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Earth life support systems (pt2) - Coggle Diagram
Earth life support systems (pt2)
Carbon cycle
Carbon is found in the:
Pedosphere
Hydrosphere
Atmosphere
Lithosphere
Biosphere
Cyrosphere
Types of carbon cycle
Fast carbon cycle
This is where there is a large flow of carbon rapidly moving between stores.
Key areas
Carbon spends at most 6 years in the atmosphere.
Carbon spends at most 25 years in the surface oceans.
Carbon spends at most 18 years in vegitation.
Carbon spends 10 years in peats and soils.
Example of the fast carbon cycle
Plants absorb CO2 from the atmosphere through photosynthesis.
CO2 is released through respiration and digestion as carbohydrates are broken down.
Bacteria and fungi breakdown carbohydrates during decompsotion and this releases carbon into the pedosphere.
When wild fires burn plants this will also lead to the release of carbon.
Slow carbon cycle
This is the huge stores of carbon in sedimentary rocks that slowly form.
Key areas
Carbon can spend 1250 years in the Deep Oceans.
Carbon can spend more that 1000 years as sediments.
Carbon can spend 150,000,000 years as sedimentary rock.
Carbon can spend 1 million years as fossil feuls.
Example of the slow carbon cycle
Carbon in the atmosphere is sequested into the oceans.
Marine creates use carbon to form shells.
When these creatures die they pile up on the sea floor and can form sedimentary rocks.
The melting of these rocks occurs within the bienoff zone and the carbon can be released into the fast cycle durring volcanic eurptions.
Processes and stores within the carbon cycle
Precipitation
-- rainwater has disolved CO2 in it which can lead to the carbonation of rocks.
Photosynthesis
-- this is the conversion of carbon and water into glucose and oxygen.
Biological weathering
-- plants and animals can break down carbon based rocks.
Chemical weathering
-- CO2 disolved in rainwater creates carbonic acid that helps to break down rocks.
Physical weathering
-- repeated freezing and thawing of rocks helps to break them down.
Decomposition
-- bacteria and fungi breakdown dead organic matter to release carbon to the atmosphere and pedosphere.
Natural combustion
-- the natural burning of mateiral through events such as natural wildfires releases carbon to the atmosphere.
Fossil feul combustion
-- the burning of fossil feuls leads to the release of carbon.
Carbon sequestration (physical)
-- cold ocean water sinks and takes dissolved carbon with it (downwelling).
Carbon sequestration (biological)
-- phytoplankton draw carbon from surface water and use it to photosynthesis.
Vegetiation stores
-- this is where plants lock away and store lots of carbon for decades.
Ocean sediments
-- downwelling or marine snow leads to the build up of carbon deposits on the sea floor.
Sedimentary rock
-- when enough sediemnt builds up the pressure forces the water out and the sediment is compressed into rock.
Atmosphere
-- although the atmosphere is a normal store of carbon, anthopgrenic sources (human sources) are adding to the levels of carbon stored.
Respiration
-- this is when plants and animals use oxygen and carbohydrates to release CO2, water and energy (which the plants use).
Processes of carbon sequestration
Inorganic pump
This invloves the mixing of surface and deepwater ocean currents which then lead to the distribution of carbon.
Process
Carbon enters the ocean through diffususion.
Ocean currents (surface) move carbon polewards where it cools, becomes more dense and sinks (
downwelling
).
Downwelling carries individual carbon molecules to the ocean depths where they can remain for centuries.
Eventually deep ocean currents will move carbon molecules to areas of upwelling.
Cold, carbon rich water upwells to the surface where it diffuses into the atmosphere.
Biological pump
This inolves carbon moving between the atmosphere and hydrosphere through aquatic life.
Process
Phytoplankton use dissolved CO2 as well as water and sunlight to photosynethis, producing organic material.
Carbon in the phytoplankton either falls to the ocean fall as sediment or is redisolved into the oceans (both of these happen after phytoplankton die).
Animals such as mollucus and creasteans use disolved carbon and calcuim ions to produce shells.
Most carbon rich material ends up on the ocean floor and is utimalty lithified (turned into sedimentary rock) by the pressure of the ocean. In certian condiations they may also form fossil feuls.
Land use changes
Humans have modifed how land throughout the world is used transforming it from its natural habitats to land that is better suited for human demands.
This impacts both water and carbon cycles.
Urbanisation
Urbanistion
-- this is the process where urban areas expand due to increased populations.
Impacts on the water cycle
More impeamabile surfaces (tarmac and concrete) reduce inflitration.
Urban drainage systems deliever water downstream quicker then natural processes, reducing lag time and increasing flood risk down stream.
Urban development on floodplains reduces water storage capacity and leads to increased river flows and flooding.
Can be seen in the flooding of the Somerset levels where urbanisation made the flooding worse.
Impacts on the carbon cycle
Urban areas have a drasticlly lower level of vegitation and therefore a lower level of photosynthesis, decomposition and respiration (from plants).
Urban areas have high energy consumption that can lead to increased CO2 emissions.
Cement is a key component of urban areas and produces CO2 in manufacturing.
Farming
Impacts on the water cycle
Irrigation diverts water to farms and away from rivers and much of this water is lost to evaportation, impacting downstream water cycles.
Natural forests or grasslands intercept more precipitation, meaning that farmland reduces lagtime.
Inflitration is increased in farmed areas due to ploughing and artifical drainage systems that divert water back to rivers.
Use of heavy machinary can compact soil and increase run off.
Impacts on the carbon cycle
Deforesation to make way for farmland removes above ground and underground carbon stores.
Carbon stored in the soil is released when the soil is ploughed, but is not replenished as plants are havested and not left to decompose.
Carbon exchange/NPP is normally lower in farmed areas then the natural enviroment.
However, in the Great Plains wheat farms have a higher NPP then the orginal grasslands.
Rice paddies and livestock produce methane.
Forestry
Impacts on the water cycle
Forest plantations have a higher level of interception then other ecosystems.
Sitka spruce have an interecption rate of 60%, in grasslands interception is around 10-20%.
Increased evapotransipiration.
Increases the lag time between rainfalling and water entering the river. This is because of:
Increased interception.
Reduced surface runoff.
More water absorbtion.
When forests are harvested evoptransition drops, surface runoff increases and stream discharge increases (until trees are replanted).
Impacts on the carbon cycle
Drastically increases carbon storage.
Trees store 170-200 tonnes of carbon per hectare which is 10times higher then grasslands and 20times higher then heatlands.
Trees can sequest carbon from the atmosphere for hundreds of years.
Forest trees are only active carbon sinks for the first 80 to 100 years (after this they take in as much carbon as they store), this means plantations are rotated every 80 to 100 years.
Water extraction
Impacts on the water cycle
Overextraction can lead to:
Rivers drying up.
Damage to wetland ecosystems.
Can lead to sinking water tables if extraction exceeds recharge.
Sinking water tables
-- this is a reducation in the levels of groundwater.
Empty wells.
In coastal areas, water extraction of aquifers can lead to saltwater entering groundwater supplies and making them unusable.
Example: River Kennet
This is a chalk river located in the South of England, in the counties of Wiltshire and Berkshire.
Water extracted from the river upstream by Thames Water deos not re-enter the river as waste water later on.
Impacts of water extraction
Flows in the river have droped by 10-14%.
Reduced risk of flooding due to reduced flows.
Reduced areas of wetlands (which are good carbon stores) due to reduced flows.
Artesian basins
Artesian basins
-- when rocks for a basin like structure with layers of permiable and impermiable rocks an aquifer can form inbetween two layers of impermable rock.
Example: London
Groundwater is found in a chalk rock layer that is sandwiched between London Clay and Gault Clay (impeamable rock).
Aquifers are refreshed by rainfall in the North Downs and Chiltern Hills.
Over extration in the 19th and 20th centuries led to the water table droping by 90m. In the last 50 years a decline in heavy industry cut water demand and the water table began recovering.
In the 1990s it was rising at a rate of 3m per year and began to threaten buildings and tubelines, therefore since 1992 Thames Water has had limited extraction rights to prevent further rises in the water table.
Impacts of fossil feul combustion
Reasons for increased CO2 in the atmosphere
Fossil feul combustion (75% of new CO2).
Deforestion.
Melting of permafrost.
Fossil feuls and the carbon cycle
Since 1750 humans have contributed 2,000 giga tones of carbon to to enviroment (75% of that comes from burning fossil feuls).
CO2 levels are the highest they have been for at least the past 800,000 years at around 400ppm.
Oceans and the biosphere are absorbing most of the athropegenic carbon and without these carbon stores, carbon in the atmosphere would be 500ppm.
In 2013 global energy production was 87% fossil feuls, however this is declining.
Carbon sequestration
Carbon sequestration
-- this is the process in which carbon is taken out of the atmosphere and stored in solid or liquid form. This is done through both natural processes and can be done by humans from Carbon Capture and Storage (CCS).
Carbon Capture and Storage
Stage
CO2 is seperated from other by-products at the factory.
CO2 is compressed and transported through pipelines.
CO2 is injected into pourus rock deep underground (this means that impermiable rocks are between the surface and the CO2).
Problems with CCS
High capital cost (Drax and Peterhead projects in the UK will cost £1 billion).
Very energy expensive.
It requires specific geology.
However, CO2 can be transported in pipelines over 500km.
Benefits
CCS could reduce CO2 emmissions from coal and gas powerstations by 80-90%.
Long and short-term changes to the water and carbon cycle
Short term
Changes can occur on a dinernal and seasonal scale.
Dineral
-- Daily changes
Water cycle examples
Dinernal
Changes in evapotransipirtation during the day (high durring the day/low during the night).
In the tropics there is high convectional rainfall durring the day, but at night there is no rainfall.
Seasonal
Evapotranspiration is a lot higher during summer then it is during winter (for example solar input is 650W/m2 more in June then it is in December).
Carbon cycle examples
Dinernal
Durring the day CO2 flows from the atmosphere to the biosphere through photosynthesis and during the night this is reveresed and CO2 flows to the atmosphere through respiration.
There is increased CO2 production durring rush hour.
Seasonal
Photosynthesis and NPP is a lot higher in summer then it is in winter (durring summer atmospheric CO2 concentrations drop by 2ppm).
There is an explosion of phytoplanklton populations in March due to warmer oceans and this population booms peaks in mid-summer where photosynthesis in the oceans also peaks.
Long term
Over the last 400,000 years there have been there have been 4 major glacial cycles during the height of these tempretures in the 'UK' can drop by 5oc and more then half the UK and Ireland were covered in ice.
Changes in the carbon cycle
During glacial periods
More carbon is stored in permafrost.
Less carbon is stored in the biosphere.
Carbon can't escape the pedosphere due to it being covdered in ice.
More CO2 absorbed by oceans.
During inter-glacail periods
Increase in NPP/photosynthesis.
Changes in the water cycle
During glacial periods
Sea levels fall world wide by 100-130m as more water is stored in the cryosphere.
Biosphere shrinks and the water stored in the biosphere also shrinks.
During inter-glacial periods
Increased evapotranspiration.
Less water stored in the cryosphere.
This leads to increased infiltration and groundwater stores.
Oceans rise.
Increased water vapour in the atmosphere should increase latent heat in the atmosphere and therefore increase the frequency of extreme wheather events.
