Increase In Hydraulic Conductivity Research Articles

Effect of combined use of potassic fertilizer and gliricidia green leaves on soil fertility, nutrient balance and yield of rainfed cotton in Vertisols

A field experiment was conducted at research farm of AICRP for Dryland Agriculture, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola (Maharashtra), to assess the effect of potash management through gliricidia green leaves on soil fertility, nutrient balance and yield of rainfed cotton (Gossypium spp.) in Vertisols during kharif season of 2020. The results revealed that there was significant increase in hydraulic conductivity, organic carbon and available N, P, K of soil and decrease in soil pH, EC and bulk density in the gliricidia incorporated treatments as compared to control. The highest available N (211.1 kg ha-1), P (16.7 kg ha-1) and K (361.5 kg ha-1) was observed with the application of 100 % NP + 10 kg K (inorganic) + 20 kg K through gliricidia which increased by 16, 31.7 and 13.7% respectively over control. Similarly, the nutrient balance after six years of experiment was also higher with the application of 100 % NP + 10 kg K (inorganic) + 20 kg K through gliricidia being 25.4 kg ha-1 for available N, 2.15 kg ha-1 for available P and 39.6 kg ha-1 for available K. There was significant reduction in the bulk density of soil, being lowest (1.40 Mg m-3) in the treatment 100 % NP + 10 kg K (inorganic) + 20 kg K through gliricidia as compared to control. Significant improvement in the seed and stalk yield of cotton was recorded with the application of 100 % NP + 10 kg K (inorganic) + 20 kg K through gliricidia, with increment of 60, 18% and 64, 22% over control and 100% RDF, respectively

Effect of combined use of potassic fertilizer and gliricidia green leaves on soil fertility, nutrient balance and yield of rainfed cotton in Vertisols

A field experiment was conducted at research farm of AICRP for Dryland Agriculture, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola (Maharashtra), to assess the effect of potash management through gliricidia green leaves on soil fertility, nutrient balance and yield of rainfed cotton (Gossypium spp.) in Vertisols during kharif season of 2020. The results revealed that there was significant increase in hydraulic conductivity, organic carbon and available N, P, K of soil and decrease in soil pH, EC and bulk density in the gliricidia incorporated treatments as compared to control. The highest available N (211.1 kg ha-1), P (16.7 kg ha-1) and K (361.5 kg ha-1) was observed with the application of 100 % NP + 10 kg K (inorganic) + 20 kg K through gliricidia which increased by 16, 31.7 and 13.7% respectively over control. Similarly, the nutrient balance after six years of experiment was also higher with the application of 100 % NP + 10 kg K (inorganic) + 20 kg K through gliricidia being 25.4 kg ha-1 for available N, 2.15 kg ha-1 for available P and 39.6 kg ha-1 for available K. There was significant reduction in the bulk density of soil, being lowest (1.40 Mg m-3) in the treatment 100 % NP + 10 kg K (inorganic) + 20 kg K through gliricidia as compared to control. Significant improvement in the seed and stalk yield of cotton was recorded with the application of 100 % NP + 10 kg K (inorganic) + 20 kg K through gliricidia, with increment of 60, 18% and 64, 22% over control and 100% RDF, respectively.

Reactive Transport Model of Gypsum Karstification in Physically and Chemically Heterogeneous Fractured Media

Gypsum dissolution leads to the development of karstic features within much shorter timescales than in other sedimentary rocks, potentially leading to rapid deterioration of groundwater quality and increasing the risk of catastrophes caused by subsidence. Here, we present a 2-D reactive transport model to evaluate gypsum karstification in physically and chemically heterogeneous systems. The model considers a low-permeability rock matrix composed mainly of gypsum and a discontinuity (fracture), which acts as a preferential water pathway. Several scenarios are analyzed and simulated to investigate the relevance for gypsum karstification of: (1) the dynamic update of flow and transport parameters due to porosity changes; (2) the spatial distribution of minerals in the rock matrix; (3) the time evolution of water inflows through the boundaries of the model; (4) the functions relating permeability, k, to porosity, ϕ. The average porosity of the matrix after 1000 years of simulation increases from 0.045 to 0.29 when flow, transport, and chemical parameters and the water inflows through the boundary are dynamically updated according to the porosity changes. On the contrary, the porosity of the matrix hardly changes when the porosity feedback effect is not considered, while its average increases to 0.13 if the water inflow occurs through the discontinuity. Moreover, the dissolution of small amounts of highly soluble sulfate minerals plays a major role in the development of additional fractures. The increase in hydraulic conductivity is largest for the power law with an exponent of n = 5, as well as the Kozeny-Carman and the modified Fair-atch k-ϕ relationships. The gypsum dissolution front propagates into the matrix faster when the power law with n = 2 and 3 and the Verma–Pruess k-ϕ relationships are used.

Observations and challenges in simulating post-liquefaction settlements from centrifuge and shake table tests

Liquefaction-induced reconsolidation settlements occur as excess pore pressures generated during shaking dissipate and can lead to significant damage to overlying infrastructure. Designing resilient infrastructure in areas affected by liquefaction requires methods to predict these settlements for different soil types and boundary conditions. Simplified empirical models are commonly utilized to evaluate settlements but they exhibit several limitations that might hinder the accuracy of settlement predictions, including effects of partial drainage, thin layers, non-liquefiable crusts, or soil fabric. Numerical models can capture these effects but require proper calibration and validation. This study uses a numerical approach to simulate centrifuge and shake table experiments with free-field level, ground conditions and five different sands for evaluating reconsolidation settlements. The numerical platform FLAC and constitutive relationship PM4Sand are utilized. The necessity of soil-specific calibration of post-liquefaction stiffness and an excess pore pressure ratio dependent hydraulic conductivity to accurately model the observed pore pressures and settlements is analyzed. A new relationship between the increase in hydraulic conductivity due to liquefaction and grain size diameter is proposed. The numerical simulations are able to capture the general trends, but the bias in the results appears to be correlated with the grain size distribution of the tested soil.

Potential of halophytes in managing soil salinity and mitigating climate change for environmental sustainability

Soil salinization is one of the foremost factors affecting global agricultural productivity. More than half billion hectares of agricultural land are unutilized due to excess saline condition. Hence, there is a great urge in exploring scientific interventions in restoring the saline affected areas and promote high productive and effective land utilization in order to respond to today's global concerns of food security. While a sound drainage system is required as a permanent solution to the soil salinity problem in order to regulate the water table, this option cannot be used in larger area with high energy and cost-intensity.Phytoremediation, a plant – based approach is one of the promising technology in enhanced dissolution of Ca levels along with sodium removal through cultivating suitable halophytes.During the process, the proliferation of roots, aggregate stability, hydraulic conductivity and nutrient availability increases. These improvement in soil quality enables the growth of less tolerant crops, enhances the overall ecosystem and climatic conditions by increasing carbon sequestration. In this perspective, the chapter focuses on halophytes, its kinds, the effects of salinity on soil physical, chemical, biological health, the influence of halophytes in stress management and on the function of halophytes in carbon sequestration.

Consolidation and Hydraulic Conductivity of High-Plastic Clay Reinforced with Waste Tire Fibers

Abstract Extreme shrinkage, high swelling, excessive settlement, and low shear strength are some undesirable properties of clayey soils. Stabilizing the clayey soil by means of chemical admixtures has been widely adopted in the past. As an alternative to these traditional techniques, the present study proposes an economical and environmentally friendly solution that involves the use of waste tire fibers in clayey soil. The waste tire fibers of three aspect ratios of 9, 6.4, and 4.5 were mixed with four different contents, i.e., 0.25, 0.50, 0.75, and 1.00 %, in clayey soil. In the present study, the one-dimensional consolidation behavior of fiber-reinforced clayey soil was investigated with the help of various consolidation parameters. Test results have confirmed that the swelling nature of clayey soil can be controlled remarkably well with the addition of waste tire fibers. The significant reduction in the settlement was observed for the low aspect ratio fibers. The results show that the rate of consolidation of clayey soil increases considerably with the addition of longer and thicker fibers. Thus, the time required for 90 % consolidation is reduced from 64 to 40 minutes for untreated clayey soil. With an increase in fiber content and size, the void ratio in fiber-reinforced clayey soil increased, which further leads to an increase in hydraulic conductivity. It can be stated that the utilization of waste tires as a reinforcing material in clayey soil can be an economical option for the construction industry mainly because it is an ecofriendly use of tire disposal.

A finite particle method (FPM) for Lagrangian simulation of conservative solute transport in heterogeneous porous media

When a smoothed particle hydrodynamics (SPH) method, a Lagrangian and meshfree numerical scheme, is used to solve the advection-dispersion equation (ADE), SPH solutions may not be accurate when particles are irregularly distributed, i.e., the distance between two neighbor particles varies irregularly in a simulation domain. Particle irregularity may be caused by nonuniform groundwater flow in a heterogeneous field of hydraulic conductivity. This study explores for the first time whether the Finite Particle Method (FPM) can provide more accurate ADE solutions than SPH does for irregularly distributed particles. FPM is similar to SPH in theory, but uses a modified kernel gradient to construct a SPH approximation of solute concentration gradients. Performance of SPH and FPM with irregularly distributed particles is evaluated by using two numerical cases. The first case considers only diffusive transport, and has an analytical solution for the evaluation. The second case considers both advection and dispersion, and uses a numerical solution as a reference for the evaluation. For each of the two cases, several numerical experiments are conducted using multiple sets of irregularly distributed particles with different levels of particle irregularity due to different levels of heterogeneity of hydraulic conductivity. Numerical results indicate that, for the numerical experiments of this study, FPM outperforms SPH to yield more accurate ADE solutions. However, FPM solutions are still subject to numerical errors, and the errors increase when the level of heterogeneity of hydraulic conductivity increases. Further improvement of FPM is warranted in a future study.

Involvement of Reactive Oxygen Species in ABA-Induced Increase in Hydraulic Conductivity and Aquaporin Abundance.

The role of reactive oxygen species (ROS) in ABA-induced increase in hydraulic conductivity was hypothesized to be dependent on an increase in aquaporin water channel (AQP) abundance. Single ABA application or its combination with ROS manipulators (ROS scavenger ascorbic acid and NADPH oxidase inhibitor diphenyleneiodonium chloride (DPI)) were studied on detached roots of barley plants. We measured the osmotically driven flow rate of xylem sap and calculated root hydraulic conductivity. In parallel, immunolocalization of ABA and HvPIP2;2 AQPs was performed with corresponding specific antibodies. ABA treatment increased the flow rate of xylem, root hydraulic conductivity and immunostaining for ABA and HvPIP2;2, while the addition of antioxidants prevented the effects of this hormone. The obtained results confirmed the involvement of ROS in ABA effect on hydraulic conductivity, in particular, the importance of H2O2 production by ABA-treated plants for the effect of this hormone on AQP abundance.

EFFECT OF AMELIORATION PROCESSES ON SALT AFFECTED SOIL PROPERTIES AND ITS PRODUCTIVITY OF WHEAT PLANT

A field experiment were carried out saline soil at the region of Demro Village, Sidi salem City, Kafr El Shiekh Governorate, Egypt, during two successive growing winter seasons of 2018/2019 and 2019/2020. Therefore this study was carried out to evaluate the effect of leaching technique. i.e. uncontinuous process and continuous process CLP under individual and combined gypsum application rates as a percent of soil gypsum requirements GR.i.e. 0, 50 and 100 % ( G1,G2 and G3, respectively) and tillage depth .i.e. without T1, 20 cm T2 and 50 cm T3. These treatments were arranged with in the experimental plots in split-split plot at randomized complete block design in three replicates. The effect of the studied treatments on soil salinity, bulk density and hydraulic conductivity as well as productivity on wheat (Triticum aestivum, Masr3) plants were studied. Increasing rate of added gypsum as well as increasing in tillage depth resulted in a significant decrease of both soil salinity and its bulk density while resulted in a significant increase of soil hydraulic conductivity. The high changes of the studied soil properties were observed with ULP technique. In addition straw and grains yields of wheat plants were increased significantly as a resulted of gypsum applications and increase of tillage depth, where the highest yields were found with the combined treatments of GR3 and T3 with ULP technique. The data of this study show the high efficiency of combined amelioration processes in improve properties of saline soil and its productivity of crops compared with the single process.

Effect of freezing and thawing on soil permeability: newly equipment and experimental results

In a cold climate design of dams, clay barrier liners on landfills, and structures on frost-susceptible soils is a challenge for geotechnical engineers. During service life of the structures a frost heave may reach 15-20% of the depth of a frost penetration and an uplift movement are accompanied by the formation of layered or lattice cryogenic texture. When thawing, macro- and micropores are formed instead of ice lenses. Basically pores are oriented predominantly along frost front. They are a reason of horizontal water permeability increase, consequently, reduce of stability of the slopes and decrease of the effectiveness of the landfill clay barrier liners. The paper presents a new apparatus for studying water permeability and frost heave of soils which allows to carry out horizontal or/and vertical permeability tests (along and across layered cryogenic texture) after assigned number of freeze-thaw cycles without withdrawal of a soil sample from apparatus. The results for clay and fine sand samples are obtained. Clay and fine sand samples showed an increase of horizontal hydraulic conductivity after 2 - 4 freeze-thaw cycles. Relationship between water flow velocity and hydraulic gradient for non-Darcian and Darcian flow is obtained as a result of vertical permeability tests of clay samples in unfrozen state.

Hydraulic conductivity of gravelly soils with various coarse particle contents subjected to freeze–thaw cycles

Gravelly soils, characterized by a mixture of fine soil matrix and coarse gravel aggregates, are widely distributed in high mountain and cold plateau areas. These soils are frequently subjected to freeze–thaw (F-T) actions, and the hydraulic conductivity is crucial for analyzing hydrological processes and geological hazards. This study aims to investigate hydraulic conductivity in gravelly soils containing various contents of gravel particle fraction under cyclic freezing–thawing. The results show that the hydraulic conductivity in gravelly soils significantly depends on gravel content, confining stress, number of F-T cycles and initial water content. The presence of gravel particles modifies the porosity and pore connectivity/tortuosity in soil matrix, as well as affects the soil matrix-gravel interfaces. With increasing gravel content, the overall gravel assembly transforms from a state of floating in the soil matrix to forming a contacted skeleton structure. Thus, the extensively developed loose soil-gravel interfaces due to F-T cycles result in a significant increase in hydraulic conductivity. Increasing confining pressure significantly reduces the soil matrix void ratio and thereby decreases the hydraulic conductivity, while no longer recovers the degradation in soil-gravel interfaces induced by F-T cycles. Different initial compacted water content provides different compacted soil structures, divided by the optimum water content (wopt). A prominent increase of hydraulic conductivity after F-T cycles occurs in samples compacted at the dry side of wopt, while a slighter increase at its wet side.

Centrifuge modelling of the use of discretely spaced energy pile row to reinforce unsaturated silt

Discretely spaced reinforced concrete (RC) energy pile rows have been proposed to be installed at the mid-height of soil slopes. Although the pile row can provide mechanical reinforcement to slopes, the piles can also potentially be used to (a) intercept solar energy from roadways for heat storage in the ground to mitigate extremely high carriageway temperatures and (b) to extract shallow geothermal energy for road surface de-icing. In this study, a series of centrifuge model tests was conducted to evaluate the shearing behaviour of unsaturated silt with and without reinforcement by conventional piles and energy piles. Three-dimensional finite-element coupled water–vapour–heat transport analysis was also performed to understand further the effects of pile heating on the responses of temperature and pore-water pressure of the soil. The measured and computed results revealed that the primary effect of pile heating was an increase in soil hydraulic conductivity due to the heat-induced reduction in water viscosity. The heated soil had enhanced water flow and hence developed higher suction. When subjected to translational slip, the silt reinforced by a row of closely spaced RC energy piles exhibited a more ductile shearing response and a lower peak shear resistance, compared to that reinforced by conventional piles. The peak bending moments mobilised in the energy piles in the stable stratum were also smaller. At larger shear displacements, however, the shear resistance converged to a similar value, regardless of the suction and temperature. These findings suggest that piles modified with additional energy transfer functionality can continue to act as reinforcement, potentially preventing soil from a sudden brittle failure, without attracting additional flexural stresses onto the piles.

اثر دما بر ضریب نفوذپذیری خاک رسی متراکم و عایق رسی ژئوسینتتیک (GCL)

تاثیر دما در خواص نفوذپذیری خاک‌های رسی متراکم یکی از پارامترهای اساسی در طراحی لایه‌های عایق مهندسی است که در معرض شیرابه‌ها هستند. در این تحقیق اثر دما بر ضریب نفوذپذیری رس متراکم منطقه نازلوی ارومیه و عایق های رسی ژئوسینتتیک و همچنین تاثیر میزان تنش موثر و دانسیته بر نرخ تغییر ضریب نفوذپذیری نمونه های رسی بررسی شده است. دستگاه تعیین ضریب نفوذپذیری سه محوری با دیواره انعطاف پذیر برای اندازه گیری ضریب نفوذپذیری نمونه ها تحت تاثیر دما مورد استفاده قرار گرفته است. با افزایش دما ویسکوزیته محلول کاهش یافته و اثرات دمایی ساختار خاک را تغییر می دهد و تولید حفرات بزرگتر بین ذرات رس می کند و باعث ایجاد تغییر در سطح مقطع موثر جریان شده و آب جذب شده تبدیل به آب آزاد می شود و در نتیجه باعث افزایش ضریب نفذپذیری خاک رسی می شود. افزایش تنش موثر باعث می شود نرخ افزایش در ضریب نفوذپذیری در اثر افزایش دما کاهش یابد. همچنین با افزایش دانسیته خاک رسی، ضریب نفوذپذیری و نرخ افزایش آن کاهش می یابد. بر خلاف خاک‌های رسی، در عایق های رسی ژئوسینتتیک افزایش دما تاثیر چندانی در ضریب نفوذپذیری این لایه ها نداشته و زمانی که این لایه ها در معرض افزایش دما قرار گیرند به عملکرد خوب خود به عنوان یک مانع هیدرولیکی ادامه می‌دهند.

The Singular Molecular Conformation of Humic Acids in Solution Influences Their Ability to Enhance Root Hydraulic Conductivity and Plant Growth.

Some studies have reported that the capacity of humic substances to improve plant growth is dependent on their ability to increase root hydraulic conductivity. It was proposed that this effect is directly related to the structural conformation in solution of these substances. To study this hypothesis, the effects on root hydraulic conductivity and growth of cucumber plants of a sedimentary humic acid and two polymers—polyacrylic acid and polyethylene glycol—presenting a molecular conformation in water solution different from that of the humic acid have been studied. The results show that whereas the humic acid caused an increase in root hydraulic conductivity and plant growth, both the polyacrylic acid and the polyethylene glycol did not modify plant growth and caused a decrease in root hydraulic conductivity. These results can be explained by the different molecular conformation in water solution of the three molecular systems. The relationships between these biological effects and the molecular conformation of the three molecular systems in water solution are discussed.

Evaluating the effect of biochar on salt leaching and nutrient retention of Yellow River Delta soil

AbstractBiochar has the potential to decrease salinity and nutrient loss of saline soil. We investigated the effects of biochar amendment (0–10 g kg−1) on salinity of saline soil (2.8‰ salt) in NaCl leaching and nutrient retention by conducting column leaching experiments. The biochar was produced in situ from Salix fragilis L. via a fire‐water coupled process. The soil columns irrigated with 15 cm of water showed that biochar amendment (4 g kg−1) decreased the concentration Na+ by 25.55% in the first irrigation and to 60.30% for the second irrigation in sandy loam layer over the corresponding control (CK). Meanwhile, the sodium adsorption ratio (SAR) of soil after the first and second irrigation was 1.62 and 0.54, respectively, which were 15.2% and 49.5% lower than CK. The marked increase in saturated hydraulic conductivity (Ks) from 0.15 × 10–5 cm s−1 for CK to 0.39 × 10–5 cm s−1, following 4 g kg−1 of biochar addition, was conducive to salt leaching. Besides, biochar use (4 g kg−1) increased NH4+‐N and Olsen‐P by 63.63% and 62.50% over the CK, but accelerated NO3–‐N leaching. Since 15 cm hydrostatic pressure would result in salt accumulation of root zone, we would recommend using 4 g kg−1 of biochar, 30 cm of water to ease the problem of salt leaching from the surface horizon to the subsoil. This study would provide a guidance to remediate the saline soil in the Yellow River Delta by judicious application of biochar and irrigation.

Root structural plasticity enhances salt tolerance in mature olives

Roots are the first plant organ to encounter, sense, and respond to soil salinity. Like for many moderately salt tolerant species, roots of olive (Olea eurpaea) trees are the principal players in salt tolerance. We studied roots of mature olive trees in order to illuminate the yet vague mechanism(s) of root salt exclusion.Root structural traits were examined in olive trees grown in lysimeters and from a long-term salinity field trial. The distribution of salts was detected in root cross-sections using scanning electron microscopy combined with energy dispersive spectroscopy.Increased soil salinity caused a continuous decline in specific root length and an increase in root diameter, periderm thickness, and specific hydraulic conductivity. While periderm cell number was not modified, cell diameter increased linearly by a total of 50 % as root zone salinity increased nearly eight-fold. Strong compartmentation of Na within the periderm was found, with highest content in the outer periderm layer and lowest content in the stele. Increase in soil salinity was associated with decrease in stele area, yet, hydraulic conductivity was doubled due to higher fraction of large diameter xylem vessels.Our results indicate significant root structural plasticity, which underlies the salt resistance mechanisms. The dominant trait enabling salt tolerance of olive trees is the enlarged periderm serving as an apoplastic barrier that enhances salt compartmentation and exclusion from the vascular tissues.

Seasonal variation of infiltration rates through pond bed in a managed aquifer recharge system in St‐André, Belgium

AbstractIn Belgium, IWVA uses managed aquifer recharge (MAR) to recharge the aquifer with treated wastewater generated from the communities to sustain the potable water supply on the Belgian coast. This MAR facility is faced with a challenge of reduced infiltration rates during the winter season when pond water temperatures near 4°C. This study involves the identification of the predominant factor influencing the rate of infiltration through the pond bed. Several factors, including pumping rates, natural recharge, tidal influences of the North Sea and pond‐water temperature, were identified as potential causes for variation of the recharge rate. Correlation statistics and linear regression analysis were used to determine the sensitivity of the infiltration rate to the aforementioned factors. Two groundwater flow models were developed in visual MODFLOW to simulate the water movement under the pond bed and to obtain the differences in flux to track the effects of variation of hydraulic conductivity during the two seasons. A 32% reduction in vertical hydraulic gradient in the top portion of the aquifer was observed in winter, causing the recharge rates to fluctuate. Results showed that water temperature caused a 30% increase in hydraulic conductivity in summer as compared with winter and has the maximum impact on infiltration rate. Cyclic variations in water viscosity, occurring because of seasonal temperature changes, influence the saturated hydraulic conductivity of the pond bed. Results from the models confirm the impact on infiltration rate by temperature‐influenced hydraulic conductivity.

Laboratory and numerical simulations of spatio-temporal variability of water exchange between the fissures and conduits in a karstic aquifer

Fissures and conduits are main void of karstic aquifer. Karst aquifers are highly vulnerable to contamination as water exchange between fissuresystem andconduitsystem greatly influences the karstification of limestone terrains, heterogeneity of karstic aquifer, and spring flow regime. A two-dimensional tank model was constructed, and a corresponding numerical model (MODFLOW-2005 Conduit Flow Process Mode 1, CFPM1) was developed to explore the effects of rainfall intensity and intrinsic structure of karst system (hydraulic conductivity of fissures and conduit diameter) on conduit-matrix water exchange. Nine different scenarios were designed to quantitatively simulate the spatial and temporal variability of water exchange between the fissures and conduits. The study reproduced the area of fissure water recharging to conduit (recharge zone), the area of conduit water discharging to fissure water (discharge zone) and the area of fissure water moving laterally (transport zone) in both physical model and numerical model. The results from rainfall scenarios show a relatively stable ratio of exchange zone (recharge zone and discharge zone) with increasing rainfall intensity, indicating that conduit-matrix water exchange is not sensitive to rainfall intensity, and conduit water discharging to fissure water is just a short-term phenomenon. It is also found that an increase in hydraulic conductivity of fissure system enhances extensiveness of water transport, but restrains conduit-matrix water exchange. However, the enlargement of conduit can prompt the extent of conduit-matrix water exchange. A positive feedback between the extent of conduit-matrix water exchanges and karstification can be confirmed. These findings might be essential for better understanding groundwater flow dynamics in karst aquifers.

Pulsed focused ultrasound lowers interstitial fluid pressure and increases nanoparticle delivery and penetration in head and neck squamous cell carcinoma xenograft tumors

Nanocarriers offer a promising approach to significantly improve therapeutic delivery to solid tumors as well as limit the side effects associated with anti-cancer agents. However, their relatively large size can negatively affect their ability to efficiently penetrate into more interior tumor regions, ultimately reducing therapeutic efficacy. Poor penetration of large agents such as nanocarriers is attributed to factors in the tumor microenvironment such as elevated interstitial fluid pressure (IFP) and fibrillar collagen in the extracellular matrix. Our previous studies reported that pretreatment of solid tumor xenografts with nondestructive pulsed focused ultrasound (pFUS) can improve the delivery and subsequent therapy of a variety of therapeutic formulations in different tumor models, where the results were associated with expanded extracellular spaces (ECS), an increase in hydraulic conductivity, and decrease in tissue stiffness. Here, we demonstrate the inverse relationship between IFP and the penetration of systemically administered nanoparticle (NP) probes, where IFP increased from the tumor periphery to their center. Furthermore, we show that pretreatment with pFUS can safely reduce IFP and improve NP delivery; especially into the center of the tumors. These results coincide with effects generated in the fibrillar collagen network microstructure in the ECS as determined by quantitative polarized light microscopy. Whole tumor and histomorphometric analysis, however, did not show significant differences in collagen area fraction or collagen feature solidity, as well as tumor cross-sectional area and aspect ratio, as a result of the treatments. We present a biophysical model connecting the experimental results, where pFUS-mediated cytoarchitectural changes are associated with improved redistribution of the interstitial fluid and lower IFP. The resulting improvement in NP delivery supports our previous therapeutic studies and may have implications for clinical applications to improve therapeutic outcomes in cancer therapy.

Solute transport modelling to manage groundwater pollution from surface water resources

This article provides an analytical solute transport model to investigate the potential of groundwater contamination by polluted surface water in a two dimensional domain. The clogging of streambed which makes the aquifer partially penetrated by the stream, is considered in the model. The impacts of pumping process, hydraulic conductivity and clogging layer on the quality of water produced from nearby drinking water wells are evaluated. It is found that results are consistent with numerical simulation conducted by MODFLOW software. Moreover, the model is applied using data of contamination occurrence in Malaysia, where high contaminants concentrations are found close to streams. Results show that the pumping activities (rate and time period) are crucial factors when evaluating the risk of groundwater contamination from surface water. Additionally, this study illustrates that the increase in either hydraulic conductivity or leakance coefficient parameters due to the clogging layer will enlarge the area of contamination. The model is able to determine the suitable pumping rate and location of the well so that the contamination plume never reaches the extraction well, which is useful in constructing riverbank filtration sites.