Solution organic phosphorus

Plant availability and enzyme lability of soil solution organic phosphorus... 

F. S. Brown and C. R. Bury 6 obtained colloidal solutions of phosphorus pentoxide in nitrobenzene by stirring the mixture in the presence of alcohols or organic acids. The hydroxy-compound is absorbed and peptizes the pentoxide. Traces of moisture cause coagulation. Cone. soln. set to gels on keeping. 

Vaz, M.D. Ron, Edwards, A.C., Shand, C.A. and Cresser, M. (1992) Determination of dissolved organic phosphorus in soil solutions by an improved automated photo-oxidation procedure. Talanta, 39, 1479-1487. 

The solubility of neodymium carboxylates in organic solvents is also improved by the addition of electron donors such as acetylacetone, tetrahy-drofuran, N,N -dimethylformamide, thiophene, diphenylether, triethylamine, pyridine, organic phosphorus compounds etc. Also the storage stability of neodymium carboxylates in organic solutions (reduction of sediment formation) is increased by these additives. Mixtures of the Nd-precursor and the respective additives are reacted in the temperature range 0-80 °C. The sequential addition of Al-compound and halide donor yield the active polymerization catalysts [409,410]. 

Many such studies of sedimentary phosphorus profiles, also incorporating pore water measurement of soluble reactive phosphate, have demonstrated that redox-controlled dissolution of iron (hydr)oxides under reducing conditions at depth releases orthophosphate to solution. This then diffuses upwards (and downwards) from the pore water maximum to be re-adsorbed or co-precipitated with oxidized Fe in near-surface oxic sections. The downwards decrease in solid phase organic phosphorus indicates increasing release of phosphorus from deposited organic matter with depth, some of which will become associated with hydrous iron and other metal oxides, added to the pool of mobile phosphorus in pore water or contribute to soluble unreactive phosphorus . The characteristic reactions involving inorganic phosphorus in the sediments of Toolik Lake, Alaska, are shown in... 

Then, an oxidant solution (40 g/L potassium peroxodisulphate K2S2O8) is added to the sample for the photoconversion (15 min irradiation times) of the organic phosphorus forms into orthophosphates. Orthophosphates are then determined by UV-visible spectrophotometry. 

The determinations of P-, P-anions, and organic phosphorus in gases and in aqueous solutions have been studied by May (94). This method... 

Organic phosphorus compounds, primarily inositolhexaphosphates (probably more than 50% of all organic phosphates), occiu in soils. The parent cyclic polyol, inositol, exists in numerous stereoisomeric configurations, of which myo-, scyllo-, neo-, and cZZ-inositol have been isolated from soils as phosphate esters. The hexaphosphate of myoinositol (myo-IHP), phytic acid, occurs in plant tissues. It often occurs as phytin, the calcium magnesium salt. Esters of myo-IHP are readily adsorbed in acidic soil solution by clay minerals and finely divided hydrated oxides of iron and aluminum. Organic sulfur compounds present in soils probably occur primarily as amino acids—e.g., cysteine, cystine, and methionine. 

Solution NMR uses extracts of soils and environmental samples. As with any extraction procedure for soil organic phosphorus, there is always the risk of hydrolysis (Turner et aL, 2003b). There is little agreement on the most suitable extractant, but those in use include sodium hydroxide (Newman and Tate, 1980 Hawkes et aL, 1984), Bu NOH (Emsley and Niazi, 1983), the cation exchange resin Chelex in water (Adams and Byrne, 1989 Condron et aL, 1996), sodium hydroxide plus Chelex (Gressel et aL, 1996), sodium hydroxide plus sodium fluoride (Sumann et aL, 1998), and sodium hydroxide plus EDTA (Cade-... 

Both an automatic peak-picking routine in the processing software and visual inspection are used to identify peaks. Chemical shifts are then compared with literature reports. Table 2.1 shows some of the biological phosphorus compounds identihed in NMR studies of environmental samples, while Table 2.2 shows peak shifts for phosphorus minerals determined by solid-state spectroscopy. Although this chapter focuses on organic phosphorus, the overlap of peak shifts for biological and mineral phosphorus compounds must be noted. This may complicate the identification of phosphorus species in solid-state spectroscopy, because both biological and mineral phosphorus forms may be present. To further confirm peak shifts, standards such as methylene diphosphonic acid may be added directly to the sample or included as capillary tube inserts in solution NMR (e.g. Koopmans et aL, 2003). 

There are two principal pathways for the abiotic degradation of organic phosphorus compounds in the environment hydrolytic reactions and photolytic reactions. The importance of either mechanism depends to a substantial degree both on the nature of the particular compound of interest (Fig. 4.1), and on its location in the environment. Some compounds, such as the phosphorodithionate pesticide malathion, are readily broken down (malathion has a half-life of about 11 h in alkaline solution ... 

Many of the enzymes involved in the cleavage of organic phosphorus compounds require metal ions for activation. However many metal ions can also facilitate the hydrolysis of organic phosphorus compounds in the absence of enzymes. As early as 1938 it was shown that lanthanide (lanthanum and cerium) and actinide (thorium) hydroxides could accelerate the hydrolysis of a-glycerol phosphate in alkaline solution (Bamann and Mersenheimer, 1938). A similar study by Butcher and Westheimer (1955) showed that lanthanum hydroxides could accelerate the hydrolysis of three simple phosphate esters (methoxyethyl phosphate, hyrdroxyethyl phosphate and aminoethyl phosphate) by a factor of about 1000. Using... 

The productivity of many ecosystems is determined by the chemical stability of phosphate, its relative immobility in soil, and its low concentration in the soil solution (approximately 1 xM). Phosphorus uptake by plant roots occurs mainly as phosphate ions (H2P0 and HPO ) from the soil solution, which depends on the solubilization of mineral phosphates and the degradation or mineralization of organic phosphorus. During phosphate uptake, a phosphorus-depleted area is formed close to the root, since phosphate uptake is faster than its diffusion in soil (Bhat and Nye, 1973). Having... 

This chapter reviews the abiotic processes that can lead to the stabilization of organic phosphorus in soils and the aquatic environment. In particular, we examine the role of adsorption to soil minerals, complex-ation reactions, precipitation with polyvalent cations and the incorporation of organic phosphorus into humic substances in stabilizing organic phosphorus. We then discuss the effects of soil solution chemistry on these reactions, as well as the effects of these reactions on the environment. 

Details of the forms of organic phosphorus that occur in the environment can be found in several published reviews (e.g. Dalai, 1977 Anderson, 1980 Harrison, 1987) and elsewhere in this volume, but a brief overview is provided here. Advances in solution nuclear magnetic resonance spectroscopy... 

From a theoretical point of view, the term sorption is used instead of adsorption to cover any process that removes a reactant from the solution, including adsorption and precipitation (Barrow, 1993). In the adsorption process for phosphate, the concentration of phosphate in solution controls the extent of adsorption, while the extent of precipitation is determined by the solubility product of the least soluble phosphate compound, which in turn controls the phosphate concentration in solution. As with phosphate, the adsorption of organic phosphorus compounds on minerals can be described using the Langmuir equation ... 

As for phosphate, the adsorption reaction of organic phosphorus is not readily reversible, although some phosphorus can pass to the solution depending on the time of desorption, the solution-to-soil ratio, and temperature (Barrow, 1983). As solution characteristics play an important role in desorption, different approaches using free water, dilute electrolyte solutions, or chemical extractants with variable pH and ionic composition have been used to quantify the amount of phosphorus desorbable from minerals and then available to plants (Frossard et al, 1995). Desorption of inorganic and organic phosphorus was found to increase with pH (Cabrera et al, 1981 Celi et al, 2003 Martin et al, 2003), with the percentage of phosphorus saturation (Parfitt, 1979 He et a7., 1991, 1994 Martin... 

Sorption of organic phosphorus by neutral and basic soils increases or reaches a maximum with increasing organic phosphorus concentration (McKercher and Anderson, 1989), while acid soils can show similar or contrasting behaviour (Leytem et ah, 2002). The extent and rate of sorption can also be regulated by mineral properties (i.e. surface porosity, specihc area and degree of crystallinity) and soil solution chemistry. 

Pant et al. (1994) reported that organic phosphorus in soil solution is associated with a... 

---