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1 : Muhammad Iqbal To cite this version: Muhammad Iqbal. :. Agricultural sciences. AgroParisTech, English. <NNT : 2012AGPT0020>. <pastel > HAL Id: pastel Submitted on 10 Apr 2013 HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research ititutio in France or abroad, or from public or private research centers. L archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d eeignement et de recherche français ou étrangers, des laboratoires publics ou privés.

2 N :2009ENAMXXXX DoctoratParisTech THÈSE pourobtenirlegradededocteurdélivrépar L ItitutdesSciencesetIndustries duvivantetdel Environnement (AgroParisTech) Spécialité: Sciencedel environnement présentéeetsoutenuepubliquementpar MuhammadIQBAL le16mars2012 Impactdel occupationdessolsagricolescontaminéssurladisponibilitédes élémentstrace:miseenévidencedurôledesmatièresorganiquesdale casdeculturesannuellesetculturespérennesàvocationénergétique Jury: M.AlainBERMOND Professeur,AgroParisTech,Paris Président MmeLaurenceDENAIX DirecteurdeRechercheINRA,Bordeaux Rapporteur M.FrancisDOUAY EeignantChercheur,GroupeISA,Lille Rapporteur M.JeanMARTINS ChargédeRecherche,CNRS,Grenoble Examinateur M.ChristopheSCHWARTZ Professeur,UniversitédeLorraine,Nancy Examinateur MmeIsabelleLAMY DirecteurdeRechercheINRA,Versailles DirecteurdeThèse INRAUR251 PESSAC,PhysicochimieetEcotoxicologiedesSolSd'AgrosystèmesContaminés BâtimentdeScienceduSolRD VersaillesCedex,France

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4 Acknowledgements Thisdissertationwouldnothavebeenpossiblewithouttheguidanceandthehelpofseveral individualswhoinonewayoranothercontributedandextendedtheirvaluableassistancein thepreparationandcompletionofthisstudy. The grant for my research work and my stay in France were financed by the Higher EducationCommission(HEC),GovernmentofPakistan.Iwouldliketoextendmythanksto HECinthisregard. Aboveall,IamdeeplygratefultomysupervisorMmeIsabelleLAMYforprovidingmean opportunitytoworkwithher.ifindithardtoimaginethatanyonecouldbeamoresincere, kindandbetterresearchadvisorthanwhatshehasbeen.isabelle,yourthoroughanalysisof myworkandrigorouscritiquenotonlyimprovedmyoverallunderstandingofthesubject butalsothequalityofthisdissertation.yourenthusiasmtowardsscienceandyourpursuitto do goodscience helpedtoshapemyowcientificvalue.thankyouforlisteningmewith patienceandprovidingmewithvaluablesuggestiowhenevericametoyourofficewith myproblems.iwillneverforgetthemomentswepassedtogtherduringdifferentjourneys whichwehadtogetherduringthesethreeyearsfromplacedecomédieofmontpellierto RiverDanubeofViennaandfromfieldsofPierrelayetothesiteofMetaleurop.Iamreally proudofbeingyourstudent. IwouldliketoextendmysincerethankstoMmeLaurenceDENAIX,DirecteurdeRecherche INRA,Mr.FrancisDOUAY,EeignantChercheurGroupeISA,Mr.JeanMARTINS,Chargéde RerchercheCNRS,Mr.ChristopheSCHWARTZ,ProfesseurENSAIA,andMr.AlainBERMOND, ProfesseurAgroParisTechforacceptingtoevaluatemythesiswork. IwouldliketorecordmygratitudeforMr.AlainBERMONDwhoasmycorresponding ProfessoratAgroParisTechhasalwaysbeenkind,andgivencotructiveadvicestocomplete mythesisprojectsuccessfully.thanksalainforyournicesuggestioandhelpfrommy Mastertillthecompletionofthisthesis. Iferventlyextendmyzealousthankstothemembersofmythesiscommittee,Mr.Guillaume MORIN,IMPMCUPMC,MmeAnnetteDEVAUFLEURY,UniversitédeFrancheComtéand MmeChristellePRUVOT,ISAdeLillefortheircotructivecomments,scientificremarksand scholasticguidancewhichhelpedmetocotructandrunthisthesisworkwithgoodquality. IntheseyearsIhavealsobenefitedalotfromtheexteiveknowledgeandmanagerial experienceofourheadofthepessacunit,dr.christianmougin.hehasalwaysbeeo welcomingandsmilingalways.thankyousomuchchristanforyourhelpandguidancein

5 solvingmymanagerialproblemsduringtheseyearsandforgivingmeaccesstoallfacilities attheunit. ImustacknowledgeandappreciatethesuggestioIhadfromallthescientificstaffof PESSACespeciallyfromFokvanOortandMikaëlHeddeduringallthelabmeetingsoraround theworkingtablesofthelaboratoriesofgroundflooraswellasbasmentofpessac. This work would have never been accomplished without the technical help of all the technicalstaffofunitpessac.theyallhavebeeoniceandhelpingallthetimes.ispecially acknowledgethepersoofoffice106.thanksjeanpierreforhelpingmerightfrommy masterstotheendofphd.iwillrememberthejoywhichwehadtogetherwhilediningat Pakistani and Japanese restaurants of Paris...Thanks for always explaining me French lifestyleandtraditioandgivingthedetailsofflashnewswhichwehadatradiowhile workingaroundthetableinthegrandlaboratory.améliewithoutyourhelpiwouldnever hadtheresultsfromatomicabsorptiopectrophotometertotraformthemintowords forthisthesis.youwasalwayssocooperativeandsmilingevenificametoyoutentimesa daywiththeproblemswiththisapparatus.ialwayslikedyourremarkswheniusedtowork inlaborinofficeandyoualwayscametomewhilepassingbycorridors.thanksforyour throughouthelp.withthehelpofsebastienihavebeenabletocompletemysample preparationandsoilphysicalfractionationwork.thanksalotsebastienforalwaysbeing helpfulandsupportinginmylongexperiments. Specialthankstoplateaudebio,NathalieandChristelle,fortheirhelpinmyworkduringmy bioexperimentsandgivingmeaccesstotheitallatioofthebasementlabsofpessac. ThanksNathalieforyourcooperation,youhavealwaysbeenavailabletohelpevenifyou arealwaysbusyinexperiments.ialwayslikedthemuchnicecakesanddishesyoumade duringthepartiesoftheunit. IamthankfultoAnneJaulinforherhelpregardingatomicabsorptiopectrophotometer andhercommentsduringlabmeetings,jeannechantalforherguidanceregardingstats, NicoleandMehdiforsolvingmyproblemsrelatedtocomputerandsoftware,andAnitaand Célineforalwayshelpingmeinadministrativeworkswithsmilingfaces. Iamimpressedandwillneverforgetthefriendlyenvironmentandworkingrelatiohipsof thewholepessacteam.theyallhavebeeocuriousnotonlytoaskmeaboutmystudies butalsoaboutsituationofmyfamilybackinpakistan.becauseofthisfriendlyenvironmenti neverfeltthatiamawayfrommyfamilyandthesefouryearspassedjustlikeitwasashort moment.iamreallythankfultoallofthem. IamreallygreatefultothenonpermanentmembersofPESSACteamwithwhomIshared eithermyofficeorworkingplaceofthelaboratories.thankstomypresentofficefellows

6 Benjamin,Léa,SylvainandKevin.Theyallhavebeeoniceandalwayssupportedme especiallyinthisdifficulttimeofthesiswriting.thankstomalika,jeremie,cindy,olivier, Ashref,Shaharm,Stéphanie,Flavie,Fatima,SouadandallotherstudentswithwhomeI workedduringthistimeofthesis. Truegreatfriendsarehardtofind,difficulttoleaveandimpossibletoforget.Iamluckyto havefriendswhosecareandcooperationisverypreciousforme.pierre,iwillalways rememberyournicecompany,careandguidanceineverypersonal,workorfrenchlanguage matter.ienjoyedalottheparisianculturallifewithyouandnadler.cordailthankstoyou bothforhelpingmeespecilallyinmymasterstudies.pierre,iwillespeciallynotforgetmy stayinalsacewithyourfamilyinthecoldchillingweatherofdecemberandtheirmuchnice hospitality.iwishicouldhostyouallonceinpakistan. AspecialthankstomyfriendsKhalid,Ulfat,Rizwan,UmarFarooq,Ahmad,Tahir,Sarfraz, Moeez,ImranandallotherfriendsinFranceforallthememorablemomentsthatwehad sharedtogetherandmademystayinfranceunforgettable. Motto I really lack the words to say you what I want..without your help, support, encouragementandfriendshipiwouldneverhadcompletedthiswork.andneverbeat placewhereiamnow.iseeyoubehindeachwordofthisthesis.shukria. Noacknowledgementscouldeveradequatelyexpressmyfeelingsformyaffectionateand adoringfamily.theyallowedmetocontinuemystudyabroadandgivenmethestrength andcouragetofacetheproblemsoflife.iwillespeciallyacknowledgemysweetgandisister manowhoalwaysremainprayingforme.yehalagbaathakshadikbaadthoribemukhho gaiha...butiamtheoneforwhomshepraysthemostandtakescareof In the end I heartily acknowledge and extend thanks to those whose names are not mentionnedherebuttheycontributedtocompletethiswork... MuhammadIQBAL

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8 Abstract Thechangesinlanduseofagriculturalsoilsaresusceptibletomodifyqualityandquantityof soilorganicmatter.soilorganicmatterisknowntohavearoleoftrophicresourceforsoil organismsaswellastheroleofligandfortracemetalsincontaminatedsoils.changesinthe organicmatterqualityandquantityioilscanleadtowardsmodificationoftracemetal speciationioils.buttheroleofsoilorganicmatterinthedeterminismoftracemetal availabilitiesincontaminatedsoilsisnotwelldocumented.theobjectiveofthethesiswork wastoassesstheroleofsoilorganicmatterindeterminismoftracemetalavailabilitiesin contaminated agricultural soils under annual crop and under perennial energy crop miscanthus.astrategyofstudyingcu,pb,znandcdavailabilitiesoftwositesdifferinginthe soiltextureandoriginofpollutionwasadoptedi.e.thesiteofmetaleurop(northoffrance) withsiltloamsoilscontaminatedbyatmosphericmetalfalloutandthesiteofpierrelaye (ParisRegion)withsandysoilscontaminatedthroughlongtermuntreatedwastewaterinput fromcityofparis.roleoforganicmatterintracemetalavailabilitywasassessedthrough studying;1)thesoilsunderwithtwodifferentlandusesi.e.underannualcropandunder perennial energy crop miscanthus, 2) the soil samples before and after soil organic mineralizationthroughinvitrosoilincubatio,3)thesoilsampleswithandwithoutthe particulateorganicmatter(pom)fractioi.e.themostlabileorganicmatterfractioin ordertohighlightthespecificroleofthisorganicmatterfraction.acombinedapproachof metalavailabilityassessmentthroughchemicalmetalextractioandofstudyingmetal localization in different soil size fractio was used. The results of the trace metal availabilitiesofthesoilundermiscanthuscomparedtoannualcropsoilshowedthatthe influenceofchangesinorganicmatterthroughlandusewasdifferentatbothsites.forthe Metaleurop site, the availability of Cu and Pb which are the metals known to be preferentiallyboundtoorganicmatterwasdecreasedwithanincreaseintheirlocalizationin soilfinerfractio.nochangeintheavailabilityandlocalizationofznandcdwasobserved for this site. Contrarily, in the Pierrelaye site with organic matter rich sandy soils the availabilityofmetalswhichareknowntobeboundtosoilmineralphasesi.e.znandcdwas changedwithoutachangeintheirlocalizationwhilenochangewasobservedforcuandpb. Theresultsofsoilincubatiotudyrevealedthattheeffectofsoilorganicmineralizationon tracemetalavailabilitywassitedependentforpbandcdwhileeffectoncuandznwas similarinallsoilswhateverthesite.ourworkonthemetalenrichedparticulateorganic matterfractioshowedthatpombeingafreeorganicmatterfractionparticipatedinthe metalavailabilityandthatthepomassociatedcopperwasbioavailableforanorganismin our conditio. These results concerning the trace metal availabilities in the soils with varyingnatureandquantityoforganicmatterarediscussed. Keywords:Tracemetals,Cu,Pb,Zn,Cd,availability,contaminatedagriculturalsoils,organic matter,chemicalextraction,granulometricfractionation,pom

9 Tableofcontents INTRODUCTION...13 Aimsofthethesisresearch Chapter1:Literaturereview Tracemetalsandagriculturalsoils Factorsaffectingfateoftracemetalsinthesoils Soilorganicmatterasalabilesoilcotituent Bioavailabilityoftracemetalsconceptsanddefinitio Methodsoftracemetalavailabilityassessment PotentialofTrametesversicolorasabiomarkeroftracemetalavailabilityassessment 48 Chapter2:Materialandmethods Choiceofsitesandsituatio Choiceofmethods Chapter3:Impactoflanduseontracemetalavailabilitiesincontaminated agriculturalsoils Introduction Results: Influenceoflanduseontracemetalavailabilities a b c d. EDTAextractablemetalcontentsatequilibrium DTPAextractablemetalcontentsatequilibrium NH4NO3extractablemetalcontentsatequilibrium Kineticallydefinedlabileandslowlylabilemetalfractioandtheir associatedextractionratecotants a b. Influenceoflandusesontracemetallocalizationinphysicalsizefractio: Massdistributionofthesoilsinthephysicalsizefractio Distributionoforganiccarbonandtracemetalcontentsinthephysicalsize fractioofthesoils Relatiobetweeoilmetalavailabilitiesandsoilmetallocalization Discussion: Studyofsoiltracemetalavailabilitiesbythemetalextractionatequilibriumand kineticmetalextractio Effectoflanduseontracemetalavailabilitiesandmetallocalizationinphysical fractio Relatiobetweentracemetalavailabilitiesandmetallocalization Conclusion:

10 Chapter4:Soilorganicmatterasamainparameterinvolvedinchangesin tracemetalavailabilitiesofcontaminatedagriculturalsoils Introduction Resultsanddiscussion: Effectofsoilincubationooilorganicmatterandselectedsoilchemicalproperties a. Mineralizationofsoilorganicmatterduringincubation b c d a b. Effectofsoilincubationooilproperties EffectofsoilincubationonWatersolubleorganiccarboncontents EffectofsoilincubationopecificUVabsorbanceat420nm(SUVA420) Influenceofsoilincubationonavailabilityofthetracemetals thesoils c. EDTAextractablemetalcontents DTPAextractableandNH NO extractable(exchangeable)metalcontentsin Labileandslowlylabilemetalpoolsandtheirextractionratescotants Changesinmass,organiccarbonandtracemetallocalizationindifferentsize fractioduringincubation a b c. Massdistributionindifferentsizefractioofthesoils Tracemetalsdistributionindifferentsizefractioofthesoils Distributionoftotalorganiccarboncontentsintodifferentphysicalsize fractioofthesoils Relatiohipsamongtracemetalavailability,metallocalizationandorganiccarbon distributioninphysicalsizefractio Metaleurop Pierrelaye Conclusion Chapter5:Roleofparticulateorganicmatter(POM)fractiointhetrace metalavailabilityioils Introduction ResultsandDiscussion Effectofsoilincubationonparticulateorganicmatterfractioofthecontaminated soilsamples a b. Quantityofparticulateorganicmatter(POM)fractiointhesoils Effectofsoilincubationonmetalenrichmentfactorsofparticulateorganic matterfractio ComparisonoftracemetalavailabilityoftheannualcropsoilswithPOMfractio andwithoutpomfractio a. Contributionofparticulateorganicmatterassociatedmetalstototalsoil metalcontentsoftheannualcropsoilsofbothsites

11 b c. EDTAextractablecontentsatequilibrium: Labileandslowlylabilemetalpoolsandtheirextractionratescotants BioavailabilityofcoppertothefilamentousfungiTrametesversicolorinaliquid medium:comparisonofcuaddedintheformofsolutionandcopperlinkedtosoil particulateorganicmatter a b c d. Evolutionofthefungalbiomassdevelopment EvolutionofpHintheliquidmediums Evolutionofthecoppercontentsofliquidculturemediums Evolutionofthelaccaseactivitiesintheliquidmediums: Conclusion GENERALCONCLUSION LITERATURECITED

12 ListofFigures Figure1.1:Majorinputfluxesoftracemetalsintoagriculturalsoils Figure1.2:EstimationofannualinputoftracemetalsintoagriculturalsoilsofFrancewith theirprinciplesources.(valuestakenfromsorgreahademe,2007) Figure1.3:Bioavailabilityprocessesofsoiltracemetalpartitioningbetweeoilsolidand solutionphasesincludingspeciationioilsolutionanhowtheycanbeinfluencedby soilpropertiesandenvironmentalconditio.(reproducedfromhooda,2011) Figure1.4:TracemetalbioavailabilityinthesoilsasdescribedbynormeISO17402(ISO, 2008) Figure1.5:Timemetalextractionexperimentalcurve(Right)andacurveobtainedbydata modeling(left)bytwofirstorderreactionmodel Figure2.1:MapofexperimentalsiteMetaleurop Figure2.2:MapofexperimentalsitePierrelaye Figure2.3:Schematicdiagramofvariousstepsoftracemetalextraction Figure2.4:Schematicdiagramofvariousstepsofphysicalfractionationofsoils Figure2.5: SchematicdiagramofvariousstepsofCO2measurementduringsoilincubation andmaintenanceofsoilmicrocosms Figure2.6:Schematicdiagramofvariousstepsofsolubleorganiccarbonextraction Figure 2.7a: Schematic diagram of various steps followed to prepare soil samples with particulateorganicmatter Figure2.7b:Schematicdiagramofvariousstepsfollowedtopreparesoilsampleswithout particulateorganicmatter Figure2.8:Schematicdiagramofthebiotestforstudyingtracemetalavailabilitybyusing fungalcultures Figure3.1:NH NO extractablemetalcontentsofthesoilsbeforeandaftersoilincubation. 4 3 Bar graphs represent mean values of 3 replicates while the error bars represent standard deviation among these replicates. Different letters indicate statistically significantdifference(tukey stest,p<0.01)ofmetalextractabilitybetweenannualcrop andmiscanthussoilforeachsite Figure3.2:Percentagesoflabilemetalfraction(Q ),slowlylabilemetalfraction(q )ofthe 1 2 soilsamplesofpierrelaye.bargraphsrepresentmeanvaluesof5replicateswhilethe 4

13 error bars represent standard deviation among these replicates. Different letters indicatestatisticallysignificantdifference(tukey stest,p<0.01)betweenannualcrop andmiscanthussoilforeachfraction Figure3.3:Distributionofthesoilmassintodifferentphysicalsizefractioofthesoilsof Metaleurop(a)andPierrelaye(b).Bargraphsrepresentmeanvaluesof3replicates whiletheerrorbarsrepresentstandarddeviationamongthesereplicates.statistically significantdifference(tukey stest,p<0.05)betweenannualcropandmiscanthussoil foragivenfractionisshowedbydifferentletterswhile representnoignificant differences Figure3.4:Distributionofthesoiltracemetalandorganiccarboncontentsintodifferentsize fractio of the soils of Metaleurop site. Curves represent the organic carbon distributionindifferentfractio.bargraphsrepresentmeanvaluesof3replicatesfor metal distribution while the error bars represent standard deviation among these replicates.statisticallysignificantdifference(tukey stest,p<0.05)ofmetaldistribution betweenannualcropandmiscanthussoilforagivenfractionisshowedbydifferent letterswhile representnoignificantdifferences.fororganiccarbondistribution thestatisticallysignificantdifferenceisshownbythesign(*) Figure3.5:Distributionofthesoiltracemetalandorganiccarboncontentsintodifferentsize fractioofthesoilsofpierrelayesite.bargraphsrepresentmeanvaluesof3replicates for metal distribution while curves present the organic carbon distribution these fractio. The error bars represent standard deviation among these replicates. Statisticallysignificantdifference(Tukey stest,p<0.05)betweenannualcropand miscanthussoilforagivenfractionisshoweddifferentletterswhile representnon significantdifferences Figure4.1:Evolutioninthemineralizationoforganicmatterofthesoilswiththetimeof incubation(expressedaspercentageofinitialsoilorganiccarboncontents).curves represent mean values of three replicates while error bars represent standard deviatio Figure4.2:Watersolubleorganiccarboncontents(a)andSUVA (b)ofthesoilsamples before and after soil incubation. Data is presented on soil dry weight basis. The statistically significantdifference (Tukey s test, p < 0.01) for watersoluble organic carboncontentsandsuva ofeachsoilbeforeandafterincubationispresentedby 420 differentletters Figure4.3:EDTAextractablemetalcontents(atequilibrium)ofthesoilsbeforeandafter incubation. Bar graphs represent mean values of 5 replicates while the error bars representstandarddeviationamongthesereplicates.statisticallysignificantdifference 420 5

14 (Tukey stest,p<0.01)forthemetalcontentsforeachsoilbeforeandafterincubationis representedbydifferentletterswhile representnoignificantdifferences Figure4.4:DTPAextractablemetalcontentsofthesoilsbeforeandaftersoilincubation.Bar graphsrepresentmeanvaluesof3replicateswhiletheerrorbarsrepresentstandard deviationamongthesereplicates.statisticallysignificantdifference(tukey stest,p< 0.01) for extractable metal contents for each soil before and after incubation is representedbydifferentletterswhile representnoignificantdifferences Figure4.5:NH NO extractablemetalcontentsofthesoilsbeforeandaftersoilincubation. 4 3 Bar graphs represent mean values of 3 replicates while the error bars represent standarddeviationamongthesereplicates.statisticallysignificantdifference(tukey s test,p<0.01)forextractablemetalcontentsforeachsoilbeforeandafterincubationis representedbydifferentletterswhile representnoignificantdifferences Figure4.6:Labilemetalfraction(Q )andslowlylabilemetalfraction(q )ofthesoilsamples 1 2 beforeandafterincubation.bargraphsrepresentmeanvaluesof5replicateswhilethe errorbarsrepresentstandarddeviationamongthesereplicates.statisticallysignificant difference(tukey stest,p<0.01)forthemetalcontentsforeachsoilbeforeandafter incubation is represented by different letters while represent non significant differences Figure4.7:Distributionofthesoilmassintodifferentphysicalsizefractioofthesoilsof Metaleuropsitebeforeandafterincubation.Bargraphsrepresentmeanvaluesof3 replicateswhiletheerrorbarsrepresentstandarddeviationamongthesereplicates. Statisticallysignificantdifference(Tukey stest,p<0.05)forthemassofagivenfraction before and after incubation of the soils is showed by different letters while representnoignificantdifferences Figure4.8:Distributionofthesoilmassintodifferentphysicalsizefractioofthesoilsof Pierrelayesitebeforeandafterincubation.Bargraphsrepresentmeanvaluesof3 replicateswhiletheerrorbarsrepresentstandarddeviationamongthesereplicates. Statisticallysignificantdifference(Tukey stest,p<0.05)forthemassofagivenfraction before and after incubation of the soils is showed by different letters while representnoignificantdifferences Figure4.9:Distributionoftracemetalsinthedifferentphysicalsizefractioofthesoilsof Metaleurop before and after incubation. Bar graphs represent mean values of 3 replicateswhiletheerrorbarsrepresentstandarddeviationamongthesereplicates. Statisticaldifference(Tukey stest,p<0.05)forthemetalpercentageinthefractio before and after incubation of the soils is showed by different letters while representnoignificantdifferences

15 Figure4.10:Distributionoftracemetalsinthedifferentphysicalsizefractioofthesoilsof Pierrelayebeforeandafterincubation.Bargraphsrepresentmeanvaluesof3replicates whiletheerrorbarsrepresentstandarddeviationamongthesereplicates.statistical difference(tukey stest,p<0.05)forthemetalpercentageinthefractiobeforeand afterincubationofthesoilsisshowedbydifferentletterswhile representnon significantdifferences Figure4.11:Distributionoforganiccarboninthedifferentphysicalsizefractio.Bargraphs representmeanvaluesof3replicateswhiletheerrorbarsrepresentstandarddeviation amongthesereplicates.statisticaldifference(tukey stest,p<0.05)fororganiccarbon percentage in the fractio before and after incubation of the soils is showed by differentletterswhile representnoignificantdifferences Figure5.1:Massoffineandcoarseparticulateorganicmatterfractioofthesoilsbefore andafterincubation.bargraphsrepresentmeanvaluesof3replicateswhiletheerror bars represent standard deviation among these replicates. Statistically significant difference(tukey stest,p<0.05)forthemassofagivenfractionbeforeandafter incubationofthesoilsisshowedbydifferentletterswhile representnoignificant differences Figure5.2:Tracemetalcontentsoftheparticulateorganicmatterfractiooftheannual cropsoilsaspercentageoftotalsoilmetalcontents Figure 5.3: EDTA extractable metal contents of the annual crop soil of both sites at equilibrium.bargraphsrepresentmeanvaluesof3replicateswhiletheerrorbars represent standard deviation among these replicates. Different letters indicate statistically significant difference (Tukey s test, p < 0.01) in the extractable metal contentsofthesoilswithandwithoutparticulateorganicmatter(pom) Figure5.4:Percentagesoflabilemetalfraction(Q ),slowlylabilemetalfraction(q )ofthe 1 2 annualcropsoilsforthetwositeswithandwithoutparticulatesoilorganicmatter (POM).Bargraphsrepresentmeanvaluesof5replicateswhiletheerrorbarsrepresent standarddeviationamongthesereplicates.statisticallysignificantdifference(tukey s test,p<0.01)foreachmetalfractionofthesoilswithandwithoutpomisindicatedby differentletterswhile representnoignificantdifferences Figure5.5:EvolutioninthebiomassofTrametesversicolorexposedtodifferentsourceof copperduringlaboratoryincubatioinliquidmedium Figure5.6:EvolutioninthepHofliquidmediumbecauseoftheactivityofTrametesversicolor exposed to different source of copper during laboratory incubatio in the liquid medium

16 Figure5.7:PercentageofCuaccumulationinfungiduringlaboratoryincubationinliquid mediumswithcucontaminationaddedascus0 (100µg/L)andasCulinkedtoPOM fractio(50200µm) Figure5.8:LaccaseactivitiesofTrametesversicolorinliquidmediumexposedtodifferent sourceofcopperduringlaboratoryincubatiointheliquidmedium

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18 Listoftables Table1.1:Metalenrichmentfactorsoftheparticulateorganicfractioofsomesoils Table2.1:Selectedphysicochemicalcharacteristicsofthesoilsamples.Datapresentedis expressedooildryweightbasis Table2.2:Compositionoftheliquidculturemediumusedforthebiotest Table3.1:EDTAextractablemetalcontents(atequilibrium)ofthesoilsamples.Meanvalues of3replicateswithstandarddeviationamongthesereplicates.differentlettersindicate statisticallysignificantdifference(tukey stest,p<0.01)betweenannualcropand miscanthussoilofeachsite Table3.2:DTPAextractablemetalcontentsofthesoilsbeforeandaftersoilincubation. Meanvaluesof3replicateswithstandarddeviationamongthesereplicates.Different letters indicate statistically significant difference (Tukey s test, p < 0.01) of metal extractabilitybetweenannualcropandmiscanthussoilforeachsite Table3.3:Percentagesoflabilemetalfraction(Q1),slowlylabilemetalfraction(Q2)ofthe soilsamplesandthecorrespondingextractionratecotantsofthesefractiok1and K2respectivelyforthesoilsofMetaleurop.Meanvaluesof5replicates±standard deviation.differentletterswithineachcolumnindicatestatisticallysignificantdifference (Tukey stest,p<0.01)betweenannualcropandmiscanthussoilforthemetalfractio (Q1andQ2)andtheextractionratecotantsthesemetalfractio(K1andK2)foreach metal Table3.4:Extractionratecotantsoflabilemetalfraction(K )andofslowlylabilemetal fraction(k )ofthesoilsamplesofpierrelaye.meanvalues±standarddeviation(n=5). 2 Differentlettersinthecolumindicatestatisticallysignificantdifference(Tukey stest, p<0.01)betweenannualcropandmiscanthussoilfortheratecotantofeachfraction foreachmetal Table 3.5: Correlationmatrix (Pearson correlation coefficients) among metal availability parametersi.e.totaledtaextractablecontents(exedta),kineticallydefinedlabile metalfraction(q1),slowlylabilefractio(q2),dtpaandnh4no3extractablemetal contentsandthemetalandorganiccarbondistributionamongdifferentphysicalsize fractioofthesoilsofmetaleuropsite(n=6;valuesinboldaredifferentfrom0witha significancelevelp< Table 3.6: Correlationmatrix (Pearson correlation coefficients) among metal availability parametersi.e.totaledtaextractablecontents(exedta),kineticallydefinedlabile metalfraction(q ),slowlylabilefractio(q ),DTPAandNH NO extractablemetal contentsandthemetalandorganiccarbondistributionamongdifferentphysicalsize 1 9

19 fractioofthesoilsofpierrelayesite(n=6;valuesinboldaredifferentfrom0witha significancelevelp< Table3.7:Summaryoftheresultsofcomparisonoftracemetalavailabilitiesbetweenannual cropandmiscanthussoilsstudiedbyusingdifferentmethodsandextractants.thesig aftermetalsymbolspresentthetrendofchangeinmetalavailabilitiesinthesoilsunder miscanthuscomparedtoannualcropsoils(increase,decrease,nochange) Table 3.8: Summary of the correlatio between trace metal availabilities and their distributioninphysicalsizefractio.thesigassociatedwithchemicallyextracted metalfractiogivethetypeofcorrelatio(positivecorrelation+,negativecorrelation )whilethefractiounderlinearethesoilphysicalsizefractiowithwhichthemetal availabilitiesarecorrelated Table 4.1: Selected chemical characteristics of the soil samples before and after soil incubation.dataispresentedooildryweightbasis.wherepresentthedifferent lettersiuperscriptshowthestatisticallysignificantdifference(tukey stest,p<0.01) ofdifferentcharacteristicsforeachsoilbeforeandafterincubation Table4.2:Extractionratecotantsoflabilemetalfraction(K )andofslowlylabilemetal fraction(k )ofthesoilsamplesbeforeandafterincubation.meanvalues±standard 2 Deviation (n=5). Different letters in the colum indicate pairwise statistically significantdifference(tukey stest,p<0.01)fortheratecotantsofthemetalsfor eachsoilbeforeandafterincubation Table4.3:Summaryoftheresultsofchangesintracemetalavailabilitiesaftersoilincubation studiedbyusingmetalextractionatequilibriumandkineticmetalextractio.where forextractioatequilibriumext1=edta,ext2=dtpa,ext3=nh NO andforkinetic extractioq =labilepool,q =slowlylabilepool,k =Extractionrateoflabilepooland K =Extractionrateofslowlylabilepool.Thesiginfrontofmetalspresentthetrendof 2 changeinmetalavailabilitiesinthesoilsafterincubationcomparedtothesoilbefore incubation(increase,decrease,nochange) Table4.4:Percentageofmassrecoveryafterphysicalfractionationofthesoilsbeforeand aftersoilincubation Table4.5:Percentageofmetalrecoveryafterphysicalfractionationofthesoilsbeforeand incubation Table4.6:Summaryoftheresultsofchangesintracemetalandorganiccarbondistribution inphysicalsizefractioofthesoilsafterincubation.wheref =020µm,F =2050µm, 1 2 F =50200µm,andF = µmfraction.Thesiginfrontoffractioshowthe 3 4 trendofchangeindistributioninthesoilsafterincubationcomparedtothesoilbefore incubation(increase,decrease,nochange)

20 Table 4.7: Correlation matrix (Pearson correlation coefficients) among Cu availability parametersi.e.totaledtaextractablecontents(exedta),labilemetalfraction(q ), slowlylabilefractio(q ),NH NO,DTPAextractableandtheCuandorganiccarbon distributionamongdifferentphysicalsizefractioofthesoilsofmetaleuropsite(n=6; boldnumbersareforp<0.05) Table 4.8: Correlation matrix (Pearson correlation coefficients) among Pb availability parametersi.e.totaledtaextractablecontents(exedta),labilemetalfraction(q ), slowlylabilefractio(q ),NH NO,DTPAextractableandthePbandorganiccarbon distributionamongdifferentphysicalsizefractioofthesoilsofmetaleuropsite(n=6; boldnumbersareforp<0.05) Table 4.9: Correlation matrix (Pearson correlation coefficients) among Zn availability parametersi.e.totaledtaextractablecontents(exedta),labilemetalfraction(q ), slowlylabilefractio(q ),NH NO,DTPAextractableandtheZnandorganiccarbon distributionamongdifferentphysicalsizefractioofthesoilsofmetaleuropsite(n=6; boldnumbersareforp<0.05) Table 4.10: Correlation matrix (Pearson correlation coefficients) among Cd availability parametersi.e.totaledtaextractablecontents(exedta),labilemetalfraction(q ), slowlylabilefractio(q ),NH NO,DTPAextractableandtheCdandorganiccarbon distributionamongdifferentphysicalsizefractioofthesoilsofmetaleuropsite(n=6; boldnumbersareforp<0.05) Table 4.11: Correlation matrix (Pearson correlation coefficients) among Cu availability parametersi.e.totaledtaextractablecontents(exedta),labilemetalfraction(q ), slowlylabilefractio(q ),NH NO,DTPAextractableandtheCuandorganiccarbon distributionamongdifferentphysicalsizefractioofthesoilsofpierrelayesite(n=6; boldnumbersareforp<0.05) Table 4.12: Correlation matrix (Pearson correlation coefficients) among Pb availability parametersi.e.totaledtaextractablecontents(exedta),labilemetalfraction(q ), slowlylabilefractio(q ),NH NO,DTPAextractableandthePbandorganiccarbon distributionamongdifferentphysicalsizefractioofthesoilsofpierrelayesite(n=6; boldnumbersareforp<0.05) Table 4.13: Correlation matrix (Pearson correlation coefficients) among Zn availability parametersi.e.totaledtaextractablecontents(exedta),labilemetalfraction(q ), slowlylabilefractio(q ),NH NO,DTPAextractableandtheZnandorganiccarbon distributionamongdifferentphysicalsizefractioofthesoilsofpierrelayesite(n=6; boldnumbersareforp<0.05) Table 4.14: Correlation matrix (Pearson correlation coefficients) among Cd availability parametersi.e.totaledtaextractablecontents(exedta),labilemetalfraction(q ),

21 slowlylabilefractio(q ),NH NO,DTPAextractableandtheCdandorganiccarbon distributionamongdifferentphysicalsizefractioofthesoilsofpierrelayesite(n=6; boldnumbersareforp<0.05) Table 5.1: Metal enrichment factors of the fine and coarse particulate organic matter fractioofthesoils.meanvalues±standarddeviationof3replicates.differentletters indicatethestatisticallysignificantdifference(tukey stest,p<0.05)forthemetal enrichmentfactorsinthepomfractiobeforeandaftersoilincubation Table5.2:Extractionratecotantsoflabilemetalfraction(K )andofslowlylabilemetal fraction (K ) of the soil samples with and without POM. Mean values ± Standard 2 Deviation (n=5). Different letters in the colum indicate pairwise statistically significantdifference(tukey stest,p<0.01)forratecotantoflabileandslowlylabile fractioofthemetalsforeachsoilwithandwithoutpom Table5.3:Evolutionofthecopperconcentratiointheliquidmediumsduringtheexposure of Trametes versicolor to different source of copper contamination in laboratory incubatio

22 INTRODUCTION Contextofthestudy Asweenterthe21stcenturywithmorethan6.5billionworldpopulation,theworld s soilsneedtobesustainablymanagedtomeetincreasingdemandsincluding:increasedfood production,biomassproduction,restorationofdegradedlands,csequestration,increased resourceuseefficiencyinagriculture,andpreservationofbiodiversity(lal,2009).butatthe sametimeincreasedindustrializationandurbanizationtomeetthebasicnecessitiesof humanbeinghavecreatedachallengethroughstronganthropogenicperturbatioofsoil andenvironment.onetypeoftheseperturbatioistheelevatedlevelsoftracemetalsin thesoils.tracemetalsaredefinedasmetalsinnaturalmaterialsataconcentrationlower than 1000 mg kg 1 (KabataPendias and Pendias, 2001). Some of the trace metals are essentialforbiologicallifebutcanbetoxicatelevatedlevels;othersarenonessentialand canalsobetoxic.themajorchallengeincaseofsoiltracemetalcontaminationisthatthe tracemetalsarenondegradableandpersistioils.elevatedlevelsoftracemetalsnotonly causetoxicitytothesoilorganismsbutcanalsocauseserioushumanhealthhazardsby enteringthefoodchainviaplantuptakeinagriculturalsoils(ramade,2007). Despiteadvancementsicienceandtechnologies,removalofmetalpollutionfrom soilsisneithereffectivenoreasy,particularlyforagriculturalsoilswheremetalpollution levels are lower than in former industrial sites (Dickion, 2000). Sustainable use of contaminatedagriculturalsoilsshouldthusrequiremanagementinawaythatthepotential risksoftracemetalsareminimizedinparticularthroughplantuptakeifalimentarycropsare tobemaintained,oringeneralthroughsoilfunctioning.assessmentoftotalsoilmetal contentsistheinitialsteptowardsriskassessmentbutmainconcernisthedeterminationof metalfractiowhichareavailabletointeractwithsoilecologicalreceptors(harmsen, 2007).Thesemetalfractioconcernthe soilmetalsupply orthe tracemetalavailability asnamedintherecentnormiso17402aimingtodefinethebioavailabilityconcept(iso, 2008).Itiswellknownthatmetalavailabilityioilsisrelatedtosoilmetalspeciationwhich depends on many factors like the type of soil or the soil physicochemical conditio (Bermondetal.,1998).Soilbeingacomplexmediumtheassessmentofmetalspeciationis difficultandmeasurementoftracemetalavailabilityaswellasknowledgeofitsdeterminism 13

23 isstillachallenge.differentchemicalmethodsareusedtoassessmetalavailabilityioils butthereisstillnoonegenerallyacceptedmethodallowingcomparisobetweetudies. Amongthedifferentsoilcotituentssoilorganicmatterisalabilecotituentand remaiundercontinuouschangeduetodifferentturnoverofitsfractiovaryingfrom plantdebristodissolvedorganicmolecules.incaseofnoncontaminatedsoilconditiothe roleofsoilorganicmatterondifferentsoilpropertiesandooilfunctioninghasbeenan importantfocusofsoilresearchers.itisthuswellestablishedthewaythesoilorganicmatter affectssoilphysicochemicalandbiologicalcharacteristics(ekwue,1990;hussainetal., 1999;Lal,2009).Incaseofcontaminatedsoilsthesoilorganicmatterstillhasaroleasa trophicresourcefororganismsbutfurthermoreactsasaligandformetals.sothenature andquantityofsoilorganicmattercanplayanimportantroleinthedeterminismoftrace metalavailabilityincontaminatedagriculturalsoils.thereactivityandaffinityfortrace metalsofdifferentindividualsoilorganicmatterfractiohasbeenreportedinliterature (Sauvéetal.,2000;Kalisetal.,2006;Sebastiaetal.,2008).Buttheexistenceofalarge number of varieties of organic materials in the soils and the inability to completely characterizesoilorganicmattermakedifficulttoassessitsroleintracemetalavailability. Such a role has been often described in the case of new exogenous organic matter introducedintocontaminatedsoilsasamendmentslikesewagesludgeorcomposts,then assessingtheimpactontracemetalavailability(udometal.,2004;torriandlavado,2008; Smith,2009;Ingelmoetal.,2011).Butrarerarestudiesconcerningchangesinindigenous soilorganicmatterstatus,duetoachangeinlanduseormanagementpracticesratherthan additionofexogenousorganicmatter,ontracematteravailabilities.suchstudieswillbe useful,however,inthenextfuturetobringelementsofawertothechangesofcultural practices,particularlyinthecaseofmetalcontaminatedagriculturalsoilsthevocationof whichtoproducefoodculturesisquestioned. Moregenerally,effectsofchangesinlanduseormanagementpracticesonmaioil propertieslikeph,soilorganicmatterqualityandquantity,orcationexchangecapacityare wellreportedintheliterature(rossetal.,1999;sixetal.,2000;dillyetal.,2003).in contaminatedagriculturalsoilssuchmodificatioioilphysicochemicalconditioare expectedtoinducechangesinmetalspeciation,butthewaythesechangeswilloccurare notalreadyknown.thecoequenteffectsonthesoiltracemetalavailabilitiesarethen 14

24 difficult to predict. This will be particularly true in the case of changes from annual alimentarycropstoperennialnonalimentarycropslikebioenergycropsassuggestedfor marginallands(campbell,2008;gopalakrishnanetal.,2009),wheretheeffectsduetonon tillagewilladd. In this work the need to assess the impact of the adopted practices for the sustainablemanagementofcontaminatedagriculturalsoilsonthesoilorganicmatterand theresultingeffectontracemetaldynamicsioilshadbeenappliedtotheknowledgeof thechangesintracemetalavailabilities. Theworkpresentedheretookbenefitsfromtwoscientificprogramsdevelopedin thepessacresearchunit:ananrcesresearchproject(agencenationaldelarecherche Contaminants, Environnement et Santé named RESACOR (REconversion des Sols AgricolesContaminés:impactdesculturesàvocationénergétiquessurlabiodisponibilité desélémentstracesetlarelationaveclarépoedesorganismesdusol)andaninsu EC2CO(ItitutNationaldesSciencesdel Univers,)researchprojectnamed MOBIPOCu (Rôledelamatièreorganiqueetdelabiocénosedaledevenird unepollutionchronique etdiffuseaucuivredauolviticole).intheseprojectsconcerningmetalcontaminated soils,theobjectivesweretoassesstheimpactsooilpropertiesofchangesfromannual alimentarycropstoperennialmiscanthusnonalimentarycrop,andthespecificroleofsome soilorganicfractiointracemetalbioavailability.inthepresentworkfocuswasmadeon theavailabilitypartofthebioavailability,i.e.thecharacterizationandtheknowledgeofthe determinismofthetracemetalsoilsupply,aswellastheroleofaspecificfractionofthesoil organicmatter:theparticulateorganicmatters,appliedinthecaseschoseninaccordance withthesedifferentprojects. Aimsofthethesisresearch Inthiscontextthemainobjectiveoftheworkpresentedinthisthesiswastoassess theeffectsofmetalcontaminatedlandusesonthesoiltracemetalsavailabilityusingiitu contaminated soil samples and acombination of laboratory experiments. We chose to comparetwolandusesinthespecificcaseofsoilscultivatedeitherunderannualalimentary cropsorunderperennialmiscanthuscrop.wealsochosetocomparetwositeswhichmainly differ in their soil texture but also in the origin of metal pollution. But for a given 15

25 contaminated site we made comparison iide the same cultivated parcel where the changesinlanduseoccurred(annualversusmiscanthuscrops).themainhypothesiswe madeconcerntheroleofboththesoiltextureandoriginofthepollution(mainlywheites arecompared)andofthesoilorganicmatter(foragiveite,betweeoilunderannualor perennialcrops,butalsoinourcasewheitesarecompared).thustheexperimental designofsoilsamplingwasusedinordertoassessboththedeterminismoftracemetal availabilitiesandtohighlightthespecificeffectofsoilorganicmatterwhencoupledwith laboratoryexperiments. Thethesisworkthusfocusesonthreeparts: 1) Inafirstpart(chapter3)weaimedatassessingiituforagiventypeofsoilthe effecttocultivateacontaminatedparcelintwodifferentways(annualvsperennial miscanthuscrop)ontracemetalavailabilities.wehypothesizedi)thatchangesioil organicmatterstatusduetochangesioiluseaswellastheabsenceorpresenceof tillagewillaffectthetracemetalavailabilities,andii)thatthisimpactwilldependon thesoiltexture. 2) Inasecondpart(chapter4)wemadecomplementarylaboratoryinvestigatioto assessthepotentialroleoforganicmatterapartoftheeffectofpresenceofabsence oftillage.forthat,wehypothesizedthatanevolutioninthesoilorganicmatter status between soil samples (under annual vs miscanthus perennial crop and between soils of different textures) will affect differently their trace metal availabilities.forthatweenhancedthemineralizationofthesoilorganicmatterof eachsoilsamplethroughinvitrosoilincubatioandassessedtheresultingeffecton soiltracemetalavailabilities 3) Inathirdpart(chapter5)wefocusedonthemostlabilesoilorganicmatterfraction, theparticulateorganicmatters,inordertoassesstheirpotentialroleinthetrace metalavailabilities.weaimedtoassessi)whetherparticulateorganicmatterplaysa roleofsourceorsinkoftracemetalsioils,linkedtothetracemetalavailabilities andii)towhatextentthemetalsassociatedwiththisorganicmatterfractionare bioavailable,ascanbeseenusingabiotest. 16

26 Finally,thisthesisstudyisarticulatedintofivechapters.Thefirstchapterpresentsa reviewofourpresentknowledgeonthefateoftracemetalsinthesoils,thesoilorganic matter and its affinity towards trace metals and the various concepts of trace metal availabilityandthewaysofitsassessment.inthesecondchapterwepresentallthematerial andmethodsusedinthiswork.thethreefollowingchaptersarebasedontheresults obtainedduringthethesisworkcorrespondingtothethreespecificaimsofthestudy. 17

27 1.1. Tracemetalsandagriculturalsoils Chapter1 LiteratureReview Tracemetals(TMs)arenaturallypresentioils,thesocalledpedogeochemical backgroundlevelsreflectingtheoccurrenceoftracemetalsinthesoilparentmaterial.with theincreasedindustrializationandurbanization,atremendousamountofthesemetalsis addedtosoilsandwaterenvironmentannuallyfromdifferentsources(figure1.1).infrance e.g.accordingtoanassessmentpublishedin2007atotalof4869toyear 1 ofcu,696to year 1 ofpb,15190toyear 1 ofznand54toyear 1 ofcd(figure1.2)areaddedtothe soilsfromdifferentanthropogenicsources(sorgreahademe,2007).becauseoftheirnon biodegradationandpersistenceinthesoils,thetracemetalsarecoideredtobepotential environmental contaminants for the biological life. The pollutant activities lead to an irreversibleanddiffusivecontamination(contaminationfromaremotee.gvehiclesexhausts, heatingplants,wastewaterirrigationetc)inthelongterm,beinglikelytocompromisethe fertilityandthequalityoftheagriculturalsoils(chassinetal.,1996;ramade,2007).in additiontothesediffusivecontaminatio,localindustrialandurbanexploitatiocanalso cause soil contamination (e.g. case of Metaleurop in the north of France which has contaminatedthenearbyagriculturalsoils). Agriculturalpractices Mineralfertilizers Pesticides Organicamendments Atmosphericfallout SOIL=Accumulater INITIALSTOCK=geochemical backgroundlevel Parentmaterial Miningandmetallurgy Industrialandurbanactivities Figure1.1:Majorinputfluxesoftracemetalsintoagriculturalsoils. 18

28 Percentage Cu Zn Pb Cd 4869to year to year 1 696to year 1 54to year 1 AtmosphericFallout SludgeandCompost CalcicandMagnesiumAmendments AnimalWaste MineralFertilizers Plantprotectiveproducts Figure1.2:EstimationofannualinputoftracemetalsintoagriculturalsoilsofFrancewith theirprinciplesources.(valuestakenfromsorgreahademe,2007) Inthisthesiswork,wewillbeinterestedmoreparticularlyinCu,Zn,PbandCd,which arethemajortracemetalsfoundintheagriculturalsoils(ramade,2007;zheljazkovetal., 2008).CuandZnareessentialtraceelementsandarenecessaryfortheenzymaticreactio ofthebiologicalfunctioofthelivingorganisms(tyler,1981).contrary,theybecometoxic forsoilorganismsatexcessiveconcentratio.agriculturalandurbanwastesandplant protectiveproductsarethemajorsourcesofsoilcontaminationbytheseessentialelements. InFranceCuhasbeenusedintheproductsappliedtovineyardssinceseveraldecadesto fightagaittheparasitesorthe mildew.thusthevineyardssoils,nearlyamillionhectare infrance,havehighcupercentages(beyond500mg/kgofsoil),limitingincertaincasesthe microbialactivityandthendecreasingthefertilityofthesoilforanyothercrops. PbandCddonothaveaknownbiologicalrole(Maestrietal.,2010).Coideredas harmful,theycausenoxiousbiologicaleffectsevenatweakconcentratio(tyler,1981).pb contaminationofthesoilsismainlycausedbyatmosphericfalloutduetocombustio.the mineralfertilizers,especiallyphosphorusfertilizers,containcoiderablecontentsofmetals. BesidesthesearemajorinputsforCd(NziguhebaandSmolders,2008) Factorsaffectingfateoftracemetalsinthesoils Itshouldbestressedthatthedynamicsofthetracemetalsintheenvironment dependontheirspeciation(theirchemicalforminthesoil)andontheintriicphysico chemicalcharacteristicsofthesoils.thesoilorganicmatterisknownforitsreactivitywith respecttometalssuchascuandpb.thetracemetalslikeznareadsorbedtoclayortoiron 19

29 hydroxidesinthesoils(tyler,1981;labanowskietal.,2008).duetotheretentionofmetals in the surface horizo of soils the quantities of metals traferred vertically towards undergroundwaterarelowinthemajorityofsoils(chassinetal.,1996). Thespeciationoftracemetal,theirmobilityandbioavailabilityarethecharacteristics linked to each other and are defined by the interaction of trace metals with their environmenti.e.thesoil,climateandbiotopeetc. Various physicochemical parameters of the soil influence the mobility and the bioavailabilityofthetracemetalsioils.amongwhichareph,redoxpotential,natureof thecomponentsofsoil,cationexchangecapacity,porosityofthesoilmatrix,available phosphatecontents,soilorganicmattercontentsandsoilbiologicalactivities(juste,1988; Alloway,1995).Theavailabilityofsoiltracemetalsdependsasawholeontheseparameters andnotonlyonasinglemechanism.theageandthenatureofthecontamination,thesoil moistureortheinteractiobetweendifferentmajorelementsinthesoilsandtracemetals canalsoinfluencethetracemetalmobilityandbioavailability. 1.2.a. phandredoxpotential Soil ph and redox potential directly influence all chemical processes and coequentlyalsodeterminethebehaviorofmetalsioils.manyauthorsunderlinethe majorinfluenceofphonthedynamicsoftracemetalsioils(alloway,1995;rieuwertset al.,2006).increaseinphincreasesthenumberofsorptioitesofclays,ofhydroxidesorof organicmatter(ureanddavidson,2002).thiscanincreasethequantityoftracemetal adsorbed to the soil components, provided that these components have an important affinityforagivenmetalandthatquantityofsorptioitesissufficient(ureanddavidson, 2002).Oppositetothis,itwasshownthatthesolubilityofmetalcatioincreaseswiththe reductioninph(pueyoetal.,2004),whileaniobecomelesssoluble(hesterberg,1998). Theredoxpotential(Eh)makesitpossibletocharacterizetheexchangesofelectro betweenthechemicalspecies.thuslowvaluesofehsupportthedissolutionofhydroxides andinvolveanincreaseintheconcentrationofmetalsassociatedwithsoilcomponents (Chaignon,2001).Moreover,modificationoftheoxidatiotateoftheligandsorelements withwhichthemetalsareboundioilinfluencesthesolubilityoftracemetalsindirectly. Forexample,inreducingconditio,sulphatesarereducedtosulphideswhichreadilytrap 20

30 the metalelements such as Pb, Cd, Zn (DeneuxMustin et al., 2003). The influence of oxydoreductionconditioofthesoilseemsveryimportantforthemobilityofthemetal elements,butitissecondarycomparedtothesoilph.foragiveoil,thevariationinehis oppositetothechangeinph,itincreaseswhenthephdecreases(deneuxmustinetal., 2003). 1.2.b. Inorganicsoilcotituents Inorganic soil cotituents like clay minerals, oxy (hydroxides), carbonates and phosphates,becauseoftheirchemicalproperties,playanimportantroleinthebehaviorof tracemetalsinthesoils. LiandLi,(2000)showedthattracemetalscanbeadsorbedandimmobilizedbyclay mineralsoralsobecomplexedtosoilorganicmatterbyformingorganometalliccomplex. Metalscanadsorbbetweenthelayersoronthesurfaceoftheclay(permanentcharge),on theedgesofthehydroxylgroups(variablecharge)andonthebridgesformedbecauseofthe irregularityofthematrixstructure(carrillogonzálezetal.,2006;sajiduetal.,2008).the sorptionforceofcatioonclaymineralsvarieswiththetypeofclay(carrillogonzálezet al.,2006).thus,claysmadeupoftwotetrahedrallayersandoneoctahedrallayer(e.gthe montmorillonite)haveahighercationexchangecapacity,andthusabettercapacityoffixing catio,thantheclaysmadeupofonetetrahedrallayerandoneoctahedrallayer(mcbride, 1994;Dubeetal.,2001;Brigattietal.,2005). Thepresenceofdifferenttypesofoxidesandoxyhydroxidesinthesoilscanalterthe tracemetalavailabilityinthesoilsbecauseofthedegreeaffinityofthemetalstothem.fe oxides (hematite, maghemite, magnetite) and oxyhydroxides (goethite, ferrihydrite, feroxyhite,akaganeite,lepidocrocite),aioxides(corundum),hydroxides(gibbsite)andoxy hydroxides(boehmite),aswellasmnoxides(birnessite)arecommonandnaturallypresent ioils(sparks,2003).theseoxidesareveryreactiveforthetracemetalsandareabletofix themtodifferingdegree.trivediandaxe(2001)classifiedoxidesaccordingtotheircapacity ofadsorption:mnoxides>feoxides>aioxides.thecoprecipitationoftracemetalswith oxidesreducestheirsolubilityandtheiravailability.thiscapacitywasusedintheworksof remediationofstronglycontaminatedsoils,inparticularbytheadditionofshotsoffe (Boissonetal.,1998;Menchetal.,2000).Thisproduct,composedmainlyofFe(97%FeO), 21