

In Vivo Mitochondrial Oxygen Tension Measured by a Delayed Fluorescence Lifetime Technique

PubMed Central

Mik, Egbert G.; Johannes, Tanja; Zuurbier, Coert J.; Heinen, Andre; Houben-Weerts, Judith H. P. M.; Balestra, Gianmarco M.; Stap, Jan; Beek, Johan F.; Ince, Can

2008-01-01

Mitochondrial oxygen tension (mitoPO2) is a key parameter for cellular function, which is considered to be affected under various pathophysiological circumstances. Although many techniques for assessing in vivo oxygenation are available, no technique for measuring mitoPO2 in vivo exists. Here we report in vivo measurement of mitoPO2 and the recovery of mitoPO2 histograms in rat liver by a novel optical technique under normal and pathological circumstances. The technique is based on oxygen-dependent quenching of the delayed fluorescence lifetime of protoporphyrin IX. Application of 5-aminolevulinic acid enhanced mitochondrial protoporphyrin IX levels and induced oxygen-dependent delayed fluorescence in various tissues, without affecting mitochondrial respiration. Using fluorescence microscopy, we demonstrate in isolated hepatocytes that the signal is of mitochondrial origin. The delayed fluorescence lifetime was calibrated in isolated hepatocytes and isolated perfused livers. Ultimately, the technique was applied to measure mitoPO2 in rat liver in vivo. The results demonstrate mitoPO2 values of ∼30–40 mmHg. mitoPO2 was highly sensitive to small changes in inspired oxygen concentration around atmospheric oxygen level. Ischemia-reperfusion interventions showed altered mitoPO2 distribution, which flattened overall compared to baseline conditions. The reported technology is scalable from microscopic to macroscopic applications, and its reliance on an endogenous compound greatly enhances its potential field of applications. PMID:18641065

Forensic applications of nitrogen and oxygen isotopes in tracing nitrate sources in urban environments

USGS Publications Warehouse

Silva, S.R.; Ging, P.B.; Lee, R.W.; Ebbert, J.C.; Tesoriero, A.J.; Inkpen, E.L.

2002-01-01

Ground and surface waters in urban areas are susceptible to nitrate contamination from septic systems, leaking sewer lines, and fertilizer applications. Source identification is a primary step toward a successful remediation plan in affected areas. In this respect, nitrogen and oxygen isotope ratios of nitrate, in conjunction with hydrologic data and water chemistry, have proven valuable in urban studies from Austin, Texas, and Tacoma, Washington. In Austin, stream water was sampled during stremflow and baseflow conditions to assess surface and subsurface sources of nitrate, respectively. In Tacoma, well waters were sampled in adjacent sewered and un-sewered areas to determine if locally high nitrate concentrations were caused by septic systems in the un-sewered areas. In both studies, sewage was identified as a nitrate source and mixing between sewage and other sources of nitrate was apparent. In addition to source identification, combined nitrogen and oxygen isotopes were important in determining the significance of denitrification, which can complicate source assessment by reducing nitrate concentrations and increasing ??15N values. The two studies illustrate the value of nitrogen and oxygen isotopes of nitrate for forensic applications in urban areas. ?? Published by Elsevier Science Ltd. on behalf of AEHS.

Organic Matter Transformation in the Peat Column at Marcell Experimental Forest: Humification and Vertical Stratification

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

Tfaily, Malak; Cooper, Bill; Kostka,

2014-01-01

A large-scale ecosystem manipulation (Spruce and Peatland Responses under Climatic and Environmental Change, SPRUCE) is being constructed in the Marcell Experimental Forest, Minnesota, USA, to determine the effects of climatic forcing on ecosystem processes in northern peatlands. Prior to the initiation of the manipulation, we characterized the solid-phase peat to a depth of 2 meters using a variety of techniques, including peat C:N ratios, 13C and 15N isotopic composition, Fourier Transform Infrared (FT IR), and 13C Nuclear Magnetic Resonance spectroscopy (13C NMR). FT IR determined peat humification-levels increased rapidly between and 75 cm, indicating a highly reactive zone. We observedmore » a rapid drop in the abundance of O-alkyl-C, carboxyl-C, and other oxygenated functionalities within this zone and a concomitant increase in the abundance of alkyl- and nitrogen-containing compounds. Below 75-cm, minimal change was observed except that aromatic functionalities accumulated with depth. Incubation studies revealed the highest methane production rates and greatest CH4:CO2 ratios within this and 75 cm zone. Hydrology and surface vegetation played a role in belowground carbon cycling. Radiocarbon signatures of microbial respiration products in deeper porewaters resembled the signatures of dissolved organic carbon rather than solid phase peat, indicating that more recently photosynthesized organic matter fueled the bulk of subsurface microbial respiration. Oxygen-containing functionalities, especially O-alkyl-C, appear to serve as an excellent proxy for soil decomposition rate, and in addition should be a sensitive indicator of the response of the solid phase peat to the climatic manipulation.« less

High-spatial-resolution sub-surface imaging using a laser-based acoustic microscopy technique.

PubMed

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.

Soil gas screening for chlorinated solvents at three contaminated karst sites in Tennessee

USGS Publications Warehouse

Wolfe, W.J.; Williams, S.D.

2002-01-01

Soil gas was sampled using active sampling techniques and passive collectors at three sites in Tennessee to evaluate the effectiveness of these techniques for locating chlorinated solvent sources and flowpaths in karst aquifers. Actively collected soil gas samples were analyzed in the field with a portable gas chromatograph, and the passive soil gas collectors were analyzed in the lab with gas chromatography/mass spectrometry. Results of the sampling indicate that the effectiveness of both techniques is highly dependent on the distribution of the contaminants in the subsurface, the geomorphic and hydrogeologic characteristics of the site, and, in one case, on seasonal conditions. Both active and passive techniques identified areas of elevated subsurface chlorinated solvent concentrations at a landfill site where contamination remains concentrated in the regolith. Neither technique detected chlorinated solvents known to be moving in the bedrock at a manufacturing site characterized by thick regolith and an absence of surficial karst features. Passive soil gas sampling had varied success detecting flowpaths for chloroform in the bedrock at a train derailment site characterized by shallow regolith and abundant surficial karst features. At the train derailment site, delineation of the contaminant flowpath through passive soil gas sampling was stronger and more detailed under Winter conditions than summer.

Biologically induced initiation of Neoproterozoic snowball-Earth events.

PubMed

Tziperman, Eli; Halevy, Itay; Johnston, David T; Knoll, Andrew H; Schrag, Daniel P

2011-09-13

The glaciations of the Neoproterozoic Era (1,000 to 542 MyBP) were preceded by dramatically light C isotopic excursions preserved in preglacial deposits. Standard explanations of these excursions involve remineralization of isotopically light organic matter and imply strong enhancement of atmospheric CO(2) greenhouse gas concentration, apparently inconsistent with the glaciations that followed. We examine a scenario in which the isotopic signal, as well as the global glaciation, result from enhanced export of organic matter from the upper ocean into anoxic subsurface waters and sediments. The organic matter undergoes anoxic remineralization at depth via either sulfate- or iron-reducing bacteria. In both cases, this can lead to changes in carbonate alkalinity and dissolved inorganic pool that efficiently lower the atmospheric CO(2) concentration, possibly plunging Earth into an ice age. This scenario predicts enhanced deposition of calcium carbonate, the formation of siderite, and an increase in ocean pH, all of which are consistent with recent observations. Late Neoproterozoic diversification of marine eukaryotes may have facilitated the episodic enhancement of export of organic matter from the upper ocean, by causing a greater proportion of organic matter to be partitioned as particulate aggregates that can sink more efficiently, via increased cell size, biomineralization or increased CN of eukaryotic phytoplankton. The scenario explains isotopic excursions that are correlated or uncorrelated with snowball initiation, and suggests that increasing atmospheric oxygen concentrations and a progressive oxygenation of the subsurface ocean helped to prevent snowball glaciation on the Phanerozoic Earth.

North Pacific deglacial hypoxic events linked to abrupt ocean warming

USGS Publications Warehouse

Praetorius, Summer K; Mix, Alan C.; Davies, Maureen H.; Wolhowe, Matthew D; Addison, Jason A.; Prahl, Frederick G

2015-01-01

Marine sediments from the North Pacific document two episodes of expansion and strengthening of the subsurface oxygen minimum zone (OMZ) accompanied by seafloor hypoxia during the last deglacial transition1, 2, 3, 4. The mechanisms driving this hypoxia remain under debate1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11. We present a new high-resolution alkenone palaeotemperature reconstruction from the Gulf of Alaska that reveals two abrupt warming events of 4–5 degrees Celsius at the onset of the Bølling and Holocene intervals that coincide with sudden shifts to hypoxia at intermediate depths. The presence of diatomaceous laminations and hypoxia-tolerant benthic foraminiferal species, peaks in redox-sensitive trace metals12, 13, and enhanced 15N/14N ratio of organic matter13, collectively suggest association with high export production. A decrease in 18O/16O values of benthic foraminifera accompanying the most severe deoxygenation event indicates subsurface warming of up to about 2 degrees Celsius. We infer that abrupt warming triggered expansion of the North Pacific OMZ through reduced oxygen solubility and increased marine productivity via physiological effects; following initiation of hypoxia, remobilization of iron from hypoxic sediments could have provided a positive feedback on ocean deoxygenation through increased nutrient utilization and carbon export. Such a biogeochemical amplification process implies high sensitivity of OMZ expansion to warming.

Biologically induced initiation of Neoproterozoic snowball-Earth events

PubMed Central

Tziperman, Eli; Halevy, Itay; Johnston, David T.; Knoll, Andrew H.; Schrag, Daniel P.

2011-01-01

The glaciations of the Neoproterozoic Era (1,000 to 542 MyBP) were preceded by dramatically light C isotopic excursions preserved in preglacial deposits. Standard explanations of these excursions involve remineralization of isotopically light organic matter and imply strong enhancement of atmospheric CO2 greenhouse gas concentration, apparently inconsistent with the glaciations that followed. We examine a scenario in which the isotopic signal, as well as the global glaciation, result from enhanced export of organic matter from the upper ocean into anoxic subsurface waters and sediments. The organic matter undergoes anoxic remineralization at depth via either sulfate- or iron-reducing bacteria. In both cases, this can lead to changes in carbonate alkalinity and dissolved inorganic pool that efficiently lower the atmospheric CO2 concentration, possibly plunging Earth into an ice age. This scenario predicts enhanced deposition of calcium carbonate, the formation of siderite, and an increase in ocean pH, all of which are consistent with recent observations. Late Neoproterozoic diversification of marine eukaryotes may have facilitated the episodic enhancement of export of organic matter from the upper ocean, by causing a greater proportion of organic matter to be partitioned as particulate aggregates that can sink more efficiently, via increased cell size, biomineralization or increased C∶N of eukaryotic phytoplankton. The scenario explains isotopic excursions that are correlated or uncorrelated with snowball initiation, and suggests that increasing atmospheric oxygen concentrations and a progressive oxygenation of the subsurface ocean helped to prevent snowball glaciation on the Phanerozoic Earth. PMID:21825156

Subsurface-channeling-like energy loss structure of the skipping motion on an ionic crystal.

PubMed

Villette, J; Borisov, A G; Khemliche, H; Momeni, A; Roncin, P

2000-10-09

The skipping motion of Ne+ ions in grazing scattering from the LiF(001) surface is studied for velocity below 0.1 a.u. with a time-of-flight technique. It is demonstrated that suppression of electronic excitation and dominance of optical phonon excitation in the projectile stopping results in an odd 1,3,5,... progression of the energy loss peaks, a feature usually ascribed to subsurface channeling. The experimental findings are well reproduced by parameter-free model calculations where thermal vibrations are the dominant cause for the ion trapping and detrapping.

Mars Radar Opens a Planet's Third Dimension

NASA Technical Reports Server (NTRS)

2008-01-01

Radar sounder instruments orbiting Mars have looked beneath the Martian surface and opened up the third dimension for planetary exploration. The technique's success is prompting scientists to think of all the other places in the Solar System where they would like to use radar sounders.

The first radar sounder at Mars was the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on the European Space Agency's Mars Express Orbiter. It has been joined by the complementary Shallow Subsurface Radar (SHARAD), operating at a different wavelength aboard NASA's Mars Reconnaissance Orbiter. The data in this animation are from SHARAD.

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

USGS Publications Warehouse

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.

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

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

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.

Density functional theory study of atomic and electronic properties of defects in reduced anatase TiO2 nanocrystals

NASA Astrophysics Data System (ADS)

Morita, Kazuki; Yasuoka, Kenji

2018-03-01

Anatase TiO2 nanocrystals have received considerable attention owing to their promising applications in photocatalysis, photovoltaics, and fuel cells. Although experimental evidence has shown that the performance of nanocrystals can be significantly improved through reduction, the mechanistic basis of this enhancement remains unclear. To shed a light on the chemistry of reduced anatase TiO2 nanocrystals, density functional theory were used to investigate the properties of defects and excess electrons. We demonstrated that oxygen vacancies are stable both on the surface and at the sub-surface of the nanocrystal, while titanium interstitials prefer sub-surface sites. Different defect locations possessed different excess electron structures, which contributed to deep and shallow states in the band gap of the nanocrystals. Furthermore, valence band tailing was observed, resulting in band gap narrowing. The theoretical results presented here deepen our understanding, and show the potential of defects to considerably change the macroscopic properties of anatase TiO2 nanocrystals.

Past Performance analysis of HPOTP bearings

NASA Technical Reports Server (NTRS)

Bhat, B. N.; Dolan, F. J.

1982-01-01

The past performance analysis conducted on three High Pressure Oxygen Turbopump (HPOTP) bearings from the Space Shuttle Main Engine is presented. Metallurgical analysis of failed bearing balls and races, and wear track and crack configuration analyses were carried out. In addition, one bearing was tested in laboratory at very high axial loads. The results showed that the cracks were surface initiated and propagated into subsurface locations at relatively small angles. Subsurface cracks were much more extensive than was appeared on the surface. The location of major cracks in the races corresponded to high radial loads rather than high axial loads. There was evidence to suggest that the inner races were heated to elevated temperatures. A failure scenario was developed based on the above findings. According to this scenario the HPOTP bearings are heated by a combination of high loads and high coefficient of friction (poor lubrication). Different methods of extending the HPOTP bearing life are also discussed. These include reduction of axial loads, improvements in bearing design, lubrication and cooling, and use of improved bearing materials.

Bioremediation of uranium-contaminated groundwater: a systems approach to subsurface biogeochemistry.

PubMed

Williams, Kenneth H; Bargar, John R; Lloyd, Jonathan R; Lovley, Derek R

2013-06-01

Adding organic electron donors to stimulate microbial reduction of highly soluble U(VI) to less soluble U(IV) is a promising strategy for immobilizing uranium in contaminated subsurface environments. Studies suggest that diagnosing the in situ physiological status of the subsurface community during uranium bioremediation with environmental transcriptomic and proteomic techniques can identify factors potentially limiting U(VI) reduction activity. Models which couple genome-scale in silico representations of the metabolism of key microbial populations with geochemical and hydrological models may be able to predict the outcome of bioremediation strategies and aid in the development of new approaches. Concerns remain about the long-term stability of sequestered U(IV) minerals and the release of co-contaminants associated with Fe(III) oxides, which might be overcome through targeted delivery of electrons to select microorganisms using in situ electrodes. Copyright © 2012 Elsevier Ltd. All rights reserved.

Workshop on Radar Investigations of Planetary and Terrestrial Environments

NASA Technical Reports Server (NTRS)

2005-01-01

Contents include the following: Salt Kinematics and InSAR. SAR Interferometry as a Tool for Monitoring Coastal Changes in the Nile River Delta of Egypt. Modem Radar Techniques for Geophysical Applications: Two Examples. WISDOM Experiment on the EXOMARS ESA Mission. An Ice Thickness Study Utilizing Ground Penetrating Radar on the Lower Jamapa. Probing the Martian Subsurface with Synthetic Aperture Radar. Planetary Surface Properties from Radar Polarimetric Observations. Imaging the Sub-surface Reflectors : Results From the RANETA/NETLANDER Field Test on the Antarctic Ice Shelf. Strategy for Selection of Mars Geophysical Analogue Sites. Observations of Low Frequency Low Altitude Plasma Oscillations at Mars and Implications for Electromagnetic Sounding of the Subsurface. Ionospheric Transmission Losses Associated with Mars-orbiting Radar. A Polarimetric Scattering Model for the 2-Layer Problem. Radars for Imaging and Sounding of Polar Ice Sheets. Strata: Ground Penetrating Radar for Mars Rovers. Scattering Limits to Depth of Radar Investigation: Lessons from the Bishop Tuff.

Seasonal load restriction tool : Clarus regional demonstrations.

DOT National Transportation Integrated Search

2011-01-01

State transportation agencies have wanted to improve : the techniques that lead to the decisions to impose and : subsequently lift restrictions on selected roads that are prone : to road damage due to subsurface freezing/thawing processes. : The Seas...

A shallow subsurface controlled release facility in Bozeman, Montana, USA, for testing near surface CO2 detection techniques and transport models

USGS Publications Warehouse

Spangler, L.H.; Dobeck, L.M.; Repasky, K.S.; Nehrir, A.R.; Humphries, S.D.; Keith, C.J.; Shaw, J.A.; Rouse, J.H.; Cunningham, A.B.; Benson, S.M.; Oldenburg, C.M.; Lewicki, J.L.; Wells, A.W.; Diehl, J.R.; Strazisar, B.R.; Fessenden, J.E.; Rahn, T.A.; Amonette, J.E.; Barr, J.L.; Pickles, W.L.; Jacobson, J.D.; Silver, E.A.; Male, E.J.; Rauch, H.W.; Gullickson, K.S.; Trautz, R.; Kharaka, Y.; Birkholzer, J.; Wielopolski, L.

2010-01-01

A controlled field pilot has been developed in Bozeman, Montana, USA, to study near surface CO2 transport and detection technologies. A slotted horizontal well divided into six zones was installed in the shallow subsurface. The scale and CO2 release rates were chosen to be relevant to developing monitoring strategies for geological carbon storage. The field site was characterized before injection, and CO2 transport and concentrations in saturated soil and the vadose zone were modeled. Controlled releases of CO2 from the horizontal well were performed in the summers of 2007 and 2008, and collaborators from six national labs, three universities, and the U.S. Geological Survey investigated movement of CO2 through the soil, water, plants, and air with a wide range of near surface detection techniques. An overview of these results will be presented. ?? 2009 The Author(s).

Regional geothermal exploration in Egypt

NASA Technical Reports Server (NTRS)

Morgan, P.; Boulos, F. K.; Swanberg, C. A.

1983-01-01

A study is presented of the evaluation of the potential geothermal resources of Egypt using a thermal gradient/heat flow technique and a groundwater temperature/chemistry technique. Existing oil well bottom-hole temperature data, as well as subsurface temperature measurements in existing boreholes, were employed for the thermal gradient/heat flow investigation before special thermal gradient holes were drilled. The geographic range of the direct subsurface thermal measurements was extended by employing groundwater temperature and chemistry data. Results show the presence of a regional thermal high along the eastern margin of Egypt with a local thermal anomaly in this zone. It is suggested that the sandstones of the Nubian Formation may be a suitable reservoir for geothermal fluids. These findings indicate that temperatures of 150 C or higher may be found in this reservoir in the Gulf of Suez and Red Sea coastal zones where it lies at a depth of 4 km and deeper.

The design of long wavelength planetary SAR sensor and its applications for monitoring shallow sub-surface of Moon and planets.

NASA Astrophysics Data System (ADS)

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.

Determining the 3D Subsurface Density Structure of Taurus Littrow Valley Using Apollo 17 Gravity Data

NASA Technical Reports Server (NTRS)

Urbancic, N.; Ghent, R.; Stanley, S,; Johnson, C. L.; Carroll, K. A.; Hatch, D.; Williamson, M. C.; Garry, W. B.; Talwani, M.

2016-01-01

Surface gravity surveys can detect subsurface density variations that can reveal subsurface geologic features. In 1972, the Apollo 17 (A17) mission conducted the Traverse Gravimeter Experiment (TGE) using a gravimeter that measured the local gravity field near Taurus Littrow Valley (TLV), located on the south-eastern rim of the Serenitatis basin. TLV is hypothesized to be a basaltfilled radial graben resulting from the impact that formed Mare Serenitatis. It is bounded by both the North and South Massifs (NM and SM) as well as other smaller mountains to the East that are thought to be mainly composed of brecciated highland material. The TGE is the first and only successful gravity survey on the surface of the Moon. Other more recent satellite surveys, such as NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission (2011- 2012), have produced the best global gravity field to date (approx. 13km resolution). However, these satellite surveys are not sensitive enough to detect fine-scale (<1km) lunar subsurface structures. This underscores the value of the data collected at the surface by A17. In the original analysis of the data a 2D forward-modelling approach was used to derive a thickness of the subsurface basalt layer of 1.0 km by assuming a simple flat-faced rectangular geometry and using densities derived from Apollo lunar samples. We are investigating whether modern 3D modelling techniques in combination with high-resolution topographical and image datasets can reveal additional fine-scale subsurface structure in TLV.

New Active Optical Technique Developed for Measuring Low-Earth-Orbit Atomic Oxygen Erosion of Polymers

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; deGroh, Kim K.; Demko, Rikako

2003-01-01

Polymers such as polyimide Kapton (DuPont) and Teflon FEP (DuPont, fluorinated ethylene propylene) are commonly used spacecraft materials because of desirable properties such as flexibility, low density, and in the case of FEP, a low solar absorptance and high thermal emittance. Polymers on the exterior of spacecraft in the low-Earth-orbit (LEO) environment are exposed to energetic atomic oxygen. Atomic oxygen reaction with polymers causes erosion, which is a threat to spacecraft performance and durability. It is, therefore, important to understand the atomic oxygen erosion yield E (the volume loss per incident oxygen atom) of polymers being considered in spacecraft design. The most common technique for determining E is a passive technique based on mass-loss measurements of samples exposed to LEO atomic oxygen during a space flight experiment. There are certain disadvantages to this technique. First, because it is passive, data are not obtained until after the flight is completed. Also, obtaining the preflight and postflight mass measurements is complicated by the fact that many polymers absorb water and, therefore, the mass change due to water absorption can affect the E data. This is particularly true for experiments that receive low atomic oxygen exposures or for samples that have a very low E. An active atomic oxygen erosion technique based on optical measurements has been developed that has certain advantages over the mass-loss technique. This in situ technique can simultaneously provide the erosion yield data on orbit and the atomic oxygen exposure fluence, which is needed for erosion yield determination. In the optical technique, either sunlight or artificial light can be used to measure the erosion of semitransparent or opaque polymers as a result of atomic oxygen attack. The technique is simple and adaptable to a rather wide range of polymers, providing that they have a sufficiently high optical absorption coefficient. If one covers a photodiode with a uniformly thick sheet of semitransparent polymer such as Kapton H polyimide, then as atomic oxygen erodes the polymer, the short-circuit current from the photodiode will increase in an exponential manner with fluence. This nonlinear response with fluence results in a lack of sensitivity for measuring low atomic oxygen fluences. However, if one uses a variable-thickness polymer or carbon sample, which is configured as shown in the preceding figure, then a linear response can be achieved for opaque materials using a parabolic well for a circular geometry detector or a V-shaped well for a rectangular-geometry detector. Variable-thickness samples can be fabricated using many thin polymer layers. For semitransparent polymers such as Kapton H polyimide, there is an initial short-circuit current that is greater than zero. This current has a slightly nonlinear dependence on atomic oxygen fluence in comparison to opaque materials such as black Kapton as shown in the graph. For this graph figure, the total thickness of Kapton H was assumed to be 0.03 cm. The photodiode short-circuit current shown in the graph was generated on the basis of preliminary measurements-a total reflectance rho of 0.0424 and an optical absorption coefficient a of 146.5 cm(sup -1). In addition to obtaining on-orbit data, the advantage of this active erosion and erosion yield measurement technique is its simplicity and reliance upon well-characterized fluence witness materials as well as a nearly linear photodiode short-circuit current dependence upon atomic oxygen fluence. The optical technique is useful for measuring either atomic oxygen fluence or erosion, depending on the information desired. To measure the atomic oxygen erosion yield of a test material, one would need to have two photodiode sensors, one for the test material and one that uses a known erosion yield material (such as Kapton) to measure the atomic oxygen fluence.

Pt 3Re alloy nanoparticles as electrocatalysts for the oxygen reduction reaction

DOE PAGES

Raciti, David; Kubal, Joseph; Ma, Cheng; ...

2015-12-25

Development of renewable energy technologies requires advanced catalysts for efficient electrical-chemical energy conversion reactions. Here in this paper, we report the study of Pt-Re alloy nanoparticles as an electrocatalyst for the oxygen reduction reaction (ORR). An organic solution approach is developed to synthesize monodisperse and homogeneous Pt 3Re alloy nanoparticles. Electrochemical studies show that these nanoparticles exhibit an improvement factor of 4 in catalytic activity for the ORR compared to commercial Pt catalysts of similar particle sizes. Fundamental understanding of the structure-property relationship is established by combining material characterization using X-ray spectroscopy and atomically resolved electron microscopy, as well asmore » Density Functional Theory (DFT) calculations. Lastly, our work revealed that an electronic modification of the surface properties of Pt by subsurface Re (ligand effect) accounts for the catalytic enhancement.« less

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

USGS Publications Warehouse

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

2011-01-01

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

The story of Amazonian climate change on Mars as told by carbonates in Miller Range Nakhlites

NASA Astrophysics Data System (ADS)

Evans, M. E.; Niles, P. B.; Locke, D.; Chapman, P.

2017-12-01

This is a story about rocks from Mars, and how they reveal environmental changes on Mars. A specific region of volcanic rocks formed on Mars about 1.3 billion years ago (bya). This region is now known as the Nakhla lava pile. The rocks were likely formed near the surface. Chemical analysis of these rocks confirms that they formed on Mars, because rocks on Earth have different oxygen isotope values. Sometime later, perhaps 0.7 bya, very small amounts of subsurface water on Mars percolated through the lava pile. The water contained dissolved carbon dioxide (CO2) from contact with the atmosphere of Mars. Ions in the water bonded with rock ions to create tiny, white, carbonate minerals along the cracks within the lava pile. The Nakhla subsurface water temperature was likely cool ( 15°C), which is different from the hot water that possibly created minerals on older Mars rocks. About 11 million years ago, an asteroid impacted Mars over the Nakhla lava pile. The impact rebound ejected mass from the surface and subsurface, and some rocks escaped the gravity of Mars. These rocks floated in space for over 10.9 million years before they fell to Earth as meteorites. The most famous of these meteorites, named Nakhla, fell over Egypt in 1911 and fragmented into 40 pieces. A total of 11 similar meteorites, known as Nakhlites, have been collected across the Earth. Four of these meteorites fell into a remote region of Antarctica called the Miller Range (MIL). They were collected by the National Science Foundation (NSF) "Antarctica Search for Meteorite" (ANSMET) program. This study analyzed the stable isotope geochemistry of the carbonates on the four MIL Nakhlites. Antarctica is an analog for carbonate formation on recent Mars because it forms the minerals in a cold environment with a thin film of water. Carbonates from oceans are dominated by the oxygen isotopic values of the water, but in Mars and Antarctica the carbonates are also influenced by the oxygen in the atmospheric CO2. This study reveals that terrestrial carbonates have different carbon isotope values from martian carbonates. The carbon isotope values of the Mars atmospheric CO2 that formed the MIL Nakhlite carbonates was different from the modern atmosphere (as measured by the MSL Curiosity rover). This difference may be due somewhat to loss of atmospheric gas to space over the past billion years.

Monitoring of olive oil mills' wastes using electrical resistivity tomography techniques

NASA Astrophysics Data System (ADS)

Simyrdanis, Kleanthis; Papadopoulos, Nikos; Kirkou, Stella; Sarris, Apostolos; Tsourlos, Panagiotis

2014-08-01

Olive oil mills' wastes (OOMW) are one of the byproducts of the oil production that can lead to serious environmental pollution when they are deposited in ponds dug on the ground surface. Electrical Resistivity Tomography (ERT) method can provide a valuable tool in order to monitor through time the physical flow of the wastes into the subsurface. ERT could potentially locate the electrical signature due to lower resistivity values resulting from the leakage of OOMW to the subsurface. For this purpose, two vertical boreholes were installed (12m depth, 9 m apart) in the vicinity of an existing pond which is filled with OOMW during the oil production period. The test site is situated in Saint Andreas village about 15km south of the city of Rethymno (Crete, Greece). Surface ERT measurements were collected along multiple lines in order to reconstruct the subsurface resistivity models. Data acquisition was performed with standard and optimized electrode configuration protocols. The monitoring survey includes the ERT data collection for a period of time. The study was initiated before the OOMW were deposited in the pond, so resistivity fluctuations are expected due to the flow of OOMW in the porous subsurface media through time. Preliminary results show the good correlation of the ERT images with the drilled geological formations and the identification of low resistivity subsurface zone that could be attributed to the flow of the wastes within the porous layers.

Terahertz imaging for subsurface investigation of art paintings

NASA Astrophysics Data System (ADS)

Locquet, A.; Dong, J.; Melis, M.; Citrin, D. S.

2017-08-01

Terahertz (THz) reflective imaging is applied to the stratigraphic and subsurface investigation of oil paintings, with a focus on the mid-20th century Italian painting, `After Fishing', by Ausonio Tanda. THz frequency-wavelet domain deconvolution, which is an enhanced deconvolution technique combining frequency-domain filtering and stationary wavelet shrinkage, is utilized to resolve the optically thin paint layers or brush strokes. Based on the deconvolved terahertz data, the stratigraphy of the painting including the paint layers is reconstructed and subsurface features are clearly revealed. Specifically, THz C-scans and B-scans are analyzed based on different types of deconvolved signals to investigate the subsurface features of the painting, including the identification of regions with more than one paint layer, the refractive-index difference between paint layers, and the distribution of the paint-layer thickness. In addition, THz images are compared with X-ray images. The THz image of the thickness distribution of the paint exhibits a high degree of correlation with the X-ray transmission image, but THz images also reveal defects in the paperboard that cannot be identified in the X-ray image. Therefore, our results demonstrate that THz imaging can be considered as an effective tool for the stratigraphic and subsurface investigation of art paintings. They also open up the way for the use of non-ionizing THz imaging as a potential substitute for ionizing X-ray analysis in nondestructive evaluation of art paintings.

Subsurface polarimetric migration imaging for full polarimetric ground-penetrating radar

NASA Astrophysics Data System (ADS)

Feng, Xuan; Yu, Yue; Liu, Cai; Fehler, Michael

2015-08-01

Polarization is a property of electromagnetic wave that generally refers to the locus of the electric field vector, which can be used to characterize surface properties by polarimetric radar. However, its use has been less common in the ground-penetrating radar (GPR) community. Full polarimetric GPR data include scattering matrices, by which the polarization properties can be extracted, at each survey point. Different components of the measured scattering matrix are sensitive to different types of subsurface objects, which offers a potential improvement in the detection ability of GPR. This paper develops a polarimetric migration imaging method. By merging the Pauli polarimetric decomposition technique with the Krichhoff migration equation, we develop a polarimetric migration algorithm, which can extract three migrated coefficients that are sensitive to different types of objects. Then fusing the three migrated coefficients, we can obtain subsurface colour-coded reconstructed object images, which can be employed to interpret both the geometrical information and the scattering mechanism of the subsurface objects. A 3-D full polarimetric GPR data set was acquired in a laboratory experiment and was used to test the method. In the laboratory experiment, four objects-a scatterer, a ball, a plate and a dihedral target-were buried in homogeneous dry sand under a flat ground surface. By merging the reconstructed image with polarization properties, we enhanced the subsurface image and improved the classification ability of GPR.

Optoacoustic technique for noninvasive monitoring of blood oxygenation: a feasibility study

NASA Astrophysics Data System (ADS)

Esenaliev, Rinat O.; Larina, Irina V.; Larin, Kirill V.; Deyo, Donald J.; Motamedi, Massoud; Prough, Donald S.

2002-08-01

Replacement of invasive monitoring of cerebral venous oxygenation with noninvasive techniques offers great promise in the management of life-threatening neurologic illnesses including traumatic brain injury. We developed and built an optoacoustic system to noninvasively monitor cerebral venous oxygenation; the system includes a nanosecond Nd:YAG laser and a specially designed optoacoustic probe. We tested the system in vitro in sheep blood with experimentally varied oxygenation. Our results demonstrated that (1) the amplitude and temporal profile of the optoacoustic waves increase with blood oxygenation in the range from 24% to 92%, (2) optoacoustic signals can be detected despite optical and acoustic attenuation by thick bone, and (3) the system is capable of real-time and continuous measurements. These results suggest that the optoacoustic technique is technically feasible for continuous, noninvasive monitoring of cerebral venous oxygenation.

Conditions of persistent oil on beaches in Prince William Sound 26 years after the Exxon Valdez spill

NASA Astrophysics Data System (ADS)

Lindeberg, Mandy R.; Maselko, Jacek; Heintz, Ron A.; Fugate, Corey J.; Holland, Larry

2018-01-01

On March 24, 1989, the Exxon Valdez grounded on Bligh Reef in Prince William Sound, Alaska, spilling an estimated 10.8 million gallons of crude oil. Contrary to early projections, subsequent studies over several decades have shown subsurface oil persisting on impacted beaches. Here we present findings from a lingering oil survey conducted during the summer of 2015 at a small set of beaches in Prince William Sound known to have persistent subsurface Exxon Valdez oil. The objectives of the survey were to estimate how much oil remains at these sites, the oil composition, and oil retention rates compared to previous studies. Results from the survey found lingering oil was present at 8 of 9 sites that were revisited. Surveys revealed little evidence of change in oil area or mass over the last 14 years, nor has there been a change in the distribution of oiling intensities or their location on the beach. Detailed analysis of the oil indicated it has not weathered since 2001. Subsurface oils collected in 2015 have enriched concentrations of phenanthrenes and chrysenes relative to oil originating in the cargo hold indicating that buried oil has retained some toxic potential over the last two decades, but it is not currently bioavailable. Subsurface oil appears to be sequestered in sediments and protected from hydrological washing and low oxygen and nutrient levels inhibiting biodegradation. These findings are consistent with previous surveys and predictive geomorphic models suggesting the estimated 0.6% Exxon Valdez oil remaining is sequestered and not bioavailable unless disturbed and will likely persist in the environment on a decadal scale.

Asymmetric Signature of Glacial Antarctic Intermediate Water in the Central South Pacific

NASA Astrophysics Data System (ADS)

Tapia, R.; Nuernberg, D.; Ho, S. L.; Lamy, F.; Ullermann, J.; Gersonde, R.; Tiedemann, R.

2017-12-01

Southern Ocean Intermediate Waters (SOIWs) play a key role in modulating the global climate on glacial-interglacial time scales as they connect the Southern Ocean and the tropics. Despite their importance, the past evolution of the SOIWs in the central South Pacific is largely unknown due to a dearth of sedimentary archives. Here we compare Mg/Ca-temperature, stable carbon and oxygen isotope records from surface-dwelling (G. bulloides) and deep-dwelling (G. inflata) planktic foraminifera at site PS75/059-2 (54°12.9' S, 125°25.53' W; recovery 13.98 m; 3.613 m water depth), located north of the modern Subantarctic Front. Our study focuses on the temperature and salinity variability controlled by SOIWs, which were subducted at the Subantarctic Front during the Last Glacial Maximum (LGM; 29-17ka BP) and the Penultimate Glacial Maximum (PGM; 180-150ka BP). During both glacial periods conditions at the subsurface ocean were colder and fresher relative to the Holocene (<10ka) suggesting an enhanced presence of SOIWs. In spite of the comparable subsurface cooling during both glacial, the subsurface ocean during the PGM was saltier and 0.35‰ more depleted in δ13C in comparison to the LGM. Interestingly, the mean δ13C value of the PGM is comparable to the Carbon Isotope Minimum Events, which might suggests a larger contribution of "old" low δ13C deep waters to the study site during the PGM. A Latitudinal comparison of subsurface proxies suggests glacial asymmetries in the advection of SOIWs into the central Pacific, plausibly related to glacial changes in the convection depth of SOIWs at the South Antarctic Front area rather than changes in production of the SOIWs.

The Importance of pH, Oxygen, and Bitumen on the Oxidation and Precipitation of Fe(III)-(oxy)hydroxides during Hydraulic Fracturing of Oil/Gas Shales

NASA Astrophysics Data System (ADS)

Jew, A. D.; Dustin, M. K.; Harrison, A. L.; Joe-Wong, C. M.; Thomas, D.; Maher, K.; Brown, G. E.; Bargar, J.

2016-12-01

Due to the rapid growth of hydraulic fracturing in the United States, understanding the cause for the rapid production drop off of new wells over the initial months of production is paramount. One possibility for the production decrease is pore occlusion caused by the oxidation of Fe(II)-bearing phases resulting in Fe(III) precipitates. To understand the release and fate of Fe in the shale systems, we reacted synthesized fracture fluid at 80oC with shale from four different geological localities (Marcellus Fm., Barnett Fm., Eagle Ford Fm., and Green River Fm.). A variety of wet chemical and synchrotron-based techniques (XRF mapping and x-ray absorption spectroscopy) were used to understand Fe release and solid phase Fe speciation. Solution pH was found to be the greatest factor for Fe release. Carbonate-poor Barnett and Marcellus shale showed rapid Fe release into solution followed by a plateau or significant drop in Fe concentrations indicating mineral precipitation. Conversely, in high carbonate shales, Eagle Ford and Green River, no Fe was detected in solution indicating fast Fe oxidation and precipitation. For all shale samples, bulk Fe EXAFS data show that a significant amount of Fe in the shales is bound directly to organic carbon. Throughout the course of the experiments inorganic Fe(II) phases (primarily pyrite) reacted while Fe(II) bound to C showed no indication of reaction. On the micron scale, XRF mapping coupled with μ-XANES spectroscopy showed that at pH < 4.0, Fe(III) bearing phases precipitated as diffuse surface precipitates of ferrihydrite, goethite, and magnetite away from Fe(II) point sources. In near circum-neutral pH systems, Fe(III)-bearing phases (goethite and hematite) form large particles 10's of μm's in diameter near Fe(II) point sources. Idealized systems containing synthesized fracturing fluid, dissolved ferrous chloride, and bitumen showed that bitumen released during reaction with fracturing fluids is capable of oxidizing Fe(II) to Fe(III) at pH's 2.0 and 7.0. This indicates that bitumen can play a large role in Fe oxidation and speciation in the subsurface. This work shows that shale mineralogy has a significant impact on the morphology and phases of Fe(III) precipitates in the subsurface which in turn can significantly impact subsurface solution flow.

Stable and Variable Parts of Microbial Community in Siberian Deep Subsurface Thermal Aquifer System Revealed in a Long-Term Monitoring Study

PubMed Central

Frank, Yulia A.; Kadnikov, Vitaly V.; Gavrilov, Sergey N.; Banks, David; Gerasimchuk, Anna L.; Podosokorskaya, Olga A.; Merkel, Alexander Y.; Chernyh, Nikolai A.; Mardanov, Andrey V.; Ravin, Nikolai V.; Karnachuk, Olga V.; Bonch-Osmolovskaya, Elizaveta A.

2016-01-01

The goal of this work was to study the diversity of microorganisms inhabiting a deep subsurface aquifer system in order to understand their functional roles and interspecies relations formed in the course of buried organic matter degradation. A microbial community of a deep subsurface thermal aquifer in the Tomsk Region, Western Siberia was monitored over the course of 5 years via a 2.7 km deep borehole 3P, drilled down to a Palaeozoic basement. The borehole water discharges with a temperature of ca. 50°C. Its chemical composition varies, but it steadily contains acetate, propionate, and traces of hydrocarbons and gives rise to microbial mats along the surface flow. Community analysis by PCR-DGGE 16S rRNA genes profiling, repeatedly performed within 5 years, revealed several dominating phylotypes consistently found in the borehole water, and highly variable diversity of prokaryotes, brought to the surface with the borehole outflow. The major planktonic components of the microbial community were Desulfovirgula thermocuniculi and Methanothermobacter spp. The composition of the minor part of the community was unstable, and molecular analysis did not reveal any regularity in its variations, except some predominance of uncultured Firmicutes. Batch cultures with complex organic substrates inoculated with water samples were set in order to enrich prokaryotes from the variable part of the community. PCR-DGGE analysis of these enrichments yielded uncultured Firmicutes, Chloroflexi, and Ignavibacteriae. A continuous-flow microaerophilic enrichment culture with a water sample amended with acetate contained Hydrogenophilus thermoluteolus, which was previously detected in the microbial mat developing at the outflow of the borehole. Cultivation results allowed us to assume that variable components of the 3P well community are hydrolytic organotrophs, degrading buried biopolymers, while the constant planktonic components of the community degrade dissolved fermentation products to methane and CO2, possibly via interspecies hydrogen transfer. Occasional washout of minor community components capable of oxygen respiration leads to the development of microbial mats at the outflow of the borehole where residual dissolved fermentation products are aerobically oxidized. Long-term community analysis with the combination of molecular and cultivation techniques allowed us to characterize stable and variable parts of the community and propose their environmental roles. PMID:28082967

Monitoring spatial and temporal variations of permeability in constructed wetlands by time-lapse geophysical methods

NASA Astrophysics Data System (ADS)

Tapias, J. C.; Himi, M.; Lovera, R.; Blasco, R.; Folch, M.; Casas, A.

2012-04-01

Constructed wetlands are widely used for removing pollutants from wastewater in small communities because their simplicity and low operation costs. Nevertheless, with time the cleaning process can result in gradual clogging of the porous layer by suspended solids, bacterial film, chemical precipitates and compactation. The clogging development causes decrease of hydraulic conductivity, reduced oxygen supply and further leads to a rapid decrease of the treatment performance. As the investment involved in reversing clogging can represent a substantial fraction of the cost of a new system it is essential to assess in advance the evolution of clogging process and detect potential failures in the system. Since there is a lack of experiences for monitoring the functionality of constructed wedlands a combination of non-destructive geophysical methods have been tested in this study. With this purpose electrical resistivity tomography, induced polarisation, frequency domain EM and ground probing radar have been conducted at different horizontal subsurface flow municipal wastewater treatment wetlands of Catalonia (Spain). The obtained results have shown that the applied geophysical techniques may delineate the clogging expansion and help take the preventive measures for enlarge the lifetime of the treatment system.

A technique for measuring oxygen saturation in biological tissues based on diffuse optical spectroscopy

NASA Astrophysics Data System (ADS)

Kleshnin, Mikhail; Orlova, Anna; Kirillin, Mikhail; Golubiatnikov, German; Turchin, Ilya

2017-07-01

A new approach to optical measuring blood oxygen saturation was developed and implemented. This technique is based on an original three-stage algorithm for reconstructing the relative concentration of biological chromophores (hemoglobin, water, lipids) from the measured spectra of diffusely scattered light at different distances from the probing radiation source. The numerical experiments and approbation of the proposed technique on a biological phantom have shown the high reconstruction accuracy and the possibility of correct calculation of hemoglobin oxygenation in the presence of additive noise and calibration errors. The obtained results of animal studies have agreed with the previously published results of other research groups and demonstrated the possibility to apply the developed technique to monitor oxygen saturation in tumor tissue.

Sensitive Technique Developed Using Atomic Force Microscopy to Measure the Low-Earth-Orbit Atomic Oxygen Erosion of Polymers

NASA Technical Reports Server (NTRS)

deGroh, Kim D.; Banks, Bruce A.; Clark, Gregory W.; Hammerstrom, Anne; Youngstrom, Erica; Kaminski, Carolyn; Fine, Elizabeth; Marx, Laura

2001-01-01

A recession measurement technique has been developed at the NASA Glenn Research Center to determine the atomic oxygen durability of polymers exposed to the space environment for short durations. Polymers such as polyimide Kapton and Teflon FEP (fluorinated ethylene propylene, DuPont) are commonly used in spacecraft because of their desirable properties, such as flexibility, low density, and in the case of FEP, low solar absorptance and high thermal emittance. Polymers on the exterior of spacecraft in the low- Earth-orbit environment are exposed to energetic atomic oxygen, resulting in erosion and potential structural loss. It is, therefore, important to understand the atomic oxygen erosion yield (E, the volume loss per incident oxygen atom) of polymers being considered in spacecraft design. Because long-term space exposure data are rare and very costly, short-term exposures, such as on the space shuttles, are often relied on for atomic oxygen erosion determination. The most common technique for determining E is through mass-loss measurements. For limited-duration exposure experiments, such as shuttle flight experiments, the atomic oxygen fluence is often so small that mass-loss measurements are not sensitive enough. Therefore, a recession measurement technique has been developed at Glenn to obtain accurate erosion yields of polymers exposed to low atomic oxygen fluences.

Comparison of Minimally and More Invasive Methods of Determining Mixed Venous Oxygen Saturation.

PubMed

Smit, Marli; Levin, Andrew I; Coetzee, Johan F

2016-04-01

To investigate the accuracy of a minimally invasive, 2-step, lookup method for determining mixed venous oxygen saturation compared with conventional techniques. Single-center, prospective, nonrandomized, pilot study. Tertiary care hospital, university setting. Thirteen elective cardiac and vascular surgery patients. All participants received intra-arterial and pulmonary artery catheters. Minimally invasive oxygen consumption and cardiac output were measured using a metabolic module and lithium-calibrated arterial waveform analysis (LiDCO; LiDCO, London), respectively. For the minimally invasive method, Step 1 involved these minimally invasive measurements, and arterial oxygen content was entered into the Fick equation to calculate mixed venous oxygen content. Step 2 used an oxyhemoglobin curve spreadsheet to look up mixed venous oxygen saturation from the calculated mixed venous oxygen content. The conventional "invasive" technique used pulmonary artery intermittent thermodilution cardiac output, direct sampling of mixed venous and arterial blood, and the "reverse-Fick" method of calculating oxygen consumption. LiDCO overestimated thermodilution cardiac output by 26%. Pulmonary artery catheter-derived oxygen consumption underestimated metabolic module measurements by 27%. Mixed venous oxygen saturation differed between techniques; the calculated values underestimated the direct measurements by between 12% to 26.3%, this difference being statistically significant. The magnitude of the differences between the minimally invasive and invasive techniques was too great for the former to act as a surrogate of the latter and could adversely affect clinical decision making. Copyright © 2016 Elsevier Inc. All rights reserved.

Crustal modeling of the central part of the Northern Western Desert, Egypt using gravity data

NASA Astrophysics Data System (ADS)

Alrefaee, H. A.

2017-05-01

The Bouguer anomaly map of the central part of the Northern Western Desert, Egypt was used to construct six 2D gravity models to investigate the nature, physical properties and structures of the crust and upper mantle. The crustal models were constrained and constructed by integrating results from different geophysical techniques and available geological information. The depth to the basement surface, from eight wells existed across the study area, and the depth to the Conrad and Moho interfaces as well as physical properties of sediments, basement, crust and upper mantle from previous petrophysical and crustal studies were used to establish the gravity models. Euler deconvolution technique was carried on the Bouguer anomaly map to detect the subsurface fault trends. Edge detection techniques were calculated to outlines the boundaries of subsurface structural features. Basement structural map was interpreted to reveal the subsurface structural setting of the area. The crustal models reveals increasing of gravity field from the south to the north due to northward thinning of the crust. The models reveals also deformed and rugged basement surface with northward depth increasing from 1.6 km to 6 km. In contrast to the basement, the Conrad and Moho interfaces are nearly flat and get shallower northward where the depth to the Conrad or the thickness of the upper crust ranges from 18 km to 21 km while the depth to the Moho (crustal thickness) ranges from 31.5 km to 34 km. The crust beneath the study area is normal continental crust with obvious thinning toward the continental margin at the Mediterranean coast.

Subsurface geomicrobiology in a Mars terrestrial analogue, Río Tinto (SW, Spain)

NASA Astrophysics Data System (ADS)

Amils, R.; Fernández-Remolar, D.; Gómez, F.; González-Toril, E.; Rodríguez, N.; Prieto-Ballesteros, O.; Sanz, J. L.; Díaz, E.; Stoker, C.

2008-09-01

Since its discovery, only few years ago, subsurface geomicrobiology is a matter of growing interest [1]. From a fundamental point of view, it seeks to determine whether life can be sustained in the absence of radiation. From an astrobiological point of view, it is an interesting model for life in other planetary bodies, e.g., Mars, as well as early life on Earth. Río Tinto is an unusual extreme acidic environment due to its size (around 100 km), constant acidic pH (mean pH 2.3), high concentrations of heavy metals and high level of microbial diversity [2]. Río Tinto rises in the core of the Iberian Pyritic Belt, one of the biggest sulfidic ore deposits in the world [3]. Today it is well stablished that the extreme characteristics of Río Tinto are not due to acid mine drainage from mining activity, as has been suggested in the past. To explore the hypothesis that a continuous underground reactor of chemolithotrophic microorganisms thriving in the rich sulfidic minerals of the Iberian Pyritic Belt is responsible for the extreme conditions found in the system, a drilling project has been developed to detect evidence of subsurface microbial activity and potential resources to support these microbial communities in situ (MARTE project) [4]. Here we report a search for subsurface life in volcanically hosted massive sulfidic deposits from the Iberian Pyritic Belt. Aseptic core samples were obtained within and down-gradient from the massive sulfide deposits and formation water was sampled within the resulting bore holes. Microbial activity was detected in un-contaminated samples by culture-dependent and culture-independent methods. Aerobic iron- and sulfide- oxidizing bacteria, and anaerobic denitrifying thiosulfate-oxidizing bacteria, sulfate reducing bacteria and methanogenic archaea have been identified. Potential energy fluxes detected in the system include oxidation of reduced iron and sulfur, or hydrogen gas coupled to nitrite, sulfate, ferric iron, inorganic carbon or transient oxygen. These results suggest that multiple energy sources are available from sulfide-mineral weathering to support microbial metabolism, even in the absence of atmospheric oxygen. [1] Stevens, T.O and McKinley, J.P. (1995) Scienc,, 270, 450-454. [2] Amis, R. et al. (2007) Planet Space Sci, 55, 370- 381. [3] Fernández-Remolar, D. et al. (2005) Earth Planet Sci Lett, 240, 149-167. [4] Amils, R. et al. (2008) Microbiology of Extreme Soils, 205-223.

Well Planning and Construction Haynesville Shale - East Texas

EPA Pesticide Factsheets

This paper will focus on the well planning and construction techniques Devon uses in the Haynesville Shale. It will briefly cover issues that are related to designing and drilling the well safely and protecting subsurface drinking water sources.

Nutrient Estimation Using Subsurface Sensing Methods

USDA-ARS?s Scientific Manuscript database

This report investigates the use of precision management techniques for measuring soil conductivity on feedlot surfaces to estimate nutrient value for crop production. An electromagnetic induction soil conductivity meter was used to collect apparent soil electrical conductivity (ECa) from feedlot p...

Assessing and reducing hydrogeologic model uncertainty

USDA-ARS?s Scientific Manuscript database

NRC is sponsoring research that couples model abstraction techniques with model uncertainty assessment methods. Insights and information from this program will be useful in decision making by NRC staff, licensees and stakeholders in their assessment of subsurface radionuclide transport. All analytic...

MASS BALANCE ANALYSIS FOR MICROBIAL DECHLORINATION OF TETRACHLOROETHENE

EPA Science Inventory

Contamination of subsurface environments by chlorinated aliphatic solvents and petroleum hydrocarbons is a significant public health concern because groundwater is one of the major drinking water resources in the United States. Biotic and abiotic techniques have been widely exam...

Quantum chemical elucidation of the mechanism for hydrogenation of TiO2 anatase crystals

NASA Astrophysics Data System (ADS)

Raghunath, P.; Huang, W. F.; Lin, M. C.

2013-04-01

Hydrogenation of TiO2 is relevant to hydrogen storage and water splitting. We have carried out a detailed mechanistic study on TiO2 hydrogenation through H and/or H2 diffusion from the surface into subsurface layers of anatase TiO2 (101) by periodic density functional theory calculations implementing on-site Coulomb interactions (DFT + U). Both H atoms and H2 molecules can migrate from the crystal surface into TiO2 near subsurface layer with 27.8 and 46.2 kcal/mol energy barriers, respectively. The controlling step for the former process is the dissociative adsorption of H2 on the surface which requires 47.8 kcal/mol of energy barrier. Both hydrogen incorporation processes are expected to be equally favorable. The barrier energy for H2 migration from the first layer of the subsurface Osub1 to the 2nd layer of the subsurface oxygen Osub2 requires only 6.6 kcal. The presence of H atoms on the surface and inside the subsurface layer tends to promote both H and H2 penetration into the subsurface layer by reducing their energy barriers, as well as to prevent the escape of the H2 from the cage by increasing its escaping barrier energy. The H2 molecule inside a cage can readily dissociate and form 2HO-species exothermically (ΔH = -31.0 kcal/mol) with only 26.2 kcal/mol barrier. The 2HO-species within the cage may further transform into H2O with a 22.0 kcal/mol barrier and 19.3 kcal/mol exothermicity relative to the caged H2 molecule. H2O formation following the breaking of Ti-O bonds within the cage may result in the formation of O-vacancies and surface disordering as observed experimentally under a high pressure and moderately high temperature condition. According to density of states analysis, the projected density of states of the interstitial H, H2, and H2O appear prominently within the TiO2 band gap; in addition, the former induces a shift of the band gap position notably towards the conduction band. The thermochemistry for formation of the most stable sub-surface species (2HO and H2O) has been predicted. These results satisfactorily account for the photo-catalytic activity enhancement observed experimentally by hydrogenation at high temperatures and high pressures.

Subsurface Scattered Photons: Friend or Foe? Improving visible light laser altimeter elevation estimates, and measuring surface properties using subsurface scattered photons

NASA Astrophysics Data System (ADS)

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.

Identifying Hydrologic Flowpaths on Arctic Hillslopes Using Electrical Resistivity and Self Potential

NASA Astrophysics Data System (ADS)

Voytek, E.; Rushlow, C. R.; Godsey, S.; Singha, K.

2015-12-01

Shallow subsurface flow is a dominant process controlling hillslope runoff generation, soil development, and solute reaction and transport. Despite their importance, the location and geometry of flowpaths are difficult to determine. In arctic environments, shallow subsurface flowpaths are limited to a thin zone of seasonal thaw above continuous permafrost, which is traditionally assumed to mimic to surface topography. Here we use a combined approach of electrical resistivity imaging (ERI) and self-potential measurements (SP) to map shallow subsurface flowpaths in and around water tracks, drainage features common to arctic hillslopes. ERI measurements delineate thawed zones in the subsurface that control flowpaths, while SP is sensitive to groundwater flow. We find that areas of low electrical resistivity in the water tracks are deeper than manual thaw depth estimates and variations from surface topography. This finding suggests that traditional techniques significantly underestimate active layer thaw and the extent of the flowpath network on arctic hillslopes. SP measurements identify complex 3-D flowpaths in the thawed zone. Our results lay the groundwork for investigations into the seasonal dynamics, hydrologic connectivity, and climate sensitivity of spatially distributed flowpath networks on arctic hillslopes.

High-Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring and Verification Efforts

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

Lee, Ki Ha; Becker, Alex; Tseng, Hung-Wen

2004-06-16

Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic (EM) measurements at frequencies between 0.1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data canmore » be mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using the EM impedance approach (Frangos, 2001; Lee and Becker, 2001; Song et al., 2002, Tseng et al., 2003). Electric and magnetic sensors are being tested and calibrated on sea water and in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.« less

Platforms for hyperspectral imaging, in-situ optical and acoustical imaging in urbanized regions

NASA Astrophysics Data System (ADS)

Bostater, Charles R.; Oney, Taylor

2016-10-01

Hyperspectral measurements of the water surface of urban coastal waters are presented. Oblique bidirectional reflectance factor imagery was acquired made in a turbid coastal sub estuary of the Indian River Lagoon, Florida and along coastal surf zone waters of the nearby Atlantic Ocean. Imagery was also collected using a pushbroom hyperspectral imager mounted on a fixed platform with a calibrated circular mechatronic rotation stage. Oblique imagery of the shoreline and subsurface features clearly shows subsurface bottom features and rip current features within the surf zone water column. In-situ hyperspectral optical signatures were acquired from a vessel as a function of depth to determine the attenuation spectrum in Palm Bay. A unique stationary platform methodology to acquire subsurface acoustic images showing the presence of moving bottom boundary nephelometric layers passing through the acoustic fan beam. The acoustic fan beam imagery indicated the presence of oscillatory subsurface waves in the urbanized coastal estuary. Hyperspectral imaging using the fixed platform techniques are being used to collect hyperspectral bidirectional reflectance factor (BRF) measurements from locations at buildings and bridges in order to provide new opportunities to advance our scientific understanding of aquatic environments in urbanized regions.

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

Bonneville, Alain H.; Kouzes, Richard T.

Imaging subsurface geological formations, oil and gas reservoirs, mineral deposits, cavities or magma chambers under active volcanoes has been for many years a major quest of geophysicists and geologists. Since these objects cannot be observed directly, different indirect geophysical methods have been developed. They are all based on variations of certain physical properties of the subsurface that can be detected from the ground surface or from boreholes. Electrical resistivity, seismic wave’s velocities and density are certainly the most used properties. If we look at density, indirect estimates of density distributions are performed currently by seismic reflection methods - since themore » velocity of seismic waves depend also on density - but they are expensive and discontinuous in time. Direct estimates of density are performed using gravimetric data looking at variations of the gravity field induced by the density variations at depth but this is not sufficiently accurate. A new imaging technique using cosmic-ray muon detectors has emerged during the last decade and muon tomography - or muography - promises to provide, for the first time, a complete and precise image of the density distribution in the subsurface. Further, this novel approach has the potential to become a direct, real-time, and low-cost method for monitoring fluid displacement in subsurface reservoirs.« less

Methods and system for subsurface stabilization using jet grouting

DOEpatents

Loomis, Guy G.; Weidner, Jerry R.; Farnsworth, Richard K.; Gardner, Bradley M.; Jessmore, James J.

1999-01-01

Methods and systems are provided for stabilizing a subsurface area such as a buried waste pit for either long term storage, or interim storage and retrieval. A plurality of holes are drilled into the subsurface area with a high pressure drilling system provided with a drill stem having jet grouting nozzles. A grouting material is injected at high pressure through the jet grouting nozzles into a formed hole while the drill stem is withdrawn from the hole at a predetermined rate of rotation and translation. A grout-filled column is thereby formed with minimal grout returns, which when overlapped with other adjacent grout-filled columns encapsulates and binds the entire waste pit area to form a subsurface agglomeration or monolith of grout, soil, and waste. The formed monolith stabilizes the buried waste site against subsidence while simultaneously providing a barrier against contaminate migration. The stabilized monolith can be left permanently in place or can be retrieved if desired by using appropriate excavation equipment. The jet grouting technique can also be utilized in a pretreatment approach prior to in situ vitrification of a buried waste site. The waste encapsulation methods and systems are applicable to buried waste materials such as mixed waste, hazardous waste, or radioactive waste.

Increasing subterranean mobilization of organic contaminants and petroleum by aqueous thermal oxidation

DOEpatents

Leif, Roald N.; Knauss, Kevin G.; Newmark, Robin L.; Aines, Roger D.; Eaker, Craig

2002-01-01

In situ hydrous pyrolysis/partial oxidation of organics at the site of the organics constrained in an subsurface reservoir produces surfactants that can form an oil/water emulsion that is effectively removed from an underground formation. The removal of the oil/water emulsions is particularly useful in several applications, e.g., soil contaminant remediation and enhanced oil recovery operations. A portion of the constrained organics react in heated reservoir water with injected steam containing dissolved oxygen gas at ambient reservoir conditions to produce such surfactants.

Pulsating potentiometric titration technique for assay of dissolved oxygen in water at trace level.

PubMed

Sahoo, P; Ananthanarayanan, R; Malathi, N; Rajiniganth, M P; Murali, N; Swaminathan, P

2010-06-11

A simple but high performance potentiometric titration technique using pulsating sensors has been developed for assay of dissolved oxygen (DO) in water samples down to 10.0 microg L(-1) levels. The technique involves Winkler titration chemistry, commonly used for determination of dissolved oxygen in water at mg L(-1) levels, with modification in methodology for accurate detection of end point even at 10.0 microg L(-1) levels DO present in the sample. An indigenously built sampling cum pretreatment vessel has been deployed for collection and chemical fixing of dissolved oxygen in water samples from flowing water line without exposure to air. A potentiometric titration facility using pulsating sensors developed in-house is used to carry out titration. The power of the titration technique has been realised in estimation of very dilute solution of iodine equivalent to 10 microg L(-1) O(2). Finally, several water samples containing dissolved oxygen from mg L(-1) to microg L(-1) levels were successfully analysed with excellent reproducibility using this new technique. The precision in measurement of DO in water at 10 microg L(-1) O(2) level is 0.14 (n=5), RSD: 1.4%. Probably for the first time a potentiometric titration technique has been successfully deployed for assay of dissolved oxygen in water samples at 10 microg L(-1) levels. Copyright 2010 Elsevier B.V. All rights reserved.

Extracellular oxygen concentration mapping with a confocal multiphoton laser scanning microscope and TCSPC card

NASA Astrophysics Data System (ADS)

Hosny, Neveen A.; Lee, David A.; Knight, Martin M.

2010-02-01

Extracellular oxygen concentrations influence cell metabolism and tissue function. Fluorescence Lifetime Imaging Microscopy (FLIM) offers a non-invasive method for quantifying local oxygen concentrations. However, existing methods show limited spatial resolution and/or require custom made systems. This study describes a new optimised approach for quantitative extracellular oxygen detection, providing an off-the-shelf system with high spatial resolution and an improved lifetime determination over previous techniques, while avoiding systematic photon pile-up. Fluorescence lifetime detection of an oxygen sensitive fluorescent dye, tris(2,2'-bipyridyl)ruthenium(II) chloride hexahydrate [Ru(bipy)3]2+, was measured using a Becker&Hickl time-correlated single photon counting (TCSPC) card with excitation provided by a multi-photon laser. This technique was able to identify a subpopulation of isolated chondrocyte cells, seeded in three-dimensional agarose gel, displaying a significant spatial oxygen gradient. Thus this technique provides a powerful tool for quantifying spatial oxygen gradients within three-dimensional cellular models.

Spatio-temporal biodiversity of soft bottom macrofaunal assemblages in shallow coastal waters exposed to episodic hypoxic events.

PubMed

Veas, Rodrigo; Hernández-Miranda, Eduardo; Quiñones, Renato A; Carrasco, Franklin D

2012-07-01

The Humboldt Current System (HCS) has one of the three most important oxygen minimum zones (OMZ) of the global ocean. Several studies have looked at the macrofaunal benthic assemblages inhabiting the continental shelf and shallow bays off central-southern Chile associated with low oxygen areas, but little is known about open coast macrofaunal communities within this zone, which are frequently subjected to the low oxygen conditions of Equatorial Subsurface Waters (ESSW). In order to assess local and mesoscale coastal macrofauna dynamics, the sampling area (ca. 40 linear km) was divided into seven local zones (Cobquecura, southern Cobquecura, northern Itata, Itata River mouth, external, southern Itata, and Coliumo). Eight oceanographic cruises were carried out between May 2006 and February 2008 covering 16 coastal sampling sites, between 36°07'S and 36°30'S. The macrofaunal assemblage was dominated by polychaetes, crustaceans, and mollusks. Our results suggest a high degree of temporal faunal stability on the mesoscale in soft bottom communities along the open coast, given the persistence of a faunal assemblage dominated by organisms tolerant of low oxygen conditions. While there is some local variability in community attributes, the main structuring factor for soft bottom communities in the shallow coastal area off central-southern Chile is the seasonal intrusion of low oxygen ESSW. Copyright © 2012 Elsevier Ltd. All rights reserved.

Platinum-Coated Hollow Graphene Nanocages as Cathode Used in Lithium-Oxygen Batteries

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

Wu, Feng; Xing, Yi; Zeng, Xiaoqiao

2016-08-31

One of the formidable challenges facing aprotic lithium-oxygen (Li-O-2) batteries is the high charge overpotential, which induces the formation of byproducts, loss in efficiency, and poor cycling performance. Herein, the synthesis of the ultrasmall Pt-coated hollow graphene nano cages as cathode in Li-O-2 batteries is reported. The charge voltage plateau can reduce to 3.2 V at the current density of 100 mA g(-1), even maintain below 3.5 V when the current density increased to 500 mA g(-1). The unique hollow graphene nanocages matrix can not only provide numerous nanoscale tri-phase regions as active sites for efficient oxygen reduction, but alsomore » offer sufficient amount of mesoscale pores for rapid oxygen diffusion. Furthermore, with strong atomic-level oxygen absorption into its subsurface, ultrasmall Pt catalytically serves as the nucleation site for Li2O2 growth. The Li2O2 is subsequently induced into a favorable form with small size and amorphous state, decomposed more easily during recharge. Meanwhile, the conductive hollow graphene substrate can enhance the catalytic activity of noble metal Pt catalysts due to the graphene-metal interfacial interaction. Benefiting from the above synergistic effects between the hollow graphene nanocages and the nanosized Pt catalysts, the ultrasmall Pt-decorated graphene nanocage cathode exhibits enhanced electrochemical performances.« less

Rational Design of a Hierarchical Tin Dendrite Electrode for Efficient Electrochemical Reduction of CO2.

PubMed

Won, Da Hye; Choi, Chang Hyuck; Chung, Jaehoon; Chung, Min Wook; Kim, Eun-Hee; Woo, Seong Ihl

2015-09-21

Catalysis is a key technology for the synthesis of renewable fuels through electrochemical reduction of CO2 . However, successful CO2 reduction still suffers from the lack of affordable catalyst design and understanding the factors governing catalysis. Herein, we demonstrate that the CO2 conversion selectivity on Sn (or SnOx /Sn) electrodes is correlated to the native oxygen content at the subsurface. Electrochemical analyses show that the reduced Sn electrode with abundant oxygen species effectively stabilizes a CO2 (.-) intermediate rather than the clean Sn surface, and consequently results in enhanced formate production in the CO2 reduction. Based on this design strategy, a hierarchical Sn dendrite electrode with high oxygen content, consisting of a multi-branched conifer-like structure with an enlarged surface area, was synthesized. The electrode exhibits a superior formate production rate (228.6 μmol h(-1)  cm(-2) ) at -1.36 VRHE without any considerable catalytic degradation over 18 h of operation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Europe as a goal for colonization

NASA Astrophysics Data System (ADS)

Steklov, A. F.; Vidmachenko, A. P.

2018-05-01

Europe as a target for human colonization has several advantages over many other bodies of the outer solar system. Although we point out on a few problems. So, Europe has a liquid ocean of water under the ice cover, but access to this water is a serious test. In this case, the abundance of water in Europe is an advantage for possible colonization. After all, ice, fresh lakes and the ocean itself can meet the needs of colonists in the water. It can also be divided into oxygen and hydrogen. It is believed that oxygen can accumulate as a result of radiolysis of ice on the surface, and then be transferred to the subsurface ocean. There, in the ocean, it may be enough of oxygen for using by some life form. Presence of liquid water below the ice surface of Europe, and the fact that the colonists will be spend most of their time under the ice shield in order to protect themselves from radiation, can somewhat alleviate the problems associated with low temperatures. And an unstable surface can be a potential problem.

Ages of subsurface stratigraphic intervals in the Quaternary of Enewetak Atoll, Marshall Islands

USGS Publications Warehouse

Szabo, B. J.; Tracey, J.I.; Goter, E.R.

1985-01-01

Drill cores of Enewetak Atoll, Marshall Islands, reveal six stratigraphic intervals, numbered in downward sequence, which represent vertical coral growth during Quaternary interglaciations. Radiocarbon dates indicate that the Holocene sea transgressed the emergent reef platform by about 8000 yr B.P. The reef grew rapidly upward (about 5 to 10 mm/yr) until about 6500 yr B.P. Afterward vertical growth slowed to about 0.5 mm/yr, then lateral development became dominant during the last several thousand years. The second interval is dated at 131,000 ?? 3000 yr B.P. by uranium series. This unit correlates with oxygen-isotope substage 5e and with terrace VIIa of Huon Peninsula, New Guinea, and of Main Reef-2 terrace at Atauro Island. The third interval is not dated because corals were recrystallized and it is tentatively correlated with either oxygen-isotope stages 7 or 9. The age of the fourth interval is estimated at 454,000 ?? 100,000 yr B.P. from measured 234U 238U activity ratios. This unit is correlated with either oxygen-isotope stage 9, 11, or 13. ?? 1985.

Recovering the superficial microvascular pattern via diffuse reflection imaging: phantom validation.

PubMed

Chen, Chen; Florian, Klämpfl; Rajesh, Kanawade; Max, Riemann; Christian, Knipfer; Florian, Stelzle; Michael, Schmidt

2015-09-30

Diffuse reflection imaging could potentially be used to recover the superficial microvasculature under cutaneous tissue and the associated blood oxygenation status with a modified imaging resolution. The aim of this work is to deliver a new approach of local off-axis scanning diffuse reflection imaging, with the revisit of the modified Beer-Lambert Law (MBLL). To validate this, the system is used to recover the micron-scale subsurface vessel structure interiorly embedded in a skin equivalent tissue phantom. This vessel structure is perfused with oxygenated meta-hemoglobin solution. Our preliminary results confirm that the thin vessel structure can be mapped into a 2-D planar image. The distributions of oxygenated hemoglobin concentration ([Formula: see text]) and deoxygenated hemoglobin concentration ([Formula: see text]) can be co-registerated through the MBLL upon the CW spectroscopy, the scattering issue is addressed in the reformed MBLL. The recovered pattern matches to the estimation from the simultaneous optical coherence tomography studies. With further modification, this system may serve as the first prototype to investigate the superficial microvasculature in the expotential skin cancer loci, or a micro-lesion of vascular dermatosis.

Characterization and consequences of intermittent sediment oxygenation by macrofauna: interpretation of high-resolution data sets

NASA Astrophysics Data System (ADS)

Meile, C. D.; Dwyer, I.; Zhu, Q.; Polerecky, L.; Volkenborn, N.

2017-12-01

Mineralization of organic matter in marine sediments leads to the depletion of oxygen, while activities of infauna introduce oxygenated seawater to the subsurface. In permeable sediments solutes can be transported from animals and their burrows into the surrounding sediment through advection over several centimeters. The intermittency of pumping leads to a spatially heterogeneous distribution of oxidants, with the temporal dynamics depending on sediment reactivity and activity patterns of the macrofauna. Here, we present results from a series of experiments in which these dynamics are studied at high spatial and temporal resolution using planar optodes. From O2, pH and pCO2 optode data, we quantify rates of O2 consumption and dissolved inorganic carbon production, as well alkalinity dynamics, with millimeter-scale resolution. Simulating intermittent irrigation by imposed pumping patterns in thin aquaria, we derive porewater flow patterns, which together with the production and consumption rates cause the chemical distributions and the establishment of reaction fronts. Our analysis thus establishes a quantitative connection between the locally dynamic redox conditions relevant for biogeochemical transformations and macroscopic observations commonly made with sediment cores.

Exploring the Deep Biosphere in Ophiolite-hosted Systems: What Can Metabolic Processes in Surface Seeps Tell Us About Subsurface Ecosystems in Serpentinizing Fluids?

NASA Astrophysics Data System (ADS)

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 fluids are expressed. The next step is to understand what these surface systems might tell us about the subsurface biosphere. References: Cardace et al., 2015 Frontiers in Extreme Microbiology 6: doi: 10.3389/fmicb.2015.00010 Woycheese et al., 2015 Frontiers in Extreme Microbiology 6: doi: 10.3389/fmicb.2015.00044

Site investigation report mine research project GUE 70-14.10, Guernsey, Ohio.

DOT National Transportation Integrated Search

2003-06-01

Geophysical investigative techniques can be a valuable supplement to standard subsurface investigations for the : evaluation of abandoned underground coal mine workings and their potential impacts at the ground surface. The GUE : 70 - 14.10 Mine Rese...

Evaluation of Cone Penetrometer Testing (CPT) for Use with Transportation Projects Phase 1

DOT National Transportation Integrated Search

2008-07-01

The ODOT Office of Geotechnical Engineering (OGE) currently uses conventional drilling methods (e.g., hollow stem auger, solid stem auger) to perform subsurface investigations in unconsolidated materials. These techniques have been used for decades a...

Correlation of engineering parameters of the presumpscot formation to the seismic cone penetration test (SCPTU).

DOT National Transportation Integrated Search

2015-08-01

The seismic cone penetration test with pore pressure measurement (SCPTu) is a geotechnical investigation technique which : involves pushing a sensitized cone into the subsurface at a constant rate while continuously measuring tip resistance, sleeve :...

SELECTION AND CALIBRATION OF SUBSURFACE REACTIVE TRANSPORT MODELS USING A SURROGATE-MODEL APPROACH

EPA Science Inventory

While standard techniques for uncertainty analysis have been successfully applied to groundwater flow models, extension to reactive transport is frustrated by numerous difficulties, including excessive computational burden and parameter non-uniqueness. This research introduces a...

Evaluation of cone penetration testing (CPT) for use with transportation projects : executive summary report.

DOT National Transportation Integrated Search

2011-04-01

The ODOT Office of Geotechnical : Engineering (OGE) currently uses : conventional drilling methods (e.g., hollow : stem auger, solid stem auger) to perform : subsurface investigations in soil. These : techniques have been used for decades and : have ...

Where microorganisms meet rocks in the Earth's Critical Zone

NASA Astrophysics Data System (ADS)

Akob, D. M.; Küsel, K.

2011-03-01

The Earth's Critical Zone (CZ) is the critical, outer shell of the Earth that provides an arena for the interplay of diverse physical, chemical, and biological processes that are fundamental for sustaining life. As microbes are the principle drivers of biogeochemical cycles, it is necessary to understand the biodiversity of the CZ unseen majority and their impact on life-sustaining processes. This review aims to summarize the factors controlling where microbes (prokaryotes and micro-eukaryotes) live within the CZ and what is known to date about their diversity and function. Microbes live in all regions of the CZ down to 5 km depth, but due to changing habitat complexity, e.g., variability in pore spaces, water, oxygen, and nutrients, their functional role changes with depth. The abundance of prokaryotes and micro-eukaryotes decreases from a maximum of 1010 or 107 cells g soil-1 up to eight orders of magnitude with depth. Symbiotic mycorrhizal fungi and free-living decomposers are best understood in soil habitats, where they are up to 103 cells g soil-1. However, little is known about their identity and impact on weathering in the deep subsurface. The relatively low abundance of micro-eukaryotes in the deep subsurface suggests that these organisms are either limited in space or nutrients or unable to cope with oxygen limitations. Since deep regions of the CZ are limited in the recent input of photosynthesis-derived carbon, microbes are dependent on deposited organic material or on chemolithoautotrophic metabolism that allows for the establishment of a complete food chain independent from the surface. However, the energy flux available might only allow cell growth over tens to thousands of years. The recent development of "omics" technologies has provided microbial ecologists with methods to link the composition and function of in situ microbial communities. We should expect new metabolic discoveries as we have a closer look utilizing a polyphasic approach into the microbial communities of the CZ. Thus, future work is still needed to link microbial biodiversity to the exact role of microbes in weathering and geochemical cycling in the CZ, especially in subsurface habitats.

On the Subsurface Chlorophyll Maximum layer in the Black Sea Romanian shelf waters

NASA Astrophysics Data System (ADS)

Vasiliu, Dan; Gomoiu, Marian-Traian; Secrieru, Dan; Caraus, Ioan; Balan, Sorin

2013-04-01

By analyzing data recorded in 38 sampling stations (bottom depths between 16 and 200 m) covering the entire Romanian shelf, from the Danube's mouths to the southern part of the coast, the authors study Subsurface Chlorophyll Maximum (SCM) from May 2009 to April 2011. Chlorophyll a (Chla), seawater temperature, salinity, sigma T, dissolved oxygen, ph, beam attenuation, were measured over the water column depth with the CTD probe and averaged over 1-db intervals (about 1 m depth). Nutrients and phytoplankton qualitative and quantitative parameters were recorded from different depths according to water masses stratification (inscribed in the research protocol of the cruise). In late winter/early spring, due to strong mixing processes of water masses, SCM was not observed in the Black Sea shelf waters. In spring (May), the Danube's increased discharges, characteristic to that period, strongly affected the vertical distribution of Chla, particularly in the area of the Danube's direct influence, where Chla reached maximum in the surface layer (19.76 - 30.39 µg.l-1). In the deeper sampling stations, a relatively weak SCM (Chla within 0.77 - 1.21 µg.l-1) was observed, mainly at the lower limit of the euphotic zone (between 30 and 40 m depths). Here, the position and magnitude of SCM seemed to be controlled mainly by the light conditions; the seasonal thermocline was not well contoured yet. In the warm season, once the stratification becomes stronger, the magnitude of SCM increased (Chla varies between 1.45 - 2.12 µg.l-1). The SCM was well pronounced below the upper boundary of thermocline, at depths between 20 and 25 m, where the dissolved oxygen concentrations have also reached the highest values (>10 mg.l-1 O2), thus suggesting strong photosynthetic processes, where both nutrient and light conditions are favorable. A particular situation was found in July 2010, when abnormally high discharges from the Danube led to a well pronounced SCM (3.23 - 6.87 µg.l-1 Chla) above thermocline (within 8 - 12 m depths) in the shallow waters, the nutrients being not limitative factors. Keywords Chlorophyll a, Subsurface Chlorophyll Maximum layer, the Black Sea, the Danube

Export of nutrients and major ionic solutes from a rain forest catchment in the Central Amazon Basin

NASA Astrophysics Data System (ADS)

Lesack, Lance F. W.

1993-03-01

The relative roles of base flow runoff versus storm flow runoff versus subsurface outflow in controlling total export of solutes from a 23.4-ha catchment of undisturbed rain forest in the central Amazon Basin were evaluated from water and solute flux measurements performed over a 1 year period. Solutes exported via 173 storms during the study were estimated from stream water samples collected during base flow conditions and during eight storms, and by utilizing a hydrograph separation technique in combination with a mixing model to partition storm flow from base flow fluxes. Solutes exported by subsurface outflow were estimated from groundwater samples from three nests of piezometers installed into the streambed, and concurrent measurements of hydraulic conductivity and hydraulic head gradients. Base flow discharge represented 92% of water outflow from the basin and was the dominant pathway of solute export. Although storm flow discharge represented only 5% of total water outflow, storm flow solute fluxes represented up to 25% of the total annual export flux, though for many solutes the portion was less. Subsurface outflow represented only 2.5% of total water outflow, and subsurface solute fluxes never represented more than 5% of the total annual export flux. Measurement errors were relatively high for storm flow and subsurface outflow fluxes, but cumulative measurement errors associated with the total solute fluxes exported from the catchment, in most cases, ranged from only ±7% to 14% because base flow fluxes were measured relatively well. The export fluxes of most solutes are substantially less than previously reported for comparable small catchments in the Amazon basin, and these differences cannot be reconciled by the fact that storm flow and subsurface outflows were not appropriately measured in previous studies.

Improved Geologic Interpretation of Non-invasive Electrical Resistivity Imaging from In-situ Samples

NASA Astrophysics Data System (ADS)

Mucelli, A.; Aborn, L.; Jacob, R.; Malusis, M.; Evans, J.

2016-12-01

Non-invasive geophysical techniques are useful in characterizing the subsurface geology without disturbing the environment, however, the ability to interpret the subsurface is enhanced by invasive work. Since geologic materials have electrical resistivity values it allows for a geologic interpretation to be made based on variations of electrical resistivity measured by electrical resistivity imaging (ERI). This study focuses on the pre-characterization of the geologic subsurface from ERI collected adjacent to the Montandon Marsh, a wetland located near Lewisburg, PA within the West Branch of the Susquehanna River watershed. The previous invasive data, boreholes, indicate that the subsurface consists of limestone and shale bedrock overlain with sand and gravel deposits from glacial outwash and aeolian processes. The objective is to improve our understanding of the subsurface at this long-term hydrologic research site by using excavation results, specifically observed variations in geologic materials and electrical resistivity laboratory testing of subsurface samples. The pre-excavation ERI indicated that the shallow-most geologic material had a resistivity value of 100-500 ohm-m. In comparison, the laboratory testing indicated the shallow-most material had the same range of electrical resistivity values depending on saturation levels. The ERI also showed that there was an electrically conductive material, 7 to 70 ohm-m, that was interpreted to be clay and agreed with borehole data, however, the excavation revealed that at this depth range the geologic material varied from stratified clay to clay with cobbles to weathered residual clay. Excavation revealed that the subtle variations in the electrical conductive material corresponded well with the variations in the geologic material. We will use these results to reinterpret previously collected ERI data from the entire long-term research site.

Subsurface Stress Fields in FCC Single Crystal Anisotropic Contacts

NASA Technical Reports Server (NTRS)

Arakere, Nagaraj K.; Knudsen, Erik; Swanson, Gregory R.; Duke, Gregory; Ham-Battista, Gilda

2004-01-01

Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and alternating stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent high cycle fatigue (HCF) failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and non-crystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. This paper presents analytical and numerical techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts. The subsurface stress results are required for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades. An analytical procedure is presented for evaluating the subsurface stresses in the elastic half-space, based on the adaptation of a stress function method outlined by Lekhnitskii. Numerical results are presented for cylindrical and spherical anisotropic contacts, using finite element analysis (FEA). Effects of crystal orientation on stress response and fatigue life are examined. Obtaining accurate subsurface stress results for anisotropic single crystal contact problems require extremely refined three-dimensional (3-D) finite element grids, especially in the edge of contact region. Obtaining resolved shear stresses (RSS) on the principal slip planes also involves considerable post-processing work. For these reasons it is very advantageous to develop analytical solution schemes for subsurface stresses, whenever possible.

Super-smooth processing x-ray telescope application research based on the magnetorheological finishing (MRF) technology

NASA Astrophysics Data System (ADS)

Zhong, Xianyun; Hou, Xi; Yang, Jinshan

2016-09-01

Nickel is the unique material in the X-ray telescopes. And it has the typical soft material characteristics with low hardness high surface damage and low stability of thermal. The traditional fabrication techniques are exposed to lots of problems, including great surface scratches, high sub-surface damage and poor surface roughness and so on. The current fabrication technology for the nickel aspheric mainly adopt the single point diamond turning(SPDT), which has lots of advantages such as high efficiency, ultra-precision surface figure, low sub-surface damage and so on. But the residual surface texture of SPDT will cause great scattering losses and fall far short from the requirement in the X-ray applications. This paper mainly investigates the magnetorheological finishing (MRF) techniques for the super-smooth processing on the nickel optics. Through the study of the MRF polishing techniques, we obtained the ideal super-smooth polishing technique based on the self-controlled MRF-fluid NS-1, and finished the high-precision surface figure lower than RMS λ/80 (λ=632.8nm) and super-smooth roughness lower than Ra 0.3nm on the plane reflector and roughness lower than Ra 0.4nm on the convex cone. The studying of the MRF techniques makes a great effort to the state-of-the-art nickel material processing level for the X-ray optical systems applications.

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

Friedmann, S J

Carbon capture and sequestration (CCS) has emerged as a key technology for dramatic short-term reduction in greenhouse gas emissions in particular from large stationary. A key challenge in this arena is the monitoring and verification (M&V) of CO2 plumes in the deep subsurface. Towards that end, we have developed a tool that can simultaneously invert multiple sub-surface data sets to constrain the location, geometry, and saturation of subsurface CO2 plumes. We have focused on a suite of unconventional geophysical approaches that measure changes in electrical properties (electrical resistance tomography, electromagnetic induction tomography) and bulk crustal deformation (til-meters). We had alsomore » used constraints of the geology as rendered in a shared earth model (ShEM) and of the injection (e.g., total injected CO{sub 2}). We describe a stochastic inversion method for mapping subsurface regions where CO{sub 2} saturation is changing. The technique combines prior information with measurements of injected CO{sub 2} volume, reservoir deformation and electrical resistivity. Bayesian inference and a Metropolis simulation algorithm form the basis for this approach. The method can (a) jointly reconstruct disparate data types such as surface or subsurface tilt, electrical resistivity, and injected CO{sub 2} volume measurements, (b) provide quantitative measures of the result uncertainty, (c) identify competing models when the available data are insufficient to definitively identify a single optimal model and (d) rank the alternative models based on how well they fit available data. We present results from general simulations of a hypothetical case derived from a real site. We also apply the technique to a field in Wyoming, where measurements collected during CO{sub 2} injection for enhanced oil recovery serve to illustrate the method's performance. The stochastic inversions provide estimates of the most probable location, shape, volume of the plume and most likely CO{sub 2} saturation. The results suggest that the method can reconstruct data with poor signal to noise ratio and use hard constraints available from many sites and applications. External interest in the approach and method is high, and already commercial and DOE entities have requested technical work using the newly developed methodology for CO{sub 2} monitoring.« less

Efficient high-dimensional characterization of conductivity in a sand box using massive MRI-imaged concentration data

NASA Astrophysics Data System (ADS)

Lee, J. H.; Yoon, H.; Kitanidis, P. K.; Werth, C. J.; Valocchi, A. J.

2015-12-01

Characterizing subsurface properties, particularly hydraulic conductivity, is crucial for reliable and cost-effective groundwater supply management, contaminant remediation, and emerging deep subsurface activities such as geologic carbon storage and unconventional resources recovery. With recent advances in sensor technology, a large volume of hydro-geophysical and chemical data can be obtained to achieve high-resolution images of subsurface properties, which can be used for accurate subsurface flow and reactive transport predictions. However, subsurface characterization with a plethora of information requires high, often prohibitive, computational costs associated with "big data" processing and large-scale numerical simulations. As a result, traditional inversion techniques are not well-suited for problems that require coupled multi-physics simulation models with massive data. In this work, we apply a scalable inversion method called Principal Component Geostatistical Approach (PCGA) for characterizing heterogeneous hydraulic conductivity (K) distribution in a 3-D sand box. The PCGA is a Jacobian-free geostatistical inversion approach that uses the leading principal components of the prior information to reduce computational costs, sometimes dramatically, and can be easily linked with any simulation software. Sequential images of transient tracer concentrations in the sand box were obtained using magnetic resonance imaging (MRI) technique, resulting in 6 million tracer-concentration data [Yoon et. al., 2008]. Since each individual tracer observation has little information on the K distribution, the dimension of the data was reduced using temporal moments and discrete cosine transform (DCT). Consequently, 100,000 unknown K values consistent with the scale of MRI data (at a scale of 0.25^3 cm^3) were estimated by matching temporal moments and DCT coefficients of the original tracer data. Estimated K fields are close to the true K field, and even small-scale variability of the sand box was captured to highlight high K connectivity and contrasts between low and high K zones. Total number of 1,000 MODFLOW and MT3DMS simulations were required to obtain final estimates and corresponding estimation uncertainty, showing the efficiency and effectiveness of our method.

Anisotropic growth of NiO nanorods from Ni nanoparticles by rapid thermal oxidation.

PubMed

Koga, Kenji; Hirasawa, Makoto

2013-09-20

NiO nanorods with extremely high crystallinity were grown by rapid thermal oxidation through exposure of Ni nanoparticles (NPs) heated above 400° C to oxygen. Oxidation proceeds by nucleation of a NiO island on a Ni NP that grows anisotropically to produce a NiO nanorod. This process differs completely from that under mild oxidation conditions, where the surface of the NPs is completely covered with an oxide film during the early stage of oxidation. The observed novel behaviour strongly suggests an interfacial oxidation mechanism driven by the dissolution of adsorbed oxygen into the Ni NP sub-surface region, subsequent diffusion and reaction at the NiO/Ni interface. The early oxidation conditions of metal NPs impose a significant influence on the entire oxidation process at the nanoscale and are therefore inherently important for the precise morphological control of oxidized NPs to design functional nanomaterials.

The importance of topographic corrections on magnetotelluric response data from rugged regions of Anatolia

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

Guerer, A.; Ilkisik, O.M.

1997-01-01

Topographic irregularities cause some distortions of magnetotelluric (MT) fields. In the vicinity of a topographic feature, the TM-mode distortion increases with the height and inclination of the slope. It is well-known that TM-mode topographic effects are much greater than TE-mode distortions. The authors have made a study of MT anomalies in TM-mode due to two-dimensional topography. In order to reduce these effects, the distortion tensor stripping technique was used. After corrections, the resulting data can be interpreted as if they were obtained over a flat surface and depend only on the subsurface structure. However, this technique sometimes causes some geometricalmore » distortions of the real subsurface structure. One of the aims is to overcome this failure. The authors have modified the correction coefficients by considering the actual one-dimensional geology. Model studies showed that this approach is especially useful in removing the terrain effects on complex 2D subsurface structures. The other purpose of this study is to emphasize the importance of a proper terrain correction for data from sites having mountainous topography over complex geology, e.g., strike-slip faults, suture zones and rift valleys. Some examples of MT data sets collected from the North Anatolian Fault Zone and from the thrust regions of the Western Taurides will be presented.« less

Characterization of a Louisiana Bay Bottom

NASA Astrophysics Data System (ADS)

Freeman, A. M.; Roberts, H. H.

2016-02-01

This study correlates side-scan sonar and CHIRP water bottom-subbottom acoustic amplitudes with cone penetrometer data to expand the limited understanding of the geotechnical properties of sediments in coastal Louisiana's bays. Standardized analysis procedures were developed to characterize the bay bottom and shallow subsurface of the Sister Lake bay bottom. The CHIRP subbottom acoustic data provide relative amplitude information regarding reflection horizons of the bay bottom and shallow subsurface. An amplitude analysis technique was designed to identify different reflectance regions within the lake from the CHIRP subbottom profile data. This amplitude reflectivity analysis technique provides insight into the relative hardness of the bay bottom and shallow subsurface, useful in identifying areas of erosion versus deposition from storms, as well as areas suitable for cultch plants for state oyster seed grounds, or perhaps other restoration projects. Side-scan and CHIRP amplitude reflectivity results are compared to penetrometer data that quantifies geotechnical properties of surface and near-surface sediments. Initial results indicate distinct penetrometer signatures that characterize different substrate areas including soft bottom, storm-deposited silt-rich sediments, oyster cultch, and natural oyster reef areas. Although amplitude analysis of high resolution acoustic data does not directly quantify the geotechnical properties of bottom sediments, our analysis indicates a close relationship. The analysis procedures developed in this study can be applied in other dynamic coastal environments, "calibrating" the use of synoptic acoustic methods for large-scale water bottom characterization.

Characterization of steel rebar spacing using synthetic aperture radar imaging

NASA Astrophysics Data System (ADS)

Hu, Jie; Tang, Qixiang; Twumasi, Jones Owusu; Yu, Tzuyang

2018-03-01

Steel rebars is a vital component in reinforced concrete (RC) and prestressed concrete structures since they provide mechanical functions to those structures. Damages occurred to steel rebars can lead to the premature failure of concrete structures. Characterization of steel rebars using nondestructive evaluation (NDE) offers engineers and decision makers important information for effective/good repair of aging concrete structures. Among existing NDE techniques, microwave/radar NDE has been proven to be a promising technique for surface and subsurface sensing of concrete structures. The objective of this paper is to use microwave/radar NDE to characterize steel rebar grids in free space, as a basis for the subsurface sensing of steel rebars inside RC structures. A portable 10-GHz radar system based on synthetic aperture radar (SAR) imaging was used in this paper. Effect of rebar grid spacing was considered and used to define subsurface steel rebar grids. Five rebar grid spacings were used; 12.7 cm (5 in.), 17.78 cm (7 in.), 22.86 cm (9 in.), 27.94 cm (11 in.), and 33.02 cm (13 in.) # 3 rebars were used in all grid specimens. All SAR images were collected inside an anechoic chamber. It was found that SAR images can successfully capture the change of rebar grid spacing and used for quantifying the spacing of rebar grids. Empirical models were proposed to estimate actual rebar spacing and contour area using SAR images.

Subsurface Investigation of the Neogene Mygdonian Basin, Greece Using Magnetic Data

NASA Astrophysics Data System (ADS)

Ibraheem, Ismael M.; Gurk, Marcus; Tougiannidis, Nikolaos; Tezkan, Bülent

2018-02-01

A high-resolution ground and marine magnetic survey was executed to determine the structure of the subsurface and the thickness of the sedimentary cover in the Mygdonian Basin. A spacing of approximately 250 m or 500 m between measurement stations was selected to cover an area of 15 km × 22 km. Edge detectors such as total horizontal derivative (THDR), analytic signal (AS), tilt derivative (TDR), enhanced total horizontal gradient of tilt derivative (ETHDR) were applied to map the subsurface structure. Depth was estimated by power spectrum analysis, tilt derivative, source parameter imaging (SPI), and 2D-forward modeling techniques. Spectral analysis and SPI suggest a depth to the basement ranging from near surface to 600 m. For some selected locations, depth was also calculated using the TDR technique suggesting depths from 160 to 400 m. 2D forward magnetic modeling using existing boreholes as constraints was carried out along four selected profiles and confirmed the presence of alternative horsts and grabens formed by parallel normal faults. The dominant structural trends inferred from THDR, AS, TDR, and ETHDR are N-S, NW-SE, NE-SW and E-W. This corresponds with the known structural trends in the area. Finally, a detailed structural map showing the magnetic blocks and the structural architecture of the Mygdonian Basin was drawn up by collating all of the results.

Numerical investigations of internal stresses on carbon steel based on ultrasonic LCR waves

NASA Astrophysics Data System (ADS)

Ramasamy, R.; Ibrahim, Z.; Chai, H. K.

2017-10-01

Internal stresses or residual stresses in the structural elements are very crucial in carrying out in-service evaluations and fitness-for-purpose assessments. The generation of these internal stresses can occur as result of the fabrication of the steel members, installation sequence or other ad-hoc events such as accidents or impact. The accurate prediction of the internal stresses will contribute towards estimating the integrity state of the structural elements, with respect to their material allowable stresses. This paper investigates the explicit FE based numerical modelling of the ultrasonic based non-destructive technique, utilising the measurable longitudinal critical refracted wave (LCR) and relating these to the internal stresses within the structural elements by the evaluation of the material dependent acoustoelastic factors. The subsurface travel path of the LCR wave inside the structural elements makes it a sub-surface stress measurement technique and the linearised relationship with corresponding internal stresses can be systematically applied repeatedly. The numerical results are compared against laboratory tests data to correlate the findings and to establish modelling feasibility for future proof-of-concepts. It can be concluded from this numerical investigation, that the subsurface ultrasonic LCR wave has great potential to be implemented for in-situ structural residual stress measurements, as compared to other available surface measurements such as strain gauges or x-ray diffraction.

Columnar and subsurface silicide growth with novel molecular beam epitaxy techniques

NASA Technical Reports Server (NTRS)

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.

Image-guided optical measurement of blood oxygen saturation within capillary vessels (Conference Presentation)

NASA Astrophysics Data System (ADS)

Akons, Kfir; Zeidan, Adel; Yeheskely-Hayon, Daniella; Minai, Limor; Yelin, Dvir

2016-03-01

Values of blood oxygenation levels are useful for assessing heart and lung conditions, and are frequently monitored during routine patient care. Independent measurement of the oxygen saturation in capillary blood, which is significantly different from that of arterial blood, is important for diagnosing tissue hypoxia and for increasing the accuracy of existing techniques that measure arterial oxygen saturation. Here, we developed a simple, non-invasive technique for measuring the reflected spectra from individual capillary vessels within a human lip, allowing local measurement of the blood oxygen saturation. The optical setup includes a spatially incoherent broadband light that was focused onto a specific vessel below the lip surface. Backscattered light was imaged by a camera for identifying a target vessel and pointing the illumination beam to its cross section. Scattered light from the vessel was then collected by a single-mode fiber and analyzed by a fast spectrometer. Spectra acquired from small capillary vessels within a volunteer lip showed the characteristic oxyhemoglobin absorption bands in real time and with a high signal-to-noise ratio. Measuring capillary oxygen saturation using this technique would potentially be more accurate compared to existing pulse oximetry techniques due to its insensitivity to the patient's skin color, pulse rate, motion, and medical condition. It could be used as a standalone endoscopic technique for measuring tissue hypoxia or in conjunction with conventional pulse oximetry for a more accurate measurement of oxygen transport in the body.

Remote sensing science for the Nineties; Proceedings of IGARSS '90 - 10th Annual International Geoscience and Remote Sensing Symposium, University of Maryland, College Park, May 20-24, 1990. Vols. 1, 2, & 3

NASA Technical Reports Server (NTRS)

1990-01-01

Various papers on remote sensing (RS) for the nineties are presented. The general topics addressed include: subsurface methods, radar scattering, oceanography, microwave models, atmospheric correction, passive microwave systems, RS in tropical forests, moderate resolution land analysis, SAR geometry and SNR improvement, image analysis, inversion and signal processing for geoscience, surface scattering, rain measurements, sensor calibration, wind measurements, terrestrial ecology, agriculture, geometric registration, subsurface sediment geology, radar modulation mechanisms, radar ocean scattering, SAR calibration, airborne radar systems, water vapor retrieval, forest ecosystem dynamics, land analysis, multisensor data fusion. Also considered are: geologic RS, RS sensor optical measurements, RS of snow, temperature retrieval, vegetation structure, global change, artificial intelligence, SAR processing techniques, geologic RS field experiment, stochastic modeling, topography and Digital Elevation model, SAR ocean waves, spaceborne lidar and optical, sea ice field measurements, millimeter waves, advanced spectroscopy, spatial analysis and data compression, SAR polarimetry techniques. Also discussed are: plant canopy modeling, optical RS techniques, optical and IR oceanography, soil moisture, sea ice back scattering, lightning cloud measurements, spatial textural analysis, SAR systems and techniques, active microwave sensing, lidar and optical, radar scatterometry, RS of estuaries, vegetation modeling, RS systems, EOS/SAR Alaska, applications for developing countries, SAR speckle and texture.

Application of Geodetic Techniques for Antenna Positioning in a Ground Penetrating Radar Method

NASA Astrophysics Data System (ADS)

Mazurkiewicz, Ewelina; Ortyl, Łukasz; Karczewski, Jerzy

2018-03-01

The accuracy of determining the location of detectable subsurface objects is related to the accuracy of the position of georadar traces in a given profile, which in turn depends on the precise assessment of the distance covered by an antenna. During georadar measurements the distance covered by an antenna can be determined with a variety of methods. Recording traces at fixed time intervals is the simplest of them. A method which allows for more precise location of georadar traces is recording them at fixed distance intervals, which can be performed with the use of distance triggers (such as a measuring wheel or a hip chain). The search for methods eliminating these discrepancies can be based on the measurement of spatial coordinates of georadar traces conducted with the use of modern geodetic techniques for 3-D location. These techniques include above all a GNSS satellite system and electronic tachymeters. Application of the above mentioned methods increases the accuracy of space location of georadar traces. The article presents the results of georadar measurements performed with the use of geodetic techniques in the test area of Mydlniki in Krakow. A satellite receiver Leica system 1200 and a electronic tachymeter Leica 1102 TCRA were integrated with the georadar equipment. The accuracy of locating chosen subsurface structures was compared.

Surface characterization of U(AlxSi1-x)3 alloy and its interaction with O2 and H2O, at room temperature

NASA Astrophysics Data System (ADS)

Matmor, M.; Cohen, S.; Rafailov, G.; Vaknin, M.; Shamir, N.; Gouder, T.; Zalkind, S.

2018-02-01

Surface characterization and the interactions of U(AlxSi1-x)3 alloy (x = 0.57) with oxygen and water vapor were studied, utilizing X-Ray Photoelectron Spectroscopy and Direct Recoil Spectrometry, at room temperature. The U 4f spectrum of U(AlxSi1-x)3 alloy exhibits weak correlation satellites, suggesting an itinerant description of the U 5f states for this compound. The Al and Si 2p lines are chemically shifted to lower binding energies. Exposing the alloy to oxygen and water vapor results in oxidation of mainly the uranium and aluminum components, while silicon is only slightly oxidized. Oxygen was found to be a stronger oxidizer than water vapor and the trend is consistent with the more negative enthalpies of formation of metal oxides produced by the O2 reaction, as compared to H2O. During oxygen exposure, fast oxidation occurs by oxide islands nucleation and lateral growth, followed by oxidation of the sub-surface, up to ∼4 nm, at 1000 L exposure. Water initially reacts with the surface by full dissociation and oxide islands formation, which is then covered by hydroxides. Only a minor increase in the oxide thickness of up to ∼2.5 nm, was observed after coalescence.

Measuring vertical oxygen profiles in the hyporheic zone using planar optodes

NASA Astrophysics Data System (ADS)

Vieweg, M.; Fleckenstein, J. H.; Schmidt, C.

2012-04-01

On of the key parameters, controlling biogeochemical reactions in the hyporheic zone (HZ) is the distribution of oxygen. A reliable measurement of the vertical oxygen distribution is an important tool to understand the dynamic fluctuations of the aerobic zone within the HZ. With repeated measurements of continuous profiles, mixing of surface water and groundwater as well as the consumption of oxygen can be evaluated. We present a novel approach for the in situ measurements of vertical oxygen distribution in the riverbed using a planar optode. The luminescence based optode measurement enables a non invasive measurement without consumption of oxygen, no creation of preferential flow paths and only minimal disturbance of the flow field. Possible atmospheric contamination by pumping pore water into a vessel can be avoided and the readings are independent of flow velocity. A self manufactured planar optode is wrapped around an acrylic tube and installed in the riverbed. The measurement is performed by vertically moving a profiler-piston inside the acrylic tube. The piston holds a robust polymer optical fibre which emits a modulated light signal through the acrylic glass to the optode-foil and transmits the induced luminescence signal back to a commercially available trace oxygen meter. Temperature compensation is accomplished using a depth-oriented temperature probe nearby and processing the raw data within a Matlab script. Robust and unbiased oxygen profiles are obtained by averaging multiple consecutive measurements. To ensure a constant velocity of the profiler for replicating the exact measuring depths, an electric motor device is used. First results at our test site show a variable oxygen profile down to 40 cm depth which is strongly influenced by stream level and upwelling groundwater conditions. The measured oxygen profiles will serve as input parameter for a 3D solute transport and chemical reaction subsurface model of the HZ.

Correction for intravascular activity in the oxygen-15 steady-state technique is independent of the regional hematocrit

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

Lammertsma, A.A.; Baron, J.C.; Jones, T.

1987-06-01

The oxygen-15 steady-state technique to measure the regional cerebral metabolic rate for oxygen requires a correction for the nonextracted intravascular molecular oxygen-15. To perform this correction, an additional procedure is carried out using RBCs labeled with /sup 11/CO or C/sup 15/O. The previously reported correction method, however, required knowledge of the regional cerebral to large vessel hematocrit ratio. A closer examination of the underlying model eliminated this ratio. Both molecular oxygen and carbon monoxide are carried by RBCs and are therefore similarly affected by a change in hematocrit.

Method and Apparatus for Computed Imaging Backscatter Radiography

NASA Technical Reports Server (NTRS)

Shedlock, Daniel (Inventor); Sabri, Nissia (Inventor); Dugan, Edward T. (Inventor); Jacobs, Alan M. (Inventor); Meng, Christopher (Inventor)

2013-01-01

Systems and methods of x-ray backscatter radiography are provided. A single-sided, non-destructive imaging technique utilizing x-ray radiation to image subsurface features is disclosed, capable of scanning a region using a fan beam aperture and gathering data using rotational motion.

SOIL-GAS AND GEOPHYSICAL TECHNIQUES FOR DETECTION OF SUBSURFACE ORGANIC CONTAMINATION

EPA Science Inventory

From 1985 through 1987, the Air Force Engineering and Services Center funded research at the U.S. Environmental Protection Agency Environmental Monitoring Systems Laboratory in Las Vegas, Nevada through an interagency agreement. The agreement provided for investigations of subsur...

Geochemical and microbiological responses to oxidant introduction into reduced subsurface sediment from the Hanford 300 Area, Washington.

PubMed

Percak-Dennett, Elizabeth M; Roden, Eric E

2014-08-19

Pliocene-aged reduced lacustrine sediment from below a subsurface redox transition zone at the 300 Area of the Hanford site (southeastern Washington) was used in a study of the geochemical response to introduction of oxygen or nitrate in the presence or absence of microbial activity. The sediments contained large quantities of reduced Fe in the form of Fe(II)-bearing phyllosilicates, together with smaller quantities of siderite and pyrite. A loss of ca. 50% of 0.5 M HCl-extractable Fe(II) [5-10 mmol Fe(II) L(-1)] and detectable generation of sulfate (ca. 0.2 mM, equivalent to 10% of the reduced inorganic sulfur pool) occurred in sterile aerobic reactors. In contrast, no systematic loss of Fe(II) or production of sulfate was observed in any of the other oxidant-amended sediment suspensions. Detectable Fe(II) accumulation and sulfate consumption occurred in non-sterile oxidant-free reactors. Together, these results indicate the potential for heterotrophic carbon metabolism in the reduced sediments, consistent with the proliferation of known heterotrophic taxa (e.g., Pseudomonadaceae, Burkholderiaceae, and Clostridiaceae) inferred from 16S rRNA gene pyrosequencing. Microbial carbon oxidation by heterotrophic communities is likely to play an important role in maintaining the redox boundary in situ, i.e., by modulating the impact of downward oxidant transport on Fe/S redox speciation. Diffusion-reaction simulations of oxygen and nitrate consumption coupled to solid-phase organic carbon oxidation indicate that heterotrophic consumption of oxidants could maintain the redox boundary at its current position over millennial time scales.

Performance of hybrid subsurface constructed wetland system for piggery wastewater treatment.

PubMed

Zhang, X; Inoue, T; Kato, K; Harada, J; Izumoto, H; Wu, D; Sakuragi, H; Ietsugu, H; Sugawara, Y

2016-01-01

The objective of this study was to evaluate performance of a hybrid constructed wetland (CW) built for high organic content piggery wastewater treatment in a cold region. The system consists of four vertical and one horizontal flow subsurface CWs. The wetland was built in 2009 and water quality was monitored from the outset. Average purification efficiency of this system was 95±5, 91±7, 89±8, 70±10, 84±15, 90±6, 99±2, and 93±16% for biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total carbon (TC), total nitrogen (TN), ammonium-N (NH4-N), total phosphorus (TP), total coliform (T. Coliform), and suspended solids (SS), respectively during August 2010-December 2013. Pollutant removal rate was 15±18 g m(-2) d(-1), 49±52 g m(-2) d(-1), 6±4 g m(-2) d(-1), 7±5 g m(-2) d(-1), and 1±1 g m(-2) d(-1) for BOD5, COD, TN, NH4-N, and TP, respectively. The removal efficiency of BOD5, COD, NH4-N, and SS improved yearly since the start of operation. With respect to removal of TN and TP, efficiency improved in the first three years but slightly declined in the fourth year. The system performed well during both warm and cold periods, but was more efficient in the warm period. The nitrate increase may be attributed to a low C/N ratio, due to limited availability of carbon required for denitrification.

Transport and removal of viruses in saturated sand columns under oxic and anoxic conditions--Potential implications for groundwater protection.

PubMed

Frohnert, Anne; Apelt, Susann; Klitzke, Sondra; Chorus, Ingrid; Szewzyk, Regine; Selinka, Hans-Christoph

2014-11-01

To protect groundwater as a drinking water resource from microbiological contamination, protection zones are installed. While travelling through these zones, concentrations of potential pathogens should decline to levels that pose no risks to human health. Removal of viruses during subsurface passage is influenced by physicochemical conditions, such as oxygen concentration, which also affects virus survival. The aim of our study was to evaluate the effect of redox conditions on the removal of viruses during sand filtration. Experiments in glass columns filled with medium-grained sand were conducted to investigate virus removal in the presence and absence of dissolved oxygen. Bacteriophages MS2 and PhiX174, as surrogates for human enteric viruses were spiked in pulsed or in continuous mode and pumped through the columns at a filter velocity of about 1m/d. Virus breakthrough curves were analyzed by calculating total viral elimination and fitted using one-dimensional transport models (CXTFIT and HYDRUS-1D). While short-term experiments with pulsed virus application showed only small differences with regard to virus removal under oxic and anoxic conditions, a long-term experiment with continuous dosing revealed a clearly lower elimination of viruses under anoxic conditions. These findings suggest that less inactivation and less adsorption of viruses in anoxic environments affect their removal. Therefore, in risk assessment studies aimed to secure drinking water resources from viral contamination and optimization of protection zones, the oxic and anoxic conditions in the subsurface should also be considered. Copyright © 2014 Elsevier GmbH. All rights reserved.

Evaluation of diffuse and preferential flow pathways of infiltrated precipitation and irrigation using oxygen and hydrogen isotopes

NASA Astrophysics Data System (ADS)

Ma, Bin; Liang, Xing; Liu, Shaohua; Jin, Menggui; Nimmo, John R.; Li, Jing

2017-05-01

Subsurface-water flow pathways in three different land-use areas (non-irrigated grassland, poplar forest, and irrigated arable land) in the central North China Plain were investigated using oxygen (18O) and hydrogen (2H) isotopes in samples of precipitation, soils, and groundwater. Soil water in the top 10 cm was significantly affected by both evaporation and infiltration. Water at 10-40 cm depth in the grassland and arable land, and 10-60 cm in poplar forest, showed a relatively short residence time, as a substantial proportion of antecedent soil water was mixed with a 92-mm storm infiltration event, whereas below those depths (down to 150 cm), depleted δ18O spikes suggested that some storm water bypassed the shallow soil layers. Significant differences, in soil-water content and δ18O values, within a small area, suggested that the proportion of immobile soil water and water flowing in subsurface pathways varies depending on local vegetation cover, soil characteristics and irrigation applications. Soil-water δ18O values revealed that preferential flow and diffuse flow coexist. Preferential flow was active within the root zone, independent of antecedent soil-water content, in both poplar forest and arable land, whereas diffuse flow was observed in grassland. The depleted δ18O spikes at 20-50 cm depth in the arable land suggested the infiltration of irrigation water during the dry season. Temporal isotopic variations in precipitation were subdued in the shallow groundwater, suggesting more complete mixing of different input waters in the unsaturated zone before reaching the shallow groundwater.

Multi-stage hybrid subsurface flow constructed wetlands for treating piggery and dairy wastewater in cold climate.

PubMed

Zhang, Xiaomeng; Inoue, Takashi; Kato, Kunihiko; Izumoto, Hayato; Harada, June; Wu, Da; Sakuragi, Hiroaki; Ietsugu, Hidehiro; Sugawara, Yasuhide

2017-01-01

This study followed three field-scale hybrid subsurface flow constructed wetland (CW) systems constructed in Hokkaido, northern Japan: piggery O (2009), dairy G (2011), and dairy S (2006). Treatment performance was monitored from the outset of operation for each CW. The ranges of overall purification efficiency for these systems were 70-86%, 40-85%, 71-90%, 91-96%, 94-98%, 84-97%, and 70-97% for total N (TN), NH 4 -N, total P, chemical oxygen demand (COD), biochemical oxygen demand, suspended solid, and total Coliform, respectively. The hybrid system's removal rates were highest when influent loads were high. COD removal rates were 46.4 ± 49.2, 94.1 ± 36.6, and 25.1 ± 15.5 g COD m -2 d -1 in piggery O, dairy G, and dairy S, with average influent loads of 50.5 ± 51.5, 98.9 ± 37.1, and 26.9 ± 16.0 g COD m -2 d -1 , respectively. The systems had overall COD removal efficiencies of around 90%. TN removal efficiencies were 62 ± 19%, 82 ± 9%, and 82 ± 15% in piggery O, dairy G, and dairy S, respectively. NH 4 -N removal efficiency was adversely affected by the COD/TN ratio. Results from this study prove that these treatment systems have sustained and positive pollutant removal efficiencies, which were achieved even under extremely cold climate conditions and many years after initial construction.

Extremely high resolution 3D electrical resistivity tomography to depict archaeological subsurface structures

NASA Astrophysics Data System (ADS)

Al-Saadi, Osamah; Schmidt, Volkmar; Becken, Michael; Fritsch, Thomas

2017-04-01

Electrical resistivity tomography (ERT) methods have been increasingly used in various shallow depth archaeological prospections in the last few decades. These non-invasive techniques are very useful in saving time, costs, and efforts. Both 2D and 3D ERT techniques are used to obtain detailed images of subsurface anomalies. In two surveyed areas near Nonnweiler (Germany), we present the results of the full 3D setup with a roll-along technique and of the quasi-3D setup (parallel and orthogonal profiles in dipole-dipole configuration). In area A, a dipole-dipole array with 96 electrodes in a uniform rectangular survey grid has been used in full 3D to investigate a presumed Roman building. A roll-along technique has been utilized to cover a large part of the archaeological site with an electrode spacing of 1 meter and with 0.5 meter for a more detailed image. Additional dense parallel 2D profiles have been carried out in dipole-dipole array with 0.25 meter electrode spacing and 0.25 meter between adjacent profiles in both direction for higher- resolution subsurface images. We have designed a new field procedure, which used an electrode array fixed in a frame. This facilitates efficient field operation, which comprised 2376 electrode positions. With the quasi 3D imaging, we confirmed the full 3D inversion model but at a much better resolution. In area B, dense parallel 2D profiles were directly used to survey the second target with also 0.25 meter electrode spacing and profiles separation respectively. The same field measurement design has been utilized and comprised 9648 electrode positions in total. The quasi-3D inversion results clearly revealed the main structures of the Roman construction. These ERT inversion results coincided well with the archaeological excavation, which has been done in some parts of this area. The ERT result successfully images parts from the walls and also smaller internal structures of the Roman building.

Stochastic porous media modeling and high-resolution schemes for numerical simulation of subsurface immiscible fluid flow transport

NASA Astrophysics Data System (ADS)

Brantson, Eric Thompson; Ju, Binshan; Wu, Dan; Gyan, Patricia Semwaah

2018-04-01

This paper proposes stochastic petroleum porous media modeling for immiscible fluid flow simulation using Dykstra-Parson coefficient (V DP) and autocorrelation lengths to generate 2D stochastic permeability values which were also used to generate porosity fields through a linear interpolation technique based on Carman-Kozeny equation. The proposed method of permeability field generation in this study was compared to turning bands method (TBM) and uniform sampling randomization method (USRM). On the other hand, many studies have also reported that, upstream mobility weighting schemes, commonly used in conventional numerical reservoir simulators do not accurately capture immiscible displacement shocks and discontinuities through stochastically generated porous media. This can be attributed to high level of numerical smearing in first-order schemes, oftentimes misinterpreted as subsurface geological features. Therefore, this work employs high-resolution schemes of SUPERBEE flux limiter, weighted essentially non-oscillatory scheme (WENO), and monotone upstream-centered schemes for conservation laws (MUSCL) to accurately capture immiscible fluid flow transport in stochastic porous media. The high-order schemes results match well with Buckley Leverett (BL) analytical solution without any non-oscillatory solutions. The governing fluid flow equations were solved numerically using simultaneous solution (SS) technique, sequential solution (SEQ) technique and iterative implicit pressure and explicit saturation (IMPES) technique which produce acceptable numerical stability and convergence rate. A comparative and numerical examples study of flow transport through the proposed method, TBM and USRM permeability fields revealed detailed subsurface instabilities with their corresponding ultimate recovery factors. Also, the impact of autocorrelation lengths on immiscible fluid flow transport were analyzed and quantified. A finite number of lines used in the TBM resulted into visual artifact banding phenomenon unlike the proposed method and USRM. In all, the proposed permeability and porosity fields generation coupled with the numerical simulator developed will aid in developing efficient mobility control schemes to improve on poor volumetric sweep efficiency in porous media.

Modelling gas transport in the shallow subsurface in the Maguelone field experiment

NASA Astrophysics Data System (ADS)

Basirat, Farzad; Niemi, Auli; Perroud, Hervé; Lofi, Johanna; Denchik, Nataliya; Lods, Gérard; Pezard, Philippe; Sharma, Prabhakar; Fagerlund, Fritjof

2013-04-01

Developing reliable monitoring techniques to detect and characterize CO2 leakage in shallow subsurface is necessary for the safety of any GCS project. To test different monitoring techniques, shallow injection-monitoring experiment have and are being carried out at the Maguelone, along the Mediterranean lido of the Gulf of Lions, near Montpellier, France. This experimental site was developed in the context of EU FP7 project MUSTANG and is documented in Lofi et al. (2012). Gas injection experiments are being carried out and three techniques of pressure, electrical resistivity and seismic monitoring have been used to detect the nitrogen and CO2 release in the near surface environment. In the present work we use the multiphase and multicomponent TOUGH2/EOS7CA model to simulate the gaseous nitrogen and CO2 transport of the experiments carried out so far. The objective is both to gain understanding of the system performance based on the model analysis as well as to further develop and validate modelling approaches for gas transport in the shallow subsurface, against the well-controlled data sets. Numerical simulation can also be used for the prediction of experimental setup limitations. We expect the simulations to represent the breakthrough time for the different tested injection rates. Based on the hydrogeological formation data beneath the lido, we also expect the vertical heterogeneities in grain size distribution create an effective capillary barrier against upward gas transport in numerical simulations. Lofi J., Pezard P.A., Bouchette F., Raynal O., Sabatier P., Denchik N., Levannier A., Dezileau L., and Certain R. Integrated onshore-offshore geophysical investigation of a layered coastal aquifer, NW Mediterranean. Ground Water, (2012).

4D ground penetrating radar measurements as non-invasive means for hydrological process investigation

NASA Astrophysics Data System (ADS)

Jackisch, Conrad; Allroggen, Niklas

2017-04-01

The missing vision into the subsurface appears to be a major limiting factor for our hydrological process understanding and theory development. Today, hydrology-related sciences have collected tremendous evidence for soils acting as drainage network and retention stores simultaneously in structured and self-organising domains. However, our present observation technology relies mainly on point-scale sensors, which integrate over a volume of unknown structures and is blind for their distribution. Although heterogeneity is acknowledged at all scales, it is rarely seen as inherent system property. At small scales (soil moisture probe) and at large scales (neutron probe) our measurements leave quite some ambiguity. Consequently, spatially and temporally continuous measurement of soil water states is essential for advancing our understanding and development of subsurface process theories. We present results from several irrigation experiments accompanied by 2D and 3D time-lapse GPR for the development of a novel technique to visualise and quantify water dynamics in the subsurface. Through the comparison of TDR, tracer and gravimetric measurement of soil moisture it becomes apparent that all sensor-based techniques are capable to record temporal dynamics, but are challenged to precisely quantify the measurements and to extrapolate them in space. At the same time excavative methods are very limited in temporal and spatial resolution. The application of non-invasive 4D GPR measurements complements the existing techniques and reveals structural and temporal dynamics simultaneously. By consequently increasing the density of the GPR data recordings in time and space, we find means to process the data also in the time-dimension. This opens ways to quantitatively analyse soil water dynamics in complex settings.

Confocal Raman spectroscopic analysis of cross-linked ultra-high molecular weight polyethylene for application in artificial hip joints.

PubMed

Pezzotti, Giuseppe; Kumakura, Tsuyoshi; Yamada, Kiyotaka; Tateiwa, Toshiyuki; Puppulin, Leonardo; Zhu, Wenliang; Yamamoto, Kengo

2007-01-01

Confocal spectroscopic techniques are applied to selected Raman bands to study the microscopic features of acetabular cups made of ultra-high molecular weight polyethylene (UHMWPE) before and after implantation in vivo. The micrometric lateral resolution of a laser beam focused on the polymeric surface (or subsurface) enables a highly resolved visualization of 2-D conformational population patterns, including crystalline, amorphous, orthorhombic phase fractions, and oxidation index. An optimized confocal probe configuration, aided by a computational deconvolution of the optical probe, allows minimization of the probe size along the in-depth direction and a nondestructive evaluation of microstructural properties along the material subsurface. Computational deconvolution is also attempted, based on an experimental assessment of the probe response function of the polyethylene Raman spectrum, according to a defocusing technique. A statistical set of high-resolution microstructural data are collected on a fully 3-D level on gamma-ray irradiated UHMWPE acetabular cups both as-received from the maker and after retrieval from a human body. Microstructural properties reveal significant gradients along the immediate material subsurface and distinct differences are found due to the loading history in vivo, which cannot be revealed by conventional optical spectroscopy. The applicability of the confocal spectroscopic technique is valid beyond the particular retrieval cases examined in this study, and can be easily extended to evaluate in-vitro tested components or to quality control of new polyethylene brands. Confocal Raman spectroscopy may also contribute to rationalize the complex effects of gamma-ray irradiation on the surface of medical grade UHMWPE for total joint replacement and, ultimately, to predict their actual lifetime in vivo.

A new approach to define surface/sub-surface transition in gravel beds

NASA Astrophysics Data System (ADS)

Haynes, Heather; Ockelford, Anne-Marie; Vignaga, Elisa; Holmes, William

2012-12-01

The vertical structure of river beds varies temporally and spatially in response to hydraulic regime, sediment mobility, grain size distribution and faunal interaction. Implicit are changes to the active layer depth and bed porosity, both critical in describing processes such as armour layer development, surface-subsurface exchange processes and siltation/ sealing. Whilst measurements of the bed surface are increasingly informed by quantitative and spatial measurement techniques (e.g., laser displacement scanning), material opacity has precluded the full 3D bed structure analysis required to accurately define the surface-subsurface transition. To overcome this problem, this paper provides magnetic resonance imaging (MRI) data of vertical bed porosity profiles. Uniform and bimodal (σ g = 2.1) sand-gravel beds are considered following restructuring under sub-threshold flow durations of 60 and 960 minutes. MRI data are compared to traditional 2.5D laser displacement scans and six robust definitions of the surface-subsurface transition are provided; these form the focus of discussion.

Novel determination of radon-222 velocity in deep subsurface rocks and the feasibility to using radon as an earthquake precursor

NASA Astrophysics Data System (ADS)

Zafrir, Hovav; Ben Horin, Yochai; Malik, Uri; Chemo, Chaim; Zalevsky, Zeev

2016-09-01

A novel technique utilizing simultaneous radon monitoring by gamma and alpha detectors to differentiate between the radon climatic driving forces and others has been improved and used for deep subsurface investigation. Detailed long-term monitoring served as a proxy for studying radon movement within the shallow and deep subsurface, as well as for analyzing the effect of various parameters of the radon transport pattern. The main achievements of the investigation are (a) determination, for the first time, of the radon movement velocity within rock layers at depths of several tens of meters, namely, 25 m/h on average; (b) distinguishing between the diurnal periodical effect of the ambient temperature and the semidiurnal effect of the ambient pressure on the radon temporal spectrum; and (c) identification of a radon random preseismic anomaly preceding the Nuweiba, M 5.5 earthquake of 27 June 2015 that occurred within Dead Sea Fault Zone.

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

NASA Technical Reports Server (NTRS)

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

1990-01-01

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

Frequency domain electromagnetic induction survey in the intertidal zone: Limitations of low-induction-number and depth of exploration

NASA Astrophysics Data System (ADS)

Delefortrie, Samuël; Saey, Timothy; Van De Vijver, Ellen; De Smedt, Philippe; Missiaen, Tine; Demerre, Ine; Van Meirvenne, Marc

2014-01-01

Subsurface investigation in the Belgian intertidal zone is severely complicated due to high heterogeneity and tides. Near-surface geophysical techniques can offer assistance since they allow fast surveying and collection of high spatial density data and frequency domain electromagnetic induction (EMI) was chosen for archaeological prospection on the Belgian shore. However, in the intertidal zone the effects of extreme salinity compromise validity of low-induction-number (LIN) approximated EMI data. In this paper, the effects of incursion of seawater on multi-receiver EMI data are investigated by means of survey results, field observations, cone penetration tests and in-situ electrical conductivity measurements. The consequences of LIN approximation breakdown were researched. Reduced depth of investigation of the quadrature-phase (Qu) response and a complex interpretation of the in-phase response were confirmed. Nonetheless, a high signal-to-noise ratio of the Qu response and viable data with regard to shallow subsurface investigation were also evidenced, allowing subsurface investigation in the intertidal zone.

Assessing clogging processes caused by biofilm growth and organic particle accumulation in constructed wetlands using time-lapse electrical resistivity tomography method

NASA Astrophysics Data System (ADS)

Mahjoub, Himi; Tapias, Josefina C.; Lovera, Raúl; Rivero, Lluís; Font, Xavier; Casas, Albert

2016-04-01

Constructed wetlands for removing pollutants from wastewater in small communities are growing rapidly in many regions of the world. The advantages over conventional mechanical sanitation systems, where land availability is not a limiting factor, are low energy requirements, easy operation and maintenance, low sludge production and cost-effectivity. Nevertheless, with time the cleaning process can result in gradual clogging of the porous layer by suspended solids, bacterial film, chemical precipitates and compaction. The clogging development causes decrease of hydraulic conductivity, reduced oxygen supply and further leads to a rapid decrease of the treatment performance. As the investment involved in reversing clogging can represent a substantial fraction of the cost of a new system it is essential to assess in advance the evolution of clogging process and detect potential failures in the system. Since there is a lack of experiences for monitoring the functionality of constructed wetlands time-lapse electrical resistivity tomography studies have been conducted at horizontal sub-surface flow municipal wastewater treatment wetlands of Catalonia (Spain). The results of this research show that electrical resistivity tomography can be a very useful technique for assessing the extent of silting up processes that clog the subsurface flow constructed wetlands through the gravel layer. In the unsaturated zone, the electrical resistivity is greater at the end of the filter, since the pores contains air which is dielectric, while at the beginning of the filter the resistivity is lower because the electrical conduction of organic matter around the mineral grains. Conversely, in the saturated zone, the electrical resistivity is lower at the end of the filter, since pores contain a higher proportion of high ionic conductivity wastewater, while at the beginning of the filter the electrical resistivity is higher because of the lower porosity due to the clogging process.

Reactive transport modeling of subsurface arsenic removal systems in rural Bangladesh.

PubMed

Rahman, M M; Bakker, M; Patty, C H L; Hassan, Z; Röling, W F M; Ahmed, K M; van Breukelen, B M

2015-12-15

Subsurface Arsenic Removal (SAR) is a technique for in-situ removal of arsenic from groundwater. Extracted groundwater is aerated and re-injected into an anoxic aquifer, where the oxygen in the injected water reacts with ferrous iron in the aquifer to form hydrous ferric oxide (HFO). Subsequent extraction of groundwater contains temporarily lower As concentrations, because As sorbs onto the HFO. Injection, storage, and extraction together is called a cycle. A reactive transport model (RTM) was developed in PHREEQC to determine the hydrogeochemical processes responsible for As (im)mobilization during experimental SAR operation performed in Bangladesh. Oxidation of Fe(II) and As(III) were modeled using kinetic-rate expressions. Cation exchange, precipitation of HFO, and surface complexation, were modeled as equilibrium processes. A best set of surface complexation reactions and corresponding equilibrium constants was adopted from previous studies to simulate all 20 cycles of a SAR experiment. The model gives a reasonable match with observed concentrations of different elements in the extracted water (e.g., the r(2) value of As was 0.59 or higher). As concentrations in the extracted water are governed by four major processes. First, As concentration decreases in response to the elevated pH of injection water and likewise increases when native neutral pH groundwater flows in. Second, the sorption capacity for As increases due to the gradual buildup of HFO. Third, As sorption is enhanced by preferential removal of As(V). Fourth, competitive sorption of Si limits the capacity of freshly precipitated HFO for As sorption. Transferability of the developed reactive transport model was demonstrated through successful application of the model, without further calibration, to two additional SAR sites in Bangladesh. This gives confidence that the model could be useful to assess potential SAR performance at locations in Bangladesh based on local hydrogeochemical conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

Biofilm development in a hotspot of mixing between shallow and deep groundwater in a fractured aquifer: field evidence from joint flow, chemical and microbiological measurements

NASA Astrophysics Data System (ADS)

Bochet, O.; Dufresne, A.; Pédrot, M.; Chatton, E.; Labasque, T.; Ben Maamar, S.; Burté, L.; de la Bernardie, J.; Guihéneuf, N.; Lavenant, N.; Petton, C.; Bour, O.; Aquilina, L.; Le Borgne, T.

2015-12-01

Biofilms play a major role in controlling the fluxes and reactivity of chemical species transported in hydro-logical systems. Micro-organisms require both electron donors and electron acceptors for cellular growth, proliferation and maintenance of their metabolic functions. The mechanisms controlling these reactions derive from the interactions occurring at the micro-scale that depend on mineral compositions, the biota of subsurface environment, but also fluid mixing, which determines the local concentrations of nutriments, electron donors and electron acceptors. Hence, mixing zones between oxygen and nutriment rich shallow groundwater and mineralized deep groundwater are often considered as potential hotspots of microbial activity, although relatively few field data document flow distributions, transport properties, chemical gradients and micro-organisms distributions across these mixing interfaces. Here we investigate the origin of a localized biofilm development observed in the fractured granite aquifer at the Ploemeur observatory (H+ network hplus.ore.fr).This biofilm composed of ferro-oxidizing bacteria is observed in an 130m deep artesian well. Borehole video logs show an important colonization of the well by the biofilm in the shallower part (0 to 60m), while it is inexistent in the deeper part (60 to 130m). As flow is localized in a few deep and shallow fractures, we presume that the spatial distribution of biofilm is controlled by mixing between shallow and deep groundwater. To verify this hypothesis we conducted a field campaign with joint characterization of the flow and chemical composition of water flowing from the different fractures, as well as the microbiological composition of the biofilm at different depth, using pyrosequencing techniques. We will discuss in this presentation the results of this interdisciplinary dataset and their implications for the occurrence of hotspots of microbiological activity in the subsurface.

Preliminary forecasts of Pacific bigeye tuna population trends under the A2 IPCC scenario

NASA Astrophysics Data System (ADS)

Lehodey, P.; Senina, I.; Sibert, J.; Bopp, L.; Calmettes, B.; Hampton, J.; Murtugudde, R.

2010-07-01

An improved version of the spatial ecosystem and population dynamics model SEAPODYM was used to investigate the potential impacts of global warming on tuna populations. The model included an enhanced definition of habitat indices, movements, and accessibility of tuna predators to different vertically migrant and non-migrant micronekton functional groups. The simulations covered the Pacific basin (model domain) at a 2° × 2° geographic resolution. The structure of the model allows an evaluation from multiple data sources, and parameterization can be optimized by adjoint techniques and maximum likelihood using fishing data. A first such optimized parameterization was obtained for bigeye tuna ( Thunnus obesus) in the Pacific Ocean using historical catch data for the last 50 years and a hindcast from a coupled physical-biogeochemical model driven by the NCEP atmospheric reanalysis. The parameterization provided very plausible biological parameter values and a good fit to fishing data from the different fisheries, both within and outside the time period used for optimization. We then employed this model to forecast the future of bigeye tuna populations in the Pacific Ocean. The simulation was driven by the physical-biogeochemical fields predicted from a global marine biogeochemistry - climate simulation. This global simulation was performed with the IPSL climate model version 4 (IPSL-CM4) coupled to the oceanic biogeochemical model PISCES and forced by atmospheric CO 2, from historical records over 1860-2000, and under the SRES A2 IPCC scenario for the 21st century (i.e. atmospheric CO 2 concentration reaching 850 ppm in the year 2100). Potential future changes in distribution and abundance under the IPCC scenario are presented but without taking into account any fishing effort. The simulation showed an improvement in bigeye tuna spawning habitat both in subtropical latitudes and in the eastern tropical Pacific (ETP) where the surface temperature becomes optimal for bigeye tuna spawning. The adult feeding habitat also improved in the ETP due to the increase of dissolved oxygen concentration in the sub-surface allowing adults to access deeper forage. Conversely, in the Western Central Pacific the temperature becomes too warm for bigeye tuna spawning. The decrease in spawning is compensated by an increase of larvae biomass in subtropical regions. However, natural mortality of older stages increased due to lower habitat values (too warm surface temperatures, decreasing oxygen concentration in the sub-surface and less food). This increased mortality and the displacement of surviving fish to the eastern region led to stable then declining adult biomass at the end of the century.

Low Earth orbit atomic oxygen simulation for durability evaluation of solar reflector surfaces

NASA Technical Reports Server (NTRS)

Degroh, Kim K.; Banks, Bruce A.

1992-01-01

To evaluate the performance and durability of solar reflector surfaces in the atomic oxygen environment typical of low Earth orbit (LEO), one must expose the reflector surface either directly to LEO or to ground-laboratory atomic oxygen environments. Although actual LEO exposures are most desired, such opportunities are typically scarce, expensive, and of limited duration. As a result, ground-laboratory exposures must be relied upon as the most practical long-term durability evaluation technique. Plasma ashers are widely used as LEO simulation facilities by producing atomic oxygen environments for durability evaluation of potential spacecraft materials. Atomic oxygen arrival differs between ground and space exposure in that plasma asher exposure produces isotropic arrival and space solar tracking produces sweeping arrival. Differences in initial impact reaction probability occur, dependent upon the energy and species existing in these environments. Due to the variations in ground-laboratory and space atomic oxygen, quantification of in-space performance based on plasma asher testing is not straightforward. The various atomic oxygen interactions that can occur with reflector surfaces, such as undercutting in organic substrates at protective coating defect sites, ground-laboratory techniques recommended for evaluating the atomic oxygen durability of reflectors based on asher exposures, and computational techniques which make use of ground-laboratory atomic oxygen exposure to predict in-space LEO durability are addressed.

Recovery of oxygenated ignitable liquids by zeolites, Part I: Novel extraction methodology in fire debris analysis.

PubMed

St Pierre, Kathryne A; Desiderio, Vincent J; Hall, Adam B

2014-07-01

The recovery of low molecular weight oxygenates in fire debris samples is severely compromised by the use of heated passive headspace concentration with an activated charcoal strip, as outlined in ASTM E-1412. The term "oxygenate" is defined herein as a small, polar, organic molecule, such as acetone, methanol, ethanol, or isopropanol, which can be employed as an ignitable liquid and referred to in the ASTM classification scheme as the "oxygenated solvents" class. Although a well accepted technique, the higher affinity of activated carbon strips for heavy molecular weight products over low molecular weight products and hydrocarbons over oxygenated products, it does not allow for efficient recovery of oxygenates such as low molecular weight alcohols and acetone. The objective of this study was to develop and evaluate a novel method for the enhanced recovery of oxygenates from fire debris samples. By optimizing conditions of the heated passive headspace technique, the utilization of zeolites allowed for the successful collection and concentration of oxygenates. The results demonstrated that zeolites increased the recovery of oxygenates by at least 1.5-fold compared to the activated carbon strip and may complement the currently used extraction technique. Copyright © 2014. Published by Elsevier Ireland Ltd.

Accelerated aging studies of UHMWPE. I. Effect of resin, processing, and radiation environment on resistance to mechanical degradation.

PubMed

Edidin, A A; Herr, M P; Villarraga, M L; Muth, J; Yau, S S; Kurtz, S M

2002-08-01

The resin and processing route have been identified as potential variables influencing the mechanical behavior, and hence the clinical performance, of ultra-high molecular weight polyethylene (UHMWPE) orthopedic components. Researchers have reported that components fabricated from 1900 resin may oxidize to a lesser extent than components fabricated from GUR resin during shelf aging after gamma sterilization in air. Conflicting reports on the oxidation resistance for 1900 raise the question of whether resin or manufacturing method, or an interaction between resin and manufacturing method, influences the mechanical behavior of UHMWPE. We conducted a series of accelerated aging studies (no aging, aging in oxygen or in nitrogen) to systematically examine the influence of resin (GUR or 1900), manufacturing method (bulk compression molding or extrusion), and sterilization method (none, in air, or in nitrogen) on the mechanical behavior of UHMWPE. The small punch testing technique was used to evaluate the mechanical behavior of the materials, and Fourier transform infrared spectroscopy was used to characterize the oxidation in selected samples. Our study showed that the sterilization environment, aging condition, and specimen location (surface or subsurface) significantly affected the mechanical behavior of UHMWPE. Each of the three polyethylenes evaluated seem to degrade according to a similar pathway after artificial aging in oxygen and gamma irradiation in air. The initial ability of the materials to exhibit post-yield strain hardening was significantly compromised by degradation. In general, there were only minor differences in the aging behavior of molded and extruded GUR 1050, whereas the molded 1900 material seemed to degrade slightly faster than either of the 1050 materials. Copyright 2002 Wiley Periodicals, Inc.

The 20th-century development and expansion of Louisiana shelf hypoxia, Gulf of Mexico

USGS Publications Warehouse

Osterman, L.E.; Poore, R.Z.; Swarzenski, P.W.; Senn, D.B.; DiMarco, Steven F.

2009-01-01

Since systematic measurements of Louisiana continental-shelf waters were initiated in 1985, hypoxia (oxygen content <2 mg L-1) has increased considerably in an area termed the dead zone. Monitoring and modeling studies have concluded that the expansion of the Louisiana shelf dead zone is related to increased anthropogenically derived nutrient delivery from the Mississippi River drainage basin, physical and hydrographical changes of the Louisiana Shelf, and possibly coastal erosion of wetlands in southern Louisiana. In order to track the development and expansion of seasonal low-oxygen conditions on the Louisiana shelf prior to 1985, we used a specific low-oxygen foraminiferal faunal proxy, the PEB index, which has been shown statistically to represent the modern Louisiana hypoxia zone. We constructed a network of 13 PEB records with excess 210Pb-derived chronologies to establish the development of low-oxygen and hypoxic conditions over a large portion of the modern dead zone for the last 100 years. The PEB index record indicates that areas of low-oxygen bottom water began to appear in the early 1910s in isolated hotspots near the Mississippi Delta and rapidly expanded across the entire Louisiana shelf beginning in the 1950s. Since ???1950, the percentage of PEB species has steadily increased over a large portion of the modern dead zone. By 1960, subsurface low-oxygen conditions were occurring seasonally over a large part of the geographic area now known as the dead zone. The long-term trends in the PEB index are consistent with the 20th-century observational and proxy data for low oxygen and hypoxia. ?? 2009 US Government.

Circulation, eddies, oxygen and nutrient changes in the eastern tropical South Pacific Ocean

NASA Astrophysics Data System (ADS)

Czeschel, R.; Stramma, L.; Weller, R. A.; Fischer, T.

2014-09-01

A large, subsurface oxygen deficiency zone is located in the eastern tropical South Pacific Ocean (ETSP). The large-scale circulation in the eastern equatorial Pacific and off Peru in November/December 2012 shows the influence of the equatorial current system, the eastern boundary currents, and the northern reaches of the subtropical gyre. In November 2012 the Equatorial Undercurrent is centered at 250 m depth, deeper than in earlier observations. In December 2012 the equatorial water is transported southeastward near the shelf in the Peru-Chile Undercurrent with a mean transport of 1.6 Sv. In the oxygen minimum zone (OMZ) the flow is overlaid with strong eddy activity on the poleward side of the OMZ. Floats with parking depth at 400 m show fast westward flow in the mid-depth equatorial channel and sluggish flow in the OMZ. Floats with oxygen sensors clearly show the passage of eddies with oxygen anomalies. The long-term float observations in the upper ocean lead to a net community production estimate at about 18° S of up to 16.7 mmol C m-3 yr1 extrapolated to an annual rate and 7.7 mmol C m-3 yr-1 for the time period below the mixed layer. Oxygen differences between repeated ship sections are influenced by the Interdecadal Pacific Oscillation, by the phase of El Niño, by seasonal changes, and by eddies and hence have to be interpreted with care. At and south of the equator the decrease in oxygen in the upper ocean since 1976 is related to an increase in nitrate, phosphate, and in part in silicate.

Circulation, eddies, oxygen, and nutrient changes in the eastern tropical South Pacific Ocean

NASA Astrophysics Data System (ADS)

Czeschel, R.; Stramma, L.; Weller, R. A.; Fischer, T.

2015-06-01

A large subsurface oxygen deficiency zone is located in the eastern tropical South Pacific Ocean (ETSP). The large-scale circulation in the eastern equatorial Pacific and off the coast of Peru in November/December 2012 shows the influence of the equatorial current system, the eastern boundary currents, and the northern reaches of the subtropical gyre. In November 2012 the equatorial undercurrent (EUC) is centered at 250 m depth, deeper than in earlier observations. In December 2012, the equatorial water is transported southeastward near the shelf in the Peru-Chile undercurrent (PCUC) with a mean transport of 1.4 Sv. In the oxygen minimum zone (OMZ), the flow is overlaid with strong eddy activity on the poleward side of the OMZ. Floats with parking depth at 400 m show fast westward flow in the mid-depth equatorial channel and sluggish flow in the OMZ. Floats with oxygen sensors clearly show the passage of eddies with oxygen anomalies. The long-term float observations in the upper ocean lead to a net community production estimate at about 18° S of up to 16.7 mmol C m-3 yr-1 extrapolated to an annual rate and 7.7 mmol C m-3 yr-1 for the time period below the mixed layer. Oxygen differences between repeated ship sections are influenced by the Interdecadal Pacific Oscillation (IPO), by the phase of El Niño, by seasonal changes, and by eddies, and hence have to be interpreted with care. At and south of the Equator the decrease in oxygen in the upper ocean since 1976 is related to an increase in nitrate, phosphate, and in part silicate.

Simulation of oil bioremediation in a tidally influenced beach: Spatiotemporal evolution of nutrient and dissolved oxygen

NASA Astrophysics Data System (ADS)

Geng, Xiaolong; Pan, Zhong; Boufadel, Michel C.; Ozgokmen, Tamay; Lee, Kenneth; Zhao, Lin

2016-04-01

Numerical experiments of oil bioremediation of tidally influenced beach were simulated using the model BIOMARUN. Nutrient and dissolved oxygen were assumed present in a solution applied on the exposed beach face, and the concentration of these amendments was tracked throughout the beach for up to 6 months. It was found that, in comparison to natural attenuation, bioremediation increased the removal efficiency by 76% and 65% for alkanes and aromatics, respectively. Increasing the nutrient concentration in the applied solution did not always enhance biodegradation as oxygen became limiting even when the beach was originally oxygen-rich. Therefore, replenishment of oxygen to oil-contaminated zone was also essential. Stimulation of oil biodegradation was more evident in the upper and midintertidal zone of the beach, and less in the lower intertidal zone. This was due to reduced nutrient and oxygen replenishment, as very little of the amendment solution reached that zone. It was found that under continual application, most of the oil biodegraded within 2 months, while it persisted for 6 months under natural conditions. While the difference in duration suggests minimal long-term effects, there are situations where the beach would need to be cleaned for major ecological functions, such as temporary nesting or feeding for migratory birds. Biochemical retention time map (BRTM) showed that the duration of solution application was dependent upon the stimulated oil biodegradation rate. By contrast, the application rate of the amendment solution was dependent upon the subsurface extent of the oil-contaminated zone. Delivery of nutrient and oxygen into coastal beach involved complex interaction among amendment solution, groundwater, and seawater. Therefore, approaches that ignore the hydrodynamics due to tide are unlikely to provide the optimal solutions for shoreline bioremediation.

Feasibility of electrokinetic oxygen supply for soil bioremediation purposes.

PubMed

Mena Ramírez, E; Villaseñor Camacho, J; Rodrigo Rodrigo, M A; Cañizares Cañizares, P

2014-12-01

This paper studies the possibility of providing oxygen to a soil by an electrokinetic technique, so that the method could be used in future aerobic polluted soil bioremediation treatments. The oxygen was generated from the anodic reaction of water electrolysis and transported to the soil in a laboratory-scale electrokinetic cell. Two variables were tested: the soil texture and the voltage gradient. The technique was tested in two artificial soils (clay and sand) and later in a real silty soil, and three voltage gradients were used: 0.0 (control), 0.5, and 1.0 V cm(-1). It was observed that these two variables strongly influenced the results. Oxygen transport into the soil was only available in the silty and sandy soils by oxygen diffusion, obtaining high dissolved oxygen concentrations, between 4 and 9 mg L(-1), useful for possible aerobic biodegradation processes, while transport was not possible in fine-grained soils such as clay. Electro-osmotic flow did not contribute to the transport of oxygen, and an increase in voltage gradients produced higher oxygen transfer rates. However, only a minimum fraction of the electrolytically generated oxygen was efficiently used, and the maximum oxygen transport rate observed, approximately 1.4 mgO2 L(-1)d(-1), was rather low, so this technique could be only tested in slow in-situ biostimulation processes for organics removal from polluted soils. Copyright © 2014 Elsevier Ltd. All rights reserved.

EFFECTS OF THE VARIATION OF SELECT SAMPLING PARAMETERS ON SOIL VAPOR CONCENTRATIONS

EPA Science Inventory

Currently soil vapor surveys are commonly used as a screening technique to delineate subsurface volatile organic compound (VOC) contaminant plumes and to provide information for vapor intrusion and contaminated site evaluations. To improve our understanding of the fate and transp...

Dynamics of the Genetic Diversity of Subsurface Microbial Communities and Their Applications to Contaminated Site Cleanups

EPA Science Inventory

When compared to traditional approaches, the utilization of molecular and genomic techniques to soil and groundwater cleanup investigations can reduce inherent parameter variability when conducting bench and pilot-scale investigations or carrying out full-scale field applications...

Geophysical characterisation of the groundwater-surface water interface

NASA Astrophysics Data System (ADS)

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.

Application of high-resolution subsurface imaging techniques to water resource investigations. Final report

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

Sternberg, B.K.; Thomas, S.J.

1992-12-01

The overall objective of the project was to apply a new high-resolution imaging system to water resource investigations. This imaging system measures the ellipticity of received magnetic-field components. The source of the magnetic field is a long-line transmitter emitting frequencies from 30 Hz to 30 kHz. A new high-accuracy calibration method was used to enhance the resolution of the measurements. The specific objectives included: (1) refine the system hardware and software based on these investigations, (2) learn the limitations of this technology in practical water resource investigations, and (3) improve interpretation techniques to extract the highest possible resolution. Successful fieldmore » surveys were run at: (1) San Xavier Mine, Arizona - flow of injected fluid was monitored with the system. (2) Avra Valley, Arizona - subsurface stratigraphy was imaged. A survey at a third site was less successful; interpreted resistivity section does not agree with nearby well logs. Surveys are continuing at this site.« less

Depth-Resolved Multispectral Sub-Surface Imaging Using Multifunctional Upconversion Phosphors with Paramagnetic Properties

PubMed Central

Ovanesyan, Zaven; Mimun, L. Christopher; Kumar, Gangadharan Ajith; Yust, Brian G.; Dannangoda, Chamath; Martirosyan, Karen S.; Sardar, Dhiraj K.

2015-01-01

Molecular imaging is very promising technique used for surgical guidance, which requires advancements related to properties of imaging agents and subsequent data retrieval methods from measured multispectral images. In this article, an upconversion material is introduced for subsurface near-infrared imaging and for the depth recovery of the material embedded below the biological tissue. The results confirm significant correlation between the analytical depth estimate of the material under the tissue and the measured ratio of emitted light from the material at two different wavelengths. Experiments with biological tissue samples demonstrate depth resolved imaging using the rare earth doped multifunctional phosphors. In vitro tests reveal no significant toxicity, whereas the magnetic measurements of the phosphors show that the particles are suitable as magnetic resonance imaging agents. The confocal imaging of fibroblast cells with these phosphors reveals their potential for in vivo imaging. The depth-resolved imaging technique with such phosphors has broad implications for real-time intraoperative surgical guidance. PMID:26322519

A High-Sensitivity Broad-Band Seismic Sensor for Shallow Seismic Sounding of the Lunar Regolith

NASA Technical Reports Server (NTRS)

Pike, W. Thomas; Standley, Ian M.; Banerdt, W. Bruce

2005-01-01

The recently undertaken Space Exploration Initiative has prompted a renewed interest in techniques for characterizing the surface and shallow subsurface (0-10s of meters depth) of the Moon. There are several reasons for this: First, there is an intrinsic scientific interest in the subsurface structure. For example the stratigraphy, depth to bedrock, density/porosity, and block size distribution all have implications for the formation of, and geological processes affecting the surface, such as sequential crater ejecta deposition, impact gardening, and seismic settling. In some permanently shadowed craters there may be ice deposits just below the surface. Second, the geotechnical properties of the lunar surface layers are of keen interest to future mission planners. Regolith thickness, strength, density, grain size and compaction will affect construction of exploration infrastructure in terms of foundation strength and stability, ease of excavation, radiation shielding effectiveness, as well as raw material handling and processing techniques for resource extraction.

Rapid shift and millennial-scale variations in Holocene North Pacific Intermediate Water ventilation.

PubMed

Lembke-Jene, Lester; Tiedemann, Ralf; Nürnberg, Dirk; Gong, Xun; Lohmann, Gerrit

2018-05-22

The Pacific hosts the largest oxygen minimum zones (OMZs) in the world ocean, which are thought to intensify and expand under future climate change, with significant consequences for marine ecosystems, biogeochemical cycles, and fisheries. At present, no deep ventilation occurs in the North Pacific due to a persistent halocline, but relatively better-oxygenated subsurface North Pacific Intermediate Water (NPIW) mitigates OMZ development in lower latitudes. Over the past decades, instrumental data show decreasing oxygenation in NPIW; however, long-term variations in middepth ventilation are potentially large, obscuring anthropogenic influences against millennial-scale natural background shifts. Here, we use paleoceanographic proxy evidence from the Okhotsk Sea, the foremost North Pacific ventilation region, to show that its modern oxygenated pattern is a relatively recent feature, with little to no ventilation before six thousand years ago, constituting an apparent Early-Middle Holocene (EMH) threshold or "tipping point." Complementary paleomodeling results likewise indicate a warmer, saltier EMH NPIW, different from its modern conditions. During the EMH, the Okhotsk Sea switched from a modern oxygenation source to a sink, through a combination of sea ice loss, higher water temperatures, and remineralization rates, inhibiting ventilation. We estimate a strongly decreased EMH NPIW oxygenation of ∼30 to 50%, and increased middepth Pacific nutrient concentrations and carbon storage. Our results ( i ) imply that under past or future warmer-than-present conditions, oceanic biogeochemical feedback mechanisms may change or even switch direction, and ( ii ) provide constraints on the high-latitude North Pacific's influence on mesopelagic ventilation dynamics, with consequences for large oceanic regions. Copyright © 2018 the Author(s). Published by PNAS.

Early oxygenation of the terrestrial environment during the Mesoproterozoic.

PubMed

Parnell, John; Boyce, Adrian J; Mark, Darren; Bowden, Stephen; Spinks, Sam

2010-11-11

Geochemical data from ancient sedimentary successions provide evidence for the progressive evolution of Earth's atmosphere and oceans. Key stages in increasing oxygenation are postulated for the Palaeoproterozoic era (∼2.3 billion years ago, Gyr ago) and the late Proterozoic eon (about 0.8 Gyr ago), with the latter implicated in the subsequent metazoan evolutionary expansion. In support of this rise in oxygen concentrations, a large database shows a marked change in the bacterially mediated fractionation of seawater sulphate to sulphide of Δ(34)S < 25‰ before 1 Gyr to ≥50‰ after 0.64 Gyr. This change in Δ(34)S has been interpreted to represent the evolution from single-step bacterial sulphate reduction to a combination of bacterial sulphate reduction and sulphide oxidation, largely bacterially mediated. This evolution is seen as marking the rise in atmospheric oxygen concentrations and the evolution of non-photosynthetic sulphide-oxidizing bacteria. Here we report Δ(34)S values exceeding 50‰ from a terrestrial Mesoproterozoic (1.18 Gyr old) succession in Scotland, a time period that is at present poorly characterized. This level of fractionation implies disproportionation in the sulphur cycle, probably involving sulphide-oxidizing bacteria, that is not evident from Δ(34)S data in the marine record. Disproportionation in both red beds and lacustrine black shales at our study site suggests that the Mesoproterozoic terrestrial environment was sufficiently oxygenated to support a biota that was adapted to an oxygen-rich atmosphere, but had also penetrated into subsurface sediment.

Environmental TEM study of electron beam induced electro-chemistry of Pr₀̣₆₄Ca₀̣₃₆MnO₃ catalysts for oxygen evolution

DOE PAGES

Mildner, Stephanie; Beleggia, Marco; Mierwaldt, Daniel; ...

2015-03-12

Environmental Transmission Electron Microscopy (ETEM) studies offer great potential for gathering atomic scale information on the electronic state of electrodes in contact with reactants but also pose big challenges due to the impact of the high energy electron beam. In this article, we present an ETEM study of a Pr₀̣₆₄Ca₀̣₃₆MnO₃ (PCMO) thin film electro-catalyst for water splitting and oxygen evolution in contact with water vapor. We show by means of off-axis electron holography and electrostatic modeling that the electron beam gives rise to a positive electric sample potential due to secondary electron emission. The value of the electric potential dependsmore » on the primary electron flux, the sample -conductivity and grounding, and gas properties. We present evidence that two observed electro-chemical reactions are driven by a beam induced electrostatic potential of the order of a volt. The first reaction is an anodic electrochemical oxidation reaction of oxygen depleted amorphous PCMO which results in recrystallization of the perovskite structure. The second reaction is oxygen evolution which can be detected by the oxidation of a silane additive and formation of SiO 2–x at catalytically active surfaces. Recently published in-situ XANES observation of subsurface oxygen vacancy formation during oxygen evolution at a positive potential [³²] is confirmed in this work. The quantification of beam induced potentials is an important step for future controlled electro-chemical experiments in an ETEM.« less

Characterization of subsurface geologic structure for potential water resources near the Villages of Moenkopi, Arizona, 2009--2010

USGS Publications Warehouse

Macy, Jamie P.

2012-01-01

The Hopi Tribe depends on groundwater as their primary drinking-water source in the area of the Villages of Moenkopi, in northeastern Arizona. Growing concerns of the potential for uranium contamination at the Moenkopi water supply wells from the Tuba City Landfill prompted the need for an improved understanding of subsurface geology and groundwater near Moenkopi. Information in this report provides the Hopi Tribe with new hydrogeologic information that provides a better understanding of groundwater resources near the Villages of Moenkopi. The U.S. Geological Survey in cooperation with the U.S. Bureau of Reclamation and the Hopi Tribe used the controlled source audio-frequency magnetotelluric (CSAMT) geophysical technique to characterize the subsurface near Moenkopi from December 2009 to September 2010. A total of six CSAMT profiles were surveyed to identify possible fracturing and faulting in the subsurface that provides information about the occurrence and movement of groundwater. Inversion results from the six CSAMT lines indicated that north to south trending fractures are more prevalent than east to west. CSAMT Lines A and C showed multiple areas in the Navajo Sandstone where fractures are present. Lines B, D, E, and F did not show the same fracturing as Lines A and C.

Characterization of microbial communities in subsurface nuclear blast cavities of the Nevada Test Site

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

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

Characterization of Microbial Communities in Subsurface Nuclear Blast Cavities of the Nevada Test Site

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

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

Mind the Gaps: Expert and Non-Expert Differences in Conceptualising the Geological Subsurface.

NASA Astrophysics Data System (ADS)

Gibson, H.; Stewart, I. S.; Stokes, A.; Pahl, S.

2017-12-01

In communicating geoscience topics, emphasis is often given to approaches such as the use of narrative to make a message engaging and reducing the use of jargon to ensure that it is understood by as wide a group of people as possible. Whilst these are undeniably important techniques to promote effective communication, an aspect of geoscience communication that is often overlooked is the publics' conceptual frameworks about core geoscience concepts. The consideration of different conceptual frameworks fits with the need to ensure that the framing is appropriate for the message, but it extends beyond simple framing into more complicated issues of addressing and incorporating pre- and mis-conceptions in geoscience. In a study examining expert and non-expert cognitive (mental) models of the geological subsurface in south-west England, several gaps were found between the fundamental ways that experts and non-experts conceptualise this invisible realm. Of these, three gaps were considered to be particularly important and common to many participants: the use of spatial reasoning; the application of surface experiences to subsurface processes; and the connection between the surface and subsurface. This paper will examine the evidence for these three important conceptual gaps between specialists and non-specialists and will address how this type of cognitive study can help improve effective geoscience communication.

Retrieving Temperature Anomaly in the Global Subsurface and Deeper Ocean From Satellite Observations

NASA Astrophysics Data System (ADS)

Su, Hua; Li, Wene; Yan, Xiao-Hai

2018-01-01

Retrieving the subsurface and deeper ocean (SDO) dynamic parameters from satellite observations is crucial for effectively understanding ocean interior anomalies and dynamic processes, but it is challenging to accurately estimate the subsurface thermal structure over the global scale from sea surface parameters. This study proposes a new approach based on Random Forest (RF) machine learning to retrieve subsurface temperature anomaly (STA) in the global ocean from multisource satellite observations including sea surface height anomaly (SSHA), sea surface temperature anomaly (SSTA), sea surface salinity anomaly (SSSA), and sea surface wind anomaly (SSWA) via in situ Argo data for RF training and testing. RF machine-learning approach can accurately retrieve the STA in the global ocean from satellite observations of sea surface parameters (SSHA, SSTA, SSSA, SSWA). The Argo STA data were used to validate the accuracy and reliability of the results from the RF model. The results indicated that SSHA, SSTA, SSSA, and SSWA together are useful parameters for detecting SDO thermal information and obtaining accurate STA estimations. The proposed method also outperformed support vector regression (SVR) in global STA estimation. It will be a useful technique for studying SDO thermal variability and its role in global climate system from global-scale satellite observations.

Preliminary results of real-time in-vitro electronic speckle pattern interferometry (ESPI) measurements in otolaryngology

NASA Astrophysics Data System (ADS)

Conerty, Michelle D.; Castracane, James; Cacace, Anthony T.; Parnes, Steven M.; Gardner, Glendon M.; Miller, Mitchell B.

1995-05-01

Electronic Speckle Pattern Interferometry (ESPI) is a nondestructive optical evaluation technique that is capable of determining surface and subsurface integrity through the quantitative evaluation of static or vibratory motion. By utilizing state of the art developments in the areas of lasers, fiber optics and solid state detector technology, this technique has become applicable in medical research and diagnostics. Based on initial support from NIDCD and continued support from InterScience, Inc., we have been developing a range of instruments for improved diagnostic evaluation in otolaryngological applications based on the technique of ESPI. These compact fiber optic instruments are capable of making real time interferometric measurements of the target tissue. Ongoing development of image post- processing software is currently capable of extracting the desired quantitative results from the acquired interferometric images. The goal of the research is to develop a fully automated system in which the image processing and quantification will be performed in hardware in near real-time. Subsurface details of both the tympanic membrane and vocal cord dynamics could speed the diagnosis of otosclerosis, laryngeal tumors, and aid in the evaluation of surgical procedures.

Vibrational Action Spectroscopy of Solids: New Surface-Sensitive Technique

NASA Astrophysics Data System (ADS)

Wu, Zongfang; Płucienik, Agata; Feiten, Felix E.; Naschitzki, Matthias; Wachsmann, Walter; Gewinner, Sandy; Schöllkopf, Wieland; Staemmler, Volker; Kuhlenbeck, Helmut; Freund, Hans-Joachim

2017-09-01

Vibrational action spectroscopy employing infrared radiation from a free-electron laser has been successfully used for many years to study the vibrational and structural properties of gas phase aggregates. Despite the high sensitivity of this method no relevant studies have yet been conducted for solid sample surfaces. We have set up an experiment for the application of this method to such targets, using infrared light from the free-electron laser of the Fritz Haber Institute. In this Letter, we present first results of this technique with adsorbed argon and neon atoms as messengers. We were able to detect surface-located vibrations of a thin V2O3(0 0 0 1 ) film on Au(111) as well as adsorbate vibrations, demonstrating that this method is highly surface sensitive. We consider that the dominant channel for desorption of the messenger atoms is direct inharmonic vibrational coupling, which is essentially insensitive to subsurface or bulk vibrations. Another channel is thermal desorption due to sample heating by absorption of infrared light. The high surface sensitivity of the nonthermal channel and its insensitivity to subsurface modes makes this technique an ideal tool for the study of surface-located vibrations.

Vibrational Action Spectroscopy of Solids: New Surface-Sensitive Technique.

PubMed

Wu, Zongfang; Płucienik, Agata; Feiten, Felix E; Naschitzki, Matthias; Wachsmann, Walter; Gewinner, Sandy; Schöllkopf, Wieland; Staemmler, Volker; Kuhlenbeck, Helmut; Freund, Hans-Joachim

2017-09-29

Vibrational action spectroscopy employing infrared radiation from a free-electron laser has been successfully used for many years to study the vibrational and structural properties of gas phase aggregates. Despite the high sensitivity of this method no relevant studies have yet been conducted for solid sample surfaces. We have set up an experiment for the application of this method to such targets, using infrared light from the free-electron laser of the Fritz Haber Institute. In this Letter, we present first results of this technique with adsorbed argon and neon atoms as messengers. We were able to detect surface-located vibrations of a thin V_{2}O_{3}(0001) film on Au(111) as well as adsorbate vibrations, demonstrating that this method is highly surface sensitive. We consider that the dominant channel for desorption of the messenger atoms is direct inharmonic vibrational coupling, which is essentially insensitive to subsurface or bulk vibrations. Another channel is thermal desorption due to sample heating by absorption of infrared light. The high surface sensitivity of the nonthermal channel and its insensitivity to subsurface modes makes this technique an ideal tool for the study of surface-located vibrations.

Performance assessment of pilot horizontal sub-surface flow constructed wetlands for removal of diesel from wastewater by Scirpus grossus.

PubMed

Al-Baldawi, Israa Abdulwahab; Sheikh Abdullah, Siti Rozaimah; Anuar, Nurina; Suja, Fatihah; Idris, Mushrifah

2013-01-01

One of the appropriate development technology options for the treatment of wastewater contaminated with diesel is constructed wetlands (CWs). Throughout 72 days of exposure, sampling was carried out for monitoring of physical parameters, plant growth and the efficiency of total petroleum hydrocarbon (TPH) removal, as an indication for diesel contamination, to assess the pilot-scale performance. Four pilot CWs with a horizontal sub-surface flow system were applied using the bulrush of Scirpus grossus. The CWs were loaded with different diesel concentrations of 0, 0.1, 0.2 and 0.25% (Vdiesel/Vwater). The TPH removal efficiencies were 82, 71, and 67% at the end of 72 days for diesel concentrations of 0.1, 0.2, and 0.25% respectively. In addition, the high removal efficiency of total suspended solids and chemical oxygen demand (COD) were 100 and 75.4% respectively, for a diesel concentration of 0.1%. It was concluded that S. grossus is a potential plant that can be used in a well-operated CW for restoring 0.1% diesel-contaminated water.

Design, construction and performance of a horizontal subsurface flow wetland system in Australia.

PubMed

Bolton, Lise M W; Bolton, Keith G E

2013-01-01

Malabugilmah is a remote Aboriginal community located in Clarence Valley, Northern NSW, Australia. In 2006, seven horizontal subsurface flow wetland clusters consisting of 3 m × 2 m wetland cells in series were designed and constructed to treat septic tank effluent to a secondary level (Total Suspended Solids (TSS) < 30 mg/L and Biochemical Oxygen Demand (BOD5) <20 mg/L) and achieve >50% Total Nitrogen (TN) reduction, no net Total Phosphorus (TP) export and ≥99.9% Faecal Coliform (FC) reduction. The wetland cell configuration allowed the wetlands to be located on steeper terrain, enabling effluent to be treated to a secondary level without the use of pumps. In addition to the water quality targets, the wetlands were designed and constructed to satisfy environmental, economic and social needs of the community. The wetland systems were planted with a local Australian wetland tree species which has become well established. Two wetland clusters have been monitored over the last 4 years. The wetlands have demonstrated to be robust over time, providing a high level of secondary treatment over an extended period.

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

Brownlow, D.T.; Escude, S.; Johanneson, O.H.

The 1500 Area at Kelly Air Force Base (AFB) was the site of a subsurface release of approximately 1,000 gallons of JP-4 jet fuel. Preliminary studies found evidence of hydrocarbon contamination extending from 10 feet below ground surface (bgs) down to the shallow water table, at 20 to 25 feet bgs. In June of 1993, Kelly AFB authorized the installation and evaluation of a bioventing system at this site to aid in the cleanup of the hydrocarbon contaminated soils. The purpose of the bioventing system is to aerate subsurface soils within and immediately surrounding the release area, in order tomore » stimulate in-situ biological activity and enhance the natural bioremediation capacity of the soil. Augmenting oxygen to the indigenous soil microorganisms promotes the aerobic metabolism of fuel hydrocarbons in the soil. In vadose zone soils exhibiting relatively good permeability, bioventing has proven to be a highly cost effective remediation technology for treating fuel contaminated soils. In November, 1993, a Start-Up Test program consisting of an In-Situ Respiration Test (ISRT) and an Air Permeability Test was performed at the 1500 Area Spill Site.« less

Removal of nutrients from septic tank effluent with baffle subsurface-flow constructed wetlands.

PubMed

Cui, Lihua; Ouyang, Ying; Yang, Weizhi; Huang, Zhujian; Xu, Qiaoling; Yu, Guangwei

2015-04-15

Three new baffle flow constructed wetlands (CWs), namely the baffle horizontal flow CW (Z1), baffle vertical flow CW (Z2) and baffle hybrid flow CW (Z3), along with one traditional horizontal subsurface flow CW (Z4) were designed to test the removal efficiency of nitrogen (N) and phosphorus (P) from the septic tank effluent under varying hydraulic retention times (HRTs). Results showed that the optimal HRT was two days for maximal removal of N and P from the septic tank effluent among the four CWs. At this HRT, the Z1, Z2, Z3 and Z4 CWs removed, respectively, 49.93, 58.50, 46.01 and 44.44% of TN as well as 87.82, 93.23, 95.97 and 91.30% of TP. Our study further revealed that the Z3 CW was the best design for overall removal of N and P from the septic tank effluent due to its hybrid flow directions with better oxygen supply inside the CW system. Copyright © 2015 Elsevier Ltd. All rights reserved.

Thermodynamic Stability of Molybdenum Oxycarbides Formed from Orthorhombic Mo 2 C in Oxygen-Rich Environments

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

Likith, S. R. J.; Farberow, C. A.; Manna, S.

Molybdenum carbide (Mo 2C) nanoparticles and thin films are particularly suitable catalysts for catalytic fast pyrolysis (CFP) as they are effective for deoxygenation and can catalyze certain reactions that typically occur on noble metals. Oxygen deposited during deoxygenation reactions may alter the carbide structure, leading to the formation of oxycarbides, which can determine changes in catalytic activity or selectivity. Despite emerging spectroscopic evidence of bulk oxycarbides, so far there have been no reports of their precise atomic structure or their relative stability with respect to orthorhombic Mo 2C. This knowledge is essential for assessing the catalytic properties of molybdenum (oxy)carbidesmore » for CFP. In this article, we use density functional theory (DFT) calculations to (a) describe the thermodynamic stability of surface and subsurface configurations of oxygen and carbon atoms for a commonly studied Mo-terminated surface of orthorhombic Mo 2C and (b) determine atomic structures for oxycarbides with a Mo:C ratio of 2:1. The surface calculations suggest that oxygen atoms are not stable under the top Mo layer of the Mo 2C(100) surface. Coupling DFT calculations with a polymorph sampling method, we determine (Mo 2C) xO y oxycarbide structures for a wide range of oxygen compositions. Oxycarbides with lower oxygen content (y/x = 2) adopt layered structures reminiscent of the parent carbide phase, with flat Mo layers separated by layers of oxygen and carbon; for higher oxygen content, our results suggest the formation of amorphous phases, as the atomic layers lose their planarity with increasing oxygen content. We characterize the oxidation states of Mo in the oxycarbide structures determined computationally, and simulate their X-ray diffraction (XRD) patterns in order to facilitate comparisons with experiments. Our study may provide a platform for large-scale investigations of the catalytic properties of oxycarbides and their surfaces and for tailoring the catalytic properties for different desired reactions.« less

Thermodynamic Stability of Molybdenum Oxycarbides Formed from Orthorhombic Mo 2 C in Oxygen-Rich Environments

DOE PAGES

Likith, S. R. J.; Farberow, C. A.; Manna, S.; ...

2017-12-20

Molybdenum carbide (Mo 2C) nanoparticles and thin films are particularly suitable catalysts for catalytic fast pyrolysis (CFP) as they are effective for deoxygenation and can catalyze certain reactions that typically occur on noble metals. Oxygen deposited during deoxygenation reactions may alter the carbide structure, leading to the formation of oxycarbides, which can determine changes in catalytic activity or selectivity. Despite emerging spectroscopic evidence of bulk oxycarbides, so far there have been no reports of their precise atomic structure or their relative stability with respect to orthorhombic Mo 2C. This knowledge is essential for assessing the catalytic properties of molybdenum (oxy)carbidesmore » for CFP. In this article, we use density functional theory (DFT) calculations to (a) describe the thermodynamic stability of surface and subsurface configurations of oxygen and carbon atoms for a commonly studied Mo-terminated surface of orthorhombic Mo 2C and (b) determine atomic structures for oxycarbides with a Mo:C ratio of 2:1. The surface calculations suggest that oxygen atoms are not stable under the top Mo layer of the Mo 2C(100) surface. Coupling DFT calculations with a polymorph sampling method, we determine (Mo 2C) xO y oxycarbide structures for a wide range of oxygen compositions. Oxycarbides with lower oxygen content (y/x = 2) adopt layered structures reminiscent of the parent carbide phase, with flat Mo layers separated by layers of oxygen and carbon; for higher oxygen content, our results suggest the formation of amorphous phases, as the atomic layers lose their planarity with increasing oxygen content. We characterize the oxidation states of Mo in the oxycarbide structures determined computationally, and simulate their X-ray diffraction (XRD) patterns in order to facilitate comparisons with experiments. Our study may provide a platform for large-scale investigations of the catalytic properties of oxycarbides and their surfaces and for tailoring the catalytic properties for different desired reactions.« less

Disentangling atomic-layer-specific x-ray absorption spectra by Auger electron diffraction spectroscopy

NASA Astrophysics Data System (ADS)

Matsui, Fumihiko; Matsushita, Tomohiro; Kato, Yukako; Hashimoto, Mie; Daimon, Hiroshi

2009-11-01

In order to investigate the electronic and magnetic structures of each atomic layer at subsurface, we have proposed a new method, Auger electron diffraction spectroscopy, which is the combination of x-ray absorption spectroscopy (XAS) and Auger electron diffraction (AED) techniques. We have measured a series of Ni LMM AED patterns of the Ni film grown on Cu(001) surface for various thicknesses. Then we deduced a set of atomic-layer-specific AED patterns in a numerical way. Furthermore, we developed an algorithm to disentangle XANES spectra from different atomic layers using these atomic-layer-specific AED patterns. Surface and subsurface core level shift were determined for each atomic layer.

The role of water in unconventional in situ energy resource extraction technologies: Chapter 7 in Food, energy, and water: The chemistry connection

USGS Publications Warehouse

Gallegos, Tanya J.; Bern, Carleton R.; Birdwell, Justin E.; Haines, Seth S.; Engle, Mark A.

2015-01-01

Global trends toward developing new energy resources from lower grade, larger tonnage deposits that are not generally accessible using “conventional” extraction methods involve variations of subsurface in situ extraction techniques including in situ oil-shale retorting, hydraulic fracturing of petroleum reservoirs, and in situ recovery (ISR) of uranium. Although these methods are economically feasible and perhaps result in a smaller above-ground land-use footprint, there remain uncertainties regarding potential subsurface impacts to groundwater. This chapter provides an overview of the role of water in these technologies and the opportunities and challenges for water reuse and recycling.

Airborne Lidar Measurements of Atmospheric Pressure Made Using the Oxygen A-Band

NASA Technical Reports Server (NTRS)

Riris, Haris; Rodriquez, Michael; Allan, Graham R.; Hasselbrack, William E.; Stephen, Mark A.; Abshire, James B.

2011-01-01

We report on airborne measurements of atmospheric pressure using a fiber-laser based lidar operating in the oxygen A-band near 765 nm and the integrated path differential absorption measurement technique. Our lidar uses fiber optic technology and non-linear optics to generate tunable laser radiation at 765 nm, which overlaps an absorption line pair in the Oxygen A-band. We use a pulsed time resolved technique, which rapidly steps the laser wavelength across the absorption line pair, a 20 cm telescope and photon counting detector to measure Oxygen concentrations.

SURFACE FISSURE FORMATION ABOVE UNDERGROUND COALSEAM FIRES: DIMENSIONLESS RELATIONSHIPS BETWEEN SURFACE FISSURES AND SUBSURFACE SUBSIDENCE

NASA Astrophysics Data System (ADS)

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 that relationships exist between the surface displacement magnitudes and directions, and the subsurface subsidence due to coal combustion. Subsidence variables include the length, magnitude, depth and location of subsidence, as well as the weight of the overburden. Each of the four types of surface features was related to these subsurface subsidence variables using a set of dimensionless curves. The simulation results were validated with field measurements from a nearby outcrop and borehole drilling. The possibility of using InSAR data to further constrain these model results is being investigated. The simulated dimensionless curves establish a useful rules of thumb to aid the interpretation and mitigation of coal fires, since these curves can be used to relate a surface fissures aperture, an easily measurable parameter, to variables such as the magnitude of subsurface subsidence that are harder to observe

Water Velocity as a Driver of Stream Metabolism: a Parallel Application of the Open Water and Eddy Correlation Techniques

NASA Astrophysics Data System (ADS)

Koopmans, D.; Berg, P.

2013-12-01

Inland waters respire or store a large portion of net terrestrial ecosystem production. As a result their metabolism is significant to the global carbon budget. The proximal drivers of aquatic respiration are organic matter availability, temperature, nutrients, and water velocity. Among these water velocity may be the least quantified. A partial explanation is that the footprint of the open water technique is typically hundreds of meters of river length, while the effect of a change in velocity may be specific to a local benthic environment, e.g., a riffle. With the eddy correlation technique oxygen flux is calculated from the turbulent fluctuation of vertical velocity and the oxygen concentration at a point in the water column. The footprint of the technique scales with the height of the point of measurement allowing an investigation of the in situ oxygen flux at the scale of a riffle. The combination of techniques, then, can be used to investigate the coupling of hydrodynamic conditions and benthic environments in driving aquatic ecosystem metabolism. This parallel approach was applied seasonally to examine the drivers of metabolism in a nutrient-rich, sand-bed coastal stream on the Eastern Shore of Virginia. An ecosystem-scale oxygen flux was calculated with the open water technique while pool-, run-, riffle-, and freshwater tidal-scale oxygen fluxes were calculated with the eddy correlation technique. At the ecosystem scale the stream bed functioned as an effective biocatalytic filter with an average annual net oxygen consumption of 300 mmol m^-2 d^-1. Prior to a stage-discharge shift water velocity explained 90% of the variance in ecosystem respiration (n = 63 days). After the stage-discharge shift water velocity explained 96 % of it (n = 40 days). Hyporheic exchange supported respiration in this system, contributing to its close correlation with water velocity. Among the physically similar benthic environments of the run, riffle, and freshwater tidal sites, however, similar water velocities generated order of magnitude differences in oxygen flux. The smallest oxygen fluxes were observed at the tidal site followed by the riffle and pool. The patterns were consistent with the site-specific suppression of hyporheic exchange by pore water clogging. An uneven distribution of sediment organic matter may also contribute. These results demonstrate that ecosystem metabolism in this stream is hydrodynamically controlled and suggest mechanisms by which that control may be undermined. Oxygen flux measured at a stream riffle with the eddy correlation technique.

EVALUATION OF GEOPHYSICAL METHODS FOR THE DETECTION OF SUBSURFACE TETRACHLOROETHYLENE IN CONTROLLED SPILL EXPERIMENTS

EPA Science Inventory

This paper presents some of the results of five of the techniques: cross borehole complex resistivity (CR) also referred to as spectral induced polarization (SIP), cross borehole high resolution seismic (HRS), borehole self potential (SP), surface ground penetration radar (GPR), ...

OXYGEN TRANSPORT IN THE MICROCIRCULATION AND ITS REGULATION

PubMed Central

Pittman, Roland N.

2012-01-01

Cells require energy to carry out their functions and they typically use oxidative phosphorylation to generate the needed ATP. Thus, cells have a continuous need for oxygen which they receive by diffusion from the blood through the interstitial fluid. The circulatory system pumps oxygen-rich blood through a network of increasingly minute vessels, the microcirculation. The structure of the microcirculation is such that all cells have at least one nearby capillary for diffusive exchange of oxygen and red blood cells release the oxygen bound to hemoglobin as they traverse capillaries. This review focuses first on the historical development of techniques to measure oxygen at various sites in the microcirculation, including the blood, interstitium and cells. Next, approaches are described as to how these techniques have been employed to make discoveries about different aspects of oxygen transport. Finally, ways in which oxygen might participate in the regulation of blood flow toward matching oxygen supply to oxygen demand is discussed. Overall, the transport of oxygen to the cells of the body is one of the most critical functions of the cardiovascular system and it is in the microcirculation where the final local determinants of oxygen supply, oxygen demand and their regulation are decided. PMID:23025284

Optical Oxygen Micro- and Nanosensors for Plant Applications

PubMed Central

Ast, Cindy; Schmälzlin, Elmar; Löhmannsröben, Hans-Gerd; van Dongen, Joost T.

2012-01-01

Pioneered by Clark's microelectrode more than half a century ago, there has been substantial interest in developing new, miniaturized optical methods to detect molecular oxygen inside cells. While extensively used for animal tissue measurements, applications of intracellular optical oxygen biosensors are still scarce in plant science. A critical aspect is the strong autofluorescence of the green plant tissue that interferes with optical signals of commonly used oxygen probes. A recently developed dual-frequency phase modulation technique can overcome this limitation, offering new perspectives for plant research. This review gives an overview on the latest optical sensing techniques and methods based on phosphorescence quenching in diverse tissues and discusses the potential pitfalls for applications in plants. The most promising oxygen sensitive probes are reviewed plus different oxygen sensing structures ranging from micro-optodes to soluble nanoparticles. Moreover, the applicability of using heterologously expressed oxygen binding proteins and fluorescent proteins to determine changes in the cellular oxygen concentration are discussed as potential non-invasive cellular oxygen reporters. PMID:22969334

Plant-based plume-scale mapping of tritium contamination in desert soils

USGS Publications Warehouse

Andraski, Brian J.; Stonestrom, David A.; Michel, R.L.; Halford, K.J.; Radyk, J.C.

2005-01-01

Plant-based techniques were tested for field-scale evaluation of tritium contamination adjacent to a low-level radioactive waste (LLRW) facility in the Amargosa Desert, Nevada. Objectives were to (i) characterize and map the spatial variability of tritium in plant water, (ii) develop empirical relations to predict and map subsurface contamination from plant-water concentrations, and (iii) gain insight into tritium migration pathways and processes. Plant sampling [creosote bush, Larrea tridentata (Sessé & Moc. ex DC.) Coville] required one-fifth the time of soil water vapor sampling. Plant concentrations were spatially correlated to a separation distance of 380 m; measurement uncertainty accounted for <0.1% of the total variability in the data. Regression equations based on plant tritium explained 96 and 90% of the variation in root-zone and sub-root-zone soil water vapor concentrations, respectively. The equations were combined with kriged plant-water concentrations to map subsurface contamination. Mapping showed preferential lateral movement of tritium through a dry, coarse-textured layer beneath the root zone, with concurrent upward movement through the root zone. Analysis of subsurface fluxes along a transect perpendicular to the LLRW facility showed that upward diffusive-vapor transport dominates other transport modes beneath native vegetation. Downward advective-liquid transport dominates at one endpoint of the transect, beneath a devegetated road immediately adjacent to the facility. To our knowledge, this study is the first to document large-scale subsurface vapor-phase tritium migration from a LLRW facility. Plant-based methods provide a noninvasive, cost-effective approach to mapping subsurface tritium migration in desert areas.

Integrating aeromagnetic and Landsat™ 8 data into subsurface structural mapping of Precambrian basement complex

NASA Astrophysics Data System (ADS)

Kayode, John Stephen; Nawawi, M. N. M.; Abdullah, Khiruddin B.; Khalil, Amin E.

2017-01-01

The integration of Aeromagnetic data and remotely sensed imagery with the intents of mapping the subsurface geological structures in part of the South-western basement complex of Nigeria was developed using the PCI Geomatica Software. 2013. The data obtained from the Nigerian Geological Survey Agency; was corrected using Regional Residual Separation of the Total Magnetic field anomalies enhanced, and International Geomagnetic Reference Field removed. The principal objective of this study is, therefore, to introduce a rapid and efficient method of subsurface structural depth estimate and structural index evaluation through the incorporation of the Euler Deconvolution technique into PCI Geomatica 2013 to prospect for subsurface geological structures. The shape and depth of burial helped to define these structures from the regional aeromagnetic map. The method enabled various structural indices to be automatically delineated for an index of between 0.5 SI and 3.0 SI at a maximum depth of 1.1 km that clearly showed the best depths estimate for all the structural indices. The results delineate two major magnetic belts in the area; the first belt shows an elongated ridge-like structure trending mostly along the NorthNortheast-SouthSouthwest and the other anomalies trends primarily in the Northeast, Northwest, Northeast-Southwest parts of the study area that could be attributed to basement complex granitic intrusions from the tectonic history of the area. The majority of the second structures showed various linear structures different from the first structure. Basically, a significant offset was delineated at the core segment of the study area, suggesting a major subsurface geological feature that controls mineralisation in this area.

Unique microbial community in drilling fluids from Chinese continental scientific drilling

USGS Publications Warehouse

Zhang, Gengxin; Dong, Hailiang; Jiang, Hongchen; Xu, Zhiqin; Eberl, Dennis D.

2006-01-01

Circulating drilling fluid is often regarded as a contamination source in investigations of subsurface microbiology. However, it also provides an opportunity to sample geological fluids at depth and to study contained microbial communities. During our study of deep subsurface microbiology of the Chinese Continental Scientific Deep drilling project, we collected 6 drilling fluid samples from a borehole from 2290 to 3350 m below the land surface. Microbial communities in these samples were characterized with cultivation-dependent and -independent techniques. Characterization of 16S rRNA genes indicated that the bacterial clone sequences related to Firmicutes became progressively dominant with increasing depth. Most sequences were related to anaerobic, thermophilic, halophilic or alkaliphilic bacteria. These habitats were consistent with the measured geochemical characteristics of the drilling fluids that have incorporated geological fluids and partly reflected the in-situ conditions. Several clone types were closely related to Thermoanaerobacter ethanolicus, Caldicellulosiruptor lactoaceticus, and Anaerobranca gottschalkii, an anaerobic metal-reducer, an extreme thermophile, and an anaerobic chemoorganotroph, respectively, with an optimal growth temperature of 50–68°C. Seven anaerobic, thermophilic Fe(III)-reducing bacterial isolates were obtained and they were capable of reducing iron oxide and clay minerals to produce siderite, vivianite, and illite. The archaeal diversity was low. Most archaeal sequences were not related to any known cultivated species, but rather to environmental clone sequences recovered from subsurface environments. We infer that the detected microbes were derived from geological fluids at depth and their growth habitats reflected the deep subsurface conditions. These findings have important implications for microbial survival and their ecological functions in the deep subsurface.

Global Visualization in Water using AnodizedAluminum PressureSensitive Paint and Dissolved Oxygen as Tracer

NASA Astrophysics Data System (ADS)

Ozaki, Tatsuya; Ishikawa, Hitoshi; Sakaue, Hirotaka

2009-11-01

We have developed anodized-aluminum pressuresensitive paint (AA-PSP) for flow visualization in water using dissolved oxygen as a tracer. Developed AA-PSP is characterized using water calibration setup by controlling a dissolved oxygen concentration. It is shown that the developed AA-PSP gives 4.0 percent change in luminescence per 1 mg/l of oxygen concentration. This AA-PSP is applied to visualize flows in a water tunnel. Oxygen concentrations of the water tunnel and the dissolved oxygen are 9.5 mg/l and 20 mg/l, respectively. We can capture horseshoe vortices over the base of 10 mm cylinder by using this technique at Reynolds number of 1000 and a water speed of 100 mm/s, respectively. Unlike conventional tracers such as ink, milk, and fluorescent dyes, this visualization technique gives flow information on the AA-PSP coated surface without integrating flows between the AA-PSP and an optical detector. Because of using dissolved oxygen as a tracer, it holds the material properties of testing water except for the amount of oxygen. The tracer does not interfere with optical measurements and it does not contaminate the testing water. A conventional visualization technique using milk as a tracer is also employed for comparison.

Measurement of dissolved oxygen during red wines tank aging with chips and micro-oxygenation.

PubMed

Nevares, I; del Alamo, M

2008-07-21

Nowadays, micro-oxygenation is a very important technique used in aging wines in order to improve their characteristics. The techniques of wine tank aging imply the use of small doses of oxygen and the addition of wood pieces of oak to the wine. Considering the low dissolved oxygen (DO) levels used by micro-oxygenation technique it is necessary to choose the appropriate measurement principle to apply the precise oxygen dosage in wine at any time, in order to assure its correct assimilation. This knowledge will allow the oenologist to control and run the wine aging correctly. This work is a thorough revision of DO measurement main technologies applied to oenology. It describes the strengths and weaknesses of each of them, and draws a comparison of their workings in wine measurement. Both, the traditional systems by electrochemical probes, and the newest photoluminescence-based probes have been used. These probes adapted to red wines ageing study are then compared. This paper also details the first results of the dissolved oxygen content evolution in red wines during a traditional and alternative tank aging. Samples have been treated by three different ageing systems: oak barrels, stainless-steel tanks with small oak wood pieces (chips) and with bigger oak pieces (staves) with low micro-oxygenation levels. French and American oak barrels manufactured by the same cooperage have been used.

A simplified method for determining heat of combustion of natural gas

NASA Technical Reports Server (NTRS)

Singh, Jag J.; Chegini, Hoshang; Mall, Gerald H.

1987-01-01

A simplified technique for determination of the heat of combustion of natural gas has been developed. It is a variation of the previously developed technique wherein the carrier air, in which the test sample was burnt, was oxygen enriched to adjust the mole fraction of oxygen in the combustion product gases up to that in the carrier air. The new technique eliminates the need for oxygen enrichment of the experimental mixtures and natural gas samples and has been found to predict their heats of combustion to an uncertainty of the order of 1 percent.

In vivo microcirculation imaging of the sub surface fingertip using correlation mapping optical coherence tomography (cmOCT)

NASA Astrophysics Data System (ADS)

Dsouza, Roshan I.; Zam, Azhar; Subhash, Hrebesh M.; Larin, Kirill V.; Leahy, Martin

2013-02-01

We describe a novel application of correlation mapping optical coherence tomography (cmOCT) for sub-surface fingerprint biometric identification. Fingerprint biometrics including automated fingerprint identification systems, are commonly used to recognise the fingerprint, since they constitute simple, effective and valuable physical evidence. Spoofing of biometric fingerprint devices can be easily done because of the limited information obtained from the surface topography. In order to overcome this limitation a potentially more secure source of information is required for biometric identification applications. In this study, we retrieve the microcirculation map of the subsurface fingertip by use of the cmOCT technique. To increase probing depth of the sub surface microcirculation, an optical clearing agent composed of 75% glycerol in aqueous solution was applied topically and kept in contact for 15 min. OCT intensity images were acquired from commercial research grade swept source OCT system (model OCT1300SS, Thorlabs Inc. USA). A 3D OCT scan of the fingertip was acquired over an area of 5x5 mm using 1024x1024 A-scans in approximately 70 s. The resulting volume was then processed using the cmOCT technique with a 7x7 kernel to provide a microcirculation map. We believe these results will demonstrate an enhanced security level over artificial fingertips. To the best of our knowledge, this is the first demonstration of imaging microcirculation map of the subsurface fingertip.

Positron states and annihilation characteristics of surface-trapped positrons at the oxidized Cu(110) surface

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Olenga, Antoine; Weiss, A. H.

2013-03-01

The process by which oxide layers are formed on metal surfaces is still not well understood. In this work we present the results of theoretical studies of positron states and annihilation characteristics of surface-trapped positrons at the oxidized Cu(110) surface. An ab-initio investigation of stability and associated electronic properties of different adsorption phases of oxygen on Cu(110) has been performed on the basis of density functional theory and using DMOl3 code. The changes in the positron work function and the surface dipole moment when oxygen atoms occupy on-surface and sub-surface sites have been attributed to charge redistribution within the first two layers, buckling effects within each layer and interlayer expansion. The computed positron binding energy, positron surface state wave function, and annihilation probabilities of surface trapped positrons with relevant core electrons demonstrate their sensitivity to oxygen coverage, elemental content, atomic structure of the topmost layers of surfaces, and charge transfer effects. Theoretical results are compared with experimental data obtained from studies of oxidized transition metal surfaces using positron annihilation induced Auger electron spectroscopy. This work was supported in part by the National Science Foundation Grant DMR-0907679.

Oxygenic Photosynthesis and the Oxidation State of Mars

NASA Technical Reports Server (NTRS)

Hartman, Hyman; McKay, Christopher P.

1995-01-01

The oxidation state of the Earth's surface is one of the most obvious indications of the effect of life on this planet. The surface of Mars is highly oxidized, as evidenced by its red color, but the connection to life is less apparent. Two possibilities can be considered. First, the oxidant may be photochemically produced in the atmosphere. In this case the fundamental source of O2 is the loss of H2 to space and the oxidant produced is H2O2. This oxidant would accumulate on the surface and thereby destroy any organic material and other reductants to some depth. Recent models suggest that diffusion limits this depth to a few meters. An alternative source of oxygen is biological oxygen production followed by sequestration of organic material in sediments - as on the Earth. In this case, the net oxidation of the surface was determined billions of years ago when Mars was a more habitable planet and oxidative conditions could persist to great depths, over 100 m. Below this must be a compensating layer of biogenic organic material. Insight into the nature of past sources of oxidation on Mars will require searching for organics in the martian subsurface and sediments.

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

Detwiler, Michael D.; Majumdar, Paulami; Gu, Xiang-Kui

Changes in surface chemistry and morphology of Re–Pt surfaces synthesized by ultra-high vacuum chemical vapor deposition (UHV-CVD) of Re on Pt(111) were studied by a combination of experiment and density functional theory (DFT) modeling. A Re oxide formed following exposure of the as-deposited Re to 1 × 10- 6 mbar oxygen at 600–673 K. Subsequent annealing at 973 K resulted in oxygen desorption and a decrease in Re coverage, as calculated by XPS and as observed by STM. This observation was explained by DFT calculations which showed that a clean Pt surface slab with subsurface Re is thermodynamically more favorablemore » than Pt(111) with Re on the surface. DFT calculations also predicted weaker O and CO binding on this surface compared to both monometallic Pt and Re, and HREELS and temperature desorption measurements suggested that O binds weakly to the Pt skin surface, with oxygen on the Pt skin desorbing from this surface following annealing at 373 K. Trends in adsorption energies were consistent with DFT calculated d-band centers of surface atoms for model Pt–Re structures. Comparison of HREELS data and STM images with DFT calculated vibrational frequencies have been used to understand the structure of rhenium oxide on Pt(111).« less

Unraveling the oxygen vacancy structures at the reduced Ce O2(111 ) surface

NASA Astrophysics Data System (ADS)

Han, Zhong-Kang; Yang, Yi-Zhou; Zhu, Beien; Ganduglia-Pirovano, M. Verónica; Gao, Yi

2018-03-01

Oxygen vacancies at ceria (Ce O2 ) surfaces play an essential role in catalytic applications. However, during the past decade, the near-surface vacancy structures at Ce O2(111 ) have been questioned due to the contradictory results from experiments and theoretical simulations. Whether surface vacancies agglomerate, and which is the most stable vacancy structure for varying vacancy concentration and temperature, are being heatedly debated. By combining density functional theory calculations and Monte Carlo simulations, we proposed a unified model to explain all conflicting experimental observations and theoretical results. We find a novel trimeric vacancy structure which is more stable than any other one previously reported, which perfectly reproduces the characteristics of the double linear surface oxygen vacancy clusters observed by STM. Monte Carlo simulations show that at low temperature and low vacancy concentrations, vacancies prefer subsurface sites with a local (2 × 2) ordering, whereas mostly linear surface vacancy clusters do form with increased temperature and degree of reduction. These results well explain the disputes about the stable vacancy structure and surface vacancy clustering at Ce O2(111 ) , and provide a foundation for the understanding of the redox and catalytic chemistry of metal oxides.

Nitrogen and chemical oxygen demand removal from septic tank wastewater in subsurface flow constructed wetlands: substrate (cation exchange capacity) effects.

PubMed

Collison, Robert S; Grismer, Mark E

2014-04-01

The current article focuses on chemical oxygen demand (COD) and nitrogen (ammonium and nitrate) removal performance from synthetic human wastewater as affected by different substrate rocks having a range of porosities and cation exchange capacities (CECs). The aggregates included lava rock, lightweight expanded shale, meta-basalt (control), and zeolite. The first three had CECs of 1 to 4 mequiv/100 gm, whereas the zeolite CEC was much greater (-80 mequiv/100 gm). Synthetic wastewater was gravity fed to each constructed wetland system, resulting in a 4-day retention time. Effluent samples were collected, and COD and nitrogen species concentrations measured regularly during four time periods from November 2008 through June 2009. Chemical oxygen demand and nitrogen removal fractions were not significantly different between the field and laboratory constructed wetland systems when corrected for temperature. Similarly, overall COD and nitrogen removal fractions were practically the same for the aggregate substrates. The important difference between aggregate effects was the zeolite's ammonia removal process, which was primarily by adsorption. The resulting single-stage nitrogen removal process may be an alternative to nitrification and denitrification that may realize significant cost savings in practice.

Oxygenation as a driver of the Great Ordovician Biodiversification Event

NASA Astrophysics Data System (ADS)

Edwards, Cole T.; Saltzman, Matthew R.; Royer, Dana L.; Fike, David A.

2017-12-01

The largest radiation of Phanerozoic marine animal life quadrupled genus-level diversity towards the end of the Ordovician Period about 450 million years ago. A leading hypothesis for this Great Ordovician Biodiversification Event is that cooling of the Ordovician climate lowered sea surface temperatures into the thermal tolerance window of many animal groups, such as corals. A complementary role for oxygenation of subsurface environments has been inferred based on the increasing abundance of skeletal carbonate, but direct constraints on atmospheric O2 levels remain elusive. Here, we use high-resolution paired bulk carbonate and organic carbon isotope records to determine the changes in isotopic fractionation between these phases throughout the Ordovician radiation. These results can be used to reconstruct atmospheric O2 levels based on the O2-dependent fractionation of carbon isotopes by photosynthesis. We find a strong temporal link between the Great Ordovician Biodiversification Event and rising O2 concentrations, a pattern that is corroborated by O2 models that use traditional carbon-sulfur mass balance. We conclude that that oxygen levels probably played an important role in regulating early Palaeozoic biodiversity levels, even after the Cambrian Explosion.

Volatile hydrocarbons and fuel oxygenates: Chapter 12

USGS Publications Warehouse

Cozzarelli, Isabelle M.

2014-01-01

Petroleum hydrocarbons and fuel oxygenates are among the most commonly occurring and widely distributed contaminants in the environment. This chapter presents a summary of the sources, transport, fate, and remediation of volatile fuel hydrocarbons and fuel additives in the environment. Much research has focused on the transport and transformation processes of petroleum hydrocarbons and fuel oxygenates, such as benzene, toluene, ethylbenzene, and xylenes and methyl tert‐butyl ether, in groundwater following release from underground storage tanks. Natural attenuation from biodegradation limits the movement of these contaminants and has received considerable attention as an environmental restoration option. This chapter summarizes approaches to environmental restoration, including those that rely on natural attenuation, and also engineered or enhanced remediation. Researchers are increasingly combining several microbial and molecular-based methods to give a complete picture of biodegradation potential and occurrence at contaminated field sites. New insights into the fate of petroleum hydrocarbons and fuel additives have been gained by recent advances in analytical tools and approaches, including stable isotope fractionation, analysis of metabolic intermediates, and direct microbial evidence. However, development of long-term detailed monitoring programs is required to further develop conceptual models of natural attenuation and increase our understanding of the behavior of contaminant mixtures in the subsurface.

Possibility of accommodation in a satellite Europe

NASA Astrophysics Data System (ADS)

Steklov, A. F.; Vidmachenko, A. P.

2018-05-01

It is believed that the presence of liquid water below the surface makes the satellite one of the most probable potential targets in Solar system, suitable for finding life there. Taking into account the fact that the radiation of Jupiter and Sun constantly affects Europe, free oxygen and a number of other oxidants are formed in the ice. In the old days, it was active oxygen led to the emergence of multicellular life on Earth. Now we know that the oceans of Europe contain much more oxygen than previously thought. And this increases the likelihood of the existence of life in Europe. In 2010 it was pointed out the possibility of the existence in ice of Europe of extensive lenses with liquid water, whose composition is significantly different from the composition of water in the ocean. This provides a mechanism for the possible transfer of vital chemicals created in the sunlit areas on the surface, and near of it in deeper layers. That is, such lakes can be another potential place of habitations. Thus, the subsurface ocean and lakes of Europe should be considered one of the best places for the existence of some forms of life.

Augmentation of oxygen transport by various hemoglobins as determined by pulsed field gradient NMR.

PubMed

Budhiraja, Vikas; Hellums, J David; Post, Jan F M

2002-11-01

Diffusion of oxyhemoglobin has been shown to augment the oxygen transport inside the red blood cells. Measurement of hemoglobin diffusion coefficients by pulsed-field gradient (PFG) nuclear magnetic resonance (NMR) technique can be used for estimating this augmentation effect. Self-diffusion coefficients of polymerized and unpolymerized bovine hemoglobin (Hb) and several other proteins were measured using this technique. The Hb diffusion coefficient was used to determine the effective permeability of oxygen and augmentation of oxygen transport through samples of Hb solutions due to diffusion of oxyhemoglobin. The values compared well with our previous diffusion cell measurements of effective diffusivity and augmentation. Our NMR studies show that even at low concentrations the augmentation of oxygen transport due to diffusion can be significant. The PFG NMR technique can thus provide an accurate and easy method for measuring augmentation of oxygen transport, especially in dilute samples of Hb. The results on polyhemoglobin and high-molecular-weight hemoglobin are of both basic interest and practical value in assessing the promise and performance of hemoglobin-based blood substitutes.

Groundwater assessment in Salboni Block, West Bengal (India) using remote sensing, geographical information system and multi-criteria decision analysis techniques

NASA Astrophysics Data System (ADS)

Jha, Madan K.; Chowdary, V. M.; Chowdhury, Alivia

2010-11-01

An approach is presented for the evaluation of groundwater potential using remote sensing, geographic information system, geoelectrical, and multi-criteria decision analysis techniques. The approach divides the available hydrologic and hydrogeologic data into two groups, exogenous (hydrologic) and endogenous (subsurface). A case study in Salboni Block, West Bengal (India), uses six thematic layers of exogenous parameters and four thematic layers of endogenous parameters. These thematic layers and their features were assigned suitable weights which were normalized by analytic hierarchy process and eigenvector techniques. The layers were then integrated using ArcGIS software to generate two groundwater potential maps. The hydrologic parameters-based groundwater potential zone map indicated that the `good' groundwater potential zone covers 27.14% of the area, the `moderate' zone 45.33%, and the `poor' zone 27.53%. A comparison of this map with the groundwater potential map based on subsurface parameters revealed that the hydrologic parameters-based map accurately delineates groundwater potential zones in about 59% of the area, and hence it is dependable to a certain extent. More than 80% of the study area has moderate-to-poor groundwater potential, which necessitates efficient groundwater management for long-term water security. Overall, the integrated technique is useful for the assessment of groundwater resources at a basin or sub-basin scale.

Passive Super-Low Frequency electromagnetic prospecting technique

NASA Astrophysics Data System (ADS)

Wang, Nan; Zhao, Shanshan; Hui, Jian; Qin, Qiming

2017-03-01

The Super-Low Frequency (SLF) electromagnetic prospecting technique, adopted as a non-imaging remote sensing tool for depth sounding, is systematically proposed for subsurface geological survey. In this paper, we propose and theoretically illustrate natural source magnetic amplitudes as SLF responses for the first step. In order to directly calculate multi-dimensional theoretical SLF responses, modeling algorithms were developed and evaluated using the finite difference method. The theoretical results of three-dimensional (3-D) models show that the average normalized SLF magnetic amplitude responses were numerically stable and appropriate for practical interpretation. To explore the depth resolution, three-layer models were configured. The modeling results prove that the SLF technique is more sensitive to conductive objective layers than high resistive ones, with the SLF responses of conductive objective layers obviously showing uprising amplitudes in the low frequency range. Afterwards, we proposed an improved Frequency-Depth transformation based on Bostick inversion to realize the depth sounding by empirically adjusting two parameters. The SLF technique has already been successfully applied in geothermal exploration and coalbed methane (CBM) reservoir interpretation, which demonstrates that the proposed methodology is effective in revealing low resistive distributions. Furthermore, it siginificantly contributes to reservoir identification with electromagnetic radiation anomaly extraction. Meanwhile, the SLF interpretation results are in accordance with dynamic production status of CBM reservoirs, which means it could provide an economical, convenient and promising method for exploring and monitoring subsurface geo-objects.

Detection of Silver Nanoparticles in Vadose Zone Environments using Complex ConductivityMeasurements

EPA Science Inventory

The emergence of engineered nano-materials (ENMs) in the global marketplace and their accidental introduction into the subsurface pose a potential risk to the environment and public health. There is a need for the development of techniques to detect their presence and transport i...

Subsurface microscopy of interconnect layers of an integrated circuit.

PubMed

Köklü, F Hakan; Unlü, M Selim

2010-01-15

We apply the NA-increasing lens technique to confocal and wide-field backside microscopy of integrated circuits. We demonstrate 325 nm (lambda(0)/4) lateral spatial resolution while imaging metal structures located inside the interconnect layer of an integrated circuit. Vectorial field calculations are presented justifying our findings.

Spatially offset Raman spectroscopy based on a line-scan hyperspectral Raman system

USDA-ARS?s Scientific Manuscript database

Spatially offset Raman spectroscopy (SORS) is a technique that can obtain subsurface layered information by collecting Raman spectra from a series of surface positions laterally offset from the excitation laser. The current methods of SORS measurement are typically either slow due to mechanical move...

Using electromagnetic induction technology to predict volatile fatty acid, source area differences

USDA-ARS?s Scientific Manuscript database

Subsurface sampling techniques have been adapted to measure manure accumulation on feedlot surface. Objectives of this study were to determine if sensor data could be used to predict differences in volatile fatty acids (VFA) and other volatiles produced on the feedlot surface three days following a...

Evaluation of Subsurface Engineered Barriers at Waste Sites

DTIC Science & Technology

1998-08-01

28 3-4 MATRIX FOR EVALUATING BARRIER CQA/CQC AGAINST ACCEPTABLE INDSUTRY PRACTICES...STANDARDS................................................................. 66 4-2 MATRIX FOR EVALUATING CAP AGAINST ACCEPTABLE INDSUTRY PRACTICES...stated previously, the most widely used technique for containment is the soil-bentonite slurry wall. It is typically the most economical , utilizes low

The Use of Molecular and Genomic Techniques Applied to Microbial Diversity, Community Structure, and Activities at DNAPL and Metal Contaminated Sites

EPA Science Inventory

A wide variety of in situ subsurface remediation strategies have been developed to mitigate contamination by chlorinated solvent dense non-aqueous phase liquids (DNAPLS) and metals. Geochemical methods include: zerovalent iron emplacement, various electrolytic applications, elec...

SUMMARY OF TECHNIQUES AND UNIQUE USES FOR DIRECT PUSH METHODS IN SITE CHARACTERIZATION ON CONTAMINATED FIELD SITES

EPA Science Inventory

Site characterization of subsurface contaminant transport is often hampered by a lack of knowledge of site heterogeneity and temporal variations in hydrogeochemistry. Two case studies are reviewed to illustrate the utility of macro-scale mapping information along with spatially-...

Effect of biocrust: study of mechanical and hydraulic properties and erodibility

NASA Astrophysics Data System (ADS)

Slavík, Martin; Bruthans, Jiří; Schweigstillová, Jana

2016-04-01

It is well-known that lichens and other organisms forming crust on soil or rock surface play important role in weathering but may also protect underlying material from fast erosion. So far, there have been only few measurements comparing mechanical or hydraulic properties of biocrust with its subsurface on locked sand and friable sandstones, so the overall effect of the biocrust is not well-understood. Objective of our study is to quantify the effect of the biocrust on mechanical and hydraulic properties of friable sandstone and locked sand of Cretaceous age in six different localities with varying aspect and inclination and age of exposure in sandpit Strelec (Czech Rep.). On the artificial exposures, biocrust developed within last 10-30 years. Beside measurements of mechanical and hydraulic properties, SEM and mercury intrusion porosimetry in crust and subsurface was performed. Drilling resistance technique was found an excellent method to distinguish the biocrust from its subsurface (~3 mm thick biocrust has up to 12 times higher drilling resistance than underlying material). Surface zone with the biocrust has 3 - 25 times higher tensile strength than the subsurface material (1 - 25 kPa). In comparison with the subsurface, the biocrust is considerably less erodible (based on water jet testing). Biocrust saturated hydraulic conductivity is 15 - 240 times lower than the subsurface (6*10 -5 - 1*10 -4 m/s) and its permeability for water vapor is 4 - 9 times lower than subsurface. Presence of the biocrust slows down capillary absorption of water 4 - 25 times. The biocrust is thus forming firm surface which protects underlying material from rain and flowing water erosion and which considerably modifies its hydraulic properties. Material with crust exposed to calcination, leaching by concentrated peroxide and experiments with zymoliase enzyme strongly indicate that major contribution to crust hardening is provided by organic matter. Based on DNA sequencing the crust is formed by fungi including components of lichens which differ at individual localities. This research was funded by the Czech Science Foundation (GA CR No. 13-28040S) and Grant Agency of Charles University (No. 386815)

Depositionally controlled recycling of iron and sulfur in marine sediments and its isotopic consequences

NASA Astrophysics Data System (ADS)

Riedinger, N.; Formolo, M.; Arnold, G. L.; Vossmeyer, A.; Henkel, S.; Sawicka, J.; Kasten, S.; Lyons, T. W.

2011-12-01

The continental margin off Uruguay and Argentina is characterized by highly dynamic depositional conditions. This variable depositional regime significantly impacts the biogeochemical cycles of iron and sulfur. Mass deposit related redeposition of reduced minerals can lead to the reoxidation of these phases and thus to an overprint of their geochemical primary signatures. Due to rapid burial these oxidized phases are still present in deeper subsurface sediments. To study the effects of sediment relocation on the sulfur and iron inventory we collected shallow and deep subsurface sediment samples via multicorer and gravity cores, respectively, in the western Argentine Basin during the RV Meteor Expedition M78/3 in May-July 2009. The samples were retrieved from shelf, slope and deep basin sites. The concentration and sulfur isotope composition of acid volatile sulfur (AVS), chromium reducible sulfur (CRS), elemental sulfur and total organic sulfur were determined. Furthermore, sequential iron extraction techniques were applied assess the distribution of iron oxide phases within the sediment. The investigated sediments are dominated by terrigenous inputs, with high amounts of reactive ferric iron minerals and only low concentrations of calcium carbonate. Total organic carbon concentrations show strong variation in the shallow subsurface sediments ranging between approximately 0.7 and 6.4 wt% for different sites. These concentrations do not correlate with water depths. Pore water accumulations of hydrogen sulfide are restricted to an interval at the sulfate-methane transition (SMT) zone a few meters below the sediment surface. In these deeper subsurface sediments pyrite is precipitated in this zone of hydrogen sulfide excess, whereas the accumulation of authigenic AVS and elemental sulfur (up to 2000 ppm) occurs at the upper and lower boundary of the sulfidic zone due the reaction of iron oxides with limited amounts of sulfide. Furthermore, our preliminary results indicate that there is a link between modern deposition in the shallow subsurface sediments and the long-term signals being buried and preserved in the deep subsurface layers. The data show that the burial of elemental sulfur into deep subsurface sediments can fuel the deep biosphere and has consequences for isotopic overprints tied, for example, to oxidation and disproportionation processes in the deeper sediments.