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DOE OSTI2021

Conducting thermal energy to the membrane/water interface for the enhanced desalination of hypersaline brines using membrane distillation

Membrane distillation (MD) is a membrane-based thermal desalination process capable of treating hypersaline brines. Standard MD systems rely on preheating the feed to drive the desalination process. However, relying on the feed to carry thermal energy is limited by a decline of the thermal driving force as the water moves across the membrane, and temperature polarization. In contrast, supplying heat directly into the feed channel, either through the membrane or other channel surfaces, has the potential of minimizing temperature polarization, increasing single-pass water recoveries, and decreasing the number of heat exchangers in the system. When solar thermal energy can be utilized, particularly if the solar heat is optimally delivered to enhance water evaporation and process performance, MD processes can potentially be improved in terms of energy efficiency, environmental sustainability, or operating costs. Here we describe an MD process using layered composite membranes that include a high-thermal-conductivity layer for supplying heat directly to the membrane-water interface and the flow channel. Here, the MD system showed stable performance with water flux up to 9 L/m 2 /hr, and salt rejection >99.9% over hours of desalinating hypersaline feed (100 g/L NaCl). In addition to bench-scale system, we developed a computational fluid dynamics model that successfully described the transport phenomena in the system.

42 ENGINEERING↗

DOE OSTI2019

Estimates of Acetonitrile Generation from Scale Melter Testing of LAW Simulants (VSL-19S4573-1, Rev A)

With high nitrate feeds, such as Hanford low activity waste (LAW) feeds, the addition of reductants is necessary in order to control foaming of the molten glass pool in the melter because such foaming can lead to extensive downtime. Sugar, which was used for this purpose at the West Valley Demonstration Project vitrification facility, has been selected as the baseline reductant for the Hanford Waste Treatment and Immobilization Plant (WTP). The amount of sugar required increases with the amount of nitrates present in the feed and decreases with the amount of waste organics present in the feed, which themselves act as reductants. Excessive additions of reductants can be deleterious, leading to over-reduction of the melt and formation of sulfides and molten metals. Consequently, the oxidants and reductants in the feed must be suitably balanced. The basis for achieving this balance was developed by VSL and Atkins for the vitrification of high-sodium-nitrate feeds at Savannah River's M-Area and has been successfully applied to the processing of a wide variety of simulated WTP feeds over many years and was ultimately incorporated into the WTP process control models. The reaction of sugar with nitrates and nitrites in the cold cap controls the redox state of the underlying melt, which prevents foaming, and also significantly decreases the amount of NOx produced. In addition, however, small amount of organics reaction products are formed. Extensive testing at VSL over the past more than 20 years has shown that acetonitrile is the most prevalent such organic species. That testing has also shown that a significant amount of acetonitrile is captured in the liquid scrubbers in the WTP off-gas treatment system and will therefore be present in the secondary liquid effluents. In particular, acetonitrile is prevalent in the submerged bed scrubber (SBS) and wet electrostatic precipitator (WESP) liquid effluents from WTP LAW off-gas treatment. When these liquids are concentrated in the WTP Effluent Management Facility (EMF) evaporator in the direct feed LAW (DFLAW) flow-sheet, VSL testing has shown that the majority of the acetonitrile partitions to the evaporator condensate. Since the evaporator condensate is directed to the Hanford Effluent Treatment Facility (ETF), this creates a potential issue with the ETF waste acceptance criteria. Consequently, there is a need to assess the available test data in order to develop projections of the likely concentrations of acetonitrile in the streams to ETF. The objective of the present report is to provide such an assessment in order to provide input to flow-sheet model projections.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2013

The role of plasma evolution and photon transport in optimizing future advanced lithography sources

Laser produced plasma (LPP) sources for extreme ultraviolet (EUV) photons are currently based on using small liquid tin droplets as target that has many advantages including generation of stable continuous targets at high repetition rate, larger photons collection angle, and reduced contamination and damage to the optical mirror collection system from plasma debris and energetic particles. The ideal target is to generate a source of maximum EUV radiation output and collection in the 13.5 nm range with minimum atomic debris. Based on recent experimental results and our modeling predictions, the smallest efficient droplets are of diameters in the range of 20–30 μm in LPP devices with dual-beam technique. Such devices can produce EUV sources with conversion efficiency around 3% and with collected EUV power of 190 W or more that can satisfy current requirements for high volume manufacturing. One of the most important characteristics of these devices is in the low amount of atomic debris produced due to the small initial mass of droplets and the significant vaporization rate during the pre-pulse stage. In this study, we analyzed in detail plasma evolution processes in LPP systems using small spherical tin targets to predict the optimum droplet size yielding maximum EUV output. We identified several important processes during laser-plasma interaction that can affect conditions for optimum EUV photons generation and collection. The importance and accurate description of modeling these physical processes increase with the decrease in target size and its simulation domain.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Modeling and Analysis of a Heat Pump Clothes Dryer with Thermal Energy Storage

Clothes drying is an energy-intensive process that causes significant electricity consumption and carbon emissions in the US. Approximately 83% of Households in the US own a tumble clothes dryer at home and 80% of dryers are electrical resistance dryers with low energy efficiency. Heat pump technology makes it possible for highly efficient and clean drying. Additionally, the ventless design of heat pump clothes dryers (HPCD) provides more installation flexibility. HPCD involves three primary mediums: wet clothes, a closed air loop, and a refrigerant circuit. The evaporator is used to dehumidify the wet air and the condenser is used to re-heat the dry air. One of the critical technological barriers to HPCD market penetration is its long drying time, primarily due to the relatively low discharging temperature and the slow response during the warm-up period. In this study, the thermal energy storage (TES) technology is adopted to address this challenge by providing pre-heating of air prior to the condenser to increase the operating temperature of the process air. The heat pump will charge the phase change material (PCM) in the TES device with heating energy during clothes washing and the PCM will discharge the stored heat to facilitate air heating during clothes drying. To analyze the optimal design and potential for energy saving and drying time reduction, a mathematical model of the HPCD system was developed. The HPCD is a highly dynamic system with a coupled heat and mass transfer and heat pumping cycle. This paper provides solutions to simulate the transient behavior of the system while maintaining low computational cost. The modeling result indicates reduced energy consumption and drying time by integrating TES with HPCD, as compared to electrical resistance dryers. The study can provide significant insights into improving building flexibility with TES and smart appliances.

Liu, Xiaoli↗

DOE OSTI2021

A Case Study on Pathogen Transport, Deposition, Evaporation and Transmission: Linking High-Fidelity Computational Fluid Dynamics Simulations to Probability of Infection

A high-fidelity, low-Mach computational fluid dynamics simulation tool that includes evaporating droplets and variable-density turbulent flow coupling is well-suited to ascertain transmission probability and supports risk mitigation methods development for airborne infectious diseases such as COVID-19. A multi-physics large-eddy simulation-based paradigm is used to explore droplet and aerosol pathogen transport from a synthetic cough emanating from a kneeling humanoid. For an outdoor configuration that mimics the recent open-space social distance strategy of San Francisco, maximum primary droplet deposition distances are shown to approach 8.1 m in a moderate wind configuration with the aerosol plume transported in excess of 15 m. In quiescent conditions, the aerosol plume extends to approximately 4 m before the emanating pulsed jet becomes neutrally buoyant. A dose–response model, which is based on previous SARS coronavirus (SARS-CoV) data, is exercised on the high-fidelity aerosol transport database to establish relative risk at eighteen virtual receptor probe locations.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2021

A Predictive Model for Offgas Composition in Waste Glass Melters - Spring 2021 SULI General Audience Abstract

Approximately 56 million gallons of nuclear waste are currently stored in 177 underground storage tanks at the Hanford site in Washington state. A portion of the tank waste is targeted for immobilization by converting the nuclear waste to borosilicate glass through a process called vitrification. During vitrification, emissions are produced in addition to the intended glass product. These emissions, contained in a volume above the molten glass called the plenum, are composed of water vapor, air components, aerosols, particulates, and other gaseous species that result from evaporation, reactions, and air influx. The formation of these gasses causes the surface of the glass to foam. To reduce foaming, sucrose is added to the waste stream before the conversion to glass. Sucrose also reduces the formation of hazardous gasses in the plenum including nitrous oxides, NOx, and carboxides, COx. However, if excess sucrose is present, the reactions that produce the gasses in the plenum will be incomplete, and increased levels of NOx and COx can be observed. The Waste Treatment and Immobilization Plant at the Hanford site is equipped with the technology to treat the plenum emissions. Though many tests have been run to determine the presence of particulates in the plenum emissions, there is does not exist an established method to confidently predict the composition of the gaseous species in the plenum prior to treatment without physical testing. A model was created in the process modeling software Aspen Plus to predict the composition of NOx and COx in the plenum. The model employs a constant stirred tank reactor and user-defined reaction chemistry to determine the plenum composition. To verify the model, the offgas predicted by the model were compared to available offgas data for ten different feed compositions. It is demonstrated that the developed Aspen Plus model is capable of predicting the composition of NOx and COx in the plenum.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2013

Study of the formation of 3-D titania nanofibrous structure by MHz femtosecond laser in ambient air

In this study, we describe the formation mechanism of web-like three-dimensional (3-D) titania nanofibrous structures during femtosecond laser ablation of titanium (Ti) targets in the presence of background air. First, we demonstrate the mechanism of ablation of Ti targets by multiple femtosecond laser pulses at ambient air in an explicit analytical form. The formulas for evaporation rates and the number of ablated particles, which is analogous to the deposition rate of the synthesized nanofibers, for the ablation by a single pulse and multiple pulses as a function of laser parameters, background gas, and material properties are predicted and compared to experimental results. Afterwards, the formation of nanofibrous structures is demonstrated by applying an existing simplified kinetic model to Ti targets and ambient conditions. The predicted theory provides nanofiber diameter dependency with the combination of laser parameters, target properties, and ambient gas characteristics. Experimental studies are then performed on titania nanofibrous structures synthesized by laser ablation of Ti targets using MHz repletion-rate femtosecond laser at ambient air. The models' predictions are then compared with the experimental results, where nanostructures with different morphologies are manufactured by altering laser parameters. Our results indicate that femtosecond laser ablation of Ti targets at air background yields crystalline titania nanostructures. The formation of crystalline titania nanostructures is preceded by thermal mechanism of nucleation and growth. The results point out that laser pulse repetition and dwell time can control the density, size, and pore size of the engineered nanofibrous structure. As the deposition rate of nanostructures is analogous to the ablation rate of the target, higher density of nanofibrous structure is seen at greater laser fluences. The predicted theory can be applied to predict ablation mechanism and nanofiber formation of different materials.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Stratigraphic and structural controls on groundwater flow in an outcropping fossil fan delta: the case of Sant Llorenç del Munt range (NE Spain)

Hydrogeological models of mountain regions present the opportunity to understand the role of geological factors on groundwater resources. The effects of sedimentary facies and fracture distribution on groundwater flow and resource exploitation studied in the ancient fan delta of Sant Llorenç de Munt (central Catalonia, Spain) by integrating geological field observations (using sequence stratigraphy methods) and hydrogeological data (pumping tests, hydrochemistry and environmental isotopes). A comprehensive analysis of data portrays the massif as a single unit, constituted by different compartments determined by specific layers and sets of fractures. Two distinct flow systems—local and regional—are identified based on pumping test analysis as well as hydrochemical and isotopic data. Drawdown curves derived from pumping tests indicate that the behavior of the saturated layers, whose main porosity is given by the fracture network, corresponds to a confined aquifer. Pumping tests also reflect a double porosity within the system and the occurrence of impervious boundaries that support a compartmentalized model for the whole aquifer system. Hydrochemical data and associated spatial evolution show the result of water–rock interaction along the flow lines. Concentration of magnesium, derived from dolomite dissolution, is a tracer of the flow-path along distinct stratigraphic units. Water stable isotopes indicate that evaporation (near a 5% loss) occurs in a thick unsaturated zone within the massif before infiltration reaches the water table. The hydrogeological analysis of this outcropping system provides a methodology for the conceptualization of groundwater flow in similar buried systems where logging and hydrogeological information are scarce.

58 GEOSCIENCES↗

DOE OSTI2021

Inkjet printing of epitaxially connected nanocrystal superlattices

Access to a blossoming library of colloidal nanomaterials provides building blocks for complex assembled materials. The journey to bring these prospects to fruition stands to benefit from the application of advanced processing methods. Epitaxially connected nanocrystal (or quantum dot) superlattices present a captivating model system for mesocrystals with intriguing emergent properties. The conventional processing approach to creating these materials involves assembling and attaching the constituent nanocrystals at the interface between two immiscible fluids. Processing small liquid volumes of the colloidal nanocrystal solution involves several complexities arising from the concurrent spreading, evaporation, assembly, and attachment. The ability of inkjet printers to deliver small (typically picoliter) liquid volumes with precise positioning is attractive to advance fundamental insights into the processing science, and thereby potentially enable new routes to incorporate the epitaxially connected superlattices into technology platforms. In this study, we identified the processing window of opportunity, including nanocrystal ink formulation and printing approach to enable delivery of colloidal nanocrystals from an inkjet nozzle onto the surface of a sessile droplet of the immiscible subphase. We demonstrate how inkjet printing can be scaled-down to enable the fabrication of epitaxially connected superlattices on patterned sub-millimeter droplets. Furthermore, we anticipate that insights from this work will spur on future advances to enable more mechanistic insights into the assembly processes and new avenues to create high-fidelity superlattices.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2018

Microstructural Evolution of the Thin Films of a Donor–Acceptor Semiconducting Polymer Deposited by Meniscus-Guided Coating

Crucial to the development and refinement of organic electronics is a fundamental understanding of how deposition processes affect the active material’s resulting microstructure in the thin film. Meniscus-guided coating (MGC) methods are attractive because of their amenability to high-throughput, industrially relevant continuous processes like roll-to-roll deposition, but the mechanism of solid film formation has not been elucidated and is valuable for the precise control of thin-film morphology and thus ultimate device performance. Here, in this work, we investigate the microstructural evolution of thin films of a diketopyrrolopyrrole–terthiophene donor–acceptor polymer semiconductor using both in situ and ex situ X-ray diffraction methods. On the basis of a comparison of disorder between the film bulk and the top surface and a depth profiling of the out-of-plane orientation of crystallites, we find that faster coating speeds introduce more disorder into the resulting films because the stochastic nucleation of disordered crystallites at the meniscus air–liquid interface becomes more dominant than substrate-mediated nucleation. Our results suggest that there exist three separate deposition regimes—namely the shear-dominate, disorder-dominate, and Landau–Levich–Derjaguin regimes—revealed by observing both polymer alignment via dry film thickness and optical dichroism, a property sensitive to the flow and shear fields. At low coating speeds, the shear strain imparted upon the solution directly induces polymer alignment, causing an increase in dichroism as a function of coating speed. When solvent evaporation becomes too rapid as coating speeds increase, a decrease in the dichroic ratio is observed before the classical Landau–Levich–Derjaguin regime occurs at the highest coating speeds, resulting in isotropic films. The preservation of out-of-plane crystalline texture throughout the thickness of the films is seen only for lower coating speeds, and a study of different deposition temperatures similarly indicates that the lower overall solvent evaporation is conducive to this process. Increased paracrystalline disorder (i.e., peak broadening) is observed by grazing-incidence wide-angle X-ray diffraction at the top interface of the dry films and at higher coating speeds. Together, these results indicate that more rapid solvent evaporation at higher coating speeds causes increased disorder, which can cause the nucleation of misaligned crystallites, affect the dichroic ratio, and may frustrate the alignment of polymer molecules in the amorphous regions of the film. Finally, because the polymer studied and the deposition technique used are representative models, these results are likely general for aggregating, semicrystalline donor–acceptor polymers deposited with MGC.

36 MATERIALS SCIENCE↗

DOE OSTI2026

Impacts of Mean State Ocean Heat Transport on Climate and Its Response to CO 2 Forcing

Simulations of the slab ocean configuration of the coupled Energy Exascale Earth System Model (E3SM) were used to isolate the role of poleward ocean heat transport (OHT) in shaping the climate and its response to CO 2 forcing. Imposed changes to mean-state OHT produce compensating changes in atmospheric heat transport (AHT) that are mediated by changes in surface evaporation. A reduction of maximum OHT by 0.56 PW (32%) reduces the global mean surface air temperature by 3.6°C. However, this cooler mean state exhibits 1.2°C more warming under CO 2 quadrupling, with the largest differences occurring at high latitudes. The amplified warming arises from stronger surface albedo and lapse rate feedbacks in polar regions and a shortwave cloud feedback in the southern midlatitudes. These results highlight the critical role of mean-state OHT in modulating mean-state climate, the partitioning between the OHT and AHT, and climate sensitivity.

Atmosphere-ocean-ice interactions↗

DOE OSTI2020

Improving AHU Performance by Minimizing Approach Temperature, Reducing Air Maldistribution, and Efficiently Handling Sensible and Latent Loads (Phase 1 Interim Final Technical Report)

Residential air handling units (AHUs) have stayed the same in form and efficiency for the past 30+ years, with incremental improvements made to address safety, functionality, and energy-efficiency. The purpose of this research in Phase I, Topic 9a: Next Generation Residential Air Handlers, was to improve AHU performance by minimizing heat exchanger (HX) approach temperature, reducing air maldistribution, and developing alternative system configurations which more efficiently handle sensible and latent loads. In this research Optimized Thermal Systems (OTS) developed, modeled, and evaluated multiple alternative system concepts. A dual vapor compression system separate sensible and latent cooling (SSLC) concept was studied to inform work on alternative concepts and to show best-case performance benefit. System concepts included ejector enhanced vapor compression cycles, desiccant assisted dehumidification, dual evaporator SSLC, and alternative AHU HX configurations. A dual vapor compression system showed COP improvement of 20%, however, required additional components, increased unit size, and increased cost. Two types of ejector enhanced vapor compression cycles with dual evaporators improved system COP by 9 to 11%, and reduced AHU losses by as much as 18%, with design changes limited to the AHU, no unit physical size increase, and a moderate increase to system first cost. Desiccant assisted air-conditioning required increased air flow rate resulting in higher fan power and the desiccant wheel increased sensible heat load leading to increased compressor power and reduced system COP. Dual evaporator cycles were found to degrade performance due to increased expansion losses. Optimized single slab HX designs used in place of the traditional A-coil HX led to 44–49% reduction in aluminum, 47–60% less refrigerant charge, and improved HX velocity distribution.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2022

Clean energy technology pathways from research to commercialization: Policy and practice case studies

Clean energy research and development (R and D) leading to commercial technologies is vital to economic development, technology competitiveness, and reduced environmental impact. Over the past 30 years, such efforts have advanced technology performance and reduced cost by leveraging network effects and economies of scale. After demonstrating promise in applied R and D, successful clean energy and energy efficiency technologies are incorporated into an initial product sold by the private sector. Despite its importance, processes by which first commercialization occurs are difficult to generalize while capturing specific insights from practitioners in markets and technologies. This paper presents a policy-focused qualitative assessment of the first commercialization of four diverse energy technologies: thin film photovoltaics, wind turbine blades, dual-stage refrigeration evaporators, and fuel cells for material handling equipment. Each technology presents distinct value propositions, markets, and regulatory drivers. The case studies indicate three common characteristics of successful first commercialization for new energy technologies: 1) good fit between the technology, R&D infrastructure, and public-private partnership models; 2) high degree of alignment of government regulations and R&D priorities with market forces; and 3) compatibility between time scales required for R&D, product development, and opportunities. These findings may inform energy investment decision-making, maximize benefits from R&D, and advance the transition to a low-emission future.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

DOE OSTI2016

Quantifying shallow subsurface water and heat dynamics using coupled hydrological-thermal-geophysical inversion

Improving our ability to estimate the parameters that control water and heat fluxes in the shallow subsurface is particularly important due to their strong control on recharge, evaporation and biogeochemical processes. The objectives of this study are to develop and test a new inversion scheme to simultaneously estimate subsurface hydrological, thermal and petrophysical parameters using hydrological, thermal and electrical resistivity tomography (ERT) data. The inversion scheme – which is based on a nonisothermal, multiphase hydrological model – provides the desired subsurface property estimates in high spatiotemporal resolution. A particularly novel aspect of the inversion scheme is the explicit incorporation of the dependence of the subsurface electrical resistivity on both moisture and temperature. The scheme was applied to synthetic case studies, as well as to real datasets that were autonomously collected at a biogeochemical field study site in Rifle, Colorado. At the Rifle site, the coupled hydrological-thermal-geophysical inversion approach well predicted the matric potential, temperature and apparent resistivity with the Nash–Sutcliffe efficiency criterion greater than 0.92. Synthetic studies found that neglecting the subsurface temperature variability, and its effect on the electrical resistivity in the hydrogeophysical inversion, may lead to an incorrect estimation of the hydrological parameters. The approach is expected to be especially useful for the increasing number of studies that are taking advantage of autonomously collected ERT and soil measurements to explore complex terrestrial system dynamics.

58 GEOSCIENCES↗

DOE OSTI2017

Near-Complete Retention of Technetium During Vitrification of Hanford Low Activity Waste With Recycle - 17315

Technetium is one of the more volatile radionuclides for which retention in low activity waste (LAW) glass under the high temperature conditions during vitrification can vary depending on feed composition, feed chemistry, and melter operating parameters. High retention of technetium in the glass is desirable in order to minimize the fraction of technetium that is directed to secondary waste streams, which include liquid off-gas treatment system effluents. Consequently, test data are crucial to assess and underpin the assumptions underlying such mass balance projections, the compositions of secondary waste streams, and, in particular, the effects of recycle on increasing the incorporation of technetium in the glass products and minimizing the fraction in non-glass waste forms. Previous testing performed on a scaled melter system that incorporates prototypical off-gas treatment components and real-time recycle of the liquid effluents back to the melter feed demonstrated that recycle resulted in significant increases of the incorporation of technetium into the LAW glass product and behavior that was in good agreement with process models for the system. However, the maximum technetium retention achieved in those tests was less than predicted. Tests conducted in the present work demonstrated, for the first time, near-complete retention of technetium in the LAW glass product with recycle. Holdup of technetium in the vacuum evaporator, which concentrates the liquid effluents prior to their recycle to the melter feed, was identified as the primary reason for the previously observed shortfall. The fate of other volatile constituents was also assessed. In particular, in addition to technetium, rhenium, which is frequently used as a non-radioactive surrogate for technetium, was included in these tests. This allows for a direct comparison of the behavior of rhenium and technetium during vitrification and in the down-stream processes. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2023

An ensemble of 48 physically perturbed model estimates of the 1/8° terrestrial water budget over the conterminous United States, 1980–2015

Terrestrial water budget (TWB) data over large domains are of high interest for various hydrological applications. Spatiotemporally continuous and physically consistent estimations of TWB rely on land surface models (LSMs). As an augmentation of the operational North American Land Data Assimilation System Phase 2 (NLDAS-2) four-LSM ensemble, this paper describes a dataset simulated from an ensemble of 48 physics configurations of the Noah LSM with multi-physics options (Noah-MP). The 48 Noah-MP physics configurations are selected to give a representative cross-section of commonly used LSMs for parameterizing runoff, atmospheric surface layer turbulence, soil moisture limitation on photosynthesis, and stomatal conductance. The dataset spans from 1980 to 2015 over the conterminous United States (CONUS) at a monthly temporal resolution and a 1/8° spatial resolution. The dataset variables include total evapotranspiration and its constituents (canopy evaporation, soil evaporation, and transpiration), runoff (the surface and subsurface components), as well as terrestrial water storage (snow water equivalent, four-layer soil water content from the surface down to 2 m, and the groundwater storage anomaly). The dataset is available at https://doi.org/10.5281/zenodo.7109816. Evaluations carried out in this study and previous investigations show that the ensemble per forms well in reproducing the observed terrestrial water storage, snow water equivalent, soil moisture, and runoff. Noah-MP complements the NLDAS models well, and adding Noah-MP consistently improves the NLDAS es timations of the above variables in most areas of CONUS. Besides, the perturbed-physics ensemble facilitates the identification of model deficiencies. The parameterizations of shallow snow, spatially varying groundwater dynamics, and near-surface atmospheric turbulence should be improved in future model versions.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2018

Heterogeneity in Warm‐Season Land‐Atmosphere Coupling Over the U.S. Southern Great Plains

Abstract Heterogeneity in warm‐season (May–August) land‐atmosphere (LA) coupling is quantified with the long‐time, multiple‐station measurements from the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program and the Moderate Resolution Imaging Spectroradiometer satellite remote sensing at the Southern Great Plains (SGP). We examine the coupling strength at seven additional locations with the same surface type (i.e., pasture/grassland) as the ARM SGP central facility (CF). To simultaneously consider multiple factors and consistently quantify their relative contributions, we apply a multiple linear regression method to correlate the surface evaporative fraction (EF) with near‐surface soil moisture (SM) and leaf area index (LAI). The observations show moderate to weak terrestrial segment LA coupling with large heterogeneity across the ARM SGP domain in warm season. Large spatial variabilities in the contributions from SM and LAI to the EF changes are also found. The coupling heterogeneities appear to be associated with differences in land use, anthropogenic activities, rooting depth, and soil type at different stations. Therefore, the complex LA interactions at the SGP cannot be well represented by those at the CF/E13 based on the metrics applied here. Overall, the LAI exerts more influence on the EF than does the SM due to its overwhelming impacts on the latent heat flux. This study complements previous studies based on measurements only from the CF and has important implications for modeling LA coupling in weather and climate models. The multiple linear regression provides a more comprehensive measure of the integrated impacts on LA coupling from several different factors.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2014

Combined UHV/high-pressure catalysis setup for depth-resolved near-surface spectroscopic characterization and catalytic testing of model catalysts

An ultra-high vacuum (UHV) setup for “real” and “inverse” model catalyst preparation, depth-resolved near-surface spectroscopic characterization, and quantification of catalytic activity and selectivity under technologically relevant conditions is described. Due to the all-quartz reactor attached directly to the UHV-chamber, transfer of the catalyst for in situ testing without intermediate contact to the ambient is possible. The design of the UHV-compatible re-circulating batch reactor setup allows the study of reaction kinetics under close to technically relevant catalytic conditions up to 1273 K without contact to metallic surfaces except those of the catalyst itself. With the attached differentially pumped exchangeable evaporators and the quartz-microbalance thickness monitoring equipment, a reproducible, versatile, and standardised sample preparation is possible. For three-dimensional near-surface sample characterization, the system is equipped with a hemispherical analyser for X-ray photoelectron spectroscopy (XPS), electron-beam or X-ray-excited Auger-electron spectroscopy, and low-energy ion scattering measurements. Due the dedicated geometry of the X-ray gun (54.7°, “magic angle”) and the rotatable sample holder, depth analysis by angle-resolved XPS measurements can be performed. Thus, by the combination of characterisation methods with different information depths, a detailed three-dimensional picture of the electronic and geometric structure of the model catalyst can be obtained. To demonstrate the capability of the described system, comparative results for depth-resolved sample characterization and catalytic testing in methanol steam reforming on PdGa and PdZn near-surface intermetallic phases are shown.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗