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Surface

By Lorraine Boyd,2014-09-08 17:42
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Surface

    Surface

    ;Pedosphere,Vo1.1,No.3,PP.207217,1991

    ;SurfaceChemicalPropertiesofColloidsinMainSoilsofChina

    ;MAYI-JIEandYUANCHA0-LIANG

    ;InstituteofSoilScience,AcademiaSinica,P.0.Box821,Nanjing210008(China)

    ;(ReceivedNovember30,l990;revisedDecember13,1990)

    ;ABSTRACT

    ;Surfacechemicalpropertiesofsoilcolloidsaretheimportantfactoraffectingsoilfertilityandgenesis.Toprovide

    ;scientificbasisforsoilgeneticclassification,promotionofsoilfertilityandreasonablefertilization,thespecificsur

    ;faceareaandelectricchargeofsoilcolloidsinrelationtoclaymineralsandorganicmatterarefurtherdiscussedon

    ;thebasisoftheresultsobtainedfromthestudiesonsurfacechemicalpropertiesofsoilcolloidsinfivemainsoilsof

    ;China.Resultsfromthestudiesshowthattheefrectofclaymineralsandorganicmatteroilthesurfacechemical

    ;propertiesofsoilcolloidsisverycomplicatedbecausethesiloxanesurface,hy

dratedoxidesurfaceandorganicmatter

    ;surfacedonotexistseparately,buttheyarealwaysmixedtogetherandinfluencedeachother.Theunderstandingof

    ;therelationshipamongclayminerals,organicmatterandsurfacechemicalpropertiesofsoilcolloidsdependsupon

    ;furtherstudyoftherelevantdisciplinesofsoilscience,especiallythestudyonthemechanismsoforgano?mineral

    ;complexes.

    ;KeyWords:electriccharge,soilcolloids,specificsurfacearea,surfacechemicalproperties

    ;Theimportanceofsoilsurfacechemistryinsoilscienceisiustthesameasthat ;biochemistryinbiology(Greenland,1978).Forsoilcolloidspossessasurfacewithvery

    ;largespecificareaandstrongeractivity,thesurfacechemicalpropertiesofsoilcolloidare

    ;theimportantfactoraffectingsoilfertilityandgenesis.Therefore,studyonsurfacechem-

    ;icalpropertiesofsoilcolloidhasbeentheresearchpriorityinthefieldofsoilchemistry.

    ;Inthepresentpaper,thespecificsurfaceandelectricchargeofsoilcoiloidinrelationto

    ;claymineralsandorganicmatterarediscussedonthebasisoftheresultsobtain

edfrom

    ;thestudiesonsurfacechemicalpropertiesofsoilcolloidsinfivesoilsofthemainregions

    ;inChina,soastoprovidescientificbasisforsoilgeneticclassification,promotionofsoil

    ;fertilityandreasonablefertilization.

    ;PRoPERTIESoFSPECIFICSURFACEAREAANDELECTRICCHARG

    EoF

    ;SoILCOLLoIDS

    ;Baverf1972)haspointedoutthatthesoildifferingfromquartzandunweathered

    ;primarymineralsisduechieflytohigherspecificsurfaceareaofsoilcolloidswhichis

    ;closelyrelatedtotheabilityofsoilforretentionandsupplyofnutrientsandwaterre.

    ;quiredbycrops.ItisshownfromthedatainTableIthatthemagnitudeofthespecific

    ;surfaceareaofsoilcolloidsisinconformitywithitscompositionofdominantclaymin.

    ;erals.Relatively,thecolloidofblacksoilisthehighestinspecificsurfaceareaduetoits

    ;

;208Y.J.MAANDC.L.YUAN

    ;highercontentofmontmorilloniteandillite.thatoflatosoliSthelowestduetoitshigher

    ;contentofkaoliniteandiron.aluminumoxides.andthoseofyellowcultivatedloessial

    ;soilandyellowbrowneartharebetweenthetwomentionedaboveduetotheirhigher

    ;contentofmicaceousminerals.Thecolloidofyellowbrownearthishigherinspecificsur-

    ;faceareathanthatofyellowcultivatedloessialsoildueprobablytothehighercontentof

    ;vermiculiteoftheformerthanthatofthelatter.ThecolloidofredearthiSslightlyhigher

    ;inspecificsurfaceareathanthatoflatosolduetoitshighercontentofkaoliniteand

    ;iron-aluminumoxideswithasmallamountofillite.vermiculiteandchlorite. ;TABLEI

    ;Specificsurfaceareaandelectricchargeofsoilcolloidandclayminerals ;Determinedbythemethodsinthereferences(Ma,l98l:Ruo,l958) ;ASshowninTableIthenegativechargesofthecolloidsofthefivesoilsareina ;descendingorderofblacksoil>yellowbrownearth>yellowcultivatedloessialsoil>

    ;redearth>latoso1.Thenegativechargesofsoilcolloidsdominatedby2:llaminated

    ;silicatesarehigher,whilethoseofsoilcolloidsdominatedbyl:llaminatedsilicatesand

    ;lron-aluminumoxidesarerelativelylower.Resultsobtainedbypotentiometrictitration

    ;ofthefivesoilcolloids(Fig.1)haveshownthatthezeropointofcharge(ZPC)ofthefive

    ;soilcolloidsdecreasesfromsouthtonorth.i.e.theZPCofthecolloidofsoilsinsouth

    ;ChinaishigherthanthatinnorthChina.TheZPCoflatoso1.redearth.yellowbrown

    ;earth,yellowcultivatedloessialsoilandblacksoilare4.O0,3.O0,2.35,2.25and2.15

    ;

    ;

    ;

    ;2lO

    ;TABLE?

    ;PositionofZPCofsoilcolloids

    ;Y.J.MAANDC.L.YUAN

    ;Determinedbythemethodsinthereference(VanRaijandPeech,1972)

;RELATIONSHIPBETWEENSURFACECHEMICALPROPERTIESOF

    SOIL

    ;COLLOIDANDCLAYMINERALS

    ;Specificsurfaceareaandelectricchargepropertiesofsoilcolloidsareimportant

    ;characteristicsofsoilcolloids.Resultsofresearchesreportedhaveshownthatnegative

    ;chargeofsoilcolloidsispositivelycorrelatedtoitsspecificsurfacearea(DeKimpeeta1.,

    ;1979).Inpresentpaper,theresultsobtainedareinthesametrend(Fig.2).Boththenega?

    ;tivechargeandspecificsurfaceareaofsoilcolloidarecloselyrelatedtoitsclaymineral

    ;composition.

    ;Thesurfaceofclaymineralsisroughlydistinguishedintotwogroups,i.e.,siloxane

    ;surfaceandhydrMedoxidesurface.SiloxanesurfacerefeFSmainlytothesurfaceof

    ;laminatedsilicates.whilethehydratedoxidesurfacedenotesthesurfacewithactive

    ;groupsofM?OMsuchasthoseofFe,Al,MnandSioxidesandtheirhydratesand

    ;non?laminatedsilicatesincludingallophane,imogolite,etc.(Greenland,1978).Thesur?

    ;faceofthetwotypesofmineralsiscloselyrelatedwiththeirpropertiesofsurfacechem.

    ;istryandbehaviorsoftheirinterfacechemistry.ItcanbeobservedfromFig.3thatthe

    ;specificsurfaceispositivelycorrelatedwith2:1claymineralsincludinghydromica.

    ;/

    ;.

    ;/

    ;0l0203040

    ;Negativecharge(cmolkg’)

    ;Fig.2Re|ationshipbetweenspecificsurfaceareaofsoilcolloidanditsnegativecharge.

    ;

    ;T山】?uEJJ=?I3?ds

    ;

    ;

    ;

    ;2l2Y.J.MAANDC.L.YUAN

    ;faceofthetwosoilsmentionedaboveismuchgreaterthanthatofkaolinite.Jao(

1981)

    ;haspointedoutthatinsometropicalsoils.surfacederivedfromironoxidemayamount

    ;uptO50%Ofthetotalsurfacearea;however,somesoilscontainingthesameamountof

    ;ironoxidecontributelittletosurfacearea.Therefore,forthesoilscontainingironoxide,

    ;theeffectOfthesurfaceactivityofironoxideonitssurfaceareaismoreimportantthan

    ;thatofitsquantity.Basedonthisfact.thehighlyweatheredironoxidesinsoilsarefur-

    ;therdividedintohigh.specific.surfaceironoxidesandlow-specific-surfaceironoxides,

    ;whichareusedasoneofthecriteriafordivisionofsoilspeciesinsoilclassification.The

    ;apparentspecificsurfaceoffreeironoxideinlatosolofChinaisl70mg.thatofred

    ;earthderivedfromQuaternaryredclayisl87mg-1(Zhang.1979).Removaloffreeiron

    ;oxidefromthecolloidalfractionsof>lpmandl

    5pmresultedinreductionoftheir

    ;specificsurfaceareabyabout20%and30%respectively.whichfurtherindica

teS”the

    ;contributionoffreeironoxidetothespecificsurfaceoflatoso1.

    ;o

    ;?

    ;25

    ;l5

    ;10

    ;5

    ;FreeFe203(×10g)

    ;Fig.5CorrelationbetweenthecontentoffreeFe203andtheZPC, ;Chargescarriedbysoilparticlesarebasicallyconcentratedonsoilcolloidalfraction

    ;ofwhichthechargequantityiscloselyrelatedwithclaymineralcompositionofsoil

    ;colloids.Fig.4showsthatthenegativechargequantityofthefivesoilcolloidsispositive-

    ;lycorrelatedwiththecontentOf2:lclaymineralsandnegativelycorrelatedwiththecon.

    ;tentsofkaoliniteandfreeironoxide.TheeffectOffreeironoxideonthepropertiesofthe

    ;chargescarriedbysoilcolloidsisverycomplicated.AccordingtotheworkofZ

hang

    ;(1979),thenetnegativechargesofredearth,lateriticredearthandlatosolincreased

    ;significantlyunderacidconditionafterremovaloffreeironoxide.whichindicatesthat

    ;ironoxidecarriespositivechargeunderisoelectricpoints,andthenegativechargeis

    ;increasdbyremovaloffreeironoxide.ZPCisalsopositivelycorrelatedwithfreeironox.

    ;ide(Fig.5).TheZPCoflatosolinChinaisgenerallylowerthanthatofferralliticsoils.it

    ;isprobablyduetoitshighercontentofkaoliniteandlowercontentofironoxide.Ifthe

    ;distancefromZPCtOZPTisexpressedby

    1,allthecolloidsofthesoilsexceptlatosol

    ;shifttowardtheacidside;itispossiblyduetotheexistenceofpermanentnegativechar.

    ;ges(Espinozaeta1.,l975;Gallezeta1.,l976).ThedistancefromZPCtoZPTofthe

    ;

    ;SURFACECHEMISTRYoFSoILCoLLoIDS

    ;TABLE?

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