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BGC

BGC. Biogeochemical Cycles. Pathways of mater (element or chemicals). Nutrient Budgets. Inorganic --> organic --> inorganic Atm <--> land <--> water Inputs (sources) Outputs (sinks) Pathways ******HUMAN IMPACTS on the system. Hydrologic Cycle. Water is essential to living organisms

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BGC

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  1. BGC Biogeochemical Cycles

  2. Pathways of mater (element or chemicals)

  3. Nutrient Budgets • Inorganic --> organic --> inorganic • Atm <--> land <--> water • Inputs (sources) • Outputs (sinks) • Pathways • ******HUMAN IMPACTS on the system

  4. Hydrologic Cycle • Water is essential to living organisms • Dissolves/transports essential element • Precipitation • Evaporation • Transpiration • Evapotranspiration • Infiltration/percolation • runoff

  5. Water Cycle

  6. Human Impacts-water • Dams: water supply & flood control • Pavement-impervious surfaces • Air Pollutant: Aerosols • light scattering, brighter clouds • less sunlight reaching surface so less NRG to drive the cycle!

  7. Essential Elements • C, N, P, K, Mg, Ca, S  “Cycle” through trophic levels • Producers obtain them from the atmosphere or dissolved as ions in water • Consumers eat producers • Decomposers break down complex forms and create simple forms useable again by producers

  8. Carbon Cycle • 20% by weight • Backbone for long chains of organic molecules • SIX Processes: • Photosynthesis • Respiration • Exchange • Sedimentation and burial • Extraction • Combustion

  9. Carbon Cycle • Fast parts with living organisms • Slow part: rocks & soils, hydrocarbons • Photosynthesis = respiration; decomposition • CO2 into oceans  CaCO3(ppt) = limestone & dolomite rock • Fossilized C  Petroleum • EXTRACTION of fossil fuels by humans causes COMBUSTION

  10. Carbon Cycle

  11. Carbon Storage • marine sediments & sedimentary rocks (organisms shells (diatoms)) • Oceans • Fossil Fuels • Soil Organic matter • Forests

  12. Human Impacts-Carbon Cycle • w/o humans: • Earth/atmosphere C exchange is a steady state (entering = leaving): 10,000 yrs • Industrial Revolution • Excess CO2 in atmosphere: Global warming • Tree harvesting • C storage in wood • Cutting/Burning • pastures, croplands, grasslands

  13. Human Impacts-Net Carbon Release • Deforestation • Combustion since Industrial Revolution • Fossil Fuels: especially coal • Burning wood: cooking, heating

  14. Atmospheric CO2

  15. MOVIE: The Carbon Bomb

  16. Nitrogen Cycle • Limiting Nutrient (on land) • Amino acids • Nucleic acids (DNA/RNA) • 3% by mass • 78% atmosphere = N2 • FIXATION: N2 NH3 by cycanobacteria & legumes, then NH4+ into soils

  17. Nitrogen Cycle-5 steps • Fixation (atmosphere-->soil) • Assimilation (soil into biological organisms) • Ammonification (biological --> inorganic) • Nitrification (in soil) • Denitrification (back to atmosphere)

  18. (1)N-Fixation • unuseable --> useable form by organisms • Lightning/Combustion • Cyanobacteria • Fix in absence of oxygen

  19. (1)N-Fixation • Legume plants • Mutualistic relation with Rhizobium • Nodules

  20. (1) Fixation • N2 fixed abiotically in nature: N2 NO3- • Lightning • Combustion • Humans synthesize fertilizers from N2

  21. (2)Assimilation • ammonia, ammonium and nitrates into plant tissues • creation of biological nitrogen compounds

  22. (3)Ammonification • biological nitrogen compounds back to NH3& NH4+ • organic to inorganic form • Wastes have urea (urine & scat) • Decomposers • Ammonifying bacteria

  23. (4)Nitrification • NH4+ to NO2-to NO3- • Nitrifying bacteria • NO3- LEACHES through soil

  24. (5)Denitrification • Conversion of NO3-to N2O to N2 • Denitriying bacteria (O2 free areas)

  25. Nitrogen Cycle

  26. Nitrogen Cycle

  27. Human Impacts-N • Human Produced: Commercial Fertilizer overuse (fixed-N) = mobility • Eutrophication & fish kills • Groundwater contamination

  28. Human Impacts-N • Combustion of Fossil Fuels • NOx and autos • Global warming & Ozone depletion • Photochemical smog • Acid rain

  29. Human Impacts-N • In the 20th century, humans have doubled the amount of fixed nitrogen entering the global nitrogen cycle (source: R&B:p.108) • Half the fertilizer used in history have been applied since 1984 (source: NYT: 12/10/1996)

  30. MOVIE: China’s Carbon Emissions

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