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Effects_1

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Effects_1Effect

    Effects

Pedosphere18(5):599610,2008

    ;ISSN1002?-0160/CN32?-1315/P

    ;?2008SoilScienceSocietyofChina

    ;PublishedbyElsevierLimitedandSciencePress

    ;PED0SPHERE

    ;,wwwelseviercom/locate/pedosphere

    ;EffectsofSoilPropertiesonPhosphorusSubsurface

    ;MigrationinSandySoils

    ;ZHANGMingKui

    ;CollegeofNaturalResourceandEnvironmentalSciences,Zh~iangUniversity,HuajiachiCampus,Hangzhou310029

    ;(China).Email:mkzhang@zju.edu.cn

    ;(ReceivedJanuary26,2008;revisedMay20,2008)

    ;ABSTRACT

    ;Thesoilfactorsinfluencingthepotentialmigrationofdissolvedandparticulatephosphorus(P)fromstructurally

    ;weaksandysubsoilswereevaluatedbymeansofsoilcolumnleachingexperiments.Soilcolloidswereextractedfromtwo

    ;typesofsoilstomakethecolloidboundformsofPsolution.Eightsandysoilswithdiverse

    propertieswerecollectedfor

    ;packingsoilcolumns.Theeffe?ctsofinfluentsolutionsvaryinginconcentrationsofcolloids,P,andelectrolyte,onthe

    ;transportofPandqualityofleachateswerecharacterized.Pmigrationinthesoilswansoi1property-dependent.High

    ;soilelectricalconductivityvaluesretardedthemobilityofcolloidsandtransportabilityofcolloid-associatedPfparticulate

    ;P).SoilelectricalconductivitywasnegativelycorrelatedwithcolloidsandreactiveparticulateP(RPP)concentrations

    ;intheleachates,whereas,thetotalreactiveP(TRP)anddissolvedreactiveP(DRP)concentrationsintheleachates

    ;weremainlycontrolledbythePadsorptioncapacityandthePlevelsinthesubsoil.ThereactiveparticulatePinthe

    ;leachateswaspositivelycorrelatedwiththecolloidalconcentration.Increasedcolloidalconcentrationintheinfluentcould

    ;significantlyincreasethecolloidalconcentrationintheleachates.ElevatedPconcentrationintheinfluenthadlittleefFect

    ;onPrecoveryintheleachates.butitresultedinsignificantincreasesintheabsolutePconcentrationintheleachates.

    ;KeyWords:colloidaltype,electricalconductivity,Padsorptioncapacity,Psubsoilmigrati

on,sandysoil

    ;Citation:Zhang,M.K.2008.Effectsofsoilpropertiesonphosphorussubsurfacemigrationinsandysoils.Pedosphere

    ;18(5):599410.

    ;INTR0DUCT10N

    ;Moststudiesdealingwithphosphoruslossesfromsoilstosurfacewaters,concentratedonerosion,

    ;surfacerunoff,andsubsurfacerunoffthroughtiledrainagesystems(Sharpleyeta1.,2000).Leaching

    ;wasmostlyconsideredtobeofminorimportanceexceptwherethesoilswereexcessivelysaturatedwith

    ;P.ThisviewwassupportedbythehighsorptionaffinityofdissolvedPtomanysoilminerals,resulting

    ;instronglyelevatedPconcentrationsinthefertilizedtopsoil.althoughleavingthedeeperlayersofthe

    ;soilprofilenearlyunafiected.Asaconsequence,Pconcent,rationscanbemuchlowerindrainagewaters

    ;thaninthesurfacerunoff.Nevertheless,recentfieldstudieshavesuggestedthatleachingmaya]sobe

    ;importantforPtransferfromsoilstosurfacewatersundercertainconditions,suchassandysoils,soil

    ;highinorganicmatter,andregionswithalongtermhistoryoffertilizerapplications(Cull

    eyeta1.,1983;

    ;Beauchemineta1.,1998).PhosphorusleachingisnowaverywidespreadprobleminsomeCOUntriesin

    ;EuropeandUSA(Culleyeta1.,1983;Beauchemineta1.,1998).Downwardphosphorusmovementin

    ;soilsispresentinbothdissolvedandparticulateforms.ParticulatePincludesPassociatedwithsoil

    ;colloidsandorganicmatter.SomestudieshavereportedadominanceofdissolvedoverparticulateP

    ;forms(Culleyeta1.,1983;JordanandSmith,1985;Heckratheta1.,1995;Stammeta1.,1998;Hoodaet

    ;a1.,1999).Incontrast,someotherstudieshaveshownthatparticulateformsarethedominantfraction

    ;transportedthroughdrainage(Beauchemineta1.,1998;Haygartheta1.,1998;Simardeta1.,2000;

    ;Uusitaloeta1.,20011.Ithasbeenfoundthattheconcent,rationandformsofPtransportcouldvary

    ;“ProjectsupportedbytheNaturalScienceFoundationofZhejiangProvince,China(No.R306011)

    ;

    ;M.K.ZHANG

    ;greatlyindifferentsoils(Hoodaeta1.,1999;Stammeta1.,1998;Simardeta1.,2000).

    ;Recentresearchresultssuggestthatdispersiblecolloidalparticlesinthesolidphasemayalsobe

    ;mobileinsubsurfaceenvironmentsandthustransportsignificantamountsofcontaminants,suchas

    ;phosphorusandheavymetals,togroundwater(HensandMerckx,2001;Hesketheta1.,2001;McGechan

    ;andLewis,2002;deJongeeta1.,2004a’b;Siemenseta1.,2004).Theknowledgeandunderstandingof

    ;thecolloidassociatedcontaminanttransportinporousmediahaveincreasedsubstantiallyoverthelast

    ;decade(SenandKhilar,2006).Thecontaminanttransportcapacityofdispersiblecolloidsenteringthe

    ;aquaticsystemdependsonsolutionchemistryandtoagreaterextent,onthecolloidsphysicochemical

    ;charcteristics(EvangelouandKarathanasis,1991;SetaandKarathanasis,1997;Maeta1.,2005).

    ;Siemenseta1.(2004)reportedthatsubsurfacetransportofdissolvedPcontributedsubstantiallytothe

    ;lossofPfromthesoils,andaccumulationofPinsoilsincreasestheriskofcolloidfacilitate

    dleaching

    ;ofP.Hesketheta1.(2001)suggestedthatcolloidsaregoodsorbentsforpollutants,andsoilsexcessively

    ;fertilizedwithanimalmanurehadahighpotentialforsubsurfacePlossbycolloidalparticles.Djodjic

    ;ea1.(2004)foundthatsubsoilpropertiesseemedtobemoreimportantforPlcachingthanthesoil

    ;testPvalueinthetopsoil.andtheythoughtthatsite-specificfactorsmightserveasindicatorsforP

    ;leachinglosses.However,todate,thewaysinwhichthefactorseffectthedownwardmigrationofP

    ;insubsoilshavestillnotbeencompletelyunderstood.Sandysoil.distributedwidelyintheworld.isa

    ;sensitivesoilforpollutionofenvironments.

    ;ThisstudywasconductedtounderstandthefactorsinfluencingthesubsurfacemigrationofPin

    ;sandysoilswithweaklydevelopedsoilstructure.inwhichPleachinginbothdissolvedandparticulate

    ;formsisaproblem.

    ;MATERIALSANDMETH0DS

    ;Soilcolumnpreparation

    ;Eightsandysoils(S1

    S8)weresampledfromthe20-40cmlayerofcultivatedcitrusandvegetable ;soilsineightdifferentlocationsofSt.LucieandMartincounties,Florida,wherethepotentialrelease

    ;ofsoilcolloidsintogroundwaterhasattractedconsiderableattentionbecauseoftheirassociationwith

    ;Pandheavymetals(Zhangeta1.,2003).Thestructureofthosesandysoilswasveryweaklydeveloped

    ;becauseofverylowclayinthesoils,therefore,theauthorusedhomogeneouslypackedsoilcolumnsfor

    ;theexperiment.Eachcolumnwaspreparedinthelaboratoryusingplexiglassleachingcolumns(33cm

    ;long,witha7.5

    cminnerdiameter).Thebottomofthecolumnwasmadeofaplexiglassplatewith ;severalholes,witha5

    mmdiameter.Thetopoftheplatewascoveredwithanylonmeshandgluedto

    ;thebottomofthecolumn.Soilsamplesfrom20-40cmsoildepthwerepackedincolumnstoadepth

    ;of20cm.Soilwaspackedintocolumnsbyconsistentlytappingthetopofthecolumn,evenasthesoil

    ;Wasslowlypouredin.Thecolumnswerepackedsuchthattheresultingbulkdensitieswerethesameas

    ;foundinthefield.SelectedphysicochemicalpropertiesofthesoilsarepresentedinTableI. ;Colloidseparation

    ;,?

    ater-dispersiblecolloidswerelsolatedfromthesubsurfaceoftwosoils:S1fNettlessand:sandy,

    ;siliceous,hyperthermic,ortsteinalficarenichaplaquods)andS8(Rivierasand:sandysiliceous,hyper-

    ;thermic,arenicglossaqualfs).Theextractionofthewaterdispersiblecolloidsf<2m)wasobtainedby

    ;sedimentationandsiphoning,aftermixing80gofsoilwith800

    mLdeionizedwaterinplasticbottles,

    ;andshakenovernight.Theconcentrationofthecolloidswasdeterminedgravimetrically,anddilutedto

    ;2000mgL

    asastocksuspensionthatcontained0.001%ofCHC13tosuppressthemicrobialactiv

    ;ity.ChemicalpropertiesofthecolloidalstocksuspensionareshowninTableII.PHvalueofRiviera

    ;colloidswashigherthanthatofNettlescolloids.TheECvalueofRivieracolloidswasgreaterthan

    ;thatofNettlescolloids.Thedissolvedcationsinthecolloidalsuspensionsweremainlydivalent,andthe

    ;proportionofthedissolvedcationsinthedivalentwasgreaterintheRivieracolloids(84%1thaninthe

    ;

    ;PSUBSURFACEMIGRATIONINSANDYSOILS

    ;TABLEI

    ;Selectedphysico-chemicalpropertiesofthesoilspackedintocolumnsusedintheleachingexperiments

    ;60l

    ;)Nettlessand:sand~siliceous

    ;,hyperthermic,ortsteinalficarenichaplaquods;Wabassosand:sandy,siliceous,hyperthe

    ;rmicalficalaqods;Windervariantsand:sand~siliceous,hyperthermictypicglossaqualfs;Rivierasand:sandysiliceous

    ;,

    ;hyperthermic,axenicglossaqualfs.

    ;b)Electricalconductivity.

    ;)Maximumadsorptionofphosphorus.

    ;TABLEII

    ;Chemicalpropertiesofthewaterdispersiblecolloidalstocksuspensionsusedasinfluentsintheleachingexperiments

    ;)Electricalconductivity

    ;b)Tota1reactiveP.

    ;c)DissolvedreactiveP.

    ;Nettlescolloids(56%).Thestabilityofcolloids,characterizedbythepercentageofcolloidalconcen

    ;trationremaininginthesuspensionasafunctionoftime,atadepthof5cmina200

    mLbottle,was

    ;significantlyhigherinNettlessoilthaninRivierasoil(Fig.1),becauseofthehigherECvalueandthe

    ;higherproportionofthedivalentcationsinthetotaldissolvedcationsoftheRivieracolloidsthanthose

    ;1OO

    ;8O

    ;6O

    ;2O

    ;O

    ;0501O015O200

    ;Settingtime(h)

    ;Fig.1Settlingratesofwater.disperslecolloidsfromRivieraandNettlessoils ;一一co?LJQ??

    ;LJLJLJE.1Do=o

    ;

    ;602M.K.ZHANG

    ;intheNettlescolloids.ClaymineralsintheNettlessoilincludedillite,montmorillonite,andkaolinite,

    ;andthoseintheRivierasoilincludedilliteandkaolinite.

    ;Leachingexperiment

    ;Twofilterarticles(Whatman2)wereplacedonthetopofthesoilcolumntopreventthedisturbance

    ;bywaterdropletsduringleaching.Priortosettinguptheleachingexperiment,thesoilcolumnswere

    ;saturatedfromthebottomupwardwithdeionizedwatertoremovetheairpockets.Thenthecolumns

    ;weresetupinthestandsfor2daysatroomtemperature.Atotalof3-3.5porevolumesofdifferent

    ;influentswereappliedtoeachsoilcolumn.About0.33porevolumeofinfluentswasappliedonadaily

    ;basisandrepeatedfor9-10daysatarateof5mLmin

    1.Thisapplicationratedidnotallowany

    ;pondingonthetopofthecolumn.

    ;Priortouse,aseriesofinfluentsolutionswerepreparedfordifferentleachingexperiments,bydiluting

    ;thecolloidalstocksuspensionswithdeionizedwatertoobtainthedesiredconcentrationofcolloidsand

    ;spikingitwithP(intheformofKH2PO4)andCaC12.Intotal,fourleachingexperimentsbyapplying

    ;differentinfluentsolutionswerecarriedout.Forexperimentsonthecolloidal-typeeffectsonPleaching,

    ;fourinfluentsolutionsincludingdeionizedwater,5mgPL_.,5mgPL

    +Riviera’scolloids,and5

    ;mgPL

    +Nettles’scolloidswereused.andtheconcentrationofcolloidsinallinfluentsolutionswas

    ;500mgL1.

    ;ForanexperimentoncolloidalconcentrationeffectsonPleaching,5mgPLsolutions

    ;withthreeconcentrationgradientsofRiviera’scolloidsorNettles’scolloids(300,500,and1

    000mgL)

    ;wereusedasinfluents.ForanexperimentonPconcentrationeffectsonPleaching,threedifferentP

    ;concentrationsolutions(1,5,andi0mgL),accompaniedwith500mgL_.Rivieracolloids,wereused

    ;asinfluents.ForexperimentsonelectrolyteconcentrationeffectsonPleaching,5mgPL

    solutions

    ;withfourgradientsofCaC12concentrations(0,0.001,0.005,and0.01molL)wereusedasinfluents.

    ;Priortoeach1eachingexperimentinfluentsolutionswerestoredforonedayandanalyzedfortota1

    ;reactivephosphorus(TRP)anddissolvedreactivephosphorus(DRP).Theleachateswerecollectedin

    ;1000

    mLbeakersbelowthesoi1columnsandtransferredintopolyethylenebottlesforanalysis.AU ;leachingexperimentswererunintriplicate.

    ;Analysisofleachates,soil,andcolloidproperties

    ;Filteredf0.45ttm1andunfilteredleachatesampleswereanalyzedformolybdatereactiveP(

Kuo,

    ;19961.MolybdatereactivePinfiltered(0.45m)andunfilteredleachatesampleswasreferredtoas

    ;dissolvedreactiveP(DRP)andtota1reactiveP(TRP),respectively.ParticulatereactiveP(PRP)

    ;wascalculatedbythedifierencebetweenTRPandDRP.Theconcentrationofcolloidsintheleachates

    ;wasdeterminedbymeasuringtheturbidityofthesuspensionswithaturbiditymeter(DRT100B,HF

    ;ScientificInc.,FortMyers,FL,USA)andconvertingittomilligramsperliterofcolloids,accordingtoa

    ;standardcurveofthecolloids.RatiosofTRPandDRPconcentrationsofemuent(1eachate)toinfluent

    ;concentration(C/)werealsocalculated.

    ;Soi1PHandelectrica1conductivity(EC)weremeasuredusinganAccumetMode150pH/ion/conducti

    ;vitymeterinthesupernatantatsoil:waterratioof1:1and1:2,respectively.Siltandclaycontentswere

    ;evaluatedbythemicropipettemethodafterbeingpretreatedwithH202anddispersedovernightin

    ;NaOHfMillerandMiller,1987).CaCO3contentwasdeterminedbyback-titratinganexcessof0.5

    ;mo1L

    1HC1addedto1gofsoi1samplewith0.5mo1LNaOH(AllisonandMoodie,1965).Soi1 ;amorphousFewasextractedbyacidammoniumoxalateandmeasuredusinganinductivelycoupled

    ;plasmaatomicemissionspectrometer(ICPAES,Ultima,JYHoribaInc.Edison,NJ)(M

    ckeagueand

    ;Day,1966).0lsenPandMehlich1-Pofthesoilswereextractedby0.5mo1L_.NaHCO3andMehlichI

    ;solution(0.05mo1L

    HC1+0.0125mo1LH2SO4),respectively,anddeterminedbytheascorbicacid ;method(Kuo,1996).Hydraulicconductivitywasestimatedbyadding10amofwatertowater-saturated

    ;soilinthecolumn,withfourreplicates.Maximumadsorptionofphosphorus(Qm)wasdeterminedbythe

    ;

    ;PSUBSURFACEMIG;RATIONINSANDYSOILS603

    ;Langmuirisotherm,basedonthefollowingequation:Q=KCQm/(1+KC),whereQistheamountof

    ;Padsorbed,Cistheequilibriumconcentration,andKisaconstantrelatedtothePbindingstrength.

    ;Electrica1conductivityfEC)andpHofthewaterdispersiblecolloida1stocksuspension

    sweredeter

    ;minedusingthepH/ion/conductivitymeter.Wlaterdissolvedcationsandtota1Feinthe1eachateswere

    ;determinedusingtheICPAES.

    ;Austatistica1analysiswascarriedoutusingSASsoftware,release6.12(SASInstitute,1994).The

    ;significantdifferencesintheconcentrationsofcolloids,tota1reactiveP(TRP),dissolvedreactiveP

    ;fDRP),andreactiveparticulateP(RPP)elutedfromsoi1columnsamongdifferenttreatmentswere

    ;analyzedstatisticallybythegeneral1inearmode1(GLM)procedure.Correlationsbetweenthesoi1prop

    ;ertiesandmeanconcentrationsofcolloids,TRP,DRP,andRPP,meanandstandarddeviationof

    ;concentrationsofcolloids,TRP,DRP,andRPPwereperformedbytheregressionprocedureofSAS.

    ;RESUrSANDDISCUSS10N

    ;Effectofcolloidaltypesandsoilproperties

    ;Afterthreeporevolumesofleaching,theaverageTRP,DRP,andRPPconcentrationsinthe ;leachatesrangedfrom0.0052to8.67,0.0005to7.70,and0.0042to1.91mgL_.,respectively,de

    ;pendingonthecolloidaltypesintheinfluentsandsoiltypes(TableIII).Colloidsgeneratedfromthe

    ;NettlessandhadsignificantlyhighertransportabnitythanthosefromtheRivierasand. ;TABLEIII

    ;Meanconcentrationsofcolloids,totalreactiveP(TRP),dissolvedreactiveP(DRP),andreactiveparticulateP(RPP)

    ;elutedfromsoilcolumns(S1s8)

    ;a)I:deionizedwater;II:5mgPL:III:5mgPL+Riviera’Scolloid;IV:5mgPL

    +Nettles’Scolloid.Concentration

    ;ofcolloidininfluentwas500mgL.

    ;)Meanvaluesfollowedbythesameletter(s)withinacolumn,foreachPformorcolloid,arenotdifferentatP=0.05by

    ;Fisher’Sprotectedleastsignificantdifference.

    ;Totalreactivephosphorusconcentrationinleachatesforallcolumnsshowedrapidchangeandreached

    ;arelativeconstantatoneofporevolume(Fig.2).However,TRPinleachatesvariedwithsoilcolumns

    ;

    ;604M.K.ZHANG

    ;andinfluentcomponents.ForS8.aUtheinfluentscontainedsimilarandverylowTRPconcentration

    ;in1eachates.andnoobviousdifierenceinleachateTRPconcentrationwasfoundamongthefourkinds

    ;ofinfluents.ForS2.1eachateTRPconcentrationsincreasedintheorderoftreatmentswithd

eionized

    ;water,5mgPL+Riviera’scolloids,5mgPL,and5mgPL+Nettles’scolloids.Compared

    ;withtreatmentof5mgPL.using5mgPL+Riviera’scolloidsasinfluentsobviouslydecreased

    ;theTRPconcentrationsintheleachates,whereas,using5mgPL+Nettlescolloidsasinfluents ;increasedtheTRPconcentrationintheleachates.ForS6.additionofPfl.ominfluents.inclu

    ding5mg

    ;PLl,5mgPL+Riviera’scolloids,and5mgPL+Nettles’scolloids,significantlyincreasedthe ;TRPconcentrationinthe1eachates,andtheTRPconcentrationsinleachatesfortreatments

    with5mg

    ;PL—lRiviera’scolloidsand5mgPL一上

    Nettles’scolloidswerelowerthanthosefortreatments

    ;with5mgPL?

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