What are all the sources and sinks for the following: Carbon Oxygen Nitrogen Sulfur Phosphorus Water Silica Methane

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To answer this we need to understand what a source and sink of a substance are. A source is a method of release (natural or artificial) of the substance into the environment. A sink is a method of capture of that substance such that it cannot freely dissipate around the atmosphere or oceans. It is impossible to list every single sink or source of a substance so I will instead list general sinks and sources.

Carbon moves most freely around the atmosphere as carbon dioxide. This is created naturally by respiration by living beings and also by man made combustion processes of fuels such as biomatter and fossil fuels. The sinks of carbon dioxide include photosynthesis by plants, chemically turning the carbon into sugars and the ocean also acts as a sink by both biological processes and by simply dissolving the carbon dioxide.

Oxygen is a major constituent gas of our atmosphere and is largely released by plants in the process of photosynthesis from water. Oxygen sinks include biological organisms who use it in respiration which creates water as a byproduct along with various other combustion and corrosion processes.

Nitrogen is the greatest constituent of our atmosphere and is captured by many biological sources as it is one of the main elements within proteins. It is typically captured by nitrogen fixing bacteria for the use in plants. Denitrifying microorgansims are the major source in the nitrogen cycle.

There is very little sulphur within the atmosphere; it is mostly contained within the oceans and other bodies of water. These bodies of water are the main sink and the largest source of sulphur is volcanic activity, whilst human combustion of fossil fuels is also releasing a large amount.

Various microbes are both the major sink and source of phosphorous. Phosphorous is also used in biological processes by plants so they are also a major sink.

Oceans and rivers are both the major source and sink of water. Clouds form from water evaporated to precipitate on land and sea also affecting the water cycle.

Silica is the major constituent of the earths crust and thus weathering of the crust is the main source. Major sinks include deposits as sediment in the waters and the use of silica by various biological organisms.

Methane is a greenhouse gas with many various sources, the greatest of which include methogenic bacteria and animals who produce methane in their gut. Human fossil fuels are also a major source. Once in the atmosphere it reacts with oxygen to create water and carbon dioxide, in addition to being absorbed by methanotrophic organisms.

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