scholarly journals Influence of electrolyte concentration, sodium adsorption ratio and cation combinations on relative saturated hydraulic conductivity of saline soil

2021 ◽  
Vol 22 (1) ◽  
pp. 132-138
Author(s):  
Anežka čelková ◽  
Anton Zvala
Keyword(s):  
Hydraulic Conductivity ◽  
Electrolyte Concentration ◽  
Saline Soil ◽  
Sodium Adsorption Ratio ◽  
Saturated Hydraulic Conductivity

Influence of sodium adsorption ratio on sodium and calcium breakthrough curves and hydraulic conductivity in soil columns

Soil Research ◽  
2007 ◽  
Vol 45 (8) ◽  
pp. 586 ◽  
Author(s):  
Oagile Dikinya ◽  
Christoph Hinz ◽  
Graham Aylmore
Keyword(s):  
Hydraulic Conductivity ◽  
Electrolyte Concentration ◽  
Soil Aggregates ◽  
Breakthrough Curves ◽  
Sodium Adsorption Ratio ◽  
Threshold Concentration ◽  
Critical Threshold ◽  
Soil Columns ◽  
Clay Particles ◽  
The Matrix

The paper examines the effects of electrolyte concentration and sodium adsorption ratio (SAR) on the relative saturated hydraulic conductivity (RHC) and the ionic behaviour of calcium (Ca) and sodium (Na) ions in the Na–Ca exchange complex. Batch binary exchange and saturated column transport experiments were carried out to quantify these effects using an agricultural Balkuling soil and a mining residue. Generally, RHC has been found to decrease with time, with increasing SAR, and with decreasing electrolyte concentration. The more rapid decrease in RHC in the mining residue, particularly at the lowest concentration (1 mmol/L), was consistent at all SAR values. The decreases in RHC were likely to be caused by partial blocking of pores by dispersed clay particles, as evidenced by the appearance of suspended clay particles in the effluent during leaching. Significant differences in RHC were observed in the passage of fronts of decreasing electrolyte concentrations for CaCl2 and SAR 15 solutions through the soil columns. These differences were attributable to structural alterations (slaking) of the media and the nature of the particles released and mobilised within the porous structure at any given point in the column. Measurements at the critical threshold concentration and turbidity concentration at SAR 15 revealed structural breakdown of the pore matrix system as evidenced by decreased RHC. The increase in SAR to 15 is initially accompanied by erratic RHC, presumably due to the break up of soil aggregates under the increased swelling forces. The less coherent mining residue soil was substantially more vulnerable to blockage of pores than the Balkuling soil in which clay particles are likely to be more readily mobilised, and hence available to re-deposit and occlude the matrix pores.

CALCULATION OF HYDRAULIC CONDUCTIVITY DECREASES IN THE PRESENCE OF MIXED NaCl-CaCl2 SOLUTIONS

1978 ◽  
Vol 58 (2) ◽  
pp. 145-152 ◽  
Author(s):  
J. H. DANE
Keyword(s):  
Hydraulic Conductivity ◽  
Electrolyte Concentration ◽  
Solid Phase ◽  
Particle Density ◽  
Sodium Adsorption Ratio ◽  
Soil Porosity ◽  
Swelling Soils ◽  
Swelling Model ◽  
Good Agreement ◽  
Swelling Factor

A model was developed to calculate hydraulic conductivity decreases in swelling soils in the presence of mixed NaCl-CaCl2 solutions. A calculated swelling factor, based on a demixed-ion clay swelling model, was used to compute an effective soil porosity corresponding to each electrolyte solution. The procedure required knowledge of the total electrolyte concentration (C) and sodium adsorption ratio (SAR) of the solution phase, and of the fraction of expansible minerals, the bulk density, and the particle density of the solid phase. The calculated effective soil porosities were used to predict hydraulic conductivity values corresponding to solutions of decreasing C or increasing SAR values. A hydraulic conductivity value, corresponding to a solution which suppressed all swelling, had to be experimentally determined in order to make the prediction. Good agreement was found between predicted and experimental hydraulic conductivity values for two soils containing different amounts of expansible minerals and subjected to salt solutions of varying compositions.

Prediction of unsaturated hydraulic conductivity changes of a loamy soil in different salt solutions by using the equivalent salt solutions concept

Soil Research ◽  
1992 ◽  
Vol 30 (5) ◽  
pp. 565 ◽  
Author(s):  
NS Jayawardane
Keyword(s):  
Hydraulic Conductivity ◽  
Salt Solution ◽  
Electrolyte Concentration ◽  
Saline Water ◽  
Saturated Hydraulic Conductivity ◽  
Sodium Absorption ◽  
Published Data ◽  
Salt Solutions ◽  
Solution Series ◽  
Water Contents

Equivalent salt solutions series have been previously defined as solutions with combinations of sodium absorption ratio (SAR) and electrolyte concentration (E,) producing the same extent of clay swelling in a given soil. These equivalent salt solutions series values have yielded satisfactory predictions of changes in saturated hydraulic conductivity, with changes in salt solution composition and concentrations. In the present study, previously published data on changes in saturated and unsaturated hydraulic conductivities of Gilat soil in salt solutions of cationic ratio 0-50 (mmol dm-3)1/2 and electrolyte concentration 2-50 (m.e. dm-3) were used to compare the equivalent salt solution series values for hydraulic conductivities at different water contents. The equivalent salt solution series causing a given change in saturated hydraulic conductivity of a loamy Gilat soil were derived. These equivalent salt solution values were used to predict the unsaturated hydraulic conductivities of this soil at low water contents. Predictions of unsaturated conductivity at relative water contents (�) ranging from 0.80 to 0.20 agreed closely with the measured values. Coefficients log a1 and b1 for Gilat soil, in the equation log Ec = log a1+b1 log SAR, relating the Ec and SAR values of each equivalent salt solutions series were determined at � values between 1.00 and 0.20. The relationship between log a1 and bl was similar at all water contents, in agreement with the equivalent salt solutions concept. Therefore, equivalent salt solution parameters derived from saturated hydraulic conductivity measurements could be used to predict changes in unsaturated conductivities and hence flow rates of saline water under specified boundary conditions.

Use of gamma emission computed tomography to study the effect of electrolyte concentration on regions of preferred flow and hydraulic conductivity in deep regolith materials

Soil Research ◽  
2008 ◽  
Vol 46 (2) ◽  
pp. 101 ◽  
Author(s):  
M. L. Turner ◽  
R. S. B. Greene ◽  
M. Knackstedt ◽  
T. J. Senden ◽  
A. Sakellariou ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Fluid Flow ◽  
Hydraulic Conductivity ◽  
Pore Structure ◽  
Electrolyte Concentration ◽  
Sodium Adsorption Ratio ◽  
Emission Computed Tomography ◽  
Saline Aquifer ◽  
Gamma Emission ◽  
Emission Computed

Understanding fluid flow, displacement, and mixing processes in natural porous media is fundamentally dependent upon the accurate characterisation of complex 3-dimensional structures. This current study delineated the distribution of conducting regions within a suite of regolith materials as they interacted with electrolyte solutions of different concentrations. Previous studies on the effects of electrolyte concentration on clay swelling and dispersion and the concomitant changes in pore structure, and hence soil permeability, have mainly been carried out on repacked samples of disturbed surface soils. This study used unconsolidated materials recovered as undisturbed cores from a saline aquifer from the deeper regolith (8.0–55.8 m). Progressive dilution of the electrolyte concentration of the percolating fluid (while maintaining a constant sodium adsorption ratio) was used to alter the pore structure of these saturated regolith materials. The electrolyte concentration was reduced from an initial value of 383 m.e./L (the original electrolyte concentration of the saline aquifer) to below the threshold concentration, and finally the cores were rinsed with deionised water. The corresponding changes to the regions conducting fluid and therefore pore structure, and the major fluid pathways followed during the percolation process, were imaged using gamma emission computed tomography. Five experimental core samples from depths of 8, 28, 30 (×2), and 55 m were used in the experiments. The average hydraulic conductivity was measured and found to decrease as a function of electrolyte concentration. The regions containing the major fluid pathways were found to decrease in volume as a function of electrolyte concentration. Clay mineralogy, sodium adsorption ratio, and grain size characteristics were found to be positively correlated with reductions in the average hydraulic conductivity. This method has the potential to aid in our understanding of the fundamental processes that govern the dynamics of pore structure changes and hence fluid flow in porous regolith materials, particularly in relation to changes in the electrolyte concentration and sodium adsorption ratio of the pore fluid. Such data will add significantly to our understanding of factors that affect the hydraulic properties of regolith materials under saline/sodic conditions.

Saturated Hydraulic Conductivity of Clayey Tills and the Role of Fractures

1990 ◽  
Vol 21 (2) ◽  
pp. 119-132 ◽  
Author(s):  
Johnny Fredericia
Keyword(s):  
Hydraulic Conductivity ◽  
American Studies ◽  
Field Measurements ◽  
Present Knowledge ◽  
Saturated Hydraulic Conductivity ◽  
Field Observations ◽  
Laboratory Measurements ◽  
Vertical Hydraulic Conductivity ◽  
Data Field

The background for the present knowledge about hydraulic conductivity of clayey till in Denmark is summarized. The data show a difference of 1-2 orders of magnitude in the vertical hydraulic conductivity between values from laboratory measurements and field measurements. This difference is discussed and based on new data, field observations and comparison with North American studies, it is concluded to be primarily due to fractures in the till.

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