Using variable charge characteristics to understand the exchangeable cation status of oxic soils

Soil Research ◽  
1984 ◽  
Vol 22 (1) ◽  
pp. 71 ◽  
Author(s):  
GP Gillman
Keyword(s):  
Surface Charge ◽  
Soil Ph ◽  
Negative Charge ◽  
Positive Charge ◽  
Exchangeable Cations ◽  
Point Of Zero Charge ◽  
Exchangeable Cation ◽  
Charge Measurement ◽  
Variable Charge ◽  
Variable Surface

The model of Uehara and Gillman was used to estimate the amounts of permanent surface charge, and variable surface charge at soil pH, in two soils from the high rainfall region of coastal Queensland. For each soil series, samples from virgin rain-forest were compared with soil collected from nearby sugarcane fields. One soil contained relatively large amounts of permanent negative charge (up to 3 m.e. per 100g), and hence was moderately supplied with exchangeable cations, while the other soil was dominated by variable charge components and at soil pH contained sufficient positive charge to reduce exchangeable cations to near zero values, despite the presence of about 1 m.e. per 100 g of permanent negative charge. In the latter the position of soil pH with respect to the point of zero charge is of utmost importance for the development of cation exchange capacity. The effect of adsorbed sulfate on positive charge measurement, and valency of the ion used for negative charge measurement, are briefly discussed.

The influence of organic matter extracted from humified clover on the properties of amorphous aluminosilicates. I. Surface charge

Soil Research ◽  
1978 ◽  
Vol 16 (3) ◽  
pp. 327 ◽  
Author(s):  
KW Perrott
Keyword(s):  
Surface Charge ◽  
Negative Charge ◽  
Positive Charge ◽  
Degree Of Polymerization ◽  
Aqueous Extracts ◽  
Hydrous Oxides ◽  
Soil Clays ◽  
Charge Balancing ◽  
Inorganic Components ◽  
Allophanic Soil

A series of synthetic amorphous aluminosilicates, hydrous oxides and allophanic soil clays were treated with aqueous extracts of humified clover. The resulting changes in surface charge due to organic treatment were determined by comparing the charge characteristics of these organic treated samples and samples treated with a synthetic mixture of the inorganic components of the humified clover extract. Organic treatment caused a change of net surface charge to more negative values. The change in surface charge varied with the mole ratio Al/(Al+Si) of the aluminosilicate, being largest at low values of Al/(Al+Si). Where the aluminosilicates contain positive charges these are reduced by the organic treatment. This is a major contributor to the alteration of net surface charge in the more aluminous samples. The effect of organic treatment on the charge characteristics of allophanic soil clays was similar to that for the synthetic aluminosilicates of intermediate composition. The inorganic treatments also caused an increase in negative charge, and this is attributed to the neutralization of positive charge by the adsorption of phosphate and the removal of charge-balancing aluminium-hydroxy material. The effect of the organic and inorganic treatments on the positive and negative charge components of amorphous aluminosilicates is discussed in terms of the degree of polymerization of chargebalancing hydroxy-aluminium as envisaged in current models of the structure of amorphous aluminosilicates.

Clay mineralogy and surface charge characteristics of basaltic soils from Western Samoa

Clay Minerals ◽  
1997 ◽  
Vol 32 (4) ◽  
pp. 545-556 ◽  
Author(s):  
R. Naidu ◽  
R. J. Morrison ◽  
L. Janik ◽  
M. Asghar
Keyword(s):  
Surface Charge ◽  
Potential Model ◽  
Negative Charge ◽  
Positive Charge ◽  
Clay Mineralogy ◽  
Ph Values ◽  
Western Samoa ◽  
Infrared Studies ◽  
Constant Potential ◽  
Basaltic Soils

AbstractThe clay mineralogy and surface charge characteristics of four basaltic soils from Western Samoa have been studied. The soils contained subordinate to dominant amounts of poorly ordered allophanic material in addition to varying amounts of crystalline free iron oxide minerals. Infrared studies revealed the presence of trace to subordinate amounts of kaolin minerals in all the soils. The surface charge-pH curves followed a constant potential model indicating the presence of substantial amounts of pH-dependent charge. Some negative charge was present, however, at pH values as low as 3.0 and small quantities of positive charge were detected at pH values as high as 9. Values for PZC ranged from 2.2 to 3.9 and these were generally higher than the pHo determined by the ΔpH method.

Potassium - calcium exchange in electropositive oxisols: description of exchange sites

Soil Research ◽  
2003 ◽  
Vol 41 (8) ◽  
pp. 1423 ◽  
Author(s):  
M. E. Alves ◽  
A. Lavorenti
Keyword(s):  
Negative Charge ◽  
Positive Charge ◽  
Batch Experiments ◽  
Charge Balance ◽  
Adsorption Method ◽  
Exchange Site ◽  
Variable Surface ◽  
Ca Ions ◽  
Calcium Exchange ◽  
Possible Cause

Potassium–calcium exchange was studied in batch experiments carried out with 2 oxisols exhibiting positive charge balance. The experimental data were quantitatively described with the Rothmund–Kornfeld formulation of the Gaines–Thomas approach, and the permanent and variable surface negative charges were measured using the caesium-adsorption method. For both soils, no appreciable involvement of permanent negative charges was observed in the potassium–calcium exchange, which, in turn, seemed to occur solely on the variable negative charges. The preference for potassium over calcium exhibited by both soils was well described by the Rothmund–Kornfeld formulation of the Gaines–Thomas approach. It was hypothesised that the exchange sites could be divided into 2 groups with different potassium selectivities. The proportions and selectivities of these exchange site groups were estimated combining the Rothmund–Kornfeld formulation with the Dufey–Delvaux multisite model. For both soils, there was excellent agreement between experimental and modelled data and it was possible to estimate the amounts of exchange sites (cmolc/kg) presenting greater and lower potassium selectivity. The existence of variable negative charge pools more accessible to K than to Ca ions but not evenly accessible to the former was considered as a possible cause of the non-ideal behaviour of the studied soils in relation to the potassium–calcium exchange.

scholarly journals Physicochemical Properties and Surface Charge Characteristics of Arid Soils in Southeastern Iran

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
A. H. Moghimi ◽  
J. Hamdan ◽  
J. Shamshuddin ◽  
A. W. Samsuri ◽  
A. Abtahi
Keyword(s):  
Physicochemical Properties ◽  
Surface Charge ◽  
Negative Charge ◽  
Clay Content ◽  
Significant Negative Correlation ◽  
Point Of Zero Charge ◽  
Net Charge ◽  
Excess Negative Charge ◽  
The Common ◽  
The Arid Regions

The majority of previous studies on surface charge characteristics were done on tropical and subtropical soils. Information of such studies in the arid regions is limited. A study was conducted to investigate the relation between soil chemical and mineralogical properties and surface charge characteristics of an arid region in Southeastern Iran. Eight soil pedons, representing the alluvial and the colluvial deposits, were described, and their mineralogical and physicochemical properties were examined. The common clay minerals in the studied area are smectite, palygorskite, kaolinite, chlorite, and illite. The point of zero charge (pH0) values are low (2.85–3.35) in all soils mostly affected by organic carbon (OC) and free iron oxide (Fed).pH0has a significant negative correlation with pH under field conditions (r=−0.45∗,P<0.05). The point of zero net charge (PZNC) levels for all the soils were <2, due to the excess negative charge in these soils. The estimated PZNC values were less thanpH0in all soils because of the high permanent negative charge in these soils. The permanent negative charge (σp) of the soils studied is high and it has a significant positive correlation with pH, CEC, Na, Mg, SAR, clay content, palygorskite, OC, andFed.

Surface charge characteristics of variable charge soils in Thailand

Soil Research ◽  
2010 ◽  
Vol 48 (4) ◽  
pp. 337 ◽  
Author(s):  
W. Wisawapipat ◽  
I. Kheoruenromne ◽  
A. Suddhiprakarn ◽  
R. J. Gilkes
Keyword(s):  
Organic Matter ◽  
Surface Charge ◽  
Negative Charge ◽  
Clay Fraction ◽  
Base Cation ◽  
Exchange Capacity ◽  
Rate Of Change ◽  
Phosphate Sorption ◽  
Variable Charge ◽  
A Charge

Surface charge characteristics were investigated using a charge fingerprinting procedure for 90 samples from 32 profiles of highly weathered Oxisols and Ultisols derived from shale/limestone, basalt, granite, local alluvium, sedimentary, and metasedimentary rocks under tropical savanna and tropical monsoonal climates in Thailand. The charge fingerprints of 5 whole soils, after removal of organic matter and of kaolin and ion oxides from these soils, were also measured to clarify factors contributing to the variable charge behaviour. Phosphate sorption was determined and related to charge properties. Kaolin was the dominant mineral of the clay fraction with moderate amounts of goethite and hematite. Gibbsite was present in Oxisols formed on limestone and basalt under more humid conditions. All soils exhibited variable charge behaviour but the magnitude and rate of change in variable charge with pH varied greatly between Oxisols and Ultisols. Oxisols had higher amounts of variable charge than Ultisols, reflecting the differences in amounts of clay and extractable Fe and Al. Oxisols formed on basalt and limestone under more humid conditions had high values of anion exchange capacity (AEC) due to the contributions of goethite, gibbsite, and boehmite. The relationships of base cation exchange capacity (CECB) and AEC with pH were linear. Rates of change with pH of both negative and positive variable charge (Ac, Aa) were closely related to CEC, specific surface area (SSA), pH(NaF), and various forms of extractable Fe, Al, and Mn. The charge fingerprints of soil after removal of organic matter indicated that organic matter exerted a strong influence on both the magnitude of negative charge and rate of change with pH. Kaolin had permanent and variable charge, with SSA and crystal size (MCD001) being highly predictive of the rate of change in variable negative charge with pH. Iron oxide concentrates exhibited strongly pH-dependent charge and the mean coherently diffracting length (MCD110) of hematite was highly predictive of both the magnitude and rate of change in variable positive charge with pH. Charge coefficients (Ac, Ba) had highly significant (P = 0.005) positive relationships with Langmuir and Freundlich phosphate sorption maximum coefficients (Xm, k), indicating that the surfaces of amorphous, poorly ordered, and crystalline Fe and Al oxides are prime sites for both P sorption and variable charge.

Changes in the surface charge of bacteria caused by heavy metals do not affect survival

1996 ◽  
Vol 42 (7) ◽  
pp. 621-627 ◽  
Author(s):  
Y. E. Collins ◽  
G. Stotzky
Keyword(s):  
Heavy Metals ◽  
Surface Charge ◽  
Negative Charge ◽  
Positive Charge ◽  
Agrobacterium Radiobacter ◽  
Charge Reversal ◽  
Ph Values ◽  
A Charge ◽  
Net Positive Charge ◽  
Cu And Zn

Bacillus subtilis and Agrobacterium radiobacter remained viable when exposed to Ni (1 × 10−4 M; ionic strength (μ) = 3 × 10−4) at pH values known to cause a change of the net negative charge of the cells to a net positive charge (charge reversal). The gross morphology, as determined by scanning electron microscopy, of these and other bacteria and of Saccharomyces cerevisiae was not altered in the presence of Ni, Cu, and Zn (1 × 10−4 M; μ = 3 × 10−4), which caused a charge reversal at pH values between 6.0 and 9.0. Similar results were obtained in the presence of Na and Mg, which did not cause charge reversal at the same μ and pH values. These results confirmed that cells remain viable when their surface charge is changed in the presence of some heavy metals at high pH values.Key words: heavy metals, electrokinetic properties, survival of bacteria.

scholarly journals Zerumbone Inhibits Helicobacter pylori Urease Activity

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2663
Author(s):  
Hyun Jun Woo ◽  
Ji Yeong Yang ◽  
Pyeongjae Lee ◽  
Jong-Bae Kim ◽  
Sa-Hyun Kim
Keyword(s):  
Helicobacter Pylori ◽  
Carbon Atom ◽  
Natural Compound ◽  
Urease Activity ◽  
Negative Charge ◽  
Positive Charge ◽  
Gastric Epithelium ◽  
Functional Inhibition ◽  
Electrical Gradient ◽  
H Pylori

Helicobacter pylori (H. pylori) produces urease in order to improve its settlement and growth in the human gastric epithelium. Urease inhibitors likely represent potentially powerful therapeutics for treating H. pylori; however, their instability and toxicity have proven problematic in human clinical trials. In this study, we investigate the ability of a natural compound extracted from Zingiber zerumbet Smith, zerumbone, to inhibit the urease activity of H. pylori by formation of urease dimers, trimers, or tetramers. As an oxygen atom possesses stronger electronegativity than the first carbon atom bonded to it, in the zerumbone structure, the neighboring second carbon atom shows a relatively negative charge (δ−) and the next carbon atom shows a positive charge (δ+), sequentially. Due to this electrical gradient, it is possible that H. pylori urease with its negative charges (such as thiol radicals) might bind to the β-position carbon of zerumbone. Our results show that zerumbone dimerized, trimerized, or tetramerized with both H. pylori urease A and urease B molecules, and that this formation of complex inhibited H. pylori urease activity. Although zerumbone did not affect either gene transcription or the protein expression of urease A and urease B, our study demonstrated that zerumbone could effectively dimerize with both urease molecules and caused significant functional inhibition of urease activity. In short, our findings suggest that zerumbone may be an effective H. pylori urease inhibitor that may be suitable for therapeutic use in humans.

scholarly journals Effect of Hyperglycemia on the Total Surface Charge of the Erythrocyte Membrane in Patients with Metabolic Syndrome

2019 ◽  
Vol 15 (3) ◽  
pp. 322-327
Author(s):  
V. I. Podzolkov ◽  
T. V. Koroleva ◽  
M. G. Kudryavtseva
Keyword(s):  
Metabolic Syndrome ◽  
Surface Charge ◽  
Erythrocyte Membrane ◽  
Negative Charge ◽  
Fasting Blood Glucose ◽  
Microvascular Blood Flow ◽  
Erythrocyte Membranes ◽  
Vascular Changes ◽  
Group 2 ◽  
Group 1

Aim. To study the effect of hyperglycemia on the total surface charge of the erythrocyte membrane (SCEM) in patients with metabolic syndrome (MS).Material and methods. 112 MS patients were examined (45 men and 67 women) (mean age 61.4±7.2 years, average MS duration 8.7±5.2 years). The level of SCEM was determined by adsorption of a positive cationic dye (cationic blue O) on the surface of the plasma membrane of erythrocytes to completely neutralize their negative charge, followed by photometry of the solution and calculation of the number of charges on the cell surface of erythrocytes.Results. In the main group of patients with MS, abdominal obesity was observed in 100% of patients, arterial hypertension – in 73%, hyperglycemia – in 75%, dyslipidemia – in 80%. The level of glycated hemoglobin (HbA1c) was determined in all patients with MS, which was 7.3±1.9%. Patients with MS were conditionally divided according to the level of HbA1c into 2 groups (group 1 – HbA1c from 6.6 to 7.8%, group 2 – more than 7.8%). In MS patients with hyperglycemia, the SCEM values were significantly lower than in the group of patients without hyperglycemia (1.58±0.05×107 and 1.64±0.03×107, respectively; p=0.001)., Significant negative correlations between SCEM and the fasting blood glucose level, hyperglycemia duration, HbA1c level were found in patients with MS.Conclusion. SCEM indices reliably depended on the presence, severity and duration of hyperglycemia, which indicated the effect of impaired carbohydrate metabolism on the state of electric charge of erythrocyte membranes and, therefore, on the mechanisms of microvascular blood flow, thereby contributing to the development of vascular changes in patients with MS.

Effect of arsenate on adsorption of Zn(II) by three variable charge soils

Soil Research ◽  
2007 ◽  
Vol 45 (6) ◽  
pp. 465 ◽  
Author(s):  
Jing Liang ◽  
Ren-kou Xu ◽  
Diwakar Tiwari ◽  
An-zhen Zhao
Keyword(s):  
Zeta Potential ◽  
Surface Charge ◽  
Iron Oxides ◽  
Initial Concentration ◽  
Variable Charge ◽  
Study Results ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Enhanced Adsorption ◽  
Variable Charge Soils

The effect of arsenate on adsorption of Zn(II) in 3 variable charge soils (Hyper-Rhodic Ferralsol, Rhodic Ferralsol, and Haplic Acrisol) and the desorption of pre-adsorbed Zn(II) in the presence of arsenate were investigated in this study. Results showed that the presence of arsenate led to an increase in both the adsorption and desorption of Zn(II) in these variable charge soils. It was also suggested that the enhanced Zn(II) adsorption by arsenate was mainly due to the increase in negative surface charge of the soils induced by the specific adsorption of arsenate, and the increase in electrostatically adsorbed Zn(II) was responsible for the increase in the desorption of Zn(II). The effect of arsenate on Zn(II) adsorption primarily depends on the initial concentration of arsenate and Zn(II), the system pH, and the nature of soils. The enhanced adsorption of Zn(II) increased with the increase in the initial concentration of arsenate and the amount of arsenate adsorbed by the soils. The presence of arsenate decreased the zeta potential of soil suspensions and soil IEP and thus shifted the adsorption edge of Zn(II) to a lower pH region. The effect of arsenate on Zn(II) adsorption in these 3 soils followed the order Hyper-Rhodic Ferralsol > Rhodic Ferralsol > Haplic Acrisol, which was consistent to the contents of iron oxides in these soils and the amount of arsenate adsorbed by the soils.

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