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Full-Text Articles in Physical Sciences and Mathematics
Lignin: A Likely Precursor Of A Significant Fraction Of Humic Substances Via Oxidative Transformations, Seyyedhadi Khatami
Lignin: A Likely Precursor Of A Significant Fraction Of Humic Substances Via Oxidative Transformations, Seyyedhadi Khatami
Chemistry & Biochemistry Theses & Dissertations
Lignin is a major component of decaying terrestrial vegetation in soils and has been arguably reported to contribute substantially to the formation of soil carbon humus, and natural dissolved organic matter (DOM). To better understand the process by which this humification occurs, lignin and lignin-derived monomers were subjected to both biotic and abiotic oxidation processes. Two well-known oxidative transformation strategies were employed. The first involved the fungal degradation of brown-rot degraded wood subjected to a white-rot fungus (Phanerochaete chrysosporium) whose enzymes are particularly effective in lignin degradation via enzymatic oxidation. This enzymatic attack was monitored by ultrahigh resolution …
Alicyclic And Aromatic Carboxylic Acids In Soil Organic Matter: An Investigation Of Potential Origin And Association With Plutonium Using Advanced Analytical Techniques, Nicole Didonato
Chemistry & Biochemistry Theses & Dissertations
Carboxylic acids are a defining component of soil organic matter, responsible for many of the physical and chemical properties, including metal-organic matter interactions, which govern its role as an important constituent of soils. However, there is a shortage of detailed molecular level information regarding orientation and structural arrangement of carboxylic acids within soil organic matter. This dissertation utilizes electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) as well as solid-state and multi-dimensional nuclear magnetic resonance (NMR) to investigate the molecular formula composition within several organic matter sources and the primary structures that feature carboxylic acids. Soil organic matter …
Study Of Photochemical Formation Of Hydroxyl Radical In Natural Waters, Luni Sun
Study Of Photochemical Formation Of Hydroxyl Radical In Natural Waters, Luni Sun
Chemistry & Biochemistry Theses & Dissertations
This dissertation mainly focuses on the sources of the hydroxyl radical (•OH) from photochemical reactions in natural waters, in particular from reactions involving dissolved organic matter (DOM). Firstly, an accurate method for estimating •OH formation rate during long-term irradiation was developed. It was observed that previous methods for measuring •OH formation rates in the natural waters, which were based upon sequentially determined cumulative concentrations of probe photoproducts, significantly underestimated actual •OH formation rates. It was found that the underestimation was mainly due to the degradation of the probe photoproducts and that only ‘instantaneous’ formation rates were appropriate for accurately estimating …