Environmental Engineering Reference
In-Depth Information
Source: Environmental Protection Agency
Phosphorus Cycle
The phosphorus cycle is probably the easiest of the biogeochemical cycles to describe. Phosphorus does not
exist in the atmosphere except in dust particles. It is necessary for living organisms, as it is the backbone of
nucleic acids (DNA and RNA) and other important biological molecules. Phosphorus tends to move through a
local cycle, whereas the other cycles are global in nature, mostly because of the Earth's weather. Since phos-
phorus is limited in the atmosphere, it is unlikely to move great distances.
Phosphorus is found in soil, rock, and sediments. It is released from these rock forms through chemical weath-
ering in the form of phosphate (PO
4
3-
). Phosphate is highly soluble in aqueous solutions and can be absorbed
from the soil into plants through their roots. Often phosphorus is a limiting factor for plant growth, as little of it
is released into the environment.
