Лекция: Phosphorus Cycle

Phosphorus, mainly in the of phosphate ions, is an essential nutrient of both plants and animals. It is a major constituent of the genetic material coded in DNA molecules and the main component of bones and teeth. It is also used in some commercial fertilizers.

Various form of phosphorus are cycled through the lower atmosphere, water, soil, and living organisms by the phosphorus cycle. The major reservoirs of phosphorus are phosphate rock deposits on land and in shallow ocean sediments. Some phosphates released by the slow breakdown of phosphate rock deposits are dissolved in soil water and taken up by plant roots. Animals get their phosphorus by eating plants or animals that have eaten plants. Animal wastes and the decay products of dead animals and plants return much of this phosphorus to the soil, rivers, and eventually to the ocean bottom as insoluble forms of phosphate rock. Large amounts of phosphate are eroded from the land to the oceans each year by natural processes and human activities.

People intervene in the phosphorus cycle in several ways. First, large quantities of phosphate rock are dug up, mostly from shallow ocean deposits, and used primarily to produce commercial fertilizers and detergents. Second, discharge from sewage treatment plants and runoff of commercial fertilizers can overload aquatic ecosystems with phosphate ions. As in the case of nitrate ions, an excessive supply can explosive growth of blue-green algae and other aquatic plants that can disrupt life in aquatic ecosystems.

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