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
What are the main chemical forms of nitrogen in the lithosphere?
Soil: ammonium, nitrites and nitrates
Rocks: minerals containing nitrogen
What are the main chemical forms of nitrogen in the hydrosphere?
Dissolved nitrates and ammonium ions
What are the main processes in the nitrogen cycle?
Ionisation, fixation, food chains, nitrification, denitrification, leaching, root absorption and ammonification
What are the physical processes in the nitrogen cycle?
Ionisation and leaching
What is ionisation?
Processes such as lightning and meteor trails provide the energy for atmospheric nitrogen and oxygen to react and produce oxides of nitrogen
What is fixation?
Some micro-organisms can chemically reduce nitrogen to ammonia
What micro-organisms cause fixation?
Free-living bacteria within soil and symbiotically living bacteria in root nodules of legumes
How does nitrogen pass in the food chain?
Proteins and amino acids within food
What is nitrification?
Oxidation of ammonium ions to nitrites, then nitrates, by nitrifying bacteria in the soil
What is denitrification?
The chemical reduction of nitrates in the soil to nitrogen and nitrogen oxide gases, by denitrifying bacteria in the soil
What does denitrification do and what are the conditions?
Reduces soil fertility and normally occurs under anaerobic conditions
What are the benefits of leaching?
The movement into water bodies allows them to act as nutrients for aquatic plants and algae
In what form do roots absorb nitrogen?
Mainly as nitrates, but also as ammonium ions
What is ammonification?
The release of amino acids and ammonium ions by dead organic matter decomposition
What are the human impacts on the nitrogen cycle?
Haber process, agriculture and pollution
What are the required conditions for the Haber process to take place?
400C and 250atm
Iron catalyst present
What is the Haber process?
The industrial manufacture of ammonia for agricultural fertiliser
What problems may the use of nitrate fertilisers increase?
Leaching, including eutrophication, if application is followed by heavy rain or applied close to a river
How does the drainage of fields affect the nitrogen cycle?
Makes the soil more aerobic, increasing the number of nitrifying bacteria and decreasing the number of anaerobic denitrifying bacteria
How does ploughing affect the nitrogen cycle?
Increases the rate of decomposition of dead organic matter which releases more nitrogen oxides into the air
How do leguminous plants affect the nitrogen cycle?
Increase the amount of nitrogen compounds within the soil
How does pollution affect the nitrogen cycle?
Oxides of nitrogen are released into the atmosphere by combustion processes and may subsequently increase the quantity of nitrates washed into the soils by rain
What are some methods of sustainable management of the nitrogen cycle?
Control of combustion processes, control of NOx release, management of biological wastes, eutrophication, organic fertilisers and management of soil processes
How can the control of NOx release be managed?
The use of catalytic converters or urea sprays in post-combustion technology
What is eutrophication?
Biological wastes being washed into water bodies by surface runoff or they may be deliberately dumped there
What’s used in organic fertilisers?
Wastes such as manure, sewage and food prodution
How are organic fertilisers used?
Ploughed into the soil, applied to the surface, composted aerobically or digested anaerobically
How does composting and digestion reduce carbon content?
Carbon dioxide and methane gases are lost leaving a more nitrogen-rich fertiliser
What are some soil management methods to increase nitrogen content?
Cultivation of legumes, crop rotation, minimal pesticides, control of leaching, no fertilisers when rain, low-solubility fertilisers, low-tillage techniques, buffer strips
What are some biological functions of phosphorus?
Component of bones, DNA, RNA, ATP, cell membranes and proteins
Why is there no gaseous reservoir of phosphorus?
Low-solubility
What are the main processes in the phosphorus cycle?
Absorption by roots, decomposition, sedimentation and mountain building and weathering `
How do plants absorb phosphate?
Have symbiotic relationships with mycorrhizal fungi in the soil, these have extensive networks of fungal hyphae which increase SA for phosphorus absorption
How does decomposition affect the phosphorus cycle?
Decomposition of phosphorylated proteins in DOM releases phosphates that are often more soluble by soil microbes so they can be absorbed by plants
How does sedimentation affect phosphorus availability in marine organisms?
Planktonic organisms that die and sink to the ocean floor have phosphorus incorporated into their sediments
When may phosphorus in marine sediments become available again?
Continental drift forms new mountain ranges and weathering of rocks releases the phosphates
What are the human impacts on the phosphorus cycle?
Mining of phosphate rocks and fertiliser use
In what form is phosphate mined?
Calcium phosphate
What form do we create of phosphorus and why?
Ammonium phosphate as it’s more soluble
What are the advantages and disadvantages of phosphorus use in fertiliser?
Increases crop production but can also contribute to eutrophication
What are some sustainable management methods of phosphorus?
Reducing the removal of biomass, biological wastes as fertiliser, crop breeding programmes
How is reducing the removal of biomass sustainable management of phosphorus?
Phosphate shortages is the limiting factor on crop productivity for large areas of farmland, availability of phosphates reduced
Why should biological wastes be used for fertilisers?
Maintain phosphate nutrient availability
How do crop breeding programmes help phosphorus availability issues?
Increasing the efficiency of phosphate crop absorption
What’s an example of solar energy causing nitrogen fixation?
Lightning provides energy to convert N2 into NOx
What’s an example of biotic nitrogen fixation?
Bacteria convert N2 into ammonia or ammonium ions for use in soil
