N Cycle

Question 1

N in atmosphere, biosphere, lithosphere, hydrosphere

Answer 1

Atmosphere - N 2 (gas)
NOx
Biosphere - living organisms - DNA 🧬, proteins
DOM - proteins release ammonium compounds as decompose
Lithosphere - soil: ammonium compounds, nitrites, nitrates
Rocks: minerals containing N
Hydrosphere- dissolved nitrites and ammonium ions

Question 2

Main processes in Ncycle

8

Answer 2

Ionisation ( lightening, meteor trails energy —> O + N -> NOx

Fixation - microorganisms Chem reduce N to ammonia. May b free living Bacteria in soil or symbiotically live in root nodules of legumes

Food chain - N pass between organisms in amino acids + proteins

Nitrification - oxidation ammonium ions to nitrites then nitrates, by nitrifying bacteria in soil.

Denitrification - chem reduce nitrates in soil -> nitrogen / NOx, by denitrifying bacteria, reduce soil fertility (normally anaerobic)

Leaching - highly soluble Nitrates leached our soil -> h2o body where nutrients for aquatic plants + algae

Root absorption- absorb N as soluble ions (nitrates and ammonium ions)

Ammonification - amino acids grps in protiens releases as ammonium ions by action of bacteria + fungi + detrivitores as the decompose DOM.

Question 3

Human impacts in N cycle

Disrupt natural equilibriums

Answer 3

Haber process- produce ammonia from H and N using iron catalyst at High temp and pressure. Artificial fixation of N to Ammonia - lots energy. Ammonia -> nitrates -> ag fertiliser

Agriculture - nitrate fertilisers ^ leaching problems inc. eutrophication.
- drainage of field ^ aerobic ^ no. Nitrifying bacteria and reduce no. Anaerobic denitrifying bacteria.
- soil disturbance by ploughing ^ rate decomposition of DOM -> ^ releasing of NOx into atmosphere.
Legeuminous plants ^ N compounds in soil - crops absorb.

Pollution- NOx released to atmosphere by combustion processes -> ^ quantity nitrates washed into soil by rain

Question 4

Sustainable management of N cycle (6)

Answer 4

Control of combustion processes - reduce fossil fuels and adopt circular economy- stop high manufacturing temps

Control NOx releases - catalytic converters and urea spays

Management of biological wastes - their decomposition release ammonium ions as amino acids in proteins are deaminated ( bacteria remove amino grp)

Eutrophication - biological wastes into water body. Ammonium -> nitrates and nitrites

Organic fertilisers- see book

Management of soil processes
Farming can max ad processes that increase soil nitrate levels by eg
- cultivating legumes
- crop rotation
- min pesticide that harm soil biota use
- not apply fertilisers when rain likely
- use of low tillage techniques to reduce soil disturbance
- uncultivated ‘ buffet strips’ along river
- min nitrate fertiliser use where likely leach into aquifer