The electrical conductivities (ECs) of suspensions containing 25 and 30 gkg^(-1) solids prepared from the electrodialyzed clay fraction (< 2μm in diameter) of latosol,yellow-brown soil, and black soil, dispersed i...The electrical conductivities (ECs) of suspensions containing 25 and 30 gkg^(-1) solids prepared from the electrodialyzed clay fraction (< 2μm in diameter) of latosol,yellow-brown soil, and black soil, dispersed in various nitrate solutions having concentrations of 1X 10^(-4)/z mol L^(-1), where z is the valence, and in distilled water, were measured at fieldstrengths ranging from 14 kV cm^(-1) to 210 kV cm^(-1). On the basis of analyses of the chargedensity and exchangeable ion composition on the surfaces of soil particles in the suspensions, andof the characters of the EC-field strength curves of the various suspensions, it was inferred thatthe increment of EC (ΔEC) and/or relative electrical conductivity (REC) can indicate the bondingstrength between cations and soil particles. The bonding strengths of various cations with the soilsdiminished in the order: K^+ > Zn^(2+) > Mg^(2+) = Ca^(2+) > Na^+ for latosol, Ca^(2+) > Zn^(2+) >Mg^(2+) = K^+ > Na^+ for yellow-brown soil, and Zn^(2+) ≥ Ca^(2+) ≥ Mg^(2+) > K^+ > Na^+ for blacksoil.展开更多
The electrical conductivity of suspensions and their supernatants from theelectrodialyzed clay fractions of latosol, yellow-brown soil and black soil equilibrated withnitrate solutions were determined at different fie...The electrical conductivity of suspensions and their supernatants from theelectrodialyzed clay fractions of latosol, yellow-brown soil and black soil equilibrated withnitrate solutions were determined at different field strengths using a short high-voltage pulseapparatus to demonstrate the Wien effect in soil suspensions and to investigate factors affectingit. It was found that Wien effect was much stronger in suspensions with a clay content of 30 gkg^(-1) from the soils equilibrated with a 1 X 10^(-4) KNO_3 solution than in their supernatants.The threshold field strength (TFS), at which the relative conductivity is equal to 1.05, i.e., theWien effect begins to be obvious, of the yellow-brown soil suspensions (clay content of 30 gkg^(-1)) equilibrated with different nitrate solutions of a concentration of 1 X 10^(-4)/z molL^(-1), where z is the valence, varied with the type of nitrates, being lowest for NaNO_3 (47 kVcm^(-1)) and highest for Ca(NO_3)_2 (98 kV cm^(-1)). At high field strengths (larger than 130 kVcm^(-1)), the relative conductivities of yellow-brown soil suspensions containing different nitratesdiminished in the order: NaNO_3 > KNO_3 > Mg(NO_3)_2 > Zn(NO_3)_2 > Ca(NO_3)_2. The rates andintensities of the Wien effect in the suspensions of the three soils equilibrated with 5 X 10^(-5)mol L^(-1) Ca(NO_3)_2 solution were in the order of the yellow-brown soil > the latosol > the blacksoil. The results for the yellow-brown soil suspensions (clay concentration of 30 g kg )equilibrated with KNO_3 solutions of various concentrations clearly demonstrated that the moredilute the solution, the lower the TFS, and the larger the relative conductivity of the suspensionsat high field strengths. The results for yellow-brown soil suspensions with different clayconcentrations indicated that as the clay concentration increased, the low field electricalconductivity, EC_0, also increased, but the TFS decreased, and the Wien effect increased.展开更多
Suspensions of a latosol with a clay concentration of 30 g kg^(-1) wereprepared from electrodialyzed clay fractions, less than 2 μm in diameter, five nitrate solutionswith a concentration of 1 X 10^(04)/z mol L^(-1),...Suspensions of a latosol with a clay concentration of 30 g kg^(-1) wereprepared from electrodialyzed clay fractions, less than 2 μm in diameter, five nitrate solutionswith a concentration of 1 X 10^(04)/z mol L^(-1), where z is the valence, and five sodium saltsolutions with a concentration of 3.3 X 10^(-5)/2 mol L^(-1). The direct current (DC) electricalconductivities (ECs) of the colloidal suspensions were measured at a constant temperature of 25 ℃,using a newly established method of measuring the Wien effect in soil suspensions at field strengthsranging from 13.5 to 150 kV cm^(-1), to determine their electrical conductivity-field strengthrelationships and to infer the order of the bonding strength (retaining force) between soilparticles and various ions. The measurements with the latosol suspensions in NaNO_3, KNO_3,Ca(NO_3)_2, Mg(NO_3)_2 and Zn(NO_3)_2 solutions resulted in increments of the suspension ECs, ΔECs,of 7.9, 5.0, 7.1, 7.0 and 5.8 μS cm^(-1), respectively, when the applied field strength increasedfrom 14.5 to 142 kV cm^(-1). As for the suspensions in NaNO_3, NaCl, Na_2SO_4, Na_3PO_4 andNa_3AsO_4 solutions, the ΔECs were 6.2, 5.3, 4.1, 4.0 and 3.7μS cm^(-1), respectively, when theapplied field strength increased from 13.5 to 90 kV cm^(-1). Thus, it can be deduced that theretaining forces of the clay fraction of the latosol for the cations were in the descending orderK^+ > Zn^(2+) > Mg^(2+) ≥ Ca^(2+) > Na^+, and for the anions in the descending order H_2AsO_4^- >H_2PO_4^-≥ SO_4^(2-) > Cl^- > NO_3~ -.展开更多
Gibbs free binding energy and adsorption energy between cations and charged soil particles were used to evaluate the interactions between ions and soil particles. The distribution of Gibbs free adsorption energies cou...Gibbs free binding energy and adsorption energy between cations and charged soil particles were used to evaluate the interactions between ions and soil particles. The distribution of Gibbs free adsorption energies could not be determined experimentally before the development of Wien effect measurements in dilute soil suspensions. In the current study, energy relationships between heavy metal ions and particles of Hapli-Udic Argosol （Alfisol） and Ferri-Udic Argosol were inferred from Wien effect measurements in dilute suspensions of homoionic soil particles （〈 2 μm） of the two soils, which were saturated with ions of five heavy metals, in deionized water. The mean Gibbs free binding energies of the heavy metal ions with Hapli-Udic Argosol and Ferri-Udic Argosol particles diminished in the order of Pb^2＋ 〉 Cd^2＋ 〉 Cu^2＋ 〉 Zn^2＋ 〉 Cr^3＋, where the range of binding energies for Hapli-Udic Argosol （7.25-9.32 kJ mol^-1） was similar to that for Ferri-Udic Argosol （7.43-9.35 kJ mol^-1）. The electrical field-dependent mean Gibbs free adsorption energies of these heavy metal ions for Hapli-Udic Argosol and for Ferri-Udic Argosol descended in the order： Cu^2＋ 〉 Cd2^＋ 〉 Pb^2＋ 〉 Zn^2＋ 〉 Cr^3＋, and Cd^2＋ 〉 Cu^2＋ 〉 Pb^2＋ 〉 Zn^2＋ 〉 Cr^3＋, respectively. The mean Gibbs free adsorption energies of Cu^2＋, Zn^2＋, Cd^2＋, Pb^2＋, and Cr^3＋ at a field strength of 200 kV cm^-1, for example, were in the range of 0.8-3.2 kJ mo1^-1 for the two soils.展开更多
基金Project(Nos.49771046 and 49831005)supported by the National Natural Science Foundation of China and the Center for International Cooperation,Ministry of Foreign Affairs,State of Israel.
文摘The electrical conductivities (ECs) of suspensions containing 25 and 30 gkg^(-1) solids prepared from the electrodialyzed clay fraction (< 2μm in diameter) of latosol,yellow-brown soil, and black soil, dispersed in various nitrate solutions having concentrations of 1X 10^(-4)/z mol L^(-1), where z is the valence, and in distilled water, were measured at fieldstrengths ranging from 14 kV cm^(-1) to 210 kV cm^(-1). On the basis of analyses of the chargedensity and exchangeable ion composition on the surfaces of soil particles in the suspensions, andof the characters of the EC-field strength curves of the various suspensions, it was inferred thatthe increment of EC (ΔEC) and/or relative electrical conductivity (REC) can indicate the bondingstrength between cations and soil particles. The bonding strengths of various cations with the soilsdiminished in the order: K^+ > Zn^(2+) > Mg^(2+) = Ca^(2+) > Na^+ for latosol, Ca^(2+) > Zn^(2+) >Mg^(2+) = K^+ > Na^+ for yellow-brown soil, and Zn^(2+) ≥ Ca^(2+) ≥ Mg^(2+) > K^+ > Na^+ for blacksoil.
基金Project(Nos.49771046 and 49831005)supported by the National Natural Science Foundation of China.
文摘The electrical conductivity of suspensions and their supernatants from theelectrodialyzed clay fractions of latosol, yellow-brown soil and black soil equilibrated withnitrate solutions were determined at different field strengths using a short high-voltage pulseapparatus to demonstrate the Wien effect in soil suspensions and to investigate factors affectingit. It was found that Wien effect was much stronger in suspensions with a clay content of 30 gkg^(-1) from the soils equilibrated with a 1 X 10^(-4) KNO_3 solution than in their supernatants.The threshold field strength (TFS), at which the relative conductivity is equal to 1.05, i.e., theWien effect begins to be obvious, of the yellow-brown soil suspensions (clay content of 30 gkg^(-1)) equilibrated with different nitrate solutions of a concentration of 1 X 10^(-4)/z molL^(-1), where z is the valence, varied with the type of nitrates, being lowest for NaNO_3 (47 kVcm^(-1)) and highest for Ca(NO_3)_2 (98 kV cm^(-1)). At high field strengths (larger than 130 kVcm^(-1)), the relative conductivities of yellow-brown soil suspensions containing different nitratesdiminished in the order: NaNO_3 > KNO_3 > Mg(NO_3)_2 > Zn(NO_3)_2 > Ca(NO_3)_2. The rates andintensities of the Wien effect in the suspensions of the three soils equilibrated with 5 X 10^(-5)mol L^(-1) Ca(NO_3)_2 solution were in the order of the yellow-brown soil > the latosol > the blacksoil. The results for the yellow-brown soil suspensions (clay concentration of 30 g kg )equilibrated with KNO_3 solutions of various concentrations clearly demonstrated that the moredilute the solution, the lower the TFS, and the larger the relative conductivity of the suspensionsat high field strengths. The results for yellow-brown soil suspensions with different clayconcentrations indicated that as the clay concentration increased, the low field electricalconductivity, EC_0, also increased, but the TFS decreased, and the Wien effect increased.
基金Project supported by the National Natural Science Foundation of China (Nos. 49771046 and 49831005) the Center for International Cooperation, Ministry of Foreign Affairs, State of Israel.
文摘Suspensions of a latosol with a clay concentration of 30 g kg^(-1) wereprepared from electrodialyzed clay fractions, less than 2 μm in diameter, five nitrate solutionswith a concentration of 1 X 10^(04)/z mol L^(-1), where z is the valence, and five sodium saltsolutions with a concentration of 3.3 X 10^(-5)/2 mol L^(-1). The direct current (DC) electricalconductivities (ECs) of the colloidal suspensions were measured at a constant temperature of 25 ℃,using a newly established method of measuring the Wien effect in soil suspensions at field strengthsranging from 13.5 to 150 kV cm^(-1), to determine their electrical conductivity-field strengthrelationships and to infer the order of the bonding strength (retaining force) between soilparticles and various ions. The measurements with the latosol suspensions in NaNO_3, KNO_3,Ca(NO_3)_2, Mg(NO_3)_2 and Zn(NO_3)_2 solutions resulted in increments of the suspension ECs, ΔECs,of 7.9, 5.0, 7.1, 7.0 and 5.8 μS cm^(-1), respectively, when the applied field strength increasedfrom 14.5 to 142 kV cm^(-1). As for the suspensions in NaNO_3, NaCl, Na_2SO_4, Na_3PO_4 andNa_3AsO_4 solutions, the ΔECs were 6.2, 5.3, 4.1, 4.0 and 3.7μS cm^(-1), respectively, when theapplied field strength increased from 13.5 to 90 kV cm^(-1). Thus, it can be deduced that theretaining forces of the clay fraction of the latosol for the cations were in the descending orderK^+ > Zn^(2+) > Mg^(2+) ≥ Ca^(2+) > Na^+, and for the anions in the descending order H_2AsO_4^- >H_2PO_4^-≥ SO_4^(2-) > Cl^- > NO_3~ -.
基金Project supported by the National Natural Science Foundation of China(Nos.40401030 and 20577054).
文摘Gibbs free binding energy and adsorption energy between cations and charged soil particles were used to evaluate the interactions between ions and soil particles. The distribution of Gibbs free adsorption energies could not be determined experimentally before the development of Wien effect measurements in dilute soil suspensions. In the current study, energy relationships between heavy metal ions and particles of Hapli-Udic Argosol （Alfisol） and Ferri-Udic Argosol were inferred from Wien effect measurements in dilute suspensions of homoionic soil particles （〈 2 μm） of the two soils, which were saturated with ions of five heavy metals, in deionized water. The mean Gibbs free binding energies of the heavy metal ions with Hapli-Udic Argosol and Ferri-Udic Argosol particles diminished in the order of Pb^2＋ 〉 Cd^2＋ 〉 Cu^2＋ 〉 Zn^2＋ 〉 Cr^3＋, where the range of binding energies for Hapli-Udic Argosol （7.25-9.32 kJ mol^-1） was similar to that for Ferri-Udic Argosol （7.43-9.35 kJ mol^-1）. The electrical field-dependent mean Gibbs free adsorption energies of these heavy metal ions for Hapli-Udic Argosol and for Ferri-Udic Argosol descended in the order： Cu^2＋ 〉 Cd2^＋ 〉 Pb^2＋ 〉 Zn^2＋ 〉 Cr^3＋, and Cd^2＋ 〉 Cu^2＋ 〉 Pb^2＋ 〉 Zn^2＋ 〉 Cr^3＋, respectively. The mean Gibbs free adsorption energies of Cu^2＋, Zn^2＋, Cd^2＋, Pb^2＋, and Cr^3＋ at a field strength of 200 kV cm^-1, for example, were in the range of 0.8-3.2 kJ mo1^-1 for the two soils.
