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Slide 1A first look at spatial variationSlide 3Slide 4Classification of elementsSlide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Lecture 3Trace Metals in SeawaterWhat are trace elements?Why are they important?Principal of Oceanographic Consistency.Profiles shapes as clues for controlling processes.A first look at spatial variationWhat are the different “types” of elements?Trace elements in seawaterDefinition: Those elements that do not contribute to salinityAll elements less than 1 mg kg-1. But usually use mole units!Why are they important?1. many are micronutrients (e.g. Fe, Cu) – speciation is important2. others are toxic (e.g. Cu, Hg)3. some are tracers for redox conditions (Mn, Fe, Cr, I, Re, Mo, V, U)4. some are enriched in economic deposits such as manganese nodules (e.g. Cu, Co, Ni, Cd)5. some have man made sources and are tracers of pollution (e.g. Pb, Pu, Ag)** Difficult to collect samples for without contamination and difficult to analyze.Oceanographic consistencyAcceptance of data must satisfy two criteria:1. Vertical profiles should be smooth, not spiky. Ocean mixing produces smooth profiles2. Correlations should exist with other elements that share the same controlling mechanisms.First Example – Cu in surface waters south of New Zealand (Boyle and Edmond, 1975, Nature, 253, 107)SST-SiPO4NO3Classification of elementsConservative(or “bio-unlimited”)Bio-limiting(and “biointermediate”)ScavengedSome have a style of their own (e.g. O, Ar, Bi, Hg)Shapes of Profiles – clues for controlsConservative - Cesium (Cs); Molybdenum (Mo) - under oxic conditionsNutrient Like – Biological control Shallow (soft parts) and Deep (hard parts) RegenerationZinc Cadmium Nickel CopperBariumSurface Enrichment – Atm input, River/Coastal inputsLeadManganeseMid-depth Maximum – Hydrothermal inputs, Oxygen minimum Sediment SourceManganeseIronNear Bottom Enrichment – sediment sourceNorth Sea Metals (Cd, Cu, Mn)Deep Depletion - scavengingLead-210AluminumManganeseSuperposition of vertical biological flux on horizontal circulationResults in low surface water and highdeep water concentrations.Results in higher concentrations inthe older deep Pacific than the younger deep AtlanticNutrient Like ProfilesExample: Comparison of vertical profiles of nutrients from the Atlantic and PacificPO4ShallowSiDeepNutrient Like ExamplesCd, Zn, Cu, NiBut what aboutMn, Pb ??Ba and Si strongly correlated.But Why??BaNutrient Like-Deep Regeneration-Hard PartsCd and PO4 stronglycorrelated.But Why??CdNutrient Like-Shallow Regeneration-Soft PartsUse the Cd-PO4 correlationas a tool to determine paleoPO4 concentrations.Modern DataPaleo ReconstructionAl profilesMediterranean toAtlantic to PacificAlAtmospheric InputandScavengingDepth (km)Depth (km)Mid-depth Maximum (~200 – 1000m)MnMurray et al (1981)DissolvedTotalOxygen Minimum Zone - ETNPMOR Hydrothermal System – Mid-Depth Maximum and ScavengingFe and Mn Hydrothermal plume from the Juan de Fuca RidgeFeMnT anomalyparticlesCoale et al (1991) Nature, 352, 325Mid-Depth Maximum (~2000m)Atmospheric inputPb in Greenland snowPbAtmospheric InputAnthropogenic OriginPbSurface MaximumFlegal and Patterson, 1983Sediment SourceHigh Trace Metal Concentrationson the Continental ShelfKremling (1983) Nature 303, 225CdCuMnSiPO4SpCu = - log Cu2+ Cutotal = Cu2+ + inorganic complexes + organic complexesMetal Limitation and Toxicity – Cu – Role of Free Metal IonCu SpeciationandPlankton GrowthCu Speciation – Ocean DistributionsTotal CopperStrong Organic LigandsFree Cu2+Total CuAll Fe data as of 1997 (Johnson et al)Quiz – What processes control the distribution of Fe in seawater?Ocean Periodic Table (from Ken Johnson, MBARI)http://www.mbari.org/chemsensor/pteo.htmThen click on any element of interest for example


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UW OCEAN 520 - Trace Metals in Seawater

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