Phosphate in soil

Ruby MV, Davis A, Nicholson A. 1994. In situ formation of lead phosphates in soils as a method to immobilize lead. Environ Sci Technol 28 646-654. 

A more recent study of the effect of drying on various species of phosphate in soil showed that drying had little effect on some species while having a pronounced effect on others [13]. In nature, soil is never heated to the temperatures used in oven drying, and thus the results of analysis of oven-dried soils are not considered representative of the soils natural conditions. 

An excellent example of this type of analysis involves the determination of phosphate in soil extracts. Soil is extracted with an appropriate extractant and added to a solution of acid molybdate, with which the phosphate reacts to produce a purple- or blue-colored solution of phosphomolybdate. Standard phosphate solutions are prepared, reacted with acid molybdate, and the intensity of the phosphomolybdate color produced is measured. A standard curve (also called a calibration curve) is prepared (see Section 14.10) from which the intensity of the color is directly related to the concentration of phosphate in the extract. 

Turner BL, Richardson AE. Identification of scyllo-inositol phosphates in soil by solution phosphorus-31 nuclear magnetic resonance spectroscopy. Soil Sci. Soc. Am. J. 2004 68 802-808. 

Ingram et al. [2] applied static secondary ion mass spectrometry to determine down to 70pg nr2 of tributyl phosphate in soil surfaces. 

Saunders and Williams [79] have discussed ignition methods for the determination of organic phosphorus in soils. Sodium carbonate fusion has also been used to solubilize phosphate in soil analyses. 

The AOAC alkalimetric ammonium molybdophosphate and photometric molybdovanadate methods for animal feed are described by Padmore (1990, pp. 87-88), and for plants by Isaac (1 990, p. 56). A spectrophotometric molybdovanadate procedure is also described in MAFF/ADAS (1986, pp. 181-182). The official Bran-rLuebbe AutoAnalyzer method for phosphate in soil, plant and fertilizer extracts is reproduced with permission in Appendix 6. 

Nriagu, J. O. 1984. Formation and stability of base metal phosphates in soils and sediments. In Nriagu, J. O. Moore, P. B. (eds) Phosphate Minerals. Springer-Verlag, Berlin, 318-329. 

Murphy J. P. and Riley J. P. (1962). A modified single solution method for the determination of phosphate in soils 1 Extraction Method. Anal. Chim. Acta 27, 31-36. 

The solubility of metal-phosphates in soils is highly pH dependent because of the protonation potential of the phosphate species, and the various Kip values of a number... 

Using equilibrium equations demonstrate the solubility of phosphate in soil. 

Xia, K. Pierzynski, G. Competitive Sorption between Oxalate and Phosphate in Soil An En-... 

Sites of prehistoric human activity may be evident where the human activity has disrupted natural chemical processes. This is particularly true in areas where the weathering processes do not include a great deal of leaching by aqueous solutions. For example, the ultimate source of all phosphates in soils is the breakdown of the phosphate minerals that are weathered from surrounding geological formations (9). Human activity may lead to decreases in the soil s phosphate levels (e.g., by agricultural activities) or increases in these levels when low-solubility phosphate compounds are deposited in the soil (e.g., by burials). The acidity of a soil may also be affected by human activities. 

R.A.Kiihnel, H.J Roorda and J.J.Steensma, Clays and Clay Miner., 23 (1975) 349. K.A.Norrish and H.Rosser, Mineral Phosphate, in Soils an Australian Viewpoint, Division of Soils, CSIRO, Academic Press, Melbourne, pp.335-361, 1983. 

Formation of Pb phosphates in laboratory and greenhouse experiments as well as in held observations clearly demonstrates the stability of Pb phosphates in soils. Such data also provide a sound basis for using P to effectively immobilize Pb in soils. 

Q ammonium, potassium, nitrate and phosphate in soil and fertilizers ... 

One colorimetric technique still in use in archaeology is a field test for soil phosphate. Phosphate in soils and sediments is an indicator of past human activity. Phosphate testing of soil samples is used to look for such indications (Fig. 4.4). A small sample of soil is mixed with hydrochloric and ascorbic acid to release soluble phosphates. The reaction produces a distinctive blue color in the presence of phosphate and the intensity of the color reflects its concentration. Results can be determined by eye or with the use of an instrument. 

The analysis of sediments is potentially one of the most informative aspects of archaeological chemistry. Soils may contain information on site extent, boundaries, activities, chronology, resource availability, agricultural fields, or past environments. One of the first applications of this kind involved the analysis of phosphate in soils. The Swede Olaf Arrhenius in 1929 first documented a correlation between soil phosphate and human activity and used that information to find buried prehistoric sites. Since that time, archaeologists and soil scientists have tried to find new ways to look into the earth with chemical analysis. 

Arsenate has chemical behavior similar to that of phosphate in soils it is chemisorbed by Fe and A1 oxides, noncrystalline aluminosilicates, and, to a smaller extent, layer silicate clays. Being the anion of the strong acid, H3ASO4, with pKa values (2.24, 6.94, and 11.5) similar to those of phosphoric acid, arsenate adsorbs most effectively at low pH. Consequently, its mobility is fairly low in acid soils with high clay or oxide content. In neutral to alkaline soils, especially those that are sodic, As may be mobile in the soluble Na arsenate form. Soil microbes and Mn oxides are able to promote the oxidation of arsenite to arsenate under aerobic conditions. 

This innovation generally involves modifications to the operation of the sampler and random access reagent selection, and can be implemented in both segmented and unsegmented flow analysers. For unsegmented flow analysis, the spectrophotometric determination of zinc and phosphate in soil extracts [368] is a good example. Zinc was determined only when phosphate was present at concentrations above a threshold level. The number of determinations required was reduced by 30%. Analogously, an expert flow system was proposed for the turbidimetric determination of chloride and sulphate in natural waters [369]. Both methods were implemented in the same manifold, and the need for sulphate determination was dependent on the chloride concentration determined. 

Phosphate chemistry in soils has been studied more intensively than that of any other element save nitrogen. Phosphate added to soils is first adsorbed quickly and is later fixed into increasingly less soluble states as time increases. Despite this great effort, quantitative predictions of phosphate concentrations in soil solutions are poor and no techniques have been devised to release the large amounts of unavailable phosphate in soils, nor to prevent fixation of fertilizer phosphate by soils. The uncertainties about soil phosphate chemistry and the difficulty of increasing phos-... 

The rate of phosphate loss from soils by weathering is about the same as the overall weathering rate, so the total amount of phosphate in soils tends to remain constant throughout soil development. The availability of phosphate to plants, however, decreases as soils become more acid and the proportion of phosphorus as aluminium and iron phosphate increases. 

Perrott, K.W. and Wise, R.G. (2000) Determination of residual reactive phosphate in soil. Comm Soil Science Plant Anal, 31 (11-14), 1809-1824. 

Phosphates in Soils, Sediments and Sludge Samples and Other Organic Solids... 

Gel chromatography, which depends primarily on molecular weight differences, has been used (a) to separate mono-, di-, and tri-alkylated phosphates and (b) for the estimation of organic phosphates in soil. It is interesting to note a reversal of roles tri-n-octylphosphine oxide-treated cellulose has successfully separated gold, antimony, and thallium. ... 

Rossman GR (1994) Colored varieties of the sihca minerals In Silica, Vol 29. Heaney PJ, Prewitt CT, Gibbs GV (eds) Mineralogical Society of America, Washington DC, p 433-467 Roussel C, Bril H, Fernandez A (2000) Arsenic speciation Involvement in evaluation of environmental impact caused by mine wastes. J Env Qual 29 182-188 Ruby MV, Davis A, Nicholson A (1994) In situ formation of lead phosphates in soils as a method to immobilize lead. Env Sci Tech 28 646-654... 

Nriagu JO (1984) Formation and stability of base metal phosphates in soils and sediments. In Phosphate Minerals. Nriagu JO, Moore PB (eds) Springer-Verlag, New York, p. 318-329 Oberti R, Ottolini L, Della Ventura G, Pardon GC (2001) On the symmetiy and crystal chemistiy of britholite New stmctural and microanalytical data. Am Mineral 86 1066-1075 Ohkubo Y (1968) EPR spectra of manganese(II) ions in synthetic calcium chloride fluoride phosphates. J Appl Phys 39 5344-5345... 

Anion-exchange chromatography has been used extensively for the separation of inositol phosphate in soils (Cosgrove, 1969a), sediments (Sommers et ah, 1972 Weimer and Armstrong, 1977 Suzumura and Kamatani, 1995) and waters (Minear et ah, 1988) (Fig. 1.4). Many early reports of ion-exchange separations used large col-... 

Makarov, M.L, Haumaier, L. and Zech, W. (2002a) The nature and origins of diester phosphates in soils a NMR study. Biology and Fertility of Soils 35, 136-146. 

He, Z.L., Yuan, K.N., Zhu, X.Z. and Zhang, Q.Z. (1991) Assessing the fixation and availability of sorbed phosphate in soil using an isotopic exchange method. Journal of Soil Science 42, 651-669. 

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