A5085834581- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Ionosphere and magnetosphere dynamics
- Radioactive element chemistry and processing
- Radioactive contamination and transfer
- Heavy metals in environment
- Advanced Battery Materials and Technologies
- Mercury impact and mitigation studies
- Geochemistry and Elemental Analysis
- Advanced battery technologies research
- Membrane-based Ion Separation Techniques
- Phosphorus and nutrient management
- Membrane Separation Technologies
- Heavy Metal Exposure and Toxicity
- Geochemistry and Geologic Mapping
- Atmospheric and Environmental Gas Dynamics
- Soil Carbon and Nitrogen Dynamics
- Crystallization and Solubility Studies
- Adsorption and biosorption for pollutant removal
- Arsenic contamination and mitigation
- X-ray Diffraction in Crystallography
- Geological and Geochemical Analysis
- Iron-based superconductors research
- Advancements in Battery Materials
- Groundwater and Isotope Geochemistry
SLAC National Accelerator Laboratory
2017-2025
Stanford Synchrotron Radiation Lightsource
2014-2024
Fermi National Accelerator Laboratory
2023
Menlo School
2023
Los Alamos National Laboratory
2018-2019
Stanford University
2014-2017
University of California, Berkeley
2011-2014
Lawrence Berkeley National Laboratory
2014
Babeș-Bolyai University
2014
Woods Hole Oceanographic Institution
2006-2007
Uranium is an important carbon-free fuel source and environmental contaminant that accumulates in the tetravalent state, U(IV), anoxic sediments, such as ore deposits, marine basins, contaminated aquifers. However, little known about speciation of U(IV) low-temperature geochemical environments, inhibiting development a conceptual model U behavior. Until recently, was assumed to exist predominantly sparingly soluble mineral uraninite (UO2+x) sediments; however, studies now show this not often...
By using coordinating anions such as acetate, a water-in-salt-like coordination environment of Zn ions is achieved in relatively dilute conditions, leading to prolonged and efficient cycling zinc metal anodes.
Evaluating the nature of chemical bonding for actinide elements represents one most important and long-standing problems in science. We directly address this challenge contribute a Cl K-edge X-ray absorption spectroscopy relativistic density functional theory study that quantitatively evaluates An–Cl covalency AnCl62– (AnIV = Th, U, Np, Pu). The results showed significant mixing between 3p- AnIV 5f- 6d-orbitals (t1u*/t2u* t2g*/eg*), with showing more pronounced covalent than 5f-orbitals....
Applications of aqueous zinc batteries for grid-scale energy storage are limited by their poor reversibility and the competing water splitting reaction. The recent invention a water-in-salt (WIS) electrolyte concept provides new route enabling stable highly reversible battery chemistry. In present work, mixed bis(trifluoromethane sulfonyl)imide (Zn(TFSI)2) LiTFSI WIS was studied using X-ray total scattering, absorption, Fourier transform infrared spectroscopy in conjunction with classical...
Lithium–sulfur (Li-S) batteries with high energy density and low cost are promising for next-generation storage. However, their cycling stability is plagued by the solubility of lithium polysulfide (LiPS) intermediates, causing fast capacity decay severe self-discharge. Exploring electrolytes LiPS has shown results toward addressing these challenges. here, we report that moderate more effective simultaneously limiting shuttling effect achieving good Li-S reaction kinetics. We explored a...
We measured the mercury (Hg) in groundwater, aquifer sediments, and surface water Waquoit Bay (Massachusetts) found that this toxic metal (range: <3.2−262 pM) was being released within subterranean estuary, with similarly high levels 18−256 waters of bay. None dissolved species (DOC, chloride, Fe) normally observed to influence Hg partitioning correlated well concentrations. It hypothesized part due variable loading time space onto sands combination seasonality groundwater flow through...
Mercury (Hg) is a toxicant of global concern that accumulates in organisms as methyl Hg. The production Hg by anaerobic bacteria may be limited anoxic sediments the sequestration divalent [Hg(II)] into solid phase or formation elemental [Hg(0)]. We tested hypothesis nanocrystalline mackinawite (tetragonal FeS), which abundant where methylated, both sorbs and reduces Hg(II). Mackinawite suspensions were equilibrated with dissolved Hg(II) batch reactors. Examination using LIII-edge extended...
A major chemical challenge facing implementation of 225Ac in targeted alpha therapy—an emerging technology that has potential for treatment disease—is identifying an chelator is compatible with vivo applications. It unclear how to tailor a Ac binding because coordination chemistry poorly defined. Most inferred from radiochemical experiments carried out on microscopic scales. Of the few compounds have been characterized spectroscopically, success only reported simple inorganic ligands. Toward...
Organo-mineral and organo-metal associations play an important role in the retention accumulation of soil organic carbon (SOC). Recent studies have demonstrated a positive correlation between calcium (Ca) SOC content range types. However, most these focused on soils that contain carbonate (pH > 6). To assess importance Ca-SOC lower pH soils, we investigated their physical chemical interaction grassland Point Reyes National Seashore (CA, USA) at spatial scales. Multivariate analyses our bulk...
Mackinawite is a naturally-occurring layer type FeS mineral well-known to be important in biogeochemical cycles and, more recently, the development of microbial fuel cells. Conflicting results have been published as magnetic properties this mineral, with M\"ossbauer spectroscopy indicating no ordering and density functional theory predicting an antiferromagnetic ground state, similar Fe-based high-temperature superconductors which it isostructural for known that magnetism suppressed by...
Cm<sup>III,</sup>Am<sup>III</sup>, and Ac<sup>III</sup>have been characterized by solution L<sub>3</sub>-edge X-ray absorption spectroscopy as a function of nitric acid concentration. This enabled the first experimental determination Cm Ac nitrate distances.
Uranium contamination threatens the availability of safe and clean drinking water globally. This toxic element occurs both naturally as a result mining ore-processing in alluvial sediments, where it accumulates tetravalent U [U(IV)], form once considered largely immobile. Changing hydrologic geochemical conditions cause to be released into groundwater. Knowledge chemical form(s) U(IV) is essential understand release mechanism, yet relevant species are poorly characterized. There growing...
Groundwater uranium (U) concentrations have been measured above the U.S. EPA maximum contaminant level (30 μg/L) in many aquifers, including areas not associated with anthropogenic contamination by milling or mining. In addition to carbonate, nitrate has correlated groundwater two major aquifers. However, date, direct evidence that mobilizes naturally occurring U from aquifer sediments presented. Here, we demonstrate influx of high-nitrate porewater through High Plains alluvial silt bearing...
Residential lead (Pb) exposure is of critical concern to families globally as Pb promotes severe neurological effects in children, especially those less than 5 years old, and no blood level deemed safe by the US Center for Disease Control. House dust soils are commonly thought be important sources exposure. Probing relationship between house soil understanding residential exposure, bioavailability highly influenced and/or species. We investigated paired collected from homes built before 1978...
Abstract In biogeochemical phosphorus cycling, iron oxide minerals are acknowledged as strong adsorbents of inorganic and organic phosphorus. Dephosphorylation is attributed only to biological processes, but oxides could also catalyze this reaction. Evidence abiotic catalysis has relied on monitoring products in solution, thereby ignoring both catalysts adsorbents. Here we apply high-resolution mass spectrometry X-ray absorption spectroscopy characterize dissolved particulate species,...
Iron oxides, which are documented phosphorus (P) sinks as adsorbents, have been shown to catalyze organic P dephosphorylation, implicating these minerals catalytic traps in cycling. However, quantitative evaluation of this abiotic catalysis is lacking. Here, we investigated the dephosphorylation kinetics eight ribonucleotides, with different nucleobase structures and stoichiometry, reacting common iron oxides. X-ray absorption spectroscopy determined that 0–98% mineral-bound was recycled...
Ion exchange shows promise for recovering phosphate from wastewater as value-added products, but requires high selectivity to compete with conventional treatment. Hybrid anion (HAIX) resins, which contain non-selective basic functional groups and selective iron oxide nanoparticles (FeOnp), can effectively remove wastewater. However, knowledge gaps remain regarding the mechanisms of influence competing ions, hindering needed efforts model adsorption dynamics design scalable processes varying...
Biogeochemically modified pore waters from subterranean estuaries, defined as the mixing zone between freshwater and saltwater in a coastal aquifer, are transported to through submarine groundwater discharge (SGD). SGD has been shown impact perhaps global trace metal budgets. The focus of this study was investigate biogeochemical processes that control arsenic cycling estuaries. Total dissolved As, well suite other metals nutrients, were measured series wells sediment cores at head Waquoit...
Virus removal from water using microfiltration (MF) membranes is of great interest but remains challenging owing to the membranes' mean pore sizes typically being significantly larger than most viruses. We present microporous grafted with polyzwitterionic brushes (N-dimethylammonium betaine) that combine bacteriophage in range ultrafiltration (UF) permeance MF membranes. Brush structures were two steps: free-radical polymerization followed by atom transfer radical (ATRP). Attenuated total...
Biochars can remove potentially toxic elements, such as inorganic mercury [Hg(II)] from contaminated waters. However, their performance in complex water matrices is rarely investigated, and the combined roles of natural organic matter (NOM) ionic composition removal Hg(II) by biochar remain unclear. Here, we investigate influence NOM major ions chloride (Cl–), nitrate (NO3–), calcium (Ca2+), sodium (Na+) on a wood-based (SWP700). Multiple sorption sites containing sulfur (S) were located...
Aquifers in the Upper Colorado River Basin (UCRB) exhibit persistent uranium (U) groundwater contamination plumes originating from former ore processing operations. Previous observations at Rifle, Colorado, have shown that fine grained, sulfidic, organic-enriched sediments accumulate U its reduced form, U(IV), which is less mobile than oxidized U(VI). These sediment bodies can subsequently act as secondary sources, releasing back to aquifer. There a need understand if U(IV) accumulation...