Solute Movement Research Articles

In vivo cytological and chemical analysis of Casparian strips using stimulated Raman scattering microscopy

The Casparian strip, a barrier to the apoplastic movement of solutes from the cortex to the stele, is essential for the exclusion of salts, selective nutrient uptake, and many other processes. To date, extensive studies have focused on the physiological functions of endodermal Casparian strips. However, the chemical deposition nature of Casparian strips, as well as its relevance with respect to diffusion barrier functions, remains to be further elucidated. Here, we revealed three developmental stages of Casparian strips in maize primary roots using a traditional fluorescent staining method. Apoplastic permeability tests demonstrated that the barrier function of Casparian strips is largely related to their developmental stage and the pattern of lignin and suberin deposits. Fourier transform infrared (FTIR) analysis showed that the Casparian strips from the roots exhibited significant absorption bands characteristic of lignin and suberin, implying that the Casparian strips in maize primary roots consist largely of lignin and suberin. Furthermore, we developed a new method for label-free, in vivo structural, and biochemical analysis of Casparian strips based on stimulated Raman scattering (SRS) microscopy. Using SRS microscopy, we found that lignin and suberin accumulate simultaneously during the Casparian strip formation process. Based on these results, we propose a potential application of SRS for the chemical composition analysis of plant Casparian strips in situ.

Acute and chronic fluid misdirection syndrome: pathophysiology and treatment

PurposeTo summarize our current understanding of the specific pathogenic mechanisms of the fluid misdirection syndrome and possible treatment methods.MethodsWe used the PubMed web platform to find relevant studies using the following keywords: infusion misdirection syndrome, aqueous misdirection syndrome, ciliary block, ciliovitreal block, capsular block, intraoperative fluid misdirection, subcapsular fluid entrapment, acute intraoperative rock-hard eye syndrome, positive vitreous pressure glaucoma, and malignant glaucoma. Other publications were also considered as a potential source of information when referenced in relevant articles.ResultsWe collected and analyzed 55 articles dated from 1951 to 2016. Acute intraoperative rock-hard eye syndrome is characterized by a very shallow anterior chamber with the absence of suprachoroidal effusion or hemorrhage and no noticeable pathology of the iris–lens diaphragm. It usually occurs during uneventful phacoemulsification, particularly in hyperopic eyes. The pathophysiology of acute fluid misdirection syndrome is based on inappropriate movement of balanced salt solution via the zonular fibers. This syndrome has also been described as occurring from hours to months, or years, after the initial surgery. The pathophysiology of malignant glaucoma is based on similar mechanisms of cilio-lenticular block of aqueous flow leading to the misdirection of aqueous posteriorly into or besides the vitreous gel. Faced with these situations, vitreous decompression is required, preferably with hyaloido-capsulo-iridectomy. In phakic eyes, concomitant cataract extraction would be desirable.ConclusionsWe believe both of these clinical conditions should be considered as one syndrome. We suggest the term acute fluid misdirection syndrome for the cascade of events during phacoemulsification surgery. Chronic fluid misdirection syndrome better describes the nature of malignant glaucoma.

Diffusion coefficient in biomembrane critical pores.

Diffusion is fundamental to the random movement of solutes in solution throughout biological systems. Theoretical studies of diffusing solutes across cell membranes confined in a microscopic size of pores have been an interesting subject in life and medical sciences. When a solute is confined in a critical area of membrane pores, which shows a quite different behavior compared to the homogeneous-bulk fluid whose transport is isotropic in all directions. This property has novel features, which are of considerable physiological interest.

A computationally efficient pseudo-3D model for the numerical analysis of borehole heat exchangers

Ground-Source Heat Pump (GSHP) systems represent one of the most efficient renewable energy technologies. Their efficiency is highly influenced by the thermal properties of the ground, which are often measured in-situ using the Thermal Response Tests (TRTs). While three-dimensional mechanistic models offer significant advantages over analytical solutions for the numerical interpretation of TRTs, their computational cost represents a limiting factor. Moreover, most of the existing models do not include a comprehensive description of hydrological processes, which have proven to strongly influence the behavior of GSHP. Thus, in this study, we propose a computationally efficient pseudo-3D model for the numerical analysis and interpretation of TRTs. The numerical approach combines a one-dimensional description of the heat transport in the buried tubes of the exchanger with a two-dimensional description of the heat transfer and water flow in the surrounding subsurface soil, thus reducing the dimensionality of the problem and the computational cost. The modeling framework includes the widely used hydrological model, HYDRUS, which can simulate the movement of water, heat, and multiple solutes in variably-saturated porous media. First, the proposed model is validated against experimental data collected at two different experimental sites in Japan, with satisfactory results. Then, it is combined with the Morris method to carry out a sensitivity analysis of thermal properties. Finally, the model is exploited to investigate the influence of groundwater and lithologic heterogeneities on the thermal behavior of the GSHP.

Upward capillary leaching

Upward capillary leaching is a method of extracting useful components from solutions by filtering them through a column. This method is based on the natural movement of solutions in the column aeration zone. The vadose zone is a geochemical evaporation barrier.The solution moves upward from the water table to the surface via capillaries in the vadose zone, and the water evaporates during its upward movement, resulting in the concentration and deposition of metal salts. In this study, laboratory experiments using a special set-up show that water-soluble metal compounds can be directionally redistributed in a column. Flotation tailings from the Norilsk industrial region were packed into the laboratory column, and drinking water was employed as the leaching agent. The kinetics of the upward solution flow through the column capillaries were investigated. Elemental redistribution in the column aeration zone was confirmed by geochemical analysis.

Test of the 'glymphatic' hypothesis demonstrates diffusive and aquaporin-4-independent solute transport in rodent brain parenchyma.

Transport of solutes through brain involves diffusion and convection. The importance of convective flow in the subarachnoid and paravascular spaces has long been recognized; a recently proposed 'glymphatic' clearance mechanism additionally suggests that aquaporin-4 (AQP4) water channels facilitate convective transport through brain parenchyma. Here, the major experimental underpinnings of the glymphatic mechanism were re-examined by measurements of solute movement in mouse brain following intracisternal or intraparenchymal solute injection. We found that: (i) transport of fluorescent dextrans in brain parenchyma depended on dextran size in a manner consistent with diffusive rather than convective transport; (ii) transport of dextrans in the parenchymal extracellular space, measured by 2-photon fluorescence recovery after photobleaching, was not affected just after cardiorespiratory arrest; and (iii) Aqp4 gene deletion did not impair transport of fluorescent solutes from sub-arachnoid space to brain in mice or rats. Our results do not support the proposed glymphatic mechanism of convective solute transport in brain parenchyma.

The Use of Thermography Images in the Description of the Humidification Bulb in Soilless Culture

ABSTRACTThermography is a tool used in many scientific disciplines, including agriculture. Determining the behavior of a nutritive solution in soilless culture containers using substrates is very important in order to establish the position of drippers, drainage holes, the use of humidification agents, and fertigation management in culture units. This paper describes the application of thermography to determine the humidification bulb in horticulture crops to rapidly diagnose the best way to advance fertigation in different horticultural substrates in soilless culture. Thermography was seen to be an excellent tool for evaluating the movement and distribution of the nutritive solution within the soilless culture container with different substrates.

The Role of Pore Structure on Nitrate Reduction in Peat Soil: A Physical Characterization of Pore Distribution and Solute Transport

Soil type is an important factor defining terrestrial ecosystems and plays a major role for the movement of solutes and cycling of nutrients and carbon. This paper focuses on the effect of peat complex dual-porosity structure on nitrate reduction, with the main objective to show how this process is controlled by pore-scale mass transfer and exchange of nitrate between mobile and immobile pore fractions. A mesocosm experiment was conducted where input solutions of bromide (Br−) and nitrate (NO3 −) were continuously supplied downward into 40 cm depth of peat. Br− and NO3 − breakthrough curves were used to constrain transport parameters and nitrate reduction rates in the peat depth profile. The vertical distribution of potential nitrate reduction rates were compared with depth distributions of partitioning mobile-immobile pores and the exchange coefficient between the pores. The results showed that an increase of immobile pore fractions with depth increases the common interface surface area between mobile and immobile pores which constitutes to a more pronounced exchange between the two transport domains and enhances the nitrate reduction. Hence, the pore structure with mobile-immobile pore fractions and exchange rate of solutes between mobile and immobile phases play a major role in nitrate reduction in peat soils.

Physically Triggered Morphology Changes in a Novel Acremonium Isolate Cultivated in Precisely Engineered Microfabricated Environments.

Fungi are strongly affected by their physical environment. Microfabrication offers the possibility of creating new culture environments and ecosystems with defined characteristics. Here, we report the isolation of a novel member of the fungal genus Acremonium using a microengineered cultivation chip. This isolate was unusual in that it organizes into macroscopic structures when initially cultivated within microwells with a porous aluminum oxide (PAO) base. These “templated mycelial bundles” (TMB) were formed from masses of parallel hyphae with side branching suppressed. TMB were highly hydrated, facilitating the passive movement of solutes along the bundle. By using a range of culture chips, it was deduced that the critical factors in triggering the TMB were growth in microwells from 50 to 300 μm in diameter with a PAO base. Cultivation experiments, using spores and pigments as tracking agents, indicate that bulk growth of the TMB occurs at the base. TMB morphology is highly coherent and is maintained after growing out of the microwells. TMB can explore their environment by developing unbundled lateral hyphae; TMB only followed if nutrients were available. Because of the ease of fabricating numerous microstructures, we suggest this is a productive approach for exploring morphology and growth in multicellular microorganisms and microbial communities.

Can a Time Fractional-Derivative Model Capture Scale-Dependent Dispersion in Saturated Soils?

Time nonlocal transport models such as the time fractional advection-dispersion equation (t-fADE) were proposed to capture well-documented non-Fickian dynamics for conservative solutes transport in heterogeneous media, with the underlying assumption that the time nonlocality (which means that the current concentration change is affected by previous concentration load) embedded in the physical models can release the effective dispersion coefficient from scale dependency. This assumption, however, has never been systematically examined using real data. This study fills this historical knowledge gap by capturing non-Fickian transport (likely due to solute retention) documented in the literature (Huang et al. 1995) and observed in our laboratory from small to intermediate spatial scale using the promising, tempered t-fADE model. Fitting exercises show that the effective dispersion coefficient in the t-fADE, although differing subtly from the dispersion coefficient in the standard advection-dispersion equation, increases nonlinearly with the travel distance (varying from 0.5 to 12 m) for both heterogeneous and macroscopically homogeneous sand columns. Further analysis reveals that, while solute retention in relatively immobile zones can be efficiently captured by the time nonlocal parameters in the t-fADE, the motion-independent solute movement in the mobile zone is affected by the spatial evolution of local velocities in the host medium, resulting in a scale-dependent dispersion coefficient. The same result may be found for the other standard time nonlocal transport models that separate solute retention and jumps (i.e., displacement). Therefore, the t-fADE with a constant dispersion coefficient cannot capture scale-dependent dispersion in saturated porous media, challenging the application for stochastic hydrogeology methods in quantifying real-world, preasymptotic transport. Hence improvements on time nonlocal models using, for example, the novel subordination approach are necessary to incorporate the spatial evolution of local velocities without adding cumbersome parameters.

Simulating the Fate and Transport of Coal Seam Gas Chemicals in Variably-Saturated Soils Using HYDRUS

The HYDRUS-1D and HYDRUS (2D/3D) computer software packages are widely used finite element models for simulating the one-, and two- or three-dimensional movement of water, heat, and multiple solutes in variably-saturated media, respectively. While the standard HYDRUS models consider only the fate and transport of individual solutes or solutes subject to first-order degradation reactions, several specialized HYDRUS add-on modules can simulate far more complex biogeochemical processes. The objective of this paper is to provide a brief overview of the HYDRUS models and their add-on modules, and to demonstrate possible applications of the software to the subsurface fate and transport of chemicals involved in coal seam gas extraction and water management operations. One application uses the standard HYDRUS model to evaluate the natural soil attenuation potential of hydraulic fracturing chemicals and their transformation products in case of an accidental release. By coupling the processes of retardation, first-order degradation and convective-dispersive transport of the biocide bronopol and its degradation products, we demonstrated how natural attenuation reduces initial concentrations by more than a factor of hundred in the top 5 cm of the soil. A second application uses the UnsatChem module to explore the possible use of coal seam gas produced water for sustainable irrigation. Simulations with different irrigation waters (untreated, amended with surface water, and reverse osmosis treated) provided detailed results regarding chemical indicators of soil and plant health, notably SAR, EC and sodium concentrations. A third application uses the HP1 module to analyze trace metal transport involving cation exchange and surface complexation sorption reactions in a soil leached with coal seam gas produced water following some accidental water release scenario. Results show that the main process responsible for trace metal migration in soil is complexation of naturally present trace metals with inorganic ligands such as (bi)carbonate that enter the soil upon infiltration with alkaline produced water. The examples were selected to show how users can tailor the required model complexity to specific needs, such as for rapid screening or risk assessments of various chemicals nder generic soil conditions, or for more detailed site-specific analyses of actual subsurface pollution problems.

Soil variability in La Violada Irrigation District (Spain): II Characterizing hydrologic and salinity features

The recent modernization of 1.1Mha of irrigated land in Spain calls for the evaluation of these transformations in terms of environmental impact and resource use efficiency. The available data for this evaluation has increased with the transformation (better, digital and spatially distributed data) allowing for the use of distributed soil water and solute movement models. But most hydrological models require soil hydrologic properties that are costly and time-consuming to gather and soil information in Spain is generally scarce. This paper focuses in analyzing the soil hydrologic features in La Violada Irrigation District (VID; a 5234ha semi-arid irrigated area recently modernized in northeast Spain) usable in soil water models for the evaluation of the new irrigation system.The recent soil map of the VID (presented in a companion paper) gathered the hydrologic and salinity properties of the horizons in the described soil units. The hydraulic conductivity (Ks) of the horizons was also assessed by the inverse auger-hole method. From these data, the VID was disaggregated in three homogeneous units according to their hydrologic features and Pedotransfer Functions (PTFs) were built for the whole VID (General Model) and separately for the homogeneous soil units (Distributed Model). These PTFs allowed for obtaining field capacity (FC) and wilting point (WP) from texture and organic matter, while Ks depended upon texture and gypsum content.Apparently, there were no salinity issues in VID soils due to irrigation. The high Ca2+ and Mg2+ levels in the saturation extract resulted in generally low SAR, what along with the high gypsum and carbonate contents may help to prevent soil degradation by sodicity.As a result, the homogeneous hydrologic zones defined in VID may be used to recommend specific irrigation practices and as the basis for the application of distributed soil water movement models. These hydrologic properties may be applied directly as inputs to the models while the PTFs may allow for setting adequate parameters in nearby areas with similar soils from more readily available soil information (texture, organic matter and gypsum).

Use of Ultrasound to Modified Electrodeposited Silver and Silver-Tin Microstructures and Composition without Chemical Additives

Properties of electrodeposited coatings are directly related to their morphology and structure, which are strongly influenced, among others, by the presence of organic additives and electrodeposition parameters (current density, DC vs pulsed current). An attractive possibility results in the use of ultrasound to influence the microstructure without using chemicals, or at least, by reducing their quantity. Ultrasound is expected to have several effects on deposits, by heating the liquid or by generating solution movements that cause convection flows or cavitation bubbles, accompanied by chemical effects. Many works in the literature describe the beneficial effect of ultrasound in plating, reporting finer grains, reduced porosity and increased brightness. Even the penetration of nickel in complex geometric pattern has been reported. In the present study, conventional cyanide silver as well as silver-tin electrolytes were used to examine the effect of current density and ultrasound on the composition, structure and texture of the coatings. Silver-tin alloys were used for such materials as electric contacts because of the excellence in hardness and wear resistance. The goal was to determine the effect of ultrasound (20 kHz and 575 kHz) on sample microstructure and morphology. To insulate the effect of cavitation bubbles from convection flow, all coatings had to be elaborated exactly with the same agitation in absence or presence of ultrasound, at an “equivalent flow” condition. Plotting the silver structures identified by XRD vs. current density in still conditions, two main categories appeared: one poorly structured and the other following the [110] orientation. This is confirmed by SEM and EBSD measurements. When changing from still to mechanically stirred conditions, the value of the current density threshold moves from 2.5mA/cm² to 5mA/cm². This coating microstructure modification threshold is situated at higher current density values when coatings are produced under sonication (575 kHz or 20 kHz), while agitation is kept constant. In both cases, the shift is about 15 mA/cm². It is interesting to note that silver electrodeposits elaborated under 20 kHz ultrasound conditions appear to be less oriented than those obtained under high frequency conditions, with RTChklvalues dropping from 12 to 8 for the [110] orientation. Use of ultrasound during silver coating elaboration, irrespective of hydrodynamic conditions kept otherwise constant, makes it possible to modify significantly the microstructures and morphology of deposits without relying on chemical additives. In the case of silver-tin alloy electrodeposition, it is important to note that the current density variations coupled to the use of ultrasound leads to significant variations in properties of coatings (color, crystalline composition and alloy composition). For equivalent hydrodynamic agitation, silver is predominant at low current density and tin prevails at higher ones. If low frequency ultrasound is applied, Ag3Sn replace the tin, and for high frequency ultrasound, the coating is formed by an intermetallic compound of tin and silver irrespective of the current density. Finally, in all cases, agitation is always beneficial to widen the current density range favourable for structural modifications without the risk of coating deterioration due to burning. Moreover, at the same level of agitation, use of ultrasound offers more advantages because it ensures harder and less structured deposits in increased current density ranges, and offer modifications equally important as in the case of chemical additives use. Figure 1: crystalline orientation of silver deposits at various current densities in presence of ultrasound or at an “equivalent” agitation Figure 2: composition of silver-tin alloy in presence of ultrasound or at an “equivalent” agitation Figure 1

A diagnostic approach to constraining flow partitioning in hydrologic models using a multiobjective optimization framework

AbstractHydrologic models are often tasked with replicating historical hydrographs but may do so without accurately reproducing the internal hydrological functioning of the watershed, including the flow partitioning, which is critical for predicting solute movement through the catchment. Here we propose a novel partitioning‐focused calibration technique that utilizes flow‐partitioning coefficients developed based on the pioneering work of L'vovich (1979). Our hypothesis is that inclusion of the L'vovich partitioning relations in calibration increases model consistency and parameter identifiability and leads to superior model performance with respect to flow partitioning than using traditional hydrological signatures (e.g., flow duration curve indices) alone. The L'vovich approach partitions the annual precipitation into four components (quick flow, soil wetting, slow flow, and evapotranspiration) and has been shown to work across a range of climatic and landscape settings. A new diagnostic multicriteria model calibration methodology is proposed that first quantifies four calibration measures for watershed functions based on the L'vovich theory, and then utilizes them as calibration criteria. The proposed approach is compared with a traditional hydrologic signature‐based calibration for two conceptual bucket models. Results reveal that the proposed approach not only improves flow partitioning in the model compared to signature‐based calibration but is also capable of diagnosing flow‐partitioning inaccuracy and suggesting relevant model improvements. Furthermore, the proposed partitioning‐based calibration approach is shown to increase parameter identifiability. This model calibration approach can be readily applied to other models.

Effects of diabetic retinopathy on the barrier functions of the retinal pigment epithelium

Diabetic retinopathy is a debilitating microvascular complication of diabetes mellitus. A rich literature describes the breakdown of retinal endothelial cells and the inner blood-retinal barrier, but the effects of diabetes on the retinal pigment epithelium (RPE) has received much less attention. RPE lies between the choroid and neurosensory retina to form the outer blood-retinal barrier. RPE’s specialized and dynamic barrier functions are crucial for maintaining retinal health. RPE barrier functions include a collection of interrelated structures and activities that regulate the transepithelial movement of solutes, including: diffusion through the paracellular spaces, facilitated diffusion through the cells, active transport, receptor-mediated and bulk phase transcytosis, and metabolic processing of solutes in transit. In the later stages of diabetic retinopathy, the tight junctions that regulate the paracellular space begin to disassemble, but there are earlier effects on the other aspects of RPE barrier function, particularly active transport and metabolic processing. With advanced understanding of RPE-specific barrier functions, and more in vivo-like culture models, the time is ripe for revisiting experiments in the literature to resolve controversies and extend our understanding of how diabetes affects the outer blood-retinal barrier.

Tiny protein detection using pressure through solid-state nanopores.

Solid-state nanopore is a promising tool to detect proteins and its complexes. Small proteins (sub-35 kDa) translocate very fast which could not be detected by normal patch-clamp recording instrument due to low temporal resolution. We first introduce pressure into protein study and detection. The pressure-derived force, combined with the voltage bias, makes very tiny protein (MW < 6.5 kDa) detection possible. Capture rate for Aprotinin is enhanced five times more than that in traditional voltage-driven method by fine tuning of pressure and voltage. Temporal resolution of Aprotinin detection has improved by decreasing effective driving force. Moreover, we provide potential method to locate the equilibrium range for BSA movement in ionic solution by modulating driving pressure and retard voltage. Our study is of fundamental significance in nanopore research and provides unique platforms to study small proteins and other tiny biomolecules.

Role of LOTR1 in Nutrient Transport through Organization of Spatial Distribution of Root Endodermal Barriers

The formation of Casparian strips and suberin lamellae at the endodermis limits the free diffusion of nutrients and harmful substances via the apoplastic space between the soil solution and the stele in roots [1-3]. Casparian strips are ring-like lignin polymers deposited in the middle of anticlinal cell walls between endodermal cells and fill the gap between them [4-6]. Suberin lamellae are glycerolipid polymers covering the endodermal cells and likely function as a barrier to limit transmembrane movement of apoplastic solutes into the endodermal cells [7, 8]. However, the current knowledge on the formation of these two distinct endodermal barriers and their regulatory role in nutrient transport is still limited. Here, we identify an uncharacterized gene, LOTR1, essential for Casparian strip formation in Arabidopsis thaliana. The lotr1 mutants display altered localization of CASP1, an essential protein for Casparian strip formation [9], disrupted Casparian strips, ectopic suberization of endodermal cells, and low accumulation of shoot calcium (Ca). Degradation by expression of a suberin-degrading enzyme in the mutants revealed that the ectopic suberization at the endodermal cells limits Ca transport through the transmembrane pathway, thereby causing reduced Ca delivery to the shoot. Moreover, analysis of the mutants showed that suberin lamellae function as an apoplastic diffusion barrier to the steleat sites of lateral root emergence where Casparian strips are disrupted. Our findings suggest that thetransmembrane pathway through unsuberized endodermal cells, rather than the sites of lateral root emergence, mediates the transport of apoplastic substances such as Ca into the xylem.

The endothelial border to health: Mechanistic evidence of the hyperglycemic culprit of inflammatory disease acceleration.

The endothelial cell (EC) layer constitutes a barrier that controls movements of fluid, solutes and cells between blood and tissue. Further, the endothelial layer regulates vascular tone and directs local humoral and cellular inflammatory processes. The strategic position makes it an important player for maintenance of health and for development of a number of diseases. Endothelial dysfunction is known to be an important component of type 2 diabetes, but is also assumed to be involved in many other diseases, for example, rheumatoid arthritis, inflammatory bowel disease, asthma, and cardiovascular diseases. We here suggest that the EC plays a pivotal role in disease pathophysiology through initiation, potentiation, and maintenance of several inflammatory mechanisms. Our contention is based on the observation that hyperglycemia-intermittent or sustained, local or systemic-is a major culprit for several endothelial dysfunctions. There is also mounting epidemiological evidence that dietary intake of refined sugars is important for the development of a number of diseases beyond obesity and type 2 diabetes. Various diseases involving inflammatory and immunological components are accelerated by hyperglycemic events because the endothelium transduces "high glucose" signaling into significant pathophysiological phenomena leading to reduced endothelial barrier function, compromised vascular tone regulation and inflammation (e.g., cytokine secretion and RAGE activation). In addition, endothelial extracellular proteins form epitopes for potential specific antibody formation upon interactions with reducing sugars. This paper reviews the endothelial metabolism, biology, inflammatory processes, physical barrier functions, and summarizes evidence that although stochastic in nature, endothelial responses to hyperglycemia are major contributors to disease pathophysiology. We present molecular and mechanistic evidence that both biological and physical barriers, protein function, specific immunity, and inflammatory processes are compromised by hyperglycemic events and thus, hyperglycemic events alone should be considered risk factors for numerous human diseases. © 2017 IUBMB Life, 69(3):148-161, 2017.

Monitoring of Water and Solute Transport in the Vadose Zone: A Review

Core IdeasSoil solution sampling is essential to better understand water and solute movement in soils.A review of different types of soil solution samplers is provided in this paper, including: drainage lysimeter or soil column, pan lysimeter, resin bags or membranes, wick lysimeters, suction cup, and suction plate.Recent developments, modifications, and recommendation criteria are provided for selecting appropriate soil solution extraction samplers.A number of contaminants including agrochemicals (fertilizers, pesticides), heavy metals, trace elements, and pathogenic microbes along with pharmaceuticals and hormones used in animal production move through the soil and are responsible for degradation of groundwater quality. Therefore, it is essential to sample soil solution for better understanding of movement and environmental fate of various contaminants in soils. We review different soil solution extraction samplers. The soil solution samplers discussed here are: drainage lysimeter or soil column, pan lysimeter, resin bags or membranes, wick lysimeters, suction cup, and suction plate. We have reviewed 304 journal articles representing a wide array of scientific disciplines. A brief history of soil solution monitoring and terminology used for describing various soil solution samplers is also provided. This review classifies literature on the basis of type of soil solution extraction samplers, soil type, land use–land cover (LULC), and analytes measured. Recommendation criteria are provided for selecting appropriate soil solution extraction samplers based on spatial and temporal variation, cost, soil type, amount of disturbance caused during installation of soil solution samplers, and monitoring of leachates involving different cations, anions, carbon, pH, EC, colloids, pesticides, and microbes. Use of advanced techniques with lysimeters for monitoring soil moisture content, soil water potential and flux is also discussed in this review.

Solution flow behavior in response to key operating parameters in heap leaching

Solution percolation through packed ore beds provides essential substances for leaching reactions to occur and mobilizes reaction products through ore beds. Understanding key factors that control solution movement is the prerequisite to forecasting and optimizing the performance of a heap under leach. In this study, the responses of the solution flow behavior to four key design parameters were investigated using the HeapSim-2D model: irrigation rate, dripper spacing, heap height, and initial moisture content. The model was calibrated and validated against monitoring data provided by the Quebrada Blanca mine, a copper heap bioleaching operation located in northern Chile. The modelling results showed that solution breakthrough times were shorter at higher irrigation rates, larger dripper spacing, lower heap heights and higher initial moisture contents. However, higher irrigation rates and larger dripper spacing resulted in more uneven moisture distributions at steady state. After irrigation was terminated, the bulk of the mobile solution retained in the leach unit was drained out within two days. The modelling results can provide mine operations with information on how to control key parameters that determine the solution flow behavior for the optimization of heap leach design.