Recent lbnl_ees_eg items

In situ quantification of fracture slip induced by hydraulic injections in a deep borehole: A comparison of two different borehole techniques

Wed, 13 May 2026 00:00:00 +0000

In situ measurements of fracture deformation during fluid injection are rare, yet essential for understanding the mechanical response of fractured rock. In this study, we evaluate the reliability of two methods by comparing their slip vector estimates: high-resolution borehole acoustic televiewer images captured before and after injection tests, and displacement data from a three-component borehole deformation probe recorded during the injections. Acoustic televiewer images capture only final in-plane displacement, whereas three-component borehole deformation measurements provide full 3D, transient fracture movement. Four injection tests in a fractured granitic rock mass along an inclined borehole at the Bedretto Underground Laboratory (Switzerland), beneath more than 1100 m of overburden, were analyzed. The two methods yielded consistent kinematics and comparable slip magnitudes, typically in the range of 0.2 – 0.6 mm. Angular differences between estimated slip directions...

Geomechanical properties of the Meletta sandstone - the high-temperature heat storage reservoir rock of DeepStor

Wed, 13 May 2026 00:00:00 +0000

The DeepStor project aims at storing excess heat at temperatures up to 140 °C in the depleted Leopoldshafen oil field at a depth of about 1300 m. In order to gain knowledge on the target horizons, the different layers of the Meletta sandstone, samples cored in a block retrieved in a quarry near Nussloch where the Meletta sandstone outcrops were studied. Several petrophysical properties were investigated including mineralogy, porosity, permeability, thermal conductivity, P- and S-wave velocities and quality factor. A mechanical study focused on compressive strength under uniaxial and triaxial stress conditions, tensile strength, critical pressure and stress-dependence of physical properties. Our results show that the Meletta sandstone is heterogeneous, anisotropic, mechanically weak, stress-sensitive and prone to water weakening. Petrophysical measurements on few Meletta sandstone cores retrieved in boreholes at about 1250 m depth showed that the outcrop samples are significantly...

Model‐Based Interpretation of Solute Exports and Carbon Partitioning During Shale Weathering in a Mountainous Hillslope

Fri, 24 Apr 2026 00:00:00 +0000

Abstract The weathering of sedimentary rocks in high‐elevation catchments influences freshwater quality and the global carbon cycle. While individual biogeochemical mechanisms involved in this process are relatively well understood, quantifying their contributions to solute export and carbon fluxes under natural, transient conditions remains challenging. Here, we implement a numerical multidimensional and multiphase model to simulate coupled hydrological and biogeochemical processes in a shale‐underlain, snow‐dominated hillslope in the Rocky Mountains, Colorado. The model captures the dynamic interplay between soil respiration, mineral weathering, and climate‐driven hydrological forcing, reproducing observed soil CO 2 dynamics, groundwater chemistry, and subsurface flow. Our results reveal that seasonal snowmelt enhances carbonate weathering by promoting the infiltration of CO 2 ‐rich water to depth, while pyrite oxidation is primarily sensitive to low water saturation that facilitates...

Sequential Fracture Activation and Stress Evolution During EGS Stimulation at Utah FORGE Revealed by Waveform Cross‐Correlation

Fri, 24 Apr 2026 00:00:00 +0000

Abstract Mapping fracture networks in Enhanced Geothermal Systems (EGS) is essential for optimizing reservoir performance, yet complex fracture evolution during stimulation remains difficult to resolve. This study examines the evolution of microseismicity and fracture networks during stage 3 of the 2022 EGS stimulation at the Utah Frontier Observatory for Research in Geothermal Energy site. We map the fracture network represented by 20 clusters of seismic events identified by waveform similarities with cross‐correlation. We characterize their geometric properties such as strike, dip, length, and width, and analyze the time evolution of activated fractures. The results reveal a systematic fracture evolution: early activation of pre‐existing natural fractures, complex network development during peak injection, and continued activation of less favorably oriented fractures post‐injection. Magnitude calibration using the Principal Component Analysis of cross‐correlated waveforms improves...

Organic Colloid Composition in Variable-Redox Porewaters within a Mountainous Floodplain

Fri, 24 Apr 2026 00:00:00 +0000

Redox gradients, often driven by changes in sediment moisture levels in porous, heterogeneous groundwater systems, create dynamic conditions that may promote the production and transport of colloids within natural waters. While much research has focused on the inorganic composition of colloids, the organic composition remains less well understood. Organic matter (OM) in colloids may associate with minerals, complex metal ions, and serve as an electron donor for microbial respiration; therefore, its composition is of high interest. We examined the composition of porewater OM along a redox gradient in a riparian soil located along the Slate River in Crested Butte, Colorado, USA as a function of depth (90, 130, 200, and 350 cm below ground surface). All depths were oxic to suboxic, except 200 cm, where the products of iron and sulfate reduction were observed concomitant with an increase in dissolved and/or colloidal OM, pH, alkalinity, and conductivity. We investigated the composition...

Production of Agricultural Water and Nutrients from Brackish Water Sources

Tue, 21 Apr 2026 00:00:00 +0000

Arid agricultural regions worldwide face critical challenges of water scarcity and soil salinization, significantly reducing crop production. This study investigates a circular economy and systems approach to desalination with nutrient recovery (DNR), economically producing irrigation-quality water while recovering valuable nutrients from brackish waters. A preliminary design tool for sizing the calcium (Ca) and magnesium (Mg) hardness ion removal component was developed through laboratory testing of the cation exchange (CIX) process. Key findings include (1) KCl and NaCl salts effectively regenerated the CIX resin, reducing and facilitating recovery of scale-causing Ca and Mg ions by greater than 99.5% to approximately 1 mg/L as CaCO3. KCl benefits agriculture and the environment relative to traditional NaCl regenerant as K can be recovered, along with the Ca and Mg, and used locally as plant nutrients, reducing fertilizer production/importation and waste generation. (2) The...

Inference of pile capacity from distributed strain sensing via PDE-constrained optimization

Thu, 16 Apr 2026 00:00:00 +0000

Distributed fiber-optic sensing (DFOS) provides high-resolution, continuous strain measurements along piles, offering new opportunities for detailed assessment of pile quality and soil–structure interaction. However, field DFOS data often exhibit oscillatory patterns traditionally treated as noise, obscuring actual physical insights into variations in pile radius and shaft friction for example. To address this challenge, we propose a numerical framework that formulates the strain-matching problem as a partial differential equation constrained optimization (PDECO) problem. This approach not only infers pile quality and soil response profiles from noisy DFOS data, but also rigorously enforces mechanical equilibrium at each loading step, yielding a physically consistent interpretation of high-resolution distributed measurements. Numerical benchmarks and application to a DFOS-monitored pile load test demonstrate that the PDECO scheme is robust to measurement noise and capable of reconstructing...

A Boundary Element Model for Assessing Large‐Scale Pressurization in Faulted Geological Storage Systems

Tue, 14 Apr 2026 00:00:00 +0000

Assessing large‐scale pressurization at the regional scale—a possible outcome of large subsurface storage applications such as wastewater injection and geological carbon sequestration—presents significant computational challenges. These challenges are particularly pronounced when accounting for complex geologic structures with multiple reservoir and caprock layers, fault zones, and wells. This study introduces a computationally efficient model that integrates single‐phase semi‐analytical solutions with a boundary element (BE) approach. The model simulates pressure propagation in multilayered 3D systems, including vertical faults, caprock, basement, and confining units. We apply this new model to a representative scenario involving CO2 injection near a partially sealing fault with verification against an independent two‐phase flow model. Results demonstrate that our model accurately captures far‐field pressure responses and that, outside the CO2 plume zone, pressure predictions...

Insights into the hydro-mechanical behavior of a decimeter-scale fracture using the mini-SIMFIP probe

Mon, 13 Apr 2026 00:00:00 +0000

ABSTRACT: Understanding hydro-mechanical couplings in fractured rocks is essential for predicting the rock mass response during high-pressure fluid injection, including the stimulation of enhanced geothermal systems. However, fluid-driven fracture dislocations are challenging to measure due to the need for local displacement data at high fluid pressures. In this study, fluid-driven displacement across a decimeter-scale laboratory fracture was investigated using the mini-SIMFIP (step rate injection method for fracture in-situ properties) probe, which is a smaller version of the SIMFIP tool (Guglielmi et al., 2014). The mini-SIMFIP probe is able to resolve the full 3D displacement vector of a fracture. The probe was installed in one of two boreholes across a decimeter-scale saw-cut granite fracture. Two pressure step injection tests were conducted under the same isotropic stress conditions. By varying injection between the boreholes, we estimated the aperture profile across the...

Why Firn Quakes

Fri, 10 Apr 2026 00:00:00 +0000

Abstract Snow dampens sounds, but anecdotal reports concisely describe audible propagating collapse events—firnquakes—in Antarctic and Arctic snowfields. We propose combining granular and continuum mechanics to form a testable theory for conditioning, triggering, and propagation of firnquakes consistent with scarce data. A central condition for collapse events is unconsolidated firn at depth. As firn grains compact, stresses are transmitted along force chains which carry the overburden and transition into a continuous medium by pressure sintering. This granular legacy creates solid‐like supports of denser layers that keep the material below unconsolidated. Dynamic amplification triggers local brittle failure of the supports, which induces a cascade of collapse propagation. Using bulk density from ice cores as proxy for stiffness, we find the flexural wave speed by collapsing supports matches the recorded firnquake velocities on the order of 100 m/s. Our theory is to be tested...

International Collaboration Activities in Geologic Disposal R&D: FY25 Progress Report Spent Fuel and High-Level Waste Disposition

Thu, 2 Apr 2026 00:00:00 +0000

International Collaboration Activities in Geologic Disposal R&D: FY25 Progress Report Spent Fuel and High-Level Waste Disposition

Coupling geophysical, geological, geochemical and mineralogical assessments to exlamine preferential contaminant transport pathways in interbedded fractured bedrock

Thu, 2 Apr 2026 00:00:00 +0000

This study shows that a multi-faceted approach, combining borehole geophysical logging and surface seismic P-wave first-arrival tomography with confirmatory coring, well installation, and chemical and mineralogical analysis, is effective for identifying difficult-to-locate preferential contaminant transport pathways in deeper fractured bedrock. Seismic tomography detected porous 10-20m wide elongated fractured conduits that allow acidic groundwater contaminated with uranium (U) and nitrate (NO3 -) to migrate within interbedded shale-limestone bedrock over 1000m from a former disposal facility (S-3 Ponds site) located at the DOE Y-12 National Security Complex in Tennessee (USA). Conventional drilling techniques would easily miss these conduits because they are oriented parallel with fractured bedding planes. Synchrotron analysis of aquifer solids revealed that >95% of the U is hexavalent (UVI). This uranyl (UO 2 2+ ) species is coordinated with carbonate, iron oxide, silicate...

Microstructure of amide-functionalized polyethylenes determined by NMR relaxometry

Tue, 31 Mar 2026 00:00:00 +0000

NMR relaxation studies reveal that pendant amidyl groups on polyethylenes alter microstructure and chain dynamics. These groups are localized in the rigid amorphous fraction of the polymers and lead to changes in bulk properties.

Thermo-hydro-mechanical analysis of subsurface ice-based thermal energy storage

Mon, 30 Mar 2026 00:00:00 +0000

Ice-based thermal energy storage systems are widely utilized for cooling and managing peak electrical demand globally, offering daily or weekly storage capabilities for both individual homes and larger office buildings. However, scaling these systems for district-level cooling or integrating them with renewable energy sources presents challenges, especially in accommodating larger volumes and addressing seasonal storage requirements in densely populated urban areas. This paper proposes a novel solution by evaluating subsurface ice-based thermal energy storage, in which the underground is subjected to seasonal freeze/thaw cycles. However, these cycles may influence ground behavior, affecting pore pressure and inducing ground movement. To systematically investigate these challenges, we enhance the TOUGH-FLAC simulator by integrating water/ice phase change capabilities and updating the effective stress–strain constitutive relation. Both modifications are validated against analytical...

Depth of nutrient uptake by deep-rooted plants is regulated by water availability

Mon, 30 Mar 2026 00:00:00 +0000

The capacity of some plants to access water and nutrients at depths greater than one meter is a critical functional trait that confers resistance to drought and impacts both belowground and shallow soil processes. Here, we report water and strontium isotopic data from an alpine meadow transect showing the correlation between water and nutrient acquisition depths. The isotopic compositions of Sr (⁸⁷Sr/⁸⁶Sr ratio) and water in rock and soil, and in plant leaf tissues, reveal that deeper-rooted plants acquire a higher proportion of water, Sr, and cation nutrients that are derived from the saprolite, a zone of silicate weathering, than shallow-rooted grass. A three-decade dendrochemical record reveals that reductions of wet precipitation drive deep-rooted plants to acquire cation nutrients from deeper saprolite or bedrock regions. Thus, the depth of cation nutrient acquisition by deep-rooted plant species at this site is tightly coupled with, and likely determined...

Real-Time GPU-Accelerated OFDR with an Integrated Auxiliary Interferometer

Wed, 25 Mar 2026 00:00:00 +0000

A GPU-accelerated optical frequency domain reflectometry (OFDR) system with an improved integrated auxiliary interferometer is proposed. Unlike conventional approaches that require separate auxiliary interferometers and multiple detection channels, the proposed OFDR system embeds this functionality directly into the signal via an intentional beat component. This enables self-calibration of laser nonlinearity while maintaining a cost-effective hardware configuration. Building on this simplified configuration, the system leverages GPU acceleration with an NVIDIA RTX 4070 Ti to achieve real-time performance, delivering high-throughput signal processing for continuous OFDR interrogation. The signal processing pipeline comprises signal capture, resampling for nonlinearity compensation, and frequency shift computation, all optimized for parallel execution. Hardware benchmarking demonstrates substantial acceleration over CPU implementations, achieving up to a 45× speedup for resampling...

Real-time well integrity monitoring in underground gas storage wells using distributed temperature and strain sensing: a field demonstration

Fri, 20 Mar 2026 00:00:00 +0000

This article presents the first successful field demonstration of a combined distributed temperature and strain sensing (DTSS) system installed directly on newly replaced tubing in a 5400-ft-deep operational underground gas storage well. The DTSS system uses a single optical fiber to monitor temperature and strain in real-time, providing a cost-effective solution for long-term well integrity assessment. In this study, the strain–stress correlation of the tubing—representative of material behavior analysis—is investigated as a potential method for monitoring tubing integrity throughout its lifetime. Moreover, the DTSS system’s capability to support both continuous and discrete monitoring is evaluated by comparing future data with historical records, enabling the early detection of issues such as material fatigue, corrosion, or deformation. Overall, the work examines the effectiveness and scalability of the DTSS system for real-time monitoring of well operations and integrity in...

Coupled Thermo-Hydrological-Mechanical-Chemical Behavior of Anisotropic Granite for Geologic Disposal of High-Level Radioactive Waste: A Core-Scale Laboratory Investigation

Thu, 19 Mar 2026 00:00:00 +0000

The coupled thermo-hydrological-mechanical-chemical (THMC) behavior of rock within an Excavation Damaged Zone (EDZ) is critical for the safety and long-term performance of a geological repository for high-level radioactive wastes. While many laboratory experiments have been conducted to investigate EDZ rocks, the flow and deformation characteristics resulting from anisotropic rock textures and microcrack distribution under triaxial loading and elevated temperatures remain poorly understood. Particularly, cracks at various scales serve as fast paths for fluid flow and solute transport and present as focal points of mechanical weakness, which complicate the coupled THMC processes in anisotropic EDZ rocks and challenge modeling predictions. In this study, a series of core-scale experiments was conducted on three granite samples under repository-relevant conditions. These rock samples were obtained from the Grimsel Underground Research Laboratory (URL), featured by anisotropic minerals...

3D Deep Learning Joint Inversion of Active Seismic Full Waveform and Passive Seismic Traveltime Data for Reservoir Imaging and Uncertainty Quantification

Thu, 19 Mar 2026 00:00:00 +0000

ABSTRACT We present deep learning (DL) networks for three‐dimensional (3D) joint inversion of active seismic full waveform and passive seismic traveltime data to image reservoirs and their properties and quantify imaging uncertainties. Active seismic full‐waveform data can provide high‐resolution monitoring images but are collected only intermittently because of their high acquisition cost. In contrast, passive seismic data can be gathered at relatively low cost between regular active surveys, although their imaging quality can be compromised by factors such as low signal‐to‐noise ratios and limited ray coverage of the target. Although these datasets are routinely acquired together at CO 2 storage sites, their combined inversion within a 3D DL framework has not been previously demonstrated. To our knowledge, this is the first study to address this gap, combining the strength of both data types. For efficient data storage and DL training with large 3D seismic datasets, we use...

A Method for Rapid and Precise Triple Oxygen Isotope Measurements via High-Temperature Conversion to CO Followed by Nickel-Catalyzed CO to CO2 Conversion and Laser Spectroscopy

Fri, 13 Mar 2026 00:00:00 +0000

Triple oxygen isotopic compositions (¹⁶O, ¹⁷O, ¹⁸O) have conventionally been measured via isotope ratio mass spectrometry using O₂ as an analyte. Conversion of sample oxygen to O₂ typically utilizes fluorination chemistry or catalytic equilibration between CO₂ and O₂. Recently, laser spectroscopy has become a viable alternative for triple oxygen isotope (Δ'¹⁷O) measurements due to its ease and rapid throughput. Laser spectrometers are currently available for Δ'¹⁷O analysis of either H₂O or CO₂ as the analyte gas. So far, these instruments have been used to measure Δ'¹⁷O of water, carbonate (CO₂ liberated by acid digestion), and atmospheric CO₂ samples. We present a new method for high-precision Δ'¹⁷O analysis of CO₂ via tunable infrared laser direct absorption spectroscopy that is compatible with a wider...

Determining the extent of potential fugitive fluid migration from geologic carbon storage in hydrocarbon-bearing reservoirs: Insights from one-dimensional numerical modeling

Wed, 11 Mar 2026 00:00:00 +0000

Numerical modeling of Geologic Carbon Sequestration in permeable reservoirs initially containing hydrocarbons is conducted using the multi-phase, multi-component thermohydrologic simulator TOGA (TOUGH Oil, Gas, Aqueous; TOUGH stands for Transport Of Unsaturated Groundwater and Heat), to determine how phase and composition of the original fluids influence the extent of the zone where upward fugitive fluid migration could potentially occur, denoted Rf . The area within Rf comprises regions of substantially elevated pressure and free-phase CO2 saturation, where a breach in reservoir sealing capacity would lead to upward fugitive fluid migration. The model examines the conditions within the storage reservoir that could lead to fugitive flow, but does not model the fugitive flow itself. A one-dimensional radial model of the storage reservoir is used, and three initial phase conditions are considered: single-phase aqueous, two-phase gas-aqueous, and three-phase oil-gas-aqueous. Components...

Autonomous elemental characterization enabled by a low cost robotic platform built upon a generalized software architecture

Wed, 11 Mar 2026 00:00:00 +0000

A generalized software architecture based on dual-layer action servers facilitates the development of autonomous experimental systems. An autonomous elemental characterization platform serves as an example of such a system. Despite the rapidly growing applications of robots in industry, the use of robots to automate tasks in scientific laboratories is less prolific due to the lack of generalized methodologies and the high cost of hardware. This paper focuses on the automation of characterization tasks necessary for reducing cost while maintaining generalization and proposes a software architecture for building robotic systems in scientific laboratory environments. A dual-layer (Socket.IO and ROS) action server design is the basic building block, which facilitates the implementation of a web-based front end for user-friendly operation and the use of ROS Behavior Trees for convenient task planning and execution. A robotic platform for automating mineral and material sample characterization...

Strain release through hydrogen bond–mediated layer twisting

Wed, 4 Mar 2026 00:00:00 +0000

Strain engineering, enabling the precise control over structure and functional properties, is a key strategy for the design of advanced materials. However, the mechanisms governing strain evolution and release at the nanoscale remain largely unexplored. In this study, we leverage in situ heating transmission electron microscopy and synchrotron x-ray spectroscopy to investigate the strain relaxation pathways of boehmite (γ-AlOOH) at 575 kelvin by revealing real-time structural dynamics. Through tracking the moiré pattern evolution, we identify distinct strain release mechanisms, including layer twisting, defect formation, and domain restructuring. Our neural network potential calculations reveal that energy fluctuations at small twist angles are dominated by an interference-like interaction modulation of hydrogen bonds between boehmite interlayers, with metastable twisted structures corresponding to local minima of the potential energy landscape. This work establishes a previously...

Coupled geomechanical investigation of depletion-induced fault reactivation

Tue, 3 Mar 2026 00:00:00 +0000

Fault reactivation during subsurface fluid production pose significant challenges to safe and sustainable resource extraction. This study presents a three-dimensional coupled geomechanical framework to investigate the processes driving fault reactivation, capturing the interactions between reservoir dynamics and geomechanical responses. Verification against theoretical estimations based on linear poroelasticity confirms the model's capacity in representing reservoir background stress responses. However, the study reveals that relying solely on background stress states can underestimate or overestimate fault reactivation potential, emphasizing the importance of including localized stress perturbations such as differential compaction and stress redistribution. Applied to a fault (M1) inspired by the geological characteristics of the Groningen field, the model shows slip initiation at 2965 m depth with 16.0 MPa depletion, aligning with field observations where seismicity...

Modeling glass degradation and release of radionuclides from vitrified waste for performance assessment simulations

Thu, 26 Feb 2026 00:00:00 +0000

The release of radionuclides initially encapsulated in a slowly degrading solid waste form and contained in an eventually corroding canister defines the source term for numerical simulations for the assessment of a geologic repository for high-level radioactive waste. While the details of waste degradation, canister corrosion, and dissolution and mobilization of the radionuclides in pore water include complex chemical reaction and transport processes that are coupled to the thermal, hydrological, microbiological, and mechanical conditions in the repository, the source-term model suitable for use in a numerical performance assessment model should be a defensible abstraction of these mechanisms. We developed a radiological source-term model and implemented it into a non-isothermal flow and transport simulator. While the proposed source-term model is applicable to various waste forms, canister systems, and disposal concepts, we specifically considered radionuclide releases from vitrified...

Quantifying Earth's Topography: Steeper and Larger Than Projected in Digital Terrain Models

Tue, 24 Feb 2026 00:00:00 +0000

Abstract Grid‐ or pixel‐based models, used across various scientific disciplines from microscopic to planetary scales, contain an unquantified error that bias our interpretation of the data. The error is produced by projecting 3D data onto a 2D grid. For Digital Terrain Models (DTMs) the projection error affects all slope‐dependent topographic metrics, like surface area or slope angle. Due to the proportionality of the error to the cosine of the slope, we can correct for it. We quantify the error and test the correction using synthetic landscapes for which we have analytical solutions of their metrics. Application to real‐world landscapes in California, reveal the systematic underestimation of surface area by up to a third, and mean slope angles by up to 10° in steep topography in current DTMs. Correcting projection errors allow for true estimates of surface areas and slope distributions enabling physics‐based models of surface processes at any spatial scale. Plain Language Summary...

PhaseT3M: 3D imaging at 1.6 Å resolution via electron cryo-tomography with nonlinear phase retrieval

Wed, 11 Feb 2026 00:00:00 +0000

Electron cryo-tomography (cryo-ET) enables 3D imaging of complex, radiation-sensitive structures with molecular detail. However, image contrast from the interference of scattered electrons is nonlinear with atomic density and multiple scattering further complicates interpretation. These effects degrade resolution, particularly in conventional reconstruction algorithms, which assume linearity. Particle averaging can reduce such issues but is unsuitable for heterogeneous or dynamic samples ubiquitous in biology, chemistry, and materials sciences. Here, we develop a phase retrieval-based cryo-ET method, PhaseT3M. We experimentally demonstrate its application to an approximately 7 nm Co3O4 nanoparticle on an approximately 30 nm carbon substrate, achieving a maximum resolution of 1.6 Å, surpassing conventional limits using standard cryo-TEM equipment. PhaseT3M uses a multislice model for multiple scattering and Bayesian optimization for alignment and computational aberration correction,...

A ModEx Framework for Watershed Subsurface Investigation With Limited Geophysical Data Using Machine Learning and Hydrologic Modeling

Thu, 5 Feb 2026 00:00:00 +0000

Abstract Subsurface heterogeneity influences watershed hydrology strongly but remains difficult to characterize at catchment scales with sparse and costly field data. Geophysical surveys such as electromagnetic induction (EMI) provide local spatial subsurface images yet scaling them to watershed scales and converting EMI‐derived resistivity into hydraulic properties remains a challenge. We present a Model–Experiment (ModEx) framework that integrates limited EMI data with machine learning (ML) and hydrologic modeling to improve process representation and guide field investigations. Sparse EMI surveys were scaled to the catchment scale using a Random Forest model, and the resulting resistivity fields were combined with nearby borehole constraints to parameterize a hydrologic model. The EMI‐informed hydrological simulations improved predictions of streamflow sustained by subsurface flow and shallow saturation patterns. By combining EMI data and ML with hydrologic modeling, the ModEx...

SeaFOAM: A Year-Long DAS Deployment in Monterey Bay, California

Wed, 28 Jan 2026 00:00:00 +0000

Abstract Distributed acoustic sensing (DAS) is being explored in a variety of environments as a promising technology for the recording of seismic signals in dense array configurations. There is a particular interest for deploying DAS arrays on the ocean floor, presenting formidable challenges for conventional seismology. Taking advantage of the availability of a dark fiber on the Monterey Bay Accelerated Research System (MARS) 52 km offshore cable at Monterey Bay, California, in July 2022, we installed a DAS interrogator at the shore end of the cable with the intention of acquiring continuous data for a period of one year. Here, we describe the experiment and present examples of observations over the first six months of the deployment.

Benchmarking greenhouse gas emissions from US wastewater treatment for targeted reduction

Tue, 27 Jan 2026 00:00:00 +0000

Here, to assess the national climate impact of wastewater treatment and inform decarbonization, we assembled a comprehensive greenhouse gas inventory of 15,863 facilities in the contiguous USA. Considering location and treatment configurations, we modelled on-site CH4, N2O and CO2 production and emissions associated with energy, chemical inputs and solids disposal. Using Monte Carlo simulations, we estimated median national emissions at 47 million tonnes of CO2 equivalent per year, with on-site process CH4 and N2O emissions exceeding current government estimates by 41%. Treatment configurations with anaerobic digesters are responsible for 16 million tonnes of CO2 equivalent per year of fugitive methane, outweighing benefits achieved through on-site electricity generation. Systems designed for nutrient removal have the highest greenhouse gas emissions intensity, attributable to energy requirements and N2O production, demonstrating current trade-offs between meeting water quality...

Multi-omics reveals nitrogen dynamics associated with soil microbial blooms during snowmelt

Tue, 27 Jan 2026 00:00:00 +0000

Snowmelt triggers a soil microbial bloom and crash that affects nitrogen (N) export in high-elevation watersheds. The mechanisms underlying these microbial dynamics are uncertain, making soil nitrogen processes difficult to predict as snowpack declines globally. Here, integration of genome-resolved metagenomics, metatranscriptomics and metabolomics in a high-elevation watershed revealed ecologically distinct soil microorganisms linked across the snowmelt time-period by their unique nitrogen cycling capacities. The molecular properties and transformations of dissolved organic N suggested that degradation or recycling of microbial biomass provided N for biosynthesis during the microbial bloom. Winter-adapted Bradyrhizobia spp. oxidized amino acids anaerobically and had the highest gene expression for denitrification during the microbial bloom. A pulse of nitrate was driven by spring-adapted Nitrososphaerales after snowmelt, but dissimilatory nitrate reduction to ammonia (DNRA) gene...

The Role of Snowmelt and Subsurface Heterogeneity in Headwater Hydrology of a Mountainous Catchment in Colorado: A Model‐Data Integration Approach

Thu, 22 Jan 2026 00:00:00 +0000

Abstract Mountainous headwater streams are sustained by both snowmelt‐driven streamflow and groundwater discharge in the Upper Colorado River Basin. However, predicting headwater stream discharge magnitude and peak flow timing is challenging in mountainous terrains, where snowmelt rates vary with vegetation type and elevation, and heterogeneous subsurface physical properties influence groundwater storage and its release. We used a model‐data integration approach to investigate the roles of snowmelt and subsurface structure in stream discharge and groundwater level. We ran an ensemble of 100 integrated surface‐subsurface hydrologic models for a mountainous headwater catchment near Crested Butte, Colorado, USA. We also evaluated and calibrated these models against observed data sets, including snow depth measurements using distributed temperature probes, stream discharge, and groundwater levels. Calibration with multiple data sources using neural density estimators has further constrained...

Hydrology controls thermokarst and alters carbon cycling and methane emissions in peatlands near the southern limit of permafrost

Wed, 21 Jan 2026 00:00:00 +0000

Permafrost peatlands store vast amounts of frozen carbon across northern landscapes. When ground ice melts, surface subsidence produces thermokarst landforms that expand wetlands at the edges of permafrost plateaus. Thermokarst represents an accelerating climate feedback, but uncertainties remain about how ground ice, hydrology, and vegetation interact to shape landscape change and carbon fluxes. We extended the process-based model ecosys to simulate thermokarst dynamics in laterally coupled 2D transects at a well-characterized boreal peatland site in Canada’s Northwest Territories. After benchmarking against site observations, we varied ground ice content and hydrologic boundary conditions across ranges typical near the southern permafrost limit. Simulations revealed distinct degradation regimes governed by the elevation difference between the frost table and the external water table. Rates of lateral retreat, the thaw-driven encroachment of wetlands into adjacent plateaus, ranged...

A review of thermo-hydro-mechanical modeling of coupled processes in fractured rock: From continuum to discontinuum perspective

Tue, 20 Jan 2026 00:00:00 +0000

Coupled thermo-hydro-mechanical (THM) processes in fractured rock are playing a crucial role in geoscience and geoengineering applications. Diverse and conceptually distinct approaches have emerged over the past decades in both continuum and discontinuum perspectives leading to significant progress in their comprehending and modeling. This review paper offers an integrated perspective on existing modeling methodologies providing guidance for model selection based on the initial and boundary conditions. By comparing various models, one can better assess the uncertainties in predictions, particularly those related to the conceptual models. The review explores how these methodologies have significantly enhanced the fundamental understanding of how fractures respond to fluid injection and production, and improved predictive capabilities pertaining to coupled processes within fractured systems. It emphasizes the importance of utilizing advanced computational technologies and thoroughly...

High-Temperature Aquifer Thermal Energy Storage (HT-ATES) Projects in Germany and the Netherlands—Review and Lessons Learned

Thu, 15 Jan 2026 00:00:00 +0000

Aquifer thermal energy storage (ATES) is a concept that can help to address heating and cooling needs through the use of the subsurface as a seasonal thermal energy storage (STES) system. Over 2800 ATES systems have been deployed with storage temperatures typically below 25 °C and only a few with higher temperatures (>40 °C), which would increase the energy density and utility of the stored thermal fluids. Until now, only a few high-temperature aquifer thermal energy storage (HT-ATES) projects have been initiated and are still in operation. These HT-ATES projects have encountered a range of technical and non-technical challenges. This study reviews ten such projects: four in Germany and six in the Netherlands. The non-technical issues include public acceptance, a lack of regulatory framework for these systems, managing overlapping uses of the subsurface, managing changes with the providers and off-takers of thermal energy, and obtaining financing to implement these projects....

Phytoremediation potential of Nerium oleander and Salix alba for heavy metal removal in rock-amended soils: a natural and cost-effective approach

Thu, 15 Jan 2026 00:00:00 +0000

Enhanced weathering (EW) through the application of ground rock is a competitive carbon removal strategy. Adoption of this technology at a meaningful scale requires a systematic assessment of its long-term feasibility, especially with regard to soil quality from the application of rock amendments that contain varying levels of heavy metal (loid)s (HM) such as Cu, Ni, Cr, Co, and Pb. The potential accumulation of these metal (loid)s could be an unintended consequence of repeated large-scale EW applications, necessitating careful evaluation for use in croplands. This study explores the idea of using phytoremediation as a natural, low-cost means of remediating rock-amended soils. Specifically, we examined the ability of Nerium oleander and Salix alba species to remove HM from rock-amended soils in their tissues (i.e., leaves, stems, and roots). In this study, the relative abundance of HM accumulation in hyperaccumulator plants followed the order: Si > Rb > Cu > Sn > Cr...

Estimating Soil Thermal Inertia Profiles From the Passive Equilibration of a Temperature Probe

Wed, 14 Jan 2026 00:00:00 +0000

Abstract Knowledge of the distribution of soil thermal properties is important for understanding subsurface hydrological and biogeochemical processes. This study describes and evaluates quick thermal profiling (QTP), a new measurement technique aimed at providing rapid, depth‐resolved measurements of soil thermal inertia at numerous locations across the landscape. A cylindrical probe with temperature sensors at multiple depths is quickly inserted into the ground, and soil thermal inertia is estimated from how quickly the probe temperature equilibrates with the soil. To this end, a finite volume heat transfer model is used to generate temperature equilibration time series across combinations of controlling factors, and a gridded search inversion approach is applied to infer soil thermal inertia. Field tests in the Arctic indicate that QTP measurements have a minimum uncertainty of 0.14 J m −2 K −1 s −1/2 and covary with dual‐probe heat pulse thermal analyzer...

In-situ laboratory monitoring of cyanobacterial influence on calcite dissolution

Tue, 13 Jan 2026 00:00:00 +0000

Microbial interactions with mineral surfaces play a critical role in biogeochemical cycles, yet their dynamic coupling with mineral reactivity remains poorly constrained. Here, in-situ time-resolved monitoring of topographic evolution of the calcite-bacteria interface was performed using a fluid cell coupled to vertical scanning interferometry (VSI). The cyanobacterial strain Chroococcidiopsis thermalis PCC 7203 was inoculated onto polished and pre-etched calcite surfaces under conditions strongly undersaturated or closer to calcite saturation. The formation of localized topographic highs, produced by dissolution of surrounding material, was found to correlate with the residence time of attached cells at Ω = 0.0, but not at Ω = 0.3. Physiological tests suggested that the composition of the bulk fluid modulates microbial activity, thereby influencing interfacial pH, and in turn, calcite reactivity. Moreover, calcite reactivity was found to exert a stronger control on bacterial...

Ultraselective sequestration of Li+ and Mg2+ from brines via a reusable polyoxoniobate-based ion sponge

Mon, 12 Jan 2026 00:00:00 +0000

Lithium (Li) and magnesium (Mg) are designated as critical mineral materials (CMM) due to their essential roles in clean energy technologies. However, extracting high-purity Li⁺ from brine remains a formidable challenge owing to the presence of Mg²⁺, a physicochemical similar ion that often exists in excess. Here, we introduce a polyoxoniobate-based "Mg-PONb sponge" that enables ultraselective and rapid Li⁺/Mg²⁺ separation across an exceptionally broad range of Mg/Li ratios (0.02 to 200.63). This framework achieves >99.9% Mg²⁺ removal with negligible Li⁺ loss in under 1 min, yielding Li⁺/Mg²⁺ selectivity values exceeding 5000. The sponge demonstrates excellent recyclability, maintaining >99% Mg²⁺ rejection and Li⁺ permeability across five regeneration cycles without structural degradation. Mechanistic investigations reveal that selective Mg²⁺ capture originates...

Insights Into Seismicity Associated With Flexibly Operating Enhanced Geothermal System From Real‐Time Distributed Acoustic Sensing

Fri, 19 Dec 2025 00:00:00 +0000

Abstract Enhanced Geothermal Systems (EGS) have the capacity to broaden the accessible resource pool for geothermal power generation. Traditionally viewed as a “baseload” resource, their flexible operation might also enable dispatchable load‐following generation and long‐term energy storage, aligning them with the evolving landscape of decarbonized electricity systems. However, increasing permeability and extracting energy during EGS operations can induce microseismic events; for many prior EGS efforts, some associated seismicity has been observed. While energetically beneficial, the flexibility of EGS operations prompts our inquiry into whether new types of operations will yield previously unseen seismicity patterns. We demonstrate the use of distributed acoustic sensing (DAS) with real‐time edge computing to monitor seismicity during a pilot test of a cyclically operated EGS facility at the Blue Mountain geothermal field. Our focus lies in uncovering seismicity insights from...

Investigation of Site Amplifications Using Ambient-Noise-Derived Shallow Velocity Structures Under a Dense Array in Oklahoma

Tue, 16 Dec 2025 00:00:00 +0000

ABSTRACT The shear-wave velocity (VS) structure plays an important role in characterizing site amplification. The Large-n Seismic Survey in Oklahoma (LASSO; 1820 stations) revealed large vertical ground-motion variability in a 25 km × 32 km area in northern Oklahoma. The LASSO array has a relatively simple and flat topography, typical in a sedimentary basin environment in the central United States. In this study, we use the dense array to investigate the velocity structure under the LASSO array and how vertical ground motions relate to the shallow-to-deep structures. We extract the fundamental-mode Rayleigh wave by cross-correlating one month of ambient noise (0.7–5 Hz). We use double-beamforming to measure the group and phase velocities and anisotropy. By jointly inverting the group and phase velocities, we obtain the VS structure. We observe correlations between VS at depths of 0.1–1.5 km and vertical ground motions using sites on the stiffer Permian formations....

Complex Dependence of Calcite Crack Kinetics on Salinity: The Role of DLVO and Hydration Forces

Mon, 15 Dec 2025 00:00:00 +0000

Abstract Subcritical crack growth (SCG) plays an important role in many geological processes such as delayed earth rupture and rock weathering. The complex dependency of SCG on the in‐crack fluid chemistry, however, is still poorly understood. In this study, we utilize the newly developed surface force‐based fracture theory (SFFT) to elucidate the relative contributions of surface forces and solute transport to the crack growth kinetics of calcite in NaCl solutions. Expanding on Barenblatt's cohesive crack model, SFFT introduces an effective stress intensity at the crack tip that encompasses all the relevant intermolecular forces across the crack in addition to the external far‐field stresses. The nonlinear system of equations portraying the crack opening profile, the solute distribution in a propagating crack, and the crack growth velocity are numerically solved via an implicit scheme. After carefully calibrating the model for calcite‐water systems, the SFFT is used to predict...

Compression–tension cell with sample manipulator for in situ X‐ray nanotomography experiments

Thu, 11 Dec 2025 00:00:00 +0000

In situ X-ray nanotomography experiments where tensile or compressive force is applied on the sample require specialized equipment. A compression-tension device with fluid flow-through capability has been designed for X-ray nanotomography beamlines. The compression-tension cell is equipped with a triaxial stage for sample alignment and a high sensitivity loadcell for measurement of applied force. To handle the <100 µm samples used for X-ray nanotomography imaging and for loading samples on the compression-tension cell a sample manipulator has been built. The sample manipulator is capable of selecting a single <100 µm particle for nanotomography scanning while viewing multiple samples under an optical microscope. To test the functionality of these two devices an initial compression experiment involving two glass beads was performed. To demonstrate instrument stability two spherical glass beads were compressed from a no load condition until one of the beads fractured. Nanotomography...

Denoising Autoencoder for Reconstructing Sensor Observation Data and Predicting Evapotranspiration: Noisy and Missing Values Repair and Uncertainty Quantification

Thu, 4 Dec 2025 00:00:00 +0000

Abstract Machine learning (ML) methods applied in scientific research often deal with interrelated features in high‐dimensional data. Reducing data noise and redundancy is needed to increase prediction accuracy and efficiency especially when dealing with data from field sensors. We explored an unsupervised learning method, the denoising autoencoder (DAE), to extract the underlying data structure from noisy raw data in the context of predicting hydrologic quantities from multiple field sensors. These sensors have intrinsic instrumental noise and occasional malfunctions that cause missing values. Our DAE neural network reconstructed meteorological sensor data containing noise and missing values to predict evapotranspiration in a mountainous watershed. The DAE reconstructed the sensor variables with a mean coefficient of determination value of 0.77 across 15 dimensions representing individual sensors. It reduced variance and bias uncertainties compared to a classical autoencoder...

Rapid wavefield forecasting for earthquake early warning via deep sequence to sequence learning

Tue, 2 Dec 2025 00:00:00 +0000

We propose a deep learning model, WaveCastNet, to forecast high-dimensional wavefields. WaveCastNet integrates a convolutional long expressive memory architecture into a sequence-to-sequence forecasting framework, enabling it to model long-term dependencies and multiscale patterns in both space and time. By sharing weights across spatial and temporal dimensions, WaveCastNet requires significantly fewer parameters than more resource-intensive models such as transformers, resulting in faster inference times. Crucially, WaveCastNet also generalizes better than transformers to rare and critical seismic scenarios, such as high-magnitude earthquakes. Here, we show the ability of the model to predict the intensity and timing of destructive ground motions in real time, using simulated data from the San Francisco Bay Area. Furthermore, we demonstrate its zero-shot capabilities by evaluating WaveCastNet on real earthquake data. Our approach does not require estimating earthquake magnitudes...

Cosserat rod-based modeling and stochastic analysis for distributed fiber optics shape-sensing

Tue, 2 Dec 2025 00:00:00 +0000

Distributed Fiber Optic Sensors (DFOS) enable continuous strain measurement along a sensor path, providing data at multiple spatial locations that can be used to back-calculate structural deformations. Shape sensing technology, usually utilizing DFOS, has been explored in various applications such as surgery, motion tracking, and soft robotics. However, without a systematic framework, shape estimation in existing studies is often compromised by deviations and biases, making error analysis problematic. This research presents a comprehensive mathematical framework for accurate shape monitoring using DFOS. A system of differential equations based on Cosserat rod theory is formulated to model the spatial deformation of rods, accounting for nonlinear initial configurations. Then, an analytical solution to this system is derived under the assumption of piecewise constant strain measurements. To address measurement uncertainties, the deterministic model is extended to a system of stochastic...

Wind turbine gearbox operation monitoring using high-resolution distributed fiber-optic sensing

Tue, 2 Dec 2025 00:00:00 +0000

Abstract. Efficient gearbox monitoring is vital for improving fault detection, enhancing design, and reducing operation and maintenance (O&M) costs, particularly for offshore wind turbines. This paper introduces an innovative approach using high-resolution distributed fiber-optic sensing (DFOS) based on optical frequency domain reflectometry (OFDR) to measure gearbox strain in real time. By bonding a single optical fiber around the full circumference of the outer surface of a 2.152 m diameter ring gear of the first planetary stage in a 3.75 MW wind turbine gearbox, we measured circumferential strain from planetary gear passage every 2.6 mm around the ring gear under different input torque levels. Our results show accurate identification of planet gear locations in real time and rotation speed (10.42 revolutions per minute), with a strong linear correlation (R2=0.9997) between applied torque and measured strain across all 2500 measured locations. Strain variations of approximately...

Structural health monitoring of offshore wind turbines using distributed acoustic sensing (DAS)

Tue, 2 Dec 2025 00:00:00 +0000

This paper presents the results of a first of its kind application and validation of fiber optic strain sensing for structural health monitoring of offshore wind turbines. A full-scale wind turbine was tested at the University of California, Berkeley’s shaking table. The test employed two Rayleigh-based Distributed Fiber Optic Sensing (DFOS) technologies to monitor dynamic strain profiles in a wind turbine that was subjected to strains representative of a typical offshore wind turbine environment. The two technologies used were Optical Frequency-Domain Reflectometry (OFDR), which can measure strain (tens of meters), and Phase-sensitive Optical Time-Domain Reflectometry (ϕ$$\phi$$-OTDR), a technology used in DAS, which can measure strain over large distances (several kilometers). Target dynamic strain profiles were determined prior to testing using a prototype floating offshore wind turbine simulated in the computational software, OpenFAST. Fiber optic cables were installed onto...

Brief communication: Decadal changes in topography, surface water and subsurface structure across an Arctic coastal tundra site

Mon, 1 Dec 2025 00:00:00 +0000

Abstract. In ice-rich polygonal tundra, spatiotemporal heterogeneity in ground-ice melt reshapes topography, impacting infrastructure, water and carbon cycles. This study evaluates changes in topography and subsurface structure at a coastal Arctic site by comparing data from two surveys conducted a decade apart. Each survey includes electrical resistivity tomography, active layer thickness, photogrammetry, and topographic data. Results reveal subsidence and decrease in permafrost table elevation with varying intensity and spatial distribution across polygons, alongside diverse thermal-hydrological responses, such as thermokarst pool formation in high-centered-polygons and more even subsidence in flat-centered-polygons. The study also underscores the value and limitations of sporadic surveys.

Correction: Generating H2 during the CO2 sequestration in basalt formations

Mon, 1 Dec 2025 00:00:00 +0000

In this article [1], the author’s name Carl Steefel was incorrectly written as Carl Stefeel. The original article has been corrected.

Baseflow Identification via Explainable AI With Kolmogorov‐Arnold Networks

Fri, 21 Nov 2025 00:00:00 +0000

Abstract Hydrological models often involve constitutive laws that may not be optimal in every application. We propose to replace such laws with the Kolmogorov‐Arnold networks (KANs), a class of neural networks designed to identify symbolic expressions. We demonstrate KAN's potential on the problem of baseflow identification, a notoriously challenging task plagued by significant uncertainty. KAN‐derived functional dependencies of the baseflow components on the aridity index outperform their original counterparts; they demonstrate that water availability, rather than potential evapotranspiration, drives baseflow by constraining actual evapotranspiration under arid conditions. On a test set, they increase the Nash‐Sutcliffe efficiency (NSE) by 65%, decrease the root mean squared error by 29%, and increase the Kling‐Gupta efficiency by 34%. This superior performance is achieved while reducing the number of fitting parameters from three to two. Next, we use data from 378 catchments...

A review of Geological Thermal Energy Storage for seasonal, grid-scale dispatching

Fri, 21 Nov 2025 00:00:00 +0000

Energy storage is essential for the decarbonization of the U.S. energy grid, especially with the increasing deployment of variable renewable energy sources like solar and wind. Geological thermal energy storage (GeoTES) has emerged as a promising long duration, grid scale solution, providing stability and security through flexible operations and valuable grid services. GeoTES utilizes subsurface reservoirs to store thermal energy for power generation and direct-use heating and cooling. This approach significantly enhances the use of low-temperature reservoirs, which would otherwise be unsuitable for geothermal power plants. It also aligns well with depleted oil and gas reservoirs, concentrating solar power, non-flexible renewables (photovoltaic and wind), and geothermal-related power cycles. Given the favorable marginal costs of GeoTES as storage duration increases, it becomes particularly competitive for seasonal, grid-scale dispatch, where few technologies are viable. This paper...

Coupled THM modeling of bentonite heating and hydration in tank tests with a new temperature-dependent water retention model

Thu, 20 Nov 2025 00:00:00 +0000

This study presents a coupled thermo-hydro-mechanical (THM) model for simulating the heating and hydration behavior of bentonite, a buffer material in deep geological repositories (DGRs). The model incorporates a new temperature-dependent soil water retention curve which captures the thermal-induced shift in water retention behavior. It also distinguishes between liquid and gas permeability, modeling intrinsic gas permeability as a function of accessible porosity to improve vapor transport and desaturation predictions. The model was validated against two large-scale tank tests, demonstrating good agreement with measured temperature, relative humidity, and water inflow data. It revealed a complex porosity evolution driven by thermal expansion, vapor movement, vapor condensation, and hydration-induced swelling during heating and hydration processes. The simulation results also suggest that the permeability of the hydration layer plays a critical role in controlling water intake....

Factors controlling injection-induced rupture of intersecting faults during geological sequestration of CO2

Thu, 20 Nov 2025 00:00:00 +0000

This study addresses coupled multiphase fluid flow and geomechanics effects on potential fault activation associated with subsurface CO2 injection around intersecting faults. An enhanced fault-representation model is used to capture geomechanical responses of two intersecting faults with finite length during CO2 injection. The faults are embedded in a strike-slip stress regime of a caprock-reservoir-basement system with the faults represented by zero-thickness interfaces with adjacent finite-thickness damage zones. A sensitivity analysis is conducted to study the effect of fault permeability, slip-weakening behavior, well location relative to the orientation of faults, and well placement (the number and location of injection wells). Five metrics (pressure, CO2 plume, shear state on the fault, as well as shear displacement and stress path at selected fault monitoring points) are selected to assess CO2 migration and reactivation of intersecting faults. The results show that induced...

Efficient machine learning interatomic potentials robust for liquid and multiple solid polymorphs of NaF and KF

Tue, 4 Nov 2025 00:00:00 +0000

Achieving atomic-level understanding of crystallization of molten salts is of importance to a wide range of technological applications. Recent work [Fan , ] revealed that crystal nucleation in molten LiF salt is a multistage process according to the molecular-dynamics (MD) simulations based on an atomic cluster expansion (ACE) machine-learning interatomic potential (MLIP). In order to understand the influence of increasing cation size on nucleation pathways and nucleation rates of molten fluoride salts, here we develop two new ACE MLIPs for NaF and KF. The two ACE MLIPs feature DFT-SCAN-level accuracy for liquid and multiple solid polymorphs over a wide temperature (0–2000 K) and pressure (0–100 GPa) range, and also reproduce well a number of experimental data for solid and liquid equilibrium properties. The efficiency of the two ACE MLIPs enable million-atom-scale or microsecond-scale MD simulations. The two general-purpose ACE MLIPs are expected to be useful for atomistic...

Opportunistic Short-term Water Uptake Dynamics by Subalpine Trees Observed via in situ Water Isotope Measurements

Wed, 22 Oct 2025 00:00:00 +0000

Opportunistic Short-term Water Uptake Dynamics by Subalpine Trees Observed via in situ Water Isotope Measurements

Ubiquity and Causes of Soil Water Preferential Flow Across 17 Ecoregions

Wed, 22 Oct 2025 00:00:00 +0000

Abstract Preferential flow (PF) in soil causes the rapid transport of water, nutrients, and contaminants into the subsurface, influencing groundwater recharge and streamflow. Data scarcity has hindered the quantification of PF occurrence and the identification of its drivers across diverse ecoregions. We address this gap by analyzing high‐frequency, multi‐depth soil moisture data across 17 ecoregions in the USA, using ∼1,500 sensors at 40 sites. We discovered that PF is widespread, with sites experiencing PF in up to 60% of rainfall events ≥2 mm. Multiple approaches consistently show that PF is more likely to occur with increased peak rainfall intensity, finer textured material, low soil moisture variability, humid climate, and higher net primary productivity. This suggests that PF patterns could shift with projected climate changes, increasing uncertainty in predictions of groundwater recharge, water quality, and streamflow generation. Plain Language Summary Water can bypass...

Defect-Mediated Diffusion Pathways in Spodumene Accelerate Lithium Transport

Fri, 10 Oct 2025 00:00:00 +0000

Lithium extraction from naturally occurring α-spodumene is hindered by poor lithium diffusivity, necessitating high-temperature phase transformation to a low-density β polymorph. Although β spodumene exhibits up to 5 orders of magnitude higher lithium-ion diffusivity, both phases have diffusion activation energies between 0.8 and 1 eV, indicating that polymorph density is not the controlling factor over diffusivity. We show that aluminum vacancies facilitate lithium-ion diffusion in α-spodumene by reducing the migration barrier from 2.4 to 0.9 eV. Bond valence site energy and nudged elastic band calculations show a new lithium local minimum site which promotes a one-dimensional percolation network by reducing the lithium intersite distance from 4.5 Å to 2.9 Å. However, aluminum vacancies are energetically unfavorable to percolate through the whole structure, resulting in very low net lithium diffusivity and highlighting the critical role of nonstoichiometric defects in facilitating...

Impact of geothermal expansion and lithium extraction in the Salton Sea known geothermal resource area (SS-KGRA) on local water resources

Thu, 9 Oct 2025 00:00:00 +0000

Saline brines currently being brought to the surface to produce geothermal energy in the Salton Sea region of California contain high concentrations of lithium that could potentially be extracted before the brine is reinjected back into the geothermal reservoir. This would create a new supply chain of domestically sourced lithium for the United States to produce lithium-based batteries that will help drive the transition to a renewable-based energy grid. Plans to expand geothermal production along with lithium extraction are being considered in the Salton Sea known geothermal resource area. We discuss water availability and quality issues and potential concerns about water pollution associated with this geothermal expansion and lithium production in the context of potential future restrictions on water extractions from the Colorado River Basin. We estimate that water demand for currently proposed geothermal production and lithium extraction facilities only accounts for ∼4% of...

Characterization of Li in the Salton Sea Geothermal Field

Thu, 9 Oct 2025 00:00:00 +0000

Abstract The behavior of lithium during geothermal brine and host-rock interactions in the Salton Sea geothermal field is underconstrained. The lithium brine reservoir inventory is between 4 and 18 million metric tons of lithium carbonate equivalent, with an even larger amount present within the reservoir rock mineral phases. Here, we present bulk-rock and brine Li concentration and δ7Li, and in situ Li concentrations of minerals from the California State 2-14 scientific drill core and commercial wells in the Salton Sea geothermal field to identify the mineral hosts of Li and constrain Li behavior during brine-rock interactions. Lithium contents are highest in chlorite (270–580 ppm, ~2,358 m), which encases pyrite, indicating that Li is fixed from the brine into the host rocks during hydrothermal alteration. Lithium abundances in chlorite decrease with depth (70–100 ppm, ~2,882 m), as does whole-rock Li content, whereas whole-rock δ7Li increases (δ7Li = 2.0–4.3‰,...

Quantifying Groundwater Response and Uncertainty in Beaver‐Influenced Mountainous Floodplains Using Machine Learning‐Based Model Calibration

Wed, 8 Oct 2025 00:00:00 +0000

Abstract Beavers ( Castor canadensis ) alter river corridor hydrology by creating ponds and inundating floodplains, and thereby improving surface water storage. However, the impact of inundation on groundwater, particularly in mountainous alluvial floodplains with permeable gravel/cobble layers overlain by a soil layer, remains uncertain. Numerical modeling across various floodplain structures considers topographic and sediment complexity and multidirectional flow, linking inundation to groundwater response. This study develops a model‐data integration workflow to address uncertainty in groundwater response to beaver‐induced inundations in a mountainous alluvial floodplain in the Upper Colorado River Basin. Uncertain factors include seasonal hydrologic dynamics, hydraulic conductivities, floodplain structures, and meteorological forcings. We employed an ensemble of groundwater models, based on geophysical and hydrologic data, with machine learning‐based calibration using a neural...

Impact of Salinity on Ground Ice Distribution Across an Arctic Coastal Polygonal Tundra Environment

Wed, 8 Oct 2025 00:00:00 +0000

ABSTRACT The heterogeneous distribution of ground ice in the Arctic is a key driver of uneven ground subsidence as permafrost thaws, significantly impacting infrastructure and surface/subsurface hydrology. These topographic and hydrological changes contribute to major uncertainties in energy and carbon fluxes and storage in a warming Arctic. This study aims to improve our understanding of the controls on ground ice and organic matter distribution within the top 3 m of permafrost in coastal polygonal tundra near Utqiagvik, Alaska. To this end, we apply a neural network approach to bulk density distributions derived from nondestructive X‐ray tomography of soil cores, trained with laboratory analyses, to improve the resolution and spatial coverage of estimates of dry bulk density, ice content, and organic matter content. In addition, we use capacitively coupled geophysical imaging to map soil electrical conductivity and salinity variations. The results show that sedimentary deposits...

Atomic-scale 3D structural dynamics and functional degradation of Pt alloy nanocatalysts during the oxygen reduction reaction

Tue, 7 Oct 2025 00:00:00 +0000

Pt-based electrocatalysts are the primary choice for fuel cells due to their superior oxygen reduction reaction (ORR) activity. To enhance ORR performance and durability, extensive studies have investigated transition metal alloying, doping, and shape control to optimize the three key governing factors for ORR: geometry, local chemistry, and strain of their surface and subsurface. However, systematic optimization remains incomplete, as it requires an atomic-scale understanding of these factors and their dynamics over potential cycling, as well as their relationship to ORR activity. Here, we implement neural network-assisted atomic electron tomography to measure the 3D atomic structural dynamics and their effects on the functional degradation of PtNi alloy catalysts. Our results reveal that PtNi catalysts undergo shape changes, surface alloying, and strain relaxation during cycling, which can be effectively mitigated by Ga doping. By combining geometry, local chemistry, and strain...

Micromechanical Modeling of Shale-Indentation Experiments Imaged by Synchrotron X-Ray Micro-Tomography

Wed, 1 Oct 2025 00:00:00 +0000

We present micromechanical modeling of an indentation experiment on Green River Shale with simultaneous X-ray micro-computed tomography of internal sample deformation that provides new insights into the ductile-brittle micromechanical behavior of shales relevant to proppant embedment. Brittle wing cracks appear from the indenter along the shale bedding, but indentation depth is dominated by ductile plastic shear deformations governed by extreme compressive stress magnitudes below the indenter-shale contact. Simultaneous analysis of the experimental loading-unloading indentation curves and the imaged shale deformations were used to constrain elasto-plastic properties and strength anisotropy of the tested Green River shale sample.

Development of an ERT‐Based Framework for Bentonite Buffers Monitoring From Laboratory Tests: 1. Characterizing Thermal–Hydrological–Mechanical Processes

Mon, 8 Sep 2025 00:00:00 +0000

Abstract Bentonite clay is widely used in engineered barrier systems for the permanent disposal of high‐level radioactive waste due to its low permeability, high swelling capacity, and thermal stability. However, the complex thermal‐hydrological‐mechanical (THM) processes induced by heating from decaying radioactive waste and hydration from surrounding rock can lead to heterogeneous changes that are difficult to measure and predict. This study develops an Electrical Resistivity Tomography (ERT)‐based framework for monitoring THM processes, progressing from sample‐scale to bench‐scale tests, to inform field‐scale applications. Sample‐scale tests analyzed small bentonite samples under controlled variations in water content, temperature, and porosity to establish fundamental resistivity relationships. Bench‐scale tests involved larger bentonite columns subjected to heating (up to 200°C) and hydration under controlled pressure, simulating repository conditions. ERT measurements, complemented...

Deep learning forecasts the spatiotemporal evolution of fluid-induced microearthquakes

Mon, 8 Sep 2025 00:00:00 +0000

Microearthquakes generated by subsurface fluid injection record the evolving stress state and permeability of reservoirs. Forecasting their spatiotemporal evolution is therefore critical for applications such as enhanced geothermal systems, carbon dioxide sequestration and other geoengineering applications. Here we propose a transformer neural network model that ingests hydraulic stimulation history and prior microearthquake observations to forecast four key quantities: cumulative microearthquake count, cumulative logarithmic seismic moment, and the 50th- and 95th-percentile extents of the microearthquake cloud. Applied to the EGS Collab Experiment 1 dataset, the model achieves R2 > 0.98 for the 1-s forecast horizon and R2 > 0.88 for the 15-s forecast horizon across all targets, and supplies uncertainty estimates through a learned standard deviation term. These accurate, uncertainty-quantified forecasts enable real-time inference of fracture propagation and permeability...

Development of an ERT‐Based Framework for Bentonite Buffers Monitoring From Laboratory Tests: 2. Quantitative Moisture Dynamics Estimation Model

Mon, 8 Sep 2025 00:00:00 +0000

Abstract The long‐term containment of high‐level radioactive waste in geological disposal repositories relies on Engineered Barrier Systems (EBS), with bentonite clay emerging as a candidate material due to its unique properties. Understanding moisture dynamics within bentonite buffers is crucial for EBS performance, as it directly influences the material's swelling capacity, thermal and hydraulic conductivity, mechanical properties, and long‐term evolution under complex thermal‐hydrological‐mechanical (THM) processes. This study develops an advanced Electrical Resistivity Tomography (ERT)‐based framework to quantitatively monitor moisture dynamics under THM conditions. Our framework extends the Waxman‐Smits model to incorporate the coupled effects of temperature, water content, fluid chemistry, and mechanical changes on bentonite's electrical properties. Utilizing HotBENT‐Lab data from our companion paper, which includes electrical conductivity, CT density, and thermocouple measurements,...

Methanogenesis and Acetogenesis in Hydrogenotrophy with Carbonate Minerals: Dependence on Mineral Surface Area, Biofilm Growth, and Microbial Community

Mon, 8 Sep 2025 00:00:00 +0000

The production, storage, and use of hydrogen are anticipated to grow substantially to achieve energy and climate goals. Consequently, microbial communities in many terrestrial and subsurface Earth environments could be exposed to elevated hydrogen concentrations. Hydrogen stimulates metabolic processes that reduce aqueous chemical species, such as bicarbonate or sulfate, that can exchange with solid mineral phases, but the controls on microbial hydrogenotrophy with mineral sources of electron acceptors are not fully understood. Herein, we applied laboratory experiments and biogeochemical modeling to study the response of a natural microbial community to an elevated partial pressure of hydrogen in the presence of carbonate minerals of varying composition, solubility, and size. Experimental incubations and simulation results showed that hydrogen consumption by microbial communities was initially dominated by sulfate reduction and, subsequently, transitioned to acetogenesis and methanogenesis....

Opportunistic Short‐Term Water Uptake Dynamics by Subalpine Trees Observed via In Situ Water Isotope Measurements

Fri, 5 Sep 2025 00:00:00 +0000

Abstract Variations in tree water sources are important to understand in semi‐arid ecosystems because climatic shifts towards lower snowpack and increased drought affect water availability in subalpine forests of the western US. Here, we use daily in situ measurements of stable isotopes ( 2 H & 18 O) in soil and tree stem water, soil matric potential and sap flow to study tree water uptake dynamics. We instrumented three soil profiles down to 90 cm, as well as three aspen and engelmann spruce trees near Gothic, Colorado, in the East River watershed. We observed the fate of natural isotopic variations in rainfall, soil, and plants from June to October 2022, and in August 2023 we conducted a 2 H labeled irrigation experiment. Our observations showed that all studied aspen trees compensated for water scarcity in the shallow soil by shifting the dominant water source at 60(±20) cm to ⅔ of uptake from 90 cm within a few days of a dry period. Both species relied on snowmelt...

Stable isotope equilibria in the dihydrogen-water-methane-ethane-propane system. Part 2: Experimental determination of hydrogen isotopic equilibrium for ethane-H2 from 30 to 200 °C and propane-H2 from 75 to 200 °C

Tue, 2 Sep 2025 00:00:00 +0000

The stable isotopic compositions of light n-alkanes, including methane, ethane, and propane, are often used to identify the sources and thermal maturity of natural gas samples. Though stable isotopic compositions of these molecules are commonly assumed to be controlled by kinetic isotope effects, recent studies have proposed both carbon and hydrogen isotopic equilibrium may also occur in some samples. Assessing whether samples are in isotopic equilibrium requires knowledge of light alkane equilibrium fractionation factors over geologically relevant temperatures for formation and storage (up to ∼300 °C). In this study, we report experimental results of hydrogen isotopic equilibrium between ethane and H2 from 30 to 200 °C and propane and H2 from 75 to 200 °C. We compare these results with high-level theoretical calculations and provide a preferred polynomial fit to describe equilibrium fractionation factors. Comparison of these fractionation factors with a compilation...

Automated electron microscopy sample preparation system

Tue, 26 Aug 2025 00:00:00 +0000

An automated, modular, solvent-free system enabling preparation of powder samples for electron microscopy in self-driving labs. EMSBot addresses challenges in automating sample preparation and improves consistency and reproducibility. The emergence of self-driving laboratories (SDLs) promises to innovate chemistry and materials science by incorporating autonomous systems for experimental design and execution. Advanced material characterization techniques, such as electron microscopy, are crucial for determining the materials synthesized by SDLs, and integrating these techniques into the SDL workflow is of paramount importance. Despite recent advancements, automated preparation of samples for electron microscopy remains challenging due to the specialized and hard-to-replicate human processes involved in powder dispensing and sample transfer. In this work, we introduce an automated electron microscopy sample preparation robot (EMSBot) that is designed for the preparation of powder...

Monitoring Fracture Hydromechanical Evolution in the Lab and Field Using Unsupervised Metric Learning

Tue, 19 Aug 2025 00:00:00 +0000

Abstract Fractures evolve in time through thermal‐hydraulic‐mechanical‐chemical (THMC) processes that alter their long‐range hydraulic transport properties and modify subsurface behavior and activities. The location of subsurface fractures makes it necessary to use remote sensing techniques such as passive or active seismic monitoring for fracture characterization. In this paper, we develop a machine learning approach to monitor the evolution of fracture properties using passive seismic sources in a laboratory setting and using active seismic monitoring from the Sanford Underground Research Facility in Lead, South Dakota, at a depth of 1.25 km in amphibolite rock during stimulation of natural fractures as well as during induced fracturing. The unsupervised metric learning technique applies tandem neural networks (twin (Siamese) or triplet) with contrastive loss and adaptive margins to track slowly varying systems for which class or similarity labels are not available. The...

Multistage nucleation pathway in LiF molten salt mirrors the crystal–melt interface structure

Fri, 15 Aug 2025 00:00:00 +0000

Despite over a century of studies, fundamental questions remain about the processes governing crystal nucleation from melts or solutions. Research over the past three decades has presented mounting evidence for kinetic pathways of crystal nucleation that are more complex than envisioned by the simplest forms of classical theory. Such observations have been presented for colloidal and elemental systems with covalent and metallic bonding. Despite the technological and geochemical importance of molten salts, similar studies for these ionically bonded systems are currently lacking. Here we develop a machine learning interatomic potential for a model ionic system: LiF. The potential features quantum-level accuracy for both liquid and multiple solid polymorphs over wide temperature and pressure ranges and accurately reproduces experimentally measured properties. Thanks to the efficiency of the potential, which enables microsecond-scale molecular dynamics simulations, induction times...

Extending TOUGH + HYDRATE with a parallel particle transport simulator: numerical investigation of sand production during gas production from hydrate deposits

Thu, 14 Aug 2025 00:00:00 +0000

A new parallel code for simulating particle transport in porous media is integrated with the TOUGH + HYDRATE simulator to investigate sand production associated with gas production from unconsolidated gas hydrate-bearing sediments (HBS). The parallel coupled simulator is named THMPT and uses the integral finite difference method to describe the Darcian and non-Darcian flow of fluids and heat transport, the finite element method to describe the associated geomechanical changes, and the discrete element method to track the trajectory of individual sand particles within the HBS. The THMPT simulator is written in Fortran, incorporates multiple optimized algorithms, and can comprehensively address the coupled flow, thermal, chemical, geomechanical, and particle transport processes that characterize the system behaviors during gas production from HBS. The simulator can capture all processes involved in sand particle transport in porous media, including sand detachment, collision, clogging...

Building confidence in models for complex barrier systems for radionuclides

Thu, 14 Aug 2025 00:00:00 +0000

The modeling and simulation of the Cement-clay Interaction-Diffusion field (CI-D) experiment at the Mont Terri site in Switzerland presented here demonstrates that it is possible to capture the multiscale physical and chemical features of natural and engineered barrier systems for radionuclides. The simulations are successfully carried out with the newly developed CrunchODiTi high-performance computing software that accounts for multiple continua, including a continuum representing the electrical double layer (EDL) developed along negatively charged clay particles in clay rock. The simulation also accounts for both the complex three-dimensional (3D) geometry, expected as the norm in a geological waste repository, and the anisotropy of the geological formation. In addition, the high resolution of the model makes it possible to include "skin effects" developed at the interface between highly reactive materials, in this case between the high pH cement and the circumneutral but electrostatic...

Modeling supercritical CO2 injection induced rupture of a minor fault embedded in a poroelastic layered reservoir-caprock system

Wed, 13 Aug 2025 00:00:00 +0000

CO2 injection for geologic carbon sequestration involves hydromechanical processes that lead to changes in fluid pressure and stresses that can activate existing faults. This paper presents a new method and workflow of modeling fault activation considering more complex three-dimensional geometry of natural faults using the TOUGH-FLAC multiphase fluid flow and geomechanical simulator. In this method and workflow, FLAC3D mechanical interfaces and TOUGH3 finite volume elements are discretized using computer aided design and gridding software along with a tailored mesh translation routine. The method and workflow are demonstrated with a model of a curved minor fault embedded in a poro-elastic layered reservoir-caprock system. The model is used for a comprehensive sensitivity analysis of fault responses to fault length, injection mass rate, injection schedule, well-fault distance, and well locations versus fault location. Four metrics (CO2 plume, shear state of fault, pressure and...

Estimating shallow compressional velocity variations in California’s Central Valley

Sat, 2 Aug 2025 00:00:00 +0000

A theory for modelling the evolution of elastic moduli of grain packs under increasing pressure is combined with a method that accounts for the presence of fine-grained particles to develop a new conceptual framework for computing the seismic velocities of compacting sediments. The resulting formulation is then used to construct a seismic velocity model for California’s Central Valley. Specifically, a set of 44 sonic logs from the San Joaquin Valley are combined with soil textural data to derive the 3-D velocity variations in the province. An iterative quasi-Newton minimization algorithm that allows for bounded variables provided estimates of the nine free parameters in the model. The estimates low- and high-pressure exponents that resulted from the fit to the sonic log velocities are close to 1/2 and 1/3, respectively, values that are observed in laboratory experiments. Our results imply that the grain surfaces are sufficiently rough that there is little or no slip between grains....

Soft interface instability and gas flow channeling in low-permeability deformable media

Tue, 29 Jul 2025 00:00:00 +0000

Understanding gas percolation through a clay layer or a shale formation is of great importance for the development of a geologic repository for nuclear waste disposal, a subsurface system for gas storage, and an engineering approach for hydrocarbon extraction from unconventional reservoirs. Gas injection experiments have revealed complex dynamic behaviours of gas percolation through water saturated compacted bentonite, characterized by a high breakthrough pressure, rapid breakthrough, a pressure/stress decay after the breakthrough, a relatively high migration rate, high-frequency periodic/nonperiodic variations in flow rate, stepwise rate reductions during relaxation, and low gas saturation over the whole process, all indicating channelling nature of the processes. Using linear stability analyses, we show that this channelling can autonomously emerge from the instability of the deformable interface between the injected gas and the compacted bentonite matrix driven by local stress...

TensorSearch: Parallel Similarity Search on Tensors

Tue, 29 Jul 2025 00:00:00 +0000

Existing similarity search methods, often limited to scalar or vector data, struggle to identify complex patterns found in scientific datasets, such as 2D seismic events or 3D magnetic flux ropes. We introduce TensorSearch, a novel parallel similarity search paradigm designed to identify known patterns in high-dimensional tensors. By directly employing tensor representations, TensorSearch captures intricate pattern structures more effectively than traditional vector-based approaches. Furthermore, its parallel architecture optimizes cache and I/O operations, enabling efficient processing of large-scale scientific data. Our performance evaluations demonstrate that TensorSearch outperforms state-of-the-art vector-based systems like Milvus by up to 10x, and achieves up to a remarkable 55x advantage over custom solution developed in Matlab used by the domain scientists. In these tests, TensorSearch exhibits linear scalability, supporting up to 2240 CPU cores.

Importance of Considering Near-Surface Attenuation in Earthquake Source Parameter Estimation: Insights from Kappa at a Dense Array in Oklahoma

Mon, 28 Jul 2025 00:00:00 +0000

ABSTRACT Separating earthquake source spectra from propagation effects is challenging. The propagation effect contains a site-dependent term related to the high attenuation of shallow sediments. Neglecting the site-dependent attenuation can cause large biases and scattering in the corner-frequency (fc) estimates, resulting in significant stress-drop deviations. In this study, we investigate shallow attenuation at the LArge-n Seismic Survey in Oklahoma (LASSO) and site-related biases and scattering in source parameter measurements due to simplified attenuation models. We measure the high-frequency spectral decay parameter kappa on the vertical acceleration spectra of regional earthquakes (125 km away). The site-dependent kappa (κ0,acc) suggests that attenuation increases rapidly at shallow depth and is highly site-dependent. 10%–75% of the attenuation is site-dependent for S waves and even larger for P waves. The quality factor for S waves (QS) ranges from 10 to 100 in the...

Distributed fiber-optic sensing in a subscale high-temperature superconducting dipole magnet

Fri, 25 Jul 2025 00:00:00 +0000

High-temperature superconductors, such as REBa2Cu3O7−x (REBCO, RE = rare earth), are becoming pivotal for high-field magnet technology for future circular colliders and compact fusion reactors. The U.S. Magnet Development Program, in collaboration with industry, is developing REBCO magnet technology using round conductors consisting of multiple REBCO tapes. For these multi-tape cables, traditional instrumentation, such as voltage taps and resistive strain gauges, become insufficient to help measure and understand the performance-limiting factors in these model magnets. Distributed fiber-optic sensing (DFOS) is a potential solution to address this challenge. Although DFOS is well established for various applications, measuring temperature and strain in high-temperature superconducting magnets is in its infancy. Here we report the detailed implementation and test results of DFOS based on Rayleigh scattering in a subscale canted cosθ (CCT) dipole magnet using high-temperature superconducting...

Distributed Acoustic Sensing for Whale Vocalization Monitoring: A Vertical Deployment Field Test

Fri, 25 Jul 2025 00:00:00 +0000

Abstract There is growing interest in floating offshore wind turbine (FOWT) technology, where turbines are installed on floating structures anchored to the seabed, allowing wind energy development in areas unsuitable for traditional fixed-platform turbines. Responsible development requires monitoring the impact of FOWTs on marine wildlife, such as whales, throughout the operational lifecycle of the turbines. Distributed acoustic sensing (DAS)—a technology that transforms fiber-optic cables into vibration sensor arrays—has been demonstrated for acoustic monitoring of whales using seafloor telecommunications cables. However, no studies have yet evaluated DAS performance in dynamic, engineered environments, such as floating platforms or moving vessels with complex, dynamic strain loads, despite their relevance to FOWT settings. This study addresses that gap by deploying DAS aboard a boat in Monterey Bay, California, where a fiber-optic cable was lowered using a weighted and suspended...

PFSA-Ionomer Adsorption to C and Pt/C Particles in Fuel-Cell Inks

Fri, 25 Jul 2025 00:00:00 +0000

Catalyst inks used to make fuel-cell electrodes consist of Pt/C catalyst particles and a perfluorosulfonic acid (PFSA) ionomer dispersed in water/alcohol solvent mixtures. PFSA ionomer in the ink adsorbs to the surface of the catalyst particles, dictating the dispersion colloid properties. Following adsorption, the subsequent distribution of excess nonadsorbed ionomer in the ink then governs the final structure of the electrode. Here, we characterize the adsorption of the PFSA ionomer onto Pt/C catalyst particles. PFSA adsorption is largely irreversible. Adsorbed sulfonic-acid moieties impart a negative charge on the catalyst surface, causing electrostatic repulsion between the free ionomer in solution and the ionomer-covered Pt/C particle surface. The amount of adsorption is limited by the resulting electrostatic charge that grows as more ionomer adsorbs, and the catalyst surface becomes more negatively charged. Attenuating electrostatic repulsion by increasing the ink ionic...

Continuous surface-to-distributed acoustic sensor snapshots explain reactivation of individual natural fractures during an unconventional reservoir stimulation

Thu, 24 Jul 2025 00:00:00 +0000

ABSTRACT Fiber-optic sensing technologies allow petroleum engineering teams to detect hydraulic fracture interaction with boreholes during unconventional reservoir stimulation. In combination with high-repeatability seismic sources, the same distributed acoustic sensors (DASs) enable vertical seismic profiling (VSP) of the fracture evolution away from the boreholes. We discovered clear signatures of seismic scattering on activated fractures during nine days of continuous seismic monitoring of the fracturing stages at the Austin Chalk/Eagle Ford Field Laboratory. The present study applies a novel approach for quantitative analysis of the scattering events in terms of the evolution of the geometry and elastic stiffness of individual fractures. Our characterization strategy sequentially refines the fracture models: from a stack of 1D soft layers to 3D rectangular inclusions. First, we estimate the number of fracture locations and reflectivity using a modified sparse-spike deconvolution...

Techno-economic performance of reservoir thermal energy storage for data center cooling system

Thu, 24 Jul 2025 00:00:00 +0000

Electronic equipment in data centers generates heat during operation, which should be dissipated through a cooling system to prevent overheating and maintain optimal performance. Electricity consumption for the data center cooling system becomes significant as the demand for data-intensive services increases. Although various technologies have been developed and integrated into the data center cooling system, there are limited high-efficiency alternatives for data center cooling. In this study, we designed a reservoir thermal energy storage (RTES) system that stores cooling energy during winters and produces it during summers for data center cooling. We then demonstrated the techno-economic performance of the RTES incorporated with dry coolers and heat recovery for a year-round 5 MW cooling load. The RTES cooling production was reliable during the 20-year lifetime. We estimated the levelized cost of cooling as $5/MWh, significantly lower than $15/MWh for the base scenario...

Revealing complex subsurface dynamics with continuous seismic monitoring: Observations using distributed acoustic sensing and surface orbital vibrators during hydraulic fracturing

Thu, 24 Jul 2025 00:00:00 +0000

ABSTRACT Understanding hydraulic fracturing is crucial to improving the stimulation of unconventional reservoirs and increasing fluid production. This study develops a novel seismic monitoring technology using distributed acoustic sensing (DAS) and surface orbital vibrators (SOV) to capture fracture seismic response and mechanical properties at high temporal intervals. We analyze continuous time-lapse vertical seismic profiling (VSP) data acquired every hour during the first nine days of treatment of an unconventional reservoir in the Austin Chalk/Eagle Field Laboratory. The VSP data contain clear seismic signals scattered from the activated fractures. The spatiotemporal changes of the fracture reflectivity revealed by the SOV/DAS data correlate well with the observations of fracture locations inferred from low-frequency DAS data. These results capture the fracture opening and closure processes, as well as highlight potential prestage activations of the fractures due to hydraulic...

Sulfate Promotes Compact CaCO3 Formation and Protects Portland Cement from Supercritical CO2 Attack

Tue, 22 Jul 2025 00:00:00 +0000

Supercritical (sc) CO₂ in geologic carbon sequestration (GCS) can chemically and mechanically deteriorate wellbore cement, raising concerns for long-term operations. In contrast to the conventional view of "sulfate attack" on cement, we found that adding 0.15 M sulfate to the acidic brine can significantly reduce the impact of scCO₂ attack on Portland cement, resulting in stronger cement than that found in a sulfate-free system. Scanning electron microscopy revealed a decreased total attack depth in reacted cement in the presence of sulfate. With a newly defined minimum porosity term in reactive transport modeling, our model suggests that sulfate caused CaCO₃ to fill more nanopore spaces in the cement. Small angle X-ray scattering experiments also showed that sulfate can decrease the pore sizes of the carbonate layer. The results suggest that the interactions between sulfate and cement can generate a less porous CaCO₃ layer, which better...

DECOVALEX-2023: An international collaboration for advancing the understanding and modeling of coupled thermo-hydro-mechanical-chemical (THMC) processes in geological systems

Tue, 22 Jul 2025 00:00:00 +0000

The DECOVALEX initiative is an international research collaboration (www.decovalex.org), initiated in 1992, for advancing the understanding and modeling of coupled thermo-hydro-mechanical-chemical (THMC) processes in geological systems. DECOVALEX stands for “DEvelopment of COupled Models and VALidation against EXperiments”. The creation of this international initiative was motivated by the recognition that prediction of these coupled effects is an essential part of the performance and safety assessment of geologic disposal systems for radioactive waste and spent nuclear fuel. DECOVALEX emphasizes joint analysis and comparative modeling of the complex perturbations and coupled processes in geologic repositories and how these impact long-term performance predictions. The most recent phase of the DECOVALEX Project, here referred to as DECOVALEX-2023, started in early 2020 and ended in late 2023. More than fifty research teams associated with 17 international DECOVALEX partner organizations...

DeFault: DEep‐Learning‐Based FAULT Delineation Using the IBDP Passive Seismic Data at the Decatur CO2 Storage Site

Mon, 21 Jul 2025 00:00:00 +0000

Abstract The carbon capture, utilization, and storage (CCUS) framework is an essential component in reducing greenhouse gas emissions, with its success hinging on the comprehensive knowledge of subsurface geology and geomechanics. Passive seismic event relocation and fault detection offer vital insights into subsurface structures and the ability to monitor fluid migration pathways. Accurate identification and localization of seismic events, however, face significant challenges, including the necessity for high‐quality seismic data and advanced computational methods. To address these challenges, we introduce a novel deep learning method, , specifically designed for passive seismic source relocation and fault delineating for passive seismic monitoring projects. By leveraging data domain‐adaptation, allows us to train a neural network with labeled synthetic data and apply it directly to field data. Using , the passive seismic sources are automatically clustered based on their recording...

Degradation of Fuel Cell Membrane Electrode Assemblies from Buses Operated More than 25,000 h

Fri, 18 Jul 2025 00:00:00 +0000

This study investigates the performance losses and degradation of proton-exchange-membrane fuel-cell stacks taken from the Alameda Contra Costa Transit District (AC Transit) bus system (Alameda and Contra Costa counties, California, United States) that were operated for over 25,000 h. Here, we focus on the origin of differences in electrochemical performance between beginning-of-life (BOL) and end-of-life states as well as diagnostic data acquired during the lifetime of the buses. In doing so, we employ in- and ex- situ characterization methods such as polarization curves, electrochemical impedance spectroscopy, electron microscopy, and X-ray characterization. Uniform degradation of the catalyst layer including Pt agglomeration/migration and electrode thinning was observed in all of the post-teardown measurements compared to BOL materials resulting from years of field operation. Despite these changes, the measured post-teardown performance suggests a sufficient output for the...

Functionalized Porous Polymer Networks as High-Performance PFAS Adsorbents