What are the sources and sinks of greenhouse gases and which process involves carbon moving directly from the biosphere into the geosphere?
The ocean, soil and forests are the world's largest carbon sinks. A carbon source releases carbon dioxide into the atmosphere. Examples of carbon sources include the burning of fossil fuels like gas, coal and oil, deforestation and volcanic eruptions. Now, increased human activity is upsetting the balance. Including landfill sites, soils are estimated to account for about 45% of global methane production. The major sink for atmospheric methane is through chemical reaction with hydroxyl radical in the troposphere. However, oxidation of methane by soils is also a significant sink, representing about 10% of the total sink. The biggest sink appears to be oxidation in the atmosphere, but some oxidation occurs in soils as well. The main sources are rice fields, wetlands, biomass burning, ruminants, landfills, natural gas production, and coal mining. As the planet's greatest carbon sink, the ocean absorbs excess heat and energy released from rising greenhouse gas emissions trapped in the Earth's system.The largest source of anthropogenic methane emissions is agriculture, responsible for around a quarter of the total, closely followed by the energy sector, which includes emissions from coal, oil, natural gas and biofuels. Methane, carbon dioxide, nitrous oxide and water vapour are the primary greenhouse gases that contribute to the greenhouse effect. The biogeochemical cycle in which carbon is exchanged between Earth's terrestrial biosphere, hydrosphere, geosphere, and atmosphere is called the carbon cycle. Carbonic acid in the rain falls into bodies of water moving carbon into the hydrosphere. Rocks also absorb carbon from the rain in a process called weathering that moves carbon into the lithosphere. Chemical weathering is initiated when acidic substances (ex. carbonic acid) come into contact with rocks. The carbon cycle is the exchange of carbon from biosphere to geosphere, hydrosphere and atmosphere. Carbon is stored in the atmosphere, vegetation, soil, deep layers of the crust and in surface and deep water. These are the reservoirs, or sinks, through which carbon cycles. Carbon is released back into the atmosphere when organisms die, volcanoes erupt, fires blaze, fossil fuels are burned, and through a variety of other mechanisms. Respiration, excretion, and decomposition release the carbon back into the atmosphere or soil, continuing the cycle. The ocean plays a critical role in carbon storage, as it holds about 50 times more carbon than the atmosphere.
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