Lecture 6 biogeochemical cycles
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The document discusses the oxygen cycle on Earth, including the major sources and sinks of oxygen. It notes that photosynthesis by plants and phytoplankton is the primary source of oxygen, producing about 30,000 teragrams of oxygen per year. Respiration by animals and decay of organic matter act as sinks and consume a similar amount, keeping atmospheric oxygen concentrations relatively stable over time.
Lecture 6 biogeochemical cycles
- 3. • • • • • • • • • • •
- 5. Ecosystem Pool Turnover Time = = Coffee Cup Time it takes for all coffee molecules in Residence Time cup to be = replaced with Average time that new coffee one coffee molecule spends inside cup “sink” Steady State Non-Steady State Non-Steady State input = output input > output input < output
- 7. %, percent of Earth’s water y, years d, days
- 8. Video Everglades, coral reef, restoration, agriculture, irrigation: http://video.nationalgeographic.com/video/player/environment/going-green- environment/conservation-in-action/everglades.html
- 9. photosynthesis produces O2 • • Oxidation of Earth’s Minerals e.g., oxidation of iron (rust) – transfer of electrons from Fe2+ to O2 • 4 Fe2+ + O2 4 Fe3+ + 2 O2 •
- 10. 3.7 x 107 8400 8384 2.4 x 105 16 16 Units are 16 x 108 1012 moles O2 / year By far the largest reservoir of Earth's oxygen is within the silicate and oxide minerals of the Earth’s crust and mantle (99.5%). Only a small portion has been released as free molecular O2 to the biosphere (0.01%) and atmosphere (0.5%).
- 11. Walker, J. C. G. (1980) The oxygen cycle in the natural environment and the biogeochemical cycles, Springer-Verlag, Berlin. 16,000,000,000,000,000 Biosphere 1,400,000,000,000,000,000 Atmosphere 290,000,000,000,000,000,000 Lithosphere (Geosphere)
- 12. Annual gains and losses of atmospheric oxygen (1010 kg O2 per year) Gains Photosynthesis (land) 16,500 Photosynthesis (ocean) 13,500 Photolysis of N2O 1.3 Photolysis of H2O 0.03 Total Gains ~ 30,000 Losses - Respiration and Decay Aerobic Respiration 23,000 Microbial Oxidation 5,100 Combustion of Fossil Fuel 1,200 Photochemical Oxidation 600 Fixation of N2 by Lightning 12 Fixation of N2 by Industry 10 Oxidation of Volcanic Gases 5 Losses - Weathering Chemical Weathering 50 Surface Reaction of O3 12 Total Losses ~ 30,000
- 13. Video, Antarctica ecosystems (research on seals and whales): http://www.pbs.org/wnet/nature/episodes/under-antarctic-ice/video-full- episode/1430/
- 18. Cutting Cows’ Greenhouse Gas Emissions: http://video.nationalgeographic.com/video/player/news/environment- news/uk-cowgas-apvin.html