Total reactive phosphorus

The second reason for acid-digestion is the determination of the total soil elemental content of, e.g. potassium, phosphorus or trace elements. This is seldom done for potassium in normal soil samples, mainly because the total K in soils is of no value as an index to the availability of K to plants, nor is it always of value in tracing the movement or accumulation of applied fertilizer K (Pratt, 1965). The unreactive soil phosphorus is obtained by subtracting the naturally leached reactive phosphorus from the total phosphorus, and a method for determining the latter by extraction with sulphuric acid and potassium persulphate is cited by Turner and FHaygarth (2000). They analysed... 

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. 

Maher, W. and L. Woo. 1998. Procedures for the storage and digestion of natural waters for the determination of filterable reactive phosphorus, total filterable phosphorus and total phosphorus. Anal. Chim. Acta 375 5 -7. 

The cycling and availability of P in estuaries is largely dependent on P specia-tion. Consequently, total P has traditionally been divided into total dissolved P and total particulate P fractions, which can be further divided into dissolved and particulate organic P and dissolved and particulate inorganic P pools. Another defined fraction within the TP pool is reactive phosphorus, which has been used to describe the potentially bioavailable P. Much of the work to date has focused on the soluble reactive P, which is characterized as the P fraction that forms a phosphomolybdate complex under acidic conditions. 

Two questions can be raised regarding the use of these phosphothioates in studies with phospholipase A2. The first is the low total reactivity of phospholipase A2 toward DPPSC as compared to DPPC (without the thio substituent), which is only 4% relative to the natural isomer. The second question relates to the possible chirality of the phosphorus in a membrane phosphoglyceride. To date, the first question appears not to be of immediate importance since the course of the reaction is similar in the thio and nonthio derivatives. As regards the second question, it has not been possible to establish with confidence the configuration of the phosphorus in membrane-bound phosphoglycerides. 

As noted in Table 2, between 40% and 75% of phosphorus buried in continental margin sediments is potentially reactive, and 90% to 100% of phosphorus buried in abyssal sediments is potentially reactive. The reactive phosphorus fraction of the total sedimentary phosphorus reservoir represents that which may have passed through the dissolved state in oceanic waters, and thus represents a true phosphorus sink from the ocean. The minimum reactive phosphorus burial flux was calculated as the sum of 0.4(sFjs) -I- 0.9 (sF ) the maximum reactive phosphorus burial flux was calculated as the sum of 0.75(sFes) -i- 1(sF ). Both the flux estimates and the % reactive phosphorus estimates have large uncertainties associated with them. 

We noted earlier that mass spectrometry had not been used to any extent in speciation studies of organic phosphorus in natural environments. Here we define phosphorus speciation as the determination of actual molecular formulas and structures of molecules containing phosphorus, and not the more commonly accepted, broad classes of phosphorus such as filterable reactive phosphorus, total filterable phosphorus, filterable organic phosphorus, etc. While a few studies have focused on particular classes of organic phosphorus, such as the inositol phosphates, we are not aware of any attempt to broadly speciate... 

The organic phosphorus content of solutions is generally determined by the difference between total phosphorus and molybdate-reactive phosphorus. As this fraction may also contain condensed phosphates (Ron Vaz etal., 1993), the operational term molybdate-unreactive phosphorus is used throughout the chapter, rather than organic phosphorus, which is used in a generic sense. 

The phosphorus concentration in each operationally defined fraction is typically detected using the phosphomolybdate-blue colorimetric reaction and spectrophoto-metric detection (American Public Health Association, 1995), with or without pre-treatment and/or filtration. The term total phosphorus applies to samples subjected to hydrolysis and/or oxidation pretreatment intended to convert all forms of phosphorus to phosphate (Maher and Woo, 1998 Monaghan and Ruttenberg, 1999). Phosphorus that reacts with molybdate in untreated samples is referred to as reactive phosphorus . Samples may be unfiltered or filtered. When samples are unfiltered, the operationally defined fractions are total... 

Figure 8.2 shows the commonly analyzed fractions of phosphorus that can be determined depending on which sample pretreatment procedure is employed. Of these fractions, total phosphorus (TP) and filterable reactive phosphorus (FRP) are perhaps the most... 

Preliminary sample treatment often involves filtration, which helps to "arbitrarily" separate the particulate and the dissolved phases. Filtration is required to obtain filterable reactive and total filterable reactive phosphorus and is highly recommended at site just... 

Cambella and Antia [385] determined phosphonates in seawater by fractionation of the total phosphorus. The seawater sample was divided into two aliquots. The first was analysed for total phosphorus by the nitrate oxidation method capable of breaking down phosphonates, phosphate esters, nucleotides, and polyphosphates. The second aliquot was added to a suspension of bacterial (Escherichia coli) alkaline phosphatase enzyme, incubated for 2h at 37 °C and subjected to hot acid hydrolysis for 1 h. The resultant hot acid-enzyme sample was assayed for molybdate reactive phosphate which was estimated as the sum of enzyme hydrolysable phosphate and acid hydrolysable... 

Total phosphorus content of phosphate rocks is relatively unimportant, since what really matters is its reactivity in the soil, which in turn depends on the soil itself, the rock mineralogy and the level of rock grinding. 

From an elemental perspective, most of the mass of POM and DOM is carbon. Thus, DOC and POC concentrations are generally representative of the entire DOM and POM pools. Because DOC and POC concentrations are more easily measured than those of the other elements (nitrogen, phosphorus, oxygen, and hydrogen), far more data has been collected on their concentrations and reactivity as compared to that of DON, PON, DOP, or POP. DOM and POM concentrations are not measured for technical reasons and because the total mass of organic matter provides little insight into the biogeochemical processes responsible for its formation and destruction. 

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