06-生物地球化學(xué)-13C

1、,Geochemistry of Stable Isotopes,Reconstruction of biogeochemical processes by characteristic changes in the isotopic composition,d13C,d34S,d15N,Primary production,Remineralization,Geochemie der Stabilen Isotope,primary production,CO2 + H2O,CH2O + O2,Photosynthesis,Respiration,Geochemistry of Stable

2、 Isotopes,Organic matter oxidation pathways and their free energy yields,Reaction,DG (KJ mol-1 of CH2O),aerobic respiration:CH2O + O2 CO2 + H2Odenitrification:5CH2O + 4NO3- 2N2 + 4HCO3- + CO2 + 3H2OMn-oxide reduction:CH2O + 3CO2 + H2O + 2MnO2 2Mn2+ + 4HCO3-Fe-oxide reduction:CH2O + 7CO2 + 4Fe(OH)3 4

3、Fe2+ +8HCO3- + 3H2Osulfate reduction:2CH2O + SO42- H2S + 2HCO3-methanogenesis:2CH2O + 2H2O 2CO2 + 4H2 and4H2 + CO2 CH4 + 2H2O,-475-448-349-114-77-58,from Berner (1982),Geochemistry of Stable Isotopes,d13Ccarb,d13Corg,eP,org,Carbon Cycle,Geochemistry of Stable Isotopes,AtmosphereHydrosphereBiosphereU

4、nlithified Sediments,CarbonateMinerals,OrganicCarbon,Geological Rock Cycle,Reaction Chamber,dcarb,dorg,dinput,UpliftWeatheringErosionMetamorphismOutgassingVolcanism,Carbon released byprocesses of,Carbon immobilizedin sedimentary rocks as,from Hayes & Summons (1992),Geochemistry of Stable Isotopes,-5

5、0,-40,-30,-20,-10,0,10,20,-60,Clark & Fritz (1997),d13C (, VPDB),Atmospheric CO2,C3,C4,CAM,Plants,Soil CO2,Groundwater DIC,Freshwater Carbonates,Ocean DIC,Marine Limestone,Mantle CO2 Metamorphic CO2,Coal Petroleum,Atmospheric CH4 Biogenic CH4,-110 ,Thermogenic CH4,Meteorite Graphite,-50,-40,-30,-20,

6、-10,0,10,20,-60,Chondrite carbonate,+40 to +60 ,Geochemistry of Stable Isotopes,-50,-40,-30,-20,-10,0,10,20,-60,d13C (, VPDB),atmospheric CO2,C3 plants,C4 plants,CAM plants,ocean DIC,marine limestone,biogenic CH4,-110 ,-50,-40,-30,-20,-10,0,10,20,-60,eukaryotic algae,cyanobacteria (cultured),cyanoba

7、cteria (natural),photosynthetic bacteria,methanogenic bacteria,-35,-30,-25,-20,-15,-10,-5,0,5,-35,-30,-25,-20,-15,-10,-5,0,5,atmospheric,CO2,marine carbonate dissolved inorganic carbon,marine phytoplankton kerogen lipids,biogenic methane,d13C (),eP,Dcarb,eP,C3 plants,C4 plants,soil carbonate groundw

8、ater DIC,methano-genesis,methano-trophy,The Exogenic Carbon Cycle,Marine Ecosystems,Terrestrial Ecosystems,Geochemistry of Stable Isotopes,CaCO3,CO32-,HCO3-,CO2(aq),Cprimary,TOC,CaCO3,CO2(aq),H2O,H+,H2O,H+,H+,H+,Ca2+,Ca2+,Diagenesis,Lithification,Photosynthetic,Fixation,Secondary,Processes,bicarbona

9、tepumping“,Fractionation of 13C bykinetic isotope effects,Fractionation of 13C byequilibrium isotope effects,Geochemistry of Stable Isotopes,Factors controlling 13C contents of sedimentary organic compounds: Principles and evidence,Hayes, J.M. (1993), Marine Geology, 113: 111-125.,Geochemistry of St

10、able Isotopes,Control parameters,d13Corg,d13C-value of carbon source,Isotopic fractionation during carbon assimilation,Isotopic fractionation duringcarbon fixation and biosynthesis,Carbon budget at different branchpoints,Geochemistry of Stable Isotopes,from Hayes (1993),Geochemistry of Stable Isotop

11、es,from Hayes (1993),Geochemistry of Stable Isotopes,Isotope and mass balance:,RdR = UdU + PdP, : carbon flow (moles/s)d : isotopic composition of reactant (R), unused reactant (U) and product (P),A kinetic isotope effect is associated with the reaction (CR CP), resulting in a 13C-depleted product a

12、nd a 13C-enriched pool of remaining carbon (CR),Geochemistry of Stable Isotopes,from Hayes (1993),Geochemistry of Stable Isotopes,from Hayes (1993),Geochemistry of Stable Isotopes,Isotopic fractionation during carbon uptake,CO2,CO2,de,di,Ce,Ci,i, de- et,i, de- et,et : 0.7 for diffusion of CO2 in wat

13、er at 25C (OLeary, 1984),cell,boundary,Geochemistry of Stable Isotopes,Isotopic fractionation during carbon fixation,CO2,Cn(H2O)n,di,Ci,f, di- ef,ef : 27 (Farquhar et al., 1982),cell,boundary,df,Geochemistry of Stable Isotopes,i(de et) = o(di et) + f(di ef),mass balance for CO2 inside the cell:,. if

14、 the carbon fluxes in and out of the cell depend upon theconcentrations (Ce, Ci), then .,o/ i = Ci/ Ce,and,f/ i = 1 - Ci/ Ce,di(df + ef),and,then .,de et = (Ci/ Ce)(df + ef et) + (1 - Ci/ Ce)df,rearrangement yields .,eP = de df = et + (Ci/ Ce)(ef et),(a),(b),(c),Geochemistry of Stable Isotopes,eP,.

15、overall isotope effect, i.e. theisotopic difference between fixed carbon (df) and the carbon source (de) .,0.7 eP 27 ,Known KIE discriminates against 13C, thus, resulting in organic carbon, that is 13C-depleted relative to CO2(aq). However, .,Geochemistry of Stable Isotopes,from Hayes (1993),Geochem

16、istry of Stable Isotopes,. as a result of bicarbonate pumping“, eP 0, thus, resulting in organic matter, that is enriched in 13C when compared to dissolved CO2 (but still depleted in 13C when compared to the bicarbonate) .,Geochemistry of Stable Isotopes,Effect of phytoplankton cell geometryon carbo

17、n isotope fractionation,Popp, B.N., Laws, E.A., Bidigare, R.R., Dore, J.E., Hanson, K.L.,Wakeham, S.G. (1993), Geochim. Cosmochim. Acta, 62: 69-77.,Geochemie der Stabilen Isotope,Chemostat growth experiments: marine diatom Phaeodactylum tricornutum marine haptophyte Emiliana huxleyi marine cyanobact

18、erium Synechococus marine diatom Porosira glacialis (Antarctica) Organisms show different cell size and cell geometry.,Geochemistry of Stable Isotopes,from Popp et al. (1998),Geochemistry of Stable Isotopes,eP,The isotopic effect during primaryproduction of organic matter depends on the CO2-existenc

19、e, on the growth rate and on cell geometry.,eP = 25.3 182 (/Ce)(V/S),Quantification of eP ?,d13C of DIC or CaCO3 d13C of photosynthesis products (GC/C/IRMS),Geochemistry of Stable Isotopes,from Hayes et al. (1999),eP = 8 18 in the modern ocean,Geochemistry of Stable Isotopes,But .,eP = dcarb - dP,eT

20、OC = dcarb - dorg,Reflection of isotopicfractionation duringprimary production,Reflection of isotopicfractionation betweeninorganic carbon source and total sedimentaryorganic material,PRIMARY SIGNAL,SECONDARY PROCESSES,Geochemistry of Stable Isotopes,Carbon and hydrogen isotope systematics of bacter

21、ial formationand oxidation of methane,Whiticar, M.J. (1999), Chemical Geology, 161: 291-314.,Geochemistry of Stable Isotopes,from Whiticar (1999),Geochemistry of Stable Isotopes,from Whiticar (1999),Geochemistry of Stable Isotopes,from Whiticar (1999),Geochemistry of Stable Isotopes,Identification o

22、f carbon source andreconstruction of principal pathways for carbon flow,total organic carbon (TOC) compound-specific carbon,Global carbon cycle,13Corg, 13Ccarb TOC, P org,FILM,Geochemistry of Stable Isotopes,-50,-30,-10,10,-20,-40,0,13Corg (),Perry & Ahmad (1977),Schidlowski et al. (1979),Hayes et a

23、l. (1983),Mojzsis et al. (1996),Rosing (1999),Early Life on Earth? The Isua Metasediments,Geochemistry of Stable Isotopes,Compound-Specific Isotope RatioMass Spectrometry (GC/C/IRMS),Evidence from carbon isotope measurements for diverse origins of sedimentary hydrocarbons. Freeman, K.H., Hayes, J.M.

24、, Trendel, J.-M., Albrecht, P. (1990)Nature, 343: 254-256.,Isotopic compositions and probable origins of organic molecules in the Eocene Messel Shale. Hayes, J.M., Takigiku, R., Ocampo, R., Callot, H.J., Albrecht, P. (1987)Nature, 329: 48-51.,Geochemistry of Stable Isotopes,Compound-Specific Isotope

25、 Ratio Mass Spectrometry,Eocene Messel Shale,Total carbonate Total organic carbon, kerogen Total extractable organic material Total extract fractionated on SiO2 column: Hexane eluent Toluene eluent Methanol eluent Alkyl porphyrin fraction (Strasbourg) Total porphyrins (Bloomington) Acid porphyrin fr

26、action (Strasbourg),+7.340.12 -28.210.03 -29.720.10 -33.660.14 -29.660.03 -28.300.07 -22.600.08 -23.430.06 -23.910.04,Sample Identification,13CPDB(),Geochemistry of Stable Isotopes,1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21,1,679 1,722 1,812 2,040 2,602 3,161 3,571 3,688 3,883 3,957 3,977 4,100 4,156 4,210 4,256 4,364 4,392 4,552 4,692 5,010 5,408,1.1 1.0 0.7 2.0 1.0 1.3 1.3 2.6 0.9 6.8 2.0 1.6 2