GEOC 38 |
| The impact of fluctuating soil moisture content on nutrient sorption mechanisms remains poorly understood. This study investigated the effect of (de)hydration on (bi)sulfate adsorption at the Fe-(hydr)oxide-H2O interface. Hybrid molecular orbital/density functional theory (MO/DFT) cluster and periodic DFT models were compared for prediction of inner-sphere (bi)sulfate adsorption geometries. MO/DFT cluster calculations were performed using the PBE0, B3PW91, and B3LYP exchange-correlation functionals with combinations of relativistic effective core potential and/or all-electron basis sets. Differences in binding strength between sulfate and bisulfate complexes were qualitatively assessed using Natural Population Analysis. Periodic DFT calculations were performed using a plane-waves basis set on a (010) surface slab of goethite. Reasonable agreement between MO/DFT and periodic DFT calculations was demonstrated with notable exceptions. A potential pathway for bisulfate desorption was determined. Desorption involves protonation of sulfate to form bisulfate, which may occur upon soil drying. Upon rehydration, monodentate bisulfate may be unstable and desorb. |
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General Poster Session
7:00 PM-9:00 PM, Sunday, 10 September 2006 Moscone Center -- Hall D, Poster
Division of Geochemistry |