Physical and Potentiometric Constant of Ferrous and Ferric Phytate Applied to Organic Phosphate Transport in Poorly Drained Soil

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2005-08-16

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Inositol phosphates are metabolically derived organic phosphates that increasingly appear to be an important sink and source of phosphate in the environment. Inositol hexakis dihydrogen phosphate or phytic acid is the most common inositol phosphate in the environment. Iron is abundant in many terrestrial systems. Mobility of phytic acid iron complexes are potentially pH and redox responsive. Ferric and ferrous complexes of phytic acid were investigated by proton nuclear magnetic resonance spectroscopy, enzymatic dephosphoralation and potentiometrically in solution. The redox potential and concentration of iron were measured in a soil column containing a benchmark poorly drained soil from Maryland (Elkton). Ferrous phytate was found to form quickly and persist for a longer period then ferric phytate. Dissociation constants were 1.113 and 1.186 and formation constants were 0.899 and 0.843 for ferric and ferrous phytate respectively. Enzymatic dephosphoralation recoveries supported the magnitude of the kinetic and equilibrium rate constants.

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