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Several solid-state 13C nuclear magnetic resonance (NMR) techniques were used to characterize soil organic matter spiked with 13C-labeled organic compounds spanning a range of hydrophobicities (benzoic acid, benzophenone, naphthalene, phenanthrene, and palmitic acid). The chemical shifts of NMR resonances of the sorbed species were shifted by up to 3 ppm relative to those of the neat compounds. Sorption also resulted in increased resonance linewidth for the compounds containing a single 13C label, indicating the presence of a range of different chemical environments at the sites of sorption. On the other hand, sorption decreased the linewidth of the resonance of naphthalene, which was uniformly 13C-labeled. This was attributed to the removal of intermolecular 13C-13C dipolar coupling. Heterogeneity of the organic matter was demonstrated using the spectral editing technique proton spin relaxation editing (PSRE), which enabled the identification and quantification of charcoal-rich domains characterized by rapid rates of proton spin-lattice relaxation in the static frame (T1H), and humic domains characterized by slow rates of T1H relaxation. Furthermore it was demonstrated that the sorbed 13C-labeled molecules "inherit" the T1H "signature" of the organic matrix in their immediate vicinity. Thus PSRE on the spiked soils enabled evaluation of the relative affinity of the two domain types for the sorbate molecules. The charcoal-rich domains were shown to have a twofold to tenfold greater affinity for the organic compounds, with greater differences found for the more hydrophobic compounds.

Six sewage sludges from five sewage treatment plants in Australia were incubated for up to 21 months. Carbon losses at the end of the 21-mo incubation varied substantially. The remaining organic matter was isolated by treatment with hydrofluoric acid (HF) and characterized using a range of solid-state (13)C nuclear magnetic resonance (NMR) spectroscopic techniques. By every measure (signal distribution in cross polarization [CP] and Bloch decay [BD] spectra, carbon NMR observability determined by spin counting, and the appearance of proton spin relaxation editing subspectra), the chemical composition of the residual organic matter appeared to be little different from that of the original sludges, even for those sludges that experienced the greatest carbon losses. Importantly, these NMR properties distinguish sewage sludge organic matter from soil organic matter. Thus, it should be possible to follow the decomposition of sewage sludge organic matter applied to soils in the field using solid-state (13)C NMR spectroscopy.

Two novel solid-state 13C nuclear magnetic resonance (NMR) spectroscopic techniques, PSRE (proton spin relaxation editing) and RESTORE [Restoration of Spectra via T(CH) and T(1rho)H (T One Rho H) Editing], were used to provide detailed chemical characterization of the organic matter from six Australian sewage sludges. These methods were used to probe the submicrometer heterogeneity of sludge organic matter, and identify and quantify spatially distinct components. Analysis of the T1H relaxation behavior of the sludges indicated that each sludge contained two types of organic domains. Carbon-13 PSRE NMR subspectra were generated to determine the chemical nature of these domains. The rapidly relaxing component of each sludge was rich in protein and alkyl carbon, and was identified as dead bacterial material. The slowly relaxing component of each sludge was rich in carbohydrate and lignin structures, and was identified as partly degraded plant material. The bacterial domains were shown, using the RESTORE technique, to also have characteristically rapid T(1rho)H relaxation rates. This rapid T(1rho)H relaxation was identified as the main cause of underrepresentation of these domains in standard 13C cross polarization (CP) NMR spectra of sludges. The heterogeneous nature of sewage sludge organic matter has implications for land application of sewage sludge, since the two components are likely to have different capacities for sorbing organic and inorganic toxicants present in sewage sludge, and will decompose at different rates.

Six sewage sludges from five sewage treatment plants in Australia were characterized using solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Spectra were acquired both before and after removal of mineral components through treatment with hydrofluoric acid (HF). Carbon mass balance indicated that little organic matter was lost on HF treatment, which significantly improved NMR sensitivity and spectral resolution, and decreased acquisition time and hence cost of NMR analysis. Two NMR techniques were used, the standard cross polarization (CP) technique and Bloch decay (BD). The BD technique had not been applied previously to the analysis of sewage sludge. For each sludge sample, both before and after HF treatment, the BD spectrum contained significantly more alkyl carbon. Spin counting, another technique applied to sewage sludge here for the first time, showed that the BD spectra of the HF-treated sludges were quantitative, while approximately 30% of the CP NMR signal went undetected. The discrepancy between CP and BD spectra was attributed to the presence of alkyl carbon with such high molecular mobility that the efficiency of cross polarization is affected. This study shows that sewage sludge organic matter is significantly different in chemistry to soil organic matter and has implications for the application of sewage sludge to agricultural land.

The effects of paramagnetic species on solid state 13C nuclear magnetic resonance (NMR) spectra were quantified in a series of doping experiments. The degree of signal loss caused by paramagnetic metals was shown to depend not only on the quantity, but also on the nature of the paramagnetic species, as well as the intimacy of contact with the organic substrate and the type of NMR experiment. Two mechanisms of signal loss were distinguished--signal loss via loss of magnetic field homogeneity, which affects all 13C nuclei in a sample, and signal loss via interaction between electronic and nuclear spins, the effects of which were localized to the close environment of the paramagnetic species. Loss of field homogeneity is important for manganese species, but not for copper species, and is equally important for both cross polarization and Bloch decay experiments. The interaction between electronic and nuclear spins is highly dependent on the spin-lattice relaxation rate constant of the free electron (T1e), as cations with very short T1e values (e.g., Pr3+) cause less signal loss than cations with longer T1e values (e.g., Cu2+, Mn2+). Cross polarization spectra are shown to be more susceptible than Bloch decay spectra to this mechanism of signal loss. Signal loss and increased relaxation rates brought about by paramagnetic species can be used to provide information on soil organic matter (SOM) heterogeneity in the submicron range. This is demonstrated for SOM doped with paramagnetic cations where selective signal loss and increased relaxation rates are used to determine the nature of cation exchange sites.