教程分析教案lecture 13 metal

CHEMISTRYOFNATURALWATERS

Tuesday,March9th,2010

Traceelementsaremostlymetalsandmetalloids

Tracemetals=traceelements

Concentration<100μmol/kg

Importance

Macronutrients-openocean

ExtendedRedfieldratio

(C106N16P1)x1000Fe8Mn4Zn0.8Cu0.4Co0.2Cd0.2

Iron-limitationtheory(Martinetal.,1990)

Othermetals:Zn,Co,etc.

Toxic–coastalarea

Pb,Hg,Cu

Facilitatephyto nktongrowth

Molecular-levelstructure

MorelFMMetal.,2003

Sources

Riverrunoff

Groundwaterseeps

Atmosphericinput

Diageneticremobilizationfromnearshoresediment

Hydrothermalvent

Sinks

Scavenging

Clayminerals

Metaloxyhydroxides

POM

Memoryrecordofsediment:

ZnloadinginsedimentsofLakeZurich(AdaptedfromBeerandSturm,1992)

Sinks

Incorporationintobiogenicmaterial

Enri entfactor(EF):

EF=

MetalconcentrationinbiogenicmaterialMetalconcentrationinseawater

Internalcyclingprocesses

AtmosphericDeposition

Rivers&Sewage

Me

Me

Me

Particles

ExchangewithOceans

Land

Me Me

Me

Me Particles

Me

Scavenging

BenthicFlux

MeParticles

Burial

11

MercuryBalanceforNarragansettBay

PointSources(21%)

Atmospheric(10%)

OceanEstuaryExchange

~50%

Rivers(69%)

Sediments

~50%

OpenOceanverticalprofile

Conservative-type

Nutrient-type

Scavenging-type

Hybrid-type

Mixed

BrulandandLohan,2003

NearBermuda

SchauleandPatterson,1983(a);WuandBoyle,1997(b)

Physicalforms

Operationallydefined

Particulateform(>0.45μm)

Dissolvedform(<0.45μm)

Colloidalvs.Trulydissolved(1kDa)

Particulateform

Particlesurfaceasacarrieroffunctionalgroupsthatbindsmetals:-COOH,-OH,-NH2,-SH,etc.

Partitioncoefficient(KD):

(literkg-1)

where,Cs=theconcentrationinthesolidparticles(molkg-1)Cw=theconcentrationinwater(molliter-1)

Dissolvedform–metalspeciation

Organicvs.Inorganiccomplexes

metalion

i

Labilevs.non-labilecomplexes

diss

[Me ]Me

2K

MeX

Me2[X]K

MeL Me

2[L]

i

i

i

i i

Importanceoforganicmatter

Strongorganiccomplexation

Metal

%Complexed

Cu

>99

Zn

>98

Fe

>99

Pb

10–95?

Cd

~80

Hg

>98?

Ag

0

Cu

speciation

OpenOceanverticalprofile

Moreletal.,2003

Moffettetal.,1997

ToxicEffectofCu

pMe=-log[Men+]

Moffettetal.,1997

RedoxEffect

In ctionofbiogeochemicalcyclingofnitrogenandFespeciation–ArabianSea.

Moffettetal.(2007)

yticalMethod–

dissolved/particulatemetal

Challenge

Contamination

Labor-intensive

Time-consuming

Complexmatrix

Inductivelycoupled sma-massspectroscopy(ICP-MS)

Pre-treatsamples

Chemiluminescence,etc.

yticalMethod–metalspeciation

Electrochemistry(DASV,CLE-ACSV)

Others

Diffusivegradientinthinfilm(DGT)

Selectiveionelectrode

Ourwork:SAFIR

Summary

Recentadvancesinsamplingand yticaltechniqueshaveshownthatmetalconcentrationsfarlowerthanoriginallythought(nmol–fmol/kgrange)

Metaldistributionsareoceanographicallyconsistentandmostreflectbiogeochemicalprocesses

Summary(cont.)

Speciationcontrolledbynumerousfactors

Inorganiccomplexation

Organiccomplexation

Redoxcycling

Sorption

Photochemicaltransformation

Speciationisoffundamentalimportancei