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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Influence of LaFeO 3 Surface Termination on Water Reactivity

The polarity of oxide surfaces can dramatically impact their surface reactivity, in particular with polar molecules such as water. The surface species that result from this interaction change the oxide electronic structure and chemical reactivity in applications such as photoelectrochemistry, but are challenging to probe experimentally with atomic-scale understanding. Here we report a detailed study of the surface chemistry and electronic structure of the perovskite LaFeO3 in humid conditions using ambient pressure X-ray photoelectron spectroscopy. Comparing the two possible terminations of the polar (001)-oriented surface, we find that the LaO surface is more reactive toward water, forming hydroxyl species and adsorbing molecular water at lower relative humidity than its FeO2-terminated counterpart. Our results demonstrate how the termination of a complex oxide can dramatically impact its reactivity, providing insight into the design of catalyst materials.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2020

Thin Cation-Exchange Layers Enable High-Current-Density Bipolar Membrane Electrolyzers via Improved Water Transport

With suitable water dissociation (WD) catalysts, bipolar membranes (BPMs) can efficiently dissociate water into H + and OH – at the junction between anion- and cation-exchange layers (AEL and CEL, respectively). First, however, water must be transported through the AEL or CEL and thus against the outward flow of hydrated H + and OH – . This is a challenge intrinsic to the BPM architecture and limits operation to current densities typically less than ~0.5 A·cm –2 . Here we explore how water transport affects durability and performance in reference alkaline and acidic membrane electrolyzers, and we use the insight gained to design BPMs with improved water transport. We demonstrate a thin-CEL BPM (2-μm Nafion CEL|~200 nm TiO 2 |~200 nm NiO + ionomer|50 μm Sustainion AEL) which maintains a pH difference of ~14 units between the anode and cathode for current densities of up to 3.4 A·cm –2 with a total water electrolysis voltage of ~4 V and an estimated WD overpotential of ~1.5 V. Finally, such high-current-density operation is crucial for key emerging BPM applications, including in water and carbon-dioxide electrolyzers and in (regenerative) fuel cells.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Water Dynamics from the Surface to the Interior of a Supramolecular Nanostructure

Water within and surrounding the structure of a biological system adopts context-specific dynamics that mediate virtually all of the events involved in the inner workings of a cell. These events range from protein folding and molecular recognition to the formation of hierarchical structures. Water dynamics are mediated by the chemistry and geometry of interfaces where water and biomolecules meet. Here we investigate experimentally and computationally the translational dynamics of vicinal water molecules within the volume of a supramolecular peptide nanofiber measuring 6.7 nm in diameter. Using Overhauser dynamic nuclear polarization relaxometry, we show that drastic differences exist in water motion within a distance of about one nanometer from the surface, with rapid diffusion in the hydrophobic interior and immobilized water on the nanofiber surface. Furthermore, these results demonstrate that water associated with materials designed at the nanoscale is not simply a solvent, but rather an integral part of their structure and potential functions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Congo Basin Water Balance and Terrestrial Fluxes Inferred From Satellite Observations of the Isotopic Composition of Water Vapor

Large spatio-temporal gradients in the Congo basin vegetation and rainfall are observed. However, its water-balance (evapotranspiration minus precipitation, or ET - P) is typically measured at basin-scales, limited primarily by river-discharge data, spatial resolution of terrestrial water storage measurements, and poorly constrained ET. We use observations of the isotopic composition of water vapor to quantify the spatio-temporal variability of net surface water fluxes across the Congo Basin between 2003 and 2018. These data are calibrated at basin scale using satellite gravity and total Congo river discharge measurements and then used to estimate time-varying ET - P over four quadrants representing the Congo Basin, providing first estimates of this kind for the region. We find that the multi-year record, seasonality, and interannual variability of ET - P from both the isotopes and the gravity/river discharge based estimates are consistent. Additionally, we use precipitation and gravity-based estimates with our water vapor isotope-based ET - P to calculate time and space averaged ET and net river discharge within the Congo Basin. These quadrant-scale moisture flux estimates indicate (a) substantial recycling of moisture in the Congo Basin (temporally and spatially averaged ET/P > 70%), consistent with models and visible light-based ET estimates, and (b) net river outflow is largest in the Western Congo where there are more rivers and higher flow rates. Our results confirm the importance of ET in modulating the Congo water cycle relative to other water sources.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Hydration structure and water exchange kinetics at xenotime–water interfaces: implications for rare earth minerals separation

Hydration of surface ions gives rise to structural heterogeneity and variable exchange kinetics of water at complex mineral–water interfaces. In this work, we employ ab initio molecular dynamics (AIMD) simulations and water adsorption calorimetry to examine the aqueous interfaces of xenotime, a phosphate mineral that contains predominantly Y 3+ and heavy rare earth elements. Consistent with natural crystal morphology, xenotime is predicted to have a tetragonal prismatic shape, dominated by the {100} surface. Hydration of this surface induces multilayer interfacial water structures with distinct OH orientations, which agrees with recent crystal truncation rod measurements. The exchange kinetics between two adjacent water layers exhibits a wide range of underlying timescales (5–180 picoseconds), dictated by ion–water electrostatics. Adsorption of a bidentate hydroxamate ligand reveals that {100} xenotime surface can only accommodate monodentate coordination with water exchange kinetics strongly depending on specific ligand orientation, prompting us to reconsider traditional strategies for selective separation of rare-earth minerals.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

On the representation of many-body interactions in water

Recent work has shown that the many-body expansion of the interaction energy can be used to develop analytical representations of global potential energy surfaces (PESs) for water. In this study, the role of short- and long-range interactions at different orders is investigated by analyzing water potentials that treat the leading terms of the many-body expansion through implicit (i.e., TTM3-F and TTM4-F PESs) and explicit (i.e., WHBB and MB-pol PESs) representations. It is found that explicit short-range representations of 2-body and 3-body interactions along with a physically correct incorporation of short- and long-range contributions are necessary for an accurate representation of the water interactions from the gas to the condensed phase. Similarly, a complete many-body representation of the dipole moment surface is found to be crucial to reproducing the correct intensities of the infrared spectrum of liquid water.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

A Review of Water Quality Responses to Air Temperature and Precipitation Changes 1: Flow, Water Temperature, Saltwater Intrusion

Abstract Anticipated future increases in air temperature and regionally variable changes in precipitation will have direct and cascading effects on United States (U.S.) water quality. In this paper, and a companion paper by Coffey et al., we review technical literature addressing the responses of different water quality attributes to historical and potential future changes in air temperature and precipitation. The goal is to document how different attributes of water quality are sensitive to these drivers, to characterize future risk to inform management responses, and to identify research needs to fill gaps in our understanding. Here we focus on potential changes in streamflow, water temperature, and salt water intrusion (SWI). Projected changes in the volume and timing of streamflow vary regionally, with general increases in northern and eastern regions of the U.S., and decreases in the southern Plains, interior Southwest, and parts of the Southeast. Water temperatures have increased throughout the U.S. and are expected to continue to increase in the future, with the greatest changes in locations where high summer air temperatures occur together with low streamflow volumes. In coastal areas, especially the mid‐Atlantic and Gulf coasts, SWI to rivers and aquifers could be exacerbated by sea level rise, storm surges, and altered freshwater runoff. Management responses for reducing risks to water quality should consider strategies and practices robust to a range of potential future conditions.

Paul, Michael J.↗
DOE OSTI2020

The Water‐Year Water Balance of the Colorado River Basin

Abstract Model‐estimated monthly water balance components (i.e., potential evapotranspiration, actual evapotranspiration, and runoff ( R )) for 146 United States (U.S.) Geological Survey 8‐digit hydrologic units located in the Colorado River Basin (CRB) are used to examine the temporal and spatial variability of the CRB water balance for water years 1901 through 2014 (a water year is the period from October 1 of one year through September 30 of the following year). Results indicate that the CRB can be divided into six subregions with similar temporal variability in monthly R . The water balance analyses indicated that approximately 75% of total water‐year R is generated by just one CRB subregion and that most of the R in the basin is derived from surplus ( S ) water generated during the months of October through April. Furthermore, the analyses show that temporal variability in S is largely controlled by the occurrence of negative atmospheric pressure anomalies over the northwestern conterminous U.S. (CONUS) and positive atmospheric pressure anomalies over the southeastern CONUS. This combination of atmospheric pressure anomalies results in an anomalous flow of moist air from the North Pacific Ocean into the CRB, particularly the Upper CRB. Additionally, the occurrence of extreme dry and wet periods in the CRB appears to be related to variability of the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation.

McCabe, Gregory J.↗
DOE OSTI2021

Evolution of water structures in metal-organic frameworks for improved atmospheric water harvesting

Designing water uptake Although the locations of water molecules in some porous materials have been determined with diffraction techniques, determining the filling sequence of water sites has been challenging. Hanikel et al . used single-crystal x-ray diffraction to locate all of the water molecules in pores of the metal-organic framework MOF-303 at different water loadings (see the Perspective by Öhrström and Amombo Noa). They used this information on the water molecule adsorption sequence to modify the linkers of this MOF and control the water-harvesting properties from humid air for different temperature regimes. —PDS

Science & Technology - Other Topics↗
DOE OSTI2014

The functional potential of microbial communities in hydraulic fracturing source water and produced water from natural gas extraction characterized by metagenomic sequencing

Microbial activity in produced water from hydraulic fracturing operations can lead to undesired environmental impacts and increase gas production costs. However, the metabolic profile of these microbial communities is not well understood. Here, for the first time, we present results from a shotgun metagenome of microbial communities in both hydraulic fracturing source water and wastewater produced by hydraulic fracturing. Taxonomic analyses showed an increase in anaerobic/facultative anaerobic classes related to Clostridia , Gammaproteobacteria , Bacteroidia and Epsilonproteobacteria in produced water as compared to predominantly aerobic Alphaproteobacteria in the fracturing source water. Thus, the metabolic profile revealed a relative increase in genes responsible for carbohydrate metabolism, respiration, sporulation and dormancy, iron acquisition and metabolism, stress response and sulfur metabolism in the produced water samples. These results suggest that microbial communities in produced water have an increased genetic ability to handle stress, which has significant implications for produced water management, such as disinfection.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

General circulation models simulate negative liquid water path–droplet number correlations, but anthropogenic aerosols still increase simulated liquid water path

General circulation models' (GCMs) estimates of the liquid water path adjustment to anthropogenic aerosol emissions differ in sign from other lines of evidence. This reduces confidence in estimates of the effective radiative forcing of the climate by aerosol–cloud interactions (ERFaci). The discrepancy is thought to stem in part from GCMs' inability to represent the turbulence–microphysics interactions in cloud-top entrainment, a mechanism that leads to a reduction in liquid water in response to an anthropogenic increase in aerosols. In the real atmosphere, enhanced cloud-top entrainment is thought to be the dominant adjustment mechanism for liquid water path, weakening the overall ERFaci. We show that the latest generation of GCMs includes models that produce a negative correlation between the present-day cloud droplet number and liquid water path, a key piece of observational evidence supporting liquid water path reduction by anthropogenic aerosols and one that earlier-generation GCMs could not reproduce. However, even in GCMs with this negative correlation, the increase in anthropogenic aerosols from preindustrial to present-day values still leads to an increase in the simulated liquid water path due to the parameterized precipitation suppression mechanism. This adds to the evidence that correlations in the present-day climate are not necessarily causal. We investigate sources of confounding to explain the noncausal correlation between liquid water path and droplet number. These results are a reminder that assessments of climate parameters based on multiple lines of evidence must carefully consider the complementary strengths of different lines when the lines disagree.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1975

Water hyacinths for removal of phenols from polluted waters

Removal of phenol by water hyacinths (Eichhornia crassipes (Mart.) Solms) in static water was investigated. 2.75 g dry weight of this aquatic plant demonstrated the ability to absorb 100 mg of phenol per plant per 72 hours from distilled water, river water, and bayou water. One hectare of water hyacinth plants is shown to be potentially capable of removing 160 kg of phenol per 72 hours from waters polluted with this chemical.

Wolverton, B. C.↗
NASA NTRS1989

Airborne discrimination between ice and water - Application to the laser measurement of chlorophyll-in-water in a marginal ice zone

The concurrent active-passive measurement capabilities of the NASA Airborne Oceanographic Lidar have been used to (1) discriminate between ice and water in a large ice field within the Greenland Sea and (2) achieve the detection and measurement of chlorophyll-in-water by laser-induced and water-Raman-normalized pigment fluorescence. Passive upwelled radiances from sea ice are significantly stronger than those from the neighboring water, even when the optical receiver field-of-view is only partially filled with ice. Thus, weaker passive upwelled radiances, together with concurrently acquired laser-induced spectra, can rather confidently be assigned to the intervening water column. The laser-induced spectrum can then be processed using previously established methods to measure the chlorophyll-in-water concentration. Significant phytoplankton patchiness and elevated chlorophyll concentrations were found within the waters of the melting ice compared to ice-free regions just outside the ice field.

Hoge, Frank E.↗
NASA NTRS1992

A systems approach to water recovery testing for space life support - Initial biomedical results from the ECLSS Water Recovery Test and plans for testbed utilization

Among the challenges of designing and constructing Space Station Freedom is the development of the water system. A review of past efforts in reclaiming waste water in enclosed environments reveals that there are many gaps in the biomedical understanding of this process. Some of the key uncertainties of human interaction with a closed water system include determining potential contaminants and establishing safe levels of multiple compounds in the enclosed system of Space Station. Another uncertainty is the microbial constituency of such a system and what impact it could have on crew health and performance. The use of iodine as the passive biocide may have both an indirect and direct impact on the crew. In this paper the initial results of the Water Recovery Test are reviewed from a biomedical perspective, revealing areas where more information is needed to develop the ECLSS water system. By including the approach of 'man as a subsystem', consideration is given to how man interacts with the total water system. Taking this systems approach to providing the crew with a safe source of water gives useful insight into the most efficient design and utilization of closed system testbeds.

Aten, Laurie A.↗
NASA NTRS1951

Analysis of thrust augmentation of turbojet engines by water injection at compressor inlet including charts for calculating compression processes with water injection

A psychrometric chart having total pressure (sum of partial pressures of air and water vapor) as a variable, a Mollier diagram for air saturated with water vapor, and charts showing the thermodynamic properties of various air-water vapor and exhaust gas-water vapor mixtures are presented as aids in calculating the thrust augmentation of a turbojet engine resulting from the injection of water at the compressor inlet. Curves are presented that show the theoretical performance of the augmentation method for various amounts of water injected and the effects of varying flight Mach number, altitude, ambient-air temperature, ambient relative humidity, compressor pressure ratio, and inlet-diffuser efficiency. Numerical examples, illustrating the use of the psychrometric chart and the Mollier diagram in calculating both compressor-inlet and compressor-outlet conditions when water is injected at the compressor inlet, are presented.

Wilcox, E Clinton↗
NASA NTRS1996

Excess chemical potential of small solutes across water--membrane and water--hexane interfaces

The excess chemical potentials of five small, structurally related solutes, CH4, CH3F, CH2F2, CHF3, and CF4, across the water-glycerol 1-monooleate bilayer and water-hexane interfaces were calculated at 300, 310, and 340 K using the particle insertion method. The excess chemical potentials of nonpolar molecules (CH4 and CF4) decrease monotonically or nearly monotonically from water to a nonpolar phase. In contrast, for molecules that possess permanent dipole moments (CH3F, CH2F, and CHF3), the excess chemical potentials exhibit an interfacial minimum that arises from superposition of two monotonically and oppositely changing contributions: electrostatic and nonelectrostatic. The nonelectrostatic term, dominated by the reversible work of creating a cavity that accommodates the solute, decreases, whereas the electrostatic term increases across the interface from water to the membrane interior. In water, the dependence of this term on the dipole moment is accurately described by second order perturbation theory. To achieve the same accuracy at the interface, third order terms must also be included. In the interfacial region, the molecular structure of the solvent influences both the excess chemical potential and solute orientations. The excess chemical potential across the interface increases with temperature, but this effect is rather small. Our analysis indicates that a broad range of small, moderately polar molecules should be surface active at the water-membrane and water-oil interfaces. The biological and medical significance of this result, especially in relation to the mechanism of anesthetic action, is discussed.

NASA Center ARC↗