The Earth Phosphate Cycle
The earth phosphate cycle is outlined in detail, from phosphate mining and production to phosphate disposal in lakes and oceans.
Most phosphate deposits are of marine sedimentary origin, and contain approximately 30% P2O5. Large amounts of wastes-gaseous, liquid, and solid-are generated during the enrichment of the mineral and the conversion to phosphate fertilizer, phosphoric acid, or elemental phosphorus; the most difficult to control are air and water pollution by fluorides.
The major phosphate applications are for fertilizers, detergents, anti-corrosion agents, and insecticides. The excess phosphate from human and animal diet is eliminated, and becomes part of sewage or runoff waters; sewage phosphate could be recovered through tertiary sewage treatment systems. Excess phosphate addition to natural waters is a major contribution to lake eutrophication. The phosphate that reaches the ocean is precipitated and eventually forms extensive deposits located mainly along the continental coasts.
The world production and demand of phosphates have been increasing exponentially, with a doubling rate of 10-15 years. If this rate of use continues, land reserves could be exhausted in a fairly near future. Ocean deposits can supply additional amounts, but discontinuing the use of phosphate in detergents, application of correct amounts of fertilizers, and recycling of sewage phosphates would also be advisable.
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