a

b

c

d

e

f

g

h

i

j

k

l

m

n

o

p

q

r

s

t

u

v

w

x

y

z

phosphates

Definition

See PHOSPHORUS.A common inorganic element. Phosphorus is one of the most important nutrients in primary productivity and it is involved in many metabolic processes occurring in nucleic acids, in ATP ADP and AMP as well as in membrane phospholipids. The forms of phosphorus found in natural waters are usually reported as ionisation products, of orthophosphoric acid (H3PO4) and are colloquially referred to as "phosphates". These forms can be summarised as follows: H3PO4 = H+ + H2PO4- H2PO4- = H+ + HPO42- HPO42- = H+ + PO43- In addition to the orthophosphates, condensed phosphates (pyro-, meta- and poly-) and organically bound forms are also found in nature. The phosphates in water bodies can be derived from geological substrates and from exogenous sources e.g. effluent discharges, including intensive aquaculture units. Phosphates are an essential nutrient for plant growth and this element can be limiting in freshwater systems. Commonly, phosphate levels are used as an indicator of the productivity of water bodies. In chemistry of water quality a variety of fractions are recognised, though the distinction between these fractions is largely defined by analytical protocols and physical states rather than by chemical forms. The common fractions are: (i) filterable orthophosphate also termed "soluble" or "dissolved" orthophosphate; (ii) total phosphate also called "whole sample" including both filterable and particulate forms.

English Greek Portuguese Swedish