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What are biogeochemical cycles?

What are biogeochemical cycles?. Earth system has four parts Atmosphere Hydrosphere Lithosphere Biosphere Biogeochemical cycles: The chemical interactions (cycles) that exist between the atmosphere, hydrosphere, lithosphere, and biosphere.

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What are biogeochemical cycles?

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  1. What are biogeochemical cycles? • Earth system has four parts • Atmosphere • Hydrosphere • Lithosphere • Biosphere • Biogeochemical cycles: The chemical interactions (cycles) that exist between the atmosphere, hydrosphere, lithosphere, and biosphere. • Abiotic (physio-chemical) and biotic processes drive these cycles • Focus on carbon, nitrogen, water cycles (but could include all necessary elements for life)

  2. What is common amongst them? • Typical exist in all four parts of the Earth System • There are ‘pools’ • Are transformed chemically or biochemically • There are fluxes between the pools • Transformations are important • Transformations can lead to positive and negative consequences

  3. Examples of Transformations Carbon cycle: Organic compounds to CO2 (process: decomposition or fire) Carbon cycle: CO2 to organic compounds (process: photosynthesis) Nitrogen cycle: N2 to NO3 (atmospheric nitrogen to plant utilizable nitrate) (process: N-fixation) Nitrogen cycle: N2 to NH3 (plant utilizable ammonia) (process: Haber-Bosch Industrial N-fixation) Water cycle: Liquid water to water vapor (process: evaporation and evapo-transpiration) Water cycle: Water vapor to liquid water (process: condensation) Transformations

  4. Carbon Cycle 760 59 5000 http://www.epa.gov/climatechange/kids/carbon_cycle_version2.html

  5. Key Aspects of the Carbon Cycle • Carbon is the skeleton of all life. • Carbon dioxide is a critical gas: • Taken up by plants in photosynthesis • Released by plants and animals in respiration • Released during decomposition (and fires) • Greenhouse gas (greenhouse effect - your car in the sun)

  6. Forms of Nitrogen N2 - inert gas, 78% of the atmosphere NO, N20, NO2 - other gases of nitrogen, not directly biologically important. Part of the gases found in smog. NO3- and NH4+ -- ionic forms of nitrogen that are biologically usable. • Forms & Sources of biologically available nitrogen • For plants • NO3- • NH4+ • Sources: N-fixation by plants (N2 to NH3 and N2 to NO3), lightening, bacteria decomposition of organic N (amino acids & proteins) • For animals • Organic forms: amino acids and proteins (from plants or other animals) • Losses of nitrogen from system • In bogs, lakes (places of low oxygen), NO3- is converted to N2 by bacteria (get their oxygen from the NO3) • Volatilization of NH4+ (urea) to ammonia gas (NH3) - warm, dry conditions. • Leaching of NO3- (nitrate) • Erosion • Fire (combustion) Nitrogen Cycle http://soil.gsfc.nasa.gov/NFTG/nitrocyc.htm

  7. Nitrogen Sources over time

  8. Nitrogen Cycle: Key Points • Nitrogen is in the atmosphere as N2 (78%) • N2 is an inert gas and cannot be used by plants or animals • N2 can be converted to a usable form via • Lightening • N-fixing plants and cyanobacteria • Industrial process • Nitrogen limits plant growth

  9. Summary • 1. What are systems? • 2. What are biogeochemical cycles? • 3. Why are they important? • 4. What is common about them? • 5. Carbon and nitrogen cycles

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