Outflow Solutions Research Articles

Experimental study on optimizing tailwater reinjection technology for weakly consolidated sandstone geothermal reservoirs

The difficulty of recharging the weakly consolidated sandstone geothermal reservoirs (WCSGR) is a macroscopic manifestation of the interplay of multiple factors associated with both fluids and formation properties. However, current studies predominantly focus on the influence mechanisms of individual factors on the reinjection of WCSGR. To address this limitation, a high temperature–pressure core flow experimental platform, combined with an orthogonal experimental design, is employed to investigate the dynamic reinjection process of WCSGR under the combined effects of multiple factors. The research indicates that high temperatures significantly impact the movement of 3 μm microspheres, leading to a rapid decrease in core permeability. Additionally, in experiments conducted at flow rates of 2 mL/min, 3 mL/min, and 4 mL/min, the pH stabilization time of the outflow solution decreased, while both the pH value and turbidity of the outflow solution increased, compared to the experiments conducted at flow rate of 0.5 mL/min and 1 mL/min. The permeability damage rate (%) was used as the experimental evaluation index. The primary and secondary order of influence of each factor on the permeability is: microsphere size > flow rate > turbidity > confining pressure > temperature. The optimal levels for each factor are 5 μm, 4 mL/min, 2 mg/L, 1.4 MPa, and 25 °C, respectively. Consequently, the reinjection technology of GT in WCSGR is optimized.

A unified accretion disc model for supermassive black holes in galaxy formation simulations: method and implementation

ABSTRACT It is well established that supermassive black hole (SMBH) feedback is crucial for regulating the evolution of massive, if not all, galaxies. However, modelling the interplay between SMBHs and their host galaxies is challenging due to the vast dynamic range. Previous simulations have utilized simple subgrid models for SMBH accretion, while recent advancements track the properties of the unresolved accretion disc, usually based on the thin α-disc model. However, this neglects accretion in the radiatively inefficient regime, expected to occur through a thick disc for a significant portion of an SMBH’s lifetime. To address this, we present a novel ‘unified’ accretion disc model for SMBHs, harnessing results from the analytical advection-dominated inflow–outflow solution (ADIOS) model and state-of-the-art general relativistic (radiation-)magnetohydrodynamics (GR(R)MHD) simulations. Going from low to high Eddington ratios, our model transitions from an ADIOS flow to a thin α-disc via a truncated disc, incorporating self-consistently SMBH spin evolution due to Lense–Thirring precession. Utilizing the moving mesh code arepo, we perform simulations of single and binary SMBHs within gaseous discs to validate our model and assess its impact. The disc state significantly affects observable luminosities, and we predict markedly different electromagnetic counterparts in SMBH binaries. Crucially, the assumed disc model shapes SMBH spin magnitudes and orientations, parameters that gravitational wave observatories like LISA and IPTA are poised to constrain. Our simulations emphasize the importance of accurately modelling SMBH accretion discs and spin evolution, as they modulate the available accretion power, profoundly shaping the interaction between SMBHs and their host galaxies.

Study of Advective Energy Transport in the Inflow and Outflow of Super-Eddington Accretion Flows

Photon trapping is believed to be an important mechanism in super-Eddington accretion, which greatly reduces the radiative efficiency as photons are swallowed by the central black hole before they can escape from the accretion flow. This effect is interpreted as the radial advection of energy in one-dimensional height-integrated models, such as the slim-disk model. However, when multidimensional effects are considered, the conventional understanding may no longer hold. In this paper, we study the advective energy transport in super-Eddington accretion based on a new two-dimensional inflow–outflow solution with radial self-similarity, in which the advective factor is calculated self-consistently by incorporating the calculation of radiative flux instead of being set as an input parameter. We found that radial advection is actually a heating mechanism in the inflow due to compression, and the energy balance in the inflow is maintained by cooling via radiation and vertical (θ-direction) advection, which transports entropy upward to be radiated closer to the surface or carried away by the outflow. As a result, fewer photons are advected inward, and more photons are released from the surface, so that the mean advective factor is smaller and the emergent flux is higher than the fluxes predicted by the slim-disk model. The radiative efficiency of super-Eddington accretion thus should be higher than that of the slim-disk model, which agrees with the results of some recent numerical simulations.

Time-Series Deep Learning Models for Reservoir Scheduling Problems Based on LSTM and Wavelet Transformation

In 2022, as a result of the historically exceptional high temperatures that have been observed this summer in several parts of China, particularly in the province of Sichuan, residential demand for energy has increased. Up to 70% of Sichuan’s electricity comes from hydropower, thus creating a sensible and practical reservoir scheduling plan is essential to maximizing reservoir power generating efficiency. However, classical optimization, such as back propagation (BP) neural network, does not take into account the correlation of samples in time while generating reservoir scheduling rules. We proposed a prediction model based on LSTM neural network coupled with wavelet transformation (WT-LSTM) to address the problem. In order to extract the reservoir scheduling rules, this paper first gathers the scheduling operation data from the Xiluodu hydropower station and creates a dataset. Next, it uses the feature of the time-series prediction model with the realization of a complex nonlinear mapping function, time-series learning capability, and high prediction accuracy. The results demonstrate that the time-series deep learning network has high learning capability for reservoir scheduling by comparing evaluation indexes such as root mean square error (RMSE), rank-sum ratio (RSR), and Nash–Sutcliffe efficiency (NSE). The WT-LSTM network model put forward in this research offers better prediction accuracy than conventional recurrent neural networks and serves as a reference base for scheduling decisions by learning previous scheduling data to produce outflow solutions, which has some theoretical and practical benefits.

Double flows anchored in a Kerr black hole horizon – I. Meridionally self-similar MHD models with loading terms

ABSTRACT Recent observations of supermassive black holes have brought us new information on their magnetospheres. In this study, we attempt a theoretical modelling of the coupling of black holes with their jets and discs, via three innovations. First, we propose a semi-analytical MHD description of a steady relativistic inflow–outflow structure characteristic to the extraction of the hole rotational energy. The mass-loading is ensured in a thin layer, the stagnation surface, by a two-photon pair production originating to a gamma-ray emission from the surrounding disc. The double flow is described near the polar axis by an axisymmetric meridionally self-similar MHD model. Secondly, the inflow and outflow solutions are crossing the MHD critical points and are matched at the stagnation surface. Knowledge of the MHD field on the horizon gives us the angular momentum and energy extracted from the black hole. Finally, we illustrate the model with three specific examples of double-flow solutions by varying the energetic interaction between the MHD field and the rotating black hole. When the isorotation frequency is half of the black hole one, the extracted Poynting flux is comparable to the one obtained using the force-free assumption. In two of the presented solutions, the Penrose process dominates at large colatitudes, while the third is Poynting flux dominated at mid-colatitudes. Mass injection rate estimations, from disc luminosity and inner radius, give an upper limit just above the values obtained for two solutions. This model is pertinent to describe the flows near the polar axis, where pair production is more efficient.

Quantitative measurement of corrosion at the nanoscale by in situ spectral modulation interferometry

This research study presents a novel application of a quantitative phase microscopy technique, spectral modulation interferometry (SMI), for in situ nanoscale characterization of corrosion of an aluminum alloy in real time. SMI offers high sensitivity, rapid image acquisition, and speckle-free images; thus, real-time quantification of surface topography evolution during corrosion can be obtained accurately to evaluate the temporally- and spatially-dependent corrosion rates. With an innovative additive-manufactured fluid cell, experiments were performed in situ under flowing solution conditions. Electrochemical tests via stepwise polarization and solution chemistry through collected aliquots of outflow solution were also performed alongside the nanoscale SMI experiment to simultaneously provide a corroborating corrosion rate measurement. Based on the quantitative 3D height profiles across the corroded surface, pit formation resulting from rapid local corrosion was predominant, appearing at different times and are heterogeneously distributed across the surface. The computed time-dependent dissolution rates of aluminum also varied as the experiment proceeded, with the combination of linear and nonlinear surface normal distributions. An initial mean linear dissolution rate of [0.40 ± 0.007] μmol m−2 s−1 transitioned to a more rapid mean rate of [1.95 ± 0.035] μmol m−2 s−1, driven by the anodic polarization. Dissolution rates from the three performed methods follow similar trends and there is the visibility of linking the nanoscale in situ SMI data to the electrochemical corrosion measurements and ex situ chemical solution analysis. At the end of the corrosion period, rates of 118 μmol m−2 s−1, 71 μmol m−2 s−1, and 2.45 μmol m−2 s−1 were obtained from electrochemical measurements, ex situ solution analyses, and in situ SMI corrosion measurement, respectively. Finally, these experimental results validate the applicability of SMI for in situ nanoscale characterization of a corroding alloy surface.

Three-dimensional General-relativistic Simulations of Neutrino-driven Winds from Rotating Proto-neutron Stars

We explore the effects of rapid rotation on the properties of neutrino-heated winds from proto-neutron stars (PNS) formed in core-collapse supernovae or neutron-star mergers by means of three-dimensional general-relativistic hydrodynamical simulations with M0 neutrino transport. We focus on conditions characteristic of a few seconds into the PNS cooling evolution when the neutrino luminosities obey erg s−1, and over which most of the wind mass loss will occur. After an initial transient phase, all of our models reach approximately steady-state outflow solutions with positive energies and sonic surfaces captured on the computational grid. Our nonrotating and slower rotating models (angular velocity relative to Keplerian Ω/ΩK ≲ 0.4; spin period P ≳ 2 ms) generate approximately spherically symmetric outflows with properties in good agreement with previous PNS wind studies. By contrast, our most rapidly spinning PNS solutions (Ω/ΩK ≳ 0.75; P ≈ 1 ms) generate outflows focused in the rotational equatorial plane with much higher mass-loss rates (by over an order of magnitude), lower velocities, lower entropy, and lower asymptotic electron fractions, than otherwise similar nonrotating wind solutions. Although such rapidly spinning PNS are likely rare in nature, their atypical nucleosynthetic composition and outsized mass yields could render them important contributors of light neutron-rich nuclei compared to more common slowly rotating PNS birth. Our calculations pave the way to including the combined effects of rotation and a dynamically important large-scale magnetic field on the wind properties within a three-dimensional GRMHD framework.

The Dynamical Structure of the Outflows Driven by a Large-scale Magnetic Field

Abstract A large-scale magnetic field is crucial in launching and collimating jets/outflows. It is found that the magnetic flux can be efficiently transported inward by a fast-moving corona above a thin disk. In this work, we investigate the dynamical structure of the outflows driven by the large-scale magnetic field advected by a hot corona. With the derived large-scale magnetic field, the outflow solution along every field line is obtained by solving a set of magneto-hydrodynamic equations self-consistently with boundary conditions at the upper surface of the corona. We find that the terminal speeds of the outflows driven from the inner region of the disk are ∼0.01–0.1c. The temperatures of the outflows at a large distance from the black hole are still as high as several ten keV. The properties of the magnetic outflows derived in this work are roughly consistent with the fast outflows detected in some luminous quasars and X-ray binaries (XRBs). The total mass-loss rate in the outflows from the corona is about 7%–12% of the mass-accretion rate of the disk. The three-dimensional field geometry, the velocity, temperature, and density of the outflows derived in this work can be used for calculating the emergent spectra and their polarization of the accretion disk/corona/outflow systems. Our results may help understand the features of the observed spectra of XRBs and active galactic nuclei.

Relativistic jet acceleration region in a black hole magnetosphere

We discuss stationary and axisymmetric trans-magnetosonic outflows in the magnetosphere of a rotating black hole (BH). Ejected plasma from the plasma source located near the BH is accelerated far away to form a relativistic jet. In this study, the plasma acceleration efficiency and conversion of fluid energy from electromagnetic energy are considered by employing the trans-fast magnetosonic flow solution derived by Takahashi & Tomimatsu (2008). Considering the parameter dependence of magnetohydrodynamical flows, we search for the parameters of the trans-magnetosonic outflow solution to the recent M87 jet observations and obtain the angular velocity values of the magnetic field line and angular momentum of the outflow in the magnetized jet flow. Therefore, we estimate the locations of the outer light surface, Alfv\'en surface, and separation surface of the flow. We also discuss the electromagnetic energy flux from the rotating BH (i.e., the Blandford-Znajek process), which suggests that the energy extraction mechanism is effective for the M87 relativistic jet.

Radiatively driven, time dependent bipolar outflows

ABSTRACT We study the radiatively driven fluid jets around a non-rotating black hole. The radiation arising from the inner compact corona and outer sub-Keplerian part of the disc accelerates the jets. We obtain the steady state, semi-analytical, radiatively driven outflow solutions. The thermodynamics of the outflow is described by a variable adiabatic index equation of state. We develop a total variation diminishing (TVD) routine to investigate the time dependent behaviour of the radiatively driven bipolar outflow. We inject with flow variables from the steady state outflow solutions in the TVD code and allow the code to settle into steady state and match the numerical results with the steady state solution. The radiation arising out of the accretion disc can provide a wide range of jet solutions, depending upon parameters like the intensity of disc, location of the inner corona etc. We induce the time dependence of the radiation field by inducing oscillation of the inner corona of the accretion disc. The radiation field then makes the bipolar outflow time dependent. We show that a non-steady radiation field arising out of disc oscillations can generate the internal shocks closer to the jet base. Depending on the disc geometry, there might be transient shocks in the jet and there might be multiple non-stationary shocks in the jet, which are of much interest in jet physics.

Constraints on the Mass Accretion Rate onto the Supermassive Black Hole of Cygnus A Using the Submillimeter Array

Abstract We present the first detailed polarimetric studies of Cygnus A at 230 GHz with the Submillimeter Array (SMA) to constrain the mass accretion rate onto its supermassive black hole. We detected the polarized emission associated with the core at a fractional polarization of . This low fractional polarization suggests that the polarized emission is highly depolarized. One of the possible explanations is due to a significant variance in the Faraday rotation measure within the synthesized beam. By assuming the Faraday depolarization caused by inhomogeneous column density of the magnetized plasma associated with the surrounding radiatively-inefficient accretion flow within the SMA beam, we derived the constraint on the mass accretion rate to be larger than 0.15 yr−1 at the Bondi radius. The derived constraint indicates that an adiabatic inflow–outflow solution or an advection-dominated accretion flow should be preferable as the accretion flow model in order to explain the jet power of Cygnus A.

Cardioprotective effect of H2S and glutathione synthesis modulation is mediated by inhibition mitochondrial permeability transition pore opening

Hydrogen sulfide (H2S) was recently classified as the third gaseous transmitter produces by two cytosolic cystathionine γ-lyase (CSE) and cystathionine β-synthase, and one mitochondrial enzyme – 3-mercaptopyruvate sulfurtransferase. It was clearly shown that H2S protects against cardiac ischemia/reperfusion (I/R) injury in a wide range of exogenously applied doses of H2S donors. Cell damage within I/R injury is caused by extensive reactive oxygen species (ROS) mainly produced by mitochondria. ROS fleshes are associated with massive opening of mitochondrial permeability transition (MPT) pores and contribute to deterioration of heart function. However, it may be prevented in case of pharmacological inhibition of MPT pores opening. Mixture of mitochondrial metabolites released through the opened MPT pores can be detected in situ as increased optical density of outflow solutions at a wavelength of 245-250 nm and was called mitochondrial factor (MF). One of the most powerful antioxidant agents that preserve redox status in tissues is tripeptide glutathione. It forms in two ATP-depended reactions and exists in two forms reduced and oxidized one. Glutathione and H2S have a common precursor – amino acid L-cysteine. In this study, we used Langendorff isolated rat heart model to investigate the effect of H2S and glutathione synthesis modulation on MPT pores opening in I/R injury. Rats were pretreated intraperitoneally with D,L-propargylglycine (11,3 mg/kg), an inhibitor of H2S-producing enzyme CSE, L-cysteine (121 mg/kg) and buthionine sulfoximine (BSO, 22,2 mg/kg) an inhibitor of first step of glutathione synthesis. Cardiac function, oxygen metabolism and MPT pores opening in situ were measured. We clearly showed that treatment with PAG and L-cysteine provided pharmacological precondition and exerted cardioprotective effect inhibiting MPT pores opening as greatly decreased MF release from isolated heart. Pretreatment with BSO abolished cardioprotective effect of PAG+L-cysteine combination. Absorbance spectra in L-cysteine pretreated group did not differ from the control. Thus, we demonstrate that PAG+L-cysteine induced cardioprotection mediated via inhibition of MPT pores opening.

Structure of the self-gravitating accretion discs in the presence of outflow

ABSTRACT Numerical simulations of self-gravitating accretion discs have shown that the evolution of such systems depends strongly on the rate at which it cools. In this work, we study the vertical structure of the self-gravitating accretion discs and also investigate the effect of the cooling rate on the latitudinal structure of such accretion discs. In the spherical coordinates, we write the hydrodynamics equations and simplify the basic equations based on the assumptions of axisymmetric and steady state. We use the self-similar method for solving the equations in the radial direction and we find proper boundary conditions. We find inflow–outflow solutions by considering the meridional component of the velocity field. In order to formulate the cooling term in energy equation, we introduce the new parameter β as a free constant that is the cooling time-scale in units of the dynamical time-scale. Our numerical solutions show that the thickness of the disc decreases with smaller β (or increasing the cooling term in energy equation) and it makes the disc colder and outflows form in the regions with lower latitude. So by increasing the cooling rate in the disc, the regions which belong to inflow decrease.

Two-dimensional Inflow–Outflow Solution of Supercritical Accretion Flow

Abstract We present the two-dimensional inflow–outflow solutions of radiation hydrodynamic equations of supercritical accretion flows. Compared with prior studies, we include all components of the viscous stress tensor. We assume steady-state flow and use self-similar solutions in the radial direction to solve the equations in the r–θ domain of spherical coordinates. The set of differential equations have been integrated from the rotation axis to the equatorial plane. We find that the self-similarity assumption requires that the radial profile of density is described by ρ(r) ∝ r −0.5. Correspondingly, the radial profile of the mass inflow rate decreases with decreasing radius as . An inflow–outflow structure has been found in our solution. Inflow exists in the region θ > 65°, while above that the flow moves outward and outflow could launch. The driving forces of the outflow are analyzed and it is found that the radiation force is dominant and pushes the gas particles outward with poloidal velocity ∼0.25c. The properties of the outflow are also studied. The results show that the mass flux-weighted angular momentum of the inflow is lower than that of the outflow, thus the angular momentum of the flow can be transported by the outflow. We also analyze the convective stability of the supercritical disk and find that in the absence of a magnetic field, the flow is convectively unstable. Our analytical results are fully consistent with the previous numerical simulations of supercritical accretion flow.

Outflows from inflows: the nature of Bondi-like accretion

ABSTRACT The classic Bondi solution remains a common starting point both for studying black hole growth across cosmic time in cosmological simulations and for smaller scale simulations of active galactic nuclei (AGN) feedback. In nature, however, there will be inhomogeneous distributions of rotational velocity and density along the outer radius (Ro) marking the sphere of influence of a black hole. While there have been many studies of how the Bondi solution changes with a prescribed angular momentum boundary condition, they have all assumed a constant density at Ro. In this Letter, we show that a non-uniform density at Ro causes a meridional flow and due to conservation of angular momentum, the Bondi solution qualitatively changes into an inflow–outflow solution. Using physical arguments, we analytically identify the critical logarithmic density gradient |$\partial \ln \rho/\partial \theta$| above which this change of the solution occurs. For realistic Ro, this critical gradient is less than 0.01 and tends to 0 as Ro → ∞. We show using numerical simulations that, unlike for solutions with an imposed rotational velocity, the accretion rate for solutions under an inhomogeneous density boundary condition remains constant at nearly the Bondi rate $\dot{M}_\mathrm{ B}$, while the outflow rate can greatly exceed $\dot{M}_\mathrm{ B}$.

Effect of plasma composition on magnetized outflows

In this paper, we study magnetized winds described by variable adiabatic index equation of state in Paczyński & Wiita pseudo-Newtonian potential. We identify the flow solutions with the parameter space of the flow. We also confirm that the physical wind solution is the one which passes through the slow, Alfvén, and fast critical points. We study the dependence of the wind solution on the Bernoulli parameter E and the total angular momentum L. The adiabatic index, which is a function of temperature and composition, was found to be variable in all the outflow solutions. For the same values of the Bernoulli parameter and the total angular momentum, a wind in strong gravity is more accelerated, compared to a wind in Newtonian gravity. We show that flow variables such as the radial and azimuthal velocity components and temperature all depend on the composition of the flow. Unlike the outflow solutions in hydrodynamic regime, the terminal speed of a magnetically driven wind also depends on the composition parameter.

Radial Convection in Hot Accretion Flows

Abstract In this work, we study the vertical structure of a hot accretion flow by taking into account radial transportation of angular momentum and energy due to the presence of turbulence, convection, and outflow. We write the hydrodynamics equations in the spherical coordinates, and, based on the assumptions of axisymmetric and steady state, we simplify the basic equations. Employing self-similar solutions in the radial direction and finding proper boundary conditions, we solve the ordinary differential equations with respect to the polar angle. Considering the meridional component of the velocity field, we find inflow–outflow solutions. In order to formulate the convection term, we introduce two parameters, i.e., α c and g as free parameters. The first one is called the convection parameter and the greater value of it makes the convection more effective in changing the flow dynamics. The second one, g, varies between zero and unity (where g = 1 implies that the convection behaves similarly to the turbulence viscosity and g = 0 means the convection behaves in the opposite direction of viscosity). Our results show that the accretion rate decreases with greater α c and it makes the disk warmer and intensifies the outflows from the disk's surface. On the other hand, the g parameter affects the flow in an opposite manner compared to the convection parameter and makes the disk rotate and accrete faster.

Fourier Analysis of Advection-dominated Accretion Flows

Abstract We implement a new semi-analytical approach to investigate radially self-similar solutions for the steady-state advection-dominated accretion flows (ADAFs). We employ the usual α-prescription for the viscosity, and all components of the energy–momentum tensor are considered. In this case, in the spherical coordinate, the problem reduces to a set of eighth-order, nonlinear differential equations with respect to the latitudinal angle θ. Using the Fourier expansions for all the flow quantities, we convert the governing differential equations to a large set of nonlinear algebraic equations for the Fourier coefficients. We solve the algebraic equations via the Newton–Raphson method, and investigate the ADAF properties over a wide range of model parameters. We also show that the implemented series are truly convergent. The main advantage of our numerical method is that it does not suffer from the usual technical restrictions that may arise for solving ADAF differential equations near the polar axis. In order to check the reliability of our approach, we recover some widely studied solutions. Further, we introduce a new varying α viscosity model. New outflow and inflow solutions for ADAFs are also presented, using Fourier expansion series.

The 2D Disk Structure with Advective Transonic Inflow–Outflow Solutions around Black Holes

Abstract We solved analytically viscous two-dimensional (2D) fluid equations for accretion and outflows in spherical polar coordinates (r, θ, ϕ) and obtained explicitly flow variables in r- and θ-directions around black holes (BHs). We investigated global transonic advection-dominated accretion flow (ADAF) solutions in an r-direction on an equatorial plane using Paczyński–Wiita potential. We used radial flow variables of ADAFs with symmetric conditions on the equatorial plane as initial values for integration in the θ-direction. In the study of 2D disk structure, we used two azimuthal components of viscous stress tensors—namely, and . Interestingly, we found that the whole advective disk does not participate in outflow generation, and the outflows form close to the BHs. Normally, outflow strength increased with increasing viscosity parameter (α 1), mass-loss parameter (s), and decreasing gas pressure ratio (β). The outflow region increased with increasing s, α 1 for and decreasing α 2 for . The is effective in angular momentum transportation at high latitude and outflows collimation along an axis of symmetry, since it changes polar velocity ( ) of the flow. The outflow emission is also affected by the ADAF size and decreases with it. Transonic surfaces formed for both inflows ( , very close to BH) and outflows ( ). We also explored no outflows, outflows, and failed outflows regions, which mainly depend on the viscosity parameters.

Rapid immobilisation of U(VI) by Eucalyptus bark: Adsorption without reduction

Organic matter is increasingly shown to influence the mobility of uranium (U) in the environment. The mobility of U likely depends on whether the organic matter is in dissolved or solid form, with the latter able to retard U mobility. In this work, column experiments were used to reveal that solid organic matter, in the form of well characterized tree bark from Eucalyptus globulus, dramatically reduced the mobility of aqueous U(VI) which was introduced as uranyl nitrate [UO2(NO3)2]. Eucalyptus globulus bark contains high levels of carboxylic and phenolic acid groups which are known to bind to U. Admixtures containing 20 wt. % tree bark and sand were compared to columns containing sand only. We show that soluble U is adsorbed onto the tree bark, likely via a cation exchange with calcium, with no change in U oxidation state as confirmed by X-ray Absorption Near Edge Structure (XANES) analyses. Cation concentrations in column outflow solutions indicated that U was retained in the columns containing tree bark but was released from the sand-only columns. These results demonstrate that solid organic matter such as tree bark has potential applications in trapping U, possibly within permeable reactive barriers, without necessitating further engineering to reduce U(VI) to U(IV). Building on previous work on organic sedimentary U-deposits, this study also helps understand processes of U enrichment from groundwater as observed in environments high in organic matter including wetlands and sediment-hosted ore deposits.