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1、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
2、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。,Trace elements occur in minute quantities and are usually measured in parts per billion (ppb). -even in small quantities they can be important for either promoting or killing life.,Trace Elements,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
3、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）,Classification of Elements,TypeConcentration Major 0.05 to 550 mM Minor 0.05 to 50 M Trace0.05 to 50 nM,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。,Broeckers Classification,Unlimited: All M
4、ajor except Ca, C and Si Biolimited: N, Si, and P (Fe) Intermediate:O, Ca, C, Sr, Ba, Ra, Se and most minor elements,Goldbergs Classification of Metals,do Cations Metals with rare gas configuration Na+, Mg2+, Ca2+, K+ d10 Cations Metals with 18 outer electrons Ag+, Zn2+, Ga3+, Ge4+ Transition Metals
5、 Metals between d0 and d10 Mn2+, Fe2+, Co2+, Ni2+, Cu2+,Electronic Configuration of Atom,K L M N _ _ _ Period Z Element s s p s p d sp 1 1 H 1 2 He 2 2 3 Li 2 1 4 Be 2 2 5 B 2 21 6 C 2 22 7 N 2 23 8 O 2 24 9 F 2 25 10 Ne 2 2 6,K L M N _ _ _ Period Z Element s s p s p d sp 3 11 Na 2 26 1 12 Mg 2 2 6
6、2 13 Al 2 2 6 2 1 14 Si 2 2 6 22 15 P 2 26 23 16 S 2 2 6 2 4 17Cl 2 2 6 2 5 18 Ar 2 2 6 2 6 419 K 2 2 6 2 6 1 20Ca 2 26 26 2 21 Sc 2 2 6 2 6 1 2 22Ti 2 2 6 2 62 2 23V 2 26 26 3 2 24Cr 2 2 6 26 5 1 25 Mn 2 2 6 265 2 26Fe 2 26 26 6 2 27Co 2 2 6 2 6 7 2 28Ni 2 26 2 68 2 29 Cu 2 2 6 2 6 10 1 30Zn 2 26 2
7、 6 10 2 31Ga 2 2 6 2610 2 1 32Ge 2 26 2610 22,d0 Cations,Forms Few Complexes with Ligands 只能氟离子或含氧酸离子形成络合物 Complexes or Ion Pairs that are Formed are Electrostatic in Nature (Strength Z/r where Z is the Charge and r is the Radius),M + L ML KML = ML/ML Ion Log KMF Log KMOH Radius Be2+ 4.29 10.28 0.31
8、 Mg2+ 1.82 2.3 0.65 Ca2+ 1.04 1.4 0.99 Sr2+ - 0.9 1.13 Ba2+ 0.45 0.8 1.35,d10 Cations（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 + L ML KML = ML/ML Log KML Complex F- Cl- Br- I- AgL 0.3 3.0 4.3 8.1 CuL - 2.7 3.2 5.7,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
9、势,Hg2+ + Cl- HgCl+ Hg2+ + 2Cl- HgCl2 Hg2+ + 3Cl- HgCl3-,随氯离子浓度的增加，可形成下列系列络合物:,Transition Metals (d0 to d10),Forms Strong Complexes with Organic Ligands Irving - Williams Order: Mn2+ Zn2+,Log KMX _ Ion EDTA Ethylenediamine Nitrilotriacetic acid Mn2+14 2.7 7.4 Fe2+ 14 4.3 8.3 Co2+16 5.9 10.5 Ni2+ 18 7
10、.9 11.4 Cu2+19 10.5 12.8 Zn2+ 16 6.0 10.5,Residence Times of Elements,Input of Elements Into the Oceans 1. The fallout of substances from the atmosphere 2. Influx of river water 3. Interior of earth,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+), = Concentration in Ocean/Amount Supplied,dA/d
11、t = R - S = 0 Steady State Condition S = k A = 1/k = A/R = A/S R = River Input to Oceans (also Atm. and Interior) S = Sedimentation Rates,Residence Times of Some Elements in Seawater (My),Element River Input Sedimentation Na 210 260 Mg 22 45 Ca 1 8 K 10 11 Sr 10 19 Si 0.935 0.01 Li 12 19 Rb 6.1 0.27
12、 Ba 0.05 0.084 Al 0.0031 0.0001 Mo 2.15 0.5 Cu 0.0430.05 Ni 0.0150.018 Ag 0.252.1 Pb 0.000560.002,Comparison of Ratio of Saturated Concentration to Measured Values and Residence Times,Metal Insoluble Ra Years Compound Sat Conc./Meas. Pb2+ PbCO310,000 - 20,000 2,000 Ni2+ Ni(OH)210,000 - 225,000 18,00
13、0 Co2+ CoCO3 50,000 - 400,00018,000 Cu2+CuCO3 133 - 26650,000 Ba2+BaSO4 3.784,000 Zn2+ ZnCO3 120 - 250180,000 Cd2+ CdOHCl 40,000 - 10,000,000500,000 Ca2+CaCO3 0.25 - 1.28,000,000 Sr2+ SrCO3 2.75190,000,000 Mg2+ MgCO3 27 450,000,000 a) Measure of degree of Undersaturation. R = saturation conc./measur
14、ed conc.,Water samples must be collected in inert containers and isolated as they are recovered so as to prevent contamination.,The Niskin bottle has valves at each end which are automatically closed when a weight, called a messenger, is sent down the cable and causes the bottle to flip over and sea
15、l itself. Sample depth can be determined from cable inclination and length or with a pulsating sound source.,Distribution of Elements in the Oceans,Conservative Profiles Nutrient Type Profiles Surface Enrichment and Depletion at Depth Mid-Depth Minima Mid-Depth Maxima Mid-Depth Maxima or Minima in t
16、he sub-oxic layer Anoxic Waters,1. Conservative Profiles,Constant Ratio of Concentration to Cl or S (Major Ions, 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。,Elements have essentially constant concentrations with depth. Elements behave like maj
17、or ions, having long residence times and being well-mixed. Not major components of seawater owing to very low crustal(外壳的) abundances. Elements form simple anions or cations with low Z/r, e.g., Cs+, Br-, or complex oxyanions, e.g., WO42-, MoO42-. Little involvement in biological cycles.,EXAMPLES OF
18、CONSERVATIVE BEHAVIOR,2. Nutrient Type Profiles,Removed by Phytoplankton(浮游植物；浮游植物(群落) in Surface Waters and Regenerated in Deep Waters (Follow Nutrients) Soft Parts Cd （km） Hard PartsSiO2, Ba, Zn, Ge, Be CombinationNi, Se,Production of biological material removes nutrient elements from surface seaw
19、ater. On the death of organisms, this biological material sinks through the water column, decomposing and releasing the nutrients. Involvement in biological cycling involves chemical transformations. Elements showing nutrient behavior tend to have long residence times.,EXAMPLES OF NUTRIENT BEHAVIOR,
20、3. Surface Enrichment and Depletion (损耗)at Depth,Input from Atmosphere(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。,Elements that are hi
21、ghly particle-reactive, characterized by high Z/r. They have a minimum concentration at an intermediate depth and a maximum concentration at the surface. Initial decreasing concentration with depth is a result of adsorption and cation exchange on particle surfaces. These elements have short residenc
22、e times; the river inputs are largely removed by estuarine processes. The atmosphere provides the main input of these elements to the open ocean (e.g., input of Pb from gasoline emissions can be traced in corals). The element concentration may increase again after a certain depth if particles become
23、 unstable with depth, e.g., reduction of Fe-Mn oxyhydroxides or decomposition of organic matter.,4. Mid-Depth Minima,Surface Input and Regeneration at Bottom (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
24、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-Depth Maxima,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-Depth Maxima or Minima in the sub-oxic layer,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. Anoxic Water
25、s,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）。,Vertical profiles Biolimiting trace metals will be depleted in surface waters If a trace element is associated with org. matter
26、, there will be a mid water column maxima If a trace element is associated with CaCO3 shell material there will be a a deep water maxima (CCD) If a trace element is associated with opaline(蛋白石(似)的，发乳光的。) shell material, its conc.will be correlated to Si,海洋中微量元素的浓度,Metals in Atlantic and Pacific Deep
27、 Waters (nM) Metal Atlantic Pacific P/A Cd 0.290.94 3.2 Zn 1.5 8.25.5 Ni 5.7 10.4 1.8 Cu1.7 2.71.6 Mn 0.6 - -,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？,Metals on Shelf versus Open Sea Surface Waters Metal Shelf Open Mn21 nM 2.4 nM Ni5.9 nM 2.3 nM Cu 4.0 nM 1.2 nM Zn2.4 nM 0.06 nM Cd 200 pM 2 pM,陆架区高于
28、大洋，表明为陆源输入,Metals in Central Gryes,MetalAtlanticPacific Mn2.4 nM1.0 nM Cu1.2 nM0.5 nM Ni2.1 nM2.4 nM Zn0.06 nM0.06 nM Cd2 pM2 pM,高浓度表明是大气输入,Illustration in a global biogeochemical model: regulation of macro-nutrient pathways by aeolian iron source (Dutkiewicz et al., 2005),Modeled Surface Chl (mg m-
29、3),Sensitivity studies with uniform “high” and “low” aeolian iron flux.,More dust, higher productivity,More dust, lower productivity,Pacific basin reflects regulation of intergyre exchange,地球化学平衡,Present Concentration (mol cm-2 of surface) of Major Components of Seawater Compared with the Amount Add
30、ed by Rivers over Last 100 Million Years Na Mg Ca K Cl SO4 CO3NO3 Present 129152.8 2.7 150 80.3 0.01 Added by Rivers 196122268 421578434211 Excess Added671072653977634211,Ocean to Atmosphere G. Suspended Load from New Rocks B. Atmosphere to Streams H. Suspended Load from Old Rocks C. Total Suspended
31、 Load of Streams I. Flux from New Rocks to Old Rocks D. Total Sediment Flux J. Dissolved Load from New Rocks E. Dissolved Load of Streams K. Dissolved Load from Old Rocks F. Total Flux Dissolved from Rocks NEW ROCKS BIOSPHERE 4800 x 1020 g of 0.01 x 1020 gC Living elements (150 x 106 y) 0.04 x 1020 gC Dead OLD ROCKS ATMOSPHERE OCEAN 8450 x 1020 g of0.065 x 1020 g C500 x 1020 g of elements (663 x 106 y)as CO2elements,