Chemical Oceanography Ryan Lecture 10 - April 15, 2003 · Chemical Oceanography Metal Geochemistry Dr. David K. Ryan. Department of Chemistry. ... Chemical Reactivity – d0, d10,

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ChemicalOceanographyMetal Geochemistry

Dr. David K. RyanDepartment of ChemistryUniversity of Massachusetts Lowell&Intercampus Marine Sciences Graduate Program

http://faculty.uml.edu/David_Ryan/84.653

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Metal Geochemistry

Read Emerson & Hedges Chapter 12Read paper Donat & Bruland (1995)Read paper by Nieboer & Richardson (1980)

(Papers are posted on website for today’s class)

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Concerned with Metal Ions (Geochemistry)

Typically cations (Cu2+, Cd2+)Some anions (CrO4

2-, MoO42-, AsO4

3-)General properties of interest Reactivity

Redox – oxidation/reduction reactions Complexation or Sorption Speciation – forms

Cycling – ultimate fate Transport – mobility Toxicity/Bioavailability/Bioaccumulation

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Biogeochemical Processes

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Classification Schemesfor Metals

Concentration – Major, Minor, TraceBiological Reactivity – Biolimiting, Biointermediate, Biounlimited, NoncyclingChemical Reactivity – d0, d10, Intermediate or Class A, Class B, IntermediateOverall Reactivity – Nutrient Type, Particle Reactive, OtherEnvironmental Origin – Crustal, Pollutant (anthropogenic)

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Concentration levels

Major ions – discussed previouslymetals & non metals (Ca2+, Mg2+, Na+ , K+)Minor ions – some mention (Ba2+, Sr2+, etc.)Trace ions (Trace Metals) – all the restMillero Major: 0.05 to 750 mM Minor: 0.05 to 50 μM Trace: 0.05 to 50 nM

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Depth Profiles for Mo & WConservative behavior (Millero 2006)

Major Components, Rb+, Cs+, etc.

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Depth Profiles for Cd & PNutrient behavior (Millero 2006)

Nitrate, Silicate, Zinc, Barium, etc.

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Depth Profiles for AlMid-depth minimum (Millero 2006)

Copper, Tin, etc.

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Depth Profiles for PbSurface enriched (Millero 2006)

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Depth Profile for MnSurface enriched(Millero 2006)

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Depth Profile for FeRedox (Millero 2006)

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Depth Profile for MnAnomolous (Millero 2006)

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Classification Schemesfor Metals

Concentration – Major, Minor, TraceBiological Reactivity – Biolimiting, Biointermediate, Biounlimited, NoncyclingChemical Reactivity – d0, d10, Intermediate or Class A, Class B, BorderlineOverall Reactivity – Nutrient Type, Particle Reactive, OtherEnvironmental Origin – Crustal, Pollutant (anthropogenic)

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Nieboer & Richardson 1980

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Importance of Humic MaterialsGlobal Carbon ReservoirTake Part in Interfacial PhenomenaUndergo Coagulation and AggregationInvolved in Photochemical ReactionsContain RadicalsKnown Reducing AgentsMethylate MetalsForm Chlorinated Species, THMs DBPsDetoxify MetalsLimit Bioavailability of MetalsAlter SolubilityInfluence TransportBind Metals & Organic PollutantsTerminal Electron Acceptor for Bacteria

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Metal Complexationby Humic Materials

Leenheer et al. (1998)Morel (1983)

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Importance of Humic MaterialsGlobal Carbon ReservoirTake Part in Interfacial PhenomenaUndergo Coagulation and AggregationInvolved in Photochemical ReactionsContain RadicalsKnown Reducing AgentsMethylate MetalsForm Chlorinated Species, THMs DBPsDetoxify MetalsLimit Bioavailability of MetalsAlter SolubilityInfluence TransportBind Metals & Organic PollutantsTerminal Electron Acceptor for Bacteria

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Humic material will aggregate & may“salt out” with cations

Leenheer, J.A. et al. (1998) Environ. Sci. Technol. 32, 2410

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Dissolved Metal Species

Mx+(aq)

InorganicMetal

Complexes

MetalOrganic

Complexes

Oxidizedor Reduced

Forms

OrganometallicSpecies

Metals Sorbed toParticles/Colloids

All Dissolved Organic Compounds

Organic

Dissolved

Natural

Carbon

Matter

HumicMaterials

Substances

Humic AcidFulvic Acid

OCDOCNOC

OMNOMDOM

HM

HS

HAFA

Chromophoric or Colored DOM

CDOM

Humic Subset

23NOMy- = natural organic matter of varying negative charge y-

NOMy-

NOMy-

NOMy-

M-NOM(x-y)-

Mx+

Mx+

Mx+

Mx+ = metal ion, toxic or non, of charge x+ (e.g., Cu2+, Al3+, etc.)

Metal Organic Complexes

Mx+

M-NOM(y-x)- = metal complex of natural organic matter