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Study　on　Water－Soluble　Organic　Reducing　Substances：Ⅲ．Electrochemical　Properties　of　Decomposition　Products　of　Rice　Straw　and　Their　Interactions　with　variable　charge　soils

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Pedosphere 1996年第2期6卷 167-173页

作者： WU YOUXIAN(Institute of Soil Science,Acodemia Sinica,P.O.Box 821,Nanjing 210008 China) Institute of Soil Science Academia Sinica P. O. Box 821 Nanjing 210008 China

Some electrochemical properties,such as PH,Eh,and voltammetric behavior,of the decomposition products of rice straw and the in eractions of these products with soils were *** PH,Eh,and amounts of organic reducing substances changed markedly during the 60-day anaerobic *** decreased sharply to pH 5 on the tenth day and then increased gradually to 7 on the 45th *** amouats of organic reducing substances increased almost synchronously with the fall of redox potential during the first 15 *** differential pulse voltammetric(dpv) behavior changed not only in the peak current but also in the peak *** fractions with apparent molecular weights lower than 200 dations appeared to be active in dpv *** electric charge of organic reducing substances was closely related to the decomposition *** 6th day of incubation was the crucial time before and after which the major part of the components was negatively charged and positively charged, *** group with a low apparent molecular weight and a negative charge was the main components responsible for the lower anodic peak *** were oxidized first during the interactions of the organic reducing substances with soils.

关键词： electrochemical properties organic reducing substances rice straw variable charge soils

Types　of　Crystalline　Iron　Oxides　and　Phosphate　Ad－sorption　in　variable　charge　soils

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Pedosphere 1994年第1期4卷 35-46页

作者： LIU FAN XU FENG-LIN LI XUE-YUAN WANG YI-JUN and ZENG GUANG-QIAO(Department of Soil and Agrochemistry, Huazhong Agricultural University, Wuhan 430070 (China))

The types, contents and morphologies of crystalline Fe oxides and their relations to phosphate adsorptionon the clay fractions in soils with variable charge in southern China were investigated by means of XRD, TEM,EMA and chemical analysis *** indicated that the types and contents of crystalline Fe oxidesvaried with the soils examined. The dominant crystalline Fe oxide was hematite in the latosols and goethitesin the red *** yellow-brown soils, the only crystalline Fe oxide was *** difference between Aldand Alo came mainly from the Al substituting for Fe in the pe oxides. The crystal morphology of goethiteappeared mainly as subrounded flat or iso-dimensional rather than acicular particles. Hematites occurredin plates of various thickness. Their MCDa/MCDc ratios in the latosols and red soils were generally above1.5 and below 1.5, respectively. The MCD values of goethites and hematites were 15-25nm and 20-35nm,and their specific surface areas were 80-120m￣2/g and 35-75m￣2/g, *** goethite crystals weregenerally smaller. Variations of the total amounts of crystalline Fe oxi es in clay fractions were not related tophosphate adsorption. The types, contents and morphologies of crystalline Fe oxides in the soils remarkablyaffected phosphate adsorption characteristics of the soils. The phosphate adsorption of goethite was muchgreater than that of hematite. The higher the MCD /MCDc rotio of hematite, the lower the phosphateadsorption.

关键词： crystalline Fe oxides goethite hematite phosphate adsorption variable charge soils

Contribution of Iron and Aluminum Oxides to Electrokinetic Characteristics of variable charge soils in Relation to Surface charge

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Pedosphere 1992年第1期2卷 31-42页

作者： ZHANGHONG ZHANGXIAO－NIAN Instituteofsoilscience AcademiaSinicaP.O.Box821Nanjing210008（China） Instituteofsoilscience Academia

The contribution of iron and aluminum oxides to electrokinetic characteristics of variable charge soils was studied through determination of electrophoretic mobilities of the red soils treated with either removal of iron oxides or coating of aluminum oxides, and of those deferrated under natural conditions. After removal of the iron oxides, zeta potentials of the latosol and the red earth decreased obviously with a shift of IEP to a lower pH, from 6.4 to 5.3 and 4.1 to 2.4 for the former and the latter, respectively, and the electrokinetic change for the latosol was greater than for the red earth. Zeta potentials of the kaolinite sample increased markedly after coated with iron oxides. The striking effect of iron oxides on electrokinetic properties of the soils was also demonstrated by the electrokinetic differences between the samples from the red and white zones of a plinthitic horizon formed naturally, and between the samples from the gley and bottom horizons of a paddy soil derived from a red earth. The coatings of aluminum oxides on the latosol and the yellow earth made their zeta potentials rise pronouncedly and their IEPs move toward higher pHs, from 6.2 to 6.8 and 4.3 to 5.3 for the former and the latter, respectively. The samples with different particle sizes also exhibited some electrokinetic variation. The experiment showed that the effects of iron and aluminum oxides were closely related to the pH and type of the soils.

关键词： electrokinetic characteristics iron and aluminum oxides variable charge soils

Effect of Specific Adsorption of Ions on Electrokinetic Properties of variable charge soils

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Pedosphere 1991年第1期1卷 41-50页

作者： ZHANG HONG and ZHANG XIAO-NIANInstitute of Soil Science, Academia Sinica, and Laboratory of Material Cycling in Pedosphere, Academia Sinica, P.O. Box 821. Nanjing ( China) Instituteofsoilscience AcademiaSinicaandLaboratoryofMaterialCyclinginPedosphereAcademiaSinicaP.O.B

Studies were carried out by using electrophoretic method on the effects of the specific adsorption of the anions,such as SO4^2-,PO4^3-,and F^- ions,the cations,such as Ca^2+,Mn^2+,Zn^2+,and Cu^2+,ions,and the anions and cations coexisting,such as Zn^2+ and SO4^2= ions,on electrokinetic properties of the red soils as typical variable charge soils in China concerning variation in the specific ion species and concentrations,with an emphasis on the interaction between soil colloid surfaces and the ions in soil *** results showed that the adsorption of specific ions led to a very pronounced decrease in zeta potentials of the soil colloids and a shift of the IEPs to lower values for specific anions,and an obvious increase in zeta potentials of the soil colloids and a shift of the IEPs to higher values for specific *** circumstances of the specific anions and cations coexisting,for instance,Zn^2+ and SO4^2- ions,the zeta potentials changed with values higher than the value for SO4^2- alone and lower than that for Zn^2+ alone,and the IEP was between that for Zn^2+ and that for SO4^2-.The adsorption of Zn^2+ and Cu^2+ ions resulted in a reversal of the zeta potentials,and appearance of two IEPs for Zn^2+ and no IEP for Cu^2+,exhibiting interesting special effects of these kinds of metal *** higher the concentrations of the ions,the greater the change of the electrokinetic properties.

关键词： Electrokinetic properties specific adsorption variable charge soils

Effect of Zn Adsorption on charge of variable charge soils

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Pedosphere 1993年第3期3卷 239-246页

作者： SUN HAN-YUANInstitute of Soil Science, Academia Sinica. P. O. Box 821, Nanjing 210008 (China) Instituteofsoilscience AcademiaSinicaP.O.Box821Nanjing210008（China）

The variation in apparent charge of two typical variable charge soils resulting from Zn adsorption were studied by KC1 saturation and NH4NO3 replacement methods. Results showed that zinc were adsorbed specifically to those sites with negative charge. As in different pH ranges, the percentages of specific and electrostatic adsorptions of zinc and the mechanisms of specific adsorption were different, the effects of Zn adsorption on apparent charge were varied and could be characterized as: when 1 mmol Zn2+ was adsorbed, a change about 1 mmol in the apparent charge was observed in the low pH range (Ⅰ), 1.4 to 1.5 mmol in the moderate pH range (Ⅱ) and 0.55 to 0.6 mmol in the high pH range (Ⅲ). These experimental data, in terms of soil charge, proved once more author's conclusion in the preceding paper (Sun, 1993) that in accordance with the behaviors of Zn adsorption by the variable charge soils in relation to pH, three pH ranges with different adsorption mechanisms were delineated; that is, in Range Ⅰ, specific adsorption was the predominant mechanism, in Ranges Ⅱ and Ⅲ, specific and electrostatic adsorptions co-existed, but their specific adsorption mechanisms were not identical.

关键词： apparent charge electrostatic and specific adsorption pH variable charge soils zinc

Adsorption of Potassium and Sodium Ions by variable charge soils

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Pedosphere 1992年第3期2卷 245-254页

作者： LIHONG－YAN JIGUO－LIANG Instituteofsoilscience AcademiaSinicaP.O.Box821Nanjing210008（China） Instituteofsoilscience Academia

Adsorption of potassium and sodium ions by four typical variable charge soils of South China was studied. The results indicated that the variable charge soils saturated with H and Al showed a much higher preference for potassium ions relative to sodium ions, and this tendency could not be changed by such factors as the pH, the concentration of the cations, the dielectric constant of solvent, the accompanying anions and the iron oxide content etc., suggesting that this difference in affinity is caused by the difference in the nature of the two cations. It was observed that a negative adsorption of sodium ions by latosol and lateritic red soil in a mixed system containing equal amount of potassium and sodium ions at low pH, which is caused by a competitive adsorption of potassium and sodium ions and repulsion of positive charge on the surfaces of soil particles for cations. The adsorption of potassium and sodium ions increased with the decreases in the dielectric constant of solvent and the iron oxide content. Sulfate affected the adsorption of potassium and sodium ions through changing the surface properties of the soils.

关键词： adsorption potassium ions sodium ions variable charge soils

A Model for Anion Electric Adsorption on variable charge soils

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Pedosphere 1991年第2期1卷 169-176页

作者： HU GUO-SONGInstitute of Soil Science, A cademia Sinica, P. O Box 821, Nanjing 210008 (China)

A model was established for anion electric adsorption on variable charge surfaces and an equation to describe the relationship of adsorption amount with equalibrium concentration and suspension pH was derived according to the principles of surface reaction between variable charge surface and *** adsorption behaviours of nitrate and chloride on variable charge soils were modelled and the results showed that the model could describe the adsorption of nitrate very well.

关键词： anion electric adsorption,model variable charge soils

Cu Secondary Adsorption by Some variable charge soils After Adsorbing SO_4^(2-)

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Pedosphere 1993年第2期3卷 173-180页

作者： DONGYUAN－YAN WANGSHU－YU DepartmentofBasicSciences HuazhongAgriculturalUniversityWuhan430070（China） DepartmentofBasicSciences

Cu secondary adsorption by three variable charge soils collected from hubei Province and Hunan Province was *** amount of Cu secondary adsorption increased with that of SO4^2- elementary adsorption and conformed with the Langmuir,freundlich and Temkin *** of secondary-adsorbed Cu indicated that the hysteresis ratio decreased as Cu secondary adsorption increased,which meant that secondry-adsorbed Cu existed not only in the exchangeable form but also in the bridge form and specifically adsorbed *** amount of Cu secondary adsorption increased with the temperature.

关键词： Cu hysteresis ratio secondary adsorption variable charge soils

Adsorption of Phosphate on variable charge soils

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Pedosphere 1992年第3期2卷 273-282页

作者： HUGUO－SONG ZHUZU－XIANG 等 Instituteofsoilscience AcademiaSinicaP.O.Box821Nanjing210008（China） DepartmentofSoilandAgricultural

The study about the adsorption of phosphate on four variable charge soils and some minerals revealed that two stage adsorption appeared in the adsorption isotherms of phosphate on 4 soils and there was a maximum adsorption on Al-oxide-typed surfaces between pH 3.5 to pH 5.5 as suspension pH changed from 2 to 9, but the adsorption amount of phosphate decreased continually as pH rose on Fe-oxide typed surfaces. The adsorption amount of phosphate and the maximum phosphate adsorption pH decreased in the order of yellow-red soil > lateritic red soil > red soil > paddy soil, which was coincided with the content order of amorphous Al oxide. The removement of organic matter and Fe oxide made the maximum phosphate adsorption pH rise from 4.0 to 5.0 and 4.5, respectively. The desorption curves with pH of four soils showed that phosphate desorbed least at pH 5. Generally the desorption was contrary to the adsorption with pH changing. There was a good accordance between adsorption or desorption and the concentration of Al in the suspension. The possible mechanisms of phosphate adsorption are discussed.

关键词： adsorption of phosphate desorption of phosphate maximum adsorption pH suspension pH variable charge soils