Biogeochemical system

Question 1

Closed system

Answer 1

Stores = where c is held
Fluxes = flows which move c between stores
Processes = physical mechanisms which drive the fluxes between stores - diffusion and photosynthesis

No matter enters or leaves

Question 2

Source

Answer 2

Add c to atmosphere

Question 3

Store

Answer 3

Remove c from atmosphere

Question 4

When source = sink

Answer 4

Dynamic equilibrium

Question 5

Reservoir turnover

Answer 5

The rate carbon enters and leaves a store

Question 6

Geological processes/interactions - chemical weathering

Answer 6

1. water reacts with co2 in atmosphere forming carbonic acid = reaches surface as rain dissolving surface minerals
2. Rivers transport the calcium ions from land to ocean which combine with bicarbonate ions to form calcium carbonate
3. Deposition and burial turns the calcite sediment to limestone
4. Subduction of the seafloor exposes buried limestone
5. Some carbon rises back to surface within magma which is returned to the atmosphere as co2

Global warming therefore increases the rate of weathering and as it increases the rate of reaction and increases precipitation levels.

Studies have suggested that an increase of 7C would double the rate of chemical weathering.

Simplified:

Chemical weathering transfers carbon from the atmosphere to the hydrosphere and biosphere

Atmospheric carbon reacts with water vapour to form a weak carbonic acid

On condensation, acid rain is formed

When this acid falls onto rocks, a chemical reaction occurs which dissolves calcium carbonate in the rocks

This reaction produces carbon ions which wash into rivers and then get carried to to sea

Deposition/sedimentation turns the carbon ions into limestone - this then becomes exposed

Carbon rises back to surface within magma which is returned to the atmosphere as co2

Global warming therefore increases the rate of weathering and as it increases the rate of reaction and increases precipitation levels.

Studies have suggested that an increase of 7C would double the rate of chemical weathering.

Question 7

Geological processes/interactions - volcanic outgassing

Answer 7

Earth’s crust has pockets of c distributed by volcanic eruptions or seismic activity - release of this gas that has been dissolved, trapped, frozen or absorbed in rock = outgassing

happens at = volcanic zones associated with plate boundaries, and areas with no current volcanic activity (Yellowstone), direct emissions from fractures in the earths crust

Emit 0-15 to 0-26 GT co2 annually
Fossil fuels emit about 35 GT so relatively insignificant in comparison to human activity

Only 1% of Earth’s total carbon is above ground the rest is contained within the crust, mantle and core

Volcanic Outgassing

Question 8

Slowest part of carbon system

Answer 8

Geological carbon cycle

Question 9

Fastest part of carbon system

Answer 9

Bio-geochemical carbon cycle

Question 10

Geological types

Answer 10

Weathering of rocks:
- Mechanical, chemical and biological weathering results in the breakdown of rocks

Decomposition:
- Plant and animal particles from decomposition after death store carbon

Transportation:
- Rivers can carry particles to the ocean, where they will be deposited

Sedimentation:
- Over time, sediments build up, burying older sediments below e.g. shale and limestone

Metamorphosis:
- Pressure builds over time in the layers of sediment which eventually leads to deeper sediment changing to rock e.g. limestone becomes marble, shale becomes slate

Carbon in rocks = 80% of carbon containing rocks in the ocean is from shell-building organisms (corals) and plankton

Question 11

Chemical weathering simplified

Answer 11

Chemical weathering transfers carbon from the atmosphere to the hydrosphere

CO₂ in the atmosphere reacts with water vapour to form weak carbonic acid, which falls as acid rain

This acid reacts with calcium carbonate in rocks, dissolving them and releasing carbon ions

These ions are then washed into rivers and carried to the sea