4.3 Carbon Cycling Flashcards
What is carbon cycling?
Biogeochemical cycle whereby carbon is exchanged between the different spheres of the Earth
What are the four spheres of the Earth?
Atmosphere, lithosphere(ground), hydrosphere, biosphere
What forms is carbon exchanged? (4 ways)
Atmospheric gases - CO2, CH4 (methane)
Oceanic carbonates - bicarbonates dissolved in water, calcium carbonate in corals and shells
Organic material - carbohydrates, lipids, proteins
Non-living remains - detritus, fossil fuels
Why should carbon dioxide in the air always be at a higher concentration in the atmosphere than in the plant?
Autotrophs use CO2 for photosynthesis (so should be low)
What are compensation points?
When the uptake of CO2 is balanced by the production of CO2 by respiration
(The net carbon dioxide assimilation is zero)
What 2 things can carbon dioxide do when it dissolve in water? (Plus equation)
- remain as dissolved gas
- combine with water to form carbonic acid
CO2 + H2O <-> H2CO3
What happens to carbonic acid after? and equation and effect? (2)
- Disassociates to form hydrogen carbonate ions (H2CO3 <-> HCO3- +H+)
- releases hydrogen ions and pH changes
What occurs when hydrogen carbonate ions come into contact with rocks and sediments on the ocean floor? (3)
- They acquire metal ions
- Resulting in the formation of calcium carbonate
- Then the development of limestone
What occurs when living organisms combine hydrogen carbonate ions and calcium? (1)
what do the organisms use it for?? (2)
- It forms calcium carbonate
- forms hardened exoskeletons of coral (and main component of Mollusca shells)
- Wen organism dies and settles to sea floor, the hardened components may become fossilized in the limestone
What is the summary of Carbon conversion (equations) in aquatic environments? (5 steps)
- CO2 (atmosph) <-> CO2 (dissolved)
- CO2 (dissolved) + H2O <-> H2CO3 (carbonic acid)
- H2CO3 <-> HCO3- (bicarbonate ions) + H+
- HCO3- <-> CO3^2- (carbonate ions) + H+
- CO3^2- + Ca^2+ <-> CaCO3 (calcium carbonate)
What are methanogens?
Archean microorganisms that produce methane (CH4) as a metabolical byproduct in anaerobic conditions
What anaerobic conditions can methanogens can be found? (3)
- wetlands
- marine sediments
- digestive tract of ruminant animals
What do methanogens have two byproducts of anaerobic digestion? (2) (Equations)
- acetic acid = Acetic acid-> methane and carbon dioxide (CH3COO- + H+ -> CH4 + CO2)
- CO2 = Carbon dioxide and hydrogen -> methane and water (CO2 + 4H2 -> CH4 + 2H2O)
How can methane accumulate under the ground or diffuse into the atmosphere? (2)
-organic matter is buried in anoxic conditions, deposits of methane may form underground
-rising global number of domesticated cattle may be increasing levels of methane by releasing into atmosphere
How long does methane persist in the atmosphere for and what happens afterwards?
For 12 years
- methane will be naturally oxidised to form carbon dioxide and water (CH4 +2O2 -> CO2 + 2H2O)
What is partial decomposition?(3)
- When saprotrophs bacteria and fungi which decompose matter lack oxygen (anaerobic conditions)
- The anaerobic respiration by organisms produces organic acids (acidic conditions)
- The bacteria and fungi can’t function effectively in anaerobic/acidic conditions preventing decomposition
How is coal formed? (3)
- Organic mater does not fully decompose in waterlogged solid, carbon rich molecules remain in the soil and form peat
- the deposits of peat are compressed under sediments, the heat and pressure force out impurities and remove moisture
- the remaining material has high carbon concentration and undergoes a chemical transformation to produce coal
How is oil/natural gas formed? (5) (takes place over millions of years)
As a result of decay of marine organisms on ocean floor
- sediments are deposited on top of the organic matter
- creating anoxic condition preventing decomposition
- result of burial and compaction, organic matter becomes heated and hydrocarbons are formed
- hydrocarbons form oil and gas which are forced out of the rock and accumulate in porous rock
What occurs when compounds rich in hydrocarbons are heated in the presence of oxygen?
Undergo combustion reaction
What are the characteristic of combustion? And where does it go usually? (2)
-Exergonic and releases water and carbon dioxide as by-product
-carbon dioxide is released into atmosphere increasing concentration of gas in the air
Why is the combustion of fossil fuels non-renewable energy source?
Geological process takes millions of years
Why is combustion of biomass a renewable energy source? (3 steps)
- Living organisms produce hydrocarbons as a part of their biomass (either for use or as waste produ)
- Hydrocarbons can be extracted and purified to produce fuel source (eg. bioethanol/diesel)
- As long as new raw materials are provided and waste products are removed it is renewable
What are carbon fluxes?
The rate of exchange of carbon between carbon sinks/reservoirs
What are the four carbon sinks?
Lithosphere, hydrosphere, atmosphere, biosphere
