磷酸盐吸附对可变电荷土壤正负电荷的影响

本文研究了华南地区不同类型的可变电荷土壤，并对磷酸盐的吸附量和吸附磷后土壤的正、负电荷的变化，以及ｐＨ和游离氧化铁对这种变化的影响进行了研究。结果表明，土壤吸磷量与土壤游离氧化铁含量成良好的正相关。土壤吸磷后正电荷减少，负电荷增加，土壤电荷量与吸磷量之间呈抛物线状相关。吸附１摩尔磷酸盐对土壤净负电荷的贡献在０．３－１．０摩尔之间。土壤中的游离氧化铁使吸附的磷对土壤负电荷的贡献减少。     

恒电荷土壤和可变电荷土壤动电性质的研究 Ⅰ.阳离子吸附和pH的影响

本工作研究了阳离子和吸附和ＰＨ对恒电荷土壤和可变电荷土壤动电动性质的影响。研究结果表明,砖红 不同溶液中的ζ电位随ＰＨ升高由正值变为负值,均有一个等电点：ＰＨ〉５时,在不同溶液之间砖红壤ζ电位的变化顺序为：ＭｎＣｌ２〉ＺｎＣｌ２≥ＣａＣｌ２〉ＮａＣｌ。     

关于土壤可变电荷数量和表现的讨论

在70年代,人们根据土壤粘粒矿物的表面结构特性,把土壤粘粒表面分为硅氧烷表面和水合氧化物型表面两类。     

低分子量有机酸对可变电荷土壤中铝吸附的影响

铝毒是酸性土壤上植物生长不良的主要限制因素,铝的生物毒性与铝离子的化学形态有密切的关系[1, 2],而铝的化学形态又受包括低分子量有机酸在内的多种因素的影响[3, 4].低分子量有机酸是土壤中广泛存在的一类非常活泼的物质,植物在生长过程中其根系会不断分泌出各种有机酸,植物残体分解过程中和土壤微生物代谢过程中均会产生有机酸[5, 6].一些有机酸阴离子可以被可变电荷土壤吸附,并影响土壤的某些表面化学性质;另一方面某些有机酸阴离子能够与铝形成稳定的络合物从而改变铝离子在溶液中的存在形态,这两方面的原因都有可能对可变电荷土壤中铝的吸附产生影响.     

多种有机酸共存对可变电荷土壤吸附磷的影响

研究了２种或３种有机酸在不同浓度组合时对可变电荷土壤吸附磷酸根离子的影响,结果表明:（１）有机酸的种类、各自的浓度及总浓度对土壤吸附磷有显著影响;（２）土壤组成及表面性质不同时,有机酸与磷的竞争效果也不大相同;（３）多种有机酸混存对土壤吸附磷量的影响不等于各单一有机酸贡献的简单加和。因此,根际环境中有机酸、磷在土壤表面的相互作用还有许多待探讨的问题。     

阴离子对可变电荷土壤吸附铜离子的影响机理

根据NO-3、Cl-和SO24-对可变电荷土壤和恒电荷土壤吸附Cu2+的影响的比较,探讨了阴离子对可变电荷土壤吸附Cu2+的影响机理。结果表明,当3种阴离子的浓度相同时,在SO24-体系中铁质砖红壤对Cu2+的吸附率较在NO3-和Cl-体系中大得多,而在浓度相同的3种阴离子体系中,黄棕壤对Cu2+的吸附率相差不大。在离子强度相近的NaCl体系中,砖红壤对Cu2+的吸附率相近。在3种阴离子体系中,随着pH升高,砖红壤对Cu2+的吸附率均增大;但在NO-3体系和Cl-体系中Cu2+的吸附率相近;而在SO24-体系中Cu2+的吸附率最大。随着Na2SO4浓度的增大,铁质砖红壤和砖红壤对Cu2+的吸附率减小。但在0.005 mol L-1和0.05 mol L-1Na2SO4体系中,Cu2+的吸附率大于在不含Na2SO4的体系中者。而在0.5 mol L-1Na2SO4体系中,Cu2+吸附率小于在不含Na2SO4体系中者。在3种浓度的Na2SO4体系中,黄棕壤对Cu2+的吸附率均小于在不含Na2SO4体系中者。总之,阴离子可通过离子强度、专性吸附和形成离子对影响土壤对Cu2+的吸附。在可变电荷土壤中,阴离子对Cu2+吸附的影响机理较在恒电荷土壤中复杂得多。     

CrO42-对两种可变电荷土壤表面电荷的影响

对两种可变电荷土壤的研究结果表明,加入铬酸根(CrO42-)能增加土壤的表面负电荷,减小土壤的表面正电荷的量。CrO42-对表面正电荷的影响程度随体系pH的增加而减小,对负电荷的影响呈相反的趋势。CrO42-对表面电荷的影响程度也随其加入量的增加而增加。CrO42-主要通过自身的吸附来影响土壤的表面电荷,因为伴随着土壤表面电荷的变化,CrO42-在土壤中发生明显的吸附。而且土壤对CrO42-的吸附量随其加入量的增加而增加,随pH的升高而减小,与土壤电荷的变化趋势基本一致。     

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     

配位体交换在减慢由酸雨造成的可变电荷土壤酸化速度中的意义

For the purpose of evaluating the role of ligand exchange of sulfate ions in retarding the rate of acidification of variable charge soils,the changes in pH after the addition of different amounts of HNO3 or H2SO4 to representative soils of China were measured .A difference between pH changes caused by the two kinds of acids was observed only for variable charge soils and kaolinite,but not for constant charge soils and bentonite,The larger the proportion of H2SO4 in the HNO3-H2SO4 mixture,the lower the calculated H^ ion activities remained in the suspension.The difference in H^ ion activities between H2SO4 systems and HNO3 systems was larger for soils with a low base-saturation(BS) percentage than those with a high BS percentage.The removal of free iron oxides from the soil led to a decrease in the difference,while the coating of Fe2O3 on a bentonite resulted in a remarkable appearance of the difference.The effect of ligand exchange on the acidity status of the soil varied with the soil type.Surface soils with a high organic matter content showed a less pronounced effect of ligand exchange than subsoils did.It was estimated that when acid rain chiefly containing H2SO4 was deposited on variable charge soils the acidification rate might be slower by 20%-40% than that when the acid rain chiefly contained HNO3 for soils with a high organic matter content,and that the rate might be half of that caused by HNO3 for soils with a low organic matter content,especially for latosols.     

电渗析可变电荷土壤中氢氧根离子的释放与氯离子吸附的关系

The release of hydroxyl ions from two variable charge soils associaed with the adsorption of chloride in NaClO4 solutions was examined.The complete release required about 10 minutes The release decreased with the increase in the NaClO4 concentration at first and eventually was little affected by the latter.The adsorption of Cl^-1 was almost linearly related with the quantity of NaCl added to the system,while the OH^- release-NaCl curve varied with the soil type and the concentration of NaClO4.The logarithm of the quantity of released OH^- was linearly related with the pH ,The ratio of release OH^- to adsorbed Cl^- was larger in dilute NaClO4 solutions than in concentrated solutions and decreased with increasing NaCl.     

硫酸盐对锌和镉在可变电荷土壤上吸附的影响

SO4^2- and Zn^2 or Cd^2 were added to three variable charge soils in different sequences.In one sequence sulfate was added first ,and in the other,Zn^2 or Cd^2 first.The addition of sulfate to the system invariably caused an increase in adsorption of the heavy metal added,with the effect more remarkable whn the soil reacted with the sulfate prior to the metal.the shift in pH50 for both Zn and Cd adsorption was aslo comparatively larger in the first sequence of reactions .It was suggested that the increase in negative charge density and the resultant negative potential of the soil were the primary cause of the pronounced effect of sulfate on adsorption of Zn or Cd,and the formaiton of the ternary surface complex-S-SO4-M might also play a role in the effect.     

Influences of aluminum ions on the determination of zpc (zero point of charge) of variable charge soils

Influence of Al dissolution on soil ZPC (zero point of charge) measured by a potentio-metric titration (PT) method and a modified salt titration (STPT) method was examined using two strongly weathered soils from Thailand and two volcanic ash soils from Japan. The amount of dissolved Al ions increased with the increase in the concentration of a supporting electrolyte for the strongly weathered soils, while the increase was negligible for the volcanic ash soils.

ZPC value of the strongly weathered soils determined by the PT method was lower than that by the STPT method, due to the greater Al dissolution associated with the higher electrolyte concentration used in the PT method. Al ions adsorbed onto the soil surface would shift the ZPC to a higher pH value not as a result of the formation of hydroxy Al polymers, but due to the blocking of permanent negative charge sites, which could otherwise lower the ZPC. The σp value, as a measure of permanent charge or the amount of 11 or O11 adsorbed by a soil required to attain the ZPC, could be used to describe this phenomenon.

In the STPT method, the salt concentration was not high enough to causc a significant Al dissolution at the ZPC, which is considered to be a more suitable condition than in the PT method because the ZPC value can be evaluated at a low salt concentration as in the ease of field conditions for crop production. Thus, the STPT method is rccommendcd for the determination of the ZPC.     

可变电荷或永久电荷土壤上的电荷特征与土壤对Cu2+的吸附－解吸之间的交互作用

Charge characteristics and Cu^2 adsorption-desorption of soils with variable charge(latosol)and permanent charge(brown soil)and the relationship between them were studied by means of back-titration and adsorption equilibrium respectively.The amount of variable negative charge was much less in variable-charge soil than in permanent-charge soil and increased with the pH in the system,but the opposite trend occurred in the points of zero charge(PZCs).The amount of Cu^2 ions sorbed by permanent-charge soil was more than that by variable-charge soil and increased with the increase of Cu^2 concentration within a certain range in the equilibrium solution.The amount of Cu^2 ions desorbed with KCl from permanent-charge soil was more than that from variable-charge soil,but the amount of Cu^2 ions desorbed with de-ionized water from permanent-charge soil was extremely low whereas there was still a certain amount of desorption from variable-charge soil.The increase of PZC of soils with variable or permanent change varied with the increment of Cu^2 ions added.When the same amount of Cu^2 ions was added,the increments of PZC and variable negative surface chargc of permanent-charge soil were different from those of variable-charge soil.     

Effect of anion composition of simulated acid rain on nutrient behavior in reclaimed saline soils

Abstract

Field experiments with the “Taikichi” taro cultivar were conducted in volcanic ash soil of Kagoshima Prefecture, Japan, in order to determine the effects of potassium applied with fertilizers and manures on the growth and yield of taro. The experimental design was accord ing to the L27 (3¹³) orthogonal factorial experiment, the three factors selected being the manures, nitrogen fertilizers and amount of potassium application.

“Metsubure” corm formation was infrequent in hog manured plots without potassium application, but was significantly increased by the application of potassium fertilizer. Furthermore, the occurrence of “Metsubure” corms was significantly lower in fields prepared with hog manure than in those prepared with plant residue and cattle manure.

Chemical analysis of the taro plants and manures revealed that the plants absorbed much more calcium when planted in hog manure than in other manures. The CaO/K₂O ratio was also higher. The main reason for this was assumed to be the lower content of potassium in the hog manure (0.37% K₂O on a dry basis).

The analytic results suggest that potassium disturbs the calcium uptake ability of the taro plant causing “Metsubure” corm formation.

The authors also attempted to determine the effects of several kinds of nitrogen fertilizers on “Metsubure” corm formation, but no clear results were obtained in this experiment.     

支持电解质浓度对磷酸根在可变电荷土壤表面吸附和解吸的影响

研究了离子强度对2种可变电荷土壤中磷酸根吸附和解吸的影响。结果表明,当pH分别大于3.7和4.0时,红壤和砖红壤对磷酸根的吸附量随离子强度的增加而增加;当pH分别小于3.7和4.0时,红壤和砖红壤对磷酸根的吸附量随离子强度呈相反的变化趋势。电解质主要通过改变离子专性吸附面上的电位来影响磷酸根的吸附。Zeta电位的测定结果表明,当pH大于土壤胶体的等电点(IEP)时,吸附面上电位为负值,且随离子强度增加数值减小,对磷酸根的排斥力减小,土壤表面对磷酸根的吸附量增加;当pH小于IEP时,吸附面上的电位为正值,它随离子强度增加而减小,不利于磷酸根的吸附。解吸实验的结果表明,吸附于可变电荷土壤表面的磷酸根在去离子水中的解吸量高于0.1 mol L-1NaNO3体系中的解吸量。这同样由于电解质浓度对土壤表面吸附面上的电位的影响所致。     

电解质阴离子和pH对可变电荷土壤硫酸盐吸附的影响

The effects of three electrolyte anions, ionic strength and pH on the adsorption of sulfate by two variable charge soils, with different surface charge properties were studied. Under the conditions of the same pH and ionic strength the effect of electrolyte anions on the adsorption of sulfate was in the order of Cl^- > NO₃^- > ClO₄^-, indicating the difference of the nature among these three anions. For Ferralsol in the same concentration of chloride and perchloride solutions, the two sulfate adsorption-pH curves could intersect at certain pH value. When pH was higher than the intersecting point, more sulfate was adsorbed in the perchloride solution, while when it was lower than the intersecting point, more sulfate was adsorbed in the chloride solution. In different concentrations of electrolyte solution, the curves of the amount of oxy-acid anion adsorbed, which changed with pH, could intersect at a certain pH, which is termed point of zero salt effect (PZSE) on adsorption. The nature of electrolyte anions influenced obviously the appearance of PZSE for sulfate adsorption. For ferralsol the curves of adsorption converged to about pH 7 in NaCl solution seemed to intersect in NaNO₃ solution and to have a typical PZSE for sulfate adsorption in NaClO₄ solution. For Acrisol the three curves of adsorption were nearly parallel in NaCl and NaNO₃ solutions and converged to pH 6.5 in NaClO₄ solution.     

Effect of low-molecular-weight organic acids on Cl- adsorption by variable charge soils

Low-molecular-weight (LMW) organic acids exist widely in soils and have been implicated in many soil processes.The objective of the present paper was to evaluate effect of two LMW organic acids, citric acid and oxalic acid, on Cl^- adsorption by three variable charge soils, a latosol, a lateritic red soil and a red soil, using a batch method. The results showed that the presence of citric acid and oxalic acid led to a decrease in Cl- adsorption with larger decreases for citric acid. Among the different soils Cl- adsorption in the lateritic red soil and the red soil was more affected by both the LMW organic acids than that in the latosol.     

A review of the problems associated with applying the terms surface charge and zero point of charge to soils

Abstract

Many soil properties are determined by the surface charge on the soil particles. A range of methods for determining the surface charge properties is available from the literature. However, the interpretation of the results obtained and the theoretical basis of some of the methods is confusing with different terms having different meanings for different authors. Thus, the study of surface charge properties and the theoretical basis is particularly difficult for a newcomer to the field. This paper presents a review of the major concepts as used in the current literature and highlights the problems encountered when applying these concepts to the determination of the surface charge properties.