Biogeochemical cycles Flashcards
What are the main processes of the carbon cycle?
Photosynthesis, respiration, food webs, fossilisation and combustion
What are the 4 reservoirs of carbon in the carbon cycle?
Atmosphere, Hydrosphere, Lithosphere and Biosphere
What are the main chemical forms of carbon in the atmosphere?
Carbon dioxide
Methane
Carbon monoxide
What are the main chemical forms of carbon in the hydrosphere?
Hydrogen carbonate ions
Dissolved carbon dioxide
What are the main chemical forms of carbon in the biosphere?
Carbohydrates, proteins, lipids
Living organisms and dead organisms
What are the main chemical forms of carbon in the lithosphere?
Carbonaceous rocks (CaCO3) and fossil fuels
Sedimentary carbonates
In what form does anaerobic respiration usually return carbon to the atmosphere?
Methane
How does fossilisation occur?
Incomplete decomposition of dead organic matter, often under anaerobic respiration
What are some organisms that produce exoskeletons?
Molluscs, coral and many planktonic organisms
What’s an example of combustion occurring naturally?
Natural fires in forests and grasslands may be started by lightning
How do humans affect the rate of photosynthesis?
Deforestation, afforestation, marine pollution kills phytoplankton which increases CO2 levels, melting of sea ice removes algae habitat
How do humans affect the rate of aerobic respiration?
Ploughing increases O2 supply and the rate of aerobic decomposition of organisms within soil
How do humans affect the rate of anaerobic respiration?
Anaerobic respiration in soil organisms gradually releases methane
We create: rice padi fields, landfill sites, anaerobic sediments in reservoirs and livestock intestines
We destroy (drainage): waterlogged fields, marshlands and peat bogs
How do humans affect the rate of carbonic acid concentration in the sea?
25% of all anthropogenic CO2 from fossil fuels is take up by the ocean
How is methane released from fossil fuels?
Extraction
How do humans affect the rate of biomass movements?
Addition of compost/mulch to improve soil fertility
Deforestation and crop harvesting leading to reduced soil organism matter and soil erosion
Sewage discharge into the sea
Marine biomass into the terrestrial system by fishing
What are some methods of sustainable management of the carbon cycle?
Conservation of biomass carbon stores, the use of alternatives to fossil fuels, carbon sequestration and carbon capture and storage
How does the conservation of biomass counteract the impacts on the carbon cycle?
Protecting habitats such as peat bogs and forests prevents CO2 release
How does the use of alternatives to fossil fuels counteract the impacts on the carbon cycle?
Renewable energy resources and nuclear power produce lower CO2 emissions than fossil fuels
How does carbon sequestration counteract the impacts on the carbon cycle?
Afforestation removes CO2 to slow down or reduce rising CO2 levels, once a tree reaches full size there will be no net removal of carbon so it can be felled and a new tree planted
What are the three methods of reducing carbon using CCS?
Pre-combustion technology, post-combustion technology and storage
When is pre-combustion technology most appropriate?
Small-scale carbon emissions, such as road vehicles, as it’s more efficient to modify the fuel in large-scales before it reaches the car to increase efficiency of the process- the removal of carbon from the fuel before burning
What is gasification?
Conversion of fuels such as coal into gaseous hydrogen and CO2, the removal of CO2 for storage and the use of hydrogen for fuels- producing H2O and no CO2
What are some methods of removing CO2 from exhaust gases of fossil fuels (post-combustion)?
Dissolving in a solvent, high pressure membrane filtration, adsorption/desorption processes, cryogenic separation and graphene adsorption
What are the issues with post-combustion technology?
None of the methods are fully developed and the costs for large scale removal are uncertain
What percent of gases produced by combustion in air is carbon dioxide?
20%
What are some suitable geological structures for the storage of carbon?
Depleted aquifers, oil fields or gas fields
When is nitrogen used within living organisms?
DNA, RNA, ATP, proteins, enzymes and many other biological molecules
What are the main chemical forms of nitrogen in the atmosphere?
Nitrogen gas (N2) or nitrous oxides (NOx)
What are the main chemical forms of nitrogen in the biosphere?
Living organisms: DNA, proteins (cell membranes, hormones and enzymes)
Dead organisms: proteins, which release ammonium compounds as they decompose