Soluble reactive phosphorus

For these reasons, numerous attempts have been made to identify and characterize DOP, but with little success because it is usually present in very low concentrations. Typical values in lake waters range from 5 to 100 xg of P/L in oligotrophic to eutrophic systems. Colorimetric methods have been used extensively to detect and differentiate between soluble reactive phosphorus (SRP) and soluble unreactive phosphorus (SUP) at concentrations as low as 10 xg of P/L (I). SRP is generally considered to consist of only orthophosphate compounds, whereas SUP is composed of all other phosphorus species, primarily organic phosphorus compounds. The sum of SRP and SUP is equal to the total soluble phosphorus (TSP). These methods were used to study the dynamics of bulk phosphorus fractionation between the sediments, suspended particulate matter, the biota, and the dissolved fraction (2). Despite these studies, very little is known regarding the identity and characteristics of the DOP in the hydrosphere. 

Lake-Water Samples. Ten lake-water samples were collected from September 1990 to May 1991. The total soluble phosphorus concentration for the concentrated samples ranged from 23.8 to 60.8 mg of P/L, and the soluble reactive phosphorus concentrations ranged from 1.0 to 18.1 mg of P/L (Table I). Dissolved organic carbon concentration values for the concentrated samples ranged from 5000 to 20,000 mg of C/L. The signal-to-noise ratios from 12-14-h runs achieved for the NMR spectra range from 3.0 to 7.0. The pH of the concentrated samples after the addition of FeEDTA fell between the values of 7.00 and 8.00. Addition of the FeEDTA increased the pH by only a few tenths of a pH unit. 

Orthophosphate chemical structure is H2PO4- and it represents a significant fraction of the soluble reactive phosphorus (SRP) pool. 

Soluble reactive phosphorus (SRP) the P fraction which forms a phosphomolybdate complex under acidic conditions. 

The chemical form of phosphorus in the water column available for uptake by biota is important. The biologically available phosphorus is usually taken to be soluble reactive phosphorus (orthophosphate) , i.e. which, upon acidification of a water sample, reacts with added molybdate to yield molybdophosphoric acid, which is then reduced with SnCl2 to the intensely-coloured molybdenum blue complex and is determined spectrophotometrically (Imax = 882 nm). Reduction in inputs of phosphate, for example from point sources or by creating water meadows and buffer strips to contain diffuse runoff, has obviously been one of the major approaches to stemming eutrophication trends and... 

J. Ma, D.X. Yuan, Y. Liang, Sequential injection analysis of nanomolar soluble reactive phosphorus in seawater with HLB solid phase extraction, Mar. Chem. Ill (2008) 151. 

Gachter, R. and Mares, A. (1985) Does settling seston release soluble reactive phosphorus in the hypolimnion of lakes Limnology and Oceanography 30, 364-371. 

Routine water quality measurements typically include the determinations of several forms of phosphorus including dissolved/soluble reactive phosphorus (DRP or SRP, respectively), dis-solved/soluble organic P (DOP or SOP), and suspended PP. The DRP or SRP, by definition, includes only the DIP in the form of orthophosphate (H2PO4, HPO ", or PO "), depending on the pH (see Figure 9.8). Orthophosphate is the phosphate form most readily available for biological uptake. Specific activity of phosphate ions can be measured by ion-specific electrodes or ion chromatography. 

Suspended inorganic clays and periphyton are common to aquatic environments, and both can strongly influence physical and chemical water conditions. The uptake rate of soluble reactive phosphorus (from periphytons) by suspended clays in water is tested through artificial stream channels. 

Tarapchak, S.J., Soluble reactive phosphorus measurements in lake water Evidence for molybdate-enhanced hydrolysis. Journal of Environmental Quality 12,105,1983. 

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