电解质对酸性土壤铝的溶解及铝形态在土壤溶液中的分布的影响

KCl, CaCl₂, NH₄Cl, NaCl, K₂SO₄ and KF solutions were used for studying the effects of cations and anions on the dissolution of aluminum and the distribution of aluminum forms respectively. Power of exchanging and releasing aluminum of four kinds of cations was in the decreasing order Ca²⁺ >K⁺ >NH₄⁺ >Na⁺. The dissolution of aluminum increased with the cation concentration. The adsorption affinity of various soils for aluminum was different. The aluminum in the soil with a stronger adsorption affinity was difficult to be exchanged and released by cations. The Al-F complexes were main species of inorganic aluminum at a low concentration of cations, while Al³⁺ became major species of inorganic aluminum at a high concentration of cations. The results on the effect of anions indicated that the concentrations of total aluminum, three kinds of inorganic aluminum (Al³⁺, Al-F and Al-OH complexes) and organic aluminum complexes (Al-OM) when SO₄^2- was added into soil suspension were lower than those when Cl^- was added. The dissolution of aluminum from soils and the distribution of aluminum forms in solution were affected by the adsorption of F^- on the soil. For soils with strong affinity for F^-, the concentrations of the three inorganic aluminum species in soil solution after addition of F^- were lower than those after addition of Cl^-; but for soils with weak affinity for F^-, the concentrations of Al³⁺ and Al-OM were lower and the concentrations of Al-F complexes and total inorganic aluminum after addition of F^- were higher than those after addition of Cl^-. The increase of F^- concentration in soil solution accelerated the dissolution of aluminum from soils.     

Chemical Behavior of Chromium in Soils: Ⅲ. Mechanism of Cr(Ⅵ) Adsorption by Soils

An analysis of Cr (Ⅵ)-sorbed surface of the soils by using a scanning electron microscope and an electron probe microscope has proved that aluminium is the chief element affecting Cr (Ⅵ) adsoption. As the ionic strength of the solution increased, the amounts of Cr (Ⅵ) adsorbed by goethite and soils decreased. Cr (Ⅵ) adsorption was greatly depressed in the presence of SO₄^2-, WO₄^2-, MoO₄^2-, HPO₄^2- and H₂PO^4- which competed for anion adsorption sites. The depressing extent of these anions was found to follow the sequence: HPO₄^2-, H₂PO^4->MoO₄^2->WO₄^2->SO₄^2->>Cl^-, NO^3-. The amounts of Cr (Ⅵ) desorption varied with different extractants.     

高岭石和氧化土悬液中铝的水解行为及有机酸对铝水解反应的影响

To evaluate the role of kaolinite and variable charge soils on the hydrolytic reaction of Al, the hydrolysis of Al ions in suspensions of a kaolinite and an Oxisol influenced by organic anions was investigated using changes of pH, Al adsorption, and desorption of pre-adsorbed Al. Kaolinite and the Oxisol promoted the hydrolytic reaction of Al above a certain initial Al concentration (0.1 mmol L^-1 for kaolinite and 0.3 mmol L^-1 for the Oxisol). The Al hydrolysis accelerated by kaolinite and the Oxisol increased with an increase in initial concentration of Al and was observed in the range of pH from 3.7 to 4.7 for kaolinite and 3.9 to 4.9 for the Oxisol. The acceleration of Al hydrolysis also increased with the increase of solution pH, reached a maximum value at pH 4.5, and then decreased sharply. Al hydrolysis was promoted mainly through selective adsorption for hydroxy-Al. Soil free iron oxides compensated a portion of the soil negative charge or masked some soil surface negative sites leading to a decrease in Al adsorption, which retarded acceleration to some extent. For the Oxisol organic anions increased the proportion of adsorbed Al³⁺ in total adsorbed Al with the increase in soil negative surface charge and eliminated or reduced the acceleration of Al hydrolysis. Different organic anions inhibited the hydrolysis of Al in the order: citrate > oxalate > acetate (under initial pH of 4.5). The formation of Al-organic complexes in solution also inhibited the hydrolysis of Al.     

伴随阴离子对马铃薯种植冲击土中钾素固持与淋溶的影响

A column study was carried out to assess the influence of accompanying anions on potassium (K) leaching at potato growing sites with different soil textures (sandy loam and clay loam) in northwestern India. Potassium was applied in the top 15 cm layer of soil column at 30 and 60 mg K kg^-1 through different sources having different accompanying anions (Cl^-, SO₄^2-, NO₃^- and H₂PO₄^-). Maximum K was retained in the top 0--15 cm layer with a sharp decrease in K content occurring in 15--30 cm layer of the soil column. The trend was similar for both levels of applied K as well as frequency of leaching and soil type. The decrease of K content in soil column after four leaching events was maximum in case of Khanaura sandy loam, while only minor decrease was observed in Hundowal clay loam when K was applied at 60 mg K kg^-1, indicating higher potential of clay rich soil to adsorb K. In general, the K leaching in presence of the accompanying anions followed the order of SO₄^2- ≤ H₂PO₄^2- < NO₃^- = Cl^-. Highest 1 mol L^-1 CH3COONH4-extractable K was retained when K was applied along with SO42- and H2PO4- anions, and the least was retained when accompanying anion was Cl^-1. The influence of anions was more pronounced in the light textured soil and at high amounts of K application. Higher levels of K application resulted in higher losses of K, especially in sandy loam soil as observed from the leachate concentration. Among the different K sources, the maximum amount of K leaching was noticed in the soil column amended with KCl. After four leachings, the maximum amount of K leached out was 6.40 mg L^-1 in Hundowal clay loam and 9.29 mg L^-1 in Khanaura sandy loam at 60 mg K kg^-1 of soil application through KCl. These concentrations were lower than the recommended guideline of the World Health Organisation (12.00 mg L^-1).     

不同阴离子溶液中怀俄明州蒙脱石的Na-Zn交换选择性

The effect of background anion on cation exchange reactions, such as Na-Ca and Na-Cu exchange reactions, on montmorillonites has been studied, but the results are not always clear and discrepancies exist in the literature. In this study, the exchange of zinc (Zn²⁺) for sodium (Na⁺) on Wyoming montmorillonite was investigated at 298°K using Cl^-, ClO₄^-, NO₃^-, OAc^-, and SO₄^2- solution media at a constant total metal charge concentration of 0.0200 molc L^-1. Results indicated that the clay CEC values were essential similar for Cl^-, ClO₄^-, NO₃^- and SO₄^2- solution media with an average CEC of 0.856 ± 0.008 molc kg^-1; in an OAc⁺ solution the clay CEC was much higher than that in other anion media. The specific adsorption of Zn (SAZn), as defined by the extraction of Zn using 0.05mol L^-1 Na₂-EDTA, was different in the various background solutions. The highest value for SAZn was 0.359 ± 0.0350molc kg^-1, which occurred in OAc-solution. There was essentially no difference in the total apparent adsorbed metals (the sum of adsorbed equivalents of Na and Zn per kilogram of clay, Q) among the various background solutions. The average Q for all anion media was 0.807 ± 0.011 mol_c kg^-1 and was independent of exchanger composition. Experimental results indicated that there were no significant monovalent cation complexes such as ZnCl⁺ or ZnNO₃⁺ that were adsorbed by montmorillonite. The Na-Zn exchange isotherms indicated that there was an adsorption preference for Zn over Na on Wyoming montmorillonite.     

不同液土比和温度条件下塿土铵离子吸附

Effects of NH₄⁺ concentration, solution/soil ratio and temperature on NH₄⁺ adsorption were studied in a Eum-Orthic Anthrosol. The slopes of the soil NH₄⁺ adsorption isotherms and the fitted n, the coefficient for the adsorption intensity, and k, the coefficient related to adsorption capacity, of the Freundlich equation increased with increasing solution/soil ratio (SSR) and with decreasing temperature (T). For the range of experimental conditions, the value of ∂q/∂c, the rate of change of the amount of NH₄⁺ adsorbed in the soil solid phase (q) with respect to the equilibrium concentration of NH₄⁺ in soil solution (c), was 0.840, indicating that q increased with increasing c. From 2 to 45 ℃, ∂q/∂SSR, the rate of change of q with respect to SSR, decreased from 2.598 to 1.996, showing that q increased with increasing SSR, while its increasing rate decreased with temperature. From SSR 1:1 to 20:1, ∂q/∂T, the rate of change of q with respect to T, decreased from -0.095 to -0.361, indicating that q decreased with increasing temperature, and at the same time the negative effect of temperature became larger as SSR increased. Thus under the experimental conditions the order of importance in determining the amount of NH₄⁺ adsorbed in the soil solid phase was ∂q/∂SSR > ∂q/∂c > |∂q/∂T|, indicating that the greatest effect on the amount of NH₄⁺ adsorbed was with the solution/soil ratio; the equilibrium concentration of NH₄⁺ had a lesser effect; and temperature had the least effect.     

水培和土培条件下氮素供应对燕麦生长和磷素吸收的影响

Plants show different growth responses to N sources supplied with either NH₄⁺ or NO₃^-. The uptake of different N sources also affects the rhizosphere pH and therefore the bioavailability of soil phosphorus, particularly in alkaline soils. The plant growth, P uptake, and P availability in the rhizosphere of oat (Avena nuda L.) grown in hydroponics and in soil culture were investigated under supply with sole NH₄⁺-N, sole NO₃^--N, or a combination. Sole NO₃^--fed oat plants accumulated more biomass than sole NH₄⁺-fed ones. The highest biomass accumulation was observed when N was suppliedw ith both NH₄⁺-N and NO₃^--N. Growth of the plant root increased with the proportion of NO₃^- in the cultural medium. Better root growth and higher root/shoot ratio were consistently observed in NO₃^--fed plants. However, root vigor was the highest when N was supplied with NO₃^-+NH₄⁺. NH₄⁺ supply reduced the rhizosphere pH but did not affect P uptake by plants grown in soils with CaHPO₄ added as P source. No P deficiency was observed, and plant P concentrations were generally above 2 g kg^-1. P uptake was increased when N was supplied partly or solely as NO₃^--N, similarly as biomass accumulation. The results suggested that oat was an NO₃^--preferring plant, and NO₃^--N was essential for plant growth and the maintenance of root absorption capacity. N supply with NH₄⁺-N did not improve P nutrition, which was most likely due to the absence of P deficiency.     

磷的吸附和表面电荷特征及其与华南地区某些土壤矿物的关系

The phosphate adsorption and surface charge characteristics of the tropical and subtropical soils derived from different parent materials in China were determined, and their relations to soil mineralogy were analysed. The results showed that all soil phosphate adsorption curves were well fitted by Freundlich equation and Langmuir equation. The maximum buffering capacity of P ranged from 66 to 9 880 mg kg^-1, with an increasing order of purple soil, skeletal soil, red soil, lateritic red soil, yellow soil and latosol; and the highest value was 149 times the lowest value, which indicated great differences among these soils in phosphate adsorption and supplying characteristics. The pH₀ (zero point of charge) values obtained by salt titration-potential titration varied from 3.03 to 5.49, and the highest value was found in the latosol derived from basalt whereas the lowest value was found in the purple soil. The correlation analysis indicated that the main minerals responsible for phosphate adsorption in the soils were gibbsite, amorphous iron oxide and kaolinite; and the pH₀ was mainly controlled by kaolinite, gibbsite and oxides.     

盐胁迫下硝态氮对囊果碱蓬根系发育和氮吸收的影响

The effiects of NaCl salinity and NO₃^- on growth, root morphology, and nitrogen uptake of a halophyte Suaeda physophora were evaluated in a factorial experiment with four concentrations of NaCl (1, 150, 300, and 450 mmol L^-1) and three NO₃^- levels (0.05, 5, and 10 mmol L^-1) in solution culture for 30 d. Addition of NO₃^- at 10 mmol L^-1 significantly improved the shoot (P < 0.001) and root (P < 0.001) growth and the promotive effect of NO₃^- was more pronounced on root dry weight despite the high NaCl concentration in the culture solution, leading to a significant increase in the root:shoot ratio (P < 0.01). Lateral root length, but not primary root length, considerably increased with increasing NaCl salinity and NO₃^- levels (P < 0.001), implying that Na⁺ and NO₃^- in the culture solution simultaneously stimulated lateral root growth. Concentrations of Na⁺ in plant tissues were also significantly increased by higher NaCl treatments (P < 0.001). At 10 mmol L^-1 NO₃^- , the concentrations of NO₃^- and total nitrogen and nitrate reductase activities in the roots were remarkably reduced by increasing salinity (P < 0.001), but were unaffected in the shoots. The results indicated that the fine lateral root development and effective nitrogen uptake of the shoots might contribute to high salt tolerance of S. physophora under adequate NO₃^- supply.     

亚硒酸盐和可变电荷土壤表面羟基离子的交换反应: Ⅰ.电解质种类及pH的影响

Hydroxyl release of red soil and latosol surfaces was quantitatively measured using a self-made constant pH automated titration instrument, to study the changes of hydroxyl release with different added selenite amounts and pH levels, and to study the effects of electrolytes on hydroxyl release. Hydroxyl release increased with the selenite concentration, with a rapid increase at a low selenite concentration while slowing down at a high concentration. The pH where maximum of hydroxyl release appeared was not constant, shifting to a lower valus with increasing selenite concentration. Hydroxyl release decreased with increasing electrolyte concentration, and the decrease was very rapid at a low electrolyte concentration but slow at a high electrolyte concentration. For NaClO₄, NaCl and Na₂SO₄ hydroxyl release was in the order of NaClO₄ > NaCl 》 Na₂SO₄, and the difference was very significant. But for NaCl, KCl and CaCl₂, the order of hydroxyl release was NaCl > KCl > CaCl₂, and the difference was smaller. The amount of hydroxyl release from Xuwen latosol was greater than that from Jinxian red soil. Hydroxyl release existed in a wider range of pH with Xuwen latosol than with Jinxian red soil, due to their difference in soil properties. However, both soils had similar curves of hydroxyl release, indicating the common characteristics of variable charge soils.     

Increase in Cation Adsorption Induced by Surface Complexation of Sulfate on Andisols and Prediction by “Four-Plane Model”

Abstract

The “Four-plane model” is one of the surface complexation models developed for analyzing the electrostatic charge of synthetic oxides. This model which was applied to the B horizon of Andisols, was equilibrated with an electrolyte solution containing KCl, KNO₃, K₂SO₄ in the concentration range of 0.0033, 0.01, 0.033, 0.1 M, and pH range of 2 to 11. The amounts of NO₃ ^-, Cl^-, SO₄ ^2-, and K⁺ adsorbed were determined from the products remaining in the liquid phase. The increase in the pH value results in the increase of K⁺ adsorption, and decrease of anion adsorption. The increase in the equilibrium concentration increased both K⁺ and anion adsorption. The parameters of the model were determined by measurements and the iterative method. The model have a good agreement between calculated and measured values of cation and anion adsorption. Among the anion species, the amount of adsorbed anions was in the order of SO₄ ^2-?Cl^->NO₃ ^-. The differences in the degree of adsorption were mainly associated with the differences in the equilibrium constants of surface complexation. The surface complexation of the anions produced a negative charge and increased cation adsorption. The degree of surface complexation was most significant in the K₂SO₄ solution, and the phenomenon was considered to be important not only for anion adsorption but also for cation adsorption on Andisols.     

恒电荷土壤和可变电荷土壤动电性质的研究 Ⅱ.阴离子吸附和pH的影响

本工作研究了阴离子吸附和ＰＨ对恒电荷土壤（黄棕壤和黑土）和可变电荷土壤（砖红壤）动电性质的影响。结果表明,砖红壤吸附不同阴离子后的ζ电位随ＰＨ升高由正电位移至负电位,在ζ电位－ＰＨ曲线上均有一个等电点（ＩＥＰ）在ＰＨ３．５～８之间,相同ＰＨ升高由正电红壤的ζ电位随吸附阴离子的负移顺序是ＨＰＯ４＾２－〉Ｆ＾－〉ＳＯ４＾２－〉Ｃｌ＾－〉ＮＯ３＾－。作为恒电荷土壤的黄棕壤和黑土,在不同电解发质溶液中的ε     

Ionic strength effects on surface charge and adsorption of phosphate and sulphate by soils

Two surface soils (Patua and Tokomaru) of contrasting mineralogy were incubated with several levels of either CaCO₃ or HC1. The effects of ionic strength on pH, on surface charge, and on the adsorption of phosphate and sulphate were measured in three concentrations of NaCl. The pH at which the net surface charge was zero (point of net zero charge—PZC) was 1.8 for the Tokomaru soil and 4.6 for the Patua soil: differences that can be related to mineralogical composition. There was an analogous point of zero salt effect (PZSE) that occurred at pH 2.8 for the Tokomaru soil and at 4.6 for the Patua soil. The presence of permanent negative charge in the Tokomaru soil resulted in an increase in PZSE over PZC. The effect of ionic strength on adsorption varied greatly between phosphate and sulphate. For phosphate, there was a characteristic pH above which increasing ionic strength increased adsorption and below which the reverse occurred. This pH (PZSE for adsorption) was higher than the PZC of the soil and was 4.1 for the Tokomaru soil and 5.3 for the Patua soil. In contrast, increasing ionic strength always decreased sulphate adsorption and the adsorption curves obtained in solutions of different ionic strengths converged above pH 7.0. If increasing ionic strength decreases adsorption, the potential in the plane of adsorption must be positive. Also, if increasing ionic strength increases adsorption, the potential must be negative. This suggests that, depending upon pH, phosphate is adsorbed when the potential in the plane of adsorption is either positive or negative, whereas sulphate is absorbed only when the potential is positive.     

Effects of Organic Acids,o-Phenylenediamine and Pyrocatechol on Cadmium Adsorption and Desorption in Soil

This article studied the interaction of cadmium (Cd) and lowmolecular weight organics in Indicotic black (IB) soil.Cadmium adsorption isotherm in this soil was satisfactorilysimulated using Freundlich equation as Q = 905.6C^0.49 with high correlation (r² = 0.984), and its adsorption quantity increased with increasing pH. The presence of citricacid and EDTA significantly reduced Cd adsorption in soil,which was due to the formation of soluble Cd-organic complex. Concentration of cadmium ions in equilibrium solution was determined and percentages of [CdH₂Cit⁺]/[Cd-complex_Total],[CdHCit]/[Cd-complex_Total] and [CdCit^-]/[Cd-complex_Total] vs. pH were successfully calculated. Desorption percentage ofCd, adsorbed in the presence of citric acid and EDTA decreased, compared with that adsorbed in NaNO₃ media. It suggeststhat free sites for Cd adsorption in soil increased in thepresence of organic acid. When o-phenylenediamine, pyrocatechol and aminoethonic acid appeared in Cd equilibrium media, Cd adsorption quantity increased by increasing cation exchange ofpositively charged cadmium complex with soil at low pH. Compared with that performed in the absence of these organics, the exchangeable Cd, desorbed by 0.1 mol L^-1 NaNO₃, reduced obviously, which suggests that Cd-complex was moredifficult to be desorbed than Cd²⁺. Moreover, % Cd desorbedwas linearly correlated with the reverse of the total Cd adsorptionunder unsaturated adsorption.     

ANION ADSORPTION BY GOETHITE AND GIBBSITE

The desorption of specifically adsorbed (ligand exchanged) anions, such as phosphate, selenite, and fluoride, from the surface of gibbsite and goethite has been studied by repeatedly washing the adsorption complex with solutions of constant pH and ionic strength but containing no specifically adsorbable anions. The desorption of the anions varies between complete reversibility and almost complete irreversibility. Measurements of surface charge by the uptake of Na⁺ and Cl^- revealed that, on washing the adsorption complex, the surface charge returned to its value at the given pH in the absence of specifically adsorbed anions. Thus when the isotherm was irreversible, OH^- was desorbed (or H⁺ adsorbed) in preference to the desorption of the specifically adsorbed anion, whereas when the isotherm was reversible the specifically adsorbed anion was desorbed. Irreversibility appears to involve the nature of the adsorption complex at the surface. Where only monodentate ligands form, for example fluoride adsorption, the isotherm is reversible, whereas bridging or multidentate ligands and the formation of ring structures at the surface favour irreversibility.     

镁对土壤某些理化性质的影响

本文研究了镁离子在土壤中的吸附特性和交换性镁对土壤某些物理性质的影响。试验结果表明:镁盐阴离子对镁离子侵入土壤吸收复合体能力的影响为:CO₃^2->SO₄^2->Cl^-。在低浓度下,Mg²+在Na⁺陪伴下较其单独存在时更易被含MgCO₃的石灰性土壤吸附。在混合盐溶液中,当盐渍度和SAR一定时,Na⁺在Na⁺-Mg²⁺体系中比在Na⁺-Ca²⁺体系中更易被土壤吸附。当ESP一定时,随着土壤吸收复合体中交换性镁百分率(EMP)的增加,分散系数逐渐增加,饱和导水率和毛管水上升高度逐渐降低,当EMP>60%时,不再发生变化。随着ESP的增加,交换性镁的不良影响逐渐变小。     

恒电荷土壤与可变电荷土壤对Cl~-和NO_3~-吸附的差异及其机理

对 3种可变电荷土壤和 4种恒电荷土壤在不同 pH、不同浓度、不同相伴阴阳离子下混合体系中Cl-和NO3-的吸附进行了测定。结果表明 ,在Cl-和NO3- 共存体系中 ,Cl-比例增大使可变电荷土壤Na+吸附量及OH-释放量增加 ,而对恒电荷土壤影响不大。Cl-和NO3-吸附量随平衡Cl-和NO3-浓度增加而增大 ,随pH升高而减少。但恒电荷土壤在上述各种条件下对Cl-和NO3-吸附均相同 ,而可变电荷土壤对Cl-吸附量大于NO3-的吸附量 ;NO3-、Cl-的选择系数为 0.51～0.78,Cl-和NO3-的相对吸附量分别为56.9%和 43.1%。在不同相伴阳离子下 ,可变电荷土壤平衡溶液Cl-/NO3-比值均小于 1,且为Na+K+Ca2+Mg2+Fe3+;而恒电荷土壤Cl-/NO3-比值为 1左右 ,且不受阳离子类型的影响。由此认为 ,Cl-和NO3-在两类土壤中均以电性吸附为主 ,恒电荷土壤对Cl-和NO3-的亲合力及吸附机理相同 ;而可变电荷土壤对Cl-的亲合力 NO3- ,Cl-存在着专性吸附     

可变电荷土壤中铜离子的解吸

研究了我国四种可变电荷土壤红壤、赤红壤、砖红壤和铁质砖红壤以及二种恒电荷土壤黄棕壤和黑土中吸附性铜离子的解吸特征。研究结果表明 ,可变电荷土壤吸附的一部分铜离子可以被去离子水解吸 ,而且在pH～解吸率曲线上在一定pH值时出现解吸率最大值。在最大值时不同土壤中铜离子解吸率的大小与土壤中氧化铁的含量有关。氧化铁的含量越高 ,在最大值时铜离子的解吸率越大。当用中性电解质解吸可变电荷土壤吸附的铜离子时 ,电解质的浓度越大 ,解吸率越低。与此相反 ,恒电荷土壤吸附的铜离子不能被去离子水解吸 ,只能被中性电解质解吸 ,且电解质的浓度越高 ,解吸率越大。这表明 ,可变电荷土壤中吸附性铜离子的解吸规律 ,完全不同于恒电荷土壤中者。本文初步讨论了其原因     

恒电荷土壤及可变电荷土壤与离子间相互作用的研究 Ⅰ.共存离子对NO3-吸附的影响

研究了我国典型3种可变电荷土壤和4种恒电荷土壤在陪伴阳离子分别为K+、Na+、Ca2+时和1mmolL-1KCl、K2SO4支持电解质中NO-3的吸附.结果表明,NO-3吸附量随pH的增加而减小.在添加相同浓度NO-3时,3种可变电荷土壤对NO-3的吸附量顺序为Ca(NO3)2＞KNO3＞NaNO3＞KNO3+KCl＞KNO3+K2SO4;在初始NO-3浓度0.5～5mmolL-1的范围内,吸附量随浓度变化的关系符合Langmuir等温吸附式.由此求出与NO-3吸附结合能有关的常数(K)在不同共存离子存在下数值较小且差异不大,因此认为不同陪伴阳离子和不同伴随阴离子对NO-3吸附的电性机理影响不大,只是改变了土壤表面的正电荷数量从而使吸附量发生变化.4种恒电荷土壤对NO-3的吸附量通常很小,其中在Ca(NO3)2介质中较在其他介质中稍大,最大吸附量仅为1.5mmolkg-1左右,约为可变电荷土壤的1/10,且在浓度较低时常观察到负吸附.