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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Visible, Durable, Enforceable Institutional Controls: Weldon Spring Site - A 10-Year Journey - 13190

The DOE Office of Legacy Management's (LM's) mission is to manage the DOE's post-closure responsibilities and ensure the future protection of human health and the environment. LM has control and custody of legacy land, structures, and facilities and is responsible for maintaining them at levels suitable for their long-term use. This includes all engineered and institutional controls (ICs) designed as another level of assurance to prevent exposure to residual contamination and waste. The development and management of ICs has been, and continues to be, a critical component to the success of LM surveillance and maintenance activities. Many major federal laws, Executive Orders, regulations, and various other drivers influence the establishment and use of ICs at LM sites. LM uses a wide range of ICs to appropriately limit access to, or uses of, land, facilities, and other real and personal properties; protect the environment; maintain the physical safety and security of DOE facilities; and prevent or limit inadvertent human and environmental exposure to residual contaminants and other hazards. The ICs at the Weldon Spring, Missouri, Site were developed in close coordination with federal and state regulators. An Explanation of Significant Differences (ESD) was issued in February 2005, which clarified the use restrictions necessary for the remedial actions specified in the Records of Decision for the separate operable units to remain protective over the long-term. The operable units included the Chemical Plant Operable Unit, the Chemical Plant Groundwater Operable Unit, and the Quarry Residuals Operable Unit. The ESD clarified specific requirements for each site area that needed use restrictions and established how DOE would implement, maintain, and monitor the specific requirements. DOE developed the Long-Term Surveillance and Maintenance Plan for the U.S. Department of Energy Weldon Spring, Missouri, Site (LTS and M Plan) that addressed the full scope of the site management activities necessary to ensure that the Weldon Spring Site remains protective over the long-term. The LTS and M Plan is revised periodically to ensure its applicability to changing site, regulatory, or procedural conditions. In addition to addressing such activities as long-term groundwater monitoring and disposal cell maintenance, the LTS and M Plan was developed and issued to ensure that the use restrictions identified in the ESD were properly imposed and maintained. The LTS and M Plan included a detailed IC Implementation Plan, which includes a process for evaluating and identifying specific IC mechanisms that best accomplish the objectives set out in the ESD. Consistent with EPA guidance on selecting ICs, various IC mechanisms were evaluated, including government controls, proprietary controls, enforcement tools, and informational devices. Where appropriate, redundant mechanisms were employed to increase the effectiveness of the ICs. Information in the IC Implementation Plan includes: (1) a discussion of current site conditions (reflecting post-remedial action conditions for the Chemical Plant and Quarry Areas and the risk-basis for why use restrictions are needed); (2) the objectives of, or performance expectations for, the use restrictions; (3) specific ICs already in place and additional mechanisms identified for implementation; (4) a schedule for implementing additional ICs; (5) procedures for maintaining the ICs and for conducting periodic inspections; and (6) general provisions for the implementing ICs for the site. The actual agreements and documentation of the various ICs are included in an appendix of the LTS and M Plan. These documents are also available via the internet from the authorizing agencies (County, Missouri Department of Natural Resources, EPA, etc.) The Weldon Spring Site personnel have been successful in finalizing each of the ICs that were established for the site. The planning, establishment, and implementation of the ICs was a long and detailed process with several lessons-learned that were identified along the way. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

CO 2 supplementation eliminates sugar-rich media requirement for plant propagation using a simple inexpensive temporary immersion photobioreactor

In vitro plant propagation systems such as temporary immersion bioreactors (TIBs) are valuable tools that enable production of disease-free plants with improved traits. However, TIB systems can be expensive, difficult to implement, and prone to contamination due to sugar rich propagation media. Using rapidly growing chicory root cultures to expedite design-build-test cycles, we report here an improved, low-cost version of a previously reported Hydrostatically-driven TIB (Hy-TIB) that facilitates economical use of gas mixtures. Bioreactor improvements include decreased material costs, expanded modes of operation, and a horizontal orientation of a plastic film plant growth chambers that increase propagule light exposure. To take advantage of these improvements, we describe here experiments that evaluate the impacts of elevated CO 2 on propagation of cacao (Theobroma cacao) secondary embryos and nodal cultures of yam (Dioscorea spp.) during both phototrophic and photomixotrophic growth. Our experiments show that elevated CO 2 during plant propagation significantly improved both cacao and yam propagule development and eliminated the need for supplemental sugars in tissue culture growth media. Thus, our improved Hy-TIB shows potential as a simple, low-cost, and scalable propagation platform with cost-effective gas composition control and reduced risk of contamination overgrowth. We provide detailed instructions for assembly of this Hy-TIB design and discuss the implications of its adoption in food-insecure regions of the world.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Overcoming Technical Challenges During Demolition of the West Valley Vitrification Facility - 19387

In February 2019, CH2M Hill BWXT West Valley, LLC will complete demolition and waste disposal of the first vitrification facility in the history of the United States. This project marked the largest and most complex radiological demolition project undertaken at the U.S. Department of Energy-led West Valley Demonstration Project (WVDP) to date. Provisions put in place during demolition monitored for and mitigated contamination migration during demolition. The work was carried out in a well-planned manner to address specific areas where higher levels of radiological activity were known to exist and where difficult and oversized equipment removal or sensitive items required special handling. Inaccessible contamination on ceiling mounted equipment, controlled removal of two massive steel shield doors, intact removal of lead glass shield windows and a confined demolition boundary area were some of the limiting factors that required special consideration during demolition. This paper contains a discussion of planning and implementation of special handling techniques utilized during some of the more difficult evolutions encountered during open-air demolition of the Vitrification Facility. The work techniques, provisions to mitigate inclement weather and lessons learned have been incorporated into the planning for follow-on radiological demolition work at the WVDP. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

Final Report: Geoelectrical Measurement of Multi-Scale Mass Transfer Parameters

Mass transfer affects contaminant transport and is thought to control the efficiency of aquifer remediation at a number of sites within the Department of Energy (DOE) complex. An improved understanding of mass transfer is critical to meeting the enormous scientific and engineering challenges currently facing DOE. Informed design of site remedies and long-term stewardship of radionuclide-contaminated sites will require new cost-effective laboratory and field techniques to measure the parameters controlling mass transfer spatially and across a range of scales. In this project, we sought to capitalize on the geophysical signatures of mass transfer. Previous numerical modeling and pilot-scale field experiments suggested that mass transfer produces a geoelectrical signature—a hysteretic relation between sampled (mobile-domain) fluid conductivity and bulk (mobile + immobile) conductivity—over a range of scales relevant to aquifer remediation. In this work, we investigated the geoelectrical signature of mass transfer during tracer transport in a series of controlled experiments to determine the operation of controlling parameters, and also investigated the use of complex-resistivity (CR) as a means of quantifying mass transfer parameters in situ without tracer experiments. In an add-on component to our grant, we additionally considered nuclear magnetic resonance (NMR) to help parse mobile from immobile porosities. Including the NMR component, our revised study objectives were to: 1. Develop and demonstrate geophysical approaches to measure mass-transfer parameters spatially and over a range of scales, including the combination of electrical resistivity monitoring, tracer tests, complex resistivity, nuclear magnetic resonance, and materials characterization; and 2. Provide mass-transfer estimates for improved understanding of contaminant fate and transport at DOE sites, such as uranium transport at the Hanford 300 Area. To achieve our objectives, we implemented a 3-part research plan involving (1) development of computer codes and techniques to estimate mass-transfer parameters from time-lapse electrical data; (2) bench-scale experiments on synthetic materials and materials from cores from the Hanford 300 Area; and (3) field demonstration experiments at the DOE’s Hanford 300 Area. In a synergistic add-on to our workplan, we analyzed data from field experiments performed at the DOE Naturita Site under a separate DOE SBR grant, on which PI Day-Lewis served as co-PI. Techniques developed for application to Hanford datasets also were applied to data from Naturita.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

Geoelectrical Measurement of Multi-Scale Mass Transfer Parameters

Mass transfer affects contaminant transport and is thought to control the efficiency of aquifer remediation at a number of sites within the Department of Energy (DOE) complex. An improved understanding of mass transfer is critical to meeting the enormous scientific and engineering challenges currently facing DOE. Informed design of site remedies and long-term stewardship of radionuclide-contaminated sites will require new cost-effective laboratory and field techniques to measure the parameters controlling mass transfer spatially and across a range of scales. In this project, we sought to capitalize on the geophysical signatures of mass transfer. Previous numerical modeling and pilot-scale field experiments suggested that mass transfer produces a geoelectrical signature—a hysteretic relation between sampled (mobile-domain) fluid conductivity and bulk (mobile + immobile) conductivity—over a range of scales relevant to aquifer remediation. In this work, we investigated the geoelectrical signature of mass transfer during tracer transport in a series of controlled experiments to determine the operation of controlling parameters, and also investigated the use of complex-resistivity (CR) as a means of quantifying mass transfer parameters in situ without tracer experiments. In an add-on component to our grant, we additionally considered nuclear magnetic resonance (NMR) to help parse mobile from immobile porosities. Including the NMR component, our revised study objectives were to: 1. Develop and demonstrate geophysical approaches to measure mass-transfer parameters spatially and over a range of scales, including the combination of electrical resistivity monitoring, tracer tests, complex resistivity, nuclear magnetic resonance, and materials characterization; and 2. Provide mass-transfer estimates for improved understanding of contaminant fate and transport at DOE sites, such as uranium transport at the Hanford 300 Area. To achieve our objectives, we implemented a 3-part research plan involving (1) development of computer codes and techniques to estimate mass-transfer parameters from time-lapse electrical data; (2) bench-scale experiments on synthetic materials and materials from cores from the Hanford 300 Area; and (3) field demonstration experiments at the DOE’s Hanford 300 Area. In a synergistic add-on to our workplan, we analyzed data from field experiments performed at the DOE Naturita Site under a separate DOE SBR grant, on which PI Day-Lewis served as co-PI. Techniques developed for application to Hanford datasets also were applied to data from Naturita.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Land-use planning scenarios for contaminated land: comparing EPA, state, and tribal scenarios - 15642

Land-use planning focusing on future disposition of public lands, forests and, former agricultural or industrial land, must take into account demographic and economic factors as well as future needs and availability of recreational open space, arable land, and water for growing populations. Planning requires the balancing of competing interests for 'growth', open space, and preservation of cultural, ecological and natural resources Landscapes with soil, surface water, and groundwater contaminated by former military, industrial, mining or agricultural uses, pose special challenges, many of which have been addressed under the rubric of 'brown-fields'. Land-use decisions or recommendations can be based mainly on economic/social interests taking into account projected demographic changes, or they can be based mainly on environmental issues taking into account contamination levels, remediation costs and technologies, and health risk issues. Future land-use is interwoven with cleanup goals. Where unrestricted future land-use is anticipated or desired, cleanup levels for soil and groundwater must be low enough to allow such uses without unacceptable health risks. Where such cleanup levels are unattainable for fiscal or technological reasons, residual contamination will remain, and future uses, particularly for groundwater, must be restricted, requiring engineered barriers and institutional controls to interdict future exposure pathways from contaminated environmental media to receptors (residents, recreationists, employees). Although contamination and hazard may persist for centuries, planning beyond a generation or two incurs great uncertainties in demographics, policies, economic, and climate-related changes. The Environmental Protection Agency and various states have established categories of clean-up levels corresponding to future industrial, recreational and residential use, with variations on these themes. This paper examines the spectrum of land-uses, and emphasizes a distinctions between -residential- and -unrestricted- as applied to future land-uses, particularly involving groundwater. Land-use determinations can be proposed and evaluated by a myriad of regulatory policies, guidance documents, and processes, including comprehensive land-use planning documents, Baseline Risk Assessments, Remedial Investigation/Feasibility documents and Records of Decision - which are not the focus of this study. This study instead focuses on gradations in different residential, recreational and industrial land-use scenarios and their relation to contamination of soil and groundwater. The Consortium for Risk Evaluation with Stakeholder Participation (CRESP) instituted this study to help understand the varying land-use versus clean-up decisions at the Department of Energy's environmental management sites, particularly Hanford (Washington State). (authors)

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Management of multiple groundwater contaminant plumes extending beyond property boundaries at the young - Rainey STAR Center (Science, Technology, and Research Center) - 15623

The US DOE Pinellas Plant-now known as the Young - Rainey STAR Center, located in Largo, Florida-manufactured components for nuclear weapons from 1956 to 1995. During decades of operations, chlorinated solvents were released from a drum storage area and from underground piping at multiple points adjacent to and beneath a 4.5-hectare (11-acre) building. Two groundwater contaminant plumes associated with contaminant sources beneath the building have been identified, delineated, and are being monitored. During a focused delineation campaign in 2008 to better define the plume boundaries prior to municipal construction projects in the area, the plumes were determined to extend beyond the site boundaries, beneath the adjacent roadway easements, and beneath four adjacent privately owned properties. US DOE has performed a number of activities in response to the discovery of the offsite contaminant plumes, including performing a high-resolution delineation of contaminant plumes; coordinating with local municipalities to complete two linear construction projects requiring dewatering in the vicinity of the plumes; performing risk assessment, risk management, risk communication, and community relations tasks associated with the project; coordinating with state regulators to identify a risk-based corrective action regulatory approach; and coordinating with impacted property owners to develop and implement institutional controls. During the replacement of a 1.2-meter (48-inch) municipal potable water line directly over the contaminant plume area, US DOE (1) constructed infrastructure to receive and treat dewatering effluent at a rate of 20 gallons per minute around the clock for 6 weeks, and (2) conducted breathing-zone air monitoring during excavation of a 3.0-meter (10-foot) deep trench. This degree of diligence was necessary to ensure and document that no site workers were exposed to chlorinated solvent vapors during the construction process, and that a large volume of potentially contaminated groundwater was properly treated and dispositioned. US DOE also took aggressive actions to pro-actively address claims regarding loss of property value on two properties associated with the groundwater contamination, which resulted in a teaming arrangement with each party for future management of the ongoing corrective actions. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

The continuum and leading twist limits of parton distribution functions in lattice QCD

In this study, we present continuum limit results for the unpolarized parton distribution function of the nucleon computed in lattice QCD. This study is the first continuum limit using the pseudo-PDF approach with Short Distance Factorization for factorizing lattice QCD calculable matrix elements. Our findings are also compared with the pertinent phenomenological determinations. Inter alia, we are employing the summation Generalized Eigenvalue Problem (sGEVP) technique in order to optimize our control over the excited state contamination which can be one of the most serious systematic errors in this type of calculations. A crucial novel ingredient of our analysis is the parameterization of systematic errors using Jacobi polynomials to characterize and remove both lattice spacing and higher twist contaminations, as well as the leading twist distribution. This method can be expanded in further studies to remove all other systematic errors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

A new hybrid gadolinium nanoparticles-loaded polymeric material for neutron detection in rare event searches

Experiments aimed at direct searches for WIMP dark matter require highly effective reduction of backgrounds and control of any residual radioactive contamination. In particular, neutrons interacting with atomic nuclei represent an important class of backgrounds due to the expected similarity of a WIMP-nucleon interaction, so that such experiments often feature a dedicated neutron detector surrounding the active target volume. In the context of the development of DarkSide-20k detector at INFN Gran Sasso National Laboratory (LNGS), several R&D projects were conceived and developed for the creation of a new hybrid material rich in both hydrogen and gadolinium nuclei to be employed as an essential element of the neutron detector. Thanks to its very high cross-section for neutron capture, gadolinium is one of the most widely used elements in neutron detectors, while the hydrogen-rich material is instrumental in efficiently moderating the neutrons. In this paper results from one of the R&Ds are presented. In this effort the new hybrid material was obtained as a poly(methyl methacrylate) (PMMA) matrix, loaded with gadolinium oxide in the form of nanoparticles. We describe its realization, including all phases of design, purification, construction, characterization, and determination of mechanical properties of the new material.

Dark Matter detectors (WIMPs, axions, etc.)↗
DOE OSTI2017

Isovector charges of the nucleon from 2+1-flavor QCD with clover fermions

Here, we present high-statistics estimates of the isovector charges of the nucleon from four 2 + 1-flavor ensembles generated using Wilson-clover fermions with stout smearing and tree-level tadpole improved Symanzik gauge action at lattice spacings 𝑎 ≈ 0.127 and 0.09 fm and with 𝑀 𝜋 ≈ 280 and 170 MeV. The truncated solver method with bias correction and the coherent source sequential propagator construction are used to cost-effectively achieve 𝑂⁡(1⁢0 5 ) measurements on each ensemble. Using these data, the analysis of two-point correlation functions is extended to include four states in the fits, and of three-point functions to three states. Control over excited-state contamination in the calculation of the nucleon mass, the mass gaps between excited states, and in the matrix elements is demonstrated by the consistency of estimates using this multistate analysis of the spectral decomposition of the correlation functions and from simulations of the three-point functions at multiple values of the source-sink separation. The results for all three charges, 𝑔 𝐴 , 𝑔 𝑆 , and 𝑔 𝑇 , are in good agreement with calculations done using the clover-on-HISQ lattice formulation with similar values of the lattice parameters.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Proton Isovector Helicity Distribution on the Lattice at Physical Pion Mass

We present a state-of-the-art calculation of the isovector quark helicity Bjorken-x distribution in the proton using lattice-QCD ensembles at the physical pion mass. We compute quasi-distributions at proton momenta P z ϵ {2.2; 2.6; 3.0} GeV on the lattice, and match them systematically to the physical parton distribution using large-momentum effective theory (LaMET).We reach an unprecedented precision through high statistics in simulations, large-momentum proton matrix elements, and control of excited-state contamination. The resulting distribution with combined statistical and systematic errors is in agreement with the latest phenomenological analysis of the spin-dependent experimental data; in particular, Δ$\bar{u}$(x) > Δ$\bar{d}$(x).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Composite Sampling of a Bacillus anthracis Surrogate with Cellulose Sponge Surface Samplers from a Nonporous Surface

A series of experiments was conducted to explore the utility of composite-based collection of surface samples for the detection of a Bacillus anthracis surrogate using cellulose sponge samplers on a nonporous stainless steel surface. Two composite-based collection approaches were evaluated over a surface area of 3716 cm 2 (four separate 929 cm 2 areas), larger than the 645 cm 2 prescribed by the standard Centers for Disease Control (CDC) and Prevention cellulose sponge sampling protocol for use on nonporous surfaces. The CDC method was also compared to a modified protocol where only one surface of the sponge sampler was used for each of the four areas composited. Differences in collection efficiency compared to positive controls and the potential for contaminant transfer for each protocol were assessed. The impact of the loss of wetting buffer from the sponge sampler onto additional surface areas sampled was evaluated. Statistical tests of the results using ANOVA indicate that the collection of composite samples using the modified sampling protocol is comparable to the collection of composite samples using the standard CDC protocol (p = 0.261). Most of the surface-bound spores are collected on the first sampling pass, suggesting that multiple passes with the sponge sampler over the same surface may be unnecessary. The effect of moisture loss from the sponge sampler on collection efficiency was not significant (p = 0.720) for both methods. Contaminant transfer occurs with both sampling protocols, but the magnitude of transfer is significantly greater when using the standard protocol than when the modified protocol is used (p<0.001). The results of this study suggest that composite surface sampling, by either method presented here, could successfully be used to increase the surface area sampled per sponge sampler, resulting in reduced sampling times in the field and decreased laboratory processing cost and turn-around times.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Closure Report Central Nevada Test Area Subsurface Corrective Action Unit 443 January 2016

The U.S. Department of Energy (DOE) Office of Legacy Management (LM) prepared this Closure Report for the subsurface Corrective Action Unit (CAU) 443 at the Central Nevada Test Area (CNTA), Nevada, Site. CNTA was the site of a 0.2- to 1-megaton underground nuclear test in 1968. Responsibility for the site’s environmental restoration was transferred from the DOE, National Nuclear Security Administration, Nevada Field Office to LM on October 1, 2006. The environmental restoration process and corrective action strategy for CAU 443 are conducted in accordance with the Federal Facility Agreement and Consent Order (FFACO 1996, as amended 2011) and all applicable Nevada Division of Environmental Protection (NDEP) policies and regulations. This Closure Report provides justification for closure of CAU 443 and provides a summary of completed closure activities; describes the selected corrective action alternative; provides an implementation plan for long-term monitoring with well network maintenance and approaches/policies for institutional controls (ICs); and presents the contaminant, compliance, and use-restriction boundaries for the site.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

A Critical Review of the Impacts of Leaking CO 2 Gas and Brine on Groundwater Quality

Geological carbon sequestration (GCS) is a global carbon emission reduction strategy involving the capture of CO 2 emitted from fossil fuel burning power plants, as well as the subsequent injection of the captured CO 2 gas into deep saline aquifers or depleted oil and gas reservoirs. A critical question that arises from the proposed GCS is the potential impacts of CO 2 injection on the quality of drinking-water systems overlying CO 2 sequestration storage sites. Although storage reservoirs are evaluated and selected based on their ability to safely and securely store emplaced fluids, leakage of CO 2 from storage reservoirs is a primary risk factor and potential barrier to the widespread acceptance of geologic CO 2 sequestration (OR Harvey et al. 2013; Y-S Jun et al. 2013; DOE 2007). Therefore, a systematic understanding of how CO 2 leakage would affect the geochemistry of potable aquifers, and subsequently control or affect elemental and contaminant release via sequential and/or simultaneous abiotic and biotic processes and reactions is vital.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Information on Technical Impracticability for Remediation of Iodine-129 Contamination

Groundwater in the 200-UP-1 operable unit (OU) is contaminated with carbon tetrachloride, uranium, nitrate, chromium (total and hexavalent), iodine-129, technetium-99, and tritium, associated with past nuclear weapons production activities at Hanford. The preferred alternative described in the 2012 Record of Decision (ROD) for the 200-UP-1 OU Interim Remedial Action includes 35 years of active remediation using a combination of groundwater pump-and-treat and monitored natural attenuation (MNA) for portions of the contaminated groundwater, followed by institutional controls until cleanup levels are met for unrestricted use. As noted in the 200-UP-1 OU interim ROD, no treatment technology for iodine-129 had been found that could achieve the drinking water standard (DWS) of 1 pCi/L for the iodine-129 concentrations present in the 200-UP-1 OU groundwater. Therefore, the 200-UP-1 OU interim ROD specified hydraulic containment of the iodine-129 plume, update of the conceptual model for iodine-129, and further evaluation of potentially applicable iodine-129 treatment technologies. The 200-UP-1 OU interim ROD further stated that in the event a viable treatment technology is not available, the use of a technical impracticability (TI) waiver may need to be considered as part of the final remedy and that this information be gathered concurrently with the technology evaluation. Hence, this report provides information relevant to a TI waiver consideration on the current federal 1 pCi/L DWS for iodine-129 in the 200-UP-1 groundwater OU of the Hanford Site.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Nucleon Charges from 2+1+1-flavor HISQ and 2+1-flavor clover lattices

Precise estimates of the nucleon charges g A , g S and g T are needed in many phenomenological analyses of SM and BSM physics. In this talk, we present results from two sets of calculations using clover fermions on 9 ensembles of 2+1+1-flavor HISQ and 4 ensembles of 2+1-flavor clover lattices. In addition, we show that high statistics can be obtained cost-effectively using the truncated solver method with bias correction and the coherent source sequential propagator technique. By performing simulations at 4–5 values of the source-sink separation t sep , we demonstrate control over excited-state contamination using 2- and 3-state fits. Using the high-precision 2+1+1-flavor data, we perform a simultaneous fit in a, M π and M π L to obtain our final results for the charges.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Synthesis of High Surface Area VS2 for Nitrogen Reduction

Ammonia synthesis from dinitrogen provides a critical chemical feedstock to agriculture worldwide. The dominant process for ammonia synthesis is the Haber-Bosch process, which is fossil-fuel dependent and energy intensive. The electrochemical nitrogen reduction reaction (NRR) could provide a more environmentally friendly route to industrial ammonia synthesis. We have worked to realize electrochemical NRR by developing transition metal dichalcogenide NRR catalysts. In the first part of this presentation, a VS2-based NRR electrocatalyst, which has shown promising activity and selectivity, will be presented. The synthesis of this VS2-based catalyst is straightforward and results in few-layer VS2 or VSx, (x < 2) nanoflakes. Additionally, the proposed mechanism of NRR on VS2 will be discussed, and we will discuss DFT simulation of NRR on VS2 and MoS2 as well as planned in-situ Raman experiments to probe this mechanism. In the second part of this presentation, we will share several lessons learned during our early NRR research including important points of electrochemical cell design and experimental controls to reduce environmental ammonia contamination of experiments. Finally, we will address areas of opportunity for electrochemical NRR.

dichalcogenide↗
DOE OSTI2016

Lateral Gene Transfer in a Heavy Metal-Contaminated-Groundwater Microbial Community

ABSTRACT Unraveling the drivers controlling the response and adaptation of biological communities to environmental change, especially anthropogenic activities, is a central but poorly understood issue in ecology and evolution. Comparative genomics studies suggest that lateral gene transfer (LGT) is a major force driving microbial genome evolution, but its role in the evolution of microbial communities remains elusive. To delineate the importance of LGT in mediating the response of a groundwater microbial community to heavy metal contamination, representative Rhodanobacter reference genomes were sequenced and compared to shotgun metagenome sequences. 16S rRNA gene-based amplicon sequence analysis indicated that Rhodanobacter populations were highly abundant in contaminated wells with low pHs and high levels of nitrate and heavy metals but remained rare in the uncontaminated wells. Sequence comparisons revealed that multiple geochemically important genes, including genes encoding Fe 2+ /Pb 2+ permeases, most denitrification enzymes, and cytochrome c 553 , were native to Rhodanobacter and not subjected to LGT. In contrast, the Rhodanobacter pangenome contained a recombinational hot spot in which numerous metal resistance genes were subjected to LGT and/or duplication. In particular, Co 2+ /Zn 2+ /Cd 2+ efflux and mercuric resistance operon genes appeared to be highly mobile within Rhodanobacter populations. Evidence of multiple duplications of a mercuric resistance operon common to most Rhodanobacter strains was also observed. Collectively, our analyses indicated the importance of LGT during the evolution of groundwater microbial communities in response to heavy metal contamination, and a conceptual model was developed to display such adaptive evolutionary processes for explaining the extreme dominance of Rhodanobacter populations in the contaminated groundwater microbiome. IMPORTANCE Lateral gene transfer (LGT), along with positive selection and gene duplication, are the three main mechanisms that drive adaptive evolution of microbial genomes and communities, but their relative importance is unclear. Some recent studies suggested that LGT is a major adaptive mechanism for microbial populations in response to changing environments, and hence, it could also be critical in shaping microbial community structure. However, direct evidence of LGT and its rates in extant natural microbial communities in response to changing environments is still lacking. Our results presented in this study provide explicit evidence that LGT played a crucial role in driving the evolution of a groundwater microbial community in response to extreme heavy metal contamination. It appears that acquisition of genes critical for survival, growth, and reproduction via LGT is the most rapid and effective way to enable microorganisms and associated microbial communities to quickly adapt to abrupt harsh environmental stresses.

59 BASIC BIOLOGICAL SCIENCES↗