the nitrogen cycle

Question 1

what are the main reservoirs for nitrogen

Answer 1

1) atmosphere- nitrogen gas, oxides of nitrogen
2) biosphere- DNA, proteins
3) lithosphere - ammonium compounds in the soil, nitrites, nitrates
4) hydrosphere- dissolved nitrates and ammonium ions

Question 2

list the main processes of the nitrogen cycle

Answer 2

1) ionisation
2) fixation
3) food chains
4) nitrification
5) denitrification
6) leaching
7) root absorption
8) ammonification

Question 3

outline the process of ionisation

Answer 3

processes such as lightening provide energy for atmospheric nitrogen and oxygen to react producing oxides of nitrogen and nitrate ions

Question 4

outline the process of nitrogen fixation

Answer 4

microorganisms reduce nitrogen into ammonium ions such as azotobacterial or rhizobium

Question 5

outline the process of food chains

Answer 5

nitrogen passes between organisms as amino acids and proteins in food

Question 6

outline the process of nitrification

Answer 6

the oxidation of ammonium ions into nitrites then into nitrates by nitrifying bacteria such as nitrosomonas and nitrobacteria

Question 7

outline the process of denitrification

Answer 7

the chemical reduction of nitrates in the soil into nitrogen gas by bacteria such as pseadosomonas

Question 8

outline the process of leaching

Answer 8

the high solubility of nitrates means they easily leach out of the soil into water bodies where they act as nutrients for aquatic plants

Question 9

outline the process of root absorption

Answer 9

plants absorb nitrogen as soluble ions

Question 10

outline ammonification

Answer 10

the amino groups of proteins are releases as ammonium ions by the action of bacteria and fungi

Question 11

list the human impacts on the nitrogen cycle

Answer 11

1) Haber process
2) agriculture
3) pollution

Question 12

outline the impact of the Haber process

Answer 12

• an industrial process for producing ammonia from nitrogen and hydrogen using high temps and pressure
• artificial fixation uses high energy and is often used for agricultural fertilizers

Question 13

outline the impact of agriculture

Answer 13

• use of fertilizers may increase leaching causing eutrophication
• drainage of fields makes soil more aerobic increasing the number of nitrifying bacteria and decreasing the number of denitrifying bacteria
• plowing increases the rate of decomposition
• leguminous plants increase nitrogen compounds in the soil

Question 14

outline the impact of pollution

Answer 14

oxides of nitrogen are released into the atmosphere by combustion processes

Question 15

list the sustainable management techniques of the nitrogen cycle

Answer 15

1) control combustion processes
2) control nox release
3) manage biological wastes
4) management of soil processes

Question 16

list some soil management techniques

Answer 16

• cultuvation of legumes
• crop rotation
• control of nitrate leaching
• low soluble fertiliser use
• minimal use of nitrate fertilisers where leaching into aquifers is likley