4.9 Carbon Cycle

1. Photosynthesis

CO2 + H20 -(chlorophyll + light)-> C6H12O6 + O2

CO2 - Atmosphere 0.03%

Photosynthesis reduces atmospheric CO2

2. Feeding

Passage of carbon through different trophic levels

Producer -> Primary consumer -> Secondary consumer

Primary con. takes carbon molecules from producer etc..

Carbon is passed down through chain

3. Respiration

C6H12O6 + O2 -(enzymes in cell)-> Energy + CO2 + H2O

Adds CO2 to atmosphere

(All trophic levels/consumers/producers respire)

4. Decomposition

All organisms die

Organic molecules -(bacteria, fungi)-> CO2

Decomposition releases CO2

5. Combustion

a) Fossil fuels [oils, coals] -> CO2

(formed by compression and pressure of biomass)

industrial/cars, lorries etc

b) Occurrence in environment naturally

e.g. Lightning striking trees, causing forest fires etc

http://www.windows2universe.org/earth/climate/images/carboncycle_sm.jpg

4.11 Gas Pollution

Pollution of air by sulphur dioxide and carbon monoxide

1. Sulphur dioxide (SO2)
Added to atmosphere by combustion of fossil fuels
- Factories
- Vehicles (oils, petrols)
SO2 + H20 -> Sulphuric acid
Sulphur + Water vapour

Sulphuric acid = Acid rain
Affects plants and animals
Plants 'burned' by acid rain
- Top of conifers dead
- Causes Ca2+ and Mg2+ ions to be leached from system, causes yellowing of leaves (chlorosis)
Acid rains form streams, lakes
- reduces pH (acidic)
- release of aluminium ions
- thickening of mucus that lines the gills of fish
- O2 from H2O reduced
- fish suffocates

2. Carbon monoxide (CO)
Produced when fossil fuels (coal, gas) burned with insufficient oxygen
Combines with haemoglobin in red blood cells
Forms molecule called Carbaminohaemoglobin
Blocks haemoglobin from carrying O2
Reduces O2 circulation
Toxic -> fatal