# Phosphate

Last updated
Phosphate
 Aromatic ball and stick model of phosphate Space-filling model of phosphate
Names
Systematic IUPAC name
Phosphate [1]
Identifiers
•
3D model (JSmol)
3903772
ChEBI
•
ChemSpider
•
1997
MeSH
PubChem CID
UNII
•
Properties
PO3−
4
Molar mass 94.9714 g mol−1
Conjugate acid Hydrogen phosphate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
(what is   ?)
Infobox references

A phosphate is a chemical derivative of phosphoric acid. The phosphate ion (PO3−
4
) is an inorganic chemical, the conjugate base that can form many different salts. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Of the various phosphoric acids and phosphates, organic phosphates are important in biochemistry and biogeochemistry (and, consequently, in ecology), and inorganic phosphates are mined to obtain phosphorus for use in agriculture and industry. [2] At elevated temperatures in the solid state, phosphates can condense to form pyrophosphates.

Phosphoric acid (also known as orthophosphoric acid or phosphoric(V) acid) is a weak acid with the chemical formula H3PO4. Orthophosphoric acid refers to phosphoric acid, which is the IUPAC name for this compound. The prefix ortho- is used to distinguish the acid from related phosphoric acids, called polyphosphoric acids. Orthophosphoric acid is a non-toxic acid, which, when pure, is a solid at room temperature and pressure. The conjugate base of phosphoric acid is the dihydrogen phosphate ion, H
2
PO
4
, which in turn has a conjugate base of hydrogen phosphate, HPO2−
4
, which has a conjugate base of phosphate, PO3−
4
. Phosphates are essential for life.

In chemistry, a salt is an ionic compound that can be formed by the neutralization reaction of an acid and a base. Salts are composed of related numbers of cations and anions so that the product is electrically neutral. These component ions can be inorganic, such as chloride (Cl), or organic, such as acetate ; and can be monatomic, such as fluoride (F), or polyatomic, such as sulfate.

Organic chemistry is a subdiscipline of chemistry that studies the structure, properties and reactions of organic compounds, which contain carbon in covalent bonding. Study of structure determines their chemical composition and formula. Study of properties includes physical and chemical properties, and evaluation of chemical reactivity to understand their behavior. The study of organic reactions includes the chemical synthesis of natural products, drugs, and polymers, and study of individual organic molecules in the laboratory and via theoretical study.

## Contents

In biology, adding phosphates to—and removing them from—proteins in cells are both pivotal in the regulation of metabolic processes. Referred to as phosphorylation and dephosphorylation, respectively, they are important ways that energy is stored and released in living systems.

Biology is the natural science that studies life and living organisms, including their physical structure, chemical processes, molecular interactions, physiological mechanisms, development and evolution. Despite the complexity of the science, there are certain unifying concepts that consolidate it into a single, coherent field. Biology recognizes the cell as the basic unit of life, genes as the basic unit of heredity, and evolution as the engine that propels the creation and extinction of species. Living organisms are open systems that survive by transforming energy and decreasing their local entropy to maintain a stable and vital condition defined as homeostasis.

Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific three-dimensional structure that determines its activity.

The cell is the basic structural, functional, and biological unit of all known living organisms. A cell is the smallest unit of life. Cells are often called the "building blocks of life". The study of cells is called cell biology or cellular biology.

## Chemical properties

The phosphate ion is a polyatomic ion with the empirical formula PO3−
4
and a molar mass of 94.97 g/mol. It consists of one central phosphorus atom surrounded by four oxygen atoms in a tetrahedral arrangement. The phosphate ion carries a −3 formal charge and is the conjugate base of the hydrogen phosphate ion, HPO2−
4
, which is the conjugate base of H
2
PO
4
, the dihydrogen phosphate ion, which in turn is the conjugate base of H
3
PO
4
, phosphoric acid. A phosphate salt forms when a positively charged ion attaches to the negatively charged oxygen atoms of the ion, forming an ionic compound.

A polyatomic ion, also known as a molecular ion, is a charged chemical species (ion) composed of two or more atoms covalently bonded or of a metal complex that can be considered to be acting as a single unit. The prefix poly- means "many," in Greek, but even ions of two atoms are commonly referred to as polyatomic. In older literature, a polyatomic ion is also referred to as a radical, and less commonly, as a radical group. In contemporary usage, the term radical refers to free radicals that are species with an unpaired electron.

In chemistry, the empirical formula of a chemical compound is the simplest positive integer ratio of atoms present in a compound. A simple example of this concept is that the empirical formula of sulphur monoxide, or SO, would simply be SO, as is the empirical formula of disulfur dioxide, S2O2. This means that sulfur monoxide and disulfur dioxide, both compounds of sulfur and oxygen, will have the same empirical formula. However, their molecular formulas, which express the number of atoms in each molecule of a chemical compound, may not be the same.

In chemistry, the molar massM is a physical property defined as the mass of a given substance divided by the amount of substance. The base SI unit for molar mass is kg/mol. However, for historical reasons, molar masses are almost always expressed in g/mol.

Many phosphates are not soluble in water at standard temperature and pressure. The sodium, potassium, rubidium, caesium, and ammonium phosphates are all water-soluble. Most other phosphates are only slightly soluble or are insoluble in water. As a rule, the hydrogen and dihydrogen phosphates are slightly more soluble than the corresponding phosphates. The pyrophosphates are mostly water-soluble. Aqueous phosphate exists in four forms:

Solubility is the property of a solid, liquid or gaseous chemical substance called solute to dissolve in a solid, liquid or gaseous solvent. The solubility of a substance fundamentally depends on the physical and chemical properties of the solute and solvent as well as on temperature, pressure and presence of other chemicals of the solution. The extent of the solubility of a substance in a specific solvent is measured as the saturation concentration, where adding more solute does not increase the concentration of the solution and begins to precipitate the excess amount of solute.

Water is a transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's streams, lakes, and oceans, and the fluids of most living organisms. It is vital for all known forms of life, even though it provides no calories or organic nutrients. Its chemical formula is H2O, meaning that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. Water is the name of the liquid state of H2O at standard ambient temperature and pressure. It forms precipitation in the form of rain and aerosols in the form of fog. Clouds are formed from suspended droplets of water and ice, its solid state. When finely divided, crystalline ice may precipitate in the form of snow. The gaseous state of water is steam or water vapor. Water moves continually through the water cycle of evaporation, transpiration (evapotranspiration), condensation, precipitation, and runoff, usually reaching the sea.

Rubidium is a chemical element with symbol Rb and atomic number 37. Rubidium is a soft, silvery-white metallic element of the alkali metal group, with a standard atomic weight of 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other alkali metals, including rapid oxidation in air. On Earth, natural rubidium comprises two isotopes: 72% is the stable isotope, 85Rb; 28% is the slightly radioactive 87Rb, with a half-life of 49 billion years—more than three times longer than the estimated age of the universe.

• In strongly basic conditions, the phosphate ion (PO3−
4
) predominates,
• In weakly basic conditions, the hydrogen phosphate ion (HPO2−
4
) is prevalent.
• In weakly acidic conditions, the dihydrogen phosphate ion (H
2
PO
4
) is most common.
• In strongly acidic conditions, trihydrogen phosphate (H
3
PO
4
) is the main form.

More precisely, considering these three equilibrium reactions:

H
3
PO
4
H+ + H
2
PO
4
H
2
PO
4
H+ + HPO2−
4
HPO2−
4
H+ + PO3−
4

the corresponding constants at 25 °C (in mol/L) are (see phosphoric acid):

${\displaystyle K_{\mathrm {a1} }={\frac {[{\mbox{H}}^{+}][{\mbox{H}}_{2}{\mbox{PO}}_{4}^{-}]}{[{\mbox{H}}_{3}{\mbox{PO}}_{4}]}}\simeq 7.5\times 10^{-3}}$      (pKa1 ≈ 2.12)
${\displaystyle K_{\mathrm {a2} }={\frac {[{\mbox{H}}^{+}][{\mbox{HPO}}_{4}^{2-}]}{[{\mbox{H}}_{2}{\mbox{PO}}_{4}^{-}]}}\simeq 6.2\times 10^{-8}}$      (pKa2 ≈ 7.21)
${\displaystyle K_{\mathrm {a3} }={\frac {[{\mbox{H}}^{+}][{\mbox{PO}}_{4}^{3-}]}{[{\mbox{HPO}}_{4}^{2-}]}}\simeq 2.14\times 10^{-13}}$      (pKa3 ≈ 12.67)

### Speciation

The speciation diagram obtained using these pK values shows three distinct regions. In effect, H
3
PO
4
, H
2
PO
4
and HPO2−
4
behave as separate weak acids because the successive pK values differ by more than 4. For each acid, the pH at half-neutralization is equal to the pK value of the acid. The region in which the acid is in equilibrium with its conjugate base is defined by pH ≈ pK ± 2. Thus, the three pH regions are approximately 0–4, 5–9 and 10–14. This is a simplified model, assuming a constant ionic strength. It will not hold in reality at very low and very high pH values.

For a neutral pH, as in the cytosol, pH = 7.0

${\displaystyle {\frac {[{\mbox{H}}_{2}{\mbox{PO}}_{4}^{-}]}{[{\mbox{H}}_{3}{\mbox{PO}}_{4}]}}\simeq 7.5\times 10^{4}{\mbox{ , }}{\frac {[{\mbox{HPO}}_{4}^{2-}]}{[{\mbox{H}}_{2}{\mbox{PO}}_{4}^{-}]}}\simeq 0.62{\mbox{ , }}{\frac {[{\mbox{PO}}_{4}^{3-}]}{[{\mbox{HPO}}_{4}^{2-}]}}\simeq 2.14\times 10^{-6}}$

so that only H
2
PO
4
and HPO2−
4
ions are present in significant amounts (62% H
2
PO
4
, 38% HPO2−
4
. Note that in the extracellular fluid (pH = 7.4), this proportion is inverted (61% HPO2−
4
, 39% H
2
PO
4
).

Phosphate can form many polymeric ions such as pyrophosphate), P
2
O4−
7
, and triphosphate, P
3
O5−
10
. The various metaphosphate ions (which are usually long linear polymers) have an empirical formula of PO
3
and are found in many compounds.

### Biochemistry of phosphates

In biological systems, phosphorus is found as a free phosphate ion in solution and is called inorganic phosphate, to distinguish it from phosphates bound in various phosphate esters. Inorganic phosphate is generally denoted Pi and at physiological (homeostatic) pH primarily consists of a mixture of HPO2−
4
and H
2
PO
4
ions.

Inorganic phosphate can be created by the hydrolysis of pyrophosphate, denoted PPi:

P
2
O4−
7
+ H2O 2 HPO2−
4

However, phosphates are most commonly found in the form of adenosine phosphates (AMP, ADP, and ATP) and in DNA and RNA. It can be released by the hydrolysis of ATP or ADP. Similar reactions exist for the other nucleoside diphosphates and triphosphates. Phosphoanhydride bonds in ADP and ATP, or other nucleoside diphosphates and triphosphates, can release high amounts of energy when hydrolyzed which give them their vital role in all living organisms. They are generally referred to as high-energy phosphate, as are the phosphagens in muscle tissue. Compounds such as substituted phosphines have uses in organic chemistry, but do not seem to have any natural counterparts.

The addition and removal of phosphate from proteins in all cells is a pivotal strategy in the regulation of metabolic processes. Phosphorylation and dephosphorylation are important ways that energy is stored and released in living systems. Cells use ATP for this.

Reference ranges for blood tests, showing 'inorganic phosphorus' in purple at right, being almost identical to the molar concentration of phosphate

Phosphate is useful in animal cells as a buffering agent. Phosphate salts that are commonly used for preparing buffer solutions at cell pHs include Na2HPO4, NaH2PO4, and the corresponding potassium salts.

An important occurrence of phosphates in biological systems is as the structural material of bone and teeth. These structures are made of crystalline calcium phosphate in the form of hydroxyapatite. The hard dense enamel of mammalian teeth consists of fluoroapatite, a hydroxy calcium phosphate where some of the hydroxyl groups have been replaced by fluoride ions.

Plants take up phosphorus through several pathways: the arbuscular mycorrhizal pathway and the direct uptake pathway.

## Occurrence and mining

Phosphates are the naturally occurring form of the element phosphorus, found in many phosphate minerals. In mineralogy and geology, phosphate refers to a rock or ore containing phosphate ions. Inorganic phosphates are mined to obtain phosphorus for use in agriculture and industry. [2]

The largest global producer and exporter of phosphates is Morocco. Within North America, the largest deposits lie in the Bone Valley region of central Florida, the Soda Springs region of southeastern Idaho, and the coast of North Carolina. Smaller deposits are located in Montana, Tennessee, Georgia, and South Carolina. The small island nation of Nauru and its neighbor Banaba Island, which used to have massive phosphate deposits of the best quality, have been mined excessively. Rock phosphate can also be found in Egypt, Israel, Western Sahara, Navassa Island, Tunisia, Togo, and Jordan, countries that have large phosphate-mining industries.

Phosphorite mines are primarily found in:

In 2007, at the current rate of consumption, the supply of phosphorus was estimated to run out in 345 years. [4] However, some scientists thought that a "peak phosphorus" will occur in 30 years and Dana Cordell from Institute for Sustainable Futures said that at "current rates, reserves will be depleted in the next 50 to 100 years". [5] Reserves refer to the amount assumed recoverable at current market prices, and, in 2012, the USGS estimated 71 billion tons of world reserves, while 0.19 billion tons were mined globally in 2011. [6] Phosphorus comprises 0.1% by mass of the average rock [7] (while, for perspective, its typical concentration in vegetation is 0.03% to 0.2%), [8] and consequently there are quadrillions of tons of phosphorus in Earth's 3 * 1019 ton crust, [9] albeit at predominantly lower concentration than the deposits counted as reserves from being inventoried and cheaper to extract; if it is assumed that the phosphate minerals in phosphate rock are hydroxyapatite and fluoroapatite, phosphate minerals contain roughly 18.5% phosphorus by weight and if phosphate rock contains around 20% of these minerals, the average phosphate rock has roughly 3.7% phosphorus by weight.

Some phosphate rock deposits, such as Mulberry in Florida, [10] are notable for their inclusion of significant quantities of radioactive uranium isotopes. This syndrome is noteworthy because radioactivity can be released into surface waters [11] in the process of application of the resultant phosphate fertilizer (e.g. in many tobacco farming operations in the southeast US).

In December 2012, Cominco Resources announced an updated JORC compliant resource of their Hinda project in Congo-Brazzaville of 531 Mt, making it the largest measured and indicated phosphate deposit in the world. [12]

## Production

The three principal phosphate producer countries (China, Morocco and the United States) account for about 70% of world production.

Production and global reserves of natural phosphate by country in 2015
(USGS, 2016) [13]
CountryProduction
(millions kg)
Mondial part
(%)
Mondial reserves
(millions kg)
Algeria 1,2000.542,200,000
Australia 2,6001.171,030,000
Brazil 6,7003.00315,000
China 100,00044.833,700,000
Egypt 5,5002.471,250,000
India 1,1000.4965,000
Iraq 2000.09430,000
Israel 3,3001.48130,000
Jordan 7,5003.361,300,000
Kazakhstan 1,6000.72260,000
Mexico 1,7000.7630,000
Morocco 30,00013.4550,000,000
Peru 4,0001.79820,000
Russia 12,5005.601,300,000
Saudi Arabia 3,3001.48956,000
Senegal 1,0000.4550,000
South Africa 2,2000.991,500,000
Syria 7500.341,800,000
Togo 1,0000.4530,000
Tunisia 4,0001.79100,000
United States 27,60012.371,100,000
Vietnam 2,7001.2130,000
Other countries2,6001.17380,000
Total223,00010069,000,000

## Ecology

In ecological terms, because of its important role in biological systems, phosphate is a highly sought after resource. Once used, it is often a limiting nutrient in environments, and its availability may govern the rate of growth of organisms. This is generally true of freshwater environments, whereas nitrogen is more often the limiting nutrient in marine (seawater) environments. Addition of high levels of phosphate to environments and to micro-environments in which it is typically rare can have significant ecological consequences. For example, blooms in the populations of some organisms at the expense of others, and the collapse of populations deprived of resources such as oxygen (see eutrophication) can occur. In the context of pollution, phosphates are one component of total dissolved solids, a major indicator of water quality, but not all phosphorus is in a molecular form that algae can break down and consume. [14]

Calcium hydroxyapatite and calcite precipitates can be found around bacteria in alluvial topsoil. [15] As clay minerals promote biomineralization, the presence of bacteria and clay minerals resulted in calcium hydroxyapatite and calcite precipitates. [15]

Phosphate deposits can contain significant amounts of naturally occurring heavy metals. Mining operations processing phosphate rock can leave tailings piles containing elevated levels of cadmium, lead, nickel, copper, chromium, and uranium. Unless carefully managed, these waste products can leach heavy metals into groundwater or nearby estuaries. Uptake of these substances by plants and marine life can lead to concentration of toxic heavy metals in food products. [16]

## Related Research Articles

Phosphorus is a chemical element with symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Earth. It has a concentration in the Earth's crust of about one gram per kilogram. With few exceptions, minerals containing phosphorus are in the maximally oxidized state as inorganic phosphate rocks.

In chemistry, a pyrophosphate are phosphorus oxyanions that contain a P-O-P linkage. A number of pyrophosphate salts exist, such as Na2H2P2O7, as well as the normal pyrophosphates. Often pyrophosphates are called diphosphates. The parent pyrophosphates are derived from partial or complete neutralization of pyrophosphoric acid. Important salts are disodium pyrophosphate and tetrasodium pyrophosphate. The pyrophosphate bond, as found in ATP, is very important in biochemistry.

Calcium phosphate is a family of materials and minerals containing calcium ions (Ca2+) together with inorganic phosphate anions. Some so-called calcium phosphates contain oxide and hydroxide as well. They are white solids of nutritious value.

Tetrasodium pyrophosphate, also called sodium pyrophosphate, tetrasodium phosphate or TSPP, is an inorganic compound with the formula Na4P2O7. As a salt, it is a white, water-soluble solid. It composed of pyrophosphate anion and sodium ions. Toxicity is approximately twice that of table salt when ingested orally. Also known is the decahydrate Na4P2O7 · 10(H2O).

Diammonium phosphate (DAP) (chemical formula (NH4)2HPO4, IUPAC name diammonium hydrogen phosphate) is one of a series of water-soluble ammonium phosphate salts that can be produced when ammonia reacts with phosphoric acid. Solid diammonium phosphate shows a dissociation pressure of ammonia as given by the following expression and equation:

Phosphorous acid, is the compound described by the formula H3PO3. This acid is diprotic (readily ionizes two protons), not triprotic as might be suggested by this formula. Phosphorous acid is an intermediate in the preparation of other phosphorus compounds. Organic derivatives of phosphorous acid, compounds with the formula RPO3H2, are called phosphonic acids.

Hydroxyapatite, also called hydroxylapatite (HA), is a naturally occurring mineral form of calcium apatite with the formula Ca5(PO4)3(OH), but it is usually written Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two entities. Hydroxyapatite is the hydroxyl endmember of the complex apatite group. The OH ion can be replaced by fluoride, chloride or carbonate, producing fluorapatite or chlorapatite. It crystallizes in the hexagonal crystal system. Pure hydroxyapatite powder is white. Naturally occurring apatites can, however, also have brown, yellow, or green colorations, comparable to the discolorations of dental fluorosis.

There are various kinds of phosphoric acids and phosphates. Of the many phosphorus oxoacids, the phosphoric acids constitute the largest and most diverse group. The simplest phosphoric acid series begins with monophosphoric (orthophosphoric) acid, continues with many oligophosphoric acids such as diphosphoric (pyrophosphoric) acid and concludes in the polyphosphoric acids. But, phosphoric acid units can bind together into rings or cyclic structures, chains (catenas), or branched structures, with various combinations possible. Each of these can form phosphates.

Ammonium phosphate is the salt of ammonium and phosphate. It is a highly unstable compound with the formula (NH4)3PO4. Because of its instability, it is elusive and of no commercial value. A related "double salt", (NH4)3PO4.(NH4)2HPO4 is also recognized but is too unstable for practical use. Both triammonium salts evolve ammonia. In contrast to the fragile nature of the triammonium salts, diammonium phosphate (NH4)2HPO4 is a valuable material, mainly as a fertilizer. Also of value is monoammonium salt (NH4)H2PO4, which is also valued as a fertilizer. These two salts provide plants with fixed nitrogen and phosphorus.

Tricalcium phosphate (sometimes abbreviated TCP) is a calcium salt of phosphoric acid with the chemical formula Ca3(PO4)2. It is also known as tribasic calcium phosphate and bone phosphate of lime (BPL). It is a white solid of low solubility. Most commercial samples of "tricalcium phosphate" are in fact hydroxyapatite.

Monocalcium phosphate is an inorganic compound with the chemical formula Ca(H2PO4)2 ("AMCP" or "CMP-A" for anhydrous monocalcium phosphate). It is commonly found as the monohydrate ("MCP" or "MCP-M"), Ca(H2PO4)2·H2O. Both salts are colourless solids. They are used mainly as superphosphate fertilizers and are also popular leavening agents.

Sodium monofluorophosphate, commonly abbreviated MFP, is an inorganic compound with the chemical formula Na2PO3F. Typical for a salt, MFP is odourless, colourless, and water-soluble. This salt is an ingredient in some toothpastes.

Dicalcium phosphate is the calcium phosphate with the formula CaHPO4 and its dihydrate. The "di" prefix in the common name arises because the formation of the HPO42– anion involves the removal of two protons from phosphoric acid, H3PO4. It is also known as dibasic calcium phosphate or calcium monohydrogen phosphate. Dicalcium phosphate is used as a food additive, it is found in some toothpastes as a polishing agent and is a biomaterial.

Fluorapatite, often with the alternate spelling of fluoroapatite, is a phosphate mineral with the formula Ca5(PO4)3F (calcium fluorophosphate). Fluorapatite is a hard crystalline solid. Although samples can have various color (green, brown, blue, yellow, violet, or colorless), the pure mineral is colorless as expected for a material lacking transition metals. Along with hydroxylapatite, it can be a component of tooth enamel.

Disodium phosphate (DSP), or sodium hydrogen phosphate, or sodium phosphate dibasic, is the inorganic compound with the formula Na2HPO4. It is one of several sodium phosphates. The salt is known in anhydrous form as well as forms with 2, 7, 8, and 12 hydrates. All are water-soluble white powders; the anhydrous salt being hygroscopic.

Monosodium phosphate (MSP), also known as monobasic sodium phosphate and sodium dihydrogen phosphate, is an inorganic compound of sodium with a dihydrogen phosphate (H2PO4) anion. One of many sodium phosphates, it is a common industrial chemical. The salt exists in an anhydrous form, as well as mono- and dihydrates.

Dimagnesium phosphate is a compound with formula MgHPO4. It is a Mg2+ salt of monohydrogen phosphate. The trihydrate is well known, occurring as a mineral.

Hypophosphoric acid is a mineral acid with the formula H4P2O6, with phosphorus in a formal oxidation state of +4. In the solid state it is present as the dihydrate, H4P2O6·2H2O. In hypophosphoric acid the phosphorus atoms are identical and joined directly with a P−P bond. There is an isomeric form isohypophosphoric acid which has a different structure with non-identical phosphorus atoms, one of which has a directly bonded H atom and an oxidation state of +3, which is joined by a P−O−P bridge to the second phosphorus atom which has an oxidation state of +5.

Vanadium phosphate are inorganic compounds with the formula VOxPO4 as well related hydrates with the formula VOxPO4(H2O)n. Some of these compounds are used commercially as catalysts for oxidations.

## References

1. "Phosphates – PubChem Public Chemical Database". The PubChem Project. USA: National Center of Biotechnology Information.
2. "Phosphate Primer". Florida Industrial and Phosphate Research Institute. Florida Polytechnic University. Archived from the original on 29 August 2017.
3. Campbell, Neil A.; Reece, Jane B. (2005). Biology (Seventh ed.). San Francisco, California: Benjamin Cummings. p. 65. ISBN   0-8053-7171-0.
4. Reilly, Michael (May 26, 2007). "How Long Will it Last?". New Scientist . 194 (2605): 38–9. Bibcode:2007NewSc.194...38R. doi:10.1016/S0262-4079(07)61508-5.
5. Leo Lewis (2008-06-23). "Scientists warn of lack of vital phosphorus as biofuels raise demand". The Times.
6. U.S. Geological Survey Phosphate Rock
7. Floor Anthoni. "Abundance of Elements". Seafriends.org.nz. Retrieved 2013-01-10.
8. American Geophysical Union, Fall Meeting 2007, abstract #V33A-1161. Mass and Composition of the Continental Crust
9. Central Florida Phosphate Industry: Environmental Impact Statement. 2. United States. Environmental Protection Agency. 1979.
10. C. Michael Hogan (2010). Mark McGinley and C. Cleveland (Washington, DC.: National Council for Science and the Environment), ed. "Water pollution". Encyclopedia of Earth . Archived from the original on 2010-09-16.
11. Hochanadel, Dave (December 10, 2010). "Limited amount of total phosphorus actually feeds algae, study finds". Lake Scientist. Retrieved June 10, 2012. [B]ioavailable phosphorus – phosphorus that can be utilized by plants and bacteria – is only a fraction of the total, according to Michael Brett, a UW engineering professor ...
12. Schmittner KE, Giresse P (1999). "Micro-environmental controls on biomineralization: superficial processes of apatite and calcite precipitation in Quaternary soils, Roussillon, France". Sedimentology. 46 (3): 463–76. Bibcode:1999Sedim..46..463S. doi:10.1046/j.1365-3091.1999.00224.x.
13. Gnandi, K.; Tchangbedjil, G.; Killil, K.; Babal, G.; Abbel, E. (March 2006). "The Impact of Phosphate Mine Tailings on the Bioaccumulation of Heavy Metals in Marine Fish and Crustaceans from the Coastal Zone of Togo". Mine Water and the Environment. 25 (1): 56–62. doi:10.1007/s10230-006-0108-4.