KQ1: How important are water and carbon to life on earth? Carbon Cycle

Question 1

Give reasons why carbon Is important to life on earth

Answer 1

1. Carbon is of biological significance, biological molecules such as proteins and carbohydrates are made up of carbon
2. Carbon Is used as an economic resource, fossil fuels such as gas and oil are used to power the global economy
   ▪︎Oil is used as a raw starting material in the manufacturing of many products such as plastics and paints
   ▪︎Agricultural crops and trees contain mass amounts of carbon and are used for food and textiles .etc

Question 2

What is the largest carbon store on the planet?

Answer 2

Sedimentary(carbonate) rocks hold up to 99% of all carbon on the planet

Question 3

How much carbon is stored in the oceans?

Answer 3

Up to 38,700 billion tonnes of carbon, mainly as dissolved CO2

Question 4

How much carbon is stored in the atmosphere and plants/ soil?

Answer 4

Atmosphere (600 billion tonnes) and plants and soil ( 560 and 2300 billion tonnes), despite being a minute fraction of total carbon store they represent most of the carbon in circulation

Question 5

what are the 6 principal carbon stores?

Answer 5

▪︎oceans
▪︎atmosphere
▪︎carbonate rocks
▪︎plants
▪︎soil
▪︎fossil fuels

Question 6

How much carbon is circulated in the slow carbon cycle every year as an estimate?

Answer 6

10 to 100 million tonnes

Question 7

How are the oceans involved in the slow carbon cycle?

Answer 7

Oceans absorb CO2 from the atmosphere where marine organisms suchas clams and corals make shells and skeletons by fixing dissolved CO2 with calcium to form CaCO3, on death, these sink to the sea floor and over millions of years are though to compress into sedimentary rock by digenesis

Question 8

How can CO2 be released from rocks?

Answer 8

1. Sedimentary rock subducted at the upper mantle near plate boundaries can be vented to the atmosphere by volcanic eruptions.
2. Others exposed at or near the surface can be attacked by chemical weathering. E.g. carbonation, where precipitation a weak acid can attack carbonate minerals to release co2 into atmosphere or in dissolved form to the rivers and streams

Question 9

Explain how carbonaceous rocks such as coal and natural gas form and how they are part of the slow carbon cycle

Answer 9

Partly decomposed organic material can become buried under younger sediments to form carbonaceous rocks, these can act as carbon sinks for millions of years

Question 10

Between which stores does carbon circulate the fastest, and how much faster is this than the fast carbon cycle?

Answer 10

Atmosphere, oceans, biosphere and soils, the exchanges between these are up to 10 to 1000x faster than slow carbon cycle

Question 11

Describe how land plants and microscopic phytoplankton are a key component of the fast carbon cycle.

Answer 11

They carry out photosynthesis to absorb Carbon dioxide, this produces carbohydrates, this process is fundamental in the food chain. These also respire (animals do the same), this releases carbon dioxide back into the atmosphere,. Decomposition of dead organic material by decomposers also releases carbon dioxide into the atmosphere as well as into the soil

Question 12

How does carbon exchange occur between the atmosphere and oceans as part of the fast carbon cycle?

Answer 12

Atmospheric co2 can dissolve into the oceans whilst oceans ventilate them back, through this they can be stored by natural sequestration for a long period of time, the average residence time is around 350 years

Question 13

what are the 6 main carbon exchanges?

Answer 13

1. Precipitation (Polly)
2. Photosynthesis (Pets)
3. Weathering (white)
4. Respiration (rabbits)
5. Decomposition (delicately)
6. Combustion (carefully)

Question 14

Explain the role of precipitation as carbon flux and how it’s effects have exacerbated as well as the impacts of this exacerbation.

Answer 14

Precipitation contains dissolved carbon dioxide and this forms a weak carbonic acid, which is a natural process, however rising co2 concentrations by anthropogenic emissions can increase acidity of rainfall, this imbalance could have potentially negative consequences on marine life.

Question 15

Explain the role of carbon flux in photosynthesis

Answer 15

Land and phytoplankton use co2 from the atmosphere and water to convert light energy to chemical energy, in the form of glucose, this energy is used to maintain growth reproduction and other processes

Question 16

How much carbon is exchanged from atmosphere to land plants and phytoplankton each year?

Answer 16

averaged around 120 GT `

Question 17

what is weathering?

Answer 17

The in situ breakdown of rock by biological, chemical and physical processes

Question 18

What is the main process by which rock is weathered? and when is it most effective?

Answer 18

Carbonation of limestone and chalk, carbon dioxide derived from the soil or atmosphere mixes with rainwater to form a weak carbonic acid which breaks down rock. This releases co2 into atmosphere, rivers and streams .etc, carbonation is most effective beneath a cover of soil due to higher concentrations of co2, making rainwater more acidic

Question 19

How much co2 is released each year into atmosphere and oceans by chemical weathering each year?

Answer 19

0.3 billion years

Question 20

where can the effectiveness of chemical weathering be shown?

Answer 20

At Norber brow, Yorkshire, where the surface has been lowered by an estimate of half a meter in the last 13000 years.

Question 21

What is the role of physical weathering on co2 released?

Answer 21

Doesn’t cause chemical change but does increase the exposure of rocks to chemical attacks as surface areas

Question 22

What is the role of chelation on co2 released?

Answer 22

Dead organic material mixes with rainwater to form humid acids that attack rocks and break them down, so more co2 released, this is particularly important in humid climates such as tropical rainforests where decomposition is rapid

Question 23

What is the role of respiration in the carbon exchange?

Answer 23

Absorbs oxygen to release energy stored in glucose, water and energy is released as well as CO2, one of the most important components of the fast carbon cycle

Question 24

What is the role of decomposition in carbon exchange?

Answer 24

Fungi and bacteria ~(decomposers) release co2 and nutrients into the soil to gain energy, rate is dependent upon climatic conditions, fastest in humid tropical climates and slowest in the tundra

Question 25

Why is combustion important in rocky mountains and coniferous forests?

Answer 25

A natural fuel to these ecosystems as leaf litter builds up as decomposition is slow, log jams can be cleared by fires to release co2 and nutrients back into the soil, can also open up the first layer of the canopy to increase biodiversity

Question 26

Explains 2 ways humans have increased rates of global combustion deliberately

Answer 26

1. Firing of forests and grasslands to clear land for cultivation or improve quality of grazing
2. Combustion of fossil fuels to release energy, despite efforts to curb co2 emissions, rates of consumption continue to rise, currently around 10GT is released every year

Question 27

Describe the role of the physical pump in carbon sequestration

Answer 27

1. Carbon initially enters via diffusion from the atmosphere
2. Surface ocean currents transports it poleward where it becomes cool, dense and then sinks, this downwelling occurs in a handful of places e.g. between Greenland and Iceland,
3. Carbon may remain for centuries before it reaches areas of upwelling and rises to the surface where it diffuses into the atmosphere

Question 28

How much co2 enters by photosynthesis through the biological pump?

Answer 28

Around 50GT

Question 29

Explain how the biological pump works

Answer 29

1. Marine organisms such as phytoplankton absorb co2, using light and water they produce organic material. wither through natural death or being consumed by the food chain, these can end up on sediment floor or decompose
2. Molluscs and crustaceans may use calcium and carbonate ions, extraction from sea water to form plates, shells and skeletons
3. All of this can accumulate on the ocean floor, and eventually lithified into chalk and limestone

Question 30

Expalin how vegetation fixates carbon

Answer 30

By photosynthesis, it can be locked up for a long period of time