Topic 7: Carbon Cycle Flashcards
What does it mean that the carbon cycle is in a state of dynamic equilibrium naturally?
- the processes cancel each other out
- there is little to no change in the amount of carbon in each reservoir in the cycle
What do humans do to the natural equilibrium that the carbon cycle is in?
-they alter the dynamic equilibrium it is in because they alter many of the processes in the carbon cycle
- so some reservoirs become depleted, whereas other reservoirs of carbon are increased
Main reservoirs of the carbon cycle
Lithosphere,biosphere,hydrosphere,atmosphere
Stores of carbon in the lithosphere
Carbonaceous rocks e.g. limestone
Fossil fuels
Stores of carbon in the biosphere
Carbohydrates,proteins, lipids
Living organisms
Dead organic matter
Stores of carbon in the hydrosphere
Hydrogen carbonate ions
Dissolved carbon dioxide
Stores of carbon in the atmosphere
Carbon dioxide, methane, carbon monoxide
5 main processes of the carbon cycle
Respiration
Food webs
Photosynthesis
Fossilation
Combustion
Respiration as a process in the carbon cycle
Releases energy captured in photosynthesis, which is used to drive metabolic processes
Aerobic respiration returns carbon to atmosphere as CO2
It breaks down organic molecules more completely than anaerobic respiration and releases more energy
Anaerobic returns carbon to the atmosphere as methane
Food webs as a process of the carbon cycle
Carbs,lipids,proteins are produced by plants
Some of these are eaten by herbivores, which may then be eaten by carnivores
These feeding relationships form food webs
Photosynthesis as a process in the carbon cycle
Captures light energy using chlorophyll, and converts low—energy substances like CO2 and H2O into high energy carbs, which might be converted to other substances like proteins and lipids
Combustion as a process in the carbon cycle
Burning of organic matter
Releases carbon dioxide
Natural fires in forests & grasslands may be started by lightning
What is fossilisation?
The incomplete combustion of dead organic matter
Often under anaerobic conditions and can produce substances that form long-term carbon stores
Fossilisation as a process of the carbon cycle
Can produce long term carbon stores
E.g. organisms with exoskeletons, like coral, contain calcium carbonate
This may produce rocks like limestone, which contain most of the carbon in the lithosphere
6 ways that humans affect the carbon cycle
Changes to respiration
Changes to photosynthesis
Carbonic acid concentration in the sea
Biomass movements
Combustion
Methane releases from fossil fuels
How do humans affect the carbon cycle through combustion?
Increase CO2 in the atmosphere by the combustion of fossil fuels and wood
How do humans affect the carbon cycle by increasing methane?
Methane may be released into the atmosphere during the extraction of fossil fuels
How do humans alter the carbon cycle by biomass movements?
Humans move large amounts of carbon in biomass between areas, this can have environmental impacts because it reduces local changes
E.g. movement of marine biomass to terrestrial ecosystem by fishing
- movement of biomass into the sea when sewage is discharges
How do humans increase the carbonic acid concentration in the sea?
More CO2 in the atmosphere
More CO2 is dissolved in the sea
More hydrogen ions
Higher PH
How do humans cause changes to aerobic respiration?
Ploughing increases the oxygen supply to decomposers,so more aerobic decomposition and the amount of carbon in dead organic matter in the soil is reduced and the amount in the atmosphere is increased
How do humans cause changes to anaerobic respiration?
Methane is produced by anerobic respiration
Anerobic environments: rice padi fields,landfill,anaerobic sediments in reservoirs, livestock intestines
Anerobic environments are destroyed by the drainage of marshlands or peat bogs
How do humans cause changes in photosynthesis?
Deforestation, afforestation
Marine pollution itch toxic material reduces phytoplankton, so more CO2 in atmosphere not marine sediments
Algae that live on ice will die when it melts
Suggest 4 ways that the carbon cycle can be sustainably managed
Conservation of biomass carbon stores
Use of alternatives to fossil fuels
Carbon sequestration
CCS-carbon capture and storage
Explain the conservation of biomass carbon stores
Habitats e.g. peat bogs are protected from exploitation or land use change to prevent further CO2 releases
Explain the use of alternatives to fossil fuels
Renewable energy sources and nuclear power to produce lower CO2 emissions than fossil fuels
Explain carbon sequestration
Large scale tree planting will remove a lot of CO2 from the atmosphere then act as a reservoir when trees are fully grown
Still a store if they are kept and used to build houses
3 elements of CCS
Pre-combustion technology
Post-combustion technology
Storage
What is pre-combustion technology?
Changing the fuel or way that it is combusted, may be more expensive and require new technology bit makes CO2 removal more efficient
example of pre-combustion technology
Whilst post-combustion technology is useful for small sources, this captures carbon before fuel is used so it isnt released
E.g. gasification turns coal into gaseous hydrogen and CO2 , when burnt the excess gas+water not CO2
Post combustion technology
Carbon dioxide can be removed from the exhaust gases of fossil fuel combustion using several methods
E.g. dissolving in solvent,cryogenic separation,graphene absorption
Storage (CCS)
Proposals to use underground geological structures to store CO2
Or use it in secondary oil recovery
