Environmental Spheres and Biogeochemical Cycles

One of the most important ways of relating the environmental chemistry of the five environmental spheres is through biogeochemical cycles. These are commonly expressed in terms of key elements, including essential nutrient elements. Often, as is the case with the nitrogen cycle, they contain an atmospheric component, though in some cases, such as the phosphorous cycle, the atmospheric component is not significant. Before the appearance of humans on Earth, the anthrospheric 

Other important cycles of matter are linked to the carbon cycle. The oxygen cycle describes movement of oxygen in various chemical forms through the five environmental spheres. At 21% elemental oxygen by volume, the atmosphere is a vast reservoir of this element. This oxygen becomes chemically bound as carbon dioxide by respiration processes of organisms and by combustion. 

Photosynthesis adds oxygen to the atmosphere. Oxygen is a component of biomass in the biosphere and most rocks in Earth s crust are composed of oxygen-containing compounds. With its chemical formula of H2O, water in the hydrosphere is predominantly oxygen. In addition to the carbon and oxygen cycles described above, three other important life-element cycles are those of nitrogen, sulfur, and phosphorus  

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