科研之友
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摘要
Iron and manganese oxides are common minerals in a wide range of soils, and they largely control the fate of P. It is often implicitly assumed that phosphate does not exchange O atoms with minerals and water during adsorption, desorption, and precipitation reactions, but this has not yet been fully verified. In this study, we applied an O-18 stable isotope labeling technique to individually label O atoms in Fe and Mn oxides, water, and phosphate, and tested the exchange of O among them during phosphate sorption and desorption reactions. Physico-chemical properties of O-18-labeled goethite, hematite, hausmannite, and birnessite minerals were characterized using X-ray diffraction, Brunauer-Emmett-Teller (BET) surface area and pore size distribution, and scanning electron microscopy. All sorption and desorption results showed fast initial kinetics, with hausmannite having the highest sorption capacity, followed by a relatively slower sorption-desorption reaction before reaching equilibrium. Oxygen isotope ratios in Fe and Mn oxides, phosphate, and water showed no exchange of O between phosphate and mineral or water during either sorption or desorption reactions. These results attest to the integrity of the P-O bond during these reactions and thus enable the phosphate O isotope composition to be used as a reliable tool for tracing phosphate sources in soils and other environments.
- 出版日期2015-10
