4.3 Carbon Cycling Flashcards
What is the density of carbon dioxide?
It is a much heavier gas than most components
Where can carbon dioxide be found due to its density and why is it dangerous?
It usually diffuses to the lower layers of the forest or canyons which is a problem as carbon dioxide is the waste product
Relationship between carbon dioxide solubility and pressure. How does this relate to interaction with water?
As pressure increases so will the solubility. As it sinks, it will be at higher pressure at water’s surface and so dissolve into the water
Carbon dioxide + water (Formula)
Carbonic acid
CO2 + H2O –> H2CO3
What does carbonic acid dissociate into and why?
It is unstable so it dissociates easily in water to form H+ ions and HCO3- ions
How do H+ ions affect water?
It lowers pH of the water, making it more acidic
What are HCO3- ions?
Bicarbonate ions
How does mouth to mouth resuscitation work?
When CO2 combines with water in blood, it lowers the pH. This is detected by the brain which gives signal for person to breathe
How do aquatic autotrophs ingest carbon?
In the form of bicarbonate ions and dissolved CO2`
How do land plants take up carbon dioxide?
As a gas through the stomata at the underside of the leaves
Do plants respire?
Yes
What do plant cells have to respire?
Mitochondria
When does respiration and photosynthesis occur in plants and how can it help?
During day, carbon dioxide from respiration is produced and then taken by photosynthesis. Respiration can also occur at night
Why does CO2 in atmosphere increase in northern hemispheres?
- Plants lose many of their leaves so conc. increases due to less absorption
- More fuel is burnt to heat houses
- Heterotrophs are still respiring
Methane
Carbon molecule produced in anaerobic conditions by bacteria and can oxidize into carbon dioxide and water
Where can methane be found?
- In anoxic environments:
marshes, bogs, swamps, ruminant guts, termites
How do methanogenic archaeans obtain energy?
By synthesis of methane from CO2 and H2O
Ruminants
Mammals which have mutual relationship with bacteria to help them digest cellulose
Methane: Hydrolysis (Step 1)
Ruminants chew on plants to break down molecules into monomers using saliva
Methane: Acidogenesis (Step 2)
Organic matter is changed to organic acids and alcohol by bacteria
Methane: Acetogenesis (Step 3)
Other bacteria convert organic acids and alcohol into acetate, carbon dioxide and hydrogen
Methane: Methanogenesis (Step 4)
Methanogenic bacteria produces methane either through:
- Reaction of CO2 and H2
- Breakdown of acetate
Is saprotroph digestion aerobic or anaerobic?
Aerobic process
Where is peat formed?
In anoxic conditions like stagnant water so saprotrophs cannot grow
Outline steps by which peat is formed
- Environment becomes slowly acidified
- Saprotrophs die and remaining organic matter is partially digested
- New layers of leaf litter and other organic debris fall on top of older layers
- Layers become compressed
Peat
Partially digested organic matter that forms in acidic, water-saturated soil.
What can peat be compressed into?
Coal
Why should we conserve peat?
To regulate climate change as it contains a lot of CO2
Uses of peat
- Substitute for firewood in cooking and heating
- Increase moisture holding capacity for soil
- Acidify soils for specific pot plants
- Increase water infiltration rate of soils
What can be formed from decomposition of organic matter?
Oil, gas and coal
Why are oil and coal considered non-renewable?
Because fossil fuels are being consumed faster than they can be formed
Where is coal found?
In thick layers beneath the surface
Where is oil and gas found?
In porous rock. Gases are found as liquid as reservoirs are in high pressure
How is carbon returned back to atmosphere?
Combustion of biomass and burning of fossil fuels as well has respiration
Combustion
Process of burning which releases CO2 from organic material
Where is calcium carbonate found?
In shells, exoskeletons of corals and crustaceans
Which porous rock can CaCO3 be found in?
Limestone/Sedimentary rock
What does CaCO3 dissolve in and how does that affect it’s function?
In acidic solutions. As most oceans are slightly alkaline, ideal conditions are created for formation of sedimentary rocks
Reservoir
Accumulated pool or store of a certain element. A.k.a. sink
Flux
Process that moves an element from one reservoir to another
Example of flux
Photosynthesis: Conversion of atmospheric CO2 into glucose by autotrophs
Unit for measuring carbon
Gigatonnes (10^15g)
Why is estimation of amounts of carbon dioxide very uncertain?
There may be increase in human activity, change in season, natural causes like volcano explosions
What are peaks and troughs in global CO2 conc. graphs known as?
Fluctuations
Why could fluctuations in CO2 conc. happen?
CO2 can vary with seasons due to availability of foliage on plants
Which CO2 conc. graphs would not show many peaks and trough?
Those with variations in years or decades as the average becomes bigger
