Environmental Engineering Reference
In-Depth Information
BOX 8.1
FORMS OF PHOSPHORUS
Phosphorus in natural waters is divided
into three operational parts: soluble reactive
phosphorus (SRP), soluble unreactive phos-
phorus (SUP), and particulate phosphorus
(PP; Rigler 1973). The sum of all phosphorus
components is termed total phosphorus (TP).
Soluble phosphorus (SP) is all filterable
forms of P, both organic and inorganic.
(Organic P is P that is bound to living or dead
tissues or dissolved biological molecules
(such as ATP and DNA) of organisms, and
inorganic P is P that is not associated with
organic material.) Soluble and particulate
phosphorus are differentiated by whether or
not they pass through a 0.45
Soluble reactive phosphorus (SRP)
is fil-
tered P (not captured by a 0.45
m mem-
brane) that reacts with certain reagents
used to measure it. It is usually primarily
inorganic orthophosphate (PO
4
), the form
directly taken up by plant cells.
Soluble unreactive phosphorus (SUP) is
filterable P that does not readily react
with reagents and is typically measured
as the difference between SP and SRP.
It is made up of organic P and chains
of inorganic P molecules called polypho-
sphates.
Particulate phosphorus (PP) is all P cap-
tured by a 0.45
µ
m filter. SP is
divided into two parts: SRP and SUP.
m filter, including organic
and inorganic particles and colloids.
µ
µ
FIGURE 8.2
Summary of the phos-
phorus cycle in the modern world.
Standing stocks in rocks given in bil-
lions of metric tonnes (petagrams);
other fluxes and stocks given in mil-
lions of metric tonnes (teragrams).
(Based on
Cordell et al. 2009
, MacDonald
et al. 2011, and FAO 2007.)
Phosphate
rocks
(65)
Phosphate
mining (23)
Weathering
Fertilizer
containing
phosphate (21.5)
Weathering (15-20)
Crops
Animals
Animal waste
and decomposition
9.6
Plants
22
Soil
phosphates
Phosphate
rocks
Excretion and
decomposition
Dissolved
phosphates
Animals
Marine
sediments
Algae
