第三课海水中的微量元素ppt课件

.,4.海水中微量元素,.,本章要点：,海水中微量元素的含量、分布和存在形式微量元素在海洋中的化学过程、生物过程、再循环模型,.,海水中微量元素的含量和分布,周期表中14种元素的浓度超过1mg/L:,O,H,Cl,Na,K,Mg,S,Ca,Br,C,Sr,B,Si,F,其中活性元素：,Si,.,微量元素,通常把海水中含量小于1mg/L的元素称为微量元素。仅占海水总量的0.1左右。海水中除了14种元素（O、H、Cl、Ca、Mg、S、K、Br、C、S、Sr、B、Si、F)浓度大于1mg/L外，其余所有元素的浓度均低于此值，因此可以把这些元素称为“微量元素”。微量元素在海水中涉及的平衡有络合(螯合)、氧化还原、生物吸收、颗粒物的吸附与解吸等。,.,Traceelementsoccurinminutequantitiesandareusuallymeasuredinpartsperbillion(ppb).-eveninsmallquantitiestheycanbeimportantforeitherpromotingorkillinglife.,TraceElements,.,微量元素的来源,陆地径流海底火山活动大气尘埃降落夹带的微量元素大气输入沥滤岩石人类活动,.,微量元素的特点,非保守性（地球化学活性较大；生物活性大；区域性变化大）含量低微量元素循环及迁移转化复杂（水动力迁移；化学过程；生物迁移）研究难度大（测定方法限制；采水器；样品贮存；分析方法检出限）,.,ClassificationofElements,TypeConcentrationMajor0.05to550mMMinor0.05to50MTrace0.05to50nM,.,.,.,.,.,.,.,.,.,微量元素的分布及其变化，受其来源及海洋环境中各种过程的影响。其中最主要过程：生物过程吸附过程海气交换过程热液过程海水沉积物界面交换过程等。,.,BroeckersClassification,Unlimited:AllMajorexceptCa,CandSiBiolimited:N,Si,andP(Fe)Intermediate:O,Ca,C,Sr,Ba,Ra,Seandmostminorelements,.,GoldbergsClassificationofMetals,doCationsMetalswithraregasconfigurationNa+,Mg2+,Ca2+,K+d10CationsMetalswith18outerelectronsAg+,Zn2+,Ga3+,Ge4+TransitionMetalsMetalsbetweend0andd10Mn2+,Fe2+,Co2+,Ni2+,Cu2+,.,ElectronicConfigurationofAtom,KLMN_PeriodZElementsspspdsp11H12He223Li214Be225B2216C2227N2238O2249F22510Ne226,.,KLMN_PeriodZElementsspspdsp311Na226112Mg226213Al2262114Si2262215P2262316S2262417Cl2262518Ar22626419K22626120Ca22626221Sc226261222Ti226262223V226263224Cr226265125Mn226265226Fe226266227Co226267228Ni226268229Cu2262610130Zn2262610231Ga22626102132Ge226261022,.,d0Cations,FormsFewComplexeswithLigands只能氟离子或含氧酸离子形成络合物ComplexesorIonPairsthatareFormedareElectrostaticinNature(StrengthZ/rwhereZistheChargeandristheRadius),M+LMLKML=ML/MLIonLogKMFLogKMOHRadiusBe2+4.2910.280.31Mg2+1.822.30.65Ca2+1.041.40.99Sr2+-0.91.13Ba2+0.450.81.35,.,d10Cations（阳离子）,单价d10金属阳离子与d0金属完全不同，和卤素能形成强络和物随着原子量或配位体体积的增加，稳定性增加。,M+LMLKML=ML/MLLogKMLComplexF-Cl-Br-I-AgL0.33.04.38.1CuL-,由于海水中氯的浓度最高，因此氯的络合物在海水中是主要的。OH-跟氯有竞争logKMCl-logKMOH必须大于-5.4,氯化物才占优势,.,Hg2+Cl-HgCl+Hg2+2Cl-HgCl2Hg2+3Cl-HgCl3-,随氯离子浓度的增加，可形成下列系列络合物:,.,TransitionMetals(d0tod10),FormsStrongComplexeswithOrganicLigandsIrving-WilliamsOrder:Mn2+Zn2+,LogKMX_IonEDTAEthylenediamineNitrilotriaceticacidMn2+142.77.4Fe2+144.38.3Co2+165.910.5Ni2+187.911.4Cu2+1910.512.8Zn2+166.010.5,.,.,ResidenceTimesofElements,InputofElementsIntotheOceans1.Thefalloutofsubstancesfromtheatmosphere2.Influxofriverwater3.Interiorofearth,海洋中某一种元素浓度较低的原因：1、反应活跃，快速转移到沉积物中(Al3+)2、源头浓度低(Cs+),.,=ConcentrationinOcean/AmountSupplied,dA/dt=R-S=0SteadyStateConditionS=kA=1/k=A/R=A/SR=RiverInputtoOceans(alsoAtm.andInterior)S=SedimentationRates,.,ResidenceTimesofSomeElementsinSeawater(My),ElementRiverInputSedimentationNa210260Mg2245Ca18K1011Sr1019Si0.9350.01Li1219Rb6.10.27Ba0.050.084Al0.00310.0001Mo2.150.5Cu0.0430.05Ni0.0150.018Ag0.252.1Pb0.000560.002,.,ComparisonofRatioofSaturatedConcentrationtoMeasuredValuesandResidenceTimes,MetalInsolubleRaYearsCompoundSatConc./Meas.Pb2+PbCO310,000-20,0002,000Ni2+Ni(OH)210,000-225,00018,000Co2+CoCO350,000-400,00018,000Cu2+CuCO3133-26650,000Ba2+BaSO43.784,000Zn2+ZnCO3120-250180,000Cd2+CdOHCl40,000-10,000,000500,000Ca2+CaCO30.25-1.28,000,000Sr2+SrCO32.75190,000,000Mg2+MgCO327450,000,000a)MeasureofdegreeofUndersaturation.R=saturationconc./measuredconc.,.,Watersamplesmustbecollectedininertcontainersandisolatedastheyarerecoveredsoastopreventcontamination.,TheNiskinbottlehasvalvesateachendwhichareautomaticallyclosedwhenaweight,calledamessenger,issentdownthecableandcausesthebottletoflipoverandsealitself.Sampledepthcanbedeterminedfromcableinclinationandlengthorwithapulsatingsoundsource.,.,.,.,.,DistributionofElementsintheOceans,ConservativeProfilesNutrientTypeProfilesSurfaceEnrichmentandDepletionatDepthMid-DepthMinimaMid-DepthMaximaMid-DepthMaximaorMinimainthesub-oxiclayerAnoxicWaters,.,1.ConservativeProfiles,ConstantRatioofConcentrationtoClorS(MajorIons,Rb+,Li+,Cs+,WO42-,MoO42-)在海水中比较稳定，反应活性低垂直分布断面从表层到底层均匀与海水中常量元素一样可视为保守型元素，保守型元素在海水中逗留时间较长，浓度较大。,.,Elementshaveessentiallyconstantconcentrationswithdepth.Elementsbehavelikemajorions,havinglongresidencetimesandbeingwell-mixed.Notmajorcomponentsofseawaterowingtoverylowcrustal(外壳的)abundances.ElementsformsimpleanionsorcationswithlowZ/r,e.g.,Cs+,Br-,orcomplexoxyanions,e.g.,WO42-,MoO42-.Littleinvolvementinbiologicalcycles.,.,EXAMPLESOFCONSERVATIVEBEHAVIOR,.,2.NutrientTypeProfiles,RemovedbyPhytoplankton(浮游植物；浮游植物(群落)inSurfaceWatersandRegeneratedinDeepWaters(FollowNutrients)SoftPartsCd（km）HardPartsSiO2,Ba,Zn,Ge,BeCombinationNi,Se,.,Productionofbiologicalmaterialremovesnutrientelementsfromsurfaceseawater.Onthedeathoforganisms,thisbiologicalmaterialsinksthroughthewatercolumn,decomposingandreleasingthenutrients.Involvementinbiologicalcyclinginvolveschemicaltransformations.Elementsshowingnutrientbehaviortendtohavelongresidencetimes.,.,EXAMPLESOFNUTRIENTBEHAVIOR,.,.,3.SurfaceEnrichmentandDepletion(损耗)atDepth,InputfromAtmosphere(dust),Rivers,Land(Pb,Mn,Ra,Cr,Sn,Co)主要由大气输入海洋表层，接着在水体中被清除。例如Pb。主要由河流输入海洋表层或由大陆架沉积物中释放，通过水平混合进入海水表层，导致表层产生最大值。如Mn,Ra等。在海洋表层中，因生物的还原作用与整个水体的氧化-还原平衡相结合，使某些元素的氧化态或颗粒态在表层中富集。如Cr（III）,As（III）和I（-1价）等。,.,Elementsthatarehighlyparticle-reactive,characterizedbyhighZ/r.Theyhaveaminimumconcentrationatanintermediatedepthandamaximumconcentrationatthesurface.Initialdecreasingconcentrationwithdepthisaresultofadsorptionandcationexchangeonparticlesurfaces.Theseelementshaveshortresidencetimes;theriverinputsarelargelyremovedbyestuarineprocesses.Theatmosphereprovidesthemaininputoftheseelementstotheopenocean(e.g.,inputofPbfromgasolineemissionscanbetracedincorals).Theelementconcentrationmayincreaseagainafteracertaindepthifparticlesbecomeunstablewithdepth,e.g.,reductionofFe-Mnoxyhydroxidesordecompositionoforganicmatter.,.,.,4.Mid-DepthMinima,SurfaceInputandRegenerationatBottom(Cu,Al)因Gibbs原理和有机配体的络合作用，以及颗粒物的交换吸附和“浮选”原理等综合结果，导致在海洋微表层中元素富集。几乎所有的有机物、营养盐和金属等无机物都可为例。表层因大气或河流输入而具有浓度较大值，中层真光层因生物作用而减少，如营养盐。深层或海底因物质再循环或悬浮物再溶解，再生作用与清除作用的综合结果。如Al,Cu等。,.,5.Mid-DepthMaxima,冬季保留所致，例如溶解氧等；洋中脊水热流的注入引起，如Mn和He等。,.,6.Mid-DepthMaximaorMinimainthesub-oxiclayer,在东热带太平洋和北印度洋发现有典型的亚氧化层的分布，在水柱或在邻近斜坡沉积物中，由于还原作用而会出现微痕量元素的最大值和或最小值。如果元素的还原形式相对于其氧化形式是可溶解的，将出现最大值。如锰和铁。当元素的还原形式比其氧化形式更难溶时或易于与固体结合时，将出现最小值，如Cr（III）,.,7.AnoxicWaters,在水循环受限制的区域，由于氧化一还原电对SO42-H2S的产生而变为缺氧状态并产生还原条件，例如Cariaco海沟和Saanich海湾。此时又分成两种情况:当某元素的还原形式比其在氧化条件下存在的形式更易溶时，曲线出现最大值，例如Mn2+和Fe2+当某元素还原形式相对而言比较难溶或易于与固体相结合时，就出现最小值，例如Cr（III）。,.,VerticalprofilesBiolimitingtracemetalswillbedepletedinsurfacewatersIfatraceelementisassociatedwithorg.matter,therewillbeamidwatercolumnmaximaIfatraceelementisassociatedwithCaCO3shellmaterialtherewillbeaadeepwatermaxima(CCD)Ifatraceelementisassociatedwithopaline(蛋白石(似)的，发乳光的。)shellmaterial,itsconc.willbecorrelatedtoSi,.,.,.,.,.,.,.,.,.,.,.,海洋中微量元素的浓度,MetalsinAtlanticandPacificDeepWaters(nM)MetalAtlanticPacificP/ACd0.290.943.2ZnNi5.710.41.8CuMn0.6-,.,为什么太平洋深层水中微量元素浓度比大西洋高？,.,Pb和Al与其它元素不同，为什么？,.,.,.,MetalsonShelfversusOpenSeaSurfaceWatersMetalShelfOpenMn21nM2.4nMNi5.9nM2.3nMCu4.0nM1.2nMZn2.4nM0.06nMCd200pM2pM,陆架区高于大洋，表明为陆源输入,.,MetalsinCentralGryes,MetalAtlanticPacificMn2.4nM1.0nMCu1.2nM0.5nMNi2.1nM2.4nMZn0.06nM0.06nMCd2pM2pM,高浓度表明是大气输入,.,.,.,.,.,.,.,.,.,Illustrationinaglobalbiogeochemicalmodel:regulationofmacro-nutrientpathwaysbyaeolianironsource(Dutkiewiczetal.,2005),ModeledSurfaceChl(mgm-3),.,Sensitivitystudieswithuniform“high”and“low”aeol