Interacción fósforo-sustancias húmicas. Caracterización fisicoquímica y efectos sobre la adsorción del fósforo en el suelo

Resumen

Numerous studies have described the relationship between soil phosphorus bioavailability and soil organic matter content. One of the most described mechanisms of interaction is the formation of phosphate-metal-humic complexes, in which metals such as Fe, Al and Ca, act as metal bridges. However, few is known about their stability, their structural features or their role in soil phosphorus dynamics. In this work, a methodological approach was employed to study the formation and physicochemical properties of phosphate-metal-humic complexes, by means of an anion exchange resin. This method was validated by another employing ultrafiltration and, by means of the Scatchard method, maximum complexing abilities and stability constants were calculated for the most common metals in soil, and a Leonardite-origin humic acid. Later, as only a little part of the complexed metal was involved in phosphate complexation, size distribution by ultrafiltration, maximum complexing abilities and stability constants were compared when varying the complexes synthesis methods. The structural and electronic features of the interaction were approached by studying Fe, Al and Zn complexes FTIR and Synchronous Fluorescence spectra. Moreover, a molecular modelling study of these complexes, highlighted how the stability of phosphate-metal-humic complexes was inversely related with the metal-humic complexes stability. Finally, the adsorption study of Fe, Al and Ca complexes in three different soils, showed how phosphate-metal-humic complexes can affect soil phosphorus dynamics.