oxygen triple isotope composition for estimating photosynthesis rates l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Oxygen triple isotope composition for estimating photosynthesis rates PowerPoint Presentation
Download Presentation
Oxygen triple isotope composition for estimating photosynthesis rates

Loading in 2 Seconds...

play fullscreen
1 / 10

Oxygen triple isotope composition for estimating photosynthesis rates - PowerPoint PPT Presentation


  • 166 Views
  • Uploaded on

Oxygen triple isotope composition for estimating photosynthesis rates. Nir Krakauer niryk@caltech.edu June, 2006. O isotopes. 17 O/ 16 O ≈ 3.8 ∙ 10 −4 18 O/ 16 O ≈ 2.0 ∙ 10 −3 Isotope mass ratio, (m 17O − m 16O ) / (m 18O − m 16O ) = 0.5010 Different standard materials:

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Oxygen triple isotope composition for estimating photosynthesis rates' - oswald


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
oxygen triple isotope composition for estimating photosynthesis rates

Oxygen triple isotope composition for estimating photosynthesis rates

Nir Krakauer

niryk@caltech.edu

June, 2006

o isotopes
O isotopes
  • 17O/16O ≈ 3.8 ∙ 10−4
  • 18O/16O ≈ 2.0 ∙ 10−3
  • Isotope mass ratio, (m17O − m16O) / (m18O − m16O) = 0.5010
  • Different standard materials:
    • Standard mean ocean water
    • PDB carbonate
    • Atmospheric O2

Coplen et al 2002

mass independent fractionation
Mass-independent fractionation
  • Discovered in 1980s: ozone produced by O(3P) + O2 + M → O3 + M has equally high δ17O and δ18O
  • Explanations:
    • Self-shielding of abundant isotopologue
    • Greater energy-level density for asymmetric species (e.g. Liang et al 2004)
application ocean gross o 2 production rate
Application: Ocean gross O2 production rate
  • Define Δ17O ≡δ17O – 0.521∙δ18O: unaffected by respiration & evaporation
  • Δ17O of dissolved O2 at equilibrium with atmosphere: 16 per meg (Δeq)
  • Δ17O of photosynthetically produced O2: 159 per meg (Sea of Galilee); 249 per meg (Ocean) (Δmax)
  • By isotope mass balance, for the surface ocean I∙Δeq + GP∙Δmax = (E+R)∙Δdiss where
    • Δdiss = surface-ocean Δ17O
    • GP = gross O2 production
    • I = O2 invasion
    • E = O2 evasion
    • R = respiratory O2 consumption
  • equivalently, GP = K∙C0∙(Δdiss– Δeq)/(Δmax– Δeq) where
    • K = air-sea gas transfer velocity
    • C0 = equilibrium water O2 concentration
  • Largest uncertainty seems to be the accuracy to which K is known, no better than 30%.

Luz and Barkan 2000

upper ocean 17 o
Upper-ocean Δ17O

Juranek and Quay 2005

net o 2 release photosynthesis ratio
Net O2 release / photosynthesis ratio
  • Independent of gas transfer velocity
  • Export ratio for productive ocean should be around 0.1

Juranek and Quay 2005

more ratios southern ocean
More ratios (Southern Ocean)

Hendricks et al 2004

17 o of co 2
Δ17O of CO2
  • Increases in the stratosphere because of O exchange with photolyzed ozone, decreases toward 0 from O exchange with water in plants and the ocean
  • If the stratospheric contribution is known, high-precision measurements could provide an estimate of gross CO2 flux through land plants, otherwise hard to measure

Hoag et al 2005

references
References

Coplen, T. B., J. K. Bohlke, P. De Bievre, et al. (2002), Isotope-abundance variations of selected elements - (IUPAC Technical Report), Pure and Applied Chemistry, 74(10), 1987-2017.

Hendricks, M. B., M. L. Bender and B. A. Barnett (2004), Net and gross O-2 production in the Southern Ocean from measurements of biological O-2 saturation and its triple isotope composition, Deep-Sea Res. Part I-Oceanogr. Res. Pap., 51(11), 1541-1561.

Hoag, K. J., C. J. Still, I. Y. Fung, et al. (2005), Triple oxygen isotope composition of tropospheric carbon dioxide as a tracer of terrestrial gross carbon fluxes, Geophys. Res. Lett., 32(2).

Juranek, L. W. and P. D. Quay (2005), In vitro and in situ gross primary and net community production in the North Pacific Subtropical Gyre using labeled and natural abundance isotopes of dissolved O-2, Global Biogeochem. Cycles, 19(3).

Luz, B. and E. Barkan (2000), Assessment of oceanic productivity with the triple-isotope composition of dissolved oxygen, Science, 288(5473), 2028-2031.

Thiemens, M. H. (2006), History and applications of mass-independent isotope effects, Annu. Rev. Earth Planet. Sci., 34, 217-262.