Phosphate Speciation under Organic‐Acid‐Promoted Dissolution of Phosphorus‐Sorbed Ferrihydrite–Boehmite Mixtures: Implications For Soil Phosphorus
- Biomineral Systems LLC South Bend IN 27695
Core Ideas Phosphate speciation determines its bioavailability in soils. Phosphate molecular speciation changes occur upon organic‐acid‐promoted dissolution. Results imply that phosphate in acid soils preferentially associated with Fe(III) oxides. Organic‐acid‐promoted dissolution of phosphate is a primary mechanism for enhancing the bioavailability of sorbed, inorganic soil phosphate. Bioavailability of P is, however, dependent on its speciation. Hence, the main objective of this study was to characterize changes in phosphate speciation as a function of pH levels (4–8) during citrate‐promoted dissolution of phosphate adsorbed on ferrihydrite–boehmite mixtures using two different sizes of ferrihydrite. A combination of batch dissolution kinetics and P K‐X‐ray absorption near‐edge structure (XANES) spectroscopy was used. Trends in shifts of white‐line peak energy and full width at half maximum height of P K‐XANES spectra indicated that the phosphate bonding configuration on ferrihydrite–boehmite as single minerals and mineral mixtures was predominantly binuclear–bidentate complexes at pH levels of 4, 6, and 8. When citrate was added to the ferrihydrite–boehmite mixtures with bound phosphate (pH 4 and 6), phosphate was preferentially released from boehmite, resorbed onto ferrihydrite, and precipitated to form noncrystalline FePO 4 minerals. A reverse trend was observed at alkaline pH. These results suggest the potential for excessive P release in P‐enriched acidic soils during a redox event due to preferential association of P to Fe(III) phases.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 1581857
- Journal Information:
- Soil Science Society of America Journal, Journal Name: Soil Science Society of America Journal Vol. 80 Journal Issue: 4; ISSN 0361-5995
- Publisher:
- Wiley Blackwell (John Wiley & Sons)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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