Type of Document Dissertation Author Schilling, Michael Author's Email Address firstname.lastname@example.org URN etd-07192004-151534 Title Characterization of Soil Organic Matter by High-Resolution Solid-State Carbon-13 Nuclear Magnetic Resonance Spectroscopy Degree Doctor of Philosophy Department Chemistry and Biochemistry, Department of Advisory Committee
Advisor Name Title William T. Cooper Committee Chair John Dorsey Committee Member Oliver Steinbock Committee Member Thorsten Dittmar Committee Member Keywords
- NMR Relaxation Rates
- Proton Spin Lattice Relaxation Editing
- Mineral Soils
- Copper Binding
- Soil Organic Matter
- Cross Polarization Magic Angle Spinning Carbon-13
Date of Defense 2004-07-14 Availability unrestricted AbstractSolid-state carbon-13 nuclear magnetic resonance (NMR) spectroscopy has come to be considered the pre-eminent analytical technique for the study of soil organic matter in its entirety. Despite its widespread use, carbon-13 CP-MAS NMR of soils, especially mineral soils, has been hindered by low carbon content, and in many cases, by the presence of paramagnetic species such as iron. Chemical treatment methods, which must not severely compromise the chemistry of the original soil organic matter, have been developed to remedy these problems. However, the effects of these treatments on soils have only been examined in a qualitative fashion on a limited number of soil types. Therefore, the effectiveness of commonly employed treatment agents in the removal of paramagnetics from mineral soils was examined, along with the resulting quantitative reliability of the NMR spectra and spin dynamics of these soils, both of which provide organic matter structural information. Major differences in functional group distributions were found in certain treatment method/soil type combinations as well as discrepancies in sample spin dynamics.
Carbon-13 CP-MAS NMR spectroscopy also is an excellent analytical technique to probe the metal binding properties of soil organic matter. This advantage is due to the tendency of paramagnetic cations to enhance NMR relaxation phenomena at the molecular sites in which they are present. Metal-humate interactions were investigated using paramagnetic doping of unmodified and chemically modified peat to follow changes in sample spin dynamics. Such an approach allowed for the functionalities involved in metal binding to be discerned. Carboxyl and as well as O-alkyl functionalities were found to be the predominant sites involved in metal binding, and to a lesser extent phenol-type sites. Possible evidence for structural conformational changes in soil organic matter resulting from the blockage of particular sites was shown.
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