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Effect of Crop-Straw Derived Biochars on Pb(Ⅱ) Adsorption in Two variable charge soils

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Journal of Integrative Agriculture 2014年第3期13卷 507-516页

作者： JIANG Tian-yu XU Ren-kou GU Tian-xia JIANG Jun State Key Laboratory of soil and Sustainable Agriculture/Institute of soil Science Chinese Academy of Sciences College of Resource and Environment Nanjing Agriculture University Wuhan Environmental Monitoring Center Wuhan Environmental Protection Bureau Nanjing Foreign Language School

Two variable charge soils were incubated with biochars derived from straws of peanut, soybean, canola, and rice to investigate the effect of the biochars on their chemical properties and Pb（II） adsorption using batch experiments. The results showed soil cation exchange capacity （CEC） and pH significantly increased after 30 d of incubation with the biochars added. The incorporation of the biochars markedly increased the adsorption of Pb（II）, and both the electrostatic and non-electrostatic adsorption mechanisms contributed to Pb（II） adsorption by the variable charge soils. Adsorption isotherms illustrated legume- straw derived biochars more greatly increased Pb（II） adsorption on soils through the non-electrostatic mechanism via the formation of surface complexes between Pb（II） and acid functional groups of the biochars than did non-legume straw biochars. The adsorption capacity of Pb（II） increased, while the desorption amount slightly decreased with the increasing suspension pH for the studied soils, especially in a high suspension pH, indicating that precipitation also plays an important role in immobilizing Pb（II） to the soils.

关键词： crop-straw derived biochar Pb(II) adsorption and desorption variable charge soil surface chemical properties

Release of Hydroxyl Ions Associated with Chloride Adsorption in Electrodialyzed variable charge soils

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Pedosphere 1998年第4期8卷 317-324页

作者： ZHANGGANGYA ZHANGXIAONIAN 等 InstituteofsoilScience theChineseAcademyofSciencesNanjing210008（CHina） InstituteofsoilScience theChi

The release of hydroxyl ions from two variable charge soils associated 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- was almost linearly related with the quantity of NaCl added to the system, while the OHrelease-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 released OH- to adsorbed Cl- was larger in dilute NaClO4 solutions than in concentrated solutions and decreased with increasing NaCl.

关键词： chloride adsorption hydroxyl release variable charge soil

Significance　of　Ligand　Exchange　Relating　to　Sulfate　in　Retarding　Acidification　of　variable　charge　soils　Caused　by　Acid　Rain

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Pedosphere 1996年第1期6卷 11-22页

作者： WANGJINGHUA YUTIANREN InstituteofsoilScience AcademiasinicaNanjing210008China InstituteofsoilScience AcademiasinicaNanji

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 HNO_3 or H_2SO_4 to representative soils of China were measured. A difrerence between pH changes caused by the two kinds of acids was observed only for variable charge soils and kaolinite, but not for consted charge soils and bentonite. The larger the proportion of H_2SO_4 in the HNO_3-H_2SO_4 mixture, the lower the calculated H￣+ ion activities remained in the suspension. The difference in H￣+ ion activities between H_2SO_4 systems and HNO_3 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 Fe_2O_3 ona 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 hash organic matter content showed a less pronounced effect of ligand exchange than subsoils did. It was estimated that when acid rain chiefly containing H_2SO_4 was deposited on variable charge soils the acidilication rate might be slower by 20%-40% than that when the acid rain chiefly contained HNO_3 for soils with a high organic matter content, and that the rate might be half of that caused by HNO_3 for soils with a low organic matter content, especially for latosols.

关键词： acid rain ligand exchange soil acidification sulfate adsorption variable charge soil

Factors Affecting Sensitivity of variable charge soils to Acid Rain

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Pedosphere 1995年第3期5卷 193-202页

作者： WANG JING-HUA(Institute of soil Science, Academia Sinica, Nanjing 210OO8 China)

The sensitivity of a large number of variable charge soils to acid rain was evaluated through examiningpH-H_2SO_4 input curves. Two derivative parameters, the consumption of hydrogen ions by the soil and theacidtolerant limit as defined as the quantity of sulfuric acid required to bring the soil to PH 3.5 in a 0.00lmolLi￣(-1) Ca(NO_3)_2 solution, were used. The sensitivity of variable charge soils was higher than that of constantcharge soils, due to the predominance of kaolinite in clay mineralogical composition. Among these soils thesensitivity was generally of the order lateritic red soil >red soil >latosol. For a given type of soil within thesame region the sensitivity was affected by parent material, due to differences in clay minerals and *** sensitivity of surface soil may be lower or higher than that of subsoil, depending on whether organicmatter or texture plays the dominant role in determining the buffering capacity. Paddy soils consnmedmore acid within lower range of acid input when compared with upland soils, due to the presence of moreexchangeable bases, but consumed less acid within higher acid input range, caused by the decrease in claycontent.

关键词： acid-tolerant limit sensitivity to acid rain variable charge soil

Adsorption of Chloride, Nitrate and Perchlorate by variable charge soils

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Pedosphere 1992年第4期2卷 317-326页

作者： JIGUO－LIANG KONGXIAO－LING InstituteofsoilScience.AcademiaSinica P.O.Box821Nanjing210008（China） InstituteofsoilScience.Academia

Two cells consisting of a chloride-selective electrode and a nitrate-selective electrode or of a chloride-selective electrode and a perchlorate-selective electrode were directly put in the soil suspension to determine the concentration ratios Cl-/ NO3- or Cl-/ ClO4- for studying the adsorption of the three anions by variable charge soils. It was found that all the concentration ratios CCl- / CNO3- and CCl- / CClO4- in suspension were smaller than unity when soil samples were in equilibrium with mixed KCl and KNO3 or KCl and KClO4 solutions of equal concentration. The order of the amount of chloride, nitrate and perchlorate adsorbed by variable charge soils was Cl-> NO3-> ClO4- when the soils adsorbed these anions from the solution containing equal concentrations of Cl-, NO3- and ClO4-. Such factors as the pH of the suspension, the iron oxide content of the soil etc. could affect the amounts and the ratios of anions adsorbed. The adsorption was chiefly caused by coulombic attraction, but a covalent force between the anion and the metal atom on the surface of soil particles may also be involved, at least for Cl- ions, even for NO3- ions.

关键词： adsorption chloride nitrate perchlorate variable charge soil

Adsorption of Potassium and Calcium Ions by variable charge soils

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Pedosphere 1992年第3期2卷 255-264页

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

Interactions of potassium and calcium ions with four typical variable charge soils in South China were examined by measuring pK-0.5pCa value with a potassium ion-selective electrode and a calcium ion-selective electrode,and pK value with a potassium ion-selective *** results showed that adsorption of potassium and calcium ions increased with soil suspension pH,and the tendency of the pK-0.5pCa value changing with pH differed with respect to pH range and potassium to calcium *** of equal amount of calcium and potassium ions led to release of an identical number of protons,suggesting similar adsorption characteristics of these two ions when adsorbed by variable charge *** with red soil,latosol and lateritic red soil had higher adsorption selectivities for calcium *** red soil had a greater affinity for potassium ion than that for calcium ion at low concentration,which seems to result from its possession of 2:1 type minerals,such as vermiculite and mica with a high affinity for potassium *** results indicated that adsorption of potassium and calcium ions by the variable charge soils was chiefly caused by the electrostatic attraction between the cations and the soil ***,it was found that sulfate could affect the adsorption by changing soil surface properties and by forming ion-pair.

关键词： adsorption calcium ion ion-selective electrode potassium ion variable charge soil

Effect of Fe/Al Hydroxides on Desorption of K^+ and NH_4^+ from Two soils and Kaolinite

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Pedosphere 2013年第1期23卷 81-87页

作者： WANG Yan-Ping XU Ren-Kou LI Jiu-Yu State Key Laboratory of soil and Sustainable Agriculture Institute of Soil Science Chinese Academy of Sciences University of Chinese Academy of Sciences

Potassium （K） and nitrogen （N） are essential nutrients for plants. Adsorption and desorption in soils affect K＋ and NH4＋ avail- abilities to plants and 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 by neutralization of positive and negative charges. We studied the effect of iron （Fe）/aluminum （Al） hydroxides on desorption of K＋ and NH4＋ from soils and kaolinite and proposed desorption mechanisms based on the overlapping of diffuse layers between negatively charged soils and mineral particles and the positively charged Fe/Al hydroxide particles. Our results indicated that the overlapping of diffuse layers of electricM double layers between positively charged Fe/Al hydroxides, as amorphous Al（OH）3 or Fe（OH）3, and negatively charged surfaces from an Ultisol, an Alfisol, and a kaolinite standard caused the effective negative surface charge density on the soils and kaolinite to become less negative. Thus the adsorption affinity of these negatively charged surfaces for K＋ and NH4＋ declined as a result of the incorporation of the Fe/Al hydroxi- des. Consequently, the release of exchangeable K＋ and NH4＋ from the surfaces of the soils and kaolinite increased with the amount of the Fe/A1 hydroxides added. The greater the positive charge on the surfaces of Fe/Al hydroxides, the stronger was the interactive effect between the hydroxides and soils or kaolinite, and thus the more release of K＋ and NH4＋. A decrease in pH led to increased positive surface charge on the Fe/Al hydroxides and enhanced interactive effects between the hydroxides and soils/kaolinite. As a result, more K＋ and NH4＋ were desorbed from the soils and kaolinite. This study suggests that the interaction between oppositely charged particles of variable charge soils can enhance the mobility of K＋ and NH4＋ in the soils and thus increase their leaching loss.

关键词： amorphous Al(OH)3 amorphous Fe(OH)3 electrical double layer surface charge variable charge soil

Relationship Between Iron Oxides and Surface charge Characteristics in soils

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Pedosphere 1991年第1期1卷 29-39页

作者： SHAOZONG－CHEN WANGWEI－JUN InstituteofsoilScience AcademiaSinicaP.O.Box821Nanjing（China） InstituteofsoilScience AcademiaSinica

The relationship between iron oxides and surface charge characteristics in variable charge soils ( latosol and red earth ) was studied in following three ways. ( 1 ) Remove free iron oxides ( Fed ) and amorphous iron oxides ( Feo ) from the soils with sodium dithionite and acid ammonium oxalate solution respectively. ( 2 ) Add 2% glucose ( on the basis of air-dry soil weight ) to soils and incubate under submerged condition to activate iron oxides, and then the mixtures are dehydrated and air-dried to age iron oxides. ( 3 ) Precipitate various crystalline forms of iron oxides onto kaolinite. The results showed that free iron oxides ( Fed ) were the chief carrier of variable positive charges. Of which crystalline iron oxides ( Fed-Feo ) presented mainly as discrete particles in the soils and could only play a role of the carrier of positive charges, and did little influence on negative charges. Whereas the amorphous iron oxides ( Feo ) , which presented mainly as a coating with a large specific surface area, not only had positive charges, but also blocked the negative charge sites in soils. Submerged incubation activated iron oxides in the soils, and increased the amount of amorphous iron oxides and the degree of activation of iron oxide, which resulted in the increase of positive and negative charges of soils. Dehydration and air-dry aged iron oxides in soils and decreased the amount of amorphous iron oxides and the degree of activation of iron oxide, and also led to the decrease of positive and negative charges. Both the submerged incubation and the dehydration and air-dry had no significant influence on net charges. Precipitation of iron oxides onto kaolinite markedly increased positive charges and decreased negative charges. Amorphous iron oxide having a larger surface area contributed more positive charge sites and blocked more negative charge sites in kaolinite than crystalline goethite.

关键词： amorphous iron oxide degree of activation of iron oxide free iron oxide surface charge variable charge soil