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  2. 2. FAQ NITROGEN CYCLE <ul><li>What is Fixing? </li></ul><ul><li>What is Nitrogen fixation? </li></ul><ul><li>Do plants need Nitrogen? And Why? </li></ul><ul><li>How is nitrite turned into nitrate in the soil? </li></ul><ul><li>Name the bacteria responsible for turning soil nitrate into nitrogen in the atmosphere. </li></ul> HOME WORK RESEARCH QUESTIONS
  3. 3. YOU SHOULD KNOW More than half of nitrogen fixing occurs through natural processes. However only 30% of fixing is accounted for by the Haber process.
  4. 4. NUTRIENTS IN THE SOIL <ul><li>Soil nutrients are present in the form of compounds of </li></ul><ul><li>Nitrogen </li></ul><ul><li>Potassium </li></ul><ul><li>Phosphorus </li></ul>
  5. 5. FERTLISERS These are chemicals used to replenish soil nutrients that have been removed by growing crops on farm land and to improve the fertility of the soil
  6. 6. TASK ONE Nitrogen in the Atmosphere <ul><li>Process A (blue box above) shows nitrogen being taken from the air and put into the ground. In which two ways can this happen? </li></ul><ul><li>Put ticks (✓) next to the two correct answers, and explain why. </li></ul><ul><li>Bacteria in the soil that turn nitrates into nitrogen. </li></ul><ul><li>Bacteria in the roots of some plants. </li></ul><ul><li>Lightning. </li></ul><ul><li>Decomposition. </li></ul>Nitrates in the soil Process A Visit:
  7. 7. TASK TWO Two science students Patrick and Mark read an article about how to help farmers in less developed countries. Richer developed countries send synthetic fertilizers to help these farmers grow more food and boost food supply. Patrick advocates organic farming. He says it is better to use manure as synthetic fertilisers will harm the soil structure. Suggest reasons why it is not practical (technically feasible) to send manure to developing countries
  8. 8. NITROGEN FIXING Is a natural process (either biological or abiotic) by which Nitrogen (N 2 ) is made into compounds. In simple term(s), it is how nitrogen (N 2 ) gets &quot;fixed&quot; by bacteria to become available for plant use.
  10. 10. What is nitrogen cycle? How have humans interfered with the nitrogen cycle?
  11. 11. <ul><li>Four processes participate in the cycling of nitrogen through the biosphere: </li></ul><ul><li>nitrogen fixation </li></ul><ul><li>decay </li></ul><ul><li>nitrification </li></ul><ul><li>denitrification </li></ul>Denitrification Denitrification refers to the process in which nitrate is converted to gaseous compounds (nitric oxide, nitrous oxide and N2) by micro organisms. The sequence usually involves the production of nitrite (NO2-) as an intermediate step is shown as &quot;5&quot; in the diagram above.
  12. 12. NITROGEN FIXATION DIAGRAM Nitrogen Fixation The nitrogen molecule (N2) is quite inert. To break it apart so that its atoms can combine with other atoms requires the input of substantial amounts of energy. Three processes are responsible for most of the nitrogen fixation in the biosphere: atmospheric fixation by lightning biological fixation by certain microbes — alone or in a symbiotic relationship with plants industrial fixation
  13. 13. DENITRIFICATION Denitrification-Replenishing Nitrogen in the Atmosphere Four processes participate in the cycling of nitrogen through the biosphere: 1.nitrogen fixation , 2.Nitrification and 3.Decay The three processes above remove nitrogen from the atmosphere and pass it through ecosystems.
  14. 14. Denitrification Denitrification reduces nitrates to nitrogen gas, thus replenishing the atmosphere. Once again, bacteria are the agents. They live deep in soil and in aquatic sediments where conditions are anaerobic. They use nitrates as an alternative to oxygen for the final electron acceptor in their respiration. Thus they close the nitrogen cycle.
  15. 15. Human Impact On Nitrogen Cycle The activities of humans have severely altered the nitrogen cycle. Can you suggest/write down how we have influenced the nitrogen cycle
  16. 16. Fossil Fuel Increased deposition of nitrogen from atmospheric sources because of fossil fuel combustion and forest burning. Both of these processes release a variety of solid forms of nitrogen through combustion.
  17. 17. Pop quiz:     How have humans interfered with the nitrogen cycle? A. Dumping of untreated sewage and urban runoff B. Burning fossil fuels and wood C. The use of inorganic fertilizers D. Over harvesting of legumes and nitrogen-rich mines E. All of the above
  18. 18. Nitrogen Overload When we cause nitrogen overload in an ecosystem, there are many drastic effects.  Dumping of raw sewage contains nitrogenous wastes, along with urban runoff.  When large amounts of nitrogen collect in a water body, eutrophication can result.  This is an accumulation of excess nutrients which causes an algae bloom. 
  19. 19. Burning Of Fossil Fuels Burning fossil fuels and wood contributes to a large amount of nitric oxide in the atmosphere.  Nitric oxide can combine with oxygen gas to for nitrogen dioxide, which reacts with water vapour to form a strong acid (nitric acid).  This can precipitate out of the atmosphere in the form of the deadly acid rain 
  20. 20. ACID RAIN FROM FOSSIL FUELS The acid can damage trees and kill fish.  Over mining nitrogen also alter an ecosystem.