Diffuse-porous and ring-porous xylem types did not influence branch hydraulic responses along a rural-urban gradient

Time-dependent permeability evolution in saline-affected sandy clay soils: Coupled experimental and microstructural analysis

Machinery traffic–induced compaction has detrimental effects on soil structure and physical properties, leading to the degradation of soil physical functionality. However, the potential of cover crops to mitigate the deleterious effects of cotton harvester traffic in sandy soils remains poorly investigated. This study aimed to evaluate how different cover crops grown either as sole crops or in mixtures can mitigate the adverse effects of cotton harvester traffic on the physical quality of a tropical sandy loam Oxisol in southeastern Brazil. The experiment was established in 2015 using a randomised complete block design with five cover crop treatments: Ruzigrass ( Urochloa ruziziensis ); Millet ( Pennisetum glaucum ) + Ruzigrass; Millet + Sunn hemp ( Crotalaria juncea ); Mixture (Ruzigrass + millet + radish ( Raphanus sativus ) + sunn hemp); and a control treatment (Fallow - weed). The harvester passed only once over each experimental plot, which were subdivided into trafficked and non-trafficked zones. Undisturbed soil samples were collected from the 0.00–0.10 and 0.10–0.20 m soil layers. Soil bulk density and degree of compaction, total porosity, mesoporosity and macroporosity, plant-available water, saturated and unsaturated soil hydraulic conductivity, matrix and relative soil aeration capacity, soil water storage capacity, and an index of soil resistance to compaction were determined for both soil layers. The results showed that the first harvester traffic substantially degraded soil physical quality, particularly in the 0.00–0.10 m layer, with increases in soil bulk density of up to 49% and reductions of 35% in saturated soil hydraulic conductivity, 28% in mesoporosity, 44% in macroporosity and 55% in relative soil aeration capacity, compared with non-trafficked soil, irrespective of the cover crop. The soil resistance to compaction index indicated that 96% of the increase in the degree of compaction occurred after the first machine pass, with the treatment Fallow exhibiting a 97% increase. The Millet + Ruzigrass treatment exhibited the lowest soil bulk density (1.57 Mg m⁻³) and degree of compaction (84%), as well as the highest values of total porosity (0.41 m³ m⁻³), saturated soil hydraulic conductivity (8.58 cm h⁻¹) and plant-available water (0.20 m³ m⁻³) following harvester traffic. The Mixture treatment showed the highest unsaturated soil hydraulic conductivity at a matric potential of −100 hPa (0.149 cm day⁻¹). Overall, the results suggest that the adoption of cover crops, particularly the Millet + Ruzigrass and Mixture, represents an agronomically efficient strategy to mitigate the negative impacts of harvester traffic on the soil physical quality. Improvements in soil physical attributes promoted by cover crops are essential for maintaining soil physical functionality, ensuring greater soil water and air availability. • Cover crops reduced soil compaction caused by harvester traffic. • Increased soil compaction enhanced water storage capacity but impaired soil aeration. • Increased soil bulk density markedly decreased macroporosity and saturated hydraulic conductivity. • Soil bulk density increase due to harvester traffic in the 0.10–0.20 m corresponded to 50% of that observed in the 0-0.10 m.

We present a novel method for estimating lithology-specific hydraulic conductivities from catchment-scale effective values, each interpreted as a linear combination of the conductivities of the underlying lithologies. The method particularly applies to discharge-derived estimates of effective conductivity, where river networks integrate the influence of predominantly shallow groundwater flows from adjacent hillslopes. Lithological area fractions are used as weights to formulate an overdetermined linear system, which is solved using a modified method of moments under the assumption of lognormally distributed conductivities to account for spatial variability. The method was validated on synthetic cases and applied to 113 catchments in the Armorican Massif (France). It shows good convergence properties and achieves high predictive accuracy: in 85% of cases, the modeled conductivities fall within a 90% confidence interval of the observed values. Convergence analysis indicates that using five catchments per lithology is sufficient to reach 75% predictive success, with mean and standard deviation parameters estimated within 6% and 30%, respectively. With 80 catchments, prediction accuracy increases to 80%, and parameter estimation errors are reduced to 3% and 15%. The method is computationally efficient and generalizable, offering a powerful tool to explore lithology-specific conductivity datasets at regional scales. It may also be adapted to other variables, such as porosity, where linear averaging applies, enabling broader applications in hydrogeological modeling. • New method to retrieve lithology-specific hydraulic conductivity from catchment values. • Effective tool to expand regional lithology-specific conductivity datasets. • Method validated with synthetic data and applied to 113 Armorican Massif catchments. • The method demonstrates high predictive accuracy in hydraulic conductivity estimation. • 85% of modeled conductivities fall within a 90% confidence interval of observed values.

Laboratory-scale analyses of matrix-conduit exchange in a karst aquifer system using coupled physical and numerical modeling.

Experimental investigation on mechanical behaviour, hydraulic conductivity, and microstructure of cement-stabilized soil mixed with biochar

Energy tunnels represent an innovative solution for meeting heating and cooling needs through heat exchange with the ground. Among the key factors influencing their thermal performance, there is the groundwater flow which drives continuous thermal recharge of the surrounding ground. The extent to which this recharge occurs depends significantly on the flow velocity, which is mainly governed by hydraulic gradient and permeability. While previous studies typically assumed homogeneous hydraulic properties, the effect of spatial variability on the thermal exchange remains unexplored. Therefore, this study investigates how spatial variability of intrinsic permeability impacts the thermal performance of an energy tunnel under seepage. A numerical model was developed and validated against field tests data available in the literature. Then, lognormally distributed, autocorrelated random fields of intrinsic permeability were generated and incorporated into the model as a series of Monte Carlo simulations (MCS). The results indicate that assuming homogeneity is acceptable when the coefficient of variation of permeability ( C O V κ ) is below 1.0, in both heating (winter) and cooling (summer) modes. However, for higher variability ( C O V κ > 1.0), this effect becomes significant and assuming homogeneous conditions may lead to a substantial underestimation or overestimation of the heat exchange. Only in cases with a large difference between internal air temperature and fluid temperature, the homogeneous assumption may remain reasonably valid even at high C O V κ up to 4.0. The effect of spatial variability increases with increasing groundwater flow velocity up to 0.5 m/d, beyond which the variability effect remains similar. This study highlights the critical importance of field measurements of hydraulic properties in order to accurately estimate the heat exchange rates of energy tunnels.

The mechanical response of cemented calcareous soils to water immersion is critically influenced by the complex architecture of their particulate framework and cementing materials. Understanding the mechanical and hydrochemical properties of these soils under saturated conditions is crucial for assessing the stability of geoengineering structures. The research detailed in this manuscript evaluates the influences of water immersion on the mechanical and hydrochemical characteristics of cemented calcareous soil collected near the Jinsha River. Additionally, the study discusses the implications of these soil properties for geological phenomena located in proximity to the sampling area. The results showed that prolonged immersion precipitates substantial alterations in the hydraulic conductivity of cemented calcareous soil, accompanied by extensive ion dissolution that modifies its hydrochemical properties. The soaking solution exhibits alkalinity with high concentrations of Ca 2+ and HCO 3 − . Initial short-term immersion augments the strength of cemented calcareous soil, while a progressive decline in strength occurs as the immersion period extends, with the natural state displaying markedly greater strength relative to the dried state. Long-term immersion facilitates the moisture infiltration into the interstitial spaces between particles, dissolving the cementing material and undermining the interparticle bonds, which critically impairs the mechanical properties and stability of the soil. Furthermore, localized seepage facilitates the migration and precipitation of soluble salts in moisture-prone environments, exacerbating the weathering and degradation processes. Such long-term immersion results in structural transformations within the soil, undermining the cementation structure and potentially precipitating soil collapse.

Prediction of the saturated hydraulic conductivity based on X-ray CT analysis of a permeable mixture bonded with a polyurethane binder

Drought rather than nitrogen addition drives the coordination of hydraulic conductivity and photosynthesis in three coniferous tree species

Tree species can exert strong and species-specific controls on water infiltration in forest soils. However, the magnitude and meteorological sensitivity of these effects remain poorly quantified under standardised site conditions. We measured unsaturated hydraulic conductivity ( K ) and soil water repellency index ( R ) in the A horizon beneath seven single-species stands – lime ( Tilia cordata ), sycamore ( Acer pseudoplatanus ), maple ( Acer platanoides ), beech ( Fagus sylvatica ), oak ( Quercus robur ), larch ( Larix decidua ), and Douglas-fir ( Pseudotsuga menziesii ) – in a common-garden experiment on sandy Dystric Gleyic Cambisols. Measurements were conducted in five campaigns representing contrasting 10-day antecedent weather conditions. Broadleaved species such as lime, maple, and sycamore maintained low repellency and high K regardless of preceding weather, indicating low susceptibility to hydrophobicity. In contrast, conifers (Douglas-fir and larch) rapidly developed strong repellency and sharply reduced infiltration following dry spells. Beech and oak showed intermediate responses, with repellency emerging under drought but receding after wet periods. These patterns reveal that species differ not only in baseline hydraulic properties but also in the speed and magnitude of their response to short-term meteorological variability. Our study highlights the importance of species-specific functional traits in regulating soil hydraulic behaviour. Selecting species that sustain infiltration and resist the onset of hydrophobicity could help improve water retention, limit runoff, and enhance forest resilience under projected increases in drought frequency. • Unsaturated hydraulic conductivity and soil repellency were measured in humus-mineral soil horizon beneath seven tree species. • Five campaigns represented distinct 10-day antecedent weather conditions ranging from dry to wet. • Conifers (Douglas-fir, larch) rapidly developed high water repellency and infiltration loss after short dry spells. • Lime, maple, and sycamore remained wettable under all conditions, indicating resistance to drought-induced hydrophobicity. • Beech and oak showed intermediate sensitivity, with repellency peaking only after prolonged dryness.

• A root water uptake model with waterlogging effects on root hydraulics was built. • The model effectively estimated plant hydraulic conductance and transpiration. • The model improved estimation accuracy, especially after prolonged waterlogging. • Transpiration was controlled by root hydraulics under moderate evaporative demand. In humid regions, intensive and intermittent precipitation has increased due to climate change, resulting in frequent waterlogging. Although waterlogging severely impedes the root hydraulic functions of a broad range of plant species, only a few studies have attempted mechanistic representation of plant responses to waterlogging. We hypothesized that incorporating plant hydraulic response to waterlogging into root water uptake model improves the estimation accuracy of water dynamics in humid regions. To test this hypothesis, we constructed two models: reference soil–plant–atmosphere continuum model, in which plant hydraulic resistance is constant, and a modified model (MM), in which plant hydraulic resistance increases with waterlogging. The performance of the models was tested using observed data of the soybean canopy cultivated in paddy field under humid climate. The MM accurately reproduced the increase in plant hydraulic resistance during the cultivation period. Modifying the model improved the estimation accuracy of the evapotranspiration rate and leaf water potential, especially on clear days after prolonged waterlogging. This performance improvement of MM was observed when evaporative demands exceeded 0.4 mm h −1 and was not dependent on soil water availability. An increase in plant hydraulic resistance due to soil waterlogging caused an imbalance between the atmospheric evaporative demand and the water uptake capacity of the roots, resulting in a midday depression in the evapotranspiration rate. These findings highlight that a process-based model incorporating the response of plant hydraulic resistance to waterlogging is useful for improving the understanding of water dynamics and leaf gas exchange in humid climates.

Expansive soils exhibit pronounced swelling-shrinkage behavior, low shear strength, and high moisture sensitivity, posing significant challenges to the stability of geotechnical structures such as embankments and tailings dam slopes. In this study, a sustainable stabilization strategy integrating enzyme-induced carbonate precipitation (EICP) with iron ore tailings is investigated to improve the hydro-mechanical performance of expansive soils. A comprehensive experimental program was conducted to evaluate changes in unconfined compressive strength (UCS), swelling pressure (Ps), hydraulic conductivity (Ks), cohesion (c), and internal friction angle (φ). Microstructural characterization using scanning electron microscopy and X-ray diffraction was performed to examine calcium carbonate precipitation and its cementation effects within the soil matrix. The results demonstrate that the combined EICP-iron ore tailings treatment significantly enhances soil performance, with UCS, c, and φ increasing by approximately 113%, 48%, and 98%, respectively, while Ps and Ks decrease by approximately 98% and 69%. Furthermore, seepage and slope stability analysis using GeoStudio (SEEP/W and SLOPE/W) indicate that the stabilized soil achieves a markedly higher factor of safety (FoS = 1.896) compared to untreated soils. The findings confirm that the synergistic integration of EICP and iron ore tailings provides an effective, environmentally sustainable, and engineering-feasible solution for stabilizing expansive soils and improving slope performance in tailings dam applications.

Quantifying and localizing groundwater discharge is inherently difficult. It requires knowledge about hydraulic conductivity and the hydraulic gradient on the scale of interest. Conventional hydraulic testing, such as pumping tests, may fail in the presence of heterogeneity and complex structural boundaries. While advanced 2D and 3D hydraulic tomography may resolve small-scale heterogeneity, it is typically limited to small spatial scales and requires costly field installations. We propose a simplified tomographic approach using a limited number of pumping and observation wells spatially distributed over a well profile in the order of 100 m transverse to the direction of ambient flow. To infer the spatially variable hydraulic-conductivity field from drawdown data with its uncertainty, we apply an iterative ensemble smoother. Subsequently, the posterior ensemble of hydraulic-conductivity fields is used to calculate total and specific discharge based on the observed ambient hydraulic heads in the same wells. We test our approach in a synthetic scenario mimicking a channel-like aquifer such as the quaternary fill in a small river valley. The results demonstrate that multiple spatially distributed pumping tests are suitable to quantify total discharge and its associated uncertainty. The approach is more reliable than a conventional one that estimates effective transmissivity from fitting analytical solutions to pumping-test data. The tomographic analysis additionally allows locating spatial patterns of specific discharge at a resolution similar to the spacing of the wells, which may be important when assessing and remediating contaminant plumes.

Study on microstructure and permeability of modified cut-off wall materials under chemical environmental effects.

Transport and retention of polypropylene microplastics through vadose zones: Experimental observation and numerical prediction.

Although groundwater flow directions are influenced by hydraulic gradients and density gradients, density gradients are often assumed negligible outside coastal zones and saline lake environments. Density gradients are rarely considered in mining studies, but can alter groundwater flow patterns, and cause outflow of water from pit lakes despite inward hydraulic gradients. Open mine pits often intersect regional water tables, requiring dewatering during mining operations. At the end of mine life, groundwater abstraction ceases, frequently leading to the development of pit lakes. Due to prolonged water residence time, and evaporation, pit lake water quality may deteriorate with salinization being a common problem. While salinity differences between pit lake water and groundwater are small initially, they increase with time, inducing density contrasts. Consequently, dense pit lake water may move along density gradient towards less dense groundwater. This changes the flow patterns around the pit lake and impact on surrounding aquifer water quality. In this study, we advance process understanding of how density effects alter flow and salinity patterns in pit lake environments post-mining using numerical modeling. We show the impact of ambient groundwater salinity, regional hydraulic gradients, evaporation rates, and hydraulic conductivities on the interaction between a pit lake and the surrounding aquifer. We demonstrate how density effects can substantially increase lake water outflow and decrease pit lake water salinities. Pit lakes can turn from terminal sinks into throughflow systems purely due to variable-density flow. Understanding the hydraulic and salinity evolution of pit lakes is crucial for planning post mining rehabilitation.

Excessive fluoride in landfill leachate has been increasingly reported across Asia due to both geogenic and anthropogenic inputs, posing long-term risks to groundwater and public health. However, the barrier performance of compacted clay liners (CCLs) against fluoride migration remains insufficiently quantified, especially under bentonite-amended conditions. This study systematically evaluated the fluoride barrier performance of compacted clay amended with 0-10% bentonite through a series of laboratory tests including Atterberg limits, standard proctor compaction, specific gravity, free swelling indices, cation exchange capacity (CEC), batch sorption, column diffusion, and hydraulic conductivity tests, complemented by analytical prediction. Results indicated that the clay specimen with 10% bentonite exhibited 64.4% liquid limit, 5.2mL/2g free swelling index, and CEC value of 36.5meq/100g, respectively. After adding 0-10% bentonite, the distribution coefficient of the clay specimen ranged from 2.1 to 3.4L/kg, moreover, the hydraulic conductivity decreased from 1.4×10-10 to 4.9×10-11 m/s, and the effective diffusion coefficient decreased from 1.6×10-10 to 7.6×10-11 m2/s, respectively. Analytical modeling predicts a maximum fluoride breakthrough time of 150years for a compacted clay liner with 10% bentonite. Mechanism interpretation indicates that increased swelling, CEC, and tortuosity jointly contribute to the improved barrier performance. Findings from this study suggest that adding approximately 5% bentonite provides a cost-effective improvement for CCLs in landfills containing low-fluoride leachate.

Permeable pavements are gaining popularity as an innovative solution to mitigate urban stormwater runoff and reduce the environmental impact of traditional impermeable pavements. This study examines the viability of producing permeable pavement blocks by partially substituting plastic aggregate with conventional coarse aggregate. The study employs a rigorous experimental methodology that encompasses material characterization, mechanical testing, permeability evaluations, and environmental impact assessments. Plastic aggregates are used to partially replace coarse aggregates at varying replacement levels of 0%, 5%, 10%, 15%, 20%, and 25% by weight, to evaluate their influence on the mechanical strength and durability of the permeable pavement blocks. Additionally, the hydraulic conductivity of the modified blocks is measured under controlled conditions to determine their effectiveness in managing stormwater runoff. Results demonstrate that the incorporation of plastic aggregates maintains structural integrity while significantly improving water permeability, offering potential benefits for stormwater management and urban flood mitigation, considering factors such as reduced carbon emissions and decreased landfill waste. This study further integrates a Technology Readiness Level (TRL) assessment, highlighting the current developmental stage of this technology and its potential for real-world implementation. The findings from this research contribute to the ongoing efforts to develop sustainable construction practices by reducing the dependence on traditional coarse aggregates and promoting the recycling of plastic waste. This paper provides valuable insights into the potential applications of plastic aggregate in permeable pavement construction and emphasizes the importance of environmentally responsible urban infrastructure development.

Global climate change is intensifying the frequency of drought events and altering forest light environments, yet the interactive effects of drought and shade on dioecious tree species remain poorly understood. In this study, we selected female and male Populus cathayana cuttings as research objects to explore their growth, photosynthesis, anatomical and hydraulic characteristics responses to drought, shade and their interactive stress. The results revealed that the growth and photosynthetic capacity of both sexes were reduced under drought and shade stress, and the total biomass and net photosynthesis rates of both sexes were lower under interactive stress than single drought stress, indicating that shade aggravates the negative effects of drought stress. Compared with females, P. cathayana males presented greater biomass, net photosynthesis rate and xylem hydraulic conductivity, and a lower percentage loss of conductivity under drought, shade and their interactive stress. In addition, under drought and shade stress, males presented greater leaf thickness, palisade tissue thickness, palisade tissue thickness to spongy tissue thickness ratio, number of vessels and total vessel area and had a smaller average vessel area, which was favorable for males to maintain water transport and utilization in stressful environments. Collectively, these coordinated anatomical and hydraulic advantages enabled males to sustain superior physiological performance under drought, shade and their interactive stress. Our findings highlight pronounced sexual dimorphism in stress tolerance and suggest that increasing drought and shade under future climates may bias natural populations toward males, with potential consequences for population productivity and ecosystem function.