Carbon cycle Flashcards
What is a carbon sink?
A store which takes in more carbon than it emits. E.g. an intact tropical rainforest
What is a carbon store?
A store that emits more carbon than it stores e.g. a damaged tropical rainforest
Main carbon stores in order from largest to smallest
Marine and sedimentary rocks 100,000 metric tons
Ocean 38000 metric tons
Fossil fuel deposits 4000 metric tons
Soil organic matter 1500 metric tons
Atmosphere 750 metric tons
Terrestrial plants 560 metric tons
What are the main transfers operating in the carbon cycle?
Photosynthesis, respiration, decomposition, combustion and burial and compaction, carbon sequestration, weathering
What is respiration
Respiration is a chemical process that happens in all ce,llls and is common to both plants and animals. Glucose is converted into energy that can be used for growth and repair, movement and control of body temperature in mammals. Carbon dioxide is then returned to the atmosphere mostly by exhaled air
What is decomposition
When organisms die, they are consumed by decomposers such as bacteria, fungi and earthworms. During this process of decomposition, carbon from their bodies is returned to the atmosphere as carbon dioxide. Some organic material passes into the soil where it may be stored for hundreds of years
What is photosynthesis
The process where plants use the light energy from the sun to produce carbohydrates in the form of glucose
- Green plants absorb the light energy using chlorophyll (a green substance found in chloroplasts in plant cells) in their leaves
- their absorbed light energy converts carbon dioxide in the air and water from the soil into glucose. During this process, oxygen is released into the air.
- some glucose is used in respiration, the rest is converted into starch, which is insoluble but can be converted back into glucose for respiration
What is combustion
Organic material contains carbon. When it is burned in the presence of oxygen (coal in a power station) it is converted into energy, carbon dioxide and water. This is combustion. The carbon dioxide is released into the atmosphere, returning carbon that might have been stored in rocks for millions of years
What is burial and compaction
Burial and compaction is where organic matter is buried by sediments and becomes compacted. Over millions of years these organic sediments containing carbon may form hydrocarbons such as coal and oil.
Corals and shelled organisms take up carbon dioxide from the water and convert it to calcium carbonate, used to build their shells. When they die, the shells accumulate on the seabed. Some of the carbonates dissolve, releasing carbon dioxide. The rest become compacted to form limestone, storing carbon for millions of years
What is carbon sequestration
An umbrella term used to describe the transfer of carbon from the atmosphere to plants soils, rock formations and oceans. Sequestration is both a natural and human process. Carbon capture and storage (CSS) is a recent term, used to describe the technological ‘capturing’ of carbon emitted from power stations. Smaller-scale sequestration can also take place, for example by a change in farming practices
What is weathering
Weathering involves the breakdown or decay of rocks in situ . When carbon dioxide is absorbed by rainwater it forms a mildly acidic carbonic acid. Through a series of complex chemical reactions, rocks will slowly dissolve with the carbon being held in solution. Transported via the water cycle to the oceans, this carbon can then be used to build the shells of marine organisms
Wildfires and the carbon cycle?
Wildfires can be started naturally by lightning strikes. However, increasingly they are started deliberately by people. Despite being restricted to tint parts of the Earth’s surface wild fires can have regional impacts. 2013 large fires in Indonesia burned out of control for months. Smoke spread across South East Asia. The fires released a large quantity of carbon dioxide onto the atmosphere, causing a noticeable spike in the rising trend of carbon emissions recorded since the late 1950s.
Wildfires can turn forests from being a carbon sink to being a carbon source, as combustion returns huge quantities of carbon back into the atmosphere
What are the physical causes of change in the carbon cycle?
Volcanic activity+ wildfires
