Читать книгу Encyclopedia of Renewable Energy - James Speight G., James G. Speight - Страница 187

A biogeochemical cycle (also called the substance turnover or cycling of substances) is a pathway by which a chemical substance moves through biotic compartments the biosphere) and through abiotic compartments of the Earth (such as the atmosphere, the hydrosphere, and the lithosphere).

There are biogeochemical cycles for the chemical elements (such as calcium, carbon, hydrogen, mercury, nitrogen, oxygen, phosphorus, selenium, and sulfur) as well as ; molecular cycles for water and silica; macroscopic cycles such as the rock cycle as well as human-induced cycles for synthetic compounds such as polychlorinated biphenyl derivatives (PCBs). In some cycles, there are reservoirs where a substance remains for a long period of time.

The biogeochemical cycles operate at the global scale and involve all of the main components of the Earth system in which materials are transferred continually between the atmosphere, the aquasphere, and the geosphere. However, since the biogeochemical cycles involve elements that are essential for life, organisms play a vital part in those cycles. Typically then, the biogeochemical cycles involve an inorganic component (the abiotic part of the cycle, including sedimentary and atmospheric phases) and an organic component (comprising plants and animals, both living and dead). Like other environmental systems, biogeochemical cycles involve the flow of substances between stores (also known as reservoirs) in the geosphere, atmosphere, hydrosphere, and biosphere. Water plays a vital role in mediating many of the flows between stores. Three of the key biogeochemical cycles are the nitrogen, carbon, and sulfur cycles.

Finally, it must be noted that the biogeochemical cycles have been modified substantially by human activities which is necessary for consideration to understand the various environmental issues related to human activities.