Size Distribution, Complexing Capacity, and Stability of Phosphate-Metal-Humic Complexes

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• 作者：Iñ ; aki Guardado ; Oscar Urrutia ; Jose M. Garc&iacute ; a-Mina
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2007
• 出版时间：January 24, 2007
• 年：2007
• 卷：55
• 期：2
• 页码：408 - 413
• 全文大小：248K
• 年卷期：v.55,no.2(January 24, 2007)
• ISSN：1520-5118

文摘

Size distribution, maximum complexing ability, and stability constants for phosphate-metal-humic(PO₄^3--M-HA) complexes involving two trivalent (Fe and Al) and five divalent metal (M) bridges(Zn, Cu, Mn, Ca, and Mg) were investigated at the pH values 4, 6, and 8. Results highlighted theexisting competition between metal-humic acid (M-HA) aggregation and the formation of PO₄^3--M-HA complexes. However, the fact that only a very low fraction of complexed metal is involved inPO₄^3- fixation seems to be related to the existence of specific electronic and/or steric requirementsin the binding site in the metal-humic complex. The importance of the ionic form of phosphate (H₂PO₄^-or HPO₄^2-) and the involvement of phenolic and especially carboxylic groups in the phosphate bindingare discussed. Finally, the order of stability obtained for PO₄^3--M-HA complexes was similar tothat of M-HA complexes. This result suggests that PO₄^3--M-HA might play a significant role in thedynamics of phosphorus in certain soil types.