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Carbon Cycle (Change Over Time (Trends (Processes responsible for cycle…

- - - - Bc of the 25% increase in CO2 due to human emission
  - - - Photosynthesis + decomposition
  - - - Plants take in less CO2 = increased atmospheric CO2
      - Forest fires = increased CO2
    - - Increased by 25% since 1997
      - Combined with El Nino
- - - - Bc resp. is more sensitive to temp. than phtotsynthesis
  - - - = increased length of time that they can absorb CO2
  - - - Not a natural part of the ST cycle
    - - More C-containing compounds = increased greenhouse effect
      - Balance of cycle is disrupted
- - - - C stored in rocks, sea floor sed. + fossil fuels is locked away for million of year
      - Total amount of C circulated in 10-100 m tonnes/year
      - Co2 diffuses from atmosphere into oceans
        
        Marine orgs. fix dissolved C with C = CaCO3 to make their shells
        
        On death, remains of orgs. sink to the sea bed
        
        The accumulate over millions of year - heat + pressure = C-rich sed. rocks
      - C-rich sed. rocks
        
        Residence time for C in rocks is 150 million years
        
        Some subducted into the upper mantle at tectonic plate boundaries, are vented into the atmosphere at volcanic eruptions
        
        Others exposed at or near the surface by erosion and tectonic movements are weathered
        
        Chem. weathering e.g. carboantion - acid attacks minerals in rock, releasing CO2 into atmosphere + dissolved in streams
      - Partly decomposed organic matter can be buried beneath younger sed. = carbonaceous rocks e.g. coal, oil + natural gas
        
        Like deep-ocean seds., these fuels act as C sinks that endure for millions of year
      - Diffusion
        
        Movement of CO2 from atmosphere to oceans - high conc. to low conc.
      - Fixing
        
        Marine orgs. fix dissolved C with Ca = CaCO3
      - Natural Sequestration
        
        When C atoms are stored for 350 years in oceans
        
        C-exchange between ocean + atmosphere
    - - Main stores:
        
        Atmosphere, oceans, biosphere, (soils)
      - Transfers are 10-100 times faster than those in slow C cycle
      - Key components: land plants + microscopic phytoplankton
        
        Absorb CO2 from atmosphere thru phtotsynthesis + combine it with water = carbohydrates + glucose
        
        Photosyn. is a fundamental process of the food chain
      - C exchange between atmosphere + oceans
        
        Atmospheric CO2 dissolves in ocean surface water whilst oceans ventilate CO2 back into atmosphere
        
        Via this exchange, indv. C atoms are stored (by natural sequestration) in oceans for 350 years avg.
      - Main processes:
        
        Photosynthesis, respiration, decomposition
    - - Oceans act as stores
      - Used by living orgs.
      - C exchange between atmosphere + oceans
        
        C is dissolved into oceans but released via diff. methods
      - Atmosphere - plants - soil - deep underlying rock
  - - - Mauna Loa, Hawaii + South Pole
    - - Increased in winter bc of veg. decay
      - Decreased in summer bc of photosynthesis
- - - - Inorganic C - weathering of carbonates
      - Organic C - humus (plant remains)
    - - Carbonate rocks
      - Deep sea carboantes
    - - Planktonic orgs. die + skeletons accumulate on seabed
    - - CO2 is important trace gas
      - 0.035% of atmosphere
    - - Largest living space on E
      - Orgs. are mostly micrscopic e.g. phytoplankton + zooplankton
    - - Below the depths that light can penetrate into
      - Resp. via marine orgs., inc. bacteria
    - - 86% in forests
      - Forests are sig. for C sequestering
    - - Non-renewable sources of primary energy
  - - - Glucose + O2 react in cells
      - = CO2 + H20 + releases energy
      - Occurs in all living cells + all biomes
      - Releases C into atmosphere
    - - Dead organic matter breaks down into organic C
      - Decomposers + detritivores
      - Recycles C from living orgs. back into atmosphere
      - Occurs rapidly in tropical ecosystems; slower in arctic ones
    - - CO2 + H2O = carboydrates
      - Moves C from atmosphere to biomass
      - Occurs in all biomes
      - Factors
        
        Light, temp. + availability of nutrients
    - - Some soil C is oxidised to CO2
      - C released into atmosphere
      - When fields are ploughed + soil is turned over and brought into contact with the atmosphere
    - - Breakdown of carbonate rocks by carbonation) releases C into streams + rivers as bicarbonate ions
      - Occurs in fast, tropical climates where there is limestone
      - Store????
    - - C-rich sed. rocks are subducted into the upper mantle
      - CO2 outgassed at SDZ into atmosphere
      - Heat + pressure of SDZ metamorphoses carbonate rocks into silicates, releasing CO2
      - Island arcs, where sediments are being subducted
    - - Natural wildfires
      - Burning fossil fuels
      - 85% of UK's electricity from fossil fuels
  - - - Atmospheric CO2 dissolves in rainwater = weak carbonic acid
      - Anthropogenic emissions = rising atmospheric CO2 levels = increased rainfall acidity
        
        = increased acidity of ocean surfaces + effects on marine life
    - - 6CO2 + 6H20 = C6H12O6 + 602
      - Plants
      - Phytoplankton
    - - In situ decomposition of rocks at/near E's surface
      - Carbonation
        
        Rainwater dissolves limestone + chalk via carbonation
        
        Carbonation - caCO3 + H2CO6 = Ca(HCO3)2
        
        Releases C from rocks into streams, rivers, oceans + biosphere
        
        Most effective beneath soil cover bc higher conc. of CO2 in soil = highly acidic rainwater
        
        Rainwater containing dissolved CO2 can be derived from soil + atmosphere
      - Freeze-thaw
        
        Increases surface area exposed to chemical attack
      - Chelation
        
        Rainwater + d.o.m in soil = humid acids that attack rock minerals
        
        Imp. in tropical environs.
        
        Decomp. is rapid
        
        Forest trees = abundant leaf litter
    - - CH2O + O2 = CO2 + H20 + energy
      - Resp. + photosyn. are the 2 most imp. processes in fast cycle
        
        Vol. of CO2 exchanged each year is *1000 than slow cycle
    - - Decomposers = bacteria + fungi
      - Release CO2 to atmosphere + minerals to soil
      - Rate depends on climatic conds.
        
        Warm, humid environ. = rapid decomp.
    - - Organic mat. reacts in presence of O2
      - Natural fuel for many ecosystems: Wildfires, Rocky Mts.
        
        Long, cold winters slow decomp. of forest litter = build up on forest floor
        
        Fire frees C + nutrients previously inaccessible to forest trees
        
        Opens the forest canopy = new habitats + increased BD
      - Fossil fuels
        
        Transfer 10GT of CO2/year from geological store to:
        
        Atmosphere
        
        Oceans
        
        Biosphere
- - - - = more even distribution of C geographically + vertically
- - - - Organic mat. is built form this
    - - They are v. active
      - Diff. routes + options for the C atoms
        
        Atoms can exchange routes + skip stages
      - Is a complex system
    - - C6H12O6 + 6O2 = C6H12O6 + 6O2
      - Some CO2 is taken up by plants is returned to atmosphere via respiration
      - Respiration releases the energy stored in organic matter
      - Respiration also provides energy for the plant to sustain itself e.g. making new tissues
      - Most of the C in each org. goes into respiration
      - Respiration removes waste products, regulates temp. + releases energy
      - In respiration C atoms join with O2 atoms
      - C not released back into atmosphere via plant resp. is net primary production
        
        Is the C incorporated into plant tissues
        
        Diff. world biomes (large-scale ecosystems) have diff. NPP rates
    - - 6CO2 + 6H20 = C6H12O6 + 6O2
      - There is gross primary production
        
        Total amount of C fixed
        
        Grams of C per unit time (normally per year)
  - - - Bc there is so much veg. and climate is appropriate for year-round plant growth
      - Reduces global warming by reducing C
    - - Suitable climate = evergreen plants = year-round photosyn. + respiration
      - Higher density of veg.
      - Sun is very high in sky = increased intensity
- - - - But accumulate large amounts of organic matter as peat
    - - Already being seen in Arctic
    - - But increased plant growth will eventually = increased C storage in soil
  - - - Increases as CO2 increases
      - Future - more C may be stored in woody tissue or as organic matter in soils
      - Enhanced storage = sink for excess CO2 = neg. feedback +
      - Vegetation growth is a consequence of climate change
        
        As planet warms, areas that were too cold for plants to grow are not able to sustain plant growth
      - For now, plant growth may be helping to sustain climate change
    - - Rate of increasing CO2 levels have slowed since the century
        
        May be bc of phototsyn.
      - Photosyn. is a sink bc it removes CO2 from the air
      - CO2 is converted into sugars stored in wood + leaves - which are used to make more plant matter
      - 60% of CO2 emitted each year by people has removed via photosyn. - was 50%
        
        Suggest E's sinks are becoming more effective
        
        Bc of faster growing plants
        
        CO2 levels ruse = photosynthesis quickens
        
        Plants can photosynthesis 40% faster when CO2 concs. are around 500 ppm
    - - Increased photosyn. only slows climate change, not reverses it
      - Increase in photosyn. won't last
        
        World will become drier = less water for photosyn.
        
        Intisification of extreme events
        
        Change in rainfall patterns
        
        Plants suffer LT when temps. become too high
      - Much of the greening has occurred in colder regions
        
        More greening here = more warming eventually = release of methane as permafrost melts
      - High temps. - could kill tropical forests
      - For every degree of warming, tropical forests may release greenhouse gases equiv. to 5 years of human emissions