Carbon Cycle

• Carbon atoms can be arranged in many different physical forms called allotropes.
• Examples of carbon sinks:

  • atmosphere
  • soil organic matter
  • ocean
  • marine sediment
  • terrestrial plants
  • fossil fuel deposits
  • permafrost & ice
• Movement of carbon:

  Plants take in carbon dioxide from the atmosphere in the process of photosynthesis

  Produces glucose which is a carbon compounds, which is stored in roots and leaves

  Animals eat plants and digest them

  The digestive process releases the glucose, which is absorbed into the blood

  In this respiration process animals release carbon dioxide as a waste product back into the atmosphere
• Positive feedback example:

  • increased temperatures due to climate change causing melting of permafrost
• Negative feedback example:

  • increased atmospheric carbon dioxide leads to increased temperatures, promoting plant growth and rate of photosynthesis.
• Fluxes - measurements of the rate of flow of material between the stores
• carbon store - store that absorbs more carbon than it releases
• carbon sink - releases more carbon than it absorbs
• Photosynthesis equation:

  carbon dioxide + water = glucose + oxygen
• Respiration

  Plants use some of the stored carbohydrates as an energy source to carry out

  Glucose is converted into energy that can be used for growth and repair
• Decomposition:

  • when organisms die they are consumed by decomposers (bacteria)
  • During this, carbon from their bodies is returned to the atmosphere as carbon dioxide
  • Some organic matter passes into the soil where it is stored
• Combustion:

  • organic material contains carbon
  • when it is burnt in the presence of oxygen it is converted into energy, carbon dioxide and water.
• Burial & compaction:

  • organic material is buried by sediments and becomes compacted
  • over time, these organic sediment containing carbon may form hydrocarbons such as oil and coal
  • e.g corals
• Carbon sequestration - describes the transfer of carbon from the atmosphere to the plants, soil, rock formations and oceans.
• Geological sequestration - carbon dioxide is captured as its source and then ejected in liquid form to store underground. e.g Carbon capture
• Terrestrial/biological sequestration - plants capture carbon dioxide from the atmosphere and store t is carbon in the stems/roots of the plant as well as in the soil
• Weathering:

  involves the breakdown of rocks

  when carbon dioxide is absorbed by rainwater it forms an acidic carbonic acid

  though reactions, rocks will slowly dissolve with the carbon being held in the solution

  this is transported via the water cycle to the oceans and carbon can then be used to build shells of marine organisms
• Oceanic carbon pumps:

  • operates within the oceans transferring carbon from upper layers to the sea bed
  • this way it exports carbon dioxide and prevents it from further contact with the atmosphere
• Deforestation:

  • trees and vegetations store carbon dioxide by absorbing it from the atmosphere in order to carry out photosynthesis
  • when vegetation are cut down this means that all the carbon dioxide is released back into the atmosphere leading to a faster rate of global warming.
• Slow organic carbon cycle - takes hundreds of millions of years, involves long term sequestration of the remains of marine creatures and terrestrial forests of fossil deposits of oil, gas and coal.
• Slow non-organic carbon cycle - involves the transfer of carbon from the atmosphere to the hydrosphere and to the sedimentary rich rocks in the lithosphere which are recycled via tectonic movements
• fast organic carbon cycle - operates from months to centuries, mainly involves transfers of organic carbon via living things between the atmosphere, soil & biosphere
• fast non-organic carbon cycle - involves ocean to atmosphere exchange of carbon dioxide depending on the relative conditions of both
• sere - a community of plants at any given stage of succession.

  as habitats progress over time they go through a sequence of changes called vegetation succession
• Temperature on carbon cycle:

  cooler:

  • cold rain water can hold more CO2 - chemical weathering more active
  • forest coverage would very different - affects distribution of processes such as photosynthesis and respiration
  • decomposers less effective - carbon transfer to soils is reduced
  • more water stored as ice - less transferred to oceans
  • soil is frozen - stopped CO2 soil transfer
• Temperature on carbon cycle:

  warmer:

  • melting of permafrost - releases trapped gases - enhances greenhouse effect - positive feedback
• State some natural changes in carbon cycle:

  • wildfires
  • volcanic activity
  • eccentricity
• Natural affect to carbon cycle

  Wildfires:

  can be started naturally by lightning strikes

  • 1997-8 & 2003 Indonesia had lots of wildfires that burnt out of control for months
  • smoke spread across south-east Asia
  • released large amounts of CO2 into the atmosphere
  • turned forest into a source
• Natural affect to carbon cycle

  Volcanic activity:

  • returns carbon that has been trapped in the lithosphere for millions of years
  • During Palaeozoic era, volcanoes were much more active
  • CO2 was emitted into the atmosphere, where it remained for a long period of time
  • now, volcanoes emit 130-180 million tonnes of CO2 each year whereas human activities release 30 billion tonnes form burning fossil fuels.
• Natural affect to carbon cycle

  Eccentricity (shape of orbit):

  • when the earth obits the sun elliptical we spend less time clse to the sun
  • this means we get less solar energy, cooling the earth
  • less insolation = lower temperatures = CO2 trapped in ice = decreased greenhouse affect = enhances lower global temperatures
  • as temperatures start to rise at the end of glacial period, there is a surge in CO2 released
• Lake Nyros - Volcanoes

  • Cameroon 1986
  • 1,700-2,000 died
  • 3,500 cattle died
  • crater lake in the north west region
  • inactive volcanoes but 80km beneath is a pool of magma
  • the gases traveled up through the earth
  • cloud released has large concentrations of CO2, which is denser than oxygen.
  • travelled down the mountain, settling into valleys where it suffocated all inhabitants
• Volcanoes release gases but do not contribute to global warming due to the sulphur dioxide creates sulphur aerosols that actually reflect the suns rays. Global cooling
• Hydrocarbons - substances that only contains carbon and hydrogen. e,g coal, oil or natural gas
• Fossil fuel formation:

  • formed from prehistoric plants and animals
  • when dead, they decompose and become buries under layers of mad, sand and rock
  • they slowly decompose into organic materials ad form fossil fuels
  • overtime, work upwards through the crust until reaching rock formations called cap-rocks that are dense and prevent them seeping to the surface
• Land use - human affect to carbon cycle

  • impacts short term stores
  • responsible for 10% of carbon released
  • when soil is ploughed, the soil layer invert with eachother
  • livestock, ruminate and masticate which produces methane as a by-product
  • methane is also produced from cultivation of rice. Contributes up to 20% of global methane emissions
• Shimplings pack farm

  • Bury St Edmunds, Suffolk
  • a large organic arable farm specialising in wheat, barley, oats and quinoa
  • farm has calculated its carbon emissions 1150 tonnes CO2, mainly from fuel for machinery also nitrous oxide emissions from crop residues and green manures.
  • flock of 250 sheep contributes 6.6% of emissions
  • 40% emissions are offset by carbon sequestration from the farm
  • significant carbon sinks
• Positives of Shimplings farm pack

  • carbon sequestration in soils
  • organic agriculture can remove air
  • to increase yield in drought years as the additional carbon stored helps it to hold more water
  • By 2030, agriculture sector could be carbon neutral
• Human impacts on carbon cycle

  Deforestation:

  • logging operations remove forests, some act illegally also build roads to access more remote forest
  • forests also cut down due to urban sprawl
  • some in unintentional
  • rainforests could vanish in 100 years
  • forests soils are moist but without any protection from tree cover will ry out
  • trees also maintain the water cycle by returning vapour back to the atmosphere through transpiration
  • without trees many former forest land can quickly turn into barren deserts
• Carbon budget

  • limit levels of carbon dioxide in the atmosphere
  • reduce the impacts created when the dynamic equilibrium is lost