C cycle
Natural dynamic equilibrium processes cancelling each other out
C reservoirs
Atmosphere - CO2,methane, CO
Hydrosphere - hydrogen carbonate ions
Dissolved CO2
Biosphere - carbs, proteins, lipids
Lithosphere- carbonaceous rocks eg limestone, mainly as calcite (calcium carbonate)
Fossil fuels ( mainly as Cs and Hydrocarbons)
Main processes in C cycle
Photosynthesis - low energy CO2 and H2o to high energy carbs which —> lipids and proteins
Respiration - aerobic - CO2
Anaerobic- methane
Food webs
Fossilisation - incomplete decomposition DOM often under anaerobic conditions produce long term C stores ie fossil fuels.
Organisms exoskeleton calcium carbonate —> limestone
Combustion -
How humans affect C cycle
Upset natural dynamic equilibrium and change C distribution in reservoirs
Changes in photosynthesis
Changes in photosynthesis
- deforestation - less C atmosphere -> biomass
- afforestation - more c atmosphere -> biomass
- marine pollution reduce phytoplankton populations - reduce absorption of dissolved CO2 - if sink increase C in marine sediment. CO2 can’t dissolve in oceans and be used so increase atmosphere CO2
- Algae underside sea ice photosynthesis and C sink to sea bed when dead and faeces of krill eating algae - CC less ice - less CO2 removed from sea.
How humans affect C cycle
Upset natural dynamic equilibrium and change C distribution in reservoirs
Changes in aerobic and anaerobic respiration
Anaerobic env created/ destroyed by drainage
Aerobic - C in dead matter gradually released by aerobic soil organisms - ploughing increase O to them — more rapid resp ^ CO2 to atmosphere from DOM Anaerobic- absence of O, in anaerobic soil organisms —> methane gas. Methane released to atmosphere, oxidised to CO2. Anaerobic env. by human activities: - Rice paid fields - Landfill sites - Anaerobic sediments in reservoirs - Livestock intensities Anaerobic env destroyed by drainage - waterlogged field - marshland - peatbogs
How humans affect C cycle
Carbonic acid concentration in sea
Human activities affecting CO2 conc in atmosphere affect CO2 dissolving / exsolving from sea create new equilibrium .
Dissolved CO2 at equilibrium w carbonic acid which dissociates you form hydrogen carbonate and h ions. Conc H ions affect ph so ^ CO2 dissolving in oceans … ^ h ions conc and make sea more acidic.
How humans affect C cycle
Methane releases from fossil
During fossil fuel extraction
How humans affect C cycle
Combustion
Biomass movement
Combustion fossil fuels and wood
Adding compost soil
Deforestation and crop matter reduce soil DOM and soil erosion
Biomass into sea in sewage discharge
Movement marine biomass into terrestrial system - fishing/ aquaculture
Sustainable management of C cycle
- Conservation of biomass c stores - peat-bog and - forest conservation.
- Alt to fossil fuels
- Carbon sequestration
- C Capture and Storage (CCS) - capture CO2 b4 atmosphere
- Precombustion tech - capture c large scale b4 fuel burnt. Gasification concert fuel into gaseous hydrogen and CO2 ( removed for storage) H use vehicle, homes, industry.
Oxy-fuel combustion systems use pure O so only CO2 and water vapour produced. Water vapour removes by cooling the gases so that it condenses and then CO2 on own and easily captured.
2. Post-combustion tech
CO2 removed from exhaust gases of fossil fuel combustion by:
- dissolving in solvent
- high pressure membrane filtration
- absorption/ desorption processes
- cryogenic separation
- graphene adsorption
None fully developed cost uncertain - only abt 20% gases produced by combustion = CO2
3. Storage - storage underground in suitable geographical structures eg aquifers, oil fields, gas fields.
Also used secondary oil recovary
Research suggests CO2 pumped into fractured basalt may react w minerals in rock —> solid carbonate minerals
- Precombustion tech - capture c large scale b4 fuel burnt. Gasification concert fuel into gaseous hydrogen and CO2 ( removed for storage) H use vehicle, homes, industry.
