Interactions of 100 μmol L-1 mugineic acid (MA) with synthetically produced Fe (hydr)oxides (goethite, hematite, lepidocrocite, and ferrihydrite) as influenced by 100 mmol L-1 SO4 2- and phosphate were studied at equilibrium in the pH range from 3 to 11. In the presence of SO4 2-, the concentrations of total MA [i.e., free MA+Fe(III)-MA complexes] and Fe(III) dissolved by MA in the filtrates were higher than those in the presence of 100 mmol L-1 Cl- at pH<7. Sulfate increased the formation of Fe(III)-MA complexes indirectly by reducing the adsorption of MA and Fe(III)-MA by the Fe (hydr)oxides. The adsorption of MA by the Fe (hydr)oxides and consequently the MA-promoted dissolution of Fe(III) from ferrihydrite and lepidocrocite were greatly inhibited by the adsorption of phosphate. The slight dissolution of Fe(III) between pH 5 and 9 is partly attributed to the formation of soluble Fe(III)-phosphate complexes. Although MA does not react directly with Fe (hydr)oxides in the presence of excess phosphate, MA would promote the dissolution reaction of Fe(III) by phosphate. The sequence of adsorption affinity for the Fe (hydr)oxides was found to be: phosphate≫MA>Fe(III)-MA, SO4 2->Cl-. Our results suggest that SO4 2- and especially phosphate applied as fertilizers may inhibit the MA-promoted dissolution of Fe(III) from Fe (hydr)oxides in soils mainly by displacement of MA from the surface of Fe (hydr)oxides.
|Number of pages||7|
|Journal||Soil Science Society of America Journal|
|Publication status||Published - Jan 1 1998|
All Science Journal Classification (ASJC) codes
- Soil Science