Biogeochemical cycles

Question 1

What are the main reservoirs in the carbon cycle?

Answer 1

Atmosphere
Hydrosphere
Biosphere
Lithosphere

Question 2

What does carbon exist as in the atmosphere?

Answer 2

CO2, methane and carbon monoxide

Question 3

What is carbon stored as in the hydrological cycle?

Answer 3

Dissolved CO2
Hydrogen carbonate ion

Question 4

What does the biosphere reservoir contain?

Answer 4

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

Question 5

What does the lithosphere contain carbon as?

Answer 5

Fossil fuels as carbon/hydrocarbons
Carbonaceous rocks like limestone

Question 6

What are the main processes in the carbon cycle?

Answer 6

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.

Question 7

What do human activies do to biogeochemical cycles?

Answer 7

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

Question 8

How do human activities produce changes in photosynthesis?

Answer 8

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

Question 9

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

Answer 9

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.

Question 10

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

Answer 10

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

Question 11

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

Answer 11

Drainage

Question 12

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

Answer 12

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.

Question 13

What human activities affect the amount of carbon in biomass?

Answer 13

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

Question 14

How could conservation be used to increase carbon in biomass

Answer 14

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

Question 15

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

Answer 15

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

Question 16

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

Answer 16

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,

Question 17

How is pre-combustion technology used in CCS

Answer 17

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.

Question 18

How is post combustion technology used in CCS

Answer 18

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

Question 19

How is carbon stored in CCS?

Answer 19

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.

Question 20

What is nitrogen stored as in the atmosphere?

Answer 20

N2 and NOX

Question 21

What is nitrogen stored as in the biosphere?

Answer 21

In living organisms, dna/protein
DOM

Question 22

What is nitrogen stored as in the lithosphere?

Answer 22

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

Question 23

What is nitrogen stored as in the hydrosphere

Answer 23

Dissolved nitrates and ammonium ions

Question 24

Draw the nitrogen cycle and label the main processes

Answer 24

PG 153

Question 25

What is the haber process?

Answer 25

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

Question 26

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

Answer 26

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

Question 27

What do biogeochemical cycles involve?

Answer 27

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

Question 28

How can the activities of agriculture affect the nitrogen cycle?

Answer 28

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

Question 29

How is NOx released into the atmosphere?

Answer 29

By combustion processes

Question 30

How can NOx be controlled?

Answer 30

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

Question 31

Why should organic fertilisers be used instead of inorganic?

Answer 31

No eutrophication
They increase nutrients and humus in the soil

Question 32

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

Answer 32

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

Question 33

Why is phosphorus a limiting factor on biological processes?

Answer 33

It has low solubility
No gaseous reservoir

Question 34

How is phosphorus changed in the phosphorus cycle

Answer 34

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

Question 35

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

Answer 35

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