Experimental evaluation of salinity geosynthetics capillary barriers

This paper explores the transient upward flow of saline water in one-dimensional soil and soil-geosynthetics columns to evaluate preventive measures to mitigate salinity rise. Unsaturated soil concepts are utilised to elucidate the salinity movement through geotextile and geocomposite drain interfaces. The presence of a geotextile layer slowed down the capillary rise of the saline water. However, it did not prevent the breakthrough of the saline water due to the hydrophilicity of the geotextile and the suction at the geotextile base being close to the geotextile's water entry suction value. In contrast, using a geocomposite drain mitigated the upward saline wetting front. It acted as a salinity capillary barrier due to the initial hydrophobicity of its geotextile component and the air gap present in the geonet core.

Capillary Barriers during Rainfall Events in Pyroclastic Deposits of the Vesuvian Area

In the present paper, the capillary barrier formation at the interface between soil layers, which is characterized by textural discontinuities, has been analyzed. This mechanism has been investigated by means of a finite element model of a two-layer soil stratification. The two considered formations, belonging to the pyroclastic succession of the “Pomici di Base” Plinian eruption (22 ka, Santacroce et al., 2008) of the Somma–Vesuvius volcano, are affected by shallow instability phenomena likely caused by progressive saturation during the rainfall events. This mechanism could be compatible with the formation of capillary barriers at the interface between layers of different grain size distributions during infiltration. One-dimensional infiltration into the stratified soil was parametrically simulated considering rainfall events of increasing intensity and duration. The variations in the suction and degree of saturation over time allowed for the evaluation of stability variations in the layers, which were assumed as part of stratified unsaturated infinite slopes.

MRI With Gadolinium as a Measure of Blood-Labyrinth Barrier Integrity in Patients With Inner Ear Symptoms: A Scoping Review

Objective: Capillaries within the inner ear form a semi-permeable barrier called the blood-labyrinth barrier that is less permeable than capillary barriers elsewhere within the human body. Dysfunction of the blood-labyrinth barrier has been proposed as a mechanism for several audio-vestibular disorders. There has been interest in using magnetic resonance imaging (MRI) with intravenous gadolinium-based contrast agents (GBCA) as a marker for the integrity of the blood labyrinth barrier in research and clinical settings. This scoping review evaluates the evidence for using intravenous gadolinium-enhanced MRI to assess the permeability of the blood-labyrinth barrier in healthy and diseased ears.Methods: A systematic search was conducted of three databases: PubMed, EMBASE, CINAHL PLUS. Studies were included that used GBCA to study the inner ear and permeability of the blood-labyrinth barrier. Data was collected on MRI protocols used and inner ear enhancement patterns of healthy and diseased ears in both human and animal studies.Results: The search yielded 14 studies in animals and 53 studies in humans. In healthy animal and human inner ears, contrast-enhanced MRI demonstrated gradual increase in inner ear signal intensity over time that was limited to the perilymph. Signal intensity peaked at 100 min in rodents and 4 h in humans. Compared to controls, patients with idiopathic sudden sensorineural hearing loss and otosclerosis had increased signal intensity both before and shortly after GBCA injection. In patients with Ménière's disease and vestibular schwannoma, studies reported increased signal at 4 h, compared to controls. Quality assessment of included studies determined that all the studies lacked sample size justification and many lacked adequate control groups or blinded assessors of MRI.Conclusions: The included studies provided convincing evidence that gadolinium crosses the blood-labyrinth barrier in healthy ears and more rapidly in some diseased ears. The timing of increased signal differs by disease. There was a lack of evidence that these findings indicate general permeability of the blood-labyrinth barrier. Future studies with consistent and rigorous methods are needed to investigate the relationship between gadolinium uptake and assessments of inner ear function and to better determine whether signal enhancement indicates permeability for molecules other than gadolinium.

Plot test in a 50-year abandoned mine tailings dam

Knowing the evolution of water content in a tailings dam is essential when analysing its stability. The case study is a small tailings dam abandoned more than 50 years ago, located in the Andes region of San Juan province, Argentina, where the climate is arid. This paper presents the results obtained in a plot test to study the interaction of tailings with the atmosphere, and to explain the reasons that generate internal zones in the dams with surprisingly high degrees of saturation, despite the strong water deficit of the site. The plot was hydraulically isolated on the four lateral faces where ten capacitive sensors were installed at different depths (volumetric moisture, matrix suction and temperature). At the beginning of the test, a major rainfall event was simulated with a sprinkler irrigation system. The plot was then allowed to interact freely with the atmosphere for an additional period of one and a half years. The records obtained suggest that the stratigraphy of the hydraulically deposited tailings has a preponderant influence on the interaction with the atmosphere. Heterogeneous flow phenomena and multiple capillary barriers during the infiltration and evaporation processes, respectively, appear to control the long-term moisture state of the tailings dam.

Development of flume model of inclined capillary barrier (clay silt/CDW) in a subtropical climate scenario

Interest in research on capillary barrier (CB) in regions with humid climates (tropical and subtropical) is increasing. One of the main advantages of such cover type is the greater flexibility regarding the materials that could compose it. A possibility is the use of construction and demolition wastes (CDW), which would contribute to the solution of CDW destination, a problem in urban centers. Thus, the present work aimed an experimental evaluation of CB cover with CDW in its composition. A CB cover system was reproduced in a physical model in acrylic box, with clay soil as capillary layer and CDW as capillary block, given its granulometric and hydraulic contrast. The layers were arranged with the usual landfill slope, of 1:3, and a very heavy rain, of 90 mm, was simulated. Three tests were performed on the flume model, in which initial CDW saturation degree (S0) was varied in 4,5%, 10,3% and 17,3%. Results indicate formation, indeed, of capillary barrier between the two used materials. The most efficient model was the one with lowest initial CDW S0, of 4,5%. As the CWD S0 increased, time of flow permanence at materials interface decreased, indicating a CWD S0 in which such capillary barriers no longer function effectively. Regarding percolation rate, the maximum for a 90 mm rainfall was 2,7%, which fits the landfill cover projects criteria consulted.

Use of Soil-Structured Capillary Barrier can Mitigate the Impact of Saline-Irrigation Water on Marigold Grown Under Field Condition

Capillary barriers (CBs) as engineered porous composites is novel and promising technology for mitigating salinity and drought stress of plants. This study aimed to imitate a naturally formed CB structure recently discovered in the reservoir bed of Al-Khoud dam at the Governorate of Muscat in northern Oman and to test the impact of this unique CB on mitigating the salinity stress of marigold plants grown under an open field condition. A plot was constructed and divided into “structured” (engineered cascade CB design) and “unstructured” soils and planted with marigold (Tagetes erecta) plants that were subjected to four salinity treatments (control with ECi ≈ 0.6 dS m-1 ; 3 dS m-1; 6 dS m-1; and 9 dS m-1). Plant physiological, vegetative, and reproductive growth parameters were measured in each treatment. The results showed that the structured soil significantly saved irrigation water and reduce salts accumulation. Structured soil improved all vegetative and reproductive plant parameters measured and helped in reducing the effects of salinity stress on the growth and production of the marigold under arid-climate field conditions. The results also showed the capability of structured soil in water saving and improving water use efficiency. This study substantiates a novel method in mitigating salinity problem and in water saving in arid and semi-arid regions, in particular in Oman. Further studies are required to test the use of the engineered cascade CB design with different crops and with alternative (e.g. subsurface) irrigation methods.

Monitoring soil moisture dynamics in multilayered Fluvisols

The identification of drought-sensitive areas (DSAs) in floodplain Fluvisols of high textural pedodiversity is crucial for sustainable land management purposes. During extended drought periods moisture replenishment is only available by capillary rise from the groundwater. However, moisture flux is often hindered by capillary barriers in the interface between layers of contrasting textures. The results of HYDRUS-1D simulations run on multilayered soil profiles were integrated into textural maps to determine the spatial distribution of water dynamics on the floodplain of the Drava River (SW Hungary). Model runs and field data revealed limited moisture replenishment by capillary rise when both contrasting textural interfaces and sandy layers are present in the profile. By implementing these textural and hydraulic relations, a drought vulnerability map (DSA map) of the operational area of the Old Drava Programme (ODP) was developed. According to the spatial distribution of soils of reduced capillary rise, 52% of the ODP area is likely threatened by droughts. Our model results are adaptable for optimisation of land- and water-management practices along the floodplains of low-energy and medium-sized rivers under humid continental and maritime climates.

Landfill Final Cover Systems Design for Arid Areas Using the HELP Model: A Case Study in the Babylon Governorate, Iraq

The main purpose of selecting proper designs for landfills is to accommodate quantities of waste without having a negative effect on the surrounding environment and human health. The Babylon Governorate (province) in Iraq was taken as an example of an arid area with very shallow groundwater and where irregular waste disposal sites had developed that had not been subject to international standards when they were selected for landfill use. In the current study, the suggested design for landfills is a base liner and final cover system. In this suggested design, the final cover system allows for three scenarios. The first scenario considers an evapotranspiration soil cover (ET) (capillary barriers type), the second scenario is a modified cover design of “RCRA Subtitle D”, and the third scenario is a combination of the first and second scenarios. The HELP 3.95 D model was applied to the selected landfill sites in the governorate to check if there was any penetration of the leachate that might in future percolate from the landfill’s bottom barrier layer in arid areas. The results from the suggested landfill design showed that there was no leachate percolation from the bottom barrier layer using the second and third scenarios. For the first scenario, however, there was a small amount of leachate through the bottom barrier layer in the years 2013 and 2014.