The carbon cycle Flashcards
What are some elements that carbon is found in?
- Sedimentary rocks
- Diamonds
- Graphite
- coal
- Petroleum oil
Coal one of the most chemically versatile elements. More than 10 million carbon compounds in existence.
What are examples of carbon compounds?
- Carbon dioxide (Co2) gas found in atmosphere, soils and oceans.
- Methane(CH4) a gas found in the atmosphere, soils oceans and sedimentary rock
- Calcium carbonate (CaC03) solid compound found in calcareous rocks, oceans and in skeletons and shells of ocean creatures
- Hydrocarbons, solids, liquids, or gases usually found in sedimentary rocks
- Bio-molecules, complex carbo compounds produced in living things. E.g proteins, carbohydrates, fats and oils, and DNA are all examples of bio-molecules
What are the origins of carbon on earth?
- Primary source of Co2 in earths interior
- Stored in the mantle when earth was formed
- Escapes from the mantle at constructive and destructive plate boundaries as well as hot spot volcanoes
- Some Co2 remains in atmosphere, some dissolved in oceans, some carbon held in biomass living or dead/decaying organisms
- Carbon removed into long-term storage by burial of sedimentary rock layers, especially coal and black shales(store organic carbon from undecayed biomass and carbonate rocks like limestone (calcium carbonate)
what is a gigatone of carbon dioxide equivalent (GtC)?
1 Gt amounts to 1 billion tonnes
What is Anthropogenic CO2?
what is the Biosphere?
What is carbon sequestration?
Anthropogenic CO2 is carbon dioxide generated by human activity
Biosphere is the total sum of all living matter
Carbon sequestration is the capture of CO2 from the atmosphere or capturing anthropogenic co2 from large-scale stationary sources like power plants before its released into atmosphere. Once captured put into long-term storage.
What is a carbon sink?
what are greenhouse gases?
What is the lithosphere?
What is weathering?
A store of carbon that absorbs more carbon than it releases
Any gaseous compound in the atmosphere that is capable of absorbing infrared radiation, thereby trapping and holding heat in the atmosphere
The crust and uppermost mantle: constitutes the hard and rigid outer layer of the earth
Weathering is the breakdown of rocks by a combination of weather, plants and animals
What does the lithosphere contain and what spheres does it react with?
- Lithosphere includes the crust and the uppermost mantle, constitutes hard rigid outer layer of earth.
- Upper most part of lithosphere chemically reacts with the atmosphere, hydrosphere and biosphere through soil forming process called pedosphere.
- Can also occur when cryosphere crushes rock in Lithosphere to create pedoshpere
- Atmosphere-Lithosphere Volcanoes emitting gases into atmosphere/ gases and moisture are removed due to weathering of rocks. (precipitation)
- Hydrosphere-Lithosphere Water flowing downhill rocks alter the way water flows. Also hydrosphere impacts deposition and erosion of rocks e.g saltation suspension
- Biosphere-Lithosphere plants and soil
Name bot the inorganic and organic form that carbon is stored in
inorganic- these include coal, oil and natural gas, oil shale and carbonate-based sedimentary deposits like limestone.
organic- litter, organic matter and humic substances found in soil (from plants, animals, and microbial residues
How is carbon distributed between these stores?
- Marine sediments and sedimentary rocks contain up to 100 GtC
- soil organic matter between 1500 and 1600 GtC
- Fossil fuel deposites of coal and gas aprx 4,100 GtC
- Peat (dead but undecayed organic matter found in boggy areas) aprx 250GtC
The hydrosphere
Explain the 3 main stores
And how much GtC the sedimentary layer holds
- The surface layer (euphotic Zone) where sunlight penetrates so photosynthesis can take place contains 900 GtC
- the intermediate (twilight zone) and deep layer of water contain 37,100 GtC
- Living organic matter(fish, plankton, bacteria etc) amount to 30 GtC and dissolved organic matter 700 GtC
When organisms die their dead cells, shells and other parts sink to deep water.
- Some material sinks right to bottom, where forms carbon-rich sediments.
- Over millions of years chemical and physical processes turns into rocks.
- Estimated sedimentary layer could store 100 million GtC
The biosphere
What is the estimated carbon stored in the terrestrial biosphere?
What are the main stores of carbon in terrestrial biosphere?
- It is estimated at 3,170 GtC
Living Vegetation: Global level 19 per cent of carbon stored in plants. Unlike ocean stored directly in tissue. The below-ground biomass( Root system) must be considered. Carbon in biomass varies from 35- 65 per cent depending: dry weight, location and vegetation type. Estimated half of carbon in forests occur in high latitude forests, over third low. E.g largest forest reservoirs in Russia (25% of worlds forest carbon) and amazon basin 20 per cent
Plant litter: Defined fresh, undecomposed, easily recognisable plant debris. E.g Leaves cones, needles, twigs, bark, seeds/nuts. Type of litter directly affected by ecosystem. Leaf tissue 70 per cent of litter in forests, woody litter increases with age of forest.
What are the main stores of carbon in terrestrial biosphere?
Soil humus: originates from litter decomposition. thick brown or black substance that remains after most organic litter decomposed. In all forests 31 per cent stored biomass, 69 per cent in soil. Tropical forests 50 in biomass 50 in soil. soil carbon organic(1,550 GtC) inorganic (950 GtC) containing carbon itself, calcite, dolomite and gypsum. Soil carbon pool 3.1 times larger than atmospheric pool 800 GtC.
Peat: Accumulation of partially decayed vegetation or organic matter that is unique to natural areas called peatlands or mires. Forms in wetland conditions flat land, forest cover and sponge-like nature ensures peat remain wet. (lot of rain occurs there) It stops the decomposition process and carbon remains locked in solid state. Estimated peat stores of 250 GtC.
Animals: Play small role in storage of carbon. Very important in generation of movement of carbon through the cycle.
The atmosphere
What have been the highest ppm and the lowest ppm of carbon in the atmosphere?
How much GtC is stored in the atmosphere?
Highest values possible topping 7,000 ppm (parts per million) in Cambrian period around 500 million years ago. Lowest concentration past 2 million years during Quaternary glaciation when it sank to 180 ppm.
Overall amount of carbon vary from 720 GtC to 800 GtC. (0.04 per cent of atmosphere). Co2 is potent green house gas which plays vital role in regulating earths surface temperature.
Mauna Loa Observatory (MLO) part of American National oceanic atmospheric administration( NOAA) measurements show global annual mean concentration of Co2 has increased a lot from industrial revolution from 280pm to 317.7 ppm in March 1958 to 400.3 ppm February 2015.
Keeling curve backed u by Co2 trapped in ice cores give ‘proxy’ measure of Co2 in atmosphere at the time snow was laid down. Accelerating at 2ppm/year and accelerating.
What is the geological component of the carbon cycle?
The geological component of carbon cycle is when it interacts with rock cycle in process of weathering, subduction and volcanic eruptions.
- In atmosphere carbon dioxide is removed from atmosphere by dissolving in water and forming carbonic acid.
- As this weakly acid reaches surface as rain, it reacts with minerals at earths surface and dissolves them into component ions through process chemical weathering.
- These component ions are carried in surface waters e.g streams eventually to ocean they settle as minerals ( e.g calcite) a form of calcium carbonate (CaCO3)
What landforms are created by calcium carbonate?
- Calcium carbonate also precipitated from calcium and bicarbonate ions in seawater by marine organisms e.g foraminifera, coccoliths or molluscs.
- When these creature die, their skeletons sink to bottom of ocean where they collect sediment.
- Burial by overlying eventually turn these sediments into sedimentary limestone.
- Coral also extracts CaCO3 from seawater. Dead coral is built upon by later generations of live coral and is also buried
- Carbon is now stored below sea floor in layer of limestone. Example is Himalayas
Describe how weathering, burial, subduction and tectonic forces move carbon
- Tectonic forces cause plate movement to push sea floor under continental margins in process of subduction
- Carbonaceous sea-floor deposits pushed deep into the Earth where they heat up, melt and rise back up to surface through volcanic eruptions or in seeps, vents or Co2 rich hot springs.
- Co2 returns to the atmosphere
Describe the process of Photosynthesis
- Tiny marine plants (phytoplankton) sunlit surface waters (euphotic Zone) of oceans as well as terrestrial plants, turn the carbon into organic matter by process of photosynthesis
- Use energy from sunlight to combine with carbon dioxide from atmosphere with water to form carbohydrates
- These carbohydrates store energy and oxygen is a by-product
Carbon dioxide + Water +sunlight —> carbohydrate + oxygen
Describe process of respiration
- Plants use stored carbohydrates from photosynthesis as an energy source to carry out their lifer functions by process of respiration
- Some carbohydrates remain as biomass( Bulk of plant). Consumers e.g animals and bacteria get energy from this excess biomass.
- Oxygen from the atmosphere is combined with carbohydrates to liberate stored energy, creating water and Co2 as by-products
Oxygen + carbohydrate —> energy+ water + carbon dioxide
What is the difference between photosynthesis and respiration?
- Photosynthesis and respiration are essentially opposite from one another.
- Photosynthesis removes CO2 from the atmosphere and replaces it with O2.
- Respiration takes o2 from the atmosphere and replaces it with Co2.
- Not all matter is oxidized, some is buried in sedimentary rocks, so over time more oxygen has been put in atmosphere than Co2.
Describe process of Decomposition
- In broad terms, decomposition includes physical, chemical and biological mechanisms that transform organic matter into stable forms.
- Animals, wind and other plants can cause this fragmentation
- Leaching and transport in water is also another physical mechanism
- Chemical transformations include oxidation and condensation.
- Biological mechanisms involve feeding and digestion by enzymes.
- Decomposers special role is to break down cells and tissues in dead organisms into large biomolecules and the into individual atoms
- Decomposers ensures important elements of life- carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur, and magnesium can continually recycled into the soil.
- e.g plant can’t make its own DNA molecules unless it has a supply of nitrogen, phosphorus and sulphur atoms from soil. Plant growth limited by availability of nitrogen, phosphorus, magnesium and sulphur atoms and to availability of Co2, water, and light energy.
What is oceanic carbon pumps
- Water is able to dissolve co2. There is a negative correlation between temperature of water and amount of Co2 that can be dissolved.
- This leads to vertical deep mixing, term sed to describe most important movement of Co2 in oceans.
- Occurs when warm water in oceanic surface currents is is carried from warm tropics to cold polar regions.
- Here water is cooled making it dense enough to sink below surface layer.
- When cold water returns to surface and warms again, it loses Co2 to the atmosphere.
- This vertical circulation acts as a carbon pump, giving ocean more carbon than it would if this surface water was not being constantly replenished
What is a biological pump?
- Living things move carbon from atmosphere into surface waters, then down into deeper ocean eventually into rocks.
- When organisms die, their dead cells, shells and other parts sink into deep water.
- Decay releases Co2 into deep water, over millions of years chemical and physical processes turning these sediments into rocks. (lock up carbon for millions of years)
What is combustion?
- Combustion occurs when organic material is reacted(burned) in the presence of oxygen to give off the products of Co2, water and energy.
- They can be organic material e.g vegetation or fossil fuels e.g oil or coal.
- If other elements present they combine with oxygen to form a variety of pollutant molecules e.g sulphur oxides and nitrogen oxides
What is Biomass combustion?
- This is burning of living and dead vegetation
- Happens most in the boreal( northern) forest in Alaska, Canada, Russia, china, and Scandinavia
- Savannah grasslands in Africa
- Tropical forest in Brazil, and Indonesia
- Forests have a life cycle: trees die after sever fire, setting new stage of growth
- If forest fully replaces itself, there will be no net carbon change over that life cycle.
- New trees grow (storing carbon) , old trees decompose (emitting carbon) and organic layer of soil accumulates (storing carbon). This balance between production and decomposition determines wether forest is et source or sink.
-Every year fires burn 3 to 4 million km2 of earths lad surface area. northern latitude forests also considered a carbon sink because heavy canopy blocks sunlight from reaching forest floor, slowing decomposition of forest litter
Explain Volcanic activity and how it relates to the carbon cycle
- According united states geological survey ‘ the carbon dioxide released in recent volcanic eruptions has never caused detectable global warming of the atmosphere’
- This is because of:
- The warming effect of emitted Co2 is counterbalanced by the large amount of sulphur dioxide that is given out. Conversion of sulphur dioxide to sulphuric acid, forms fie droplets, increasing reflection of radiation from sun back into space, cooling earths lower atmosphere.
- Amount of Co2 released have not been enough to produce detectable global warming
- It has been proposed that intense volcanic release of Co2 in the deep geologic past did cause a large enough increase in atmospheric Co2 to cause a rise in atmospheric temperatures and possible ass extinctions, though scientific debate
Explain hydrocarbon extraction and burning
- Dead animals or plants turn into fossil fuels following burial
- Pressure from multiple layers of sediment leads to anoxic ( oxygen free) environment that allows for decomposition to take place without oxygen
- When combined with heat from the earth, the carbon in sugar molecules is rearranged to form other compounds
- Animal remains tend to form petroleum (crude oil)
- Plant matter more likely to form coal or natural gas
- When burnt Co2 and water is released into the atmosphere
How does cement manufacturing affect the environment?
- Cement manufacture contributes CO2 to the atmosphere when calcium carbonate is heated, producing lime and CO2
- Estimated cement industry produces around 5 per cent of global anthropogenic CO2 emissions, of which 50 per cent is produced from the chemical process itself, and 40 per cent from burning fuel to power
- The amount of cO2 emitted by cement industry is more than 900 kg of CO2 for every 1000 kg of cement produced
- In 2013 global CO2 emissions due to fossil fuel and cement production was 36 GtC.
- 61 per cent higher than 1990 (Kyoto protocol) and 2.3 per cent higher than 2012.
- Emissions dominated by China (28 per cent), USA (14 per cent), and India (7 Per cent).
- 2013 CO2 emissions: coal (43), oil (33), gas (18) , cement (5.5), and gas from oil wells (0.6)
How do Farming practices affect carbon emissions?
Soil Ploughing
- When soil ploughed, soil layers invert, air mixes in, and soil microbial activity dramatically increases.
- Leads soil organic matter being broken down much faster, carbon lost from soil into atmosphere
- Also emissions from tractors increases CO2 levels
Main source of Carbon is enteric fermentation
- Methane (CH4) is produced by livestock during digestion and released by belches.
- In 2011 accounted for 39 per cent of sectors total greenhouse gas outputs.\
Greenhouse gases resulting from biological processes e.g rice paddies
- Generate methane make up 10 per cent of total agricultural emissions, while burning of tropical grasslands accounts for 5 per cent
According to Food and Agriculture organization (FAO) in 2011, 44 per cent of agriculture- related greenhouse gas outputs occurred in Asia, America (25), Africa (15), Europe (12), and Oceania (4)
how does Land use change affect CO2 emissions? E.g Deforestation
- Land use change (mainly deforestation) account up to 30 per cent of anthropogenic Co2 emissions
Deforestation
- Most driven because of need of extra agricultural land. subsistence farmers (for own) will clear few hectares to feed their families by cutting down trees and ‘slash and bur’ agriculture
- Logging (some illegal), remove forest and also build roads to access more and more remote forests, which leads to further deforestation
- Urban sprawl also result of deforestation.
- Deforestation can not be intentional e.g wildfires or overgrazing, which could prevent re-establishment of young trees
FOA estimated 13 million ha (Roughly equivalent to Greece) are cut down for forests and converted to other land uses every year.
Explain Deforestation planting/ How much we are losing
- Planting trees resulted in forests being established or expanded onto abandoned agricultural land.
- Reduced net loss of total forest area
- In period 1990 to 2000 the worlds is estimated to have suffered a net loss of 8.9 million ha of forest each year
- 2000 5to 2005 reduced to an estimated 7.3 million ha/year.
- world lost about three per cent of forests in period 1990 to 2005
- At present Losing about 200km2 of forest each day, worlds rainforests could completely vanish in a hundred years at current rate
Explain what happens when forest are cleared for conservation to agriculture
And how trees play an important role in maintaining forests
- Large proportion of above-grounds biomass may be burned, rapidly releasing most of CO2 into atmosphere
- Some wood used as wood products, preserved for longer amount of time
- Forest clearing also accelerates decay of dead wood, litter and below-ground organic carbon
- Fossil fuels are moist, but without the shade from tree cover they quickly dry out.
- Trees help maintain water cycle by returning by return water vapour back into atmosphere through transpiration
- without trees to fill these roles, many former forestlands quickly become barren deserts
Explain how Urban growth affects CO2 emissions
- For first time, over half of worlds population live in urban areas.
- As cities grow, land use changes from either natural vegetation or agriculture to one which is built up.
- CO2 emissions resulting from energy consumption for transport, industry and domestic use, added to CO2 emitted in cement manufacture required for all buildings and infrastructure have increased.
- 2012 cities responsible for around 47 per cent of global carbon emissions.
- Even greater concentration can be observed ed for carbon emissions growth from 2012 to 2030
- In total cities are projected to be responsible for 56 per cent of global increase in carbon emissions, with 10 cities contributing 10 per cent of global emissions growth, 28 cities contributing 20 per cent and 193 contributing 50 per cent.
Explain carbon sequestration- Two main types
- carbon sequestration involves capturing CO2 from atmosphere and putting it into long-term storage.
- Two main types: Geologic sequestration and Terrestrial or biological sequestration
- Geological sequestration: CO2 captured in source (e.g power plat or industrial processes) and then injected in liquid form into stores underground. These could be depleted oil and gas reservoirs, and the deep ocean.
- Ocean very capable of absorbing much more additional carbon than terrestrial systems simply because of its sheer size. Advantage is that CO2 is literally ‘sunk’ within weeks or months of being captured from air/water. Once in deep ocean it is in circulation system measured in thousands of years. By the time carbon reaches seabed it has entered the earth’s geological cycle.
Terrestrial or biological sequestration: Involves the use of plants to capture CO2 from the atmosphere and then store it as carbon in the stems and roots of the plants as well as in soil.
- Aim to develop set of land management practices that maximises amount of carbon that remains stored in soil and plant material for long time. increases wildlife.
- Disadvantages: forest planted to capture carbon might lose that carbon back to the air in forest fire or if the forest suffers disease or infestation.
- land-based sequestration plantations slow growing and require active monitoring and management for the lifetime of the plantation. carbon within those systems is never removed permanently from atmospheric system.
