The Carbon Cycle Flashcards
What is carbon?
- one of the most chemically versatile elements
- forms more compounds than any other element
- found in all life forms + needed to survive
Where is carbon found?
Carbon is found in all life forms as well as sedimentary rocks, diamond, graphite, coal, oil and gas
What is the route that carbon follows known as?
The carbon cycle
What is the carbon cycle the process of?
Transforming organic carbon into inorganic carbon
Give some examples of carbon compounds
- bio-molecules
- CO2 (carbon dioxide)
- CH4 (methane)
- CaCO3 (calcium carbonate)
- hydrocarbons
Bio-molecules
Produced in living things, e.g., fats, oils and DNA
CO2
A gas found in the atmosphere, soils and oceans
CH4
A gas found in the atmosphere, oceans, soils and sedimentary rocks
CaCO3
Solid compound found in rocks, oceans and skeletons
Hydrocarbons
Solid, liquid or gas found in sedimentary rocks
The carbon cycle: stores
This is effectively how much carbon there is and where it is. For example, soils are a major store of carbon within the terrestrial carbon system.
The carbon cycle: fluxes
Measurements of the rate of flow of carbon between the stores.
The carbon cycle: processes
The physical mechanisms which drive the flux of carbon between stores. For example, one of the key processes which drives the flux of carbon from the atmosphere to the vegetation store is photosynthesis.
What is the difference between the fast and slow carbon cycle?
The fast carbon cycle focuses primarily on the biosphere, while the slow carbon cycle is more involved with the hydrosphere, lithosphere and atmosphere.
What is a carbon sink?
A carbon sink is a store that absorbs more carbon than it releases (e.g., the Amazon Rainforest)
What is a carbon source?
A carbon source releases more carbon than it absorbs (e.g., permafrost)
Fast carbon cycle
This is where changes are rapid, occurring over years, decades and centuries
Slow carbon cycle
This is where changes are slow, occurring over millions of years.
Organic carbon
Carbon found in nature through plants and living things
Inorganic carbon
Carbon extracted from ores and minerals
Give some natural processes that drive change in the carbon cycle
- decomposition (organic, fast)
- hydrocarbon formation (inorganic, slow)
- photosynthesis (organic, fast)
- forest fires (organic, fast)
- volcanic eruptions (inorganic, fast)
- respiration (organic, fast)
- sedimentary rock forming (inorganic, slow)
- water -> air carbon transfer and deep oceans (inorganic, fast and slow)
- weathering (inorganic, fast and slow)
Give some human processes that drive change in the carbon cycle
- burning fossil fuels, combustion (inorganic, fast)
- forest fires (organic, fast)
- agriculture, animals + growing products (organic, fast)
- cars and factories (inorganic, fast)
Photosynthesis
- process where plants use light energy from the sun to produce carbohydrates in the form of glucose
- green plants absorb the light energy using chlorophyll in their leaves
- the absorbed light energy coverts carbon dioxide and water into glucose, releasing oxygen into the air
- some glucose is used in respiration and the rest is converted back to starch
Respiration
- chemical process that happens in all cells and is common to both plants and animals
- plants use some of the stored carbohydrates as an energy source to carry out their life processes by means of respiration
- glucose is converted into energy that can be used for growth and repair, movement and control of body temperature in mammals.
- carbon dioxide is then returned to the atmosphere, mostly by exhaled air.
Decomposition
- when organisms die, they are consumed by decomposers, such as bacteria, fungi and earthworms
- during this process of decomposition, carbon from their bodies is returned to the atmosphere as carbon dioxide.
- some organic material passes into the soil, where it may be stored for hundreds of years.
Combustion
- organic material contains carbon. When it is burned in the presence of oxygen (e.g., coal in a power station), it is converted into energy, carbon dioxide and water. This is known as combustion.
- the organic material can be vegetation or fossil fuels, such as natural gas (methane), oil or coal
- the carbon dioxide is released into the atmosphere, returning carbon that might have been stored in rocks for millions of years.
- wildfires and smouldering of peat accumulations contribute to a more rapid release of carbon compounds into the atmosphere.
Burial and compaction
- organic matter is buried by sediments and becomes compacted
- over millions of years, these organic sediments containing carbon may form hydrocarbons, such as oil and coal
- corals and shelled organisms, for example, take up carbon dioxide from the water and convert into calcium carbonate to build up their shells. When they die, the shells accumulate on the sea bed. Some of the carbonates dissolve, releasing carbon dioxide. The rest becomes compacted to form limestone, storing carbon for millions of years.
Weathering
- involves the breakdown or decay of rocks in their original place or close to the surface
- when carbon dioxide is absorbed by rainwater, it forms an acidic carbonic acid
- through a series of complex chemical reactions, rocks will slowly dissolve with the carbon being held in the solution.
- this is transported via the water cycle to the oceans and the carbon can then be used to build the shells of marine organisms
What is sequestration?
The process of capturing and storing atmospheric carbon dioxide
Give some types of sequestration
- carbon sequestration
- geological sequestration
- terrestrial or biological sequestration
Carbon sequestration
- the transfer of carbon from the atmosphere to the plants, soils, rock formations and oceans
- both a natural and human process, but should be classified as natural to distinguish it from the current human process of burying carbon known as carbon capture and storage
Geological sequestration
- CO2 is captured at its source (e.g., power plants) and then injected in liquid form to store underground, e.g., in depleted oil and gas reserves. This technique is still in experimental stage - carbon capture and storage (CCS).
Terrestrial or biological sequestration
- plants capture CO2 from the atmosphere and then store it as carbon in the stems and roots of the plants as well as in the soil
- CO2 dissolves in the surface of the ocean by diffusion where it is transferred to the cold deep ocean known as the ‘physical pump’
- phytoplankton also fix carbon through photosynthesis
- carbon is removed from the seawater by shell-building organisms
Why is recycling of carbon essential for life on earth?
Because it enables food to be provided for plants and animals and energy sources are created to fuel industrial development
Where is the primary source of carbon on Earth?
In the Earth’s interior. Carbon was stored in the mantle when the Earth formed, escaping at constructive and destructive plate boundaries. Some of the carbon, however, remains as CO2 in the atmosphere, some is dissolved in oceans, held as biomass in living/dead organisms and some is bound in rocks.
Organic carbon examples
Leaf litter, organic matter and humic substances found in soils
Inorganic carbon examples
Fossil fuels (oil, gas, coal) and carbonate-based sedimentary deposits like limestones.
What is peat?
Dead, undecayed organic matter found in boggy areas
What are the different spheres where carbon can be found?
In the lithosphere, biosphere, atmosphere and hydrosphere
Where is most carbon stored in the biosphere?
In tropical forest and boreal forest
Where is most carbon stored?
Majority is found in marine sediments and sedimentary rocks. Following this, is the ocean.
How much more heat does methane trap than carbon dioxide?
Methane traps 20x more heat than carbon dioxide.
What is the pedosphere?
The uppermost part of the lithosphere
What are the main stores of carbon?
- atmosphere
- biosphere
- cryosphere
- pedosphere
- lithosphere
- hydrosphere
The carbon cycle
The complex process carbon undergoes as it transforms from organic carbon to inorganic carbon and back again.
How much carbon is released per year through human activity into the atmosphere?
6.7 billion tonnes of carbon
What does Carbon Capture and Storage (CCS) involve?
Capturing the CO2 produced by power generation or industrial activity, such as steel or cement making, transporting it and then storing it deep underground.
Give a power plant CCS project
Boundary Dam in Canada
What does the Boundary Dam CCS scheme intend to do?
It will capture 90% of the emissions from a 110 megawatt coal unit. The project will eventually capture 1 million tonnes of carbon dioxide annually from the power station’s chimney. It will produce 115 megawatts (MW) of power, which is enough to power about 100,000 Saskatchewan homes.
What is biosynthesis?
The production of complex molecules within living organisms or cells
Physical factors affecting carbon stores
- volcanic activity
- natural climate change: sunspots, orbital changes (the Milankovitch Cycles), volcanic eruptions
- wildfires
- extreme weather events of cold snaps and heat waves
Human factors affecting carbon stores
- having more cars and burning more fossil fuels
- deforestation / afforestation
- disruption to the peat bog environment
- urbanisation
- growth of industry, fossil fuels, combustion
- agriculture, land use change, intensive farming of animals- the growth in dairy and meat consumption
What is the most polluting part of urbanisation in affecting carbon stores?
Creating cement, which is done by quarrying rock, such as chalk
How do wildfires affect the carbon cycle?
- when forests burn, vast amounts of stored carbon is emitted. This means that there are higher carbon levels in the atmosphere as a result.
- increased carbon in the atmosphere is a problem, because it traps heat, worsening climate change. Climate change is an issue as it threatens ecosystems and human livelihoods, through rising sea levels or more frequent extreme weather events, for example.
What are the most common causes of wildfires?
- burning debris
- unattended campfires
- electrical power
- other causes (such as cigarettes, equipment use and malfunctions, vehicle crashes and engine sparks)
Give an example of a forest fire
Yellowstone National Park forest fire
When did the Yellowstone National Park forest fire occur?
1988
Where did the Yellowstone National Park forest fire occur?
In Western USA
Yellowstone National Park forest fire of 1988 overview
- almost 250 different fires started in Yellowstone and the surrounding national forests between June and August
- 7 of them were responsible for 95% of the total burned area
- the wildfires burned around 683,000 of the park’s 2.2 million acres
- most of the fires were caused by lightning
- in response, more than $120 million was spent fighting the fires in the Greater Yellowstone Ecosystem.
How did the Yellowstone forest fires affect the carbon cycle?
- when a wildfire occurs, they release more carbon into the atmosphere than the area is able to capture
- on average, Yellowstone park emits about 44 million tons of carbon dioxide, so after the wildfires of 1988, it is likely that this figure was higher.
What are wildfires?
A wildfire is an unplanned fire that burns in a natural area, such as a forest or grassland
What are some of the responses to stopping wildfires once they have started?
- fire fighters act by spraying the allocated area with water and foam
- spraying ahead of wildfires to stop the fire spreading
- create fire breaks by removing a line of vegetation or digging a trench to stop the fire spreading
- back burning is where areas ahead of the fire are deliberately burnt in a controlled way to remove the fire’s fuel supply
What are some of the responses to preventing wildfires in the future?
- removing dead leaves and branches in areas prone to wildfires
- organising controlled burning to remove fuel
- giving fines to those who are caught starting fires