reactive phosphate

Soluble reactive Phosphate (SRP) or Total Reactive Phosphate (TRP)
Phosphorus form that responds to colorimetric test without preliminary hydrolysis or digestion. Although reactive phosphate is comprised largely of orthophosphates, it may include easily hydrolyzable inorganic and organic forms of P (APHA, 1989, Baldwin, 1998). Reactive phosphate maybe measured in both filtered* (dissolved SRP, the most commonly measured form of SRP) or unfiltered (total reactive phosphate) (EPA, 1979).