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Environmental Science > Biogeochemical cycles > Flashcards

Biogeochemical cycles Flashcards

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1
Q

What are the main reservoirs in the carbon cycle?

A

Atmosphere
Hydrosphere
Biosphere
Lithosphere

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2
Q

What does carbon exist as in the atmosphere?

A

CO2, methane and carbon monoxide

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3
Q

What is carbon stored as in the hydrological cycle?

A

Dissolved CO2
Hydrogen carbonate ion

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4
Q

What does the biosphere reservoir contain?

A

Carbon in plants/animals stored as
Proteins
Lipids, animal fats/vegetable oils
Carbohydrates, cellulose lignin

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5
Q

What does the lithosphere contain carbon as?

A

Fossil fuels as carbon/hydrocarbons
Carbonaceous rocks like limestone

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6
Q

What are the main processes in the carbon cycle?

A

Photosynthesis- converts CO2 into carbohydrates
Respiration- Aerobic returns CO2 to atmosphere, Anaerobic returns carbon to atmosphere as methane
Food webs- plants containing lipids/carbs/protein will be eaten this forms food webs and transfers carbon to different trophic levels
Fossilisation- Incomplete decomposition of DOM under anaerobic conditions produces fossil fuels. Calcium carbonate exoskeletons produces limestone
Combustion- burning of organic materials releases CO2.

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7
Q

What do human activies do to biogeochemical cycles?

A

Human activities can alter the rate of movement of carbon/nitrogen etc which can unbalance the dynamic equilibrium and change the distribution of carbon/nitrogen etc

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8
Q

How do human activities produce changes in photosynthesis?

A

Deforestation- less carbon in biomass
Afforestation- more carbon in biomass
Marine toxic pollution- reduced phytoplankton, less CO2 absorbed
Sea ice melting- algae living on sea ice absorbs CO2 from water, this is eaten by krill carbon is released in faeces to the sea bed sediments. less ice less algae so more CO2 in water

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9
Q

What can be done in agriculture to increase CO2 in the atmosphere?

A

Adding DOM to soils, aerobic respiration by soil biota from the breakdown will release CO2.
Ploughing of soils increases the oxygen conc so decomposition happens faster, therefore CO2 is released into the atmosphere faster.

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10
Q

What environments does anaeorbic respiration occur in and what does it release?

A

Anaerobic respiration releases methane, some anaerobic conditions are:
Rice padi fields
landfill sites
livestock intestines
waterlogged fields
marsh lands
peat bogs

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11
Q

What could be done to waterlogged fields, marsh lands or peat bogs to reduce the anaerobic conditions?

A

Drainage

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12
Q

As atmospheric CO2 concentrations rise what will happen to carbonic acid?

A

More CO2 means more will dissolve into the oceans producing carbonic acid.
Carbonic acid will dissociate into hydrogen carbonate and hydrogen ions causing the oceans to become more acidic.

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13
Q

What human activities affect the amount of carbon in biomass?

A

Adding compost/mulch for soil fertility, so more carbon in soil
Deforestation, less DOM and more soil erosion so less carbon in soil
Sewage dumping into the sea, more carbon in the sea
Fish biomass moved to land biomass in aquaculture/fishing

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14
Q

How could conservation be used to increase carbon in biomass

A

Protecting peat bogs and forests from exploitation to prevent release of CO2.

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15
Q

What methods can be used to manage the of the carbon cycle?

A

Using alternatives to fossil fuels
Carbon sequestration
CCS
Matching afforestation to deforestation
Increasing soil OM
Conserving peat bogs

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16
Q

How can carbon sequestration be used to decrease CO2 in atmosphere.

A

Afforestation to remove CO2, once trees are fully grown and wont take in any more CO2 they can be cut down and used in buildings which wont release any CO2, they only release CO2 in decay or combustion.
New trees can be grown,

17
Q

How is pre-combustion technology used in CCS

A

Modifying fuel before use so it does not release CO2.
Gasification- converts coal to CO2 and hydrogen, CO2 can be stored and when hydrogen is burnt in engines/home no CO2 is produced.

18
Q

How is post combustion technology used in CCS

A

CO2 can be removed from products of fossil fuel combustion by:
dissolving in a solvent
high pressure filtration
adsorption onto graphene

19
Q

How is carbon stored in CCS?

A

Storage underground in geological structures like depleted aquifers, oil/gas fields.
Could also be injected into oil reservoirs to provide pressure in secondary oil recovery.

20
Q

What is nitrogen stored as in the atmosphere?

A

N2 and NOX

21
Q

What is nitrogen stored as in the biosphere?

A

In living organisms, dna/protein
DOM

22
Q

What is nitrogen stored as in the lithosphere?

A

Soil- ammonia, nitrite, nitrate
Rocks- minerals containing nitrogen

23
Q

What is nitrogen stored as in the hydrosphere

A

Dissolved nitrates and ammonium ions

24
Q

Draw the nitrogen cycle and label the main processes

A

PG 153

25
Q

What is the haber process?

A

An industrial process producing ammonia from nitrogen and hydrogen to make fertilisers. Uses large amounts of energy.

26
Q

What are the consequences of human inputs to the nitrogen cycle?

A

Eutrophication will be more common with more fertilisers being used.
Global climate change- NOX from fertiliser denitrification is a GH gas
NOx toxicity- from combustion of fossil fuels produces nitric acid so acid rain
Photochemical smogs- NOX reacting with UV light and unburnt hydrocarbons to produce PANs

27
Q

What do biogeochemical cycles involve?

A

Inter-linked processes that allow materials to be recycled and repeatedly re-used

28
Q

How can the activities of agriculture affect the nitrogen cycle?

A

Nitrate fertilisers causing eutrophication if applied in heavy rain or if applied close to rivers.
Drainage of fields to make them more aerobic reducing denitrification.
Ploughing disturbs the soil and increases the rate of decomposition so more NOx released.
Growing more legumes will increase nitrogen in soils

29
Q

How is NOx released into the atmosphere?

A

By combustion processes

30
Q

How can NOx be controlled?

A

Reducing the use of fossil fuels would reduce the amount of NOx released.
Using catalytic convertors in engines of cars which reduces NOx back to oxygen and nitrogen

31
Q

Why should organic fertilisers be used instead of inorganic?

A

No eutrophication
They increase nutrients and humus in the soil

32
Q

What farming methods could be used to increase soil nitrate levels?

A

Cultivating legume crops
Crop rotation
Don’t apply fertilisers in the rain
Use low solubility fertilisers
Buffer strips next to rivers to stop nutrients contaminating the water

33
Q

Why is phosphorus a limiting factor on biological processes?

A

It has low solubility
No gaseous reservoir

34
Q

How is phosphorus changed in the phosphorus cycle

A

Phosphorus mobilised to more soluble forms to be used in fertilisers, however this contributes to eutrophication.

35
Q

How can phosphates be managed to increase the concentration in plants?

A

Biological wastes should be used as fertilisers
Crop breeding programmes to increase the efficiency that they can adsorb phosphates.
Provide suitable conditions for soil mycorrhizal fungi to increase uptake of phosphates

Environmental Science (21 decks)

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