Surface charge characteristics of a variable charge soil (Rhodic Ferralsols) in the Central Highlands

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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Effect of the size of variable charge soil particles on cadmium accumulation and adsorption

Journal of Soils and Sediments ◽

10.1007/s11368-017-1712-6 ◽

2017 ◽

Vol 17 (12) ◽

pp. 2810-2821 ◽

Cited By ~ 15

Author(s):

Guannan Liu ◽

Juan Wang ◽

Wei Xue ◽

Jinbo Zhao ◽

Jing Wang ◽

...

Keyword(s):

Cadmium Accumulation ◽

Soil Particles ◽

Variable Charge ◽

Variable Charge Soil

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Acidity

Chemistry of Variable Charge Soils ◽

10.1093/oso/9780195097450.003.0014 ◽

1997 ◽

Author(s):

X. L. Kong ◽

X. N. Zhang

Keyword(s):

Surface Charge ◽

Soil Acidity ◽

Solid Phase ◽

Hydrogen Ions ◽

Variable Charge ◽

Aluminum Ions ◽

Acid Reaction ◽

The Relationship ◽

Constant Charge ◽

Variable Charge Soils

For variable charge soils, acidity is a property that is of equal importance as the surface charge. These two properties may affect each other, with the effect of the former on the latter more remarkable than the reverse. In the previous chapters it was shown that pH affects many other properties of the soil by affecting the surface charge. Therefore, soil acidity is more significant than surface charge in some aspects. Owing to a similar reason, the importance of acidity for variable charge soils may exceed that for constant charge soils. Soil acidity generally manifests itself in the form of hydrogen ions. Actually, these hydrogen ions are chiefly the product of the hydrolysis of aluminum ions. Therefore, when examining soil acidity it is necessary to examine the properties of aluminum ions. In the previous chapter the transformation of hydrogen ions into aluminum ions has already been mentioned. In this chapter the relationship between aluminum ions and hydrogen ions will be discussed in greater detail. Another difference between variable charge soils and constant charge soils with respect to acidity is that, not only hydrogen ions, but also hydroxyl ions can participate in chemical reactions between the solid phase and the liquid phase. In constant charge soils the quantity of hydroxyl ions is an induced variable and is determined by the quantity of hydrogen ions in the solution and the ionic product of water. In variable charge soils, on the other hand, the quantity is also determined by the chemical equilibrium of that ion species itself at the solid-solution interface. Thus, hydroxyl ions can, in turn, affect the quantity of hydrogen ions in solution. In this chapter the nature of acidity of variable charge soils will be discussed mainly from these characteristics. In the field of soil chemistry, there has been an interesting history with regard to the nature of soil acidity. Soon after the recognition of the relationship between acid reaction and hydrogen ions in chemistry, this concept of the nature of acidity was introduced into soil science, and the significance of hydrogen ions was invariably associated with it whenever soil acidity was considered.

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Interactions BetweenEscherchia coliand the Colloids of Three Variable Charge Soils and Their Effects on Soil Surface Charge Properties

Geomicrobiology Journal ◽

10.1080/01490451.2014.967419 ◽

2014 ◽

Vol 32 (6) ◽

pp. 511-520 ◽

Cited By ~ 11

Author(s):

Zhao-Dong Liu ◽

Zhi-Neng Hong ◽

Jiu-Yu Li ◽

Jun Jiang ◽

Ren-Kou Xu

Keyword(s):

Surface Charge ◽

Soil Surface ◽

Variable Charge ◽

Variable Charge Soils

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Charge characteristics of soil in a lowland tropical moist forest in Panama in response to dry-season irrigation

Soil Research ◽

10.1071/sr00061 ◽

2002 ◽

Vol 40 (2) ◽

pp. 269 ◽

Cited By ~ 8

Author(s):

Joseph B. Yavitt ◽

S. Joseph Wright

Keyword(s):

Surface Charge ◽

Surface Soil ◽

Soil Nutrient ◽

Soil Surface ◽

Nutrient Status ◽

Dry Season ◽

Soil Nutrient Status ◽

Variable Charge ◽

Subsurface Soil ◽

Moist Forest

Although the hot, moist tropics in the Republic of Panama receive more than 2000 mm of rain per year, soils dry considerably during the 4-month dry season. We examined the effect of seasonal drought by irrigating two 2.25-ha plots of lowland tropical moist forest on Barro Colorado Island (BCI) for 5 consecutive dry seasons. Irrigation decreased soil permeability and improved soil nutrient status, which prompted this study of soil charge characteristics in the irrigated and control plots. Soil was an Alfisol, and thus it was not clear a prioriwhether variable-charge or permanent-charge components dominated. Surface soil (0–15 cm) had a pH(H2O) of 5.5 and pH(KCl) of 4.8. Subsurface soil (30–45 cm) had a pH(H2O) of 4.8 and a pH(KCl) of 3.5. The point of zero salt effect (PZSE), measured by titration, varied from 3.7 to 5.0 in surface soil and from 3.5 to 4.2 in subsurface soil. Variable charge of surface soil was 2.6 cmolc/kg.pH unit after the dry season in April versus 3.2 cmolc/kg.pH unit after the wet season in December in both control and dry-season irrigated plots, reflecting seasonal differences in pH and PZSE. The point of zero net charge (PZNC), measured by ion retention, was at pH <2.0, indicating that permanent-charge components dominated the soil surface charge. Five years of dry-season irrigation resulted in pH(H2O) increasing by 0.6 units and pH(KCl) increasing by 0.2 units. As well, irrigation increased the amount of permanent charge and cation retention, leading to less sorption of phosphate and sulfate. The results have important ecological implications, showing mechanistically how wetter conditions affected soil surface charge leading to improved soil nutrient status. permanent charge, soil pH, tropical forest soil, variable charge, water regime.

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

Soil Research ◽

10.1071/sr9840071 ◽

1984 ◽

Vol 22 (1) ◽

pp. 71 ◽

Cited By ~ 46

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.

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An analytical tool for understanding the properties and behaviour of variable charge soils

Soil Research ◽

10.1071/sr06117 ◽

2007 ◽

Vol 45 (2) ◽

pp. 83 ◽

Cited By ~ 17

Author(s):

G. P. Gillman

Keyword(s):

Surface Charge ◽

Large Scale ◽

Graphical Representation ◽

Resource Assessment ◽

Ideal Condition ◽

Soil Resource ◽

Variable Charge ◽

Ph Range ◽

Soil Resource Assessment ◽

Insight Into

Routine analyses for soil cation exchange properties usually give only limited insight into the properties and management of soils containing significant amounts of variable charge. In this paper a procedure for determining a soil Charge Fingerprint is fully described, a model developed from simplified theory to underpin the methodology is discussed, and examples of the usefulness of the approach are given. Operationally defined cation and anion exchange capacities (CEC and AEC) are determined over an appropriate pH range (pH 4 to pH 6 is suggested) using Ca and Cl as the index cations. At low pH, Ca does not always fully saturate the CEC, so that it is necessary to distinguish a Basic CEC (Ca ads.) from the Total CEC (Ca + Al ads.). The graphical representation of CECT, CECB, and AEC v. pH constitutes the Charge Fingerprint. Though not intended as a routine instrument, its determination on key samples in a characterisation exercise places routinely determined basic and acidic cations in context. Examples are given of large scale characterisation studies that link soils from different continents having similar surface charge characteristics; of the assessment of the success or otherwise of producing permanent positive charge in synthetically prepared Ti-substituted goethites; and of the evaluation of the effect of adding crushed basic rock amendment on the surface charge properties of a variable charge soil. The formulation of a Depreciation Index, which classifies soils in terms of their departure in basic cation content from an arbitrarily defined ‘ideal’ condition, is suggested for use in soil resource assessment.

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Impact of pre-existing sulphate on retention of imported chloride and nitrate in variable charge soil profiles

Geoderma ◽

10.1016/j.geoderma.2004.02.001 ◽

2004 ◽

Vol 123 (3-4) ◽

pp. 205-218 ◽

Cited By ~ 9

Author(s):

V. Rasiah ◽

J.D. Armour ◽

N.W. Menzies ◽

D.H. Heiner ◽

M.J. Donn

Keyword(s):

Soil Profiles ◽

Variable Charge ◽

Variable Charge Soil

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The role of clay minerals and the effect of H+ ions on removal of heavy metal (Pb2+) from contaminated soils

Canadian Geotechnical Journal ◽

10.1139/t99-106 ◽

2000 ◽

Vol 37 (2) ◽

pp. 296-307 ◽

Cited By ~ 31

Author(s):

Loretta Y Li ◽

Raymond S Li

Keyword(s):

Heavy Metals ◽

Heavy Metal ◽

Surface Charge ◽

Clay Minerals ◽

Contaminated Soils ◽

Surface Charges ◽

Buffer Solution ◽

Soil System ◽

Variable Charge ◽

Acid Leach

The importance of the surface charge of clay minerals (fixed or variable) and the effect of H+ ions on the adsorption and removal of Pb2+ ions from contaminated soil are investigated using kaolinite (variable charge) and two illitic (fixed charge) soils with pH 3.9 and 9.2. The adsorption-desorption characteristics of Pb2+ ions were determined using batch equilibrium tests and acid leach tests with various acids used to leach the soils. Under the same adsorption conditions, illitic soil adsorbed much more Pb2+ ions than kaolinite. The difference is largely due to the surface charges on the clay minerals. Removal of Pb2+ ions from variable-charge minerals (e.g., kaolinite) requires much less effort than removal of Pb2+ ions from constant-charge minerals (e.g., illite). The surface charge of a clay mineral has an important effect. By increasing the number of H+ ions available in the soil system with a buffer solution such as NaOAc-HOAc, heavy metals adsorbed on the clay surface are expelled to pore water. The increase in H+ ions in the soil system also assists in dissolving any metal carbonates, thereby increasing the solubility of heavy metals in illitic soil. The more H+ ions available in the pore fluid, the more Pb2+ ions can be released from the system.Key words: clay minerals, sorption, desorption, heavy metal, hydrogen ion, electrokinetic, acid leach.

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Effect of Fe/Al oxides on desorption of Cd2+ from soils and minerals as related to diffuse layer overlapping

Soil Research ◽

10.1071/sr10148 ◽

2011 ◽

Vol 49 (3) ◽

pp. 231 ◽

Cited By ~ 11

Author(s):

Yan-ping Wang ◽

Ren-kou Xu ◽

Jiu-yu Li

Keyword(s):

Charge Density ◽

Surface Charge ◽

Surface Charge Density ◽

Charged Particles ◽

Double Layers ◽

Mineral Particles ◽

Variable Charge ◽

Electrical Double Layers ◽

Oppositely Charged ◽

Positively Charged

Cadmium is a toxic metal with high reactivity in acid variable charge soils. Adsorption and desorption of Cd2+ in soil and mineral particles can be affected by the interaction between the electrical double layers on oppositely charged particles, because the interaction can decrease the surface-charge density of the particles. We studied the effect of Fe/Al oxides on desorption of Cd2+ from soils and minerals and proposed the desorption mechanisms based on the overlapping of diffuse layers between negatively charged soils and mineral particles and positively charged Fe/Al oxide particles. Our results indicate that the overlapping of diffuse layers of electrical double layers between positively charged Fe/Al oxides [crystalline and amorphous Al(OH)3 and amorphous Fe(OH)3] and negatively charged Ultisol, Alfisol, kaolinite, and bentonite caused the effective negative surface-charge density on the soils and minerals to become less negative, and thus the adsorption affinity of these negatively charged surfaces for Cd2+ declined as a result of the incorporation of the Fe/Al oxides. Consequently, the release of exchangeable Cd2+ from the surfaces of the soils and minerals increased with the amount of Fe/Al oxides added. The more positive the charge on the surfaces of the Fe/Al oxides, the stronger the interaction of the electrical double layers between the oxides and soils and minerals, and thus the greater the release of Cd2+ from the soils and minerals. A decrease in pH led to an increase in the positive surface charge on the Fe/Al oxides and enhancement of the interaction of the electrical double layers between the oxides and soils and minerals. As a result, more Cd2+ was desorbed from the soils and minerals. This study suggests that the interaction between oppositely charged particles of variable charge soils can enhance the mobility of cadmium in the soils and thus increase its environmental risk.

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