1. Botkin & Keller Environmental Science 5e Chapter 5 The Biogeochemical Cycles

2. Botkin & Keller Environmental Science 5e The Geologic Cycle The Geologic Cycle: –The processes responsible for formation and change of Earth materials –Best described as a group of cycles: Tectonic Rock hydrologic Biochemical

3. Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers

4. Tectonic Cycle Creation and destruction of the Lithosphere Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers

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6. Botkin & Keller Environmental Science 5e The Rock Cycle The rock cycle: –Numerous processes that produce rocks and soils –Depends on other cycles: tectonic cycle for energy Hydrologic cycle for water for erosion –Rock is classified as Igneous – high heat, volcanic Sedimentary – weathering & erosion Metamorphic – compact, melting

7. Botkin & Keller Environmental Science 5e How Chemicals Cycle Biogeochemical Cycle –The complete path a chemical takes through the four major components – or reservoirs – of Earth’s systems 1.Atmosphere 2.Hydrosphere 3.Lithosphere 4.Biosphere

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9. Botkin & Keller Environmental Science 5e Biogeochemical Cycles and Life: Limiting Factors Macronutrients –Elements required in large amounts by all life –Include the “big six” elements that form the fundamental building blocks of life: carbonoxygen hydrogenphosphorus nitrogensulfur Micronutrients –Elements required either in small amounts by all life or moderate amounts by some forms of life and not all by others Limiting factor –When chemical elements are not available at the right times, in the right amounts, and in the right concentrations relative to each other

10. Major Chemical Cycles Water (hydrologic) Carbon Nitrogen Phophorus Botkin & Keller Environmental Science 5e

11. Botkin & Keller Environmental Science 5e The Hydrologic Cycle The Hydrologic Cycle: –The transfer of water from the oceans to the atmosphere to the land and back to the oceans. POWERED BY THE SUN !! –Includes: Evaporation of water from the oceans Precipitation on land Evaporation from land Runoff from streams, rivers, and sub-surface groundwater Transpiration from plants

12. Human Impacts Withdrawal: –Removal from society & industry faster than recharged (overdraft) Increased flooding: –Removal of wetlands & creating non-pourous tracts Deforestation: –Clearing land reduces transpiration, therefore there is a decrease in precipitation. Botkin & Keller Environmental Science 5e

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14. Botkin & Keller Environmental Science 5e

15. The Carbon Cycle 4 th most abundant element in the universe Building block of life Cycles through the geosphere, biosphere, ocean and atmosphere Two types of cycling –Geological carbon cycle –Biological carbon cycle Botkin & Keller Environmental Science 5e

16. Geological Carbon Cycle Botkin & Keller Environmental Science 5e

17. How does this work? CO 2 reacts with atmospheric water and minerals to produce calcium carbonate. Calcium carbonate rock (limestone) weathered by water – dissolves and travels to ocean. Forms sedimentary layers in the ocean. Through plate tectonics, sediments subduct and melts. Carbon is released into the atmosphere during volcanic eruption as CO2 Botkin & Keller Environmental Science 5e

18. Biological Carbon Cycle Botkin & Keller Environmental Science 5e

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21. Carbon Reservoirs Ocean – dissolved, calcium carbonate of marine organisms shells Geosphere – soils, fossil fuels Biosphere –living organisms Atmosphere – 0.038% of troposphere –(Acts as natural thermostat for Earth) Botkin & Keller Environmental Science 5e

22. Human impacts Increases Carbon Dioxide in the atmosphere by: –Burning of fossil fuels –Clear cutting of trees Botkin & Keller Environmental Science 5e

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24. Botkin & Keller Environmental Science 5e

25. Botkin & Keller Environmental Science 5e The Nitrogen Cycle The nitrogen cycle: –Limiting factor for primary productivity –2 forms as nutrients: NH 4 and NO 3 –Conversion of N 2 gas into nutrients – lightning & nitrogen fixing bacteria Nitrogen reservoirs: –Atmosphere 78% of Troposphere

26. Common nitrogen compounds N 2 - nitrogen gas NH 4 - ammonium NH 3 - ammonia NO 3 - nitrate NO 2 - nitrite N 2 O - nitrous oxide NO 2 - nitrogen dioxide HNO 3 - nitric acid Botkin & Keller Environmental Science 5e

27. Steps in the Nitrogen Cycle Nitrogen fixation: –N 2 converted to NH 4 or NH 3 by bacteria Ammonification (mineralization) –Decomposers turn organic material into NH 4 or NH 3 Nitrification –Bacteria convert NH 4 & NH 3 into NO 3 for plant uptake Denitrification –Bacteria convert NH 4 & NH 3 into N 2 & N 2 O Botkin & Keller Environmental Science 5e

28. Nitrogen fixation In order to be used by most living organism nitrogen must by in the form of NH 3 or NO 3. Nitrogen is ‘fixed’ by lightning or bacteria. ‘Fixing’ allows nitrogen to be made biologically available. Can be found on the roots of legumes. Botkin & Keller Environmental Science 5e

29. Nitrification Soil bacteria convert ammonia (NH 4 ) into a form that plants can use –NO 3 Botkin & Keller Environmental Science 5e

30. Assimilation Plants absorb ammonium (NH 3 ), ammonia (NH 4 ) and nitrate (NO 3 ) through their roots. Heterotrophs (or organisms that receive energy from consuming other organisms) obtain nitrogen from consuming plant proteins or other animals. Botkin & Keller Environmental Science 5e

31. Ammonification Decomposing bacteria convert dead organisms and other waste to ammonia (NH 3 ) or ammonium (NH 4 ), which can be reused by plants Botkin & Keller Environmental Science 5e

32. Denitrification Specialized bacteria (anaerobic) convert ammonia back to nitrates and nitrites THEN back into nitrogen gas and nitrous oxide, where they enter the atmosphere. Botkin & Keller Environmental Science 5e

33. Nitrogen Cycle Botkin & Keller Environmental Science 5e

34. Additional Info Assimilation: –Plants take up inorganic nitrogen (NH 3 & NO 3 ) and convert to organic compounds (amino acids) Botkin & Keller Environmental Science 5e

35. Human Impacts Excess Nitrates –Animal waste, municipal discharge Can promote algae growth Burning of Fossil Fuels –Released NO, NO 2 and HNO 3 Use of inorganic fertilizers –Increases denitrification by anaerobic bacteria, and therefore releases more NO 2 into the atmosphere. Botkin & Keller Environmental Science 5e

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37. The Phosphorus Cycle The phosphorus cycle: –Involves the movement of phosphorus throughout the biosphere and lithosphere –Important because phosphorus is an essential element for life and often is a limiting nutrient for plant growth. Botkin & Keller Environmental Science 5e

38. Phosphorus Reservoirs Ocean sediments Terrestrial rock layers –Erosion releases PO4 for producers –Limiting factor for primary productivity Botkin & Keller Environmental Science 5e

39. Guano Island Botkin & Keller Environmental Science 5e

40. Human Impacts Phosphate run-off from –Sewage, mining & fertilizers –Algal blooms Botkin & Keller Environmental Science 5e

41. Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers

42. Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers