4.10 Nitrogen Cycle

N2 - 78 - 79% of the Atmosphere (fairly un-reactive)

1) Plants:
- NO3 (nitrate) ---> Amino acids ----> Protein (required for growth)
- DNA controls growth

2) Lightning combines N2 + O2 ---> NO3

3) Plants take in Nitrate to form Amino Acids which contain C.H.O.N. ---> Proteins

4) Food Chain:
- Producer ---> Primary Consumer ---> Secondary Consumer
- The nitrogen passes through the trophic levels in feeding in the form of protein

5) Animal - Nitrogen excretion (Urea + H20 ---> Urine)
- Return of nitrogen from the trophic levels back into soil

6) Death - Decomposers:
- Take the Urine/Urea along with the decaying organic molecules making ammonia (NH3)

7) Ammonia is converted into NO2 - (nitrite) ----> NO3 (Nitrate)
- This is done by a group of bacteria by: nitrifying bacteria

8) Plants:
- In the soil a bacteria called free-living, it takes atmospheric nitrogen (in air/soil) and turn it into nitrate

- Nodules in Leguminous plants such as Beans and clover. These plants also take in atmospheric nitrogen and turn it into nitrate for the plants

9) Denitrifying Bacteria:
- They take nitrate and convert it back to nitrogen and completing the cycle.

4.9 Carbon Cycle

1) Photosynthesis:
- CO2 and H2O are combined in photosynthesis using chlorophyll and light energy is trapped and used to form organic molecules
- Photosynthesis is responsible to reduce the amount of Carbon Dioxide in the atmosphere

2) Feeding:
- Producer ---> Primary Consumer ---> Secondary Consumer
- All the organisms put CO2 into the atmosphere by the process of respiration
- The primary consumer takes in the carbon from the producer and uses it to grow
- Carbon passes along the food chain
- In each stage, each organism carries out the process of .... =

3) Respiration
- Starts with glucose and oxygen ---> Energy + CO2
- Respiration adds CO2 to the atmosphere

4) Decomposition
- All of the organisms eventually die and the organic molecules that remain are broken down by the decomposers (bacteria and fungi)
- This results to the release of Carbon Dioxide into the atmosphere

5) Combustion
- Fossil fuels (oils and coals) -----> C02
- examples: industrial and motor vehicle (e.g. cars, lorries, aeroplanes etc.) where they combust fuels for their movement
- combustion occurs in the environment naturally (e.g. lightning striking vegetation = forest fires and grassland fires)

4.14 Enhanced Greenhouse Effect

1) Pollution:
- molecules such as CO2, CH4 and water vapour (all Greenhouse gasses) = increase in concentration in their upper atmosphere
- consequences: The infra-red light from the planet surface will be increasingly re-emitted backwards towards the surface rather than escaping into deep space.
- consequences of this = raise the average global temperature = global warming
- consequences of global warming:

• Melting of ice-caps in the polar regions = raise sea levels, Ocean currents changed, Change the way which winds are generated
• Deserts would expand
• Carnivorous forest distribution would change = Changes in the distribution of the worlds biomes to the major vegetation ecosystems
• Climate change

4.13 Greenhouse gases

1) Human activity: burning of fossil fuels - from factories, vehicles and domestic combustion of fossil fuels
- Results in the formation of more CO2 (Greenhouse gases), NO2 (Greenhouse gasses) and SO2

2)Farming:
- Animals (Cows) emit methane gas to the atmosphere which makes up 9% of the atmospheric gases. Significant contribute to the Greenhouse effect.

3) Evaporation - of H2O into water vapour
- Cloud are a significant contribute to the Greenhouse effect

4) Refrigeration/Solvents/Propellents - CFC
- CFC - combination of Chlorine, Florine and Carbon (e.g. CCL3F) it is well associated with the absorption of UV Light and catalyzing the breakdown of the O-zone layer

4.12 Greenhouse Effect

a) UV Light from the sun - short wavelength or high energy
b) 50% of the light is reflected back out into space the main cause of this are things like clouds
c) Absorption on the outer surface where the UV Light is converted and emitted as Infrared
d) Infrared light - long wave
e) Space - heat
f) Greenhouse gasses - water vapour, CO2, CH4 etc.
- the infrared light hits the greenhouse gas
- it will absorb the energy and then re-emitts it in all directions (including downwards) = re-emitts infrared and re-distributes
- some of the gasses which goes downwards to the surface raises the surface temperature a little bit higher

Enhanced greenhouse effect:
- if we raise level of pollution gasses, they will absorb more of the infrared radiation and emits it backwards towards the earth making the temperature higher = leading to climate change

CFC:
- known for their effect on ozone layer
- 03
- CCl3F ----(sunlight)---> CCL2F- + Cl-
- catalyses the breakdown of O3 into O2
- O3 is better at absorbing UV Light than O2

4.11 Gas Pollution

1. Sulphur Dioxide - SO2 (gas)
- added to atmosphere when we have the combustion of fossil fuels in factories
- fossil fuels (coals, oils) result to SO2 gas given off
- significant contributions to SO2 production comes from vehicles
- in the atmosphere: sulphur dioxide + water vapour ------> forms sulphuric acid
- sulphuric acid is found within the water which condenses: clouds and when rains = acid rain
- acid rain effects plants and animals in variety of ways:

• the trees and plants are often burned by the direct effect of the sulphuric acid on the surface.
• the top of tree dies
• causes calcium ions and magnesium ions to be leached out of the soil = the plant cant obtain calcium and magnesium and resulting to the leaves going yellow and the plant cant grow
• acid precipitation from streams which will form into the lakes. This reduces the pH making it acidic. Releases aluminium ions and this effects fish
• the aluminium causes thickening of the mucus that lines the gills of a fish and reduces the fishes ability to take oxygen from water = the fish suffocates and it dies

2. Carbon Monoxide - CO

- produced when fossil fuels (coal, gas) are burned with insufficient oxygen

- it combines with haemoglobin inside red blood cells and forms a molecules called carbaminohaemoglobin = blocks haemoglobin from carrying oxygen

- reducing oxygen circulation

- toxic and too much CO can be fatal

- difficult to get the CO to be released from the haemoglobin

- carbon monoxide pollution