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THE NITROGEN CYCLE. Warm Up How much of the atmosphere is made up of Nitrogen? Why do plants and animals need nitrogen? Read “The nitrogen cycle” and.

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Presentation on theme: "THE NITROGEN CYCLE. Warm Up How much of the atmosphere is made up of Nitrogen? Why do plants and animals need nitrogen? Read “The nitrogen cycle” and."— Presentation transcript:

1 THE NITROGEN CYCLE

2 Warm Up How much of the atmosphere is made up of Nitrogen? Why do plants and animals need nitrogen? Read “The nitrogen cycle” and answer questions 1-10

3 What is Nitrogen? -the most abundant element in the earths atmosphere (78% of the atmosphere) -can’t be absorbed by animals/plants until it is converted by the nitrogen cycle -needed to make protein

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5 Nitrogen Fixation-converting nitrogen to ammonia. Bacteria along with electrical storms can help convert Nitrogen gas (N 2 ) into ammonia (NH 4 + ) Lightning provides sufficient energy to split the nitrogen atoms of nitrogen gas Forming oxides of nitrogen NO x and NO 2 © 2008 Paul Billiet ODWSODWS

6 Nitrification-Ammonia to Nitrates by Bacteria This involves two oxidation processes The ammonia produced by ammonification is first converted to nitrite (by bacteria):  NH / 2 O 2  NO H 2 O The nitrite is then converted to nitrate (by bacteria):  NO / 2 O 2  NO 3 - The bacteria to do this are chemoautotrophs © 2008 Paul Billiet ODWSODWS

7 Ammonification-Nitrogen to Ammonia by decomposition. Nitrogen enters the soil through the decomposition of protein in dead organic matter  Creates ammonia © 2008 Paul Billiet ODWSODWS

8 Denitrification-Returning Nitrogen to the Atmosphere Nitrates and nitrites can be used for their oxygen for bacteria once the oxygen is used.....Nitrogen (N 2 ) is returned to atmosphere. 2NO 3 -  3O 2 + N 2 2NO 2 -  2O 2 + N 2 © 2008 Paul Billiet ODWSODWS

9 Root uptake Nitrate NO 3 - Plant protein Soil organic nitrogen Nitrogen from the atmosphere Biological fixation Atmospheric fixation Out gasing Atmospheric Nitrogen Gt © 2008 Paul Billiet ODWSODWS

10 University of Sydney Alafalfa (Medicago sativa) USDA - ARS Root nodules

11 The nitrogen fixers Cyanobacteria are nitrogen fixers that also fix carbon (these are photosynthetic) Rhizobium bacteria are mutualistic with certain plant species e.g. Legumes They grow in root nodules Azotobacter are bacteria associated with the rooting zone (the rhizosphere) of plants in grasslands © 2008 Paul Billiet ODWSODWS

12 Nitrate NO 3 - Atmospheric fixation Out gassin g Plant protein Atmospheric Nitrogen Ammonium NH 4 + Soil organic nitrogen The human impact Biological fixation Industrial fixation © 2008 Paul Billiet ODWSODWS

13 Industrial N-Fixation The Haber-Bosch Process N 2 + 3H 2  2NH 3 High temperatures (500°C) High pressures (250 atmospheres) The energy require comes from burning fossil fuels (coal, gas or oil) Hydrogen is produced from natural gas (methane) or other hydrocarbon © 2008 Paul Billiet ODWSODWS

14 The different sources of fixed nitrogen Sources of fixed nitrogenProduction / M tonnes a -1 Biological175 Industrial50 Internal Combustion20 Atmospheric10 © 2008 Paul Billiet ODWSODWS

15 Eutrophication-Nitrogen into water. Nitrogen finding its way into bodies of water Usually washed from draining soil When fertiliser is added to these soils it too will be washed out into water bodies This leads to a serious form of water pollution © 2008 Paul Billiet ODWSODWS

16 Fertilisers washed into river or lake New limiting factor imposes itself Sewage or other organic waste Eutrophication © 2008 Paul Billiet ODWSODWS

17 Increased Biochemical Oxygen Demand (BOD) Hot water from industry (Thermal pollution) Pollution from oil or detergents Reduction in dissolved O 2 Making things worse! © 2008 Paul Billiet ODWSODWS

18 The death of a lake Death/emigration of freshwater fauna Methaemoglobinaemia in infants Stomach cancer link (WHO limit for nitrates 10mg dm -3 ) Increased nitrite levels NO 3 -  NO 2 - Reduction in dissolved O 2 © 2008 Paul Billiet ODWSODWS


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