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Studies of solute transport in unconfined coastal aquifers typically neglect oceanic oscillations and assume a static seaward boundary condition defined by the mean annual sea level. In this paper, an image monitoring method is used to establish the quantitative relationship between the concentration of a colored tracer and the hue value of the image. The digital image was used to determine the tracer concentration distribution. Controlled laboratory experiments were conducted to quantitatively study the relationship between the tidal amplitude and the solute transport time and dispersion. Experiments show that the solute transport time is not associated with the tidal amplitude, but only with the average hydraulic gradient between the seaward boundary and the landward boundary. The dispersion range of the solute plume increases with the increase of the tidal amplitude. On large-scale beaches in nature, when the average hydraulic gradient of the aquifer between the sea side and the land side is small enough, the dispersion coefficient is proportional to the tidal amplitude in equal proportion. Therefore, when it comes to the transport time of pollutants, it is possible to set the seaward boundary as the mean annual sea level. In a study of the dispersion range of pollutants, it is inappropriate to set the seaward boundary as the mean annual sea level. [ABSTRACT FROM AUTHOR]

Background: The rhizosphere is the influence-sphere of the root. It is a local ecosystem with complex functions that determine nutrient uptake, cycling of resources, and plant health. Mathematical models can quantitatively explain and help to understand rhizosphere complexity. To interpret model predictions and relevance of processes, we require understanding of the underlying concepts. Conceptualization of rhizosphere processes bridges mathematical modeling and experimental work and thus is key to understanding the rhizosphere. Scope: We review concepts and assumptions foundational to the modeling of soil-plant-microorganism processes in the rhizosphere. Rhizosphere models are designed to simulate a plurality of components (solutes, substrates, and microorganisms). They specify components and interactions, drawing from the disciplines of soil science, botany, microbiology, and ecology. Solute transport models are applied to describe bioavailability in the rhizosphere. The root is typically a sink (e.g. nutrient uptake) or source (e.g. exudation) for one or more solutes. Microorganisms are usually described in time only, neglecting possible spatial movement. Interactions between components, e.g. chemical reactions and substrate-dependent bacterial growth rates, are usually described by coupling via reaction terms. Conclusions: Rhizosphere models share concepts that we organized in a collective framework. This collective framework facilitates the development of new models. The interdisciplinary approach in which knowledge from soil ecology, botany, and soil physics are combined in rhizosphere models has proven fruitful for applications in plant and soil systems. We advocate multi-component-multi-interaction ecosystems around the root, with each component represented by an advection-diffusion-motility-reaction equation. [ABSTRACT FROM AUTHOR]

We empirically test our earlier theoretical arguments about simplification of continuous‐time random walk (CTRW) solute transport models, namely that without loss of generality the velocity‐like term, vψ, may be set to mean groundwater velocity, the dispersion‐like term, Dψ, defined by a classical, velocity‐independent dispersivity, and the so‐called time constant, τ, to unity. We also argue that for small‐scale heterogeneous advection (HA) and mobile‐immobile mass transfer (MIMT) CTRW transition time distributions, ψ(t), are unaffected by mean flow velocity. To experimentally test these claims, we re‐analyze two bench‐scale transport experiments—one for HA, one for MIMT—each performed at multiple flow rates in otherwise identical conditions, and show it is possible to simultaneously explain all breakthrough curves in each, subject to the above constraints. We compare our calibrations with earlier efforts for the same data sets. In the HA calibration we identify a ψ(t) of the same functional form as previous authors, and which yielded breakthrough predictions essentially identical to theirs, but with greatly differing parameters. This illustrates how values of individual CTRW parameters may not map one‐to‐one onto underlying physics. We recommend reporting complete model descriptions, discuss how the simplified approach assists in this and other theoretical considerations. Key Points: We show how a simplified, physically‐constrained continuous‐time random walk (CTRW) approach and velocity‐independent transition time distributions explain experimental dataBreakthrough curves (BTCs) at multiple flow rates are fit with true velocities and shared CTRW parameters (with unit time constant) for two physical setupsWe show by example how distinct sets of CTRW parameters may fit the same BTC ensemble; parameters cannot be interpreted individually [ABSTRACT FROM AUTHOR]

Clay soils, usually in an unsaturated state, are widely used as barrier materials in solid waste landfills. When the saturation of clay soils is high, the gas phase will be in the form of entrapped bubbles. The entrapped bubbles can directly affect the soil hydraulic behavior, which further affects solute transport in clay liner. Therefore, based on the stress balance, fluid mass conservation, and solute mass conservation equations, and combined with the relationship between pore water pressure and air pressure in unsaturated state, a coupled hydro-mechanical-chemical model has been put forward to study the influence of entrapped bubbles on solute transport process. Using the proposed model, a series of numerical calculations are carried out through the finite element simulation software COMSOL Multiphysics. The numerical results show that the increase of entrapped bubble content can enlarge soil deformation and slow down the rates of excess pore fluid pressure dissipation and solute transport. In particular, when the degree of saturation in air phase increases from 0 to 0.2, the difference of influence depth at the transport time 10 years reaches 28 cm, and the breakthrough time of solute is prolonged by 17.8 years. [ABSTRACT FROM AUTHOR]

We present a numerical simulation study of advective–diffusive scalar transport in three-dimensional high-contrast discontinuous permeability fields, generated with a truncated pluri-Gaussian geostatistical approach. The numerical experiments are run with an Eulerian approach using a novel unified numerical framework based on the finite-volume library OpenFOAM®(Weller et al. in Comput Phys 12(6):620–631, 1998), for (1) generating random pluri-Gaussian porous media, (2) solving the steady state Darcy-scale flow, (3) solving the advection diffusion equation, (4) computing post-processing quantities such as first order statistics, spatial probability density functions and breakthrough curves. A range of permeability contrasts, correlation lengths, and Péclet numbers are tested to assess their relative weight on transport control and for the first time, the deviation of a calibrated macrodispersive model from the Fickian transport is quantified. We identify a hierarchy of non-Fickian transport triggering factors. From the tested scenarios, permeability contrast is the main controlling parameter for the anomalous transport behaviour as it enhances the generation of preferential flow paths which are characterised by high advective flow velocities. The Péclet number and the characteristic length at which facies transitions are observed as secondary factors. [ABSTRACT FROM AUTHOR]

Land use within a watershed impacts stream channel morphology and hydrology and, therefore, in‐stream solute transport processes and associated transient storage mechanisms. This study evaluated transport processes in two contrasting stream sites where channel morphology was influenced by the surrounding land use, land cover, climate and geologic controls: Como Creek, CO, a relatively undisturbed, high gradient, forested stream with a gravel bed and complex channel morphology, and Clear Creek, IA, an incised, low‐gradient stream with low‐permeability substrate draining an agricultural landscape. We performed conservative stream tracer injections at these sites to address the following questions: (1) How does solute transport vary between streams with differing morphologies? and (2) How does solute transport at each stream site change as a function of discharge? We analysed in‐stream tracer time series data and compared results quantifying solute attenuation in surface and subsurface transient storage zones. Significant trends were observed in these metrics with varying discharge conditions at the forested site but not at the agricultural site. There was a broad range of transport mechanisms and evidence of substantial exchange with both surface and hyporheic transient storage in the relatively undisturbed, forested stream. Changing discharge conditions activated or deactivated different solute transport mechanisms in the forested site and greatly impacted advective travel time. Conversely in the simplified agricultural stream, there was a narrow range of solute transport behaviour across flows and predominantly surface transient storage at all measured discharge conditions. These results demonstrate how channel simplification inhibits available solute transport mechanisms across varying discharge conditions. [ABSTRACT FROM AUTHOR]

Past studies on concentration‐discharge (C‐Q) relationships have focused on short‐term or low‐temporal resolution data. While advancing understanding of catchment processes, these studies provided limited insight on catchment response over time or to climate change. Using 15 solutes from 1992 to 2015 at Sleepers River Research Watershed, Vermont, we compared C‐Q relationships over decades, years, and seasons to elucidate controls on stream chemical variation. We applied end‐member mixing analysis (EMMA) to identify solute sources and flow path routing. EMMA identified three end‐members: near‐surface runoff (NSR), riparian groundwater, and hillslope hollow groundwater. Shifting mixing proportions of these end‐members accounted for the temporal variability of conservative (no chemical reaction en route from source to stream) solutes in streamflow. For example, an increase in NSR fraction, typical of high flow, caused flushing (increased concentrations) of NO3−, DOC, Al, and Fe, which were greatest in NSR, dilution of specific conductance and base cation, SO42−, Si, Sr, Ba, and Mn concentrations, which were greatest in the two groundwater end‐members. This behaviour is reflected in the b‐coefficient of the C‐Q relation (C = aQb), which indicates the strength of dilution (b < −0.1) and flushing (b > 0.1) effects. For conservative solutes, the b‐coefficient decreased significantly (p < 0.01) with an increase in the groundwater to NSR concentration ratio. Solutes that are conservative and have relatively constant concentrations in end‐members over time showed consistent annual C‐Q patterns over years and decades. Furthermore, the strength of dilution or flushing was stronger during the snowmelt period, when the NSR fraction peaked, than during the dormant and growing seasons. With shorter snowmelt periods and snow to rain shifts, the flushing or dilution power of snowmelt runoff will weaken and alter catchment response to climate change. These insights provide more tools for the interpretation of catchment processes and responses to climate change. [ABSTRACT FROM AUTHOR]

Future Arctic tundra primary productivity and vegetation community composition will partly be determined by nitrogen (N) availability in a warmer climate. N mineralization rates are predicted to increase in both winter and summer, but because N demand and –mobility varies across seasons, the fate of mineralized N remains uncertain. N mineralized in winter is released in a "pulse" upon snowmelt and soil thaw, with the potential for lateral redistribution in the landscape. In summer, the release is into an active rhizosphere with high local biological N demand. In this study, we investigated the ecosystem sensitivity to increased lateral N input and near-surface warming, respectively and in combination, with a numerical ecosystem model (CoupModel) parameterized to simulate ecosystem biogeochemistry for a tundra heath ecosystem in West Greenland. Both measurements and model results indicated that plants were poor utilizers of increased early-season lateral N input, indicating that higher winter N mineralization rates may have limited impact on plant growth and carbon (C) sequestration for a hillslope ecosystem. The model further suggested that, although deciduous shrubs were the plant type with overall most lateral N gain, evergreen shrubs appear to have a comparative advantage utilizing early-season N. In contrast, near-surface summer warming increased plant biomass and N uptake, moving N from soil to plant N pools, and offered an advantage to deciduous plants. Neither simulated high lateral N fluxes nor near-surface soil warming suggests that mesic tundra heaths will be important sources of N2O under warmer conditions. Our work highlights how winter and summer warming may play different roles in tundra ecosystem N and C budgets depending on plant community composition. [ABSTRACT FROM AUTHOR]

The solute mixing phenomena of filler and base metal melts during dissimilar-filler metal-inert gas (MIG) welding are simulated by a multi-phase lattice Boltzmann (LB) model for predicting macrosegregation formation in the weld joint. The LB models incorporates the calculations of fluid field and solute transport, and the quantitative capalibity is validated through the problem of one-dimensional liquid diffusion. For the MIG welding of AA6063 sheets with an ER5183 filler wire, the simulation results reveal that the periodic impingement of heterogeneous filler metal droplets leads to symmetrical vortex flows accompanied by the unmixed zones formed in the center. These unmixed zones locate in the bulk weld pool and would develop into macrosegregation in the weld joint. In addition, the fluid flow near the fusion boundary remains almost stagnant, which gives rise to the appearance of the thereby continuous unmixed zone. The predicted distribution of unmixed zone in the weld pool agree well with the macrosegregation patterns in the weld joint observed in the experiments. For partially mimicking the effect of external magnetic field on droplet movement recorded by a high-speed camera, random droplet flight directions are arranged in the LB simulations. With the increase of droplet impact speed (Weber number) and the arrangement of random droplet flight direction, the simulated Mg concentration in the weld pool becomes more uniform, implying that the risk of macrosegregation formation is reduced. The LB simulations provides insight for better understanding the formation of weld defects during MIG welding with a dissimilar filler metal.

The impact of normal stress-induced closure on fluid flow and solute transport in a single rock fracture is demonstrated in this study. The fracture is created from a measured surface of a granite rock sample. The Bandis model is used to calculate the fracture closure due to normal stress, and the fluid flow is simulated by solving the Reynold equation. The Lagrangian particle tracking method is applied to modeling the advective transport in the fracture. The results show that the normal stress significantly affects fluid flow and solute transport in rock fractures. It causes fracture closure and creates asperity contact areas, which significantly reduces the effective hydraulic aperture and enhances flow channeling. Consequently, the reduced aperture and enhanced channeling affect travel time distributions. In particular, the enhanced channeling results in enhanced first arriving and tailing behaviors for solute transport. The fracture normal stiffness correlates linearly with the 5th and 95th percentiles of the normalized travel time. The finding from this study may help to better understand the stress-dependent solute transport processes in natural rock fractures.

It is proved that a transient 3D distribution of 18O concentration in a regional-scale heterogeneous multi-layered aquifer system can be numerically simulated by codes MODFLOW-2005 and MT3DMS as a boundary problem. An optimum method of the transition of the observed negative δ18O values to respective positive units of the absolute 18O concentration needed for simulations has been substantiated. The practical applicability of the elaborated method has been verified by the reconstruction and interpretation of the geohydrological history of the Estonian Artesian Basin during the Late Pleistocene and Holocene. The adequacy of regional hydrodynamic calculations proceeded by eight consecutive modelling scenarios has been verified by a good correlation between the measured and simulated 18O values. The set of functionally interconnected groundwater flow and 18O transport models forms an integral hydrogeological model of the Estonian Artesian Basin for the last 22 ka. The paper contributes to a wider application of 18O concentration as a conservative tracer in the investigation of the complex problem of groundwater flow and transport in real-world conditions.

Solute transport through the clay liner is a significant process in many waste landfills or unmanaged landfills. At present, researchers mainly focus on the test study about semi-membrane property of clay material, however, the influence of chemical osmosis caused by membrane effect on solute transport and fluid velocity is insufficient. In this investigation, based on the classical advection-diffusion equation, a one-dimensional solute transport model for low-permeable clay material has been proposed, in which the coupled fluid velocity related with hydraulic gradient and concentration gradient is introduced, and the semi-membrane effect is embodied in the diffusion mechanism. The influence of chemical osmosis on fluid velocity and solute transport has been analyzed using COMSOL Multiphysics software. The simulated results show that chemical osmosis has a significant retarded action on fluid velocity and pollutant transport. The proposed model can effectively reveal the change in process of coupled fluid velocity under dual gradient and solute transport, which can provide a theoretical guidance for similar fluid movement in engineering.

Brain waste is largely cleared via diffusion and advection in cerebrospinal fluid (CSF). CSF flows through a pathway referred to as the glymphatic system, which is also being targeted for delivering drugs to the brain. Despite the importance of solute transport, no brain-wide models for predicting clearance and delivery through perivascular pathways and adjacent parenchyma existed. We devised such a model by upgrading an existing model of CSF flow in the mouse brain to additionally solve advection-diffusion equations, thereby estimating solute transport. We simulated steady-state transport of 3 kDa dextran injected proximal to the perivascular space (PVS) of the middle cerebral artery, mimicking in vivo experiments. We performed a sensitivity analysis of 11 biological properties of PVSs and brain parenchyma by repeatedly simulating solute transport with varying parameter values. Parameter combinations that led to a large total pressure gradient, poor CSF perfusion or a steep solute gradient were deemed unrealistic. Solute concentrations in parenchyma were most sensitive to changes in pial PVS size, as this parameter linearly affects volume flow rates. We also found that realistic transport requires both highly permeable penetrating PVSs and high-resistance parenchyma. This study highlights the potential of brain-wide models to provide insights into solute transport processes.

To investigate the general laws of solute transport in homogeneous and heterogeneous soil,this study conducts column experiments in the laboratory to observe and monitor hydrodynamic dispersion under different conditions.The measured breakthrough curves of solute are fitted and analyzed by the classical advection-diffusion equation (ADE).The results reveal that the solute concentration has little effect on the hydrodynamic diffusion coefficient in homogeneous soil;however,the flow rate of solute transport can promote hydrodynamic diffusion,namely that a higher flow rate can lead to a larger hydrodynamic diffusion coefficient,and the breakthrough curves can be completed faster.There is a positive correlation between the hydrodynamic diffusion coefficient and the mean particle size of the sand at a certain flow rate.In addition,the scale effect is prominent in the solute transport process in soil;generally,the hydrodynamic diffusion coefficient increases with the traveling distance.Compared with the case of homogeneous soil,the heterogeneity and different layered structures of layered soil have a more significant influence on hydrodynamic dispersion.

Subsurface hydrodynamics underpin the eco-functions of salt marshes. Many studies have investigated these processes under various conditions. However, the impact of soil stratification (a low-permeability mud layer overlying a high-permeability sand layer) on the variable-density groundwater flow (particularly unstable flow) and solute transport in regularly tide-flooded marshes remains poorly understood. The present study numerically explored this question based on a 2D cross-creek section of salt marshes, by comparing cases with and without stratification. Results show that, the low-permeability mud layer delays the initiation of unstable flow and leads to smaller and denser salt fingers. Consequently, solute plume stays in the marsh soil for a longer time and spreads more widely than that in the homogeneous case. Also, soil stratigraphy extends the duration and shrinks the zone of solute discharge across the tidal creek. Sensitivity analysis was conducted based on three key controlling variables: hydraulic conductivity contrast between mud layer and sand layer (Kmud/Ksand), salinity contrast between surface water and groundwater (Csea/Cpore), and mud layer thickness (Dmud). The results demonstrate that the residence time of solute plume in a two-layered salt marsh is less sensitive to Csea/Cpore than to Kmud/Ksand and Dmud. Moreover, the commencement and duration of solute discharge are more sensitive to Kmud/Ksand and Dmud than to Csea/Cpore. While the location of solute discharge zone is highly sensitive to Dmud and slightly influenced by Kmud/Ksand and Csea/Cpore. Findings from this study would facilitate a deeper understanding of the eco-functions of salt marshes.

We consider a system of coupled equations modeling a shallow water flow with solute transport and introduce an artificial dissipation in order to improve the dissipation properties of the original cell-vertex central-upwind numerical scheme applied to these equations. Namely, a formulation is proposed which involves an artificial dissipation parameter and guarantees a consistency property between the continuity equation and the transport equation at the discrete level and, in addition, ensures the nonlinear stability and positivity of the scheme. A well-balanced positivity-preserving reconstruction is stated in terms of the conservative variable describing the concentration. We establish that constant-concentration states are preserved in space and time for any hydrodynamic flow field in the absence of source terms in the transport equation. Furthermore, we prove the maximum and minimum principles for the concentration. A suitable discretization of the diffusion term is used in combination with the proposed reconstruction procedure and artificial dissipation formulation and this allows us to prove the positivity of the concentration in the presence of diffusion effects. Finally, our numerical experiments confirm the well-balanced and positivity-preserving properties when the artificial dissipation is introduced in the central-upwind scheme, and the accuracy of the scheme for modeling surface water flows with transport processes. [ABSTRACT FROM AUTHOR]

Heterogeneity significantly effects the accuracy of flow and contaminant transport prediction in subsurface formations. The spatial correlation structure of hydraulic conductivity (K) is a crucial factor to characterize the heterogeneous architecture. In presented study, the relationship between the spatial correlation structure of K and plume dispersion is analyzed through the integration of experimental and numerical simulation approaches. A detailed description on the sedimentary facies types in a column experiment is obtained to ensure the accuracy of the heterogeneous characterization. The spatial correlation structure of K is analyzed with the components of ln(K) covariance and facies transition probability structures. Lagrangian-based models are developed to estimate solute dispersion in nonreactive tracer injection experiments. The results show that the model can predict plume spreading accurately when the spatial correlation structure is well defined. The dispersivities calculated by the Lagrangian-based model are slightly higher than those obtained from the solute transport experiments. Further, the upscaled dispersivity derived from the transition probability is dominated by the cross-transition probability structure, while the contribution of the auto-transition terms is quite small. The numerical modeling results confirm that the upscaled dispersivity can reproduce the solute breakthrough in the heterogeneous sediment well. The scale dependence of dispersion is strengthened when the flow direction is perpendicular to the bedding plane where the conductivity dramatically changes along the flow path in a layered bedding sediment. [ABSTRACT FROM AUTHOR]

A problem of porous media cleaning by a pulsating external flow is studied numerically. We consider a closed domain of porous media, which was initially clogged by an impurity. The purification of such a domain is performed by an external vertical pulsating flow of a pure fluid. The transport of the impurity with immobilization process is modeled into framework of the nonlinear MIM model with saturation of the immobile phase. The clogging of media is taken into account which, in turn, leads to a decrease of the pore volume due to the immobilized impurity on the pores. The one dimensional solution as in the form of vertical seepage was obtained. It is shown that the most effective cleaning is achieved for the maximal possible value of the external flow intensity and can be controlled by the variation of the pulsation frequency and amplitude. However at the high intensities of the external flow the one dimensional solution becomes unstable. The stability problem was solved within the quasistatic approach. The critical curves in the system parameters are obtained and discussed. [ABSTRACT FROM AUTHOR]

Understanding N budgets of tundra ecosystems is crucial for projecting future changes in plant community composition, greenhouse gas balances and soil N stocks. Winter warming can lead to higher tundra winter nitrogen (N) mineralization rates, while summer warming may increase both growing season N mineralization and plant N demand. The undulating tundra landscape is inter-connected through water and solute movement on top of and within near-surface soil, but the importance of lateral N fluxes for tundra N budgets is not well known. We studied the size of lateral N fluxes and the fate of lateral N input in the snowmelt period with a shallow thaw layer, and in the late growing season with a deeper thaw layer. We used 15N to trace inorganic lateral N movement in a Low-arctic mesic tundra heath slope in West Greenland and to quantify the fate of N in the receiving area. We found that half of the early-season lateral N input was retained by the receiving ecosystem, whereas half was transported downslope. Plants appear as poor utilizers of early-season N, indicating that higher winter N mineralization may influence plant growth and carbon (C) sequestration less than expected. Still, evergreen plants were better at utilizing early-season N, highlighting how changes in N availability may impact plant community composition. In contrast, later growing season lateral N input was deeper and offered an advantage to deeper-rooted deciduous plants. The measurements suggest that N input driven by future warming at the study site will have no significant impact on the overall N2O emissions. Our work underlines how tundra ecosystem N allocation, C budgets and plant community composition vary in their response to lateral N inputs, which may help us understand future responses in a warmer Arctic. [ABSTRACT FROM AUTHOR]

In karst groundwater, a common phenomenon in the solute transport process is solute transient storage. The mechanism of transient solute storage between karst conduit and fissures are revealed using a constructed physical model of conduit-fissures. Quantitative tracer tests were conducted under concentrated recharge conditions, and the solute transport processes were simulated using the Dual Region Advection Dispersion model. With enhanced concentrated recharge hydrodynamic conditions, the quantity of transient water storage in fissures tends to increase linearly; and the breakthrough curves transform from single peak to double-peaks. A negative correlation between the average flow velocity in conduit and fissures was confirmed. Breakthrough curve shapes are defined by the difference between solute retention times in conduit and fissures. The overall findings are that solute transient storage induces a tailing effect and the phenomenon of double-peaks in breakthrough curves, significantly controlling solute transport processes in karst groundwater. [ABSTRACT FROM AUTHOR]

This study proposes two-dimensional (2D) pollutant migration in a semi-infinite geological formation with spatial varying transport parameters. Because the groundwater flow is bidirectional, the impact of off-diagonal dispersion also was taken into account. A decay parameter was considered in the aqueous phase as well as in the solid phase. We assumed that the groundwater reservoir was not plume-free, because some scale-varying pollutant exists there very initially, decaying with space. A change in the source at the inlet boundary in the presence of off-diagonal dispersion (ODD) alters the strength of pollutant concentration. The existing solutions can be reduced into other existent solutions for various geological formations. The Laplace transform technique (LTT) was applied to obtain the pollutant concentration profile in the 2D anisotropic heterogeneous porous medium. The Crank–Nicolson finite-difference (CNFD) technique was adopted for a numerical simulation. We demonstrated the validity of the analytical result. The numerical result and some previously available data from literature were compared and good agreement was found. [ABSTRACT FROM AUTHOR]

Background: Ammonia is produced and excreted by the kidney, contributing to systemic acid‐base homeostasis through the production of bicarbonate. Disorders of acid‐base balance can lead to many clinical problems and measuring ammonia excretion helps in determining if the kidneys are responding to acid‐base challenges appropriately. Reference intervals are integral to clinical decision‐making, and there is no current RI for the urine ammonia‐to‐creatinine ratio (UACR) in dogs. Objective: This study aimed to generate an RI for the UACR in healthy adult dogs. Methods: The study used adult, client‐owned dogs that were presented to the University of Florida Primary Care and Dentistry service (n = 60). Physical examinations were performed and serum chemistry and urinalysis samples were obtained. Urine ammonia and creatinine concentrations were determined. Dogs were excluded if there were significant abnormalities in either their urinalysis or serum chemistry results. The RI for the UACR was calculated according to the recommendation of the American Society for Veterinary Clinical Pathology. Data were evaluated for correlation with serum bicarbonate, weight, age, and sex. Results: The RIs for the UACR were 0.16‐23.69 with 90% confidence intervals for the lower and upper limits of (0.13‐1.17) and (20.50‐23.75), respectively. No significant impact of age, sex, or weight was found. There was no discernable relationship between serum bicarbonate and UACR. Conclusions: Establishing an RI for UACR in healthy adult dogs will allow for further studies to determine if alterations are observed during specific disease states. [ABSTRACT FROM AUTHOR]

It is well established that clays can exhibit semipermeable membrane behavior and osmotic efficiency is used to describe the membrane behavior of clays. Several experimental results have already verified that osmotic efficiency is not constant when pore-fluid chemistry changes. In this article, based on the mechanical balance, generalized Darcy's law and the principle of mass conservation, an improved fully coupled hydro-chemo-mechanical model is proposed for saturated clayey materials, in which osmotic efficiency is treated as a variable that depends on the solute concentration, grain density, porosity of soil, and cation exchange capacity. Numerical simulations are conducted to investigate the influence of variable osmotic efficiency on solute transport. The results show that solute transport is very sensitive to osmotic efficiency and when the transport time is 10 years, the difference in influence depth reaches about 13.6 cm with constant (0.069) and variable (initially 0.069) osmotic efficiencies, this indicates that semipermeable membrane behavior of clays with variable osmotic efficiency restricts the solute transport effectively and slows down the solute movement strongly. The difference in breakthrough time reaches 15.8 years with osmotic efficiency (0.069). The proposed coupled model can be used to guide the design of clay liners and evaluate their service performance. [ABSTRACT FROM AUTHOR]

The article dealt with an analytic study on the electroosmotic flow and mass transport of an electro neutral solute through polyelectrolyte layer (PEL)-coated canonical nanopore under the imposed alternative current electric field for Maxwell fluids. The PEL of uniform thickness contains positive charge density, while surface potential of nanopore is negatively charged. The permittivities of the electrolyte solution and PEL are assumed to be different which creates the ion-partitioning effects. The Born formula is incorporated to account the ion-partitioning effects. For low surface charge, the distribution of the ionic species are governed by the modified Boltzmann distribution and using the Debye–Hückel approximation, linearized Poisson–Boltzmann equation gives the distribution of induce potential inside and outside of the PEL. The modified Cauchy momentum equation with the Maxwell constitutive equation is used for the fluid flow distribution interior and exterior of the PEL. The analytic solutions for the distribution of induced potential and axial velocity are established using modified Bessel function for the Maxwell fluid. The importance of the bulk ionic concentration, oscillating Reynolds number, PEL fixed charge density, relaxation time, permittivity ratio between PEL and electrolyte solution and softness parameter is studied in this investigation. The convection–diffusion equation is considered to transport of neutral solute between two reservoirs, connected with nanopore. An analytic solution for the distribution of solute concentration is also presented. The effects of the flow characteristics on volumetric flow rate, average mass transport, and neutralization factor are described in this study. [ABSTRACT FROM AUTHOR]

To investigate the effect of irregular shape and distribution of porous media on groundwater flow and solute transport, a double-layer herringbone structure was artificially constructed and numerical simulations of groundwater flow and transport were performed. Such a structure simulates the existing inclined cross- bedding geological features and forms macroscopic anisotropic hydraulic conductivity field. The results show that the macroscopic anisotropic structure creates helical flow, leading to the stretching and folding of the streamlines and the irregular deformation of the solute plume, and thus, solute dilution is enhanced significantly. The vertical relative position between the macroscopic anisotropic structure and the solute plume has a remarkable effect on solute transport. [ABSTRACT FROM AUTHOR]

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Solute transport under single-phase flow conditions in porous micromodels was studied using high-resolution optical imaging. Experiments examined loading (injection of ink-water solution into a clear water-filled micromodel) and unloading (injection of clear water into an ink-water filled micromodel). Statistically homogeneous and fine-coarse porous micromodels patterns were used. It is shown that the transport time scale during unloading is larger than that under loading, even in a micromodel with a homogeneous structure, so that larger values of the dispersion coefficient were obtained for transport during unloading. The difference between the dispersion values for unloading and loading cases decreased with an increase in the flow rate. This implies that diffusion is the key factor controlling the degree of difference between loading and unloading transport time scales, in the cases considered here. Moreover, the patterned heterogeneity micromodel, containing distinct sections of fine and coarse porous media, increased the difference between the transport time scales during loading and unloading processes. These results raise the question of whether this discrepancy in transport time scales for the same hydrodynamic conditions is observable at larger length and time scales. Article Highlights: Even at the representative elementary volume scale, time scale of solute transport during unloading was found larger than during loading. The dispersion coefficient for unloading is larger than that for loading. Flow field heterogeneity increases the discrepancy between loading and unloading dispersion coefficients. [ABSTRACT FROM AUTHOR]

Objective: The objectives of this study were: first, to compare solute uptake driven by sliding to cyclic uniaxial compression. And secondly, to evaluate the role of the superficial region on passive diffusion to determine if mechanical action is merely overcoming the low permeability of the superficial region or exceeding equilibrium capacity of the tissue.Design: Tests were performed on osteochondral plugs under two types of conditions: cyclic loading (sliding vs axial compression) and unloaded passive diffusion (intact vs superficial zone removed). The articular surfaces were exposed to a fluorescent bath and uptake was quantified from the surface to the subchondral bone using fluorescent microscopy. Primary outcome measures were total mass transfer, mass transfer rate, and surface partition factor.Results: Mass transfer was 2.1-fold higher at 0.5 h for sliding compared to uniaxial compression (p = 0.004). This increased to 4.4-fold at 2 h (p = 0.002). Solute transport for both loading conditions at 2 h had reached or exceeded intact passive diffusion at 12 h. Total mass transport and mass transport per hour was higher in samples without the superficial region compared to intact samples at equilibrium. Rate of mass transfer was not declining for samples subject to sliding indicating solute uptake induced by sliding would exceed passive tissue capacity.Conclusions: These results are the first to quantify solute uptake between two components of joint articulation. The study demonstrates that sliding is a larger driver of solute transport compared to cyclic uniaxial compression. This has implications for cell nutrition, tissue engineering and biochemical signaling. [ABSTRACT FROM AUTHOR]

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• A physical laboratory model was designed and used for tests with varying conditions. • The increase in the vadose zone thickness will intensify the buffer effect. • Karstification degree impacts infiltration differently with or without epikarst. • Epikarst influences the soil layer's drainage channel and storage capacity. Groundwater in karst systems is a vital resource, which is often highly vulnerable to contaminants that infiltrate through the vadose zone. Understanding the processes of water and contaminant infiltration in the vadose zone is extremely important for protecting and managing karst water resources. A laboratory-scale physical model based on a typical conceptual model of the karst vadose zone was constructed to characterize the influence of the rainfall intensity and internal structure on the infiltration process and solute transport in the karst vadose zone under controlled conditions. Five factors, including the rainfall intensity, the surface slope, the degree of karstification, the thickness of the transfer zone, and the existence of epikarst, were considered in laboratory experiments. A corresponding lumped-parameter model was subsequently developed to further analyze and investigate the water and solute infiltration processes in the laboratory scale physical model. Recession- and breakthrough curves generated from the lab experiments and the water and solute loss from each reservoir generated from the simulation results were analyzed. The downward trend of breakthrough curves' peak value and the variation of solute loss's proportion in three rainfall events demonstrate that both the increase in thickness and karstification degree will intensify the buffer effect of the karst vadose zone, and this buffer effect is mainly affected by the slow flow system which can be inferred from the increasing percentage of cumulative discharge of slow reservoir (q S). With increasing karstification degree, the recession coefficient (α) exhibits opposite trends depending on the existence of epikarst or not, indicating the karstification degree has a more significant effect on hydraulic conductivity (K) when an epikarst is present while affecting effective porosity (φ) more noticeably in the absence of epikarst. The rainfall intensity affects the results of both experimental and numerical simulation most significantly. The percentage of discharge and solutes flowing from the slow reservoir (q S and m soil_S) have negative correlations with rainfall intensity, suggesting a greater influence on fast flow with increasing rainfall intensity. [ABSTRACT FROM AUTHOR]

Resolving solute transport in heterogeneous porous media is a complex task, because of the sparse experimental data and the high computational cost of numerical simulations. This work proposes a unique two-stage deep learning architecture comprising a dual-branch autoencoder and a geo-guided super-resolution generative adversarial network (Gg-SRGAN) to address this dual challenge. The dual-branch autoencoder addresses the issue of sparsity by constructing a continuous, but coarse representation of concentration and pressure profiles from a sparse, discontinuous profile with up to 85% missing data points. The Gg-SRGAN is then employed to generate a finer representation of field variables from the outputs generated by the dual-branch autoencoder (i.e., downscaling). We train and test our framework using six solute transport cases with varying levels of heterogeneity and compare the results with standalone methods, namely the vanilla autoencoder and vanilla SRGAN, in addition to ground truth profiles generated by the finite element method (FEM). The comparisons are performed based on several statistical metrics, such as absolute point error (APE), mean squared error (MSE), peak signal-to-noise ratio (PSNR), structural similarity index (SSIM), and learned perceptual image patch similarity (LPIPS). The first four cases are used for training, evaluation, and testing. The last two cases are utilized for blind testing to determine the generalizability of the framework. Our results show that the dual-branch autoencoder outperforms the vanilla autoencoder, and the Gg-SRGAN outperforms the SRGAN during both the training and evaluation phases. Moreover, the proposed framework can successfully construct the fine representation of concentration profiles, compared to FEM, using the coarse representation of the pressure, concentration, and domain permeability fields. When tested using the two blind test cases, the proposed dual-branch autoencoder and Gg-SRGAN exhibit superior performance compared to their counterparts in terms of all evaluation metrics. • A two-stage deep learning framework is developed to resolve solute transport in porous media. • The framework addresses the dual challenge of data sparsity and spatial downscaling. • The framework incorporates geological information to comprehend the underlying physics. • The framework outperforms conventional algorithms in terms of accuracy. [ABSTRACT FROM AUTHOR]

Nowadays, with the increasing population in Iran, especially in arid and semi-arid areas, as a result of the growing importance of the quality of water resources, including groundwater, field experiments and many simulations have been conducted for the development of groundwater contamination through powerful and up- to- date software. However, in most cases, there is a tangible difference between the measured data in laboratories and the data produced with software; this is why the scientific validation and verification of the research results could be declined. In this study, in order to justify and correct these data, the calibration principle was used to minimize the error of testing and modeling. The purpose of this study was to validate and verify the SUTRA model for different scenarios of the solute transport in a sand tank with heterogeneous hydraulic conductivity to evaluate transverse dispersivity. In this study, coding was initially performed for the configuration and calibration of the SUTRA numerical model to simulate different scenarios of the solute transport in a heterogeneous sand Tank in the Hydraulic Laboratory of the University of Kassel, Germany, until acceptable values were obtained. Then the results were compared with the experimental model. In order to validate and verify the data obtained from the simulation with the SUTRA model, the relevant concentration profiles were compared with the results of the experimental model. The results of the numerical and laboratory models revealed the density effects by sinking the geometric center of the mixing zone for the low concentrations of salt, C0 = 250 ppm. The results also showed that the width of the mixing zone between salt and fresh water depended on the amount of longitudinal dispersivity, especially the transverse dispersivity. By analyzing the results of simulation and experiment, it was observed that with increasing the velocity, reducing the amount of sinking and raising the input concentration, the time needed to achieve the steady dispersion was decreased.

Deterioration of groundwater resources in coastal regions due to the progression of saline water in aquifers in these regions is currently one of the important issues in providing water needs in these areas. In coastal regions, saline water enters the aquifer from below in shape of wedge. Due to the difference in the density between fresh and salty water, an interface zone forms between two fluids. In order to better understanding the importance of this issue, experiments and numerical investigations of density-depended flow and transport through a tank filled with a variety of sand, are great help in achieving this. In this research, the real sand tank was simulated using SUTRA model. This simulation includes configuration, discretization, property assignment and boundary conditions determination. Finally, the transverse macro-dispersivity coefficient was estimated for different scenarios of the solute transport in this tank. The purpose of this research is to analyze of the solute dispersion, in mixing salt and fresh water, and the effect of seepage velocity, concentration of pollutant source and heterogeneity of porous media on the flow dispersivity property. In this research, after studying the effect of different boundary conditions in SUTRA model on the development of the salt water plume, simulation of the model of heterogeneous sand tank and comparing its results with laboratory model and homogeneous model were performed. As a practical result of this research, the diagram of changes in the coefficient of transverse dispersivity against the source concentration and seepage flow velocity was plotted. In numerical simulation of heterogeneous Porous media, for all concentrations, with the exception of the concentration C0= 35000, with increasing flow velocity, the values of the transverse dispersivity coefficient AT calculated by SUTRA decreased. Also AT for all seepage velocities, with the exception of seepage velocity u=4 m/day, increased with increasing source concentration. Also, the values obtained AT from the SUTRA model were more than the values of AT obtained from experiments. In numerical simulation of the homogeneous porous media, for all velocities, as the concentration source C0 increases, the transvers macro dispersivity coefficient AT increases. According to the applied results, suitable solutions can be found to improve the quality of groundwater and prevent the mixing of fresh and saltwater resources.

Abstract Background Tumor numerical models have been used to quantify solute transport with a single capillary embedded in an infinite tumor expanse, but measurements from different mammalian tumors suggest that a tissue containing a single capillary with an infinite intercapillary distance assumption is not physiological. The present study aims to investigate the limits of the intercapillary distance within which nanoparticle transport resembles solute extravasation in a breast tumor model as a function of the solute size, the intercapillary separation, and the flow direction in microvessels. Methods Solute transport is modeled in a breast tumor for different vascular configurations using mixture theory. A comparison of a single capillary configuration (SBC) with two parallel cylindrical blood vessels (2 BC) and a lymph vessel parallel to a blood vessel (BC_LC) embedded in the tissue cylinder is performed for five solute molecular weights between 0.1 kDa and 70 kDa. The effects of counter flow (CN) versus co-current flow (CO) on the solute accumulation were also investigated and the scaling of solute accumulation-decay time and concentration was explored. Results We found that the presence of a second capillary reduces the extravascular concentration compared to a single capillary and this reduction is enhanced by the presence of a lymph vessel. Varying the intercapillary distance with respect to vessel diameter shows a deviation of 10–30% concentration for 2 BC and 45–60% concentration for BC_LC configuration compared to the reference SBC configuration. Finally, we introduce a non-dimensional time scale that captures the concentration as a function of the transport and geometric parameters. We find that the peak solute concentration in the tissue space occurs at a non-dimensional time, Tpeak∗ $$ {T}_{peak}^{\ast } $$ = 0.027 ± 0.018, irrespective of the solute size, tissue architecture, and microvessel flow direction. Conclusions This work suggests that the knowledge of such a unique non-dimensional time would allow estimation of the time window at which solute concentration in tissue peaks. Hence this can aid in the design of future therapeutic efficacy studies as an example for triggering drug release or laser excitation in the case of photothermal therapies.

Abstract Background Aquaporins (AQPs) facilitate transport of water and small solutes across cell membranes and play an important role in different physiological processes in plants. Despite their importance, limited data is available about AQP distribution and function in the economically important oilseed crop peanut, Arachis hypogea (AABB). The present study reports the identification and structural and expression analysis of the AQPs found in the diploid progenitor genomes of A. hypogea i.e. Arachis duranensis (AA) and Arachis ipaensis (BB). Results Genome-wide analysis revealed the presence of 32 and 36 AQPs in A. duranensis and A. ipaensis, respectively. Phylogenetic analysis showed similar numbers of AQPs clustered in five distinct subfamilies including the plasma membrane intrinsic proteins (PIPs), the tonoplast intrinsic proteins (TIPs), the nodulin 26-like intrinsic proteins (NIPs), the small basic intrinsic proteins (SIPs), and the uncharacterized intrinsic proteins (XIPs). A notable exception was the XIP subfamily where XIP1 group was observed only in A. ipaensis genome. Protein structure evaluation showed a hydrophilic aromatic/arginine (ar/R) selectivity filter (SF) in PIPs whereas other subfamilies mostly contained a hydrophobic ar/R SF. Both genomes contained one NIP2 with a GSGR SF indicating a conserved ability within the genus to uptake silicon. Analysis of RNA-seq data from A. hypogea revealed a similar expression pattern for the different AQP paralogs of AA and BB genomes. The TIP3s showed seed-specific expression while the NIP1s’ expression was confined to roots and root nodules. Conclusions The identification and the phylogenetic analysis of AQPs in both Arachis species revealed the presence of all five sub-families of AQPs. Within the NIP subfamily, the presence of a NIP2 in both genomes supports a conserved ability to absorb Si within plants of the genus. The global expression profile of AQPs in A. hypogea revealed a similar pattern of AQP expression regardless of the subfamilies or the genomes. The tissue-specific expression of AQPs suggests an important role in the development and function of the respective organs. The AQPs identified in the present study will serve as a resource for further characterization and possible exploitation of AQPs to understand their physiological role in A. hypogea.

Dissolution of gypsum has great influence on water flow and solute transport occurring ingypsiferous-calcareous soils. Many models based on convection and diffusion processes havebeen developed to describe transport in soil. Constraints of estimation of transport parameters ingypsiferous-calcareous soils are mainly due to gypsum influence .The objectives of this study,were to i: modeling the transport of solute (36Cl) in gypsiferous-calcareous soil treated with fuelof FO on dissolution of gypsum associated with calcium carbonate content. Radiotracer ofchloride as carrier free of 36Cl was applied to surfaces of saturated soil columns that have 20, 250and 500 g kg-1 gypsum treated with 0, 1, 2, and 4% of fuel oil and leached with water untilcomplete displacement of chloride. During leaching, samples of effluent were collected andmeasured for Cl36 . The application of 1 to 2% FO improved the transport properties due tomodification in soil structure. The applied models gave good fit between measured and predictedbreakthrough curves of 36Cl with significant linear correlation coefficient (r) that ranged between0.972 and 0.999. They gave a calculated dispersion coefficient (D) ranging from 2.1 to 79.2 cm2day-1, and retardation factor (R) ranging from 0.92 to 1.58. It was found that D was also linearlyrelated to pore water velocity (v). Also, the results indicate the possibility of predicting thedistribution of chloride in gypsiferous-calcareous soil for different time periods using correctboundary conditions. Experimental results show that gypsum dissolution in the soil columns ismainly determined by the flow velocity, soil saturation and then partially coating with FO. Therole of lime was not well explained in reducing gypsum dissolution because the co-existence ofgypsum and lime is not clear enough.

A typical fresh–saline water interface in a coastal aquifer is characterized by saline-water circulation below the interface and freshwater flow above. Both flows are perpendicular to the shoreline. The flow pattern near two separated saline lakes is more complicated. For example, in the Middle East, the Dead Sea northern basin and the evaporation ponds of the Dead Sea Works are adjacent to each other but separated. The northern basin level is dropping by 1.1 m/year and the evaporation ponds' levels are increasing by 0.2 m/year. The fresh–saline water interface in such situation is numerically simulated. Streamlines parallel or semiparallel to the shoreline are significant. Moreover, the fresh–saline water interface intrudes landward adjacent to the higher saline lake and is pushed lakeward adjacent to the lower saline lake. The simulation results support field observations showing that the interface migrates vertically at a faster rate relative to the changes in the water table and the lake levels. [ABSTRACT FROM AUTHOR]

Sabkha Matti is a potential discharge point for regional groundwater systems in the Rub' al Khali topographic basin of Saudi Arabia. The hydrogeochemical evolution of this sabkha (salt flat) and the underlying aquifers were assessed by using a combination of geological, hydraulic, hydrochemical, and isotopic approaches. A compilation of the geologic structure and lithology in combination with boron isotope data attributed the origin of salinity in the regional aquifers underlying Sabkha Matti to the entrapment of ancient seawater in a coastal lagoon environment during the depositional time of the late Oligocene-Miocene formations. Major ionic constituents and strontium isotope ratios from the trapped paleo-seawater were observed to resemble those obtained from the near-surface sabkha brine. These data, along with hydrostatic head measurements, suggest that the origin of the solutes in Sabkha Matti is associated with brines ascending from the underlying formations. The data also show that solute concentrations in Sabkha Matti are increasing over time through a combination of evaporation, mineral dissolution by recharge, and a density-driven convection mechanism that circulates the solutes. On the other hand, stable isotopes of water (δ18O, δ2H) and radio isotope data (14C and 3H) suggest that the existing waters in the sabkha and the underlying aquifers are relatively recent and were recharged during the wet phase in the late Pleistocene-Holocene between 3,200 and 14,000 BP. This study shows that the water and solutes in Sabkha Matti area are a combination from different sources. [ABSTRACT FROM AUTHOR]

Low-permeability media such as clay appear in nearly all hydrogeological systems. To date, although significant efforts have been put forward by hydrologists, transport mechanism is still not well understood in such media, especially in an aquifer-aquitard system. In this study, two-dimensional experiments of groundwater flow and solute transport were conducted in a clay-sand two-layer system to investigate the characteristics of flow and transport in such a system. Sodium chloride (NaCl) (a conservative tracer) from a tank was injected after passing by the pre-inlet reservoir where the mixing effect and flow transiency were analyzed. A new numerical model considering the mixing effect and flow transiency was developed to interpret the experimental data based on the finite-element COMSOL Multiphysics platform. Transport parameters were assessed by best fitting the observed breakthrough curves (BTCs). Several important results were obtained. Firstly, aquitard advection was found to be non-negligible and should be considered in a proper mathematical model for describing the transport process. Secondly, advective velocities were temporally variable and showed decreasing trends in the sand and clay layers, mainly due to the impacts of physical and biological clogging. Thirdly, the mixing effect in the pre-inlet reservoir led to a lower tracer concentration in the sand layer at early times. Finally, the observed BTCs exhibited early arrivals in the clay layer, possibly resulting from preferential flow pathways. These findings can provide hints for contamination remediation works in aquifer-aquitard systems. [ABSTRACT FROM AUTHOR]

Ebb-and-flow is a well-known and common greenhouse irrigation system. In this paper, a specific numerical model for a sensor-based flood-floor ebb-and-flow irrigation system has been developed using one-dimensional Richards' equation for water flow and two-site sorption advection-dispersion model for simulation of solute transport. The model was validated against analytical and numerical results proposed in the literature, and acceptable agreement was obtained in all cases. Maximum RMSE (MAE) was 0.053 m (0.273 m) for water flow and 0.021 (0.065) for solute transport. The model was then used for a parametric study of how different factors (such as salinity of irrigation water, triggering and cutoff thresholds, sensor position and flooding depth) would affect transpiration of sensor-equipped solitary pot under ebb-and-flow irrigation system for two different crops. It was revealed that sensor position and water salinity were significantly influential on transpiration of the pots. Finally, the synchronized sensor equipped-sensorless module of the numerical model was used to optimize the flood-floor ebb-and-flow irrigation system considering different factors using Taguchi approach. It was concluded that installing a water content sensor, whose triggering and cutoff thresholds were at −10 and −2 m, at the upper-half of the center-positioned pot would result in higher transpiration and lower unevenness of water distribution. [ABSTRACT FROM AUTHOR]

Background: Flexible vegetation is an important part of the riverine ecosystem, which can reduce flow velocity, change turbulence structure, and affect the processes of solute transport. Compared with the flow with rigid vegetation, which has been reported in many previous studies, bending of flexible vegetation increases the complexity of the flow–vegetation–solute interactions. In this study, laboratory experiments are carried out to investigate the influence of flexible vegetation on solute transport, and methods for estimating the lateral and longitudinal diffusion coefficients in the rigid vegetated flow are examined for their applications to the flow with flexible vegetation. Results: The experimental observations find that vegetation can significantly reduce flow velocity, and the Manning coefficient increases with increasing vegetation density and decreases with inflow discharge. Under all the cases, the vertical peak of the solute concentration moves towards the bottom bed along the flow, and the values of vertical peak concentration longitudinally decreases from the injection point. The lateral diffusion coefficients Dy increase with vegetation density, while the longitudinal diffusion coefficients DL are opposite. Both Dy and DL increase with the inflow discharge. To estimate the Dy and DL in the flow with flexible vegetation, an effective submerged vegetation height considering vegetation bending is incorporated in the methods proposed for flow with rigid vegetation (Lou et al. Environ Sci Eur 32:15, 2020). The modified approach can well predict the diffusion coefficients in the experiments with the relative errors in the range of 5%–12%. Conclusions: The methods proposed in this study can be used to estimate the lateral and longitudinal diffusion coefficients in flows through both rigid and flexible vegetations using the effective submerged vegetation height. [ABSTRACT FROM AUTHOR]

In order to describe the solute transport process and characteristics in the filling fracture, the solute transport test model of filling frace was designed and manufactured. The solute transport tests under different flow velocity conditions were carried out. The solute transport aracteristics in the filling fracture were studied and the internal solute transport process was described in detail combining with the real-time dymic monitoring data of self-potential (SP) at different measuring points. The results showed that: 1)In the range of 0.073 3~0.963 0 mm/s, the meability coefficient of the filling fracture was 1.85 mm/s, which was close to the permeability coefficient of the filled porous medium 1.79 m/s, and the water flow complies with Darcy's law; 2) When the actual average flow velocity was 0.247 mm/s, 0.431 mm/s, 0.661 mm/s, the ak solute concentration at the sampling point was 5.14 g/L, 5.50 g/L, 5.78 g/L, and the initial and peak solute arrival times were all reduced, h the initial arrival times of 4 640 s, 2 640 s, and 1 560 s, and the peak arrival times of 5 480 s, 3 360 s and 2 040 s, respectively. 3) Under the nditions of the actual flow velocity of the three kinds of water currents, the SP response showed similar characteristics during the solute transt. The absolute value of the SP peak at the measuring electrode was gradually reduced from 1# to 6# along the flow direction, and the steepness gradually decreased when the peaks came out in sequence. In addition, both the solute dispersion front and the solute dispersion peak concentra- tion point were moving at a uniform speed with the flow of water, and the corresponding average initial flow velocity of the solute dispersion front were 0.214 mm/s, 0.396 mm/s, 0.685 mm/s, and the average flow velocity peaks corresponding to the solute dispersion peaks were 0.189 mm/s, 0.347 mm/s and 0.571 mm/s. 4) The actual average flow velocity based on the peak SP calculation was basically the same as the calculation result using the peak solute concentration, but the peak SP calculation result was closer to the actual average flow velocity (flow calculation result), and the accuracy was increased by 1.5%; as the flow rate continued to increase, the macro-average flow velocity error calculated from the peak SP was reduced by 9.9%. 5) The test showed that compared with the peak SP value, the macroscopic average velocity of the filling fractured flow calculated using the initial SP value was closer to the macroscopic average velocity of the flow calculated from the flow data. [ABSTRACT FROM AUTHOR]