Biogeochemistry:
Marc ELSKENS
- C isotope fractionation during carbon fixation by plants: explain the mass balans.
- Graph: correlation between the carbon isotopic signature and AOU in the Atlantic and the Pacific. Explain. Why the huge differences between the Pacific and the Atlantic?
- Isotopic signiture values of DIC in northern European rivers and the Amazon river. Why is the value for the Amazone much more negative?
- Graph: seasonal variability in carbon isotopic signature of atmospheric CO2. In which hemisphere?
- O signiture in carbonates and paleothermometry
- The Rayleigh fractionation proces of water condensing from vapour (see p162 of the book on biogeochemistry on dropbox). - simplified global ocean N isotope budget.
- Check point carré for the figures that go with the questions:
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- Q1 (HE + O&L): The graph shows the evolution of the oxygen isotopic composition during the process of water evaporation and condensation. Identify the different curves and explain their evolution along the X-axis. What model of isotopic fractionation does describe these processes? Does ε stay constant, or not ?
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- Q2 (HE + O&L): The equation below models the isotopic fractionation during carbon fixation (or nutrient uptake) by plants. Identify the different terms. What are the extreme values for εp that may exist ? What are common value for δ for C-3 and C-4 plants? For this kind of model to apply, what is the basic assumption regarding diffusion of the substrate through the membrane ?
- (Note that p stands for final product; t for transport; f for fixation; e for exterior and i for interior)
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- Q3 (HE + O&L): Dissolved inorganic carbon pools of river waters can have quite different C isotopic compositions, as shown below for rivers in NW Europe and for the Amazon. What are the two different possible explanations for such
differences? -
- Q4 (HE + O&L): The graph shows the relationship between δ13C of DIC and Apparent Oxygen Utilisation (AOU) in the deep ocean. Explain this relationship and the reason why Atlantic and Pacific waters do not overlap in the plot.
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- Q5 (HE + O&L): The graph below relates fractionation factor to temperature for the constituents of the H2O
molecule. What does the fractionation factor express ? What is the implication of such a relationship for the science domain of paleo- ecology, paleo-climatology?
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- Q6 (HE + O&L): Explain the evolution of CO2 and its C isotopic composition over time, as shown in the graph below. In which hemisphere could such data have been recorded ?
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- Q7 (only O&L): The graph below shows the N-inflow to the ocean due to N2 fixation and the N-outflow due to
denitrification. Setting the isotopic effect due to overall denitrification (OUT) equal to the one of N2 fixation (δIN = δOUT) is imposed by a basic assumption about ocean dynamics; what is this assumption? Why is sedimentary denitrification considered to have such a different impact (in fact the graph shows the apparent fractionation is zero) compared to water column denitrification (strong apparent effect of
