3.1.1.3- carbon cycle

Question 1

stores of carbon (what spheres have largest- smallest)

Answer 1

(in order of decreasing magnitude)
(%= % of total carbon in each store)

LITHOSPHERE- 99.983%
HYDROSPHERE- 0.0076%
PEDOSPHERE- 0.0031%
CRYOSPHERE- 0.0018%
ATMOSPHERE- 0.0015%
BIOPSHERE- 0.0012%

Question 2

what can every carbon store be?

Answer 2

carbon source-release more carbon than absorbs

or

carbon sink- absorbs more carbon than releases

Question 3

lithosphere what’s carbon stored in + for how long?

Answer 3

• sedimentary rocks e.g. limestone (calcium carbonate), hydrocarbons (fossil fuels), marine sediments (shells + skeletons)
• long-term storage (240-300mill years)

Question 4

hydrosphere what’s carbon stored in + for how long?

Answer 4

• 90%= oceanic carbon dissolved as bicarbonate, carbonate ions dissolved + dissolved as CO2
• storage= dynamic –> surface= 25 years, deep= 1250 years

Question 5

pedosphere what’s carbon stored in + for how long?

Answer 5

• soil stores, 300bn tonnes of carbon as organic matter, soil organisms + remains of dead plants + animals
• peat soils hold highest amount of carbon
• storage= days to 1000 years

Question 6

cryosphere what’s carbon stored in + for how long?

Answer 6

• permafrost (frozen ground) of tundra + artic regions contains plant material
• storage= 1000s of years, ice cores=millions of years

Question 7

atmosphere what’s carbon stored in + for how long?

Answer 7

• carbon forms= CO2, methane (CH4)
• storage= 6 years

Question 8

biosphere what’s carbon stored in + for how long?

Answer 8

• forms of carbon= living plants + animals
• storage= 18 years

Question 9

is the carbon cycle an open or closed system?

Answer 9

closed

Question 10

abiotic vs biotic components

Answer 10

abiotic components= move carbon slower through cycle
biotic= move carbon through cycle quickly

Question 11

transfers of carbon?

Answer 11

photosynthesis
respiration
decomposition
combustion
weathering
sequestration
burial + compaction

Question 12

photosynthesis

Answer 12

• living organisms convert CO2 from atmosphere + water from soil into oxygen + glucose using light energy
  ( removes CO2 from atmosphere) e.g. phytoplankton

Question 13

respiration

Answer 13

converts glucose into energy + returns CO2 to atmosphere

Question 14

decomposition

Answer 14

• when living organisms die they’re broken down by decomposers (bacteria, fungi) which respire= returns co2 to atmosphere + carbons from dead organisms body return to atmosphere as CO2. other carbons= returned to soil
• decomposition= temp dependent, warmer= faster + more activity water regulates decomposition rate + release of carbon. Heavily water logged areas e.g. peats= slow rate of decomposition

Question 15

combustion

Answer 15

• e.g. burning fossil fuels, wildfires, tectonic activity etc
• releases CO2 to atmosphere after being stored in rocks for thousands/millions of years

Question 16

weathering

Answer 16

• chemical weathering= carbonation
  –> CO2 in atmosphere combines with water vapour= produces weak acid called carbonic acid= makes precip acidic= calcium carbonate in rocks reacts with acidic water + forms calcium bicarbonate which is soluble + removed in solution by percolating water via rivers, oceans etc + eventually back to atmosphere

Question 17

sequestration

Answer 17

natural sequestration= carbon removed from atmosphere + stored in liquid/solid form
carbon capture + storage= term to describe process of capturing co2 from industrial sources e.g. power stations –> then it’s transported to long-term storage location

Question 18

burial + compaction

Answer 18

• oceans absorb carbon from atmosphere which goes into shells + skeletons of marine creatures as CACO3
  –> when they die it sinks + overtime becomes compact to create sedimentary rocks e.g. limestone
  –> heat + pressure= carbon from organic matter is converted to hydrocarbons

Question 19

carbon transfer at local/plant scale

Answer 19

e.g. tree
- carbon store –> takes carbon from atmosphere (photosynthesis)
- fallen leave= carbon transferred to soil
- soil + leaf litter= stores of carbon
- carbon lost from soil due to soil respiration, tree respiration= carbon returns to atmosphere or decomposition of organic matter or combustion from wild fires

Question 20

transfer of carbon at a continental scale

Answer 20

• involves all fast + slow carbon cycles
• rate of transfers varies due to changing conditions on planet
• human activity has influences

Question 21

carbon transferred at SERE scale

Answer 21

• e.g. lithosere (example of terrestrial carbon cycle)
• ‘sere’= stage in the succession of vegetation in an ecosystem
• lithosere= vegetation succession that occurs on bare rock
• hydrosere= occurs in freshwater
• halosere= occurs in salt-rich conditions
• psammosere= occurs in sandy areas
• when environmental equilibrium is reached= further successions stop + final stage of sere is reached
  –> this is usually in response to climate so is called ‘climatic climax’
• climax vegetation for lithosere in UK= deciduous wood
• normally involves complex stores + transfers