Lecture 36 Global N 261 2009 forWeb

Lecture 36 Global N 261 2009 forWeb - When: Mon. Dec. 14,...

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FINAL EXAM When: Mon. Dec. 14, 2:00 – 4:30 pm Where: Warren Hall, B45 Now Dec 14 Human Alteration of the Global N Cycle 3 Outline • Global N budget: history, main terms • N Cascade – Coastal impacts –N 2 O production • A U.S. Case Study 4 1772: N Isolated (“discovered”) Daniel Rutherford , Scottish chemist • Isolates “noxious air” and publishes results 5 1790: Elemental N Added to Periodic Table Jean Antoine Claude Chaptal • Named the element “nitrogene” • Recognized as contributor to “nitre”, aka KNO 3 , aka saltpeter – used in gunpowder, explosives 6 1913 Industrial N Fixation: the Haber-Bosch Process Fritz Haber Nobel Prize Chemistry 1918 Photos: Nobelprize.org Carl Bosch Nobel Prize Chemistry 1931
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7 N 2 (g) + 3 H 2 (g) Æ 2 NH 3 (g) • Needs iron catalyst + very high pressure • 3-5% of world’s natural gas production consumed for fertilizer production –CH 4 used as a source for H 2 (releasing CO 2 ) – Energy for industrial process 1913 Industrial N Fixation: the Haber-Bosch Process 8 Nitrogen and Human History • Before H-B: N salts mined from deserts, very limited supply • After H-B: rapid population expansion – More than half of all food today from H-B N 9 Nitrogen and Human History Galloway & Cowling 2002 Human population (10 9 ) Haber-Bosch N prod (Tg/y) 10 Vitousek et al. 1997 Changes to the global N cycle have occurred more rapidly than for any other major factor of global change. 11 The Big Units 1 Tg, Teragram = 10 12 g = 1 MMt, 1 Million (10 6 ) metric tons (10 6 g) 1 Pg, Petagram (Pet'-uh-gram) = 10 15 g = 1 Gt, Gigaton = 1 billion (10 9 ) metric tons (10 6 g) • Other units: 1 km 2 = 100 ha 12 Human activities have roughly doubled the natural rate of production of “fixed” N.
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Lecture 36 Global N 261 2009 forWeb - When: Mon. Dec. 14,...

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